Importance

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Abstract

A rearview mirror system for a vehicle having a reflective element with a reflective surface and a variable light transmission element includes an optical display device behind the reflective element in order to produce a visual display to the driver. A control is provided having a light sensor that senses light conditions in the vicinity of the vehicle and produces a continuously variable light signal indicative of such sensed light conditions. The control further includes a drive circuit that is responsive to the light signal in order to supply a drive signal to the reflective element and thereby establish the light transmission level of the light transmission element. The control further includes an intensity control circuit that varies the intensity of the optical display as a function of the value of the sensed light in the vicinity of the vehicle in order to accommodate physiological changes in the driver's eyes. The intensity control circuit further varies the intensity of the optical display device as a function of the drive signal supplied to the reflective element in order to compensate for reduced light transmission levels of the light transmission element. The intensity control circuit sums values of the light signal and the drive signal and processes the sum to a pulse-width modulated signal using a non-linear processor. The intensity control also provides a substantially constant high intensity of the optical display device for all values of sensed light above a predetermined high light.

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First Claim