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Digital imaging control with selective intensity resolution enhancement

  • US 6,788,340 B1
  • Filed: 12/30/1999
  • Issued: 09/07/2004
  • Est. Priority Date: 03/15/1999
  • Status: Expired due to Term
First Claim
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1. A method of automatic gain control in an image processor having a programmable amplifier, the programmable amplifier having a reference voltage input and a signal input and a programmable gain value and having a differential output coupled to an analog to digital converter (ADC), the analog to digital converter outputting a digital code corresponding to the output of the programmable amplifier, the method comprising:

  • reading a frame of luminance data, determining an average luminance value of the frame and the digital code output by the ADC corresponding to average luminance value;

    calculating a reference voltage that will cause the digital code output by the ADC to be at a target value when the input to the programmable amplifier is set to the average luminance value;

    calculating a gain that will cause the digital code output by the ADC to be at the target value when the input to the programmable amplifier is set to the average luminance value;

    setting the reference voltage and the gain to the calculated values and reading the next frame;

    wherein the gain is calculated from the difference in (1) the digital code output by the ADC when the signal input to the programmable amplifier is set to the average luminance value, and (2) a pre-determined digital code output by the ADC.

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