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Homework Help: Photo-Source (OLED)& Photo-sensor (pTFT)

  1. Mar 21, 2007 #1
    Hello to everybody. This is my first post.

    I have a trouble calculating the light illuminance that senses a light sensor.

    Analytically. I have a light source (OLED) that is at the same surface as the light sensor (polysilicon-TFT). Also, the emitting area of the source is three or four times larges that the area of the senor. For the light source it is given the luminance from a figure of cd/m^2 to Voltages applied to it. For the light-sensor i have a equation that uses lux (lx) to calculate the production of current from it.
    I need to calculate how much of light (in lux) is sensing the light-sensor from the light source. (assuming that there isn't another light source)

    1st Question: The light source is emmitting light to any direction or only straight forward?
    2nd : if straightforward what is the steradian of the emmition? (if it is at any direction, the steredian of the emmition is 2pi)
    3rd : depending of the answer of the 1st question, is the light-sensor sensing any light?

    I know that cd/m^2=lm/m^2.sr=lux/sr. if the steradian of the light source is 2pi and the emmitting light luminance is A cd/m^2 the sensed light illumination of the sensor is A*2pi ? Am i right?
  2. jcsd
  3. Apr 27, 2007 #2
    If the source gives 10cd of light to any direction. A sensor of area 100x100um how many lux does it read?

    So, the lumens are 10*4pi lm , and the illuminance: 10*4pi/(100um*100um) lux?
    Am i right?
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