A Real-Time Measurement Method of Air Refractive Index Based on Special Material Etalon

Abstract

In the precise displacement measurement based on laser interferometry, the measurement technology for the refractive index of air is widely used to improve the measurement accuracy. However, the existing measurement method of the refractive index of air based on direct measurement is not easy to realize in practical work because of its complex measurement principle and the huge volume of the measurement device; while the measurement accuracy and speed based on the indirect method cannot adapt to the real-time, fast and accurate measurement requirements of industrially changing environments, resulting in distortion of the results. In this study, a measurement method of the refractive index of air based on a special material etalon is proposed. The method enables rapid and direct measurement of the air refractive index when the environment changes and it is given the realization process. Finally, the experimental results show that the deviation between this method and the modified Edlen formula is about 2.5 × 10 −7 , and that this method can quickly reflect the changes of the environment, which prove the correctness of this method and its ability manage rapid environmental responses. This method is worth popularizing in industrial measurement.

Special Issue on Precision Dimensional Measurements

“…Therefore, a grating diffraction method is employed to real-time detect the wavelength. Ren et al from Tianjin University developed a different method to measure air refractive index based on the special material Etalon [21]. Professor Zhang's group of Tsinghua University describes the unique frequency-shifted optical feedback measurement technologies using a solid-state microchip laser [22].…”

A New Computational Model of Step Gauge Calibration Based on the Synthesis Technology of Multi-Path Laser Interferometers

“…Based on the analysis of the advantages and disadvantages of the above-mentioned instruments, this paper proposes a new computational model of step gauge calibration based on the Synthesis Technology of Multi-Path Laser Interferometers (SMLI), in which three of four interferometers are used for distance measurement, and the fourth channel is used for the wavelength compensation of the laser [12][13][14], thereby establishing our own step gauge calibration device on the platform of Leitz CMM. By adding four laser interferometers in the measurement platform, the spatial position relationship model of three out of four lasers is constructed, and the synthetic optical path of these lasers is translated to the measurement line of the measured step gauge, which can effectively eliminate the influence of the Abbe error of the CMM on the measurement result, and compensate the errors of pitch and yaw.…”