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, only it is much cheaper. What is the difference between the types of media and how information is recorded on them?
Stamping and burning
In the industrial production of discs with music, films or games, data is written to the media by stamping - this process is similar to the manufacture of gramophone records. Information on disks is stored in the form of tiny depressions. Computer and consumer DVD recorders perform this task differently - they use a laser beam.
The first recordable optical media were CD-Rs with write-once capability. When data is stored on such discs, the laser beam heats the working layer of the disc, which consists of a dye, to about 250 ° C, which causes a chemical reaction. Dark opaque spots are formed at the place of laser heating. This is where the word "burn" comes from.
Similarly, the transfer of data to a DVD with the possibility of a single write. But on the surface of rewritable CDs, DVDs and Blu-ray discs, dark dots do not form. The working layer of these drives is not a dye, but a special alloy. When heated by a laser to about 600 °C, it passes from the crystalline state to the amorphous state. The areas exposed to the laser have a darker color, and hence other reflective properties.
Information carriers
Home recording discs are the same thickness (1.2 mm) and the same diameter (12 or 8 cm) as commercially recorded discs. Optical media have a multilayer structure.
Substrate. The basis for discs, which is made of polycarbonate, is a transparent, colorless and fairly 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. To create a layer from which the laser beam is reflected, aluminum, silver or gold are used.
protective layer. They are only available on CDs and Blu-ray discs. It is a hard lacquer.
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 is 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 capacity. A Blu-ray disc can store up to 25 GB of data, a DVD can store 5 times less information, and a CD can store 35 times less information. Blu-ray drives use a blue laser to read and write data. Its wavelength is about 1.5 times shorter than in red laser DVD and CD drives. This allows you to record a much larger amount of information on an equal disk surface.
Media formats
The following types of optical media are currently on the market.
CD-R. Recordable CDs can hold up to 700 MB of information. There are also discs with a capacity of 800 MB, but they are not supported by all recorders and consumer players. 8 cm miniCDs can store 210 MB of data.
CD-RW. Rewritable media has the same storage 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 prefix DL means Dual Layer (DVD-R) or Double Layer (DVD+R), which corresponds to a two-layer media. Capacity - 8.5 GB. Up to 2.6 GB is placed on an eight-centimeter disk.
DVD-RW/DVD+RW. Single-layer media of this type are capable of withstanding several hundred write cycles. Like DVD record-once, 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 dual-layer discs that hold twice as much information. DVD-RAM can withstand up to 100,000 write cycles, but only a few DVD players work with these discs. Data is written not on a spiral track, but in sectors on ring tracks, as on hard disk platters. The marks that define the boundaries of the sectors 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 holds 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 1000 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. In the beginning, the computer industry relied on the "plus" format, while consumer electronics manufacturers promoted the "minus" format as the standard for recordable DVDs. Modern recorders and players support both formats.
None of them has clear advantages over the other. Both media types use the same materials. Therefore, there are no significant differences between "plus" and "minus" disks of the same manufacturer.
Recording quality
The recording quality of media of the same format can vary greatly. Much depends on the recorder model used. The recording speed also plays an important role: the lower it is, the fewer errors and the higher the quality.
Recorder and media compatibility
Not every recorder is able to record on discs of all formats without exception. There are certain restrictions.
CD recorders. Cannot work with DVD and Blu-ray discs.
DVD recorders. They burn CDs and DVDs, but do not support Blu-ray format.
Blu-ray recorders. They record both on Blu-ray and on any CD and DVD.
Disc signatures
The media on which the information is posted should be signed immediately so as not to be confused later. This can be done in different ways.
Blanks with the possibility of printing. 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. Discs don't differ in price from ordinary ones.
Signature with a recorder. The recorder's support for LightScribe or Labelflash technology allows one-color images and text to be applied to the surface of specially designed media. True, the process can take up to 30 minutes, and the cost of LightScribe discs is about twice the cost of conventional discs. Labelflash-enabled media will cost even more.
New LabelTag technology. Developed by the manufacturer of recorders Lite-On and involves the application of text on the working surface of the disc. This eliminates the need for special media. However, disk space is wasted because the text is applied directly to the track. Yes, and the inscription is well read only if the areas with text contrast brightly with empty fragments.
Signature made by hand. To do this, you need to purchase special markers with a soft, rounded at the end of the rod and solvent-free ink. Other markers may corrode the disc surface and cause scratches.
Use of stickers. You can print stickers on any printer. However, sticking 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 while playing the disc. In this case, the optical drive is likely to be damaged.
Data retention period
Disk manufacturers often state that data on the media will be stored for 30 years or more. However, this duration is only possible under ideal storage conditions - in a dry, cool and dark place. The recording quality must be high.
With frequent use, the life of self-recorded discs will be greatly reduced. During playback, media is exposed to high temperatures and mechanical stress. Data loss can also be caused by scratches or dirt.
Transferring information to disk
All optical media, with the exception of DVD-RAM, has a spiral track that runs from the center of the disc to the outer edge. Information is recorded on this track by a laser beam. When burned, the laser beam forms tiny spots on the reflective layer - pits (from the English pit - pit). Areas that were not exposed to the laser are called lands (from the English land - surface). When translated into binary storage language, pit is 0 and land is 1.
When playing a disc, information is read using a laser. Due to the different reflectivity of pits and lands, the drive recognizes dark and light areas of the disc. Thus, a sequence of zeros and ones is read from the media, which make up all physical files without exception.
With the development of technology, there was a gradual decrease in the wavelength of the laser beam used in the recorders, which made it possible to significantly improve the accuracy of focusing. The track has become narrower, the pits are smaller, and a larger amount of data is placed on an equal area of \u200b\u200bthe disk. The shorter the wavelength, the smaller 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 mold a plastic substrate, polycarbonate, heated to 350 ° C, is fed into a mold by 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. Not only is data written to this track, it also contains a signal to synchronize the recorder's 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 usually consist of two polycarbonate layers, each 0.6 mm thick. For single-layer recordable DVDs, only one of the layers is further processed as described in steps 2-3, while for dual-layer DVDs, both. 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. With the help of a dispenser, the dye is injected onto the surface of the disk rotating at a constant speed in the region of the central hole and evenly distributed over the surface of the carrier.
3. The reflective layer is deposited on the disc by 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 successively applied to the disc. 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 the second base, a lacquer 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 discs that can be printed on a printer.
What can be a carrier of information? That on which everything that we need to remember can be preserved, for human memory is short-lived. Our ancestors left important data on the ground, and on stone, and on wood, and on clay until paper appeared. It turned out to be a material that meets the most important requirements for a data carrier. It was light, durable, easy to record and compact.
These requirements are met by modern storage media - optical(these are CDs or laserdiscs). True, at the transitional stage (since the beginning of the 20th century), between paper and disks, magnetic tape helped us a lot. But her days are over. To date, the most convenient and reliable receptacle and storage of information are disks.
And how to put the information on the disk? The concept of "recording a cassette" has been known to us for more than a dozen years. We are also talking about disks. Only this process has become much easier and cheaper.
Today we will talk about optical storage media: device, recording technology, main differences.
CD-R became the very first recordable optical media. They had the ability to record only once. The data were stored when the working layer was heated by a laser, causing its chemical reaction (at t? = 250°C). At this point, dark spots are formed in places of heating. That's where the concept of "burn" came from. DVD-R discs are burned in a similar way.
The situation is slightly different with CD, DVD and Blu-ray discs that have an overwrite 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 up to 600°C. Then, the areas of the disk surface that fell under the laser beam become darker and more reflective.
At the moment, in addition to CD discs, which can be considered pioneers in a number of optical media, discs such as DVD and Blu-ray have appeared. These types of discs are different from each other. For example, capacity. A Blu-ray disc can hold data up to 25 GB, a DVD disc can hold up to 5 GB, and a CD disc can hold up to 700 MB in total. The next difference is the way data is read and written to Blu-ray drives. The blue laser is responsible for this process, the wavelength of which is one and a half times less than that of the red laser of CD or DVD drives. That is why on the surface of Blu-ray discs, equal in area to discs of other types, you can record information many times larger.
laser disc formats
The three types of laser discs listed above can also be classified according to their formats:
1. CD-R, CD-RW discs are the same in size (up to 700; sometimes 800 MB, but such discs are not readable by all devices). The only difference is that CD-R is a one-time recordable disc, while CD-RW is reusable.
2. DVD-R, DVD+R, and DVD-RW format discs differ only in the ability to rewrite DVD-RW discs multiple times, but otherwise the parameters are the same. 4.7 GB is the size of a standard DVD and 1.4 GB is the size of an 8 cm DVD.
3. DVD-R DL, DVD+R DL are double-layer discs that can hold 8.5 GB of information.
4. Formats BD-R - Blu-ray discs are single-layer, 25 GB and BD-R DL - Blu-ray discs are double-layer, 2 times larger.
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) is the leader for the computer industry, and "-" (DVD-R) is the quality standard for consumer electronics. Now almost all equipment easily recognizes discs of both formats. None of them have clear 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 commercially produced discs. The structure of all optical media is multilayer.
- The basis of each is the 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, a special alloy that changes the phase state.
- Then comes the reflective layer. It serves to reflect the laser beam, and may include aluminum, gold or silver.
- Fourth - protective layer. The protective layer, which is a hard varnish, covers only CDs and Blu-ray discs.
- The last layer is the label. This is the name of the top layer of varnish that can quickly absorb moisture. It is thanks to him that all the ink that falls on the surface of the disc during the printing process dries quickly.
the process of transferring information to disk
Now a drop of scientific theory. All optical storage media have a spiral track running from the very center to the edge of the disk. It is along this track that the laser beam records information. The spots formed during the "burning" of the laser beam are called "pits". 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 very sequence of ones and zeros inherent in all physical files. Gradually, it became possible to increase the accuracy of focusing due to the development of technologies that have achieved a reduction in the wavelength of a laser beam. Now a much larger amount of information can be placed on the same area of the disk as before. the distance between the laser and the working layer directly depends on the wavelength. Shorter wave means shorter distance.
disc burning methods
- Recording a disc in domestic conditions occurs with the help of a laser beam. It is also called "burning" or "cutting".
Recording in the industrial production of discs is called stamping. In this way, discs with recording of music, movies, computer games are produced in large quantities. All the information that gets on the disk during stamping is a lot of tiny depressions. Something similar happened when gramophone records were made.
organization of the recording process on optical media
Stage 1. Media type recognition. We loaded the disc and wait until the recorder gives out information about the appropriate recording speed and the most optimal power of the laser beam.
Stage 2. The recording management program queries the recorder about the type of media being 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 make a list of files that require writing to disk.
Stage 4. The program transfers all the 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 with media of the same format, the quality of the recording can be drastically different. 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 speed and vice versa. The recorder itself, namely, its model, also plays a significant role.
signature on optical discs
It is advisable to immediately sign the disk on which some information appeared, 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, with the support of 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;
- a signature made independently by hand (with a special marker);
- LabelTag technology - the text is applied directly to the disk work surface. The inscription may not always be well read;
- labels printed separately on any of the printers. Their use is not welcome, because. they can damage the surface of the disc, come off at the time of its playback.
duration of storage of optical storage media
On the labels of new discs, you can see a period that indicates how long you can save data on this medium. Sometimes this figure corresponds to 30 years. In reality, such a period is practically impossible. During its existence, the disk can be subjected to various influences and damage. If it was recorded at home, then its shelf life is reduced even more. Only ideal storage conditions will keep all the data on the disks safe and sound.
1. Introduction
3.1. Technical features of competitors
4. Prospects for the development of optical storage.
5. Comparative analysis of optical drives
5.1 ASUS DRW-1608P
5.2 NEC ND-3540A
6. Safety precautions when working with a PC
6.1 Organization of the workplace
6.2 Safety
Conclusion
List of used literature
1. Introduction
Over the past few years, optical storage has undergone significant changes. Today, the optical drive is an integral part of the PC - which determines the relevance of the chosen topic.
The optical drive has become an integral part of the PC, because. various software products (especially games and databases) began to take up a significant amount of space, and their supply on floppy disks turned out to be excessively expensive and unreliable. Therefore, they began to be supplied on optical discs (the same as regular music), and some games and programs work directly from an optical disc, without requiring copying to a hard drive.
Also, a modern computer is a powerful multimedia center that allows you to play music, watch movies.
The purpose of this thesis is to study optical storage devices. During the study, the following questions will be explored:
¾ The history of the optical drive
¾ The history of the development of optical storage
¾ Prospects for the development of optical storage
¾ Comparative analysis of optical drives
¾ Safety precautions when working with a PC
2. The history of the creation of an optical drive
Optical discs are practically the same age as personal computers. And they even have their parents - vinyl records. The year of arrival of optical discs in modern technology is considered to be 1982. It was then that the two largest companies Philips and Sony took up new developments. Akio Morita, executive director of Sony, who also became famous for authoring the famous Walkman player, believed that such discs should be designed for listening to classical music. And the standard for the duration of the sound was the time of the sound of Beethoven's 9th symphony, which is approximately 73 minutes. It was decided to make the standard playing time equal to 74 minutes 33 seconds. This is how the Red Book standard was born, in which the CD-DA (CD-Digital Audio) disc standard was described. Moreover, its predecessor was the standard of an ordinary vinyl record with a duration of 45 minutes, which has the worst sound quality and performance characteristics of the carrier incomparable with CD. Along with Sony, Philips also took part in the formation of the Red Book standard. Strict requirements were introduced for size, sound quality, data encoding method and the use of a single spiral track.
On CD-DA, the data is presented as follows.
Structurally, the entire disk can be divided into three main parts: lead-in (introductory zone that stores all information about the structure and ownership of the disk), PMA (Program Memory Area - the data itself) and lead-out (output zone, consisting of almost one " zeros" and is essentially an indicator of the end of the disk).
All information is recorded on CD-DA as tracks separated by gaps (pre-gap) equal to 2 seconds. There can be 99 such tracks, and each of them can be divided into 99 fragments. The concept of tracks is somewhat secondary, but well suited to the simplest description of the structure of a disk.
In fact, the information on the disk is presented in the form of blocks-segments, which have a standard size (2352 bytes) and a standard reading speed of 75 blocks per second. That is, if we are talking about a gap of two seconds, then we mean 150 "empty" blocks-segments. The tracks themselves consist of blocks filled with information.
The block segment, in turn, consists of 98 microframes, each of which has a size of 24 bytes (192 bits). 24 bytes may contain a description of the values of six discrete samples of the right and left channels. And the given value of 2352 bytes can be obtained by simply multiplying 98 by 24. So, speaking of this segment size, we are talking only about purely audio information.
3. The history of the development of optical storage
Developed by Philips and Sony, a new specification for storing digital data on CD media became known as the "Yellow Book", and the media itself became known as CD-ROM (Read Only Memory). A block segment of 2352 bytes has been converted. That is, according to the standard, Mode 1 types were provided for storing digital computer data, and Mode 2 - compressed graphic, text and sound data. The block sector of the Mode 1 type stores information on the correction and correction of errors EDC / ECC (Error Detection Code / Error Correction Code) and is the most common. 288 bytes are allocated for correction and error correction in each sector. As a result, 2064 bytes remain for information, 12 of which are allocated for synchronization and 4 bytes for the sector header.
Thus, the basic minimum unit in the CD-DA format is the track, while in the CD-ROM it is the segment.
Device drives on CD-ROM.
After the arrival of two standards, described by the "Red" and "Yellow" books, there was one significant problem: media were strictly tied to the types of drives. That is, the combination of audio and digital data was not implemented at that time. Mixed-format discs have appeared that store both CD-ROM and CD-DA data. Moreover, the first data (CD-ROM) was recorded at the beginning of the disc. This is not very convenient, because audio drives try to read the first track, which can harm the audio equipment, and CD-ROM drives cannot read the program and play audio at the same time.
In November 1985, representatives of the leading CD-ROM manufacturers met to discuss the problem of compatibility and a common type of file system structuring for all media. That is, a standard was required for the file system, the structure of writing and reading, and so on. A document was compiled which was a specification (the name of the specification is HSG) that defines the logical and file formats of CDs. The document was advisory in nature, and although it subsequently determined a lot for the technology industry as a whole, the color of the book was never found for it. The format proposal of the HSG specification was largely based on the representation of the structure of a floppy disk containing a zero track or system track, which stores data about the media type and its file structure with directories, subdirectories and files. The CD is organized a little differently. That is, all data of this type is stored in the service and system areas. The first stores the information necessary for synchronization between the carrier and the drive. The second one has a file structure, and the direct addresses of files in subdirectories are indicated, which reduces the search time.
Three years later (1988) the international standard ISO-9660 was adopted, the main provisions of which were very similar to the HSG representation. This standard described the CD-ROM file system and had three levels. The first level looks like this:
Filenames can be up to 8 characters long;
File names use only uppercase characters, numbers, and the "_" symbol;
Special characters are not allowed in file names - "-,~,=,+";
Directory names cannot have extensions;
Files cannot be fragmented.
The second and third levels of ISO-9660 only facilitate and expand the possibilities of the first. In particular, restrictions on file and directory names have been removed at the second level (for example, it is already allowed to create names with a length of 32 characters), at the third level it is already allowed to fragment files. It is worth noting that ISO-9660 of the first level standardizes mainly the MS-DOS and HFS (Apple Macintosh) file system formats. The second level in these systems is no longer readable.
For the Apple Macintosh, there is a separate standard for the HFS (Hierarchical File System) file system format. This computer platform has its own special file system hierarchy, which is why this standard is in demand. Several file system formats can be written to one disc at the same time.
The specification, developed in 1991, was released as Orange Books. There are two of them. The first standardizes magneto-optical storage devices that can erase and rewrite information. The second book is about write-once drives that can only write to. That is, in the second book we are talking about CD-R (Recordable). Gradually, modern technology began to allow rewriting discs. We are talking about CD-RW (Rewritable) or CD-E (Erasable), which, in fact, are the same. These media and drives most likely fall under the first of the "Orange Books".
In 1993, the "White Book" was published, which standardized a new product - Video CD, developed jointly by JVC, Matsushita, Sony and Philips. This standard is based on the Karaoke video system developed by JVC. The new format allows you to store 72 minutes of video with stereo sound. The compression format is familiar to many - MPEG (Motion Picture Experts Group). The first track is recorded in CD-ROM/XA format, followed by a data block containing compressed video. Based on the acquisitions obtained through the White Book standard, the experts subsequently made significant changes to the Green Book.
At the end of the last century, CD-R drives, which by that time had reached 8X/24X write / read speeds, were supplanted by more versatile CD-RW drives that allow you to write not only write-once discs, but also rewritable ones.
Unlike organic dyes used to form the active layer in CD-R discs, in CD-RW the active layer is a special polycrystalline alloy (silver-indium-antimony-tellurium), which becomes liquid at strong (500-700°C) ) laser heating. During the subsequent rapid cooling of the liquid regions, they remain in an amorphous state; therefore, their reflectivity differs from polycrystalline regions. The return of amorphous regions to the crystalline state is carried out by weaker heating below the melting point, but above the crystallization point (about 200 °C). Above and below the active layer are two dielectric layers (usually silicon dioxide), which remove excess heat from the active layer during the recording process; from above, all this is covered with a reflective layer, and the entire "sandwich" is applied to a polycarbonate base, in which spiral recesses are pressed out, necessary for precise positioning of the head and carrying address and time information.
It's no secret that the story began with gramophone records. It is problematic to store information at home, and only sound was stored on it. How it works is no secret vinyl disc has been popular for over a hundred years and is still used and kept by collectors and DJs. It was cool to watch how the needle, while scrolling the disc, seemed to be shaking on a perfectly even spiral. On this the principle of obtaining sound was built. When the depth and width of the groove changed, the sound wave changed and was further amplified by the pipe (gramophones, gramophones). With the development of electronics, the principle of information removal was made on a piezoelectric needle and a modern, until recently, record player was obtained.
Here come the 70s. And there was a jump in storage media (we'll skip magnetic tapes). They invented a disc made of polycarbonate, which had transparency, with aluminum sputtering. Polycarbonate served as a base and protected the deposition from external influences, and depressions were burned on the deposition in a spiral. The principle of removing and recording information is based on this, as you can see, they have not gone far from a gramophone record. A thin beam was reflected from the deposition surface and came to the light receiver, which in turn determined the changes and units and zeros were created relative to the information received. And then according to the principle of the alphabet morse information is converted into music, movies, photos, files, etc.
Now let's take a look at the notation CDs:
But with DVD disks, everything turned out much more complicated. This disk was created to store information in a large volume and was developed by a large number of companies (DVD-R and DVD-RW). Different coatings had various characteristics and household players of various companies began to conflict with discs, hence the versatility was lost. Therefore, having united, they invented a new type of disk, called DVD+R and DVD+RW They cost, oddly enough, cheaper. Now it doesn't matter which disc to use, as consumer players have adapted. There is only a difference in rewritable discs, DVD-RW must be completely erased before recording, and DVD+R it is enough to erase the "cap" and overlay the record on top.
As they say, no matter how much you give us, it's not enough for us. That's why progress didn't stop there. bilateral And two-layer and two in one disks. Well with bilateral, everything is simple, the coating was applied on both sides, and like an audio cassette, you need to turn the disc over. Double layer- this is one of the layers close to the laser, they made it translucent, and you don’t need to get up from the sofa to turn the disk over. Well, with the last option, take two two-layer and glue together.
So we have reached the peak of the development of the modern world of the optical disc, this is - HD DVD and Blu-ray.
HD DVD- this is a disk that was made based on our hard worker described above, but using a blue laser.
Blu-ray- a completely different development, a blue laser is used.
If we recall the spectrum (rainbow), it will be seen that from the blue beam, you can get a much thinner beam, so these disks turned out to be much more voluminous. But more on that in the next topic.
It seems to be everything for today. It remains only to tell a little about storage and disk usage. A disc is not tasty, you don’t need to gnaw it, well, unless someone has a lack of plastic in the body. And also this is not a tool for playing on the nerves, so you don’t need to drive your claws over it. It is advisable not to bend, although it breaks difficult, but fragments can get where they should not, and this will affect your body. Also, a constant bend breaks the coating inside, it cracks and the zeros of the unit will no longer coincide with you. Do not fry him in the sun, he has an element D not needed at all, but turn into a zyuobrazny product and you won’t shove it anywhere. Do not insert a disk with a crack into the drive, otherwise you will have to spend money either on repairs or on the purchase of a new one.
I hope YOU competent and you do not need to list everything point by point, you need to treat things with care and they YOU will be thanked for this.
Recording and reading of information in optical drives is carried out contactlessly using a laser beam. These devices primarily include CD-ROM, CD-R, CD-RW and DVD (ROM, R and RW) drives.
CD-ROM devices. In CD-ROM (Compact Disk Read-Only Memory) devices, the information carrier is an optical disk (CD) manufactured in a mass production using stamping machines and intended for reading only.
The CD is a transparent polymer disc with a diameter of 12 cm and a thickness of 1.2 mm, on one side of which a reflective aluminum layer is sprayed, protected from damage by a layer of transparent varnish. The coating thickness is several ten-thousandths of a millimeter.
Information on a disk is represented as a series of pits and ridges (their level corresponds to the surface of the disk) located on a spiral track emerging from the area near the axis of the disk (on the surface of a hard disk, only a few hundred tracks fit in an inch along the radius). The capacity of such a CD reaches 780 MB, which makes it possible to create reference systems and educational complexes with a large illustrative base on its basis. One CD in terms of information capacity is equal to almost 500 floppy disks. Reading information from a CD-ROM occurs at a fairly high speed, although noticeably slower than the speed of hard disk drives.
CD-R (CD-Recordable) drives. They allow, along with reading conventional CDs, to record information once on 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 of a special light-sensitive layer of organic material on them, which darkens when heated. During the recording process, the laser beam heats up the selected points of the layer, which darken and stop transmitting light to the reflective layer, forming areas similar to depressions.
Writing information to CD-R discs is a cheap and fast way to store large amounts of data.
Drives CD-RW (CD-ReWritable). Allows you to write multiple times to a disk. The information volume of such disks is 700 MB.
CD-ROM drive - allows you to only read information from any CD-ROMs. Accordingly, such devices will differ in read speed and cache memory among themselves. The CD-R drive - read and write, and the CD-RW drive not only reads, but also rewrites (erases information and overwrites it with a new one). These 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 somewhere in 96-97 of the last century. DVD is an excellent storage medium for any type of data and is used as an ordinary computer storage medium.
From the outside, the DVD looks like a regular CD, and even up close, it's hard to tell the difference. However, DVDs have much more possibilities. DVDs can store 26 times more data than CD-ROMs.
DVD technology has become a huge leap in the field of storage media. A standard single sided single layer disc can store 4.7 GB of data. But DVDs can be made to the dual-layer standard, which allows you to increase the amount of data stored on one side up to 8.5 Gb.
In addition, DVD discs are double-sided, which increases the capacity of the disc up to 17 Gb. True, in order to read a DVD disc, you need a new device (DVD-ROM), but DVD technology is compatible with CD technology, and the DVD-ROM drive also reads CD discs, and in different formats.
On sale you can find various combined drives for optical discs. For example, DVD-CD R/RW allows you to read DVDs and CDs and write/rewrite to CDs. Another option is DVD-RW - CD-RW. Allows you to read, write and rewrite DVDs and CDs.
