JPH03142726A - Optical disk device - Google Patents

Abstract

PURPOSE:To prevent recording defect or reproducing defect from being generated even when a temperature is changed by detecting the light quantity of a light output means in a state before generating the temperature change, holding a peak value at the time of recording and a peak value at the time of reproducing and afterwards generating a driving signal based on this peak value. CONSTITUTION:In the state before generating the temperature change, the light emitting amount of a semiconductor laser oscillator is detected by a photodetector 13 and this amount is held in a low-power side peak detection circuit 40 and a high-power side peak detection circuit 41 respectively as the peak value of a reproducing signal at the time of reproducing and the peak value of a recording signal at the time of recording. At the time of reproducing, the driving signal is generated based on the peak value of the reproducing signal held in the low-power side peak detection circuit 40; and at the time of recording, the driving signal is generated based on the peak value of the recording signal held in the high-power side peak detection circuit 41 so as to drive the semiconductor laser oscillator. Thus, the reproducing defect or the recording effect can be prevented without lowering the light output by the temperature change at the time of recording or reproducing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an optical disc device for recording and reproducing information on and from an optical recording medium such as an optical disc.

(Prior Art) Conventionally, in an optical disk device that optically records or reproduces information on an optical recording medium such as a write-once or erasable optical disk, a relatively small continuous beam of light is emitted from a semiconductor laser as a light source. While the information on the optical disk is read by the output, the information is recorded on the optical disk by the optical output which intermittently changes at a relatively large predetermined value or more.

An optical output control circuit 14 that adjusts the optical output of the semiconductor laser in such an optical disc device to a predetermined laser power.
is configured, for example, as shown in FIG. In the figure, 5 is a semiconductor laser oscillator, and the intensity of the laser light generated by this semiconductor laser oscillator 5 is photoelectrically converted into a photocurrent by a laser monitoring photodetector 13, and detected as an optical output monitor signal S5. It looks like this. The optical output monitor signal S5 detected by this photodetector 13 is
The current-voltage conversion circuit 25 in the optical output control circuit 14 converts the voltage signal into a voltage signal and supplies it to the drive signal generation circuit 26. Further, in the drive signal generation circuit 26, the drive signal for the transistor Tr1 and, by extension, the semiconductor laser oscillator 5 is converted into a voltage signal. generated. The drive signal generated by the drive signal generation circuit 26 is a signal that acts to bring the voltage signal from the current-voltage conversion circuit 25 closer to the reference voltage generated by the reproduction power reference voltage generation circuit 27. The drive signal generated by the drive signal generation circuit 26 is supplied to the base of the transistor Tri as a driver 28 via a sample hold circuit 29 consisting of an analog switch SW1, a resistor R1, and a capacitor C3. A drive current for reproduction is applied to the semiconductor laser oscillator 5 from the collector of this transistor Tri. Note that the emitter of the transistor Tri is grounded through the resistor R2. In such a configuration, during reproduction, a servo loop is formed by closing the two analog switches SW of the sample and hold circuit by a control signal Sll from a control section (not shown), and the optical output of the semiconductor laser oscillator 5 is held constant. controlled to do so.

The configuration for recording is as follows. The waveform shaping circuit 32 generates a recording pulse signal S7,
It is composed of a drive signal generation circuit 33 and a reference voltage generation circuit 34 for recording power. Recording data 510 supplied from a control section (not shown) is manually input to the drive signal generation circuit 33. The drive signal generation circuit 33 into which this recording data S10 is input shapes the recording data S10 so that it becomes equal to the reference voltage generated by the recording power reference voltage generation circuit 34, and outputs the recording pulse signal S7 as a recording pulse signal S7. Supply to the base.

A recording drive current is applied to the semiconductor laser oscillator 5 from the collector of this transistor Tr2. Note that the emitter of the transistor Tr2 is grounded via a resistor R1. In such a configuration,
During recording, the analog switch SW of the sample hold circuit 29 is activated by a control signal S11 from a control section (not shown).
The servo loop is disconnected by opening 2 and 2, and the transistor Tri receives the voltage V charged in the capacitor C1.
60. is driven by. On the other hand, the transistor Tr2 is driven by the recording pulse signal S7. As a result, the semiconductor laser oscillator 5 is driven by the signals superimposed on the respective collectors of the transistors Tri and Tr2, and the semiconductor laser oscillator 5 obtains an optical output according to the recording data.
Recording is performed on an optical disc.

However, as shown in FIG. 4, the semiconductor laser oscillator 5 generally has a property that its power output characteristics with respect to input current change depending on its temperature. For example, the input current vs. power output characteristic at room temperature has a characteristic line of 0.
1, if the temperature rises, it changes as shown by characteristic line G2. Such a temperature rise is a phenomenon that always occurs due to the large current flowing for recording. When such a change in characteristics occurs, as shown by the dotted line in the figure, there is a drawback that both the optical output during reproduction and the optical output during recording decrease, resulting in defective reproduction or recording.

(Problems to be Solved by the Invention) As described above, when the temperature of the semiconductor laser oscillator increases, the power output characteristics change, and both the optical output during reproduction and the optical output during recording decrease, resulting in reproduction failure. Another object of the present invention is to provide an optical disk device which can prevent reproduction defects or recording defects even if the temperature of a semiconductor laser oscillator changes and the power output characteristics change. With the goal.

[Structure of the Invention] (Means for Solving the Problems) The optical disk device of the present invention comprises: a light output means for emitting a light beam; a detection means for detecting the amount of light beam emitted by the light output means; a first holding means for holding a first peak value of the signal detected by the detection means; and generating a drive signal for the optical output means in accordance with the first peak value held in the first holding means. a first drive signal generation means for generating a signal detected by the detection means; a first drive means for driving the light output means according to a drive signal generated by the first drive signal generation means; a second holding means for holding a second peak value; a drive signal generation means 'M42 for generating a drive signal for the light output means in accordance with the peak value held in the second holding means; Second
a second drive means for driving the light output means in accordance with a drive signal generated by the drive signal generation means;
and recording and reproducing means for recording and reproducing information using the optical output means driven by the second driving means.

(Function) The present invention detects the light amount of the light output means in a state before the power output characteristics of the light output means change due to temperature, for example, and detects the first peak value during reproduction and the first peak value during recording. During subsequent reproduction, a drive signal is generated based on the first peak value held above to drive the optical output means, and during recording, the first peak value held above is held separately. A drive signal is generated based on the second peak value to drive the light output means. This results in
For example, even if the power output characteristics of the optical output means change due to a change in temperature, the optical output means can be driven in a state before the change due to temperature occurs, so that poor reproduction or recording can be prevented. ing.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. Note that parts equivalent to those described in the conventional example will be described with the same reference numerals.

FIG. 2 shows a schematic configuration of the optical disc device of the present invention. In the figure, an optical disk 1 is formed by coating a metal film layer of tellurium, bismuth, or the like in a donut shape on the surface of a circularly molded substrate made of, for example, glass or plastic.

The optical disc 1 is rotated by a spindle motor 2. This spindle motor 2 is
A motor control circuit (not shown) that operates in response to a control signal (not shown) from the control circuit 3 controls the start and stop of rotation, the number of rotations, etc.

The control circuit 3 is composed of, for example, a microcomputer, and in addition to controlling the rotation of the spindle motor 2,
Controls various controls described below.

An optical head 4 is disposed below the optical disc 1 . This optical head 4 records or reproduces information on the optical disc 1, and includes a semiconductor laser oscillator 5, a collimator lens 6, and a polarizing beam splitter 7.
, objective lens 8, cylindrical lens 9 and convex lens 1
The astigmatism optical system includes a well-known astigmatism optical system 11, a 4-split photodetector 12, a photodetector 13, and the like. This optical head 4 is configured to move in the radial direction of the optical disc 1 by a moving mechanism constituted by, for example, a linear motor (not shown). And control circuit 3
The target track for recording or reproduction is moved in accordance with a control signal (not shown) from the controller.

The semiconductor laser oscillator 5 generates a diverging laser beam (light beam) according to the drive signal S1 from the optical output control circuit 14, and when recording information on the recording film of the optical disc 1, the recording A strong laser beam whose light intensity is modulated according to the information to be transmitted is generated, and the information is transferred to the optical disc 1.
When reading and reproducing data from the recording film, a weak laser beam having a constant light intensity is generated.

The diverging laser beam generated by the semiconductor laser oscillator 5 is converted into a parallel beam by a collimator lens 6 and guided to a polarizing beam splitter 7. The laser beam guided to the polarizing beam splitter 7 passes through the polarizing beam splitter 7 and enters the objective lens 8, and is focused by the objective lens 8 toward the recording film of the optical disc 1.

The objective lens 8 is supported movably in the forward axis direction by a lens actuator 15 as a lens drive mechanism. The focused laser beam that has passed through the objective lens 8 is projected onto the surface of the recording film of the optical disc 1 by being moved in the optical axis direction by the servo signal S2 from the focus servo circuit 16, and the minimum beam spot is is formed on the surface of the recording film of the optical disc 1. In this state, the objective lens 8 is in a focused state.

The objective lens 8 is also movable in a direction perpendicular to the optical axis, and is moved in the direction perpendicular to the optical axis by a servo signal from a tracking servo circuit (not shown). It has become. Then, the focused laser beam that has passed through the objective lens 8 is projected onto the surface of the recording film of the optical disc 1, and is irradiated onto the recording track formed on the surface of the recording film of the optical disc 1. ing. In this state, the objective lens 8 is in a matching track state. In the focused point and focused track state, information can be written and read.

On the other hand, the diverging laser beam reflected from the recording film of the optical disc 1 is converted into a parallel beam by the objective lens 8 when it is focused, and is returned to the polarizing beam splitter 7 again.

Then, it is reflected by this polarizing beam splitter 7 and guided onto a 4-split photodetector 12 by an astigmatism optical system 11 consisting of a cylindrical lens 9 and a convex lens 10, and an image is formed in a state where defocus appears as a change in shape. It is now possible to do so. The four-split photodetector 12 is composed of four photodetection cells that convert the light imaged by the astigmatism optical system 11 into electrical signals. Two sets of signals output from two photodetection cells arranged diagonally with each other in this four-split photodetector 12 are supplied to amplifiers 17 and 18, respectively.

The focus servo circuit 16 includes one differential amplifier that performs differential amplification by inputting two signals amplified by the amplifiers 17 and 18, and a phase correction circuit 20 that corrects the phase of the output signal of this one differential amplifier. , an analog switch 21 that controls whether or not to supply the output signal of the phase correction circuit 20 to the driver 22, and a driver 2 that amplifies the signal from the analog switch 21 and drives the actuator 15.
2. When this analog switch 21 is turned on by the focus on/off signal S3 from the control circuit 3, a focus servo loop is formed by supplying the signal from the phase correction circuit 20 to the actuator 15 via the driver 22. It has become so.

Further, the output signals from the amplifiers 17 and 18 are supplied to an adder 23. The signal added by the adder 23 reflects the recorded content of the optical disc 1, and is sent to the binarization circuit 24.

The binarization circuit 24 is composed of, for example, a comparator, and performs binarization by comparing the analog signal output from the adder 23 with a predetermined threshold level Th. The reflected light signal S4 binarized by the binarization circuit 24 is supplied to the control circuit 3. After being subjected to predetermined processing in the control circuit 3, it is sent as a reproduction signal to a host device (not shown).

The waveform shaping circuit 32 waveform-shapes the recording data S10,
This signal is supplied as a recording pulse signal S7 to a driver 28 in the optical output control circuit 14, which will be described later. The waveform shaping circuit 32 includes a drive signal generation circuit 33 and a recording power reference voltage generation circuit 34. The recording data S10 supplied from the control circuit 3 is input to the drive signal generation circuit 33. The drive signal generation circuit 33 to which this recording data S10 is input shapes the recording data S10 so that it becomes equal to the reference voltage generated by the recording power reference voltage generation circuit 34,
The waveform-shaped recording pulse signal S7 is supplied to the base of a transistor Tr2 serving as a driver 28.

The photodetector 13 is constituted by a photoelectric conversion element such as a photodiode, which is provided facing a light emitting port of the semiconductor laser oscillator 5 on the side opposite to the light emitting port for recording or reproducing laser light. When the photodetector 13 is irradiated with monitor light from the semiconductor laser oscillator 5,
The monitor light is converted into an electric signal (photocurrent) and supplied to the light output control circuit 14 as the light output monitor signal S5 of the semiconductor laser oscillator 5.

The optical output control circuit 14 controls the optical output of the semiconductor laser oscillator 5 to maintain it at a predetermined value by inputting the optical output monitor signal S5 output from the semiconductor laser oscillator 5 and performing feedback control. Figure 1 shows
The configuration of the optical output control circuit 14, and the semiconductor laser oscillator 5 and photodetector 1 connected to the optical output control circuit 14.
3 and a waveform shaping circuit 32. That is, the optical output control circuit 14 mainly includes a current-voltage conversion circuit 25,
It is composed of a low power side peak detection circuit 40, a high power side peak detection circuit 41, a drive signal generation circuit 26, a reproduction power reference voltage generation circuit 27, a driver 28, and the like.

The semiconductor laser oscillator 5 is driven by a drive signal S1 output from the optical output control circuit 14 to emit light. The intensity of the laser light generated by the semiconductor laser oscillator 5 is photoelectrically converted by the photodetector 13, and is extracted as a current signal corresponding to the light intensity received by the photodetector 13, that is, the optical output of the semiconductor laser oscillator 5. It is detected as an output monitor signal S5. The optical output monitor signal S5 detected by the photodetector 13 is supplied to a current-voltage conversion circuit 25.

The current-voltage conversion circuit 25 converts the optical output monitor signal S5, which is a current signal detected by the photodetector 13, into a voltage signal S6. The signal S6 converted into a voltage by the current-voltage conversion circuit 25 is supplied to a low power side peak detection circuit 40 and a high power side peak detection circuit 41.

The low power side peak detection circuit 40 detects and holds the peak value of the signal S6 converted into the voltage during reproduction at a predetermined timing. The output of this low power side peak detection circuit 40 is supplied to the drive signal generation circuit 26.

The drive signal generation circuit 26 generates a signal to be supplied to the base of the transistor Tri serving as the driver 28. The collector current of the transistor Tri is controlled by the signal generated by the drive signal generation circuit 26, and the optical output of the semiconductor laser oscillator 5 during reproduction is controlled.

Further, the high power side peak detection circuit 41 detects and holds the peak value of the signal S6 converted into the voltage during recording at a predetermined timing. The output S12 of this low power side peak detection circuit 41 is supplied to a drive signal generation circuit 33 within the waveform shaping circuit 32.

The drive signal generation circuit 33 generates a signal to be supplied to the base of the transistor Tr2 serving as the driver 28. The collector current of the transistor Tr2 is controlled by the signal generated by the drive signal generation circuit 33, and the optical output of the semiconductor laser oscillator 5 during recording is controlled.

The driver 28 includes a transistor Tri that generates reproduction light.
and a transistor Tr2 that generates recording light, and these transistors Tri.

Each collector of Tr2 is connected to semiconductor laser oscillator 5. Further, the emitter of the transistor Tri is grounded via a resistor R2, and the emitter of the transistor Tr2 is grounded via a resistor R1.

The transistor Tri generates a low-intensity laser beam during reproduction. A signal generated by the drive signal generation circuit 26 based on the voltage value previously held in the low power side peak detection circuit 40 is applied to the base of the transistor Tri, regardless of whether it is during reproduction or recording. 5's optical output level is kept constant.

Further, the transistor Tr2 generates a laser beam with high intensity during recording. The base of this transistor Tr2 is supplied with a recording pulse signal S7 whose output value has been shaped by the drive signal generation circuit 33 of the waveform shaping circuit 32 based on the voltage value previously held in the high power side peak detection circuit 41. It is now possible to do so. As a result, the semiconductor laser oscillator 5 is driven by the superimposed signals of the respective collectors of the transistors Tr1 and Tr2 to emit intermittent laser light of high luminous intensity, thereby recording information on the optical disk. .

Next, the operation of the optical disc device configured as described above will be explained.

First, before performing a recording operation, an initial operation is performed to check the validity of the optical output of the semiconductor laser oscillator 5.

That is, a linear motor (not shown) is driven by a control signal from the control circuit 3, and the objective lens 8 is made to face the non-recorded area of the optical disc 1. This non-recording area is provided on the innermost or outermost side of the optical disc 1, and is a portion where no information is recorded. Optical head 4 is placed in such a position.
By initially moving the laser beam, even if the laser beam emits abnormally for some reason, the low recorded data will not be destroyed.

Next, the analog switch 21 is turned off by outputting the focus on/off signal S3 from the control circuit 3. As a result, the focus servo loop is disconnected, and the objective lens 8 is released from focusing control. Next, a signal (not shown) for forcibly moving the lens actuator 15 is sent from the control circuit 3 to the driver 2.
2 to the lens actuator 15. As a result, the objective lens 8 is forcibly moved to the position shown by the dotted line in FIG. 2, creating a defocused state. In this defocused state, power is supplied to the optical output control circuit 14 to turn on the semiconductor laser oscillator 5 and start outputting a laser beam. As a result, the monitor light generated from the semiconductor laser oscillator 5 is converted into a current according to the light output by the photodetector 13 and output as a light output monitor signal S5. The current-voltage conversion circuit 25 is
This optical output monitor signal S5 is converted into a voltage signal S6 and supplied to a low power side peak detection circuit 40 and a high power side peak detection circuit 41. Then, a signal indicating the peak value of the reproduced light held in the low power side peak detection circuit 40 is supplied to the drive signal generation circuit 26. The drive signal generation circuit 26 generates a signal to be supplied to the base of the transistor Tri in order to drive the semiconductor oscillator 5.

This signal is detected by the photodetector 13, and if the signal held in the low power side peak detection circuit 40 is too large, the optical output of the semiconductor laser oscillator 5 is decreased, and if it is too small, the optical output of the semiconductor laser oscillator 5 is decreased. This is a signal that increases the volume. Thereby, even if the input current-power output characteristics of the semiconductor laser oscillator 5 change due to temperature, its optical output is maintained at the initial optical output.

Next, the control circuit 3 drives the actuator 15 via the driver 22 to move the objective lens 8 toward the in-focus position. When it is determined that the in-focus position has been reached, the analog switch 21 is turned on to connect the focus servo loop and complete the initial operation. Thereafter, automatic focus control is performed by a focus servo loop, and normal operations such as reading and writing information from the optical disc 1 are performed.

In such a state, the recording operation is performed as follows. First, recording data sent from a host device (not shown) is input to the control circuit 3.

As a result, the control circuit 3 outputs the pulsed recording data S10.
is output. This recorded data S10 is stored in the waveform shaping circuit 3.
The signal is supplied to the drive signal generation circuit 33 of No. 2. The drive signal generation circuit 33 to which the recording data 810 is supplied receives the signal S1 held in the low power side peak detection circuit 40.
2 is input, the error with the reference voltage generated by the recording power reference voltage generation circuit 34 is calculated, the recording data S10 is waveform-shaped so that these become equal, and the recording pulse signal S7 is used as the driver 28. It is supplied to the base of the transistor Tr2. As a result, the semiconductor laser oscillator 5 is supplied with a drive current in which the respective collector outputs of the transistors Tri and Tr2 are superimposed, and emits intermittent high-output laser light according to recording data. This laser light is converted into a parallel beam by a collimator lens 6 and guided to a polarizing beam splitter 7. The laser beam guided to the polarizing beam splitter 7 passes through the polarizing beam splitter 7, enters the objective lens 8, and is focused by the objective lens 8 toward the recording film of the optical disc 1. Information recording is performed.

On the other hand, the reproduction operation is performed as follows. That is, by supplying the signal generated by the drive signal generation circuit 26 to the base of the transistor Tri serving as the driver 28, the semiconductor laser oscillator 5 emits laser light with a constant level of low optical output. This laser beam is transmitted through the collimator lens 6
is converted into a parallel beam by the polarizing beam splitter 7
guided by. The laser beam guided to the polarizing beam splitter 7 passes through the polarizing beam splitter 7 and enters the objective lens 8, and is focused by the objective lens 8 toward the recording film of the optical disc 1. And optical disc 1
The diverging laser beam reflected from the recording film is converted into a parallel beam by the objective lens 8 and returned to the polarizing beam splitter 7 again. Then, it is reflected by this polarizing beam splitter 7, and is reflected by the cylindrical lens and convex lens 1.
An image is formed on a four-split photodetector 12 by an astigmatism optical system 11 consisting of 0 and 0. Signals photoelectrically converted by this four-split photodetector 12 are supplied to amplifiers 17 and 18, respectively. One of the signals amplified by the amplifiers 17 and 18 is sent to the focus servo circuit 1 below the differential amplifier 19.
6 and used for force-shing control. Further, the other of the signals amplified by the amplifiers 17 and 18 is supplied to the adder 23 and added, and then the binarization circuit 24
is supplied to

The binarization circuit 24 compares the signal from the adder 23 with a predetermined threshold level T'h, so that
A binarized reflected light signal S4 is output. This reflected light signal S4 is then supplied to the control circuit 3. Then, it is sent to a host device (not shown) via this control circuit 3,
Display, printing, etc. are performed.

As described above, the amount of light emitted by the semiconductor laser oscillator 5 is detected by the photodetector 13 in a state before the power output characteristics of the semiconductor laser oscillator 5 change due to temperature, for example, and this is used as a reproduction signal during reproduction. and the peak value of the recording signal during recording are held in the low power side peak detection circuit 40 and the high power side peak detection circuit 41, respectively, and during subsequent reproduction, the peak value is held in the low power side peak detection circuit 40. A drive signal is generated based on the peak value of the held reproduction signal to drive the semiconductor laser oscillator 5, and during recording, a drive signal is generated based on the peak value of the recording signal held in the high power side peak detection circuit 41. is generated to drive the semiconductor laser oscillator 5. Therefore, even if the input current-power output characteristic of the semiconductor laser oscillator 5 changes due to a change in temperature, for example, the above-mentioned Since the semiconductor laser oscillator 5 can be driven, the optical output during reproduction or recording does not decrease, and therefore it is possible to prevent reproduction defects or recording defects.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide an optical disc device that can prevent poor reproduction or recording even if the temperature of the semiconductor laser oscillator changes and the power output characteristics change. .

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is a circuit diagram showing the configuration of an optical output control circuit, and FIG. 2 is a block diagram showing the schematic configuration of an optical disc device. Third
4 and 4 are for explaining servo control of a conventional semiconductor laser oscillator. FIG. 3 is a circuit diagram showing the configuration of an optical output control circuit, and FIG.
FIG. 3 is a diagram showing output characteristics. DESCRIPTION OF SYMBOLS 1... Optical disk, 3... Control circuit, 5... Semiconductor laser oscillator (light output means) 12... 4-split photodetector, 13... Photodetector (detection means), 25... - Current-voltage conversion circuit, 26... Drive signal generation circuit (first drive signal generation means), 27... Reference voltage generation circuit for reproduction power, 28... Driver, 32... Waveform shaping circuit, 33... Drive signal generation circuit (second drive signal generation means), 34... Reference voltage generation circuit for reproduction power, 4
0...Low power side peak detection circuit (first holding means)
, 41...High power side peak detection circuit (second holding means), Trl...transistor (first driving means)
, T r 2...transistor (second driving means).

Claims (1)

[Claims] A light output means for emitting a light beam; a detection means for detecting the amount of the light beam emitted by the light output means; and a first peak value of the signal detected by the detection means. a first holding means for generating a drive signal for the light output means in accordance with a first peak value held in the first holding means; a first driving means for driving the optical output means in accordance with a drive signal generated by the signal generating means; a second holding means for holding a second peak value of the signal detected by the detection means; a second drive signal generation means for generating a drive signal for the optical output means according to the peak value held in the second holding means; a second driving means for driving the optical output means; and a recording/reproducing means for recording and reproducing information by the optical output means driven by the first and second driving means. optical disk device.