# LED Shoppe Green 5mW vs 50mW



## entoptics (May 14, 2010)

Just got a couple of green lasers from the LED Shoppe, both 2xAAA pen lasers, one is 5 mw and the other is 50 mw.

I should be able to tell the difference between the 5 and the 50 in bright ambient light, right? Both show a visible spot at 40 feet in bright sunlight, but the 50 MW is indistinguishable from the 5 mW in terms of spot brightness, and neither one has particularly obvious beam even in a dimly lit room.

From what I read, the 50 mW should be noticeably brighter than the 5 mW, and should have an easily visible beam in a dim room.

Both lasers are identical in dimensions, but the 50 mW has a silver battery compartment, and has a slightly different warning label, which includes <50 mW instead of <5 mW.

Any comments? Did I just get screwed? The $10 5 mW light is quite good for it's intended use as a presentation and class pointer, but I was under the impression that the $20 50 mW would be far brighter, and suitable for star gazing, and even pointing to stuff at 50 yds in the daylight.


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## bshanahan14rulz (May 14, 2010)

try 'em out at night, see if one beam looks brighter than the other, side by side.

Another trick is to put the aperature up against your upper lip and then turn it on. If you feel one heat more than the other, it is putting out more power than the other, as long as both are the same color.


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## entoptics (May 15, 2010)

Ayup, tried a lip "heat test" and the night test, and the 50 mW is more potent. I'm just surprised at how little.

I'm contemplating sending the 50 mW back, but am VERY pleased with the $10 5mW.

The 5 mW puts a faint dot on my work building at a measured 0.6 miles (~1 km) in the "dark". Street lamps and such are burning bright, so we're not talking wilderness blackout.

The 50 mW puts a slightly more obvious dot, and has a slightly brighter beam, but it's not 10x as bright to the naked eye. Hell, $20 vs $10 and I'm not sure the dot was even $twice$ as bright.

Perhaps I need some education. What should I expect from a 5 vs 50 mW green laser.


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## LED_astray (May 15, 2010)

I'm very new to lasers and have many similar questions I've been trying to answer. The key point, for green lasers, that's driving me crazy is that they may emit large amounts of IR. (As I understand it there aren't practical green laser diodes. Green light is generated by converting an 808nm (IR) beam to 1064nM (IR) beam and then to a 532nm (Green) beam with crystals.) Cheap lasers are notorious for being out of spec and for not being properly IR filtered.

Given that, it is possible your 5mW is brighter than 5mW and your 50mW is less than 50mW and has a significant percentage of that energy in the IR space. I haven't discovered any way to check without several hundreds of dollars in test equipment. (If you find a less expensive way, please do tell!) Some estimates I've seen suggest a cheap 5mW is typically 15-25mW and a cheap 50mW is typically between 35-40mW, with upto 20% IR. (In the extremes that would make your lasers 25mW versus 28mW of visible green light.)

BTW- the possibility of IR scares me the most. It is invisible, hence no blink reflex, and can do as much damage as any other wave length. I'm also looking for reasonably price laser safety glasses now.


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## entoptics (May 15, 2010)

I've considered the same things Astray, but I think the "IR blast" is for the most part a "myth".

The physics is real of course, but the application of said physics is flawed. IR emission from a laser should be in a relatively tight beam similar to the main beam. If you don't point it at eyeballs, it won't hurt eyeballs.

I think part of the "mythical" status may come from folks who were wearing laser goggles for a particular green wavelength, and then received direct eye exposure. The goggles are wavelength specific, so they could have sustained damage from IR during a direct hit from an otherwise goggle filtered beam.

Point is, don't point it at eyeballs EVER, goggles or none.

I'm leaning towards the same conclusion you made regarding the difference in my pen lasers. Perhaps the 5 mW is firing at >5 and the 50 is firing at <50 and I got "screwed" in terms of real difference.

No experience with handheld pointers though, so I can't say for sure. I'm gonna take my two specimens up to the lab at my work and hope to find out the truth come Monday.


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## LED_astray (May 15, 2010)

entoptics said:


> ... No experience with handheld pointers though, so I can't say for sure. I'm gonna take my two specimens up to the lab at my work and hope to find out the truth come Monday.



Hey, if you've got real measurement equipment available please do post actual values. With lots of googling, I've found only a handful of actual datapoints. (Lots of A/B visual comparisons and speculation though.) In summary, the over/under power problems seem real, at least as far as visual output, and the IR situation is unclear to me. The power meter measurements of over/under power are more common (less uncommon) and very consistent with visual comparisons. IIRC- I only found one actual person doing measurements with a power meter and appropriate quality filters to separate the wavelengths. One of his units was bad, (the 20% IR outlier I mentioned before,) but even there he didn't have a way to check divergence of the IR beam. It may have dispersed too quickly to be very dangerous.

I wish there were inexpensive ($20-40) glasses that filtered all IR plus reduced other wavelengths, e.g. green, to safer levels for hobbyists (for moderate power levels, say <250mW. If I'm spending $$$ on an extremely powerful model, it'd be easier to justify the $$ for professional safety glasses.) Just for piece of mind, about reflections and slips, if nothing else. I haven't found them yet.


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## blasterman (May 15, 2010)

For the sake of arguement, I have a $20 50mw DX (before the ban went into place) and a rather expensive 5mw single click (forget the brand, but nicely made).

With fresh batteries the DX is visible in daylight and easily has a range of miles at night. The beam point on a white wall is too bright to look at in an average room. 

Only reason you can't hurt somebody with the DX is because the optics are so cruddy the spot is very diffused. If it had the optics of the 5mw it would be scary.


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## DrQuantum (May 16, 2010)

Those DX 5mW's always seem a tad overpowered ~10mW which would be good if they would stop overheating so quickly. 

I don't know how they manage to make the 50mW ones so cheap (although whether or not they actually are that high is questionable). Granted the ones at O-like might be closer to the specs but for a slightly below 50mW laser at 20$ I would not mind.


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## entoptics (May 18, 2010)

Well, our testing rig isn't registering either laser. I suspect this is due to operator error, since the wavelength and sensitivity for our detector and meter should register them according to manual specs. The equipment is intended for a 20w laser though, so I'm sure we've screwed something up for my little pen lasers.

The meter is a Coherent Field Max II. Can't remember detector model (it's Coherent too), but according to the manual specs (3 mJ minimum), it should be picking up the 2 LED Shoppe beams.

Anyway, I'll goof around with it and hopefully get some real data. I'm a COMPLETE laser newb (other than working around them a lot), so I'm game for any tips or hints about getting the data. At this point I'm not gonna spend much more effort than google unless my boss gets interested.


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