The dispersive interferometry provides an instantaneous surface measurement in a single camera frame, making it resistant to environmental disturbances and ideal for in-process surface metrology. It also benefits from the extended measurement ranges in both depth and lateral directions by incorporating hyperspectral imaging technology and cylindrical beam illumination, respectively. This paper reports on an in-house developed cylindrical lens-based dispersive interferometer for high-accuracy surface inspection, particularly for structured surfaces. The obtained spectral interferogram is analyzed using the fringe order algorithm, in which the phase slope method is used to calculate the initial height to resolve the fringe order ambiguity and eventually an improved height value can be obtained using the exacted phase of a single wavelength. Experiments demonstrate that the measurement noise of the developed interferometry system is less than 1 nm within the measurement range. A brass step sample made by a diamond turning machine was measured and the experimental results closely align with those given by the commercial white light interferometer -Talysurf CCI 3000.
Polarized angle-resolved spectroscopy is introduced to measure transparent anisotropic films with back focal plane imaging by virtue of its rich information provided at various incident and azimuthal angles. The polarized angle-resolved spectroscopy provides a conoscopic interferogram and angle-resolved spectrum to deal with the complex characterization parameters of an anisotropic film, including the thickness, principal refractive index, and optical axis. Firstly, the optics model of a transparent anisotropic film is built by superpositioning the incoherent waves from the front and rear surfaces with coherency matrices formalism when the optical length is larger than the coherent length, and the incoherent issue arises. Then the optical axis of the anisotropic sample can be determined by the conoscopic interference image with the melatope, which marks zero phase difference between the ordinary and extraordinary waves. The measured angle-resolved reflectance spectrum and anisotropic interference phase are fitted to the optics model of the film with coherency matrix formalism, utilizing the Levenberg-Marquardt algorithm to calculate the thickness and dispersion principal refractive index within a single shot. The thickness and anisotropic refractive index are determined for sapphire and polyethylene terephthalate (PET) samples with our homemade polarized angle-resolved spectrometer. The thickness measurement results show that the relative error of the proposed method is less than 1.45%.
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