JP2003016677A - Optical disk device and its tilt control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stable tilt control. SOLUTION: A photodetector 19 receives light reflected on an optical disk 1 and feeds an optical detection signal to a signal processor 23. The signal processor 23, on the basis of the optical detection signal, supplies a RF signal, an FE signal, a TLE signal, etc., to a posture controller 24. On the basis of these signals, the posture controller 24 controls an actuator 17. The actuator 17 is a four-shaft actuator having a tilt function. The posture controller 24, with the signal level of the RF signal at or above a prescribed criterion, discriminates the objective lens 16 approaching the optical disk 1 to perform tilt control and, with the signal level below the criterion, discriminates the objective lens 16 receding from the optical disk 1 to stop tilt control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device and a tilt control method therefor.

[0002]

2. Description of the Related Art In an optical disk device for recording data on an optical disk such as a CD, DVD, MD or reproducing the recorded data, tracking control and focus control are required to accurately record and reproduce the data. And it is necessary to perform tilt control.

The tracking control is a control for correcting a tracking error due to the rotation axis, the eccentricity of the optical disk, etc., and causing the optical axis to follow the track in which the data pit is formed.

Focus control is control for focusing light on the surface of the optical disk. The tilt control is control for making the optical axis of the light beam perpendicular to the surface of the optical disc in order to follow the warp of the optical disc.

Regarding the tilt control, a tilt control device of an optical disk device for adjusting the optical axis of a light beam by tilting an optical pickup has been conventionally known (Japanese Utility Model Publication No. 60-127630, etc.). reference). In such a conventional optical disc device, the optical pickup itself does not have a tilt function, and the tilt control is performed after the initial position is set at the start of operation.

However, in such an optical disk device,
The part where the tilt is detected may be different from the surface that is actually recorded or reproduced. Further, since the optical pickup itself is heavy, there is a problem that the response speed is slow and it cannot follow at high speed. By the way, in recent years, the recording density of optical discs has increased, and it has become necessary to detect a slight inclination of the surface of the optical disc that is being recorded or reproduced.

Therefore, an optical disk device has been developed in which an actuator for controlling the attitude of an objective lens is provided in an optical pickup so that tilt control can be performed without tilting the optical pickup.

[0008]

However, in such an optical disk device, since the objective lens is constructed so as to move in the tilt direction, the initial position of the objective lens is not always the optimum position. There is. That is, the optical axis of the light beam may not be perpendicular to the recording surface of the optical disc.

Further, when the tilt servo is operated in a state where the reflected light from the optical disk is small during the focus control,
The tilt error signal may become indefinite and the objective lens may be displaced, and the focus servo will not work.

The present invention has been made in view of such conventional problems, and an object thereof is to provide an optical disk device and a tilt control method therefor capable of stably performing tilt control.

[0011]

In order to achieve this object, an optical disk apparatus according to a first aspect of the present invention uses an objective lens to irradiate a light beam on an optical disk to perform tilt control and data recording. An optical disk device for reproducing or recording, wherein the light receiving means for receiving the reflected light of the light applied to the optical disk and the signal level of a signal generated based on the reflected light received by the light receiving means When the determination means determines whether the objective lens is approaching the optical disc, and when the determination means determines that the objective lens is approaching the optical disc, tilt control is performed and the objective lens moves away from the optical disc. When the determination means determines that the tilt control is performed, the tilt control means for stopping the tilt control is provided.

A signal processing means for generating at least one of a reproduction signal, a focus error signal, and a tilt error signal in the radial direction and the tangential direction based on the reflected light received by the light receiving means may be provided. Good.

The signal processing means generates a reproduction signal based on the reflected light received by the light receiving means, and the judging means is
The signal level of the reproduction signal generated by the signal processing means is compared with a preset determination value, and if the signal level of the reproduction signal is equal to or higher than the determination value, the objective lens is approaching the optical disc. May be determined.

The signal processing means generates a focus error signal based on the reflected light received by the light receiving means, and the judging means presets the signal level of the focus error signal generated by the signal processing means. It may be determined that the objective lens is approaching the optical disc if the signal level of the focus error signal is higher than or equal to the determination value by comparing with the determination value.

The signal processing means generates tilt error signals in the radial direction and the tangential direction based on the reflected light received by the light receiving means, and further adds both tilt error signals to obtain a sum signal of both tilt error signals. Generate,
The determination means compares the signal level of the sum signal generated by the signal processing means with a preset determination value, and if the signal level of the sum signal is equal to or higher than the determination value, the objective lens is It may be determined that the optical disk is approaching.

The light receiving means may include photoelectric conversion means for receiving the reflected light of the light beam applied to the optical disk and photoelectrically converting the received reflected light into an electric signal.

According to a second aspect of the present invention, there is provided a tilt control method for an optical disk device, wherein an objective is obtained based on a step of receiving reflected light of a light beam and a signal level of a signal generated based on the received reflected light. A step of determining whether the lens is approaching the optical disc, a step of performing tilt control when it is determined that the objective lens is approaching the optical disc, and a step of stopping the tilt control when determining that the objective lens is away from the optical disc. , Are provided.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An optical disk device according to an embodiment of the present invention will be described below in detail with reference to the drawings. First, the optical disk device according to the first embodiment will be described. In this device, the tilt servo is turned on and off based on the signal level of an RF (Radio Frequency) signal generated from the reflected light.

This optical disk device comprises a spindle motor 2, an optical pickup 11, and a control section 21. The spindle motor 2 is a motor for rotating the optical disc 1. The optical pickup 11 is for reading data from the optical disc 1, and includes a laser diode 12, a collimator lens 13, a polarization beam splitter 14, a quarter wavelength plate 15, an objective lens 16, an actuator 17, and It is configured to include a condenser lens 18 and a photodetector 19.

The laser diode 12 is a light source that emits a light beam for irradiating the optical disc 1. The collimator lens 13 is a lens for collimating the light beam emitted by the laser diode 12 into parallel light. The laser diode 12 is arranged so that its light emitting point is located at the focal position of the collimator lens 13.

The polarization beam splitter 14 is for separating the reflected light from the optical disk 1 from the incident light on the optical disk 1. The quarter-wave plate 15 is for converting linearly polarized light in incident light into circularly polarized light.

The objective lens 16 is the collimator lens 1
3, the light beam that has passed through the polarization beam splitter 14 and the quarter-wave plate 15 is condensed on the recording surface of the optical disc 1,
This is a lens for making the reflected light reflected by the optical disc 1 parallel light.

The actuator 17 supports the objective lens 16 and controls its posture.
It should be noted that, for example, Japanese Patent Application No. 2001-0
The 4-axis actuator disclosed in 57222 is used. This structure will be described later.

The condenser lens 18 is a lens for condensing the reflected light on the photodetector 19, and is a lens which imparts astigmatism. The photodetector 19 includes four light receiving elements 19a to 19d as will be described later, receives the reflected light from the optical disc 1, and outputs an electric signal having a signal level corresponding to the intensity of the reflected light as four light detection signals. It is a thing.

The control unit 21 comprises a driver 22, a signal processing unit 23, and an attitude control unit 24. The driver 22 is for driving the laser diode 12.

The signal processing section 23 includes a photo detector 19
RF signal, FE (focus error) signal, RSE (radial tilt error signal), TSE (tangential tilt error) based on the light detection signal output by
And a TLE signal.

The RF signal is a reproduction signal, and the FE signal is a signal indicating the deviation between the recording surface of the optical disc 1 and the focal point of the objective lens 16. The RSE signal is a signal indicating the deviation in the radial direction between the normal line on the recording surface of the optical disc 1 and the optical axis of the light beam. The TSE signal is
It is a signal indicating the deviation in the tangential direction between the normal line on the recording surface of the optical disc 1 and the optical axis of the light beam. The TLE signal is a sum signal of the RSE signal and the TSE signal, and is also a tilt detection signal indicating the tilt of the objective lens 1 in the radial direction and the tangential direction.

The attitude control unit 24 controls the actuator 17 to perform tracking control, control the distance between the recording surface of the optical disc 1 and the objective lens 16 (focus control), and objective lens to the recording surface of the optical disc 1 is controlled. The tilt of 16 is controlled (tilt control). In the present embodiment, only focus control and tilt control will be described. The attitude control unit 24 stores in advance a determination value S _{th 1} for determining the signal level of the RF signal.

The structure of the actuator 17 is shown in FIG.
FIG. 2 shows an actuator 1 included in this optical disk device.
It is a perspective view which illustrates the structure of FIG.

This actuator 17 is
The coil type (MC method) is used. As shown in FIG. 2, the actuator 17 includes a focus coil 31, a tracking coil 32, tilt coils 33 and 34, a magnet 35, a lens base 36, a yoke 37, a damper 38, a holder 39, and It is provided with a silicone rubber 40 and a holding portion 41.

The focus coil 31 is for adjusting the distance between the optical disk 1 and the actuator 17 and moving the focal position of the light beam by the electromagnetic force that acts when energized. The focus coil 31 is a magnet 35.
The objective lens 16 is wound around the lens base 36 so as to be sandwiched by the magnetic circuit constituted by the yoke 37 and the yoke 37.

The tracking coil 32 causes the actuator 17 to move to the optical disk 1 by the electromagnetic force acting when energized.
It is for moving in the radial direction of. The tracking coil 32 is wound around the tilt coils 33 and 34 provided on both sides of the lens base 36. The tracking coil 32 on the right side of FIG.
Is omitted because it illustrates the tilt coils 33 and 34 inside.

The tilt coil 33 is composed of two serially connected coils.
It is composed of two coils (not shown), and is for adjusting the inclination of the optical axis in the objective lens 16 by an electromagnetic force acting between the coil and the magnet. The two coils forming the tilt coil 33 are provided at diagonal positions of the lens base 36 with the objective lens 16 as the center, and when energized, an electromagnetic force in the direction of tilting the objective lens 16 acts. That is, for example, when two coils provided in the horizontal position are energized, electromagnetic forces acting in opposite directions (vertical direction) from the horizontal position act between the magnet 35, and the tilt of the optical axis in the objective lens 16 is adjusted. To do.

The tilt coil 34 is connected in series with two
It is composed of two coils (not shown), and is for adjusting the inclination of the optical axis in the objective lens 16 by an electromagnetic force acting between the coil and the magnet. The two coils forming the tilt coil 34 are provided at diagonal positions of the lens base 36 centered around the objective lens 16 and at diagonal positions different from the positions where the two coils are arranged. Electromagnetic force acts in the direction of tilting the lens 16.

The magnet 35 is a permanent magnet for generating an electromagnetic force when the tilt coils 33, 34 are energized.
The objective lens 16 is installed at the center of gravity of the lens base 36. The lens base 36 is for supporting the objective lens 16, and is connected to the holding portion 41 via the silicone rubber 40.

The yoke 37 is made of, for example, a ferromagnetic material, forms a magnetic circuit with the magnet 35, and generates an electromagnetic force between the focus coil 31, the tracking coil 32, and the tilt coils 33 and 34. It is for making it. The damper 38 connects the holder 39 and the holding portion 41, and holds the lens base 36 with a degree of freedom in the radial direction of the optical disc 1. Holder 3
Reference numeral 9 is for supporting the damper 38.

The silicone rubber 40 has elasticity to connect the lens base 36 and the holding portion 41 to each other.
For holding the optical disc 1 with a degree of freedom in the tangential direction. The holding portion 41 is for holding the lens base 36 via the silicone rubber 40.

Next, the structures of the photo detector 19 and the signal processing unit 23 are shown in FIG. The photo detector 19 is
As described above, the four light receiving elements 19a, 19b, 19
c, 19d and I / V amplifiers 20a, 20b, 20c,
20d.

The four light receiving elements 19a to 19d receive the reflected light reflected by the optical disk 1 as a spot (SP) and generate a current having a magnitude corresponding to its intensity. The four light receiving elements 19a to 19d are arranged as shown in FIG.

The I / V amplifiers 20a to 20d convert the current signals generated by the light receiving elements 19a to 19d into light detection signals (voltage signals) Sa to Sd having signal levels corresponding to the intensities of the reflected light, respectively. It is an amplifier.

The signal processing section 23 includes adder circuits 51, 52,
53, 54, 55, 56, 57, 65 and the subtraction circuit 5
8, 59, 60 and phase compensation circuits 61, 62, 63, 6
4 and 4 are provided.

The adder circuit 51 is a circuit for adding the light detection signals Sa and Sb. The adder circuit 52 uses the light detection signal S
This is a circuit for adding b and Sc. The adder circuit 53 is a circuit that adds the light detection signals Sc and Sd. The adder circuit 54 is a circuit that adds the light detection signals Sa and Sc. The adder circuit 55 is a circuit that adds the light detection signals Sb and Sd. The adder circuit 56 detects the light detection signals Sa and Sd.
This is a circuit that adds and.

The adder circuit 57 adds the outputs (Sa + Sb) and (Sc +) output from the adder circuits 51 and 53, respectively.
Sd) and a circuit for adding. The subtraction circuit 58 outputs the addition output (Sa + Sc) output from the addition circuit 54 and the addition output (Sb + Sd) output from the addition circuit 55.
Is calculated.

The subtraction circuit 59 calculates the difference between the addition output (Sa + Sd) output from the addition circuit 56 and the addition output (Sb + Sc) output from the addition circuit 52. The subtraction circuit 60 calculates the difference between the addition output (Sa + Sb) output from the addition circuit 51 and the addition output (Sc + Sd) output from the addition circuit 53.

The phase compensating circuit 61 is connected to the adding circuit 57, performs phase compensation of its output signal, and outputs an RF signal. The phase compensation circuit 62 is connected to the subtraction circuit 58, performs phase compensation of its output signal, and outputs an FE signal.

The phase compensation circuit 63 is connected to the subtraction circuit 59, performs phase compensation on the output signal thereof, and outputs an RSE (radial tilt error) signal. Phase compensation circuit 6
Reference numeral 4 is connected to the subtraction circuit 60, performs phase compensation of its output signal, and outputs a TSE (Tangential Tilt Error) signal. The adder circuit 65 includes the phase compensation circuit 6
The RSE signal and the TSE signal respectively output from 3 and 64 are added, and the TLE signal as the sum of the inclination detection signals is output.

Next, the operation of the optical disk device according to the first embodiment will be described. The spindle motor 2 rotates the optical disc 1. The control unit 21 uses the optical pickup 11
To the target position.

The attitude control unit 24 causes the optical pickup 11 to follow the pit train indicating the recording data by performing tracking control. The driver 22 supplies the laser diode 12 with a current necessary for emitting laser light,
The laser diode 12 emits light when this current flows.

The light beam output from the laser diode 12 passes through the collimator lens 13 and becomes parallel light. The light beam passes through the polarization beam splitter 14 and the quarter-wave plate 15, is condensed by the objective lens 16, and is applied to the optical disc 1.

The light beam is reflected by the recording surface of the optical disc 1 and passes through the objective lens 16 and the quarter-wave plate 15. The polarization beam splitter 14 reflects the reflected light toward the condenser lens 18. The reflected light is reflected by the polarization beam splitter 14
Then, it is branched from the light beam from the laser diode 12 and reaches the photodetector 19 via the condenser lens 18.

The light receiving element 19 of the photo detector 19
The spots SP on a to 19d have aberrations due to the condenser lens 18. Each of the light receiving elements 19a to 19d is
The reflected light is received and a current according to the intensity of the reflected light is generated.
The light detection signals Sa to Sd are converted into Sd and are supplied to the signal processing unit 23.

The signal processing section 23 generates an RF signal, an FE signal, and a TLE signal based on the supplied photodetection signals Sa to Sd. First, the adder circuits 51, 53, and 57 add the photodetection signals Sa to Sd according to the following formula 1 to calculate the added value S1.

## EQU1 ## S1 = Sa + Sb + Sc + Sd

The phase compensation circuit 61 performs phase compensation of the added value S1 calculated by the addition circuit 57. Then, the signal processing unit 23 outputs the phase-compensated signal. This signal is RF
Become a signal. This RF signal is a signal based on the recording data recorded on the optical disc 1.

An example of this RF signal is shown in FIG. As shown in FIG. 4, if the record data recorded on the optical disc 1 is 1, 0, 0, 1, ...
An RF signal is output. By waveform-shaping this RF signal, the recorded data recorded on the optical disc 1 is reproduced.

The addition circuits 54 and 55 and the subtraction circuit 58 are
Photodetection signals Sa to Sd are added / subtracted according to the following formula 2,
The value S2 is calculated.

## EQU00002 ## S2 = (Sa + Sc)-(Sb + Sd) The phase compensation circuit 62 performs phase compensation of the value S2 calculated by the subtraction circuit 58. Then, the signal processing unit 23 outputs the phase-compensated signal. This signal is the FE signal.

As described above, since the condenser lens 18 gives astigmatism, the light receiving elements 19a to 19d are provided.
The spot SP above has an aberration. When the recording surface of the optical disc 1 is in focus, the signal level of the FE signal becomes the smallest.

The adding circuits 52 and 56 and the subtracting circuit 59 are
Photodetection signals Sa to Sd are added / subtracted according to the following formula 3,
The value S3 is calculated.

## EQU3 ## S3 = (Sa + Sd)-(Sb + Sc) The phase compensation circuit 63 performs phase compensation of the value S3 calculated by the subtraction circuit 59. Then, the signal processing unit 23 outputs the phase-compensated signal. This signal becomes the RSE signal.

The adding circuits 51 and 53 and the subtracting circuit 60 are
The light detection signals Sa to Sd are added and subtracted according to the following formula 4,
The value S4 is calculated.

## EQU00004 ## S4 = (Sa + Sb)-(Sc + Sd) The phase compensation circuit 64 performs phase compensation of the value S4 calculated by the subtraction circuit 60. Then, the signal processing unit 23 outputs the phase-compensated signal. This signal becomes the TSE signal.

The adder circuit 65 adds the RSE signal output from the phase compensation circuit 63 and the TSE signal output from the phase compensation circuit 64. This added signal is TLE
Become a signal. If the optical axis of the light beam coincides with the normal line on the recording surface of the optical disc 1, the RSE signal, the TSE signal,
The signal level of the TLE signal is the smallest.

The signal processor 23 generates the generated RF signal, F
The E signal, the RSE signal, the TLE signal, and the TSE signal are supplied to the attitude control unit 24. The attitude control unit 24 controls the actuator 17 based on these supplied signals.

When performing tilt control, the attitude control unit 24
Turns the tilt servo on or off according to the flowchart shown in FIG. The attitude control unit 24 takes in an RF signal (step S11). The attitude control unit 24 compares the signal level S _RF of the fetched RF signal with a preset threshold S _th1 (step S12).

The attitude control unit 24 compares the signal level S _RF of the RF signal with the threshold value S _th1 . As a result, if the signal level S _RF of the RF signal is less than the threshold value S _th1 , the objective lens 16
Is determined to be away from the recording surface of the optical disc 1 and the tilt servo is turned off (step S13). If the threshold S _th1 or more, it is determined that the objective lens 16 is approaching the recording surface of the optical disc 1 and the tilt servo is turned on. It is turned on (step S14).

Here, the tilt servo is turned on in this way,
The reason for turning off will be described. The control unit 21 turns on the focus servo, moves the objective lens 16 up and down, and detects the in-focus point with the optical disc 1. In the case of the actuator 17 having the tilt mechanism, since the optical disc device is configured to tilt the objective lens 16 in the tilt direction, when the focus servo is turned off, the objective lens 1
6 is displaced from the initial position, that is, the position where the TLE signal can be detected to some extent. That is, the inclination of the objective lens 16 is determined by the mechanical mounting position of the actuator 17.

Therefore, the tilt servo is turned on after the tilt error signal can be detected to some extent.

When the tilt servo is turned on, the attitude control section 24 supplies a current to the tilt coils 33 and 34. The amount of current supplied is determined based on the RSE signal and the TSE signal. When a current is supplied to the tilt coils 33 and 34, an electromagnetic force acts between the tilt coils 33 and 34 and the magnet 35, and the tilt of the optical axis of the objective lens 16 is adjusted.

Next, an example of the operation of the attitude control section 24 is shown in FIG. The signal level of the RF signal is less than the judgment value + S _th1 until time t11 after the focus servo is turned on. In this case, the attitude control unit 24 determines that the reflected light has not reached the level for performing tilt servo, and turns off the tilt servo.

From time t11 to t12, the signal level of the RF signal becomes the judgment value + S _th1 or more. In this case, the posture control unit 24 determines that the reflected light has reached the level for performing tilt servo, and turns on the tilt servo.

After time t12, the signal level of the RF signal again becomes less than the judgment value + S _th1. Therefore, the attitude control unit 24
Turns off the tilt servo.

As described above, according to this embodiment, it is determined whether the objective lens 16 is approaching the optical disc 1 based on the signal level of the RF signal, and the tilt coils 33 and 34 are energized. Until the tilt control is performed, the positioning of the objective lens 16 is performed with the mechanical accuracy of the actuator 17, and the tilt control is performed when the objective lens 16 approaches the optical disc 1, so that the stable tilt control is performed. be able to. Then, the focus control can be performed in a state in which the optimum tilt control is performed, and the pull-in operation is also favorable.

Various modes are conceivable for carrying out the present invention, and the present invention is not limited to the above-described modes. For example, the actuator 17 is the above-mentioned Japanese Patent Application No. 2001.
The moving magnet type (MM type) disclosed in -057222 may be used.

In the optical pickup 11, two photodetectors, one for attitude control and one for reproduction, may be used, and the reflected light from the optical disk 1 may be separated by a half mirror. The optical pickup 11 does not have to have an actuator with a tilt mechanism.

Further, the optical disc is constructed as long as the light emitted from the laser diode is applied to the recording surface of the optical disc through the objective lens and the photodetector receives the reflected light through the objective lens. It is not limited to the embodiment.

Next, an optical disk device according to the second embodiment will be described. This is one in which the tilt servo is turned on and off based on the signal level of the FE signal output while the focus servo is on.

The posture control unit 24 stores in advance the judgment values + S _th2 and -S _th2 for judging the signal level of the FE signal.

Next, the attitude control unit 2 according to the second embodiment.
The operation of No. 4 will be described with reference to the flowchart of FIG.

The attitude control unit 24 takes in the FE signal (step S21). The attitude control unit 24 determines whether or not the focus servo is turned on (step S
22).

When the attitude control section 24 determines that the focus servo is on, it then determines whether or not the signal level of the FE signal is within a predetermined range (step S).
23).

When the attitude control section 24 determines that the signal level of the FE signal is within the predetermined range, the objective lens 1
When it is determined that 6 is approaching the recording surface of the optical disc 1, the tilt servo is turned on (step S24).

On the other hand, when the attitude control unit 24 determines that the focus servo is off, or when the signal level of the FE signal is not within the predetermined range, the objective lens 16 moves from the recording surface of the optical disc 1. The tilt servo is turned off when it is determined to be away (step S2).
5).

Next, an example of the operation of the attitude control section 24 is shown in FIG. In this example, it is assumed that the focus servo is turned on from time t21 to time t26, and before and after that, the focus servo is turned off. In addition, the time at which the signal level of the FE signal becomes maximum (from time t22 to time t
23) and the minimum time (from time t24 to time t)
Up to 25) is the focus pull-in range.

Since the focus servo is off until time t21, the attitude control unit 24 turns off the tilt servo, judging that the intensity of the reflected light has not reached a level at which the tilt servo can be performed.

At time t21, the focus servo is turned on. When the focus servo is turned on, the attitude control unit 2
Reference numeral 4 supplies a current to the focus coil 31 of the actuator 17. When a current is supplied to the focus coil 31, the focus coil 31 moves the focal position of the light beam by adjusting the distance between the optical disk 1 and the actuator 17 by the electromagnetic force that works when energized.

At time t21, the signal level of the FE signal is within the range of threshold _values + S _th2 to -S _th2 . The thresholds + S _th2 and −S _th2 are determination values for determining whether or not the signal level of the FE signal is a level at which tilt control can be performed, and the attitude control unit 24 determines the threshold + S _th2 .
S _th2 and −S _th2 are stored in advance.

The signal level of the FE signal is the threshold value + S _th2 ~-
If it is within the range of S _th2 , the posture control unit 24
It is determined that the signal level of the E signal is at a level at which tilt control can be performed, and the tilt servo is turned on.

From time t22 to t23, the signal level of the FE signal is outside the range of the judgment value + S _th2 to -S _th2 . In this case, the attitude control unit 24 turns off the tilt servo.

From time t23 to t24, the signal level of the FE signal is again within the range of the judgment value + S _th2 to -S _th2 .
The attitude control unit 24 turns on the tilt servo. Similarly, the attitude control unit 24 controls the times t24 to t25 and the times t25 to t.
At 26, the tilt servo is turned off and on, respectively, and after time t26, the tilt servo is turned off.

If the tilt servo is kept on before the focus search is turned on, the TLE signal becomes indefinite and the objective lens 16 is not oriented in the correct direction. Therefore, the attitude control unit 24
The tilt control is performed while the focus search is on, and the tilt control is completed before the focus search is turned off.

As described above, according to the present embodiment, the tilt servo is turned on based on the signal level of the FE signal output when the focus servo is turned on,
Since it is turned off, as in the first embodiment,
The tilt control is performed with the objective lens 16 approaching the optical disc 1, stable tilt control can be performed, and optimal pull-in operation can be performed also in focus control.

Further, since the tilt control is completed before the focus servo is turned off, the tilt control is quickly performed and the response speed of the attitude control is increased. It is also possible to determine whether or not the focus servo is on after determining whether or not the signal level of the FE signal is within a predetermined range. It is not limited to the embodiment. Further, the RF signal and the FE are combined by combining the first embodiment and the second embodiment.
Tilt control can also be performed using the signal and.

Next, a third embodiment will be described. This is one in which the tilt servo is turned on and off based on the signal level of the TLE signal.
The attitude control unit 24 stores in advance a judgment value S _th3 for judging the signal level of the TLE signal.

The operation of the attitude control unit 24 according to the third embodiment will be described with reference to the flowchart of FIG.

The attitude control unit 24 takes in the TLE signal (step S31). The attitude control unit 24 compares the signal level of the TLE signal with a predetermined determination value S _th3 and determines whether the signal level of the TLE signal is equal to or higher than this determination value S _th3 (step S32).

The attitude control section 24 compares the signal level of the TLE signal with a predetermined judgment value S _th3, and when it judges that the signal level of the TLE signal is equal to or higher than this judgment value S _th3 , the objective lens 16 causes the optical disk to move. It is determined that the recording surface 1 is approaching, and the tilt servo is turned on (step S3
3) If it is determined that the signal level of the TLE signal is less than the determination value S _th3, it is determined that the objective lens 16 is far from the recording surface of the optical disc 1 and the tilt servo is turned off (step S34).

As described above, according to the present embodiment, the tilt servo is turned on / off based on the signal level of the TLE signal. Therefore, the tilt servo of the first and second embodiments is different from that of the first and second embodiments. Similarly, the tilt control is performed by the objective lens 1.
6 is performed in a state of approaching the optical disc 1, stable tilt control can be performed, and optimum pull-in operation can be performed also in focus control.

[0095]

As described above, according to the present invention,
Tilt control can be performed stably.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing the structure of the actuator of FIG.

FIG. 3 is a diagram showing a configuration of a photo detector and a signal processing unit of FIG.

FIG. 4 is a diagram showing an operation in which the signal processing unit of FIG. 1 generates an RF signal.

FIG. 5 is a flowchart showing an operation of the attitude control unit according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an operation of the posture control section according to the first embodiment of the present invention.

FIG. 7 is a flowchart showing an operation of the attitude control unit according to the second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing an operation of an attitude control unit according to the second embodiment.

FIG. 9 is a flowchart showing an operation of the attitude control unit according to the third embodiment of the present invention.

[Explanation of symbols]

1 optical disc 11 Optical pickup 16 Objective lens 17 Actuator 19 Photo detector 19a to 19d Light receiving element 23 Signal processing unit 24 Posture control unit

Claims (7)

[Claims] 1. An optical disk device for reproducing or recording data while irradiating a light beam on an optical disk using an objective lens to perform tilt control, wherein the light receiving device receives reflected light of the light irradiated on the optical disk. Means for determining whether or not the objective lens is approaching the optical disc based on a signal level of a signal generated based on the reflected light received by the light receiving device; and the objective lens for the optical disc. Tilt control means for performing tilt control when the determination means determines that the tilt angle is approaching, and tilt control means for stopping the tilt control when the determination means determines that the objective lens is away from the optical disc.
An optical disk device comprising: 2. A signal processing means for generating at least one of a reproduction signal, a focus error signal, and a tilt error signal in the radial direction and the tangential direction based on the reflected light received by the light receiving means. The optical disk device according to claim 1, wherein: 3. The signal processing means generates a reproduction signal based on the reflected light received by the light receiving means, and the judging means presets the signal level of the reproduction signal generated by the signal processing means. 3. When the signal level of the reproduction signal is equal to or higher than the determination value as compared with the determination value, it is determined that the objective lens is approaching the optical disc. Optical disk device. 4. The signal processing means generates a focus error signal based on the reflected light received by the light receiving means, and the judging means presets the signal level of the focus error signal generated by the signal processing means. It is determined that the objective lens is approaching the optical disc if the signal level of the focus error signal is equal to or higher than the determination value as compared with the determined determination value. The optical disk device described. 5. The signal processing means generates tilt error signals in the radial direction and the tangential direction based on the reflected light received by the light receiving means, and further adds both tilt error signals to add the two tilt error signals. Generating a signal, the determining means compares the signal level of the sum signal generated by the signal processing means with a preset determination value, and if the signal level of the sum signal is equal to or higher than the determination value, The optical disc device according to claim 2, wherein the objective lens determines that the objective lens is approaching the optical disc. 6. The light receiving means comprises photoelectric conversion means for receiving reflected light of a light beam applied to the optical disk and photoelectrically converting the received reflected light into an electric signal. The optical disk device according to claim 1. 7. A step of receiving reflected light of a light beam, and a step of determining whether or not an objective lens is approaching an optical disk based on a signal level of a signal generated based on the received reflected light, Tilt control is performed when it is determined that the objective lens is approaching the optical disc, and tilt control is stopped when the objective lens is determined to be away from the optical disc.
A tilt control method for an optical disk device, comprising: