M. Daneman

Linear microvibromotor for positioning optical components

We report an electrostatically driven linear microvibromotor fabricated using surface-micromachining technology. This device is developed for use in actuated micro-optical systems on silicon. Its submicron positioning resolution and a travel range of over 350 /spl mu/m are excellent properties for this application. Vibromotor precision and velocity are characterized, and various drive methods are discussed. A simulation of the vibromotor dynamics is presented to explore optimization and control issues for this device.

Surface-micromachined mirrors for laser-beam positioning

Abstract Actuated surface-micromachined polysilicon micromirrors for laser-beam positioning have been designed and fabricated. Two types of beam-steering mirrors are discussed which use microhinge technology to achieve the required vertical dimensions and functionality. One mirror, intended for precise beam positioning as needed in optical alignment, is actuated by linear microvibromotors. The other mirror is appropriate for laser-beam scanning and uses electrostatic comb-drive actuators. Four layers of polycrystalline silicon are micromachined to form these devices. Environmental stress testing carried out on the beam-positioning mirror has shown its structure to be relatively insensitive to vibrations below 60 kHz. Further testing has shown negligible changes in mirror position for temperatures varying between 25 and 200°C, and stability under the stress of laser irradiation of 375 mW at 1.06 μm wavelength.

Laser-to-fiber coupling module using a micromachined alignment mirror

We report the fabrication of a laser-to-fiber coupling module that incorporates a movable silicon-micromachined alignment micromirror. The micromirror can position a beam on a fiber within a 0.17 /spl mu/m standard deviation and has a range of motion of more than 200 /spl mu/m. Measurements on the module have shown a reproducible coupling efficiency of 40%. The coupling module provides a means to compensate for placement inaccuracies of passively assembled optical components.

Quadrature FM gyroscope

A dual mass vibratory gyroscope sensor demonstrates the quadrature frequency modulated (QFM) operating mode, where the frequency of the circular orbit of a proof mass is measured to detect angular rate. In comparison to the mode-matched open loop rate mode, the QFM mode receives the same benefit of improved SNR but without the penalties of unreliable scale factor and decreased bandwidth. A matched pair of gyroscopes, integrated onto the same die, is used for temperature compensation, resulting in 6 ppb relative frequency tracking error, or an Allan deviation of 370 deg/hr with a 70 kHz resonant frequency. The integrated CMOS electronics achieve a capacitance resolution of 0.1 zF/rt-Hz with nominal 6 fF sense electrodes.

11.2 3D ultrasonic fingerprint sensor-on-a-chip

The increasing popularity of mobile devices such as smart phones in applications including smart payments and personal health sets a pressing need for improved security without compromised ease of use. Fingerprint recognition has emerged as a particularly attractive option. Unfortunately, present capacitive solutions suffer from poor accuracy in the presence of contamination such as perspiration, and in addition are easily compromised, e.g., with fingerprints recovered from the device surface.

A 6×5×4mm 3 general purpose audio sensor node with a 4.7μW audio processing IC

We present a complete, fully functional energy-autonomous audio sensor node with 6×5×4mm3 form factor. The system uses a new audio processing IC integrated with a MEMS microphone, general purpose 32-bit processor, 8Mb Flash, RF transceiver with custom 3D antenna, PV cells for energy harvesting and battery. The 4.7μW audio processing IC performs audio acquisition with 4–32× compression. The complete stand-alone system achieves 38mins of speech recording and energy-autonomous operation in room light.