Using a minimal number of parameters for correcting the response of color image sensors
First Claim
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1. A method comprising:
- generating a first matrix to correct the response of a reference image sensor associated with an image sensor manufacturing process, based on measured responses to color stimuli of a plurality of image sensors built using the process;
generating a plurality of sensor-specific correction matrices that correct for deviations in the responses of the plurality of image sensors, respectively, from that of the reference image sensor, each sensor-specific correction matrix being a product of a separate second matrix and an inverse of the first matrix; and
generating a set of parameters that model variation among corresponding elements of the plurality of sensor-specific correction matrixes.
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Abstract
Methods for generating a set of parameters and an associated methodology that model a portion of the variation in a number of sensor-specific correction matrices. The parameters are fewer than the number of elements in one of the sensor-specific correction matrices yet adequately model variations in the IC manufacturing process used to fabricate color image sensors. Storage circuitry aboard an IC die containing the sensor can be configured to store the parameters.
24 Citations
22 Claims
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1. A method comprising:
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generating a first matrix to correct the response of a reference image sensor associated with an image sensor manufacturing process, based on measured responses to color stimuli of a plurality of image sensors built using the process;
generating a plurality of sensor-specific correction matrices that correct for deviations in the responses of the plurality of image sensors, respectively, from that of the reference image sensor, each sensor-specific correction matrix being a product of a separate second matrix and an inverse of the first matrix; and
generating a set of parameters that model variation among corresponding elements of the plurality of sensor-specific correction matrixes. - View Dependent Claims (2, 3, 4)
computing each of the sensor-specific correction matrices using {tilde over (T)}={tilde over (K)}sensor{tilde over (K)}base− - 1
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5. An imaging device comprising:
- storage circuitry for storing a plurality of parameters for modeling the elements of a correction matrix {tilde over (T)}, {tilde over (T)} and a base matrix {tilde over (K)}base being factors of a color transformation matrix {tilde over (K)}sensor used to adjust pixel data derived from an image sensor built using an IC manufacturing process, wherein {tilde over (T)} is proportional to a product of {tilde over (K)}sensor and {tilde over (K)}base−
1, and the parameters are fewer than the number of matrix elements in {tilde over (K)}sensor. - View Dependent Claims (6, 7, 8, 9, 10)
- storage circuitry for storing a plurality of parameters for modeling the elements of a correction matrix {tilde over (T)}, {tilde over (T)} and a base matrix {tilde over (K)}base being factors of a color transformation matrix {tilde over (K)}sensor used to adjust pixel data derived from an image sensor built using an IC manufacturing process, wherein {tilde over (T)} is proportional to a product of {tilde over (K)}sensor and {tilde over (K)}base−
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11. A method of encoding correction information for a color image sensor, comprising:
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a) illuminating a first image sensor with known color stimuli to obtain in response thereto a first plurality of measured pixel values, the first sensor being manufactured as part of an integrated circuit (IC) die using a semiconductor fabrication process;
b) computing a color transformation matrix {tilde over (K)}sensor associated with the first sensor;
c) computing a base matrix {tilde over (K)}base based on responses to color stimuli of a plurality of image sensors built using the process;
d) computing a correction matrix {tilde over (T)} based on {tilde over (K)}base and {tilde over (K)}sensor, where {tilde over (T)}={tilde over (K)}sensor*{tilde over (K)}base−
1; and
e) computing a plurality of coefficients kn which minimize the error in an estimate {circumflex over (T)}ij for an element Tij of the matrix {tilde over (T)}, the estimate {circumflex over (T)}ij being obtained by a linear combination of kn and Pn, where Pn are related to the first measured pixel values. - View Dependent Claims (12, 13, 14)
storing information corresponding to the plurality of Pn in the IC die.
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13. The method of claim 12 wherein the step of storing comprises storing a plurality of pointers in the IC die to the plurality of Pn.
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14. A method as in claim 12 wherein the step of storing comprises storing the information in a non-volatile storage in the IC die.
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15. A method of recovering correction information for a color image sensor, comprising:
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computing a first matrix based on a plurality of parameters and based on information that characterizes the IC manufacturing process used for fabricating the color image sensor, the parameters modeling a portion of the variation in a plurality of sensor-specific correction matrices for a population of color image sensors built using the manufacturing process, the parameters being fewer than the number of elements in one of the sensor-specific correction matrices;
computing a second matrix based on the first matrix and based on said information that characterizes the IC manufacturing process, wherein the second matrix is proportional to a product of the first matrix and a third matrix that incorporates some of said information; and
applying the second matrix for correcting image data captured by the image sensor. - View Dependent Claims (16, 17, 18)
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19. An article comprising:
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a machine-readable medium having instructions that when executed by a processor cause computing a first matrix based on a plurality of parameters and based on information that characterizes the IC manufacturing process used for fabricating the color image sensor, the parameters modeling a portion of the variation in a plurality of sensor-specific color correction matrices, the parameters being fewer than the number of elements in one of the sensor-specific matrices;
computing a second matrix based on the first matrix and based on said information that characterizes the IC manufacturing process, wherein the second matrix is proportional to a product of the first matrix and a third matrix that incorporates some of said information; and
applying {tilde over (K)}est for correcting image data captured by the image sensor. - View Dependent Claims (20, 21, 22)
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Specification