| 摘要 |
PURPOSE:To detect upper and lower alignment marks on both ends of each of two sheets of upper and lower plates without a positional deviation error in spite of a gap between the plates by a method wherein a telecentric lens system is used as an image-forming lens. CONSTITUTION:A telecentric lens system 35 is used in a detection optical system 3' as an image-forming lens. In an alignment, a constant gap G is formed between a color filter 1 and a TFT substrate 2 to place the substrate 2 on a moving table, illuminating light LT is emitted on these of the filter 1 and the substrate 2, the respective optical axes CC and CT of reflected lights LRC and LRT of upper and lower marks MC and MT on both sides of each of the filter 1 and the substrate 2 are vertically incided in the system 35 and respective refracted lights are emitted on the same optical axis. That is, as the optical axes of the reflected lights LRC and LRT of the upper and lower marks MC and MT on the right side of each of the filter 1 and the substrate 2 coincide with each other, a projected image is formed on a TV camera 34A on the left side of TV cameras 34A and 34B without generating a positional deviation error. Also about the reflected lights of the upper and lower marks on the left side of each of the filter and the substrate, a projected image is formed on the TV camera 34B in the same manner as the above manner. |
