Camera Calibration Using Annular Pattern Edge Detection

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Solution Overview

Problem

Existing camera calibration methods using solid circle patterns result in low accuracy of image coordinates, leading to less accurate camera calibration results, especially for cameras with low resolution.

Innovation Solution

A camera calibration method utilizing a calibration board with annular patterns, where the inner and outer edges of each annular pattern are used to jointly determine the image coordinates of the center point, improving accuracy by smoothing the edges to sub-pixel level.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If solid circle pattern is used for calibration, then the calibration process is simple, but the calibration accuracy is low

Engineering Contradiction:

Improvecalibration accuracyVSAvoidpattern complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The solid circle pattern is segmented into an annular pattern with distinct inner and outer edges. This segmentation allows for more precise detection of edge positions, which in turn improves the accuracy of determining the center point coordinates, thereby resolving the contradiction between calibration accuracy and pattern complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The calibration pattern parameters are changed from solid circles to annular patterns with specific inner and outer radii. This parameter change enables the use of edge detection algorithms to find the inner and outer edges, calculate their average position, and determine the center point with higher precision, thus improving calibration accuracy without excessive complexity.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If edge detection is performed at pixel level only, then the processing is fast, but the coordinate precision is insufficient

Engineering Contradiction:

Improvecoordinate precisionVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Edge detection is first performed at the pixel level to obtain initial edge positions. This preliminary action provides a starting point for subsequent sub-pixel level refinement, reducing the computational burden of high-precision processing while still achieving accurate coordinate measurements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of performing full sub-pixel level processing on all edges, the method applies sub-pixel refinement selectively and partially. The inner and outer edge positions are refined to sub-pixel accuracy, and their average is calculated to obtain the center point coordinates, achieving sufficient precision without excessive processing time.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentEP4040392B1Camera calibration method and apparatus and electronic device

Publication Date: 2025.06.04 SHENZHEN GOODIX TECH CO LTD

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AI summary

The present application provides a camera calibration method, apparatus and an electronic device, the method includes: obtaining a calibration board image, where the calibration board image includes a plurality of annular patterns; obtaining an inner edge and an outer edge of each annular pattern in the calibration board image; determining image coordinates of a center point of each annular pattern according to the inner edge and the outer edge of each annular pattern; and determining internal and external parameters of a camera according to the image coordinates and corresponding world coordinates of the center point of each annular pattern. The accuracy of camera calibration is improved.