Practical Technology Of Laser Self - Mixing Interference Signal Processing

Along with the theory research of the laser self-mixing interference becoming more mature increasingly, this technology is applied in vibration, distance, micro-displacement, velocity measurement, and so on. However, the accuracy of the technology is required higher and higher. At the same time, the higher requirements of the system’s size, cost, display, real-time and other practical technologies are proposed.In this paper, a multifunctional signal generator based on MCU and DDS technology is designed, which is used for the modulation signal source in the current-modulated laser self-mixing interferometer. This signal generator has the advantages of small size, low cost, simple structure and convenient operation. Optional waveform, adjustable frequency and settable phase can be realized in this signal generator. The results of the experiment show that this signal generator is high accuracy and good stability; the waveform frequency is the same as the set one, and the output frequency range is large; the linearity of the triangular wave is also good. Because of these advantages, this signal generator can be met the requirements of the current-modulated laser self-mixing interferometer.In this paper, a LabVIEW program is designed for the acquisition and processing of the laser self-mixing interference signal, which is based on the demodulation principle of four-quadrant integral and used in the system of the EOC-modulated laser self-mixing interferometer. The experiment proves that this program has the characteristics of simple operation, beautiful display, etc.. And the system’s hardware circuit and software programming can be simplified. The real-time of the signal acquisition and data processing can be made.The Agilent5529A dual-frequency laser interferometer is selected to be the calibration device, and used for calibrating the measurement results of the EOC-modulated laser self-mixing interferometer. The AQB signal is used to control the5529A to make the dual-frequency laser interferometer and the laser self-mixing interferometer measure the same target synchronously, and realize the real-time calibration. A design of4-channel digital AQB signal is proposed in this paper, which is also based on LabVIEW. The hardware circuit can be simplified and the real-time calibration of the measurement results can be achieved.