DETECTION OF POSITIONING MARK ON BOARD

PURPOSE:To accurately detect a positioning mark by irradiating the positioning mark on a printed board and the periphery thereof with polarized light and transmitting only reflected light from the periphery of said mark with a deflecting plate provided on the front surface of a camera on which the reflected light is made incident. CONSTITUTION:The positioning mark M on the printed board P on a table T and the printed board P around the mark M are irradiated with the light from a light source 11 which is lighted by a power source 10 through the deflecting plate 14. The light reflected on the mark M and the periphery thereof is picked up to be into an image by the camera 12 through the deflecting plate 15. The reflected light from the mirror surface of the mark M formed by soldering to be swollen is not made incident on the camera 12 by operating the deflecting plate 15. Meanwhile, the light is irregularly reflected in all the directions on the periphery of the mark M and the reflected light is made incident on the camera 12. The image picked up by the camera 12 is detected by an image sensor 16, binarized 17, processed in terms of image 18 and projected on a monitor TV 13 to form the silhouette image of the mark M. Thus, the positioning mark can be accurately detected.