High-precision wide-range low-coherent interference shift demodulation device and demodulation method thereof

Abstract

The invention relates to a high-precision wide-range low-coherent interference shift demodulation device, which comprises a light source, an optical circulator, a self-focusing collimation lens, a fixed reflecting mirror, an optical fiber splicer, a beam extender lens, a polarizer, a birefringent optical wedge, a stair-shaped birefringent phase shifter, an analyzer, a planar array camera and a processing unit. A demodulation method comprises the following steps: dividing the light emitted from the light source into two parts after the light passes through the optical circulator and reaches the self-focusing collimation lens at the sensing side, wherein one part is directly reflected and the other part is reflected after entering the reflecting mirror fixed on an object to be detected, andthe two parts of reflection light have an optical path difference (OPD); guiding the two parts of reflection light to pass through the optical circulator again so as to reach the optical fiber splicer and then reach the birefringent optical wedge and the stair-shaped birefringent phase shifter through the beam extender lens and polarizer; realizing the wide-range optical path difference (OPD) scanning under the combined action of the birefringent optical wedge and the stair-shaped birefringent phase shifter; generating an interference fringe behind the analyzer; receiving the interference fringe by using the planar array camera; and detecting the shift information through digital processing by a computer or an embedded system.

Description

technical field [0001] The invention relates to the field of displacement information demodulation. The displacement sensing demodulation method can be used for high-precision detection of displacement, or demodulation of other sensors such as strain, temperature, thickness, group refractive index and pressure that can be converted into displacement. Background technique [0002] The low-coherence interferometry technology used for displacement demodulation mainly includes time-scanning and space-scanning. The time-scanning method such as Miho Song et al. (Minho Song, Byoungho Lee, An effective optical evaluation technique using visible low-coherence interferometry, Optics and Lasers in Engineering, 1997, 27:441-449) conducts the The optical path difference is scanned to match the displacement to be measured. The space scanning type is to make a linear distribution of the optical path difference in space, so that the space scanning of the optical path difference can be real...

AI Technical Summary

Problems solved by technology

[0003] The time scanning method can measure a large range, but due to the need to mechanically scan one of the mirrors, its long-term reliability and stability are poor, and the measurement accuracy is only on the order of microns

Space scanning uses linear array CCD devices for electrical scanning, which has high long-term reliability, but the pixels of linear array CCD are limited, and its measurement range is usually small, only tens of microns

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