Extended dynamic range in color imagers

• US 20050248667A1
• Filed: 06/03/2004
• Published: 11/10/2005
• Est. Priority Date: 05/07/2004
• Status: Active Grant

• Current Assignee: Gula Consulting Limited Liability Company (Intellectual Ventures LLC)
• Original Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Inventors: Knoedgen, Horst, Dosluoglu, Taner, Schweng, Detlef
• Granted Patent: US 8,723,995 B2
• Time in Patent Office: Days
• US Class Current: 348/234
• CPC Class Codes: H04N 2209/045 using mosaic colour filter
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/133 including elements passing panchromatic light, e.g. filters passing white light
• CPC Class Codes: H04N 25/135 based on four or more different wavelength filter elements

Abstract

A digital color imager providing an extended luminance range, an improved color implementation and enabling a method for an easy transformation into another color space having luminance as a component has been achieved. Key of the invention is the addition of white pixels to red, green and blue pixels. These white pixels have either an extended dynamic rang as described by U.S. patent (U.S. Pat. No. 6,441,852 to Levine et al.) or have a larger size than the red, green, or blue pixels used. The output of said white pixels can be directly used for the luminance values Y of the destination color space. Therefore only the color values and have to be calculated from the RGB values, leading to an easier and faster calculation. As an example chosen by the inventor the conversion to YCbCr color space has been shown in detail.

Claims

1. A digital color imager providing an extended luminance range and an improved color representation comprising red, green, blue and white pixels, wherein said white pixels are extended dynamic range pixels.

2. The imager of claim 1 wherein said red, green and blue pixels have correspondent color filters.

3. A digital color imager providing an extended luminance range and an improved color representation comprising red, green, blue and white pixels, wherein said white pixels have a larger size compared to the red, green or blue pixels used.

4. The imager of claim 3 wherein said red, green and blue pixels have correspondent color filters.

5. The imager of claim 3 wherein said white pixels are non-XDR pixels.

6. A method to convert pixel color values of a digital color imager into another color space having luminance as a component is comprising:

providing an digital color imager comprising red, green, blue and white pixels;

use sensor output of white pixel for luminance value Y;

calculate color values of destination color space from the output of the red, green and blue pixels using the correspondent conversion matrix.

7. The method of claim 6 wherein said white pixels are of XDR-type.

9. The method of claim 6 wherein said white pixels have a larger size as the red, green, or blue pixels used.

8. The method of claim 8 wherein said white pixels have a similar size as the red, green, or blue pixels used.

10. The method of claim 10 wherein said white pixels are non-XDR type pixels.

11. A method to convert pixel color values of a digital color imager into YcbCr color space:

providing an digital color imager comprising red, green, blue and white pixels;

use sensor output of white pixel for luminance value Y;

calculate color values Cb and Cr from the output of the red, green and blue pixels using transformation parameters.

12. The method of claim 11 wherein said calculation of the Cb and Cr components of YCbCr color space is performed according to the following equation:

13. The method of claim 11 wherein said white pixels are of XDR-type.

14. The method of claim 13 wherein said white pixels have a similar size as the red, green, or blue pixels used.

15. The method of claim 11 wherein said white pixels have a larger size as the red, green, or blue pixels used.

16. The method of claim 15 wherein said white pixels are non-XDR type pixels.