Folding-fabry-perot-cavity-based cavity length measurement method and device

Abstract

The invention discloses a folding-fabry-perot-cavity-based absolute distance measurement method and a device, and belongs to the field of laser interference precise measurement. The method comprises the following steps of: dividing incident intrinsic light into two beams of orthogonal polarized light; performing up frequency shifting and down frequency shifting on the two beams of orthogonal polarized light respectively by an acousto-optic variable frequency shifter respectively to form orthogonal polarized light beams with frequency difference; making the orthogonal polarized light beams enter a folding fabry-perot cavity; and performing resonance on the orthogonal polarized light beams with the frequency difference and an adjacent resonance order of the folding fabry-perot cavity respectively, wherein the frequency difference of the adjacent resonance order is a free spectrum range corresponding to the cavity length of the folding fabry-perot cavity and thus, measuring the absolute distance of the cavity length of the fabry-perot cavity according to the free spectrum range. The device for implementing the method can realize nanometer level measurement precision and magnitude measurement range of dozens of millimeters, and is suitable for nonlinear error calibration of nanometer and sub nanometer precision in the magnitude measurement range of dozens of millimeters and a nanometer displacement measurement system with high precision and a wide range.

Description

technical field [0001] The invention belongs to the field of laser interference precision measurement, and relates to a cavity length measurement method and device based on a folded Fabry-Perot cavity. Background technique [0002] With the development of science and technology, higher and higher requirements are put forward for the measurement of large range and high precision. Two-beam laser interferometry is widely used in industrial measurement and scientific research. In two-beam interferometry, the change of interference fringe is a sinusoidal function of displacement change. There are large-scale nanometer resolution measurements realized by optical subdivision or electronic subdivision. Periodic non-linear errors within half a wavelength, which are not measured with nanoscale precision in the metrology sense. [0003] The Fabry-Perot interferometer is a nano-displacement measurement device based on multi-beam interference. The multi-beam interference fringes with hi...

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Problems solved by technology

[0003] The Fabry-Perot interferometer is a nano-displacement measurement device based on multi-beam interference. The multi-beam interference fringes with high-precision constants are applied to incremental displacement measurement, and the displacement measurement greater than half the wavelength is converted into the detection of interference fringes. Integer level change, displacement measurement conversion within half wavelength to detect the change of resonant frequency of high-fine interference fringes, on the one hand, it improves the optical resolution of displacement measurement greater than half wavelength, and at the same time converts displacement measurement within half wavelength into frequency Measurement, so that the displacement measurement has nanometer or even picometer precision, and this beat-type Fabry-Perot interferometer is especially suitable for the half-wavelength nonlinear error calibration measurement of the laser heterodyne interferometer, but its measurement The range has been limited to a few hundred microns due to the limitation of the tuning range of the laser source and the frequency response of the detector

Therefore, it is difficult for the Fabry-Perot interferometer applied to incremental displacement measurement to achieve large-scale nanoscale displacement measurement

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