A parallax barrier is a device placed in front of an image source, such as a liquid crystal display

Liquid crystal display

A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....

, to allow it to show a stereoscopic image

3D display

A 3D display is any display device capable of conveying a stereoscopic perception of 3-D depth to the viewer. The basic requirement is to present offset images that are displayed separately to the left and right eye. Both of these 2-D offset images are then combined in the brain to give the...

 or multiscopic image

Multiscopy

In contrast with 3D binocular stereoscopy , 3D multiscopy displays multiple angles at once...

 without the need for the viewer to wear 3D glasses. Placed in front of the normal LCD, it consists of a layer of material with a series of precision slits, allowing each eye to see a different set of pixel

Pixel

In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....

s, so creating a sense of depth through parallax

Parallax

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...

 in an effect similar to what lenticular printing

Lenticular printing

Lenticular printing is a technology in which a lenticular lens is used to produce images with an illusion of depth, or the ability to change or move as the image is viewed from different angles...

 produces for printed products. A disadvantage of the technology is that the viewer must be positioned in a well-defined spot to experience the 3D effect. Another disadvantage is that the effective horizontal pixel count viewable for each eye is reduced by one half; however, there is research attempting to improve these limitations.

Applications

In addition to films and computer games, the technique has found uses in areas such as molecular modelling

Molecular modelling

Molecular modelling encompasses all theoretical methods and computational techniques used to model or mimic the behaviour of molecules. The techniques are used in the fields of computational chemistry, computational biology and materials science for studying molecular systems ranging from small...

and airport security

Airport security

Airport security refers to the techniques and methods used in protecting airports and aircraft from crime.Large numbers of people pass through airports. This presents potential targets for terrorism and other forms of crime due to the number of people located in a particular location...

. It is also being used for the navigation system in the 2010-model Range Rover

Range Rover

The Range Rover is a large luxury four-wheel drive sport utility vehicle produced by British car maker Land Rover. The model, launched in 1970, is now in its third generation...

, allowing the driver to view (for example) GPS directions, while a passenger watches a movie. It is also used in the Nintendo 3DS

Nintendo 3DS

The is a portable game console produced by Nintendo. The autostereoscopic device is able to project stereoscopic 3D effects without the use of 3D glasses or any additional accessories. The Nintendo 3DS features backward compatibility with Nintendo DS series software, including Nintendo DSi software...

 hand-held game console and LG's Optimus 3D smartphone, HTC's EVO 3D as well as Sharp's Galapagos Android SmartPhone series.

The technology is harder to apply for 3D television sets, because of the requirement for a wide range of possible viewing angles. A Toshiba 21-inch 3D display uses parallax barrier technology with 9 pairs of images, to cover a viewing angle of 30 degrees.

Overview

There are 3 main types of Autostereoscopy

Autostereoscopy

Autostereoscopy is any method of displaying stereoscopic images without the use of special headgear or glasses on the part of the viewer. Because headgear is not required, it is also called "glasses-free 3D" or "glassesless 3D"...

 displays with Parallax barrier

• Early experimental prototypes would just put a series of precision slits on regular LCD screen to see if it had any potential.
  • Pros
    • Easily attachable
  • Cons
    • Lowest image quality
• First fully developed "Parallax barrier displays" would have have precision slits as one of its optical components over the Subpixels. This blocks the Image
  Image
  An image is an artifact, for example a two-dimensional picture, that has a similar appearance to some subject—usually a physical object or a person.-Characteristics:...
  
   from one eye and shows it to another.
  • Pros
    • Cheaper for Mass Production
      Mass production
      Mass production is the production of large amounts of standardized products, including and especially on assembly lines...
      
      
  • Cons
    • Least efficient with backlight
      Backlight
      A backlight is a form of illumination used in liquid crystal displays . As LCDs do not produce light themselves , they need illumination to produce a visible image...
      
      ,
    • Needs twice as much backlight as normal displays
    • Small viewing angles
• The newest and most convenient design, commercial products like the Nintendo 3DS
  Nintendo 3DS
  The is a portable game console produced by Nintendo. The autostereoscopic device is able to project stereoscopic 3D effects without the use of 3D glasses or any additional accessories. The Nintendo 3DS features backward compatibility with Nintendo DS series software, including Nintendo DSi software...
  
  , HTC Evo 3D
  HTC EVO 3D
  The HTC Evo 3D is an Android 2.3 smartphone that allows for the creation and viewing of 3D content through the use of two 5 MP rear-facing cameras and a glasses-free 3D-capable 4.3" qHD touch screen. In the United States, the Evo 3D is available exclusively on the Sprint/Nextel network...
  
  , and LG Optimus 3D
  LG Optimus 3D
  The LG Optimus 3D, or LG Thrill 4G in the USA, is a Android 2.2 froyo 3D mobile device released on 7 July 2011 in the UK and has been touted as the worlds first full 3D mobile phone. It has 512MB of RAM and 8GB of onboard storage which can be expanded by up to 32GB using a micro SDHC card...
  
   do not have the physical parallax barrier in front of the Subpixels, but behind the Subpixels and in front of the Backlight
  Backlight
  A backlight is a form of illumination used in liquid crystal displays . As LCDs do not produce light themselves , they need illumination to produce a visible image...
  
  . They thus send not different images to the two eyes but different light to each. This allows the two channels of light to pass through the Subpixels, allowing Glare
  Glare (vision)
  Glare is difficulty seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Because of this, some cars include mirrors with automatic anti-glare functions....
  
   over the opposite Pixels giving the best image quality.
  • Pros
    • Clearest image
    • Only uses 20-25% more backlight than normal displays
    • Largest viewing angle
  • Cons
    • More expensive for Mass Production
      Mass production
      Mass production is the production of large amounts of standardized products, including and especially on assembly lines...
      
      

External links

• Principle of autostereo display - Java applet illustrating the idea