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Online surface defect detection method based on photometric stereo method

A photometric three-dimensional, defect detection technology, applied in optical testing flaws/defects, measuring devices, material analysis by optical means, etc. Simple structure and good robustness

Inactive Publication Date: 2021-04-09
TIANJIN UNIV
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  • Claims
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Problems solved by technology

However, the traditional photometric stereo method needs to ensure that the measured part can be detected under static conditions, and it is difficult to achieve online detection

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  • Online surface defect detection method based on photometric stereo method

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Embodiment Construction

[0018] The present invention designs an online surface defect detection method based on the photometric stereo method. During the detection process, the measured part can move in the assembly line, and the surface curvature map of the part (including two-dimensional and three-dimensional information of the surface of the part) can be quickly obtained. , defect information can be extracted by image processing algorithm. The device used is composed of three parts: camera, conveyor belt and light source. During the inspection process, the parts continue to move with the conveyor belt. When they reach the inspection area, the light sources distributed around the inspection area light up in a cycle, and the camera simultaneously takes photos under the lighting conditions of light sources in different directions. During the whole process, the parts continue to move with the conveyor belt. Since the position of the parts has moved during the process of taking different pictures, it i...

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Abstract

The invention relates to an online surface defect detection method based on a photometric stereo method, which comprises the following steps: in the detection process, parts continuously move along with a conveyor belt, when the parts reach a detection area, light sources distributed around the detection area are circularly lightened, and meanwhile, a camera synchronously shoots pictures under the illumination conditions of the light sources in different directions; wherein in the whole process, the parts continuously move along with a conveying belt, in the process of shooting different pictures, and the positions of the parts move; the surface defect detection step comprises the steps that a template is manufactured by extracting edge information, and unification of the positions of the parts in the multiple pictures is achieved according to template matching so as to meet the precondition of subsequent photometric stereo method calculation; then the gradient and curvature information of the surface of the part are recovered under different stations through a photometric three-dimensional method; the surface defects of the part are extracted through binarization, edge detection and connected domain detection feature extraction means in sequence, and preliminary screening is conducted according to a threshold value to judge whether the machining quality of the part to be detected is qualified or not.

Description

technical field [0001] The invention relates to a visual detection method for surface defects of parts, in particular to an online surface defect detection method. Background technique [0002] Due to the limitation of manufacturing process and transportation conditions, industrially produced parts often have surface defects during production and transportation. In order to ensure the product quality of automatic production, the surface defect detection of parts is an indispensable key link. In the past, the detection methods of such parts were often divided into manual detection and automatic detection. Among them, manual detection usually refers to human eye observation. Compared with automatic detection, manual detection is slower, reliability cannot be guaranteed, and labor costs are increased. Traditional automatic inspection methods are mostly based on machine vision technology, which collects surface images of parts and performs corresponding image processing to ext...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N21/89
CPCG01N21/8901G01N2021/8908
Inventor 张效栋刘皓玥闫宁吴曦旸
Owner TIANJIN UNIV
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