Robert Quimby

Professor of Astronomy, SDSU
Director, Mount Laguna Observatory
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CCD Readout Demonstrator

The display above is an interactive demonstration of how charged coupled devices (CCDs) operate. Note that this toy model does not properly handle the physics; it simply demonstrates schematically the basic process through which charges on a CCD are trapped, moved from one place to another, and ultimately measured.


  • Click anywhere on the detector (excluding the serial register along the bottom edge) to simulate a particle event and excite an electron into the conduction band.
  • Click the "Open Shutter" button to simulate exposing the CCD to a uniform light source. Once open, you can click the "Close Shutter" button to end the exposure.
  • Click the "Toggle Voltage" buttons to change the potentials between the low and high states. Try to shift the accumulated changes from one row down to the serial register at the bottom edge, then little by little to the amplifier ("Amp") in the lower right.
  • To see a demonstration of how a numerical value is assigned to each column in a detector row, make sure the B voltage is in the low state (blue) and all other voltages are in the high state (red), then click the "Readout Row" button. You can also change the binning before hand to see how charges from different pixels are combined on the detector.