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为了进一步提高主动探测系统的回波信噪比和时空分辨率,采用蒙特卡罗法建立了参与性介质中超短脉冲激光的双程瞬态辐射传输模型。基于该模型,分析了各向同性散射介质中介质物性参数和目标反射特性对高斯脉冲激光回波信号角度特性的影响。研究表明,光学厚介质中,目标回波信号的入射天顶角已达到稳定状态,峰值角度区间为30°~40°,能量集中范围为30°~50°,且其时间展宽特性与所处角度区间无关;光谱衰减系数对回波信号的能量衰减和脉冲宽度均存在强烈影响,散射反照率则着重体现在后期回波信号的能量衰减上;镜反射引起的高强度前期回波信号减弱,镜-漫反射间目标回波信号的绝对差值极其微小,呈现弱关联性。可为选通摄像机的设计选型及脉冲激光器的波长选取提供参考借鉴。
In order to further improve the echo signal-to-noise ratio and space-time resolution of the active detection system, a two-way transient radiative transfer model of ultrashort pulse laser in participant medium was established by Monte-Carlo method. Based on the model, the influence of the medium parameters and the target reflection properties in the isotropic scattering medium on the angular characteristics of the Gaussian pulse laser echo signal is analyzed. The results show that the incident zenith angle of the target echo signal has reached a steady state in optically thick media with the peak angle of 30 ° ~ 40 ° and the energy concentration range of 30 ° ~ 50 °. The spectral attenuation coefficient has a strong influence on the energy attenuation and the pulse width of the echo signal, the scattering albedo is mainly reflected in the energy attenuation of the latter echo signal; the high-intensity pre-echo signal caused by the mirror reflection is weakened, The absolute difference of the target echo signal between the mirror and the diffuse reflection is extremely small, showing a weak correlation. It can provide references for design selection of strobe camera and wavelength selection of pulsed laser.