在几何光学近似下，研究了非稳腔中的离焦像差的演化，解析地给出了正支共焦非稳腔中离焦像差的线性修正公式。结合氧碘化学激光器的模拟结果表明：光腔的放大率越小，像差演化的影响越明显；变形镜直接放在凹面镜处的补偿效果最好。对比直接补偿，考虑像差演化的补偿可以使光束质量的β值平均降低35%。

The evolvement of defocus aberration in unstable resonator is studied in geometric optical approximation. Linear correction in a positive branch cavity is obtained analytically. The simulation results from oxygen iodine chemical laser show that the smaller the magnification of the resonator is, the greater the influence of aberration evolvement becomes. Deformable mirror located at concave mirror can obtain the best compensation effect. The value of β can be reduced by 35% on average with considered aberration sensitivity compensation compared to the direct compensation.