Methods and apparatus for reducing plenoptic camera artifacts

• US 8,189,089 B1
• Filed: 01/20/2010
• Issued: 05/29/2012
• Est. Priority Date: 01/20/2009
• Status: Active Grant

• Current Assignee: Adobe Inc.
• Original Assignee: Adobe Systems Incorporated (Adobe Inc.)
• Inventors: Georgiev, Todor G., Lumsdaine, Andrew
• Primary Examiner(s): Pasiewicz, Daniel M
• Application Number:
  US12/690,871
• Time in Patent Office: 860 Days
• Field of Search: 348/335, 348/340, 348/343, 348/345, 348/369, 250/208.1, 359/619, 359/626
• US Class Current: 348/343
• CPC Class Codes: G02B 27/1066 for enhancing image performance, like resolution, pixel numbers, dual magnifications or dynamic range, by tiling, slicing or overlapping fields of view
• CPC Class Codes: H04N 13/232 using fly-eye lenses, e.g. arrangements of circular lenses
• CPC Class Codes: H04N 23/635 Region indicators; Field of view indicators
• CPC Class Codes: H04N 23/957 Light-field or plenoptic cameras or camera modules

Abstract

Methods and apparatus for reducing plenoptic camera artifacts. A first method is based on careful design of the optical system of the focused plenoptic camera to reduce artifacts that result in differences in depth in the microimages. A second method is computational; a focused plenoptic camera rendering algorithm is provided that corrects for artifacts resulting from differences in depth in the microimages. While both the artifact-reducing focused plenoptic camera design and the artifact-reducing rendering algorithm work by themselves to reduce artifacts, the two approaches may be combined.

Claims

1. A camera, comprising:

a photosensor configured to capture light projected onto the photosensor;

an objective lens, wherein the objective lens is configured to refract light from a scene located in front of the camera to form an image of the scene at a focal plane of the objective lens, wherein the focal plane is located at focal length F of the objective lens, and wherein the scene is at distance A from the objective lens;

a microlens array positioned between the objective lens and the photosensor, wherein the microlens array comprises a plurality of microlenses, wherein the plurality of microlenses are focused on the focal plane and not on the objective lens, and wherein a is distance from the microlenses to the focal plane;

wherein each microlens of the microlens array is configured to project a separate portion of the image of the scene formed at the focal plane on which the microlens is focused onto a separate location on the photosensor; and

wherein the camera is configured so that the value of a is greater than the focal length F squared divided by the distance A.

2. The camera as recited in claim 1, wherein b is distance from the microlenses to the photosensor, wherein magnification M of the microlenses is defined by

3. The camera as recited in claim 2, where the magnitude of M is between 5 and 10, inclusive.

4. The camera as recited in claim 1, wherein the photosensor is configured to capture a flat comprising the separate portions of the image of the scene projected onto the photosensor by the microlens array, wherein each of the separate portions is in a separate region of the flat.

5. The camera as recited in claim 4, wherein the camera is configured to store the captured flat to a memory device.

6. The camera as recited in claim 4, wherein the captured flat is configured to be processed according to an artifact-reducing rendering module to generate a final image, wherein the module is configured to:

for each of the plurality of separate portions in the captured flat, determine a magnification value M_i via registration with one or more neighbor portions;

for each of the plurality of separate portions;

magnify the portion according to its respective magnification value M_i to generate a magnified portion; and

extract a crop from the magnified portion; and

appropriately assemble the crops extracted from the magnified portions to produce the final image.

7. A method, comprising:

obtaining a flat comprising a plurality of separate portions of an image of a scene, wherein each of the plurality of portions is in a separate region of the flat;

determining a magnification value M_i for each of the plurality of separate portions;

for each of the plurality of separate portions;

magnifying the portion according to its respective magnification value M_i to generate a magnified portion; and

extracting a crop from the magnified portion; and

appropriately assembling the crops extracted from the magnified portions to produce a final high-resolution image.

8. The method as recited in claim 7, wherein said determining a magnification value M_i for each of the plurality of separate portions comprises:

determining a value k_i for each of the plurality of separate portions, where k_i is a measure of depth of the particular portion; and

determining the magnification value M_i for each of the plurality of separate portions according to the determined value of k_i for the respective portion.

9. The method as recited in claim 8, wherein said determining a value k_i for each of the plurality of separate portions comprises performing registration on each of the plurality of separate portions to determine the value k_i for the respective portion.

10. The method as recited in claim 9, wherein said performing registration on a given portion comprises registering the given portion with two or more adjacent portions by overlaying the given portion on each of the adjacent portions and shifting the given portion to align the given portion with the respective adjacent portion.

11. The method as recited in claim 10, wherein the value k_i is determined according to amounts of shift needed to align the given portion with each of the adjacent portions.

12. The method as recited in claim 7, further comprising capturing the flat with a camera, wherein said capturing comprises:

receiving light from the scene at an objective lens of the camera, wherein the scene is at distance A from the objective lens;

refracting light from the objective lens to form an image of the scene at a focal plane of the objective lens, wherein the focal plane is located at focal length F of the objective lens;

receiving light from the focal plane at a microlens array positioned between the objective lens and a photosensor of the camera, wherein the microlens array comprises a plurality of microlenses, wherein the plurality of microlenses are focused on the focal plane and not on the objective lens, and wherein a is distance from the microlenses to the focal plane; and

receiving light from the microlens array at the photosensor, wherein the photosensor receives a separate portion of the image of the scene formed at the focal plane from each microlens of the microlens array at a separate location on the photosensor;

wherein the camera is configured so that the value of a is greater than the focal length F squared divided by the distance A.

13. The method as recited in claim 12, wherein b is distance from the microlenses to the photosensor, wherein magnification M of the microlenses is defined by

14. A non-transitory computer-readable storage medium storing program instructions, wherein the program instructions are computer-executable to implement:

obtaining a flat comprising a plurality of separate portions of an image of a scene, wherein each of the plurality of portions is in a separate region of the flat;

determining a magnification value M_i for each of the plurality of separate portions;

for each of the plurality of separate portions;

magnifying the portion according to its respective magnification value M_i to generate a magnified portion; and

extracting a crop from the magnified portion; and

appropriately assembling the crops extracted from the magnified portions to produce a final high-resolution image.

15. The computer-readable storage medium as recited in claim 14, wherein, in said determining a magnification value M_i for each of the plurality of separate portions, the program instructions are computer-executable to implement:

determining a value k_i for each of the plurality of separate portions, where k_i is a measure of depth of the particular portion; and

determining the magnification value M_i for each of the plurality of separate portions according to the determined value of k_i for the respective portion.

16. The computer-readable storage medium as recited in claim 15, wherein, in said determining a value k_i for each of the plurality of separate portions, the program instructions are computer-executable to implement performing registration on each of the plurality of separate portions to determine the value k_i for the respective portion.

17. The computer-readable storage medium as recited in claim 16, wherein, in said performing registration on a given portion, the program instructions are computer-executable to implement registering the given portion with two or more adjacent portions by overlaying the given portion on each of the adjacent portions and shifting the given portion to align the given portion with the respective adjacent portion.

18. The computer-readable storage medium as recited in claim 17, wherein the value k_i is determined according to amounts of shift needed to align the given portion with each of the adjacent portions.

19. The computer-readable storage medium as recited in claim 14, wherein the flat is captured with a camera, wherein said capturing comprises:

receiving light from the scene at an objective lens of the camera, wherein the scene is at distance A from the objective lens;

refracting light from the objective lens to form an image of the scene at a focal plane of the objective lens, wherein the focal plane is located at focal length F of the objective lens;

receiving light from the focal plane at a microlens array positioned between the objective lens and a photosensor of the camera, wherein the microlens array comprises a plurality of microlenses, wherein the plurality of microlenses are focused on the focal plane and not on the objective lens, and wherein a is distance from the microlenses to the focal plane; and

receiving light from the microlens array at the photosensor, wherein the photosensor receives a separate portion of the image of the scene formed at the focal plane from each microlens of the microlens array at a separate location on the photosensor;

wherein the camera is configured so that the value of a is greater than the focal length F squared divided by the distance A.

20. The computer-readable storage medium as recited in claim 19, wherein b is distance from the microlenses to the photosensor, wherein magnification M of the microlenses is defined by