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Television camera equipped with continuously-variable-speed electronic shutter function

  • US 5,448,293 A
  • Filed: 07/01/1994
  • Issued: 09/05/1995
  • Est. Priority Date: 04/24/1991
  • Status: Expired due to Term
First Claim
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1. A video camera comprising:

  • an image sensor, including a continuously-variable-speed electronic shutter, for converting an optical signal into an electrical signal and outputting a video signal;

    a lens for focusing an image of a subject on said image sensor;

    an amplifier for amplifying said video signal and outputting an amplified signal;

    signal processing means for processing said amplified signal and outputting a processed video signal;

    video level detecting means for detecting a level of said processed video signal for each field and outputting a signal representing a detected video signal level;

    gain control means for controlling a gain of said amplifier so as to maintain the signal representing the detected video signal level at a fixed value in an AGC mode;

    shutter control means for calculating an estimated shutter amount, in a shutter mode, said shutter control means comprising means for (i) subtracting a target value of the video level from the detected video signal level to obtain a difference, (ii) multiplying the difference by a coefficient and a current shutter amount, corresponding to a preceding estimated shutter amount, to obtain a correction shutter amount, and (iii) adding said correction shutter amount to the current shutter amount to obtain said estimated shutter amount;

    shutter pulse generating means for supplying a shutter pulse to said image sensor in accordance with said estimated shutter amount; and

    control mode decision means for automatically placing said gain control means and the image sensor in said AGC mode or said shutter mode, in accordance with (i) said signal representing the detected video signal level, (ii) said estimated shutter amount, and (iii) said gain of said amplifier, said control mode decision means operating independently of whether an amount of light of the optical signal is constant.

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