JPS5987630A - Optical head driver - Google Patents

Abstract

PURPOSE:To obtain an optical head driver with which the loss is reduced for the light quantity of an objective lens and no lateral shift is produced with the reflected light, by driving the objective lens in the optical axis direction and at the same time driving simultaneously both the objective lens and a mirror which changes the direction of the light beam going in the radius direction of a disk toward the optical axis of the objective lens in the radius direction of the disk. CONSTITUTION:An objective lens 2 is driven in the optical axis direction of an objective lens 2 to the fluctuation of an information track (1-1) toward the optical axis which is due to the revolution of an optical disk 1. Therefore the condensing point of a light beam 4 follow the above-mentioned fluctuation. While the follow-up is secured for the fluctuation of the track (1-1) in its radius direction by driving a mirror 3 set into the optical path of the beam 4 and the lens 2 in the radius direction of the disk 1. A sliding cylinder 5 is driven in the optical axis direction by flowing a driving current to an optical direction driving coil 11. Therefore the lens 2 is driven in the optical axis direction. When the driving current is supplied a radius direction driving coil, both the lens 2 and the mirror 3 are driven in a bodt in the radius direction.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an optical head drive device used for recording and reproducing optical information discs (hereinafter simply referred to as discs) such as optical video discs and optical information files. It is related to.

[Prior art]

An optical head is used to record information on a disk or to reproduce information recorded on a disk. This optical head is configured so that a laser beam guided from a light source to an objective lens by a mirror is focused on the information surface of the disk, and a light receiving element detects the reflected light modulated by the diffraction phenomenon caused by the bits of the information track. ing. However, since the position of the information track on the disk changes due to deformation, eccentricity, etc. of the disk, it is necessary to make the focal point of the laser beam follow this change.

For this reason, conventionally, objective lens driving devices as shown in FIGS. 1 and 2 have been used.

In FIG. 1, the objective lens 2 is not shown for variations in the optical axis direction (hereinafter referred to as the Z-axis direction in the drawings) of the objective lens 2 of the information track (1-1) due to the rotation of the disk 1. By driving in the optical axis direction using a voice coil type linear motor or the like, the focal point of the light beam 4 is made to follow this variation. In addition, in response to fluctuations in the radial direction (hereinafter referred to as the X-axis direction in the drawings) of the disk 1 on the information track (1-1), the light beam is 4 to make the focal point follow this variation.

In such a system as shown in FIG. 1, the objective lens has a diameter of 20 mm.
It is necessary to make the incident light beam diameter d of the light beam 4 larger by the size of the lateral deviation r of the incident light beam due to the deflection of the light beam 4. Therefore, there is a drawback that the objective lens 2 becomes larger.

In addition, since the angle of incidence of the light beam 4 entering the objective lens 2 changes, the objective lens 2 suffers from comatic aberration in addition to spherical aberration.
It is necessary to correct field curvature, etc., which makes it expensive. Furthermore, there is a drawback that the reflected light (4-2) of the light beam 4 undergoes lateral movement due to the deflection of the light beam 4, making it difficult to accurately control the focal point. FIG. 7 is an explanatory diagram showing another method of the objective lens driving device. In FIG. 2, in order to make the convergence point of the light beam 4 follow the fluctuations in the optical axis direction and the radial direction of the information track, the objective lens 2 is used, for example, in accordance with Japanese Patent Application Laid-Open No.
It is driven in the optical axis direction and radial direction by the method shown in the above publication.

By the way, in the system shown in FIG. 2, the mirror 3 is fixed, and the angle of incidence of the light beam 4 entering the objective lens 2 does not change. For this reason, the objective lens 2 only needs to correct spherical aberration, making it cheaper than the system shown in FIG. However, the incident luminous flux diameter d of the light beam 4 needs to be larger than the aperture of the objective lens 2 by the amount of movement of the objective lens 2 in the radial direction, which has the drawback of a large light loss.

Furthermore, as the objective lens 2 moves in the radial direction, the reflected light (4-2) of the light beam 4 moves laterally, making it difficult to accurately control the focal point. Purpose] An object of the present invention is to provide an optical head that eliminates the drawbacks of conventional objective lens drive devices, allows the use of inexpensive objective lenses, reduces light loss in the objective lens, and prevents lateral movement of reflected light. The purpose of the present invention is to provide a driving device.

[Summary of the invention]

In order to achieve the above object, the present invention drives the objective lens in the optical axis direction, and uses a 1W" objective lens to direct the light beam traveling in the radial direction of the disk in the optical axis direction of the objective lens. The mirror that changes direction is simultaneously driven in the radial direction of the disk.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 3 is a diagram explaining the principle of the optical head driving device according to the present invention. In FIG. 3, by driving the objective lens 2 in the optical axis direction, the optical beam 4
The focal point of the light is made to follow this fluctuation. In addition, for the radial variation of the tit report track-1), the light beam 4
The mirror 3 and objective lens 2 provided in the optical path of the optical disc 1 are moved in the radial direction of the optical disc 1 to follow this variation.

In the 30th system, the objective lens 2 may be an inexpensive one that corrects only spherical aberration, and the aperture of the objective lens 2 and the luminous flux diameter of the light beam 4 can be made approximately equal, resulting in less visual loss. Further, since no j'ji movement occurs in the reflected light (4-2), precise control of the focal point can be performed.

FIG. 4, FIG. 5, and FIG. 6 are a plan view, a side view, and an exploded perspective view, respectively, showing an embodiment of an optical head driving device according to the present invention. In these figures, objective lens 2
is coaxially attached to the sliding tube 5, and the sliding tube [5 is supported by the support tube 6 so as to be slidable in the optical axis direction (Z-axis direction) of the objective lens 2. One end of the support tube 6 is fixed to the side surface of the support tube 6, and the other end is fixed to the protrusion (7-1) of the base 7 in the radial direction of the disk ( It is supported so that it can be displaced only in the X-axis direction. Since the groove (5-1) provided on the side surface of the sliding tube 5 engages with the support body 8, rotation of the sliding tube 5 and the support tube 6 is restricted.

Further, a mirror 3 is fixed to the support cylinder 6, which is parallel to the disk surface and for changing the direction of the optical path of the light beam in the radial direction of the disk toward the optical axis direction of the objective lens 2.
A protrusion (6-1) through which the light beam passes is provided. As an electromagnetic drive means for driving the sliding tube 5 in the optical axis direction of the objective lens 2 and the radial direction of the disk, an optical axis direction driving coil 11 whose winding surface is the XZ plane is installed on the side surface of the sliding tube 5.
and the radial drive coil 10 are fixed, and the part where the tension lines of the two intersect at right angles is the permanent magnet (9-1) and the yoke (9-2).
, (9-3) in the magnetic gap of the magnetic circuit 9. The magnetic circuit 9 is connected to the protrusion of the base 7 (7-2
) FIG. 7 is an explanatory diagram of the electromagnetic driving means. Since the permanent magnet (9-1) has magnetic poles on both sides in the X-axis direction, lines of magnetic force 12 in the X-axis direction are present at the part where the wires of the optical axis direction drive coil 11 and the radial direction drive coil 10 intersect at right angles. Therefore, when the drive current (11-1) is applied to the optical axis direction drive coil 11, the optical axis direction drive coil 11 is driven in the optical axis direction, and similarly, the drive current (10-1) is applied to the radial direction drive coil 10. ), the radial drive coil is driven in the radial direction.

In the above configuration, by applying a drive current to the optical axis direction drive coil 11, the sliding tube 5 is moved in the optical axis direction, and therefore the objective lens 2 is driven in the optical axis direction. When a drive current is applied to the radial drive coil, the sliding tube 5 and the support tube 6 are driven together in the radial direction, and therefore the objective lens 2 and the mirror 3 are driven together in the radial direction.

In this embodiment, the support body 8 is made of a plate spring or a plate rubber, but any support body 8 may be used as long as it supports the support tube 6 so that it can be displaced only in the radial direction. Further, the electromagnetic driving means may have a different configuration as long as it drives the sliding tube 5 in the optical axis direction and the radial direction.

As explained above, in the conventional objective lens drive device, the optical axis of the reflected light shifts laterally, making it difficult to accurately control the focal point and requiring an expensive and large objective lens. However, in the optical head drive device of the present invention, the objective lens is driven in the optical axis direction, and the objective lens and the disk surface are connected to each other. By driving the mirror in the radial direction of the disk and the mirror that redirects the parallel light beam in the radial direction of the disk in the direction of the optical axis of the objective lens, there is no lateral movement of the optical axis of the reflected light, making it possible to create an inexpensive objective lens. Furthermore, the loss of light quantity is small, making it possible to solve the above-mentioned drawbacks of the prior art.

[Brief explanation of the drawing]

1 and 2 are diagrams explaining the principle of a conventional objective lens drive device, FIG. 3 is a diagram explaining the principle of an optical head drive device according to the present invention, and FIGS. 4, 5, and 6 are respectively A plan view, a top view, and an exploded perspective view showing an embodiment of the optical head drive device according to the present invention, and FIG. 7 is an explanatory diagram of the electromagnetic drive means in this embodiment. Objective lens, 3...Mirror, 5
...Sliding tube, 6... Support tube, 8...
...Elastic support agent Patent attorney Akio NamikigtFigure 2Figure #4Figure tJ5Figure wE 3Figure 7Figure 6

Claims (1)

[Claims] 1) An optical head that includes at least an objective lens for focusing light on the information recording/reproducing surface of the disk and a mirror for guiding a light beam from a light source to the objective lens relative to the disk. An optical head driving device for moving the objective lens, the device comprising: a first member that holds the objective lens; a second member; a third member movably supporting the second member in the radial direction of the disk; a first driving means for driving the first member in the optical axis direction; and a second driving means for driving the second member in the disk radial direction, so that only the objective lens can be driven in the optical axis direction, and the objective lens and the mirror can be driven simultaneously in the disk radial direction. An optical head drive device featuring: