Systems and methods for manufacturing camera modules using active alignment of lens stack arrays and sensors

• US 10,261,219 B2
• Filed: 09/18/2017
• Issued: 04/16/2019
• Est. Priority Date: 06/30/2012
• Status: Active Grant

• Current Assignee: FotoNation Limited (Adeia Inc.)
• Original Assignee: FotoNation Limited (Adeia Inc.)
• Inventors: Duparre, Jacques, McMahon, Andrew Kenneth John, Lelescu, Dan
• Primary Examiner(s): Teitelbaum, Michael E
• Assistant Examiner(s): Haiem, Sean N.
• Application Number:
  US15/707,747
• Publication Number:
  US 20180081090A1
• Time in Patent Office: 575 Days
• Field of Search: 348187, 348345, 3482181, 348 46, 382131, 382299, 382154, 345419, 257294, 430 9
• CPC Class Codes: G02B 3/0062 Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between
• CPC Class Codes: G02B 3/0075 characterized by non-optical structures, e.g. having integrated holding or alignment means
• CPC Class Codes: G02B 7/003 Alignment of optical elements G02B7/001, G02B7/002 take precedence; for mirrors G02B7/1822
• CPC Class Codes: G02B 7/005 Motorised alignment
• CPC Class Codes: H04N 17/002 for television cameras
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof
• CPC Class Codes: H04N 23/57 Mechanical or electrical details of cameras or camera modules specially adapted for being embedded in other devices
• CPC Class Codes: H04N 23/67 Focus control based on electronic image sensor signals
• CPC Class Codes: H04N 25/41 Extracting pixel data from a plurality of image sensors simultaneously picking up an image, e.g. for increasing the field of view by combining the outputs of a plurality of sensors

Abstract

Systems and methods in accordance with embodiments of the invention actively align a lens stack array with an array of focal planes to construct an array camera module. In one embodiment, a method for actively aligning a lens stack array with a sensor that has a focal plane array includes: aligning the lens stack array relative to the sensor in an initial position; varying the spatial relationship between the lens stack array and the sensor; capturing images of a known target that has a region of interest using a plurality of active focal planes at different spatial relationships; scoring the images based on the extent to which the region of interest is focused in the images; selecting a spatial relationship between the lens stack array and the sensor based on a comparison of the scores; and forming an array camera subassembly based on the selected spatial relationship.

Claims

1. A method comprising:

providing a lens stack array having a plurality of active focal planes in conjunction with a sensor, where each focal plane comprises a plurality of rows of pixels that also form a plurality of columns of pixels and each focal plane is contained within a region of the lens stack array that does not contain pixels from another focal plane;

capturing images of a known target using the plurality of active focal planes at different spatial relationships between the lens stack array and the sensor, where the lens stack array comprises a plurality of lens stacks, and where each lens stack corresponds to a focal plane of the plurality of focal planes;

scoring the images captured by the plurality of active focal planes, where the resulting scores provide a direct comparison of the extent to which a central and a peripheral region of interest are each focused in each of the images at each of the spatial relationships, and where the resulting scores are indicative of each active lens stack'"'"'s ability to focus;

comparing the resulting scores of captured images, wherein the comparison of scores further comprises computing;

a first best-fit plane that defines a spatial relationship between the lens stack array and the sensor based on each active lens stack'"'"'s ability to focus on the central region of interest according to a first predetermined criterion;

a second best-fit plane that defines a spatial relationship between the lens stack array and the sensor based on each active lens stack'"'"'s ability to focus on the peripheral region of interest according to a second predetermined criterion; and

at least a third intervening plane between the first and second best-fit planes; and

determining a final spatial relationship arrangement between the lens stack array and the sensor utilizing the comparison of the scores

wherein the images are scored such that a score is provided for each region of interest visible in each image, the score being indicative of the extent to which the respective region of interest is focused in the image; and

the comparison of scores comprises determining mathematical relationships for each of a plurality of active focal planes that characterize the relationships between;

the scores of the extent to which the central region of interest is focused in the images captured by the respective active focal plane and the spatial relationship between the lens stack array and the sensor; and

the scores of the extent to which the at least one peripheral region of interest is focused in the images captured by the respective active focal plane and the spatial relationship between the lens stack array and the sensor.

2. The method of claim 1, wherein scoring the images captured by the plurality of active focal planes comprises computing modulation transfer function (MTF) scores for the images.

3. The method of claim 1, wherein the comparison of the scores of images captured by a plurality of the active focal planes is based upon:

a comparison of the scores of the images captured by a plurality of the active focal planes at the selected spatial relationship to the scores of images captured by the same active focal planes at different spatial relationships; and

the variation between the scores of the images captured by the active focal planes at the selected spatial relationship.

4. The method of claim 1, wherein the comparison of scores comprises omitting from consideration an image captured by an active focal plane, when the score of the image captured by the active focal plane fails to satisfy at least a third predetermined criterion.

5. The method of claim 4, wherein the at least third predetermined criterion includes the score of the image captured by the active focal plane being within a predetermined range.

6. The method of claim 4, further comprising deactivating an active focal plane, when the score of the image captured by the active focal plane fails to satisfy the at least third predetermined criterion.

7. The method of claim 1 further comprising varying the spatial relationship between the lens stack array and the sensor.

8. The method of claim 1, wherein the final spatial relationship arrangement minimizes the variance of the scores between the images of the plurality of active focal planes.

9. The method of claim 1, wherein the first predetermined criterion is based upon:

at each spatial relationship defined by the computed planes, averaging the scores indicative of the extent to which the central region of interest is focused, the scores being averaged across all active focal planes at the respective spatial relationship; and

assessing the variance in the average scores between the spatial relationships.

10. The method of claim 7, wherein varying the spatial relationship between the lens stack array and the sensor involves sweeping the lens stack array relative to the sensor.

11. The method of claim 10, wherein the lens stack array is swept in a direction substantially normal to the surface of the sensor.

12. The method of claim 1, wherein a spatial relationship between the lens stack array and the sensor is selected to be used when constructing an array camera module based upon the final spatial relationship arrangement.

13. The method of claim 1, wherein the second predetermined criterion is based upon:

at each spatial relationship defined by the computed planes, averaging the scores indicative of the extent to which the peripheral region of interest is focused, the scores being averaged across all active focal planes at the respective spatial relationship; and

assessing the variance in the average scores between the spatial relationships.

14. The method of claim 1, wherein the ability to focus of a first active lens stack'"'"'s ability to focus varies from a second active lens stack.

15. The method of claim 14, wherein the variance in ability to focus between the first and second lens stack is due to a manufacturing process.