Small form factor microsensor system using optical MEMS for passive optical digital communications (PODC)

摘要

A small form factor microsensor system with optical MEMS devices is discussed in this paper. The key components in the microsensor system include a temperature and humidity sensor for environmental monitoring, a microprocessor for signal processing, and an optical MEMS device (active corner cube retroreflector or CCR) for remote free space optical communication. A flexible circuit design and a folded packaging scheme have been utilized to minimize the overall form factor. Flat, flexible polymer batteries are incorporated to minimize the vertical profile to a few millimeters. The entire fully packaged sensor system is about 30mmx30mmx6 mm. MEMS design of the CCR, fabrication, hermetic packaging of CCR, flexible circuit design and fabrication, flip chip bonding of die form microprocessor, and a battery replacement scheme for extended operation lifetime are crucial elements for the development of a real product for the microsensor system. Optical MEMS CCR is a torsion mirror design and was fabricated using surface micromachining with Si3N4 as a structural layer. A finite element analysis (FEA) model was developed to optimize design and performance of the MEMS structures. The sensor system has a miniature mechanical switch for local actuation and an optical switch for remote actuation. The applications of such a microsensor system include both tracking, tagging, locating (TTL) and remote sensing.