Can one use a CCD in same way as photosensitive paper? When one has very low intensity like in single photons double slit experiment to see the interference pattern one puts a photosensitive paper at the screen and waits as long as it needs even day to see the interference pattern. Does CCD has such mode e.g to read out after a certain time meanwhile accumulating the charges from single photons? If yes how can this be done?

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    $\begingroup$ any ccd can do this but there is always extra noise electrons in the pixel .... so you need more signal to get a good s:n. Many astro cameras have very good sensors and cooling helps. $\endgroup$ Feb 3 at 19:07
  • $\begingroup$ Ok it can work in integration regime but how is that achieved technically? Must there be a electron circuit to command when to stop reading? $\endgroup$
    – Mercury
    Feb 3 at 19:18
  • $\begingroup$ you can buy a raspberry pi camera ... it has great performance. $\endgroup$ Feb 4 at 4:22

1 Answer 1


Sure. Clock it to flush the charge out, and then just hold the clocks static. When you're ready to end the exposure, clock out and measure the charge. The only issue is dark current: thermal electrons mimicking photoelectrons. You can limit this by running the CCD cold.

  • $\begingroup$ Is there a builtin clock in a CCD with stopper? Or it is to be attached separately? $\endgroup$
    – Mercury
    Feb 3 at 19:23
  • $\begingroup$ @Mercury CCDs have little builtin circuitry. The clock signals are generally provided externally. $\endgroup$
    – John Doty
    Feb 3 at 21:46

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