JP2000149302A - Semiconductor laser driving device, optical head, optical disk device and optical disk recording and reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize a laser power output by superposing a high frequency signal on a driving signal and varying the frequency and/or amplitude of the high frequency signal of a high frequency superposing means according to the information recording and the information reading operation mode in an optical disk device. SOLUTION: The laser driver 5 of an optical pickup generates a prescribed laser driving signal based on a recording signal at the time of a record mode and generates a prescribed laser driving signal at the time of a reproduction mode to supply them to a high frequency superposing circuit 6. The high frequency superposing circuit 6 superposes a high frequency coming from the high frequency oscillation circuit incorporated in the circuit 6 on the laser driving signal via a modulation means. At this time, a superposing frequency variable circuit 7 generates a control signal varying the superposing frequency in the high frequency superposing circuit 6 in accordance with a mode changeover signal CMOD from a control circuit 2 to supply it to the high frequency superposing circuit 6, which changes the frequency and the amplitude of the high frequency signal which is to be superposed on the laser driving signal based on the control signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a write-once type optical disk which can be written only once by irradiating a laser beam on an optical disk such as a compact disk (CD) or a DVD, and a rewritable type optical disk which can be rewritten any number of times. The present invention can be applied to an optical disk device and an optical disk recording method using a recordable optical disk.

[0002]

2. Description of the Related Art When a semiconductor laser is used as a light source of an optical disk drive, noise of the semiconductor laser occurs due to light reflected from a recording medium. As a method for reducing the noise of such a semiconductor laser, there is known a high-frequency current superimposing method in which a high-frequency AC current from a high-frequency current drive circuit is superimposed on a DC current to flow through the semiconductor laser.

The above-described high-frequency superimposition of a semiconductor laser is mainly performed at the time of reading information with a low output laser power. For example, Japanese Patent Application Laid-Open No. Hei 5-197994 discloses that a light source that is stable against fluctuations in the amount of return light can be obtained by increasing the amount of superimposition of a high-frequency current by a high-frequency superimposing circuit during focus control pull-in by a focus servo system. A semiconductor laser noise reduction circuit and an optical disk device that can be used are disclosed. Also, Japanese Patent Application Laid-Open No.
No. 5732 discloses a noise reduction circuit of a semiconductor laser that suppresses heat generation of a current drive circuit by changing the amplitude of a high-frequency AC current superimposed on a DC current in response to error detection due to an increase in noise during information reproduction. Have been.

[0004] Also, Japanese Patent Application Laid-Open No. 3-97130 discloses that
There is disclosed a noise reduction circuit for a semiconductor laser that controls the amount of superposition of a high-frequency current superimposed on a direct current by varying the gain of a variable gain amplifier to obtain an appropriate degree of modulation and reduce noise. Japanese Patent Application Laid-Open No. Hei 4-6635 discloses that the noise returning to a semiconductor laser is sufficiently reduced by varying the pulse lighting frequency of a laser beam and controlling the return light noise to be equal to or less than a reference amount. An optical information recording / reproducing device is disclosed. In addition, Japanese Unexamined Patent Publication No.
No. 52569 discloses laser noise reduction which can reduce noise without affecting a reproduced information signal even when a frequency of a superimposed signal added for oscillating a laser diode in multiple modes is low. An apparatus is disclosed.

[0005]

The above-described high-frequency superimposition of the conventional semiconductor laser is performed at the time of focus control pull-in or over a track after pull-in, or at the time of reproduction, according to an error signal or a differential quantum efficiency of the laser. The amplitude of the current is varied, and the frequency of the high-frequency superimposed current is varied by the amount of noise and the clock signal. No consideration was given to writing or erasing of the used information. For this reason, noise at the time of recording or erasing information cannot be reduced, and laser power cannot be optimized to improve the S / N ratio in each operation mode.

Accordingly, an object of the present invention is to propose a semiconductor laser driving device, an optical head, an optical disk device, and a recording / reproducing method which can optimize the laser power output in each operation mode of the optical disk device. .

[0007]

SUMMARY OF THE INVENTION A semiconductor laser driving device, an optical head, and an optical disk device according to the present invention include a laser driver for supplying a semiconductor laser with a drive signal according to an operation mode of the optical disk device, and a high frequency signal for the drive signal. The high frequency superimposing means for superimposing, and the superimposed high frequency signal varying means for varying the frequency and / or the amplitude of the high frequency signal of the high frequency superimposing means in accordance with the information recording and reading operation mode in the optical disc device. Further, according to the optical disk recording / reproducing method of the present invention, a superposition frequency for superposing a high-frequency current on a semiconductor laser and a superposition frequency for varying the frequency and / or amplitude of the high-frequency signal in the high-frequency superposition step according to an operation mode in the optical disk recording method. And a variable step.

According to the semiconductor laser driving device, the optical head, the optical disk device and the optical disk recording / reproducing method of the present invention, according to the operation mode of the optical disk device,
A second output power of at least the first output power of the semiconductor laser;
Since the respective superimposed frequencies and amplitudes of the output powers are changed, high-frequency superimposition of a plurality of frequencies can be performed, and laser noise can be easily controlled by optimizing according to a mode such as signal output.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. Optical discs include read-only optical discs, write-once optical discs that can be written only once, and rewritable optical discs that can be rewritten any number of times.

This embodiment is based on one of the above optical disks.
It is applied to a write-once optical disk that can be written only once and a recordable optical disk such as a rewritable optical disk that can be rewritten a plurality of times. First, as a write-once optical disk that can be written only once, for example, a CD-R
Will be described. The CD-R forms pits on which information is recorded by causing the dye in the dye recording layer to undergo a thermal change when heated by heating with laser light, and the change in reflectance due to the presence or absence of recording pits by laser light irradiation is a digital signal. And read the information. Next, as a rewritable optical disk that can be rewritten a plurality of times, for example, CD-
The outline of the RW will be described. CD-RW records and erases information by causing a crystallographic phase change in the structure of the recording thin film by heating and irradiating with a laser beam, resulting in a change in the optical constant during that phase. A phase-change type recording thin film that enables phase-change recording in which information is reproduced by detecting a change in reflectance is used.

FIG. 1 is a block diagram showing a configuration of a semiconductor laser driving device in an optical disk recording device according to an embodiment of the present invention. This optical disc device uses an optical disc 1 with laser light emitted from a semiconductor laser.
The digital data output from the information source is recorded and reproduced on the computer 1. Further, in the optical disk device, a high frequency superimposed signal output from the high frequency superimposing circuit is also superimposed on the laser light. Generally, a guide groove called a pre-groove is formed in advance on a recordable optical disk, and this pre-groove is slightly modulated by FM modulation. Therefore, a clock signal is obtained by demodulating this FM modulation, and based on this, a PLL servo can be applied to control the spindle motor.

That is, in this optical disk device, a spindle motor (not shown) rotationally drives the optical disk 11 and rotationally drives the optical disk 11 at a predetermined rotational speed based on the clock signal.

The information signal supplied from the information source 1 is subjected to signal processing such as recording modulation in the control circuit 2 and supplied to the optical pickup 4 as a recording signal. More specifically, an error correction code generation circuit (ECC) (not shown) receives digital data output from an information source, adds an error correction code, performs interleaving processing, and outputs an 8-bit digital signal. In this way, by adding an error correction code to data to be recorded, correct information can be read even if there is a defect on the disk.

In the optical pickup 4, a laser driver 5 generates a predetermined laser drive signal based on a recording signal in a recording mode and a predetermined laser drive signal in a reproduction mode, and supplies the generated laser drive signal to a high frequency superimposing circuit 6. The high-frequency superimposing circuit 6 superimposes a high-frequency signal from a built-in high-frequency oscillation circuit on a laser drive signal via a modulating means. At this time, the superposition frequency variable circuit 7 generates a control signal for changing the superposition frequency in the high frequency superposition circuit 6 according to the mode switching signal CMOD from the control circuit 2 and supplies the control signal to the high frequency superposition circuit 6. The high frequency superimposing circuit 6 changes the frequency and amplitude of the high frequency signal superimposed on the laser drive signal based on the control signal. Further, one of the frequency and the amplitude may be changed.

The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 emits a laser beam based on a laser drive signal and supplies the laser beam to the optical system 9. The recording laser from the laser diode 8 is constituted by a semiconductor laser or the like, and is emitted as a laser beam onto the optical disk 11. The laser beam is a light beam that includes both the signal components of the high-frequency signal and the information signal at the same time because the intensity of the laser beam is changed according to the information signal during the information writing operation.

The laser beam obtained in this way is bent toward the optical disk 11 by a mirror (not shown) in the optical system 9 and travels toward the optical disk 11, and is then focused on the optical disk 11 by an objective lens (not shown). .
The mirror and the objective lens are sequentially moved in the outer peripheral direction of the optical disk 11 by a thread mechanism (not shown) in synchronization with the rotation of the optical disk 11, whereby the irradiation position of the laser beam is sequentially displaced in the outer peripheral direction of the optical disk 11.

Thus, in this optical disk apparatus, while the optical disk 11 is rotationally driven, a track is spirally scanned by moving a mirror and an objective lens, and a laser beam corresponding to two signals of an information signal and a high-frequency signal is applied to the track. Beam irradiation is performed. By performing recording after the laser light has passed through the objective lens, a change in the traveling direction of the laser light is recorded as a position change of a spot focused on the optical disk. As described above, in the present embodiment, it is possible to optimize the irradiation of the laser light and the detection of the reflected light at each laser output power by changing the frequency and the amplitude of the high-frequency signal to be superimposed on the information signal according to the operation mode. .

The reflected light of the laser light (not shown) from the optical disk 11 is detected by a photodetector in accordance with the amount of reflected light, and the detection signal is fed back to the control circuit 2. The control circuit 2 generates a servo signal based on the detection signal and supplies the servo signal to the servo circuit 3. The servo circuit 3 generates drive signals for the focus coil and the tracking coil based on the servo signals and supplies the drive signals to the biaxial actuator 10. The two-axis actuator 10 drives a focus coil and a tracking coil based on a drive signal. Thus, it is possible to irradiate a laser beam having a high frequency superimposed on a focal position at a desired track position on the optical disc 11.

More specifically, at the time of recording on a rewritable optical disk, the laser power is previously set to the erase power level by the laser driver 5 to erase the information of the non-recorded portion, and the laser power is adjusted to the write power level. The information signal is recorded at the target track position, and at the time of reproduction, the laser power is adjusted to the read power level by the laser driver 5 to reproduce the information signal recorded at the target track position. Record here,
In each of the erasing and reproducing modes, a laser beam on which a corresponding high-frequency signal is superimposed is emitted.

After the optical pickup 4 is positioned at the target track position, the recording or reproducing operation is performed as follows. At the time of reproduction, the control circuit 2 supplies a reproduction command to the laser driver 5. Laser driver 5
Adjusts the laser emission power to a reproduction power level, generates a laser drive signal, and supplies the laser drive signal to the high frequency superimposing circuit 6. The high-frequency superimposing circuit 6 superimposes a signal supplied from a built-in high-frequency oscillation circuit on a laser drive signal via a modulating means. At this time, the superimposed frequency variable circuit 7
The superimposing frequency in the high frequency superimposing circuit 6 is controlled in accordance with the mode switching signal CMOD from the control circuit 2. The high-frequency superimposing circuit 6 changes the frequency and amplitude of the high-frequency signal superimposed on the laser drive signal based on the above control to a relatively low frequency for reproduction and a relatively large amplitude. Further, one of the frequency and the amplitude may be changed.

The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 irradiates a laser beam to the optical disk 11 via the lens of the optical system 9 based on a laser drive signal. In the case of a CD-R, the change in reflectance due to the presence or absence of pits recorded by heating and heating by laser light irradiation is read as a digital signal to reproduce information, and in the case of a CD-RW, phase change recording is performed in an amorphous state. The change in the reflectance of the recorded mark is read as a digital signal to reproduce information.

The photodiode inside the optical pickup 4 receives the laser beam reflected by the optical disk on a plurality of divided light receiving surfaces. The photodiode converts the received laser light into an electric signal and supplies the electric signal to the adder. The adder adds a plurality of divided signals to generate a reproduced RF signal.

The adder supplies the reproduced RF signal to an RF amplifier circuit. The RF amplifier circuit amplifies the reproduced data at a high frequency and supplies it to a demodulation circuit. The demodulation circuit demodulates the reproduced data by 8/14 using EFM. The demodulation circuit supplies the demodulated reproduced data to the ECC decoding circuit. The ECC decoding circuit performs an error correction process on the reproduced data using a Reed-Solomon product code and outputs the reproduced data. The decoded information signal is supplied to a host computer.

At the time of recording, the control circuit 2 supplies a recording command to the laser driver 5. The recording data supplied from the host computer is supplied to an ECC encoding circuit. The ECC encoding circuit adds an error correction code to the recording data using a Reed-Solomon product code.
The ECC encoding circuit supplies the recording data added with the error correction code to the modulation circuit. The modulation circuit converts the recording data to which the error correction code is added by EFM into 8 /
14 modulation. The modulation circuit supplies the modulated recording data to the laser driver 5. Laser driver 5
The pulse width modulation of the 8/14 modulated recording data based on the recording command generates a laser drive signal of a write power level, which is supplied to the high frequency superimposing circuit 6.
The high-frequency superimposing circuit 6 superimposes a high-frequency signal from a built-in high-frequency oscillation circuit on a laser drive signal via a modulating means. At this time, the superimposing frequency variable circuit 7 controls the superimposing frequency in the high frequency superimposing circuit 6 to be variable according to the mode switching signal CMOD from the control circuit 2. The high frequency superimposing circuit 6 changes the frequency and amplitude of the high frequency signal superimposed on the laser drive signal to a relatively high frequency for recording and a relatively small amplitude under the control of the superimposing frequency variable circuit 7. Further, one of the frequency and the amplitude may be changed.

The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 irradiates a laser beam to the optical disk 11 via the lens of the optical system 9 based on a laser drive signal. When the recording thin film of the optical disc 11 is heated by a laser beam, and in the case of a CD-R, a pit on which information is recorded is formed by causing a thermal change in the dye of the dye recording layer by heating and raising by laser beam irradiation, In the case of a CD-RW, recording data is recorded at a target track position by phase change recording in a state where the crystal is made amorphous by melting and quenching.

FIG. 2 is a circuit diagram of the superimposed frequency variable circuit according to the present embodiment. 2, the superimposed frequency variable circuit 7 includes a terminal 25 connected to a transistor 27, a terminal 21-1 to which a mode switching signal CMOD1 is supplied, a gate G connected to a terminal 21-1, and a source S connected to the ground. FET1 (field effect transistor) 22 which is connected and whose drain D is connected to one end of a resistor (R2-1) 23-1
-1 and a resistor (R2-
1) 23-1, a terminal 21-2 to which a mode switching signal CMOD2 is supplied, a gate G connected to the terminal 21-2, a source S connected to the ground, and a drain D connected to a resistor (R2-2). FET2 (field effect transistor) 22-2 connected to one end of 23-2, resistor (R2-2) 23-2 connected to the other end of terminal 25-2, one end connected to ground, Is connected to the terminal 25 (R
1) 24. Here, FET (1)
22-1 and FET (2) 22-2 are resistors (R1)
24 is a switch for switching whether or not to connect the resistor (R2-1) 23-1 and the resistor (R2-2) 23-2 in parallel.

In the thus configured superposed frequency variable circuit, the mode switching signal CMO
When D1 is at high level H, FET1 is turned on and FE
Assuming that the ON resistance of T1 is a resistance (Ron1), a resistor (R1) 24, a resistor (Ron1) and a resistor (R2-
1) The resistance of the parallel connection with the resistance connected in series with 23-1 becomes the combined resistance Radj1. Therefore, the combined resistance R
adj1 = (Ron1 + R2-1) · R1 / (Ron1
+ R2-1 + R1). And the combined resistance Radj1
, The current Icnt of the transistor 27 becomes the first current value Icnt1. Here, the resistance value (R2-1)
Assuming that: = resistance value (R2-2), resistance component (Ron1) = resistance component (Ron2), the same state occurs when FET1 is off and FET2 is on.

As a second mode, when both the mode switching signal CMOD1 and the mode switching signal CMOD2 are at the high level H, the FET1 and the FET2 are turned on. R1) 24, a resistor (Ron1) and a resistor (R2-1) 23-1 connected in series, and a resistor (Ron2) and a resistor (R2-2) 23-2 connected in series. The resistance of the parallel connection with the added resistance is the combined resistance Ra.
dj2. Therefore, the combined resistance Radj2 = ｛(Ro
n1 + R2-1) .R1 + (Ron1 + R2-1).
(Ron2 + R2-2) + (Ron2 + R2-2) · R
1｝ / (Ron1 + R2-1 + Ron2 + R2-2 + R
1). Then, the current Icnt of the transistor 27 is changed to the second current value Icnt according to the value of the combined resistance Radj2.
It becomes 2.

Here, resistance value (R2-1) = resistance value (R2-2), resistance component (Ron1) = resistance component (Ron
2), the resistance (Ron1) and the resistor (R2-
1) With respect to the resistor connected in series with 23-1, the resistor (Ron1) and the resistor (R2-1) 23-1 connected in series, the resistor (Ron2) and the resistor (Ron2) are connected in series. R2-
2) The resistance in parallel connection with the resistance connected in series with 23-2 has a value of １ ／ of that in the first mode.

In the third mode, when both the mode switching signal CMOD1 and the mode switching signal CMOD2 are at the low level L, the FET1 and the FET2 are turned off, and the FET1 and the FET2 are opened. The combined resistance becomes Radj3. Therefore, the combined resistance Radj3 = R1. Then, the current Icnt of the transistor 27 at this time becomes the third current value Icnt3.

Thus, the mode switching signal CMOD is
1 and the mode switching signal CMOD2 is at the high level H or the low level L, the value of the combined resistor Radj changes to Radj1 to Radj3, and the current of the transistor 27 is switched by the mode switching from the first mode to the third mode. Since Icnt changes to Icnt1 to Icnt3, the frequency and amplitude of the high-frequency signal of the oscillation circuit (VCO) 28 may be changed using the transistor 27 of the high-frequency superimposing circuit 6. Also,
Only the frequency may be changed, or only the amplitude may be changed. Further, a terminal 21-3 to which a mode switching signal CMOD3 is supplied is provided for the superimposed frequency variable circuit 7 of FIG.
The gate G is connected to the terminal 21-3, the source S is connected to the ground, and the drain D is connected to the resistor (R2-3) 23-3.
FET3 (field effect transistor) connected to one end of
22-3 and a resistor (R2
-3) 23-3, and the mode switching signal CMOD3
, The number of modes may be further increased. Further, the control means for changing the frequency and / or the amplitude of the high frequency signal of the oscillation circuit (VCO) 28 can be realized by another configuration.

At this time, for example, the oscillating circuit (VCO) 28 of the high frequency superimposing circuit 6 is an oscillator that oscillates by varying a plurality of types of sine waves at predetermined frequencies. The oscillation frequency f2 of the oscillator B may be an integral multiple of the oscillation frequency f1 of the oscillator A. Further, the oscillation frequency f3 of the oscillator C is
It may be another integer multiple of f1. Further, the oscillation frequency f4 of the oscillator D may be set to another integer multiple of f1. Further, the output from each of these oscillators is amplified by an amplifier circuit to a fraction of an integer, another fraction of an integer, and another fraction of another integer, so that the signal amplitude decreases when the frequency is high. ing. Further, only the frequency or only the amplitude may be changed.

The specific operation when the optical disk 11 is a write-once optical disk which can be written only once and when a rewritable optical disk which is rewritable a plurality of times is used will be described. First, a case where a CD-R is used as a write-once optical disk will be described as an example. In the CD-R, the dye in the dye recording layer undergoes a thermal change when heated by laser light irradiation to form a pit on which information is recorded, and different signal values are recorded depending on the length of the recording pit.

FIG. 3 is a waveform diagram showing a recording operation of the CD-R according to the present embodiment. The ILD signal shown in FIG. 3A shows the signal value on the vertical axis and the time on the horizontal axis, and the laser adjusted to the read power level IR output from the laser driver 5 and the laser emission power of the recording power levels IW1 and IW2. Drive signal. Here, the reading power laser IR is a power level output when no recording pit is formed, and is equivalent to the power during a normal reproducing operation in which only reproducing is performed. The W / XR signal shown in FIG. 3B is a recording (WR) output from the control circuit 2.
ITE: High level H) or Read (READ: Low level L) command signal. OD shown in FIG. 3C
The ON signal is a control signal for the laser driver 5 output from the control circuit 2. ENBL shown in FIG. 3D
The signal is an enable signal output from the information source 1 for permitting the operation of the control circuit 2. 3E and 3
The CMOD1 signal and the CMOD2 signal indicated by F are mode switching signals for changing the frequency and / or amplitude of the high frequency signal of the oscillation circuit (VCO) 28 by the superimposed frequency variable circuit 7. The PLD shown in FIG. 3G is a high frequency signal superimposed on the laser drive signal supplied to the laser diode 8 by the high frequency superimposing circuit 6. T1
A period T2 indicates a period during which the laser beam of the reading power level IR is irradiated, a period T2 to T4 indicates a period in which a recording operation for forming a pit is performed, and a period T4 to T5 indicates a period during which the reading power level IR is used. The period during which laser light is irradiated is shown. In this embodiment (FIG. 3), T1 to T1
Although only the period of T5 is shown, this is performed continuously during the actual printing operation.

In FIG. 3, during the period from T1 to T2, the mode switching signal CMOD1 and the mode switching signal CMOD2 shown in FIGS. 3E and 3F are both at the low level L in the superposition frequency variable circuit 7 shown in FIG. The frequency variable circuit 7 outputs a low-level L mode switching signal CMO.
The current Icnt of the transistor 27 is varied so as to set the superimposition frequency in the high-frequency superimposition circuit 6 according to D1 and the mode switching signal CMOD2, and the third current value Ic
nt3. The high frequency superimposing circuit 6 changes the frequency and / or amplitude of the high frequency signal superimposed on the laser drive signal based on the current Icnt. The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 emits a laser beam based on a laser drive signal on which a high-frequency signal is superimposed, and supplies the laser beam to the optical system 9. At this time, the high frequency signal shown in FIG. 3G has a relatively large amplitude P1 at a relatively low frequency F1. The operation of high-frequency superimposition during the period from T1 to T2 corresponds to the above-described third mode.

In the period from T2 to T3, the mode switching signal CMOD1 shown in FIG. 3E is at the high level H, and the mode switching signal CMOD2 shown in FIG.
The superposition frequency variable circuit 7 sets the current value Icn of the transistor 27 so as to set the superposition frequency in the high-frequency superposition circuit 6 according to the high-level H mode switching signal CMOD1.
The variable t is set to the first current value Icnt1. The high-frequency superimposing circuit 6 changes the frequency and amplitude of the high-frequency signal superimposed on the laser drive signal based on the current value Icnt. The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 emits a laser beam based on a laser drive signal on which a high-frequency signal is superimposed, and supplies the laser beam to the optical system 9. At this time, the high-frequency signal shown in FIG. 3G has a relatively medium frequency F2 (F2> F1) and a relatively medium amplitude P2 (P2 <P1) that is smaller than P1. The operation of high-frequency superposition during the period from T2 to T3 corresponds to the above-described first mode.

In the period from T3 to T4, the mode switching signals CMOD1 and CMO shown in FIGS.
D2 is at a high level H, and the superimposed frequency variable circuit 7
Are high-level H mode switching signals CMOD1 and CMOD1
The current Icnt of the transistor 27 is varied so as to set the superimposition frequency in the high-frequency superimposition circuit 6 in accordance with MOD2 to obtain a second current value Icnt2. The high frequency superimposing circuit 6 changes the frequency and amplitude of the high frequency signal superimposed on the laser drive signal based on the current Icnt. The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 emits a laser beam based on a laser drive signal on which a high-frequency signal is superimposed, and supplies the laser beam to the optical system 9. At this time,
The high frequency signal shown in FIG. 3G has a relatively high frequency F3 (F3
>F2> F1), a relatively small amplitude P3 compared to P1
(P3 <P2 <P1). The operation of high-frequency superimposition during the period from T3 to T4 corresponds to the above-described second mode.

In the period from T4 to T5, the mode switching signal CMOD1 and the mode switching signal C shown in FIGS. 3E and 3F in the superposition frequency variable circuit 7 shown in FIG.
MOD2 is both at the low level L, and the superposition frequency variable circuit 7 outputs the high-frequency superposition circuit 6 in response to the low-level L mode switching signal CMOD1 and the mode switching signal CMOD2.
To set the superimposed frequency at
Of the current Icnt is changed to a third current value Icnt3. The high frequency superimposing circuit 6 changes the frequency and amplitude of the high frequency signal superimposed on the laser drive signal based on the current Icnt. The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 emits a laser beam based on a laser drive signal on which a high-frequency signal is superimposed, and supplies the laser beam to the optical system 9. At this time, the high frequency signal shown in FIG. 3G has a relatively large amplitude P1 at a relatively low frequency F1. This T4
The operation of high-frequency superimposition during the period from T5 to T5 corresponds to the above-described third mode.

It should be noted that the ILD signal shown in FIG. 3A is switched to the relatively large recording power level IW1 and the relatively medium recording power level IW2 during the periods T2 to T3 and T3 to T4. In the first half of the recording operation, in the state where the dye of the dye recording layer is liable to undergo a thermal change due to heating by laser beam irradiation, a pit in which information is recorded is formed and stabilized in the second half of the recording operation,
This is because the standard is determined in order to improve the recording characteristics of the CD-R.

Further, during the period from T2 to T3, a high-frequency signal having a relatively medium frequency F2 and a relatively medium amplitude P2 shown in FIG. 3G is superimposed on the ILD signal shown in FIG. 3A. In order to prevent this, the condition is that the peak value of the laser power output after superposition is lower than the allowable peak value of the laser power. Therefore, if the allowable peak value is low depending on the type of laser diode, T2
In the period of T3, as in the period of T3 to T4, FIG.
G, a relatively small amplitude P3 at a relatively high frequency F3
May be superimposed on the ILD signal shown in FIG. 3A. Also, if it is within the range of the allowable peak value,
Only the amplitude may be changed at the same frequency. Similarly, if it is within the range of the allowable peak value, T2
During the period from T3 to T3, a high-frequency signal having a relatively high frequency F3 and a relatively small amplitude P3 is superimposed, and during the period from T3 to T4,
A high frequency signal having a relatively medium frequency F2 and a relatively medium amplitude P2 may be superimposed.

Next, as a rewritable optical disk, C
A case where D-RW is used will be described as an example. First,
The principle of phase change recording will be described. In general, a phase-change disk is initially in a crystal (crystalline) state, and is recorded by changing the crystalline state to an amorphous (non-crystalline) state, and is erased by changing the amorphous state to a crystalline state. . In other words, at the time of recording, the temperature of the recording thin film of the optical disk is raised to the melting point by irradiation with a laser beam of write power, and the temperature is rapidly lowered so as to prevent coagulation from occurring, whereby the amorphous state is formed by rapid cooling. During erasing, the temperature of the recording thin film on the optical disk is raised to the melting point by irradiating a laser beam of erase power, and the cooling rate is reduced to slowly cool the crystal, or the crystal is maintained by maintaining the temperature above the amorphization temperature for a certain period of time. Return to the state. In particular, crystallization from a state in which the temperature is raised to a melting point or higher is called melt crystallization or liquid phase crystallization, and crystallization from a supercooled liquid state is called solid phase crystallization.

Using such a recording thin film, the recording thin film is heated and heated by irradiating a laser beam to cause a crystallographic phase change in its structure, thereby recording and erasing information.
Information is reproduced by detecting a change in reflectance caused by a change in optical constant during the phase.

The above-mentioned amorphous state is obtained by heating the recording thin film to a temperature equal to or higher than its melting point by irradiating a laser beam, melting the recording thin film, and then rapidly cooling it. The crystalline state can be obtained by heating to a temperature below the melting point and above the crystallization temperature.

Since the amorphous state can be obtained by melting and quenching, the time can be shortened as long as the laser power allows. However, since the crystal state is a primordial rearrangement, the crystallization depends on the material properties. Need time for. That is, it is required that the material used for the phase change optical disk not only has a stable amorphous state but also crystallizes in a short time.

The crystallization speed of the material is sufficiently large, the crystallization time is short, and if the crystallization is performed within the passage time of the laser beam, the laser power is changed between the write (amorphous state) power and the erase (crystallization) power. The overwrite operation by a single beam in which new data is written while erasing data already recorded by one beam becomes possible.

When recording is performed on a track where data has been recorded with new data using a pulse-width-modulated laser beam, a portion irradiated with write power is melted and quenched irrespective of the previous state and becomes amorphous. State
Similarly, the portion irradiated with the erase power becomes a crystalline state regardless of the previous state. In this way, new data can be overwritten and recorded while erasing previous data by one laser beam irradiation. Therefore, during the recording operation period, both erasing (erasing) and recording (writing) are performed.

The overwriting of the phase change recording of the CD-RW according to the present embodiment will be described with reference to FIG. FIG. 4 is a waveform diagram showing the operation of the CD-RW according to the present embodiment. FIG.
The ILD signal shown in A indicates the signal value on the vertical axis and the time on the horizontal axis, and is adjusted to the laser emission power of the reading power level IR, the erasing power level IE, and the recording power level IW output from the laser driver 5. Laser drive signal. The W / XR signal shown in FIG. 4B is a recording (WRITE: high level H) or reading (READ: low level L) command signal output from the control circuit 2. Here, the reading power level IR is a power level output when no recording pits are formed or recorded pits are not erased, and is equivalent to a laser power during a normal reproducing operation in which only reproducing is performed. The ODON signal shown in FIG. 4C is a control signal for the laser driver 5 output from the control circuit 2.
The ENBL signal shown in FIG. 4D is an enable signal output from the information source 1 to permit the operation of the control circuit 2. The CMOD1 signals and C shown in FIGS. 4E and 4F
The MOD2 signal is a mode switching signal for changing the frequency and amplitude of the high frequency signal of the oscillation circuit (VCO) 28 by the superimposed frequency variable circuit 7. PLD shown in FIG. 4G
Is a high frequency signal superimposed on the laser drive signal supplied to the laser diode 8 by the high frequency superimposing circuit 6. A period from T11 to T12 indicates a period during which the laser beam of the reading power level IR is irradiated, and T12 to T12.
A period of 13 indicates a period during which the laser light of the erasing power level IE is irradiated, a period of T13 to T14 indicates a period of the irradiation of the laser light of the recording power level IW, and T1
The period from 4 to T15 indicates a period during which the laser beam of the reading power level IR is irradiated. In the embodiment shown in FIG. 4, the period from T11 to T15 is shown continuously, but during the actual recording operation, information is recorded by repeating the period from T12 to T14 repeatedly. T11-
T12 and T14 to T15 show a state during a normal reproduction operation. Here, the states at the time of each operation are continuously shown for easy comparison.

In FIG. 4, during the period from T11 to T12, the superimposed frequency variable circuit 7 shown in FIG.
The mode switching signal CMOD1 and the mode switching signal CMOD2 shown in FIG. 3F are both at a low level L, and the superposition frequency variable circuit 7 The current Icnt of the transistor 27 is varied so as to set the superimposition frequency to obtain a third current value Icnt3. The high-frequency superposition circuit 6 outputs the current Icn
The frequency and / or amplitude of the high frequency signal superimposed on the laser drive signal is changed based on t. The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 emits a laser beam based on a laser drive signal on which a high-frequency signal is superimposed, and supplies the laser beam to the optical system 9. At this time, the high-frequency signal shown in FIG. 4G has a relatively large amplitude P10 at a relatively low frequency F10. The operation of high-frequency superimposition during the period from T11 to T12 corresponds to the above-described third mode.

In the period from T12 to T13, FIG.
And mode switching signals CMOD1 and CMOD1 shown in FIG.
MOD2 is at the high level H, and the superposition frequency variable circuit 7 sets the current Icnt of the transistor 27 so that the superposition frequency in the high-frequency superposition circuit 6 is set according to the high-level H mode switching signals CMOD1 and CMOD2.
Is changed to a second current value Icnt2. The high frequency superimposing circuit 6 changes the frequency and / or amplitude of the high frequency signal superimposed on the laser drive signal based on the current Icnt. The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 emits a laser beam based on a laser drive signal on which a high-frequency signal is superimposed, and supplies the laser beam to the optical system 9. At this time, the high-frequency signal shown in FIG. 4G has a relatively high frequency F30 (F30> F10) as compared with F10 and a relatively small amplitude P30 (P30 <P10) as compared with P10.
The operation of high-frequency superimposition during the period from T12 to T13 corresponds to the above-described second mode.

In the period from T13 to T14, FIG.
When the mode switching signal CMOD1 shown in FIG.
F, the mode switching signal CMOD2 is at the low level L, and the superposition frequency variable circuit 7 sets the current Ic of the transistor 27 so as to set the superposition frequency in the high frequency superposition circuit 6 in accordance with the high level H mode switching signal CMOD1.
nt is changed to a first current value Icnt1. The high frequency superimposing circuit 6 changes the frequency and / or amplitude of the high frequency signal superimposed on the laser drive signal based on the current Icnt. The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 emits a laser beam based on a laser drive signal and supplies the laser beam to the optical system 9. At this time, the high-frequency signal shown in FIG. 4G has a relatively medium frequency F20 (F30>
F20> F10) and a relatively medium amplitude P20 (P30
<P20 <P10). The operation of high-frequency superimposition during the period from T13 to T14 corresponds to the above-described first mode.

In the period from T14 to T15, the superimposed frequency variable circuit 7 shown in FIG.
F, the mode switching signal CMOD1 and the mode switching signal CMOD2 are both at the low level L, and the superimposed frequency variable circuit 7 outputs the low-level L mode switching signal CMOD1.
The current Icnt of the transistor 27 is varied so as to set the superimposition frequency in the high-frequency superimposition circuit 6 according to the mode switching signal CMOD2, and the third current value Icnt
3 is assumed. The high-frequency superimposing circuit 6 changes the frequency and / or amplitude of the high-frequency current superimposed on the laser drive signal based on the current Icnt. The laser drive signal on which the high frequency signal is superimposed is supplied to the laser diode 8. The laser diode 8 emits a laser beam based on a laser drive signal and supplies the laser beam to the optical system 9. At this time, the high frequency signal shown in FIG.
At 0, the amplitude becomes relatively large P10. This T14-T1
The operation of superimposing high frequency during the reproduction operation of No. 5 corresponds to the third mode described above.

A high frequency signal having a relatively high frequency and a relatively small amplitude P30 shown in FIG. 4G is superimposed on the ILD signal shown in FIG. 4A during the period from T12 to T13. The condition is that it is sufficiently lower than the value of the recording power IW. This is because when the amplitude is large, there is a possibility that the laser power output becomes equivalent to the recording power IW, and there is a possibility that pits are formed by mistake. Therefore, when the difference between the value of the erasing power IE and the value of the recording power IW is large, T12 to T12
In the period of 13 as well as the period of T13 to T14,
A high frequency signal having a relatively medium frequency F20 and a relatively medium amplitude P20 shown in FIG. 4G may be superimposed on the ILD signal shown in FIG. 4A. If the recording power IW is within the range of the allowable peak value, the frequency may be changed and only the amplitude may be changed. Similarly, if it is within the range of the allowable peak value, during the period from T12 to T13, the relatively medium frequency F20 and the relatively medium amplitude P20
And a relatively small frequency P30 at a relatively high frequency F30 during the recording operation of T13 to T14.
High frequency signal.

At the recording power IW at which the recording operation can be performed at a high level output, since the light pulse is subjected to the PWM modulation, the peak value of the laser power output after superimposition is lower than the allowable peak value of the laser power. That is the condition. Therefore, the high-frequency signal superimposed at the recording power IW has an amplitude P20 higher than that at the reading power IR.
Is set to be small.

FIG. 5 is a specific waveform chart showing the operation of the present embodiment. FIG. 5 shows the mode switching signal CMOD of FIG.
It is the figure which expanded the switching point of 1 and 2 and one specific example of current Icnt. In FIG. 5, the mode switching signal CMOD
When the gate voltage of the FET 22 shown in FIG.
The amplitude is 350 μV at Hz. When the gate voltage of the mode switching signal CMOD41 of the FET 22 shown in FIG.
Has a frequency of 215 MHz and an amplitude of 180 μV. At this time, the relatively low frequency is 94 MHz, the relatively large amplitude is 350 μV, and the relatively high frequency is 215 MHz.
The relatively small amplitude at 180 Hz is 180 μV, and the medium amplitude at a medium frequency has an intermediate value.

Here, for example, in FIG.
Is in the period of T2 to T3, the mode switching signal CM
CMOD1 of OD41 as High Label H
2 is a low level L, the high-frequency signal 42 is a medium amplitude signal of the above-described medium frequency, and the mode switching signal C when the operation of the CD-R is in the recording period of T3 to T4.
The CMOD1 and CMOD2 of the MOD 41 may both be at the high level H, and the high frequency signal 42 may be the relatively high frequency and relatively small amplitude signal described above. In this way,
The period of T2 to T3 and the period of T3 to T in the period of T2 to T4
By superimposing the optimum frequency in accordance with the mode in the period of 4, the laser noise of the CD-R can be easily suppressed. In addition, since the optimum amplitude is set according to each mode, a laser drive signal that emits laser light with a laser power output higher than the allowable peak value is not input to the laser diode, and the laser diode is stably operated. Driving can be performed.

For example, in FIG. 4, the CD-RW
During the period T12 to T13, both the CMOD1 and CMOD2 of the mode switching signal CMOD41 are set to the high level H, and the high-frequency signal 42 is set to the relatively high frequency and the relatively small amplitude output described above. T
During the period from 13 to T14, the mode switching signal CMOD4
One CMOD1 may be set to the high label H and the CMOD2 may be set to the low level L, and the high-frequency signal 42 may have the above-mentioned medium frequency and medium amplitude output. In this manner, the CD-RW is superimposed on the optimum frequency in accordance with the mode of erasing in the period T12 to T13 and recording in the period of T13 to T14 in the period of T12 to T14.
Laser noise can be easily suppressed. In addition, in order to set the high-frequency signal to the optimum amplitude according to each mode, the laser diode does not receive a laser drive signal that emits with a laser power output higher than the allowable peak value. Driving can be performed.

Further, since a plurality of amplitude settings can be switched and used during the recording operation, a stable recording operation can be performed without erroneously forming pits during erasing.

[0058]

As described above, in the present invention, in addition to the superposition of the high-frequency signal on the laser drive signal during the reproducing operation, the superposition of the high-frequency signal having the optimum frequency and / or amplitude is also performed during the recording operation. This can be realized by using a superposition circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a semiconductor laser driving device according to the present embodiment.

FIG. 2 is a circuit diagram of a superimposed frequency variable circuit according to the present embodiment.

3A and 3B are waveform diagrams showing the operation of the CD-R according to the present embodiment, FIG. 3A shows a laser drive signal ILD, FIG. 3B shows a read / write signal W / XR, FIG. 3C shows a laser drive control signal ODON, and FIG. Is an enable signal ENBL,
3E shows the mode switching signal CMOD1, FIG. 3F shows the mode switching signal CMOD2, and FIG. 3G shows the high frequency signal PLD.

FIG. 4 is a waveform diagram showing an operation of the CD-RW according to the present embodiment. FIG. 4A is a laser drive signal ILD, and FIG.
Is a read / write signal W / XR, FIG. 4C is a laser drive control signal ODON, and FIG. 4D is an enable signal ENB.
L, FIG. 4E shows the mode switching signal CMOD1, FIG. 4F shows the mode switching signal CMOD2, and FIG. 4G shows the high frequency signal PLD.

FIG. 5 is a specific waveform chart showing the operation of the present embodiment.

[Explanation of symbols]

1 ... information source, 2 ... control circuit, 3 ... servo circuit, 4
…… Optical pickup, 5 …… Laser driver, 6
…… High frequency superposition circuit, 7 …… Superposition frequency variable circuit, 8…
... Laser diode, 9 ... Optical system, 10 ... Two-axis actuator, 11 ... Optical disk, 21-1 ... Terminal, 22-1 ... FET1, 23-1 ... Resistor, 21
-2 ... terminal, 22-2 ... FET2, 23-2 ... resistor, 24 ... resistor, 25 ... terminal, CMOD1, 2
... mode switching signal, 41 ... CMOD, 42 ... high frequency signal,

Claims (19)

[Claims] 1. A semiconductor laser driving apparatus for driving a semiconductor laser in an optical disc apparatus for recording and reading information by irradiating a laser beam from a semiconductor laser onto an optical recording medium. A laser driver that supplies a drive signal according to an operation mode; a high-frequency superimposition unit that superimposes a high-frequency signal on the drive signal; and a high-frequency signal of the high-frequency superimposition unit according to an operation mode of recording and reading information in the optical disk device. And a superimposed high-frequency signal varying means for varying the frequency and / or amplitude of the semiconductor laser. 2. The semiconductor laser driving device according to claim 1, wherein in the information recording operation mode of the optical disk device, the superimposed high-frequency signal variable means sets the frequency and / or amplitude of the high-frequency signal to a first value. Changing the frequency and / or the first amplitude, and changing the frequency and / or the amplitude of the high-frequency signal to the second frequency and / or the first frequency lower than the first frequency in the information reading operation mode.
A second amplitude greater than the second amplitude. 3. The semiconductor laser driving device according to claim 2, wherein the drive signal is such that the laser power in the information recording operation mode is higher than the laser power in the information reading operation mode. A semiconductor laser driving device characterized by being supplied from a driver. 4. The semiconductor laser driving device according to claim 1, wherein in the information recording operation mode of the optical disk device, the superimposed high-frequency signal variable means changes the frequency and / or amplitude of the high-frequency signal to a first value. Changing the frequency and / or the first amplitude, and changing the frequency and / or the amplitude of the high-frequency signal to the second frequency and / or the first frequency lower than the first frequency in the information reading operation mode.
And in the information erasing operation mode, the frequency and / or amplitude of the high-frequency signal is changed to a third frequency higher than the first frequency and / or to a second amplitude higher than the first amplitude. A semiconductor laser driving device wherein the amplitude is changed to a small third amplitude. 5. The semiconductor laser driving device according to claim 4, wherein the drive signal is such that the laser power in the information recording operation mode is higher than the laser power in the information reading operation mode. A semiconductor laser driving device characterized by being supplied from a driver. 6. The semiconductor laser driving device according to claim 5, wherein the laser power in the information erasing operation mode is a laser power in the information recording operation mode and a laser power in the information reading operation mode. A semiconductor laser driving device, wherein a drive signal having a value between powers is supplied from the laser driver. 7. The semiconductor laser driving device according to claim 1, wherein the superimposed high-frequency signal varying means changes a superimposed frequency and / or an amplitude of the high-frequency current by switching a current supplied to the high-frequency superimposing means. A semiconductor laser driving device characterized in that: 8. An optical head for recording and reading information by irradiating a laser beam from a semiconductor laser onto an optical disk, comprising: a semiconductor laser for emitting a laser beam; and an optical unit for irradiating the laser beam to the optical disk. A laser driver that supplies a drive signal to the semiconductor laser according to an operation mode in the optical disc device; a high-frequency superimposing unit that superimposes a high-frequency signal on the drive signal; and an operation mode of recording and reading information in the optical disc device And a superimposed high-frequency signal varying means for varying the frequency and / or amplitude of the high-frequency signal of the high-frequency superimposing means according to 9. The optical head according to claim 8, wherein in the information recording operation mode, the superimposed high-frequency signal varying means changes the frequency and / or amplitude of the high-frequency signal to a first frequency and / or a first frequency. And in the information reading operation mode, the frequency and / or amplitude of the high-frequency signal is changed to a second frequency lower than the first frequency and / or a second amplitude higher than the first amplitude. An optical head characterized by being changed. 10. The optical head according to claim 9, wherein the drive signal is such that the laser power in the information recording operation mode is higher than the laser power in the information read operation mode. An optical head, wherein the optical head is supplied. 11. The optical head according to claim 8, wherein in the information recording operation mode, the superimposed high-frequency signal variable means changes the frequency and / or amplitude of the high-frequency signal to a first frequency and / or a first frequency. And in the information reading operation mode, the frequency and / or amplitude of the high-frequency signal is changed to a second frequency lower than the first frequency and / or a second amplitude higher than the first amplitude. Changing the frequency and / or amplitude of the high-frequency signal to a third frequency higher than the first frequency and / or a third amplitude lower than the first amplitude in the information erasing operation mode. An optical head characterized in that: 12. The optical head according to claim 11, wherein the laser power in the information recording operation mode is larger than the laser power in the information reading operation mode, and the laser power in the information erasing operation mode. An optical head, wherein a drive signal is supplied from the laser driver so that the laser power has a value between the laser power in the recording operation mode and the laser power in the reading operation mode. . 13. The optical head according to claim 8, wherein the superimposed high-frequency signal varying means changes a superimposed frequency and / or amplitude of the high-frequency current by switching a current supplied to the high-frequency superimposing means. An optical head characterized in that: 14. An optical disk device for recording and reading information by irradiating a laser beam from a semiconductor laser onto an optical disk, wherein the semiconductor laser emits a laser beam, and an optical means for irradiating the laser beam onto the optical disk Driving means for rotating the optical disc; laser driver for supplying a drive signal to the semiconductor laser according to an operation mode in the optical disc apparatus; high-frequency superimposing means for superposing a high-frequency signal on the drive signal; An optical disc device comprising: a superimposed high-frequency signal varying unit that varies a frequency and / or an amplitude of a high-frequency signal of the high-frequency superimposing unit according to an information recording and reading operation mode in the device. 15. The optical disk device according to claim 14, wherein in the information recording operation mode, the superimposed high-frequency signal variable means changes the frequency and / or amplitude of the high-frequency signal to a first frequency and / or a first frequency. And in the information reading operation mode, the frequency and / or amplitude of the high-frequency signal is changed to a second frequency lower than the first frequency and / or a second amplitude higher than the first amplitude. An optical disk device characterized by being changed. 16. The optical disk device according to claim 15, wherein a drive signal such that the laser power in the information recording operation mode is higher than the laser power in the information reading operation mode is output from the laser driver. An optical disk device characterized by being supplied. 17. The optical disk device according to claim 14, wherein in the information recording operation mode, the superimposed high-frequency signal variable means changes the frequency and / or amplitude of the high-frequency signal to a first frequency and / or a first frequency. And in the information reading operation mode, the frequency and / or amplitude of the high-frequency signal is changed to a second frequency lower than the first frequency and / or a second amplitude higher than the first amplitude. Changing the frequency and / or amplitude of the high-frequency signal to a third frequency higher than the first frequency and / or a third amplitude lower than the first amplitude in the information erasing operation mode. An optical disk device characterized by the following. 18. The optical disk device according to claim 17, wherein the laser power in the information recording operation mode is larger than the laser power in the information reading operation mode, and the laser power in the information erasing operation mode. An optical disc device, wherein a drive signal is supplied from the laser driver so that the laser power has a value between the laser power in the recording operation mode and the laser power in the reading operation mode. . 19. An optical disk recording / reproducing method for recording information by irradiating a laser beam from a semiconductor laser onto an optical disk, comprising: a high-frequency superimposing step of superposing a high-frequency current on the semiconductor laser; Superimposing frequency varying step of varying the frequency and / or amplitude of the high-frequency signal in the high-frequency superimposing step in accordance with the operation mode in the optical disk recording method.
In the information recording operation mode, the superimposed high-frequency signal variable unit changes the frequency and / or amplitude of the high-frequency signal to a first frequency and / or first amplitude, and in the information reading operation mode, An optical disk recording / reproducing method, wherein the frequency and / or amplitude of the high frequency signal is changed to a second frequency lower than the first frequency and / or a second amplitude higher than the first amplitude.