Method for correcting image data from an image sensor having image pixels and non-image pixels, and image sensor implementing same

• US 8,902,330 B2
• Filed: 01/28/2013
• Issued: 12/02/2014
• Est. Priority Date: 02/06/2012
• Status: Expired due to Fees

• Current Assignee: Harvest Imaging BVBA
• Original Assignee: Harvest Imaging BVBA
• Inventors: Theuwissen, Albert
• Primary Examiner(s): Ho, Tuan
• Assistant Examiner(s): CAMARGO, MARLY S.B.
• Application Number:
  US13/751,204
• Publication Number:
  US 20130135500A1
• Time in Patent Office: 673 Days
• Field of Search: 348/345, 348/222.1, 348/333.04, 348/225.1, 348/248, 348/243, 348/223.1, 348/220.1, 821/62, 821/67, 822/55, 822/46, 382/162, 382/167, 382/255, 382/246
• US Class Current: 348/223.1
• CPC Class Codes: G06T 3/4015 Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements
• CPC Class Codes: H04N 25/60 Noise processing, e.g. detecting, correcting, reducing or removing noise
• CPC Class Codes: H04N 25/62 Detection or reduction of noise due to excess charges produced by the exposure, e.g. smear, blooming, ghost image, crosstalk or leakage between pixels
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 25/671 for non-uniformity detection or correction

Abstract

A method for correcting image data, in particular for color correction and cross-talk reduction of image data obtained by an image sensor comprising image pixels (R, G, B) and non-image pixels (F), the image pixels (R,G,B) being overlaid with a color filter array (CFA) and having a different spectral sensitivity than the non-image pixels, comprises determining a set of color components (rold, gold, bold) for the image pixels (R,G,B) based on raw image data (rraw, graw, braw) read only from the image pixels (R,G,B) of the image sensor (10); correcting the set of color components of non-direct neighbors of the non-image pixels (F) by means of a first color correction matrix (CCM1); and correcting the set of color components of direct neighbors of the non-image pixels by means of a second color correction matrix (CCM2) different from the first color correction matrix. An image sensor (10) and an auto-focus camera using same are also disclosed.

Claims

1. A method for correcting image data retrieved from an image sensor comprising a plurality of image pixels and non-image pixels, the image pixels being overlaid with a color filter array and having a different spectral sensitivity than the non-image pixels, the method comprising:

a) determining a set of color components for the image pixels based on raw image data read only from the image pixels of the image sensor, whereby one color component is assigned the raw image data obtained from the sensor for said image pixel, and the other color components are determined from raw image data obtained from the sensor for image pixels in the vicinity of said image pixel;

b) determining a corrected set of color components for the image pixels that are not directly adjacent to the non-image pixels by means of a first color correction matrix using the formula;

2. The method according to claim 1, further comprising determining the corrected set of color components for the non-image pixels.

3. The method according to claim 2, wherein determining the corrected set of color components for the non-image pixels comprises:

determining the set of color components for the non-image pixels based on the raw image data of the image pixels; and

determining the corrected set of color components for the non-image pixels by means of a third color correction matrix.

4. The method according to claim 3, wherein determining the corrected set of color components for the non-image pixels comprises multiplying the set of color components of said non-image pixels with the third color correction matrix.

5. The method according to claim 2, wherein determining the corrected set of color components for the non-image pixels uses raw image data only from image pixels that are not directly adjacent to the non-image pixels, and whereby the third color correction matrix is the same as the first color correction matrix.

6. The method according to claim 2, wherein determining the corrected set of color components for the non-image pixels uses raw image data from at least one image pixel that is directly adjacent to the non-image pixels, and whereby the third color correction matrix is the same as the second color correction matrix.

7. The method according to claim 2, wherein determining the corrected set of color components for the non-image pixels comprises:

determining the corrected set of color components for the non-image pixels based on the corrected set of color components of one or more image pixels in the vicinity of said non-image pixel.

8. An image sensor comprising:

a plurality of image pixels overlaid with a color filter array and at least one non-image pixel, the image pixels having a different spectral sensitivity than the non-image pixels, and

a processor unit adapted for;

a) determining a set of color components for the image pixels based on raw image data read only from the image pixels of the image sensor, whereby one color component is assigned the raw image data obtained from the sensor for said image pixel, and the other color components are determined from raw image data obtained from the sensor for image pixels in the vicinity of said image pixel;

b) correcting a set of color components of image pixels that are not directly adjacent to the non-image pixels using the formula;

9. The image sensor according to claim 8, wherein the processor unit is further adapted for determining the corrected set of color components for the non-image pixel locations.

10. The image sensor according to claim 8, further comprising a memory for storing image data for the image pixels, the processor unit being operatively connected to the memory.

11. The image sensor according to claim 10, wherein the processor unit is further adapted for determining the set of color components for the image pixels based on raw image data stored in the memory.

12. A digital camera comprising an image sensor according to claim 8, wherein the non-image pixels are adapted for being used as auto-focus pixels, the digital camera further comprising auto-focus circuitry for generating a control signal and for applying the control signal to a drive mechanism for moving a lens for focusing an image on the image sensor.