JPH117640A - Structure for supporting objective lens and method for correcting position of objective lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens supporting structure that holds the neutral position of an objective lens in a lens actuator and that has the latitude of design. SOLUTION: The structure is such that a light beam outputted from a light source is emitted to the surface of an optical disk 9 through an objective lens means 1 and that adequate information is either read out from the optical disk 9 or written in it. In this case, the objective lens means 1 is loaded and servo-driven by a proper control means at least in one direction, either in the focusing or the tracking direction against the surface of the optical disk 9. In addition, a shape memory alloy is used in a part of the objective lens supporting structure 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device used in an information reproducing system of an optical recording / reproducing apparatus for recording / reproducing optical information using an optical disk on which information is optically recorded. More particularly, the present invention relates to a neutral position adjusting means for an objective lens related to a lens actuator mechanism for driving and controlling an objective lens having a high aperture ratio for achieving high density in a focusing direction and a tracking direction. .

[0002]

2. Description of the Related Art Optical memory technology as a high-density and large-capacity optical disk is a digital video disk with a high-density and large-capacity that is at least seven times as large as that of a conventional digital audio disk, video disk, and data file. Disks have also been put to practical use.

In this optical memory technology, information is recorded and reproduced with high reliability through a light beam focused on the order of microns, so that the performance of the optical system technology of an optical head device is greatly enhanced. The basic functions of an optical head device with integrated optical system technology are the light-condensing function that forms a diffraction-limited minute spot, the focus control of the minute spot of the optical system, and the function of detecting a pit signal. The tracking control function of the minute spot of the optical system is roughly divided into three.

[0004] Among them, regarding focus control and tracking control of a minute spot, when recording and reproduction are performed on the recording medium surface, the light beam emitted from the optical head device is subjected to mechanical precision such as surface deflection and eccentricity of the recording medium. Is configured to follow the spot control with high accuracy by a lens actuator. When this surface runout and eccentricity occur, 1μ
The light beam converged to about m deviates from the information signal storage portion provided on the optical disc. For this purpose, conventionally, an objective lens in an optical head device is mounted on a predetermined lens holder, and the lens holder is driven through predetermined control means to drive a lens actuator. By performing the movable control, the spot condensed by the objective lens held by the lens holder is focused on the information signal portion of the optical disc with high precision.

Next, a conventional optical head device will be described with reference to the drawings. FIG. 5 is a block diagram of an optical system as an example of a conventional optical head device. This conventional optical head device comprises a semiconductor laser 16, a diffraction grating 17, a beam splitter 18, an objective lens 1, a photodetector 19, and a lens holding the objective lens for driving the objective lens in a focus direction and a track direction. A lens actuator section 20 including predetermined coils 3 and 4 mounted on the holder 2 and an appropriate magnet 6 facing the coils, whereby a light beam is formed on the optical disk 9 in the form of a minute spot. Irradiated, necessary information is recorded on the optical disc 9 and, using the reflected light,
It is configured to reproduce predetermined information from the optical disc.

In the optical head device having such a configuration,
The light emitted from the semiconductor laser 16 passes through the diffraction grating 17, for example, creates a beam for detecting a tracking error signal if necessary, and then passes through the beam splitter 18, and passes the objective lens 1 through the objective lens 1. 9 is collected. The reflected light from the signal surface of the optical disk 9 is incident on the light receiving surface of the photodetector 19 via the objective lens 1 and the beam splitter 18 and is converted into an electric signal to obtain an information signal.

On the other hand, a minute spot can be accurately formed on the optical disk 9.
In order to irradiate the information signal on the order of microns on the upper side, it is necessary to accurately detect the direction and displacement of the surface deviation or eccentricity of the optical disk 9. Therefore, in the conventional focusing error signal detection for controlling a minute spot by following the surface deflection of the optical disk 9, for example, the light reflected from the optical disk 9 is incident on the objective lens 1 again, and is reflected by the beam splitter 18, for example. Then, the optical path is changed to produce astigmatism by the cylindrical lens 21, and the astigmatism is guided to the signal detection optical system and made incident on the photodetector 19 to detect a focusing error.

Accordingly, when the minute spot irradiated on the optical disk 9 deviates from the focal position, an error signal corresponding to the amount of surface deflection of the optical disk 9 can be obtained. Therefore, a control signal for canceling the error signal is applied to the lens actuator. It can be controlled so that a minute spot is always irradiated to the in-focus position. On the other hand, examples of the control method for following the eccentricity of the optical disk 9 include, for example,
Among the beams created by the above-described diffraction grating 17, ± 1st-order lights are shifted ± 1 in front and rear with respect to the traveling direction of the tracking pit.
The rotation position of the diffraction grating is set so that the next light is located, and +1
There is known a tracking error signal detection method in which a tracking error signal is detected by calculating the difference between the signals of the primary light and the minus first light.

As a result, an error signal corresponding to the eccentricity of the optical disk can be obtained when the minute spot irradiated on the optical disk 9 deviates from the target track position, similarly to the focusing mechanism. By applying the voltage to the actuator, a minute spot on the target track can always be controlled. On the other hand, the objective lens supporting method of the conventional lens actuator has a structure in which the objective lens 1 is fixed to the holder 2 and the focusing direction and the tracking direction are movable with four wires or four leaf springs. Set up a holder,
There has been a shaft sliding type in which the shaft slides in the focus direction and rotation about the shaft center is used for tracking.

In such a conventional optical disk apparatus, when reproducing the recorded information of the optical disk, there is an optical system for obtaining an error signal of a focusing direction and a tracking method, so that the objective lens is positioned at a neutral position of an initial design value. Is an essential condition. However, in the conventional method, it is difficult to hold the objective lens at the neutral position due to the deflection of the objective lens and the lens holder due to its own weight. Various proposals have been made to solve these problems.

For example, Japanese Patent Application Laid-Open No. 7-311964 discloses that an objective lens is moved in a tracking direction by a plurality of first shape memory alloy actuators and is moved in a focusing direction by a plurality of second shape memory alloy actuators. A lens actuator configured to be moved is shown. In this case, the lens holder portion of the objective lens is made of a spring material made of a U-shaped conductive shape memory alloy, and the spring material is driven in the focus direction by using a restoring force when the shape recovers. Alternatively, a spring material made of the U-shaped conductive shape memory alloy is disposed at equal angular intervals with respect to the objective lens, and the objective lens is driven in the tracking direction.

However, in such a configuration, since the shape memory alloy itself functions as an actuator, the control operation for moving the objective lens is slow, and the shape memory alloy of Considering that it is also difficult to control the characteristics uniformly, it is not suitable for fine position control of the objective lens, and even though it is suitable for extremely simple and coarse control, it is practical to perform high-frequency control. It is impossible.

An example in which the shape memory alloy as described above is applied to an actuator is disclosed in Japanese Patent Application Laid-Open No. Hei 8-22650.
As disclosed in Japanese Patent Application Laid-Open No. H07-157, as a driving means for raising and lowering a magnetic head of a magneto-optical disk drive.
As described in Japanese Patent No. 4376, in an optical disk device, a shape memory alloy is used to control a cooling fan, and when an ambient temperature inside the device rises to a predetermined temperature or more, a spring of the shape memory alloy increases synthesis and frees. There has been a configuration in which a switch is used to control a cooling fan control actuator by deforming it so that its length is extended.

Further, in Japanese Patent Application Laid-Open No. 5-20757, in order to fix an optical disk and a spindle motor in a disk device so as to minimize the eccentricity of an information track, a metal material or a metal material having a large variation with respect to a temperature change is used. A method of controlling the amount of heat applied to each element by using a shape memory alloy to fix the information recording disk to the displacement of the element has been considered.

In addition to the application to actuators, Japanese Patent Laid-Open Publication No. 3-59824 discloses a configuration in which a cleaning mechanism for an objective lens uses a shape memory alloy as a drive source and heat of laser light emitted from an optical head device is used as a switch. In JP-A-63-29222, there is an example of an optical temperature sensor using an optical fiber and a shape memory alloy. But,
Neither method could satisfy the neutral point control of the objective lens and the basic characteristics of the lens actuator.

As a result, the cost of the optical head device is increased, the yield of the optical head device is increased, and the size and weight of the lens actuator are increased.

[0017]

That is, the first problem relating to the control of the focal position of the objective lens in the above-mentioned conventional method is, in particular, an optical head device for reproducing a high-density optical disk. In the lens actuator of the above, when the objective lens is supported, there is a problem in that the supporting portion is bent by the weight of the objective lens and the holder, causing an optical axis shift and adversely affecting the error signal.

The reason is that the condensed beam on the recording surface of the optical disk must be positioned on the information track with high precision, and the design of the acceleration sensitivity and the primary resonance point of the lens actuator are contradictory designs of high rigidity and damping. However, the conventional structure has a small degree of freedom, and it is extremely difficult to optimize the design. Therefore, conventionally, in order to obtain a neutral position, a magnetic levitation system using an iron piece and a magnet or a means for obtaining a neutral position with damping rubber has been adopted.

In these cases, the lens holding member must be light in order to reach the neutral position, but on the other hand, there is a condition that a rigid member is required to achieve a high band. Therefore, the degree of freedom in designing the acceleration sensitivity characteristic and the primary resonance point, which are the basic characteristics of the actuator, is lost. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the above-mentioned drawbacks of the prior art, to maintain a neutral position of an objective lens in a lens actuator, and to provide an objective lens support structure having a degree of freedom in design.

[0020]

In order to achieve the above-mentioned object, the present invention employs the following basic technical structure. That is, it is configured to irradiate the surface of the optical disk with a light beam output from the light source via the objective lens means, to read out appropriate information from the optical disk or write appropriate information to the optical disk. The optical information processing device is provided with the objective lens means mounted thereon, and the objective lens means is servo-driven in at least one of a focusing direction and a tracking direction with respect to the surface of the optical disc by appropriate control means. And a shape memory alloy is used for at least a part of the support structure of the objective lens.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The objective lens supporting structure according to the present invention employs the above-mentioned technical structure. Therefore, a shape memory alloy supporting member for supporting the lens holder, for example, a one-side grip connecting member. Using, in the shape memory alloy, at the time of the first setting, the objective lens stores the neutral position of the objective lens in the optical head device,
Even when the connecting member is deformed or bent by long-term use, by applying electricity, a predetermined heat is generated to return the shape memory alloy to the neutral position. Thus, it is possible to always set the objective lens at a predetermined neutral position.

Of course, in the present invention, only when the neutral position of the objective lens needs to be set accurately must the energization process be performed, the structure is simple and lightweight. It is possible to achieve the excellent effect of being economical.

[0023]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a supporting structure for an objective lens according to an embodiment of the present invention. That is, FIG. 1 is a plan view showing the structure of a specific example of a supporting structure for an objective lens according to the present invention, and FIG. 2 is a side view thereof.

That is, FIGS. 1 and 2 show that the light beam output from the light source is irradiated onto the surface of the optical disk 9 via the objective lens means 1 to read out appropriate information from the optical disk 9 or 9 is provided in an optical information processing apparatus configured to write appropriate information to the optical disc 9 and the objective lens means 1 is mounted on the optical disc 9 by appropriate control means. An objective lens support structure 30 that is servo-driven in at least one of a focusing direction and a tracking direction with respect to the surface of the objective lens, wherein at least a part of the objective lens support structure 20 uses a shape memory alloy. A lens support structure 30 is shown, and more specifically, the shape memory alloy includes a lens holder portion on which the objective lens 1 is mounted. And from that of the objective lens 1 is intended to be used in the connecting member 5 for connecting the support frame 25 which is fixedly arranged independent.

That is, the connecting member 5 according to the present invention.
Although the configuration of the optical disk 9 is not particularly limited, the optical disk 9 is formed in a narrow and long body so that the surface of the optical disk 9 can be freely deformed in at least one of a focusing direction and a tracking direction. More specifically, it is desirable to have a leaf spring shape such as a leaf spring.

In the objective lens support structure 30 according to the present invention, one end of the connecting member 5 is fixedly held by the support frame 25, while the other end is It is preferable that it is formed of a cantilever type beam structure joined to the lens holder 2. The structure and operation of the objective lens support structure 30 according to the present invention will be described in more detail. As shown in FIG. 1, the objective lens 1 is used for focusing control and / or tracking control of a conventionally used objective lens 1. Lens actuator 20
Is configured to drive a lens holder 2 holding an objective lens 1.

The lens holder 2 includes a focusing coil 3 for generating a force for driving the objective lens in the focusing direction and a tracking coil 4 for generating a force for driving the objective lens in the track direction. Further, in order to form a magnetic circuit configuration with the focusing coil 3 and the tracking coil 4, a magnet 6 is disposed on a yoke 7 which is a fixing member of the lens actuator.

In the present invention, the magnet 6 of the magnetic circuit is
It is arranged at a position facing the focusing coil 3 and the tracking coil 4 provided on the lens holder 2 which is a movable part. The support member of the objective lens which is a movable part driven by the magnetic circuit in the lens actuator 20, that is, the lens holder 2, can be controlled to move in one or both of the focusing control direction and the tracking control direction. As shown in FIGS. 1 and 2, a connecting member 5 composed of a leaf leaf spring is attached in a cantilevered structure, and preferably, the connecting member 5 is, as shown in FIG. It is composed of a total of four leaf springs.

By using the four connecting members 5, the necessary strength for supporting the lens holder 2 can be obtained, and the movable member can be easily moved in the tracking control direction. 1 can move in parallel along the focusing control direction. In the present invention, the connection member, for example, the leaf leaf spring 5 is made of a shape memory alloy without changing the conventional lens actuator structure.

That is, as shown in FIG.
The connecting member 5 composed of a leaf leaf spring is fixed by a cantilever configuration between the support frame 25 and the lens holder 2 or a fixed member that constitutes a part of the lens actuator unit 20 of the optical head device. It has a configuration in which two connecting members 5 are arranged in parallel in the direction.

In the present invention, the distance between the upper and lower portions of the connecting member 5 and the length, thickness, and width of the leaf leaf spring are adjusted in accordance with mechanical characteristics such as eccentricity, surface runout, and rotation speed of the optical disk for recording and reproduction. It is desirable to design optimally. Furthermore,
The design of statically holding the objective lens at the neutral position of the design does not match the dynamic design following the reproduction of the recorded information on the optical disk. Therefore, in the present invention, a shape memory alloy is used for a leaf leaf spring which is an example of the connecting member 5.

The shape memory alloy used in the present invention comprises:
It is desirable that the objective lens has a function of generating heat by energization and restoring the shape stored in advance, thereby returning the objective lens to the neutral position. That is, in the present invention, when the shape memory alloy is used as the connecting member 5, the shape memory alloy forming the connecting member 5 becomes the objective lens 1 when a predetermined energizing process is performed. It is desirable to design in advance such that the optical head device is deformed and fixed to the neutral position in the optical head device.

In the present invention, when the shape memory alloy constituting the connecting member 5 is operated, when the optical head device is switched from the stopped state to the operating state, or the operation mode is continued. At a predetermined interval while the objective lens 1 is at a predetermined neutral position, it is determined whether or not the objective lens 1 is at a predetermined neutral position. The energization process is performed, and thereafter, the energization operation is not performed.

That is, the shape memory alloy desirably has a configuration in which, for example, a suitable spring material is used as a base, and a metal film that is deformed by electric heating and returns to a predetermined shape is bonded thereto. The metal film as the shape memory alloy used in the present invention is preferably a titanium-nickel alloy film.

FIG. 3 shows an example of the structure of the connecting member 5 using the shape memory alloy of the present invention. That is, as shown in FIG. 3A, for example, a titanium-nickel alloy (TiNi alloy) is used as a first alloy film 11 that is deformed by electric heating on a spring material 10 made of an appropriate material. The connecting member 5 is configured as a leaf spring that restores the stored shape so that the objective lens 1 returns to the normal neutral position.

That is, in the present invention, the position corresponding to the neutral position of the objective lens 1 is stored in the first alloy film 11 and the TiNi film constituting the leaf spring shape. As shown in FIG. 3B, a second metal film 12, for example, a Ni film may be deposited on the one alloy film 11 in a reinforcing manner. Thus, by forming a composite structure in which a Ni film is formed on a thin film of TiNi,
Normally, the Ni film maintains a constant state by its spring force, and when the connecting member 5 is deformed or bent,
When electricity is supplied to the TiNi film, N
Since the force for restoring the shape of the TiNi film overcomes the spring force of the i film, the connecting member 5 returns to the state stored in advance.

That is, in the shape memory alloy according to the present invention, it is desirable that a nickel film is formed on the surface of the titanium-nickel alloy film. On the other hand, as another specific example of the shape of the connecting member 5 used in the present invention, FIG.
As shown in FIG. 4B, the mounting portion 15 for the objective lens 1, the portion 14 for mounting on the fixed support, and the two opposing connecting members 5, 5 'are integrally formed. You can also.

As described above, by integrally forming the connecting member 5, the wire of the magnetic circuit and the supporting structure of the objective lens can be made common, and the reinforcing effect and the neutralization of the objective lens when electricity is supplied can be achieved. Accuracy in determining the position is improved. By forming the connecting member 5 in such a shape, it is possible to eliminate higher-order resonance by increasing the rigidity of the connecting member 5.

Also, in this embodiment, as shown in FIG. 4B, the connecting members 5 having the structure shown in FIG. 4A are arranged in two stages in the focus direction. By doing so, rolling and pitching in supporting the objective lens can be effectively removed. In other words, as another aspect of the present invention, the connecting member 5 is a pair of narrow elongated members arranged so as to be parallel to two opposing side surfaces of the lens holder 2. A support frame engaging portion 14, which is a portion attached to a fixed support portion 25 that connects the end portions 5, 5 'and one end portions 26, 26' of the long body portions 5, 5 ', and the long body The other end 27 of the part 5, 5 ',
27 'is an objective lens support structure having a shape integrally formed with a lens holder support portion 15 which constitutes a mounting portion of the objective lens 1 for connecting the objective lenses 1 to each other.

Further, as a third aspect according to the present invention,
As is apparent from the above description, the surface of the optical disk is irradiated with the light beam output from the light source via the objective lens means, and the appropriate information is read from the optical disk or the appropriate information is written to the optical disk. It is provided in an optical information processing apparatus configured to write, and the objective lens means is mounted, and the objective lens means is moved in a focusing direction and a tracking direction with respect to the surface of the optical disc by appropriate control means. In a supporting structure for an objective lens that is servo-driven in at least one direction, a connecting member made of a shape memory alloy in which a predetermined neutral position of the objective lens is stored in at least a part of the supporting structure for the objective lens. To provide the memory function of the shape memory alloy when the objective lens is offset from the neutral position. So it is a position correction method of the configured objective lens as being constructed as to return the objective lens to the neutral position.

In the objective lens position correcting method having the above-described structure, the shape memory alloy used for the connecting member is configured to return to the neutral position of the objective lens stored in advance by energization. In addition, the energizing operation for the shape memory alloy is a method of correcting the position of the objective lens which is performed only at the time of the offset adjustment operation of the objective lens.

[0042]

Since the present invention has the above-mentioned technical configuration, the first effect obtained thereby is that the neutral position of the objective lens can be controlled by performing the energizing operation, and at the same time, There is an effect that a design in which the resonance mode in the rolling and pitching directions generated by higher-order resonance can be reduced.

The reason is that, since the objective lens supporting member is formed of a shape memory alloy, it is possible to control the objective lens to a neutral position by energization. Is an integral structure, so that rolling and pitching can be reduced.
Further, the second effect of the present invention is that the support member of the objective lens can be used in common with the wire of the magnetic circuit, and can be used for recording and reproduction of a high-density disk that requires high-precision reproduction performance. Thus, the capacity of the optical recording / reproducing apparatus can be increased.

The reason is that a minute spot required for recording and reproduction on a high-density disk can always be irradiated to the optical disk without causing a relative inclination between the objective lens and the optical axis in focus control and tracking control. It is.

[Brief description of the drawings]

FIG. 1 is a plan view showing the configuration of a specific example of a support structure for an objective lens according to the present invention.

FIG. 2 is a side view showing a configuration of a specific example of a support structure for an objective lens according to the present invention.

FIG. 3A and FIG. 3B are cross-sectional views showing an example of a shape memory alloy constituting a connecting member used in the present invention.

FIG. 4A is a plan view showing the configuration of another specific example of the connecting member used in the present invention, and FIG.
Is a perspective view showing the state of use.

FIG. 5 is a block diagram showing a configuration example of a conventional optical head device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Objective lens 2 ... Lens holder 3 ... Focus coil 4 ... Track coil 5 ... Connecting member 6 ... Magnet 7 ... Yoke 9 ... Optical disk 10 ... Spring material 11 ... First alloy film (TiNi film) 12 ... Second metal Film (Ni film) 14 Support frame engaging part 15 Lens holder support part 16 Semiconductor laser 17 Diffraction grating 18 Beam splitter 19 Photodetector 20 Lens actuator 21 Cylindrical lens

Claims (13)

[Claims] 1. A method of irradiating a light beam output from a light source to the surface of an optical disk via an objective lens means to read out appropriate information from the optical disk or write appropriate information to the optical disk. The optical information processing apparatus is provided with the objective lens means, and the objective lens means is moved in at least one of a focusing direction and a tracking direction with respect to the surface of the optical disc by appropriate control means. An objective lens support structure for a servo-driven objective lens, wherein a shape memory alloy is used in at least a part of the objective lens support structure. 2. The shape memory alloy is used as a connecting member for connecting a lens holder portion on which the objective lens is mounted and a support frame which is fixedly arranged independently of the objective lens. The support structure for an objective lens according to claim 1, wherein: 3. The connecting member is formed in a narrow elongated body, one end of the connecting member is fixedly held by the support frame, while the other end is connected to the lens holder. 3. The supporting structure for an objective lens according to claim 2, wherein the supporting structure is a cantilever type beam structure joined to the portion. 4. The lens holder according to claim 3, wherein a plurality of the connecting members are used in parallel with each other and on each side of the lens holder.
A supporting structure for the objective lens described in the above. 5. The structure according to claim 4, wherein the shape memory alloy used in said connecting member is restored to a previously stored shape by energization, and the objective lens is returned to a neutral position. A supporting structure for the objective lens described in the above. 6. The object according to claim 5, wherein the shape memory alloy has a configuration in which a metal film that is deformed by electric heating and returns to a predetermined shape is bonded to an appropriate spring material. Lens support structure. 7. The supporting structure for an objective lens according to claim 6, wherein said metal film is a titanium-nickel alloy film. 8. The supporting structure for an objective lens according to claim 7, wherein said metal film further comprises a nickel film formed on a surface of a titanium-nickel alloy film. 9. The pair of narrow elongated body portions and one of the elongated body portions arranged so as to be parallel to two opposing side surfaces of the lens holder portion. It is characterized in that the supporting frame engaging portion for connecting the end portions and the lens holder portion supporting portion for connecting the other end portions of the long body portion have a shape integrally formed. The supporting structure for an objective lens according to claim 1. 10. The connecting member having the integrated shape,
10. The objective lens supporting structure according to claim 9, wherein a plurality of the lens holders are used in a focusing direction. 11. A method of irradiating a light beam output from a light source to the surface of an optical disk via an objective lens means to read out appropriate information from the optical disk or write appropriate information to the optical disk. The optical information processing apparatus is provided with the objective lens means, and the objective lens means is moved in at least one of a focusing direction and a tracking direction with respect to the surface of the optical disc by appropriate control means. In the supporting structure of the objective lens to be servo-driven, at least a part of the supporting structure of the objective lens is provided with a connecting member made of a shape memory alloy in which a predetermined neutral position of the objective lens is stored. When the objective lens is offset from the neutral position, the memory function of the shape memory alloy is exhibited to A position correcting method for an objective lens, characterized in that the objective lens is returned to a position. 12. The objective lens according to claim 11, wherein the shape memory alloy used for the connection member is configured to return to a neutral position of the objective lens stored in advance by energization. Position correction method. 13. The method for correcting the position of an objective lens according to claim 12, wherein the energizing operation for the shape memory alloy is performed only during an offset adjustment operation of the objective lens.