JPH025233A - Objective lens drive device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an objective lens driving device that drives an objective lens, and for example, optically records, reproduces, and records information by irradiating a recording medium with a light beam. Alternatively, it is used in an optical information recording/reproducing device that performs erasing or the like.

[Conventional technology]

As shown in FIG. 4, in an optical information recording/reproducing apparatus using a magneto-optical recording medium as a recording medium, a light beam is generated by driving a motor 2 for rotating a magneto-optical disk 1 and an objective lens 6 vertically and horizontally. an objective lens driving device 4 that causes a light spot 7 to follow along a track (not shown) of the magneto-optical disk 1; and a light beam 7 irradiated from a laser light source 3a.
to the recording medium 1a of the magneto-optical disk 1 via the mirror 3b.
a coil 5 that applies a constant magnetic field to the recording medium 1a when recording and erasing information, and the optical head 3 and objective lens driving device 4 described above.
The vehicle is equipped with a linear motor 8, etc., which allows high-speed access to the target track by moving the target track.

As shown in FIG. 5, the objective lens driving device 4 is provided with a lens barrel 9 that supports the objective lens 6 so that the optical axis of the objective lens 6 is perpendicular to the rotating surface of the magneto-optical disk. The lens barrel 9 is supported by an intermediate support 11 via a pair of focusing direction movable elastic bodies 10.

The intermediate support 11 is supported by support members 14 erected on the fixed support 13 via a pair of elastic bodies 12 movable in the tracking direction. The tracking direction movable elastic bodies 12, 12 have a so-called "V" shape, with the fixed end distance on the intermediate support ll side set smaller than the fixed end distance on the support members 14, 14 side. .

Near the lens barrel 9, there is an elastic body 10.1 movable in the focus direction.
A focus drive means 30 that drives the objective lens 6 supported by the lens barrel 9 in the focus direction by elastically deforming the lens 0, and a focus drive means 30 that elastically deforms the tracking direction movable elastic bodies 12, A tracking drive means 31 is provided for driving the camera in the tracking direction.

By the way, in an optical information recording/reproducing apparatus provided with such an objective lens driving device 4, information recording, reproduction,
When erasing, first, the objective lens driving device 4 performs focus servo, and the linear motor 8 moves the optical lid 3 in the tracking direction to bring it close to the target track, so-called rough access. be exposed. After this rough access, the tracking drive means 31 is operated to make the objective lens 6
Precise access is performed by displacing and driving the lens barrel 9 supporting the light beam 7 in the tracking direction, and the convergence position of the light beam 7 is made to follow the recording track.

However, immediately after the rough access by the linear motor 8 is completed and the linear motor 8 is stopped, the lens barrel 9 supported by the tracking direction movable elastic bodies 12 tends to cause free vibration due to inertial force. This quiescent waiting time has caused a problem in that the start of precision access is delayed.

Therefore, it is optically detected that the objective lens 6 is displaced in the tracking direction due to the inertia force generated at the start of rough access, that is, when the linear motor 8 starts moving.If the amount of displacement of the objective lens 6 is large, the linear motor The objective lens 6 is locked in position until the lens 8 stops. This suppresses the free vibration of the objective lens 6 after the linear motor 8 has stopped, making it possible to hasten the start of the subsequent precision access.

Detection of the displacement of the objective lens 6 is performed by an objective lens displacement detection means 32' comprising a light irradiator 23 and a photodetector 24, as shown in FIG. The light irradiator 23 is made of an LED or the like, and is attached to the intermediate support 11 so that its optical axis faces in a direction (GH direction) perpendicular to the tracking direction (EF direction). On the other hand, the photodetector 24 is disposed facing the fixed support 13 with its light receiving surface 24a oriented substantially perpendicular to the optical axis of the light irradiator 23. Therefore, the displacement of the objective lens 6 is indirectly detected by the displacement of the intermediate support 11.

However, if the light irradiator 23 is disposed at the center of the intermediate support body 1 and the photodetector 24 is installed at a position a little apart from the center of the intermediate support body 11 in the G direction, for example, When the objective lens driving device 4 is attached to an optical disk recording/reproducing device, there is a risk of collision because a sufficient gap with the cartridge window cannot be secured. Therefore, while maintaining the positional relationship between the light irradiator 23 and the photodetector 24, and with the optical axis of the light irradiator 23 set perpendicular to the tracking direction, the E By shifting in this direction, space for these arrangements is secured.

[Problem to be solved by the invention]

However, the tracking direction movable elastic body 12.1
2 is formed in a V-shape, as shown in FIG. 7, when the objective lens 6 is displaced, the intermediate support 11 is displaced along an arcuate locus. Therefore, if the positional relationship between the light irradiator 23 and the photodetector 24 is set as in the conventional manner, the light irradiator 23 cannot move parallel to the light receiving surface 24a of the photodetector 24, and the tracking direction This will draw a trajectory with an angle to. For this reason, the distance between the light irradiator 23 and the photodetector 24 changes significantly, and as shown in FIG. This caused the problem of

[Means to solve the problem]

In order to solve the above problems, an objective lens driving device according to the present invention includes a pair of focus direction movable elastic bodies that support an objective lens, and an intermediate support that supports the pair of focus direction movable elastic bodies substantially in parallel. a pair of tracking direction movable elastic bodies that support the intermediate support; and a fixed support that supports the pair of tracking direction movable elastic bodies with a fixed end distance longer than the fixed end distance of the intermediate support. , a focus drive means for driving the objective lens in the focus direction, a tracking drive means for driving the objective lens in the tracking direction, and a light irradiator and a photodetector provided in a light receiving relationship, one of which is located at the intermediate point. In the objective lens drive device, the light irradiator in the objective lens displacement detection means is configured to emit the light of The photodetector is provided so that its axis is inclined at a certain angle with respect to a direction perpendicular to the tracking direction, while the photodetector is provided so that its light receiving surface is approximately perpendicular to the optical axis. It is characterized by

[For production].

When the intermediate support moves in an arcuate trajectory due to the displacement of the objective lens in the tracking direction, the light irradiator (or photodetector) provided at the side end of the intermediate support
It will move while drawing a trajectory with an angle to the tracking direction, but if the inclination angle of the optical axis of the light irradiator is set to be almost the same as the inclination angle of the trajectory above, the light irradiator will not be able to track. Even if the optical axis moves while drawing a trajectory at an angle to the direction, the optical axis will remain approximately perpendicular to the trajectory. On the other hand, since the light-receiving surface of the photodetector is arranged almost perpendicular to the optical axis, even if the light irradiator moves in a trajectory with an angle to the tracking direction, , the light receiving surface of the photodetector can receive the light from the light irradiator almost vertically, and
The distance between the light irradiator and the light irradiator is kept almost constant. Therefore, sufficient nearness can be ensured in the relationship between the displacement amount of the intermediate support and the output of the photodetector.

Note that, of course, it is desirable that the inclination angle of the optical axis of the light irradiator is set to be approximately the same as the inclination angle of the trajectory, but it is not limited to this angle. In other words, it is sufficient that the angle is tilted to an extent that can reduce changes in the distance between the light irradiator and the photodetector.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. For convenience of explanation, members having the same functions as those in the conventional example are given the same reference numerals.

As shown in FIG. 1, the objective lens driving device 4 includes a lens barrel 9 that supports the objective lens 6 so that the optical axis of the objective lens 6 is perpendicular to the rotating surface of a magneto-optical disk (not shown).
is provided. The lens barrel 9 is supported by a pair of focus direction movable elastic bodies 10, 10, and the focus direction movable elastic bodies 10, 10 are supported by an intermediate support body 11.

This intermediate support body 11 is supported by a pair of tracking direction movable elastic bodies 12, 12, and this pair of tracking direction movable elastic bodies 12, 12 are supported by support members 14, 14 erected on a fixed support body 13. Supported. The fixed end distance of the pair of tracking direction movable elastic bodies 12 on the support members 14 side is set longer than the fixed end distance on the intermediate support body 11, and is arranged in a so-called "C" shape. It is set up.

At the bottom of the lens barrel 9, there are elastic bodies 10 that are movable in the focus direction.
A focus coil 15 is provided which drives the objective lens 6 supported by the lens barrel 9 in the focusing direction by elastically deforming the lens. The magnetic gap 19a of the focus magnetic circuits 19, 19 consisting of
・We are facing within 19a. Therefore, by energizing the focus coils 15, 15, the lens barrel 9 supports the objective lens 6 by the action of the electromagnetic force generated at that time.
is displaced and driven in the focus direction. The above focus coil 5 and focus magnetic circuit 19/19
The focus driving means 30 is constituted by these.

Additionally, tracking coils 16 are disposed on both side walls of the lens barrel 9 to drive the objective lens 6 supported by the lens barrel 9 in the tracking direction by elastically deforming the tracking direction movable elastic bodies 12. A portion of each tracking coil 16 faces into a magnetic gap 22a of a tracking magnetic circuit 22 constituted by magnets 20, 20 and a yoke 21. Therefore, by energizing the tracking coils 16, 16,
The lens barrel 9 supporting the objective lens 6 is displaced and driven in the tracking direction (A-B direction) by the action of the electromagnetic force generated at that time. Tracking coil 1 above
A tracking drive means 31 is constituted by the tracking magnetic circuits 6 and 16 and the tracking magnetic circuits 22 and 22.

An inclined portion 11a is formed at one side end of the intermediate support 11, and is inclined clockwise by a certain angle X with respect to the tracking direction.
A light irradiator 23 is provided following the inclination.

Therefore, the optical axis of the light irradiator 23 is at a constant angle α (α=X) with respect to the direction perpendicular to the tracking direction (C-D direction).
It is now tilted only. On the other hand, a photodetector 24 is provided on the fixed support 13 and near the light irradiator 23, and this photodetector 24 has its light receiving surface 24a approximately parallel to the optical axis of the photodetector 23. It is set vertically. The light irradiator 23 and the photodetector 24 provided in the above-mentioned light receiving relationship constitute an objective lens displacement detecting means 32.

In the above configuration, when the intermediate support 11 is displaced in a circular arc trajectory due to the displacement of the objective lens 6 in the tracking direction, the inclined portion 1 at the side end of the intermediate support 11 is displaced.
As shown in FIG. 2, the light irradiator 23 installed at 1a moves in a trajectory having an angle X' with respect to the tracking direction. are set to be almost the same, the inclination angle α of the optical axis of the light irradiator 23 is almost the same as the inclination angle X' of the trajectory, so that the light irradiator 23 has the angle Even if it moves while drawing a trajectory, its optical axis will remain approximately perpendicular to the trajectory.

On the other hand, since the light-receiving surface 24a of the photodetector 24 is disposed substantially perpendicular to the optical axis, the light irradiator 23 moves along a trajectory having the angle X'. However, the light receiving surface 24a of the photodetector 24 always receives the light from the light irradiator 23 almost vertically, and
The distance between them will always be kept almost constant. Therefore, as shown in FIG. 3, it is possible to ensure sufficient linearity by examining the relationship between the amount of displacement of the intermediate support 11 and the output of the photodetector 24. By ensuring this linearity, the detection accuracy of the objective lens displacement detection means 32 can be significantly improved, and the electrical position lock control of the objective lens 6 can be performed with high precision during high-speed access of the objective lens drive device 4. It can be carried out.

Note that it is of course desirable that the inclination angle α of the optical axis of the light irradiator 23 (that is, the inclination angle X of the inclined part 11a) is set to be approximately the same as the inclination angle X' of the trajectory.
It is not limited to this angle. It is sufficient that the angle is tilted to an extent that can reduce changes in the distance between the light irradiator 23 and the photodetector 24. Furthermore, if the optical axis of the light irradiator 23 is set in a direction perpendicular to the tracking direction and only the photodetector 24 is tilted by the above angle Although the function of always keeping the distance between the two substantially constant is achieved, a problem arises in that the optical axis of the light irradiator 23 enters the photodetector 24 obliquely.

〔Effect of the invention〕

As described above, the objective lens driving device according to the present invention includes a pair of focus direction movable elastic bodies that support the objective lens, an intermediate support body that supports the pair of focus direction movable elastic bodies substantially parallel to each other, and an intermediate support body that supports the pair of focus direction movable elastic bodies substantially parallel to each other. a pair of elastic bodies movable in the tracking direction that support the support body; a fixed support body that supports the pair of elastic bodies movable in the tracking direction with a fixed end distance longer than the fixed end distance in the intermediate support body; and the objective object described above. A focus drive means for driving the lens in the focus direction, a tracking drive means for driving the objective lens in the tracking direction, and a light irradiator and a photodetector provided in a light receiving relationship, one of which is on the side of the intermediate support. In the objective lens driving device, the light irradiator in the objective lens displacement detection means has an optical axis in the tracking direction. The photodetector is provided so as to be inclined at a certain angle with respect to a direction perpendicular to the optical axis, while the photodetector is provided so that its light receiving surface is substantially perpendicular to the optical axis.

Therefore, it is possible to prevent the distance between the light irradiator and the photodetector from changing significantly, and to ensure sufficient linearity in the relationship between the amount of displacement and the output of the photodetector.

As a result, the detection accuracy of the objective lens displacement detecting means can be significantly improved, and the position lock control of the objective lens can be performed with high precision during high-speed access of the objective lens drive device.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a plan view of an objective lens driving device, FIG. 2 is a plan view of the main parts in FIG. 1, and FIG. is a graph showing the relationship between the amount of displacement of the intermediate support and the output of the photodetector, FIG. 4 is a schematic configuration diagram showing an optical information recording/reproducing device, and FIGS. 5 to 8 show conventional examples. 5 is a perspective view of the objective lens driving device, FIG. 6 is a plan view of the objective lens driving device, FIG. 7 is a plan view of the main parts in FIG. 6, and FIG. 8 is a displacement amount of the intermediate support. 2 is a graph showing the relationship between the output of the photodetector and 4 is an objective lens drive device, 9 is a lens barrel, 10 is an elastic body movable in the focusing direction, 11 is an intermediate support, 12 is an elastic body movable in the tracking direction, 13 is a fixed support, 23 is a light irradiator, and 24 is a photodetector. 24a is a light receiving surface, 30 is a focus drive means, 31 is a tracking drive means, and 32 is an objective lens displacement detection means. 13 Figure Displacement of the intermediate support

Claims (1)

[Claims] 1. A pair of focus direction movable elastic bodies that support an objective lens, an intermediate support body that supports the pair of focus direction movable elastic bodies substantially in parallel, and a pair of intermediate support bodies that support this intermediate support body. A tracking direction movable elastic body, a fixed support supporting the pair of tracking direction movable elastic bodies with a fixed end distance longer than a fixed end distance in the intermediate support, and driving the objective lens in the focus direction. A focus drive means, a tracking drive means for driving the objective lens in the tracking direction, and a light irradiator and a photodetector provided in a light receiving relationship, one of which is fixed to the side end of the intermediate support and the other fixed to the above. In an objective lens drive device equipped with objective lens displacement detection means each disposed on a support, the light irradiator in the objective lens displacement detection means has an optical axis that is perpendicular to the tracking direction. An objective lens driving device characterized in that the photodetector is provided so as to be tilted by a certain angle, while the photodetector is provided so that its light receiving surface is substantially perpendicular to the optical axis.