Focused Laser Self-Mixing Interference And The Application In Angle Measurement

Self-mixing interference(SMI) is that when the light emitted from the laser is reflected back through the external object, interferes with the light inside of the laser. Compared with traditional optical interferometer, laser self-mixing interference measurement system has only one optical channel. Therefore it has the advantages of compact and simple structure, easy collimation.Angle change of the external reflection caused the optical path length change of feedback light. The change can be calculated based on the relative positional relationship. But the size of the mouth of laser is too small. So it is difficult to achieve a wide using of measuring angle.This paper discusses the phenomenon of focused laser self-mixing interference. And it measures the focal length of lens according to the feature of laser self-mixing interference. This paper presents a new method of angle measurement based on focused laser self-mixing interference. It greatly improve the angle measurement range.This paper builds the angle measurement model based on focused laser beam mixing interference. And the experimental system has been set up. Experiments confirmed that the accuracy of angle measurement based on focused laser self-mixing interference up to 10-4 degrees. And it increases the angle measurement range from 0.06 degrees to 1.06 degrees. The measuring range increases nearly 20 times. With decreasing the focal length of the microscope objective, the measurement range can be further expanded.