空间目标褶皱表面成像仿真方法研究

Imaging Simulation Method for Studying the Fold Surface of Space Targets

为得到空间目标高质量仿真图像,正确仿真目标包覆温控材料形成的褶皱表面十分重要。采用反向光线跟踪方法建立辐射传输模型,针对常用温控材料聚酰亚胺的褶皱表面引发的二次反射和材料的菲涅耳反射现象,采用余弦权重重要性采样对二次反射计算时的光线区间进行优化,改进了可描述菲涅耳反射现象的双向反射分布函数(BRDF)模型。利用3D建模软件生成并量化褶皱平面,在严重褶皱上重要性采样的均方根误差比均匀采样减小了63.42%,通过与实测BRDF值对比,改进BRDF模型能更好地描述菲涅耳反射,从褶皱平面仿真图像中可看到离散的强镜反亮斑。仿真的卫星图像褶皱表面细节纹理展示良好,阴影效果逼真,可为空间目标视觉导航算法研究提供图像数据。

To obtain high quality simulation images of a space target,simulating the folded surface of the target covered temperature-controlled material is important.This study employed the inverse ray tracing method to establish a radiation transfer model.The aim of this study is to calculate the secondary reflection that occurs on the folded surface of a polyimide material and the Fresnel reflection of the material.The cosine weight importance sampling method was used to optimize the ray interval during the calculation of the secondary reflection.Consequently,the bidirectional reflection distribution function(BRDF)model,which can describe the Fresnel reflection,was improved.Using a three-dimensional software program for generating and quantifying the fold plane,the root mean square error of importance sampling on severe folds was reduced by 63.42%compared with uniform sampling.Moreover,compared with the measured BRDF model,the improved BRDF model can better describe the Fresnel reflection and discrete strong mirror reflection spots were observed in the simulation image of the fold plane.Furthermore,the simulated satellite image shows the detailed texture of the folded surface effectively,and the shadow effect is realistic,which can provide image for the research of space target visual navigation algorithm.