Enhanced Data-Processing Algorithms for Dispersive Interferometry Using a Femtosecond Laser

Abstract

Dispersive interferometry based on a femtosecond laser is extensively utilized for achieving absolute distance measurements with high accuracy. However, this method cannot measure arbitrary distances without encountering a dead zone, and deviations in its output results are inevitable due to inherent theory limitations. Therefore, two enhanced data-processing algorithms are proposed to improve the accuracy and reduce the dead zone of dispersive interferometry. The principles of the two proposed algorithms, namely the truncated-spectrum algorithm and the high-order-angle algorithm, are proposed after explaining the limitations of conventional methods. A series of simulations were conducted on these algorithms to show the improved accuracy of measurement results and the elimination of the dead zone. Furthermore, an experimental setup based on a dispersive interferometer was established for the application of these proposed algorithms to the experimental interference spectral signals. The results demonstrated that compared with the conventional algorithm, the proposed truncated-spectrum algorithm could reduce the output distance deviations derived from direct inverse Fourier transforming by eight times to reach as low as 1.3 μm. Moreover, the unmeasurable dead zone close to the zero position of the conventional algorithm, i.e., the minimum working distance of a dispersive interferometer, could be shortened to 22 μm with the implementation of the proposed high-order-angle algorithm.

Impact of Cyclic Error on Absolute Distance Measurement Based on Optical Frequency Combs

“…Therefore, single-wavelength interferometry is used for incremental measurements. To realize absolute distance measurement with nanometer resolution, researchers usually combine single-wavelength interferometry with other methods that offer a larger NAR, such as synthetic wavelength interferometry [ 6 , 7 , 8 ], dispersive interferometry [ 9 , 10 , 11 , 12 , 13 ], and time-of-flight measurement [ 3 , 14 , 15 , 16 , 17 , 18 ]. The dispersive interferometry offers a high update rate and a high resolution but suffers from the trade-offs in NAR and resolution.…”