Story of CD, DVD and Blue Ray
These CDs, DVDs, and VCDs are commonly referred to as CDs. That’s because they are made according to the same technology. The difference is in the way it stores information.
A CD is a combination of the words “Compact Disc” and the letters “C” and “D”. DVD stands for “Digital Versatile Disc” or “Digital Video Disc”. VCD stands for “Video Compact Disc”.
Each of these discs is made by placing a very thin thin aluminum plate between two layers of plastic. This plate is made of gold if you want to retain information for a long time. The surface of the tray is covered with a thin layer of acrylic plastic. Underneath is a layer of solid polycarbonate plastic.
The information on the disk is stored by making annular holes (pits) on the aluminum plate. This hole is at least 100 nanometers deep. 500 nanometers wide. But according to the information contained, the width and depth of these holes vary slightly. The distance between the two holes in the rings is about 1.6 6m. The part between two holes is called the lands.
The distance between two slots on a CD (1.6 μm) is less than the distance between two slots on a CD (0.74 μm). Blue-Ray discs have a spacing of 0.32μm. That is, most information can be stored on Blue-Ray disks.
The information stored on a CD is read by a 780μm wavelength infrared beam that strikes the polycarbonate layer beneath it. When this hits a disk, it reflects according to the pattern of holes and holes in the disk. The reflector pattern is captured by the sensor in the CD writer. It then redirects to the computer. Its circuits then read the information stored in it. A red light beam with a wavelength of 650μm is used to read the information on a DVD. Blue light beam with a wavelength of 405μm is used to read information on a blue-ray disc.
These are the details of the typical disks. They are discs that can permanently store information (ROMs (i.e. CD ROMs and DVD ROMs). However, in the case of one-size-fits-all R (ie CD R and DVD R) and repeatable RW (i.e. CD RW and DVD RW) discs, a dye layer is used, not an aluminum plate, to write the information.
The information on the discs is stored in an annular cavity in the dye layer, which heats up in front of a beam of light emitted from a CD or DVD writer. The cyan-ine discs are green in color. Discs using pthalo-cyanine are yellow / golden. The official color is metal-azo dyed disc. I think now you can differentiate CDs, DVDs and Blue rays.
