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  • 8/13/2019 Bluray Working


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    Blu-Ray Technology WorkingJOHNMARCH - 10 - 2010


    After the invention ofthe Digital Versatile Disc [DVD], the true digital sound effect and high clarity video effects were brought to all homes. But the hunger for high-definition videos andaudio along with a high-capacity storage disc led to the invention ofthe Blu-ray Disc [BD]. They have the same capabilities ofa DVD, storing audio, video as well as photos.



    Blue-ray disc

    Blu-rayDisc Definition

    A Blu-ray Disc is a high density optical disc storage medium, which is used for the storage ofall high-definition digital formats like audio, video, and play-station games and soon. They have the same physical appearance as a DVD. The name BLU-RAYis actually a combination ofthe colour blue and ray. Here blue refers to the blue colour ofthe laser that is used for its reading and ray refers to the optical ray. While trade marking a product, youare not supposed to include a commonor everyday used word. Thus the letter e from the word blue was omitted.

    Blu-RayDisc Specifications

    1. BD is present in both single layer and double layer. The single layer Blu-Ray Disc has a capacity of up to 25 GB anddouble layer has a capacity of 50 GB. Though this is a practical storage capacity meant for the present Blu-Ray
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    players, there are BDs that have capacities up to 200 GB. These discs, though not marketed yet, can be played inany Blu-Ray player without any additional equipment.

    2. Blu-Ray Disc needs a wavelength of 400 nanometer violet-blue laser for its reading at different speeds like 4.5MBPS, 9 MBPS, 18 MBPS, 27 MBPS, 36 MBPS and 54 MBPS.

    3. Blu-Ray disc can run formats that are encoded in MPEG-4 and MPEG-2.4. BD is used for data storage, playing 1080p HD video and audio, 3-D Stereophonic and so on.

    Blu-RayTechnology History

    There havebeen many questions on who invented the Blu-Ray technology.But this can be explained only by explaining the history ofBlu-Ray technology.

    Even though the High Definition TV was invented, there was no particular storage format, recorder or playerfor it. Thus companies like Toshiba started experiments on making a bigger size DVD. Lately,they released their own Blu-Ray player.During this war for HDtechnology, researches provedthat short wavelengths (shorter than that ofa DVDBlu-ray Disc) were enough to make discs with higher storage capacities along with optical capabilities. It was at this time that a researcher, Shuji Nakamura invented the violet-blue laser diode which was apt for a Blu-Ray Disc.

    This invention was first applied by Sony Company.They were able to create Ultra Density Optical and alsoDVRBlue along with the help ofPioneer. These were considered to be the first replicas ofBlu-Ray Disc. This was later exhibited to the world at February 2002and an association was formed. It consisted ofnine members, who were considered to be the inventors ofBlu-Ray disc. The association was called the Blu-ray Disc Association. This association has now expanded with more than 5000 members all overthe world. This association consists ofmany makers ofelectronic goods, computer hardwares and alsomotion pictures.

    Blu-RayDisc (BD)vsDVD

    Both of them have the same physical appearence. [Thickness = 1.2 mm] The single layer Blu-ray disc can store up to 27 GB data. A singe layer DVD can hold only 4.7 Gb of data. Thus a BD

    can hold almost 13 hours of normal video and 2 hours of high-definition video. A double layer BD gas a storagecapacity of 50 GB which can play almost 20 hours of normal video and 5 hours of HD.

    A DVD needs two substrates and they should be bonded. But a Blu-ray disc requires only one substrate. The production cost of Blu-ray is lesser than that of a DVD because there is no need for bonding of substrates. Thus

    the production materials are lessened. This causes a lesser production time than that for a DVD.

    The Blu-Ray disc uses violet-blu laser with improved lens specifications, while a DVD uses red laser. This causes thefocus to increase, thus helping in the recording of both small and high density pits on the BD.

    The wavelength used for BD is 400 nanometers. DVD has a wavelength of 650 nanometers. This decrease inwavelenth helps in high density medium storage.

    The layer in a blu-Ray disc is very close to the laser lens on its player. Thus the precision of the data displayed willbe higher with less distortion than a DVD.

    Take a look at the comparison between DVDand BDfrom the figures below.

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    Similar toa DVD, BD also has different versions according to its application. The commontypes are

    1. Read only memory Blu-Ray disc [BD-Rom] This type of BD can only be read but cannot be written over. Thecontent will be pre-recorded.

    2. Recordable Blu-Ray disc [BD-R]This BD is mainly used for storage of PC data.3. Re-writable Blu-Ray disc [BD-RW]This BD is mainly used for storage of PC data. The contents in this disc can be

    written over and over.4. Re-writable Blu-Ray disc [BD-RE]This BD is mainly used for recording of data to be used in HDTV. This disc can

    also be written over again and again.

    Constructionand Working ofBlu-Ray Disc

    Like a DVD, the BDalso has pits and bumps. The only difference is that the pits and bumps are smaller and very closely packed. Blu-ray disc also has spiral tracks running from the centre to t he edges ofthe disc. The information is stored in these tracks in the form ofaudio and video. These audio a nd video are introduced into the DVDafter encoding it.

    As told earlier a blue laser is used to focus on the DVD. The laser has a small wavelength ofprecisely 405 nanometers and must be highly accurate because the pits and bumps are smallerand packed closely.The information stored in the Blu-Ray disc is usually very small in size. They are only 0.15 x 10-6 meters long. Sinceall these are very small in size, a single-layeritselfis more than enough tohold more than 25 GBofdata. Thus ifa double layeris used, they can easily hold information up to5o GB.

    The Blu-Ray disc does not have these issues because the data is stored on topofa poly-carbonate layerwhich is about 1 millimeter thick. This stops the problem ofbirefringence and causes no distortion to the reading ofdata. This alsohas an advantage in regard to the closeness ofthe data to the objective lens. Due to this closeness to the surface, the BD has a outside hard coverto prevent scratching and finger prints.

    Because the data is closer to the surface, a hard coating is placed on the outside ofthe disc to protect it from scratches and fingerprints. The simple design helps in manufacturing these discs at a cheaper rate than a DVD. There is noneed ofmoulding like a DVD.

    Advantagesof Blu-RayTechnology

    The sleek design helps in skipping from any part of the disc to the other Multiple programs like using the same disc for watching a video as well as recording on it can be done at the same


    Watch HD in its maximum quality with very little loss. You can make your own playlists. The programs present on the disc can be re-ordered in any way you like. Use of subtitles is possible for movies.

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