The stereoscopic vision

We do not see exactly the same with the right eye as we do with the left. This difference is called horizontal disparity, retinal disparity or binocular disparity

When we look, however, we see just one image of things and not two different ones, which would make it much more difficult to go about our normal daily lives. Man’s capacity for the brain to integrate the two images being seen into one is what enables us to enjoy so-called stereoscopic vision. To make this possible, our brain analyses the data it receives from both eyes and generates a single, 3D image. Therefore, both eyes and the brain must function correctly to use this capacity.

Childhood in 2D

However, when we are born, this capacity is not fully developed. During childhood we develop binocular vision (with both eyes), as the human brain needs several years to merge the stimuli of a world in 3D. According to a study from London University, we practically do not see perfectly in 3D until after 12 years of age. Some people are never able to see in stereoscopic vision. This "stereoblindness" or "flat vision" could be due to the incorrect alignment of the eyes or a problem in the way the brain functions. According to different sources, this dysfunction could affect between 4% and 10% of the population, particularly children. The most frequent reason is the existence of microstrabisms that prevent the eyes from acting co-ordinately and sending the right signals to the brain. With children, training and exercise have proven to have a high rate of success, whereas in adults this rate is much lower.

Depth perception

Binocular vision is the ability to perceive the world in three dimensions. This does not mean, however, that small children and people who never fully develop binocular vision are unable to possess three-dimensional information on a scene based on a 2D image, as not all of the data that the brain needs to see in depth requires both eyes. Our brain uses other data for information on distances, such as the sharpness of the image: the farther away an object, the less clear it is seen, changes in size: objects moving farther away appear to become smaller and those moving closer seem to become larger, speed of lateral movement: when we move, objects closer to us seem to move more quickly that those in the background. If you look out of a train window, for example, the trees near the track pass by very quickly and those farther away much more slowly.

The source of 3D technology

The stereoscope was invented in 1838 by the British physicist Charles Wheatstone. The appliance gave the impression of seeing a photo in three dimensions. The effect was obtained by photographing the same scene twice, each from a different angle (to simulate the separation between the eyes). The two photos were then mounted in the appliance and the images merged using mirrors. Toy viewers can still be found today that are based on Wheatstone’s invention, on which 3D-effect films are also based.