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Phase information in the recognition of natural images




Fourier phase plays an important role in determining global image structure. For example, when the phase spectrum of an image of a flower is swapped with that of a tank, we usually perceive a tank, even though the amplitude spectrum is still that of the flower. Similarly, when the phase spectrum of an image is randomly swapped across frequencies, that is its Fourier energy is randomly distributed over the image, the resulting image becomes impossible to recognise. Our goal was to evaluate the effect of phase manipulations in a quantitative manner. Subjects viewed two images of natural scenes, one of which contained an animal (the target) embedded in the background. The spectra of the images were manipulated by adding random phase noise at each frequency. The phase noise was the independent variable, uniformly distributed between 0° and ±180°. Subjects were remarkably resistant to phase noise. Even with ±120° noise, subjects were still 75% correct. The proportion of correct answers closely followed the correlation between original and noise-distorted images. Thus it appears as if it was not the global phase information per se that determines our percept of natural images, but rather the effect of phase on local image features.

Author(s): Braun, DI. and Wichmann, FA. and Gegenfurtner, KR.
Journal: Perception
Volume: 31
Number (issue): ECVP Abstract Supplement
Pages: 133
Year: 2002
Month: August
Day: 0

Department(s): Empirical Inference
Bibtex Type: Poster (poster)

Digital: 0
Event Name: 25th European Conference on Visual Perception
Event Place: Glasgow, UK
Organization: Max-Planck-Gesellschaft
School: Biologische Kybernetik

Links: Web


  title = {Phase information in the recognition of natural images},
  author = {Braun, DI. and Wichmann, FA. and Gegenfurtner, KR.},
  journal = {Perception},
  volume = {31},
  number = {ECVP Abstract Supplement},
  pages = {133},
  organization = {Max-Planck-Gesellschaft},
  school = {Biologische Kybernetik},
  month = aug,
  year = {2002},
  month_numeric = {8}