One chip, low light level color camera

• US 20030210332A1
• Filed: 05/08/2002
• Published: 11/13/2003
• Est. Priority Date: 05/08/2002
• Status: Active Grant

• Current Assignee: Ball Aerospace & Technologies Corporation (Ball Corporation)
• Original Assignee: Ball Aerospace & Technologies Corporation (Ball Corporation)
• Inventors: Frame, Wayne W.
• Granted Patent: US 7,012,643 B2
• Time in Patent Office: Days
• US Class Current: 348/216.1
• CPC Class Codes: H04N 2209/045 using mosaic colour filter
• CPC Class Codes: H04N 2209/047 using multispectral pick-up elements
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements

Abstract

A high sensitivity, single chip, low light level imaging device is provided. The imaging device of the present invention utilizes sparse color sampling, to maximize the luminance information gathered. In particular, color information is gathered by a small proportion of the pixels included in an image sensor, while the remaining pixels operate at full spectrum sensitivity. The present invention allows the correct hue of objects to be determined, while providing high sensitivity to available luminance information in a scene. In addition, the present invention allows hue information to be ascribed to objects in a scene, even in combination with luminance data collected over a spectrum that includes the near infrared and infrared wavelengths.

Claims

1. A method for providing a low light level camera, comprising:

providing an image sensor comprising a plurality of pixels;

filtering image information to a first proportion of said pixels for sensitivity to a selected first spectral region;

filtering image information to a second proportion of said pixels for sensitivity to a selected second spectral region, wherein less than half of said pixels of said image sensor pixels receive filtered image information.

2. The method of claim 1, wherein more than half of said pixels of said image sensor receive unfiltered image information and wherein said more than half of said pixels are sensitive to light having a wavelength greater than about 780 nanometers.

3. The method of claim 2, wherein said unfiltered image information comprises a luminance signal, and wherein said filtered image information comprises a chrominance signal.

4. The method of claim 1, further comprising:

filtering image information to a third proportion of said pixels for sensitivity to a selected third spectral region, wherein less than half of said image sensor pixels receive filtered image information.

5. The method of claim 1, wherein said first and second spectral regions overlap.

6. The method of claim 1, wherein said first proportion of pixels and said second proportion of pixels are randomly distributed among all of said pixels of said image sensor.

7. The method of claim 1, wherein said first proportion of pixels and said second proportion of pixels are pseudo-randomly distributed among all of said pixels of said image sensor.

8. The method of claim 1, wherein said first proportion of pixels and said second proportion of pixels are distributed about lines that are not parallel to sides of said image sensor.

9. The method of claim 4, wherein a plurality of elements comprising four filter units for four of said image sensor pixels are formed, wherein for each of said elements first and second of said filter units passes energy in said first spectral region, a third of said filter units pass energy in said second spectral region, and a fourth of said filter units passes energy in said third spectral region.

10. The method of claim 9, wherein said elements are distributed randomly among said pixels of said image sensor.

11. The method of claim 9, wherein said elements are distributed about lines that are not parallel to edges of said image sensor.

12. The method of claim 3, further comprising outputting an image sensed by said low light level camera, wherein at least a first area of said image comprising a pixel receiving unfiltered image information is provided with chrominance information derived from at least a first pixel receiving filtered image information located at least one of within and proximate to said at least a first area.

13. The method of claim 3, further comprising outputting an image sensed by said low light level camera, wherein at least a first area of said image comprising a pixel receiving unfiltered image information is provided with chrominance information derived from a plurality of pixels receiving filtered image information.

14. The method of claim 3, further comprising:

adjusting a gain associated with said chrominance signal.

15. The method of claim 14, wherein said gain is reduced in response to a decrease in a signal to noise ratio of said chrominance signal.

16. The method of claim 3, further comprising:

delaying at least one of a frame and a field of said chrominance signal relative to a corresponding at least one of a frame and a field of said luminance signal; and

performing a signal processing operation with respect to said chrominance signal.

17. The method of claim 3, further comprising:

averaging a plurality of at least one of frames and fields of said chrominance signal.

18. The method of claim 3, wherein said image sensor comprises a first set of pixels comprising a first frame and a second set of pixels comprising a second frame, said method further comprising:

generating said chrominance signal with respect to said first frame but not said second frame.

19. The method of claim 3, wherein in a first mode of operation said chrominance signal is processed and displayed and wherein in a second mode of operation said chrominance signal is not processed and is not displayed.

20. A device for color imaging in low light level conditions, comprising:

an image sensor, wherein said image sensor comprises;

a first plurality of pixels particularly sensitive to luminance;

a second plurality of pixels particularly sensitive to chrominance, wherein said first plurality of pixels comprises more than half a total number of pixels of said image sensor.

21. The device of claim 20, wherein said second plurality of pixels are arranged in groups of three, wherein each of said groups comprises a first pixel having sensitivity to a first spectral band, a second pixel having sensitivity to a second spectral band, and a third pixel having sensitivity to a third spectral band.

22. The device of claim 20, wherein said second plurality of pixels are arranged in groups of four, wherein each of said groups comprises first and second pixels having sensitivity of a first spectral band, a third pixel having sensitivity of a second spectral band, and a fourth pixel having sensitivity to a third spectral band.

23. The device of claim 20, wherein said second plurality of pixels are pseudo-randomly distributed about said image sensor.

24. The device of claim 20, wherein said second plurality of pixels are weighted about lines that are not parallel to edges of said image sensor.

25. The device of claim 20, wherein said second plurality of pixels are distributed about diagonals of said image sensor.

26. The device of claim 20, further comprising a plurality of filters, wherein a first filter type allows light within said first spectral band to reach said first and second pixels, wherein a second filter type allows light within said second spectral band to reach said third pixels, and wherein a third filter type allows light within said third spectral band to reach said fourth pixels.

27. The device of claim 20, further comprising a switch, wherein said switch is operable to selectively turn off a signal from said second plurality of pixels.

28. The device of claim 20, wherein said second plurality of pixels comprises less than 4% of a total number of pixels of said image sensor.

29. A low light level image sensor, comprising:

an image sensor comprising a plurality of pixels;

a color filter, wherein a first plurality of said pixels are provided with image information filtered to within a first spectrum defined by a first band pass filter, wherein a second plurality of said pixels are provided with image information filtered to within a second spectrum defined by a second band pass filter, wherein a third plurality of said pixels are provided with image information filtered to within a third spectrum by a third band pass filter, and wherein said first, second, and third pluralities of pixels provided with filtered image information comprise less than half a total number of said pixels of said image sensor.

30. The low light level image sensor of claim 29, wherein a majority of said pixels of said image sensor receive image information at wavelengths greater than 780 nanometers.

31. The low light level image sensor of claim 29, wherein said first, second, and third pluralities of pixels provided with filtered image information are distributed randomly among said pixels of said image sensor

32. The low light image sensor of claim 29, wherein said first, second and third pluralities of pixels provided with filtered image information are distributed about said image sensor in groups comprising at least one of each of said first, second and third pluralities of pixels.

33. The low light image sensor of claim 29, further comprising a switch, wherein signals from said first, second, and third pluralities of pixels can be selectively switched off.