JPS5968841A - Driver of objective lens - Google Patents

Abstract

PURPOSE:To control accurately the position of an objective lens, by coupling a connecting member for yoke vibration prevention to an upper open end of a magnetic yoke formed in channel shape, and enclosing the upper open end of the yoke to decrease the sound of a driver. CONSTITUTION:A quadrangle frame is formed with the yokes 4a, 4b and the connecting members 7a, 7b. The vibration of the yokes 4a, 4b is blocked and the frequency peak of the unpleasantest sound at the driving of an objective lens is reduced by about >=10dB. Further, the vibration of the yokes 4a, 4b and the permanent magnets 5a, 5b is blocked, the magnetic field formed with the permanent magnets 5a, 5b and the yokes 4a, 4b is stable without oscillation allowing to control accurately the objective lens in terms of time and space. Moreover, no magnetic field is oscillated, unnecessary oscillation of the objective lens 1 is eliminated, an abnormal oscillation in an electric circuit for position control of the objective lens 1 using a reflected light from the disc is prevented and the gain control range is extended by about >=20dB.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a disk-shaped recording medium (hereinafter simply a disk 218,
In a playback device that reads information optically by projecting a light spot onto an information track on which a high-density digital signal is recorded (called ``-''), the position of the optical nubosoto is accurately corrected and controlled for the signal on the information track. The present invention relates to an objective lens driving device that controls the position of an objective lens relative to a disk surface in order to do so.

In more detail, for example, the amount of eccentricity of the information track with respect to the center of rotation of the disk, that is, the tracking control that corrects the relative positional deviation in the radial direction of the disk, the warping of the disk itself, and the relative occurrence due to the rotational movement of the disk. Focus control is performed to control the distance between the objective lens and the information track position in response to the deflection of the Dinuk surface.

Conventional Structure and Problems Generally, this type of optical information reading device is used in video discs on which video signals are recorded and digital audio discs on which encoded audio signals are recorded. -0・ It is applied to high-density information recording and reproducing devices such as those related to users.

This involves recording encoded video signals, audio signals, and various information on a disk as information tracks.
While rotating this disk at high speed, light emitted from a light source such as a laser beam is focused on the information rack of the disk, and by reading the reflected light from the edges of the disk surface, the original recorded information can be retrieved. It is something to be regenerated.

This optical information reading device can record information at an extremely high density, and has the advantage of being able to record information at a higher density, with higher precision, and with higher performance than conventional analog systems.

On the other hand, since the width and pitch of the information tracks are extremely small, in order to faithfully reproduce this high-density information, the convergence diameter of the optical spot for reading must also be kept extremely small. In order to accurately follow the optical spot with respect to the information track, there is a problem in that the objective lens must be accurately driven and controlled so as to prevent relative positional deviation from the disk.

In order to solve this problem, conventional techniques have been used to electrically detect the reflected light from the disk surface and control the reading light spot position to match the information track position.

A conventional objective lens driving device will be explained below. FIG. 1 is an exploded perspective view of a conventional objective lens drive device.
1 is an objective lens; 2 is a holding part for holding the objective lens 1; 3a and 3b are fixed to a case (not shown) at both ends, which are the holding part 2 and a fixed part, respectively; Supporting means 4a and 4b for making the lens 1 follow the information track of the disk are U-shaped magnetic yokes, the lower part of which is fixed to a case which is a fixed member. Permanent magnets 5a and 6b are fixed to the yokes 4a and 4b, and as shown in FIG. 1, they are coaxial and magnetized in opposite directions, and a magnetic gap is formed by the yokes 4a and 4b, respectively. are doing. ea and eb are two coils wound around the holding part 2 so as to cross 51.

The operation of the objective lens driving device for the sub-freezer configured as described above will be described below.

Since the two support means 3a and 3b are each formed by two parallelogram frame bodies made of an elastic body and a rigid body, the objective lens 1 is movable in the F direction and the T direction in FIG. It is restricted from moving in a direction perpendicular to these two directions. Therefore, if you control the direction and amount of current flowing through the two coils/l/6a and 6b, these coils)v6
The objective lens 1 can be freely moved in the F direction and the T direction by the electromagnetic action acting between the T & 6b and the permanent magnets 5a and 5b.

In particular, forming the yokes 4a and 4b in a U-shape as described above has the advantage that even if the focal length of the objective lens 1 is short, magnetic leakage is small and magnetic flux can be concentrated in the magnetic gap.

However, in the above conventional configuration, the coils 6a,
Ibis and carp 7 that move the objective lens 1 by passing a current through 6b
Due to the magnetic field generated by 1z6a, 6b, permanent magnet 51L, sb and yokes 4a, 4b
receives the magnetic force, and as shown in FIG. 3, the yoke 4a.

The upper open end of 4b vibrates. That is, the yoke 4a,
Since 4b is formed in a U-shape, the yokes 4a, 4
Both pieces of b resonate as if they were a tuning fork and generate sound. This sound has the problem of greatly degrading the quality of products equipped with this objective lens drive device, such as digital audio disc players. Furthermore, when the yokes 4a and 4b resonate as shown in ``2'',
The permanent magnets 5a and 5b fixed to the yokes +a and 4b vibrate minutely, and the magnetic fields created by the permanent magnets 5a and 6b that must not fluctuate accordingly vibrate in small increments.
There has been a problem in that it is difficult to accurately control and move the objective lens temporally and spatially. Furthermore, when the reflected light from the disk surface is electrically detected and the position of the objective lens 1 is controlled so that the position of the lens coincides with the position of the information track, the above-mentioned permanent magnet 51L,
In order to prevent the small-step vibrations of the magnetic field generated by the magnetic field 5b from causing the objective lens 1 to vibrate unnecessarily in small steps, the electrical circuit for controlling the position of the objective lens 1 using the reflected light from the disk oscillates. However, the gain control range becomes narrower.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems, suppresses the noise generated by the resonance of the yoke, increases the quality of the product, and improves the quality of the product.
Furthermore, the objective lens can be precisely controlled temporally and spatially,
Another object of the present invention is to provide an objective lens driving device that can increase control gain by reducing oscillation of a servo circuit for controlling an objective lens.

DESCRIPTION OF THE INVENTION According to the present invention, the open ends of a yoke formed in a U-shape are connected by a connecting member. By doing this, yoke resonance can be reliably prevented and problems caused by yoke resonance can be solved all at once.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 3, mainly in terms of its differences from the conventional apparatus shown in FIG. 1.

In FIG. 3, the same components as in FIG. 1 are given the same numbers, 1 is the objective lens, 2 is the holding member, 3a and 3
b is a support means, 4a and 4b are magnetic material yokes, 5a and 5b
is a permanent magnet, and 6a and 6b are two coils wound crosswise around the holding member 2, which have the same structure as the conventional example. 7a and 7b are connecting parts made of non-magnetic material for vibration prevention of the yokes 4a and 4b, and the convex parts of the connecting members 7a and 7b are inserted into the recessed parts of the upper open ends of the yokes 4a and 4b formed in a U-shape. are fitted and glued. As a result, the upper open ends of the yokes 4a and 4b are closed, and the fourth
As shown in the figure, yokes 4a and 4b and connecting members 7 colors and 7b
This forms a rectangular frame, which is much stronger against bending than the conventional examples shown in FIGS. 1 and 2.

As a result, the vibrations of the yokes 4a and 4b are inhibited, and the frequency peak of the most annoying sound when driving the objective lens is reduced by about 10 dB or more, making it audible and 9% quieter. The quality of the product increases. Furthermore, since the vibrations of the yokes 4a and 4b and the permanent magnets 5a and 6b are prevented,
The magnetic field formed by the permanent magnets 5a and 6b and the yokes 4a and 4b is stable without vibration, and the objective lens can be controlled temporally and spatially accurately. Furthermore, since the magnetic field does not oscillate, unnecessary vibrations of the objective lens 1 are eliminated, and abnormal oscillations of the electric circuit for controlling the position of the objective lens 1 using reflected light from the disk are eliminated, and the usable control range is approximately 20 + iB. Can be expanded.

In the above embodiment, the first magnetic generator is a permanent magnet of 5N.
, 5b, and the second magnetic generator is a carp zL/6a,
sb, but the former may be composed of a coil and the latter a permanent magnet, or both may be composed of a coil and a coil. , a moving iron type electromagnetic effect can also be used. However, in the embodiment, permanent magnets 6 are provided in the yokes 4a and 4b.
a, 5b, and this permanent magnet 6&, 6107
Since the upper end of b is quite close to the connecting parts 7a and 7b, the connecting members 7a and yb are made of non-magnetic material in order to avoid leakage of magnetic flux, but there is no problem like this. If so, it may be made of magnetic material.

Effects of the Invention As described above, the present invention connects a coupling member for preventing yoke vibration to the upper open end of a U-shaped magnetic yoke, thereby closing the two-part open end of the yoke. This is what I did. In this way, the sound of the objective lens drive device can be significantly reduced, which not only increases the quality of the product, but also
An excellent effect can be obtained in that the position of the objective lens can be accurately controlled.

[Brief explanation of drawings]

Figure 1 is an exploded perspective view of a conventional objective lens drive device;
3 is a perspective view of an embodiment of the present invention, and FIG. 4 is a sectional view of the main part. 1... Objective lens, 2... Holding member,
3...Supporting means, 4...Yoke, 6.
... Permanent magnet, 6. Old... 11 K--. Coil, 7... Connection member. Name of agent: Patent attorney Toshio Nakao and 16 others 244

Claims (1)

[Claims] A holding member movably disposed facing the encoded information track provided on a disk-shaped recording medium, an objective lens attached to this holding member, and a fixing member such as a case or chassis for fixing the holding member. a support means movably supported with respect to Vc and for causing the objective lens to follow the information trunk; and a yoke made of a magnetic material disposed near the holding member and formed in a U-shape. and,
a first magnetic generator attached to the yoke; a connecting member coupled between both ends of each yoke so as to close the U-shaped open end of the yoke; and a second magnetic generator attached to the holding member. An objective lens driving device comprising: a generator;