JPH06168475A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the noise of a laser emitting output in a laser diode at the time of reproduction and to simultaneously stabilize the laser emitting output in the laser diode at the time of recording. CONSTITUTION:An optical information recording/reproducing device equalizes the power source supplying timing of a supplying power source to a laser driver 17 for driving a laser diode 4 with that of the supplying power source to a high frequency current generating circuit 31 for generating a high frequency current. The high frequency current is made to superimpose on the laser emitting output corresponding to the reproducing period at the time of reproduction and a recording pulse at the time of recording.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus having a semiconductor laser oscillator used as a light source for an optical disk device, for example.

[0002]

2. Description of the Related Art As is well known, for example, an optical system for recording information on an information recording medium (optical disc) or reading information recorded on an optical disc by laser light emitted from a semiconductor laser oscillator in an optical head. Various information recording / reproducing devices have been developed and put into practical use.

As such an optical information recording / reproducing apparatus, as disclosed in Japanese Patent Publication No. 63-43819,
A large signal due to the monitor light of the recording beam light can be blocked by using the sample and hold circuit, and since the signal at the time of reproduction is stored and held by the sample and hold circuit, the influence of the monitor light signal can be eliminated, and the reproduction beam light The stabilization control of the semiconductor laser oscillator is performed only with respect to the monitor light output level.

Further, in JP-A-59-9086,
During reproduction, the high-frequency oscillation output current is superposed on the driving current of the semiconductor laser oscillator to make the laser emission output multi-mode, thereby suppressing the noise of the laser emission output of the semiconductor laser oscillator. However, in this example, there is no description about the laser emission output characteristic during the recording period (recording pulse) at the time of recording. Therefore, at the time of recording, there is a drawback that the laser emission output of the semiconductor laser oscillator fluctuates and stable recording cannot be performed.

That is, FIG. 5 shows the current and laser emission output characteristics of the semiconductor laser oscillator. The solid line a represents the characteristics when there is no high frequency superimposed current. At this time, the supply current of the laser driver when the laser emission output of the semiconductor laser oscillator is 2 mw is Io = 45 mA.

Here, when the superposition current from the high frequency current superposition circuit is increased, the characteristics shown in b and c of FIG. 5 are exhibited. The current supplied from the laser driver at this time is I when the laser emission output is 2 mw. ₁ and I ₂ decrease. The laser emission output states of the respective semiconductor laser oscillators when the supply current from the laser driver is I ₁ and I ₀ are shown in FIGS.
Shown in. In both cases, the control is performed so that the average laser emission output is 2 mw.

This situation is the description of the reproduction period at the time of reproduction or recording. Next, the recording period at recording (corresponding to the recording pulse) will be described. In this case, Japanese Patent Application Laid-Open No. 59-9086 describes the case of reproduction, but does not describe the laser emission output characteristic corresponding to the recording pulse at the time of recording.

Therefore, the high frequency superimposed current is not superposed corresponding to the recording pulse at the time of recording, and the laser light emission output corresponding to the recording pulse should originally be recorded at I ₀ + I _w , but corresponds to the recording pulse. Laser emission output is I ₁
Recording will be done with + I _w . For example, as shown in FIG. 7, 20 mw should be output, but it decreases by ΔPo. The above-mentioned fluctuation is a fluctuation of 2 to 3 mw as ΔPo, which is a problem for accurate recording.

[0009]

SUMMARY OF THE INVENTION As described above, the present invention eliminates the drawback that the laser emission output of the semiconductor laser oscillator fluctuates during recording and stable recording cannot be performed. Another object of the present invention is to provide an optical information recording / reproducing apparatus capable of stable recording without the laser emission output of the semiconductor laser oscillator fluctuating.

[0010]

In the optical information recording / reproducing apparatus of the present invention, information is recorded on the recording medium or is recorded on the recording medium by irradiating the recording medium with laser light. In reproducing information,
The first level and the second output level, which is a level higher than the first level, can be switch-controlled, and when recording information on the recording medium, the laser light of the second output level is changed. A semiconductor laser oscillator that oscillates, a conversion unit that detects monitor light from the semiconductor laser oscillator and converts it into an electric signal, and an error signal between the electric signal and the reference voltage from the conversion unit when oscillating at the first level. The semiconductor laser oscillator is driven with a drive current according to the second level, and the semiconductor laser oscillator is driven with a drive current according to the error signal immediately before the oscillation of the second level during oscillation at the second level. Driving means, high-frequency current generating means for generating high-frequency current, superimposing means for superposing the high-frequency current generated by the high-frequency current generating means on the drive current output from the driving means, and the driving means They are connected in common to the means and the high-frequency current generating means, and a power supply voltage supplying means for supplying a power supply voltage at the same power supply timing.

[0011]

According to the present invention, in the above structure, the driving means for driving the semiconductor laser oscillator and the high-frequency current generating means for generating the high-frequency current are supplied at the same power supply timing, and at the time of reproduction and recording. Since the high-frequency current is superimposed on the laser emission output corresponding to the reproduction period and the recording pulse of, the noise of the laser emission output of the semiconductor laser oscillator during reproduction is reduced and the laser emission output of the semiconductor laser oscillator during recording is reduced. The stabilization of can be done together.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an optical disk device as an optical information recording / reproducing device of the present invention.

This optical disc apparatus records information on the optical disc 1 or reproduces information recorded on the optical disc 1 by irradiating the optical disc 1 with laser light.

That is, the optical disc 1 is composed of the motor 2 described above.
Is rotated at a constant speed, for example. This motor 2
Are controlled by a motor control circuit (not shown). Recording of information on the lower surface side of the optical disc 1,
The reproduction is performed by the optical head 3 provided below the optical disc 1.

The optical head 1 comprises a laser diode 4 as a semiconductor laser oscillator, a collimator lens 5, a beam splitter 6, an objective lens 7, a condenser lens 8, photodetectors 9 and 10, and drive coils 11 and 12. Has been done.

The laser diode 4 emits laser light. That is, the laser diode 4 generates a laser beam of a first level during reproduction, and generates a laser beam of a second output level which is higher than the first level during recording according to recording data. To do. The collimator lens 5 collimates the laser light generated from the laser diode 4 into parallel light.

The beam splitter 6 guides the laser light from the collimator lens 5 to the objective lens 7 and reflects the light from the objective lens 7 (reflected light from the optical disk 1) to the condenser lens 8 and guides it. . The objective lens 7 is
The optical disk 1 is irradiated with the laser light from the beam splitter 6.

The objective lens 7 is held by a wire or a leaf spring (not shown). The objective lens 7 is moved in the focusing direction (optical axis direction of the lens) by the drive coil 10 and in the tracking direction by the drive coil 11. It is movable in the direction (perpendicular to the optical axis of the lens). The condenser lens 8 is the beam splitter 6
The light from is condensed on the photodetector 9. The photodetector 9 is composed of four-division photodiodes,
It outputs an electric signal used for focusing and tracking.

As a result, the laser light generated by the laser diode 4 is applied to the optical disc 1 through the collimator lens 5, the beam splitter 6, and the objective lens 7, and the reflected light from the optical disc 1 is reflected by the objective lens 7. ,
Photodetector 9 via beam splitter 6 and condenser lens 8
Be led to. The output signal of the photodetector 9 is sent to a signal processing circuit (not shown) and used as a reproduction signal, a focusing control signal, a tracking control signal, and the like. The optical head 3 is moved in the radial direction of the optical disc 1 by a linear motor (not shown).

The photodetector 10 includes the laser diode 4 described above.
The monitor light output from the rear side of is detected and converted into an electric signal, and is composed of a photodiode. The output signal of the photodetector 10 is supplied to the laser control circuit 13.

The laser control circuit 13 outputs a drive current corresponding to the error signal between the electric signal from the photodetector 10 and the reference voltage during reproduction, and during recording, the drive current is output as the error signal immediately before the recording. The corresponding drive current is output. The laser control circuit 13 includes an amplifier 14, an error amplifier 15, a sample hold circuit 16, and a laser driver 17. The amplifier 14 integrates and amplifies the output signal of the photodetector 10, and its output is supplied to the error amplifier 15.

The error amplifier 15 amplifies the difference between the output signal from the amplifier 14 and a preset reference signal, and its output is supplied to the sample hold circuit 16. Here, the reference signal is a set voltage for setting the output level of the reproduction beam light.

The sample hold circuit 16 samples and holds the output signal from the error amplifier 15 in accordance with the sample hold control signal supplied from the control circuit 20. That is, during playback, it is in the sample state,
The output signal from the error amplifier 15 is output as it is, and the error amplifier 1 immediately before that is in the hold state during recording.
The output signal from 5 is stored and held and output. The output of the sample hold circuit 16 is supplied to the laser driver 17.

The laser driver 17 outputs a drive current corresponding to the output signal from the sample hold circuit 16, the recording data signal supplied from the control circuit 20, and the laser emission control signal. This drive current is supplied to the laser diode 4.

As shown in FIG. 3, the laser driver 17 is composed of PNP type transistors 21, 22, 23 and 24, resistors R1 and R2, and an inverter circuit 25. The transistor 21 is used as a current amplifier, and the transistor 23 is used as a switching element.

That is, during reproduction (reproduction period), the transistor 22 is turned off because the laser emission control signal supplied from the control circuit 20 is at "0" level. As a result, a current due to the power supply voltage Vcc from the switch circuit 33 described later flows through the resistor R1, the transistor 21, and the laser diode 4. At this time, the transistor 2
Reference numeral 1 changes the drive current output to the laser diode 4 according to an error signal as an output signal from the sample hold circuit 16 to control the recording light amount. Therefore,
Laser light corresponding to the amount of reproduction light is generated from the laser diode 4.

During recording (recording period), the transistor 22 is on because the laser emission control signal supplied from the control circuit 20 is at "1" level. As a result, the current due to the power supply voltage Vcc from the switch circuit 33, which will be described later, becomes
When the transistor 23 is turned on by the recording data signal supplied from the control circuit 20 through the resistor R1, the transistor 21, and the laser diode 4, a current due to the power supply voltage Vcc causes the resistor R2, the transistors 22, and 2 to flow.
3 and laser diode 4.

Therefore, in the state where the laser light of the reproducing light quantity is generated, the laser diode 4 is driven according to the recording data signal supplied from the control circuit 20 to generate the laser light of the recording light quantity.

In addition to the drive current output from the laser driver 17, a high frequency current from the high frequency current generation circuit 31 is supplied to the laser diode 4 via a coupling capacitor 32 as a superposition circuit. That is, the drive current output from the laser driver 17 is supplied with the high frequency current from the high frequency current generation circuit 31 to the laser diode 4. The high frequency current generation circuit 31 is composed of a pulse oscillator such as an unstable multivibrator and generates a high frequency current.
The frequency (f1) of this high frequency current is a frequency (several hundred MHz) which is sufficiently higher than the frequency of the information to be reproduced from the optical disc 1.

The laser driver 17 and the high frequency current generating circuit 31 are connected to the power source section 3 via a switch circuit 33.
The power supply voltage Vcc from 4 is commonly supplied, and the power supply timings are the same.
That is, at the time of recording (consisting of a reproduction period and a recording pulse),
The high-frequency current from the high-frequency current generating circuit 31 is always superimposed regardless of the reproduction. As shown in FIG. 1, the switch circuit 33 includes an NPN transistor 4
1, 42 and resistors R3 and R4.

The switch circuit 33 has a transistor 42 when the switching control signal from the control circuit 20 is at "1" level.
Is turned on, the base voltage of the transistor 41 becomes zero volt. As a result, the transistor 41 remains off, and the power source voltage Vcc from the power source unit 34 is kept.
Is not applied to the laser driver 17 and the high frequency current generation circuit 31.

The switch circuit 33 is the control circuit 20.
When the switching control signal from is at "0" level, the transistor 42 is turned off, so that the transistor 41 is turned on. Accordingly, the power supply voltage Vcc from the power supply unit 34
However, the laser driver 17 is connected via the transistor 41.
And applied to the high frequency current generation circuit 31. The control circuit 20 controls the entire optical disk device.

The control circuit 20 is provided with a sample hold control signal, a laser emission control signal, a recording data signal, and a switching control according to a signal supplied from an external device (not shown) indicating reproduction or recording and recording data. It is designed to output a signal.

According to the above configuration, during reproduction,
The high frequency current from the high frequency current generation circuit 31 is added to the driving current from the laser driver 17 as the coupling capacitor 3.
It is superposed via 2 and supplied to the laser diode 4. As a result, the laser diode 4 obtains a laser emission output of 2 mW corresponding to the reproduction, as shown in FIG. Since the laser diode 4 has a laser non-emission period and stops the laser emission during this period, the laser emission does not become unstable or generate noise due to the returning light. Therefore, the laser emission output of the laser diode 4 at the time of reproduction is a predetermined output level (2
The laser light is stabilized at mW) and noise-removed.
Further, during the reproduction period during recording, the laser emission output level (2 mW) of the laser diode 4 during reproduction described above.
Is emitting light.

Then, in response to the recording pulse at the time of recording, the high frequency current from the high frequency current generating circuit 31 is superimposed on the drive current from the laser driver 17 through the coupling capacitor 32 and is supplied to the laser diode 4. To be done.

As a result, the laser diode 4 obtains a laser emission output of 2 mW during the reproducing period and a laser emission output of 20 mW corresponding to the recording pulse as shown in FIG.

As described above, the power supply timings of the power supply to the laser driver for driving the laser diode and the high-frequency current generating circuit for generating high-frequency current are the same, and the reproduction period and the recording pulse during reproduction and recording are set. A high-frequency current is superimposed on the corresponding laser emission output.

This makes it possible to reduce noise in the laser emission output of the laser diode during reproduction and stabilize the laser emission output of the laser diode during recording.

[0039]

As described above in detail, according to the present invention,
It is possible to provide an optical information recording / reproducing apparatus capable of performing stable recording without changing the laser emission output of the semiconductor laser oscillator during recording.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of a laser control circuit shown in FIG.

FIG. 3 is a circuit diagram showing the configuration of the laser driver shown in FIG.

FIG. 4 is a diagram for explaining a laser emission output during a reproduction period during recording and a laser emission output corresponding to a recording pulse.

FIG. 5 is a diagram showing current and laser emission output characteristics of a semiconductor laser oscillator.

FIG. 6 is a diagram showing a laser emission output state of a semiconductor laser oscillator during reproduction.

FIG. 7 is a diagram for explaining a laser light emission output during a reproduction period and a laser light emission output corresponding to a recording pulse during conventional recording.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 3 ... Optical head, 4 ... Laser diode, 10 ... Photodetector, 13 ... Laser control circuit, 17 ... Laser driver, 20 ... Control circuit, 31 ... High frequency current generation circuit, 32 ... Coupling capacitor, 33 ... switch circuit, 34 ... power supply section.

Claims (1)

[Claims] 1. An optical information recording / reproducing apparatus which records information on a recording medium or reproduces information recorded on the recording medium by irradiating the recording medium with laser light. The level and a second output level higher than the first level can be switch-controlled, and a semiconductor that oscillates laser light of the second output level when recording information on the recording medium. A laser oscillator, a conversion means for detecting monitor light from the semiconductor laser oscillator and converting the monitor light into an electric signal, and an error signal between the electric signal and the reference voltage from the conversion means during oscillation at the first level. The semiconductor laser oscillator is driven by a driving current according to the second level, and at the time of oscillation at the second level, the semiconductor laser oscillator is driven by a driving current according to the error signal immediately before the oscillation at the second level. Driving means for driving, high-frequency current generating means for generating high-frequency current, superimposing means for superposing the high-frequency current generated by the high-frequency current generating means on the driving current output from the driving means, the driving means and high-frequency current An optical information recording / reproducing apparatus comprising: a power supply voltage supply unit that is commonly connected to a current generation unit and supplies a power supply voltage.