Ultra Density Optical (UDO) is an optical disc format designed for high-density storage of high-definition video and data. The format was introduced by Sony to replace the Magneto-optical disc format.


An Ultra Density Optical disc, or UDO, is a 133.35 mm (5.25") ISO cartridge optical disc which can store up to 30 GB (gigabytes) of data. The second generation UDO2 media format was introduced in April 2007 and has a capacity of up to 80 GB. It utilizes a design based on the Magneto-optical disc, but uses Phase Change technology combined with a blue violet laser. A UDO/UDO2 disc that can store substantially more data than a magneto-optical (MO) disc. This is due to the shorter wavelength (405 nm) of the blue-violet laser employed. MOs use a 650 nm-wavelength red laser. Because its beam width is shorter when burning to a disc than a red-laser for MO, a blue-violet laser allows more information to be stored digitally in the same amount of space.

Current generations of UDO2 media store up to 60 GB.[1]


UDO optical disc storage media was developed as a replacement for the 9.1 GB Magneto-optical digital storage medium. The Ultra Density Optical was first announced by Sony on November 1, 2000.[2] It was later adopted with heavy investment by Plasmon, a UK technology company with extensive experience with computer archival backup systems and solutions.[3]

Currently, UDO/UDO2 is being championed by its development partners Plasmon, Asahi Pentax (responsible for the opto-mechanical assembly design), Mitsubishi Chemical, parent company of the Verbatim media storage brand, and various computer and IT solutions companies. Mitsubishi Chemical is the second major development partner of UDO media and the sole manufacturer of UDO media as of the 4th quarter of 2008.

On November 10, 2008, Plasmon creditors (led by Silicon Valley Bank) closed down Plasmon LMS (company) as CEO Stephen 'FX' Murphy was unable to secure funding to keep the money-losing company afloat. The UDO media factory in the UK was shut down and dismantled.

On January 13, 2009, Alliance Storage Technologies, a Colorado Springs Manufacturer of optical technology and Service Provider, acquired the assets of Plasmon (including UDO and UDO2 technology) in a liquidation sale. ASTI currently sells and supports UDO technologies sold under the Plasmon brand.[4]


ECMA-380: Data Interchange on 130 mm Rewritable and Write Once Read Many Ultra Density Optical (UDO) Disk Cartridges –Capacity: 60 Gigabytes per Cartridge – Second Generation[5]

Writing technology

UDO uses a Phase Change recording process that permanently alters the molecular structure of the disc surface.

Disc format

There are three versions of UDO/UDO media: a True WORM (Write Once Read Many), an R/W (Rewritable), and Compliant WORM (shreddable WORM).

The UDO Rewritable format uses a specially formulated Phase Change recording surface that allows recorded data to be deleted and modified. In practice, UDO rewritable media operates like a standard magnetic disc. Files can be written, erased and rewritten, dynamically reallocating disc capacity. Rewritable media is typically used in archive applications where the stability and longevity of optical media are important, but archive records change on a relatively frequent or discretionary basis. Rewritable media is typically used in archive environments where data needs to be deleted or media capacity re-used.
True write once
The UDO True Write Once format uses a different phase change recording surface than the rewritable media. Unlike rewritable media, the write once recording surface cannot be erased or altered, making Write Once the most stable in terms of data integrity, because the physical record is kept authentic. This level of data integrity is not usually matched by other magnetic disc or tape technologies using normal write once emulation.
Compliant write once media
UDO Compliant Write Once media has the same operational properties as UDO True Write Once media but with one clear and important difference. Through the use of a specially designed “shred” operation, individual records written to Compliant Write Once media can be destroyed once their retention period expires. The shred function is controlled at an application level and operates only on Compliant Write Once media.

Magneto-optical comparison

The table below summarizes the differences between conventional Magneto-Optical specifications and those of the enhanced Ultra Density Optical disc.[6]

Disc 5.25-inch UDO Rewriteable 5.25-inch UDO Write Once 5.25-inch MO system (9.1 GB)
Disc diameter 130 mm 130 mm 130 mm
Disc thickness 2.4 mm 2.4 mm 2.4 mm
Cartridge size Same as ISO 130 mm (135 x 153 x 11 mm) Same as ISO 130 mm (135 x 153 x 11 mm) ISO 130 mm (135 x 153 x 11 mm)
Number of physical tracks 96,964 96,964 49,728
Sector size 8 kB 8 kB 4 kB
Number of sectors 2,504,407 2,504,407 1,118,880
Data area 29.0-61.0 mm 29.0-61.0 mm 29.7-62.5 mm
Designated[a] laser wavelength Violet (405 nm) Violet (405 nm) 660 nm
Objective lens (NA) 0.85 0.85 0.575
Recording layer Phase change Phase change Magneto-optical
Recording format Land & groove Land & groove Land & groove
Recording side Both sides Both sides Both sides
Track pitch 0.33 μm 0.33 μm 0.65 μm
Minimum bit length 0.13 μm 0.13 μm 0.3 μm
Recording density 15.0 Gb/in² 15.0 Gb/in² 3.3 Gb/in²
Transfer rate 4-8 MB/s 4-8 MB/s 3-6 MB/s
Error correction LDC LDC LDC
Modulation RLL (1,7) RLL (1,7) RLL (1,7)
  1. ^ Different types of lasers may read the disc depending on the pit sizes but not write.

Drive mechanism

UDO Drives Specifications Summary

UDO comes in both internal and external drive guises. External drives are also available as part a robotic autoloader. All current drives are designed for heavy duty use.

Laser and optics

UDO systems use a blue-violet laser operating at a wavelength of 405 nm, similar to the one used in Blu-ray Disc, to read and write data. Conventional MOs use red lasers at 660 nm.[7]

The blue-violet laser's shorter wavelength makes it possible to store more information on a 13 cm sized UDO disc. The minimum "spot size" on which a laser can be focused is limited by diffraction, and depends on the wavelength of the light and the numerical aperture of the lens used to focus it. By decreasing the wavelength, using a higher numerical aperture (0.85, compared with 0.575 for MO), the laser beam can be focused much more tightly. This produces a smaller spot on the disc than in existing MOs, and allows more information to be physically stored in the same area. [1]

The opto-mechanism design of current Plasmon UDO drives was jointly developed with Asahi Pentax.


Archival storage

Currently UDO has an expected data archival life of around 50 years. Apart from the storage size, the discs (like Magneto Optical discs) are designed for durability and long term reliability.

Secure video

A company called Blu-Laser Cinema announced in June 2005 that it was launching a new player using the UDO format to provide a secure viewing and editing platform for film production houses. Targeted towards the high-end video editing and production community, the unit featured a smart card reader and a USB dongle with an embedded biometric fingerprint reader to allow access only to authorized users.[8]


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The core technology for UDO is essentially similar to Blu-ray Discs, as well as PDD (all were developed by Sony), although there are a number of key differences; the primary ones being:

Data authenticity and integrity
UDO provides absolute data authenticity for applications where archived information must remain 100% unchanged – banks and legal institutions, for example. UDO uses a phase change recording process that permanently alters the molecular structure of true write once media, ensuring data is integral at the most fundamental level.
Long-term data retention
Long term archival storage. The design of the UDO, with a tested, stable recording surface, protective coating, and encasement in a cartridge, is expected to give it at least 50 years storage life, minimizing the frequency of data migration and management for firms requiring storage for large amounts of important data. The UDO disc design is a robust design and reduces the potential for contamination of media.
High capacity and scalability
Blue laser technology gives the 30 GB UDO more than three times the capacity of previous generation MO (Magneto Optical) and DVD technologies. Being removable, UDO cartridges, combined with off-line media management capabilities typical of optical storage libraries, makes UDO a much more scalable format.[clarification needed] Rarely used data can be removed from a library, freeing up capacity yet remaining managed and accessible.[clarification needed]
Rapid information access
UDO has a fast 35-millisecond random access capability. An 8 KB sector size helps read/write performance across a wide range of file sizes. UDO is slightly faster[clarification needed] as it operates at Constant Angular Velocity (CAV); during reads and writes, the disc spins continuously at a very high speed. In rewritable applications, UDO has a unique, direct over-write capability, doubling rewrite speeds by eliminating the need for a dedicated erase pass.[clarification needed]
Low total cost of ownership
The cost of a UDO media compares favorably with MO or DVD solutions and has a higher capacity. UDO's ISO standard 5.25-inch (133 mm) media cartridge allows the use of MO and UDO media in the same library, if supported by the connectivity software and the controlling application. EMC Legato DiskXtender, one of the most popular Library management and connectivity software does not support this mode of operation.


  1. ^ "Plasmon Launches UDO2". 2007. Retrieved 2007-04-07.
  2. ^ "Sony Develops Next Generation Optical Disk Storage System For the Data Server Market". 2006. Retrieved 2006-08-25.
  3. ^ "Plasmon Adopts New High Capacity 5.25 inch Optical Data Format" (PDF). 2006. Retrieved 2006-08-25.
  4. ^ "Alliance Storage Technologies Announces Successful Completion of the Purchase of Plasmon Assets". 2006. Retrieved 2009-01-13.
  5. ^ Ecma International (December 2007). "Data Interchange on 130 mm Rewritable and Write Once Read Many Ultra Density Optical (UDO) Disk Cartridges –Capacity: 60 Gbytes per Cartridge – Second Generation" (PDF).
  6. ^ "Sony Develops Next Generation Optical Disk Storage System For the Data Server Market" (Press release). Sony. November 1, 2000. The press releases on this website are provided for historical reference purposes only.
  7. ^ "Sony Develops Next Generation Optical Disk Storage System For the Data Server Market". 2006. Retrieved 2006-08-25.
  8. ^ "Sony Develops Next Generation Optical Disk Storage System For the Data Server Market" (PDF). 2006. Retrieved 2006-08-25.