MOEMS Display Technology
Transmissive Electrostatic Micro-Optic Switches
Kerwin Wang, Karl F. Böhringer
Mike Sinclair, Gary Starkweather, Microsoft Research
This work presents likely the world's smallest electrostatic visible light
highly space-efficient transmissive micro-optical switches (TMOS) for an
integrated MEMS optical display system. Each TMOS represents one pixel with
150µm x 150µm spacing in a display module. It is demonstrated
that a zigzag electrostatic actuator of 47µm x 160µm size can
achieve a maximum static lateral displacement of 10µm at 38V. Depending
on the zigzag actuator design, these devices have a mechanical resonance
frequency of up to 18.6kHz.
|Figure 1: A high contrast, low power
consumption, highly space-efficient transmissive optical switch is
at the heart of the integrated MEMS optical display system.
||Figure 2: The cross section of a
shutter; made from Poly1, Poly2 and Gold. The dimples work together
with PECVD carbon fluoride coating to reduce sticking. The channel
is dry etched by DRIE and RIE for light transmission.
The TMOS consists of an electrostatic "zigzag" actuator pair, overlapping
shutters and a miniaturized optical tunnel. The dimensions of these three
components are mainly depending on the optical configuration. A microlens
array can focus light into the aperture to minimize the optical loss.
A second microlens array placed behind the TMOS array will image the light
onto a display screen area or a projector lens. Assuming the light presented
to the first microlens array has a nearly planar wave front, then each
microlens focuses its portion of the light into the aperture adjacent
to the shutter (Figure 2). The shutter can modulate the light by controlling
its opening. A small spot size only needs a small shutter and movement
to fully turn the light on and off. It also implies low driving voltage,
low power consumption, and higher frequency operations. The minimal spot
size and the profile of the optical tunnel are mainly constrained by the
depth of focus, diffraction spot size and the numerical aperture of the
selected microlens system.
|Figure 3: The shutter
can successfully switch the light on and off. Optical test results
show that this TMOS can achieve near-ideal contrast ratios.
- Kerwin Wang, Karl F. Böhringer, Mike Sinclair, Gary Starkweather,
"Highly Space-efficient Electrostatic Zigzag Actuator for Transmissive
Micro-Optic Switches." The 12th
International Conference on Solid-State Sensors and Actuators (Transducers'03),
Boston, MA, June 6-12, 2003. Paper.
A complete list of our publications
(many of them available online) can be found here.
- Supported by Microsoft Research
© Karl F. Böhringer, Department of Electrical Engineering, Box
352500, Seattle, WA 98195-2500, USA