Highly sensitive optical motion detector

With the growing trend in optical devices, Micro Opto Electro Mechanical Systems (MOEMS) are becoming commonplace in our lives. In the area of motion detection, there have been various types of seismic motion detectors but MOEMS still provide an edge over the others with its innate nature of being resilient to electromagnetic interference, having fast detection and also high sensitivity. The device mentioned here has a MEMS layer that has been successfully fabricated using double-sided deep reactive ion etching (DRIE) on an SOI wafer, which has never been used before in MOEMS. Design of the MEMS layer is based on a simple four-beam proof mass etched with 25 1500μm×30μm gratings through the proof mass. Light emitted from an 850nm laser module above the gratings will pass through to the photodiode below which captures the deflection of the proof mass due to inertial forces during motion. Proof-of-concept experimentations have been conducted on the device using a mechanical setup that would produce a force of maximum 10.42N unto the wafer. Results obtained have also successfully shown a waveform that has lower noise influence as compared to a commercial accelerometer used as a reference in experiments. The advantage of this device in motion detection, is that the size of the device can be greatly reduced due to simplified packaging without electromagnetic considerations. Manufacturing of the device would also be cheaper than other optical motion detector devices due to simplicity of design and usage of off-the-shelf laser modules and photodetectors.