JPH03232127A - Optical pickup device - Google Patents

Abstract

PURPOSE:To use a same optical system as a case in accessing a DRAW type optical disk even when a magneto-optical disk in accessed by providing a switching mechanism arranging a 1/4 wavelength plate on an optical path from a beam splitter till a disk recording face when the DRAW type optical disk is accessed and arranging an optical component on the optical path from the beam splitter till the disk recording face when the magneto-optical disk is accessed. CONSTITUTION:The switching mechanism is provided, in which in the case of accessing the DRAW type optical disk 6, the 1/4 wavelength plate 4 is ar ranged on an optical path from a beam splitter 3 till the disk recording face of the disk 6 and an optical component 20 is arranged on an optical path from the beam splitter 3 till the disk recording face in the case of accessing magneto- optical disk. That is, when the magneto-optical disk is accessed, the optical component whose refraction characteristic is nearly the same as that of the 1/4 wavelength plate is arranged in place of the 1/4 wavelength plate. Thus, even when the magneto-optical disk is accessed, the same optical system as the case in accessing the DRAW type optical disk is used.

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 devices for computer systems. This optical disk device uses an optical storage medium as a storage medium,
There are two types of optical disk devices: write-once optical disk devices that cannot rewrite stored data, and magneto-optical disk devices that use a magneto-optical storage medium as a storage medium and can rewrite stored data at will.

FIGS. 5(a) and 5(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 at a temperature of
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 polarized beam splinter 3,
It is guided to a quarter wavelength plate 4.

The P-polarized signal light transmitted through the quarter-wave plate 4 is converted into circularly polarized light by the 174-wave plate 4, and then passed through the objective lens 5.
The light is focused and imaged on 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, 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 1/4 wavelength 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 l for focusing error detection whose light-receiving surface is divided into two by a dividing line parallel to the edge 118a of the split mirror 8.
is incident on O.

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 element 9 and the light-receiving element 10.

FIG. 6 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. 5 (
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. 5(a) and (b)
The same or corresponding parts 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. 3
This P-polarized signal light is transmitted through the polarizing beam splitter 3, reflected by the polarizing prism 12, and guided to the objective lens 5. ).

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.

As a result, the reflected light LL from the polarized beam splinter 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''1, 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 processed as shown in FIG. A tracking 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 configuration of their main parts.

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 FIGS. 8 and 9.
As shown in the figure. Note that the objective lens 5 that focuses the laser beam on the write-once optical disk 6 or the magneto-optical disk 6' is omitted in the figure, and the same parts and parts as in FIGS. 5(a), (b) and 6 are omitted. Corresponding parts are given the same reference numerals.

FIG. 8 shows a case where data is recorded/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, the same optical system as shown in FIGS. 5(a) and 5(b) can be constructed, and FIG. 5(a) l (
It becomes possible to record/reproduce data on/from the write-once optical disc 6 in the same manner as in the optical pickup device for a write-once optical disc in b).

Furthermore, as shown in FIG. 9, if the 174 wavelength plate 4 placed between the polarizing beam splitter 3 and the polarizing prism 12 is removed, the same optical system as shown in FIG. 6 can be constructed. Similarly to the optical pickup device for a magneto-optical disk shown in FIG.

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, in order to prevent the flare light from the 174-wave plate 4 from entering the light-receiving surface of the light-receiving element 9.10.16, the 174-wave plate 4 is aligned with respect to the optical axis, as shown in FIG. It is arranged with a predetermined inclination θ.

Therefore, the optical axis of the reflected light from the write-once optical disc 6 is the optical axis of the signal light incident on the 174-wave plate 4, and the following equation (
It is displaced by the distance Wdl shown in 1).

di'=, 2t(1-(1/n)) (θ+△θ)
=0.631(θ+Δθ) Here, t is the thickness dimension of the 174-wave plate 4 (=0.9 mm), and n is the refractive index of the 174-wave plate 4 (=1.54
(crystal)), 80 is the tolerance of the slope θ.

The magnitude of the inclination θ is determined by the layout of the optical system, but for example, if it is set to 5 degrees, the optical axis deviation distance di
is approximately 55 (micrometers).

Therefore, the polarizing beam splitter 3 and the polarizing prism 1
With a quarter-wave plate 4 inserted between 2 and 2.

When the optical axes of the tracking error detection mechanism and focusing error detection mechanism are aligned, the magneto-optical disk 6
When the 174 wavelength plate 4 is removed in order to record/reproduce data on the magneto-optical disk 6', the optical axis of the reflected light from the magneto-optical disk 6' becomes
It deviates from the set optical axis by a distance dI.

As a result, an inconvenience has arisen in that error signals obtained from the tracking error detection mechanism and the focusing error detection mechanism include offset components.

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 provides a beam splitter that separates incident light from a semiconductor laser element and reflected light from a disk recording surface, a 174-wave plate that converts the polarization axis of the incident light, and a 174-wave plate that converts the polarization axis of the incident light. An optical component with almost the same refraction characteristics as a wavelength plate is used, and a 174-wave plate is placed on the optical path from the beam splitter to the disk recording surface when accessing a write-once optical disk, and a 174-wave plate is placed on the optical path from the beam splitter to the disk recording surface when accessing a magneto-optical disk. It is equipped with a switching mechanism that arranges optical components on the optical path to the surface.

[Effect: Therefore, when accessing a magneto-optical disk,
Instead of the 174-wave plate, an optical component that handles this 1/4 wavelength and has almost the same refractive characteristics is placed, so the optical axis shift that occurs before and after the 1/4 wavelength plate, or the same problem before and after this optical component, is placed. Therefore, the same optical system can be used when accessing a magneto-optical disk as when accessing a write-once optical disk.

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

1 and 2 show an optical pickup device according to an embodiment of the present invention. In addition, in the figure, the eighth
Identical and corresponding parts to those in the figures are given the same reference numerals. Also, in the figure, as in FIG. 8, the objective lens for focusing the laser beam on the write-once optical disk 6 or the magneto-optical disk 6' is omitted.

In the figure, the optical glass 20 is made of a material that has the same thickness as the 174-wave plate 4 and has the same refractive index as the quarter-wave plate 4 for light of the wavelength output by the semiconductor laser element 1. It is a parallel flat plate, and is attached to the 174-wavelength plate 4 at an angle of 90 degrees by a holder 21 placed between the polarizing beam splitter 3 and the polarizing prism 12.

Therefore, as shown in FIG. 1, when the holder 21 is displaced so that the quarter-wave plate 4 is disposed on the optical axis, the write-once optical disc optical disc 6 is used for recording/reproducing data on the write-once optical disc 6. The same optical system as the pickup device can be configured, thereby making it possible to record/reproduce data on the write-once optical disc 6.

On the other hand, as shown in FIG. 2, instead of the 174 wavelength plate 4,
By displacing the holder 21 so that the optical glass 20 is placed on the optical axis, it is possible to configure the same optical system as an optical pickup device for a magneto-optical disk that records/reproduces data on the magneto-optical disk 6'. This makes it possible to record/reproduce data on the magneto-optical disk 6''.

Furthermore, since the optical glass 20 has the same thickness and refractive index as the quarter-wave plate 4, the refractive properties of the optical glass 20 are as follows.
It is the same as the 174 wavelength plate 4.

Therefore, if the angle of inclination of the 174-wave plate 4 and the angle of inclination of the optical glass 20 with respect to the optical axis are set to be the same,
The distance of the deviation between the optical axis of the output light from the semiconductor laser element 1 that enters the optical glass 20 and the optical axis of the reflected light from the magneto-optical disk 6' is determined by The distance is the same as the distance of deviation between the optical axis of the output light from the laser element 1 and the optical axis of the reflected light from the write-once optical disc 6.

As a result, when the 174 wavelength plate 4 is placed on the optical axis,
When the optical glass 20 is placed on the optical axis, there is no misalignment of the optical axis incident on the light receiving elements 9 and 10, which is included in the tracking error signal and focusing error signal when accessing the magneto-optical disk 6'. Offset components can be suppressed.

3 and 4 show the 174 wavelength plate 4 and the optical glass 2.
An example of a displacement mechanism of the holder 21 that holds 0 is shown.

This displacement mechanism consists of a solenoid 25 and a solenoid 2.
The plate 2 has a pin 27 implanted in the actuator 26 of No. 5, and a hole 28 that engages with the pin 27.
9, a gear 31 that meshes with the teeth 30 formed on this plate 29, a shaft 32 that passes through the gear 31, and a shaft 3.
2, an angle 35 for attaching the solenoid 25 to the housing CA of the optical pickup device, and a spring 36 for biasing the actuator 26 of the solenoid 25 in the projecting direction. A holder 21 is attached to.

Further, long holes 37 and 38 are bored in the plate 29 and extend in the direction of movement of the actuator 26.
．． 40 is inserted, thereby causing the plate 29
The direction of movement of the actuator 26 is restricted 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 in the protruding direction, and the shaft 32 rotates in the direction of arrow R1 in FIG.

As a result, the holder 21 rotates, and 17
The four-wavelength plate 4 is now positioned.

Also, when the solenoid 25 is on.

The actuator 26 is retracted against the biasing force of the spring 36, whereby the plate 29 moves in the retracting direction of the actuator 26, and the shaft 32 rotates in the direction of arrow R2 in FIG. 4.

Thereby, the holder 21 rotates, and the optical glass 20 is positioned on the optical axis.

The plate 29 also includes a stopper (path shown) that restricts the position of the plate 29 so that the 174-wave plate 4 forms a predetermined angle with the optical axis when the solenoid 25 is turned off, and a stopper (path shown in the figure) that restricts the position of the plate 29 so that the 174-wave plate 4 forms a predetermined angle with the optical axis when the solenoid 25 is turned off. Optical glass 20
A stopper (path shown) is provided for regulating the position of the plate 29 so that the plate 29 forms a predetermined angle with the optical axis.

Therefore, when it is detected that the write-once optical disk 6 is installed in the optical disk device incorporating this optical pickup device, the solenoid 25 is turned on, and the magneto-optical disk 6' is installed in the optical disk device. If this is detected, by turning off the solenoid 25, the optical pickup device can be switched to a state in which data is recorded/reproduced on the write-once optical disk 6 and the magneto-optical disk 6', respectively.

In the above-described embodiment, the 174-wave plate and the optical glass are attached to the same holder so as to make an angle of 90 degrees to each other, and by rotating this holder, one of the 174-wave plate or the optical glass is aligned with the optical axis. Although the switching mechanism between the 174 wavelength plate and the optical glass is not limited to this.

Further, in the above-mentioned embodiment, the thickness dimension and the refractive index are 1.
Although it uses the same optical glass as the 74-wave plate, it has the same refractive properties as the 174-wave plate with respect to the light of the wavelength output by the semiconductor laser element, and has no polarization dependence.
Other optical components can be used as long as the transmittance is approximately 100%.

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.

C. Effects of the Invention] As explained above, according to the present invention, there is provided a beam splitter that separates incident light from a semiconductor laser element and reflected light from a disk recording surface, and a beam splitter that converts the polarization axis of the incident light.
A 4-wave plate, an optical component with almost the same refractive properties as the 174-wave plate, and one optical component on the optical path from the beam splitter to the disc recording surface when accessing a write-once optical disc.
In addition to arranging a 74-wavelength plate, when accessing a magneto-optical disk, a switching mechanism is provided to place an optical component on the optical path from the beam splitter to the disk recording surface. Then, an optical component having almost the same refraction characteristics as this 174-wave plate is arranged.

Optical axis misalignment occurs before and after the quarter-wave plate, or similarly occurs before and after this optical component, so the same optical system must be used when accessing a magneto-optical disk as when accessing a write-once optical disk. This has the effect of being able to.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example in which an optical pick-up device according to an embodiment of the present invention accesses a write-once optical disk, and FIG. A schematic diagram illustrating an example of access, FIG. 3 is a schematic perspective view illustrating a switching mechanism between a 174-wave plate and optical glass, and FIG. 4 is an exploded perspective view illustrating a switching mechanism between a 174-wave plate and optical glass. Figure 5(a)
, (b) is a schematic diagram showing an example of an optical system of an optical pickup device for a write-once optical disk, FIG. 6 is a schematic diagram showing an example of an optical system of an optical pickup device for a magneto-optical disk, and FIG. 8 is a perspective view showing the case where a write-once optical disk is accessed by a shared optical pickup device, and FIG. 9 is a graph diagram showing the case where a write-once optical disk is accessed by a shared optical pickup device. FIG. FIG. 10, a perspective view showing the case, is a schematic diagram for explaining the optical axis deviation that occurs before and after the 174-wave plate. 20... Optical glass, 21... Holder, 25...
・Solenoid, 26...actuator, 27, 39
, 40... Pin, 28... Hole, 29... Plate, 30... Teeth, 31... Gear, 32... Shaft, 33. 34... Bearing, 36... spring.

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. a 1/4 wavelength plate for converting the 1/4 wavelength plate, an optical component having almost the same refraction characteristics as this 1/4 wavelength plate, and 1/4 wavelength plate on the optical path from the beam splitter to the disc recording surface when accessing a write-once optical disc. An optical pickup device comprising a switching mechanism that disposes a wavelength plate and disposes the optical component on an optical path from the beam splitter to the disk recording surface when accessing a magneto-optical disk. (2) The optical pickup device according to claim 1, wherein the switching mechanism arranges the quarter-wave plate and the optical component at a constant inclination with respect to the optical axis. (3) The optical pickup device according to claim 1, wherein the optical component has substantially the same thickness and refractive index as the quarter-wave plate.