REAL-TIME DEFECT DETECTION IN VIDEO IMAGES

In this paper we present a method for the real-time detection of defec ts in pel iodic structures. Video images play an important role in aut omated manufacturing and quality, control. The video image of the obje ct to be inspected is displayed on a liquid crystal display (LCD), whi ch modulates a coherent read-out beam. The modulated coherent beam is Fourier trans formed with the help of a lens and is filtered from all periodic components by a nonlinear optical element. As nonlinear optic al elements photorefractive crystals and optically addressed liquid cr ystals cart be applied. After a second Fourier transform only defects remain visible in a resulting image. In this paper we discuss the proc edure and present examples in order to demonstrate the ability of filt ering technical objects like the grid of a solar concentrator cell.