# Shanghai Daheng DHL GB-100 100mW 532nm Laser Pen - Eval Report



## Lew Fong (Jul 5, 2007)

Hi Folks,

I was fortunate enough to secure a small quantity of very-high quality 100+ mW, 532 nm DPSS laser pens made by Shanghai Institute of Optics and Fine Mechanics ( Shanghai Daheng Optics and Fine Mechanics Company, Ltd.), model DHL GB-100. These are the finest quality laser pens I have seen so far at any price, and represent the upper limits of what is possible given the state of the art in 12mm DPSS lasers, in my humble opinion. I recently distributed four of these units to the CPF membership, and am expecting further review and input from those members after they have had a chance to look them over. I am not a dealer of laser pens, but I do integrate the units into OEM devices that I manufacture. The intent of this article is simply to offer an impartial technical appraisal of the unmodified devices as-built.

All of the units I purchased measured anywhere from 102 to 120 mW peak on my Coherent Lasercheck. Peak power is achieved after only 5 seconds typically from a cold start, and maximum continuous operating time is specified as 45 seconds. Power de-rates gracefully to about 10-15% below maximum on average at the highest operating temperature. In intermittent operation, the proper ON/OFF ratio appears to be about 1:4 to keep the output power in the high-power portion of the power vs. temperature characterstic curve. I have not tried thermo-electric augmentation yet.

I know that many of you collect lasers for the challenge and fun of modifying and tweaking. This unit is not one to experiment with for two reasons: First, there is no advantage in doing so. The units are already peaked for maximum performance right out of the box. Secondly, the units are built so solidly that it is _extremely_ difficult to take them apart. I sacrificed two of mine in the name of science and good old-fashioned American reverse-engineering, only to discover that there is no way to peak them any further. The pen barrel has a really nice pearl-grey, deep gloss finish with gunmetal-chrome trim and pocket clip. I had no other choice than to destroy the pen barrel by cutting in two different places with a miniature pipe cutter to access the laser module. I have taken a lot of laser pens apart. Unless you are very skilled and very careful, you will be lucky to still have a working unit if you try to take this one apart. Trust me on this! (yes, I have a dead one).

Quality of the units is evident in every aspect of the laser assembly. For example, there is a locking set-screw to fix the LD in place after factory alignment, rather than the typical spin-on lock ring that inevitably moves the LD out of the optimum position during tightening. The focus barrel and LD holder threads are tight and were cut accurately. The MCA input and output lenses are K-9 glass, as is the objective lens. The unit is well filtered against infra-red emissions, and produces nearly all of its output power at the 532nm line. The alignment of the optical components is such that the output beam is nearly perfectly coaxial. Alignment of the LD is already optimized in the X-Y and rotational axes with respect to the large (2.5mm?) MCA. The PCB is well supported within the pen barrel by a plastic shoe that fits snugly around the board, flush to the inner surface of the pen, to prevent damage by pushing the ON button too hard. There is a potentiometer on the PCB, but it is already set for optimum performance and efficiency. Advancing the control only increases current consumption of the regulator without increasing output power. However, power may be _reduced_ with this control. I was able to reduce power as low as 45 mW before experiencing mode-ing on most units. One must use care not to short the control to the case during adjustment....this will cause instantaneous destruction of the laser diode. (yes, I ate one).

Quality of the product extends to the driver board as well, which is beautifully silkscreened and conformally coated....a really nice job for such a small PCB. The regulator circuit is reverse-voltage protected by a diode in series with the battery supply, and current regulation appears to be achieved with the popular current-mirror method. There is no optical feedback or other APC circuit, so the driver holds the LD voltage and current constant over the entire duty cycle. Surprizingly, output power stability is quite good, which I attribute to the design of the MCA/optical cavity and LD holder. The design offers a much more effective heat-sink for the LD and MCA than other designs I have seen, somewhat dampening the effects of heating upon output power. The assembly draws about 650 mA of current from a 3VDC source ( two AAA Lithium photo-type cells). Considering that the unit dissipates nearly two Watts in operation, it is amazing that output power stability is as good as it is, given that there is no optical feedback. It seems clear that the designers chose to address the problem of power stability at it's source - heat management - rather than to build a more complex, less efficient, and more expensive optical feedback topology. Lifetime of the laser is rated at greater than 5000 hours, and may perform well beyond that due to the effectiveness of heat transfer from the LD and crystal assembly. In addition, the LD itself is a 9mm type rather than the 5.6mm cans typically found in lasers of this power class.

Beam characteristics are excellent, with diameter <<1mm and divergence at <1.2 milliradians. I have not determined the coherence length of the beam nor investigated the unit's suitability for holographic purposes, but it is obvious even by visual inspection that the units exhibit very low-noise for the type, and may be useful for holography or other lab work. This is an extraordinary statement to make about any DPSS laser pointer, as many of you will already understand. As I said, I believe that these units are the best available in a 12mm laser pointer. (Why can't America produce something as good?)

The pens are available at retail in the US from ultralasers.com, and can be found on eBay by seller shawnwang. I am curious to know if other CPFers have gained experience with these units yet, and what your impressions and observations have been, so please add your comments! 

Cheers All,

Lew


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## dirtbikepilot (Jul 5, 2007)

I got my laser today! I won't post a thorough review because I don't have the experience or equipment necessary to to be very accurate. I have only put alkaline batteries in it so far, but it's a lot brighter than my tweaked leadlight that I got a few years back from atlasnova. I can see the beam well in a dimly lit room and feel a bit of a burning sensation if I point it at my hand (nothing extremely painful though). The build quality seems fine although the threads don't mesh together very tightly, like the inner threads could be significantly bigger and still fit into the outer threads. It unscrews in the middle unlike the leadlight that has a cap in the rear. The button switch kind of sucks because it will turn off/flicker sometimes while holding the button down making it necessary to release and press again to get it to work. I have always been very careful with my leadlight, making sure to never get it near anyone's eyes. This one seems like it could do substantially more damage, even from a distance. That's all for now. Overall I think it's cool! :twothumbs


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## allthatwhichis (Jul 6, 2007)




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## picrthis (Jul 6, 2007)

Why so high in cost? These are over twice the cost of the ones from DX and are being sold for 8x the cost. Making a profit is one thing but come on thats over the top......Good luck. :sick2:


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## greenlight (Jul 6, 2007)

Even without pics, it was a decent read.


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## [email protected] (Jul 7, 2007)

Mine arrived as well today, I like it. 
Daheng on top:




A quick comparision pic in daylight:
107mW Daheng vs 30 mW DX





The DX one is a bright sucker, but the Daheng dwarfs it.


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## dirtbikepilot (Jul 7, 2007)

Wow. I don't know if it's just the camera or not, but mine doesn't look anywhere near that bright in a room lit at about the same level. Mine doesn't even look nearly as bright as the 30 mw in that pic. :thinking:


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## nerdgineer (Jul 7, 2007)

dirtbikepilot said:


> ...Mine doesn't even look nearly as bright as the 30 mw in that pic. :thinking:


Does your look as right as a 30 mw in your hand? Pictures are deceiving as an absolute measure. They're only useful as a comparative measure, as that picture shows.


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## dirtbikepilot (Jul 7, 2007)

So much for this laser. :thumbsdow I was playing with mine a little tonight and it died! Now it's maybe 1/10 as bright as my leadlight. This sucks!!!!


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## [email protected] (Jul 8, 2007)

Dang, that sucks...


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## GJW (Jul 9, 2007)

dirtbikepilot said:


> So much for this laser. :thumbsdow I was playing with mine a little tonight and it died! Now it's maybe 1/10 as bright as my leadlight. This sucks!!!!



Did you get it direct off of eBay or from the group-buy that happened here not long ago?
Not that is should matter but did the seller know you were a CPF member?


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## dirtbikepilot (Jul 9, 2007)

I got it from Lew (above). I tried to contact him and have had no response so far. It sucks to have $153 go ............ sigh....


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## starfiretoo (Jul 10, 2007)

I thought Lew checked the lasers before shipping? Not just dead batteries?




dirtbikepilot said:


> So much for this laser. :thumbsdow I was playing with mine a little tonight and it died! Now it's maybe 1/10 as bright as my leadlight. This sucks!!!!


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## Lew Fong (Jul 10, 2007)

Hi Folks,

Sorry I have been away...my internet service has been off the air for a few days. The cable company is making things "better". (build-out for digital voice)

First, I am alarmed at the apparent failure. Please, check the batteries, of course. But also check that the little spring on the PCB is not pushed over, shorting out the batteries. They will get pretty hot if this happens.

Sometimes too I have noticed on many different models that if you gently turn the barrel where the batt cap screws on while pushing the ON switch, you may find a point where it turns on. If so, you have a poor connection from the positive end of the batteries to the case, or from the case to the laser module via the barrel where it is threaded. I have gone so far as to drop a piece of foil into the barrel first, before putting the batteries in, in order to get a better connection on the positive (+) end. But as far as I have seen that isn't a general problem with these lasers. In fact, I checked them all again prior to shipping. I used Energizer Lithium cells. But that's something you can try. 

About profit and cost....I am not a dealer of laser pens. These were sold to the CPFers for the same price I paid. I am interested though in the reference you make above, picrthis, about the DX laser. You seem to indicate that the Dahengs are either twice the price or eight times the price, but that isn't clear...which is correct? After all, if we can get as good and as powerful a unit for eight times less in price, or even half this price, then that is good news! Can you tell me more about it?

[email protected], thanks for the nice pictures! 

To dirtbikepilot, I feel terrible about the situation. I hope you can get it working again. I'll check back again soon.

Cheers All,

Lew :shakehead


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## dirtbikepilot (Jul 11, 2007)

I've checked everything. It's definitely not something I can fix. :sigh:


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## jonashn (Jul 12, 2007)

Lew Fong said:


> Hi Folks,
> About profit and cost....I am not a dealer of laser pens. These were sold to the CPFers for the same price I paid. I am interested though in the reference you make above, picrthis, about the DX laser. You seem to indicate that the Dahengs are either twice the price or eight times the price, but that isn't clear...which is correct? After all, if we can get as good and as powerful a unit for eight times less in price, or even half this price, then that is good news! Can you tell me more about it?


 
Just take a look! http://www.dealextreme.com/products.dx/category.911

And read this thread: https://www.candlepowerforums.com/threads/159962
Be sure to look at the last page, there is talk about their new 50mw laser which costs only 26$!

And hello everyone! This is my first post


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## [email protected] (Jul 12, 2007)

Is there a way to clean the lens without ruining it? Mine has far more speckling as my 30 mW DX one. 
Collimation seems better with the DX one as well. I must say the expectations are not met regarding extra quality...


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## Lew Fong (Jul 12, 2007)

Chris,

I sent an email on your behalf to the distributor today, asking him to please replace your pen. When I bought the pens, it was with the undersatanding that any that did not perform properly would be replaced. I am sure that Mr. Wang will honor that pledge. His website indicates that the units are conditionally guaranteed against pre-mature failure for three months after purchase. 

It seems a little silly for you to send the unit to me just so I can ship it to him, with the resulting round-robbin return trip as well. So I asked him to please accept the return directly to him. I am awaiting his reply, and have given him the URL for this thread. Perhaps he will respond here directly. Here is the contact information:


Shawn Wang
610-3050 Pharmacy Avenue
Scarborough ON 
Canada M1W2N7
[email protected]
647-201-8069

Please give him a call and ask him to look at his email or this thread, and briefly explain the situation. If you have any problem at all, please let me know asap.

Bart... the lens is glass so you shouldn't be able to damage it if cleaned gently. I like to use a Q-tip and a little Windex...that usually works well.

To Jonashn....thanks for the info! I will look it over very carefully. It seems too good to be true, but I may buy one for eval purposes.

Cheers All,

Lew


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## Lew Fong (Jul 12, 2007)

Bart,

It's difficult to assess the true quality of the devices unless you examine the innards. I have taken a lot of lasers apart over the last 30 years or so, and based my comments upon comparison of the construction techniques and methods used in this laser vs others I have seen. Also, if one makes a careful comparison of the technical parameters such as power output, density, stability, spectral purity, divergence, noise, etc., I think it would be a hard unit to beat compared to other 12mm laser pointers. I especially like the fact that the units are not under-tuned as many other lasers are. As you know, many CPFers have made an avocation out of disassembling laser pointers to peak them up for maximum performance. As I said in my original posting, not only do you NOT want to take these apart, there is just no reason to do so. I still think these units are outstanding performers for the price, especially considering that only one in a hundred Leadlights will tune up well enough to deliver 100 mW! To me, this is an oustanding technical achievement, unduplicated elsewhere to my knowledge in a 12mm DPSS module or laser pointer. Every other 100 mW, 12mm unit I have seen either has no IR filter, or suffers from non-coaxial beam alignment, or has serious power stability issues ( poor heat management), poor or sometimes no focus, mode-ing, noise, etc. Most exhibit more than one of these failings. I must have a few thousand dollars worth of cheap-Charlie eBayser bodies laying around the shop in various states of order. Some of the units from otherwise reputable sellers are so haphazardly constructed and so dangerous for lack of an IR filter that I am amazed that the producers are still in business! AixiZ comes to mind immediatley. So when I saw this one, I was thrilled. You have to take a look inside to know that these fellows have done it right. 

BTW, have you measured power? Any other measurements? Let us know after you clean the objective!

Cheers,

Lew


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## Lew Fong (Jul 12, 2007)

Jonashn,

I looked at the links you provided...thank you. I left a few comments over there:

https://www.candlepowerforums.com/posts/2078169#post2078169

I have seen these New Wish lasers before. I wouldn't buy another unless they were selling for a buck apiece. No filter, poor QC, no repeatability, and you never know what you will actually get until you get it. Please check out my comments.

Cheers,
Lew


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## [email protected] (Jul 12, 2007)

Thanks Lew, glad to learn I can safely clean it. 

Obviously I haven't looked inside, so I can't comment on that. My observations are purely visible. 

When looking at the dot you can see it isn't round, but starshaped, as my picture shows.
There also is a faint round sidespill visible from light bounced of the sides of the aperture, and some speckling.
I hope cleaning the lens will fix it... :shrug:


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## Lew Fong (Jul 12, 2007)

Bart....I hope so too! Shouldn't be a problem.

Chris...I just heard back from Shawn. He says you can go ahead and ship it back to him directly and he will replace it for you. Shawn is a good guy.

I'll send you a PM as well.

Cheers,

Lew


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## Tropmonky (Jul 13, 2007)

Hello all, I got one of these off Ebay before they closed down all the high power lasers on the site... I have to say this thing lives up to it's power settings, I have a 100mw. The overall build quality is slightly above average when it comes to cost effective units. I DO like how the batts aren't loaded from the back of the unit. Divergence doesn't seem to be the greatest, but not that bad. I can pop balloons easy up to around 7-10ft with no lens.

As far as people commenting on the heat/pain when pointed on skin, this varies GREATLY depending on the color/tint of your skin. For instance, I have pretty olive colored skin, but the underside of my forearms are quite white, and the laser only is WARM at that spot. But when I hit a dark MOLE, DAAAAMN it's hot within half a second... And I mean burning hot, .

Matches are lit quite easy from within a foot or so and no lens as long as the match head is sharpied black. 

I personally was looking for an inexpensive high power laser for my Lasersaber from lasersaber.com and this one fits perfect and works perfect with them. MUCH MUCH cheaper than a WL and gets the job done!

The unit does start to warm up with usage as with any SMALL high power laser device. I'm starting to think that the 80mw might have been a better choice for me with the Lasersaber so that I don't worry about the heat as much with prolonged usage, but I love the burning power of the 100mw.

REMEMBER TO USE EYE PROTECTION!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
For Greenies I use these http://www.toolbarn.com/product/dewalt/DW0714/?ref=base
They are a little darker than the more expensive glasses out there, but at around $10ea they can't be beat.

Overall opinion of the unit: I love it, however am still considering getting a higher quality greenie in the future. For now I'm wanting to get a high power RED laser pointer that will fit my LaserSaber. So far I think I'm going to have to build my own, but it has to fit the LaserSaber so I can't use the sweet looking LED flashlight trick..... DOH..

K-


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## dirtbikepilot (Jul 18, 2007)

I'd like to send a big thanks out to Lew and Shawn. I sent the old one back to Shawn and he's exchanging it for me. He even shipped the new one out a week before he will get the old one back. :thumbsup:


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## GJW (Jul 20, 2007)

Well, I just got mine and I have mixed feelings.
It's bright as all get out but I'm not crazy about the construction.
Putting the threads in the middle of the casing seems like a weak design structurally and I think it adds to battery rattle/wobble. I added some little Post-It Notes inside the battery compartment and that greatly reduced the wobble but the larger diameter around the body join still makes putting it into and taking it out of shirt pockets a little awkward. I also don't like that the warning sticker mentions neither the class nor the power.

I have no way to take measurements but it's supposed to be 110mW which I'm guessing is peak. My previous greenie was a 30mW and it could produce enough light to read by when doing a ceiling bounce test in the dark but this one literally lights up the entire room. Reading book titles on a shelf 6-feet away is no problem. Even in daylight, with no room lights, a ceiling bounce produces enough peripheral light to be noticed.

My coworker bought a greenie at a local flea market that was advertised as 130mW and it looks just like the one in Bart's comparison pic above only it's matte silver with chrome. With lithiums, his can burn through the bottom of a black plastic Solo plate (the thinnest part) in about 5 seconds. With Duracell ProCells, mine can do it in about 6 seconds and in two bursts of 15 seconds each, I can burn through the thicker bowl of a black plastic spoon. Both can pop balloons and both can make pinholes in electrical tape but neither one will cut the tape "like butter" as some others have claimed.

Shining it on his own hand, an other coworker burned himself with mine in about 4 seconds (Hey, I warned him).

The main difference between these two, though, is the beam. At 15 feet or less, mine produces a single dot. Without goggles I can't tell if it's a round or an oval dot but it's a single dot with the usual expected scatter. His produces a dot which is always un-centered within an oval corona of dimmer green light. And when I spin the pointer along its long axis my dot doesn't change noticeably. But when he spins his you can see the oval corona spinning along with it. Hard to describe but once you've seen one you know it. My old 5mW from Z-Bolt exhibited the same thing. It's almost like the corona of a reflectored LED except that it doesn't gradually fade from light to dark. It's just a constant even-brightness oval corona with an intense dot in the not-so-center. My coworker says his is more powerful and it probably is but he sure envies my beam.


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## GJW (Jul 24, 2007)

So after a week of pocket carry, the writing is coming off of the warning sticker.
The pen might be high-quality but the sticker sure ain't.


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