| 摘要 |
PURPOSE:To enable discrimination of a defect in monochromatic manner, by performing a detection processing based on data as obtained by subtracting image data after the displacement of a cyclic pattern from that before the displacement thereof to inspect the cyclic pattern efficiently at a high accuracy. CONSTITUTION:A pattern 6 to be inspected is lighted by a transmission lighting section made up of a DC power source 9, an incandescent lamp 8 and a diffusion plate 7 and the inspection area is photographed with a TV camera 1. An image processor 2 converts the output signal of the TV camera 1 into digital from analog to be a digital image data and various processings including addition and subtraction on the screen are performed with a frame memory and an arithmetic unit. A control section 3 controls the image processor 2 and a pattern shifting mechanism composed of an X-Y stage 10 and a driving section 5. Then, when subtraction is done between image data before and after the shifting of the pattern, changes in the video signal due to a unit pattern with no defect are cancelled by changes in the video signal due to shading or the like in a photography system to reduce to virtually zero so that the value varies locally at only the defective point. Thus, the defect can be detected based on this fact. |
