JPH11185261A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variations in detecting sensibilities for every device and fluctuations of detecting sensibilities due to operationg environments and the secular change of the characteristic of a detecting element by detecting the position of an objective lens as two signals having the phase difference of 90 deg.C and arithmetically processing two signals and making the processed result the position detection signal of the objective lens. SOLUTION: A light emitting element 90, photodetectors 91a, 91b and a fixed slit 93 are provided on a base 80 and a movable slit 92 is provided on a lens holder 20. Opening parts 92a whose width are P/2 are provided in the movable slit 92 with an interval P and opening parts 93a, 93b whose widths are P/2 are provided by being shifted by P/2 in the moving dirtection of the movable slit 92. When the moving amount of the slit 92 is defined as (x), output signals S1, S2 of the photodetectors 91a, 91b respectively become S1=A sin(2πx/ P), S2=A cos(2πx/P). Here, signals which are not depended on an amplitude A are obtained by detecing the moving amount of the objective lens, based on S1/S2 and S1/(S1<1> +S2<2> )<1/2> .

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 optically recording or reproducing information on or from an optical recording medium.
In particular, the present invention relates to an optical disk device suitable for performing high-speed seek.

[0002]

2. Description of the Related Art An optical disk device that performs high-speed seek moves at a high speed in an optical disk radial direction (tracking direction).
By performing an access operation, a seek operation for track detection is performed.

In such an optical disk device, the moving speed of an optical pickup is detected based on a track cross signal. However, when performing a high-speed seek operation, the tracking servo is turned off and the object moves at a high speed, so that a vibration in the tracking direction occurs in the objective lens. Due to the occurrence of this vibration, the detection of the moving speed of the optical pickup becomes inaccurate, and the tracking servo becomes unstable even if the tracking servo is turned on again after the objective lens has reached the vicinity of the track to which the optical pickup has moved. was there.

As a countermeasure for such a problem, there has been proposed a method of detecting a moving amount of an objective lens in a tracking direction and performing servo control. For example, Japanese Patent Application Laid-Open No. 2-281431
According to the technique described in Japanese Patent Application Laid-Open Publication No. H11-207, in order to detect the position of the objective lens in the tracking direction, the light emitting diode 1 and the photodiode 2 are arranged opposite to each other as shown in FIG.
The slit plate 3 and the light shielding plate 4 are arranged between them.

In this position detection method, the light emitting diode 1
Is output by the photodiode 2 via the slit plate 3, and at this time, a part of the light output from the light emitting diode 1 is blocked by the light shielding plate 4 that moves together with the objective lens holder 5.

[0006]

However, in the above-mentioned method, the distance between the light emitting diode 1 and the photodiode 2 is reduced.
Differences in the amount of light received by the photodiode 2 occur due to variations in the characteristics of the light emitting diode 1, the drive power supply of the light emitting diode 1, and the like. Was difficult. In addition, since the amount of light output from the light emitting diode 1 also changes due to changes in the operating environment and the characteristics of the light emitting diode 1 over time, it is difficult to keep the amount of light received by the photodiode 2 constant. Was.

In Japanese Patent Application Laid-Open No. 2-281431,
By taking the difference between the output signals of the photodiodes that change in opposite phase, the disturbance common-mode frequency component is removed.
The amount of light received by the photodiode cannot be made uniform or constant.

In the present invention, two output signals that change at a phase difference of 90 ° in accordance with the amount of movement of the objective lens are processed by an arithmetic circuit, and the amount of movement of the objective lens is detected based on the processed signal. This provides an optical disk device that achieves uniform and constant detection sensitivity of the movement amount.

[0009]

According to a first aspect of the present invention, there is provided an optical disk apparatus for optically recording or reproducing data on or from an optical recording medium, comprising position detecting means for detecting the position of an objective lens. The position detecting means outputs two signals having a phase difference of 90 °, and has an arithmetic circuit that performs an arithmetic process on the two signals to obtain a position detection signal of the objective lens. By using it, the sensitivity for detecting the position of the objective lens is made uniform or constant.

[0010] Here, the term "uniform" refers to suppressing variations in the detection sensitivity of each apparatus, and the term "constant" refers to suppressing variations in the detection sensitivity due to changes over time in the operating environment and the characteristics of the detection elements.

According to a second aspect of the present invention, in the optical disk device of the first aspect, the position detecting means is an optical detecting means including a light emitting element and a light receiving element.

According to a third aspect of the present invention, in the optical disk device of the first aspect, the position detecting means is a magnetic detecting means including a permanent magnet and a magnetic detecting element. .

According to a fourth aspect of the present invention, in the optical disk device of the first aspect, the two signals S
1, wherein the arithmetic processing for S2 is S1 / S2.

According to a fifth aspect of the present invention, in the optical disk device of the first aspect, the two signals S
1, wherein the arithmetic processing for S2 is S1 / (S1 ² + S2 ² ) ^1/2 .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In an optical disk drive according to the present invention, an arithmetic circuit processes two output signals which change with a phase difference of 90.degree. In accordance with the amount of movement of an objective lens. By detecting the amount of movement of
The detection sensitivity of the movement amount is made uniform and constant.

Here, assuming that the amplitude of the two output signals changing with a phase difference of 90 ° is A, the two output signals S1 and S2
Is given by the following equation: Here, α is a variable that changes according to the amount of movement of the objective lens.

S1 = Asin α (1) S2 = Asin (π / 2−α) = Acos α (2) In the above equation 1, near the output signal S1 = 0 (α = 0) Since the movement amount (displacement) of the objective lens and the level (voltage value) of the output signal S1 have a substantially proportional relationship, the output signal S
1 allows the position of the objective lens (movable part) to be detected. However, when the value of the amplitude A changes, the output level of the output signal S1 changes, so that the detection sensitivity (change rate of the output signal with respect to the movement amount (displacement)) also changes.

On the other hand, in the present invention, the output signals S1,
S2 is subjected to arithmetic processing to obtain a signal independent of the amplitude A, and the amount of movement of the objective lens is detected based on the signal. Therefore, even if the value of the amplitude A changes, the detection sensitivity (the amount of movement No change occurs in (change rate of the processed signal) with respect to (displacement).

For example, the movement amount of the objective lens may be detected based on S1 / S2.

S1 / S2 = tanα (3) The movement amount of the objective lens may be detected based on S1 / (S1 ² + S2 ² ) ^1/2 .

S1 / (S1 ² + S2 ² ) ^1/2 = A sin α / A (sin ² α + cos ² α) ^1/2 = sin α (4) That is, the amplitude A An independent signal can be obtained, and in the vicinity of α = 0, tan α ≒ α sin α ≒ α, and an output signal proportional to the amount of movement of the objective lens can be obtained. Further, the proportional constant can be kept constant without being affected by a change in the value of the amplitude A.

Next, a specific configuration of the present invention will be described in detail with reference to the drawings.

[First Configuration] FIG. 1 is a perspective view showing a peripheral portion of an objective lens driving device of an optical disk device according to the present invention.

The movable part of this objective lens driving device is constituted by a lens holder 20 having an objective lens 10, a focusing coil 30 and a tracking coil 40. Further, the fixing portion is composed of a base 80 having a supporting base 81 for fixing the permanent magnet 50 and the elastic member 70 and a base substrate 82.
0 is folded up. Further, the movable part is supported by four elastic members 70 from a fixed part.

The focusing coil 30 and the tracking coil 40 provided on the movable portion are arranged in a magnetic gap of a magnetic circuit composed of a permanent magnet 50 and a yoke 60 provided on the fixed portion. , A driving force in the focusing direction or the tracking direction is obtained. The driving force and the support force from the elastic member 70 are applied to the movable portion, and position control for moving the objective lens 10 in the focusing direction or the tracking direction is performed by balancing the two.

In this optical disk device, the light emitting element 90 and the light receiving elements 91a and 91b are arranged to face each other via the movable slit 92 and the fixed slit 93. Here, the light emitting element 90, the light receiving elements 91a and 91b, and the fixed slit 9
3 is installed on the base 80, and the movable slit 92 is installed on the lens holder 20. Therefore, the light emitting element 90
The movable slit 92 disposed between the lens holder 20 and the light receiving elements 91a and 91b moves according to the amount of movement of the lens holder 20.

As shown in FIG. 2, the movable slit 92 is provided with an opening 92a having an interval P and a width P / 2. The fixed slit 93 has an opening 93 having a width P / 2.
a and the opening 93 b move in the direction of movement of the movable slit 92.
/ 2 offset.

Here, the opening 92a of the movable slit 92
The light passing through the opening 93a of the fixed slit 93 is received by the light receiving element 91a, and the light is transmitted through the opening 9a of the movable slit 92.
The light passing through 2a and the opening 93b of the fixed slit 93 is received by the light receiving element 91b.

Accordingly, the amount of light received by the light receiving element 91a is maximum when the opening 92a of the movable slit 92 and the opening 93a of the fixed slit 93 overlap, and the amount of light received decreases as the position deviates therefrom. I do. Further, since the openings 92a of the movable slit 92 are provided at intervals P, when the movable slit 92 is moved in a fixed direction, the amount of light received by the light receiving element 91a increases and decreases at a fixed cycle. repeat.

On the other hand, the amount of light received by the light receiving element 91b is maximum when the opening 92a of the movable slit 92 and the opening 93b of the fixed slit 93 overlap with each other.
The amount of received light decreases as the position deviates therefrom. Further, since the opening 93a and the opening 93b are provided shifted by P / 4 in the moving direction of the movable slit 92, the light receiving element 91b
The cycle of increasing or decreasing the amount of received light is shifted by 1/4 cycle from the cycle of increasing or decreasing the amount of received light of the light receiving element 91a.

The output signal S1 of the light receiving element 91a and the output signal S2 of the light receiving element 91b are given by the following equations, where x is the amount of movement of the movable slit 92.

S1 = Asin (2πx / P) (5) S2 = Acos (2πx / P) (6) where S1 / S2 and S1 / (S1 ² + S2 ² ) ^1/2 If the amount of movement of the objective lens is detected based on the signal, a signal independent of the amplitude A can be obtained. In the vicinity of x = 0,
An output signal proportional to the amount of movement of the objective lens can be obtained, and the proportional constant can be kept constant without being affected by the change in the value of the amplitude A.

[Second Configuration] Next, a multi-pole magnetized permanent magnet is mounted on a lens holder (movable part) that moves together with the objective lens, and an MR is mounted on a fixed part opposite to the permanent magnet.
An example in which a magnetic detection sensor such as a sensor (magnetoresistive sensor) is attached and the position of the objective lens is detected magnetically will be described.

FIG. 3 is a perspective view showing a peripheral portion of the objective lens driving device of the optical disk device according to the present invention.

The structure of the fixed part and the movable part of the objective lens driving device is the same as that of the first structure.
Position detecting permanent magnet 1 provided on lens holder 20
01 and the MR sensor 100 provided on the base 80 are opposed to each other. Here, the position detecting permanent magnet 101 is a multi-pole magnetized magnet, and the MR sensor 100 is a sensor constituted by a magnetoresistive element whose resistance value changes according to the strength of the magnetic field.

In the above configuration, the position detecting permanent magnet 1
01 moves in the tracking direction, the magnetic field acting on the magnetoresistive element constituting the MR sensor 100 changes. Therefore, the amount of movement (displacement) of the movable part is regarded as a change in the resistance value. Can be detected.

FIG. 4 shows the position detecting permanent magnet 101 and the MR.
The relative relationship of the sensor 100 is schematically shown. Here, the magneto-resistive elements RA, R constituting the MR sensor 100
B is a magnetization pitch P / P of the position detecting permanent magnet 101 at a position where the magnetic field of the position detecting permanent magnet 101 can be sensed.
2 are arranged at substantially the same interval. + Vcc and -Vc
The absolute values of c are adjusted to be equal.

The magnetic resistances of the magnetoresistive elements RA and RB are set so that the resistance value increases when the N pole is sensed. In this case, the resistance of the magnetoresistive elements RA and RB increases when the N pole is sensed, and decreases when the S pole is sensed.

The magneto-resistance elements RA and RB are arranged at an interval P /
2, when the resistance value of the magnetoresistive element RA is maximized, the resistance value of the magnetoresistive element RB is minimized, and when the resistance value of the magnetoresistive element RA is minimized, The resistance value of the magnetoresistive element RB becomes maximum.

In this configuration, the position detecting permanent magnet 101 is used.
Are moved in a certain direction, the magnetoresistive elements RA, R
The divided voltage value V1 of B repeatedly increases and decreases at a constant cycle.

On the other hand, the magnetoresistive elements RC and RD are also arranged at an interval of P / 2 similarly to the magnetoresistive elements RA and RB, and a magnetic bias is applied so that the resistance value increases when the N pole is sensed. It was set. Regarding the relative positional relationship between the magnetoresistive elements RC and RD and the magnetoresistive elements RA and RB, the magnetoresistive elements RC and RD correspond to the magnetoresistive elements RA and RB.
Are shifted from each other by an interval P / 4.

Accordingly, when the position detecting permanent magnet 101 is moved in a fixed direction, the divided voltage value V1 of the magnetoresistive elements RA and RB and the divided voltage value V1 of the magnetoresistive elements RC and RD.
The increase / decrease cycle of 2 is shifted by 1/4 cycle.

In the above-mentioned position detecting section, if the moving amount of the position detecting permanent magnet 101 is x and the resistances of the magneto-resistive elements RA and RB are set to be equal when the objective lens is at the reference position ( If the divided voltage value V1 is set to be 0 V), the divided voltage value V1 of the magnetoresistive elements RA and RB and the divided voltage value V2 of the magnetoresistive elements RC and RD become
As a function of the moving amount x of the position detecting permanent magnet 101, it is given by the following equation.

V1 = Asin (2πx / P) (7) V2 = Acos (2πx / P) (8) Here, S1 / S2 and S1 / (S1 ² + S2 ² ) ^1/2 If the amount of movement of the objective lens is detected based on the signal, a signal independent of the amplitude A can be obtained. In the vicinity of x = 0,
An output signal proportional to the amount of movement of the objective lens can be obtained, and the proportional constant can be kept constant without being affected by a change in the value of the amplitude A.

Incidentally, other magnetic detecting means such as a Hall sensor may be used instead of the MR sensor.

[0046]

As described above, in the optical disk apparatus according to the present invention, the number of movements of the objective lens depends on the amount of movement of the objective lens.
An arithmetic circuit processes two output signals that change with a phase difference of 0 °, and detects the amount of movement of the objective lens based on the processed signal, thereby making the detection sensitivity of the amount of movement uniform and constant. Can be.

Therefore, even when the installation position of the detection element, the characteristics of the detection element, the operating power supply, and the like vary, the detection sensitivity hardly varies. Further, the detection sensitivity hardly changes due to the change over time in the operating environment and the characteristics of the detection element.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration example of an optical disc device according to the present invention (first configuration).

FIG. 2 is a drawing showing a movable slit according to the optical disc device of the first configuration.

FIG. 3 is a perspective view showing a configuration example of an optical disc device according to the present invention (second configuration).

FIG. 4 is a schematic diagram showing a relative relationship between a position detecting permanent magnet and an MR sensor according to the optical disc device of the first configuration.

FIG. 5 is a perspective view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Objective lens 20 Lens holder 30 Focusing coil 40 Tracking coil 50 Permanent magnet 60 Yoke 70 Elastic member 80 Base 81 Supporting base 82 Base substrate 90 Light emitting element 91a, 91b Light receiving element 92 Movable slit 92a Opening (opening of movable slit) 93 Fixed slits 93a, 93b Openings (openings of fixed slits) 100 MR sensor 101 Position detecting permanent magnet

Claims (5)

[Claims] 1. An optical disk device for optically recording or reproducing data on or from an optical recording medium, comprising: a position detecting means for detecting a position of an objective lens;
A signal processing circuit that outputs two signals having a phase difference of 、, performs an arithmetic operation on the two signals, and uses the signal as a position detection signal for the objective lens, and determines the position of the objective lens by using the position detection signal. An optical disk device that makes the detection sensitivity uniform or constant. 2. An optical disk device according to claim 1, wherein said position detecting means is an optical detecting means comprising a light emitting element and a light receiving element. 3. The optical disk device according to claim 1, wherein said position detecting means is a magnetic detecting means comprising a permanent magnet and a magnetic detecting element. 4. The optical disk device according to claim 1, wherein the arithmetic processing on the two signals S1 and S2 is S1 / S2. 5. The optical disk device according to claim 1, wherein the arithmetic processing on the two signals S1 and S2 is S1 / (S1 ² + S2 ² ) ^1/2 .