We experimentally demonstrate a method for absolute distance measurement using a triple-comb-based multi-heterodyne interferometer which has the capacity to simultaneously balance the non-ambiguous range, resolution, update rate, and cost. Three flat-top electro-optic combs generated via cascaded intensity and phase modulators are adopted to form a measurement scheme including rough and fine measurements, and the unknown distance is determined by detecting the phase changes of the consecutive synthetic wavelengths. Experimental results demonstrate an agreement within 750 nm over 80 m distance at an update rate of 167 μs.
Method to accurately measure both refractive index and the thickness of glass is investigated. The method combines equal inclination interference with dispersive interferometry. The interference signal, which is detected by the spectrometer, contains different frequencies and can be demodulated with high accuracy. The experiments indicate that the standard deviation of the thickness is better than the 35 nm, while the standard deviation of the measured refractive indices is below 5.76 × 10 −6. Furthermore, absolute angles, between 0 • and 51 • , can be measured with a repeatability within 5 .
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