CN-121978701-A - Rotational Doppler speed measurement method and device for Gaussian mode emission and multimode optical fiber reception

CN121978701ACN 121978701 ACN121978701 ACN 121978701ACN-121978701-A

Abstract

The invention discloses a rotational Doppler speed measurement method and a rotational Doppler speed measurement device for Gaussian mode emission and multimode optical fiber reception, belongs to the technical field of photoelectric detection and sensing, and aims to solve the technical problems of complex system, high cost and poor robustness caused by dependence on active orbital angular momentum modulation and filtering in the conventional rotational Doppler speed measurement technology. The method comprises the steps of emitting single-mode Gaussian beams to a rotating target, receiving scattered echoes of the single-mode Gaussian beams by utilizing a multimode optical fiber, exciting a plurality of OAM modes, detecting optical signals output by the multimode optical fiber, obtaining a beat frequency time domain signal generated by multimode interference, carrying out spectrum analysis on the signal, obtaining a rotating Doppler spectrum containing equidistant spectral peaks, and calculating the rotating speed according to the spectral peak intervals. The device comprises a laser emitting module, a light receiving and converting module and a signal processing module which are connected in sequence. The invention can realize rotation speed measurement by using a conventional optical device without active OAM modulation and filtering.

Inventors

ZHANG YANXIANG
ZHANG ZIJING

Assignees

哈尔滨工业大学

Dates

Publication Date: 20260505
Application Date: 20260203

Claims (10)

1. The rotational Doppler speed measurement method for Gaussian mode emission and multimode optical fiber reception is characterized by comprising the following steps of: s1, light emission and scattering, namely emitting a single-mode Gaussian beam to the surface of a rotating target, wherein the Shan Mogao Gaussian beam is scattered by the surface of the target to form a scattered light field carrying target rotation information; S2, receiving the scattered light field by utilizing a multimode optical fiber, coupling the scattered light field into the multimode optical fiber, and exciting a plurality of transmission modes with different orbital angular momentum orders; S3, detecting optical signals output by the multimode optical fibers to obtain beat frequency time domain signals generated by pairwise interference among the transmission modes; and S4, performing spectrum analysis and speed measurement on the beat frequency time domain signal to obtain a rotating Doppler spectrum comprising a series of equidistant spectral peaks, and calculating the rotating speed of the rotating target according to the frequency interval between adjacent spectral peaks.
2. The method for measuring the speed of rotation doppler by gaussian mode emission and multimode optical fiber reception according to claim 1, wherein in step S1, a single-mode gaussian beam is emitted to the surface of a rotation target, specifically comprising: the method comprises the steps of generating narrow linewidth laser, coupling the narrow linewidth laser into a single-mode fiber for transmission, sequentially expanding, collimating and modulating a Gaussian beam output by the single-mode fiber into a linearly polarized single-mode Gaussian beam with controllable parameters, and irradiating the linearly polarized single-mode Gaussian beam onto a rotating target surface.
3. The rotational doppler velocimetry method for gaussian mode emission and multimode optical fiber reception according to claim 1, wherein said receiving the scattered light field by multimode optical fiber in step S2 specifically comprises: The method comprises the steps of collecting echo light scattered by a target surface by using a receiving optical system, arranging a band-pass filter in a light path of the receiving optical system to filter stray light except laser wavelength in the echo light, and coupling the filtered echo light into an input end face of a multimode optical fiber.
4. The rotational doppler velocimetry method for gaussian mode emission and multimode fiber reception according to claim 1, wherein in step S4, the rotational doppler spectrum is The method comprises the following steps: In the formula, In order to be a frequency of the light, For the orbital angular momentum order difference between adjacent pairs of modes, In order for the rotational speed to be the same, In order for the amplitude to be a magnitude, Is a dirac function.
5. The method for measuring the rotational doppler velocity by gaussian mode emission and multimode optical fiber reception according to claim 4, wherein in step S4, the rotational velocity of the rotating target is calculated according to the frequency interval between adjacent spectral peaks, and specifically comprises: Obtaining the frequency interval between adjacent spectral peaks in the rotating Doppler frequency spectrum According to the formula Calculating a rotation speed of the rotation target 。
6. A rotational doppler velocimetry for gaussian mode emission and multimode optical fiber reception according to claim 1, for implementing the method according to any one of claims 1 to 5, comprising: the laser emission module is used for generating and shaping a single-mode Gaussian beam and irradiating the single-mode Gaussian beam to the surface of a rotating target (12); The light receiving and converting module is used for receiving scattered back wave light from the surface of the target (12) and converting the scattered back wave light into an electric signal; The signal processing module is used for processing the electric signals to obtain the rotation speed of the rotation target; Wherein the light receiving and converting module comprises a multimode optical fiber (8) for receiving the scattered back wave light and exciting a plurality of transmission modes therein, and the electrical signal is a beat signal generated by interference between the plurality of transmission modes.
7. The rotational doppler velocimetry of gaussian mode emission and multimode fiber reception of claim 6, wherein the laser emission module comprises: a narrow linewidth laser (1) for generating a Gaussian fundamental mode beam; The input end of the single-mode optical fiber (2) is connected with the output end of the narrow linewidth laser (1) and is used for transmitting single-mode Gaussian light; the beam expansion collimator (3) is connected with the output end of the single-mode optical fiber (2) and is used for modulating and outputting the radius and the divergence angle of the single-mode Gaussian light; and the polarization modulation component is arranged in an emergent light path of the beam expansion collimator (3) and used for modulating the polarization state of the output light beam.
8. The rotational doppler velocimetry device of gaussian mode emission and multimode fiber reception of claim 7, wherein the polarization modulation assembly comprises: The half wave plate (4) is arranged in a light path behind the beam expanding collimator (3) and is used for adjusting the proportion of horizontal and vertical polarization components; And the linear polarizing plate (5) is arranged in the light path behind the half-wave plate (4) and is used for controlling the output light to be linearly polarized light.
9. The rotational doppler velocimetry of gaussian mode emission and multimode optical fiber reception of claim 8, wherein the light receiving and converting module comprises: a bandpass filter (6) for filtering out a rotational Doppler echo signal of a specific wavelength; the receiving optical system (7) is arranged in a scattered echo light path behind the band-pass filter (6) and is used for collecting echo light signals scattered by a target, wherein the echo light signals scattered by the target are multimode light signals; The multimode optical fiber (8) has an input end surface positioned at the image plane or conjugate plane position of the receiving optical system (7) and is used for transmitting the received multimode optical signal; And the photoelectric detector (9) is connected with the output end of the multimode optical fiber (8) and is used for converting the multimode interference optical signal output by the multimode optical fiber (8) into a beat frequency time domain electric signal.
10. The rotational doppler velocimetry of gaussian mode emission and multimode fiber reception of claim 9, wherein the signal processing module comprises: The data acquisition card (10) is connected with the photoelectric detector (9) and is used for converting the beat frequency time domain electric signal into a digital signal; And the host computer (11) is connected with the data acquisition card (10) and is used for carrying out spectrum analysis on the digitized time domain signals, identifying spectrum peaks with equal intervals in a spectrum, calculating frequency intervals and further calculating the rotation speed according to the frequency intervals.

Description

Rotational Doppler speed measurement method and device for Gaussian mode emission and multimode optical fiber reception Technical Field The invention relates to the technical field of photoelectric detection and sensing, in particular to a non-contact speed measurement method and device based on a rotating Doppler effect. Background The rotating Doppler effect is the phenomenon that the frequency of the received light is moved due to the rotation movement, and the frequency shift is [ ]) From orbital angular momentum (orbital angular momentum, OAM) order of internal mouldAnd rotational speedSize determination, i.e.. Unlike conventional linear Doppler effect, which can only detect the axial velocity of a target, the rotational Doppler effect can directly respond to the transverse rotational motion of the target, and can not only measure the rotational velocity, but also distinguish the rotational direction. The sensor based on the effect has the advantages of non-contact, high response speed, wide measurement range, high precision and the like, and has great application potential in the fields of deep space celestial body detection, dynamic target identification, aerodynamic test, turbulence monitoring, industrial nondestructive detection and the like. At present, the technical scheme for realizing the rotational Doppler velocity measurement mainly surrounds the generation and detection expansion of OAM light, and mainly can be divided into two types: the first type is internal mold coherent detection. The method generally adopts optical elements such as a spatial light modulator, a q-plate or a spiral phase plate, and the like, and the fundamental mode Gaussian light is modulated into an OAM light beam with a specific topological charge number at a transmitting end and irradiated to a rotating target. The receiving end receives the light beam modulated by the target and carrying the opposite OAM mode, heterodynes interference with the reference light, and inverts the rotation speed by measuring the frequency shift of the beat signal. Such methods require precise phase modulation devices and stable interference light paths. The second type is mode filtering detection. The method comprises the steps of transmitting Gaussian beams to a rotating target, filtering out specific OAM mode components from scattered echoes by using a mode selection device (such as another piece of spatial light modulator or a mode diffraction grating) at a receiving end, converting the specific OAM mode components back to Gaussian mode, coupling the Gaussian mode components into a single-mode fiber, and analyzing the intensity modulation frequency of the Gaussian beam after receiving the Gaussian beam by a photoelectric detector. Such methods also rely on complex pattern demodulation means. The above prior art, while verifying the feasibility of rotational doppler velocimetry, all suffer from the common limitation that the core relies on active modulation or selective filtering of the OAM optical field. This results in the system having to integrate expensive and light path alignment sensitive optics such as liquid crystal spatial light modulators, spiral phase plates, etc., which not only makes the whole set of apparatus costly, complex in structure, bulky, but also reduces its long-term stability and robustness in non-ideal environments such as vibration, temperature variations, etc. In addition, the complex modulation and demodulation process also limits the real-time nature of the measurement and the reliability of the system. Therefore, developing a rotational Doppler velocity measurement method and device without active OAM modulation/demodulation, which has simple structure, low cost and stable performance, becomes a key for pushing the technology to practical application. Disclosure of Invention The invention provides a rotational Doppler speed measurement method and device for Gaussian mode emission and multimode optical fiber reception, which aims to solve the technical problems of complex system, high cost and poor robustness caused by dependence on active orbital angular momentum modulation and filtering in the conventional rotational Doppler speed measurement technology. In a first aspect of the present invention, a rotational doppler velocimetry method for gaussian mode emission and multimode optical fiber reception is provided, comprising the steps of: s1, light emission and scattering, namely emitting a single-mode Gaussian beam to the surface of a rotating target, wherein the Shan Mogao Gaussian beam is scattered by the surface of the target to form a scattered light field carrying target rotation information; S2, receiving the scattered light field by utilizing a multimode optical fiber, coupling the scattered light field into the multimode optical fiber, and exciting a plurality of transmission modes with different orbital angular momentum orders; S3, detecting optical signals output by the multimode optical fibers