Single-panel optical architectures are a unique capability of Digital Light Processing (DLP TM ) projection system that is possible because of the fast on-off transition time of the Digital Micromirror Device (DMD TM ). A method is described that includes a clear or white segment to the color modulation that significantly improves the optical efficiency of this architecture resulting in both improved brightness and contrast of the projected image. Brightness improvements of 25% and more are possible over 1st generation DLP systems. Objectives & BackgroundA typical single-panel DLP TM architecture is shown in Figure 1. A lamp arc is imaged onto the plan of a color disk drive assembly which consists of a set of red, green, and blue dichroic filters that rotate at a speed synchronized to the input data rate. This spot is then imaged on the DMD TM which spatio-temporally modulates the light through the projection lens. Figure 1. Single-Panel DLP TM ArchitectureWith the incorporation of a clear segment to a convention colorwheel, not only is system brightness improved considerably, but the operation of the signal processing emulates the characteristics of CRT systems which typically "punch-up" edges and small bright areas to create an image with much more perceived contrast. The added advantage to the DLP TM method is that most full-field areas of the image may use the clear segment time in addition to edges.The fundamental concept of the clear segment architecture is to extract the luminance signal from the input signal and apply a gain to it when it exceeds a predefined threshold. If any of the RGB channels exceeds their maximum dynamic range (> 255 in 8-bit systems) then luminance is enabled in the white segment.The objectives of the new colorwheel approach are to increase system brightness by the incorporation of a clear or white segment. This led to a unique application of color matching theory such that the white segment could be blended into the image without perceived contouring or other artifacts. Tolerances for lamp, optics and dichroic filter production variations also required consideration. ResultsThe inclusion of the white segment in a sequential color projection system allows for an increase in both the brightness and the contrast of the system. This is accomplished by shifting of some the luminance signal into the white filter segment. The shifting of this luminance signal then allows the RGB levels to continue to increase to greater levels, thus increasing the overall brightness of the images.The size of the white segment determines the percent of increase in brightness the system achieves. The larger the segment, the more of the luminance signal which can be transferred into it. Figure 2 shows a plot of the percent of lumens increase that is achieved for a given white segment size. The system uses a xenon lamp and has color wheel using a red, green, and blue segments that are always of equal size for the given white segment size.

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Since first public release of parts in the spring of 1996, DLP® Products has produced several tens of millions of projection systems for a variety of applications ranging from ultra-bright cinema systems capable of handling >100k lumens down to small-form-factor ('pico') projection with dimensions on the order of a thumb-nail and light outputs of ~30-300 lumens. This versatility has resulted in exploration of several technology directions which will be charted along with the historical journey of the DMD.

Texas Instruments' Digital Light Processing (DLP) technology provides aM-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.

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