JPH11213439A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device capable of performing focus control by a simple and small-sized structure. SOLUTION: A freely rotatably and freely parallelly movably supported mirror 32 is arranged at the part of non-parallel light in an optical path, a moving coil 34 for parallelly moving the mirror 32 is provided and the focus control is performed by supplying a focus control current to the moving coil 34, almost parallelly moving the mirror 32 and changing the length of the optical path. The structure is simple and miniaturization is facilitated. Also, since the mass of a reflection element can be reduced generally, a response speed is accelerated, the responsiveness of the focus control is improved or the like and the effects are large.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical device, for example, a magneto-optical disk drive, a write-once disk drive,
The present invention relates to an information recording / reproducing apparatus for recording and / or reproducing information on an optical recording medium such as a phase change disk drive, a CD-ROM, a DVD, and an optical card, and an optical pickup apparatus such as an optical scanner. More specifically, the present invention relates to an optical pickup device provided with a focus control device having a simple structure and good response characteristics.

[0002]

2. Description of the Related Art In an optical pickup device as described above,
It is necessary to perform tracking control to accurately position the light spot condensed by the optical system on the optical recording medium, and if necessary, focus to precisely converge the light spot on the optical recording medium Control is needed.

The above-mentioned tracking control includes mechanical tracking control for mechanically moving a carriage or the like provided with an optical system, and deflecting the angle of a light beam by a rotating mirror such as a galvanometer mirror to position the light spot. There is an optical tracking control for controlling the speed, and many of them are used in combination. In many cases, the focus control is performed by, for example, moving a conversion lens of an optical system.

In the above focus control, a relatively large and large-mass conversion lens or the like is moved, so that the lens supporting and guiding mechanism and the driving mechanism are large and the response speed is low. There was a defect and it was not always satisfactory.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an optical pickup device which has a simple structure, can be formed in a small size, and can perform focus control with good response characteristics. It is intended to do so.

[0006]

According to a first aspect of the present invention, there is provided an optical system for an optical pickup device, comprising a reflecting element which is disposed at a non-parallel light portion of an optical path of an optical system and is supported at least in a freely movable manner. In addition, a driving mechanism for driving the above-mentioned reflection element is provided.

Therefore, by moving the above-mentioned reflecting element substantially in parallel by the above-mentioned driving mechanism, focus control can be performed by changing the length of the optical path of the non-parallel light, and the structure is simple and compact. Easy. In addition, since the mass of the reflective element can be generally reduced, the response speed is increased, and the responsiveness of the focus control is improved.

According to a second aspect of the present invention, the reflecting element is supported so as to be able to translate and rotate freely.
The reflection element rotates together with the parallel movement, and corrects a tracking error accompanying the parallel movement for focus control by the rotation. Therefore, it is possible to automatically correct the tracking error due to such focus control, and it is not necessary to provide an optical element or the like for correcting the tracking error, and the structure is simple and the miniaturization is easy.

According to a third aspect of the present invention, the driving mechanism includes a magnet and a moving coil that translates the reflecting element. Therefore, it has the same structure as a moving coil or moving magnet type drive mechanism generally used for a conventional galvanometer mirror or the like, and can be implemented easily and at low cost only by adding a small modification to an existing mechanism. Further, by controlling the current supplied to the moving coil, the movement of the reflecting element can be controlled, and the configuration of the control circuit and the like is simple and the same control circuit as the existing one can be used.

According to a fourth aspect of the present invention, the reflecting element is a mirror of a galvano mirror that performs a fine tracking operation. Therefore, this galvanomirror can be used for both the functions of fine tracking control and focus control, so that the structure is simplified and the optical pickup device can be made more compact.

According to a fifth aspect of the present invention, the galvanomirror includes a fixed member and a movable member, and the movable member is rotatable and parallel movable with respect to the fixed member. A mirror is attached to the front surface of the movable member, and a pair of permanent magnets arranged on both sides of the movable member are attached to the fixed member side. A rotating coil for rotating the movable member and the mirror is attached to the movable member, and a pair of permanent magnets are provided on both sides of the movable member to oppose the pair of permanent magnets and move the movable member and the mirror in parallel. A moving coil is attached.

Therefore, the present invention can be implemented only by adding a moving coil to the conventional galvanometer mirror used for tracking control and the like, and the structure is simple and the manufacturing cost can be greatly reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 6 show a first embodiment of the present invention. In this embodiment, the present invention is applied to a galvano mirror of an optical pickup device of an information recording / reproducing apparatus using a magneto-optical disk as a recording medium. Is the case.

First, a schematic arrangement of the optical elements of the optical pickup device will be described with reference to FIG. In the figure, reference numeral 1 denotes a magneto-optical disk, and an arm-shaped carriage 2 is provided along the recording surface of the magneto-optical disk 1.
An optical system described later is provided in the carriage 1.
This optical system connects a light spot P on the recording surface of the magneto-optical disk 1 to write and read information.

The above-mentioned carriage 2 is rotated by a drive mechanism (not shown) about the rotation shaft 3 and mechanically moves its distal end to perform coarse access. Further, the above-mentioned optical system is provided with a galvanomirror 20, which will be described later, and performs fine tracking by optically moving the light spot P. The galvanomirror 20 incorporates a focus control mechanism of the present invention described later.

Although the specific structure of the above-mentioned carriage 2 is not shown, it is formed by, for example, die casting of a magnesium alloy or molding of a plastic, and the above-mentioned optical system is built therein. In addition to the above-mentioned magnesium alloy die-cast, the carriage 2 is made of aluminum alloy die-cast, polyphenylene sulfide (PPS), liquid crystal plastic (LCP), polyetherimide (PEI).
And the like.

This optical system has a laser diode 11 as a light source, and a part of the light emitted from the laser diode 11 is reflected on the surface of a beam splitter 12, and this reflected light enters a collimating lens 13 and becomes a parallel light. Becomes Then, the parallel light is collected by the relay lens 14. Further, this optical system is provided with a galvano mirror 20 described later, and the light condensed by the relay lens 14 is reflected by the mirror 21 of the galvano mirror 20 slightly before the focal position, and is converted by the conversion lens 15. Is converted into parallel light again. The parallel light travels along the longitudinal direction of the arm portion of the carriage 2 and is reflected by a fixed mirror 16 provided at the tip of the arm portion. This reflected light enters the objective lens 17 and connects the light spot P on the recording surface of the magneto-optical disk 1 described above.

A part of the return light reflected from the recording surface of the magneto-optical disc 1 passes through the beam splitter 12 and enters the photodetector 18. The output from the photodetector 18 provides signals such as an information reproduction signal, a focusing error signal, and a tracking error signal. And, for example, the above focusing error signal, tracking error signal, etc.
It is sent to a control circuit (not shown) of the optical pickup device, and the control signal from the control circuit causes the mirror 21 of the galvanomirror 20 to rotate around its mirror rotation axis, whereby the light spot P The above-described fine tracking is performed by moving the position optically in the tracking direction. The relay lens 14 is driven in the optical axis direction by a drive mechanism (not shown) by a control signal from the control circuit to control the focus of the light spot P on the magneto-optical disk 1.

In this embodiment, the optical paths from the laser diode 11 to the fixed mirror 16 and the photodetector 18 are all arranged in a plane parallel to the rotation plane of the carriage 2. ing.

Next, the configuration of the main part of the galvanometer mirror 20 used in the optical pickup device of this embodiment will be described. FIG. 2 is a front view of the galvanomirror of the embodiment as viewed from the front. FIG. 3 is a side view in which a part along line 3-3 in FIG. 2 is broken, and FIG. 4 is a cross-sectional view along line 4-4 in FIG.

Reference numeral 21 in the drawing denotes a fixing member, and the fixing member 21 is formed of a synthetic resin material. The fixing member 21 has a cantilever shape, and has an integral arm portion 23 at both upper and lower ends. A mounting portion 24 for mounting a spring to be described later is provided at a central portion of these arm portions 23.
Are formed. Reference numeral 22 in the drawing denotes a movable member, and the movable member 22 is formed of a synthetic resin material. The movable member 22 has, for example, a rectangular block shape, and mounting portions 25 for mounting a spring are formed at both upper and lower ends thereof.

The movable member 22 is rotatable about a vertical axis, that is, an axis parallel to the illustrated Z axis, with respect to the fixed member 21 by a pair of springs 26, and is substantially movable in the front-rear direction, that is, the Y direction illustrated. It is supported so that it can move in parallel. The spring 26 is made of a thin plate made of a spring material such as beryllium copper alloy. In the case of this embodiment, the spring 26 has a narrow band shape as a whole, and the end on the side of the mounting portion 24 is easily deformed. Y-shaped part 26a branched to fork
Are formed. And these springs 26 are arranged along the vertical direction, and the upper and lower ends thereof are fixed members 2.
The first mounting portion 24 and the mounting portion of the movable member 22 are mounted on the mounting portion 25, respectively. Then, as the springs 26 are torsionally deformed, the movable member 22 is rotatably supported around a rotation center axis passing through the center axis of the springs 26 as shown in FIG. Further, as the Y-shaped portion 26a of these springs 26 is mainly deformed, these springs 26 are extended, and the movable member 22 is moved relative to the fixed member 21 in the front-rear direction perpendicular to the reflection surface of the mirror 32, ie, in the Y direction. And is supported so as to be movable substantially in parallel with.

A rectangular mirror 32 is mounted on the front surface of the movable member 22. The galvanometer mirror 20 is disposed such that the mirror 32 makes an angle of approximately 45 ° with the light beam of the optical system of the optical pickup device, reflects the light beam by the mirror 32, and And mirror 32 is Z
By rotating about an axis parallel to the axis, the light beam is deflected to perform optical fine tracking.

Fixed permanent magnets 31 are provided on both sides of the movable member 22, respectively, and these permanent magnets 31 are attached to the fixed member 21 side. The polarities of the permanent magnets 31 are arranged so as to be opposite to each other with respect to the movable member 22.

The movable member 22 is provided with a rotary coil 33 and a pair of movable coils 34 as movable side coils. The rotating coil 33 is a substantially rectangular ring-shaped coil arranged so as to surround the periphery of the mirror 32, and its coil axis is arranged perpendicular to the reflection surface of the mirror 32. . The pair of moving coils 34 are disposed on both sides of the movable member 22 so as to face the permanent magnets 31, respectively, and have a substantially rectangular ring shape. The rotary coil 33 and the moving coil 34 are configured to be supplied with a control current for fine tracking and a control current for focus control from a control circuit (not shown) via a power supply path (not shown). I have.

As shown in FIG. 6, the mirror 32 of the galvanometer mirror 20 is provided between the non-parallel light portion, for example, the relay lens 14 and the conversion lens 15 in the optical path of the optical system of the optical pickup device. As described above, the light from the relay lens 14 is arranged at an angle of about 45 ° to reflect the light at an angle of about 90 °, and the mirror 32 rotates to reflect the light. To perform optical fine tracking as described above.

Next, the operation of the galvanomirror 20 will be described with reference to FIGS. FIG. 5 is a diagram schematically showing the permanent magnet 31, the mirror 32, the rotating coil 33, the moving coil 34, and the like of the galvanometer mirror 20. FIG. 6 is a diagram showing the relationship between a part of the optical system of the optical pickup device and the mirror 32. In FIG. 6, the portions corresponding to FIG. 1 are denoted by the same reference numerals. FIG.
The fixed mirror 16 described above is omitted in FIG.

First, when the tracking control current from the control circuit is supplied to the rotary coil 33, electromagnetic forces in opposite directions are generated on both sides of the rotary coil 33 as shown by arrows in FIG. As a result, the mirror 32 rotates about its rotation axis, deflects the reflected light, and performs optical tracking control as described above. This structure and operation are the same as those of a conventionally known galvanomirror.

At the same time, a focus control current is supplied to the moving coil 34 from the control circuit. Each of the moving coils 34 is supplied with a focus control current so that an electromagnetic force in the same direction is generated as shown by an arrow in FIG. Therefore, the mirror 32 moves substantially perpendicular to the reflection surface, and moves as shown in FIG. Therefore, the light reflected by the mirror 32 is displaced to the position indicated by LA in FIG.
The optical path length between 4 and the conversion lens 15 changes by D. That is, optically, the imaging lens 14
Becomes closer to the relay lens 15. Since this light is non-parallel light, the light emitted from the conversion lens 15 changes in the divergent direction due to the change in the optical path length, and the focal position of the objective lens 17 is shifted in the optical axis direction away from the objective lens 17. Is displaced.

Therefore, for example, when the mirror 32 is located at the position shown by the two-dot chain line in FIG. 6 and the light spot P, that is, the focal point is shifted to the position shown by the two-dot chain line, as described above, By moving the mirror 32 in parallel to the position indicated by the solid line in FIG. 6, the light spot P is accurately positioned on the recording surface of the optical recording medium 1 as indicated by the solid line,
Focus control can be performed.

When the mirror 32 is moved in parallel in the reverse direction of FIG. 6, the light emitted from the conversion lens 15 changes in the direction of convergence, and the focal position of the objective lens 17 is shifted in the optical axis direction. Can be displaced in a direction approaching.

In this case, as shown in FIG. 5, the reflected light LA at the mirror 32 is displaced by D,
The position of the light spot P is also displaced, causing an error in tracking. In order to eliminate such an error, FIG.
As shown by B, by moving the mirror 32 in parallel and tilting it by a predetermined angle, the reflected light is deflected like LB, thereby canceling the tracking error as described above. .

To correct the tracking error due to the inclination of the mirror 32 as described above, a focus control current is supplied to the moving coil 34 to move the mirror 32 in parallel, and at the same time, a tracking error correction current is supplied to the rotating coil 33. This can be achieved by rotating the mirror 32 by a predetermined angle together with the parallel movement, and tilting the mirror 32 as shown in B above. Note that such correction of the tracking error can also be achieved by tilting the mirror 32 by giving a predetermined difference to the focus control current supplied to the left and right moving coils 34. Also, a difference may be given to the characteristics of the left and right moving coils 34, for example, by giving a difference in the number of turns of the left and right moving coils 34 in advance.

In the first embodiment, a moving coil 34 is added to a galvanomirror for performing tracking control, and the mirror 32 is moved in parallel, so that the function of focus control is also used. Therefore, the structure is simple and downsizing is easy, and it can be easily implemented only by adding a small-scale modification to a conventional existing galvanomirror, and the manufacturing cost can be reduced.

The present invention is not limited to the first embodiment. In the first embodiment, the galvanometer mirror that performs the tracking control by rotating the mirror includes:
Although the function of controlling the focus by moving the mirror in parallel is also used, the present invention is not limited to this, and a dedicated optical element for controlling the focus by moving a reflective element such as a mirror may be configured. For example, as described above, when an optical element that does not double as a galvanomirror that performs tracking control is configured, it can be configured as in the second embodiment illustrated in FIG.

The second embodiment includes a support mechanism (not shown) for rotating the mirror 32 about a rotation center R at a predetermined position laterally separated from the mirror 32. Further, the rotary coil as in the first embodiment is omitted. In this embodiment, when the mirror 32 is translated by the moving coil 34, the mirror 32 rotates about the rotation center R and tilts by a predetermined angle as shown in FIG. Then, a tracking error accompanying the parallel movement of the mirror 32 is corrected.
The position of the rotation center R is set such that the parallel movement amount and the tilt angle of the mirror 32 have a predetermined relationship according to the optical system and other characteristics.

Further, the present invention is not limited to the above embodiments. For example, when an optical element such as a galvanometer mirror for performing tracking control is separately provided, it is not always necessary to tilt the mirror as in the above-described second embodiment. The tracking error due to the movement may be corrected by a galvanometer mirror or the like provided separately. The reflecting element is not limited to a mirror, but may be a reflecting element such as a prism.
Further, in the above embodiment, the coil is provided on the movable member side. However, on the contrary, a permanent magnet may be provided on the movable member side, and the coil may be provided on the fixed member side.

The mirror for substantially parallel movement only needs to be in the non-parallel light beam. For example, the mirror may be arranged in the optical path between the laser diode 11 and the collimator lens 13.

Further, the present invention is not limited to the so-called swing arm type access mechanism as in the above embodiment, but may be, for example, a linear drive mechanism.

[0040]

As described above, according to the present invention, the focus control is performed by moving the reflecting element arranged in the non-parallel light portion substantially in parallel by the driving mechanism and changing the length of the optical path of the non-parallel light portion. And the structure is simple and downsizing is easy. Generally, since the mass of the reflective element can be reduced, the response speed is increased, and the effect of the focus control is improved.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an optical pickup device according to a first embodiment of the present invention.

FIG. 2 is a front view of a main part of the galvanomirror of the first embodiment as viewed from the front.

FIG. 3 is a side view showing a part along a line 3-3 in FIG. 2 in cross section;

FIG. 4 is a sectional view taken along the line 4-4 in FIG. 2;

FIG. 5 is a schematic view showing the operation of a mirror.

FIG. 6 is a schematic view showing the operation of a part of an optical system and a mirror.

FIG. 7 is a schematic view of a second embodiment.

[Explanation of symbols]

 2 Carriage 20 Galvano mirror 21 Fixed member 22 Movable member 26 Spring 31 Permanent magnet 32 Mirror 33 Rotary coil 34 Moving coil

Claims (5)

[Claims] An optical path of an optical system of the optical pickup device, wherein the optical element includes a reflection element which is disposed at a portion of the non-parallel light and is supported so as to be movable at least substantially in parallel; and a driving mechanism for driving the reflection element is provided. An optical pickup device, comprising: 2. The reflection element is supported so as to be able to translate and rotate freely, and this reflection element rotates together with the parallel movement, and a tracking error accompanying the parallel movement for focus control is caused by the rotation. 2. The optical pickup device according to claim 1, wherein the correction is performed. 3. The optical pickup device according to claim 1, wherein the driving mechanism includes a magnet and a moving coil that translates the reflecting element. 4. The optical pickup device according to claim 1, wherein the reflection element is a mirror of a galvanometer mirror that performs a fine tracking operation. 5. The galvanomirror includes a fixed member and a movable member. The movable member is rotatably and translationally supported with respect to the fixed member. A mirror is mounted on the front surface, and a pair of permanent magnets disposed on both sides of the movable member are mounted on the fixed member side.The movable member and the mirror are mounted on the movable member. A rotating coil for rotating is mounted, and a pair of moving coils for moving the movable member and the mirror in parallel with the pair of permanent magnets are mounted on both sides of the movable member. The optical pickup device according to claim 4, wherein