Seminar on 3D Television
Three-dimensional TV is expected to be the next revolution in the TV history. They implemented a 3D TV prototype system with real-time acquisition transmission, & 3D display of dynamic scenes. They developed a distributed scalable architecture to manage the high computation & bandwidth demands. 3D display shows high-resolution stereoscopic color images for multiple viewpoints without special glasses. This is first real time end-to-end 3D TV system with enough views & resolution to provide a truly immersive 3D experience.Japan plans to make this futuristic television a commercial reality by 2020as part of abroad national project that will bring together researchers from the government, technology companies and academia. The targeted "virtual reality" television would allow people to view high definitionimages in 3D from any angle, in addition to being able to touch and smell the objects being projected upwards from a screen to the floor.
The evolution of visual media such as cinema and television is one of the major hallmarks of our modern civilization. In many ways, these visual media now define our modern life style. Many of us are curious: what is our life style going to be in a few years? What kind of films and television are we going to see? Although cinema and television both evolved over decades, there were stages, which, in fact, were once seen as revolutions:
1) at first, films were silent, then sound was added;
2) cinema and television were initially black-and-white, then color was introduced;
3) computer imaging and digital special effects have been the latest major novelty.
BASICS OF 3D TV
Human gains three-dimensional information from variety of cues. Two of the most important ones are binocular parallax & motion parallax.
A. Binocular Parallax
It means for any point you fixate the images on the two eyes must be slightly different. But the two different image so allow us to perceive a stable visual world. Binocular parallax defers to the ability of the eyes to see a solid object and a continuous surface behind that object even though the eyes see two different views.
B. Motion Parallax
It means information at the retina caused by relative movement of objects as the observer moves to the side (or his head moves sideways). Motion parallax varies depending on the distance of the observer from objects. The observer's movement also causes occlusion (covering of one object by another), and as movement changes so too does occlusion. This can give a powerful cue to the distance of objects from the observer.
C. Depth perception
It is the visual ability to perceive the world in three dimensions. It is a trait common to many higher animals. Depth perception allows the beholder to accurately gauge the distance to an object. The small distance between our eyes gives us stereoscopic depth perception[7]. The brain combines the two slightly different images into one 3D image. It works most effectively for distances up to 18 feet. For objects at a greater distance, our brain uses relative size and motion As shown in the figure, each eye captures its own view and the two separate images are sent on to the brain for processing. When the two images arrive simultaneously in the back of the brain, they are united into one picture. The mind combines the two images by matching up the similarities and adding in the small differences. The small differences between the two images add up to a big difference in the final picture ! The combined image is more than the sum of its parts. It is a three-dimensional stereo picture.
ARCHITECTURE OF 3D TV
The whole system consists mainly three blocks:
1 Aquisition
2. Transmission
3. Display Unit
A. Acquisition
The acquisition stage consists of an array of hardware-synchronized cameras. Small clusters of cameras are connected to the producer PCs. The producers capture live, uncompressed video streams & encode them using standard MPEG coding. The compressed video then broadcast on separate channels over a transmission network, which could be digital cable, satellite TV or the Internet.
Generally they are using 16 Basler A101fc color cameras with 1300X1030, 8 bits per pixel CCD sensors.
1) CCD Image Sensors: Charge coupled devices are electronic devices that are capable of transforming a light pattern (image) into an electric charge pattern (an electronic image).
2) MPEG-2 Encoding: MPEG-2 is an extension of the MPEG-1 international standard for digital compression of audio and video signals. MPEG-2 is directed at broadcast formats at higher data rates; it provides extra algorithmic 'tools' for efficiently coding interlaced video, supports a wide range of bit rates and provides for multichannel surround sound coding. MPEG- 2 aims to be a generic video coding system supporting a diverse range of applications. They have built a PCI card with custom programmable logic device (CPLD) that generates the synchronization signal for all the cameras. So, what is PCI card?
3) PCI Card:
There's one element the bus. Essentially, a bus is a channel or path between the components in a computer. We will concentrate on the bus known as the Peripheral Component Interconnect (PCI). We'll talk about what PCI is, how it operates and how it is used, and we'll look into the future of bus technology.
All 16 cameras are individually connected to the card, which is plugged into the one of the producer PCs. Although it is possible to use software synchronization, they consider precise hardware synchronization essential for dynamic scenes. Note that the price of the acquisition cameras can be high, since they will be mostly used in TV studios. They arranged the 16 cameras in regularly spaced linear array
3D DISPLAY
3This is a brief explanation that we hope sorts out some of the confusion about the many 3D display options that are available today. We'll tell you how they work, and what the relative tradeoffs of each technique are. Those of you that are just interested in comparing different Liquid Crystal Shutter glasses techniques can skip to the section at the end. Of course, we are always happy to answer your questions personally, and point you to other leading experts in the field[4]. Figure shows a diagram of the multi-projector 3D displays with lenticular sheets.
They use 16 NEC LT-170 projectors with 1024'768 native output resolution. This is less that the resolution of acquired & transmitted video, which has 1300'1030 pixels. However, HDTV projectors are much more expensive than commodity projectors. Commodity projector is a compact form factor. Out of eight consumer PCs one is dedicated as the controller. The consumers are identical to the producers except for a dual-output graphics card that is connected to two projectors. The graphic card is used only as an output device. For real-projection system as shown in the figure, two lenticular sheets are mounted back-to-back with optical diffuser material in the center. The front projection system uses only one lenticular sheet with a retro reflective front projection screen material from flexible fabric mounted on the back. Photographs show the rear and front projection
