Auto focus circuit for video camera
First Claim
1. An auto focus circuit for a video camera including a focusing motor for focusing, comprising:
- a high-pass filter circuit to which a luminance signal of a video signal is applied so that 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 connected to said absolute value calculating circuit for converting an analog absolute value output signal provided from said absolute value calculating circuit to a digital signal,a calculating circuit connected to said A-D converting circuit for adding the converted digital signal with a predetermined period cycle,a comparing circuit connected to said calculating circuit for comparing the output of calculation in one predetermined period and the output of calculation in the predetermined period coming one predetermined period ahead of said predetermined period, anda focusing motor control circuit connected to said comparing circuit for providing a signal for controlling the rotation of the focusing motor included in said video camera in the clockwise direction or in the counterclockwise direction based on the output of said comparing circuit.
1 Assignment
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Accused Products
Abstract
An auto focus circuit for a video camera comprises an A-D converting circuit (7) for converting to a digital amount a high frequency component absolute value output of a luminance signal in a sampling area for focusing. The A-D converting circuit (7) is connected so that the high frequency component absolute value output of a luminance signal is directly converted to a digital amount. Then, the signal converted to a digital amount is added in an integrating circuit (12) for each field and the signal amount in one field and the signal amount in the coming one field ahead of it or behind it are compared in a comparing circuit (10) so that the output of comparison serves for control of focusing. Thus, addition processing of the high frequency component of the luminance signal, that is, averaging processing is performed digitally in the integrating circuit (12). Accordingly, as compared with the case of analog averaging processing of a signal, the processing operation is stable and as a result the focusing precision is improved.
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Citations
9 Claims
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1. An auto focus circuit for a video camera including a focusing motor for focusing, comprising:
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a high-pass filter circuit to which a luminance signal of a video signal is applied so that 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 connected to said absolute value calculating circuit for converting an analog absolute value output signal provided from said absolute value calculating circuit to a digital signal, a calculating circuit connected to said A-D converting circuit for adding the converted digital signal with a predetermined period cycle, a comparing circuit connected to said calculating circuit for comparing the output of calculation in one predetermined period and the output of calculation in the predetermined period coming one predetermined period ahead of said predetermined period, and a focusing motor control circuit connected to said comparing circuit for providing a signal for controlling the rotation of the focusing motor included in said video camera in the clockwise direction or in the counterclockwise direction based on the output of said comparing circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification