Correction method of defective pixel in image pickup device and image processing apparatus using the correction method

• US 7,657,116 B2
• Filed: 09/30/2004
• Issued: 02/02/2010
• Est. Priority Date: 10/08/2003
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Udagawa, Yoshiro, Matsuoka, Masaaki
• Primary Examiner(s): Kim; Charles
• Assistant Examiner(s): Lee; John W
• Application Number:
  US10/955,446
• Publication Number:
  US 20050078204A1
• Time in Patent Office: 1,951 Days
• Field of Search: 382/274, 358/400, 348/246, 348/247, 348/600
• US Class Current: 382/274
• CPC Class Codes: H04N 25/68 applied to defects
• CPC Class Codes: H04N 25/683 by defect estimation performed on the scene signal, e.g. real time or on the fly detection

Abstract

Location information representing the location of a defective pixel in an image pickup device and pixel defect level information representing the pixel defect level of the defective pixel are stored beforehand in a memory. The defect level of the defective pixel is determined after shipment of the image pickup device, and the pixel defect information is updated based on the defect determination result. If a new defective pixel is detected at a location different from the location of the defective pixel with the pixel defect information stored in the memory, the pixel defect information of that defective pixel is added. If a defective pixel is detected at the same location as the defective pixel with the pixel defect information stored in the memory, and if the defect level of the detected defective pixel is worse than the original defect level, the defect level of the defective pixel is updated.

Claims

1. An image processing apparatus comprising:

a detecting device configured to detect a defect level of a defective pixel contained in an image pickup device including a plurality of pixels and output second information relating to the detected defect level;

a memory configured to store first information relating to a stored defect level of the defective pixel in the image pickup device;

a correcting device configured to correct an image signal output from the image pickup device using the first information; and

a pixel defect updating circuit configured to compare the first information to the second information, wherein the pixel defect updating circuit is configured to;

update the first information with the second information, if the detected defect level of the defective pixel as detected by the detecting device is higher than the stored defect level of the defective pixel; and

not update the first information with the second information, if the detected defect level matches the stored defect level, or if the stored defect level is higher than the detected defect level.

2. An image processing apparatus according to claim 1, further comprising:

a synthesizing device configured to synthesize third information relating to a defective pixel contained in the image pickup device based on the first information and the second information;

wherein the synthesizing device is configured to synthesize the third information using one of the first information and the second information, whichever has a higher defect level if information of the same pixel is contained in both the first information and the second information, and the memory is configured to store the third information synthesized in the synthesizing device, as the first information.

3. An image processing apparatus according to claim 2, wherein the second information includes a plurality of pieces of information for each of a plurality of image pickup conditions, and the synthesizing device is configured to synthesize the third information relating to the defective pixel using one of the plurality of pieces of information.

4. An image processing apparatus according to claim 1, further comprising:

a lens configured to focus an image on the image pickup device;

an analog-to-digital converter configured to convert a signal from the image pickup device from analog to digital; and

a record controlling device configured to control a recorder to record a signal output from a correcting device.

5. An image processing apparatus according to claim 1, wherein the detecting device is configured to detect a defective pixel based on a detection parameter comprising temperature.

6. An image processing apparatus according to claim 1, wherein the detecting device is configured to detect a defective pixel based on a detection parameter comprising shutter speed.

7. An image processing apparatus according to claim 1, wherein the detecting device is configured to detect a defective pixel based on a detection parameter comprising effective gain.

8. An image processing method comprising:

detecting a defect level of a defective pixel contained in an image pickup device including a plurality of pixels and outputting second information relating to the detected defect level;

correcting an image signal output from the image pickup device using first information relating to a stored defect level of the defective pixel contained in the image pickup device, the stored defect level being stored in a memory; and

updating pixel defect information by comparing the first information to the second information,

wherein the first information is updated with second information, if the detected defect level of the defected pixel is higher than the stored defect level of the defective pixel, and

wherein the first information is not updated with the second information, if the detected defect level matches the stored defect level, or if the stored defect level is higher than the detected defect level.

9. An image processing method for reading defective pixel information stored in a memory and correcting an image signal output from an image pickup device comprising:

detecting a defect level of a defective pixel located at a defective pixel location in an image pickup device;

reading the defective pixel information stored in the memory;

determining if information for the defective pixel at the defective pixel location is stored in the memory as the defective pixel information;

if the information for the defective pixel at the defective pixel location is not stored in the memory as the defective pixel information, storing the detected defect level of the defective pixel at the defective pixel location in the memory as the detective pixel information;

if the information for the defective pixel at the defective pixel location is stored in the memory as the defective pixel information, determining if the detected defect level of the defective pixel at the defective pixel location is higher than a stored defect level of the defective pixel at the defective pixel location stored in the defective pixel information stored in the memory;

if the detected defect level of the defective pixel at the defective pixel location is higher than the stored defect level of the defective pixel at the defective pixel location stored in the defective pixel information stored in the memory, updating the defective pixel information for the defective pixel at the defective pixel location in the memory with the detected defect level; and

if the detected defect level of the defective pixel at the defective pixel location matches the stored defect level of the defective pixel at the defective pixel location stored in the defective pixel information stored in the memory, or if the stored defect level is higher than the detected defect level, not updating the defective pixel information for the defective pixel at the defective pixel location in the memory with the detected defect level.