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Rich99

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I don't imagine your DIY LPM is calibrated in any way?
Nope, just followed the instructions on the image. I imagine the readings are + or - a few %.

113mw was the peak power achieved over 3 tests with new batteries.
 

Rich99

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I've also used a technique using a CCTV camera or cellphone to determine if there is IR, it won't tell you how much. If there is only a little IR, you may not see anything so be aware. I originally used this technique to compute the beam angle of various IR LEDs for another project.

With the room a little on the dark side, from 3'-4' away shine the laser onto a wall. If there is a fair amount of IR, through the camera you should see fairly distinct rings/circles around the bright green one in the center. Because of the different wavelengths the beam 'cones' spread differently through the lens. Longer wavelengths produce larger circles. Your eyes will tell you which one is from 532nm (the visible one in the center), but the cameras may also see the surrounding circles produced by IR.

If the 532nm is quite bright, it may wash out the IR circles in the image so your mileage may vary. The safety goggle suggestion for use as a filter might remedy the 532nm but make sure you don't physically damage the goggles. Cheap ones are probably plastic, don't want to accidentally burn a hole in it. And watch out for reflected light off the goggles (or any DIY lens) too.
Just tried this but couldn't make out any rings. The dot on the wall is too bright to make out detail. I have tried to post a picture. (Only got my tab, sorry for bad formatting/rotation).
 

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Rich99

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If you have an LPM, just having two decent sets of goggles will also work just fine. Block off the green light, and what you're left with is IR. I found it easier to do testing that way, vs taping on little IR filters onto lasers. You may even be able to use the "better than nothing" goggles from my signature for that, though I'd test the goggles themselves first to make sure they work.
I will try this when I get some goggles
 

diachi

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Nope, just followed the instructions on the image. I imagine the readings are + or - a few %.

113mw was the peak power achieved over 3 tests with new batteries.

Hmmm, I'd be surprised if it's that accurate - but you never know I guess. That said, it still gives you some relative readings for different lasers, even without any calibration, so that's a good start!

Perhaps send one of your lasers off to someone with an LPM to compare and see how accurate it is? Or have someone send you a laser of known power to compare?

Also ... please avoid multi-posting :( Just bugs me more than anything ... That's what the multi-quote button is for! ;) Sorry to be a pain! :D
 

Rich99

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Ah yes, multi quote.

Sorry, don't use forums much.

Well it does light matches so I guess that suggests it is moderately accurate at >100mw. Will be fun to test the batch of cheap ones on the way.
 

diachi

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Ah yes, multi quote.

Sorry, don't use forums much.

Well it does light matches so I guess that suggests it is moderately accurate at >100mw. Will be fun to test the batch of cheap ones on the way.
All good - takes a bit to get into the habit! :D



Lighting matches isn't a great indicator of power either. It gives you an idea of the lowest power it could be. I'd say it's safe to say what you have is >50mW at least. Last time I metered my cheap green it was doing ~90mW - it'll light matches no problem. Actually it'll light red tipped matches faster than my pocket series from Sanwu which is supposedly nearly 3x the power - colour makes a big difference! ;)

As I said - it's still a good indicator of relative power either way! :yh:
 

Rich99

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I'm interested. More knowledge is always good in this hobby.
Ok, first batch in of six (two of each). All advertised as 1mw
650 1 - 8mw (wow, one that might actually be safe to use as a damn pointer... just)
650 2 - 14mw
532 1 - 25mw
532 2 - 61mw (just about puts holes through very very thin black plastic-won't light match)
405 1 - 17mw
405 2 - 24mw (destroyed in the name of science)

Original ebay green reading ~mw120 with new li batteries and focus adjusted.

It is brighter than all the others put together.
 

Rich99

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Another 532 and 405 arrived.

The 405 is putting out ~40mw and the unit comes apart very nicely in order to adjust the focus. I discovered that using a glass of sunflower oil is perfect to adjust the focus as it produces a very clear beam allowing you to see where the maximum focus is. It now burns up bin bags at 4 feet!

Also a glass of neat blackcurrant works for separating the green from the ir using a phone camera.

Anyways, after having a good look around it is clear that I have neither the knowledge or access to kit I would like to start the project I wanted. Buying complete lasers or completed self assembly kits would feel like cheating!

It's a shame nobody does courses on this in the UK as I learn best when being shown.

Ah well, mods delete account pls
 




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