Blu-ray disc

Seminar Report on 2011-2012

ABSTRACT
Optical disks share a major part among the secondary storage devices.Blu-ray Disc is a next-generation optical disc format. The technology utilizes a blue laser diode operating at a wavelength of 405 nm to read and write data. Because it uses a blue laser it can store enormous more amounts of data on it than was ever possible. Data is stored on Blu-Ray disks in the form of tiny ridges on the surface of an opaque 1.1-millimetre-thick substrate. This lies beneath a transparent 0.1mm protective layer. With the help of Blu-ray recording devices it is possible to record up to 2.5 hours of very high quality audio and video on a single BD. Blu-ray also promises some added security, making ways for copyright protections. Blu-ray discs can have a unique ID written on them to have copyright protection inside the recorded streams. Blu-ray disc takes the DVD technology one step further, just by using a laser with a nice color.

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TABLE OF CONTENTS
ABSTRACT 2 1. HISTORY OF BLU-RAY DISC3 2. GLOSSARY OF TERMS...4 3. OPTICAL DATA STORAGE FOR DIGITAL VIDEO....8 4. DIFFERENT FORMATS OF BD....17 5. TWO VERSIONS OF RECORDING....18 6. BLU-RAY DISC STRUCTURE...19 7. SPECIFICATIONS...20 8. BASIC BLU-RAY CHARACTERISTICS. .....21 9. BLU-RAY FOUNDERS..21 10. COMPARISONS...22 11. ADVANTAGES.............................................................. .......23 12. APPLICATIONS...25 13. REQUIREMENTS.26 14. CONCLUSION...26 15. REFERENCES.26

1.History of Blu-ray Disc

1.1 First Generation
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When the CD was introduced in the early 80s, it meant

an enormous leap from traditional media. Not only did it offer a significant improvement in audio quality, its primary application, but its 650 MB storage capacity also meant a giant leap in data storage and retrieval. For the first time, there was a universal standard for prerecorded, recordable and rewritable media, offering the best quality and features consumers could wish for themselves, at very low costs.

1.2 Second Generation

Although the CD was a very useful medium for the recording and distribution of audio and some modest dataapplications, demand for a new medium offering higher storage capacities rose in the 90s. These demands lead to the evolution of the DVD specification and a five to ten fold increase in capacity. This enabled high quality, standard definition video distribution and recording. Furthermore, the increased capacity accommodated more demanding data applications.

1.3 Third Generation

Now High Definition video is demanding a new solution. History proved that a significant five to ten time increase in storage capacity and the ability to play previous generation formats are key elements for a new format to succeed. This new format has arrived with the advent of Blu-ray Disc, the only format that offers a considerable increase in storage capacity with its 25 to 50 GB data capacity. This allows for the next big application of optical media: the distribution and recording of High Definition video in the highest possible quality. In fact, no other proposed format can offer the data capacity of Blu-ray Disc, and no other format will allow for the same

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high video quality and interactive features to create the ultimate user experience. The Blu-ray Disc specification was officially announced in February 2002. Blu-ray Disc recorders were first launched in Japan in 2003.

1982 1983 1985 1996 1999 2003

-First working CD player developed by Philips. -First CD players sold -CD-ROM introduced not popular at first -DVD introduced -DVD becomes mainstream -BD introduced

1990s - CD-R and CD-RW introduced big success.

2. Glossary of Terms
2.1 HDTV (High Definition Video)
This high resolution 16:9 ratio, progressive scan format can now be recorded to standard miniDV cassettes Consumer high definition cameras are becoming available but this is currently an expensive, niche market. It is also possible to capture video using inexpensive webcams. These normally connect to a computer via USB. While they are much cheaper than DV cameras, webcams offer lower quality and less flexibility for editing purposes, as they do not capture video in DV format. Digital video is available on many portable devices from digital stills cameras to mobile phones. This is contributing to the emergence of digital video as a standard technology used and shared by people on a daily basis.

2.2 MPEG
MPEG, the Moving Picture Experts Group, overseen by the International Standards Organization (ISO), develops standards for

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digital video and digital audio compression. MPEG-1 with a default resolution of 352x240 was designed specifically for Video-CD and CDimedia and is often used in CD-ROMs. MPEG-1 audio layer-3 (MP3) compression evolved from early MPEG work. MPEG1 is an established, medium quality format (similar to VHS) supported by all players and platforms. Although not the best quality it will work well on older specification machines. MPEG-2 compression (as used for DVD movies and digital television set-top boxes) is an excellent format for distributing video, as it offers high quality and smaller file sizes than DV. MPEG2 is becoming more common as a capture format. Editing and encoding MPEG2 requires more processing power than DV and should be done on well specified machines. It is not suitable for internet delivery. MPEG-4 is a set of video and audio standards intended to deliver quality video over limited bandwidths that also support a range of other media types such as text, still image and animation. MPEG-4 offers high-quality, scaleable streaming over a range of bandwidths, including those provided by mobile networks.. MPEG4 is beginning to be supported in other areas such as mobile video (3G), mobile television, set-top boxes and video on demand (VoD).

2.3 Gigabyte (GB)

A gigabyte equals about 1,000 megabytes (MB). A Bluray Disc capable of recording 50 GB therefore stores about 50,000 megabytes

2.4 Layer
In Blu-ray Disc, data is recorded on a single side of the disc. However, a disc can store two data layers, both at the same side. The read-out or recording laser of the Blu-ray Disc device will first read

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from or record to one layer, and then re-focuses on the second layer. All this is done automatically without any user interference. A double layer Blu-ray Disc can store up to 50 GB of data.

2.5 SDTV
Standard Definition Television. Generic term used for conventional television sets, based on the NTSC or PAL standards. SD television consists of 480 to 570 visible lines.

2.6 Numerical Aperture and Resolution

The numerical aperture of a microscope objective is a measure of its ability to gather light and resolve fine specimen detail at a fixed object distance. Image-forming light waves pass through the specimen and enter the objective in an inverted cone as illustrated in Figure 1. A longitudinal slice of this cones of light shows the angular aperture, a value that is determined by the focal length of the objective.

The angle is one-half the angular aperture (A) and is related to the numerical aperture through the following equation: Numerical Aperture (NA) = n (sin )

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Where n is the refractive index of the imaging medium between the front lens of the objective and the specimen cover glass, a value that ranges from 1.00 for air to 1.51 for specialized immersion oils. Many authors substitute the variable for in the numerical aperture equation. From this equation it is obvious that when the imaging medium is air (with a refractive index, n = 1.0), then the numerical aperture is dependent only upon the angle whose maximum value is 90. The sin of the angle , therefore, has a maximum value of 1.0 (sin90 = 1), which is the theoretical maximum numerical aperture of a lens operating with air as the imaging medium (using "dry" microscope objectives).

2.7 THE BLUE LASER

The laser used with the Blu-ray disc has a wavelength of 405nm.Though the red and the green lasers were discovered much earlier, it was only in 1996 that the blue laser was discovered. Actually, the wavelength 405nm would correspond to the blue-violet part of the visible light, in the spectrum. This achievement is attributed to the efforts of Shuji Nakamura of Nichia Corporation, Japan. The device utilizes a GaN diode as its laser source. The operating current is kept between 60mA and 70mA for optimum performance. For writing into the disc, the power of the laser used is about 6mW. For reading from the disc, much lesser power is required, only about 0.7mW.The GaN source can give a power of about 65mW. So, it is an ideal choice for the laser source to be used with the Blu-ray disc. Due to the much lower wavelength involved, the amorphous mark size (bit size) is small, leading to higher storage

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capacity on disc of the same size, about five to six times the capacity

3. Optical Data Storage for Digital Video

3.1 Introduction
Optical data storage is commercially successful in the form of Compact Discs (CDs) for audio and software distribution and Digital Versatile Discs (DVDs) for video distribution. CDs and DVDs look very similar because the fundamental optical technology for both devices is the same. This similarity is also true for the next generation of optical data storage, which may be used for digital home theater recording and HDTV distribution. However, CDs, DVDs and next generation products are different in terms of specific optical components in the drive, in how data are managed and in details of the disk structure used to store the information. These differences allow a larger volume of data to be recorded on each successive generation. Larger data volumes translate into higher quality video and longer playing time.

3.2 Parameters for HD Video Storage with Optical Disks

Optical Parameters Disk Structure Parameters Data Management Parameters
Optical parameters include laser wavelength, objective lens numerical aperture, protective layer

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thickness and free working distance. Data management parameters include data rate, video format, HDTV play time and bit-rate scheme. Disk structure parameters are user data capacity, minimum channel bit length and track-to-track spacing.

3.2.1 Optical Parameters

Fig 1 Digital information is stored on optical disks in the form of arrangements of data marks in spiral tracks. The process for exposing data marks on a recordable optical disk is shown in Fig. 1, where an input stream of digital information is converted with an encoder and modulator into a drive signal for a laser source. The laser source emits an intense light

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beam that is directed and focused onto the surface by the objective lens. As the surface moves under the scanning spot, energy from the intense scan spot is absorbed, and a small, localized region heats up. The surface, under the influence of heat beyond a critical writing threshold, changes its reflective properties. Modulation of the intense light beam is synchronous with the drive signal, so a circular track of data marks is formed as the surface rotates. The scan spot is moved slightly as the surface rotates to allow another track to be written on new media during the next revolution.

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Fig 2 Readout of data marks on the disk is illustrated in Fig.2, where the laser is used at a constant output power level that does not heat the data surface beyond its thermal writing threshold. The laser beam is directed through a beam splitter into the objective lens, where the beam is focused onto the surface. As the data marks to be read pass under the scan spot, the reflected light is modulated.

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Modulated light is collected by illumination optics and directed by the beam splitter to servo and data optics, which converge the light onto detectors. The detectors change light modulation into current modulation that is amplified and decoded to produce the output data stream. A fundamental limitation to the number of data marks per unit area is due to the size of the focused laser beam that illuminates the surface. Small laser spots are required to record and read out small data marks. More data marks per unit area translate into higher capacity disks, so evolution of optical data storage is toward smaller spot sizes. The laser irradiance approaching the surface, where irradiance is defined as the laser power per unit area. Maximum irradiance is located at the recording material, along with the smallest spot size s. As the distance increases away from the ideal

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focus, the spot size increases and the peak irradiance decreases.

Fig 4 Instead of focusing directly on the recording surface, optical disks focus through a protective layer, as shown in Fig.4 for a simple CD-ROM. The protective layer prevents dust and other contamination from

lens from the spinning disk. This separation protects the disk against accidental contact between the objective lens and the disk.

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In order to maximize disk capacity, the optical system uses high NA and short wavelength. For maximum contamination protection, the protective layer should be as thick as possible. However, the combination of thick protective layer and high NA is not easily accomplished. High NA systems are sensitive to changes in substrate thickness and disk tilt. Manufacturing variations create thickness no uniformities, which are usually a small percentage of the total disk thickness. Sensitivity of the spot to degradation from thickness variations and disk tilt is plotted in Fig. 5 as a function of total protective layer thickness for two values of NA. In order to limit these effects, the substrate is made as thin as possible without sacrificing contamination protection.

Fig 5

The most conservative technology is the Video CD. Its thick protective layer, relatively low NA and long laser wavelength produce a stable system that is not very sensitive to environmental

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factors like dust and scratches. The ideal spot size is about 0.78/0.5 = 1.6 micrometers. Although the cover layer is thick at 1.2 mm, the sensitivity to thickness variations and disk tilt is low because of the low NA. DVD technology uses a shorter wavelength laser, higher NA optics and a thinner protective layer. The combination of short wavelength and higher NA produce a spot size of about 1.1 micrometers. The protective layer had to be made thinner, because the sensitivity to thickness variations and disk tilt is too high otherwise. DVDs are slightly more sensitive to dust and scratches than CDs. The net effect is not great, because higher NA reduces the focal depth and DVDs have a more robust error management strategy. The Advanced Optical Disk and Blu-Ray systems both use a new blue laser source that emits 0.405 micrometer light. The Advanced Optical Disk system uses the same protective layer thickness as a DVD, and it uses the same NA objective lens. Due to the short wavelength, the spot size for the Advanced Optical Disk is about 0.62 micrometers. Sensitivity to dust and scratches is about the same as a DVD, as well as the sensitivity to thickness variations and disk tilt. The Blu-Ray system uses both higher NA and thinner cover layer. The spot size is 0.405/0.85 = 0.48 micrometers, which is the smallest spot size of all the technologies. Blu-Ray disks are sensitive to dust and scratches. The free working distance is nearly is same for all technologies except Blu-Ray. Blu-Ray systems utilize more complicated lens systems due to the high NA, so working distance had to be reduced.

To the user all generation of optical disks Blu-Ray disk very similar. They all are round disks that are approximately 120 mm in

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diameter, have a central mounting hole and are approximately 1.2 mm side are very thin at 0.1 mm. In this case, data are recorded on the substrate, which does not serve as the protective layer. Instead, a protective layer resin is spun on and hardened or a thin protective sheet is bonded on each side of the substrate. Because of the thin protective layer, the Blu-Ray disk must also be used with a cartridge. The only optical disk technology that plans to use a Cartridge is the Blu-Ray system. The Blu-Ray cartridge is necessary for contamination Protection, but the working distance of around 0.1 mm and protective layer thickness of 0.1 mm are large compared to the contact recording

3.2.3 Data Management Parameters

The logical organization of data on the disk and how those data are used are considerations for data management. Data management considerations have important implications in the application of optical disk technology to storage for HDTV. Data rate, video format, bit-rate scheme and HDTV play time are all data management issues. For HDTV, acceptable picture quality is obtained by using MPEG-2 with a maximum data rate of about 13-25 Mbps for most scenes. During a slow scene, not as many files are accessed, and much less storage area on the disk is used. This architecture leaves room on the disk for the data associated with faster-moving scenes.

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constant rate,

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Fixed-rate schemes, like magnetic tape, supply data at a

no matter what the requirements of the scene. During fast-moving scenes, the data stream from the tape supplies an adequate data rate. The tape speed and data rate for these devices are set by the upper limit of the scene requirements. Since the tape does not slow down during slower scenes, the data stream is padded at these times with useless information that takes up valuable storage area on the tape. Overall, the random-access architecture of optical disks is a much more efficient way to use the available storage area. That is, optical disks do not require as many gigabytes of user data capacity for an equivalent length and quality HDTV presentation. Blu-ray has slightly higher capacity and data rate.. Blu-Ray should easily provide two hours or longer of prerecorded HDTV per side compressed with MPEG-2. MPEG-2 is a technique for compressing video data and replaying the data associated with certain rules that are defined in the MPEG-2 specifications. The action of the optical disk system is not to compress data or interpret the video information rules. Instead, the optical disk system only stores and retrieves data on command from the video operating system. Therefore, as video operating systems and associated compression technology become more advanced, no fundamental changes are required to the optical disk system. MPEG-4 technology

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is an advanced video compression scheme that utilizes advanced pre-filtering

post-filtering, in addition to a rule-based algorithm. Estimated improvement in compression is a around a factor of three beyond MPEG-2.

4. Different Formats of Blu-ray Disc

BD-ROM: a read only format developed for
prerecorded content

BD-R
for PC storage

: a write once format developed : a rewritable format developed : a rewritable format developed

BD-RW
for PC storage

BD-RE

for HDTV recording

5. Two Versions of Recording

5.1 One Time Recording
Making permanent changes to a disc. If we use BD-R the material on the disc itself is changed forever. There is no way to get the material back into its old state. The recording material is crystalline in nature. As scan spot falls on the surface it changes to amorphous. We cannot change it back to crystal state.

5.2 Record Many Times

If we use a BD-RW the material on the disc itself changes, but can be changed back again .We can do this as long as the material doesnt get worn out. By heating up the crystals, they change form. Now when we quickly cool them, they stay in that form

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itself. That is the material is changed from crystal state to amorphous Now, if we want to erase the BD-RW, we have to make sure that we lose all the data. So we want to get rid of that amorphous state. By heating up the material again, but this time taking more time and less heat, the material gradually wants to take its old form again, and thus the information is erased. This state is called the crystalline state. So, by very quickly heating it and very quickly cooling it, give the crystal another state (Amorphous state) which thus contains the data and by very quite slowly heating it and cooling it, we can give the crystals their old form back (crystalline state) which contains no more data. Its a constant change of phases. And so it is called as phase change recording. Data is stored in the form of grooves, on an optical disc. Next to the grooves, there are lands. Lands are the borders between the grooves. Grooves and lands have a sinus form. This is called a wobbled groove. In the groove, pits are formed to store data.

6. Blu-ray Disc Structure

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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.

7. Specifications:

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8. Basic Blu-ray Disc Characteristics

8.1 Large Recording Capacity

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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.

8.2 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.

8.3 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.

9. Blu-ray Founders
The following companies have jointly established the basic specifications Blu-ray disc video recording format

Hitachi , Ltd LG Electronics Inc. Matsushita Electric Industrial Co. Ltd. Mitsubishi Electric Corporation Pioneer Corporation Royal Philips Electronics Samsung Electronics Co. Ltd. Sharp Corporation Dept of Computer Engineering G.P.T.C.Kaduthuruthy 10

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Sony Corporation Thomson

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10. Comparisons

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11. Advantages
The main advantages of the Blu-ray disc are

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.

Format Developed with Input from Motion Picture

The features of the content protection system are Studios Strong Copy Protection by

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Renewability with Renewal Key Block and Device Key Enhanced Encryption Algorithm: AES 128 bit Physical Hook Against Bit by Bit Encrypted Content Title-based Expandable Content Control File Production Process Control Works Against Professional 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

12. Applications

High Definition Television Recording

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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 topof-the-line specifications mean that it is suitable for a full range of other purposes as well.

13. Requirements
1) Blue laser 2) Detector 3) Advanced objective lens 4) New disk and cartridge manufacturing technologies

14.Conclusion
The BD represents a major advancement in capacity as well as data transfer rate. It would be an ideal choice for the secondary storage purposes.The semiconductor storage for secondary memory is large, consumes more power and is more expensive. HDTV video recording and reproducing would essentially require the large storage capacity and data transfer rates, as offered by the Blu-ray disc. The Blu-ray

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disc has a wide variety of applications and is the ultimate storage device that would lead to digital convergence, ultimately leading to the convergence of the PC and CE technologies.

15. References
1.
Digital Digest Magazine Published by Digital Tech Consulting

L.L.C, September 2003, Blu-Ray Format Positioning As Next Generation DVD.

2. 3.

Optical Recording: A Technical Overview, AddisonMassachusetts,pp321-323(1990)

Wesley,

Reading, Technology

Optical Disc Systems Dec 2002,The Blue Disc Recording

4. Spectrum, Magazine Published by IEEE, June 2003, The Great

Gallium Nitride Gamble

5. www.bluray.com 6. www.google.com 7. www.opticaldisc_system.com

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