Design Of Real-time System For Presswork Defect Detection Based On DSP

With rapid development of printing technology, the high standard requirement of efficient and precise presswork detection is negatively meet by traditional presswork detecting method. However, the technology of presswork defect detection based on machine vision is positively focused on and accepted by related industry due to its state-of-art detecting precision and speed recently.Many domestic and foreign methods on the subject of quality detection of presswork image are researched. And the image processing knowledge and method are systematically analyzed that the procedure Grayscale and enhance of image process is carried on the presswork image collected already. The pattern matching method is utilized for the image localization to obtain the image offset; afterwards, the effective localization is fulfilled by image geometric transformation with the offset. In accordance with the requisition on certain press precision, the image is detected and determined whether the defect occurs or not, which is resulted from the image differentials between image to be detected and standard image with different configured thresholds.Nowadays, It is well known that the TMS320DM642 chip from TI is regarded by industry as the digital vision processor with the most outstanding performance. The requirements of vision signal processing can be easily meet with its excellent processing performance and abundant peripherals on-chip. The study is mainly focused on TMS320DM642 as the core which the detection system is built onto. The collection unit, processing unit and display unit of image is achieved as the hardware platform for the research. The collection unit, which is for digital image extraction and storage of frame, is composed with camera and visual decode chip SAA7115. The function of processing unit is defined as data reading, processing and outputting, then realized with DSP. The function of image displaying, correspondingly, is fulfilled by linear programmable array screen and visual encoding chip SAA7105. Based on the design of hardware and the language of Assembly and C, the software of the detection system is actualized by the application of DSP/BIOS real-time operation core and the RF5 referential structure.In comparison with traditional presswork defect detection system, the on-line print defect detection system based on the platform of TDS642EVM is positively proved by the significant advantages of feasibility integrity and minimum size during the detection experiments.