Scattering Of Gaussian Beam By Object With Rough Surface And Its Application On Laser One-dimensional Range Profile

Study on Gaussian beam scattering from object with rough surface is of significant academic value and extensive application background in national defence and civilian technological fields. In this dissertation, the frequency and time domain scattering characteristic of Gaussian beam incidence on rough surface and object is systematically investigated, and some problem on laser one-dimensional range profile simulation are also discussed. The main works and results are as follows:1. Based on Kirchhoff approximation theory and plane wave spectrum expansion, the formula of the coherent scattering cross section of Gaussian beam scattering by two dimensional dielectric randomly rough surface is derived. When the beam waist radius approaches to infinity the result of beam scattering can reduce to that of plane wave case. The influence of beam parameters, rough surface dielectric property and polarization on the scattering cross sections is also numerically analyzed.2. The coherent and incoherent scattering cross sections of paraxial Gaussian beam scattering from arbitrarily shaped rough object with electric large size are studied and the calculated formulas are derived using plane wave spectrum expansion and physical optics approximation. The characteristic of beam scattering by some typical objects is analyzed, emphasis on the effect of beam parameters, roughness statistical parameters and dielectric property on laser radar scattering cross section (LRCS).3. Scattering of pulse plane wave and pulse beam by two dimensional dielectric randomly rough surface is investigated. The expressions of the two frequency mutual coherent function and pulse impulse response are obtained using the pulse scattering theory and Kirchhoff approximation. It is shown that the rough surface root-mean-square height is the main factor for pulse plane wave scattering. The frequency domain result of Gaussian beam scattering from rough surface is extended to the time domain and the effect of the beam waist radius is also discussed.4. According to Ishimaru's pulse wave scattering theory and the frequency domain solution of Gaussian beam scattering by rough object, the scattering of pulse Gaussian beam incidence on arbitrarily shaped rough object with electric large size is discussed. The coherent component of two frequency mutual coherent functionand pulse impulse response can be expressed as the product of frequency domain function and frequency difference function or time domain transfer function. Suppose that the velocity of object is much less than the speed of light and the pulse resolution element is much less than the object size, the pulse scattered power of moving rough object is obtained. It is shown that with the narrow pulse beam illumination the scattered return waveform will shift in the time coordinate and the phenomenon of the pulse spreading or compression will be observed. 5. Laser one-dimensional range profile simulation is studied based on the theory of beam scattering by rough object and the calculated formula of one-dimensional range profile is obtained. Consider the engineering application, the pulse laser radar equations with narrow pulse illumination is found. As examples, the range profile simulations are done for Lambert plate, sphere, circular cone and tank. The influence of pulse width, beam parameters and object shape on the simulation results is also analyzed.