Machine Vision Surface Defect Inspection Automatic Visual Inspection

Surface defects are localized inhomogeneous areas of physical or chemical properties on the surface of a product, such as metal screws, bearings, gears and other precision parts of length and width, diameter, scratches, nicks, defects and other surface dimensional defects. Surface defects not only affect the aesthetics and comfort of the product, but also adversely affect the performance of the product, so manufacturers attach great importance to the detection of surface defects on the product in order to detect defects in a timely manner, so as to be able to effectively control the quality of the product, according to the results of the test to analyze the production process of some of the problems,vision system companies so as to avoid or reduce the production of defective products, to prevent potential trade disputes, and to safeguard the reputation of the enterprise.

1、Machine vision surface defect detection

Machine vision design technology is a non-contact, non-destructive automatic inspection data technology, is to realize the enterprise equipment management automation, intelligent and precision control of the effective means of teaching, with China's safety work reliably, the spectral response range is wide, and can be in the harsh social environment for a long time and life production and management efficiency of the problem of high outstanding advantages. Machine vision inspection network system mainly through an appropriate light source and image sensor (CCD camera) to obtain the surface image of the relevant products, the use of providing the appropriate image processing algorithms to extract the image feature information, and then we according to the different features of the information resources for surface defects such as positioning,automated inspection system identification, grading and other discriminatory and statistical, storage, query and other operations.

2.The basic composition of machine vision surface defect detection system

It mainly includes image acquisition module, image processing module, image analysis module, data management and human-machine interface module.

Image acquisition module consists of industrial camera, optical lens, light source and its clamping device. Under the irradiation of the light source, the product surface is imaged on the camera sensor through the optical lens. The optical signal is first converted into an electrical signal and then into a digital signal that can be processed by a computer. Currently, industrial cameras mainly use CCD or CMOS chips, CCD is the most commonly used image sensor in machine vision.

Machine vision light source directly affects the image quality, its role is to overcome the interference of ambient light, to ensure the stability of the image, to obtain the highest possible contrast image. Currently commonly used light sources are halogen lamps, fluorescent lamps and light-emitting diodes (led). LED light source with its small size, low power consumption, fast response, good monochromaticity, high reliability, light-emitting uniformity and stability, easy to integrate and other advantages have been widely used.

Lighting control system can be constituted by the light source according to its irradiation treatment method can be divided into bright field lighting and dark field lighting, structured light lighting and strobe lighting. Bright field and dark field main problem describes the relationship between a camera and the location of the light source, bright field lighting refers to the camera by directly affecting the reception of different light sources on the target of the reflected light, generally use the camera and the light source of the distribution of the opposite side of the teaching as well as to facilitate the installation of the enterprise; dark field lighting refers to the camera or indirectly lead to the reception of the signal light source in the target of the scattered light, generally including the camera and the light source of the same side of the distribution of the camera, and it is advantageous that Can obtain high contrast images. Structured light illumination is a grating or line light source, etc. projected onto the object to be measured, according to analyze the aberrations generated by their development, demodulated three-dimensional data information of the object to be measured. Frequency flash illumination is a high-frequency light pulse irradiated on the target object, the camera shooting technology requires synchronization with the light source.

Image processing module mainly includes image denoising, image enhancement and recovery, defect detection and target segmentation. As the field environment, photoelectric conversion of CCD images, transmission circuits and electronic components will produce image noise, reducing image quality and affecting the processing and analysis of the image, it is necessary to pre-process the image to eliminate noise. The purpose of image enhancement is to purposefully emphasize the global or local features of the image in a given application, so that the original unclear image becomes clear or emphasize certain features of interest, this image processing method can expand the differences between different target features, suppress uninteresting features, improve image quality, enrich the information, and enhance the interpretation of the image and the recognition of the effect. Image restoration is the process of reconstructing or restoring degraded images through computer processing. Image restoration usually uses the same methods as image enhancement, but the results of image enhancement need to be verified in the next stage to recover degraded images, such as removal of additive noise, motion blur recovery, etc. The purpose of image segmentation is to segment the target region in the image for further processing.

3、Surface defect detection applications

The application field is very wide, mainly including new energy power battery, PCB circuit board, semiconductor, precision hardware components, electronic components, food packaging, medical packaging, textile accessories and other fields.

Why use surface defect inspection system

1. High efficiency: machine vision inspection is fast, hundreds or even thousands of components can be detected per minute, and can work continuously for 24 hours.

2. Strong accuracy: the human eye has the limitations of physical teaching conditions, but also subject to subjectivity, physical energy and other factors, can not be in order to ensure data accuracy. Machine learning is not subject to subjective control, as long as the parameters can be set a no cultural differences, with the same configuration of multiple machines can be obtained to ensure the same accuracy of the enterprise.

3. Lower overall cost: the machine is more efficient than manual inspection, in the long run, machine vision inspection is cheaper.

4. Information Integration: Machine vision inspection can use multi-station measurement methods to measure multiple technical parameters at once, such as the contour of the inspected product, dimensions, cosmetic defects, product height and so on.

5. Numerical statistics management: Measurement data and generate reports after measurement, no need to manually add one by one.

6. Can be applied to dangerous detection environment: in the harsh and dangerous environment, in the human vision is difficult to meet the needs of the situation, the machine can well complete the detection work.

7. Will not cause student contact damage to the enterprise product development: machine vision in the process of detecting the workpiece, do not need to contact the workpiece, will not cause social contact damage to the workpiece. Artificial intelligence detection technology must have direct contact detection of the workpiece, which can easily lead to contact damage.

8. Objective stability: In the process of manual testing, the test results will be affected by personal standards, emotions,automatic visual inspection system energy and other factors. This machine is strictly in accordance with the set standards for the test, the test results are more objective, reliable and stable.

9. Avoid secondary pollution: manual operation will sometimes bring uncertain sources of pollution and contaminated workpiece.

Simple maintenance: low technical requirements for operators, long service life and other advantages.