Systems and methods for measuring depth using an array of independently controllable cameras

• US 9,240,049 B2
• Filed: 07/11/2014
• Issued: 01/19/2016
• Est. Priority Date: 08/21/2012
• Status: Active Grant

• Current Assignee: FotoNation Limited (Adeia Inc.)
• Original Assignee: Pelican Imaging Corporation
• Inventors: Ciurea, Florian, Venkataraman, Kartik, Molina, Gabriel, Lelescu, Dan
• Primary Examiner(s): Du, Haixia
• Application Number:
  US14/329,754
• Publication Number:
  US 20140321712A1
• Time in Patent Office: 557 Days
• US Class Current: 1/1
• CPC Class Codes: G02B 27/0075 with means for altering, e.g. increasing, the depth of field or depth of focus
• CPC Class Codes: G06T 15/20 Perspective computation
• CPC Class Codes: G06T 2200/21 involving computational photography
• CPC Class Codes: G06T 2207/10012 Stereo images
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/10052 Images from lightfield camera
• CPC Class Codes: G06T 7/557 from light fields, e.g. from plenoptic cameras
• CPC Class Codes: G06T 7/593 from stereo images
• CPC Class Codes: G06T 7/85 Stereo camera calibration
• CPC Class Codes: H04N 13/128 Adjusting depth or disparity
• CPC Class Codes: H04N 13/232 using fly-eye lenses, e.g. arrangements of circular lenses
• CPC Class Codes: H04N 13/243 using three or more 2D image sensors
• CPC Class Codes: H04N 2013/0081 Depth or disparity estimation from stereoscopic image signals
• CPC Class Codes: H04N 2013/0088 Synthesising a monoscopic image signal from stereoscopic images, e.g. synthesising a panoramic or high resolution monoscopic image
• CPC Class Codes: H04N 23/16 Optical arrangements associated therewith, e.g. for beam-splitting or for colour correction

Abstract

Systems in accordance with embodiments of the invention can perform parallax detection and correction in images captured using array cameras. Due to the different viewpoints of the cameras, parallax results in variations in the position of objects within the captured images of the scene. Methods in accordance with embodiments of the invention provide an accurate account of the pixel disparity due to parallax between the different cameras in the array, so that appropriate scene-dependent geometric shifts can be applied to the pixels of the captured images when performing super-resolution processing. In a number of embodiments, generating depth estimates considers the similarity of pixels in multiple spectral channels. In certain embodiments, generating depth estimates involves generating a confidence map indicating the reliability of depth estimates.

Claims

1. A camera array, comprising:

a plurality of cameras configured to capture images of a scene from different viewpoints;

a processor; and

memory containing an image processing application;

wherein the image processing application stored in memory directs the processor to;

separately configure the imaging parameters for each of the plurality of cameras;

read out image data from the plurality of cameras including a set of images captured from different viewpoints;

store the image data in the memory;

select a reference viewpoint relative to the viewpoints of the set of images captured from different viewpoints;

normalize the set of images to increase the similarity of corresponding pixels within the set of images;

determine initial depth estimates for pixel locations in an image from the reference viewpoint based upon the disparity at which corresponding pixels in the set of images have the highest degree of similarity;

compare the similarity of the corresponding pixels in the set of images to detect mismatched pixels;

when an initial depth estimate does not result in the detection of a mismatch between corresponding pixels in the set of images, selecting the initial depth estimate as the depth estimate for the pixel location in the image from the reference viewpoint; and

when an initial depth estimate results in the detection of a mismatch between corresponding pixels in the set of images, updating the depth estimate for the pixel location in the image from the reference viewpoint by;

determining a set of candidate depth estimates using a plurality of competing subsets of the set of images based upon the disparities at which corresponding pixels in each of a plurality of competing subsets of images have the highest degree of similarity; and

selecting the candidate depth of the subset having the corresponding pixels with the highest degree of similarity as the updated depth estimate for the pixel location in the image from the reference viewpoint.

2. The camera array of claim 1, wherein the optics within each camera are configured so that the pixels of the camera sample the same object space with sub-pixel offsets.

3. The camera array of claim 2, wherein the image processing application further directs the processor to:

determine the visibility of the pixels in the set of images from the reference viewpoint by;

identifying corresponding pixels in the set of images using the current depth estimates; and

determining that a pixel in a given image is not visible in the reference viewpoint when the pixel fails a photometric similarity criterion determined based upon a comparison of corresponding pixels; and

fuse pixels from the set of images using the depth estimates to create a fused image having a resolution that is greater than the resolutions of the images in the set of images by;

identifying the pixels from the set of images that are visible in an image from the reference viewpoint using the visibility information;

applying scene dependent geometric shifts to the pixels from the set of images that are visible in an image from the reference viewpoint to shift the pixels into the reference viewpoint, where the scene dependent geometric shifts are determined using the depth estimates; and

fusing the shifted pixels from the set of images to create a fused image from the reference viewpoint having a resolution that is greater than the resolutions of the images in the set of images.

4. The camera array of claim 3, wherein the image processing application further directs the processor to synthesize an image from the reference viewpoint by performing a super-resolution process based upon the fused image from the reference viewpoint, the set of images captured from different viewpoints, the depth estimates, and the visibility information.

5. The camera array of claim 1, wherein at least one camera in the plurality of cameras is a monochrome camera.

6. The camera array of claim 5, wherein at least one camera includes a Bayer color filter pattern.

7. The camera array of claim 5, wherein the image processing application further directs the processor to select the viewpoint of a camera in the plurality of cameras that captures image data in multiple color channels as the reference viewpoint.

8. The camera array of claim 1, wherein at least one camera in the plurality of cameras captures image data in multiple color channels.

9. The camera array of claim 1, wherein different cameras within the plurality of cameras capture image data with respect to different portions of the electromagnetic spectrum.

10. The camera array of claim 1, wherein different cameras within the array camera module capture image data with respect to different portions of the electromagnetic spectrum.

11. The camera array of claim 1, wherein the array camera module further comprises light filters within each optical channel formed by the lens stacks.

12. The camera array of claim 11, wherein the light filters are applied to the pixels of the focal planes.

13. A camera array, comprising:

an array camera module comprising;

an imager array including an array of focal planes, where each focal plane includes a plurality of rows of pixels that also forms a plurality of columns of pixels, and each focal plane is contained within a region of the imager that does not contain pixels from another focal plane; and

an optic array including an array of lens stacks, where each lens stack creates an optical channel that forms an image of the scene on an array of pixels within a corresponding focal plane;

a processor; and

memory containing an image processing application;

wherein the image processing application stored in memory directs the processor to;

independently control the imaging parameters of the focal planes in the array camera module;

read out image data from the array camera module forming a set of images captured from different viewpoints;

store the image data in the memory;

select a reference viewpoint relative to the viewpoints of the set of images captured from different viewpoints;

normalize the set of images to increase the similarity of corresponding pixels within the set of images;

determine initial depth estimates for pixel locations in an image from the reference viewpoint based upon the disparity at which corresponding pixels in the set of images have the highest degree of similarity;

compare the similarity of the corresponding pixels in the set of images to detect mismatched pixels;

when an initial depth estimate does not result in the detection of a mismatch between corresponding pixels in the set of images, selecting the initial depth estimate as the depth estimate for the pixel location in the image from the reference viewpoint; and

when an initial depth estimate results in the detection of a mismatch between corresponding pixels in the set of images, updating the depth estimate for the pixel location in the image from the reference viewpoint by;

determining a set of candidate depth estimates using a plurality of competing subsets of the set of images based upon the disparities at which corresponding pixels in each of a plurality of competing subsets of images have the highest degree of similarity; and

selecting the candidate depth of the subset having the corresponding pixels with the highest degree of similarity as the updated depth estimate for the pixel location in the image from the reference viewpoint.

14. The camera array of claim 13, wherein the lens stack within each optical channel is configured so that the pixels of each focal plane sample the same object space with sub-pixel offsets.

15. The camera array of claim 14, wherein the image processing application further directs the processor to:

determine the visibility of the pixels in the set of images from the reference viewpoint by;

identifying corresponding pixels in the set of images using the current depth estimates; and

determining that a pixel in a given image is not visible in the reference viewpoint when the pixel fails a photometric similarity criterion determined based upon a comparison of corresponding pixels; and

fuse pixels from the set of images using the depth estimates to create a fused image having a resolution that is greater than the resolutions of the images in the set of images by;

identifying the pixels from the set of images that are visible in an image from the reference viewpoint using the visibility information; and

applying scene dependent geometric shifts to the pixels from the set of images that are visible in an image from the reference viewpoint to shift the pixels into the reference viewpoint, where the scene dependent geometric shifts are determined using the depth estimates; and

fusing the shifted pixels from the set of images to create a fused image from the reference viewpoint having a resolution that is greater than the resolutions of the images in the set of images.

16. The camera array of claim 15, wherein the image processing application further directs the processor to synthesize an image from the reference viewpoint by performing a super-resolution process based upon the fused image from the reference viewpoint, the set of images captured from different viewpoints, the depth estimates, and the visibility information.

17. The camera array of claim 13, wherein at least one camera in the array camera module is a monochrome camera.

18. The camera array of claim 17, wherein at least one camera in the array camera module includes a Bayer color filter pattern.

19. The camera array of claim 17, wherein the image processing application further directs the processor to select the viewpoint of a camera in the plurality of cameras that captures image data in multiple color channels as the reference viewpoint.

20. The camera array of claim 13, wherein at least one camera in the array camera module captures image data in multiple color channels.