| 摘要 |
PURPOSE:To alter the position of an illumination system with respect to the alteration of the thickness and the material of reticles in a short time by movably providing the system with respect to the incident optical axis direction of a projection optical system and providing means for regulating the position in response to the optical path length. CONSTITUTION:The light of an LED 10 is reflected on reticles 12, and the reflected light is received by photoreceptors 11 to detect the distance from a reticle holder 13 to the upper surface of the reticles 12, i.e., the thickness of the reticles 12. A calculation controller 30 calculates the moving distances of an illumination system 6 and an alignment optical system 26 by the value of the thickness of the reticles 12 as the output of a thickness detector made of the LED 10 and the photoreceptors 11 and the refractive index in response to the quality of the reticle 12 input from a refractive index setter 31. Further, the controller 30 applies a command of the moving distance of the calculated result to an illumination system moving mechanism 7 and an alignment optical system moving mechanism 27 to move them. |
