Automatic focusing device using a video aperture signal in low contrast situations
First Claim
1. An automatic focusing device, comprising:
- extraction means for extracting a signal corresponding to a degree of focus from an input image signal;
focus control means for detecting a focus state from the signal extracted from said extraction means, and for providing a driving signal for driving a focusing lens in accordance with the results of the detection;
determination means for determining whether said image signal has a low contrast;
aperture signal extraction means for extracting a video aperture signal from the image signal by emphasizing a predetermined component of the image signal corresponding to edge portions of an image aperture; and
control means for supplying the aperture signal output from said aperture signal extraction means to said focus control means when the results of the determination by said determination means indicate a low contrast.
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Abstract
An automatic focusing device which uses a video aperture signal in low contrast situations includes an extraction circuit for extracting a signal corresponding to a degree of focus from an input image signal. A focus control circuit is provided for detecting a focus state from the signal extracted from the extraction circuit, and for providing a driving signal for driving a focusing lens on the basis of the results of the detection. A determination circuit is provided for determining whether the image signal has a low contrast. An aperture signal extraction circuit extracts a video aperture signal from the input image signal. Control circuitry is provided for supplying the aperture signal output from the aperture signal extraction circuit to the focus control circuit on the basis of the results of the determination by the determination circuit.
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Citations
18 Claims
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1. An automatic focusing device, comprising:
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extraction means for extracting a signal corresponding to a degree of focus from an input image signal; focus control means for detecting a focus state from the signal extracted from said extraction means, and for providing a driving signal for driving a focusing lens in accordance with the results of the detection; determination means for determining whether said image signal has a low contrast; aperture signal extraction means for extracting a video aperture signal from the image signal by emphasizing a predetermined component of the image signal corresponding to edge portions of an image aperture; and control means for supplying the aperture signal output from said aperture signal extraction means to said focus control means when the results of the determination by said determination means indicate a low contrast. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An automatic focusing device, comprising:
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extraction means for extracting a focus signal corresponding to a degree of focus from an input image signal; focus control means for detecting a focus state from the signal extracted from said extraction means, and for providing a driving signal for driving a focusing lens in accordance with the results of the detection; determination means for comparing an output of said extraction means with a predetermined value; aperture signal extraction means for extracting a video aperture signal from the image signal by emphasizing a predetermined component of the image signal corresponding to edge portions of an image aperture; and control means for causing the aperture signal output from said aperture signal extraction means to be provided to said focus control means when the comparison by said determination means with the focus signal produces a predetermined result. - View Dependent Claims (8, 9, 10)
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11. A video camera focusing apparatus, comprising:
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imaging means for photoelectrically converting an object image into an image signal, and for outputting the image signal; an aperture correcting circuit for extracting and emphasizing a predetermined component of the image signal corresponding to edge portions of an image aperture; and focusing means for, in a low contrast situation, performing focusing using the emphazized predetermined component of said aperture correcting circuit image signal. - View Dependent Claims (12, 13, 14)
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15. A video camera focusing apparatus, comprising:
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extraction means for extracting a focus signal corresponding to a degree of focus from an input image signal; first focus control means for detecting a focus state from the signal extracted from said extraction means and for outputting a driving signal for driving a focusing lens using the results of the detection; aperture signal extraction means for extracting and emphasizing a predetermined component of the image signal corresponding to edge portions of an image aperture and outputting the emphasized aperture signal; second focus control means for outputting a driving signal for driving the focusing lens using the focus signal output from said extracting means and the aperture signal output from said aperture signal extraction means; and change-over means for changing between said first and second focus control means in accordance with a predetermined photographing state. - View Dependent Claims (16, 17, 18)
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Specification