JP2005267747A - Magneto-optical recording / reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical recording / reproducing apparatus capable of accurately recording / reproducing without being affected by a leakage magnetic field from an adjacent track.
SOLUTION: There are provided two systems for correcting asymmetry of a recording signal or a reproduction signal corresponding to a land and a groove. At the time of information recording or information reproduction, the correction amount of the asymmetry correction means is switched between the land portion and the groove portion of the magneto-optical recording medium. As a result, asymmetry that occurs in the recording bit or the like is canceled, and stable recording / reproduction is performed regardless of the land or groove.
[Selection] Figure 1

Description

  The present invention relates to a magneto-optical recording / reproducing apparatus that records or reproduces information by a light beam using a magneto-optical effect.

  In recent years, as a rewritable high-density recording method, a magneto-optical recording medium and a recording / reproducing apparatus for recording information by writing magnetic domains in a magnetic thin film using the thermal energy of a semiconductor laser and reading the recorded information using a magneto-optic effect Is attracting attention. The magneto-optical recording medium has been widely used as a large-capacity removable information recording medium such as a computer.

  Recently, data handled by computers and other information processing devices has been diversified into various types of information such as voice, images, and moving images, and the data size required for them has been increasing. Therefore, the recording density of this magneto-optical recording medium has been reduced. There is an increasing demand for higher-capacity recording media.

  The magneto-optical recording medium is superior to other optical recording media in terms of recording density in that a recording mark smaller than the resolution limit of the optical system can be recorded and reproduced. For example, Japanese Patent Laid-Open No. 7-334877 (Patent Document 1) discloses a magnetic super-resolution reproduction system which is an example of such a magneto-optical recording / reproducing method. Further, as a method for recording a magnetic domain smaller than the resolution limit of the optical system, a magnetic field modulation method in which the modulation speed of the external magnetic field is sufficiently increased is generally known.

Japanese Patent Application Laid-Open No. 6-290498 (Patent Document 2) discloses that a domain wall moving layer having a small domain wall coercive force is provided on the reproduction light incident side in a magneto-optical recording medium, and a domain wall is utilized by utilizing a temperature gradient in the reproduction spot. A method is disclosed in which a domain wall of a moving layer is moved to a high temperature side and a magnetic domain is enlarged and reproduced in a spot. According to the publication, even if the recording mark size is reduced, the signal is reproduced while enlarging the magnetic domain. Therefore, the reproduction light can be used effectively, and the resolving power can be increased without reducing the signal amplitude.
Japanese Patent Laid-Open No. 7-334877 Japanese Patent Application Laid-Open No. 6-290496

  The reproduction method using domain wall motion disclosed in Patent Document 2 is a method that is particularly excellent in linear recording density among super-resolution methods. In other words, if the amount of movement of the domain wall is always constant, a constant reproduction signal amplitude can be obtained regardless of the size of the recording magnetic domain.

  On the other hand, as the density of magneto-optical recording media is pursued, in addition to increasing the linear density, a narrow track pitch is required. As one means, information is recorded in both the land / groove portion of the track guide groove. A method of recording is effective. However, this method has the following problems.

  FIG. 7 is a diagram schematically showing a cross section when the domain wall moving medium disclosed in Patent Document 2 is combined with a land groove substrate. FIG. 7A is a diagram for explaining the case of recording in a groove. Recording / reproducing light is incident from the substrate side and is condensed on a magnetic film (a general term from the moving layer 1 to the memory layer 3), and at the same time by the coil 36. An external magnetic field is applied to the magnetic film.

  As a result, in the memory layer 3 of the groove indicated by diagonal lines, the portion that reaches the Curie temperature by laser irradiation follows the direction of the external magnetic field, and information is recorded. Actually, however, the leakage magnetic field Hleak 11-14 corresponding to the magnetization state of the adjacent track indicated by hatching and the external magnetic field from the coil 36 are superimposed and applied to the memory layer 3 of the recording track, and an offset is added to the recording magnetic field. Become a shape. As a result, as shown in FIG. 8, a deviation of ΔT occurs at the external magnetization reversal timing and the recording magnetic domain formation position, rising and falling, respectively, and asymmetry occurs in the recording bit. 8A shows the clock CLK, FIG. 8B shows the external magnetic field Hw, and FIG. 8C shows the formation position of the recording magnetic domain.

  FIG. 7B shows a case where recording is performed on a land. When recording is performed in the same manner as in the groove recording, asymmetry occurs because leakage magnetic fields Hleak 21 to 24 from the adjacent tracks are also applied. However, as is clear from comparison between FIGS. 7A and 7B, the land recording and the groove recording have different three-dimensional positional relationships with adjacent tracks, and therefore the influence from the leakage magnetic field is also different. Therefore, even if a measure for canceling the influence of the leakage magnetic field is taken, it is difficult to achieve an optimum recording state for both the land and the groove.

  Further, FIG. 9 is a diagram showing the influence of a leakage magnetic field from an adjacent track during information reproduction. In the domain wall moving medium disclosed in Patent Document 2, it is known that the domain wall movement may be affected by an external magnetic field, resulting in asymmetry. FIG. 9A shows the groove, and FIG. 9B shows the leakage magnetic field received from the adjacent track when the land is reproduced. In this case as well, since the magnitude of the influence differs between the groove and the land as in the recording. The amount of asymmetry that occurs is also different. In other words, it has been difficult to achieve both optimal reproduction conditions for land and groove.

  The present invention has been made to solve the above-described conventional problems. The object of the present invention is to change the asymmetry correction amount between the land portion and the groove portion of the magneto-optical recording medium at the time of information recording or reproduction, thereby allowing adjacent tracks to be recorded. It is an object of the present invention to provide a magneto-optical recording / reproducing apparatus capable of accurately recording / reproducing without being affected by a leakage magnetic field from the image.

  In order to solve the above problems, the present invention provides a recording signal or reproduction in a magneto-optical recording / reproducing apparatus for recording or reproducing recording data on a magneto-optical recording medium having a plurality of lands and grooves. Means is provided for correcting the asymmetry of the signal, and the amount of correction of the asymmetry correcting means is switched between the land portion and the groove portion when recording or reproducing information.

  According to the present invention, an optimum asymmetry correction circuit is provided for each land and groove, and at the time of recording or reproduction, the amount of asymmetry correction is switched according to the land and groove, so that stable information recording and reproduction can be performed at all times. is there.

  Next, the best mode for carrying out the invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing an embodiment in which asymmetry correction is performed during recording according to the present invention. First, recording data processed by a circuit such as a CPU and an encoder (not shown) is added with a synchronization signal or the like by a data generation circuit 31 to be a signal to be actually recorded on a disk (not shown) which is a magneto-optical recording medium. Converted. Normally, an output signal from the data generation circuit 31 is input to the driver circuit 33, and the driver circuit 33 drives the coil 36 in accordance with the input signal. As a disk, for example, the layer structure shown in FIG. 7 is used, and information is recorded or reproduced on both lands and grooves. The coil 36 is a coil of a magnetic head (not shown) arranged close to the disk surface.

  At this time, the emission power of a semiconductor laser (not shown) is set to a high power, and information is recorded on the medium by driving the coil 36 according to the recording signal while raising the memory layer 3 to the Curie temperature. In this embodiment, the bias of the power supplies 35a and 35b is supplied to the driver circuit 33 through the switch 34, thereby adding an offset to the recording magnetic field generated from the coil 36.

  FIG. 2 is a diagram showing the signals of the respective parts at this time. 2A shows a basic clock for data recording, FIG. 2B shows a recording magnetic field generated from the coil 36, and FIG. 2C shows a data recording timing. In the case of this medium, if information recording is performed without applying an offset magnetic field, the positive side pits are recorded longer by 2 × ΔT. Therefore, in this embodiment, the offset magnetic field is applied to the negative side, and the asymmetry at the time of recording is canceled to perform recording in synchronization with the clock as shown in FIG.

Furthermore, E power for setting the offset magnetic field _L, includes E _G and dual, by switching the switch 34 depending on whether the track to be recorded land and groove by the polarity switch 32, suitable lands, each groove Applying an offset magnetic field, the optimum information recording is always performed. That is, the power supply E _L is set to a voltage value for giving an offset magnetic field suitable for performing the optimum recording on the land, the voltage value for giving an offset magnetic field power supply E _G is suitable for performing the optimum recording on the groove is set to, when recording information on a land to the power supply E _L, when recording information on grooves by switching the power source E _G, lands, perform optimal recording in grooves both.

(Second Embodiment)
FIG. 3 is a block diagram showing a second embodiment of the present invention. In the figure, the same parts as those in FIG. The recording signal generated by the data generation circuit 31 is input to the logical product circuit 38 and the delay circuits 37a and 37b. The output signals of the delay circuits 37a and 37b are input to the switch 34, and the polarity switch 32 selects either the recording track according to the land or the groove. Then, a logical product of the recording signal and the selected delay circuit is obtained by the logical product circuit 38 and supplied to the driver circuit 33.

  FIG. 4 shows signals at various parts in FIG. FIG. 4A shows a basic clock for data recording. 4B to 4E correspond to the signals of FIGS. 3B to 3E, FIG. 4B shows the output signal of the data generation circuit 31, and FIG. 4D is an output signal of the AND circuit 38, and FIG. 4E is a recording magnetic field generated from the coil. Further, FIG. 4F shows recording data.

  The delay amount of the delay circuit is set to 2xΔT, and the input signal to the driver circuit 33 has a duty cycle shortened by 2xΔT. Due to this and the difference ΔT between the timing of the recording magnetic field and the recorded information, the recorded information bit is formed with a delay of ΔT from the clock in both rising and falling.

  Here, ΔT to be delayed differs between the land and the groove, the delay time of the delay circuit 37a is set to ΔT in which asymmetry of recording bits does not occur when recording on the land, and the delay time of the delay circuit 37b is set to the groove. When recording, the recording bit is set to ΔT that does not cause asymmetry. The polarity switching circuit 32 switches the switch 34 according to the land and the groove, thereby switching to the delay circuit 37a when recording on the land and switching to the delay circuit 37b when recording on the groove. Therefore, optimum recording can be performed on each of the land and the groove.

  Also, normally, the recording and reproduction clocks are generated separately, and the reproduction clock is generated by multiplying the reproduction signal and the PLL, so that the recording bit is substantially delayed from the recording clock. There is no problem.

(Third embodiment)
FIG. 5 is a block diagram showing an embodiment in which asymmetry correction is performed during reproduction according to the present invention. In the figure, 41 is a binarization circuit for binarizing a reproduction signal reproduced by an optical pickup (not shown), and 42, 45 and 46 are JK-FF circuits. 43 is a crystal oscillator, 45 is a PLL circuit, 48a and 48b are delay circuits, 49 is a switch, 50 is a polarity switch, 51a is a rising edge detection circuit for detecting the rising edge of the reproduction signal, and 51b is a falling edge of the reproduction signal. This is a falling edge detection circuit for detecting. Reference numeral 52 denotes a signal processing circuit that performs signal processing based on the output signals of the rising edge detection circuit 51a and the falling edge detection circuit 51b to reproduce information. It is assumed that the disc has a layer structure shown in FIG. 7, for example, and information on both land and groove is reproduced.

  FIG. 6 shows signals of each part. The signals in FIGS. 6A to 6G correspond to the signals in FIGS. 5A to 5G. First, FIG. 6A shows an MO reproduction signal detected by an optical pickup (not shown). The MO signal is converted into a digital signal by a binarization circuit 41 as shown in FIG. Then, first, it inputs into the JK-FF circuit 42, and only a rising edge is extracted as shown in FIG.6 (c).

  The PLL circuit 45 locks the phase of the output from the crystal oscillator 43 having a frequency twice that of the data reproduction signal clock and the output of the JK-FF 42. FIG. 6D shows an output signal of the PLL circuit 45. The output signal of the PLL circuit 45 is divided by two at the rising edge using the JK-FF circuit 46 as shown in FIG. 6E, and further divided by two at the falling edge using the JK-FF circuit 47. Is done. As a result, an edge extraction window is generated as shown in FIG.

  On the other hand, the rising edge detection circuit 51a detects the rising edge from the output of the binarization circuit 41 using a differentiation circuit or a monostable multivibrator and compares it with the data window generated by the JK-FF circuit 47. The rising edge timing is determined at which position the rising edge is generated with respect to the reference clock.

  Further, the falling edge detection circuit 51b includes a falling edge detected from the output of the binarization circuit 41 and a data window (FIG. 6 (g)) obtained by delaying the output of the JK-FF circuit 47 by 2 × ΔT. By comparing, the timing of the falling edge is determined. In this manner, the timing of the rising edge and the falling edge is discriminated with an optimal window, and the signal processing circuit 52 combines both to demodulate the data, thereby reproducing the correct information.

  Here, the delay circuits 48a and 48b delay the output of the jK-FF circuit 47 by 2 × ΔT to create a data window. However, ΔT to be delayed is a land and a groove as in the second embodiment. Is different. That is, the delay circuit 48a is provided for the land, and the delay circuit 48b is provided for the groove. The delay time ΔT is set so as to cancel asymmetry when the land and the groove are reproduced. Then, the polarity switching circuit 50 reproduces while switching the switch 49 according to the land and the groove, so that the land and the groove always reproduce the optimum information.

(Fourth embodiment)
In the fourth embodiment, the power supplies E _L and E _G and switches shown in FIG. 1 are replaced with D / A converters, and the offset magnetic field can be controlled by digital signals. This makes it possible to deal with variations among individual media, and when the medium is inserted into the apparatus, it is also possible to perform actual information recording / reproduction after obtaining the optimum offset magnetic field for each land and groove in a known test area. It is.

1 is a block diagram showing a first embodiment of a magneto-optical recording / reproducing apparatus according to the present invention. FIG. It is a figure which shows the waveform of each part of embodiment of FIG. It is a block diagram which shows the 2nd Embodiment of this invention. It is a figure which shows the waveform of each part of embodiment of FIG. It is a block diagram which shows the 3rd Embodiment of this invention. It is a figure which shows the waveform of each part of embodiment of FIG. It is a figure explaining the stray magnetic field applied from an adjacent track at the time of recording. It is a figure explaining the asymmetry which arises at the time of recording. It is a figure explaining the stray magnetic field applied from an adjacent track at the time of reproduction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Domain wall moving layer 2 Blocking layer 3 Memory layer 21 Land 22 Groove 31 Data generation circuit 32, 50 Polarity switch 33 Driver circuit 34, 49 Switch 35a, 35b Power supply 36 Coil 37a, 37b, 48a, 48b Delay circuit 38 AND circuit 41 Binarization circuit 42, 46, 47 JK-FF circuit 43 Crystal oscillator 45 PLL circuit 51a Rising edge detection circuit 51b Falling edge detection circuit 52 Signal processing circuit 101 Substrate 102 Interference layer 103 Protection layer

Claims (4)

In a magneto-optical recording / reproducing apparatus for recording recording data on a magneto-optical recording medium having a plurality of land portions and groove portions, or for reproducing the recording data, a means for correcting the asymmetry of the recording signal or the reproducing signal is provided. A magneto-optical recording / reproducing apparatus, wherein the correction amount of the asymmetry correction means is switched between a land portion and a groove portion during recording or reproduction. 2. The magneto-optical recording / reproducing apparatus according to claim 1, wherein the asymmetry correction unit corrects asymmetry by switching an offset applied to a recording magnetic field applied to a recording medium between a land portion and a groove portion. 2. The magneto-optical recording / reproducing apparatus according to claim 1, wherein the asymmetry correcting unit corrects asymmetry by switching a delay time of a recording signal between a land portion and a groove portion. The asymmetry correction means corrects asymmetry by switching a window for discriminating the timing of a rising edge and a falling edge of a binary signal of a reproduction signal between a land portion and a groove portion. 2. The magneto-optical recording / reproducing apparatus according to 1.