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Jim Rehg
College of Computing
Georgia Institute of Technology
Shadow Elimination and Occluder Light Suppression for Multi-Projector Displays
Online Slides
We are developing ubiquitous display technology based on systems of multiple
projectors and cameras. Using this technology, any surface in a home or
office environment can be transformed into a flexible, interactive display.
Displays are configured dynamically by coordinating the outputs of multiple
projectors using feedback from one or more cameras. A key technical
challenge in any front projection approach is to deal with the obstruction
of projected light by people and objects in the environment. There are two
subproblems which must be addressed: (i) shadows cast on the display by the
users, and (ii) projected light falling on and distracting the users.
In this talk I will describe a computational framework for solving these two
problems using multiple overlapping projectors and cameras. The overlapping
projectors are automatically aligned to display the same dekeystoned image.
The system detects when and where shadows are cast by occluders and is able
to identify the occluded pixels from each projector. Through a visual
feedback control loop, the contributions of unoccluded pixels from other
projectors are boosted in the shadowed regions, thereby eliminating the
shadows. In addition, pixels which are being occluded are blanked, thereby
preventing the projected light from falling on a user. This can be
accomplished even when the occluders are not visible to the camera. I will
show results from a number of experiments demonstrating that the system
converges with low steady-state errors.
This is joint work with Tat-Jen Cham (Nanyang Technological University,
Singapore) and Rahul and Gita Sukthankar (Compaq Cambridge Research Lab,
Boston).
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