Depth perception in autostereograms: 1/f noise is best

An autostereogram is a single image that encodes depth information that pops out when looking at it. The trick is achieved by setting a basic 2D pattern and continuously replicating the local pattern at each point in the image with a shift defined by the desired disparity. In this work, we explore the dependency between the ease of perceiving depth in autostereograms and the choice of the basic pattern used for generating them. We report the results of three sets of psychophysical experiments using autostereograms generated from 2D random noise patterns having power spectra of the form 1/f(β) The experiments were designed to test the ability of human subjects to identify smooth low-resolution surfaces, as well as detail, in the form of higher-resolution objects in the depth profile, and to determine limits in identifying small objects as a function of their size. In accordance with the theory, we discover a significant advantage of the 1/f noise pattern (pink noise) for fast depth lock-in and fine detail detection, showing that such patterns are optimal choices for autostereogram design.