3D Visual Communications

3.1 Depth Cues and Applications to 3D Display

To perceive a 3D scene by a human visual system (HVS), the display system should be designed to present sufficient depth information for each object such that the HVS can reconstruct each object's 3D positions. The HVS recognizes an objects' depth in the real 3D world through depth cues, so the success of a 3D display depends on how well the depth cues are provided such that the HVS can observe a 3D scene. In general, depending on how many viewpoints are provided, the depth cues can be classified into two main categories: monocular and binocular.

3.1.1 Monocular Depth Cues

The category of monocular depth cue consists of depth cues observed from only one sequence of 2D images captured from one viewpoint. Depending on the availability of temporal information, it can be further classified into two subcategories: spatial monocular depth cue and spatial-temporal monocular depth cue. We list three major spatial monocular depth cues in [1]:

• Focus/defocus cues: The HVS associates the focus with a known depth plane, which is often refered to as accommodation. For an image captured by an aperture camera, the objects associated with the focusing plane of the optics are sharper than the other objects located away from this focusing plane. HVS can perceive an object's depth by differentiating the sharper objects from the blurred objects through accommodation.
• Geometric cues: Geometric cues include linear perspective, known size, relative size, ...