The Three-dimensional Displacement Scanner Based On Planar Grating

Recently years, the rapid development of the industrial production put higher forward on the measuring accuracy, measurement dimension, measurement speed and volume system of precision displacement measurement technique.This topic research the integration of 3-dimensional displacement measurement system based on 2-dimensional grating, which can measure three-axis displacements simultaneously. At the same time, Littrow configuration is introduced in the optical system, which make the measuring range of z-axis enlarged. Combinated with a eight channels data acquisition card and the host computer display systems, the displacement measurement system can measurement the three-dimensional displacement synchronous and display real-time.The main contents are as follows:We propose the actual three-dimensional displacement measuring system, and complete the integration of the optical system. In the optical system, double grating splitting optical system is designed, which has the advantages of simple optical structure、easyly install and adjustment. In theory, the splitting optical system can be miniaturized to the size of 4 × 4 × 23 mm, which can meet the requirements of the optical system integration; A four step grating refractive element is des igned, compared to the previous two steps refractive elements, it doubles the diffractive efficiency, and effectively eliminate the interference of diffraction classes to the the optical signa. The four step refractive element solve the problem that the di aphragm must be inserted between the refractive elements and grating to filter out the interference of other diffraction times, which shorten the distance between the refractive elements and the gratings. Compared with the plane mirrors refractive element or lenses,the four-step refractive element is easier to install and adjustable, which can meet the requirements of the optical system integration; the installation and adjusting mechanical structure are designed depends on the optical path structure and optical components of the optical element size, and at last completed the integration of the three-dimensional displacement measuring system.In the circuit system, a eight-channel input data acquisition card is designed, which can real-timely collect and process the three-dimensional displacement signals. Firstly, research the identifying and counting principle, and analysis the look-up table method to quantify tangent segments. Then complete the design principles of the program’s 80 segments. Secondly, designing a data acquisition card based on FPGA, which can complete the eight channels acquisition and data processing, and programm PC system to complete data display and storage.At last test the overall system,the Final integrated optical system has the size of 130 × 130 × 683 mm, from the overall optical system‘s test results we can see, the integrated optical system can produce contrast clear optical signal, and the phase-change of the optical signal is in accordance with the displa cement of the mobile grating, all the testing results suggest the integrated design of the optical system is reasonable; The resolution of the data acquisition card test results show that it can achieve 80 segments features; the three-dimensional displacement measuring system‘s overall test showed, the measuring system has the resolution of 4nm in z-axis, while the three-dimensional displacement measuring system can measure 3-D displacement Real-time.