Sub pixel edge based circle center detecting method

A sub-pixel edge and detection method technology, which is applied in the field of image processing, can solve the problems of slow operation speed, low stability, and high complexity of interpolation algorithm, and achieve the effect of small amount of calculation, fast operation speed and high accuracy

Inactive Publication Date: 2017-12-26
UNIV OF SHANGHAI FOR SCI & TECH
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Problems solved by technology

The interpolation algorithm has high complexity and slow operation speed, and the operation accuracy of the moment method is only lower than that of the fitting algorithm, but its stability is not high

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  • Sub pixel edge based circle center detecting method
  • Sub pixel edge based circle center detecting method
  • Sub pixel edge based circle center detecting method

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Embodiment Construction

[0029] In order to make the technical means, creative features, goals and effects of the present invention easy to understand, the following embodiments will specifically illustrate the sub-pixel edge-based circle center detection method of the present invention in conjunction with the accompanying drawings.

[0030] A method for detecting the center of a circle based on a sub-pixel edge is used to accurately obtain the center of a circular target, including the following steps:

[0031] Step 1.1: Coarse localization of image edges

[0032] Using the Canny edge detection operator, the rough positioning edge of the circular target and the image coordinate value of the edge point, the background gray level h of the edge image, and the gray level difference b between the edge and the background are obtained. The steps of Canny edge detection are as follows: first, Gaussian filtering is performed on the image to remove noise interference; then the gradient magnitude and direction ...

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Abstract

The invention provides a sub pixel edge based circle center detecting method. The method includes steps of 1, utilizing a Canny operator to performing rough positioning on an image edge, acquiring the gradient magnitude and gradient direction of integer pixel point edge; 2, establishing a positive direction taking the integer pixel point as the origin and the taking the gradient direction as the x axis, taking 7 pixel points in central symmetry in the gradient direction, wherein the symmetry center which is the integer pixel point is among the 7 pixel points, performing gray level fitting on the 7 pixel points by adopting a hyperbolic tangent function in a formula of I(x)=-b / 2 tanh(p(x-R))+h+b / 2, wherein I(x) indicates the gray level in x position, x indicates the distance between the pixel point to the origin, h indicates background gray level, b indicates the gray level difference value of the edge and the background, p is a fuzzy factor, and R is the edge position; and 3, obtaining a sub pixel edge point according to the formula in the step 2, performing least square fit on the sub pixel edge point according to a circle and obtaining circle center coordinates.

Description

technical field [0001] The invention relates to the technical field of image processing, in particular to a method for detecting the center of a circle based on sub-pixel edges. Background technique [0002] Camera calibration is one of the key technologies for constructing an accurate visual measurement system. For the dot calibration board, the center of the circular target is the calibration feature point. Therefore, the precise positioning of the center of the circle is the key to building a visual measurement system. [0003] At present, the detection methods of the center of the circle mainly include the Hough transform method, the centroid method and the least square method. The Hough transform method is greatly affected by the degree of discretization of the parameter space; the centroid method has higher requirements on the uniform gray distribution of the imaging image; the least squares fitting method is used to fit the edge points of the image, so the edge point...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06T7/60G06T7/13G06T7/70
CPCG06T7/60G06T7/13G06T7/70
Inventor 姚强王亚刚胡杰陈锁
Owner UNIV OF SHANGHAI FOR SCI & TECH
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