The Ultimate Guide to 3D Glasses

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The Ultimate Guide to 3D Glasses

Although it’s currently in a resurgence in popularity, 3D technology has actually been around since the 1900’s. This infographic by Sony shows how 3D cinema has fallen in and out of fashion over the last 100 years.

Sony infographic 3D

(For a closer look follow this link:
3D technology has continually evolved over this time and has leapt over boundaries in the last 20-30 years. Technology has gone from the blue cyan 3D glasses typical of the 80’s to the now widely-used ‘passive’ 3D glasses that manipulate the polarisation of light without effecting viewing quality.

Today, the way we watch 3D films in the cinema is by wearing passive 3D glasses, such as the ‘Real D 3D’ glasses. These are cheap to produce and a highly effective way to achieve the 3D effect. They work by using Polaroid film lenses to filter the two different images that are projected onto the screen. The blurred image you when not wearing the glasses is two separate images that have been taken by a camera with two lenses. Typically the two rolls of film are projected simultaneously at the screen. One of them will be circularly polarised to the left and the other will be circularly polarised to the right. The filters in the lenses will be different so that the each eye will receive a different image, tricking your brain into seeing ‘3D’.


Active 3D glasses

The next challenge was bringing 3D into the home. A typical television set cannot produce two different types of light, like projectors in a cinema can. ‘Active’ 3D glasses were produced as the answer. By looking at the frames within a film they are able to alternate the frames between the two different views. This all happens far too quickly for the human eye to see and so the picture becomes fuzzy and duplicated on the screen. What the active 3D glasses do is to shut off the vision to the left and right eye alternatively, using liquid crystal lenses, in order to match the frames in the film. Because of this, you see one 2D version of the film in one eye and a second 2D version in the other eye, tricking the brain into perceiving depth on screen.

Active 3D glasses are powered by electricity and made up of very sophisticated technology and thus are very expensive compared to the passive ones the cinema uses. Although being commended on picture quality and effective 3D quality, active 3D glasses have a number of issues. Firstly, because of their expensive and delicate structure they are not very child friendly. They are also electric powered (either by charger or battery) which means if you forget to charge them you won’t be able to watch your film. Other usage issues that have cropped up with use, including the need to keep your head perfectly upright while watching the movie – laying on your side means vision can be impaired in one of the lenses.


Passive 3D glasses (for TV)

Focusing on the way cinema produces a 3D effect using polarisation, a passive 3D TV was created which worked by assigning half the lines of pixels on the screen to the left image, and half to the right image i.e. line 1 is for the left image, line 2 for the right, line 3 for the left etc.

With this method of achieving 3D the resolution is essentially halved, making what should appear in HD a more standard definition. Because passive 3D glasses depend on the TV itself to do the hard work, the type of 3D television you have can massively affect the image quality. Opinions are varied as to whether picture quality is impaired when using passive 3D glasses, due to being largely dependent on the TV set.

This method is still popular mainly due to the cheapness of the glasses (making them much more family friendly), the comfort of them compared to the clunky active glasses and the ease of use from day to day. Because most passive 3D glasses use circular polarisation you’re free to be comfortable at any angle when viewing.

A further adaptation on this idea has produced a new type of 3D television that has a FPR (Film Pattern Retarder) filter built into the screen. This filter has small angled holes that manipulate the 3D image on the screen and sends out the two 3D layers circularly polarised to the left or circularly polarised to the right. The passive glasses then filter this out to each eye, just like in the cinema.

In of the newer passive televisions you can even use the glasses you get from the cinema when viewing your TV at home:

This definitely has to be the route home cinema is taking. By putting all the technology in the TV itself there are less likely to be issues with the technology breaking.

A final note – 10% of the world’s population can’t the 3D effect at all, much like colour-blindness. If you are unable to the 3D effect at all, you may be stereo-blind, otherwise referred to as having monocular vision, being a flat-viewer or lacking depth perception. The most common reasons for stereo-blindness are medical disorders that prevent the eyes focusing and/or aligning correctly (e.g. amblyopia, strabismus, optic nerve hypoplasia) or the loss of vision in one eye. So be sure to check that you are able to view 3D before making the financial commitment to a 3D TV.

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