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US3902011A
Expired / Lapsed
US
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Image analysing
Assignee: MELDRETH ELECTRONICS Ltd
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Filing: 1973-05-09
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Granted: 1975-08-26
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Expires: 1993-05-09
Abstract
Abstract The invention provides a method and apparatus for correcting shading distortion in a source of scanned video signal. A multiple location store is provided for storing a signal indicative of the shading correction required at each of a number of selected, spaced apart points in the scannable region of the source and signal interpolation means is provided for interpolating between the stores values of correction in both line and frame scan directions for other points in the region. The invention also provides a method and apparatus for loading the correction signals into the store locations automatically during a number of frame scans of the region. This is achieved by correcting the video signal at each point by a known amount, comparing the corrected signal with a reference signal and storing a signal indicative of this amount of correction if the comparison indicates that the correction has improved the shading of the video signal. The final correction signal stored at each store location is derived by a method of successive approximations.
Inventors
- 👤 Leon Andre Pieters
- 👤 James Frank Wren
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 19:18
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/80; H04N23/81
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
173 words
A method of generating and storing information signals in a memory which on subsequent address can be used to control the amplitude of a video signal so as to correct for shading in each of plurality of separate regions which together make up the scanned region of a source of video signal, each said region being substantially larger in area than the area of a scanning spot, comprising, in combination the steps of, subjecting the scanned region to uniform illumination, for each said region comparing with a constant reference voltage having an amplitude other than zero the video signal amplitude from said source at only a single selected point in that region, generating a correction signal in response to this comparison, the correction signal being such as to produce a given amplitude level of the video signal if the latter is then modified by said correction signal, and loading the correction signals corresponding to said selected points into a memory in spatial correspondence with the position of said points in said scanned region.
Claim 2
Independent Claim
173 words
A method of generating and storing information signals in a memory which on subsequent address can be used to control the amplitude of a video signal so as to correct for shading in each of plurality of separate regions which together make up the scanned region of a source of video signal, each said region being substantially larger in area than the area of a scanning spot, comprising, in combination the steps of, subjecting the scanned region to uniform illumination, for each said region comparing with a constant reference voltage having an amplitude other than zero the video signal amplitude from said source at only a single selected point in that region, generating a correction signal in response to this comparison, the correction signal being such as to produce a given amplitude level of the video signal if the latter is then modified by said correction signal, and loading the correction signals corresponding to said selected points into a memory in spatial correspondence with the position of said points in said scanned region.
Claim 3
Dependent Claim
41 words
A method as set forth in claim 1 in which the source employs fixed raster scanning and the location of the points in the scanned region of the source are related to time, based on the frame and line scanning rates.
Claim 4
Dependent Claim
38 words
A method as set forth in claim 1 in which the number of selected points per unit area of the scanned region of the source is greater in at least one portion thereof than in the remainder thereof.
Claim 5
Dependent Claim
32 words
A method as set forth in claim 1 wherein the video signal amplitude sampled at each selected point is the average of the video signal amplitude at and near the selected point.
Claim 6
Independent Claim
126 words
A method of generating and storing a shading correction signal for each of a plurality of separate points in a scanned region of a source of video signal comprising the steps of: subjecting the scanned region to uniform illumination, scanning the region generating a correction signal and modifying therewith the amplitude of the video signal obtained by scanning the region, comparing the modified video signal amplitude corresponding to each point with a constant reference voltage, generating an information signal from the comparison if the modified video signal bears a predetermined relation to the reference voltage, and storing the corRection signal for each point at which an information signal is generated in a memory in spatial correspondence with the position of the point in the scanned region.
Claim 7
Independent Claim
126 words
A method of generating and storing a shading correction signal for each of a plurality of separate points in a scanned region of a source of video signal comprising the steps of: subjecting the scanned region to uniform illumination, scanning the region generating a correction signal and modifying therewith the amplitude of the video signal obtained by scanning the region, comparing the modified video signal amplitude corresponding to each point with a constant reference voltage, generating an information signal from the comparison if the modified video signal bears a predetermined relation to the reference voltage, and storing the corRection signal for each point at which an information signal is generated in a memory in spatial correspondence with the position of the point in the scanned region.
Claim 8
Dependent Claim
41 words
The method as set forth in claim 5 in which the source employs fixed raster scanning thd the location of the points in the scanned region of the source are related to time, based on the frame and line scanning rates.
Claim 9
Dependent Claim
34 words
A method as set forth in claim 5 wherein the modified video signal amplitude sampled at each selected point is the average of the modified video signal amplitudes at and near the selected point.
Claim 10
Dependent Claim
154 words
Apparatus for deriving a correction signal for compensating for shading at each of a plurality of selected points in the scanned region of a source of video signal and inserting the derived signal for each point into a store location of a multi-location store, comprising, in combination with a source of video signal and a multi-location store, constant reference voltage source means for generating a reference voltage other than zero volts, signal comparator means for comparing with the reference voltage the video signal amplitude obtained by scanning the region when the latter is uniformly illuminated, means for generating a difference signal whose magnitude is proportional to any difference between the video signal amplitude and the reference voltage, means for addressing the store location appropriate to the position of the scanning of the spot at any instant and means for inserting into the appropriate store location the difference signal which obtains at each selected point.
Claim 11
Dependent Claim
154 words
Apparatus for deriving a correction signal for compensating for shading at each of a plurality of selected points in the scanned region of a source of video signal and inserting the derived signal for each point into a store location of a multi-location store, comprising, in combination with a source of video signal and a multi-location store, constant reference voltage source means for generating a reference voltage other than zero volts, signal comparator means for comparing with the reference voltage the video signal amplitude obtained by scanning the region when the latter is uniformly illuminated, means for generating a difference signal whose magnitude is proportional to any difference between the video signal amplitude and the reference voltage, means for addressing the store location appropriate to the position of the scanning of the spot at any instant and means for inserting into the appropriate store location the difference signal which obtains at each selected point.
Claim 12
Independent Claim
225 words
A method of deriving a correction signal in binary digital form for compensating for shading at each of a plurality of selected points in the scanned region of a source of video signal and inserting the binary digital signals into a multilocation store, comprising the steps of, subjecting the scanned region to uniform illumination, scanning the region a first time and applying a first level of correction to the video signal amplitude, comparing the corrected amplitude at the selected points with a reference voltage, generating one of two binary signals if the corrected amplitude exceeds the reference voltage and the other binary signal if the corrected amplitude is below the reference voltage, inserting the generated binary signal into a store location corresponding to each selected point and during each of (n - 1) successive scans applying in turn each of (n - 1) different levels of correction to the video signal amplitude and inserting the appropriate binary signal from each comparison into the store locations corresponding to the selected points thereby to build up a parallel binary word of n bits at each store location describing the level of correction required to the video signal amplitude at each selected point, the corrected video signal amplitude sampled at each selected point being the average of the corrected video signal amplitudes at and near the selected point.
Claim 13
Independent Claim
225 words
A method of deriving a correction signal in binary digital form for compensating for shading at each of a plurality of selected points in the scanned region of a source of video signal and inserting the binary digital signals into a multilocation store, comprising the steps of, subjecting the scanned region to uniform illumination, scanning the region a first time and applying a first level of correction to the video signal amplitude, comparing the corrected amplitude at the selected points with a reference voltage, generating one of two binary signals if the corrected amplitude exceeds the reference voltage and the other binary signal if the corrected amplitude is below the reference voltage, inserting the generated binary signal into a store location corresponding to each selected point and during each of (n - 1) successive scans applying in turn each of (n - 1) different levels of correction to the video signal amplitude and inserting the appropriate binary signal from each comparison into the store locations corresponding to the selected points thereby to build up a parallel binary word of n bits at each store location describing the level of correction required to the video signal amplitude at each selected point, the corrected video signal amplitude sampled at each selected point being the average of the corrected video signal amplitudes at and near the selected point.
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) | 1978-08-25 | 1979-02-24 | 1979-08-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-25 | 1983-02-24 | 1983-08-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-25 | 1987-02-24 | 1987-08-26 | $7700.00 | Window Closed / Lapsed |