| 摘要 |
PROBLEM TO BE SOLVED: To precisely measure displacement even for an object to be detected having a smooth surface. SOLUTION: A light spot 26 is formed on a stop object 25 to be measured with a movable mirror 23 and an objective lens 24 by rays from a light-emitting element 21, the movable mirror 23 is moved for scanning the object 25 to be measured, and reflection light from the light spot 26 is applied to a light receiving element 29 for obtaining signals. Similarly, signals are obtained, based on reflection light from the object 25 to be measured after travel. A signal processing section 30 calculates the correlation coefficient in a specific section between a signal before travel and that after travel, and measures displacement in the object 25 to be measured, based on the maximum position of the correlation coefficient. In this case, the spot diameter of the light spot 26 is set to be 50μm or less, thus obtaining a signal having improved S/N ratio for indicating the surface state (irregularities on the surface) of the object 25 to be measured from the light receiving element 29. In this manner, as far as the surface of the object 25 to be measured is not a mirror surface, the displacement can be precisely measured even in a relatively smooth surface. COPYRIGHT: (C)2004,JPO&NCIPI
|
