Study On Grating Displacement Metrical System Using Phase Demodulation

In this paper,measurement principle and development state of optical grating technology are briefly introduced.The advantages and disadvantages of several grating measuring circuit designs are analyzed and compared with each other,and then a new plan is introduced to realize motive position measurement on the base of phase demodulation and a method of using FPGA devices with high speed is put forward to realize integrating designation.In this paper,measurement principle and the development state of grating technology are introduced.The paper briefly introduced programmable devices and hardware description language Verilog HDL.The procedure to realize this plan is set forth in details: first,in the light of modulation theory,the displacement signal is translated into the time signal;then,through digital phase detection,electronic division is achieved.The paper introduces the analogical circuit which realizes the modulation and digital circuit which realizes the function of division.The part of analogical circuit introduces the process of modulation of the grating system and presents the circuit of every part.The design of the digital circuit for the system has the character of modularization and all-purpose.The hardware is validated and optimized.The function is realized through the digital logic in a Ze5,and the number of the IC is decreased compared the traditional circuit.The new plan of design has the characters:High subdivision and convenient adjust; Subdivision and the direction-distinguished is achieved at the same time;The digital system is realized with credible capability;The design of hardware uses the method of soft-ware with the capability of ISP.The correct of the circuit is convenient.The debug of system improves the theory of the phase-distinguished is feasible.The system realizes the number of subdivision reaches 100 based on the 20um grating.The resolving power of the system reaches 0.2um.The highest tracking speed reached 120m/min.The paper presents the report of the integrate error analysis.