CN-116147500-B - Micro-displacement measuring device and method based on Laguerre-Gaussian beam conjugate interference

CN116147500BCN 116147500 BCN116147500 BCN 116147500BCN-116147500-B

Abstract

The invention relates to a micro-displacement measuring device and method based on Laguerre-Gaussian beam conjugate interference, belonging to the technical field of laser interferometry. The conjugate interference component carries out conjugate interference based on the LG light and the Mach-Zehnder interferometer, the imaging component shoots an interference process before and after displacement of an object to be detected, a pre-displacement interference image and a post-displacement interference image are obtained, the processor processes the pre-displacement interference image and the post-displacement interference image, the displacement size and the direction of the object to be detected are obtained, whether the object has displacement change can be observed simply in real time, and micro-displacement measurement of picometer level can be realized.

Inventors

ZHAO DONGE
MA YAYUN
YANG XUEFENG
ZHANG BIN
CHU WENBO
LI YUAN

Assignees

中北大学

Dates

Publication Date: 20260512
Application Date: 20230224

Claims (5)

1. The micro-displacement measuring device based on Laguerre-Gaussian beam conjugate interference is characterized by comprising a conjugate interference component, an imaging component and a processor; the conjugate interference component comprises an LG light generating component and a Mach-Zehnder interferometer, wherein the LG light generating component is in optical path connection with the Mach-Zehnder interferometer, the LG light generating component is used for generating first LG light with any controllable topological charge number and transmitting the first LG light to the Mach-Zehnder interferometer, and the Mach-Zehnder interferometer is used for transmitting the first LG light to an object to be detected and receiving second LG light which is reflected by the object to be detected and is conjugate with the first LG light and interfering the first LG light and the second LG light; The LG light generating assembly comprises a laser, a first light splitting prism and a spatial light modulator, wherein the first light splitting prism and the spatial light modulator are sequentially arranged along the laser transmission direction, the laser is used for emitting laser, the first light splitting prism is used for transmitting the laser to the spatial light modulator, the spatial light modulator is used for carrying out phase modulation on the laser to generate first LG light with randomly adjustable topological charges and returning the first LG light to the first light splitting prism, the first light splitting prism is also used for reflecting the first LG light to the Mach-Zehnder interferometer, and the spatial light modulator is of phase modulation type; A polarizing plate is arranged between the laser and the first beam splitting prism and used for adjusting the polarization angle of the laser so as to be matched with the spatial light modulator, so that the spatial light modulator is in a pure-phase working mode; the imaging component is used for shooting the interference process of the first LG light and the second LG light before the displacement of the object to be detected to obtain a pre-displacement interference image, and shooting the interference process of the first LG light and the second LG light after the displacement of the object to be detected to obtain a post-displacement interference image; the processor is used for processing the interference image before displacement and the interference image after displacement to obtain the displacement size and direction of the object to be measured; Processing the interference image before displacement and the interference image after displacement to obtain the displacement size and direction of the object to be measured specifically comprises the following steps: The method comprises the steps of processing a pre-displacement interference image to obtain a pre-displacement light intensity curve, specifically, carrying out image enhancement on the pre-displacement interference image to obtain an enhanced image, carrying out communication area identification and centroid calibration on the enhanced image, determining the centroid of each communication area, which is an independent petal, carrying out circumference fitting on the basis of all centroids to obtain a fitting circle center and a centroid radius, and carrying out scanning on the pre-displacement interference image on the basis of the fitting circle center and the centroid radius, wherein the fitting circle center is taken as an origin, the centroid radius is taken as a radius, and carrying out anticlockwise extraction on the light intensity on the circumference of the pre-displacement interference image to obtain a pre-displacement light intensity curve, wherein the light intensity curve is a light intensity value variation curve along with an angle; Processing the interference image after displacement to obtain a light intensity curve after displacement; Determining the displacement size and direction of the object to be measured according to the light intensity curve before displacement and the light intensity curve after displacement, wherein the method specifically comprises the steps of recording a first angle of a peak point in the light intensity curve before displacement, recording a second angle of the peak point in the light intensity curve after displacement, calculating a difference value between the second angle and the first angle, taking an absolute value of the difference value as a rotation angle, and taking positive and negative of the difference value as a rotation direction; θ=k /l; k=2π/λ; wherein θ is the rotation angle, k is the wave vector of light; the displacement is the magnitude of displacement, l is the topological charge number, and lambda is the wavelength of incident laser.
2. The micro-displacement measurement device according to claim 1, wherein a collimating and beam expanding device is arranged between the laser and the first beam splitting prism, and the collimating and beam expanding device is used for collimating and expanding the laser.
3. The micro displacement measurement device according to claim 1, wherein the mach-zehnder interferometer comprises a second prism, a first standard mirror, a second standard mirror and a third prism, wherein the second prism is used for transmitting the first LG light to the first standard mirror and the second standard mirror, respectively, the first standard mirror is used for reflecting the first LG light to the third prism, the third prism is used for transmitting the first LG light to the object to be measured and receiving the second LG light conjugated with the first LG light reflected by the object to be measured, the second standard mirror is used for reflecting the first LG light to the third prism, and the third prism is used for combining the first LG light and the second LG light so that the first LG light and the second LG light interfere.
4. A micro-displacement measurement method based on lager-gaussian beam conjugate interference, for controlling the operation of the micro-displacement measurement device according to any one of claims 1 to 3, comprising: Receiving a pre-displacement interference image shot by an imaging component before displacement of an object to be detected and a post-displacement interference image shot after displacement of the object to be detected; Processing the interference image before displacement and the interference image after displacement to obtain the displacement size and direction of the object to be detected; Processing the interference image before displacement and the interference image after displacement to obtain the displacement size and direction of the object to be measured specifically comprises the following steps: The method comprises the steps of processing a pre-displacement interference image to obtain a pre-displacement light intensity curve, specifically, carrying out image enhancement on the pre-displacement interference image to obtain an enhanced image, carrying out communication area identification and centroid calibration on the enhanced image, determining the centroid of each communication area, which is an independent petal, carrying out circumference fitting on the basis of all centroids to obtain a fitting circle center and a centroid radius, and carrying out scanning on the pre-displacement interference image on the basis of the fitting circle center and the centroid radius, wherein the fitting circle center is taken as an origin, the centroid radius is taken as a radius, and carrying out anticlockwise extraction on the light intensity on the circumference of the pre-displacement interference image to obtain a pre-displacement light intensity curve, wherein the light intensity curve is a light intensity value variation curve along with an angle; Processing the interference image after displacement to obtain a light intensity curve after displacement; Determining the displacement size and direction of the object to be measured according to the light intensity curve before displacement and the light intensity curve after displacement, wherein the method specifically comprises the steps of recording a first angle of a peak point in the light intensity curve before displacement, recording a second angle of the peak point in the light intensity curve after displacement, calculating a difference value between the second angle and the first angle, taking an absolute value of the difference value as a rotation angle, and taking positive and negative of the difference value as a rotation direction; θ=k /l; k=2π/λ; wherein θ is the rotation angle, k is the wave vector of light; the displacement is the magnitude of displacement, l is the topological charge number, and lambda is the wavelength of incident laser.
5. The method of claim 4, wherein the performing image enhancement on the pre-displacement interference image to obtain an enhanced image specifically comprises: Denoising the interference image before displacement to obtain a denoised image; Thresholding the denoised image to obtain a binarized image; And carrying out morphological operation on the binarized image to obtain an enhanced image, wherein the morphological operation comprises swelling and corrosion.

Description

Micro-displacement measuring device and method based on Laguerre-Gaussian beam conjugate interference Technical Field The invention relates to the technical field of laser interferometry, in particular to a micro-displacement measuring device and method based on Laguerre-Gaussian beam conjugate interference. Background The laser interferometry technology has important importance in micro-displacement measurement research by the high-precision optical standard scale, the geometric shapes of interferometers are different, but the basic functions of the interferometers are similar, the wave front from the reference surface can be compared with the wave front from the measured lens or surface and interfere, and a quantitative and qualitative result of the parameter to be measured can be obtained by analyzing the obtained interference pattern. Laguerre-Gaussian (LG) has spiral phase, annular intensity physical properties that make LG widely used in optical manipulation, resolution microscopy imaging, optical communication, quantum communication, and optical measurement. The Mach-Zehnder interferometer has simple testing principle and small noise, and can realize specific measurement by flexibly improving the optical path. However, at present, no micro-displacement measurement technology based on LG light with adjustable topological charge number and Mach-Zehnder interferometer exists. Disclosure of Invention The invention aims to provide a micro-displacement measuring device and method based on Laguerre-Gaussian beam conjugate interference, which can be used for carrying out conjugate interference based on Laguerre-Gaussian beams and Mach-Zehnder interferometers to realize the measurement of micro-displacement. In order to achieve the above object, the present invention provides the following solutions: a micro-displacement measuring device based on Laguerre-Gaussian beam conjugate interference comprises a conjugate interference component, an imaging component and a processor; the conjugate interference component comprises an LG light generating component and a Mach-Zehnder interferometer, wherein the LG light generating component is in optical path connection with the Mach-Zehnder interferometer, the LG light generating component is used for generating first LG light with any controllable topological charge number and transmitting the first LG light to the Mach-Zehnder interferometer, and the Mach-Zehnder interferometer is used for transmitting the first LG light to an object to be detected and receiving second LG light which is reflected by the object to be detected and is conjugate with the first LG light and interfering the first LG light and the second LG light; the imaging component is used for shooting the interference process of the first LG light and the second LG light before the displacement of the object to be detected to obtain a pre-displacement interference image, and shooting the interference process of the first LG light and the second LG light after the displacement of the object to be detected to obtain a post-displacement interference image; The processor is used for processing the interference image before displacement and the interference image after displacement to obtain the displacement size and direction of the object to be measured. In some embodiments, the LG light generating component comprises a laser, a first beam splitting prism and a spatial light modulator, wherein the first beam splitting prism and the spatial light modulator are sequentially arranged along the laser transmission direction, the laser is used for emitting laser, the first beam splitting prism is used for transmitting the laser to the spatial light modulator, the spatial light modulator is used for carrying out phase modulation on the laser to generate first LG light with any adjustable topological charge number, the first LG light is returned to the first beam splitting prism, and the first beam splitting prism is further used for reflecting the first LG light to the Mach-Zehnder interferometer. In some embodiments, a polarizer is disposed between the laser and the first beam splitter prism, and the polarizer is used to adjust the polarization angle of the laser to adapt to the spatial light modulator. In some embodiments, a collimating and beam expanding device is arranged between the laser and the first beam splitting prism, and the collimating and beam expanding device is used for collimating and expanding the laser. In some embodiments, the Mach-Zehnder interferometer comprises a second beam splitting prism, a first standard reflector, a second standard reflector and a third beam splitting prism, wherein the second beam splitting prism is used for transmitting the first LG light to the first standard reflector and the second standard reflector respectively, the first standard reflector is used for reflecting the first LG light to the third beam splitting prism, the third beam splitting prism is used for tran