Magneto-optical drive
Encyclopedia
A magneto-optical drive is a kind of optical disc drive capable of writing and rewriting data upon a magneto-optical disc. Both 130 mm (5.25 in) and 90 mm (3.5 in) form factors exist. The technology was introduced commercially in 1985. Although optical, they appear as hard disk drives to the operating system
and do not require a special filesystem; they can be formatted as FAT
, HPFS, NTFS
, etc. Magneto optical drives are common in some countries such as Japan but have fallen into disuse in other countries.
The disc consists of a ferromagnetic material sealed beneath a plastic coating. The only physical contact is during recording when a magnetic head is brought into contact with the side of the disc opposite to the laser. During reading, a laser
projects a beam on the disk and, according to the magnetic state of the surface, the reflected light varies due to the Magneto-optic Kerr effect
. During recording, the laser power is increased so it can heat the material up to the Curie point
in a single spot. This allows an electromagnet
positioned on the opposite side of the disc to change the local magnetic polarization, and the polarization is retained when temperature drops.
Each write cycle requires both a pass to erase a region, and another pass to write information. Both passes use the laser
to heat the recording layer, the magnetic field is used for actually changing the magnetic orientation of the recording layer. The electromagnet reverses polarity for writing, and the laser is pulsed to record spots of "1" over the erased region of "0". As a result it takes twice as long to write data as it does to read it.
In 1996, a Direct Overwrite technology was introduced for 90 mm discs, to avoid the initial erase pass when writing. This requires special media.
By default, Magneto-optical drives verify information after writing it to the disc, and are able to report any problems to the operating system immediately. This means that writing can actually take three times longer than reading, but it makes the media extremely reliable, unlike the CD-R or DVD-R technologies upon which data is written to media without any concurrent data integrity checking. Using a magneto-optical disc is a lot more like using a diskette drive than using a CD-RW.
In a read cycle, the laser is operated at a lower power setting, emitting polarized light. The reflected light has a change in Kerr Rotation and Kerr Ellipticity which is measured by an analyzer and corresponds to either a logical 0 or 1.
Progress in magneto-optical technology received a boost in the spring of 1997 with the launch of Plasmon’s DW260 drive. This used Light Intensity Modulated Direct OverWrite
technology to achieve an increased level of performance over previous magneto-optical drives.
The 130mm drives were available in capacities from 650MB to 9.2GB. However, this was split in halves per the sides of the disk. The 2.6GB disks, for example, had a formatted capacity of 1.2GB per side. The 130mm drives were always SCSI. The 90mm discs had their entire capacity on one side with no capability to flip them over. The 90mm drives were available in SCSI, IDE, and USB formats. Capacities ranged from 128MB to 2.3GB.
While they were never particularly popular with consumers (the main consumer marketing being for the 90mm drives), the 130mm drives had some lasting service in corporate storage and retrieval. Optical libraries, such as the Hewlett Packard 40XT, were created to automate loading and storing of the disks. A self contained unit holding 16 or more disks and connected by SCSI to a host computer, the library required specialized archival software to store indexes of data and select disks. Popular uses were for legal document storage and medical imaging, where high reliability, long life, and (for the time) high storage capacity were required. The optical libraries could also manually be used on a Windows 2000/XP machine by selecting and ejecting discs under the Computer Management icon's Removable Storage Service, but this was cumbersome in practice.
computer was the first to offer this technology, but Canon eventually provided it to other customers.
Sony
MiniDisc
s are magneto-optical, and Sony produces many other formats of magneto-optical media.
Pinnacle Micro was a major manufacturer of magneto optical drives. 3.5" drives were 128MB and 230MB. 5.25" drives produced were 650MB and 1.3GB (Sierra), 2.6GB (Vertex) and 4.6GB (Apex). The Vertex and Apex were non-ISO standard drives and used proprietary media. Pinnacle Micro has ceased production of these products.
Maxoptix, a spin-off of Maxtor Corporation
, is a major manufacturer of 130 mm or 5.25″ magneto optical drives. A current model is the T7-9100 drive, which has a maximum capacity of 9.1GB and is downward read and write compatible with 5.2GB, 4.8GB, 4.1GB, 2.6GB, and 2.3GB magneto-optical disks, and read compatible with 1.3GB, 1.2GB, 650MB, and 600MB magneto-optical disks. Popular older models of 5.25″ Maxoptix MO drives are the T6 Star, T6-5200 and T5-2600 MO drives.
Fujitsu
was a major manufacturer of 90 mm magneto-optical drives, exceeding 2 GB in capacity, but they have discontinued production and sale of this product category.
PDO Konica Minolta is now the only manufacturer of 90 mm 3.5" magneto-optical drives. They have a 3.5" 1.3GB USB external pocket drive available for sale in the United States and Europe. Sources for this drive are, in the United States techwaredist.com, and in Europe teclogserv.com.
drives, which likewise combine ferromagnetic and optical technologies, albeit in a different manner. Flopticals are 21 megabyte 90 mm magnetic diskettes using optical tracks to increase the tracking precision of the magnetic head; from the usual 135 tracks per inch to 15,000 tracks per inch. No laser or heating is involved; a simple infrared LED
is used to follow the optical tracks, while a magnetic head touched the recording surface. The drives can also read and write traditional 90 mm diskettes, although not the 2.88 megabyte variety. Flopticals were manufactured by Insite Peripherals, a company founded by Jim Burke
.
in January 2004, Sony revealed a 1 gigabyte
capacity MiniDisc
known as "Hi-MD
." This sixfold increase in capacity is performed using a magneto-optical trick. To record a standard MiniDisc the writer uses an infrared
laser
to heat a spot of ferromagnetic material on the disc to above its Curie point
, then it is magnetised by a recording head as it cools. In contrast a high capacity MiniDisc uses tracks that are one sixth of the width of those used in standard MiniDiscs. By employing three magnetic layers, when a high capacity MiniDisc is read, the track expands to readable size. Specifically the three layers are, from read-face to print-face: a displacement layer, a switching layer, and a memory layer. When it isn't being read, the magnetic field in the memory layer is the same as those in the displacement and switching layers. When a laser shines on the track, the switching layer, which has a lower Curie point than the other layers, demagnetises. It decouples from the displacement layer, whose "magnetic fence" around the track weakens, temporarily causing the track to swell to a readable size. Hi-MD recorders can also double the capacity of regular minidiscs with special formatting that renders the disc unreadable (or writable) by non-Hi-MD minidisc recorders.
As with all removable storage media, the advent of cheap CD/DVD drives and flash memory has made them largely redundant. Magneto-optical disks in particular were expensive when new, and while highly reliable, the slow writing time also was a detriment.
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
and do not require a special filesystem; they can be formatted as FAT
File Allocation Table
File Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...
, HPFS, NTFS
NTFS
NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7....
, etc. Magneto optical drives are common in some countries such as Japan but have fallen into disuse in other countries.
Technical aspects
Initially the drives were 130 mm and had the size of full-height 130 mm hard-drives (like in IBM PC XT). 130 mm media looks similar to a CD-ROM enclosed in an old-style caddy, while 90 mm media is about the size of a regular 1.44MB floppy disk, but twice the thickness. The cases provide dust resistance, and the drives themselves have slots constructed in such a way that they always appear to be closed. Originally, MO discs were WORM (write once, read many) drives, but later read/write MO drives became available.The disc consists of a ferromagnetic material sealed beneath a plastic coating. The only physical contact is during recording when a magnetic head is brought into contact with the side of the disc opposite to the laser. During reading, a laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
projects a beam on the disk and, according to the magnetic state of the surface, the reflected light varies due to the Magneto-optic Kerr effect
Magneto-optic Kerr effect
Magneto-optic Kerr effect is one of the magneto-optic effects. It describes the changes of light reflected from magnetized media.-Definition:The light that is reflected from a magnetized surface can change in both polarization and reflected intensity...
. During recording, the laser power is increased so it can heat the material up to the Curie point
Curie point
In physics and materials science, the Curie temperature , or Curie point, is the temperature at which a ferromagnetic or a ferrimagnetic material becomes paramagnetic on heating; the effect is reversible. A magnet will lose its magnetism if heated above the Curie temperature...
in a single spot. This allows an electromagnet
Electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...
positioned on the opposite side of the disc to change the local magnetic polarization, and the polarization is retained when temperature drops.
Each write cycle requires both a pass to erase a region, and another pass to write information. Both passes use the laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
to heat the recording layer, the magnetic field is used for actually changing the magnetic orientation of the recording layer. The electromagnet reverses polarity for writing, and the laser is pulsed to record spots of "1" over the erased region of "0". As a result it takes twice as long to write data as it does to read it.
In 1996, a Direct Overwrite technology was introduced for 90 mm discs, to avoid the initial erase pass when writing. This requires special media.
By default, Magneto-optical drives verify information after writing it to the disc, and are able to report any problems to the operating system immediately. This means that writing can actually take three times longer than reading, but it makes the media extremely reliable, unlike the CD-R or DVD-R technologies upon which data is written to media without any concurrent data integrity checking. Using a magneto-optical disc is a lot more like using a diskette drive than using a CD-RW.
In a read cycle, the laser is operated at a lower power setting, emitting polarized light. The reflected light has a change in Kerr Rotation and Kerr Ellipticity which is measured by an analyzer and corresponds to either a logical 0 or 1.
Progress in magneto-optical technology received a boost in the spring of 1997 with the launch of Plasmon’s DW260 drive. This used Light Intensity Modulated Direct OverWrite
LIMDOW technology
Light Intensity Modulated Direct OverWrite technology uses a different write technology which significantly improves on the performance levels of earlier Magneto-optical devices and claims to be a viable alternative to hard disk drives in terms of performance and cost of ownership.LIMDOW disks and...
technology to achieve an increased level of performance over previous magneto-optical drives.
The 130mm drives were available in capacities from 650MB to 9.2GB. However, this was split in halves per the sides of the disk. The 2.6GB disks, for example, had a formatted capacity of 1.2GB per side. The 130mm drives were always SCSI. The 90mm discs had their entire capacity on one side with no capability to flip them over. The 90mm drives were available in SCSI, IDE, and USB formats. Capacities ranged from 128MB to 2.3GB.
While they were never particularly popular with consumers (the main consumer marketing being for the 90mm drives), the 130mm drives had some lasting service in corporate storage and retrieval. Optical libraries, such as the Hewlett Packard 40XT, were created to automate loading and storing of the disks. A self contained unit holding 16 or more disks and connected by SCSI to a host computer, the library required specialized archival software to store indexes of data and select disks. Popular uses were for legal document storage and medical imaging, where high reliability, long life, and (for the time) high storage capacity were required. The optical libraries could also manually be used on a Windows 2000/XP machine by selecting and ejecting discs under the Computer Management icon's Removable Storage Service, but this was cumbersome in practice.
Vendors
The NeXTNeXT
Next, Inc. was an American computer company headquartered in Redwood City, California, that developed and manufactured a series of computer workstations intended for the higher education and business markets...
computer was the first to offer this technology, but Canon eventually provided it to other customers.
Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
MiniDisc
MiniDisc
The disc is permanently housed in a cartridge with a sliding door, similar to the casing of a 3.5" floppy disk. This shutter is opened automatically by a mechanism upon insertion. The audio discs can either be recordable or premastered. Recordable MiniDiscs use a magneto-optical system to record...
s are magneto-optical, and Sony produces many other formats of magneto-optical media.
Pinnacle Micro was a major manufacturer of magneto optical drives. 3.5" drives were 128MB and 230MB. 5.25" drives produced were 650MB and 1.3GB (Sierra), 2.6GB (Vertex) and 4.6GB (Apex). The Vertex and Apex were non-ISO standard drives and used proprietary media. Pinnacle Micro has ceased production of these products.
Maxoptix, a spin-off of Maxtor Corporation
Maxtor
Maxtor Corporation, founded in 1982 and acquired by Seagate Technology in 2006, was an American manufacturer of computer hard disk drives, the third largest in the world immediately prior to acquisition...
, is a major manufacturer of 130 mm or 5.25″ magneto optical drives. A current model is the T7-9100 drive, which has a maximum capacity of 9.1GB and is downward read and write compatible with 5.2GB, 4.8GB, 4.1GB, 2.6GB, and 2.3GB magneto-optical disks, and read compatible with 1.3GB, 1.2GB, 650MB, and 600MB magneto-optical disks. Popular older models of 5.25″ Maxoptix MO drives are the T6 Star, T6-5200 and T5-2600 MO drives.
Fujitsu
Fujitsu
is a Japanese multinational information technology equipment and services company headquartered in Tokyo, Japan. It is the world's third-largest IT services provider measured by revenues....
was a major manufacturer of 90 mm magneto-optical drives, exceeding 2 GB in capacity, but they have discontinued production and sale of this product category.
PDO Konica Minolta is now the only manufacturer of 90 mm 3.5" magneto-optical drives. They have a 3.5" 1.3GB USB external pocket drive available for sale in the United States and Europe. Sources for this drive are, in the United States techwaredist.com, and in Europe teclogserv.com.
Floptical drives
Magneto-optical drives should not be confused with FlopticalFloptical
Floptical refers to a type of disk drive that combines magnetic and optical technologies to store large amounts of data on media similar to 3½-inch floppy disks. The name is a portmanteau of the words 'floppy' and 'optical'...
drives, which likewise combine ferromagnetic and optical technologies, albeit in a different manner. Flopticals are 21 megabyte 90 mm magnetic diskettes using optical tracks to increase the tracking precision of the magnetic head; from the usual 135 tracks per inch to 15,000 tracks per inch. No laser or heating is involved; a simple infrared LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
is used to follow the optical tracks, while a magnetic head touched the recording surface. The drives can also read and write traditional 90 mm diskettes, although not the 2.88 megabyte variety. Flopticals were manufactured by Insite Peripherals, a company founded by Jim Burke
Jim Burke
Jim Burke may refer to:*Jim Burke , American author*Jim Burke , Australian cricketer*Jim Burke , American illustrator*Jim Burke, the real name of the prolific letter column contributor TM Maple...
.
Recent progress
At the Consumer Electronics ShowConsumer Electronics Show
The International Consumer Electronics Show is a major technology-related trade show held each January in the Las Vegas Convention Center, Las Vegas, Nevada, United States. Not open to the public, the Consumer Electronics Association-sponsored show typically hosts previews of products and new...
in January 2004, Sony revealed a 1 gigabyte
Gigabyte
The gigabyte is a multiple of the unit byte for digital information storage. The prefix giga means 109 in the International System of Units , therefore 1 gigabyte is...
capacity MiniDisc
MiniDisc
The disc is permanently housed in a cartridge with a sliding door, similar to the casing of a 3.5" floppy disk. This shutter is opened automatically by a mechanism upon insertion. The audio discs can either be recordable or premastered. Recordable MiniDiscs use a magneto-optical system to record...
known as "Hi-MD
Hi-MD
In January 2004, Sony announced the Hi-MD media storage format as a further development of the MiniDisc format. With its release in later 2004 came the ability to use newly-developed, high-capacity 1 gigabyte Hi-MD discs, sporting the same dimensions as regular MiniDiscs.- Main features :* The...
." This sixfold increase in capacity is performed using a magneto-optical trick. To record a standard MiniDisc the writer uses an infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
to heat a spot of ferromagnetic material on the disc to above its Curie point
Curie point
In physics and materials science, the Curie temperature , or Curie point, is the temperature at which a ferromagnetic or a ferrimagnetic material becomes paramagnetic on heating; the effect is reversible. A magnet will lose its magnetism if heated above the Curie temperature...
, then it is magnetised by a recording head as it cools. In contrast a high capacity MiniDisc uses tracks that are one sixth of the width of those used in standard MiniDiscs. By employing three magnetic layers, when a high capacity MiniDisc is read, the track expands to readable size. Specifically the three layers are, from read-face to print-face: a displacement layer, a switching layer, and a memory layer. When it isn't being read, the magnetic field in the memory layer is the same as those in the displacement and switching layers. When a laser shines on the track, the switching layer, which has a lower Curie point than the other layers, demagnetises. It decouples from the displacement layer, whose "magnetic fence" around the track weakens, temporarily causing the track to swell to a readable size. Hi-MD recorders can also double the capacity of regular minidiscs with special formatting that renders the disc unreadable (or writable) by non-Hi-MD minidisc recorders.
As with all removable storage media, the advent of cheap CD/DVD drives and flash memory has made them largely redundant. Magneto-optical disks in particular were expensive when new, and while highly reliable, the slow writing time also was a detriment.
See also
- Domain Wall Displacement DetectionDWDDThe DWDD is a new magneto-optical reproducing technology developed Canon and Sony. The DWDD technology uses a physics phenomenon called domain wall displacement, which shortens the masks but does not need to change the laser beam. With such technology, the density of the magneto-optical disc could...
(DWDD), a new magneto-optical reproducing technology developed by Canon Inc.Canon Inc.is a Japanese multinational corporation that specialises in the manufacture of imaging and optical products, including cameras, camcorders, photocopiers, steppers and computer printers. Its headquarters are located in Ōta, Tokyo, Japan.-Origins:...
and SonySony, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
. - FlopticalFlopticalFloptical refers to a type of disk drive that combines magnetic and optical technologies to store large amounts of data on media similar to 3½-inch floppy disks. The name is a portmanteau of the words 'floppy' and 'optical'...
- Ultra Density OpticalUltra Density OpticalUltra Density Optical is an optical disc format designed for high-density storage of high-definition video and data.- Overview :...