EP0331502A2
Expired / Lapsed
EP
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Focus control apparatus and methods
Assignee: Sony Corp
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Filing: 1989-03-03
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Granted: —
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Expires: 2009-03-03
Abstract
Abstract A focus control system for a video camera determines a first gradient (ϑ₀) indicative of a change in value of a predetermined frequency component in the video signal for first and second lens positions (lm, lm+1) obtained from the signal of predetermined frequency component in the video signal sampled at the first lens position (lm) and at the second lens position (lm+1), and determines a second gradient (ϑ₁) indicative of a change in value of the predetermined frequency component in the video signal for the second lens position (lm+1) and a third lens position (lm+2) obtained from the signal of the predetermined frequency component in the video signal sampled at the third lens position (lm+2). The speed of longitudinal movement of the lens is controlled in accordance with changes in the first and second gradients (ϑ₀, ϑ₁), thereby permitting faster focusing and reducing the amount of overrun of the lens during focusing.
Inventors
- 👤 Koji C/O Patents Division Iwamoto
- 👤 Kenichi Patents Division Hamada
- 👤 Katsuaki C/O Patents Division Hirota
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 10:29
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/60; H04N23/67; H04N23/673; H04N23/63; H04N23/633; H04N23/635
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
239 words
Focus control apparatus for a video camera in which a component of a video signal is maximised for performing focus control, the apparatus comprising: means (5A, 5B) for extracting a signal having a predetermined frequency component from a video signal; means (2) for moving a position of a lens (1) of the camera; means (8, 9) for sampling the signal of predetermined frequency component extracted from the video signal at continuous, successive at least first, second, and third lens positions (lm, lm+1, lm+2); means (10) for determining a first gradient (ϑ₀) indicative of a change in value of the signal of predetermined frequency component for a change in lens position between said first and second lens positions (lm, lm+1) from the signal of the predetermined frequency component sampled at the first lens position (lm) and the signal of predetermined frequency component sampled at the second lens position (lm+1); means (10) for determining a second gradient (ϑ₁) indicative of a change in value of the signal of predetermined frequency component for a change in lens position between said second and third lens positions (lm+1, lm+2) from the signal of the predetermined frequency component sampled at the second lens position (lm+1) and the signal of predetermined frequency component sampled at the third lens position (lm+2); and means (11) for controlling the speed of movement of the lens (1) in response to a relationship between said first and second gradients (ϑ₀, ϑ₁).
Claim 2
Dependent Claim
239 words
Focus control apparatus for a video camera in which a component of a video signal is maximised for performing focus control, the apparatus comprising: means (5A, 5B) for extracting a signal having a predetermined frequency component from a video signal; means (2) for moving a position of a lens (1) of the camera; means (8, 9) for sampling the signal of predetermined frequency component extracted from the video signal at continuous, successive at least first, second, and third lens positions (lm, lm+1, lm+2); means (10) for determining a first gradient (ϑ₀) indicative of a change in value of the signal of predetermined frequency component for a change in lens position between said first and second lens positions (lm, lm+1) from the signal of the predetermined frequency component sampled at the first lens position (lm) and the signal of predetermined frequency component sampled at the second lens position (lm+1); means (10) for determining a second gradient (ϑ₁) indicative of a change in value of the signal of predetermined frequency component for a change in lens position between said second and third lens positions (lm+1, lm+2) from the signal of the predetermined frequency component sampled at the second lens position (lm+1) and the signal of predetermined frequency component sampled at the third lens position (lm+2); and means (11) for controlling the speed of movement of the lens (1) in response to a relationship between said first and second gradients (ϑ₀, ϑ₁).
Claim 3
Dependent Claim
22 words
Focus control apparatus according to claim 1, wherein said means for extracting a predetermined frequency component comprises bandpass filter means (5A, 5B).
Claim 4
Dependent Claim
74 words
Focus control apparatus according to claim 2, wherein said bandpass filter means includes a first bandpass filter (5A) and a second bandpass filter (5B) having a higher centre frequency than said first bandpass filter (5A), and comprising means (6) for selecting said first bandpass filter (5A) when an object forming the image of the video camera has a weak contrast, and selecting said second bandpass filter (5B) when said image has a strong contrast.
Claim 5
Independent Claim
128 words
A method of focus control for a video camera, the method comprising the steps of: detecting the maximum value of a luminance component (Y) in an image pickup signal; adjusting the rotational position of a focusing ring (1a) of an image pickup lens (1) on the basis of the result of the detection; and when said maximum value is detected, rotating said focusing ring (1a) at a low speed for a predetermined time to discriminate an increasing direction of the luminance component (Y) from a start point and, thereafter, until said luminance component (Y) exceeds a predetermined level, rotating the focusing ring (1a) at a high speed, and rotating the focusing ring (1a) at a low speed when said level is set to at least the predetermined level.
Claim 6
Independent Claim
128 words
A method of focus control for a video camera, the method comprising the steps of: detecting the maximum value of a luminance component (Y) in an image pickup signal; adjusting the rotational position of a focusing ring (1a) of an image pickup lens (1) on the basis of the result of the detection; and when said maximum value is detected, rotating said focusing ring (1a) at a low speed for a predetermined time to discriminate an increasing direction of the luminance component (Y) from a start point and, thereafter, until said luminance component (Y) exceeds a predetermined level, rotating the focusing ring (1a) at a high speed, and rotating the focusing ring (1a) at a low speed when said level is set to at least the predetermined level.
Claim 7
Independent Claim
148 words
A method of focus control for a video camera wherein a video signal level from the camera is maximised by movement of the lens (1) through continuous positions to the in-focus position, the method comprising the steps of: extracting (5A, 5B) a signal having a predetermined frequency component from the video signal; sampling (8, 9) the extracted signal at at least three successive points corresponding to three respective lens positions (lm, lm+1, lm+2); deriving (10) a first gradient (ϑ₀) indicative of a change in value between said extracted signal at a first sample point and a second sample point; deriving (10) a second gradient (ϑ₁) indicative of a change in value between said extracted signal at said second sample point and a third sample point; comparing the first and second gradients (ϑ₀, ϑ₁); and controlling the speed of movement of the lens (1) in response to the comparison.
Claim 8
Independent Claim
148 words
A method of focus control for a video camera wherein a video signal level from the camera is maximised by movement of the lens (1) through continuous positions to the in-focus position, the method comprising the steps of: extracting (5A, 5B) a signal having a predetermined frequency component from the video signal; sampling (8, 9) the extracted signal at at least three successive points corresponding to three respective lens positions (lm, lm+1, lm+2); deriving (10) a first gradient (ϑ₀) indicative of a change in value between said extracted signal at a first sample point and a second sample point; deriving (10) a second gradient (ϑ₁) indicative of a change in value between said extracted signal at said second sample point and a third sample point; comparing the first and second gradients (ϑ₀, ϑ₁); and controlling the speed of movement of the lens (1) in response to the comparison.
Claim 9
Dependent Claim
230 words
A focus control system for automatically setting the lens (1) of a video camera to an in-focus position, the system comprising: an image pickup element (3) for receiving an image through the lens (1) of the video camera and producing an output signal therefrom; a video signal processing circuit (4) for receiving said output signal from said image pickup element and producing a video signal including at least a luminance signal (Y) and a chrominance signal (C); bandpass filter means (5A, 5B) for receiving said luminance signal (Y) and extracting a signal therefrom having predetermined frequency components; means (2) for moving the lens over predetermined lens travel limits; means (8, 9) for sampling the extracted signal at at least three sample points corresponding to three respective continuous lens locations (lm, lm+1, lm+2); means (10) for producing a first gradient (ϑ₀) indicative of a change in value of the sampled extracted signal between a first sample point and a second sample point, and for producing a second gradient (ϑ₁) indicative of a change in value of the sampled extracted signal between said second sample point and a third sample point; means for comparing said first and second gradients (ϑ₀, ϑ₁) and producing an output indicative of the comparison; and means for controlling the speed of said means (2) for moving the lens in response to said output of said comparing means.
Claim 10
Dependent Claim
230 words
A focus control system for automatically setting the lens (1) of a video camera to an in-focus position, the system comprising: an image pickup element (3) for receiving an image through the lens (1) of the video camera and producing an output signal therefrom; a video signal processing circuit (4) for receiving said output signal from said image pickup element and producing a video signal including at least a luminance signal (Y) and a chrominance signal (C); bandpass filter means (5A, 5B) for receiving said luminance signal (Y) and extracting a signal therefrom having predetermined frequency components; means (2) for moving the lens over predetermined lens travel limits; means (8, 9) for sampling the extracted signal at at least three sample points corresponding to three respective continuous lens locations (lm, lm+1, lm+2); means (10) for producing a first gradient (ϑ₀) indicative of a change in value of the sampled extracted signal between a first sample point and a second sample point, and for producing a second gradient (ϑ₁) indicative of a change in value of the sampled extracted signal between said second sample point and a third sample point; means for comparing said first and second gradients (ϑ₀, ϑ₁) and producing an output indicative of the comparison; and means for controlling the speed of said means (2) for moving the lens in response to said output of said comparing means.
References Cited (Backward Citations)
JPS62146628A
Cited
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