# FAT NEEDLE 400 - a concept study with 400kcd. looong throw, thin beam (now beamshot)



## Dr.Jones (Jun 28, 2010)

Hi again... After I posted the CAT100, some asked me about my next project, and here it is. While the CAT100 already wasn't a serious flashlight, this one is even less one. I would't dare to post it if it didn't have quite an interesting property: it's long throw ability.

The setup is very simple: just a LED and a big lens, mounted on a rail for optics experiments.






Specs are in the image. LED is thermo-glued on a 4cm*8cm*2mm copper plate, driven with a buck driver at 1.25A. Input is anything within 4-16V.
I just took a small power supply, but 2*18650 should perform equally.

I measured 472 lx @ 29.6m, which gives *414kcd* (or "414000 lux @ 1m calculated", as it's often noted a bit improperly).

The beam is very thin: 10cm @ 29.6m, that's *3.4 mrad*.
A good laser pointer has 1 mrad, a bad one has 2 mrad, and this thrower has 3.4 mrad... That's why I called it "needle".

I posted an earlier version with 270kcd (lower LED specs) in a thread on throw and decided to pimp it a bit 

*Update:*
After some vacation and another trip I found time to make this one 'mobile' - i.e. slightly more compact and powered by batteries. Since it's still unwieldy, I thought it's better to carry it as a construction kit and assemble it in the field. Thus I named it Field Assembled Thrower 
(I hope you recognize that naming those things is not meant seriously and should be taken with several grains of salt.)





The batteries are in a rolled paper case again... The buck driver (1.25A) is in a heat shrink tube. No switch, just plug and play 
If I find the time I might finally do that one right and use an EZ900 instead, probably driven at 1.4A. I hope it then will exceed the 0.5 Megacandela 

Here's a beamshot at 250m:




Small beam indeed... (oops, ignore the excess "E", please)
Need to find a good, more distant target.


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## JulianP (Jun 28, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*

Great prototype. Can you collimate the beam further, by using multiple optics?


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## Dr.Jones (Jun 28, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*

Yes. I actually did that. It will increase the flux (lumen) caught by the lens, that however will not increase throw (actually reduces throw due to additional losses), but increase the spot size.
Using a lens with shorter focal length but same diameter would be alike.

(There's some exception: If your main lens has some aberrations, an additional 'pre-collimator' might help reducing their influence and this increases throw a bit. But NEEDLE's lens works fine without.)


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## Kestrel (Jun 28, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*

Sir, you are a very welcome new member to have here. I predict a brilliant future for you here at CPF. :thumbsup:


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## Walterk (Jun 28, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*

Beamshots !

Testbenches are fun ..!

Edit: And oh, why dont you use wax instead of the hot-glue...


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## Dr.Jones (Jun 29, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*

I didn't take it outside yet, so beamshots are not very interesting. Here is one anyway (wall at 29.6m):




It's over-exposed for the interesting green ring to show up 

And by thermo-glue I meant thermally conductive silicone glue, not hot glue...


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## saabluster (Jun 29, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*



Dr.Jones said:


> I didn't take it outside yet,


Well get to it!


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## IMSabbel (Jun 29, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*



Dr.Jones said:


> Hi again... After I posted the CAT100, some asked me about my next project, and here it is. While the CAT100 already wasn't a serious flashlight, this one is even less one. I would't dare to post it if it didn't have quite an interesting property: it's long throw ability.
> 
> The setup is very simple: just a LED and a big lens, mounted on a rail for optics experiments.
> 
> ...



You might even get this focal length workable if you fold the optical path cassegrain-style...


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## easilyled (Jun 29, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*

So the led is 50cm back from the lens?

This would make for a pretty long flashlight.


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## Dr.Jones (Jun 30, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*



IMSabbel said:


> You might even get this focal length workable if you fold the optical path cassegrain-style...


Yes, good idea, but I think I'll lose to much lens area and induce too much loss. For the same reason I don't use pre-collimators, which would shorten it, too. Well, actually I did try that, but that dropped me to 370kcd, and I wanted to stay above 400 




easilyled said:


> So the led is 50cm back from the lens?
> This would make for a pretty long flashlight.


Yes. As I said, it's not meant seriously. The previous version I mentioned was made only to prove that a big diameter lens gives long throw, regardless of (effective) focal length.
This simple big lens setup outthrows any LED light I have read about.
Although it won't be too useful with 1.7m spot size at 500m...

I'll be away for a while (some kind of business trip and holidays), but afterwards I want to wrap it up somehow, add a battery pack, and take it outside for some throwing fun, ehrm, tests.


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## broadgage (Jun 30, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*

This project somewhat reminds me of an extreme range, but not very practical light that I made 40? years ago as a school kid.

This consisted a large lens, similar to the one illustrated, and a lens ended flashlight bulb.
The lens end of the bulb was a crude but suprisingly effective pre-colliminator. The beam diameter from the bulb just about filled the lens, with little wasted spill.
The lens was fitted to the end of a suitable cardboard tube, with the MES lampholder being a push fit through a central hole in a cardboard disk on the other end of the tube.
Range was over half a mile, and that from a lamp of less than a watt.


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## Dr.Jones (Jul 1, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*

That's what I wanted to point out. Mere throw is as simple as having a big (and sufficiently good) lens and a high luminance light source. That bulb probably had a very small filament.


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## Paul Baldwin (Jul 1, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*

Hi, how much does the centering of the led effect the output, it looks like your setup can be pretty finely tuned? I was also idly wondering if you shone the led thru a pinhole exactly centred over the led how bright and how narrow would the beam be? Cheap laser? Or how about a tiny stencil cutout and the worlds furthest throwing bat-signal to date! lol


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## kengps (Jul 1, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*

You need a pre-collimator on that thing. Looks like over 95% of the light is used to light up the room, and 5% strikes the lens.


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## saabluster (Jul 2, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*



kengps said:


> You need a pre-collimator on that thing. Looks like over 95% of the light is used to light up the room, and 5% strikes the lens.


But then he wouldn't have his 400kcd. Besides I don't think he was going for practicality here.


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## Dr.Jones (Jul 3, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*



Paul Baldwin said:


> Hi, how much does the centering of the led effect the output, it looks like your setup can be pretty finely tuned? I was also idly wondering if you shone the led thru a pinhole exactly centred over the led how bright and how narrow would the beam be? Cheap laser? Or how about a tiny stencil cutout and the worlds furthest throwing bat-signal to date! lol


Positioning the LED _slightly_ off-axis doesn't have any visible effect, but if it's more than a few millimeters, the lens produces comatic aberrations. 

A pinhole would give an even thinner beam, but lens aberrations would be more critical in that case and the intensity would drop. If everything went perfectly, the divergence is easy to calculate: Halving the effective die size results in half the divergence and half the spot size.

For a bat-signal I'd recommend using an SST-90 



saabluster said:


> But then he wouldn't have his 400kcd. Besides I don't think he was going for practicality here.


Yes, and I found that thin beam somehow funny.


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## Paul Baldwin (Jul 4, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*



Dr.Jones said:


> Positioning the LED _slightly_ off-axis doesn't have any visible effect, but if it's more than a few millimeters, the lens produces comatic aberrations.
> 
> A pinhole would give an even thinner beam, but lens aberrations would be more critical in that case and the intensity would drop. If everything went perfectly, the divergence is easy to calculate: Halving the effective die size results in half the divergence and half the spot size.



Thankyou for your reply  Now I've seen your success with this I've just done a quick comparison of the lenses I was playing with on my projector project and can't believe I wasted so much time on it! The DX 66mm lense is definately badly flawed and I cannot achieve a crisp image of the die no matter what I do. I thought it was my bodged setup/poor positioning etc but a side by side comparison with the KD [email protected] lense shows this to not be the case at all!
Maybe that SST-90 is all I need after all? Thanks for the inspiration


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## MikeAusC (Jul 13, 2010)

*Re: NEEDLE400 - a concept study with 400kcd. looong throw, thin beam*



Paul Baldwin said:


> . . . The DX 66mm lense is definately badly flawed and I cannot achieve a crisp image of the die no matter what I do. . . . .


 
Try their 50mm Aspheric - www.dealextreme.com/details.dx/sku.12834

It produces a clean image of the emitter.


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## Dr.Jones (Aug 28, 2010)

I modified that simple setup to take it out and get a beam shot. I updated the first post.


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## CarpentryHero (Aug 30, 2010)

Just imagine if more lights had there batteries housed by the projector, and have the driver, LED and switch at the back. 
It's cool, practical or not thanks for posting


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## Walterk (Aug 30, 2010)

Great beamshot !
Still a nice concept


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## Th232 (Aug 30, 2010)

CarpentryHero said:


> Just imagine if more lights had there batteries housed by the projector, and have the driver, LED and switch at the back.
> It's cool, practical or not thanks for posting



A shoulder mounted rocket... err... photon launcher? That'd be fun to make.


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