JP3149455B2 - Information recording apparatus, information reproducing apparatus and information recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical information processing apparatus, in particular information recording RokuSo location such as an optical disk, an information reproducing apparatus及<br/> beauty information recording method.

[0002]

2. Description of the Related Art Conventionally, since the basic recording / reproducing method of the optical disk was proposed, up to the present practical stage, as in the case of a recording apparatus based on the recording principle using magnetism, a concentric track is formed in a circular track. Data is recorded in chronological order along the circumferential direction. The adjacent track interval is set so as to eliminate data interference between tracks (referred to as crosstalk). There is no correlation.

As a technique for improving the recording density of an optical disk, there is, for example, Japanese Patent Application Laid-Open No. 2-53223.

[0004]

The information recording / reproducing apparatus is always required to have a higher density. As a measure for this, in the conventional magnetic recording method, the measures for improving the recording surface density are to independently increase the track spacing and the bit density in the circumferential direction, respectively, and a similar approach has been taken for optical disks.

In the conventional magnetic recording head, the track density and the bit density differ by about one digit because the resolution in the circumferential direction and the resolution in the radial direction are asymmetric. However, since the spot used for recording and reproduction is isotropic in the optical disc, the track density and the linear density are almost equal in the optical disc for recording and reproducing data. However, even if the light spot shape is isotropically reduced to improve the density, the linear density can be improved, but the track interval cannot be improved as in the linear density. This is due to the fact that there are many spot position fluctuation factors in the radial direction, so that the fluctuation amount is large and it is difficult to narrow the track interval.

[0006]

For the above purpose, the above-mentioned optical disk utilizes the isotropy of the spot which is superior to a conventional recording apparatus.

To achieve the above object of the information recording / reproducing apparatus of the present invention, a buffer means for storing continuous storage data in units converted into two dimensions; n × m two-dimensional units corresponding to the unit data Means for converting to a data array of m; m light sources, and converting the n × m two-dimensional data array into m columns of 1
Recording means for reading out data divided into dimensional data strings and controlling the m light sources in accordance with these data strings; optical means for converging light beams from the m light sources to form m spots on a disk surface The recording data is recorded as a group of optically identifiable information identifiers having a two-dimensional spread of n × m on the disk surface.

The information recording / reproducing apparatus of the present invention converts continuous data into data having a two-dimensional spread of n × m, and records the data as optically identifiable pit groups on an optical disk. An information recording / reproducing apparatus for reproducing data stored by a storage method, comprising: m light sources; optical means for converging light beams from the m light sources to form m spots on a disk surface; m spots
Positioning means for positioning the pit group on the disk surface; m detecting means for detecting reflected light from the pit group corresponding to each spot; m columns from the reflected light detected by each detecting means Generating means for generating a one-dimensional data sequence of n and combining n pieces of the data to generate n × m two-dimensional data; demodulating means for demodulating continuous data from the n × m two-dimensional data Consists of

According to the information recording / reproducing method of the present invention, a step of encoding recorded information in two dimensions; a step of converting the information into a one-dimensional information array; and a method of modulating a plurality of laser light sources using the information array. Recording a two-dimensional code on the disk surface;
Reproducing the dimensional information; photoelectrically converting the reproduced signal; detecting a one-dimensional array signal from the photoelectrically converted signal;
Decoding the dimension information.

Further, the information recording / reproducing method according to the present invention stores continuous recording data in units converted into two dimensions; and encodes the data into an n × m two-dimensional data array corresponding to the data in the units. Reading the nxm two-dimensional data array into m one-dimensional data arrays and controlling the m light sources in accordance with these data arrays; and luminous fluxes from the m light sources. Converging and forming m spots on the disk surface; and recording data to be recorded as optically identifiable pit groups having an n × m two-dimensional spread on the disk surface. Positioning the m spots in the pit group on the disk surface; detecting the reflected light from the pit group corresponding to each spot; and detecting each step. 1 from in the detected reflected light of m column
Generating a two-dimensional data string and combining n pieces of the data to generate n × m two-dimensional data;
Decoding continuous data from the n × m two-dimensional data.

According to the present invention, the data to be recorded is divided, and the divided data does not correspond to a one-dimensional array as in the conventional encoding, but corresponds to a two-dimensional array. I do.

At the time of recording, the two-dimensional array is divided into a plurality of one-dimensional arrays. A plurality of light sources corresponding to a plurality of one-dimensional arrays are used, and light beams from the light sources are converged on a disk surface to form a plurality of spots. Each light source is modulated according to the data of each one-dimensional array, and an optically identifiable pit group having a two-dimensional spread in a radial direction and a circumferential direction is recorded on the disk surface.

At the time of reproduction, light beams from a plurality of light sources are converged to form a plurality of spots on a disk surface, and the spot groups are formed in the optically identifiable pit groups having a two-dimensional spread. The position is determined, and reflected or transmitted light modulated by the pit group corresponding to each spot is detected. A one-dimensional data array corresponding to the trajectory of each spot is generated using each detected time-series signal, and a set of data corresponding to the set of the plurality of one-dimensional data arrays is decoded to decode the disc. Read out the information recorded in.

[0014]

According to the present invention, by recording data at a plurality of spots at once, it is possible to reduce the amount of spot position variation in the radial direction between the one-dimensional arrays. Also,
From a two-dimensional array that takes into account signal processing at the time of detection (at the time of reproduction), data can be reliably detected even if the interval in the track radial direction between data of each one-dimensional array is narrowed.

[0015]

First, an outline of the system of the present invention will be described with reference to FIG. In this embodiment, as shown in FIG.
The stored data is converted into 4 × 2 two-dimensional data, and 4 rows 2
It shall be stored in the state of the pit in the row.

In this embodiment, at the time of recording, the continuous storage information 901 is divided into 8 (4 × 2) units, and
It is encoded into a two-dimensional array with two rows and two columns (902),
The row 2 column is converted into a one-dimensional information array of one column at a time and read (903), the laser 905 is modulated based on the one-dimensional information array (904), and the laser light is And two rows of pits 90 on the disk surface
8,909 are formed. At the time of reproduction, the laser 90
5 is condensed on the pit by the optical system 906, the reflected light from the pit is received by the light receiver 910, and this is photoelectrically exchanged (911), and a one-dimensional array signal is detected from the photoelectrically converted signal. (912), a two-dimensional code is obtained from this, and it is decoded to reproduce continuous information (914).

Hereinafter, a more specific structure of the present invention will be described.

FIG. 2 shows one embodiment of a basic encoding pattern of a group of optically identifiable pits formed on a disk surface according to the present invention. For convenience of explanation, an encoding pattern of two matrices will be described first as an example. As shown in the figure, a grid consisting of four vertical and horizontal lines is taken as one block, and there is no round hole pit 30 at a position centered on four grid points (points where grids intersect) in the block. Express the data by In this case, since there are four grid points (two rows and two columns) in one block, the possible data array is 2
, That is, 4-bit data.
An example of correspondence with the recording data is shown below the figure. Example 2
Dimensional encoding refers to associating recording data with a pattern as shown in the drawing, which is arranged two-dimensionally.

FIG. 3 is an explanatory diagram of the pits recorded on the disk. The blocks 1 to 18 are arranged in the circumferential direction as a dashed line as a data array in the disk circumferential direction (arrow). Equally spaced gaps are provided between the tracks in the track direction so that it can be determined that the blocks are between the blocks. Data is recorded between the guide grooves 20, 21, 22, and 23 of a normal continuous servo system, and a track shift signal for locating a recording spot is obtained by using a normal track shift detection method and using diffracted light from the guide grooves. To detect.

In the embodiment shown in the figure, the pits are overlapped. However, the pits may be recorded so as not to overlap. At this time, although the areal density is low, a complicated signal processing system is not used during reproduction, and multiple rows of pits can be recorded at once compared to the conventional method, so the track pits can be reduced by the track deviation fluctuation. it can.

If the lattice spacing in the track radial direction is smaller than the round hole pit diameter, the pits overlap in the two-dimensional array pattern as shown in the figure. In this case, it is necessary to create a code rule in consideration of processing at the time of reproduction. This will be described later with reference to FIG.

In order to record a pattern as in the present invention, it is necessary to accurately control the positional relationship between recording pits.

A method of recording a pit group for accurately controlling the positional relationship will be examined. When a method of recording one pit row for each rotation and then recording one adjacent pit row as in a conventional optical disc is used in this embodiment, the state of light spot control of the apparatus changes. Then, the positional relationship of the pits in the track radial direction is shifted.

Therefore, in this embodiment, a plurality of spots are used to record the pit groups in the two-dimensional array at least during the same rotation period.

FIG. 29 shows a specific positional relationship between spots. In FIG. 29, the circular portion covered by oblique lines is the light spot 10.
0, 101, an axis 102 connecting these spots
Are slightly inclined with respect to the track circumferential direction, and are shifted from each other in the track radial direction due to the inclination. Originally, it is desirable to place two spots close to each other,
Considering the characteristics of the current semiconductor laser, the spot interval on the disk surface must be 10 microns or more.
That is, considering the wide angle of the semiconductor laser and the light use efficiency, the numerical aperture of the lens for coupling the light from the semiconductor laser is about 0.15 to 0.3, and the numerical aperture of the objective lens is determined by the characteristics of the disk substrate It cannot be so large, and is about 0.5 to 0.6, so that the overall lateral magnification of the optical system is about 2 to 4. The emission interval of the laser is set to 50 due to reasons such as eliminating thermal interference with the current semiconductor laser.
μm or more. Further, since the grid interval must be at least 1.6 μm or less and 1.5 μm or less in the conventional track pitch, spots are separated in the track circumferential direction at the current technical level. This shift amount is defined as the above-mentioned interval in the track radial direction of the lattice.

In FIG. 29, the two-dimensional array after recording is shown on the right track (the track between the grooves 21 and 22) for convenience of explanation, and the relationship between the light spot and the pit in the process of recording this is shown on the left track ( Track between grooves 20 and 21).
Here, it is assumed that the disk plate is rotating in the direction of the arrow. The pits 30 ′, 31 ′, 33 ′, 34 ′, 35 ′, and 36 ′ that have already passed through the recording spot 101 and have been recorded.
With a solid line. The pits to be recorded are indicated by dotted lines.

In this arrangement of spots, the same block is not recorded simultaneously, but after a time difference corresponding to the spot interval in the track circumferential direction, that is, during the same rotation period, the recording is completed.

In order to form a two-dimensional array, the irradiation intensity of each recording spot is modulated according to the data of each one-dimensional array, and recording is performed one-dimensionally in the track circumferential direction.

A predetermined coding table is used to convert this two-dimensional array into a one-dimensional array corresponding to each recording spot. An encoding table corresponding to the two-dimensional array in FIG. 2 is as shown in FIG. This encoding table is stored in ROM
(Read only memory), and searches for data that realizes a two-dimensional array corresponding to the data to be recorded. In order to obtain a one-dimensional array for modulating a plurality of (two in the example of FIG. 4) light sources from this data, since the data is 4 bits as shown in FIG.
1 modulating the light source forming the leading spot with bits
The lower two bits correspond to a one-dimensional array for modulating the light source forming the succeeding spot. Further, the order in the one-dimensional array is shifted from the upper bit of the data.

The operation of the recording signal processing system using such an encoding table will be described with reference to FIG. Data 1 to be recorded
10 is input to the latch circuit 111, and data is stored every four bits in accordance with the latch control signal 112. The four bits are input to the ROM 113, and 4-bit data for realizing a two-dimensional array is searched. Retrieved data 114
Is stored in the latch circuit 116 in accordance with the latch control signal 115. The lower bits of the data 114 are read in accordance with the first clock signal 117 and stored in a shift register 118 of finite length in synchronization with the clock signal 117. The upper bit of the data 114 is set to the second clock signal 1
19, and is stored in the shift register 120 longer than the length of the shift register in synchronization with the clock signal 119. Each shift register 118, 1
The outputs of 20 are connected to modulators 121 and 122, respectively, and the binary signals from the shift registers 118 and 120 are converted into analog signals 123 and 12 for modulating the emission intensity of the laser.
Convert to 4. Here, in order to control the shape of the pit after recording, the light emission waveform of the light pulse is controlled. For example,
It is known that, in order to stably record a round hole pit as shown in FIG. 1, it is better to record with a higher light emitting power and a pulse shorter than a data clock. I do. Further, depending on the linear velocity and the recording medium, the modulator performs complicated waveform control such as increasing the recording power for a certain period at the start of recording.

The laser driving circuits 125 and 126 are operated in accordance with the signals 123 and 124 from the modulator to modulate the emission power from the light sources 127 and 128 forming the respective spots.

In this block diagram, the length of the shift register is changed. This is because the positional shift of the two recording spots in the circumferential direction shown in FIG. 29 is changed by shifting the recording timing of the succeeding spot. The correction is performed on a periodic basis. Also, the first and second clock signals 117 and 119
Have the same period but a different phase relationship. This shift amount corresponds to a correction amount for controlling the position of a finer light spot within a clock cycle, in addition to the position shift correction by the shift register described above. Further, the first and second clock signals 117 and 119 have a period in which there is no clock at regular intervals in order to provide the aforementioned gap between blocks.

A method of reproducing data will be described below with reference to FIG. The light spots 100 and 101 used for recording to reproduce the recording pit group are used. Similar to the recording, the tracking adjustment using the diffracted light from the guide grooves 21 and 22 is performed, and a one-dimensional pit row in the circumferential direction corresponding to the one-dimensional array data from which each light spot is to be read (the center line is defined as 130, 131). In order to detect data, it is necessary to determine whether there is a pit at a grid point. For this purpose, a strobe pulse corresponding to the position of the grid point is created, the level of the signal read from each spot is sampled and held by this pulse, and the read signal level at the grid point is detected. By comparing this detection signal level with a specific level, it is determined whether or not there is a pit at the lattice point.

Here, using a normal optical system having an objective lens having a numerical aperture of 0.53 and a laser wavelength of 830 nm, a pit row composed of two pits having a diameter of 0.8 μm is changed by changing the interval between the two pits. 19, 20, and 21 show whether a reproduced signal at the time of reproduction is obtained by simulation.
FIG. 19 when the nearest interval between adjacent pits is 0.4 μm, FIG. 20 where the nearest interval between adjacent pits is 0.0 μm (that is, in a state of being in contact), and FIG. 21 where pits overlap. By comparison, it is difficult to distinguish between FIG. 20 and FIG. 21 from the viewpoint of the level margin, but FIG. 19 and FIG. Accordingly, the following coding rules are used to determine the positional relationship between the pits so that FIG. 20 and FIG. 21 do not occur at the same time.

Here, the encoding rule (code arrangement relationship) of this embodiment will be described with reference to FIGS.

[0036] That is, the overlap of the pits and the pit in this embodiment is acceptable, the overlap is the overlap of a plurality of pits
It is desirable that a pit group and which the adjacent overlapping pits group are arranged as close as possible to the density of the optical disk. However, for receiving the interference of the pits and the pit at the time of reading, among the overlapping pit group overlap each
The outermost pits provided in the pit group are separated from each other by an interference distance determined by the optical system.

When storing a round hole pit, the pit size is W and the read spot size is Ws. First, interference between single pits will be described with reference to FIG.

For example, when the spot is located at the position 701-1 between the pits 700 and 701, the edge of the spot is affected by the outer periphery of the pit 700, and therefore, the signal level of the center 701-1 of the pit 701 is affected. May be received. The condition under which this effect can be ignored is 70
This is when the distance L between 0-1 and 701-1 satisfies the following condition.

L ≧ W / 2 + Ws / 2
(Equation 1) Ws is, in principle, assuming that the laser wavelength is λ and the numerical aperture of the objective lens is NA, Ws = k × λ / NA
(Equation 2) k becomes 0.85, but it becomes about 1.0 in an actual optical system due to assembling and manufacturing. The above is shown in FIGS.
Well agrees with the simulation results. It is clear from the result of the simulation that if the pits overlap, the simple superposition of the solitary waves often used in conventional magnetic disks and the like cannot be established. The reason for this is that there is no optical resolution and that the optical characteristics at the overlapped portion are not different from the optical characteristics at the non-overlapping portion. Therefore, even if they are overlapped as in the simulation, the signal level at the overlapped portion changes only slightly. As specific numerical values, a wavelength of 830 nm, NA of 0.2.
Assuming that the pit diameter is 53 microns, L is about 1.2 microns. In the embodiment, the lattice spacing is selected to be 0.4 μm, which is ３ of this length.

Mutual interference between pits is two-dimensionally isotropic not only in the track direction but also in the track radial direction. For this reason, the lattice spacing in the track direction is a, and the lattice spacing in the track radial direction is b, and a and b are now made equal.
Then, a circle having a diameter equal to the spot diameter is drawn from the center of one pit, and the circle is arranged so that the edge of the other pit does not touch the circle and the center of the pit comes to a lattice point.

Next, the case where the pits are not alone but overlap will be described with reference to FIGS. 26 and 27. FIG. In the present embodiment, it is recognized that the pits overlap like the pits 708 and 709. At this time, the pits 709 and 710 corresponding to the outermost pits are the same distance as the pits 700 and 701 in the track direction in the above-described example. You need to take a relationship. Overlap is the overlap pit group pits led by the pits overlap is formed
Each overlapping peak relationship pit group overlaps with the pit group
In other words, the pits of the other overlapping pit groups are not in contact with the circle having the spot diameter as the center with the center of the outermost pit forming the set group . In this embodiment, FIG.
As shown in FIG. 7, when both the lattice spacings a and b are 0.4 μm, the pit diameter is 0.8 μm, and the spot diameter is 1.6 μm, an overlapping pit group composed of pits 711 ′, 712 ′ and 713 ′. The grid points where pits of other overlapping pit groups can exist are indicated by white circles, and the lattice points that cannot be present are indicated by black circles. It has been described a two-dimensional pit sequences in more than on information tracks, is as follows for between tracks.

As shown in FIG. 1, if the distance of a laser spot formed from a plurality of light sources in the radial direction of the disk is L, the track pitch of a two-dimensional code is p, and the spot size is Ws, the following relationship is obtained. is necessary.

P ≧ L + Ws Next, a method for generating the above-described strobe pulse will be described.

In order to generate a strobe pulse, it is necessary to detect a reference signal for generating a timing for generating a pulse from recording data. As this signal, there is also a self-clocking system in which a data signal is used as it is. However, as shown in No. 15 in FIG. There is a possibility that a signal for timing production cannot be detected from the obtained data. Therefore, as shown in FIG.
32 ', 133 and 133' are provided, and the format of the recording data is determined so that these always appear at specific intervals.

This synchronization mark is preferably provided in advance on the disk, but can also be formed by the recording / reproducing apparatus of this embodiment at the time of recording. This way,
Although the data efficiency is slightly lowered, the reference signal for strobe pulse generation can be detected stably.

The synchronization mark 133, 133 'of FIG. 6, 13
2,132 'does not appear in the recorded data. In this pattern, three pits are overlapped, and one pit 134, 134 ', 135, 135' is separated thereafter. First, a pattern in which three pits are overlapped is detected, and isolated pits 134, 134 ', and 13 that are separated from the pattern by a predetermined distance.
Predict the position of 5,135 '. Isolated pit 134,1
34 ′, 135, 135 ′, and by finding the zero cross point, the isolated pit 13
The center position of 4,134 ', 135, 135' is detected. Since the center position of the isolated pit coincides with the lattice point, a reference position for detecting the timing of the lattice point can be obtained. Such reference points are detected at regular intervals, and P
A reference clock is generated by a well-known clock generating means such as LL (phase locked loop).

The reproduction signal processing system will be described with reference to FIGS. Here, the light source of the recording apparatus of FIG. 5 can be used in common. The light from the light source is applied to the pits as spots, and the reflected light from each spot is detected by the photodetectors 140 and 141 corresponding to each spot. The signals after photoelectric conversion are amplified by the amplifiers 142 and 143, and the peak detection circuits 144 and 145 and the synchronization part detection circuits 146 and 147,
Input to the sample and hold circuits 148 and 149. As described above, the peak detection circuits 144 and 145 differentiate the signals from the isolated pits 134, 134 ', 135 , and 135' to check for zero, and determine whether or not the pulses 150, 145 correspond to the peak point.
151 is generated.

As shown in FIG. 6, the synchronization detection circuits 146 and 147 detect pit patterns 132, 132 ', 133 and 133' in which three round hole pits overlap from the reproduced signal. For this purpose, the reproduced signal is sliced at a specific level, and it is detected that the pulse length after slicing is within a certain range of the specific length. In normal data, three round hole pits do not overlap due to the coding rules.
The detection of the synchronization mark part is possible.

After a predetermined time from the synchronizing section, a gate pulse 1 of a fixed width covering the position of the isolated pit
52 and 153 are created. This gate pulse 152, 1
53 and the output pulse 15 of the peak detection circuits 144 and 145
0, 151 are input to the gate circuits 154, 155, and the pulse 15 corresponding to the center of the isolated pit immediately after the synchronization unit is input.
6,157 is created.

The signals 156 and 157 are transmitted to the PLL 158,
159, and generates clock signals 160 and 161 synchronized with the signals 156 and 157 and having a frequency that is an integral multiple of the repetition frequency of the signals 156 and 157. The clock frequencies 160 and 161 correspond to the recording clock 11 described above.
The frequency is almost equal to 7, 119.

The synchronization detection pulses 162 and 163 and the clock signals 160 and 1 are supplied to the sample and hold circuits 148 and 149, respectively.
61, the level of the reproduced signal from the data pit is sampled and held. The outputs 164 and 165 are input to level comparators 166 and 167, and are converted into binary signals depending on whether the level of the input signal is higher than a specific level. The binarized signals 168 and 169 are input to first-in / first-out memories 170 and 171, and the timings 172 and 172 of a control clock signal described later are used.
According to 173, the data is accumulated in the memories 170 and 171. The above configuration is a configuration of a series of processing circuits corresponding to each spot, and in the present embodiment, there are two systems of the same processing system described above in this embodiment. Hereinafter, in order to distinguish the elements of each constituent block, first and second numbers are given. One-dimensional array data 17 stored in two memories 170 and 171
4,175 must be read and rearranged in a two-dimensional array of data. For this purpose, the one-dimensional array of binary data recorded at the same radial position on the disk surface must be aligned. Therefore, the synchronization mark units 132, 132 ', 133, and 13 are selected from the data of each one-dimensional array.
Each data is clocked with reference to 3 ′.
Numbers are assigned in units of 0,161. After that, data of the same number stored in each memory is read out at the same timing 176, 177 for each one-dimensional array. For this purpose, first and second timing control circuits 178 and 17 for controlling the timing of storing data in the memories 170 and 171 are provided.
9 is provided. The write first and second timing control circuits 179 and 178 of the memory use the first and second PLLs 15 and
Using the clocks 160 and 161 and the synchronization detection pulses 162 and 163 created in steps 8 and 159,
Pulses 17 for writing data to the memories 170 and 171 in order from the detection of 2, 132 ', 133 and 133'
2,173 is created. Then, each memory 170, 171
Have synchronization mark parts 132, 132 ', 133, 133'
, The data of the one-dimensional array is sequentially accumulated.

The read timing is determined by the read pulses 176 and 17 from the read timing generating circuit 180.
7, the respective memories 170 and 171 are controlled. The timings 176 and 177 correspond to the first and second synchronization detecting sections 14 respectively.
6 and 147, the pulses 176 and 177 for starting reading are generated after the arrival of the later synchronization pulse. The pulse cycle may be created from the reference clock 181 having a fixed cycle, or a clock created by a PLL used in a signal processing system having a later synchronization pulse or a created clock may be used. . Thus, the first and second serial data 174, 175 read from the memory are read.
Means that the recording radius positions are completely aligned.

The serial data 174 and 175 are shown in FIG.
Is taken into the latch circuit 182 for each block. The data latch signal 183 is created by dividing the clock 181 by two in the read timing control circuit 180 described above. The 4-bit data 184 indicating the two-dimensional array for each block is input to a ROM (read only memory) 183 having a conversion table opposite to that of FIG.
A set of data 185 is retrieved and taken into the latch circuit 186.

This data 186 becomes data 187 demodulated by the signal processing circuit.

Up to now, the pit group of the recording block is (2
Although an example using four grid points (row 2 column) has been described, examples of 6 (3 row 2 column) and 8 (4 row 2 column) grid points are shown below. FIG. 9 shows a case where there are six grid points (three rows and two columns).
This is an example of a dimensional array, and bit data can theoretically be represented as recording data. However, if the number of pits in this block is too large, the amount of reflected light at the time of reproduction is reduced. Therefore, in this example, use of these blocks is avoided and 5-bit data is displayed. When recording, it is converted into two (two-row) one-dimensional arrays. In the conversion table, 5 bits correspond to 6 bits. Each one-dimensional array uses the upper 3 bits and lower 3 bits of these 6 bits. Each one-dimensional array is recorded in order from the upper bit.

FIG. 1 shows an example in which pits are recorded on a disk using this method.

FIGS. 10 to 13 show an example of a two-dimensional array in which there are eight child points. It is preferable that the recording data represent 7-bit data for the same reason as described above.
When recording, it is converted into two (two-row) one-dimensional arrays.

In the conversion table, 7 bits correspond to 8 bits. Each one-dimensional array uses the upper 4 bits and lower 4 bits of these 8 bits. In any case where each one-dimensional array is recorded in order from the most significant bit, in order to demodulate the data, an inverse conversion table corresponding to the modulation is used as described when the recording data is 4 bits.

FIG. 28 shows an embodiment in which the number of grid points is further increased in the row direction and the column direction. Track direction (row direction)
There are 56 grid points of 7 in the track radial direction (row direction). Since there is a relationship of C = K-1 between the number of lattice points K and the number of data bits C that can be represented by this, data of about 55 bits can be represented in this embodiment as well.
From the viewpoint of the areal recording density, the encoding according to the present invention can be improved over the conventional method, but the relationship between the density improvement ratio and the number of grid points is estimated to be saturated with an increase in the number of grid points according to trial calculation. One digit improvement can be expected, and at the same time, the transfer rate can be expected one digit improvement. In order to record the pit arrangement of this embodiment, each of LD1 and LD2 in FIG. 22 described later is constituted by an array laser equipped with four commercially available lasers. As a result, spots 103, 104, 105, and 106 are formed on the disk surface by one array laser, and spots 101, 102, and
107 and 108 are formed by another array laser. The pits recorded by these spots are formed according to the code rules described with reference to FIGS.

Further, if the distance between pits and the distance between tracks in a one-dimensional array are reduced for higher density, mutual interference between signals becomes stronger and the level margin of signal detection may be reduced. Therefore, a method of eliminating interference between signals and improving a detection margin will be described.

When reproducing a spot as shown in FIG. 1, the signal detected from the right column is I ₁ (t) and the signal detected from the left column is I ₂ (t). of the time delay spot tau, the coefficient of mutual interference between the signals eta, When xi], a signal without interference i ₁ (t), the approximate to the _{i 2 (t) I 1 (} t −τ) = i ₁ (t−τ) + ηi ₂ (t) I ₂ (t) = i ₂ (t) + ξi ₁ (t−τ) Thus, a signal without interference is obtained by the following equation.

[0062] Therefore, by performing this calculation from the detection signal, it is possible to detect data without interference. In the example of FIG. 6, the coefficient η of this interference is about 0.3 to 0.4.

FIG. 1 shows a specific circuit configuration for performing this operation.
It is shown in FIG. The same members as those in the embodiment shown in FIG. 7 use the same reference numbers. In this embodiment, the signals are A /
D conversion and digital processing are performed. The signals 200 and 201 from the detectors 140 and 141 are sampled and held by the sample and hold circuit 14.
8 and 149, the levels of signals corresponding to grid points are fetched using clocks 160 and 161 created in the same manner as described in the embodiment of FIG.
03, and converted into digital signals 204 and 205. This signal is fetched into memories FI / FO (first in first out) 206 and 207, and the time lag between the two spots is corrected as described with reference to FIG.
The digital value of the signal level at the same position on the disk radius is stored in the first and second parallel data 20 for each spot.
8, 209 are detected. This data signal 208,2
As shown in FIG. 15 , 09 is input to the arithmetic units 210 and 211, and the arithmetic operation corresponding to the above-mentioned formula is performed, and the signals 212 and 213 without interference are output. This is comparator 2
14, 215 and serial comparison is performed to detect serial data 1, 2, 174 ', 175'. In the subsequent processing, the same processing as in FIG. 8 is performed, and data 187 corresponding to this is demodulated from the data of the two-dimensional array.

When the number of columns in the vertical direction as shown in FIG. 28 increases to q, the detection signal Inp (t) of the p-th column is Ip (t) = ip (t) + ξip-1 (t−τ) + ηip + 1 (T + τ) By solving the n-dimensional simultaneous equations, it is possible to obtain the signal ip from the p-th column without interference. At this time, i-1 and iq + 1 are set to zero. Here, 0 ≦ p ≦ q.

A further embodiment will be described with reference to FIG.

In the embodiment shown in FIG. 15, it is necessary to give the interference coefficients 必要 and η to the calculators 210 and 211. This coefficient ξ,
η changes according to track deviation, spot shape, and track pitch. In this embodiment, these effects are reduced,
It is an object of the present invention to further increase the density. That is,
In the present embodiment, the relative levels are compared by taking the difference between the signals I ₁ and I ₂ from the two spots on the right and left sides, and even if there is interference between adjacent pits, the data is highly reliable. Is detected. This method can be expressed by using the above equation: I ₁ (t−τ) −I ₂ (t) = i ₁ (t−τ) −i ₂ (t) + ηi ₂ (t) −ξi ₁ (t −τ) Assuming that η and ξ are almost equal, I ₁ (t−τ) −I ₂ (t) ≒ (1−η) × [i ₁ (t−τ) −i ₂ (t)] Only. In this way AGC
(Auto gain control) By compensating the fluctuation by a circuit or the like, a difference between signals without interference can be detected stably. The difference signal takes three values, + level, 0 level, and-level, depending on the pit arrangement. First parallel data 208
Is defined as CH1 and the signal processing sequence for generating the second parallel data 209 is defined as CH2. When the difference between the first parallel data 208 and the second parallel data 209 is calculated, the ternary level and the data for each CH are calculated. The relationship is as follows.

[0067]

[Table 1]

From this table, the presence or absence of an adjacent pit can be determined. That is, when the level is positive, there is a pit hole on the right side in FIG. 1 and no pit hole on the left side. Conversely, when the level is negative, there is no pit hole on the right side, and there is a pit hole on the left side.

Here, if the data of CH1 and CH2 are the same, the level becomes zero and it cannot be determined whether the left and right pits are present or not. Therefore, in this case, the levels of CH1 and CH2 are changed to another binary comparator 2
20, 221 are detected. That is, the outputs of the ternary comparator 222 and the binary comparators 220 and 221 are input to the logic processing unit 223, and when the data of CH1 and CH2 are the same, determination is made using the values of the data of CH1 and CH2.

In the case of the write-once type medium, the reflected light decreases when there is a pit as obtained by the waveform simulation. Therefore, to detect the presence or absence of the pit, the signal from the pit is used as a sample 1 and a certain value. For example, when the detection level is low, it is determined that there is a pit, and the data is "1".

When the data of CHs 1 and 2 is 1, adjacent left and right pits are present, and when the data is 0, neither pit is present. The determination results are output as first and second serial data 174 ″ and 175 ″, respectively, which are data at the same radial position of CH1 and CH2. Subsequent processes are the same as those in FIG. 15, and the corresponding data is demodulated from the two-dimensional array data.

Further, a pit arrangement suitable for this detection method will be described with reference to FIG. The right end is the recording pattern of the pit arrangement described in the above embodiment. Here, the recording positions of the data of the two one-dimensional arrays at the right end (the centers of the pit arrays are assumed to be 300 and 301, respectively) are made to coincide with the disk radius. When the centers of the pit trains are set to 302 and 303, respectively, the pits are shifted from each other so that the data recording position of one arrangement (the center of the pit train is 303) is recorded at the position of the gap between the blocks so far. In this manner, the data of each one-dimensional array does not overlap at any radial position of the disc with any recording data, and the zero of the level difference between CH1 and CH2 described in the above table does not occur.

Therefore, the signals of each one-dimensional array can be detected independently only by taking the difference between CH1 and CH2, and the processing when the level difference is zero becomes unnecessary. Needless to say, when detecting the signals of each one-dimensional array, the timings of the clocks for recording and reproducing are shifted. However, it is not necessary to essentially change the circuit configuration described so far. This configuration is shown in FIG.

Further, this method is not limited to a two-dimensional array,
The conventional one-dimensional array can also be applied to data recording. That is, the data of the conventional one-dimensional array can be divided every two bits and recorded alternately as CH1 and CH2. Also, two independent one-dimensional arrays can be recorded alternately. The pit arrangement on the disk surface and the recording / reproducing signal processing system in the two-dimensional recording have been described above.

Next, an optical system and a spot control method for realizing these will be described in detail. FIG. 22 shows an example of realizing two spots. This is a 2
This is an example using a laser array 400 in which one laser chip is housed in one package. As shown in FIG. 1A, a semiconductor laser array in which two laser chips LD1 and LD2 having different wavelengths are mounted in one package with their active layers facing each other is used as a light source. LD1 has a wavelength of 780
nm laser. On the other hand, LD2 is a laser having a wavelength of 830 nm. Light spots SP1 (780 nm wavelength) and S formed by both laser light sources on the disk
The positional relationship of P2 (wavelength 830 nm) is shown in FIGS.
Spot SP on the same track as in (b)
2 ahead.

FIG. 23 shows an embodiment relating to a specific structure of the optical head according to the present invention. This is an embodiment in which a two-wavelength hybrid laser array 400 in which two laser chips having two different wavelengths are arranged facing each other and housed in one package is used as a semiconductor laser light source. Laser beam 80 emitted from two-wavelength hybrid laser array 400
1 (wavelength; λ1 = 830 nm) and laser beam 802
(Wavelength; λ2 = 780 nm) is the collimating lens 40
At 2, the beam becomes a substantially parallel beam.

The two laser beams enter the beam splitter 403 as p-polarized light. Then, the optical path is turned back by the rising mirror 804, and the aperture lens 401
It is narrowed down on the disk 404. The two laser beams reflected by the disk are reflected by the beam splitter 403, pass through the convex lens 812, and pass through the wavelength separation filter 40.
Reaches 5. The wavelength separation filter transmits a laser beam 801 having a wavelength of 830 nm and reflects a laser beam 802 having a wavelength of 780 nm. The laser beam 802 reflected from the wavelength separation filter 405 is guided to a detection optical system using a detection prism 808, and forms a first photodetector 810-1 and a second photodetector 810 constituting a front-rear differential focus defocus detector. -2
Is received at. From the first photodetector 810-1, a data signal, an address signal, a focus error signal, and a tracking error signal are obtained. On the other hand, the wavelength separation filter 405
The laser beam 801 transmitted through the third light detector 807
Is received at. A data signal from the third photodetector 807;
Obtain an address signal and a tracking signal.

The stop lens 401 is attached to a stop lens actuator (not shown). The aperture lens actuator moves the aperture lens in the disk vertical swing direction and the track shift direction.
A so-called two-dimensional actuator may be used, or an actuator that moves the aperture lens only in the vertical oscillation direction of the disk may be used. Further, although the rising mirror 804 draws a prism in the figure, it goes without saying that it may be a so-called galvano mirror.

Next, the detection prism optical system will be described with reference to FIG. Each detector has a light receiving surface divided into four as shown in the figure. First and second detectors Left and right two receivers 40
5, 406, 405 ', and 406' are taken by differential amplifiers 409 and 410, respectively, and the difference between the detectors is taken as the differential amplifier 41.
By taking the value at 1, the defocus signal AF is detected. The tracking shift signal TR1 has the first and second
Light receivers 407, 408, 407 ', 40 above and below the detector
The difference is obtained by taking the difference of 8 'by the differential amplifiers 409 and 410 and taking the difference between the detectors by the differential amplifier 414. λ ₂
A data signal and a pre-pit signal from a pit on the side to be read by a laser beam having a wavelength of are detected from the sum of the respective light receiving surfaces of the first and second photodetectors. Further, the third detector 807
24 has a shape similar to that of the above-described detector as shown in FIG.
The data signal detected from the difference between 7 ″ and 408 ″ and from the pit on the side to be read by the laser beam having the wavelength of λ ₁ is detected from the sum of the respective light receivers of the third detector. Here, the case where the write-once type is used as the recording film has been described as an example, so the intensity of the reflected light obtained by reading the pit information is used. However, when the magneto-optical recording film is used, the domain information uses the polarization of the reflected light. Can be read.

The control signal processing method at the time of recording and reproduction will be described below.

For controlling the light spot, it is necessary to detect a track shift and a focus shift. Here, a case where a write-once type is used as a recording film will be mainly described. This is because the data does not affect the detection of the tracking control signal when the magneto-optical recording film is used, so that the signal processing described below is not particularly necessary. Further, the focus shift detection has less problems such as gain fluctuation and offset than the track shift detection, and thus can be detected by detecting only the low frequency components of the reflected light during recording and reproduction. Specifically, an amplifier 412 having a low frequency characteristic is used, and a signal W / R-MODE4 indicating a recording / reproducing mode is determined in advance by an amount that the level of the reflected light during recording is larger than that during reproduction.
13 is used to switch the gain of the amplifier 412. The following tracking control signal is a tracking error signal. As shown in FIG. 1, when recording is performed using a hatched spot, the tracking control signal of the light spot from the succeeding spot is affected by the pits recorded by the preceding spot. In the write-once type recording film, in the case of the perforated type, the amount of reflected light is reduced at a portion where a data pit is present, and the detection sensitivity of a tracking control signal is reduced, or an offset may occur in some cases. In the present embodiment, in order to prevent the influence of the recording pit, the tracking control signal is detected only in this part by using the fact that the recording pit does not exist between the blocks. As a method for this, since the reflected light level increases where no recording pits exist, the portion where the reflected light level is high is selectively detected from the output waveform from the photodetector for detecting the control signal. During recording, the recording power is increased only in the block portion. Since the recording timing is known, the value immediately before the detection signal is sampled and held only when the recording pulse is emitted. At the time of reproduction, a portion where the reflected light level is large is selectively detected from the output waveforms from the photodetector for detecting the control signal for both the leading spot and the trailing spot.

FIG. 2 shows a circuit configuration for performing the signal processing described above.
4 will be described. Each light receiver 407, 408,
The outputs from 407 ', 408', 407 ", 408" are sampled and held by circuits 424, 426, 428, 43.
0, 418, and 419, and the first and second gate signals WR-GATE42 generated from the respective recording pulses.
Using 0,432, control is performed so as to hold during the recording period. The output of the peak hold circuits 421, 422,
425, 427, 429, and 431, and continuously detects a high signal level. After these signal processings, differential amplifiers 412, 413, 414, and 423 calculate the difference between the light receivers. In this embodiment, the analog processing has been described. However, the output of the optical receiver may be first subjected to A / D (analog / digital) conversion, and then processing such as sample, hold, and peak detection may be performed.

The track shift signal TR must be a signal such that the position of the preceding spot and the position of the following spot are located at a distance from the center of the track, for example, on both sides. To detect such a signal,
The sum of the track shift signal TR1 from the preceding spot and the track shift signal TR2 from the following spot is calculated. Assuming that the position deviation of the spot is α, β, the track pitch is p, the detected amplitude is A, and the position deviation variable of the spot is X, the track deviation signal from each spot can be expressed as follows.

[0084]

(Equation 1)

[0085]

(Equation 2)

Taking the sum of these,

[0087]

(Equation 3)

The position of the zero point of the detected signal TR is the middle point of each spot. If this signal is used, the positions of the preceding spot and the following spot are positioned at equal distances on both sides from the center of the track.

In the embodiments described above, an example of an optical disk has been described. However, the present invention can be applied to an optical information recording / reproducing medium such as an optical drum and an optical card. Further, it goes without saying that the present invention can be used not only for a recording / reproducing device but also for a device dedicated to recording or reproduction. Further, the present invention is applicable not only to the write-once recording film described in the embodiment but also to a magneto-optical recording film.

This method is suitable for CLV (Constant Linya Density) or MCAV (Modified Constant Linya Density), which is used as a data recording system for optical disks. That is, in both systems, the recording method is such that the bit density at the radial recording position of the disc is substantially equal, so that the spot interval in the track traveling direction is constant as in this method, and the interval varies depending on the radial position of the disc. Otherwise, the number of bits within the interval hardly changes depending on the recording radius position. Thereby, the shift register 12 shown in FIG.
The number of registers of 0 and the capacity of the first-in first-out memory for correcting the timing deviation at the time of reproduction shown in FIG. 7 can be set to a constant value regardless of the recording radius. In the case of CLV (constant linear density), the clock pulse in FIG. 5 and the reference clock generated from the reference clock generation circuit 181 in FIG. 7 may be constant regardless of the recording radius. In Lina density, the above clock needs to be changed according to the disk radial position. For this purpose, in order to detect the radial position of the disk, a mark capable of optically identifying the radial position is recorded in advance on the disk, and the radial position is recognized using the mark, and the predetermined clock frequency is set. Set. Alternatively, there is a method in which the position of the recording / reproducing head is read by a scale located at a position different from that of the disk, and the clock frequency is set to a predetermined clock frequency.

[0091]

According to the present invention, the density of information stored on an optical disk can be increased.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a two-dimensional array of pit groups on an optical disc according to one embodiment of the present invention.

FIG. 2 is an explanatory view of a pit group in a two-dimensional array according to the present invention.

FIG. 3 is an explanatory diagram of an array of recorded pit groups.

FIG. 4 is an encoding table for creating a two-dimensional array

FIG. 5 is a block diagram of a signal recording system.

FIG. 6 is a pattern diagram of a synchronization mark portion for creating a clock.

FIG. 7 is a block diagram of a data reproducing system.

FIG. 8 is a block diagram of a data reproducing system.

FIG. 9 is an explanatory diagram of a two-dimensional array corresponding to 5 bits of recording data.

FIG. 10 is an explanatory diagram of a two-dimensional array corresponding to 7 bits of recording data.

FIG. 11 is an explanatory diagram of a two-dimensional array corresponding to 7 bits of recording data.

FIG. 12 is an explanatory diagram of a two-dimensional array corresponding to 7 bits of recording data.

FIG. 13 is an explanatory diagram of a two-dimensional array corresponding to 7 bits of recording data.

FIG. 14 is a block diagram of a reproduction processing system when interference between one-dimensional arrays is strong.

FIG. 15 is a block diagram of a reproduction processing system when interference between one-dimensional arrays is strong.

FIG. 16 is a block diagram of a reproduction processing system when interference between one-dimensional arrays is strong.

FIG. 17 is a block diagram of a reproduction processing system when interference between one-dimensional arrays is strong;

FIG. 18 is an explanatory diagram of a pit arrangement for reducing interference;

FIG. 19 is a diagram showing a relationship between a pit interval and a signal output.

FIG. 20 is a diagram showing a relationship between a pit interval and a signal output.

FIG. 21 is a relationship diagram between a pit interval and a signal output.

FIG. 22 is a configuration diagram of an optical system for forming two spots.

FIG. 23 is a block diagram illustrating a method for detecting a control signal from an optical system that forms two spots.

FIG. 24 is a block diagram illustrating a method of detecting a control signal from an optical system that forms two spots.

FIG. 25 is a diagram showing an encoding rule according to the embodiment of the present invention.

FIG. 26 is a diagram showing an encoding rule according to the embodiment of the present invention.

FIG. 27 is a diagram showing an encoding rule according to the embodiment of the present invention.

FIG. 28 shows that grid points of a recording block are 7 in the track direction;
Explanatory drawing of the embodiment provided with 8 in the track radial direction

FIG. 29 is an explanatory diagram of a relationship between a recording / reproducing spot and a pit group.

FIG. 30 is a system diagram showing an outline of the present invention.

[Explanation of symbols]

901: continuous stored information, 905: laser, 906 ...
Optical system, 908... Two rows of pits, 909... Two rows of pits, 910.

Continuation of front page (56) References JP-A-2-78019 (JP, A) JP-A-2-53223 (JP, A) JP-A-63-214919 (JP, A) JP-A-1-296432 (JP) JP-A-63-302425 (JP, A) JP-A-2-267733 (JP, A) JP-A-1-179225 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB G11B 7/00-7/013 G11B 7/14

Claims (3)

(57) [Claims] 1. A spot forming means for forming m light spots arranged on a track arranged on a recording surface such that light spots overlap in a direction perpendicular to the track and do not overlap in the direction of the track. The information identifier corresponds to a reflected signal obtained by irradiating each of the m light spots to columns of blocks arranged in n rows and m columns with information identifiers overlapping along the track on the recording surface. A reproducing unit for reproducing a signal; m memories for storing data reproduced by the reproducing unit for each column; and data stored in each of the m memories in the track on the recording surface. Computing means for computing between adjacent data using data recorded at the same position in the vertical direction and overlapping each other on the recording surface as adjacent data. Information reproducing apparatus for the butterflies. 2. Each information identifier of the information identifier group is n rows and m
2. A method according to claim 1, wherein said calculating means is means for converting the data into a two-dimensional array of n rows and m columns for each block. 1 information reproducing apparatus. 3. The information according to claim 1, wherein p ≧ L + Ws, where p is a track pitch, L is a distance of the m spots in a direction perpendicular to the track, and Ws is a spot size. Playback device.