JP3628533B2 - Laser output stabilizing device and information recording / reproducing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser output stabilizing device and a laser output stabilizing device for an optical disk drive such as a phase change optical disk drive or a light-modulated magneto-optical disk drive for recording information on an optical disk such as an MO by an optical modulation method. The present invention relates to an information recording / reproducing apparatus provided .
[0002]
[Prior art]
Conventionally, a configuration using a semiconductor laser element as a light source is known in an optical disk drive.
Such an optical system of the optical disk drive irradiates most of the laser light emitted from the semiconductor laser element onto the recording medium (medium), and receives most of the reflected light by the light receiving element installed in the optical disk drive. Designed.
[0003]
However, part of the reflected light from the medium returns to the semiconductor laser element due to factors based on the birefringence of the medium, the design of the optical element, and variations.
This return laser beam destabilizes the internal oscillation of the semiconductor laser element and causes fluctuations in the laser output. The influence of the return laser beam on the semiconductor laser element is significant in a high-power recording semiconductor laser element having a relatively large transmittance at the laser output end face.
[0004]
As a method for suppressing the fluctuation of the laser output, a method of superimposing a high-frequency component on the laser drive current of the semiconductor laser element to turn on / off the laser output at high speed and making the oscillation inside the semiconductor laser element multi-mode (for example, (See Japanese Patent Publication No. 59-9086) and is widely used in optical disk drives.
[0005]
However, in the method as described above, the laser is turned ON / OFF to superimpose the high frequency component, so that in order to obtain the target (average) power, a laser output approximately twice the average is required when ON.
Therefore, when the laser beam is used at a high output, the absolute rating of the laser output is exceeded, so that it can be usually used only for the reproduction power.
[0006]
As an improvement to this point, a high-frequency superposition method for a semiconductor laser that superimposes a high-frequency component with different amplitude and duty from that for reproduction on the laser drive current of the semiconductor laser element at the time of high output such as recording power or erase power (For example, refer to JP-A-5-73948).
[0007]
According to this method, the maximum output exceeds the absolute rating when the high frequency modulation circuit (High Frequency Modulation: HFM) is operated so as to obtain a high level average power required for recording and erasing. The average power is increased by changing the duty of the high frequency component so that the laser power is turned off, but the laser output at the time of turning on is reduced to allow superposition of the high frequency component at the time of recording and erasing.
[0008]
By the way, at the time of recording or erasing, the data recorded on the medium is not reproduced, but the position of the light spot on the medium is accurately controlled by the servo signal or address signal detected from the light receiving element, Since the recording mark length is finely controlled by adjusting the laser power, it is not allowed that the laser output fluctuates.
[0009]
[Problems to be solved by the invention]
However, in the semiconductor laser high-frequency superposition method as described above, only the amplitude and duty of the high-frequency current are changed during reproduction and recording or erasing, and the superposition operation is changed according to the type of recording data. I couldn't.
[0010]
For example, when recording information on a phase change medium or a light modulation MO medium, at least three values of read power, erase power, and write power are used: a read mark, a write mark (record data 1), and a write space (record). In order to create an accurate recording mark by using data 0), complicated laser power control such as setting a numerical power level or changing the time width of each power is performed.
[0011]
There has been a problem that when a superposition operation of a high-frequency component by the semiconductor laser high-frequency superposition method as described above is executed during a recording operation requiring such complicated laser power control, a problem occurs.
[0012]
In addition, in order to properly set the superposition of high-frequency components to the highest output recording power, a semiconductor laser element with a sufficient margin for the laser rated output is required, and an appropriate fluctuation reduction effect at the erase power can be obtained. I can't.
[0013]
If the erase power, which is the intermediate power between recording and playback, is adjusted, the power of the high-frequency component is insufficient for the write power and the laser output does not turn off. There is a possibility.
[0014]
Of course, it is possible if the laser rated output has a sufficient margin compared to the recording power, but at present, the limit of the laser output and the recording power are almost equal due to the restriction of the thermal characteristics (life) of the semiconductor laser element, Providing a high-power semiconductor laser device is very expensive in terms of cost.
[0015]
Therefore, at the time of recording to the magnetic field modulation MO or at the time of erasing the light modulation MO, the semiconductor laser element has a constant output higher than the reproduction power (the recording power and the erasing power are almost equal and generally lower than the recording power of the phase change medium) ), The conventional semiconductor laser high-frequency superimposing method does not cause a problem even when the high-frequency component superimposing operation is performed by the conventional semiconductor laser high-frequency superimposing method. If the superposition operation of the high frequency component by the method is executed, a problem occurs.
[0016]
The present invention has been made in view of the above points. When recording information on a recording medium such as a phase change medium or an optical modulation MO medium, the laser output is achieved even if a high frequency component is superimposed on the laser driving current of the semiconductor laser element. It aims at stabilizing.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a laser output stabilizing device for superimposing a high frequency component on a laser drive signal of a semiconductor laser element that emits laser light for recording and reproducing information on a recording medium. Control for controlling the operation and stop of superposition of the high-frequency component according to the type of information recorded on the recording medium at the time of recording. Means are provided , and the control means is a means for controlling operation and stop of superposition of the high-frequency component on the laser drive signal by a switch arranged on the semiconductor laser element side of the high-frequency coupling capacitor .
[0018]
Further, in the laser output stabilizing device as described above, the control means operates the superimposition of the high frequency component at a timing at which the laser beam output level is emitted at the highest power value, and other timings. Then, it is preferable to provide means for stopping the superposition of the high frequency components.
[0019]
Further, in the laser output stabilizing apparatus as described above, the control means may be provided with means for operating the superposition of the high frequency components during space recording and stopping the superposition of the high frequency components during mark recording.
[0020]
Further, in the laser output stabilizing device as described above, means for generating the high frequency component based on a reproduction setting value and a recording setting value stored in advance at the time of reproduction and recording may be provided.
[0021]
Further, in the laser output stabilizing device as described above, it is preferable to provide means for changing the amplitude or duty of the high-frequency component when changing the recording power of the laser light.
[0022]
Further, in the laser output stabilizing device as described above, means for changing the frequency of the high frequency component at the time of reproduction and at the time of recording may be provided.
[0023]
Further, in the laser output stabilizing device as described above, it is preferable to provide means for setting the frequency of the high frequency component to 1.7 times or more of the reference clock.
[0025]
Further, the information recording / reproducing apparatus includes the laser output stabilizing device as described above, and condenses the laser light on the recording medium and condenses the reflected light from the recording medium again on the light receiving element. Optical system means, reproducing means for detecting information on the recording medium from the light receiving element, servo signal calculating means for detecting position information of the recording medium and the condensed laser light from the light receiving element, and the position Servo means for controlling the position of the laser light on the recording medium based on information and mechanism system means for moving the position of the laser light are provided, and the laser light is emitted from the semiconductor laser element based on the laser drive signal. Thus, information may be recorded on the recording medium.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a laser output stabilization circuit according to an embodiment of the present invention.
[0027]
This laser output stabilization circuit is a circuit that superimposes a high-frequency component on a laser drive signal of a semiconductor laser element that emits laser light for recording and reproducing information on a recording medium such as a phase change medium and a light modulation MO medium. .
The write controller 1 is a control circuit for recording operation, and outputs a read / write switching signal: sig1 and a recording data signal: sig2.
[0028]
The timing generation circuit 2 outputs a timing signal: sig3 such as read, erase, write, and bias to the LD driver 3 that determines the laser drive signal: sig4 of the laser diode (semiconductor laser element) 11 from the two signals. A superposition operation / stop signal: sig5 of the high frequency superposition circuit (High Frequency Modulation: HFM) 4 and an oscillation characteristic switching signal: sig6 for changing the oscillation characteristic of the HFM4 are output.
[0029]
The HFM 4 superimposes a high frequency component signal: sig 7 oscillated based on the oscillation frequency, amplitude, and duty selected by the oscillation characteristic switching signal: sig 6 on the laser drive signal: sig 4 through the coupling capacitor 5.
The superposition operation (ON) / stop (OFF) is switched by the switch 6, and a control signal instructing the switching is output from the timing generation circuit 2.
[0030]
When changing the oscillation characteristics of the HFM 4, it may be switched based on a reference signal voltage, a variable resistor, a variable capacitor, etc., but two types of circuits composed of fixed parameters are prepared and switched by a switch. Anyway.
[0031]
FIG. 2 is a block diagram showing a configuration of an information recording / reproducing apparatus including the laser output stabilization circuit shown in FIG.
The laser drive signal sig4 output from the laser output stabilization circuit 10 drives the laser diode 11 to emit a laser beam.
[0032]
The laser beam is converted into parallel light by the collimating lens 12, reflected by the beam splitter 13, and condensed on the recording surface on the recording medium 21 by the objective lens 14.
The laser beam reflected from the recording medium 21 passes through the objective lens 14 again, passes through the beam splitter 13, and is condensed on the light receiving element 16 by the condenser lens 15.
[0033]
The laser beam is converted into a signal by the light receiving element 16 and supplied to the reproduction circuit 17 and the servo signal calculation circuit 18, and the reproduction circuit 17 generates an information reproduction signal and an address signal at the time of recording.
The servo signal calculation circuit 18 calculates position information of the laser spot on the recording medium 21, and the servo circuit 19 moves the mechanism system 20 based on the calculation result to control the laser spot position to the target position.
[0034]
That is, each of the above-described units performs the following function.
The timing generation circuit 2 or the like changes the amplitude or duty of the high frequency component between reproduction and recording on the recording medium, and at the time of recording, the high frequency component is superimposed depending on the type of information recorded on the recording medium. It functions as a control means for controlling operation and stoppage.
[0035]
The timing generation circuit 2 or the like operates the superimposition of the high frequency component at a timing at which the laser beam output level is emitted at the highest power value, and stops the superposition of the high frequency component at other timings. Also fulfills the function.
Further, the timing generation circuit 2 or the like also functions as means for operating the superposition of high frequency components during space recording and stopping the superposition of high frequency components during mark recording.
[0036]
The HFM 4 or the like functions as means for generating a high-frequency component based on a reproduction setting value and a recording setting value stored in advance during reproduction and recording, respectively.
Further, the HFM 4 or the like also functions as means for changing the amplitude or duty of the high frequency component when changing the recording power of the laser beam.
[0037]
The HFM 4 or the like also functions as means for changing the frequency of the high frequency component during reproduction and during recording.
Further, the HFM 4 or the like also functions as means for setting the frequency of the high frequency component to 1.7 times or more of the reference clock.
[0038]
The timing generation circuit 2 and the like are means for controlling operation and stop of superposition of the high frequency component on the laser drive signal by the switch 6 disposed on the laser diode 11 side which is a semiconductor laser element rather than the high frequency coupling capacitor 5. Fulfills the function.
[0039]
Further, the collimating lens 12, the beam splitter 13, the objective lens 14, the condensing lens 15 and the like condense the laser light on the recording medium and condense the reflected light from the recording medium again on the light receiving element. Serves as a means.
[0040]
Furthermore, the reproducing circuit 17 functions as reproducing means for detecting information on the recording medium from the light receiving element, and the servo signal calculation circuit 18 detects the position information of the laser beam condensed from the light receiving element and the recording medium. Serves as a servo signal calculation means.
[0041]
Further, the servo circuit 19 functions as a servo means for controlling the position of the laser beam on the recording medium based on the position information, and the mechanism system 20 functions as a mechanism system means for moving the position of the laser beam. The laser output stabilization circuit 10 functions as means for emitting laser light from the semiconductor laser element based on the laser drive signal and recording information on the recording medium.
[0042]
Next, when the information recording / reproducing apparatus is an optical disk drive for recording by optical modulation, particularly a phase change optical disk drive for performing PWM (Pit Width Modulation) recording or an optical modulation MO drive, one recording mark is accurately formed. For this purpose, the intensity of the light source, here the laser diode 11 (semiconductor laser element) is modulated into a high-speed multi-value.
[0043]
FIG. 3B shows a recording light source intensity modulation waveform in the case of a phase change type disk drive using quaternary (Pr, Pe, Pw, Pb) laser output, and FIG. 4 shows a recording light source intensity modulation waveform in the case of a phase change type disk drive using a ternary (Pr, Pe, Pw) laser output.
[0044]
These waveforms have different optimum conditions depending on the recording film characteristics of the recording medium.
Pe is called erase power. In the phase change recording medium, the power is a power at which the recording film changes to a crystalline state. In the MO, the power does not reach the Curie temperature. In both cases, laser light is emitted at the above erase power: Pe during writing (corresponding to the space 30 shown in FIG. 3A), the laser output is changed according to the recording data, and FIG. The recording mark 31 shown is formed.
[0045]
The information recording / reproducing apparatus of this embodiment can be applied not only to this waveform but also to a recording system that modulates the intensity of the light source to high-speed multi-value to form the recording mark 31.
First, when the laser power is modulated at high speed, it is difficult to switch the high-frequency superposition characteristics according to each laser power. On the other hand, in order to obtain the required power, the output becomes unstable with the same characteristics. Since the laser beam must be driven with a current exceeding the laser rating when the output of the laser beam is ON, it is not sufficient to switch the HFM characteristics only at the time of reading and writing.
[0046]
Therefore, the laser output stabilization circuit 10 of the information recording / reproducing apparatus not only changes the HFM characteristics between reading and writing, but also stops the HFM operation when a complicated laser power output for forming the recording mark 31 is changed.
[0047]
3C shows the waveform of the output change of the recording data signal: sig2, FIG. 3D shows the waveform of the output change of the HFM superposition operation / stop signal: sig5, and FIG. 3E reads the waveform of the output change. / Writing signal: sig1 and oscillation characteristic switching signal: sig6.
[0048]
In this information recording / reproducing apparatus, the read / write switching signal: sig1 and the oscillation characteristic switching signal: sig6 are the same, but different timings may be used depending on the characteristics of the HFM4.
[0049]
In addition, the output timings of the laser powers are adjusted as shown in FIG. 3B and FIG. Further, FIG. 3G shows the operating state of the HFM 4, where OFF indicates the stop of superposition, A indicates the read characteristic, and B indicates the write (space) characteristic.
[0050]
In this way, when the read power is output, the HFM 4 operates in the A state. When writing is started, the HFM 4 operates in the B state during space recording and stops during mark recording. A and B are an HFM set value (frequency, amplitude, duty) during reproduction and a set value during recording, respectively.
[0051]
Next, in the case of (b) in FIG. 3 and (f) in the same figure, the timing at which the laser output level for operating the superposition of high frequency components is emitted at the highest power is the space recording corresponding to Pe. However, the phase change recording medium has different recording film characteristics from the current situation, or optically modulates to space recording such as in the case of MO, and emits at a constant power level when recording marks are formed, and the laser output is high speed during space recording In the case of modulation, it is the timing at the time of recording mark formation.
[0052]
FIG. 4 is a diagram illustrating a waveform of a laser driving current and a waveform of emitted light on which a current-light output characteristic and a high-frequency component are superimposed when laser light is emitted.
The laser diode 11 hardly emits light below a threshold current: Ith. The current-light output characteristic is maintained almost linearly from the threshold current: Ith, and the linearity is lost at the rated current: Imax, and then it is destroyed. The output at that time is rated output: Pmax and rated current: Imax.
[0053]
As shown in FIG. 4A, the HFM 4 at the time of reading oscillates with a relatively small amplitude. At this time, the laser beam is output as shown in FIG. Is obtained.
[0054]
On the other hand, at the time of writing (at the time of space recording), as shown in FIG. 4B, the HFM 4 oscillates with a relatively large amplitude, and the duty is also changed to lower the power level when the laser is ON. .
As in the case of reading, the emission light waveform of the laser light is as shown in FIG. 4D, and the average power: Pe is obtained. When the laser beam output is ON at this time, it is necessary to make it smaller than Pmax.
[0055]
Further, regarding Pw necessary for forming the recording mark, there is no high frequency component to turn off the HFM 4, and Pw may be output in a DC manner. Of course, it is below Pmax. In this way, different high frequency component characteristics are required for reproduction and recording.
[0056]
Furthermore, it is better to set the respective optimum values because the set values from which the fluctuation reduction effect is greatly obtained are different.
That is, for the transmission frequency of the HFM 4, a value having the effect of minimizing the fluctuation of the laser light output is selected. At this time, although it is largely determined by the characteristics (wavelength, etc.) of the laser beam emitted from the laser diode 11 and the distance between the laser beam and the recording medium, the optimum laser beam emission OFF for obtaining the fluctuation reduction effect by the laser beam output is OFF. Since there is time, it is better to fine-tune the frequency at the same time than just adjusting the amplitude and duty.
[0057]
Next, the high frequency component is superimposed on the laser drive signal via the coupling capacitor 5. When the recording mark 31 is formed, high-speed modulation is required as shown in FIG. 3B, but when the coupling capacitor 5 is directly attached, the capacitance of the capacitor itself is shown in FIG. As shown by the dotted line, the waveform becomes dull.
[0058]
Therefore, by arranging the switch 6 having a terminal capacitance smaller than that of the coupling capacitor 5 between the laser diode 11 and the coupling capacitor 5, it is possible to avoid waveform dullness.
[0059]
Next, the high-frequency component that reduces the fluctuation of the laser beam output becomes noise for the detection of the information reproduction signal from the recording medium and the address reproduction signal at the time of recording.
Usually, since the HFM 4 operates at a frequency much higher than that of the reproduction signal, it is separated and removed by a reduction pass filter or the like. However, as the wavelength of the laser beam becomes shorter and the recording / reproduction speed is improved, There is a tendency to operate at a frequency close to the reproduction signal.
However, because of the above-mentioned noise problem, provisions should be made for the HFM operating frequency.
[0060]
FIG. 5 is a diagram of the transfer function of a first order low pass filter.
In this diagram, the horizontal axis indicates frequency, and information reproduction signal frequency: fD, its reference clock frequency: fCLK, and HFM operating frequency fHFM.
[0061]
First, the frequency component of the address reproduction signal at the time of recording is almost the same as the information reproduction signal. In order to remove noise as a general characteristic, a frequency separation of 10 times or more the carrier frequency (in this case, fD) is required.
This can be attenuated to a frequency having an effect of “−20 dB” when viewed with a first-order filter, that is, 1/10. Moreover, if a realistic secondary filter is used, it can be attenuated to 1/100.
[0062]
At present, a typical modulation / demodulation method used in an optical disk as a recording medium is called EFM, EFM +, (2, 7) RLL, and the minimum unit for changing data “1” and “0” is 3 channels. Is a bit. Therefore, the frequency component considering repetition is as shown in Equation 1.
[0063]
[Expression 1]
fD = fCLK / 6
[0064]
On the other hand, when the frequency of the HFM 4 is matched with the frequency at which the attenuation effect of “−20 dB” can be obtained with the first-order low-pass filter, the following formula 2 is obtained.
[0065]
[Expression 2]
fHFM ≧ 10 × fD
[0066]
Here, fHFM can be obtained from Equation 1 and Equation 2 as shown in Equation 3.
[0067]
[Equation 3]
fHFM ≧ 10 × fCLK / 6≈1.7 × fCLK
[0068]
As is apparent from the equation (3), it is recommended that the operating frequency of the HFM 4 be 1.7 times or more of the reference clock.
[0069]
In this way, the information recording / reproducing apparatus of this embodiment changes the characteristics of the high-frequency component during reproduction and recording and operates / stops the superposition of the high-frequency component according to the recording information. In addition, even when information is recorded by optical modulation, a stable laser output can be obtained without exceeding the laser rating.
[0070]
In addition, since the high-frequency component is superimposed at the timing when the laser beam is emitted with the highest frequency of the output level, a stable laser output can be obtained during recording.
[0071]
In addition, high-frequency components are superimposed during space recording, and superposition is stopped during recording mark formation, so when recording to phase change media, the laser rating is not exceeded at the time of high power output necessary for recording mark formation. A stable laser output can be obtained.
[0072]
In addition, since the settings at the time of reproduction and recording are set to pre-stored setting values, both can be switched quickly, and abnormal laser output light emission in an indefinite state that occurs during switching can be prevented.
[0073]
Furthermore, since the characteristics of the high-frequency component are changed when the recording power is changed, the optimum fluctuation reduction effect can always be maintained, and the necessary average power can be obtained with the minimum power.
[0074]
Further, since the frequency of the high frequency component is changed during reproduction and recording, the fluctuation reduction effect can be stably obtained regardless of the difference in laser power.
[0075]
Furthermore, since the frequency of the high frequency component is 1.7 times or more that of the reference clock, the information reproduction frequency or the address signal frequency at the time of recording can be detected with high accuracy.
[0076]
In addition, since the operation / stop of high-frequency component superposition is performed by a switch arranged on the laser diode side from the coupling capacitor, the recording power at the time of laser modulation for recording mark formation is slowed by the capacitance of the capacitor. And high-speed modulation can be performed.
[0077]
Furthermore, since information is recorded on the recording medium using the laser output stabilizing circuit, a stable laser output can be obtained even when recording on a phase change medium that performs optical modulation.
[0078]
【The invention's effect】
As described above, according to the laser output stabilizing device and the information recording / reproducing device according to the present invention, the high frequency component is included in the laser drive current of the semiconductor laser device during recording on a recording medium such as a phase change medium or an optical modulation MO medium. Even if they are superimposed, the laser output can be stabilized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a laser output stabilization circuit according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of an information recording / reproducing apparatus including the laser output stabilization circuit shown in FIG.
3 is a diagram showing a recording light source intensity modulation waveform and the like by the laser output stabilization circuit shown in FIG. 1; FIG.
4 is a diagram showing a waveform of a laser drive current and an emitted light waveform on which a high-frequency component is superimposed on a current-light output characteristic when a laser beam is emitted by the laser output stabilization circuit shown in FIG. 1;
FIG. 5 is a diagram of a transfer function of a first-order low-pass filter for providing a definition for the HFM operating frequency in the laser output stabilization circuit shown in FIG. 1;
[Explanation of symbols]
1: Write controller 2: Timing generation circuit 3: LD driver 4: High frequency superimposing circuit (HFM)
5: Coupling capacitor 6: Switch 10: Laser output stabilization circuit 11: Laser diode 12: Collimating lens 13: Beam splitter 14: Objective lens 15: Condensing lens 16: Light receiving element 17: Reproduction circuit 18: Servo signal calculation circuit 19 : Servo circuit 20: Mechanism system 21: Recording medium sig 1: Read / write switching signal sig 2: Recording data signal sig 3: Timing signal sig 4: Laser drive signal sig 5: Superposition operation / stop signal sig 6: Oscillation characteristic switching signal sig 7: High frequency component signal

Claims (8)

In a laser output stabilizing device that superimposes a high frequency component on a laser drive signal of a semiconductor laser element that emits laser light for recording and reproducing information on a recording medium,
The amplitude or duty of the high frequency component is changed between reproduction and recording with respect to the recording medium, and at the time of recording, the superposition operation and stop of the high frequency component are performed according to the type of information to be recorded on the recording medium. A control means for controlling ,
Stabilization of laser output characterized in that the control means is means for controlling operation and stop of superposition of a high-frequency component on a laser drive signal by a switch arranged on the semiconductor laser element side of a high-frequency coupling capacitor apparatus. The laser output stabilizing device according to claim 1, wherein
The control means is provided with means for operating the superposition of the high-frequency component at a timing at which the laser beam output level is emitted at a power value with the highest frequency, and stopping the superposition of the high-frequency component at other timings. A laser output stabilizing device characterized by that. The laser output stabilizing device according to claim 1, wherein
The laser output stabilizing device according to claim 1, wherein the control means is provided with means for operating the superposition of the high-frequency component during space recording and stopping the superposition of the high-frequency component during mark recording. In the laser output stabilization device according to any one of claims 1 to 3,
A laser output stabilization device comprising means for generating the high-frequency component based on a reproduction setting value and a recording setting value stored in advance at the time of reproduction and recording, respectively. In the laser output stabilization device according to any one of claims 1 to 3,
An apparatus for stabilizing laser output, comprising means for changing the amplitude or duty of the high-frequency component when changing the recording power of the laser light. In the laser output stabilizing device according to claim 5 or 6,
A laser output stabilizing device characterized by comprising means for changing the frequency of the high-frequency component at the time of reproduction and at the time of recording. The laser output stabilizing device according to claim 6, wherein
Means for stabilizing laser output comprising means for increasing the frequency of the high-frequency component to 1.7 times or more of a reference clock. An information recording / reproducing apparatus comprising the laser output stabilizing device according to any one of claims 1 to 7 ,
Optical system means for condensing the laser light on the recording medium and condensing the reflected light from the recording medium on the light receiving element; and reproducing means for detecting information on the recording medium from the light receiving element; Servo signal calculation means for detecting position information of the laser beam focused on the recording medium from the light receiving element, servo means for controlling the position of the laser light on the recording medium based on the position information, and the laser An information recording system comprising: a mechanism system for moving the position of light; and recording information on the recording medium by emitting laser light from the semiconductor laser element based on the laser drive signal Playback device.

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