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

• Current Assignee: Ichikoh Industries Limited (Valeo SE)
• Original Assignee: Ichikoh Industries Limited (Valeo SE)
• Inventors: Miyaji, Mitsuo
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Shami, Khaled
• Application Number:
  US07/161,482
• Time in Patent Office: 694 Days
• Field of Search: 250/201, 350/279, 350/357, 350/281, 350/278
• US Class Current: 250/206
• CPC Class Codes: B60R 1/088 using a cell of electrically changeable optical characteristic, e.g. liquid-crystal or electrochromic mirrors

Abstract

The light reflectivity control for use with an automotive rearview mirror according to the present invention has a first and second photosensors to detect the brightness of the surroundings including the front of a car in which the inside rearview mirror is equipped and that of the surroundings including the rear of the car, respectively. These photosensors deliver output signals in inverse proportion to the respective brightnesses of the surroundings of the car. The output signals are supplied to a first and second comparators each having at least a reference value predetermined correspondingly to the brightness of the surroundings, in which the output signals are compared with the reference values, respectively. Based on the signal including the information concerning the brightness of the surroundings including the front and rear, respectively, of the car and that are delivered from the comparators, voltages for application to the electrochromic elements and then the electrochromic elements are connected. Thereby, the voltage for application to the electrochromic elements are automatically and stepwisely correspondingly to the brightness of the surroundings of the car.

Claims

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.

2. A light reflectivity controller according to claim 1, in which said second switching means is so adapted that said electrochromic elements are connected to the ground potential when the output signal from said first photosensor is higher than a predetermined reference value of said first comparing means that corresponds to a predetermined brightness of the surroundings including the front of the car or when the output signal from said second photosensor is lower than the predetermined reference value of said first comparing means that corresponds to the predetermined brightness of the surroundings including the front of the car.

3. A light reflectivity controller according to claim 1, in which said electrochromic elements are connected to said control voltage generating means when the output signal from said first photosensor is lower than a predetermined reference value of said first comparing means that corresponds to a predetermined brightness of the surroundings including the front of the car.

4. A light reflectivity controller utilized with an automotive rearview mirror having an electrochromic element therein, comprising:

first photosensor means for detecting the brightness associated with the front of a car in which said rearview mirror is equipped and for providing a signal corresponding to the detected brightness;

second photosensor means for detecting the brightness associated with the rear of the car and for providing a signal corresponding to the detected brightness;

first comparing means for comparing the signal provided by said first photosensor means with a reference value and for providing a first control signal based on the comparison result;

second comparison means for comparing the signal provided by said second photosensor means with a plurality of reference values and for providing a plurality of second control signals based on the comparison result;

a control voltage generating means for generating different levels of voltage to said electrochromic element, said different levels of voltage being determined in accordance with said first control signal and said plurality of second control signals;

switching means for selectively connecting said electrochromic element between said control voltage generating means and ground potential in accordance with said first control signal and said plurality of control signals so as to stepwisely change the reflectivity of said rearview mirror by altering the voltage applied to said electrochromic element; and

timer means for forcing said switching means to connect said electrochromic element to the ground potential for a predetermined period of time and thereafter to said control voltage generating means in which would require a lower voltage to be applied to said electrochromic element and thus effect a change in the reflectivity of said rearview mirror.