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Exposure control in electronic cameras by detecting overflow from active pixels

  • US 6,833,871 B1
  • Filed: 07/16/2001
  • Issued: 12/21/2004
  • Est. Priority Date: 02/26/1998
  • Status: Expired due to Term
First Claim
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1. A method for controlling the exposure of an active pixel array disposed on a semiconductor substrate, comprising the steps of:

  • adjusting a charge barrier in each said pixel to a first overflow level;

    integrating photocurrent in each said pixel during a first integration time period while said charge barrier is set at said first overflow level;

    collecting overflow charge from all said pixels in said array during said first integration time period;

    developing an overflow signal;

    adjusting said charge barrier for each said pixel to a second overflow level when said overflow signal exceeds a predetermined threshold;

    determining a duration for a second integration time period;

    integrating photocurrent in each said pixel during said second integration time period while said charge barrier is set at said second overflow level; and

    terminating said second integration time period after said determined duration.

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