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Electrochromic device capable of prolonged coloration

  • US 5,384,578 A
  • Filed: 06/14/1993
  • Issued: 01/24/1995
  • Est. Priority Date: 12/11/1990
  • Status: Expired due to Fees
First Claim
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1. A variable electrochromic light transmission system comprising:

  • an electrochromic element having a continuously variable transmission characteristic;

    said element being responsive to a momentary application of a signal by coloring to a partial light transmission level and being responsive to removal of said signal by maintaining a transmission level that is within a given percentage from said partial transmission level;

    said partial light transmission level selectable from a continuum of light transmission levels in a range from a highest light transmission level to a lowest light transmission level;

    input means for selecting a light transmission level of said electrochromic element;

    circuit means responsive to said input means for intermittently applying a drive signal to said electrochromic element in successive pulses separated by holding periods;

    said drive signal having a level corresponding to the selected light transmission level; and

    said circuit means being responsive to at least one of the magnitude and the rate of change of magnitude of said input means to provide momentary overshoot of said drive signal level upon a change in said input means that increases said drive signal level and momentary undershoot of said drive signal upon a change in said input means that decreases said drive signal level.

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