US3617633A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Improvements in or relating to television camera automatic focus control system
Assignee: Rank Organization Ltd
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Filing: 1968-11-29
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Granted: 1971-11-02
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Expires: 1988-11-29
Abstract
Abstract A system for automatically maintaining the focus of a television camera in which the camera focus setting is modulated, preferably at half the frame or line scan frequency, and the camera video output passed through a high pass filter to a phase-sensitive detector. The output of the detector is indicative of the magnitude and sense of the departure of the camera focus setting from sharp focus, and is used to control a focus servo.
Inventors
- 👤 John Denzil Barr
- 👤 Dexter Robert Plummer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 19:01
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/60; H04N23/67; H04N23/673
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
148 words
In a television camera, an automatic focusing system comprising: a focus modulator effective to cyclically modulate the focus setting of the camera with a substantially square waveform at a focus modulation frequency which is synchronous with the frame scan frequency of the camera, a high-pass filter connected to the video output of the camera adapted to pass high-frequency components of said video output, a detector responsive to the output component of the high-pass filter at the modulation frequency, phase-sensitive demodulator means, means synchronizing the phase-sensitive demodulator means to the focus modulation frequency, said phase-sensitive demodulator means providing a focus error signal indicative of the sense and magnitude of the departure of the focus setting and from a sharp focus setting, servo means effective to adjust the camera focus setting in response to said focus error signal and in a sense to reduce the magnitude of said error signal.
Claim 2
Dependent Claim
148 words
In a television camera, an automatic focusing system comprising: a focus modulator effective to cyclically modulate the focus setting of the camera with a substantially square waveform at a focus modulation frequency which is synchronous with the frame scan frequency of the camera, a high-pass filter connected to the video output of the camera adapted to pass high-frequency components of said video output, a detector responsive to the output component of the high-pass filter at the modulation frequency, phase-sensitive demodulator means, means synchronizing the phase-sensitive demodulator means to the focus modulation frequency, said phase-sensitive demodulator means providing a focus error signal indicative of the sense and magnitude of the departure of the focus setting and from a sharp focus setting, servo means effective to adjust the camera focus setting in response to said focus error signal and in a sense to reduce the magnitude of said error signal.
Claim 3
Dependent Claim
34 words
System as claimed in claim 1 including means adjusting the focal length setting of the camera, whereby the depth of focus modulation remains substantially constant irrespective of the focal length setting of the camera.
Claim 4
Dependent Claim
44 words
System as claimed in claim 1 including gating means through which the video output of the camera is applied to the high-pass filter, said gating means selecting a predetermined part of the video output to be used to control the focus of the camera.
Claim 5
Dependent Claim
47 words
System as claimed in claim 3, including a monitor effective to indicate, in combination, the gating signal and the selected part of the camera video output, thereby indicating the position of the selected zone of the picture viewed by the camera to which focus control is applied.
Claim 6
Dependent Claim
47 words
System as claimed in claim 3, including selector means controlling the gating means and effective to select the predetermined part of the video output, corresponding to a selected zone of the field of view of the camera, which is passed by the gating means to the filter.
Claim 7
Dependent Claim
29 words
System as claimed in claim 5, wherein the gating means include a gating signal generator synchronized with respect to the scanning waveforms of the camera and effective to produce
Claim 8
Dependent Claim
48 words
System as claimed in claim 1, in which the focus modulator comprises at least one optical element movable within the optical path of the camera to cause cyclic fluctuation of the camera focus setting, while the picture size and position as viewed in the camera remain substantially constant.
Claim 9
Dependent Claim
60 words
System as claimed in claim 7, in which the focus modulator comprises a pair of light-transmitting elements of varying optical thickness, and means effecting oscillation of said elements in phase opposition substantially perpendicular to the optical axis of the camera to cause cyclic variation of the total effective thickness of the said elements in the optical path of the camera.
Claim 10
Dependent Claim
34 words
System as claimed in claim 8, in which the light-transmitting elements are of uniformly varying thickness and are arranged with their thicknesses varying in opposite directions, perpendicular to the optical axis of the camera.
Claim 11
Dependent Claim
34 words
System as claimed in claim 9, in which the light-transmitting elements are substantially identical wedge-shaped elements arranged transversely to the optical axis of the cameras with their apices on opposite sides of said axis.
Claim 12
Dependent Claim
44 words
System as claimed in claim 9, in which the light-transmiTting elements comprise respectively a wedge-shaped element arranged transversely to the optical axis of the camera and a light-transmitting block having means defining a wedge-shaped recess into which the wedge-shaped element at least partially fits.
Claim 13
Dependent Claim
148 words
In a television camera, an automatic focusing system comprising: a focus modulator effective to cyclically modulate the focus setting of the camera with a substantially square waveform at a focus modulation frequency which is half the line scan frequency of the camera, a high-pass filter connected to the video output of the camera and adapted to pass high frequency components of said video output, a detector responsive to the output component of the high-pass filter at the modulation frequency, phase-sensitive demodulator means, means synchronizing the phase-sensitive demodulator means to the focus modulation frequency, said phase-sensitive demodulator means providing a focus error signal indicative of the sense and magnitude of the departure of the focus setting from a sharp focus setting, servo means effective to adjust the camera focus setting in response to said focus error signal and in a sense to reduce the magnitude of said error signal,
Claim 14
Dependent Claim
148 words
In a television camera, an automatic focusing system comprising: a focus modulator effective to cyclically modulate the focus setting of the camera with a substantially square waveform at a focus modulation frequency which is half the line scan frequency of the camera, a high-pass filter connected to the video output of the camera and adapted to pass high frequency components of said video output, a detector responsive to the output component of the high-pass filter at the modulation frequency, phase-sensitive demodulator means, means synchronizing the phase-sensitive demodulator means to the focus modulation frequency, said phase-sensitive demodulator means providing a focus error signal indicative of the sense and magnitude of the departure of the focus setting from a sharp focus setting, servo means effective to adjust the camera focus setting in response to said focus error signal and in a sense to reduce the magnitude of said error signal,
Claim 15
Dependent Claim
48 words
System as claimed in claim 12 in which the focus modulator comprises at least one optical element movable within the optical path of the camera to cause cyclic fluctuation of the camera focus setting, while the picture size and position as viewed in the camera remain substantially constant.
Claim 16
Dependent Claim
44 words
System as claimed in claim 12 including gating means through which the video output of the camera is applied to the high-pass filter, said gating means selecting a predetermined part of the video output to be used to control the focus of the camera.
Claim 17
Dependent Claim
47 words
System as claimed in claim 14, including selector means controlling the gating means and effective to select the predetermined part of the video output, corresponding to a selected zone of the field of view of the camera, which is passed by the gating means to the filter.
Claim 18
Dependent Claim
47 words
System as claimed in claim 15, wherein the gating means include a gating signal generator synchronized with respect to the scanning waveforms of the camera and effective to produce gating signals at predetermined parts of the line scan of the camera, as determined by the selector means.
Claim 19
Dependent Claim
47 words
System as claimed in claim 14, including a monitor effective to indicate, in combination, the gating signal and the selected part of the camera video output, thereby indicating the position of the selected zone of the picture viewed by the camera to which focus control is applied.
Claim 20
Dependent Claim
34 words
System as claimed in claim 12, including means adjusting the focal length setting of the camera, whereby the depth of focus modulation remains substantially constant irrespective of the focal length setting of the camera.
Claim 21
Dependent Claim
147 words
In a television camera, an automatic focusing system comprising: a focus modulating effective to cyclically modulate the focus setting of the camera with a substantially square waveform at a focus modulation frequency which is half the frame scan frequency of the camera, a high-pass filter connected to the video output of the camera and adapted to pass high-frequency components of said video output, a detector responsive to the output component of the high-pass filter at the modulation frequency, phase-sensitive demodulator means, means synchronizing the phase-sensitive demodulator means to the focus modulation frequency, said phase-sensitive demodulator means providing a focus error signal indicative of the sense and magnitude of the departure of the focus setting from a sharp focus setting, servo means effective to adjust the camera focus setting in response to said focus error signal and in a sense to reduce the magnitude of said error signal.
Claim 22
Dependent Claim
147 words
In a television camera, an automatic focusing system comprising: a focus modulating effective to cyclically modulate the focus setting of the camera with a substantially square waveform at a focus modulation frequency which is half the frame scan frequency of the camera, a high-pass filter connected to the video output of the camera and adapted to pass high-frequency components of said video output, a detector responsive to the output component of the high-pass filter at the modulation frequency, phase-sensitive demodulator means, means synchronizing the phase-sensitive demodulator means to the focus modulation frequency, said phase-sensitive demodulator means providing a focus error signal indicative of the sense and magnitude of the departure of the focus setting from a sharp focus setting, servo means effective to adjust the camera focus setting in response to said focus error signal and in a sense to reduce the magnitude of said error signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-01 | 1975-05-03 | 1975-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-01 | 1979-05-03 | 1979-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-01 | 1983-05-03 | 1983-11-02 | $7700.00 | Window Closed / Lapsed |