| 摘要 |
PROBLEM TO BE SOLVED: To detect replacement in a height direction of measured members laminated with high accuracy and to perform a high speed and stable measurement.SOLUTION: A measuring light L0 from a light source 10 is divided into a first light flux L1 which becomes an object light to enter a measured member 1 and a second light flux division part L2 which becomes a reference light. The first light flux L1 reflected by a measured surface 1a of the measured member 1 is diffracted by a diffraction grating 14 and reflected again by the measured surface 1a of the measured member 1 so as to be returned to the light flux division part 12. The second light flux L2 is reflected by a reflection part 18 so as to be returned to the light flux division part 12. Based on an interference light intensity obtained by a light receiving part 30A which receives the first light flux 1 and the second light flux L2 superposed by the light flux division part 12, an adjustment is made so that light path lengths of the first light flux L1 and the second light flux L2 are matched by light path length adjusting means 17 for adjusting at least one of the light path lengths of the first light flux L1 and the second light flux L2 when replacement information in height direction of the measured surface 1a is obtained by a relative position information output part 20B. |
