Method of detecting glass defects based on phase image processing

Abstract

The invention relates to a method of detecting glass defects based on a phase image processing. The method utilizes a glass defect detection system based on the phase image processing; and comprises that light emitted from a light source passes through a raster and forms moire showing a cosine distribution of light intensity on surfaces of to-be-detected glasses, a high-speed linear-array camera collects the moire patterns on the surfaces of the glasses which are then transmitted to an industrial control computer through an image acquisition card, and a defect detection and processing software installed on the industrial control computer timely processes the moire patterns to obtain binary defect images. The method is characterized by firstly subtracting corresponding points of main value images of reference phases respectively containing glass defects and being free of defects, eliminating hopping in the subtraction results by using a hopping error correction algorithm, segmenting into binary images for the glass defects through a mathematical morphology and a segmentation algorithm of combined high and low thresholds, and finally determining the glass defects according to data of the binary images. The method can greatly reduce influences of system noises, improve an operation speed and realize rapid and accurate detection for the glass defects.

Description

technical field [0001] The invention belongs to the technical field of defect detection, and in particular relates to a glass defect detection method based on phase image processing. Background technique [0002] The machine vision defect detection method based on projection grid is an effective means to realize glass defect detection. Using the projection grid method to detect defects in glass is to project a cosine grating with equal grid pitch onto the glass surface, forming light and dark moire on the glass surface. Compared with the non-defective moiré image, the existence of glass defects will lead to defects. The moiré at the position is deformed, and the phase of the deformed moiré contains glass defect information. Ideally, when the moiré image contains defects, the phase difference with the non-defective moire image is not zero, otherwise it is zero, so a defect-free reference moiré image can be stored in advance before detection, and The phase of the reference m...

AI Technical Summary

Problems solved by technology

The path-correlation algorithm has a fast unfolding speed, but its anti-interference ability is poor, and the accuracy of the unfolding result is low, so that the unfolded real phase image still contains discontinuous points; while the path-uncorrelated phase unwrapping algorithm has strong anti-interference ability, but the unfolding result is low. Slow speed, not suitable for glass defect detection with high real-time requirements

[0004] In addition, because the real phase difference between the moiré phase at the defect and the reference moiré phase changes smoothly, and there is a zero-crossing point in the center of the defect, the defect area cannot be completely segmented using the currently commonly used edge and threshold segmentation algorithms. Instead, a complete defect is divided into multiple isolated areas, resulting in misjudgment of defects

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