A Novel Micro-displacement Measurement System of Optic PathModulation Based on FPGA

摘要

A method for measuring micro-displacement using double gratings and two relative movable optical wedges isdescribed. Based on the theoretic analysis in Talbot image regionll in double gratings interferometer, we found that moire fringe only shifts with the optic path variation while its contrast does not decrease with both image distance and the thickness of phased object. A micro-displacement measurement sensor is designed based on this characteristic and verified by MATLAB simulation. In moire fringe hardware detecting system double-grating and phototransistors are employed, through which the moire fringe with the information of displacement is converted to sine electrical voltage in proportion to the intensity of moire fringe. Further than that, the signal process circuit, i.e. direction recognizing, eight-subdivision and counting circuit, is designed by using programmable logic device FPGA. And through the logical and timing simulation by VHDL software, the feasibility of method is proved.