Error calibration for digital image sensors and apparatus using the same

• US 6,819,358 B1
• Filed: 04/26/1999
• Issued: 11/16/2004
• Est. Priority Date: 04/26/1999
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Odinak, Gilad, Kagle, Jonathan C.
• Primary Examiner(s): Christensen, Andrew
• Assistant Examiner(s): TRAN, NHAN T
• Application Number:
  US09/299,257
• Time in Patent Office: 2,031 Days
• Field of Search: 348/246, 348/247, 348/251, 348/241, 348/187, 358/504
• US Class Current: 348/246
• CPC Class Codes: H04N 17/002 for television cameras
• CPC Class Codes: H04N 25/68 applied to defects

Abstract

Disclosed is a digital apparatus, such as a digital camera, which generates a digital representation of an image. The digital apparatus includes an image sensor having an array of pixels. An analog-to-digital converter converts electrical signals from the array of pixels into digital data representative of the image. Information indicative of locations of defective pixels in the pixel array is stored in a pixel defect memory. Compensation circuitry compensates the digital data representative of the image using the information indicative of the locations of the defective pixels. Also disclosed are methods of manufacturing a digital apparatus having compensation for defective pixels.

Claims

1. An apparatus for generating a digital representation of an image, the apparatus comprising:

an image sensor having an array of pixels that generate analog electrical signals in proportion to intensity of light striking the pixels;

an analog-to-digital converter coupled to the image sensor and converting the electrical signals into digital data representative of the image;

pixel defect memory storing information indicative of locations of defective pixels in the image sensor array of pixels, wherein the pixel defect memory stores information indicative of at least one group of pixels by including in the at least one group of pixels at least one non-defective pixel and at least one defective pixel; and

compensation circuitry coupled to the analog-to-digital converter and to the pixel defect memory, the compensation circuitry compensating the digital data representative of the image using the information indicative of the locations of the defective pixels to provide compensated digital data representative of the image, wherein compensating the digital data to provide the compensated digital data further comprises adjusting portions of the digital data corresponding to each of the pixels in the at least one group.

2. The apparatus of claim 1, and further comprising:

an imaging pipeline coupled to the compensation circuitry and receiving the compensated digital data representative of the image, the imaging pipeline converting the compensated digital data representative of the image into formatted image data in a predetermined digital image data format; and

image storage memory coupled to the imaging pipeline and storing the formatted image data.

3. The apparatus of claim 1, wherein the pixel defect memory stores the information indicative of the at least one group of pixels to be compensated by the compensation circuitry such that the at least one group of pixels to be compensated includes all pixels in a first row of the array of pixels.

4. The apparatus of claim 3, wherein the pixel defect memory stores the information indicative of the at least one group of pixels to be compensated by the compensation circuitry such that the at least one group of pixels to be compensated includes all pixels in the first row of the array of pixels if a number of defective pixels in the first row of pixels exceeds a predetermined threshold.

5. The apparatus of claim 1, wherein the pixel defect memory stores the information indicative of the at least one group of pixels to be compensated by the compensation circuitry such that the at least one group of pixels to be compensated includes all pixels in a first column of the array of pixels.

6. The apparatus of claim 5, wherein the pixel defect memory stores the information indicative of the at least one group of pixels to be compensated by the compensation circuitry such that the at least one group of pixels to be compensated includes all pixels in the first column of the array of pixels if a number of defective pixels in the first column of pixels exceeds a predetermined threshold.

7. The apparatus of claim 1, wherein the pixel defect memory stores the information indicative of the at least one group of pixels to be compensated by the compensation circuitry such that the at least one group of pixels to be compensated includes all pixels in a first rectangular shaped region of in the array of pixels.

8. The apparatus of claim 1, wherein the pixel defect memory stores the information indicative of the at least one group of pixels to be compensated by the compensation circuitry such that the at least one group of pixels to be compensated includes all pixels in a range of consecutively positioned pixels in the array of pixels.

9. The apparatus of claim 1, wherein the compensation circuitry compensates the digital data representative of the image by replacing data associated with defective pixels with data interpolated from non-defective pixels.

10. A method of manufacturing a digital camera that includes an image sensor having an array of pixels, the method comprising:

identifying defective pixels in the image sensor array of pixels by grouping at least one non-defective pixel with at least one defective pixel in a group, and categorizing the group as containing only defective pixels; and

storing in memory of the digital camera information indicative of locations of defective pixels in the image sensor array of pixels, including storing in memory information indicative of the location of the group.

11. The method of claim 10, wherein identifying defective pixels further comprises:

exposing the image sensor to light having a first intensity, wherein in response to the light having the first intensity non-defective pixels in the array of pixels provide an output indicative of the first intensity; and

identifying the defective pixels in the image sensor array of pixels as those pixels that provide an output indicative of intensities which are different than the first intensity by at least a predetermined amount.

12. The method of claim 11, wherein exposing the image sensor to light having the first intensity includes exposing the image sensor to high intensity white light.

13. The method of claim 11, wherein exposing the image sensor to light having the first intensity includes exposing the image sensor to darkness.

14. The method of claim 11, wherein exposing the image sensor to light having the first intensity includes exposing the image sensor to light having an intensity that causes non-defective pixels in the array of pixels to provide an output which is substantially in the middle of a maximum possible pixel output and a minimum possible pixel output.

15. The method of claim 10, and further comprising identifying rows and columns of defective pixel elements and storing in memory information indicative of the locations of the defective rows and columns.

16. A method of compensating a digital representation of an image captured with a digital camera having an image sensor, the method comprising:

obtaining a digital representation of an image captured with an image sensor;

retrieving defective pixel information from memory in the digital camera, the defective pixel information being indicative of locations of a group of pixels in the image sensor to be compensated, the group of pixels to be compensated including at least one defective pixel and at least one non-defective pixel; and

replacing portions of the digital representation of the image associated with all of the pixels in the group of pixels with data interpolated from portions of the digital representation of the image associated with pixels which are not in the group.