Off-axis placement of light projectors induces significant planar
parallax on the display surface. Although commodity solutions exist for
removing this distortion, they involve iterative, menu-driven user
interaction or physical alignment of the projector, and in either case
interrupt the use of the display.
User interaction is infeasible in a number of scenarios including mechanically aligned multi-projector displays that are subject to mechanical drift
and situations in which projectors are often reconfigured.
We
present a general technique for continuous rectification of arbitrary
off-axis distortions that does not require user interaction.
A camera automatically detects when the projector's
orientation has changed, without requiring explicit fiducials or targets in
the world.
The method runs in concert with interactive display applications
and has minimal impact on framerate.
An initial rectifying transform is recovered automatically by projecting
target points and observing them in the camera.
The display is then warped and passively monitored for calibration
error and motion of the projector. The technique distinguishes between
distortions due to miscalibration and intentional framebuffer changes.
A consistency score is measured by generating a predicted view based on the
current framebuffer contents and correlating this prediction with the camera's
captured image.
Poor correlation scores indicate that the projector has moved and re-calibration
and geometric correction is required.
Initial experiments show that the calibration consistency measures are
sufficiently robust to distinguish small motion of the projector from
continuously changing imagery.