利用干涉法测量自由曲面的面形时，针对曲面曲率梯度较大的局部区域，由于干涉条纹的密度过大，无法通过干涉图获取对应的面形信息。针对这一问题提出一种基于多光束的自由曲面干涉检测方法。在干涉测试臂中，采用不同角度的多光束作为测试光，当测试光的入射角与局部被测曲面的曲率相匹配时，该区域形成的干涉条纹密度降低。通过将不同入射角度的光束照射至曲面，实现对被测曲面全口径面形的测量。该方法不需要补偿元件，也不需要机械装置调节自由曲面的位置。对测量过程中形成的干涉图进行仿真，为系统的设计和构建提供基础。

When the test wavefront is strongly aspheric, the minimum fringe spacing is too small to acquire the phase value for interferometry. A technique for the measurement of free surfaces based on multiple test beams is presented. Multiple test beams under different in cident angles illuminate the free surface. When the incident angle matches with the curvature of an area under test, the fringe density in this area is reduced. In this way, the full-aperture measurement of free surfaces can be performed. The advantage of the method is that no null and no mechanical movements of the test surface are needed. In order to support the system design, the interferogram of the system is simulated and analyzed.