Design And Implementation Of Online Shadow Mask Defect Detection System

Nowadays, information technology is developing faster and faster that makes people need to process information rapidly. In image information processing field, real-time image processing has been caught more and more attractions. With the development of embedded technology, more and more high-efficiency DSP (digital signal processor) chips that work specifically for digital image processing make techniques of digital image processing can be used more frequently in the practical systems. These systems promote the development of new technique and application field, In this paper, a defect detection system of the shadow mask is designed and implemented based on TMS320DM6437 high-efficiency digital video development board produced by TI. It detects the defects by the real-time processing of the image of shadow mask.Shadow mask plays an important part in cathode-ray tube. It lets the electron beam reach specified position of the phosphorescence layer accurately. Traditionally, people detect the projective image of shadow mask by eyes and determine whether the shape, size and position of the holes of the shadow mask meet the product standard. But this method of detection has some disadvantages such as the holes can not be located precisely, detecting speed is slowly and many defects can not be checked out. The detection system in this paper gets the amplified image of shadow mask by camera and does the real-time processing on TMS320DM6437 high-efficiency digital video development board. Area, filling rate and centre position which are the three characteristic parameters of shadow mask holes are computed by the algorithm designed by the technique in digital image processing field, and then whether there are defects on shadow mask by calculating and comparing these characteristic parameters are determined. Experimental results show that this system locates holes precisely and has few detection mistakes.TMS320DM6437 produced by TI is a digital signal processor that used for developing high-efficiency, low-cost digital video application. Its dominant frequency is 600MHz, calculating ability can reach 4800MIPS, and it has specific digital image process LIB, so it is very fit for the developing of digital image processing system. This paper has researched TMS320DM6437 digital video development evaluation board, analyzed its DSP/BIOS real-time operation system and made general designs of devices drivers and software based on DSP/BIOS; this paper has also analyzed the image of shadow mask and designed an algorithm of shadow mask defect detection by the technique in digital image processing field; this paper has implemented the algorithm by C language programming, debugged program on TMS320DM6437 and finally implemented a standalone online shadow mask defect detection system.