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1.1 ABSTRACT

The stereoscopic display technology has become a main research issue in recent years

because of its unique human-computer interaction. Three dimensional (3D) displays,

mostly stereoscopic, are becoming part of our life. There are several technologies to

achieve the 3D effects. Stereoscopic display technology is used to create a illusion of

depth to human eyes in the photo or video which is being watched. Nowadays most

of the devices come with 3D display capability, and all this devices are using

stereoscopic display technology to give 3D effect.

This report analyzes the principle of stereoscopic display and then briefly introduces the

different types of available stereoscopic display technologies and the devices used in this

technology meanwhile it also talks about the principles, applications, advantages and

disadvantages of stereoscopic display technologies, and at last talks about stereo window

concept in this technology and what is next following this technology in future.

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1.2 INTRODUCTION

Stereoscopy is a technique for creating or enhancing the illusion of depth in an image by

means of stereopsis for binocular vision. Most stereoscopic methods present two offset

images separately to the left and right eye of the viewer. These two-dimensional images are

then combined in the brain to give the perception of 3D depth. This technique is

distinguished from 3D displays that display an image in three full dimensions, allowing the

observer to increase information about the 3-dimensional objects being displayed by head

and eye movements.

Stereoscopy creates the illusion of three-dimensional depth from given two-dimensional

images. Human vision, including the perception of depth, is a complex process which only

begins with the acquisition of visual information taken in through the eyes; much

processing ensues within the brain, as it strives to make intelligent and meaningful sense of

the raw information provided. One of the very important visual functions that occur within

the brain as it interprets what the eyes see is that of assessing the relative distances of

various objects from the viewer, and the depth dimension of those same perceived objects.

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2.1 NEED FOR STEREOSCOPY

Initially in early 19th century, there were no television box for watching videos, and people

used to perform skits in theatre and as time went by theatres came into picture where screen

was used to project the movies which were recorded using a bulky video recorder, and then

slowly as time went on more research and more inventions resulted in making a smaller

television set for watching movies in our home comfortably and by the end of 19 th century ,

television set was so affordable that everyone had one television set at home , and now

people got bored of it slowly and they wanted something new , something more exciting

and something more entertaining than plain old 2D supporting Television box.

This led to beginning of research on enabling a totally new kind of experience while

watching the video, a feeling of being inside the movie or giving depth to the images and

videos that are seen in the movies. This gave rise to invention Stereoscopic display

technology, which helps in giving 3D illusion to the movie or images that people are

watching.

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2.2 WHAT IS STEREOSCOPY?

Stereoscopy also called as 3D imaging is a technique for creating or enhancing the illusion

of depth in an image by means of stereopsis for binocular vision. The word stereoscopy

derives from Greek word “stereos”, meaning "firm, solid", and “skopeo” meaning "to look,

to see". Any stereoscopic image is called stereogram. And any devices used for stereoscopy

are called stereoscope.

One of the very important visual functions that occur within the brain as it interprets what

the eyes see is that of assessing the relative distances of various objects from the viewer,

and the depth dimension of those same perceived objects. The brain makes use of a number

of cues to determine relative distances and depth in a perceived scene, including Stereopsis,

Accommodation of the eye, Overlapping of one object by another Subtended visual angle

of an object of known size, Linear perspective, Vertical position, Haze, and Change in size

of textured pattern detail

Fig 2.1: An early stereoscopic card for viewing a scene from nature

Stereoscopic display technology uses all the above mentioned cues to trick the mind and

create an illusion of depth by giving two seperate images to two eyes. Fig 2.1 shows the old

picture used for stereoscopic view in early 19th century.

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Although the term "3D" is ubiquitously used, it is also important to note that the

presentation of dual 2D images is distinctly different from displaying an image in three full

dimensions. The most notable difference is that, in the case of "3D" displays, the observer's

head and eye movement will not increase information about the 3-dimensional objects

being displayed. Holographic displays or volumetric display are examples of displays that

do not have this limitation. Similar to the technology of sound reproduction, in which it is

not possible to recreate a full 3-dimensional sound field merely with two stereophonic

speakers, it is likewise an overstatement of capability to refer to dual 2D images as being

"3D". The accurate term "stereoscopic" is more cumbersome than the common misnomer

"3D", which has been entrenched after many decades of unquestioned misuse. Although

most stereoscopic displays do not qualify as real 3D display, all real 3D displays are also

stereoscopic displays because they meet the lower criteria as well.

Traditional stereoscopic photography consists of creating a 3D illusion starting from a pair

of 2D images, a stereogram. The easiest way to enhance depth perception in the brain is to

provide the eyes of the viewer with two different images, representing two perspectives of

the same object, with a minor deviation equal or nearly equal to the perspectives that both

eyes naturally receive in binocular vision.

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2.3 TYPES OF STEREOSCOPIC DISPLAY TECHNOLOGY

Stereoscopic Display technology can be divided into two groups

1. Manual Stereoscopic Display Technology

2. Automatic Stereoscopic Display Technology

Manual Stereoscopic Display Technology is the most widely used stereoscopic display

technology in present days. In this technology viewers need to wear a glass in order to

enjoy the stereoscopic display. The glasses can be either active or passive devices. Active

devices uses electronic device to power the glasses and to synchronise the glass shutters.

Example for this active device is Shutter Glass Stereoscope. Passive devices are those

which doesn’t need any kind of electronic device in the glass, this are the most famous and

widely used devices in stereoscopic display technology. Examples for passive devices are

anaglyph glasses and polarization glasses.

Automatic Stereoscopic Display Technology is the latest innovation in stereoscopic display

technology in recent times and still not yet developed to its full capacity. This technology

does not need the viewer to use any kind of glasses while watching the movie or image.

People can get the Depth Illusion with the bare eyes. Nintendo 3DS is the example of this

technology.

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3.1 DEPTH ANALYSIS

We need to understand how human eye analyses depth in order to understand the principle

of stereoscopic display technology. When we watch an object with one eyed covered and

then watch the same object with other eye closed this time and we see two different images.

This is ofcourse because our eyes are a few inches apart; this is called the “interocular

distance” and it varies from person to person. We should also note that when we look at

something close, objects appear in double in the background. It’s because we are actually

rotating our eyes so they both point directly at what we are focusing on. This is called

“convergence,” and it creates a sort of X, the center of the X being what’s being focused

on.

Fig 2.2: Formation of convergence X by eye

So the objects at the center of the X are aligned at the same points on our respective retinas,

but because of the interocular, that means that things in front and behind of that X are going

to hit different points on those retinas — resulting in a double image.

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Once the two images have been presented to our retinas, they pass back through the optic

nerve to various visual systems, where an incredibly robust real-time analysis of the raw

data is performed by several areas of the brain at once. Some areas look for straight lines,

some for motion, some perform shortcut operations based on experience and tell us that yes

indeed, the person did go behind that wall, they did not disappear into the wall, and that sort

of thing. Eventually (within perhaps 20 milliseconds) all this information filters up into our

consciousness and we are aware of color, depth, movement, patterns, and distinct objects

within our field of view, informed mainly by the differences between the images hitting

each of our retinas. It’s important to note that vision is a learned process, and these areas in

our visual cortex are “programmed” by experience as much as by anatomy and, for lack of

instinct.

Fig 2.3: Picture describing how the image are sent to brain from retina

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To understand how Stereoscopic Display Technology works we need to understand the

above mentioned concepts, which are native 3D acquisition tools.

Stereoscopic Display technology use those concepts to create the illusion to the brain,

before we used to focus on one plan 2D image and hence we could only get the depth or

distance between that image and eyes and not the depth of the objects in the image , but

now we display two different images to both the eyes of the same scene which tricks the

brain as if we are seeing the real live view of the video and hence we are able the get the

depth in the image or video that we are watching.

That’s the most simple principle of this technology that is it creates the illusion of depth by

presenting a different image to each eye. And that’s something that all 3D displays have in

common, no matter what. But how best to display it? Everyone differs in their opinions.

standards were even developed that encode a 3D stream similarly to normal stream, except

with totally separate left and right eye images baked right in. There are variations, of

course, but it’s a surprisingly practical approach they agreed on.

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3.2 ENCODING METHODSOne way to distribute the 3D content is to deliver left and right views independently.

However, this is not much of an encoding, quite wasteful in terms of bandwidth, packaging,

and may be problematic to keep the two views correctly synchronized.

Hence separate encoding methods had to be used inorder to distribute the 3D content

Presently there are 4 types of encoding methods for 3D content that are being used

1. Spatial Compression2. Temporal Interleaving3. 2D+ some form of Metadata4. Colour Shifting

SPATIAL COMPRESSION

This is useful when trying to deliver a 3D signal over the existing HD video infrastructure.

It is also referred as ‘frame compatible’ as it squeezes the left and the right image into

one HD frame. In order to do so it employs some kind of pixel sub sampling, so the

downside is the loss in resolution. There are two aspects of this approach that need to be

considered: the spatial sub-sampling and the frame packaging.The proposed spatial sub-

sampling schemes are: taking alternate lines, taking alternate columns or sampling

diagonally using a quincunx filter. After the sampling the images are repackaged in side-

by-side or over/under format. The quincunx sampling is used and repackaged for

transmission because its format is not efficient for direct compression. The quincunx signal

can be used directly in HD interfaces that deal with the co-called checkerboard pattern and

this is the signal format of choice for DLP displays.

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TEMPORAL INTERLEAVING

This method presents sequentially left and right images as full resolution frames. Therefore

it requires doubling the frame rate and therefore doubling the bandwidth required for a

normal 2D HD signal. Compression can use prediction between left and right views, but

this tends to be no better than the normal temporal prediction. So the main saving is the

reduction of the number of I frames.

2D + SOME FORM OF META DETAThe idea with this compression technique is to transmit a 2D signal and then some

information that allows the reconstruction of a second 2D signal. This would be compatible

with existing 2D displays, it may save bandwidth and it is included in MPEG. The most

popular types of data suggested in order to supplement the 2D are

• a depth map (2D + depth);

• an optimized disparity map indicated as Delta (2D + D);

• a set of depth, occlusion and transparency maps (2D + DOT).

Other suggestions include supporting multiple view coding as a way to future-proof the

encoding standards to the possible adoption of auto stereoscopic and holographic displays.

COLOUR SHIFTINGColour shifting, associated with the anaglyph technique, uses red/green or red/cyan or some

other two colour pairing. It is compatible with 2D displays, offers full resolution and

glasses are inexpensive, but it is mainly a legacy technology.

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HSPA(High Speed Packet Access)4.1 STEREOSCOPE

DEVICES

A stereoscope is a device for viewing stereographic displays, which are display’s that

contain two separate images that are printed side by side to create the illusion of a three-

dimensional image.

There are two types of Stereoscope Devices

1. ACTIVE DEVICES

2. PASSIVE DEVICES

Active devices are those devices which need an small electronic component on the glass

which powers the glass system and also helps in synchronizing the signal. These devices

are mostly used in theatres. Example of this type of device is shutter glass system

Passive devices are those devices which need no electronic help and don’t need any power

to run the glass system and there are no synchronizing of signals involved. This devices are

used mostly in home entertainment systems because they are cheaper then the active

devices and maintenance is also less. Example for this are Polarization system, Interference

Filter system ,Chroma depth System and colour anaglyph system.

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4.2 ACTIVE DEVICE

4.2.1 SHUTTER SYSTEMS

This is the current method of choice for most 3D entertainment companies. The media is

displayed at a high framerate, and the glasses rapidly switch between black and clear using

a pair of low-latency transparent LCD screens. In this way, one eye sees nothing (for as

little as a hundredth of a second or so) while the other sees its “correct” image, and a few

microseconds later, the situation is reversed: the opposite eye’s image is displayed and the

LCDs have switched. The benefit is that each eye is getting the “full” image whenever it’s

getting anything (unless they’re cheating and doing it via interlaced field switching).

Fig 4.1: Active Shutter System

There are number of objections to this technology like different company glasses vary in

their performance , no single standard and the technology is still being improved, the

glasses are costlier compared to other passive devices and maintenance cost is also very

high and position and tilt can affect the image 3D depth.

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4.3 PASSIVE DEVICE

4.3.1 POLARIZATION SYSTEMS

To present a stereoscopic picture, two images are projected superimposed onto the same

screen through different polarizing filters. The viewer wears eyeglasses which also contain

a pair of polarizing filters oriented differently (clockwise/counterclockwise with circular

polarization or at 90 degree angles, usually 45 and 135 degrees, with linear polarization).

As each filter passes only that light which is similarly polarized and blocks the light

polarized differently, each eye sees a different image. This is used to produce a three-

dimensional effect by projecting the same scene into both eyes, but depicted from slightly

different perspectives. Additionally, since both lenses have the same color, people with one

dominant eye (amblyopia), where one eye is used more, are able to see the 3D effect,

previously negated by the separation of the two colors.

Fig 4.2 Polarized Systems

Circular polarization has an advantage over linear polarization, in that the viewer does not

need to have their head upright and aligned with the screen for the polarization to work

properly.

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4.3 PASSIVE DEVICE

4.3.2 COLOR ANAGLYPH SYSTEM

In an anaglyph, the two images are superimposed in an additive light setting through two

filters, one red and one cyan. In a subtractive light setting, the two images are printed in the

same complementary colors on white paper. Glasses with colored filters in each eye

separate the appropriate images by canceling the filter color out and rendering the

complementary color black. A compensating technique, commonly known as Anachrome,

uses a slightly more transparent cyan filter in the patented glasses associated with the

technique. Process reconfigures the typical anaglyph image to have less parallax.

Fig 4.2: Red-Cyan Anaglyph System

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4.3 PASSIVE DEVICE

4.3.3 INTERFERENCE FILTER SYSTEM This technique uses specific wavelengths of red, green, and blue for the right eye, and

different wavelengths of red, green, and blue for the left eye. Eyeglasses which filter out the

very specific wavelengths allow the wearer to see a full color 3D image. Special

interference filters (dichromatic filters) in the glasses and in the projector form the main

item of technology and have given the system this name. It is also known as spectral comb

filtering or wavelength multiplex visualization.

This technology eliminates the expensive silver screens required for polarized systems such

as RealD, which is the most common 3D display system in theaters. It does, however,

require much more expensive glasses than the polarized systems. Dolby 3D uses this

principle.

Fig 4.3: Interference Filter System

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4.3 PASSIVE DEVICE

4.3.4 CHROMA DEPTH SYSTEM

Chromadepth is a patented system from the company Chromatek that produces a

stereoscopic effect based upon differences in the diffraction of color through a special

prism-like holographic film fitted into glasses. Chromadepth glasses purposely exacerbate

chromatic aberration and give the illusion of colors taking up different positions in space,

with red being in front, and blue being in back. This works particularly well with the sky,

sea or grass as a background, and redder objects in the foreground.

Fig 4.4:A sample image used to demonstrate Chroma Depth system and the glass used for it

Any media piece can be given a 3D effect as long as the color spectrum is put into use with

the foreground being in red, and the background in blue. From front to back the scheme

follows the visible light spectrum, from red to orange, yellow, green and blue. As a result,

ChromaDepth works best with artificially produced or enhanced pictures, since the color

indicates the depth.

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HSPA(High Speed Packet Access)4.4 AUTOSTEREOSCOPY

Autostereoscopy is any method of displaying stereoscopic images (adding binocular

perception of 3D depth) 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". There are two broad approaches currently used to accommodate motion parallax and

wider viewing angles: eye-tracking, and multiple views so that the display does not need to

sense where the viewers' eyes are located. Examples of autostereoscopic displays

technology include lenticular lens, parallax barrier, volumetric display, holographic and

light field displays and Nintendo 3DS.

Fig 4.5 NINTENDO 3DS

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HSPA(High Speed Packet Access)4.5 STEREO WINDOW

For any branch of stereoscopy the concept of the stereo window is important. If a scene is

viewed through a window the entire scene would normally be behind the window, if the

scene is distant, it would be some distance behind the window, if it is nearby, it would

appear to be just beyond the window.

To truly understand the concept of window adjustment it is necessary to understand where

the stereo window itself is. In the case of projected stereo, including "3D" movies, the

window would be the surface of the screen. With printed material the window is at the

surface of the paper. When stereo images are seen by looking into a viewer the window is

at the position of the frame. In the case of Virtual Reality the window seems to disappear as

the scene becomes truly immersive.

The entire scene can be moved backwards or forwards in depth, relative to the stereo

window, by horizontally sliding the left and right eye views relative to each other. Moving

either or both images away from the centre will bring the whole scene away from the

viewer, whereas moving either or both images toward the centre will move the whole scene

toward the viewer. Any objects in the scene that have no horizontal offset, will appear at

the same depth as the stereo window.

Considerations in deciding where to place the scene relative to the window involves

deciding where individual objects are placed relative to the window. It would be normal for

the frame of an actual window to partly overlap or "cut off" an object that is behind the

window. Thus an object behind the stereo window might be partly cut off by the frame or

side of the stereo window. So the stereo window is often adjusted to place objects cut off by

window behind the window. If an object, or part of an object, is not cut off by the window

then it could be placed in front of it and the stereo window may be adjusted with this in

mind. This effect is how swords, bugs, flashlights, etc. often seem to "come off the screen"

in 3D movies.

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HSPA(High Speed Packet Access)5.1.1 ADVANTAGES

Enhances cinema experience. Cheap and lightweight 3D glasses that are affordable.  A very simple system and quite easy to set up.

5.1.2 DISADVANTAGES

Viewers need to be in the ideal watching zone else they won’t be able to see the 3D effect at its best.

Viewers need to use glasses in order to see the 3D effect Stereoscopic content can in some cases cause varying degrees of eye-strain to some

viewers, especially after watching for long periods of time. For standard Cable TV broadcasts, it is not possible to achieve 1080i High

Definition for 3D content using the existing cable TV standards. Instead, 3D content is broadcast in a lower resolution format

3D TV’s and 3D movies are expensive then watching normal 2D counterparts.

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HSPA(High Speed Packet Access)5.2 WHAT’s NEXT ?

Now -a-days more amount of research is going on how to get the effect of stereoscopic

effect without uses of glasses that is Auto Stereoscopy field.

Focus is put more on REAL 3D display where instead of illusion real 3D images and videos

are displayed.

Many new technologies have been discovered and are under developing mode

Two of the most famous such technologies are

1. Holographic Display

2. Volumetric Display

Holographic display is a type of display technology that has the ability to provide all four

eye mechanisms : binocular disparity, motion parallax, accommodation and convergence.

(a)Holographic Display (b)Volumetric Displays

Fig5.1

Volumetric displays use some physical mechanism to display points of light within a volume. Such displays use voxels instead of pixels. Volumetric displays include multiplanar displays, which have multiple display planes stacked up, and rotating panel displays, where a rotating panel sweeps out a volume.

6.1 CONCLUSION21

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Stereoscopic 3D viewing provides greater immersion into a movie.

Stereoscopy is widely used technology for almost 90% of the 3D display systems. Devices

are getting more improved and 3D stereo displays are (still) too expensive and (still) carry

too many limitations to be of interest to the broader PC market . and hence focus is made on

making the devices as cheap as possible so that every individual can afford it for day to day

use in home and completely replace the older plain 2D Television boxes .

Now the research is more towards the Auto stereoscopic mode where 3D display is

achieved without the glasses. But one thing is sure that no matter how perfected, stereo 3D

will never be confused with a Real Environment.

Of course, the development of 3D stereo technology is moving ahead. X3D has already

announced a stereoscopic 17" TFT display for PC gamers that should cost somewhere

around $1000.

Using the software published by More3D, practically any 3D software can be displayed in

3D stereo. NVIDIA is also continuing the development and support of its consumer 3D

stereo drivers.

6.2 BIBLIOGRAPHY22

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[1] http://www.stereoscopy.com/

[2] http://techcrunch.com/2010/06/19/a-guide-to-3d-display-technology-its-principles-

methods-and-dangers/

[3] “Recent development in stereoscopic display technology” published in

Communication Technology and Application (ICCTA 2011), IET International Conference by

Lina Zhao,Fei Wang , Wei Liu

[4] Wang Dong-cui, Wang Hui-nan. About Stereoscopic Vision and True 3D Volumetric

Display Technology[J].Advanced Display,2009(9]

[5] http://en.wikipedia.org/wiki/Stereoscopy

[6] http://en.wikipedia.org/wiki/Stereo_display

[7] Er Dong. Brief Discussion on three-dimensional display technology[J].Satellite TV &

IP Multimedia, 2009(11] 

[8] http://www.stereobank.com/

[9] http://en.wikipedia.org/wiki/Autostereoscopy

[10] http://en.wikipedia.org/wiki/Integral_imaging

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