I did my senior design project on an infrared related area. Things look really weird in the infrared.
http://imgur.com/SLGvT,y79tC
First image - can you guess which one is diet coke, and which one is water?
Second image - I was shining a 940 nm IR LED through my hand, you can see veins.
I can make this more interesting!
So webcams generally always respond to IR light. If you look at the front of your remote with our camera phone and press a button, you will see a bluish whitish light. Well, that seems a little weird at first. The light that's coming out of the LED should be closest to red... Well, when CMOS camera companies make their cameras, they heavily rely on the blocking abilities of the IR filter. They want to get amazing signal to noise ratios for the visible spectrum, and the combination of materials that does this is also absorb IR light as well. They can just use a coverall filter to get rid of the infrared light.
http://imgur.com/SLGvT,y79tC First image - can you guess which one is diet coke, and which one is water? Second image - I was shining a 940 nm IR LED through my hand, you can see veins.
I can make this more interesting!
So webcams generally always respond to IR light. If you look at the front of your remote with our camera phone and press a button, you will see a bluish whitish light. Well, that seems a little weird at first. The light that's coming out of the LED should be closest to red... Well, when CMOS camera companies make their cameras, they heavily rely on the blocking abilities of the IR filter. They want to get amazing signal to noise ratios for the visible spectrum, and the combination of materials that does this is also absorb IR light as well. They can just use a coverall filter to get rid of the infrared light.
Here's the spectral response for the D200 - http://www.maxmax.com/images/Cameras/Technical/NikonD200_Spe...