离轴抛物面镜广泛应用于高能短脉冲激光装置的无像差聚焦打靶，随着对焦斑能量的需求越来越高，大多采用多路激光聚焦打靶，对聚焦元件提出了新的要求。大口径拼接抛物面镜可确保光学元件面型精度优于λ/4，且具有较好的可扩展性，90°离轴设计能有效增加激光的聚焦效率。基于几何光学和衍射光学，分析了90°拼接离轴抛物面镜作为聚焦终端时，拼接子镜的角度和位置失调对聚焦光斑的影响。结果表明，面外角度倾斜和光轴方向面外位置失调对焦斑斯特列尔比和20 μm直径环围功率比的影响远大于面内旋转角和位置失调，在进行拼接设计时无需补偿面内失调量；计算得到角度倾斜与位置失调的精度分别为±0.5 μrad和±105.3 nm，并采用蒙特卡罗误差分析对拼接后抛面镜的空间聚焦性能进行了预测，在该精度条件下可满足要求。

Off-axis parabolic mirror is extensive used in non-aberrant targeting by high energy short-pulse solid-state laser. With the incremental requirement for focal energy, the multi-laser focal target is often applied, which puts forward a new request for focusing element. The large-bore tiling parabolic mirror can ensure more that the profile accuracy is over λ/4 and has good augmentability. 90° off-axis design can effectively increase focal efficiency. Based on geometrical optics and diffraction optics, the focal character of 90° off-axis segmented parabolic mirrors has been studied and the misalignment of angle and position are concerned. The results show that the out-of-plane tilt/tip and piston are the main factor affecting strehl ratio and power ratio in a 20 μm-dia meter barrel, discarding the in-plane rotary and decent in active control. The accuracy of tilt/tip and pistion are respective ±0.5 μrad, ±105.3 nm, and the focal performance is predicted by Monte-Carlo tolerance analysis. Under the situation, the ideal focal spot can be afforded for application.