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Topic: DIY Laser Listening Devices (Read 24233 times) previous topic - next topic

DIY Laser Listening Devices

Build the Long Range Laser Spy System

http://www.lucidscience.com/pro-laser%20spy%20device-1.aspx

Quote
You can use any laser you like for this project, and there will be no quality difference whatsoever between a state-of-the art lab laser and a $2 pointer. The only disadvantage to using a cheap laser pointer is that you will have to modify it for an external battery pack if you plan to have it on for more than a few minutes at a time, but that is an easy task.

Basic Test System



Very Simple Light to Sound Converter



Laser Spy Light to Sound Receiver Schematic



Final Laser Spy Light to Sound Receiver Schematic



Final Version


Re: DIY Laser Listening Devices

Reply #1
I actually saw this years ago in an electronics book but cannot remember the name of the book or the writer (who is pretty famous, darn bad memory!)

But still a good project. Only if I had some people to listen to... :)

Re: DIY Laser Listening Devices

Reply #2
A good thing about this project is that it's well documented, and who doesn't want a cheap laser listening device.

DP could make gadgets like this (laser to be acquired separately), they should sell well.
 

Re: DIY Laser Listening Devices

Reply #3
Are there infrared lasers so that the tell-tale red dot is not visible?

Re: DIY Laser Listening Devices

Reply #4
Invisible Lasers  (@ Laser Community)

http://www.lasercommunity.com/invisible-lasers-f13.html

Quote
With IR lasers the idea is that it is "more or less" invisible. If you are suggesting getting a 10mW IR laser, you wont really see anything. If you buy a 400+ mW 808nm IR laser you will see a slightly red tinted dot. So the voltage of running a 10mW IR laser is totaly irrelevant. Bottom line is, its 10mW and more or less invisible.

If you want to see a "bright" dot at 50 or so foot, you want a green. But if your heart is set on IR then 10mW is WELL to low of a power for seeing a "bright" dot. Especialy at that wavelength. I dont know your application, however if its just gonna be a bit of a big boys toy, then a 10mW Ir at 980nm isnt really going to be any fun.

Re: DIY Laser Listening Devices

Reply #5
Lasers can damage your eyesight.  With an IR laser, I think you may be able to damage your eye without actually seeing the beam.

"Do not stare into this laser with remaining eye."

Re: DIY Laser Listening Devices

Reply #6
Wow, color me surprised, but nobody can spell collimated in the Laser Community.

Re: DIY Laser Listening Devices

Reply #7
[quote author="blarson"]Lasers can damage your eyesight.  With an IR laser, I think you may be able to damage your eye without actually seeing the beam.[/quote]Good point, but listening in to remote environments is usually illegal, so it's probably best to not get caught.  Maybe you could pair a red laser with an IR laser, use the red for sighting and then turn it off once the whole thing has been aimed properly.

Re: DIY Laser Listening Devices

Reply #8
[quote author="rsdio"]
[quote author="blarson"]Lasers can damage your eyesight.  With an IR laser, I think you may be able to damage your eye without actually seeing the beam.[/quote]Good point, but listening in to remote environments is usually illegal, so it's probably best to not get caught.  Maybe you could pair a red laser with an IR laser, use the red for sighting and then turn it off once the whole thing has been aimed properly.
[/quote]
This project works the same way. You turn the red laser for just "target acquisition", the spoof with IR laser.

Re: DIY Laser Listening Devices

Reply #9
[quote author="tayken"]This project works the same way. You turn the red laser for just "target acquisition", the spoof with IR laser.[/quote]Thanks.  The Laser Community site also seems to reveal that green laser pointers are actually IR lasers with a crystal that cuts the frequency in half and shifts the IR to green.  Remove the focusing crystal and it's IR.

Also, the Theremin version used IR without the laser.  Cool stuff.

Re: DIY Laser Listening Devices

Reply #10
This seems like a really easy kit to put together, there's probably already one at adafruit or makershed?
Got a question? Please ask in the forum for the fastest answers.

Re: DIY Laser Listening Devices

Reply #11
[quote author="rsdio"]
The Laser Community site also seems to reveal that green laser pointers are actually IR lasers with a crystal that cuts the frequency in half and shifts the IR to green.  Remove the focusing crystal and it's IR.[/quote]
Not all IR is created equal(ly invisible). Green lasers use 808nm IR laser diodes. 808nm is listed as IR but when powerful or focused it can been seen as dim red. Also the crystals aren't all that efficient so the 808nm diode is much more powerful (dangerous) then the resulting green 532nm beam.
A 5mW 980nm laser would be better. Aixiz.com has one, not sure if its suitable since divergence (beam spread) isn't listed. Technically even 980nm can be seen if your hit straight in the eye but its a lot less visible then 808 at least.
LaserPointerForums.com (LPF) is a great source of info. I'm actually a wandering LPF member.

Thought I would mention in case anyone really is interested in building one.

Re: DIY Laser Listening Devices

Reply #12
Really this thread needs a  very significant safety warning, lasers are NOT toys they are a danger to yourself and the people around you, and unless you are prepared to pay several hundred $ for safety equipment, your risking your long term vision.


If you can "see" the beam /dot you are already in danger of going blind.....*.
Then there is the issue of lasers that are out of your "visible" spectrum, they will STILL damage your  retina, this also includes  the new LED diodes especially BLUE. Read the research, guarantee you will not be looking directly at modern LED's again.


*it always amazes me that people think that once laser light has bounced, it is somehow magically different. When you see a laser beam/spot, exactly what do you think you are looking at? the lazed photons are STILL entering your retina otherwise you could not see them, just the damage takes longer.

Re: DIY Laser Listening Devices

Reply #13
[quote author="hardcore"]Then there is the issue of lasers that are out of your "visible" spectrum, they will STILL damage your  retina, this also includes  the new LED diodes especially BLUE. Read the research, guarantee you will not be looking directly at modern LED's again.

*it always amazes me that people think that once laser light has bounced, it is somehow magically different. When you see a laser beam/spot, exactly what do you think you are looking at? the lazed photons are STILL entering your retina otherwise you could not see them, just the damage takes longer.[/quote]Can you link to some of the research that you mention?  I thought that the only reason lasers were dangerous to the eye is because of the coherent beam.  LEDs and reflected laser light is no longer coherent.  High wattage is also an issue, so I can believe that non-coherent light could be a problem if it is high-powered enough.

Re: DIY Laser Listening Devices

Reply #14
Hi,
yes you are correct , but what is a 'coherent' source?
Take a laser , shine it in a mirror and look into the mirror,  Yes I know it is an 'exaggeration' but it will give you a faster result than the laser being reflected from another surface.

I've been looking for my papers on 'Blue' light and free radical damage to optical systems , but its been 3 years all I can find is this:

Okuno, Tsutomu (2008) Hazards of solar blue light.

It relates to 'solar' radiation but the interesting conclusions were the fact that certain frequencies "oxidise" the chemical structure of the eye releasing 'free radicals" more so than other frequencies.


Several years ago we were manufacturing LED lighting, and we ran into a number of 'issues' related to the workers on a Q.A Production line, so we did some research into it, and we were rather surprised by the findings and the more we dug the more 'interesting' it became.

Other issue relate to exactly what power is classed as "high", initially LED lighting was not covered  by  Safety requirement for  emissions, but mid 2000, the British Standard institute and Europe suddenly started to introduce an emissions standard for LED lighting.(which annoyingly I have misplaced)

The real issue is that there have not been any realistic long term studies into more recent semiconductor LED's and laser chips.