CN-116125487-B - Vortex beam comprehensive Doppler frequency shift measurement system and method

CN116125487BCN 116125487 BCN116125487 BCN 116125487BCN-116125487-B

Abstract

The invention discloses a system and a method for measuring comprehensive Doppler frequency shift of vortex beams. The system comprises a frequency modulation light source module, a superposition vortex light generation module, a mode selection and purity module, a moving target module and a signal receiving and processing module which are sequentially arranged, wherein the method is used for measuring the comprehensive Doppler frequency shift of a complex moving object with linear speed and rotation speed by changing the topological charge and the optical frequency based on a Doppler frequency shift formula by constructing a proper vortex light beam measuring system, so that the linear speed and the angular speed of the target object are obtained. Based on the comprehensive Doppler effect of vortex beams, the measuring light consists of superimposed vortex rotation with opposite topological charges, and the multidimensional movement information of the compound movement of an object is measured by fully extracting the movement information from the structured light interference field, so that the method has simple and direct extraction mode and strong operability. The invention has simple light path design, less use of complex optical elements and equipment, simple operation and strong subsequent integrability.

Inventors

CHEN JIA
WANG XINJIAN
WANG DAPENG
ZHANG RONGXIN

Assignees

厦门大学

Dates

Publication Date: 20260505
Application Date: 20230201

Claims (8)

1. The system for measuring the comprehensive Doppler frequency shift of the vortex beam is characterized by comprising a frequency modulation light source module, a superposition vortex light generation module, a mode selection and purity module, a moving target module and a signal receiving and processing module which are sequentially arranged; The frequency modulation light source module comprises a tunable laser, a superposition vortex light generation module, a mode selection and purity module, a moving target module, a signal receiving and processing module, a Doppler frequency shift obtaining module and a Doppler frequency shift obtaining module, wherein the tunable laser is used for generating laser radiation with different wavelengths to the superposition vortex light generation module, the superposition vortex light generation module is used for receiving the laser and then generating superposition vortex light with positive and negative topological charges and reflecting the superposition vortex light to the mode selection and purity module; The frequency modulation light source module comprises a tunable laser, a half-wave plate, an attenuation sheet, a first collimating mirror and a beam expander, wherein the tunable laser, the half-wave plate, the attenuation sheet, the first collimating mirror and the beam expander are sequentially arranged along the first light path direction along the same optical axis, and the tunable laser generates laser with different wavelengths, irradiates along the first light path direction, and irradiates to the superposition vortex light generating module after being polarized by the half-wave plate, attenuated by the attenuation sheet, collimated by the first collimating mirror and expanded by the beam expander.
2. A system for integrated Doppler shift measurement of a vortex beam as claimed in claim 1, The half-wave plate is used for matching the polarization direction of the laser with the polarization direction of the superposition vortex light generation module.
3. A system for integrated Doppler shift measurement of a vortex beam as claimed in claim 1, The superimposed vortex rotation generating module comprises a superimposed vortex rotation device and a loading server electrically connected with the superimposed vortex rotation device, wherein the loading server generates a phase diagram of topological charges, the superimposed vortex rotation device modulates laser into superimposed vortex light of positive and negative topological charges by utilizing the phase diagram, and the superimposed vortex rotation of the positive and negative topological charges is radiated to the mode selecting and purifying module along the direction of a second optical path.
4. A system for integrated Doppler shift measurement of a vortex beam as claimed in claim 3, The vortex light superposition method of the vortex light superposition device comprises one or more of a geometric mode conversion method, a spiral phase plate, a calculation holographic method and a spatial light modulator method.
5. A system for integrated Doppler shift measurement of a vortex beam as claimed in claim 1, The mode selection and purification module comprises a mode selector and a purifier which are sequentially arranged along the third light path direction and along the same optical axis, wherein the mode selector selects a specific mode of superposition vortex rotation and then reflects the specific mode to the third light path direction, the purifier comprises a first lens, a diaphragm and a second lens which are sequentially arranged along the third light path direction and along the same optical axis, the focal lengths of the first lens and the second lens are equal, and the diaphragm is used for filtering stray light of superposition vortex rotation.
6. A system for integrated Doppler shift measurement of a vortex beam as claimed in claim 5, wherein, The mode selector comprises one or more of blazed gratings, lenses, mirrors.
7. A system for integrated Doppler shift measurement of a vortex beam as claimed in claim 1, The moving object module comprises a motor for simulating the rotation of a moving object and a translation table which is movably connected with the motor and simulates the movement of the moving object, wherein the motor is provided with rotating pieces with different roughness, and after the superimposed vortex light is radiated to the rotating pieces, the rotating pieces generate scattering rebound waves and are captured by the signal receiving and processing module.
8. A system for integrated Doppler shift measurement of a vortex beam as claimed in claim 1, The signal receiving and processing module comprises a photoelectric detector and a signal acquisition card electrically connected with the photoelectric detector, wherein the photoelectric detector is used for capturing scattered rebound waves reflected on the moving target module, and the signal acquisition card is used for recording the scattered rebound waves captured by the photoelectric detector.

Description

Vortex beam comprehensive Doppler frequency shift measurement system and method Technical Field The invention relates to the technical field of Doppler frequency shift measurement, in particular to a system and a method for measuring comprehensive Doppler frequency shift of vortex beams. Background The vortex beam (OV) contains a spiral phase factor with a completely new degree of freedom-orbital angular momentum (orbital angular momentum, OAM). The topology charge can be any integer in theory, so photons have countless OAM orthogonal eigenstates, namely vortex light has high-dimensional characteristics. At present, due to the vortex and high-dimensional properties of OAM, OAM modes are applied to numerous classical and quantum fields, such as quantum entanglement, quantum invisible transmission, optical tweezers, super-resolution microscopic imaging, detection of rotating particles or physical angular velocity, etc. The vortex beam carrying OAM irradiates to the rotating physics to generate rotating Doppler frequency shift proportional to topological charge number and rotating speed. By utilizing the characteristics, richer and unique object attribute information can be acquired in object detection, such as accurate measurement of object (rotation) motion perpendicular to the direction of vision, and description of object surface attribute information can be acquired by measuring the orbital angular momentum spectrum of the object. Conventional methods for measuring and identifying targets are mostly centralized independent (translational or rotational), unidirectional measurements, such as translational measurements corresponding to the linear doppler effect and angular velocity measurements corresponding to the rotational doppler effect. However, in a practical environment, the action track of a moving object is generally multi-dimensional. How to extract and measure the multidimensional information of the target to obtain the physical data thereof is the bottleneck of the current research. Disclosure of Invention In view of the above, the present invention is directed to a system and a method for measuring a comprehensive doppler shift of a vortex beam, which can be used for measuring multidimensional motion information of an object, including a translational speed and a rotational direction in a spiral motion. According to one aspect of the invention, a system for measuring the comprehensive Doppler frequency shift of vortex beams is provided, which comprises a frequency modulation light source module, a superimposed vortex light generation module, a mode selection and purity module, a moving target module and a signal receiving and processing module which are sequentially arranged, wherein the frequency modulation light source module generates laser radiation with different wavelengths to the superimposed vortex light generation module, the superimposed vortex light generation module receives the laser to generate superimposed vortex light with positive and negative topological charges and reflects the superimposed vortex light to the mode selection and purity module, the mode selection and purity module selects the superimposed vortex light to emit purified superimposed vortex light to the moving target module after stray light is removed, the moving target module simulates a complex moving target with linear velocity and angular velocity, the purified superimposed vortex light emits to the moving target module to generate scattered rebound waves, and the signal receiving and processing module captures the scattered rebound waves and performs signal processing of feature extraction and target identification according to linear Doppler and rotational Doppler effects. According to another aspect of the present invention, there is provided a method for measuring a comprehensive doppler shift of a vortex beam, wherein the method includes: Converting the scattered rebound wave signals collected by the signal receiving and processing module into time domain light intensity signals, and obtaining Doppler frequency shift after the time domain light intensity signals are subjected to fast Fourier transform; Calculating by using vortex light with different topological charges and different frequencies, and measuring to obtain a complex moving target with rotational Doppler frequency shift and linear Doppler frequency shift. It can be found that, by constructing a proper vortex beam measuring system, based on a Doppler frequency shift formula, the comprehensive Doppler frequency shift of a complex moving object with linear speed and rotation speed is measured by changing topological charge and optical frequency, so as to obtain the linear speed and angular speed of a target object. The tunable range of the frequency modulation light source module is large, so that the frequency change generated by the Doppler effect is obvious, and the motion characteristics of the inversion target are more accurate. Based on t