主三反射镜支撑结构是离轴三反生物成像系统研制过程中的关键技术难点之一，为了减少工作环境下主三镜面形变化，满足支撑系统稳定性要求，利用有限元方法对主三镜组件进行了优化设计。首先，根据光学系统设计要求确定了反射镜及其支撑结构的材料和支撑方式。接着，优化布局了反射镜底部3点和侧面6点支撑位置，设计了轻量化镜室结构。根据优化数学模型设计了圆弧悬臂梁式柔性铰链结构，分析了在重力工况下和温度载荷工况下各参数对镜面面形精度的影响。然后，对反射镜支撑组件进行了静力学和热力学仿真分析，分析结果为重力工况下镜面均方根值RMS为1.529 nm，温度变化4 ℃时镜面均方根值RMS为2.426 nm。最后，采用Zygo干涉仪对支撑作用下的主三反射镜和系统波像差进行检测，实测反射镜镜面RMS值为0.025 λ，系统波像差RMS值为0.102 λ(λ=632.8 nm)，基本满足了生物成像系统技术指标（主三镜镜面RMS≤λ/40，系统波像差RMS≤λ/10）要求。

Supporting structure for primary and tertiary mirror is one of the most challenging technical points during development of off-axis three-mirror anastigmatism (TMA) biological imaging system. In order to minish the shape error of the mirror and meet the stability of the supporting structure which was working, the mirror supporting structure was designed and optimized with finite element method. First, based on requirement of optical design, materials and supporting mode for the mirror and its supporting structure were decided. Then, a weight reduction structure of the mirror cell was designed which had three-point backside and six-point lateral support structure. The flexible hinge with circular and cantilever beam was made according to the optimized mathematical model. The influence of the parameters on the precision of mirror surface were analyzed under the load conditions of gravity and uniform temperature rise of 4 ℃. Then, the static analysis and thermal analysis for the mirror subassembly were performed. The Finite Element Analysis (FEA) indicated that the surface error (RMS) was 1.529 nm at self-weight. RMS value was 2.426 nm when the temperature rised 4 ℃. Finally, the surface figure test and the wavefront aberrations test were carried out by using Zygo interferometer. The test RMS value of the surface figure is 0.025 λand the wavefront aberrations of the optical system is 0.102 λ (RMS). The results show that this supporting system could meet the technical indicator requirements of biological imaging system (RMS value of the shape error ≤λ/40, RMS value of the wavefront aberrations≤λ/10).