I’m trying to figure out a robust filter design for the finger tracking camera of my future touch screen.  Using an unfiltered lens and an Edmund Optics NT43-954 visible light filter, I get very poor results, this should be called the “sunglasses” setup.  However, using the lens of a Logitech webcam in combination with the NT43-954 I get superb results, almost complete ambient light cut off but still able to see IR leds.  I’m guessing with the latter setup I will have to crank up the number of IR leds I use quite a bit, since I will not have the benefit of looking directly at an LED itself, but rather a reflection.  I must assume that the Logitech lens has an IR filter of some sort installed, does anyone use an IR filter in addition to a visible light filter?  Overall, can anyone recommend a good filter solution or “weak” IR filter?

I’m pretty sure you wont see the blobs if you use the original lens.

You will want to get a longpass filter that cuts off as much visible light as possible.  dont look for photographic filters, you will probably have more luck with sites that sell optical filters for research etc. I got a 850nm long pass filter for about £10.

You need to use your table in the dark/indoors to stop IR light polution from the sun and certain types of lighting.

you can get a bandpass filter that only lets in the wave length of light from your leds, but these are more expensive