JP3659524B2 - Optical information recording method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical information recording method and apparatus for recording information on an information recording medium using a multivalued multi-pulse recording waveform.
[0002]
[Prior art]
FIG. 9 is a block diagram showing an example of a conventional magneto-optical recording / reproducing apparatus. FIG. 9 shows an example of an apparatus in which information can be rewritten by a light modulation overwrite method (see Japanese Patent Laid-Open No. Sho 62-175948), and as a recording method, high-density recording is possible by a pit edge recording method. ing. Note that the (1-7) modulation method is adopted as the data modulation method. In FIG. 9, reference numeral 1 denotes a magneto-optical disk as an information recording medium, in which a recording layer 3 is formed on a transparent substrate 2 such as glass or plastic, and a protective layer 4 is further formed on the surface of the recording layer 3. Yes. The magneto-optical disk 1 is supported on a rotating shaft of a spindle motor by magnet chucking or the like (not shown), and rotates at a predetermined speed by driving the spindle motor.
[0003]
An optical head for recording and reproducing information on the disk by irradiating a light beam is disposed on the lower surface of the magneto-optical disk 1. Various optical elements including a semiconductor laser 6 as a light source are provided inside the optical head. The optical head will be described. First, the light beam emitted from the semiconductor laser 6 is collimated by the collimator lens 8, then passes through the polarization beam splitter 9 and enters the objective lens 7. Then, the incident light beam is focused by the objective lens 7 and condensed on the disk 1 as a minute light spot.
[0004]
A part of the light thus collected is reflected by the disk surface and again enters the polarizing beam splitter 9 through the objective lens 7. This incident light is reflected by the polarization plane of the polarizing beam splitter 9 toward the ½λ wavelength plate 10 and separated from the incident light from the semiconductor laser 6. The separated reflected light enters the polarization beam splitter 11 via the ½λ wavelength plate 10 and is split into two light beams according to the magnetization direction of the recording layer 3. Each of the divided light beams is detected by the optical sensor 13 via the sensor lens 12, and the light reception signal of each optical sensor 13 is differentially detected by the differential amplifier 14, so that the reproduction signal becomes a magneto-optical signal. can get.
[0005]
In addition, a control optical system is provided inside the optical head so that reflected light from the disk 1 is detected, and an error signal detection circuit generates a focus error signal and a tracking error signal based on the detection signal. Is done. In the servo control circuit, the actuator 5 is driven based on these servo error signals, and the objective lens 7 is displaced in the focus direction and the tracking direction, so that the light beam from the optical head is on the recording layer 3 of the disk 1. Focus control is performed so that the light beam is focused, and tracking control is performed so that the light beam scans following the information track of the disk 1. In FIG. 9, these control optical system, error signal detection circuit, and servo control circuit are omitted.
[0006]
A magnetic head 19 is disposed on the upper surface of the magneto-optical disk 1 so as to face the optical head. The magnetic head 19 is driven by a driving current supplied from the magnetic head driver 20 and applies magnetic fields having different polarities to the disk 1 in accordance with recording and erasing of information. In this case, the magnetic head 19 applies a magnetic field having the same intensity over the entire radial direction of the disk 1, and by applying a magnetic field having a different polarity to the light beam irradiation site in accordance with recording and erasing, Record and delete information.
[0007]
The controller 17 is a main control circuit that controls each part in the apparatus, and performs rotation control of a spindle motor (not shown), control of the magnetic head driver 20, control of the LD driver 18 that is a drive circuit of the semiconductor laser 6, and the like. . Further, the controller 17 performs a modulation process for processing the recording data transferred from the external host control device into a signal suitable for recording. Since the apparatus of FIG. 9 uses the (1-7) modulation method as described above, the controller 17 (1-7) encodes the recording data accordingly, and the obtained recording signal is converted into the multipulse circuit 15. To be supplied. Here, in FIG. 9, as described above, a pit edge recording method is adopted in which information is given to the edges of the recording pits. In this case, recording is performed using a multi-valued multi-pulse recording waveform.
[0008]
9 uses a quaternary multipulse recording waveform in which recording is performed with a quaternary recording power as will be described in detail later. In the multipulse circuit 15, quaternary multipulse recording is performed in accordance with a recording signal from the controller 17. A signal is generated and supplied to the LD driver 18. The LD driver 18 has four current sources corresponding to four values, and supplies the drive current to the semiconductor laser 6 in accordance with the four-value multi-pulse recording signal, thereby controlling the recording power of the semiconductor laser 6 and on the disk 1. To record information.
[0009]
FIG. 10 is a circuit diagram showing a specific configuration of the multipulse circuit 15. In FIG. 10, (1-7) data is a recording signal after (1-7) modulation is performed by the controller 17, and a channel clock is a clock signal of a constant frequency generated by a clock generator (not shown). The recording signal is synchronized with the channel clock. One period of the channel clock is T (T: 1 channel width). The multi-pulse circuit 15 includes a logic circuit in which flip-flop circuits 100 and 101, an AND circuit 102, an inverter circuit 103, flip-flop circuits 104 and 105, an OR circuit 106, and AND circuits 107 and 108 are combined. -7) When data (recording signal) is input, modulation signals corresponding to the multilevel recording powers PH1, PH2 and PL are output accordingly. That is, the OR circuit 106 outputs a modulation signal corresponding to PH1, the AND circuit 108 outputs a modulation signal corresponding to PH2, and the flip-flop 101 outputs a modulation signal corresponding to PL. These PH1, PH2, and PL will be described in detail later.
[0010]
FIG. 11 is a time chart showing signals at various parts of the multi-pulse circuit 15 of FIG. The signals in FIGS. 11A to 11J correspond to the signals shown in FIGS. 10A to 10J. FIG. 11A shows a channel clock, and FIG. 11B shows a recording signal output from the controller 17. The recording signal is input to the flip-flop circuits 100 and 101, and the channel clock is input to the flip-flop circuit 104 via the flip-flop circuits 100, 101, 105 and the inverter circuit 103. 11C shows the output signal of the flip-flop circuit 100, FIG. 11D shows the output signal of the flip-flop circuit 101, FIG. 11E shows the output signal of the flip-flop circuit 104, and FIG. The output signal of the flip-flop circuit 105 is shown.
[0011]
The output signals of the flip-flops 104 and 105 are ORed by the OR circuit 106, and the output signal is output as a modulation signal corresponding to the recording power PH1 as shown in FIG. Further, the output signal of the flip-flop circuit 100, the output signal of the flip-flop circuit 101 (inverted output), and the output signal of the flip-flop circuit 105 (inverted output) are ANDed by the AND circuit 107, and FIG. It becomes a signal like this. This signal is ANDed with the output signal of the inverter circuit 103 by the AND circuit 108, and the output signal is output as a modulation signal corresponding to the recording power PH2 as shown in FIG. Further, the output signal (inverted output) of the flip-flop circuit 101 is output as a modulation signal corresponding to the recording power PL as shown in FIG. In this way, the multipulse circuit 15 generates modulation signals corresponding to PH1, PH2 and PL, respectively, and the obtained modulation signals are supplied to the LD driver 18 through the laser power switching line of FIG.
[0012]
In the LD driver 18, a drive current is supplied to the semiconductor laser 6 in accordance with the modulation signal from the multipulse circuit 15, whereby the light of the semiconductor laser 6 is converted into a quaternary multipulse recording waveform as shown in FIG. Information is recorded by controlling the output. In FIG. 11 (k), PL is a recording power level for forming a low temperature level state (a state causing a low temperature process disclosed in Japanese Patent Laid-Open No. 62-175948) in the recording layer 3 of the disk 1, and PH1 and PH2 are The recording power level, Pb, which forms the high temperature level state (the state causing the high temperature process disclosed in the publication), Pb is a constant value at the bottom value (reproducing power) of the recording power. Further, in the LD driver 18, the modulation signals corresponding to PH1, PH2, and PL are supplied in parallel from the multi-pulse circuit 15 as described above, and these modulation signals have priorities. In the LD driver 18, a modulation signal is selected according to the priority order, and a drive current is supplied to the semiconductor laser 6 accordingly.
[0013]
More specifically, FIGS. 11 (h), (i), and (j) are modulation signals corresponding to PH1, PH2, and PL as described above. When these modulation signals are all 1, The modulation signal with the highest priority is selected. The priority order is PH1, PH2, PL, Pb. As shown in FIGS. 11 (h) to 11 (j), when PH1 is 1, PH2 is 0, and PL is 1, the LD driver 18 is used. Then, since the PH1 and PL modulation signals are 1, a PH1 modulation signal having a higher priority is selected. Next, as shown in FIGS. 11H to 11J, when the PH1 modulation signal is 0, the PH2 modulation signal is 0, and only the PL modulation signal is 1, the only modulation signal is 1 in this case. Therefore, the modulation signal of PL is selected.
[0014]
Subsequently, when the modulation signal of PH1 is 0, the modulation signal of PH2 is 1, and the modulation signal of PL is 1, in this case, the modulation signal of PH2 having a higher priority is selected from among the modulation signals PH2 and PL of 1. Is done. In this way, the LD driver 18 selects the modulation signal. In addition, a current source corresponding to PL, PH1, PH2, and Pb is provided inside the LD driver 18, and a drive current is supplied to the semiconductor laser 6 from a current source corresponding to the selected modulation signal. As shown in FIG. 11 (k), the recording power of the semiconductor laser 6 is controlled to a quaternary multi-pulse recording waveform.
[0015]
Here, in FIG. 11 (k), PH1 is 1.5T and PH2 is turned on and off at intervals of 0.5T, and one cycle of PH2 pulse lighting corresponds to the length of 1T of the pit. Yes. In the example of FIG. 11, the top multi-pulse recording waveform shows a recording waveform when 3T pits are recorded. By turning on 0.5T PH2 for one period after 1.5T PH1, FIG. As shown in l), 3T pits are recorded on the information track of the disc 1. In the example of FIG. 11, 0.5T Pb is provided before PH1, and 1.0T Pb is provided after PH2, but these front and rear Pb are called cooling gaps. . Next, a 1.5T PH1 and 0.5T PH2 two-cycle recording waveform corresponds to 4T pits, and the next 1.5T PH1 recording waveform corresponds to 2T pits. By irradiating a light beam having a pulse recording waveform, 4T pits and 2T pits can be recorded as shown in FIG.
[0016]
In FIG. 11, only 2T to 4T recording waveforms are shown, but when 5T pits are recorded, PH2 of 0.5T interval is 3 periods after PH1 of 1.5T, and PH1 is the same for 6T pits below. PH2 is 4 cycles, PH2 is 5 cycles for 7T pits, and PH2 is 6 cycles for 8T pits. (1-7) In modulation, the shortest pit is 2T, and the longest pit is 8T. Thus, recording from the shortest pit to the longest pit is performed by using the multi-pulse recording waveform corresponding to the pit length as described above. Can do. Thus, by turning on PH1 and then turning on PH2 in pulses, the temperature of the recording medium can be maintained at a predetermined temperature, and an excessive rise in temperature can be prevented. The pit edge recording is a recording method in which information is given to the position of the pit edge as described above. However, in the recording method using the quaternary multi-pulse recording waveform as described above, the fluctuation of the pit edge can be suppressed. In particular, it can be suitably used for pit edge recording.
[0017]
Next, when reproducing the information recorded on the magneto-optical disk 1, the LD driver 18 controls the recording power of the semiconductor laser 6 to a constant reproduction power (Pr) based on the control of the controller 17, and this reproduction power. Are scanned onto the target information track. At this time, a magneto-optical signal is obtained from the differential amplifier 14 as described above, and the magneto-optical signal is binarized in a signal processing circuit (not shown), and further, predetermined signal processing is performed using the binarized signal. As a result, reproduction data can be obtained and recorded information can be reproduced.
[0018]
[Problems to be solved by the invention]
By the way, in the conventional magneto-optical recording / reproducing apparatus, if the recording medium is different, the thermal structure is also different, so that the recording characteristics vary depending on the recording medium, and the accuracy of the pit edge position also changes. Therefore, in order to prevent this, it is necessary to adjust the recording power level such as PH1 and PH2 according to the recording medium. However, in pit edge recording, since the accuracy of the pit edge position is particularly required, the power level of PH1 and PH2 needs more precise control, and the drive current to the semiconductor laser of the LD driver is also highly accurate. Required. For this reason, when the recording power levels of PH1 and PH2 are controlled in this way, there is a problem that the control load of the control circuit increases and the scale of the control circuit also increases.
[0019]
Therefore, in view of the above-described conventional problems, an object of the present invention is to provide an optical information recording method and apparatus capable of reducing the control load and optimally adjusting the light output of a light source with a simple configuration. Is.
[0020]
[Means for Solving the Problems]
An object of the present invention is to multi-pulse the light output of a light source in accordance with a recording signal and a clock signal having a constant frequency synchronized with the recording signal, and irradiate the information recording medium with the light beam of the multi-pulsed light output. In the optical information recording method for recording a mark corresponding to the recording signal, The clock signal includes a first light output for recording a mark having a predetermined length of the multi-pulsed light output, and then a second light periodically irradiated according to the length of the mark. A first clock signal and a second clock signal respectively corresponding to the outputs, and by changing the duty of the first clock signal and the second clock signal, respectively, the first and second optical outputs Changing the pulse width This is achieved by an optical information recording method.
[0021]
Another object of the present invention is to provide means for converting the light output of the light source into a multi-pulse in accordance with a recording signal and a clock signal synchronized with the recording signal, and recording the light beam of the multi-pulsed light output for information recording. In an optical information recording apparatus for recording a mark corresponding to the recording signal by irradiating the medium, The clock signal includes a first light output for recording a mark having a predetermined length of the multi-pulsed light output, and then a second light periodically irradiated according to the length of the mark. A first clock signal and a second clock signal respectively corresponding to the outputs, and the pulse widths of the first and second optical outputs are changed by changing the duties of the first and second clock signals, respectively. Has control means to change This is achieved by an optical information recording apparatus characterized by the above.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In this embodiment, it is assumed that the magneto-optical disk 1 as a recording medium rotates at a constant linear velocity. In FIG. 1, the same parts as those of the conventional apparatus of FIG. That is, the magneto-optical disk 1, the magnetic head 19, and the magnetic head driver 20 are the same as those in FIG. An optical head for recording and reproducing information on the disk 1 is the same, and a semiconductor laser 6, a collimator lens 8, a polarizing beam splitter 9, an objective lens 7, an actuator 5, and a 1 / 2λ wavelength plate 10 provided therein. The polarizing beam splitter 11, the condensing lens 12, and the optical sensor 13 are the same as those in FIG.
[0023]
The light beam emitted from the semiconductor laser 6 is focused by the objective lens 7 and condensed on the magneto-optical disk 1 as a minute light spot. In this case, also in FIG. 1, an error signal detection circuit that detects a focus error signal and a tracking error signal based on the reflected light from the disk 1, and a servo that performs focus control and tracking control based on these servo error signals. A control circuit is provided. Then, the light beam emitted from the optical head by the control operation of the servo control circuit is controlled so as to follow the information track of the rotating disk 1 while keeping the focused state on the recording layer 3. .
[0024]
In the present embodiment, an envelope detection circuit 21 that detects the envelope of the magneto-optical signal output from the differential amplifier 14, a binarization circuit 22 that binarizes the magneto-optical signal, and a binary signal mark and space A phase comparator 23 is provided for outputting a signal corresponding to the length of the signal. These circuits are used to adjust the recording power of the semiconductor laser 6 by changing the pulse width of the multi-pulse recording waveform as will be described in detail later. The envelope detection circuit 21 has a peak detection circuit for detecting the peak value of the magneto-optical signal, a bottom detection circuit for detecting the bottom value, and an intermediate value based on the peak value and the bottom value obtained by the two detection circuits. It consists of an output circuit. An intermediate value between the peak value and the bottom value of the magneto-optical signal obtained by the envelope detection circuit 21 is output as a slice level to the binarization circuit 22, and the binarization circuit 22 uses this intermediate value to output the magneto-optical signal 2. It is priced. In the phase comparator 23, the pulse width of the mark and space of the binarized signal is detected, and a signal corresponding to the difference between the pulse widths is output. A signal corresponding to the difference in pulse width is sent to the multipulse circuit 15 as an electric signal such as a voltage.
[0025]
The multipulse circuit 15 is a circuit that generates a multipulse signal according to the recording signal modulated by (1-7) modulation as described above. In the present embodiment, as described above, a signal corresponding to the difference between the pulse widths of the mark and the space is fed back from the phase comparator 23 to the multipulse circuit 15, and the multipulse circuit 15 performs multipulse recording in accordance with this signal. The pulse width of the waveform is variable. The configuration and operation of the multipulse circuit 15 will be described in detail later. The LD driver 18 is the same as that shown in FIG. 9 and is a laser drive circuit for driving the semiconductor laser 6 in accordance with the multipulse signal sent from the multipulse circuit 15. Reference numeral 16 denotes a temperature sensor provided close to the disk 1. The temperature sensor 16 will be described later in detail.
[0026]
The controller 17 is a main controller of the magneto-optical recording apparatus of this embodiment, and controls the rotation of the magneto-optical disk 1 by controlling a spindle motor (not shown), and records, erases and reproduces the magnetic head driver 20. The magnetic field of the magnetic head 19 is controlled according to the operation mode. The controller 17 also controls the LD driver 18 to set the recording power of the semiconductor laser 6 during recording and reproduction, and seek control to seek the optical head to the target information track of the disk 1. Further, the controller 17 modulates the recording data by (1-7) to generate a recording signal and a channel clock. In this manner, the controller 17 controls information recording on the disk 1 and reproduction of recorded information by controlling data processing and each unit in the apparatus. As will be described in detail later, the controller 17 performs control for optimally adjusting the pulse width of the multi-pulse recording waveform in accordance with the characteristics of the disk 1 when the disk 1 is set in the apparatus.
[0027]
FIG. 2 is a circuit diagram showing a specific example of the multi-pulse circuit 15 used in this embodiment. In FIG. 2, first, channel clocks CK 1 and CK 2 are clock signals generated from the channel clock sent from the controller 17 and the output signal of the phase comparator 23. 2 is provided with a sawtooth signal generation circuit (not shown) that generates a sawtooth signal having the same frequency as that based on the channel clock from the controller 17. Two channel clocks CK1 and CK2 having the same frequency and different duties are generated by binarizing the state signal using two comparators at different slice levels.
[0028]
The two slice levels change in accordance with the output signal of the phase comparator 23, and the duty of the two channel clocks CK1 and CK2 changes in accordance with the change. As another method of changing the duty of the channel clocks CK1 and CK2, for example, a programmable pulse generator is used to input a reference clock as a trigger, and the program is preliminarily programmed according to the output of the phase comparator 23. It is also possible to obtain a clock with a specified duty.
[0029]
The multipulse circuit 15 in FIG. 2 will be further described. 2, the same parts as those in the multi-pulse circuit of FIG. 10 are denoted by the same reference numerals, and flip-flop circuits 100, 101, 104, 105, AND circuits 102, 107, 108, an inverter circuit 103, and an OR circuit 106 are shown. Is the same as FIG. However, in FIG. 10, the output of the inverter circuit 103 and the AND circuit 107 is ANDed with the AND circuit 108 to obtain a modulation signal corresponding to PH2, but in this embodiment, an inverter circuit 109 is newly provided. The AND circuit 108 obtains a PH2 modulation signal by taking the logical product of the output of the inverter circuit 109 and the output of the AND circuit 107.
[0030]
The channel clock CK1 described above is input to the flip-flop circuit 104 via the flip-flop circuits 100, 101, and 105 and the inverter circuit 103, and the channel clock CK2 is input to the inverter circuit 109. Then, the (1-7) modulated recording signal is input to the flip-flop circuits 101 and 102, and a multi-pulse modulation signal corresponding to the recording signal is generated. That is, the OR circuit 106 outputs a modulation signal corresponding to PH1, the AND circuit 108 outputs a modulation signal corresponding to PH2, and the inverted output of the flip-flop circuit 101 outputs a modulation signal corresponding to PL.
[0031]
FIG. 3 is a time chart showing signals of each part of the multi-pulse circuit 15. FIG. 3 shows signals of respective parts after the pulse widths of PH1 and PH2 are adjusted according to the medium characteristics. Further, FIG. 3 shows signals when a medium having characteristics of slow thermal diffusion and large heat accumulation is used as a characteristic of the recording medium. In this embodiment, the control is performed so as to optimally form the recording mark by adjusting the pulse widths of PH1 and PH2 of the multi-pulse recording waveform. A method for adjusting the pulse width of the multi-pulse recording waveform will be described in detail later. To do. FIG. 3A shows the sawtooth signal output from the sawtooth signal generation circuit as described above.
[0032]
This sawtooth signal is compared with slice levels having different levels as shown in FIG. 3A by two comparators, and as a result, the channel clock CK1 as shown in FIG. 3B and as shown in FIG. 3C. A channel clock CK2 is generated. As described above, the duty of the channel clocks CK1 and CK2 changes in accordance with the output signal of the phase comparator 23, whereby the pulse widths of the multi-pulse recording waveforms PH1 and PH2 change. FIG. 3D shows a (1-7) modulated recording signal.
[0033]
3 (e) is an output signal of the flip-flop circuit 100 in the multi-pulse circuit 2, FIG. 3 (f) is an output signal (normal output) of the flip-flop circuit 101, and FIG. 3 (g) is a flip-flop. The output signal of the circuit 104 and FIG. 3H show the output signal of the flip-flop circuit 105 (normal output). The output signal of the flip-flop circuit 104 in FIG. 3 (g) and the output signal of the flip-flop circuit 105 in FIG. 3 (h) are ORed by the OR circuit 106, and the output is PH1 as shown in FIG. 3 (j). Is output as a modulation signal corresponding to. Also, the AND circuit 108 ANDs the output signal of the AND circuit 107 in FIG. 3I and the signal obtained by inverting the channel clock CK2 in FIG. Thus, a modulation signal corresponding to PH2 is output. Further, the output signal (inverted output) of the flip-flop circuit 101 is directly output as a modulation signal corresponding to PL as shown in FIG.
[0034]
The multipulse modulation signal generated by the multipulse circuit 15 in this way is supplied in parallel to the LD driver 18. As described above, the LD driver 18 has four current sources corresponding to PL, PH1, PH2, and Pb. When these modulation signals are 1, according to the priority order determined in advance as described above. A modulation signal is selected, and a driving current is supplied to the semiconductor laser 6 from a current source corresponding to the modulation signal. As a result, the recording power of the semiconductor laser 6 is controlled to a quaternary multi-pulse recording waveform corresponding to the recording signal as shown in FIG. Then, by irradiating the disc 1 with a light beam having such a recording waveform, a recording pit corresponding to the recording signal is recorded as shown in FIG.
[0035]
Here, in FIG. 3, as described above, it has been described that the signal is a signal when a medium having a slow thermal diffusion and a large thermal accumulation is used as a characteristic of the recording medium. The duty of CK1 is reduced and the pulse width of PH1 is increased. That is, in this case, since the thermal diffusion of the recording medium is slow and the heat accumulation is large, the recording power is substantially increased by extending the PH1 pulse width, thereby substantially increasing the recording power. The formation of the recording mark is controlled so that the temperature rise of the medium at the tip is advanced and the tip portion of the pit can be recorded in an appropriate shape. FIG. 3 (k) shows a modulation signal corresponding to the conventional PH1, that is, the modulation signal when the duty of the channel clock CK2 is 50%. As is apparent from a comparison between this and the modulation signal corresponding to PH1 of this embodiment in FIG. 3 (j), the pulse width of PH1 in FIG. 3 (j) is wider, and the difference in pulse width is This corresponds to an increase in the pulse width of PH1.
[0036]
On the other hand, the duty of the channel clock CK2 is increased, and accordingly, the pulse width of PH2 is decreased. That is, in this case, since the thermal diffusion of the recording medium is slow and the heat accumulation is large, the pulse width of PH2 is narrowed, the irradiation time of PH2 is shortened, and the recording power is substantially reduced, so The formation of the recording mark is controlled so that an increase in the medium temperature at the rear end portion can be suppressed and the proper shape can be recorded at the rear end portion of the pit. FIG. 3 (m) shows a conventional modulation signal corresponding to PH2, that is, a modulation signal when the duty of the channel clock CK1 is 50%. As apparent from comparison with FIG. 3 (l), FIG. The 3 (l) PH1 modulation signal is narrower, and the difference corresponds to the decrease in the PH1 pulse width. FIG. 3 (o) shows a modulation signal corresponding to a conventional PL, which is the same as FIG. 3 (n) of the present embodiment. In this way, by controlling the pulse widths of PH1 and PH2 of the multi-pulse recording waveform according to the characteristics of the recording medium as shown in FIG. 3 (p), the lengths of the respective lengths as shown in FIG. 3 (q) are obtained. The recording mark can be recorded in an appropriate shape.
[0037]
Next, in contrast to the previous recording medium, the pulse widths of PH1 and PH2 are controlled in the opposite direction in the recording medium having the characteristics of fast thermal diffusion and small heat accumulation. FIG. 4 is a time chart showing signals of the respective parts at this time. 4A to 4Q correspond to FIGS. 3A to 3Q, respectively. First, the channel clock CK1 changes so that the duty increases as shown in FIG. Along with this, the pulse width of the PH1 modulation signal becomes narrower as shown in FIG. 4 (j), and the pulse width of PH1 of the multi-pulse recording waveform also changes in the direction of becoming narrower as shown in FIG. 4 (p). In other words, in this case, since the thermal diffusion of the medium is fast and the heat accumulation is small, an increase in the medium temperature at the pit tip is suppressed by narrowing the pulse width of PH1, and the shape of the pit tip is recorded in an appropriate shape. It controls to be able to.
[0038]
Next, the channel clock CK2 changes so that the duty becomes small as shown in FIG. 4C, and accordingly, the pulse width of PH2 of the multi-pulse recording waveform also widens as shown in FIG. 4P. . In this case, since the thermal diffusion of the medium is fast and the heat accumulation is small, a decrease in the temperature of the medium is suppressed by widening the pulse width of PH2, and the pit shape is recorded in an appropriate shape at the pit rear end. To control. As a result, the recording mark is recorded in an appropriate shape as shown in FIG. Needless to say, depending on the characteristics of the medium, the pulse widths of PH1 and PH2 can both be widened, and the pulse widths of PH1 and PH2 can both be narrowed. As described above, in this embodiment, the recording mark is controlled so as to be properly recorded by varying the pulse width of the multi-value multi-pulse recording waveform in accordance with the characteristics of the recording medium.
[0039]
Therefore, a specific method for adjusting the pulse width of the multi-pulse recording waveform of this embodiment will be described with reference to FIGS. This adjustment of the pulse width is performed, for example, when the disk 1 is set in the apparatus. In this embodiment, the adjustment when a medium having a slow thermal diffusion and a large heat accumulation is used as a characteristic of the recording medium will be described as an example. First, when the disk 1 is set, the controller 17 controls the multipulse circuit 15 to set the duty of the channel clocks CK1 and CK2 to a predetermined duty. In the present embodiment, as shown in FIGS. 5A and 5B, the duty of the channel clocks CK1 and CK2 is set to 50%. Next, the controller 17 causes the optical head to seek to a predetermined write test area of the disk 1, and when it reaches the write test area, it controls each part to record a predetermined signal.
[0040]
The signal to be recorded is preferably a pattern in which the asymmetry of the reproduced signal appears clearly when it is reproduced, that is, a pattern in which the difference in the intermediate value of the reproduced signal appears clearly. In this embodiment, (1-7) 8T mark and space which are the longest pits of modulation and 2T mark and space which are the shortest pits are recorded. FIG. 5C shows the (1-7) modulated 8T mark, 8T space, 2T mark, and 2T space recording signals at this time, and FIG. 5D shows the multipulse recording waveform of the semiconductor laser 6 at this time. Show. When the disk 1 is irradiated with the light beam having this multi-pulse recording waveform and a magnetic field in a certain direction is simultaneously applied from the magnetic head 19, the 8T mark, 8T space, 2T space, 2T mark and the 2T mark are recorded as shown in FIG. Is done. In FIG. 5 (e), as described above, the medium has a slow thermal diffusion and a large heat accumulation. Therefore, the 8T mark has a teardrop shape with a narrow tip and then gradually spreading toward the rear, and also in the 2T mark. It is shorter than the ideal mark.
[0041]
When the recording is completed, the controller 17 controls each part to move the optical head to the head position of the previously recorded light test area and scans the light test area with the reproduction light beam, thereby recording the recorded signal. Perform playback. At this time, as shown in FIG. 5 (f), the reproduction signal is reproduced from the differential amplifier 14 as a magneto-optical signal and sent to the envelope detection circuit 21 and the binarization circuit 22. Here, regarding the reproduction signal of FIG. 5F, the amplitude of the reproduction signal of the 2T mark is naturally small because the 2T mark is small. Therefore, the intermediate value of the reproduction signal amplitude of the 2T mark is offset to the negative side of the intermediate value of the reproduction signal amplitude of the 8T mark, and asymmetry is large as described above.
[0042]
The envelope detection circuit 21 detects an intermediate value of the amplitude of the reproduction signal, and the binarization circuit 22 binarizes the reproduction signal using the intermediate value as a slice level. That is, the reproduction signal of 8T mark and 8T space is a slice level with an intermediate amplitude value as shown in FIG. 5 (f), and the reproduction signal of 2T mark and 2T space is also binary at the slice level of an intermediate value of the amplitude. It becomes. The phase comparator 23 uses the reference clock from the controller 17 to detect the pulse width difference between the binary signals of the 8T mark and the 8T space, and the signal corresponding to the difference between the pulse width of the mark and the space is converted into a multi-pulse. It is output to the circuit 15. Similarly, a difference between the pulse widths of the 2T mark and 2T space binarized signals is detected, and a signal corresponding to the difference is output to the multipulse circuit 15.
[0043]
In the multi-pulse circuit 15, the duty of the channel clocks CK1 and CK2 changes according to the output signal of the phase comparator 23, and the pulse widths of the modulated signals PH1 and PH2 change accordingly. At this time, the duty of the channel clocks CK1 and CK2 changes in a direction in which the difference between the pulse widths of the 8T mark and the 8T space and the difference between the pulse widths of the 2T mark and the 2T space respectively decrease. The pulse width of each modulation signal also changes in such a direction that the difference between the pulse widths of the preceding mark and space disappears.
[0044]
More specifically, for example, a channel clock in a direction in which there is no difference in the pulse widths of the binary signals of 8T mark and 8T space. CK2 The duty cycle of PH2 is changed to change the pulse width of PH2, and then the channel clock is shifted in such a direction that there is no difference between the pulse widths of the 2T mark and 2T space binary signals. CK1 The pulse width of PH1 is changed by changing the duty cycle.
[0045]
When these series of operations are completed, the controller 17 controls each part in the same manner as described above, and again records the 8T mark, 8T space, 2T mark, and 2T space on the disc 1, and reproduces them to reproduce the 8T mark. Pulse of PH1 and PH2 by changing the duty of channel clocks CK1 and CK2 in such a direction that there is no difference between the pulse width of binary signal of 2T mark and 2T space, and the difference of pulse width of binary signal of 2T mark and 2T space Change the width. In this way, a series of operations such as recording, reproduction, and adjustment of the pulse widths of PH1 and PH2 by changing the duty of channel clocks CK1 and CK2 are repeated, and the difference between the pulse widths of the 8T mark and 8T space binary signals, and When the difference between the pulse widths of the 2T mark and the 2T space binarized signal disappears, the adjustment of the pulse widths of PH1 and PH2 ends.
[0046]
FIG. 6 is a diagram showing signals at various parts after the adjustment of the pulse widths of PH1 and PH2 is completed. FIGS. 6A to 6F correspond to FIGS. 5A to 5F before the adjustment, respectively. The channel clock CK1 has a small duty as shown in FIG. 6A, and the channel clock CK2 has a large duty as shown in FIG. 6B. As the channel clocks CK1 and CK2 change, the pulse width of PH1 is wide and the pulse width of PH2 is narrow as shown in FIG. 6 (d).
[0047]
That is, in the present embodiment, as described above, since the medium has a slow thermal diffusion and a large thermal accumulation, the duty of the channel clock CK1 is reduced to form the 2T mark or the 8T mark tip. The width is increased, and the irradiation time of PH1 is adjusted accordingly. Further, the duty of the channel clock CK2 is increased to reduce the pulse width of PH2 for forming the marks after the 2T mark, and the irradiation time of PH2 is adjusted correspondingly. By adjusting the pulse widths of PH1 and PH2 in this way, as described with reference to FIG. 3, the temperature rise of the medium at the leading edge of the mark is accelerated, and the temperature rise of the medium is suppressed up to the trailing edge of the mark thereafter. Therefore, as shown in FIG. 6E, it can be seen that the 8T mark is recorded in an appropriate shape without becoming a teardrop shape. It can also be seen that the 2T mark is recorded in an appropriate shape without being reduced in shape. Therefore, when the recording mark of FIG. 6E is reproduced, the intermediate values of the amplitudes of the reproduction signal of the 8T mark and 8T space and the reproduction signal of the 2T mark and 2T space coincide as shown in FIG. 6F. A reproduction signal without asymmetry can be obtained.
[0048]
In this embodiment, the pulse widths of PH1 and PH2 of the multi-pulse recording waveform are adjusted according to the characteristics of the recording medium. By adjusting the irradiation time width of the light beam of the semiconductor laser optimally, the shape of the recording mark can be controlled to be an appropriate shape. Therefore, the shape of the recording mark does not become a teardrop shape or smaller than an appropriate shape, and recording can be performed in an appropriate shape regardless of the characteristics of the recording medium. Therefore, it is possible to obtain a reproduction signal with a low error rate, and it can be suitably used particularly for pit edge recording in which information is given to the pit edge. Moreover, since the irradiation time width of the semiconductor laser light beam is adjusted by changing the pulse width of the multi-pulse recording waveform, it is controlled compared to the conventional method of adjusting the laser power value by controlling the current of the LD driver. The load can be reduced and the adjustment can be made with a simple configuration.
[0049]
Next, in FIG. 1, the temperature sensor 16 is disposed close to the lower surface of the disk 1 as described above, and the adjustment of the pulse width of the multi-pulse recording waveform according to the temperature detected by the temperature sensor 16 will be described below. . The temperature sensor 16 detects the environmental temperature of the apparatus, particularly the ambient temperature in the vicinity of the laser irradiation portion of the disk 1, and the controller 17 constantly monitors the temperature detected by the temperature sensor 16. Here, in this embodiment, for example, every time the temperature changes by 5 ° C., the pulse widths of PH1 and PH2 of the multi-pulse recording waveform are readjusted. For example, when the temperature at the previous adjustment is 25 ° C. and rises to 30 ° C., the controller 17 controls each part in the same manner as described above to adjust the pulse widths of PH1 and PH2. Thus, by adjusting the pulse widths of PH1 and PH2 according to the temperature, stable recording can be performed regardless of the temperature change.
[0050]
When adjusting the pulse widths of PH1 and PH2, a normal information recording / reproducing apparatus needs to repeatedly perform operations such as recording, reproduction, and adjustment of the pulse width based on the mark and space of the reproduction signal as described above. However, in an information recording / reproducing apparatus having a direct verify function using two beams or the like, reproduction is performed almost simultaneously with recording each time recording is performed so that the difference between the binary signal mark and space pulse width is eliminated. A method of feeding back to the pulse widths of PH1 and PH2 can be adopted. Therefore, in such an apparatus, one adjustment can be completed during the operation of recording, so that the pulse width can be adjusted in a short time. The power value of the semiconductor laser is set to four values Pb, PL, PH1, and PH2. However, the same method is used when multipulse recording is performed by setting these values to three values, that is, PH1 and PH2. Then, the pulse width of the multi-pulse recording waveform can be adjusted. Furthermore, the adjustment of the pulse width of the multi-pulse recording waveform as described above may be performed not only when the disk is replaced, but also before recording, or may be performed periodically at regular intervals after the disk is inserted. Needless to say.
[0051]
Next, an embodiment in which the disk 1 rotates at a constant angular velocity as in the CAV method or the zone CAV method will be described. In this embodiment, the pulse widths of PH1 and PH2 of the multi-pulse recording waveform are adjusted at the plurality of radial positions of the disk 1 by the method as described above, and the values of the pulse widths at that time are stored in the memory. When data is recorded in 1, the pulse width of PH1 and PH2 is adjusted according to the radial position of the disk 1 using the value. By doing this, when the disk 1 rotates at a constant angular velocity and the recording position of the disk 1 changes from the inner circumference to the outer circumference, the same recording power is obtained over the entire area of the disk 1 without changing the power values of PH1 and PH2. In this way, stable recording is performed.
[0052]
More specifically, first, recording power values such as PH1 and PH2 are set so that ideal recording marks can be recorded with the channel clocks CK1 and CK2 around 50% in the middle circumference area of the disc 1, respectively. deep. That is, this is because the linear velocity is slow at the inner circumference of the disk 1 and the recording pulse width of the multi-pulse recording waveform is narrowed because less energy is required to form the recording mark, and the linear velocity is faster at the outer circumference. Therefore, since a large amount of energy is required to form a recording mark, it is necessary to change the duty of the channel clock in the direction of widening the pulse width. For example, this is based on the reason that a wide dynamic range can be taken when adjusting the pulse widths of PH1 and PH2. The pulse widths of PH1 and PH2 at this time are stored in the memory.
[0053]
Next, the pulse width difference of the 8T mark and 8T space binarized signal, and the 2T mark and 2T space binarized signal at predetermined positions on the inner and outer circumferences of the disk 1 in exactly the same manner as in the previous embodiment. The pulse widths of PH1 and PH2 of the multi-pulse recording waveform are adjusted so that the difference in pulse width is eliminated, and the obtained pulse width value is stored in the memory. When the pulse widths of PH1 and PH2 at the inner, middle, and outer circumferences of the disk 1 are stored in the memory as described above and data is actually recorded on the disk 1, PH1 and PH2 according to the recording radius position of the disk 1 are recorded. Are obtained by interpolating the pulse widths at the inner, middle, and outer circumferences stored in the memory, and the pulse widths of PH1 and PH2 are adjusted to the obtained values.
[0054]
FIG. 7 is a diagram showing signals at various portions when recording is performed on the inner circumference of the disk 1 with the pulse width adjusted as described above. 7A shows the channel clock CK1, FIG. 7B shows the channel clock CK2, and FIG. 7C shows the (1-7) modulated recording signal. 7D is an output signal of the flip-flop circuit 100 in the multipulse circuit 15 of FIG. 2, FIG. 7E is an output signal of the flip-flop circuit 101, and FIG. 7F is a flip-flop circuit 104. 7 (g) shows the output signal of the flip-flop circuit 105, and FIG. 7 (h) shows the output signal of the AND circuit 107.
[0055]
On the inner periphery of the disk 1, the duty of the channel clocks CK1 and CK2 changes as shown in FIGS. 7A and 7B, and accompanying this, the modulated signals of PH1 and PH2 are also shown in FIGS. k), the pulse widths of PH1 and PH2 of the multi-pulse recording waveform are narrower than when the duty of the channel clocks CK1 and CK2 is 50% as shown in FIG. 7 (o). That is, since the linear velocity is low at the inner circumference of the disk 1 and less energy is required to form the recording mark, the pulse widths of PH1 and PH2 are larger than the pulse width at the middle circumference of the disk 1 as shown in FIG. Is also narrower. Thus, PH1 and PH2 are adjusted to the optimum pulse width according to the recording radius position of the disk 1, and the mark is recorded in an appropriate shape as shown in FIG. 7 (j), FIG. 7 (l), and FIG. 7 (n) show PH1, PH2, and PL modulated signals when the channel clocks CK1 and CK2 have a duty of 50%, respectively.
[0056]
FIG. 8 is a diagram showing signals at various parts when recording is performed on the outer periphery of the disk 1 by adjusting the pulse widths of PH1 and PH2 as described above. FIGS. 8A to 8P correspond to FIGS. 7A to 7P, respectively. At the outer periphery of the disk 1, the duty of the channel clocks CK1 and CK2 changes in the opposite direction to that at the inner periphery as shown in FIGS. 8 (a) and 8 (b). As shown in FIG. 8 (o), the channel clocks CK1 and CK2 are wider than when the duty is 50%. That is, at the outer periphery of the disk 1, the linear velocity is fast and a lot of energy is required to form a mark, so that the pulse widths of PH 1 and PH 2 are wider than the pulse width at the intermediate periphery of the disk 1. Also in this case, since the pulse widths of PH1 and PH2 are adjusted to the optimum values according to the recording radius position of the disc 1, the mark can be recorded in an appropriate shape as shown in FIG.
[0057]
In the above embodiment, it has been described that the pulse widths of PH1 and PH2 are adjusted on the inner circumference, the middle circumference, and the outer circumference of the disk 1. However, the pulse width is adjusted for each predetermined radial position with a narrower interval than that. It is desirable to store the pulse width at the position in the memory and to interpolate the pulse width at each radial position of the disk based on that. Also in this embodiment, similarly to the previous embodiment, the controller 17 monitors the temperature detected by the temperature sensor 16, and when the temperature changes by a predetermined temperature, the duty of the channel clocks CK1 and CK2 is changed to PH1 and PH2. The pulse width of is adjusted again.
[0058]
Further, in this embodiment, as in the previous embodiment, the adjustment of the pulse width at a predetermined recording radius position of the disk 1 is performed when the disk 1 is inserted, before recording, or at regular intervals. Needless to say, this embodiment can also be applied to the case of ternary recording power as in the previous embodiment. Further, in the optical modulation overwrite method, when the recording power PL has a function of generating a low temperature process as in this embodiment, in order to optimize the power, the PL power is changed according to the linear velocity of the disk 1. It is desirable to control the value.
[0059]
【The invention's effect】
As described above, the present invention has the following effects.
(1) By changing the pulse width of the multi-pulse recording waveform by changing the duty of the clock signal, the control load of the light output of the light source can be greatly reduced compared to the conventional one, and optimal adjustment is made with a simple circuit configuration. be able to.
(2) By adjusting the pulse width of the multi-pulse recording waveform according to the characteristics of the recording medium, the recording mark can always be recorded in an appropriate shape regardless of the characteristics of the recording medium, and highly reliable information can be recorded. Can be realized.
(3) By adjusting the pulse width of the multi-pulse recording waveform in accordance with the linear velocity of the recording medium, the recording power can be controlled uniformly over the entire area of the recording medium, and the recording mark can be set appropriately regardless of the recording position. The shape can be recorded.
(4) By adjusting the pulse width of the multi-pulse recording waveform according to the environmental temperature, it is possible to always record an appropriate mark regardless of the temperature change.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of an optical information recording apparatus of the present invention.
FIG. 2 is a circuit diagram showing a specific example of the multi-pulse circuit of the embodiment of FIG.
FIG. 3 is a time chart for explaining the operation of the embodiment of FIGS. 1 and 2 as an example in the case of using a medium having a slow thermal diffusion and a large heat accumulation.
4 is a time chart for explaining the operation of the embodiment of FIGS. 1 and 2 as an example in the case of using a medium with quick thermal diffusion and small heat accumulation. FIG.
FIG. 5 is a diagram for explaining a method of adjusting a pulse width of a multi-pulse recording waveform according to the present invention.
FIG. 6 is a diagram showing a signal of each part after adjustment of a pulse width of a multi-pulse recording waveform, a recording mark, and a reproduction signal.
FIG. 7 is a diagram showing signals of respective parts at the inner peripheral position when the pulse width is adjusted according to the recording radius position when the disk rotates at a constant angular velocity in another embodiment of the present invention. .
FIG. 8 is a diagram showing signals of respective portions at the outer peripheral position when the pulse width is adjusted in accordance with the recording radius position when the disk rotates at a constant angular velocity in another embodiment of the present invention.
FIG. 9 is a block diagram showing a conventional magneto-optical recording / reproducing apparatus.
10 is a circuit diagram showing in detail the multi-pulse circuit of FIG. 9;
FIG. 11 is a time chart showing signals at various parts in FIGS. 9 and 10;
[Explanation of symbols]
1 Magneto-optical disk
3 Recording layer
5 Actuator
6 Semiconductor laser
7 Objective lens
13 Optical sensor
14 Differential amplifier
15 Multi-pulse circuit
16 Temperature sensor
17 Controller
18 LD driver
19 Magnetic head
20 Magnetic head driver
21 Envelope detection circuit
22 Binarization circuit
23 phase comparator
100, 101, 104, 105 flip-flop circuit
102, 107, 108 AND circuit
103,109 Inverter circuit
106 OR circuit

Claims (12)

The optical output of the light source is multipulsed in accordance with a recording signal and a clock signal having a constant frequency synchronized with the recording signal, and the information recording medium is irradiated with the light beam of the multipulsed optical output, whereby the recording signal In the optical information recording method for recording a mark corresponding to the first signal , the clock signal includes a first light output for recording a mark having a predetermined length of the multipulsed light output, and a length of the mark following the first light output. The first clock signal and the second clock signal respectively corresponding to the second optical output irradiated periodically according to the frequency, and the duty of the first clock signal and the second clock signal are respectively changed. Thus, the pulse widths of the first and second optical outputs are changed .   2. The optical information recording method according to claim 1, wherein a duty of the clock signal is changed in accordance with characteristics of the recording medium, thereby changing a pulse width of the multipulsed optical output to form a recording mark. An optical information recording method comprising controlling operation.   2. The optical information recording method according to claim 1, wherein a duty of the clock signal is changed in accordance with a linear velocity of the recording medium, thereby changing a pulse width of the multi-pulsed optical output to change a recording power. An optical information recording method, wherein the optical information recording method is controlled to be substantially constant.   2. The optical information recording method according to claim 1, wherein a duty of the clock signal is changed according to a temperature around the recording medium.   3. The optical information recording method according to claim 2, wherein the characteristic of the recording medium is a thermal characteristic based on a thermal structure of the recording medium. Means for multi-pulsing the light output of the light source according to a recording signal and a clock signal synchronized with the recording signal, and irradiating the information recording medium with a light beam of the multi-pulsed light output, In the optical information recording apparatus for recording a mark corresponding to a recording signal, the clock signal includes a first optical output for recording a mark having a predetermined length of the multi-pulsed optical output, followed by the mark The first clock signal and the second clock signal respectively corresponding to the second light output periodically irradiated according to the length, and the duty of the first and second clock signals are respectively changed. The optical information recording apparatus further comprises control means for changing the pulse widths of the first and second optical outputs . 7. The optical information recording apparatus according to claim 6 , wherein the control means changes a pulse width of the multi-pulsed optical output by changing a duty of the clock signal according to characteristics of the recording medium. An optical information recording apparatus for controlling a forming operation of a recording mark. 7. The optical information recording apparatus according to claim 6 , wherein the control means changes a pulse width of the multi-pulsed optical output by changing a duty of the clock signal according to a linear velocity of the recording medium. And recording power is controlled to be substantially constant. 7. The optical information recording apparatus according to claim 6 , wherein the control unit records a mark and a space having a predetermined length on the recording medium, reproduces the recorded mark and space, and sets the length of the mark and space. Means for outputting a signal corresponding to the difference in height, and based on this signal, the duty of the clock signal is changed so as to eliminate the difference in length between the mark and the space. apparatus. 9. The optical information recording apparatus according to claim 8 , wherein the control means determines a duty of the clock signal so that an optimum recording power can be obtained at a plurality of recording radius positions with different linear velocities of the recording medium. Storage means for storing the duty value of the clock signal, and changing the duty of the clock signal according to the linear velocity of the recording position of the recording medium based on the duty value stored in the storage means An optical information recording apparatus. 7. The optical information recording apparatus according to claim 6 , wherein the control unit changes the duty of the clock signal in accordance with the temperature of a temperature sensor provided in the vicinity of the recording medium. 8. The optical information recording apparatus according to claim 7 , wherein the characteristic of the recording medium is a thermal characteristic based on a thermal structure of the recording medium.

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