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We present a 0.38" liquid-crystal-on-silicon (LCOS) backplane for color-sequential and color-filter microdisplays. This LCOS has a monochrome VGA resolution for color-sequential operation, and could become a QVGA display when RGBW color filters are coated. With a space dithering algorithm, we also demonstrated a virtual VGA resolution on the color-filter mode. IntroductionAs the mobile devices become smaller in size and the display contents are increased due to a larger data bandwidth, the conventional direct-view liquid crystal displays (LCDs) cannot meet this small-size and high-resolution request. Therefore, there is an increasing demand for pico projectors, which are small in size, but can project a large image of higher resolution. Today, there are quite a few of pico projector technologies available that can deliver large projection with a small size [1][2][3][4][5]. Among them, we believe the liquid-crystal-on-silicon (LCOS) microdisplays and the associated projectors are the best candidates because they could leverage on the best display technology in LCD, the best semiconductor technology in silicon, and the best light source technology in light-emitting diode (LED). We also see the application of the LCOS projectors in various mobile devices has been increased significantly in recent months because of its potential advantages [6].There are two kinds of single-panel LCOS projectors; that is, single-LED color-filter LCOS (CF-LCOS) projector and multiple-LED color-sequential LCOS (CS-LCOS) projector as illustrated in Figure 1. It can be seen from the figure that both types of the projectors share the same polarizing beam splitter (PBS) and projection lenses if the LCOS microdisplays are of the same size. The difference would be on the LED illumination in which the CF-LCOS projector uses a white LED, while the CS-LCOS projector requires red (R), green (G) and blue (B) LEDs. Figure 1 shows an X-cube RGB LED illumination unit for examples, but it could be any other RGB LED illumination approach. Figure 1 Schematics of single-LED CF-LCOS and multiple-LED CS-LCOS projectors.In this paper, we further explore the possibility of using a same LCOS backplane for both the single-panel color-filter and colorsequential projectors. By this arrangement, both the single-panel LCOS projectors could share the same components in projection lenses, PBS and the LCOS backplane. The preparation of the projector components could be leveraged with each other and the time to market for the development of the projector could be shorten. The LCOS Microdisplay and Projector The 0.38" LCOS microdisplayIn our earlier work, we have developed a 0.59" CS-LCOS microdisplay of 15μm pixel and of SVGA resolution or 800x600 pixels [7]. A frame buffer was integrated onto the silicon backplane to accelerate the data upload time, and a thin mixed twisted nematic (MTN) LC mode was used for fast LC response [8]. This 0.59" LCOS microdisplay was a true color-sequential display and showed excellent optical performance [9], but its associated projecto...