Scene Geometry from Projector Defocus
Digital projection technologies, such as Digital Light Processing (DLP) and Liquid Crystal Display (LCD), are increasingly used in consumer, commercial and scientific applications. For these applications, projectors need to produce bright, focused images on a single flat screen. As a result, they are made with large apertures and hence narrow depths of field. In this project, we analyze projector defocus with two goals in mind. The first is to exploit projector defocus to robustly recover scene geometry and the second is to compensate for projector defocus to enable a projector to display high quality images on non-planar surfaces. We have developed a a simple linear model for projector defocus. Based on this model, we have developed a novel temporal defocus method to recover scene depth at each image pixel using its intensity variation over time. Unlike most depth recovery methods, this method generates image-complete depth maps with sharp discontinuities. Using the same projector defocus model, we also develop a defocus compensation method that filters a projection image in a scene-adaptive manner to minimize its defocus blur after it is projected onto the scene. This technique effectively increases the depth of field of a projector without modifying its optics. Finally, we present an algorithm that exploits projector defocus to reduce the strong pixelation artifacts produced by all digital projectors, while preserving the quality of the projected image. We have experimentally verified each of our methods using real scenes.

Publications

"Projection Defocus Analysis for Scene Capture and Image Display,"
L. Zhang and S. K. Nayar,
ACM Trans. on Graphics (also Proc. of ACM SIGGRAPH),
Jul, 2006.
[PDF] [bib] [©]

Videos

  SIGGRAPH Video (Extended version)
This video shows all our examples of scene capture and image display based on projection defocus analysis. (With narration)
  Scene Geometry using Temporal Defocus Analysis:
This video shows how our depth estimation method generates image-complete depth maps with clean discontinuity boundaries, even in the presence of specular reflections and complex occlusions. (With narration)
  Focused Projection at Multiple Depths:
This video demonstrates shows how a single projector can be used to project well-focused images on multiple planes at different depths as well as on curves surfaces. (With narration)
  Depixelation by Defocusing:
This video illustrates the idea of depixelating a projector using slight defocusing followed by defocus compensation. (With narration)

Slides

SIGGRAPH 2006 presentation     With videos (zip file)

Related Projects

Depth from Defocus

Shape from Focus


Project Anywhere: Radiometric and Geometric Compensation