Video camera device having an exposure control circuit

  • US 5,400,074 A
  • Filed: 02/25/1993
  • Issued: 03/21/1995
  • Est. Priority Date: 03/05/1992
  • Status: Expired due to Term
First Claim
Patent Images

1. A video camera device comprising:

  • a lens block for taking in light from a subject to be photographed;

    an iris for limiting a quantity of light from said lens block in response to a control signal;

    an image pickup device for converting light passing through said iris into an electric signal;

    an automatic gain control circuit for varying a level of an output signal from said image pickup device in response to said control signal;

    an analog-to-digital converter for converting an output signal from said automatic gain control circuit into a digital signal;

    a video signal processing circuit for converting the digital signal from said analog-to-digital converter into a predetermined video signal;

    a signal level detecting circuit for detecting a light level in the digital signal output from said analog-to-digital converter;

    a comparator for comparing an output signal of said signal level detecting circuit and a reference level;

    a zoom lens position detecting circuit for detecting the position of a zoom lens contained in said lens block;

    a read only memory containing values of a brightness attenuating characteristic of said zoom lens corresponding to positions of said zoom lens, said memory being read out in response to an output from said zoom lens position detecting circuit; and

    a control amount computing circuit for determining an opening amount of said iris and a gain of said automatic gain control circuit on the basis of an output signal of said comparator and an output from said read only memory and for producing said control signal fed to said iris and to said automatic gain control circuit to correct the brightness attenuating characteristic of said zoom lens.

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