DL Viper 637nm 50mW

I'm a longtime laser fan who is just starting to get back into the hobby after a long time away. I've always preferred the 'warm' colors, but found there to be a distinct lack of warm colored lasers available in the hobby! Years and years ago, I had a 40mW 594nm, which was about perfect IMO. I had always wanted another 'warm' laser that could enter the green laser brightness range, but I didn't want to spend tons of money on another yellow.

One day as I was perusing Dragon Lasers, I happened across their red lasers category. "Hmmm, could be interesting" I thought to myself. I clicked into the category expecting your run of the mill 200mW 660s, but no! Here be 637s!

I was intrigued and immediately decided that I had to drop coin on one lol.​

Nothing special to write home about here. Adam was responsive and quick with my questions, and the laser made it from China to Florida in five days. Can't complain!​

Upon opening the laser, the first thing that I did was look it over. It seems to be a standard CNI glp case with a normal diode in it. Honestly, I was hoping for all of that space in the barrel to be filled with some fancy optics to give a really high quality beam profile, but no luck. Just a typical setup way down in the barrel. I'll wager that this thing will be a PITA to clean.


After dropping in some generic AAAs and firing it up, I was utterly shocked. I've never seen a red so brilliant! (Though not being a fan of burning, I can't speculate on how it compares to a 660nm burner) This bad boy definitely falls into the category of 'annoyingly bright' like the 20ish mW greens are to the uninitiated. It is dramatically brighter than my APC <5mW leadlight. More on power later.

One of the first things that I habitually do with a new laser is take off the end cap (if possible) and see what happens when I do. On this laser, I noticed a much larger dot with tons of splash.


I found the dramatic change in the amount of rings and splash on this laser without the endcap to be quite puzzling. It appears as though CNI used the endcap to attempt to 'round out' the beam's profile. I believe that this is how they got the 'nearly round dot' that CNI/DL purports this laser to have. As it turns out, the hole in the endcap of the laser is smaller than the diameter of the beam. This was costing roughly a 20% power loss as measured by my iffy power meter, but also cleaning up the dot very nicely.

I rectified the situation by measuring the output of the laser without the endcap, then slowly drilling out the hole 1mm at at time until the power output was nearly the same as the uncapped measurement, while still managing to avoid any significant splashing or artifacts. I'm quite happy with the end result.

***I wish to caveat immediately that I don't trust my LPM. It has consistently given me numbers that are 'right' for what my lasers are supposed to be producing, but take the measurements given hearin with a grain of salt!***

Click here for details on the power meter

When I dropped this bad boy on my LPM, I got a shocking result of 79mW! Well over spec, but somehow unsurprising with a CNI laser. It is significantly brighter than an APC <5mW Leadlight, which is consistent with this power level.


For divergence, I measured thusly: the dimensions of the beam at the aperture subtracted from the dimensions of the beam at distance divided by the distance.

At the aperture, the lasers beam is round, but the hot spot is roughly 4mm by 3.5mm. I sat the laser on the back of my car and put the dot on a telephone pole 190 feet away, or 57.91 meters. The dot on the telephone pole was 30mm by 35mm for an average divergence of .496. Pretty damn good IMO! (I have acreage, so this was safe to do).​

Visibility of the dot is VERY good. I am incredibly surprised at the visibility of this thing. However, the beam is mediocre. Even with how much brighter the dot is than a 5mW greenie, I found the beam to be very comparable to one. When viewed in clear air, the beam is definitely very visible when you're viewing on axis. Curiously, the visibility of the beam drops off very quickly when you go off axis, unlike greens or blues. I suspect that this is directly related to Rayleigh scattering.

When viewed in the fog however, this thing turns into a monstrously bright lance of liquid fire! A very impressive beast in this regard!

Inside with the lights on, there's not really anything for a visible beam. The lack of visibility of the beam was expected however, and doesn't count against the laser IMO.

In the following pics, the clear air pics were taken tonight, the foggy pics were taken last night. Last night, there was enough fog for one to tell that it was foggy, but not so much as to obscure vision or make it difficult to drive.