Lightweight mirror design method using topology optimization

Lightweight mirrors experience optical image degradation due to mechanical loadings such as self-weight, polishing pressure, and vibration. Optical surface deformation of a lightweight primary mirror is an important factor that affects optical performance. We use topology optimization to design a lightweight primary mirror under self-weight and polishing pressure. For the optimization, we used a 3-D model of the mirror and based our calculations on the rms surface error of the mirror as an objective function constrained by the maximum weight of the mirror. In the first example of topology optimization, we consider the mirror's self-weight loading. In the second example, we include the polishing pressure. We present the results of the optimized design topology for the mirror with various mass constraints. To examine the optimal design results, we manufacture a prototype of the mirror. (c) 2005 Society of Photo-Optical Instrumentation Engineers.