Lecture on the topic: Optical disks. Optical disk: what is it and all its characteristics? Optical discs, their types and purpose
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.
On this moment, in addition to CD discs, which can be considered pioneers in the range of optical media, discs such as DVD and Blu-ray appeared. These types of disks are different from each other. For example, capacity. Blu-ray disc holds up to 25 GB of data, DVD disc– up to 5GB, and a CD – only 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 – volume standard disk 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. Only CD and Blu-ray discs are covered with a protective layer, which is a hard varnish.
- The last layer is the label. That's what they call it upper layer 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". According to the language binary system 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 in large quantities CDs are produced with recordings of music, films, and 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.
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.
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 the recorder, with its support special technologies, 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.
It's no secret that the story began with gramophone records. Storing information at home is problematic, and only audio was stored on it. The principle of operation is not a secret, but vinyl disc has been popular for over a hundred years and is still used and preserved by collectors and DJs today. It was funny to watch how the needle, while scrolling the disk, seemed to shake on a perfectly even spiral. The principle of sound production was built on this. 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 collecting information was made on a piezoelectric needle and a modern, until recently, record player was obtained.
The 70s are here. And there was a leap in storage media (we will skip magnetic tapes). They invented a disk made of polycarbonate, which was transparent, coated with aluminum. Polycarbonate served as the basis and protected the coating from external influences, and depressions were burned into the coating in a spiral. The principle of capturing and recording information is based on this, as you can see we have not gone far from the gramophone record. A thin beam reflected from the coating surface and arrived at the light receiver, which in turn determined the changes and created ones and zeros based on the information received. And then according to the ABC principle Morse information is converted into music, movies, photos, files, etc.
Now let's look at the notation on CDs:
But with DVD disks, everything turned out much more complicated. This disk was created to store large amounts of information and was developed by a large number of companies (DVD-R and DVD-RW). Different coatings had different characteristics and household players from different companies began to conflict with discs, hence the loss of versatility. Therefore, having united, they invented a new type of disk, called DVD+R and DVD+RW, they are, oddly enough, cheaper. Now it doesn’t matter which disc to use, since household players have adapted it. The only difference is in the re-writable discs, DVD-RW must be completely erased before recording, and DVD+R Just erase the “header” and put the recording on top.
As they say, no matter how much you give us, it’s not enough for us. Therefore, progress did not stop there, double sided And two-layer and two in one discs. 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 closest to the laser, made translucent, and you don’t need to get up from the couch to turn the disk over. Well, with the last option, take two two-layer and glue them together.
We've reached the peak of development. modern world optical disk, this is HD-DVD and Blu-ray.
HD-DVD- this is a disk that was made based on our workaholic described above, but using a blue laser.
Blu-ray- a completely different development, a blue laser is used.
If you remember the spectrum (rainbow), you will see that from a blue beam you can get a much thinner beam, so these disks turned out to be much more voluminous. But this will be discussed in the next topic.
It seems like that’s all for today. It remains only to tell a little about storage and use of the disk. The disc is not tasty, there is no need to chew it, well, unless someone has a lack of plastic in the body. And also this is not a tool for playing on nerves, so you don’t need to run your claws over it. It is advisable not to bend it, although it is difficult to break, but fragments can end up where they shouldn’t, and this will affect your body. Also, the constant bending is disrupted by the coating inside, it cracks and the zeros of the unit will no longer coincide. Don't fry it in the sun, it's an element D It’s not needed at all, but it will turn into a thin 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 buying a new one.
I hope YOU literate and you don’t need to list everything point by point, you need to treat things with care and they YOU they will be grateful for this.
A data carrier in the form of a plastic or aluminum disk, intended for recording and/or playback of sound (CD), images (video), alphanumeric information, etc. using a laser beam. Recording density St. 108… … Big Encyclopedic Dictionary
A disk containing digital data readable using optical technology. [GOST 25868 91] Equipment topics. periphery processing systems information EN optical disk...
OPTICAL DISK, in computing, a compact storage device consisting of a disk on which information is written and read using a laser. The most common type is CD ROM. Audio CDs also represent... ... Scientific and technical encyclopedic dictionary
A data carrier in the form of a plastic disk designed for recording and playing back sound (CD), images (video disc), alphanumeric information, multimedia (CD ROM, DVD), etc. using a laser beam. The first optical... ... Encyclopedia of technology
Data carrier in the form of a disk made of transparent material (glass, plastic, etc.) with metallization. layer, on which microscopy, recesses (pits) are formed using digital optical recording, collectively forming spiral or annular... ... Big Encyclopedic Polytechnic Dictionary
A storage medium intended for recording and/or reproducing information using focused laser radiation. It consists of a rigid (usually optically transparent) base, on which a photosensitive or reflective layer is applied and... ... encyclopedic Dictionary
147 optical disk: A disk containing digital data read using optical technology Source: GOST 25868 91: Peripheral equipment for information processing systems. Terms and Definitions … Dictionary-reference book of terms of normative and technical documentation
According to GOST 25868–91, “Peripheral equipment for information processing systems. Terms and Definitions” – a disk containing digital data read using optical technology... Records management and archiving in terms and definitions
A storage medium intended for recording and/or reproducing information using focused laser radiation. It consists of a rigid (usually optically transparent) base, on which a photosensitive or reflective layer is applied and... ... Natural science. encyclopedic Dictionary
Blu Ray Discs (BD) are a new generation of storage media for storing high-definition video (HDTV) and high-density data. The Blu Ray standard was jointly developed by a group of consumer electronics and computer companies... Technical Translator's Guide
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- , Kuzmenko Galina. IN textbook the content side of the manifestation of the psychological and pedagogical skill of a trainer in the development of social and emotional intelligence in a system of significant qualities is presented...
Optical storage
Optical drives are designed to read and usually write/rewrite from optical discs. Optical disks 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.
The technology for creating CD-ROM discs is as follows. First, a disk is made on which only those places where a unit of information is located are burned out, and places with zero values remain unchanged. 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 a recommendation standard arose High Sierra, on the basis of which the ISO 9660 standard soon appeared. For this standard, the disk has a table of contents and a data area. 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. These discs are often supplied with computer devices and contain software, there are music CDs, 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 discs, CD-RW) or CD-ROM discs (Compact Disk - CD; 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 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.
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.
For 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”. To a certain extent, you can get rid of such unwanted distortions by using a special Audio Master mode, 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, disks dissipate information worse than standard CD-ROM disks, so they cannot always be read on standard media.
The more capabilities a device has, the more limitations it has. The simpler the discs, 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. Higher data density is achieved by reducing the disk area per bit and using 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 a globe with numbers indicating which zones the 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 makes it possible to increase 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 this disk, after which the switch to maximum speed.
Unlike CDs, DVDs have their own file system UDF or for ISO -9660 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 than CD speed. 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 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, at the same time as CD and DVD drives They 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 into 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.
BIOS latest versions allows you to boot your computer from CD and DVD discs. 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.
The procedure for installing a new optical drive is the same as 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. Special test programs are used to check the disk. 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, need to:
Turn off computer;
Remove the protective cover 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.
Technical installation Installing an optical drive is similar to installing a hard drive.
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.
Lecture 4
Optical disks: main characteristics and purposes
CD-disks, their types, history of creation
Optical music CDs replaced vinyl CDs in 1982, around the same time as the first CDs. personal computers companies IBM
These devices were the result of a fruitful collaboration between two giants of the electronics industry = a Japanese company Sony and Dutch Philips.
The strictly defined capacity of CDs is associated with such an interesting story.
Executive Director of the company Sony Akio Morita decided that CDs should meet the needs of classical music lovers only - nothing more and nothing less. After the development team conducted a survey, it turned out that the most popular classical piece in Japan at that time was Beethoven's 9th Symphony, which lasted 72-73 minutes. Therefore, it was decided that the CD should be designed for exactly 74 minutes of sound, or more precisely, 74 minutes and 33 seconds. Thus was born the standard known asRed Book (RedBook ). When 74 minutes were converted into megabytes, the result was 640 MB.
Philips specialists determined minimum requirements to the quality of sound recording and regulated, for example, such characteristics of audio CDs as their size, data encoding method and the use of a single spiral track. In particular, the sampling frequency of stereo signals was determined at the level of 44.1 kHz (for one channel 22.05 kHz), and the bit depth of each = 16 bits.
The two companies mentioned above also played a leading role in the development of the first specification for digital compact discs = the so-calledYellow Book| (YellowBook), or simply CD-ROM. She served as the basis for creating CDs with a comprehensive presentation of information, that is, capable of storing not only audio, but also text and graphic data ( CD-DigitalAudio, CD-DA ). In this case, the drive, reading the disc header, itself determined its type = audio or digital data. In this format, however, the logical and file formats of CDs were not regulated, since the resolution of these issues was completely left to the manufacturing companies. This, in particular, meant that a CD that complied with the requirements of the Yellow Book could only work on specific model drive. This state of affairs, especially in connection with the great commercial success of CDs, of course, could not satisfy the manufacturers of such devices. In the common interests, it was urgent to find a compromise.
That is why the specification became the second de facto standard for digital CDs HSG (HighSierraGroup), or simply HighSierra . This document was, generally speaking, advisory in nature and was proposed by the major manufacturers of digital compact discs in order to ensure at least some compatibility. This specification already defined both logical and file formats of CDs.
The specification created turned out to be so attractive that the standard ISO -9660 (1988) for digital compact discs, in principle, coincided with the main provisions HSG . Please note that all CDsmeeting the requirements of the standard ISO-9660, which defines their logical and file formats, are compatible with each other. Specifically, this document specifies how to locate the contents of a CD. The basic format proposed in HSG -specifications, was in many ways similar to the floppy disk format. As you know, the system track (track 0) of any floppy disk not only identifies the floppy disk itself (its density, type of OS used), but also stores information about how it is organized into directories, files and subdirectories.
Leading Data Track on a CD begins with a service area necessary for synchronization between the drive and the disk. Next is the system area, which contains information about disk structuring. The system area also contains directories for this volume with pointers or addresses to other areas of the disk. The significant difference between the structure of a compact disc and, for example, a floppy disk is that on CD The system area contains the direct address of files in subdirectories, which should make them easier to find.
The physical device of the CD.
The CD consists of made of several layers combined into a single, round, thin plate. The diameter of the vast majority of CDs is 120 mm, which is equal to five inches. A standard 5-inch disk contains 640-700 MB of information.
CD - ROM , created industrially, consists of three layers (Fig. 3.19,A). The disc base, made of transparent polycarbonate, occupies the main volume of the disc. When a base is made by stamping or injection molding, an information pattern is applied to it, resulting in a transparent plastic plate that is smooth on one side and contains many microscopic depressions on the other (sometimes called pits, fromEnglish pit - recess), the depth of which is measured from the surface ( land ). Next, a reflective metal layer is applied to the base (most often aluminum, although other metals or alloys can be used), and then a protective coating of a thin polycarbonate film or special varnish, on which printing is often placed - various drawings and inscriptions
Rice. 3.19. CD structure ("); surface micrograph CD ( 6 )
CD drive ( CD - ROM ). Reading information from a CD, just like writing it, occurs using a laser beam, but, of course, with less power.
The laser emits coherent light consisting of synchronized waves of the same length (Fig. 3.20,A). The beam, hitting a light-reflecting surface, is deflected through a splitting prism to a photodetector, which interprets this as “1”, and when it enters the cavity, it is scattered and absorbed - the photodetector records “0”.
Unlike hard drives, whose tracks are concentric circles, a CD has one physical track in the shape of a continuous spiral, running from the outside to the inside of the disk. However, one physical track can be divided into several logical ones: each of its 360-degree fragments is considered as separate track similar to magnetic disks.
CD - R . Write-once optical disc type ( Write Once / Read Many storage - WORM ) has been known since the late 1980s.
When writing data to WORM physical marks (marks) are made on the surface of the media with a low-power laser and since these marks cannot be erased, the recording is done only once.
If normal CD - ROM made by mechanical stamping of recesses (marks, “pits”), when recording CD - R A laser is used to “burn out” marks in an organic dye. Once heated to a critical temperature, the “burned” area becomes opaque (or absorbent) and, when read, reflects less light than adjacent areas that were not heated by the laser. This technology imitates the way information is read from a regular CD when light is completely reflected from the surface (" land "), but is dissipated by a depression (" pit »).
Unlike technology WORM , disks CD - R do not allow you to erase previously recorded data, but they do allow you to sequentially add them over several sessions (or sessions) to free areas of the disk. The problem is that such multi-session disks may not be fully readable for more than earlier versions players, computers or when using outdated operating systems.
CD - R disposable without the ability to add
CD + R disposable with the ability to add
CD - RW - rewritable CD ( rewritable CD ). A standard was proposed in mid-1997 CD - RW (known as Orange Book III ), which allows the user to record over old data or delete separate files. Specifications CD - RW guarantee compatibility within the CD reader family as well as compatibility with CD - ROM .
Recording layer placed between layers of dielectric, which remove excess heat from it during the recording process.
As a recording medium CD - RW usually uses a transparent composition composed of compounds of silver, indium, antimony and tellurium. During the recording process, a focused laser beam selectively heats areas of the material above the melting point (500-700 °C), and after sufficiently rapid cooling, the substance passes into the so-called amorphous state.
When abraded, the layer is heated to a temperature that is below the melting point but above the crystallization temperature (200 °C) for sufficient time, and the atoms return to an ordered (transparent) state.
To obtain these effects in the recording layer, the writing laser of the device CD - RW uses three power levels:
high, so-called “recording power”, creates opaque (absorbing) areas in the recording layer;
medium (“erasing power”), melts a section of the recording layer and converts it to a reflective (transparent) state;
low (“read power”), does not change the state of the sensitive layer and can be used to read data.
Transparent areas allow the metallized layer to reflect light, while opaque areas absorb it. The problem that arises is that the disk reflects less light than CD - ROM or CD - R and therefore the disks CD - RW can only be read on devices that support the new specification Multiread (Multi-reading).
Overcoming buffer insufficiency. By the end 1999 G. performance doubled to 8x/24x, but a problem known as buffer underrun (or write buffer underrun) arose when the speed of the machine and the MD began to lag behind the speed of the devices CD - R (the device is ready to write to disk, but the information in the write buffer is already exhausted and there is “nothing to write” - as a result, the disk turns out to be damaged). To avoid such effects, firstly, they began to use cache memory located on the writing device. CD -player (sizes from 256 KB to 2 MB), secondly, devices began to adapt to the speed of information flow, reducing or increasing the recording speed.
DVD media
Track width DVD is 0.8 or 0.74 µm, and the minimum pit length is 0.44 or 0.40 µm. To read data in DVD -drives use a red laser with a wavelength of 650 nm and an optical system with a numerical aperture of 0.6. Capacity standard DVD is 4.7 GB (for 80 mm media - 1.4 GB). Unlike CDs, DVD -carriers can be double-layered or double-sided. Double layer capacity DVD is 8.5 GB, double-sided - 9.4 GB. Double-sided discs are essentially two identical media glued together (the disc must be flipped over to read the second side).
Universal digital disk (digital versatile disc - DVD) is a type of storage device that, unlike CDs, was designed for wide use from the moment it entered the market.
There are five physical DVD formats (or books) , which are not much different from the various “shades” of CD:
DVD-ROM is a high-capacity read-only storage medium;
DVD-video is a digital storage medium for films;
DVD audio - audio storage only; format similar to audioCO;
DVD-R - write once, read many times; format similar to CD-R;
DVD-RAM is a rewritable (erasable) version of DVD, which was the first to appear on the market and subsequently found DVD-RW and DVD+RW formats as competitors. The same size as a standard CD (diameter 120 mm, thickness 1.2 mm), DVDs provide up to 17 GB of storage with transfer speeds faster than CD-ROM, access times similar to CD-ROM, and are available in four versions :
DVD-5 - single-sided single-layer disc with a capacity of 4.7 GB;
DVD-9 - single-sided double-layer disc 8.5 GB;
DVD-10 - double-sided single-layer disc 9.4 GB;
DVD-18 - capacity up to 17 GB on a double-sided, double-layer disc.
For the first At a glance, a DVD is no different from a CD: a plastic disc with a diameter of 120 mm and a thickness of 1.2 mm, both use lasers to read data recorded in the grooves of a spiral track. However, DVD's sevenfold increase in data capacity over CD was largely achieved by pushing all the tolerances of its predecessor system.
Firstly, the tracks are placed more densely, the DVD track pitch (distance between them) is reduced to 0.74 microns, more than 2 times compared to 1.6 microns for a CD.
Secondly, the DVD specification allows information to be read from more than one layer by changing the focus of the reading laser beam.
Third, DVD allows you to use double-sided discs.
The DVD format has been plagued with compatibility issues from the very beginning. Some of these are now permitted, but others, particularly rewritable and video disc compatibility, remain. Incompatible with some CD-R drives and CD-RW has been a long-standing problem. The blanks used in some of these devices cannot properly reflect the laser beam used in DVD-ROM readers, which makes them "unreadable". For CD-RW media, this problem was easily solved by the Multi-Reading standard and by equipping the DVD-ROM device with lasers with two different wavelengths. However, getting DVD-ROM drives to reliably read everything CD-R media is a much bigger problem. The laser of a DVD reader has difficulty reading CD-Rs due to the reduced reflectivity of the surface in light at 650 nm, while at 780 nm it is almost the same as for CD-ROMs.
Recordable DVD Disc Formats There are five versions of recordable DVDs:
DVD-R regular;
DVD-RAM (rewritable);
DVD-RW;
DVD+RW.
All recordable DVD formats include a set of specifications that define the physical characteristics of the recording environment. This level of operation is the "physical layer of the media", and the ability to read a disc on a particular player or drive depends on its ability to support the appropriate physical layer regardless of what data is written.
CD drives can only work with media belonging to the group CD. DVD drives allow you to work with DVD and CD media. The classification of optical discs is given below:
In each of the media groups, there are three main types of disks:
1. read-only disks ( CD-ROM, DVD-ROM);
2. write-once discs ( CD- R, DVD- R, DVD+ R, DVD- RDL, DVD+ RDL);
3. rewritable discs ( CD-RW, DVD-RW, DVD+ RW, DVD-RAM).
Differences between formats
DVD+ R/RW devices are in no way inferior to storage devices DVD-R/RW , and with some improvements they can outperform their competitors in performance and reliability. For example, the write speed of drives DVD+ RW higher than most devices DVD-RW . Some disks DVD-R are recorded at a speed close to that of DVD+ R , and with the advent of models DVD-RW The performance gap has narrowed even further.
Another difference between the “-” and “+” technologies is the way the disks in the drives are rotated. Drives CD, DVD-ROM and DVD-RW - These are constant line rate devices that provide a constant data transfer rate when reading disks. In these drives, the disks spin more slowly when reading information from external, longer tracks.
Types of optical drives
Depending on the functions available, optical drives can be divided into several main types.
1. CD- ROM- drives that allow reading information from media belonging to the group of compact discs.
2. DVD- ROM- drives that allow you to read information from different types CD and DVD media.
3. CD- RW- drives that allow you to read information from optical discs belonging to the CD group, as well as write to CD-R and CD-RW.
4. DVD- ROM/ CD- RW- so-called combined drives that allow you to read information from different types CD and DVD -media, as well as recording on CD-R and CD-RW.
5. DVD- RW, DVD+ RW, DVD± RW- universal recording drives that allow you to read information from different types CD and DVD media, as well as recording on CD-R, CD-RW , writable and rewritable DVD (set of supported DVD -carriers depend on the specific model).
To measure the speed characteristics of optical drives, conventional units are used, which differ for CD and DVD formats. The data read speed of 150 KB/s was chosen as the reference point (1x) for the CD group media. Therefore, 8x for CD drive corresponds to a data transfer rate of 1200 KB/s, 12x - 1800 KB/s, etc.
In case of DVD devices, the single speed is already 1350 KB/s. So 4x for DVD media corresponds to a speed of 5400 KB/s - which is equivalent to 36x on the scale CD .
In the characteristics of drives that support reading and/or writing of different types of opticaldisks, the maximum speed for each of them is usually indicated. Short designationThe speed characteristics of the carrier are called the speed formula. For example, in the case of a drive DVD - ROM speed formula 8/52 means maximum reading speed equivalent to 52x for CD and 8x for DVD . For drive CD - RW speed formula 32/24/48 means the maximum recording speed on CD - R And CD - RW respectively 32x and 24x and maximum speed readings 48x.
TechnologyLightScribe
One of the most interesting technological innovations of 2005 in the field of recordable optical discs was the technology LightScribe . It allows you to apply monochrome images to the decorative surface of disks High Quality directly into the recording drive.
The principle underlying the technology LightScribe , quite simple. As is known, under the influence of a laser beam, the active layer of recordable discs loses its transparency. By illuminating some areas of the working layer with a laser and leaving others untouched, a monochrome image can be formed using a recording drive.
At the beginning of 2004 the company HP announced the creation of an improved direct disc labeling system ( DirectDiscLabelingSystem ), which later received the commercial name LightScribe . This technology developed by specialists MitsubishiKagakuMedia (MKM) and HP . Unlike other technology - DiscT@2, LightScribe involves applying images not to the working layer of the disk, but from reverse side- where the label is usually located (of course, recordable discs for this must be equipped with an additional photosensitive layer).
To take advantage of technology LightScribe , you need to have three components: LightScribe -compatible recording drive, media with an additional photosensitive layer and special software. In this case, after finishing recording information, the user can turn the disk over and use a recording drive to apply an image to its decorative surface.
Of course, the implementation additional features will entail a slight increase in prices for recording drives and blank media. True, according to HP , implementation of support LightScribe will lead to an increase in the cost of the recording drive by about $10. Regarding media LightScribe , they are understandably more expensive to produce than conventional recordable discs, but the price difference will also be negligible.
In 2005 HP signed agreements to sell licenses to use this technology to some large manufacturers recording drives (in particular, LG, Toshiba, Philips and Lite-On (Sony)).
High-density optical media
Improvements in the capabilities of media systems and, as a consequence, the need for high quality data (video and audio) have led to the fact that this type of information has become cramped on the standard DVD . The development of new formats has been and is being carried out by various companies, but two standards have matured for commercial use.
1. Blu- rayDisc(from English blueray - “blue ray”, abbreviated BD ) - new generation optical drives high density, developed by a consortium of companies led by Sony . This standard has no common roots with DVD . The recording density per layer is 25 GB.
Note
When choosing a name for the new standard, the developers had to distort the word blue, since if spelled correctly it could not be used to register a trademark.
2. HDDVD ( High- DefinitionDVD) - new generation format developed Toshiba and NEC versus Blu-ray. HDDVD recognized as an evolutionary development of the standard DVD . The recording density of discs of this format is 15 GB per layer.
Until the end of 2007, it was not clear which standard would become dominant in the industry. However, the beginning of 2008 put the finishing touches on “ i". Toshiba Company announced the abandonment of this project in favor of the construction of factories for the production of flash memory, which it considers more promising.
Regarding Blu-ray , then it did not become popular and widespread overnight. As it turned out, the positions DVD are still strong, but consumers are in no hurry to switch to the new format. The rapid spread of the “blue ray” is also hampered by the high cost of the devices themselves. In light of global economic turmoil, it is still unclear how price dynamics for this type of device will develop in 2010. Discs Blu-ray retained the same dimensions that were characteristic of their predecessors CD and DVD : 120 and 80 mm. Due to the technological features of the coating, they were initially very sensitive to various types of mechanical stress. The developers of the prototypes even thought about protecting the media with a special cartridge. In the future, such a nuance would clearly not be in favor of the new standard. Therefore, engineering minds were still able to solve this problem. A new polymer coating has been found that can protect data from external influences. According to some sources, new disks can remain functional even if scratched by a screwdriver. It should be noted that these impressive capabilities have led to increased production costs for these media.
In Blu-ray technology A blue-violet laser with a wavelength of 405 nm is used for reading and writing. Let us remember that the usual DVD and CD use red and infrared lasers with wavelengths of 650 and 780 nm, respectively. This reduction made it possible to narrow the track by half compared to the usual DVD - up to 0.32 microns - and increase the data recording density.
Base speed 1x for BD is 36,864 Kbps, which is 27 times more than DVD , and is 243 times greater than CD . 2x bit rate players are capable of exceeding 73,000 Kbps.
Important characteristic new media is the volume. Native Compatibility BD with disks previous generations not provided for by the standard, but the association BDA recommends that all manufacturers implement support DVD to ensure backward compatibility.
Disk versions with a capacity of 100 GB and higher are in the process of development.
Latest generation of optical discs
Holographic multi-purpose disk (HolographicVersatileDisc) - a promising technology for the production of optical disks, which involves significantly increasing the amount of data stored on the disk compared to And .
It uses technology known as , which uses two : one - red, and the second - green, combined into one parallel beam. laser reads data encoded in a grid with layer close to the surface of the disk, while a laser is used to read auxiliary signals from a conventional CD layer deep within the disk. Auxiliary information is used to track reading position like a system on a regular hard drive. On or this information is embedded in the data.
