IPT-EGVE Symposium (2007) Short Papers B. Fröhlich, R. Blach, and R. van Liere (Editors) A Single Chip DLP Projector for Stereoscopic Images of High Color Quality and Resolution A. Hopp 1 and S. Havemann 2 and D. W. Fellner 2,3 1 digital IMAGE, Overath, Germany 2 Institut für ComputerGraphik & Wissensvisualisierung, TU Graz, Austria 3 TU Darmstadt & Fraunhofer IGD, Germany Abstract We present a novel stereoscopic projection system. It combines all the advantages of modern single-chip DLP technology – attractive price, great brightness, high contrast, superior resolution and color quality – with those of active stereoscopy: invariance to the orientation of the user and an image separation of nearly 100%. With a refresh rate of 60 Hz per eye (120 Hz in total) our system is flicker-free even for sensitive users. The system permits external projector synchronisation which allows to build up affordable stereoscopic multi-projector systems,e.g., for immersive visualisation. Categories and Subject Descriptors (according to ACM CCS): B.4.2 [Input/Output Devices]: Image display I.3.1 [Computer Graphics]: Three-dimensional displays 1. Introduction and State of the Art There are numerous approaches to realize stereoscopic pro- jection systems, each with its strengths and weaknesses. In the following we give a short overview of the various tech- niques. This is then contrasted by user wish list, according to which our new stereoscopic projection system, which is the key contribution of this paper, performs very well. Stereoscopic imaging systems can be roughly classified by the way the images are encoded: time encoded (frame in- terleaved) systems with shutter glasses, wavelength encoded systems using anaglyph style glasses, wavelength multiplex systems, and systems exploiting the light wave orientation using polarisation [Dom81]. 1.1. Time encoded systems In time encoded systems the images for the right and left eye are displayed one after another. Typically the viewer wears a shutter glasses that separate the images of the two eyes. At any given moment, only one eye can see an image, the other sees black. When used with a CRT monitor, both scan line and full page modes are available. In scan line mode the image (and eye shutter) is swapped every scan line, in page mode the images are swapped every full frame. CRT monitors, however, are losing market shares, and this mode requires very fast shutters. Figure 1 shows the typical, very short synchronisation impulses, the control line for shutter emitters, and the resulting states of the shutter glasses. If the frequency of the alternating images in page flip mode is high enough, normally above 120 Hz, the observer does not rec- ognize any flicker. Time encoded images may also be gen- erated by projection systems with one or two projectors, for instancde using a CRT projector instead of a CRT monitor. In [Wer02] Texas Instruments describes a 3-chip DLP sys- tem with an associated quad buffer, i.e., with a front and a back buffer for each eye, very similar to the quad-buffers of an stereo capable OpenGL graphics board. This system is used in the well known stereo projectors from Christie Dig- ital and Barco. Systems with two sources need a very accurate blanking mechanism, such as the one from Ling [ Lin89] using various rotating shutters. Another alternative are external LC (liquid crystal) shutters, furthermore [Wer02] uses the blanking of DMD columns to remove the unwanted part of the image. – We have also built a two projector setup for DLP systems, one that uses the projector’s own digital micro mirror device (DMD) as a shutter [Hop03], which will be described in sec- tion 3.1 later in this paper. c  The Eurographics Association 2007.