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DIY laser power meter

T

toked323

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anyone know anything about these a guy on ebay sells them that you hook straight to a multimeter anyone know how to build them i did google but only found 1 place
 





i wouldn't bother with those, they tend to not be very accurate especially if using a different wavelength to that which it was calibrated
 
Toked - Those things have been proven to be garbage, and not even worth the postage. The ebay seller even leaves unprovoked negative feedback on people.
 
oh, see i want the coherent handheld power meter but it costs a bit i thought these would be cheaper but on Sam's Laser facts shows its more trouble than what its worth
 
i too would love to measure laserpower.. the lasercheck as the cheapest, err, least expensive commercial model still is out of my reach. and isnt that great neither, "only" silicon sensor, not too accurate (5%), only low range etc.

there is a project on die4laser: die4laser.com/D4Thing/D4Thing.html (i may not post links)
this just looks *great*, powermeter, very versatile, use "any" sensor you like, calibrate it yourself, and has an integrated hotplate-function as well. if anyone cares/dares to solder laserdiode-chips :-)

so.. how to get one of those beauties?
only ebay?

manuel
 
so where can you get a laser sensor like the one shown?
the same thing could be done (without the extrapolation feature) using a lcd voltmeter like this one:
http://www.dse.com.au/cgi-bin/dse.storefront/4744cc7709ca2e36273fc0a87f9c06ed/Product/View/Q2220
and a resistor voltage divider, which you could calculate if you know the output of the sensor in mv/W and the input of the lcd, which for this one is 200mv (it will display 1999 for 199.9mV)
unless you wish to test different sensors or use the extrapolation, i think for a diy meter, this will do
 
Does anyone know how to make one? It would be a very helpful instrument for the tuning of my lasers
 
Well, if I was going to try such a feat, I'd use a small silicon cell, and a concave lens to difuse the beam before hitting the cell. I'd just hook it to a cheap meter movement (yup, an old coil-driven meter). I'd experiment with resistors (if necessary) to avoid FSD on the meter.

I'd mount the lens and cell so that there was always a fixed distance, and so that the spot was a convenient size for measuring (covering about 50% of the area of the cell). Then I'd put the lens/cell assembly into a light-tight enclosure with only the hole at the lens for the laser beam to enter.

Then, I'd test the system with a few KNOWN power lasers of a single wavelength... a 5mW, 50mW, 100mW, 200mW, and I'd physically mark those readings on the meter. I'd repeat the same for each color I wanted to use - red, green...

Now this is the barest of cobbled-together, cheap, duct-tape chic power meters you can get... but you'd be AMAzed at how useful such items can be!

The biggest challenge is getting access to KNOWN power lasers. Not all manufacturers have the same standard apparently, from reading posts here.

Let me know if this helps.

D
 
woop said:
so where can you get a laser sensor like the one shown?
the same thing could be done (without the extrapolation feature) using a lcd voltmeter like this one:
http://www.dse.com.au/cgi-bin/dse.storefront/4744cc7709ca2e36273fc0a87f9c06ed/Product/View/Q2220
and a resistor voltage divider, which you could calculate if you know the output of the sensor in mv/W and the input of the lcd, which for this one is 200mv (it will display 1999 for 199.9mV)
unless you wish to test different sensors or use the extrapolation, i think for a diy meter, this will do
Click to expand...


Hey Woop -

Can you re-check that link ? Nothing pops up other than, "You must be logged in to buy stuff"
 
xanatos - That's exactly what I started with. What I found was that the silicon cell will max out at a VERY low light level, even if I expand the beam to be considerably larger than the cell. I didn't want to use ND filters (mainly because I don't have any). What I'm looking at now is bouncing off a piece of plain glass to get maybe a 95% reduction, possibly in 2 stages if necessary before hitting the cell.
 
OK, good to know. Yeah - I'd probably be doing the same thing you are, except that I have a few NDFs laying around. Sorry I didn't have anything more robust for you.

D
 
As a possible means of reducing hte strength of hte beam, you can use opaque plastic (like white). As long as you have the capacity to do the math for the conversion factor, you won't flood the cell at that point. The whole idea is to get as much of the beam, dot, etc measured, to as accurate a point as possible, right ? So - using an ND filter, or anything opaque, or a reflector of sorts really is just up to taste, and functionality is secondary - as long as you know at what level the power is being reduced - you will be good to go.
 
I figure I don't even have to determine how much of the light is being eliminated, since the whole rig will need calibrating against a reference meter anyway (and at each wavelength I want to be able to measure).

The biggest problem I have with using a 5% reflection is where to send the 95% beam without either smoking something, or bouncing light back into the measuring area. I guess I could let it pass right on out the other end of the case. That might be good anyway because then I could tell when I had the beam aligned.
 
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