EP0878970A2
Expired / Lapsed
EP
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Imager registration error and chromatic aberration measurement system for a video camera
Assignee: Panasonic Corp
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Filing: 1998-05-06
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Granted: —
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Expires: 2018-05-06
Abstract
Abstract A system for detecting and measuring registration errors and chromatic aberration in color images derived from a color video camera includes an edge locator which finds edges in respective zones of the color images and stores sets of samples representing picture elements of each of at least two component color signals. A microprocessor processes the stored sample sets to identify a coarse displacement between corresponding samples of the two component color signals. The microprocessor then determines a fine displacement between the two color signals. The coarse displacement may be determined by performing a cross correlation on the two sample sets or by calculating respective sums of absolute difference between the two sample sets for different displacements between corresponding samples of the two samples sets. The fine displacement may be determined by interpolating samples interstitial to the samples of the first sample set surrounding the sample which is closest to the identified edge and interpolated samples interstitial to the samples of the second samples set which are displaced from the first set of samples by the coarse displacement and then performing a cross correlation on the resulting original and interstitial samples. The fine displacement may also be determined by fitting a parabolic curve to either the cross correlation values of the original sample values or to the calculated sum of absolute difference values for the two sample sets. The fine displacement, is added to or subtracted from the coarse displacement to obtain a measure of the registration error and/or chromatic aberration in the images to sub-pixel resolution.
Inventors
- 👤 Lee Dischert
- 👤 Thomas J. Leacock
- 👤 Robert T. Topper
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 17:11
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/10; H04N23/13; H04N23/15
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
190 words
A method for measuring registration errors and chromatic
aberration in video signals, said video signals being represented as least first and
second color signals and said registration errors and chromatic aberration appearing as
misaligned edges of the first and second color signals in an image reproduced from the
video signals, the method comprising the steps of: a) selecting a first set of N samples of the first color signal and a second
set of N samples of the second color signal, where N is an integer greater than 2; b) analyzing the set of samples of the first color signal to determine
whether the first set of samples contains M samples representing an edge in the image,
where M is an integer less than N, and storing the first and second sets of samples if
the first set of samples is determined to contain the M samples representing the edge;
and c) comparing the stored first set of samples to the stored second set of
samples to determine a displacement between the M samples in the first set of samples
with M corresponding samples in the second set of samples.
Claim 2
Dependent Claim
57 words
A method according to claim 1, wherein step a) further includes
the steps of: calculating a measure of color balance between the first set of samples
and the second set of samples; and discarding the first and second sets of samples if the measure of color
balance has a value which is not within a predetermined range.
Claim 3
Dependent Claim
149 words
A method according to claim 2, wherein the first and second sets
of samples represent image picture elements (pixels) in a line of the image and step a)
further includes the steps of: selecting third and fourth sets of samples of said first color signal, each
of the samples in the third and fourth sets of samples corresponding to a pixel which is
immediately adjacent to a respective pixel element in said first set of samples; analyzing the first, third and fourth sets of samples to determine whether
the first set of samples is adjacent to an edge which is parallel to the line of the image
or represent an edge which intersects the line of the image on a diagonal; and discarding the first, second, third and fourth sets of samples if the first
set of samples is adjacent to the parallel edge or represents the diagonal edge.
Claim 4
Dependent Claim
68 words
A method according to claim 1, wherein M equals 2 and step b)
includes the steps of: calculating difference values between successive ones of the samples in
the first set of samples; comparing each of the calculated difference values to an edge threshold
value; and indicating that the set of samples represents an edge if any of the
calculated difference values is greater than the edge threshold value.
Claim 5
Dependent Claim
205 words
A method according to claim 1, wherein step c) includes the steps of: performing a cross correlation between the stored first set of samples
and the stored second set of samples to identify a coarse displacement between
respective edges in the first and second sets of samples to a nearest intersample
distance; selecting the M samples from the stored first set of samples and M
corresponding samples from the stored second set of samples, wherein each of the
samples from the second set is displaced by the identified displacement from the
respective sample in the first set; interpolating S samples between successive ones of the M samples of
each of the first and second sets of samples, where S is an integer; performing a cross correlation between the respective M original and
interpolated samples of the first and second sets of samples to identify a fine
displacement between the first and second sets of samples which is less than one
intersample distance of the original samples from a central sample of the M samples
of the first set of samples; and combining the coarse displacement and the fine displacement to obtain
the measure of the registration errors and chromatic aberration errors in the video
signals.
Claim 6
Dependent Claim
129 words
A method according to claim 1, wherein step c) includes the steps of: performing a cross correlation between the stored first set of samples
and the stored second set of samples to identify a coarse displacement between
respective edges in the first and second sets of samples to a nearest intersample
distance and storing a correlation value at each displacement considered in the cross
correlation; selecting at least three of the stored correlation values including the
correlation value corresponding to the identified displacement; fitting a parabolic curve to the selected correlation values; determining a maximum point of the parabolic curve as a fine
displacement; and combining the coarse displacement and the fine displacement to obtain
the measure of the registration errors and chromatic aberration errors in the video
signals.
Claim 7
Dependent Claim
242 words
A method according to claim 1, wherein step c) includes the steps of: generating respective measures of sum of absolute difference between
the M samples of the first stored set of samples and M samples of the second stored
set of samples for respectively different displacements between the first stored set of
samples and the second stored set of samples; identifying a coarse displacement as the sum of absolute difference
measures which is less than or equal to any other one of the sum of absolute
difference measures; selecting the M samples from the stored first set of samples and M
corresponding samples from the stored second set of samples, wherein each of the
samples from the second set is displaced by the coarse displacement from the
respective sample in the first set; interpolating S samples between successive ones of the M samples of
each of the first and second sets of samples, where S is an integer; performing a cross correlation between the respective M original and S
interpolated samples of the first and second sets of samples to identify a fine
displacement between the first and second sets of samples which is less than one
intersample distance of the original samples from a central sample of the M samples
of the first set of samples; and combining the coarse displacement and the fine displacement to obtain
the measure of the registration errors and chromatic aberration errors in the video
signals.
Claim 8
Dependent Claim
142 words
A method according to claim 1, wherein step c) includes the steps of: generating respective measures of sum of absolute difference between
the M samples of the first stored set of samples and M samples of the second stored
set of samples for respectively different displacements between the first stored set of
samples and the second stored set of samples; identifying a coarse displacement as the sum of absolute difference
measures which is less than or equal to any other one of the sum of absolute
difference measures; selecting at least three of the measures of sum of absolute difference
including the measure corresponding to the coarse displacement; fitting a parabolic curve to the selected measures; determining a minimum point of the parabolic curve as a fractional
intersample distance to be combined with the identified displacement to produce the
measured displacement value.
Claim 9
Dependent Claim
196 words
Apparatus for measuring registration errors and chromatic
aberration in video signals, said video signals being represented as least first and
second color signals and said registration errors and chromatic aberration appearing as
misaligned edges of the first and second color signals in an image reproduced from the
video signals, the method comprising: means for selecting a first set of N samples of the first color signal and a
second set of N samples of the second color signal, where N is an integer greater than
2; a video memory; means for analyzing the set of samples of the first color signal to
determine whether the first set of samples contains M samples representing an edge in
the image, where M is an integer less than N, and storing the first and second sets of
samples in the video memory if the first set of samples is determined to contain the M
samples representing the edge; and means for comparing the stored first set of samples to the stored second
set of samples to determine a displacement between the M samples in the first set of
samples with M corresponding samples in the second set of samples.
Claim 10
Dependent Claim
65 words
Apparatus according to claim 9, wherein the means for selecting
further includes: means for calculating a measure of color balance between the first set of
samples and the second set of samples; and means for inhibiting the storage of the first and second sets of samples
into the memory if the measure of color balance has a value which is not within a
predetermined range.
Claim 11
Dependent Claim
156 words
Apparatus according to 10, wherein the first and second sets of
samples represent image picture elements (pixels) in a line of the image and the means
for selecting further includes: means for selecting third and fourth sets of samples of said first color
signal, each of the samples in the third and fourth sets of samples corresponding to a
pixel which is immediately adjacent to a respective pixel element in said first set of
samples; means for analyzing the first, third and fourth sets of samples to
determine whether the first set of samples is adjacent to an edge which is parallel to
the line of the image or represent an edge which intersects the line of the image on a
diagonal; and means for inhibiting the storage of the first and second sets of samples if
the first set of samples is determined to be adjacent to the parallel edge or represents
the diagonal edge.
Claim 12
Dependent Claim
70 words
Apparatus according to claim 9, wherein M equals 2 and the means
for analyzing includes: means for calculating difference values between successive ones of the
samples in the first set of samples; means for comparing each of the calculated difference values to an edge
threshold value to indicate that the set of samples represents an edge if any of the
calculated difference values is greater than the edge threshold value.
Claim 13
Dependent Claim
219 words
A method according to claim 9, wherein the means for comparing
includes: first correlation means for performing a cross correlation between the
stored first set of samples and the stored second set of samples to identify a coarse
displacement between respective edges in the first and second sets of samples to a
nearest intersample distance; means for selecting the M samples from the stored first set of samples
and M corresponding samples from the stored second set of samples, wherein each of
the samples from the second set is displaced by the identified displacement from the
respective sample in the first set; means for interpolating S samples between successive ones of the M
samples of each of the first and second sets of samples, where S is an integer; second correlation means for performing a cross correlation between the
respective M original and S interpolated samples of the first and second sets of
samples to identify a fine displacement between the first and second sets of samples
which is less than one intersample distance of the original samples from a central
sample of the M samples of the first set of samples; and means for combining the coarse displacement and the fine displacement
to obtain the measure of the registration errors and chromatic aberration errors in the
video signals.
Claim 14
Dependent Claim
137 words
Apparatus according to claim 9, wherein the means for comparing
includes: means for performing a cross correlation between the stored first set of
samples and the stored second set of samples to identify a coarse displacement
between respective edges in the first and second sets of samples to a nearest
intersample distance and storing a correlation value at each displacement considered in
the cross correlation; means for selecting at least three of the stored correlation values
including the correlation value corresponding to the identified displacement; means for fitting a parabolic curve to the selected correlation values; means for determining a maximum point of the parabolic curve as a fine
displacement; and means for combining the coarse displacement and the fine displacement
to obtain the measure of the registration errors and chromatic aberration errors in the
video signals.
Claim 15
Dependent Claim
252 words
Apparatus according to claim 9, wherein the means for comparing
includes: means for generating respective measures of sum of absolute difference
between the M samples of the first stored set of samples and M samples of the second
stored set of samples for respectively different displacements between the first stored
set of samples and the second stored set of samples; means for identifying a coarse displacement as the sum of absolute
difference measures which is less than or equal to any other one of the sum of
absolute difference measures; means for selecting the M samples from the stored first set of samples
and M corresponding samples from the stored second set of samples, wherein each of
the samples from the second set is displaced by the coarse displacement from the
respective sample in the first set; means for interpolating S samples between successive ones of the M
samples of each of the first and second sets of samples, where S is an integer; means for performing a cross correlation between the M original and S
interpolated samples of the first and second sets of samples, respectively, to identify a
fine displacement between the first and second sets of samples which is less than one
intersample distance of the original samples from a central sample of the M samples
of the first set of samples; and means for combining the coarse displacement and the fine displacement
to obtain the measure of the registration errors and chromatic aberration errors in the
video signals.
Claim 16
Dependent Claim
150 words
Apparatus according to claim 9, wherein the means for comparing
includes: means for generating respective measures of sum of absolute difference
between the M samples of the first stored set of samples and M samples of the second
stored set of samples for respectively different displacements between the first stored
set of samples and the second stored set of samples; means for identifying a coarse displacement as the sum of absolute
difference measures which is less than or equal to any other one of the sum of
absolute difference measures; means for selecting at least three of the measures of sum of absolute
difference including the measure corresponding to the coarse displacement; means for fitting a parabolic curve to the selected measures; means for determining a minimum point of the parabolic curve as a
fractional intersample distance to be combined with the identified displacement to
produce the measured displacement value.
References Cited (Backward Citations)
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