Shadow elimination and occluder light suppression for multi-projector displays

Two related problems of front projection displays which occur when users obscure a projector are: (i) undesirable shadows cast on the display by the users, and (ii) projected light falling on and distracting the users. This paper provides a computational framework for solving these two problems based on 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 determine the pixels which are occluded in different projectors. Through a 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 when they occlude the display. This can be accomplished even when the occluders are. not visible to the camera. The paper presents results from a number of experiments demonstrating that the system converges rapidly with low steady-state errors.