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FrozenGate by Avery

Laser for low tech communication- testing laser power

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lowtech

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Aug 17, 2018
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Hi-
I use Class II lasers (>1 mW) to make low tech communication aids for people who are paralyzed and can't speak. (The laser attaches to a pair of glasses, and allows a person to point to letters and words on a paper communication board using head movement.)

I'm looking for an inexpensive way to test the class/power on about 40 laser modules... (I got these a long time ago, and I want to double check to make sure that these are >1mW).

I appreciate any suggestions- Thanks!
 





What are you trying to assert here?

Class II (old system, roman numerals) requires a maximum of 1 mW, so no laser >1 mW visible can conform to that class, and the same applies to current system 'class 2'.

(this is assuming the beams are fairly narrow)

What colour are these lasers?
 
Hi Ben-

Thanks for writing back.

Just to be clear, I'm not asserting anything- I'm asking for help.

I have a product that I make that uses a Class 2 >1 mW laser module. The beam is red.

I have about 40 used laser modules that I want to test, to make sure that they are Class 2 lasers. I don't know how to do this. I'm looking for a relatively inexpensive way to test the power output. (The lasers are going to be used by people with disabilities).

Thanks,
Margaret
 
lowtech said:
Hi-
I use Class II lasers (>1 mW) to make low tech communication aids for people who are paralyzed and can't speak. (The laser attaches to a pair of glasses, and allows a person to point to letters and words on a paper communication board using head movement.)

I'm looking for an inexpensive way to test the class/power on about 40 laser modules... (I got these a long time ago, and I want to double check to make sure that these are >1mW).

I appreciate any suggestions- Thanks!
Click to expand...

Have you heard of a device known as a laser power meter? Any other way would amount to a rough approximation.
 
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As Steve said, you’ll need a laser power meter. Use the search bar at the bottom of the page, you’ll get a few hobby options.

Why are you using a red laser? Green would be more visible. Such a low power red may be difficult to see in lit settings.
 
Hi Gazen-
Thanks for writing back...
I wasn't familiar with the laser power meter... thanks for mentioning that.... I think it's out of my price range, but I'll see if I can find someone locally who has one who can help me out.

The reason I'm using a red laser is that it has to be Class 2 (under 1 mW) for safety reasons... (my product is used in schools, etc.) I wasn't able to find that many green Class 2 laser modules. The other reason is cost- I pay about $10.30 for the red laser modules. The Class 2 green laser module that I was able to locate was 4-5 times the cost. Thanks for the thought, though.
Margaret
 
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A laser power meter that can measure powers that low will use a photodetector instead of a TEC and will necessitate using a table to match the wavelength to a % that you will have to use to calibrate the meter to. These are not cheap if they are new and recently calibrated. You might look into getting some guaranteed 1 mW laser modules.
 
Hi Paul-
That's very helpful... I appreciate it.
(I do purchase new 1 mW laser modules for my product... I just happen to have these 40 laser modules... But I'm just going to let it go- it's not worth it for me to get a laser tester just to test these 40 lasers.

Thanks again for taking the time to write.
Margaret
 
If you want absolute numbers, i.e. exactly how much power your mystery modules put out then you'll need a specialty meter designed for low powers. If all you need is a relative measurement then you could use a solar cell and a DMM (set for mA). Take a laser of known power and defocus it to cover a small solar cell (say 2x2cm) and measure the current output of the cell. Then do the same experiment with one of your unknown modules and compare the measurement to the first. Less current=less power, more=more. This only works if the lasers are the same wavelength though as the response curve of silicon solar cells is pretty nonlinear.
 
You are most welcome, Margaret. If I can help you in any way just ask. We like to see new members here that have a scientific interest in lasers. Hope you get your project up and working. :yh:
 
Hi WizardG-
Good idea! Thanks!
I'll see if someone can help me with that...

Margaret
 
So you want to make sure they are under 1 mW for safety reasons, a wise precaution.

Next question is what device to measure this with. The laser power meters used by people on this forum are not suitable for measuring that low a power level, they are more intended for thousands of mW readings, and a mW more or less is mostly noise to them. These meters are mostly thermal though since we want to be able to measure any wavelength or mix of them.

Since you have known-wavelength red lasers you can use an optical detector that is sensitive enough for the 1 mW you want to test.

A product like this would be ideal: https://www.coherent.com/measurement-control/measurement/lasercheck - apart from the price tag.

There are lot of cheap optical meters for sale, but most of them are not certified in any way, so i'm not sure how critical it is that the lasers are within limits for your applications.
 
lowtech said:
Hi-
I use Class II lasers (>1 mW) to make low tech communication aids for people who are paralyzed and can't speak. (The laser attaches to a pair of glasses, and allows a person to point to letters and words on a paper communication board using head movement.)

I'm looking for an inexpensive way to test the class/power on about 40 laser modules... (I got these a long time ago, and I want to double check to make sure that these are >1mW).

I appreciate any suggestions- Thanks!
Click to expand...
Sper scientific 840011 laser power meter about 200 bucks new. Just got one. works great. microwatt to 40mW.
 
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