Color disparity correction in image sensors methods and circuits

• US 7,956,871 B2
• Filed: 04/27/2006
• Issued: 06/07/2011
• Est. Priority Date: 04/28/2005
• Status: Active Grant

• Current Assignee: Transchip Israel Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Fainstain, Eugene
• Primary Examiner(s): Richer; Aaron M
• Application Number:
  US11/413,605
• Publication Number:
  US 20070109316A1
• Time in Patent Office: 1,867 Days
• Field of Search: 345/606
• US Class Current: 345/606
• CPC Class Codes: H04N 2209/046 Colour interpolation to calculate the missing colour values
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements

Abstract

A method of displaying a captured image includes using an array of pixels to capture an image. The array of pixels includes a first plurality of pixels of a first color, a second plurality of pixels of a second color, and a third plurality of pixels of a third color. The pixels are arranged into rows and columns and the pixels of the third plurality of pixels have two different arrangements within the array of pixels with respect to neighboring pixels. The method includes, for each pixel in the third plurality of pixels, normalizing the pixel'"'"'s value as a function of the pixel values of at least six other pixels in the third plurality of pixels. The method also includes displaying the captured image using a normalized value for the pixel value of each pixel in the third plurality of pixels.

Claims

1. A method of displaying a captured image, comprising:

using an array of pixels to capture an image, wherein the array of pixels includes a first plurality of pixels of a first color, a second plurality of pixels of a second color, and a third plurality of pixels of a third color, wherein the pixels are arranged into rows and columns, and wherein the pixels of the third plurality of pixels have two different arrangements within the array of pixels with respect to neighboring pixels;

for each pixel in the third plurality of pixels, normalizing a pixel value of said each pixel as a function of pixel values of at least six other pixels in the third plurality of pixels; and

displaying the captured image using the normalized pixel value of said each pixel in the third plurality of pixels, wherein

a first arrangement of the two different arrangements includes a green pixel having red pixels in its row and blue pixels in its column, and

a second arrangement of the two different arrangements includes a green pixel having blue pixels in its row and red pixels in its column; and

wherein normalizing the pixel value includes;

combining the values of four pixels that are immediately diagonally adjacent to the pixel to produce a first average;

combining the first average with the pixel value to produce a second average;

combining limited pixel values for the four pixels that are immediately diagonally adjacent to the pixel to produce a third average, wherein the limited pixel values are a function of the second average;

combining limited pixel values for two additional pixels in the third plurality of pixels to produce a fourth average, wherein the limited pixel values are a function of the second average and wherein the two additional pixels include two pixels nearest the pixel that are not immediately adjacent to the pixel;

subtracting the fourth average from the third average to produce a result;

dividing the result by two to produce a divided result; and

combining the divided result with the pixel value to produce the normalized pixel value.

2. The method of claim 1, wherein the third color comprises green.

3. The method of claim 1, further comprising preprocessing the pixel value.

4. The method of claim 1, further comprising post-processing the pixel value.

5. The method of claim 1, wherein the array of pixels is arranged into a Bayer array.

6. The method of claim 1, wherein combining, in each instance, comprises adding the values followed by truncating one or more least significant bits.

7. The method of claim 1, wherein combining, in each instance, comprises averaging the values followed by rounding the result to the nearest integer.

8. The method of claim 1, wherein the two additional pixels are in the same row as the pixel.

9. The method of claim 1, wherein the two additional pixels are in the same column as the pixel.

10. The method of claim 1, wherein the limited pixel values are a monotonic function of the second average.

11. The method of claim 1, wherein the limited pixel values are a non-monotonic function of the second average.

12. A method of displaying an image captured by an image sensor array, wherein the array comprises a plurality of red pixels, a plurality of blue pixels, and a plurality of green pixels arranged in a Bayer array, each pixel having a pixel value associated therewith, wherein the pixels are arranged into rows and columns, wherein a first plurality of the green pixels, designated Gr pixels, are comprised by rows of pixels having only red and green pixels, and a second plurality of the green pixels, designated Gb pixels, are comprised by rows of pixels having only blue and green pixels, wherein the rows of pixels having Gr pixels and the rows of pixels having Gb pixels are in an alternating relationship in the image sensor array, the method comprising:

for each of a plurality of Gb pixels in the pixel array;

receiving a pixel value for the Gb pixel, wherein the Gb pixel comprises a subject pixel;

receiving pixel values for four Gr pixels that are in an immediately adjacent diagonal relationship with the subject Gb pixel;

receiving pixel values for two additional Gb pixels, wherein the subject Gb pixel and the two additional Gb pixels are comprised by a common row, wherein the subject Gb pixel is between the two additional Gb pixels, and wherein the two additional Gb pixels are each in an immediately adjacent diagonal relationship with two of the four Gr pixels;

combining the pixel values of the four Gr pixels to produce Avg(Gr);

combining the pixel value of the subject Gb pixel with Avg(Gr) to produce a first LimInput;

combining limited pixel values of the four Gr pixels to produce LimAvg(Gr), wherein the limited pixel values are a function of the first LimInput;

combining limited pixel values of the two remaining Gb pixels to produce LimAvg(Gb), wherein the limited pixel values are a function of the first LimInput; and

subtracting LimAvg(Gb) from LimAvg(Gr), dividing the result by two, then using the divided result to correct the pixel value of the subject Gb pixel, thereby producing a corrected pixel value; and

displaying the captured image using one or more corrected pixel values.

13. The method of claim 12, further comprising:

for each of a plurality of Gr pixels in the pixel array;

receiving a pixel value for the Gr pixel, wherein the Gr pixel comprises a subject pixel;

receiving pixel values for four Gb pixels that are in an immediately adjacent diagonal relationship with the subject Gr pixel;

receiving pixel values for two additional Gr pixels, wherein the subject Gr pixel and the two additional Gr pixels are comprised by a common row, wherein the subject Gr pixel is between the two additional Gr pixels, and wherein the two additional Gr pixels are each in an immediately adjacent diagonal relationship with two of the four Gb pixels;

combining the pixel values of the four Gb pixels to produce Avg(Gb);

combining the pixel value of the subject Gr pixel with Avg(Gb) to produce a second LimInput;

combining limited pixel values of the four Gb pixels to produce LimAvg(Gb), wherein the limited pixel values are a function of the second LimInput;

combining limited pixel values of the two remaining Gr pixels to produce LimAvg(Gr), wherein the limited pixel values are a function of the second LimInput; and

subtracting LimAvg(Gr) from LimAvg(Gb), dividing the result by two, then using the divided result to correct the pixel value of the subject Gr pixel, thereby producing a corrected pixel value.

14. The method of claim 13, wherein combining, in each instance, comprises adding the values followed by truncating one or more least significant bits.

15. The method of claim 13, wherein combining, in each instance, comprises averaging the values followed by rounding the result to the nearest integer.

16. The method of claim 13, wherein the limited pixel values are a monotonic function of the first and second LimInput.

17. The method of claim 13, wherein the limited pixel values are a non-monotonic function of the first and second LimInput.

18. An arrangement configured to process pixel values relating to an image captured by an image capture device, the image capture device being a hardware based system and including a Bayer array of pixels, the Bayer array of pixels including a first plurality of pixels of a first color, a second plurality of pixels of a second color, and a third plurality of pixels of a third color, wherein the pixels are arranged into rows and columns, and wherein the pixels of the third plurality of pixels have two different arrangements within the Bayer array of pixels with respect to neighboring pixels, the arrangement comprising:

means for normalizing a pixel value of each pixel in the third plurality of pixels of the Bayer array of pixels as a function of pixel values of at least six other pixels in the third plurality of pixels of the Bayer array of pixels, and

means for displaying the captured image using the normalized pixel value of said each pixel in the third plurality of pixels, wherein

a first arrangement of the two different arrangements includes a green pixel having red pixels in its row and blue pixels in its column, and

a second arrangement of the two different arrangements includes a green pixel having blue pixels in its row and red pixels in its column; and

wherein the means for normalizing the pixel value includes;

means for averaging the values of four pixels that are immediately diagonally adjacent to the pixel to produce a first average;

means for averaging the first average with the pixel value to produce a second average;

means for averaging limited pixel values for the four pixels that are immediately diagonally adjacent to the pixel to produce a third average, wherein the limited pixel values are a function of the second average;

means for averaging limited pixel values for two additional pixels in the third plurality of pixels to produce a fourth average, wherein the limited pixel values are a function of the second average and wherein the two additional pixels include two pixels nearest the pixel that are not immediately adjacent to the pixel;

means for subtracting the fourth average from the third average to produce a result;

means for dividing the result by two to produce a divided result; and

means for combining the divided result with the pixel value to produce the normalized pixel value.

19. The arrangement of claim 18, wherein the third color comprises green.

20. A circuit configured to process pixel values relating to an image captured by an image capture device, the image capturing device including an array of pixels, wherein the array of pixels includes a first plurality of pixels of a first color, a second plurality of pixels of a second color, and a third plurality of pixels of a third color, wherein the pixels are arranged into rows and columns, and wherein the pixels of the third plurality of pixels have two different arrangements within the array of pixels with respect to neighboring pixels, the circuit comprising:

an arrangement configured to normalize the pixel value of each pixel in the third plurality of pixels as a function of the pixel values of at least six other pixels in the third plurality of pixels, wherein

a first arrangement of the two different arrangements includes a green pixel having red pixels in its row and blue pixels in its column, and

a second arrangement of the two different arrangements includes a green pixel having blue pixels in its row and red pixels in its column; and

wherein the arrangement configured to normalize the pixel value includes;

a first adder configured to average the values of four pixels that are immediately diagonally adjacent to the pixel to produce a first average;

a second adder configured to average the first average with the pixel value to produce a second average;

a third adder configured to average limited pixel values for the four pixels that are immediately diagonally adjacent to the pixel to produce a third average, wherein the limited pixel values are a function of the second average;

a fourth adder configured to average limited pixel values for two additional pixels in the third plurality of pixels to produce a fourth average, wherein the limited pixel values are a function of the second average and wherein the two additional pixels include two pixels nearest the pixel that are not immediately adjacent to the pixel;

a subtractor configured to subtract the fourth average from the third average to produce a result;

a divider configured to divide the result by two to produce a divided result; and

a fifth adder configured to combine the divided result with the pixel value to produce the normalized pixel value.

21. The circuit of claim 20, wherein the third color comprises green and wherein the array of pixels is arranged into a Bayer array.