Generalized Image Acquisition and Analysis

Discovering the Structure of a Planar Mirror System from Multiple Observations of a Single Point

We investigate the problem of identifying the position of a viewer inside a room of planar mirrors with unknown geometry in conjunction with the room’s shape parameters. We consider the observations to consist of angularly resolved depth measurements of a single scene point that is being observed via many multi-bounce interactions with the specular room geometry. Applications of this problem statement include areas such as calibration, acoustic echo cancelation and time-of-flight imaging. We theoretically analyze the problem and derive sufficient conditions for a combination of convex room geometry, observer, and scene point to be reconstructable. The resulting constructive algorithm is exponential in nature and, therefore, not directly applicable to practical scenarios. To counter the situation, we propose theoretically devised geo- metric constraints that enable an efficient pruning of the solution space and develop a heuristic randomized search algorithm that uses these constraints to obtain an effective solution. We demon- strate the effectiveness of our algorithm on extensive simulations as well as in a challenging real-world calibration scenario.

Three-Dimensional Kaleidoscopic Imaging

Ilya Reshetouski, Alkhazur Manakov, Hans-Peter Seidel, and Ivo Ihrke
CVPR 2011 (oral)
  Abstract

  We introduce three-dimensional kaleidoscopic imaging, a promising alternative for recording multi-view imagery.
  The main limitation of multi-view reconstruction techniques is the limited number of views that are available from multi-camera systems, especially for dynamic scenes.
  Our new system is based on imaging an object inside a kaleidoscopic mirror system. We show that this approach can generate a large number of high-quality views well distributed over the hemisphere surrounding the object in a single shot. In comparison to existing multi-view systems, our method offers a number of advantages: it is possible to operate with a single camera, the individual views are perfectly synchronized, and they have the same radiometric and colorimetric properties.
  We describe the setup both theoretically, and provide methods for a practical implementation. Enabling interfacing to standard multi-view algorithms for further processing is an important goal of our techniques.

  Example of labeling process:

=> => => =>
Source image Silhouette image Chambers extraction Visual hull
estimation
Labeling of views

  Files

Paper [pdf]
Supplemental materials [pdf]
Presentation [ppt]
Labeling data example (with MatLab loader) [zip]
Labeling of the dynamic scene example: Input movie [mpg], Segmentation movie [mpg], Labeling movie [mpg]