Separate measurement of geometrical thickness and refractive index by an interference confocal microscope

In this paper we first survey non-contacting and separate measurement of thickness and refractive index of a transparent plate or film. Then we describe the separate measurement of refractive index and geometrical thickness of multiple layers which uses a combination of confocal microscopy and low-coherence interferometry. The measurement has been accelerated by replacing the low-coherence interferometry by wavelength-scanning heterodyne interferometry using a laser diode. Finally, accuracy of the measurement has been experimentally studied and display of a cross-sectional image of a stack of glass plates has been demonstrated.