Liquid crystal closed-loop controlled mirror systems

  • US 4,690,508 A
  • Filed: 05/17/1985
  • Issued: 09/01/1987
  • Est. Priority Date: 12/15/1982
  • Status: Expired due to Term
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First Claim
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1. A variable brightness mirror assembly comprising a reflecting surface for reflecting to an observer a field of view which is incident on the mirror assembly and an electrically controlled optical transmission plate disposed over said reflecting surface, said optical transmission plate being operable to any of a number of different states of light transmission, reference establishing means for establishing any desired level of a reference signal over a range of possible reference signal levels corresponding to a range of different brightnesses for light from the field of view which is incident on said reflecting surface, sensor means disposed to provide a detection signal related to the brightness of the incident field of view on the mirror assembly, and control means coupling said sensor means and said reference establishing means in electrical control of said optical transmission plate for causing the brightness of the light from the field of view which is incident on said reflecting surface to be closed-loop regulated to a particular level established by said desired reference signal for any intensity of brightness of the field of view incident on the mirror assembly within a range of different intensities of incident brightness on the mirror assembly, said control means comprising an amplifier stage for causing said optical transmission plate to operate to a state of light transmission which is correlated with both the level of said desired reference signal and the level of said detection signal so as to render the brightness of the field of view incident on said reflecting surface substantially insensitive to change in the incident brightness on the mirror assembly over said range of different intensities of incident brightness for any given level of said desired reference signal over said range of possible reference signal levels while allowing the brightness which is incident on said reflecting surface to be set to any desired brightness within said range of different brightnesses by operation of said reference establishing means, including observer-settable means settable by the observer to set a desired brightness of light from the field of view which is incident on said reflecting surface and causing said control means to closed-loop regulate the light transmission of said optical transmission plate in correlation with the setting of said observer-settable means, and also including an ambient light sensor means for sensing the prevailing ambient light level and causing said control means to closed-loop regulate the light transmission of said optical transmission plate also in correlation with changes in sensitivity of the observer'"'"'s eyes due to changes in ambient light level, said observer-settable means, said first-mentioned sensor means, and said ambient light sensor means all being in an input circuit relationship to said amplifier stage so as to have an interactive effect on said amplifier stage in performing the closed-loop regulation of said optical transmission plate.

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