在由反射物旋转引起的非聚焦激光束自混合干涉基础上，研究观察了由反射体旋转引起的聚焦激光束自混合干涉现象。由此提出了一种聚焦激光束自混合干涉的角度测量方法。由于激光器出光口的孔径限制，利用非聚焦激光束的自混合干涉角度测量范围很小。在光路中添加聚焦透镜，使偏离出射光方向的激光束聚焦后重新反馈回激光谐振腔，进而产生自混合干涉。从而使得引起自混合干涉现象的旋转角变化范围扩大了一个数量级以上。由此提出的利用聚焦激光束自混合干涉现象的角度测量方法，测量范围可显著提高，并随着聚焦透镜的焦距减小，测量范围可逐步扩大。

Rotation of a reflector leads to a phenomenon of self-mixing interference (SMI) of a beam of unfocused laser. There are methods proposed for a measurement of angle by using the unfocused-laser SMI. However, the range of angle measurement is limited by the size of the utilized laser aperture. The SMI of the beam of focused laser is studied. A new approach to measure an angle by use of focus-laser SMI is proposed. The approach is able to achieve an angle measurement with an order of magnitude higher than the existent methods do. The increase of range in angle measurement by the proposed approach is achieved by placing a focusing lens into the optical path. The lens are used to collect the light, which deviates from emergent one, back into the resonator of laser. The SMI occurrs as a consequence of the collected light. The proposed approach is experimentally validated. The experiments also show that the increase in the focal length of the utilized lens can enlarge the range of angle measurement.