JPH03260928A - Optical pickup device - Google Patents

Abstract

PURPOSE:To simplify the structure of a switching mechanism and to miniaturize the optical pickup device by oscillating a quarter wave plate in the direction parallel with an incident surface and inserting/removing the quarter wave plate into and from the optical path from a beam splitter to the recording surface of a disk. CONSTITUTION:The quarter wave plate 4 is so held that the plate can be inserted/removed into and from the optical path between a polarizing prism 12 and an objective lens by the switching mechanism. The same optical system as the optical system of the optical pickup device for the DRAW type disk which records/reproduces the data to and from the DRAW type optical disk 6 is constituted in the state in which the quarter wave plate 4 is disposed on the optical axis. The recording/reproducing of the data on and from the DRAW type optical disk 6 are possible in this way. On the other hand, the same optical system is constituted if the quarter wave plate 4 is removed from the optical disk. The recording/reproducing of the data on and from the magneto-optical disk 6 are executed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical pickup device that can access both write-once optical disks and magneto-optical disks.

[Prior Art] In recent years, optical disk devices have been put into practical use as external storage for computer systems. These optical disk devices are broadly divided into write-once optical disk devices that use an optical storage medium as a storage medium and cannot rewrite stored data once, and write-once optical disk devices that use a magneto-optical storage medium as a storage medium and store stored data. There are two types of magneto-optical disk drives that can be rewritten arbitrarily.

FIGS. 6(a) and 6(b) show an example of an optical system of an optical pickup device for a write-once disc for recording/reproducing data on a storage medium (hereinafter referred to as a write-once optical disc) in a write-once optical disc device. It shows.

Note that this optical pickup device for a write-once disc uses a push-pull method as a tracking error detection method, and a knife method as a focusing error detection method.

In the figure, signal light output from a semiconductor laser device 1 is converted into parallel light by a coupling lens 2,
The P polarized light enters the polarizing beam splitter 3, and this P polarized light enters the polarizing beam splitter 3.
The polarized signal light passes through the polarization beam splitter 3,
174 wavelength plate 4.

The P-polarized signal light transmitted through the 1/4 wavelength Fi, 4 is 17
After being converted into circularly polarized light by the four-wavelength plate 4, the light is focused by the objective lens 5 and imaged onto the recording surface of the write-once optical disc 6.

The reflected light from the write-once optical disc 6 passes through the objective lens 5 and is converted into substantially parallel light, and then enters the 174-wavelength plate 4 again. As a result, the reflected light that has passed through the 174-wavelength plate 4 is converted into linearly polarized light whose direction is orthogonal to the incident light.
This causes the light to be reflected by the polarizing beam splitter 3.

In this way, the reflected light from the write-once optical disc 6 reflected by the polarizing beam splitter 3 is focused by the lens 7, and approximately half of the light beam is reflected by the splitting mirror 8 constituting the knife beam in the tracking direction. T (that is, the radial direction of the write-once optical disc 6;
The light is incident on the light receiving element 9 for tracking error detection whose light receiving surface is divided into two as shown in b).

In addition, the remaining part of the luminous flux focused by the lens 7 is
A light-receiving element 10 for detecting focusing errors, whose light-receiving surface is divided into two by a dividing line parallel to the ridgeline 8a of the split mirror 8.
is incident on the

Then, a tracking error signal is obtained based on the difference between the light-receiving signals output from the two divided light-receiving surfaces of the light-receiving element 9, and the difference between the light-receiving signals output from the two divided light-receiving surfaces of the light-receiving element 10. A focusing error signal is obtained based on. Moreover, the sum of the light reception signals of the light receiving element 9,
Alternatively, a reproduced signal from the write-once optical disc 6 is obtained based on the sum of the light-receiving signals of the light-receiving elements 9 and 3-10.

FIG. 7 shows an example of an optical system of an optical pickup device for a magneto-optical disk for recording/reproducing data on a storage medium (hereinafter referred to as a magneto-optical disk) in a magneto-optical disk device.

This optical pickup device for magneto-optical disks is shown in Fig. 7 (
Although it is provided with a tracking error detection mechanism and a focusing error detection mechanism similar to those of the write-once optical disk optical pickup device shown in a) and (b), illustration thereof is omitted. In addition, in the same figure, FIGS. 7(a) and (b)
The same parts and corresponding parts Ic are given the same reference numerals.

Note that in the following description, explanation regarding the principle of data recording/reproduction on the magneto-optical disk will be omitted.

In the figure, signal light output from a semiconductor laser device 1 is converted into parallel light by a coupling lens 2, and the cross-sectional shape of the parallel light beam is shaped into a circle by a beam shaping prism 11, and then 4-polarized light is generated. It enters the beam splitter 3 as P-polarized light, and this P-polarized light
The polarized signal light passes through the polarizing beam splitter 3, is reflected by the polarizing prism 12, is guided to the objective lens 5, and is imaged by the objective lens 5 on the recording surface (not shown) of the magneto-optical disk.

The reflected light from the magneto-optical disk is given a Kerr rotation according to the recorded information on the imaged recording surface of the magneto-optical disk, that is, the direction of magnetization, and becomes linearly polarized light whose direction has been rotated by about ±0.7 degrees. After being converted into substantially parallel light by the objective lens 5, it is reflected by the polarizing prism 12,
The light is incident on the polarizing beam splitter 3.

Here, the polarization characteristics of the polarization beam splitter 3 are such that, for example, the transmittance of P polarized light is 70%, the reflectance is 30%, and S
When the transmittance of polarized light is 0% and the reflectance is 100%, as shown in FIG. 30% of polarized light is reflected and 100% of S-polarized light is reflected.
% reflected.

Thereby, the reflected light LL from the polarizing beam splitter 3
At ', the Kerr rotation angle increases from θk to θ′. This phenomenon is called "increase in apparent Kerr rotation angle."

The reflected light LL' from the polarizing beam splitter 3 is guided to a polarization-independent half mirror 13 having a reflectance of 70% and a transmittance of 30%, for example.

The component reflected by the half mirror 13 is the optical rotator 14
After its orientation is rotated by 45 degrees, the light enters the Wallaston prism 15, where it is separated into P-polarized light and S-polarized light. The light is incident on the respective light receiving surfaces 16a and 16b.

A reproduced signal from the magneto-optical disk is then obtained based on the difference between the light-receiving signals of the light-receiving surfaces 16a and 16b.

In addition, the component transmitted through the half mirror 13 is guided to a tracking error detection mechanism and a focusing detection mechanism, and is tracked in the same manner as the optical pickup device for a write-once optical disc shown in FIGS. 6(a) and 6(b). An error detection signal and a focusing error detection signal are obtained.

In this way, the optical pickup device for write-once optical disks and the optical pickup device for magneto-optical disks have the same main part vK.

Therefore, a shared optical pickup device that can record/reproduce data on both write-once optical disks and magneto-optical disks has also been proposed, examples of which are shown in Figures 9 and 1.
Shown in Figure 0. In addition, in the figure, a write-once optical disc 6
Alternatively, the objective lens 5 for focusing the laser beam on the magneto-optical disk 6' is omitted, and the same or corresponding parts as in FIGS. 6(a), (b) and 7 are given the same reference numerals. are doing.

FIG. 9 shows a case where data is written/reproduced on the write-once optical disc 6, and a 174-wavelength plate 4 is disposed between the polarizing beam splitter 3 and the polarizing prism 12.

As a result, it is possible to configure the same optical system as shown in FIGS. 6(a) and (b).
Similarly to the optical pickup device for a write-once optical disk in b), data can be recorded/reproduced on the write-once optical disk 6.

In addition, as shown in FIG. 10, a polarizing beam splitter 3
If the quarter-wave plate 4 disposed between the polarizing prism 12 and the polarizing prism 12 is removed, the same optical system as shown in FIG. 7 can be constructed, and the optical pickup device for the magneto-optical disk shown in FIG. In the same manner as above, data can be recorded/reproduced on the magneto-optical disk 6'.

An example of a mechanism for moving this 174-wavelength plate 4 is shown in the first example.
Shown in Figure 1.

This mechanism includes a solenoid 25, a pin 27 implanted in the actuator 26 of the solenoid 25, a plate 29 in which a hole 28 that engages with the pin 27 is bored, and the plate 29. A gear 31 meshing with the teeth 30, a shaft 32 passing through the gear 31, bearings 33 and 34 of the shaft 32, an angle 35 for attaching the solenoid 25 to the housing CA of the optical pickup device, and the solenoid 25. The L/4 wavelength plate 4 is attached to the approximate center of the shaft 32.

Further, long holes 37 and 38 extending in the direction of movement of the actuator 26 are bored in the plate 29, and pins 39.
40 is inserted, thereby restricting the direction of movement of the plate 29 to the direction of movement of the actuator 26.

Therefore, when the solenoid 25 is off,
The actuator 26 protrudes due to the biasing force of the spring 36, thereby causing the plate 29 to move toward the actuator 2.
6, and the shaft 32 rotates in the direction of arrow R1 in FIG.
is located.

Further, when the solenoid 25 is on, the actuator 26 is pulled in against the biasing force of the spring 36, so that the plate 29 is pulled into the actuator 26.
As the shaft 32 rotates in the direction of arrow R2 in FIG. 4, the 174-wave plate 4 is removed from the optical axis.

In this way, it is possible to realize an optical pickup device that can be used commonly for the write-once optical disk 6 and the magneto-optical disk 6'.

[Problems to be Solved by the Invention] However, such shared optical pickup devices have conventionally had the following disadvantages.

That is, since the structure of the mechanism for arranging/removing the 174-wavelength plate 4 on the optical axis is large, miniaturization of the optical pickup device is hindered. Also, since the weight of the mechanism becomes heavier,
Since the weight of the optical pickup device increases and the load on the moving mechanism that moves the optical pickup device in the disk radial direction increases, it becomes difficult to downsize the optical disk moving device as a whole.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup device that can solve the problems of the conventional device and properly access write-once optical disks and magneto-optical disks.

[Means for Solving the Problems] The present invention includes a beam splitter that separates incident light from a semiconductor laser element and reflected light from a disk recording surface, and a quarter-wave plate that converts the polarization axis of the incident light. When accessing a write-once optical disk, the 174-wave plate is placed on the optical path from the beam splitter to the disk recording surface by swinging the 1/4-wave plate in a direction parallel to its incident surface, while the magneto-optical When accessing the disk
The apparatus is equipped with a switching mechanism for removing the quarter wavelength plate from the first optical path.

[Function] Therefore, the switching mechanism for inserting/removing the 174-wavelength plate on the optical axis has a simple structure, and the optical pickup device can be downsized.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an optical pickup device according to an embodiment of the present invention. In this figure, the same parts and corresponding parts as in FIG. 9 are given the same reference numerals. Also, in this figure, as in FIG. 9, the objective lens for focusing the laser beam on the write-once optical disk 6 or the magneto-optical disk 11-12-iscro'' is omitted.

In the figure, the quarter-wave plate 4 is held so that it can be inserted/removed on the optical axis between the polarizing prism 12 and the objective lens (not shown) by a switching mechanism (not shown).
As shown in the figure, when the quarter-wave plate 4 is placed on the optical axis, the same optical system as an optical pickup device for a write-once optical disc that writes/reproduces data on the write-once optical disc 6 is configured. As a result, write-once optical disc 6
It becomes possible to record/play back data.

On the other hand, if the 174-wave plate 4 is removed from the optical axis, the 10th wave plate 4
An optical system identical to that shown in the figure can be constructed, thereby
It becomes possible to record/reproduce data on the magneto-optical disk 6''.

FIGS. 2 and 3 show an embodiment of a switching mechanism for moving the quarter-wave plate 4. FIG.

In the figure, the holder 51 is provided with a hollow sleeve 52 on the lower surface of the approximately central part thereof, and one end thereof has a hollow sleeve 52.
A step 53 for holding the /4 wavelength plate 4 is formed.

This step 53 extends from the top surface of the holder 51 toward the bottom surface.
It is inclined at a predetermined angle, and has an opening 54 through which the laser beam passes. Further, a permanent magnet 55 is fixed to the lower surface of the end of the holder 51 opposite to the step 53, and a stopper 56 for regulating the rotational position of the holder 51 is provided.

In this way, since the step 53 is inclined, the normal line of the 174-wave plate 4 is inclined with respect to the optical axis of the laser beam, and as a result, the light reflected from the surface of the quarter-wave plate 4 is Flare light is prevented from returning to the light source.

A shaft 61 that is inserted into the sleeve 52 of the holder 51 and rotatably supports the holder 51 is fixed to the plate 60, and a positioning shaft 61 that is raised from the casing (not shown) of the optical pickup device is fixed to the plate 60. A hole 63 is bored through which the bottle 62 is inserted.

The yoke member 65 is shaped according to the range in which the permanent magnet 55 moves when the holder 51 rotates, and is wound with a coil 66 that intersects with the magnetic field of the permanent magnet 55. Further, the height of the yoke member 65 from the plate 60 is set so that the permanent magnet 55 and the coil 66 face each other with a predetermined gap distance.

Further, the pin 6 is inserted into the hole 67 formed in the yoke member 65.
2 is inserted through the yoke member 65, thereby positioning the yoke member 65.

The plate 60 has one end fixed to the casing of the optical pickup device with a screw 71, and the other end, together with a yoke member 65, to the casing with a screw 72. Further, the pin 73 is for preventing the holder 51 from coming off the shaft 61. Further, as shown in FIG. 4, a drive current is supplied to the coil 66 by a coil drive control section 80. This coil drive control section 80 controls the opening current supplied to the coil 66 in accordance with a command signal SC from the control section of the optical disk drive device.

With the above configuration, the coil drive control section 80 receives the command signal SC
When it is notified that a write-once optical disc has been loaded, immediately after that, a forward opening current IA of the magnitude at startup is supplied to the coil 66 for a certain period of time, and then,
The magnitude of the opening current IA is reduced to the value at the time of holding, and that state is held.

In this way, when the forward opening current IA is supplied to the coil 66, the current flows in the magnetic field of the permanent magnet 55, so that a driving force according to Fleming's left hand rule is applied to the coil 66.
6, and as a result, the holder 5 rotates in the direction of arrow A until the stopper 56 abuts against the pin 62, as shown in FIG. 5(a).

As a result, the aperture 54 moves to a position directly above the polarizing prism 12 and is maintained at that position, and as a result, the quarter-wave plate 4 is inserted on the optical axis between the polarizing prism 12 and the objective lens. As described above, an optical system that can access the write-once optical disc 6 is configured.

In addition, since the opening current IA is controlled to a large value at startup for an initial certain period of time, and is then held at a small value during holding, the magnitude of the driving force acting on the coil 66 also depends on the opening current IA. Changes depending on the value.

Therefore, the holder 51 moves to the stopper 5 immediately after the start of movement.
6 quickly moves until it hits the pin 62, and then is urged against the pin 62 with a force that is not affected by vibrations when accessing the write-once optical disc 6.

On the other hand, when it is notified by the command signal SC that a magneto-optical disk has been mounted, the coil drive control unit 80 applies an opening current IB in the opposite direction to the magnitude at startup to the coil 66 for a certain period of time immediately thereafter. After that, the opening current I
The magnitude of B is reduced to the value at the time of holding, and that state is held.

In this way, when the rotating current A in the opposite direction is supplied to the coil 66, a current in the opposite direction to that in the above case flows into the magnetic field of the permanent magnet 55, so that the driving force in the opposite direction to that in the above case is generated. acts on the coil 66, and as a result, the holder 51
is rotated in the direction of arrow B until one end of the step 53 abuts against the pin 62, as shown in FIG. 5(b).

As a result, the 174 wavelength plate 4 is removed from the optical axis between the polarizing prism 12 and the objective lens, and as described above,
An optical system that can access the magneto-optical disk 6' is constructed.

16- Also, since the magnitude of the opening current IB is controlled in the same way as the opening current IA, the holder 51 moves quickly until the step 53 hits the pin 62 immediately after starting the movement, and then the light The pin 62 is biased with a blade that is not affected by vibrations when accessing the magnetic disk 6.

In this way, the quarter-wave plate 4 is inserted/removed on the optical axis between the polarizing prism 12 and the objective lens.

As described above, in this embodiment, the 174-wave plate is moved by the opening mechanism made of a combination of a permanent magnet and a coil, so the device configuration is very simple, and therefore the optical pickup It is possible to easily downsize the device.

By the way, in the above embodiment, the 1/4 wavelength plate was placed on the optical axis between the polarizing prism and the objective lens.
The present invention can be similarly applied even when a four-wavelength plate is placed on the optical path between the polarizing beam splitter and the polarizing prism.

Further, the present invention can be similarly applied to an optical pickup device including an optical system with a tracking error detection method and a focusing error detection method different from those described above.

[Effects of the Invention] As explained above, according to the present invention, by swinging the 174-wave plate in a direction parallel to its incidence plane, the optical path from the beam splitter to the disk recording surface is changed to 174-wavelength plates.
Since the wave plate is inserted/removed, the structure of the switching mechanism becomes simple, and the optical pickup device can be miniaturized.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example in which an optical pickup device according to an embodiment of the present invention accesses a write-once optical disc, and FIG. 2 shows an example of a switching mechanism for inserting/removing a 174-wavelength plate from an optical path. 3 is a schematic sectional view illustrating the switching mechanism, FIG. 4 is a block diagram illustrating the control section of the switching mechanism, and FIGS. 5(a) and 5(b) explain the operation of the switching mechanism. 6(a) and 6(b) are schematic diagrams showing an example of an optical system of an optical pickup device for a write-once optical disk, and FIG. 7 is an example of an optical system of an optical pickup device for a magneto-optical disk. FIG. 8 is a graph for explaining the apparent increase in Kerr rotation angle, FIG. 9 is a perspective view showing the case where a write-once optical disc is accessed by a shared optical pickup device, and FIG. FIG. 11 is a perspective view showing a case where a magneto-optical disk is accessed by a shared optical pickup device, and a schematic diagram showing a conventional example of a switching mechanism for inserting/removing a 174-wavelength plate on an optical path. 4...1/4 wavelength plate, 51...Holder, 52...
Sleeve, 53...step, 54...opening, 55.
...Permanent magnet, 56...Stopper, 60...Plate, 61...Shaft, 62.73...Pin, 63, 6
7... Hole, 65... Yoke member, 66... Coil, 80... Coil movement control section.

Claims (3)

[Claims] (1) In an optical pickup device that can access both write-once optical disks and magneto-optical disks, a beam splitter that separates incident light from a semiconductor laser element and reflected light from a disk recording surface, and a polarization axis of the incident light are provided. When accessing a write-once optical disc, the 1/4 wavelength plate is oscillated in a direction parallel to its incidence plane, and the 1/4 wavelength plate is placed on the optical path from the beam splitter to the disc recording surface. 1. An optical pickup device comprising a switching mechanism that disposes a quarter wavelength plate and removes the quarter wavelength plate from the optical path when accessing a magneto-optical disk. (2) The switching mechanism links a holding member that holds the quarter-wave plate at one end, a permanent magnet disposed at the other end of the holding member, and the magnetic field of the permanent magnet. The optical pickup device according to claim 1, comprising a coil and a support member that rotatably supports the holding member. (3) The optical pickup device according to claim 2, wherein a minute holding current is applied to the coil in a disk access state.