Active laser detection technique based on cat-eye effect has the advantages of long detection distance and high orientation precision. The reflected light intensity of the cat-eye system is 2–4 orders of magnitude higher than the general diffuse reflection intensity. Thus, laser active detection technology based on the cat-eye effect may realize accurate aiming and directional confrontation. However, few studies focus on the influence of a multi-band laser with a large incident angle on the echo distribution.
In a study published in Optics and Laser Technology, a research group led by Prof. CHEN Fei and his Doctoral student LV Zhe from Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) proposed a three-dimensional echo distribution calculation model of an obliquely incident multi-band laser based on the Collins diffraction integral formula and aperture function expansion as the sum of complex Gaussian functions. This three-dimensional echo-distribution calculation model is used to obliquely incident the multi-band laser on a cat-eye target. The spot centroid coordinates and target-missing quantity are introduced into the spot echo image for quantitative analysis.
By introducing the focal length dispersion formula into the optical transmission matrix, the analytical formula of three-dimensional light field distribution at the return of multi-band Gaussian beam after passing through the cat-eye optical lens under large angle oblique incidence can be derived. This can quantitatively analyze the wavelength factors and solve the lack of research on the influence of incident light wavelength in the study of cat-eye effect.
In the numerical simulation, the influence of the incident light wavelength and the incident light angle on the echo light field of the cat-eye target is mainly considered. The research shows that after the different wavelengths of the same central band of cat-eye target entering, the diffraction limit will be affected due to the factors of the wavelength itself. After reaching a certain distance, the maximum peak light intensity appears when the incident angle is zero. And when the incident angle reaches a certain value, the echo light intensity will drop sharply, which provides a new idea and method for obtaining the size of cat-eye target detector.
The theoretical model in this study provides a new method to obtain the target working band and target detector size for laser active detection, and it offers a trajectory-prediction theory for the laser active detection of cat-eye targets moving at high speed.
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