基于Skew-Ray追迹法的均匀准直照明TIR透镜设计

依据LED点光源模型发光特性,以特定尺寸圆目标屏获得均匀准直照明为目标,采用Skew-Ray追迹法描述光线和设计TIR透镜,其中将透镜全反射区域进行简化处理,主要通过折射区域的双自由曲面相互配合控制光线实现照明目标。经过对透镜设计结果与1mm×1mm的LED扩展光源模型的组合进行非序列光线追迹模拟,模拟结果表明在距离光源2m范围内特定尺寸目标屏所获得光能利用率至少可达到79.6%,同时目标屏在近场和远场处照明均匀度可分别达到95.9%和83.9%,若以±1°作为光线准直半角标准,目标屏准直光线百分比可分别达到88.6%和73.8%。     

分级多尺度变换的水下偏振图像融合法

提出了一种分级多尺度融合的水下偏振图像处理方法.首先,利用非负矩阵分解对偏振参量图像进行融合增强,得到所含局部特征信息完整且冗余度低的偏振参量融合图像;在此基础上,基于二维经验模式分解分别将偏振参量融合图像与偏振强度图像进行多尺度变换,对得到的高低频子图像分别进行加权平均融合,融合权重是采用穷举搜索法计算得到;最后,将高低频融合结果反变换得到最终融合图像.实验仿真结果表明该融合方法在增强图像细节信息及提高水下偏振图像对比度方面具有显著效果.     

Single-camera panoramic stereo system model based on skew ray tracing

This study integrates panoramic imaging and stereo vision theory to propose an innovative 3D optical positioning method for single-camera panoramic stereo imaging systems. The conventional single-viewpoint theory based on pinhole modeling is replaced by a skew ray tracing methodology to establish the geometrical relationships of object and image. An analytical model of a single-CCD panoramic stereo imaging system is then established by adopting a catadioptric imaging system, a single-CCD stereo panoramic vision system and the presented skew ray camera calibration method.     

Performance evaluation of GRIN lenses by ray tracing method

Plastic gradient-index lenses produce clear images with negligible aberration and distortion. One of the methods for fabricating these lenses involves pulling up the core fiber vertically from a polymer solution whose refractive index has been adjusted to the desired value. Since the molecules from the solution diffuse into the inner layer, the monomer components are distributed in the radial direction. The monomer distribution is fixed in the photopolymerization process, and this forming process is repeated several times with adjusting the composition of the solution; hence, a specific refractive index distribution is obtained. We considered a numerical model of the interdiffusion process and analyzed refractive index distribution that could well reproduce the experimental results. Moreover, we employed the ray tracing method to calculate the modulation transfer function and used the transfer function to evaluate the GRIN lens performance. Simulation results showed that our evaluation method well duplicates the experimental results. We thus developed an integrated simulation method for the fabrication and performance evaluation of GRIN lenses.     

三维声线追踪的正三棱锥前向伸展算法

提出一种在三维空间中求取声路径的高速声线追踪算法。该算法在声线前进方向的局部微小空间作一小正三棱锥,以使其内部的声速场可近似为线性;由于在线性声速场中声线轨迹总是在一个平面内,所以可使用二维空间中的三角形前向伸展算法确定声路径。完成了该算法的理论推导,并通过数值模型对其进行了检验。实验数据显示该算法有较高的运算速度和精确度,比传统三维算法更加简洁可靠,可望应用于三维超声层析像重建的散射修正。     

激光光路追踪Wigner分布函数方法

提出了一种考虑衍射效应的激光几何光路追踪方法。引入由激光标量场定义的Wigner激光能量相空间分布函数,并给出该函数满足的刘维尔运动方程。Wigner分布函数用来描述经过空间任一点沿任一方向传输的激光光线上的能量分配。激光能量沿由波包色散关系定义的光线轨迹保持不变（真空中）或者衰减（等离子体中）。与传统几何光路追踪方法相比,该方法从理论上给出了激光光线初始携带能量份额的计算方法,并且将激光标量场的相位信息自然地包含在Wigner分布函数的定义里。算例表明,该方法与解析模型及广泛使用的菲涅耳衍射积分方法结果一致。     

激光光路追踪Wigner分布函数方法

提出了一种考虑衍射效应的激光几何光路追踪方法。引入由激光标量场定义的Wigner激光能量相空间分布函数,并给出该函数满足的刘维尔运动方程。Wigner分布函数用来描述经过空间任一点沿任一方向传输的激光光线上的能量分配。激光能量沿由波包色散关系定义的光线轨迹保持不变（真空中）或者衰减（等离子体中）。与传统几何光路追踪方法相比,该方法从理论上给出了激光光线初始携带能量份额的计算方法,并且将激光标量场的相位信息自然地包含在Wigner分布函数的定义里。算例表明,该方法与解析模型及广泛使用的菲涅耳衍射积分方法结果一致。     

一种结合室内空间剖分的声线跟踪法

声线跟踪法是应用于室内声场预测的几何声学模拟经典方法之一,但该方法的计算效率随着室内空间布局复杂度的增加而降低。为了高效地应用于各种室内空间布局,提出了一种结合室内空间剖分的声线跟踪法,该方法将整个室内空间剖分成有限个凸多面体子空间,以减少在声线跟踪过程中与声线求交点的墙面数量,并省略了碰撞点有效性判断,显著提高了计算效率,尤其适用于大型复杂的室内空间布局。     

A solar concentrator with two reflection mirrors designed by using a ray tracing method

Solar concentrators with two reflection mirrors are numerically designed by using a ray-tracing method to obtain higher concentration ratio when the concentrator tracing error is existed. The primary reflection mirror adopts paraboloidal mirror; the secondary mirror adopts hyperboloidal or ellipsoidal mirror. The optimal designed shape parameters for hyperboloidal and ellipsoidal cases are obtained, respectively. It is found that, when the concentrator tracing errors are 0°, 0.5° and 1°, the concentration ratios for hyperboloidal case are about 5837, 1954 and 1127 at f-number₁=0.22 and NA₂=0.62 and the one for ellipsoidal case are about 5860, 1993 and 1193 at f-number₁=0.25 and NA₂=0.62, respectively. Obviously, the concentrator with the ellipsoidal mirror is slightly better than the one with the hyperboloidal mirror.     

Geometrical optics-based ray field tracing method for complex source beam applications

Due to the fact that traditional ray field tracking approaches require a large number of geometrical optical(GO) ray tubes,they are very inefficient in many practical applications.An improved ray model scheme for a complex source beam(CSB) tracking technique is proposed in this paper.The source field can be expressed by a superposition of CSBs,then every CSB basis function has a Gaussian-type amplitude distribution and is suitable for replacing a GO ray tube in the ray tracing approach.The complex phase matching technique is adopted to find the reflected beam in the reflection point where local approximation is used to represent the curved surface in its neighborhood.A new solution to multiple reflections using the conventional right-handed reflected system is used to track the field easily.Numerical results show the accuracy of the proposed method.     

Application of the ray tracing method in studying tracks in SSNTDs

The ray tracing method was applied to study etched tracks from α-particles in CR-39 solid-state nuclear track detectors. The transmission mode of a microscope operation was simulated. A track was considered as a set of small triangular elements, and the brightness of all elements was calculated systematically through the entire track to create the final image. Preliminary results are given for α-particle tracks in the CR-39 detector for initial energies of 4 and 4.5 MeV, and incident angles of 40 and 90°, respectively. Total reflection, as well as the slope of a surface element in the track wall, were identified as the main factors that affect the brightness of that element. At this stage, comparisons with experimental results can be made in terms of the average grey levels for the entire tracks.