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ned only to store digital data and were not initially capable of use as a digital video medium most first generation disc devices had an infrared laser reading head the minimum size of the laser spot is proportional to the wavelength of the laser so wavelength is a limiting factor upon the amount of information that can be stored in a given physical area on the disc the infrared range is beyond the long wavelength end of the visible light spectrum so it supports less density than shorter wavelength visible light one example of high density data storage capacity achieved with an infrared laser is 700 mb of net user data for a 12 cm compact disc other factors that affect data storage density include the existence of multiple layers of data on the disc the method of rotation constant linear velocity clv constant angular velocity cav or zoned cav the composition of lands and pits and how much margin is unused is at the center and the edge of the disc sony and philips developed the cd in the mid 1980s 16 bit samples of the analog signal were taken at the rate of 44 100 samples per second this sample rate was based on the nyquist rate of 40 000 samples per second required to capture the audible frequency range to 20 khz without aliasing with an additional tolerance to allow the use of less than perfect analog anti aliasing filters 21 the standard allows up to 74 minutes of music or 650 mb of data storage types of read only optical discs compact disc cd and derivatives audio cd video cd vcd super video cd cd video cd interactive laserdisc gd rom double density compact disc ddcd minidisc md md data hi md laserdisc edit in the netherlands in 1969 philips research physicist pieter kramer invented an optical videodisc in reflective mode with a protective layer read by a focused laser beam u s patent 5 068 846 filed 1972 issued 1991 kramer s physical format is used in all optical discs in 1975 philips and mca began to work together and in 1978 commercially much too late they presented their long awaited laserdisc in atlanta mca delivered the discs and philips the players however the presentation was a commercial failure and the cooperation ended in japan and the u s pioneer succeeded with the laserdisc until the advent of the dvd in 1979 philips and sony in consortium successfully developed the audio compact disc cd rom edit the cd rom format was developed by sony and philips introduced in 1984 as an extension of compact disc digital audio and adapted to hold any form of digital data the same year sony demonstrated a laserdisc data storage format with a larger data capacity of 3 28 gb 22 types of recordable optical discs magneto optical disc phase change dual write once read many worm magneto optical drive edit magneto optical discs are erasable media they can be written and read many times the media and drives were first introduced in late 1987 and early 1988 by sharp mci sony and others all using scsi interface capacity ranged from 512 mb on 130 mm media to 160 mb on 90 mm media 23 by 1998 there were more than 50 models offered by 12 vendors with media of 86 and 130 mm in diameter and offering capacities up to 2 600 mb almost all using scsi interface 24 worm drive edit in 1979 exxon star systems in pasadena ca built a computer controlled worm drive that utilized thin film coatings of tellurium and selenium on a 12 diameter glass disk the recording system utilized blue light at 457 nm to record and red light at 632 8 nm to read star systems was bought by storage technology corporation stc in 1981 and moved to boulder co development of the worm technology was continued using 14 diameter aluminum substrates beta testing of the disk drives originally labeled the laser storage drive 2000 lsd 2000 was only moderately successful many of the disks were shipped to rca laboratories now david sarnoff research center to be used in the library of congress archiving efforts the stc disks utilized a sealed cartridge with an optical window for protection u s patent 4 542 495 second generation edit second generation optical discs were for storing great amounts of data including broadcast quality digital video such discs usually are read with a visible light laser usually red the shorter wavelength and greater numerical aperture 25 allow a narrower light beam permitting smaller pits and lands in the disc in the dvd format this allows 4 7 gb storage on a standard 12 cm single sided single layer disc alternatively smaller media such as the dataplay format can have capacity comparable to that of the larger standard compact 12 cm disc 26 dvd and derivatives dvd video dvd audio dualdisc digital video express divx dvd ram dvd r hi vision ld nintendo gamecube game disc minidvd derivative wii optical disc dvd derivative super audio cd sacd enhanced versatile disc dataplay universal media disc umd ultra density optical dvd rom edit in 1995 a consortium of manufacturers sony philips toshiba panasonic developed the second generation of the optical disc the dvd 27 the dvd disc appeared after the cd rom had become widespread in society third generation edit third generation optical discs are used for distributing high definition video and videogames and support greater data storage capacities accomplished with short wavelength visible light lasers and greater numerical apertures blu ray disc and hd dvd uses blue violet lasers and focusing optics of greater aperture for use with discs with smaller pits and lands thereby greater data storage capacity per layer 25 in practice the effective multimedia presentation capacity is improved with enhanced video data compression codecs such as h 264 mpeg 4 avc and vc 1 blu ray and derivatives up to 400 gb experimental 28 29 bd r and bd re high fidelity pure audio avchd and avcrec bdxl and blu ray 3d ultra hd blu ray 4k blu ray and 8k blu ray 30 wii u optical disc 25 gb per layer hd dvd discontinued disc format up to 51 gb triple layer cbhd a derivative of the hd dvd format hd vmd professional disc announced but not released digital multilayer disk fluorescent multilayer disc forward versatile disc blu ray and hd dvd edit the third generation optical disc was developed in 2000 2006 and was introduced as blu ray disc first movies on blu ray discs were released in june 2006 31 blu ray eventually prevailed in a high definition optical disc format war over a competing format the hd dvd a standard blu ray disc can hold about 25 gb of data a dvd about 4 7 gb and a cd about 700 mb comparison of various optical storage media fourth generation edit the following formats go beyond the current third generation discs and have the potential to hold more than one terabyte 1 tb of data and at least some are meant for cold data storage in data centers 32 dubious discuss ultra hd blu ray archival disc optical disc archive announced but abandoned holographic versatile disc announced but not released ls r protein coated disc stacked volumetric optical disc 5d dvd 3d optical data storage not a single technology examples are hyper cd rom and fluorescent multilayer disc in 2004 development of the holographic versatile disc hvd commenced which promised the storage of several terabytes of data per disc however development stagnated towards the late 2000s due to lack of funding in 2006 it was reported that japanese researchers developed ultraviolet ray lasers with a wavelength of 210 nanometers which would enable a higher bit density than blu ray discs 33 as of 2022 no updates on that project have been reported overview of optical types edit name capacity experimental note 1 years note 2 laserdisc ld n a 1971 2007 write once read many disk worm 0 2 6 0 gb 1979 1984 compact disc cd 0 7 0 9 gb 1982 present electron trapping optical memory etom 6 0 12 0 gb 1987 1996 minidisc md 0 14 1 0 gb 1989 2025 magneto optical disc mod 0 1 16 7 gb 1990 present digital versatile disc dvd 4 7 17 gb 1995 present limdow laser intensity modulation direct overwrite 2 6 gb 10 gb 1996 present gd rom 1 2 gb 1997 2006 fluorescent multilayer disc 50 140 gb 1998 2003 versatile multilayer disc vmd 5 20 gb 100 gb 1999 2010 hyper cd rom 1 pb supposedly no working prototype 100 eb only theoretically 1999 present dataplay 500 mb 1999 2006 ultra density optical udo 30 60 gb 2000 present forward versatile disc fvd 5 4 15 gb 2005 2006 34 enhanced versatile disc evd dvd 2002 2004 hd dvd 15 51 gb 1 tb citation needed 2002 2008 blu ray disc bd 25 gb 50 gb 2002 present bdxl 100 gb 128 gb 1 tb 2010 present professional disc for data pdd 23 gb 2003 2006 professional disc 23 128 gb 2003 present digital multilayer disk 22 32 gb 2004 2007 multiplexed optical data storage mods disc 250 gb 1 tb 2004 present universal media disc umd 0 9 1 8 gb 2004 2014 holographic versatile disc hvd 6 0 tb 2004 2012 protein coated disc pcd 50 tb 2005 2006 m disc 4 7 gb dvd format 25 gb blu ray format 50 gb blu ray format 100 gb bdxl format 35 2009 present archival disc 0 3 1 tb 2014 2024 optical disc archive 0 3 5 5 tb 2012 2024 ultra hd blu ray 50 gb 66 gb 100 gb 128 gb 2015 present notes edit prototypes and theoretical values years from known start of development till end of sales or development recordable and writable optical discs edit main article optical disc recording technologies there are numerous formats of optical direct to disk recording devices on the market all of which are based on using a laser to change the reflectivity of the digital recording medium in order to duplicate the effects of the pits and lands created when a commercial optical disc is pressed formats such as cd r and dvd r are write once read many or write once while cd rw and dvd rw are rewritable more like a magnetic recording hard disk drive hdd media technologies vary for example m disc media uses a rock like layer to retain data for longer than conventional recordable media while being read only compatible with existing dvd and blu ray drives m disc media can only be written to using a stronger laser specifically made for this purpose which is built into fewer optical drive models surface error scanning edit this section needs expansion you can help by adding missing information july 2020 error rate measurement on a dvd r the error rate is still within a healthy range optical media can predictively be scanned for errors and media deterioration well before any data becomes unreadable 36 optical formats include some redundancy for error correction which works until the amount of error exceeds a threshold a higher rate of errors may indicate deteriorating or low quality media physical damage an unclean surface or media written using a defective optical drive precise error scanning requires access to the raw uncorrected readout of a disc which is not always provided by a drive as a result support of this functionality varies per optical drive manufacturer and model on ordinary drives without this functionality it is possible to still look for unexpected reduction in read speed as an indirect much less reliable measure 37 optical media such as cds and dvds can be scanned to detect errors and signs of deterioration well before data becomes unreadable these formats include built in error correction mechanisms which function by adding redundant data however once the rate of errors surpasses the correction threshold the media becomes vulnerable to failure a high error rate can signal physical deterioration low quality manufacturing surface contamination or data recorded by a faulty optical drive several specialized tools are available for performing error scans on optical media popular programs include nero discspeed k probe opti drive control previously known as cd speed 2000 and dvd info pro for windows for cross platform users qpxtool is available to help monitor and maintain optical media integrity each of these tools allows for detailed analysis of the error rates and conditions affecting optical discs error types edit there are different types of error measurements including so called c1 c2 and cu errors on cds and pi po parity inner outer errors and the more critical pi po failures on dvds finer grain error measurements on cds supported by very few optical drives are called e11 e21 e31 e21 e22 e32 cu and pof represent uncorrectable errors on data cds and dvds respectively thus data loss and can be a result of too many consecutive smaller errors 38 due to the weaker error correction used on audio cds red book standard and video cds white book standard c2 errors already lead to data loss however even with c2 errors the damage is inaudible to some extent blu ray discs use so called ldc long distance code s and bis burst indication subcode s error parameters according to the developer of the opti drive control software a disc can be considered healthy at an ldc error rate below 13 and bis error rate below 15 39 optical disc manufacturing edit main article cd manufacturing optical discs are made using replication this process can be used with all disc types recordable discs have pre recorded vital information like manufacturer disc type maximum read and write speeds etc in replication a cleanroom with yellow light is necessary to protect the light sensitive photoresist and to prevent dust from corrupting the data on the disc a glass master is used in replication the master is placed in a machine that cleans it as much as possible using a rotating brush and deionized water preparing it for the next step in the next step a surface analyzer inspects the cleanliness of the master before photoresist is applied on the master the photoresist is then baked in an oven to solidify it then in the exposure process the master is placed in a turntable where a laser selectively exposes the resist to light at the same time a developer and deionized water are applied to the disc to remove the exposed resist this process forms the pits and lands that represent the data on the disc a thin coating of metal is then applied to the master making a negative of the master with the pits and lands in it the negative is then peeled off the master and coated in a thin layer of plastic the plastic protects the coating while a punching press punches a hole into the center of the disc and punches excess material the negative is now a stamper a part of the mold that will be used for replication it is placed on one side of the mold with the data side containing the pits and lands facing out this is done inside an injection molding machine the machine then closes the mold and injects polycarbonate in the cavity formed by the walls of the mold which forms or molds the disc with the data on it the molten polycarbonate fills the pits or spaces between the lands on the negative acquiring their shape when it solidifies this step is somewhat similar to record pressing the polycarbonate disc cools quickly and is promptly removed from the machine before forming another disc the disc is then metallized covered with a thin reflective layer of aluminum the aluminum fi...