CA1229164A - High density codes for optical recording - Google Patents
High density codes for optical recordingInfo
- Publication number
- CA1229164A CA1229164A CA000458854A CA458854A CA1229164A CA 1229164 A CA1229164 A CA 1229164A CA 000458854 A CA000458854 A CA 000458854A CA 458854 A CA458854 A CA 458854A CA 1229164 A CA1229164 A CA 1229164A
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- Prior art keywords
- holes
- symbol
- positions
- hole
- groups
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Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/2407—Tracks or pits; Shape, structure or physical properties thereof
- G11B7/24085—Pits
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/14—Digital recording or reproducing using self-clocking codes
- G11B20/1403—Digital recording or reproducing using self-clocking codes characterised by the use of two levels
- G11B20/1407—Digital recording or reproducing using self-clocking codes characterised by the use of two levels code representation depending on a single bit, i.e. where a one is always represented by a first code symbol while a zero is always represented by a second code symbol
- G11B20/1419—Digital recording or reproducing using self-clocking codes characterised by the use of two levels code representation depending on a single bit, i.e. where a one is always represented by a first code symbol while a zero is always represented by a second code symbol to or from biphase level coding, i.e. to or from codes where a one is coded as a transition from a high to a low level during the middle of a bit cell and a zero is encoded as a transition from a low to a high level during the middle of a bit cell or vice versa, e.g. split phase code, Manchester code conversion to or from biphase space or mark coding, i.e. to or from codes where there is a transition at the beginning of every bit cell and a one has no second transition and a zero has a second transition one half of a bit period later or vice versa, e.g. double frequency code, FM code
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/14—Digital recording or reproducing using self-clocking codes
- G11B20/1403—Digital recording or reproducing using self-clocking codes characterised by the use of two levels
- G11B20/1423—Code representation depending on subsequent bits, e.g. delay modulation, double density code, Miller code
- G11B20/1426—Code representation depending on subsequent bits, e.g. delay modulation, double density code, Miller code conversion to or from block codes or representations thereof
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/007—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track
- G11B7/013—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track for discrete information, i.e. where each information unit is stored in a distinct discrete location, e.g. digital information formats within a data block or sector
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- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Optical Recording Or Reproduction (AREA)
- Signal Processing For Digital Recording And Reproducing (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Disclosed is a high density code for optical recording. Eight bits of binary data are encoded into a 4/15 block code with the constraint that there be at least two symbol positions between holes or groups of holes. Additionally, a hole is never written in the 15th symbol position, and codes having a high number of sequential holes either within a symbol or between symbols are eliminated.
Disclosed is a high density code for optical recording. Eight bits of binary data are encoded into a 4/15 block code with the constraint that there be at least two symbol positions between holes or groups of holes. Additionally, a hole is never written in the 15th symbol position, and codes having a high number of sequential holes either within a symbol or between symbols are eliminated.
Description
The invention relates generally to the field of optical recording apparatus and more specifically to codes for recording data on the optical media.
In high density optical recording, it often is preferred to have a clock or pilot signal prerecorded on the optical media which is read by the optical system when the data is read. In order to read a prerecorded pilot signal or clock the data must be recorded in such a manner that there appears a null in the frequency spectrum upon reading the data. The frequency of the clock is chosen to coincide with the null in the frequency spectrum of the data.
One such code generating a null in the frequency spectrum is the so-galled quad phase code. In this code two bits of binary code are encoded into a symbol. In optical recording, the two bits are encoded by writing holes corresponding to the bit pattern in the first half of a symbol and writing holes corresponding to the inversion of the bit pattern in the second half of the symbol. Thus every symbol has four symbol positions. A binary 00 would be written with two holes in symbol positions 1 and 2 and 2 spaces written in symbol positions 3 and 4. Binary pattern 01 would have a hole in symbol position 1 and a hole in symbol position with no holes in positions 2 and 3.
Binary 10 would have a hole in positions 2 and 3 and no holes in positions 1 and 4 and bit binary 11 would have no holes in positions 1 and 2 and holes in positions 3 and 4.
Quad phase coding produces a null in the frequency spectrum of the data at a frequency Fox corresponding to l/2 of the frequency of symbol post-lions. This frequency coincidentally is the frequency of the binary data, i.e. 4 symbol positions correspond to 2 bits of binary data.
In high density optical recording it is desirable to space the sum-boy positions so closely together that the size of a hole, that is the diameter of a hole J may be greater than 1 symbol position. This produces obvious problems when reading and decoding a symbol in that the signal due to a symbol "spreads" into adjacent symbol positions. This problem is magnified due to the optics of the laser read beams commonly employed in optical recording systems. These beam spots are yo-yo I
1 nut sharply defined beams but rather possess the form of a
In high density optical recording, it often is preferred to have a clock or pilot signal prerecorded on the optical media which is read by the optical system when the data is read. In order to read a prerecorded pilot signal or clock the data must be recorded in such a manner that there appears a null in the frequency spectrum upon reading the data. The frequency of the clock is chosen to coincide with the null in the frequency spectrum of the data.
One such code generating a null in the frequency spectrum is the so-galled quad phase code. In this code two bits of binary code are encoded into a symbol. In optical recording, the two bits are encoded by writing holes corresponding to the bit pattern in the first half of a symbol and writing holes corresponding to the inversion of the bit pattern in the second half of the symbol. Thus every symbol has four symbol positions. A binary 00 would be written with two holes in symbol positions 1 and 2 and 2 spaces written in symbol positions 3 and 4. Binary pattern 01 would have a hole in symbol position 1 and a hole in symbol position with no holes in positions 2 and 3.
Binary 10 would have a hole in positions 2 and 3 and no holes in positions 1 and 4 and bit binary 11 would have no holes in positions 1 and 2 and holes in positions 3 and 4.
Quad phase coding produces a null in the frequency spectrum of the data at a frequency Fox corresponding to l/2 of the frequency of symbol post-lions. This frequency coincidentally is the frequency of the binary data, i.e. 4 symbol positions correspond to 2 bits of binary data.
In high density optical recording it is desirable to space the sum-boy positions so closely together that the size of a hole, that is the diameter of a hole J may be greater than 1 symbol position. This produces obvious problems when reading and decoding a symbol in that the signal due to a symbol "spreads" into adjacent symbol positions. This problem is magnified due to the optics of the laser read beams commonly employed in optical recording systems. These beam spots are yo-yo I
1 nut sharply defined beams but rather possess the form of a
2 Gaussian curve, with Hoff power widths about equal to the
3 diameter of the holes produced in writing with the same spot.
4 For holes or groups of holes, the half power width of a signal caused my the reading roughly corresponds to the diameter ox 6 the holes. Thus there will be considerable read signal power 7 extending beyond the diameter of a hole.
9 These two problems, i.e. hole diameter versus symbol position spacing and read signal overlap, combine together to 11 limit the bit densities in optical recording.
18 There are a very larcJe number of fixed block codes that 14 will generate a null in the frequency spectrum. however, the I prior art his not shown a methodology to find the code or codes 16 which permit the highest recording density in an optical 18 recording environment.
lug .
21 the invention comprises maintaining a predetermined 22 spacing between menials or between menials and groups of 23 holes or between groups of holes in fixed block codes having 24 symbols which contain at a minimum greater than two holes.
I waving symbols with more symbol positions and more holes 26 permits a greater number of bits to be encoded by a symbol.
2? ~aintainln3 a minimum spacing between menials, etc., permits 28 symbol position spacing to be minimized relative to hole size 29 and still permit correct decoding of the symbol. As a result, more bits my be recorded vow lets physical space.
1 The spacing between menials, etc., must be a multiple of 2 symbol positions Applicant therefore specifies that the 3 minimum spacing be two or more symbol positions, ire , Do or 4 greater. The choice of D 2, Do Do etc., depends upon the characteristics of the particular optical recording 6 environment. Generally, the higher the ratio of the largest 7 expected hole diameter to symbol position size, the larked 8 must be.
Within the family of codes which have a null in their 11 frequency spectrum to permit the use of a prerecorded clock, 12 the number of holes within a symbol must. be a multiple of two, 13 i.e., two, four, six eight. The inventor has determined that 14 the following pre-clock compatible codes permit the highest bit densities of 3 or fewer bits in optical recording for hole 16 diameters of 1.~5 micron or less hod for greater than 1.45 Al microns, respectively, both with a laser spot diameter of 18 approximately 0.8 microns.
The first code is a 4/15 code and the second a 6/13 code.
22 The first code essentially comprises a symbol of 15 positions 23 shaving therein four holes with the following constraints:
there must be at least two empty symbol positions between hole 24 or groups of hole, the Thea position must never have a hole 26 and pattern having four holes in a row within a symbol or 27 three hole in a row adjacent symbol boundaries being 28 eliminated. The second code essentially comprise a symbol of 29 18 positions having therein holes with the following constraint: there mutt be At least 3 empty position between holes or groups of holes, the Thea and Thea position must never 31 have a hole and patterns having 6 and 5 holes in a row or 4 32 holes in a row at the first your position being eliminated.
The requirement of specifying thy limit on the number of holes in a row reduces the burden on the laser diodes commonly employed in optical recording systems.
Thus, in accordance with a broad aspect of the invention, there is provided a system for recording and reading coded symbols from a record carrier, comprising a record carrier adapted for having two media states, an unaltered state and an altered state; means for inducing and sensing a signal responsive to said media states, the signal strength varying according to the media state, and being stronger for said altered state, and further varying to a degree according to the length of the altered state, the longer the altered state, the stronger the signal; information recorded on said record carrier in the form of altered media states, a hole comprising an altered media state of a predetermined length, a Manuel comprising a hole having unaltered media states before and after the altered state of a single hole, a group of holes comprising a plurality of adjacent holes with substantially no unaltered media states between adjacent holes and unaltered media states before and after the group of holes; said information further recorded on said record carrier with a spacing between groups of holes and other groups of holes or menials such that the signal strength read at a point midway between the group of holes and the other groups of holes or menials is less than the maximum signal strength caused by a Manuel.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a graph of the intensity of the signal detected by the read optics of an optical disk recording system vs. symbol position where the hole diameter is 0.9 microns, the symbol position size is 0.6 microns and the half power width of the light spot 0.8 microns;
foe - 5 -I
Figure 2 is a graph of the same code pattern as in Figure 1, but with a hole diameter of 1.25 microns;
Figure 3 is a graph similar to Figures 1 and 2 but with a hole pattern having two consecutive holes/ a space, followed by a hole;
Figure 4 is a graph similar to Figure 3 but with two consecutive holes, two spaces, followed by a hole;
Figure 5 is a graph of the worst case "eye" openings of several codes. The ordinate represents fractions of the Manuel amplitude and the abscissa represents the hole size parameter divided by the distance traveled during one clock period; and Figure 6 is a block diagram of optical recording apparatus for implementing the code of -the preferred embodiment.
pa - pa -3L2;~6 3 In many optical recording systems coded symbols represent 4 binary data. It it conventional for block code with a fixed number of holes Jo determine the location of the hole or holes 6 within these symbols by comparing the signals received from 7 each symbol position with the signals received from each of the 8 other symbol positions and choosing the M highest signals 9 detected to by the location of the hole or holes. ON is the lo number of holes in a symbol, a predetermined fixed number.) 11 For example, if a given symbol has four positions out of which 12 two positions must contain holes, conventional optical reading 13 apparatus compares the hole-associated signal power in each of 14 the four positions, and Chihuahuas the two highest powered positions as briny the positions where the holes are located.
The abscissa of Fig. l represents the snowball pattern 18 Lyle written on optical media, with the ones corresponding 19 to holes and the Eros corresponding to spaces. In this on regard, the spaces are represented a elevations on the 21 abscissa and holes are represented as depressions along the 22 abscissa. the entire group of eight positions represent one 23 symbol. Thy ordinate of jig. l represents the intensity of the 24 signals generated by the holes in conventional optical recording read optics and electronics. (If the signal is 26 observed in reflection, the signal kissed by a hole it 27 actually the inversion of the power ox the reflected beam 28 while if the signal is measured in transmission where the beam 29 from one wide of the dyes is observed from the other bidet the signal is a direct function of received laser power.) The ~Z1~9~6~
1 dotted curves in the Figure are top intensity of the read inlay associated with each owe the three holes in thy Figure.
3 These curve ore approximately Gaussian in shape with the half 4 power level of the signal roughly corresponding to the teeter 6 of the hole. In the Figure the hole diameter is taken to be 6 .9 microns while tube yummy position width, or the distance 7 between symbol center, is taken to be .6 microns. The solid & line in the Figure represents the summation ox the signals 9 caused by adjacent holes.
11 Inspection of this Figure shows that at no point does the 12 signal generated by the holes or adjacent holes sum to a level 13 where the peak, generated by the holes themselves, are 14 indistinguishable. An optical system can correctly read the 16 symbol pattern shown in Fig. 1 because it can correctly 16 identify the peaks associated with the holes and also determine 17 the valleys associated with the spaces.
19 however, media sensitivity variations and variations in the optical recording system (light intensity/ beam 21 aberrations) will result in a distribution of hole diameters.
22 Occasionally, holes of considerably layer diameter are 23 written. For example, in Fig. 2, the hole diameter it now 1.25 24 microns. The same symbol pattern, 01010010, it represented along the beta as way represented in Fig 1. Again, the 26 dotted line represent signal venerated by the holes and the 27 solid line represent the summation of the iguanas generate by nearby hole. inspection of the Figure shows hut there it;
I very little fall-off in signal strength between the holes of the 30 101 pattern Conventional ~nalogue comparison system I
1 attempting to determine whether this space was a hole or a I. space Jay incorrectly decide that it was a hole and not a 3 space. The last hole in the Figure may then be read as a 4 space, as the comparison system will identify only three holes 6 in a symbol, not four.
7 The first two Figures represent symbol patterns generated 8 by isolated single holes, otherwise known a menials. Fig. 3 shows a signal pattern generated by two holes written in a row. The symbol pattern yin Pig. 3 along the abscissa it a 11 01101001 pattern. The diameter of a hole is 1.25 microns and 12 the symbol positron dance is 0.6 microns. When two holes 13 are written adjacent to each other, they overlap end will look 14 like one large, long hole as illustrated in the Figure. This one large, long hole generates a signal of somewhat higher 16 intensity than a ~lgnal generated by a signal hole, as shown in 17 the Figure. Compare the signal generated by the group of two 18 holes with the signals generated by the following two I menials .
20 .
21 Again, in the Figure, the dotted Lowe represent the 22 signal generated by the holes themselves. As before the 23 only patterns are Gurney in shape, hut thy Renewal from 24 the double hole has Gaussian shaped edges and a flatter top.
The solid line represent the summation of the igloos of 26 nearby holes. Apparatus looking for the symbol positions with 27 the four highest signals would incorrectly find holes at 28 positions 2, 3, 4 and 5 and space at all other positions 29 because at option 2, I end S, toe signal strength 30 generated by the hole pattern 1101 at these poStionJ; it higher 81 at all point, including the space, than the signal generated I by the Manuel at position 8.
lZZ9164 1 Now turning to Fig. 4, the abscissa shows a symbol pattern 2 of 01100100 and a hole diameter of 1.25 microns and a symbol 3 petunia distance of Jo micron. The read apparatus can 4 correctly decode the p~51t$0ns of the three holes because the signal due to the double hole and the signal of the following 6 Manuel do not sum at the spaces to a signal which 7 approximately equals or exceed the signal generated by the 8 Manuel itself, this even though the signal generated by the 9 double hole it greater in magnitude than the signal generated by the subsequent Manuel and overlaps with significant signal 1 power three position away.
I The above process can be extended to groups so three hole 14 in a row. However, the signal power generated by three holes in a row it not significantly greater than the signal power 18 generated by two holes in a row. Again, referring to Fig. 4, 17 the pattern generated by having holes in the first three 18 positions of the illustrated symbol rather than having holes 19 generated in only positions 2 and 3, would be Mueller to the illustrated pattern and the read apparatus could correctly 21 decode the holes at positions I 2, 3 and 6 and spaces in 22 positions 4 and 5.
24 As illustrated in figure 3 and 4, it is necessary that there be at least one empty position between adjacent symbols.
I Otherwise, ascent Smalley having a 1101 or a 1011 pattern 27 across the boundary may incorrectly have the space identified I as a hole. These patterns may futile occur with an acceptor 29 position between ~yTnbol~, however whether the signal strength of a hole it present at Tess extra position it irrelevant, 'I ;~Z9164 1 because it it not included in the comparison apparatus as one 2 of the positions that may have a hole.
4 Fig 4 have been analyzed to owe that the presence of 6 two puce between holes and wrap ox holes permit correct 6 decoding of the symbol. Similar reasoning indicates the 7 further advantage of having 3 spaces between hoses or strings 8 of holes and at least two empty positions at symbol boundaries 9 when the size of the hole diameter relative to the size of the 10 fumble position increases.
I .
12 In determining which code will generate the maximum bit 13 density, it is desirable to inspect only those codes which 14 encode a multiple of the power of two bits, that is, two bits, 15 four bit, eight bits, sixteen bits, etc. For example, the quad phase code encodes two bits, and has four symbol positions 17 and two holes within a symbol. A occlude two out of eight :18 position code tiptop), has eight positions in the symbol and 19 encodes four bits of information. In general, in order to encode two bits of information in a snowball, the code must have I at least 4 different hole patterns To decode four bit in a : symbol the rode just have at least sixteen different hole I patterns. Similarly, to encode eight bits of information, the 24 code must have at least two hundred fifty-six different I pattern.
27 To a certain limit, the more holes there are in symbol, the 28 greater the number of possible pattern that can by contained 29 within the symbol. For example, in a four position symbol, if the code was constrained to have only one hole per symbol, ~229~64 1 there would be only four different patterns possible, that is a 2 hole in position one in position two in position three or in 3 position four. however, if the ~ymhol could have 2 holes the number of possible codes is now 6, i.e.
Lowe 1~10 Lyle 0110 lo 0011 inn the quad phase code the patterns 1010 and 0101 are 9 eliminated because they do not follow the constraint that the pattern of the first two positions be inverted in the second 11 two positions 80 a to permit a null in the frequency spectrum,) 13 It can be seen that finding the code which will optimize 14 the number of bits encoded over a unit ox space is difficult and complex Fig. 5 represents the finings of the inventor.
16 The abscissa in Fig. 5 represents hole size parameter sigma 17 divided by the minimum symbol position spacing or distance 18 traveled over half a clock period. For the laser poetizes 19 used, below a hole diameter of .95 microns the hole size parameter's calculation depends upon the particular optics and 21 the size of the hole. The formula for its calculation it I complex an not relevant to our discussion, as well, it is 23 known to those skilled in the art. However, for hole sizes 24 above .95 microns, sigma is approximately equal to thus the I hole diameter. Thus 9 the dimension of the abscissa it directly 26 related to hole diameter/ generally by the factor of Thea of 27 the hole diameter. The dimension of the balsa it further 28 inversely related to symbol position spacing. the bit 29 densities are held constant, i.e., lo micron bit the symbol position spicing varies inversely with the number of position 31 within a ~y~bol. Thus;, the abscissa dimension Lyon varies 32 directly with the nuJnber of symbol positiveness of a code.
.
2;~9~
l The ordinate of the Figure represents the worst case wrap 2 opening in fractions of the signal generated in the read 3 apparatus by nonohole. An eye opening can be defined as 4 the difference between the amplitude of the signal due to a 6 Manuel and the amplitude of a summation signal due to 6 adjacent holes measured at a space, Lee Fits. lo Formulae 7 for calculating an Eye pattern from a given code pattern, 8 ¦ hole size, spot size, etc., are known to the art. The worst 9 ¦ case eye" can be derived by inspection by loolcing at the code 10 ¦ patterns having the least distance between holes or groups of if 1 holes. The smaller the eye", the higher the chance of 12¦ erroneous decoding because of the inevitable noise in the 13 ¦ system.
I . .
15 ¦ slaving defined the methodology by which to determine the 16 worst case eye pattern of a given code, the inventor also 17 made the following comparison criteria. Compared codes were to 18 ¦ hove the same bit density, that is that the same number Of bin 19 cry bits were to be encoded per unit of lengtl1 on the Ned.
MU The standard example owe comparison way chosen to be lo microns 21 ¦ per bit (one bit per 1.2 microns). Symbols having different 22 1 real lengths and position spacing may be compared meaningfully 23 ¦ in this manner. If two bits are encode the entire symbol 24 ¦ is 2.4 microns in length lo micron bit x to bits)). If I four bits are encoded, the symbol is 4.8 microns long. If 26 eight bits are encoded, the symbol is 9.6 microns long.
I
I All odes shown in Figure 5 hove the same bit density, lo 29 micron per bit. All have a null in the frequency spectrum.
30 The first idea line in the Figure represents the worst case 1 Rove" opening for DYE ode where Do Moses that there is a 2 minimusn of 1 symbol position between menials or between 3 Manuel and groups of holes or between groups of holes. The 4 second solid line is the worst case Sue opening for Do B codes. Roy third solid line is for O'G3 codes. The eye-6 opening were determined for three hole diameter issue: I .95 q micron, I 1.25 microns and I 1.45 microns. The code 8 having the best worst case eye patterns are lis'c~d on the 9 Figure. The Tony code represented by a dot is a so-called 2 out of 9 code. This is tile same as a out ox 8 code 11 ¦ ("'wrap ) previously mentioned With the addition of Thea "empty"
12 position. (Both TOWN and TOP encode four bits. ) The 2 out of lo 8 position code (atop) is represented by a square. The 6 out 14 of 12 code it represented by an up~ide-down delta. the 6 out of 12 code encodes 8 Betsy The 4 out of 15 God it 16 represented by an X. Kit encodes 8 bits.) The 6 out of 18 17 code is represented by a delta (It encodes 8 bits.
I Inspection of the Figure shows that fur 1.2 microns/bit density and for Poles less than or equal to 1 . 45 microns in 21 diameter, the 4 out ox lo code generates the best eye, that 22 is, its worst case eye opening is 0.6 of the Manuel 23 ¦ amplitude for a OOZE micron Cole diameter and 0.3 for a 1.2S
24 micron hole diameter; while other code for similar diameters generate worse essay The 6 out of 18 code generates a better I eye for holes larger than 1.45 microns. It also generates the 27 bet eye at a hl~h~r bit ~enslty for smaller holes.
., 29 Fig. 5 illustrates that in most situatic)nfi the best worst cave eye" for a given bit density lo achieved by the 4 out of ~2Z9~
1 15 code. In some cases, the out of 18 code may be preferred although it pow a heavier burden on the laser. Applicants 3 codes may achieve the highest binary bit density in optical 4 recording or Betty pre~clock compatible block codes, 6 Applicant's 4 out of 15 code has its Thea symbol position 7 constrained always to have no hole. It is also constrained to venerate a null in the frequency spectrum 80 a to permit a 9 preclock system by using an equal number of hole on odd and even positions, respectively. These constraints combine to 11 leave remaining 44I different possible patterns. Out of these 12 441 different possible patterns, a certain number must be 13 eliminated as only 256 are needed. The first vines eliminated 14 are the ones not satisfying a Do con trait, i.e., the ones not having at least two spaces between menials or between 16 menials and groups of holes or between group of holes. The 17 ones eliminated next are the patterns which place the highest 18 burden on the laser diodes of conventional optical recording I devices. Laser diodes in most optical recording devices should not be pulsed at write power for a significant amount of time.
21 The last constraint eliminates patterns having three holes in a 2~1 row near symbol boundaries and all patterns having four holes 28 in a row.
26¦ The specific jet of 256 patterns dewed by the inventor to I venerate thy optl~al bit rode or layer diode optical 27 ¦ recording aye listed in Table 1.
12%916~L
1 Table 1. 4/15 I rode, Pr~-~lock Capably 3 1 2 3 4 5 6 7 8 9 10 b c d e 4 O X X X Jo 13 9 X X X it . 10 it X X X
X X X . X
lo X X N X
I X X X X
I
26 27 it Jo X X
I
I
1 2;29i64 1 1 2 3 4 5 6 7 8 10 b c d e X X
X X X X
11 33 X .X X X
13 I X X X . X
9 These two problems, i.e. hole diameter versus symbol position spacing and read signal overlap, combine together to 11 limit the bit densities in optical recording.
18 There are a very larcJe number of fixed block codes that 14 will generate a null in the frequency spectrum. however, the I prior art his not shown a methodology to find the code or codes 16 which permit the highest recording density in an optical 18 recording environment.
lug .
21 the invention comprises maintaining a predetermined 22 spacing between menials or between menials and groups of 23 holes or between groups of holes in fixed block codes having 24 symbols which contain at a minimum greater than two holes.
I waving symbols with more symbol positions and more holes 26 permits a greater number of bits to be encoded by a symbol.
2? ~aintainln3 a minimum spacing between menials, etc., permits 28 symbol position spacing to be minimized relative to hole size 29 and still permit correct decoding of the symbol. As a result, more bits my be recorded vow lets physical space.
1 The spacing between menials, etc., must be a multiple of 2 symbol positions Applicant therefore specifies that the 3 minimum spacing be two or more symbol positions, ire , Do or 4 greater. The choice of D 2, Do Do etc., depends upon the characteristics of the particular optical recording 6 environment. Generally, the higher the ratio of the largest 7 expected hole diameter to symbol position size, the larked 8 must be.
Within the family of codes which have a null in their 11 frequency spectrum to permit the use of a prerecorded clock, 12 the number of holes within a symbol must. be a multiple of two, 13 i.e., two, four, six eight. The inventor has determined that 14 the following pre-clock compatible codes permit the highest bit densities of 3 or fewer bits in optical recording for hole 16 diameters of 1.~5 micron or less hod for greater than 1.45 Al microns, respectively, both with a laser spot diameter of 18 approximately 0.8 microns.
The first code is a 4/15 code and the second a 6/13 code.
22 The first code essentially comprises a symbol of 15 positions 23 shaving therein four holes with the following constraints:
there must be at least two empty symbol positions between hole 24 or groups of hole, the Thea position must never have a hole 26 and pattern having four holes in a row within a symbol or 27 three hole in a row adjacent symbol boundaries being 28 eliminated. The second code essentially comprise a symbol of 29 18 positions having therein holes with the following constraint: there mutt be At least 3 empty position between holes or groups of holes, the Thea and Thea position must never 31 have a hole and patterns having 6 and 5 holes in a row or 4 32 holes in a row at the first your position being eliminated.
The requirement of specifying thy limit on the number of holes in a row reduces the burden on the laser diodes commonly employed in optical recording systems.
Thus, in accordance with a broad aspect of the invention, there is provided a system for recording and reading coded symbols from a record carrier, comprising a record carrier adapted for having two media states, an unaltered state and an altered state; means for inducing and sensing a signal responsive to said media states, the signal strength varying according to the media state, and being stronger for said altered state, and further varying to a degree according to the length of the altered state, the longer the altered state, the stronger the signal; information recorded on said record carrier in the form of altered media states, a hole comprising an altered media state of a predetermined length, a Manuel comprising a hole having unaltered media states before and after the altered state of a single hole, a group of holes comprising a plurality of adjacent holes with substantially no unaltered media states between adjacent holes and unaltered media states before and after the group of holes; said information further recorded on said record carrier with a spacing between groups of holes and other groups of holes or menials such that the signal strength read at a point midway between the group of holes and the other groups of holes or menials is less than the maximum signal strength caused by a Manuel.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a graph of the intensity of the signal detected by the read optics of an optical disk recording system vs. symbol position where the hole diameter is 0.9 microns, the symbol position size is 0.6 microns and the half power width of the light spot 0.8 microns;
foe - 5 -I
Figure 2 is a graph of the same code pattern as in Figure 1, but with a hole diameter of 1.25 microns;
Figure 3 is a graph similar to Figures 1 and 2 but with a hole pattern having two consecutive holes/ a space, followed by a hole;
Figure 4 is a graph similar to Figure 3 but with two consecutive holes, two spaces, followed by a hole;
Figure 5 is a graph of the worst case "eye" openings of several codes. The ordinate represents fractions of the Manuel amplitude and the abscissa represents the hole size parameter divided by the distance traveled during one clock period; and Figure 6 is a block diagram of optical recording apparatus for implementing the code of -the preferred embodiment.
pa - pa -3L2;~6 3 In many optical recording systems coded symbols represent 4 binary data. It it conventional for block code with a fixed number of holes Jo determine the location of the hole or holes 6 within these symbols by comparing the signals received from 7 each symbol position with the signals received from each of the 8 other symbol positions and choosing the M highest signals 9 detected to by the location of the hole or holes. ON is the lo number of holes in a symbol, a predetermined fixed number.) 11 For example, if a given symbol has four positions out of which 12 two positions must contain holes, conventional optical reading 13 apparatus compares the hole-associated signal power in each of 14 the four positions, and Chihuahuas the two highest powered positions as briny the positions where the holes are located.
The abscissa of Fig. l represents the snowball pattern 18 Lyle written on optical media, with the ones corresponding 19 to holes and the Eros corresponding to spaces. In this on regard, the spaces are represented a elevations on the 21 abscissa and holes are represented as depressions along the 22 abscissa. the entire group of eight positions represent one 23 symbol. Thy ordinate of jig. l represents the intensity of the 24 signals generated by the holes in conventional optical recording read optics and electronics. (If the signal is 26 observed in reflection, the signal kissed by a hole it 27 actually the inversion of the power ox the reflected beam 28 while if the signal is measured in transmission where the beam 29 from one wide of the dyes is observed from the other bidet the signal is a direct function of received laser power.) The ~Z1~9~6~
1 dotted curves in the Figure are top intensity of the read inlay associated with each owe the three holes in thy Figure.
3 These curve ore approximately Gaussian in shape with the half 4 power level of the signal roughly corresponding to the teeter 6 of the hole. In the Figure the hole diameter is taken to be 6 .9 microns while tube yummy position width, or the distance 7 between symbol center, is taken to be .6 microns. The solid & line in the Figure represents the summation ox the signals 9 caused by adjacent holes.
11 Inspection of this Figure shows that at no point does the 12 signal generated by the holes or adjacent holes sum to a level 13 where the peak, generated by the holes themselves, are 14 indistinguishable. An optical system can correctly read the 16 symbol pattern shown in Fig. 1 because it can correctly 16 identify the peaks associated with the holes and also determine 17 the valleys associated with the spaces.
19 however, media sensitivity variations and variations in the optical recording system (light intensity/ beam 21 aberrations) will result in a distribution of hole diameters.
22 Occasionally, holes of considerably layer diameter are 23 written. For example, in Fig. 2, the hole diameter it now 1.25 24 microns. The same symbol pattern, 01010010, it represented along the beta as way represented in Fig 1. Again, the 26 dotted line represent signal venerated by the holes and the 27 solid line represent the summation of the iguanas generate by nearby hole. inspection of the Figure shows hut there it;
I very little fall-off in signal strength between the holes of the 30 101 pattern Conventional ~nalogue comparison system I
1 attempting to determine whether this space was a hole or a I. space Jay incorrectly decide that it was a hole and not a 3 space. The last hole in the Figure may then be read as a 4 space, as the comparison system will identify only three holes 6 in a symbol, not four.
7 The first two Figures represent symbol patterns generated 8 by isolated single holes, otherwise known a menials. Fig. 3 shows a signal pattern generated by two holes written in a row. The symbol pattern yin Pig. 3 along the abscissa it a 11 01101001 pattern. The diameter of a hole is 1.25 microns and 12 the symbol positron dance is 0.6 microns. When two holes 13 are written adjacent to each other, they overlap end will look 14 like one large, long hole as illustrated in the Figure. This one large, long hole generates a signal of somewhat higher 16 intensity than a ~lgnal generated by a signal hole, as shown in 17 the Figure. Compare the signal generated by the group of two 18 holes with the signals generated by the following two I menials .
20 .
21 Again, in the Figure, the dotted Lowe represent the 22 signal generated by the holes themselves. As before the 23 only patterns are Gurney in shape, hut thy Renewal from 24 the double hole has Gaussian shaped edges and a flatter top.
The solid line represent the summation of the igloos of 26 nearby holes. Apparatus looking for the symbol positions with 27 the four highest signals would incorrectly find holes at 28 positions 2, 3, 4 and 5 and space at all other positions 29 because at option 2, I end S, toe signal strength 30 generated by the hole pattern 1101 at these poStionJ; it higher 81 at all point, including the space, than the signal generated I by the Manuel at position 8.
lZZ9164 1 Now turning to Fig. 4, the abscissa shows a symbol pattern 2 of 01100100 and a hole diameter of 1.25 microns and a symbol 3 petunia distance of Jo micron. The read apparatus can 4 correctly decode the p~51t$0ns of the three holes because the signal due to the double hole and the signal of the following 6 Manuel do not sum at the spaces to a signal which 7 approximately equals or exceed the signal generated by the 8 Manuel itself, this even though the signal generated by the 9 double hole it greater in magnitude than the signal generated by the subsequent Manuel and overlaps with significant signal 1 power three position away.
I The above process can be extended to groups so three hole 14 in a row. However, the signal power generated by three holes in a row it not significantly greater than the signal power 18 generated by two holes in a row. Again, referring to Fig. 4, 17 the pattern generated by having holes in the first three 18 positions of the illustrated symbol rather than having holes 19 generated in only positions 2 and 3, would be Mueller to the illustrated pattern and the read apparatus could correctly 21 decode the holes at positions I 2, 3 and 6 and spaces in 22 positions 4 and 5.
24 As illustrated in figure 3 and 4, it is necessary that there be at least one empty position between adjacent symbols.
I Otherwise, ascent Smalley having a 1101 or a 1011 pattern 27 across the boundary may incorrectly have the space identified I as a hole. These patterns may futile occur with an acceptor 29 position between ~yTnbol~, however whether the signal strength of a hole it present at Tess extra position it irrelevant, 'I ;~Z9164 1 because it it not included in the comparison apparatus as one 2 of the positions that may have a hole.
4 Fig 4 have been analyzed to owe that the presence of 6 two puce between holes and wrap ox holes permit correct 6 decoding of the symbol. Similar reasoning indicates the 7 further advantage of having 3 spaces between hoses or strings 8 of holes and at least two empty positions at symbol boundaries 9 when the size of the hole diameter relative to the size of the 10 fumble position increases.
I .
12 In determining which code will generate the maximum bit 13 density, it is desirable to inspect only those codes which 14 encode a multiple of the power of two bits, that is, two bits, 15 four bit, eight bits, sixteen bits, etc. For example, the quad phase code encodes two bits, and has four symbol positions 17 and two holes within a symbol. A occlude two out of eight :18 position code tiptop), has eight positions in the symbol and 19 encodes four bits of information. In general, in order to encode two bits of information in a snowball, the code must have I at least 4 different hole patterns To decode four bit in a : symbol the rode just have at least sixteen different hole I patterns. Similarly, to encode eight bits of information, the 24 code must have at least two hundred fifty-six different I pattern.
27 To a certain limit, the more holes there are in symbol, the 28 greater the number of possible pattern that can by contained 29 within the symbol. For example, in a four position symbol, if the code was constrained to have only one hole per symbol, ~229~64 1 there would be only four different patterns possible, that is a 2 hole in position one in position two in position three or in 3 position four. however, if the ~ymhol could have 2 holes the number of possible codes is now 6, i.e.
Lowe 1~10 Lyle 0110 lo 0011 inn the quad phase code the patterns 1010 and 0101 are 9 eliminated because they do not follow the constraint that the pattern of the first two positions be inverted in the second 11 two positions 80 a to permit a null in the frequency spectrum,) 13 It can be seen that finding the code which will optimize 14 the number of bits encoded over a unit ox space is difficult and complex Fig. 5 represents the finings of the inventor.
16 The abscissa in Fig. 5 represents hole size parameter sigma 17 divided by the minimum symbol position spacing or distance 18 traveled over half a clock period. For the laser poetizes 19 used, below a hole diameter of .95 microns the hole size parameter's calculation depends upon the particular optics and 21 the size of the hole. The formula for its calculation it I complex an not relevant to our discussion, as well, it is 23 known to those skilled in the art. However, for hole sizes 24 above .95 microns, sigma is approximately equal to thus the I hole diameter. Thus 9 the dimension of the abscissa it directly 26 related to hole diameter/ generally by the factor of Thea of 27 the hole diameter. The dimension of the balsa it further 28 inversely related to symbol position spacing. the bit 29 densities are held constant, i.e., lo micron bit the symbol position spicing varies inversely with the number of position 31 within a ~y~bol. Thus;, the abscissa dimension Lyon varies 32 directly with the nuJnber of symbol positiveness of a code.
.
2;~9~
l The ordinate of the Figure represents the worst case wrap 2 opening in fractions of the signal generated in the read 3 apparatus by nonohole. An eye opening can be defined as 4 the difference between the amplitude of the signal due to a 6 Manuel and the amplitude of a summation signal due to 6 adjacent holes measured at a space, Lee Fits. lo Formulae 7 for calculating an Eye pattern from a given code pattern, 8 ¦ hole size, spot size, etc., are known to the art. The worst 9 ¦ case eye" can be derived by inspection by loolcing at the code 10 ¦ patterns having the least distance between holes or groups of if 1 holes. The smaller the eye", the higher the chance of 12¦ erroneous decoding because of the inevitable noise in the 13 ¦ system.
I . .
15 ¦ slaving defined the methodology by which to determine the 16 worst case eye pattern of a given code, the inventor also 17 made the following comparison criteria. Compared codes were to 18 ¦ hove the same bit density, that is that the same number Of bin 19 cry bits were to be encoded per unit of lengtl1 on the Ned.
MU The standard example owe comparison way chosen to be lo microns 21 ¦ per bit (one bit per 1.2 microns). Symbols having different 22 1 real lengths and position spacing may be compared meaningfully 23 ¦ in this manner. If two bits are encode the entire symbol 24 ¦ is 2.4 microns in length lo micron bit x to bits)). If I four bits are encoded, the symbol is 4.8 microns long. If 26 eight bits are encoded, the symbol is 9.6 microns long.
I
I All odes shown in Figure 5 hove the same bit density, lo 29 micron per bit. All have a null in the frequency spectrum.
30 The first idea line in the Figure represents the worst case 1 Rove" opening for DYE ode where Do Moses that there is a 2 minimusn of 1 symbol position between menials or between 3 Manuel and groups of holes or between groups of holes. The 4 second solid line is the worst case Sue opening for Do B codes. Roy third solid line is for O'G3 codes. The eye-6 opening were determined for three hole diameter issue: I .95 q micron, I 1.25 microns and I 1.45 microns. The code 8 having the best worst case eye patterns are lis'c~d on the 9 Figure. The Tony code represented by a dot is a so-called 2 out of 9 code. This is tile same as a out ox 8 code 11 ¦ ("'wrap ) previously mentioned With the addition of Thea "empty"
12 position. (Both TOWN and TOP encode four bits. ) The 2 out of lo 8 position code (atop) is represented by a square. The 6 out 14 of 12 code it represented by an up~ide-down delta. the 6 out of 12 code encodes 8 Betsy The 4 out of 15 God it 16 represented by an X. Kit encodes 8 bits.) The 6 out of 18 17 code is represented by a delta (It encodes 8 bits.
I Inspection of the Figure shows that fur 1.2 microns/bit density and for Poles less than or equal to 1 . 45 microns in 21 diameter, the 4 out ox lo code generates the best eye, that 22 is, its worst case eye opening is 0.6 of the Manuel 23 ¦ amplitude for a OOZE micron Cole diameter and 0.3 for a 1.2S
24 micron hole diameter; while other code for similar diameters generate worse essay The 6 out of 18 code generates a better I eye for holes larger than 1.45 microns. It also generates the 27 bet eye at a hl~h~r bit ~enslty for smaller holes.
., 29 Fig. 5 illustrates that in most situatic)nfi the best worst cave eye" for a given bit density lo achieved by the 4 out of ~2Z9~
1 15 code. In some cases, the out of 18 code may be preferred although it pow a heavier burden on the laser. Applicants 3 codes may achieve the highest binary bit density in optical 4 recording or Betty pre~clock compatible block codes, 6 Applicant's 4 out of 15 code has its Thea symbol position 7 constrained always to have no hole. It is also constrained to venerate a null in the frequency spectrum 80 a to permit a 9 preclock system by using an equal number of hole on odd and even positions, respectively. These constraints combine to 11 leave remaining 44I different possible patterns. Out of these 12 441 different possible patterns, a certain number must be 13 eliminated as only 256 are needed. The first vines eliminated 14 are the ones not satisfying a Do con trait, i.e., the ones not having at least two spaces between menials or between 16 menials and groups of holes or between group of holes. The 17 ones eliminated next are the patterns which place the highest 18 burden on the laser diodes of conventional optical recording I devices. Laser diodes in most optical recording devices should not be pulsed at write power for a significant amount of time.
21 The last constraint eliminates patterns having three holes in a 2~1 row near symbol boundaries and all patterns having four holes 28 in a row.
26¦ The specific jet of 256 patterns dewed by the inventor to I venerate thy optl~al bit rode or layer diode optical 27 ¦ recording aye listed in Table 1.
12%916~L
1 Table 1. 4/15 I rode, Pr~-~lock Capably 3 1 2 3 4 5 6 7 8 9 10 b c d e 4 O X X X Jo 13 9 X X X it . 10 it X X X
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I X X X X
I
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1 2;29i64 1 1 2 3 4 5 6 7 8 10 b c d e X X
X X X X
11 33 X .X X X
13 I X X X . X
5 37 X X X X
20 ' I X X X X
I X X X X
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30 5? X X X X
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1 1 2 3 4 5 6 7 8 9 I a b c d e
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7 I X it X X
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14 66 X X Jo X
16 68 X . X X X
19 71 X Y X . X
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22 74 X it X X
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31 83 % X it I
1;~2!3164 1 1 2 3 5 6 7 10 a b c d e 2 I X it X X
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14 66 X X Jo X
16 68 X . X X X
19 71 X Y X . X
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22 74 X it X X
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Lo 94 X Jo X X
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14 96 X X X X .
16 go X X X X
19 I 101 it X X . '' X
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8 ¦ 1?0 I X X X
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71 12~ X X X X
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10 152 X x X X
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16 go X X X X
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1 ¦ I 2 3 4 5 6 7 8 10 a b c d e 2 1 1~4 X X X
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4 ¦126 X N X X
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71 12~ X X X X
191131 X X . ` X X
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I 1 ~37 X X X X
2~;1 13~ X I X Jo 291 1~1 X X X X
so l 1~2 I X X
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7 1~9 x X X
9 151 X X x X
10 152 X x X X
I 1~3 X X X X
12 1154 X X X
13 1 I X X x X
1~6 X X X X
lo 159 X X X X
18 160 X ` it X X
I 161 it X X X
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I 1~7 Jo X Jo it go 168 X X X X
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28 17~ X X X it 80 17Z X it X X
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4 ~76 X X X
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I 1~7 Jo X Jo it go 168 X X X X
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28 17~ X X X it 80 17Z X it X X
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17 1~9 X X X X
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19 191 XX Jo X
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27 19~ X X X X
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1 2 3 5 67 8 9 10 a b c d e 3 ~05 X X X X
4 20~ X X I Jo 11) 21~ X X X X
12 21~ X X X X
13 ~15 X X X X
14 2~6 X X X X
17 1~9 X X X X
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15 217 X X X X
16 218 X I X
17 21g X X X X
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20 ?22 X X X X
21 22~ X X X X
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28 ~30 X % X
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9 1 2~1 X X X X
10 1 ~42 X X X X
I 1 ~44 X X X X
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20 ?22 X X X X
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12;~9164 1 ¦ 1 2 3 4 5 6 7 8 9 10 b c d e 24û X I X X
9 1 2~1 X X X X
10 1 ~42 X X X X
I 1 ~44 X X X X
18 1 245 X X X X
141 ~46 X X X X
17 1 2~9 X X X X
18 1 25û X X X X
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17 1 2~9 X X X X
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21 1 ~53 X X X X
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I I
lZ;~9164 1 ¦ applicant I 6 out ox lo code his its Thea and Thea 2 ¦ position constrained always to have no hole. It is Lowe 3 ¦ constrained to generate a null in the frequency spectrum.
4 ¦ these contraltos combine to leave remaining 3136 different 6 ¦ possible pattern. Out of these patterns, the ones not 6 satisfying the D-3 constraints Syria eliminated, leaving 316 7 ¦ patterns. Secondly patterns with 6 and 5 holes in a row and 8 ¦ with 4 holes in the first 4 positions were eliminate leaving 9 ¦ the 256 needed patterns listed on Table 2. due to limitation 0 ¦ on the size of the page, only 16 out of the lo symbol positions 11 are shown. The last two positron always have no holes. ) I
13 Tale I. Al do rode. Pre~Clock Compatible l 2 3 4 5 S 7 8 9 10 a b c e _ _ _ _ _ _ _ _ _ _ _ _ _ _ 16 û X X X X X X
17 l X X X X X
~52 X X X X
21 1 ~53 X X X X
22 1 ~54 X X X X
I X X X X
I I
lZ;~9164 1 ¦ applicant I 6 out ox lo code his its Thea and Thea 2 ¦ position constrained always to have no hole. It is Lowe 3 ¦ constrained to generate a null in the frequency spectrum.
4 ¦ these contraltos combine to leave remaining 3136 different 6 ¦ possible pattern. Out of these patterns, the ones not 6 satisfying the D-3 constraints Syria eliminated, leaving 316 7 ¦ patterns. Secondly patterns with 6 and 5 holes in a row and 8 ¦ with 4 holes in the first 4 positions were eliminate leaving 9 ¦ the 256 needed patterns listed on Table 2. due to limitation 0 ¦ on the size of the page, only 16 out of the lo symbol positions 11 are shown. The last two positron always have no holes. ) I
13 Tale I. Al do rode. Pre~Clock Compatible l 2 3 4 5 S 7 8 9 10 a b c e _ _ _ _ _ _ _ _ _ _ _ _ _ _ 16 û X X X X X X
17 l X X X X X
20 d, X X X X X X
X X X X X X
22 X X X , X X
I g X X X X X X
I if X X X X X X
I I X X X X
2.1 - 24 -1 1 2 3 4 5 b 7 8 10 by c d e f 7 lug X X X X X
X X X X X X
22 X X X , X X
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21 33 X X X X X X
22 I X X X X X
23 35 X X X X X X
24 36 X X X X X
- 25 -29~
1 1 2 3 4 5 6 7 8 lo a b c d e f ~41 55 X X X X I
~51 56 X X X X X
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26 67 X X XX X
27 68 X X X X X X
28 I X X XX X
29 70 X X X X N X
30 71 X X X X X X
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32 .~2~J~ ok "`
1 2 3 4 56 7 B 9 10 a b c d e f _ _ _ _ _ _ _ _ _ 2 l 3 X X X X X
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32 .. 30 -~:Z2!~164 1 1 2 5 6 l 8 9 10 a b c d e f 6 93 X X X . X X
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I 1 ~35 X X X . X X X
201 ~36 X X X X X X
211 ~37 I X X X X X
22 1 23~ X X I I X X
I 2~9 X X X X X X
I 24Q it X X X X I
25 1 Al X X X X X X
I 1 2~3 X X X X X
281 2~4 X X X X XX
29 1 ~45 X X X X X
801 24~ X X X X X X
3~1 1 l 2 3 4 5 S 7 9 I a b c d e _______________.
3 24~ X X XX I X
24g XX 'XXXX
25~ X X I X
~51 X X X X X X
8 ~53 X X X X X
2~4 I X X X X X
10 25~ X X X X X
11 ., 12 Apparatus for implementing applicants invention it Sheehan 13 in Yip. 6. Laser disk lo comprises a disk of optically 14 r~.El~c9:~ve littoral in wish holes mazy be burred 'co reduce the reflectivity of the surface at the holy. the disk 10 ill 17 typically composed of grooves snot shown stamped in a substrate by a replication process. The grooves are depth 18 modulated with a clock frequency. Thereafter, the surface of 19 'eke substrate is coated with an optically reflective material suitable for recording data thereon in the form of holes 21 according to the present invention. Motor 12 rotate disk lo 22 both Dixon recording of data and during reading ox data.
23 Laser lo it used both to record data and to road data. In a 24 recording mode, the laser is operated at a higher power than I when reading data. The power it at a level such that it burns a hole in the reflective material of the disk lo In this 27 regard, to write a hole, the laser itself, which may be 28 comer used of a laser diode, may be pulsed or the hem of the 29 laser, such a from aye or, may be deflected away from the optical disk I In the reading mode, the laser operates 31 continuously at lets power, irl~;ufflcient to alter the I
l;~Z9164 1 reflective nature of the optical Fisk 10. The laser OR under 2 the control of a loser control 1&. Cl3ritrol 16 controls the 3 laser 's power level arid its pulsation or hem deflection . The 4 data to be written comes from data encode lo. Data encode 18 receive binary data to be wry mitten on optical disk 10, encodes 6 it according to the present invention in a 4 out of 15 or 6 out 7 of I code, transmits the encoded data to loser control 16, 8 which in turn controls layer I to write the data on the 9 rotating optical dî~k lo 11 Whetter in a write mode or a rend mode, read mean I
12 detects the reflection of the laser beam from the optical disk 13 lo Mean for detection are conventionally a photo diode which 14 convert hi into elect teal signals . The output of the read I mean 20 is provided to a servo means 24, which maintains the 16 position ox the laser and read appear 14 and 20 directly 17 above a truck on optical disk lo the output of the read 18 apparatus 20 also supplied to data decode I and to a lug read-after-write verify circuit 26. the read-after-write 20 verify circuit I compares the data written on a Fisk with the 21 data read from a disk during write to verify that the data has I been correctly wry mitten on the disk 10 . YE tube data ha been 23 incorrectly written on the Delco 10, a rewrite may be lnitiat~d or error correction means Jay be employed. In the read mode, I the data provided to date decode is decoded from the 4 out of 26 15 or 6 out of lo code to the bit binary code of the original 27 data. on the preferred embodiment error correction (not 28 shown) it performed on the 8 bit binary data I
- I -if I
1 In summary, the f first code of applicant 's invention 2 comprises a symbol hazing I positions, equally spaced within a 3 symbol, fur encoding 8 bits ox binary data. Holes are written A centered on a symbol and Jay have diameters larger than the 6 symbol position spacing. Exactly four hole, and only four 6 ¦ holes, appear within each symbol . For each hole appear in in 7 an even posltiosl, there appears a hole in an odd potion and 8 visa versa. This generates a null in the frequency spectrum so 9 the prerecorded clock signal can be read and decoded by other 10 electronics not shown. The Thea position never has a hole. At 11 least 'cow snowball positions appear between menials or between 12 menials and grollp~ of holes or between groups of holes.
Wylie not essential to the invention the following 15 constraint; have been further applied to reduce the number ox 16 ¦ codes from ~41 to 256. All symbols hying four consecutive 17 ¦ holes have been eliminated. All symbols having three hole in symbol positions, 1, 2 and 3, in positions 2, 3 and 4, or in 1~.3 ¦ position 12, 13 and 14 have been eliminated.
20 .
applicants 6 jut of 18 code it constructed similarly 22 with Do and wow empty spaces at the end of each symbol ( two 23 empty space Litton symbols ) . Symbols ha irk f ivy and six 24 holes in a row as well as four in a row at position 1-4 have I been of imitated .
I
Thea specification of the elemerlts of the preferred 28 embodiment should not be taken as a limitation on the scope of Z9 the appended clowns
1 2 3 4 56 7 B 9 10 a b c d e f _ _ _ _ _ _ _ _ _ 2 l 3 X X X X X
5 I X X it X X
6 77 X X X X it X
I I X X X X X X
18 8g X X X X X X
20 go X X X X X X
24 go X X X X X
29 ~00 X X X X X
~2~9 1 1 2 3 4 5 6 7 8 9 10 a b c d e 2 102 X X X X X X .
5 1~5 X X X X X X
6 1~6 X X X X X X
10~ X X X X X X
9 1~9 X X X X X X .
I ha x x x x x x 22 1?2 X X X X X X
26 126: X X X X X X
29 1~9 X X X X X
32~ - 28 -I
1 1 2 3 4 5 6 7 8 9 10 a b c d e f ___~_____. _______ 9 13~3 X X X X X X
10 13g X X X X X X
20 149 X Jo X X X X
26 loss XX X X X X
29 15~ X X X X X X
:12 I 29 -l;~Z~4 1 1 2 3 4 5 6 7 8 9 10 a b c d e f _ _ _ _ _ _ _ _ _ _ _ _ 2 6û X X X X X X
5 ~63 X X X X X X
7 16~ X X X X X Jo 9 lS7 X X X X X I
14 l72 X X X X X X
16 17~ X X X X X X
18 l76 X X X X X X
20 17~ X X X X X X
21 i79 X X X X X . X
22 . 180 X X X X X X
23 81 X X Jo X X X
29 By X X X X X X
32 .. 30 -~:Z2!~164 1 1 2 5 6 l 8 9 10 a b c d e f 6 93 X X X . X X
7 I X X X X X it lo 97 X X X X X X
13 ~00 X X X X X X
16 ~03 X X X X X
18 70~ X X X X X X
19 ~06 X X X X X X
21 70~ X X X X X X
22 70g X X X X X X
24 ~11 X X X X X X
2!j 71 2 X X X X X
27 ~14 X X X X X So 29 ~16 X X X X X X
30 ~17 X X X X X X
! I
1 I 1 2 3 4 5 6 78 9 10 a b c d e f I
2 21B X X X X . X X
6 1 221 X X X X Jo 6 ?22 X X X X X X
~24 X X X X X X
101 22~ X X X X X X
ill 227 X X X X X X
121 22~ X X X X Jo X
131 ~29 X X X X X X
161 I X X XX . X X
17 1 ~33 X X XX X
18 1 ~34 X X X X X
I 1 ~35 X X X . X X X
201 ~36 X X X X X X
211 ~37 I X X X X X
22 1 23~ X X I I X X
I 2~9 X X X X X X
I 24Q it X X X X I
25 1 Al X X X X X X
I 1 2~3 X X X X X
281 2~4 X X X X XX
29 1 ~45 X X X X X
801 24~ X X X X X X
3~1 1 l 2 3 4 5 S 7 9 I a b c d e _______________.
3 24~ X X XX I X
24g XX 'XXXX
25~ X X I X
~51 X X X X X X
8 ~53 X X X X X
2~4 I X X X X X
10 25~ X X X X X
11 ., 12 Apparatus for implementing applicants invention it Sheehan 13 in Yip. 6. Laser disk lo comprises a disk of optically 14 r~.El~c9:~ve littoral in wish holes mazy be burred 'co reduce the reflectivity of the surface at the holy. the disk 10 ill 17 typically composed of grooves snot shown stamped in a substrate by a replication process. The grooves are depth 18 modulated with a clock frequency. Thereafter, the surface of 19 'eke substrate is coated with an optically reflective material suitable for recording data thereon in the form of holes 21 according to the present invention. Motor 12 rotate disk lo 22 both Dixon recording of data and during reading ox data.
23 Laser lo it used both to record data and to road data. In a 24 recording mode, the laser is operated at a higher power than I when reading data. The power it at a level such that it burns a hole in the reflective material of the disk lo In this 27 regard, to write a hole, the laser itself, which may be 28 comer used of a laser diode, may be pulsed or the hem of the 29 laser, such a from aye or, may be deflected away from the optical disk I In the reading mode, the laser operates 31 continuously at lets power, irl~;ufflcient to alter the I
l;~Z9164 1 reflective nature of the optical Fisk 10. The laser OR under 2 the control of a loser control 1&. Cl3ritrol 16 controls the 3 laser 's power level arid its pulsation or hem deflection . The 4 data to be written comes from data encode lo. Data encode 18 receive binary data to be wry mitten on optical disk 10, encodes 6 it according to the present invention in a 4 out of 15 or 6 out 7 of I code, transmits the encoded data to loser control 16, 8 which in turn controls layer I to write the data on the 9 rotating optical dî~k lo 11 Whetter in a write mode or a rend mode, read mean I
12 detects the reflection of the laser beam from the optical disk 13 lo Mean for detection are conventionally a photo diode which 14 convert hi into elect teal signals . The output of the read I mean 20 is provided to a servo means 24, which maintains the 16 position ox the laser and read appear 14 and 20 directly 17 above a truck on optical disk lo the output of the read 18 apparatus 20 also supplied to data decode I and to a lug read-after-write verify circuit 26. the read-after-write 20 verify circuit I compares the data written on a Fisk with the 21 data read from a disk during write to verify that the data has I been correctly wry mitten on the disk 10 . YE tube data ha been 23 incorrectly written on the Delco 10, a rewrite may be lnitiat~d or error correction means Jay be employed. In the read mode, I the data provided to date decode is decoded from the 4 out of 26 15 or 6 out of lo code to the bit binary code of the original 27 data. on the preferred embodiment error correction (not 28 shown) it performed on the 8 bit binary data I
- I -if I
1 In summary, the f first code of applicant 's invention 2 comprises a symbol hazing I positions, equally spaced within a 3 symbol, fur encoding 8 bits ox binary data. Holes are written A centered on a symbol and Jay have diameters larger than the 6 symbol position spacing. Exactly four hole, and only four 6 ¦ holes, appear within each symbol . For each hole appear in in 7 an even posltiosl, there appears a hole in an odd potion and 8 visa versa. This generates a null in the frequency spectrum so 9 the prerecorded clock signal can be read and decoded by other 10 electronics not shown. The Thea position never has a hole. At 11 least 'cow snowball positions appear between menials or between 12 menials and grollp~ of holes or between groups of holes.
Wylie not essential to the invention the following 15 constraint; have been further applied to reduce the number ox 16 ¦ codes from ~41 to 256. All symbols hying four consecutive 17 ¦ holes have been eliminated. All symbols having three hole in symbol positions, 1, 2 and 3, in positions 2, 3 and 4, or in 1~.3 ¦ position 12, 13 and 14 have been eliminated.
20 .
applicants 6 jut of 18 code it constructed similarly 22 with Do and wow empty spaces at the end of each symbol ( two 23 empty space Litton symbols ) . Symbols ha irk f ivy and six 24 holes in a row as well as four in a row at position 1-4 have I been of imitated .
I
Thea specification of the elemerlts of the preferred 28 embodiment should not be taken as a limitation on the scope of Z9 the appended clowns
Claims (19)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A system for recording and reading coded symbols from a record carrier, comprising a record carrier adapted for having two media states, an unaltered state and an altered state;
means for inducing and sensing a signal responsive to said media states, the signal strength varying according to the media state, and being stronger for said altered state, and further varying to a degree according to the length of the altered state, the longer the altered state, the stronger the signal;
information recorded on said record carrier in the form of altered media states, a hole comprising an altered media state of a predetermined length, a monohole comprising a hole having unaltered media states before and after the altered state of a single hole, a group of holes comprising a plurality of adjacent holes with substantially no unaltered media states between adjacent holes and unaltered media states before and after the group of holes;
said information further recorded on said record carrier with a spacing between groups of holes and other groups of holes or monoholes such that the signal strength read at a point midway between the group of holes and the other groups of holes or monoholes is less than the maximum signal strength caused by a monohole.
means for inducing and sensing a signal responsive to said media states, the signal strength varying according to the media state, and being stronger for said altered state, and further varying to a degree according to the length of the altered state, the longer the altered state, the stronger the signal;
information recorded on said record carrier in the form of altered media states, a hole comprising an altered media state of a predetermined length, a monohole comprising a hole having unaltered media states before and after the altered state of a single hole, a group of holes comprising a plurality of adjacent holes with substantially no unaltered media states between adjacent holes and unaltered media states before and after the group of holes;
said information further recorded on said record carrier with a spacing between groups of holes and other groups of holes or monoholes such that the signal strength read at a point midway between the group of holes and the other groups of holes or monoholes is less than the maximum signal strength caused by a monohole.
2. A system as claimed in claim 1 wherein the information further comprises a fixed block code having the following characteristics:
a symbol having a predetermined number of positions;
each symbol having a predetermined number of holes greater than two;
each symbol having a first predetermined number of symbol positions between monoholes or between monoholes and groups of holes or between groups of holes, the predetermined number being two or more;
each symbol having a second predetermined number of empty symbol positions at the boundary of the symbol, said second predetermined number being one less than said first predetermined number.
a symbol having a predetermined number of positions;
each symbol having a predetermined number of holes greater than two;
each symbol having a first predetermined number of symbol positions between monoholes or between monoholes and groups of holes or between groups of holes, the predetermined number being two or more;
each symbol having a second predetermined number of empty symbol positions at the boundary of the symbol, said second predetermined number being one less than said first predetermined number.
3. A system according to claim 2 for recording and reading coded binary data on a recording media of a type in which holes are made in the media to represent one state and the absence of a hole represents the complementary state and further of a type having a null in the frequency spectrum upon recording or reading whereby the media may include a prerecorded clock signal for assisting in the writing and reading of the data, comprising:
a symbol having fifteen positions equally spaced within the symbol for encoding eight binary bits of data;
a constraint that exactly four holes and only four holes appear within each symbol;
a constraint that for each hole appearing in an even position, there appear a hole at an odd position;
a constraint that the fifteenth position never have a hole;
a constraint that at least two positions appear between monoholes or between monoholes and groups of holes or between groups of holes.
a symbol having fifteen positions equally spaced within the symbol for encoding eight binary bits of data;
a constraint that exactly four holes and only four holes appear within each symbol;
a constraint that for each hole appearing in an even position, there appear a hole at an odd position;
a constraint that the fifteenth position never have a hole;
a constraint that at least two positions appear between monoholes or between monoholes and groups of holes or between groups of holes.
4. The system of claim 3 further including a constraint that four holes never be consecutively recorded.
5. The system of claim 3 further including a constraint that groups of three holes not be recorded in positions 1, 2 and 3, in positions 2, 3 and 4 or in positions 12, 13 and 14.
6. The system of claim 4 further including a constraint that groups of three holes not be recorded in positions 1, 2 and 3, in positions 2, 3 and 4 or in positions 12, 13 and 14.
7. Optical recording and reading apparatus for recording and reading a code according to claim 2 comprising:
optical disk means;
means for moving said disk;
laser means for directing a laser beam onto said disk;
means for controlling said laser beam;
means four optically detecting said laser beam after having impinged upon said disk;
means for encoding data into a predetermined format;
said means for controlling said laser means being responsive to said means for encoding for recording said encoded data onto said disk by burning holes into said disk according to said predetermined format;
means, responsive to said means for detecting said laser beam, for decoding said encoded data;
said predetermined format comprising:
a symbol having fifteen sequential positions equally spaced within the symbol, said symbol positions comprising the sequential locations on the disk where a hole may be burned into the optical disk by said laser means, each burned hole having a diameter equal to or greater than the length of a symbol position on said optical disk;
each symbol having exactly four holes and only four holes;
each symbol having two holes in even positions;
each symbol having two holes in odd positions;
each symbol having no holes in the fifteenth position;
each symbol having at least two symbol positions between monoholes or between monoholes and groups of holes or between groups of holes; wherein a monohole comprises a hole at a symbol position with the absence of hole at adjacent positions, and a group of holes comprises more than one hole in adjacent positions.
optical disk means;
means for moving said disk;
laser means for directing a laser beam onto said disk;
means for controlling said laser beam;
means four optically detecting said laser beam after having impinged upon said disk;
means for encoding data into a predetermined format;
said means for controlling said laser means being responsive to said means for encoding for recording said encoded data onto said disk by burning holes into said disk according to said predetermined format;
means, responsive to said means for detecting said laser beam, for decoding said encoded data;
said predetermined format comprising:
a symbol having fifteen sequential positions equally spaced within the symbol, said symbol positions comprising the sequential locations on the disk where a hole may be burned into the optical disk by said laser means, each burned hole having a diameter equal to or greater than the length of a symbol position on said optical disk;
each symbol having exactly four holes and only four holes;
each symbol having two holes in even positions;
each symbol having two holes in odd positions;
each symbol having no holes in the fifteenth position;
each symbol having at least two symbol positions between monoholes or between monoholes and groups of holes or between groups of holes; wherein a monohole comprises a hole at a symbol position with the absence of hole at adjacent positions, and a group of holes comprises more than one hole in adjacent positions.
8. The optical recording and reading apparatus of claim 7 further including each symbol never having four consecutive holes.
9. The optical recording and reading apparatus of claim 7 further including each symbol never having groups of three holes recorded in symbol positions 1, 2 and 3, in positions 2, 3 and 4 or in positions 12, 13 and 14.
10. The optical recording and reading apparatus of claim 8 further including each symbol never having groups of three holes recorded in symbol positions 1, 2 and 3, in positions 2, 3 and 4 or in positions 12, 13 and 14.
11. A system according to claim 2 for recording and read-ing binary data on an optical recording media of a type in which holes are made in the media to represent one state and the absence of a hole represents the complementary state and further of a type having a null in the frequency spectrum upon recording or reading whereby the optical media may include a prerecorded clock signal for assisting in the writing and reading of the data, comprising:
a symbol having eighteen positions equally spaced within the symbol for encoding eight binary bits of data;
a constraint that exactly six holes and only six holes appear within each symbol;
a constraint that for each hole appearing in an even position, there appear a hole at an odd position;
a constraint that the seventeenth and eighteenth positions never have a hole;
a constraint that at least three positions appear between monoholes or between monoholes and groups of holes or between groups of holes.
a symbol having eighteen positions equally spaced within the symbol for encoding eight binary bits of data;
a constraint that exactly six holes and only six holes appear within each symbol;
a constraint that for each hole appearing in an even position, there appear a hole at an odd position;
a constraint that the seventeenth and eighteenth positions never have a hole;
a constraint that at least three positions appear between monoholes or between monoholes and groups of holes or between groups of holes.
12. The system of claim 11 further including a constraint that five or six holes never be consecutively recorded.
13. The system of claim 11 further including a constraint that groups of four holes not be recorded in at positions 1, 2, 3 and 4.
14. The system of claim 12 further including a constraint that groups of four holes not be recorded at positions 1, 2, 3 and 4.
15. Optical recording and reading apparatus for recording and reading a code according to claim l comprising:
optical disk means;
means for moving said disk;
laser means for directing a laser beam onto said disk;
means for controlling said laser beam;
means for optically detecting said laser beam after having impinged upon said disk;
means for encoding data into a predetermined format;
said means for controlling said laser means being responsive to said means for encoding for recording said encoded data onto said disk by burning holes into said disk according to said predetermined format;
means, responsive to said means for detecting said laser beam, for decoding said encoded data;
said predetermined format comprising:
a symbol having eighteen sequential positions equally spaced within the symbol, said symbol positions comprising the sequential locations on the disk where a hole may be burned into the optical disk by said laser means, each burned hole having a diameter equal to or greater than the length of a symbol position on said optical disk;
each symbol having exactly six holes and only six holes;
each symbol having three holes in even positions;
each symbol having three holes in odd positions;
each symbol having no holes in the seventeenth and eighteenth positions;
each symbol having at least three symbol positions between monoholes or between monoholes and groups of holes or between groups of holes; wherein a monohole comprises a hole at a symbol position with the absence of hole at adjacent positions, and a group of holes comprises more than one hole in adjacent positions.
optical disk means;
means for moving said disk;
laser means for directing a laser beam onto said disk;
means for controlling said laser beam;
means for optically detecting said laser beam after having impinged upon said disk;
means for encoding data into a predetermined format;
said means for controlling said laser means being responsive to said means for encoding for recording said encoded data onto said disk by burning holes into said disk according to said predetermined format;
means, responsive to said means for detecting said laser beam, for decoding said encoded data;
said predetermined format comprising:
a symbol having eighteen sequential positions equally spaced within the symbol, said symbol positions comprising the sequential locations on the disk where a hole may be burned into the optical disk by said laser means, each burned hole having a diameter equal to or greater than the length of a symbol position on said optical disk;
each symbol having exactly six holes and only six holes;
each symbol having three holes in even positions;
each symbol having three holes in odd positions;
each symbol having no holes in the seventeenth and eighteenth positions;
each symbol having at least three symbol positions between monoholes or between monoholes and groups of holes or between groups of holes; wherein a monohole comprises a hole at a symbol position with the absence of hole at adjacent positions, and a group of holes comprises more than one hole in adjacent positions.
16. The optical recording and reading apparatus of claim 14 further including each symbol never having five or six consecutive holes.
17. The optical recording and reading apparatus of claim 16 further including each symbol never having groups of four holes recorded at symbol positions 1, 2, 3 and 4.
18. The optical recording and reading apparatus of claim 17 further including each symbol never having groups of four holes recorded at symbol positions 1, 2, 3 and 4.
19. The system of claim 1 wherein the information further comprises a fixed block code having the following character-istics:
a symbol having a predetermined number of positions;
each symbol having a predetermined number of holes;
each symbol having a first predetermined number of symbol positions between menials or between menials and groups of holes or between groups of holes;
each symbol having a second predetermined number of empty symbol positions at the boundary of the symbol, said second predetermined number being one less than said first predetermined number.
a symbol having a predetermined number of positions;
each symbol having a predetermined number of holes;
each symbol having a first predetermined number of symbol positions between menials or between menials and groups of holes or between groups of holes;
each symbol having a second predetermined number of empty symbol positions at the boundary of the symbol, said second predetermined number being one less than said first predetermined number.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US54175383A | 1983-10-13 | 1983-10-13 | |
| US541,753 | 1983-10-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1229164A true CA1229164A (en) | 1987-11-10 |
Family
ID=24160893
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000458854A Expired CA1229164A (en) | 1983-10-13 | 1984-07-13 | High density codes for optical recording |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPH0721941B2 (en) |
| AU (1) | AU574722B2 (en) |
| CA (1) | CA1229164A (en) |
| DE (1) | DE3416547C2 (en) |
| FR (1) | FR2557344B1 (en) |
| GB (1) | GB2148670B (en) |
| NL (1) | NL8403044A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60231980A (en) * | 1983-12-29 | 1985-11-18 | レーザー マグネテイツク ストーリツジ インターナシヨナル コンパニー | High-density code for optical recording |
| US4881076A (en) * | 1987-12-01 | 1989-11-14 | International Business Machines Corporation | Encoding for pit-per-transition optical data recording |
| JPH06325369A (en) * | 1993-03-08 | 1994-11-25 | Philips Electron Nv | Combined optical recording and reading device |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1122711A (en) * | 1976-07-14 | 1982-04-27 | Sperry Rand Corporation | Method and apparatus for encoding and recovering binary digital data |
| JPS55141852A (en) * | 1979-04-24 | 1980-11-06 | Sony Corp | Data converting system |
| NL8006165A (en) * | 1980-11-12 | 1982-06-01 | Philips Nv | SYSTEM FOR TRANSFER OF DIGITAL INFORMATION, CODER FOR APPLICATION IN THAT SYSTEM, DECODER FOR APPLICATION IN THAT SYSTEM AND RECORD CARRIAGE FOR APPLICATION IN THAT SYSTEM. |
| US4377805A (en) * | 1981-04-20 | 1983-03-22 | Emi Limited | Magnetic recording |
| FR2507035B1 (en) * | 1981-06-02 | 1988-09-16 | Thomson Csf | BINARY DATA CODING METHOD AND DIGITAL VIDEO SIGNAL TRANSMISSION DEVICE IMPLEMENTING SUCH A METHOD |
| JPS5846751A (en) * | 1981-09-11 | 1983-03-18 | Sony Corp | Binary code modulating method and recording medium and its reproducer |
-
1984
- 1984-05-04 DE DE19843416547 patent/DE3416547C2/en not_active Expired - Fee Related
- 1984-06-12 JP JP12063484A patent/JPH0721941B2/en not_active Expired - Lifetime
- 1984-07-13 CA CA000458854A patent/CA1229164A/en not_active Expired
- 1984-09-19 GB GB08423669A patent/GB2148670B/en not_active Expired
- 1984-10-03 AU AU33789/84A patent/AU574722B2/en not_active Ceased
- 1984-10-05 NL NL8403044A patent/NL8403044A/en not_active Application Discontinuation
- 1984-10-12 FR FR8415717A patent/FR2557344B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3416547A1 (en) | 1986-01-09 |
| FR2557344B1 (en) | 1989-01-06 |
| JPS6083225A (en) | 1985-05-11 |
| GB2148670A (en) | 1985-05-30 |
| AU3378984A (en) | 1985-04-18 |
| AU574722B2 (en) | 1988-07-14 |
| FR2557344A1 (en) | 1985-06-28 |
| GB8423669D0 (en) | 1984-10-24 |
| DE3416547C2 (en) | 1994-10-06 |
| NL8403044A (en) | 1985-05-01 |
| GB2148670B (en) | 1987-07-08 |
| JPH0721941B2 (en) | 1995-03-08 |
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