通过对几何光学和物理光学模型的数值计算，分析了自适应光学系统中小像差畸变波前在空间自由传播时自身的变化情况，进而给出了系统中对变形镜和波前探测器与被校正瞳面之间共轭位置关系的要求和允许范围。结果表明，波前自由传播时的变化程度决定于像差自身的类型和大小、光束的口径以及传播的距离，大口径小像差波前近距离传播时波前变化误差很小。一般来说，变形镜和波前传感器偏离被校正瞳面共轭位置距离满足菲涅尔数大于1000 时，对系统校正效果的影响可以忽略。实际应用中，应该根据校正对象的特征来具体计算波前误差随传播距离的变化，从而设计波前传感器和变形镜的位置，以及选择使用4F 光学系统。本文的分析可以为自适应光学系统的整体光路设计提供一定理论参考。

Based on the geometry optical theory and the diffraction optical theory, the variety of wavefront error with the propagation distance in free space is analyzed, so the spatial conjugation request of deformable mirrors, wavefront sensors and the corrected pupil in the Adaptive Optics (AO) system are presented. The results show that the propagation distance, the aperture of beam and the magnitude of the aberration affect wavefront error together. The wavefront variety is not distinct for small aberrations near propagating with a big aperture. Generally, the system’s compensation capability doesn’t decrease when the wavefront sensors and deformable mirrors depart from the conjugation position in some range whose Fresnel number is more than 1000. The positions of wavefront sensors and deformable mirrors should be designed and the 4F optical system is selected according to the character of the aberrations. This paper will provide some theoretical reference for the optical design of the AO system.