Double Grating Interference Based Displacement Sensor And Its Circuit System

With the development of modern manufacturing toward high precision level, displacement sensors with a large range and high accuracy are needed widely for accurate displacement measurement and calibration, precision positioning and etc. In this respect, a novel displacement sensor with large range and high resolution based on double grating diffraction and interference principle is introduced. The main contents and results of thesis are as follows:(1)The principle of double grating diffraction and interference based displacement measurement is analyzed. The structure of the displacement measuring sensor based on flexure hinge is developed.(2)Signal processing circuits for interference fringes are studied and designed. A photoelectric detector array and the analog signal conditioning circuit with low noise are adopted to convert the fringe signals to orthogonal sine signals.(3)A direction recognizing circuit based on hysteresis comparators and differentiators is developed to solve the problem that the counting accuracy is affected by noises in orthogonal sine signals. Counters based on MCU are designed,combined with the subdivision in software system, higher resolution is obtained(4)An analog signal sampling circuit based on USB and related software are developed to show the detector's sine signals on PC in real time, and a data transmission and display circuit based on RS232 are designed.(5)Testing experiments are conducted, factors which affect system accuracy and measuring range are analyzed, and some measures for improvement are proposed.Experimental results prove the strong anti-disturbance ability of this sensor, and its 2.5mm range with 10nm resolution and 1μm accuracy.