WO2007114046A1

WO2007114046A1 - Optical head device

Info

Publication number: WO2007114046A1
Application number: PCT/JP2007/055644
Authority: WO
Inventors: Akira Kouno; Makoto Kawamura; Shinichi Nagahara
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 performing a polarization process or non-polarization process on the laser beam or the signal light according to the optical disc type so as to introduce the laser beam into the first or the second objective lens in accordance with the optical disc type and introduce the signal light into the light reception element. The polarization process is a light synthesis or light separation depending on the polarization state and the non-polarization process is light synthesis or light separation not depending on the polarization state.

Description

Specification

Optical head device

Technical field

TECHNICAL FIELD [0001] 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 discs that require different light sources such as a BD (Blu-ray Disc) and a DVD. .

Background art

[0002] This type of optical head device has a plurality of types of laser light sources so that different types of laser light can be emitted depending on the type of optical disc set in an optical disc player or recorder. The laser beam is configured to irradiate the optical disk through a common objective lens as a laser beam on a single optical path by passing through a beam splitter or a mirror 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, it is expected that there will be a practical problem that the essential significance as a compatible optical head device 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 light condensed on the recording surface via the first or second objective lens, the laser light and the signal At least with light On the other hand, one of the polarization treatment that is at least one of photosynthesis and light separation depending on the polarization state and the non-polarization treatment that is at least one of photosynthesis and light separation independent of the polarization state, And an optical system that guides the laser light to the first or second objective lens according to the type of the optical disc and guides the signal light to the light receiving element.

[0008] According to the optical head device of the present invention, when the optical head device is set to the optical head device, for example, one of the two or more types of optical discs, for example, blue, for example, blue Laser light power for the set optical disk such as laser is emitted from light source means such as a semiconductor laser device. This laser beam is condensed on the recording surface of the one type of optical disc by the first objective lens via the optical system. Then, the signal light based on the laser light irradiated on the recording surface by optical actions such as reflection, transmission, diffraction, refraction, and scattering on the recording surface passes through the first objective lens and the optical system, and passes through a single light. Guided to the light receiving element.

On the other hand, among two or more types of optical discs, for example, when set against another type of optical disc (eg, DVD or CD) optical head device, for example, a red laser or infrared laser Laser light power for the set optical disk such as one laser is emitted from a light source means such as a semiconductor laser device. This laser beam is condensed on the recording surface of the other type of optical disc by the second objective lens via the optical system. Then, due to the optical action on the recording surface, the signal light based on the laser light irradiated on the recording surface is guided to one light receiving element via the second objective lens and the optical system.

[0010] Here, in particular, in an optical system interposed between the light source means and the first or second objective lens, polarization processing that depends on the polarization state of laser light or signal light and non-dependence on the polarization state. It is applied to laser light and signal light according to the processing power S of polarization processing and the type of optical disc set. For example, laser light for one type of optical disk (for example, BD) is guided to the first objective lens by polarization processing such as selective reflection and transmission according to the polarization state in the polarization beam splitter. The corresponding signal light is guided to the light receiving element. Alternatively, for example, laser light for other types of optical discs (eg, DVD) is guided to the second objective lens by non-polarization processing such as reflection and transmission independent of the polarization state in the dichroic mirror or half mirror. The corresponding signal light is guided to the light receiving element.

[0011] In this manner, by appropriately using polarization processing and non-polarization processing according to the type of optical disc, a method of condensing laser light with two types of objective lenses can be made relatively easily. In this way, the signal light can be guided to one (ie, common) light receiving element. At this time, since two types of objective lenses are used, it becomes possible to obtain signal light under different optical conditions for different types of optical discs, and it is easy to relate to the reliability and optical configuration related to signal light. It is possible to increase both the efficiency and the efficiency very efficiently.

In one aspect of the optical head device of the present invention, the light source means includes a plurality of laser light sources that emit laser light for each of the plurality of types of optical disks.

[0013] According to this aspect, in the light source means, laser light for one type of optical disk and laser light for another type of optical disk are separately emitted from the initial stage. For example, the light source means

A blue laser light source and a red laser light source may be included.

[0014] However, the light source means separates the laser light for one type of optical disk and the laser light for another type of optical disk after generating one light source force, so that they are separated toward the optical system. The structure which radiates | emits may be taken. That is, the light source means may have, for example, one laser light source and a device for performing light separation, or the optical system is configured to separate the laser light from one laser light source. You can do it.

In another aspect of the optical head device of the present invention, the optical system performs reflection and transmission depending on the polarization state on a polarization beam splitter surface as at least a part of the polarization treatment, and As at least a part of the non-polarization treatment, reflection and transmission independent of the polarization state on the dichroic mirror surface or the first mirror surface are performed.

[0016] According to this aspect, for example, laser light for one type of optical disc (for example, BD) is selectively reflected or transmitted according to the polarization state of a special mirror or prism including a polarization beam splitter surface. Through this polarization process, the light is guided to the first objective lens and the corresponding signal light is guided to the light receiving element. In this case, for example, an optical member such as a λ / 2 plate or a λ / 4 plate may be arranged in the optical path 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). . On the other hand, laser light for other types of optical discs (for example, DVD, CD), such as reflection and transmission independent of the polarization state of special mirrors and prisms including dichroic mirror surfaces and noise mirror surfaces, etc. By the non-polarization process, the light is guided to the second objective lens and the corresponding signal light is guided to the light receiving element.

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.

[0018] 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 is a schematic plan view showing a state of polarization switching on the polarization beam splitter surface.

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 mirror surface

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 order for each embodiment based on the drawings.

<Configuration of optical head device> 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 An OEIC (Opto-Electron Integrated Circuit) 760 as an example of the “light receiving element” and a prism P01 and a prism P02 as examples of the “optical system” according to the present invention are provided. It constitutes a so-called multi-drive, V, which can read and write information to and from optical discs such as CD, BD or HD—DVD.

The laser diode 601 includes, for example, a semiconductor laser. 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 (ie, a non-dedicated laser beam dedicated to DVD). 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. As an example of the “common laser beam” according to the present invention, a so-called blue laser beam having a wavelength of 405 nm (ie, for BD and HD DVD) Common laser light) is emitted as forward light.

[0026] The DVD coupling lens 501 is a lens for supplying forward light emitted from the laser diode 601 to the prism P01.

[0027] 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.

[0029] The liquid crystal SW (Switch) element 623 can be switched between ON (ON) and ZOFF (OFF). For example, when ON, incident common laser light (linearly polarized light) is emitted as it is, and when OFF, incident common laser light (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.

[0031] Polarizing grating 640 for DVDZCD is a laminated structure of wavelength selective grating 6402 (CD), wavelength selective grating 6403 (DVD), and polarizing 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.

[0032] 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 in combination with the broadband 1Z4 wavelength plate 730. Reduce the amount of light.

[0033] The reflection mirror M01 and the reflection mirror M03 appropriately change the optical path of the laser beam by reflecting the irradiated laser beam.

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

[0035] Here, the half mirror surface P01H is disposed 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 signal light related thereto (return light), and the non-common laser light (outward light) and the related signal light ( This is the surface that transmits the return light. Of the common laser light, the polarization beam splitter surface P0 It is the optical path of the part that transmits 2P (for example, P-polarized light) and is disposed in the optical path of a part of the non-common laser light.

[0037] The prism P02 includes a polarization beam splitter surface P02P and a second dichroic mirror surface P0 2D.

[0038] Here, the polarization beam splitter surface P02P is disposed in the optical path of the common laser light (outward light). For example, the electric field component of the common laser light reflects S-polarized light that is perpendicular to the incident surface. 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, the signal light returning from the BD objective lens 740 (return light) is transmitted, and the signal light returning from the DVDZCDZHD—D VD objective lens 740 is reflected.

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.

[0040] DVD / CD / HD—DVD collimator 660 and BD collimator 663 convert incident laser light into parallel light.

[0041] 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.

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

[0043] The rising 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.

The liquid crystal aberration correction element 720 includes a liquid crystal, for example, and adjusts the optical path of each laser beam by utilizing 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).

[0045] The broadband 1Z4 wavelength plate 730 includes, for example, a crystal, and converts a wide-range laser beam such as a raised non-common laser beam or a common laser beam from linearly polarized light to circularly polarized light. Thus, the circularly polarized light is converted to linearly polarized light. [0046] The BD objective lens 743 focuses incident laser light (outgoing light) on the recording surface of the optical disc (BD), and signal light (return light) from the recording surface based on the collected laser light. To the OE IC760.

[0047] 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

[0048] FM (Front Monitor: FM) mirror FM0 and FM mirror FM3 are common laser light, non-common laser light, or signal light when recording or reproducing optical discs (DVD, CD, BD or HD-DVD). It is configured to guide a part of this to a front monitor (not shown).

[0049] 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 light collection rate. .

[0050] The OEIC 760 includes, for example, a photodiode, 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 this example 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 It explains using.

<<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.

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) is transmitted through the Dyke mouth prism 630, generates a sub-beam when passing through the wavelength selective grating 6403 (DV D) of the polarization grating 640 for DVDZCD, and is reflected by the reflecting mirror M01. Is done. 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 the present embodiment, information recording or reproduction is suitably performed on a DVD.

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

Subsequently, referring to FIG. 4, the optical head device 1 according to this example records information on the CD. Or the operation | movement at the time of reproducing | regenerating is demonstrated. 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.

As shown in FIG. 4, when information is recorded on or reproduced from a CD, first, the laser diode 602 is driven to, for example, a laser beam having a wavelength of 780 nm (ie, a non-common laser beam 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 suitably 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, with a laser beam having a wavelength of 405 nm (that is, for BD and HD-DVD). Common laser beam). The emitted laser light (outgoing light) is converted into S-polarized light perpendicular to the incident surface when it is incident on the polarization beam splitter surface P02P by the shaping element 613. It passes through the liquid crystal SW element 623 that has been enlarged and is switched on, and a sub-beam is generated when it passes 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 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 to circularly polarized light by the broadband 1Z4 wavelength plate 730. And the recording surface of the optical disc (BD) is irradiated by the objective lens 743 for 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 preferably performed on a 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.

[0058] 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 case of 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. Emitted The laser beam (forward 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 P02P, and after that, the same optical path as in the case of BD recording described above is taken, and the BD is passed through the BD objective lens 743 to the BD. Information reproduction is preferably performed. 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 a 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. A collimator moving stepping motor 666 and various aberrations (e.g. coma, astigmatism and spherical aberration) together with the liquid crystal aberration correction element 720. ) Is configured to correct.

The tangential and radial coma aberrations are corrected using the liquid crystal aberration correction element 720.

[0062] 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 types of aberration that may occur when dealing with a plurality of types of optical disks are preferably corrected.

As described above with reference to FIGS. 3 to 7, according to the optical head device 1 of this embodiment, it is possible to realize a so-called multi-drive that can handle a plurality of types of optical disks.

Next, among the optical head devices 1 described above, in particular, the half mirror surface P01H, the polarization beam splitter surface P02P, the first dichroic mirror surface P01D, and the second dichroic mirror surface P

The basic concept of the arrangement of each surface of 02D will be explained using 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).

[0067] (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, “logic inversion” for wavelength selection means transmission or reflection for one wavelength and transmission or reflection for another wavelength. Says that is reversed. 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 guided to one objective lens. 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.

(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. That is, the first dichroic mirror surface P01D and the second dichroic mouth It may be arranged so as to eliminate the optical path difference between a plurality of laser beams separated from the optical 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.

[0069] (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.

[0070] (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, it is difficult to make both the polarization system for blue and the non-polarization system for red with one film configuration by setting m2 and n2 to 0, respectively. 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.

[0071] (5) For example, even in the case of laser light having the same wavelength (λ 1 = 405 nm), when it is desired to switch 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 on the outgoing path to the optical path 1 that leads to the BD objective lens 743. Outgoing light) is transmitted through the outgoing path and separated into DVDZCDZHD—DVD objective lens 740, which is separated into optical path 2 respectively, and the returned S-polarized light (return light) and P-polarized light (return light) are combined 1 Light can be received by one light receiving element OEIC760. Therefore, it is possible to suitably cope with a plurality of types of optical disks.

[0072] 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 and non-polarization are appropriately performed, and the laser beam (outgoing light) is condensed separately by two types of objective lenses with relative ease. This makes it possible to guide the signal light (return light) to one light receiving element OEIC760.

<<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 regarding the arrangement of each surface described above in the presence / absence of a prim and the number of surfaces. The number of the faces The number of laser diodes and objective lenses associated with the difference. 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 inverted compared to the second dichroic mirror surface P02D and arranged so as to be diagonally opposite each other, the wavelength λ 3 This laser beam is also focused by the CD objective lens 745 in the same manner as the laser beam of wavelength λ2. 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 in that the optical head between the surfaces is different. It is a 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 has a conjugate function. The person in charge is kept.

<<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, a DVD / CD / HD—DVD collimator 660, a BD collimator 663, and a cylinder lens 755 are 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 having the wavelength λ 1 This is the optical path of light (outgoing light). This is because, for example, the laser beam having the wavelength λ 1 incident on the polarizing beam splitter surface Ρ02 とする is converted into linearly polarized light consisting of only S-polarized light, or the polarized beam splitter. Instead of the surface P02P, it can be realized by using a half mirror (ie, changing the polarization processing performed on the polarization beam splitter surface P02P 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 support 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, the number of reflections from each optical disk (each objective lens) is N If f times and Mf times, I Nf-Mf I must be 0 or even.

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 is satisfied, the images do not invert each other, and the above-described condition regarding the 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, on Satisfy the condition regarding the number of reflections described above. 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 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 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 only in the return path from each optical disk. In other words, the outbound route is also 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 functions as a presetter), and has one light receiving element OEIC760 and laser diode 603. The incident angle is 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 image of the light that constitutes the signal light (return light) caused by the same light source is different when the objective lens 740 for DVD / CD / HD-DVD is used and when the objective lens 743 for BD is used. Thus, it is possible to avoid reversing each other 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 shown in FIG. 20, the DVDZCDZHD—DVD objective lens 740 and the BD objective lens 743 do not have to be reversed with respect to each other. Since it finally comes together, 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.

[0086] 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 of the claims or 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 an optical head device such as an optical pickup capable of dealing with a plurality of types of optical disks that require different light source light such as BD (Blu-ray Disc) and DVD. Is available.

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;

For at least one of the laser light and the signal light, polarization treatment that is at least one of light synthesis and light separation depending on the polarization state and non-polarization that is at least one of light synthesis and light separation independent of the polarization state One of the processes is performed according to the type of the optical disc, whereby the laser light is guided to the first or second objective lens according to the type of the optical disc and the signal light is transmitted to the light receiving element. An optical head device comprising: an optical system that leads to

2. The optical head device according to claim 1, wherein the light source means includes a plurality of laser light sources that emit laser light for each of the plurality of types of optical disks.

[3] The optical system performs reflection and transmission depending on the polarization state on a polarization beam splitter surface as at least a part of the polarization process, and a dichroic mirror surface as at least a part of the non-polarization process. 2. The optical head device according to claim 1, wherein reflection and transmission independent of the polarization state on the half mirror surface are performed.