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Amount of photons per pixel

  1. Feb 23, 2008 #1
    A fresh question.
    I want to find the number of photons falling on a pixel in a CCD. A very simple model:
    * bigger source area gives larger response ([tex]A_s [/tex])
    * when object farther away, smaller response: [tex]\frac{1}{R^2} [/tex]
    * bigger detector area gives larger response ([tex]A_d [/tex])
    * size of the lens is [tex]\pi r^2 [/tex], with r the radius of the lens
    * the larger the focal length, the smaller the amount of light on the detector: [tex]\frac{1}{f^2}[/tex]
    * atmospheric damping gives extra coefficient of D
    * spectral response dependence: [tex]QE(\lambda)[/tex]
    * amount of energy from the source: E

    gives something like this:

    [tex] A_s A_d\frac{1}{R^2}\int^{\lambda_e}_{\lambda_s} QE(\lambda)E d\lambda[/tex]

    If I understand correctly, if this is calculated (the quantum efficiency can be modeled like e.g. 3 small parts), and the answer is divided by the photon energy, the amount of photons per pixel should appear.

    I don't really know how to put in the energy from the source. The radiant exitance looks good, but I don't know what to do with it. And I can't find a source of information on how large these quantities should be.
    Last edited: Feb 23, 2008
  2. jcsd
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