Stereoscopic Display

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Transcript of Stereoscopic Display

HSPA(High Speed Packet Access) 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 mostof 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.

1.2INTRODUCTIONStereoscopy 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.

2.1NEED FOR STEREOSCOPYInitially 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 19th 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.

2.2WHAT 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 natureStereoscopic 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.

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.

2.3TYPES OF STEREOSCOPIC DISPLAY TECHNOLOGY

Stereoscopic Display technology can be divided into two groups1. Manual Stereoscopic Display Technology2. 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 doesnt 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.

3.1DEPTH 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. Its 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 whats 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.

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. Its 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

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 t