JPH1166605A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the problem in the constitution of a device such as miniaturization, the increase in power consumption and the decrease in the life of a light source since the movable range of an objective lens is required to be designed larger by the falling amount in order to prevent the objective lens from falling by gravity in the tracking direction. SOLUTION: A gravity sensor 19 for perceiving gravity in the tracking direction 35 is provided in an optical disk device and an offset current is made to flow through a tracking coil so that a thrust so as to cancel the perceived gravity is generated in an objective lens driving device 14. Since the fall by gravity of the objective lens 1 is reduced and it is not necessary to incorporate the portion of falling by gravity into the movable range of the objective lens at the time of designing the objective lens driving device 14, the movable range of the objective lens is reduced and thus, the diameter of an incident beam on the objective lens is miniaturized. Consequently, the miniaturization of the device, the reduction of a necessary light emitting amount, etc. are realized.

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 for recording and reproducing information.

[0002]

2. Description of the Related Art The prior art will be described with reference to FIGS. 5, 6 and 7. FIG.

FIG. 5 is a schematic configuration diagram illustrating a conventional optical disk device.

In an optical disk apparatus, a tracking servo control for positioning a focused beam 13 for recording and reproducing information on a disk medium on a specific track 9 on the optical disk 8 and an optical pickup 12 on the target track 9 quickly. Access control for moving is widely performed. For this purpose, an objective lens driving device 14 for moving the condensed beam 13 and a pickup feeding mechanism for moving the optical pickup 12 in the radial direction of the optical disk 8 are used.

[0005] Therefore, in the conventional optical disk apparatus, the optical disk 8 as the information recording medium is configured to be rotated by the spindle motor 11 mounted on the chassis 10.

The optical pickup 12 is provided with the optical disk 8
Is attached to the chassis 10 on the lower surface side of the optical disk 8 and in a state where the optical disk 8 can move in the radial direction. This allows
The optical pickup 12 can write and read information by irradiating the condensed beam 13 condensed by the objective lens 1 onto the track 9 of the optical disc 8.

On the other hand, the rotating motor 1 is mounted on the chassis 10.
5, a feed screw 16, a guide rail 17, etc. are provided.
Rotates to move the optical pickup 12 to the guide rail 17.
, A so-called pickup feed mechanism for moving the optical disc in eight radial directions.

In the tracking servo control of the optical disk apparatus, the condensed beam 13 must follow the track 9 which is displaced by a maximum of several tens of microns with the rotation of the optical disk 8 with an error and accuracy of about 0.1 μm or less. .

For this purpose, an objective lens driving device 14 for moving the objective lens 1 for condensing the condensed beam 13 in the tracking direction is mounted on the optical pickup 12.

Next, a configuration example of a conventional objective lens driving device will be described with reference to FIG.

The objective lens driving device shown in FIG. 7 shows a so-called four-wire system among several types of objective lens driving devices.

The four-wire type objective lens driving device has a feature that the device itself can be configured to be smaller in size than other types, and is often employed in a small optical disk device.

In FIG. 7, an objective lens holder 2 for supporting an objective lens 1 has a total of four leaf springs 3.
Thus, it is attached to the support portion 6 with a degree of freedom mainly in the focus direction and the tracking direction. A focus coil 4 and a tracking coil 5 are fixed to the objective lens holder 2. The focus coil 4 and the tracking coil 5 are combined with the magnetic circuit 7 to constitute an actuator that drives the objective lens 1 in the focus direction and the tracking direction.

The objective lens 1, objective lens holder 2, focus coil 4, tracking coil 5, and magnetic circuit 7 are collectively called an objective lens driving device.

The objective lens driving device 14 is configured to control the position of the condensed beam 13 and the track 9 on the optical disk 8.
Tracking error signal 3 output by a tracking error signal detector (not shown) for detecting a positional deviation from
Using 2, the servo following operation is performed so that the positional deviation between the focused position of the focused beam 13 and the track 9 on the optical disk 8 is within an allowable range.

However, since the tracks 9 on the optical disk 8 are generally arranged in a spiral shape, if information is read or written continuously, the objective lens 1 that follows the information in the tracking direction will be in the tracking direction. It reaches the limit of the movable range (generally ± 200 to 400 μm).

Next, the control circuit 18 of the optical disk apparatus shown in FIG. 5 controls the optical pickup 12 by using the pickup feed mechanism so that the amount of movement of the objective lens 1 is within the movable range. .

There are the following three types of two-stage servo systems, which are systems for tracking drive of an optical disk device in which the objective lens driving device 14 and the pickup feed mechanism are combined.

A first method is to drive the objective lens driving device 14 and the pickup feed mechanism based on the tracking error signal.

The second is a method in which only the objective lens driving device 14 is driven by a tracking error signal, and the pickup feed mechanism is driven by a signal from an objective lens movement amount detector mounted on the objective lens driving device 14.

Third, as in the second method, only the objective lens driving device 14 is driven by a tracking error signal. However, the objective lens driving device 14 does not have an objective lens moving amount detector, and This is a method of detecting the servo current supplied to the tracking coil 5 of the device 14 and driving the pickup feed mechanism.

Since the first method requires a high performance of the pickup feed mechanism, the first method is often used for a high-grade optical disk apparatus in which a linear motor is used for the pickup feed mechanism.

The second method is used for some high-grade optical disc devices because an objective lens moving amount detector is required for the objective lens driving device.

The third method is widely used in an optical disk device such as a low-cost CD player because it does not require a pickup pickup mechanism to have such a high performance and does not require an objective lens movement amount detector.

Hereinafter, a method of controlling the pickup feed mechanism according to the third method will be specifically described.

First, the apparatus is arranged so that a current proportional to the low frequency component of the servo current 33 supplied to the tracking coil 5 of the objective lens driving device 14 for moving the objective lens 1 is supplied to the rotary motor 15 of the pickup feed mechanism. Configure it.

When the focus position is moved by a continuous information reading operation or the like, the objective lens driving device 1 for the objective lens 1 is moved.
Since the required movement amount in the tracking direction with respect to 4 increases, the low frequency component of the servo current 33 supplied to the tracking coil 5 of the objective lens driving device 14 increases. As a result, the current 34 supplied to the rotary motor 15 also increases. When the current 34 supplied to the rotary motor 15 becomes large enough to overcome the frictional force or the like of the pickup feed mechanism, the rotary motor 15 rotates the feed screw 16 so that the optical pickup 12 moves the objective lens 1 to the objective lens driving device 14. It is moved in the same direction as the direction relatively moving in the tracking direction.

Since the objective lens driving device 14 mounted on the optical pickup 12 moves at the same time by the movement of the optical pickup 12 in the tracking direction, the required movement amount of the objective lens 1 in the tracking direction with respect to the objective lens driving device 14 is reduced. Decrease.

When the required amount of movement of the objective lens 1 in the tracking direction decreases, the low frequency component of the servo current 33 supplied to the objective lens driving device 14 decreases, so that the current 34 supplied to the rotary motor 15 also decreases. Therefore, the rotation of the feed screw 16 stops, and the movement of the optical pickup 12 also stops.

That is, the optical pickup 12 moves so that the amount of movement of the objective lens 1 with respect to the objective lens driving device 14 in the tracking direction is reduced.

Thus, the amount of movement of the objective lens 1 can be kept within the movable range.

In the conventional optical disk device, the focusing position is moved over the entire area of the optical disk while the amount of movement of the objective lens is within the movable range of the objective lens driving device by the objective lens driving device and the optical pickup feeding mechanism as described above. It is configured to be able to.

However, the light beam incident on the objective lens and condensed on the disk covers the entire movable range of the objective lens so that a sufficient amount of light can be supplied wherever the objective lens is located within the movable range. A light beam diameter enough to cover is required.

FIG. 6 shows this state.

The larger the movable range 28 of the objective lens 1 is, the larger the required beam diameter 29 of the light beam incident on the objective lens is. Therefore, the light source 30 of the light beam is required to emit a larger amount of light.

Further, when the beam diameter 29 is increased, a larger optical component 31 is required, which hinders downsizing of the apparatus. Further, when the required light output amount of the light source 30 increases, problems such as an increase in power consumption and a reduction in the life of the light source occur.

[0037]

Conventionally, an objective lens 1
When there is a possibility that the objective lens 1 may fall under its own weight, the movable range of the objective lens 1 of the optical disk device is designed to be larger by the amount of its own weight.

However, if the movable range of the objective lens is designed to be large by the weight drop, a problem occurs in the device configuration as described with reference to FIG.

As a method of preventing the object from falling under its own weight and reducing the movable range of the objective lens, there is a method of using an objective lens driving device which is insensitive to gravity in the tracking direction.

As an objective lens driving device having no sensitivity to gravity in the tracking direction, there are a shaft sliding system and a hinge system (Compact disk reader (revised 3rd edition), page 217 by Ohtaro, co-authored by Heitaro Nakajima and Hiroshi Ogawa).・
32).

However, an objective lens driving device which is insensitive to gravity in the tracking direction, represented by the shaft sliding method, has sensitivity to gravity in the tracking direction, but is small and widely used in small optical disk devices. There is a disadvantage that the size is large as compared with the 4-wire type objective lens driving device. For this reason, the size of the pickup becomes large, and it is difficult to use it in a small optical disk device in which the size of the device is prioritized.

When an objective lens driving device having a sensitivity to gravity in the tracking direction is used, a position detector for measuring the amount of displacement of the objective lens in the tracking direction is mounted on the objective lens driving device. There are ways to alleviate the problem.

However, also in this case, since the position detector must be mounted on the objective lens driving device, a problem that the size of the objective lens driving device becomes large occurs.

An object of the present invention is to have sensitivity to gravity in the tracking direction typified by the 4-wire system, but even if the objective lens driving device can be manufactured in a small size, any additional device should be added to the objective lens driving device itself. An object of the present invention is to provide a compact and high-performance optical disc device by reducing the amount of self-weight drop due to gravity in the tracking direction and reducing the movable range of the objective lens without providing the optical disc device.

[0045]

According to a first aspect of the present invention, there is provided an optical disc apparatus comprising: an objective lens for condensing a light beam on a recording medium; and a focus for generating a driving force for moving the objective lens in a focus direction. An object having a coil, a tracking coil for generating a driving force for moving in a tracking direction, and a magnetic circuit member, and performing a focus servo operation or a tracking servo operation by flowing a current from a servo circuit to each coil during operation. In an optical disc device including a lens driving device and a gravity sensor that detects the amount of gravity in the tracking direction, when the optical disc device operates, the amount of gravity in the tracking direction is detected,
By applying a thrust that offsets the amount of gravity to the objective lens driving device, a position shift of the objective lens with respect to the objective lens driving device by the weight of the objective lens is adjusted.

According to a second aspect of the present invention, there is provided the optical disk device according to the first aspect, wherein a plurality of gravity sensors for detecting the amount of gravity acting in the tracking direction of the objective lens driving device are provided so as to surround the objective lens. It is characterized by being arranged individually.

According to a third aspect of the present invention, there is provided the optical disk device according to the first aspect, wherein the gravity sensor for detecting the amount of gravity acting in the tracking direction of the objective lens driving device is provided in the tracking direction of the objective lens driving device. A displacement portion configured to be displaced in the direction by gravity acting on the displacement portion, an elastic portion supporting the displacement portion, and a displacement sensor for measuring a displacement amount.

According to a fourth aspect of the present invention, there is provided the optical disk device according to the first aspect, wherein the gravity sensor for detecting the amount of gravity acting in the tracking direction of the objective lens driving device is provided in the tracking direction of the objective lens driving device. A displacement portion configured to be displaced in the direction by gravity acting on the displacement portion, an elastic portion supporting the displacement portion, and a plurality of portions set to be conductive when the displacement of the displacement portion reaches a predetermined amount. And electrical contacts.

[0049]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. 1 to 4 and FIG.

A first embodiment of the present invention will be described with reference to FIGS. 1 to 3 and FIG.

FIG. 1 is a schematic configuration diagram of an optical disk device according to one embodiment of the present invention.

In FIG. 1, the optical pickup 12 has the configuration shown in FIG.
The objective lens driving device 14 shown in FIG.

A gravity sensor 19 for detecting a component of the gravity acting on the objective lens 1 in the tracking direction of the objective lens driving device 14 is provided on the chassis 10 of the optical disk device.

FIG. 2 is a schematic configuration diagram showing one embodiment of the gravity sensor 19.

The displacement portion 20 is supported by the elastic portion 21 so as to be displaceable in the tracking direction 35 of the objective lens driving device 14.

When gravity acts on the displacement portion 20 in the tracking direction 35, the displacement portion 20 moves by a displacement amount determined by the weight of the displacement portion 20 and the spring constant of the elastic portion 21.

The displacement amount of the displacement section 20 is measured by the displacement sensor 22.

The displacement sensor 22 includes a light source 23 mounted on the displacement unit 20 and a light receiving unit 24 fixed on the chassis 10 side.
The electric signal output from the light receiving unit 24 changes according to the movement of the light source 23.

Accordingly, the magnitude of the gravity component acting on the objective lens 1 in the tracking direction of the objective lens driving device 14 can be measured by the signal output from the displacement sensor 22.

The control circuit 18 controls the servo current of the tracking coil 5 mounted on the objective lens driving device 14 shown in FIG. 7 by a current proportional to the gravity acting in the tracking direction of the objective lens driving device 14 thus measured. By supplying the offset tracking coil current 33 to the tracking coil 5, the tracking coil 5 is configured to generate a thrust having the same magnitude as the gravity acting in the tracking direction of the objective lens driving device 14 and in the opposite direction. ing.

When gravity acts on the optical disk device in the tracking direction of the objective lens driving device 14, the signal 37 output from the gravity sensor 19 derives the component of the gravity acting on the objective lens 1 in the tracking direction of the objective lens driving device 14. The size can be detected.

The control circuit 18 calculates the amount of current supplied to the tracking coil 5 such that a thrust having a direction opposite to the detected gravity acts on the objective lens 1, and supplies this current to the tracking coil 5. It is added to the existing servo current as an offset.

At this time, the rotation motor current 34 supplied to the rotation motor 15 is configured to be generated from the low frequency component of the tracking coil servo current before the offset is performed.

As a result, in the tracking coil 5, in addition to the servo current, a thrust is generated so that the magnitude of the gravity acting on the objective lens 1 in the tracking direction of the objective lens driving device 14 is equal in magnitude and opposite in direction. As a result, the tracking coil 5 generates a thrust whose direction is opposite to that of the tracking direction component of the objective lens driving device 14 of gravity, and acts on the objective lens 1.

Therefore, the component of the gravitational force acting on the objective lens 1 in the tracking direction of the objective lens driving device 14 is in the same direction as the component of the gravitational force acting on the objective lens 1 generated by the tracking coil 5 in the tracking direction. Objective lens 1 is offset by the opposite thrust.
The weight of the vehicle falls.

When the self-weight drop of the objective lens 1 decreases, the amount of extending the movable range of the objective lens 1 by the self-weight drop at the time of designing the objective lens driving device decreases, so that the light beam incident on the objective lens shown in FIG. Required beam diameter 29 can be reduced. Therefore, the size of the optical component can be reduced and the emission power of the light source can be reduced, so that the size, cost, and power consumption of the optical disk device can be reduced.

Further, since the gravity sensor of the present embodiment can measure a changing gravity and an intermediate gravity, it can operate normally even if the device is moved or tilted.

FIG. 3 is a schematic configuration diagram showing another embodiment of the gravity sensor 19.

The displacement section 20 is supported by an elastic section 21 so as to be displaceable in the tracking direction of the objective lens driving device 14.

When gravity acts on the displacement portion 20 in the tracking direction, the displacement portion 20 moves by a displacement determined by the weight of the displacement portion 20 and the spring constant of the elastic portion 21.

The movable portion 20 is provided with a movable electrical contact 25, and fixed portions of the gravity sensor 19 are provided with fixed electrical contacts 26 and 27.

Normally, as shown in FIG. 3A, the movable electrical contact 25 and the fixed electrical contacts 26, 27 are in an insulated state.

Next, as shown in FIG. 3B, when the gravitational force 36a acts on the displacement portion 20 to displace the predetermined displacement amount, the movable electrical contact 25 and the fixed electrical contact 26 provided on the displacement portion 20 come into contact. Then, a conduction state is established.

As shown in FIG. 3C, when the gravity 36b acts in the opposite direction to the case of FIG.
0 is displaced by a predetermined amount in the reverse direction, and the movable electrical contact 25 provided on the displacement portion 20 and the fixed electrical contact 27 come into contact with each other to be in a conductive state.

Accordingly, the gravity sensor 19 detects the presence or absence and the direction of gravity in the tracking direction of the objective lens driving device 14 acting on the objective lens 1 based on the conduction state between the movable electrical contact 25 and the fixed electrical contacts 26 and 27. can do.

The control circuit 18 includes the objective lens driving device 14
When the gravity in the tracking direction is detected, a predetermined amount of offset current is added to the servo current of the tracking coil 5 mounted on the objective lens driving device 14 in FIG. This offset current amount is set so that the tracking coil 5 generates a thrust force whose direction is opposite to the direction of gravity acting on the tracking direction of the objective lens driving device 14.

As a result, in addition to the servo current, the tracking coil 5 and the objective lens driving device 1
Since a current that generates a thrust that is equal in magnitude and opposite in direction to the gravity acting in the tracking direction of 4 flows, the tracking coil 5 has a direction opposite to the gravity in the tracking direction of the objective lens driving device 14. Such a thrust is generated and acts on the objective lens 1.

When the weight drop of the objective lens 1 decreases, the amount of extending the movable range of the objective lens 1 by the weight drop at the time of designing the objective lens driving device decreases, so that the required beam diameter of the light beam incident on the objective lens is reduced. 29 can be made smaller. Accordingly, the gravity in the tracking direction of the objective lens driving device 14 acting on the objective lens 1 is opposite to the gravity in the tracking direction of the objective lens driving device 14 acting on the objective lens 1 generated by the tracking coil 5. This is offset by the thrust and the falling of the objective lens 1 under its own weight is reduced.

Further, since the gravity sensor shown in this embodiment is not an expensive displacement sensor but an inexpensive electric contact, it can be constructed at low cost.

The displacement sensor 22 used in the gravity sensor 19 may be, for example, a sensor using a change in capacitance or a sensor using a change in electric resistance, in addition to the sensor shown in the above embodiment.

A second embodiment of the present invention will be described with reference to FIGS.

This embodiment is different from the first embodiment in that a plurality of gravity sensors are used.

FIG. 4 is a schematic configuration diagram of the optical disk device of the present embodiment.

In FIG. 4, two gravity sensors 19a
And 19 b are arranged so as to surround the objective lens driving device 14 and are fixed to the chassis 10.

When gravity acts on the optical disc device in the tracking direction of the objective lens driving device 14, each of the gravity sensors 19a and 19b detects the magnitude of the gravity.

In this embodiment, the gravity sensors 19a and 19a
The signal to which the signal b is added is used as a signal obtained by detecting the component of the gravity acting on the objective lens 1 in the tracking direction of the objective lens driving device 14.

The control circuit 18 calculates the amount of current supplied to the tracking coil 5 shown in FIG. 7 so that a thrust having a direction opposite to the detected gravity is applied to the objective lens 1, and sends this current to the tracking coil 5. It is added as an offset to the supplied servo current.

As a result, in the tracking coil 5, in addition to the servo current, a current that generates a thrust whose direction is opposite to the tracking direction component of the gravity of the objective lens driving device that acts on the objective lens flows in the tracking coil 5. The coil 5 generates a thrust having a direction opposite to the tracking direction component of the gravity objective lens driving device, and acts on the objective lens 1.

Therefore, the component of the gravitational force acting on the objective lens 1 in the tracking direction of the objective lens driving device 14 is opposite in direction to the tracking direction component of the gravitational force acting on the objective lens generated by the tracking coil 5. The objective lens 1 is reduced by its own weight due to such thrust.

On the other hand, when the entire optical disk device is rotating, even if gravity does not act in the tracking direction of the objective lens driving device 14, the gravity sensor 19 may detect gravity generated as centrifugal force. is there.

In this case, in a device having only one gravity sensor, the mechanism for preventing the objective lens from falling due to its own weight may malfunction. In this embodiment, however, two gravity sensors 19a and 19b drive the objective lens. It is arranged so as to surround the device 14 and is fixed to the chassis 10, and detects a tracking direction component of the objective lens driving device of gravity acting on the objective lens 1 by adding a signal output from the gravity sensors 19 a and 19 b. It is configured to be used as a signal.

Accordingly, the gravity due to the centrifugal force that does not act on the objective lens driving device 14 is canceled, and the component of the gravity acting on the objective lens 1 in the tracking direction of the objective lens driving device can be mainly detected. This can prevent malfunction.

Although the same gravity sensor as in the first embodiment is used, the same gravity sensor can be applied. Further, other than the sensors described above, for example, a sensor using a change in capacitance or a sensor using a change in electric resistance may be used.

[0094]

As described above, in the optical disk device of the present invention, the following effects can be achieved in each claim.

According to a first aspect of the present invention, a gravity sensor for detecting gravity acting in the tracking direction of the objective lens driving device is provided, and the servo current of the tracking coil of the objective lens driving device is applied to the gravity current detected by the gravity sensor. In this configuration, a current that generates a thrust in the opposite direction is applied as an offset.

Therefore, a thrust which cancels the gravity of the objective lens driving device acting on the objective lens in the tracking direction is generated in the objective lens driving device, and the self-weight drop of the objective lens is reduced. At the time of design, the amount by which the movable range of the objective lens is expanded by the weight of the objective lens is reduced, and the diameter of the light beam incident on the objective lens can be reduced. Therefore, the size of the optical component can be reduced and the emission power of the light source can be reduced, so that the size, cost, and power consumption of the optical disk device can be reduced.

In the present invention, a plurality of gravity sensors are disposed so as to surround the objective lens driving device.

Therefore, it is possible to distinguish the gravity generated by the centrifugal force due to the rotation of the optical disk device from the gravity in the tracking direction of the objective lens driving device acting on the objective lens to be canceled, thereby preventing malfunction. Can be.

According to a third aspect of the present invention, the gravity sensor comprises: a displacement portion that is displaced in the tracking direction of the objective lens driving device by gravity in the tracking direction of the objective lens driving device; an elastic portion that supports the displacement portion; It consists of a displacement sensor that measures the displacement of the part.

Therefore, since the apparatus can cope with a changing gravity or an intermediate amount of gravity, it is possible to move the apparatus in a tracking direction of the objective lens driving apparatus such as when the apparatus moves or tilts.
Even in the state where the gravitational force of 00% is not acting, since the weight of the objective lens can be accurately compensated for by its own weight, it can operate normally.

According to a fourth aspect of the present invention, the gravity sensor comprises: a displacement portion that is displaced in the tracking direction of the objective lens driving device by gravity in the tracking direction of the objective lens driving device; an elastic portion that supports the displacement portion; It is composed of a plurality of electrical contacts set to conduct when the displacement of the part reaches a predetermined amount.

Therefore, it can be manufactured at a low cost compared to a configuration using a gravity sensor using a displacement sensor.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a gravity sensor according to the first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram illustrating another gravity sensor according to the first embodiment of the present invention.

FIG. 4 is a schematic configuration diagram illustrating a second embodiment of the present invention.

FIG. 5 is a schematic perspective view illustrating a conventional optical disk device.

FIG. 6 is a side view illustrating a relationship between a movable range of an objective lens and a light beam diameter.

FIG. 7 is a perspective view illustrating an objective lens driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 4 Focus coil 5 Tracking coil 7 Magnetic circuit 8 Optical disk 14 Objective lens drive 19 Gravity sensor 20 Displacement part 21 Elastic part 22 Displacement sensor

Claims (4)

[Claims] An objective lens for condensing a light beam on a recording medium, a focus coil for generating a driving force for moving the objective lens in a focusing direction, and a tracking coil for generating a driving force for moving the objective lens in a tracking direction. An objective lens driving device having a magnetic circuit member and performing a focus servo operation or a tracking servo operation by flowing a current from a servo circuit to each coil during operation, and a gravity sensor for detecting a gravity amount in a tracking direction. In the optical disk device including: the optical disk device detects the amount of gravity in the tracking direction during the operation of the optical disk device, and applies a thrust that cancels the amount of gravity to the objective lens driving device to drop the objective lens under its own weight with respect to the objective lens driving device. Optical disc device characterized by adjusting the positional displacement of . 2. The optical disk device according to claim 1, wherein a plurality of gravity sensors for detecting the amount of gravity acting in the tracking direction of the objective lens driving device are arranged so as to surround the objective lens. 3. A gravity sensor for detecting the amount of gravity acting in the tracking direction of the objective lens driving device, wherein the gravity sensor detects the amount of gravity acting in the tracking direction of the objective lens driving device.
2. The optical disk device according to claim 1, comprising a displacement portion configured to be displaced in the direction, an elastic portion that supports the displacement portion, and a displacement sensor that measures a displacement amount. 4. A gravity sensor for detecting the amount of gravity acting in the tracking direction of the objective lens driving device, wherein the gravity sensor detects the amount of gravity acting in the tracking direction of the objective lens driving device.
A displacement portion configured to be displaced in the direction, an elastic portion supporting the displacement portion, and a plurality of electrical contacts set to be conductive when the displacement of the displacement portion reaches a predetermined amount. The optical disk device according to claim 1, wherein: