Emilio Volpi

Wafer-level vacuum packaged resonant micro-scanning mirrors for compact laser projection displays

Scanning laser projection using resonant actuated MEMS scanning mirrors is expected to overcome the current limitation of small display size of mobile devices like cell phones, digital cameras and PDAs. Recent progress in the development of compact modulated RGB laser sources enables to set up very small laser projection systems that become attractive not only for consumer products but also for automotive applications like head-up and dash-board displays. Within the last years continuous progress was made in increasing MEMS scanner performance. However, only little is reported on how mass-produceability of these devices and stable functionality even under harsh environmental conditions can be guaranteed. Automotive application requires stable MEMS scanner operation over a wide temperature range from -40° to +85°Celsius. Therefore, hermetic packaging of electrostatically actuated MEMS scanning mirrors becomes essential to protect the sensitive device against particle contamination and condensing moisture. This paper reports on design, fabrication and test of a resonant actuated two-dimensional micro scanning mirror that is hermetically sealed on wafer level. With resonant frequencies of 30kHz and 1kHz, an achievable Theta-D-product of 13mm.deg and low dynamic deformation <20nm RMS it targets Lissajous projection with SVGA-resolution. Inevitable reflexes at the vacuum package surface can be seperated from the projection field by permanent inclination of the micromirror.

A mixed-signal embedded platform for automotive sensor conditioning

A mixed-signal embedded system called Intelligent Sensor InterFace (ISIF) suited to fast identify, trim, and verify an architecture to interface a given sensor is presented. This system has been developed according to a platform-based design approach, a methodology that has proved to be efficient for building complex mixed-signal embedded systems with short time-to-market. Such platform consists in a wide set of optimized high-performance analog, digital, and software intellectual property (IP) modules for various kinds of sensors. These IPs can be easily defined for fast prototyping of the interface circuit for the given sensor. Final ASIC implementation for the given sensor conditioning can be easily derived with reduced risk and short development time. Some case examples are presented to demonstrate the effectiveness and flexibility of this system.

Design of an integrated scanning micromirror driver in BCD technology

The paper presents the design and characterization of a smart IC driver for MEMS scanning micromirrors. The driver integrates in 0.18 μm BCD technology the cascade of the following circuits: resistor-string DAC circuitry for direct interface to a host digital processing unit, a voltage buffer between the DAC and the High-Voltage (HV) stage, and a fully-differential HV amplifier with programmable output common mode. A couple of the designed DACs permits to generate, starting from digital samples, low-voltage analog stimuli. This signal amplified up to 25 V by the HV stage provides the electrostatical actuation of the micromirror. When compared to state-of-the-art the driver offers an integrated solution with good dynamic performances.

A fast-developing and low-cost characterization and test environment for a double axis resonating micromirror

Testing and characterization of Micro-Electro-Mechanical Systems (MEMS) and Micro-Opto-Electro-Mechanical Systems (MOEMS) can be very challenging due to the multi-domain nature of these devices. Nowadays high volume, high-cost, and accurate measuring systems are necessary to characterize and test MEMS and MOEMS especially to examine motions, deflections and resonance frequencies. This paper presents a fast-developing and low-cost environment for MEMS and MOEMS testing and characterization. The environment is based on a flexible mixed-signal platform, named ISIF (Intelligent Sensor InterFace). As a case study we consider the characterization of a double axis scanning micromirror. The testing environment has been validated by comparing measurement results with results obtained by Finite Element Method simulation performed with Comsol Multiphysics™. Finally, these results have been used to create an electrical equivalent model of the micromirror.

Design of a high voltage fully differential driver for a double axis scanning micromirror

The design of a high voltage fully differential driver in a 0.18 µm Bipolar-CMOS-DMOS (BCD) technology for the actuation of a double axis scanning micromirror is presented. The proposed circuit has a driving voltage capability up to 25 V and a low Total Harmonic Distortion in order to prevent the excitation of unwanted micromirrors higher resonating modes. This design features a low voltage input stage and a programmable output common mode voltage. After a description of the circuit, results of simulations performed with an equivalent electrical model of the micromirror are presented.

SYSTEM STUDY FOR A HEAD-UP DISPLAY BASED ON A FLEXIBLE SENSOR INTERFACE

This work presents the system study for an innovative and miniaturized head–up display based on a flexible sensor interface for automotive applications. After a brief introduction, in the second section the basic structure of a head–up display is described. Finally, in the third section our specific design is presented.

A non linear ADC for sensor linearization

A successive approximation ADC with nonlinear characteristic is presented as an effective method for sensor linearization. Drastic simplification of the ADC structure was obtained by implementing a piece wise linear approximation of the required non linear curve. The design and simulated performance of an 8-bit prototype, applied to the linearization of a real flow sensor, are presented.

CHARACTERIZATION AND TESTING OF A DOUBLE AXIS SCANNING MICROMIRROR

Testing and characterization of Micro-Electro-Mechanical Systems (MEMS) and Micro-Opto-Electro-Mechanical Systems (MOEMS) can be very challenging due to the multi-domain nature of these devices. Nowadays high volume, high-cost, and accurate measuring systems are necessary to characterize and test MEMS and MOEMS especially to examine motions, deflections and resonance frequencies that are the distinguishing characteristics of these systems. This paper presents an environment for MEMS and MOEMS testing and characterization. The environment is based on ISIF (Intelligent Sensor InterFace) platform developed by SensorDynamics AG in collaboration with the University of Pisa. The environment has been used to perform several measurements on a scanning micromirror developed by the Fraunhofer Institute for Silicon Technology (ISIT). The testing environment has been validated comparing measurement results with results obtained by FEM simulation performed with Comsol Multiphysics™ Finally, these results have been used to create an electrical equivalent model of the micromirror.

Design of a high voltage high side driver with programmable output current

The design and laboratory tests of a high voltage driver with programmable output current are presented. The proposed solution is designed to work in the range of low frequencies (PWM output current up to 100 KHz) and with output currents between 50 mA and 130 mA. The presented topology exploits a feedback loop that allows fixing the output current to the desired value with high precision not easy to achieve with high voltage devices. Measurements performed on a prototype, designed and fabricated in a 0.35 μm Bipolar-CMOS-DMOS technology prove the effectiveness of the proposed solution.