To be read after Lesson 10

Laser Technology

In the last decade there was outstanding progress in the devel­opment of laser technology and its application in science, industry and commerce. Laser cutting, welding and machining are begin­ning to be big business. The market for laser systems represents around 2.5 % of the world machine tool market.

Which country is the biggest producer and consumer of lasers? Why, Japan, naturally: Japan produced 46 % of world's lasers in 1989, while figures for Europe and the USA are 32 % and 22 %. Ja­pan is building 1,200 to 2,000 CO2 lasers per year of which some 95 % are over 500 W power and 80 % of them are used for cutting operations.

Europe is the second largest user and the third largest producer. In 1990 Europe's market for lasers was $128 million, of which Germany consumed about $51 million, and Italy — $12 million.

The Germany met 90 % of its demands through domestic produc­ers. Growth rate of the European market is estimated at 10 to 15 % per year.

In the future the main trend influencing the industry will be la­ser source prices. The prices are dropping. There appear lasers of modular construction. The complexity of laser machines is rising. Multi-axes systems are in more use now. Recently a 7-axis CNC la­ser machining center has been introduced. In addition to X,Y and Z axes, there are two rotary axes, A and C, and two more linear axes, U and V, to give a trepanning (прорезать большие отвер­стия) motion to the laser.

Optical Disks and Drives

Optical disks can store information at much higher densities than magnetic disks. Thus, they are ideal for multimedia applica­tions where images, animation and sound occupy a lot of disk space. Besides, they are not affected by magnetic fields. This means that they are secure and stable, e.g. they can be transported through airport metal detectors without damaging the data. However, opti­cal drives are slower than hard disks. While there are hard drives with an average access time of 8 milliseconds (ms), most CD-ROM drives have an access time of 150 to 20 ms.

There are various types of optical drives, which have become a reality. CD-ROM systems use optical technology. The data is re­trieved using a laser beam. To read CD-ROM disks, you need an optical drive (a CD-ROM player). A typical CD-ROM disk can hold 650 MB (megabytes) of sound, text, photographs, music, mul­timedia materials and applications. In addition, most CD-ROM drives can be used to play audio CDs. Do you remember that CD stands for compact disk?

Yet CD-ROM technology has one disadvantage. The data on a CD-ОМ cannot be changed or «written» to, i.e. it is impossible to add your own material to what is on the disk. It is like a music CD. It is not designed for you to write on, it is designed to hold a lot of information that the user doesn't need to change.

Magneto-optical (MO) drives use both a laser and an electro­magnet to record information. Consequently, MO disks are rewritable, that is they can be written to, erased, and than written again. They are available in two formats. Their capacity may be more than 2 GB (gigabyte) or 230 to 640 MB. Such combined de­vices are good for back up purposes and storage of large amounts of information such as a dictionary or encyclopaedia.