IR Diode's that do not produce a bar..?

[DaveC]

Hi All....

First post for me, and won't be the last, I'm sure I will have a string of dumb questions....

So, first one...

I have made myself, and works very well, an IR Laser illuminator for my night vision setup. My Night vision consists of a Sony camcorder with night shot mode bolted to the back of the telescopic sigh on my air rifle, with this I hunt. Before this I had this setup with a IR torch, but this only worked at very short range and was not much use in the field.

I have built a IR laser using a 300mW 808nm diode and found a lens of one of the board CCTV cameras worked very nicely, I have a lathe and making the housing was a simple job. The image I get is good and can now see a good 100+ yards (not that I shoot at that range, 40yards is the max for me), so happy so far....

But....

The shape of the IR beam bugs me, although it does the job and works OK, I think I can do better, I do not like the bar or letter box shape of the beam. I have read through as much as I can find on this forum but not found the answer yet.

Are there any IR 808nm diodes (200mW+) available that produce a dot (round) rather then a bar...?

The other alternative is to use a 780nm Diode, not tried these yet, assuming these will work with my setup, are these the same shape bar output, or are these round. If they are not a bar where can I get a 200mW diode from..? I have tried eBay and can't seem to find any.

There is another IR 940, but I tried an IR torch of this wavelength and just could not see it at all, so no point trying these.

Thanks in advance,

Dave

 

[Eudaimonium]

Hey DaveC, welcome to the forum

A lot of high power IR diodes produce the bar instead of round or eliptical beam profile, it's simply because of how the emitter of the diode is constructed - it's wide, but thin. If it were of regular dimensions, power emitted drops significantly.

You can try 780nm diodes from CD burners (or DVD burners), those do produce fairly eliptical beam profile however they do not go much above 150mW with good life.

Instead, I'd reccomend you to look for diodes with integrated FAC lens.

FAC stands for Fast Axiz Correct, and fast axiz is that axiz of the beam profile which diverges more rapidly, producing wider beam than it is tall (slow axiz).

You can also correct the beam yourself with a couple of extra optic pieces if the diode does not have the lens integrated. There are two ways that come to mind right now - cylindrical lens (crude, but will do for your application), or anamorphic prism pair, which is more expensive but more precise solution.

Hope it helps a little bit If you have anything else to ask, you can always send me a Personal Message instead of opening new threads (if you don't feel that the questions don't deserve a seperate discussion on a thread).

 

[Fiddy]

^^^ on the money!

I harvested a 780nm reader diode from a car audio CD player, heres a movie shot through my night vision monocular at night of its dot at say ~30m away.
Using a axiz 3 element glass lens too.

the divergence isnt as bad as a 1W 808nm diode, as you can see its still a multimode diode that produces a smaller bar.

 

[DaveC]

Thanks guys, some interesting information there.

I may try a 780nm diode of a lower power, I have seen some 100mW ones on ebay and cheep enough not to worry if they don't work.

I have two night vision units, the one on the gun which is a Sony Camcorder and the other is a Yukon Gen 1 hand held unit I use for spotting. The camcorder can't see the illuminator on the Yukon unit, but the Yukon can pick up the 808nm laser. I did try a 940nm illuminator, which is supposed to be good for digital NV, thought it may have worked with the camcorder, but nothing, could not see it at all. So hopefully the 780nm will work well. Worth a try.

Thanks again for the replies.

Dave

 

[Fiddy]

yep! my gen 1 yukon equipment see's 780 & 808m, but not 980nm.
Although my Yukon Digital Ranger uses 980nm for its on-board illuminator and can see 780,808 and 980nm