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CN-122017865-A - Generalized Doppler effect measurement method and device

CN122017865ACN 122017865 ACN122017865 ACN 122017865ACN-122017865-A

Abstract

The invention discloses a generalized Doppler effect measuring method and a generalized Doppler effect measuring device, belongs to the technical field of photoelectric detection and motion sensing, and aims to solve the problems that in the existing laser Doppler measuring technology, linear, rotary and vector effects are mutually independent, and complete vector information of a moving target cannot be obtained at one time through single laser. The method comprises the steps of generating and transmitting a spin-double-track angular momentum coupling light field to a moving target, receiving a scattering signal of the spin-double-track angular momentum coupling light field, converting the scattering signal into a time domain electric signal after polarization analysis, carrying out spectrum analysis on the signal to obtain a generalized spectrum containing a traditional Doppler signal peak, a Doppler polarization signal peak and two Doppler polarization vortex signal peaks, calculating the frequency shift according to the position of the frequency spectrum peak, and judging the moving direction according to the relative phase difference. The corresponding device comprises a narrow linewidth laser, a polarization modulation and coupling light field generation module, a 4F imaging system, a digital micromirror target simulation unit and a signal detection analysis unit.

Inventors

  • ZHANG YANXIANG
  • ZHANG ZIJING

Assignees

  • 哈尔滨工业大学

Dates

Publication Date
20260512
Application Date
20260203

Claims (10)

  1. 1. A generalized doppler effect measurement method, comprising the steps of: s1, generating and transmitting a beam of spin-double-track angular momentum coupling light field to a moving target, wherein the light field carries non-zero polarization order at the same time And non-zero orbital angular momentum order ; S2, receiving signal light scattered or reflected by the moving target; s3, enabling the signal light to pass through an analysis polaroid with adjustable transmission axis angle, and converting the signal light into a time domain electric signal by a photoelectric detector ; S4, the time domain electric signal Performing spectrum analysis to obtain generalized Doppler frequency spectrum containing four characteristic peaks, wherein the four characteristic peaks respectively correspond to a traditional Doppler signal peak, a Doppler polarized signal peak, a first Doppler polarized vortex signal peak and a second Doppler polarized vortex signal peak; S5, calculating the Doppler frequency shift according to the frequency position of the characteristic peak, and judging the direction of the Doppler frequency shift according to the relative phase difference between signals under different polarization analysis conditions.
  2. 2. The method according to claim 1, wherein in step S1, the electric field of the spin-double orbit angular momentum coupled light field is in a cylindrical coordinate system Is expressed as: Wherein, the For a complex amplitude that is related to the radial position, For the azimuth angle, For the initial polarization angle of the light beam, And Is of two orbital angular momentum orders and satisfies 。
  3. 3. The method according to claim 2, wherein in step S3, the time domain electrical signal The expression of (2) is: Wherein, the For the transmission axis angle of the analytical polarizer, Or (b) Respectively corresponding to right hand circular polarization or left hand circular polarization, For the time-varying phase introduced by the motion of the object, A plurality of doppler polarization vortex signal peaks is represented, including a first doppler polarization vortex signal peak and a second doppler polarization vortex signal peak.
  4. 4. A generalized Doppler effect measurement method according to claim 3, characterized in that, when the object is in a rotational motion, Wherein For the rotation angular velocity of the target, for the time domain electrical signal Performing time-phase differentiation or spectrum analysis to obtain Doppler frequency shifts corresponding to four characteristic peaks, wherein the Doppler frequency shifts are respectively as follows: In the formula, For the doppler polarization frequency shift, For the first doppler polarization vortex frequency shift, For a conventional doppler shift, For a second doppler polarization vortex frequency shift.
  5. 5. A method according to claim 3 or 4, wherein in step S5, the direction of the doppler shift is determined by analyzing the initial polarization angle shift Or linear polarization angle difference Induced relative phase difference Identification: Wherein, the The sign function is represented by a sign function, For Doppler polarization frequency shift First Doppler polarization vortex frequency shift Or a second Doppler polarization vortex frequency shift Linear polarization angle difference To analyze the amount of angle change of the polarizer.
  6. 6. The method according to claim 1, wherein in step S1, the spin-double orbital angular momentum coupling light field is generated by modulating a spatial light modulator in cascade with a vortex half-wave plate, specifically, the spin-double orbital angular momentum coupling light field is generated by modulating the spatial light modulator and then modulating the light field by using the vortex half-wave plate.
  7. 7. A generalized doppler effect measurement device for implementing the method of any one of claims 1 to 6, comprising, in order along an optical path: A narrow linewidth laser (1) for generating a Gaussian fundamental mode beam; the polarization modulation module is used for modulating the Gaussian beam into a horizontal linear polarization state; The coupled light field generating module is used for receiving the horizontally linearly polarized light and generating the spin-double-track angular momentum coupled light field and at least comprises a spatial light modulator (4) and a vortex half-wave plate (6); a first 4F imaging system for imaging the generated coupled light field to a target surface; The target simulation unit is arranged on the image surface of the first 4F imaging system and is used for simulating a target with set motion parameters; The signal collection module is used for collecting the signal light acted by the target simulation unit and comprises a non-polarized beam splitter (7), a second 4F imaging system and a band-pass filter (11); The polarization analysis and detection module is used for carrying out polarization screening on the signal light and converting the signal light into an electric signal and comprises an analysis polaroid (12) with an adjustable transmission axis angle and a photoelectric detector (13); And the signal processing unit (14) is connected with the photoelectric detector (13) and is used for collecting and analyzing the electric signals and obtaining generalized Doppler frequency spectrum.
  8. 8. The generalized Doppler effect measurement device according to claim 7, wherein the target simulation unit is a digital micromirror device (9), and the flip state and refresh frequency of the reflecting mirror plate are controlled by programming to simulate moving targets with different angular velocities, angular accelerations and rotation directions.
  9. 9. The generalized Doppler effect measurement device according to claim 7, wherein the polarization modulation module comprises a half-wave plate (2) and a first linear polarizer (3) which are sequentially arranged in a light path behind the narrow linewidth laser (1), and the analysis polarizer (12) is a second linear polarizer.
  10. 10. The generalized Doppler effect measurement device according to claim 7, characterized in that the first 4F imaging system is composed of a first plano-convex lens (5) and a second plano-convex lens (8), the second 4F imaging system is composed of the second plano-convex lens (8) and a third plano-convex lens (10), the unpolarized beam splitter (7) is placed at a confocal plane of the first 4F imaging system, and the signal processing unit (14) is an oscilloscope, has a fast Fourier transform function, and is used for transforming the electric signal from a time domain to a frequency domain and extracting the four characteristic peaks.

Description

Generalized Doppler effect measurement method and device Technical Field The invention belongs to the technical field of photoelectric detection and motion sensing, in particular relates to a Doppler effect measuring method and device based on a light field with a special structure, and particularly relates to a generalized measuring scheme capable of unifying and expanding the traditional linear, rotary and vector Doppler effects. Background The laser Doppler measurement technology plays an important role in the fields of fluid velocity measurement, structural vibration monitoring, atmospheric wind field remote sensing, moving target detection and the like by virtue of high response speed, wide measurement range, excellent precision and non-contact characteristics. Particularly in the real-time tracking and early warning scene of a high-speed dynamic target, the technology is not easily influenced by the change of atmospheric conditions, supports continuous observation, is well matched with a high-speed motion carrier, and shows considerable application prospect. Conventional doppler measurement techniques evolve mainly in two relatively independent directions. One is the linear doppler effect, which is based on planar lightwaves for detection. Since the direction of the energy flow of the plane wave is strictly parallel to the optical axis, the method can only be sensitive to the velocity component of the target along the axial direction of the light beam, and cannot be used for the transverse movement of the target. The second is the rotating doppler effect, which uses an orbital angular momentum beam with a helical phase wavefront. The energy flow direction of such a beam forms an angle with the optical axis, so that a rotation or a lateral translation of the object can be detected. Based on this principle, researchers have developed a variety of motion information inversion schemes suitable for different signal-to-noise ratios, working distances and alignment conditions. However, neither the linear nor the rotational Doppler method can determine the magnitude and direction of the Doppler shift simultaneously in one measurement by only a single laser shot and a single detection channel. To distinguish whether the target is approaching or moving away, existing schemes typically require the introduction of additional reference or comparison mechanisms. For example, heterodyne detection requires the introduction of a separate reference light path, the use of dual frequency vortex light requires complex frequency modulation of the light source, and the rotating laser light source approach relies on mechanically moving parts. These measures undoubtedly increase the complexity, cost and instability of the system, deviating from the principle that the measurement system should be pursued compact and robust. In recent years, the coupling phenomenon of spin angular momentum and orbital angular momentum in a light field becomes a research hot spot due to the high controllability and the richness of physical connotation. Based on this, the vector doppler effect is generated. The technology utilizes vector light beams (such as column vector light) with polarization states which are unevenly distributed in space as detection light, realizes the capability of simultaneously acquiring the size and direction information of Doppler frequency shift only by single transmission and reception, and marks the important progress of Doppler measurement from scalar information acquisition to vector information acquisition. It is worth noting that the vector doppler effect currently implemented is based on the coupling of spins with a single orbital angular momentum mode. The Doppler polarization signal generated by the method contains direction information, but is an independent form of a plurality of Doppler effects, and lacks of an essential theoretical correlation between a classical linear Doppler signal and a rotating Doppler signal, so that a more high-level universal framework capable of containing and unifying the effects is not formed. In view of the current situation, the laser doppler measurement field is continuously advanced and simultaneously faces a fundamental challenge that three effects of linear doppler, rotational doppler and vector doppler are in mutually separated and independently developed states for a long time. Each employing a different physical model and experimental setup for a particular motion component. The prior art cannot organically integrate the three components by a simple and unified principle and method, and obtain the complete vector information of the moving target in a single measurement by utilizing a single light beam without ambiguity. Therefore, a unified theory and technology system which can contain the existing Doppler effect and realize full-vector single-shot measurement in the true sense is constructed, and the method has become a key scientific problem and technical bottleneck