Extended color processing on pelican array cameras
View Patent ↗Systems and methods for extended color processing on Pelican array cameras in accordance with embodiments of the invention are disclosed. In one embodiment, a method of generating a high resolution image includes obtaining input images, where a first set of images includes information in a first band of visible wavelengths and a second set of images includes information in a second band of visible wavelengths and non-visible wavelengths, determining an initial estimate by combining the first set of images into a first fused image, combining the second set of images into a second fused image, spatially registering the fused images, denoising the fused images using bilateral filters, normalizing the second fused image in the photometric reference space of the first fused image, combining the fused images, determining a high resolution image that when mapped through a forward imaging transformation matches the input images within at least one predetermined criterion.
1. A method of generating a high resolution image of a scene using an imager array including a plurality of imagers that each capture an image of the scene, and a forward imaging transformation for each imager, the method comprising:
obtaining input images captured by a plurality of imagers, where a first set of input images includes image information captured in a first band of visible wavelengths and a second set of input images includes image information captured in a second band of visible wavelengths and non-visible wavelengths;
determining an initial estimate of at least a portion of a high resolution image using a processor configured by software to:
combine image information from the first set of input images into a first fused image;
combine image information from the second set of input images into a second fused image, wherein the first fused image and the second fused image have the same resolution and the resolution is higher than the resolution of any of the input images;
spatially register the first fused image and the second fused image;
denoise the first fused image using a first bilateral filter;
denoise the second fused image using a second bilateral filter;
normalize the second fused image in the photometric reference space of the first fused image; and
combine the first fused image and the second fused image into an initial estimate of at least a portion of the high resolution image; and
determining a high resolution image that when mapped through the forward imaging transformation matches the input images to within at least one predetermined criterion using the initial estimate of at least a portion of the high resolution image using the processor configured by software;
wherein each forward imaging transformation corresponds to the manner in which each imager in the imaging array generated the input images; and
wherein the high resolution image has a resolution that is greater than any of the input images.
2. The method of claim 1 , wherein the first band of visible wavelengths and the second band of visible and non-visible wavelengths have some degree of overlap.
3. The method of claim 1 , wherein the second band of visible and non-visible wavelengths includes green, red, and near-infrared light.
4. The method of claim 1 , wherein:
the first set of input images are captured by a first set of imagers from the plurality of imagers and the first set of imagers are sensitive to light in the first band of visible wavelengths; and
the second set of input images are captured by a second set of imagers from the plurality of imagers and the second set of imagers are sensitive to light in the second band of visible and non-visible wavelengths.
5. The method of claim 4 , wherein the processor being configured to combine image information from the first set of input images into a first fused image utilizes analog gain and noise information from the first set of imagers and the processor being configured to combine image information from the second set of input images into a second fused image utilizes analog gain and noise information from the second set of imagers.
6. The method of claim 1 , wherein the first bilateral filter and the second bilateral filter utilize weights that are a function of both the photometric and geometric distance between a pixel and pixels in the neighborhood of the pixel.
7. The method of claim 1 , wherein the first bilateral filter is a cross-channel bilateral filter utilizing weights determined for the second fused image.
8. The method of claim 1 , wherein the first set of input images are captured by a first set of imagers from the plurality of imagers and the first bilateral filter is a cross-channel bilateral filter utilizing weights determined for the second fused image when an analog gain value of the first set of imagers is above a predetermined threshold.
9. The method of claim 1 , wherein normalizing the second fused image in the photometric reference space of the first fused image comprises applying gains and offsets to pixels of the second fused image.
10. The method of claim 9 , wherein the gain for each pixel of the second fused image is determined by the equation:
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and the bias for each pixel of the second fused image is determined by the equation:
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11. The method of claim 1 , wherein determining an initial estimate of at least a portion of a high resolution image using a processor configured by software further comprises the processor being configured to cross-channel normalize the first fused image in the photometric reference space of the second fused image.
12. The method of claim 11 , wherein the processor being configured to cross-channel normalize the first fused image in the photometric reference space of the second fused image comprises the processor being configured to apply gains and offsets to pixels of the first fused image.
13. The method of claim 12 , wherein the gain for each pixel of the first fused image is determined by the equation:
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14. The method of claim 1 , wherein the processor being configured to normalize the second fused image in the photometric reference space of the first fused image comprises the processor being configured to:
select a first pixel of interest in the second fused image and a first collection of similar pixels in the neighborhood of the first pixel of interest;
select a second pixel of interest in the first fused image corresponding to the first pixel of interest and a second collection of similar pixels in the neighborhood of the second pixel of interest;
determine the intersection of the first collection of similar pixels and the second collection of similar pixels;
calculate gain and offset values using the intersection of the two collections; and
apply the gain and offset values to the appropriate pixels in the second fused image.
15. The method of claim 14 where the intersection of the first collection of similar pixels and the second collection of similar pixels is the set of pixels in the first and second collections having the same corresponding locations in each of the first and second fused images.
16. The method of claim 14 wherein the gain for each pixel in the intersection of the two collections within the second fused image is determined by the equation:
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e is the second fused image, g is the first fused image, N r and N c are the number of pixels horizontally and vertically of the neighborhood of pixels around the pixel, and r and c are row and column indices into the images within the bounds defined by N r and N c .
17. An array camera configured to generate a high resolution image of a scene using an imager array including a plurality of imagers that each capture an image of the scene, and a forward imaging transformation for each imager, the array camera comprising:
an imager array including a plurality of imagers; and
a processor configured by software to:
obtain input images captured by the plurality of imagers, where a first set of input images includes image information captured in a first band of visible wavelengths and a second set of input images includes image information captured in a second band of visible wavelengths and non-visible wavelengths;
determine an initial estimate of at least a portion of a high resolution image by:
combining image information from the first set of input images into a first fused image;
combining image information from the second set of input images into a second fused image, wherein the first fused image and the second fused image have the same resolution and the resolution is higher than the resolution of any of the input images;
spatially registering the first fused image and the second fused image;
denoising the first fused image using a first bilateral filter;
denoising the second fused image using a second bilateral filter;
normalizing the second fused image in the photometric reference space of the first fused image;
combining the first fused image and the second fused image into an initial estimate of at least a portion of the high resolution image; and
determine a high resolution image that when mapped through the forward imaging transformation matches the input images to within at least one predetermined criterion using the initial estimate of at least a portion of the high resolution image using the processor configured by software;
wherein each forward imaging transformation corresponds to the manner in which each imager in the imaging array generated the input images; and
wherein the high resolution image has a resolution that is greater than any of the input images.
18. The array camera of claim 17 , wherein the first band of visible wavelengths and the second band of visible and non-visible wavelengths have some degree of overlap.
19. The array camera of claim 17 , wherein the second band of visible and non-visible wavelengths includes green, red, and near-infrared light.
20. The array camera of claim 17 , wherein:
the first set of input images are captured by a first set of imagers from the plurality of imagers and the first set of imagers are sensitive to light in the first band of visible wavelengths; and
the second set of input images are captured by a second set of imagers from the plurality of imagers and the second set of imagers are sensitive to light in the second band of visible and non-visible wavelengths.
21. The array camera of claim 20 , wherein combining image information from the first set of input images into a first fused image utilizes analog gain and noise information from the first set of imagers and combining image information from the second set of input images into a second fused image utilizes analog gain and noise information from the second set of imagers.
22. The array camera of claim 17 , wherein the first bilateral filter and the second bilateral filter utilize weights that are a function of both the photometric and geometric distance between a pixel and pixels in the neighborhood of the pixel.
23. The array camera of claim 17 , wherein the first bilateral filter is a cross-channel bilateral filter utilizing weights determined for the second fused image.
24. The array camera of claim 17 , wherein the first set of input images are captured by a first set of imagers from the plurality of imagers and the first bilateral filter is a cross-channel bilateral filter utilizing weights determined for the second fused image when an analog gain value of the first set of imagers is above a predetermined threshold.
25. The array camera of claim 17 , wherein normalizing the second fused image in the photometric reference space of the first fused image comprises applying gains and offsets to pixels of the second fused image.
26. The array camera of claim 25 , wherein the gain for each pixel of the second fused image is determined by the equation:
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e is the second fused image, g is the first fused image, N r and N c are the number of pixels horizontally and vertically of the neighborhood of pixels around the pixel, and r and c are row and column indices into the images within the bounds defined by N r and c .
27. The array camera of claim 17 , wherein the processor is further configured to cross-channel normalize the first fused image in the photometric reference space of the second fused image.
28. The array camera of claim 27 , wherein the processor being configured to cross-channel normalize the first fused image in the photometric reference space of the second fused image comprises the processor being configured to apply gains and offsets to pixels of the first fused image.
29. The array camera of claim 28 , wherein the gain for each pixel of the first fused image is determined by the equation:
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and the bias for each pixel of the first fused image is determined by the equation:
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e is the first fused image, g is the second fused image, N r and N c are the number of pixels horizontally and vertically of the neighborhood of pixels around the pixel, and r and c are row and column indices into the images within the bounds defined by N r and c .
30. The array camera of claim 17 , wherein normalizing the second fused image in the photometric reference space of the first fused image comprises:
selecting a first pixel of interest in the second fused image and a first collection of similar pixels in the neighborhood of the first pixel of interest;
selecting a second pixel of interest in the first fused image corresponding to the first pixel of interest and a second collection of similar pixels in the neighborhood of the second pixel of interest;
determining the intersection of the first collection of similar pixels and the second collection of similar pixels;
calculating gain and offset values using the intersection of the two collections;
applying the gain and offset values to the appropriate pixels in the second fused image.
31. The array camera of claim 30 where the intersection of the first collection of similar pixels and the second collection of similar pixels is the set of pixels in the first and second collections having the same corresponding locations in each of the first and second fused images.
32. The array camera of claim 30 wherein the gain for each pixel in the intersection of the two collections within the second fused image is determined by the equation:
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and the bias for each pixel in the intersection of the two collections within the second fused image is determined by the equation:
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where:
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