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LED light diffraction, scattering

  1. Jan 28, 2008 #1
    I am constructing a 'white line detector' to use on the underside of a robot. The crucial components are an ultrabright red LED and a light-to-voltage converter. My initial idea is to leave the LED as it is, i.e. unshielded. I have to light-to-voltage converter, which is a phototransistor with a lens (TSL-257), connected nearby and it is shielded using heat-shrink tubing to block out ambient light. it is being used to detect a change in color from black to white.

    My question is, do I need to worry about "shielding" the LED to guard against scattering. If I just shield the TSL257, I get a voltage reading of 125mV, and when it crosses over to white, it is about 2V. This is perfectly fine, but the other members of my team want to put a heat-shrink tube over the LED as well because they think it will concentrate the light into more of a "beam". My concern is, the black heat-shrink tube will absorb the LED light and the intensity that is emitted to the floor will be weaker than if it just left alone.

    Which is more justified? placing a tube over the LED or just letting it shine?

    Thanks!
     
  2. jcsd
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