WO2007114045A1

WO2007114045A1 - Optical head device

Info

Publication number: WO2007114045A1
Application number: PCT/JP2007/055643
Authority: WO
Inventors: Akira Kouno
Original assignee: Pioneer Corporation
Priority date: 2006-03-31
Filing date: 2007-03-20
Publication date: 2007-10-11

Abstract

An optical head device includes: light source means for emitting a laser beam for each of a plurality of types of optical discs; a first objective lens for collecting the laser beam emitted from the light source means onto a recording surface of one type of optical disc and a second objective lens for collecting the laser beam onto a recording surface of the other type of optical disc; one light reception element for receiving a signal light from the recording surface; and an optical system for introducing the laser beam into the first or the second objective lens, performing light synthesis or light separation accompanied by at least a partial reflection on the signal light according to the optical disc type and introducing the signal light to the light reception element, wherein a difference between the number Nb of reflections from the one type of optical disc to the light reception element and a number Mb of the reflections from the other type of optical disc to the light reception element is 0 or an even number.

Description

Specification

Optical head device

Technical field

[0001] The present invention is compatible with a plurality of types of optical disks that use the same light source, such as BD (Blu-ray Disc) and HD-DVD, and more preferably, BD (or HD-DVD). The present invention relates to the technical field of an optical head device such as an optical pickup that can handle a plurality of types of optical disks that require different light sources such as a DVD.

Background art

This type of optical head device has a plurality of types of laser light sources so that the same or different laser beams can be irradiated depending on the type of the optical disc set in the optical disc player or recorder, and emitted from these laser light sources. The laser beam is configured to irradiate the optical disc through a common objective lens as a laser beam on a single optical path by passing it through a beam splitter or a noise mirror (see Patent Documents 1 and 2). .

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-149689

Patent Document 2: JP-A-2004-234818

Disclosure of the invention

Problems to be solved by the invention

However, for example, according to the technology disclosed in the background art, since a common objective lens is used, it is fundamental to reproduce each optical disc under optical conditions suitable for reproducing each optical disc. Finally, there is a technical problem that it is practically impossible to construct a state in which the reliability of the signal light is high for any type of optical disk.

On the other hand, if a plurality of objective lenses are used, it will be possible or easy to reproduce each optical disk under optical conditions suitable for reproducing each optical disk. However, in this case, in addition to multiple laser light sources, multiple objective lenses and multiple light-receiving elements are also required. Eventually, the optical configuration becomes complex and sophisticated, and multiple types of optical disks can be handled. In other words, the essential significance as a compatible optical head device It is expected that there will be a practical problem that may disappear.

The present invention has been made in view of, for example, the above-described problems, and is compatible with a plurality of types of optical discs that are relatively reliable with respect to signal light and whose optical configuration is simplified. It is an object to provide a possible optical head device.

Means for solving the problem

In order to solve the above problems, the optical head device of the present invention is an optical head device that can handle a plurality of types of optical disks, and can emit laser light for each of the plurality of types of optical disks. Light source means and a first objective for condensing the emitted laser light on the recording surface of one type of optical disk set with respect to the optical head device among the plurality of types of optical disks A second objective lens for condensing the laser beam emitted from the light source means on the recording surface of another type of optical disc set to the optical head device among the plurality of types of optical discs; One light receiving element for receiving the signal light from the recording surface based on the laser beam condensed on the recording surface through the first or second objective lens, and the laser light to the optical disc. The kind of And at least one of photosynthesis and light separation involving at least partial reflection with respect to at least the signal light of the laser light and the signal light. An optical system that guides the signal light to the light receiving element by performing processing according to the type of the optical disk, and the optical system reflects the reflection from the one type of optical disk to the light receiving element. The difference between the number of times Nb and the number of reflections Mb from the other type of optical disk to the light receiving element is zero or even.

[0008] According to the optical head device of the present invention, when the optical head device is set, for example, one type of optical disc (eg, BD) force among the plural types of optical discs, for example, a blue laser Laser light power for the set optical disk such as a semiconductor laser device is emitted from light source means such as a device. This laser beam is focused on the recording surface of this kind of optical disk by the first objective lens. Then, the signal light based on the common laser light irradiated on the recording surface is guided by the optical system through the first objective lens by optical actions such as reflection, transmission, diffraction, refraction, and scattering on the recording surface. . In this case, especially in the optical system Is at least partially applied to the signal light, for example, by reflection, semi-transmission reflection, reflection according to frequency or reflection according to the polarization state by a half mirror, a dichroic mirror, a polarization beam splitter, etc. Photosynthesis and light separation with specular reflection are applied according to the type of optical disc set. As a result, the signal light passing through the first objective lens is guided to one light receiving element via the optical system. For example, an optical member such as a λ / 2 plate or a λ / 4 plate so that the polarization state changes between the optical path of the laser light (outward path) and the optical path of the signal light (return path) via the first objective lens. May be placed in the light path.

On the other hand, for example, when another type of optical disk (for example, HD-DVD or DVD or CD) is set on the optical head device, laser light is emitted from the same or different light source means. Is emitted. This laser light is focused on the recording surface of the other type of optical disk by the second objective lens. Then, the signal light based on the laser light irradiated on the recording surface is guided by the optical system through the second objective lens by the optical action on the recording surface. In this case, in particular, in the optical system, for example, reflection by a half mirror, dichroic mirror, polarization beam splitter, reflection by semi-transmission, reflection according to frequency, reflection according to the polarization state, etc. Thus, at least partial reflection and light synthesis and light separation are performed according to the type of optical disc set. As a result, the signal light passing through the second object lens is guided to one light receiving element via the optical system. For example, the λ / 2 plate, λ / 4 plate, etc. so that the polarization state changes between the optical path of the common laser light (outward path) and the optical path of the signal light (return path) through the second objective lens. An optical member may be disposed in the optical path.

Here, in particular, in the optical system, the number of reflections Nb of signal light from one type of optical disk, in other words, from the first object lens to the light receiving element, and other types of optical discs. Thus, in other words, the difference from the number Mb of signal light reflected from the second objective lens to the light receiving element is zero or even. Therefore, it is possible to reliably and effectively avoid reversing the image of the light constituting the signal light between the case where the first objective lens is used and the case where the second objective lens is used. As a result, the light receiving element can receive light with the highest light receiving sensitivity regardless of which type of optical disk is set. [0011] In this way, the image of the signal light is inverted to one (ie, a common) light receiving element while adopting a form in which the laser light is separately collected by two types of objective lenses, relatively easily. It will be possible to guide without this. At this time, since two types of objective lenses are used, signal light can be obtained under different optical conditions for different types of optical disks (typically BD and HD-DVD). Both the reliability related to light and the simplicity related to the optical configuration can be improved very efficiently.

In one aspect of the optical head device of the present invention, the light source means emits laser light for the one type of optical disk and laser light for the other type of optical disk separately. Laser light source.

[0013] According to this aspect, one type of laser light source emits laser light for one type of optical disc, and the other type of laser light source emits laser light for another type of optical disc. Therefore, if the number of reflections between the signal lights is limited as described above, it is not necessary to limit the number of reflections between these laser lights. Thereby, the design freedom concerning an optical system is raised notably.

In another aspect of the optical head device of the present invention, the light source means emits the laser light for the one type of optical disk and the laser light for the other type of optical disk in common. The optical system also performs at least one of photosynthesis and light separation accompanied by at least partial reflection on the laser light according to the type of the optical disc. The laser light is guided to the first or second objective lens according to the type of the optical disk, and the optical system is configured to count the number of reflections Nf from the one laser light source to the one type of optical disk. The one laser light source power is configured such that the difference from the number of reflections Mf to reach the other type of optical disk is zero or an even number.

[0015] According to this aspect, the laser light for one type of optical disc and the laser light for another type of optical disc are emitted in common from one laser light source. That is, when one kind of optical disk is set, the laser light is separated by the light separation in the optical system, and is guided partially or selectively to the first objective lens. Alternatively, when another type of optical disk is set, this can be achieved by photosynthesis or light separation in the optical system. Are separated and selectively guided to the second objective lens. In particular, the difference between the number of reflections N f from one laser light source power to one type of optical disk and the number of reflections M f from one laser light source to another type of optical disk is zero or It is assumed to be an even number. Therefore, it is reliable and effective that the image of the light constituting the signal light caused by the same light source is inverted between the case of using the first objective lens and the case of using the second objective lens. Can be avoided. As a result, the light receiving element can receive light with the highest light receiving sensitivity even when any type of optical disk is set.

As described in detail above, according to the optical head device of the present invention, the light source means, the first and second objective lenses, the one light receiving element, and the optical system are provided. It is possible to handle a plurality of types of optical discs while increasing the optical configuration and simplifying the optical configuration.

[0017] The operation and other advantages of the present invention will be clarified in the embodiment described below.

Brief Description of Drawings

FIG. 1 is a perspective view showing a basic configuration of an optical head device according to an embodiment of the present invention.

FIG. 2 is a plan view showing a basic configuration of an optical head device according to an example.

FIG. 3 is a plan view showing a state where the optical head device according to the example records or reproduces information on a DVD.

FIG. 4 is a plan view showing a state where the optical head device according to the example records or reproduces information on a CD.

FIG. 5 is a plan view showing a state where the optical head device according to the example records information on a BD.

FIG. 6 is a plan view showing a state in which the optical head device according to the example reproduces information from a BD or HD-DVD.

FIG. 7 is a plan view showing correction of aberrations in the optical head device according to the example.

FIG. 8 is a schematic plan view showing a first embodiment relating to the arrangement of each surface.

FIG. 9 is a schematic plan view showing the basic arrangement of each surface.

[Fig. 10] Schematic plan view showing the state of polarization switching on the polarization beam splitter surface. It is.

FIG. 11 is a schematic plan view showing an optical system of a second embodiment relating to the arrangement of each surface.

FIG. 12 is a schematic plan view showing an optical system of a third example according to the arrangement of each surface.

FIG. 13 is a schematic plan view showing an optical system of a fourth example relating to the arrangement of each surface.

FIG. 14 is a schematic plan view showing an optical system of a fifth example according to the arrangement of each surface.

FIG. 15 is a schematic plan view showing the optical system of Example 6 according to the arrangement of each surface.

FIG. 16 is a schematic plan view showing the optical system of the first example relating to the number of reflections.

FIG. 17 is a schematic plan view showing an optical system of a second example according to the number of reflections.

FIG. 18 is a schematic plan view showing an optical system of a third example relating to the number of reflections.

FIG. 19 is a schematic plan view showing an optical system of a fourth example according to the number of reflections.

FIG. 20 is a schematic plan view showing an optical system of a fifth example relating to the number of reflections. Explanation of symbols

1 Optical head device

601 laser diode

602 laser diode

603 laser diode

501 DVD coupling lens

502 CD coupling lens

613 shaping element

623 Liquid crystal SW element

630 Dyke mouth prism

640 DVDZCD polarization grating

643 Polarization grating

M01 Reflection mirror

M03 Reflective mirror

P01 Prism

P01H Half mirror surface

P01D 1st Dichroic Cummira P02 Prism

P02P Polarized beam splitter surface

P02D 2nd dichroic mirror surface

660 DVD / CD / HD—DVD collimator

663 Collimator for BD

673 1Z2 wave plate

703 BD hologram

710 Launch mirror

720 Liquid crystal aberration correction element

730 broadband 1Z4 wave plate

743 BD objective lens

740 DVDZCDZHD— DVD objective lens

Mirror for FMO FM

FM3 FM mirror

750 multi lens

760 OEIC

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described in each embodiment in order with reference to the drawings.

A basic configuration of the optical head device according to the embodiment will be described with reference to FIG. 1 and FIG. FIG. 1 is a perspective view showing the basic configuration of the optical head apparatus according to the embodiment of the present invention. FIG. 2 is a plan view showing the basic configuration of the optical head apparatus according to the embodiment.

As shown in FIG. 1 and FIG. 2, the optical head device 1 according to the present embodiment mainly includes a laser diode 601, a laser diode 602, and a laser diode 603 as examples of “light source means” according to the present invention. , BD objective lens 743 as an example of “first objective lens” according to the present invention, DVDZCDZHD—DVD objective lens 740 as an example of “second objective lens” according to the present invention, and OEIC (Opto- Electronic In tegrated Circuit) 760 and prism P01 and prism P02 as an example of the “optical system” according to the present invention, for a plurality of types of optical disks (for example, DVD, CD, BD or HD-DVD). V, so-called multi-drive that can read and write information.

The laser diode 601 includes a semiconductor laser, for example, and as an example of the “non-common laser beam” according to the present invention, a laser beam having a wavelength of 650 nm (that is, a so-called red laser beam)

, DVD non-common laser light) is emitted as forward light (hereinafter, laser light from each laser diode to the optical disk is also referred to as “forward light” as appropriate).

The laser diode 602 includes a semiconductor laser, for example, and as an example of the “non-common laser beam” according to the present invention, a laser beam having a wavelength of 780 nm (that is, a non-common laser beam dedicated to CD) is forwarded. Emits as light.

The laser diode 603 includes a semiconductor laser, for example, and as an example of the “common laser light” according to the present invention, a laser light having a wavelength of 405 nm (that is, a so-called blue laser light (that is,

Common laser light for BD and HD—DVD is emitted as forward light.

[0025] The DVD coupling lens 501 is a lens for supplying forward light emitted from the laser diode 601 to the prism P01.

The CD coupling lens 502 is a lens for supplying forward light emitted from the laser diode 602 to the prism P01.

The shaping element 613 is a lens that enlarges and shapes the common laser light emitted from the laser diode 603.

[0028] The liquid crystal SW (Switch) element 623 is switched between ON (ON) and ZOFF (OFF). For example, when the switch is ON, the incident common laser beam (linearly polarized light) is emitted as it is, and when it is OFF, The incident common laser beam (linearly polarized light) is converted into circularly polarized light and emitted. If it is not necessary to support HD-D VD, the liquid crystal SW element 623 may be omitted.

The Dyke mouth prism 630 is disposed on the intersection of the optical path of the laser light emitted from the laser diode 601 and the optical path of the laser light emitted from the laser diode 602, and is emitted from the laser diode 601. The laser beam is transmitted and reflected by the laser beam emitted from the laser diode 602, so that the optical paths of both laser beams are aligned. [0030] Polarization grating 640 for DVDZCD is a laminated structure of wavelength selective grating 6402 (CD), wavelength selective grating 6403 (DVD), and polarization filter 6401 (return light countermeasure) (see enlarged view in Fig. 2) ) To generate a sub beam for tracking error, and reduce the amount of light returning to each laser diode by combining with the broadband 1Z4 wavelength plate 730.

[0031] The polarization grating 643 generates a sub beam for tracking error by diffracting the incident laser beam (common laser beam), and returns to the laser diode by combining with the broadband 1Z4 wavelength plate 730. Reduce the amount of light.

[0032] The reflection mirror M01 and the reflection mirror M03 appropriately change the optical path of the laser light by reflecting the irradiated laser light.

[0033] The prism P01 includes a half mirror surface P01H and a first dichroic mirror surface P01D.

[0034] Here, the half mirror surface P01H is arranged in the optical path of the non-common laser beam, and transmits a part of the non-common laser beam to the DVDZCDZHD—DVD objective lens 740 and DVDZCDZHD—DVD. The signal light returning from the objective lens 740 (hereinafter, the laser light reflected by the optical disk and reaching the OEIC 760 is also referred to as “return light” as appropriate)

Here, the first dichroic mirror surface P01D reflects the common laser light (outward light) and the related signal light (return light), and the non-common laser light (outward light) and the related signal light ( This is the surface that transmits the return light. And it is the optical path of the part (for example, P polarized light) which permeate | transmits polarization beam splitter surface PO2P among common laser lights, and is arrange | positioned in the one part optical path of non-common laser light.

The prism P02 includes a polarization beam splitter surface P02P and a second dichroic mirror surface PO 2D.

Here, the polarization beam splitter surface P02P is arranged in the optical path of the common laser light (outward light). For example, the electric field component of the common laser light reflects the S-polarized light perpendicular to the incident surface, and the BD In addition to guiding to the objective lens 740 for DVD, the electric field component transmits P-polarized light parallel to the incident surface to guide it to the DVDZCDZHD—DVD objective lens 740. In addition, for BD Transmits the signal light (return light) returning from the objective lens 740 and DVDZCDZHD—D

The signal light returning from the VD objective lens 740 is reflected.

[0038] Here, the second dichroic mirror surface P02D is a surface that transmits the signal light (forward light) related to the common laser light and reflects the signal light (return light) related to the non-common laser light. And it is an optical path of the signal light related to the common laser light (forward light), and is arranged in the optical path of the part reflected by the half mirror surface P01H among the signal light (return light) related to the non-common laser light.

[0039] DVD / CD / HD—DVD collimator 660 and BD collimator 663 convert incident laser light into parallel light.

[0040] The 1Z2 wave plate 673 converts the incident linearly polarized light into linearly polarized light orthogonal to the incident linearly polarized light and emits it.

[0041] The BD hologram 703 is configured to correct the spherical aberration of the three beams (0th-order diffracted light and first-order diffracted light) included in the BD laser light.

[0042] The raising mirror 710 converts the laser light made into parallel light into the BD objective lens 743 or D.

VDZCDZHD—configured to force the DVD objective lens 740 up.

[0043] The liquid crystal aberration correction element 720 includes, for example, a liquid crystal, and adjusts the optical path of each laser beam using the dielectric constant and the anisotropy of the refractive index of the liquid crystal, thereby coma aberration (tangential direction and Configured to correct for radial) and astigmatism (0 and 45 degrees).

[0044] The broadband 1Z4 wavelength plate 730 includes a crystal, for example, and converts laser light over a wide band, such as the launched non-common laser light or common laser light, from linearly polarized light to circularly polarized light, Thus, the circularly polarized light is converted to linearly polarized light.

[0045] The BD objective lens 743 focuses incident laser light (forward path light) on the recording surface of the optical disc (BD), and signal light (return path light) from the recording surface based on the focused laser light. The OE

Configured to communicate to IC760.

[0046] DVDZCDZHD—DVD objective lens 740 condenses incident laser light (outgoing light) on the recording surface of an optical disc (DVDZCDZHD—DVD), and a signal from the recording surface based on the condensed laser light. Configured to transmit light (return light) to OEIC760

[0047] FM (Front Monitor: FM) mirror FM0 and FM mirror FM3 are optical discs ( During recording or playback of DVD, CD, BD or HD-DVD), a part of common laser light, non-common laser light, or signal light is guided to a front monitor (not shown).

[0048] The multi-lens 750 is configured to condense the signal light (return light) from the recording surface of the optical disc (DVD, CD, BD or HD-DVD) onto the OEIC 760 with a relatively high condensing rate. .

[0049] The OEIC 760 includes a photodiode, for example, and receives the signal light (return light) from the recording surface of the DVD, CD, BD or HD-DVD collected by the multi-lens 750 to receive the optical disc. It is configured to be used for recording or playback (DVDZCDZHD—DVD).

As described above, the optical head device 1 according to the present embodiment includes the laser diode 601, the laser diode 602, and the laser diode 603 as examples of the “light source unit” according to the present invention, and the “ BD objective lens 743 as an example of the “first objective lens”, DVDZCDZHD—DVD objective lens 740 as an example of the “second objective lens” according to the present invention, and an example of the “light receiving element” according to the present invention And the prism P01 and the prism P02 as an example of the “optical system” according to the present invention, it is possible to deal with a plurality of types of optical disks.

Next, in addition to FIGS. 1 and 2, the operations when recording or reproducing various optical disks using the optical head device 1 according to the present embodiment configured as described above are illustrated in FIGS. 7 is used for explanation.

<<Operation when recording or playing back information on DVD>>

First, the operation when the optical head device 1 according to this embodiment records or reproduces information on a DVD will be described with reference to FIG. FIG. 3 is a plan view showing how the optical head device according to the embodiment records or reproduces information on the DVD.

[0051] As shown in FIG. 3, when recording or reproducing information on a DVD, first, the laser diode 601 is driven to, for example, a laser beam having a wavelength of 650 nm (ie, a non-common laser dedicated to DVD). Light). The emitted laser light (outgoing light) passes through the Dyke mouth prism 630. Then, when passing through the wavelength selective grating 6403 (DV D) of the polarization grating 640 for DVDZCD, a sub beam is generated and reflected by the reflecting mirror M01. Part of the reflected forward light is reflected by the half mirror surface P01H and guided to the front monitor via the FM mirror FM01, and the rest is transmitted through the half mirror surface P01H and the first dichroic aperture mirror surface P01D in the prism P01. The DVDZCDZHD—DVD collimator 660 makes the beam parallel, and the rising mirror 710 raises the DVDZCDZHD—DVD objective lens 740. The outgoing forward light is corrected for coma (tangential and radial) and astigmatism (0 and 45 degrees) by the liquid crystal aberration correction element 720, and is converted from linearly polarized light by the broadband 1Z4 wavelength plate 730. After being converted into circularly polarized light, the DVDZCD ZHD—DVD objective lens 740 irradiates the DVD recording surface. In addition, the signal light from the recording surface (return light) based on the laser light irradiated to DV D is the force that reverses the forward path to the first dichroic mirror surface P01D. Is different. That is, of the return light that passes through the first dichroic mirror surface P01D, the light that passes through the half mirror surface P01H is reduced in light amount by the polarization filter 6401 in the DVDZCD polarization grating 640. The return light reflected by the dichroic mirror surface P02D is received by the OEIC 760 via the multi lens 750.

As described above with reference to FIG. 3, according to the optical head device 1 of this embodiment, information is recorded or reproduced on a DVD.

<<Operation when recording or playing back information on a CD>>

Next, the operation when the optical head device 1 according to the present embodiment records or reproduces information on the CD will be described with reference to FIG. FIG. 4 is a plan view showing how the optical head device according to the embodiment records or reproduces information on the CD. In this case, the main differences from the DVD described above are mainly the type of optical disk used (CD, not DVD), the wavelength of the laser beam (780 nm compared to 650 nm), and the laser diode (laser diode 601) that emits it. Not only the laser diode 602), but also the optical path from the emitted light to the half mirror surface P01H. Other than that, it is basically the same as the case of the above-described DVD, so that the description will be omitted as appropriate.

[0053] As shown in FIG. 4, when recording or reproducing information on a CD, first, a laser die is used. The ode 602 is driven to emit laser light having a wavelength of, for example, 780 nm (that is, non-common laser light dedicated to CD). The emitted laser light (outgoing light) is reflected by the Dyke mouth prism 630 and reaches the half mirror surface P01H. After that, the recording surface of the optical disc (CD) is irradiated in the same way as in the case of DVD. In addition, signal light (return light) from the recording surface based on the collected laser light is received by the OEIC 760 in the same manner as in the case of DVD.

As described above with reference to FIG. 4, according to the optical head device 1 of the present embodiment, information recording or reproduction is preferably performed on a CD.

<<Operation when recording information on BD>>

Next, the operation when the optical head device 1 according to the present embodiment records information on a BD will be described with reference to FIG. FIG. 5 is a plan view showing how the optical head device according to the embodiment records information on the BD. At this time, the main differences from the DVD described above are mainly the type of optical disk used (BD instead of DVD), the wavelength of the laser beam (405 nm compared to 650 nm), and the laser diode (Laser Diode 601) that emits it. Laser diode 603), objective lens (DVDZCDZHD—BD objective lens 743 instead of DVD objective lens 740), and the associated optical path. Other than that, it is basically the same as the case of the DVD described above, so the description will be omitted as appropriate.

As shown in FIG. 5, when recording information on a BD, first, the laser diode 603 is driven, for example, a laser beam having a wavelength of 405 nm (ie, for BD and HD-DVD). Common laser beam). The emitted laser light (outgoing light) is enlarged and shaped by the shaping element 613 as S-polarized light perpendicular to the incident surface when entering the polarization beam splitter surface P02P, and passes through the liquid crystal SW element 623 with the switch turned on. Then, a sub beam is generated when passing through the polarization grating 643 and enters the prism P02. At this time, since the incoming forward light is S-polarized light whose electric field component is perpendicular to the incident surface, the reflected S-polarized light is reflected by the polarization beam splitter surface P02P and collimated by the BD collimator 663, and the 1Z2 wavelength plate It is converted into linearly polarized light by 673, guided to the BD hologram 703 by the reflecting mirror M03, and the spherical aberration of the three beams (0th order diffracted light and ± 1st order diffracted light) contained in itself is corrected by the BD hologram 703. Then, it is raised toward the object lens 743 for BD by the raising mirror 710. The outgoing forward light is corrected for liquid crystal aberration. Element 720 corrects coma (tangential and radial) and astigmatism (0 and 45 degrees), converts from linearly polarized light to circularly polarized light by broadband 1Z4 wave plate 730, and optical disk by BD objective lens 743 Irradiated to the recording surface of (BD). The signal light (return light) from the recording surface based on the laser light irradiated on the BD travels in the reverse direction up to the second dichroic mirror surface P02D. Different. That is, of the return path light, the light reflected by the polarization beam splitter surface P02P is a force that reduces the amount of light by the polarization grating 643. The return path light transmitted through the second dichroic mirror surface P02D passes through the multi lens 750. And received by the OEIC760.

As described above with reference to FIG. 5, according to the optical head device 1 of the present embodiment, information recording is suitably performed on the BD.

<<BD or HD—Operation when playing back information on DVD>>

Next, the operation when the optical head device 1 according to this embodiment reproduces information from a BD or HD-DVD will be described with reference to FIG. FIG. 6 is a plan view showing how the optical head device according to the embodiment reproduces information from a BD or HD-DVD. In this case, the main difference from the case of the recording related to the BD described above is that the liquid crystal SW element 623 is turned OFF and the optical path of the polarized light associated therewith is different. The rest is basically the same as in the case of the recording related to the BD described above, and the description is omitted as appropriate.

[0057] As shown in FIG. 6, when information is reproduced from a BD or HD-DVD, the laser diode 603 is driven in the same manner as in the recording related to the BD, for example, at a wavelength of 405 nm. The light (that is, common laser light common to BD and HD-DVD) is emitted. The emitted laser light (outgoing light) is enlarged and shaped by the shaping element 613 as S-polarized light perpendicular to the incident surface when entering the polarization beam splitter surface P02P. Here, in particular, unlike in the case of recording according to BD, since the switch of the liquid crystal SW element 623 is OFF, the emitted outgoing light is converted into linearly polarized light and circularly polarized light. In any case, this circularly polarized light includes elliptical polarized light. In any case, this circularly polarized light is s-polarized light that is perpendicular to the incident surface when incident on the polarized beam splitter surface P02P, and incident on the polarized beam splitter surface P02P. Contains P-polarized light parallel to the plane of incidence. Therefore, the S-polarized light component of the forward light is reflected by the polarization beam splitter surface P02P, and then the same optical path as in the case of BD recording described above is adopted. Information is suitably reproduced from the BD via the BD objective lens 743. On the other hand, when the P-polarized component of the forward light passes through the polarization beam splitter surface P02P and is reflected by the first dichroic mirror surface P01D, the same as in the above-described DVD or CD recording. The optical path is taken, and the DVD-CD / HD DVD objective lens 740 irradiates the HD-DVD recording surface. In addition, the signal light (return light) from the recording surface based on the laser light applied to the HD-DVD is reflected by the first dichroic mirror surface P01D, unlike DVD or CD. The reflected return light is further reflected by the polarized beam splitter surface P02P, and is transmitted through the first dichroic mirror surface P01D and received by the OEIC 760 via the multi lens 750, unlike the case of the force DVD or CD.

As described above with reference to FIG. 6, according to the optical head device 1 of the present embodiment, information is preferably reproduced from the BD or HD-DVD.

<<Aberration correction in optical head device 1>

Next, correction of aberration in the optical head device 1 according to the present embodiment will be described with reference to FIG. FIG. 7 is a plan view showing aberration correction in the optical head device according to the example.

In FIG. 7, the optical head device 1 according to the present embodiment particularly has a collimator slider 665 for simultaneously sliding the collimators 660 and 663 along the optical path of the laser beam, and a mechanism for moving the collimator slider 665. It further includes a collimator moving stepping motor 666, and is configured to correct various aberrations (for example, coma aberration, astigmatism, and spherical aberration) in combination with the liquid crystal aberration correction element 720.

The coma aberration in the tangential direction and the radial direction is corrected using the liquid crystal aberration correction element 720.

[0061] Astigmatism of 0 degrees and 45 degrees is also corrected using the liquid crystal aberration correction element 720.

When correcting the spherical aberration, correction is performed by appropriately moving the collimator slider 665 by the collimator moving stepping motor 666.

As described above with reference to FIG. 7, various aberrations that can occur when dealing with a plurality of types of optical discs are suitably corrected.

As described above with reference to FIGS. 3 to 7, according to the optical head device 1 of the present embodiment, A so-called multi-drive capable of dealing with a plurality of types of optical discs can be realized. <About the arrangement of each side>

Next, among the above-described optical head device 1, in particular, the basic concept of the arrangement of the half mirror surface P01H, the polarization beam splitter surface P02P, the first dichroic mirror surface P01D, and the second dichroic mirror surface P02D The explanation will be explained with reference to Figs.

<<First example concerning the arrangement of each surface>>

First, the first embodiment relating to the arrangement of each surface will be described with reference to FIGS. FIG. 8 is a schematic plan view showing the first embodiment relating to the arrangement of each surface, FIG. 9 is a schematic plan view showing the basic arrangement of each surface, and FIG. FIG. 5 is a schematic plan view showing a state of polarization switching on a beam splitter surface P02 P.

In FIG. 8, an optical head device 1 has a plurality of laser drivers that emit a plurality of laser beams having different wavelengths, and is a half-mirror surface P 01H that is suitable for a plurality of types of optical disks. Arrange the presetter plane P02P, the first dichroic mirror plane P01D, and the second dichroic mirror plane P02D while paying attention to the following (1) to (5).

[0066] (1) The first dichroic mirror surface P01D and the second dichroic mirror surface P02D are arranged so that their logics are reversed with respect to wavelength selection and are positioned diagonally to each other. In addition, a light separation / synthesis film (a first mirror surface P01H and a first polarization beam splitter surface P02P) having different functions is disposed on the other diagonal. Here, “the logic is inverted” with respect to wavelength selection means that the transmission or reflection for a certain wavelength and the transmission or reflection for another wavelength are inverted. Specifically, the first dichroic mirror surface P01D reflects a laser beam having a short wavelength (for example, λ l = 405 nm) along the round trip path, and a laser beam having a long wavelength (for example, λ 2 = 660 or 3 = 785 nm). Is transmitted through the round-trip path, the second dichroic mirror surface P02D transmits the short-wavelength laser light along the round-trip path and reflects the long-wavelength laser light along the round-trip path (see Fig. 9). ). If each surface is arranged in such a relationship, the optical path of the laser beam can be appropriately separated and combined according to the wavelength. For example, the first dichroic mirror surface P01D synthesizes the respective optical paths by reflecting the short-wavelength forward light and transmitting the long-wavelength laser light in the forward path. Both laser beams are combined into one objective lens. Led by Furthermore, since the first dichroic mirror surface P01D reflects the short-wavelength return light and transmits the long-wavelength laser light even in the return path, each optical path is separated this time. After that, the second dichroic mirror surface P02D, whose logic is inverted with respect to the first dichroic mirror surface P01D in terms of wavelength selection, returns the short wavelength return light and reflects the long wavelength laser light in the return path. Then, the respective optical paths are combined, and finally, both the return path lights are received by one light receiving element. In addition, according to the present embodiment, in addition to the wavelength-dependent laser beam optical path separation Z synthesis as described above, the polarization treatment by the polarization beam splitter surface P02P having polarization dependence, and the polarization dependence! Since the non-polarization treatment by the mirror surface P01H is also applied, SZN can be suitably secured by applying polarization treatment to the short-wavelength laser light and the light from each objective lens. Use efficiency improves. On the other hand, non-polarized light is applied to the long-wavelength laser light to reduce the amount of return light and birefringence is reduced.

[0067] (2) At this time, the line segments (ml + m2) and (nl + n2) should be equal. In other words, the optical distance (ie, optical path length) between the surfaces should be set so that (ml + m2)-(nl + n2) = 0. Where ml is the optical path length between the half mirror surface P01H and the second dichroic mirror surface P02D on the laser light path, and m2 is the half mirror surface P01H and the first dichroic mirror surface on the laser light path. Nl is the optical path length between the plane of the polarization beam splitter P02P on the optical path of the laser beam P02P and the first dichroic mirror plane P01D, and n2 is the polarization beam path on the optical path of the laser beam. The optical path length between the presetter surface P02P and the second dichroic mirror surface PO 2D is shown. In other words, it is preferable to dispose the optical path difference between a plurality of laser beams separated between the first dichroic mirror surface P01D and the second dichroic aperture mirror surface P02D and passing through different optical paths. When arranged in this way, the laser beams can maintain a conjugate relationship with each other.

[0068] (3) Even if a plurality of types of laser beams are used, it is desirable that a plurality of signal beams be received by one OEIC 760. This is a request from the simplification of the system configuration. This requirement can be met by combining the optical paths according to the arrangement of the surfaces described above.

[0069] (4) m2 and n2 (see FIG. 8) should be as small as possible. This allows for a multilayer structure, which promotes miniaturization and reduces costs. However, m2 and n2 are set to 0 and 1 It is difficult to achieve both a polarizing system for blue and a non-polarizing system for red by one film configuration. If a single film configuration is used, phase disturbance or the like may occur in each of the short wavelength range (for example, a wavelength range including 405 nm) and the long wavelength range (for example, a wavelength range including 660 nm and 785 nm). Because. Therefore, the values of m2 and n2 are based on experimental, empirical, simulation, etc., and the trade-off problem of phase disturbance and miniaturization is found. What is necessary is just to predetermine, for example according to the kind or solid of a film | membrane so that it may be satisfied. In this way, the polarization system and the non-polarization system have different film configurations, and by logically inverting the dike mouth surface as described above, the difficulty of film formation is reduced, and the short to long wavelength range is achieved. Thus, the desired characteristics can be stably obtained.

[0070] (5) For example, even in the case of laser light having the same wavelength (λ 1 = 405 nm), when switching the optical path depending on the situation, the polarization state (linearly polarized light, circularly polarized light) as in the liquid crystal SW element 623 is changed. It is advisable to provide a switching element (see Figure 10). When the polarization state is switched by the liquid crystal SW element 623, the reflection or transmission of the polarization beam splitter surface P02P is switched accordingly. For example, on the polarization beam splitter surface P02P, S-polarized light can be reflected on the forward path and transmitted on the return path, and P-polarized light can be transmitted on the forward path and reflected on the return path. In this case, for example, even laser light of the same wavelength is not transmitted in the forward path if it is linearly polarized light having only S-polarized light. On the other hand, when this laser light is switched from linearly polarized light to circularly polarized light including both S-polarized light and P-polarized light by the liquid crystal SW element 623, as shown in FIG. 10, the polarized light beam splitter surface P02P causes S-polarized light ( Outgoing light) is reflected in the outgoing path to the optical path 1 that leads to the BD objective lens 743, and P-polarized light (outgoing light) is transmitted in the outgoing path and separated to the optical path 2 that leads to the DVDZCDZHD—DVD objective lens 740. The S-polarized light (return light) and the P-polarized light (return light) that have been returned are combined and can be received by one light receiving element OEIC760. Therefore, it is possible to suitably cope with a plurality of types of optical disks.

As described above with reference to FIGS. 8 to 10, the half mirror surface P01H, the polarization beam splitter surface P02P, the first dichroic mirror surface P01D, and the second dichroic mirror surface PO 2D are arranged. Depending on the type of optical disk or the wavelength range of the laser beam, polarization processing and non-polarization processing are appropriately performed. It is possible to guide the signal light (return light) to one light receiving element OEIC760 while adopting the form of condensing the light (forward light) separately.

<<2nd example concerning arrangement of each side>>

Next, a second embodiment relating to the arrangement of each surface will be described with reference to FIG. 11 in addition to FIG. 8 to FIG. FIG. 11 is a schematic plan view showing the optical system of the second embodiment relating to the arrangement of each surface.

In FIG. 11, the optical head device 1 according to the present embodiment differs from the optical head device 1 according to the first embodiment relating to the arrangement of each surface described above in the number of prisms. Specifically, instead of the prisms P01 and P02 that are two prisms, the prism P03 that is one prism is provided, and other configurations are common. Thus, even if the number of prisms changes, the arrangement of the half mirror surface P01H, the polarization beam splitter surface P02P, the first dichroic mirror surface P01D, and the second dichroic mirror surface P02 D in each prism If they are the same, a plurality of types of optical discs can be suitably handled as in the first embodiment described above. At this time, two prisms are not necessarily required.

<<Third example of arrangement of each surface>>

Subsequently, a third embodiment relating to the arrangement of each surface will be described with reference to FIG. 12 in addition to FIG. 8 to FIG. FIG. 12 is a schematic plan view showing the optical system of the third example relating to the arrangement of the surfaces.

In FIG. 12, the optical head device 1 according to the present embodiment differs from the optical head device 1 according to the first embodiment relating to the arrangement of each surface described above in the presence / absence of a prim and the number of surfaces. , The number of laser diodes and objective lenses associated with the difference in the number of the surfaces. Specifically, the prisms P01 and P02, which are the two prisms, are not! /, The third dichroic mirror surface P03 D and the half mirror surface P03H are further provided, and the waves toward the half mirror surface P03H are provided. This is the CD objective lens 745 irradiated with the laser beam having the length λ3 and the laser beam, and other configurations are common. As described above, even if there is no prism, the arrangement of the half mirror surface P01H, the polarization beam splitter surface P02P, the first dichroic mirror surface P01D, and the second dichroic mirror surface P02D in each prism is the same as described above. As in the first embodiment, it is possible to suitably cope with a plurality of types of optical disks. in addition, If the logic for wavelength selection of the third dichroic mirror surface P03D is reversed as compared with the second dichroic mirror surface P02D and arranged so as to be diagonally opposite to each other, the laser light of wavelength λ 3 In the same manner as in the case of the laser light having the wavelength λ 2, the light is condensed by the CD objective lens 745. That is, it is possible to guide the signal light (return light) to one light receiving element OEIC 760 while adopting a form that condenses laser light (forward light) separately by three types of objective lenses with relative ease. . In this case, the number of objective lenses and surfaces that do not necessarily require the prism itself can be increased to 8, 10, and so on.

<<Fourth embodiment related to the arrangement of each surface>>

Next, a fourth embodiment relating to the arrangement of each surface will be described with reference to FIG. 13 in addition to FIG. 8 to FIG. FIG. 13 is a schematic plan view showing the optical system of the fourth example according to the arrangement of the surfaces.

In FIG. 13, the optical head device 1 according to the present embodiment is mainly different from the optical head device 1 according to the first embodiment relating to the arrangement of the surfaces described above between the surfaces. It is an optical distance. Specifically, it is not (nl + n2)-(ml + m2) force ^). In this case, the interval between the light receiving parts provided in the OEIC 760 should be the same length as (nl + n2) − (ml + m2). Or, conversely, if the intervals between the light receiving parts of the OEIC 760 are large, the distance between the surfaces is such that (nl + n2)-(ml + m2) is the same length as the distance between the light receiving parts. It is good to adjust. If the other configurations are common, even if the spacing between the surfaces or the spacing between the light receiving parts changes in this way, it is possible to cope with a plurality of types of optical discs, as in the first embodiment. It becomes. At this time, each laser beam (return light) in the OEIC 760 maintains a conjugate relationship.

<<5th Example concerning arrangement of each side>>

Next, a fifth embodiment relating to the arrangement of each surface will be described with reference to FIG. 14 in addition to FIG. 8 to FIG. FIG. 14 is a schematic plan view showing the optical system of the fifth example according to the arrangement of the surfaces.

In FIG. 14, the optical head device 1 according to the present embodiment is mainly different from the optical head device 1 according to the first embodiment relating to the arrangement of each surface described above in the configuration of the optical system. is there. Specifically, DVD / CD / HD—DVD collimator 660 and BD collimator 663, and The cylinder lens 755 is provided, and other configurations are common. Thus, even if the configuration of the optical system changes, the half mirror surface P01H, the polarization beam splitter surface P02P, the first dichroic mirror surface P01D, and the second dichroic mirror surface P02D in each prism If the arrangement is the same, a plurality of types of optical disks can be suitably handled as in the first embodiment. In particular, it is possible to guide laser light (outgoing light) of wavelength λ 1 to two different lens systems, for example, BD and HD—DVD. At this time, DVDZCDZHD—DVD collimator in each lens system. The magnification of 660 and the magnification of BD collimator 663 can be set independently. That is, a desired RIM value and coupling intensity can be set independently for each lens system. As a result, even when correcting astigmatism, the S-shaped range and the beam diameter on the OEIC 760 can be set independently. Not only the first embodiment but also the other embodiments described above can be provided with a collimator and a cylinder lens as in this embodiment.

<<Sixth embodiment related to the layout of each surface>>

Next, a sixth embodiment relating to the arrangement of each surface will be described with reference to FIG. 15 in addition to FIG. 8 to FIG. FIG. 15 is a schematic plan view showing the optical system of the sixth example according to the arrangement of the surfaces.

In FIG. 15, the optical head device 1 according to the present embodiment is mainly different from the optical head device 1 according to the first embodiment relating to the arrangement of each surface described above in that the laser beam having the wavelength λ 1 (outward path) Light). This is because, for example, the laser beam having the wavelength λ 1 incident on the polarization beam splitter surface とする 02Ρ is converted into linearly polarized light consisting of only S-polarized light, or a half mirror is used instead of the polarization beam splitter surface Ρ02Ρ (that is, Can be realized by changing the polarization processing performed on the polarization beam splitter surface Ρ02Ρ to non-polarization processing). Other configurations are common. In this way, even if the optical path of the laser beam having the wavelength λ 1 is changed, the optical path of the other (specifically, the laser beam having the wavelength 2 or 3) is the same as in the first embodiment described above. Thus, it is possible to suitably cope with a plurality of types of optical discs such as DVD, CD, and BD. In addition to the first embodiment, not only the first embodiment but also the other embodiments described above can be suitably adapted to, for example, DVD, CD, and BD by changing the optical path of the laser light having the wavelength λ 1 as in this embodiment. Become. As described above, when each surface is arranged as shown in FIGS. 8 to 15, it is possible to suitably cope with a plurality of types of optical disks.

Next, the conditions regarding the number of reflections on the half mirror surface P01H, the polarization beam splitter surface P02P, the first dichroic mirror surface P01D, the second dichroic mirror surface P02D, etc. will be described with reference to FIGS. I can see you.

The condition regarding the number of times of reflection is imposed because a plurality of objective lenses are used to cope with a plurality of types of optical disks. Specifically, a plurality of objective lenses (for example, DVD ZCDZHD—DVD objective lens 740 and BD objective lens 743) corresponding to a plurality of types of optical discs (eg, DVD, CD, BD, HD-DVD), An optical head device 1 having a single light receiving element (for example, OEIC760) capable of receiving signal light (return path light), and receiving each one of a plurality of types of signal light passing through optical paths having different objective lens strengths. This is because when receiving light with an optical element, it is necessary to project the two axes of the radial direction and the tangential direction of each optical disc so that they are the same coordinate axis on the light receiving element. This is because the tracking error, which is positional information in the radial direction, is correctly obtained in each optical disk, and in addition, the lens deflection direction in each optical disk needs to be aligned. And in order to satisfy the above-mentioned conditions regarding the axis, the optical paths are finally aligned when reaching the light receiving element, and in consideration of the direction of the image from each optical disk, The number of reflections from falling down to the force light receiving element must further satisfy the prescribed condition. That is, if the number of reflections from each optical disk (each objective lens) is N f times and Mf times, I Nf− Mf I needs to be 0 or an even number.

[0079] Therefore, if this condition, that is, the condition regarding the number of reflections that I Nf-Mf I needs to be 0 or an even number, the images do not invert each other, and the condition regarding the above-mentioned axis is satisfied. It becomes possible to deal with a plurality of types of optical discs. The specific aspect will be clarified by the following examples relating to the number of reflections.

<<First example concerning the number of reflections>>

First, the first embodiment relating to the number of reflections will be described with reference to FIG. FIG. 16 is a schematic plan view showing the optical system of the first example relating to the number of reflections. According to FIG. 16, the optical head device 1 according to this example includes two objective lenses (DVDZCDZ HD—DVD objective lens 740 and BD objective lens 743), four mirrors (mirror Ml, mirror M2). , Mirror M3, mirror M4, of which mirror M4 also functions as a half mirror) and one light-receiving element OEIC760, and each mirror has an incident angle of 45 degrees. The mirror Ml and the mirror M2 are, for example, the reflecting mirror M03 shown in FIG. 2, the mirror M3 is, for example, the first dichroic mirror surface P01D shown in FIG. 2, and the mirror M 4 is the polarization beam splitter surface P02P shown in FIG. Correspond to each. In such a configuration, if the number of reflections is calculated, I Nf -Mf I = 2-2 = 0. In other words, the above-mentioned condition regarding the number of reflections is satisfied. Therefore, according to the configuration of FIG. 16, the images do not have to be inverted, and the optical paths are finally aligned when reaching the OEIC 760, so that it can be said that it can cope with a plurality of types of optical disks.

<<Second example of the number of reflections>>

Next, a second embodiment relating to the number of reflections will be described with reference to FIG. 17 in addition to FIG. FIG. 17 is a schematic plan view showing the optical system of the second example relating to the number of reflections.

In FIG. 17, the optical head device 1 according to the present embodiment is mainly different from the optical head device 1 according to the first embodiment regarding the number of reflections described above in the number of mirrors. Specifically, two mirrors (mirror M2, mirror M4, of which mirror M4 also functions as a half mirror) are provided, and each mirror has an incident angle of 45 degrees. In such a configuration, if the number of reflections is calculated, I Nf-Mf I = 1–1 = 0. That is, the above-mentioned condition regarding the number of reflections is satisfied. Therefore, according to the configuration of FIG. 17, the images do not have to be inverted, and the optical paths are finally aligned when reaching the OEIC 760. Therefore, it can be said that it can be used for a plurality of types of optical disks.

<<Third example of the number of reflections>>

Next, a third embodiment relating to the number of reflections will be described with reference to FIG. 18 in addition to FIG. FIG. 18 is a schematic plan view showing the optical system of the third example relating to the number of reflections.

In FIG. 18, the optical head device 1 according to the present example performs the first operation related to the number of reflections described above. The main difference from the optical head device 1 according to the embodiment is the incident angle. Specifically, the incident angle from DVDZCDZHD—DVD objective lens 740 to mirror Ml and the incident angle from BD objective lens 743 to mirror M3 are not 45 degrees. In such a configuration, if the number of reflections is calculated, I Nf -Mf I = 2-2 = 0. That is, the above-mentioned condition regarding the number of reflections is satisfied. Therefore, according to the configuration of FIG. 18, the images do not have to be reversed, and the optical paths are finally aligned when reaching the OEIC 760, so it can be said that it can cope with a plurality of types of optical disks. According to the present embodiment, since the incident angle does not have to be limited to 45 degrees, the degree of freedom in designing the optical system is improved. For example, even if the beam is not shaped, it is extremely advantageous in practice because it prevents the loss of accuracy to the extreme and improves the reliability of the optical adjustment of the three beams for tracking errors.

<<Fourth embodiment related to the number of reflections>>

Next, a fourth embodiment relating to the number of reflections will be described with reference to FIG. 19 in addition to FIG. FIG. 19 is a schematic plan view showing the optical system of the fourth example according to the number of reflections.

In FIG. 19, the optical head device 1 according to the present embodiment is mainly different from the optical head device 1 according to the first embodiment relating to the number of reflections described above in addition to the return path from each optical disc as well as the forward path. Is also to be considered. Specifically, two objective lenses (DVDZCDZH D—DVD objective lens 740 and BD objective lens 743), four mirrors (mirror Ml, mirror M2, mirror M3, mirror M4, of which mirror M4 is a polarized beam It also has a single light receiving element OEIC 760 and a laser diode 603, and each mirror is configured to have an incident angle of 45 degrees. Here, since the mirror M4 also functions as a polarization beam splitter, the laser light (outgoing light) emitted from the laser diode 603 is divided into, for example, S-polarized light and P-polarized light according to the polarization state, and the two objective lenses are separated. Each led to In such a configuration, when the number of reflections is calculated, I Nf-Mf I = 2-2 = 0 for the forward path and I Nf-Mf I = 2-2 = 0 for the return path. That is, the conditions regarding the number of reflections described above are satisfied for both the forward path and the return path. Therefore, according to the configuration shown in FIG. 19, the images do not have to be inverted, and the optical paths are finally aligned when reaching the OEIC 760. Therefore, it can be said that it can be used for a plurality of types of optical disks. That is, the same The image of the light that constitutes the signal light (return light) caused by the light source is opposite between the case of using the DVD / CD / HD-DVD objective lens 740 and the case of using the BD objective lens 743. Rolling can be avoided reliably and effectively. As a result, the OEIC 760 can receive light with the highest light receiving sensitivity regardless of which type of optical disk is set.

<<5th example concerning the number of reflections>>

Next, a fifth embodiment relating to the number of reflections will be described with reference to FIG. 20 in addition to FIG. FIG. 20 is a schematic plan view showing the optical system of the fifth example relating to the number of reflections.

In FIG. 20, the optical head device 1 according to the present embodiment is mainly different from the optical head device 1 according to the first embodiment relating to the number of reflections described above in the number of objective lenses and the number of mirrors. is there. Specifically, three objective lenses (DVDZCDZHD—DVD objective lens 740, BD objective lens 743, and third objective lens 744), three mirrors (mirror M2, mirror M4, mirror M5, of which mirrors M4 and mirror M5 also function as a half mirror) and one light-receiving element OEIC760, and each mirror has an incident angle of 45 degrees. In such a configuration, when the number of reflections is first calculated for the DVDZCDZHD—DVD objective lens 740 and the BD objective lens 743, | Nf—Mf I = 2−2 = 0. That is, the above-described condition regarding the number of reflections is satisfied. Therefore, according to the configuration of FIG. 20, the DVDZCDZHD—DVD objective lens 740 and the BD objective lens 743 do not have to be reversed with each other, and in addition, the optical path is finally aligned when reaching the OEIC760. Therefore, it can be said that it can cope with a plurality of types of optical disks. However, if the number of reflections is calculated for DVD ZCDZHD—DVD objective lens 740 and third objective lens 744 or for BD objective lens 743 and third objective lens 744, I Nf-Mf I = 2— 1 = 1. In other words, the condition regarding the number of reflections described above is not satisfied, and the situation is reversed. Even in such a case, the optical system taking into account the above-mentioned conditions regarding the number of reflections is redesigned.For example, by adding an odd number of reflection mirrors on the optical path from the third objective lens 744 to the mirror M4, The above-mentioned conditions regarding the number of reflections are satisfied, and a plurality of types of optical disks can be handled. [0085] As described above with reference to FIGS. 16 to 20, by arranging each mirror so as to satisfy the above-described conditions regarding the number of reflections, signal light (return light) caused by the same light source In the case where different objective lenses are used, it is possible to reliably and effectively avoid reversing the image of the light that constitutes. Thus, the OEIC 760 can receive light with the highest light receiving sensitivity regardless of which type of optical disk is set. This makes it possible to correctly obtain the tracking error, which is positional information in the radial direction, in each optical disc, and in addition, it is possible to properly align the lens deviation direction in each optical disc, which is very advantageous in practice. .

It should be noted that the present invention is not limited to the above-described embodiments, and can be appropriately changed within the scope of the invention and the gist of the invention, which can also read the entire specification, and the spirit of the invention. An optical head device with the above is also included in the technical scope of the present invention.

Industrial applicability

The optical head device according to the present invention is compatible with a plurality of types of optical discs using the same light source, such as BD (Blu-ray Disc) and HD-DVD, and more preferably BD (Blu-ray Disc). It can also be used in optical head devices such as optical pickups that can handle multiple types of optical discs that require different light sources such as HD-DVD and DVD.

Claims

The scope of the claims

[1] An optical head device capable of supporting a plurality of types of optical disks,

Light source means capable of emitting laser light for each of the plurality of types of optical discs, and the light source means power of the laser light emitted from the plurality of types of optical discs set to the optical head device No. for focusing on the recording surface of different types of optical discs

1 objective lens,

A second objective lens for condensing the laser light emitted from the light source means on a recording surface of another type of optical disc set to the optical head device among the plurality of types of optical discs;

One light receiving element for receiving the signal light from the recording surface based on the laser light condensed on the recording surface via the first or second objective lens;

The laser light is guided to the first or second objective lens according to the type of the optical disc, and at least the signal light of the laser light and the signal light is combined with at least partial reflection. An optical system that guides the signal light to the light receiving element by performing at least one of the light separation processes according to the type of the optical disk,

The optical system has a zero difference between the number of reflections Nb from the one type of optical disk to the light receiving element and the number of reflections Mb from the other type of optical disk to the light receiving element. Or it is configured to be even!

An optical head device.

[2] The light source means includes two laser light sources for separately emitting laser light for the one type of optical disk and laser light for the other type of optical disk. 2. An optical head device according to item 1 of the range.

[3] The light source means has one laser light source that emits the laser light for the one type of optical disk and the laser light for the other type of optical disk in common.

The optical system also applies the laser light to the laser light by performing at least one of photosynthesis and light separation with partial reflection according to the type of the optical disc. The first or second objective lens according to the type of optical disc Guiding,

The optical system includes the one laser light source power and the number of reflections Nf until reaching the one type of optical disk and the one laser light source power and the number of reflections Mf until reaching the other type of optical disk. The optical head device according to claim 1, wherein the difference is zero or an even number!