US4701782A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of automatic focussing by digital analysis of the contours of an image
Assignee: US Philips Corp
•
Filing: 1986-03-31
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Granted: 1987-10-20
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Expires: 2006-03-31
Abstract
Abstract Method of automatic focussing of a video pickup device having an objective and producing a digital image. According to the invention, this method comprises analyzing the image, within a window, with the aid of at least one digital operator. The digital operator takes the derivatives, in a given direction, of the contours of the image. Thereafter, the absolute values of these derivatives are computed. Finally, a quality parameter defined by the sum, in the window, of the absolute values of the derivatives is calculated. The position of the objective of the pickup device is controlled so as to maximize the value of the quality parameter.
Inventors
- 👤 Jean-Louis Duvent
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 10:13
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/60; H04N23/67; H04N23/673
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
125 words
A method of automatically focusing an image onto a video pickup device, said method comprising the steps of: arranging an objective in front of the pickup device to direct radiation onto the pickup device; generating a contour signal representing the intensity of the radiation on the pickup device as a function of the position on the pickup device; generating a first derivative signal representing the derivative of the contour signal with respect to position along a line on the pickup device; generating an absolute value signal representing the absolute value of the first derivative signal; generating a quality parameter representing the integral of the absolute value signal with respect to position; and controlling the position of the objective so as to maximize the quality parameter.
Claim 2
Independent Claim
125 words
A method of automatically focusing an image onto a video pickup device, said method comprising the steps of: arranging an objective in front of the pickup device to direct radiation onto the pickup device; generating a contour signal representing the intensity of the radiation on the pickup device as a function of the position on the pickup device; generating a first derivative signal representing the derivative of the contour signal with respect to position along a line on the pickup device; generating an absolute value signal representing the absolute value of the first derivative signal; generating a quality parameter representing the integral of the absolute value signal with respect to position; and controlling the position of the objective so as to maximize the quality parameter.
Claim 3
Dependent Claim
17 words
A method as claimed in claim 1, characterized in that all of the signals are digital signals.
Claim 4
Dependent Claim
37 words
A method as claimed in claim 2, characterized in that the first derivative signal represents the derivative of the contour signal with respect to position on a plurality of lines in a window on the pickup device.
Claim 5
Dependent Claim
14 words
A method as claimed in claim 3, characterized in that the lines are straight.
Claim 6
Dependent Claim
17 words
A method as claimed in claim 4, characterized in that the lines are parallel to each other.
Claim 7
Dependent Claim
27 words
A method as claimed in claim 5, characterized in that: the lines are field lines; and the first derivative is generated by a [+1, -1] digital operator.
Claim 8
Dependent Claim
28 words
A method as claimed in claim 5, characterized in that: the lines are field lines; and the first derivative is generated by a [+1, 0, -1] digital operator.
Claim 9
Dependent Claim
28 words
A method as claimed in claim 5, characterized in that: the lines are perpendicular to field lines; and the first derivative is generated by a ##EQU12## digital operator.
Claim 10
Dependent Claim
22 words
A method as claimed in claim 4, characterized in that the lines comprise both field lines and lines perpendicular to field lines.
Claim 11
Dependent Claim
45 words
A method as claimed in claim 4, characterized in that the step of generating the quality parameter further comprises: comparing the absolute value signal with a threshold value; and reducing to zero any portions of the absolute value signal which do not exceed the threshold.
Claim 12
Dependent Claim
57 words
A method as claimed in claim 4, characterized in that the position of the objective is controlled by the steps of: generating an error signal equal to the derivative of the quality parameter with respect to the position of the objective; and controlling the position of the objective so as to drive the error signal to zero.
Claim 13
Independent Claim
167 words
A method of automatically focusing an image onto a video pickup device, said method comprising the steps of: arranging an objective in front of the pickup device to direct radiation onto the pickup device; generating a contour signal representing the intensity of the radiation on the pickup device as a functon of the position on the pickup device; generating a first derivative signal representing the derivative of the contour signal with respect to position along a line on the pickup device; generating a first absolute value signal representing the absolute value of the first derivative signal; generating a second derivative signal representing the derivative of the first absolute value signal with respect to position along the line on the pickup device; generating a second absolute value signal representing the absolute value of the second derivative signal; generating a quality parameter representing the integral of the second absolute value signal with respect to position; and controlling the position of the objective so as to maximize the quality parameter.
Claim 14
Independent Claim
167 words
A method of automatically focusing an image onto a video pickup device, said method comprising the steps of: arranging an objective in front of the pickup device to direct radiation onto the pickup device; generating a contour signal representing the intensity of the radiation on the pickup device as a functon of the position on the pickup device; generating a first derivative signal representing the derivative of the contour signal with respect to position along a line on the pickup device; generating a first absolute value signal representing the absolute value of the first derivative signal; generating a second derivative signal representing the derivative of the first absolute value signal with respect to position along the line on the pickup device; generating a second absolute value signal representing the absolute value of the second derivative signal; generating a quality parameter representing the integral of the second absolute value signal with respect to position; and controlling the position of the objective so as to maximize the quality parameter.
Claim 15
Dependent Claim
17 words
A method as claimed in claim 12, characterized in that all of the signals are digital signals.
Claim 16
Dependent Claim
61 words
A method as claimed in claim 13, characterized in that: the first derivative signal represents the derivative of the contour signal with respect to position on a plurality of lines in a window on the pickup device; and the second derivative signal represents the derivative of the first absolute value signal with respect to position on the same plurality of lines.
Claim 17
Dependent Claim
14 words
A method as claimed in claim 14, characterized in that the lines are straight.
Claim 18
Dependent Claim
17 words
A method as claimed in claim 15, characterized in that the lines are parallel to each other.
Claim 19
Dependent Claim
27 words
A method as claimed in claim 16, characterized in that: the lines are field lines; and the first derivative is generated by a [+1, -1] digital operator.
Claim 20
Dependent Claim
28 words
A method as claimed in claim 16, characterized in that: the lines are field lines; and the first derivative is generated by a [+1, 0, -1] digital operator.
Claim 21
Dependent Claim
28 words
A method as claimed in claim 16, characterized in that: the lines are perpendicular to field lines; and the first derivative is generated by a ##EQU13## digital operator.
Claim 22
Dependent Claim
22 words
A method as claimed in claim 15, characterized in that the lines comprise both field lines and lines perpendicular to field lines.
Claim 23
Dependent Claim
47 words
A method as claimed in claim 15, characterized in that the step of generating the quality parameter further comprises: comparing the first absolute value signal with a threshold value; and reducing to zero any portions of the first absolute value signal which do not exceed the threshold.
Claim 24
Dependent Claim
57 words
A method as claimed in claim 15, characterized in that the position of the objective is controlled by the steps of: generating an error signal equal to the derivative of the quality parameter with respect to the position of the objective; and controlling the position of the objective so as to drive the error signal to zero.
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Cited
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Cited
US4354204A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-10-19 | 1991-04-20 | 1991-10-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-10-19 | 1995-04-20 | 1995-10-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-10-19 | 1999-04-20 | 1999-10-20 | $7700.00 | Window Closed / Lapsed |