提出了一种可用于小口径光束波面检测的横向剪切干涉仪。该干涉仪由偏振分光棱镜、光轴与其表面平行的晶体平板、1/4波片、反射镜及CCD构成。被测光束由偏振分光棱镜进行透射起偏和反射检偏，利用反射镜的反射两次经过晶体平板、1/4波片来实现剪切光束的等光程干涉。通过晶体平板剪切复制波面以获得小的剪切量，可用于小口径光束波面的检测。晶体平板的旋转可以改变剪切量，实现了不同口径不同波前的光束波面检测。对该干涉仪进行了仿真分析，得到了不同入射角情况下的剪切干涉图，仿真结果与理论分析结果相一致。实验中，旋转晶体平板得到的剪切干涉图与仿真结果相一致，很好地验证了该剪切干涉仪的有效性。

A lateral shearing interfeometer for the wavefront test of small beam is proposed. The interferometer is composed of a polarization beam splitter, a crystal plate, a quarter-wave plate, a mirror and a CCD detector. The polarization beam splitter is used both as a polarizer and an analyzer. The interferometer can test wavefront of low coherent light for its equal optical path length. Small shearing amount can be obtained by the crystal plate whose optical axis is parallel to its surface, thus it′s suitable for the wavefront test of small beam. The shearing amount can be continuously adjusted by rotating the crystal plate. Using ASAP software, the lateral shearing interferometer is simulated. The simulation result is well coincident with the theoretical derivation. In the experiments, the interferometer is built to obtain interferogram by rotating the crystal plate. The experimental result is well coincident with the simulation result. The usefulness of the interferometer is verified.