Micro defect detection in solar cell wafer based on hybrid illumination and near-infrared optics

In this paper, an defect detection system based on hybrid illumination and near-infrared optics, is developed for solar cell wafer. It consists of geometrical camera optics, hybrid illumination device(HID), near-infrared(NIR) camera optics, machinery and control system and algorithm of defect detection and software. Especially, illumination conditions in HID is determined for reliable defect detection. Optimum illumination conditions in the HID are found with contrast analysis of RGB LED image, based on design of experiment. As a result, various surface micro defects are accurately detected. It is shown that the developed defect detection system can accurately detect micro defects of solar cell wafer.