Wafer-level vacuum-packaged two-axis MEMS scanning mirror for pico-projector application

Abstract

Hermetic wafer level packaging of optical MEMS scanning mirrors is essential for mass-market applications. It is the key to enable reliable low-cost mass producible scanning solutions. Vacuum packaging of resonant MEMS scanning mirrors widens the parameter range specifically with respect to scan angle and scan frequency. It also allows extending the utilizable range of mirror aperture size based on the fact that the energy of the high-Q oscillator can be effectively conserved and accumulated. But there are also some drawbacks associated with vacuum packaging. This paper discusses the different advantageous and disadvantageous aspects of vacuum packaging of MEMS scanning mirrors with respect to laser projection displays. Improved MEMS scanning mirror designs are being presented which focus on overcoming previous limitations. Finally an outlook is presented on the suitability of this technology for very large aperture scanning mirrors to be used in high power laser applications

Scanning MEMS Mirror for High Definition and High Frame Rate Lissajous Patterns

“…Microscanners play a vital role in various low-power and compact scanning applications, including in display [1,2,3,4], sensing [5,6,7,8], and biomedical imaging [9,10,11,12,13,14,15,16]. In particular, resonant MEMS (micro-electro-mechanical system) mirrors provide a focus beam with a small size and high energy efficiency at any distance [17,18,19,20] and the monolithic fabrication facilitates low-cost commercialization [21,22].…”

PZT-Actuated and -Sensed Resonant Micromirrors with Large Scan Angles Applying Mechanical Leverage Amplification for Biaxial Scanning

“…Depending on designed frequency difference of the two axes, different Lissajous figures will repeat and fill the field. Previous works show that very good results regarding high light density can be realized, if the two axes have a frequency difference of 60 Hz [ 13 ]. However, such low frequency difference causes inevitably so strong mechanical coupling of the two axes, that complex controlling is needed to decouple the biaxial motions [ 11 ].…”

The Exploration for an Appropriate Vacuum Level for Performance Enhancement of a Comb-Drive Microscanner

“…With the development of micro-electro-mechanical system (MEMS) technology, MEMS devices have been used in many fields, such as RF-MEMS, optical-MEMS, sensors, energy harvesters, and bio-MEMS. Among them, the microscanner, a promising optical-MEMS device, is widely used in LiDAR [ 1 , 2 ], pico-projectors [ 3 ], barcode readers [ 4 ], VR (Virtual Reality)/AR (Augmented Reality) applications [ 5 ], and so on. Mainstream actuation techniques used in microscanners are electrostatic [ 6 ], electromagnetic (EM) [ 7 ], piezoelectric [ 8 ], and electrothermal [ 9 ] actuations, and the drive forces are electrostatic forces, Lorentz or magneto-static forces, piezoelectric effects, and metal thermal effects, respectively.…”

“…To achieve a large scanning angle, enhancing the input energy or reducing the loss energy (mainly caused by air damping) is expected. Therefore, two methods have been used to meet the requirement of a low driving voltage and a large scanning angle in its application: adopting hybrid actuation mechanisms to drive the microscanner [ 11 ] (enhancing input) and vacuum packaging [ 3 , 12 ] (reducing loss). However, the hybrid actuation combined electrothermal actuators and electromagnetic actuators, which is complex in fabrication and control.…”