High-Quality Microlenses and High-Performance Systems For Optical Microelectromechanical Systems

Major opportunities exist for optical microelectromechanical systems (MEMS) and, despite recent economic setbacks for companies working in the field, concentrated research on optical MEMS is underway at many locations. Most of the research reported thus far has been focused on activated-mirror-micro-optical systems-which have instantly recognizable applications in the display and fiber-optic-switching fields. Optical components other than activated mirrors must, however, be available for designers to produce micro-optical systems for other applications that are already of proven value in macro designs. Chief among the needed components are lenses with high optical quality that can be accurately formed and placed at specified locations in an optical system. Another need is for polarized-light beam splitters that can be fabricated using the materials and technologies that are generally available to MEMS designers. Research at the Berkeley Sensor & Actuator Center (BSAC) has led to important advances in producing both precise high-quality lenses and high-performance polarization-beam splitters for micro-optical MEMS [1], [2]. In this White Paper, we first make clear the need for precision microlenses and then describe an important new MEMS optical system that would be made possible by precision microlenses. We begin with a review of the significant progress that we have already made in building high-quality lenses as well as high-performance polarizationbeam splitters at BSAC. We then describe some opportunity areas that have been opened through this progress. In a final section we present guidelines and milestones that will advance this work and lead to new optical-MEMS capabilities. Microlenses in Optical MEMS We are developing simple yet precise microlens-fabrication technology that is compatible with and exploitive of the technologies already developed at BSAC for surface micromachining. For example, we have developed means to fabricate precise microlenses and to mount them on mechanical structures such as the BSAC-invented “pop-up” supports, and to drive them with the interdigitated combdrive actuators also invented and heavily developed at BSAC. Our goal is to exploit the attributes of each technology (microlens fabrication and the technology for structural MEMS) in a complementary manner. Our success in this project will enable new, extremely useful, optical Microsystems. We have placed our initial focus on the development of a ShackHartmann (SH) system built with a unique MEMS-microlens array in which each individual lens image can be identified by means of its pre-assigned vibrational frequency. With this new design incorporating the new BSAC high-quality lenses, our SH system will advance the field by providing improved sensitivity and broader dynamic range than can be attained by present SH systems. In this White Paper, we describe the BSAC program after providing an introduction to SH systems and of the performance limitations of available SH systems. This discussion leads us to a review of ongoing research by groups active in the SH field after which we describe our