Development and real-time implementation of a rule-based auto-focus algorithm

  • Authors:
  • N. Kehtarnavaz;H.-J. Oh

  • Affiliations:
  • Department of Electrical Engineering, EC33, University of Texas at Dallas, PO Box 830688, Richardson, TX;Texas Instruments, Inc.

  • Venue:
  • Real-Time Imaging
  • Year:
  • 2003

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Abstract

This paper presents the development and real-time implementation of a rule-based approach to passive auto-focusing for digital still cameras. The implementation is performed on the processor DM310 which is specifically manufactured by Texas Instruments for digital still cameras. The squared-gradient sharpness function is considered to measure the amount of high-frequency content in an out-of-focus image. This sharpness function is then used within a rule-based search algorithm to obtain the focused lens position via moving the lens head step-motor. The developed rule-based approach is compared to the commonly used global search and binary search algorithms in terms of focusing speed and power consumption. It is shown that the introduced rule-based search algorithm achieves a lower number of focusing iterations or faster focusing speed, and a lower number of steps or lower power consumption.