Integrated machine vision technology for line-scan applications

There is clear need for integrated and affordable machine vision systems in line-scan applications, e.g. for width measurement and defect detection. These applications require sensor-like solutions in a price range not achievable with traditional machine vision systems consisting of a line-scan camera, host computer, frame grabber and possibly one or more dedicated processing boards. Since an integrated solution would make a separate host computer and associated boards unnecessary, we set out to study the feasibility of integrated machine vision technology for such applications. Analyses of several potential applications were used to define the requirements for an integrated line-scan camera-based vision system. In order to demonstrate the feasibility of the concept, a research prototype was designed based on these requirements. This is a complete machine vision system with camera front end, fast hardware for corrections, the necessary logic and a computer for higher-level data analysis and I/O. A 4096-pixel CCD array followed by 20 MHz 10 A/D conversion forms the front end. Illumination correction, geometric correction, 7×7 convolution, multilevel pixelwise thresholding and histogramming are all implemented with fast Erasable Programmable Logic Device (EPLD) circuits. A compact PC/104 with a 486 processor takes care of the high-level processing and control. Communication facilities include 12 TTL-level I/O lines, a serial line and a video output.