# Die luminance, emittance and advanced die heatsinking



## Dr.Jones (Jun 26, 2010)

For bare throw, the most important factors are lens diameter and LED die luminance (usually referred to as surface brightness) - and then of course all the losses and the measures to reduce them.
While the optics part is covered in other threads, I couldn't find much info on die luminance. Is there any list?

If not, maybe we could compile one.
One could try to deduce that from the specs, but the specified LED flux (lumen) includes light strayed within the LED, which does not contribute to throw, thus this method over-estimates luminance.

The best method seems to be Ra's proposal: Measure the LEDs beam intensity (maximum) with a lux meter at 1m distance, then divide that by the apparent(!) die size as seen from ahead.

Measuring apparent die size might not be that simple, so I measured some typical LEDs with 1-2 methods:
a) measuring the width using an 100x low-NA microscope with scale and subtracting the contact pads (not good for XP-G, since the apparent area isn't a square any more)
b) taking a close-up image from the LED and counting pixels.

With the two XR-Es I applied both, and the results were within 3%

*Apparent die sizes:*
XR-E EZ900: 2.07mm²
XR-E EZ1000: 2.76mm²
XP-G: 3.50mm²

For luminance in cd/mm² just divide your measured beam intensity (it's proper unit is candela (cd), equivalent to [email protected]) and divide it by that area.
For standard units (cd/m²) multiply by 1 000 000.

Maybe we can collect some...

EDIT: Since gathering that data currently doesn't go that well, I'll post some die emittance (lumen per mm²) data meanwhile that I derived from the specs.
Theoretically the luminance is the emittance divided by pi, but as I wrote above this doesn't account for emitter package internal stray light.






The XR-E EZ1000 is reported to perform slightly (1-2%) better than stated at 1A.


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## Walterk (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*

What do you mean with apparant size.... is that as how it looks to the eye when looking at the led ?
As opposed to cutting the led in half and measuring the actual size?
(Beacuse then you could also use the data-sheets dimension sketch.)


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## Ra (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Walterk said:


> What do you mean with apparant size.... is that as how it looks to the eye when looking at the led ?
> As opposed to cutting the led in half and measuring the actual size?
> (Beacuse then you could also use the data-sheets dimension sketch.)



That's exactly what is ment: The dome already acts as a kind of precollimating lens, so you need the apparent die-size. After all, it is the apparent surface that creates a certain amount of [email protected]

That also was one of the major conclusions we ended up with in the "formula for calculating throw"-thread..


Regads,

Ra.


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## Ra (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Dr.Jones said:


> For bare throw, the most important factors are lens diameter and LED die luminance (usually referred to as surface brightness) - and then of course all the losses and the measures to reduce them.
> While the optics part is covered in other threads, I couldn't find much info on die luminance. Is there any list?
> 
> If not, maybe we could compile one.
> ...



Oh yes, we can !!!

You have found quite a nice and accurate way to measure die sizes.. That's something we can work with !
I just received some led's, hope to be able to measure them soon..

I'm looking into the relationship between the several led-constructions and their overdrivabillity, which also is directly related to surface brightness.

Example: I still do not know why Cree choose to a base of aluminium-oxide.. Which has much lower thermal conduction than aluminium, let alone copper.

Some numbers on thermal conductivity: In W/mK

Al-oxide : 30
Aluminium : 250
Copper : 401
Silver : 429

And to make a remark that certainly will raise some eyebrouws:

I'm testing led's right now with a revolutionary heatsink material, with a thermal conductivity of.... 2000 ! Yep, that's a two with three zero's !!


Laterrrr..

Ra.


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## Th232 (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Ra said:


> Some numbers on thermal conductivity: In W/mK
> 
> Al-oxide : 30
> Aluminium : 250
> ...



I think diamond has a thermal conductivity about 5x that of copper, have you found a block of diamond?


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## Ra (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Th232 said:


> I think diamond has a thermal conductivity about 5x that of copper, have you found a block of diamond?



Uhh... If this was a quiz, you would have been excluded from it..

You're right !! Diamond... CVD or industrial diamond to be precise..
It's a disc, 20mm diameter and 1.2mm thick..
The idea is to spread the heat from the led over a bigger surface, and then take it away with a copper heatsink..
That means that I can overdrive the led much more than with a conventional heatsink..


Regards,

Ra.


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## Th232 (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*

That is very neat!

I dread to ask, and I understand if you don't want to say, but how much did it set you back?


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## Ra (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Th232 said:


> That is very neat!
> 
> I dread to ask, and I understand if you don't want to say, but how much did it set you back?



Almost nothing!! A friend of mine could get his hands on it for me.. And in return, I'm going to build him a telescope..

To all:

Note that this is a one time oppertunity for me !! So I must say no beforehand to any questions that start with: "I do not dare to ask, but is there a possibillity that...." !! Sorry...


Regards,

Ra.


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## Th232 (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*

Good trade!


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## saabluster (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Dr.Jones said:


> The best method seems to be Ra's proposal: Measure the LEDs beam intensity (maximum) with a lux meter at 1m distance, then divide that by the apparent(!) die size as seen from ahead.


Although you may have inferred it you did not directly state. Are you saying to use a lens to project an image of the die or not? If you do not use a lens the project an image then it seems to me all conclusions would be faulty. I have been doing this testing for some time although I have a specific distance I like to test at and I see no need to do any dividing but maybe I am missing something. Assuming you are indeed using a projected image of the die I have one little fly in your ointment. The luminance varies across the surface significantly. If you take the peak number and go with that you may be skewing the results. 

You need super high quality lenses for this to really work. I found that some specialty projector parts that have 5 lenses in it which have extremely low aberration and allow me to get very clean measurements.
Interestingly the Nichia Raijin warm white has a higher surface brightness than the XP-E R3 at lower output levels.

Another means of measuring surface brightness would be to take images of the LED itself. I did not make this up. I read it somewhere but I don't remember where anymore. I'm sure it would require some specialized equipment though.



Ra said:


> Uhh... If this was a quiz, you would have been excluded from it..
> 
> You're right !! Diamond... CVD or industrial diamond to be precise..
> It's a disc, 20mm diameter and 1.2mm thick..
> ...


I thought about doing that myself. I even looked at trying to find a chunk of SiC to use. In the end I don't think it is worth the effort as you can get a heatpipe that would only cost a few dollars and do a far better job at thermal transfer while weighing much less. The only advantage I could find to using diamond was that I could directly mount the LED die without the heatsink becoming part of the electrical path.


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## Ray_of_Light (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*

http://www.electrochem.org/meetings/scheduler/abstracts/214/2252.pdf

Anthony


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## McGizmo (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*

Hi guys,
This is probably a stupid question but that has never stopped me before. Is it possible with a lens group to condense the apparent image of the LED die into a smaller image somewhere forward on the Z axis and then treat this convergence point as the source to be collimated? Clearly we can take parallel sunlight and condense it to an intense point with a single lens. 

I guess in other words, is is possible with a lens group to create a smaller apparent image enjoying greater surface brightness than the original LED source?


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## saabluster (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



McGizmo said:


> Hi guys,
> This is probably a stupid question but that has never stopped me before. Is it possible with a lens group to condense the apparent image of the LED die into a smaller image somewhere forward on the Z axis and then treat this convergence point as the source to be collimated? Clearly we can take parallel sunlight and condense it to an intense point with a single lens.
> 
> I guess in other words, is is possible with a lens group to create a smaller apparent image enjoying greater surface brightness than the original LED source?


No it is not possible.


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## Ra (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



saabluster said:


> Another means of measuring surface brightness would be to take images of the LED itself. I did not make this up. I read it somewhere but I don't remember where anymore. I'm sure it would require some specialized equipment though.



Yep, Dr.Jones did that in the first post.. What you need? A camera...


Regards,

Ra.


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## Ra (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Ray_of_Light said:


> http://www.electrochem.org/meetings/scheduler/abstracts/214/2252.pdf
> 
> Anthony



Hi Anthony,

Your very short post is more informative than some much longer posts I've seen lately!! Thanks ! :bow:


Regards,

Ra.


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## Ra (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



saabluster said:


> I thought about doing that myself. I even looked at trying to find a chunk of SiC to use. In the end I don't think it is worth the effort as you can get a heatpipe that would only cost a few dollars and do a far better job at thermal transfer while weighing much less. The only advantage I could find to using diamond was that I could directly mount the LED die without the heatsink becoming part of the electrical path.



Uhhh, SiC ??? :duh2:

SiC has a thermal conductivity of 120 W/mK.. Copper has 401 !

http://www.accuratus.com/silicar.html


Regards,

Ra.


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## saabluster (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Ra said:


> Yep, Dr.Jones did that in the first post.. What you need? A camera...
> 
> 
> Regards,
> ...


No he mentioned using it to measure die size. I am talking about taking images that will tell you the actual brightness by comparing the brighttness of one image to another. I am looking for the article but the first time I found it it was quite buried in the halls of the net.


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## saabluster (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Ra said:


> Uhhh, SiC ??? :duh2:
> 
> SiC has a thermal conductivity of 120 W/mK.. Copper has 401 !
> 
> ...


Sorry I should have been more specific. Moissanite


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## Ra (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



saabluster said:


> Sorry I should have been more specific. Moissanite



Better... But:

Moissanite has a thermal conductivity between 360 and 460 W/mK...
Depending on the cristal-structure.. So practicly the same as copper..

http://en.wikipedia.org/wiki/Silicon_carbide


CVD Diamond has 2000..


Ra.


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## gcbryan (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*

Just curious...so is the primary limitation regarding driving an emitter conducting the heat away or is there something inherent in the die design?

Meaning...I understand when driving within an emitter's spec that conducting heat away is crucial to maintaining that output but when pushing above spec is the main limitation still just conducting heat away or is there an internal limitation to the emitter itself? I assume the answer is yes but I'd appreciate a little clarification.


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## saabluster (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Ra said:


> Uhhh, SiC ??? :duh2:
> 
> SiC has a thermal conductivity of 120 W/mK.. Copper has 401 !
> 
> ...



SiC is an excellent thermal conductor. Heat will flow more readily through SiC than other semiconductor materials. In fact, at room temperature, SiC has a higher thermal conductivity than any metal. This property enables SiC devices to operate at extremely high power levels and still dissipate the large amounts of excess heat generated.


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## Ra (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



saabluster said:


> SiC is an excellent thermal conductor. Heat will flow more readily through SiC than other semiconductor materials. In fact, at room temperature, SiC has a higher thermal conductivity than any metal. This property enables SiC devices to operate at extremely high power levels and still dissipate the large amounts of excess heat generated.



That's obviously a typo !!! At the Cree site, SiC is compared to other semi-conductor materials, not metal.

Their specs:

3.0-3.8 W/cmK @ Room temperature equals 300-380 W/mK So just below copper...

Edit: According to wiki, the highest possible value is for SiC is 460 W/mK, that would indeed be higher than any metal !! Still 1540 W/mK to go to meet CVD diamond...


All the best,

Ra.


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## Ra (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



gcbryan said:


> Just curious...so is the primary limitation regarding driving an emitter conducting the heat away or is there something inherent in the die design?
> 
> Meaning...I understand when driving within an emitter's spec that conducting heat away is crucial to maintaining that output but when pushing above spec is the main limitation still just conducting heat away or is there an internal limitation to the emitter itself? I assume the answer is yes but I'd appreciate a little clarification.



The heat from the die needs to travel through the base of the led before you can take it away with a heatsink. Heat only flows to colder regions, with a heatsink, you create that colder region. The colder that region is, the quicker the heat flows away from the die.
The limits are in the thermal conductivity of the material (s) between the die and the heatsink (because you cannot change them..). But that's not a hard boundary: Better (colder) heatsinks always result in lower temperatures of the die, but at the edge of possibillities, the differences will be small.


Regards,

Ra.


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## Walterk (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*

@Saabluster; I think you found your wonderflonium. From Wiki:
While rare on Earth, silicon carbide is remarkably common in space. It is a common form of stardust found around carbon-rich stars, and examples of this stardust have been found in pristine condition in primitive (unaltered) meteorites. 
 The low thermal expansion coefficient, high hardness, rigidity and thermal conductivity make silicon carbide a desirable mirror material for astronomical telescopes. 
 Moissanite has become popular as a diamond substitute, and may be misidentified as diamond, since its thermal conductivity is much closer to that of diamond than any other diamond substitute.

Back on topic, die surface and brightness: using my left eye, my petzl and caliper;

XRE R2 - 1,85 x 1,85mm ( authentic, bincode will follow)
XRE R2 - 1,8 x 1,8mm ( bincode unknown, from 5$ headlamp advertised as R2)
SST90 - 5,0 x 4,85mm (bin unknown, marked 004022)

The dome of the SST90 made the die look having a belly on the sides.
Counting pixels might be more suitable, but I like caliper better.


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## Mettee (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*

very cool topic and interesting reading, I will try to keep up:thinking:


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## Dr.Jones (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



saabluster said:


> Although you may have inferred it you did not directly state. Are you saying to use a lens to project an image of the die or not?



No (at least no other than the camera/microscope lens for apparent die size measurement). That 'apparent' die size is really just the size of the die as you see it (enlarged) through the dome, and the intensity is bare emitter forward intensity without any additional lenses, just LED and lux-meter.

Consider a bare emitter (no dome, but think of adding a dummy glass pane to get the same losses), and you measure illuminance (lux) in 1m distance (no lens in between) to get it's forward intensity (cd, same as lux in that distance). To get the luminance (surface brightness), you divide the intensity by the die area. That's what we want.

Now you have the dome, which is a small collimator. It creates an enlarged virtual image of the die, which can be seen as a new, 'virtual' light source. It gives more beam intensity (due to the bigger virtual emitter area, or equivalently, because it's a bit collimated), thus the lux-meter will show a higher value. At the same time the viewing angle is reduced, but the luminance (surface brightness) of that virtual light source is the same.
Luminance is the higher intensity divided by the bigger virtual (apparent) die area resulting in the same luminance as above.

Since you usually don't want to shear the dome off and add a loss-equivalent dummy, just use the second method with the dome, yielding the same result.


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## saabluster (Jun 26, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Ra said:


> Edit: According to wiki, the highest possible value is 460 W/mK, that would indeed be higher than any metal !! Still 1540 W/mK to go to meet CVD diamond...


Yes it doesn't match diamond but I was just looking at all the alternatives and trying to find something better than silver. Every little bit helps. The thing is even CVD diamond can't compete with with a cheap heatpipe that you can get off ebay for a couple dollars. Of course it is not as exotic as the diamond and diamond would allow one to directly mount the die without having to have the heatsink be electrically active.

How do you plan to mount the LED to the diamond? Epoxy I assume? What kind? I have a suggestion in that regard.


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## Ra (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*



saabluster said:


> Yes it doesn't match diamond but I was just looking at all the alternatives and trying to find something better than silver. Every little bit helps. The thing is even CVD diamond can't compete with with a cheap heatpipe that you can get off ebay for a couple dollars. Of course it is not as exotic as the diamond and diamond would allow one to directly mount the die without having to have the heatsink be electrically active.
> 
> How do you plan to mount the LED to the diamond? Epoxy I assume? What kind? I have a suggestion in that regard.



Ok, only because this post will still de interesting for the members who want to stay on topic, I'll answer this..( because it will have suggestions for reaching the highest surface brightness )

I got my diamond for free !! So much cheaper than any heatpipe.. You think commercially, you want to sell lights. That makes the use of diamond a no go. I don't think commercially, I just want to create another 'one of a kind' superlight..


Back to topic:

@Dr.Jones: (cc walterk...)

I don't know if you already did the following during die-measurement: You didn't mention it in your first post..

Yesterday, I effectively measured the apparent die-size of a Seoul SSC-P4 led: 1.77 mm2

This is how: Any type of Li-Ion cell with a 10k-Ohm resistor makes it light up faintly, now, with a microscope or eyepiece, you can clearly see, and measure the (apparent) active region of the die. That should be close enough for our needs I think..

BTW: Using a diamond disk, yesterday, I safely pushed the Seoul P4 to 130 [email protected] !

When I do the math whith a 30mm TIR-optic, It would give a mere 49,250 cp !!
With a 75mm TIR optic: 325,000 cp !!!

I have no reason to doubt these numbers: All my former TIR-based ledlights almost exactly behave according to these theoretical calculations..

But there is more: (answering part of Saablusters question)...

I found that indeed it's very important how to mount the led: I nearly blasted a few led's to 'the next world' by not paying (much) attention to this..

Thermal paste has a thermal conductivity of around 8 W/mK.. Quite low for our needs. But this also means that we want an amount, as small as possible between led and heatsink. With the smaller led-footprints of today, this will be hard to do, one little dustpartikle between led and heatsink can (and will!) ruin things.

So it is very understandable that most choose the already star-mounted types: Soldered to the star, proper heatexchange is granted. Solder-tin has a heat conductivity of approx 40 W/mK, way, way better than any paste.

Not all of you know this, but I have direct access to optical multilayer deposition machines (sorry, don't recal the english term for it) So I can provide the diamond, and the led's with a silver layer, that alowes me to solder them together! So that's what I'm going to do... UNLESS>>

I also have the possibillity of polishing things, with extreme accuracy.. Grinding the led's base up to just 0.2mm away from 'disasterpoint', I then can polish the base. And now it comes: Polishing the ceramic of a Cree-led can create the possibillity of 'optical bonding' !!

Now I hear you shout: Optical bonding ?? What the heck is that !!??

Let me tell you:

In optics, when you have two, extremely flat surfaces (or curved, exactly fitting together), then you have the oppertunity of bonding them without the use of any glue, or paste! When the two surface are clean enough, they can come extermely close to eachother, within the region of monecular attraction !! For optics, this is the best glue there is: There is no glue (there is no spoon.. remember?), so no refractive index, no thermal resistance, no aging of the bond ! But very difficult to do.

So my next step: Trying to give a led the super flat surface needed for optical bonding, my diamond disk already has a super flat surface.. Hope it's going to work..

Ill keep you posted on this..


Any questions??

Regards,

Ra.


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## Th232 (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*

One small question. With the optical bonding, what kind of surface roughness do you require? I'm curious because my undergrad thesis involves loose abrasive polishing, reported surface roughness with this particular technique is ~3.25 nm, but that was when polishing silica glass.


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## Ra (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Th232 said:


> One small question. With the optical bonding, what kind of surface roughness do you require? I'm curious because my undergrad thesis involves loose abrasive polishing, reported surface roughness with this particular technique is ~3.25 nm, but that was when polishing silica glass.



Surface roughness approx 2nm, overall surface flattness Lambda/20..

But you don't need to go that far: Whith a roughness of 3.25nm, you can come very close. The beauty of the diamond disc is that it's transparent! Trough the other side, I can see how close I am by looking at the interference pattern. Colors mean distance, but close to optical bonding, the colors dissapear and the pattern goes white. I played with that using two diamond disks: White is good enough for exellent thermal conduction.. I can do this when I can't reach the optical bonding requirements. But then I have to close the side of the led airtight by putting some epoxy to the sides, closing the outer rim. Then it will stay put and cannot come off, because of the vacuum it would create inside.. Ofcource, this is much harder (nearly impossible) to do this on a copper heatsink..


Regards,

Ra.


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## saabluster (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Ra said:


> Ok, only because this post will still de interesting for the members who want to stay on topic, I'll answer this..( because it will have suggestions for reaching the highest surface brightness )
> 
> I got my diamond for free !! So much cheaper than any heatpipe.. You think commercially, you want to sell lights. That makes the use of diamond a no go. I don't think commercially, I just want to create another 'one of a kind' superlight..


No I *don't* think commercially. That's why I don't make money. I like to figure out what the absolute best way to make something is and rarely is that ever something the marketplace could bare. And I do it anyway but don't charge enough.



Ra said:


> When I do the math whith a 30mm TIR-optic, It would give a mere 49,250 cp !!
> With a 75mm TIR optic: 325,000 cp !!!
> 
> I have no reason to doubt these numbers: All my former TIR-based ledlights almost exactly behave according to these theoretical calculations..


:thumbsup: Be very interesting to see how well the end product matches those numbers.



Ra said:


> But there is more: (answering part of Saablusters question)...
> 
> I found that indeed it's very important how to mount the led: I nearly blasted a few led's to 'the next world' by not paying (much) attention to this..
> 
> ...


You are of course referring to the pathetic stuff most people buy. Here is what I buy. It's the one on the very right and at the top.




Ra said:


> Not all of you know this, but I have direct access to optical multilayer deposition machines (sorry, don't recal the english term for it) So I can provide the diamond, and the led's with a silver layer, that alowes me to solder them together! So that's what I'm going to do... UNLESS>>


That is a huge ace up your sleeve. It was the first thought of mine too but I have no access.:mecry: Oh the things I could accomplish with more tools. They need a DIY kit. 



Ra said:


> I also have the possibillity of polishing things, with extreme accuracy.. Grinding the led's base up to just 0.2mm away from 'disasterpoint', I then can polish the base. And now it comes: Polishing the ceramic of a Cree-led can create the possibillity of 'optical bonding' !!
> 
> Now I hear you shout: Optical bonding ?? What the heck is that !!??
> 
> ...



I got to admit that is a new one on me. So are you saying that if you get it just right when you push down it will not come back up? Would it need some glue around the edges to insure it didn't move?


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## Ra (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*



saabluster said:


> I got to admit that is a new one on me. So are you saying that if you get it just right when you push down it will not come back up? Would it need some glue around the edges to insure it didn't move?



Yep... But like all types of glue, optical bonding has it's limits in strength, mostly caused by very small imperfections at the two surfaces, like the surface roughness we mentioned earlier (which is very important for this)
Given that fact, and the fact that the led's are getting smaller and smaller, then yes, it would be wise to apply glue around the edges to fix it in place..

EDIT: @Saabluster... The Diemat link you posted: I never thought that thermal epoxy's could ever go that far !!! You made my day !! Thanks...


Regards,

Ra.


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## HarryN (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*

Hi Ra, just for fun, double check your diamond for conductivity by direction. Usually very high conductivity materials like that have quite large differences in conductivity with the crystal directions.

CVD diamond is pretty amazing stuff. I used to sell equipment that did that in a funny sort of egg shaped plasma cvd machine.

Coming back to the original topic - surface brightness measurements, I was curious how we should approach a package like a Rebel? Some of them have the phos over quite a large area of the dome, not just the die, at least it looks like that.


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## Ra (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*



HarryN said:


> Hi Ra, just for fun, double check your diamond for conductivity by direction. Usually very high conductivity materials like that have quite large differences in conductivity with the crystal directions.
> 
> CVD diamond is pretty amazing stuff. I used to sell equipment that did that in a funny sort of egg shaped plasma cvd machine.
> 
> Coming back to the original topic - surface brightness measurements, I was curious how we should approach a package like a Rebel? Some of them have the phos over quite a large area of the dome, not just the die, at least it looks like that.



I'll see into it.. But playing with them didn't give any hint of directionabillityness..

About the Rebel: I don't have any (yet..) to take measurements from.. However, the pictures on the web always show a very clear Rebel-dome, so I think the method I mentioned in post #24 should work, right?


Regards,

Ra.


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## Dr.Jones (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*

 Awesome!
Can the ceramics be polished that microscopically flat?



> *Ra* wrote:
> Yesterday, I effectively measured the apparent die-size of a Seoul SSC-P4 led: 1.77 mm2
> This is how: Any type of Li-Ion cell with a 10k-Ohm resistor makes it light up faintly, now, with a microscope or eyepiece, you can clearly see, and measure the (apparent) active region of the die. That should be close enough for our needs I think.


Good idea. With the LEDs I measured I didn't need that, but for the SSCs it's the way to go. Did you subtract the contact pads?
Can you provide binning and luminance at various currents, preferably including 350mA, as that is the standard current for the specs? 
And preferably at 25°C, using only short current pulses, similar to what the manufacturers do.


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## Ra (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Dr.Jones said:


> Awesome!
> Can the ceramics be polished that microscopically flat?



Yes.. The aluminium oxide base of the Cree led's has almost the same density as saphire.. Hard to polish, but small surfaces are doable..




Dr.Jones said:


> Good idea. With the LEDs I measured I didn't need that, but for the SSCs it's the way to go. Did you subtract the contact pads?
> Can you provide binning and luminance at various currents, preferably including 350mA, as that is the standard current for the specs?
> And preferably at 25°C, using only short current pulses, similar to what the manufacturers do.



Don't start asking difficult questions now !! I don't have the electrical equipment (yet...) to do this with reliable results.. And it takes time too, I don't have that with all the things I want to test and build.. So for the moment, I concentrate on the things I want to test before I'm going to create the allmighty 'LedBlaster' ....wait for it...
And.... I did an estimate on the contact pads of the SSC...

EDIT: With my new diamond setup, I immidiately noticed that the output from the led's stayes very stable over time: It's one way to determine the temperature increase of the die: Most manufacturers post nice graphs in which you can see the relationship between flux and die-temperature.. When you make a test-setup with a lux meter at fixed distance, you can clearly notice the flux-drop caused by the increase of the die's temperature. Lower flux-drop means higher heatsink efficiency.. (note that you need stable power to led.. no batteries, because increasing internal risistance also causes flux-drop..)



Regards,

Ra.


----------



## Paul Baldwin (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*

Hi,
good thread  I thought I may be able to contribute slightly? http://en.wikipedia.org/wiki/Gauge_block

I used to use these when inspecting cnc work I used to do. Theres a bit of text on that page explaining the phenomena. It is suprising just how well they do stick to each other with no glue involved!

Paul.


----------



## Al Combs (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*



saabluster said:


> You are of course referring to the pathetic stuff most people buy. Here is what I buy. It's the one on the very right and at the top.


So I had to check out a silver epoxy with thermal conductivity better than solder. The data sheet for DM6030Hk states a minimum cure temp of 175°C or 347°F for a dwell time interval of 45 minutes. Remarkable stuff, but is that high a temperature practical for use with LED's? The data sheet for the DM4030LD says it requires baking at 150°C for 30-60 minutes. That's a little better, but it only has 1/4 the thermal conductivity of the DM6030. SSC's pdf on the P4 and P7 both list a max storage temp of 100°C. Perhaps some reflection on the plastic case material they use? The doc file for the Cree XR-E doesn't list a maximum storage temp. Just a temp as it refers to possible damage from soldering caused by moisture absorption from relative humidity.


----------



## Ra (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Al Combs said:


> So I had to check out a silver epoxy with thermal conductivity better than solder. The data sheet for DM6030Hk states a minimum cure temp of 175°C or 347°F for a dwell time interval of 45 minutes. Remarkable stuff, but is that high a temperature practical for use with LED's? The data sheet for the DM4030LD says it requires baking at 150°C for 30-60 minutes. That's a little better, but it only has 1/4 the thermal conductivity of the DM6030. SSC's pdf on the P4 and P7 both list a max storage temp of 100°C. Perhaps some reflection on the plastic case material they use? The doc file for the Cree XR-E doesn't list a maximum storage temp. Just a temp as it refers to possible damage from soldering caused by moisture absorption from relative humidity.



When you read the reflow diagram of the Cree led's, temperatures of 260°C are mentioned, for a short time of cource. But the ramping temp already is 150°C..
I think they will survive a 45 mintute 175°C curing time... They are quite rugged: I got one smoking during testing (bad heatsink contact, or it just likes to smoke..) and it still works fine.. only the dome is a frosted dome now...(XP-G r4) I don't know how this is for the SSC's...


Regards,

Ra.


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## saabluster (Jun 27, 2010)

*Re: Die luminance (surface brightness, important for throw)*



Ra said:


> Grinding the led's base up to just 0.2mm away from 'disasterpoint',


BTW Have you been reading my threads?



Al Combs said:


> So I had to check out a silver epoxy with thermal conductivity better than solder. The data sheet for DM6030Hk states a minimum cure temp of 175°C or 347°F for a dwell time interval of 45 minutes. Remarkable stuff, but is that high a temperature practical for use with LED's? The data sheet for the DM4030LD says it requires baking at 150°C for 30-60 minutes. That's a little better, but it only has 1/4 the thermal conductivity of the DM6030. SSC's pdf on the P4 and P7 both list a max storage temp of 100°C. Perhaps some reflection on the plastic case material they use? The doc file for the Cree XR-E doesn't list a maximum storage temp. Just a temp as it refers to possible damage from soldering caused by moisture absorption from relative humidity.


I have used this with many XR-Es and they can handle the cure schedule needed for the epoxy just fine. As far as SSC's stuff I don't know. I have played with their stuff a bunch but not any "serious" fun as they just can't handle the high current densities like the XR-E can.

Keep in mind the storage temp is not the one you want to be looking at. In the data sheets you will find solder schedules/profile for the LEDs and the maximum allowable temp will be listed. For the XR-E I think it is 260C.


----------



## Ra (Jun 28, 2010)

*Re: Die luminance (surface brightness, important for throw)*



saabluster said:


> BTW Have you been reading my threads?:



No,, But I did just now... I'm doing the same thing with the XP-G R5 right now.. Two are finished.. Still 4 to go..


Regards,

Ra.


----------



## bshanahan14rulz (Jun 28, 2010)

*Re: Die luminance (surface brightness, important for throw)*


Cree uses SiC substrates in xr-e, much like what was described in Anthony's link. 
Also, fans of How It's Made might like this clip, showing how they do binocular lenses. At one point, the head lens grinder shows how he uses optical mounting to secure a prism to be ground. http://science.discovery.com/videos/how-do-they-do-it-binocular-lenses.html
I like seeing the big on-the-edgers exchanging ideas so enthusiastically too. Brain Storms for the win!
So yeah...


----------



## Ra (Jun 29, 2010)

*Re: Die luminance (surface brightness, important for throw)*



bshanahan14rulz said:


> Cree uses SiC substrates in xr-e, much like what was described in Anthony's link.
> Also, fans of How It's Made might like this clip, showing how they do binocular lenses. At one point, the head lens grinder shows how he uses optical mounting to secure a prism to be ground. http://science.discovery.com/videos/how-do-they-do-it-binocular-lenses.html
> I like seeing the big on-the-edgers exchanging ideas so enthusiastically too. Brain Storms for the win!
> So yeah...



SiC is a big advantage.. Do they use the same in the XP-G and XP-E led's ??


Ra.


----------



## Dr.Jones (Jul 5, 2010)

I added some die emittance data to first post.


----------



## Ray_of_Light (Jul 5, 2010)

Take a look at this PPT presentation:

http://www.group4labs.com/ppt/G4L_THREADS-Presentation_v13.ppt

it goes somewhat into detail - with comparisons about SiC vs CVD substrates.

I personally believe that the next generation of power LED will be based the use of InGaN semiconductor on CVD substrates. Technology will bring the costs down, as usual.

Regards

Anthony


----------



## saabluster (Jul 5, 2010)

Dr.Jones said:


>



Nice work. I would say however that I've never seen any evidence that the XP-E has the ez900. As far as I know it is only the XR-E. Also the XP-E comes in R3 as the top bin. 

As to the ez900 vs ez1000 it should be noted that the ez900 die cannot produce the same amount of output at 1A as the ez1000 version even if they are binned the same. This from a Cree internal document. I'm not sure I can post it as it says confidential although I don't see what's so secret about the info contained within. Anyway thought you might like to know.


----------



## Dr.Jones (Jul 5, 2010)

Thanks for that info. I updated the list and added XP-C.
XP-E and XP-C seem to be quite interesting choices...



saabluster said:


> As to the ez900 vs ez1000 it should be noted that the ez900 die cannot produce the same amount of output at 1A as the ez1000 version even if they are binned the same. This from a Cree internal document. I'm not sure I can post it as it says confidential although I don't see what's so secret about the info contained within. Anyway thought you might like to know.


Hm, I see. That means the flux-vs-current graph is inaccurate for EZ900, which sounds plausible. Also thermal sag might be worse. Did they give any estimated values on that?


----------



## saabluster (Jul 5, 2010)

Dr.Jones said:


> Thanks for that info. I updated the list and added XP-C.
> XP-E and XP-C seem to be quite interesting choices...
> 
> 
> Hm, I see. That means the flux-vs-current graph is inaccurate for EZ900, which sounds plausible. Also thermal sag might be worse. Did they give any estimated values on that?


It's not much at 1A. They don't have the data spelled out, just a graph. I'd say the ez900 is down about 6 lumens at 1A to the ez1000. However for people who overdrive it should be noted that that gap gets bigger and bigger as the current rises. Both dies are at the same levels until about 450mA when the ez900 starts to tail off a bit. Again nothing major at normal drive levels but there is a difference.


----------



## Al Combs (Jul 5, 2010)

Dr.Jones said:


>


Thanks for pulling all this data together for us. Could I ask where you got the thermal resistance figures for the SST-50 and the SST-90? The Luminus doc's say the SST-50 has a thermal resistance of 2.45 °C/W and the SST-90 is 0.64 °C/W.


----------



## Walterk (Jul 5, 2010)

I am surprised to find the SST90 this high in the ranking. Nice though!
And it explains the performorance of the FlyDragon.


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## Dr.Jones (Jul 5, 2010)

Al Combs said:


> Thanks for pulling all this data together for us. Could I ask where you got the thermal resistance figures for the SST-50 and the SST-90? The Luminus doc's say the SST-50 has a thermal resistance of 2.45 °C/W and the SST-90 is 0.64 °C/W.


I took the junction-to-heatsink value, page 12. Might not be the best idea, since the values for the CREEs are junction-to-solder-point. I'll change that later.


----------



## Ra (Jul 10, 2010)

So to rebump this thread, I did some testing (and still do..)

As there is much discussion about the best setup for throw (and lumens output), I decided to put some things to the test.
The results are reason to start a new thread (in a few weeks..or months..) about the various collimator setups, and their effect on throw and lumens output (torchlumens).

But the thing I want to share right now: In my quest for bigger glass based TIR optics, I just made a 35mm diameter TIR. Below is the 35mm test setup with a Cree XR-E R2 (EZ1000)








And the next picture immidiately shows why so many people prefer the TIR over the aspheric lens:






Compare that to the spot of the aspheric setup: (note that differences in spot brightness are due to different camera settings!)






Now the purpose of these test setups: The big question that is asked many times: Which is better for throw, aspheric lens or TIR optic ?

I carefully created two very identical setups, one with the 51mm aspherical lens, and one with the 35mm TIR. In each setup, I used the same led, provided exactly the same current, and measured exactly at the same distance, using exactly the same lux meter (as I only have one..)
For correcting the difference in size, I recalculated the data from the asphere to the level of the 35mm TIR, and to be sure, I also used an exact diaphragm on the asphere to bring the effective apperture down to that of the 35mm TIR..

(Please note that the aspheric lens and TIR-optic I used during these tests are both uncoated.)


Here are the results: (3.6 mtr measuring distance, 750mA to led)

51mm Aspheric lens without diaphragm : 4,620 Lux (59,875 [email protected])

35mm TIR optic : 2,020 Lux (26,179 [email protected])

Aspheric lens 35mm diaphragm : 2,182 Lux (28,279 [email protected])


So the aspheric lens wins !!!!???? Not so fast guyzz !! :

My 35mm TIR has a 10.5mm diameter 'refraction chamber' that does not play along until an extra collimation lens is placed, and I've not placed it yet..
So that means the overall effective surface of my 35 mm TIR is not 962 square mm as with the 35mm aspheric setup, but more like 875 square mm !!

This means that when the TIR is finished (with central lens) it will give 2,219 lux.. (28,758 [email protected])

Conclusion: (surface recalculation included)

Aspheric lens 51mm : 29.31 lux/mm2 (@1m)

35mm TIR : 29.91 lux/mm2 (@1m)

35mm asphere (diaphragm) : 29.40 lux/mm2 (@1m)


As these results are only 2% apart, I hope you'll agree that these differences are not big enough to declare a winner! So, aspheric lenses (of decent quallity of cource) give the same throw as high quality TIR optics with the same diameter.

But almost everyone knows that TIR optics give a much nicer beam with more usefull sidespill (more lumens) and no extra colors.

The main reason why so many use aspheric lenses is that they are cheap and commonly aviable, the aviabillity of TIR optics are limited by size and material (30mm tops, acrylic based, damaged easily).
Certainly the glass based TIR optics cannot be found anywhere (correct me if I'm wrong..) I think that right now, I'm the only one that makes them..

I'm working on a 65mm diameter high quatily TIR optic right now. It will be finished next week.. I hope...

Edit: Pushing the limits, with the XR-E R2 at 2amp, I managed to reach 45,000 cp with my 35mm TIR. When recalculating, that would give like 140,000 cp with the 65mm TIR ! (DEFT killer?)

And here is a picture of the illumination of the internal surface of the 35mm TIR optic:








Now some claim that throw with a aspheric lens can be improved by adding a pre-collimator lens close to the led.. This is not true !! In a high quality setup, it only improves the overall lumens output.
When a pre-collimator lens gives better throw with an aspheric lens, the only possible conclusion would be that the aspheric lens has imperfections that are overcome by the pre-collimator lens.

In fact: Compared to a single high quality aspheric lens, a pre-collimator setup has (somewhat) less throw, caused by the reflection and absorbtion losses within the pre-collimator!


Regards,

Ra.


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## Al Combs (Jul 10, 2010)

Wow, a 65 mm TIR.:bow: Would love to hear some details on how you make glass TIR's. If it's not proprietary info of course. I ground and polished a few telescope mirrors years ago. Can't begin to imagine how those techniques would apply to a parabola that steep. Or whatever type of conic section it is.


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## Ra (Jul 10, 2010)

Al Combs said:


> Wow, a 65 mm TIR.:bow: Would love to hear some details on how you make glass TIR's. If it's not proprietary info of course. I ground and polished a few telescope mirrors years ago. Can't begin to imagine how those techniques would apply to a parabola that steep. Or whatever type of conic section it is.



Hi Al,

Especially for you, I made picture of the not yet finished 67 (!) mm TIR optic:
The refraction chamber is the hardest part, but it's finished now (after two day's..)






As you propably can see, alot of glass still needs to be removed! A dutch sculpterer once said: "The shape of the sculpture is already there, I only need to remove the material around it.."

I cannot explain how to make them without making this the longest post ever! Sorry about that.. It mostly is work by hand.


Regards,

Ra.


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## Al Combs (Jul 10, 2010)

Nice. Thanks for the look see. Also I never realized Michelangelo was Dutch.

Hey if you put a CSM-360 in that TIR optic, would there be a donut? Can't wait to see what you do with that.


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## ma_sha1 (Jul 10, 2010)

Woe, 67mm TIR, that's too cool!


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## EasyB (Jul 10, 2010)

I'll chime in with respect to throw and simple lenses. A lens just projects an image of the LED far away. If you want the image to be very far away, you put the LED very close to the focal point of the lens. The size of the image can be calculated from the fact that the image magnification is equal to i/o where i is the image distance and o is the distance from the LED to the lens. So approximately, we see that the size of the image of the LED is i/f times the LED size. So the longer the focal length of your lens, the tighter your beam will be. 

Of course, if you have a long focal length lens your LED is very far from the lens and you are losing a lot of light to the sides. This is why you would want a larger lens and/or possibly a collection lens close to the LED like in my SST-50 spotlight. The effects of the collection lens I must admit I understood better when I was designing my spotlight, but it is a compromise between light collection and enlarging the effective LED size. 

This little thing:
http://www.shermanlab.com/science/physics/optics/ThinLens.php

helped me visualize what's going on better when your LED is within the focal length of the lens, which is the case for the collection lens in my spotlight.


----------



## Ra (Jul 10, 2010)

Al Combs said:


> Nice. Thanks for the look see. Also I never realized Michelangelo was Dutch.
> 
> Hey if you put a CSM-360 in that TIR optic, would there be a donut? Can't wait to see what you do with that.



Maybe Michelangelo knew the dutch sculpturer... 


CSM-360 ? :huh: Never saw that before ! Thanks..

The TIR optic acts like a lens with a very short focal length: Very narrow focus area (compared to size), so with the 36 square millimeter of the 360, I think you indeed need at least a 50mm TIR for the CSM-360 to grab it's full potential.
Fortunately, as you can see in the pictures above, the TIR does not give the annoying die image of the led.. But how it reacts to the CSM-360 setup, I don't know yet.


Do you happen to know where I can get a 360 ? (and are they expensive??)


The 67mm TIR is for my new LedBlaster, with one Cree XR-E R2 pushed to the limits: max 2.3 Amp heatsinked on CVD Diamond ! (CVD Diamond has more than 5 times the heat conductivity of copper)
With the diamond setup, the led runs much cooler than ever possible with a copper heatsink, so there is a gain in efficiency (which already is very poor at those currents)


Regards,

Ra.


----------



## Ra (Jul 10, 2010)

And....

As for advanced heatsinking: Sanding down the base of the Cree led's significantly improves heatsink effectivity! No mater if you use aluminium, copper, silver or CVD diamond for heatsinking, the ceramic base of the Cree has a thermal conductivity of around 30 W/mK.
Aluminium has a thermal conductivity of 250, copper 400, silver 429 and CVD diamond aprox 2000 !
So the closer you can get the die to one of those materials, the better your heatsink will work!

I already sanded down almost all of my led's.. Here's an example of a sanded down XP-G R5: (small led closest to the (BIG!) XR-E)






The remaining ceramic base is so thin that it becomes transparent..



Regards,

Ra.


----------



## Al Combs (Jul 10, 2010)

Ra said:


> The TIR optic acts like a lens with a very short focal length: Very narrow focus area (compared to size), so with the 36 square millimeter of the 360, I think you indeed need at least a 50mm TIR for the CSM-360 to grab it's full potential. Fortunately, as you can see in the pictures above, the TIR does not give the annoying die image of the led..


Do you have a 16 mm refraction chamber hole? That's the size of the CSM-360's dome.



> But how it reacts to the CSM-360 setup, I don't know *yet*.


Does that mean what I think it does?:naughty:



> Do you happen to know where I can get a 360 ? (and are they expensive??)


In the United States I would buy a CSM-360 from Avnet. They have a top Bin GV100 for $157.07. Unfortunately I've seen from several people in Europe they want a $75 shipping fee. That would pretty much make them a last resort for you. Pepko has a thread on a CBM-360 MagLite. He said in post #16 he bought it, "through local (czech) distributor EBV". They are listed as the European dealer at the bottom of the Luminus CSM-360 link as well. The CBM-360 is the one without the lambertian dome and slightly less powerful. The CBM-360 has a top bin WX and a 4,300 to 5,100 lumen output @ 6.3 amps. The CSM-360 has a top bin WV and a 3,600 to 4,300 lumen output @ 3.15 amps. Pixel interpolation from their, "Relative Luminous Flux vs. Forward Current" graph on page 9 of the specs gives a 193.2% boost @ 6.3 amps for a total output of 6,955.2 to 8,307.6 lumens.:devil:


----------



## Walterk (Jul 10, 2010)

Interesting! 
Seems a lot of work, grinding and polishing glass? Is it on a machine like a lathe, the machine doing the work, and you measuring and adjusting?



Ra said:


> The 67mm TIR is for my new LedBlaster, with one Cree XR-E R2 pushed to the limits: max 2.3 Amp heatsinked on CVD Diamond ! (CVD Diamond has more than 5 times the heat conductivity of copper) With the diamond setup, the led runs much cooler than ever possible with a copper heatsink, so there is a gain in efficiency (which already is very poor at those currents)Ra.



@Ra:Out of curiosity; what was the surface brigtness of the die ??

@EasyB: Cant grasp your explanation nor the application. From the following constructions, what line determines the beam/projection?
Is the application valid for aspherics, that are supposed to be focused at infinity? (if I say it correctly)
Focussed, there is only one angle, so thats obvious.
For the two other positions I cant understand what the two angled lines say about the beam...

(out of focus, focussed, over focused )


----------



## Ra (Jul 11, 2010)

Al Combs said:


> Do you have a 16 mm refraction chamber hole? That's the size of the CSM-360's dome.



The refraction chamber hole is 20mm, but as I desingned the 67mm TIR for use with the XR-E, the 360 will be more behind the central hole and some lumens will be lost to the side.
Because of the beam angle from the XR-E (90 degrees), matching TIR optics must have a different shape compared to those used with for example XP-G, or SSC led's. They have a beam angle of close to 170 degrees! (in specsheets, mostly 140-145 degrees is claimed, but if you go wider, you still can grab some precious lumens..)




Al Combs said:


> Does that mean what I think it does?:naughty:



Could be.. but when the 67mm is finished, I'm first going to test how it reacts to two XP-G leds close together.. The chip distance on the 360 is aprox 1.5mm (estimated from drawing), so I can sand down the upper edge of two XP-G's and place them together as close as that..




Al Combs said:


> In the United States I would buy a CSM-360 from Avnet. They have a top Bin GV100 for $157.07. Unfortunately I've seen from several people in Europe they want a $75 shipping fee. That would pretty much make them a last resort for you. Pepko has a thread on a CBM-360 MagLite. He said in post #16 he bought it, "through local (czech) distributor EBV". They are listed as the European dealer at the bottom of the Luminus CSM-360 link as well. The CBM-360 is the one without the lambertian dome and slightly less powerful. The CBM-360 has a top bin WX and a 4,300 to 5,100 lumen output @ 6.3 amps. The CSM-360 has a top bin WV and a 3,600 to 4,300 lumen output @ 3.15 amps. Pixel interpolation from their, "Relative Luminous Flux vs. Forward Current" graph on page 9 of the specs gives a 193.2% boost @ 6.3 amps for a total output of 6,955.2 to 8,307.6 lumens.:devil:



So indeed they are quite expensive... At 6-7 dollars each, I don't mind a XP-G not surviving extensive testing.. But this...


Regards,

Ra.


----------



## EasyB (Jul 11, 2010)

Walterk said:


> @EasyB: Cant grasp your explanation nor the application. From the following constructions, what line determines the beam/projection?
> Is the application valid for aspherics, that are supposed to be focused at infinity? (if I say it correctly)
> Focussed, there is only one angle, so thats obvious.
> For the two other positions I cant understand what the two angled lines say about the beam...



I realize now that this was not the most appropriate thread for my remarks, but my post was in reference to the original post by Dr.Jones that says the lens diameter is the important factor in determining throw, when it is more directly the lens focal length that determines the size of the beam at a given distance. The take home message is that for a single lens and LED system meant to throw a beam far, the beam diameter far away is equal to (diameter of LED)(distance to illuminated object)/(focal length of lens). I'm a physicist so I like to break it down like this.


----------



## Al Combs (Jul 11, 2010)

EasyB said:


> I realize now that this was not the most appropriate thread for my remarks, but my post was in reference to the original post by Dr.Jones that says the lens diameter is the important factor in determining throw, when it is more directly the lens focal length that determines the size of the beam at a given distance. The take home message is that for a single lens and LED system meant to throw a beam far, the beam diameter far away is equal to (diameter of LED)(distance to illuminated object)/(focal length of lens). I'm a physicist so I like to break it down like this.


Ra had a couple of posts in another recent thread about this. Here's his concept post and this one has some actual measurements. Say you have two lenses of the same diameter and one has double the focal length of the other. The one with the longer focal length creates an image in the distance half the size of the other or 1/4 the surface area. But it's also only gathering 1/4 as much light from the LED. The net result is a lux meter put on both these flashlights would read the same. So it is fair to say that a lens' diameter is the only determining factor with regards to throw, all other things being equal. Which makes your SST Spotlight a monster with that Fresnel lens you're using.


----------



## csshih (Jul 11, 2010)

Ra said:


> Do you happen to know where I can get a 360 ? (and are they expensive??)



wow, I am out of my league posting in this thread... 
A CSM-360 will set you back roughly 180 usd.. 


edit: oh wait that information has already been posted....carry on..


----------



## EasyB (Jul 11, 2010)

Al Combs said:


> Ra had a couple of posts in another recent thread about this. Here's his concept post and this one has some actual measurements. Say you have two lenses of the same diameter and one has double the focal length of the other. The one with the longer focal length creates an image in the distance half the size of the other or 1/4 the surface area. But it's also only gathering 1/4 as much light from the LED. The net result is a lux meter put on both these flashlights would read the same. So it is fair to say that a lens' diameter is the only determining factor with regards to throw, all other things being equal. Which makes your SST Spotlight a monster with that Fresnel lens you're using.



Fair enough; that's under the condition that the light output from the LED is omnidirectional. Under a different condition, namely that all the light from the LED is collected and directed towards the lens, it's only the focal length that matters in determining throw. This condition can be approached by using a collector lens, which is half of what makes my spotlight a monster.


----------



## Ra (Jul 12, 2010)

EasyB said:


> Fair enough; that's under the condition that the light output from the LED is omnidirectional. Under a different condition, namely that all the light from the LED is collected and directed towards the lens, it's only the focal length that matters in determining throw. This condition can be approached by using a collector lens, which is half of what makes my spotlight a monster.



Please let's not confuse people... again..

This discussion can be found in many threads, and we all agreed that focal length DOES NOT! affect throw. It only affects the lumens output.
A collimating lens is only used for compensating the lumens loss, caused by the longer focal length of the main (front) lens.
EDIT: To complete this: A collimating lens also can be used to correct abberations in the main (mostly aspherical) lens. The above is theoretical and applies to lenses that are of enough quality to be up for the job..


Regards,

Ra.


----------



## EasyB (Jul 12, 2010)

Ra said:


> Please let's not confuse people... again..
> 
> This discussion can be found in many threads, and we all agreed that focal length DOES NOT! affect throw. It only affects the lumens output.
> A collimating lens is only used for compensating the lumens loss, caused by the longer focal length of the main (front) lens.
> ...



I agree with you now after thinking about it more. The throw increasing effect of the collector lens (more light collected) is canceled by the throw decreasing effect (larger effective LED size).


----------



## Al Combs (Jul 12, 2010)

Well actually the collector lens you used in addition to increasing the amount of light from the LED that hits the Fresnel lens, also increases the size of the LED's virtual image. The net effect of that lens is to throw more lumens downrange, not more lux. Of course if you can convert uncaptured rays of light into a larger hotspot, that can only be a good thing. It just doesn't necessarily give you more throw. The only way to know for sure is to buy a cheap lux meter and try it with and without the smaller lens.

That same thread I linked to the other day had a post on page 4 from Dr. Jones. Actually that whole thread had a lot of interesting things in it. He uses a pre-collimator to collect more light from the LED. The second version of his "super-thrower" has a compound system very similar to yours in concept. Using a pre-collimator he gets a spot twice the size, with only a slight drop in the lux meter reading. But that is kind of the point of that test. He got basically the same lux reading from all three systems.

It does seem counter intuitive but it's the lens system diameter, having nothing to do with focal length, that determines lux output or throw. Dr. Jones had another thread using the same lens he called Needle400. When I first looked at that I thought, how can over 400K lux not be about the focal length? But his lens has a 116 mm diameter. The guys with their 60,000 lux XR-E aspheric MagLites have a bezel ID of 47.5 mm. Which is roughly a 6 fold increase in area. Also I think he was using an ez900 XR-E emitter which is ≈ 0.9 mm wide and he was using a higher current. Anyway his cat food aspheric had an ez900.:laughing:


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## Al Combs (Jul 12, 2010)

Opps, my bad...

I went away and ate lunch while I was typing that thread


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## Ra (Jul 12, 2010)

Hi Guyzz,

My new toy....:








I had to bring it back to 64.7mm diameter... But who cares..

The 64mm TIR optic in action:








It's not finished yet: The inner rim of the reflector side does not play along for throw, so I'll have to refigure the side. But as it is now, it already puts out 95,000 cp (XR-E R2 at 2.0Amp) Recalculated with the part that doesn't play along, it should give 150,000 cp when finished. Impressive, but still no match for my mini-HID ! (250,000cp from 48mm diameter CA)

The only bad thing: On my quest for a glass type very transparent, and with a refractive index on which a single layer AR-coating is more effective, I forgot to look at the dispersion: The projected spot looks fine at the picture, but in real life it is quite a colorfull display! Not as much as a projected spot of an aspherical lens, but clearly noticable. (one of many reasons I don't use aspherical lenses)

Maybe making another one using low dispersion BK7 optical glass is the only option to get rid of most of that..


Regards,

Ra.


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## Al Combs (Jul 12, 2010)

That was fast! This definitely deserves its own thread. I thought it was some type of glass you can cut on a lathe. But if you're thinking of using BK7, it must be something else.

Sorry to hear about your color fringe problem. But since you have to start over with a new chunk of glass anyway, I'll be happy to take it off your hands.


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## Walterk (Jul 12, 2010)

Looks great ! 
How long did it take to machine the glass?
Hope you'll succeed with a BK7-type of TIR. Can imagine there is a lot of trial and error to be done to shape the beam as desired, or is it more like subtle finetuning?


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## saabluster (Jul 13, 2010)

Ra said:


> Now the purpose of these test setups: The big question that is asked many times: Which is better for throw, aspheric lens or TIR optic ?


Since I've never seen a TIR that competes with an aspheric lens I'd have to give it to the lens. If you can prove otherwise I'd love to see it though.





Ra said:


> Edit: Pushing the limits, with the XR-E R2 at 2amp, I managed to reach 45,000 cp with my 35mm TIR. When recalculating, that would give like 140,000 cp with the 65mm TIR ! (DEFT killer?)


Well I wouldn't call that a DEFT killer. You might be able to beat some of the FTP models which ran the LED at 1.4A and averaged 135K but the best of my HO model at 1.7A can hit 200k. And I have test pieces well over that.




Ra said:


> Now some claim that throw with a aspheric lens can be improved by adding a pre-collimator lens close to the led.. This is not true !! In a high quality setup, it only improves the overall lumens output.
> When a pre-collimator lens gives better throw with an aspheric lens, the only possible conclusion would be that the aspheric lens has imperfections that are overcome by the pre-collimator lens.
> 
> In fact: Compared to a single high quality aspheric lens, a pre-collimator setup has (somewhat) less throw, caused by the reflection and absorbtion losses within the pre-collimator!
> ...


I have said that the pre-collimator increases throw and that was because it is the truth. You say so yourself but at the same time make the overriding assertion that it is not true.

You are of course correct that with a high quality lens the pre-c will not increase throw but my experience is that it is extremely difficult to find these lenses. I actually make the lenses that go in the DEFT myself. I only did that because despite searching the world over for quality lenses in the size I needed none were to be found. I am still looking actually. I recently bought a 75mm aspheric condenser lens from Thorlabs with high quality optical glass and the most beautiful AR coat I have ever seen in my life but the beam was horrible. The plastic lenses I make work far better.


I propose a friendly little competition. You seem pretty sure you can make a TIR out-throw an aspheric. I say bring it on. I don't mean you testing your TIR against your own aspheric setup. Let's see who can build the longest throwing LED flashlight. Since you already have your TIR crafted at 64.7mm(beautiful BTW) I will match that diameter. After that we can send them to a third party for testing. You up for the challenge?

BTW I am taking the "stuff" to the post office tomorrow. It is much thicker now than when new but should still work. It should be there by early next week.


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## Th232 (Jul 13, 2010)

Now that's a challenge I'd love to see!

Are we going to have fixed power limits, or will it be whatever the LED can take without frying?


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## Ra (Jul 13, 2010)

Walterk said:


> Looks great !
> How long did it take to machine the glass?
> Hope you'll succeed with a BK7-type of TIR. Can imagine there is a lot of trial and error to be done to shape the beam as desired, or is it more like subtle finetuning?



Hi Walter,

Short cource TIR manufacturing:

It all starts on the drawing board: Carefully drawing the internal refraction champer (scale 2:1 or bigger..) Then I do some raytracing by hand, drawing a few different ray-angles from the middle of the die, and draw the exact angle when they enter the glass.
That gives a pretty acurate outline of the side of the TIR.

Then, with diamond tools, I remove the glass around it. Checking the shape by holding it in front of the drawing.

And then I polish the sides a bit (with the central chamber already finished.) so I can just see if the angle is right. But it indeed is mostly trail and error: When I must go back to grinding the side, I must do the entire side, not only the part that does not play along..

With the smaller TIR's (like the 35mm..) I didn't need to rework them, but the 65mm TIR is more dificult as the overall shape must be more accurate. The more distance the die has to the reflecting surface, the more exact the angle must be.


Today, I already started making a 67mm BK-7 TIR, not sure when it will be finished because of other work to do..




@ Saabluster:

I never contradicted myself on the subject pre-collimator and throw! If you read carefully, you'll notice that I already said the same you did: If the use of a pre-collimator gives better throw, then the aspherical lens has not enough quality to be used on it's own.

I also never said that a high quality TIR will outthrow an aspherical lens setup! I said it will be it's equal.


All I was saying was based on theoretics, I know that in real life things sometimes cannot be expected that perfect, certainly when you depend on supplier's if you cannot make things yourself.

Glass based TIR's are a lot of work, and I propably will not make more than a few bigger ones.. So I don't think I'll take the risk to send them over the world for a simple competition.. Sorry.


I absolutely don't mean to be harsh on you, and I very much appriciate your help on certain things. I just don't like when people say I made certain statements when I didn't


With my projects of the past, I think I'm alowed to be very confident about the lights I create, and their performance. :drunk:



Regards,

Ra.


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## ma_sha1 (Jul 13, 2010)

At optimal focus, TIR could throw as far as Aspheric make sense to me.

I have seen some TIRs when it's perfectly focused, it actually show Square die image. (I even have a SST-90 show square die image when perfectly focused via Mag Rebel Deep SMO reflector, I had to de-focus a bit to get the nice round spot). 

I'd imagine that a TIR with a nice round spot may be an indication that the led die is not perfectly focused, thus one would not expect max throw being achieved at this point. Although, the TIR beam is much more useful. 

My guess is that to meet Aspheric in throw, one really need to fine tune the TIR until a square spot appears. 

However, the questions is: Is it worth the extra throw to sacrifice the beauty of the beam? Lets say, at 90% of Aspheric throw with a beautiful round spot to boot, it'll be a more useful & desirable flashlight. 

The beautiful beam of E2DL is worth more than an Aspheric swap, something that could perhaps throw 10% more.
.
.


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## Ra (Jul 13, 2010)

ma_sha1 said:


> At optimal focus, TIR could throw as far as Aspheric make sense to me.
> 
> I have seen some TIRs when it's perfectly focused, it actually show Square die image. (I even have a SST-90 show square die image when perfectly focused via Mag Rebel Deep SMO reflector, I had to de-focus a bit to get the nice round spot).
> 
> ...



My thoughts exactly !!

But there is one thing: Perfect TIR optics do never project a square spot ! Due to the optical internal reflections the projected spot becomes octagonal, and that's not far from round. I've never seen a square spot comming out of my TIR-optic's..

There is however one possibillity: Some smaller production TIR's have an additional lens at the center, to boost the efficiency.. If that lens has a significant surface compared to the TIR-section, the square shaped spot, projected over the TIR-spot, can result in a more or less overall square. Mostly smaller TIR's (less than 17mm diameter) have that effect, but never as 'badly' as aspheric lenses do.

When the surface of the TIR section is much, much bigger than the surface of the central lens, you will have a nice round spot because the square from the central lens is overpowered by the spot of the TIR-section..

However..

The deep SMO reflector is another story, that one does not project octagonal, so if it has a nice parabolic form, it will project a quare shaped spot



When of high quality, TIR optics behave like one lens element. When fully coated, efficiency can reach 95%! (that's for both throw and lumens output). Theoretically, a high quality, fully coated aspheric lens can reach an efficiency of 98% (only on throw !!) That means that the aspheric lens will win on throw.. (not on lumens..) 

So when an aspherical setup throws 300meter, replacing the lens by a high quality TIR of the same diameter will make it throw 295.5 meter !! (note that this is theoretical..)

Adding a pre collimator to the aspherical setup to increase the lumens efficiency will (again theoretically) decrease the candlepower output by at least another 2 % due to the losses of an extra optical 
element..


No before anyone bigins to write "theoretical is one thing, real life is another", I can tell you that all the things I've tested lately, still follow those theoretics !


Regards,

Ra.


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## saabluster (Jul 13, 2010)

Ra said:


> @ Saabluster:
> 
> I never contradicted myself on the subject pre-collimator and throw! If you read carefully, you'll notice that I already said the same you did: If the use of a pre-collimator gives better throw, then the aspherical lens has not enough quality to be used on it's own.


I read your post just fine and know *we* are on the same page. But...



Ra said:


> Please let's not confuse people... again..




Now here is where I think you run the risk of going against your previously mentioned desire to not confuse. 



Ra said:


> Now some claim that throw with a aspheric lens can be improved by adding a pre-collimator lens close to the led.. This is not true !!



You do of course add a footnote of sorts directly after this but the voracity with which you make the first assertion seems to override the second exclusion. To say with such certainty that "This is not true !!" makes it sound like the idea of a pre-collimator is a lie. We are both on the same page here as far as understanding what's involved but I think many people will be confused by statements like this and only grab hold of the "not true" part and move on. Want proof? From the thread "Formula for calculating throw using aspheric lens".



ma_sha1 said:


> This is a myth buster on pre-collimation will increase throw, nice job!
> .



Just the same as one could not make an overriding assertion that a pre-collimator= more throw they could also not make the assertion that a pre-collimator does not increase throw as it just depends on the setup. Therefore an attempt to call me out on the whole pre-collimator issue is disingenuous at best. 



Ra said:


> So, aspheric lenses (of decent quallity of cource) give the same throw as high quality TIR optics with the same diameter.


Here is where I will contend your statement. There is no way in this world you can make the best TIR setup beat the best aspheric setup. Not even close actually. 



Ra said:


> But almost everyone knows that TIR optics give a much nicer beam with more usefull sidespill (more lumens) and no extra colors.



I will also contend this. A lens setup gives you far more ways to manipulate the beam. The TIR is more of a one-trick-pony. The spill, especially in a dedicated throw light, can be a hinderance to long range visibility and can cause unwanted dazzling in many situations. 
The beam from an aspheric can be broadened and shaped in many ways within one optical package. I won't say that any lens setup will beat a TIR for throughput but on all other accounts the lens is superior in its potential for beam quality and throw. 








Ra said:


> I also never said that a high quality TIR will outthrow an aspherical lens setup! I said it will be it's equal.


Sorry if I took what you said a bit too far. I thought for sure I'd had seen somewhere where you had said in theory a TIR should beat an aspheric for throw. I also saw you post your calculations showing the TIR you made should beat an aspheric although you clearly did say right after that that neither could be declared a victor. 

Despite that though I can see no way whatsoever that a TIR could keep up with the aspheric. I say this because of technology that has recently surfaced from Wavien. You will find a little bit of my feedback on it there.






Ra said:


> Glass based TIR's are a lot of work, and I propably will not make more than a few bigger ones.. So I don't think I'll take the risk to send them over the world for a simple competition.. Sorry.
> 
> With my projects of the past, I think I'm alowed to be very confident about the lights I create, and their performance. :drunk:



Well it's certainly your call. While I, and I think I can safely say everyone else, are thoroughly impressed with your accomplishments in the HID world do you seriously think those accomplishments give you a free pass here? Maybe I misunderstood the point of this new light of yours. I thought it was supposed to be the LED equivalent of the maxablaster. If so the standout point of that light was its throw. If you think you can do what you did on the maxablaster(beating the snot out of everyone else) I have a little something to say about that. I say there is no way in the world you will even be anywhere close to my best as long as you continue down the TIR route. 




Ra said:


> I absolutely don't mean to be harsh on you, and I very much appriciate your help on certain things. I just don't like when people say I made certain statements when I didn't
> 
> Regards,
> 
> Ra.


I haven't taken anything you have said to be too harsh and I hope you feel the same for what I have written. I have been blunt in parts but I hope it did not offend. BTW the package is in the mail.


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## Walterk (Jul 13, 2010)

Sidenote: When you want to compare a design concept, make sure the variable parameters are the same as far as possible. For example same diameter, same Led, same powersource. It is not about comparing one flashlight against an other as that is another challenge .


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## Ra (Jul 14, 2010)

saabluster said:


> Despite that though I can see no way whatsoever that a TIR could keep up with the aspheric. I say this because of technology that has recently surfaced from Wavien. You will find a little bit of my feedback on it there.



Now that's a very neat solution! I'm going to make myself a few collars !! Thanks for mentioning this..




saabluster said:


> I haven't taken anything you have said to be too harsh and I hope you feel the same for what I have written. I have been blunt in parts but I hope it did not offend. BTW the package is in the mail.



No offence taken.. And thanks for sending the pakkage. Please send a PM with the total costs, then I can send Mr (or Mrs, or Miss?) PayPal...


Regards,

Ra.


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## Ra (Jul 23, 2010)

I did some advanced heatsinking today:

One of my collegues created a fairly compact heatsink (following my design) for the LedBlaster project: I've done some testing with a XR-E R2 at 2,0 Amp:
The fluxdrop as a result of the die heating up is not more than 1.4 % !

At an ambient temperature of 21.4 degrees Centigrade, the heatsink temperature stabilizes at 32.4 degrees (measured at 1mm from the led's base..)

I'll post pictures in three weeks after more extensive testing (during my vacation)


Regards,

Ra.


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## Walterk (Jul 24, 2010)

Talking about more or less advanced heatsinking; 
What would be appropriate (and easy ) ways to put a sink to the test?

For example I've got this:






I put power in, and don't want the Led to get to hot.

Thinking of putting a solderingtool to the center of the core, and feel next to it the temperature of the aluminium. When its to hot to the skin temperature would be above 50 degrees.

What is suitable to measure the temperature locally?
The modern distant/infrared household ear-thermometers? 

How to put in heat within the Led-surface area?
A Led that might be sacrificed?
A solder-tip with a pool of soldering lead?

Edit: Ok, I did the solder test. After 20minutes resting a 25Watt soldertip to it, it was hot on all sides.
Actually I was very pleased, as all the fins, even the long ones with less contact, were heated evenly.
The core was not to hot to touch, but definately to hot to use pressure for longer then 10 seconds. 
The front and the back side where different, but to my gues not more then 10 degrees.
BTW The dimensions are 90diax30mm depth, and choose it for the good fanless operation due to the open structure. 
I have the 75mm depth version on its way to me.

But I agree, it gives an idea, but is no test for using a 30Watt Led. Sometime later maybe.

Edit:I've read a Bridgelux datasheet, and my eye catched the rule of thumb mentioning 10 square inch surface area for each Watt to dissapate.

I have calculated the surface.
The 90dia x 30mm (3.5 x 1.18inch) - 93.600mm2 or 145 sq inch, say 14.5 Watt
The 90dia x 75mm (3.5 x 2.9inch) - 272.700mm2 or 423 sq inch, say 42 Watt.(But due to depth probably less efficient.)


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## Ra (Jul 24, 2010)

Walterk said:


> Talking about more or less advanced heatsinking;
> What would be appropriate (and easy ) ways to put a sink to the test?
> 
> For example I've got this:
> ...



Whow, where did you get that heatsink? I want one too !! What is the diameter of that beauty?

It's not easy to measure the heatsink temperature. I use the wire like, very small thermocouple (?) Which has very low mass. With tape and an insulating pad, I force the thermo tip against the heatsink (close to the led..)

Infrared will not work because of the reflectance of the aluminium: You will measure temperatures way under actual (measurements of 20-40 degrees C below the real temperature are common)

Another way to tell if the die is overheating is a setup with a lux meter: When after startup the lux is dropping by the second, you definitely have a problem, and soon after, your led will be toast!
In specsheets you can find the graphs of flux related to die temperature. With most led's, the flux goes down 20-30% towards max die temperature (mostly 150 deg C.)
As this graph mostly is a strait line, you can easily recalculate the die temperature by looking at the actual fluxdrop of the led at your testbench.


Regards,

Ra.


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## MikeAusC (Jul 24, 2010)

For more accurate temperature measurement near the emitter, you could buy a thermometer with a small remote probe, drill a hole near the center of the heatsink and install the probe using heatsink compound.

For a load to simulate an LED you could buy a high-current MOSFET and install it in place of the LED. Connect the Source to battery +ve and Drain to battery negative. Get a potentiometer of around 10kohm and connect the centre to the Gate. Connect the Anticlockwise side to -ve and clockwise side to +ve.

As you turn the Potentiometer the current drawn from the battery will increase - I assume you have a meter to monitor current - it will vary with temperature for this basic setup.


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## Ra (Jul 25, 2010)

saabluster said:


> Here is where I will contend your statement. There is no way in this world you can make the best TIR setup beat the best aspheric setup. Not even close actually.
> 
> I say there is no way in the world you will even be anywhere close to my best as long as you continue down the TIR route.



I needed some time to give you an answer to that one...

Well, here is the proof that I'm right, and you're wrrr.. wrrr... also right (in a sence..)!

You've propably never seen a glass based TIR, well there is your answer.. I did a simple test:






It's all about transparency.. The test is simple: put a plaine evenly lit surface under the optic. The optic shows the surface brightness of that surface. Every bit of decreased surface brightness within the optic is caused by internal losses.

You can clearly see that the glass based TIR at the left side of the pic is much more transparent than the acrylic one at the right, especially the TIR section.. That immidiately affects throw (and throughput..) in a positive way. Glass based TIR's are just as transparent as single lenses.

The part where you're right is that you propably compared a glass based aspheric lens with an acrylic TIR.. Then indeed you can expect a difference in throw..

You made the remark that my past achevements in the short arc world do not give me a free pass here.. Well, maybe not, but I can test led's as well as you or anyone else can.
And as an optical specialist, I do have something to say here, after all, making high performance light's is at least 85% optics, no matter if they are led, or incan, or short arc based..



BTW: I received your pakkage, stuff looks great. Thanks. I will start testing during or after my vacation..



Regards,

Ra.


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## Ra (Jul 25, 2010)

Ahh, what the .... Cant wait three weeks..


OK, here are a few pics of my new heatsink..














The flash froze the fanblades, which definitely were turning..

IMHO, it's the best way to effectively cool a led: Taking the heat away from right under it's feet (or foot..). Copper pinn's inside create the high efficiency.
The fan is a 5Volt, 40mm diameter, extremely silent one with a 6-7 cubic meter per hour air dissplacement. (@ 3.8 volts)

Like I said earlier: According to the measured fluxprop, I have reason to beleve that the die temperature of a XR-E R2 a @ 2.0 Amp stayes well below 40 deg Centigrade at 23 C ambient..

Not a very water risistant solution, but I'm working on that.. 

It's a small step closer to the completion of the LedBlaster. SST-50 or SST-90.. I do not know yet, but testing will tell..


Regards,

Ra.


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## MikeAusC (Jul 25, 2010)

Interesting that you use a fan - I think many people underestimate how effective a fan can be for cooling, considering how efficient modern brushless-fan motors are.

Their power consumption is trivial compared with a high-pwered LED.

My gut-feel tells me that fins would be better than pins, by weight or by volume, considering you need a large surface area to transfer heat to air.


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## Ra (Jul 25, 2010)

MikeAusC said:


> Interesting that you use a fan - I think many people underestimate how effective a fan can be for cooling, considering how efficient modern brushless-fan motors are.
> 
> Their power consumption is trivial compared with a high-pwered LED.
> 
> My gut-feel tells me that fins would be better than pins, by weight or by volume, considering you need a large surface area to transfer heat to air.




Your gut-feel is correct, but this was much easier to do, and still very effective.

And.. It pays off: there is a significant gain in flux caused by the lower die temp!
That more than compensates for the slightly higher current draw of the total setup!


Regards,

Ra.


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## saabluster (Jul 26, 2010)

Ra said:


> I needed some time to give you an answer to that one...
> 
> Well, here is the proof that I'm right, and you're wrrr.. wrrr... also right (in a sence..)!
> 
> ...


Well the lack of any available glass TIRs aside my statement is based on the fact that the wavien collar allows you to do something that I do not think can be applied in the same manner or to the same effect as can be done with a lens. Glass or not has nothing to do with it. With the collar you can have a plastic lens that will beat even the best glass TIR. 




Ra said:


> You made the remark that my past achevements in the short arc world do not give me a free pass here.. Well, maybe not, but I can test led's as well as you or anyone else can.
> And as an optical specialist, I do have something to say here, after all, making high performance light's is at least 85% optics, no matter if they are led, or incan, or short arc based..



I don't doubt your ability to test LEDs one bit. I also don't doubt your ability to make beautiful and effective optics. I do however doubt you, or anyone else for that matter, can make an LED flashlight of a given diameter throw farther than one built by me. But who knows If anyone has a chance it is you so that's why I put up the challenge. I need the motivation to better materialize some of my own ideas anyway. 





Ra said:


> BTW: I received your pakkage, stuff looks great. Thanks. I will start testing during or after my vacation..
> 
> 
> 
> ...


Can't wait to hear what you think. I find it does a good job adhering with the ceramic base of the Crees. I had less than stellar results with the metal base of the MC-Es. It may have been a CTE mismatch or even the way the underside of the MC-E is not flat that was causing the problems. Either way it should not be a problem with the ones you are working with.


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## Dr.Jones (Jul 26, 2010)

saabluster said:


> Well the lack of any available glass TIRs aside my statement is based on the fact that the wavien collar allows you to do something that I do not think can be applied in the same manner or to the same effect as can be done with a lens. Glass or not has nothing to do with it. With the collar you can have a plastic lens that will beat even the best glass TIR.



Hm... The wavien collar reflects the light emitted to the sides and reflects it back to the die to increase it's surface brightness. With a reflector design, you want those side rays, but you can perhaps waive the light emitted to the front, if you don't need spill anyway. You could put a reflecting cap on the top of the dome, reflecting the center rays back to the die to increase the die luminance, while the side rays hit the main reflector. Maybe I should patent this... :thinking:


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## MikeAusC (Jul 26, 2010)

I've just bought a 2.5-degree reflector from Cutter to see how good a small optic can create a narrow beam. It has a small fresnel lens infront of the LED so that the light which misses the reflector still gets focussed onto a distant target.

I'll post some photos when I get it mounted on an XR-E.


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## saabluster (Jul 26, 2010)

Dr.Jones said:


> Hm... The wavien collar reflects the light emitted to the sides and reflects it back to the die to increase it's surface brightness. With a reflector design, you want those side rays, but you can perhaps waive the light emitted to the front, if you don't need spill anyway. You could put a reflecting cap on the top of the dome, reflecting the center rays back to the die to increase the die luminance, while the side rays hit the main reflector. Maybe I should patent this... :thinking:


Sorry but I got you beat on that one. Although it can be made to work with a reflector I do not think it will be as effective at increasing throw as with the lens


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## Dr.Jones (Jul 26, 2010)

saabluster said:


> Sorry but I got you beat on that one.


Damn... 



> Although it can be made to work with a reflector I do not think it will be as effective at increasing throw as with the lens



You're right. 
A typical die emits about 25% of it's flux into the 60°-cone (30° half width) around the optical axis. So the collar, assuming a 60°-aperture, back-reflects 75% of the total flux to the die to increase th surface brightness... (not accounting for the losses).
The other way around, only 25% would be back-reflected.


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## Al Combs (Jul 26, 2010)

Dr.Jones said:


> Hm... The wavien collar reflects the light emitted to the sides and reflects it back to the die to increase it's surface brightness. With a reflector design, you want those side rays, but you can perhaps waive the light emitted to the front, if you don't need spill anyway. You could put a reflecting cap on the top of the dome, reflecting the center rays back to the die to increase the die luminance, while the side rays hit the main reflector. Maybe I should patent this... :thinking:


How about if instead of a reflector, you aluminized a dot right on the Lambertian dome? Or wouldn't an aluminized donut be the equivalent of a Wavien collar? I wonder if an assembled LED could go into the vacuum chamber? The LED might either be damaged or some of the materials an LED is made from might cause an outgassing problem that would hinder coating. Sounds like an experiment for Ra (post #28).:naughty:

If the LED manufacturers ever become convinced of the benefits, they could manufacture special purpose LED's with amplifying central spots or peripheral collars. The bare glass hemisphere could easily be aluminized before assembly.


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## saabluster (Jul 26, 2010)

Al Combs said:


> How about if instead of a reflector, you aluminized a dot right on the Lambertian dome? Or wouldn't an aluminized donut be the equivalent of a Wavien collar? I wonder if an assembled LED could go into the vacuum chamber? The LED might either be damaged or some of the materials an LED is made from might cause an outgassing problem that would hinder coating. Sounds like an experiment for Ra (post #28).:naughty:
> 
> If the LED manufacturers ever become convinced of the benefits, they could manufacture special purpose LED's with amplifying central spots or peripheral collars. The bare glass hemisphere could easily be aluminized before assembly.


I have actually already looked into this. The LEDs do fine in vacuum. There is of course silvering that does not require a vacuum to apply. The problem is that you really need the reflective surfaces to be farther away from the die to be effective. Too close and you can't capture as much as you can from farther while not blocking some of the die surface to the reflector. Then there is the issue with the XR-E for instance where the die is not at the focal point if the dome was turned into a reflector. 

It really does need to be farther out. I would love to see an LED with a very large dome and designed with the silvering in mind but this will never happen.


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## Al Combs (Jul 26, 2010)

Parallax would definitely be more noticeable closer to the LED. But that doesn't mean there wouldn't be an improvement. Not optimal doesn't mean not effective. Have you actually aluminized an LED to test the effects? There are several examples of Osram and Luminus LED's that are the same except for the presence of the dome. The domed versions has as much as 50% higher lumen output. Perhaps the need for a different phosphor to maintain the color temperature plays a role. But I think it's mostly just the 4% reflection from the dome that does it. Even an out of focus XR-E dome makes a difference in its absence. How much more effective would a boost to the 91% of aluminum vs 4% for bare glass be? Even if it's over a much smaller area than the entire dome. In the case of a reflector collar for an aspheric, it's light that's not being used anyway.

I was thinking an easy way to tell would be if one of the guys with a lux meter wrapped a strip of aluminum foil around the base of an SST-50, SST-90 or a P7. And then did a before and after test. I'm sure aluminum foil doesn't reflect anywhere near 91%. But enough to give a good indication. A hole punch of aluminum foil might be the right size for a central spot to be used with a reflector. The surface tension of a small drop of water or some other non-volatile liquid might be enough to hold it in place for a simple test. Since a central spot would block the best part of the beam, the lumen output in an integrating sphere probably wouldn't increase. But a lux meter reading of the spot just might. I'm guessing the strip collar you would use with an aspheric would be the more effective of the two. I don't personally own either type of meter. But perhaps for someone who does...


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## saabluster (Jul 26, 2010)

Al Combs said:


> Parallax would definitely be more noticeable closer to the LED. But that doesn't mean there wouldn't be an improvement. Not optimal doesn't mean not effective.


Parallax has nothing to do with our problems here. On the XR-E for instance the surfaces on the side just don't reflect towards the die. You could of course design it with the built in collar in mind and that should work fine. The SST might work OK. 

The other problem with doing it on the top so that it works for a reflector is that creating a reflector that close to the die means that in order for the silvered part to not block even part of the die from the reflector it would have to be so small as to not even matter if it was even possible at all(would depend on the reflector). In that arrangement you most certainly would have to have it farther away but then you are limited in how large you can make it without cutting into the exiting ray path of the base of the reflector. 



Al Combs said:


> Have you actually aluminized an LED to test the effects? There are several examples of Osram and Luminus LED's that are the same except for the presence of the dome. The domed versions has as much as 50% higher lumen output.


Not as yet. I've just researched silvering agents and done some calculating to see if it was worth the effort. The XR-E will not benefit from this technique but the SST-90 may. I also have not seen anything approaching a 50% loss from removing a dome. Ever.



Al Combs said:


> Perhaps the need for a different phosphor to maintain the color temperature plays a role.


They do not change the phosphor based on whether it is domed or not. 



Al Combs said:


> But I think it's mostly just the 4% reflection from the dome that does it. Even an out of focus XR-E dome makes a difference in its absence. How much more effective would a boost to the 91% of aluminum vs 4% for bare glass be? Even if it's over a much smaller area than the entire dome. In the case of a reflector collar for an aspheric, it's light that's not being used anyway.


You are really getting off track here. The loss in lumens from removing the dome is due to an increase in internal reflection.




Al Combs said:


> I was thinking an easy way to tell would be if one of the guys with a lux meter wrapped a strip of aluminum foil around the base of an SST-50, SST-90 or a P7. And then did a before and after test. I'm sure aluminum foil doesn't reflect anywhere near 91%. But enough to give a good indication. A hole punch of aluminum foil might be the right size for a central spot to be used with a reflector. The surface tension of a small drop of water or some other non-volatile liquid might be enough to hold it in place for a simple test. Since a central spot would block the best part of the beam, the lumen output in an integrating sphere probably wouldn't increase. But a lux meter reading of the spot just might. I'm guessing the strip collar you would use with an aspheric would be the more effective of the two. I don't personally own either type of meter. But perhaps for someone who does...


You might possibly see some increase with an experiment like this but I wouldn't expect it to be much at all.


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## Al Combs (Jul 26, 2010)

Respectfully disagree with everything you just said.


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## saabluster (Jul 26, 2010)

Al Combs said:


> Respectfully disagree with everything you just said.


:thinking: OK...Care to enlighten everyone?


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## Al Combs (Jul 26, 2010)

saabluster said:


> Parallax has nothing to do with our problems here.
> 
> The other problem with doing it on the top so that it works for a reflector is that creating a reflector that close to the die means that in order for the silvered part to not block even part of the die from the reflector it would have to be so small as to not even matter if it was even possible at all(would depend on the reflector).


What you describe as "other problem" is a fair description of parallax.



> I also have not seen anything approaching a 50% loss from removing a dome. Ever.


Well technically a 50% increase was what I said. That's the equivalent of a 33% loss. Osram lists in their pdf doc's the Ostar LE W E3B with the silicon dome as having an optical efficiency of 50 lm/W at 350 mA vs the Ostar LE W E3A that has an optical efficiency of 36 lm/W at 350 mA. That's an efficiency increase of *39%* by adding the dome.

The top bin (WX) of the Luminus CBM-360 is 4,300 to 5,100 lumens @ 6.3 amps. The CBM-360 is output binned at full power. The CSM-360 WV bin is rated at 3,600 4,300 lumens @ 3.15 amps. On page 9 of the CSM-360 specs is a graph called, "Relative Luminous Flux vs. Forward Current". From that I extrapolated by pixel couting a 193.6% increase from 3.15 to 6.3 amps or 6,969.6 to 8324.8 lumens. That's an increase of *62%* on the low side of the range vs *63%* on the high side. The CBT-90 is binned at 9.0 amps and shows a ratio increase of 1.34 at 13.5 amps. The top (WR) bin is 1,750 to 2,100 lumens for an adjusted 13.5 amp output of 2,345 to 2,814 lumens. The CST-90 has the same top bin as the SST-90, namely the WN that is 1,000 to 1,200 lumens but at 3.15 amps. It's 13.5 amp multiplier is 340.8% for a total output of 3,408 to 4089.6 lumens. That's an output increase of *45%*.



> They do not change the phosphor based on whether it is domed or not.


Here is a picture you posted of an SST with and without the Wavien reflector. You commented on the "warming of the color". I think it's a reasonable inference that if a secondary fluorescence from the royal blue peak causes a color shift to the warm, the only way two LED's, both with and without a dome, could have the same color is by using a different phosphor. That's just an educated guess on my part. If you have inside information from the LED manufacturers that allows you to say that's not so, I'd love to hear it.



> You are really getting off track here. The loss in lumens from removing the dome is due to an increase in internal reflection.


I don't think it's off track at all. Newbie correctly pointed out the test would have been more accurate if a single XR-E had its dome removed. But jtr1962's test results indicate a 30% increase in output for the normal XR-E over the XR-E with no dome. If you say that's nothing but internal reflection. I both disagree and ask that you explain that statement. Is it based on something other than your best guess? The CSM-360 being 60% brighter than the CBM-360 has to be due to something other than internal reflections. 



> You might possibly see some increase with an experiment like this but I wouldn't expect it to be much at all.


And that is just your guess. Which as I said I respectfully disagree with. For the sake of people who read these posts and just assume an unchallenged rebuttal is an admission of error.

Finally I have some personal experience of my own. In a failed experiment on two DSVNI P7's I bought from PhotonFanatic, removing the dome on one made it's output much dimmer than its twin(?) brother. The hotspot was much smaller but overall output when the reflector housing was removed from the MagLites I had them in, removed that advantage. It was both much dimmer and of a different color than its twin, after the removal of the dome.


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## saabluster (Jul 28, 2010)

Al Combs said:


> What you describe as "other problem" is a fair description of parallax.


Maybe you are not following my line of reasoning well enough. It would be best if I made a drawing i suppose but I can see no application of parallax in this situation. 



Al Combs said:


> Well technically a 50% increase was what I said. That's the equivalent of a 33% loss. Osram lists in their pdf doc's the Ostar LE W E3B with the silicon dome as having an optical efficiency of 50 lm/W at 350 mA vs the Ostar LE W E3A that has an optical efficiency of 36 lm/W at 350 mA. That's an efficiency increase of *39%* by adding the dome.


Obviously by my response I assumed you were speaking of the lumen penalty in removing the dome not the benefit in adding a dome. Going in the other direction certainly helps your case but even then 39% is not 50%.



Al Combs said:


> The top bin (WX) of the Luminus CBM-360 is 4,300 to 5,100 lumens @ 6.3 amps. The CBM-360 is output binned at full power. The CSM-360 WV bin is rated at 3,600 4,300 lumens @ 3.15 amps. On page 9 of the CSM-360 specs is a graph called, "Relative Luminous Flux vs. Forward Current". From that I extrapolated by pixel couting a 193.6% increase from 3.15 to 6.3 amps or 6,969.6 to 8324.8 lumens. That's an increase of *62%* on the low side of the range vs *63%* on the high side. The CBT-90 is binned at 9.0 amps and shows a ratio increase of 1.34 at 13.5 amps. The top (WR) bin is 1,750 to 2,100 lumens for an adjusted 13.5 amp output of 2,345 to 2,814 lumens. The CST-90 has the same top bin as the SST-90, namely the WN that is 1,000 to 1,200 lumens but at 3.15 amps. It's 13.5 amp multiplier is 340.8% for a total output of 3,408 to 4089.6 lumens. That's an output increase of *45%*.


You can just throw all your figuring out the window on this one. First off you used two different LEDs with datasheets from different dates. The thermal resistance does not match between the two.
Second I am calculating roughly a 20-29% increase in adding the dome.

There is also one other thing you may be missing. The difference is not as great at low power densities but as power rises and the package is stressed to the limits the extra amount of light lost in the domeless package dies as heat and that *heat* will make the spread between the domed and domeless larger not the optical losses or gains in and of themselves. 



Al Combs said:


> Here is a picture you posted of an SST with and without the Wavien reflector. You commented on the "warming of the color". I think it's a reasonable inference that if a secondary fluorescence from the royal blue peak causes a color shift to the warm, the only way two LED's, both with and without a dome, could have the same color is by using a different phosphor. That's just an educated guess on my part. If you have inside information from the LED manufacturers that allows you to say that's not so, I'd love to hear it.


That is not a reasonable inference. The phosphor does not need to change to get a different color only the amount or percentages of phosphor used. Besides the effect seen from adding the collar is far more drastic than would be seen by just what bounces back from internal reflections due to no dome.



Al Combs said:


> I don't think it's off track at all. Newbie correctly pointed out the test would have been more accurate if a single XR-E had its dome removed. But jtr1962's test results indicate a 30% increase in output for the normal XR-E over the XR-E with no dome.


I confirmed jtr1962's results in my own tests and I used only one LED. That said we are still at 30% not 50%.



Al Combs said:


> If you say that's nothing but internal reflection. I both disagree and ask that you explain that statement. Is it based on something other than your best guess?


 It is based on my knowledge of light extraction and most certainly is not a guess. The information is on the web for all who care to look for it. 



Al Combs said:


> And that is just your guess. Which as I said I respectfully disagree with. For the sake of people who read these posts and just assume an unchallenged rebuttal is an admission of error.
> 
> Finally I have some personal experience of my own. In a failed experiment on two DSVNI P7's I bought from PhotonFanatic, removing the dome on one made it's output much dimmer than its twin(?) brother. The hotspot was much smaller but overall output when the reflector housing was removed from the MagLites I had them in, removed that advantage. It was both much dimmer and of a different color than its twin, after the removal of the dome.


As far as whether or not the aluminum foil test would work or not...well yeah that is a guess. And a good one at that. 

Showing me a picture of a chopped off P7 dome is hardly refuting my assertion that the foil will have little to no effect to increase surface brightness though.


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## Al Combs (Jul 29, 2010)

saabluster said:


> ...


I think this is the point where we'll have to agree to disagree. :wave:


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## saabluster (Aug 1, 2010)

Al Combs said:


> I think this is the point where we'll have to agree to disagree. :wave:


So be it.:wave:


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## mpteach (Dec 17, 2011)

I'm making a led worklight and might use a tir or aspheric. There will be 3 groups, the large main group on top for ceiling bouncing to light up the whole room and weaker groups on the left and right sides with elliptical optics for occasionally shining down the walls to find flaws.The main beam has to be just wide enough of an angle to diffuse lots of lumens off a normal height ceiling without glare or afterimages in my eyes from the reflection. Also there should be almost no spill in that beam, too much light going sideways from the worklight will also cause glare in my eyes, especially when standing near the light.

I was originally thinking of 9 cree xml and 9 tir 16mm optics for the main array, with a 2" square piece of glass and a hinged shroud on top to absorb the spill.

Now im wondering if i could use one of those really big bridgelux leds and one big aspheric lens instead of the small xmls and tirs.

I want a large percentage of the beam to have even brightness but don't mind many small shadows or color spots since its just reflecting off the ceiling!
The smaller the diameter of the glass the less area i have to clean. This light will have cleaning supplies in it.

Ra how did you make a diy reflecting collar? Also how much did the color temperature shift?


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## Pizeer (Oct 8, 2012)

*Re: Die luminance (surface brightness, important for throw)*

So you were testing Graphite crystals? How did that turn out?


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