JP2005063521A - Magneto-optical recording / reproducing method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce and improve an edge shift caused by a stray magnetic field generated depending on a recorded magnetic field state, and to reduce a PLL error and improve a bit error rate. And a magneto-optical recording / reproducing apparatus.
In a magneto-optical recording method for recording information by irradiating a magneto-optical recording medium 3 with a light beam and modulating a magnetic field in accordance with a recording signal, a mark pattern to be recorded is detected and an edge shift pattern is detected. The recording mark row information is recorded so as to correct the recording signal edge position by changing the magnetic domain formation position by changing the temperature distribution at the tip of each mark so as to reduce the dependency. (Temperature distribution changes include pulse recording power, pulse width, and pulse phase.)
[Selection] Figure 1

Description

  The present invention relates to a magneto-optical recording / reproducing method and apparatus for recording / reproducing information by utilizing a magneto-optical effect, and more particularly to a magneto-optical recording / reproducing method and apparatus that enable recording / reproducing of a minute mark below an optical system diffraction limit.

  As a rewritable high-density recording method, there is a magneto-optical recording medium that records information by writing magnetic domains on a magnetic thin film using the thermal energy of a semiconductor laser and reads out the information using a magneto-optical effect. In recent years, there has been an increasing demand for a recording medium having a large capacity by further increasing the recording density of the magneto-optical recording medium. The linear recording density of an optical disk such as a magneto-optical recording medium greatly depends on the laser wavelength of the reproducing optical system and the numerical aperture of the objective lens. That is, when the laser wavelength λ of the reproducing optical system and the numerical aperture NA of the objective lens are determined, the diameter of the beam waist is determined, and therefore, the spatial frequency at the time of reproducing the recording mark is limited to about 2 NA / λ. Therefore, in order to realize high density with the conventional optical disc, it is necessary to shorten the laser wavelength of the reproducing optical system and increase the NA of the objective lens. However, there is a limit in improving the laser wavelength and the numerical aperture of the objective lens. For this reason, a technique for improving the recording density by devising the configuration of the recording medium and the reading method has been developed. For example, recording data on a recording layer of a multilayer film having a reproducing layer and a recording layer that are magnetically coupled, and recording data on the recording layer using a temperature gradient caused by irradiation with a heating light beam The magnetic layer of the recording mark of the reproducing layer is moved without changing the value, and the reproducing layer is magnetized so that almost the entire area of the reproducing light beam spot has the same magnetization. A signal reproducing method and apparatus for detecting a change and reproducing a recording mark below the diffraction limit of light have been proposed (see Patent Document 1). According to this method, the reproduction signal becomes rectangular, a recording mark below the diffraction limit of the optical system can be reproduced without lowering the reproduction signal amplitude, and the recording density and transfer speed can be greatly improved. A playback method is possible.

  FIG. 15 shows the configuration of a conventional magneto-optical recording / reproducing apparatus according to an embodiment. In the figure, reference numeral 1 denotes a substrate 2 made of glass or plastic, using a temperature gradient caused by irradiation of a light beam, moving the magnetic wall of the recording mark of the reproducing layer without changing the recording data of the recording layer, The magneto-optical recording medium 3 capable of reproducing the recording mark below the diffraction limit of the optical system is applied, and a protective film 4 is formed. This is a magneto-optical disk 1. The magneto-optical disk 1 is supported by a spindle motor by magnet chucking or the like, and has a structure that is rotatable with respect to a rotating shaft. 5 is a schematic diagram of an optical head that irradiates the magneto-optical disk 1 with laser light and obtains information from the reflected light. A condensing lens (ex. NA: 0.60), an actuator for driving the condensing lens, a semiconductor laser (ex .λ: 650 nm), a beam splitter, a polarizing beam splitter, and the like. Laser light emitted from the semiconductor laser is applied to the magneto-optical disk 1 through the optical component group. At this time, the condenser lens is controlled by the actuator to move in the focusing direction and the tracking direction so that the laser beam is successively focused on the magneto-optical recording medium 3, and is engraved on the magneto-optical disk. It is configured to track along the guide groove. The laser beam reflected by the magneto-optical disk 1 is condensed on each sensor by the difference in deflection direction according to the polarity of magnetization of the magneto-optical recording medium 3 through the optical component group, and differentially amplifies them. To output a magneto-optical signal.

  The controller 6 outputs the recording power, the recording signal, etc., using the rotational speed of the magneto-optical disk 1, the recording radius / recording sector information, and the environmental temperature as input information, and the LD driver 7, the magnetic head driver 8, etc. It is something to control.

  Reference numeral 9 denotes a magnetic head for applying a modulation magnetic field to the laser irradiation portion of the magneto-optical disk during a recording operation, and is disposed so as to face the optical head 5 with the magneto-optical disk 1 interposed therebetween. At the time of recording, a recording laser beam is irradiated from the optical head 5, and at the same time, the magnetic head 9 generates magnetic fields having different polarities corresponding to recording signals by the magnetic head driver 8. The magnetic head 9 moves in the radial direction of the magneto-optical disk 1 in conjunction with the optical head 5 and records information by sequentially applying a magnetic field to the laser irradiation portion of the magneto-optical recording medium 3 during recording. It has become.

  A recording operation will be described with reference to FIG. In the figure, a) is a recording signal, b) a recording power, c) a modulation magnetic field, d) a recording mark row, and e) a reproduction signal. When recording a recording signal as shown in a), the laser power outputs a predetermined recording power as shown in b) when the recording operation starts, and a modulation magnetic field c) based on the recording signal a) is applied. . Here, a case where so-called pulse magnetic field modulation recording is used in which the applied magnetic field is modulated in accordance with the recording information and the recording LD light is modulated in a pulse shape at a steady period as shown in the recording power b). By these operations, a recording mark row d) is formed in the cooling process of the recording medium. The shaded part and the white part represent magnetic domains having opposite magnetization directions.

  The reproduction operation will be described with reference to FIG. Here, the recording layer 14 for storing the recording mark, the domain wall moving layer 15 in which the domain wall moves and directly contributes to the reproduction signal, and the switching layer 16 for switching the coupling state between the recording layer 14 and the domain wall moving layer 15 are provided. The case of the layer structure will be described.

  a) is a schematic diagram showing a magnetic domain reproduction state, b) is a recording film state diagram, c) is a medium temperature state diagram, and d) is a reproduction signal. At the time of reproduction, as shown in a), it is heated to a Ts temperature condition in which the domain wall of the reproduction layer of the domain wall moving medium moves by light beam irradiation. The switching layer 16 shown in b) is in a state of being coupled to the recording layer 14 and the domain wall motion layer 15 by exchange coupling in a temperature region lower than Ts. When the medium is heated to the Ts temperature or higher by irradiation with the light beam, the switching layer 16 reaches the Curie point, and the domain wall moving layer 15 and the recording layer 14 are disconnected. For this reason, at the same time when the domain wall of the recording mark reaches this Ts temperature region, the domain wall of the domain wall moving layer 15 is located at a position where the domain wall is stable in terms of energy with respect to the temperature gradient of the domain wall moving layer 15, that is, light beam irradiation. The domain wall instantaneously moves across the land to the highest temperature point in the linear density direction of the temperature rise due to. As a result, most of the magnetization state of the area covered by the reproduction light beam becomes the same. Therefore, even in the case of a minute recording mark that cannot be reproduced in the normal light beam reproduction principle, a rectangular shape as shown in the figure. It is possible to obtain a reproduction signal in a state close to

Therefore, a reproduction signal e) can be obtained by reproducing a recording mark string as shown in FIG. 16 d) with a light beam. According to this method, since the magnetization state covered by the light beam is mostly the same, the reproduction signal becomes nearly rectangular as shown in e) in the figure, and the optical system is hardly reduced without substantially reducing the reproduction signal amplitude. Recording marks below the diffraction limit can be reproduced, and a magneto-optical recording medium and reproducing method that can greatly improve the recording density and transfer speed.
Japanese Patent Laid-Open No. 06-290496

However, according to the conventional example, the following problems occur.

  During recording in magneto-optical recording, the temperature of the laser light irradiated portion of the magneto-optical recording medium reaches the Curie point (Tc) by the laser light irradiation, and the magnetization disappears. However, magnetization exists in a peripheral portion where the temperature does not rise to Tc, and a stray magnetic field due to magnetization exists as shown in FIG. The domain wall that is the end of the recording mark is formed at the rear end in the light beam traveling direction. When the domain wall that is the end of the recording mark is formed, these stray magnetic fields are superimposed on the modulation magnetic field applied by the magnetic head from the outside for forming the domain wall. Act on. The magnitude of this stray magnetic field varies depending on the interval between the domain wall formed immediately before and the domain wall to be formed next, that is, the recording mark length to be formed, and the mark length located in front of it. Therefore, as described above, the stray magnetic field strength acting on the domain wall formation site varies depending on the mark length or mark length string to be recorded.

  The position where the domain wall is formed is determined by the relationship between the temperature and the magnetic field strength. Here, the laser beam intensity and the applied magnetic field intensity from the magnetic head are kept in a steady state, and when the recording mark length or the recording mark length string is different, the superimposed floating magnetic field intensity is different. The magnetic field strength applied to the magnetic domain formation position is the magnetic field strength from the magnetic head + the floating magnetic field strength. As described above, the magnetic field strength substantially applied to the magnetic domain formation portion is the recording mark length to be formed, or the recording mark length string. Varies by As a result, a phenomenon in which the domain wall formation position varies depending on the recording mark length appears.

  Further explanation will be given with reference to FIG. In the figure, (A) shows the case where the longest and shortest recording marks on the recording code are sequentially formed, and (B) shows the case where the shortest and longest recording marks on the recording code are sequentially formed. In the figure, 21 indicates a laser beam, 22 indicates the magnetization state of the recording layer of the magneto-optical recording medium, arrow 23 indicates the intensity and direction of the applied magnetic field from the magnetic head, and arrow 24 indicates the magnetization state immediately before the domain wall formation. The stray field strength and direction are shown. An arrow 25 indicates the stray magnetic field intensity and direction from the recording mark positioned further forward. Here, due to the characteristics of the magneto-optical recording medium, the direction of the stray magnetic field indicated by the arrow 24 is applied in the direction of increasing the applied magnetic field from the magnetic head when the domain wall is formed, and the direction of the stray magnetic field indicated by the arrow 25 is from the magnetic head when forming the domain wall. Is applied in the direction of decreasing the applied magnetic field. Therefore, as shown in the figure, the sum of the applied magnetic fields of the arrows 23, 24, and 25 at the domain wall formation site is different in the cases (A) and (B), and a stronger magnetic field strength is applied in the case (B). . As a result, the domain wall formation position is formed at a position shifted by ΔA in the case of (A) when viewed from a certain reference position, and is formed at a position shifted by ΔB in the case of (B), and the relationship between ΔA and ΔB is ΔA <ΔB. Result.

  FIG. 19 shows the result of the pattern dependency caused by the above-described factors. In the figure, the horizontal axis indicates the Nth mark length measured by the time interval analyzer, the vertical axis indicates the N + 1th mark length, and 1E + 5 measurement data is plotted as dots. The intersection of the grids shown in the figure is the ideal position. Here, 1-7 modulation code is adopted. For example, when (N, N + 1) is (8T, 2T), it can be confirmed that the time interval distribution is shifted from the grid intersection and an edge shift occurs. Due to this factor, there is a problem that the jitter value when a random signal is recorded is greatly deteriorated compared to the jitter value when the same mark length is continuously recorded.

Furthermore, a magneto-optical recording / reproducing method capable of dramatically improving the linear recording density that can eliminate the restrictions of the optical system resolution like the domain wall motion type magneto-optical medium mentioned in the present invention is adopted. The recording mark length will be shortened,
The change of the magnetization state in a certain range from the domain wall formation position becomes more complicated, and the change of the stray magnetic field also becomes complicated, so that the edge shift due to the recording mark length becomes complicated.

  As the edge shift amount due to the above factors increases the recording linear density and shortens the mark length, the ratio to the mark length becomes larger than before, and the edge shift problem due to the stray magnetic field becomes obvious.

  The edge shift problem due to intersymbol interference due to the optical system resolution has been removed, and the edge shift problem due to stray magnetic fields has become apparent.

  These factors also contribute to the above problems.

  As described above, when mark rows having different recording mark lengths are recorded, so-called edge shifts in which the respective mark lengths deviate from the normal mark lengths occur, resulting in an increase in PLL error and a deterioration in error rate in data reproduction. There is a problem of inviting.

  That is, in magneto-optical recording / reproduction, the magnetic domain row is formed at a position deviated from the regular domain wall position due to the influence of the leakage magnetic field of the magnetic domain row recorded in advance. A tendency of this depending on the recorded mark length can be confirmed, and so-called edge length dependency of edge shift becomes obvious. An object of the present invention is to correct the mark length dependency of the edge shift during recording.

  In view of the above-mentioned problems of the prior art, the object of the present invention is to reduce / improve edge shift caused by a stray magnetic field generated depending on the recorded magnetization state, thereby reducing PLL error, To provide a magneto-optical recording / reproducing method and a magneto-optical recording / reproducing apparatus capable of improving the bit error rate.

The magneto-optical recording / reproducing method of the present invention comprises:
In a magnetic field modulation recording type magneto-optical recording / reproducing method in which information is recorded by irradiating a magneto-optical recording medium with a light beam and applying a modulation magnetic field corresponding to a recording signal. By changing the temperature rise, the domain wall formation position is changed to form a recording mark row to record information.

  Further, the temperature increase may be changed by changing the recording power at the domain wall position forming portion.

  The light beam irradiation may be a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the temperature increase may be changed by changing the recording pulse width at the domain wall position formation site. .

  The light beam irradiation may be a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the temperature increase may be changed by changing the recording pulse phase at the domain wall position formation site. .

  The light beam irradiation is a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the temperature rise is changed by changing the recording pulse width at the domain wall position formation site, and The recording may be performed by changing the recording power at the domain wall position forming portion.

  Further, the irradiation of the light beam is irradiation of a pulsed light beam synchronized with the channel clock of the recording signal, and the temperature rise is changed by changing the recording pulse phase in the domain wall position formation site, and The recording may be performed by changing the recording power at the domain wall position forming portion.

  The light beam irradiation is a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the temperature rise is changed by changing the recording pulse width at the domain wall position formation site, and The recording may be performed by changing the recording pulse phase at the domain wall position forming portion.

  The light beam irradiation is a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the temperature rise is changed by changing the recording pulse width at the domain wall position formation site, and The recording may be performed by changing the recording pulse phase at the domain wall position formation site and by changing the recording power at the domain wall location formation site.

The magneto-optical recording / reproducing apparatus of the present invention comprises:
In a magnetic field modulation recording type magneto-optical recording / reproducing apparatus that records information by irradiating a magneto-optical recording medium with a light beam and applying a modulated magnetic field corresponding to a recording signal, the magnetic wall position forming portion is recorded at the time of recording. A means for changing the temperature rise is provided, and the means for changing the temperature rise is used to change the domain wall formation position to form a recording mark row to record information.

  Further, the means for changing the temperature rise may be performed by means for changing the recording power at the domain wall position forming portion.

  The light beam irradiation is a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by the means for changing the recording pulse width at the domain wall position formation site. Also good.

  The light beam irradiation is a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by the means for changing the recording pulse phase at the domain wall position formation site. Also good.

  Further, the light beam irradiation is a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by means for changing the recording pulse width at the domain wall position formation site, In addition, it may be performed by means for changing the recording power at the domain wall position forming portion.

  Further, the irradiation of the light beam is irradiation of a pulsed light beam synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by the means for changing the recording pulse phase at the domain wall position formation site, In addition, it may be performed by means for changing the recording power at the domain wall position forming portion.

  Further, the light beam irradiation is a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by means for changing the recording pulse width at the domain wall position formation site, In addition, it may be performed by means for changing the recording pulse phase at the domain wall position formation site.

  Further, the light beam irradiation is a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by means for changing the recording pulse width at the domain wall position formation site, In addition, it may be performed by means for changing the recording pulse phase at the domain wall position forming portion and by means for changing the recording power at the domain wall position forming portion.

  According to the magnetic field modulation type magneto-optical recording / reproducing method subjected to recording correction according to the present invention, an edge shift caused by a stray magnetic field generated depending on a recorded magnetic field state can be reduced, and a PLL error can be reduced. The bit error rate can be improved, and the recording magnetic field strength can be reduced, so that a higher-density and higher-speed information recording apparatus can be provided. In addition, since the domain wall motion type magneto-optical reproduction method can have a feature of faithfully reading the recorded domain wall position without being affected by the resolution of the optical system, it is not easily influenced by the spot quality of the optical system. It is a reproduction method, and the combination with the present invention enables correct recording correction without being affected by individual differences in spot quality of the drive to be recorded. There is no worry and this is a suitable combination.

(First Embodiment of the Invention)
In the first embodiment of the present invention, recording correction by changing the recording power value will be described.

  FIG. 1 shows the configuration of the magneto-optical recording / reproducing apparatus according to the first embodiment of the present invention. In the figure, reference numeral 1 denotes a substrate 2 made of glass or plastic, using a temperature gradient caused by irradiation of a light beam, moving the magnetic wall of the recording mark of the reproducing layer without changing the recording data of the recording layer, The magneto-optical recording medium 3 capable of reproducing the recording mark below the diffraction limit of the optical system is applied, and a protective film 4 is formed. This is a magneto-optical disk. The magneto-optical disk 1 is supported by a spindle motor by magnet chucking or the like, and has a structure that is rotatable with respect to a rotating shaft. 5 is a schematic diagram of an optical head that irradiates the magneto-optical disk 1 with laser light and obtains information from the reflected light. A condensing lens (ex. NA: 0.60), an actuator for driving the condensing lens, a semiconductor laser ( ex.λ: 650 nm), a beam splitter, a polarizing beam splitter, and the like. Laser light emitted from the semiconductor laser is applied to the magneto-optical disk 1 through the optical component group. At this time, the condenser lens is controlled by the actuator to move in the focusing direction and the tracking direction so that the laser beam is successively focused on the magneto-optical recording medium 3, and is engraved on the magneto-optical disk. It is configured to track along the guide groove. The laser beam reflected by the magneto-optical disk 1 is condensed on each sensor by the difference in the deflection direction according to the polarity of magnetization of the magneto-optical recording medium through the optical component group, and differentially amplifies them. Outputs magneto-optical signals.

  The controller 6 outputs the recording power, the recording signal, etc., using the rotational speed of the magneto-optical disk, the recording radius / recording sector information, and the environmental temperature as input information, and controls the LD driver 7, the magnetic head driver 8 and the like. To do.

  The LD driver 7 is configured to be capable of LD power modulation at a multi-value level of three or more values upon receiving recording power correction information. In this embodiment, modulation of the LD pulse will be described with respect to pulse magnetic field modulation in which one pulse of LD irradiation is performed in one cycle of the channel clock of the modulation code.

  Reference numeral 9 denotes a magnetic head for applying a modulation magnetic field to the laser irradiation portion of the magneto-optical disk during a recording operation, and is disposed so as to face the optical head 5 with the magneto-optical disk 1 interposed therebetween. At the time of recording, a recording laser beam is irradiated from the optical head 5, and at the same time, the magnetic head 9 generates magnetic fields having different polarities corresponding to recording signals by the magnetic head driver 8. The magnetic head 9 moves in the radial direction of the magneto-optical disk 1 in conjunction with the optical head 5 and records information by sequentially applying a magnetic field to the laser irradiation portion of the magneto-optical recording medium 3 during recording. It has become.

  Reference numeral 10 denotes a recording correction circuit including a pattern detection circuit 11 and an LD modulation correction circuit 12. Reference numeral 11 denotes a pattern detection circuit for detecting a predetermined pattern of the recording signal. Reference numeral 12 denotes an output from the pattern detection circuit 11 to receive a multi-value recording power. It is an LD modulation correction circuit that generates an LD modulation pulse train corresponding to the correction. The output train of the LD modulation correction circuit 12 is input to the LD driver 7 and the LD is modulated by multi-values of three or more values so that the recording correction is performed.

  The pattern detection circuit 11 is a circuit that detects how many T the recording signal sequence is with respect to the channel clock T. For example, the pattern detection circuit 11 has a continuous “1” level in the NRZI signal of 1-7 modulation code, “ The configuration is such that the number of 0 ”levels is sequentially counted by the channel clock.

  In this embodiment, paying attention to 2T having a high presence frequency in the modulation mark row, a system for correcting the recording power when the 2T recording mark is formed will be described below. The correction amount in 2T is assumed to be the same, and the recording power value when correction is performed is 1 value, that is, the case where recording correction is performed by ternary LD modulation will be described below.

  The operations of the pattern detection circuit 11 and the LD modulation correction circuit 12 will be described with reference to FIG. In the figure, (a) is a modulation signal clock, (b) is a recording pattern sequence after modulation, (c) is a 2T detection signal, (d) is an LD irradiation pulse sequence 1 after correction, and (e) is after correction. LD irradiation pulse train 2, (f) shows a corrected LD irradiation power train. The recording pattern detection circuit 11 detects a 2T recording pattern from the modulated signal clock (a) and the modulated recording pattern sequence (b). At this time, the 2T pattern is detected regardless of the polarity of the recording signal. In other words, regardless of whether “1” is continuous or “0” is continuous, all the two bits having the same polarity are detected. Based on the detected 2T pattern (c), the LD modulation correction circuit 12 deletes the first LD irradiation pulse of the pattern following 2T shown in (d), and the pattern following 2T shown in (e). An LD irradiation pulse train 2 is generated in which LD irradiation is performed only on the head of the laser beam. Upon receiving these LD irradiation pulse trains 1 and 2, the LD is modulated and irradiated onto the recording medium as shown in (f).

  A recording operation will be described with reference to FIG. In the figure, a) is a recording signal, b) a recording power pulse train output from the LD modulation correction circuit 12 and subjected to LD modulation, c) a modulation magnetic field, d) a recording mark train, and e) a reproduction signal. When a recording signal as shown in a) is recorded, the laser power is output in pulses corresponding to the correction signal as shown in b) at the start of the recording operation, and the modulated magnetic field based on a) c ) Is applied. By these operations, a recording mark row d) is formed in the cooling process of the recording medium. The shaded part and the white part represent magnetic domains having opposite magnetization directions.

  Here, the recording power sequence b) takes three recording power values of Pw1, Pw2, 0. Pw1 and 0 have the same value as the conventional recording power value, and Pw1 and Pw2 have a relationship of Pw2> Pw1.

  A description will be added regarding this. As described above with respect to the problem, the domain wall formed at the rear end of the long recording mark is formed by receiving a larger magnetic field by superimposing the stray magnetic field of the portion where the magnetization is already determined on the external modulation magnetic field. For this reason, the domain wall is formed at a lower temperature position in the temperature distribution. Accordingly, the domain wall at the rear end of the long mark is formed with a short shift mark. On the other hand, the domain wall at the rear end of the next short mark receives a smaller stray magnetic field than when a long mark is formed, resulting in the formation of a domain wall at a higher temperature position. As a result, the following short mark is formed longer. In order to reduce or improve this phenomenon, the present embodiment responds by changing the recording power. In this embodiment, by increasing the recording power of the magnetic domain wall forming portion at the rear end corresponding to the recording mark that becomes long as a result, the temperature region in which the magnetic domain is formed at this time is expanded and changed, thereby forming the domain wall. It is possible to adjust and correct so that the position is formed at a desired position.

  7A and 7B show the experimental measurement results when the recording power correction described above is performed. In (a), the horizontal axis indicates the Nth mark length measured by the time interval analyzer, the vertical axis indicates the N + 1th mark length, and 1E + 5 measurement data is plotted in dots. Yes. The intersection of the grids shown in the figure is the ideal position. Here, the 1-7 modulation code is adopted, and the same point pointed out in the problem, (N, N + 1): (8T, 2T), is compared to the case where the recording power is not corrected. It can be confirmed that the time interval distribution is distributed around the grid intersection and the edge shift is improved. Further, (b) in the figure shows a histogram of the time interval at this time. In the figure, a histogram when the recording power is not corrected for comparison is also shown. From this result, it can be confirmed that the peak position of the frequency distribution at each mark length is closer to the ideal value (each grid position). By the recording correction of this example, the jitter value σsum of the jitter distribution normalized by each mark length has been improved to σsum = 3.5 ns compared to σsum = 3.8 ns when recording correction is not performed. It could be confirmed.

  Further, FIG. 8 shows a characteristic difference in recording magnetic field strength dependency depending on whether or not recording power is corrected. In the figure, the horizontal axis represents the recording magnetic field strength, and the vertical axis represents the value obtained by normalizing the jitter value σsum value of the jitter distribution normalized by the respective mark lengths by the modulation code window width Tw. In the figure, the white plot is a characteristic of the recording magnetic field dependency of the recording correction not performed, and the black mark is the recording compensation. As shown in the figure, it can be seen that the characteristics are more excellent at a low magnetic field, and the improvement effect is great. As described above, the improved bottom characteristic not only widens various margins, but also reduces the required recording magnetic field, and more effectively acts on the drive power consumption and further the increase in modulation frequency.

  In the present embodiment, the correction of the recording power is limited to 2T, but the present invention is not limited to this. Other examples will be described with reference to FIGS. 4, 5, and 6.

  FIG. 4 shows a recording operation diagram in the case where not only 2T but also 3T portion is subjected to the recording power correction processing by the leading edge pulse of the mark following 3T in the same manner as FIG. 3, and the magnetic wall position at the rear end of the 3T mark is corrected. It is shown.

  FIG. 5 shows a recording operation diagram in the case where the magnetic domain wall position at the rear end of the 3T mark is corrected, and the recording power is corrected at a pulse position different from a). In this case, the correction amount difference between 2T and 3T is compensated, and the correction of the domain wall position at the rear end of the 3T mark is not corrected for the pulse directly acting on the domain wall formation, but preheating is performed in consideration of heat accumulation. Thus, the temperature is increased and the domain wall formation temperature distribution is corrected. For this purpose, the recording power of one pulse before the magnetic domain forming part is changed. By this method, the correction amount can be adjusted without increasing the multi-value number of the recording power.

  FIG. 6 shows a recording operation diagram in the case where correction is made to the domain wall position at the rear end of the 2T mark. In this case, the recording power of the 2T head pulse is not increased, but is acted in the decreasing direction. As a result, the domain wall at the tip of the 2T is corrected, and correction is performed in the direction in which the 2T mark is formed short.

  Although several examples have been described above, the correction method is not limited to this. For example, it is conceivable to correct the above method for all mark lengths. What kind of correction is performed depends on characteristics of the recording medium (pattern dependency), specifications on the apparatus side (recording density, cross light margin, etc.), improvement effect by correction, and multi-value of LD multi-level modulation. It may be determined in consideration of the device load due to the increase.

  In this embodiment, the pulse magnetic field modulation has been described as an example. However, the present invention is not limited to this, and the domain wall formation position is corrected based on the same idea for the magnetic field modulation recording of the type in which the LD is DC-irradiated. Is possible. In this case, similar to the timing at which the recording power of Pw2 is set in the above-described embodiment, if the LD power is set high in a convex shape during the DC irradiation of the LD, the same improvement effect as in this embodiment can be obtained. .

  Furthermore, a recording power setting method in the present invention will be mentioned. The setting of the recording power in the present invention will be described with reference to the flowchart of FIG. First, in the recording power test operation, Pw1 = Pw2 is set (S0). In this state, recording is performed while gradually changing the recording power Pw1 in the same manner as in the conventional recording power test (S1), and then the recording mark string is reproduced, and evaluation indices (for example, jitter, BER, SAM ( The optimum recording power in this state is selected as Pw1 (S2). Thereafter, recording is performed in the same manner while changing only Pw2 in a stepwise manner (S3). Thereafter, the recording mark string is reproduced, and the optimum recording power Pw2 is set using the evaluation parameters (S4). In the case of performing more corrections by multi-value recording, it is necessary to verify the magnitude of the correction effect in advance, repeat the recording power test in the order of the correction effect in the order of the correction effect, and set each correction recording power. Good.

(Second Embodiment of the Invention)
In the second embodiment of the present invention, recording correction by changing the recording pulse width and recording pulse phase will be described.

  FIG. 10 shows the configuration of the magneto-optical recording / reproducing apparatus according to the second embodiment of the present invention. A description of the same parts as those in the first embodiment of the present invention is omitted.

  In the present embodiment, the LD driver 7 is configured to be capable of LD power modulation at a binary level. In this embodiment, modulation of the LD pulse will be described with respect to pulse magnetic field modulation in which one pulse of LD irradiation is performed in one cycle of the channel clock of the modulation code.

  Reference numeral 10 denotes a recording correction circuit including a pattern detection circuit 11 and an LD pulse correction circuit 13. Reference numeral 11 denotes a pattern detection circuit for detecting a predetermined pattern of the recording signal. Reference numeral 13 denotes a pulse width of a predetermined pulse in response to the output of the pattern detection circuit 11. And / or an LD pulse correction circuit that changes the pulse phase and generates an LD modulated pulse train. The output train of the LD pulse correction circuit 13 is input to the LD driver 7 and the LD is modulated to perform recording correction.

  The recording pattern detection circuit 11 is a circuit that detects how many T the recording signal sequence is with respect to the channel clock T. For example, a continuous “1” level in the NRZI signal of 1-7 modulation code, The configuration is such that the number of “0” levels is sequentially counted by the channel clock.

  In this embodiment, paying attention to 2T having a high presence frequency in the modulation mark row, a system for correcting the LD irradiation pulse width or pulse phase when forming a 2T recording mark will be described below. The correction amount in 2T is assumed to be the same amount, and the following description will be made regarding the case where recording correction is performed.

  The operations of the recording pattern detection circuit 11 and the LD modulation correction circuit 13 will be described with reference to FIG. In the figure, (a) is the clock of the modulation signal, (b) is the recording pattern train after modulation, (c) is the 2T detection signal, (d) is the LD irradiation pulse train after correction, and (e) is the LD after correction. The irradiation power train is shown. The recording pattern detection circuit 11 detects a 2T recording pattern from the modulated signal clock (a) and the modulated recording pattern sequence (b). At this time, the 2T pattern is detected regardless of the polarity of the recording signal. In other words, regardless of whether “1” is continuous or “0” is continuous, all the two bits having the same polarity are detected. Based on the detected 2T pattern (c), the LD pulse correction circuit 12 generates an LD irradiation pulse train in which the pulse width and pulse phase of the leading LD irradiation pulse in 2T shown in (d) are changed to ΔW and δp, respectively. . Upon receiving these LD irradiation pulse trains, the LD is modulated and irradiated onto the recording medium as shown in (e).

  A recording operation will be described with reference to FIG. In the figure, a) is a recording signal, b) is a recording power pulse train output by the LD pulse correction circuit 13 and subjected to LD modulation, c) is a modulation magnetic field, d) is a recording mark train, and e) is a reproduction signal. When recording a recording signal as shown in a), the laser power is output corresponding to the correction signal as shown in b) at the start of the recording operation, and a modulated magnetic field c) based on a) is applied. Is done. By these operations, a recording mark row d) is formed in the cooling process of the recording medium. The shaded part and the white part represent magnetic domains having opposite magnetization directions.

  Here, the correction amounts ΔW (pulse width) and δp (pulse phase) of the correction LD pulse take a state where ΔW is a positive value and the pulse phase is advanced (negative value) in the case of independent correction, When both are combined, it is not limited to this, and it is desirable to determine by a recording test.

  A description will be added regarding this. As described above with respect to the problem, the domain wall formed at the rear end of the long recording mark is formed by receiving a larger magnetic field by superimposing the stray magnetic field of the portion where the magnetization is already determined on the external modulation magnetic field. For this reason, the domain wall is formed at a lower temperature position in the temperature distribution. Therefore, the domain wall at the rear end of the long mark is shifted from the desired position, and the mark is formed shorter. In this embodiment, the recording pulse width and the pulse phase are changed in order to reduce or improve this phenomenon. By changing the recording pulse width and recording pulse phase of the domain wall forming section, it is possible to change the temperature rise profile of the recording medium, and by adjusting the recording pulse width and recording pulse phase, the domain wall is formed at the desired position. It becomes possible to do.

  FIGS. 13A and 13B show the experimental measurement results when the recording pulse width and the recording pulse phase described above are corrected. In (a), the horizontal axis indicates the Nth mark length measured by the time interval analyzer, the vertical axis indicates the N + 1th mark length, and 1E + 5 measurement data is plotted in dots. Yes. The intersection of the grids shown in the figure is the ideal position. Here, 1-7 modulation code is used, and the same point pointed out in the problem, (N, N + 1): (8T, 2T) Compared to the above, it can be confirmed that the time interval distribution is distributed around the grid intersection and the edge shift is improved. Further, (b) in the figure shows a histogram of the time interval at this time. In the figure, a histogram in the case where correction of the recording pulse width / phase is not performed for comparison is also shown. From this result, it can be confirmed that the peak position of the frequency distribution at each mark length is closer to the ideal value (each grid position). According to the recording correction of the present embodiment, the jitter value σsum of the jitter distribution normalized by each mark length is improved to σsum = 3.5 ns compared to σsum = 3.8 ns when recording correction is not performed. I was able to confirm.

  In the present embodiment, the correction of the recording pulse width / phase is limited to 2T, but the present invention is not limited to this. It is also possible to correct the pulse width and the pulse phase based on the same idea as in FIGS. 4, 5, and 6 described in the first embodiment. Further, the present invention is not limited to these, and it is conceivable to correct all mark lengths. What kind of correction is performed depends on the characteristics of the recording medium (pattern dependency), the specifications on the device (recording density, cross-write margin, etc.), the improvement effect due to the correction, and the increase in the multi-level of LD multi-level modulation It may be determined in consideration of the device load due to the above.

  Furthermore, a recording power setting method in the present invention will be mentioned. The recording power setting in the present invention will be described with reference to the flowchart of FIG. First, in the recording power test operation, the pulse width and pulse phase correction values are set to zero (S0). In this state, recording is performed while gradually changing the recording power Pw in the same manner as in the conventional recording power test (S1), and then the recording mark string is reproduced and evaluation indices (for example, jitter, BER, SAM ( The optimum recording power Pw in this state is selected using (Sequenced Amplitude Margin) etc. (S2). Thereafter, recording is performed in the same manner while changing only one of the pulse width and the pulse phase in a stepwise manner (S3), and then the record mark row is reproduced and an optimum correction value is set using the evaluation parameter. (S4). Next, record in the same way while changing the correction parameter that was not changed in (S3) (S5), then play back the record mark row and set the optimum value for the other correction value using the evaluation parameter. (S6). The order of the recording test of the pulse width and pulse phase may be verified by selecting in advance parameters that are more effective. In addition, when performing individual correction for many mark lengths, the magnitude of the correction effect is verified in advance, and in the order of increasing correction effect, either the pulse width or the pulse phase is used as in the above method. The recording power test is repeated for the other parameter, and then the recording power test for the other parameter is repeated to set each correction pulse width and correction pulse phase.

It is a basic lineblock diagram of a 1st embodiment of the present invention. FIG. 3 is a schematic diagram of recording correction in the first embodiment of the present invention. FIG. 3 is a recording timing chart according to the first embodiment of the present invention. FIG. 10 is another recording timing chart in the first embodiment of the invention. FIG. 10 is another second recording timing chart in the first embodiment of the present invention. FIG. 10 is another third recording timing chart in the first embodiment of the present invention. (a) It is a time interval distribution map which shows the result of the 1st Embodiment of this invention. (b) It is a time interval histogram which shows the result of the 1st Embodiment of this invention. It is a recording magnetic field characteristic view for the result of the first embodiment of the present invention. It is a flowchart which shows the recording test of the 1st Embodiment of this invention. It is a basic block diagram of the 2nd Embodiment of this invention. It is the schematic of the recording correction | amendment in the 2nd Embodiment of this invention. FIG. 3 is a recording timing chart according to the first embodiment of the present invention. (a) It is a time interval distribution map which shows the result of the 1st Embodiment of this invention. (b) It is a time interval histogram which shows the result of the 1st Embodiment of this invention. It is a flowchart which shows the recording test of 1st Example of this invention. It is a conceptual diagram which shows the principle which becomes the basis of this invention. It is a basic composition figure of a prior art example. It is a recording timing diagram in a conventional example. FIG. 2 is a diagram illustrating the principle of reproduction of a domain wall motion type magneto-optical recording medium used in the present invention. It is a time interval distribution figure in a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 2 Substrate 3 Magneto-optical recording medium 4 Protective film 5 Optical head 6 Controller 7 LD driver 8 Magnetic head driver 9 Magnetic head 10 Recording correction circuit 11 Pattern detection circuit 12 LD modulation correction circuit 13 LD pulse correction circuit 14 Recording layer DESCRIPTION OF SYMBOLS 15 Domain wall moving layer 16 Switching layer 21 Laser beam 22 Magnetization state of recording layer 23 Intensity / direction of magnetic field applied from magnetic head 24 Floating magnetic field intensity / direction by magnetization state just before formation of domain wall 25 Floating from recording mark located in front Magnetic field strength / direction

Claims (16)

In a magneto-optical recording / reproducing method of a magnetic field modulation recording type in which information is recorded by irradiating a magneto-optical recording medium with a light beam and applying a modulation magnetic field corresponding to a recording signal.
A magneto-optical recording / reproducing method, wherein information is recorded by forming a recording mark row by changing a magnetic wall forming position by changing a temperature rise during recording of a magnetic wall position forming portion. 2. The magneto-optical recording / reproducing method according to claim 1, wherein the change in the temperature rise is performed by changing a recording power in the domain wall position forming portion. The irradiation of the light beam is irradiation of a pulsed light beam synchronized with a channel clock of a recording signal, and the change in the temperature is performed by changing a recording pulse width at the domain wall position forming portion. 2. The magneto-optical recording and reproducing method according to claim 1, wherein The irradiation of the light beam is irradiation of a pulsed light beam synchronized with the channel clock of the recording signal, and the change in the temperature rise is performed by changing the recording pulse phase at the domain wall position forming portion. 2. The magneto-optical recording and reproducing method according to claim 1, wherein The irradiation of the light beam is irradiation of a pulsed light beam synchronized with a channel clock of a recording signal, and the change in the temperature rise is performed by changing a recording pulse width in the domain wall position formation site, and 2. The magneto-optical recording / reproducing method according to claim 1, wherein the magneto-optical recording / reproducing method is performed by changing a recording power at the domain wall position forming portion. The irradiation of the light beam is irradiation of a pulsed light beam synchronized with a channel clock of a recording signal, and the change in the temperature rise is performed by changing a recording pulse phase in the domain wall position formation site, and 2. The magneto-optical recording / reproducing method according to claim 1, wherein the magneto-optical recording / reproducing method is performed by changing a recording power at the domain wall position forming portion. The irradiation of the light beam is irradiation of a pulsed light beam synchronized with a channel clock of a recording signal, and the change in the temperature rise is performed by changing a recording pulse width in the domain wall position formation site, and 2. The magneto-optical recording / reproducing method according to claim 1, wherein the magneto-optical recording / reproducing method is performed by changing a recording pulse phase in the domain wall position forming portion. The irradiation of the light beam is irradiation of a pulsed light beam synchronized with a channel clock of a recording signal, and the change in the temperature rise is performed by changing a recording pulse width at the domain wall position forming site, and 2. The magneto-optical recording / reproducing operation according to claim 1, wherein the magneto-optical recording / reproducing is performed by changing a recording pulse phase at the domain wall position forming portion and changing a recording power at the domain wall position forming portion. Method. In a magnetic field modulation recording type magneto-optical recording / reproducing apparatus that records information by irradiating a magneto-optical recording medium with a light beam and applying a modulation magnetic field corresponding to a recording signal.
It comprises means for changing the temperature rise at the time of recording of the domain wall position forming portion, and the means for changing the temperature rise changes the domain wall formation position to form a recording mark row to record information. Magneto-optical recording / reproducing apparatus. 10. The magneto-optical recording / reproducing apparatus according to claim 9, wherein the means for changing the temperature rise is performed by means for changing the recording power at the domain wall position forming portion. The light beam irradiation is a pulsed light beam irradiation synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by means for changing the recording pulse width at the domain wall position forming portion. The magneto-optical recording / reproducing apparatus according to claim 9. The irradiation of the light beam is irradiation of a pulsed light beam synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by means for changing the recording pulse phase at the domain wall position forming portion. The magneto-optical recording / reproducing apparatus according to claim 9. The irradiation of the light beam is irradiation of a pulsed light beam synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by means for changing the recording pulse width at the domain wall position formation site. 10. The magneto-optical recording / reproducing apparatus according to claim 9, wherein the magneto-optical recording / reproducing apparatus is performed by means for changing a recording power at the domain wall position forming portion. The irradiation of the light beam is irradiation of a pulsed light beam synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by means for changing the recording pulse phase at the domain wall position formation site. 10. The magneto-optical recording / reproducing apparatus according to claim 9, wherein the magneto-optical recording / reproducing apparatus is performed by means for changing a recording power at the domain wall position forming portion. The irradiation of the light beam is irradiation of a pulsed light beam synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by means for changing the recording pulse width at the domain wall position formation site. 10. The magneto-optical recording / reproducing apparatus according to claim 9, wherein the magneto-optical recording / reproducing apparatus is performed by means for changing a recording pulse phase at the domain wall position forming portion. The irradiation of the light beam is irradiation of a pulsed light beam synchronized with the channel clock of the recording signal, and the means for changing the temperature rise is performed by means for changing the recording pulse width at the domain wall position formation site. 10. The magneto-optical method according to claim 9, wherein the magneto-optical recording is performed by means for changing a recording pulse phase at the domain wall position forming portion and by means for changing a recording power at the domain wall position forming portion. Recording / playback device.

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