CD & DVD & Blu-ray

Last updated: August 30, It's amazing CD & DVD & Blu-ray you think about it: Although compact discs CDs have been around for more than 30 years, they are still one of the most popular ways of storing music and computer data.

Let's take a closer look! Throughout this article, we'll talk about CDs. What is a CD? A compact disc is a thin, circular disc of metal and plastic about 12cm just over 4.

It's actually made of three layers. Most of a CD is made from a tough, brittle plastic called polycarbonate. Sandwiched in the middle there is a thin layer of aluminum. Finally, on top of the aluminum, is a protective layer of plastic and lacquer. The first thing you notice about a CD is that it is shiny on one side and dull on the other. The dull side usually has a label on it telling you what's on the CD; the shiny side is the important part.

It's shiny so that a laser beam can bounce off the disc and read the information stored on it. A small portable compact disc player made by Technics.

Gadgets like this have now largely been superseded by MP3 players such as iPods, which are much smaller and lighter and pack lots more music into the same space by compressing it digitally. Read more about this in our main article on MP3 players. How CDs use optical laser technology Until CDs were invented, music was typically stored on vinyl plastic LP long-playing records and cassette tapes.

LPs scratched easily, while tapes could stretch and distort and sometimes snapped or seized up entirely. Both of these ways CD & DVD & Blu-ray storing music were primitive compared to CDs. LPs were played on turntables with a moving arm that bounced along a groove in the plastic, reading back the music as it went. Record players or gramophones, as they were sometimes known used mechanical technology for recording and playing back sound: CD & DVD & Blu-ray tapes used in such things as the CD & DVD & Blu-ray Sony Walkmans worked a different way.

CD & DVD & Blu-ray stored sounds using magnetic technology. When you put a cassette into your Walkman, a small electric motor dragged the tape past a little electromagnet. The electromagnet detected the pattern of magnetism on the tape and an electronic circuit changed this back into the sounds that fizzed and popped in your headphones. Great music, rotten CD! CDs were billed as virtually indestructible, but some early ones have fallen victim to a problem called disc rot: With the invention of CDs, people finally had a more reliable way of collecting music.

CD players are neither mechanical nor magnetic but optical: One of the main problems with LPs and cassettes was the physical contact between the player and the record or tape being played, which gradually wore out. In a CD player, the only thing that touches the CD is a beam of light: Another advantage is that the CD player can move its laser quickly to any part of the disc, so you can instantly flip from track to track or from one part of a movie to another.

How CDs are recorded and CD & DVD & Blu-ray back Note: In the explanations that follow, I'm deliberately going to simplify how CDs store music as patterns of zeros and ones. It's much more complex than I'm going to make it seem, and it's beyond the scope of an introductory article like this, but I will briefly describe what really happens at the very end.

LP records stored music as bumps on the surface of plastic, while cassettes stored it using patterns of magnetism. These are called analog technologies, because the sound is stored as a continuously varying pattern of bumps in the plastic of a record or fluctuations CD & DVD & Blu-ray the magnetism on a cassette tape. In a CD, music or other information is stored digitally as a long string of numbers. After the music has been recorded, it is converted into numbers by a process called sampling.

Almost 50, times a second 44, to be exacta piece of electronic equipment measures the sound, turns the measurement into a number, and stores it in binary format as a pattern of zeros and ones. The sampling process turns a CD track lasting several minutes into a string of millions of zeros and ones. This is the information stored on your CD. In other words, there is no music on a CD at all—just a huge long list of numbers.

An ordinary CD is a sandwich of plastic in which bumps have been pressed by a master discreflective aluminum, and protective polycarbonate plastic. CDs are made from an original "master" disc. The master is "burned" with a laser beam that etches bumps called pits into its surface. A bump represents the number zero, so every time the laser burns a bump into the disc, a zero is stored there.

The lack of a bump which is a flat, unburned area on the disc, called a land represents the number one. Thus, the laser can store all the information sampled from the original track of music by burning some areas to represent zeros and leaving other areas unburned to represent ones. Although you can't see it, the disc holds this information in a tight, continuous spiral of about 3—5 billion pits. If you could unwrap the spiral and lay it in a straight line, it would stretch for about 6 km roughly 3.

Each pit occupies an area about two millionths of a millionth of a square meter. That's pretty tiny! Once the master disc has been made, it is used to stamp out millions of plastic duplicates—the CDs that you buy and put into your music player or computer. Once each disc is pressed, it's coated with a thin aluminum layer so it will reflect laser lightcovered with protective polycarbonate and lacquer, and the label is printed on top.

Inside your CD player, there is a miniature laser beam called a semiconductor diode laser and a small photoelectric cell an electronic light detector. When you press play, an electric motor not shown in this diagram makes the disc rotate at high speed up to rpm. The laser beam switches on and scans along a track, with the photocell, from the center of the CD to the outside in the opposite way to an LP record. Otherwise, as the CD & DVD & Blu-ray from the center increased, the actual surface of the disk would CD & DVD & Blu-ray moving faster and faster past the laser and photocell, so there would be more and more information to be read in the same amount of time.

The laser red flashes up onto the shiny under side of the CD, bouncing off the pattern of pits bumps and lands flat areas on the disc. The lands reflect the laser light straight back, while the pits scatter the light. Every time the light reflects back, the photocell blue detects it, realizes it's seen a land, and sends a burst of electric current to an electronic circuit green that generates the number one.

When the light fails to reflect back, the photocell realizes there is no land there and doesn't register anything, so the electronic circuit generates the number zero. Thus the scanning laser and electronic circuit gradually recreates the pattern of zeros and ones binary digits that CD & DVD & Blu-ray originally stored on the disc in the factory. Another electronic circuit in the CD player called a digital to analog converter or DAC decodes these binary numbers and converts them back into a changing pattern of electric currents.

A loudspeaker transforms the electric currents into sounds you can hear by changing their electrical energy into sound energy. Don't try to fiddle with your CD player to see the laser lit-up inside. It could damage your eyes or blind you. All CD players are designed to stop you looking at the lasers by mistake. Don't ever fool around with them! It wasn't long before computer companies realized they could use CDs to distribute software programs very cheaply, and ordinary computer users soon saw that CDs would be even better if CD & DVD & Blu-ray could write music and data on them as well as just read from them.

That's how recordable CDs CD-Rs came to be CD & DVD & Blu-ray, but the snag was that they could only be written on once; you couldn't erase and reuse them. Soon enough, though, the computer whizzkids developed rewritable CDs CD-RWs that you could erase and rewrite any number of times.

In theory, if you wanted to make ordinary CDs in CD & DVD & Blu-ray own home, you'd need to install a huge and expensive CD-pressing machine. Fortunately, you don't need to do this—and that's because recordable CDs CD-Rs work in a completely different way. This time, there are no pits and lands imprinted on plastic. Instead, in between the protective polycarbonate and the reflective aluminum, there's a layer of dye. Normally the dye is translucent: So far so good, but how do we store information on a compact disc like this?

A CD-R writer has a higher-powered laser than normal, which generates heat when it strikes the disc, "burning" the dye and making a tiny black spot. Later, when a CD reader aims its laser at that spot, the light is completely absorbed and doesn't reflect back.

CD & DVD & Blu-ray indicates that a zero "0" is stored on the disc at that point. In places where the dye is unburned, the laser light reflects straight back again, indicating that a "1" is stored on the disc. See where this is going? By creating areas of "burned" dots, and other places where the dye is left alone, a CD-R writer creates a pattern of binary zeros and ones that can CD & DVD & Blu-ray used to store information.

Unfortunately, once the dye is "burned" it's permanently transformed: And that's why you can only write a CD-R disc once. Just in passing, we should note that, although CD writers are widely referred to as CD burners, they do not actually burn things combust them with oxygen: With a CD-R, binary information is stored as "burned" areas 0 and unburned areas 1 in the dye layer sandwiched between the protective polycarbonate and the reflective CD & DVD & Blu-ray.

Let's say you're charged with the task of developing a type of compact disc that can be written to or erased over and over again. Clearly you can't use either of the methods we've discussed so far the pits and lands method from read-only audio CDs or the "burned"-dye method used in CD-Rs.

What you really need is a CD made from a substance that can easily be converted back and forth between two different forms, so it can be used to store a pattern of zeros and ones, then erased and used to store a different pattern later on if necessary. Most of us learned in school that the atoms or molecules in solids, liquids, and gases CD & DVD & Blu-ray themselves in different positions, with atoms in solids tightly locked together. Some solid materials are more complex than this: Solid carbon, for example, can exist in very different phases that include graphite and diamond.

That's just what we need to make a CD-RW disc. Instead of having a layer of dye, a CD-RW has a layer of metallic alloy that can exist in two different solid forms and change back and forth between them.

CD and DVD players

Find the perfect deal for CD DVD and Blu-ray Players with free shipping for many items at eBay. Shop by features such as remote control, full hd, disc changer. Compare Item NexStar DX USB External Enclosure for SATA Blu-Ray/CD/DVD Drive> Compare Vantec NexStar DX USB External Enclosure for SATA Blu-Ray/CD/DVD Drive. Generally, people use CD’s to store music, DVD to store standard definition movies, and Blu-ray to store high definition videos. Wondering why storing movies on a CD is next to impossible? CD’s comes with very small data storage space and capability. Let’s Find Out More About CD, DVD, And Blu-Ray; #Compact Disc (CD).

CD & DVD & Blu-ray

WATCH:

CDs, DVDs, BluRays - Working and Secrets Explained in Detail

Related Links: OEM Photoshop Elements 9 | How Much Does It Cost For PowerDVD 10 Ultra 3D?

Tag Cloud:SharePoint Server, ZoneAlarm, TurboTax