Design and noise consideration of an accelerometer employing modulated integrative differential optical sensing

A novel design of an open loop micromachined accelerometer is presented. Th e mechanical structure of the accelerometer is fabricated using bulk microm achining, which is then attached to a CMOS chip containing photodiodes and their readout electronics. The photodiodes are used to sense the movements of the proof-mass due to acceleration. Modeling of the accelerometer includ ing the mechanical, electrical and optical behavior of the sensor as well a s analysis of all its noise sources is described. A general expression for the noise equivalent acceleration (NEA) of the sensor is derived. A cantile ver suspended accelerometer is presented as a case study, its NEA is derive d and its optimal design with respect to the NEA is discussed. Finally, the fabrication and characterization of a first prototype are presented. The p rototype shows a NEA of about 85 mu g/root Hz, a natural frequency of about 1.2 kHz and a maximum acceleration > 5g. (C) 2000 Elsevier Science S.A. Al l rights reserved.