Cross-polarization laser feedback grating interferometer of phase modulation type, and measurement method thereof

Abstract

The invention relates to a cross-polarization laser feedback grating interferometer of a phase modulation type, and a measurement method thereof. The measurement principle is based on the grating diffraction, optical Doppler effect, Lamb semi-classical theory and time-domain orthogonal demodulation principle. The orthogonally polarized light outputted by a birefringent dual-frequency helium-neon laser is perpendicularly incident to a polarization beam splitting prism and is divided into two linearly polarized light beams in different polarization directions. The two polarized light beams respectively pass through two different electrooptical modulators and then are respectively reflected by a reflector at a + / -1-order Littrow incidence angle to a reflection-type diffraction grating. The diffracted light returns to the laser cavity along the respective incident light, and performs self-mixing interference with the light in the cavity. The backward output light of the laser passes through a polarizer and then only the single-mode light is retained and accepted by a photodetector. An output signal of the photodetector is outputted to a data processing module for data processing, and the two-dimensional displacement of a target to be measured is obtained. The grating interferometer has the advantages of simple structure, large measuring range and high measurement resolution.

Description

technical field [0001] The invention belongs to the technical field of precision displacement measurement, and in particular relates to a phase modulation type orthogonal polarization laser feedback grating interferometer for two-dimensional measurement and a measurement method thereof. Background technique [0002] Nano-measurement is the key technology for the development of advanced manufacturing industry, and also the forerunner and foundation of the entire field of nano-technology. With the development of ultra-precision machining and ultra-fine machining technology, the demand for real-time high-precision two-dimensional positioning system is growing rapidly. Laser interferometer and grating interferometer are widely used in high-precision displacement measurement due to their advantages of non-contact, high resolution and wide dynamic measurement range. Typically, laser interferometry is used to measure out-of-plane displacements, while grating interferometry is used...

AI Technical Summary

Problems solved by technology

However, such systems generally face two problems: when the target moves a certain distance in an out-of-plane direction, the optical path of these systems will also change, resulting in a deviation between the detection light and the photodetector

Therefore, the measurement of out-of-plane displacement is usually used to compensate the in-plane displacement measurement; and these optical path systems are often very complicated and difficult to adjust

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