For bright flashes of visible light, xenon flash tubes are the choice. But when I want a really bright flash on about 800-900 nm, what approach is the best? One application is a security camera taking a snapshot without alerting the adversary with a flash. (Could be a good system against black-bag jobs.) Another application, with higher flash frequency, could be a stroboscope throwing the AGC circuits in cameras off-track, Macrovision-style. What would be the best approach? The energies here are more in the range of rotation/vibration changes than electrons jumping up and down between the energy states. How to convert a blast of electrical energy into a shower of near-IR photons?
Thomas Shaddack <shaddack@ns.arachne.cz> wrote:
What would be the best approach? The energies here are more in the range of rotation/vibration changes than electrons jumping up and down between the energy states. How to convert a blast of electrical energy into a shower of near-IR photons?
If all you're trying to do is screw with surveillance cameras, a Xenon tube is crushing a fly with a crane. You can probably get away with an IR laser and a diffuser or something to that effect. It would be cheap (diode laser) and easy to build (for a strobe-like effect it would take, what? a 555, a couple resistors, a cap, and the diode). If you want, you can probably extend this idea to much more IR output just by adding more diodes and more juice. I don't remember the numbers off the top of my head, but IIRC the efficiency of a diode is substantially greater than the efficiency of a Xenon tube. Just took a quick look around, and it seems like a Xenon would still work at 900nm: http://msp.rmit.edu.au/Article_03/02a.html Apparently, Xenon tubes put out lots of crap around 900nm. In fact, it's somewhat more than they do in the visible spectrum. If you get yourself a good enough filter, you might be able to pull off a mega-photon-dump setup. -- Riad Wahby rsw@jfet.org MIT VI-2 M.Eng
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Riad S. Wahby -
Thomas Shaddack