3D Television

3D TelevisionThe future of televisionElliott ELLIS – David METGE – Paul VERGE – Romain ZIBA09/03/2010[Tapez le résumé du document ici. Il s'agit généralement d'une courte synthèse du document. Tapez le résumé du document ici. Il s'agit généralement d'une courte synthèse du document.]Introduction (3)The Stereoscopic solution: from the old Italy to hightech pubs ! (4)Principle (4)Evolution (5)The first tries (5)Photography (5)The 3D video (6)Multiview (7)Holography (9)INTRODUCTIONBorn since January, 27th of 1926, television has established itself in our homes as an essential, a unifying item, putting rhythm in our daily life. The history of television is both complex and far-reaching, involving the work of many inventors and engineers in several countries over many decades. Initially, work proceeded along two different but overlapping lines of development: those designs employing both mechanical and electronic principles, and those employing only electronic principles. Electromechanical television would eventually be abandoned in favor of all-electronic designs. Nevertheless, we can notice three big steps in the evolution of television.The first step was achieved in the past, in the fifties for the USA or in the sixties for the Europe. From black and white television, people now would see the scenes and the characters in their real color for the first time, thanks to SECAM in France, or PAL in the Europe, or even NTSC in the USA. In France for example, the programs were broadcasted in color on October 1st of 1967, but only 1500 television sets were in use at this time.The second revolution is being achieved. From analog broadcasts, we go digital. This step enabled us to see the high definition coming. Now, the viewers are offered an exceptional image quality, improving the visual comfort and making the image more realistic. With the digitalization of television, we can now have it everywhere thanks to several means of telecommunications. Analog broadcast is shutting down gradually: nowadays, only ten countries have totally abandoned this technology in favor of digital broadcast only, using DVB-T mainly in the Europe and ATSC (evolution of NTSC) in the USA. Another aspect of this revolution is the fact that screens go thinner: we are far from the days of the CRTs (Cathode Ray Tube). Plasmas, LCD and now LED screens allow us to put TV everywhere like we did with frames, and especially to consume less while being elegant.Finally, we have now a magnificent image and a pure sound, but television stays in two dimensions. So, the third step to come would be a three dimensions television. With that technology, the viewer could submerge deeply into the movie, thus creating new sensations in his mind and experiencing a totally new TV revolution. With the success of the movie Avatar (more than one billion of dollars at the box office), we definitely can say that three dimensions will be obvious in the coming years. Many companies are ready to launch such channels, like Canal+ which consider starting a 3D channel before the end of 2010. However this technology requires some standards which are not all ready yet.In this report, we will try to summarize the different aspects of 3D television. In the first part, we will strive to present the various 3D technologies and how each works. Then, in the second part, we will focus on the transmission chain, from the camera which shoots a movie to the screen which displays it, through the transmitting part, which we will emphasize. Indeed, our first goal is to determine which standard is better for a satellite broadcast 3D television. Eventually, we will see what could be done in the near future and the far future to improve the viewer sensations.THE STER EOSCOPIC SOL UTION: FROM THE OLD ITALY TO HIG HTECH PUBS The principle of Stereoscopy is to take two pictures that are taken with a slight horizontal offset. The resulting images are each displayed to a single eye. The brain does the job of merging the two together in a single image. A good 3D image will trick the viewer into perceiving depth in an otherwise flat image. Perspective is often confused with 3D, which is not quite true, because the third dimension (Depth) is only "simulated". Therefore, 2½D would be a more appropriate expression.The process by which the brain exploits the parallax due to the different views from the eye, to gain depth perception and estimate distances to objects is call “stereopsis”. It appears to be processed in the visual cortex in binocular cells having receptive fields in different horizontal positions in the two eyes. Such a cell is active only when its preferred stimulus is in the correct position in the left eye and in the correct position in the right eye, making it a disparity detector.THE FIRST TRIESMost people assumed that the principle of stereoscopy was invented by Sir Charles Wheatstone in the middle of th XIX century, with the creation of the photography, but surprisingly the true precursor could be Jacopo Chimenti, an Italian painter of the XVI century. He was representing subjects with a minor deviation. Perceiving th illusion was probably difficult at this time, but the idea was the correct one to produce the illusion.PHOTOGRAPHYThe true development of the stereoscopy goes with the photography, and the possibility to take pictures with two cameras separated by the common space between eyes (6mm). The first to use this progress was Charles Wheatstone. He build a device (the stereoscope) based on a combination of prisms and mirrors to allow a person to see 3D images from 2D pictures.The most interesting way to use stereoscopy is of course the video. Strictly reserved for movies at the beginning, the latest technologies allowed live programs to be broadcast in 3D.Stereoscopic motion pictures can be produced through a variety of different methods. It began in the late 1890s when British film pioneer Willima Friese-Greene filed a patent for a 3-D movie process. In his patent, two films were projected side by side on screen. The viewer looked through a stereoscope to converge the two images.After a golden era in the 50es, 3D movies popularity dropped and and were almost forgot until the mid 80es when the IMAX society began a large production of 3D content.A key point was that this production, emphasized mathematical correctness of the 3D rendition and thus largely eliminated the eye fatigue and pain that resulted from the approximate geometries of previous 3D incarnations.3D movies really re-entered the theater in 2003, pushed by the desire of one man: James Cameron. He is responsible for a very large amount of progress in 3D content, and more important in the development of 3D HD cameras. His master piece, Avatar, benefits from state of the art 3D technologies like 3D DOLBY or IMAX 3D, and can state as the best today technologies can produce in term of 3D content.The next challenge of 3D video is the broadcasting of live events in 3D. This is far more complicated challenge because of real-time constraint. Problems come from the fact that technologies developed for movies needs very important time of proceed. Despite this major issue, the first experiments have already been made, this is how English football fans were able to watch some games of their favorite teams in 3D in some London's pubs specially equipped.MULTIVIEWStereoscopic displays are currently used and work quite well. This is the first approach of the 3D displays and it follows the evolution of the technology used in the 7th art. Apparently, this kind of technology does not fit the needs of the “everyday life” user. Indeed, do you think you could wear glasses every time you want to watch television? Even when you’re eating? That’s the reason why research is working on displays called “multiview” or “auto stereoscopic”. Multiview will be used to drive the next generation 3D displays. These displays enable viewing of high resolution stereoscopic images without the need of glasses but from arbitrary positions. Moreover, compression will be needed because of the increase in the amount of data. New compression techniques exploiting the temporal correlation but also the inter-view correlation, since all cameras capture the same scene from different viewpoints, are studied. The main standard is the known H.264/AVC for time correlation.Actually, good compression efficiency will be achieved if there is a significant gain with multiview coding compared to independent compression of each view.Compression efficiency measures the tradeoff between cost (in terms of bit-rate) and benefit (in terms of video quality). However, there can be other contradictory requirements: compression efficiency and low delay for example.Autostereoscopic displays are using additional optical elements aligned on the surface of the screen, to ensure that the observer sees different images with each eye. Typically, autostereoscopic displays present multiple views to the observer, each one seen from a particular viewing angle along the horizontal direction. The basic operational principle of an autostereoscopic display is to cast different images towards each eye of the observer, by using a special optical layer, additionally mounted on the screen surface which redirects the light passing through it. There are two common types of optical filters:- lenticular sheet which works by refracting the light-Parallax barrier which works by blocking the light in certain directions.In both cases, the intensity of the light rays passing through the filter changes as a function of the angle, as if the light is directionally projected.Fig. 1 - methods for image separation: a)lenticular sheet and b) parallax barrierThe main advantage of parallax barrier is that we can choose to use it or not. As a consequence, you can watch multimedia content either in 3D or in 2D. The main disadvantage of the parallax barrier is that it blocks part of the light, resulting in a lowered brightness of the display.HOLOGRAPHYAnother lead to 3D research is holography. Holography is different from the other technologies discussed previously because it has no need for expensive and advanced display devices. Some European projects have started researches along side with the ones on 3D television. The goals are slightly less ambitious then the ones for regular 3D television. When we have seen that in three years time, the aims of the 3DTV projects are to have a complete broadcasting chain and the proposal of standards for capturing 3D content, coding schemes, compression, but also transmitting and broadcasting live content; for holograms the goal is to be able to capture a real-world object, process and display it. The process of holograms that was unthinkable just a few years ago is now conceivable thanks to the digital representation of holograms. Their strength is that they can be processed, analyzed, and transmitted electronically.Digital holography is the technology of acquiring and processing holographic measurement data, typically via a CCD camera (charged-couple device camera) or a similar device. The captured object is reconstructed numerically from the data acquired. The reconstruction is different from the one that can be obtained optically because with holography the aspect, the structure and the texture and the object can be reproduced. With the 3D digital holograms we typically feel the optical surface and thickness of the real-world object.Capturing a digital hologram:There are different techniques to capture a hologram. Indeed no proper way is normalized and thus various techniques are used. Hereafter is the most common one.Digital holograms are multiplexed by recording a few fringe patterns using the same CCD. Different techniques including one or multiple reference beams with different angles can be used in order to obtain interference fringe patterns which will transcribe more or less accurately the object. Next, all the captured holograms are superimposed in one CCD frame; each hologram can be inversely reconstructed using a digital spatial filtering. For the de-multiplexing each holograms is treated with the digital Fourier transform of the pre-multiplexed hologram. A pass-band filter is used to select the desired hologram. Finally the inverse Fourier transform on the previous result is applied to obtain a separate digital hologram for every multiplexed signal.a.Amplitude reconstruction of one hologram in the lens focal planeb.Amplitude of the synthetic spectrum obtained by the numerical multiplexing in the LFPof 100 digital hologramsHere is what the capturing, processing and displaying of a digital hologram looks like from end to end. The actual object is reconstructed for the observer that in theory can hardly make a difference between the real-world object and the 3D digital hologram. Digital holographic imaging can be seen a very important and increasing solution for 3D- visualization. Evaluation of the human visual system to perceive digital holograms of 3D images is a quite new research area and only few results about researches and especially related to visual perception of digital holograms have been found. The main requirements to display holograms are to provide natural viewing conditions for the human visual system and separate the reconstructed images from the display device that has to be almost invisible to the viewer.For now, standards are out of the questions for two reasons. On the one hand the holographic technology is that much younger then 3DTV that researches on a longer time period need to be conducted before one can think about standardization. On the other hand is seems that the market is leaning towards 3DTV perhaps closer to HDTV and thus easier to implant in homes and more likely to obtain an economical success.。