High-precision laser modulation interference air refractive index absolute measurement device and method

Abstract

The invention discloses a high-precision laser modulation interference air refractive index absolute measurement device and a high-precision laser modulation interference air refractive index absolutemeasurement method. A laser output by a single-frequency laser is split into two parallel light beams by a lateral displacement spectroscope after being subjected to optical isolation and sinusoidalphase modulation, and the two parallel light beams are emitted to a sinusoidal phase modulation interferometer to obtain measurement and compensation interference signals which are received by two detectors; a length-variable vacuum cavity is placed in a measurement light path of the sinusoidal phase modulation interferometer and is parallel to a light propagation direction, and the two parallel light beams respectively pass through an internal vacuum light path and an external air light path of the vacuum cavity. During measurement, a linear displacement workbench drives a moving light-transmitting window to move for a distance, the phase variation of two paths of interference signals is calculated in real time, and the air refractive index is solved. The measurement device and method arehigh in measurement precision and high in environmental interference resistance, and can be widely applied to the technical field of laser interference precision measurement.

Description

technical field [0001] The invention relates to an air refractive index measurement method, in particular to a high-precision laser modulation interference air refractive index absolute measurement device and method. Background technique [0002] The detection and calibration of the refractive index of air is the basic measurement problem of the precision measurement method based on the laser wavelength as the length. The existing air refractive index measurement methods are mainly PTF formula method and laser interferometry. The Edlén formula method based on PTF sensing is limited by the accuracy of the sensor and the uncertainty of the formula itself, so it is difficult to improve the measurement accuracy. Laser interferometry usually uses the refractive index of vacuum as a standard to measure the number of interference fringes produced by the optical path difference when the laser beam passes through the vacuum and air optical paths of length L, mainly including the pum...

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Problems solved by technology

For the pumping method, the pumping or deflation during the measurement process will cause a sharp non-uniform change in the temperature and air pressure in the cavity in a short period of time, resulting in interference fringe jitter, and changes in atmospheric pressure will also cause deformation of the vacuum cavity. These factors will make the air Refractive index measurement accuracy is limited; for a closed vacuum chamber method with a fixed length, only fractional interference fringes corresponding to the optical path difference can be measured, and the air refractive index measurement range is limited

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