| 摘要 |
PURPOSE:To detect the focal position or the angle of inclination of a photosensitive substrate over a wide detection range without arranging a complicated optical system near the side of the photosensitive substrate in a projection optical system even when the projection optical system becomes large. CONSTITUTION:Detection light AL from a light-sending system 20 is applied to a measuring point Q on a glass substrate 102 via a projection optical system 100 and a mirror 9A, and a slit image is projected obliquely onto the measuring point Q. Reflected light from the slit image is guided to a light-receiving system 21 via a mirror 9B and the projection optical system 100, and the focal position of the galss substrate 102 is detected on the basis of the transverse deviation amount of the slit image which has been formed again inside the light-receiving system 21. |
