A Perfect 3D Display could be defined by

Full spectrum of colors Wide viewing angle Visible to multiple viewers, without discomfort No special equipment worn by the viewer Computer generated image (CGI) Objects behind as well as in front of display Four physiological depth perception cues In a conventional two-dimensional image there are usually several psychological cues presented to the observer that provide the perception of depth. These cues include object size, shadow, linear perspective, and object overlapping. However, a two-dimensional image is unable to provide any physiological cues and thus cannot provide a true perception of depth. The four physiological depth perception cues are: accommodation, convergence, binocular parallax, and monocular movement parallax. Accommodation is a cue given by the adjustment of the focal length of the eye's crystalline lens when an eye focuses on a particular object. Convergence is a cue given by the angle made by the two viewing axes of observer's eyes. Binocular parallax is a cue caused by the difference between the views seen by the two eyes of an observer. Monocular movement parallax is a cue observed when a person is moving and is caused by the changing view in each of the person's eyes. Accommodation and monocular parallax are available even when we see an object with a single eye.