JPH0474317A - Method and device for optical recording/reproducing and recording medium - Google Patents

Abstract

PURPOSE:To enable multivalued recording and to increase the recording density without losing the noise capacity by recording information by using both states of presence/absence of marks and displacement of marks in transverse direction to the traveling direction of the track. CONSTITUTION:Multivalued recording is performed by providing marks or no mark for the information and by shifting marks in transverse direction of pits, namely, in the perpendicular direction to the traveling direction of the track. In this case, it is not required to decrease the recording density so as to increase the length of the shortest pit. For example, when a pit is shifted in the transverse direction by a small amt. about 1/15 of the track period, S/N of the signals obtained from the variation of light coming back to the objective lens hardly changes. Thereby, three-valued recording can be substantially performed with using the state whether marks are provided or not and using displacement of marks in the right and left directions. Thereby, the recording density is substantially increased by 1.5 time compared to the conventional recording using binary recording state whether pit is provided or not.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical recording and reproducing method for optically recording information, a recording and reproducing apparatus, and a recording medium.

2. Description of the Related Art In recent years, optical disks, which are recording media for optically reproducing information, have become widely used for music and video, and have also begun to be used as external storage devices for computers. This optical disk has a feature that magnetic disks do not have, in that it is easy to reproduce a large number of reproduction-only disks by molding.

Taking advantage of this feature, optical discs exclusively used for music and video playback are now on the market. In all of these, information is recorded by the presence or absence of minute irregularities called bits, which partially change the phase of the irradiated light spot. In particular, for music, a recording method is used in which a music signal is converted into PCM, digitally modulated, converted into a binary channel signal, and the presence or absence of bits is associated with this channel signal.

Hereinafter, an example of a recording medium recorded by the above-described conventional optical recording method will be described with reference to the drawings.

FIG. 7 shows an enlarged perspective view of a part of a conventional recording medium. In FIG. 6, 80 is a recording medium.

81 is an information track, 82 is a bit, and the bit 82 is formed along the center line of the information track 81 shown by a broken line.
Information is recorded depending on the presence or absence of. 83 is a substrate, and 84 is a reflective film. Bits 82 are formed on the substrate 83, and a reflective film 84 is formed thereon. 85 is a light beam, 86
is a light spot, and the light beam 85 is applied to the substrate 83 and the reflective film 8
4 and forms a light spot 86 on the information track 81.

The operation of the method for recording and reproducing information on the recording medium configured as described above will be explained.

First, as shown in FIG. 7, when reading information from a recording medium 80 on which information is recorded depending on the presence or absence of bits 82, a light beam 85 is converged to form a light spot 86 on an information track 81. The normal light beam 85 is emitted light from a semiconductor laser, and has a wavelength of about 780 nm. The objective lens that converges the light beam 85 has N
The diameter of the light spot 86 is approximately 1.6 μm. When viewed from the direction in which the light beam 85 is irradiated, the bit 82 is a protrusion of about 10() nm and has a width of about 0.5 μm. When the light spot 86 illuminates a portion without the bit 82, the light beam 85 is specularly reflected by the reflective film 84 and returns to the objective lens again. However, when illuminated onto the bit 82, the light beam 85 is diffracted and scattered, reducing the intensity of the light returning to the objective lens. In this way, since the amount of light returning to the objective lens changes depending on the presence or absence of the bit 82, the presence or absence of the bit 82 can be read from the change. (For example, [Compact Disc Reader] page 84) Problems to be Solved by the Invention However, with the above configuration, in order to record only by the presence or absence of bits, the optical spot must be narrowed down to make it possible to record. The problem was that it was difficult to improve the linear density.

In view of the above-mentioned problems, the present invention provides an optical recording and reproducing method that can improve the recording linear density even if the same optical spot as the conventional one is used.

Means for Solving the Problems In order to solve the above problems, the optical recording and reproducing method of the present invention determines the presence or absence of a mark that imparts a phase change to the irradiated light, and the small amount of this mark in the lateral direction. Digital information is recorded by assigning information to both the displacement of The presence or absence of a mark is detected from the sum of the marks, and the displacement of the mark is detected from the difference.

Operation According to the present invention, with the above-described configuration, information can be recorded in a superimposed manner by the displacement of marks, thereby making it possible to improve the recording density. The reason for this will be explained in more detail below.

Generally, the limit of information transmission capacity is determined by the bandwidth and noise characteristics of the transmission path. In the case of optical discs, the diameter of the optical spot is the main cause of limiting the bandwidth of the transmission path. That is, as the length of the bit becomes shorter than the diameter of the optical spot, the change in the amount of light returning to the objective lens becomes smaller, and the signal amplitude decreases. Particularly in the case of digital signals, this appears as a decrease in the aperture ratio of the eye diagram.

Information can be read correctly if this aperture is opened to the extent necessary for noise present in the transmission path. That is, the recording linear density can be increased to the limit where the minimum aperture necessary to tolerate the noise of the recording medium is secured. If you try to perform multi-level recording, for example ternary recording, by changing the height and width of the bit in order to increase the recording linear density, the amplitude for the signal at the shortest recording wavelength will need to be more than twice that of binary recording. Since the length of becomes longer,
The recording linear density does not improve as much as expected.

However, in addition to the presence or absence of the bit, the horizontal direction of the bit,
In other words, when multiplexing information by carrying information even with minute displacements in the direction perpendicular to the direction in which the information track extends, it is not necessary to lower the recording linear density so that the length of the shortest pit becomes longer. do not have. This is because, even if the bit is shifted left and right by a minute amount, for example, about 1/15 of the track period, the S/N ratio of the signal based on the change in the amount of light returning to the objective lens hardly changes. Therefore, for example, ternary recording is essentially performed by a state where there is no bit, a bit displaced by a minute amount to the left, and a bit displaced by a minute amount to the right, whereas conventional binary recording is performed only by the presence or absence of bits. The recording linear density can be substantially improved by 1.5 times.

Embodiment Hereinafter, a recording apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of a recording apparatus in a first embodiment of the present invention. In FIG. 1, numeral 1 denotes a distribution circuit which distributes input digital information at a ratio of 2:1 and outputs two digital signals Dl and RI. 2 is a first digital modulator, and 3 is a second digital modulator, which performs digital modulation on digital signals R and R, respectively, and outputs two channel signals C7 and C7. 4 is a light modulator drive circuit, 6 is a light source, and 7 is a light modulator, and this light modulator 7 transmits the parallel light flux emitted from the light source 6 according to the output signal from the light modulator drive circuit 4. Acts as a light valve that blocks or blocks light. 5 is a deflector drive circuit, 8 is a deflector, and this deflector 8
deflects the direction of the parallel light beam in accordance with the output signal of the deflector drive circuit 5.

Furthermore, 9 is an objective lens, 10 is a recording medium, and the objective lens 9 directs the parallel light beam output from the deflector 8 to the recording medium 10.
converges on top of.

The operation of the optical recording apparatus configured as described above will be explained below with reference to FIGS. 1 and 2.

First, the distribution circuit 1 divides the input signal to be recorded into two digital signals at a ratio of 2:1.

Allocate to. The allocation at this time is 2 bits and 1 bit.
The bits may be sequentially and alternately distributed, or the data may be sequentially distributed 2:1 in units of 2 bytes and 1 byte, or even larger units. The first digital modulator 2 and the second digital modulator 3 receive the digital signals 1 and 0. are digitally modulated to become a first channel code and a second channel code, respectively.
and a second channel code signal C1 are output. The first channel code is
One adjustment bit is inserted into every 4 bytes of the first information, and this is NRZT modulated, that is, each time "1" appears in the channel code, two states are created (hereinafter referred to as "Ho" and "L"). Modulation is performed so as to transition from one side to the other side (expressed as "), and this is output as the first channel code signal CI. At this time, the adjustment bits are set such that the channel bit where the first channel code signal C1 is H' is L, and the bit where the first channel code signal C1 is 'L' is -.
Either 0' or l' is selected so that the absolute value of DSV, which is the cumulatively added value of 1, becomes small. As a result, fluctuations in the DC component of the first channel code are suppressed, resulting in a so-called DC-free code.

FIG. 2 conceptually shows the process of actually forming a mark on a recording medium based on the channel code, and the subsequent operation will be further explained with reference to the same figure.

The optical modulator drive circuit 4 receives the first channel code signal C
A so-called RZ modulation signal is obtained by converting the pulse width of 0 into a pulse shorter than the width of the channel bits constituting the channel code, and is amplified to a voltage and power sufficient to drive the optical modulator 7 and output. . The optical modulator 7 transmits the parallel light beam emitted from the light source 6 in response to the output of a pulse from the optical modulator drive circuit 4, and blocks the parallel light beam when no pulse is output.

On the other hand, as in the case of the first digital modulator 2, the second digital modulator 3 receives the second information 0. every 4 bytes! Insert adjustment bits according to the bits and convert this to NR
ZT modulation is performed to obtain a second channel code signal C1.

This second channel code signal C7 has a channel bit of the second channel code signal C1 set to 1 for each “Ho” channel bit of the first channel code signal C1.
Output by sending out bits. The above adjustment bit is also selected to be O' or "1" so that the second channel code signal C7 is DC-free.The transmission capacity of this second channel code is the same as that of the first channel code signal C7.
Although it depends on the frequency with which H' channel bits appear in 1, since the first channel code is DC-free, this transmission capacity is kept constant on average.

However, when dividing information into sectors of a predetermined size and recording each sector, the number of H' bits of the first channel code signal C1 within a sector is not always more than half, so In this case, the H' bit of the first channel code signal C1 is insufficient, and the second
There is a possibility that the last part of the information cannot be recorded. However, the first channel code signal C7 is D
Since a bit is inserted to adjust the SV, “
Ho's channel bits are never more than 4 bytes short of half. Therefore, after the first channel code signal C7 modulated with the first information, a signal with a length equivalent to 4 bytes is added.
By adding H' channel bits, it is possible to record second information with half the amount of information of the first information. The deflector drive circuit 5 amplifies the second channel code signal Ct so that the voltage and power are sufficient to drive the deflector 8. The deflector 8 deflects the parallel light beam emitted from the light source 6 by a minute angle in accordance with the output signal of the deflector drive circuit 5. The objective lens 9 converges the deflected parallel light beam onto the recording medium 10. At this time, the recording light spot focused on the recording medium 10 is slightly displaced in the left and right directions in the figure, depending on the deflection angle by the deflector 8. A so-called photoresist is coated on the surface of the recording medium 10, and the recording light spot moves in a direction perpendicular to the plane of the drawing. That is, an information track is formed in a direction perpendicular to the plane of the drawing, and the exposed mark is displaced by a minute amount to the left and right with respect to the center of the information track. The recording medium 10 recorded in this manner is developed to remove the photoresist at the mark portions exposed by the recording light spot. As a result, the recording medium 10
On the top, as shown in FIG. 2, bits 12, which are minute depressions, are formed in rows with minute displacements to the left and right of the center 11 of the information track. Although information can be directly read from the recording medium 10 recorded in this way, a stamper is created by plating and peeling off the recording medium 10, and a large amount of recording media is molded from this stamper. It can also be copied.

FIG. 3 shows a block diagram of a reproducing apparatus that reproduces information from the recording medium manufactured as described above. Third
In the figure, 2o is a recording medium on which information is recorded as in the above embodiment. 21 is a semiconductor laser, 22 is an objective lens, and the objective lens 22 converges the irradiation light beam emitted from the semiconductor laser 21 to the recording medium 20.
A reproduction light spot is formed on the top. A beam splitter 23 separates the reflected light beam from the recording medium 20 from the irradiated light beam. 26 is a photoelectric detector; 24 and 25 are light receiving cells; the light receiving cells 24 and 25 are included in the photoelectric detector 26;
It outputs an electrical signal according to the intensity of the incident light. 27
and 28 are buffer amplifiers, and light receiving cells 24 and 2
Impedance conversion is performed on the output signal from 5. 29 is an adder, and 32 is a differential amplifier, which calculates and outputs a sum signal and a difference signal of the detection signals output from the buffer 7 amplifiers 27 and 2B, respectively. 30 is a voltage comparator; 31 is a loop filter; the voltage comparator 30 shapes the waveform by comparing the sum signal with a threshold value and outputs a rectangular wave; the loop filter 31 outputs a rectangular wave; A closed loop is formed to control the threshold by negative feedback. 33 is a voltage comparator, 34 is a transfer gate,
35 is a loop filter, and the voltage comparator 33 shapes the waveform by comparing the difference signal with a threshold value and outputs a rectangular wave.The transfer gate 34 and the loop filter 35 cooperate to The output signal of 30 is “
Only when the voltage is H', the output of the voltage comparator 33 is negatively fed back to form a closed loop for controlling the threshold value. 36 and 37 are a positive peak detection circuit and a negative peak detection circuit, respectively;
The timings of the positive peak and negative peak of the upper and second difference signals are detected, respectively, and pulses are output at the respective timings. Sample and hold circuits 38 and 39 sample and hold the sum signal at the timing using the pulses output from the positive peak detection circuits 36 and 37 as strobe pulses, respectively. 40 is a differential amplifier; 41 is a changeover switch; the differential amplifier 40 outputs a difference signal between the output signals of the sample-and-hold circuit 38 and the sample-and-hold circuit 39; One of the outputs of the differential amplifier 32 is switched and output.

The operation of the optical reproducing apparatus configured as described above will be explained below using FIG. 3.

The semiconductor laser 21 emits an irradiation light beam for irradiating the recording medium 2o. The irradiation light beam passes through the beam splitter 23 and is converged onto the recording medium 20 by the objective lens 22 to form a reproduction light spot for reading information. The objective lens 22 condenses the reflected light from this reproduction light spot into a reflected light flux, and this reflected light flux is reflected by the beam splitter 23 and separated from the irradiation light flux. The separated reflected light flux forms a far-field image of the reproduction light spot on the light receiving cells 24 and 25 of the photoelectric detector 26. The puffer amplifiers 27 and 28 impedance-convert the current signals output from the light receiving cells 24 and 25, respectively, into low-impedance voltage signals and output the converted signals.

Adder 29 outputs a sum signal obtained by adding the detection signals output from buffer amplifiers 27 and 28. This sum signal indicates a change in the total amount of reflected light flux, and when the reproduction light spot illuminates the bit portion, the level of the sum signal decreases. Therefore, by comparing this sum signal with a threshold value and shaping the waveform using the voltage comparator 30, a binary signal representing the presence or absence of pits can be obtained. This binarized sum signal is read as a first channel code signal C9. At this time, if the above threshold is incorrect, 2
Value conversion will not be performed correctly and errors will occur. The first channel code signal C1 is DC-free, and if the threshold value is correct, the DC component of the output signal of the voltage comparator 30 should be a predetermined voltage value. The threshold value is controlled to a correct value by extracting a low frequency component from the output signal, comparing it with a predetermined voltage value, and feeding back the error.

Differential amplifier 32 outputs a difference signal between the outputs of buffer amplifiers 27 and 28. This difference signal indicates the amount of imbalance in the light intensity distribution of the reflected light flux.Since the information track extends perpendicularly to the plane of the figure in the area of the reproduction light spot, the change in the light intensity distribution described above is due to the bit This is caused by a minute displacement in the left and right direction. Therefore, the voltage comparator 33 compares the difference signal with an appropriate threshold value and shapes the waveform, thereby making it possible to reproduce the second channel code signal C recorded by the left and right displacement of the pit. However, since the difference signal is likely to be offset due to tracking error, disk inclination, displacement of the objective lens 22, etc., the voltage comparator 33
The threshold of Therefore, taking advantage of the fact that the second channel code signal C1 is also DC-free, only the signal when a bit exists is extracted from the output signal of the voltage comparator 33 by the transfer gate 34, and then the signal is extracted by the loop filter 35. The threshold value is controlled to the correct value by extracting the low frequency component, comparing it with a predetermined voltage value, and feeding back the error.

The first channel code signal C1 and the second channel code signal C2 reproduced as described above are
digital modulator 2 and second digital modulator 3
The original information can be restored by a decoder that operates in reverse.

On the other hand, it is also possible to detect tracking errors by utilizing the fact that the pits are slightly displaced left and right. Next, its operation will be explained. The positive peak detection circuit 36 and the negative peak detection circuit 37 detect the positive peak and negative peak of the difference signal output from the differential amplifier 32, respectively, and output a pulse at the same time as detecting each peak. If the difference signal changes in the positive direction when the pit is displaced to the right, and changes in the negative direction when the pit is displaced to the left, the positive peak detection circuit 36 detects when the reproduction light spot scans the bit portion displaced to the right. The negative peak detection circuit 37 generates a pulse when scanning the pit portion displaced to the left. When a pulse is output from the positive peak detection circuit 36 and the negative peak detection circuit 37, respectively, the sample and hold circuits 38 and 39 use this as a strobe pulse to sample and hold the sum signal output from the adder 29. . By doing this, when the reproduction light spot is tracking the center of information tracking, the sample and hold circuits 3B and 39
The values held by the sample and hold circuit 38 are approximately equal, but when the tracking shifts to the right, the value held by the sample and hold circuit 38 becomes larger than the value held by the sample and hold circuit 39, and vice versa when the tracking shifts to the left.

Therefore, the tracking error can be detected by calculating the difference between the output signals of the sample and hold circuits 38 and 39 using the differential amplifier 40.

However, if the tracking error becomes large enough to significantly exceed the amount of horizontal displacement of the bit, peak detection by the positive peak detection circuit 36 and the negative peak detection circuit 37 becomes unstable, so that the initial pull-in of tracking control becomes unstable. becomes difficult. The changeover switch 41 is provided to solve this problem, and is switched to detect the tracking error using the difference signal output from the differential amplifier 32 when the tracking control is pulled in. In tracking control based on this difference signal, offset is likely to occur due to the inclination of the disk or the displacement of the objective lens, so after the tracking control is completed, the differential amplifier 40
The changeover switch 41 is switched so that the tracking error is detected from the output. By doing so, highly accurate and stable tracking control can be realized.

As described above, according to this embodiment, since information is recorded based on both the presence or absence of bits and minute displacements in the horizontal direction, the recording density can be increased. Further, a tracking error can also be detected by comparing a sum signal when scanning bits displaced to the right with a sum signal when scanning bits displaced to the left.

Furthermore, since the information to be recorded is divided into first information and second information, and the first information is recorded using only the presence or absence of marks, the recording/reproducing means for the first information is It can also be used as a recording/reproducing means using a conventional recording medium for recording.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a conceptual diagram showing a recording method in a second embodiment of the present invention. In the figure, 50 indicates a bit formed in this embodiment. The configuration of the recording device is similar to that shown in FIG.

The only difference from the configuration shown in FIG. 1 is the operation of the distribution circuit 1, first digital modulator 2, and second digital modulator 3.

The operation of the above recording method will be explained below.

As shown in FIG. 1, the distribution circuit 1 distributes input information to be recorded into first information D2 and second information D2 at a ratio of 8:5, as in the first embodiment.

In this embodiment, the first digital modulator 2 receives the first information 0. are grouped every 8 bits to form a data word,
A first channel code is generated by converting these into an 11-bit channel word. These channel words contain 4 bits of "1".In other words, this first channel code is a 4-out-of-11 code (hereinafter referred to as 4/11).
It is called a code (denoted as a code). There are a total of 33 combinations in which 4 bits out of 11 bits are °l".
Since there are 0 ways, all 256 ways of 8-bit data words can be expressed. After inverting this first channel code, NRZ modulation is performed, that is, the state of "l" of the first channel code is L', and the state of "0" is °H'
It is modulated so that it becomes the state of "
A bit is formed corresponding to 0'.

On the other hand, the second digital modulator 3 groups the second information O7 into data words in units of 5 bits, and generates a second channel code by converting these into 7-bit channel words. Three bits of '1' are included in these channel words. That is, this second channel code is 3/
7 code. Since there are a total of 35 combinations in which 3 out of 7 bits are '1', all 32 data words consisting of 5 bits can be expressed. Of these 3/7 code channel words, the odd numbered ones are left as they are, and the even numbered ones are inverted and then NRZ modulated to output the second channel code signal C2. Bits 50 are formed as shown in the figure by slightly displacing the bits in the left and right directions in accordance with the polarity of the second channel code signal C7. As mentioned above, the second channel code signal C2 alternately uses the original 3/7 code and the inverted version of the 3/7 code, so the bits shifted to the right and the bits shifted to the left are on average have the same number of bits.

As mentioned above, the first information can be expressed as N
By using the /i code, it is possible to always record the second information with a constant number of bits in each channel word.

Note that in the above embodiment, the first channel code is 4/
11 code, but any so-called I/N code may be used. Further, although the second channel code is also a 3/7 code, other modulation codes may be used.

FIG. 5 is a block diagram showing an example of a reproducing apparatus for reproducing information from a recording medium in this embodiment. In the figure, the steps up to the point where the adder 29 and the differential amplifier 32 calculate and output the sum and difference of the outputs from the light receiving cells 24 and 25, respectively, are the same as in the case of FIG. What differs is the operation of the changeover switch 60, A/D converter 61, and identification circuit 62. These operations will be explained below. The changeover switch 60 outputs the output of the adder 29 when information is recorded based on the presence or absence of a mark on the recording medium, and outputs the output from the adder 29 when information is recorded based on both the presence or absence of a mark and a small amount of displacement in the horizontal direction. 32 outputs are selected and supplied to the A/D converter 61, respectively. The A/D converter 61 samples the input signal at a cycle of each channel bit and supplies the sampled value to the identification circuit 62 .

When information is recorded only by the presence or absence of marks on the recording medium, 4 out of 11 bits are recorded using the 4/11 code.
It is recorded by converting it into a channel code in which marks are formed only on bits. When reading information from such a recording medium, the identification circuit 62 includes an adder 2.
A sample value obtained by sampling the sum signal of the detection signals output from 9 at a channel bit period is input. The identification circuit 62 divides the input sample values into channel words each consisting of 11 channel bits, and rearranges the 11 sample values within each channel word in substantially ascending order. If the level of the sum signal decreases when there is a mark, the channel code is reproduced by assuming that the mark is formed corresponding to four sample values starting from the smallest of the rearranged sample values.

On the other hand, when information is recorded on a recording medium based on the presence or absence of marks and their horizontal displacement, the information is recorded by inverting the 4/11 code and forming marks on 7 out of 11 bits. In addition, more information is recorded by configuring the 7-bit mark as a combination of 3 bits shifted by a minute amount to the left and 4 bits shifted by a minute amount to the right. When reading information from such a recording medium, a sample value obtained by sampling the difference signal of the detection signal output from the differential amplifier 32 in synchronization with the channel bit is input to the identification circuit 62. The identification circuit 62 partitions the input sample values into channel words consisting of channel bit II bits, and sorts the 11 sample values within each channel word in substantially ascending order. Assuming that the difference signal changes in the positive direction when the mark shifts to the left, a mark that shifts to the left is formed corresponding to the three sample values starting from the larger sample value, and the mark shifts from the smaller sample value to the left. The channel code is reproduced by assuming that marks shifted to the right corresponding to the four sample values are formed.

As described above, when reproducing information from a recording medium that records a combination of bits shifted in one left-right direction and bits shifted in the other direction, the channel code is reproduced only from the difference signal of the detection signal. can do.

FIG. 6 is a block diagram showing a recording apparatus in a third embodiment of the present invention. In the figure, 70 is a ternary digital modulator which converts the input signal into a 2-bit data string (w19wt) and outputs each bit in parallel.

71 is a first light source drive circuit; 73 is a first light source;
The light source drive circuit 71 drives the first light source 73 to emit a luminous flux according to wl output from the ternary digital modulator 70.

72 is a second light source driving circuit; 74 is a second light source;
The light source drive circuit 72 drives the second light source 74 to emit a luminous flux in accordance with W output from the ternary digital modulator 70. A combining prism 75 combines the light beam emitted by the first light source 73 and the light beam emitted by the second light source 74 so that their angles are slightly different. Thereafter, the process of converging these light beams onto the recording medium 10 to form marks is the same as in the first embodiment.

The operation of the recording apparatus configured as described above will be explained with reference to the drawings.

First, the ternary digital modulator 70 converts the input signal into (L-I
t) into a 2-bit data string, (L-It)
The combinations are (0,0), (0,1), (1,0)
Choose one of the following three types. A method for converting a binary input data string into a ternary data string is, for example, by dividing the input data string into information words of every 3 bits, and converting each idiomatic FG word into a channel word consisting of 2 digits. Alternatively, as in the N/i code in the second embodiment, data words obtained by dividing input data into M bits may be converted into N-digit channel words, and each channel word has The digit (0°1) may be converted into a channel code such that the digit (1w O) is jsN-13 and the digit is (0,0). Specifically, for example, M=12, N=
IO1i-=j=3. Each digit (L, i
t), the first light source drive circuit 71 and the second light source drive circuit 72 drive the first light source 73
and drives the second light source 74. Therefore, the first light source 73 and the second light source 74 have these outputs (Wt,
A light beam is emitted according to each bit of Wt), and these light beams are combined by a combining prism 75. At this time, these light beams are combined at slightly different angles in a direction perpendicular to the moving direction of the recording medium 10, so that in the recording medium 10, they are combined in a direction perpendicular to the traveling direction of the information track. Forming light spots in slightly different locations. Therefore, when a mark is formed on the recording medium 10, it will be formed at one of two slightly different locations in the left and right direction toward the traveling direction of the information track. In this way, for each channel bit, the recording medium 10 is in one of three states: no mark, a mark shifted to the left, and a mark shifted to the right. will be selected.

As described above, since three values are essentially recorded on the recording medium, and the three values are obtained by a combination of mark presence/absence and transition, there is very little deterioration in noise margin. Therefore, it is possible to increase the recording capacity by approximately 1.5 times.

Effects of the Invention As described above, the present invention records information based on both the presence or absence of marks and the displacement of marks in the left and right direction in the direction of movement of the track, so that it is possible to record information using substantially multiple values without sacrificing noise margin. Recording becomes possible, and the recording capacity I can be increased.

Furthermore, by dividing the information to be recorded into first information and second information, and configuring the first information to be recorded based on the presence or absence of a mark, and the second information based on the transition of the mark, This has the effect of making it easier to maintain compatibility with conventional recording media in which recording is performed using only the presence or absence of marks.

Further, by converting the first information into a DC-free channel code, an effect can be obtained in that the capacity for recording the second information is kept constant.

Furthermore, by setting the first information as the N/i code,
The reliability of reading is improved, and since the transmission speed of the first information and the second information is always kept constant, the effect of facilitating signal processing is also obtained.

In addition, ternary recording is possible by taking advantage of the fact that the information to be recorded can be in three states: no mark, a state with a mark shifted to one side, and a state shifted to the other side. By doing so, it is possible to obtain the effect that the recording capacity can be increased by 15 times without dividing the first information and the second information and with almost no loss in noise margin.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a recording device in a first embodiment of the present invention, FIG. 2 is a conceptual diagram explaining the operation of the first embodiment, and FIG. 3 is a block diagram of a reproducing device in the first embodiment. 4 is a conceptual diagram showing a recording method in the second embodiment, FIG. 5 is a block diagram showing an example of a playback device in the second embodiment, and FIG. 6 is a recording device in the third embodiment. FIG. '7 is a partially enlarged perspective view of a conventional recording medium. ■-----Distribution circuit, 2---First digital modulator, 3-----Second digital modulator, 4
-1.-Light modulator drive circuit, 5-----1 Deflector drive circuit, 8.-11--Deflector, 30.33--1.
-Voltage comparator, 31° 35--Loop filter, 34--Transfer gate, 3
6-------・-Positive peak detection circuit, 37-------
Negative peak detection circuit, 38.39-----11 sample/hold circuit, 41.60-----All changeover switch, 70-----3-value digital converter, 7
1--m-.--First light source drive circuit, 72-.--
1--Second light source drive circuit, 73-.--First light source, 74--Second light source, 75-.--Synthesizing prism. Dai I! Length treatment #1 hair 1 Awano 14 j5 force ゛ ln 6 Figure 1 Figure 2 41--”- = '911t swift measure 6 Figure 7

Claims (1)

[Claims] (1) The presence or absence of a mark that changes the phase of the irradiated light on the information track of the recording medium, and the displacement of the mark in the lateral direction by a minute amount that is sufficiently smaller than the period of the information track. An optical recording method characterized by recording digital information by allowing both to carry information. (2) First information recorded based on the presence or absence of a mark and second information recorded based on the displacement of the mark are superimposed and recorded, and the first information is digitally modulated to suppress the DC component. The optical recording method according to claim 1, wherein the optical recording method is characterized in that recording is performed after the recording is performed. (3) The optical recording method according to claim (2), wherein the second information is also recorded after performing digital modulation to suppress the DC component. (4) The first information is M(
M is a natural number) is divided into information words of bits, and this information word is divided into N bit information words.
(N is a natural number greater than 2) bits are converted into channel words consisting of channel bits, and marks are formed for only i bits (i is a natural number greater than or equal to N/2) of the channel bits included in each channel word. 2. The optical recording method according to claim 2, wherein the optical recording method is configured such that the recording is performed after digitally modulating the data so as to make the recording. (5) The optical recording method according to claim (4), wherein M is 8, N is 11, and i is 7. (6) The mark is formed at either a position displaced from the substantial center of the information track in one direction or a position displaced from the other direction.
The optical recording method described in section 1). (7) Divide the digital information to be recorded into information words of M (M is a natural number) bits, convert this information word into channel words consisting of N (N is a natural number greater than 2) bits, and each The channel word includes i (where i is a natural number less than N) bits of channel bits displaced in one direction and j (where j is a natural number less than N−i) bits of channel bits displaced in the other direction. The optical recording method according to claim (6), characterized in that the optical recording method is converted and recorded as follows. (8) The optical recording method according to claim (7), wherein M is 8, N is 11, and i and j are 4. (9) The optical recording method according to claim (7), wherein M is 8, N is 11, i is 4, and j is 3. (10) M is 8, N is 11, and the channel word of i is 4 and j is 3, and the channel word of i is 3 and j is 4. ) The optical recording method described in section 2. (11) The information is recorded by finally forming a mark that changes the phase of the light along the information track on the recording surface of the recording medium according to the input digital information. The mark is selectively formed in the lateral direction of the information track at one of a plurality of predetermined positions that differ by a minute amount that is sufficiently smaller than the period of the information track, and the position of the mark and the presence or absence of the mark are An optical recording device characterized in that it is configured to record the above-mentioned digital information by making both of the above-mentioned information bear information. (12) splitting means for splitting and converting input digital information into two digital signals, a first channel signal and a second channel signal; a light source means for emitting a luminous flux and changing the amount of the emitted luminous flux according to the first channel signal, and converging the luminous flux emitted from the light source means to form a light spot on the recording surface of the recording medium. and a light shifting means for shifting the position of the light spot in the lateral direction of the information track in accordance with the information second channel signal. 11) The optical recording device according to item 11). (13) The optical recording device according to claim (12), wherein the first channel signal is digitally modulated so as to suppress a DC component. (14) The optical recording device according to claim (13), wherein the second channel signal is also digitally modulated to suppress DC components. (15) The first channel signal is a series of channel words consisting of N (N is a natural number greater than 2) channel bits, where i (i is N) among the channel bits included in each channel word. 13. The optical recording device according to claim 12, wherein the optical recording device is configured so that marks are formed only in correspondence to bits (a natural number of /2 or more). (16) The optical recording device according to claim (15), wherein N is 11 and i is 7. (17
) Mark is formed at either a position displaced by a predetermined amount in one direction from the substantial center of the information track or a position displaced by a predetermined amount in the other direction from the substantial center of the information track. Optical recording device as described in section. (18) Divide the input digital information into M (M is a natural number) bit information words, and convert these information words into N (N is 2) bits.
a conversion means for converting into a channel word consisting of digits (larger natural number), each digit taking one of the first, second and third values; A beam of light is emitted to form a mark at a position displaced by a predetermined minute amount in one direction from the substantial center of the information track, and when the second value is reached, a mark is formed at a position displaced by a predetermined minute amount in the other direction. and a light source means for emitting a luminous flux such that a mark is formed at a third value, and reducing the amount of the emitted luminous flux so as not to form a mark at any position when the third value is reached, and is included in the above channel term. The number of digits taking the first value and the number of digits taking the second value are respectively i and j (i and j are natural numbers, i<N, j<N and i+j≦N). An optical recording device according to claim (17). (19) The optical recording device according to claim (18), wherein M is 8, N is 11, and i and j are 4. (20) The optical recording device according to claim (18), wherein M is 8, N is 11, i is 4, and j is 3. (21) M is 8, N is 11, and the channel word where i is 4 and j is 3 and the channel word where i is 3 and j is 4 appear alternately. An optical recording device according to claim (18). (22) Information is carried by both the presence or absence of a mark that changes the phase of the irradiated light on the information track of the recording medium, and the displacement of the mark in the lateral direction by a minute amount that is sufficiently smaller than the period of the information track. An optical recording medium characterized in that digital information is also recorded. (23) The information to be recorded is digitally modulated and recorded so that the average density of marks along the information track becomes a predetermined value.
) The optical recording medium described in item 2. (24) Divide the information to be recorded into information words consisting of M (M is a natural number) bits, convert this information word into channel words consisting of N (N is a natural number greater than 2) bits, and each Claim (23) characterized in that the mark is formed corresponding to only i (i is a natural number of N/2 or more) bits among the channel bits included in the channel word. optical recording medium. (25) Information to be recorded is recorded so that the ratio of the average value of the number of marks displaced in one direction to the number of marks displaced in the other direction with respect to the substantial center of the information track becomes a predetermined value. The optical recording medium according to claim 22, wherein the optical recording medium is recorded using digital modulation. (26) Marks formed along the information track are substantially grouped by a predetermined number, and within the group, marks are displaced in one direction and marks are displaced in the other direction. 26. The optical recording medium according to claim 25, wherein the number of marks on the optical recording medium is controlled to be equal. (27) Divide the digital information to be recorded into M (M is a natural number) bit information words, and divide these information words into N (N is 2) bits of information words.
digits (larger natural number), each digit takes one of the first, second, and third values, and one of the three values corresponds to the first value of said digits. a mark is formed at a position displaced in the direction; a mark is formed at a position displaced in the other direction corresponding to a second value; Claim (22) characterized in that the numbers of digits taking the values are i and j (i and j are each predetermined natural numbers, i<N, j<N and i+j≦N). Optical recording medium as described in section. (28) The optical recording medium according to claim (27), wherein M is 8, N is 11, and i and j are 4. (29) The optical recording medium according to claim (27), wherein M is 8, N is 11, i is 4, and j is 3. (30) M is 8, N is 11, and a channel word in which i is 4 and j is 3 and a channel word in which i is 3 and j is 4 appear alternately. An optical recording medium according to claim (27). (31) Digital information is recorded by having information carried by both the presence or absence of a mark that causes a phase change in the irradiated light and the displacement of the mark in the horizontal direction by a minute amount that is sufficiently smaller than the period of the information track. A light spot is focused on an information track of a recording medium, and the reflected or transmitted light is received and guided onto a photoelectric detector to form a far-field image thereon.
An optical reproduction method characterized in that the presence or absence of the mark is detected from a change in the amount of light in the far-field image, and the lateral displacement of the mark is detected from a change in the distribution of light amount. (32) The recording medium is designed such that the average ratio of the number of marks displaced in one direction to the number of marks displaced in the other direction with respect to the substantial center of the information track is a predetermined value. The information to be recorded is digitally modulated and recorded, and the difference between the output signals output from the two parts of the photoelectric detector is substantially compared with a threshold value to shape the waveform, and the waveform-shaped signal is 32. The optical reproduction method according to claim 31, wherein the threshold value is controlled so that the average value becomes a predetermined value. (33) On the recording medium, the mark rows formed along the information track are divided into N (N is a natural number of 2 or more) marks and are essentially grouped, and within each group, the marks are displaced in one direction. The number of marks displaced in one direction and the number of marks displaced in the other direction are recorded such that they are i (i is a natural number smaller than N) and N-i, respectively, and the number of marks displaced in the other direction is recorded on the photoelectric detector from the two parts. The substantial difference in the output signal is sampled for each mark, and when the mark is displaced in one direction, the direction in which the difference value changes is positive, and when the mark is displaced in the other direction, the direction in which it changes is defined as positive. When negative, select i sample values from the larger one in the positive direction among the sample values sampled by N marks constituting the same group, and select the selected sample values in one direction. The optical reproduction method according to claim 31, characterized in that the displacement of the mark is identified as corresponding to a mark that has been displaced and the other sample value corresponds to a mark that has been displaced to the other. (34) The recording medium has a unit of channel word consisting of N (N is a natural number of 2 or more) digits, and within this channel word there are i (i is a natural number of N or less) displaced in one direction. ) marks and j(
j is a natural number equal to or less than N-i) marks are recorded, and the substantial difference signal between the output signals from the two parts of the photoelectric detector is sampled in synchronization with the repetition period of the digits. However, when the direction in which the difference signal changes when the mark is displaced in one direction is positive,
Among the N sample values sampled within the same channel word, the mark corresponds to the mark in which i sample values are displaced in one direction in order from the largest value in the positive direction, and the mark j in order from the largest value in the negative direction. The optical system according to claim 31, characterized in that one sample value corresponds to a mark displaced in the other direction, and the remaining sample values are recognized as corresponding to unmarked digits. How to play. (35) Digital information is recorded by having information carried by both the presence or absence of a mark that causes a phase change in the irradiated light and the displacement of the mark in the lateral direction by a minute amount that is sufficiently smaller than the period of the information track. irradiation means for converging a light spot onto an information track of a recording medium; and receiving reflected or transmitted light from the light and guiding it onto a photoelectric detector, which spreads across a plurality of light receiving cells thereon to detect the far field of the light spot. a light receiving means for forming an image; a mark detecting means for detecting the presence or absence of the mark from the sum of output signals of the plurality of light receiving cells;
1. An optical reproducing device comprising: mark displacement detection means for detecting displacement of the mark in the lateral direction from the value of the difference between the output signals of at least two light-receiving cells. (36) The mark displacement detection means detects the displacement of the mark by substantially binarizing the value of the difference between the output signals of the light receiving cells only when the output signal of the mark detection means has a value indicating the presence of the mark. Claim No. (35) characterized in that
Optical reproducing device as described in Section 1. (37) The recording medium is controlled so that the ratio of the temporal average value of the number of marks displaced in one direction to the number of marks displaced in the other direction is a constant value, and the mark displacement The detection means compares the difference between the means signals with a predetermined threshold value, binarizes the difference, and substantially extracts the binarized output signal only when the output signal of the mark detection means indicates the presence of a mark. Claim 3, characterized in that the threshold value is controlled by negative feedback of the averaged value.
6) The optical reproducing device according to item 6). (38) The average value of the sum of the output signals of the light receiving cells when the binarized signal outputted by the mark displacement detection means is one value, and the average value of the sum of the output signals when the binarized signal output from the mark displacement detection means is the other value. 38. The optical reproducing apparatus according to claim 37, further comprising tracking control means for controlling the position of the light spot so that the positions of the light spots are approximately equal. (39) Claim (38) characterized in that the tracking control means substantially stops the operation of taking the average value when the sum of the output signals from the light receiving cells exceeds a predetermined level. The optical reproduction device described. (40) The recording medium has bits that are minute irregularities that separate the information to be recorded into two information series, the first information series and the second information series, and give a phase change to the light. By recording the first information series, and displacing the bits left and right by an infinitesimal amount that is sufficiently smaller than the repetition period of the information track, the read-only part in which the second information series is recorded and the mark are partially separated. a recordable portion on which information can be recorded by forming a recording medium, a reading means for reading information from the read-only portion of the recording medium, and a recording medium using the same digital modulation method as the first information series. 1. An optical recording/reproducing device comprising: a recording means for recording information on a possible portion.