Volumetric 3D Displays
7.1 The Nature of Volumetric Displays
Stereoscopic and autostereoscopic displays use two images, one for the left and one for the right eye, to create a 3D effect. Volumetric displays, as a rule, provide one image for both eyes while the 3D effect is created by a stack of images in the form of planar displays on top of each other, each at a different depth or distance from the eyes. These distances will be essential for generating the sensation of depth. Referring to the volume of these multi-depth displays, they are called a volumetric display. When the stack of displays is stationary, it is referred to as a static volume display. The perception of volume, that is, the third dimension, can also be stimulated by mechanical displays, where a rotational or translatory movement sweeps through the volume while emitting images at various depths. This volumetric mechanical arrangement is called a swept volume display .
The next section will be devoted to static volume displays, which is followed by a section on swept volume displays.
In all volumetric displays the eyes focus on images at different depths, in that way creating a 3D perception which avoids the mismatch between accommodation (focus) and vergence (rotation) of the eyeballs. The mismatch was treated in Chapter 1 and especially in Figure 1.1. If the eyes focus on P in Figure 1.1, then the axes of the eyes rotate (the vergence) by the disparity angles γ out of the fovea. The focus on P (distance, ...