BLU RAY DISC1. INTRODUCTION

Blu-ray Disc, or BD, is an optical disc that uses state-of-the-art blue-violet laser technology to enable consumers to record high-definition TV broadcasting. Developed by the "Blu-ray Disc Founders" group, these companies include Hitachi, LG, Matsushita, Pioneer, Philips, Samsung, Sharp, Sony, and Thomson. Although Blu-ray Disc was primarily designed to be a "consumer high definition video recording format", its very high storage capacities and high-speed data transfer rates also make Blu-ray Disc suitable for storage libraries and ultimately other applications.A Blu-ray Disc has the same physical size as a DVD (12cm) but has higher data and track densities that give it between roughly three to six times the storage capacity of a standard 4.7GB DVD-R. This feat is made possible using a 405 nm (405 billionth of a meter) blue-violet laser, actually violet-purple, (see figure 1) and an optical pickup head with a 0.85 NA (numerical aperture) lens. Because a blue-violet light laser has a shorter wavelength (405 nm) than the red light (650 nm) used in CD and DVD systems, it allows the laser beam to make a smaller spot on the disc surface. With each bit of data taking up less space on the disc, more data can be stored on a 4.7-inch disc.1st GENERATION:Compact disc (CD): --- 650/700 MBIt is with us for over 20 years.Wavelength of laser which reads data: 780 nmColor of laser: Red2nd GENERATION:Digital versatile disc (DVD): --- 4.7 GBIt offers high quality sound and video than CD.Wavelength of laser which reads data: 650 nmColor of laser: Red3rd GENERATION:Blu-ray disc (BD): --- 25/50 GB-Next generation optical disc format.-Developed by blu-ray disc association (which includes Apple, Hitachi, HP, LG, Panasonic, Pioneer, Philips, Samsung, Sharp, Sony)-Wavelength of laser which reads data: 405 nm-Color of laser: Blue-violetFORMAT OF BD:It comes in four different formats: BD-ROM (read only) :for reading recorded content. BD-R (recordable) :for PC data storage. BD-RW (rewritable) :for PC data storage. BD-RE (rewritable) :for HDTV (high definition television) recording.

1.1. TYPES OF BLUE RAY DISC

1.1.1. SINGLE LAYER :Can hold data up to 25/27 GB that means 2 hrs of HD video or about 13 hrs of standard video.1.1.2. DOUBLE LAYER :Can hold data up to 50 GB that means 4.5 hrs of HD video or more than 20 hrs of standard video.2. BLU-RAY DISC RECORDING LAYER

A distinct feature of the Blu-ray Disc is the position of the recording layer within the disc. For DVD, the recording layer is sandwiched between two 0.6-mm thick layers of polycarbonate plastic. But the recording layer in a Blu-ray Disc sits near the surface of a 1.1-mm thick plastic substrate and is protected by a mere 0.1-mm thin cover layer. This not only allows for better disc readout, as the laser does not have to travel far to the point of focus, but serves to increase the recording density because the laser can be more narrowly focused by the larger 0.85 NA lens aperture (see figure 1 above). In addition, it minimizes tilt problems associated with substrate stresses which can occur during the injection molding process used to produce them. This can cause the laser light to split into two separate beams, refer to as birefringence, and if it becomes excessive, the drive cannot read data reliably from the disc.But having the recording layer closer to the surface has its disadvantages as it leaves the disc exposed to accidental abrasions, dust, and fingerprint marks. To overcome this, a specially formulated protective hard-coat is applied on top of the cover layer. This protective coat is hard enough to prevent accidental abrasions and also allows fordust and fingerprints to be removed from the disc by simply wiping.

3. WHY THE NEED FOR SO MUCH CAPACITY?High-definition video (720p or 1080i) requires five times the recording capacity of standard definition video (480i). The actual HDTV transmission is based on a 19.4 Mbps (Mega bits per second) digital data stream but the maximum data transfer for DVD is about 10 Mbps. Thus, theres simply not enough bandwidth to put an HDTV program on a recordable DVD format. To achieve the density necessary to put this amount of data on a single-sided 12 cm optical disc, the size of the spots burned into the disc need to be smaller. In addition, the high-definition video will need to undergo compression to be able to store this high-definition picture.Video and Audio CodecsThe Blu-ray Disc format employs MPEG-2, Video Codec 9 (VC-1 based on the Windows Media 9 format), or H.264/MPEG-4 AVC video compression techniques in order to lower the data rate (i.e., use less digital data) of the high-definition video. The excellent efficiency of the latest MPEG-4 AVC and VC-1 codec allow image data to be compressed to about one-third the size achieved by MPEG-2 and replay of high quality digital images.But regardless of the codec utilized, the idea is to compress enough to decrease the bit rate to data capacity levels while trying to preserve the high-definition picture quality to a reasonable standard. This allows the high-definition signal to be recorded without excessive compression, preserving the detail of the original high-definition picture. The audio formats for BD extend beyond the current DVD specifications to include every type of audio codec available. Though, at this writing, the more robust DTS Digital Surround had been selected as the audio technology of choice for Blu-ray Disc (BD).

Capacitieof blu-ray discBlu-ray Disc may have three single-sided single-layer structure capacities of 23.3GB, 25GB, 27GB, and three single-sided dual-layer structure capacities of 46.6GB, 50GB and 54GB (without flipping sides) compared to current DVDs which can hold between 4.7GB and 9.4GB of data. However, recent press announcements had circulated that a "Hybrid" disc was being proposed by the Blu-ray Disc Founders that would be comprised of a double-sided single-layer containing an 8.5GB capacity standard-definition and a 25GB capacity high-definition version.CompatibilityBlu-ray Disc is a totally new and radical optical storage medium requiring retooling and or construction of new disc manufacturing and replication plants. Thus, Blu-ray Disc does not share compatibility with current DVD technologies.

4. OUTLINE OF BLUE RAY TECH

The Blu-ray disc system not only employs a short wavelength blue-violet laser (405nm), but also uses an objective lens with a numerical aperture (NA) of 0.85. Its small spot size can allows 5 times higher recording capacity than a standard DVD. The Blu-ray discs are designed with a 0.1 mm optically transparent protection layer, which diminishes aberration caused by disc tilt, yet is durable enough to protect the discs recording layer. The track pitch on the discs is a mere 0.32 m, nearly half that ofthe DVD.

Pits : spiral grooves that run from the centre of the disc to its edgesBumps :other sides of these edges.Track pitch :it is the distance between the two tracks (of pits) on the surface.Pit size 0.15 microns ( more than twice as small as the pits on DVD )

Track-pitch is : 0.32 micronsLaser needed : blue-violet laser (405 nm)Data transfer rate : 36 Mbps

5. BLY-RAY DISC ADVANTAGE

A. Much more ROBUST than todays polycarbonate-based CD/DVDs (and HD DVDs)B. Hard-coating technology provides resistance to:- Finger prints- Marks- Scratches- DustC. Various hard coating technologies make Bly ray disc most durable and family -friendly

D. Higher density enables better data seek timesE. Shorter to travel for same amount of data results in faster data seekF. Better for random access of data

G. REWRITE

The vertical axis shows the performance index (whether recording marks are well written) of the recording properties called jitter. Specifically, it shows the variation of the gap between the recording mark edge and the data clock edge. A smaller value represents fewer errors when reading data.The horizontal axis shows the number of overwrite cycles. Ordinarily, jitter rapidly worsens after a certain number of overwrite cycles due to recording layer deterioration.This is why Sony developed a durable recording layer. Jitter hardly rises even after repeated overwrites, resulting in stable recording/playback.

H. SCRATCH GUARD

These photos on the left show the results of abrasion tests. When abrasion rings were run on the recording surface of a DVD disc (the outer track) to forcibly create a situation in which discs are apt to be scratched, numerous scratches arouse on the disc without the hard coat. Meanwhile, there were hardly any scratches found on Sonys disc with high performance hard coat. This clearly demonstrates the high scratch-resistance of Sonys high performance hard coat.Notes 1.Testing method conforms to JIS K7204 standards

2. Result after one rotation of the abrasion ring

I. ANTI STATIC

These photos on the left show how finely cut pieces of expanded polystyrene adhere to disc after the surface of the discs have been wiped once by tissue paper. While expanded polystyrene adhered to the overall surface of a disc without hard coat, Sonys disc with high performance hard coat had virtually no expanded polystyrene adhering to it. This is because there is extremely low electrostatic charge, making it difficult for static electricity to be generated.

J. ARCHIVAL RELIABILITYClear picture can be playedback without distortionafter long archive

The chart above shows the acceleration test results for Sony disc storage properties. This error rate increase causes representation deterioration is extremely small, and a stable and low error rate is maintained even after long archive.Sony has utilized its highly reliable recording material design and thorough manufacturing control to realize a disc that is extremely resistant to image corruption and deterioration due to long archive.

6. COMPARISON IN BUILDING BD AND DVD

ParametersDVD Blu-ray Disc

Capacity per layer (GB)4.725

Max number of layers22

Max number of sides22

Substrate + cover layer (mm)0.6 + 0.61.1 + 0.1

Laser wavelength (nm)650405

Numerical aperture0.600.65

CartridgeNoNo

Hard coating neededNoYes

Complexity to read DVD-More complex

Maximum Data Rate (Mbps)11.08 (1X)36.55 (1X)

Maximum Recording Time (HDTV)Single-Layer-2 hours

Dual-Layer-4 hours

BD Data is placed on top of a 1.1 mm thick polycarbonate layer Doesnt suffer from BIREFRINGENCE Doesnt suffer from DISC TILT Hard coating is placed outside to protect from scratches or fingerprints

DVD Data is sandwiched b/w two polycarbonate layers, each 0.6 mm thick Suffer from BIREFRINGENCE Suffer from DISC TILT No such hard coating is placed

7. FEATURES OF BD Record HDTV without any quality loss Instantly skip to any spot on disc Record one program while watching other on the disc Create playlists Edit or reorder programs recorded on disc Automatically search for an empty space on the disc to avoid recording over a program Access to web to download subtitles and other extra featuresAnd many more

REFERENCE

www.wikepedia.com www.seminartopics.com www.bestneo.com

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