Moiré fringe measurement system of optical length modulation based on FPGA

A novel method for measuring moiré fringe is proposed according to moiré fringe characteristics in each interference region of double grating interferometer. Moiré fringe pattern in Talbot image region II only shifts with the thickness of phased object when adjusting its position. The phased object is composed by two relative movable optic wedges. The method of micro-displacement measurement using this optic characteristic in this region can be verified by MATLAB. A new embedded differential direction recognizing and 4-subdividing method for moiré fringes is adopted by using EP2C8Q208. In moiré fringe hardware detecting system, 4-subdividing, direction recognizing and counting module are designed, and logical and timing diagram is simulated by VHDL. In comparison with others, this design possesses low cost, high flexibility, high system synchronization and easy upgrade.