JP2008505426A - Method and apparatus for reproducing super-resolution information recording medium - Google Patents

Abstract

A data reproduction method and apparatus for a super-resolution information recording medium is disclosed. The method of reproducing data recorded on a super-resolution information recording medium capable of reproducing data recorded with a mark having a size less than the resolution of the incident light beam according to the present invention is different for the information recording medium. Irradiating a first beam having a power at which a super-resolution phenomenon occurs at a position and a second beam having a power at which the super-resolution phenomenon does not occur; a first reproduction signal by the first beam; and a second beam by a second beam. Detecting a reproduction signal, and calculating a time difference between the first reproduction signal and the second reproduction signal. According to such a configuration, the reproduction signal characteristic is improved by eliminating the signal reflected in the peripheral area other than the super-resolution area of the spot of the reproduction beam.

Description

  The present invention relates to a method and apparatus for reproducing data recorded on a super-resolution information recording medium. More specifically, the present invention relates to a reproduction signal characteristic by eliminating inter-signal interference (ISI) in a super-resolution information recording medium. The present invention relates to a data reproduction method and apparatus for a super-resolution information recording medium that can be improved.

  An optical recording medium is used as an information recording medium of an optical pickup device that records and reproduces information in a non-contact manner, and is required to increase the recording density of information stored with industrial development. . Therefore, an optical recording medium has been developed that can reproduce a recording mark having a size smaller than the resolution of the laser beam by using a super-resolution phenomenon.

  Generally, when the wavelength of a light source for reproducing data recorded on a recording medium is λ and the numerical aperture of an objective lens is NA, λ / 4NA is the limit of the reproduction resolution. That is, generally, a recording mark whose light emitted from a light source is smaller than λ / 4NA cannot be distinguished, and data reproduction is generally impossible.

  By the way, a super-resolution phenomenon capable of reproducing a recording mark having a size exceeding the resolution limit has occurred, and cause analysis and research and development for such a super-resolution phenomenon are progressing. According to the super-resolution phenomenon, it is possible to reproduce even a recording mark having a size exceeding the resolution limit. Therefore, the super-resolution information recording medium meets the requirements of high density and high capacity. It can be made.

  In order to commercialize a super-resolution information recording medium, it is necessary to satisfy the recording characteristics and the reproduction characteristics that are basically required as a recording medium. In particular, since a super-resolution information recording medium uses a recording beam and a reproducing beam having relatively higher power than a general information recording medium, a signal-to-noise ratio (Carrier-to-Noise Ratio: CNR) is used. ), Ensuring of reproduction signal characteristics such as jitter characteristics and RF signals and realizing the stability of the reproduction signals are the main problems of the super-resolution information recording medium. In order to put the super-resolution information recording medium into practical use, the reproduction signal characteristics must first be satisfied.

  With reference to FIG. 1, the region where the super-resolution phenomenon occurs at the spot of the reproduction beam irradiated on the super-resolution information recording medium will be described. Referring to FIG. 1, a mark 110 is recorded along a track 100 of a super-resolution information recording medium, and a temperature distribution change or optical change is caused by a partial light intensity difference in a light spot 120 focused on the super-resolution layer. Since the characteristic change occurs, it is possible to reproduce even the mark 110 having a size exceeding the resolution limit. That is, it is considered that a temperature distribution change or an optical characteristic change occurs in a partial region of the light spot 120, and such a change does not occur in the peripheral region 140 of the partial region. As shown in FIG. 1, the partial area where the change occurs becomes the center or the latter half of the light spot 120, and such a partial area forms the super-resolution area 130. Such division of the optical property changing region may be continuous or discontinuous.

  There have been many reports that a CNR that can be considered for practical use was obtained from marks of the same length smaller than the resolution by super-resolution reproduction using various super-resolution materials. However, in actual optical recording, marks of the same length are not recorded at the same interval. Marks of the same length are recorded at different intervals (mark position detection method), or marks of different lengths are recorded. Are recorded at different intervals (mark length detection method). In particular, when a CD or DVD is put to practical use, when the clock frequency is T, marks having various lengths from 3T to 11T are used in combination. At present, there is no example in which any of the above-described super-resolution techniques has successfully reproduced such a complex signal.

  The reason is that the signal reflected from the optical recording medium does not appear only in the region where the optical characteristics change, but is obtained from the entire laser spot. If there is no signal reflected from the area excluding the optical characteristic changing area, the actual spot size is reduced, so that the composite signal can be reproduced. However, in the previous super-resolution technique, the difference in optical characteristics between the optical property changing area and the surrounding area is used, and the difference is relatively small, so that the signal reflected from the surrounding area has the spot size reduced. Acts as a disturbing element to shrink. As a result, an inter-signal interference (ISI) problem that occurs during a series of mark reproduction occurs, so that the composite signal cannot be reproduced clearly.

  2A is a diagram showing a recording pattern of marks recorded on the information recording medium, and FIG. 2B is a diagram showing an RF signal obtained by reproducing the mark having such a pattern. When the laser beam wavelength is 405 nm, the NA is 0.85, and the resolution is about 119 nm, the recording pattern includes a mark having a 75 nm length smaller than the resolution, a mark having a length of 300 nm larger than the resolution, and a space. The recording pattern by combination is shown. 2B, it can be seen that when a mark or space having a length of 300 nm is in the vicinity of the light spot, the mark having a length of 75 nm is not clearly detected due to the influence of the mark and the space. Such a portion is represented by A, B, C, D, E, and F. It can also be seen that the level of the reproduction signal varies depending on the number of 75 nm marks and spaces. For example, the level of the detected signal is different between the portion D where two 75 nm marks are recorded and the portion E where three 75 nm marks are recorded. Further, when there are a mark and a space having a length of 75 nm, the signal level is not constant depending on the situation around the mark, and it is detected with an inclination.

  Such a problem occurs due to ISI caused by a signal obtained from a peripheral region other than the super-resolution region of the light spot.

  The present invention was created in order to solve the above-described problems, and a super-resolution region in which a temperature distribution change or an optical characteristic change occurs when a reproduction beam is irradiated onto a super-resolution information recording medium. An object of the present invention is to provide a method and an apparatus capable of accurately reproducing recorded data by eliminating a reproduction signal from the peripheral area and preventing inter-signal interference.

  A method for reproducing data recorded on an information recording medium according to the present invention is recorded on a super-resolution information recording medium capable of reproducing data recorded with a mark having a size smaller than the resolution of the incident light beam. In the method for reproducing data, the step of irradiating a first beam having a power at which a super-resolution phenomenon occurs at different positions of the information recording medium and a second beam having a power at which the super-resolution phenomenon does not occur, Detecting a first reproduction signal by the first beam and a second reproduction signal by the second beam, and calculating a time difference between the first reproduction signal and the second reproduction signal.

  Preferably, the calculating step includes a step of differentially calculating the first reproduction signal and the second reproduction signal. The different positions are preferably different positions on the same track.

  Preferably, the irradiating step includes a step of splitting the beam emitted from one light source into the first beam and the second beam using a spectroscopic element. Among the plurality of diffracted beams generated from the spectroscopic element in the spectroscopic step, a + k order diffracted beam may be used as the first beam, and a −k order diffracted beam may be used as the second beam. Of the plurality of diffracted beams generated from the spectroscopic element, a -k order diffracted beam can be used as the first beam, and a + k order diffracted beam can be used as the second beam. The spectroscopic element is preferably a blazed grating element.

  Preferably, the irradiating step includes a step of irradiating from a first light source and a second light source each having the first beam and the second beam independently.

  Another feature of the present invention is a method for reproducing data recorded on a super-resolution information recording medium capable of reproducing data recorded with a mark having a size less than the resolution of the incident light beam. Irradiating the information recording medium with a first beam of resolving power; irradiating a second beam of non-super resolving power at a predetermined time difference to the same position irradiated with the first beam; Detecting a final reproduction signal based on a first reproduction signal by the first beam and a second reproduction signal by the second beam.

  The detecting step may further include a step of compensating for the predetermined time difference between the first reproduction signal and the second reproduction signal.

  The detecting step further includes a step of compensating the predetermined time difference so that jitter or bER of the final reproduction signal is minimized, or reproducing predetermined discriminating information not used for prepits or user data by the first beam. And a step of compensating for the predetermined time difference using a difference between a predetermined time and a time for reproducing predetermined discrimination information not used for pre-pits or user data by the second beam, or using the wobble signal Preferably, the method further includes a step of compensating for.

  Still another feature of the present invention is an apparatus for reproducing data recorded on a super-resolution information recording medium capable of reproducing data recorded with a mark having a size less than the resolution of the incident light beam. A pickup unit that irradiates a first beam having a power at which a super-resolution phenomenon occurs at different positions of the information recording medium and a second beam having a power at which a super-resolution phenomenon does not occur, and a first beam by the first beam. A signal processing unit that detects a reproduction signal and a second reproduction signal by the second beam and compensates and calculates a time difference between the first reproduction signal and the second reproduction signal; and a signal input from the signal processing unit And a control unit that controls the pickup unit.

  Still another feature of the present invention is an apparatus for reproducing data recorded on a super-resolution information recording medium capable of reproducing data recorded with a mark having a size less than the resolution of the incident light beam. A pickup unit that irradiates the information recording medium with a first beam of super-resolution power, and irradiates a second beam of non-super-resolution power at a predetermined time difference to the same position irradiated with the first beam; A signal processing unit for detecting a final reproduction signal based on a first reproduction signal by the first beam and a second reproduction signal by the second beam, and a control for controlling the pickup unit using an output signal from the signal processing unit A part.

  The data reproduction method of the super-resolution information recording medium according to the present invention is a method for reproducing optical data recorded with a mark having a size less than the resolution. By eliminating the signal reflected in the peripheral region other than the super-resolution region where the distribution change occurs, the reproduction signal characteristic can be improved. If the method for controlling Time Delay according to the present invention is used, the accuracy of the reproduction signal can be further improved by accurately controlling the distance between spots. Such a method contributes to the practical use of a super-resolution information recording medium by improving the characteristics of a signal obtained by reproducing data recorded with a random pattern.

  Further, the data reproducing apparatus for the super-resolution information recording medium according to the present invention can improve the reproduction signal characteristics of the super-resolution information recording medium by simple signal processing without greatly changing the existing reproducing apparatus.

  By improving the data reproduction performance of the super-resolution information recording medium using the data reproduction method and apparatus according to the present invention, a high-quality, high-density, high-capacity information recording medium can be put into practical use.

  Further, the super-resolution information recording medium to which the reproducing method of the present invention is applied is shown in the above example in which the multi-layer structure of five or seven layers on the substrate and the super-resolution layer is limited to a specific material. This is merely an example, and can be variously applied to an information recording medium in which a super-resolution phenomenon occurs.

  Hereinafter, a method and apparatus for reproducing data recorded on a super-resolution information recording medium according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  The data reproducing method according to the present invention is applied to a super-resolution information recording medium capable of reproducing information recorded with a recording mark having a size exceeding the resolution limit.

  Prior to the description of the reproducing method according to the present invention, an example of a super-resolution information recording medium to which the reproducing method according to the present invention is applied will be described, and then the present invention will be described in detail.

  Referring to FIG. 3, the super-resolution information recording medium includes a substrate 310, a first dielectric layer 320, a recording layer 330, a second dielectric layer 340, and a super-resolution reproduction formed sequentially on the substrate 310. A layer 350, a third dielectric layer 360, and a cover layer 370 are included. Here, the beam used for recording / reproducing information is transmitted through the cover layer 370 and focused by the objective lens (OL).

  The substrate 310 is made of any one material selected from polycarbonate, polymethyl methacrylate (PMMA), amorphous polyolefin (APO), and glass material, and one surface thereof, that is, the first dielectric layer 320. It is desirable that a reflective film for reflecting the incident beam be formed on the surface facing the surface.

  The first to third dielectric layers 320, 340, and 360 are layers for controlling optical and / or thermal characteristics. The cover layer 370 is a layer formed so as to cover the layer formed on the substrate 310 including the recording layer 330 and the super-resolution reproduction layer 350. Here, it is needless to say that the first to third dielectric layers 320, 340, 360 and the cover layer 370 are not essential components, and information can be reproduced even without this layer.

The first to third dielectric layers 320, 340, and 360 are preferably made of at least one of oxide, nitride, carbide, sulfide, and fluoride. That is, the first to third dielectric layers 320, 340, and 360 are formed of silicon oxide (SiO _x ), magnesium oxide (MgO _x ), aluminum oxide (AlO _x ), titanium oxide (TiO _x ), and vanadium oxide (VO _x ). ), Chromium oxide (CrO _x ), nickel oxide (NiO _x ), zirconium oxide (ZrO _x ), germanium oxide (GeO _x ), zinc oxide (ZnO _x ), silicon nitride (SiN _x ), aluminum nitride (AlN _x ) , Titanium nitride (TiN _x ), zirconium nitride (ZrN _x ), germanium nitride (GeN _x ), silicon carbide (SiC), zinc sulfide (ZnS), zinc sulfide-silicon dioxide compound (ZnS—SiO ₂ ), magnesium fluoride It is composed of at least one material selected from (MgF ₂ ) It is desirable.

  The recording layer 330 has a structure in which a cross-sectional shape of a recording mark recorded by a beam incident with a predetermined recording power is made to be a rectangle or a shape close to a rectangle. Here, the recording mark includes a mark having a size smaller than the resolution of the optical pickup used for reproduction.

  Here, in order to reproduce data repeatedly using the super-resolution phenomenon, the chemical reaction temperature Tw in the recording layer 330 is higher than the temperature Tr at which the super-resolution phenomenon occurs in the super-resolution reproduction layer 350.

  Therefore, in order to form the recording mark, the recording layer 330 has at least two kinds of substances having different physical properties and chemically react with each other at a predetermined temperature (for example, two of A and B shown in FIG. 3). It is a layer of a single layer structure in which seed substances are mixed and formed.

  For example, the recording layer 330 in a form in which the substances A and B are mixed is described. Before the recording, that is, before the chemical reaction between the substances A and B occurs, the recording layer 330 has the substance A. And a substance B are mixed. When a recording beam having a predetermined power is irradiated to the recording layer 330, the substance A and the substance B are in a region where the light spot is focused by the recording power beam, The compound A + B has physical properties different from the form in which the substances A and B are mixed. Thus, the modified compound A + B forms a recording mark, and this recording mark has a different reflectance when compared with other regions.

  Here, an example of the substance A is tungsten (W), and an example of the substance B is silicon (Si). This is because when a Ge-Sb-Te material is used as a super-resolution reproduction layer, which will be described later, the temperature at which the super-resolution phenomenon occurs at the time of reproduction is about 350 ° C., and it must be recorded above this reproduction temperature. It was decided. That is, since the reaction temperature is about 600 ° C., the W—Si alloy is not affected by the reproduction power.

When the W and Si materials are selected in this way, the recording layer 330 is formed by mixing so that the atomic ratio between the two materials is W: Si≈1: 2 in consideration of the atomic weight and density difference between the two materials. It is desirable to form. In this case, if a chemical reaction occurs, the predetermined region of the recording layer 330 focused on the recording power beam becomes a WSi ₂ compound. Here, the atomic ratio between W and Si is merely illustrative, and is not limited thereto.

  Further, although both W and Si substances have been described as examples of the recording layer material, this is merely an example, and a chemical reaction occurs at a temperature higher than the reproduction temperature within a temperature range that can be recorded by a laser beam. Two or more substances may be arbitrarily selected within the range of substances to be processed. For example, vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), germanium (Ge), selenium (Se), niobium (Nb), molybdenum (Mo), silver (Ag) ), Tin (Sn), antimony (Sb), tellurium (Te), titanium (Ti), zirconium (Zr), and a lanthanum element may be included.

  The super-resolution reproduction layer 350 is a layer made of a phase change material having a property that the temperature distribution or optical characteristics of a partial region of the incident beam spot changes. That is, the super-resolution reproduction layer 350 is composed of a chalcogenide phase change material that is a material containing at least one of sulfur (S), selenium (Se), and tellurium (Te). Is desirable. For example, the super-resolution reproduction layer 350 includes selenium-sulfur (Se-S), selenium-tellurium (Se-Te), sulfur-tellurium (S-Te), phosphorus-sulfur (PS), phosphorus-tellurium ( P-Te), phosphorus-selenium (P-Se), arsenic-sulfur (As-S), arsenic-selenium (As-Se), arsenic-tellurium (As-Te), antimony-sulfur (Sb-S), Antimony-selenium (Sb-Se), antimony-tellurium (Sb-Te), silicon-sulfur (Si-S), silicon-selenium (Si-Se), silicon-tellurium (Si-Te), germanium-sulfur (Ge -S), germanium-selenium (Ge-Se), germanium-tellurium (Ge-Te), tin-sulfur (Sn-S), tin-selenium (Sn-Se), tin-tellurium (Sn-Te), silver -Sulfur (Ag-S), Silver-Selenium (Ag-Se) , Silver-tellurium (Ag-Te), aluminum-sulfur (Al-S), aluminum-selenium (Al-Se), aluminum-tellurium (Al-Te), gallium-sulfur (Ga-S), gallium-selenium ( Ga-Se), gallium-tellurium (Ga-Te), indium-sulfur (In-S), indium-selenium (In-Se), indium-tellurium (In-Te) based compounds or at least one of them Includes compounds containing two elements. Preferably, the super-resolution reproduction layer 350 is made of a germanium-antimony-tellurium (Ge-Sb-Te) or silver-indium-antimony-tellurium (Ag-In-Sb-Te) phase change material.

  Accordingly, the super-resolution reproduction layer 350 has a super-resolution region in which the temperature distribution changes or the optical characteristics change in a part of the beam spot by changing from one crystal to another at a constant temperature. Information can be reproduced for recording marks having the following sizes.

  As described above, the super-resolution region in which the temperature distribution change or the optical characteristic change is caused by the reproduction beam becomes a partial region of the spot of the reproduction beam, and this partial region can occur in the center or the latter half of the spot.

  The information recording medium is only an example for explaining the super-resolution phenomenon, and the reproducing method according to the present invention can be applied to any information recording medium in which the super-resolution phenomenon occurs.

  Next, a method for reproducing data from an information recording medium according to a preferred embodiment of the present invention will be described.

  In the data reproducing method of the information recording medium according to the present invention, as shown in FIG. 4, the information recording medium is irradiated with the relatively high power first beam B1 and the relatively low power second beam B2. A mark is recorded along a track of the information recording medium, and the first beam B1 and the second beam B2 are irradiated adjacent to different positions on the same track.

  The first beam B1 and the second beam B2 may be generated by splitting a beam irradiated from one light source using a spectroscopic element, or may be generated using two light sources that irradiate beams having different powers. . As the spectroscopic element, a grating element or a diffraction element such as a hologram can be used.

The first beam B1 has a reproduction power (super-resolution power) that causes a super-resolution phenomenon, and the second beam B2 has a reproduction power (non-super-resolution power) that does not cause a super-resolution phenomenon. The first beam B1 and the second beam B2 are irradiated simultaneously.
As shown in FIG. 5A, the region irradiated with the first beam B1 is a super-resolution region in which a temperature distribution change or an optical characteristic change occurs in a partial region of the entire light spot and a super-resolution phenomenon occurs. The super-resolution phenomenon does not occur in the peripheral region of the partial super-resolution region. In the region irradiated with the second beam B2, the super-resolution phenomenon does not occur in the entire light spot as shown in FIG. 5B.

  When the wavelength of the first beam B1 is λ and the numerical aperture is NA1, the resolution of the first beam B1 is λ / (4 * NA1). When one light source is used, the wavelength of the second beam B2 is λ like the wavelength of the first beam B1, and when the numerical aperture of the second beam B2 is NA2, the second beam B2 The resolution is λ / (4 * NA2). The numerical aperture of the beam is defined as a value obtained by dividing the radius of the beam by the focal length of the objective lens. The present invention is based on the fact that by subtracting the signal reflected in the peripheral area from the signal reflected in the entire light spot area, only the signal reflected in the super-resolution area of the light spot can be extracted.

  FIG. 6A shows a reproduction signal obtained by irradiating a mark recorded with the pattern shown in FIG. 2A by a data reproduction method according to the present invention with a super-resolution power beam, and FIG. 6B shows a data reproduction according to the present invention. FIG. 6C shows a differential signal between FIG. 6A and FIG. 6B. FIG. 6C shows a reproduction signal obtained by irradiating the mark recorded with the pattern shown in FIG.

  That is, FIG. 6A is a reproduction of the mark recorded with the mark pattern shown in FIG. 2A, and is a first reproduction signal in which a super-resolution phenomenon has occurred, and FIG. 6B shows a super-resolution phenomenon. The second reproduction signal does not occur. The first reproduction signal by the first beam B1 is a mixture of the signal of the super-resolution area of the light spot and the signal of the peripheral area, and the second reproduction signal by the second beam B2 is the signal of the peripheral area. Is the same signal.

  If the time difference between the first reproduction signal and the second reproduction signal is compensated and then subjected to differential signal calculation processing, the differential between the first reproduction signal and the second reproduction signal as shown in FIG. 6C is performed. A signal value is obtained. That is, since the signal reflected in the peripheral area of the light spot is excluded from the difference signal and only the signal in the resolution area remains, the ISI problem due to the peripheral area is solved. Referring to FIG. 6C, 75 nm marks and spaces smaller than the resolution are accurately reproduced in the A, B, C, D, E, and F portions, and the signal level is detected regardless of the number of marks and spaces. Is done. It can also be seen that the signal level is constant even when the 300 nm mark and space are adjacent to the 75 nm mark and space. In addition, since the flat area appeared at the high level and low level for the 300 nm mark smaller than the overall size of the light spot, it was confirmed that the effect that the effective beam size used for reproduction was smaller than the actual spot size was obtained. Yes.

  On the other hand, in the above example, the difference signal between the first reproduction signal and the second reproduction signal is simply used, but it goes without saying that various other arithmetic processes are possible.

  Next, the results of reproducing the data recorded in the random recording pattern by the reproducing method of the present invention are shown in FIGS. 7A, 7B and 7C.

  7A shows a first reproduction signal reproduced with a first beam having super-resolution power, and FIG. 7B shows a second reproduction signal reproduced with a second beam having a non-super-resolution power smaller than the super-resolution power. FIG. 7C shows a differential signal between the first reproduction signal and the second reproduction signal. 7A and 7B, since the level of the reproduction signal is not constant, it can be understood that the recording mark cannot be reproduced correctly even if slicing is performed at a constant level. However, the differential signal between the first reproduction signal and the second reproduction signal shown in FIG. 7C has a constant level of the reproduction signal. Therefore, if the slice is performed at a certain level, the recording mark is reproduced correctly. It becomes possible.

  FIG. 8 shows an eye pattern obtained from the differential signal of FIG. 7C, and it can be seen that the jitter characteristics of the reproduced signal are very good. That is, it can be confirmed that the data reproduction method according to the present invention can be effectively applied to data recorded in a random pattern on the super-resolution information recording medium.

  As described above, the data reproduction method according to the present invention irradiates the beam of super-resolution power and the beam of non-super-resolution power with a time difference, and the first reproduction signal and non-super-resolution by the beam of super-resolution power. After the time difference from the second reproduction signal due to the power beam is compensated, the calculation process is performed by an optimum method. Thereby, the reproduction signal characteristic can be easily improved by solving the inter-signal interference problem caused by the peripheral area of the super-resolution area at the spot of the reproduction beam.

  FIG. 9A is a diagram illustrating a playback apparatus that can implement the data playback method according to the present invention.

  A data reproducing apparatus 900 according to the present invention includes an optical pickup 910, a recording / reproducing signal processing unit 920, and a control unit 930. Specifically, the optical pickup 910 includes a light source 911 that emits a beam, a spectroscopic element 912 that splits the beam emitted from the light source 911, a collimating lens 913 that collimates the beam that has passed through the spectroscopic element 912, and an incident beam. A beam splitter 914 that converts the traveling path and an objective lens 915 that focuses the beam that has passed through the beam splitter 914 on the information recording medium 300 are provided.

  The beam emitted from the light source 911 is split into a first beam and a second beam through the spectroscopic element 912. The powers of the first beam and the second beam can be adjusted by changing the diffraction pattern of the spectroscopic element 912. As the spectroscopic element 912, a grating element or a diffraction element such as a hologram is used.

  Then, the first beam and the second beam reflected by the information recording medium 300 are reflected by the beam splitter 914 and received by the photodetector 915. The first beam and the second beam received by the photodetector 915 are converted into electrical signals and output to the reproduction signal through the signal processing unit 920.

  In the signal processing unit 920, the first beam signal photoelectrically converted through the photodetector 915 is amplified by the amplifier 921, and the second beam signal compensates the time delay through the compensation unit 922. The first beam reproduction signal and the second beam reproduction signal are processed through the calculation unit 923, output as an RF signal through the channel 1 Ch1, and output as a push-pull signal through the channel 2 Ch2.

  The control unit 930 emits a super-resolution power beam and a non-super-resolution power beam required by the material characteristics of the information recording medium in order to reproduce a recording mark having a size smaller than the resolution. The optical pickup 910 is controlled. The controller 930 implements focusing servo and tracking servo using the RF signal and push-pull signal.

  The spectroscopic element 912 will be described in more detail. The first beam having the super-resolution power and the second beam having the non-super-resolution power described above must further satisfy the aberration amount condition in addition to the power condition. That is, the aberration amount of the first beam and the aberration amount of the second beam are required to be substantially the same. The meaning that the aberration amount of the first beam is different from the aberration amount of the second beam means that the spot shape focused on the super-resolution information recording medium by the first beam and the spot focused by the second beam. This means that there is a difference in shape. If there is a difference between the shape of the spot formed by the first beam and the shape of the spot formed by the second beam, it is difficult to achieve the object of the present invention.

  In order to satisfy the power condition and aberration amount condition of the first beam and the second beam, according to an embodiment of the present invention, a blaze type grating element is used as the spectroscopic element 912.

  FIG. 9B is a diagram illustrating a blazed grating element 912 according to an embodiment of the present invention. If the beam 951 emitted from the light source 911 is incident on the blaze type grating element 912 shown in FIG. A plurality of diffracted beams such as a beam (not shown) or a ± Nth order diffracted beam (not shown) are emitted. In this case, N is theoretically an infinite integer.

  The aberration amount of the + 1st order diffracted beam 953 and the aberration amount of the −1st order diffracted beam 954 are substantially the same. Also, those skilled in the art will appreciate that the + 1st order diffracted beam 953 has a high power, the −1st order diffracted beam 954 has a relatively low power, or the + 1st order diffracted beam 953 has a low power, The blazed grating element 912 according to an exemplary embodiment of the present invention may be easily implemented such that the −1st order diffracted beam 954 has a relatively high power. On the other hand, the power of the 0th-order diffracted beam 952 is very weak and can be ignored.

  The data reproducing apparatus shown in FIG. 9A includes a spectroscopic element for generating the first beam and the second beam. In addition, the data reproducing apparatus emits a super-resolution power beam as shown in FIG. The first light source 941a and the second light source 942a that irradiates the beam with non-super-resolution power can be provided independently to generate the first beam and the second beam. Here, an example in which the first light source 941a and the second light source 941b are configured as an optical module packaged is shown. However, it is also possible to configure the first light source and the second light source independently, and to dispose the first light source and the second light source at different positions without using the optical module. Thus, when providing a 1st light source and a 2nd light source independently, it is not necessary to provide the spectroscopic element for producing a 1st beam and a 2nd beam.

  In the apparatus shown in FIG. 10, members using the same reference numerals as those in FIG. 9 are members that perform the same functions and operations as those described above, and detailed descriptions thereof are omitted here.

  On the other hand, the light detector 942 reflects the first beam emitted from the first light source by the information recording medium 300 and receives the on-beam, and the second beam emitted from the second light source. Includes a second light detection unit 942b for receiving the beam reflected by the information recording medium 300. After compensating for the time delay between the first reproduction signal by the first beam and the second reproduction signal by the second beam, an RF signal having excellent signal characteristics in which ISI is eliminated is obtained by arithmetic processing.

  Thus, when the 1st light source and the 2nd light source are constituted independently, there is an advantage that any one of the 1st light source and the 2nd light source can be used as a light source for data recording. Furthermore, since the first light source and the second light source can be configured so that the optical pickup can be used interchangeably with information recording media of different formats, the applicable range can be expanded.

  As described above, the embodiment of the present invention has been described by taking as an example the case where the super-resolution information recording medium is irradiated with the first beam having the super-resolution power and the second beam having the non-super-resolution power. However, according to another embodiment of the present invention, data reproduction according to the present invention can be performed by generating a plurality of beams having non-super-resolution power using a spectroscopic element or a plurality of light sources. That is, after irradiating a super-resolution information recording medium with a plurality of beams having non-super-resolution power, the reproduction signal obtained from each beam having non-super-resolution power is used by the following equation (1). A final reproduction signal is obtained.

前記式（１）で、ＲＦ_１は、超解像パワーを有するビームから得た再生信号であり、ＲＦ_２ないしＲＦ_Ｎは非超解像パワーを有する（Ｎ−１）個のビームから得た再生信号である。ＲＦ_２ないしＲＦ_Ｎは、ＲＦ_１との時間差が補償された信号である。ｇ_１ないしｇ_Ｎ−１は、所定の係数である。当業者ならば、前記式（１）によって最終ＲＦ信号が得られる。

In Equation (1), RF ₁ is a reproduction signal obtained from a beam having super-resolution power, and RF ₂ to RF _N are obtained from (N−1) beams having non-super-resolution power. It is a reproduction signal. RF ₂ to RF _N are signals in which the time difference from RF ₁ is compensated. g ₁ to g _N−1 are predetermined coefficients. A person skilled in the art can obtain the final RF signal according to the equation (1).

  FIG. 11 is a flowchart showing a process of a reproduction method performed by the reproduction apparatus 900 shown in FIG. 9 or 10 according to the present invention. Referring to FIG. 11, first, the optical pickup 910 irradiates the information recording medium 300 with a first beam with super-resolution power (1100).

  Next, the optical pickup 910 irradiates the same position of the information recording medium 300 irradiated with the first beam with a second beam having non-super-resolution power with a predetermined time difference (1110). Here, the meaning of “irradiating at a predetermined time difference” does not mean that the optical pickup 910 actually irradiates intentionally at a time difference, but as shown in FIG. It means the time difference that occurs when the second beam passes after the first beam passes.

  The signal processing unit 920 uses the first beam reflected by the first beam irradiated on the information recording medium and the second beam reflected by the second beam irradiated on the information recording medium. Is compensated for the time difference from the second reproduction signal, and the final reproduction signal is output by performing arithmetic processing such as subtracting the second reproduction signal from the first reproduction signal (1120).

  While super-resolution playback is possible with high power, when performing the calculation process of subtracting the second playback signal from the first playback signal, if the time difference between the two signals (time delay) is not accurately reflected, Signal characteristics deteriorate. That is, after obtaining the first reproduction signal from the spot 1 that enables super-resolution reproduction with high power and obtaining the second reproduction signal from the spot 2 that performs general reproduction without super-resolution reproduction with low power, FIG. Alternatively, a subtraction operation is performed by giving an appropriate gain to the second reproduction signal by the amplifier 922 as shown in FIG. At this time, the delay unit 921 adjusts the time difference between the signals generated from the spatial difference between the two spots. If such a time difference is not accurately reflected, the quality of the reproduction signal is degraded. Of course, if the spatial distance and linear velocity between the spots are first known, the time difference can be derived, but various disturbances may occur in disc reproduction. For example, if there is a slight difference in the rotation speed of the spindle motor, radial or tangential tilt, the distance between spots in the actual disk will fluctuate. If this is not controlled properly, the quality of the playback signal will be degraded. To do.

  FIG. 12 is a diagram illustrating a result obtained by simulating signal jitter after subtraction by the delay time. Under the simulation conditions shown in FIG. 12, when the spot linear velocity is 5 m / s and the jitter is 10% as a reference, a margin of ± 0.04T is obtained, which corresponds to ± 0.03 nsec, It can be seen that the delay time margin is very narrow. Therefore, it can be confirmed that a means for accurately controlling the delay time is necessary.

  Several methods can be considered to accurately control the time difference between the first reproduction signal and the second reproduction signal. The first method is to use jitter or bER, the second method is to use pre-pits or predetermined discrimination information, and the third method is to use a wobble signal. It is. A method using a wobble signal may use discontinuous points of the wobble signal.

  First, a method using jitter or bER for accurately controlling the time difference will be described. In the method using jitter or bER, the jitter or bER of the final reproduction signal obtained based on the first reproduction signal and the second reproduction signal is monitored, and the time difference is set so that the jitter or bER becomes a minimum value. This is a compensation method.

  FIG. 13 is a diagram illustrating an example of a signal processing unit that performs compensation using jitter in the reproduction apparatus illustrated in FIG. 9 or 10. Referring to FIG. 13, the light reflected from the information recording medium 300 by the first beam is detected by the spot 1 942a, and the light reflected by the second beam is detected by the spot 2 942b.

  The delay unit 1421 of the signal processing unit 1420 receives the light output from the spot 1 942a, delays it by the first order time difference in order to compensate for the time difference between the spot 1 and the spot 2, and provides this to the calculation unit 1423. . The amplifying unit 1422 receives the light output from the spot 2 942b, amplifies the light, and provides the amplified light to the arithmetic unit 1423. The calculation unit 1423 performs a calculation for subtracting the second reproduction signal from the first reproduction signal.

  Here, the primary time difference is a basic method by which the time difference between the first spot and the second spot can be calculated. As shown in FIG. 12, the first time difference is between the first beam B1 and the second beam B2. This is a value obtained by calculating the time difference t between the first beam B1 and the second beam B2 from the distance d and the linear velocity v of the spot by d / v. The delay unit 1421 can compensate for the time difference between the first spot and the second spot by first delaying the first reproduction signal by such a primary time difference.

  In addition, according to an example of the present invention, the delay unit 1421 further compensates for the time difference between the first spot and the second spot using the jitter value. Specifically, the jitter or bER measured from the reproduction signal output from the calculation unit 1423 is monitored, and the jitter compensation unit 1424 calculates a compensation value that minimizes such jitter or bER to obtain a primary value. Such a compensation value is added to or subtracted from the time difference to obtain a secondary time difference, and such a secondary time difference is provided to the delay unit 1421. Accordingly, the delay unit 1421 can control the time difference between the first spot and the second spot more precisely by delaying the first reproduction signal based on the received secondary time difference.

  FIG. 15 is a flowchart illustrating a process of compensating for the time difference between the first beam and the second beam using jitter according to an example of the present invention. Referring to FIG. 15, a primary time difference is obtained from the distance between the centers of the first spot and the second spot and the linear velocity (1500).

  Next, the detection signal of the spot 1 is delayed based on the primary time difference, and the reproduction signal is obtained by performing arithmetic processing with the detection signal of the spot 2 (1510).

  Next, the jitter or bER of the reproduction signal is obtained, and a secondary time difference at which the jitter or bER is minimized is calculated (1520).

  Next, the spot 1 detection signal is delayed based on the secondary time difference, and the spot 2 detection signal is arithmetically processed to obtain a reproduction signal (1530).

  Next, a method of using pre-pits or predetermined discrimination information for accurately controlling the time difference will be described. The predetermined discrimination information refers to additional information periodically recorded so that predetermined additional information other than user data can be easily discriminated.

  First, the pre-pits will be briefly described with reference to FIG. FIG. 16 is a diagram showing an example of a super-resolution information recording medium in which pre-pits are generated in a predetermined area of a track. An optical recording medium such as a DVD-RAM includes a header area in which header information is stored and a user data area in which user data is recorded. A DVD-RAM has 128 bytes of header information per sector, and the header information is recorded in a pre-pit when the disk substrate is manufactured. The pickup device recognizes the sector number, sector type, land track / groove track, etc. through the information recorded in the header area composed of the pre-pits when the substrate is manufactured, and can also perform servo control. That is, the header area in which the concave / convex prepits are formed is arranged in a predetermined area of the sector, and the pickup device provided in the recording / reproducing device can easily search for a desired position through the information recorded in the header area. Go.

  Referring to FIG. 16, on the super-resolution information recording medium to which the present invention is applied, land tracks and groove tracks, which are user data areas in which user data is recorded, are formed, and header information is recorded in pre-pits. A header area 1600 is arranged.

  The super-resolution information recording medium can also be provided with a header area formed of pre-pits as shown in FIG. 16 in a predetermined area of the medium for header information.

  FIG. 17 is a flowchart illustrating a process of compensating for the time difference between the first beam and the second beam using pre-pits or discrimination information according to another example of the present invention.

  First, a primary time difference is obtained from the distance between the centers of the first spot and the second spot and the linear velocity (1700).

  Next, the spot 1 detection signal is delayed based on the primary time difference, and the spot 2 detection signal is arithmetically processed to obtain a reproduction signal (1710).

  Next, a predetermined time difference is compensated using the difference between the time when the pre-pit or discrimination information is reproduced by the first beam and the time when the pre-pit or discrimination information is reproduced by the second beam (1720).

  Next, based on the compensated predetermined time difference, the spot 1 detection signal is delayed, and the spot 2 detection signal is arithmetically processed to obtain a reproduction signal (1730).

  If information that can be easily discriminated in addition to the pre-pit or information recorded by the user is recorded in this way, the subsequent beam is pre-pit or discriminated from the time when the preceding beam reproduces the pre-pit or discrimination information as described above. The time until information is reproduced can be used as a time difference value.

  The present invention can be applied to a data reproducing method and apparatus for a super-resolution information recording medium.

FIG. 6 is a reference diagram for explaining a region where a super-resolution phenomenon occurs at a spot of a reproduction beam irradiated on a super-resolution information recording medium. It is a figure which shows the recording pattern recorded with the mark which has the magnitude | size below the resolution, and the mark which has the magnitude | size beyond the resolution. It is a figure which shows RF signal obtained by reproducing | regenerating the information recorded with the recording pattern of FIG. 2A with the beam of super-resolution power. 1 is a schematic cross-sectional view of an example of a super-resolution information recording medium to which a reproducing method according to the present invention is applied. FIG. 3 is a diagram illustrating a state where an information recording medium is irradiated with a super-resolution power beam and a non-super-resolution power beam by a data reproduction method according to an embodiment of the present invention. FIG. 5 is an enlarged view showing areas of each beam when an information recording medium is irradiated with a super-resolution power beam and a non-super-resolution power beam by a data reproduction method according to a preferred embodiment of the present invention. FIG. 2B is a diagram showing a reproduction signal obtained by irradiating a mark recorded with the pattern shown in FIG. 2A with a beam of super-resolution power by the data reproduction method according to the present invention. FIG. 3 is a diagram showing a reproduction signal obtained by irradiating a beam recorded with the pattern shown in FIG. 2B with a beam of non-super-resolution power by the data reproduction method according to the present invention. It is a figure which shows the differential signal of FIG. 6A and FIG. 6B. It is a figure which shows the reproduction | regeneration signal obtained by irradiating the beam of super-resolution power to the mark recorded with the random pattern by the data reproduction | regeneration method by this invention. It is a figure which shows the reproduction | regeneration signal obtained by irradiating the beam of non-super-resolution power to the mark recorded with the random pattern by the data reproduction | regeneration method by this invention. It is a figure which shows the differential signal of FIG. 7A and FIG. 7B. It is an eye pattern obtained from the differential signal shown in FIG. 7C. 1 is a schematic diagram of a data reproducing apparatus for a super-resolution information recording medium according to an exemplary embodiment of the present invention. It is a figure which shows the blazed grating device by one Embodiment of this invention. FIG. 6 is a schematic diagram illustrating a modification of the data reproducing apparatus for the super-resolution information recording medium according to the preferred embodiment of the present invention. 3 is a flowchart showing a process of a reproduction method according to the present invention. It is a figure which shows the result obtained by simulating the jitter of the signal after subtraction by a time difference. It is a figure for demonstrating the primary time difference in the reproducing | regenerating method shown by FIG. It is a figure which shows an example of the signal processing part which performs compensation using a jitter with the reproducing | regenerating apparatus shown by FIG. 9 or FIG. 4 is a flowchart illustrating a process of compensating for a time difference between a first beam and a second beam using jitter according to an example of the present invention. It is a figure which shows an example of the super-resolution information recording medium with which the prepit was produced | generated in the predetermined area | region of the track | truck. 6 is a flowchart illustrating a process of compensating for a time difference between a first beam and a second beam using pre-pits or discrimination information according to another embodiment of the present invention.

Claims (40)

In a method of reproducing data recorded on a super-resolution information recording medium capable of reproducing data recorded with a mark having a size less than the resolution of the incident light beam,
Irradiating different positions of the information recording medium with a first beam having a power that causes a super-resolution phenomenon and a second beam having a power that does not cause a super-resolution phenomenon;
Detecting a first reproduction signal by the first beam and a second reproduction signal by the second beam;
And a step of compensating for a time difference between the first reproduction signal and the second reproduction signal. The calculation step includes:
2. The data reproduction method according to claim 1, further comprising a step of performing a differential operation on the first reproduction signal and the second reproduction signal.   2. The data reproducing method according to claim 1, wherein the different positions are different positions on the same track. The irradiation step includes
The data reproducing method according to claim 1, further comprising the step of splitting the beam emitted from one light source into the first beam and the second beam using a spectroscopic element. The irradiation step includes
2. The data reproducing method according to claim 1, further comprising the step of irradiating each of the first light source and the second light source separately from the first light source and the second light source. In the spectroscopic step,
4. The plurality of diffracted beams generated from the spectroscopic element, wherein a + k order diffracted beam is used as the first beam and a -k order diffracted beam is used as the second beam. Data playback method. In the spectroscopic step,
The -k-order diffracted beam is used as the first beam and a + k-order diffracted beam is used as the second beam among a plurality of diffracted beams generated from the spectroscopic element. Data playback method.   The data reproducing method according to claim 6, wherein the spectroscopic element is a blaze type grating element.   The data reproducing method according to claim 1, wherein the spectroscopic element is a blaze type grating element. In a method of reproducing data recorded on a super-resolution information recording medium capable of reproducing data recorded with a mark having a size less than the resolution of the incident light beam,
Irradiating the information recording medium with a first beam of super-resolution power;
Irradiating a plurality of second beams with non-super-resolution power at a predetermined time difference to the same position irradiated with the first beam;
A method of reproducing data, comprising: detecting a final reproduction signal based on a first reproduction signal by the first beam and a second reproduction signal by the second beam. The detection step includes
11. The data reproduction method according to claim 10, further comprising a step of differentially calculating the first reproduction signal and the second reproduction signal. The detection step includes
The method of claim 11, further comprising compensating for the predetermined time difference between the first reproduction signal and the second reproduction signal. The detection step includes
The method of claim 11, further comprising compensating for the predetermined time difference so that a jitter or bER of the final reproduction signal is minimized. The detection step includes
Using the difference between the time when the predetermined discrimination information not used as prepit or user data is reproduced by the first beam and the time when the predetermined discrimination information not used as prepit or user data is reproduced by the second beam. The method of claim 11, further comprising compensating for the predetermined time difference. The detection step includes
The method of claim 11, further comprising: compensating for the predetermined time difference using a wobble signal.   11. The data reproduction method according to claim 10, further comprising the step of splitting the beam emitted from one light source into the super-resolution beam and the plurality of non-super-resolution beams using a spectroscopic element. . In an apparatus for reproducing data recorded on a super-resolution information recording medium capable of reproducing data recorded with a mark having a size smaller than the resolution of the incident light beam,
A pickup unit that irradiates a first beam having a power at which a super-resolution phenomenon occurs at different positions of the information recording medium and a second beam having a power at which the super-resolution phenomenon does not occur;
A signal processing unit that detects a first reproduction signal by the first beam and a second reproduction signal by the second beam and compensates and calculates a time difference between the first reproduction signal and the second reproduction signal;
And a control unit that controls the pickup unit using a signal input from the signal processing unit. The signal processing unit
18. The data reproducing apparatus according to claim 17, further comprising an arithmetic unit that performs a differential operation on the first reproduction signal and the second reproduction signal.   The data reproducing apparatus according to claim 17, wherein the different positions are different positions on the same track. The pickup unit is
A light source;
18. The data reproducing apparatus according to claim 17, further comprising a spectroscopic element that splits the beam emitted from the light source into a first beam and a second beam.   21. The first beam corresponds to a + k-order diffracted beam among a plurality of diffracted beams generated from the spectroscopic element, and the second beam corresponds to a −k-order diffracted beam. The data reproducing device described in 1.   21. The first beam corresponds to a −k order diffracted beam among the plurality of diffracted beams generated from the spectroscopic element, and the second beam corresponds to a + k order diffracted beam. The data reproducing device described in 1.   The data reproducing apparatus according to claim 20, wherein the spectroscopic element is a blaze type grating element.   The data reproducing apparatus according to claim 22, wherein the spectroscopic element is a blaze type grating element.   The data reproducing apparatus according to claim 17, wherein the pickup unit includes a first light source that irradiates the first beam and a second light source that irradiates the second beam. In an apparatus for reproducing data recorded on a super-resolution information recording medium capable of reproducing data recorded with a mark having a size smaller than the resolution of the incident light beam,
A pickup unit that irradiates the information recording medium with a first beam of super-resolution power, and irradiates a plurality of second beams of non-super-resolution power at a predetermined time difference to the same position irradiated with the first beam; ,
A signal processing unit for detecting a final reproduction signal based on the first reproduction signal by the first beam and the second reproduction signal by the second beam;
And a control unit that controls the pickup unit using an output signal from the signal processing unit. The signal processing unit
27. The data reproducing apparatus according to claim 26, further comprising an arithmetic unit that performs a differential operation on the first reproduction signal and the second reproduction signal. The signal processing unit
28. The data reproduction apparatus according to claim 27, further comprising a compensation unit that compensates for the predetermined time difference between the first reproduction signal and the second reproduction signal. The compensation unit
29. The data reproducing apparatus according to claim 28, wherein the predetermined time difference is compensated so that jitter or bER of the final reproduction signal is minimized. The compensation unit
The difference between the time when the predetermined discrimination information not used as prepit or user data is reproduced by the first beam and the time when the predetermined discrimination information not used as prepit or user data is reproduced by the second beam is used. 29. The data reproducing apparatus according to claim 28, wherein a predetermined time difference is compensated. The compensation unit
29. The data reproducing apparatus according to claim 28, wherein the predetermined time difference is compensated using a wobble signal. The pickup unit is
A light source;
27. The data reproducing apparatus according to claim 26, further comprising: a spectroscopic element that splits the beam emitted from the light source into a first beam and a plurality of second beams. The pickup unit is
27. The data reproducing apparatus according to claim 26, comprising a first light source that irradiates the first beam and a second light source that irradiates the plurality of second beams. In a method for reproducing data recorded on a recording medium,
Irradiating a mark formed on the recording medium with a first beam having a first resolution;
Irradiating the mark formed on the recording medium with a second beam having a second resolution;
Detecting a first reproduction signal based on the first beam and a second reproduction signal based on the second beam;
Processing the first and second reproduction signals;
And calculating a time delay between the first and second reproduction signals based on the processed first and second reproduction signals.   The reproduction method according to claim 34, wherein the time delay between the first reproduction signal and the second reproduction signal is calculated by a jitter or bER method.   The time delay between the first reproduction signal and the second reproduction signal is calculated using pre-pits formed on the recording medium or using predetermined identification information. Playback method.   The reproduction method of claim 34, wherein a time delay between the first reproduction signal and the second reproduction signal is calculated using a wobble signal.   3. The reproducing method according to claim 2, wherein the signal component reflected from the peripheral region of the first and second beams is excluded from the differential signal.   3. The reproducing method according to claim 2, wherein only the signal component from the super-resolution area remains in the differential signal.   The reproducing method according to claim 1, wherein the aberration amounts of the first and second beams are substantially the same.

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