JPH03168933A - Optical system driver - Google Patents

Abstract

PURPOSE:To contrive the improvement in driving sensitivity and resonance frequency by forming a magnetic circuit in such a manner as to vary the direction of the effective magnetic field acting on the driving coil of a holding member and the direction of the effective magnetic field acting on the driving coil of a movable member. CONSTITUTION:The driving force is generated in a focusing direction cooperatively with the magnetic field in the direction Y of a magnet 16 when an electric current is passed to a focusing coil 7. Springs 3, 4 are then deformed in the focusing direction and a condenser lens 2 is moved in the focusing direction. The driving force is generated in the tracking direction cooperatively with the magnetic field in the direction Z of the magnet 16 when the current is passed to a coil 10. A carriage 8 is then moved in the tracking direction via rails 11 to make access. A galvanomirror is provided in a stationary optical system 18 to form a series of optical paths, by which the weight of the carriage 8 is reduced and the servo band in the tracking direction is widened. The yoke of the magnetic circuit for driving the carriage 8 and the magnetic circuit of a spindle motor 13 are integrated to a base 12. The spring 3 is placed above the yoke 15 and the spring 4 in a magnetic gap to reduce the size and weight of the carriage 8. The sensitivity and the higher resonance frequency are this improved.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an optical information recording and reproducing apparatus that optically records and reproduces information by irradiating a recording surface of a recording medium with a laser beam. It relates to a system drive device.

[Conventional technology]

When recording and reproducing information on recording media such as optical discs,
In order to properly irradiate a light spot onto the recording surface of a recording medium, a condensing lens that irradiates a light spot is driven in a focusing direction and a tracking direction.

Further, a driving section including a holding member that holds the condensing lens is largely driven in the tracking direction.

Such access is necessary for high-speed recording and reproduction of information.
High speed is required. For this reason, an optical system drive device that aims to reduce the weight by sharing a magnetic circuit for driving the condenser lens and a magnetic circuit for driving a drive unit equipped with a condenser lens holding member is particularly popular. Kaisho 59-1356
It is disclosed in Publication No. 38. As shown in FIGS. 9 and 10, the device is supported such that each stator magnet 31, 32 forms a magnetic gap 38, 39! t=33,
34, the surface of the magnetic strip facing the associated support rods 33, 34 extends parallel to the translation path and the optical axis of the condensing lens 35 to condense the light. The actuator coil means of the lens 35 is composed of two magnetic gears,
At least one of the seven panels is movable.

[Problem to be solved by the invention]

As mentioned above, in an information recording and reproducing apparatus using an optical disc or the like as a recording medium, it is desirable to increase the rotational speed of the optical disc in order to record and reproduce information at high speed. In this case, the acceleration of surface wobbling and eccentricity of the optical disk is 2 times the rotational speed.
Since the value increases in proportion to the power of the power, it is necessary to increase the drive sensitivity of the optical system drive device and to increase the resonance frequency in order to expand the frequency band of drive control.

However, in the conventional example, since the magnetic gaps 38 and 39 formed by providing the actuator coils 36 and 37 of the condenser lens 35 are large, the actuator coils 36 and 37 are located far away from the condenser lens 35. This results in an increase in the size of the condenser lens holding member. For this reason, the weight of the movable part becomes large, and the drive sensitivity in the focus direction decreases, and the resonant frequency of the condenser lens holding member is low, resulting in problems in drive control.

The present invention is proposed to solve the above-mentioned problems.
The purpose of this is to reduce the weight of the optical system drive device, improve the drive sensitivity, and improve the resonance frequency.

[Means and effects for solving the problems] In order to achieve the above object, the present invention provides a holding member for holding an optical element;
a movable member including the holding member; a first coil for driving the holding member in a predetermined direction relative to the movable member;
An optical system drive device including a second coil for driving a movable member in a tracking direction of a recording medium, and a magnetic circuit having a common magnet that generates a magnetic field acting on the first and second coils, A magnetic circuit is formed such that a first direction of an effective magnetic field acting on the first coil and a second direction of an effective magnetic field acting on the second coil are different. Since the required magnetic circuit is formed using a common magnet in this way, the driving coil can be disposed near the condensing lens, and the movable part can be made smaller and lighter.

〔Example〕

1 to 3 show a first embodiment of the present invention, of which FIG. 1 is a partially cutaway perspective view, and FIG. 2 is a partially cut away perspective view.
A sectional view and FIG. 3 are explanatory diagrams showing the magnetic flux distribution of the magnetic circuit.

A condensing lens 2 is fixed on the upper side of the holder l, one end of the two spring members 3 is fixed on the upper side of the holder l, and the other end is fixed on a fixing member 5 fixed to a carriage 8 made of plastic. The two spring members 4 are also fixed in the same manner. This spring member is made of a thin metal such as beryllium copper, and has a damper integrally attached to its outer periphery. Furthermore, two focus coils 6 and 7 wound in a square shape are bonded to both sides in the Y direction (tangential direction). An opening 8a opening toward the holder 1 is formed at the center of the carriage 8, and a reflecting prism 9 is provided for allowing light incident from an opening 8b formed at the side of the carriage 8 to enter the condenser lens 2. Openings 8c are formed on both sides of the opening 8a, and the carriage 8 is inserted into the openings 8c.
A coil 10 wound in the shape of a rectangular column for driving the motor in the tracking direction is fixed. Further, holes 8d for bearings are formed at both ends of the carriage 8 in the parallel direction of the coils 10, and the rails 11 are inserted through the holes 8d, thereby making the carriage 8 movable.

12 is a base formed by pressing an iron plate;
This base 12 is provided with a spindle motor 13 together with its drive circuit, and a turntable 14 is mounted on the spindle motor 13. An outer yoke 15 is formed by punching out a slit in the center of the base 12. A magnet 16 magnetized in the Z direction (focus direction) is fixed to the lower surface of the outer yoke 15, and the coil 10 is attached below the magnet 16. An inner yoke 17 is provided which passes through the inside of the yoke and has both ends fixed to the base 12. In addition, outer yoke 1
The spring 3 is located above the carriage 5, and the spring 4 is located on the side of the carriage 8 in the X direction (tracking direction). Spindle motor 13 of base 12
A fixed optical system 18 having a light emitting element, a light receiving element, etc. is fixed to the lower side of the other end corresponding to .

FIG. 3 is for explaining the magnetic flux distribution, and of the two sides parallel to the X direction of the focus coil 7, a portion 7a is located slightly above the upper surface of the magnetic eye 6, and a portion 7b is The lower surface is made to be at approximately the same height as the lower surface of the magnetic eye 6. The direction of the magnetic field between the magnet eye 6 and the inner yoke l7 is from the magnet 16 to the inner yoke 17.
, and the direction of the magnetic field on the side surface of the magnet 16 in the Y direction is N
It leaves the pole and moves in an arc toward the south pole. Therefore, a magnetic field approximately in the Y (-) direction acts on the portion 7b of the focus coil 7, and a magnetic field approximately in the Y (10) direction acts on the portion 78. As a result, when a current is passed through the focus coil 7, the forces in the focus direction generated in the coils 7a and 7b are in the same direction, and a driving force in the focus direction can be obtained. The reason why the width of the outer yoke 12 in the Y direction is made shorter than the width of the magnet 16 in the Y direction is to increase the magnetic field acting on the portion 7a of the focus coil 7.

In this embodiment, as described above, when a current is passed through the focus coil 7, a driving force in the focus direction is generated in cooperation with the Y-direction magnetic field of the magnet 16, and the spring 3
, 4 are deformed in the focus direction, and the condenser lens 2 can be moved in the focus direction. Also, coil 1
When a current is applied to 0, a driving force in the tracking direction is generated in cooperation with the magnetic field of the magnet 16 in the Z direction, and the carriage 8
moves in the tracking direction via the rail 11 to access it. In addition, in this embodiment, a galvano mirror (not shown) is provided in the fixed optical system 18,
The weight of the carriage 8 is reduced by forming a series of optical paths, and the servo band in the tracking direction is increased.

According to this embodiment, the yoke of the magnetic circuit for driving the carriage 8 and a part of the magnetic circuit of the spindle motor 13 are integrated into the base 12, so the number of parts is reduced and the device is made smaller. At the same time, assembly of the device becomes easy. Furthermore, since one of the springs 3 and 4 supporting the holder 1 is located above the outer yoke 15 and the other in the magnetic gap, the space near the springs 3 and 4 is reduced, and the carriage 8 is made smaller. It is possible to realize weight reduction, improve drive sensitivity, and improve high-order resonance frequency.

Furthermore, since the four springs 3 and 4 can be spaced apart from each other in the Z direction and the . Furthermore, since two of the four sides of the focus coil 7 are used as effective parts, the utilization rate of the coil is high. Further, since the holder 1 does not have a large opening for installing an inner yoke or the like, the rigidity is high and the resonance frequency can be improved. In addition, since the magnetic gap of the magnetic circuit is provided with the outer yoke 15 without opening in the 2(+> direction), the magnetic gap of the magnetic circuit is Z(10).
Since the leakage magnetic field in the direction is small, it is possible to reduce the adverse effects when recording and reproducing, for example, a magneto-optical recording medium.

4 to 7 show a second embodiment of the present invention, and parts corresponding to those in the first embodiment are given the same reference numerals.

A condensing lens 2 is provided on the top of the holder 1.
Four tracking coils 19 are attached to the side corners, which are wound in a square shape and bent along the corners. Furthermore, a focus coil 7 is wound around the outer periphery of the tracking coil 19.

A bearing hole 20 is formed in the center of the holder 1, and a shaft 21 is inserted through the hole 20 so that the holder 1 can be moved in the focusing direction and the shaft rotation direction. A damper 22 made of silicone rubber is bonded to the protrusion 1a formed on the lower surface of the holder 1 and the protrusion 8e formed on the upper part of the carriage 8, so that the holder 1 is elastically supported with respect to the carriage 8. There is. A reflecting prism 9 is provided in the holder 1 portion below the condensing lens 2, and the holder 1
Two yokes 23 are provided on the inner side of the yokes 23 so as to partially correspond to the focus coil 7 and the tracking coil 19. Two openings 8 formed in the carriage 8
c is provided with two coils 1o for driving the carriage 8 in the tracking direction. Further, the rails 11 are inserted into bearing portions 8d formed at both ends of the inner yoke 17 of the carriage 8 in the parallel direction, thereby making the carriage 8 movable in the tracking direction. A cover 24 with a gap formed only around the condenser lens 2 is provided on the upper part of the carriage, and a spindle motor 13 is provided on a base 12 formed by pressing an iron plate.

An opening 25 for arranging the carriage 8 is formed in the center shaft of the base 12, and an outer yoke 26 is arranged in the outer circumferential direction at the lower end of the opening 25, and an outer yoke 26 is arranged at the upper part of the outer yoke 26 near the opening 25. A magnet 16 is fixed. As shown in FIG. 7, the X of the magnet 16 on the base 12
A protrusion 28 is formed on the upright portion 27, which is formed by bending the vicinity of the directional end by 90'', and is fitted into a recess 29 formed at the end of the inner yoke 17, thereby positioning and fixing the protrusion 28.

Note that a rail receiving portion 30 is formed in the upright portion 27, and the rail 11 is brought into contact with the rail receiving portion 30, and is positioned and fixed by a spring (not shown). Spindle motor 1 of base l2
A fixed optical system 18 is disposed at the opposite end corresponding to 3.

FIG. 6 is an explanatory diagram showing the magnetic flux distribution. The yoke 23 has a U-shaped cross section, and one end faces the magnetic pole surface on the inner yoke 17 side of the magnet 16.
The other end faces the side surface of the outer yoke 26.

Then, the magnetic flux leaving the magnet 16 heads in the Z direction, passes through the coil 10, passes through the inner yoke 17, passes through the outer yoke 26, and returns to the magnet 6, and the magnet 1.
The magnetic flux emitted from the X-direction end of the magnet 6 heads in the Y direction, passes through the focus coil 7 and the tracking coil 19, passes through one end of the yoke 23, passes through the outer yoke 26 from the other end of the yoke 23, and returns to the second magnet 16. The magnetic path is strictly controlled.

Since this embodiment is configured as described above, when a current is applied to the focus coil 7, the magnet l-16 and the yoke 2
3, a driving force in the focus direction is generated, the holder 1 rubs in the Z direction along the shaft 21, and the condenser lens 2 moves in the focus direction. On the other hand, when current is applied to the tracking coil 19, the holder 1
rotates around the shaft 21, and the condenser lens 2 moves in the tracking direction. Further, when a current is passed through the coil 10, it cooperates with the magnetic field in the Z direction of the magnet 16, and a driving force in the tracking direction is generated, so that the carriage 8 moves in the tracking direction along the rail 11 and accesses.

In this embodiment, since the yoke 23 is fixed to the carriage 8, the magnetic path acting on the focus coil 7 and the tracking coil 19 becomes a closed circuit, and a higher uniform magnetic field is obtained, which improves the drive sensitivity of the holder 1. will improve. Also,
The carriage 8 has a yoke 21, which makes the movable part heavier when accessing it, but since this is a part of the magnetic circuit for driving the holder IN that corresponds to the yoke, the increase in weight is due to the magnetic circuit for driving the holder l. This is approximately 1/4 or less compared to the case where all of them are fixed to the carriage 8, so there is no problem. Further, since the outer yoke 26 uses a part of the base 12 and is not formed separately, the part that can be used as a magnetic circuit can be not only the part in contact with the magnet 16 but also the entire surface. In addition, when the outer yoke is cut out as in the first embodiment, it is necessary to increase the cross-sectional area so that the magnetic flux passing through the outer yoke does not become saturated, so the plate thickness of the base 12 is increased. Must.

However, in the case of this embodiment, since the entire surface of the base 12 can be used as a magnetic circuit, the plate thickness of the base 12 can be made thinner, so that the workability of the base 12 is good and the base 12 can be used as a magnetic circuit.
The weight can be reduced.

FIG. 8 shows a third embodiment of the present invention.
In this embodiment, a yoke 3 is attached to one corner of the magnet 16.
1 is fixed, and the magnetic field acting on the focus coil 7 and the tracking coil 19 between the yoke 31 and the yoke 23 is made higher, thereby improving the drive sensitivity. Note that if the yoke 23 and the yoke 26 are integrated, the weight of the movable part can be reduced, which will be more advantageous for high-speed access.

[Effects of the Invention] As described above, according to the present invention, a common magnet can be used to combine a coil for driving an optical element holding member in a predetermined direction and a coil for driving a movable member including the optical element holding member in a predetermined direction. Since the magnetic circuit is formed so that the direction of the effective magnetic field is different, the driving coil can be placed near the condensing lens, making the movable part smaller and lighter, and improving the driving sensitivity of the condensing lens. It is possible to improve the Furthermore, the resonant frequency of the optical element holding member can be increased and control becomes easier.

Furthermore, by reducing the weight of the movable member, high-speed access is possible when driving largely in the tracking direction.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of the first embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of the same, FIG. 3 is an explanatory diagram of the magnetic flux distribution of the magnetic circuit, and FIG. teeth,
The plan view according to the second embodiment of the present invention, FIG.
A cross-sectional view, FIG. 6 is an explanatory diagram of the magnetic flux distribution of the same magnetic circuit, and FIG.
FIG. 8 is a perspective view of the fixing location of the inner yoke.
The explanatory diagrams of the magnetic circuit according to the embodiment, FIGS. 9 and 10, show conventional examples.1.
・Holder 2...Condensing lens 3...Spring 4...Spring 6...Focus coil 8...Carriage 10...Coil 12...Base 15...Outer yoke 16... Magnet 17... Inner yoke Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A holding member that holds an optical element, a movable member including the holding member, a first coil for driving the holding member in a predetermined direction with respect to the movable member, and a movable member. An optical system drive device including a second coil for driving a member in a tracking direction of a recording medium and a magnetic circuit having a common magnet that generates a magnetic field acting on the first and second coils, a first direction of an effective magnetic field acting on the first coil;
An optical system driving device characterized in that a magnetic circuit is formed so that the second direction of an effective magnetic field acting on the second coil is different from the second direction.