CN-116908819-B - Laser radar rotation Doppler correction method based on elliptical vortex beam

Abstract

The invention relates to a laser radar rotation Doppler correction method based on elliptical vortex beams. Vortex beams with structural phases are very sensitive to rotation and can be used for accurate measurement of rotational speed. However, when the vortex beam emitted by the laser radar does not coincide with the object rotating shaft, the rotating Doppler spectrum can be widened, and the signal-to-noise ratio of the signal is reduced, so that the application scene of the vortex optical laser radar is greatly limited. Aiming at the problem, a laser radar rotation Doppler correction method based on elliptical vortex beams is provided. Firstly, the intensity and the phase distribution of the vortex beam are adjusted by using a complex amplitude modulation method to prepare the elliptical vortex beam. By detecting an inclined rotating object by adopting an elliptical vortex beam with proper ellipticity, the rotating Doppler broadening effect can be almost completely counteracted, and the signal-to-noise ratio of a frequency domain signal is improved. The method is simple to operate, flexible and controllable, high in redundancy, capable of greatly increasing the detection distance and wide in application prospect in telemetry.

Inventors

• REN YUAN
• LIU ZHENGLIANG
• ZHU XIANGYANG
• FAN YAOHUI
• Tu Dianya
• WEN XINYI
• CHEN XIAOCEN
• LIU TONG
• TANG RUOYU
• DING YOU

Assignees

• 中国人民解放军战略支援部队航天工程大学

Dates

Publication Date

20260505

Application Date

20230714

Claims (1)

1. 1. A method for correcting the rotation Doppler of laser radar based on elliptical vortex beam includes such steps as preparing elliptical vortex beam for laser radar detection by complex amplitude modulation and coordinate conversion, detecting the inclined rotation object by said beam, receiving the scattered light from object by photoelectric detector to obtain time-domain signal, and Fourier transform to obtain corrected rotation Doppler spectrum; the method comprises the steps of using a complex amplitude modulation method and coordinate conversion to adjust the intensity and phase distribution of an overlapped vortex beam, preparing an overlapped elliptical vortex beam hologram with different ellipticity, loading the hologram on a spatial light modulator, using linearly polarized light to irradiate and spatially filter to obtain an overlapped elliptical vortex beam with ellipticity corresponding to the inclination angle of an object, and establishing an inclined rotation Doppler frequency shift model of the elliptical vortex beam as follows , Representing the rotational doppler shift frequency, Representing ellipticity, defined as the minor axis of the ellipse Divided by the long axis , The number of topological charges is represented, Represents the rotation speed of the motor, Representing the azimuth angle of the beam, Represents an inclination angle; Secondly, adopting the prepared ovality as Is the vortex beam detection dip angle When the ellipticity and the inclination angle are determined, parameters can be substituted into the formula according to the established rotating Doppler frequency shift model of the elliptical vortex beam to obtain a corrected rotating Doppler frequency spectrum, and when the ellipticity and the inclination angle of the object meet the relation In the time-course of which the first and second contact surfaces, Is degenerated into The corrected rotational Doppler spectrum is not widened any more, and the signal to noise ratio of the signal is improved compared with that before correction.

Description

Laser radar rotation Doppler correction method based on elliptical vortex beam Technical Field The invention relates to the technical field of interaction of laser radar, light and substances, in particular to a laser radar rotation Doppler correction method based on elliptical vortex light beams. Background Rotational movement is common in real life, and accurate measurement of the rotational speed of an object is a very difficult and important issue. Vortex beams are a type of wave front with spiral phase and carry spiral phase termsIs a special structure beam of (1), whereinRepresenting the number of topological charges and the number of topological charges,Is the coordinates of the azimuth of the device,Is imaginary. Unlike the radial linear doppler effect used by conventional radars, the rotational doppler effect is the frequency shift of echoes that a swirling beam can be sensitive to the rotational motion of an object. In the field of light-substance interactions, the swirling beam is therefore extremely sensitive to the rotational movement of the object, making it highly advantageous in terms of object rotation speed measurement. In 2013, lavery et al have first achieved rotational speed measurements of real objects using an overlapping vortex beam. However, most of the current studies on rotational speed measurement are performed under the condition that the optical axis coincides with the rotation axis of the object, and since this condition is hardly satisfied in reality, song et al studied the rotational doppler effect under the non-coaxial condition, and the studies indicate that the corresponding rotational doppler spectrum is widened when the vortex beam is obliquely incident to the rotating object. When the inclination angle is too large, the spectrum broadening effect is aggravated, the amplitude of the effective signal is reduced, the effective signal is gradually submerged in noise, and the rotating speed of an object cannot be extracted. In practical measurement, misalignment detection of a rotating object is quite common, so that the signal-to-noise ratio of a rotating Doppler signal is improved under the condition of inclination, and the rotating speed measurement accuracy is improved, which is a difficult problem to be solved. Disclosure of Invention In view of the above, the invention provides a laser radar rotation Doppler correction method based on elliptical vortex beams, which can improve the signal-to-noise ratio of laser radar echo signals under the condition of inclination detection. In order to achieve the above purpose, the technical scheme of the invention is as follows: A method for correcting the rotation Doppler of laser radar based on elliptical vortex beam includes such steps as creating the oblique Doppler frequency shift model based on elliptical vortex beam, using complex amplitude modulation method and coordinate transformation to obtain elliptical vortex beam, detecting the oblique rotation object by said beam, receiving the scattered light from object by photoelectric detector to obtain time-domain signal, and Fourier transform to obtain corrected rotation Doppler spectrum. The method comprises the steps of using a complex amplitude modulation method and coordinate conversion to adjust intensity and phase distribution of an overlapped vortex beam, preparing an overlapped elliptical vortex beam hologram with different ellipticity, loading the hologram on a spatial light modulator, using linearly polarized light to irradiate and performing spatial filtering to obtain an overlapped elliptical vortex beam with ellipticity corresponding to the inclination angle of an object. Wherein, firstly, a oblique rotation Doppler frequency shift model of the elliptical vortex beam is established: , Representing the rotational doppler shift frequency, Representing ellipticity, defined as the minor axis of the ellipseDivided by the long axis,The number of topological charges is represented,Represents the rotation speed of the motor,Representing the azimuth angle of the beam,Representing the inclination angle, detecting an inclined rotating object by adopting the prepared elliptical vortex beam, and obtaining a corrected rotating Doppler frequency spectrum by carrying out Fourier transform on the received time domain signal. Advantageous effects (1) The scheme is simple in design and convenient to regulate and control, on the basis of the original vortex-based optical laser radar detection scheme, an additional light path and an additional device are not required to be added, an elliptical vortex detection light source required by the laser radar can be modulated only by changing a phase hologram loaded to a spatial light modulator, meanwhile, the elliptical vortex light beam is simple to prepare, and the elliptical vortex light beams with different ellipticity can be prepared by modifying a single parameter. (2) The method can greatly improve the signal-to-noise ratio of the rotat