A Three-degree-of-freedom Detection System Based On Laser Interference Type

In the field of modern high-tech like precision and ultra-precision machining, microelectronics, automation testing and aerospace, using laser interference method to measure three-degree-of-freedom of working table or motion guide has great theoretical and practical significance. Based on the case of domestic and foreign research on the multiple degrees measurement with laser interference, a new optical system for simultaneous detection of three-degree-of-freedom is designed, using the relevant theoretical knowledge. The main research contents are as follows:Firstly, referenced to the traditional Michael interference system, the three-degreeof-freedom measurement system based on laser interference is designed. Through the beam propagation vector analysis, the optical system can be proven feasible to realize. The optical system optimized the measuring light path which don’t contain feedback light. At the same time, using PZT to modulate dynamic fringes and using four-quadrant photodetector to recognize the interference fringes.Secondly, the mathematical model between the fringe shape parameters and the deflection angle of guide rail is established. Then the relationship of theory between fringe shape parameter and the four-quadrant photodetector phase is deduced. So it is easy to get the deflection of the worktable by the phase difference of the quadrant photodetector. The displacement measurement is completed by conventional four major subdivision of the counts, which the main theory of it is the change of fringe shift measured. What’s more, the validity of the fringe signal which satisfies the counting condition is analyzed.Thirdly, the overall design of the subject is described. The optical structures are designed and machining.Meantime the paper have designed and finished machining optical structures. Using the STM32 which based on ARM Cortex-M3 kernel to acquire and process the signal of interference fringe. The communication between STM32 and piezoelectric ceramic controllers through human-computer interaction interface. Interactive interface is an intermediary in communication between the PZT controller and the STM32. Interference fringe signal through the four-way AD sampling, which can be used to measure the workbench angle deflection by the application of ellipse fitting algorithm to extract the phase difference. And two of the four sampling signals are used to measure workbench linear displacement by differential and reshaping and then subdivision counting,;Finally, through the actual project of micro cantilever vibration displacement measurement, using the algorithm which have been proposed to verify the theories of measurement are correct. The result of the ultimate displacement measurement achieve high accuracy. This can totally indicate that the feasibility of the extraction of the phase difference and the reliability of the programming. At last, the equivalent phase distance between the four quadrant photoelectric detector is verified by simulation.