Banyal Ravinder K, Ravindra B, Chatterjee S
Indian Institute of Astrophysics, Bangalore -560034, India.
Opt Express. 2013 Mar 25;21(6):7065-81. doi: 10.1364/OE.21.007065.
In this paper, an opto-thermal analysis of a moderately heated lightweighted solar telescope mirror is carried out using 3D finite element analysis (FEA). A physically realistic heat transfer model is developed to account for the radiative heating and energy exchange of the mirror with surroundings. The numerical simulations show the non-uniform temperature distribution and associated thermo-elastic distortions of the mirror blank clearly mimicking the underlying discrete geometry of the lightweighted substrate. The computed mechanical deformation data is analyzed with surface polynomials and the optical quality of the mirror is evaluated with the help of a ray-tracing software. The thermal print-through distortions are further shown to contribute to optical figure changes and mid-spatial frequency errors of the mirror surface. A comparative study presented for three commonly used substrate materials, namely, Zerodur, Pyrex and Silicon Carbide (SiC) is relevant to vast area of large optics requirements in ground and space applications.
本文利用三维有限元分析（FEA）对适度加热的轻量化太阳望远镜镜面进行了光热分析。建立了一个符合物理实际的传热模型，以考虑镜面与周围环境的辐射加热和能量交换。数值模拟清楚地显示了镜坯的非均匀温度分布和相关的热弹性变形，模拟了轻量化基底的潜在离散几何形状。利用表面多项式分析计算得到的机械变形数据，并借助光线追踪软件评估镜面的光学质量。进一步表明，热穿透变形会导致镜面形状变化和镜面表面的中空间频率误差。对三种常用基底材料，即微晶玻璃、派热克斯玻璃和碳化硅（SiC）进行的对比研究，与地面和空间应用中大面积大光学元件的需求密切相关。
