Single frame surface inspection system: Frequency multiplexed spatio-temporally modulated illumination

We have proposed surface inspection system for detecting small defects on painted surface. The system used single orientation stripe pattern, so that there were difficulties to detect defects that are orthogonal to the stripes. In this paper, we have enabled to detect such directional defects by using frequency multiplexed orthogonal stripes. The system consists of frequency multiplexed spatio-temporally modulated illumination and correlation image sensor. The frequency multiplexed spatio-temporally modulated illumination has orthogonal stripes moving each directions to generate different temporal frequency. Frequency multiplexed two different patterns can be simultaneously demodulated by correlation image sensor.