liquid crystal on silicon (LCoS)
LCoS projectors work according to the reflective method with LCoS displays. The projection light is projected via a special mirror onto the LCoS display, where it is reflected by each individual LCoS ( liquid crystal on silicon) cell.
In terms of construction, an LCoS projector consists of the projector lamp, whose beam is beamed onto a polarizing beamsplitter ( PBS) via a lens system consisting of a converging lens and dichroic filters. These projectors use the polarizing beam spitter instead of the usual prisms. Since LCoS projectors operate according to the RGB color model with additive color mixing, the light is split into the three primary colorsred, green and blue and cast via polarizers onto the three reflecting LCoS chips. The beam reflections of the three LCoS chips are bundled in the projector lens and projected onto the projection surface.
LCoS chips consist of three layers: the top layer is a transparent electrode, on the middle layer, which is about 3 µm thin, are the liquid crystals. And the bottom layer is the electrodes arranged as an array with their address conductor tracks for driving the individual pixels. The conductor tracks are located behind the reflective layer and thus do not absorb any light.
LCoS projections are suitable for high quality large screen projection with a resolution that can even exceed Ultra-XGA( UXGA). This is due to the small LCoS cells, which have a diameter of only 8 µm. They feature an excellent contrast ratio of over 10,000:1 and have a high brightness.
Sony has developed a proprietary variant of LCoS technology with Silicon X-tal Reflective Display (SXRD), which can display videos in the 4K standard and has a contrast ratio of 1,000,000:1.