Detecting IR light using a CCD

Remote controls for devices like televisions, cable boxes, and DVD players typically operate in the infrared. On the front of the remote is a light emitting diode (LED) that produces light in the infrared region. The light flashes quickly to produce a sequenced pattern, which the device being controlled then reads and interprets as a command.

Materials

  • TV/cable/DVD remote control
  • Webcam or camera phone

Directions

Point a cheap CCD camera (camera phone or webcam) at the LED on the front of the remote control and view the image on the phone/computer. Now start pressing buttons on the remote. Without the camera, you will not see the LED light up, as the radiation is outside the visible range. Through the camera, you should see the LED get very bright when you press buttons. The light is being produced by the LED, but your eyes cannot see into the IR like the camera.

Explanation

Digital cameras are typically made from silicon CCD’s, which can detect light from the visible out to the near end of the infrared. The IR light does not focus as well, so it is usually blocked by a special filter so that it never reaches the CCD chip. This helps improve the camera’s picture quality. Generally, the cheaper the camera is, the more IR light the camera can pick up. Thus, cheap digital cameras can be used to image the infrared. Webcams and camera phones are usually lower quality, so they work best for viewing IR.