Research On Several Key Techniques And Instrumentation Of Nd:YAG Microchip Laser Feedback Interferometer

Microchip Nd:YAG laser feedback interferometers (LFI) can be applied to the non-contacted measurement of the displacement of objects with low reflectivity, which shows a bright prospect of application. However, in practical application, there still exists some aspects need to be improved and researched in the performance of LFI. For instance, it is difficult to collimation, there needs special sensitive card to get the laser beam and the measurement range small, without air compensation of refractive index, the original qusi-common path can’t meet the demand and etc. In this study, experiments are carried out to study the structure of LFI and the main factors of application on the basis of the research of basic characteristics of microchip Nd:YAG laser, and a set of more convenient for use with a larger range and higher accuracy Nd:YAG laser feedback interferometers which performance is high are designed.Microchip Nd:YAG laser is the core of LFI. In the research work of the basic characteristics of microchip Nd:YAG laser, power stability, polarization characteristics, waist radius, divergence and angle shift studied by experiment, which provide the required parameters for the optimization design of LFI; a device for laser adjusting is designed, which greatly improve the adjusting efficiency of microchip laser; a visible light indicating device is added for facilitating application; a collimating and beam expanding device which customized according to the basic parameters of microchip laser is added for measurement range expanding, the optimal beam expanding multiples is determined by experiment, and then the experiment of calibrated span is carried out for different roughness of the target; the refractive index of air compensating system which use automatic compensation is added for the real time compensation, and the compensation effect is verified by the experiment; a new common path device which can be moved freely is designed for extending the common optical path to reduce the measurement error.The optimization and instrumentation of LFI are completed in this dissertation, and some application researches are carried out, for instance, measuring the vibration of sound, measuring the thermal expansion of the object which under high temperature and etc. The measurement operation is just adjusting the propagation direction of LFI’s laser beam to make it shoot onto the surface of the target. The whole measurement process is handiness, high precision and non-contacted.