热图法测量激光强度时空分布的重构理论研究

为了把量热法应用于远场激光强度时空分布测量,研究了基于热像仪靶面温度测量反演入射激光强度时空分布的重构理论。针对背光面两种不同边界条件(对流-辐射热流边界和恒定温度边界)推导出了由靶面温度分布反演激光束时空分布的重构表达式。获得的分析表达式对广泛的材料具有适用性。通过引入广义参量F0=α/L2,分别就F0》1和F0《1情况给出了重构近似表达式,并对满足F0》1条件的回推算法进行了数值模拟验证。数值结果表明,两种背光面边界条件下回推得到的激光束时空分布与原始激光束达到了很好的一致,但存在一与靶材傅里叶数相关的最小起始回推时间τ0。成果可用于强激光远场参量测量设备的研制。

Reconstruction Theory of Laser Beam Intensity Temporal and Spatial Distribution Measurement by Thermal Image Method

To measure the far-field temporal and spatial distribution of laser intensity by using the calorimetric method, the reconstruction theory of incident laser intensity temporal and spatial distribution by calorimeter based target surface temperature inversion is studied. The reconstructing formula to inverse laser beam temporal and spatial distribution with target surface temperature distribution is derived, for different back surface boundary conditions, convection-irradiation heat current boundary and constant temperature boundary. The achieved expression is of extensive application for general materials. A generalized parameter F0=α/L2 is introduced, and the reconstructing formula is cataloged for F01 and F01 respectively. The above inversion algorithm is numerically simulated for F1. The numerical results show that the retrieved laser beam intensity distribution agrees well with the initial laser beam, and there exists a retrieving-time origin τ0 related to Fourier number of targets. The theoretical result can be applied to the development of high-intensity laser far-field parameters measurement system.