Rearview mirror control circuit

  • US 4,793,690 A
  • Filed: 04/27/1987
  • Issued: 12/27/1988
  • Est. Priority Date: 07/18/1986
  • Status: Expired due to Fees
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First Claim
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1. An automatic rearview mirror system for a vehicle comprising:

  • a reflective element actuable between at least two different reflective conditions;

    a forward light sensor to detect light forward of the mirror;

    a rear light sensor to detect light rearward of the mirror;

    a control circuit means coupled to said reflective element, said forward light sensor, and said rear light sensor for causing said reflective element to assume a reflective state dependent upon the output of said forward and rear light sensors, said control circuit means including a time-filter means for time filtering an ambient light signal which is at least partially dependent on the output of said forward sensor, said time-filter means providing faster time filtering of the signal during periods of increasing ambient light than during periods of decreasing ambient light, whereby said time-filter means and therefore said control circuit means approximates the adaptation of the human eye to changing ambient light levels.

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