| Measurement technique has close relationship to every department of the national economy and the development of the science and technology in all fields. High precision planar displacement measurement has been a hot in area of precision measurement research. The rapid development of modern science and technology, particularly information technology, MEMS technology, nano-technology, aerospace technology, have the growing demands for measurement technology. In micro-displacement measurement method, grating technology with high accuracy, large range of measurement, relatively low environmental requirements and the advantages of wide application. In particular, in recent years, grating measurement systems develop to the nano-precision. Grating for the high-precision measurement applications has a broad application prospects. Modern precision measurement technology is a set of optical,electronic,sensors,image,manufacturing and computer technology. It involves a wide range of subject areas, so the development of it needs a large number of related subjects for their support. Integrated current precision measurement technology development, precision measurement technology generally towards the measurement of high-speed, systematic, more compact structure stability, maneuverability and further improve the level of automation in the direction of development.At home and abroad, the method with the nanometer level measuring accuracy by the tunneling microscopy (STM), atomic force microscopy (AFM) of the technical resolution (0.1mm) and the measuring accuracy is highest. Used to detect nano-scale spatial variability, this two kinds of technical representative of the modern survey entered molecular and atomic era. However, the current scope of the measurement equipment smaller, usually dozens of micron measurement and harsh environmental requirements, need to take measures to improve the isolation and equipped with sophisticated sensor movement servo control system, the high cost of equipment. The laser has been published since 1960, because the laser has monochromatic, the coherence and the directivity good, the light intensity higher characteristic, very quickly becomes the precise optical measurement the ideal light source, each kind of type laser interferometer takes the linear measure datum by the vacuum in laser wave length, not only can realize the high accuracy fast non- contact survey, moreover the system structure is simple, the ingredient is low, therefore obtained the rapid development in the ultra precision measurement domain.Concentric 2D grating technology has the merit of one-dimensional grating measurement, simultaneously on two-plane direction of the displacement measurements, providing a solution to the high precision 2D measurement. So the concentric circles grating precision measurement applications in the study have practical significance.In this paper, we make an investigation to the rings grating displacement measurement system and its key technology for a theoretical and experimental study, the main contents and work include:(1) We established the mathematic model of two concentric-circle gratings. By analyzing the moire fringe of two concentric circle gratings, we proposed a measure method of two-dimensional plane displacement. (2) By using a low-pass to moire fringe we obtain the real moire fringe. Then we used the Fourier series transformation technique and the phase analyze, calculated out the eccentricity magnitude and direction.(3) We discussed the influence of noise. The computer simulation experiment demonstrates that this method has high precision. The measuring accuracy of angle is less than 0.002 radian, the measuring accuracy of eccentricity is less than 0.04 pixel when eccentricity within 20 pixels. And moreover, this measure method has the betteranti-noise property. |
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