Digital image system and method for combining demosaicing and bad pixel correction

• US 20040032516A1
• Filed: 08/16/2002
• Published: 02/19/2004
• Est. Priority Date: 08/16/2002
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Avago Technologies Sensor IP Pte. Ltd. (Broadcom, Inc.)
• Inventors: Kakarala, Ramakrishna
• Granted Patent: US 7,015,961 B2
• Time in Patent Office: Days
• US Class Current: 348/246
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 3/4015 Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/77 Retouching; Inpainting; Scratch removal
• CPC Class Codes: G06T 7/0004 Industrial image inspection
• CPC Class Codes: H04N 23/12 with one sensor only
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/68 applied to defects

Abstract

A digital image system and method for combining bad pixel correction and demosaicing in a single process is provided by interpolating sensor values for pixels immediately spatially adjacent to the current pixel being examined to detect defective pixels, and using the interpolated values for demosaicing. If the sensor value of the current pixel being examined is outside of a range of sensor values determined from the interpolated values by more than a configurable threshold amount, the current pixel is considered defective, and replaced using an estimated value from the neighboring pixels. The interpolated values calculated for use in detecting bad pixels can further be used as the interpolated values for demosaicing purposes

Claims

1. A digital image system for correcting sensor values generated by pixels within an array of pixels, each of said pixels within said array of pixels producing a respective one of said sensor values for an image, said digital image system comprising:

a buffer for storing at least a portion of said sensor values produced by said pixels for said image, one of said stored sensor values being a current sensor value in a first color plane produced by a current one of said pixels; and

a processor connected to receive said sensor values stored in said buffer, compute interpolated sensor values in said first color plane for said pixels spatially adjacent to said current pixel using said stored sensor values and determine whether said current pixel is defective using said interpolated sensor values.

2. The digital image system of claim 1, wherein said processor is further configured to determine a threshold amount and calculate a range of sensor values for said current pixel using at least said interpolated values, said current pixel being defective when said current sensor value is outside of said range of sensor values by more than said threshold amount.

3. The digital image system of claim 2, wherein said range of sensor values includes a maximum value and a minimum value from at least said interpolated sensor values, said current pixel being defective when said current sensor value either exceeds said maximum value by more than said threshold amount or falls below said minimum value by more than said threshold amount.

4. The digital image system of claim 3, wherein said maximum value and said minimum value are determined from both said interpolated values and said sensor values in the first color plane produced from said pixels immediately spatially adjacent to said current pixel.

5. The digital image system of claim 2, wherein said range of sensor values includes a rank order statistic value produced from at least said interpolated sensor values, said current pixel being defective when said current sensor value either exceeds said rank order statistic value by more than said threshold amount or falls below said rank order statistic value by more than said threshold amount.

6. The digital image system of claim 2, wherein said processor is further configured to replace said current sensor value with a replacement sensor value calculated using said interpolated sensor values when said current pixel is defective.

7. The digital image system of claim 6, wherein said replacement sensor value is a median value of said interpolated sensor values.

8. The digital image system of claim 6, wherein said processor is further configured to demosaic said sensor values using said interpolated sensor values and said replacement sensor value.

9. The digital image system of claim 2, wherein said threshold amount is pre-configured.

10. The digital image system of claim 2, wherein said threshold amount is variable based on said sensor values.

11. The digital image system of claim 1, wherein said processor is further configured to compute said interpolated sensor values using a median interpolation technique.

12. The digital image system of claim 11, wherein said processor is further configured to compute each of said interpolated sensor values using the median of four of said sensor values in said first color plane associated with surrounding ones of said pixels to said immediately spatially adjacent pixels of said current pixel.

13. The digital image system of claim 12, wherein said four sensor values include two of said interpolated sensor values for two of said surrounding pixels and two of said sensor values produced by two of said surrounding pixels.

14. A method for correcting sensor values generated by pixels within an array of pixels, each of said pixels within said array of pixels producing a respective one of said sensor values for an image, said method comprising:

receiving at least a portion of said sensor values produced by said pixels for said image, one of said received sensor values being a current sensor value in a first color plane produced by a current one of said pixels;

computing interpolated sensor values in said first color plane for said pixels spatially adjacent to said current pixel using said received sensor values; and

determining whether said current pixel is defective using said interpolated sensor values.

15. The method of claim 14, wherein said step of determining further comprises:

determining a threshold amount,

calculating a range of sensor values for said current pixel using at least said interpolated sensor values; and

determining that said current pixel is defective when said current sensor value is outside of said range of sensor values by more than said threshold amount.

16. The method of claim 15, wherein said range of sensor values includes a maximum value and a minimum value from at least said interpolated sensor values, and said step of determining that said current pixel is defective further comprises:

determining that said current pixel is defective when said current sensor value either exceeds said maximum value by more than said threshold amount or falls below said minimum value by more than said threshold amount.

17. The method of claim 16, wherein said step of calculating said range of sensor values further comprises:

calculating said maximum value and said minimum value from both said interpolated sensor values and said sensor values in the first color plane produced from said pixels immediately spatially adjacent to said current pixel.

18. The method of claim 15, wherein said range of sensor values includes a rank order statistic value produced from at least said interpolated sensor values, and said step of determining that said current pixel is defective further comprises:

determining that said current pixel is defective when said current sensor value either exceeds said rank order statistic value by more than said threshold amount or falls below said rank order statistic value by more than said threshold amount.

19. The method of claim 15, further comprising:

replacing said current sensor value with a replacement sensor value calculated using said interpolated sensor values when said current pixel is defective.

20. The method of claim 19, wherein said replacement sensor value is a median value of said interpolated sensor values.

21. The method of claim 19, further comprising:

demosaicing said sensor values using said interpolated sensor values and said replacement sensor value.

22. The method of claim 15, wherein said determining said threshold amount further comprises:

pre-configuring said threshold amount.

23. The method of claim 15, wherein said determining said threshold amount further comprises:

configuring said threshold amount based on said sensor values

24. The method of claim 14, wherein said computing further comprises:

computing said interpolated sensor values using a median interpolation technique.

25. The method of claim 24, wherein said computing further comprises:

computing each of said interpolated sensor values using the median of four of said sensor values in said first color plane associated with surrounding ones of said pixels to said immediately spatially adjacent pixels of said current pixel.

26. The method of claim 25, wherein said four sensor values include two of said interpolated values for two of said surrounding pixels and two of said sensor values produced by two of said surrounding pixels.