Optimized hybrid MOEMS sensors based on noise considerations

Micro mechanical light flux modulators enable high resolution inertial displacement sensors that are virtually free from reaction forces. The presented MOEMS (Micro-Opto-Electro-Mechanical System) transducer modulates the light flux of an LED by the relative movement of two aperture gratings one etched into a seismic mass and the other fixed to the sensor package. The modulated flux is registered by a photo transistor and amplified using a transimpedance amplifier. Theoretical examinations suggested that apertures featuring a high aspect ratio are performing best. Applying these design rules, an increase in sensitivity by a factor 4.72 to 0.532 μA/nm at a frequency of 10 kHz and an improvement in displacement resolution from 10.7 pm/ √Hz to 2.26 pm/ √Hz was found when compared to prior prototypes featuring a comparable mechanical characteristic. The system was also found to follow a linear characteristic over the tested amplitude range.