How Pulfrich 3D Glasses Work

3D glasses have been used to give audiences experiences beyond what is normally seen on a movie or television screen for years, and the use of Pulfrich 3D glasses is one way that this has been done. The glasses themselves come in a variety of styles, but they have one characteristic in common. The lenses of the glasses are one clear lens and one dark grey shaded lens.

The lenses are based on what is called the Pulfrich effect, an effect named for the German physicist Carl Pulfrich who first described it in 1922. This effect is a psycho-optical phenomenon that gives those wearing the glasses the illusion of a third dimension. Any type of lateral motion in objects within the field of vision is seen as having a depth component. This component is the result of how the brain interprets what the eyes are seeing.

The darker lens causes the brain to interpret what that eye is seeing at a slower rate than what the eye covered by the clear lens is seeing. The eyes naturally process what is seen in dimmer light slower than what is seen in bright light, and this results in a 3D optical effect with those wearing the glasses.

There are limits to this effect that give it limited use in things like television and games. The effect only works with objects that move in and out of the visual field as well as from side to side. The glasses do nothing to change how the eyes see up and down motions.

The glasses saw limited use during the 1990s. Various TV specials and travelogues made in the Netherlands used the effect, and some games for the Nintendo and Super Nintendo Entertainment System also made use of the effect created by the glasses. Millions of sets of glasses were also distributed to viewers throughout America when the Discovery Channel aired its Shark Week specials. One of the key benefits to these glasses over other 3D glasses is that they are one of the only ways that viewers can experience 3D effects with broadcast television.

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