JP2000099983A - Optical pickup device and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device capable of recording/reproducing information in plural kinds of optical disks with light rays different in wavelength without deteriorating the characteristic of a reproducing signal and reducing cost, and to provide an optical disk device provided with the optical pickup device. SOLUTION: A semiconductor laser element 1 is provided with a laser diode chip for emitting a laser beam of 650 nm wavelength, and a laser diode chip for emitting a laser beam of 780 nm wavelength. A parallel flat plate 2 includes a first wavelength selecting film 24 for reflecting the laser beam of 650 nm wavelength and transmitting the laser beam of 780 nm wavelength, a substrate 23 for transmitting a light, and a second wavelength selecting film 22 for reflecting the laser beam of 780 nm wavelength in this order. By adjusting the thickness of the substrate 23 and the incident angle of the laser beam, the optical path of the laser beam of 650 nm wavelength is matched with that of the laser beam of 780 nm wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device capable of recording and reproducing information on and from an optical disk with a plurality of lights having different wavelengths, and an optical disk device provided with the same.

[0002]

2. Description of the Related Art Various optical disks such as DVD (digital video disk), CD-R (writable compact disk), and AS (Advanced Storage) -magneto-optical disk have been developed as optical recording media. In a DVD, information is recorded or reproduced by laser light having a wavelength of 650 nm. On the other hand, in a CD-R, recording or reproduction of information is performed by a laser beam having a wavelength of 780 nm. An optical disk device that records or reproduces information on such a plurality of types of optical disks has been proposed.

FIG. 20 is a schematic diagram showing a schematic configuration of a conventional optical disk device compatible with two types of optical disks on which information is recorded or reproduced by laser beams of different wavelengths. FIG. 21 is a side view of a semiconductor laser device in the optical disk device of FIG. 20, and FIG.
FIG. 4 is a diagram showing a Wollaston prism and a photodetector in the optical disk device of FIG.

The optical disk device shown in FIG. 20 includes a semiconductor laser device 1, a collimator lens 6, an objective lens 7, a photodetector 8, a parallel plate 9, and a Wollaston prism 10. As shown in FIG. 21, the semiconductor laser device 1 includes a laser diode chip 11 that emits laser light having a wavelength of 650 nm and a laser diode chip 12 that emits laser light having a wavelength of 780 nm. The distance d between the laser light emitting position of the laser diode chip 11 and the laser light emitting position of the laser diode chip 12 is about 110 μm.

In FIG. 20, a laser beam emitted from a semiconductor laser device 1 is reflected by a parallel flat plate 9, converted into a parallel beam by a collimator lens 6, and collected on an optical disk 100 by an objective lens 7. Optical disk 1
The return light (reflected light) from 00 passes through the objective lens 7 and the collimator lens 6, further passes through the parallel plate 9 and the Wollaston prism 10, and enters the photodetector 8. Thereby, information recorded on the optical disc 100 is detected.

As shown in FIG. 22, a laser beam 101 having a wavelength of 650 nm and a laser beam 102 having a wavelength of 780 nm are set to have different polarization directions. In FIG. 22, black circles indicate that the polarization direction is perpendicular to the paper surface, and arrows indicate that the polarization direction is parallel to the paper surface.

As shown in FIG. 21, the laser beam emitting position of the laser diode chip 11 and the laser beam emitting position of the laser diode chip 12 are about 110 μm apart, so that the optical path of the laser beam 101 and the laser beam 102 Is about 110 μm away from the optical path.

The light detector 8 has a four-divided sensor 81.
The laser beam 101 travels straight through the Wollaston prism 10 and forms a light spot 201 at the center of the four-divided sensor 81 of the photodetector 8. The laser beam 102 is refracted by the Wollaston prism 10 and forms a light spot 201 at the center of the four-divided sensor 81 of the photodetector 8.

As described above, in the conventional optical disk drive, the two laser beams 101 and 102 having different wavelengths can be detected by the photodetector 8 by using the Wollaston prism 10.
To the four-divided sensor 81.

When the Wollaston prism 10 is not provided, the laser beam 102 forms a light spot at a position off the quadrant sensor 81 of the photodetector 8 as shown by a dotted line.

[0011]

In the above-mentioned conventional optical disk apparatus, two laser beams 101 and 10 having different wavelengths are used.
A Wollaston prism 10 is required to receive 2 by the common photodetector 8. As a result, component costs are increased.

Further, since the optical axes of the two laser diode chips 11 and 12 of the semiconductor laser device 1 are separated from each other, the optical path of the two laser beams emitted from both laser diode chips 11 and 12 is changed to the collimator lens 6. In addition, the optical axis of the objective lens 7 cannot be accurately matched. That is, two laser diode chips 11,
When the optical path of the laser light emitted from one of the 12 is matched with the optical axis of the collimator lens 6 and the objective lens 7, the optical path of the laser light emitted from the other is shifted from the optical axis of the collimator lens 6 and the objective lens 7. . As a result, wavefront aberration occurs, and the characteristics of the reproduced signal deteriorate.

An object of the present invention is to provide an optical pickup device capable of recording or reproducing information on or from a plurality of types of optical disks with light of different wavelengths without deteriorating the characteristics of a reproduced signal and capable of reducing costs. An object of the present invention is to provide an optical disk device provided with the above.

[0014]

SUMMARY OF THE INVENTION An optical pickup device according to a first aspect of the present invention is an optical pickup device that irradiates light to an optical disk and receives return light from the optical disk, and has different wavelengths. A plurality of light sources that emit a plurality of lights, and a parallel plate that reflects light emitted from each of the plurality of light sources, the parallel plate reflects one light of a different wavelength among the plurality of lights. A plurality of wavelength selection films that transmit light of the remaining wavelengths are sequentially included from the front side through the light transmission film, and the optical paths of the plurality of light beams respectively reflected by the plurality of wavelength selection films and emitted from the front side match. It is arranged as follows.

In the optical pickup device according to the present invention, a plurality of lights having different wavelengths are emitted from a plurality of light sources. Light emitted from each of the plurality of light sources is reflected by one of the plurality of wavelength selection films of the parallel plate.

In this case, parallel flat plates are provided so that the optical paths of a plurality of light beams respectively reflected by the plurality of wavelength selection films and emitted from the front side coincide with each other. Thereby,
It is possible to make the optical paths of a plurality of lights having different wavelengths coincide with the optical axis of the optical system. As a result, information can be recorded or reproduced on a plurality of types of optical discs with light of different wavelengths without deteriorating the characteristics of the reproduced signal.

Further, a plurality of return lights of different wavelengths from the optical disk can be received by a common photodetector without providing a special optical element. Therefore, cost reduction can be achieved.

An optical pickup device according to a second aspect of the present invention comprises:
An optical pickup device for irradiating an optical disc with light and receiving return light from the optical disc, comprising: a first light source for emitting light of a first wavelength; and a second light source for emitting light of a second wavelength. And a parallel plate that reflects light emitted from each of the first and second light sources.
A first wavelength selection film that reflects light of the first wavelength and transmits light of the second wavelength, a light transmission film that transmits light of the second wavelength, and reflects light of the second wavelength. A second wavelength selection film and a second wavelength selection film sequentially reflected from the first wavelength selection film, and a second wavelength selection film reflected from the second wavelength selection film and emitted from the surface side. They are arranged so that the optical paths of light of the wavelengths coincide.

In the optical pickup device according to the present invention, light of the first wavelength is emitted from the first light source, and light of the second wavelength is emitted from the second light source. The light of the first wavelength emitted from the first light source is reflected by the parallel plate-like first wavelength selection film. The second light emitted from the second light source
Is transmitted through the first wavelength selection film and the light transmission film of the parallel plate, is reflected by the second wavelength selection film, passes through the light transmission film and the first wavelength selection film again, and becomes the surface side. Is emitted from.

In this case, the optical paths of the light of the first wavelength reflected by the first wavelength selection film and the light of the second wavelength reflected from the second wavelength selection film and emitted from the front surface coincide. Parallel plates are arranged as described above. Thereby,
The optical paths of the light of the first wavelength and the light of the second wavelength can coincide with the optical axis of the optical system. As a result, information can be recorded or reproduced on a plurality of types of optical discs with light of different wavelengths without deteriorating the characteristics of the reproduced signal.

Further, the feedback light of the first wavelength and the second feedback light from the optical disk can be received by the common photodetector without providing a special optical element. Therefore, cost reduction can be achieved.

An optical pickup device according to a third aspect of the present invention comprises:
In the configuration of the optical pickup device according to the second invention,
It further includes a photodetector for detecting light, and an optical element for guiding light reflected by the parallel flat plate to the optical disc and guiding return light from the optical disc to the photodetector.

The light reflected by the parallel flat plate is guided to the optical disk by the optical element, and the return light from the optical disk is guided to the photodetector by the optical element. In this case, the optical paths of the light of the first wavelength and the light of the second wavelength reflected by the parallel flat plate can be made coincident with the optical axis of the optical element, and the feedback light of the first wavelength from the optical disc and the light of the first wavelength can be adjusted. The optical path of the feedback light having the wavelength of 2 can be made coincident with the optical axis of the optical element. Also, the feedback light of the first wavelength and the feedback light of the second wavelength can be made incident on the same point of the photodetector. Therefore, the characteristics of the reproduced signal are improved.

An optical pickup device according to a fourth aspect of the present invention comprises:
An optical pickup device for irradiating an optical disc with light and receiving return light from the optical disc, comprising: a first light source for emitting light of a first wavelength; and a second light source for emitting light of a second wavelength. And a parallel plate that reflects light emitted from each of the first and second light sources.
A first wavelength selection film that reflects a part of the light of the first wavelength and transmits light of the second wavelength, a light transmission film that transmits light of the first and second wavelengths, A second wavelength selection film that transmits light of the wavelength and reflects a part of the light of the second wavelength in order from the front side, and the light of the first wavelength reflected by the first wavelength selection film and The second wavelength selective film is disposed so that the optical paths of the light of the second wavelength reflected from the surface side and emitted from the front side coincide with each other.

In the optical pickup device according to the present invention, light of the first wavelength is emitted from the first light source, and light of the second wavelength is emitted from the second light source. Part of the light of the first wavelength emitted from the first light source is reflected by the parallel plate-like first wavelength selection film. Light of the second wavelength emitted from the second light source passes through the first wavelength selection film and the light transmission film of the parallel plate. Part of the light of the second wavelength is
The light is reflected by the second wavelength selection film,
Again passes through the wavelength selection film and is emitted from the surface side.

In this case, the optical paths of the light of the first wavelength reflected by the first wavelength selection film and the light of the second wavelength reflected by the second wavelength selection film and emitted from the front surface coincide. The parallel plate is arranged as described above. Thereby,
The optical paths of the light of the first wavelength and the light of the second wavelength can coincide with the optical axis of the optical system. As a result, information can be recorded or reproduced on a plurality of types of optical discs with light of different wavelengths without deteriorating the characteristics of the reproduced signal.

Also, the feedback light of the first wavelength and the feedback light of the second wavelength from the optical disk can be received by the common photodetector without providing a special optical element.
Therefore, cost reduction can be achieved.

An optical pickup device according to a fifth aspect of the present invention comprises:
In the configuration of the optical pickup device according to the fourth invention,
A photodetector that detects light, and an optical element that guides light reflected by the parallel plate to the optical disk and guides return light from the optical disk to the parallel plate, further comprising:
It is arranged to receive the feedback light of the first wavelength and the feedback light of the second wavelength transmitted through the parallel plate.

The light reflected by the parallel flat plate is guided to the optical disk by the optical element. A part of the feedback light of the first wavelength from the optical disk is transmitted through the parallel plate first wavelength selection film, further transmitted through the light transmission film and the second wavelength selection film, and guided to the photodetector. In addition, the second
Is transmitted through the first parallel plate and the first wavelength selection film and the light transmission film. Then, a part of the feedback light of the second wavelength passes through the second wavelength selection film and is guided to the photodetector.

In this case, the first light reflected by the parallel flat plate
The optical paths of the light of the second wavelength and the light of the second wavelength can coincide with the optical axis of the optical element, and the first optical path from the optical disk can be adjusted.
The optical paths of the return light having the wavelength of and the return light having the second wavelength can be made to coincide with the optical axis of the optical element. Also, the feedback light of the first wavelength and the feedback light of the second wavelength can be made incident on the same point of the photodetector. Therefore, the characteristics of the reproduced signal are improved.

An optical pickup device according to a sixth aspect of the present invention comprises:
An optical pickup device for irradiating an optical disc with light and receiving return light from the optical disc, comprising: a first light source for emitting light of a first wavelength; and a second light source for emitting light of a second wavelength. And a third light source that emits light of a third wavelength; and a parallel plate that reflects light emitted from each of the first, second, and third light sources. A first wavelength selection film that reflects light of the wavelength and transmits light of the second and third wavelengths; a first light transmission film that transmits light of the second and third wavelengths; A second wavelength selection film that reflects light of the wavelength and transmits light of the third wavelength, a second light transmission film that transmits light of the third wavelength,
And a third wavelength selection film that reflects light of a third wavelength in order from the front side, and the first wavelength reflection film reflected by the first wavelength selection film.
, The second wavelength light reflected by the second wavelength selection film and emitted from the front side, and the third wavelength light reflected by the third wavelength selection film and emitted from the front side Are arranged so that the optical paths of the two coincide with each other.

In the optical pickup device according to the present invention, light of the first wavelength is emitted from the first light source, light of the second wavelength is emitted from the second light source, and light of the third wavelength is emitted from the third light source. Is emitted. The light of the first wavelength emitted from the first light source is reflected by the parallel plate-like first wavelength selection film. The light of the second wavelength emitted from the second light source is transmitted through the first wavelength selection film and the first light transmission film of the parallel plate, is reflected by the second wavelength selection film, and becomes the first light. The light passes through the transmission film and the first wavelength selection film again and is emitted from the surface side. The light of the third wavelength emitted from the third light source is a parallel plate of a first wavelength selection film, a first light transmission film,
The third light transmitting film transmits through the second wavelength selection film and the second light transmitting film,
Is reflected by the second wavelength selection film, passes through the second light transmission film, the second wavelength selection film, the first light transmission film, and the first wavelength selection film again, and is emitted from the surface side.

In this case, the light of the first wavelength reflected by the first wavelength selection film, the light of the second wavelength reflected by the second wavelength selection film and emitted from the surface side, and the third wavelength A parallel flat plate is provided so that the optical path of the light of the third wavelength reflected from the selective film and emitted from the surface side coincides. Thereby, the optical paths of the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength can be made coincident with the optical axis of the optical system. As a result, information can be recorded or reproduced on a plurality of types of optical discs with light of different wavelengths without deteriorating the characteristics of the reproduced signal.

Further, the feedback light of the first wavelength, the feedback light of the second wavelength, and the feedback light of the third wavelength from the optical disk can be received by the photodetector without providing a special optical element. Therefore, cost reduction can be achieved.

An optical pickup device according to a seventh aspect of the present invention comprises:
In the configuration of the optical pickup device according to the sixth invention,
It further includes a photodetector for detecting light, and an optical element for guiding light reflected by the parallel flat plate to the optical disc and guiding return light from the optical disc to the photodetector.

The light reflected by the parallel plate is guided to the optical disk by the optical element, and the return light from the optical disk is guided to the photodetector by the optical element. In this case, the optical paths of the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength reflected by the parallel plate can be made coincident with the optical axis of the optical element, and the first optical path from the optical disk can be adjusted. The optical paths of the return light having the wavelength of 2, the return light having the second wavelength, and the return light having the third wavelength can be made to coincide with the optical axis of the optical element. Further, the first wavelength feedback light, the second wavelength feedback light, and the third wavelength feedback light can be made incident on the same point of the photodetector. Therefore, the characteristics of the reproduced signal are improved.

The optical disk device according to the eighth invention has a first
An optical pickup device according to any one of the first to seventh aspects,
An optical head having an objective lens for irradiating the optical disk with light from the optical pickup device and guiding return light from the optical disk to the optical pickup device.

In the optical disk device according to the present invention,
Light from the optical pickup device according to any one of the first to seventh inventions is applied to the optical disk by the objective lens of the optical head, and return light from the optical disk is guided to the optical pickup device through the objective lens of the optical head. .

In this case, the optical paths of a plurality of light beams of different wavelengths guided from the optical pickup device to the objective lens of the optical head can be made coincident with the optical axis of the objective lens, and a plurality of feedback light beams of different wavelengths from the optical disk can be obtained. Can be made to coincide with the optical axis of the objective lens. Therefore,
Information can be recorded or reproduced on a plurality of types of optical disks with light of different wavelengths without deteriorating the characteristics of the reproduced signal.

Further, a plurality of return lights of different wavelengths can be received by a common photodetector without providing a special optical element in the optical pickup device. Therefore, cost reduction can be achieved.

An optical disk device according to a ninth aspect of the present invention is the
In the configuration of the optical disk device according to the invention, the optical head further includes a solid immersion lens that collects light transmitted through the objective lens and irradiates the optical disk with near-field light.

In this case, since the beam spot diameter is reduced by the solid immersion lens of the optical head, the areal recording density of the optical disk is increased.

An optical disk device according to a tenth aspect of the present invention is the optical disk device according to the ninth aspect, wherein the solid immersion lens has a partially spherical entrance surface and a planar exit surface having a predetermined diameter at the center. And the lower surface around the emission surface is formed as a surface different from the emission surface.

In this case, since the lower surface around the exit surface of the solid immersion lens is formed on a surface different from the exit surface, the optical axis of the solid immersion lens is easily aligned.

[0045]

FIG. 1 is a schematic diagram showing a schematic configuration of an optical disk device according to a first embodiment of the present invention. FIG. 2 is a schematic diagram mainly showing a detailed configuration of a parallel flat plate in the optical disk device of FIG.

In FIG. 1, the optical disk device includes an optical pickup device 101 and an optical head 200.
The optical head 200 includes the objective lens 7. The optical pickup device 101 includes a semiconductor laser device 1, a parallel plate 2,
It includes a beam splitter 5, a collimator lens 6, and a photodetector 8. The configuration of the photodetector 8 is the same as the configuration shown in FIG.

As shown in FIG.
Is provided with a laser diode chip 11 for emitting laser light having a wavelength of 650 nm and a laser diode chip 12 for emitting laser light having a wavelength of 780 nm. The configuration of the semiconductor laser device 1 is the same as that of the semiconductor laser device 1 shown in FIG.
The configuration is the same as that described above.

The parallel plate 2 has a laminated structure of a substrate (light transmission film) 21 made of glass, a second wavelength selection film 22, a substrate (light transmission film) 23 made of glass, and a first wavelength selection film 24. In the figure, R means reflection and T means transmission. The first wavelength selection film 24 reflects light having a wavelength of 650 nm and transmits light having a wavelength of 780 nm. Second wavelength selection film 2
2 reflects light having a wavelength of 780 nm.

Therefore, the laser diode chip 11
The laser light having a wavelength of 650 nm emitted from is reflected by the first wavelength selection film 24. Laser diode chip 12
The laser light having a wavelength of 780 nm emitted from the first wavelength selection film 24 and the substrate 23 is transmitted through the second wavelength selection film 2
2 and again pass through the substrate 23 and the first wavelength selection film 24.

In FIG. 1, laser light having a wavelength of 650 nm emitted from the semiconductor laser device 1 is reflected by the first wavelength selection film 24 of the parallel plate 2 and enters the beam splitter 5. The laser light transmits through the beam splitter 5, is converted into parallel light by the collimator lens 6, and is condensed on the optical disc 100 by the objective lens 7. Return light (reflected light) with a wavelength of 650 nm from the optical disc 100
Transmits through the objective lens 7 and the collimator lens 6,
The light is reflected by the beam splitter 5 and enters the photodetector 8.

The wavelength 7 emitted from the semiconductor laser device 1
The 80 nm laser light is applied to the first wavelength selection film 2 of the parallel plate 2.
4, the light is transmitted through the substrate 23, is reflected by the second wavelength selection film 22, is transmitted again through the substrate 23, and is transmitted through the first wavelength selection film 24.
And is incident on the beam splitter 5. The laser light transmits through the beam splitter 5, is converted into parallel light by the collimator lens 6, and is condensed on the optical disc 100 by the objective lens 7. Return light (reflected light) having a wavelength of 780 nm from the optical disc 100 passes through the objective lens 7 and the collimator lens 6, is reflected by the beam splitter 5, and enters the photodetector 8.

In the optical disk device of this embodiment, the laser light having a wavelength of 650 nm is reflected by the first wavelength selection film 24 of the parallel plate 2, while the laser light having a wavelength of 780 nm transmits through the substrate 23 of the parallel plate 2. And the second wavelength selection film 22
And is transmitted again through the substrate 23 and emitted.
By adjusting the thickness of the substrate 23 and the angle of incidence of the laser beam on the parallel flat plate 2, it becomes possible to make the optical path of the laser beam having a wavelength of 650 nm coincide with the optical path of the laser beam having a wavelength of 780 nm. Thereby, the optical path of the laser light having the wavelength of 650 nm and the optical path of the laser light having the wavelength of 780 nm can be matched with the optical axes of the collimator lens 6 and the objective lens 7. As a result, the characteristics of the reproduced signal detected by the photodetector 8 are improved.

The wavelength of 6 is applied to the four-divided sensor of the photodetector 8.
Since it is not necessary to provide a Wollaston prism to form a light spot of a laser beam of 50 nm and a laser beam of a wavelength of 780 nm, cost can be reduced.

FIG. 3 is a schematic sectional view showing an example of the configuration of the first wavelength selection film 24 in the parallel plate 2 of FIGS. 1 and 2. FIG. 4 is a diagram showing the wavelength dependence of the reflectance of the first wavelength selection film 24 of FIG.

As shown in FIG. 3, the first wavelength selection film 24
Is a four-layer TiO ₂ film 24a and a three-layer MgF ₂ film 2
4b are alternately stacked. Here, the incident angle of light on the first wavelength selection film 24 is 30 °. Each TiO ₂ film 2
4a has a refractive index n of 2.7 and a thickness of 52 nm. The refractive index n of each MgF ₂ film 24b is 1.38 and the thickness is 101 nm. The refractive index n of the substrate 23 is 1.5 and the thickness is 180 μm.

As shown in FIG. 4, the reflectance of the first wavelength selection film 24 of FIG. 3 is about 1.0 at a wavelength of 650 nm and about 0.1 at a wavelength of 780 nm. Therefore, the first wavelength selection film 24 has a wavelength of 650 n
m can be reflected and light having a wavelength of 780 nm can be transmitted.

FIG. 5 is a diagram showing a simulation result of a wavefront aberration generated when a laser beam having a wavelength of 780 nm is transmitted through a parallel flat plate. In FIG. 5, the horizontal axis represents the position of the laser diode when the standard position is set to 0, and the vertical axis represents the RMS (effective value) of the wavefront aberration.

As shown in FIG. 5, even when the position of the laser diode deviates from the reference position by ± 0.2 mm, the RMS of the wavefront aberration is as small as about 0.07λ. In addition,
λ is the wavelength of the laser light of 780 nm.

FIG. 6 is a schematic diagram showing a schematic configuration of an optical disk device according to a second embodiment of the present invention. FIG.
FIG. 7 is a schematic diagram mainly showing a configuration of a parallel plate in the optical disk device of FIG. 6.

In FIG. 6, the optical disk device includes an optical pickup device 102 and an optical head 200.
The optical head 200 includes the objective lens 7. The optical pickup device 102 includes a semiconductor laser device 1, a parallel plate 3,
It includes a collimator lens 6 and a photodetector 8.

As shown in FIG. 7, the parallel flat plate 3 has a substrate (light transmitting film) 31 made of glass, a second wavelength selection film 32,
It has a laminated structure of a substrate (light transmission film) 33 made of glass and a first wavelength selection film 34. The first wavelength selection film 34 is
It has a reflectance of 50% for light having a wavelength of 650 nm and transmits light having a wavelength of 780 nm. The second wavelength selection film 32
It transmits light having a wavelength of 650 nm and has a reflectance of 50% for light having a wavelength of 780 nm.

Therefore, the laser diode chip 11
50% of the laser light having a wavelength of 650 nm emitted from
The remaining laser light reflected by the first wavelength selection film 34 passes through the first wavelength selection film 34, the substrate 33, the second wavelength selection film 32, and the substrate 31. The laser light having a wavelength of 780 nm emitted from the laser diode chip 12 passes through the first wavelength selection film 34 and the substrate 33. 50% of the laser light having a wavelength of 780 nm is reflected by the second wavelength selection film 32,
The laser beam passes through the substrate 33 and the first wavelength selection film 34 again, and the remaining laser light passes through the second wavelength selection film 32 and the substrate 31.

In FIG. 6, 50% of the laser light having a wavelength of 650 nm emitted from the semiconductor laser device 1 is reflected by the first wavelength selection film 34 of the parallel plate 3 and enters the collimator lens 6. The laser light is transmitted through a collimator lens 6.
Is converted into parallel light, and is converged on the optical disc 100 by the objective lens 7. Wavelength 6 from optical disk 100
The 50 nm return light (reflected light) passes through the objective lens 7 and the collimator lens 6. 50% of the return light is
The light is refracted by the first wavelength selection film 34 of the parallel plate 3,
The light passes through the second wavelength selection film 32 and the substrate 31 and enters the photodetector 8.

Wavelength 7 emitted from semiconductor laser device 1
The 80 nm laser light is applied to the first wavelength selection film 3 of the parallel plate 3.
4, the light is transmitted through the substrate 33, is reflected by the second wavelength selection film 32, is transmitted again through the substrate 33, and is transmitted through the first wavelength selection film 34.
And is incident on the collimator lens 6. The laser light is converted into parallel light by the collimator lens 6 and is focused on the optical disk 100 by the objective lens 7. Return light (reflected light) with a wavelength of 780 nm from the optical disc 100
Is transmitted through the objective lens 7 and the collimator lens 6. The return light is refracted by the first wavelength selection film 34 of the parallel plate 3 and passes through the substrate 33. Furthermore, the 5
0% is transmitted through the second wavelength selection film 32 and the substrate 31,
Light is incident on the photodetector 8.

In the optical disk device of this embodiment, the laser light having a wavelength of 650 nm is reflected by the first wavelength selection film 34 of the parallel plate 3, while the laser light having a wavelength of 780 nm transmits through the substrate 33 of the parallel plate 3. And the second wavelength selection film 32
And is transmitted again through the substrate 33 and emitted.
By adjusting the thickness of the substrate 33 and the incident angle of the laser beam, the optical path of the laser beam having a wavelength of 650 nm and the wavelength of 780 nm are adjusted.
It is possible to match the optical path of the laser light of nm. Thereby, the optical path of the laser light having the wavelength of 650 nm and the optical path of the laser light having the wavelength of 780 nm can be matched with the optical axes of the collimator lens 6 and the objective lens 7. As a result, the characteristics of the reproduced signal detected by the photodetector 8 are improved.

The wavelength of 6 is applied to the four-divided sensor of the photodetector 8.
Since it is not necessary to provide a Wollaston prism to form a light spot of a laser beam of 50 nm and a laser beam of a wavelength of 780 nm, cost can be reduced.

FIG. 8 is a schematic sectional view showing an example of the configuration of the first wavelength selection film 34 in the parallel plate 3 of FIGS. 6 and 7. FIG. 9 is a diagram showing the wavelength dependence of the reflectance of the first wavelength selection film 34 in FIG.

As shown in FIG. 8, the first wavelength selection film 34
Are five TiO ₂ films 34 a and four MgF ₂ films 3
4b are alternately stacked. Here, the incident angle of light on the first wavelength selection film 34 is 30 °. Each TiO ₂ film 3
4a has a refractive index n of 2.7 and a thickness of 41 nm. Further, each MgF ₂ 34b has a refractive index n of 1.38 and a thickness of 80 nm. The refractive index n of the substrate 33
Is 1.5 and the thickness is 180 μm.

As shown in FIG. 9, the reflectance of the first wavelength selection film 34 of FIG. 8 is about 0.5 at a wavelength of 650 nm and about 0.1 at a wavelength of 780 nm. Therefore, the first wavelength selection film 34 has a wavelength of 650 n
It reflects about half of the light of m and can transmit light of wavelength 780 nm.

FIG. 10 is a schematic sectional view showing an example of the configuration of the second wavelength selection film 32 in the parallel plate 3 of FIGS. 6 and 7. FIG. 11 shows the second wavelength selection film 32 of FIG.
FIG. 4 is a diagram showing the wavelength dependence of the reflectance of the present invention.

As shown in FIG. 10, the second wavelength selection film 32
Is formed by alternately stacking four layers of MgF ₂ films 32a and four layers of Sb ₂ S ₃ films 32b. Here, the incident angle of light on the second wavelength selection film 32 is set to 20 °. Each MgF ₂ film has a refractive index n of 1.38 and a thickness of 80 nm. The refractive index n of each Sb ₂ S ₃ film 32b is 3.0,
The thickness is 37 nm. The refractive index n of the substrate 31 is 1.5 and the thickness is 1 mm.

As shown in FIG. 11, the second wavelength selection film 32 of FIG. 10 has a reflectance of about 0.5 at a wavelength of 650 nm.
1 and the reflectance is about 0.4 at a wavelength of 780 nm. Therefore, the second wavelength selection film 32 has a wavelength of 650
nm light, and about half of the 780 nm wavelength light can be reflected.

FIG. 12 is a schematic diagram showing a schematic configuration of an optical disk device according to the third embodiment of the present invention. FIG. 13 is a schematic diagram mainly showing the configuration of a parallel flat plate in the optical disk device of FIG.

In FIG. 12, the optical disk device includes an optical pickup device 103 and an optical head 200. The optical head 200 includes the objective lens 7. The optical pickup 103 includes a semiconductor laser element 1a, a parallel plate 4, a beam splitter 5, a collimator lens 6, and a photodetector 8.

As shown in FIG. 13, the semiconductor laser device 1
a includes a laser diode chip 11 that emits a laser beam with a wavelength of 650 nm, a laser diode chip 12 that emits a laser beam with a wavelength of 780 nm, and a laser diode chip 13 that emits a laser beam with a wavelength of 410 nm.

The parallel flat plate 4 includes a third wavelength selection film 45, a glass substrate (light transmission film) 41, and a second wavelength selection film 4.
2. It has a laminated structure of a substrate (light transmission film) 43 made of glass and a first wavelength selection film 44. First wavelength selection film 44
Reflects light having a wavelength of 410 nm, transmits light having a wavelength of 650 nm, and transmits light having a wavelength of 780 nm. The second wavelength selection film 42 reflects light having a wavelength of 650 nm and has a wavelength of 780 nm.
nm light. The third wavelength selection film 45 has a wavelength of 78
Reflects light of 0 nm.

Therefore, the laser diode chip 13
The laser light having a wavelength of 410 nm emitted from is reflected by the first wavelength selection film 44. Laser diode chip 11
The laser light having a wavelength of 650 nm emitted from the first wavelength selection film 44 and the substrate 43 passes through the second wavelength selection film 4.
2 and is transmitted again through the substrate 43 and the first wavelength selection film 44. The laser light having a wavelength of 780 nm emitted from the laser diode chip 12 is supplied to the first wavelength selection film 44,
The light passes through the substrate 43, the second wavelength selection film 42, and the substrate 41, is reflected by the third wavelength selection film 45, and transmits again through the substrate 41, the second wavelength selection film 42, the substrate 43, and the first wavelength selection film 44.

In FIG. 12, the laser light having a wavelength of 410 nm emitted from the semiconductor laser device 1a is
Is reflected by the first wavelength selection film 44 of the beam splitter 5
Incident on. The laser light transmits through the beam splitter 5, is converted into parallel light by the collimator lens 6, and is condensed on the optical disc 100 by the objective lens 7. Return light (reflected light) with a wavelength of 410 nm from the optical disc 100
Transmits through the objective lens 7 and the collimator lens 6,
The light is reflected by the beam splitter 5 and enters the photodetector 8.

The laser light having a wavelength of 650 nm emitted from the semiconductor laser element 1 a is refracted by the first wavelength selection film 44 of the parallel plate 4, passes through the substrate 43, and passes through the second wavelength selection film 42.
Reflected by the first wavelength selection film 4
The light is refracted at 4 and enters the beam splitter 5. The laser light transmits through the beam splitter 5, is converted into parallel light by the collimator lens 6, and is condensed on the optical disc 100 by the objective lens 7. Return light (reflected light) having a wavelength of 650 nm from the optical disc 100 passes through the objective lens 7 and the collimator lens 6, is reflected by the beam splitter 5, and enters the photodetector 8.

The laser light having a wavelength of 780 nm emitted from the semiconductor laser device 1a is refracted by the first wavelength selection film 44 of the parallel plate 4, passes through the substrate 43, the second wavelength selection film 42 and the substrate 41, and The light is reflected by the wavelength selection film 45, passes through the substrate 41, the second wavelength selection film 42, and the substrate 43 again, is refracted by the first wavelength selection film 44, and is refracted by the beam splitter 5
Incident on. The laser light transmits through the beam splitter 5, is converted into parallel light by the collimator lens 6, and is condensed on the optical disc 100 by the objective lens 7. Return light (reflected light) with a wavelength of 780 nm from the optical disc 100
Transmits through the objective lens 7 and the collimator lens 6,
The light is reflected by the beam splitter 5 and enters the photodetector 8.

In the optical disk device of this embodiment, the laser light having a wavelength of 410 nm is reflected by the first wavelength selection film 44 of the parallel plate 4, while the laser light having a wavelength of 650 nm transmits through the substrate 43 of the parallel plate 4. And the second wavelength selection film 42
And is transmitted again through the substrate 43 and emitted. The laser light having a wavelength of 780 nm is applied to the substrate 43 of the parallel flat plate 4.
Then, the light passes through the substrate 41 and is reflected by the third wavelength selection film 45, passes through the substrates 41 and 43 again, and is emitted. Therefore, by adjusting the thickness of the substrate 43 and the substrate 41 and the angle of incidence of the laser beam on the parallel flat plate 4,
The optical path of the laser light having a wavelength of 410 nm, the optical path of the laser light having a wavelength of 650 nm, and the optical path of the laser light having a wavelength of 780 nm can be matched. Thereby, the wavelength 410
The optical path of the laser light of nm, the optical path of the laser light of wavelength 650 nm, and the optical path of the laser light of wavelength 780 can be aligned with the optical axes of the collimator lens 6 and the objective lens 7. As a result, the characteristics of the reproduced signal obtained by the photodetector 8 are improved.

The wavelength division 4 sensor of the photodetector 8 is
Since it is not necessary to provide a Wollaston prism to form a light spot of a 10-nm laser beam, a 650-nm laser beam, and a 780-nm laser beam, cost can be reduced.

FIG. 14 shows the parallel plate 4 of FIGS. 12 and 13.
FIG. 4 is a schematic cross-sectional view illustrating an example of a configuration of a first wavelength selection film 44 in FIG. FIG. 15 is a diagram showing the wavelength dependence of the reflectance of the first wavelength selection film 44 of FIG.

As shown in FIG. 14, the first wavelength selection film 44
Is a four-layer TiO ₂ film 44a and a three-layer MgF ₂ film 4
4b are alternately stacked. Here, the incident angle of light on the first wavelength selection film 44 is set to 48 °. Each TiO ₂ film 44
The refractive index n of a is 2.7 and the thickness is 33 nm.
Each MgF ₂ film 44b has a refractive index of 1.38 and a thickness of 65 nm. The refractive index n of the substrate 43 is 1.5 and the thickness is 144 μm.

As shown in FIG. 15, the first wavelength selection film 44
, The reflectance is about 0.9 at a wavelength of 410 nm, the reflectance is about 0.2 at a wavelength of 650 nm, and
The reflectance is about 0.1 at 80 nm. Therefore, the first wavelength selection film 44 can reflect light having a wavelength of 410 nm, transmit light having a wavelength of 650 nm, and transmit light having a wavelength of 780 nm.

FIG. 16 shows the parallel plate 4 shown in FIGS.
FIG. 4 is a schematic cross-sectional view showing an example of the configuration of a second wavelength selection film 42 in FIG. FIG. 17 is a diagram showing the wavelength dependence of the reflectance of the second wavelength selection film 42 in FIG.

As shown in FIG. 16, the second wavelength selection film 42
Is a four-layer TiO ₂ film 42a and a three-layer MgF ₂ film 4
2b are alternately stacked. Here, the incident angle of light on the second wavelength selection film 42 is 30 °. Each TiO ₂ film 42
The refractive index n of a is 2.7 and the thickness is 52 nm.
Each MgF ₂ film 42b has a refractive index n of 1.38 and a thickness of 101 nm. The refractive index n of the substrate 41 is 1.
5, and the thickness is 144 μm.

As shown in FIG. 17, the second wavelength selection film 42
Has a reflectance of about 0.9 at a wavelength of 650 nm and a reflectance of about 0.1 at a wavelength of 780 nm.
Therefore, the second wavelength selection film 42 can reflect light having a wavelength of 650 nm and transmit light having a wavelength of 780 nm.

In the optical disk devices of the first to third embodiments, a floating optical head of a near-field (near field) recording / reproducing system and an optical disk may be used. FIG.
FIG. 8 is a schematic view showing a flying optical head and an optical disk of a near-field recording / reproducing method.

As shown in FIG. 18, in an optical disc 300 used for the near-field recording / reproducing method, a signal recording film 302 is formed on the front side of a substrate 301. The floating optical head 50 includes an objective lens 51 and a solid immersion lens (SIL) 52. The laser light is narrowed down by the objective lens 51 and enters the SIL 52.

The SIL 52 is obtained by flattening and polishing a part of a sphere made of a transparent material having a large refractive index such as glass. The focal point of the laser light incident on the SIL 52 coincides with the polished surface, and the polished surface corresponds to the laser light emission surface.

Assuming that the refractive index of the SIL 52 is n and the wavelength of the laser beam in the air is λ, the wavelength of the laser beam at the SIL 52 is λ / n. Therefore, the spot diameter of the laser beam on the emission surface of the SIL 52 is 1 / n of the spot diameter collected by the objective lens 51.

When the laser beam emitted from the SIL 52 enters the air, it returns to the original spot diameter again. However, SIL5
In the range where the distance from the emission surface of No. 2 is up to １ ／ of the wavelength of the laser light (about 100 nm or less), that is, in the near-field region, the laser light seeps out with the same properties as in the SIL 52. The light leached in this way is called evanescent light. The spot diameter of the evanescent light is as small as 1 / n of the spot diameter collected by the objective lens 51. By using such evanescent light, it is possible to increase the areal recording density of the optical disc 300.

FIG. 19 is a view showing another example of the SIL used in the flying optical head 50 of FIG.

The SIL 81 shown in FIG. 19A has a substantially hemispherical upper surface and a flat lower surface, and has a columnar convex portion 82 at the center of the flat lower surface. The center of the lower surface of the convex portion 82 and S
The distance R between the top of the spherical surface of the IL 81 and the radius R is set to be the same as the radius of the spherical surface. As a result, the laser light that is perpendicularly incident on the spherical surface is focused on the center of the lower surface of the projection 82. This S
In the IL 81, the lower surface of the projection 82 serves as a laser light emission surface.

When the SIL 81 is used, the optical axis of the SIL 81 can be adjusted by aligning the convex portion 82 with the optical axis of the optical system, so that the assembling and adjustment of the floating optical head are facilitated.

The SIL 83 shown in FIG. 19B has a partially spherical upper surface and an inverted truncated conical lower surface. SIL83
R between the center of the central portion 84 of the lower surface of the sphere and the top of the spherical surface
Is set to be the same as the radius of the spherical surface. As a result, the laser beam that is perpendicularly incident on the spherical surface is focused on the center of the central portion 84 on the lower surface. In this SIL 83, the central portion 84 on the lower surface serves as a laser light emission surface.

When this SIL 83 is used, the central portion 84 on the lower surface is aligned with the optical axis of the optical system, so that the SIL 83
Can be aligned, so that the assembling and adjustment of the floating optical head are facilitated.

The SIL 85 shown in FIG. 19C has a substantially hemispherical upper surface and a flat lower surface, and has a cylindrical concave portion 86 at the center of the flat lower surface. The distance R between the center of the bottom surface of the recess 86 and the top of the spherical surface is set to be the same as the radius of the spherical surface. As a result, the laser beam that is perpendicularly incident on the spherical surface is focused on the center of the bottom surface of the concave portion 86. In the SIL 85, the bottom surface of the concave portion 86 becomes the laser light emission surface.

When this SIL 85 is used, the optical axis of the SIL 85 can be adjusted by aligning the concave portion 86 with the optical axis of the optical system, so that the assembling and adjustment of the floating optical head are facilitated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of an optical disk device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram mainly showing a configuration of a parallel plate in the optical disk device of FIG. 1;

FIG. 3 is a schematic cross-sectional view illustrating an example of a configuration of a first wavelength selection film in the parallel flat plate of FIGS. 1 and 2;

FIG. 4 is a diagram illustrating the wavelength dependence of the reflectance of the first wavelength selection film of FIG. 3;

FIG. 5 is a diagram illustrating a simulation result of a wavefront aberration generated when a laser beam having a wavelength of 780 nm transmits through a parallel plate.

FIG. 6 is a schematic diagram showing a schematic configuration of an optical disc device according to a second embodiment of the present invention.

FIG. 7 is a schematic diagram mainly showing a configuration of a parallel plate in the optical disk device of FIG. 6;

8 is a schematic cross-sectional view illustrating an example of a configuration of a first wavelength selection film in the parallel flat plates of FIGS. 6 and 7. FIG.

9 is a diagram showing the wavelength dependence of the reflectance of the first wavelength selection film of FIG.

FIG. 10 is a schematic cross-sectional view showing an example of a configuration of a second wavelength selection film in the parallel flat plates of FIGS. 6 and 7.

11 is a diagram showing the wavelength dependence of the reflectance of the second wavelength selection film of FIG.

FIG. 12 is a schematic diagram showing a schematic configuration of an optical disc device according to a third embodiment of the present invention.

FIG. 13 is a schematic diagram mainly showing a configuration of a parallel plate in the optical disk device of FIG. 12;

FIG. 14 shows a first example of the parallel plate shown in FIGS. 12 and 13.
FIG. 3 is a schematic cross-sectional view illustrating an example of a configuration of a wavelength selection film.

FIG. 15 is a diagram illustrating the wavelength dependence of the reflectance of the first wavelength selection film of FIG. 14;

FIG. 16 shows a second example of the parallel plate shown in FIGS. 12 and 13;
FIG. 3 is a schematic cross-sectional view illustrating an example of a configuration of a wavelength selection film.

17 is a diagram showing the wavelength dependence of the reflectance of the second wavelength selection film of FIG.

FIG. 18 is a schematic diagram showing a flying optical head of a near-field recording / reproducing method.

FIG. 19 is a diagram illustrating another example of the SIL used in the flying optical head.

FIG. 20 is a schematic diagram showing a schematic configuration of a conventional optical disk device.

FIG. 21 is a diagram showing a semiconductor laser element in the optical disk device of FIG.

FIG. 22 is a diagram illustrating a Wollaston prism and a photodetector in the optical disc device of FIG. 20;

[Explanation of symbols]

 1, 1a Semiconductor laser element 2, 3, 4 Parallel plate 5 Beam splitter 6 Collimator lens 7, 51 Objective lens 8 Photodetector 11, 12, 13 Laser diode chip 21, 23, 31, 33, 41, 43 Substrate 24, 34, 44 First wavelength selection film 22, 32, 42 Second wavelength selection film 45 Third wavelength selection film 50 Floating optical head 52, 81, 83, 85 SIL 101, 102, 103 Optical pickup device 200 Optical head

Claims (10)

[Claims] 1. An optical pickup device for irradiating an optical disc with light and receiving return light from the optical disc, comprising: a plurality of light sources for emitting a plurality of lights having different wavelengths; A parallel plate that reflects the emitted light, wherein the parallel plate reflects a plurality of wavelength selection films that reflect one of light of different wavelengths among the plurality of lights and transmit light of the remaining wavelengths. Including sequentially from the surface side through the permeable membrane,
An optical pickup device, wherein the plurality of light beams are respectively reflected by the plurality of wavelength selection films and emitted from the front surface side so that the optical paths of the plurality of light beams coincide with each other. 2. An optical pickup device for irradiating an optical disk with light and receiving return light from the optical disk, comprising: a first light source for emitting light of a first wavelength; and a light source for emitting light of a second wavelength. A second light source that emits light; and a parallel flat plate that reflects light emitted from each of the first and second light sources. The parallel flat plate reflects light of the first wavelength, and A first wavelength selection film that transmits light of the second wavelength, a light transmission film that transmits the light of the second wavelength, and a second wavelength selection film that reflects the light of the second wavelength. From the side, the optical path of the light of the first wavelength reflected by the first wavelength selection film and the light of the second wavelength reflected from the second wavelength selection film and emitted from the front side Optical pickups, which are arranged so that Apparatus. 3. A light detector for detecting light, and an optical element for guiding light reflected by the parallel plate to the optical disk and guiding return light from the optical disk to the light detector. The optical pickup device according to claim 2, wherein: 4. An optical pickup device that irradiates an optical disk with light and receives return light from the optical disk, comprising: a first light source that emits light of a first wavelength; and a light source that emits light of a second wavelength. A second light source that emits light; and a parallel flat plate that reflects light emitted from each of the first and second light sources, wherein the parallel flat plate reflects a part of the light having the first wavelength. With the second
A first wavelength selection film that transmits light of the first wavelength, a light transmission film that transmits the light of the first and second wavelengths, and a light transmission film that transmits the light of the first wavelength and the second wavelength. A second wavelength selection film that reflects part of the light and a second wavelength selection film in order from the surface side, wherein the light of the first wavelength reflected by the first wavelength selection film and the second wavelength selection film are reflected by the second wavelength selection film. An optical pickup device provided so that the optical paths of the light of the second wavelength emitted from the front surface coincide with each other. 5. A light detector for detecting light, and an optical element for guiding light reflected by the parallel plate to the optical disk and guiding return light from the optical disk to the parallel plate, further comprising: 5. The optical pickup device according to claim 4, wherein the device is arranged to receive the feedback light of the first wavelength and the feedback light of the second wavelength transmitted through the parallel plate. 6. An optical pickup device for irradiating an optical disk with light and receiving return light from the optical disk, comprising: a first light source for emitting light of a first wavelength; and a light source for emitting light of a second wavelength. A second light source that emits light, a third light source that emits light of a third wavelength, and a parallel flat plate that reflects light emitted from each of the first, second, and third light sources, The parallel plate reflects a light of the first wavelength and transmits a light of the second and third wavelengths, and transmits a light of the second and third wavelengths. A first light transmission film, a second wavelength selection film that reflects the light of the second wavelength and transmits the light of the third wavelength, and a second light that transmits the light of the third wavelength. A light-transmitting film and a third wavelength-selective film that reflects light of the third wavelength are arranged in order from the surface side Light of the first wavelength reflected by the first wavelength selection film, light of the second wavelength reflected from the second wavelength selection film and emitted from the front side, and the third light The third light reflected by the wavelength selection film and emitted from the surface side
An optical pickup device, wherein the optical paths of the light having the wavelengths are arranged so as to coincide with each other. 7. A light detector for detecting light, and an optical element for guiding light reflected by the parallel plate to the optical disk and guiding return light from the optical disk to the light detector. 7. The optical pickup device according to claim 6, wherein: 8. An optical pickup device according to claim 1, further comprising: an objective lens for irradiating the optical disk with light from the optical pickup device and guiding return light from the optical disk to the optical pickup device. An optical disc device comprising: an optical head having the same. 9. The optical disk according to claim 8, wherein the optical head further comprises a solid immersion lens that collects light transmitted through the objective lens and irradiates near-field light to the optical disk. apparatus. 10. The solid immersion lens,
It has a partially spherical entrance surface and a lower surface including a planar exit surface with a predetermined diameter at the center, and a lower surface around the exit surface is formed as a surface different from the exit surface. The optical disk device according to claim 9.