Method for quickly positioning circular mark in PCB visual detection

Abstract

The invention discloses a round sub-pixel detection algorithm based on point Hough transform and Legendre moments, and provides a method for quickly positioning a circular mark in polymerase chain reaction (PCR) visual detection. The method comprises the following steps of: performing edge detection and Hough transform to acquire a circular mark pixel-level reference value by using a Canny arithmetic operator; filtering off noise points in edge points by using the circular mark pixel-level reference value; analyzing a sub-pixel edge positioning method based on Legendre orthogonal moments, and an error; evaluating sub-pixels of the edge points from which the noise points are filtered off by using the Legendre orthogonal moments and an error method; and finally fitting the edge points by a fast least square method to acquire accurate circle center positioning parameter and radius parameter of a round. By the method, the characteristic of high speed of point Hough transform operation is kept; and the method has the characteristics of high positioning accuracy, high noise resistance, accuracy, high speed and robustness and meets the requirements of high accuracy and real-time property in the PCB visual detection.

Description

technical field [0001] The invention belongs to the field of PCB visual inspection, and in particular relates to a fast circular mark positioning method in PCB visual inspection. Background technique [0002] In the visual inspection of PCB products, the precise positioning of its positioning marks is one of the keys to production and inspection. Traditional circle detection methods include template matching, shape analysis, loop integral differential method, circle Hough transform, point Hough transform Wait. The circular Hough transform is widely used in circle detection because of its high reliability, and it can still achieve ideal results under the conditions of noise, deformation, and even partial area loss. However, the disadvantage of this method is that the calculation is complex, and it runs in three-dimensional space, requiring a lot of resources. In order to reduce the computational complexity, some scholars assume that the radius of the circle is known, so tha...

AI Technical Summary

Problems solved by technology

[0003] Aiming at the shortcomings of the traditional circular positioning mark positioning calculation complex, low efficiency and low detection accuracy in the visual detection of the above-mentioned PCB products, the present invention uses a round sub-pixel detection algorithm (Round Sub-pixel Detection Algorithm Based on point Hough transform and Legendre moment) Point Hough Transform and Legendre Moments (referred to as RHLSP algorithm) provides a fast circular mark positioning method in PCB visual inspection. This method not only retains the characteristics of fast calculation speed of point Hough transform, but also has a positioning accuracy of 0.056 pixels and strong anti-noise ability , has the characteristics of accuracy, rapidity and robustness, and meets the requirements of high precision and real-time performance in PCB visual inspection

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