Pcb factory: principle and applICation of AOI optical detector

People know that objects are judged by the amount of light reflected back. Most of the reflected amount is bright, while less is dark. AOI has the same principle as human judgment. AOI uses artificial light source LED light to replace natural light, and optical lens and CCD to replace human eyes. AOI compares, analyzes and judges the amount reflected from the light source with the programmed standard. AOI working principle There are various forms of AOI technology applied in SMT, but its basic principle is the same (as shown in Figure 1), that is, the measured object's figure is obtained by optical means. Generally, a sensor (CAMera) is used to obtain the illumination image of the detected object and digitize it, and then

People know that objects are judged by the amount of light reflected back. Most of the reflected amount is bright, while less is dark. AOI has the same principle as human judgment. AOI uses artificial light source LED light to replace natural light, and optical lens and CCD to replace human eyes. AOI compares, analyzes and judges the amount reflected from the light source with the programmed standard.

How AOI Works

There are various forms of AOI technology applied in SMT, but its basic principle is the same (as shown in Figure 1), that is, to obtain the measured object graph by optical means, generally to obtain the illumination image of the detected object through a sensor (camera) and digitize it, and then to compare, analyze, test and judge in a certain way, which is equivalent to automating and intelligentizing the manual visual inspection.

Different AOI software and hardware designs have their own characteristics. In general, their analysis and judgment algorithms can be divided into two types, namely, design rule check (DRC) and pattern recognition check.

(1) DRC method detects graphics according to some given rules. For example, PCB circuit graphics shall be detected by rules such as taking all connecting wires as the end points, and the width and spacing of all leads shall not be less than a certain specified value. The DRC method can guarantee the correctness of the inspected graph from the algorithm, the corresponding AOI system is easy to manufacture, the algorithm logic is easy to realize high-speed processing, the amount of program editing is SMAll, and the data takes up less space. However, the method has poor ability to determine the boundary, and often requires the design of a specific method to determine the boundary position.

(2) The pattern recognition method is to compare the digitized graphics stored in the AOI system with the experimental detection images to obtain the detection results. For example, when detecting PCB circuits, first establish the detection according to a good PCB or a computer-aided design model.

PCB manufacturers and PCB designers will explain the principle and application of AOI optical detector.