As shown in Figure 4, the transparent surface that is near the top, is one of the writing layers, and the opaque layer below that is the other. What sets the DVD drive apart in terms of storage space, however, is that it has two separate surfaces for writing stripes and lands.
CD DISK LED LIGHT SOFTWARE
These electric impulses are then converted into 0s and 1s by the drive, and sent in as a string of binary or digital data to the software controlling the device. Alternatively, when the light beam comes in contact with a stripe, it is scattered off in all directions. When the laser beam comes in contact with a land, the reflective material sends the light back into the head, triggering an electric impulse. By focusing a laser beam from the read head on to the surface of the disc, the light can either reflect back or scatter, as shown in Figure 3. Also, the read head on the DVD drive is equipped with a magnetic coil that allows it to change the flow of current through the laser, enabling the focus of the light beam so that it may be concentrated on either of the two surface layers (Figure 2).Īnother similarity between DVD and CD technology is the way stripes and lands on the surface of the discs are read. This permits a greater amount of stripes and lands to be held on the two surfaces of the digital video disk, which leads to a thirteen-fold increase in the capacity of a normal compact disc. But unlike the CD-ROM, the DVD drive uses a relatively smaller beam of light to read the information put on the disc surface.
Similar to a CD-ROM drive, a DVD drive uses a light beam (laser) to read the stripes and lands on the surface of a disc. The combination of these rivets and flat surfaces on not one, but two separate surfaces is what separates the DVD from a compact disc in terms of data capacity. And also like a compact disc, the data is transferred onto a DVD through the use of stripes (or pits) and lands. Finally, a protective layer of plastic is added to the foundation. Above that is a thin layer of opaque, reflective material, followed by a transparent layer of thin film. The first layer is made up of a thick polycarbonate plastic, like that of a compact disc. The process of creating a finished DVD product begins with the construction of the disc, which consists of four main layers (Figure 1). Along with that history, there is a complicated process for creating a digital video disk. For nearly a year, these competing manufacturing groups tried to prove the technological superiority of their products, which in time led to the established standards of the DVD. Then Time-Warner and Toshiba followed suit, creating a double-sided disk. Initially led by Phillips and Sony, a singled sided, dual layered high-density disk was developed. Molecular Expressions: How a Digital Video Drive Worksĭuring the later months of 1994 and the early months of 1995, four companies began production of the standards that eventually led to the design of the digital video disk (DVD).