针对某型高分辨率空间遥感相机的性能特点，设计了一种调焦机构以补偿相机的离焦量。从传动机构、光电编码器和调焦控制系统等部分对调焦机构的精度进行了分析，论述了误差大小及产生的原因，计算了调焦机构总误差的理论值。采用闭环控制方式对机构的调焦精度进行测试，运用比对方法——分别处理调焦镜的直线位置变化数据和与之对应的光电编码器角度位置变化数据——得到调焦机构的精度为±3.1127 μm，与理论分析一致，验证了调焦机构设计的有效性。最后对测试方法及结果进行了分析，论述了两者产生差异的原因。实验数据表明，调焦机构的精度满足相机对调焦机构±10 μm的精度要求。

In accordance with the characteristics of a high resolution space remote sensing camera, a focusing mechanism is designed to compensate for defocusing. The accuracy of focusing mechanism is analyzed from the transmission mechanism, the photoelectric encoder and the focusing control system. Before calculating the total errors of the focusing mechanism, all of the causes and values of error are discussed. After testing the accuracy of the focusing mechanism with closed-loop control mode, the data of the encoder codes and the focusing mirror displacements are processed respectively. Contrasting the results, the accuracy of the focusing mechanism is obtained, equal to ±3.1127 μm, which is in accordance with the theoretical value, and it proves that the design of the focusing mechanism is effective. Finally, the reason of differences between the accuracy results of the encoder codes and the focusing mirror displacements is obtained after analyzing the testing method. The experiments show that the accuracy of the focusing mechanism meets the camera′s accuracy requirement of ±10 μm.