Vision alignment system is usually used in high performance vision mounter. The visual alignment system uses digital image processing technology. When the nozzle on the chip head picks up the assembly, it is obtained by moving the camera fixed on the chip head or a certain position on the body to the chip position. Through the optical density distribution of the image detection elements, these optical densities digitally pass through the CCD optical coupler array composed of many small and accurate photosensitive elements on the camera to output the gray value from 0 to 255.

The gray value is proportional to the optical density. The larger the gray value is, the clearer the digital image is. The digital information is stored, coded, amplified, classified and analyzed, then the results are fed back to the control unit, and the processed results are output to the servo system to adjust the position deviation absorbed by the compensation component, and finally the placement operation is completed.

Then, how to automatically correct the placement position and achieve accurate placement after the visual Mounter takes pictures of the reference points and components on the PCB?

In this process, the vision Mounter locates the mounting target of the component by transforming a series of coordinate systems. We will show how the system works throughout the placement process. First, the PCB is transferred to a fixed position by a transfer device and fixed by a clamping mechanism. Move the mounting head of the vision Mounter to the top of the PCB reference point, and the camera on the head takes pictures of the reference point on the PCB. There are four coordinate systems: substrate coordinate system (XP, YP), head camera coordinate system (xca1, ycal), image coordinate system (Xi, Yi) and machine coordinate system (XM, YM). After shooting the reference point, the machine converts the substrate coordinate system into the machine coordinate system through the association with the camera and image coordinate system, so as to determine the position of the target.

Then, the picker picks up the component and moves it to the fixed camera position, and the fixed camera will take pictures for the component. At this time, there are four coordinate systems: head coordinate system is also nozzle coordinate system (xn, yn), fixed camera coordinate system (xca2, yca2), image coordinate system (Xi, Yi) and machine coordinate system (XM, YM). After photographing the component, the machine will calculate the central position coordinates of the component features in the image coordinate system, and convert them into the machine coordinate system through the association with the camera and the image coordinate system. At this time, the part center coordinate and suction are compared in the same coordinate system. The coordinates of the mouth center. The difference between the two coordinates is the required position deviation compensation value. Then, according to the target placement position determined in the same coordinate system, the machine control unit and the servo system can control the machine for accurate placement.