强偏折场的光偏折层析重建技术

Deflection Tomographic Reconstruction of Strongly Refracting Asymmetric Refractive-index Field

强偏折场的重建是光学层析技术测量复杂流场领域的难点问题。在研究现有重建算法及其适用性的基础上,结合光线追迹算法提出基于曲线路径反演的正则化修正重建技术。该技术克服了现有重建技术中光路直进的假设,基于几何光学原理设计了光线通过强偏折场的积分路径追踪算法。使用代数重建技术和正则化重建技术相结合的思想,通过偏折角投影数据的迭代修正实现非线性反演。使用该技术对强偏折场进行数值重建,证实了其在有限角投影数据条件下重建大梯度折射率分布的有效性,并显示了其在刻画场关键特性方面相对于现有算法的优势。

When tomography is performed with strongly refracting field,refraction may cause sufficient bending of the probing rays.Ordinary reconstruction algorithm,based on the assumption of straight rays,does not yield accurate results.A new approach to curved-ray tomographic reconstruction of strongly refracting refractive-index distribution is proposed to realize a nonlinear inversion.A digital ray tracing method is designed for calculation of ray trajectory in inhomogeneous media.An initial estimate of the field is made by algebraic reconstruction technique.This estimate is then corrected by an iterative process in which computational ray tracing is used to generate deflection angles that are indirectly compared with the measured values.The reconstruction technique was tested by using simulated projection data of strongly refracting field for incomplete projection situation,and some reconstructed errors were discussed.