Human-Computer Interaction Institute
School of Computer Science, Carnegie Mellon University


Projector-Based Location Discovery and Tracking

Johnny Chung Lee

May 2008

Ph.D. Thesis


Keywords: Image projection, projector calibration, augmented reality, location tracking, motion capture, high-speed projection, infrared projection, multi-projector applications, projector alignment, incremental tracking

Today, the primary use of projection technology is for creating large flat displays that provide a shared viewing experience for presentations or entertainment applications. While research projects have explored the powerful ability for projected light to create illusions that can reshape our perception and our interaction with surfaces in the environment, very few of these systems have had success in terms of commercial and consumer adoption. Part of this limited adoption can be attributed to the lack of practicality in the cost-of-operation due to the complexity of installation and reliability of execution. Often these systems require expert knowledge to perform system setup and calibration between the projected image and the physical surfaces to make these illusions effective. In this thesis, I present a technique for inherently adding object location discovery and tracking capabilities to commercial projectors. This is accomplished by introducing light sensors into the projection area and then spatially encoding the image area using a series of structured light patterns. This delivers a unique pattern of light to every pixel in the projector's screen space directly encoding the location data using the projector itself.

By unifying the image projection and location tracking technologies, many of the difficult calibration and alignment issues related to interactive projection and projected spatial augmented reality applications can be eliminated simplifying their implementation and execution. Furthermore, by creating a hybrid visible light and infrared light projector, a single calibration-free device can perform invisible location tracking of input devices while simultaneously presenting visible application content. I present a detailed description of the projector-based location discovery and tracking technique, a description of three prototype implementations, and a demonstration of the effectiveness of this simplification by re-implementing, and in some cases improving upon, several location-sensitive projector applications that have been previously executed using external calibration and tracking technologies.

106 pages

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