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Why not to look at the diode beam

racerxdl

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I see that most people who starts to playing with lasers get some CD-ROM lasers and when power up it, get disapointed with the bright. Only a little red light coming from it.

DONT EVER LOOK INTO IT!

But most people dont know why. So I will explain here :D

Green lasers uses a crystal to make a 1064nm IR light to excite other crystal to make the 532nm light (green), but a few IR will be with the green light too, and the human eye can only see from 720nm to 380nm. And if that isnt enought, the response of human eye is not the same at different colors. This graphic shows what human eye sees with a all-light-colors ideal emitter (A true white emitter):

(Got from Maxim-IC led site)​

As you can see, going far from orange, entering on red, the human eye gets less sensitive to the light exposure, that means, you need more power to see. (That is the same for violet)

You cannot see infrared, but something that you have in your house can. A video camera (cellphone or webcam).

Ok, I get one diode from a laser printer. I am not sure what is the frequency of it, but I think is the same as a CD-ROM laser. I got my camera a take a pic from it running in a 30mW Green DPSS driver (260mA)

Hmm, its not too strong isnt it? But its more than you can see. :tired:

:thinking:Ok but what if I say that your camera have a IR filter? yes, it have. Wanna see a pic WITHOUT the Infrared filter? Or, in other words, the REAL bright of the laser? Ok, I taked one pic with a Common CCD Camera with the IR Filter removed, here is it:


More powerfull huh? It can even pass through my fingers!

Ok, wanna see a photo with the TWO images at same time? Ok, hooked up the CCD camera on my computer, and filmed the screen of the computer and the IR laser diode. Here is the pic:

You can see a little pink light in the picture, that is the laser, its weak even at a normal camera, but see on the screen what is the brightness.
And here you can see, the laser pointed to the desk:

So, the little dim red that you see on the diode, its in fact a REALLY powerfull beam, that you cannot see, but it will make some damage at your eye. Maybe a little powered one <5mW doesnt do a instant damage to your retina, but not use a Safety Glasses can make your eye worse over the time.

:tsk:So DONT be fooled with the dim red light :D


This laser doesnt even makes light on my desk with the lights turned off and seeing with a camera, but with a IR camera, you can see how powerfull is it. If you want to know what is the power of that laser above, its only 10mW with no lens.

Soon I will put a video here that shows that laser diode, and complete with more information. So if you know something that I should put here too, say it :D

I hope this helps people understand why use safety glasses, I dont know if its already something like that I made, but I wrote this by myself for help the forum :D

Good luck :D
 
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Just one clarification, a diode only emits a single color. Red, blue, and violet laser diodes don't emit any IR light. Only IR diodes emit IR light.

Green modules produce green light by starting with an IR, so the IR leaking out of green lasers is just that, leakage coming from the IR diode behind the crystals that convert IR-to-green.
 

chipdouglas

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good job on promoting safety. and those pix are pretty good too

michael
 

Toke

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I have just ordered an IR webcam on ebay for the exorbitant sum of £5 with shipping.
If nothing else it should be able to tell me if an IR diode is on or not. :D
 
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Just one clarification, a diode only emits a single color. Red, blue, and violet laser diodes don't emit any IR light. Only IR diodes emit IR light.

Green modules produce green light by starting with an IR, so the IR leaking out of green lasers is just that, leakage coming from the IR diode behind the crystals that convert IR-to-green.
Dont forget the 1064nm created by the KTP, green lasers are pumped by 808nm but
emit a total of 3 wavelengths out the aperture. (unless IR filtered that is)

808nm, 1064nm, and finally 532nm.



I have just ordered an IR webcam on ebay for the exorbitant sum of £5 with shipping.
If nothing else it should be able to tell me if an IR diode is on or not. :D

A good rule of thumb if hooking up IR LD's. is always wear appropriate goggles
if your intent is to power it up.

Mistakes are even easier to make when you cant see a physical indicator
as you would have with a visible wavelength.
 
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qumefox

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Actually the ND:YVO4 is responsible for the 1064nm.

The 808nm pumps the ND:YVO4, which generates the 1064nm. The KTP then doubles the 1064nm into 532nm. So what you actually get out of green DPSS is 1064nm and 532nm. Very little 808nm makes it through.
 
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Actually the ND:YVO4 is responsible for the 1064nm.

The 808nm pumps the ND:YVO4, which generates the 1064nm. The KTP then doubles the 1064nm into 532nm. So what you actually get out of green DPSS is 1064nm and 532nm. Very little 808nm makes it through.

LOL, typing while thinking will get you every time...
I stand corrected :beer:

The 808 will vary in strength depending on the setup.

I was taking some pics while testing 808's, both on my LPM
and seen in this pic there is a noticeable presence of 808 NIR.
The 1064 appears more whitish, and the 808 almost a pink.
808 actually looks similar to a NIR 780nm on my cam.
To see the 1064 you would have to block 808 and 532,
this I have yet to do.


This isnt the best reference pic, but you can see some of the
IR at the base here. The less efficent the conversion becomes,
the more 808 will make it through. If you have a dead crystal,
or poor alignment, the 808 still passes and makes it into the optics.

This is more of a problem when the laser does not use an FAC.
An FAC will drastically reduce the amount of 808 that can pass
by the rapid divergence and fine focal point used for pumping.

If there are no optics between the pump and the medium, the
808 uses the medium like a tunnel.

Ill be adding some other pics to my 532 thread, and will include some
showing the IR and the filter assembly...



I made up this test jig to verify my 1W LD's wavelength's... The crystal
set is in front of the LD, with no FAC...
 

BShanahan14rulz

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great post! Interesting to note that the camera with the IR filter still sees the IR, but as a dim, pink light. So, if you see a dim pink light on camera, don't assume that it's a really weak IR diode.
 

racerxdl

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Yes, as you can see in the pictures, in a CCD camera without IR Filter, the light blinds completely the camera, and can illuminate my desk (In fact, it can illuminate my entire room with only a SINGLE laser diode, so it IS powerfull), but a common camera doesnt see 90% of the light.
 




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