JPS6187232A - Objective supporting device - Google Patents

Abstract

PURPOSE:To move an objective accurately in a tracking direction by arranging elastic support members which expand and contract freely at both sides of the objective in the tracking direction. CONSTITUTION:The objective 21 is fitted to a holding cylinder 22. The holding cylinder 22 is coupled with a coil bobbin 25 through two expanding/contracting leaf springs 23 and 24 which are arranged at both sides of the objective in the tracking direction and have corrugations. The objective 21 is supported by those two leaf elastic spings 23 and 24, so it moves accurately in the tracking direction (X direction); tracking corrections are made properly and tracking causes neither the inclination of the optical axis nor the rotation of the objec tive. Further, the leaf springs 23 and 24 are extended at right angles to the tracking direction, so spaces are secured at both sides of the objective in the tracking direction and electromagnets 33 and 33' are arranged here.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a support device for an objective lens of an optical information reading device.

When playing back a video disc or an audio disc on which information is optically recorded, focusing and tracking must be performed in order to properly focus the reading light beam onto the information trunk on the disc surface. Since this focusing and tracking must be performed with very small amplitude and at high speed, the mechanism for performing these tasks is a problem.

Various proposals have been made regarding such a mechanism, but the most common one is to move the objective lens in the focusing direction for focusing, and to place a galvano mirror in the optical path of the reading beam for tracking. This is done by swinging the reading light beam in the tracking direction. However, in such a configuration, the reading light beam passes obliquely to the optical axis of the optical system such as the objective lens due to the tracking operation, so even in such a case, it is necessary to ensure that the light beam is focused correctly. In this case, it becomes necessary to use an optical system that does not have not only spherical aberration but also astigmatism, etc., which complicates the structure of the optical system and increases its weight, deteriorating the characteristics of the focusing control system.

In order to eliminate such drawbacks, it is possible to consider a method of configuring the optical system, especially the objective lens, so that the beam does not enter the optical system obliquely. In this case, it is important that the movement of the objective lens in the desired directions, the tracking direction and the focusing direction, is carried out correctly, and that these movements do not result in undesired movements in other directions.

Japanese Unexamined Patent Publication No. 51-61726 describes such an objective lens driving device. Figure 1 shows the plan view (
FIG. 2 shows a sectional view taken along the line AA' in FIG. 1. In the figure, the X direction is the track direction, and the Y direction is the track direction.
The direction is perpendicular to the track, and a deviation in the Y direction is a deviation from the track, so it is a tracking error, and a deviation in the X direction is a time deviation in the read signal, so it is called a time base error. I'll decide. The objective lens 1 is attached to a lens holder 2, and this holder 2 is attached to a frame 3 made of an elastic member.

Note that the reference numeral 4 indicates a side plate bridged over the frame 3.

The frame 3 is made of a magnetic material, and when an electric current is passed through an electromagnet 5 or 5'' placed opposite to the outside of the frame 3, a force is applied by this magnetic force.The frame 3 is fixed to a support 6.6'. Therefore, the entire lens 1 does not move due to this force, but it bends as shown by the broken line in the figure, and the lens 1 moves in parallel in the Y direction.The portion 7 inside the frame 3 is coated with silicone rubber, silicone grease, etc. This acts as a damper.Furthermore, if desired, the entire device for moving in the Y direction may be housed in a drive device for moving in the X direction, which has a similar configuration, to compensate for tracking errors and to correct the time base. Errors can be corrected.A configuration for moving the lens in the optical axis direction, that is, the Z direction for focusing is not shown in FIG. The above-mentioned publication describes that if a mechanism for this purpose is incorporated, the lens 1 can be moved in the Z direction to adjust the focus.

However, in the structure shown in Fig. 1, the support of frame 3 is 6°6'.
Since the surfaces 8, 8'' attached to the lens 1 are also deflected as shown by the two-dot chain line in the figure, the positioning of the lens 1 in the Y direction cannot be performed reliably. There is a drawback that an undesired movement in the Y direction occurs with the movement, or a movement in the Y direction also occurs due to external vibrations, resulting in a time base error.

By increasing the width of the supports 6 and 6゛, it is possible to eliminate the deflection shown by the two-dot chain line of the frames 8 and 8゜, but this will limit the deformation of the frame in the desired direction, that is, the Y direction. You will end up being rejected. Because pillars 6 and 6 are frame 3.
A surface 9 that deforms as the lens 1 moves in the Y direction,
This is because they are provided at both ends of the 9".

Furthermore, if the driving device that moves in the Z direction for focusing is housed within the lens holder 2, the mass of the movable part that performs tracking will increase, and the entire device will need to be large in order to perform good control. There was a drawback. In other words, the amplitude of the movement for focusing needs to be one order of magnitude larger than the movement for tracking, so the drive device for this inevitably becomes large, and it is difficult to configure it to move it for tracking. It's unreasonable.

SUMMARY OF THE INVENTION An object of the present invention is to provide an objective lens support device that can support an objective lens so that it can move accurately in the tracking direction, and that does not tilt the optical axis due to tracking correction.

The present invention provides a device that supports an objective lens for optically reading information recorded on a recording medium so as to be movable in a tracking direction perpendicular to its leading axis. This objective lens is characterized in that it is supported by elastic supporting members that are disposed on both sides of the objective lens and can be expanded and contracted.

The invention will now be described in detail with reference to the drawings.

FIG. 3 is a sectional view showing one embodiment of the objective lens support device according to the present invention, taken along a plane perpendicular to the optical axis. 4 is a sectional view taken along line BB' in FIG. 3. The objective lens 21 is attached to a cylindrical holding tube 22. The holding cylinder 22 holds the coil bobbin 2 by telescopic leaf springs 23 and 24 with two corrugations placed on both sides of the objective lens in the tracking direction.
It is connected to 5. Coil pobbin 25 has coil 26
A magnet 27 is placed between the bobbin 25 from the inside and outside. Inner cylinder part 2 of magnet 27
8 has a hole 29.8 through which the upper plate spring 23.24 passes.
30 is opened so that the coil bobbin 25 and the lens holding tube 22 can move freely in the optical axis direction, and the coil bobbin 25 is also connected to the frame 31 that supports the magnet 27.
is held by a spiral focusing leaf spring 32. Therefore, when current is applied to the coil 26, the bobbin 25 and the lens holding cylinder 22 move together in the optical axis direction, and this movement can be controlled by the current applied to the coil 26. Focusing can be performed with such a configuration. Next, a mechanism related to tracking will be explained.

Two electromagnets 33 and 33' are attached to the inner surface of the inner cylinder portion 28 of the magnet, facing each other in the tracking direction.
When a current is passed through one of these, the magnetic force generated by this acts on the magnetic holding cylinder 22 and attracts it, causing the objective lens 21 to move in the tracking direction perpendicular to the optical axis.
-B'Moves in the force direction. Therefore, tracking control can be performed by controlling the current flowing through the electromagnet 33 or 33'. Of course, these tracking and focusing controls are performed based on tracking errors and focusing signals detected by some method.

According to the above configuration, the objective lens 21 is supported by the two extensible leaf springs 23 and 24, so that it can accurately move in the tracking direction (X direction) and perform suitable tracking correction. In addition, the optical axis does not tilt or the objective lens rotates due to tracking.

Further, since the leaf springs 23 and 24 extend in a direction perpendicular to the tracking direction, a space can be secured on both sides of the objective lens when viewed in the tracking direction, and the electromagnet 3
3.33' can be placed.

Note that the present invention is not limited only to the above-described embodiments. There are many other possible variations of the spring mechanism that supports the objective lens. Figure 5 shows an example of this as seen from the optical axis direction.
．． The free end of the lens 87 is fixed to the holding cylinder 22 of the objective lens while being shifted in the tracking direction shown by the broken line.

According to the present invention, since the elastic supporting members are disposed on both sides of the objective lens when viewed in the tracking direction, it is possible to support the objective lens so that it moves accurately in the tracking direction, and the objective lens accompanying tracking can be supported. There is no rotation or tilting of the optical axis. Furthermore, a large space can be secured on both sides of the objective lens when viewed in the tracking direction, and a tracking drive device can be placed here.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the configuration of an example of a conventional objective lens drive device, FIG. 2 is a sectional view taken along the optical axis of FIG. A cross-sectional view of one embodiment taken along a plane perpendicular to the optical axis, Figure 4 is Figure 3B.
-B' is a sectional view taken along line B', and FIG. 5 is a line diagram showing a modified example of the objective lens support device of the present invention. 21...Objective lens 22...Lens holding tube 23, 24...Circular plate spring 25 for tracking
・Coil bobbin 27...Magnet 32...Focusing leaf spring 33.33'...Tracking electromagnet 86, 87・
... Tracking leaf spring patent Applicant: Olympus Optical Industry Co., Ltd. Figure 3, Figure 4 (llQ2B2θ

Claims (1)

[Claims] 1. In a device that supports an objective lens for optically reading information recorded on a recording medium so as to be movable in a tracking direction perpendicular to its optical axis, the objective lens is 1. An objective lens support device, characterized in that the objective lens support device is supported by stretchable elastic support members disposed on both sides of the objective lens support device.