Seeking safe, low power IR laser diode. Advi

[astronomerroyal]

Wondering if you could offer some advice. I'm looking for a very safe, very low power IR laser diode.

requirements
>800nm
I think a Class 1 or Class 2 rating would suffice.
It must be safe to use around animals and humans.
Cheap.

Is it possible to use an IR diode from a DVD burner in combination with, say, a potentiometer, to achieve very low power ratings, perhaps ~1mW? Or will the relatively high powered laser diodes simply not work at these low levels?

The application is a' laser tripwire' that fires a camera. I'm currently using red laser pointer diodes. I want to replace these with IR, since I want to photograph wild animals (and so desire an invisible 'tripwire' that is safe).

Thanks in advance for any pointers (no pun intended).

 

[SenKat_Stonetek]

Re: Seeking safe, low power IR laser diode.  

Wondering if you could offer some advice. I'm looking for a very safe, very low power IR laser diode.

requirements
>800nm
I think a Class 1 or Class 2 rating would suffice.
It must be safe to use around animals and humans.
Cheap.

Is it possible to use an IR diode from a DVD burner in combination with, say, a potentiometer, to achieve very low power ratings, perhaps ~1mW? Or will the relatively high powered laser diodes simply not work at these low levels?

The application is a' laser tripwire' that fires a camera. I'm currently using red laser pointer diodes. I want to replace these with IR, since I want to photograph wild animals (and so desire an invisible 'tripwire' that is safe).

Thanks in advance for any pointers (no pun intended).

Since laser diodes are creatures of current - you can reduce the current going to the diode, and reduce the emissions to just above the lasing threshold....I would still be careful, as IR is tricky to work with...if you have some NOD's or night vision on your camera - you can most likely adjust the diode's output by observing the beam THROUGH the NOD's. Be careful - I am sure you will want to see your pictures, so don't booger up your eyes !

 

[astronomerroyal]

Re: Seeking safe, low power IR laser diode.  

So do you think the '200mW' OEM IR diodes that your company is selling would be appropriate. i.e. Is the lasing threshold very low, effectively couple of mW? Seems a long way from 200mW to 1-2mW.

mouser and digikey didn't return anything feasible.

Also I can't take a 'pulse-width modulation' approach to reducing the time averaged power since the sensors are fed into a microcontroller that expects a constant laser signal.

I have night vision equipment for testing. I also have some potentially useful blue filter gels for extra reduction (curiously they have an increasing transmissivity longward of 700nm), but want to keep power consumption as low and efficient as possible.

 

[SenKat_Stonetek]

Re: Seeking safe, low power IR laser diode.  

So do you think the '200mW' OEM IR diodes that your company is selling would be appropriate. i.e. Is the lasing threshold very low, effectively couple of mW? Seems a long way from 200mW to 1-2mW.

mouser and digikey didn't return anything feasible.

Also I can't take a 'pulse-width modulation' approach to reducing the time averaged power since the sensors are fed into a microcontroller that expects a constant laser signal.

I have night vision equipment for testing. I also have some potentially useful blue filter gels for extra reduction (curiously they have an increasing transmissivity longward of 700nm), but want to keep power consumption as low and efficient as possible.

I would work with the IR diode from a cd/dvd burner first off - although it is 780nm (approx) you would get a good feel for the type of driver you need, as well as the initial setup. After you experiment, and figure out HOW to do it, then spend money on other diodes The 200mw Ir diodes I sell are decent, but powerful - you will need to build a good current limiting circuit - and test carefully. When blocking IR from your eyes - be certain that you are not blocking ambient light at the same time - that allows your pupils to dilate, and can let in more Laser Radiation. IR diodes are dangerous "toys" since you cannot see the beam you are working with most times. Be careful in your approach !

 

[astronomerroyal]

Re: Seeking safe, low power IR laser diode.  

Thanks for all the advice. Clearly this project is going to take a lot longer than I anticipated. Finding a cheap, borken DVD burner doesn't seem like a trivial business either...

Regards,
AR.

 

[MarioMaster]

Re: Seeking safe, low power IR laser diode.  

why not just take apart a CD ROM drive? you can get them for less than $10 in some places and they have ~5mW 780nm IR diodes that would be perfect for your project

the problem is finding one that has a normal diode can that you could say put into an axiz housing

 

[MarioMaster]

Re: Seeking safe, low power IR laser diode.  

http://cgi.ebay.com/INDUSTRIAL-LASE...VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247

the price isn't real cheap but this would work well for your project - it's completely assembled and ready to go

 

[astronomerroyal]

Re: Seeking safe, low power IR laser diode.  Advi

Excellent find, thanks. Although they don't actually provide a datasheet, the 785nm 3mW module looks promising and reasonably affordable (time is money etc.) I may fork out for the 980nm, since I'm not entirely sure 780nm is completely invisible.

Cheers.
AR.

 

[SenKat_Stonetek]

Re: Seeking safe, low power IR laser diode.  

808 is not entirely invisible, either....it is deep, dark red ! It is so deep though - that is loses most of its' brilliance early on in the beam.

 

[Kage]

Re: Seeking safe, low power IR laser diode.  

Don't forget that although the DVD and CD 780 diodes collimate pretty well, most 808 pump diodes Don't.

 

[MarioMaster]

Re: Seeking safe, low power IR laser diode.  

yes, but that's only with high powered multimode diodes, the 5mW and such lasers will have standard diodes and should collimate fairly well

 

[hutch123]

Re: Seeking safe, low power IR laser diode.  

I think that astonimerroyal needs to be aware of the frequency of the IR diode, and the type of camera he's using. He said he wanted to photograph animals with a invisible tripwire.

Many digital cameras see IR quite well, and it would probably show up on the image taken by the camera. I assume that if you see it on the preview screen, then it will also be captured on the image. Of course, I haven't actually done this yet, so it's just theory...

Good luck!

 

[astronomerroyal]

Re: Seeking safe, low power IR laser diode.  

The device I built turns the lasers off when the laser tripwires are broken, therefore they won't appear in the photograph. I use a microcontroller to take care of the details.

specific requirements:

1). the time averaged laser flux density hitting the animal is within a safe level (particularly concerned about eyes).
2). the flux density falling on the sensor is large enough that it can easily be discriminated against ambient light levels.
3). the beam is sufficiently collimated that it won't diverge much as it travels towards the sensor, thus allowing for large emitter/sensor separations without the 'inverse square law ' becoming problematic.

Using a IR laser (as opposed to an IR LED) guarantees points 2 and 3.

I was thinking of buying those 5mW 980nm ebay laser modules (I assume there isn't generally much competing ambient 980nm light), using them somewhat defocused, and driving them as weakly as possible. The seller didn't provide the lasing threshold when I requested the datasheet, but I assume if 5mW is the upper limit then I can probably get down to 2-3mW by simply adding a potentiometer.

*Alternatively* I can also turn the lasers off when the microcontroller isn't checking the tripwires, and then turn them on just before the microcontroller wants to check the tripwires. The duty cycle might be sufficient that the time averaged ON state is small, <<100%, and the time-avergaed flux density is correspondingly small.

Q) this might be beyond the forum's scope, but does anyone have a feeling for the turn-on time of a generic lower power laser diode? For the above idea to work it would have to turn on in less than 10^-5 seconds.

Many thanks for the comments.

 

[artix]

Re: Seeking safe, low power IR laser diode.  Advi

why not try a CD player :

 

[Chicxulub]

Re: Seeking safe, low power IR laser diode.  

808 is not entirely invisible, either....it is deep, dark red ! It is so deep though - that is loses most of its' brilliance early on in the beam.

I have a roughly 70mw 808 that used to be a pot modded Leadlight, and my dogs, who are absolutely psychotic about chasing lasers, can't see it.

Just a point for the OP.


edit- For the OP, when you get this working, please check back to let us know how your project fared. I for one am dying to know how this will work out for you.