Video Processing for Dlptm Display Systems

Texas Instruments’ Digital Light ProcessingTM (DLPTM) technology provides all-digital projection displays that offer superior picture quality in terms of resolution, brightness, contrast, and color fidelity. This paper provides an overview of the digital video processing solutions that have been developed by Texas Instruments for the all-digital display. The video processing solutions include: progressive scan conversion, digital video resampling, picture enhancements, color processing, and gamma processing. The real-time implementation of the digital video processing is also discussed, highlighting the use of the Scanline Video Processor (SVP) and the development of custom ASIC solutions. INTRODUCTION The Digital Micromirror DeviceTM (DMDTM) is a binary spatial light modulator developed at Texas Instruments. The DMD consists of an array of movable micromirrors functionally mounted over a CMOS SRAM. Each mirror is independently controllable and is used to modulate reflected light, mapping a pixel of video data to a pixel on display. A DMD mirror is controlled by loading data into the memory cell located below the mirror. The data electrostatically controls the mirror’s tilt angle in a binary fashion, where the mirror states are either +10 degrees (ON) or -10 degrees (OFF). Light reflected by the ON mirrors is then passed through a projection lens and onto a screen. The DMD forms the heart of Digital Light Processing (DLP) all-digital display systems. DLP systems are being developed in various forms, suitable for applications such as conference room projectors, institutional projectors, home theater, standard television, high definition displays, and motion pictures. These systems are characterized by: • All digital display: DLP display systems are completely digital in that, except for the A/D conversion at the front end, all data processing and display are digital. • Progressive display: DMD displays are inherently progressive, displaying complete frames of video. For interlace inputs such as most current video inputs, this necessitates an interlace to progressive scan conversion. Progressive scan display also has the advantage of improving display quality by removing interlace artifacts such as flicker. • Square pixels, fixed display resolution: DMD display resolution is fixed by the number of mirrors on the DMD. This, combined with the 1:1 aspect ratio of the pixels, requires resampling of various input video formats to fit onto the DMD array. • Digital color creation: Spectral characteristics of the color filters and the lamp are coupled to digital color processing in the system. • Digital display transfer characteristic: DMD displays exhibit a linear relationship between the gray scale value used to modulate the micromirrors and the corresponding light intensity. A “degamma” process is performed as part of the video processing, prior to DMD display, to compensate for video signal gamma and prepare the data for DMD display. VIDEO PROCESSING FOR DLPTM DISPLAY SYSTEMS Vishal Markandey, Todd Clatanoff, Greg Pettitt Digital Video Products, Texas Instruments, Inc. P.O.Box 655012, MS 41, Dallas, TX 75265