空间相机调焦机构需具有一定的锁止能力，以应对火箭发射中的冲击与振动，因此，对机构的自锁特性进行评价是保证空间光学遥感器正常工作的关键。针对某型空间相机调焦机构，研究了螺纹接触面的滑移机理，建立了工程分析模型，详细分析了两种螺距(1 mm，1.5 mm)的螺纹的接触应力、切应力分布特征及其自锁性。结果表明：螺纹螺距为1 mm的调焦机构Mises应力值大于其自锁标定值，自锁失效；螺距为1.5 mm的调焦机构Mises应力值小于其自锁标定值，满足自锁要求。最后，对调焦机构进行了振动试验，结果显示：螺距为1 mm的调焦机构焦平面位移达2 753 μm，自锁失效；螺距为1.5 mm的调焦机构焦平面位移为6 μm，小于测量误差，机构自锁正常,验证了分析方法的可靠性。这种动力学环境下研究机构自锁性的新方法对工程应用具有重要的意义。

Focusing mechanisms in space camera needs to possess self-locking ability to resist the shock and vibration in the process of launching. Therefore, a self-locking analysis on the mechanism is the key of ensuring the space optics remote sensors work properly. This paper studied the sliding mechanism of thread contact surface under environments of vibration, and built a engineering models of the focusing mechanism of certain space camera with two types of screw pitch (1 mm,1.5 mm). Contact stress, shear stress distribution and self-locking ability of the mechanism were researched in detail. The results showed that the Mises stress value of focusing mechanism with screw pitch 1 mm was bigger than its calibration value of self-locking, which means self-locking lost efficacy. The Mises stress value of focusing mechanism with screw pitch 1.5 mm was under its calibration value of self-locking, which means self-locks was effective. Finally, a random variation test was performed on the focusing mechanism. The results showed that the focal plane's displacement of the mechanism with 1 mm screw pitch reached 2 753 μm, resulting in failure of self-locking. On the contrary, the focal plane's displacement of the mechanism with 1 mm screw pitch reached 6 μm, which was less than measuring error, the mechanism worked properly. It can be seen that the analysis approach proposed is effective, reliable, and provides a new way of researching the self-locking of focusing mechanism under the dynamic environment.