NL8403044A - HIGH DENSITY CODE FOR CODED RECORDING OF DATA AND EQUIPMENT FOR RECORDING AND READING ITS. - Google Patents

Description

- 1 -

High-density code for the coded recording of data and equipment for recording and reading it.

The invention relates to high-density codes for the coded recording of data and to recording and reading equipment therefor and, although not limited thereto, to high-density codes for coded optical recording of data. In high density optical recording, it is often preferred to pre-record a clock or guide signal on an optical medium which is read by an optical system when the data is read.

In order to read the pre-recorded clock or lead signal, the data must be recorded in such a way that a zero in the frequency spectrum arises after reading the data. The frequency of the clock or lead signal is selected to coincide with zero in the frequency spectrum of the data. j

Such a code, which forms a zero in the frequency spectrum, is the so-called quad-phase code. In this code, two bits of a binary code are encoded into a symbol. In the optical recording, the two bits are encoded by reading holes corresponding to the bit pattern of the first half of the symbol and reading holes corresponding to the inverse of the bit pattern in the second half of the symbol. In this way, each symbol has four places. In a binary 00 it would be written with two holes in symbol places 1 and 2 and two gaps read in symbol places 3 and 4.

The binary pattern 01 would have a hole at the symbol location 30 and a hole at the symbol location 4 with no holes. in places 2 and 3. Binary 10 would have a hole in places 2 and 3 and no holes in places 1 and 4 and binary bit 11 would have no holes in places 1 and 2 and holes in places 3 and 4 Quad phase encoding 35 generates a zero in the frequency spectrum of the data 8403044 X> t - 2 - \ at a frequency FQ corresponding to 1/2 of the frequency of the symbol sites. This frequency is coincidentally a frequency of the binary data, i.e. 4 symbol locations correspond to 2 bits of binary data.

In high density optical recording, it is desirable to make the distance between the symbol sites so small that the size of a hole, that is, the diameter of a hole, may be greater than one symbol location. This clearly leads to problems in reading and decoding a symbol, because the signal from a symbol "spreads" to adjacent symbol locations. This problem is exacerbated by the laser reading beam optics commonly used in optical recording systems. These beam spots are not sharply defined beams, but rather have the shape of a Gaussian curve, in which the half-value width is approximately equal to the diameter of the holes made when reading with the same spot. For 20 holes or groups of holes, the half-value width of a signal caused during reading roughly corresponds to the diameter of the holes. Consequently, there will be a significant readout signal energy that extends beyond the centerline of the hole.

These two problems, ie hole diameter with respect to symbol location distance and overlap of the readout signal, cooperate to limit the bit densities in optical recording.

There are a large number of fixed block codes, which will generate a zero in the frequency spectrum. However, no prior art has been disclosed in the prior art to find the code or codes that allow the highest recording density in an optical recording medium.

According to an aspect of the invention, there is provided a high-density code for encoding binary data with a number of symbols each having a number of symbol locations, four or more even number of holes, and at least one empty symbol - have a place at the boundary of the symbol, where there are 40 no empty symbol places between adjacent holes 8403044 t * - 3 - or two or more empty symbol places between adjacent holes-

In one embodiment, holes are made in a medium for displaying a state where the hole interrupting represents the complementary state and a zero is present in the frequency spectrum after recording or reading, the optical medium being able to record a pre-recorded clock signal to assist in reading and reading the 10 data, where the high-density code contains: a symbol with fifteen places equidistant within the symbol for encoding eight binary data bits, a constraint that only four holes occur in any symbol, a constraint that for every hole that occurs in an even place, a hole occurs in an odd place, a constraint that the fifteenth place never has a hole, and a constraint that there is either no empty symbol place or at least two empty symbol places between adjacent holes. The high density code may contain a limitation that four holes are not recorded consecutively. Furthermore, the high-density code may contain a limitation that groups of three holes are not recorded in positions 1, 2 and 3, positions 2, 3 and 4, or positions 25 12, 13 and 14.

In another embodiment of the present invention, holes are made in the medium to represent one state and the absence of a hole represents the complementary state where a zero is set.

30 the frequency spectrum occurs after recording or reading, the optical media may include a pre-recorded clock signal to assist in reading and reading the data, according to a high-density code containing: a symbol with eighteen plate · * 35 sen, which are equidistant within the symbol for encoding eight binary bits of data, a constraint that only six holes occur in each symbol, a constraint that for each hole that occurs in an even place gap occurs in an odd place, · 40 a constraint that the 17th and 18th places 8403044 - 4 - I η * ϊ I 1 are never a gap, and a constraint that there is either no empty symbol space or at least three empty symbol spaces between adjacent holes to be. The high density code may contain a limitation that five or six holes are not recorded consecutively. The high-density code may further include a limitation that groups of four holes are not recorded in positions 1, 2, 3, and 4.

According to a further aspect of the present invention, readout equipment comprising: 10 disk means carrying data encoded according to a high density code according to the present invention is provided; means for moving these disc means; laser means for directing a laser beam at said disc means; control means for controlling said laser beam; detecting means for optically detecting this laser beam after it has fallen onto the disc means; and means responsive to said detection means for decoding said encoded data. According to another aspect of the present invention, recording equipment is provided comprising: disk means; means for moving the disk means; laser means for directing the laser beam at said disc means; control means for controlling the laser beam; Detecting means for optically detecting the laser beam after it has fallen onto the disc means; and encoding means in use for encoding high density code data of the present invention on said disc means; Which control means respond to said encoding means to cause the laser means to record encoded data on said disc means.

According to yet a further aspect of the invention, there is provided a method of recording data comprising encoding data according to a high density code of the present invention on the disk means. This data can be optically encoded.

According to still another aspect 40 of the invention, disc means are provided which are provided with 8403044 * έ * - 5 - encoded data by a method according to the present invention. The invention is, by way of illustration only, provided in the accompanying drawings, in which; Fig. 1 is a graph of the intensity of a signal detected by read optics of recording equipment having an optical disc relative to symbol locations, wherein the hole diameter is 0.9 microns, the symbol location size is 0.6 microns, and the half-value width in energy of a light spot 0.9 microns; FIG. 2 is a graph analogous to FIG. 1 but with a hole diameter of 1.25 microns; FIG. 3 is a graph analogous to FIGS. 1 and 2 but with a hole pattern consisting of two consecutive holes, a gap and then a hole; Figure 4 shows a graph analogous to Figure 3 but with a hole pattern consisting of two consecutive holes, two interstices, followed by a hole; FIG. 5 is a worst case graph of 20 "eye" apertures of different codes, where the ordinate represents fractions of the one hole amplitude and the abscissa represents the hole size parameter divided by the distance traveled during a clock period; and FIG. 6 is a block diagram of an optical recording and reading apparatus according to the present invention.

In many optical recording systems, encoded symbols represent binary data. It is common for block codes with a fixed number of holes to locate the hole or holes within these symbols by comparing the signals received from each symbol location with the signals received from each other symbol location and choosing the N highest signals detected to be the location of the hole or holes (N is the number of holes in a symbol and is a predetermined fixed number). For example, if a given symbol has four places, two of which should contain holes, a conventional optical reading equipment compares the signal energy associated with each hole with each of the four, and selects 8403044 V% v ....

<- 6 - the two places with the highest energy as the places where the holes are present.

The abscissa of Fig. 1 shows the symbol pattern 01010010 written in an optical medium, the ones corresponding to the holes and the zeros to the spaces.

In this regard, the gaps are shown as elevations on the abscissa and the gaps are shown as decreases along the abscissa. The entire group of eight places represents one symbol. The ordinate of FIG. 1 represents the intensity of the signals generated in the holes with conventional recording and reading optics and electronics. If the signal is reflected in reflection, the signal "caused" by a hole in the magnitude is the inversion of the energy of the reflected beam. When measuring the signal in transmission in which the beam is sensed from one side of the disk on the other side, the signal is a direct function of the received laser power. The dotted curves in Fig. 1 show the intensity of the readout signal associated with each of the three holes.

These curves are approximately the shape of a. curve of Gauss with the half value in energy of the signal roughly corresponding not to the diameter of the hole.

In Fig. 1, the hole diameter is assumed to be 0.9 microns while the symbol position width or the distance between the centers of the symbols is assumed to be 0.6 microns. The solid line in Figure 1 represents the summing of the signals caused by adjacent holes.

Examination of Fig. 1 shows that at no point is the signal generated by the holes or in the vicinity of the holes summed to a level where the peaks generated by the holes themselves are no longer distinguishable. An optical system can correctly read the symbol pattern shown in FIG. 1 35 because it can correctly identify the peaks associated with the holes and also the valleys associated with the gaps.

The media sensitive variations and variations in the optical recording equipment (light intensity, beam-40 aberrations) will lead to a spread in hole diameters.

8403044 - 7 - '%

Every now and then holes of considerably larger diameter are read in. For example, in Figure 2, the hole diameter is now 1.25 microns. The same symbol pattern, 01010010, is displayed along the abscissa in the same manner as in Fig. 1. Again, dotted lines represent signals generated by the holes and the solid lines represent the sum of the signals generated by nearby holes. Inspection of Fig. 2 teaches that there is very little drop in signal strength between the holes of the 101 pattern. Conventional analogous comparison schemes, which attempt to determine whether this space was a hole or a gap, may incorrectly decide that it was a hole and not a gap. The last hole 15 in Fig. 2 can then be read as a gap since the comparison system would identify only three holes in a symbol, not four.

Fig. 1 and 2 show: ·, symbol patterns, which are generated by insulated single holes also known as 20 monoholes. Fig. 3 shows a signal pattern generated by two holes read in a row. The symbol pattern in Fig. 3 is along the abscissa 01101001. The diameter of the hole is 1.25 microns and the symbol spacing is 0.6 microns. When two holes are read adjacent to each other they overlap and will look like one big long hole, as shown in Fig. 3. This large long hole generates a signal of slightly higher intensity than the signal generated by a single hole, as shown. Compare the signal given by i

the group of two holes is generated with the signals, I.

generated by the next two monoholes.

Again in Fig. 3 the dotted lines represent the signal generated by the holes themselves.

As before, the monohole patterns are of the Gauss type, but the signal from the double hole has flanks of the Gauss type and a flatter top. The solid lines show the sum of the signals from nearby holes. Equipment searching for symbol locations 40 with the four highest signals would incorrectly find holes 8403044 j - 8 - * in positions 2, 3, 4 and 5 and gaps in all other places because in positions 2, 3/4 and 5 the signal strength generated by the hole pattern 1101 at these locations is greater at all points including the gaps of the signal generated by a monohole at the. place 8.

Returning to Figure 4, the abscissa shows a symbol pattern 01100100 and a hole diameter of 1.25 microns and a symbol spacing of 0.6 microns. The equipment 10 can correctly decode the locations of three holes because the signal coming from the double hole and the signal from the subsequent single hole do not sum at the gaps to a signal that is approximately equal to the signal passing through it. -only -. 15 standing hole itself is generated or exceeds it, and this is so even though the signal generated by the double hole is larger than the signal generated by the subsequent single hole and overlaps with a significant signal-20 level three places further.

The above process can be extended to groups of three holes in a row. However, the signal energy generated by three holes in a row is not significantly greater than the signal energy generated by two holes in a row. Referring again to Fig. 4, it will be seen that the pattern generated by having holes in the first three locations of the symbol shown, rather than having only holes made in positions 2, 2 and 3, will be analogous to the pattern shown where the equipment could not correctly detect holes in positions 1, 2, 3 and 6 and the gaps in positions 4 and 5.

As shown in Figures 3 and 4, it is necessary that there is at least one empty space between adjacent symbols. Otherwise, symbols with a 1101 and 1011 pattern across the boundary may have incorrectly identified the gaps as a hole. These patterns can still occur with an "extra" place between the symbols. However, whether 40 the signal strength of a hole is present at this 8403044-9 "extra" place is irrelevant, because it is not included in the comparison equipment as one of the places, which may have a hole.

Fig. 1-4 have been analyzed to show that the presence of two gaps between holes and groups of holes allows proper decoding of a symbol.

Analogous reasoning indicates the further advantage of three gaps between holes or rows of holes and at least two voids at symbol boundaries as the hole diameter size increases relative to the symbol location size.

When determining which code will generate the maximum bit density, it is desirable to use only that code. that encode a multiple of the energy of a power 15 of two bits, that is, two bits, four bits, eight bits, sixteen bits, etc. For example, the guad phase code encodes two bits and has four symbol locations and two holes in a symbol. A so-called two-out-of-eight place code ("TOEP") has four places in the symbol and 20 encodes four bits of information. In general, in order to!

coding two bits of information in a symbol, the code I.

i have at least four different hole patterns.

To encode four bits in a symbol, the j code must have at least sixteen different hole patterns.

Analogously, to encode eight bits of information, the code must have at least two hundred fifty-six different patterns.

To a certain limit, the more holes there are in a symbol, the greater the number of possible patterns that can be obtained with the symbol. For example, in a four-position symbol, if the code was limited to having only one hole per symbol, only four different patterns would be possible, i.e. a hole in place one, place two, 35 on the place three, or place four. However, if the symbol can have two holes, the number of possible codes is 6, namely: 1100 1010 1001 0110 0101 0011 (In a quad phase code, patterns 1010 and 0.101 are eliminated because they do not meet the restriction that the 8403044 - pattern of the first two places is inverted in the second two places to allow zero in the frequency spectrum).

It will be recognized that finding the code, which optimizes the number of bits that can be encoded in a given space, is difficult and complex. Referring to FIG. 5, it is noted that the abscissa represents the hole size parameter sigma divided by the minimum symbol space or distance traveled over a half clock period. For a laser spot size used below a hole diameter of 0.96 microns, the hole size calculation depends on the particular optics and size of the hole. The formula for this calculation is complex and not currently relevant 15 and is also known. For hole sizes above 0.95 microns, however, sigma is approximately equal to 5/7 of the hole diameter. Consequently, the size of the abscissa is directly linked to the hole diameter generally with the factor 5/7 of the hole diameter. The size 20 of the abscissa is further inversely coupled to the symbol spacing. When the bit densities are kept constant, i.e., 1.2 microns per bit, the symbol location varies inversely with the number of places within a symbol. Consequently, the axis size again varies directly with the number of symbol locations of a code.

The ordinate in Figure 5 represents the worst case of an "eye" opening in fractions of the signal generated in the reading equipment by a single hole. An "eye" aperture can be defined as the difference between the amplitude of the signal attributable to a single hole and the amplitude of a summation signal attributable to adjacent holes measured at a gap ( Fig. 1-4). Formulas for calculating an "eye" pattern from a given code pattern, a given hole size, spot size, etc. are known in the art. The worst-case "eye" can be derived by examining the code patterns, which have the smallest distance between holes or 40 groups of holes. The smaller the "eye", the smaller the chance of incorrect decoding due to the unavoidable noise in the system.

After describing the methodology by which the worst-case "eye" pattern of a given code can be determined, the following comparison criteria have been made: Compared codes had to have the same bit density, ie the same number of binary bits had to be encoded per unit of length on a medium. The standard example of comparison was chosen at 1.2 microns per bit (one bit per 1.2 microns). The symbols having different actual lengths and spacing were used. meaningfully compared in this way If two bits are encoded, the total symbol has a length of 2.4 microns.

If four bits are encoded, the symbol is 4.8 microns long. If eight bits are encoded, the symbol has a length of 9.6 microns.

All codes shown in Figure 5 have the same bit density, ie 1.2 microns per bit. All 20 have a zero in the frequency spectrum. The first solid line in Figure 5 represents the worst case of an “eye11 opening for D = 1 codes, where D = 1 means that there is a minimum of one symbol space between single holes or between single holes and groups of holes 25 - or is present between groups of holes. The second solid line is the worst case of the (eye) opening for D = 2 codes. The third solid line applies for D = 3 codes. The eye holes were determined for three hole diameter dimensions: 1) 0.95 micron, (2) 1.25 30 micron and (3) 1.45 micron The best worst case codes for "eye" cartridges are listed in Figure 5.

A SHOW code, which is indicated by a dot, is the so-called two-out-of-nine code. This is the same as the two-out-eight code (TOEP) mentioned earlier, with the addition of a ninth "empty" place. Both TONE and TOEP encode four bits. The two-out-eight place code (TOEP) is shown with a square.

The six-out-of-twelve code, encoding eight bits, is represented by an inverted triangle. The. four-out-fifteen 40 code, encoding eight bits, is represented by an 840 304 4 "X".

V

- 12 -

The six-out-eighteen code encoding eight bits is represented by a triangle.

Examination of Figure 5 shows that for the density 5 of 1.2 microns per bit and for holes with a diameter less than or equal to 1.45 microns, the four-out-of-twelve code is the best "eye" i.e., the worst-case "eye" aperture is 0.6 of the amplitude for an individual hole with a diameter of the holes of 0.95 microns and 0.3 for a diameter of the holes with 1.25, while the other codes for matching diameters generate a worse "eye." The six-out-twelve code generates a better "eye" for holes with a diameter larger than 1.45 microns. It also generates the best "eye" at higher bit density for smaller holes.

Fig. 5 shows that in most cases the worst case for an "eye" for a given density is obtained from the four out of fifteen code.

In some cases, the six-out-eighteen code may be preferable, although it places a heavier burden on the laser. Codes of the present invention can achieve the highest binary bit density in optical recording or eight bit block codes compatible with a previous clock. The four-out-fifteen code according to the invention is subject to the limitation that the fifteenth symbol must always have no hole.

Also, limitingly, a zero is generated in the frequency spectrum to allow a pre-clocking system by an equal number of holes on odd resp. use places. These constraints together determine that 441 different possible patterns remain. Of these 441 different possible patterns, a certain number must be eliminated, as only 256 are required. The first to be eliminated are those that do not meet D = 2 constraint, that is, those that do not have at least two gaps between individual holes or between individual holes and groups of holes or between 40 groups of holes. in other words, either no 8403044, ψ * -13 spacing, or at least two spacings between adjacent holes. The ones that are eliminated as follows are the cartridges which place the highest load on the laser diodes of conventional optical recording equipment.

Laser diodes in most optical recording devices should not be pulsed with the reading power for a significant period of time. The last limitation eliminates patterns that have three holes in a row near the symbol boundaries and also patterns that have four holes in a row.

The specific set of 256 patterns that make up this optimal bit code is listed in Table 1.

| - table 1 - 8403044 - 14 - - table 1 - 4/15 (D = 2) code, front clock, compatible 1 234567 89 10 «be d e

0 X XXX

IX XXX

2 X XXX

3 X X XX

4 X X X X

5 X X X X

6 X X X X

7 X X X X

8 X X XX

9 X X X X

10 X X X X

11 X X X X

12 X XXX

13 X XX X

14 XXX X

15 X X X X

16 X XX X

17 X XX X

18 X XXX

19 X X X X

20 X X XX

21 X X XX

22 X X X X

23 X X X X

8403044 1 23456789 10 «pray -15- 24 X X x x 25 X X x x

26 X X x X

27 X X x X.

28 X X XX

29 X X x x 30 XXX x

31 X XXX

32 X x x X

33 X X x X

34 X XX X

35 XXX .X

36 X X X X

37 X X X X

38 X X XX

39 X X XX

40 X X X X

41 X X X X

* 42 X X XX

43 X X XX | 44 X X XX | 45 X X XX!

46 X X XX

47 X X X X

48 X X XX

49 X XXX

50 X XXX

51 X XXX

52 X XXX

53 X X X * 84 0 3 0 4 4 - 16 - 123456789 10 abcde 54 X X X x

55 X X X X

56 X X XX

57 X X XX

58 X X X X

59 XX XX

60 X X XX

61 X X XX

62 X X XX

63 X X XX

64 X X XX

65 X X XX

66 X X XX

67 X XXX

68 X XXX

69 XXX X.

70 X X X x

71 X X X X

72 X X X X.

73 XX XX

74 X X XX

75 X X X X

76 X X X X

77 X X XX

78 X X X X.

79 X X X X

80 X X XX

81 X X X x

82 X X XX

83 X X XX

8403044 - 17 - 1 234 56 7 8 9 10 * bc de

84 X * X X

85 XXX X

86 XXX-X

87 X X X X

88 X X x X

89 X X XX

90 X X X X

91 X X X X

92 XX XX

93 XX 'XX

94 XX X X

95 X X X X

96 XX XX

97 XX X X

98 XX X X

gg X XX X

100 X XX X

101 X x x X

102 X XX X

103 X X X X

104 X X XX

105 X X X X

106 X X x

107 XXX X

108 XX x X

109 X X XX

no x x xx m x x x x

112 XX XX

113 xx XX

8403044 1 23456789 10 * b c d e - 18 -

114 X X XX

X5 X X XX

116 X X X X

117 X XXX

118 X XX X

119 X X X X

120 X X X X

121 X X X X

122 X X XX

t

123 X X XX

124 X X X X

125 XX X X

126 X X X X

127 X X XX

128 X X XX

129 X X X X

130 XX X X

131 X X X X

• 132 X X X X

133 X X X X

134 X X XX

135 XXX X

136 X X X X

137 X X. X X

138 X X X X

139 X X X X

140 X X XX

141 X X X X

142 X X X X

143 X X X X

8 9 ίτν · ti β * -¾ u ύ ü s

1 I

- 19 - 12-34-56 78 9 10 * petition

144 X X XX

145 XX XX

146 XX X * X

147 XX X X

148 XX x X

149 X X X X.

150 X X XX

151 X X XX

152 X XXX

153 XXX X

154 X XX X

155 X XX X

156 X XXX

157 X X X X.

158 X X X X

159 XXX X.

160 X X XX

161 X X XX

162 X X X X

163 XX XX

164 XX XX

165 XX XX

166 XX XX

167 XX * X

168 X XXX

169 X XX X

170 X X X X

171 X X X x

172 X X X X.

173 X X X X

8403044 j - 20 - 1 2 3 4 5 6 7 8 9 10 * b c d e 174 XXX x

175 X X X X.

176 X X X X

177 X x X X

178 XXX X

179 XX X X

180 XX XX

181 XX XX

182 XX XX '

183 XX XX

184 X X X X

185 XXX X.

186 X X X X.

187 X XX X

18C X X X X

189 X X X X

190 X X X X.

191 X X X X

192 X X X X.

193 X X XX

194 X X XX

195 XXX X.

196 XXX X

197 XX X X

198 X X X X

199 XX XX

200 XX XX

201 XX XX

202 X XXX

203 X XXX

8403044 1 23456789 10 tbcde - 21 -

204 X X X X

205 X X X X

206 X X X X

207 X X X X

206 X X X X

209 X X X X.

210 x X X X

211 X X XX

212 X X X X.

213. * X XX X

214 X X X X.

215 X X X X.

216 X X X X.

217 XX XX

218 XX XX

219 X X X X.

220 X XX X

221 X X. X X

222 X X X X.

223 X X X X.

224 X XX X

225 X X X X.

226 X X X X

227 X X XX

228 X X X X.

229 X X X X.

230 X X XX

231 XXX X.

232 X X X X

233 XX X X

8403044-22- I23456 7'89 10abcde

234 X X XX

235 X XXX

235 X X X 'X

237 X XXX

238 X X X X

239 X X X X.

240 X XXX

241 X XX X

242 X XXX

243 X X X X

244 X XXX

245 X XXX

246 X XXX

247 X XX X

248 X XX X

249 X XX X

250 X X X X

251 X X XX

252 XX XX

253 XXX X

254 XXX X

255 X X X X

«8403044 - 23 - '

The six-out-eighteen code of the present invention has the limitation that its seventh and eighth positions must always not contain a hole.

A limitation is also imposed on generating a zero in frequency spectrum. The restrictions combine to leave 3,136 different possible patterns.

Of these patterns, those that do not meet the D = 3 constraints are eliminated, leaving 316 patterns. In the second place, six and five hole patterns in a row and four hole patterns in the first four places are eliminated, leaving the 256 required patterns, which are indicated in Table 2. (Thanks to the page size limitation only sixteen of the eighteen symbol places are displayed (the last two places always have no hole).

- table 2 - 6/18 (D = 3) code, front clock, compatible 0 x x x xx x 1 X X X XX x

2 X X X XX X

3 X X X X x X

* X X X XXX

δ X X X XX X

6 X X X XX X

7 X X X X xx

8 X X X x X X

9 X X X X XX

10 X X X X XX

Flu X X X XX X

12 X X X XX X

13 X X X X X x 8403044 - 24 - 12 3 4 5 6 7 14 X X X x x x 15 X X X x x x 16 X X X x x x

17 X X X XXX

18 XXX XXX

19 X X X X X X

20 X X XXX X

21 X X XXX x

22 X X XX XX

23 X X XX X X

24 XX XX XX

25 XX .XX X X

26 X X XX XX

27 X X XX XX

2fi X X x XX X

29 X X X XXX

30 X X X X xx

31 X X X XXX

32 X X X X X X

33 X X XXX X

34 X X XXX X

35 X X XX X x 36 X X XX x x 37 XX XX X x

38 X X XX. XX

39 X X X X X

40 X X X XXX

41 X X X XXX

42 X X X X X X

8403044 - 25 - 12 3 4 5 6 789] 0abcdef

43 X X XXX X

44 X X X X X X

45 X X X X X X

46 X X X X X X

47 X X X XXX

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49 X X X XX X

50 X X XX X X

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52 X X X X X X

53 X X X X X X

54 X X XX X X

55 X X X X X X

56 X X X X X X

X X X X.

57 X X.

58 X X X X X x

59 X X X X X X

60 X X X X X X

61 X XXX X X

62 X X X XXX

63 X .XX XX X

¥ Y x X X i 64 X XX *

65 X XX XX X

66 X XX XXX

67 X XX X X X

68 X X XXX X

69 X X X X X X

70 x X X X 'X x

71 X X X X X X

72 X XXX XX

8403044 w - - 26 - 12 3 4 5

73 X XXX XX

74 X XXX XX

75 X XXX XX

76 X XX XXX

77 X XX XXX

78 X XX XXX

79 X X X X X X

80 X x XX X X

81 X X X X X X

82 X X X X X X

83 X X X X X X

84 X X X X X X

85 X X X X X X

86 X XX XXX

87 X XX XXX

88 X X X X X X

89 X XXX XX

90 X XXX XX

91 X XX XXX

92 X X X X X X

93 X X x x x x

94 X X X X X X

95 X XX XXX

96 X X X X XX

97 X X X X X X

98 X X X X X X

99 X X X X X X

100 X X X X X X

101 X X X X XX

8403044 - 27 - 1 2 3 4 5 £ l ££ l £ ®.-ll--

102 X X X X X X

103 X X X X XX

104 X X X X X X

105 X X X X X X

106 X X X X XX

107 X X X XX X

108 X X X XX X

109 X x x XXX

no xxx X x x

111 X X X X XX

112 X X X X XX

113 X x x X x x

114 X x X X X

115 X x X XXX

116 X x x X x x

117 X x x XXX

118 X x X X X X

119 X X XXX x

120 X X XXX X

121 X x XX x x

122 X x XX XX

123 X X XX XX

124 X X XX XX

125 X X X X X

126 XX X XXX

127 X X X XXX

128 X X X X X X

129 X X XXX X

130 X X XX X X

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131 X X XX XX

132 X X XX XX

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8403044 - 33 -

An embodiment of the optical recording equipment of the present invention is shown in FIG.

A laser disc 10 includes a disc of optically reflective material, into which holes can be burned to reduce the reflectivity of the surface at the hole. The disc 10 is typically composed of grooves (not shown) pressed into a substrate by a replica process. The grooves are depth modulated at a clock frequency. Then, the surface of the substrate is coated with an optically reflective material suitable for recording data on it in the form of holes. A motor 12 rotates the disk 10 during both recording of the data and during reading of the data. A laser 14 is used both for recording data and for reading data. In the recording mode, the laser is operated with a higher energy than in the reading mode. The energy is at such a level that it burns a hole in the reflective material of the disc 10.

In this regard, before reading a hole, the laser, which itself can be formed by a laser diode, can be pulsed, while it is also possible for the laser beam, such as from a gas laser, to be deflected from the disk 10.

In the read mode, the laser continuously operates at a lower power, which is insufficient to change the reflective nature of the disk 10. The laser is under the control of a laser controller 16. The laser controller 16 controls the energy level of the laser and its pulsation or beam deflection. The data to be read comes from a data encoder 18, which receives binary data to be read on the disk 10, which according to the present invention encodes a four-out-fifteen or a six-out-eighteen code, and the encoded transfers data to the laser controller 16, which in turn controls the laser 14 to read data onto the disk 10, which rotates.

In both the read-in mode and the read-out mode, a reading means 20 detects the reflection of the laser beam on the disk 10. The reading means usually contains a photodiode, which converts light into 8403044 W4.34 electrical signals. The output of the reading means 20 is supplied to a servo 24, which maintains the location of the laser 14 and the reading means 20 directly above the path on the disk 10. The output of the reading means 20 is also added to a data encoder 22 and a read-after-read-in verification chain 26. The read-after-read-in verification chain 26 compares the data read into the disc with the data read out from the disc during the read-in to verify that the data has been read correctly. If the data has been incorrectly read into the disk 10, a reread can be initiated or error correction means can be used. In the readout mode, the data supplied to the data decoder 18 is decoded from the 15 four-out-sixteen or the zas-booty-eighteen code to the eight-bit binary code of the original data. In the present embodiment, (not shown) error correction performed on the eight bit binary data.

In summary, the displayed first code of the present invention includes a fifteen-spaced symbol equidistant within a symbol for encoding eight bits of binary data.

Holes are read with centering on a symbol and have diameters greater than the distance of the symbol plaques. Exactly four holes and only four holes occur in a symbol. For every hole that occurs in an even place, a hole is present in an odd place and vice versa. This generates a zero in the frequency spectrum so that a pre-recorded clock signal 30 can be read out and decoded with other electronics (not shown). Fifteenth place never has a hole. At least two symbol locations appear between individual holes or between individual holes and groups of holes or between groups of holes.

To decrease the number of codes from 441 to 256, those that do not meet the D = 2 limitation are eliminated. In addition, while not essential to the invention, all symbols having four consecutive holes have been eliminated. All symbols, 40 which have three holes in symbol positions 1, 2 and 3 or 8403044 -35 - positions 2, 3 and 4 or in positions 12, 13, and 14, have been eliminated.

The six-out-eighteen code is similarly constructed with D = 3 and two empty spaces at the end 5 of each symbol. Symbols with five and six holes in a row as well as four in a row in positions 1 to 4 have been eliminated.

In general, for a symbol with Y and X places holes (Z places at the boundary that never have a hole) and in which for every hole that occurs in an even place, a hole occurs in an odd place, the maximum possible number codes given by: '_55lÏ

15 XI / Y-X-ZM

2 ITJ J

This maximum possible number is then reduced by a D = N (where N is at least 2).

- conclusions - 8403044

Claims (14)

High-density code for the coded recording of binary data, characterized in that it has a number of symbols, each of which has a number of symbol places, four or more even number of holes and at least one empty symbol place at the boundary of the symbol, where there are either no empty symbol places between adjacent holes or two or more empty symbol places between adjacent holes. High-density code according to claim 1, characterized in that the holes are made in a medium for displaying one state and that the absence of a hole indicates a complementary state, and that, a zero in the frequency spectrum is present after recording or reading, whereby the optical medium may include a pre-recorded clock signal to assist in reading out reading data containing high density code; a fifteen-spaced equidistant symbol within the symbol for encoding eight 20 binary data bits, with a limitation that only four holes occur in each symbol, a further constraint that applies to each hole that occurs in an even place one. hole occurs in an odd place, a constraint that the fifteenth place is never a hole, and a constraint that either there is no empty symbol place or at least two empty symbol places between adjacent holes. High density code according to claim 2, characterized in that it satisfies the limitation that the four holes are not recorded consecutively. 1 8403044 High-density code according to claim 2 or 3, characterized by the limitation that groups of three holes are not recorded in positions 1, 2 and 3, positions 2, 3 and 4 or positions 12, 13 and 14. - 37 - High-density code according to claim 1, characterized in that the holes are provided in a medium for displaying one state and the absence of a hole indicates the complementary state, and wherein a zero is present in the frequency spectrum after recording or reading, allowing the optical media to include a pre-recorded clock signal to assist in reading and reading data, which contains high-density code: a symbol having 10 eighteen places equidistant within the symbol for encoding eight binary data bits, under the restriction that only six holes occur within each symbol, the restriction that for every hole that occurs in an even place, a hole occurs in an odd 15 place, the restriction that the seventeenth and eighteenth places never have a gap and the limitation that there is either no empty syrabole place or at least three empty symbol places between aa adjacent holes. 6. High density code according to claim 5, characterized in that it satisfies the restriction that five or six holes are not recorded consecutively. High density code according to claim 5 or 6, characterized in that it meets the constraint that groups of four holes are not recorded in positions 1, 2, 3 and 4. I Recording device, characterized by: disk means (10) carrying data encoded according to a high-density code according to one or more of the preceding claims; means (12) for moving the disk means; laser means for directing a laser beam at the disc means (10); control means (16) for controlling the laser beam after it has fallen onto the disc means (10); and means (22) responsive to said detection means for decoding said coded data. 8403044 «r ί - 38 - 9. Recording device, characterized in that it contains: disc means (10)? means (12) for moving the disk means? laser means (14) for directing a laser beam at the disk; 5 control means (16) for controlling the laser beam? detecting means (20) for detecting the laser beam optically after it has fallen onto the disc means? and coding means (18) used for coding data according to a high-density 10 code according to one or more of claims 1 to 7 on said disk means, said control means (16) responding to said coding means (18) about the laser beam (14) have encrypted data recorded on said disk means * A method of recording data, characterized by encoding data according to a high-density code according to one or more of claims 1-7 on the disk means. Method according to claim 10, characterized in that the data is optically encoded. 1 2 3 8403044 High density equipment for data recorded on a medium, characterized in that a number of symbols are present, each containing: a 2 predetermined number of places, each place having the same predetermined length; four or a large even number of holes comprising a first medium state, each hole centered on a symbol location and of variable length, the maximum of which is predetermined? the medium state of the pendant of a symbol has a second medium state? 3 reading means for reading the symbols and for determining the location of the symbol location of the center of the holes? readout means including means for inducing measurement signals indicative of the medium states? wherein the strength of these signals depends on the length of the media states and decreases from the boundary of the media state according to a Gaussian curve centered at a predetermined distance from the edge of a media state; the location of the centers of the holes is spaced by a predetermined number of symbol locations such that the signals from one or more holes centered on adjacent symbol locations and measured in a non-centered location is less than the signal caused by a single hole of nominal size; and at least one symbol location at 10 a first boundary of the symbol has no hole centered thereon * A high density device according to claim 12, characterized in that said predetermined maximum hole length is less than the length of two symbol locations, the number of holes in a symbol being four and the holes being such are arranged to be centered on adjacent symbol places or on symbol places which are at least two symbol places apart. High density device according to claim 12 or 13, characterized in that the predetermined maximum length of a hole is less than the length of two symbol locations, the number of holes in a symbol is six and the holes are centered on 25 adjacent symbol places or centered on symbol places that are at least three symbol places apart and that there are at least two symbol places at a first boundary on which no holes are centered. Disk means, characterized in that data is encoded thereon according to a method according to claim 12 or 13.