language: en

Telecentric Optics for Computational Vision

Masahiro Watanabe and Shree K. Nayar
Department of Computer Science, Columbia University
New York, N.Y. 10027

Abstract A novel approach to constant-magnification imaging is proposed. Magnification variations due to changes in focus setting pose problems for important vision techniques, such as, depth from defocus. It is shown that magnification of a conventional lens can be made invariant to defocus by simply adding an aperture at an analytically derived location. The resulting optical configuration is called "telecentric." It is shown that most commercially available lenses can be turned into telecentric ones. The procedure for calculating the position of the additional aperture and a detailed analysis of the photometric and geometric properties of telecentric lenses are discussed. The magnification invariance of telecentric optics and its application to the problem of depth from defocus are experimentally demonstrated in [ Watanabe and Nayar-1995 ] . The proposed optics was found to result in significantly improved depth maps than those obtained using a conventional lens.

1 Introduction