OPTICAL SYSTEM POSITION MEASURING DEVICE

PURPOSE:To accurately measure the position and the thickness of an object to be measured by correcting the position of the centroid of light quantity based on reflectance and transmittivity inside and outside the object to be measured and the thickness of the object to be measured by means of a correction operation part. CONSTITUTION:In the case that the object to be measured 1A is a light- transmissive one, the position of the centroid of the light quantity of scattered light on a light position detecting element 6 is corrected by the correction operation part 15 based on the reflectance on the surface of the object 1A, the reflectance and transmittivity inside the object 1a and the thickness of the object 1A. At such a time, a signal in proportion to the position of the centroid of the light quantity from a signal processing part 3 calculates the actual position of the centroid of the light quantity and the apparent position of the centroid of the light quantity is corrected by the correction operation part 15 based on several values inputted from a numeric value input device 14 and stored 16. Thus, the position and the thickness of the object to be measured 1A is accurately measured.