3D glasses – passive/active

Anaglyph 3D glasses - red and cyan

Although 3D glasses are a very simple artifact, they play a crucial role in 3D projectors, since both are needed to provide 3 dimensional appearances of objects being projected on screen.

3D glasses are an invention that has been around for a while. They have been in existence since 1853 and were created by Wilhelm Rollmann. They work by creating an illusion of depth in an image looked by a binocular apparatus (in this case the glasses) by delivering two pictures separately to both eyes. When the brain processes these two images a new image is formed that gives the illusion of an object or landscape in three dimensions. It’s a simulation of how human naturally sees the world around him.

There are three main types available: Color filter (Anaglyph, Omega glasses), polarized and shutter glasses. The color filter and polarized ones fall into the category of passive glasses, while the shutter  glasses belong to the category of active 3D.

The anaglyph stereoscopic glasses are one of the most ancient ones, dating from almost the times of the industrial revolution. These are the ones that have cyan and red lenses in them. These somewhat outdated lenses can actually be handmade, done by anyone at home with relatively simple components. Yes, that means you can even make your own! These glasses are very popular but they might be replaced by more advanced ones since there has been a great deal of advance in 3D. One drawback of the anaglyphs  is that colors of the image are very distorted

Anaglyph 3D glasses - red and cyan
Anaglyph 3D glasses

Polarized glasses are the next on the list. These are normally given in cinemas to watch 3D movies. These glasses are not the best looking glasses out there and are very similar in its design as Groucho Marx´s glasses. These glasses have two polarizing filters in transparent lenses. These filters fool the brain into believing that the image the person is watching comes in 3D. The difference between anaglyph and polarized glasses is pretty much on how the filters (or lenses) of each one of the glasses decompose the rays of light.

Passive 3D glasses
Passive 3D glasses

Finally, there are the shutter 3D glasses. The anaglyph and polarized glasses are a passive 3D method, while the shutter glasses use well…an active 3D method. By passive 3D method is meant that the glasses filter the image through a lens which filters it and transmit the impression to the brain that it is watching a 3D image when it is not.

On the other hand, the active 3D method used by shutter glasses is a bright technological advance. These glasses work with LCD screen technology which works by blackening each lens alternately so at first one lens is dark and at the next moment the other one is dark meanwhile the first one just got back to normal. The active stereoscopic glasses needs a battery to function. This is what gives them the energy to change the darkening of the image in each of the lenses one time after another.

Normally due to LCD technology, battery and more stylish designs, shutter active glasses are more expensive than passive glasses.

Talking about design, you can actually look futuristic and cool with active 3D glasses, this does not happen with passive 3D glasses which have a simple frame and either a transparent lens or cyan and red lenses as mentioned before.

Passive 3D glasses are by far the cheapest method, costing from $5 to $20 depending on the frame chosen. On the other hand, active 3D glasses might quintuple the price of its passive 3D counterparts. Active 3D glasses can be found within a price range of $50 to $150.

Each 3D method has its good things as well as its drawbacks, so for considering any of the two, many factors such as price, quality, style, etc. should be taken into account.

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