The scientific research of optical screening machine vision inspection technology originated in the 1950s. Its purpose is to replace the human eye to engage in inspection and discrimination work for a long time, and then greatly improve the efficiency and accuracy of the inspection, and reduce the difference in the inspection effect caused by human factors.

The level of optical screening machine vision detection technology has been developed so far, and it has exceeded the human eye detection in terms of detection accuracy, detection efficiency and detection stability. For example, in the detection of screws and nuts, the machine vision detection efficiency of the optical screening machine can reach 2000PCS/min, and the detection accuracy of the magnetic material CCD screening machine is as high as 0.001mm. Such accuracy and efficiency can not be reached in the traditional human eye detection, although the machine vision detection of the optical screening machine can exceed manual detection in many fields, but it must ensure its reliability and stability in order to play a full role. Whether from the camera, lens, light source and other hardware design or from the image processing software design, it has a crucial impact on the stability of machine vision.

Imaging system is an important part of optical screening machine vision, according to the above analysis of CCD camera and CMOS camera, CCD sensor is an important indicator to ensure image quality and stability, and the resolution and frame rate of the camera are mainly based on the accuracy and efficiency of the inspection to choose, according to the size of the inspected object, As well as the distance between the camera to choose the appropriate resolution of the camera, the frame rate is to consider the motion of the object to be detected beam, in the object moving at high speed to achieve high precision detection effect, it is necessary to choose a high frame rate camera.

As far as the lens is concerned, the bearing defect detection is relatively demanding, and it is necessary to consider the limit resolution of the camera to select the appropriate lens. In the selection process, not only the focal length of the lens should be calculated according to the operating distance and field of view, but also the appropriate depth of field should be selected according to the spacing change between the inspected object and the camera. In addition to the above basic requirements, you can also consider using a telecentric lens with less distortion, which not only has less distortion, but also reduces the deviation caused by changes in the distance between objects.

Light source consideration should first choose LED light source, in the acquisition of image quality, LED light source is better than halogen lamps, fluorescent lamps and other light sources, but also low power consumption, long service life, no pollution to the environment and other advantages, some high-precision detection requirements of the project, you can also consider increasing the light source box to reduce the external light stability of the visual system.