JP2006179047A - Optical information recording medium and optical information processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium of a reproduction system which has high productivity and wherein multi-value information is recorded and to provide an optical information processing apparatus by which a track error signal can be formed even to an optical information recording medium of a reproduction system with a large capacity (pits are made small). <P>SOLUTION: In the optical information recording medium 100 which has pits 101p wherein a reflection layer 102 is formed in a recessed part of a track region of a transparent substrate 101 and wherein a reproducing signal is formed from a reflection light quantity of a laser beam L with which the pits 101p are irradiated, an arrangement pattern of the pits 101p in the track region has an arrangement pattern for a synchronization signal wherein pits having the maximum pit occupation ratio are disposed before and behind a pit having the minimum pit occupation ratio for forming the synchronization signal used for demodulation of the multi-value reproducing signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical information recording medium and an optical information processing apparatus.

  In recent years, optical recording media such as a CD having a recording capacity of 0.65 GB and a DVD having a recording capacity of 4.7 GB have been widely used as means for storing video information, audio information, or data on a computer. At present, there is a strong demand for further improvement in recording density and capacity.

  As means for increasing the recording density of such an optical recording medium, in an optical information processing apparatus for writing or reading information on the optical recording medium, the numerical aperture (NA) of the objective lens is increased, or the wavelength of the light source It is effective to reduce the diameter of the beam spot that is condensed by the objective lens and formed on the optical recording medium by shortening the length of the beam spot.

  Therefore, for example, in the “CD optical recording medium”, the numerical aperture of the objective lens is 0.50 and the wavelength of the light source is 780 nm, whereas the recording density is higher than that of the “CD optical recording medium”. In the “DVD optical recording medium” in which the objective lens is formed, the numerical aperture of the objective lens is 0.65, and the wavelength of the light source is 660 nm. As described above, the optical recording medium is desired to further improve the recording density and increase the capacity. For this purpose, the numerical aperture of the objective lens is further larger than 0.65, or the wavelength of the light source. Is desired to be shorter than 660 nm. As such a large-capacity optical recording medium and optical information processing apparatus, there is a system proposal that uses a light source in a blue wavelength region to satisfy a large capacity (for example, see Non-Patent Document 1).

  However, when the numerical aperture of the objective lens is increased or the wavelength of the light source is shortened, there is a problem that the margin associated with various fluctuations of the optical recording medium is lowered. For example, there is a problem that coma generated by the tilt of the optical recording medium is increased. When coma occurs, a spot formed on the information recording surface of the optical recording medium deteriorates, so that normal recording / reproducing operation cannot be performed. The coma generated by the tilt of the optical recording medium is generally given by the following equation.

W ₃₁ = ((n ² −1) / (2n ³ )) × (d × NA ³ × θ / λ)

  Here, n is the refractive index of the transparent substrate of the optical recording medium, d is the thickness of the transparent substrate, NA is the numerical aperture of the objective lens, λ is the wavelength of the light source, and θ is the tilt amount of the optical recording medium. From this equation, it can be seen that the shorter the wavelength and the higher the NA, the larger the aberration. Similarly, since the spherical aberration caused by the difference in the substrate thickness of the optical recording medium is proportional to the numerical aperture: the fourth power of NA and the wavelength: the first power of λ, the spherical aberration becomes larger as the wavelength is shorter and the NA is higher.

  Therefore, as another proposal, a multi-value recording / reproducing method for controlling the signal level of the pit formed on the optical recording medium to a value of two or more has been proposed. That is, in the conventional optical recording medium, a signal is read using a change in the amount of reflected light depending on the presence or absence of pits when the reading laser beam scans the optical recording medium, whereas Patent Document 1 discloses that. A multi-value recording / reproducing method for reading out a signal from a change in the amount of reflected light depending on the combination of the pit depth and the pit width, and a change in pit depth, pit width, and pit misalignment as disclosed in Patent Document 2. A multi-value recording / reproducing method for reading out from the recording medium has been proposed.

  In binary recording data, as shown in Patent Document 3 (FIG. 6), a synchronization signal is generated from a signal reproduced from data (referred to as a self-clock method). On the other hand, unlike a binary recording data, a multilevel reproduction signal cannot generate a synchronization signal from a signal reproduced from the data. For this reason, in multi-level recording, it is necessary to periodically insert a synchronization pattern (denoted as CM) for generating a synchronization signal in addition to data into the data. In Patent Document 3, a sync signal array pattern is formed by repeating a combination of a non-recorded cell and a cell in which a mark of the maximum size is recorded.

  Further, in Patent Document 4, regarding the method of recording multi-value information by the recording mark occupancy rate method, in the case of uneven phase pits, the optical characteristics of the phase pits are maximized so that the signal gain of the Rf signal is maximized. It is described that the groove depth is λ / 4.

JP 58-215735 A Japanese Unexamined Patent Publication No. 07-121881 Japanese Patent No. 2914732 JP 2002-157734 A ISOM2001 Proceedings "Next Generation Optical Disc" Hiroshi Ogawa, p6-7

  However, the sync signal array pattern of Patent Document 3 is composed of a repetition of a combination of a non-recorded cell and a cell in which a mark of the maximum size is recorded. In this method, since the CNR of the reproduction signal waveform generated from the synchronization signal array pattern is low, in order to improve the accuracy of the synchronization signal, a signal obtained by repeating the combination at least several tens of times is used as the synchronization signal array pattern. Need to be averaged. When the synchronization signal array pattern becomes longer, redundant information increases and the volume of recordable user data decreases, so that it is a problem to accurately synchronize with a short synchronization signal array pattern.

Further, as in Patent Documents 1 and 2, the optical recording medium on which multi-value data based on the pit depth and the pit width is recorded has a very poor productivity.
That is, when controlling the pit depth in the conventional master stamper manufacturing process by photolithography, it is necessary to control the exposure amount in the step of exposing the photoresist to form pits having a plurality of depths. However, in that case, the bottom is not flat, that is, a round or surface roughness occurs, which causes signal noise in the recording medium. For this reason, an area modulation method that changes the pit occupancy in the cell is desirable for multilevel information.

On the other hand, when the cell length is shortened for high-density recording, particularly when the cell length is C and the reproduction beam diameter defined by the light intensity 1 / e ² is R, 2 ≦ (R / C). When the cell length is reduced to such a length, a method for generating a track error signal becomes a problem. That is, it becomes impossible to generate a track error signal by a method called a phase difference method or a DPD (Differential Phase Detection) method which has been adopted for conventional DVD reproducing optical recording media.

  Here, the DPD method means that when the light spot irradiated on the optical recording medium passes over the pit, the mapping (diffraction pattern) of the pit on the light receiving element changes due to the deviation of the light spot from the center of the pit. The light receiving element is configured to have a region divided in the track length direction of the pit mapping, and how to change the output signal level according to the amount of light received in each region is Depending on the direction and amount of deviation of the light spot from the pit center, the output of the light receiving element is binarized at a predetermined level, and then the phase of the binarized signal is compared. It is possible to obtain a track error signal indicating the direction and amount of the deviation of the light spot by seeing whether the level has changed and the time difference (phase difference) of the level change.

  Examples thereof are shown in FIGS. 1 to 3 show intensity distribution patterns (far-field images) of reflected light amounts received by the light receiving regions a, b, c, and d of the four-part light receiving sensor 3 when the light spot 1 passes over the information pit 2. In the example of change, (a) in each of these figures represents the positional relationship between the light spot 1 and the information pit 2, and (b) is a far field of the amount of reflected light when the light spot 1 passes over the information pit 2. Each image is shown. When the light spot 1 is on the information track of the recording medium, the far field image has uniform brightness. When the light spot 1 passes through the center of the information pit 2, as shown in FIG. 2, the far-field image changes while being left-right symmetric. As shown in FIGS. 1 and 3, when the light spot 1 passes through from the center, the left-right symmetry of the far-field image breaks down, and a time difference (phase difference) occurs in the way of change. When the spot 1 passes the right side from the center of the information pit 2, as shown in FIG. 1B, the spot 1 changes so as to rotate clockwise, and conversely, the light spot 1 moves to the left side from the center of the information pit 2. When passing, it changes so as to rotate counterclockwise as shown in FIG. This pattern change becomes clearer when the light spot 1 is shifted from the center of the information pit 2. Thus, the track error signal as shown in FIG. 4 can be obtained by converting the light quantity into an electrical signal and performing the process of detecting the time difference.

  As shown in FIGS. 1 to 3, the track error signal is received by the light receiving areas a, b, c, and d of the four-divided light receiving sensor 3, and the light receiving areas a, c, b located at the respective diagonals. , D, the track error signal becomes zero if the signal difference is taken, and the light spot 1 is in an on-track state immediately above the track. On the other hand, when the light spot 1 deviates from the information pit, the symmetry of the intensity distribution of the far-field image is broken according to the amount of light and a track error signal is generated.

  However, in a large-capacity optical recording medium in which the beam diameter is larger than the diameter of the pit, if there are a plurality of edges in one beam, a plurality of diffraction patterns are mixed, and the DPD The method could not be used.

  The present invention has been made in view of the above problems in the prior art, and provides a reproduction type optical information recording medium on which multi-value information with easy productivity is recorded, and has a large capacity (small pit size). It is an object of the present invention to provide an optical information processing apparatus capable of generating a track error signal even for an optical information recording medium of a reproduction system.

The present invention provided to solve the above-described problems has a pit formed with a reflective layer in a recess in a track area of a transparent substrate, and a reproduction signal is generated from the reflected light amount of the laser beam irradiated to the pit. In the optical information recording medium, the track region is divided into cells having the same area, and a multi-value reproduction signal is generated according to a pit occupancy that is an area ratio of the pits in the cell. The pits are selected from a plurality of pits having an area size (including no pits) and are formed for each cell. The depth H of the pits is the wavelength of the laser beam to be irradiated, and the refractive index of the transparent substrate. n,
λ / 6 · n <H <λ / 4 · n
The pit track area array pattern has a maximum pit occupancy ratio before and after the pit with the minimum pit occupancy ratio to generate a synchronization signal used for demodulating the multilevel reproduction signal. An optical information recording medium having an array pattern for synchronizing signals in which pits are arranged (claim 1).

Here, when the number of cells in which the pit occupancy of the synchronization signal array pattern is maximum is x, the cell length is C, and the beam diameter of the laser beam defined by the light intensity 1 / e ² is R,
2 ≦ x ≦ (R / C)
Is preferably satisfied.

  In order to solve the above problems, the present invention provides an irradiation optical system for condensing and irradiating a laser beam onto a pit formed on an optical information recording medium, and at least two parts, and reflecting light from the optical information recording medium. A light receiving optical system that receives light and a detection signal received by the light receiving optical system generate a sum signal, differentiate the sum signal to detect a peak position of the sum signal, and then based on the peak position detection result Signal processing means A for generating a synchronizing signal and signal processing means B for generating a push-pull signal based on the detection signal received by the light receiving optical system and generating a track error signal from the push-pull signal A sum signal based on the sync signal array pattern by the signal processing means A using the optical information recording medium according to claim 1 or 2. The tracking position is detected discretely, the tracking error signal is generated from the push-pull signal based on the synchronization signal array pattern by the signal processing means B at the peak position detection timing, and the tracking servo is applied by the tracking error signal. An optical information processing apparatus characterized by the above (claim 3).

  The present invention, which is provided to solve the above-mentioned problems, splits a laser beam by a grating so that the main light is on the main track of the optical information recording medium, and the first and second sub-lights are on the tracks adjacent to the main track. A laser beam irradiation optical system for condensing and irradiating each of the first light receiving optical system and a first light receiving optical system for receiving reflected light of the main light from the optical information recording medium. A second signal and a third light receiving optical system that respectively receive reflected light of two sub-lights, and a sum signal based on the detection signal received by the first light receiving optical system; A signal processing means A that generates a synchronization signal based on the peak position detection result, and generates a push-pull signal based on the detection signal received by the first to third light receiving optical systems, Push push 3. An optical information processing apparatus comprising: a signal processing unit having a signal processing unit B that generates a track error signal from a signal, wherein the signal processing unit A uses the optical information recording medium according to claim 1 or 2. To discretely detect the peak position of the sum signal based on the sync signal array pattern, and generate a tracking error signal from the push-pull signal based on the sync signal array pattern by the signal processing means B at the peak position detection timing. The optical information processing apparatus is characterized in that tracking servo is applied by the tracking error signal.

  As an effect of the present invention, according to the first aspect of the present invention, a region where pits are formed is divided into cells having the same area, and a multilevel reproduction signal is generated according to the pit occupancy for each cell. Since one area-modulated pit is formed for each cell, multi-value information is not recorded by depth modulation, but multi-value information is recorded by area modulation. It is possible to provide a reproduction type optical recording medium in which a stable development process for performing exposure up to a glass substrate can be secured, and multi-value information with easy productivity is recorded. At this time, the pit depth is from λ / 6n at which the push-pull signal amplitude is maximum to λ / 4n at which the amplitude separation of the reproduction signal at each pit size is maximum, that is, the S / N of the reproduction signal is maximum. By setting the value within the range, a track error signal is detected by a push-pull method generally used for a recording optical information recording medium even for a reproducing optical information recording medium in which pits are formed. Therefore, compatibility with the generation of the track error signal of the optical information recording medium of the recording system can be achieved. In particular, it is desirable to set the push-pull signal and its intermediate value at which the reproduction signal can be sufficiently obtained, in the vicinity of λ / 5n. Also, the sync signal array pattern for generating the sync signal used for demodulating the multilevel reproduction signal is a pattern in which pits having the maximum pit occupancy ratio are arranged before and after the pits having the minimum pit occupancy ratio. Yes, since the sum signal of the reproduction signals of the sync signal array pattern has a peak at the center of the cell, there is no need to shift the time in order to generate the sync signal. It can be simplified.

  According to the invention of claim 2, even in high-density recording in which the cell length is 1/2 or less with respect to the beam diameter of the laser beam, since 2 ≦ x ≦ (R / C) is satisfied, intersymbol interference is reduced. Since it is small, the CN ratio is large. In other words, even if the cell length is reduced for high-density recording, it is possible to synchronize accurately with a short sync signal array pattern, so that the data area can be enlarged and recording density can be further increased. It is.

  According to the third aspect of the invention, since the optical information recording medium according to the first or second aspect is targeted, the recording system can be applied to such a reproduction type optical information recording medium in which pits are formed. The track error signal can be detected by a push-pull method generally used in an optical information recording medium. In other words, when playback information is recorded in cell units based on the pit occupancy rate, as a result, the structure in which the pits are continuously arranged is observed as if the continuous spot was formed in the beam spot. It is to be done. Furthermore, since the sync signal array pattern, which is a combination of the pits having the minimum pit occupancy ratio and the pits having the maximum pit occupancy ratio, has a push-pull signal whose amplitude is several steps larger than the random array pattern in the data area, A tracking error signal is discretely detected by the reproduced push-pull signal of the synchronization signal array pattern, and tracking servo is applied by the tracking error signal, so that stable tracking can be performed.

  According to the invention of claim 4, when the simple push-pull method is used, the optical axis of the objective lens is shifted (shifted) or tilted (tilt) from the optical axis of the fixed optical system. Although there is a problem that an offset occurs in the track error signal because the light quantity distribution is biased, the main light and the first and second sub-lights are condensed on the main track and the adjacent track using the grating as in the present invention. A laser beam irradiation optical system for irradiation; a first light receiving optical system for receiving reflected light of the main light from the optical recording medium divided into at least two; and a first light receiving optical system for receiving reflected light of the first and second sub-lights. Solved by detecting the tracking error signal discretely with a differential push-pull signal, having a second and third light receiving optical system and a signal processing unit that performs signal processing based on the detection signal received by these light receiving optical systems To do.

The configuration of the optical information recording medium according to the present invention will be described below.
FIG. 5 shows an example of a cross-sectional structure of the optical information recording medium according to the present invention.
As shown in FIG. 5, the optical information recording medium 100 has a pit 101p in which a reflective layer 102 is formed in a recess in a track area of a transparent substrate 101, and the amount of reflected light of the laser light L irradiated to the pit 101p. From this, a reproduction signal is generated. Here, the transparent substrate 101 may be a polycarbonate substrate having a thickness of 0.6 mm, for example. The transparent substrate 101 has a substrate 104 bonded to the reflective layer 102 side through an adhesive layer 103.

  Further, in the optical information recording medium 100, the track area is divided into cells having the same area, and a multilevel reproduction signal is generated according to the pit occupancy ratio which is the area ratio of the pits 101p occupying the cell. In addition, the pits 101p are selected from a plurality of pits having an area size (including no pits) and formed for each cell. The pit 101p is preferably a cylindrical hole having a bottom diameter φ and a depth H.

  Here, in the optical information recording medium 100, the cell pitch in the beam traveling direction of the laser light L is 0.24 μm, the track pitch is 0.43 μm, and the pit 101p has a constant depth H of 0 nm (no pit), 80 nm. , 110 nm, 140 nm, 170 nm, 190 nm, 210 nm, and 230 nm, and the following pit arrangement patterns selected from eight diameters φ were formed.

<Pit arrangement pattern>
ML0, ML0, ML0, ML0, ML7, ML7, ML7, ML7, ML6, ML7, ML7, ML5, ML7, ML7, ML4, ML7, ML7, ML3, ML7, ML7, ML2, ML7, ML7, ML1, ML7, ML7, ML0, ML7, ML7

  In the arrangement pattern, when there is no pit, multivalue data 0 (indicated as ML0), multivalue data 1 (ML1), multivalue data 2 (ML2), multivalue data 3 ( ML3), multi-value data 4 (ML4), multi-value data 5 (ML5), multi-value data 6 (ML6), multi-value data 7 (ML7), and multi-value data minimum is ML0. Data maximum means ML7.

  The optical information recording medium 100 was used to reproduce the pit arrangement pattern by using an optical pickup device including a light source emitting a laser beam having a wavelength of 405 nm and an objective lens having an NA of 0.65 as an irradiation optical system. The reproduction signal is shown in FIG. Here, it was found that 8-level multi-value information was recorded. At this time, the dynamic range is 0.87 V, and the modulation is 49.7%.

  In the present invention, in order to generate a synchronization signal used for demodulating a multilevel reproduction signal as an array pattern of the track area of the pit 101p, before and after the pit (ML0) having the minimum pit occupancy as shown in FIG. It is characterized by having an array pattern for synchronizing signals in which pits (ML7) having the maximum pit occupancy are arranged. The synchronization signal array pattern is appropriately arranged in the pit array pattern in the data area.

  FIG. 7 also shows a reproduction signal (sum signal) when this synchronization signal array pattern is reproduced. The CN ratio is larger than that of the reproduction signal of the conventional synchronization signal array pattern shown in FIG. .

  In the present invention, the pit depth H is larger than λ / 6n where the amplitude of the push-pull signal is maximum when the wavelength of the irradiated laser light is λ, and the refractive index of the transparent substrate is n, and the S of the reproduction signal. The range is smaller than λ / 4n where / N is maximum. Here, it is particularly preferable to set the pit depth H to the intermediate value (λ / 5n). As a result, even in the reproducing optical information recording medium 100 in which the pits 101p are formed, it becomes possible to detect the track error signal by the push-pull method generally used in the recording optical information recording medium. . That is, when reproduction information is recorded in units of cells by the pit occupancy rate, as a result, the configuration in which the pits 101p are continuously arranged is equivalent to that in which continuous grooves are formed in the beam spot. This is because it is observed, and compatibility with the generation of the track error signal of the optical information recording medium of the recording system can be taken. In this case, since it is not necessary to observe the edge between the pits in the traveling direction of the beam spot, the problem of the DPD method is solved.

  Further, since the sum signal of the sync signal array pattern of the present invention shown in FIG. 7 has a larger CN ratio than the sum signal of the sync signal array pattern of the prior art, the sync signal is accurately obtained with a short sync signal array pattern. Can be generated. Furthermore, the sync signal array pattern of the present invention has a large PP signal amplitude due to a large pit area ratio in the reproduction beam.

Next, the configuration of the optical information processing apparatus according to the present invention will be described.
An optical information processing apparatus according to the present invention splits a laser beam by a grating and collects main light on a main track of an optical information recording medium and collects first and second sub-lights on tracks adjacent to the main track. A laser beam irradiation optical system for irradiating; a first light receiving optical system for receiving reflected light of the main light from the optical information recording medium; and at least for dividing the first and second sub-lights. A sum signal is generated based on the second and third light receiving optical systems that receive the reflected light and the detection signal received by the first light receiving optical system, and the sum signal is differentiated to obtain the peak position of the sum signal. Signal processing means A that detects and then generates a synchronization signal based on the peak position detection result, and generates a push-pull signal based on the detection signal received by the first to third light receiving optical systems, and the push-pull signal From the track An optical information processing apparatus comprising a signal processing unit having a signal processing unit B that generates an error signal, wherein the synchronization signal array is formed by the signal processing unit A using the optical information recording medium of the present invention described above. The peak position of the sum signal based on the pattern is discretely detected, and the tracking error signal is generated from the push-pull signal based on the synchronization signal array pattern by the signal processing means B at the peak position detection timing. The tracking servo is applied.

The operation content of the optical information processing apparatus of the present invention will be described with reference to FIGS.
FIG. 9 is a schematic diagram showing the configuration of the optical information processing apparatus of the present invention, and shows an optical pickup (an optical component of the optical information processing apparatus) employing a grating.
In this optical information processing apparatus, information is reproduced as follows using the optical information recording medium 100 of the present invention.

  First, the beam emitted from the semiconductor laser 5 is collimated by the collimating lens 6 and then diffracted by the grating 7 and branched into 0th order and ± 1st order diffracted light. Then, the branched light is condensed and irradiated onto the optical information recording medium 100 by the objective lens 8 as shown in FIG. At this time, the spot of the main light M1 that is the 0th-order diffracted light is connected to the main track T of the optical information recording medium 100, and the spots of the first and second sub-lights S1 and S2 that are ± 1st-order diffracted light are the main light. It leads and follows the spot of M1, and is connected so as to deviate by ± 1/2 track pitch in the radial direction of the optical information recording medium 100.

  Next, the main light M 1 reflected from the optical information recording medium 100 and passed through the objective lens 8 and the first and second sub-lights S 1 and S 2 are separated from the irradiation light by the beam splitter 10, and the light receiving element via the detection lens 11. 12 receives light. As shown in FIG. 10B, the light receiving element 12 includes a first photodetector 13a that receives the main light M1, and second and third photodetectors 13b that receive the first and second sub-lights S1 and S2, respectively. , 13c. These first to third photodetectors 13 a to 13 c are each composed of two divided plates that are independently photoelectrically converted and divided in the radial direction of the optical recording medium 9.

  Here, the first photodetector 13a performs signal processing based on the received light signal that is received and output from the reflected light of the sync signal array pattern discretely on the track of the optical information recording medium of the present invention, A synchronization signal is generated. That is, the sum signal (reproduced signal) of the detection signal received by the first photodetector 13a is processed by a differentiator as shown in FIGS. 11 and 12 to become a differentiated waveform, and the peak of the sum signal is derived from this differentiated waveform. The position is detected, and a synchronization signal is generated based on the peak position detection result.

  When the peak position of the sum signal of the synchronization signal array pattern is detected, the push-pull signal is detected based on the detection signal of the reflected light of the synchronization signal array pattern received by the first to third photodetectors 13a to 13c. And a track error signal is generated from the push-pull signal. Specifically, signal processing is performed as follows.

The first to third differential amplifiers 14, 15, and 16 receive the detection signals of the first to third photodetectors 13 a, 13 b, and 13 c (the detection signals of the reflected light of the synchronization signal array pattern), respectively. The first to third push-pull signals are output. The first amplifier 17 amplifies the third push-pull signal to a predetermined gain G1, and the second amplifier 18 amplifies the sum signal of the signal output from the first amplifier 17 and the second push-pull signal to a predetermined gain G2. The fourth differential 19 outputs a track error signal by differentiating the signal input from the second amplifier 18 and the first push-pull signal from the main light M1 input from the first differential 14. The gains G1 and G2 of the first and second amplifiers 17 and 18 are set in consideration of the intensity of the main light M1 and the first and second sub-lights S1 and S2.
A predetermined tracking servo is applied by the tracking error signal.

The configuration of the optical information processing apparatus of the present invention may be a configuration in which the grating 7 is omitted in FIG. Further, the light reception detection system is configured by only the first photodetector 13a and the first differential amplifier 14 in FIG. 10B.
That is, the optical information processing apparatus of the present invention receives the reflected light from the optical information recording medium which is divided into at least two parts, the irradiation optical system for condensing and irradiating laser light onto the pits formed on the optical information recording medium. A sum signal is generated based on the light receiving optical system and the detection signal received by the light receiving optical system, the sum signal is differentiated to detect the peak position of the sum signal, and then synchronized based on the peak position detection result A signal processing unit including a signal processing unit A that generates a signal and a signal processing unit B that generates a push-pull signal based on the detection signal received by the light-receiving optical system and generates a track error signal from the push-pull signal; The signal processing means A discretely detects the peak position of the sum signal based on the sync signal arrangement pattern using the optical information recording medium of the present invention. By the signal processing unit B by the position detection timing to generate a tracking error signal from the push-pull signal based on the synchronization signal sequence pattern, and is characterized in applying a tracking servo by the tracking error signal.

  Here, as an operation content of the optical information processing apparatus of the present invention, the first photodetector 13a receives and outputs the reflected light of the sync signal array pattern discretely on the track of the optical information recording medium of the present invention. Signal processing is performed based on the received light signal, and a synchronization signal is generated. That is, the sum signal (reproduced signal) of the detection signal received by the first photodetector 13a is processed by a differentiator as shown in FIGS. 11 and 12 to become a differentiated waveform, and the peak of the sum signal is derived from this differentiated waveform. The position is detected, and a synchronization signal is generated based on the peak position detection result.

  When the peak position of the sum signal of the synchronization signal array pattern is detected, a push-pull signal is generated based on the detection signal of the reflected light of the synchronization signal array pattern received by the first photodetector 13a. A track error signal is generated from the push-pull signal. That is, the first differential amplifier 14 differentially outputs the detection signal (the detection signal of the reflected light of the synchronization signal array pattern) input from the first photodetector 13a, and outputs a tracking error signal. A predetermined tracking servo is applied.

Example 1
In the optical information recording medium 100 shown in FIG. 5, only the sync signal arrangement pattern shown in FIG. 7 is arranged in the track region, and a light source for emitting laser light having a wavelength of 405 nm for the optical information recording medium 100, NA 0.65 The pit arrangement pattern was reproduced using an optical pickup device including an objective lens as an irradiation optical system.
The push-pull signal at that time is shown in FIG.
Further, as a comparative example 1, FIG. 14 shows a push-pull signal obtained by arranging only the sync signal arrangement pattern shown in FIG. 8 in the track area and reproducing the same.
In the synchronization signal array pattern of the present invention, the push-pull signal amplitude was 29.7% of the RF signal, and in the synchronization signal array pattern of Comparative Example 1, the amplitude was 17.7%.

(Example 2)
The optical information recording medium shown in FIG. 5 provided with the sync signal array pattern shown in FIG. 7 is used for reproduction by the light irradiation and light receiving optical system having the configuration shown in FIG. The synchronization signal was generated by the processing as shown in FIG. Also, the reproduced push-pull signal (PP) of the sync signal array pattern is discretely detected to obtain a tracking error signal (TE signal), and the reproduced signal is subjected to the tracking servo based on the tracking error signal. Went.

Table 1 shows SDR values of the reproduction signal at this time. In addition, as Comparative Example 2, an SDR value when a reproduction signal is performed by continuously detecting push-pull signals and applying tracking servo as a tracking error signal is also shown. Here, the SDR value is a ratio between the average value of the standard deviation σi of each multilevel signal when the number of multilevel gradations is n and the dynamic range DR of the signal. Signal quality corresponding to jitter in value recording.
SDR = Σσi / (n × DR)

  In general, when the number n of multi-value gradations is constant, the SDR value becomes smaller as the standard deviation σi of the multi-value signal is smaller and the dynamic range DR is larger, and the separability of the multi-value signal is better as the SDR value is smaller. Thus, the error rate becomes low. In Example 2, since the tracking was stable, it was found that the SDR value was low and the quality of the reproduced signal was excellent.

It is explanatory drawing which shows the light spot and light reception state for demonstrating the conventional DPD method. It is explanatory drawing which shows the light spot and light reception state for demonstrating the conventional DPD method. It is explanatory drawing which shows the light spot and light reception state for demonstrating the conventional DPD method. It is explanatory drawing which shows a mode that a track error signal is obtained. It is explanatory drawing which shows the structure of the optical information recording medium of this invention. It is explanatory drawing which shows the reproduction signal (sum signal) of the optical information recording medium of this invention. It is a figure which shows the arrangement | sequence pattern for synchronous signals of the optical information recording medium of this invention, and its reproduction signal (sum signal). It is a figure which shows the arrangement pattern for synchronous signals of the optical information recording medium of a prior art, and its reproduction | regeneration signal (sum signal). It is an optical pick-up block diagram of the optical information processing apparatus of this invention. It is a block diagram which shows the light reception detection system of DPP method. It is explanatory drawing which shows the block diagram of the reproduction signal process of the optical information processing apparatus of this invention. It is explanatory drawing which shows the synchronous signal generation process of the optical information processing apparatus of this invention. FIG. 6 is a diagram illustrating an integration signal of a reproduction signal of the synchronization signal array pattern according to the first embodiment. FIG. 10 is a diagram illustrating an integration signal of reproduction signals of a synchronization signal array pattern of Comparative Example 2;

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical spot 2 Information pit 3 4 division | segmentation light reception sensor 5 Semiconductor laser 6 Collimating lens 7 Grating 8 Objective lens 10 Beam splitter 11 Detection lens 12 Light receiving element 13a, 13b. 13c photodetector 14, 15, 16, 19 differential amplifier 17, 18 amplifier 100 optical information recording medium 101 transparent substrate 101p pit 102 reflecting layer 103 adhesive layer 104 substrate

Claims (4)

In an optical information recording medium having a pit formed with a reflective layer in a recess in a track region of a transparent substrate, and a reproduction signal is generated from a reflected light amount of laser light irradiated to the pit,
The track area is divided into cells having the same area, and the pit has a plurality of area sizes so that a multi-valued reproduction signal is generated according to a pit occupancy ratio that is an area ratio of the pit occupying the cell. Selected from pits (including no pits) and formed for each cell,
The depth H of the pit is such that the wavelength of the irradiated laser light is λ, and the refractive index of the transparent substrate is n.
λ / 6 · n <H <λ / 4 · n
Satisfied,
The array pattern of the track area of the pits is arranged with pits having the maximum pit occupancy before and after the pits having the minimum pit occupancy in order to generate a synchronization signal used for demodulating the multilevel reproduction signal. An optical information recording medium having a synchronized signal array pattern. When the number of cells that maximizes the pit occupancy of the synchronization signal array pattern is x, the cell length is C, and the beam diameter of the laser beam defined by the light intensity 1 / e ² is R,
2 ≦ x ≦ (R / C)
The optical information recording medium according to claim 1, wherein: An irradiation optical system for condensing and irradiating laser light onto pits formed on the optical information recording medium;
A light receiving optical system which is divided into at least two and receives reflected light from the optical information recording medium;
A signal that generates a sum signal based on a detection signal received by the light receiving optical system, differentiates the sum signal to detect a peak position of the sum signal, and then generates a synchronization signal based on the peak position detection result Optical information processing comprising processing means A and a signal processing unit having signal processing means B for generating a push-pull signal based on the detection signal received by the light-receiving optical system and generating a track error signal from the push-pull signal A device,
3. The peak position of the sum signal based on the sync signal array pattern is discretely detected by the signal processing means A using the optical information recording medium according to claim 1 or 2, and the signal is detected at the peak position detection timing. An optical information processing apparatus, characterized in that a processing unit B generates a tracking error signal from a push-pull signal based on the synchronization signal array pattern and applies tracking servo by the tracking error signal. A laser beam irradiation optical system that divides and irradiates the main beam on the main track of the optical information recording medium by splitting the laser beam with a grating, and the first and second sub beams on both adjacent tracks of the main track;
A first light receiving optical system that receives the reflected light of the main light from the optical information recording medium; and a second and a second light receiving optical system that receives the reflected light of the first and second sub-lights. A third light receiving optical system;
Generates a sum signal based on the detection signal received by the first light receiving optical system, differentiates the sum signal to detect the peak position of the sum signal, and then generates a synchronization signal based on the peak position detection result Signal processing means A, and a signal processing means B that generates a push-pull signal based on the detection signal received by the first to third light receiving optical systems and generates a track error signal from the push-pull signal. An optical information processing apparatus comprising a unit,
3. The peak position of the sum signal based on the sync signal array pattern is discretely detected by the signal processing means A using the optical information recording medium according to claim 1 or 2, and the signal is detected at the peak position detection timing. An optical information processing apparatus, characterized in that a processing unit B generates a tracking error signal from a push-pull signal based on the synchronization signal array pattern and applies tracking servo by the tracking error signal.