| 摘要 |
PURPOSE:To improve the checking performance of a minute defective part, by arranging the first and second light shielding masks on the image forming surfaces of the opening parts at the back surface on the lighting side and the front surface of a through hole with respect to an image forming lens, which is arranged on the surface side of an electric member. CONSTITUTION:A through hole 12 comprising a non-light-transmitting conductive layer 13 is formed in a light transmitting substrate 11 in a print plate 10. A shielding mask 14 is arranged in the vicinity of an opening 12a at the back surface of the plate 10. A single image forming lens 16 is arranged so as to face an opening 12c of the surface of a the hole 12. Illuminating light 15 is arranged on the side of the back surface of the mask 14. Part of the light 15 is reflected between the mask 14 and the plate 10 and leaks in the hole 12. The light becomes mask leaked light P1. Part of the light leaks through a defective part 12b of the hole 12 and becomes defective leaked light P2. Part of the light is outputted from the outside of a land part 13a of the layer 13 and becomes substrate transmitted light P3. First and second light transmitting masks 17 and 18 are arranged at the positions of the image forming surfaces of the openings 12a and 12c, and the light beams P1 and P3 are shielded. |
