In this study, an improved MOEMS (micro-optical electronic mechanical system) accelerometer based on integrated grating with phase modulation is proposed. This device is composed of a laser diode, an optoelectronic processing circuit, a sensing chip (consisting 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 a coherent light source, whose intensities are modulated by the relative distance between the grating and the proof mass. The intensities of the interference fringes varied with alterations in the distance caused by external accelerations that are proportional to the acceleration. The magnitude of acceleration can be calculated by using a differential circuit detecting the distance. The modified structure introduced in this paper obtains high sensitivity and reduces cross-sensitivity between different sensitive axes. The 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 x 310V/g and very low crosstalk.
Phase modulation detection with liquid crystal light valve and digital holography
