JP2009252326A - Optical disk recording/reproducing apparatus and optical disk recording/reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide recording/reproducing apparatus/method for correcting crosstalk of a main beam more precisely than a conventional one. <P>SOLUTION: When recording and reproducing data, an optical information recording medium is irradiated with a main beam and a sub-beam. The spot of the sub-beam has a shape with a width narrower than the width of a spot of the main beam. The apparatus is arranged in such a way that a groove adjacent to a track with which the main beam is irradiated with the spot of the sub-beam, or an edge of the spot of the sub-beam is brought into contact with an edge of the spot of the main beam and it is brought into contact with a tangent parallel to a track direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording method and a recording / reproducing apparatus for detecting the occurrence of crosstalk and correcting signal deterioration due to the crosstalk, for an optical disc that performs high-density recording, such as a recordable Blu-ray disc (BD-R). Is.

  An optical disc such as a recordable CD (CD-R), a recordable DVD (DVD ± R) or a write-once Blu-ray disc (BD-R) has a recording layer, a reflective layer, and a necessary layer on one surface of a disc-shaped substrate. Accordingly, a protective layer is formed. In addition, a spiral or concentric groove called a groove is formed on one surface of the substrate, and a convex part called a land is formed between adjacent grooves. In such an optical disk, recording is performed by irradiating a recording laser beam on a recording layer on the groove to form pits. The length of the pits, the portion between the pits (hereinafter referred to as a space). ) And their arrangement are reproduced by irradiating a reproduction laser beam and reading the reflected light as a reproduction signal. This arrangement of pits and spaces is hereinafter referred to as a track.

In such an optical disk, a recording laser beam and a reproducing laser beam are irradiated to the recording layer through the light transmission layer. Here, the light transmissive layer is a recording layer on a light transmissive disk-shaped substrate (the thickness is 1.2 mm for CD-R and 0.6 mm for DVD ± R) in the case of CD-R and DVD ± R. Since the reflective layer is sequentially formed, the light transmissive disc-shaped substrate corresponds to the light transmissive layer. In the case of BD-R, a reflective layer and a recording layer are sequentially formed on a light transmissive disc-shaped substrate having a thickness of 1.1 mm, and a transparent cover layer having a thickness of 0.1 mm is formed on the recording layer. Therefore, the transparent cover layer corresponds to the light transmission layer.

In such an optical disc, tracks are arranged in a radial direction at a predetermined interval, that is, a track pitch. This track pitch becomes narrower as the recording density increases. For example, a 4.7 GB DVD-R on one side has a track pitch of 0.74 μm, whereas a 25 GB BD-R on one side has a track pitch of 0.32 μm. In the future, it is expected that the track pitch will be further narrowed in the next generation optical disc having a higher recording density than the BD-R.

Along with the narrowing of the track pitch, it is necessary to reduce the spot diameters of the recording laser beam and the reproducing laser beam. In order to reduce the spot diameter, there is a method of increasing the numerical aperture (NA) of the lens in addition to shortening the wavelength of the laser beam. For example, it is 0.45 for CD-R, 0.6 for DVD ± R, and 0.85 for BD-R. However, when the numerical aperture is increased, the space between the lens and the optical disk is also reduced, so there is a limit to reducing the spot diameter. For this reason, in the next generation optical disc having a higher recording density than the BD-R, it is expected that the spot diameter with respect to the track pitch is larger than the BD-R.

Thus, when the track pitch is narrowed, the spot of the laser beam is applied to the track adjacent to the track irradiated with the laser beam, and the signal from the pit formed in the adjacent track is read. So-called crosstalk is likely to occur. When this crosstalk occurs, the signal from the pit of the track to be read is superimposed on the signal from the pit of the adjacent track, which causes a problem that data cannot be read out. As a countermeasure against such crosstalk, as disclosed in Japanese Patent Laid-Open Nos. 7-182658 and 7-320269, a crosstalk generated in the main beam is detected using a signal obtained from the sub beam. A method of correcting crosstalk by calculating the difference between the main beam signal and the sub beam signal has been proposed.

JP 7-182658 A JP 7-320269 A

However, in the above known technology, as shown in FIG. 6, the spot diameters of the main beam and the sub beam are substantially the same size. For this reason, crosstalk also occurs in the sub beam itself. If crosstalk occurs in the sub-beam, the reliability of the sub-beam signal itself for correcting the crosstalk generated in the main beam is lowered, so that the crosstalk of the main beam cannot be corrected.

The present invention provides a recording / reproducing apparatus and a recording / reproducing method capable of preventing the occurrence of such sub-beam crosstalk and correcting the crosstalk of the main beam with higher accuracy than in the past.

  In the present invention, as a first solution, when recording and reproducing data in an optical information recording / reproducing apparatus that records and reproduces data by irradiating an optical information recording medium having a spiral groove with laser light. The optical information recording medium is irradiated with a main beam and a sub beam, and the spot of the sub beam has a shape narrower than the spot of the main beam, and the groove adjacent to the groove irradiated with the main beam is irradiated. An optical information recording / reproducing apparatus arranged as described above is proposed. Here, the spot width is the spot size in the radial direction of the optical disk, that is, in the direction orthogonal to the track direction.

According to the first solution, since the width of the sub beam is narrower than that of the main beam, for example, an elliptical shape, the occurrence of crosstalk is reduced for the sub beam. Therefore, the reliability of the sub beam signal is improved. In the first solution, the sub beam is irradiated to the groove adjacent to the groove irradiated with the main beam, and the cross beam is detected by detecting whether the sub beam is out of the adjacent groove. Correction is performed so that the groove is irradiated. This makes it possible to correct the crosstalk of the main beam with higher accuracy than before. In the first solution described above, if the width of the sub beam is substantially the same as the width of the groove, it is possible to detect whether or not the sub beam is out of the adjacent groove due to a change in the signal intensity of the sub beam. Can be detected and corrected.

In the present invention, as a second solution, the sub beam spot has a narrower shape than the main beam spot, and is in contact with an edge of the main beam spot and parallel to the track direction. Then, an optical information recording / reproducing apparatus arranged so that the edge of the sub-beam spot touches is proposed.

According to the second solution, since the width of the sub beam is narrower than that of the main beam, for example, an ellipse, as in the first solution, the occurrence of crosstalk is reduced for the sub beam. Further, in the second solution, since the edge of the main beam and the edge of the sub beam are aligned with respect to the track direction, the sub beam reads the pit of the adjacent groove when the main beam hits the adjacent groove. . The signal can be corrected by calculating the difference between the obtained sub-beam signal and the main beam signal. In particular, when the arrangement of the sub-beams is within a region sandwiched between the inner tangent and the outer tangent, the portion where the main beam is applied and the portion where the sub-beam is applied in the adjacent groove are the same. The level of the adjacent groove signal read by can be easily made substantially equal to the level of the adjacent groove signal superimposed on the main beam by calculation. Thereby, crosstalk correction with higher accuracy is possible.

According to the present invention, it is possible to realize a recording / reproducing apparatus and a recording / reproducing method capable of preventing the crosstalk of the sub beam and correcting the crosstalk of the main beam with higher accuracy than before.

  A functional block diagram of a recording apparatus according to an embodiment of the present invention will be described with reference to FIG. The optical disc recording / reproducing apparatus 100 includes a calculation unit 122 including a memory circuit in which a program for performing processing described below is recorded, and a laser diode drive control unit (controlling the recording laser beam and the reproducing laser beam). (Not shown), an RF signal intensity detector 121 that detects the intensity of the RF signal of the main beam and the sub beam, an optical pickup 110, an optical pickup drive controller that controls the direction of laser light emitted from the optical pickup, A rotation control unit (not shown) and a motor (not shown) of the optical disc 150, a servo control unit for the optical pickup 110, and the like are included.

The optical pickup 110 also splits the light from the objective lens 114, the beam splitter 116, the detection lens 115, the collimating lens 113, the laser diode 111, the photodetector 117, and the laser diode 111 into a main beam and a sub beam. An optical branching unit 112 such as a diffraction grating is included. In the optical pickup 110, an actuator (not shown) operates according to the control of the servo control unit, and focusing and tracking are performed. The photodetector 117 includes a detector PDm that detects the reflected light of the main beam, and detectors PDs1 and PDs2 that detect the reflected light of the sub beam. The light branching means 112 may be integrated with the collimating lens 113 or the objective lens 114.

  The arithmetic unit 122 is connected to an RF signal intensity detector 121, an optical pickup drive controller, a laser diode drive controller (not shown), a rotation controller (not shown), a servo controller, and the like. Further, the arithmetic unit 122 can perform various arithmetic operations and instructions by executing a program stored in the memory circuit. Further, the RF signal intensity detection unit 121 is connected to the photodetector 117 and the calculation unit 122. The calculation unit 122 is also connected to an input / output system (not shown) via an interface unit (not shown).

  Next, an outline of processing when data is recorded on the optical disc 150 will be described. First, the arithmetic unit 122 or a separately provided data modulation circuit (not shown) performs a modulation process on data to be written on the optical disc 150, and the data after the modulation process is converted into a laser diode drive control unit ( (Not shown). The laser diode drive control unit drives the laser diode 111 with the received data according to the specified recording condition to output a recording laser beam. The recording laser light is irradiated onto the optical disc 150 through the light branching means 112, the collimating lens 113, the beam splitter 116, and the objective lens 114, thereby forming spaces and pits in the groove of the optical disc 150.

  An outline of processing when data recorded on the optical disc 150 is reproduced will be described. A laser diode drive control unit (not shown) drives the laser diode 111 according to an instruction from the calculation unit 122 to output a reproduction laser beam. The reproducing laser light is irradiated onto the optical disc 150 through the light branching means 112, the collimating lens 113, the beam splitter 116, and the objective lens 114. The reflected light from the optical disk 150 is input to the PD 117 via the objective lens 114, the beam splitter 116, and the detection lens 115. The PD 117 converts the reflected light from the optical disc 150 into an electrical signal by the RF signal intensity detector 121 and outputs it to a data demodulation circuit (not shown) or the like. The data demodulating circuit performs predetermined decoding processing on the output reproduction signal, and displays the decoded data on an input / output system (not shown) via the arithmetic unit 122 and the interface unit (not shown). To display the playback data.

  Next, a first method of crosstalk correction according to the present invention will be described. FIG. 2 is a partially enlarged view showing a state in which the optical disc 150 is irradiated with the main beam, the preceding sub beam, and the subsequent sub beam. Grooves GV1, GV2, and GV3 are recorded grooves and are arranged at a track pitch TP. A land LN1 is formed between the groove GV1 and the groove GV2, and a land LN2 is formed between the groove GV2 and the groove GV3. The main beam is irradiated with the spot on the groove GV2 to form a main spot MB. The preceding sub-beam is irradiated with the spot on the groove GV3 to form the preceding sub-spot SB1. The preceding sub spot SB1 is arranged in front of the traveling direction of the main spot MB. The trailing sub-beam is irradiated with the spot on the groove GV1 to form the trailing sub-spot SB2. The trailing sub spot SB2 is arranged behind the main spot MB in the traveling direction. Reflected light from the main spot MB, the preceding sub-spot SB1, and the succeeding sub-spot SB2 are detected by the detectors PDm, PDs1, and PDs2, respectively, thereby generating a reproduction signal and a sub-beam RF signal. In the following drawings, the left side in the traveling direction is the outer peripheral side, and the right side is the inner peripheral side.

  The preceding sub-spot SB1 and the succeeding sub-spot SB2 are formed with a width narrower than that of the main spot MB. As a result, the possibility that the preceding sub-spot SB1 and the succeeding sub-spot SB2 are applied to the adjacent grooves can be reduced, so that crosstalk can be prevented from occurring in the sub-spot. As a method for making the width of the sub-spot narrower than that of the main spot, a method of forming the sub-beam narrower by using the light branching means 112 of FIG. There are a method of forming a narrow beam, a method of forming a narrow beam by giving coma aberration to a sub beam by shifting an optical axis using a mirror or the like.

  In this first method, the occurrence of crosstalk is detected by detecting whether or not the sub-spots are out of the respective grooves. In order to detect that the sub spot is out of the groove, it is performed by detecting a change in the intensity of the reflected light from the sub spot. That is, a change in the intensity of the reflected light detected by the detector PDs 1 or PDs 2 is detected by the RF signal intensity detection unit 121, converted into an electrical signal, and transmitted to the calculation unit 122. If there is a change in the peak voltage, the arithmetic unit 122 determines that the sub spot is out of the groove. The main spot is detected by detecting that the sub spot is out of the groove and transmitting a signal from the calculation unit 122 to the optical pickup drive control unit or the servo control unit to drive the optical pickup 110 and correct the position of the sub spot. Can be prevented from being applied to adjacent grooves. Thereby, crosstalk of the main spot can be reduced.

  In this first method, as shown in FIG. 2, it is preferable that the width of the sub-spot is made substantially the same as the width of the groove. If the width of the sub-spot is made substantially the same as the width of the groove, if the sub-spot deviates from the groove, of course, the peak voltage due to the sub-spot changes even when the sub-spot is deviated. The effect of reducing the main spot crosstalk is further improved.

  In FIG. 2, the sub-spot and sub-spots are arranged in two, the preceding sub-spot SB1 and the succeeding sub-spot SB2, so that the tracking function by the three-beam method can be used. The combined sub spot SB2 may also be arranged as a preceding sub spot.

  Next, a second method of crosstalk correction according to the present invention will be described. 3 and 4 are partial enlarged views showing a state in which the optical disc 150 is irradiated with the main beam, the preceding sub beam, and the subsequent sub beam. The difference from the first method is that the edge of the sub spot SB1 is arranged so as to be in contact with the tangent line SS1, and the sub spot SB2 is arranged so as to be in contact with the tangent line SS2. The tangent SS1 is a tangent that is in contact with the inner peripheral edge of the main spot MB and parallel to the track direction, and the tangent SS2 is an tangent that is in contact with the outer peripheral edge of the main spot MB and parallel to the track direction. In FIG. 3, the sub-spot SB1 and the sub-spot SB2 are arranged in a region between the tangent line SS1 and the tangent line SS2. In FIG. 4, the sub spot SB1 and the sub spot SB2 are arranged outside the region between the tangent line SS1 and the tangent line SS2.

  This second method is the same as the first method described above in that the widths of the preceding sub spot SB1 and the succeeding sub spot SB2 are formed narrower than the width of the main spot MB. Similarly, the possibility that the preceding sub-spot SB1 and the succeeding sub-spot SB2 are applied to adjacent grooves can be reduced so that crosstalk does not occur in the sub-spot. The feature of the second method is that when the main spot MB is applied to an adjacent groove and crosstalk occurs, the sub spot SB1 or the sub spot SB2 reads the pit of the adjacent groove, so that the adjacent groove obtained by the sub spot is detected. The crosstalk generated in the signal of the main spot can be corrected by calculating the difference from the signal obtained by the main spot using the above signal as the correction signal.

  In the second method, the form shown in FIG. 3, that is, the form in which the sub-spot SB1 and the sub-spot SB2 are arranged in the region between the tangent line SS1 and the tangent line SS2 is preferable. In such a form, the portion where the main spot is applied to the adjacent groove is the same as the portion where the sub spot is applied to the adjacent groove. By using parameters such as the size ratio or area ratio between the sub spot and the main spot, and the area ratio between the detector PDm of the main spot and the detector PDs1 or PDs2 of the sub spot, the adjacent superimposed on the signal of the main spot. The level of the groove signal and the level of the adjacent groove signal read by the sub-spot can be made substantially the same. This facilitates the calculation of the difference between the main spot signal and the sub spot signal and enables highly accurate correction.

  The operation of the second method will be described with reference to FIG. 5, taking the form of FIG. 3 as an example. In FIG. 5, the main spot MB is aligned with the groove GV1, and crosstalk occurs in the adjacent groove GV2. The main spot MB and the preceding sub-spot SB1 are in contact with the tangent line SS1.

  In this state, the main spot MB reads the pit. Then, the detector PDm of the photodetector 117 senses the reflected light from the main spot, converts it to an electrical signal by the RF signal intensity detector 121 and transmits it to the calculator 122. The signal waveform shown in A of FIG. A signal from the groove GV2 is superimposed on the signal from the main spot.

  The preceding sub spot SB1 reads the pit of the groove GV2. The reflected light from the preceding sub spot SB1 is detected by the detector PDs1 of the photodetector 117, converted into an electric signal by the RF signal intensity detector 121, and transmitted to the calculator 122. A signal waveform shown in FIG. 5B is obtained by calculating using parameters such as the size ratio or area ratio between the sub-spot and the main spot in the calculation unit 122. The waveform B of the preceding sub spot SB1 is corrected to substantially the same level as the signal of the adjacent groove GV2 superimposed on the waveform A of the main spot MB by the calculation in the calculation unit 122. Further, since the preceding sub spot SB1 and the main spot MB have a deviation in the time for reading the same pit of the adjacent groove GV2, the calculation unit 122 corrects the deviation and the waveform B of the preceding sub spot SB1 and the waveform of the main spot MB. Synchronize with A.

  Subsequently, when the difference between the obtained waveform A and waveform B is calculated by the calculation unit 122, the waveform of the signal shown in C of FIG. 5 is obtained. This waveform C is a signal obtained from the pit read by the groove GV1, that is, the main spot MB. In the second method, signals of adjacent tracks superimposed by crosstalk can be removed in this way.

  3 and 4, as in the first method described above, the sub-spot and sub-spots are arranged in the same manner as the preceding sub-spot SB1 and the subsequent sub-spot so that the tracking function by the three-beam method can be used. Although two spots SB2 are provided, the sub spot SB2 aligned with the groove GV1 may also be arranged as a preceding sub spot.

  The embodiment of the present invention has been described above, but various modifications can be made within the scope of the present invention. For example, a method other than the method disclosed in the present invention can be applied to the method of making the width of the sub-spot narrower than that of the main spot.

It is a functional block diagram which shows the optical disk recording / reproducing apparatus of this invention. It is the elements on larger scale which show the 1st method of this invention. It is the elements on larger scale which show the 2nd method of this invention. It is the elements on larger scale which show another example of the 2nd method of this invention. It is a figure for demonstrating the method of the crosstalk correction | amendment in the 2nd method of this invention. It is a figure which shows the trouble of the prior art.

Explanation of symbols

100 Optical disc recording / reproducing apparatus
110 Optical pickup
111 Laser diode
112 Optical branching means 113 Collimating lens
114 Objective Lens 115 Detection Lens 116 Beam Splitter 117 Photodetector 121 RF Signal Strength Detection Unit 122 Calculation Unit 150 Optical Disk

Claims (6)

In an optical information recording / reproducing apparatus for recording and reproducing data by irradiating an optical information recording medium having a spiral groove with laser light, a main beam and an optical information recording medium are recorded on the optical information recording medium when recording and reproducing data. A sub-beam is irradiated, and the spot of the sub-beam has a shape narrower than the spot of the main beam, and is arranged so as to irradiate a groove adjacent to the groove irradiated with the main beam. An optical information recording / reproducing apparatus.   2. The optical information recording / reproducing apparatus according to claim 1, wherein the spot of the sub beam is substantially the same as the width of the groove.   In an optical information recording / reproducing apparatus for recording and reproducing data by irradiating an optical information recording medium having a spiral groove with laser light, a main beam and an optical information recording medium are recorded on the optical information recording medium when recording and reproducing data. The spot of the sub beam is irradiated with a sub beam, and the spot of the sub beam is narrower than the spot of the main beam. The spot of the sub beam is in contact with the edge of the spot of the main beam and parallel to the track direction. An optical information recording / reproducing apparatus, wherein the edges are arranged so as to contact each other.   4. The optical information recording / reproducing apparatus according to claim 3, wherein the sub-beam is disposed in a region sandwiched between an inner peripheral tangent and an outer peripheral tangent. In an optical information recording / reproducing method for recording and reproducing data by irradiating a laser beam onto an optical information recording medium having a spiral groove, a main beam and an optical information recording medium are recorded on the optical information recording medium when data is recorded and reproduced. A sub-beam is irradiated, and a groove adjacent to the groove that is irradiating the main beam is irradiated with a sub-beam having a narrower shape than the main beam, and the sub-beam is irradiating the main beam. An optical information recording / reproducing method, wherein crosstalk is detected by detecting whether or not the groove is adjacent to the adjacent groove. In an optical information recording / reproducing method for recording and reproducing data by irradiating a laser beam onto an optical information recording medium having a spiral groove, a main beam and an optical information recording medium are recorded on the optical information recording medium when data is recorded and reproduced. The sub-beam spot has a shape narrower than the main beam, and the edge of the sub-beam spot is in contact with the edge of the main beam spot and parallel to the track direction. An optical information recording / reproducing method comprising: correcting a signal by calculating a difference between a signal obtained by the sub beam and a signal obtained by the main beam.

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