Improvement of Distance Measurement Based on Dispersive Interferometry Using Femtosecond Optical Frequency Comb

Abstract

Since the dispersive interferometry (DPI) based on optical frequency combs (OFCs) was proposed, it has been widely used in absolute distance measurements with long-distance and high precision. However, it has a serious problem for the traditional DPI based on the mode-locked OFC. The error of measurements caused by using the fast Fourier transform (FFT) algorithm to process signals cannot be overcome, which is due to the non-uniform sampling intervals in the frequency domain of spectrometers. Therefore, in this paper, we propose a new mathematical model with a simple form of OFC to simulate and analyze various properties of the OFC and the principle of DPI. Moreover, we carry out an experimental verification, in which we adopt the Lomb–Scargle algorithm to improve the accuracy of measurements of DPI. The results show that the Lomb–Scargle algorithm can effectively reduce the error caused by the resolution, and the error of absolute distance measurement is less than 12 μm in the distance of 70 m based on the mode-locked OFC.

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

“…In other words, the attainable results by dispersive interferometry are limited to integer times of L res . Therefore, the error between the output results and the real distance is inevitable, and its value varies within the interval of [− , + ] [ 32 , 33 , 36 ]. The only way to mitigate this error is to increase the spectral width to reach a smaller value for the distance resolution L res .…”

“…Hence, research on eliminating the minimum working distance l min is a critical issue in micrometer-order short-range absolute distance measurement. Niu et al made great contributions to analyzing the limitations of dispersive interferometry [ 36 , 37 ]. Based on the Nyquist sampling condition, the resolution of the time delay is determined by the reciprocal of the spectral width, giving rise to the measurement results by dispersive interferometry characterized as a step-like pattern as the target distance increases.…”

Improved Algorithms of Data Processing for Dispersive Interferometry using Optical Frequency Comb

“…An optical frequency comb (OFC), which provides numerous ultra-narrow linewidth wavelengths over a broad optical spectral range, is the Fourier transform of femtosecond ultrashort pulses from a mode-locked laser in the time domain. It enables versatile advanced absolute distance measurement methods, including synthetic wavelength interferometry (SWI) [12,[23][24][25], multiwavelength interferometry (MWI) [26][27][28][29][30], dispersive interferometry (also known as spectrally resolved interferometry, SRI) [31][32][33][34], dual-comb interferometry [35][36][37][38][39], and time-of-flight (TOF) measurement [40][41][42][43][44]. Compared with other methods, the dispersive interferometry can achieve a high resolution of distance measurement.…”

Improved Algorithms of Data Processing for Dispersive Interferometry Using a Femtosecond Laser

“…An optical frequency comb (OFC), which provides numerous ultra-narrow linewidth wavelengths over a broad optical spectral range, is the Fourier transform of femtosecond ultrashort pulses from a mode-locked laser in the time-domain. It enables versatile advanced absolute distance measurement methods, including synthetic wavelength interferometry (SWI) [ 12 , 23 , 24 , 25 ], multi-wavelength interferometry (MWI) [ 26 , 27 , 28 , 29 , 30 ], dispersive interferometry (also known as spectrally resolved interferometry (SRI)) [ 31 , 32 , 33 , 34 ], dual-comb interferometry [ 35 , 36 , 37 , 38 , 39 ], and time-of-flight (TOF) measurement [ 40 , 41 , 42 , 43 , 44 ]. Compared to other methods, dispersive interferometry can achieve a high resolution of distance measurement.…”