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Light measuring device

  • US 4,465,370 A
  • Filed: 06/30/1981
  • Issued: 08/14/1984
  • Est. Priority Date: 07/01/1980
  • Status: Expired due to Fees
First Claim
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1. A light measuring device having a plurality of ranges for measuring light and comprising:

  • a light responsive means for receiving light and for producing an electrical signal as a function of the received light;

    an integration means including a capacitor means for integrating said electrical signal so as to change the amount of charge stored in said capacitor means;

    a first control means for controlling the integration means such that said electrical signal is integrated during a predetermined period of time;

    a means for setting said capacitor means to a predetermined initial condition before the integration of said electrical signal;

    a means for producing a plurality of constant currents having different levels;

    a means for selecting one of said plurality of constant currents in dependence on said changed amount of charge in said capacitor means;

    a second control means for controlling said constant current producing means such that said selected constant current is supplied to or withdrawn from said capacitor means subsequent to the completion of said integration of said electrical signal for said predetermined periodd of time;

    so as to again place said capacitor means to its predetermined initial condition;

    a means for detecting the moment of time when said capacitor means again reaches said predetermined initial condition due to said selected constant current; and

    a means for measuring the time interval from the moment of time when said constant current producing means starts to supply said selected constant current to said capacitor means to the moment of time when said detecting means detects that said capacitor means has again reached said predetermined initial condition.

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