| 摘要 |
PURPOSE:To perform measurement continuously while changing the measuring point by moving a part near an object lens in the state where optical axes of object lenses of two in-focus state discriminating optical systems having internal light sources coincide with each other and providing a movement extent measuring means. CONSTITUTION:An in-focus state discriminating optical system 2 consisting of a light source 6, an object lens 12, an optical sensor 18, etc. and an in-focus state discriminating optical system 2' having the same constitution are arranged on both sides of an object 30 to be measured so that an optical axis X is shared, and casings 4 and 4' are servo-driven along the optical axis X by actuators 20 and 20' to perform auto-focusing. Extent of movement of casing 4 and 4' from reference positions are measured by length measuring means 22 and 22', and the thickness of the object 30 to be measured is measured on a basis of outputs of means 22 and 22' by a processing means 32. Light sources 6 and 6' emit lights different in wavelength to prevent the crosstalk between both optical system 2 and 2' in case of measurement of a transparent object to be measured. |
