Study Of Laser Simultaneous Measurement Of Five-degree-of-freedom Errors

It’s the important means for high precision and high quality of product to measure the geometric positional errors of NC(Numerical Control) machine tools and typical three-axis machine centres in precise manufacturing. Dual-frequency laser interferometer, which measures one parameter each time, is a conventional method with low efficiency. Therefore, a highly integrated system for multi-degree-of-freedom measurement is in demand.A five-degree-of-freedom measurement system is investigated in this thesis and the method provides further analysis for six-degree-of-freedom measurement. The semiconductor laser module is used in this system due to its small volume and easy for pumping. The coupling of laser module with single-mode fiber reduces displacement and angular drift of laser beam, therefore’the accuracy of measurement reference can be guaranteed. The moving target, which consists of beam-splitter and cube-corner retroreflecor, is favorable for long-distance measurement due to its small volume and non-cable-connection property. The optical-to-electrical signal transform is achieved by using quadrant-detector(QD) and position-sensitive detector(PSD), which can detect the errors in the degree of freedom and convert them into analog signal. The data is collected by the single-chip microcomputer and sent back to computer via serial port. Therefore, the five-degree-of-freedom simultaneously measurement can be realized. In conclusion, the advantages of the system are small volume, high accuracy and low cost.The work accomplished in the thesis includes the design of optical system, the design of circuit, the software coding and the overall test. Based on the experimental results, the system has good repeatability and stability.In the range of working distance of lm, the resolution of the system is0.1μm for the straightness measurement and0.3" for angle measurement. The accuracy of the system is3u m for the straightness measurement in the range of±200, μm and2" for angle measurement in the range of±200".