By Robert Earl Patterson, Infinite Z
Interactive stereo displays allow for the existence of a natural interaction between the user and the stereo images depicted on the display. In the type of display discussed here, this interaction takes the form of tracking the user’s head and hand/arm position. Sensing the user’s head position allows for the creation of motion parallax information, an immersive depth cue that can be added to the binocular parallax already present in the display. Sensing the user’s hand or arm position allows the user to manipulate the spatial attributes of virtual objects and scenes presented on the display, which can enhance spatial reasoning. Moreover, allowing the user to manipulate virtual objects may permit the creation of a sense of spatial relations among elements in the display via proprioception, which may augment the two parallax cues. The congruence among binocular parallax, motion parallax, and proprioception should increase the sense of depth in the display and increase viewing comfort, as well as enhance the ability of our intuitive reasoning system to make reasoned sense out of the perceptual information. These advantages should make interactive stereo displays, which may be classified as a form of cognitive enhancement display, the display of choice of the future. Interactive stereo displays may be particularly important for applications in industry, medicine, government, and education.
Interactive stereo displays, unlike most typical stereo displays, allow for the existence of an interaction between the user and the stereo images depicted on the display. Sensors attached to the physical display, which track the head and hand/arm position of the user, enable this interaction. Sensing the position of the user’s head allows for new immersive depth information to be created and presented on the display, information beyond binocular parallax. This new depth information is called motion parallax, which can be added to the binocular parallax already present in the display. The advantage of motion parallax being added to binocular parallax is an increase in the comfort of viewing and the quality and sense of immersion of the experienced depth (Patterson & Silzars, 2009).
Sensing the position of the user’s hand or arm allows the user to manipulate or interact with the virtual objects or scenes presented on the display. This type of human-device interaction is called a direct manipulation interface (Hutchens, Hollan & Norman, 1985). Using a direct manipulation interface may allow for the creation of a sense of spatial relations among elements in the display. This sense of spatial relations would come from sensing the position and movement of one’s own body, which is called proprioception (Kandel, Schwartz & Jessel, 2000).
The congruence among binocular parallax, motion parallax, and proprioception, which is possible only in interactive stereo displays, may augment the sense of depth in the display (Keehner, Khooshabeh & Hegarty, 2008), and increase viewing comfort (Patterson & Silzars, 2009). The lack of congruence among these perceptual cues when a typical stereo display is viewed can lead to a situation that Patterson and Silzars (2009) called ‘high-level cue conflict’, which refers to multiple cues conveying different depths to a viewer, thus creating “eye” strain and discomfort. Patterson and Silzars argued that the basis for this discomfort is to be found in the mental processes of human reasoning. Specifically, immersive stereo displays that depict real-life objects or scenes primarily engage an intuitive reasoning system, which attempts (and fails) to make reasoned sense out of the conflicting perceptual information. However, when high-level cue conflict is minimized or eliminated by having congruent perceptual cues, the intuitive reasoning system should make reasoned sense out of the information that is presented.
These three topics—motion parallax, direct manipulation interfaces, and intuitive reasoning–are discussed in more detail below. But before discussing these topics, however, a brief overview of binocular vision will be given, followed by a discussion of an assumed problem with stereo displays—accommodation-vergence mismatch. These topics were discussed in detail by Patterson (2009). The issue of a mismatch between accommodation and vergence will be related to interactive stereo displays later. [more...]