MadSci Network: Physics

Re: Is my video camera sensitive to IR rays?

Date: Fri Aug 14 15:21:00 1998
Posted By: Curtis Chen, Other (pls. specify below), Webmaster, AT&T Labs
Area of science: Physics
ID: 902066038.Ph

Hi Simone--

Short answer: Yes, your video camera is sensitive to infrared (IR) radiation.

Long answer: The part of your video camera which "sees" is a semiconductor chip called a Charge Coupled Device (CCD). A CCD is basically a rectangular array of hundreds of thousands of light-sensitive cells, which respond to the light shining in through the camera lens. Each of these cells then sends an electrical impulse to the camera's recording device, which interprets and stores that information on the videotape.

IR shows up because the particular semiconductor material (e.g., germanium) used in your camera's CCD is sensitive to IR, and because the camera lens isn't filtering out IR. Most consumer CCD cameras come equipped with lens filters to prevent "invisible" light (ultraviolet, microwave, etc.) from hitting the CCD and appearing on the recorded image. Some applications of CCDs (security monitors, robot vision) use different or no filters in order to collect more information.

The radiation from your VCR remote control shows up as bluish -- instead of reddish, as you might expect -- because your video camera's CCD isn't really designed to collect IR light, and essentially makes a bad guess at the color of the light.

Some web links for more information:

Hope this helps!

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