Analysis of Multiple Layers of Transparent Objects Using a Confocal Microscope with Low-Coherence Interferometer

Abstract

In industrial applications, thickness and refractive index measurements of transparent plates and films are very important for quality control. For these purposes, several methods using lightwaves are available for noncontact and nondestructive measurement. However, because the refractive index and geometrical thickness are always correlated to each other, the separation of these two quantities is required for accurate inspection. In this review, we explain the principle and the apparatus for separate measurement of the refractive index and the geometrical thickness applicable to multiple layers. Several applications of this method are also described.