Optical audio disk

Besides the estabUshed audio CD and CD-ROM, there are other variants of optical storage disks with imprinted information which differ in the way the data are processed. 

Optical recording media for read-write applications are still in the research stage. U S. companies are roughly on par with Emopean and Japanese companies in such research. Read-only applications (e g., CD-ROM disks and compact audio disks) are largely dominated by manufacturing technology from overseas. 

Optical information storage, which has been a dream since the discovery of the laser, is now becoming a commercial reality. Read-only consumer products (video and digital audio disks) have provided a solid technological base for the development and introduction of the more sophisticated write-once and erasable recording systems. This chapter will review the current status of polymeric materials as substrates, protective layers, and active recording media in laser recording. 

Polymeric materials can be used for optical information storage, and some are ideally suited for the manufacture of optical video or digital audio disks. The information is normally transferred to the polymer using a monochromatic laser by one of four possible methods ... 

Data compression can be used to increase the capacity of numerous audio storage products such as hard and magneto-optical (MO) disk-based digital audio recorders and work stations. A modest compression ratio of 4 1 enables a 1-h stereo CD to be stored on 160 megabyte (MB) of disk space and to store some 30 s of full bandwidth stereo on a 1.44 MB, 31/2-in floppy diskette. Cinema audiences are now being offered virtual audio splendor with audio surround systems incorporating data compression. 

A total of 15,000—17,000 t of resin is used aimuaHy. Polycarbonate also has many technical uses in instmment panels and devices, especiaHy for membrane switches and insulators. Optical quaHty polycarbonate is the only suitable material for the compact disk market. Since their introduction in 1983, compact disks have shown explosive growth in the consumption of polycarbonate, with utiHty for audio, video, and computer appHcations. Consumption of optical quaHty resin more than doubled between 1988 and 1992, and as of 1995 accounted for about 20,000 t of annual production. 

Optical memory devices such as compact disks (CDs) and digital versatile disks (DVDs) are becoming essential items of audio and visual media as well as of external computer memory media. In these devices, a laser beamis used to record and read information. Because the laser spot can be focused to within a 1 fxm scale, optical memory can access higher density and capacity than conventional magnetic memories can. 

There are several pieces of backup hardware that are currently available. You can back up your information to magnetic tape, Digital Audio Tape (DAT), Digital Linear Tape (DLT), optical disk, removable hard disk, and many other removable media. The key here is that all of these media can be removed from the drive and stored in a safe place. 

D. Of the items listed, the following are valid backup hardware digital audio tape, digital linear tape, and optical disk. Because hard disks are more failure-prone than the other types listed, they make a poor backup medium. 

The standard audio GD is of diameter 120 nun and has a storage capacity of 600 megabytes it could store the entire text of the Encyclopaedia Britannka, equivalent to 1200 floppy disks. The development of polycarbonate as the material for larger optical memory discs (133 mm, 2(X) mm, and 300 nun) is in progress. 

Entertainment AppUcations. Optical disk players are a common form of home entertainment. Most play DVDs as well as CDs. As with computer apphca-tions, the presence of Blu-ray devices is rapidly increasing. Some load a single optical disk at a time others load a magazine, which holds five or six optical disks others have a capacity for several hundred disks. The higher-capacity players often have a TV interface in which the user can make a selection from a list of the disks contained within. Often, the list contains a thumbnail image of the CDs or DVDs. These devices contain audio and video outputs to... 

Data that are input to the drive over the SCSI for recording are first broken up into fixed block sizes (of, for example, 512 kilobyte or 1024 kilobytes length) and then stored in the data buffer RAM. Magneto-optic, phase-change, and WORM drives can be classified as fixed block architecture technologies in which data blocks are recorded much like in hard drives (Marchant, 1990). Blocks of data can be placed anywhere on the disk in any sequence. The current CD recordable drive is, on the other hand, an example of a non-fixed block architecture (because its roots are in CD audio). In common CD-R drives, input data are recorded sequentially (like a tape player) and can be of any continuous length. 

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