Modifying Oly C-2040 into an infrared camera
I actually did this mod almost a year ago. I bought an old (well, "old" in digital camera terms) 2,1 megapixel Olympus camera for the project because it has a good, fast lens (f/1.8-2.6) and a sensor which is pretty sensitive for infrared light already with the original hot mirror in place. Also, the C-2040's white balance correction is known for it's good range; i.e. it can correct the red tinge completely.
Turning a camera more sensitive to IR means the removal of the "hot mirror" or IR-block filter and replacing it with a visible light blocking filter. The hot mirror can't simply be trashed, because air's refractive index is different from glass (about 1 vs. 1,5) and so the consequence would be that the camera would become very near-sighted without a glass "slowing down" the light.
The IR-block/antialiasing-filter pack in the C-2040 was about 2,82 mm thick (consists of several layers) and it measured 9,96 x 8,94 mm.Â I bought some IR-filter plastic from Teknofokus, it's about 2,94 mm thick and it turned out to be just fine. The cyan filter in the picture below is the original hot mirror and the black is the one I cut.
Here's the filter plastic's attenuation graph:
The Teknofokus IR-plastic is a bit "darker" than the usual Hoya R72, letting 50 % of infrared light through @ 765 nm wavelength whereas the R72 lets 720 nm respectively.
Here's the C-2040's sensor just after dismantling the camera:
As mentioned, the original filter was 2,82 mm thick, and it seems that there are some variations as Jens had a 2,775 mm thick one and Charles 2,87 mm. 2,65 mm has apparently worked, and in aÂ Canon G1 filter thicknesses 2,57 - 3,09 mm have worked. According toÂ Don Ellis, if larger apertures are soft and smaller sharp, a thinner filter is needed and vice versa.
New filter in place.