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In ultra-precision machining, the precision displacement measurement system is required to ensure the positioning accuracy of the tool and the work-piece, and then to ensure the processing accuracy of the product. The grating displacement measurement system which adopt grating pitch as measurement reference not only has big measurement span and high-resolution advantages but also has strong anti-interference ability. So it is widely used in performance testing of surface processing equipment. The traditional two-dimensional grating measuring system realizes two-dimensional measurement by installing two one-dimensional grating measurement devices in two directions of the two-dimensional platform. It’s easy to introduce the abbe error in this way and obviously a lot of space is occupied. While the micro-displacement measurement system based on the two-dimensional grating can not only obtain the micro-displacement data information of two directions at the same time, but also has high measurement accuracy, small abbe error and compact structure. Two-dimensional grating is the core component of the two-dimensional grating measurement system. In this paper, the design two-dimensional grating is carried out. In the case of vertical incidence of the He-Ne laser with 632.8 nm wavelength, we develop the microstructure design of two-dimensional aluminum-plated and gold-plated grating with periods of 1 micron and 2 microns. Based on the rigorous coupled wave theory (RCWA) and Rsoft software, the following simulation results are obtained. Two-dimensional grating with period of 1 micron has higher diffraction efficiency compared with period of 2 microns. When the duty cycle between 0.43-0.58 and the groove depth between 140nm-200nm, the diffraction efficiency of two-dimensional aluminum grating with period of 1 micron is more than 18%. Although the diffraction efficiency of two-dimensional gold grating with period of 1 micron can also achieve 18%, its tolerance range is very small.
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