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Televison camera

  • US 5,293,238 A
  • Filed: 06/16/1992
  • Issued: 03/08/1994
  • Est. Priority Date: 06/24/1991
  • Status: Expired due to Fees
First Claim
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1. In a television camera having an optical system, an iris device, an automatic iris control device for automatically controlling opening of said iris device, a photoelectric conversion element for converting an optical image obtained through said optical system and said iris device into an electric signal, an automatic gain control device for controlling gain of the electric signal, a first detection means responsive to flickering in the electric signal at an output of said photoelectric conversion element for detecting flickering at a flickering frequency of a first illumination light source, each half cycle of the flickering frequency defining a flickering period, a signal storage time control means for controlling a signal storage time of said photoelectric conversion element such that in response to the first detection means detecting the flickering, the signal storage time is controlled to become an integer multiple of the flickering period of said first light source, whereby changing the signal storage time to an integer multiple of the flickering period substantially eliminates flicker in the electric signal at the output of the photoelectric conversion element, THE IMPROVEMENT COMPRISING:

  • a second detection means including;

    a means for storing a current iris value in response to the first detection means detecting the flickering frequency, current iris values with the stored iris value, anda means connected with the signal storage time control means for causing the signal storage time control means to change the signal storage time of said photoelectric conversion element from the integer multiple of the flickering period to a predetermined time different from the time which is the integer multiple of the flickering period when said comparing means detects a change in the iris value above a preselected minimum change indicative of a switching of said first light source to another light source.

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