Two narrow band and one wide band color filter for increasing color image sensor sensitivity

• US 20060044427A1
• Filed: 08/26/2004
• Published: 03/02/2006
• Est. Priority Date: 08/26/2004
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Hu, Shane Ching-Feng
• Granted Patent: US 7,477,304 B2
• Time in Patent Office: Days
• US Class Current: 348/266
• CPC Class Codes: H04N 23/12 with one sensor only
• 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 25/134 based on three different wavelength filter elements

Abstract

A color filter to increase the low light sensitivity of an image sensor. The color filter has two narrow band color filters and one wide band filter. Also disclosed is a unique way of processing a tri-stimulus signal to dynamically adjust color contrast depending on the illumination conditions.

Claims

1. A color filter array comprising:

a plurality of a first type of rows comprising alternating transparent and red color filters; and

a plurality of a second type of rows comprising alternating transparent and blue color filters, wherein the rows form a pattern of alternating first and second type of rows.

2. An imaging device comprising:

a plurality of imager pixel cells, each cell comprising a photosensor; and

a color filter array formed over the plurality of cells, said array comprising alternating rows of a first and second type, wherein the first type of rows comprises transparent and red color filters and the second type of rows comprises transparent and blue color filters.

3. The imaging device of claim 2, further comprising at least one of an infrared or a ultraviolet filter formed over the plurality of imager pixel cells.

4. The imaging device of claim 3, further comprising a light shield layer formed above the dielectric layer but below the color filter array, for shielding areas of said pixel cells from light exposure.

5. The imaging device of claim 2, wherein the imager pixel cells comprise CMOS imager pixel cells.

6. The imaging device of claim 2, wherein the first type of row comprises alternating transparent and red color filters.

7. The imaging device of claim 2, wherein the second type of row comprises alternating transparent and blue color filters.

8. A color imaging device comprising an array of image pixel sensors comprising:

a plurality of a first type of image sensors that produce a first signal indicative of an amount of incident light having wavelengths within a first narrow band of color;

a plurality of a second type of image sensors that produce a second signal indicative of an amount of incident light having wavelengths within a second narrow band of color; and

a plurality of a third type of image sensors that produce a third signal indicative of an amount of incident light having wavelengths within the whole visible spectrum.

9. The color imaging device of claim 8, wherein the first narrow band of color and the second narrow band of color correspond to primary colors.

10. The color imaging device of claim 9, wherein one of the first and second narrow bands of color corresponds to red.

11. The color imaging device of claim 9, wherein one of the first and second narrow bands of color corresponds to blue.

12. The color imaging device of claim 9, wherein the image sensors are arranged in an array having alternating rows of first and third image sensor types with rows of second and third image sensor types.

13. A processing system comprising:

an imaging device comprising;

a color filter array having a plurality of red, blue and transparent color filters; and

an array of image sensors located below the filter array, each sensor corresponding to one of the red, blue and transparent color filters and for producing a signal representing an amount of light received at the sensor; and

a processor for receiving and processing said signals produced by the image sensors.

14. The processing system of claim 13, wherein the color filter array comprises:

a plurality of a first type of rows comprising alternating transparent and red color filters; and

a plurality of a second type of rows comprising alternating transparent and blue color filters, wherein the rows form a pattern of alternating first and second type of rows.

15. The processing system of claim 13, wherein the image sensors are CMOS pixel sensor cells.

16. A method of processing a digital color signal comprising the acts of:

obtaining a signal from each of a plurality of image sensors, the plurality of image sensors corresponding to applied light with wavelengths in one of the red, blue and whole visible light spectrum;

producing a tri-stimulus signal for each signal obtained; and

processing the tri-stimulus signal in order to reproduce the image on an external interface.

17. The method of claim 16, wherein the step of producing a tri-stimulus signal comprises interpolation based on the signal obtained from adjacent image sensors.

18. The method of claim 16, further comprising the step of filtering the ultraviolet and infrared light.

19. The method of claim 16, wherein the external interface comprises any one of a computer monitor, a camera screen and a printer output.

20. A method of processing a digital color signal comprising the acts of:

interpolating from received signals to produce a tri-stimulus signal for each of a plurality of pixel sensor cells, wherein the received signals correspond to an amount of applied light having wavelengths within one of the ranges for blue, red, and transparent light;

transforming the tri-stimulus signal for each pixel to XYZ space;

performing a saturation adjustment; and

transforming the signal for compatibility with an external interface.

21. The method of claim 20, wherein said step of transforming the signal for compatibility comprises a D65 matrix transformation.

22. The method of claim 20, further comprising the step of dynamically adjusting the color contrast.

23. The method of claim 22, wherein the step of dynamically adjusting the color contrast comprises the steps of

externally setting at least one contrast parameter to a pre-determined value;

and

adjusting said at least one contrast parameter to an adjusted level depending on the illumination surrounding the desired image.

24. The method of claim 23, wherein the at least one adjusted contrast parameter is used in the step of performing a saturation adjustment.