Automatic focusing apparatus including improved digital high-pas

Details Automatic focusing apparatus including improved digital high-pas Automatic focusing apparatus including improved digital high-pas

1993-10-28

1995-07-11

Couso, Yon J.

Television

Camera, system and detail

Optics

348354, H04N 5232

Patent

active

054325528

ABSTRACT:
An automatic focusing apparatus includes a focus lens, an image sensing circuit, a circuit for generating a focus evaluating value in response to a video signal from image sensing circuit, a hill-climbing control circuit, a focus motor for moving focus lens in response to a control signal from hill-climbing control circuit, and a circuit for detecting the position of focus motor. The focus evaluating value generating circuit includes an A/D converter, a digital HPF, a digital integrator for integrating the level of the high frequency component in a digital luminance signal in response to a control signal from an integration period setting circuit and sequentially supplies the resultant value as a focus evaluating value to the hill-climbing control circuit for every field, and a timer circuit for producing a reset signal at H level. Thus, after passage of prescribed time period from the end of the horizontal blanking period, a reset signal is applied to digital HPF, delay register in the digital HPF is set to zero, and the digital HPF is reset. Ringing due to a rising in the horizontal blanking period disappears, part of ringing will not be integrated, and therefore accurate automatic focusing operation can be performed.

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