Noise-robust Phase Gradient Retrieval Formulation for Phase-shifting Interferometry

Abstract

Modification of the phase gradient formulation is proposed in order to make phase retrieval less susceptible to noise. The modified formulation is derived from separation of the phase terms and the intensity modulation terms of interferograms, and subsequent differentiation to reduce the noise-induced error of the phase gradient vector. Its performance is evaluated and compared to that of the conventional formulation, and noise-robust nature is confirmed.

Measurement of the Internal Structure of an Optical Waveguide Embedded in a Flexible Optical Circuit Board by Enhancing the Signal Contrast of a Confocal Microscope

“…For commercialization of O-PCBs, it is important to evaluate the quality of the optical waveguide including inspection of its internal structure. While many methods are available to inspect the surface profile or the internal structure of an optical waveguide [5,6], most of them are destructive or contact methods. However, a confocal microscope [7,8] can provide high lateral and longitudinal resolutions by using a point source and a point detector.…”