JP2003045067A - Optical head and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical head which has an excellent accuracy of positioning of a relay lens for compensating a spherical aberration. SOLUTION: The optical head is provided with a lens 33 for compensating the spherical aberration, a lens holder 27 which holds the lens, a first parallel leaf spring 25a which supports the lens holder 27 at an end, an intermediate member 28 which is mounted at the other end of the first parallel leaf spring, a second parallel leaf spring 25b which is a leaf spring arranged on the lens holder side of the boundary of the intermediate member and supports the intermediate member at an end and fixing members 29a and 29b which fix the other end of the second parallel leaf spring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for irradiating a light beam for recording information on an optical disc and reproducing information recorded on the optical disc. The present invention also relates to an optical disc device equipped with such an optical head.

[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, development of a small-sized and large-capacity optical disk recording / reproducing apparatus for handling high-definition still images and moving images has been developed. It is progressing. As a technical method for achieving 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, the information recording surface is covered with a transparent optical disc substrate, 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 cause of this angle change is the warp of the optical disc itself,
Although there are tilts of the spindle motor that rotates the optical disk and tilts that occur due to the objective lens drive mechanism mounted on the optical head, it is difficult to increase the angular accuracy in proportion to the increase in NA while maintaining mass productivity. Since the coma aberration generated by the tilt occurs when passing through the disc substrate, if the substrate thickness is made thin, the aberration decreases due to the tilt. Therefore, in an optical disc system using an objective lens with a high NA, an optical disc having a thin substrate is used. There is a method of using it to strengthen the inclination error.

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 specific optical thickness, the substrate thickness at the time of designing is small. If there is an error with respect to the assumed optical thickness, spherical aberration will occur. When two information recording surfaces are irradiated with laser light from the same direction (rather than a double-sided disk recording / reproducing from different directions) like a dual-layer disk, each layer has an optical thickness equal to the transparent layer substrate thickness. Will always be different. The spherical aberration due to this error in the substrate thickness also becomes very large as the NA increases, and the NA
With a lens having a large NA of 0.85, 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 thickness determined by the thickness of the optical disk substrate through which light is transmitted and the refractive index. Even if the optical thickness is different, the spherical aberration of the beam spot generated by passing through the substrate is The optical thicknesses are considered to be equal when the sizes of the two match. Even when the substrate is composed of a plurality of layers, the optical thickness is determined by the thickness of the substrate and the refractive index of each layer.

Now, as a method for correcting spherical aberration due to a change in the thickness of the optical disk substrate, Japanese Patent Laid-Open No. 5-151609.
Shows various schemes. Among them, an aberration correction method using a so-called relay lens composed of a convex lens and a concave lens is disclosed. By adding 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. Further, although a VCM (voice coil motor) is used as a drive mechanism for the objective lens, its structure is not shown at all. Moreover, the control method is also unknown because it is shown that a control device is used.

Japanese Unexamined Patent Publication No. 5-266511 discloses a method of driving a relay lens by mounting a rack on the side of the lens to be moved and rotating the pinion to move the rack. Also, the substrate thickness recorded on the disc,
Alternatively, there is disclosed a method in which 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 thereto.

Further, Japanese Patent Laid-Open No. 2001-28147 discloses a method of driving a relay lens using a voice coil motor.

[0008]

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

First, in Japanese Patent Laid-Open No. 5-151609, only a VCM is used for the drive mechanism, and no detailed description is given. However, as will be described later, in a lens moving mechanism for correcting spherical aberration, a general simple VCM is used.
Cannot secure sufficient performance, and therefore the technique disclosed here cannot manufacture a practical optical head.

Next, Japanese Patent Laid-Open No. 5-266511,
Here, an example using a rack and a pinion as a relay lens moving device is disclosed. However,
The optical disk device equipped with the optical head is also used in portable computers, music reproducing devices, etc., and the influence of external vibration and shock cannot be ignored. A mechanism using a rack and a pinion has no position holding ability when the pinion is directly driven by a DC motor, and if an external force is applied in the moving direction, the position cannot be held and the pinion moves, and good spherical aberration correction is possible. It will be impossible.

Furthermore, 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. Further, when the optical axis shift occurs, there is a problem that the direction of the light flux from the relay lens toward the objective lens changes and the beam spot position also changes. If the beam spot position is displaced in the disc radial direction, the tracking servo mechanism of the optical drive device tries to prevent the beam spot from moving by moving the objective lens actuator in the tracking direction. There is of course an upper limit on the allowable amount of acceleration and movement. In the conventional technology, no consideration is given to this point. Even in this conventional example, 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,
Extremely 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 an optical disk drive is mounted. The presence of backlash can be affected by these vibrations. Further, at the time of starting and stopping, vibration is generated due to the influence of the friction of the mechanism. The frequency of these vibrations is typically a few kHz, but at this frequency,
A general guide or lens support mechanism itself often has resonance, and therefore the lens also moves outside the optical axis. Since this vibration usually has a component of several kHz and is close to the control band of the tracking servo of the optical disc, it is difficult to suppress the displacement of the beam spot due to the vibration by the operation of the objective lens actuator. That is, it is difficult to operate the position of the relay lens while recording / reproducing information on / from the optical disc.

Japanese Patent Laid-Open No. 2001-28147 discloses a VCM structure as a lens moving mechanism for correcting spherical aberration. In this VCM, both sides of the lens are supported by leaf springs, but it is difficult for such a supporting structure of both ends to secure a linear characteristic in the moving direction, and only a very short stroke is practical. . For this reason, sufficient spherical aberration correction capability cannot be ensured unless the focal length is made short, but then it becomes necessary to make the lens itself an aspherical lens, and the tilt and decentration tolerance of the lens become small, which results in poor assembly. Becomes difficult. Furthermore, in such a support structure, the holding rigidity of the lens in the optical axis tilt direction is low, and the lens rotates due to vibration and shock,
It increases optical aberration. Further, since the distance between the lenses is controlled by the amount of current flowing, there is a problem in that the effects of external vibration and shock cannot be removed, and the lens also moves in the optical axis direction. Furthermore, Japanese Patent Laid-Open No.
-188301, the distance between the two objective lenses is VC
A technique for correcting spherical aberration by changing it with M is disclosed, but this is also a method of maintaining the current by maintaining the current after determining an appropriate current for correcting the distance, 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 causing the beam spot to 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 disc, and then to operate for those that do not change due to disc rotation, such as the difference in optical thickness of the transparent substrate between discs. Even if it is necessary to follow the variation in the optical thickness of the transparent substrate within the disc surface, the variation is small. Therefore, the DC-like operation is mainly performed, and the control band of several hundreds Hz is sufficient. Therefore, the moving device of the conventional example also uses a mechanism such as a gear that is not capable of high-speed reciprocating motion in order to determine a position by flowing 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 conventional example, 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 and the optical axis is bent 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 position with good accuracy, and further, vibrates from the outside. An object of the present invention is to provide an optical head equipped with a relay lens drive mechanism that is less susceptible to shocks, is suitable for DC operation, and can realize a thin optical disk device. Another object of the present invention is to provide an optical disk device equipped with such an optical head.

[0018]

In order to solve the above problems and achieve the object, the optical head and the optical disk device of the present invention are configured as follows.

(1) In the optical head of the present invention, a lens for correcting spherical aberration, a lens holder that holds the lens, a first parallel leaf spring that supports the lens holder at one end, and the first parallel leaf spring are provided. An intermediate member attached to the other end of the parallel leaf spring, and a second parallel leaf spring disposed on the lens holder side with the intermediate member as a boundary, the second parallel leaf spring supporting the intermediate member at one end. , And a fixing member for fixing the other end of the second parallel leaf spring.

(2) The present invention is an optical disk device including an optical head for irradiating an optical disk with a light beam, wherein the optical head has a lens for correcting spherical aberration and a lens for holding the lens. A holder; a first parallel leaf spring that supports the lens holder at one end;
An intermediate member attached to the other end of the parallel leaf spring, and a second parallel leaf spring disposed on the lens holder side with the intermediate member as a boundary, the second parallel leaf spring supporting the intermediate member at one end. And a fixing member that fixes the other end of the second parallel leaf spring, and the optical disc device moves the first parallel leaf spring to the optical axis of the lens in order to move the lens in the optical axis direction. It has a moving means for moving in the axial direction.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present embodiment will be described below with reference to the drawings.

1 and 2 show the main part of an optical head according to a first embodiment of the present invention. FIG. 3 is a perspective view showing the relationship between the optical disk and the optical head. 4 and 5 are perspective views showing only the relay lens driving device. FIG. 6 is a perspective view of a leaf spring that supports the movable portion of the relay lens. 7 and 10 are schematic configuration diagrams of an optical disk device according to the present invention.

The optical disc 100 is a read-only disc,
It is a recording or reproducing disk such as a phase change disk or a magneto-optical disk. 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 for correcting spherical aberration that occurs 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 then enters the objective lens 8. Here, the objective lens 8 is a lens having a high NA of about 0.85 with a combination of two lenses, 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 light emitted from the objective lens 8 passes through the cover layer of the optical disc 100,
A beam spot is formed on a desired reflecting surface.

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 7, passes through the quarter wavelength plate 5, and enters the beam splitter 4. 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 the 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, and the arithmetic circuit 13 outputs the information reproduction signal, the focus error signal and the tracking error signal. The phase compensation circuit 14 performs phase compensation on the focus error signal and the tracking error signal,
Based on the signal, the actuator drivers 15 and 16 apply a current to 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. Further, the relay lens system 7 includes the disc 100.
It is used to correct spherical aberration caused by the thickness error of the cover layer. At least one of the two lenses 32 and 33 (33 in this embodiment) is moved in the optical axis direction so as to correct the spherical aberration generated by the thickness error of the cover layer of the disc 100. At 7, spherical aberration is generated. The control method is, for example, Japanese Patent Laid-Open No.
The method disclosed in 188301 can also be applied. However, in the present embodiment, the position detection device 22 that detects the position of the relay lens 33 is provided. Here, the position detection device 22 includes a light emitting diode 34 and a photo detector 35.
Is a photo interrupter consisting of a relay lens 3
The light shielding plate 23 that operates integrally with the
By changing the amount of light emitted from the photodetector 35 to the photodetector 35 depending on the position, the relay lens 33
Position detection is possible. The output of the photo detector 35 is input to the lens position control circuit 19.
The 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 supplies a current to 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 33, 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 operate the position of the relay lens 33 within a range in which spherical aberration of an assumed substrate thickness can be corrected. Then, the position of the lens 33 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 of this 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. The movable lens 33 is attached to the lens holder 27. In the lens holder 27, the coil 21 has a lens 33.
It is attached by being wound in the direction of winding the optical axis of. The lens holder 27 is supported by two parallel leaf springs 25a and 25b. When the leaf spring is not bent, the normal line of the leaf spring is parallel to the optical axis of the lens 33. Leaf spring 25a,
The area 25-1 of 25b is fixed to the objective lens holder 27. The regions 25-2 of 25a and 25b are joined by the intermediate joining member 28. The areas 25-3a and 25-3b are the base 42.
Blocks 29a, 29b, 4 so that they do not move with respect to
It is fixed by 5a and 45b. Therefore, the leaf springs 25a and 25b are arranged in the regions 25-4a, 25-4b,
25-5 actually has a function as a leaf spring. The leaf springs 25a and 25b have a uniform thickness, and the widths of the respective regions are W48, W49a, and W49b, and there is a relationship of W48 / 2 = W49a = W49b. In addition, the lengths L46 and L of the respective regions
47a and L47b are all equal in length.

On the side of the relay lens drive coil 27 opposite to the leaf spring, a permanent magnet 26 is placed with a minute gap from the coil 21. The permanent magnet 26 is attached to the yoke 43 made of a ferromagnetic material such as a steel plate,
3 is attached to the base 42. Therefore, the permanent magnet 26 is fixed to the base 42. The permanent magnet 26 is magnetized so that the magnetic flux emitted from the permanent magnet traverses the coil 21, as indicated by the arrow in FIG.

The operation of the relay lens drive mechanism thus configured will be described. 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. As a result, a force is applied to the lens holder 27 in the optical axis direction of the lens 33. Since the lens holder 27 is supported by 25a and 25b, the leaf spring bends due to this Lorentz force,
The lens holder 27 moves in the optical axis direction. Here, since the leaf springs 25a and 25b are assembled in parallel,
The lens 33 does not tilt even if it moves in the optical axis direction. Further, since it is supported by the leaf spring, the vertical rigidity (Z direction) of the lens holder 27 shown in FIG. 4 largely depends on the large in-plane rigidity of the leaf spring, so that it does not move in the vertical direction. Next, in the Y direction, in the parallel leaf spring configuration, when bent, the length in the spring direction (Y direction in this case) is reduced. (This value cannot be calculated by a simple material mechanics formula, but even if the leaf spring bends, the length of the neutral plane does not change, that is, the length along the bend does not change, so naturally the Y direction shrinks. This can be understood by general knowledge of material mechanics. In general, this amount of shrinkage can be calculated by taking account of structural nonlinearity). That is, the distance between the lens holder 27 and the intermediate coupling member 28, the intermediate coupling member 28 and the fixing member 29a,
The distance in the Y direction from 29b becomes shorter when the lens holder 27 is displaced in the X direction and the leaf springs 25a and 25b bend. Since the dimensions of the respective portions of the leaf springs 25a and 25b are as described above, the bending rigidity of each of the regions 25-4a and 25-4b in the X direction is 1 of the bending rigidity of the region 25-5 in the X direction.
/ 2. The lens holder 27 is supported on the region 25-5 of the leaf spring, and the region 25-5 of the leaf spring is joined to the intermediate coupling member 28 at the other end thereof, and the intermediate coupling member 2 is further attached.
Reference numeral 8 denotes two leaf springs in the leaf spring regions 25-4a and 25-4b, which are supported from the same Y direction. Therefore, when the lens holder 27 is displaced in the X direction by, for example, x1, the intermediate coupling member 28 is displaced by x1 / 2. Then, the distance between the lens holder 27 and the intermediate coupling member 28 and the distance between the intermediate coupling member 28 and the fixing members 29a and 29b in the Y direction are reduced by the same distance y1. Therefore, the intermediate coupling member 28 moves y1 in the Y direction, but the lens holder 27 does not move in the Y direction.

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 two parallel springs, the rigidity of the lens 33 in the direction in which the optical axis falls is higher than that of the conventional single leaf spring, and it does not tilt due to external shock or vibration. .

It should be noted that the lower the spring rigidity in the X direction, the smaller the holding current for displacing and holding the lens 33 in the optical axis direction, and the smaller the power consumption, which is preferable, but the rigidity in the directions other than the moving direction decreases. , A problem such as inclination occurs, so that the leaf springs 25a,
The dimensions of each part of 25b may be determined.

Further, in this embodiment, the portion where the force is generated in the coil 21 is concentrated on the left side of FIG. On the other hand, the center of gravity of the movable portion is on the right side of the portion where the force is generated. Therefore, the point where the force is generated and the center of gravity of the moving part deviate,
A moment force around the Z axis is generated in the movable portion. As a result, if the frequency of the AC component of the driving force coincides with or is close to the resonance frequency of the movable portion around the Z axis, large vibration is generated and control becomes difficult. This resonance frequency is kH
The z-order can be achieved by the usual design method and materials. As described above, the control band of the relay lens drive mechanism is sufficient to be about several hundreds, which is sufficiently lower than the frequency of the rotational vibration about the Z axis. Further, it is possible to suppress to some extent by a damping material described later. When the control band is high, it is necessary to match the center of gravity and the point of action of force, but in the case of the relay lens drive mechanism, the control band is low, so it is possible to design such that the point of action of center of gravity and the point of action of force are shifted .

As described above, since the center of gravity and the point of action of force are not displaced, the relay lens drive mechanism of this embodiment can be made thin in the Z direction. That is, what limits the thickness in the Z direction is the diameter of the lens 33 and the thickness of the coil 21. By disposing elements such as permanent magnets in the Z direction, the thickness in the Z direction can be reduced. It became possible to do. Further, since there is only one magnet and the structure is the minimum necessary for generating the Lorentz force, there are advantages that the number of parts is small and the manufacturing cost is low. If it is attempted to bring the center of gravity closer to the point of action of force, it is necessary to dispose the permanent magnets symmetrically across the objective lens. However, on the right side of FIG. 4, there is a support portion composed of leaf springs 25a, 25b and the like. Therefore, the coil 21 must be arranged above and below the coil 21, which makes it impossible to make the coil thin.

Since the connecting member 28 is arranged between the leaf springs 25a and 25b, this influence causes
Resonance in the X direction also occurs. In addition, there is resonance of a mode in which the movable part rotates around the Y axis. The rotational resonance about the Y axis is designed to be symmetrical in the Z direction, so that it is not excited in principle, but it occurs due to a manufacturing error. Such resonance can be suppressed to a problem-free level by using a damping material. For example, there is also a method in which a leaf spring has a laminated structure in which a damping material is sandwiched. In this embodiment, the leaf spring regions 25-5 and 25-4 are used.
Vibration is suppressed by attaching gel materials 44a and 44b near the roots on the side of the intermediate coupling member 28 between a and 25-4b.

Next, details of the position sensor of this embodiment will be described. FIG. 8 is a perspective view showing the arrangement of the position detection device 22. FIG. 9 is a diagram showing the shape and arrangement of the light shielding plate. In this embodiment, the position detection device 22 is used as the position sensor as described above. The light emitting element 34 and the light receiving element 35 are incorporated in the element incorporating portions 22a and 22b of the position detecting device 22, and if there is no obstacle in the slit 22c, the light generated by the light emitting element 34 such as a light emitting diode is generated. The light enters the light receiving element 35 such as a photodiode. Since the light receiving element 35 outputs a signal according to the amount of received light, the light shielding plate 23 is provided in the slit 22b.
The position of the light-shielding plate 23 can be detected by letting in and out. The light blocking plate 23 is a lens holder 27.
Therefore, the position of the lens holder 27 can be detected. By the way, in the case of a small position detecting device, the effective luminous flux is small, and therefore the position detecting range is often smaller than the range in which the lens holder 27 is desired to be positioned. Therefore, in the present embodiment, the shading plate 23 is provided with the diagonal cutouts 23a to reduce the change in the shading effect due to the movement of the shading plate 23, and thereby the position detection range is set to the movable range of the lens holder 27. On the other hand, it is expanded to a sufficient size. Therefore, the control circuit enables positioning control by feedback control at any position,
As a result, the effect of not being greatly affected by the vibration shock described above occurs.

In the present embodiment, the light emitted from the light emitting element 1 is diffused and reflected by each part of the light receiving element 35 of the position detecting device 22 so that it is difficult to enter the light and the light from the outside is hard to enter. It has such a structure. That is, in the Z direction of the slit 22c, the position detection device support pillar 41a,
41b, the position detecting device itself and the lens holder 27 exist in the X direction, and the position detecting device itself also exists in the Y direction. The slit 22c is surrounded by a light shield, and extra light is received by the light receiving element 35. It has a structure that makes it difficult for light to enter. Therefore, stable position detection becomes possible.

The position detecting device 22 is arranged on the side of the mirror 6. It can be used as a place for arranging an optical element on the opposite side of the relay lens driving mechanism in the X direction (in this embodiment, the optical elements 11 and 12 are arranged). Cannot be used as a place to place. By arranging the position detecting device 22 here, space efficiency is improved, and a small optical head can be obtained.

The position sensor may be replaced with a non-contact type position sensor. For example, a position sensor using a magnet and a hall element can be used.

Next, a second embodiment of the present invention will be described with reference to the drawings. 11 and 12 are perspective views showing the outline of the optical head of the present invention. Since most of the configuration is the same as that of the first embodiment, parts having the same functions are given the same numbers, and description thereof will be omitted.

In this embodiment, unlike the first embodiment, the mirror 6 is arranged so that the light incident from the disc tangential direction enters the objective lens 8. Further, the relay lens drive mechanism is configured to drive the lens 32 on the side closer to the objective lens 8. Even in such a case, by arranging the position detecting device 22 on the outer peripheral side of the disk 100 of the mirror 6 as shown in the figure, a space-efficient and compact optical head can be realized.
That is, the optical head of the present invention can be realized regardless of the spherical aberration correction lens to be moved or the direction of the mirror 6.

Next, referring to FIGS. 13 and 15, another embodiment of the leaf spring structure of the relay lens driving device which can be used in the optical head of the present invention will be described. This has the same function as the lens support mechanism by the leaf spring of the first embodiment and the second embodiment. The lens 64 is fixed to the lens holder 65. The coil 66 is attached to the lens holder 65.
It is wound and attached so as to wind the optical axis of 4. A permanent magnet (not shown) is provided so that a force is generated in the vertical direction in the drawing when a current is applied to the coil 66. The lens holder 65 is supported by two parallel plate springs 60a and 60b. The other ends of the leaf springs 60a and 60b are held by a spacer 63a at a distance between the leaf springs, and another pair of parallel leaf springs 61a and 61b are connected via the spacers 63b and 63c. Here, the parallel leaf springs 60a and 60b and the parallel leaf springs 61a and 61b are
The spacers 63a, 63b, 63c are attached to the same side. The other ends of the leaf springs 61a and 61b are fixed to the support beams 66a and 66b. In addition, the support beam 66
The a and 66b are connected by spacers 67a and 67b. Then, the support beams 66a and 66b, the spacer 67
Some or all of a and 67b are fixed to a base (not shown).

As described above, the four leaf springs have the same length, thickness, and width in the portions functioning as leaf springs except for the fixing portion. Here, it is assumed that a current is passed through the coil 66 and a force in the X direction in the figure is generated. At this time, the spacers 63a, 63b, 63c are displaced by .DELTA.X1 in the X direction and also moved by .DELTA.Y1 in the -Y direction. Because of leaf spring Y
This is because the length in the direction hardly changes, so that if there is a displacement of ΔX1, there is no choice but to move in the −Y direction. Similarly, the leaf springs 67a and 67b also bend by ΔX2 in the X direction and Δ in the Y direction.
Y2 shrinks. However, as described above, since the four leaf springs have the same shape, ΔX1 is equal to ΔX2, and ΔY1 and ΔY2
Is also equal. Since the spacer supporting the leaf springs 67a and 67b moves by ΔY1 in the −Y direction, the leaf spring 67
Even if a and 67b shrink in the Y direction by ΔY2, that is, ΔY1, the lens 64 does not move in the Y direction and ΔX1 + in the X direction.
ΔX2 = 2ΔX1 It only moves. That is, the lens 64
Does not cause optical axis shift due to movement in the X direction. In addition, in the present embodiment, the intervals of the four leaf springs are equal, but they need not be equal. Also, the shape of the four leaf springs is
It does not necessarily have to be the same. Depending on the optical conditions, there may be a slight deviation in the optical axis, and the dimensions of each leaf spring may be set to satisfy such conditions. That is, the lens supporting mechanism of the parallel leaf springs used in the optical head of the present invention satisfies the necessary conditions as long as two sets are connected in series and the direction is reversed at the connection place. Here, one set of parallel leaf springs may be a parallel leaf spring composed of two or more pairs of parallel leaf springs operating in parallel as in the first and second embodiments.

In the above embodiment, 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.

Here, the features of the optical head of the present invention described above will be summarized.

(1) An optical head according to the present invention includes a lens for correcting spherical aberration, a lens holder for holding the lens, a first parallel leaf spring for supporting the lens holder at one end, and the first parallel leaf spring. An intermediate member attached to the other end of the parallel leaf spring, and a second parallel leaf spring disposed on the lens holder side with the intermediate member as a boundary, the second parallel leaf spring supporting the intermediate member at one end. , And a fixing member for fixing the other end of the second parallel leaf spring. As a result, the lens moves only in the optical axis direction passing through the lens, and it is possible to prevent the optical axis deviation.

(2) In addition to the description of (1), the optical head of the present invention includes a coil attached to the lens holder and attached in a direction winding the optical axis of the lens.
The permanent magnet is fixed at a position facing one end of the first parallel leaf spring with the lens holder interposed therebetween and having a predetermined gap with respect to the coil. That is, smooth driving by electromagnetic driving becomes possible as compared with driving by a motor and gears.

(3) In addition to the description of (1), the optical head of the present invention has a position sensor for detecting the position of the lens holder. As a result, the position of the lens holder can be detected, position control is possible, and the influence of external vibration and shock is eliminated.

(4) In the optical head of the present invention, in addition to the description in (3), the position sensor includes a light emitting element, a light receiving element, and a light shielding plate provided on the lens holder. In other words, 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 posture are not changed by the force, and the increase of optical aberration due to the positional deviation of the spherical aberration lens can be prevented.

(5) In the optical head according to the present invention, in addition to the description in (4), the edge (light-shielding portion) of the tip of the light-shielding plate is non-perpendicular to the moving direction of the light-shielding plate. If a small light emitting element and light receiving element are used, the effective luminous flux is small and the detection range of the position sensor cannot cover the movable range of the spherical aberration correction lens.However, by diagonally cutting the light shielding plate, the detection range is reduced. Therefore, a small optical head can be realized.

Further, as shown in FIG. 11, the light is made so that the optical axis of the relay lens is perpendicular to the objective lens of the optical head and also to the moving direction of the optical head (that is, the radial direction of the disk). Make up the head. Alternatively, the optical head is configured such that the perpendicular of the leaf spring supporting the relay lens is substantially perpendicular to the moving direction of the optical head and the objective lens. This occurs along with the radial movement of the optical head,
The inertial force applied to the relay lens can prevent the relay lens from moving. Even if the optical head fails to seek and collides with the stopper, the position can be maintained. Also, if the optical axis direction of the relay lens is the same as the optical head moving direction, when the optical head moves in the radial direction, it is necessary to generate a holding force with the same magnitude as the inertial force but in the opposite direction. There is. However, by configuring the optical head as described above, this holding force becomes unnecessary and low power consumption can be realized.

Further, the optical head is constructed so that the arrangement and shape of the leaf springs are symmetric with respect to the plane perpendicular to the optical axis passing through the center of gravity of the movable portion and the plane including the optical axis and the leaf spring supporting direction. . When the center of gravity of the movable part is displaced from the center of the distance between the two leaf springs, a moment force is generated with the movement of the optical head, which causes tilting. Since the circumference is weakest, this can be avoided, and the tilt when the optical head moves can be reduced.

The invention of the present application is not limited to the above-described embodiment, and can be variously modified at the stage of implementation without departing from the spirit of the invention. In addition, the respective embodiments may be combined as appropriate as much as possible, in which case the combined effects can be obtained. Further, the embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, the problem described in the section of the problem to be solved by the invention can be solved, and the effect described in the section of the effect of the invention If you get
A configuration in which this component is deleted can be extracted as an invention.

[0052]

According to the present invention, the position of the relay lens for correcting spherical aberration is moved with good accuracy, and it is less susceptible to external vibrations and shocks and is suitable for DC operation. An optical head provided with a relay lens drive mechanism that can be realized by the device can be provided. Also,
An optical disk device provided with such an optical head can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of an optical head having a spherical aberration correction element of the present invention.

FIG. 2 is a perspective view of a first embodiment of an optical head having a spherical aberration correction element according to the present invention, as viewed from a different angle from the perspective view shown in FIG.

FIG. 3 is a perspective view showing the relationship between the optical head and the optical disc according to the first embodiment of the present invention.

FIG. 4 is a perspective view showing a spherical aberration correction device for an optical head according to a first embodiment of the present invention.

FIG. 5 is a perspective view showing the spherical aberration correction device for an optical head according to the first embodiment of the present invention, as seen from a different angle from the perspective view shown in FIG.

FIG. 6 is a perspective view showing a leaf spring of the first embodiment of the present invention.

FIG. 7 is a schematic diagram showing a schematic configuration of an optical disc drive device using the optical head according to the first embodiment of the present invention.

FIG. 8 is a perspective view showing a position detection device.

FIG. 9 is a perspective view showing a light shielding plate according to the first embodiment of the present invention.

10 is a schematic partial cross-sectional view of the optical disk drive device shown in FIG.

FIG. 11 is a perspective view showing a relationship between an optical head and an optical disc according to a second embodiment of the present invention.

FIG. 12 is a perspective view showing the relationship between the optical head and the optical disc according to the second embodiment of the present invention, which is seen from a different angle from the perspective view shown in FIG.

FIG. 13 is a perspective view showing a lens support mechanism that can be used in the spherical aberration correction device for an optical head according to the present invention.

14 is a perspective view in which a part of the lens support mechanism shown in FIG. 13 is omitted.

[Explanation of symbols]

1 ... Light source 2 ... Collimator lens 3 ... Objective lens driving device 4 ... Beam splitter 5 ... Quarter wave plate 6 ... Mirror 7 ... Relay lens system 8 ... Objective lens 10 ... Convex lens 11 ... Focus error signal generating element 12 ... Photodetector 13 ... Arithmetic circuit 14 ... Phase compensation circuit 15, 16 ... Actuator driver 17, 18, 21 ... Coil 19 ... Lens position control circuit 20 ... Drive circuit 22 ... Position detection device 23 ... Shading plate 24 ... CPU 25a, 25b ... leaf spring 26 ... Permanent magnet 27 ... Relay lens drive coil 28 ... Intermediate coupling member 32, 33 ... Lens 34 ... Light emitting diode 35 ... Photo detector 100 ... Disc

Claims (6)

[Claims] 1. A lens for correcting spherical aberration, a lens holder that holds the lens, a first parallel leaf spring that supports the lens holder at one end, and another end of the first parallel leaf spring at the other end. An attached intermediate member, a leaf spring arranged on the lens holder side with the intermediate member as a boundary, the second parallel leaf spring supporting the intermediate member at one end, and the second parallel leaf spring An optical head, comprising: a fixing member that fixes the other end of the optical head. 2. A position which is attached to the lens holder and which is attached in a direction in which the optical axis of the lens is wound, and which is opposed to one end of the first parallel leaf spring with the lens holder interposed therebetween. The optical head according to claim 1, further comprising: a permanent magnet fixed at a position having a predetermined gap with respect to the coil. 3. The optical head according to claim 1, further comprising a position sensor that detects the position of the lens holder. 4. The optical head according to claim 3, wherein the position sensor includes a light emitting element, a light receiving element, and a light shielding plate provided on the lens holder. 5. The light entering from the light emitting element to the light receiving element is shielded by the tip portion of the light shielding plate, and the side of the tip portion is non-perpendicular to the moving direction of the light shielding plate. The optical head according to claim 4. 6. An optical disc apparatus including an optical head for irradiating an optical disc with a light beam, wherein the optical head includes a lens for correcting spherical aberration, a lens holder for holding the lens, and the lens. A first parallel leaf spring supporting the holder at one end; an intermediate member attached to the other end of the first parallel leaf spring; and a leaf spring arranged on the lens holder side with the intermediate member as a boundary. A second parallel plate spring that supports the intermediate member at one end, and a fixing member that fixes the other end of the second parallel plate spring, the optical disc device including the lens in the optical axis direction. It has a moving means to move to.