Research and development of multi-layer glass plate thickness measurement system using optical frequency comb interferometry

Abstract

We proposed a measurement system for surface profile and tomography using incoherent optical frequency comb interferometry and spatial phase modulation (a diffraction grating). By employing a spatial phase modulator to an interferometer, the axial and lateral information of a sample were simultaneously obtained in one-shot capture. An incoherent optical frequency comb, which was generated by a Fabry-Perot etalon and supper continuum (SC) light source, was also installed to extend the axial measurement range of the system. The interference fringes, which belong to the interference comb orders, were rapidly monitored on the CCD camera. Surface profile and thickness of multi-layer glass plates could be derived from the position of the inference fringes on the CCD and their calculated fringe order. Resolutions of tomography and profilometry were achieved at 8 μm and 0.7 μm, respectively. The measurment range could be extended up to 30 mm by using the optical frequency comb technology.