Liquid crystal on silicon

Liquid crystal on silicon (LCoS or LCOS) is a miniaturized reflective active-matrix liquid-crystal display or "microdisplay" using a liquid crystal layer on top of a silicon backplane. It is also referred to as a spatial light modulator. LCoS was initially developed for projection televisions but is now used for wavelength selective switching, structured illumination, near-eye displays and optical pulse shaping. By way of comparison, some LCD projectors use transmissive LCD, allowing light to pass through the liquid crystal.

In a LCoS display, a CMOS chip controls the voltage on square reflective aluminium electrodes buried just below the chip surface, each controlling one pixel. For example, a chip with XGA resolution will have 1024x768 plates, each with an independently addressable voltage. Typical cells are about 1–3 centimeters square and about 2 mm thick, with pixel pitch as small as 2.79 μm. A common voltage for all the pixels is supplied by a transparent conductive layer made of indium tin oxide on the cover glass.

General Electric first demonstrated a low-resolution LCoS display in the late 1970s. Starting in the late 1990s a number of companies attempted to develop products for both near-eye and projection applications.

At the 2004 CES, Intel announced plans for the large scale production of inexpensive LCoS chips for use in flat panel displays. These plans were cancelled in October 2004. Sony has made it to market (December 2005) with the Sony-VPL-VW100 or "Ruby" projector, using SXRD, 3 LCoS chips each with a native resolution of 1920×1080, with a stated contrast ratio of 15,000:1 using a dynamic iris.

Whilst LCoS technology was initially touted as a technology to enable large-screen, high-definition, rear-projection televisions with very high picture quality at relatively low cost, the development of large-screen LCD and plasma flat panel displays obsoleted rear projection televisions. As of October 2013, LCoS-based rear-projection televisions are no longer produced.

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