Coherent processor for real-time inspection of technical surfaces

The number of applications in product inspection is already large and grows rapidly. Fabrication processes run at high speeds, and demands on accuracy and quality are rising. Today, electronic vision systems often do not provide enough processing performance to satisfy real-time requirements of industrial applications. This motivates the development of hybrid vision systems which, by utilization of parallel optical filtering, have enough processing power to become applicable in automated product inspection. We have developed a programmable optical processor which is designed to extract defects on technical surfaces by means of optical image analysis. The processor is capable of analyzing video image sequences in real-time using liquid-crystal spatial light modulator technology. Structural defects are visually enhanced by an adaptive wavelet filtering method. We have implemented a demonstrator device and showed its operation by an example of practical relevance. The experiments confirm that optical image processing is an attractive way to do quality control in real-time.