# US 9,521,380 B2 · Imaging systems with clear filter pixels > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,521,380 B2 - Document ID: US9521380B2 - Status: Granted - Kind: B2 - Application number: 14/871,520 - Filed: 2015-09-30 - Published: 2016-01-21 - Granted: 2016-12-13 - Earliest claimed: 2012-03-19 - Assignees: Semiconductor Components Industries, LLC - Applicants: Semiconductor Components Industries, LLC - Inventors: Marko Mlinar; Brian Keelan - Web page: https://patentgrep.com/patent/US9521380B2 ## CPC - G06T 5/10: using non-spatial domain filtering - G06T 3/4015: Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns - G06T 11/60: Creating or editing images; Combining images with text - H04N 5/63: Generation or supply of power specially adapted for television receivers - H04N 23/85: for matrixing - H04N 23/88: for colour balance, e.g. white-balance circuits or colour temperature control - H04N 25/133: including elements passing panchromatic light, e.g. filters passing white light - H04N 25/134: {based on three different wavelength filter elements} - H04N 25/618: for random or high-frequency noise - G06T 2207/10024: Color image - H04N 2209/041: using solid-state devices - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An image sensor may have an array of image sensor pixels arranged in color filter unit cells each having one red image pixel that generates red image signals, one blue image pixel that generate blue image signals, and two clear image sensor pixels that generate white image signals. The image sensor may be coupled to processing circuitry that performs filtering operations on the red, blue, and white image signals to increase noise correlations in the image signals that reduce noise amplification when applying a color correction matrix to the image signals. The processing circuitry may extract a green image signal from the white image signal. The processing circuitry may compute a scaling value that includes a linear combination of the red, blue, white and green image signals. The scaling value may be applied to the red, blue, and green image signals to produce corrected image signals having improved image quality. ## Claims ### Claim 1 A method of processing image signals using an image sensor having an array of image sensor pixels and processing circuitry, wherein the array of image sensor pixels includes a first group of image sensor pixels responsive to light of a first color, a second group of image sensor pixels responsive to light of a second color, and a third group of image sensor pixels responsive to light of a third color, the method comprising: with the first group of image sensor pixels, generating first image signals in response to light of the first color; with the second group of image sensor pixels, generating second image signals in response to light of the second color; with the third group of image sensor pixels, generating third image signals in response to light of the third color; and with the processing circuitry, performing filtering operations on the first image signals, the second image signals, and the third image signals that increase noise correlations associated with first image signals, the second image signals, and the third image signals, wherein the filtering operations performed on the first, second, and third image signals that increase the noise correlations increase and decrease noise fluctuations in the first, second, and third image signals together in a correlated manner. ### Claim 2 (depends on 1) The method defined in claim 1, wherein the generated first image signals have a first spectral response width, wherein the generated second image signals have a second spectral response width, and wherein the generated third image signals have a third spectral response width that is greater than the first spectral response width and that is greater than the second spectral response width. ### Claim 3 (depends on 2) The method defined in claim 2, wherein the third spectral response width of the generated third image signals is greater than 75 percent of a sum of the first and second spectral response widths. ### Claim 4 (depends on 1) The method defined in claim 1, wherein performing the filtering operations on the first, second, and third image signals comprises: increasing the noise correlations associated with the first, second, and third image signals to greater than 70 percent of all noise associated with the first, second, and third image signals. ### Claim 5 (depends on 1) The method defined in claim 1, wherein performing the filtering operations on the first, second, and third image signals comprises: for each image sensor pixel of a given color, generating a weighted sum of image signals generated by at least 25 image sensor pixels. ### Claim 6 (depends on 1) The method defined in claim 1, further comprising: with the processing circuitry, applying a color correction matrix to the third image signal, wherein the color correction matrix extracts a green image signal from the third image signals. ### Claim 7 An imaging system, comprising: an image sensor having an array of image sensor pixels, wherein the array of image sensor pixels includes a first group of image sensor pixels configured to generate first image signals in response to light of a first color, a second group of image sensor pixels configured to generate second image signals in response to light of a second color, and a third group of image sensor pixels configured to generate third image signals in response to light of a third color; and processing circuitry configured to perform filtering operations on the first image signals, the second image signals, and the third image signals that increase noise correlations associated with first image signals, the second image signals, and the third image signals, wherein the filtering operations performed on the first, second, and third image signals that increase the noise correlations increase and decrease noise fluctuations in the first, second, and third image signals together in a correlated manner. ### Claim 8 (depends on 7) The imaging system defined in claim 7, wherein the processing circuitry is configured to apply a color correction matrix to the third image signal, wherein the color correction matrix extracts a green image signal from the third image signal. ### Claim 9 (depends on 7) The imaging system defined in claim 7, wherein the first image signals have a first spectral response width, wherein the second image signals have a second spectral response width, and wherein the third image signals have a third spectral response width that is greater than the first spectral response width and that is greater than the second spectral response width. ### Claim 10 (depends on 9) The imaging system defined in claim 9, wherein the third spectral response width of the third image signals is greater than 75 percent of a sum of the first and second spectral response widths. ### Claim 11 A method of processing image data that includes first image signals of a first color, second image signals of a second color, and third image signals using an image sensor having processing circuitry, the method comprising: with the processing circuitry, generating fourth image signals of a third color using the third image signals; with the processing circuitry, combining the first image signals, the second image signals, and the fourth image signals to form a derived luminance value; with the processing circuitry, computing an estimated luminance value based on the first image signals, the second image signals, and the third image signals; and with the processing circuitry, modifying the first image signals, the second image signals, and the fourth image signals using the derived luminance value and the estimated luminance value. ### Claim 12 (depends on 11) The method defined in claim 11, wherein the first color is different from the second color and the third color is different from the first and second colors. ### Claim 13 (depends on 11) The method defined in claim 11, further comprising: with the processing circuitry, computing a scaling value based on the derived luminance value and the estimated luminance value, wherein modifying the first image signals, the second image signals, and the fourth image signals comprises multiplying the first image signals, the second image signals, and the fourth image signals by the generated scaling value. ### Claim 14 (depends on 11) The method defined in claim 11, wherein the first image signals have a first spectral response, wherein the second image signals have a second spectral response, wherein the third image signals have a third spectral response, wherein the third spectral response is greater than the first spectral response, and wherein the third spectral response is greater than the second spectral response. ### Claim 15 (depends on 14) The method defined in claim 14, wherein the third spectral response is greater than 75 percent of a sum of the first and second spectral responses. ### Claim 16 (depends on 11) The method defined in claim 11, wherein combining the first image signals, the second image signals, and the fourth image signals to form the derived luminance value comprises computing a linear combination of the first image signals, the second image signals, and the fourth image signals using weighting factors. ### Claim 17 (depends on 11) The method defined in claim 11, wherein combining the first image signals, the second image signals, and the fourth image signals to form the derived luminance value comprises combining the third image signals with the first image signals, the second image signals, and the fourth image signals to form the derived luminance value. ### Claim 18 (depends on 11) The method defined in claim 11 further comprising: with the processing circuitry, performing filtering operations on the first image signals, the second image signals, and the third image signals that increase noise correlations associated with first image signals, the second image signals, and the third image signals; with the processing circuitry, generating difference values between the third image signals and the first image signals and between the third image signals and the second image signals; and with the processing circuitry, performing the filtering operations on the first image signals, the second image signals, and the third image signals that increase the noise correlations using the generated difference values.