How does 3D imaging work?

A futuristic helicopter passes low over the heads of the audience, robotic marines clad in exo-armor sweep away everything in their path, a hefty space shuttle shakes the air with the roar of its engines - so close and eerily real that you involuntarily press your head into your shoulders.

The recently released "Avatar" by James Cameron or 3D computer game make the viewer sitting in a chair in front of the screen feel like a participant in a fantastic action...

Very soon, alien monsters will be walking around in every home where there is a modern home theater.

But how is a flat screen able to show a three-dimensional picture?

Man in three-dimensional volumetric space...

We see the same object with the left and right eyes from different angles, thus forming two images - a stereo pair. The brain combines both pictures into one, which is interpreted by consciousness as three-dimensional.

Differences in perspective allow the brain to determine the size of an object and its distance. Based on all this information, a person receives a spatial representation with the correct proportions.

How does a three-dimensional image appear?

In order for the picture on the screen to appear three-dimensional, each eye of the viewer, as in life, must see a slightly different image, from which the brain will put together a single three-dimensional picture.

First films in 3D format, created taking into account this principle, appeared on cinema screens back in the 50s.

Since the increasingly popular television was already a serious competitor to the film industry, film businessmen wanted to get people off their couches and head to the cinema, enticing them with visual effects that no television could provide at that time: color images, wide screens, multi-channel sound and , of course, three-dimensional.

The volume effect was created in several different ways.

Anaglyph method (anaglyph – Greek for “relief”). In the early stages of 3D cinema, only black and white 3D films were released. In each appropriately equipped cinema, two film projectors were used to show them.

One projected the film through a red filter, the other displayed slightly horizontally shifted film frames on the screen, passing them through a green filter.

Visitors wore light cardboard glasses, in which pieces of red and green transparent film were installed instead of glasses, thanks to which each eye saw only the desired part of the image, and viewers perceived a “three-dimensional” picture.

However, both film projectors must be directed strictly at the screen and work absolutely synchronously.

Otherwise, a split image is inevitable and, as a result, headaches instead of viewing pleasure for viewers.

Such glasses are also well suited for modern color 3D films, in particular, those recorded using the Dolby 3D method. In this case, one projector with light filters installed in front of the lens is sufficient.

Each filter allows red and blue light to pass through to the left and right eyes. One image has a bluish tint, the other has a reddish tint. Light filters in glasses allow only relevant frames to pass through for a particular eye.

However, this technology allows achieving only minor 3D effect, with shallow depth.

Shutter method. Optimal for watching color films. Unlike anaglyph, this method involves the projector alternately displaying images intended for the left and right eyes.

Due to the fact that the alternation of images is carried out at a high frequency - from 30 to 100 times per second - the brain builds a complete spatial picture and the viewer sees a solid three-dimensional image on the screen.

Previously, this method was called NuVision, now it is more often called XpanD. To view 3D films using this method, shutter glasses are used, in which, instead of glasses or filters, two optical shutters are installed.

These small light-transmitting LCD matrices are capable of changing transparency upon command from the controller - either darkening or brightening, depending on which eye the image needs to be submitted to at the moment.

The shutter method is used not only in cinemas: it is also used in televisions and computer monitors. In the cinema, commands are given using an IR transmitter.

Some shutter glasses from the 1990s designed for PCs were connected to the computer via a cable (modern models are wireless).

The disadvantage of this method is that shutter glasses are complex electronic devices that consume electricity. Consequently, they have a fairly high (especially compared to cardboard glasses) cost and significant weight.

Polarization method. In the film industry, this solution is called RealD. Its essence is that the projector alternately displays film frames in which light waves have different directions of polarization of the light flux.

The special glasses required for viewing have filters that transmit only light waves that are polarized in a certain way. So both eyes receive images with different information, on the basis of which the brain forms a three-dimensional picture.

Polarized glasses are somewhat heavier than cardboard ones, but since they operate without a power source, they weigh and cost significantly less than shutter glasses.

However, along with polarizing filters installed on film projectors and glasses, displaying 3D films using this method requires an expensive screen with a special coating.

At the moment, preference has not been definitively given to any of these methods. It is worth noting, however, that fewer and fewer cinemas operate with two projectors (using the anaglyph method).

How 3D movies are made

The use of complex technical techniques is required already at the shooting stage, and not just during viewing of 3D films.

To create the illusion of three-dimensionality, each scene must be shot simultaneously with two cameras, from different angles.

Like human eyes, both cameras are placed close to each other, and always at the same height.

3D technologies for home use

To view 3D films The DVD still uses simple cardboard glasses, a legacy of the distant 50s. This explains the modest result - poor color rendition and insufficient image depth.

However, even modern 3D technologies are tied to special glasses, and this state of affairs, apparently, will not change soon.

Although Philips introduced a prototype of a 42-inch glasses-free LCD 3D TV in 2008, the technology will be at least 3-4 years away from reaching market maturity.

But several manufacturers announced the release of 3D TVs working in tandem with glasses at the international exhibition IFA 2009.

For example, Panasonic intends to release TV models with 3D support by mid-2010, just like Sony and Loewe, relying on the shutter method.

JVC, Philips and Toshiba are also trying to get on the 3D podium, but they prefer the polarization method. LG and Samsung develop their devices based on both technologies.

Content for 3D

The main source of 3D video content is Blu-ray discs. Content is transferred to the image source via HDMI.

To do this, the TV and player must support the appropriate technologies, as well as the recently adopted HDMI 1.4 standard - only it provides simultaneous transmission of two 1080p data streams. So far, devices that support HDMI 1.4 can be counted on one hand.

3D technologies on a computer

Initially, viewing a three-dimensional image on a computer was only available using glasses or special virtual reality helmets. Both were equipped with two color LCD displays - for each eye.

The quality of the resulting image when using this technology depended on the quality of the LCD screens used.

However, these devices had a number of shortcomings that scared off most buyers. The Forte cyber helmet, which appeared in the mid-90s, was bulky, ineffective and reminiscent of a medieval torture device.

A modest resolution of 640x480 pixels was clearly not enough for computer programs and games. And although more advanced glasses were later released, for example the LDI-D 100 model from Sony, even they were quite heavy and caused severe discomfort.

After a pause of almost ten years, technologies for forming stereo images on a monitor screen have entered a new stage of their development. It's good news that at least one of the two major graphics adapter manufacturers, NVIDIA, has developed something innovative.

The 3D Vision complex costs about 6 thousand rubles. includes shutter glasses and IR transmitter. However, to create spatial 3D images using these glasses, the appropriate hardware is required: the PC must be equipped with a powerful NVIDIA video card.

And in order for the pseudo-3D picture to not flicker, a monitor with a resolution of 1280x1024 pixels must provide a screen refresh rate of at least 120 Hz (60 Hz for each eye). The first laptop equipped with this technology was the ASUS G51J 3D.

Currently, so-called 3D profiles are also available for more than 350 games, which can be downloaded from the NVIDIA website (www.nvidia.ru). These include both modern action games, for example Borderlands, and those released earlier.

Continuing the theme of computer games, an alternative to the 3D shutter is the polarization method. To implement it, you need a monitor with a polarizing screen, for example Hyundai W220S.

Three-dimensional images become available with any powerful ATI or NVIDIA video card. However, the resolution is reduced from 1680x1050 to 1680x525 pixels, since interlaced frame output is used.

Based on materials from ComputerBild magazine

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