Camera intrinsic calibration

Patent metadata

Field	Value
Publication number	US-12236642-B2
Application number	US-202318530565-A
Country	US
Kind code	B2
Filing date	Dec 6, 2023
Priority date	Jun 16, 2020
Publication date	Feb 25, 2025
Grant date	Feb 25, 2025

Abstract

Embodiments provide image display systems and methods for a camera calibration using a two-sided diffractive optical element (DOE). More specifically, embodiments are directed to determining intrinsic parameters of a camera using a single image obtained using a two-sided DOE. The two-sided DOE has a first pattern on a first surface and a second pattern on a second surface. Each of the first and second patterns may be formed by repeating sub-patterns that are lined when tiled on each surface. The patterns on the two-sided DOE are formed such that the brightness of the central intensity peak on the image of the image pattern formed by the DOE is reduced to a predetermined amount.

First claim

What is claimed is:

1. A system for determining intrinsic parameters of a camera, the system comprising:
a camera;
a collimator assembly, wherein the camera is placed in front of the collimator assembly, wherein the collimator assembly includes a two-sided diffractive optical element, wherein a grating pattern is formed on each surface of the two-sided diffractive optical element; and
a processor coupled to the camera to receive image data from the camera, wherein the processor stores executable instructions that, when executed by the processor, cause the processor to:
receive an image from the camera, wherein the grating pattern formed on each surface of the two-sided diffractive optical element is selected to reduce a brightness of a central intensity peak on the image to a predetermined amount; and
determine intrinsic parameters of the camera based on an intensity peak on the image and virtual light source formed by the two-sided diffractive optical element that corresponds to the intensity peak.

2. The system of claim 1 , wherein the two-sided diffractive optical element comprises:
an N*N array of a first grating pattern formed on a first surface of the two-sided diffractive optical element; and
an M*M array of a second pattern formed on a second surface of the two-sided diffractive optical element,
wherein the M*M array is tiled on the second surface of the two-sided diffractive optical element to match a size of the N*N array on the first surface of the two-sided diffractive optical element, such that the image captured by the camera includes N 2 repeating sub-patterns.

3. The system of claim 2 , wherein N=3 and M=19, wherein the 19*19 array is tiled on the second surface of the two-sided diffractive optical element to match a size of the 3*3 array on the first surface of the two-sided diffractive optical element, such that the image captured by the camera includes 9 repeating sub-patterns.

4. The system of claim 2 , wherein the image includes a repeating sub-pattern without any gaps.

5. The system of claim 1 , further comprising:
a collimating lens in the collimator assembly; and
a laser source configured to emit a laser beam to the collimating lens of the collimator assembly, wherein the collimating lens of the collimator assembly is provided between the two-sided diffractive optical element and the laser source.

6. The system of claim 5 , wherein the predetermined amount is about 1.1±0.5% of the laser beam emitted from the laser source that reaches the central intensity peak of the image.

7. The system of claim 5 , wherein the image corresponds to a light pattern formed by the laser beam passing through the collimating lens and the two-sided diffractive optical element.

8. The system of claim 1 , wherein the intrinsic parameters include one or more of a focal length, a principal point, and distortion coefficient(s) of the camera.

9. The system of claim 1 , wherein the camera is configured to remain in an eye box of the two-sided diffractive optical element of the collimator assembly.

10. A method for determining intrinsic parameters of a camera, the method comprising:
providing a camera and a collimator assembly, wherein the collimator assembly includes a two-sided diffractive optical element, wherein a grating pattern is formed on each surface of the two-sided diffractive optical element;
placing the camera in front of the collimator assembly, wherein the camera is placed in front of one of the collimator assembly;
receiving, using a computing device, an image from the camera, wherein the grating pattern formed on each surface of the two-sided diffractive optical element is selected to reduce a brightness of a central intensity peak on the image to a predetermined amount; and
determining, using the computing device, intrinsic parameters of the camera based on an intensity peak on the image and virtual light source formed by the two-sided diffractive optical element that corresponds to the intensity peak.

11. The method of claim 10 , wherein the two-sided diffractive optical element comprises:
an N*N array of a first grating pattern formed on a first surface of the two-sided diffractive optical element; and
an M*M array of a second pattern formed on a second surface of the two-sided diffractive optical element,
wherein the M*M array is tiled on the second surface of the two-sided diffractive optical element to match a size of the N*N array on the first surface of the two-sided diffractive optical element, such that the image captured by the camera includes N 2 repeating sub-patterns.

12. The method of claim 11 , wherein N=3 and M=19, wherein the 19*19 array is tiled on the second surface of the two-sided diffractive optical element to match a size of the 3*3 array on the first surface of the two-sided diffractive optical element, such that the image captured by the camera includes 9 repeating sub-patterns.

13. The method of claim 10 , wherein the image includes a repeating sub-pattern without any gaps.

14. The method of claim 10 , wherein the collimator assembly includes a collimating lens, the method further comprising:
configuring a laser source to emit a laser beam to the collimating lens of the collimator assembly, wherein the collimating lens of the collimator assembly is provided between the two-sided diffractive optical element and the laser source.

15. The method of claim 14 , wherein the predetermined amount is about 1.1±0.5% of the laser beam emitted from the laser source that reaches the central intensity peak of the image.

16. The method of claim 15 , wherein the image corresponds to a light pattern formed by the laser beam passing through the collimating lens and the two-sided diffractive optical element.

17. The method of claim 10 , wherein the intrinsic parameters include one or more of a focal length, a principal point and distortion coefficient(s) of the camera.

18. The method of claim 10 , wherein the camera is configured to remain in an eye box of the two-sided diffractive optical element of the collimator assembly.

19. A system for calibrating a camera, the system comprising:
a camera;
a collimator assembly, wherein the camera is placed in front of the collimator assembly, wherein the collimator assembly includes a two-sided diffractive optical element, wherein a grating pattern is formed on each surface of the two-sided diffractive optical element; and
a processor coupled to the camera to receive image data from the camera, wherein the processor stores executable instructions that, when executed by the processor, cause the processor to:
receive an image from the camera, wherein the grating pattern formed on each surface of the two-sided diffractive optical element is selected to reduce a brightness of a central intensity peak on the image to a predetermined amount; and
calibrate the camera based on an intensity peak on the image and virtual light source formed by the two-sided diffractive optical element that corresponds to the intensity peak.

20. The system of claim 19 , further comprising a plurality of collimator assemblies and a plurality of cameras each placed in front of one of the plurality of collimator assemblies, wherein the plurality of cameras are calibrated simultaneously.

Assignees

• Magic Leap Inc

Inventors

• Jia Zhiheng
• Grossmann Etienne Gregoire
• Zheng Hao
• Dominguez Daniel Roger
• Tekolste Robert D

Classifications

• H04N23/90

  Arrangement of cameras or camera modules, e.g. multiple cameras in TV studios or sports stadiums · CPC title

• G06V10/14

  Optical characteristics of the device performing the acquisition or on the illumination arrangements · CPC title

• H04N17/002

  for television cameras · CPC title

• G02B27/4205 Primary

  having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant · CPC title

• H04N23/55

  Optical parts specially adapted for electronic image sensors; Mounting thereof · CPC title