Design Of Measurement Algorithm Of Optical Feedback Strength Factor Of Optical Feedback Self-mixing Interferometry Systems

Optical feedback self-mixing interferometry (OFSMI) effect refers to that part of light emitted by a semiconductor laser (SL) is reflected or scattered by the external target and re-returns the inner laser active cavity and mixes with original light in the cavity, which causes a change of the laser output power. As the OFSMI signal carries motion and status information of the external reflective targets and information of the parameters of the SL itself, so it can be applied to measure the mechanical quantity, geometric quantity, and the parameters of the SL.The optical feedback strength factor (denoted by C) is an important parameter of OFSMI system, which reflects the feedback level of the system. The OFSMI signal performs different features in different feedback levels. Because of this, the measurement of feedback strength factor has theoretical and practical significance.This thesis mainly studies feature point measurement algorithm and the measurement algorithm in the frequency domain of C factor. System Generator is applied to design the system-level model of the measurement algorithm in the frequency domain of C factor. The main tasks in the thesis are as follows:1. According to the theoretical model of OFSMI, the influence that the parameters of OFSMI system has on OFSMI signal is analyzed, and the influence of C factor has on OFSMI signal is emphasized. Feature points of OFSMI signal in different feedback levels is classified.2. According to the characteristics of OFSMI signal in different feedback levels, the optical feedback phase reconstruction algorithm is designed. The relationship between the phase without optical feedback and the C factor is studied, and then the feature point measurement algorithm of C factor is put forward, which isverified through simulation.3. The relationship between the phase spectrum and the feedback strength factor in the frequency domain is analyzed, and then the measurement algorithm based on the frequency domain of C factor is proposed, which is also verified through simulation. 4. Apply System Generator, a kind of design tool for FPGA, to establish the system-level hardware model of the measurement algorithm based on the frequency domain of C factor in the Matlab/Simulink circumstance. Combine the Spartan3E development board with the OFSMI experiment platform to finish the simulation and the hardware co-simulation, and verify that the hardware model is feasible to work on the hardware platform. Compare the results of measurement with the two algorithms through experiment, and the efficiency is verified.