Study on the MEMS Technique of Flat Capacitance Sensor with Double Equipotential Rings in Ultra-precise Optical Measurement

摘要

Geometric measurements based on optical methods have been studied, and the capacitance sensor is applied to detect the focusing displacement. In order to improve the edge effect of the fiat capacitance sensor, an equipotential ring is used. According to the Abbe principle, a double equipotential rings flat capacitance sensor with a central hole is developed. The axis of the optical system perforates through the hole of the sensor, thus avoiding the Abbe error. In order to get narrow gap between the equipotential ring and the electrode as well as thin electrodes, MEMS technique is applied to machine the capacitance electrodes, then the gap between the ring and the electrode can be no more than 10um, meanwhile the measurement accuracy can be promoted greatly. This paper emphasizes on the design of structure flat capacitance sensor and the manufacture of double rings capacitor with MEMS technique. After completing the circuit and finishing the experiment for testing the sensor, it can make further qualitative analysis on the result of the linearity and the sensitivity.