Bad pixel detection and correction in an image sensing device

• US 6,737,625 B2
• Filed: 06/28/2001
• Issued: 05/18/2004
• Est. Priority Date: 06/28/2001
• Status: Expired due to Term

• Current Assignee: Ovonyx Memory Technology, LLC
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Kakarala, Ramakrishna, Baharav, Izhak, Vook, Dietrich Werner, Zhang, Xuemei
• Primary Examiner(s): Allen, Stephone B.
• Application Number:
  US09/895,627
• Publication Number:
  US 20030001078A1
• Time in Patent Office: 1,055 Days
• Field of Search: 250/208.1, 348/246, 348/247, 348/615, 348/222, 348/230, 348/231, 348/230.1
• US Class Current: 250/208.1
• CPC Class Codes: H04N 25/68 applied to defects

Abstract

A sensor includes an array of photodetectors each generating an output signal of pixel data indicative of incident light intensity. This pixel data is read out from the array one line at a time and stored in a line buffer. A bad pixel processor includes a first buffer that stores pixel data obtained from the line buffer for a certain pixel in a currently read out line and pixel signal light data for pixels adjacent to the certain pixel.

Claims

1. A sensor, comprising:

an array of photodetectors, each photodetector generating pixel data indicative of incident light thereon; and

a bad pixel processor including;

a first buffer storing pixel data for a certain pixel in a current line of the array and pixel data for pixels adjacent to and, at least, on the same line as the certain pixel, the pixel data representing a magnitude of incident light;

a second buffer storing a characteristic feature for each of the pixels in a line of the array previous to the current line, the characteristic feature being a non-magnitude characteristic, said non-magnitude characteristic being at least one of an edge direction identification, a line transition identification, and a bad pixel identification; and

a detector that processes the pixel data stored in the first buffer and the characteristic features stored in the second buffer to identify whether the certain pixel in the current line is a bad pixel.

2. The sensor as in claim 1 wherein the characteristic feature consists of data identifying exclusively whether the pixel in the previous line was identified as a bad pixel.

3. The sensor as in claim 1 wherein the detector, in processing the characteristic features stored in the second buffer, precludes identification of the certain pixel in the current line as a bad pixel when the characteristic feature for an adjacent pixel in the previous line and adjacent to the certain pixel identifies the adjacent pixel as being a bad pixel.

4. The sensor as in claim 1 wherein the characteristic feature is indicative of a characteristic of a pixel in the previous line that is not related to incident light.

5. The sensor as in claim 1 wherein the first buffer further stores pixel data for pixels in the previous line.

6. The sensor as in claim 1, further including:

a corrector that processes the pixel data stored in the first buffer to determine corrected pixel data for the certain pixel if the detector identifies the certain pixel as a bad pixel.

7. The sensor as in claim 6 wherein the determined corrected pixel data comprises pixel data stored in the first buffer for at least one pixel adjacent to the certain pixel in the current read out line.

8. The sensor as in claim 6 wherein the determined corrected pixel data comprises an average or median of the pixel data stored in the first buffer for the pixel(s) adjacent to the certain pixel.

9. The sensor as in claim 1 wherein the detector processes the pixel data from the first buffer to determine a difference value that is indicative of a difference between the pixel data for the certain pixel and a reference pixel value.

10. The sensor as in claim 9 wherein the reference pixel value comprises an average or median of the pixel data stored in the first buffer for the pixels adjacent to the certain pixel in the current line.

11. The sensor as in claim 9 wherein the detector compares the difference value to a first threshold value when the characteristic feature of an adjacent pixel indicates that the adjacent pixel is a not a bad pixel, and compares the difference value to a second threshold value greater than the first threshold value when the characteristic feature of the adjacent pixel indicates that the adjacent pixel is a bad pixel, the adjacent pixel being a pixel in the previous line and adjacent to the certain pixel.

12. The sensor as in claim 11 wherein the detector identifies the certain pixel in the current line as a bad pixel when either of the comparisons indicates the difference value to exceed the first/second threshold.

13. A method for processing pixel data that is indicative of incident light that is output from pixels in a photodetector array, comprising:

storing pixel data for a certain pixel in a current line of the array and pixel data for pixels adjacent to the certain pixel, the pixel data comprising a magnitude of the incident light;

storing a characteristic feature for each of the pixels in a line of the array previous to the current line, the characteristic feature comprising non-magnitude information;

said non-magnitude information being at least one of an edge direction identification, a line transition identification, and a bad pixel identification; and

processing the stored pixel data and the stored characteristic features to identify whether the certain pixel in the current line is a bad pixel.

14. The method as in claim 13 wherein processing comprises precluding identification of the certain pixel in the current line as a bad pixel when the characteristic feature for a pixel in the previous line and adjacent to the certain pixel in the current line identifies the adjacent pixel as being a bad pixel.

15. The method as in claim 13 wherein the characteristic feature is indicative of a characteristic of the pixel in the previous line that is not related to incident light.

16. The method as in claim 13 wherein storing pixel data further includes storing pixel data for pixels in the previous line.

17. The method as in claim 13, further including:

processing the pixel data stored in a first buffer to determine corrected pixel data for the certain pixel if the detector identifies the certain pixel as a bad pixel.

18. The method as in claim 17 wherein processing comprises replacing the pixel data for the certain pixel with the pixel data for at least one of the pixels adjacent to the certain pixel in the current line.

19. The method as in claim 18 wherein processing comprises replacing the pixel data for the certain pixel with an average or median of the pixel data for the pixels adjacent to the certain pixel.

20. The method as in claim 13 wherein the characteristic feature consists of data identifying exclusively whether the pixel in the previous line was identified as a bad pixel.

21. The method as in claim 20 wherein processing comprises determining a difference value that is indicative of a difference between the pixel data for the certain pixel and a reference pixel value.

22. The method as in claim 21 wherein the reference pixel value comprises an average or median of the pixel data stored in the first buffer for the pixels adjacent to the certain pixel in the same current line.

23. The method as in claim 21 wherein processing further includes:

determining whether the characteristic feature for a pixel in the previous line that is adjacent to the certain pixel in the current line identifies the adjacent pixel as being a bad pixel; and

comparing the difference value to a threshold value;

wherein the threshold is a first threshold value if the adjacent pixel is a not a bad pixel, and is a second threshold value, that is greater than the first threshold value, when the adjacent pixel is a bad pixel.

24. The method as in claim 23 wherein processing further includes identifying the certain pixel as a bad pixel when the comparing indicates that the difference value exceeds the threshold.