CDs, DVDs, and Blu-ray discs are optical storage media that can electronically store movies, music, or other digital data. They operate primarily with digital code. On the one hand, these storage media are digital information and communication technologies, on the other hand, they are technical tools for any type of digitization, calculations, recording, archiving, processing, transmission and presentation of digital content.
CD and DVD are abbreviations, but the concept of Blu-ray disc has a slightly different nature.
CD is short for Compact Disc.
DVD is short for Digital Video Disc. A little later, the name “Digital Versatile Disc” appeared, since DVD can be used not only for recording video.
Blu-ray Disc gets its name from the blue laser (as opposed to white laser) that reads information from the disc and also writes information.
The compact disc (CD-ROM) has long been the main medium for transferring information between computers. Now it has practically given up this role to more promising solid-state media, which work much faster and take up less space.
Story
For the first time, the idea of optical recording appeared in 1965, at the American Battelle Memorial Institute, Ohio. This technology was still extremely primitive at that time - dark dots and lines were applied to the disk using a photographic method. To read the information, the disk was illuminated with a special lamp. The founder of the technology was the American physicist James Russell. But as is usually the case, he did not earn a penny from his invention. The scientist patented his technology in 1970. He also came up with the idea of using a laser as a light source.
The Compact Disc was developed in 1979 by Sony. Sony used its own PCM signal encoding method - Pulse Code Modulation, previously used in digital professional tape recorders. In 1982, mass production of CDs began at a plant in the city of Langenhagen near Hannover, Germany. The release of the first commercial music CD was announced on June 20, 1982.
According to Philips, more than 200 billion CDs have been sold worldwide in 25 years. Even though more and more people are choosing to purchase music files online, CD sales still account for about 70% of all music sales, according to IFPI.
Microsoft and Apple Computer made significant contributions to the popularization of CDs. John Sculley, then CEO of Apple Computer, said in 1987 that CDs would revolutionize the world of personal computing. One of the first mass-produced multimedia computers/entertainment centers using CDs was the Amiga CDTV (Commodore Dynamic Total Vision), later CDs were used in the Panasonic 3DO and Amiga CD32 game consoles. First standard
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In 1979, Philips and Sony entered into an agreement to jointly develop a new media. A year later, the company introduced a new standard called CD-DA (Compact Disk Digital Audio). It was a disc with a diameter of 12 centimeters and a playing time of just over an hour. The format turned out to be surprisingly successful and convenient. It quickly won the hearts of both manufacturers and buyers.
The CD format has unconditionally ruled the market for 15 years. During this time, it ceased to be just a music disc, turning into a universal storage medium. However, by the mid-90s of the last century, the amount of information that one CD could contain became sorely insufficient. 
The new format discs looked no different from regular CDs. But the volume of information was increased from 650 MB to 4.7 GB. It is also important that DVD players could play regular CDs without any problems, and therefore there were no problems with standards. Thanks to the advent of DVD, it became possible to obtain high quality sound and images at home. The format quickly became popular. Today, DVD Forum includes more than 250 companies around the world. And I can no longer believe that at one time other analysts jokingly deciphered the name of the DVD as “Dead, Very Dead,” predicting the imminent death of the standard.
Some standardization problems only emerged when the first recordable DVDs appeared. Two standards have appeared in the world - DVD+R and DVD-R. Each of them had its own advantages and disadvantages, which were unclear to the average user. However, users did not encounter any particular problems. You just had to make sure that the disc you purchased was supported by your existing player (DVD-Rs were more common). Yes, universal players and recorders supporting both standards appeared quite quickly. Today, not all users even know about the existence of various standards.
DVD repeated the history of CD. Highly specialized discs (DVD was originally developed only for working with video) have become a universal storage medium. The cost of players has dropped from several hundred dollars to several dozen. The price of the media itself is estimated at pennies.
Classification of optical discs
In each of the media groups, there are three main types of disks:
1. read-only discs (CD-ROM, DVD-ROM);
2. write-once discs (CD-R, DVD-R, DVD+R, DVD-R DL, DVD+R DL);
3. rewritable discs (CD-RW, DVD-RW, DVD+RW, DVD-RAM).
External memory
Optical discs
Optical (laser) discs are currently the most popular storage media. They use the optical principle of recording and reading information using a laser beam.
Information on a laser disk is recorded on a single spiral-shaped track, starting from the center of the disk and containing alternating sections of depressions and protrusions with varying reflectivity.
When reading information from optical disks, a laser beam installed in the disk drive falls on the surface of the rotating disk and is reflected. Since the surface of the optical disk has areas with different reflection coefficients, the reflected beam also changes its intensity (logical 0 or 1). The reflected light pulses are then converted into electrical pulses using photocells.
In the process of recording information on optical discs, various technologies are used: from simple stamping to changing the reflectivity of areas of the disc surface using a powerful laser.
There are two types of optical discs:
CDs (CD - Compact Disk, CD), on which up to 700 MB of information can be recorded; DVDs (DVD - Digital Versatile Disk, Digital Versatile Disk), which have a significantly larger information capacity (4.7 GB), since the optical tracks on them are thinner and placed more densely.
DVDs can be double-layered (8.5 GB capacity), with both layers having a reflective surface that carries information.
In addition, the information capacity of DVDs can be further doubled (up to 17 GB), since information can be recorded on two sides.Currently (2006), optical discs (HP DVD and Blu-Ray) have entered the market, the information capacity of which is 3-5 times greater than the information capacity of DVDs due to the use of a blue laser with a wavelength of 405 nanometers.
Optical disk drives are divided into three types:
- No recording option- CD-ROM and DVD-ROM
(ROM - Read Only Memory, read-only memory).
CD-ROM and DVD-ROM discs store information that was written to them during the manufacturing process. It is impossible to write new information to them.- Write once and read many times -
CD-R and DVD±R (R - recordable, recordable).
On CD-R and DVD±R discs, information can be written, but only once. Data is written to the disk using a high-power laser beam, which destroys the organic dye of the recording layer and changes its reflective properties. By controlling the laser power, alternating dark and light spots are obtained on the recording layer, which, when read, are interpreted as logical 0 and 1.- Rewriteable- CD-RW and DVD±RW
(RW - Rewritable, rewritable). On CD-RW and DVD±RW discs, information can be written and erased many times.
The recording layer is made of a special alloy, which can be heated into two different stable states of aggregation, which are characterized by different degrees of transparency. When recording (erasing), the laser beam heats a section of the track and transfers it to one of these states.
When reading, the laser beam has less power and does not change the state of the recording layer, and alternating areas with different transparency are interpreted as logical 0 and 1.Key characteristics of optical drives:
disk capacity (CD - up to 700 MB, DVD - up to 17 GB) data transfer speed from the storage medium to RAM - measured in fractions of the speed
150 KB/sec for CD drives (the first CD drives had this speed of reading information) and
1.3 MB/sec for DVD drives (This was the reading speed of the first DVD drives)
Currently, 52-speed CD drives are widely used - up to 7.8 MB/sec.
CD-RW discs are written at a lower speed (for example, 32x).
Therefore, CD drives are marked with three numbers “read speed X CD-R write speed X CD-RW write speed” (for example, “52x52x32”).
DVD drives are also marked with three numbers (for example, "16x8x6"access time - the time required to search for information on a disk, measured in milliseconds (for CD 80-400ms). If the storage rules are observed (stored in cases in an upright position) and used (without causing scratches or contamination), optical media can retain information for decades.
Additional information about disk structure
The industrially produced disc consists of three layers. An information pattern is applied to the base of the disc, created from transparent plastic by stamping. For stamping, there is a special prototype matrix for the future disk, which extrudes tracks on the surface. Next, a reflective metal layer is sprayed onto the base, and then a protective layer of thin film or special varnish is applied on top. Various drawings and inscriptions are often applied to this layer. Information is read from the working side of the disk through a transparent base.
Recordable and rewritable CDs have an additional layer. For such discs, the base does not have an information pattern, but between the base and the reflective layer there is a recording layer, which can change under the influence of high temperature. When recording, the laser heats up specified areas of the recording layer, creating an information pattern.
A DVD disc may have two recording layers. If one of them is performed using standard technology, then the other is translucent, applied lower than the first and has a transparency of about 40%. To read double-layer discs, complex optical heads with variable focal length are used. The laser beam, passing through the translucent layer, is first focused on the inner information layer, and after reading it is refocused on the outer layer.
The speed and reliability of modern recorders will be the envy of any Formula 1 car. ComputerBild explains how data ends up on CDs, DVDs and Blu-ray discs.
Recording music and films on optical media is a familiar process, like using magnetic cassettes twenty years ago, but it is much cheaper. How do the types of media differ and how is information recorded on them?
Stamping and burning
In the industrial production of discs with music, films or games, data is recorded onto the media by stamping - a process reminiscent of the production of gramophone records. Information on disks is stored in the form of tiny indentations. Computer and consumer DVD recorders perform this task differently - they use a laser beam.
The first recordable optical media was CD-R with write-once capability. When storing data on such disks, the laser beam heats the working layer of the disc, which consists of a dye, to approximately 250 ° C, which causes a chemical reaction. Dark, opaque spots form where the laser is heated. This is where the word “burn” comes from.
In a similar way, data is transferred to DVD with the ability to write once. But no dark spots form on the surface of rewritable CDs, DVDs and Blu-ray discs. The working layer of these drives is not a dye, but a special alloy. When heated by a laser to approximately 600 °C, it transforms from a crystalline state to an amorphous one. The areas exposed to the laser are darker in color and therefore have different reflective properties.
Information carriers
Discs intended for recording at home have the same thickness (1.2 mm) and the same diameter (12 or 8 cm) as discs on which data is recorded industrially. Optical media have a multilayer structure.
Substrate. The base for the discs, which is made of polycarbonate, is a transparent, colorless and quite resistant to external influences polymer material.
Working layer. For recordable CDs and DVDs, it consists of an organic dye, and for rewritable CDs, DVDs (RW, RAM) and Blu-ray discs, it is formed by a special alloy that can change the phase state. The working layer is surrounded on both sides by an insulating substance.
Reflective layer. Aluminum, silver or gold are used to create the layer from which the laser beam is reflected.
Protective layer. Only CDs and Blu-ray discs are equipped with it. It is a hard varnish coating.
Label. A layer of varnish is applied on top of the disc - the so-called label. This layer is able to absorb moisture, so that the ink that appears on the surface of the media during printing dries quickly.
Differences between CDs, DVDs and Blu-ray Discs
These media have different characteristics. First of all, different capacities. A Blu-ray disc can hold up to 25 GB of data, a DVD can store 5 times less information, and a CD can store 35 times less. Blu-ray drives use a blue laser to read and write data. Its wavelength is approximately 1.5 times shorter than that of red laser DVD and CD drives. This allows you to record a significantly larger amount of information on an equal disk surface area.
Media formats
The following types of optical media are currently available on the market.
CD-R. Recordable CDs can hold up to 700 MB of information. There are also disks with a capacity of 800 MB, but they are not supported by all recorders and home players. Eight-centimeter miniCDs can record 210 MB of data.
CD-RW. Rewritable media has the same capacity as CD-R.
DVD-R/DVD+R. Recordable DVDs hold 4.7 GB of information. miniDVD with a diameter of 8 cm – 1.4 GB.
DVD-R DL/DVD+R DL. The DL prefix stands for Dual Layer (DVD-R) or Double Layer (DVD+R), which corresponds to two-layer media. Capacity – 8.5 GB. An eight-centimeter disk can hold up to 2.6 GB.
DVD-RW/DVD+RW. Single-layer media of this type can withstand several hundred write cycles. Like write-once DVDs, rewritable discs have a capacity of 4.7 GB, while 8 cm discs have a capacity of about 1.4 GB.
DVD-RAM. These media have the same storage capacity as single-layer DVDs. There are also double-layer discs that hold twice as much information. DVD-RAM can withstand up to 100 thousand write cycles, but only a few DVD players work with these discs. Data is written not on a spiral track, but in sectors on circular tracks, like on a hard disk platter. Marks defining sector boundaries are clearly visible on the surface of DVD-RAM - by their presence it is easy to distinguish this type of media from others.
BD-R/BD-R DL. An abbreviation used to refer to recordable Blu-ray Discs. BD-R media has one working layer that can hold 25 GB of data. BD-R DL are equipped with two working layers, so their capacity is 2 times higher.
BD-RE/BD-RE DL. Rewritable Blu-ray discs are rated for 1,000 write cycles. They can store as much data as non-rewritable media.
"Plus and minus"
The presence of “plus” and “minus” media is a consequence of the long-standing war of formats. Initially, representatives of the computer industry relied on the “plus” format, and consumer electronics manufacturers promoted the “minus” format as the standard for recordable DVDs. Modern recorders and players support both formats.
Neither of them has clear advantages over the other. Both types of media use the same materials. Therefore, there are no significant differences between “plus” and “minus” disks from the same manufacturer.
Recording quality
The recording quality of media of the same format can vary significantly. Much depends on the recorder model used. The recording speed also plays an important role: the lower it is, the lower the number of errors and the higher the quality.
Recorder and Media Compatibility
Not every recorder is capable of recording to discs of all formats without exception. There are certain restrictions.
CD recorders. Cannot work with DVDs and Blu-ray discs.
DVD recorders. Writes CDs and DVDs, but does not support Blu-ray format.
Blu-ray recorders. They record to Blu-ray as well as any CD and DVD.
Signatures on discs
It is better to sign the media on which the information is located immediately, so as not to confuse it later. This can be done in different ways.
Printable blanks. The top side of these discs is varnished. On such a surface you can print text and images using inkjet printers and MFPs equipped with a special tray. The price of the discs is no different from regular ones.
Signature using a recorder. The recorder's support for LightScribe or Labelflash technology allows you to print single-color images and text on the surface of media specially designed for this purpose. True, the process can take up to 30 minutes, and the cost of LightScribe discs is approximately twice the cost of conventional discs. Media with Labelflash support will cost even more.
New LabelTag technology. Developed by the recorder manufacturer Lite-On and involves applying text to the working surface of the disc. This eliminates the need to use special media. However, disc space is wasted because the text is written directly onto the track. And the inscription is readable only if the areas with text contrast brightly with the empty fragments.
Signature made by hand. To do this, you need to purchase special markers with a soft, rounded tip and solvent-free ink. Other markers may corrode the disc surface and cause scratches.
Using stickers. You can print stickers on any printer. However, gluing them is not recommended, as this often leads to damage to the surface of the disk, and hence to data loss. It may happen that the label comes off during disc playback. In this case, the optical drive may be damaged.
Data storage period
Disc manufacturers often specify a storage life of 30 years or more for data on media. However, such a duration is only possible under ideal storage conditions - in a dry, cool and dark place. The recording quality must be high.
If used frequently, the service life of self-burned discs will be significantly reduced. During playback, media is exposed to high temperatures and mechanical stress. Data loss can also be caused by scratches or contamination.
Transferring information to disk
All optical media, with the exception of DVD-RAM, have a spiral-shaped track that runs from the center of the disk to the outer edge. Information is recorded onto this track using a laser beam. When burning, the laser beam forms tiny spots on the reflective layer - pits (from the English pit - pit). The areas that were not exposed to the laser are called lands (from the English land - surface). Translated into the language of the binary storage system, pita corresponds to 0, and land corresponds to 1.
When playing a disc, the information is read using a laser. Thanks to the different reflectivity of pits and lands, the drive recognizes dark and light areas of the disc. Thus, the sequence of zeros and ones that make up all physical files without exception is read from the media.
With the development of technology, there was a gradual reduction in the wavelength of the laser beam used in recorders, which made it possible to significantly improve focusing accuracy. The track has become narrower, the pits have become smaller, and a larger amount of data can be placed on an equal area of the disk. The shorter the wavelength, the shorter the distance between the working layer and the laser.
Media production
Using DVD as an example, ComputerBild explains how optical media is produced and how the production of other types of discs differs.
1. To cast a plastic substrate, polycarbonate, heated to 350 °C, is fed into a mold using injection molding. A microscopic spiral track in the form of a groove (Pre-Groove) is created on the surface of the base using a matrix. This track not only records data, it also contains a signal to synchronize the recorder spindle drive. After cooling the substrate to 60 °C, a central hole is made, then the temperature is reduced to 25 °C and further processing begins. DVDs typically consist of two polycarbonate layers, each 0.6mm thick. For single-layer recordable DVDs, only one of the layers undergoes further processing, as described in steps 2–3, while for dual-layer DVDs, both layers are processed further. CDs and Blu-ray discs have only one layer 1.2 mm thick.
2. The working layer of recordable CDs and DVDs is created by centrifugation. Using a dispenser, the dye is injected onto the surface of a disk rotating at a constant speed in the area of the central hole and is evenly distributed over the surface of the carrier.
3. The reflective layer is applied to the disk using ion-plasma sputtering. In a vacuum chamber, an aluminum, silver or gold plate is bombarded with charged ions, which knock out metal atoms from it - it remains on the surface of the working layer of the blank. For rewritable CDs, DVDs and Blu-ray discs, all working and reflective layers are created using ion-plasma sputtering. In four chambers, the first insulator layer, the working layer, the second insulator layer and the reflective layer are sequentially applied to the disk. When producing Blu-ray discs, these operations are performed in reverse order.
4. Two polycarbonate bases are glued together. For CDs and Blu-ray discs, instead of a second base, a varnish coating is applied, which is dried under an ultraviolet lamp. The varnish coating of Bly-ray discs is particularly durable, while DVDs do not need a protective layer of varnish.
5. At the last stage, the blanks receive a label, and an absorbent layer of varnish is applied to the printable discs.
Recording and reading of information in optical storage devices is carried out contactlessly using a laser beam. Such devices include, first of all, CD-ROM, CD-R, CD-RW and DVD drives (ROM, R and RW).
CD-ROM devices. In CD-ROM devices (Compact Disk Read-Only Memory - read-only CD), the information carrier is an optical disk (CD), manufactured in line production using stamping machines and intended for read-only.
The CD is a transparent polymer disk with a diameter of 12 cm and a thickness of 1.2 mm, on one side of which a reflective layer of aluminum is sprayed, protected from damage by a layer of transparent varnish. The coating thickness is several ten thousandths of a millimeter.
Information on the disk is represented as a sequence of depressions and protrusions (their level corresponds to the surface of the disk), located on a spiral track emerging from an area near the axis of the disk (there are only a few hundred tracks per inch radius on the surface of the hard disk). The capacity of such a CD reaches 780 MB, which makes it possible to create on its basis help systems and educational complexes with a large illustrative base. One CD has the same information capacity as almost 500 floppy disks. Reading information from a CD-ROM occurs at a fairly high speed, although noticeably lower than the speed of hard disk drives.
CD-R (CD-Recordable) drives. They allow, along with reading regular CDs, to write information once onto special optical CD-R discs. The information volume of such disks is 700 MB.
Recording on such discs is carried out due to the presence on them of a special light-sensitive layer of organic material that darkens when heated. During the recording process, the laser beam heats selected points on the layer, which darken and stop transmitting light to the reflective layer, forming areas similar to depressions.
Burning information onto CD-R discs is a cheap and fast way to store large amounts of data.
CD-RW (CD-ReWritable) drives. Allows you to write to disk multiple times. The information volume of such disks is 700 MB.
CD-ROM drive – allows you to only read information from any CD. Accordingly, such devices will differ in read speed and cache memory. The CD-R drive is read and write, and the CD-RW drive not only reads, but also rewrites (erases information and writes new information over it). Such drives differ in read/write/rewrite speed (the latter only for CD-RW) and cache size.
DVD drives (Digital Versatile Disc, general purpose digital disc). The first DVDs appeared on the market around 96–97 of the last century. DVD is an excellent storage medium for any type of data and is used as a common computer storage medium.
From the outside, the DVD looks like a regular CD, and even upon closer inspection it's hard to tell the difference. However, DVD has much more possibilities. DVDs can store 26 times more data than CD-ROMs.
DVD technology was a huge leap forward in the field of storage media. A standard single-sided, single-layer disk can store 4.7 GB of data. But DVDs can be produced using a two-layer standard, which allows you to increase the amount of data stored on one side to 8.5 Gb.
In addition, DVD discs are double-sided, which increases the disc capacity to 17 Gb. True, to read a DVD, you need a new device (DVD-ROM), but DVD technology is compatible with CD technology, and the DVD-ROM drive also reads CDs, and in different formats.
There are various combination optical drives available on the market. For example, DVD-CD R/RW allows you to read DVDs and CDs and write/rewrite onto CDs. Another option is DVD-RW - CD-RW. Allows you to read, write and rewrite DVDs and CDs.
What can be a carrier of information? Something on which everything we need to remember can be preserved, for human memory is short-lived. Our ancestors left important data on the ground, on stone, on wood, and on clay until paper appeared. This turned out to be material that meets the most important requirements for a storage medium. It was light, durable, convenient for notes and compact.
It is these requirements that modern storage media – optical(these are CDs or laser discs). True, at the transition stage (from the beginning of the 20th century), between paper and disks, magnetic tape helped us a lot. But her time is over. Today, the most convenient and reliable container and storage of information are disks.
How to put information on disk? We have known the concept of “recording a cassette” for decades. Now we are also talking about disks. Only this process has become much simpler and cheaper.
Today we will talk about optical storage media: device, recording technology, main differences.
CD-Rs were the very first recordable optical media. They only had the ability to record once. The data was saved when the working layer was heated by a laser, causing its chemical reaction (at t? = 250? C). At this moment, dark spots form in the heating areas. This is where the concept of “burning” comes from. On DVD-R discs, burning occurs in a similar way.
The situation is slightly different with CD, DVD and Blu-ray discs that have a rewriting function. Such dark dots do not form on their surface, because the working layer is not a dye, but a special alloy, which is heated by a laser to 600? C. Then, the areas of the disk surface exposed to the laser beam become darker and have reflective properties.
At the moment, in addition to CD discs, which can be considered pioneers in the range of optical media, discs such as DVD and Blu-ray have appeared. These types of disks are different from each other. For example, capacity. A Blu-ray disc can hold up to 25GB of data, a DVD can hold up to 5GB, and a CD can only hold up to 700MB. The next difference is the way data is read and written in Blu-ray drives. A blue laser is responsible for this process, the wavelength of which is one and a half times shorter than that of the red laser of CD or DVD drives. That is why on the surface of Blu-ray discs, which is equal in area to other types of discs, it is possible to record information many times larger.
Laserdisc formats
The three types of laser discs listed above can also be classified according to their formats:
1. CD-R, CD-RW disks are the same in size (up to 700; sometimes 800MB, but such disks are not readable by all devices). The only difference is that CD-R is a one-time recordable disc, and CD-RW is reusable.
2. Discs in DVD-R, DVD+R, as well as DVD-RW formats differ only in the ability to rewrite DVD-RW discs multiple times, but otherwise the parameters are the same. 4.7 GB is the capacity of a standard DVD disc and 1.4 GB is the capacity of a DVD with a diameter of 8 cm.
3. DVD-R DL, DVD+R DL – double-layer discs that can hold 8.5GB of information.
4. Formats BD-R - Blu-ray discs are single-layer, with a capacity of 25 GB and BD-R DL - Blu-ray discs are double-layer, with a capacity of 2 times more.
5. Formats BD-RE, BD-RE DL Blu-ray discs – rewritable, up to 1000 times.
Discs with “+” and “-” signs are a relic of format disputes. Initially, it was believed that “+” (for example, DVD+R) was the leader for the computer industry, and “-” (DVD-R) was the quality standard for consumer electronics. Nowadays, almost all equipment easily recognizes discs of both formats. None of them have any obvious advantages over each other. The materials for their production are also identical
what are optical discs
The disc itself, which is used at home to record information, is no different in size from industrially produced discs. The structure of all optical media is multilayer.
- The basis of each is a substrate. It is made of polycarbonate, a material resistant to various external environmental influences. This material is transparent and colorless.
- Next comes the working layer. For recordable and rewritable discs, it differs in its composition. For the former, it is an organic dye, for the latter, it is a special alloy that changes the phase state.
- Then comes the reflective layer. It serves to reflect the laser beam and may contain aluminum, gold or silver.
- The fourth is a protective layer. Only CD and Blu-ray discs are covered with a protective layer, which is a hard varnish.
- The last layer is the label. This is the name given to the top layer of varnish that can quickly absorb moisture. It is thanks to this that all ink that falls on the surface of the disc during the printing process dries quickly.
process of transferring information to disk
Now a drop of scientific theory. All optical storage media have a spiral-shaped track running from the very center to the edge of the disk. It is along this path that the laser beam records information. The spots formed when “burning” with a laser beam are called “pits”. The areas of the surface that remain untouched are called "lands". In binary language, 0 is pit and 1 is land. When the disc starts playing, the laser reads all the information from it.
“Pits” and “lands” have different reflectivity, therefore, the drive easily distinguishes all dark and light areas of the disk. And this is the same sequence of ones and zeros inherent in all physical files. Gradually, it became possible to increase the accuracy of focusing thanks to the development of technologies that reduced the wavelength of the laser beam. Now, on the same disk area as before, you can place a much larger amount of information, because the distance between the laser and the working layer directly depends on the wavelength. Shorter wave - shorter distance.
ways to burn discs
- Recording a disc at home occurs using a laser beam. It is also called “burning” or “cutting”.
Recording during the industrial production of discs is called stamping. In this way, discs with recordings of music, movies, and computer games are produced in large quantities. All the information that gets onto the disk during stamping consists of many tiny indentations. Something similar happened when gramophone records were made.
organization of the recording process on optical storage media
Stage 1. Media type recognition. We loaded the disc and wait for the recorder to provide information about the appropriate recording speed and the most optimal laser beam power.
Stage 2. The program that controls the recording makes requests to the recorder about the type of media used, the amount of free space and the speed at which the disc should be burned.
Stage 3. We indicate all the necessary data requested by the program and compile a list of files that require writing to disk.
Stage 4. The program transfers all data to the recorder and monitors the entire burning process.
Stage 5 The recorder sets the power of the laser beam and starts the recording process.
Even for media of the same format, the recording quality can differ radically. In order for the recording quality to be high, you should pay attention to the speed specified in the recording. There is a “golden rule” - fewer errors at lower speeds and vice versa. The recorder itself, namely its model, also plays a significant role.
signature on optical discs
It is advisable to immediately sign a disk on which some information appears, in order to avoid confusion. This can be done in different ways:
- printing text on blanks, the surface of which is varnished and allows you to print texts and images using an MFP with a special tray.
- using a recorder, supported by special technologies that apply text and a single-color image to a special surface. The cost of such disks can be 2 times higher than the cost of simple disks;
- signature made independently by hand (with a special marker);
- LabelTag technology – text is applied directly to the disk working surface. The inscription may not always be legible;
- stickers printed separately on any of the printers. Their use is not encouraged, because... they can damage the surface of the disc and come off during playback.
storage duration of optical storage media
On the labels of new disks you can see a period indicating how long data can be stored on this medium. Sometimes this figure corresponds to 30 years. In reality, such a period is almost impossible. During its existence, the disk can be subject to various impacts and damage. If it was recorded at home, its shelf life is reduced even further. Only ideal storage conditions will allow you to keep all the data on the disks safe and sound.
