JP2003338069A - Optical head device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical head provided with a relay lens driving apparatus which corrects the aberration of a spherical surface caused by the thickness error of the cover layer of an optical disk without being influenced by vibration, shock, etc. <P>SOLUTION: The relay lens driving apparatus 7 is provided with: a lens 32 for correcting the aberration of a spherical surface; a lens holder 27 for holding the lens 32; first and second cylindrical guide rails 25a and 25b parallel to a lens optical axis; first and second round holes 47a and 47b formed at the lens holder 27 and fitted to the guide rails 25a and 25b; a long hole 48 formed at the lens holder 27 and fitted to the second guide rail 25b; a coil 21 which has two straight parts perpendicular to the guide rails 25a and 25b, whose coiling shaft is perpendicular to the guide rails 25a and 25b, and which is fixed to the lens holder 27; and a permanent magnet 26 facing the coil 21. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head mounted on an optical disk drive, and more particularly to an optical head equipped with a relay lens for correcting spherical aberration.

[0002]

2. Description of the Related Art In recent years, for example, in the field of recording or reproducing using an optical disk as a recording medium, recording and reproducing are performed on a small-sized and large-capacity optical disk for handling high-definition still images and moving images. Development of an optical disk recording / reproducing device is in progress. As a technical method for realizing a large capacity, there is a reduction in the wavelength of the laser light source emitted from the optical pickup device and a reduction in the beam spot diameter due to the high NA (NA: numerical aperture) of the objective lens.

Generally, in an optical disc, an information recording surface is covered with a transparent optical disc substrate (cover layer), and a beam is emitted through the optical disc substrate. If the NA is increased, coma tends to occur due to a change in the angle between the objective lens and the disc substrate. The causes of this angle change include the warp of the optical disc itself, the inclination of the spindle motor that rotates the optical disc, and the inclination caused by the objective lens drive mechanism mounted on the optical head.
It is difficult to increase the angular accuracy in proportion to the increase. The coma aberration caused by the tilt occurs when passing through the disc substrate, so that if the substrate thickness is made thin, the coma aberration decreases due to the tilt. Therefore, in an optical disc system using an objective lens with a high NA, it is necessary to use an optical disc with a thin substrate to make it resistant to tilt errors.

On the other hand, since the objective lens is designed so as to form a beam spot with little spherical aberration on the information recording surface of the optical disc when passing through a substrate having a certain optical thickness, the substrate thickness is designed to be small. If there is an error with respect to the assumed optical thickness, spherical aberration will occur. In the case of irradiating a laser on two information recording surfaces from the same direction (as opposed to a double-sided disk which records and reproduces from different directions) like a two-layer disk, the optical thickness of the transparent layer substrate in each layer is , Definitely different. The spherical aberration due to this substrate thickness error also becomes very large as the NA increases, and N
With a lens having a large NA of A0.85, it becomes difficult to ignore the influence of the optical thickness error of the substrate of the optical disc manufactured by the usual manufacturing method.

The optical thickness referred to here is a value determined by the thickness and the refractive index of the optical disk substrate through which light is transmitted. Even if the optical thickness is different, the spherical aberration of the beam spot generated by passing through the substrate is spherical aberration. The optical thicknesses are considered to be equal when the sizes of the two match. Even if the substrate consists of multiple layers, depending on the thickness and refractive index of each layer,
The optical thickness of the substrate is determined. (Comment: This is done because it is not exactly a product.) Now, various methods are disclosed in Japanese Patent Laid-Open No. 5-151609 as a method for correcting spherical aberration due to a change in the thickness of the optical disk substrate. ing. Among them, an aberration correction method using a so-called relay lens composed of a convex lens and a concave lens is presented. By arranging a relay lens consisting of a convex lens and a concave lens before the light emitted from the laser diode enters the objective lens, and changing the position of either the convex lens or the concave lens, the spherical surface of the beam entering the optical disc from the objective lens. By changing the aberration and canceling the spherical aberration generated in the optical disc, a beam spot with less aberration is generated on the optical disc. In this publication, a VCM (voice coil motor) is used as a drive mechanism for the objective lens, but its structure and control method are not shown.

Japanese Laid-Open Patent Publication No. 5-266511 discloses a somewhat detailed system. Here, as a drive means for the relay lens, a system is shown in which a rack is attached to the lens side to be moved and the pinion is rotated to move the rack. Further, there is disclosed a method in which the substrate thickness recorded on the disk or the substrate thickness is measured by a measuring device provided in the recording / reproducing apparatus, and the position of the relay lens is set so as to correspond to the measurement.

Japanese Unexamined Patent Application Publication No. 2001-28147 also discloses a somewhat detailed system. In this example, the distance between the first lens and the second lens of the relay lens can be changed by the voice coil motor. This voice coil motor is designed so that the applied current and the amount of change in the lens interval have a substantially linear relationship. In order to make the lens interval suitable for recording / reproducing information of the first layer or the second layer, it is sufficient to apply currents having the same magnitude but opposite directions to the coil.

[0008]

However, the above-mentioned conventional technique has a plurality of problems.

In the case of Japanese Unexamined Patent Publication No. 5-151609, the drive mechanism using the VCM is not described in detail as described above. However, in a lens moving mechanism for correcting spherical aberration, a general simple VCM cannot secure sufficient performance, and therefore the technique disclosed in this publication cannot manufacture a practical optical head.

Japanese Patent Laid-Open No. 5-266511 discloses an example of using a rack and a pinion as a moving device for a relay lens as described above. The optical disk device in which the optical head is mounted is also used in a portable computer, a music reproducing device, etc., and is required to be extremely small. However, in the structure according to this publication, there are many components such as a rotary motor, a mechanism for converting power transmission and rotary motion of a rack and a pinion into a linear motion, and components.
It is difficult to miniaturize.

In the lens moving mechanism for correcting spherical aberration, the moving lens must be a mechanism that moves only in the optical axis direction. When the tilt and the optical axis shift occur due to the movement of the lens, aberration occurs and a good beam spot cannot be obtained. When the optical axis shifts further, the direction of the light flux from the relay lens toward the objective lens changes,
There is also a problem that the beam spot position changes. If the beam spot position is displaced in the disc radial direction, the tracking servo mechanism of the optical drive device
By moving the objective lens actuator in the tracking direction, it is attempted to prevent the beam spot from deviating from the track. However, there is an upper limit in the moving acceleration and the moving amount of the beam spot. Therefore, the tilt of the relay lens and the deviation of the optical axis must be suppressed as much as possible. In the conventional technology, no consideration is given to this point. Even in this publication, there is no description of a mechanism that satisfies this.

In practice, it is considered difficult to design a lens moving mechanism using a rack and a pinion so that these problems do not occur. For example, since there is backlash in a normal rack and pinion mechanism, vibration,
Very vulnerable to shock. Even if it's not portable
Even in stationary equipment, an optical disk drive device has a vibration generating element such as a spindle motor for rotating a disk and an objective lens actuator. In addition, a vibration source such as a fan often exists in a device such as a computer in which the optical disk drive is mounted. The presence of backlash is susceptible to these vibrations. That is, it is difficult to operate the position of the relay lens by the rack and pinion mechanism while recording / reproducing information on / from the optical disc.

In the case of the VCM disclosed in Japanese Unexamined Patent Publication No. 2001-28147, both sides of the second lens are supported by the leaf springs, but such a support structure of both ends is linear in the moving direction. It is difficult to secure the characteristics, and only a very short stroke is practical. Therefore, the first
If the focal lengths of the second lens and the second lens are short, sufficient spherical aberration correction capability cannot be ensured, but then the lens itself needs to be an aspherical lens,
Lens tilt and eccentricity tolerance are reduced, making assembly difficult. Furthermore, in such a support structure, the rigidity for holding the lens is low so that the lens optical axis does not tilt,
Vibration and shock cause the lens to rotate, increasing optical aberrations. Further, since the distance between the lenses is controlled by the amount of current flowing, there is a problem in that the influence of external vibration or shock cannot be removed, and the lens also moves in the optical axis direction. In this publication, JP-A-10-188301 is disclosed as a conventional example.
This is to correct the spherical aberration by changing the distance between the two objective lenses with VCM. Again, after determining an appropriate current for correcting the distance, the current is maintained. This is a method of maintaining the interval, and the influence of disturbance cannot be excluded.

As described above, the conventional optical head equipped with a movable lens for spherical aberration cannot maintain a good lens position, so that there are many optical aberrations and stable control is difficult. .

An objective lens driving device is mounted on the optical head as a lens moving mechanism. However, in the objective lens driving device, the objective lens is originally arranged so that the optical axis of the objective lens is shifted with respect to the light beam so that the tracking operation can be performed. Since it is designed, no consideration is given to suppressing the optical axis shift. Further, the objective lens actuator is designed and designed mainly for dynamically making the beam spot follow a movement such as eccentricity or surface wobbling of the disk up to a component of about several kHz. In this case, the main purpose is to correct spherical aberration due to the difference in the layers of the multilayer optical disk, and then to operate for things that do not change due to disk rotation, such as the difference in optical thickness of the transparent substrate between disks. If the optical thickness of the transparent substrate on the disk surface changes, it is necessary to follow it, but the change is small. Therefore, a DC-like operation is mainly performed, and a control band of several hundreds Hz is sufficient. For this reason, the moving device of the conventional example also uses a mechanism such as a rack and a pinion that is not capable of high-speed reciprocating motion in order to determine a position by supplying a constant current. Therefore, it is impossible to use the objective lens driving device as the relay lens driving mechanism.

Further, in the above-mentioned prior art, the relay lens is arranged coaxially with the optical axis of the objective lens, which causes a problem that the optical head becomes thick. The optical disk drive in which the optical head is mounted needs to be thin when used as a storage device of a computer, particularly a portable computer, but for this purpose, the optical head must not be thick. It is apparent that the optical head of the above-mentioned conventional example is thicker by the thickness of the relay lens than the optical head not using the conventional relay lens. Even if a mirror is inserted between the objective lens and the relay lens to bend the optical axis by 90 degrees, it is difficult to reduce the thickness with the drive mechanism used in the conventional example.

Therefore, the present invention has been made in order to solve the above-mentioned problems, and has a relay lens for correcting spherical aberration, moves the relay lens with good accuracy, and further, vibrates and shocks from the outside. D is not easily affected by
An object of the present invention is to provide an optical head equipped with a relay lens drive mechanism that is suitable for C operation and that can realize a thin optical disk device.

[0018]

In order to achieve the above object, an optical head according to the present invention comprises a lens for correcting spherical aberration, a lens holder for holding the lens, and a cylindrical shape parallel to the optical axis of the lens. First and second guide rails of
First and second round holes provided in the lens holder and fitted into the first guide rail, long holes provided in the lens holder and fitted into the second guide rail, and fixed to the lens holder The winding shaft includes a coil having two linear portions that are perpendicular to the guide rail and perpendicular to the guide rail, and a permanent magnet that is provided so as to face the coil.

With this configuration, the relay lens does not move in a direction other than the optical axis direction of the lens along with the movement of the lens holder, so that the optical axis of the lens does not shift. or,
Since the winding axis of the coil is perpendicular to the optical axis, the size can be reduced, and the point of action of the force can be brought closer to the main axis, preventing twisting.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. The following description is an embodiment of the present invention and does not limit the apparatus and method of the present invention.

FIG. 1 shows a structure of a main part of an optical head according to an embodiment of the present invention. 2 and 3 are perspective views showing the relationship between the optical disk and the optical head. 4 and 5 show
1 is a schematic configuration diagram of an optical disk recording or reproducing device according to the present invention. (Comment: In Fig. 5, the lens 33 moves, but please correct it so that the lens 33 moves. Modify the line connecting 33 and 23 to connect 32 and 33, and coil 21 to the lens. Please move to above 32.) FIGS. 6-8 is a perspective view which shows a relay lens drive device or its one part. 9 and 10 are a perspective view and a plan view showing a movable portion of the relay lens driving device.
FIG. 11 shows the configuration of the main part of an optical head according to another embodiment.

2 and 3, the optical disc 100 is shown.
Is a recording or reproducing disk such as a read-only disk, a phase change disk or a magneto-optical disk. As shown in FIG. 1, the light beam emitted from the light source 1 for irradiating the optical disc 100 with the light beam is collimated by the collimator lens 2, enters the beam splitter 4, and then passes through the quarter-wave plate 5. (A beam shaping prism for changing the shape of the light beam may be inserted between the collimator lens 2 and the beam splitter 4).

Next, the relay lens system 7 according to the present invention for correcting the spherical aberration generated when there is an error in the thickness of the cover layer of the disk is passed through the mirror 6 to change its direction by 90 degrees, and the objective lens 8 is formed. Incident. Here, the objective lens 8 is an N combination of two lenses 30 and 31 (see FIG. 5).
The lens has a high NA of about A0.85 and is supported by the objective lens driving device 3 so as to be movable in the optical axis direction and the disc radial direction.

The reflected light from the disc 100 passes through the objective lens 8, is reflected by the mirror 6, passes through the relay lens system in the relay lens drive mechanism 7, passes through the quarter wavelength plate 5, and is reflected by the beam splitter 4. Incident on. Then, it is reflected by the beam splitter 4 and is condensed by the convex lens 10. Next, the light beam passes through the focus error signal generating element 11 and is applied to the photodetector 12. The focus error generating element 11 may be any method as long as it can realize a focus error signal. For example, in the case of the astigmatism method, it is a cylindrical lens.

The output from the photodetector 12 is input to the arithmetic circuit 13 as shown in FIG. 4 to obtain an information reproduction signal, a focus error signal and a tracking error signal. The phase compensation circuit 14 performs phase compensation on the focus error signal and the tracking error signal. Based on the phase compensation signal from the phase compensation circuit 14, as shown in FIG.
At 16, a current is passed through the coils 17 and 18 of the objective lens driving device 3 to control the position of the objective lens 8 in the optical axis direction and the radial direction.

The relay lens system 7 is used to correct spherical aberration caused by a thickness error of the cover layer of the disc 100. At least one of the two lenses 32 and 33 (32 in this embodiment) is moved in the optical axis direction to drive a relay lens so as to correct spherical aberration caused by a thickness error of the cover layer of the disc 100. A spherical aberration is generated by the relay lens system in the mechanism 7. As the control method, for example, the method disclosed in JP-A-10-188301 can be applied. In this embodiment, the relay lens 32
A position detecting device 22 for detecting the position of is provided.

The position detecting device 22 is a reflection type photo sensor comprising a light emitting element 34 such as a light emitting diode and a photo detector 35 as shown in FIG. Relay lens 33
The light emitted from the light emitting element 34 is reflected by a reflecting plate 23 (which is preferably a white plate that diffuses and reflects) that moves together with the light, and enters the photodetector 35. Reflector 2
The amount of 3 facing the position detection device 22 changes according to the position of the relay lens 32, and thus the amount of reflected light and the amount of light incident on the photodetector 35 change. This makes it possible to detect the position of the relay lens 32. The output of the photo detector 35 is input to the lens position control circuit 19. Lens position control circuit 19
Outputs a signal to the drive circuit 20 so that the relay lens is positioned at the designated position, and the drive circuit 20 causes a current to flow through the coil 21 of the relay lens drive mechanism 7. As described above, in this device, the position control is performed by the feedback control.

There are various methods for determining the position of the relay lens 32, and the following method is used, for example. A
The CPU 24 equipped with the D / DA causes the relay lens position control circuit 19 to gradually move the position of the relay lens 32 within a range capable of correcting the spherical aberration of the assumed substrate thickness. Then, the position of the lens 32 that maximizes the amplitude of the reproduction information signal is detected, and thereafter, the value is continuously output to the relay lens position control circuit 19. In this way, position control is performed by feedback control instead of open control as in the conventional example, so the position of the relay lens is not affected even if there is external vibration or shock, and the playback information signal is not affected. It is possible to accurately detect the maximum value of and to hold the lens position thereafter. Therefore, the error of the cover layer of the disc can be corrected, and a larger capacity optical disc device can be realized.

Next, details of the relay lens drive mechanism 7 mounted on the optical head according to the present embodiment will be described. Here, of the two lenses forming the relay lens 7, the lens 32 is fixed and the lens 33 is movable.

The lens 32 is attached to the base 42 as shown in FIG. The movable lens 33 is attached to the lens holder 27 as shown in FIG. A coil 21 wound around an axis (Y direction) perpendicular to the optical axis (X direction) of the lens 33 is attached to the lens holder 27. Since the winding axis of the coil is perpendicular to the optical axis,
Can be miniaturized. The winding axis of the coil 21 has a predetermined angle with a plane including the centers of the guide rails 25a and 25b, and a perpendicular line drawn from the small iron piece 28 to the plane including the centers of the guide rails 25a and 25b indicates the guide rails 25a and 25b. It is configured to intersect between.

As shown in FIG. 8, the permanent magnet 26 is attached to a yoke 43 made of a ferromagnetic material such as a steel plate.
Are attached to the base 42. Therefore, the permanent magnet 2
6 is fixed to the base 42. Further, the permanent magnet 26 is placed with a minute gap from the coil 21.
The magnetizing direction of the permanent magnet 26 is parallel to the winding axis of the coil 21, as indicated by the arrow in FIG.
Is a two-pole magnet magnetized in the opposite direction with a boundary approximately at the middle of the optical axis direction. With such a two-pole magnetized structure, high efficiency and low power consumption can be realized. 2
It goes without saying that the same effect can be obtained by combining two monopolar magnets.

Corresponding to the respective magnetic poles of the permanent magnet 26, the coil 21 extends in the optical axis direction of the lens 33 and in the direction (Z direction) perpendicular to the winding axis of the coil 21 as indicated by 21a and 21b in FIG. Two straight line portions are provided in the optical axis direction (X direction) of the lens 33. The lens holder 27 includes two parallel guide rails 25 that are parallel to the optical axis direction of the lens 33.
It is supported by a and 25b. Guide rails 25a, 2
As shown in FIG. 8, 5b is supported by a base 42 and a sub-base 44 fixed to the base 42.

The lens holder 27 is provided with a rail receiving portion 49 as a bearing portion having a cavity 49a as shown in FIG. 7, and the rail receiving portion 49 has coaxial holes 47a and 47b.
Is provided. The guide rail 25a is provided with a hole 47 with a slight clearance so that the lens holder 27 can slide.
It penetrates through a and 47b. The cavity 49a of the rail receiving portion 49 is provided to bring the guide rail 25a and the rail receiving portion 49 into contact with each other at a position as far away as possible in the X direction, and has an effect of improving the orientation accuracy of the lens holder.

As shown in FIG. 9, the lens holder 27 is provided with an elongated hole U-shaped portion 48, and the guide rail 25b is provided there.
Penetrates slidably. Holes 47a, 47b, slot U
The character-shaped portion 48 is preferably made of a material having a small friction coefficient, for example, a material such as PPS lubricating grade. A lubricant such as grease may be applied to the surfaces of the guide rails 25a and 25b.

Further, a small iron piece 28 made of a ferromagnetic material such as a silicon steel plate is provided near the center of the coil of the lens holder 27.
(Hatched portion in the figure) is attached, and a force F is generated in the coil winding axis direction by the permanent magnet 26.

FIG. 10 is a plan view showing the movable portion of the relay lens driving device. The position of each part in the Z direction is as follows.

Holes 47a and 47b> Center of driving force F acting on coil 21 = Center of iron piece 28 ≧ Optical axis 33a of lens 33> U-shaped portion 48 Since the order is as described above, the lens holder is guided. By being pressed against the rails 25a and 25b in the coil winding direction, the contact position A between the holes 47a and 47b and the guide rail 25a and the contact position B between the elongated hole U-shaped portion 48 and the guide rail 25b are stabilized. As a result, the posture of the lens holder 27 is stabilized, and accordingly, the inclination and the axis shift of the optical axis of the lens 33 are suppressed, and the occurrence of optical aberration is suppressed.

When projected onto the XY plane, the center position 21a of the coil 21 is brought closer to the guide rail 25a, and the winding axis of the coil 21 is set in the Y direction, so that the guide rail 25 is moved.
The distance between a and the center of the driving force generated in the coil can be shortened. Therefore, the moment force on the guide rail 25a generated in the lens holder 27 is suppressed. This moment force causes holes 47a, 4
7b is pressed, and as a result, a frictional force is generated in the X direction. If this frictional force exceeds the driving force generated in the coil 21, the lens 33 becomes immovable and a so-called twisting phenomenon occurs. Therefore, when the moment force is small in this way, the holes 47a,
It is less likely that 47b will be twisted and become inoperable.

Further considering the moment when projected on the XZ plane, the guide rail 25b and the U-shaped portion 48
Since the frictional force generated between and is a moment force in the opposite direction to the force generated by the coil 21, this also reduces the risk of prying. In addition, to prevent twisting, the hole 47
It goes without saying that measures such as increasing the distance between a and 47b in the X direction as much as possible or reducing the friction coefficient with respect to the guide rails 25a and 25b are also effective.

In this embodiment, the guide rail 25a
However, in some cases, the lens holder 27 and the guide rail 25a are fixed so that the guide rail and the base 42, and the hole provided in the sub-base 44 and the guide rail 25a slide. With such a structure, the frictional force due to the moment force generated by the force generated in the coil 21 can be further reduced.

The operation of the relay lens driving mechanism constructed as described above will be described with reference to FIGS. 7 and 8. When an electric current is passed through the coil 21, the electric current passes through the magnetic field generated by the permanent magnet 26, and a Lorentz force is generated in the coil 21. In particular, the force generated in the coils 21a and 21b applies a force to the lens holder 27 in the optical axis direction of the lens 33. The lens holder 27 is a guide rail 25.
Since it is slidably supported by a and 25b, the lens holder 27 moves in the optical axis direction. Guide rail 2 here
5a and 25b are assembled in parallel with the optical axis of the lens 33 and have a force acting between the small iron piece 28 and the permanent magnet 26, so that the lens 33 tilts even if it moves in the optical axis direction,
It does not cause axis misalignment. Here, the small iron piece 28 and the permanent magnet 26 act as a pressing means for pressing the rail receiving portion 49 against the guide rail.

In the relay lens drive mechanism constructed as described above, even if the lens 33 is moved, the position is not displaced in the other directions, and good spherical aberration correction is possible. Further, since the lens is supported by the two guide rails and there is a force acting between the small iron piece 28 and the permanent magnet 26, the supporting rigidity is high and the lens is tilted due to external shock or vibration. There is no.

Further, as described above, the linear portion 21a of the coil,
Since an effective driving force is generated at two points 21b, it is possible to realize an optical head with high actuator efficiency, low power consumption, and low heat generation.

It should be noted that a magnetic spring effect is generated between the small iron piece 28 and the permanent magnet 26 in the direction in which the small iron piece 28 approaches the split position of the two-pole magnetization of the permanent magnet. Stiffness occurs.

Next, details of the position detecting device 22 of the present embodiment will be described. In this embodiment, the reflection type photo sensor is used as the position sensor as described above, but it is necessary to use a small position sensor in order to miniaturize the optical head. However, the small reflection type photosensor has a small effective luminous flux, and therefore the position detection range is often smaller than the range in which the lens holder 27 is desired to be positioned. Therefore, in the present embodiment, the light blocking plate 2
By inclining the edge of 3 which is perpendicular to the normal movement direction as 23a, the change of the area of the reflection plate 23 facing the position sensor 22 due to the movement of the lens holder 27 is reduced. As a result, the position detection range is expanded to a sufficient range with respect to the movable range of the lens holder 27. Therefore, the control circuit enables the positioning control by the feedback control at any position, and produces the effect of not being greatly affected by the vibration shock as described above. Further, since it is a non-contact type position sensor, no force is applied to the movable part such as the lens holder, the position and the posture are not changed by the force, and it is possible to prevent the increase of the optical aberration due to the positional deviation of the spherical aberration lens. The position sensor may be replaced by another non-contact type position sensor. For example, a position sensor using a magnet and a hall element can be used.

Next, the moving directions of the optical head and the relay lens 33 will be described. In this embodiment, as shown in FIGS. 2 and 3, the movement direction of the relay lens 33 is in the disc tangential direction. By moving the optical head in the radial direction of the disk, information on various radial positions on the disk is read. However, as the optical head moves, acceleration is generated and inertial force is also applied to the movable portion of the relay lens. As in the present embodiment, by making the moving direction of the movable part of the relay lens drive mechanism 7 not the radial direction of the disk but the circumferential direction, it is possible to prevent the position of the movable part from being changed by the inertial force applied to the movable part. . Further, it is not necessary to generate a holding force in the coil 21 corresponding to the inertial force, and the power consumption can be reduced. When operating the optical head in the radial direction, it is necessary to supply a large amount of power to the actuator for moving the optical head. Therefore, the power consumption of the relay lens drive mechanism 7 does not increase when the optical head moves. The effect of suppressing the peak power consumption of the optical disk drive device in which is mounted is great, and it contributes to downsizing of the power supply circuit that supplies the power.

FIG. 11 shows the structure of the main part of another embodiment of the optical head according to the present invention. The relay lens drive mechanism 7 shown in FIG. 11 differs from the relay lens drive mechanism 7 of FIG. 1 in the direction of 180 °. That is, the relay lens drive mechanism 7 is provided with the lens holder 27 on the light source 1 side. The movable lens 32 is shown in FIG. 1, but the lens 33 is a movable lens. As described above, in the two groups of relay lenses, moving the lens at a position farther than the objective lens reduces the change in the amount of light due to the movement of the lens, and generally gives good optical characteristics in many cases.

In the above description, the relay lens is composed of two lenses, but each lens may be formed by laminating a plurality of lenses. In other words, spherical aberration that occurs when the optical thickness of the substrate of the optical disc is different from the optical thickness assumed when the objective lens is designed moves one or more lenses provided separately from the objective lens in the optical axis direction. In this case, the optical head of the present invention is effective especially when the movement of the lens outside the optical axis is not allowed and the allowable range of inclination is extremely small.

Further, although the magnets magnetized with two poles are used, it is needless to say that the same effect can be obtained by combining two single pole magnets, and only one single pole magnet is used. Even if the force is generated only on one of the straight line portions 21a and 21b of 21, the power consumption is increased but can be realized. Also in this case, the effect of the magnetic spring can be obtained.

[0050]

As described above, the optical head to which the present invention is applied can correct the spherical aberration caused by the thickness error of the cover layer of the optical disk without being affected by vibration, shock and the like.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a main part of an optical head according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a relationship between an optical disc and an optical head.

FIG. 3 is another perspective view showing the relationship between the optical disk and the optical head.

FIG. 4 is a schematic configuration diagram of an optical disc recording / reproducing apparatus according to the present invention.

FIG. 5 is another schematic configuration diagram of the optical disc recording / reproducing apparatus according to the present invention.

FIG. 6 is a perspective view partially showing the configuration of a relay lens driving device according to the present invention.

FIG. 7 is another perspective view partially showing the configuration of the relay lens driving device according to the present invention.

FIG. 8 is a perspective view showing a configuration of a relay lens driving device according to the present invention.

FIG. 9 is a perspective view showing a movable part of the relay lens driving device.

FIG. 10 is a plan view showing a movable portion of the relay lens driving device.

FIG. 11 is a diagram showing a configuration of a main part of an optical head according to another embodiment.

[Explanation of symbols]

1 ... Light source, 2 ... Collimator lens, 3 ... Objective lens drive device, 4 ... Beam splitter, 5 ... 1/4 wavelength plate, 6 ...
Mirror, 7 ... Relay lens driving device, 8 ... Objective lens,
10 ... Convex lens, 21 ... Coil, 22 ... Position sensor, 2
3 ... Shading plate, 25a, 25b ... Guide rail, 26 ... Permanent magnet, 28 ... Small iron piece, 32 ... Movable lens, 42 ... Base, 43 ... Yoke, 44 ... Sub base, 47a, 47b
... hole, 48 ... U-shaped part, 100 ... optical disk

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[Procedure amendment]

[Submission date] November 18, 2002 (2002.11.
18)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

The optical thickness referred to here is a value determined by the thickness and the refractive index of the optical disk substrate through which light is transmitted. Even if the optical thickness is different, the spherical aberration of the beam spot generated by passing through the substrate is spherical aberration. The optical thicknesses are considered to be equal when the sizes of the two match. Even if the substrate consists of multiple layers, depending on the thickness and refractive index of each layer,
The optical thickness of the substrate is determined. Now, as a method for correcting spherical aberration due to a change in the thickness of an optical disk substrate, Japanese Patent Laid-Open No.
Various methods are disclosed in Japanese Patent Publication No. 151609. Among them, an aberration correction method using a so-called relay lens composed of a convex lens and a concave lens is presented. By arranging a relay lens consisting of a convex lens and a concave lens before the light emitted from the laser diode enters the objective lens, and changing the position of either the convex lens or the concave lens, the spherical surface of the beam entering the optical disc from the objective lens. By changing the aberration and canceling the spherical aberration generated in the optical disc, a beam spot with less aberration is generated on the optical disc.
In this publication, a VC is used as a drive mechanism for the objective lens.
An M (voice coil motor) is used, but its structure and control method are not shown.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

FIG. 1 shows a structure of a main part of an optical head according to an embodiment of the present invention. 2 and 3 are perspective views showing the relationship between the optical disk and the optical head. 4 and 5 show
1 is a schematic configuration diagram of an optical disk recording or reproducing device according to the present invention. 6 to 8 are perspective views showing the relay lens driving device or a part thereof. 9 and 10 are a perspective view and a plan view showing a movable portion of the relay lens driving device. FIG. 11 shows the configuration of the main part of an optical head according to another embodiment.

Continued front page    F-term (reference) 5D119 AA11 AA22 AA32 AA37 BA01                       BB01 BB02 BB04 BB05 DA01                       DA05 EA02 EA03 EC01 EC07                       FA11 JA02 JA06 JA09 JA12                       JA32 JA43 JC04 JC07 MA30                 5D789 AA11 AA22 AA32 AA37 BA01                       BB01 BB02 BB04 BB05 DA01                       DA05 EA02 EA03 EC01 EC07                       FA11 JA02 JA06 JA09 JA12                       JA32 JA43 JC04 JC07 MA30

Claims (5)

[Claims] 1. An optical head device for reading information from an optical disc, wherein a lens for correcting spherical aberration, a lens holder for holding the lens, a guide rail parallel to the optical axis of the lens, and a lens holder provided on the lens holder. A rail receiving portion for receiving the guide rail, a coil fixed to the lens holder and having a winding axis perpendicular to the guide rail, a permanent magnet provided to face the coil, and the rail receiving portion. And a pressing means for pressing the guide rail against the guide rail. 2. An optical head device for reading information from an optical disc, comprising: a lens for correcting spherical aberration, a lens holder for holding the lens, and first and second guide rails parallel to the optical axis of the lens. A first rail receiving portion provided on the lens holder for receiving the first guide rail; a second rail receiving portion provided on the lens holder for receiving the second guide rail; A coil having a winding axis fixed to the guide rail and perpendicular to the guide rail; a permanent magnet provided facing the coil and having two poles magnetized in the axial direction of the guide rail; and provided on the lens holder. , An optical head device that cooperates with the permanent magnet to generate a pressing force that presses the guide rail against the rail receiving portion. 3. The guide rails are arranged along the circumferential direction of the optical disk.
The optical head device according to item 1. 4. The winding shaft of the coil has a predetermined angle with a plane including the centers of the first guide rail and the second guide rail, and the magnetic piece extends from the first guide rail to the first guide rail. 4. The optical head according to claim 2, wherein a vertical line drawn on a plane including the center of the second guide rail intersects between the first guide rail and the second guide rail. apparatus. 5. A base, which holds the first guide rail, the second guide rail, and a permanent magnet, and a second lens fixed to the base and having an optical axis coinciding with the lens. The optical head device according to claim 1 or 2.