The principle of visual inspection of appearance defects is based on the difference of reflection of optical properties on the surface of products. For example, if there are no defects and defects on the product surface, the reflected direction will not change, and the light presented by machine vision will be uniform; when the product surface contains defects and defects, the emitted light will change, and the detected image will also change. Because of the existence of the defect, stress concentration and deformation occurred around it, and it is easy to observe in the image.
Image processing and analysis algorithm is an important content in the visual inspection system of appearance defects. The usual process includes image preprocessing, target region segmentation, feature extraction and selection, and defect recognition and classification. There are a large number of algorithms in each process, each of which has its own advantages and disadvantages and its scope of application. How to improve the accuracy, efficiency, real-time and robustness of the algorithm has been the direction of researchers.
Features of visual inspection equipment for appearance defects:
1. High speed camera and processing technology can quickly detect, classify, display and eliminate defects;
2. Excellent optical equipment is used for defect detection, even low contrast defects;
3. Intelligent classification software: defects are accurately classified into various categories according to their sources;
4. The information is accurate, real-time and reliable
5. The operation is simple and convenient, and the defect detection system can be realized without in-depth study;
6. Speed up the production speed and realize partial full inspection;
There are different definitions and types of surface defects for different products. Generally speaking, surface defects are areas with uneven physical or chemical properties on the surface of products, such as scratches, spots, holes on metal surface, color difference and indentation on paper surface, inclusion, damage and stain on glass and other non-metallic surfaces.
The working principle of the visual inspection system for appearance is: when there are defects on the surface of the product, if the light transmission type defects (such as cracks, bubbles, etc.) are encountered, the light at the defect position will be refracted, and the light intensity will be greater than that around, so the light detected on the camera target surface will be correspondingly enhanced; if the light absorption type (such as sand and other) impurities are encountered, the light at the defect position will become weak and the phase will be weak The light detected on the target surface is weaker than the surrounding light.
Machine vision is a non-contact, non-destructive automatic detection technology. It is an effective means to realize the automation, intelligence and precision control of equipment. It has the outstanding advantages of safety and reliability, wide spectral response range, long-time work in harsh environment and high production efficiency.
Appearance defects not only affect the beauty and comfort of products, but also have adverse effects on their performance. Therefore, it can be seen that the visual inspection equipment for appearance defects is of great importance to enterprises.