JPH0660405A - Mirror driving device - Google Patents

Abstract

PURPOSE:To reduce the shift amount of a light beam by the rotation of a mirror, to stabilize operation and to reduce the cost of a device. CONSTITUTION:A mirror 20 is fixed on the front surface 32a of a fixing member 32. The fixing member 32 is supported by a base 44 by means of a first and a second leaf springs 40, 42 arranged in parallel and equally spaced to each other. A step 50 is formed at the foot part 46 of the base 44. The first leaf spring 40 and the second leaf spring 42 are arranged at the front and the rear of the step 50, respectively. The upper end parts of the respective springs 40, 42 are firmly fixed on the fixing member 32 with adhesives 58 and the respective lower ends are firmly fixed on the foot part 46 with adhesives 58. Consequently, two leaf springs 40, 42 are firmly fixed on the common member and the exposed lengths of two leaf springs 40, 42 are made different by means of the step 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror driving device used in a separation type optical pickup. Here, the optical pickup means not only an optical pickup that records and reproduces information on an optical recording medium such as an optical disc, but also a magneto-optical pickup that records and reproduces information on a magneto-optical recording medium such as a magneto-optical disc. It is a name that also includes.

[0002]

2. Description of the Related Art A mirror driving device is used, for example, to move a spot irradiated on a magneto-optical disk in a tracking direction. The spot irradiated on the disc is reflected by the recording surface and detected by the detector. The tracking error of the magneto-optical disk is usually detected by the push-pull method. The detector used in the push-pull method is divided into two, and the tracking error is detected by comparing the light intensities of the spots incident on the respective segments.

As a conventional mirror driving device, one shown in FIG. 9 is known. This device is provided in a separate type magneto-optical pickup (hereinafter, simply referred to as an optical pickup) 82 for a magneto-optical disc (hereinafter, simply referred to as a disk) 80. This optical pickup 82
Has a fixed optical system 82a and a moving optical system 82b. A semiconductor laser element 84 is provided in the fixed optical system 82a.
A collimator lens 86, first and second prisms 88 and 90, a first fixed mirror 92, and a movable mirror 94 that constitutes a part of a mirror driving device. The moving optical system 82b includes a second fixed mirror 98 fixed inside the moving optical system 82b and an objective lens 100.

In this optical pickup 82, the light emitted from the semiconductor laser element 84 is collimated by the collimator lens 86 to become parallel light, and the first prism 88 for servo signal detection and the second prism 90 for magneto-optical signal detection are provided. And is reflected by the first fixed mirror 92. This light is reflected again by the movable mirror 94. The light travels substantially along the seek direction 96, is reflected by the second fixed mirror 98, and is converged on the recording surface of the magneto-optical disk 80 by the objective lens 100.

The light beam reflected by the recording surface of the magneto-optical disk 80 follows the above-mentioned optical path in reverse, and is partially reflected by the first prism 88. The reflected light enters the detector 102 shown in FIG. 11, and the tracking error is detected by the push-pull method. As a result, if a tracking error occurs, the movable mirror 94 is rotated as shown in FIG. 10, and the error is corrected. However, in this mirror driving device, when the movable mirror 94 is rotated, the optical axis 104 of the light beam deviates from the optical axis of the objective lens 100.

In the state without this deviation, as shown in FIG. 11, the position 106 of the reflected light from the disc is concentric with the light beam 108 incident on the objective lens and traveling toward the disc. However, if the above deviation occurs,
The reflected light from the disc is the dividing line 110 of the detector 102.
The position 106 in the state where there is no deviation shifts to the position indicated by the reference numeral 112 along the direction 111 orthogonal to.
When the light spot shifts to this position 112, the detector 1
Of the two 02 segments 102a and 102b, the light intensity of the lower segment 102b in the figure is higher than that of the upper segment 102b, which causes an offset in the detection signal. Therefore, if this mirror driving device is used for an optical pickup, an appropriate tracking error signal cannot be obtained if there is a deviation between the two optical axes.

In order to solve such a defect, a mirror driving device disclosed in, for example, Japanese Patent Laid-Open No. 2-294942 is known. As shown in FIG. 12, this second conventional device includes a first lens 114 and a second lens between the movable mirror 94 and the second fixed mirror 98 in the above-described first conventional device. And an afocal optical system consisting of 116.

On the other hand, a mirror is fixed to the other end of a rod-shaped support member rotatably supported at one end, and the support member is rotated by using an elastic member having a cross-shaped cross section to form the mirror. A driven mirror driving device is disclosed in Japanese Patent Application Laid-Open No. 58-58
No. 168030.

[0009]

In the second conventional example, an afocal optical system is provided in order to eliminate the offset of the detection signal, which is the drawback of the first conventional example.
However, by disposing such an optical system, the device itself becomes expensive, and aberrations increase due to this optical system, which also deteriorates the device in terms of performance.

In the device using the rod-shaped support member, that is, in the third conventional example, when the length of the support member is L and the tilt angle of the support member is θ, the displacement amount of the mirror is L · tan.
θ. Therefore, in order to increase the amount of displacement of the mirror, the length L of the support member must be increased, which is disadvantageous in terms of space. Moreover, the degree of freedom in design is limited because it depends only on the displacement amount L. An object of the present invention is to provide a low-cost mirror driving device that has a small shift amount of a light beam due to rotation of a mirror and has stable operation.

[0011]

Therefore, the mirror driving device according to the present invention is used in a separation type optical pickup having at least a light source, a beam splitter, an objective lens and a photodetector. A base arranged on an optical path between the beam splitter and the objective lens, a mirror, a fixing member for fixing the mirror, and at least one supporting member for supporting the fixing member on the base; Driving means for driving the mirror by selectively applying a force to the fixing member in a direction opposite to the above direction and a second direction opposite thereto, and when the mirror is driven, the mirror is It is characterized in that it is displaced with respect to the base and is inclined at the same time.

[0012]

The driving means selectively applies a force to the fixing member in the first direction and the second direction in the half body direction.
The fixing member moves with respect to the base while being supported by at least one supporting member, and the mirror attached to the fixing member tilts with respect to the base and is simultaneously displaced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the mirror driving device according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, the mirror driving device 2 of this embodiment constitutes a moving optical system disposed in a separation type magneto-optical pickup (hereinafter, simply referred to as an optical pickup) 4. It is arranged so as to be movable along the arrow A direction. The optical pickup 4 includes a semiconductor laser element 6 which is a light source. The light beam emitted from the semiconductor laser element 6 is collimated by the first collimator lens 8 and then transmitted through the beam splitter 10 to enter the mirror driving device 2.

As shown in FIG. 2, the mirror driving device 2 is
It has a housing 14. The first opening 16 and the second opening 1 are formed in one side wall and the upper wall of the housing 14.
8 are formed respectively. The light transmitted through the beam splitter 10 described above passes through the first opening 16, is reflected by the mirror 20, and is converged by the objective lens 22. The converged light is applied to a magneto-optical disk (hereinafter, simply referred to as a disk) 24 through the second opening 18.

The reflected light from the disk 24 passes through the second opening 18 and enters the objective lens 22, is collimated by the objective lens 22, and is reflected by the mirror 20. Then, the light passes through the first opening 16 and enters the beam splitter 10 shown in FIG. 1, and is reflected by the beam splitting surface of the beam splitter 10. This light enters the photodetector 30 via the second collimator lens 26 and the cylindrical lens 28, and information is detected.

As shown in FIG. 3, the mirror 20 of the mirror driving device 2 is fixed to the front surface 32a of a rectangular parallelepiped fixing member 32. In the rear portion 32b of the fixing member 32,
The protrusion 36 is formed. A coil 38 is wound around the protrusion 36 with the horizontal direction as the central axis. An electric circuit (not shown) is electrically connected to the coil 38, and an electric current is caused to flow therethrough.

The fixing member 32 is supported on the base 44 by the first and second plate springs 40 and 42 which are supporting members. The base 44 is fixed to the bottom wall of the housing 2 shown in FIG. 2 with screws or the like. As shown in FIG. 3, the base 44 is formed in a substantially L-shape, and is connected to the foot portion 46 extending forward and the rear end portion of the foot portion 46, and the arm portion extending upward. And 48. A step 50 is formed at the center of the foot portion 46, and the rear portion is higher than the front portion.

A slightly short cylindrical portion 52 having a central axis in the horizontal direction extends forward from the arm portion 48. A ring-shaped magnet 56 is fixed to the inner peripheral surface of the cylindrical portion 52. The magnet 56 is magnetized so that the outer peripheral side is the S pole and the inner peripheral side is the N pole. A coil 38 is arranged inside the ring-shaped magnet 56, and the coil 38 is always positioned in the magnetic field generated by the magnet 56.

The first leaf spring 40 and the second leaf spring 42 are made of the same material and have the same shape.
The leaf springs 40 and 42 are installed so as to be parallel to each other while keeping a constant interval. These leaf springs 40,
The upper end of each of 42 is a hole 3 formed in the fixing member 32.
2c and is fixed by the adhesive 58 to the fixing member 3
It is firmly fixed to 2. That is, the two leaf springs 40,
The upper end of 42 is firmly fixed to the same member (fixing member 32). On the other hand, the lower end of each is inserted into a hole 46a formed in the foot 46 of the base 44, and is firmly fixed to the base 44 by an adhesive 58. That is, the lower end portions of the two leaf springs 40 and 42 are firmly fixed to the same member (base 44).

The first leaf spring 40 has the step 5 of the base 44.
It is located in front of 0, and the second leaf spring 42 has a step 50.
It is located behind. As a result, the portion of the first plate spring 40 that is exposed to the outside without being embedded between the fixing member 32 and the base 44 (hereinafter, referred to as “exposed portion”) is larger than the second plate spring 42. It's getting longer. Therefore, the spring constant of the first leaf spring 40 having a long exposed portion is smaller than that of the second leaf spring 42 having a short exposed portion. The operation of the mirror driving device of the first embodiment having such a configuration will be described.

When a current is applied to the coil 38 from an electric circuit (not shown), the current electromagnetically acts on the magnetic field of the magnet 56, and as shown in FIGS. 4B and 4C, the fixing member 32. Forward force 60 and backward force 6
2 is added.

First leaf spring 40 and second leaf spring 42
Since the spring constants of the exposed parts are different and the two leaf springs 40 and 42 are firmly fixed to the same member,
When a forward force 60 is applied to the fixing member 32, the first and second leaf springs 40 and 42 are deformed as shown in FIG. 4B, and the fixing member 32 moves forward with respect to the base 44. Tilts clockwise while displacing. Therefore, the fixing member 32
Similarly to the fixing member 32, the mirror 20 attached to the front surface of the mirror tilts clockwise while displacing forward (see FIG. 5).
(B)).

On the contrary, when a rearward force 62 is applied to the fixing member 32, the first and second leaf springs 40 and 42 are deformed as shown in FIG. 4C, and the fixing member 32 is moved backward. Tilts counterclockwise while displacing to. Therefore mirror 2
Similarly to the fixing member, 0 also tilts in the counterclockwise direction while being displaced rearward (see (C) of FIG. 5).

By rotating the mirror in such a state, as shown in FIGS. 5A to 5C, the light beam 64 is directed to the objective lens 22 in a state where there is no displacement between the optical axes of the two. It can be made incident. As a result, the shift of the light beam due to the rotation of the mirror can be significantly reduced without providing an extra optical system.

The apparatus of this embodiment may be modified as shown in FIG. In this modified example, the protrusion 36 (shown in FIG. 3) is not formed at the rear portion of the fixing member 32, and the coil 38 is provided at the central portion of the fixing member 32, specifically, the first leaf spring 4
It is wound around the portion between 0 and the second leaf spring 42.
The cylindrical portion 52 also extends to the central portion of the fixing member 32, and the two magnets 56 face the coil 38.

A slit 52a formed by cutting out the cylindrical portion 52 is formed in the lower portion of the cylindrical portion 52. The second leaf spring 42 is inserted into the slit 52a with a predetermined play. The slit 52a extends from the front end of the cylindrical portion 52 to the vicinity of the base end portion so that the second leaf spring 42 can be sufficiently displaced.

The rear surface of the fixing member 32 is a reflecting surface 66. An optical distance meter 68 is fixed to the front surface of the arm portion 48 of the base 44 so as to face the reflection surface 66. The optical range finder 68 includes a light emitting element 70 and a light receiving element 72. The optical range finder 68 is connected to a control circuit (not shown). This control circuit
Connected to an electric circuit (not shown) for the coil 38,
The current flowing through the coil 38 is controlled.

Light is emitted from the light emitting element 70 toward the reflecting surface 66. This light is reflected by the reflecting surface 66 and received by the light receiving element 72. The light receiving element 72 sends the received light to the control circuit as a detection signal. This control circuit controls the electric circuit for the coil 38 based on this detection signal so that the displacement amount of the mirror 20 becomes a desired value. A current is passed through the coil 38 by this electric circuit, and a desired displacement amount of the mirror 20 is obtained.

If the optical rangefinder 68 is used as in this modification, it is possible to perform feedback control and use this for the two-stage track servo. Therefore, more stable tracking control can be performed.

Next, a second embodiment will be described with reference to FIG.
The same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. Hereinafter, the description of the third embodiment will be simplified by the same method.

In this embodiment, an elastic member 74 is used instead of the two leaf springs 40 and 42 of the first embodiment. The leg portion 46 of the base 44 is formed with an inclination 76 instead of a step so that the spring constant of the elastic member 74 is different between the front side and the rear side. The other structure is similar to that of the first embodiment. According to this embodiment, the same effect as that of the first embodiment can be obtained, and the number of parts can be reduced as compared with the first embodiment.

Next, a third embodiment will be described with reference to FIG.
In the present embodiment, the first leaf spring 40 and the second leaf spring 42 in the first embodiment are not installed in parallel with each other, but are installed in an open-leg state (shape of "C"). ing. Like this first
If the second leaf springs 40 and 42 are installed, the base 44
Since it is not necessary to form the step 50 (shown in FIG. 3) in the above, the shape can be simplified and the cost can be reduced.

As described above, according to the mirror driving device of the present invention, the shift amount of the light beam due to the rotation of the mirror can be reduced, the operation can be stabilized, and the device itself can be made inexpensive. In particular, the third conventional example (Japanese Patent Laid-Open No. 58-58
However, the displacement amount of the mirror is L · tan θ in the third conventional example,
In the apparatus of the present invention, when the two support members have the same length or one support member has the same length, the displacement amount can be made infinite with respect to the inclination θ of the mirror. That is, in the present invention, the mirror can be displaced without tilting the mirror. Therefore, when the mirrors are tilted at the same angle in the third conventional example and the device of the present invention, theoretically, in the present invention, the displacement amount of the mirror does not depend on the inclination of the mirror, so that the displacement amount becomes infinite. be able to. Moreover, the inclination of the mirror can be set to a desired value by changing the number and shape of the supporting members or the properties thereof. As a result, the degree of freedom in design is increased, and a large correction amount can be easily obtained, which is effective in a case where the optical path is long as in a separation optical system.

The present invention is not limited to the above embodiment, and various embodiments and modifications are possible. For example, in the above three embodiments, the mirror driving device is described as a moving optical system, but between the objective lens that irradiates the disc with light and the beam splitter that guides the reflected light from the disc to the photodetector. If it is placed in the optical path,
The present invention is effective even if it is provided inside the fixed optical system without being used as the moving optical system. Further, in the above embodiment, the device used for the separation type magneto-optical pickup has been described.
It may be used for a separate type optical pickup for an optical disc. Further, although the base is attached to the bottom wall of the housing with screws or the like, the base and the housing may be integrally formed.

[0036]

According to the present invention, it is possible to provide an inexpensive mirror driving device which has a small shift amount of a light beam due to rotation of a mirror and which is stable in operation.

[Brief description of drawings]

FIG. 1 is a schematic top view showing a state in which a mirror driving device of a first embodiment according to the present invention is arranged in a separation type optical pickup.

FIG. 2 is a side view showing the mirror driving device shown in FIG. 1 with a part thereof cut away.

3 is a side view showing the details of the mirror driving device shown in FIG.

FIG. 4 is a side view for explaining displacement of a fixing member and a mirror with respect to a base.

FIG. 5 is a side view for explaining the displacement of the mirror with respect to the objective lens.

FIG. 6 is a side view showing a modified example of the apparatus of the first embodiment with a part thereof broken away.

FIG. 7 is a side view showing a partially broken view of the device of the second embodiment.

FIG. 8 is a side view showing the device of the third embodiment with a part thereof broken away.

FIG. 9 is a side view showing a first conventional example.

FIG. 10 is a side view showing a state when the movable mirror rotates in the conventional example shown in FIG.

FIG. 11 is a top view of a photodetector for explaining the shift of the light beam in the conventional example shown in FIG.

FIG. 12 is a side view showing a second conventional example.

[Explanation of symbols]

20 ... Mirror, 22 ... Objective lens, 24 ... Disk, 3
2 ... Fixing member, 38 ... Coil, 40 ... First leaf spring, 4
2 ... second leaf spring, 44 ... base, 50 ... step, 56 ...
Magnet, 58 ... Adhesive.

Claims (1)

[Claims] 1. A mirror driving device used in a separation type optical pickup comprising at least a light source, a beam splitter, an objective lens, and a photodetector, wherein a mirror driving device is provided on an optical path between the beam splitter and the objective lens. A base that is arranged, a mirror, a fixing member that fixes the mirror, at least one support member that supports the fixing member on the base, and a second direction in the first direction and the opposite direction.
Driving means for driving the mirror by selectively applying a force with the direction of the fixed member to the fixed member, and when the mirror is driven, the mirror is displaced with respect to the base and tilts at the same time. A mirror drive device.