| 摘要 |
PURPOSE:To detect the symmetry of an angle of incidence with high accuracy by adjusting an optical member so that the detection signal from a photoelectric detector is held in a specific state when the interval between an objective optical system and a body in the direction of the optical axis is varied within a specific range. CONSTITUTION:Either of marks RM1 and RM2 on a reticle 1 is normally formed in the same reticle, the bifocal optical system consisting of an objective 21a and a birefringent material 21b is arranged horizontally in an actual alignment optical system, and a mirror M1 is fitted atop the lens 21a. The mirror M1, the objective 21a and material 21b are fixed to holding hardware 62, which is moved horizontally by a driving control system 60. Further, a relay system 17c relays a pupil surface EP1 where the material 21b is positioned to a plane EP2 nearby glass 50. Further, a mirror M2 and the relay system 17c are fixed to a device main body and the physical optical length between the material 21b and relay system 17c varies with the positions of the marks RM1 and RM2, but an image conjugation plate IP'm is invariably conjugate to the reticle 1 and a wafer because the optical path is an afocal system. |
