Tech Ques: Are the filters actual or silicon doping in a 1-ccd system?

Discussion in 'Digital Photography' started by Miguel Gonzalez, Jun 3, 2004.

  1. So, do 1-ccd dig cams have 'actual' color filters are
    is the color sensor (each cell) 'doped' (to use a term
    used in the silicon wafer biz) to be sensitive to that
    color spectrum (ie - doping is different for each of the
    3 color sensors to be sensitive only or much more so for
    that wavelength)?

    (I saw a reference to a filter 'grid' placed over the
    1-ccd to get the color spectrum split - as opposed to
    the prisms splitting the light in a 3-ccd system)

    Thanks!
     
    Miguel Gonzalez, Jun 3, 2004
    #1
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  2. Miguel Gonzalez

    DJ Guest

    In "Bayer" sensors the filter is on top of the chip. Each 4 photosites is
    covered with RGBG. 2 G's because the eye is most sensitve to Green.

    In Foveon sensors each photosite comprises 3 sensitive layers. Different light
    colours penetrate to different depths. Sounds seductive, but in practice the
    results are less than perfect.

    There are also systems with a prism and 3 chips. Very expensive.

    The overwhelming opinion is that Bayer gives the best results. One or 2
    blinkered individuals promote Foveon with such blind vigour it actually puts
    people off Foveon.

    ALL sensors also need (not all have) an anti-aliasing filter. This is a spatial
    low pass filter (read "blurring filter") at the Nyquist frequency that
    counteracts the aliasing (moires, jaggies and other ugly artifacts) that will
    occurr in any system that samples using a regularly spaced array of sampling
    points.
     
    DJ, Jun 3, 2004
    #2
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  3. The colour filtering is not done by silicon doping. Instead, there is a
    physical filtering layer on the front of the silicon. This could be
    either dye or dichroic (interference) filters; I don't know the actual
    process used.

    Dave
     
    Dave Martindale, Jun 3, 2004
    #3
  4. Charles Schuler, Jun 3, 2004
    #4
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