Chessboard angular point sub-pixel extraction method based on Harris operator

An extraction method and checkerboard technology, which is applied in the field of checkerboard corner point sub-pixel extraction, can solve problems that affect the number and tolerance of extracted corner points, false corner points and corner point clustering, and loss of corner point information.

Active Publication Date: 2013-10-09
BEIJING INSTITUTE OF TECHNOLOGYGY
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Problems solved by technology

A small threshold will lead to corner clustering, and a large threshold will lose part of the corner information;
[0006] (3) The size of the neighborhood when finding the local maximum will also affect the number and tolerance of corner points extracted
[00

Method used

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  • Chessboard angular point sub-pixel extraction method based on Harris operator
  • Chessboard angular point sub-pixel extraction method based on Harris operator
  • Chessboard angular point sub-pixel extraction method based on Harris operator

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Embodiment Construction

[0041] In order to better illustrate the purpose and advantages of the present invention, the content of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] Use a Basler 5-megapixel area array CCD, configure a Navitar12X continuous zoom lens to shoot a standard checkerboard calibration board, the placement direction of the checkerboard is parallel to the coordinate system of the image plane, the size of each checkerboard is 0.2mm, and the error is 0.1μm. Use the traditional Harris operator to extract the corners of the image, the specific steps are as follows:

[0043] (1) Set the gradient operator in the x direction to [-2-1012], set the gradient operator in the y direction to [-2;-1;0;1;2], the grayscale function G( x, y) find the partial derivative, and get G respectively x , G y , operate on it to get G x 2 , G y 2 , G x G y , then for G x 2 , G y 2 , G x G y Perform Gaussian smoothing,...

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Abstract

The invention relates to a chessboard angular point sub-pixel extraction method based on the Harris operator, and belongs to the technical field of micro-machine assembling and micro-vision detecting. The chessboard angular point sub-pixel extraction method comprises the steps that the Harris operator is used for conducing angular point detection on a chessboard; a processing result of the Harris operator is optimized and cluster points in angular points detected in the prior step are eliminated; noise points are eliminated by the utilization of the symmetric method, angular point secondary optimization is conducted in order to find out pixel-level angular points; based on secondary surface fitting, the precision of the pixel-level angular points is improved to be at the sub-pixel level. By means of the chessboard angular point sub-pixel extraction method, the angular points of the black and white chessboard can be detected precisely, fake angular points appearing in an existing algorithm cannot appear, and detecting precision reaches 0.1 pixel.

Description

technical field [0001] The invention relates to a method for extracting sub-pixels of checkerboard corner points based on a Harris operator, and belongs to the technical fields of micromechanical assembly and microscopic visual inspection. Background technique [0002] At present, the microscopic vision system plays a vital role in the assembly process of micro-small structural parts. The higher the camera calibration accuracy of the microscopic vision system is, the higher the assembly accuracy of the assembly system will be. The checkerboard template has been widely used in the camera calibration process. The common practice is to realize the camera calibration by establishing the relationship between the image coordinates of the feature points in the checkerboard template and the corner points of the black and white area of ​​the checkerboard and the corresponding world coordinates. , whether the checkerboard corner detection is accurate or not directly determines the acc...

Claims

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Application Information

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IPC IPC(8): G06T7/00G06T5/00
Inventor 叶鑫张之敬高军金鑫邵超
Owner BEIJING INSTITUTE OF TECHNOLOGYGY
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