ABOUT BLU-RAY DISC

INTRODUCTION TO BLU-RAY DISC A current, single-sided, standard DVD can hold 4.7 GB (gigabytes) of Information. That's about the size of an average two-hour, standard-definition movie with a few extra features. But a high-definition movie, which has a much clearer image (see how Digital Television Works), takes up about five times more bandwidth and therefore requires a disc with about five times more storage. As TV sets and movie studios make the move to high definition consumers are going to need playback systems with a lot more storage capacity. Blue-ray is the next-generation digital video disc. It can record, store and play back high definition video and digital audio, as well as computer data. In 1997,a new technology emerged that brought digital sound and video into homes all over the world. it was called DVD, and it revolutionized the movie industry. The industry is set for yet another revolution with the introduction of Blu-ray Disc (BD) in 2006.With their high storage capacity, Blu-ray discs can hold and playback large quantities of high-definition video and audio, as well as photos ,data and other digital content. Blu-ray is the next generation digital video disc. It can record, store and playback high-definition video and digital audio, as well as computer data. The advantage to Blu-ray is the sheer amount of information it can hold. A single-layer Blu-ray disc, which is roughly the same size as aDVd, can hold up to 27Gb of data –that’s more than two hours of high-definition video or about 13 hours of standard video. A double-layer Blu-ray disc can store up to 50GB,enough to hold about 4.5hours of high-definition video or more than 20 hours of standard video. And there are even plan in the works to develop a disc with twice that amount of storage.

BUILDING A BLU-RAY DISC Blue-ray disc not only have more storage capacity than traditional DVDs, but they also offer anew level of interactivity. User will be able to connect to the internet and instantly download subtitles and other interactive movie features. With Blue-ray, you can Record high-definition television(HDTV) without any quality loss Instantly skip to any spot on the disc Record one program while watching another on the disc Create play lists Edit or reorder programs recorded on the disc Automatically search for an empty space on the disc to avoid recording over a program Access the web to download subtitles and other extra features Discs store digitally encoded video and audio information in pits—spiral grooves that run from the center of the disc to its edges. Alaser reads the other side of the these pits –the bumps—to play the movie or program that is store on the DVD. The more data that is contained on a disc, the smaller and more closely packed the pits must be. The smaller the pits(and therefore the bumps),the more precise the reading laser must be. Unlike current DVDs, which are used a red laser to read and write data.Blu-ray disc uses blue laser(which is where the format gets its name).A blue laser has a shorter wavelength (405nm) than red laser(650nm).The smaller beam focuses mpre precisely, enabling it to read information recorded in pits that are only 0.15microns long—this is more than twice as small as the pits on a DVD. Plus, Blu-ray has reduced the track pitch from 0.74 to 0.32microns.The smaller pits, smaller beam and shorter track pitch together enable a single-layer Blu-ray disc to hold more than 25GB of information—about five times the amount of information that can be stored on a DVD. Each Blu-ray disc is about the same thickness(1.2mm) as DVD. But the two types of discs store data differently in a DVD, the data is sandwiched between two polycorbonate layers ,each 0.6-mm thick. Having a polycorbonate layer on top of the data can cause a Problem called birefringence.In which this substrate layer refracts the laser light into two separate beams. If the beam is split too widely, the disc cannot be read. Also ,if the DVD surface is not exactly flat, and is therefore not exactly perpendicular to the beam, it can lead to a problem known as disc tilt, in which the laser beam is distorted. All of these issues lead to a very involved manufacturing process. HOW BLU-RAY READS DATA The Blu-ray disc overcomes DVD-reading issues by placing the data on top of a 1.1-mm- thick polycarbonate layer. Having the data on top prevents birefringence and therefore prevents readability problems. And, with the recording layer sitting closer to the objective lens of the reading mechanism, the problem of disc tilt is virtually eliminated. Because the data is closer to the surface, a hard coating placed on the outside of the disc to protect it from scratches and fingerprints. BLU-RAY WRITING The design of the Blu-ray disc saves on manufacturing costs. Traditionly DVDs are built by injection modeling the two 0.6mm discs between which the recording layer is sandwiched .The process must be done very carefully to prevent birefringence The two discs are modeled The recording layer is added to one of the discs The two discs are glued together Blu-ray disca only do the injection modeling process on a single 1.1mm disc, which reduces cost. That savings balances out the cost of adding the protective layer, so the end prices no more than the orice of the regularDVD. Blu_ray also has a higher data transfer rate --36Mbps(mega bits per second)—than today’s DVDs, which transfer at 10 Mbps. A blu- ray disc can record 25GB of material in just over an hour and a half. We will look at some of blu-rays competitors in the next section. FORMATS Unlike DVDs and CDs, which started with read only format and only later added recordable and re-writable formats, blu-ray is initially designed in several different formats. BD-ROM(read-only)-for pre-recorded content BD-R(recordable)-for PC data storage. BD-RW(rewritable)-for PC data storage. BD-RE(rewritable)-for HDTV recording. RECORDABLE BD (BD-R) In recording process, an active material in recording layer is separated into two laminar components, the composition of which are different each other, by irradiating a high power laser beam. BD-R disc is designed that the light reflectivity of the recorded area change to very low level. In read process, a harmless low-power laser beam scans those recorded marks on a disc and retrieves playback signal by using photo detector. REWRITABLE BD(BD-RE) The recording layer of the BD-RE discs is made of the material that can change its state from a crystalline phase to an amorphous phase. When discs are produced, the recording surface is in its crystalline state(no data).If a part of the material is heated up to its melting point, and then cooled rapidly by irradiating high power and short pulse laser, the state of the part change from crystalline to amorphous phase.(recording process) in contrast, if the laser power is moderate and flat, the material change to crystalline phase.(Erase process) controlling the laser power in such a manner, actual data are overwritten repeatedly. BD-RE disc is designed that the reflectivity of the crystalline part is bright, however, amorphous part is dark. So, low read power laser spot can detect playback signal. The recording signal is read by a low-power laser beam and used for playback. The amount of reflected light depends on the crystallization state of the recording film(crystalline or amorphous).The recorded content is played back by detecting the reflected light using an optical sensor. The recording signal is read by a low- power laser beam and used for playback. the amount of reflected light depends on the crystallization state of the recording film (crystalline or amorphous).The recorded content is play back by detecting the reflected light using an optical sensors. Blue Ray Disc Structure The structure of the BD is as shown. The 0.1mm transparent cover layer is made of a spin. coated UV resin. It is formed by sandwiching a transparent layer between a protective coating and a bonding layer. This layer offers excellent birefringence. Beneath, there is a layer of Antis layer acts as a heat sink, dissipating the excess heat during the write process. A spacer layer made of ZnS.SiO2 comes next. Then, the recording layer made of AgInSbTeGe comes. Grooves are formed on this layer for recording. A reflective layer of Ag alloy falls beneath and finally a plastic substrate comes. The key features of the technology are introduced as follows Highly flat and smooth cover layer: At the high speed recording rate involved, the linear velocity of the disc reaches 20m/s or more and as a result accurate focus control becomes difficult. Various experiments showed that flatness and smoothness of the transparent cover layer have a marked influence on the focus control capability. This end is achieved by using the spin coating method for obtaining the transparent cover layer. Thus stable record ability at high speed recording is secured. Phase change film for high speed recording: The phase change film should have high recrystallisation speed to enable direct recording at the high linear velocities involved. A recording layer made of AgInSbTeGe meets this purpose. Super advanced rapid cooling structure: The excess heat from the LASER irradiation causes distortion of the recorded mark edge. So, to diffuse the remaining excess heat, a transparent di.electric film of high thermal conductivity, for example, AlN is used. MECHANISMS LASER AND OPTICS Blu-ray Disc uses a "blue" (technically violet) laser operating at a wavelength of 405 nm to read and write data. Conventional DVDs and CDs use red and near infrared lasers at 650 nm and 780 nm respectively. The blue-violet laser's shorter wavelength makes it possible to store more information on a 12 cm CD/DVD sized disc. The minimum "spot size" on which a laser can be focused is limited by diffraction, and depends on the wavelength of the light and the numerical aperture of the lens used to focus it. By decreasing the wavelength, increasing the numerical aperture from 0.60 to 0.85 and making the cover layer thinner to avoid unwanted optical effects, the laser beam can be focused to a smaller spot. This allows more information to be stored in the same area. For Blu-ray Disc, the spot size is 580 nm. In addition to the optical improvements, Blu-ray Discs feature improvements in data encoding that further increase the capacity. (See Compact Disc for information on optical discs' physical structure.) Hard-coating technology Because the Blu-ray Disc data layer is closer to the surface of the disc, compared to the DVD standard, it was at first more vulnerable to scratches.[citation needed] The first discs were housed in cartridges for protection. TDK was the first company to develop a working scratch protection coating for Blu-ray Discs. It was named Durabis. In addition, both Sony and Panasonic's replication methods include proprietary hard-coat technologies. Sony's rewritable media are spin-coated with a scratch-resistant and antistatic coating. Verbatim's recordable and rewritable Blu-ray Disc discs use their own proprietary hard-coat technology called ScratchGuard. Basic Blu-ray Disc Characteristics Large Recording Capacity The Blu.ray disc enables the recording, rewriting and playback of HD video unto 27 GB of data on a single sided single layer. It is enough to put 2.5 hours of HDTV recording on it. It also can record over 13 hours of standard TV broadcasting using the VHS/ standard definition picture quality. High Speed It has a data transfer rate of 36 Mbps. Because of this high speed transfer rates it can also record the data in very little time. In a perfect environment it would take about 2.5 hours to fill the entire BD with 27 GB of data. More than enough transfer capacity for real time recording and playback. Resistant to Scratches and Fingerprints The protective layer is hard enough to prevent accidental abrasions and allows fingerprints to be removed by wiping the disc with a tissue. COMPARISION There are great number of recording density differences between Blu-ray disc and other formats of optical media such as DVDs or CDs. The disc structure and design are very different. To increase the amount of data to be recorded in the same area, it is necessary to increase the density so that the data can be packed more tightly. Beam spot of the Blu-ray disc is much smaller to realize such a tight density. Blue-ray Disc and HD-DVD: The HD.DVD format, originally called AOD or Advanced Optical Disc, is based on much of today’s DVD principles and as a result, suffers from many of its limitations. The format does not provide as big of a technological step as Blu .ray Disc. For example, its pre. recorded capacities are only 15 GB for a single layer disc, or 30 GB for a double layer disc. Blu.ray Disc provides 67% more capacity per layer at 25 GB for a single layer and 50GB for a double layer disc. Although the HD.DVD format claims it keeps initial investments for disc replicates and media manufacturers as low as possible, they still need to make substantial investments in modifying their production equipment to create HD. DVDs. But what’s more important is that HD.DVD can be seen as just a transition technology, with a capacity not sufficient for the long term. It might not offer enough space to hold a High Definition feature along with bonus material in HD quality and additional material that can be revealed upon authorization via a network. When two discs are needed, this will degrade the so. called cost benefit substantially. It is even possible that the HD.DVD specification will be followed up by a renewed version of the technology within a few years, requiring media manufacturers to upgrade their existing production lines again, and consumers to replace their existing playback/recording equipment. other hand, the Blu .ray Disc format was designed to be a viable technology for a period of at least 10 to 15 years. Also on the application layer, the HD.DVD format incorporates many compromises. As the capacity is not likely to be sufficient to encode a full.length feature plus additional bonus material susing the MPEG.2 format, different and stronger encoding formats need to be used. Although Blu.ray Disc offers these advanced codecs as well, the disc has such high capacity that publishers can still use the MPEG.2 encoding format at bit rates up to 54 Mbit/sec. As MPEG.2 is the de.facto standard used in almost any industry involved in digital video (DVD, HDTV, digital broadcast), many authoring solutions are available. Chances are high that a full line MPEG.2 encoding suite is already available, which can be used with no or minor adaptations to encode High Definition content for Blu.ray Disc. But perhaps the most important factor for the success of Blu.ray Disc is its overwhelming industry wide support. Almost all consumer electronics companies in the world (combined market share of about 90%) and the world’s two largest computer companies support the Blu.ray Disc format. This ensures a large selection of Blu.ray Disc players, recorders, PC drives, Blu.ray Disc equipped PCs and blank media will become available. A competing format will not have the manufacturing power to penetrate the market in a level even approaching that of Blu.ray Disc. ADVANTAGES The main advantages of the Blu.ray disc are 10.1 More storage capacity on a disc of the same size. The data storage capacity on a Blu.ray disc is 27GB on a single layer and 54GBon dual layer, which is about five to six times the capacity of a DVD. It would mean about 2.5 hours of HDTV video and about 13 hours of SDTV video. High data transfer rate. The basic data transfer rate in Blu.ray disc is about 36Mbps which is about three times that of a DVD and thirty times that of a CD. Available in different versions like ROM, R and RE The BD is available in different versions like the ROM (write once), R (read only), RE (rewritable). Backward compatible. The BD drives are designed to be backward compatible, i.e. CDs and DVDs work equally well with the BD drives. Strong content protection. The features of the content protection system are Format Developed with Input from Motion Picture Studios Strong Copy Protection by Renewability with Renewal Key Block and Device Key Enhanced Encryption Algorithm: AES 128 bit Physical Hook Against Bit by Bit Encrypted Content Copy Title.based Expandable Content Control File Production Process Control Works Against Professional Piracy Public Key Based Authentication in PC Environment Compatible with analog and digital transmission. The BD fares well with analog as well as digital transmission. It offers the only means to the recording and reproducing of digital HDTV video. Format for encoding analog signals also, called SESF (Self Encoded Stream Format) is also incorporated into the BD. Higher disc life. In the case of ordinary discs, the disc life is less fir the rewritable versions, as re.writing is done repeatedly to one area of the disc most probably, the inner perimeter. This limits the disc life. But, the BDFS(Blu.ray Disc File Structure is designed so as to avoid this problem, by using a system that uses free disc spaces with equal frequency APPLICATIONS High Definition Television Recording High Definition Video Distribution High Definition Camcorder Archiving Mass Data Storage Digital Asset Management and Professional Storage The Blu.ray Disc format was designed to offer the best performance and features for a wide variety of applications. High Definition video distribution is one of the key features of Blu.ray Disc, but the format.s versatile design and top.of.the.line specifications mean that it is suitable for a full range of other purposes as well. High Definition Television Recording High Definition broadcasting is vastly expanding in the US and Asia. Consumers are increasingly making the switch to HDTV sets to enjoy the best possible television experience. The Blu.ray Disc format offers consumers the ability to record their High Definition television broadcasts in their original quality for the first time, preserving the pure picture and audio level as offered by the broadcaster. As such it will become the next level in home entertainment, offering an unsurpassed user experience. And since the Blu.ray Disc format incorporates the strongest copy protection algorithms of any format or proposal to date, the format allows for recording of digital broadcasts while meeting the content protection demands of the broadcast industry. High Definition Video Distribution Due to its enormous data capacity of 25 to 50 GB per (single sided) disc, the Blu.ray Disc format can store High Definition video in the highest possible quality. Because of the huge capacity of the disc, there is no need to compromise on picture quality. Depending on the encoding method, there is room for more than seven hours of the highest HD quality video. There is even room for additional content such as special features and other bonus material to accompany the High Definition movie. Furthermore, the Blu.ray Disc movie format greatly expands on traditional DVD capabilities, by incorporating many new interactive features allowing content providers to offer an even more incredible experience to consumers. An Internet.connection may even be used to unlock additional material that is stored on the disc, as there is enough room on the disc to include premium material as well. High Definition Camcorder Archiving As the market penetration of High Definition TV sets continues to grow, so does the demand of consumers to create their own HD recordings. With the advent of the first HD camcorders, consumers can now for the first time record their own home movies in a quality level unlike any before. As these camcorders are tape. based, consumers cannot benefit from the convenience and direct access features they are used to from the DVD players and recorders. Now, the Blu.ray Disc format, with its unprecedented storage capacity, allows for the HD video recorded with an HD camcorder to be seamlessly transferred to a Blu.ray Disc. When the HD content is stored on a Blu.ray Disc, it can be randomly accessed in a way comparable to DVD. Furthermore, the Blu.ray Disc can be edited, enhanced with interactive menus for an even increased user experience and the disc can be safely stored for many years, without the risk of tape wear. Mass Data Storage In its day, CD.R/RW meant a huge increase in storage capacity compared to traditional storage media with its 650 MB. Then DVD surpassed this amount by offering 4.7 to 8.5 GB of storage, an impressive 5 to 10 times increase. Now consumers demand an even bigger storage capacity. The growing number of broadband connections allowing consumers to download vast amounts of data, as well as the ever increasing audio, video and photo capabilities of personal computers has lead to yet another level in data storage requirements. In addition, commercial storage requirements are growing exponentially due to the proliferation of e.mail and the migration to paperless processes. The Blu.ray Disc format again offers 5 to 10 times as much capacity as traditional DVD resulting in 25 to 50 GB of data to be stored on a single rewritable or recordable disc. As Blu.ray Disc uses the same form factor as CD and DVD, this allows for Blu.ray Disc drives that can still read and write to CD and DVD media as well. Digital Asset Management and Professional Storage Due to its high capacity, low cost per GB and extremely versatile ways of transferring data from one device to another (because of Blu.ray Disc.s extremely wide adoption across the industry), the format is optimized for Digital Asset Management and other professional applications that require vast amounts of storage space. Think of medical archives that may contain numerous diagnostic scans in the highest resolution, or catalogs of audiovisual assets that need to be instantly retrieved in a random access manner, without the need to .restore. data from a storage carrier. One Blu.ray Disc may replace many backup tapes, CDs, DVDs or other less common or proprietary storage media. And contrary to network solutions, the discs can be physically stored in a different location for backup and safekeeping CHALLENGES: High cost The technology is not that popular and hence, the price of the BD recorders and players available in the market is very high. HD-DVD The HD.DVD (High Definition DVD) based on the Advanced Optical System championed by Toshiba and NEC is the primary rival to BD in the market. Though its data storage density is lower, it has lower manufacturing costs also, which may prove challenging to the Blu.ray disc. FUTURE DEVELOPMENTS: Efforts are progressing on many fronts to make the blu.ray discs, players and recorders cheaper. On 15 April 2004 for instance, Sony and Toppan Printing announced the successful development of a Blu. ray Disc that is 51% (by mass) composed of paper, which could reduce production costs and improve its environmental friendliness. The cost would come down as BD becomes more and more popular. TDK has been researching the hard coat technology that will provide protection against fingerprints and scratches. Colloidable silica dispersed UV.curable resin is being used for the researches and results are encouraging. Figure shows the cross section of the disc being developed.