Digital processing of video signals can introduce many types of artifacts visible at the final display. One artifact, called luminance contouring, occurs when the number of bits that is output from the final digital processing stage is small enough for the luminance step corresponding to one bit to be visible at the display. While luminance contouring is rarely a problem in CRT displays, it is known to occur in digital micromirror device (DMD), plasma and liquid crystal device (LCD) displays. This paper provides a method to determine if luminance contouring is likely to occur in a given display when driven by a given bit count. Also indicated are the luminance and drive levels where luminance contouring is most likely to occur in common display types, including the DMD, twisted-nematic LCD and CRT displays.
When considering several projection system designs, one of the important characteristics is the total luminous flux the system will deliver to the projection screen. This is the main factor controlling perceived brightness to the viewer for a given screen size and gain. This luminous flux depends on a number of factors, such as lamp lumen output, reflector collection efficiency, projector architecture, light valve aperture ratio and the transmission/reflection efficiency of each optical component in the system. Many of these factors are amenable to accurate estimation prior to construction of a prototype projector. However, quantitative estimates of lamp/reflector light collection efficiency are difficult to make accurately. This paper will give an analytical approach based on etendue (optical extent) that can accurately predict lamp/reflector collection efficiency prior to the construction of a prototype projector. Collection efficiencies and projector lumen throughputs for several lamp/reflector/projector combinations will be estimated with this technique.