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Several 2 GB ML CD-based recorders were developed for release in 2002 (TDK's MLCDRW1000 and
Plextor's PX-ML3630), but never came to market. This was largely a business decision influenced by the rapid fall of CD-R/RW prices and the simultaneous rise in popularity of writable DVD technology.
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industry, the technique was originally developed and patented for optical disc recording at Optex
Corporation in the early 1990s (in conjunction with the University of Rochester) for use with their Electron Trapping Optical Media (ETOM). Although simple in principle, implementation of ML was
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MultiLevel recording refers to the use of multiple reflectivity values to encode data onto an optical disc. By using more than two levels, more information can be put into the minimum feature size. The following figure illustrates a MultiLevel code (note: colors are used only to represent
195:, storing about 2.5 bits per data cell. By using this code in combination with a smaller mark size and a more efficient error-correction code, the capacity of CD media was tripled. When applied to dual-layer DVD, ML-recording can increase capacity by a factor of 1.9.
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222:, media uniformity, read-head fluctuation, etc.) than a conventional CD/DVD system. To compensate, the ML logical-format devotes a substantial portion of bits (as forward-error correction coding) to enhance robustness against media defects and
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storage, in which multiple data surfaces are combined into a single disc. Multi-layer and multiLevel technique can be combined (as in dual-layer ML-DVD ROM), where ML-modulation is applied to each individual layer of the disc.
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Earman, Allen, "Optical Data
Storage With Electron Trapping Materials Using M-ary Data Channel Coding," Proceedings of the Optical Data Storage Conference, SPIE, Feb. 1992, San Jose, California. .
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157:. The codes used in most optical disc systems are binary, meaning that resulting surface has only two states: marks and non-marks. The following figure illustrates the
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Calimetrics went on to work on more advanced DVD and Blu-ray Disc versions of their technology, including a proposal to build a next generation version of
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To store information onto a physical surface, the data must be transformed into a series of marks, using a
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Because the edges are positioned on a grid that is finer than the minimum mark size,
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was formed in 2000 to help commercialize ML technology. Members eventually included
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272:"Calimetrics and Philips demonstrate 34GB ML Rewritable System Using Blue Laser"
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37:) was a technology originally developed by Optex Corporation and promoted by
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Binary EFM code used in DVDs and CDs; example marks and corresponding signal
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achieves about 1.5 bits per minimum-mark, even though it is a binary code.
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Proposed technology to increase the capacity of optical discs
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8-level ML code; example marks and corresponding signal
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The 8-level code used on the prototype systems is a
89:(BD) to as much as 60 GB. An optionally integrated
49:proposed that ML could increase the capacity of a
97:was also suggested. An industry group called the
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229:MultiLevel recording is sometimes confused with
210:challenging, in large part because data storage
145:(EVD). Calimetrics ceased operations in 2004.
198:MultiLevel optical recording is an example of
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19:Not to be confused with multi-layer or
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41:to increase the storage capacity of
85:to 7.1 to 10 GB and a single-layer
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266:USPTO Link to Optex M-ary patent
123:Mitsubishi Chemical Corporation
119:Matsushita Kotobuki Electronics
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1:
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180:differences in intensity):
161:code used in CDs and DVDs:
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203:pulse-amplitude modulation
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91:digital rights management
315:Optical computer storage
61:to 2 GB, a single-layer
143:Enhanced Versatile Disc
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93:(DRM) system entitled
220:operating temperature
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27:MultiLevel Recording
111:Sanyo Semiconductor
193:convolutional code
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278:. 2002-09-07
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87:Blu-ray Disc
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232:multi-layer
214:are highly
103:Calimetrics
99:ML Alliance
47:Calimetrics
39:Calimetrics
294:Categories
282:2006-10-24
240:References
149:Technology
95:MovieGuard
21:dual layer
216:nonlinear
212:channels
200:baseband
127:Verbatim
276:CDRInfo
207:telecom
115:Plextor
83:DVD-RAM
135:Yamaha
79:DVD+RW
75:DVD-RW
51:CD-ROM
71:DVD+R
67:DVD-R
59:CD-RW
35:M-ary
133:and
131:Teac
55:CD-R
174:EFM
159:EFM
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107:TDK
81:or
63:DVD
57:or
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29:(
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