Checkerboard image feature central sub-pixel positioning method

A sub-pixel positioning and image feature technology, applied in the field of image processing, can solve problems such as the influence of positioning accuracy, and achieve the effect of ensuring accuracy and improving positioning accuracy

Inactive Publication Date: 2018-09-07
HUNAN UNIV OF SCI & TECH
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AI Technical Summary

Problems solved by technology

There are many sub-pixel positioning algorithms for the center of checkerboard features, which can be obtained by edge intersections, but the positioning accuracy is sensitive to lens distortion, and can also be obtained based on grayscale analysis. Commonly used are Harris, Susan, Forstner and their improvements operator, but its positioning accuracy is greatly affected by noise and gray threshold

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  • Checkerboard image feature central sub-pixel positioning method
  • Checkerboard image feature central sub-pixel positioning method
  • Checkerboard image feature central sub-pixel positioning method

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Embodiment Construction

[0024] The concrete realization process of the present invention is as follows:

[0025] a. For a checkerboard target image, use OpenCV's checkerboard feature coarse positioning function to perform pixel-level positioning on the feature center;

[0026] b. The interception window radius in the neighborhood of the feature center determined in step a is a rectangular area of ​​15 pixels;

[0027] c. With gray gain, gray offset, gray jump edge direction angle, gray diffusion factor and pixel coordinates as parameters, a theoretical model of checkerboard features is defined based on hyperbolic tangent function;

[0028] d. Optimizing the parameters of the theoretical model defined in step c to achieve the highest peak signal-to-noise ratio between the generated feature region and the rectangular region in step b;

[0029] e. Extracting the feature center parameter of the theoretical model as a compensation amount, and compensating the feature center determined in step a to realiz...

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Abstract

The invention discloses a checkerboard image feature central sub-pixel positioning method. A theoretical model of checkerboard features about grayscale gains and offsets, grayscale jumping edge direction angles and grayscale diffusion factors is established on the basis of a hyperbolic tangent function, a simulated feature region generated by the theoretical model is enabled to reach a highest peak-value signal-to-noise ratio with an already-roughly-positioned actual feature region through model parameter optimization and grayscale level adjustment, and feature center parameters of the theoretical model are extracted to be used as compensation quantity to realize sub-pixel positioning of an actual feature center. The method does not require setting of empirical threshold values, is insensitive to feature brightness variation and noises, and can significantly improve positioning precision of the checkerboard image feature center, and then ensure accuracy of parameter estimation in camera calibration and pose measurement.

Description

technical field [0001] The invention relates to the field of image processing, in particular to a sub-pixel positioning method for the feature center of a checkerboard image. Background technique [0002] Camera calibration and pose measurement are basic and popular problems in machine vision. During the processing, it is usually necessary to place a target within the camera field of view, establish the mapping relationship between the world coordinate system and the image coordinate system through the feature points on the target, and solve the PnP The problem is to obtain the internal parameters of the camera and the pose parameters of the target. The target features used today are mainly checkerboard and circle. The center coordinates of the circle feature can be obtained by ellipse fitting after sub-pixel edge extraction or the gray-scale centroid method, but the center of the ellipse is not the real projection of the center of the target circle, and there are projectio...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06T7/73G06T7/80G06T7/44
CPCG06T7/75G06T7/44G06T7/80G06T2207/10004
Inventor 赵前程杨天龙
Owner HUNAN UNIV OF SCI & TECH
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