“Three-Dimension Display” (3D Display) refers to technologies that recreate depth information of objects, making them appear nearer or farther. There are three main types of 3D display technologies based on how they present depth information:

1. Psychological Cues: This method uses cues such as shadows, occlusion, and linear perspective to convey the spatial relationships of objects. Typical two-dimensional displays (2D Display) that create a sense of depth using these cues fall into this category.

2. Binocular Parallax: This method leverages the principle of binocular disparity, where the left and right eyes perceive slightly different images (stereoscopic pairs). These images are then combined in the brain to create a sense of depth. Most modern flat-panel 3D displays use this approach.

3. Holographic Imaging: This advanced method uses techniques like holography to recreate 3D images in space, allowing the viewer to see images just as they would real objects. This method fully aligns with the natural visual functions of human eyes.

Binocular parallax occurs when viewing the same target from two points at a certain distance apart (e.g., human eyes), leading to a difference in perceived direction. The angle between the lines of sight from these two points to the target is known as the parallax angle, and the distance between the two points is called the baseline. Knowing the parallax angle and baseline length allows for calculating the distance between the target and the observer.

The typical distance between human eyes is approximately 65mm, which causes a slight displacement in the images seen by each eye. This displacement, known as parallax, is organically synthesized in the brain to produce a three-dimensional visual effect. Binocular vision provides the special ability to process information about direction and depth, forming a sense of depth perception. When viewing two objects at different distances, the brain can discern their relative positions and the distance between them.

Depth perception includes two aspects:

• Absolute Distance: Judging the distance between the observer and an object.

• Relative Distance: Judging the distance between two objects or between different parts of the same object. Experiments have shown that human eyes are significantly more accurate at judging relative distances compared to absolute distances.

Thus, binocular parallax forms the basis of stereoscopic vision and depth perception.

In flat-panel displays, 3D images are reproduced by leveraging the mechanism of binocular parallax to create a sense of depth. By presenting stereoscopic image pairs to the viewer’s left and right eyes (simulating the left and right eye views of the same object), the brain is tricked into perceiving a 3D effect. The degree of stereoscopic effect can be controlled by adjusting the amount of binocular parallax.

For a point A, the left and right eyes see corresponding points  A_L  and  A_R , analogous to the images captured by a 3D camera. When these images are displayed on a flat panel, ensuring the left eye only sees  A_L  and the right eye only sees  A_R , the viewer perceives point A as either floating in front of the display (when  A_L  is to the left of  A_R , called the “pop-out effect”) or behind the display (when  A_L  is to the right of  A_R , called the “depth-in effect”).