| 摘要 |
PURPOSE:To eliminate an error by a method wherein the displacement between the movable stand and position of an optional system when the reference position and the positional deviation are measured, and the angle of the optical system is corrected based on the result of the above-mentioned detection. CONSTITUTION:An optical system 2 is calibrated when a movable stand 1 is in a specific condition (specific X, Y and Z coordinates). When the movable stand 1 is moved and it is in the condition different from that in which calibration is performed, the displacement in Z direction of a displacement measuring section is measured by a displacement measuring device. The information obtained by the above-mentioned measurement is processed by a computer, the driving amount of an actuator 9 for correction of angle of the base stand B is computed, and the actuator 9 is driven based on the aforesaid driving quantity. Consequently, as the optical axis of the optical system 2 makes almost no change even when the movable stand 1 is moved, the error in detection of positional deviation by the change of optical axis can be reduced. |
