离轴三反空间相机调焦机构设计

Design of focusing mechanism for off-axis TMA space camera

空间相机受所处复杂运载环境(冲击、振动、过载)和空间运行环境(压力、温度、微重力)的影响易产生焦平面偏移。为提高成像质量,本文设计了一种利用丝杠螺母变向、直线导轨导向、倾斜导轨驱动且适用于反射式光学系统的新型高精度调焦机构来修正离焦量。该设计采用防冷焊措施、预压消间隙措施和双重防卡死设计,有效地提高了结构强度、刚度和可靠性,从而保证了调焦精度。介绍了其结构和工作原理,描述了相应的可靠性设计措施,最后通过精度检测试验对调焦机构进行了综合性能测试。试验结果表明:该调焦机构具备良好的自锁特性,其直线运动精度优于±2μm,重复定位精度优于±1μm;调焦行程范围内调焦反射镜摆角精度绕X轴和Y轴方向均优于±3.5″,满足用户提出的精度要求。

Space cameras are extremely vulnerable to the offset from its optimal position to the focal plane because of its complicated launch environments including shock, vibration and overload, and space operating environments, such as high vacuum, low temperature and micro-gravity. To improve the imaging quality, a new high-precision focusing mechanism for effectively compensating this offset was proposed to improve the adaptability of a camera by steering screw pairs, guiding parallel guide tracks and driving inclined-guides. In the design, schemes of anti-cold welding, gap relieving by pre- load and double anti-seize were adopted to improve the structural strength, rigidity and reliability and to guarantee the focusing precision. The structure and working principle of the mechanism were intro- duced and the design scheme for system reliability was described, then a synthetic test was performed. The test results show that the accuracy of linear movement and repeatability of the mechanism are less than ± 2μm and ±1 μm respectively, and the swing of the focusing mirror around X and Yaxes in the total focusing range are both less than ±3.5＂, which meets the requirements of the users.