Signal Processing for Stereoscopic and Multi-View 3D Displays - Signal Processing Systems - page 34

a b

Fig. 24 Selective view updating for continuous parallax: active views and visualized scene
perspective for ( a ) one observer position and ( b ) another observer position

tracking approach, estimation of the distance between the observer and the display
is not needed as a set of properly rendered views can provide proper parallax to the
eyes in a wide range of head positions. Also, real-time performance of the system
is not necessarily critical as the user is always “surrounded” by a safe margin of
properly rendered views.

4.1.2 Optimization for Viewing Distance

Both dual-view and multiview autostereoscopic displays are designed to be watched
at a particular distance. At the optimal viewing distance the intended view is seen
across the whole surface of the display, as marked with “1” on Fig. 25 a . At a distance
closer than the optimal the observer sees different visibility zones at the left and right
edges of the display, as marked with “2” on the same figure. If the distance to the
observer is known, the content on the display can be re-rendered accordingly. In
order to measure the distance to the observer, eye and face tracking is performed by
two cameras simultaneously. For more information on the algorithm the reader can
refer to [ 78 ] .
In the case of a multiview display the information is shifted between the views;
for example, the image along the right edge of the display intended for the central
view (marked with red on the Fig. 25 a ) can be rendered in the previous view
(as shown by the curved arrow). The opposite is done along the left edge. This
procedure can be expressed as a re-routing table which optimizes the image for
a given observation distance. The re-routing table should be re-calculated for any
given distance to the observer. In the case of a multiview display, pixels intended for
certain view would be re-routed to other views. An example of a multiview rerouting
table is given in Fig. 25 b . The surface of the display is separated into sub-sections