A Tale of Five 1mW Lasers

[Renato1]

I got my five cheap 1mW lasers today, and after extensive testing, I can't answer the question I posed in the other thread. I bought them from here,
http://www.ebay.com.au/itm/151247370427?ssPageName=STRK:MEWNX: IT&_trksid=p3984.m1497.l2649

Basically, what I got was two powerful lasers, two weak lasers and one in between the others. The bright ones seemed as good as what I remember 5mW ones were like. The weak lasers were actually what I'd been expecting, but one was just visible, and the other was near invisible - unless I kept pressing its button, which made it seem like there was a weak pulse into the sky.

As I was testing them, it was 11C outside, and I was resting them on the boot of my car. Then I noticed that they all got much dimmer, and two wouldn't work at all. When I went inside and read the instructions, it said their working range is between 15C and 35C.

So I put them in front of the fire and heated them up, put them in my pockets and went outside. They were much brighter again.

To summarise, three of them are great for pointing out stuff in the sky to people, one is passable, and one requires pulsing. But all would require having a spare in one's pocket to keep it warm while the other is in use on a cool night. And only the two brightest may be okay as a laser finder on a telescope, the others would dim to nothing.

The reason I couldn't answer my question is because all five lasers have different brightnesses, so that when I merged two beams together up in the sky, the brightest always dominated, and I couldn't see that I'd added much brightness-wise with the second beam. Though it was fun seeing three parallel beams heading off into space when I wasn't trying to merge them.

Cheers,
Renato

[Stardrifter_WA]

Hi Renato,

I have an old version of that laser which is rated at 5mW. Having also had an earlier 1mW hand held, the 5mW hand held is definitely brighter, however, I have also noted that the Arctic Fox 5mW rifle sight that I have is brighter than the 5mW hand held. A matter of inconsistent output on cheaper lasers.

I think that the variance across the cheaper laser is quite significant and due to their cheap costs I doubt that the output is tested, whereas, I find the output from all three of my Arctic Fox GL Lasers Weapon Sights appears to be the consistent. Being a gun sight, and being much more expensive, I would imagine that the quality control is much more rigid.

I have also noted that lasers certainly don't like the cold.

Cheers Peter

[Renato1]

Hi Peter,
Thanks. No doubt that the variance is great among the cheap stuff. Still I can't complain, I now have three good pointers for showing people objects in the sky - all they have to do is follow the beams with binocular. And I've saved the ad as proof that they are only 1mW lasers.

I was totally unaware that lasers had issues with cold - something that you were aware of.
Cheers
Renato

[Stardrifter_WA]

That is why I have more than one, just stick it in your pocket to warm it up again. :)

[MrB]

The cold is only an issue for DPSS type lasers, which includes the traditional green ones.
When the output of these drops, DO NOT think that because the beam is weak(or gone) it therefore poses less risk to your eyes, it is actually worse!

The DPSS lasers are Diode Pumped Solid State lasers, these use an invisible 1064nm infrared laser diode to pump a frequency doubling crystal. This re-emits the light into the visible spectrum at 532nm. Top quality lasers will have an IR blocking filter on the outlet of the laser(and a heater for the crystals) but often the cheaper lasers omit this filter to save money.
When the temperature drops, the crystal stops lasing and the green beam gets weak or disappears, however the full strength invisible IR beam is still being emitted!

There is a two fold problem with this, the IR diode is usually of higher power rating than the green output because the crystals are not 100% efficient, so say 5mW for a 1mW green(tho likely less), also, with the green (visible) light in your eye your iris contracts and you also would automatically react by looking away. With IR being invisible you get neither of these auto responses so the IR laser could easily be causing damage without you even being aware.

Direct green laser diodes are now here, they are still pricey but not unrealistic(under $100), certainly much, much cheaper than they were only a short time ago.
Direct green lasers do not have reduced output in cold temps as they do not have the temperature sensitive crystals used in the DPSS lasers, they also don't have IR output for the same reason.
Definitely worth spending the extra cash.

[Renato1]

Thanks Simon for that thorough explanation. I didn't point any "dead" one to my eye, but could see that hidden IR output you describe being an issue with unsupervised kids.

It was only my weakest laser that had nothing visible coming out of it when it got cold. For the most part, the two weak ones still had a green dot on whatever object they were pointed at, despite no beam being visible to that dot.

My old Nikon Coolpix4500 can detect IR in its LCD screen. I'll have to charge it up and check that laser when it's not doing visibly emitting anything.
Regards,
Renato

[Renato1]

I bought three more very inexpensive lasers from this place in China
http://www.ebay.com.au/itm/201143936609?var=500306807791&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

They got here in 9 days. Two are as bright as my other two bright 1mW ones, and one is very slightly dimmer but still very useable.
Regards,
Renato

[tlgerdes]

You just want to pretend you are a "Predator" with your helmet mounted laser targeting system, don't you? :lol:

[multiweb]

Get some little hotties (http://www.ebay.com.au/itm/40-Pairs-80-HOTTIES-Hand-Warmers-Bonus-Body-Warmer-Heat-Pack-Fuel-Gloves-Heater-/151012911228)from eBay and wrap the tube in.

[Renato1]

I hadn't thought of that - though it is a favourite movie.
But I thought there was something familiar looking about the three beams at the time.
Cheers,
Renato

[Renato1]

That's an interesting idea thanks.
Cheers,
Renato

[Renato1]

I remembered how I've often been visiting people (outdoor BBQ) and trying to point out something in the sky to them - with sometimes limited success.

So now I've now put a laser in both the back of my wife's car and my car. It will be much easier pointing out things in future.
Regards,
Renato

[koputai]

Wow, the one in your original Ebay link is $107 whereas I just bought one
that looks exactly the same from Ozlasers for $20.

My old one (that looks the same as these) has gone very low output for
some reason.

The byproduct IR scatter has always worried me with these cheap lasers
so when I mount it on my EQ6 (as an alignment tool) I will put it inside a
piece of 20mm conduit with an end cap, and just have a small hole for
the beam to come out. That way any scatter won't come out, and any
bad spectrum energy will only be coming directly out the front where
you don't look.

Cheers,
Jason.