Research Of Rotating Target Detection Technology Based On Beam OAM Characteristics

With the continuous research on the orbital angular momentum characteristics of the vortex beam,it has been found that the orbital angular momentum of the scattered vortex beam reflects the Doppler shift information by using the vortex beam to irradiate the rotating object,so that the rotation information of the object can be analyzed.This discovery not only broadens the application scope of vortex beams,but also lays the theoretical foundation for the research of vortex beams in the field of rotating target detection.In recent years,the superimposed vortex beam has attracted a lot of attention due to its unique light field distribution and orbital angular momentum characteristics.The study of the transmission and frequency shift characteristics of the superimposed vortex beam and its exploration in the field of rotating target detection is of great significance.The main contents of this thesis include:the field distribution of the superposed vortex beam is studied,the generation experiment of the superposed vortex beam is completed,the field distribution characteristics of the superposed vortex beam after rotating random rough surface at different transmission distances are studied,and the effect of different root mean square roughness of the random rough surface on the superposed vortex beam is numerically analyzed.The coherent detection principle is combined with the rotational Doppler effect to study the frequency shift characteristics of the superimposed vortex beam through the rotating random rough surface.The specific work carried out is as follows.1.Based on the Laguerre-Gauss mathematical model,the superposition state vortex beam generated by the superposition of two LG beams of equal topological charge and different sign is investigated.The light intensity distribution of the superposed vortex beams is numerically simulated,an experimental optical path is constructed to generate the superposed vortex beams,and the superposed vortex beams are obtained experimentally.2.Based on the angular spectrum diffraction theory,the expression of the light field of the superposed vortex beam after rotating random rough surface is derived,the light intensity distribution of the beam after rotating random rough surface is numerically calculated,and the effect of different root mean square roughness of the random rough surface on the light field distribution of the superposed vortex beam is analyzed.3.Based on the principle of rotational Doppler effect and coherent detection principle,the intensity-time expression of the superimposed vortex beam coherent with the reference light through the scattered field of the rotating random rough surface is derived;the intensity distribution of the scattered field superimposed with the reference light is numerically simulated,and the normalized intensity curves with time at different rotational speeds are formed,and the corresponding spectrograms are obtained,and according to the obtained frequency shifts,combined with the rotational Doppler Based on the obtained frequency shifts,the rotational speed of the rotating target is obtained by inversion with the rotational Doppler effect formula,and the correspondence between the rotational Doppler frequency shifts and the rotational speed of the rotating target is analyzed.The work carried out in this thesis provides a reference for the generation and modulation of superimposed vortex beams and their research in the field of rotating target detection.