Distance measurement using frequency scanning interferometry with mode-hoped laser

We developed a path imbalance measuring system using a reference interferometer with alterable optical path difference (OPD), aiming to eliminate the uncertainties due to synthetic wavelength measurement and remove the requirement of a known and stable reference OPD in frequency scanning interferometry. The path imbalance can be solved by using the phase ratios between the two interferometers produced before and after altering the OPD in the reference interferometer. The results have shown that the measurement uncertainty and the path imbalance are linearly related and a combined relative uncertainty of 4.9 × 10−6 (1σ) in path imbalance measurement over a range from 0.5 m to 50 m is achieved. Besides, we analyzed the contributions to the uncertainty that limit the performance of the system, and we discussed how to obtain a better measurement uncertainty.

Section: Uncertainty Evaluationmentioning

confidence: 99%

Improved path imbalance measurement of a fiber-optic interferometer based on frequency scanning interferometry

Hou

Wang

Yang

et al. 2017

“…Furthermore, the larger the sweeping range, the smaller the corresponding synthesized wavelength, and the higher the ranging accuracy under the same accuracy of fringe counting. Fabry-Perot interferometer [20], highresolution saturated absorption spectra [21] and optical frequency comb [22] have been employed to calibrate the swept frequency range, and a range of 505 GHz was calibrated by the comb using a narrow band pass filter [23]. However, the external reference standards increase the complexity and cost of the system.…”

Section: Introductionmentioning

confidence: 99%

Absolute distance measurement using frequency sweeping interferometry with large swept range and target drift compensation

Zhang

Hao

Zhang

et al. 2023

Frequency sweeping interferometry (FSI) is an attractive absolute distance measurement (ADM) method because of the advantages of large unambiguity range, simple structure and excellent flexibility. By using reference interferometer, the calibration of the frequency sweeping range in FSI can be avoided, and the complexity and cost of the system can be further reduced. Then, the measurement accuracy is associated with the accuracy of phase demodulation, the width of frequency sweeping range and the compensation of target drift. In this paper, ADM using FSI with large swept range and target drift compensation is presented. An incremental interferometer which has a complete common path with the swept source laser was employed to monitor the target drifts of the measurement and reference interferometer. Interference phases of the corresponding interferometers were extracted simultaneously using phase generated carrier (PGC) demodulation technique, and an accuracy better than 1° was verified by nanometer displacement measurement. Comparative experiments of ADM at a distance of ~ 4.5 m with different swept ranges and before and after target drift compensation were carried out, and the results demonstrated that larger swept range and target drift compensation could greatly improve the stability and accuracy of measurement.

“…For a distance measurement system based on FSI, the measured distance L can be estimated by L = cΔΦ/(2π • B • n g ), where B is the optical frequency sweeping range of the laser, ΔΦ is the phase change of the interference signal, c is the speed of light in vacuum and n g is the group refractive index of air [6,7]. The theoretical measurement accuracy and precision are subject to the sweeping range and linearity of the laser source [8].…”

Section: Introductionmentioning

confidence: 99%

High-precision frequency sweeping interferometry for absolute distance measurement using a tunable laser with sweeping range of 88 GHz

Shi

Hei

Wang

et al. 2020

Distance measurement using frequency sweeping interferometry (FSI) is an absolute distance measurement technique that allows for high accuracy over long distances. Notwithstanding, the measurement accuracy is affected by laser sweeping nonlinearity and limited sweeping range. In this work, an optimized post-processing linearization method is demonstrated to realize high accuracy arbitrary distance measurement using a laser with small modulation range. The interference signal is sparsely resampled to eliminate the influence of the sweeping nonlinearity, and the absolute distance is obtained by analyzing the phase of the resampled signal. In the measurement system, a high finesse Fabry-Perot (F-P) cavity placed in vacuum is used as the measurement reference, so the effect of dispersion mismatch is negligible. Moreover, the distance measurement result is determined by the linear fit of the phase of each resampled point. Therefore, the influence of target vibration and other external random noise can be partially eliminated, and the reliability of the result is high. In the experiment, the sweeping range of the laser source is only 88 GHz. Comparing with a fringe counting interferometer, the standard deviation of the residual errors is 34 μm within a distance of 6.7 m.