24-07-2012, 04:51 PM
The advantages of Blu-ray disc
[attachment=28772]
ABSTRACT
Blu-ray Disc format is required by the forthcoming of High Definition TV era which calls for a brand new generation of
optical storage after DVD. It is such a technology with wavelength short as 405nm and numerical aperture high as 0.85.
The format is designed to have an even wider disc tolerances than those of DVD. Thanks for those more innovative
concepts Blu-ray Disc is the most economical storage solution in terms of cost per giga byte. And it is expected to be a
long-term optical storage standard rather than an interim solution.
INTRODUCTION
Blu-ray Disc format is required by the forthcoming of High Definition TV era, which calls for a new generation of
optical storage after DVD. The storage demanding MPEG2 format HDTV normally has a data rate between 20 and 30
Mbps. For example, a 135 minutes recording of 25Mbps HDTV program requires a storage capacity about 24GB. Bluray
Disc is specifically defined for such a capacity. To have the capacity five times that of DVD, BD employs the
wavelength short as 405nm and numerical aperture high as 0.85. It is regarded the blue-violet wavelength will be the
shortest wavelength in optical disc and 0.85 will also be the highest numerical aperture used for far-field optical storage.
To ensure a quick learning curve not only for the drive manufacturing but also for the disc production, Blu-ray Disc is
designed to have even wider disc tolerances than those of DVD. Thanks for those more innovative concepts Blu-ray Disc
is the most economical storage solution in terms of cost per giga byte. We can expect an even better result at a mass
production level.
To introduce a new generation of optical storage, a long term standard is much more preferred rather than an interim
solution. It is just like what happened in the history when the DVD format was defined. At that time, an interim solution
of less capacity was proposed. Finally this solution was not introduced to the market.
THREE GENERATIONS OF OPTICAL STORAGE
The development of Fourier Optics in the middle and late 20th century provided an essential theoretical basis for the
advent of optical storage technology 1. The development during the same period in motion control technology, audio
processing technology, error-correction coding technology, etc, enabled the standardization of disc storage to be first
realized in the audio recording field, and commercialized at a low cost.
In the diffraction limit the laser beam spot size is in proportion to (λ / NA)2 . The beam spot size of BD approximates 1/5
of that of DVD allowing the capacity of a BD disc to be about 5 times the DVD capacity. The current BD specification
provides three storage capacities for single layer storage: 23.3GB, 25GB and 27GB. With such capacity, over 2 hours of
high definition TV programs or about a 40-episode TV series of VCD quality can be stored onto one single layer BD. As
a matter of fact, the capacity can be increased further to provide 35GB on a single layer applying new signal processing
technology 2. On the creation of CD specification, the capacity requirement is to be able to record on one single disc a
complete 9th symphony of Beethoven. This tradition also reflected in the requirement for video recordings, the studios
expect a disc to hold 135 minutes of program. Mainstream high definition video compression methods usually have a
code rate of 20 – 30 Mbps. Multiply the 135 minutes with the code rate and we get the requirement for disc capacity,
which is within the capacity of a BD.
0.1 mm COVER LAYER
When employing the 0.85 NA objective lens, considering the system tolerance to disc tilt, disc processing, antismudginess,
data recording and system complexity 4,5, etc, the cover layer thickness has decreased to 0.1mm in the new
specification. As a result, the physical structure of BDs is in sheer contrast to that of CDs, information is read from the
thinner side. In optical read/write systems, the optical aberration is in linear relationship with the thickness of the cover
layer, thinner cover layer has effectively less optical aberrations 6,7. BD system has better tolerance to tilt angle than
DVD especially in coma forming, avoiding the use of complex real-time tilt servo system. In spherical aberration
elimination, spherical aberration compensation is introduced in BD system, but since this compensation needs no real
time servo control, the optical head realization is much simpler. The following table shows comparison of BD, HD-DVD
and red laser DVD in two major optical aberrations as coma and spherical aberration. As we can see, all relative
tolerances of BD optical characters exceed two times that of HD-DVD.
CONCLUSION
The advantages of BD are the capacity of reaching the far-field recording limit, large tolerance in processing, the
capability of the drive to be fully compatibility with CDs and DVDs in reading/writing, lowest storage cost per gigabyte.
All these advantages make BD the first choice of storage in the high definition television era. The Blu-ray Disc
Association has included almost all major companies in the optical storage industry, covering fields from content
providing, disc processing, equipment manufacturing, product integration, to sale, and is forming a complete value chain.
[attachment=28772]
ABSTRACT
Blu-ray Disc format is required by the forthcoming of High Definition TV era which calls for a brand new generation of
optical storage after DVD. It is such a technology with wavelength short as 405nm and numerical aperture high as 0.85.
The format is designed to have an even wider disc tolerances than those of DVD. Thanks for those more innovative
concepts Blu-ray Disc is the most economical storage solution in terms of cost per giga byte. And it is expected to be a
long-term optical storage standard rather than an interim solution.
INTRODUCTION
Blu-ray Disc format is required by the forthcoming of High Definition TV era, which calls for a new generation of
optical storage after DVD. The storage demanding MPEG2 format HDTV normally has a data rate between 20 and 30
Mbps. For example, a 135 minutes recording of 25Mbps HDTV program requires a storage capacity about 24GB. Bluray
Disc is specifically defined for such a capacity. To have the capacity five times that of DVD, BD employs the
wavelength short as 405nm and numerical aperture high as 0.85. It is regarded the blue-violet wavelength will be the
shortest wavelength in optical disc and 0.85 will also be the highest numerical aperture used for far-field optical storage.
To ensure a quick learning curve not only for the drive manufacturing but also for the disc production, Blu-ray Disc is
designed to have even wider disc tolerances than those of DVD. Thanks for those more innovative concepts Blu-ray Disc
is the most economical storage solution in terms of cost per giga byte. We can expect an even better result at a mass
production level.
To introduce a new generation of optical storage, a long term standard is much more preferred rather than an interim
solution. It is just like what happened in the history when the DVD format was defined. At that time, an interim solution
of less capacity was proposed. Finally this solution was not introduced to the market.
THREE GENERATIONS OF OPTICAL STORAGE
The development of Fourier Optics in the middle and late 20th century provided an essential theoretical basis for the
advent of optical storage technology 1. The development during the same period in motion control technology, audio
processing technology, error-correction coding technology, etc, enabled the standardization of disc storage to be first
realized in the audio recording field, and commercialized at a low cost.
In the diffraction limit the laser beam spot size is in proportion to (λ / NA)2 . The beam spot size of BD approximates 1/5
of that of DVD allowing the capacity of a BD disc to be about 5 times the DVD capacity. The current BD specification
provides three storage capacities for single layer storage: 23.3GB, 25GB and 27GB. With such capacity, over 2 hours of
high definition TV programs or about a 40-episode TV series of VCD quality can be stored onto one single layer BD. As
a matter of fact, the capacity can be increased further to provide 35GB on a single layer applying new signal processing
technology 2. On the creation of CD specification, the capacity requirement is to be able to record on one single disc a
complete 9th symphony of Beethoven. This tradition also reflected in the requirement for video recordings, the studios
expect a disc to hold 135 minutes of program. Mainstream high definition video compression methods usually have a
code rate of 20 – 30 Mbps. Multiply the 135 minutes with the code rate and we get the requirement for disc capacity,
which is within the capacity of a BD.
0.1 mm COVER LAYER
When employing the 0.85 NA objective lens, considering the system tolerance to disc tilt, disc processing, antismudginess,
data recording and system complexity 4,5, etc, the cover layer thickness has decreased to 0.1mm in the new
specification. As a result, the physical structure of BDs is in sheer contrast to that of CDs, information is read from the
thinner side. In optical read/write systems, the optical aberration is in linear relationship with the thickness of the cover
layer, thinner cover layer has effectively less optical aberrations 6,7. BD system has better tolerance to tilt angle than
DVD especially in coma forming, avoiding the use of complex real-time tilt servo system. In spherical aberration
elimination, spherical aberration compensation is introduced in BD system, but since this compensation needs no real
time servo control, the optical head realization is much simpler. The following table shows comparison of BD, HD-DVD
and red laser DVD in two major optical aberrations as coma and spherical aberration. As we can see, all relative
tolerances of BD optical characters exceed two times that of HD-DVD.
CONCLUSION
The advantages of BD are the capacity of reaching the far-field recording limit, large tolerance in processing, the
capability of the drive to be fully compatibility with CDs and DVDs in reading/writing, lowest storage cost per gigabyte.
All these advantages make BD the first choice of storage in the high definition television era. The Blu-ray Disc
Association has included almost all major companies in the optical storage industry, covering fields from content
providing, disc processing, equipment manufacturing, product integration, to sale, and is forming a complete value chain.