| 摘要 |
PURPOSE:To enable to simultaneously detect a reference pattern on a reticle and a projected image of another pattern on a wafer by a method wherein an optical detecting system is composed of multiple lens groups while one or more pairs of lenses are composed of lens members void of a part thereof. CONSTITUTION:An optical detecting system 9 is composed of lens groups 13, 14 while one 13 of the lens groups is composed of lens members void of central part. A reference pattern 5 on a reticle is focused on a pattern detecting point 10 through the lens groups 13, 14. On the other hand, a projected image of pattern on a wafer above a point 6 is focused on the pattern detecting point 10 through the lens group 14 only. Through these procedures, the images of two elements at different points on an optical axis can be focused on one pattern detecting point 10 through the dual optical focusing system 9. In other words, a pattern can be detected by means of scanning a synthesized image of pattern by e.g. a slit 11 to photoelectrically convert the darkness of light transmitting the slit 11 by a photoelectric element 12. |
