Self-normalized linear tests

  • Authors:
  • Sachin Gangaputra;Donald Geman

  • Affiliations:
  • Dept. of Electrical and Computer Engineering, The Johns Hopkins University, Baltimore, MD;Dept. of Applied Mathematics and Statistics, The Johns Hopkins University, Baltimore, MD

  • Venue:
  • CVPR'04 Proceedings of the 2004 IEEE computer society conference on Computer vision and pattern recognition
  • Year:
  • 2004

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Abstract

Making decisions based on a linear combination L of features is of course very common in pattern recognition. For distinguishing between two hypotheses or classes, the test is of the form sign(L - τ ) for some threshold τ. Due mainly to fixing τ , such tests are sensitive to changes in illumination and other variations in imaging conditions. We propose a special case, a "self-normalized linear test" (SNLT), hard-wired to be of the form sign(L1 - L2) with unit weights. The basic idea is to "normalize" L1, which involves the usual discriminating features, by L2, which is composed of non-discriminating features. For a rich variety of features (e.g., based directly on intensity differences), SNLTs are largely invariant to illumination and robust to unexpected background variations. Experiments in face detection are promising: they confirm the expected invariances and out-perform some previous results in a hierarchical framework.