Abstract: Visual inspection has widely existed in manufacturing demand. And there exist two problems, one is that the light environment of instability will affect the accuracy of image processing algorithm and the other is that interaction of hardware organization and visual software is often difficult, thus affecting the visual detection function implantation. Therefore, this paper presents a vision detection system based on intelligent feedback coupling PLC, which is implemented in software and hardware integration. Firstly the images of great light and shade change and the traditional method based on gray level are analyzed; and then an algorithm of real-time feedback and threshold intelligent adjustment is put forward, and programming based on the multi-thread is achieved. In the interaction of mechanism with the software, ModBus protocol is analyzed firstly, and then based on VC, the communication of visual software with PLC is realized. Finally, the performance of mechanism is tested, the results show that the mechanism is of high precision compared with the traditional image processing method, and realizes the interaction of hardware and software at the same time.

Key words:  intelligent feedback, PLC, ModBus protocol, visual detection, image processing