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In this paper further developments [1,2] of a passive matrix projection/direct view display are presented. The device uses micromachined and electrostatic actuated Fabry-Perot filters. Applications are surface topology measurements (stereographic projection) in small cavities, laser beam writing and pattern projection e.g. in Head-Mount-displays, automotive or information panels. The display pixels with diameters in the order of 100 μm consist of a layer stack fabricated by LPCVD. The stack embeds an air gap which his created by a sacrificial etch process and a thin membrane which can be deflected electrostatically. The fabrication process has already been described elsewhere [2]. By membrane actuation the gap thickness is lowered and the interference spectrum generated by the layer stack is varied. The careful adjustment of the
layer parameters like thickness and refractive index determines the design wavelength of the switches. They are assembled in rows and columns, resulting in an n*m-display matrix, where n*m actually is 4800. In principle the display may either be fabricated for transmission or reflection mode, depending on the substrate material (quartz or silicon). This paper focuses on transmissive displays. For pattern generation, an electric potential scan is applied on the n line contacts, and a video potential, which carries the image information, is addressed on the m column contacts. After each scan cycle, the potential polarities are reversed in order to avoid charge effects and to lower cross-talk between adjacent pixels. The response time is 100 μs, which is at least an order of magnitude faster than for common LCD technology. Further advantages are high temperature stability, low power consumption and low production costs, since only five mask layers are used in the present process. In this paper especially the electrical characteristics are evaluated and an addressing scheme for future active matrix addressing is derived.
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