Machine Vision and Applications

, Volume 13, Issue 1, pp 25–37

Zoom tracking and its applications

  • Jeffrey A. Fayman
  • Oded Sudarsky
  • Ehud Rivlin
  • Michael Rudzsky
Original papers

DOI: 10.1007/PL00013268

Cite this article as:
Fayman, J., Sudarsky, O., Rivlin, E. et al. Machine Vision and Applications (2001) 13: 25. doi:10.1007/PL00013268

Abstract.

We present a new active vision technique called zoom tracking. Zoom tracking is the continuous adjustment of a camera's focal length in order to keep a constant-sized image of an object moving along the camera's optical axis. Two methods for performing zoom tracking are presented: a closed-loop visual feedback algorithm based on optical flow, and use of depth information obtained from an autofocus camera's range sensor. We explore two uses of zoom tracking: recovery of depth information and improving the performance of scale-variant algorithms. We show that the image stability provided by zoom tracking improves the performance of algorithms that are scale variant, such as correlation-based trackers. While zoom tracking cannot totally compensate for an object's motion, due to the effect of perspective distortion, an analysis of this distortion provides a quantitative estimate of the performance of zoom tracking. Zoom tracking can be used to reconstruct a depth map of the tracked object. We show that under normal circumstances this reconstruction is much more accurate than depth from zooming, and works over a greater range than depth from axial motion while providing, in the worst case, only slightly less accurate results. Finally, we show how zoom tracking can also be used in time-to-contact calculations.

Key words: Zoom tracking – Depth from zoom – Optical flow – Active vision – Autofocus 

Copyright information

© Springer-Verlag Berlin Heidelberg 2001

Authors and Affiliations

  • Jeffrey A. Fayman
    • 1
  • Oded Sudarsky
    • 1
  • Ehud Rivlin
    • 1
  • Michael Rudzsky
    • 1
  1. 1.Computer Science Department, Technion – Israel Institute of Technology, 32 000 Haifa, Israel; e-mail: {jefff,sudar,ehudr,rudzsky}@cs.technion.ac.il IL

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