AUTOMATIC DETECTION OF LENS DEVIATIONS

• US 20120050488A1
• Filed: 08/23/2011
• Published: 03/01/2012
• Est. Priority Date: 08/24/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: PrimeSense Ltd (Apple Inc.)
• Inventors: Shpunt, Alexander, Pesach, Benny, Cohen, Yohan Yehouda, Deitch, Ronen
• Granted Patent: US 9,348,111 B2
• Time in Patent Office: Days
• US Class Current: 348/46
• CPC Class Codes: G01M 11/0221 by determining the optical axis or position of lenses
• CPC Class Codes: G01M 11/0242 by measuring geometrical properties or aberrations
• CPC Class Codes: G01M 11/025 by determining the shape of the object to be tested measuring contours or curvatures by optical means G01B11/24
• CPC Class Codes: G01M 11/0257 by analyzing the image formed by the object to be tested
• CPC Class Codes: G01M 11/0264 by using targets or reference patterns
• CPC Class Codes: G02B 13/002 having at least one aspherical surface
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 17/08 Catadioptric systems used in non-imaging applications G02B19/00
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: H04N 13/239 using two 2D image sensors having a relative position equal to or related to the interocular distance H04N13/243 takes precedence
• CPC Class Codes: H04N 13/246 Calibration of cameras
• CPC Class Codes: H04N 17/002 for television cameras
• CPC Class Codes: H04N 25/61 the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4"

Abstract

Optical apparatus includes an image sensor, which outputs a signal responsively to an optical image formed on the image sensor. Objective optics focus optical radiation from an object so as to form the optical image on the image sensor, while superimposing a characteristic structure on the optical image. A processor processes the signal so as to generate an electronic image of the object while detecting, responsively to the characteristic structure, a deviation in an alignment of the objective optics relative to the image sensor.

Claims

1. Optical apparatus, comprising:

an image sensor, which is configured to output a signal responsively to an optical image formed on the image sensor;

objective optics, which are configured to focus optical radiation from an object so as to form the optical image on the image sensor, while superimposing a characteristic structure on the optical image; and

a processor, which is coupled to process the signal so as to generate an electronic image of the object while detecting, responsively to the characteristic structure, a deviation in an alignment of the objective optics relative to the image sensor.

2. The apparatus according to claim 1, wherein the deviation comprises a change in centering of the objective optics with respect to the image sensor relative to a default center of the alignment.

3. The apparatus according to claim 1, wherein the deviation comprises a change in an effective focal length of the objective optics.

4. The apparatus according to claim 1, wherein the characteristic structure comprises a pattern of calibration marks appearing in the optical image, and wherein the processor is configured to detect the deviation by extracting respective locations of the calibration marks from the electronic image.

5. The apparatus according to claim 4, wherein the objective optics have an intermediate focus and comprise, at the intermediate focus, a reticle containing the pattern.

6. The apparatus according to claim 4, wherein the objective optics comprise a final surface in proximity to the image sensor, wherein the pattern is formed on the final surface.

7. The apparatus according to claim 1, wherein the characteristic structure comprises a distortion imposed on the optical image by the objective optics, and wherein the processor is configured to detect the deviation by identifying a change in the distortion.

8. The apparatus according to claim 7, wherein the processor is configured to match pairs of points, each pair comprising an image point in the optical image and a corresponding point in an epipolar plane of the apparatus, and to find the change in the distortion using the matched pairs of the points.

9. The apparatus according to claim 8, wherein the processor is configured to estimate the distortion by finding a transformation of the pairs of the points that satisfies an epipolar constraint.

10. The apparatus according to claim 8, wherein the processor is configured to create a three-dimensional map of the object based on the pairs of the points in the optical image.

11. The apparatus according to claim 1, and comprising a projection module, which is configured to project a pattern of the optical radiation onto the object, and wherein the processor is configured to process the pattern appearing in the electronic image while correcting for the deviation in the alignment in order to generate a three-dimensional (3D) map of the object.

12. The apparatus according to claim 7, wherein the processor is configured to identify a contour in the electronic image corresponding to a presumed shape of the object, and to find distortion correction parameters by comparing the identified contour to the presumed shape.

13. A method for imaging, comprising:

focusing optical radiation from an object via objective optics onto an image sensor so as to form an optical image on the image sensor, while superimposing on the optical image a structure that is characteristic of the objective optics; and

processing a signal that is output by the image sensor so as to generate an electronic image of the object while detecting, responsively to the characteristic structure, a deviation in an alignment of the objective optics relative to the image sensor.

14. The method according to claim 13, wherein the deviation comprises a change in centering of the objective optics with respect to the image sensor relative to a default center of the alignment.

15. The method according to claim 13, wherein the deviation comprises a change in an effective focal length of the objective optics.

16. The method according to claim 13, wherein the characteristic structure comprises a pattern of calibration marks appearing in the optical image, and wherein processing the signal comprises detecting the deviation by extracting respective locations of the calibration marks from the electronic image.

17. The method according to claim 16, wherein superimposing the structure comprises providing a reticle at an intermediate focus of the objective optics.

18. The method according to claim 16, wherein superimposing the structure comprises forming the pattern on a final surface of the objective optics in proximity to the image sensor.

19. The method according to claim 13, wherein the characteristic structure comprises a distortion imposed on the optical image by the objective optics, and wherein processing the signal comprises detecting the deviation by identifying a change in the distortion.

20. The method according to claim 19, wherein detecting the deviation comprises matching pairs of points, each pair comprising an image point in the optical image and a corresponding point in an epipolar plane, and finding the change in the distortion using the matched pairs of the points.

21. The method according to claim 20, wherein finding the change in the distortion comprises finding a transformation of the pairs of the points that satisfies an epipolar constraint.

22. The method according to claim 20, wherein processing the signal comprises creating a three-dimensional map of the object based on the pairs of the points in the optical image.

23. The method according to claim 13, and comprising projecting a pattern of the optical radiation onto the object, and processing the pattern appearing in the electronic image while correcting for the deviation in the alignment in order to generate a three-dimensional (3D) map of the object.

24. The method according to claim 19, wherein identifying the change comprises identifying a contour in the electronic image corresponding to a presumed shape of the object, and finding distortion correction parameters by comparing the identified contour to the presumed shape.