A Wide Range Linear Optical Accelerometer

[[abstract]]An optical accelerometer has been designed and fabricated using conventional KOH etching of 〈100〉-orientation silicon. The seismic mass acts as an optical shutter and consists of evenly spaced vertically etched slots. The shutter is suspended by two cantilever beams and controls the amount of light flux from a red light-emitting diode (LED) source reaching a PIN diode detector. The special structure of the device and the high aspect ratio (7.5) of the cantilever beams permit freedom of movement for the seismic mass (the shutter) along only one axis. The actual size of the device is 3 mm × 4 mm and its amplified output varies linearly from −3.6 to +3.6 V for static accelerations from −84g to +84g. The dynamic response of the device shows a flat relative sensitivity up to 700 Hz and increases to 21.9 dB at 3.2 kHz, which is the resonance frequency. The second harmonic appears at 6.8 kHz with a relative sensitivity of 9.9 dB. A dual diode structure is chosen for the photodetector to compensate for temperature drift and the amplified output voltage changes by less than 40 mV for a temperature variation from 25 to 50 °C when the applied acceleration is zero.[[fileno]]2030168010025[[department]]電機工程學