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Auto focus circuit for video camera

  • US RE33,682 E
  • Filed: 01/19/1989
  • Issued: 09/03/1991
  • Est. Priority Date: 10/30/1984
  • Status: Expired due to Term
First Claim
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1. An autofocus circuit for a video camera including a focusing motor for focusing, comprising:

  • .[.a.]. high-pass filter .[.circuit.]. .Iadd.means .Iaddend.to which a luminance signal of a video signal is applied .[.so that.]. .Iadd.for extracting .Iaddend.a high frequency component higher than a predetermined frequency .[.is extracted.]. from said applied luminance signal,.[.an absolute value calculating circuit connected to said high-pass filter circuit for obtaining an absolute value of the output of said high-pass filter circuit,.]..[.an.]. A-D converting .[.circuit.]. .Iadd.means operatively .Iaddend.connected to said .[.absolute value calculating circuit.]. .Iadd.high-pass filter means .Iaddend.for converting an analog .[.absolute value.]. output signal .[.provided.]. .Iadd.derived .Iaddend.from said .[.absolute value calculating circuit to.]. .Iadd.high-pass filter means into .Iaddend.a digital signal,.[.a.]. calculating .[.circuit.]. .Iadd.means .Iaddend.connected to said A-D converting .[.circuit.]. .Iadd.means .Iaddend.for adding the converted digital signal with a predetermined period cycle,.[.a.]. comparing .[.circuit.]. .Iadd.means .Iaddend.connected to said calculating .[.circuit.]. .Iadd.means .Iaddend.for comparing the output of calculation in one predetermined period and the output of calculation in .[.the predetermined period coming one.]. .Iadd.another .Iaddend.predetermined period .[.ahead of said predetermined period.]., and.[.a.]. focusing motor control .[.circuit.]. .Iadd.means .Iaddend.connected to said comparing .[.circuit.]. .Iadd.means .Iaddend.for providing a signal for controlling the rotation of the focusing motor included in said video camera in the clockwise direction or in the counter-clockwise direction based on the output of said comparing .[.circuit.]. .Iadd.means.Iaddend..

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