鉴于马卡望远镜离轴能够减小因副镜遮挡引起的光能量损失，分析了马卡望远镜离轴使用时，合作目标和非合作目标发射和接收光路的区别。讨论了马卡望远镜在外差探测系统离轴使用时，发射能量提高，但外差效率下降的原因；在合作目标外差探测系统离轴使用时发射能量提高30%以上，外差效率也有很大提高；通过对散射体目标物和平面镜的测量，分别得到了17%和85%的外差效率，验证了马卡望远镜在合作目标外差探测系统中可以离轴使用。

The effect of off-axis use of Cassegrain telescope with different objectives on heterodyne detection probability is studied. In the non-cooperative target heterodyne detection system,when light is off-axially emitted from Cassegrain telescope,the emitted energy is increased while detection probability is declined. In cooperation target heterodyne detection system,the emitted energy is increased by 30%,detection probability is also increased greatly. The detection probabilities for the scattering object and mirror measured at laboratory are 17% and 85% respectively. It verifies that off-axis Cassegrain telescope can be used for achieving better performance in cooperation target heterodyne detection system.