Thickness measuring device, thick measuring method and computer program product for this purpose,

摘要

A thickness measuring device includes a light source which emits a light; an optical system, consisting of the light, which is emitted from said light source, is focused on an optical axis; a reflector which reflects light, which is focused by the optical system; a detector, which an intensity of the reflected light according to a position on the optical axis is detected, where the light which passes through the optical system, in a focus and focal point is located; and a computing device in which a thickness of a measured object with the use of a refractive index of the measured object and a degree of a displacement between a first focal point position and a second focal point position is calculated.