Chapter 2 Principles of Stereoscopic Depth Perception and ...

2. Principles of Stereoscopic Depth Perception and Reproduction
requires supplementary information from another cue to be interpreted.
An example would be image blur, which provides information
about the distance of an object from a fixated object, without
indicating which is nearer. Other cues, such as occlusion, familiar
size, or linear perspective may act as disambiguators.
Generally speaking, the more consistent cues are, the better an accurate
depth percept can be established. Cutting & Vishton (1995), based on
Nagata (1993), provide a thorough discussion of the relative information
potency of depth cues at various distances (see Figure 2.4). Each cue on
its own is an ambiguous indicator of distance, layout and surface structure.
However, by combining several sources of information this ambiguity
may be reduced, even to the point of near-metric accuracy.
A detailed treatment of all depth cues is beyond the purpose of this thesis,
but interested readers are referred to Cutting & Vishton (1995), Palmer
(1999), in particular chapter 5, and Sedgwick (2001).
2.3 Stereoscopic display techniques
Stereoscopic display techniques are based on the principle of taking two
images and displaying them in such a way that the left view is only seen by
the left eye, and the right view only seen by the right eye. There are a number
of ways of achieving this (Okoshi 1980, Pastoor & Wöpking 1997, Sexton
& Surman 1999). Stereoscopic displays can be categorised based on
the technique used to channel the right and left images to the appropriate
eyes. A distinguishing feature in this regard is whether the display
method requires a viewing aid (e.g., glasses) to separate the right and left
eye images. Stereoscopic displays that do not require such a viewing aid
are known as autostereoscopic displays. They have the eye-addressing techniques
completely integrated in the display itself. Other distinguishing
features are whether the display is suitable for more than one viewer (i.e.,
allows for more than one geometrically correct viewpoint), and whether
look-around capabilities are supported, a feature inherent to a number of
autostereoscopic displays (e.g., holographic or volumetric displays), but
which requires some kind of head-tracking when implemented in most
other stereoscopic and autostereoscopic displays.
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