The Blu-Ray Discd

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The Blu-Ray Disc
Sanket Shah1 , Bharat Kumawat2 , Darshan Bhatt3 4th I.T Department, SVBIT, Near Vasaniya Mahadev,Gandhinagar-Mansa Road, Dist.Gandhinagar, Gujarat, India
[email protected] 2 [email protected] 3 [email protected]

Abstract BLU-RAY disc is a next generation optical disc format meant for storage of high definition video and high density data .It can record, store and playback high digital audio as well as computer data. As technology becomes more advanced, the demand for compact disc unit with a higher quality become greater. Rather than stagnate in complacency, the approach to stored media remains ever – evolving. The future in both technological advancement and entertainment quality is already here in the form of Blu-Ray Disc. The purpose of this project is to educate individuals as to the history, criticism, public reception, and other information relevant to the Blu-Ray Disc. Part of the presentation also includes a comparision/contrast to the competing HD-DVD as well as a sampling video clip from the two. Keywords- MPEG-2, MPEG-4, BDXL, Birefringence, Disc tilt, Pit, Dolby Digital, Dolby Digital Plus

The format was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. As of June 2011, more than 2,500 Blu-ray Disc titles were available in Australia and the United Kingdom, with 3,500 in the United States and Canada. In Japan, as of July 2010, more than 3,300 titles have been released.

II.

History

I. INTRODUCTION Blu-ray Disc (official abbreviation BD) is an optical disk storage medium designed to supersede the DVD format. It is the plastic disk that is 120 mm in diameter and 1.2 mm thickness, same size as DVDs or CDs. Blue Ray Disc contain 25 GB per layer, with dual layer disks contain 50 GB, triple layer discs 100 GB and quadruple layer 128 GB are available for BD-XL re-writer discs. There are two disc size of BDXL disc 100GB for rewritable discs, and 128 GB for write once like other Blu Ray Disc. BDXL it is the latest format from Blu-Ray Disc Association, meaning Blu-Ray Disc Extra Large. The name Blu-ray disc refers to the blue laser used to read the disk which allows information to be stored at a greater density than is possible with the longer wavelength red laser used for DVDs. The first Blu-ray Disc prototypes were unveiled in October 2000, and the first prototype player was released in April 2003 in Japan. Afterwards, it continued to be developed until it official release in June 2006.

In 1983, Compact Discs (CD) were available in European market with storage capacity around 650 to 700 MB. To store and read data from CD, it was using red color beam with wavelength of 780nm. It was the first generation of storage media discs. In 1996, Digital Versatile Discs (DVD) was introduced with storage capacity of 4.7 GB. It offers high quality of sound and video quality than CD. Like CD, it was also using red color laser beam with wavelength of 650 nm. In 2004, construction of Blu-Ray Disc was completed with all physical specifications. It was having storage capacity of 25 GB per layer. However, it is also possible to increase storage capacity by increasing number of layers. It was developed by Blu-Ray Disc Association with 16 board of directors (Dell, HP, Hitachi, Apple, Pioneer, Sony, Samsung, Sharp, Panasonic, Thomson, Mitsubishi, LG, Walt, Warner Bros. Entertainment and Sun Microsystems). The name is “blu-ray” because it has blue color laser beam having wavelength of 405 nm[3].      III. Features Records high definition without any quality loss. Instantly skip to any spot on the disk Create playlists Edit or recorder programs recorded on the disc Automatically search for an empty space on the disc to avoid recording over a program

(2) Track pitch : It is the Distance between any two successive tracks. IV. Structure From the Figure above: The structure of the Blu-Ray disc is shown as below. It differs from the traditional DVD that, in a DVD the data is sandwiched between two 0.6mm polycarbonate layers. While in the case of a BD the data layer is placed on a 1.1mm polycarbonate layer. To prevent the data on the top of the disc from getting erased, the data layer is covered by a 0.1 mm protection layer. This makes the size of all the CD's DVD's & the BD's constant. This packing of the data has many advantages which will be discussed in the later sections. The minimum pit length of BD id 0.15 microns which is more than twice as small as the pits on the DVD which is at minimum 0.4 microns. Also the track pitch of the BD is 0.32 microns which is more than twice as small as that of the DVD which is 0.74 microns. This small pit & reduced track pitch enables the accommodation of a data of about 25 gb on a single sided Blu-Ray disc which is almost 5 times that of a single side traditional DVD.

V.

Storage VII. Data Access

It should be noticed that whatever form of the disc may be under consideration the data on the disc is stored on a SPIRAL TRACK running from the centre of the disc to the end of the diameter of the disc. This spiral starting from the centre of the disc gives the flexibility for the disc to be smaller in size than that of the conventional 120 mm. On this spiral tracks exists the BUMPS which actually hold the data. These bumps lie all along the spiral track. These bumps are often called pits. Viewed from the top of the disc these bumps look like PITS[4]. VI. Construction

Now a laser beam has to be chosen such that it reads the data in the small size pits. Unlike current DVDs, which use a red laser to read and write data, Blu-ray discs uses a blue laser (technically blue-violet). A blue laser has a shorter wavelength (405 nanometers) than a red laser (650 nanometers). The smaller beam focuses more precisely, enabling it to read information recorded in pits that are only 0.15 microns (µm) long. Numerical aperture=0.45 780-nm infrared laser CD Numerical aperture=0.6 650-nm red laser DVD Numerical aperture=0.8 405-nm blue laser BD From the figure above we can conclude that with the reduction in the laser beam wavelength accompanied with an effective (proportional) increase in the lens aperture, it is possible to read & write data into the pits of very small size. This way more disc space can be provided on a BD.

The construction of the bumps (spiral track) is explained here from a closer view of the disc. The view is so close that the bumps can be seen clearly. Here each white hole represents bumps (pit).For clearly understanding it is effectively compared with DVD. The key terms used here are: (1) Pit Length: It is the length of pit on the spiral track which holds the Data.

market is this type , which is available in models with a capacity of 23 GB to 25 GB[1]. (2) BD – R(write once on the BD) : This is the type of BD on which data can be written once only and can not be deleted or overwritten. It is possible to add more data until the disc reaches the full capacity, over several writing sessions, using the “additional recording” mode.

(3) BD-ROM(Replay only BD): This type of BD is for replay only and also used for retails Blu-ray discs for the distribution of high-definition movies and such where mass production or copies is possible. (4) BD-RW(rewrittable) : This is the same as BD-RE, but is used for PC data storage. VIII. Reading Issues X. Technological Aid

The till now regularly used DVD's & VCD's face two basic problems regarding their physical structure. They are: 1)Birefringence. 2) Disk tilt. Birefringence: In a DVD, the data is sandwiched between two polycarbonate layers, each 0.6-mm thick. Having a polycarbonate layer on top of the data can cause a problem called birefringence, in which the substrate layer refracts the laser light into two separate beams. If the beam is split too widely, the disc cannot be read. Disk Tilt: If the DVD surface is not exactly flat, and is therefore not exactly perpendicular to the beam (laser), it can lead to a problem known as disc tilt, in which the laser beam is distorted. This sometimes may lead to reading or writing into other undesired memory locations. 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[5][4].

1) Laser and optics Blu-ray systems use a "blue" (technically blue-violet) laser operating at a wavelength of 405 nm to read and write data. Conventional DVDs and CDs use red and 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, using a higher numerical aperture (0.85, compared with 0.6 for DVD), higher quality, dual-lens system, and making the cover layer thinner to avoid unwanted optical effects, the laser beam can be focused much more tightly at the disk surface. This produces a smaller spot on the disc and allows more information to be physically contained in the same area. In addition to the optical improvements, Blu-ray Discs feature improvements in data encoding, allowing for even more data to be packed in[3]. 2) Hard-coating Technology

IX.

Types of Blu-Ray Disc

1) BD-RE (Data Re-writable BD) : The type of BD on which written data can be deleted and new data can be written is the “BD-RE” type. The type of the Discs currently available on the

Because the Blu-ray standard places data so close to the surface of the disc, early discs were susceptible to dust and scratches & fingerprints and had to be enclosed in plastic caddies for protection. The solution to this problem arrived in January 2004 with the introduction of a clear polymer that gives Blu-ray discs unprecedented scratch resistance. The coating, developed by

TDK Corporation under the name "Durabis," allows BD’s to be cleaned safely with only a tissue. Durabis is a brand name for a clear polymer coating developed by the TDK Corporation. One of its principal applications at first will be for scratch-resistance in Blu-ray and other optical disks. In order to meet Blu-ray's specifications, TDK's coating had to be less than 0.1 mm thick, be hard enough to resist considerable damage and yet be transparent enough to be easily read. This process essentially spin-coats two layers onto discs. One is for protection against scratches and the other protects against stains and oils[3]. 3) Compatibility While it is not compulsory for manufacturers, the Blu-ray Disc Association recommends that Blu-ray drives should be capable of reading DVDs, ensuring backward compatibility. JVC has developed a three layer technology that allows putting both standard-definition DVD data and HD data on a BD/DVD combo disc. If successfully commercialized, this would enable the consumer to purchase a disc which could be played on current DVD players, and reveal its HD version when played on a new BD player[3]. 4) Codec’s The BD-ROM format specifies at least three video codec’s: MPEG-2, the standard used for DVDs; MPEG-4's H.264/AVC codec; and VC-1, a codec based on Microsoft's Windows Media 9. The first of these only allows for about two hours of high-definition content on a single-layer BD-ROM, but the addition of the two more advanced codec’s allows up to four per layer.For audio, BD-ROM supports linear (uncompressed) PCM, Dolby Digital, Dolby Digital Plus, DTS, DTS-HD, and Dolby Lossless (a lossless compression format also known as MLP).In order to remain backwards compatible, BD-RE (and by extension BD-R) will by and large support the MPEG2 codec[3]. XI. 1) Pros (1)High disc space at almost same cost price (2) Security (3) reverse compatibility (4) high speed data transfer (36Mbps) (5) online modifications 2) Cons (1)High cost of the disc reader (2) less data space than AOD (HD-DVD 30 Giga bytes) Pros & Cones 12 7 8 No. 1 2 3 4 5 6 Parameter Introduced in Storage capacity Color of Laser Wavelengt h of laser Hardcoating Physical Size (Diameter) Thickness Track Pitch

XII.

Comparision CD 1983 DVD 1996 4.7 GB Red 650 Nm 120mm BD 2004 25 GB (per layer) Blue-violet 405 Nm Yes 120 mm

650/700 MB Red 780 Nm 120mm

9 10 11

Disc tilt Birefringen ce Data Placed On disc Max. transfer rate

1.2mm 1.6 Microme ter Suffer Suffer Bottom layer of 1.2 mm thick 1.4 Mbps

1.2mm 0.74 Micrometer Suffer Suffer Sandwich b/w two PCL at 0.6 mm thick 11.08 Mbps

1.2mm 0.30 Micrometer Top at 1.1 mm thick polycarbon ate layer 36 Mbps

XIII.

Conclusion

It would definitely take a considerable time for the Blu-Ray disc to hit the market & completely takeovers the DVD share hold. Because of the low level compatibility (BD readers able to read both the DVD’s and the CD’s), the task might become a little simpler. But, the high cost of the reader might hinder its quick development. Anyways soon or later this mass storage optical device is going to replace the DVD & let the user experience a world high quality & disc space (Quality & Quantity ensured) with high level of security and privacy ensured. References [1] http://www.scribd.com/doc/47695480/blu-ray-disc [2]http://www.pioneer dvdasia.com/blu_ray/2_03.html [3] http://www.blu-raydisc.com/en/AboutBlu-ray/WhatisBlurayDisc/HistoryofBlu-rayDisc.aspx [4] http://www.blu-ray.com/info/ [5] http://www.blu-ray.com/faq/

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