Circuit for correcting lateral chromatic abberation

Patent metadata

Field	Value
Publication number	US-11350063-B2
Application number	US-202016848131-A
Country	US
Kind code	B2
Filing date	Apr 14, 2020
Priority date	Apr 14, 2020
Publication date	May 31, 2022
Grant date	May 31, 2022

Abstract

Embodiments relate to lateral chromatic aberration (LCA) recovery of raw image data generated by image sensors. A chromatic aberration recovery circuit performs chromatic aberration recovery on the raw image data to correct the resulting LCA in the full color images using pre-calculated offset values of a subset of colors of pixels.

First claim

The invention claimed is:

1. An image processor comprising:
a first correction circuit configured to:
receive pixel values of pixels of a color in a raw input image data, and
generate first corrected versions of the pixel values by performing interpolation of pixel values of a first subset of pixels of the color arranged in a first direction of the raw image input data using one or more of first interpolation coefficients corresponding to first offset values representing first distances from the pixels to corresponding virtual pixels in the first direction, the virtual pixels having pixel values that are identical to pixel values of the pixels in the raw image absent lateral chromatic aberrations; and

a second correction circuit configure to:
receive the first corrected versions of the pixel values, and
generate second corrected versions of the pixel values by performing interpolation of the first corrected versions of the pixel values of second subset of pixels of the color arranged in a second direction perpendicular to the first direction using one or more of second interpolation coefficients corresponding to second offset values representing second distances from the pixels in the raw image input data to the corresponding virtual pixels in the second direction, the second correction circuit including the second corrected versions of the pixel values as part of a corrected raw image data.

2. The image processor of claim 1 , further comprising:
an offset interpolator circuit configured to determine the first offset values and the second offset values of the pixels in the raw image input data by bilateral interpolating predetermined first offset values and predetermined second offset values associated with grid points neighboring the pixels in the raw input image data.

3. The image processor claim 2 , further comprising:
an offset look-up table configured to store the predetermined first offset values and the predetermined second offset values associated with the grid points;
a first phase look-up table configured to store the first interpolation coefficients indexed by the first distances or first parameters derived from the first distances; and
a second phase look-up table configured to store the second interpolation coefficients indexed by the second distances or second parameters derived from the second distances.

4. The image processor of claim 1 , wherein the raw input image data and the corrected raw image data is in a Bayer pattern.

5. The image processor of claim 1 , wherein the first direction is a vertical direction and the second direction is a horizontal direction.

6. The image processor of claim 5 , wherein a first corrected version of a pixel value for a pixel in the raw input image data is generated by interpolating pixel values for a number of pixels in the same column as the pixel, and a second corrected version of the pixel value for the pixel is generated by interpolating first corrected versions of pixel values for the same number of pixels in the same row as the pixel.

7. The image processor of claim 1 , wherein receiving pixel values of pixels of the color in the raw input image data includes receiving pixel values of pixels in colors of red, green, and blue, and wherein the pixel values of pixels of two of the colors are updated by the first correction circuit and the second correction circuit, and pixel values of pixels of a remaining one of the colors is not updated by the first correction circuit and the second correction circuit.

8. The image processor of claim 1 , wherein the color is blue or red, and wherein pixel values of green pixels are not updated by the first correction circuit and the second correction circuit.

9. The image processor of claim 1 , wherein the interpolation performed by the first correction circuit uses a first function defined by the one or more of the first interpolation coefficients, and the second correction circuit uses a second function defined by the one or more of the second interpolation coefficients.

10. A method comprising:
receiving pixel values of pixels of a color in a raw input image data;
generating first corrected versions of the pixel values by performing interpolation of pixel values of a first subset of pixels of the color arranged in a first direction of the raw image input data using one or more of first interpolation coefficients corresponding to first offset values representing first distances from the pixels to corresponding virtual pixels in the first direction, the virtual pixels having pixel values that are identical to pixel values of the pixels in the raw image absent lateral chromatic aberrations; and
generating second corrected versions of the pixel values by performing interpolation of the first corrected versions of the pixel values of second subset of pixels of the color arranged in a second direction perpendicular to the first direction using one or more of second interpolation coefficients corresponding to second offset values representing second distances from the pixels in the raw image input data to the corresponding virtual pixels in the second direction, the second correction circuit including the second corrected versions of the pixel values as part of a corrected raw image data.

11. The method of claim 10 , further comprising:
determining the first offset values and the second offset values of the pixels in the raw image input data by bilateral interpolating predetermined first offset values and predetermined second offset values associated with grid points neighboring the pixels in the raw input image data.

12. The method claim 11 , further comprising:
storing, in an offset look-up table, the predetermined first offset values and the predetermined second offset values associated with the grid points;
storing, in a first phase look-up table, the first interpolation coefficients indexed by the first distances or first parameters derived from the first distances; and
storing, in a second phase look-up table, the second interpolation coefficients indexed by the second distances or second parameters derived from the second distances.

13. The method of claim 10 , wherein the raw input image data and the corrected raw image data is in a Bayer pattern.

14. The method of claim 10 , wherein the first direction is a vertical direction and the second direction is a horizontal direction.

15. The method of claim 14 , wherein a first corrected version of a pixel value for a pixel in the raw input image data is generated by interpolating pixel values for a number of pixels in the same column as the pixel, and a second corrected version of the pixel value for the pixel is generated by interpolating first corrected versions of pixel values for the same number of pixels in the same row as the pixel.

16. The method of claim 10 , wherein receiving pixel values of pixels of the color in the raw input image data includes receiving pixel values of pixels in colors of red, green, and blue, and wherein the pixel values of pixels of two of the colors are updated and pixel values of pixels of a remaining one of the colors is not updated.

17. The method of claim 10 , wherein the color is blue or red, and wherein pixel values of green pixels are not updated by the first correction circuit and the second correction circuit.

18. The method of claim 10 , wherein the interpolation of the pixel values of the first subset of pixels uses a first spline function defined by the one or more of the first interpolation coefficients, and interpolation of the first corrected versions of the

Assignees

• Apple Inc

Inventors

• Wu Chihsin
• Pope David R

Classifications

• H04N25/68

  applied to defects · CPC title

• H04N25/611 Primary

  Correction of chromatic aberration · CPC title

• H04N25/61 Primary

  the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4" · CPC title

• G06T2207/10024

  Color image · CPC title

• H04N9/646

  for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters · CPC title