A MOEMS ACCELEROMETER BASED ON DIFFRACTION GRATING WITH IMPROVED MECHANICAL STRUCTURE

摘要

In this paper, an improved MOEMS accelerometer is described, which is based on integrated grating with phase modulation. This device is composed of a laser diode, an optoelectronic processing circuit and a sensing chip consisted of a piezoelectric translator, an integrated grating as a reflective mirror on a transparent substrate and a mechanical part of a bulk silicon proof mass suspended by four cantilevers whose upper surface acted as another mirror. This device generates a series of interference fringes by two diffracted beams when illuminated with coherent light, whose intensities are modulated by the relative distance between the grating and the proof mass. The intensities of the interference fringes varied with the distance alteration caused by external accelerations, which is proportional to the acceleration. It is realizable to get the magnitude of acceleration by using a differential circuit to detect the distance. A modified structure is introduced in this paper to obtain high sensitivity and reduce cross-sensitivity between different sensitive axes. Compared to experimental results before the simulation and theory analysis demonstrate that this modified MOEMS accelerometer has a good performance with higher static acceleration sensitivity of 3×10~3V/g and very low crosstalk.