JPH05242490A - Optical disk device - Google Patents

Abstract

PURPOSE:To stably and surely set focus even when disturbance is applied to an optical disk device. CONSTITUTION:The moving speed of the movable part 10 of an objective lens 8 is detected by a speed detector 12 at the time of setting focus, and a difference between the detective signal and the signal of a prescribed speed set previously and outputted from a search speed voltage generator 11 is taken by a subtracter circuit 13, and the difference signal is converted to a current by an amplifier 4 and made to flow through a focus actuator 5, and a movable part 10 is moved in the vertical direction to the light axis direction of an optical disk. Thus, the movement of the objective lens is maintained at a prescribed speed and focus is set even when disturbance is applied to the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for irradiating a recording surface of an optical disk with a light spot of laser light to record and reproduce information.

[0002]

2. Description of the Related Art In recent years, an optical disk device has been widely used for recording and reproducing information by irradiating a recording surface of an optical disk with a light spot of laser light. Such an optical disk device is provided with a focus servo system for performing focus pull-in for moving the objective lens to a position where the light spot of the laser light is focused on the recording surface of the optical disk.

FIG. 14 is a block diagram showing a structure of a portion involved in focus pull-in of a conventional optical disk device. A pair of light receiving elements 1a and 1b, a subtraction circuit 2, a servo circuit 3, an amplifier 4, a focus actuator 5, and A search voltage generator 6 is provided. First, the recording surface of the optical disk 7 is irradiated with laser light, the reflected light is irradiated onto the light receiving elements 1a and 1b through the objective lens 8, and the light amount of the laser light with which the light receiving elements 1a and 1b are irradiated. An electric current proportional to is applied to the subtraction circuit 2.

The subtraction circuit 2 converts the current from each of the light receiving elements 1a and 1b into a voltage, takes the difference between them, and outputs it to the servo circuit 3 as a focus error signal. This focus error signal is a detection signal for moving the objective lens 8 so that the light spot is focused on the recording surface of the optical disc.

FIG. 15 is a diagram showing the relationship between the distance between the objective lens 8 and the recording surface of the optical disk 7 in FIG. 14 and the focus error signal. In this way, when the distance between the objective lens 8 and the recording surface of the optical disk 7 is the focal position F, the light spot of the laser beam is focused on the recording surface of the optical disk, and the focus error signal becomes 0V.

The servo circuit 3 is composed of a phase compensation circuit for operating the focus servo system in a stable manner. The servo circuit 3 outputs a voltage corresponding to the focus error signal from the subtraction circuit 3 to the amplifier 4, and the amplifier 4 outputs the voltage. A current proportional to the output voltage is passed through the focus actuator 5. The focus actuator 5 applies a thrust force proportional to the flowing current to the objective lens 8 and vertically moves the objective lens 8 so as to move closer to or farther from the optical disk 7.

In order to perform focus pull-in, it is necessary to move the objective lens 8 to the vicinity of the in-focus position and turn on the switch SW2 to perform focus servo. Therefore, when searching for the in-focus position, the switch SW
2 is turned off, the switch SW1 is turned on, the objective lens 8 is moved to the vicinity of the focus position by the output voltage from the search voltage generator 6, and then the switch SW1 is turned off and the switch SW2 is turned on to perform focus servo. Turn it on.

For example, a focus pull-in device for lowering the vertical movement speed of the objective lens near the focus position to perform focus pull-in (for example, Japanese Patent Laid-Open No. 32-32428).
Japanese Patent Laid-Open Publication No. 63-179421) and a focus servo circuit (for example, see Japanese Patent Laid-Open No. 63-179421) that detects the position of the actuator and pulls the focus according to the detection signal.

[0009]

However, many of the objective lenses of the above-mentioned optical disk device are supported by an elastic supporting member such as a leaf spring, so that when a disturbance of a predetermined frequency is applied during the search, the conventional objective lens is not used. In technology, the objective lens vibrates at that frequency. Therefore, when the objective lens is moved to the vicinity of the in-focus position by the output voltage of the search voltage generator, there is a problem that the moving speed of the objective lens with respect to the in-focus position becomes large and the focus cannot be pulled in.

The present invention has been made in view of the above points, and it is an object of the present invention to enable stable and reliable focus pull-in even if a disturbance is applied to an optical disk device. Another object is to realize stable and reliable focus pull-in at low cost.

[0011]

In order to achieve the above object, the present invention provides a search circuit for performing focus pull-in control for moving an objective lens to a position where an irradiated laser beam is focused on a recording surface of an optical disk, and a search circuit for the focus circuit. A first selector switch for switching the search circuit on and off, a focus servo system for controlling the objective lens to be held at a position where the laser beam is focused on the recording surface, and on / off of the focus servo system. And a second changeover switch for switching the light spot on the recording surface by driving the search circuit to focus the light spot of the laser light formed through the objective lens on the recording surface. In an optical disk device that irradiates the optical disk to record and reproduce information, a search circuit is used to detect the moving speed of the objective lens. And vessels, constituted by a speed servo system for moving the objective lens by a predetermined speed, turn on the first switching switch when the focus pull-in, the second
The changeover switch is turned off, and the movement of the objective lens is controlled to a predetermined speed by the speed servo system according to the moving speed detected by the speed detector.

Further, it is preferable that the speed detector is constituted by a circuit for detecting the induced voltage of the drive coil for moving the objective lens. Further, the speed detector may be configured by a detector that detects the position of the actuator movable part of the objective lens and a differentiation circuit that differentiates the position signal output from the detector to convert the moving speed of the actuator movable part. ..

[0013]

In the optical disk device according to the present invention, when the focus is pulled in, the movement of the objective lens is controlled to a predetermined speed by the speed servo system according to the moving speed detected by the speed detector. Even if this is done, the focus can be pulled in while maintaining the movement of the objective lens at a predetermined speed. Further, if the speed detector detects the induced voltage of the drive coil for moving the objective lens, focus pull-in can be performed without increasing the cost of the apparatus for the speed detection.

Further, the position of the actuator movable part of the objective lens is detected by the detector of the speed detector, and the position signal output from the detector is differentiated by the differentiating circuit to be converted into the moving speed of the actuator movable part. By doing so, it is possible to more accurately detect the moving speed of the actuator movable portion of the objective lens and perform focus pull-in.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a portion related to the focus pull-in (hereinafter referred to as “focus pull-in device”) of the optical disk device according to the present invention, and the portions common to FIG. 14 are designated by the same reference numerals.

This focus pull-in device is composed of a focus servo system and a search circuit. The focus servo system includes light-receiving elements 1a and 1b, a subtraction circuit 2, a servo circuit 3 for controlling the objective lens 8 to be held at a position where the laser light L is focused on the recording surface of the optical disk 7, and its servo circuit. It comprises a second changeover switch SW2 for switching ON / OFF of 3 and an amplifier 4.

Further, the laser light L applied to the optical disk 7
The search circuit for performing the focus pull-in control for moving the objective lens 8 to the position where the light is focused on the recording surface is preset with the focus actuator 5, the movable portion 10 that supports and moves the objective lens 8, and the objective lens 8. A search speed voltage generator 11 that outputs a voltage for moving at a target speed, a speed detector 12 that detects the moving speed of the objective lens, a search speed voltage generator 11 and a speed detector 12.
The second subtraction circuit 13 outputs a voltage for driving the focus actuator 5 on the basis of the voltage output from each of the above, and a first changeover switch SW1 for switching on / off of the search circuit.

FIG. 2 is a circuit diagram showing the structure of the speed detector 12. With such an electric circuit, when the current I output from the amplifier 4 flows through the drive coil 5 ′ of the focus actuator 5, the movable part including the objective lens moves at the speed v, and the drive coil 5 ′ moves with it. An induced voltage kv (k is a proportional constant) is generated in ′.

At this time, the voltage Va at the connection end of the drive coil 5'with the amplifier 4 is r, where r is the resistance of the drive coil 5 '.
It can be calculated by Equation 1.

[0020]

[Equation 1] Va = I · (r + Rs) + kv

The voltage Vb at the connection end with the resistor Rs is V
b = I · Rs, and the induced voltage kv is calculated by multiplying this voltage Vb by (1 + r / Rs) by the operational amplifier circuit and taking the difference from Va. Note that r / Rs = R2 / R1. Since the induced voltage kv is a voltage proportional to the moving speed of the movable part, the moving speed of the objective lens can be detected by the induced voltage kv. Further, the cost of the device is not increased due to the speed detection.

Therefore, this focus pull-in device is for turning on the switch SW1 and turning off the switch SW2 in FIG. 1 at the time of searching, and moving the objective lens 8 at the time of searching from the search speed voltage generator 11 at a predetermined speed. The voltage is output to the subtraction circuit 13. In addition, the speed detector 12
The moving speed of the objective lens 8 is detected by and the voltage corresponding to the detected moving speed is output to the subtraction circuit 13.

The subtraction circuit 13 includes a search speed voltage generator 1
The difference between the voltages output from 1 and the speed detector 12 is calculated, and a voltage proportional to the difference is output to the amplifier 4.
Then, the amplifier 4 causes a current proportional to the voltage input from the subtraction circuit 13 to flow to the focus actuator 5 to move the objective lens 8. As a result, the objective lens 8 is controlled so as to move at a predetermined speed set in advance.

FIG. 3 shows a search voltage generator 11 for searching.
FIG. 3 is a diagram showing an example of the output voltage of the speed detector 12, the output voltage of the speed detector 12, the output voltage of the subtraction circuit 13 corresponding to these voltages, and the output waveform of the focus error signal in association with each other. For example, the search is started at time t0, the switch SW1 is turned on and the switch SW2 is turned off, and the search speed voltage generator 11 generates the voltage V1.

Then, as the moving speed of the objective lens 8 gradually increases, the output voltage from the speed detector 12 increases, and the output voltage from the second subtraction circuit 13 decreases accordingly, and when the time t1 is reached. The speed detector 12 outputs a voltage V2 and the second subtraction circuit 13 outputs a voltage of about 0 V. Thereafter, a search is performed at a predetermined moving speed until time t2.

After that, when the time t2 is reached, the switch SW
1 is turned off and the switch SW2 is turned on to turn on the focus servo. Then, the search circuit is driven to focus the light spot of the laser light formed through the objective lens 8 on the recording surface of the optical disc 7, and the light spot is irradiated on the recording surface by the control of the focus servo system to record the information. Record and play.

In this way, since the servo at the time of searching is performed according to the moving speed of the objective lens, even if a disturbance is applied to the apparatus, the moving of the objective lens is maintained at a predetermined speed and stable and reliable focus pull-in is performed. I can do it.

The speed detector is composed of a detector for detecting the position of the movable part of the focus actuator 5, and a differentiating circuit for differentiating the position signal output by the detector to convert it into the moving speed of the actuator movable part. Good to do. FIG. 4 is a front view showing a schematic configuration in the vicinity of the focus actuator in that case. The focus actuator 5 is provided with a drive coil 14 (corresponding to the drive coil 5 ′ in FIG. 4) on the outer wall of the movable portion 10 that supports the objective lens 8, and the yoke 15 in which the magnet 16 is positioned so as to face the drive coil 14. Are installed.

Therefore, the yoke 15 and the magnet 16
Since the magnetic circuit is formed by and, the movable portion 10 is moved in the optical axis direction of the objective lens 8 by passing a current through the drive coil 14 located in the gap of the magnetic circuit. Further, the light emitting LED 17 and the light receiving element 18 are fixedly arranged in the vicinity of the movable portion 10 so as to face each other, and the light emitting LED 17 and the light receiving element 18 are arranged on the outer wall of the movable portion 10 according to the movement amount thereof.
A light-shielding plate 19 is provided to shield light between and.

FIG. 5 is a block diagram showing the configuration of a focus servo system including this speed detector, and the portions common to those in FIG. I
The / V converter 20 converts the current from the light receiving element 18 into a voltage, and the differentiating circuit 21 differentiates the signal according to the voltage and sends it to the subtracting circuit 13, which in turn subtracts the search speed voltage generator 11 and the differentiating circuit 21. Output the signal with the voltage difference from.

FIG. 6 shows the moving position of the movable part 10 and the light receiving element 1.
8 is a diagram showing the relationship with the output current of FIG. 8, and when the movable portion 10 moves within the movable range, the light shielding amount by the light shielding plate 19 also changes according to the movement amount of the movable portion 10, and as a result, the light receiving element 1
8 outputs a current proportional to the moving amount of the movable portion 10. In addition, FIG. 7 shows I / I when the movable unit 10 moves at a constant speed.
It is a diagram showing an example of the change of the output voltage of the V converter, I
The / V converter 20 outputs a voltage signal proportional to the current output by the light receiving element.

Further, FIG. 8 is a diagram showing an example of a change when the differentiating circuit 21 differentiates the signal from the I / V converter 20, and the differentiating circuit 21 shows the signal from the I / V converter 20. A voltage proportional to the moving speed of the movable part is obtained by differentiating, and the search speed voltage generator 1 is based on this voltage.
It is possible to control the moving speed of the movable part so that it becomes equal to the predetermined voltage output from the optical disk 1, and move the objective lens at the predetermined speed. In this way, the moving speed of the movable portion 10 of the focus actuator 5 can be detected more accurately, and the focus pull-in can be performed based on the detection result.

By the way, a drive signal for vertically moving the objective lens in the optical axis direction during focusing is often output in a triangular waveform by the D / A converter. For example, FIG. 9 is a diagram showing an example of the triangular wave signal. Thus, when the objective lens is moved up and down by the triangular wave output of the D / A converter, undesired vibrations occur at the vertices of the triangular waveform, that is, at the position where the objective lens is farthest from the recording surface of the optical disc and the position closest to it. It can happen. Therefore, if the objective lens is moved smoothly by the output voltage of the D / A converter as described below, there is no fear of causing unwanted vibration.

FIG. 10 is a block diagram showing a structure for moving the objective lens. The optical disk controller 22 is D / A by a drive control program.
It controls the waveform output of the converter 23. The D / A converter 23 outputs a sine waveform output voltage, the objective lens drive circuit 24 outputs a drive signal for the actuator 25,
The actuator 25 moves the objective lens up and down with respect to the optical axis direction on the recording surface of the optical disc.

Next, the processing executed by the drive control program by the optical disk controller 22 will be described. First, as an initial condition, the D / A converter 23 has -2.5 V to +2.
Values up to 5 V can be set arbitrarily, and 1 bit of 7-bit data is allocated to the area for storing the voltage polarity setting data. Therefore, as shown in FIG.
A register (ORDER) for dividing the values up to F into 64 on a sine waveform, recording the divided values in a table (FODAT), and recording the order of D / A output values is provided.

FIG. 12 is a flow chart showing the processing when the objective lens is moved upward by the optical disc controller 22. First, register (ORDER)
Read the D / A output value recorded in, and DIR ≠ 0
Whether the current D / A output value is positive or negative is determined depending on whether or not the value of ORDER is moved. That is, it moves one step on the time axis shown in FIG.

Then, a table (FOD
The value is read from AT) and output from the D / A converter. By repeating such a routine, as shown in FIG.
The waveform when the lens is up as shown in 1 is output.
Also, the waveform when the lens is down is output by similar processing.

In this way, if the sine waveform as shown in FIG. 13 is output from the D / A converter and the output value drives the actuator to move the objective lens, the objective lens driving circuit moves the objective lens. It can be moved smoothly in the vertical direction.

[0039]

As described above, according to the optical disk device of the present invention, the objective lens can be moved at a predetermined speed when the focus is pulled in, so that the focus can be pulled in stably and reliably even when a disturbance is applied. ..
Further, since the moving speed of the objective lens is detected by the induced voltage of the drive coil for moving the objective lens, stable and reliable focus pull-in can be performed at low cost. Further, since the position signal obtained by detecting the position of the actuator movable portion of the objective lens is differentiated and converted into the moving speed of the actuator movable portion, stable and reliable focus pull-in can be performed with a more accurate moving speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a portion related to focus pull-in of an optical disc device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a speed detector 12 in FIG.

3 is a diagram showing the output voltages from the search voltage generator 11, the speed detector 12, and the subtraction circuit 13 and the output waveform of the focus error signal, which are associated with each other, during the search in the focus pull-in device shown in FIG. Is.

FIG. 4 is a front view showing a schematic configuration in the vicinity of a focus actuator according to another embodiment of the present invention.

5 is a block diagram showing a configuration similar to that of FIG. 1 of the same embodiment. FIG.

FIG. 6 is a diagram showing a relationship between a moving position of a movable part of a focus actuator and an output current of a light receiving element in the embodiment of FIG.

FIG. 7 is a diagram showing an example of changes in the output voltage of the I / V converter when the movable part moves at a constant speed.

8 is a diagram showing an example of a change when the differentiating circuit 21 of FIG. 4 differentiates the signal from the I / V converter 20. FIG.

FIG. 9 is a diagram showing an example of a triangular waveform output by a D / A converter for moving an objective lens up and down during focusing.

10 is a block diagram showing a circuit configuration for moving an objective lens by the triangular wave signal shown in FIG.

11 is a diagram showing an example of a waveform provided to show a process when the output waveform from the D / A converter 23 in FIG. 10 is divided.

FIG. 12 is a flow chart showing a process when the objective lens is similarly moved up.

FIG. 13 is a diagram showing an example of a sine waveform output by the D / A converter 23 to vertically move the objective lens during focusing.

FIG. 14 is a block diagram showing a configuration of a portion related to focus pull-in in a conventional optical disc device.

15 is an objective lens 8 and an optical disk 7 in FIG.
FIG. 6 is a diagram showing the relationship between the distance between the recording surfaces and the focus error signal.

[Explanation of symbols]

1a, 1b Light receiving element 2,13 Subtraction circuit 3 Servo circuit 4 Amplifier 5 Focus actuator 7 Optical disk 8 Objective lens 10 Moving part 11 Search speed voltage generator 12 Speed detector 14 Focus coil 15 York 16 Magnet 17 Light emitting LED 18 Light receiving element 19 Light-shielding unit 20 I / V converter 21 Differentiation circuit 22 Optical disc controller 23 D / A converter 24 Objective lens drive circuit 25 Actuator SW1 First changeover switch SW2 Second changeover switch

Claims (3)

[Claims] 1. A search circuit for performing focus pull-in control for moving an objective lens to a position where an irradiated laser beam is focused on a recording surface of an optical disc, and a first changeover switch for switching ON / OFF of the search circuit. A focus servo system for controlling the objective lens to be held at a position where the laser beam is focused on the recording surface; and a second for switching the focus servo system on and off.
The changeover switch for driving the search circuit to focus the light spot of the laser light formed through the objective lens on the recording surface, and control the focus servo system to move the light spot to the recording surface. In an optical disk device for irradiating the optical disk to record and reproduce information, the search circuit includes a speed detector for detecting a moving speed of the objective lens and a speed servo system for moving the objective lens at a predetermined speed. Then, when the focus is pulled in, the first changeover switch is turned on, the second changeover switch is turned off, and the movement of the objective lens is predetermined by the speed servo system according to the moving speed detected by the speed detector. An optical disk device characterized by being controlled at a speed. 2. The optical disk device according to claim 1, wherein the speed detector is composed of a circuit that detects an induced voltage of a drive coil that moves the objective lens. 3. The optical disk device according to claim 1, wherein the speed detector is a detector that detects a position of an actuator moving part of the objective lens, and the actuator outputs the position signal output from the detector by differentiating the position signal. An optical disk device comprising a differentiating circuit for converting the moving speed of a movable part.