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Optical disks main characteristics. What is Blu-ray Disc? what are optical discs

Information carriers – material that is intended for recording, storage and subsequent reproduction of information.

Storage medium - a strictly defined part of a specific information system, used for intermediate storage or transmission of information.

Storage medium is the physical environment in which it is recorded.

The media can be paper, photographic film, brain cells, punched cards, punched tapes, magnetic tapes and disks or computer memory cells. Modern technology offers more and more new types of storage media. They use the electrical, magnetic and optical properties of materials to encode information. Media are being developed in which information is recorded even at the level of individual molecules.

All computer media are divided into:

1. Perforated – have a paper basis, information is entered in the form of punches in the corresponding row and column. The volume of information is 800 bits or 100 KB.

2. Magnetic media – they use flexible magnetic disks and cassette magnetic tapes.

3. (compact discs) is a metallized plastic compact disc, 120 mm in diameter and 1.2 mm thick. On one of its sides there is a reflective aluminum layer, which is coated with a protective varnish to prevent damage. Information is recorded and read by a laser beam on a path running in a spiral from the center.

Optical storage media– (compact discs) is a metallized plastic disc with a diameter of 120 mm. And 1.2mm thick. On one of its sides there is a reflective aluminum layer, which is coated with a protective varnish to prevent damage. Information is recorded and read by a laser beam on a path running in a spiral from the center.

Types of optical disks:

1. CD-ROM (Compact Disk Read Only Memory) – a compact disc without the ability to record information.

2. CD-R (Compact Disk Recordable) – a CD with the ability to record information once.

3. CD-RW (Compact Disk Rewritable) – a CD with the ability to record information multiple times.

4. DVD (Digital Versatile Disk) – a digital multilayer disk for recording large amounts of information (up to 18 GB).

ADVANTAGES: Reliability. Ability to record large amounts of information. Wear-free.

Compact Disk (CD) is a disc with a diameter of 120 mm (4.75 inches) or 80 mm (3.1 inches) and a thickness of 1.2 mm. The depth of the stroke is 0.12 µm, the width is 0.6 µm. The strokes are arranged in a spiral, from the center to the periphery. The stroke length is 0.9–3.3 µm, the distance between the tracks is 1.6 µm. Compact discs are made up of three to six layers. A standard five-inch disc can contain 650–700 MB of information, 74–80 minutes of high-quality stereo sound with a sampling frequency of 44.1 kHz and a digitization depth of 16 bits or great amount audio in MP3 format. Three-inch disks hold about 180 MB of information. Sometimes there are disks called “business cards”. In appearance and size, they resemble a business card, but are actually three-inch disks, cut on both sides. Such a CD can store from 10 to 80 MB.

In the late 1970s, Sony and Philips began jointly developing a single standard optical media information. Philips created the laser player, and Sony developed the technology for recording on optical media. At the suggestion of Sony Corporation, the disc size was 12 cm, because... this volume made it possible to record Beethoven’s Ninth Symphony in its entirety. In 1982, in a document called the Red Book, a standard for processing, recording and storing information on laser disks was published, as well as the physical parameters of the disk, i.e.: 1. Physical size of the disk. 2. Disk structure and data organization. 2. Recording data in a single stream from the center to the periphery. 3. Read data from constant linear speed(Constant Linear Velocity, CLV).

All data on the disk is divided into frames. Each frame consists of 192 bits for music, 388 bits for modulation and error correction data, and one check bit. 98 frames make up one sector. Sectors are combined into a track. A maximum of 99 tracks can be recorded on a disc.

During recording and reading of information, when the laser beam moves from the center to the periphery, the rotation speed of the disk is ↓. This is necessary to ensure that the same amount of information can be read and written in the same amount of time. Therefore, without the use of CLV technology, when playing, for example, musical works, the performance speed would change.

Due to the relatively small size laser discs compared with vinyl records they came to be called compact discs, or CD (Compact Disk) for short. The first CDs were designed for recording and playing music and could store up to 74 minutes of high-quality stereo sound. The standard for such discs was called CD-DA (Compact Disk Digital Audio).

With the development of the computer industry, a need arose for technology that allows storing not only digital sound, but also various data on CDs. Computer programs could not fit on floppy disks, and the volumes user files became more and more.

In 1984, a standard called the Yellow Book was published. Sony and Philips companies reorganized the structure of CDs and began to use new error correction codes - EDC (Error Detection and Correction) and ECC (Error Correction Code). The main unit of data placement was the sector. One sector contains: 12 bytes for synchronization, 4 bytes for headers, 2048 bytes for user data and 288 bytes for error correction. CAV (Constant Angular Velocity) technology was developed to read computer data. CAV technology allows you to read information from a disk faster than CLV technology, since the data flow increases as the laser beam moves from the center to the periphery. Modern CD drives support both technologies. Computer laser disks were called CD-ROM - Compact Disk ReadOnly Memory (literally, “read-only memory on CDs”). In the late 1990s, the CD drive became a standard component of any computer and the vast majority of programs began to be distributed on CDs.

The consumer market was rapidly expanding, production volumes were increasing, and largest producers began developing technology that allows the user to independently record any information on a CD. In 1988, Tajio Yuden released the world's first CD-R (Compact Disk Recordable). The biggest challenge faced by CD recorder designers is finding highly reflective materials. Tajio Yuden successfully completed the task. The gold-cyanine alloy they used to make these drives had a reflectivity of over 70%. The same company developed a method for applying an active organic layer to the surface of a disk, as well as a technology for dividing the disk into tracks.

DVD, DVD-R, DVD-RW, CD, CD-R, and CD-RW discs are manufactured by various companies: AMD, Amedia, Digitex, HP, Imation, MBI, Memorex, Philips, Smartbuy, Sony, TDK, Verbatim.

DVD structure.

In December 1995, 10 companies united in the DVD Consortium officially announced the creation of a single unified standard - DVD. The abbreviation DVD first stood for Digital Video Disc, but later its meaning was changed to Digital Versatile Disc. The disc was fully compatible with the Red Book and Yellow Book standards. DVD is identical in appearance to CD, but allows you to record information that is 24 times larger in volume, that is, up to 17 GB. This became possible thanks to changes in the physical characteristics of the disk and the use of new technologies. The distance between the tracks was reduced to 0.74 μm, and the geometric dimensions of the pits were reduced to 0.4 μm for a single-layer disk and 0.44 μm for a double-layer disk. The data area has increased, the physical sizes of sectors have decreased. A more efficient error correction code, RSPC (Reed Solomon Product Code), was used, and more efficient bit modulation became possible. DVD technology provides a huge number of formats and four types of design in two sizes. A disc of this standard can be either single-sided or double-sided. There can be one or two working layers on each side.

Burning single-layer DVDs is similar to burning CDs, but burning dual-layer discs is significantly different from the process described earlier.

Double-layer discs of types DVD-2 and DVD-9 have two working layers for recording information. These layers are separated using a special translucent material. To perform its function, such a material must have mutually exclusive properties: reflect the laser beam well when reading the outer layer and at the same time be as transparent as possible when reading the inner layer. At the request of Philips and Sony corporations, 3M created a material that meets the following requirements: having a reflectivity of 40% and the necessary transparency. DVDs are 0.6mm thick. For physical compatibility with CDs, a 0.6 mm thick polycarbonate backing was additionally glued onto the DVD.

The CD specification does not provide any copy protection mechanism - discs can be freely copied and played. However, starting in 2002, various Western record companies began attempting to create copy-protected CDs. The essence of almost all methods comes down to deliberately introducing errors into the data written to the disc, so that the disc can be played on a household CD player or music center, but not on a computer. The result is a game of cat and mouse: such discs are not readable on all household players, but on some computers they are readable, software is released that allows you to copy even protected discs, etc. The recording industry, however, does not give up hope and continues try more and more new methods.

There are also magneto-optical disks : FLOPTICAL = FLOPPY (floppy disk) + OPTICAL.

The surface of the magneto-optical disk is covered with a special material, the properties of which change under the influence of temperature and magnetic fields. All these disks differ from each other in diameter and number of working surfaces. The volume of information is up to 10 GB.

Optical media are 12 cm (4.72 in) CDs or 8 cm (3.15 in) MiniDiscs. Optical media consists of three layers:

1) polycarbonate base (outer side of the disk);

2) active (recording) layer of plastic with a changeable state phase;

3) the thinnest reflective layer (inner side of the disk).

In the center of the CD is a round hole that fits onto the CD drive spindle.

Writing and reading information onto a CD is carried out by a head that can emit a laser beam. There is no physical contact between the head and the surface of the disc, which increases the life of the CD. The phase of the second plastic layer, crystalline or amorphous, changes depending on the cooling rate after the surface is heated by the laser beam during the recording process performed in the drive. When the plastic cools slowly, it turns into a crystalline state and the information is erased (a “0” is written); upon rapid cooling (if only a microscopic point is heated), the plastic element goes into an amorphous state (written “1”). Due to the difference in reflection coefficients from crystalline and amorphous microscopic points of the active layer during reading, the intensity of the reflected beam perceived by the reading head is modulated. The surface of the disk is divided into three areas. The Lead-In area is located in the center of the disk and is read first. It records the contents of the disk, a table of addresses of all records, the disk label and other service information. The middle area contains basic information and takes up most of the disk. The Lead-Out area contains the end-of-disk mark.

The information on a CD is encoded with great redundancy using a Reed-Solomon correction code, which ensures the restoration of the original information if it cannot be read from the disk.

A CD can withstand several hundred rewrite cycles. Information is read when the CD is rotated at a frequency of more than 10,000 rpm.

Depending on the read/write capabilities, all CDs can be divided into three types:

1) ROM (Read Only Memory) – read only; recording is not possible;

2) R (Recordable) – for writing once and reading multiple times; the disc can only be written to once; the recorded information cannot be changed and is read-only;

3) RW (ReWritable) – for repeated writing and reading; information on the disk can be overwritten many times.

These types of discs differ in the material from which the second plastic layer is made.

Let's look at the types of CDs (CD (Compact Disc), DVD (Digital Versatile Disc) and Blu-Ray, which have same size 4.72 inches.


CD capacity is 650 or 700 MB. Music CDs refer to CDs and are intended only for reading music from them. CD access time – 0.05-0.3 s.

The DVD format is a development of CDs; their volume is 4.7 GB due to denser recording. DVDs continue to improve. There are several competing DVD formats: DVD-, DVD+ and DVD-RAM.

Blu-ray format is further development DVD and allows you to record 25 GB of information on one layer.

The names of CD and DVD formats depending on read/write capabilities are presented in the table.

Optical storage

Optical drives are designed to read and usually write/rewrite from optical discs. Optical discs They are round and flat plates made of dense material (usually consisting of polycarbonate) with applied layers that allow information to be stored in the form of tiny pits (pits, frompit - hole, deepening). The reading process is carried out by a laser beam, which, reflected from the surface of the disk, enters a photocell, where the light is converted into an electrical signal, the magnitude of which allows the recorded information to be decoded.

The most common optical disc formats for use in personal computers are CD, DVD, Blu-ray.

CD-ROM ( Compact Disc Read Only Memory, read-only CD) a type of CD,which appeared in 1982 as a result of research by two companies - Sony and Philips. The first discs used the "Red Book" format, in which the playing time of one cassette was 74 minutes 33 seconds, which corresponds to the playing time of Beethoven's 9th Symphony, which was very popular in Japan at that time. The audio sampling frequency is 44 kHz for stereo sound and the bit depth is 16 bits. They had a capacity of 650 MB and allowed storing 75 minutes of music (starting from 200, discs with thinner recording tracks appeared, which made it possible to increase the capacity to 700 MB with recording 80 minutes of music). CD-ROM drive and initially developed as an analogue of vinyl discs and were intended for recording and playing musical information. They also have a single concentric track that runs from the outer edge to the inner, making many turns. The principle of reading information is optical, that is, the laser beam reads data that is recorded on an aluminum (or other type) substrate. In addition, the information is recorded on the disc, unlike a vinyl disc, in digital rather than analog form, and after reading it is decrypted and converted into sound. To protect the disc from damage, the aluminum substrate is covered with transparent plastic.

Creation technology CD-ROM drives next. First, a disk is made on which only those places where a unit of information is located are burned out and remain without changing the place with zero values. After this, a matrix is ​​made, with the help of which the blanks are stamped, a layer of metal (aluminum, silver, gold, etc.) is sprayed onto the information surface to increase the reflectivity of the laser beam, and they are coated with transparent plastic (varnish) to protect the data. When a disk is inserted into the drive, a laser beam slides along the concentric circle of the disk and by the reflected light it is determined whether it is recorded: a zero or a one.

Initially, CD-ROM discs were designed to store only music information. Due to the fact that disks use digital information rather than analog, they began to be used in computers.

Usually , storage device CD-ROM supports modes : Audio CD, Music Disc, Super Audio CD, CD-ROM (mode 1 & mode 2), CD-ROM/XA (mode 1, form 1 & form 2), Super Video CD, CD-Text, Video CD, CD -I/FMV, Photo-CD (Single & multisession), CD- i and others . The first drives could only handle certain formats, but eventually they could handle all formats. Therefore, the user does not need to know the format. As a rule, it is enough to know that there are audio, video discs and discs with programs (or text).

Next, the “Yellow Book” standard was developed, which contains a header that determines the type of disc: music or software. The music format was already well developed, and the software format was determined by each manufacturing company itself. Due to the rapid development of this technology, the discrepancy in the standard could not last long, so the High Sierra advisory standard arose, on the basis of which the ISO 9660 standard soon appeared. For this standard, there is a table of contents and a data area on the disk. The first track contains parameters for synchronizing the drive and disk with each other, followed by a table of contents in which the description of each file contains the direct address on the disk.

There are three types of such disks:

CD - ROM The disk is usually written in an industrial manner, and in the future it can only be read. It measures 120x1.2 mm and has a capacity of 650-879 MB. Service life 10-50 years. Such discs are often supplied with computer devices; they contain software, music discs, etc.

CD - R The disc has the same characteristics as a CD-ROM, but allows information to be written to them once.

CD - RW the disc has the same characteristics as a CD-ROM, but allows you not only to write information on them, but also to write more of it, also to erase previously recorded data and write new ones.

To work with them, CD drives were used, which have several types:

CD- ROMthe drive can only read CD disks. One of the most important characteristics of this device is reading speed information. Normal (single) speed corresponds to the speed of reading audio discs, which is 150 kb/sec. Then came CD-ROMs with 2, 4, 6, 8, 10, 12, 16, 24, 32, 36, 40, 52 times the speed. The data transfer rate is accordingly a multiple of 150 kb/sec. For example, for a 40x drive it will be equal to 40x150 = 6,000 Kb/sec, and here the maximum speed is indicated, which is equal to or lower for different types of drives, which depends on the manufacturer. The six-speed drive allows for video output at frame rates of 25 frames per second or higher, which is fast enough for on-screen viewing. Discs for use with this device are sometimes also called compact discs (this concept also includes CD-R, CD-RW discs) or CD-ROM discs (Compact Disk; see figure below).

CD - R drive is a write-once optical drive. It allows you to read CD-ROM, CD-R, CD-RW discs, but also allows you to write CD-R discs once. This drive has the characteristic of not only reading disks, but also for writing. For example, the read speed is 40 times, and the write speed is 6 times.

In such devices, a laser beam burns grooves on the surface of the disk, while the areas that reflect light are called “lands”, and the non-reflected areas are called “pits”. The combination of these sections makes it possible to encode information in a two-bit representation.

By virtue of various reasons In practice, when recording, it is impossible to achieve an ideal location of the burnt grooves, and during playback, sound defects and jitter appear, which is called “jitter.” IN to a certain extent To get rid of such unwanted distortions, you can use special regime Audio Master, when the burned grooves are forcibly increased in length. This mode is used in cases where you need to improve the quality of the recorded sound.

Typically recording is done at constant angular velocity (CAV). However, when the rotation speed changes several times (x2, x4, x8, etc.), the recording pauses and so-called “connection points” are formed, which deteriorates the quality of the recording. In such cases, a buffer underrun protection called SafeBurn is used. As a rule, it turns on only when the disk rotation speed changes, and the recording mode with constant angular velocity (CAV) is mainly used. This method of improving the quality of playback audio is called Zone Constant Line Velocity (Z-CLV) recording.

A very interesting feature on some devices for recording digital information on discs is the ability to burn text onto the surface of a laser disc, be it a list of music files or your data. For this, the DiscT2 mode is used, in which any text is typed that is worthy of reproduction on the surface of a music or other type of disc created by oneself.

CD - RW (Compact Disc-ReWritable) storage device is a reusable optical storage device. It allows you to read CD-ROM, CD-R, CD-RW discs, write CD-R discs once, but also write and re-write, as well as rewrite previously recorded CD-RW discs. This drive has the ability not only to read discs, but also to write them. For example, the read speed is 40 times, and the write speed is 6 times. There could also be a speed of additional recording.

A CD-RW device works on a different principle, that is, when writing to them, the beam does not burn out, but transforms the substrate into an amorphous state, which allows you to establish a different reflective effect. Therefore, they can write data multiple times. However, discs dissipate information worse than standard CD-ROM discs, so they cannot always be read on standard media.

The more capabilities a device has, the more limitations it has. How easier wheels, the greater the reflective effect they have. CD-ROM discs have the best reflective effect, which can be read in CD-ROM, CD-R and CD-RW drives.

CD-RW format discs have even less reflectivity and may not be readable on all older CD-ROMs and CD-R drives (old drives). It is quite difficult to say definitely which drives will be readable and which will not, since it depends on the device model. Currently, CD-R compact discs are sold on which information can be recorded. If after recording there is still free space on the disk, then additional information can be written to the disk, and so on. CD-RW discs allow you not only to record information, but also to delete unnecessary data, that is, write data repeatedly and are somewhat more expensive than CD-R discs.

In 1996 they appeared DVD -discs(Digital Versatile Disc - digital universal disk, originally stood for Digital video Disc - digital video disk. Now it is not decrypted in any way), which had a capacity of 4.7 Gigabytes due to compaction of recording tracks, that is, 7 times more than the capacity of CD-ROM disks. This is the most common type of disc, which is single-layer and single-sided. However, there are discs that have two layers on one side and have a capacity of 8.5-8.7 Gigabytes (they may be called DVD 9, the number means rounded capacity), there are discs with one layer, but with recording on two sides, with a capacity of 9.4 Gigabytes (they may be called DVD 10), double-layer and double-sided with a capacity of 17.08 Gigabytes (they may be called DVD 18). Double-layer discs have two translucent layers with powerful beam focusing, allowing information to be read from either the first or second layer. More high density data is achieved by reducing the disk space per bit and applying compression techniques. But in practice, the most common are single-sided, single-layer ones.

After the creation of a single DVD standard for recording video films on them, the whole world was divided into six zones so that films recorded in one zone could not be read in others. Therefore on old DVD the drive may have a pictogram showing the image globe with numbers indicating which zones this drive works with or ALL (all) - to work with disks in all zones. Modern DVD drives do not have such a partition.

The information on the disks is located in sectors that contain data and 882 bytes for the error correction code, which increases the reliability of reading information, since in case of failures the values ​​​​are calculated using the correction code. If there are bad sectors, the reading speed slows down and repeated reading occurs, and so on up to a certain number of attempts. As a result, either the code will be read, or a message will appear on the screen stating that it is impossible to read information from of this disk, after which it switches back to maximum speed.

Unlike CDs, DVDs have their own file system, UDF, or ISO -9660 for data. Data is stored in 2048 byte sectors. Disks can be DVD-video, DVD-audio, DVD-Data and mixed types.

Discs DVD - ROM just like CD-ROMs are read-only. They have already been recorded somewhere and are sold with the recorded information.

The standard for recording on disk was developed in two ways, one standard called MMCD was developed by Philips and Sony, the second called Super Disc by Toshiba and several others. Therefore, two formats for recording data arose - DVD -R and DVD +R. These formats are close to each other, however, the plus format is better to use, since it takes less time to rewrite and the recorded data has fewer errors. Accordingly, there are two formats of rewritable discs DVD -RW and DVD +RW.

Write-once discs that have a double layer on one surface are designated by DL symbols, for example, DVD -R DL and DVD +R DL. They have a capacity of up to 8.5 gigabytes.

To work with DVDs, DVD drives are used, which have several types:

DVD - ROM The drive can only read both DVDs and CDs. One of the most important characteristics of this device is reading speed information. The multiplicity per unit is taken as 1.32 MB/sec, which is 9 times faster speed CD. They have different speeds reading CD and DVD discs, which is indicated in the device manual.

DVD - R drive is a write-once optical drive. It allows you to read CD-ROM, CD-R, CD-RW discs, all types of DVD discs, and also allows you to write CD-R discs and DVD +R and DVD-R discs once. This drive has the ability not only to read discs, but also to write them. For example, the reading speed is 40 times, and the writing speed is 6 times, and the speed is indicated separately for CDs and DVDs and, accordingly, separately for DVD -R and DVD +R disks.

DVD - RW storage device is a reusable optical storage device. It allows you to read and burn all types of CD and DVD discs. Reading and writing speeds are indicated separately for CDs, DVD -R, DVD +R, DVD +R DL, DVD -R DL, DVD +RW, DVD -RW, DVD +RW DL, DVD -RW DL, that is, those operations , which the drive can conduct. Here it is also better to use the plus format, since the minus format requires you to first erase the information and then write it, and the plus format allows you to rewrite data in real time.

Standard Blu - ray Disc (BD ) (blue ray- blue beam and disc- disk; writing blue instead of blue- intentional)was developed by the BDA consortium, released in 2006. U of this standard there was a competitor - HD DVD from Toshiba, however, this company abandoned further support for HD discs in 2008 after the “format war”. The information reading speed (single speed) is 4.5 Mb/s. Increasing the volume of recorded information is achieved by using a laser beam in the blue-violet range with a shorter length of 405 nm, while CD and DVD drives use red and infrared lasers with wavelengths of 650 nm and 780 nm.

A single-layer disk can store 25 gigabytes, a double-layer disk can store 50 gigabytes, a three-layer disk can store 100 gigabytes, and a four-layer disk can store 128 gigabytes. A disk can have more layers. So in 2008, 20-layer disks with a capacity of 500 gigabytes were demonstrated.

Currently available are BD-ROM read-only, BD-R write-once and BD-RE write-once. There are also double-layer disks with DL symbols in the name with a capacity of up to 50 gigabytes.

Drives for these disks are Blu - Ray Read-only discs that allow you to read and write all types of CDs and DVDs, as well as read-only BDs. Respectively Blu - Ray RE allow you not only to read, but also to write all types of CDs, DVDs and BD discs (single-layer, for multi-layer you need to read the instructions).

To insert a CD or DVD into the drive, first press the button on the front panel of the drive (picture below). At the same time, a tray is pulled out of the drive, into which you need to place the disk in a special recess for it with the working surface on which the data is located, down, or with the pattern facing up. Then press the button again, and the tray slides into the drive housing. Now you can work with the disk. The tray has a second recess for disks, approximately half the diameter and currently very rarely used (they are often shown in detective and science fiction films).


For normal operation, the drive must be in a horizontal position. There is a drive that can work in a vertical position. In this case, the disk is inserted into the slot by hand, after which a special mechanism holds it and inserts it inside the drive.

The optical drive has an emergency eject hole for the tray if it does not eject. To do this, you need to insert a thin rod, for example, a straightened paper clip, and press on it. In addition, there may be a button to skip to the next song for audio CDs. A configuration switch can be installed at the back, it is advisable to install a Slave, and there is also a connector for testing the drive by the manufacturer. Some drives may come with microphones, headphones, or sound cards.

For boot disk need to:

Turn on the computer;

Press the tray open button and it will slide out;

Place the disc with the print side up on the tray;

Press the tray open button again. The tray slides in, after which you can start working.

Do not pull the tray out or in by hand. It is not advisable to keep the tray open for a long time when there is no work; you should not place foreign objects on the tray, for example, placing a cup of coffee; you should not put pressure on the tray when placing a disc.

When there is no operation, the drive goes into energy saving mode, and the drive noise stops. When a read command is received, the drive starts working automatically.

The production of a disk occurs as follows: first, a disk is made, which is called the “mother”, then a working copy is stamped - the “father”, then others are pressed on its basis.

Basic drive characteristics:

Type: interior or external. The internal drive is inserted into the system unit. The external one has a rectangular body, connects to a parallel port (in old computers), USB (in modern ones) and has a wire connected to the mains. There is also an external option for laptop computers, connected using a PCMCIA connector;

- baud rate(Data Transfer Rate, DTR), respectively indicated as two-speed, four-, thirty-two, etc.;

- buffer memory capacity(Buffer Memory). Cache memory is a RAM chip that is located on the drive board. They provide benefits, so the larger the volume, the better;

- average time between breakdowns(Mean Time Between Failure, MTBF). This characteristic available in many devices, but not described everywhere;

- interface type or bus to which it is connected;

- average access time(Access Time, AT). It is larger for CD-ROM drives than for hard drives, which is determined by fundamental differences in the design of the drive, and differs tens of times, and the greater the multiplicity, the shorter the access time. So, for a 4x drive it is approximately 150, and for a 32x it is 80 ms. This value can be found in the device passport;

- error rate(Error Time);

- list of supported formats.

There may also be other parameters, such as noise and vibration levels. In addition, when purchasing, you need to see whether the tray moves smoothly and whether it is firmly held open.

Latest BIOS versions allows you to boot your computer from CD and DVD disks. A CD-ROM disc at the beginning of the track has a service area, which contains information for synchronizing the drive and disk, then the volume table of contents (VTOC), which contains data about the organization of directories and files on the disk, then data and a label end of the volume. Thus, knowing the path and file name, you can use the table to find the file’s location on the disk and directly position the head to read data, which reduces search time and read operations.

Connects device using two cables: power and information. There are three types of drives: those connected to the SCSI bus, to the IDE bus or to the SATA connector. It's better to have a drive that connects to the IDE connector if it supports it motherboard. Since there are usually few SATA connectors and, if you need to install several optical or drives for hard drives, then there may be a problem with the presence of a free connector.

The connection to just such a bus is described below. Optical drives can be connected along with a hard drive. The data cable consists of 40 cores (shown in the figure above) and has three plugs. One is connected to the hard drive controller (on older boards) or directly to the motherboard (see also the description of the boards and hard drive). The second to the optical drive and the third to the hard drive. Do not forget that the edge of the cable, marked in red, when connecting the plug, should be located near the markings 1, 2, which indicate the first cores of the wire, the opposite end - near the numbers 33 and 34. The second power cable should be connected to the marking indicated on top of the plug, that is, red (5v), black, black and yellow.

If you have a sound card, to listen to sound from music discs, you must connect a third cord consisting of four wires. One end connects to sound card, the other - to the drive. They are marked with the symbols R and L. The wire coming from the sound card with the symbol R must match the R on the drive. The figure below shows the back of the drive, which has connectors for connecting wires.


Installation sequence for new optical drive similar to installing a floppy drive. If installed Windows system 9x, then a corresponding message about finding a new device will appear on the screen. On Windows system operating system itself recognizes new devices, including optical storage.

When working with disks, you must do following rules:

Do not touch the work surface, otherwise greasy fingerprints may remain on it;

Take the disk by the outer edges, you can take it by the edges of the central hole;

Clean the disc from the center of the disc to the outer edge with a soft, dry cloth. Do not use strong solvents such as acetone, detergents, antistatic aerosols;

Store discs in a special box or disc sleeve;

Do not bend the disc;

Do not write on the working surface of the disc;

When storing the disc, avoid exposing it to sunlight or strong heat, which may cause the disc to warp.

Disks may have defects that prevent data from being read. If there is a displacement of the concentric tracks relative to the center of the disk, then such a disk will be difficult to read, and such a defect cannot be detected by eye. Reducing the disk rotation speed may help, for example, try doing this on a slower drive. If the disk is warped, sometimes noticeable to the eye, then reducing the rotation speed can also help to read such disks.

If there are specks on the disk, then, depending on their location and size, it is sometimes possible to use such a disk. Scratches that go from the edge to the center are often harmless, but scratches that run along the edge may prevent data from being read. Therefore, you need to wipe the disc from the center to the edge. To check the disk, special test programs. When installing, use an interrupt (IRQ) - 7 and higher, base addresses 300h to 340h, DMA1. CDs are quite reliable, however, if there are cracks on the CD, it is recommended to make a copy of the disc, as new cracks may appear in the future and the information on the disc will be unreadable.

Installing the drive. To install this device, you need:

Turn off computer;

Remove the protective cover of the system unit;

Insert the drive into the guides of the system unit. After installation, be sure to tighten the screws on the sides of the device. Sometimes, in order to reach with a screwdriver and tighten the screws, you may need to remove other devices. After this, connect the wires as described above, install the protective cover, turn on the computer and check the operation of the drive.

The technical installation of an optical drive is similar to installing hard disk.

If the tray does not extend, the reason may be that the drive is tightly secured with screws inside the system unit, which causes the drive to become skewed. The sound during CD overclocking is not a sign of malfunction. After installing the optical drive for testing, you can try copying some files from the optical drive to your hard drive. You should not disassemble the drive yourself. The drive should not be exposed to rain or in a damp place.

Main optical disc formats:

CD- the most ordinary stamped CDs that are used exclusively for reading.
Music, software and other information - you could have seen all these CDs repeatedly in various stores.
Maximum capacity of this type The storage medium is 700 MB.

Speed ​​characteristics range from 40x to 56x.
For most CDs this parameter is 40x, 40x or so; 52x and 56x are rare.
At such high speeds optical drives They just howl, especially if the carrier itself is of poor quality.

CD-R- CDs for one-time recording of information.
The speed characteristics for the reading parameter are similar to their CD counterparts.
As for recording, the maximum speed at which a standard 700 MB CD-R can be written is about 40x and 48x, in practice this is 3-4 minutes.

Intermediate speed values ​​are also available.
That is, if your optical drive does not support this high speeds records or you yourself for some reason do not want to write matrices on the maximum possible x, you can limit yourself to 1, 2, 4, 8, 16, 24, 32x.

CD-RW- rewritable CDs with a resource of about 1000 times.
The capacity is the same as CD and CD-R, but the reading speed is slightly lower: most media are read at 32x and 24x speed.
CD-RWs are clearly tied to a specific write/rewrite speed: CD-RW (1-4x), Hi-Speed ​​CD-RW (4-12x), Ultra Hi-Speed ​​CD-RW (12-24x) and Ultra Hi-Speed+ CD-RW (24-32x).

As you can see, the speed flexibility of CD-Rs is not here, but do not be upset about this, modern optical drives support maximum speeds writes/rewrites for CD-RW and backward compatible with slower matrices.

DVD-ROM- stamped DVDs.
Such media can be found in any video store that sells films.
There are both single-layer and double-layer media on sale, which differ in capacity: 4.7 GB (single-layer) and 8.5 GB (double-layer).
The maximum reading speed is 16x.

DVD-R And DVD+R- DVD matrices for one-time recording of information with a capacity of 4.7 GB.
In terms of reading speed, such CDs are similar to their stamped counterparts, 16x is the maximum; if the optical drive is old, then it can read DVD-R and DVD+R at lower speeds: 8x, 10x.
There are practically no differences between plus-discs and minus-discs, these designations remained from the time of the format war, today all this is no longer relevant, and modern optical drives support both plus and minus discs.

The maximum recording speed of these media is about 16x, which corresponds to a time period of 6.5 minutes.
However, the speed flexibility of CD-R is inherent in both DVD-R and DVD+R, so you can record these discs at speeds below the maximum 16x: 1x, 2x, 4x, 8x.

DVD-R DL And DVD+R DL- these CDs are similar to DVD-R and DVD+R, but have not one layer, but two, and, as a result, their capacity is about 8.5 GB.
In terms of read and write speeds, they are significantly inferior to their single-layer ancestors: reading - 8x, and in most cases it is 4-6x, writing - 8x for DVD+R DL and 4x for DVD-R DL.

DVD-RW And DVD+RW- rewritable CDs with a limited resource, but how could it be otherwise?
The capacity is the same as that of DVD, DVD-R and DVD+R CDs - 4.7 GB.
The recording speed is 8x for DVD+RW media and 6x for DVD-RW.
As for the reading speed, it is 6-8x.

DVD-RAM- rewritable media with a capacity of 4.7 GB.
The main feature of DVD-RAM CDs is the fact that they can be written and read simultaneously.
It is also worth noting that some DVD-RAMs have a protective cartridge, which significantly increases the life of such a CD.
Read speed and write speed are the same and amount to 5x.

BD-R(Blu-ray Disk Recordable) - are disposable recordable discs.

BD-RW(Blu-ray Disk ReWritable) - rewritable disc.

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 less than that of a red CD laser 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 discs, CD-RW - identical in size (up to 700; sometimes 800MB, but such discs 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 – standard volume DVD and 1.4GB – DVD volume 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 influences. environment. 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. Protective layer, which is a hard varnish, only covers CDs and Blu-ray discs.
  • 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 him 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 during the industrial production of discs is called stamping. In this way in large quantities discs are produced with recordings of music, films, computer games. All the information that gets onto the disk during stamping consists of many tiny indentations. Something similar happened when gramophone records were made.

  • Recording a disc at home occurs using a laser beam. It is also called “burning” or “cutting”.
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 a request to the recorder about the type of media used, the quantity free space

and the speed at which the disc should be written.

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 dramatically. 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, which 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.