Recordable DVD
A recordable dvd is a blank disc that can be either written on once or rewritten multiple times via a laser rather than the standard DVD-ROM style that involves pressing the information onto the disc. This article will explain how recordable dvds store information and how they are written on, the differences between write-once and rewritable dvds, and some other key facts that you should know.
How Do DVDs Store Information
Recorable dvds use special dyes that are painted on the disc to create a canvas of data. Dvds don’t really “store” information, per se, but represent information. When the laser is passed over the disc in a certain way, it leaves behind either a “peak” or “valley” which the dvd player can then read later on to convert the colors back into information. Recordable dvds are a rather new technology and only the modern computers are equipped with the right mechanisms to “burn” information onto a disc.
How Is A DVD Made
To make a DVD, the factory first starts with a transparent piece of plastic (that part that’s on the outer edges of the disc is actually what the whole thing looks like). This plastic piece is what makes up most of the disc. The data layer is added next which is where the dye is. This layer is the main platform in which the DVD player reads the disc because this is where the data is encoded. The next layer is a metallic coating that causes the laser light to bounce off of the disc and back into the receiver after it hits the data layer. After that, a thin, plastic coating is added to provide a small amount of protection for the data layer and metallic layer. Once the plastic coating is added, a label layer is added that allows for the company or consumer to identify what’s on the disc. With CDs, it is common for you to see the band’s name along with the songs that are on the disc. DVDs found in the video store often have a picture of the title or main characters on this layer so you can easily tell what’s on the disc.
Types of DVDs
DVDs can come in many different forms. This article focuses mainly on recordable dvds but even that can be used to refer to both write-once and rewritable discs. There are also many different types of cross-reference dvds that contain the ability to be rewritten but not strictly made for that. Below is a list of different types of dvds, including write-once, rewritable, and standards dvds that can not be written onto at all.
DVD-ROM
DVD-ROM refers to DVDs that are read-only. DVD-ROMs can not be written onto and are made that way for a reason. A good example of a DVD-ROM would be a common DVD that you can pick up at the video store. These discs are encoded with spiral paths that start from the center of the disc and spiral outward. A laser in your DVD player is used to bounce light off of these pathways and a separate device is used to track the laser as it moves across the disc and records how fast the light comes back. This pattern can then be converted into information. DVD-ROMs are basically CDs but are equipped to hold more information. These discs can sometimes have an extra layer of dye to encode twice as much information. Some DVD-ROMs can even contain two sides to the disc: Side A and Side B. This makes consumer use much easier as you do not have to keep track of multiple discs.
Write-Once DVDs
Write-once dvds are dvds that can be written onto at your will but cannot be rewritten once information is already present. Forms of write-only dvds include DVD-R and DVD+R. The reason why write-only dvds can only be written on once is because the disc is covered in a completely reflective material. A writing laser, which is much stronger than a reading laser, can be shown onto this disc to heat the dye on the surface and change its transparency. The problem is that this a one time deal and the transparency can not be changed back to its original color with the dye that’s used. This is also why write-only dvds can easily be ruined by leaving them in a hot area or where there is a lot of sunlight. Keep your dvds in a cold, dark area where there’s little light to prevent damage to the disc.
Rewritable DVDs
Rewriteable DVDs are similar to write-only DVDs in that they can be written on but rewritable DVDs are a lot different than standard discs and write-only discs. Where as write-only discs use dye, rewritable discs use a compound of metallic dust that is coated over the surface of the disc. When a writing laser is passed over the dust, it changes it’s color just like any other disc. However, when a laser targets the metal at the right frequency, it actually melts the metal into a liquid which then crystallizes into a solid again. This process effectively erases any information that was on the disc so that it can be used again and again. Rewritable discs can often be rewritten over a thousand times before the structure of the disc is compromised.
