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Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
"In order for a CCD to work, as designed, the photon it detects must have a minimum energy(or maximum wavelength) for a given applied voltage. This energy/wavelength is determined by the work function of the material the device is constructed out of and the applied voltage. The applied voltage is limited by the device's construction, too much and it would fail(like overvolting a capacitor). Combined these two factors give the absolute limit, based on the photoelectric effect. The are other limits before this based on S/N." Interestingly, exactly the same logic aplies to human vision of IR, if there isn't enough energy to flip the cis form of opsin to the trans isomer then the eye cant see it. On the other hand, a fully dark adapted eye can see the IR from an IR led.
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
Getting back to topic, Ã have now completed the IR Conversion of my old Coolpix 2500. This is what the process looked like:
On top is the exposed CCD of the camera, on the bottom the material for the new filter: Microscope slide and exposed / developed negativ film. On the right you can see the resulting replacement optic, consisting of two pieces of glass sandwitching the film with expoxy glue, ground to shape with an ordinary belt sander. After putting the camera back together, I was quite surprised that it actually worked. This is me, wearing a completely black t-shirt:
Not very black to near IR, it seems. Of course this is rather boring compared to a "true" FLRI cam, but for a friday evening... btw, there is a FLRI head on eBay, item 7615428151, make sure to check it out! I am sure there are some geeks on this board who could build the electronics around it. I would buy it myself, but knowing my luck with digital electronics I better pass, and play with near IR.
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155
Filters – um don’t old Honeywell photoacoustic CO2 sensors have an IR filter? IIRC they look like a wafer of opaque ceramic. --- hmmm, I will look into this if you like. If not there are numerous IR proximity sensors that have a true filter/lens in all sorts of shapes and sizes.
As for IR active lens --- I had always wondered how well a cheap gold parabolic mirror in a retrofitted telescope optics body would work.
IIRC the original CCD cameras were cryogenically cooled with a junction device. An inverted can of liquid air (or any other gas) piped though an expansion nozzle may work. Mind you up here at certain times of the year they sell heater blankets so the video cameras will work for more than a few minutes in the cold.
btw: Light amplifier technology has been around for ages. It bypasses the limits of using only photoelectric active devices.
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Digicam IR conversion [NEW: Conversion complete with pix]
