Design and fabrication of the micromirror array for projection display

Abstract

[A new design of micromachined mirror array for display purposes is presented. Integrating multiple functions into a component and extensive use of photo-lithography make this design of mirror simple as well as easy to make. The prototype is fabricated in an array of 50 × 50 micromirrors. The size of mirror plate is 50 × 50 μm2 and the gap between them is 3 μm. The mirror plate is tilted by the electrostatic force, and the angle is designed to be 10°. Driving voltage for the finished micromirrors is 28 V and the tilt angle is measured as 8.9°. The response time from rest to full tilt and back to rest position is about 20 μs when it is driven at the natural frequency of 24.7 kHz. From the reliability point of view, the importance of anti-stiction coating cannot be over-stressed. Without one, most of the mirrors could not survive a few contacts with the substrate. However, when proper anti-stiction coating is applied and the atmosphere is controlled to eliminate humidity, 94.6% of the micromirrors were still rocking after 1.15 × 1010 cycles. In a series of experiments, it was possible to show this new design of micromirror array could be used as a display device, when they are driven at a certain combination of addressing and bias signals. A variable character generation and PWM-type brightness control is successfully demonstrated., A new vibrating gyroscope using parallel beam structure has the following significant features: (1) The sensing device does not interfere with the reference vibration of a driving device; (2) This structure can convert a small Coriolis force into a large concentrated strain; (3) Resonance frequency of the driving device and the sensing device can be easily adjusted by changing the mass of the tip; (4) Mechanical coupling can be suppressed by applied voltage to the sensing device. However, this gyroscope is unsuitable for mass-production, since the structure is complicated. In this paper, we solve this problem by a sheet metal molding and a hydrothermal method. We optimized the parallel beam gyroscope for the sheet metal molding based on FEM analysis, and applied PZT thin films by the hydrothermal method. Using these two methods, we produced a dangler type gyroscope which is suitable for mass production with the advantage of the parallel beam structure.]