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Back to the IR light source concept...
I have never found any economy in building what I can buy. Just takes
to much time. You can buy inexpensive IR gells from which you can cut out what you need. Look for a low pass gell at about 750nm. A cheep way is to process a sheet of unexposed slide film if you need a large piece. Or take some of the ends from a processed roll of 35mm or 120 slide film. You can layer them if you need it darker to visable light. Performance wise though, it is going to be hard to beat a real IR illuminator like what is use on night vision devices. Oh by the way, all CCD sensors are sensitive to IR (down to 1300nm) light. All you need to do is to remove the camera's high pass filter and replace it with a clear to IR glass. I have been playing around with a CCD digital camera with a Hoya R72 (720nm low pass) It is an Olympus 2020 and I am comparing it to Kodak HIE film with the same filter. The film is about 5 stops faster than the digital sensor. Don Bruder wrote: Some of you may recall my post a few weeks ago asking about IR LEDs, filters, and other yakkety-yak about cheap ways to fab a light source that puts out either pure IR, or "close enough to it", with little or no visible component, for use in what boils down to a homebrew "Night Vision" system designed around a video camera that has a well-demonstrated sensitivity to IR in the same region of the spectrum that TV remotes use. |
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