EP0268246A2
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EP
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Automatic focusing circuit for automatically matching focus in response to video signal
Assignee: Sanyo Electric Co Ltd
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Filing: 1987-11-16
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Granted: —
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Expires: 2007-11-16
Abstract
Abstract In an automatic focusing circuit of a video camera, automatic focusing operation is performed by a focus evaluating value formed in response to a video signal obtained by an image sensing circuit (4). A first focusing motor control circuit (15) controls the rotation of a focusing motor (3) so that a focusing lens (1) is once fixed in the position where the focus evaluating value takes the maximum value. A second focusing motor control circuit. (17) changes the focusing motor (3), by a predetermined very small amount, to determine the slope of the focus evaluating value, which change is repeated until inversion of the slope, that is , the maximal point is detected. As a result, the position of the focusing lens is corrected at the maximal point of the focus evaluating value. When the correction amount exceeds a predetermined value, first automatic focusing operation by the first focusing motor control circuit (15) is resumed.
Inventors
- 👤 Hirotsugu Murashima
- 👤 Satoru Maeda
- 👤 Shunji Hirano
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 21:21
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/60; H04N23/67; H04N23/673; G; G03; G03B; G03B13/00; G03B13/32; G03B13/34; G03B13/36
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
288 words
An automatic focusing circuit for automatically matching the focus in response to a video signal obtained from image sensing means having a focusing lens and an image sensor, comprising: focusing lens position changing means (2, 3) for changing the relative position in the direction of an optical axis of said focusing lens relative to said image sensor, focus evaluating value detecting means (5) for detecting a level of a high frequency component of the video signal obtained from said image sensing means every constant period, converting the level into either a focus evaluating value which takes the maximum value in the in-focus position or a focus evaluating value which takes the minimum value in the in-focus position, and sequentially supplying the same, first control means (10, 11, 12, 13, 14, 15, 30) connected to said focus evaluating value detecting means for controlling said focusing lens position changing means so that the position of said focusing lens is once fixed in the position where said focus evaluating value takes the maximum value or the minimum value, second control means (17, 18, 19) for changing, by a very small amount, the position of said focusing lens and detecting the change of said focus evaluating value corresponding to the very small change after the position of said focusing lens is once fixed by said first control means, so that the position of said focusing lens is corrected to the maximal point or the minimal point of said focus evaluating value, and switching control means (16, 17, 23) for resuming controlling the position of said focusing lens by said first control means when the correction amount of the position of said focusing lens by said second control means exceeds a predetermined value.
Claim 2
Dependent Claim
288 words
An automatic focusing circuit for automatically matching the focus in response to a video signal obtained from image sensing means having a focusing lens and an image sensor, comprising: focusing lens position changing means (2, 3) for changing the relative position in the direction of an optical axis of said focusing lens relative to said image sensor, focus evaluating value detecting means (5) for detecting a level of a high frequency component of the video signal obtained from said image sensing means every constant period, converting the level into either a focus evaluating value which takes the maximum value in the in-focus position or a focus evaluating value which takes the minimum value in the in-focus position, and sequentially supplying the same, first control means (10, 11, 12, 13, 14, 15, 30) connected to said focus evaluating value detecting means for controlling said focusing lens position changing means so that the position of said focusing lens is once fixed in the position where said focus evaluating value takes the maximum value or the minimum value, second control means (17, 18, 19) for changing, by a very small amount, the position of said focusing lens and detecting the change of said focus evaluating value corresponding to the very small change after the position of said focusing lens is once fixed by said first control means, so that the position of said focusing lens is corrected to the maximal point or the minimal point of said focus evaluating value, and switching control means (16, 17, 23) for resuming controlling the position of said focusing lens by said first control means when the correction amount of the position of said focusing lens by said second control means exceeds a predetermined value.
Claim 3
Dependent Claim
41 words
An automatic focusing circuit according to claim 1, wherein said first control means comprises initializing means (11, 13, 15) for initializing the direction of the change of the relative position of said focusing lens immediately after automatic focusing operation is started.
Claim 4
Dependent Claim
240 words
An automatic focusing circuit according to claim 2, wherein said focusing lens position changing means supplies information concerned with the position of the focusing lens, said first control means comprises a second memory (10) for always holding the maximum value or the minimum value of said focus evaluating value, second comparing means (12) for comparing the maximum value or the minimum value of the focus evaluating value held in said second memory with the focus evaluating value outputted from said focus evaluating value detecting means and determining that the position of said focusing lens passed through the position where said focus evaluating value takes the maximum value or the minimum value, a third memory (14) for holding information concerned with the position of said focusing lens when said focus evaluating value takes the maximum value or the minimum value, means (15) responsive to determination by said second comparing means for controlling said focusing lens position changing means so that the direction of the change of the position of said focusing lens is reversed, and third comparing means (30) for comparing the information held in said third memory with information concerned with the position of said focusing lens supplied after the direction of the change of the position of said focusing lens is reversed and controlling said focusing lens position changing means, so that the change of the position of said focusing lens is stopped when both coincide with each other.
Claim 5
Dependent Claim
119 words
An automatic focusing circuit according to claim 1, wherein said second control means comprises means (18, 19) for changing the position of said focusing lens by a predetermined amount in a predetermined direction and comparing focus evaluating values before and after said change, and thereby determining the slope of a focus evaluating value, means (17) for repeating the change by said predetermined amount until inversion of the slope of said focus evaluating value is detected, and thereby detecting the maximal point or the minimal point of said focus evaluating value, and means (17) for controlling said focusing lens position changing means so that the position of said focusing lens is fixed at said detected maximal point or minimal point.
Claim 6
Dependent Claim
34 words
An automatic focusing circuit according to claim 1, wherein correction of the position of said focusing lens by said second control means is intermittently repeated until control by said first control means is resumed.
Claim 7
Dependent Claim
72 words
An automatic focusing circuit according to claim 3, which further comprises fifth comparing means (90) for comparing the focus evaluating value when the position of the focusing lens is fixed by said first control means with the maximum value or the minimum value of the focus evaluating value held in said second memory and indicating resumption of control by said first control means when the difference therebetween exceeds a predetermined threshold value.
Claim 8
Dependent Claim
109 words
An automatic focusing circuit according to claim 3, which further comprises a circuit (100) connected to said third comparing means and having a predetermined correction amount held, said third comparing means controlling said focusing lens position changing means so that the change of the position of said focusing lens is stopped when the information held in said third memory and the information concerned with the position of said focusing lens supplied after the direction of the change of the position of said focusing lens is reversed coincide with each other and then it is determined that the position of the focusing lens further changed by said predetermined correction amount.
Claim 9
Dependent Claim
62 words
An automatic focusing circuit according to claim 7, wherein said predetermined correction amount is set to be the sum of the amount of change of the position of the focusing lens during a delay time period of detection of the focus evaluating value by said focus evaluating value detecting means and the amount of backlash in the focusing lens position changing means.
Claim 10
Dependent Claim
193 words
An automatic focusing circuit for automatically matching the focus in response to a video signal obtained from image sensing means having a focusing lens, a zoom lens, zoom lens moving means for moving said zoom lens in the direction of an optical axis and an image sensor, comprising: zoom position detecting means (54) for detecting the zoom position of said zoom lens, focus evaluating value detecting means (5) for detecting a level of a high frequency component of a video signal obtained from said image sensing means every constant period, converting the level into a focus evaluating value which takes the maximum value in the in-focus position or a focus evaluating value which takes the minimum value in the in-focus position and sequentially supplying the same, and focus control means (15, 17) connected to said zoom position detecting means and responsive to the change of the focus evaluating value supplied from said focus evaluating value detecting means for performing control in a predetermined characteristic so that said focusing lens is held in the in-focus position, said predetermined characteristic being switched in response to the zoom position detected by said zoom position detecting means.
Claim 11
Dependent Claim
193 words
An automatic focusing circuit for automatically matching the focus in response to a video signal obtained from image sensing means having a focusing lens, a zoom lens, zoom lens moving means for moving said zoom lens in the direction of an optical axis and an image sensor, comprising: zoom position detecting means (54) for detecting the zoom position of said zoom lens, focus evaluating value detecting means (5) for detecting a level of a high frequency component of a video signal obtained from said image sensing means every constant period, converting the level into a focus evaluating value which takes the maximum value in the in-focus position or a focus evaluating value which takes the minimum value in the in-focus position and sequentially supplying the same, and focus control means (15, 17) connected to said zoom position detecting means and responsive to the change of the focus evaluating value supplied from said focus evaluating value detecting means for performing control in a predetermined characteristic so that said focusing lens is held in the in-focus position, said predetermined characteristic being switched in response to the zoom position detected by said zoom position detecting means.
Claim 12
Dependent Claim
42 words
An automatic focusing circuit according to claim 9, wherein said focus control means comprises focusing lens position changing means (2, 3) for changing the relative position in the direction of the optical axis of said focusing lens relative to said image sensor.
Claim 13
Dependent Claim
67 words
An automatic focusing circuit according to claim 10, wherein said focus control means comprises first control means (10, 11, 12, 13, 14, 15, 30) connected to said focus evaluating value detecting means for controlling said focusing lens position changing means so that the position of said focusing lens is once fixed in the position where said focus evaluating value takes the maximum value or the minimum value.
Claim 14
Dependent Claim
184 words
An automatic focusing circuit according to claim 11, wherein said first control means comprises means (11, 13, 15) for initializing the direction of the change of the relative position of said focusing lens immediately after said automatic focus matching operation is started, a first memory (10) for always holding the maximum value or the minimum value of said focus evaluating value, first comparing means (12) for comparing the maximum value or the minimum value of the focus evaluating value held in said first memory with the focus evaluating value outputted from said focus evaluating value detecting means and determining that the position of said focusing lens passed through the position where said focus evaluating value takes the maximum value or the minimum value, and means (14, 15, 30) responsive to determination by said first comparing means for reversing the direction of the change of the position of said focusing lens and controlling said focusing lens position changing means so that the position of said focusing lens is returned to the position where said focus evaluating value takes the maximum value or the minimum value.
Claim 15
Dependent Claim
106 words
An automatic focusing circuit according to claim 12, wherein said first comparing means determines that the position of said focusing lens passed through the position where said focus evaluating value takes the maximum value or the minimum value when the absolute value of the difference between the maximum value or the minimum value of the focus evaluating value held in said first memory and the focus evaluating value outputted from said focus evaluating value detecting means exceeds a predetermined threshold value, and said focus control means comprises means (60) responsive to the zoom position detected by said zoom position detecting means for switching said threshold value.
Claim 16
Dependent Claim
28 words
An automatic focusing circuit according to claim 13, wherein said threshold value is the smallest when the zoom position is wide-angle and the largest when it is telephoto.
Claim 17
Dependent Claim
143 words
An automatic focusing circuit according to claim 11, wherein said focus control means comprises second control means (17, 18, 19) for changing, by a very small amount, the position of said focusing lens and detecting the change of a focus evaluating value corresponding to the very small change after the position of said focusing lens is once fixed by said first control means and then, correcting the position of said focusing lens at the maximal point or the minimal point of said focus evaluating value, switching means (16, 17, 23) for resuming controlling the position of the focusing lens by said first control means when the correction amount of the position of said focusing lens by said second control means exceeds a predetermined value, and means responsive to the zoom position detected by said zoom position detecting means for switching said predetermined value.
Claim 18
Dependent Claim
150 words
An automatic focusing circuit according to claim 15, wherein said second control means comprises means (18, 19) for changing the position of said focusing lens by a predetermined amount in a predetermined direction and comparing focus evaluating values before and after said change, and thereby determining the slope of a focus evaluating value, means (17) for repeating the change by said predetermined amount until inversion of the slope of said focus evaluating value is detected, and thereby detecting the maximal point or the minimal point of said focus evaluating value, and means (17) for controlling said focusing lens position changing means so that the position of said focusing lens is fixed at said detected maximal point or minimal point, the correction amount of the position of said focusing lens being defined by the number of repetitions of the change by a predetermined amount of the position of said focusing lens.
Claim 19
Dependent Claim
31 words
An automatic focusing circuit according to claim 15, wherein said predetermined value is the largest when a zoom is a wide-angle region and the smallest when it is a telephoto region.
Claim 20
Dependent Claim
126 words
An automatic focusing circuit according to claim 11, wherein said focus control means comprises a second memory (20) for holding said focus evaluating value at the time point when the position of said focusing lens is once fixed by said first control means, second comparing means (80, 82) for comparing the focus evaluating value held in said second memory with the focus evaluating value outputted from said focus evaluating value detecting means during operation by said second control means and indicating resumption of control of the position of the focusing lens by said first control means when the difference therebetween exceeds a predetermined threshold value, and means (81) responsive to the zoom position detected by said zoom position detecting means for switching said predetermined threshold value.
Claim 21
Dependent Claim
39 words
An automatic focusing circuit according to claim 18, wherein said threshold value is large when the zoom position is in wide-angle and telephoto regions and small when it is in the intermediate region between the wide-angle and telephoto regions.
References Cited (Backward Citations)
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