# US 2022/0044444 A1 · Stereo calibration method for movable vision system

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- Number: US 2022/0044444 A1
- Document ID: US20220044444A1
- Status: Published application
- Kind: A1
- Application number: 17/280,747
- Filed: 2019-07-18
- Published: 2022-02-10
- Earliest claimed: 2018-09-28
- Assignees: Shanghai Eyevolution Technology Co., Ltd
- Applicants: Shanghai Eyevolution Technology Co., Ltd
- Inventors: Kaifang WANG; Dongdong YANG; Xiaolin ZHANG; Jiamao LI; Wenhao WANG
- Web page: https://patentgrep.com/patent/US20220044444A1

## CPC

- G06T 7/85: {Stereo camera calibration}
- G06T 2207/10012: Stereo images
- G06T 2207/30208: Marker matrix
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

A stereo calibration method for a movable vision system. The movable vision system involved in the method comprises at least two photography components, at least one calculation component, and at least one control component. The method comprises: placing a calibration template in front of photography components; rotating the photography components by degrees of freedom of motion; obtaining one or more groups of images including calibration template features, and obtaining corresponding position information at the degrees of freedom of motion when the images are obtained; obtaining, by means of calculation, a calibration result of the photography components and the degrees of freedom of motion, i.e., a rotation matrix and a translation matrix of the rotation axis at the degrees of freedom of motion with respect to the photography components; and then obtaining in real time a stereo calibration result by combining the obtained calibration result and the position information at the degrees of freedom of motion in the vision system. The method implements stereo calibration of the photography components in a movable multiocular system in a motion state, has a good calculation real-time property, eliminates the error problem caused by machining or assembly, and has a broad application prospect.

## Claims

### Claim 1

A stereo calibration method of a movable multi-ocular vision system, wherein the movable multi-ocular vision system comprises:
at least two imaging components, each comprising at least one imaging element capable of capturing consecutive images and having an arbitrary number of motional degrees of freedom, wherein each motional degree of freedom is provided with a position acquisition device capable of acquiring rotation or translation information;
at least one calculation component capable of calculating and processing information of images and information of movement in each motional degree of freedom;
at least one control component capable of controlling movement in each motional degree of freedom, and
wherein the stereo calibration method comprises: for each imaging element, placing a calibration template in front of the imaging element; driving the imaging element to move in each motional degree of freedom; capturing a number of images containing whole of the calibration template by the imaging element and simultaneously recording position information of respective motional degree of freedom when capturing respective images; and calculating calibration results for the imaging element and each motional degree of freedom by the calculation component, the calibration results comprising rotation matrix and translation matrix of each rotation axis in respective motional degrees of freedom relative to the imaging element.

### Claim 2 (depends on 1)

The stereo calibration method of claim 1, wherein the position acquisition device is provided in respective motional degree of freedom for obtaining information of movement in respective motional degree of freedom.

### Claim 3 (depends on 1)

The stereo calibration method of claim 1, wherein at least one of the imaging components has one or more motional degrees of freedom.

### Claim 4 (depends on 1)

The stereo calibration method of claim 1, wherein the calibration template includes one of a natural static scene and an artificial standard target, wherein the natural static scene when serving as the calibration template provides invariant image features and known information of position relationship between the image features, and wherein the artificial standard target includes at least one of a two-dimensional (2D) planar target and a three-dimensional (3D) stereoscopic target.

### Claim 5 (depends on 1)

The stereo calibration method of claim 1, comprising the steps of:
for each imaging component, recording position information of the imaging component in each motional degree of freedom at a reference position; obtaining precise parameters about relative positions between imaging elements by performing a stereo calibration at the reference position; performing a calibration process for each motional degree of freedom and calculating, by the calculation component, rotation matrix and translation matrix of each rotation axis in the respective motional degree of freedom relative to an imaging element coordinate system.

### Claim 6 (depends on 1)

The stereo calibration method of claim 1, wherein the stereo calibration results include reference position information, stereo calibration results of the imaging element at the reference position, and rotation and translation relationships of each rotation axis in the respective motional degree of freedom relative to an imaging element coordinate system, the stereo calibration results of the imaging element at the reference position including rotation and translation relationships between imaging elements.

### Claim 7 (depends on 1)

The stereo calibration method of claim 1, further comprising calculating and obtaining rotation and translation matrices indicating relative positional relationships between the imaging elements by feeding the calibration results and position information of each motional degree of freedom into a relationship model between an imaging element coordinate system and a coordinate system of rotation axes in respective motional degrees of freedom.

### Claim 8 (depends on 7)

The stereo calibration method of claim 7, wherein the relationship model is
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where R′ and T′ are rotation and translation matrices in extrinsic parameter calculation results of two imaging components that constitutes a movable binocular vision sub-system at a current position respectively, the movable binocular vision sub-system made up of any two imaging components in the movable multi-ocular vision system, RBCa, TBCa are rotation and translation matrices of a rotation axis in an a-th motional degree of freedom relative to the imaging element coordinate system, respectively, Nk is a total number of motional degrees of freedom in a k-th imaging component, x, y represent serial numbers of the two imaging components, which are “left eyes” and “right eyes” in the movable binocular vision sub-system, respectively, Ra is a rotation matrix converted from a rotation angle of a rotation axis in the a-th motional degree of freedom relative to the reference position; and RI(x,y), TI(x,y) are relative rotation and translation matrices between the “left eyes” and “right eyes” at the reference position.