WO2009147827A1

WO2009147827A1 - Optical pickup and optical disc disk device, computer, optical disc disk player, optical disc disk recorder

Info

Publication number: WO2009147827A1
Application number: PCT/JP2009/002444
Authority: WO
Inventors: 田中俊靖; 山崎文朝; 金馬慶明; 若林寛爾
Original assignee: パナソニック株式会社
Priority date: 2008-06-02
Filing date: 2009-06-01
Publication date: 2009-12-10
Also published as: JP2011165224A

Abstract

Provided are a compact and inexpensive optical pickup having fewer a reduced number of parts for an optical pickup capable of recording and reproducing a high density optical disk (BD) using a blue-violet laser light source, and an optical disc disk device. The traveling range La of a coupling lens (5) is the position at one end of the coupling lens (5) when recording or reproducing a DVD by red laser light and the position at the other end of the coupling lens (5) when recording or reproducing a CD by infrared laser light. The traveling range Lb of the coupling lens (5) for correcting the spherical aberrations according to the thickness of the protective substrate of the information recording surface in the BD caused by blue-violet laser light fits into the traveling range La of the coupling lens (5) because the spherical aberrations caused by the thickness of the protective substrate of the information recording surface in the BD are corrected by blue-violet laser light.

Description

Optical pickup and optical disc apparatus, computer, optical disc player, optical disc recorder

The present invention includes an optical pickup that includes a plurality of light sources having different wavelengths and optically records or reproduces information on an information recording medium such as a plurality of types of optical discs, and an optical disc apparatus including the optical pickup, The present invention relates to a computer, an optical disc player, and an optical disc recorder provided with the optical disc apparatus.

In recent years, Blu-ray Disc (hereinafter referred to as BD), which is a high-density and large-capacity optical information recording medium, has the same size as CD (Compact Disc) and DVD (Digital Versatile Disc) with the practical use of blue-violet semiconductor lasers. It has been put into practical use. This BD uses a blue-violet laser light source with a wavelength of about 400 nm and an objective lens whose numerical aperture (NA) is increased to 0.85, and records or reproduces information. The protective substrate thickness is about 0.1 mm. This is an optical disc.

Therefore, the information recording surfaces of the optical discs having different protective substrate thicknesses are compatible with recording or reproducing information by converging laser beams of different wavelengths using a single objective lens or a plurality of objective lenses. Optical pickups have been proposed.

For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-293765), the optical axes of laser beams of different wavelengths emitted from different light sources are matched, and a single coupling lens and a single objective lens are used. An optical pickup for recording or reproducing information on an optical disc having different protective substrate thicknesses is shown. A configuration example of a conventional optical pickup disclosed in Patent Document 1 is shown in FIG.

In FIG. 20A, 101 is a light source that emits blue-violet laser light, 102 is a two-wavelength light source that emits red laser light and infrared laser light, and 103 is an optical axis of light emitted from each of the

light sources

101 and 102. , A dichroic prism 104 for coupling, a coupling lens for converting the divergence angle of divergent light from the

respective light sources

101 and 102, and 105 for condensing laser beams having a plurality of wavelengths onto optical disks having different protective substrate thicknesses. A compatible objective lens, 131 is a compatible objective lens actuator for causing the compatible objective lens 105 to follow a rotating optical disk by focus control and tracking control, 132 is a coupling lens actuator for moving the coupling lens 104 in the optical axis direction, and 151 is a high density. Optical disc (BD), 152 is DVD, 153 is A D.

In such a configuration, even when recording or reproduction is performed on any medium such as a high-density optical disc (BD) 151, a DVD 152, or a CD 153, the compatible objective lens 105 is designed when the incident light beam is substantially parallel light. A simple spot is formed on the information recording surface of each optical disc.

By the way, even if light beams having different wavelengths are converted into parallel light by the same coupling lens 104, the degree of divergence changes due to the difference in the refractive index of the lens material due to the difference in wavelength. Therefore, by moving the coupling lens 104 in the optical axis direction by the coupling lens actuator 132, the light beam incident on the compatible objective lens 105 becomes substantially parallel light at any wavelength.

Also, Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-2834) discloses that the optical axes of laser beams of different wavelengths emitted from different light sources are made coincident and different protective substrate thicknesses are obtained using a single objective lens. A configuration of another optical pickup for recording or reproducing information on or from an optical disc having the following structure is shown.

FIG. 20B shows a configuration example of a conventional optical pickup shown in Patent Document 2. In FIG. 20B, 201 is a first light source that emits blue-violet laser light, 202 is a second light source that emits red laser light, 203 is a third light source that emits infrared laser light, and 204 is A first optical path synthesis element 205 for matching the optical axes of the emitted light from the first and

second light sources

201 and 202, and a cup for converting the divergence angle of the divergent light from the first or second light source 201 and 202 A ring lens, 206 is a second optical path synthesis element that matches the optical axis of the light emitted from the third light source 203 with the first or second light flux that has passed through the

coupling lens

205, and 207 is a laser having a plurality of wavelengths. Compatible objective lens for condensing light onto optical discs of different protective substrate thicknesses, 231 is a compatible objective lens for causing the compatible objective lens 207 to follow a rotating optical disc by focus control or tracking control. 'S actuator, 232 the coupling lens actuator for moving the coupling lens 205 in the optical axis direction, 251 high density optical disc (BD), 252 is DVD, 253 is CD.

In such a configuration, the infrared laser light emitted from the third light source 203 is incident on the compatible objective lens 207 as divergent light, correcting spherical aberration caused by the difference in the thickness of the protective substrate, and compatible. The distance (working distance (work distance WD)) from the surface of the objective lens 207 facing the optical disk to the protective substrate thickness surface of the optical disk can be increased.

In addition, the coupling lens 205 is moved in the optical axis direction by the coupling lens actuator 232 to change the divergence of the blue-violet laser light and the red laser light incident on the compatible objective lens 207, so that the protective base material thickness of each optical disk is changed. It is also possible to correct the spherical aberration caused by the difference between the two and to increase the working distance WD.

In Patent Document 3 (Japanese Patent Laid-Open No. 2003-85806), a coupling lens that converts light emitted from a light source into parallel light is moved in the optical axis direction to change the parallelism of a light beam incident on the objective lens. The configuration is shown. In particular, in a high-density optical disc (BD) in which a large amount of spherical aberration occurs due to a thickness error of the protective base material thickness, the spherical aberration can be corrected with a simple configuration. A configuration is disclosed in which an optimum spherical aberration correction amount can be applied by moving the coupling lens position when focusing on the information recording surface.

JP 2005-293765 A JP 2004-281034 A JP 2003-85806 A

Patent Document 3 discloses a means for correcting spherical aberration caused by the protective substrate thickness error of an optical disk by moving the coupling lens in the optical axis direction and changing the degree of divergence of the light beam incident on the objective lens. It is shown. By applying this concept, in Patent Document 1 or Patent Document 2, the degree of divergence of a light beam from a light source having a plurality of wavelengths is changed by moving a single coupling lens in the optical axis direction. . That is, a light beam having a different degree of divergence for each wavelength is incident on a compatible objective lens to generate a predetermined spherical aberration, and a good spot with less aberration on the information recording surface of an optical disc having a different protective substrate thickness Patent Document 1 or Patent Document 2 shows a means for forming the.

However, the conventional three-wavelength optical pickup described above has the following problems.

In other words, the optical pickup compatible with a high-density optical disc (BD) corrects the amount of spherical aberration caused by the substrate thickness error of the optical disc with the configuration shown in Patent Document 3, and further supports the case of a multilayer disc. However, if the single coupling lens is used to move the coupling lens so as to be compatible with DVDs and CDs as in

Patent Documents

1 and 2, working is performed. If an attempt is made to achieve this while ensuring a sufficient distance, the range of movement of the coupling lens will increase. When the moving range of the coupling lens is increased, it is difficult to reduce the size of the optical pickup, and there is a problem that an optical disk drive device or the like on which the optical pickup is mounted is increased in size.

Further, the conventional optical pickup of the two wavelength type has the following problems.

In general, the longer the smaller NA wavelength than the shorter NA larger wavelength, the smaller the working distance due to the substrate thickness of the optical disk. The longer objective lens f is made longer than the shorter objective lens f having a large NA, and the effective diameter of the objective lens for the longer wavelength is set to be larger than the effective diameter for the shorter wavelength. The actual size should be increased.

On the other hand, in the case of the conventional optical pickup, when the divergence of the light incident on the two-wavelength compatible objective lens is different between the two wavelengths, the longer λ2 having the smaller NA (small effective diameter) and the longer λ2 The shorter wavelength λ1 having a larger wavelength (large effective diameter) has a low divergence.

As a result, there is a problem that the effective diameter of the optical component close to the objective lens of the conventional optical pickup must be large.

An object of the present invention is to provide an optical pickup, an optical disc apparatus, a computer, an optical disc player, and an optical disc recorder, in which such issues are solved in consideration of the problems of the conventional optical pickup.

The first aspect of the present invention is
A first light source that emits a divergent light beam of wavelength λ1,
A second light source that emits a divergent light beam having a wavelength λ2 (λ2> λ1) different from the wavelength λ1;
The light beam having the wavelength λ1 is condensed on the information recording surface of the first optical disk having the protective substrate thickness t1, and the light beam having the wavelength λ2 is condensed on the information recording surface of the second optical disk having the protective substrate thickness t2 different from the t1. And an objective lens for focusing
When converging the light beam having the wavelength λ1 on the information recording surface of the first optical disk, the divergence of the light beam incident on the objective lens is greater than that of the second optical disk. It is an optical pickup that is larger than the divergence of the light beam incident on the objective lens when condensing on the information recording surface.

The second aspect of the present invention
The NA of the objective lens for condensing the light beam with the wavelength λ1 on the information recording surface of the first optical disc, and NA1 of the objective lens for condensing the light beam with the wavelength λ2 on the information recording surface of the second optical disc. If NA is NA2, the optical pickup according to the first aspect of the present invention satisfies NA1> NA2.

The third aspect of the present invention provides
The combination of the wavelength λ1 and the wavelength λ2 is blue violet light (wavelength 350 nm to 450 nm) and red light (wavelength 600 nm to 700 nm), blue violet light and infrared light (750 nm to 850 nm), or red light and infrared light. The optical pickup according to the first or second aspect of the present invention, which is a combination of the above.

The fourth invention relates to
Means for making the light beams emitted from the first and second light sources the same optical axis;
A coupling lens that converts the divergence of light beams emitted from the first and second light sources;
A lens actuator that moves the coupling lens along the optical axis direction of the objective lens in the same optical axis area;
The lens actuator is configured to condense the light beam having the wavelength λ1 on the information recording surface of the first optical disk and to collect the light beam having the wavelength λ2 on the information recording surface of the second optical disk. Move the coupling lens to a different position,
The position of the coupling lens in the optical axis direction of the lens when the light beam having the wavelength λ1 is condensed on the information recording surface of the first optical disk is changed to the information on the second optical disk. The optical pickup according to any one of the first to third aspects of the present invention, wherein the coupling lens is condensed closer to the light source side than a position in the lens optical axis direction when the light is condensed on a recording surface.

The fifth aspect of the present invention relates to
When the light beam having the wavelength λ1 is condensed on the information recording surface of the first optical disc, the position of the coupling lens in the lens optical axis direction is a position where the light beam incident on the objective lens becomes parallel light. Yes, when the light beam having the wavelength λ2 is condensed on the information recording surface of the second optical disc, the position of the coupling lens in the lens optical axis direction is that the light beam incident on the objective lens becomes convergent light. This is the optical pickup according to the fourth aspect of the present invention.

The sixth invention relates to
The objective lens is the optical pickup according to any one of the first to fifth aspects of the present invention, which is a lens shared by the light beam having the wavelength λ1 and the light beam having the wavelength λ2.

The seventh invention relates to
The objective lens is the optical pickup according to any one of the first to fifth aspects of the present invention, which includes a lens for the light beam having the wavelength λ1 and a lens for the light beam having the wavelength λ2.

The eighth invention relates to
A first light source that emits a divergent light beam of wavelength λ1,
A second light source that emits a divergent light beam having a wavelength λ2 (λ2> λ1) different from the wavelength λ1;
A third light source that emits a divergent light beam having a wavelength λ3 (λ3>λ2> λ1) different from the wavelengths λ1 and λ2.
The light beam having the wavelength λ1 is condensed on the information recording surface of the first optical disk having the protective substrate thickness t1, and the light beam having the wavelength λ2 is condensed on the information recording surface of the second optical disk having the protective substrate thickness t2 different from the t1. An objective lens for condensing the light beam having the wavelength λ3 on the information recording surface of a third optical disc having a protective substrate thickness t3 different from the t1 and the t2.
Means for converting the light beams emitted from the first, second, and third light sources into the same optical axis;
A coupling lens that converts the divergence of the light beams emitted from the first, second, and third light sources;
A lens actuator that moves the coupling lens along the optical axis direction of the objective lens in the same optical axis area;
The lens actuator condensing the light beam having the wavelength λ1 on the information recording surface of the first optical disc, condensing the light beam having the wavelength λ2 on the information recording surface of the second optical disc, When condensing the light beam of wavelength λ1 on the information recording surface of the first optical disc, the coupling lens is moved to a different position,
The position of the coupling lens is an optical pickup in which the light beam having the wavelength λ3, the light beam having the wavelength λ1, and the light beam having the wavelength λ2 are collected in order from the light source. .

The ninth invention relates to
The luminous flux of wavelength λ1 is blue-violet light (wavelength 350 nm to 450 nm),
The luminous flux of wavelength λ2 is red light (wavelength 600 nm to 700 nm),
In the optical pickup according to the eighth aspect of the present invention, the light flux having the wavelength λ3 is infrared light (750 nm to 850 nm).

The tenth aspect of the present invention is
When condensing the light beam having the wavelength λ2 on the information recording surface of the second optical disk, the position of the coupling lens in the lens optical axis direction is a position where the light beam incident on the objective lens becomes convergent light. Yes,
When the light beam having the wavelength λ3 is condensed on the information recording surface of the third optical disk, the position of the coupling lens in the lens optical axis direction is a position where the light beam incident on the objective lens becomes divergent light. An eighth or ninth optical pickup according to the present invention.

The eleventh aspect of the present invention is
The objective lens is the optical pickup according to any one of the eighth to tenth aspects of the present invention, wherein the objective lens is a lens shared by the light beam having the wavelength λ1, the light beam having the wavelength λ2, and the light beam having the wavelength λ3.

The twelfth aspect of the present invention is
The objective lens is an optical pickup according to any of the eighth to tenth aspects of the present invention, which includes a lens for a light beam having the wavelength λ1 and a lens shared by the light beams having the wavelength λ2 and the wavelength λ3. is there.

The thirteenth aspect of the present invention is
The first optical disc has a plurality of information recording surfaces, and spherical aberration caused by a difference in the substantial thickness of the transparent base material from the surface to each information recording layer surface is corrected by moving the coupling lens. The fourth or eighth optical pickup of the present invention.

The fourteenth aspect of the present invention is
Any one of the first to thirteenth optical pickups of the present invention;
A motor for rotationally driving the information recording medium;
It is an optical disc apparatus provided with the said optical pick-up and the control part which controls the said motor.

The fifteenth aspect of the present invention is
A fourteenth optical disc apparatus according to the present invention;
An input means for inputting information;
A calculation means for performing calculation based on information reproduced from the optical disk device and / or information input from the input means;
An output means for outputting information reproduced from the optical disk device and / or information input from the input means and / or a result calculated by the calculation means.

The sixteenth aspect of the present invention
A fourteenth optical disc apparatus according to the present invention;
An optical disc player comprising a decoder for converting an information signal obtained from the optical disc device into image information.

The seventeenth aspect of the present invention provides
A fourteenth optical disc apparatus according to the present invention;
An optical disk recorder comprising an encoder for converting image information into an information signal for recording by the optical disk device.

According to the present invention, when a plurality of types of optical discs are recorded or reproduced using two-wavelength laser light, the effect of reducing the effective diameter of the optical component close to the objective lens is exhibited.

In addition, according to the present invention, when a plurality of types of optical discs are recorded or reproduced using laser light of three wavelengths, a compact and high-performance optical pickup and optical disc apparatus can be realized.

Further, since such an optical pickup and an optical disk device can be realized, the computer, the optical disk player, and the optical disk recorder of the present invention can be realized in a compact manner.

Schematic configuration diagram of an optical pickup when recording or reproducing a BD in Embodiment 1 of the present invention Schematic configuration diagram of an optical pickup when recording or reproducing a DVD in Embodiment 1 of the present invention Schematic configuration diagram of an optical pickup when recording or reproducing a CD in Embodiment 1 of the present invention The figure which shows typically the light beam splitting pattern of a detection hologram in Embodiment 1 of this invention. (A), (b) The figure which shows typically the structure of an objective lens in Embodiment 1 of this invention. The figure which shows typically the structure of another objective lens in Embodiment 1 of this invention. The figure which shows typically operation | movement of an objective lens actuator in Embodiment 1 of this invention. In Embodiment 1 of this invention, the figure which shows the structure of a coupling lens actuator typically (A), (c), (c) The figure which shows typically the function of a coupling lens actuator in Embodiment 1 of this invention. The figure which shows the spectral characteristics of a flat beam splitter in Embodiment 1 of this invention. The figure which shows the spectral characteristic of a wedge prism in Embodiment 1 of this invention. In Embodiment 1 of the present invention, the angle formed by the optical axis of the optical axis of the blue-violet laser light emitted from the light source and the optical axis of the red laser light emitted from the two-wavelength light source, and the incidence to the flat beam splitter and the wedge prism Illustration showing corners In Embodiment 1 of this invention, the figure explaining the incident angle dependence of the reflectance of a flat beam splitter, and arrangement | positioning of a light source The figure which shows typically the mode of the light emission point of 2 wavelength laser light source in Embodiment 1 of this invention. 1 is a schematic configuration diagram of an optical pickup using a relay lens in Embodiment 1 of the present invention. Schematic configuration diagram of an optical pickup when recording or reproducing BD in Embodiment 2 of the present invention Schematic configuration diagram of an optical pickup when recording or reproducing a DVD in Embodiment 2 of the present invention (A) Schematic configuration diagram of an optical disc apparatus according to the fifth embodiment of the present invention, (b) Schematic configuration diagram of a computer according to the sixth embodiment of the present invention. (A) Schematic configuration diagram of an optical disc player according to Embodiment 7 of the present invention, (b) Schematic configuration diagram of an optical disc recorder according to Embodiment 8 of the present invention. (A), (b) Schematic configuration diagram of conventional optical pickup having compatibility (A), (b), (c), (d) The figure which shows the step-shaped diffraction structure of a hologram lens in Embodiment 1 of this invention. (A), (e) The figure which shows the diffraction structure of the step shape of a hologram lens in Embodiment 1 of this invention. The figure which shows the diffraction efficiency of a diffraction grating in Embodiment 1 of this invention. The figure which shows the example which comprises the compatible lens of CD / DVD / BD at the time of using an optical element in Embodiment 1 of this invention. The figure which shows the movement range of a coupling lens in Embodiment 1 of this invention. Schematic configuration diagram of an optical pickup when recording or reproducing BD and DVD in Embodiment 3 of the present invention Schematic configuration diagram of an optical pickup when recording or reproducing a DVD and a CD in Embodiment 4 of the present invention

Hereinafter, embodiments of an optical pickup and an optical disc apparatus, a computer, an optical disc player, and an optical disc recorder of the present invention will be described with reference to the drawings.

(Embodiment 1)
1 to 3 are schematic configuration diagrams of the optical pickup according to the first embodiment of the present invention.

In FIG. 1, 1 is a light source for emitting blue-violet laser light, 2 is a flat beam splitter, 3 is a relay lens, 4 is a wedge prism, 5 is a coupling lens, 6 is a quarter-wave plate, 7 is a mirror, Compatible objective lens, 9 is a detection hologram, 10 is a detection lens, 11 is a two-wavelength light source that emits red laser light and infrared laser light, 12 is a diffraction grating, 20 is a light receiving element, and 30 is an objective lens 8. It is an actuator to drive. These components constitute the optical pickup 40 of the first embodiment. The flat beam splitter 2 and the wedge prism 4 are examples of the same optical axis unit of the present invention.

Reference numeral 60 denotes a BD which is an optical disk having a protective substrate thickness of about 0.1 mm.

First, the operation of the optical pickup 40 when information is recorded on or reproduced from the BD 60 will be described. The blue-violet laser light having a wavelength of 405 nm emitted from the light source 1 is incident on the flat beam splitter 2 as S-polarized light. The blue-violet laser light reflected by the flat beam splitter 2 is converted into divergent light having a different NA by passing through the relay lens 3.

The blue-violet laser light, which is the diverging light, is reflected by the wedge prism 4 and then converted into substantially parallel light by the coupling lens 5 present at the position P0. After being converted into polarized light and reflected by the mirror 7, it is converged as a light spot on the information recording surface by the objective lens 8 through the protective substrate of the BD 60.

The blue-violet laser light reflected by the information recording surface of the BD 60 is transmitted again through the objective lens 8, reflected by the mirror 7, and converted into linearly polarized light different from the forward path by the quarter wavelength plate 6, and then the coupling lens 5 Is converted into convergent light, reflected by the wedge prism 4 and transmitted through the relay lens 3 to be converted into convergent light having a different NA.

Further, the blue-violet laser light is incident on and transmitted through the flat plate beam splitter 2 with P-polarized light, and is incident on and transmitted through the detection hologram 9. When the blue-violet laser light passes through the detection hologram 9, zero-order light and ± first-order diffracted light are generated. The diffracted light is given astigmatism by the detection lens 10 and guided to the light receiving element 20.

Next, when recording or reproducing the DVD 70, which is an optical disk having a protective substrate thickness of 0.6 mm, using FIG. 2, and when recording or reproducing the CD 80, which is an optical disk having a protective substrate thickness of 1.2 mm, using FIG. The operation of the optical pickup 40 will be described.

In FIG. 2, the red laser light having a wavelength of 660 nm emitted from the two-wavelength light source 11 is separated by the diffraction grating 12 into a main beam that is 0th-order diffracted light and a sub-beam that is ± 1st-order diffracted light. Incident with polarized light. The red laser light transmitted through the wedge prism 4 is converted into a slightly convergent light by the coupling lens 5 present at the position P 1, converted from linearly polarized light to circularly polarized light by the quarter wavelength plate 6, and is reflected by the mirror 7. After being reflected, the light is converged as a light spot on the information recording surface by the objective lens 8 through the protective substrate of the DVD 70. This position P1 is located closer to the objective lens 8 than the position P0 in the case of the blue-violet laser beam described above.

The red laser beam reflected by the information recording surface of the DVD 70 is transmitted again through the objective lens 8, reflected by the mirror 7, converted into linearly polarized light different from the forward path by the quarter wavelength plate 6, and then coupled to the coupling lens 5. Is converted into convergent light. Thereafter, the red laser light is incident on the wedge prism 4 as S-polarized light, reflected, converted into convergent light having a different NA by the relay lens 3, transmitted through the flat beam splitter 2 and the detection hologram 9, and astigmatism by the detection lens 10. Is given to the light receiving element 20.

Similarly, in FIG. 3, the infrared laser light having a wavelength of 785 nm emitted from the two-wavelength light source 11 is separated into a main beam that is 0th-order diffracted light and a sub-beam that is ± 1st-order diffracted light by the diffraction grating 12, and then a wedge. The light enters the prism 4 as P-polarized light. The infrared laser light transmitted through the wedge prism 4 is converted into slightly divergent light having a different NA by the coupling lens 5 existing at the position P2, and is converted from linearly polarized light to circularly polarized light by the quarter wavelength plate 6. After being reflected by the mirror 7, it is converged as an optical spot by the objective lens 8 on the information recording surface through the protective substrate of the CD 80. This position P2 is located closer to the

light sources

1 and 11 than the position P0 in the case of the blue laser light described above.

In addition, when it says near the objective lens 8 mentioned above, or when it says near the

light sources

1 and 11, the comparison of those positions is a comparison in the area where the laser beam is made into the same optical axis. For example, in the case of FIG. 1, the area is between the wedge prism 4 and the quarter-wave plate 6.

The infrared laser light reflected by the information recording surface of the CD 80 is transmitted again through the objective lens 8, reflected by the mirror 7, and converted into linearly polarized light different from the forward path by the quarter wavelength plate 6, and then the coupling lens. 5 is converted into convergent light. Thereafter, the infrared laser light is incident on the wedge prism 4 as S-polarized light, reflected, converted into convergent light having a different NA by the relay lens 3, transmitted through the flat beam splitter 2 and the detection hologram 9, and astigmatized by the detection lens 10. After the aberration is given, the light is guided to the light receiving element 20.

On the other hand, the focus error signal for recording or reproducing the BD 60, DVD 70, and CD 80 is a so-called publicly known light detection method that detects a condensing spot given astigmatism by the detection lens 10 with a four-divided light receiving pattern in the light receiving element 20. An astigmatism method or the like can be used.

On the other hand, for example, in the BD 60, the tracking error signal is obtained by detecting the 0th-order light and the 1st-order diffracted light generated when passing through the detection hologram 9 in a predetermined light receiving region of the light receiving element 20, thereby providing the BD 60 with the tracking error signal. Suppresses fluctuations in tracking error signals caused by variations in the position, width, and depth of formed information track grooves, and tracking error signals that occur when information is recorded on information tracks and reflectivity changes Is possible. Further, by using the detection hologram 9 and the light receiving element 20 as described above, in the BD 60 having a plurality of information recording surfaces, unnecessary reflection reflected on an information recording surface different from the information recording surface to be recorded or reproduced is unnecessary. It is also possible to prevent light (stray light) from entering the light receiving region for detecting the tracking error signal.

FIG. 4 schematically shows an example of the light beam splitting pattern of the detection hologram 9. The wavy line in the figure indicates the beam diameter of the laser beam reflected on the information recording surface of the BD 60 on the detection hologram 9. The detection hologram 9 has seven types of regions 9a to 9g, and divides laser light incident on each region into 0th-order diffracted light and ± 1st-order diffracted light. The tracking error signal TE uses current signals Ia to Ig corresponding to the amount of light received by the light receiving element 20 of the + 1st order diffracted light diffracted in the respective regions 9a to 9g.
TE = (Ia−Ib) −k (Ic + Id−Ie−If)
It is obtained by the operation of

In the DVD 70 and the CD 80, a so-called three-beam method, a differential push-pull method (DPP method), or the like using a main beam and a sub beam generated by the diffraction grating 12 is used.

The detection of the focus error signal and the tracking error signal is not limited to these detection methods. For example, the BD 60 also uses a differential push-pull method (DPP) using a main beam and a sub beam generated by a diffraction grating. Method) or the like.

The objective lens 8 according to the first embodiment has a wavelength of blue-violet laser light for recording or reproducing the BD 60, red laser light for recording or reproducing the DVD 70, and infrared laser light for recording or reproducing the CD 80. The diffraction structure for converging each as a small light spot using the difference is provided.

Specifically, as shown in FIG. 5A, a blazed diffractive structure having a sawtooth cross section is formed on at least one surface of the objective lens 8, for example, the incident surface of the objective lens 8 (surface on the light source side). Yes. The blazed diffractive structure is combined with the refraction power of the objective lens 8 to diffract the laser light of each wavelength on the information recording surface of BD60, DVD70, CD80 recorded or reproduced by the laser light of each wavelength. Aberration correction is applied so that it can be converged. In this way, the objective lens 8 having a blazed diffraction structure that diffracts part of incident light can form diffraction-limited light spots on optical disks having different protective substrate thicknesses.

Note that the region for converging the infrared laser light with respect to the CD 80 is limited to the lens central portion including the optical axis, and the region for converging the red laser light with respect to the DVD 70 is the lens central portion and the outside thereof. The region for converging the blue-violet laser beam with respect to the BD 60 only in the middle peripheral portion is designed to use all of the lens central portion, the middle peripheral portion, and the outer peripheral portion on the outer side thereof, so that the NA for the CD 80 is increased. Can be limited to about 0.50, the NA for DVD 70 can be limited to about 0.65, and the NA for BD 60 can be expanded to about 0.85.

The objective lens 8 is not limited to an objective lens in which a blazed diffraction structure is formed on the entrance surface of the lens as shown in FIG. 5A. For example, as shown in FIG. 5B, a refractive positive power is used. The objective lens 8a and the separate hologram lens 8b may be integrally driven to record or reproduce the BD 60, DVD 70, or CD 80. By using such a separate hologram lens 8b, there is no need to form a diffractive structure on the incident surface of the objective lens 8 having a large tilt angle, and there is an effect that it is easy to manufacture a mold. The diffraction structure of the hologram lens 8b is not limited to the structure formed on the light source side as shown in FIG. 5B, and may be formed on the surface on the objective lens 8a side. It may be formed on both surfaces.

In addition, as shown in FIG. 6, the same effect can be obtained even when the refractive type positive power objective lens 8a ′ and the hologram lens 8b ′ having a staircase-shaped diffraction structure are integrally driven. Needless to say.

The objective lens may be, for example, a refractive objective lens using the wavelength dispersion characteristics of a plurality of glass materials. In short, a blue-violet laser beam for recording or reproducing the BD 60, and a red laser for recording or reproducing the DVD 70. It is only necessary to converge the light and the infrared laser beam for recording or reproducing the CD 80 as a minute light spot, and the present invention is not limited to the objective lens having the above-described diffraction structure.

As shown in FIG. 7, the objective lens actuator 30 includes a table 30c, a movable objective lens holder 30b that holds the objective lens 8, and a plurality of suspension wires 30a that are fixed to the table 30c and hold the objective lens holder 30b. Is provided. The objective lens actuator 30 uses the focus error signal and the tracking error signal described above to move the objective lens 8 in the focus direction (a) and the tracking direction (b) so that the light spot follows the information track of the rotating optical disk. Can drive.

Further, in addition to the displacement in the focus direction (a) and the tracking direction (b), the objective lens 8 can be tilted in the radial direction (c) of the optical disc.

The coupling lens 5 is movable in the optical axis direction of the coupling lens 5 by a coupling lens actuator 31 as shown in FIG.

FIG. 8 is a schematic configuration diagram of the coupling lens actuator 31. In FIG. 8, 5 is a coupling lens, 32 is a stepping motor, 33 is a screw shaft, 34 is a main shaft, 35 is a secondary shaft, and 36 is a lens holder. By driving the stepping motor 32 and rotating the screw shaft 33, the lens holder 36 that holds the coupling lens 5 moves along the main shaft 34 and the sub shaft 35 in the optical axis direction of the coupling lens 5.

FIG. 9 is a diagram for illustrating a corresponding method when the spherical aberration is corrected when the BD 60 is used, or when a plurality of information recording surfaces are provided.

As shown in FIG. 9, the coupling lens 5 is moved to the light source side with respect to the reference position (a) of the coupling lens 5 where the light emitted from the coupling lens 5 becomes substantially parallel light. The light emitted from the lens 5 becomes divergent light (b), and the spherical aberration that occurs when the protective substrate of the BD 60 becomes thick can be corrected.

On the other hand, by moving the coupling lens 5 to the objective lens side, the light emitted from the coupling lens 5 becomes convergent light (c), and the spherical aberration generated when the protective substrate of the BD 60 becomes thin can be corrected. That is, in the BD 60 having a plurality of information recording surfaces, the spherical aberration is corrected by moving the coupling lens 5 according to the thickness of the protective substrate of each information recording surface, thereby improving the recording or reproducing performance. Can do.

On the other hand, in the case of using the blue-violet laser beam for recording or reproducing the BD 60, the red laser beam for recording or reproducing the DVD 70, and the infrared laser beam for recording or reproducing the CD 80, respectively, The respective positions are shown in FIG. 1, FIG. 2, and FIG.

That is, as shown in FIG. 2, the coupling lens actuator 31 according to the first embodiment has a position P0 of the coupling lens 5 at the time of recording or reproducing the BD 60, which is indicated by a dotted line 5, when recording or reproducing the DVD 70. As a reference, the coupling lens 5 is moved to the position P1 on the mirror 7 side so that the red laser light emitted from the two-wavelength light source 11 enters the objective lens 8 as convergent light. On the other hand, as shown in FIG. 3, at the time of recording or reproducing the CD 80, the coupling lens 5 is set to the two-wavelength light source 11 with reference to the position P0 of the coupling lens 5 at the time of recording or reproducing the BD 60 indicated by the dotted line 5. By moving to the side position P2, the infrared laser light emitted from the two-wavelength light source 11 is made incident on the objective lens 8 as divergent light.

Next, the operation of the objective lens 8 and the like when the position of the coupling lens 5 is appropriately moved and laser light is incident on the objective lens 8 will be described. For example, the case where the configuration of FIG. 6 is used for the objective lens 8 will be described. Here, it is assumed that the diffraction structure of the hologram lens 8 b ′ having the staircase-shaped diffraction structure is a structure in which the structure shown in FIG. 21 is periodically formed. FIG. 21A shows the material shape of the lattice formed on the substrate. (B) shows the amount of phase modulation for blue-violet light. (C) has shown the phase modulation amount with respect to red light. Further, (d) shows the amount of phase modulation for red light.

In (a), the vertical direction indicates the thickness or height of the substrate in the optical axis direction. nb is the refractive index of the element material for the blue-violet light beam. For example, when the element material is BK7, there are nb = 1.5302 and some polyolefin-based resins have nb = 1.522.

One step d1 has an optical path length difference of about 1.25 wavelengths with respect to the blue-violet light beam, that is, an amount such that the phase difference is about 2π + π / 2. For example, if the unit step d1 is quartz,
d1 = λ1 / (nb−1) × 1.25 = 0.96 μm.
Similarly, in the case of a resin, d1 = 0.97 μm.

FIG. 21 (a) shows that the optical path difference caused by the unit step d1 is 1.25 times the blue-violet wavelength λ1. Since the optical path difference caused by the unit step d1 is a step / (nb-1), 1.25 is a value obtained by dividing the step / (nb-1) by λ1. In (b), (c), and (d), they are simply represented by the form of optical path difference / wavelength, but they have the same meaning except that the integer part is subtracted.

When the height (level) of the grating is an integral multiple of d1, the amount of phase modulation for blue-violet light due to this shape is an integral multiple of 2π + π / 2, which is substantially phase modulated as shown in FIG. The amount will be π / 2 per stage.

On the other hand, when the refractive index of the element material with respect to the red light beam is nr, there are nr = 1.542 when the element material is BK7 and nr = 1.505 for the polyolefin resin. The difference in optical path length generated in the red light beam due to the step d1 is d1 × (nr−1) /λ2≈0.75 regardless of whether the base material is quartz or resin. That is, the wavelength is about 3/4 times, and the phase modulation amount is about −π / 2 per stage.

Further, assuming that the refractive index of the element material with respect to the infrared light beam is ni, when the element material is BK7, there are ni = 1.51, and for the polyolefin resin, ni = 1.501. The difference in optical path length generated in the infrared light beam due to the step d1 is d1 × (ni−1) /λ3≈0.625 regardless of whether the base material is quartz or resin. That is, it is about 2/3 times the wavelength, and the phase modulation amount can be considered to be -1/3 times the wavelength per stage, and is about -2π / 3 when replaced with the phase.

As shown in FIG. 21 (a), if one step of the lattice is an integral multiple of d1, and a stepped cross-sectional shape is obtained, when one step is overlapped for the blue-violet light beam, Thus, the phase modulation amount changes by π / 2 per stage. That is, the optical path length difference changes by +1/4 of λ1. By forming four stages, the phase changes by 2π, and the diffraction efficiency of the + 1st order diffracted light is calculated to be about 80% (scalar calculation), and becomes the strongest among the diffraction orders. In FIG. 21A, eight stages are stacked to form one period p1, but since the phase changes by 2π per four stages, blue-violet light feels two periods of period p2 (p2 is half of p1). If considered as a periodic structure of p1, blue-violet light has the strongest diffraction efficiency of + 2nd order diffracted light of about 80%.

For the red light beam, when one step is overlapped, the phase modulation amount changes by −π / 2 per step as shown in FIG. That is, the optical path length difference changes by ¼ of λ2. By forming four stages, the phase changes by 2π, and the diffraction efficiency of the −1st order diffracted light is calculated to be about 80% (scalar calculation), and becomes the strongest among the diffraction orders. In FIG. 21A, one stage p1 is formed by superposing eight stages, but since the phase changes by −2π per four stages, the red light feels two periods of the period p2 (p2 is half of p1). If viewed as the periodic structure of p1, the red light has the strongest diffraction efficiency of -2nd order diffracted light of about 80%. Note that the fact that the diffraction order is negative means that the light bends in the opposite direction to the case where the diffraction order is positive.

For the infrared light beam, the steps corresponding to 5 wavelengths of blue purple and 3 wavelengths of red correspond to 5λ3 / 2, that is, the steps corresponding to 2.5 wavelengths, so the phase is changed. As shown in FIG. 21 (d), it appears that there is a periodic structure of three periods in the period p1, and a third-order diffraction efficiency is generated by about 60% with respect to the periodic structure of the period p1, It becomes the strongest among the diffraction orders. Here, the reason why the third-order diffracted light becomes strong can be understood by simply adding the phase that each step gives to the infrared light. This will be described with reference to FIG.

FIG. 22 (a) is the same as FIG. 21 (a) and shows the material shape of the lattice formed on the substrate. When the phase which each level | step difference gives to infrared light simply is added, a phase change will become like FIG.22 (e), and the sawtooth shape like a dotted line by 7 steps | paragraphs of 8 steps | paragraphs which form the period p1. It can be seen that is approximated. Since the height of the dotted sawtooth shape corresponds to three wavelengths of infrared light, strong third-order diffraction occurs. Similarly, the blue-violet light approximates a sawtooth shape with two wavelengths of blue-violet light in the opposite direction to the infrared light by the seven steps and eight-level step shape forming the period p1, so that the + second-order diffracted light is Strongly occurs. In the red light, a sawtooth shape having a height of two wavelengths of the red light is approximated in the same direction as the infrared light, so that −2nd order diffracted light is strongly generated. The diffraction efficiency of a diffraction grating having the cross-sectional shape of FIG. 21A as one period was calculated by scalar calculation. As a result, the diffraction efficiency was as shown in FIG.

23, the horizontal axis represents the actual size of one step when the resin material is the element material, and the vertical axis represents the diffraction efficiency. If a step is set around the vertical dotted line, the diffraction efficiency of blue-violet + 2nd order diffracted light and red -2nd order diffracted light is about 80%, and that of infrared −3rd order diffracted light is about 60%. Yes, both are over 50%, so they are larger than other orders. The reason why the diffraction efficiency of not only blue-violet light and red light but also infrared light can be increased to 50% or more is due to the structure shown in FIG. Each design wavelength is λ1 = 408 nm, λ2 = 660 nm, and λ3 = 780 nm.

An example of constructing a CD / DVD / BD compatible lens using this element will be described with reference to FIG. Reference numeral 8b 'denotes a diffractive or phase step type optical element, but the refracting surface may be formed on one side or both sides. By forming a concave refracting surface and canceling the lens power in combination with a convex lens type diffractive element or phase step element with respect to blue-violet light, the entire optical element 8b ′ has zero lens power with respect to the reference wavelength of blue-violet light. Can do. Then, the refractive objective lens 8a ′ used in combination with the optical element 8b ′ may be designed so as to be converged by the numerical aperture NA1 or more through the base material thickness t1 of the optical disc 60. Therefore, at the time of manufacturing the objective lens 8a ′. There is an effect that the inspection can be easily performed. In any case, the objective lens 8a ′ is designed to focus the blue-violet light beam having the wavelength λ1 on the recording surface 61 through the substrate thickness t1 of the optical disk 60 after being modulated by the optical element 8b ′ and further converged. The

Further, the red light beam having the wavelength λ2 is designed to be converged after being modulated by the diffraction grating of the optical element 8b ′ or the phase type optical element, and condensed onto the recording surface 71 through the substrate thickness t2 of the optical disk 70. The

Further, the infrared light beam having the wavelength λ3 is also designed to be converged after being modulated by the optical element 8b 'and condensed onto the recording surface 81 through the substrate thickness t3 of the optical disc 80.

The light beam of each wavelength uses the difference in wavelength, the difference in diffraction order as described above, or the difference in phase given by the phase step, and the difference in refractive index (dispersion) depending on the wavelength of the refractive objective lens. And can be designed to converge when passing through different substrate thicknesses.

On the other hand, CD, DVD, and BD have different numerical apertures NA suitable for converging light. The numerical aperture NA1 suitable for BD is 0.85 or more. The numerical aperture NA2 suitable for DVD is about 0.6 to 0.67. The numerical aperture NA3 suitable for CD is about 0.45 to 0.55. If the numerical aperture is smaller than these, the light beam cannot be sufficiently reduced on the recording surface. On the other hand, if the numerical aperture is too large, large wavefront disturbances occur when the optical disk is deformed and tilted, and it is not suitable for stable information recording and reproduction. In order to make NA3 smaller than NA2 and NA1, the optical element 8b 'is provided with three concentric regions around the optical axis. The diffraction element or the phase step described in the above embodiment is formed in the innermost region 8b '. The infrared light beam 82 incident on the innermost peripheral region 8b'-C is converged on the information recording surface 81 through a transparent substrate of about 1.2 mm as shown by a dotted line.

The red light beam 72 incident on the innermost peripheral region 8b'-C and the outer peripheral intermediate region 8b'-B is converged on the information recording surface 71 through a transparent substrate of about 0.6 mm.

The blue-violet light beam 72 incident on the innermost peripheral region 8b'-C, the outer peripheral region 8b'-B provided on the outer side, and the outer peripheral region 8b'-F provided further on the outer peripheral region 8b'-C passes through a transparent substrate of about 0.1 mm. It converges on the information recording surface 61.

Thus, the innermost peripheral region 8b'-C is a region that is used for all of the infrared light CD, the red light DVD, and the blue-violet light BD. It is desirable to correct axial chromatic aberration because blue-violet light with the shortest wavelength has a large dispersion of the refractive objective lens 8a 'and a shallow focal depth. Correction of axial chromatic aberration can be realized by designing the diffractive element portion of the optical element 8b 'to have a convex lens action. If the diffractive element structure of the first embodiment described above is used, infrared light (dotted line) and red light (two-dot chain line) are subjected to the reverse action of blue-violet light, so that the concave lens action is exhibited and the focal point is focused. The distance gets longer. In particular, since infrared light has a longer wavelength than red light, it is strongly influenced by a concave lens. For this reason, the focal length is longer in red than blue violet and longer in infrared light than red. Then, the focal position of the red light or infrared light can be moved further away from the objective lens 8 a ′, and the focal point can be focused through the thick base material of the

optical disks

70 and 80. That is, there is an effect that a distance between the surface of the objective lens 8a 'and the surface of the

optical disk

70 or 80, that is, a working distance (working distance: WD) can be secured. As shown in FIGS. 1 to 3, the optical pickup 40 according to the first embodiment using the objective lens having this configuration moves the coupling lens 5 toward the mirror 7 when recording or reproducing the DVD 70. When convergent light is incident and the coupling lens 5 is moved to the two-wavelength light source 11 side and divergent light is incident on the objective lens 8 during recording or reproduction of the CD 80, the spherical surface of the light spot collected on the information recording surface Aberration is minimized.

By using the coupling lens actuator 31 in this way, the blue-violet laser light emitted from the light source 1 and the red laser light and infrared laser light emitted from the two-wavelength light source 11 are respectively converted into parallel light, convergent light, or divergent light. Light can be incident on the objective lens 8, and spherical aberration caused by the difference in wavelength of each light source and the thickness of the protective substrate of the corresponding optical disk can be effectively corrected. Whether the laser light emitted from each light source is incident on the objective lens 8 among parallel light, convergent light, or divergent light depends on the design of the objective lens 8. The present invention is not limited to the combination of the present embodiment in which the blue-violet laser light is substantially parallel light, the red laser is convergent light, and the infrared laser light is divergent light.

In the configuration of the first embodiment, the movable distance La moved by the coupling lens actuator 31, that is, the moving range La of the coupling lens 5, is coupling during recording or reproduction of the DVD 70 as shown in FIG. The position of the lens 5 and the position of the coupling lens 5 at the time of recording or reproduction of the CD 80 are both left and right ends. Here, the moving range Lb of the coupling lens 5 for correcting the spherical aberration corresponding to the thickness of the protective substrate of the information recording surface in the BD 60 is within the moving range La of the coupling lens 5. With such a configuration, the moving range La of the coupling lens 5 can be reduced, so that the entire optical pickup can be reduced in size.

Next, an example of the moving range of the coupling lens 5 is shown. The objective lens 8 is a compatible objective lens having a focal length of about 1.8 mm for blue-violet light, a focal length of about 2.0 mm for red light, and a focal length of about 2.1 mm for infrared light. Assume that the focal length for blue-violet light is approximately 11 mm. Here, when the coupling lens 5 is in the reference position when the blue-violet light is used, that is, when the blue-violet emission light of the coupling lens 5 is parallel light, the protective substrate thickness of the BD 60 is approximately 0.0875 mm and is on the information recording surface. Assume that the spherical aberration of the light spot is minimal. At this time, when the thickness of the protective substrate of the BD 60 is approximately 0.075 mm, the spherical aberration of the light spot on the information recording surface can be minimized by shifting the coupling lens 5 to the mirror 7 side by approximately 0.25 mm. It is. Further, in order to minimize the spherical aberration of the light spot on the information recording surface when the protective substrate thickness of the BD 60 is about 0.1 mm, it is possible to shift the coupling lens 5 to the light source 1 side by about 0.25 mm. is there.

On the other hand, when recording or reproducing a DVD 70 having a protective substrate thickness of about 0.6 mm, when using red light, the coupling lens 5 is moved from the reference position to the mirror 7 side by about 2.5 mm to record information. The spherical aberration of the light spot on the surface is minimized.

In addition, when using infrared light to record or reproduce CD80 having a protective substrate thickness of approximately 1.2 mm, the coupling lens 5 is moved approximately 1.5 mm from the reference position to the two-wavelength light source 11 side, The spherical aberration of the light spot on the information recording surface is minimized.

That is, the moving range of the coupling lens 5 is approximately 1.5 mm from the reference position to the two-wavelength light source 11 side, and approximately 2.5 mm from the reference position to the objective lens 8 side. The required moving distance of the coupling lens 5 is approximately 0.25 mm from the reference position on both the light source 1 side and the objective lens 8 side, and is sufficiently within the moving range of the coupling lens 5.

Note that the amount of spherical aberration that can be corrected during recording or reproduction of the BD60 is sufficiently large, so that the range that the protective substrate thickness can take is large (for example, having three or more information recording surfaces), and can be used for the next generation BD. It is.

Note that the configuration of the coupling lens actuator that moves the coupling lens 5 in the optical axis direction is not limited to the configuration using the stepping motor 32 as shown in FIG. 8, for example, driving of a magnetic circuit or a piezoelectric element. Any configuration may be used such as an actuator. In the configuration using the stepping motor 32 shown in FIG. 8, it is not necessary to monitor the position of the coupling lens 5 in the optical axis direction, and the system can be simplified. On the other hand, an actuator driven by a magnetic circuit or a piezoelectric element has a driving part. Is suitable for downsizing of optical pickups.

Next, the flat plate beam splitter 2 and the wedge prism 4 of the first embodiment will be described in detail.

The flat plate beam splitter 2 is designed so that it substantially reflects S-polarized light and substantially transmits P-polarized light with respect to blue-violet laser light having a wavelength of about 405 nm. Further, the film is designed so that it substantially transmits red laser light having a wavelength of about 660 nm and infrared laser light having a wavelength of about 785 nm regardless of the polarization direction.

In the optical pickup 40 of the first embodiment, the blue-violet laser light for recording the BD 60 is incident on the flat plate beam splitter 2 as S-polarized light. Therefore, it is desirable to increase the S-polarized reflectance of the flat beam splitter 2 in order to ensure the efficiency of the forward path. Here, the incident angle (Brewster angle) θ that is totally reflected when S-polarized light is reflected at the boundary surface of substances having different refractive indexes is expressed by the following (Equation 1).

θ = Arctan (n2 / n1) (Formula 1)
n1 is the refractive index of air, and n2 is the refractive index of the plate beam splitter 2.

For example, if the material of the plate beam splitter 2 is BK7 and the refractive index n2 = 1.530 at a wavelength of 405 nm is θ = 56.83 °. This indicates that in order to increase the S-polarized light reflectance of the plate beam splitter 2, the incident angle θ1 of the blue-violet laser beam with respect to the plate beam splitter 2 should be close to the Brewster angle θ = 56.83 °. Yes. On the other hand, even if the incident angle θ1 exceeds the Brewster angle θ, it is not possible to obtain a reflectance higher than the total reflection. Here, as the incident angle θ1 increases, the astigmatism that occurs in the laser light that is transmitted through the plate beam splitter 2 and detected by the light receiving element 20 increases. Therefore, it is not preferable that the incident angle θ1 is not less than the Brewster angle θ. That is,
θ1 <Arctan (n2 / n1) [rad] (Formula 2)
It is preferable that

FIG. 10 shows the spectral characteristics of the flat plate beam splitter 2 according to the first embodiment. In FIG. 10, the horizontal axis indicates the wavelength of the laser light incident on the flat beam splitter 2, and the vertical axis indicates the transmittance at the wavelength. The incident angle θ1 to the flat beam splitter 2 is 50 °. As shown in FIG. 10, the S-polarized light reflectance is about 80%, the transmittance is about 20%, and the P-polarized light transmittance is about 90% for the blue-violet laser light having a wavelength of about 405 nm. On the other hand, the transmittance of the red laser beam near the wavelength of 660 nm and the infrared laser beam near the wavelength of 785 nm is almost 95% regardless of the polarization direction.

Next, the wedge prism 4 is designed so that it partially transmits and partially reflects red laser light having a wavelength of about 660 nm and infrared laser light having a wavelength of about 785 nm. Further, the film is designed so as to substantially reflect blue-violet laser light having a wavelength of about 405 nm regardless of the polarization direction.

FIG. 11 shows the spectral characteristics of the wedge prism 4 of the first embodiment. In FIG. 11, the horizontal axis indicates the wavelength of the laser light incident on the wedge prism 4, and the vertical axis indicates the transmittance at the wavelength. As shown in FIG. 12, the incident angle θ3 to the wedge prism 4 is 40 °. From FIG. 11, the transmittance of P-polarized light is about 60%, the transmittance of S-polarized light is about 50%, and the reflectance is about 50% for red laser light having a wavelength of about 660 nm and infrared laser light having a wavelength of about 785 nm. It is. On the other hand, the reflectivity of the blue-violet laser light near the wavelength of 405 nm is almost 95% regardless of the polarization direction.

Since the flat plate beam splitter 2 and the wedge prism 4 of the first embodiment have the spectral characteristics shown in FIGS. 10 and 11, respectively, in the blue-violet laser beam for recording or reproducing the BD 60, the flat plate beam splitter is used. Both the light utilization efficiency of the forward path, which is S-polarized reflection with respect to 2, and the light utilization efficiency of the return path, which is P-polarized light transmission with respect to the flat plate beam splitter 2, can be increased.

On the other hand, in the red laser light and the infrared laser light for recording or reproducing the DVD 70 and the CD 80, the light utilization efficiency of the forward path that transmits the P-polarized light to the wedge prism 4 and the S-polarized light reflection to the wedge prism 4. The light utilization efficiency of the return path can be made relatively high. Further, since the difference between the S-polarized light reflectance and the P-polarized light reflectance of the wedge prism 4 and the difference between the S-polarized light transmittance and the P-polarized light transmittance of the flat plate beam splitter 2 are small, the signal light amount (the light receiving element 20) due to the birefringence of the optical disc. Variation in the amount of received light) detected in (1) can be suppressed.

By the way, since the red laser light and the infrared laser light emitted from the two-wavelength light source 11 are diverging light, astigmatism and coma aberration are generated when passing through a parallel plate inclined with respect to the optical axis, and the objective lens 8 As a result, the light spot on the optical disk converged by the above cannot obtain sufficient performance. Therefore, as shown in FIG. 12, the wedge prism 4 according to the first embodiment is provided with a predetermined angle (vertical angle α) between the incident surface 4a and the outgoing surface 4b. The incident angles (θ2, θ3) of the respective laser beams are defined as predetermined angles. For example, the wedge prism 4 of the first embodiment is
Glass material of wedge prism 4: apex angle α of BK7 wedge prism 4 = 0.9 °
Thickness T = 1.0 mm at the center of the wedge prism 4
Red laser beam incident angle θ2 = 42.2 °
Red laser light emission angle θ3 = 40.6 °
Therefore, both the third-order astigmatism and the third-order coma aberration when the red laser light transmitted through the wedge prism 4 is converged by the coupling lens 5 and the objective lens 8 are substantially zero.

As shown in FIG. 12, the optical pickup according to the first embodiment uses the optical axis of the blue-violet laser light emitted from the light source 1 as the optical axis A and the optical axis of the red laser light emitted from the two-wavelength light source 11 as light. The incident angle (= emission angle) of the chief ray of the blue-violet laser beam with respect to the axis B, the flat plate beam splitter 2 is θ1, and the incident angle (= emission angle) θ3 of the chief ray of the blue-violet laser beam with respect to the wedge prism 4 is respectively
π / 4 <θ1 <Arctan (n2 / n1) [rad] (Formula 3)
π / 4> θ3 [rad] (Formula 4)
Therefore, the angle β between the optical axis A and the optical axis B is
β = 2 × (θ1-θ3) ≠ 0
It becomes. For example, in the first embodiment, θ1 = 50 ° and θ3 = 40.6 °, so β = 18.8 °. That is, since the optical axis A and the optical axis B are not parallel but form a predetermined angle, the distance between the flat beam splitter 2 and the wedge prism 4 can be made smaller than the distance between the light source 1 and the two-wavelength light source 11. In addition, since the optical element can be arranged in a compact manner, the optical pickup can be reduced in size.

As described above, the S-polarized light reflectance in the flat beam splitter 2 increases as the incident angle θ1 approaches the Brewster angle θ. Therefore, when diverging light is incident on the flat plate beam splitter 2 as in the first embodiment, the peripheral ray has an incident angle different from that of the principal ray. For example, as shown in FIG. 13, the blue-violet laser light emitted from the light source 1 has a higher reflectance because the incident angle of the (M) side light beam is larger than the principal light beam indicated by the alternate long and short dash line. The light beam on the (N) side with respect to the light beam has a small incident angle and thus a low reflectance. Therefore, the light quantity distribution of the FFP after being reflected by the flat beam splitter 2 with respect to the light quantity distribution of the far field pattern (far field image, FFP) of the blue-violet laser light before being reflected by the flat beam splitter 2 is Becomes asymmetric with respect to. This asymmetry of the light quantity distribution depends on the NA of the laser beam incident on the flat beam splitter 2, and the smaller the NA of the laser beam incident on the flat beam splitter 2, the principal ray, the light beam (M), and the light beam (N). As a result, the asymmetry of the light quantity distribution is suppressed.

In the optical pickup 40 according to the first embodiment, the relay lens 3 having a concave lens power is disposed between the flat beam splitter 2 and the wedge prism 4 to perform NA conversion. When the relay lens 3 is arranged in this way, the NA of the blue-violet laser light incident on the flat beam splitter 2 is relatively small compared to the case where the relay lens 3 is arranged between the light source 1 and the flat beam splitter 2. Thus, the asymmetry of the light quantity distribution can be suppressed.

Further, since the relay lens 3 is disposed between the flat beam splitter 2 and the wedge prism 4, the relay lens 3 is irradiated as compared with the case where the relay lens 3 is disposed between the light source 1 and the flat beam splitter 2. The laser light amount per unit area of the blue-violet laser light becomes relatively small. Therefore, it becomes easy to use a resin material that is less resistant to the irradiation of the blue-violet laser light than the glass material but can be molded at low cost as the material of the relay lens 3.

In order to reduce crosstalk from another information recording surface adjacent to the information recording surface to be recorded or reproduced, the optical pickup 40 of the first embodiment is used even when a large detection magnification is desired. Since the relay lens 3 having a concave lens power is disposed between the coupling lens 5 and the detection lens 10, the detection lens 10 does not require a large concave lens power. Accordingly, the radius of curvature of the detection lens 10 can be increased, and the detection lens 10 can be molded at a low cost.

By the way, when the light beam (M) shown in FIG. 13 is reflected by the BD 60 and passes through the flat beam splitter 2, the incident angle becomes smaller with respect to the principal light beam, so that the transmittance increases, and the light beam (N) becomes When the light is reflected by the BD 60 and transmitted through the flat beam splitter 2, the incident angle with respect to the principal ray is increased, so that the transmittance is reduced. That is, the light intensity distribution of the blue-violet laser beam is always on the light (M) side, whether it is converged as a light spot on the information recording surface of the BD 60 or reflected by the information recording surface of the BD 60 and detected by the light receiving element 20. It becomes asymmetric in the direction in which the amount of light increases. In order to suppress such asymmetry of the light quantity distribution, for example, as indicated by a broken line 1B in FIG. 13, it is preferable that the light source 1 is inclined in advance by a predetermined angle in a direction in which the FFP light quantity distribution becomes uniform.

The BD 60 according to the first embodiment can obtain a good recording or reproducing performance by converging a light spot having a large rim intensity in the radial direction of the optical disk.

That is, the flat plate beam splitter 2 according to the first embodiment is designed so as to substantially reflect S-polarized light and substantially transmit P-polarized light with respect to blue-violet laser light having a wavelength of about 405 nm (see FIG. 10). . Here, in the optical pickup 40 of the first embodiment, the light source 1 is arranged so that the S-polarized light is incident on the flat beam splitter 2 as shown in FIG. 1, that is, the reflectance at the flat beam splitter 2 is increased. As a result, an FFP with a large rim intensity in the radial direction of the optical disk can be obtained, so that a half-wave plate for rotating the polarization direction of the blue-violet laser light is not required.

On the other hand, the DVD 70 of the first embodiment can obtain a good recording or reproducing performance by converging a light spot having a large rim intensity in the tangential direction of the optical disk.

The wedge prism 4 of the first embodiment is designed so as to transmit P-polarized light and reflect S-polarized light more with respect to red laser light having a wavelength of about 660 nm (see FIG. 11). Here, in the optical pickup 40 of the first embodiment, the two-wavelength light source 11 is arranged so that the P-polarized light enters the wedge prism 4 as shown in FIG. 2, that is, the transmittance at the wedge prism 4 is increased. Thus, an FFP having a large rim intensity in the optical disk tangential direction can be obtained, so that a half-wave plate for rotating the polarization direction of the red laser light is not required.

Incidentally, as shown in FIG. 14, the general two-wavelength light source 11 is arranged such that the emission point 11b of the infrared laser beam is offset from the emission point 11a of the red laser beam. For this reason, since at least one of the red laser beam and the infrared laser beam is incident off-axis with respect to the objective lens 8, third-order coma aberration may occur.

Here, in the optical pickup 40 of the first embodiment, the two-wavelength light source 11 is arranged so as to be P-polarized light incident on the wedge prism 4, so that, for example, the optical axis of the red laser light and the optical axis of the objective lens 8 When the two-wavelength light source 11 is arranged so that they coincide with each other, the third-order coma aberration generated when the infrared laser light is incident off-axis with respect to the objective lens 8 is generated in the radial direction of the optical disk. Therefore, by tilting the objective lens 8 mounted on the objective lens actuator 30 in the radial direction, it is possible to correct the third-order coma aberration of the red laser light generated by off-axis incidence.

In general, the third-order coma aberration generated by off-axis incidence is substantially proportional to the angle (field angle) of the light ray incident on the objective lens 8. Therefore, if the interval δ between the emission points of the red laser beam and the infrared laser beam and the focal length of the objective lens are constant, the third-order coma aberration is inversely proportional to the (synthetic) focal length of the coupling lens. Therefore, as shown in FIG. 15, a relay lens 13 having a concave power is inserted between the coupling lens 5 and the two-wavelength light source 11, and the combined focal length is increased, so that the third order due to off-axis incidence is obtained. Coma can be suppressed.

On the other hand, in the case of using an objective lens having a relatively small third-order coma due to off-axis incidence, it is possible to reduce the combined focal length by using the relay lens 13 having a convex power and increase the light utilization efficiency. .

The relay lens 13 can be integrated with the diffraction grating 12 to reduce the number of parts. At this time, by making any one of the entrance surface and the exit surface of the relay lens 13 into a plane and forming a diffraction grating on the plane side, it is possible to easily create a lens molding die. Note that when the distance between the relay lens 13 and the two-wavelength light source 11 is changed, the magnification is changed, and when the diffraction grating is integrated, the distance between the main beam and the sub-beam to be generated is also changed. 11 is preferably inserted into an integral holder so that the distance does not change.

In the first embodiment, the case where the red laser light and the infrared laser light are emitted from the two-wavelength light source 11 has been described. However, a separate red laser light source and infrared laser light source are provided. Also good. Since the red laser light source and the infrared laser light source are separately provided, the optical axes of the red laser light and the infrared laser light can be made coincident with each other, so that coma aberration due to off-axis incidence can be suppressed.

As described above, in the first embodiment, the divergence of the light beam incident on the compatible objective lens in the configuration using one compatible objective lens corresponding to the BD / DVD / CD 3 wavelength is set to red. The order of light beam <blue light beam <infrared light beam was used. For example, when a blue light beam is incident on a compatible objective lens as parallel light during BD recording / reproduction, a red light beam is incident on the compatible objective lens in a converged state during DVD recording / reproduction, and infrared light is incident on the compatible objective lens during CD recording / reproduction. The light beam was incident in a divergent state.

With such a configuration, the infrared light beam with the shortest wavelength is used even though the wavelength difference between the red light beam and the infrared light beam is smaller than the wavelength difference between the red light beam and the blue light beam. A sufficient working distance can be secured even in the CD of the time.

Therefore, it is possible to ensure a sufficient working distance even during CD (infrared light beam) recording / reproduction using the compatible objective lens and having the smallest NA and the thickest disk base material.

Also, when recording / reproducing BD, it is necessary to change the divergence of the blue light beam in order to correspond to a multi-layer disc having two or more layers. With the above configuration, the divergence of the light beam is changed. For example, when the collimating lens is moved in the direction of the optical axis, the collimating lens needs to move rather than the divergence of the light beam incident on the compatible objective lens in the order of blue light beam <red light beam <infrared light beam. Therefore, the optical pickup can be downsized, and the operation time of the optical pickup can be shortened by shortening the moving time of the collimating lens.

As described above, the optical pickup 40 according to the first embodiment converges laser beams having different wavelengths on different types of optical disks, for example, BD 60, DVD 70, and CD 80, using one objective lens 8. Information can be recorded or reproduced.

(Embodiment 2)
16 and 17 are schematic configuration diagrams of an optical pickup according to another embodiment 2 of the present invention. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted below.

16, 7D is a first mirror, 7B is a second mirror, 8D is a first objective lens, and 8B is a second objective lens, and these constitute an optical pickup 41.

The operation of the optical pickup 41 that records or reproduces information on the BD 60 will be described. The blue-violet laser light having a wavelength of 405 nm emitted from the light source 1 is incident on the flat beam splitter 2 as S-polarized light. The blue-violet laser light reflected by the flat beam splitter 2 passes through the relay lens 3 and is converted into divergent light having a different NA. Thereafter, the blue-violet laser light is reflected by the wedge prism 4, then converted into substantially parallel light by the coupling lens 5, and converted from linearly polarized light to circularly polarized light by the quarter wavelength plate 6. Subsequently, after passing through the first mirror 7D and being reflected by the second mirror 7B, the second objective lens 8B converges as a light spot on the information recording surface over the protective substrate of the BD 60.

The blue-violet laser beam reflected by the information recording surface of the BD 60 is transmitted again through the second objective lens 8B, reflected by the second mirror 7B, transmitted through the first mirror 7D, and forwarded by the quarter wavelength plate 6. Is converted into convergent light by the coupling lens 5, reflected by the wedge prism 4, and converted into convergent light having a different NA by the relay lens 3.
Further, the blue-violet laser light is incident on and transmitted through the flat beam splitter 2 as P-polarized light, and when it passes through the detection hologram 9, zero-order light and ± first-order diffracted light are generated. Astigmatism is given and guided to the light receiving element 20.

Next, with reference to FIG. 17, a description will be given of a case where recording or reproduction is performed on a DVD 70 which is an optical disk having a protective substrate thickness of 0.6 mm.

In FIG. 17, red laser light having a wavelength of 660 nm emitted from the two-wavelength light source 11 is separated into a main beam that is 0th-order diffracted light and a sub-beam that is ± 1st-order diffracted light by the diffraction grating 12, and Incident with polarized light. The red laser light that has passed through the wedge prism 4 is converted into a slightly convergent light by the coupling lens 5, converted from linearly polarized light to circularly polarized light by the quarter wavelength plate 6, and reflected by the first mirror 7D. The first objective lens 8D converges as a light spot on the information recording surface over the protective substrate of the DVD 70.

The red laser beam reflected by the information recording surface of the DVD 70 is transmitted again through the first objective lens 8D, reflected by the first mirror 7D, and converted by the quarter wavelength plate 6 into linearly polarized light different from the forward path. Thereafter, the light is converted into convergent light by the coupling lens 5. The red laser light is incident on the wedge prism 4 as S-polarized light, reflected, converted into convergent light having a different NA by the relay lens 3, transmitted through the flat beam splitter 2 and the detection hologram 9, and astigmatism by the detection lens 10. Is given to the light receiving element 20.

On the other hand, the P-polarized infrared laser light having a wavelength of 785 nm emitted from the two-wavelength light source 11 is similarly converged as a light spot on the information recording surface through the protective substrate of the CD 80 by the first objective lens 8D. The red laser beam reflected by the information recording surface is similarly guided to the light receiving element 20.

The first objective lens 8D converges the red laser beam for recording or reproducing the DVD 70 and the infrared laser beam for recording or reproducing the CD 80 as a minute light spot using the wavelength difference. The second objective lens 8B can converge the blue-violet laser beam for recording or reproducing the BD 60 as a minute light spot. The first objective lens 8D and the second objective lens 8B are mounted on the same objective lens actuator (not shown), and light is applied to the information track of the rotating optical disc using the focus error signal and the tracking error signal, respectively. The spot is driven to follow.

Similarly to the optical pickup 40 described in the first embodiment, the optical pickup 41 according to the second embodiment also focuses laser beams having different wavelengths on different types of optical disks, for example, BD60, DVD70, and CD80. Information can be recorded or reproduced.

The movement of the coupling lens 5 by the coupling lens actuator 31 is also configured such that red convergent light is incident on the first objective lens 8D when the DVD 70 is used, and the first objective lens 8D when the CD 80 is used. A disk with a different protective substrate thickness with a single coupling lens, such as a configuration in which infrared divergent light is incident on, and a configuration in which substantially blue-violet parallel light is incident on the second objective lens 8B when the BD60 is used. In the case of corresponding to the above, the coupling lens actuator 31 can have the same configuration as that of the first embodiment, and the same effect can be obtained.

As described above, in the second embodiment, in the configuration in which two objective lenses of the BD dedicated objective lens and the DVD / CD compatible objective lens are used, when the collimating lens is commonly used in BD / DVD / CD, The divergence of the light beam incident on each objective lens was set in the order of red light beam <blue light beam <infrared light beam. For example, when a blue light beam is incident as a parallel light on a BD objective lens during BD recording / reproduction, a red light beam is incident on a convergent DVD / CD objective lens during DVD recording / reproduction, and DVD / CD is reproduced during CD recording / reproduction. An infrared light beam is incident on a CD-compatible objective lens in a divergent state.

With such a configuration, first, in the DVD / CD compatible objective lens, the working distance difference between the DVD recording / reproducing and the CD recording / reproducing can be reduced, and the movement range of the objective lens actuator can be reduced. Therefore, it is possible to reduce the drive current of the objective lens actuator and to reduce the power consumption of the optical pickup.

Also, when recording / reproducing BD, it is necessary to change the divergence of the blue light beam in order to correspond to a multi-layer disc having two or more layers. With the above configuration, the divergence of the light beam is changed. For example, when the collimating lens is moved in the optical axis direction, the collimating lens needs to move rather than the divergence of the light beam incident on the compatible objective lens in the order of blue light beam <red light beam <infrared light beam. Since the range can be reduced, the optical pickup can be downsized, and the operation time of the optical pickup can be shortened by shortening the moving time of the collimating lens.

(Embodiment 3)
FIG. 26 is a schematic configuration diagram of an optical pickup according to another embodiment 3 of the present invention. The third embodiment is an optical pickup corresponding to two wavelengths of blue-violet laser light and infrared laser light. Constituent elements common to the first embodiment are denoted by the same reference numerals, and description thereof is omitted below.

26, only an infrared laser beam having a wavelength of 785 nm is emitted from the light source 11 ′. However, the position of the coupling lens 5 is the position P3 in the case of blue-violet laser light, and is located at the position P4 closer to the objective lens 8 than the position P3 in the case of infrared laser light.

Thereby, with respect to the incidence on the objective lens 8, the divergence of the infrared laser beam having a longer wavelength is smaller than the divergence of the blue-violet laser beam having a shorter wavelength.

As described above, in the third embodiment, for the incidence on the objective lens 8, the divergence of the laser light having a longer wavelength is smaller than the divergence of the laser light having a shorter wavelength. The effect that the effective diameter of the optical component close to the lens is small is exhibited.

(Embodiment 4)
FIG. 27 is a schematic configuration diagram of an optical pickup according to another embodiment 4 of the present invention. The fourth embodiment is an optical pickup corresponding to two wavelengths of red laser light and infrared laser light. Constituent elements common to the first embodiment are denoted by the same reference numerals, and description thereof is omitted below.

27, a red laser beam having a wavelength of 660 nm and an infrared laser beam having a wavelength of 785 nm are emitted from the light source 11 ″. However, the position of the coupling lens 5 is the position of the position P5 in the case of red laser light, and is located at the position P6 closer to the objective lens 8 than the position P5 in the case of infrared laser light.

Thus, with respect to the incidence on the objective lens 8, the divergence of the infrared laser beam having a longer wavelength is smaller than the divergence of the red laser beam having a shorter wavelength.

As described above, in the fourth embodiment, for the incidence on the objective lens 8, the divergence of the laser light having a longer wavelength is smaller than the divergence of the laser light having a shorter wavelength. The effect that the effective diameter of the optical component close to the lens is small is exhibited.
It is as follows when the effect in Embodiment 3 and Embodiment 4 mentioned above is put together.

In addition, in

Embodiments

3 and 4 above, the longer NA wavelength (large effective effective diameter) has the longer wavelength and the shorter NA wavelength (small effective effective diameter) has the shorter wavelength. It has a high divergence configuration. With such a configuration, a light beam with a small effective diameter of the objective lens is in a divergent state, and a light beam with a large effective diameter of the objective lens is in a condensed state. The effective diameter can be reduced.

Especially in the case of a configuration sharing a collimating lens, the effective diameter of the optical component between the collimating lens and the objective lens can be made smaller than that of the conventional configuration.

(Embodiment 5)
FIG. 18A is a schematic configuration diagram of an optical disc apparatus according to Embodiment 5 of the present invention.

18A, reference numeral 50 denotes an optical disk device, which includes an optical disk drive unit 51, a control unit 52, and an optical pickup 53 inside the optical disk device 50. Reference numeral 60 denotes a BD, which can be replaced with a DVD 70 or a CD 80.

The optical disk drive unit 51 has a function of rotationally driving the BD 60 (or DVD 70, CD 80), and the optical pickup 53 is any one of the optical pickups described in the first embodiment or the second embodiment. The control unit 52 has a function of driving and controlling the optical disc driving unit 51 and the optical pickup 53, a function of performing signal processing of a control signal and an information signal received by the optical pickup 53, and an information signal of the optical disc device 50. Has the function of interfacing externally and internally.

Since the optical disk device 50 according to the fifth embodiment is equipped with any one of the optical pickups described in the first or second embodiment, the optical disk device 50 according to the fifth embodiment is provided with a plurality of light sources. A plurality of types of corresponding optical discs can be recorded or reproduced satisfactorily.

(Embodiment 6)
FIG. 18B is a schematic configuration diagram of a computer according to the sixth embodiment of the present invention.

In FIG. 18B, a computer 500 includes an optical disc device 50 according to the fifth embodiment, an input device 501 such as a keyboard or a mouse or a touch panel for inputting information, information input from the input device 501, An arithmetic device 502 such as a central processing unit (CPU) that performs an operation based on information read from the optical disk device 50, a cathode ray tube, a liquid crystal display device, a printer, or the like that displays information such as a result calculated by the arithmetic device 502 An output device 503 is provided.

Since the computer 500 according to the sixth embodiment includes the optical disk device 50 according to the fifth embodiment, different types of optical disks can be satisfactorily recorded or reproduced, and thus has an effect that can be applied to a wide range of applications.

(Embodiment 7)
FIG. 19A is a schematic configuration diagram of an optical disc player according to Embodiment 7 of the present invention.

19A, an optical disc player 600 includes the optical disc device 50 according to the fifth embodiment and an information-to-image conversion device (for example, a decoder 601) that converts an information signal obtained from the optical disc device 50 into an image signal. .

The optical disc player 600 can also be used as a car navigation system by adding a position sensor such as GPS and a central processing unit (CPU). Further, a mode in which a display device 602 such as a liquid crystal monitor is added is also possible.

Since the optical disc player 600 according to the seventh embodiment includes the optical disc device 50 according to the fifth embodiment, since different types of optical discs can be reproduced satisfactorily, it has the effect of being applicable to a wide range of applications.

(Embodiment 8)
FIG. 19B is a schematic configuration diagram of the optical disc recorder according to the eighth embodiment of the present invention.

In FIG. 19B, an optical disc recorder 700 includes an optical disc device 50 according to the fifth embodiment and an image-to-information conversion device (for example, an encoder 701) that converts image information into an information signal recorded on the optical disc by the optical disc device 50. Is provided. Desirably, an information-to-image conversion device (decoder 702) that converts an information signal obtained from the optical disk device 50 into image information is also provided, so that the recorded image can be reproduced. Note that an output device 703 such as a cathode ray tube, a liquid crystal display device, or a printer that displays information may be provided.

Since the optical disk recorder 700 according to the eighth embodiment includes the optical disk device 50 according to the fifth embodiment, since different types of optical disks can be recorded or reproduced satisfactorily, there is an effect that can be applied to a wide range of applications. .

The optical pickup of the present invention is capable of recording or reproducing each of a plurality of types of optical disks satisfactorily. Further, since the configuration of the optical pickup is simplified, the productivity can be improved and the optical disc apparatus can be provided at a low cost.

Furthermore, the computer, the optical disc player, and the optical disc recorder provided with the optical disc apparatus of the present invention can record and reproduce different types of optical discs, respectively, and thus have an effect that can be applied to a wide range of applications.

DESCRIPTION OF SYMBOLS 1 Light source 2 Flat beam splitter 3 Relay lens 4 Wedge prism 5 Coupling lens 6 1/4

wavelength plate

7, 7D,

7B Mirror

8, 8D, 8B Objective lens 9 Detection hologram 10 Detection lens 11 2 wavelength light source 11 'Infrared laser Light source of light 11 '' Light source of red laser light and infrared laser light 12 Diffraction grating 13 Relay lens 20 Light receiving element 30 Objective lens actuator 31 Coupling lens actuator 32 Stepping motor 33 Screw shaft 34 Main shaft 35 Sub shaft 36

Lens holder

40, 41 Optical Pickup 50 Optical Disc Device 51 Optical Disc Drive Unit 52 Control Unit 53 Optical Pickup 60 BD
70 DVD
80 CD
DESCRIPTION OF SYMBOLS 101 1st light source 102 1st flat plate beam splitter 103 1st auxiliary | assistant lens 104 2nd flat plate beam splitter 105 Coupling lens 107 Mirror 108 Objective lens 110 Detection lens 111 2nd light source 112 2nd auxiliary lens 120 Light reception Element 140 Optical pickup 500 Computer 501 Input device 502 Arithmetic device 503 Output device 600 Optical disc player 601 Decoder 602 Display device 700 Optical disc recorder 701 Encoder 702 Decoder 703 Output device P0, P1, P2, P3, P4, P5, P6 Coupling lens 5 Position of

Claims

A first light source that emits a divergent light beam of wavelength λ1,
A second light source that emits a divergent light beam having a wavelength λ2 (λ2> λ1) different from the wavelength λ1;
The light beam having the wavelength λ1 is condensed on the information recording surface of the first optical disk having the protective substrate thickness t1, and the light beam having the wavelength λ2 is condensed on the information recording surface of the second optical disk having the protective substrate thickness t2 different from the t1. And an objective lens for focusing
When converging the light beam having the wavelength λ1 on the information recording surface of the first optical disk, the divergence of the light beam incident on the objective lens is greater than that of the second optical disk. An optical pickup having a larger divergence than the light beam incident on the objective lens when the light is focused on the information recording surface.
The NA of the objective lens for condensing the light beam with the wavelength λ1 on the information recording surface of the first optical disc, and NA1 of the objective lens for condensing the light beam with the wavelength λ2 on the information recording surface of the second optical disc. The optical pickup according to claim 1, wherein NA1> NA2 where NA is NA2.
The combination of the wavelength λ1 and the wavelength λ2 is blue violet light (wavelength 350 nm to 450 nm) and red light (wavelength 600 nm to 700 nm), blue violet light and infrared light (750 nm to 850 nm), or red light and infrared light. The optical pickup according to claim 1 or 2, which is a combination of the following.
Means for making the light beams emitted from the first and second light sources the same optical axis;
A coupling lens that converts the divergence of light beams emitted from the first and second light sources;
A lens actuator that moves the coupling lens along the optical axis direction of the objective lens in the same optical axis area;
The lens actuator is configured to condense the light beam having the wavelength λ1 on the information recording surface of the first optical disk and to collect the light beam having the wavelength λ2 on the information recording surface of the second optical disk. Move the coupling lens to a different position,
The position of the coupling lens in the optical axis direction of the lens when the light beam having the wavelength λ1 is condensed on the information recording surface of the first optical disk is changed to the information on the second optical disk. The optical pickup according to any one of claims 1 to 3, wherein the optical pickup is closer to the light source side than a position in the lens optical axis direction of the coupling lens when the light is condensed on a recording surface.
When the light beam having the wavelength λ1 is condensed on the information recording surface of the first optical disc, the position of the coupling lens in the lens optical axis direction is a position where the light beam incident on the objective lens becomes parallel light. Yes, when the light beam having the wavelength λ2 is condensed on the information recording surface of the second optical disc, the position of the coupling lens in the lens optical axis direction is that the light beam incident on the objective lens becomes convergent light. The optical pickup according to claim 4, which is a position.
The optical pickup according to any one of claims 1 to 5, wherein the objective lens is a lens shared by the light beam having the wavelength λ1 and the light beam having the wavelength λ2.
The optical pickup according to any one of claims 1 to 5, wherein the objective lens includes a lens for the light beam having the wavelength λ1 and a lens for the light beam having the wavelength λ2.
A first light source that emits a divergent light beam of wavelength λ1,
A second light source that emits a divergent light beam having a wavelength λ2 (λ2> λ1) different from the wavelength λ1;
A third light source that emits a divergent light beam having a wavelength λ3 (λ3>λ2> λ1) different from the wavelengths λ1 and λ2.
The light beam having the wavelength λ1 is condensed on the information recording surface of the first optical disk having the protective substrate thickness t1, and the light beam having the wavelength λ2 is condensed on the information recording surface of the second optical disk having the protective substrate thickness t2 different from the t1. An objective lens for condensing the light beam having the wavelength λ3 on the information recording surface of a third optical disc having a protective substrate thickness t3 different from the t1 and the t2.
Means for converting the light beams emitted from the first, second, and third light sources into the same optical axis;
A coupling lens that converts the divergence of the light beams emitted from the first, second, and third light sources;
A lens actuator that moves the coupling lens along the optical axis direction of the objective lens in the same optical axis area;
The lens actuator condensing the light beam having the wavelength λ1 on the information recording surface of the first optical disc, condensing the light beam having the wavelength λ2 on the information recording surface of the second optical disc, When condensing the light beam of wavelength λ1 on the information recording surface of the first optical disc, the coupling lens is moved to a different position,
The position of the coupling lens is an optical pickup in which the light beam having the wavelength λ3, the light beam having the wavelength λ1, and the light beam having the wavelength λ2 are condensed in order from the light source.
The luminous flux of wavelength λ1 is blue-violet light (wavelength 350 nm to 450 nm),
The luminous flux of wavelength λ2 is red light (wavelength 600 nm to 700 nm),
The optical pickup according to claim 8, wherein the light flux having the wavelength λ3 is infrared light (750 nm to 850 nm).
When condensing the light beam having the wavelength λ2 on the information recording surface of the second optical disk, the position of the coupling lens in the lens optical axis direction is a position where the light beam incident on the objective lens becomes convergent light. Yes,
When the light beam having the wavelength λ3 is condensed on the information recording surface of the third optical disk, the position of the coupling lens in the lens optical axis direction is a position where the light beam incident on the objective lens becomes divergent light. The optical pickup according to claim 8 or 9, wherein there is an optical pickup.
The optical pickup according to any one of claims 8 to 10, wherein the objective lens is a lens shared by the light beam having the wavelength λ1, the light beam having the wavelength λ2, and the light beam having the wavelength λ3.
11. The objective lens according to claim 8, wherein the objective lens includes a lens for a light beam having the wavelength λ1, and a lens shared by the light beams having the wavelength λ2 and the wavelength λ3. The optical pickup described.
The first optical disc has a plurality of information recording surfaces, and spherical aberration caused by a difference in the substantial thickness of the transparent base material from the surface to each information recording layer surface is corrected by moving the coupling lens. The optical pickup according to claim 4 or claim 8.
An optical pickup according to any one of claims 1 to 13,
A motor for rotationally driving the information recording medium;
An optical disc apparatus comprising the optical pickup and a control unit that controls the motor.
An optical disk device according to claim 14;
An input means for inputting information;
A calculation means for performing calculation based on information reproduced from the optical disk device and / or information input from the input means;
A computer comprising: output means for outputting information reproduced from the optical disk device and / or information inputted from the input means and / or a result computed by the computing means.
An optical disk device according to claim 14;
An optical disc player comprising: a decoder that converts an information signal obtained from the optical disc device into image information.
An optical disk device according to claim 14;
An optical disk recorder comprising: an encoder for converting image information into an information signal for recording by the optical disk device.