Image analysing

Claim 3

The method as set forth in claim 1 in which the selected points are the points of intersection of two sets of imaginary parallel lines drawn across the scanned region, the two sets of lines being perpendicular and one set being parallel to the line scan direction.

Claim 4

The method as set forth in claim 1 in which each group comprises the store locations containing the information signals from four adjoining selected points defining a rectangle.

Claim 5

The method as set forth in claim 3 in which the signals in each group are combined by interpolating between the four information signals, the contributions of the four signals to the combined signal being dependent on the respective distances of the four selected points from the position of the scanning spot, measured parallel and perpendicular to theline scan direction.

Claim 6

The method as set forth in claim 1 in which the modification of the video signal amplitude is achieved by varying the gain of a variable gain amplifier in the path of the signal, the gain of the amplifier being increased by the control voltage in shaded areas to increase the amplitude of the video signal in those areas.

Claim 7

The method as set forth in claim 1 in which the number of selected points per unit area of the scanned region is greater in at least one portion than in the remainder thereof.

Claim 8

The method as set forth in claim 1 in which the video signal amplitude sampled at each selected point is the average of the video signal amplitudes at and near the selected point.

Claim 9

The method as set forth in claim 1 wherein the controlled amplitude video signal is compared with a reference voltage to effect an analysis of the video signal Amplitude excursions.

Claim 12

The method as set forth in claim 9 in which the reference voltage is controlled by information signals combined from four adjacent selected points defining a rectangle.

Claim 13

The method as set forth in claim 10 in which said combination of signals is effected by interpolating between the four information signals, the contributions of the four signals to thecombined signal being dependent on the respective distances of the four selected points from the position of the scanning spot measured parallel and perpendicular to the line scan direction.

Claim 14

The method as set forth in claim 9 in which the number of selected points per unit area of the scanned region is greater in at least one portion than in the remainder thereof.

Claim 15

The method as set forth in claim 9 in which the video signal amplitude sampled at each selected point is the average of the video signal amplitudes at and near the selected point.

Claim 16

Apparatus for correcting the amplitude of a video signal obtained by scanning a photosensitive region of a video signal source subject to shading distortion, comprising: means for scanning said region, a multiple location signal store, each store location serving to hold a shading correction signal for correcting the video signal amplitude at one selected point in the scanned region, means for reading the store locations in groups in correspondence with said scanning of said region to read the correction signals from said store locations, each said group containing the signals from selected points in the scanned region which define an area within which the scanning spot lies, circuit means responsive to said read signals for combining the signals to generate a control voltage therefrom, a variable gain amplifier adapted to amplify the video signal and means for supplying the control voltage to the variable gain amplifier as a gain control voltage therefor.

Claim 17

Apparatus for correcting the amplitude of a video signal obtained by scanning a photosensitive region of a video signal source subject to shading distortion, comprising: means for scanning said region, a multiple location signal store, each store location serving to hold a shading correction signal for correcting the video signal amplitude at one selected point in the scanned region, means for reading the store locations in groups in correspondence with said scanning of said region to read the correction signals from said store locations, each said group containing the signals from selected points in the scanned region which define an area within which the scanning spot lies, circuit means responsive to said read signals for combining the signals to generate a control voltage therefrom, a variable gain amplifier adapted to amplify the video signal and means for supplying the control voltage to the variable gain amplifier as a gain control voltage therefor.

Claim 18

Apparatus as set forth in claim 14, further comprising means for interpolating between the signals released in each group and generating from the plurality of signals in the group a combined correction signal corresponding to a weighted average of the said plurality of signals, the weighting of the signals from the store locations at any instant being inversely proportional to the relative distances between the points in the scanned region to which the store locations relate and the position of the scanning spot at that instant.

Claim 19

Apparatus as set forth in claim 14 further comprising a reference voltage source, a voltage comparator, and means for supplying to the comparator the reference voltage and the amplified video signal from the variable gain amplifier, said comparator being arranged to detect the amplitude excursions of the video signal relative to the reference voltage to produce a Detected video signal.

Claim 20

Apparatus for analysing the amplitude excursions of a video signal comprising in combination, a photosensitive region, means for electronically scanning the region to produce the video signal, a multiple location signal store for storing a shading correction information signal for each of a plurality of selected points in the region, means for addressing the store locations in groups in synchronism with the scanning of the region, each group of locations read containing signals corresponding to information from points in the scanned region which define an area within which the scanning spot lies, circuit means responsive to the addressed signals for generating a reference voltage therefrom, and a comparator for comparing the video signal amplitude excursions with the reference voltage to generate a constant amplitude pulse each time the amplitude exceeds the reference voltage for effecting said analysis.

Claim 21

Apparatus for analysing the amplitude excursions of a video signal comprising in combination, a photosensitive region, means for electronically scanning the region to produce the video signal, a multiple location signal store for storing a shading correction information signal for each of a plurality of selected points in the region, means for addressing the store locations in groups in synchronism with the scanning of the region, each group of locations read containing signals corresponding to information from points in the scanned region which define an area within which the scanning spot lies, circuit means responsive to the addressed signals for generating a reference voltage therefrom, and a comparator for comparing the video signal amplitude excursions with the reference voltage to generate a constant amplitude pulse each time the amplitude exceeds the reference voltage for effecting said analysis.

Claim 22

Apparatus as set forth in claim 17 further comprising, means for interpolating between the signals released in each group and generating from theplurality of signals in the group a combined correction signal corresponding to a weighted average of the said plurality of signals, the weighting of the signals from the store locations at any instant being inversely proportional to the relative distances between the points in the scanned region to which the store locations relate and the position of thescanning spot at that instant.

Claim 23

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 multilocation store comprising, in combination with a source of video signal and a multi-locationstore, a variable gain amplifier for increasing the video signal amplitude, a comparator for comparing the modified video signal amplitude with a reference voltage and generating an ''''above'''' or ''''below'''' output signal depending on whether the increased video signal amplitude is greater or less than the reference voltage, an incremental correction signal generator, means for addressing the output of the store location appropriate to the position of the spot in the source at any instant means for inserting the incremental correction signal generator output into thememory store locations, means for reading the store locations in groups and generating a gain control voltage for the variable gain amplifier from the signals in each group, each said group containing the signals from selected points in the scanned region which define an area within which the scanning spot lies, menas responsive to an ''''above'''' signal to inhibit the subsequent insertion of an incremental correction signal, means for changing the size of the incremental correction signal from frame scan to frame scan, and means for inhibiting insertion of incremental correction signals into the store locations after a predetermined number of frame scans.

Claim 24

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 multilocation store comprising, in combination with a source of video signal and a multi-locationstore, a variable gain amplifier for increasing the video signal amplitude, a comparator for comparing the modified video signal amplitude with a reference voltage and generating an ''''above'''' or ''''below'''' output signal depending on whether the increased video signal amplitude is greater or less than the reference voltage, an incremental correction signal generator, means for addressing the output of the store location appropriate to the position of the spot in the source at any instant means for inserting the incremental correction signal generator output into thememory store locations, means for reading the store locations in groups and generating a gain control voltage for the variable gain amplifier from the signals in each group, each said group containing the signals from selected points in the scanned region which define an area within which the scanning spot lies, menas responsive to an ''''above'''' signal to inhibit the subsequent insertion of an incremental correction signal, means for changing the size of the incremental correction signal from frame scan to frame scan, and means for inhibiting insertion of incremental correction signals into the store locations after a predetermined number of frame scans.

Claim 25

Apparatus as set forth in claim 19 wherein the means generating the gain control voltage interpolates between the signals supplied thereto and generates a weighted average thereof the weighting of the signals from the different store locations at any time being inversely proportional to the relative distances between the points in the scanned region to which they relate and the positions of the scanning spot at that time.

Claim 26

Apparatus as set forth in claim 20 wherein the store is adapted for storing electrical signals in digital form.