Large-scale gas refractive index real-time measuring system

Abstract

The invention belongs to the technical field of gas refractive index measurement, and in particular relates to a large-scale gas refractive index real-time measuring system. A vacuum chamber with a variable chamber length comprises three mirrors W1, W2 and W3, a vacuum chamber is formed by the mirrors W1 and W2, and the chamber length of the vacuum chamber can be changed by changing of the position of the mirror W1; the mirrors W2 and W3 are fixed, and air is between the mirrors W2 and W3; a laser interference system comprises four laser interference optical paths, light beams respectively enter the vacuum chamber with the variable chamber length from different positions, a light beam 1 is reflected by the mirror W1, a light beam 2 is reflected by the mirror W2 after passing through the mirror W1 and the vacuum chamber, a light beam 3 is reflected by the mirror W3 after passing through the mirror W1, the mirror W2 and the vacuum chamber, a light beam 4 is reflected by the mirror W3 after passing through the mirrors W1 and W2 and the air. Through comparing of phase differences of interference signals before and after the change of the chamber length of the vacuum chamber, absolute gas refractive index measurement can be realized, and by real-time measurement of the phase change of the optical path difference of the optical paths inside and outside the vacuum chamber, gas refractive index real-time measurement can be realized.

Description

technical field [0001] The invention belongs to the technical field of gas refractive index measurement, in particular to a large-range real-time gas refractive index measurement system based on laser interference technology and a variable cavity length vacuum cavity. Background technique [0002] The refractive index of gas is a physical quantity that is particularly concerned in the design of various optical systems. The accurate measurement of the refractive index of gas is the basis for precise optical measurement. In precision manufacturing and other fields that require high-precision optical measurement, real-time measurement of gas refractive index is an effective way to carry out error compensation for high-precision optical measuring instruments on site, and is one of the important means to improve the measurement accuracy of optical measuring instruments. [0003] At present, common gas refractive index measurement methods can be divided into two categories: indire...

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Problems solved by technology

Although the single measurement speed can be controlled within 1 minute, it is still impossible to achieve real-time measurement

[0005] The invention patent CN102183486B discloses a method for measuring the refractive index of gas based on an optical frequency comb. The multi-wavelength synthesis of the optical frequency comb is used to estimate the refractive index of the gas, which can realize the rapid measurement of the refractive index of the gas. However, due to the limitation of the length of the vacuum tube, The measurement range of the refractive index of gases is still limited

[0006] Invention patent CN103454247A discloses a large-range refractive index measurement device using the principle of total reflection. The refractive index is obtained through image comparison and calculation, which can be applied to the measurement of gas refractive index. However, the accuracy of this method is limited by the measurement principle and can only reach 10 -4 ~10 -5 order of magnitude, still unable to meet the high-precision measurement requirements of gas refractive index

[0007] The traditional method of relying on the F-P cavity is a well-known method in the field, but it needs to be filled and deflated during the measurement process, which cannot realize real-time measurement of the refractive index of the gas

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