Method for measuring air refractive index fluctuation by laser synthetic wavelength interferometry

Abstract

The invention discloses a method for measuring air refractive index fluctuation by laser synthetic wavelength interferometry. In a laser synthetic wavelength interferometer composed of a double-frequency laser, a spectroscope, two polarizing beam splitters, a reference pyramid prism and a measuring pyramid prism, the measuring pyramid prism of the interferometer is fixed, and then the optical path between a first polarizing beam splitter of a measuring arm and the measuring pyramid prism forms an air refractive index fluctuation sensing chamber; the light path change of the interferometer measuring arm caused by the air refractive index fluctuation in the chamber is equivalent to a minimal measured displacement; with the displacement measuring principle of laser synthetic wavelength interferometry, the measurement of the minimal measured displacement is converted into the measurement of the reference pyramid prism moving displacement (in millimeter or micron), which realizes high-precision measurement of air refractive index fluctuation. The method of the invention realizes a measuring precision of air refractive index fluctuation of up to 10-11, and is applicable to technical fields of air refractive index measurement, precise length measurement, and the like.

Description

technical field [0001] The invention relates to a method for measuring the refractive index of air, in particular to a method for measuring air refractive index fluctuations by laser synthesis wavelength interferometry. Background technique [0002] The refractive index of air is an important parameter in the field of various optical precision measurement technologies in which the laser wavelength is used as the length "ruler". Air refractive index measurement methods are divided into two categories: air refractive index absolute measurement and air refractive index fluctuation measurement. The absolute measurement of the air refractive index is a method of giving the measurement results of the air refractive index with reference to vacuum, for example, the Edlen formula method: by measuring the air pressure, temperature, relative humidity, and carbon dioxide content, and then calculating the air refraction according to the Edlen formula Interferometric methods such as Rayl...

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Problems solved by technology

Although the existing absolute measurement method of air refractive index can achieve high measurement accuracy, such as the measurement accuracy of the Edlen formula method is generally within 10 -8 order of magnitude, most interferometric air refractive index measurement accuracy reaches 10 -8 -10 -9 However, because it is difficult to obtain a true pure vacuum condition, the improvement of the absolute measurement accuracy of the air refractive index and the implementation of the measurement process are limited.

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