JP3754596B2 - Optical information recording / reproducing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical information recording / reproducing apparatus such as an optical disc drive that records and reproduces information by irradiating a recording medium such as an optical disc with a laser beam from a light source such as a semiconductor element.
[0002]
[Prior art]
Recently, with the spread of multimedia, optical discs (recording media) that are playback-only media such as music CDs, CD-ROMs, DVD-ROMs, and information that are optical disc drives that play back information recorded on the optical discs. Playback devices have been put into practical use.
[0003]
In addition to write-once optical disks that use dye media and rewritable MO disks that use magneto-optical (MO) media, optical disks that are phase-change media are also attracting attention. Also, an information recording / reproducing apparatus that is an optical disk drive that performs reproduction has been put into practical use.
[0004]
In particular, rewritable DVD media are attracting much attention as next-generation multimedia recording media and large-capacity storage media.
The phase change medium is a recording medium that records information by reversibly changing the recording material into a crystalline phase and an amorphous phase.
[0005]
Unlike the MO media, the phase change media described above do not require an external magnetic field, and can record and reproduce information using only laser light from a light source composed of a semiconductor element such as a laser diode (LD). Overwrite recording in which recording and erasing are performed at once by laser light is possible.
[0006]
As a general recording waveform for recording information on the phase change medium, for example, there is a single-pulse semiconductor laser emission waveform generated based on an 8-16 modulation code or the like. However, there are problems such as recording marks distorted like tears due to animal heat, or insufficient cooling rate due to insufficient formation of amorphous phase, resulting in low recording marks for laser light. There is.
[0007]
Therefore, as a recording method for recording information on a DVD phase change type medium, as shown in FIG. 9, a mark is formed on the phase change type medium by a laser beam having a multi-pulse waveform using a multistage recording power. This prevents the above-mentioned problems.
[0008]
As shown in FIG. 9 (c), the mark portion of the multi-pulse waveform is composed of a leading heating pulse A for sufficiently preheating the recording film of the phase change type medium to the melting point or more, and a plurality of subsequent successive pulses. It consists of a heating pulse B and a continuous cooling pulse C between them, the head heating pulse A, the light emission power (peak power) of the heating pulse B is Pw, the light emission power (bias power) of the cooling pulse C is Pb, If the read power is Pr, each light emission power is set so as to satisfy the relationship of the following formula 1.
[0009]
[Expression 1]
Pw> Pb≈Pr (1)
[0010]
The space portion of the multi-pulse waveform is composed of an erase pulse D, and the light emission power (erase power) Pe is set so as to satisfy the following formula 2.
[0011]
[Expression 2]
Pw>Pe> Pb (2)
[0012]
In this way, by making the recording waveform a multi-pulse light emission waveform, an amorphous phase is formed in the mark portion of the phase-change-type media by the heating-cooling rapid cooling condition by the heating pulses A and B and the cooling pulse C, and the space Since the crystal phase is formed in the portion under the slow cooling condition only by heating with the erase pulse D, a sufficient difference in reflectance between the amorphous phase and the crystal phase can be obtained.
[0013]
Also, when recording information on a DVD-based dye medium, the recording mark cannot be accurately generated due to animal heat in single-pulse recording, so the mark is formed by laser light having a multi-pulse waveform as shown in FIG. A recording method to be formed has been proposed.
[0014]
As shown in FIG. 10C, the light emission power (peak power) of the head heating pulse A and the heat pulse B is Pw, the light emission power (bias power) of the cooling pulse C and the space D is Pb, and the read power is Pr. Then, each light emission power is set so as to satisfy the relationship of the following formula 3.
[0015]
[Equation 3]
Pw> Pb≈Pr (3)
[0016]
When recording on the phase change medium or the dye medium as described above, it is necessary to correctly control the recording light emission power.
As a method of controlling the laser diode (LD), a method of driving a constant current to the LD regardless of fluctuations in emission power is called ACC control (AUTOMATIC CURRENT CONTROL).
[0017]
However, since the drive current-light emission power characteristics of the LD easily fluctuate due to self-heating or the like, APC control (AUTOMATIC POWER CONTROL) is generally performed as a means for stabilizing the light emission power.
[0018]
This APC control is a method in which a part of the light emitted from the LD is incident on a photodetector (PD) and the LD drive current is controlled using a monitor current generated in proportion to the light emission power of the LD.
[0019]
Here, when only information reproduction is considered, a high-frequency current is generally superimposed on the LD drive current to suppress noise, but since it is a constant current in terms of DC, a relatively low-band feedback loop. By configuring this, APC control can be easily realized.
[0020]
However, when APC is performed at the time of recording, the recording power changes at a high speed in order to form marks and spaces.
For example, in a CD system or a DVD system, if a low-band feedback loop is configured by utilizing the fact that the recording data DSV (DIGITAL SUM VALUE) becomes zero, the recording power can be reduced with a simple configuration as in the case of playback. Although it can be controlled, the exact power cannot be controlled.
[0021]
In order to solve such problems, conventionally, the level of the period during which space data is output (bias level for dye-type media and erase level for phase-change media) is sampled and held, so that a relatively low bandwidth is obtained. There has been an optical information recording / reproducing apparatus (for example, see Japanese Patent Application Laid-Open No. 8-96364) that accurately controls a bias level and an erase level during recording by a detection / control circuit.
[0022]
In such an optical information recording / reproducing apparatus, when recording is performed on a DVD-type phase change medium or a dye-type medium, multi-pulse emission is performed when recording mark data, and thus recording power is detected. In this case, if the sample-and-hold is performed when the long space data is output, the detection / control circuit can be configured with a lower band.
[0023]
For example, when recording on a CD-R medium with a recording waveform as shown in FIG. 11, 11T space and 11T mark data is output as a SYNC code for each SYNC frame (588 channel clock = 588T). Sample holding may be performed when the 11T space data is output.
[0024]
[Problems to be solved by the invention]
However, in the conventional optical information recording / reproducing apparatus as described above, when recording on a DVD-type medium, the SYNC code output for each SYNC frame (1488T) is 14T according to a predetermined rule in order to make DSV zero. Since the mark or the 14T space is selected, the 14T space data is not necessarily output periodically. In addition, long space data other than the SYNC code is also expected to be generated within a certain period of time, but is not guaranteed as a modulation rule.
[0025]
Therefore, when trying to control the laser power in an analog manner according to the output value of the sample and hold circuit, if the sampling signal is not output for a predetermined period or more, the output is lowered based on the droop characteristic of the sample and hold circuit, leading to abnormal light emission. was there.
[0026]
The present invention has been made to solve the above-described problems, and an object thereof is to accurately perform laser power control of a semiconductor laser light source even when a sampling and holding sampling signal is not output for a predetermined period or longer. .
[0027]
[Means for Solving the Problems]
In order to achieve the above object, the present invention makes a semiconductor laser light source emit pulsed light based on a predetermined light emission rule and irradiates the recording medium with laser light, and the recording medium has two bias levels and peak levels. In an optical information recording / reproducing apparatus for recording information consisting of a pulse having a length of an integer multiple of 1 or more of a channel clock period based on a predetermined recording modulation method with a laser power of a value and reproducing the information recorded on the recording medium A first laser power control means for controlling a laser drive current value of the semiconductor laser light source so that a light emission power of the laser light becomes constant according to a level change of a signal according to a level of the laser power; and the laser Second laser power control means for controlling the laser drive current value of the semiconductor laser light source at a constant value irrespective of the power level; And switching means for switching the first laser power control means and the second laser power control means, the period information to be recorded on the recording medium is 0 First A means for outputting a sampling pulse for detecting the laser power at the bias level when it occurs for a predetermined period of time, and the laser power at the bias level is detected when recording on the recording medium, and the laser power at the bias level is detected. Based on the laser power control, the sampling pulse is Second When output at intervals within a predetermined period, the switching means switches to the first laser power control means, the laser drive current value is controlled by a control signal from the first laser power control means, and the sampling pulse is the above Second Means for switching to the second laser power control means and controlling the laser drive current value by a control signal from the second laser power control means is provided when the output is not performed for a predetermined period or longer.
[0028]
Further, the semiconductor laser light source emits pulsed light based on a predetermined light emission rule and irradiates the recording medium with laser light, and the recording medium is predetermined by a ternary laser power of a bias level, an erase level, and a peak level. Information consisting of a pulse having a length of an integer multiple of 1 or more of the channel clock period based on the recording modulation method is erased, the information recorded on the recording medium is erased, the recording medium is initialized, and the recording medium is In an optical information recording / reproducing apparatus for reproducing recorded information, a laser driving current value of the semiconductor laser light source so that a light emission power of the laser light becomes constant according to a level change of a signal corresponding to the level of the laser power. A first laser power control means for controlling the laser power of the semiconductor laser light source at a constant value irrespective of the level of the laser power. A second laser power control means for controlling the current values, and switching means for switching the first laser power control means and the second laser power control means, the period information to be recorded on the recording medium is 0 First A means for outputting a sampling pulse for detecting the laser power at the bias level when it occurs for a predetermined period or more, and detecting the laser power at the erase level at the time of recording on the recording medium. Based on the laser power control, the sampling pulse is Second When output at intervals within a predetermined period, the switching means switches to the first laser power control means, the laser drive current value is controlled by a control signal from the first laser power control means, and the sampling pulse is the above Second When output is not performed for a predetermined period or longer, it is preferable to provide means for switching to the second laser power control means and controlling the laser drive current value by a control signal from the second laser power control means.
[0029]
Further, in the optical information recording / reproducing apparatus as described above, the first laser power control means switches from the first laser power control means to the second laser power control means to output the sampling pulse, and then the first laser power control means by the switching means. It is preferable to provide means for switching again to control the laser drive current value by the control signal from the first laser power control means.
[0030]
In the optical information recording / reproducing apparatus as described above, the semiconductor laser light source emits light at the bias level by a control signal of the laser drive current output from the first laser power control means or the second laser power control means. Current for driving the semiconductor laser light source to emit light at the erase level or the peak level by superimposing a current corresponding to the differential efficiency characteristic of the laser light emitted from the semiconductor laser light source on the laser light. It is preferable to provide means for driving.
[0031]
Further, in the optical information recording / reproducing apparatus as described above, a second laser power which uses the sampling pulse as a trigger input and causes the switching means to switch to the second laser power control means after a predetermined period of the trigger input. A switching signal output means for outputting a control switching signal and a second laser power control switching signal output from the switching signal output means to the switching means falls when the sampling pulse is not output for the predetermined period or longer, and then the sampling is performed. Means may be provided for controlling the second laser power control switching signal to rise when a pulse is output.
[0032]
The optical information recording / reproducing apparatus as described above operates based on a predetermined clock frequency, resets the count value by the sampling pulse, and after the count value is reset, after the predetermined count, the second switching means Counting means for outputting a second laser power control switching signal to be switched to the laser power control means, and second laser power output from the counting means (counter) to the switching means when the sampling pulse is not output for the predetermined period or longer. It is preferable to provide means for resetting the counting means and controlling the second laser power control switching signal to rise when the control switching signal falls and then the sampling pulse is output.
[0033]
Further, in the optical information recording / reproducing apparatus as described above, a differential for outputting a differential signal between a control signal output from the first laser power control means and a control signal output from the second laser power control means. During the period in which the laser drive current value is controlled by the signal output means and the second laser power control means, the differential is used instead of the signal corresponding to the level of the laser power output to the second laser power control means. By feeding back the output signal of the signal output means to the first laser power control means, the control signal output from the first laser power control means is set to the same level as the control signal output from the second laser power control means. It is preferable to provide means for holding.
[0034]
In the optical information recording / reproducing apparatus as described above, a comparison signal obtained by comparing the control signal output from the first laser power control unit and the control signal output from the second laser power control unit is output. Control signal output from the second laser power control means is controlled so that both control signals always have substantially the same level by comparing the control signals with the comparison signal output means periodically. It is recommended to provide means for
[0036]
According to a first aspect of the present invention, there is provided an optical information recording / reproducing apparatus that records and reproduces information by binary laser power of a bias level and a peak level, and uses a laser power at a bias level as laser power control at the time of recording. In order to detect and control the laser power based on the detected laser power at the bias level, and to detect the laser power at the bias level, there is a period in which the recorded information is zero. First The sampling pulse that is output when it occurs for a predetermined time or longer Second When output at intervals within a predetermined period, the laser of the semiconductor laser light source is configured so that the light emission power of the laser light becomes constant according to the level change of the signal according to the level of the laser power by the first laser power control means. The drive current value is controlled and the sampling pulse is Second When the laser beam is not output for a predetermined period or longer, the second laser power control means switches to control the laser drive current value of the semiconductor laser light source at a constant value regardless of the laser power level.
[0037]
According to a second aspect of the present invention, there is provided an optical information recording / reproducing apparatus for recording, erasing, initializing and reproducing information by using three levels of laser power of a bias level, an erase level and a peak level, and controlling laser power during recording. As described above, there is a period in which the recorded information is zero in order to detect the laser power of the erase level, control the laser power based on the detected laser power of the erase level, and detect the laser power of the erase level. First The sampling pulse that is output when it occurs for a predetermined time or longer Second When output at intervals within a predetermined period, the laser of the semiconductor laser light source is configured so that the light emission power of the laser light becomes constant according to the level change of the signal according to the level of the laser power by the first laser power control means. The drive current value is controlled and the sampling pulse is Second When the laser beam is not output for a predetermined period or longer, the second laser power control means switches to control the laser drive current value of the semiconductor laser light source at a constant value regardless of the laser power level.
[0038]
According to a third aspect of the present invention, when the sampling pulse is output after switching from the first laser power control means to the second laser power control means, the optical information recording / reproducing apparatus switches to the first laser power control means again. Control the laser drive current value.
[0039]
According to a fourth aspect of the present invention, there is provided an optical information recording / reproducing apparatus which drives a current for emitting light at a bias level by a laser driving current output from the first laser power control means or the second laser power control means, By superimposing a current corresponding to the differential efficiency characteristic on the laser beam, a current for driving laser emission at the erase level or peak level is driven.
[0040]
In the optical information recording / reproducing apparatus according to claim 5 of the present invention, the sampling pulse is used as a trigger input, and the switching signal output means switches the switching means to the second laser power control means after a predetermined period of the trigger input. 2 When the laser power control switching signal is output and the sampling pulse is not output for a predetermined period or longer, the second laser power control switching signal output from the switching signal output means to the switching means falls and then the sampling pulse is output. Control is performed so that the second laser power control switching signal rises.
[0041]
In the optical information recording / reproducing apparatus according to claim 6 of the present invention, the counting means operates based on a predetermined clock frequency, resets the count value by the sampling pulse, and after the predetermined count after the reset, the second means for the switching means. When the laser power control switching signal is output and the sampling pulse is not output for a predetermined period or longer, the second laser power control switching signal output from the counting means to the switching means falls, and then resets the counting means when the sampling pulse is output. Then, the second laser power control switching signal rises.
[0042]
According to a seventh aspect of the present invention, in the optical information recording / reproducing apparatus, the differential signal output means is a differential signal between the control signal output from the first laser power control means and the control signal output from the second laser power control means. During the period when the laser power is controlled by the second laser power control means, the differential signal of the differential signal output means is used instead of the power monitor signal output to the first laser power control means. By feeding back to the control means, the control signal output from the first laser power control means is held at the same level as the control signal output from the second laser power control means.
[0043]
In the optical information recording / reproducing apparatus according to claim 8 of the present invention, the comparison signal output means compares the control signal output from the first laser power control means with the control signal output from the second laser power control means. By outputting a comparison signal and periodically comparing the control signal output from the first laser power control means and the control signal output from the second laser power control means, both control signals always have substantially the same level. Thus, the control signal output from the second laser power control means is controlled.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be specifically described below with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a functional configuration of a main part of an optical information recording / reproducing apparatus as an embodiment of claims 1 to 5 and claims 7 to 9 of the present invention.
FIG. 2 is a block diagram showing an internal configuration of the bias level current driving apparatus shown in FIG.
[0046]
FIG. 3 is a timing chart of main signals output by the CPU shown in FIG.
FIG. 4 is a diagram showing the relationship between the drive current output from the bias level current drive device shown in FIG. 2 and the light emission power in the laser diode.
FIG. 5 is a timing chart of various signals related to ACC control by the bias level current driver shown in FIG.
[0047]
The optical information recording / reproducing apparatus according to the first embodiment shown in FIG. 1 applies an information recording method in which DVD format code data is recorded (overwritten) on an optical disc as a phase change medium (for example, a phase change disc). Mark edge (PWM: PULSE WIDTH MODULATION) recording is performed using 8-16 modulation code as a modulation method, and using such an optical disc and recording data, semiconductor laser light is emitted in multipulses to generate phase change media. Information is recorded by irradiating the recording surface and forming recording marks on the recording surface.
[0048]
This optical information recording / reproducing apparatus requires three types of recording powers: peak power: Pw and bias power: Pb for forming marks with multi-pulses, and erase power: Pe for forming spaces when recording information. Become.
[0049]
First, a normal APC operation during recording in the optical information recording / reproducing apparatus will be described.
The erase level control signal 104 and the peak level control signal 105 output from the CPU 1 set the output currents of the erase level current driving device 8 and the peak level current driving device 9, respectively.
[0050]
The erase level current driving device 8 and the peak level current driving device 9 are specifically DACs, and an erase level superimposed current signal 106 that is an analog signal based on the LD drive current information digitally set by the CPU 1. A peak level superimposed current signal 107 is output.
[0051]
The bias level current drive device 7 outputs the bias level drive current signal 108 with the configuration shown in FIG.
The LD drive device 4 sets the drive current amounts of bias power: Pb, erase power: Pe, and peak power: Pw, respectively, according to the bias level drive current signal 108, the erase level superimposed current signal 106, and the peak level superimposed current signal 107. decide.
[0052]
Further, as shown in FIG. 3A, the CPU 1 converts information to be recorded on the optical disk (not shown) into an 8-16 modulation signal, and further, as shown in FIG. A waveform is generated, and an erase power enable signal 101 and a peak power enable signal 102 are supplied to the LD driving device 4 in accordance with the waveform.
[0053]
The LD driving device 4 converts the erase level superimposed current signal 106 and the peak level superimposed current signal 107 of each level into the bias level driving current signal 108 when the erase power enable signal 101 and the peak power enable signal 102 are at the high level “H”, respectively. A driving current is supplied to the laser diode (LD) 2 in an appropriate overlapping manner.
[0054]
More specifically, as shown in FIGS. 3B and 3C, when the semiconductor laser beam is emitted at the erase level, the CPU 1 sets the erase power enable signal 101 to the high level “H” and sets the LD driving device. In 4, the erase level superimposed current signal 106 is superimposed on the bias level drive current signal 108 to obtain a drive current for the LD 2.
[0055]
When the semiconductor laser beam is emitted at the peak level, the peak power enable signal 102 is set to the high level “H”, and the LD driving device 4 superimposes the peak level superimposed current signal 107 on the bias level driving current signal 108 to generate the LD2 Drive current.
[0056]
When a driving current is supplied to the LD 2 by the LD driving device 4, the LD 2 emits a semiconductor laser beam, irradiates an optical disk (not shown), and records and reproduces information.
[0057]
At that time, part of the emitted light is incident on the monitor PD 3, and the monitor PD 3 outputs a power monitor current signal 109 proportional to the light emission power to the I / V conversion circuit 5, and the I / V conversion circuit 5 The power monitor signal 110 obtained by current-voltage conversion is output to the driving device 7, and the bias level current driving device 7 performs APC control by using the power monitor signal 110.
[0058]
In the bias level current driver 7, as shown in FIG. 2, the power monitor signal 110 output from the I / V conversion circuit 5 is branched and output to the amplifiers 701 and 703, respectively, and amplified and sampled by the sample hold circuit. Sample and hold at 702 and 704.
[0059]
The amplifier 703 and the sample hold circuit 704 are used when information is recorded on an optical disk of a phase change medium. The amplifier 701 and the sample hold circuit 702 are dye media by an optical information recording / reproducing apparatus according to a second embodiment to be described later. Used when recording information on an optical disc.
[0060]
The switch 709 selects output signals from the sample hold circuits 702 and 704 according to the media type selection signal 116. FIG. 2 shows a case where the APC / ACC output comparison signal 114 is at the high level “H”.
[0061]
In the optical information recording / reproducing apparatus of the first embodiment, the erase level is sampled and held when information is recorded on the optical disk of the phase change medium. However, in the optical information recording / reproducing apparatus of the second embodiment, which will be described later, Since the bias level is sampled and held when information is recorded on the optical disk, the output to the APC circuit 705 in the subsequent stage is made almost the same regardless of the media type. Is set higher than the gain of the amplifier 703.
[0062]
The sample hold circuit 704 outputs the power monitor signal 110 during a period in which the sampling signal 113 output from the CPU 1 is high level “H” → low level “L” when long space data is output (for example, space data continuous for 10T or more). The sample is held and output to the APC circuit 705. At that time, the switches 710, 711, and 712 have selected the high level “H”.
[0063]
The target power value signal 112 output from the CPU 1 is converted into an analog signal by the D / A converter 11, then inverted by the inverting amplifier 708 based on the reference value voltage (VREF), and added to the output signal from the sample hold circuit 704. It is output to the inverting terminal of the APC circuit 705.
[0064]
Specifically, the APC circuit 705 is an integration circuit, and outputs an output signal thereof as a bias level driving current signal 108 to the LD driving device 4 through the switch 711 to constitute an APC loop.
[0065]
The APC circuit 705 outputs so that the sum signal of the output of the sample hold circuit 704 and the output of the inverting amplifier 708 is equal to the reference voltage VREF, that is, the output of the sample hold circuit 704 and the target power value signal 112 are equal. Control the signal.
[0066]
In addition, the A / D converter 713 digitizes the bias level driving current signal 108 and outputs it to the CPU 1 as the bias current driving current digital signal 115.
In this way, the bias level drive current is controlled by sample-holding the long space data.
[0067]
Next, a constant current is superimposed on the erase level superimposed current signal 106 and the peak level superimposed current signal 107 under the control of the CPU 1, but the bias level is changed according to the fluctuation of the erase level. The level is always analog-controlled.
The erase level superimposed current and peak level superimposed current can be obtained based on the differential efficiency characteristic of the laser and the bias level drive current digital signal 115.
[0068]
As shown in FIG. 4, in the case of bias power: Pb, erase power: Pe, peak power: Pw, bias level drive current: Ib, erase level superimposed current: ΔIe, peak level superimposed current: ΔIw, differential efficiency: η is It is calculated based on the following equation (4). This differential efficiency: η is determined in advance.
[0069]
[Expression 4]
η = (Pe−Pb) / ΔIe (4)
[0070]
Based on Equation 4, the erase level superimposed current: ΔIe and the peak level superimposed current: ΔIw can be obtained by the following Equations 5 and 6, respectively.
[0071]
[Equation 5]
ΔIe = (Pe−Pb) / η (5)
[0072]
[Expression 6]
ΔIw = (Pw−Pb) / η (6)
[0073]
Next, an operation when the sampling signal 113 is not output for a predetermined period or longer will be described.
As described above, if the sampling signal 113 is not output for a long time, the output of the sample hold circuit 704 gradually decreases due to the droop characteristic, and the APC circuit 705 changes the output value according to the output of the sample hold circuit 704. Laser emission becomes abnormal.
[0074]
Therefore, when the sampling signal 113 is not output for a predetermined period, the control of the semiconductor laser light is temporarily switched to ACC control (AUTOMATIC CURRENT CONTROL).
[0075]
That is, the digital signal output from the CPU 1 is output as the ACC drive current signal 111 through the D / A converter 10 and output as the bias level drive current signal 108 through the switch 711.
Sampling signal 113 is output as a trigger to monostable multivibrator 714.
[0076]
The monostable multivibrator 714 is triggered at the rising edge of the sampling signal 113 and always outputs a high level “H” while the trigger is output within a predetermined period (for example, 150 μs), and the trigger is output for a predetermined period or longer. If not, it is configured to be low level “L”.
And when the output of the monostable multivibrator 714 becomes L, it will switch to ACC control.
[0077]
The monostable multivibrator 714 outputs an ACC control switching signal 750 to the switches 710, 711, and 712, respectively.
FIG. 5 shows the timing of the operation.
When the switch 711 becomes low level “L”, the ACC drive current signal 111 is output as the bias level drive current signal 108.
[0078]
In this state, when long space data of 10T or more is generated and the sampling signal 113 is output, the output of the monostable multivibrator 714 becomes high level “H”, so that the APC control is promptly restored.
[0079]
When the switches 710 and 712 are at a low level “L”, the differential signal between the output of the APC circuit 705 and the ACC drive current signal 111 is fed back to the APC circuit 705 by the APC circuit output feedback circuit 706 to output the APC circuit. The APC circuit 705 is operated so that the output of the feedback circuit 706 becomes equal to the reference voltage: VREF, that is, the output of the APC circuit 705 and the ACC drive current signal 111 become equal.
[0080]
In this manner, the output of the APC circuit 705 can be prevented from being saturated during the ACC control period, and the bias level drive current signal 108 can be quickly settled when returning to the APC control.
[0081]
The comparator 707 compares the output signal of the APC circuit 705 with the ACC drive current signal 111 and outputs it to the CPU 1 as an APC / ACC output comparison signal 114. The CPU 1 periodically refers to the APC / ACC output comparison signal 114 and sets the output of the ACC drive current signal 111 so that the APC output comparison signal 114 and the ACC drive current signal 111 are equal.
[0082]
In this way, even when the APC control is switched to the ACC control, a value almost the same as the output value of the APC circuit immediately before the switching is output as the bias level driving current signal 108.
[0083]
As described above, the optical information recording / reproducing apparatus according to the first embodiment irradiates the semiconductor laser light source (LD2) with the semiconductor laser light on the recording medium (optical disk) by causing the semiconductor laser light source (LD2) to emit pulses based on a predetermined light emission rule. A channel clock period (based on a predetermined recording modulation method) with a ternary laser power of a bias level (bias power: Pb), an erase level (erase power: Pe), and a peak level (peak power: Pw) with respect to the recording medium. T) records information consisting of a pulse having a length of an integer (N) times 1 or more, erases the information recorded on the recording medium, initializes the recording medium, and reproduces the information recorded on the recording medium .
[0084]
Further, the bias level current driving device 7 includes the following (1) to ( 11 ) Fulfills each function.
(1) The laser drive current value of the semiconductor laser light source (LD2) is controlled so that the emission power of the semiconductor laser light becomes constant according to the level change of the signal (power monitor current signal 109) corresponding to the laser power level. First laser power control means (APC control circuit)
[0085]
(2) second laser power control means (ACC control circuit) for controlling the laser drive current value of the semiconductor laser light source (LD2) with a constant value regardless of the level of the laser power; and the first laser power control means ( Switching means (laser drive circuit switching device) for switching between the APC control circuit) and the second laser power control means (ACC control circuit)
[0086]
(3) During recording on the recording medium, the laser power at the erase level (erase power: Pe) is detected, and the laser power is controlled based on the laser power at the erase level (erase power: Pe). There is a period in which the information recorded on the recording medium is zero in order to detect the erase level laser power (erase power: Pe). First The sampling pulse (sampling signal 113) output when it occurs for a predetermined time or longer is Second When output at intervals within a predetermined period, the switching means switches to the first laser power control means (APC control circuit), and the laser is driven by the control signal from the first laser power control means (APC control circuit). The current value is controlled, and the sampling pulse (sampling signal 113) is Second Means for switching to the second laser power control means (ACC control circuit) and controlling the laser drive current value by a control signal from the second laser power control means (ACC control circuit) when the output is not performed for a predetermined period or longer.
[0087]
(4) After switching from the first laser power control means (APC control circuit) to the second laser power control means (ACC control circuit) and outputting the sampling pulse (sampling signal 113), the switching means causes the first laser power control means (APC control circuit) to output the first pulse. Switching again to one laser power control means (APC control circuit), and means for controlling the laser drive current value by the control signal from the first laser power control means (APC control circuit)
[0088]
(5) The bias level of the semiconductor laser light source (LD2) is controlled by a laser drive current control signal output from the first laser power control means (APC control circuit) or the second laser power control means (ACC control circuit). By driving a current for emitting light with (bias power: Pb) and superimposing a current corresponding to the differential efficiency characteristic (differential efficiency: η) of the laser light emitted from the semiconductor laser light source (LD2) on the laser light Means for driving a current for causing the semiconductor laser light source (LD2) to emit light at the erase level (erase power: Pe) or the peak level (peak power: Pw).
[0089]
(6) The sampling pulse (sampling signal 113) is used as a trigger input, and the second laser power control means (ACC control circuit) is applied to the switching means (laser drive circuit switching device) after a predetermined period of the trigger input. Switching signal output means (monostable multivibrator 714) for outputting a second laser power control switching signal to be switched to
[0090]
(7) Second laser power output from the switching signal output means (monostable multivibrator 714) to the switching means (laser drive circuit switching device) when the sampling pulse (sampling signal 113) is not output for the predetermined period or longer. Means for controlling the second laser power control switching signal (ACC control switching signal 750) to rise when the control switching signal (ACC control switching signal 750) falls and then the sampling pulse (sampling signal 113) is output.
[0091]
(8) A control signal (APC control circuit output signal) output from the first laser power control means (APC control circuit) and a control signal (ACC control) output from the second laser power control means (ACC control circuit). Differential signal output means (APC circuit output feedback circuit 706) for outputting a differential signal with the circuit output signal)
[0092]
(9) The period during which the laser drive current value is controlled by the second laser power control means (APC control circuit) depends on the level of the laser power output to the second laser power control means (APC control circuit). Instead of the received signal (power monitor signal), the output signal of the differential signal output means (APC circuit output feedback circuit 706) is fed back to the first laser power control means (APC control circuit). Means for holding the control signal output from the control means (APC control circuit) at the same level as the control signal output from the second laser power control means (ACC control circuit).
[0093]
(10) A control signal (APC control circuit output signal) output from the first laser power control means (APC control circuit) and a control signal (ACC control) output from the second laser power control means (ACC control circuit). Comparison signal output means (APC / ACC output signal comparison circuit) for outputting a comparison signal as a result of comparing the circuit output signal)
[0094]
(11) The both control signals (APC control circuit output signal and ACC control circuit output signal) are periodically compared with each other by the comparison signal output means (APC control circuit output signal and ACC control circuit output signal). ) For controlling the control signal (ACC control circuit output signal) output from the second laser power control means (ACC control circuit) so that the level is always substantially equal.
[0096]
In the optical information recording / reproducing apparatus of the first embodiment, the period for switching from the APC control to the ACC control has been described as 150 ms. However, another optimum period can be set according to the system of the optical information recording / reproducing apparatus. That's fine.
[0097]
The optical information recording / reproducing apparatus of the first embodiment performs laser power control at the time of recording when information is recorded, erased, initialized, and reproduced by ternary laser power of a bias level, an erase level, and a peak level, respectively. As described above, there is a period in which the recorded information is zero in order to detect the laser power of the erase level, control the laser power based on the detected laser power of the erase level, and detect the laser power of the erase level. First The sampling pulse that is output when it occurs for a predetermined time or longer Second When output at intervals within a predetermined period, the APC control circuit controls the laser drive current value, and the sampling pulse is Second above If it is not output for a predetermined period or longer, the laser drive current value is controlled by switching to the ACC control circuit. Second above Even when the laser beam is not output for a predetermined period or longer, the laser power can be accurately controlled.
[0098]
Also, after the laser power control circuit is switched from the APC control circuit to the ACC control circuit, when a sampling pulse is output, the laser drive current value is controlled again by switching to the APC control circuit, so the ACC control period is shortened as much as possible. Therefore, the laser power can be controlled more accurately.
[0099]
Furthermore, a current for emitting light at a bias level is driven based on a laser drive current control signal output from the APC control circuit or the ACC control circuit, and a current corresponding to the differential efficiency characteristic of the laser beam is superimposed on the laser beam. As a result, the current for emitting light at the erase level or peak level is driven, so that the laser power of the bias level, erase level, and peak level can be accurately controlled.
[0100]
In addition, when the monostable multivibrator uses a sampling pulse as a trigger input, outputs an ACC control circuit switching signal to the laser drive circuit switching circuit after a predetermined period of the trigger input, and the sampling pulse is not output for a predetermined period or more, Since the ACC control circuit switching signal output from the monostable multivibrator to the laser drive circuit switching circuit falls, and then the ACC control circuit switching signal rises when the sampling pulse is output, the sampling signal of the sample hold circuit Even when is not output for a predetermined period or longer, the laser power can be accurately controlled.
[0101]
Further, the APC control circuit output feedback circuit outputs a differential signal between the APC control circuit output signal output from the APC control circuit and the ACC control circuit output signal output from the ACC control circuit, and the laser power is controlled by the ACC control circuit. During this period, the output signal from the APC control circuit output feedback circuit is fed back to the APC control circuit instead of the power monitor signal output to the APC control circuit, so that the APC control circuit output signal becomes the ACC control circuit output signal. Since it is held at the same level, the output of the APC control circuit can be prevented from being saturated during the ACC control period, and the output signal of the APC control circuit is quickly settled when returning from the ACC control to the APC control. Can be made.
[0102]
Further, the APC / ACC output signal comparison circuit outputs a comparison signal comparing the APC control circuit output signal output from the APC control circuit and the ACC control circuit output signal output from the ACC control circuit, and the APC control circuit output signal And the ACC control circuit output signal are periodically compared to control the ACC control circuit output signal so that the APC control circuit output signal and the ACC control circuit output signal always have substantially the same level. The laser power can be accurately controlled even when switching to.
[0103]
Further, since the sampling pulse is output at the timing when the period in which the record information is “0” occurs for a predetermined period or more, the APC control circuit can be configured by the low-band power detection / control circuit.
[0104]
(Second Embodiment)
Next explained is an optical information recording / reproducing apparatus according to the second embodiment of the invention.
FIG. 6 is a timing chart of main signals output by the CPU of the optical information recording / reproducing apparatus of the second embodiment.
[0105]
The optical information recording / reproducing apparatus of the second embodiment has the function described in claim 1 of the present invention, and the configuration thereof is the same as that of the optical information recording / reproducing apparatus of the first embodiment described above. In contrast, recording is performed on an optical disk that is a dye medium.
[0106]
Therefore, the recording level is a binary value of a bias level (bias power: Pb) and a peak level (peak power: Pw), and the level to be sampled and held is a bias level. Therefore, the erase power enable signal 101 output from the CPU 1 of the optical information recording / reproducing apparatus of the second embodiment is always at the low level “L” as shown in FIG.
[0107]
Also, the media type selection signal 116 shown in FIG. 2 becomes low level “L”, and the power monitor signal 110 is amplified by the amplifier 701, sampled and held by the sample hold circuit 702, and output to the APC circuit 705.
[0108]
That is, the optical information recording / reproducing apparatus of the second embodiment irradiates the semiconductor laser light source (LD2) with pulsed light emission based on a predetermined light emission rule, and irradiates the recording medium (optical disk) with the semiconductor laser light. In contrast, the binary laser power of the bias level (bias power: Pb) and the peak level (peak power: Pw) is an integer (N) times 1 or more of the channel clock period (T) based on a predetermined recording modulation system. Information consisting of length pulses is recorded and information recorded on the recording medium is reproduced.
[0109]
Further, the bias level current driver 7 fulfills the following functions (20) to (23).
(20) First controlling the laser drive current value of the semiconductor laser light source so that the emission power of the semiconductor laser light becomes constant according to the level change of the signal (power monitor current signal 109) according to the laser power level. 1 Laser power control means (APC control circuit)
[0110]
(21) Second laser power control means (ACC control circuit) for controlling the laser drive current value of the semiconductor laser light source with a constant value regardless of the level of the laser power.
(22) Switching means (laser drive circuit switching device) for switching between the first laser power control means (APC control circuit) and the second laser power control means (ACC control circuit)
[0111]
(23) During recording on the recording medium, the laser power at the bias level (bias power: Pb) is detected, and the laser power is controlled based on the laser power at the bias level (bias power: Pb). There is a period in which information recorded on the recording medium is zero in order to detect the laser power (bias power: Pb) at the bias level. First The sampling pulse (sampling signal 113) output when it occurs for a predetermined time or longer is Second When output at intervals within a predetermined period, the switching means switches to the first laser power control means (APC control circuit), and the laser is driven by the control signal from the first laser power control means (APC control circuit). The current value is controlled, and the sampling pulse (sampling signal 113) is Second Means for switching to the second laser power control means (ACC control circuit) and controlling the laser drive current value by a control signal from the second laser power control means (ACC control circuit) when the output is not performed for a predetermined period or longer.
[0112]
In the optical information recording / reproducing apparatus of the first embodiment, when information is recorded and reproduced by binary laser power of a bias level and a peak level, respectively, the laser power at the bias level is used as laser power control at the time of recording. In order to detect and control the laser power based on the detected laser power at the bias level, and to detect the laser power at the bias level, there is a period in which the recorded information is zero. First The sampling pulse that is output when it occurs for a predetermined time or longer Second When output at intervals within a predetermined period, the APC control circuit controls the laser drive current value, and the sampling pulse is Second above If it is not output for a predetermined time or longer, the laser drive current value is controlled by switching to the ACC control circuit. Second above Even when the laser beam is not output for a predetermined period or longer, the laser power can be accurately controlled.
[0113]
(Third embodiment)
Next explained is an optical information recording / reproducing apparatus according to the third embodiment of the invention.
FIG. 7 is a timing chart of various signals related to ACC control by the bias level current driver of the optical information recording / reproducing apparatus of the third embodiment.
FIG. 8 is a block diagram showing a configuration of a counter provided in the optical information recording / reproducing apparatus of the third embodiment.
[0114]
The optical information recording / reproducing apparatus of the third embodiment has the function described in claim 6 of the present invention, and its configuration is substantially the same as the optical information recording / reproducing apparatus of the first embodiment described above. A counter 7112 configured as shown in FIG. 8 is used in place of the monostable multivibrator 714 of the circuit that generates the timing for switching from the APC control to the ACC control.
[0115]
As shown in FIG. 8, this counter 7112 outputs a clock of a relatively low frequency (for example, 1 MHz) from the clock 7111, and outputs a low level “L” signal when the counter 7112 counts a predetermined count value or more. Then, the signal is reset by the sampling signal 113 and a high level “H” signal is output.
[0116]
The counter 7112 is counted by the clock 7111, and outputs an ACC control switching signal 750 to the switches 710, 711, and 712 when it is counted over a predetermined count (for example, 150 counts, 150 μs).
Since the counter 7112 is configured to be reset at the rising edge of the sampling signal 113, the high level “H” signal is continuously output while the sampling signal 113 is output within the interval of 150 μs.
[0117]
As shown in FIG. 7, if the sampling signal 113 is not output for 150 μs or longer, the counter 7112 sets the ACC control switching signal 750 to the low level “L”. Therefore, the semiconductor laser light control is switched to ACC control in the same manner as the optical information recording / reproducing apparatus of the first embodiment.
When the sampling signal 113 is output at that time, the counter 7112 is reset and the ACC control switching signal 750 is set to the high level “H” to quickly return to the APC control.
[0118]
In the optical information recording / reproducing apparatus of the third embodiment, an independent clock is used as the counter clock. However, for example, a clock obtained by appropriately dividing the channel clock may be used.
[0119]
The optical information recording / reproducing apparatus according to the third embodiment operates at a predetermined clock frequency and switches the ACC control circuit to the laser drive circuit switching circuit after a predetermined count from the counter that resets the count value by the sampling pulse. When the sampling pulse is not output for a predetermined period or longer, the ACC control circuit switching signal output from the counter to the laser drive circuit switching circuit falls, and then the counter is reset when the sampling pulse is output. Since the ACC control circuit switching signal rises, the laser power can be accurately controlled even when the sampling signal of the sample hold circuit is not output for a predetermined period or longer.
[0120]
【The invention's effect】
As described above, according to the optical information recording / reproducing apparatus of the present invention, the laser power control of the semiconductor laser light source can be accurately performed even when the sampling and holding sampling signal is not output for a predetermined period or longer.
[Brief description of the drawings]
FIG. 1 is a first to fifth and seventh aspects of the present invention; And 8 It is a block diagram which shows the function structure of the principal part of the optical information recording / reproducing apparatus which is one Embodiment.
2 is a block diagram showing an internal configuration of the bias level current driving device shown in FIG. 1; FIG.
FIG. 3 is a timing chart of main signals output by the CPU shown in FIG. 1;
4 is a diagram showing the relationship between the drive current output from the bias level current drive device shown in FIG. 2 and the light emission power in the laser diode. FIG.
FIG. 5 is a timing chart of various signals related to ACC control by the bias level current driver shown in FIG. 2;
FIG. 6 is a timing chart of main signals output by the CPU of the optical information recording / reproducing apparatus according to the second embodiment.
FIG. 7 is a timing chart of various signals related to ACC control by a bias level current driver of the optical information recording / reproducing apparatus of the third embodiment.
FIG. 8 is a block diagram showing a configuration of a counter provided in the optical information recording / reproducing apparatus of the third embodiment.
FIG. 9 is a waveform diagram showing a multi-pulse waveform using conventional recording power.
FIG. 10 is a waveform diagram showing a conventional multi-pulse waveform.
FIG. 11 is a waveform diagram showing an example of a conventional recording waveform.
[Explanation of symbols]
1: CPU 2: Laser diode (LD)
3: Monitor photodiode (monitor PD)
4: LD drive device 5: I / V conversion circuit
7: Bias level current driver
8: Erase level current driver
9: Peak level current driver
10, 11: D / A converter
101: Erase power enable signal
102: Peak power enable signal
104: Erase level control signal
105: Peak level control signal
106: Erase level superimposed current signal
107: Peak level superimposed current signal
108: Bias level drive current signal
109: Power monitor current signal
110: Power monitor signal
111: ACC drive current signal
112: Target power value signal
113: Sampling signal
114: APC / ACC output comparison signal
115: Bias level drive current digital signal
116: Media type selection signal
701, 703: Amplifier
702, 704: Sample hold circuit
705: APC circuit
706: APC circuit output feedback circuit
707: Comparator 708: Inverting amplifier
709, 710, 711, 712: switch
713: A / D converter
714: Monostable multivibrator
750: ACC control switching signal

Claims (8)

A semiconductor laser light source emits pulsed light based on a predetermined light emission rule and irradiates the recording medium with laser light, and a predetermined recording modulation method is applied to the recording medium by binary laser power of a bias level and a peak level. In an optical information recording / reproducing apparatus for recording information consisting of pulses having a length of an integer multiple of 1 or more of a channel clock period based on the information and reproducing information recorded on the recording medium
First laser power control means for controlling the laser drive current value of the semiconductor laser light source so that the light emission power of the laser light becomes constant according to the level change of the signal according to the level of the laser power;
Second laser power control means for controlling the laser drive current value of the semiconductor laser light source at a constant value regardless of the level of the laser power;
Switching means for switching between the first laser power control means and the second laser power control means;
Means for outputting a sampling pulse for detecting the laser power at the bias level when a period in which the information to be recorded on the recording medium is zero occurs for a first predetermined period or more;
During recording on the recording medium, the laser power of the bias level is detected, the laser power is controlled based on the laser power of the bias level, and the sampling pulse is output at an interval within a second predetermined period. In this case, the switching means switches to the first laser power control means, the laser drive current value is controlled by a control signal from the first laser power control means, and the sampling pulse is not output for the second predetermined period or longer. An optical information recording / reproducing apparatus comprising: a means for switching to the second laser power control means and controlling a laser driving current value by a control signal from the second laser power control means. A semiconductor laser light source emits pulsed light based on a predetermined light emission rule and irradiates the recording medium with laser light, and predetermined recording is performed on the recording medium by ternary laser power of a bias level, an erase level, and a peak level Records information consisting of pulses having a length that is an integer multiple of 1 or more of the channel clock period based on the modulation method, erases the information recorded on the recording medium, initializes the recording medium, and records the information on the recording medium. In an optical information recording / reproducing apparatus for reproducing recorded information,
First laser power control means for controlling the laser drive current value of the semiconductor laser light source so that the light emission power of the laser light becomes constant according to the level change of the signal according to the level of the laser power;
Second laser power control means for controlling the laser drive current value of the semiconductor laser light source at a constant value regardless of the level of the laser power;
Switching means for switching between the first laser power control means and the second laser power control means;
Means for outputting a sampling pulse for detecting the laser power at the bias level when a period in which the information to be recorded on the recording medium is zero occurs for a first predetermined period or more;
At the time of recording on the recording medium, the laser power at the erase level is detected, the laser power is controlled based on the laser power at the erase level, and the sampling pulse is output at an interval within a second predetermined period. In this case, the switching means switches to the first laser power control means, the laser drive current value is controlled by a control signal from the first laser power control means, and the sampling pulse is not output for the second predetermined period or longer. An optical information recording / reproducing apparatus comprising: a means for switching to the second laser power control means and controlling a laser driving current value by a control signal from the second laser power control means. The optical information recording / reproducing apparatus according to claim 1 or 2,
After switching from the first laser power control means to the second laser power control means and outputting the sampling pulse, the switching means again switches to the first laser power control means, and from the first laser power control means An optical information recording / reproducing apparatus provided with means for controlling the laser drive current value by the control signal. The optical information recording / reproducing apparatus according to claim 2.
A current for causing the semiconductor laser light source to emit light at the bias level is driven by a laser drive current control signal output from the first laser power control means or the second laser power control means, and light is emitted from the semiconductor laser light source. And means for driving a current for causing the semiconductor laser light source to emit light at the erase level or the peak level by superimposing a current corresponding to the differential efficiency characteristic of the laser light to be emitted on the laser light. Information recording / reproducing apparatus. The optical information recording / reproducing apparatus according to claim 1 or 2,
A switching signal output means for setting the sampling pulse as a trigger input, and outputting a second laser power control switching signal for causing the switching means to switch to the second laser power control means after a predetermined period of the trigger input;
When the sampling pulse is not output for the predetermined period or longer, the second laser power control switching signal output from the switching signal output means to the switching means falls, and then the second laser power control switching when the sampling pulse is output. An optical information recording / reproducing apparatus comprising means for controlling a signal to rise. The optical information recording / reproducing apparatus according to claim 1 or 2,
Second laser power control switching that operates based on a predetermined clock frequency, resets the count value by the sampling pulse, and causes the switching means to switch to the second laser power control means after a predetermined count after the count value is reset Counting means for outputting a signal;
If the sampling pulse is not output for the predetermined period or longer, the second laser power control switching signal output from the counting means to the switching means falls, and then resets the counting means when the sampling pulse is output, (2) An optical information recording / reproducing apparatus comprising means for controlling the laser power control switching signal to rise. The optical information recording / reproducing apparatus according to any one of claims 1 to 3,
Differential signal output means for outputting a differential signal between a control signal output from the first laser power control means and a control signal output from the second laser power control means;
During the period in which the laser drive current value is controlled by the second laser power control means, the output of the differential signal output means instead of the signal corresponding to the level of the laser power output to the second laser power control means Means are provided for holding the control signal output from the first laser power control means at the same level as the control signal output from the second laser power control means by feeding back the signal to the first laser power control means. An optical information recording / reproducing apparatus. The optical information recording / reproducing apparatus according to any one of claims 1 to 7,
Comparison signal output means for outputting a comparison signal as a result of comparing the control signal output from the first laser power control means and the control signal output from the second laser power control means;
Means is provided for controlling the control signal output from the second laser power control means so that the two control signals are always at substantially the same level by periodically comparing the two control signals by the means. An optical information recording / reproducing apparatus.

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