3.2: High Dynamic Range Projection Systems

Digital cinema and home theatre applications need to compete with analog film in terms of image quality. The single most important performance specification of a projection system, and the largest gap in the competition between digital and analog projectors, is the relatively low dynamic range of luminance of current digital projectors. In this paper we introduce a novel digital system capable of displaying images with a high enough dynamic range to rival analog film. The projection system described is based on a serial combination of light modulating devices, such as two liquid crystal micro-display panels within a projection light engine. One of the modulation steps can be of lower spatial resolution and contrast. This increases the optical efficiency of the system and avoids optical artifacts. We describe several hardware implementations of this approach as well as the required image processing. Finally, we present an evaluation of the designs in terms of performance, image quality and cost.