JP2003308624A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the increase of power consumption or unnecessary radiation is accompanied by the excessive high frequency current taking the margin for variance into consideration in a conventional high frequency superposing method of a semiconductor laser. <P>SOLUTION: The optical disk drive is provided with a photodetecting means for detecting a part of the emitted light quantity of the semiconductor laser, a laser driving means for driving the semiconductor laser so as to keep the detection amount of the photodetecting means to a prescribed value, a high frequency superposing means for superposing the high frequency current on the current to drive the semiconductor laser at the reproduction of information, and a high frequency superposing control means for controlling the high frequency superposing means so that the high frequency current having an amplitude decided in accordance with the driving state of the semiconductor laser at the reproduction of the information is superposed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for superposing a high frequency current on a current for driving a semiconductor laser when reproducing information.

[0002]

2. Description of the Related Art When a semiconductor laser is used as a light source of an optical disk device such as an information reproducing device, noise of the semiconductor laser is generated by reflected light from an information recording medium. As a method of reducing the noise of such a semiconductor laser, a high frequency superimposing method has been proposed in which a high frequency alternating current is superimposed on a driving current of the semiconductor laser to drive the semiconductor laser.

FIG. 8 is a block diagram of a conventional optical disk device. In FIG. 8, 101 is a semiconductor laser, 102 is a polarization beam splitter, 103 is an objective lens, 104 is an optical disk, 105 is a photodetector, 106 is a front light monitor, 1
Reference numeral 07 is an objective lens actuator. Also, 111
Is an arithmetic circuit, 112 is a servo circuit, 113 is a laser control circuit, and 114 is a high frequency superposition module.

The operation of the optical disk device configured as described above will be described below. The laser light emitted from the semiconductor laser 101 passes through the polarization beam splitter 102, enters the objective lens 103, and a light spot is formed on the optical disc 104. Optical disc 10
The laser light reflected by 4 returns to the objective lens 103,
It is incident on the polarization beam splitter 102. Depending on the polarization direction of the laser light, it is reflected by the polarization beam splitter 102 to separate the optical path, and then enters the photodetector 105.

The laser light incident on the photodetector 105 is photoelectrically converted and outputs an electric signal proportional to the amount of light incident on each light receiving region in the photodetector 105. The arithmetic circuit 111 performs a predetermined arithmetic operation on this electric signal to generate a focus error signal and a tracking error signal. The servo circuit 112 uses the focus error signal and the tracking error signal to drive the objective lens actuator 107 so as to follow the surface wobbling and the eccentricity of the optical disc 104, respectively.

On the other hand, the laser light emitted from the semiconductor laser 101 passes through the polarization beam splitter 102 and reaches the optical disc 104, but a part of the laser light (which is always a constant ratio to the laser light output). The light is reflected by the polarization beam splitter 102 and enters the front light monitor 106.
The front light monitor 106 is for detecting the intensity of the laser light, converts the intensity of the incident light into an electric signal, and outputs the electric signal to the laser control circuit 113.

The laser control circuit 113 includes a front light monitor 10
The electric signal from 6 is compared with a predetermined value, and the drive current applied to the semiconductor laser 101 is controlled so that the deviation is eliminated. That is, feedback control is performed so that the laser power of the semiconductor laser 101 is always a constant value.

When reproducing information, the laser control circuit 113 generates a high frequency superposition control voltage and applies it to the high frequency superposition module 114. The high frequency superposition control voltage determines the amplitude of the high frequency current flowing through the semiconductor laser 101 by the high frequency superposition module 114.

FIG. 9 is a circuit diagram showing the internal structure of the high frequency superposition module 114. In the figure, 115 is a capacitor, 116 is a high frequency oscillation circuit, 101 is a semiconductor laser,
Reference numeral 113 is a laser control circuit.

The high frequency oscillation circuit 116 is the laser control circuit 1.
The amplitude of the high frequency is changed according to the voltage value applied from 13. A direct current applied from the laser control circuit 113 flows through the semiconductor laser 101 and the capacitor 11
High frequency oscillator circuit 116 through several hundred MHz
High frequency current is superposed. The semiconductor laser 101 is turned on in a pulsed manner by this superimposed drive current, and the influence of return light and noise such as mode hopping are reduced.

FIG. 10 shows the relationship between the laser drive current I (horizontal axis) and the light output intensity P (vertical axis). As shown by the curve A in FIG. 10, the light output is substantially 0 up to the threshold current Ith. When the threshold current Ith is exceeded, the light output intensity increases in proportion to the increase in the drive current. . Here, the drive current shown by the curve B is the semiconductor laser 10
When it flows to 1, light is emitted when a current equal to or higher than the threshold current Ith flows, and its light output intensity becomes pulsed as shown by the curve C.

It is known that in the high frequency superimposing method, a high frequency current amplitude of a predetermined value or more is required to obtain a good noise characteristic. Therefore, in general, in consideration of variations in semiconductor laser performance due to variations in characteristics of the semiconductor laser and changes over time, the frequency and amplitude of the high frequency current should be adjusted so that the effect of high frequency superposition can be obtained even in the worst case. The various set values of are fixed at the time of manufacture.

[0013]

When compared with a stationary type optical disk device, it is desired to reduce the high frequency current in the optical disk device for mobile use from the viewpoint of battery life and shield structure. However, in the conventional high-frequency superimposing method for a semiconductor laser, power consumption and unnecessary radiation are increased due to an excessive high-frequency current considering a margin due to variations.

In view of the above problems, the present invention performs optimum information reproduction that suppresses noise in response to variations in characteristics of semiconductor lasers and changes over time, and minimizes high-frequency current amplitude for consumption. It is an object of the present invention to provide an optical disk device that can reduce electric power and unnecessary radiation.

[0015]

An optical disk apparatus of the present invention is an information recording / reproducing apparatus for recording and / or reproducing information by condensing light from a semiconductor laser on an information recording medium. Light detection means for detecting a part of the emitted light quantity, and laser drive means for driving the semiconductor laser so that the detection quantity of the light detection means is maintained at a predetermined value,
A high frequency superimposing means for superimposing a high frequency current on a current for driving the semiconductor laser at the time of reproducing information, and an amplitude of the high frequency current according to a driving state of the semiconductor laser at the time of reproducing information, and having the determined amplitude. And a high frequency superposition control means for controlling the high frequency superposition means so that the high frequency current is superposed.

Further, the high frequency superposition control means calculates the drive differential efficiency of the semiconductor laser from the detection amount of the photodetection means and the current amount for driving the semiconductor laser, and with respect to the calculated drive differential efficiency. The amplitude of the high frequency current may be determined, and the high frequency superimposing means may be controlled so that the high frequency current having the determined amplitude is superimposed.

Further, the high frequency superposition control means calculates the drive differential efficiency of the semiconductor laser from the detection amount of the light detection means and the current amount for driving the semiconductor laser, and with respect to the calculated drive differential efficiency. Alternatively, the amplitude of the high-frequency current may be determined by selecting from a plurality of preset high-frequency current amplitudes, and the high-frequency superimposing means may be controlled to superimpose the high-frequency current having the determined amplitude. Good.

Further, the high frequency superimposing control means determines the threshold value before the high frequency superimposing of the semiconductor laser from the detection amount of the photodetecting means and the current amount for driving the semiconductor laser before the high frequency superimposing of the semiconductor laser. A current value Ith and a drive current value Iop at the time of reproducing power output are calculated, and the amplitude Iw of the high frequency current is the drive current value Io at the time of reproducing power output.
The amplitude of the high frequency current is determined so as to be larger than the difference between p and the threshold current value of the semiconductor laser before the high frequency superposition multiplied by a predetermined constant, and the high frequency current having the determined amplitude is superimposed. As described above, the high frequency superimposing means may be controlled.

The high-frequency superimposition control means, before the high-frequency superposition, among the drive current values at the time of outputting the reproduction power of the semiconductor laser calculated from the detection amount of the photodetection means and the current amount driven by the semiconductor laser. Drive current value of Iop
1, the driving current value after high frequency superposition is set to Iop2, and Io
The amplitude of the high-frequency current may be determined so that p1-Iop2> 0, and the high-frequency superimposing means may be controlled so that the high-frequency current having the determined amplitude is superimposed.

Further, the light detecting means responds to a high frequency current superposed on a current for driving the semiconductor laser, and the light detecting amount of the light detecting means becomes zero within a certain time T0 during reproduction. When time is Td, Td / T0> 0
The amplitude of the high-frequency current may be determined so that the high-frequency current having the determined amplitude is superimposed, and the high-frequency superimposing means may be controlled.

Further, the high frequency superimposing control means is configured to determine the amplitude of the high frequency current at a predetermined timing such as when the information recording / reproducing apparatus is turned on, when the information recording medium is inserted, or when the information reproduction is started. You may.

Further, the high frequency superposition control means constantly detects the drive current value at the time of reproducing power output of the semiconductor laser, and when the drive current value fluctuates beyond a predetermined value, the high frequency current amplitude is changed. It may be configured to determine.

Further, the high frequency superposition control means is provided with a temperature detection means for detecting an ambient temperature, and the high frequency superposition control means, when the ambient temperature detected by the temperature detection means fluctuates by exceeding a predetermined value, the amplitude of the high frequency current. May be determined.

The high frequency superposition control means may be arranged to determine the amplitude of the high frequency current each time a predetermined time elapses.

The laser driving means may also have a function of high-frequency superimposition that superimposes a high-frequency current on the current for driving the semiconductor laser when reproducing information.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 to 6.

(Embodiment 1) FIG. 1 is a block diagram of an optical disk device showing an embodiment of the present invention. In FIG. 1, 1 is a semiconductor laser, 2 is a polarization beam splitter, 3 is an objective lens, 4 is an optical disk, 5 is a photodetector, 6 is a front light monitor corresponding to a photodetecting means, and 7 is an objective lens actuator. Further, 11 is an arithmetic circuit, 12 is a servo circuit, 13 is a laser control circuit corresponding to a laser driving means,
Reference numeral 14 is a high frequency superposition module corresponding to the high frequency superposition means, and 20 is a high frequency superposition control circuit corresponding to the high frequency superposition control means.

The operation of the optical disk device configured as described above will be described below. The laser light emitted from the semiconductor laser 1 is transmitted to the polarization beam splitter 2
Is transmitted to the objective lens 3, and a light spot is formed on the optical disc 4. The laser light reflected by the optical disk 4 returns to the objective lens 3 and enters the polarization beam splitter 2. Depending on the polarization direction of the laser light, it is reflected by the polarization beam splitter 2 to separate the optical path, and then enters the photodetector 5. The laser light that has entered the photodetector 5 is photoelectrically converted and outputs an electrical signal that is proportional to the amount of light that has entered each light-receiving region in the photodetector 5. The arithmetic circuit 11 performs a predetermined arithmetic operation on this electric signal to generate a focus error signal and a tracking error signal. The servo circuit 12 uses the focus error signal and the tracking error signal to drive the objective lens actuator 7 so as to follow the surface wobbling and the eccentricity of the optical disc 4, respectively.

On the other hand, most of the laser light emitted from the semiconductor laser 1 passes through the polarization beam splitter 2 and reaches the optical disc 4, but a part of the laser light (always a constant ratio to the laser light output). Is reflected by the polarization beam splitter 2 and enters the front light monitor 6. Front light monitor 6
Is for detecting the intensity of the laser light, converts the intensity of the incident light into an electric signal, and outputs it to the laser control circuit 13.

The laser control circuit 13 compares the electric signal from the front light monitor 6 with a predetermined value and controls the drive current applied to the semiconductor laser 1 so that the deviation is eliminated. That is, feedback control is performed so that the laser power of the semiconductor laser 1 always becomes a constant value.

At the time of reproducing information, the high frequency superposition control circuit 20 generates a high frequency superposition control voltage and applies it to the high frequency superposition module 14. The high frequency superposition control voltage determines the amplitude of the high frequency current flowing through the semiconductor laser 1 by the high frequency superposition module 14.

In the relationship between the laser drive current I and the optical output intensity P shown in FIG. 2, for example, the optical output intensity P1 at the time of reproducing information is used.
Assuming that the drive current value for obtaining Iop is Iop, the drive current value Iop is uniquely determined if the light output intensity P1 is determined. Therefore, the drive current value Iop at the reproduction power output when the output of the front light monitor 6 for detecting a part of the laser light (which is always a constant ratio with respect to the laser light output) becomes a predetermined value can be easily obtained. Obtainable.

On the other hand, the threshold current value Ith is a point at which the output of the front light monitor 6 rapidly increases, and can be similarly easily obtained. The amplitude Iw of the high frequency current to be superimposed can be obtained from the driving current value Iop and the threshold current value Ith at the time of reproducing power output thus obtained.

A specific operation of the optical disk device according to this embodiment will be described with reference to FIG. In the description of the operation of the optical disk device of FIG. 1, those with parenthesized numbers indicate which component is performing processing, or which component is performing processing to which component. It is attached for explanation.

When the optical disk device is powered on, the laser control circuit 13 applies a direct current to the semiconductor laser 1 ((1) in FIG. 1). When the laser control circuit 13 gradually increases the direct current flowing through the semiconductor laser 1, the laser power of the semiconductor laser 1 rapidly increases when the direct current value exceeds a predetermined value (Ith). .
At this time, the high frequency superposition control circuit 20 captures the moment when the output of the front light monitor 6 for detecting a part of the emitted light amount of the semiconductor laser 1 suddenly increases ((2) in FIG. 1), and the laser control circuit at that time. 13 DC current value (threshold current value) Ith
Is stored in the memory (not shown) ((3) in FIG. 1).

When the semiconductor laser 1 is adjusted so that the output of the front light monitor 6 when emitting the laser light corresponding to the reproduction power is, for example, Pf, the laser control circuit 13 causes the front light monitor 6 to operate. Output is compared with Pf, and the drive current applied to the semiconductor laser 1 is controlled so as to eliminate the deviation ((4) in FIG. 1). High frequency superposition control circuit 20
Stores the drive current value Iop at the time of reproducing power output of the laser control circuit 13 at that time in the memory (not shown) ((5) in FIG. 1).

The high frequency superposition control circuit 20 calculates the difference between the threshold current value Ith and the drive current value Iop stored in the memory, and multiplies the difference by a predetermined constant (for example, Iw = (I
(op-Ith) × 3.0) ((6) in FIG. 1), the amplitude Iw of the high-frequency current to be superimposed is obtained. The high frequency superimposition control circuit 20 controls the amplitude Iw of the high frequency current.
A high-frequency superposition control voltage is generated so that the current flows into the semiconductor laser 1, and this is applied to the high-frequency superposition module 14 ((7) in FIG. 1). The high frequency superposition module 14 superimposes a high frequency current of amplitude Iw on the drive current of the semiconductor laser 1 ((8) in FIG. 1).

By generating the high-frequency current by such a procedure, the amplitude of the high-frequency current is not fixed and set to an unnecessarily high value in consideration of the variation in the performance of the semiconductor laser, but the semiconductor used in the device is used. Since the operating characteristics of the laser 1 are examined at the time of starting the device, and a high-frequency current having an amplitude suitable for this operating characteristic is superimposed on the drive current of the semiconductor laser 1,
The amplitude of the high-frequency current, the variation in the performance of the semiconductor laser 1,
The semiconductor laser 1 can be set to an appropriate value according to the change over time, and noise can be reduced, and the amplitude Iw is the minimum necessary. Therefore, power consumption and unnecessary radiation due to high frequency superposition can be reduced.

Here, the high frequency current amplitude Iw is Iw =
Not limited to (Iop-Ith) × 3.0, Iw> (Iop
If −Ith) × 2.0, the effect of noise reduction can be obtained. Therefore, the predetermined constant K (> 2.0) multiplied by the difference between the threshold current value Ith and the drive current value Iop is the noise reduction value. An appropriate value may be selected according to the required performance such as degree. Although the case where K = 3.0 is set as the predetermined constant K has been described as an example in the present embodiment, on the other hand, when the amplitude of the high frequency superposition is large, another problem that power consumption and unnecessary radiation increase occurs. Therefore, as the range of the predetermined constant K,
2.0 <K ≦ 10.0, more preferably 2.0 <K ≦ 5.
It is preferably 0. By selecting an appropriate value according to the optical disk device in this range, it is possible to obtain the minimum high-frequency superposition amplitude necessary for noise reduction,
Power consumption and unnecessary radiation can be reduced as compared with the conventional high frequency superposition method.

Further, in the present embodiment, the threshold current value Ith and the drive current value I detected before the high frequency superimposition are detected.
corresponding to op, high frequency current amplitude Iw = (Iop-It
h) × 2.1 has been described above, but the high frequency superposition control circuit 20 calculates the differential efficiency η (see FIG. 2) of the semiconductor laser from the threshold current value Ith and the drive current value Iop. , One of a plurality of preset high frequency current amplitudes (Iw1, Iw2 ... Iwn) stored in the memory in association with the range of the differential efficiency η may be selected. Even in the case of such a configuration, it is apparent that the high frequency superposition can be performed with a small amplitude as compared with the conventional high frequency superposition method using a single high frequency current amplitude fixed at the time of manufacturing.

(Second Embodiment) FIG. 3 is a block diagram of an optical disk device showing another embodiment of the present invention. In FIG. 3, the same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted below. In FIG. 3, 20 is a high frequency superposition control circuit, 21 is a determination circuit, and 22 is a memory.

When reproducing information, the high frequency superposition control circuit 20
Generates a high frequency superposition control voltage according to the determination result of the determination circuit 21, and applies this to the high frequency superposition module 14. The high frequency superposition control voltage is applied to the high frequency superposition module 14
The amplitude of the high frequency current flowing through the semiconductor laser 1 is determined.

As shown in FIG. 4, the relationship between the laser drive current I and the optical output intensity P is as shown by the curve L before the high frequency superposition and the curve M after the high frequency superposition, and for example, the optical output intensity P1 at the time of reproducing information. Assuming that the drive current for obtaining Ip is Iop, there is a difference between the drive current Iop0 before the high frequency superposition and the drive current Iop1 after the high frequency superposition.

In the high frequency superimposing method, it is known that, in order to obtain a good noise characteristic, a high frequency current amplitude that satisfies ΔIop> 0 is required when ΔIop = Iop0-Iop1.

A specific operation of the optical disk device according to this embodiment will be described with reference to FIG. In FIG. 3, those with parenthesized numbers indicate which component is performing the process or which component is performing the process in the description of the operation of the optical disk device of FIG. It is attached for explanation. Further, FIG. 5 shows a flowchart of this operation.

When the power of the optical disk device is turned on, the laser control circuit 13 applies a direct current to the semiconductor laser 1 ((1) in FIG. 3). When a direct current is passed through the semiconductor laser 1, the laser power increases in proportion to the increase in current value.
Here, when the semiconductor laser 1 is adjusted so that the output of the front light monitor 6 when emitting a laser beam corresponding to the reproduction power is Pf, the laser control circuit 13 causes the laser control circuit 13 to output light from the front light monitor 6. The drive current supplied to the semiconductor laser 1 is controlled so as to compare the output with Pf and eliminate the deviation. The drive current Iop0 of the laser control circuit 13 at that time is stored in the memory 22 ((2) in FIG. 3).

Next, the high frequency superimposing circuit 20 generates a predetermined high frequency superimposing control voltage V1 (V1 is minute) and applies this to the high frequency superimposing module 14 to generate a minute amplitude Iw1.
The high frequency current is generated ((3) in FIG. 3). The laser control circuit 13 increases or decreases the drive current on which the high-frequency current of the amplitude Iw1 is superimposed, and controls the drive current given to the semiconductor laser 1 so that there is no deviation between the output from the front light monitor 6 and Pf (FIG. 3). (4)). The drive current Iop1 of the laser control circuit 13 at this time is stored in the memory 22 ((5) in FIG. 3).

Here, the decision circuit 21 refers to the memory 22 ((6) in FIG. 3) and calculates ΔIop = Iop0-Iop1. The calculation result ΔIop is a predetermined value ΔI0 (>
When it is less than 0), a signal is sent to the high frequency superposition control circuit 20 ((7) in FIG. 3), and V2 = V1 + ΔV (ΔV
Generates a high frequency superposition control voltage V2.
By applying this to the high frequency superposition module 14, the high frequency superposition control circuit 20 generates a high frequency current of amplitude Iw2 from the high frequency superposition module 14 ((8) in FIG. 3).
Here, even when the amplitude of the high frequency current changes from Iw1 to Iw2, the laser control circuit 13 controls the drive current applied to the semiconductor laser 1 so that the deviation between the output from the front light monitor 6 and Pf is eliminated. The average power of the laser does not change. At that time, since the drive current Iop1 becomes Iop2, the drive current Iop2 is stored in the memory 22.

Similarly, the determination circuit 21 refers to the memory 22 and calculates ΔIop = Iop1−Iop2. When the calculation result ΔIop is less than the predetermined value ΔI0, a signal is sent to the high frequency superposition control circuit 20. Send, V3 = V2
A high frequency superposition control voltage V3 that is + ΔV is generated.

By repeating the above determination procedure, ΔIop = Iop0-Iopn (n is a natural number) reaches the predetermined value ΔI0. The predetermined value ΔI0 is ΔIo.
It is a preset value so that a sufficient noise characteristic can be obtained when p reaches this value.

By generating the high frequency superposition control voltage Vn in such a procedure, it is possible to always perform the high frequency superposition with the necessary minimum amplitude Iwn.

(Third Embodiment) FIG. 6 is a block diagram of an optical disk device showing another embodiment of the present invention. 6, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted below. In FIG. 6, 20 is a high frequency superposition control circuit, and 23 is a CPU.

When reproducing information, the high frequency superposition control circuit 20
Generates a high frequency superposition control voltage according to the processing result of the CPU 23, and applies this to the high frequency superposition module 14. The high frequency superposition control voltage is applied to the high frequency superposition module 14
The amplitude of the high frequency current flowing through the semiconductor laser 1 is determined.

FIG. 7 shows the front light monitor 6 according to the present embodiment.
It is a figure which shows the output of. The front light monitor 6 detects a part of the laser light, and the detection amount is always a constant ratio with respect to the laser light output. Here, if the frequency band in which the signal can be detected by the front light monitor 6 is sufficiently larger than the frequency of high frequency superposition (usually several hundred MHz), the detection signal output waveform of the front light monitor 6 is as shown in FIG. It becomes the same as the optical output waveform.

In order to obtain a good noise characteristic in the high frequency superposition method, it is known that a high frequency current amplitude is required so that the bottom value of the laser light output modulated by the high frequency superposition becomes zero. That is, as shown in FIG. 7A, the bottom value of the output of the front light monitor 6, which is always a constant ratio to the laser light output, should be zero.
When the bottom value of the laser light output is less than zero as shown in FIG. 7B, it can be determined that sufficient noise characteristics are not obtained.

A specific operation of the optical disk device according to this embodiment will be described with reference to FIG. The parenthesized numbers in FIG. 6 indicate which constituent element is performing the processing or which constituent element is performing the processing in the description of the operation of the optical disk device of FIG. It is attached for explanation.

When the optical disk device is powered on, the laser control circuit 13 applies a direct current to the semiconductor laser 1. When a direct current is passed through the semiconductor laser 1, the laser power increases in proportion to the increase in current value.

Here, when the semiconductor laser 1 is adjusted so that the output of the front light monitor 6 when the laser light corresponding to the reproduction power is emitted becomes Pf, the laser control circuit 13 causes the front light monitor to operate. The average value of the outputs from 6 is compared with Pf, and the drive current given to the semiconductor laser 1 is controlled so that the deviation is eliminated ((1) in FIG. 6).

Next, the high frequency superposition control circuit 20 generates a predetermined high frequency superposition control voltage V1 (V1 is minute), and applies this to the high frequency superposition module 14 to generate a small amplitude I.
A high frequency current of w1 is generated ((2) in FIG. 6). The laser control circuit 13 increases or decreases the drive current on which the high frequency current of the amplitude Iw1 is superimposed, and controls the drive current given to the semiconductor laser 1 so that the deviation between the average value of the output from the front light monitor 6 and Pf is eliminated. ((3) in FIG. 6).

Here, the CPU 23 samples the output of the front light monitor 6 for a predetermined time T0 ((4) in FIG. 6), and sets T1 as the time T1 during which the output of the front light monitor 6 becomes zero. / T0 is calculated ((5) in FIG. 6). When the calculation result T1 / T0 is less than the predetermined value Tx (> 0), the CPU 23 sends a signal to the high frequency superposition control circuit 20 ((6) in FIG. 6), V2 = V1 +.
A high frequency superposition control voltage V2 having ΔV (ΔV is minute) is generated. By applying this to the high frequency superposition module 14, the high frequency superposition control circuit 20 generates a high frequency current having an amplitude Iw2 ((7) in FIG. 6). Here, even when the amplitude of the high frequency current changes from Iw1 to Iw2, the laser control circuit 13 controls the drive current applied to the semiconductor laser 1 so that the deviation between the output from the front light monitor 6 and Pf is eliminated. The average power of the laser does not change.

Similarly, the CPU 23 samples the output of the front light monitor 6, calculates T2 / T0 as the time T2 when the output of the front light monitor 6 becomes zero, and the calculated result T2 / T0 is predetermined. If the value Tx (> 0) of V3 is not satisfied, a signal is sent to the high frequency superposition control circuit 20,
The high frequency superposition control voltage V3 that is equal to V2 + ΔV is generated.

By repeating the above determination procedure, Tn / T0 (n is a natural number) reaches the predetermined value Tx.
The predetermined value Tx is set so that sufficient noise characteristics can be obtained when Tx reaches this value. By generating the high frequency superposition control voltage Vn in such a procedure,
It is possible to always perform high frequency superposition with the minimum necessary amplitude Iwn.

As described above, in the first, second and third embodiments, the procedure for detecting the power-on of the optical disk device and obtaining the high frequency current amplitude has been described. The start of is not limited to the timing when the optical disk device is powered on, but the semiconductor laser 1
May be performed when the light is emitted, that is, at the timing when the optical disc is inserted into the optical disc device. In this case, there is an advantage that it can be applied even when the reproduction power differs depending on the type of the optical disc. Further, the series of operations may be started at the timing of starting the information reproduction. In this case, there is an advantage that it can be applied even when the current for driving the semiconductor laser changes due to a change in environmental temperature or the like.

Here, the operation for obtaining the high frequency current amplitude is performed at the timing when the power of the optical disk device is turned on as described above, when the optical disk is inserted into the optical disk device, or when the information reproduction is started.
After that, it is only necessary to control to the determined high frequency current amplitude, but when the differential efficiency η of the semiconductor laser 1 changes due to a rapid change in the environmental temperature, for example, the drive current value Iop also changes. It is more desirable to reset the high frequency current amplitude again when the superposition control circuit 20 constantly detects the drive current value Iop and the drive current value Iop fluctuates beyond a predetermined value.

Further, since the differential efficiency η of the semiconductor laser 1 also changes depending on the ambient temperature, a temperature sensor (not shown), for example, as a temperature detecting means for detecting the ambient temperature is provided in the optical disk device, so that, for example, a high frequency current can be obtained. The high-frequency current amplitude may be reset again when the amplitude exceeds a predetermined temperature with respect to the environmental temperature at the time of initial setting, that is, when a predetermined temperature difference occurs.

In the conventional optical disk device, the high frequency superposition module is arranged in the vicinity of the semiconductor laser in order to superpose the drive current of the semiconductor laser at a high frequency. However, since the high frequency superposition module consumes a large amount of power, the power consumption is also the same. The laser control circuit that generates a large amount of heat is often arranged at a distance from the semiconductor laser.

Here, the present invention is applied when the laser control circuit and the high frequency superposition module, which are generally separate parts, are integrated into one part, that is, when the laser control circuit also has the function of the high frequency superposition module. By reducing the high frequency superposition amplitude, the total power consumption of the laser control circuit (also the high frequency superposition module) is reduced and heat generation can be suppressed. As a result, it becomes possible to dispose the laser control circuit (also the high frequency superposition module) in the vicinity of the semiconductor laser.

By applying the present invention as described above, the high frequency superposition module (function) is arranged in the vicinity of the semiconductor laser, and for example, even when the semiconductor laser is pulse-driven by the laser control circuit, the laser is provided in the vicinity of the semiconductor laser. By arranging the control circuit, an effect that pulse driving can be performed with higher efficiency can be obtained.

In the first, second, and third embodiments, the threshold current value Ith, the drive current value Iop, or the front light monitor output is detected, and the high frequency current amplitude is calculated. I mentioned the procedure to decide,
It goes without saying that the present invention can also be applied to other optical head devices that perform control so as to superimpose a necessary minimum high-frequency current so that the noise amount becomes a predetermined value or less according to the light emitting state of the semiconductor laser.

[0070]

As described above, according to the optical disk apparatus of the present invention, in the information recording / reproducing apparatus for condensing the light from the semiconductor laser on the information recording medium to record and / or reproduce the information, the semiconductor laser is used. Light detecting means for detecting a part of the emitted light amount of the, a laser driving means for driving the semiconductor laser so as to keep the detection amount of the light detecting means at a predetermined value, and a current for driving the semiconductor laser at the time of reproducing information. A high-frequency superimposing means for superimposing a high-frequency current, and the high-frequency superimposing means for determining the amplitude of the high-frequency current according to the driving state of the semiconductor laser at the time of reproducing information, so that the high-frequency current having the determined amplitude is superposed. Since it is provided with a high-frequency superimposition control means for controlling, even if there are variations in various characteristics of the semiconductor laser, high-frequency power control is performed in advance like a conventional optical disk device. For it is not necessary to set the amplitude, you can superimpose all times optimum and minimum frequency current,
An excellent effect of reducing power consumption and unnecessary radiation can be obtained.

Further, the high frequency superposition control means calculates the drive differential efficiency of the semiconductor laser from the detection amount of the photodetection means and the current amount for driving the semiconductor laser, and the calculated drive differential efficiency is calculated with respect to the calculated drive differential efficiency. When the amplitude of the high-frequency current is determined, and the high-frequency current having the determined amplitude is configured to be controlled to superimpose the high-frequency superimposing means, there are variations in the differential efficiency of the semiconductor laser,
When the differential efficiency of the semiconductor laser changes due to aging, the optimum and necessary minimum high-frequency current can always be superimposed, and an excellent effect of reducing power consumption and unnecessary radiation can be obtained.

Further, the high frequency superposition control means calculates the drive differential efficiency of the semiconductor laser from the detection amount of the photodetection means and the current amount for driving the semiconductor laser, and with respect to the calculated drive differential efficiency. If the configuration is such that the amplitude of the high-frequency current is selected by selecting from a plurality of preset high-frequency current amplitudes, and the high-frequency superposition means is controlled so that the high-frequency current having the determined amplitude is superposed, If the differential efficiency of the semiconductor laser varies,
When the differential efficiency of the semiconductor laser changes due to aging, the required high-frequency superimposition can be achieved with a simple circuit configuration that selects an appropriate one from the set high-frequency current amplitude. can get.

Further, the high frequency superimposing control means determines the threshold value before the high frequency superimposing of the semiconductor laser from the detection amount of the photodetecting means and the current amount for driving the semiconductor laser before the high frequency superimposing of the semiconductor laser. A current value Ith and a drive current value Iop at the time of reproducing power output are calculated, and the amplitude Iw of the high frequency current is the drive current value Io at the time of reproducing power output.
The amplitude of the high frequency current is determined so as to be larger than the difference between p and the threshold current value of the semiconductor laser before the high frequency superposition multiplied by a predetermined constant, and the high frequency current having the determined amplitude is superimposed. If the high-frequency superimposing means is controlled as described above, the required high-frequency current of the semiconductor laser varies when the differential efficiency of the semiconductor laser varies or when the differential efficiency of the semiconductor laser changes with time. It is possible to obtain an excellent effect that can be realized with a simple circuit configuration in which the amplitude is obtained by calculation using only the drive current values at two points, which can be easily measured, without using special parts and circuits.

The high-frequency superimposition control means, before the high-frequency superimposition, among the drive current values at the reproduction power output of the semiconductor laser calculated from the detection amount of the photodetection means and the current amount driven by the semiconductor laser. Drive current value of Iop
1, the driving current value after high frequency superposition is set to Iop2, and Io
If the amplitude of the high-frequency current is determined so that p1-Iop2> 0 and the high-frequency superimposing means is controlled so that the high-frequency current having the determined amplitude is superimposed, the characteristics of the semiconductor laser vary. Iop1-, which is one of the conditions showing the high frequency superimposing effect when there is a change in characteristics of the semiconductor laser due to aging.
Since the control is performed so as to satisfy Iop2> 0, it is possible to obtain an excellent effect that the optimum and always necessary minimum high-frequency current can be superimposed with higher accuracy.

Further, the photo-detecting means responds to a high frequency current superimposed on the current for driving the semiconductor laser, and the photo-detecting amount of the photo-detecting means becomes zero within a constant time T0 during reproduction. When time is Td, Td / T0> 0
When the amplitude of the high frequency current is determined so that the high frequency current having the determined amplitude is configured to be controlled so as to superimpose the high frequency current, the characteristics of the semiconductor laser may vary. When the characteristics of the semiconductor laser change due to changes over time, the drive waveform is monitored and the control is performed directly so that the drive waveform has the effect of high-frequency superimposition. An excellent effect of superimposing a minimum required high frequency current can be obtained.

Further, the high frequency superimposing control means is configured to determine the amplitude of the high frequency current at a predetermined timing such as when the information recording / reproducing apparatus is turned on, when the information recording medium is inserted, or when the information reproduction is started. By doing so, an excellent effect of determining the high-frequency current amplitude can be obtained according to the case where the reproducing power of the semiconductor laser is different, or the variation of various characteristics of the semiconductor laser due to the change of the environmental temperature and the like.

Further, the high frequency superimposing control means constantly detects the drive current value at the time of outputting the reproduction power of the semiconductor laser, and when the drive current value fluctuates beyond a predetermined value, the high frequency current amplitude is changed. If it is configured to determine, according to the fluctuation of the reproduction power of the semiconductor laser due to aging,
An excellent effect of determining the high frequency current amplitude can be obtained.

Further, the high frequency superposition control means is provided with a temperature detecting means for detecting an environmental temperature, and the high frequency superimposing control means, when the environmental temperature detected by the temperature detecting means fluctuates by exceeding a predetermined value, the amplitude of the high frequency current. Is determined, it is possible to obtain an excellent effect that the high frequency current amplitude can be determined according to changes in various characteristics of the semiconductor laser caused by changes in the ambient temperature.

Further, if the high-frequency superposition control means is configured to determine the amplitude of the high-frequency current each time a predetermined time elapses, the semiconductor laser of the semiconductor laser has a very simple circuit configuration of counting the predetermined time. An excellent effect that the high-frequency current amplitude can be determined according to changes in various characteristics can be obtained.

If the laser driving means has a function of superposing a high frequency current on the current for driving the semiconductor laser at the time of reproducing information, the laser control circuit is arranged in the vicinity of the semiconductor laser. Therefore, it is possible to obtain an excellent effect that the laser can be pulse-driven with high efficiency.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a laser drive current and an optical output intensity according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an optical disc device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a laser drive current and an optical output intensity according to the second embodiment of the present invention.

FIG. 5 is a flowchart showing a processing flow according to the second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of an optical disc device according to a third embodiment of the present invention.

FIG. 7 is a diagram showing an output of a front light monitor according to a third embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a conventional optical disc device.

FIG. 9 is a diagram showing an internal configuration of a high frequency superposition module.

FIG. 10 is a diagram showing the relationship between laser drive current and light output intensity.

[Explanation of symbols]

1,101 Semiconductor laser 2,102 Polarizing beam splitter 3,103 Objective lens 4,104 optical disc 5,105 Photodetector 6,106 Front light monitor 7,107 Objective lens actuator 11,111 arithmetic circuit 12,112 Servo circuit 13,113 Laser control circuit 14,114 High frequency superposition module 20 High frequency superposition control circuit 21 Judgment circuit 22 memory 23 CPU 115 condenser 116 high frequency oscillator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsumi Goto             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5D090 AA01 CC04 CC16 DD03 EE12                       HH02 KK03 LL08                 5D119 AA12 AA37 BA01 DA05 FA05                       HA13 HA30 HA41                 5D789 AA12 AA37 BA01 DA05 FA05                       HA13 HA30 HA41

Claims (11)

[Claims] 1. An optical disc device for recording and / or reproducing information by condensing light from a semiconductor laser on an information recording medium, and a light detecting means for detecting a part of the emitted light amount of the semiconductor laser. Laser driving means for driving the semiconductor laser so as to keep the detection amount of the light detecting means at a predetermined value; high-frequency superimposing means for superimposing a high-frequency current on a current for driving the semiconductor laser at the time of reproducing information; A high frequency superposition control means for determining an amplitude of the high frequency current according to a driving state of the semiconductor laser, and controlling the high frequency superposition means so that the high frequency current having the determined amplitude is superposed. Optical disk device. 2. The high frequency superposition control means calculates a drive differential efficiency of the semiconductor laser from a detection amount of the light detection means and a current amount for driving the semiconductor laser,
The amplitude of the high frequency current is determined with respect to the calculated drive differential efficiency, and the high frequency superimposing means is controlled so that the high frequency current having the determined amplitude is superimposed. Optical disk device. 3. The high frequency superposition control means calculates a drive differential efficiency of the semiconductor laser from a detection amount of the light detection means and a current amount for driving the semiconductor laser, and with respect to the calculated drive differential efficiency. Wherein the amplitude of the high frequency current is selected by selecting from a plurality of preset high frequency current amplitudes, and the high frequency superimposing means is controlled so that the high frequency current having the determined amplitude is superimposed. 1. The optical disk device described in 1. 4. The high frequency superposition control means, based on the detection amount of the photodetection means and the current amount for driving the semiconductor laser before the high frequency superposition of the semiconductor laser, sets a threshold value before the high frequency superposition of the semiconductor laser. The current value Ith and the drive current value Iop at the time of reproducing power output are calculated, and the amplitude Iw of the high frequency current is the difference between the drive current value Iop at the time of reproducing power output and the threshold current value of the semiconductor laser before high frequency superposition. 2. The amplitude of the high frequency current is determined so as to be larger than a value obtained by multiplying by a predetermined constant, and the high frequency superimposing means is controlled so that the high frequency current having the determined amplitude is superimposed. The optical disk device described in 1. 5. The high-frequency superposition control means, before the high-frequency superposition, among the driving current values at the time of outputting the reproduction power of the semiconductor laser calculated from the detection amount of the photodetecting means and the current amount driven by the semiconductor laser. The driving current value of Iop1 and the driving current value after the high frequency superposition are Iop2, the amplitude of the high frequency current is determined so that Iop1-Iop2> 0, and the high frequency current is superposed so that the high frequency current having the determined amplitude is superposed. The optical disk device according to claim 1, wherein the superimposing means is controlled. 6. The light detecting means responds to a high frequency current superimposed on a current for driving the semiconductor laser, and the light detecting amount of the light detecting means becomes zero within a certain time T0 during reproduction. The time is set to Td, the amplitude of the high frequency current is determined so that Td / T0> 0, and the high frequency superposition means is controlled so that the high frequency current having the determined amplitude is superposed. The optical disk device described in 1. 7. The high-frequency superposition control means determines the amplitude of the high-frequency current at a predetermined timing such as when the information recording / reproducing apparatus is turned on, when the information recording medium is inserted, or when the information reproduction is started. The optical disk device according to any one of claims 1 to 6. 8. The high frequency superposition control means constantly detects the drive current value at the time of outputting the reproduction power of the semiconductor laser, and when the drive current value fluctuates by exceeding a predetermined value, the high frequency current amplitude is adjusted. The optical disc device according to claim 1, wherein the optical disc device is determined. 9. A high-frequency superposition control means is provided with a temperature detection means for detecting an environmental temperature, and the high-frequency superposition control means, when the environmental temperature detected by the temperature detection means fluctuates by exceeding a predetermined value, an amplitude of the high-frequency current. 2. The method according to claim 1, wherein
8. The optical disk device according to any one of items 1 to 7. 10. The optical disk device according to claim 1, wherein the high-frequency superposition control means determines the amplitude of the high-frequency current every time a predetermined time elapses. 11. The optical disk device according to claim 1, wherein the laser driving means also has a high frequency superimposing function of superimposing a high frequency current on a current for driving the semiconductor laser when reproducing information.