Method and device for calibration

Patent metadata

Field	Value
Publication number	US-10924729-B2
Application number	US-201816176439-A
Country	US
Kind code	B2
Filing date	Oct 31, 2018
Priority date	Nov 1, 2017
Publication date	Feb 16, 2021
Grant date	Feb 16, 2021

Abstract

The present invention provides a method and a device for calibration applied to the field of image processing. The method includes: acquiring a common two-dimensional image and an infrared image of a calibration object, wherein the calibration object carries a first pattern; calculating coordinates of the first pattern in the common two-dimensional image, acquiring coordinates of the first pattern in a global coordinate system, and calculating intrinsic parameters of a first camera device capturing the common two-dimensional image; and calculating coordinates of the first pattern in the infrared image, acquiring the coordinates of the first pattern in the global coordinate system, and calculating intrinsic parameters of a second camera device capturing the infrared image. The method for calibration is capable of enhancing calibration efficiency by a simple calibration method when calibrating a depth camera device.

First claim

What is claimed is:

1. A method for calibration, comprising:
acquiring a common two-dimensional image and an infrared image of a calibration object, wherein the calibration object comprises a first pattern, wherein an image of the calibration object in the common two-dimensional image occupies more than a first ratio of the common two-dimensional image, and wherein an image of the calibration object in the infrared image occupies more than the first ratio of the infrared image;
calculating coordinates of the first pattern in the common two-dimensional image according to the common two-dimensional image, acquiring coordinates of the first pattern in a global coordinate system, and calculating, according to the coordinates of the first pattern in the common two-dimensional image and the coordinates of the first pattern in the global coordinate system, intrinsic parameters of a first camera device capturing the common two-dimensional image; and
calculating coordinates of the first pattern in the infrared image according to the infrared image, and calculating, according to the coordinates of the first pattern in the infrared image and the coordinates of the first pattern in the global coordinate system, intrinsic parameters of a second camera device capturing the infrared image.

2. The method according 1 , wherein:
the calibration object comprises at least three equal-sized calibration boards, wherein first patterns carried by the at least three calibration boards are identical; and
the first pattern comprises first circular points or first ellipsoidal points distributed on the calibration board, and a difference between grayscale values of the first circular points or the first ellipsoidal points and a background of the calibration board is greater than a first threshold.

3. The method according to claim 2 , wherein:
the first circular points and the first ellipsoidal points are evenly distributed in rows and columns on the calibration board.

4. The method according to claim 3 , wherein:
the step of acquiring the coordinates of the first pattern in the global coordinate system comprises acquiring coordinates of centers of the first circular points or the first ellipsoidal points in the global coordinate system;
the step of calculating the coordinates of the first pattern in the common two-dimensional image according to the common two-dimensional image comprises detecting coordinates of the centers of the first circular points or the first ellipsoidal points in the common two-dimensional image; and
the step of calculating the coordinates of the first pattern in the infrared image according the infrared image comprises detecting coordinates of the centers of the first circular points or the first ellipsoidal points in the infrared image.

5. The method according to claim 1 , wherein:
the coordinates of the same first pattern in the common two-dimensional image correspond to the coordinates of the first pattern in the infrared image.

6. The method according to claim 2 , wherein:
the at least three equal-sized calibration boards comprised in the calibration object comprise four equal-sized calibration boards comprised in the calibration object, wherein the four calibration boards are arranged in two rows and two columns; and
with the first camera device facing the four calibration boards, positions of the four calibration boards are defined as upper-left, upper-right, lower-left and lower-right, wherein for each calibration board, a vertical center axis thereof is defined as a vertical rotation axis, from which a downward direction is a positive direction of the vertical rotation axis, and a horizontal center axis thereof is defined as a horizontal rotation axis, from which a right direction is a positive direction of the horizontal rotation axis; a plane where the upper-left calibration is located is parallel to an imaging plane of the first camera device, the upper-right calibration board is rotated clockwise around the vertical rotation axis thereof by a first angle, the lower-left calibration board is rotated counterclockwise around the vertical rotation axis thereof by the first angle, and the lower-right calibration board is rotated counterclockwise around the horizontal rotation axis thereof by the first angle.

7. The method according to claim 6 , wherein:
the first angle is 30 degrees.

8. The method according to claim 1 , wherein:
the calibration object carries a pattern indicating a placement direction of the calibration board.

9. The method according to claim 8 , wherein:
the pattern indicating the placement direction of the calibration object comprises one of:
a first number of second circular points arranged in one row, and a second number of second circular points arranged in another row;
the first number of second circular points arranged in one column, and the second number of second circular points arranged in another column; and
the second circular points are arranged to form a pattern indicating the placement direction of the calibration object.

10. The method according to claim 1 , wherein:
the first camera device and the second camera device have different fields of view.

11. The method according to claim 1 , wherein:
between the first camera device and the second camera device, the camera device having a greater field of view captures an image comprising the entire calibration object;
the image of the calibration object occupies a middle part of the common two-dimensional image, and occupies more than a first ratio of the common two dimensional image; and
the image of the calibration object occupies a middle part of the infrared image, and occupies more than the first ratio of the infrared image.

12. The method according to claim 1 , wherein:
the first ratio is 80%.

13. The method according to claim 1 , wherein:
the step of acquiring the common two-dimensional image and the infrared image of the calibration object comprises simultaneously capturing one common two-dimensional image and one infrared image of the calibration object.

14. The method according to claim 1 , wherein:
the step of calculating, according to the coordinates of the first pattern in the common two-dimensional image and the coordinates of the first pattern in the global coordinate system, the intrinsic parameters of the first camera device capturing the common two-dimensional image comprises calculating, according to the coordinates of the first pattern in the common two-dimensional image, the coordinates of the first pattern in the global coordinate system, and a mapping relationship between a coordinate system of the common two-dimensional image and the global coordinate system, the intrinsic parameters of the first camera device capturing the common two-dimensional image; and
the step of calculating, according to the coordinates of the first pattern in the infrared image and the coordinates of the first pattern in the global coordinate system, the intrinsic parameters of the second camera device capturing the infrared image comprises calculating, according to the coordinates of the first pattern in the infrared image, the coordinates of the first pattern in the global coordinate system, and a mapping relationship between a coordinate system of the infrared image and the global coordinate system, the intrinsic parameters of the second camera device capturing the infrared image.

15. The method according to claim 1 , further comprising:
optimizing the intrinsic parameters and distortion coefficients of the first camera device according to a difference between real coordinates of the first pattern a

Assignees

• Arcsoft Corp Ltd

Inventors

• Yu Li
• Liu Menghan
• Miao Wang

Classifications

• H04N25/41

  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 · CPC title

• H04N23/20

  for generating image signals from infrared radiation only · CPC title

• H04N17/002 Primary

  for television cameras · CPC title

• H04N5/3415

  Electricity · mapped topic

• H04N5/33

  Transforming infrared radiation (cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20) · CPC title