METHODS AND SYSTEM FOR SPECTRAL IMAGE SAMPLING

• US 20110299768A1
• Filed: 06/03/2011
• Published: 12/08/2011
• Est. Priority Date: 06/03/2010
• Status: Active Grant

• Current Assignee: Image Algorithmics Inc.
• Original Assignee: Mritunjay Singh, Tripurari Singh
• Inventors: Singh, Tripurari, Singh, Mritunjay
• Granted Patent: US 8,644,603 B2
• Time in Patent Office: Days
• US Class Current: 382/162
• 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

The present invention relates to spectral image sampling. An image is projected onto an array of optical transformation devices. Image intensity values transmitted by said array of optical transformation devices are detected at each sensor element of an image sensor. The image sensor comprises a plurality of photosensitive sensor elements configured to detect a magnitude of incident light, wherein said sensor elements are shaped as regular polygons whose aspect ratio is controlled to minimize sensor element count while obtaining a desired image quality. The detected image intensity values are processed to infer the image.

Claims

1. A method of sampling an image comprising:

projecting an image onto an array of optical transformation devices;

detecting image intensity values transmitted by said array of optical transformation devices at each sensor element of an image sensor, the image sensor comprising a plurality of photosensitive sensor elements configured to detect a magnitude of incident light, wherein said sensor elements are shaped as regular polygons whose aspect ratio is controlled to minimize sensor element count while obtaining a desired image quality; and

processing the detected image intensity values to infer the image.

2. The method of claim 1, wherein the image is inferred by demultiplexing color components determined from said image intensity values using demosaicking techniques.

3. The method of claim 1, wherein multiple images are inferred over a period of time to construct a video sequence.

4. The method of claim 1, further comprising projecting the image through an optical low pass filter prior to projecting the image onto the color filter array and wherein the array of optical transformation devices comprises a color filter array.

5. The method of claim 1, wherein said color filter array is chosen according to a tight packing solution which packs a circular frequency support of the image into a minimum area rectangular frequency support of said image sensor.

6. The method of claim 5, wherein a color pattern of the color filter array is periodic.

7. The method of claim 5, wherein said sensor elements are rectangular with an aspect ratio given by said tight packing solution.

8. The method of claim 5, wherein the optical low pass filter has a cutoff frequency given by said tight packing solution.

9. The method of claim 1, wherein a detected chrominance signal has a resolution that is half that of a detected luminance signal.

10. The method of claim 5, wherein said tight packing solution results in a periodic color filter array with a four-by-two minimum repeating pattern with 4 unique colors and a pixel aspect ratio of one divided by the square root of two.

11. The method of claim 1, wherein the elements are selected from the group consisting of:

rectangular, hexagonal, and octagonal.

12. A method of sampling an image comprising:

projecting an image onto a color filter array wherein said color filter array is configured according to a desired resolution for a detected chrominance signal;

detecting image intensity values transmitted through said color filter array at each sensor element of an image sensor, the image sensor comprising a plurality of photosensitive sensor elements configured to detect a magnitude of incident light; and

processing the detected image intensity values to infer the image.

13. The method according to claim 12, wherein said sensor elements are square.

14. The method according to claim 12, wherein said sensor elements are rectangular with aspect ratio controlled to minimize sensor element count while retaining a desired image quality.

15. An image sampling apparatus comprising:

a color filter array comprising a plurality of color filters, the color filter array being configured such that, in at least one frequency domain representation of at least one image captured using the plurality of photosensitive elements, at least one spectral copy of a chrominance signal is positioned so as to minimize overlap between the chrominance signal and a luminance signal in the at least one frequency domain representation, and wherein the color filters of the color filter array each has a non-square rectangular shape;

an image sensor comprising a plurality of photosensitive sensor elements, each sensor element configured to detect a magnitude of incident light; and

a processor for receiving detected image intensity values.

16. The apparatus of claim 15, wherein the shape of the color filters of the color filter array is selected to maximize a bandwidth of captured image data.

17. The apparatus of claim 15, wherein the color filter array is configured according to a tight packing solution.

18. The apparatus of claim 17, wherein the tight packing solution is used with a chrominance bandwidth ratio of 0.5.

19. The apparatus of claim 15, wherein at least one of the plurality of color filters is panchromatic.

20. A method of sampling at least one image, the method comprising:

filtering electromagnetic radiation using a color filter array comprising a plurality of color filters, the color filter array being configured such that, in at least one frequency domain representation of at least one image captured using the plurality of photosensitive elements, at least one spectral copy of a chrominance signal is positioned so as to minimize overlap between the chrominance signal and a luminance signal in the at least one frequency domain representation, and wherein the color filters of the color filter array each has a non-square rectangular shape; and

detecting the filtered electromagnetic radiation with an image sensor comprising a plurality of photosensitive sensor elements, each sensor element configured to detect a magnitude of incident light; and

processing the detected electromagnetic radiation to infer an image.

21. The method of claim 20, wherein the color filter array is configured according to a tight packing solution.

22. The method of claim 21, wherein the tight packing solution is used with a chrominance bandwidth ratio of 0.5.

23. The method of claim 20, further comprising inferring a plurality of images to construct a video.

24. A method of processing at least one color image, the method comprising:

receiving a detected electromagnetic radiation, the electromagnetic radiation being representative of an image; and

storing a mosaicked representation of the image on a machine readable medium, wherein the representation of the image includes a plurality of indications of magnitudes of light, each magnitude of light corresponding to a magnitude of at least one color of light at one of a plurality of locations in the image, and wherein a frequency domain representation of the plurality of magnitudes of light has a channel shape that is substantially non-square and in which chrominance and luminance are positioned to minimize overlap in the frequency domain representation.

25. A method for image processing, the method comprising the steps of:

transforming image data into at a luminance signal and a chrominance signal wherein a frequency domain representation of the luminance signal and the chrominance signal is contained within a non-square rectangular shape and wherein overlap between the luminance signal and the chrominance signal in the frequency domain representation is minimized; and

processing the image data to infer an image.

26. The method of claim 25, further comprising a step of establishing physical characteristics of a color filter array used for obtaining the image data based at least in part on the frequency domain representation of the luminance signal and the chrominance signal.

27. The method of claim 26, wherein the physical characteristics include a color of at least one color filter comprising a color filter array.

28. The method of claim 27, wherein the color of at least one color filter is panchromatic.

29. The method of claim 26, wherein the physical characteristics include a geometric arrangement of at least one filter in a color filter array.

30. The method of claim 26, wherein the physical characteristics include a geometry of at least one color filter in a color filter array.

31. The method of claim 25, wherein said transforming comprises a step of minimizing the overlap between the luminance signal and the chrominance signal in the frequency domain representation which includes determining at least one desired aspect of the non-square rectangular shape and a desired position for at least one spectral representation of the chrominance signal in the frequency domain.

32. The method of claim 31, further comprising a step of establishing the non-square rectangular shape of the frequency domain representation.

33. The method of claim 32, wherein said establishing is performed according to a tight packing solution.

34. The method of claim 33, wherein the tight packing solution is used with a chrominance bandwidth ratio of 0.5.

35. The method of claim 31, further comprising a step of modulating a value for the at least one chrominance signal to attain the desired position.

36. The method of claim 31, wherein the step of minimizing the overlap further comprises restricting a carrier frequency of the chrominance signal in a frequency domain representation.

37. The method of claim 36, further comprising a step of restricting the carrier frequency of the chrominance signal representation to rational multiples of pi.

38. The method of claim 25, further comprising a step of reconstructing a captured image employing a completely linear reconstruction process.