OPTICAL MEASURING SYSTEM

PROBLEM TO BE SOLVED: To obtain an optical measuring system by which a substrate or the thickness or the optical characteristic of a thin-film layer on the substrate is evaluated. SOLUTION: The optical measuring system 1 is provided with a light source 10 which generates a beam of light, a static polarizing element 12 which polarizes the beam of light emitted from the light source 10 and a measuring system 9 which measures light reflected from the position of a substrate 5. The measuring system 9 contains a static beam-splitter element 60 by which the light reflected from the substrate 5 is divided into s-polarized light and p-polarized light. In addition, the measuring system 9 contains two optical sensors by which the amplitude of the s-polarized light and that of the p- polarized light as well as the intensity of the s-polarized light and that of the p-polarized light are measured separately. A control system 200 analyzes the measured amplitudes of s-polarized light and p-polarized light, and it judges a change in the topology of the substrate 5 or a change in the thickness or the optical characteristic of a thin-film layer.