JP2001202643A - Objective lens drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens position detection mechanism in which the linearity of a characteristic curve of an objective lens position detection signal to the objective lens position of the tracking direction can be taken widely and mounting adjustment is eliminated. SOLUTION: The objective lens drive device is equipped with a movable member 3 for carrying an objective lens 2, a track holder 8 for supporting the movable member 3 through focal springs 13a and 13b, a base strut 9 combined with the track holder 8 through a track spring 11 between the movable member 3 and the track holder 8, track coils 10a and 10b and magnets 7a and 7b generating electromagnetic force for driving at least the movable member 3 in the tracking direction, a reflecting plate 12 mounted on the surface of the opposite side to the movable member 3 of the track holder 8, a tilt sensor 4 disposed so as to face at a prescribed interval on the reflecting plate 12 and outputting a signal according to the tilt of the reflecting plate 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object for focusing a light beam on an optical disk and moving the light beam in order to record and / or reproduce information in an optical information recording / reproducing apparatus. Regarding the lens driving device, in particular,
The present invention relates to a position detecting mechanism of a movable objective lens.

[0002]

2. Description of the Related Art An optical head for reading / writing information from / on an optical disk is required to have high-speed access.
However, when the optical head is accessed at a high speed, a large acceleration is applied to the optical head. Therefore, even if the optical head is suddenly stopped after high-speed access, the objective lens supported via a damper in the optical head is vibrated, and there is a problem that stable tracking cannot be quickly performed. Therefore, conventionally, the objective lens driving unit detects the position of the objective lens in the tracking direction, and based on the detection signal, performs control to suppress the objective lens swinging movement due to rapid head stop ( For example, JP-A-1-
No. 211244).

FIG. 5 is a view of an objective lens driving device including an objective lens position detecting mechanism in Japanese Patent Application Laid-Open No. 1-211244 viewed from a plane parallel to an optical disk (not shown), and FIG. 6 is a schematic diagram of the objective lens driving device. It is a sectional view.

In these figures, a substrate 54 is a magnetic substrate, and a shaft 55 is set up on the substrate 54. Axis 5
A lens holder 51 is mounted on the lens 5 so as to be movable in the axial direction of the shaft 55 (focusing direction; X direction in the figure) and rotatable about the shaft 55 (tracking direction; θ direction in the figure). . The lens holder 51 includes a substantially cylindrical lower lens holder 51a, and a plate-shaped upper lens holder 51b attached to the top surface of the lower lens holder 51a and provided with an objective lens 52. Objective lens 52
Is for converging a laser beam on an optical disk (not shown). The lens holder 51 has one end supported by a projection 54 a provided on the substrate 54 via a damper 66.

A focusing coil 53 is wound around a side surface of the lower lens holder 51a. The focusing coil 53 is provided with four tracking coils (not shown) wound around a direction parallel to the substrate 54. The first through hole 5 is provided in the lower lens holder 51a.
1c and a second through-hole 51d are formed. The first through-hole 51c and the second through-hole 51d have a first inner yoke 56 and a second inner yoke 57 provided on the substrate 54, respectively. Are inserted respectively. A first magnet 58 having a horizontal magnetization direction is provided on the substrate 54 via the lens holder 51.
Similarly, a second magnet 59 having a horizontal magnetization direction is provided so as to face the second inner yoke 57 via the lens holder 51. A first outer yoke 60 is provided on a side of the first magnet 58 opposite to the lens holder 51, and a second outer yoke 61 is provided on a side of the second magnet 59 opposite to the lens holder 51.

The damper 66 of the upper lens holder 51b
A reflection plate 51e protruding in the direction of the substrate 54 is provided at an end opposite to the above. A reflection plate 51 is provided on the substrate 54.
Object lens position detecting means 67 facing e is provided. The objective lens position detecting means 67 includes the objective lens 52
The light-emitting element 68 emits the position detection light beam toward the reflector 51e, and the two light-receiving elements 69 and 70 receive the light beam reflected by the reflector 51e.

In the above configuration, when an electric current is applied to the focusing coil 53, an electromagnetic force acts on the focusing coil 53, and the lens holder 51 moves in the X direction in FIG. 6 to perform focusing. When a current is applied to a tracking coil (not shown), an electromagnetic force acts on the tracking coil, and the lens holder 51 moves in the θ direction in FIG. 5 to perform tracking. When the current flowing through both coils is turned off, the lens holder 51 returns to the neutral point due to the elasticity of the damper 66.

When the lens holder 51 is at the neutral point, the light beam emitted from the light emitting element 68 of the objective lens position detecting means 67 is reflected by the reflecting plate 51e, and is uniformly transmitted to the light receiving elements 69 and 70. Incident. However, if the lens holder 51 is slightly rotated from the neutral point, a difference occurs in the amount of light incident on the light receiving elements 69 and 70, and the light receiving element 6
A difference occurs between the voltages generated at 9, 70. Therefore, the direction of the rotation of the lens holder 51 (objective lens 52) can be detected based on the voltage difference. Based on this detection signal, the control unit of the mechanism determines the rotation of the lens holder 51. The movement is controlled to suppress the swing movement of the objective lens caused by the rapid head stop after high-speed access.

[0009]

However, Japanese Patent Laid-Open No. 1-2
In the objective lens position detection mechanism described in Japanese Patent No. 11244, a reflection type triple photoreflector in which a light emitting element is disposed at the center and light receiving elements are disposed on both sides thereof is used, so that mounting and adjustment are not easy. That is, when the supporting portion of the objective lens is at the neutral point, the mounting direction of the light emitting element and the light receiving element must also be adjusted so that the amount of reflected light from the reflecting plate equally enters each light receiving element. Was.

In addition, since the reflected light is received by the change in the amount of reflected light due to the change in the angle of the reflector, the linearity of the characteristic curve of the objective lens position detection signal corresponding to the position of the objective lens in the tracking direction is linear. Can be obtained only in a narrow range determined by the distance between the elements. In addition, since the reflection type triple photo reflector in which the light emitting element is disposed at the center and the light receiving elements are disposed on both sides thereof is not a general photo reflector, there is a problem that the cost is high.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to obtain a wide range of linearity (linearity) of a characteristic curve of an objective lens position detection signal with respect to the position of an objective lens in a tracking direction. An object of the present invention is to provide an objective lens position detecting mechanism of an objective lens driving device which is simple and does not require mounting adjustment.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an objective lens driving device for at least tracking an optical beam on an optical disk, comprising: a movable member carrying an objective lens; A support member for supporting the movable member via a first spring, and a support disposed between the movable member and the support member and coupled to the support member via a second spring substantially perpendicular to the optical disk. ,
An electromagnetic force generating means for generating at least an electromagnetic force for driving the movable member in a tracking direction which is a direction around the second spring in a plane substantially parallel to the optical disc; And a tilt sensor that is disposed so as to face the reflector at a predetermined interval and outputs a signal corresponding to the inclination of the reflector.

In the above objective lens driving device, the tilt sensor uses a light emitting diode for a light emitting portion and a two-division photodiode for a light receiving portion, and uses a differential output of the two-division photodiode as a tilt detection signal. The light emitting unit and the light receiving unit are arranged so as to be arranged in a direction parallel to the optical disk.

Further, the tilt sensor has an aspherical lens at the sensor head for converting light emitted from the light emitting diode into parallel light, and when the emitted light is at a predetermined distance from the reflector, the emitted light is It is designed so that it is reflected by the reflector and passes through the aspheric lens again to form an image on the center of the two-part photodiode.

(Operation) In the above configuration, the objective lens is pseudo-rotated in the tracking direction about the second spring, and at the same time, the reflecting plate of the support member is also relatively rotated. The amount of inclination of the reflector can be detected by the output of a tilt sensor arranged so as to face the reflector before displacement at a predetermined interval. That is, the position of the objective lens carried on the movable member can be determined from the value of the detection signal. Therefore, even if the objective lens shakes due to a sudden stop after a high-speed access, for example, the movable member is driven by the electromagnetic force generating means based on the output of the tilt sensor so as to suppress the shake, thereby achieving the objective in the tracking direction. It is possible to control the position of the lens.

Further, since the sensor head of the tilt sensor is an aspherical lens, the light emitted from the light emitting diode which is the light emitting unit becomes parallel light. When the tilt sensor is at a predetermined distance from the reflector, the emitted light is reflected by the reflector and passes through the aspheric lens again to form an image on the center of the two-part photodiode as a light receiving unit. By using the sensor designed in this way, the adjustment in the plane of the two axes perpendicular to the direction facing the reflection plate does not affect the output, so that the mounting adjustment of the tilt sensor becomes unnecessary. At the same time, the linearity of the characteristic curve of the objective lens position detection signal with respect to the position of the objective lens in the tracking direction can be widened.

Further, since the differential output of the two-segment photodiode is used as a detection signal, the offset and sensitivity of the detection signal due to fluctuations in the light emission output and light reception sensitivity of the tilt sensor due to changes in the environment of the detection mechanism. Changes can be suppressed as much as possible.

[0018]

Next, an embodiment of an objective lens position detecting mechanism attached to an objective lens driving device will be described with reference to the drawings.

FIG. 1 is a view of an objective lens driving device including an objective lens position detecting mechanism according to an embodiment of the present invention viewed from a plane parallel to an optical disk (not shown), and FIG. 2 is a schematic side view of the objective lens driving device. FIG.

In the objective lens driving device 1 shown in these figures, the objective lens 2 is carried by a movable member 3, and the movable member 3 has parallel focus springs (first springs) 13a, 13a.
b, it is coupled to a track holder 8 as a support member. There are two upper and lower focus springs 13a and 13b in parallel, and a total of four focus springs (see FIG. 2). The track holder 8 is connected to the base support 9 via a track spring (second spring) 11 located at an intermediate point between the focus springs 13a and 13b. The base support 9 is disposed between the movable member 3 and the track holder 8, and is vertically set on a substrate parallel to a recording medium (not shown) (for example, an optical disk). The track spring 8 is a plate spring perpendicular to the surface of the recording medium, and the furcus springs 13a and 13b are plate springs parallel to the surface of the recording medium.

With the above configuration, the focus spring 13
The objective lens 2 can be moved in a direction (focus direction) substantially perpendicular to the surface of the optical disk via the movable member 3 by bending the a and 13b, and the objective lens 2 is bent by bending the track spring 11. Can move through the movable member 3 in a direction (tracking direction) about the track spring 11 in a plane substantially parallel to the optical disk.

The opposed magnets 7a and 7b are disposed spatially sandwiching the movable member 3 so that parallel magnetic fields perpendicular to the focus direction and the tracking direction are formed. The track coil 10 facing the side of the movable member 3 in the parallel magnetic field
Each of a and 10b is wound around a direction substantially parallel to the optical disk, and a focus coil 14 is wound around the focus direction.

Therefore, when the power supply to the focus coil 14 is turned on, an electromagnetic force is generated in a focus direction which can be in the optical axis direction of the objective lens 2. Further, when the energization of the track coils 10a and 10b is turned on, an electromagnetic force is generated in a tracking direction which is substantially perpendicular to the optical axis direction of the objective lens 2 and centered on the track spring 11. With these electromagnetic forces, the movable member 3 carrying the objective lens 2 can be driven in two axial directions, a focus direction and a tracking direction.

The mechanism for detecting the position of the objective lens is configured as follows. The movable member 3 of the track holder 8 in which the objective lens 2 is quasi-rotatively displaced about the track spring 11 and is relatively displaced at the same time.
A reflector 12 is attached to the surface on the side opposite to the above, and the tilt sensor 4 is arranged so as to face the reflector 12 at a predetermined interval.

FIG. 3A is a perspective view of the sensor element as viewed from the upper surface of the tilt sensor 4, and FIG. 3B is an emission light when the side of the tilt sensor 4 of FIG. FIG. 3C is a perspective view showing the emitted light and the reflected light when the side surface of the tilt sensor 4 shown in FIG.

As shown in this figure, the tilt sensor 4 uses an infrared light emitting diode 15 for a light emitting portion and a two-division photodiode 16 for a light receiving portion. The tilt sensor 4 is arranged so that the light emitting unit and the light receiving unit are arranged in a direction parallel to the optical disk. Therefore, the sensor side surface viewed from the direction of arrow A in FIG. 3A corresponds to the state shown in FIG. 2, and the sensor side surface viewed from the direction of arrow B corresponds to the state shown in FIG.

Such a tilt sensor 4 has an aspheric lens 17 on the sensor head for converting the light emitted from the light emitting diode 15 into parallel light 18, and is located at a predetermined distance from the reflector 12. When the outgoing light is reflected
At the center of the photodiode 16 through the aspheric lens 17 again. Therefore, when the reflection plate 12 is tilted, the image of the reflected light is placed in a direction to move to one side of the two-divided photodiode 16, so that the output of one photodiode increases and the output of the other photodiode decreases. Become.
The arithmetic circuit 6 processes these two electric outputs into a differential signal as the objective lens position detection signal 5 (see FIG. 1).

The reason why the differential output of the two-division photodiode is used as the detection signal in this manner is that the light emission output and the light reception sensitivity of the tilt sensor 4 fluctuate due to a change in the environment of the detection mechanism, and the offset and sensitivity of the detection signal. It is to suppress the change of the as much as possible.

Further, the tilt sensor 4 need only be fixed at a predetermined interval in front of the reflection plate 12, and adjustment in a two-axis plane orthogonal to the direction facing the reflection plate 12 requires output. Since there is no effect, for example, track spring 1
It is not necessary to make an adjustment so that the extension of 1 and the center of the sensor 4 coincide with each other. At the same time, the linearity (linearity) of the characteristic curve of the objective lens position detection signal 5 with respect to the position of the objective lens 2 in the tracking direction can be widened as compared with the case of using the conventional reflection type triple photo reflector.

(Comparative Example) Next, a comparative example of this embodiment will be described. As a comparative example, a configuration in which a conventional objective lens position detection mechanism (a reflection type triple photo reflector shown in FIG. 5) is applied to the objective lens driving device having the above-described configuration will be described.

FIG. 4 is a view of an objective lens driving device including an objective lens position detecting mechanism, which is a comparative example of the present embodiment, viewed from a plane parallel to an optical disk (not shown). In this figure, the same components as those used in this embodiment are denoted by the same reference numerals.

In the comparative example, in the objective lens driving device 21 having the same configuration as that of the conventional example shown in FIG.
2 was arranged at a position facing the reflection plate 12 of the track holder 8. The light emitting elements and the light receiving elements on both sides thereof are arranged in a direction parallel to the optical disk.

In the case of this example, the two light receiving elements receive the light emitted from the light emitting element and reflected by the reflection plate 12,
When the objective lens 2 is displaced in the tracking direction, the reflector 1
2 tilts so as to face one of the two light receiving elements and turns to the other side while rotating around the track spring 11, so that the amount of light reflected and incident on the reflector 12 is symmetrical for each light receiving element. Change. The electric output of the two light receiving elements, which fluctuate symmetrically when the objective lens 2 is displaced in the tracking direction, is processed by an arithmetic circuit 6 into an objective lens position detection signal 5 which is a differential signal (see FIG. 4).

Due to such an objective lens position detecting mechanism, the distance between the photoreflector 22 and the reflector 12 is kept constant, and the photoreflector 22 and the reflector 1 are fixed.
2, the position in the adjustment direction 23 where the two light receiving elements of the photoreflector 22 are lined up needs to be mounted and adjusted so that the centerline of the photoreflector 22 and the centerline of the reflector 12 are aligned. However, this adjustment is unnecessary in the above embodiment.

The objective lens 22 in the tracking direction
The linearity of the characteristic curve of the objective lens position detection signal 5 with respect to the position
2 can be obtained only in a narrow range determined by the distance between the elements. Moreover, since the reflection type triple photoreflector in which the light emitting element is disposed at the center and the light receiving elements on both sides is not a general photoreflector, there is a disadvantage that the cost is high.

[0036]

As described above, according to the present invention, the objective lens is rotationally displaced in the tracking direction about the second spring, and at the same time, the reflecting plate of the support member is also relatively rotationally displaced. The tilt amount of the reflector can be detected by the output of a tilt sensor arranged so as to face the reflector before displacement at a predetermined interval. The position of the objective lens is known. Therefore, even if the objective lens shakes due to a sudden stop after a high-speed access, for example, the movable member is driven by the electromagnetic force generating means based on the output of the tilt sensor so as to suppress the shake, thereby achieving the objective in the tracking direction. The position of the lens can be controlled.

In particular, since the sensor head of the tilt sensor is an aspheric lens, the light emitted from the light emitting diode, which is the light emitting portion, becomes parallel light, and when the tilt sensor is at a predetermined distance from the reflector, The emitted light is reflected by the reflector, passes through the aspheric lens again, and forms an image on the center of a two-part photodiode, which is a light receiving unit. Therefore, in mounting the tilt sensor, adjustment in a plane of two axes orthogonal to the direction facing the reflection plate is unnecessary because it does not affect the output. At the same time, the linearity of the characteristic curve of the objective lens position detection signal with respect to the position of the objective lens in the tracking direction can be widened.

Furthermore, since the differential output of the two-division photodiode is used as a detection signal, the offset and sensitivity of the detection signal due to fluctuations in the light emission output and light reception sensitivity of the tilt sensor due to changes in the environment of the detection mechanism. Changes can be minimized.

In terms of cost, there is an effect by using an inexpensive general-purpose tilt sensor.

[Brief description of the drawings]

FIG. 1 shows an objective lens driving device including an objective lens position detecting mechanism according to an embodiment of the present invention as an optical disk (not shown).
FIG.

FIG. 2 is a schematic side view of the objective lens driving device of FIG.

FIG. 3 is a perspective view of the tilt sensor shown in FIG. 1 as viewed from above and from the side.

FIG. 4 shows an objective lens driving device including an objective lens position detection mechanism as a comparative example of the present embodiment, which is an optical disk (not shown).
FIG.

FIG. 5 is a diagram of an objective lens driving device including an objective lens position detecting mechanism disclosed in Japanese Patent Laid-Open Publication No. 1-211244, as viewed from a plane parallel to an optical disk (not shown).

6 is a schematic sectional view of the objective lens driving device of FIG.

[Explanation of symbols]

 1, 21 Objective lens driving device 2 Objective lens 3 Movable member 4 Tilt sensor 5 Objective lens position detection signal 6 Arithmetic circuit 7a, 7b Magnet 8 Track holder 9 Base column 10a, 10b Track coil 11 Track spring 12 Reflector 13a, 13b Focus Spring 14 Focus coil 15 Infrared light emitting diode 16 Two-segment photodiode 17 Aspherical lens 18 Parallel light 22 Photoreflector 23 Adjustment direction

Claims (3)

[Claims] 1. An objective lens driving device for performing at least tracking of a light beam on an optical disc, comprising: a movable member for carrying an objective lens; and a support member for supporting the movable member via a first spring. A support disposed between the movable member and the support member, and coupled to the support member via a second spring substantially perpendicular to the optical disc; and a center of the second spring in a plane substantially parallel to the optical disc. An electromagnetic force generating means for generating at least an electromagnetic force for driving the movable member in a tracking direction, which is a direction in which the movable member of the support member is attached to a surface opposite to the movable member; And a tilt sensor that is arranged so as to oppose at a predetermined interval and outputs a signal corresponding to the inclination of the reflector. 2. The tilt sensor uses a light emitting diode as a light emitting unit and a two-division photodiode as a light receiving unit.
2. The objective lens drive according to claim 1, wherein a differential output of the two-division photodiode is used as a tilt detection signal, and the light emitting unit and the light receiving unit are arranged so as to be arranged in a direction parallel to the optical disc. apparatus. 3. The tilt sensor has an aspherical lens on the sensor head for converting light emitted from a light emitting diode into parallel light, and the light emitted from the tilt sensor at a predetermined distance from a reflector. 3. The objective lens driving device according to claim 2, wherein the objective lens driving device is designed so that is reflected by the reflection plate and forms an image again through the aspheric lens to the center of the two-segment photodiode.