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Ongoing Thoughts 15:
By William E. Steinman:
Blue Ray:
In Ongoing Thoughts Twelve, I discussed my adventures while
finding a DVD recorder. In that, I pointed out a new DVD technology called Blu-ray Disc™ (BR) technology. This is a new format
for recording information to DVD that was developed by
a consortium of companies called the Blu-ray Disc
Association (BDA). Several companies are involved in this effort including
Apple, Dell,
Okay! The purpose of this format was to enable the
recording, rewriting, and playback of High Definition Video (HD). It also
allows for the storage of large amounts of data to DVD. The big deal is, while
a normal DVD can hold up to 4.7 gigabits (GB) of data on a single-layer disk
the new method allows up to 25 GB on a single-layer disk. The disks are the same
physical size in both technologies. Just so we are all on the same page, I
specified single-layer because there are double-layer disks available. They
hold not quite twice as much data. That is not relevant to this discussion.
How, we might ask, can they get so much more information on
the same sized disk with BR technology? The key to the difference is in the
laser recording technology. While the normal recording technique for DVD uses a
red laser, the BR technique requires a blue laser (actually blue-violet), hence
the name Blu-Ray. So what’s
the difference? At this point it will be useful for
our understanding to discuss laser technology. In this effort, I had to
research lasers so I could understand. Sooner or later,
everyone is a student. First, the word laser means light amplification by
stimulated emission of radiation. That’s a
mouthful so it was shortened to the acronym, laser. Now what does it mean?
Let’s begin with light. In
the simplest definition light is that part of the electromagnetic spectrum that
is visible to us. We can see it. We could get more complex than that, but it
would serve no purpose here. When we wear a red shirt, it appears as red
because it reflects light in the red part of the electromagnetic spectrum. What
we call the visible spectrum, the part that we can see, ranges from 0.400 to
0.750 nanometers in wavelength. The manufacturers of household light bulbs
strive to make bulbs that produce white light. White light contains all the
wavelengths of visible light. Logically total darkness, black, has no visible
light at all.
Well, what has all this to do with DVD recording? We noted
that we use laser recording technology to record to
DVD. More specifically, a laser beam is used to change
or burn the recording surface of a DVD in a pattern that represents the video
data we are recording. We literally burn a DVD disk with a laser beam when we
record. Later, we can use a laser beam in a less destructive mode to read the
data from that DVD.
The reason we use laser light instead of any old light is
that laser light is coherent. That means it is all of the same wavelength
direction and phase. By contrast, white light is composed of all of the
wavelengths, goes of in directions and is completely out is phase. It is
incoherent and cannot be finely focused. That is the
key. Laser light can be focused into a very tiny beam.
That beam can be used to burn or cut a DVD. The beam is so fine that a huge
amount of data can be recorded in a very small surface
area.
Here is the difference between regular DVD technology and BR
technology. As we said, regular technology uses a red laser and BR uses a blue
laser. If we look at the spectrum we will find that the red laser has a much
longer wavelength that the blue laser. It is just like the rainbow we see in
the sky now and then. The red is on one side and the blue is near the other
side. Lest we forget, the visible spectrum order is red, orange, yellow, green,
blue, indigo, and violet. Since blue light has a shorter wavelength than the
red, used by previous technologies it is possible to read and write data
with greater precision. The blue-violet laser has a wavelength of 405nm
compared to a red laser of wavelength 650nm.
Now we will hear and read a lot of hype about this BR
technology so it is important to proceed carefully. We will not see any hype
about the cost because it is quite steep. For example, the best price I could
find for a blank BR disk was $15.95. That was online. The local retail stores
do not even carry them. A normal DVD blank disk sells for about two-bits each. Think about that. We must read all of the
fine print before we jump in, especially since the old technology still works
well. What this new technology offers with certainty is the ability to record
about five times as much data as the old. The hype about phenomenal sound and
picture reproductions has a lot of if, ands, and buts attached to it. Read the
Q and A stuff offered by some of these outfits carefully.
Another problem I see is this BR technology is not
completely backward compatible. While, some of the units will read the old
disks, none will record to the old media. If you switch too soon, you could end
up with a big pile of perfectly good, but unusable
blank DVD disks. For me, I waited this long to get into the HD digital
revolution. I did not suffer much sadness because of that. I think I can wait a
bit longer for
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