Light-reflectivity controller for use with automotive rearview mirror using electrochromic element

  • US 4,896,030 A
  • Filed: 02/29/1988
  • Issued: 01/23/1990
  • Est. Priority Date: 02/27/1987
  • Status: Expired due to Fees
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First Claim
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1. A light reflectivity controller for use with an automotive rearview mirror having an electrochromic element on each of the reflective surfaces thereof, comprising:

  • a first photosensor for detecting the brightness of the surroundings including the front of a car in which the inside rearview mirror is equipped, to provide a signal corresponding to the detected brightness;

    a second photosensor for detecting the brightness of the surroundings including the rear of the car to provide a signal corresponding to the detected brightness;

    first means for comparing the output signal delivered from said first photosensor with at least a reference value predetermined correspondingly to the brightness of the surroundings of the car to provide at least a first control signal formed based on the result of the comparison;

    second means for comparing the output signal delivered from said second photosensor with at least a reference value predetermined correspondingly to the brightness of the surroundings of the car to provide a second control signal formed based on the result of the comparison;

    the reference values in said first and second comparing means corresponding to different brightnesses of said surroundings of the car;

    a control voltage generating means for generating different voltages for application to said electrochromic elements on said reflective surfaces;

    a first switching means for delivering to said control voltage generating means a third control signal in accordance with one of said different voltages to be delivered based on said plural control signals received from said first and second comparing means;

    a second switching means for connecting said electrochromic elements selectively between said control voltage generating means and the ground potential based on said plural control signals delivered from said first and second comparing means, whereby the voltages applied to said electrochromic elements are controlled automatically and stepwisely based on the brightness of the surroundings of the car; and

    a timer circuit adapted so as to recognize, from the change of the control signal delivered from said second comparing means, that the voltage delivered from said control voltage generating means should be changed from the predetermined voltage to any other lower voltage, and to act on said second switching means to let the latter connect said electrochromic elements to the ground potential for a predetermined short time and thereafter to said control voltage generating means.

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