Homodyne laser vibrometer with dual circular polarization interference and dual Wollastedt prisms

Abstract

The double-channel circular polarization interference without orthogonality error and the double Wollaste prism spectroscopic homodyne laser vibrometer belong to the field of laser interferometry; the interference part generates double Circularly polarized reference light and circularly polarized measurement light with orthogonal polarization directions and coincident optical paths. The reference light and measurement light of the detection part pass through two Wollaste prisms that have a specific relationship with the spatial rotation angle around the beam to generate four phases with a phase difference of 90° The photoelectric signal has the outstanding characteristic of suppressing nonlinear errors from the optical path structure and principle; the present invention uses fewer optical elements to realize four-channel homodyne orthogonal laser interferometry, which can effectively solve the polarization leakage in the optical path in the existing technical scheme Mixed with polarization, the output signal has DC offset error and non-orthogonal error, and the measurement result has significant nonlinear error. It has significant technical advantages in the field of ultra-precision vibration measurement.

Description

technical field [0001] The invention belongs to the field of laser interferometry, and mainly relates to a double-path circular polarization interference and double Wollaste prism spectroscopic homodyne laser vibrometer without orthogonal error. Background technique [0002] As an ultra-precision measuring instrument that can trace the vibration value to the laser wavelength, the laser vibrometer is widely used in the fields of dynamic displacement measurement, vibration measurement and monitoring, ultra-precision equipment and system integration, scientific research and experiments. Laser vibrometers based on laser interferometry can be divided into two categories, homodyne and heterodyne, according to the principle. The two have significant differences in working principle, optical path structure and technical characteristics. The homodyne measurement method uses a single-frequency laser as the light source, based on the classic or improved Michelson laser interference pri...

AI Technical Summary

Problems solved by technology

The disadvantages of this technical solution are: 1) Placing a polarizer on the reference arm causes the light intensity of the reference light to be greatly reduced relative to the measurement light, and introduces unequal amplitude errors of the two output signals; 2) The interference part is generated by a polarizer Linearly polarized light, the extinction ratio of the polarizer is low, and there is polarization aliasing in the interference part, which introduces nonlinear errors

Its shortcomings are: 1) The accuracy of the one-eighth wave plate device is poor, the actual phase shift is less than 45°, and the linearly polarized reference light passes through the one-eighth wave plate twice to actually obtain elliptically polarized light, resulting in The non-orthogonal phase shift error of the two actually output signals is large; 2) The detection part adopts PBS light splitting, and there is polarization leakage phenomenon, which introduces a large nonlinear error

The disadvantages of this technical solution are: 1) there are many optical elements, and there are many sources of nonlinear errors; 2) the use of polarization beam splitter PBS to split light, there is a phenomenon of polarization leakage, resulting in significant nonlinear errors

The disadvantages of this technical solution are: 1) the detection part requires an additional quarter-wave plate to generate four photoelectric signals with a phase difference of 90°; Equal amplitude and non-orthogonal errors, thus introducing nonlinear errors

The advantage of this technical solution is that the symmetry of the optical path is better, and the non-orthogonal error problem of the solution proposed by Peter is solved. The disadvantages are: 1) The detection part needs an additional quarter-wave plate to generate four Photoelectric signals with a phase difference of 90°; 2) The beam splitter used is an ordinary beam splitter BS, and the beam splitting effect is related to the polarization state of the light incident to the four-channel detection part, and has a large additional phase shift

The disadvantages of this technical solution are: 1) the detection part requires an additional quarter-wave plate to generate four photoelectric signals with a phase difference of 90°; Equal amplitude and non-orthogonal errors, thus introducing nonlinear errors

[0016] In summary, due to factors such as laser power drift, unsatisfactory optical components, and installation errors of optical components, especially the polarization leakage of optical components such as polarizing beam splitters PBS and polarizers, and the phase delay error of wave plate devices, the existing homodyne In the interference part and / or detection part of the orthogonal laser vibrometer technical solution, due to the limitation of the optical path structure, principle and the characteristics of the optical device itself, there are nonlinear errors that are difficult to overcome, and the nonlinear error can reach several nm or even dozens nm, it is difficult to meet real-time, high-precision measurement, especially the vibration measurement requirements of the next generation of sub-nanometer or even picometer-level accuracy, and nano-level amplitude

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