JPH10188317A - Optical head and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical head which is of a thin type and is miniaturized by arranging a high-density disk optical system and a conventional disk optical system in a same flat plane and also converging a luminous flux after the synthesis performed by using a light synthesizing and separating element and a polarizing element. SOLUTION: The luminous flux reflected at a polarizing beam splitter 7 is made incident on the quater-wave plate 8 made one body with the splitter 7 and is reflected on a mirror surface 9 and it passes forth and back the quater- wave plate 8 to be emitted at the side of the splitter 7. The outgoing light is coverted from an s-polarized light into a p-polarized light and the luminous flux made incident on the splitter 7 again as the p-polarized light passes through it as it is to headed to an objective lens for high-density disk 3. A luminous flux emitted from a laser module for conventional disk 2 is made incident on the spilitter 7 as an s-polarized light and the advancing direction of it is changed to be guided to an objective lens for conventional disk 4. Thus, a recording and/or a reproduction can be performed with respect to disks of one kind or more whose corresponding wavelengths and thicknesses are different.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical disk device capable of recording and / or reproducing information on a plurality of optical disks having different wavelengths by a single device, and an optical head used therefor.

[0002]

2. Description of the Related Art An optical disk apparatus is an information recording / reproducing apparatus characterized by a non-contact, large-capacity, high-speed access, and low-cost medium. It is widely used as an external storage device. In recent years, with the increase in computer data size and the practical use of recording and playback of digital video information, large-capacity optical disk devices have become necessary. I have.

One of the means for achieving a higher density of an optical disc is to reduce the size of information recording units (such as pits) of the optical disc. In this case,
It is necessary to improve the resolution by reducing the light spot focused on the information recording surface of the optical disk. The size of the light spot is determined by the wavelength of the laser used and the numerical aperture of the objective lens, and the light spot can be made smaller by shortening the wavelength used. In a DVD (ROM) standardized as a high-density optical disk, the use wavelength is set to 635 nm or 650 nm.

However, the conventional optical disk recorded corresponding to the wavelength of 780 nm cannot be used for 635 nm or 650 nm.
When reproduction is performed using a short-wavelength laser of m, there is a problem in that the reproduction / control signal is reduced due to differences in the reflectance and absorptance of the information recording surface. This tendency is remarkable in a writable CD or the like standardized as a CD-R. For example, in the CD-R standard, the reflectance is 765 to 820 nm and the reflectance is 65% or more. The reflectance at the wavelength is low, and there is a disc having a reflectance of about 5% around 635 nm. At the same time, the reproduction power is specified to be 0.7 mW or less, so that if a short wavelength laser is used, it is difficult to obtain a sufficient reproduction / control signal.

On the other hand, in the prior art described in Japanese Patent Application Laid-Open No. 8-55363, an optical system using a short-wavelength laser corresponding to a high-density optical disk (hereinafter, abbreviated as a high-density disk optical system) is used. An optical system using a conventional wavelength laser corresponding to a conventional CD or CD-R (hereinafter abbreviated as a conventional disk optical system) is mounted on one optical head, and the optical system is switched according to the disk to be reproduced. Thus, it is possible to reproduce a disc having a different corresponding wavelength. Further, a common portion is provided between the high-density disk optical system and the conventional disk optical system (CD optical system) by using a light combining / separating means such as a polarizing beam splitter to reduce the size of the optical head.

[0006]

In the prior art described above, in order to reduce the thickness of the optical head, the light beam after the light beam synthesis is guided to the objective lens by using a rising mirror (total reflection mirror). Was.

However, the optical head according to the prior art is thin because the high-density disc optical system and the conventional disc optical system are arranged on the same plane, but has a large number of parts and an objective lens and an actuator. Since the dead space is large when the position is considered, the optical head is large in the length and width directions, and this optical head is used to provide an optical disk device with a limited size for a built-in personal computer or a vehicle. It was difficult to do. That is, it has been difficult to realize a thin and small optical disk device capable of recording and / or reproducing two types of disks having different corresponding wavelengths.

In addition, since a rising mirror and a light beam combining / separating element are indispensable between the light source of the conventional disk and the light converging means, the distance from the light source to the objective lens is long, which is common in conventional optical disk devices. However, it has been difficult to apply the optical system that has been used for such a method as it is. For this reason, the conventional disk optical system also requires a new design, which has led to an increase in cost.

On the other hand, when the two optical systems are not arranged on the same plane, the thickness of the optical head is sacrificed, and the thickness of the optical disk device is increased.

[0010] Therefore, a technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art, and an object thereof is to provide a thin, small, and inexpensive optical disk device and an optical disk used for the same. The purpose is to provide a head.

[0011]

To achieve the above object, an optical head according to the present invention comprises a first laser having a wavelength corresponding to a conventional disk and a second laser having a wavelength corresponding to a high-density disk. And converging the first light beam emitted from the first laser on the information recording surface of the conventional disk and converging the second light beam emitted from the second laser on the information recording surface of the high-density disk. A light converging means for reflecting the first light flux, and reflecting a polarized light in a specific first direction in a plane perpendicular to an optical axis of the second light flux, and orthogonal to the first direction. A polarizing beam splitter that transmits polarized light in a second direction, a mirror that reflects the second light flux, and a quarter-wave plate corresponding to the wavelength of the second laser. The positional relationship can be The second laser emits the light beam as polarized light in the first direction to the polarizing beam splitter at a position where the light beam reflects the first light beam and guides the light beam to the light converging device. At a position reflected in the opposite direction, the mirror is at a position facing the light converging means with the polarizing beam splitter interposed therebetween, and the quarter-wave plate is between the beam splitter and the mirror. Place each.

With the above structure, while the high-density disk optical system and the conventional disk optical system are arranged on the same plane, the number of components or the volume occupied by the components is reduced, and the high-density disk optical system and the conventional disk optical system are reduced. A dead space is reduced by arranging the system such that the objective lens is opposed to the center, so that the optical head can be made thinner and smaller. In addition, by shortening the distance between the laser for the conventional disc and the objective lens, the optical system used in the conventional optical disc device can be applied to the conventional disc optical system as it is, and the cost increase due to the new design is suppressed. And an inexpensive optical head can be provided.

Further, by mounting the above-mentioned optical head, it is possible to provide a thin, small, and inexpensive optical disk apparatus capable of recording and / or reproducing two or more types of optical disks having different corresponding wavelengths with a single apparatus. Become.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. First, the configuration and operation of the optical head will be described with reference to the drawings.

FIG. 1 and FIG. 2 are diagrams showing the configuration of an embodiment of an optical head according to the present invention.
FIG. 2 shows the case where recording or reproduction is performed on the conventional disk 6, respectively.

1 and 2, reference numeral 1 denotes a laser diode having a wavelength corresponding to the high-density disk 5, for example, a red semiconductor laser having a wavelength of 650 nm. The laser diode 1 is arranged in such a direction that the light beam emitted from the laser diode 1 enters the polarization beam splitter 7 as s-polarized light. Since the far field pattern (hereinafter, abbreviated as FFP) of the laser diode 1 is elliptical, the spot when condensed on the high-density disk 5 also becomes elliptical. Generally, a semiconductor laser having a wavelength of 650 nm has a TE mode. , The polarization direction coincides with the short axis direction of the FFP ellipse.
The tangential direction of the disk 5 coincides with the short axis direction of the spot.

Reference numeral 2 denotes a laser module having a wavelength corresponding to the conventional disk 6, which has a wavelength of 780 n which has been conventionally used.
What is necessary is just to use the module which integrated the m semiconductor laser and the photodetector. The laser module 2 is arranged such that the light beam emitted from the laser module 2 enters the polarization beam splitter 7 as s-polarized light. 780nm wavelength
In general, the semiconductor laser also oscillates in the TE mode, and the polarization direction coincides with the minor axis direction of the FFP ellipse. The short axis direction matches. The position to be arranged is determined by the design magnification of the conventional disk objective lens 4 described later.

3 is an objective lens for a high-density disc,
The parallel light beam having the wavelength of the laser diode 1 is converted to a predetermined NA.
(For example, 0.6), which is a lens designed to focus light on the information recording surface of the high-density disk 5 with a predetermined amount of aberration or less. Reference numeral 4 denotes a conventional disk objective lens, which converts a light beam having a certain divergence angle of a wavelength of the laser module 2 into a predetermined NA (for example, 0.45) on the information recording surface of the conventional disk 6 with a predetermined aberration amount or less. It is a lens designed to focus light.

Reference numeral 5 denotes a high-density disk. The corresponding wavelength includes the wavelength of the laser diode 1, and the disk substrate has a thickness of, for example, 0.6 mm. Reference numeral 6 denotes a conventional disk, and the corresponding wavelength includes the wavelength of the laser module 2, and the thickness of the disk substrate is, for example, 1.2 mm.

Reference numeral 7 denotes a polarization beam splitter, which has a large transmittance (for example, 98%) with respect to the polarized light of the wavelength of the laser diode 1 whose polarization direction is parallel to the plane of incidence (hereinafter referred to as p-polarized light). For polarized light whose polarization direction is perpendicular to the plane of incidence (hereinafter referred to as s-polarized light), it has a property that the reflectance is large (for example, 98%). It is also assumed that the reflectance is large (for example, 98%) with respect to the s-polarized light having the wavelength of the laser module 2. In the present embodiment, both the light beam from the laser diode 1 and the light beam from the laser module 2 are s-polarized light, and are reflected to change the traveling direction.

Reference numeral 8 denotes a quarter-wave plate corresponding to the wavelength of the laser diode 1. When the light beam makes one round trip through the quarter-wave plate 8, the polarization direction of the light beam changes from s-polarized light to p-polarized light.
The p-polarized light changes to s-polarized light. Reference numeral 9 denotes a mirror surface, which reflects approximately 100% of the light beam of the wavelength of the laser diode 1. Here, the mirror surface 9 is a surface of the quarter-wave plate 8 that is not opposed to the polarization beam splitter 7.

Reference numeral 10 denotes a half mirror, which has a transmittance and a reflectance of about 5 for light of the wavelength of the laser diode 1.
0%. Reference numeral 11 denotes a collimating lens.

Reference numeral 12 denotes a detection lens system in the high-density disk optical system, which is constituted by, for example, a cylinder lens when the astigmatism method is used for focus control.
13 is a photodetector in the high-density disc optical system,
In addition to detecting a reproduction signal, a control signal for controlling the light condensing position is detected.

Reference numeral 14 denotes an objective lens driving mechanism, which comprises an objective lens 3 for a high-density disk and an objective lens 4 for a conventional disk.
This is a mechanism for switching the arrangement in the optical path. For example, this function can be realized by using a shaft sliding type objective lens actuator.

The operation of the optical head configured as described above for recording or reproducing data on or from the high-density disk 5 shown in FIG. 1 will be described below. FIG. 3 is a side view of the configuration of a light beam passing through the polarizing beam splitter 7 which is considered to be difficult to understand in FIG. FIG.
3A shows a forward light beam toward the high-density disk 5, and FIG. 3B shows a return light beam reflected by the high-density disk 5 and returned.

The objective lens driving mechanism 14 is operated to place the high-density disk objective lens 3 in the optical path as shown in FIG. Also, turn on the laser diode 1,
Turn off the laser module 2.

The wavelength 65 emitted from the laser diode 1
About 50% of the 0 nm light flux is reflected by the half mirror 10 and guided to the collimator lens 11. The light beam passes through the collimator lens 11 and is converted into a parallel light beam, and then enters the polarization beam splitter 7 as s-polarized light.

The light beam reflected by the polarization beam splitter 7 is incident on a quarter-wave plate 8 integrated with the polarization beam splitter 7, but is reflected by a mirror surface 9 and passes through the quarter-wave plate.
The light reciprocates and is emitted to the polarization beam splitter 7 side. At this time, the polarization direction of the emitted light has been converted from s-polarized light to p-polarized light. The light beam that has re-entered the polarizing beam splitter 7 as p-polarized light is transmitted as it is and travels to the high-density disk objective lens 3.

FIG. 3 shows a case where there is a space between the quarter-wave plate 8 and the mirror surface 9. In this case, the light beam reflected by the polarization beam splitter 7 is The light is converted from s-polarized light into circularly polarized light through the quarter-wave plate 8, reflected by the mirror surface 9, passes through the quarter-wave plate 8 again, is converted from circularly-polarized light into p-polarized light, and passes through the beam splitter 7. I do. FIG. 1 may be considered a special case of this.

The light beam incident on the high-density disk objective lens 3 as a parallel light beam passes through the disk substrate of the high-density disk 5 and is condensed on the information recording surface with good aberration. The light beam reflected on the information recording surface of the high-density disk 5 passes through the high-density disk objective lens 3 again, is converted into a parallel light beam, and enters the polarization beam splitter 7.

At this time, the light beam is transmitted to the polarization beam splitter 7.
, Which is transmitted as p-polarized light,
Head for. The light beam incident on the 波長 wavelength plate 8 is reflected by the mirror surface 9, makes one round trip on the 波長 wavelength plate, and is emitted to the polarization beam splitter 7 side. At this time, the polarization direction of the emitted light is converted from p-polarized light to s-polarized light.

When there is a space between the quarter-wave plate 8 and the mirror surface 9 as shown in FIG. 3, the p-polarized light transmitted through the polarizing beam splitter 7 is Are converted into circularly polarized light, reflected by the mirror surface 9 and transmitted through the quarter-wave plate 8 again to be converted into s-polarized light. FIG. 1 may be considered a special case of this.

As the s-polarized light, the polarization beam splitter 7
Is reflected, changes its traveling direction, passes through the collimator lens 11, is converted into convergent light, and travels toward the half mirror 10. Approximately 50% of the light beam reflected from the disk that has entered the half mirror 10 is transmitted and guided to the detection lens system 12, and further condensed on the photodetector 13, where a reproduction signal and a control signal are detected.

Next, the operation when recording or reproducing data on or from the conventional disk 6 shown in FIG. 2 using the optical head of this embodiment will be described below. Further, the polarization beam splitter 7
FIG. 4 shows a partial view of the configuration of a light beam passing through the lens. FIG. 4A shows a forward light beam toward the conventional disk 6, and FIG. 4B shows a backward light beam reflected by the conventional disk 6 and returned.

By operating the objective lens driving mechanism 14, the conventional disk objective lens 4 is arranged in the optical path as shown in FIG. Further, the laser module 2 is turned on and the laser diode 1 is turned off.

The wavelength 78 emitted from the laser module 2
The luminous flux of 0 nm enters the polarization beam splitter 7 as s-polarized light. Since the incident light beam is s-polarized light, it is reflected by the polarization beam splitter 7, its traveling direction is changed, and is guided to the conventional disk objective lens 4.

The luminous flux enters at a predetermined divergence angle conforming to the design specification of the conventional disk objective lens 4 and is condensed on the information recording surface with good aberration through the disk substrate of the conventional disk 6. The luminous flux reflected from the information recording surface of the conventional disc 6 is
The light passes through the conventional disk objective lens 4 again, is converted into a predetermined convergent light, and is incident on the polarization beam splitter 7.

Also at this time, since the light beam enters as s-polarized light, the light beam is reflected by the polarization beam splitter 7 and its traveling direction is changed, guided to the laser module 2, and the reproduced signal and the control signal are detected.

As described above, according to the optical head of the present embodiment, two different wavelengths and disk substrate thicknesses are used.
It is possible to record or play back more types of discs.

Next, effects brought about by configuring the optical head as in this embodiment will be described below.

The optical head according to the present embodiment, except for the high-density disk objective lens 3 and the conventional disk objective lens 4, uses the high-density disk optical system and the conventional disk optical system in the same plane parallel to the disk surface. It is placed inside to reduce the thickness. Strictly speaking, the quarter-wave plate 8 is not arranged on the same plane, but the thickness of the quarter-wave plate is sufficiently smaller than the height of other optical components (for example, the diameter of the light beam is 4 mm. Then, the height of the half mirror 10 is required to be about 6 mm, whereas the thickness of the quarter wavelength plate is about 1 mm. Therefore, it can be said that the arrangement of the optical components is substantially in the same plane.

Further, the light beams of the high-density disk optical system and the conventional disk optical system are combined by using a polarizing beam splitter, and a part of the optical path is shared, thereby reducing the size and cost.

As described above, in the known prior art, when the optical system excluding the objective lens is arranged on a plane parallel to the disk surface to reduce the thickness of the optical head, a vertical beam is guided to the objective lens. I used a raised mirror. On the other hand, according to the present embodiment, since the light beam is guided to the objective lens by using the polarization beam splitter 7, which is a light beam combining / separating unit, a rising mirror is not required. A quarter-wave plate 8 is indispensable in place of the necessity of a rising mirror. However, the occupied volume is significantly small, and it is possible to form an integral structure with the polarizing beam splitter 7. The size of the optical head can be reduced by the occupation volume of the raising mirror.

Further, since the high-density disk optical system and the conventional disk optical system are arranged so as to be opposed to the position of the objective lens, component layout is easy and
By reducing the dead space, the size of the optical head can be reduced.

In this embodiment, the light beams incident on the polarizing beam splitter 7 from the high-density disk system and the conventional disk system are both s-polarized. Therefore, a general TE mode semiconductor laser can be used as the laser diode 1 and the laser module 2, and a polarizing element such as a half-wave plate or a liquid crystal for changing the polarization direction is not required. Therefore, an inexpensive optical head can be provided. The mounting direction of the laser diode 1 and the laser module 2 is 90
It is possible to use a TM mode semiconductor laser without using a polarizing element by arranging it so that the major axis direction of the ellipse of the spot on the disk coincides with the tangential direction of the disk. In general, it is considered that the reproduction signal is better when the major axis direction of the ellipse of the spot on the disc coincides with the radial direction of the disc than when it coincides with the tangential direction of the disc.

The distance between the laser module 2 and the conventional disk objective lens 4 is only that the polarizing beam splitter 7 is disposed between the laser module 2 and the conventional disk objective lens 4. Therefore, a conventional light beam combining / separating element (for example, a polarizing beam splitter or a dichroic) is used. (For example, a prism) and a rising mirror can be shortened. Therefore, the objective lens and the laser module for the finite optical system designed for the conventional optical head for a disk can be used as it is, and an inexpensive and small optical head can be provided.

However, when a finite system is used as a conventional disk optical system as in the present embodiment, spherical aberration occurs when reflected by a polarization beam splitter.
This aberration is equivalent to spherical aberration that occurs when divergent light passes through a parallel flat plate, and there is no case in which a reproduced signal is extremely deteriorated and cannot be reproduced. However, if this spherical aberration becomes a problem, the objective lens 4 for the conventional disk is newly designed to cancel the spherical aberration, or the laser module 2 and the polarizing beam splitter 7 are used.
The conventional disk optical system may be configured as an infinite system by using an objective lens designed for an infinite optical system as the conventional disk objective lens 4 at the same time as disposing a collimator lens therebetween.

In the present embodiment, the laser module 2 is used as the conventional disk optical system. However, the present invention is not limited to this configuration. May be separated. In the present invention, since the high-density disc optical system and the conventional disc optical system are arranged to face each other with the polarizing beam splitter 7 interposed therebetween, there is no concern that both optical systems interfere with each other.
The layout is easy.

Conversely, a laser module in which a laser having a wavelength (for example, 650 nm) corresponding to the high-density disk 5 and a photodetector are integrated in the high-density disk optical system may be used. This makes it possible to provide an optical head that is smaller, cheaper, and easier to adjust.

In this embodiment, the mirror surface 9 is 1 /
Although the four-wavelength plate 8 is used as the surface, as shown in FIG. 3, the present invention is not limited to this. A mirror surface is provided on the case-side surface of the optical head where the quarter-wave plate 8 is arranged. Alternatively, a space may exist between the quarter-wave plate 8 and the mirror surface 9.

In this embodiment, an objective lens designed according to each optical system of the high-density disk objective lens 3 and the conventional disk objective lens 4 is provided as a light converging means, and is switched by the objective lens drive mechanism 14. Although the configuration is adopted, the present invention is not limited to this. With a single objective lens, various light converging means designed to enable recording or reproduction of both the high-density disk 5 and the conventional disk 6 can be used.

For example, a hologram objective lens can be used. The hologram pattern is such that, with respect to the wavelength of the laser diode 1, zero-order light is condensed on the information recording surface of the high-density disk 5 with a predetermined NA with good aberration, and primary light with respect to the wavelength of the laser module 2 It is assumed that the light is condensed on the information recording surface of the conventional disk 6 with a predetermined NA with good aberration.
The hologram may be directly engraved on the lens, or may be driven integrally with the objective lens as a separate component.

Alternatively, even if the high-density disk objective lens 3 used in this embodiment is used as it is, it is possible to record or reproduce data on a conventional disk. In normal use, a light beam having a wavelength of the laser module 2 is set to a substrate thickness of 1.2 m.
Although a good spot cannot be obtained due to the spherical aberration caused by passing through the conventional disc 6 of m.
The spherical aberration can be canceled by making the luminous flux incident on the high-density disk objective lens 3 into divergent light having an appropriate angle. That is, depending on the position of the laser module 2 (distance from the objective lens), the conventional disk 6
A good spot can be formed on the information recording surface. Alternatively, between the laser module 2 and the high-density disk objective lens 3,
A lens that converts the divergence angle or convergence angle of the light beam may be provided so that the divergence angle of the light beam incident on the light beam becomes an appropriate angle for canceling the spherical aberration.

In this case, however, the aperture limit for achieving a predetermined NA is determined by using a variable-diameter stop, by providing a non-common portion in a high-density disk optical system and a non-common portion of a conventional disk optical system, or by using a laser diode. It is necessary to use a wavelength selection film that transmits a light beam of one wavelength and blocks a light beam of the wavelength of the laser module 2 or a polarizing film that transmits polarized light in a certain direction and blocks polarized light in a direction orthogonal to the certain direction. There is.

If the optical head of the present invention is constituted by these single objective lenses, the objective lens driving mechanism 14 for switching the objective lens having a large occupied volume is unnecessary, and further thinning, miniaturization, weight reduction, The cost can be reduced.

As the optical components in the optical head of the present invention, those having ordinary performance such as the polarization beam splitter 7 and the half mirror 10 may be used, and a polarization having a special wavelength dependency as shown in the prior art. Inexpensive because no element is required.

As described above, by applying the present invention, an optical head in an optical disk apparatus for recording or reproducing a plurality of optical disks having different disk substrate thicknesses and corresponding wavelengths is provided as a thin, small, and low-cost optical head. It becomes possible.

Next, the configuration and operation of the optical disk device according to the present invention will be described with reference to the drawings.

FIG. 5 shows an optical disk drive 1 according to the present invention.
It is a block diagram of an embodiment, In this figure, 20 is an optical head in the above-mentioned embodiment.

The laser diode 1 and the laser module 2, which are the light sources of the optical head 20, turn on / off the light emission and control the output power by the laser drive circuit 21 and the laser drive circuit 22, respectively. Also,
Outputs of the photodetector 13 and the laser module 2 are supplied to a signal processing circuit 23 and a signal processing circuit 24, respectively, to generate control signals such as a focus error signal and a tracking error signal, and respective signals such as a reproduction signal. . These signals are supplied to the system control circuit 25.

The disc discriminating means 26 discriminates the type of the optical disc mounted on the optical disc device, and outputs the result to the system control circuit 25. System control circuit 2
5 turns on the laser diode 1 through the laser drive circuit 21 based on the result from the disc discriminating means 26, when the mounted disc is the high density disc 5,
When the loaded disc is the conventional disc 6, the laser module 2 is turned on through the laser drive circuit 22. Further, the objective lens driving mechanism 14 is driven to dispose the objective lens corresponding to the loaded disk in the optical path. In the case of the high-density disk 5, the signal processing circuit 23
In the case of the conventional disk 6, the focus error signal is supplied to the focus actuator drive circuit 27 and the tracking error signal is supplied to the tracking actuator drive circuit 28 based on the signal generated by the signal processing circuit 24. Thereby, focus servo and tracking servo operations are performed, and recording or reproduction of the high-density disk 5 and the conventional disk 6 is performed.

According to the optical disk device of the present embodiment, by mounting the thin, small, and inexpensive optical head according to the present invention, a plurality of disks having different corresponding wavelengths can be recorded and / or reproduced by a single device. Of optical disk devices,
It is possible to achieve a reduction in thickness, size, and cost.
This makes it possible to provide a thin and small optical disk device for a built-in personal computer or a vehicle.

[0063]

As described above, according to the present invention, in an optical head for an optical disk apparatus for performing recording and / or reproduction on two or more types of disks having different corresponding wavelengths, a high-density disk optical system is used. In addition to arranging the conventional optical system in the same plane as the disc, and using a light beam combining / separating element and a polarizing element to directly launch the combined light beam to the light converging means, it has been made thinner, smaller, and less costly. An optical head can be realized. By mounting the optical head, a thin, small, and inexpensive optical disk device can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of an optical head according to the present invention, showing a state of recording or reproduction on a high density disc.

FIG. 2 is a configuration diagram of one embodiment of an optical head according to the present invention, showing a state of recording or reproducing data on a conventional disk.

FIG. 3 is an explanatory diagram showing a main configuration of an optical head corresponding to the state of FIG. 1;

FIG. 4 is an explanatory diagram illustrating a main configuration of an optical head corresponding to the state of FIG. 2;

FIG. 5 is a configuration diagram of an embodiment of an optical disk device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser diode for high-density disk 2 laser module for conventional disk 3 objective lens for high-density disk 4 objective lens for conventional disk 5 high-density disk 6 conventional disk 7 polarizing beam splitter 8 1/4 wavelength plate 9 mirror surface 10 half Mirror 11 collimator lens 12 detection lens system 13 photodetector 14 objective lens drive mechanism 20 optical head 27 focus actuator drive circuit 28 tracking actuator drive circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshio Sugiyama 1 Kitano, Makino, Mizusawa-shi, Iwate Prefecture Inside Hitachi Media Electronics Co., Ltd. (72) Inventor Ritsuo Imada 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd. Video Information Media Division (72) Inventor Yukio Fukui 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd.Video Information Media Division (72) Inventor Yasuyuki Sugi 1410 Inada, Hitachinaka-shi, Ibaraki Prefecture In the Visual Information Media Division of Hitachi, Ltd.

Claims (18)

[Claims] A first light-emitting means, a second light-emitting means having a different wavelength from the first light-emitting means, and a first light beam emitted from the first light-emitting means being transmitted to a first disk as information. Light converging means for converging on a recording surface and converging a second light beam emitted from the second light emitting means on an information recording surface of a second disk; and reflecting the first light beam, A light beam combining / separating means for reflecting polarized light in a specific first direction in a plane perpendicular to the optical axis of the second light beam and transmitting polarized light in a second direction orthogonal to the first direction; A light beam reflecting means for reflecting the second light beam; and a polarizing means for changing the polarization direction of the second light beam by approximately 90 degrees in a plane perpendicular to the optical axis when the second light beam is transmitted back and forth, The light beam combining / separating means reflects the first light beam to the light converging means. The second light emitting means is disposed at a guiding position, and the emitted light flux is transmitted to the light flux combining / separating means by the first light emitting means.
The light converging means is arranged at a position where the light is converged and reflected in the opposite direction to the light converging means, and the light beam reflecting means is disposed at a position facing the light converging means with the light beam combining / separating element interposed therebetween. The optical head according to claim 1, wherein the polarizing unit is disposed between the light beam combining / separating unit and the light beam reflecting unit. 2. The light beam converging means according to claim 1, wherein the light converging means comprises: a first objective lens for converging the first light beam on an information recording surface of the first disk; A second objective lens for converging on an information recording surface of the second disk; and a first objective lens for recording and / or reproduction on the first and second disks, respectively. Objective lens driving means for switching the lens and disposing it in the optical path;
An optical head comprising: 3. An optical head according to claim 1, wherein said light converging means is formed by a hologram lens. 4. The optical head according to claim 1, wherein said light converging means comprises an objective lens and a hologram. 5. The device according to claim 1, wherein the first light emitting means is provided between the light converging means and the first light emitting means.
An optical head, comprising: a light beam converting means for converting a divergence angle or a convergence angle of the light beam. 6. The optical head according to claim 1, wherein the polarizing means is a quarter-wave plate. 7. The optical head according to claim 1, wherein the reflection unit is configured as a mirror surface on a surface of the polarization unit. 8. The optical head according to claim 1, wherein the light beam combining / separating means and the polarizing means are integrally formed. 9. The optical head according to claim 1, wherein the first light beam incident on the light converging means is divergent light. 10. A first light-emitting means, a second light-emitting means having a different wavelength from the first light-emitting means, and a first light beam emitted from the first light-emitting means is stored in a first disk as information on a first disk. A light converging means for converging a second light beam emitted from the second light emitting means on an information recording surface of a second disk while converging on a recording surface, and reflecting the first light beam, A light beam combining / separating unit that reflects polarized light in a specific first direction in a plane perpendicular to the optical axis of the second light beam and transmits polarized light in a second direction orthogonal to the first direction; An optical head comprising: a light beam reflecting means for reflecting the second light beam; and a polarizing means for changing the direction of polarization of the second light beam by approximately 90 degrees in a plane perpendicular to the optical axis when the second light beam is transmitted back and forth. Disc discriminating means for discriminating the type of disc loaded; and Control means for switching the operation states of the first light emitting means and the second light emitting means based on the result of the discrimination by the disc discriminating means, wherein the first and second discs can be recorded and / or reproduced. An optical disk device, wherein the light beam combining / separating means in the optical head is arranged at a position for reflecting the first light beam and leading the light beam to the light converging means, and the second light emitting means outputs the light beam. The light beam combining / separating unit is disposed at a position where the light beam is polarized in the first direction and reflected in a direction opposite to the light converging unit, and the light beam reflecting unit interposes the light beam combining / separating element. An optical disk device, which is disposed at a position opposed to the light means, and wherein the polarizing means is disposed between the light beam combining / separating means and the light beam reflecting means. 11. The light beam converging means according to claim 10, wherein the light converging means comprises: a first objective lens for converging the first light beam on an information recording surface of the first disk; A second objective lens for converging on an information recording surface of the second disk; and a first objective lens for recording and / or reproduction on the first and second disks, respectively. Objective lens driving means for switching the lens and disposing it in the optical path;
An optical disc device comprising: a driving circuit configured to drive the objective lens driving unit. 12. The optical disk device according to claim 10, wherein said light converging means is formed by a hologram lens. 13. The optical disk device according to claim 10, wherein the light converging means is constituted by an objective lens and a hologram. 14. The device according to claim 10, wherein the first light emitting means is provided between the light converging means and the first light emitting means.
An optical disc device comprising a light beam converting means for converting a divergence angle or a convergence angle of the light beam. 15. The optical disk device according to claim 10, wherein the polarizing means is a quarter-wave plate. 16. The optical disk device according to claim 10, wherein the reflection unit is configured as a mirror surface on a surface of the polarization unit. 17. The optical disk device according to claim 10, wherein the light beam combining / separating means and the polarizing means are integrally formed. 18. The optical disk device according to claim 10, wherein the first light beam incident on the light converging means is divergent light.