JPWO2008117640A1 - Lens unit for optical pickup device and optical pickup device - Google Patents

Abstract

In order to provide a lens unit for an optical pickup device and an optical pickup device that can reduce the burden on the actuator and perform highly accurate operation, the optical disk side apex of the first objective lens unit OL1 By making the distance (WD1) to the surface substantially equal to the distance (WD2) from the surface vertex on the optical information recording medium side in the second objective lens section OL2 to the CD, the burden on the actuator that drives the lens unit OE It is possible to suppress the resonance and the like, and it is possible to realize a highly accurate drive.

Description

  The present invention relates to a lens unit for an optical pickup device capable of recording and / or reproducing information on different types of optical information recording media (also referred to as optical discs), and an optical pickup device using the lens unit.

  In recent years, research and development of high-density optical disc systems that can record and / or reproduce information (hereinafter, “recording and / or reproduction” is referred to as “recording / reproduction”) using a blue-violet semiconductor laser having a wavelength of about 400 nm. Development is progressing rapidly. As an example, in an optical disc for recording / reproducing information with specifications of NA 0.85 and light source wavelength 405 nm, so-called Blu-ray Disc (hereinafter referred to as BD), DVD (NA 0.6, light source wavelength 650 nm, storage capacity 4, 7 GB) Can record information of about 25 GB per layer on an optical disc having a diameter of 12 cm, which is the same size as the above, and an optical disc for recording / reproducing information with specifications of NA 0.65 and light source wavelength 405 nm, so-called HD In a DVD (hereinafter referred to as HD), information of about 15 GB per layer can be recorded on an optical disk having a diameter of 12 cm. In the BD, since coma aberration generated due to the tilt (skew) of the optical disk increases, the protective layer is designed to be thinner than in the DVD (0.1 mm with respect to 0.6 mm of the DVD) The amount of coma due to skew is reduced. Hereinafter, in this specification, such an optical disc is referred to as a “high-density optical disc”.

  In addition, based on the reality that DVDs (digital versatile discs) and CDs (compact discs) on which a wide variety of information is recorded are currently being sold, various types of optical discs can be used with a single player. It is desired to appropriately record / reproduce information. Furthermore, considering that the optical pickup device is mounted on a notebook personal computer or the like, it is not only necessary to have compatibility with a plurality of types of optical discs, but it is important to further promote downsizing.

  Here, in the optical pickup device, it is preferable to realize compactness if it is possible to use different optical disks interchangeably using a single objective lens. However, considering the specifications of the high-density optical disk, it can be said that it is technically difficult to share the objective lens. For example, BD and HD use light beams having the same wavelength even though the protective substrate thickness is different, so that aberration correction cannot be performed using a diffractive structure, and it is difficult to share an objective lens. There is.

  Also, although DVD / CD compatible lenses have already been put into practical use, the outer diameter of compatible lenses tends to increase in order to ensure a certain degree of CD WD (working distance). Eventually, there arises a problem that the lens diameter cannot be increased to a desired size as the lens diameter increases. On the other hand, if dedicated lenses are used for DVD and CD, respectively, the DVD lens can be made small regardless of the limitation on the CD-side WD, and the thickness can be reduced particularly in the thickness direction of the pickup device. .

As described above, in the optical pickup device, in order to achieve both “compatibility” and “compact” for different optical discs and to obtain more preferable optical performance, a composite optical element in which lenses are arranged in parallel and integrally formed is used. Can be considered. Such a composite optical element has a merit that the interval between the lenses can be narrowed since the flange portion can be made common as compared with the case where two lenses molded individually are used. There is also an advantage that assembly adjustment can be simplified and cost can be reduced. An example of such a composite optical element is described in Patent Document 1.
JP-A-9-115170

  By the way, in an optical pickup device, an objective lens is generally driven for tracking and focusing by an actuator. However, since the composite optical element disclosed in Patent Document 1 has two lenses, the mass increases correspondingly, thereby increasing the burden on the actuator. In particular, when the working distance differs depending on the type of the optical disc, it is required to drive the lens within the range of the working distance corresponding to the optical disc, and the burden on the actuator due to having two lenses becomes larger. In addition, problems such as resonance may occur.

  The present invention has been made in view of the problems of the prior art, and provides a lens unit for an optical pickup device and an optical pickup device that can reduce the burden on the actuator and perform highly accurate operation. For the purpose.

  In this specification, an optical disk (also referred to as an optical information recording medium) that uses a blue-violet semiconductor laser or a blue-violet SHG laser as a light source for recording / reproducing information is generally referred to as a “high-density optical disk”, and NA0 In addition to a standard optical disc (for example, BD: Blu-ray Disc) in which information is recorded / reproduced by an objective optical system of .85 and the thickness of the protective layer is about 0.1 mm, NA 0.65 to 0.67 Information is recorded / reproduced by the objective optical system, and includes a standard optical disc (for example, HD DVD: also simply referred to as HD) having a protective layer thickness of about 0.6 mm. In addition to an optical disc having such a protective layer on its information recording surface, an optical disc having a protective film with a thickness of several to several tens of nanometers on the information recording surface, the thickness of the protective layer or protective film It also includes an optical disc with 0. In this specification, the high-density optical disk includes a magneto-optical disk that uses a blue-violet semiconductor laser or a blue-violet SHG laser as a light source for recording / reproducing information.

  Furthermore, in this specification, DVD is a generic term for DVD series optical disks such as DVD-ROM, DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW, and the like. Is a general term for CD-series optical disks such as CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW and the like. The recording density is highest for BD, and then decreases in the order of HD, DVD, and CD.

A lens unit for an optical pickup device according to claim 1 has a single or a plurality of light sources and a lens unit in which a first objective lens unit and a second objective lens unit are integrally formed. Then, the light flux from the light source is condensed on the information recording surface of the first optical information recording medium having the protective substrate thickness t1 through the first objective lens unit, so that the information is recorded on the information recording surface. Recording and / or reproduction is possible, and the light beam from the light source is condensed on the information recording surface of the second optical information recording medium having the protective substrate thickness t2 through the second objective lens unit. Thus, a lens unit for an optical pickup device capable of recording and / or reproducing information on the information recording surface,
The required numerical aperture NA1 of the first optical information recording medium is larger than the required numerical aperture NA2 of the second optical information recording medium, or the wavelength λ1 of the light beam incident on the first objective lens unit is When the wavelength of the light beam incident on the second objective lens unit is shorter than the wavelength λ2, the following expression is satisfied.
0.1 ≤ WD1 ≤ 1.5 (1)
0.1 ≦ WD2 ≦ 1.5 (2)
0.9 · WD1 ≤ WD2 ≤ 1.1 · WD1 (3)
0.76 ≦ f2 / f1 ≦ 1.46 (4)
However, WD1 (mm): the first optical information recording medium side in the first objective lens portion when a condensing spot is formed to record and / or reproduce information on the first optical information recording medium The distance WD2 (mm) from the surface vertex of the first optical information recording medium to the surface of the first optical information recording medium: when a focused spot is formed to perform information recording and / or reproduction on the second optical information recording medium, Distance f1 (mm) from the surface vertex of the second optical information recording medium side to the surface of the second optical information recording medium in the second objective lens unit: the first objective lens unit with a light beam having a wavelength λ1 Focal length f2 (mm): focal length of the second objective lens unit with a light beam having a wavelength λ1 According to the present invention, the first optical information recording in the first objective lens unit during information recording and / or reproduction First light from the top of the surface on the medium side The distance (WD1) to the surface of the information recording medium is made substantially equal to the distance (WD2) from the surface vertex on the second optical information recording medium side to the surface of the second optical information recording medium in the second objective lens unit. As a result, it is possible to suppress the burden on the actuator that drives the lens unit, and it is possible to realize high-accuracy driving by suppressing resonance and the like. Note that making WD1 and WD2 substantially equal means that the expression (3) is satisfied.

  Furthermore, by setting WD1 and WD2 to be equal to or higher than the lower limits of the expressions (1) and (2), it is possible to suppress the lens unit from interfering with the first optical information recording medium and the second optical information recording medium, (1), A compact optical pickup device can be provided by setting the value to the upper limit of the expression (2) or less. On the other hand, even if WD1 and WD2 satisfy the conditions of equations (1), (2), and (3), they are not necessarily collected properly on the information recording surfaces of the first optical information recording medium and the second optical information recording medium. It is not always possible to shine. Therefore, in the present invention, by satisfying the expression (4), even when WD1≈WD2, the light flux that has passed through the first objective lens unit is suitable for the information recording surface of the first optical information recording medium. The value of f2 / f1 is defined so that a focused spot can be formed and an appropriate focused spot can be formed on the information recording surface of the second optical information recording medium by the light beam that has passed through the second objective lens unit. .

  The first objective lens unit has a first optical surface and a second optical surface that face each other, and the curvature of the first optical surface is larger than that of the second optical surface. It is preferable that the first optical surface is on the light source side and the second optical surface is on the optical information recording medium side. Similarly, the second objective lens also has a first optical surface and a second optical surface that face each other, and the first optical surface has a larger curvature than the second optical surface.

  In this specification, “working distance (WD1, WD2)” refers to the surface vertex of the second optical surface of the objective lens unit when information is recorded / reproduced with respect to the optical information recording medium. The distance in the optical axis direction to the optical information recording medium. More specifically, the distances are shown as WD1 and WD2 in FIG. However, if it is difficult to determine the position of the surface vertex of the objective lens unit from the actual optical element, when the optical element is attached to the bobbin of the optical pickup device, the reference surface of the flange part of the optical element that contacts the bobbin The location of the second optical surface of the first objective lens portion furthest away from the (surface in contact with the bobbin) in the optical axis direction is the surface vertex, and the distance from the surface vertex to the first optical information recording medium is Similarly, the position of the second optical surface of the second objective lens portion farthest in the optical axis direction from the reference surface is defined as WD1, and the distance from the surface vertex to the second optical information recording medium is defined as WD2. It is good.

  The “optical element in which the first objective lens portion and the second objective lens portion are integrally formed” according to the present invention refers to a case where the first objective lens portion and the second objective lens portion are fused ( For example, not only when an optical element having a first objective lens part and a second objective lens part is obtained by injection molding or the like, but also, an optical element having a first objective lens part and a second objective The optical element may be an integrated optical element by separately molding an optical element having a lens portion and then fitting, adhering or engaging.

  In the present invention, the required numerical aperture NA1 of the first optical information recording medium is larger than the required numerical aperture NA2 of the second optical information recording medium, or the wavelength λ1 of the light beam incident on the first objective lens unit is It is shorter than the wavelength λ2 of the light beam incident on the second objective lens portion. Therefore, combinations of the first optical information recording medium and the second optical information recording medium to which the present invention is applied include DVD and CD, BD and DVD, BD and CD, HD and CD (NA1> NA2, and λ1 < λ2), BD and HD (λ1 = λ2, but NA1> NA2), HD and DVD (NA1 = NA2, but λ1 <λ2), and the like. The preferable values of NA and λ in each optical information recording medium are as follows.

BD: NA = 0.8 to 0.9, λ = 380 to 420 nm
(Particularly preferably, NA = 0.85, λ = 405 nm)
HD: NA = 0.5 to 0.7, λ = 380 to 420 nm
(Particularly preferably, NA = 0.65, λ = 405 nm)
DVD: NA = 0.5 to 0.7, λ = 640 to 680 nm
(Particularly preferably, NA = 0.6, λ = 655 nm)
CD: NA = 0.4-0.55, λ = 740-820 nm
(Particularly preferably, NA = 0.45 or 0.51, λ = 780 nm)
The light source of the optical pickup device will be described below. For example, when the first optical information recording medium is a BD and the second optical information recording medium is an HD, an optical pickup device may have a single light source with a wavelength of 380 to 420 nm. On the other hand, when the first optical information recording medium is a DVD and the second optical information recording medium is a CD, the optical pickup device has a first light source having a wavelength of 640 to 680 nm and a second light source having a wavelength of 740 to 820 nm. Need to be. As described above, the light source may be a single light source or a plurality of light sources depending on the type of optical information recording medium to be used.

The lens unit for an optical pickup device according to claim 2 is the following formula in the invention according to claim 1;
0.43 ≦ d1 / f1 ≦ 1.45 (5)
However, d1 (mm): The axial thickness of the first objective lens portion is satisfied.

  The on-axis thickness of the objective lens unit is the thickness of the objective lens unit on the optical axis. More specifically, for example, it refers to d1 and d2 shown in FIG.

The lens unit for an optical pickup device according to claim 3 is the following formula in the invention according to claim 1 or 2,
0.34 ≦ d2 / f2 ≦ 0.99 (6)
However, d2 (mm): The axial thickness of the second objective lens portion is satisfied.

  By setting at least one of d1 / f1 and d2 / f2 in the above range, it becomes easy to make WD1 and WD2 substantially the same.

The lens unit for an optical pickup device according to claim 4 is the following formula in the invention according to any one of claims 1 to 3.
0.24 ≦ NA1 / f1 ≦ 0.85 (7)
It is characterized by satisfying.

The lens unit for an optical pickup device according to claim 5 is the following formula in the invention according to any one of claims 1 to 4;
0.18 ≦ NA2 / f2 ≦ 0.75 (8)
It is characterized by satisfying.

  It should be noted that NA1 and NA2 in the equations (7) and (8) are preferably the actual image-side numerical apertures of the first and second objective lens portions. The required numerical aperture of the first optical information recording medium and the second optical information recording medium may be used.

The lens unit for an optical pickup device according to claim 6 is the invention according to any one of claims 1 to 5, wherein the first optical information recording medium is a DVD, The second optical information recording medium is a CD, and the following formula:
0.3 ≦ WD1 ≦ 1.5 (1 ^* )
0.3 ≦ WD2 ≦ 1.5 (2 ^* )
1.01 ≦ f2 / f1 ≦ 1.29 (4 ^* )
It is characterized by satisfying.

  By satisfying this conditional expression, not only WD1 and WD2 can be made substantially equal, but also the effective diameters of the first objective lens part and the second objective lens part can be made substantially equal, and a collimating lens or the like can be shared. .

In the following, a particularly preferable numerical range is defined for each type of optical information recording medium. First, in the above-mentioned claim 6 and the following claims 7 to 11, particularly when the first optical information recording medium is a DVD and the second optical information recording medium is a CD, A preferred numerical range is defined. In order to form a condensing spot on the information recording surface of DVD and CD while making WD substantially the same, it is preferable to satisfy the conditional expressions (1 ^* ), (2 ^* ), (4 ^* ) and (3). .

The lens unit for an optical pickup device according to claim 7 is the following formula in the invention according to claim 6;
0.4 ≦ WD1 ≦ 1.0 (1 ^** )
0.4 ≤ WD2 ≤ 1.0 (2 ^** )
1.01 ≦ f2 / f1 ≦ 1.29 (4 ^** )
It is characterized by satisfying.

The lens unit for an optical pickup device according to claim 8 is an optical pickup device according to claim 6 or 7, wherein
0.43 ≦ d1 / f1 ≦ 1.18 (5 ^* )
However, d1 (mm): The axial thickness of the first objective lens portion is satisfied.

The lens unit for an optical pickup device according to claim 9 is an optical pickup device according to any one of claims 6 to 8, in which:
0.34 ≦ d2 / f2 ≦ 0.65 (6 ^* )
However, d2 (mm): the axial thickness of the second objective lens portion is satisfied.

The lens unit for an optical pickup device according to claim 10 is an optical pickup device according to any one of claims 6 to 9, in which:
0.24 ≦ NA1 / f1 ≦ 0.77 (7 ^* )
It is characterized by satisfying.

The lens unit for an optical pickup device according to claim 11 is the following formula in the invention according to any one of claims 6 to 10.
0.18 ≦ NA2 / f2 ≦ 0.41 (8 ^* )
It is characterized by satisfying.

The lens unit for an optical pickup device according to claim 12 is the lens unit according to any one of claims 1 to 5, wherein the first optical information recording medium is a BD, and the second The optical information recording medium is HD, and the following formula:
0.1 ≤ WD1 ≤ 1.0 (1 ^*** )
0.1 ≤ WD2 ≤ 1.0 (2 ^*** )
0.77 ≦ f2 / f1 ≦ 1.23 (4 ^*** )
It is characterized by satisfying.

Next, in the above-mentioned Claim 12 and Claims 13 to 17 below, when the first optical information recording medium is BD and the second optical information recording medium is HD, A particularly preferred numerical range is defined. Conditional expressions (1 ^*** ), (2 ^*** ), (4 ^*** ) and (3) are used to form a condensed spot on the BD and HD information recording surfaces while keeping the WD substantially the same. ) Is preferably satisfied.

The lens unit for an optical pickup device according to claim 13 is an optical pickup device according to claim 12, in the invention according to claim 12,
0.5 ≤ WD1 ≤ 0.8 (1 ^*** )
0.5 ≤ WD2 ≤ 0.8 (2 ^*** )
0.77 ≦ f2 / f1 ≦ 1.23 (4 ^*** )
It is characterized by satisfying.

The lens unit for an optical pickup device according to claim 14 is the following formula in the invention according to claim 12 or 13,
1.15 ≦ d1 / f1 ≦ 1.44 (5 ^** )
However, d1 (mm): The axial thickness of the first objective lens portion is satisfied.

The lens unit for an optical pickup device according to claim 15 is an optical pickup device according to any one of claims 12 to 14, in which:
0.69 ≦ d2 / f2 ≦ 1.20 (6 ^** )
However, d2 (mm): The axial thickness of the second objective lens portion is satisfied.

The lens unit for an optical pickup device according to claim 16 is the lens unit according to any one of claims 12 to 15, in which:
0.35 ≦ NA1 / f1 ≦ 0.85 (7 ^** )
It is characterized by satisfying.

The lens unit for an optical pickup device according to claim 17 is the invention according to any one of claims 12 to 16, in which:
0.24 ≦ NA2 / f2 ≦ 0.75 (8 ^** )
It is characterized by satisfying.

Further, when the first optical information recording medium is a BD and the second optical information recording medium is a DVD,
0.2 ≤ WD1 (mm) ≤ 1.0 (1 ^****** )
0.2 ≤ WD2 (mm) ≤ 1.0 (2 ^****** )
0.79 ≤ f2 / f1 ≤ 1.02 (4 ^****** )
And it is preferable to satisfy | fill Formula (3).

Moreover, it is preferable to satisfy at least one of the following formulas.
1.15 ≦ d1 / f1 ≦ 1.44 (5 ^*** )
0.70 ≤ d2 / f2 ≤ 0.99 (6 ^*** )
0.35 ≦ NA1 / f1 ≦ 0.85 (7 ^*** )
0.28 ≦ NA2 / f2 ≦ 0.64 (8 ^*** )
More preferably, it is preferable to satisfy the four formulas (5 ^*** ), (6 ^*** ), (7 ^*** ), and (8 ^*** ).

Further, when the first optical information recording medium is HD and the second optical information recording medium is DVD, the following formula:
0.2 ≤ WD1 (mm) ≤ 1.5 (1 ^****** )
0.2 ≤ WD2 (mm) ≤ 1.5 (2 ^****** )
0.96 ≤ f2 / f1 ≤ 1.03 (4 ^****** )
And it is preferable to satisfy | fill Formula (3).

Moreover, it is preferable to satisfy at least one of the following formulas.
0.50 ≦ d1 / f1 ≦ 1.04 (5 ^*** )
0.50 ≦ d2 / f2 ≦ 0.98 (6 ^*** )
0.24 ≦ NA1 / f1 ≦ 0.57 (7 ^*** )
0.24 ≤ NA2 / f2 ≤ 0.59 (8 ^*** )
More preferably, it is preferable to satisfy four formulas (5 ^*** ), (6 ^*** ), (7 ^*** ), and (8 ^*** ).

Further, when the first optical information recording medium is HD and the second optical information recording medium is CD,
0.2 ≤ WD1 (mm) ≤ 1.5 (1 ^****** )
0.2 ≤ WD2 (mm) ≤ 1.5 (2 ^******** )
1.07 ≤ f2 / f1 ≤ 1.24 (4 ^******** )
And it is preferable to satisfy | fill Formula (3).

Moreover, it is preferable to satisfy at least one of the following formulas.
0.50 ≤ d1 / f1 ≤ 1.04 (5 ^****** )
0.34 ≦ d2 / f2 ≦ 0.59 (6 ^****** )
0.24 ≤ NA1 / f1 ≤ 0.57 (7 ^****** )
0.18 ≦ NA2 / f2 ≦ 0.38 (8 ^****** )
More preferably, it is preferable to satisfy the following four formulas (5 ^****** ), (6 ^****** ), (7 ^****** ), and (8 ^****** ).

The lens unit for an optical pickup device according to claim 18 is the lens unit according to any one of claims 1 to 17, wherein:
−0.02 <m1 <0.02 (9)
−0.02 <m2 <0.02 (10)
However, m1: magnification of the light beam emitted from the light source and incident on the first objective lens unit m2: satisfying the magnification of the light beam emitted from the light source and incident on the second objective lens unit. .

  According to the present invention, a parallel light beam or a substantially parallel light beam can be incident on the first and second objective lens portions, which is preferable. In particular, it is preferable that a parallel light beam (m1, m2 = 0) is incident on the first and second objective lens portions. However, the present invention is not limited to a mode in which a parallel light beam is incident on the objective lens unit, and can also be applied to a mode in which a divergent light beam or a convergent light beam is incident on the objective lens unit.

  The lens unit for an optical pickup device according to claim 19 is the invention according to any one of claims 1 to 18, wherein the first objective lens section and the second objective lens are used. At least one of the lenses has only an aspherical refracting optical surface.

  The lens unit for an optical pickup device according to claim 20 is the lens unit according to claim 19, wherein both the first objective lens portion and the second objective lens portion are aspherical surfaces. It has only the optical surface of the refracting surface.

In the lens unit of the present invention, the first objective lens unit and the second objective lens unit are both dedicated lenses (object lenses corresponding to only one kind of optical information recording medium using a certain wavelength in one objective lens unit). It may be a compatible lens (an objective lens corresponding to a plurality of types of optical information recording media with one objective lens unit), or a combination of a compatible lens and a dedicated lens. Particularly preferably, when both the first objective lens portion and the second objective lens portion are dedicated lenses, the effect that can be achieved by satisfying the conditional expression of the present invention becomes more remarkable. When the first objective lens unit or the second objective lens unit is a dedicated lens, it is preferable that both the first optical surface and the second optical surface are aspherical refractive surfaces. An optical path difference providing structure that reduces aberrations that occur when the wavelength is changed may be provided within the effective diameter, or an optical path difference providing structure for flaring a light beam outside the effective diameter may be provided outside the effective diameter. . When the first objective lens unit or the second objective lens unit is a compatible lens, the optical information recording medium having the highest recording density among the optical information recording media supported by the objective lens unit is selected as the first objective lens unit. It shall be regarded as an optical information recording medium and a second optical information recording medium. For example, when the first objective lens unit is a BD and HD compatible lens and the second objective lens unit is a DVD and CD compatible lens, the first optical information recording medium is a BD, and the second The optical information recording medium is a DVD, and conditional expressions (1 ^*** ), (2 ^*** ), (3), (4 ^*** ), (5 ^*** ), ( 6 ^*** ), (7 ^*** ), and (8 ^*** ) are preferably satisfied.

  The lens unit for an optical pickup device according to claim 21 is the invention according to any one of claims 1 to 20, wherein the first objective lens section and the second objective lens are used. The lens portion is integrally formed by integral molding.

  The lens unit for an optical pickup device according to claim 22 is the invention according to any one of claims 1 to 20, wherein the first objective lens section and the second objective lens are the same. The lens part is engaged and formed integrally.

  FIG. 3 shows an example of a lens unit in which the first objective lens portion and the second objective lens portion are integrally formed by engagement. A first example is shown in FIG. The second objective lens portion OL2 made of plastic forms an opening HL having a stepped portion ST in the rectangular plate-shaped flange portion FL2, and the flange portion FL1 is held by the stepped portion ST in the opening HL. In this way, the first objective lens portion OL1 made of glass or plastic is assembled from the optical axis direction and integrated by bonding or the like, and the first objective lens portion OL1 and the second objective lens portion OL2 are arranged in parallel. Thus, the optical element OE is formed.

  Another example is shown in FIG. The plastic second objective lens portion OL2 forms a notch CT2 having a step portion in the rectangular plate-like flange portion FL2, and the flange portion FL1 is held by the step portion in the notch CT2. Then, the first objective lens portion OL1 made of glass or plastic is assembled from the direction orthogonal to the optical axis and integrated by bonding or the like, and the first objective lens portion OL1 and the second objective lens portion OL2 are arranged in parallel. The formed optical element OE is formed.

  As shown in FIG. 3C, the flange portion FL1 of the first objective lens OL1 may be supported on the upper surface of the flange portion FL2 without forming a step in the opening HL or the notch CT2. Alternatively, although not shown, the first objective lens portion OL1 made of glass or plastic and the second objective lens portion OL2 made of plastic may be integrated by being assembled to a holding member which is a separate member. good. In any case, it is preferable that the holding member has an opening, and the objective lens unit is fitted therein.

  Note that either the first objective lens unit or the second objective lens unit may be a glass lens and the other may be a plastic lens, or both the first objective lens unit and the second objective lens unit may be plastic lenses or It may be a glass lens.

  The first objective lens unit, the second objective lens unit, and the holding member are all separate members, and the flat plate-like holding member holds and fixes the first objective lens unit and the second objective lens unit. By doing so, the lens unit may be configured. This aspect is also considered as an example of “the first objective lens portion and the second objective lens portion are integrally formed by engagement”.

  A lens unit for an optical pickup device according to a twenty-third aspect of the present invention is the lens unit according to any one of the first to twenty-second aspects, wherein the first objective lens portions are opposed to each other. And the second objective lens portion has a first optical surface and a second optical surface that face each other, and the first objective lens portion and the second optical surface. The first optical surface of the objective lens unit has a larger curvature than the second optical surface of the first objective lens unit and the second objective lens unit, and the second optical surface of the first objective lens unit The height in the optical axis direction of the surface vertex of the second optical surface and the surface vertex of the second optical surface of the second objective lens unit are equal.

The lens unit for an optical pickup device according to claim 24 is the lens unit according to any one of claims 1 to 23, wherein the first objective lens portions are opposed to each other. And the second objective lens portion has a first optical surface and a second optical surface that face each other, and the first objective lens portion and the second optical surface. The first optical surface of the objective lens unit has a larger curvature than the second optical surface of the first objective lens unit and the second objective lens unit, and satisfies the following conditional expression: .
1.0 ≦ {(Φ11 / SAG11) × (Φ12 / SAG12)} / {(Φ21 / SAG21) × (Φ22 / SAG22)} ≦ 1.6 (11)
Φ11 (mm): effective radius of the first optical surface of the first objective lens portion Φ12 (mm): effective radius of the second optical surface of the first objective lens portion Φ21 (mm): the above Effective radius Φ22 (mm) of the first optical surface of the second objective lens unit: Effective radius SAG11 (mm) of the second optical surface of the second objective lens unit: the first objective lens unit Sag amount SAG12 (mm) of the first optical surface: Sag amount SAG21 (mm) of the second optical surface of the first objective lens unit: The first optical of the second objective lens unit Surface sag amount SAG22 (mm): Sag amount of the second optical surface of the second objective lens unit. Thereby, coma aberration can be suppressed and image height characteristics can be improved.

  Here, the effective radius and the sag amount will be described. FIG. 8 is a cross-sectional view of the OL of the objective lens unit, where the light source side optical surface (first optical surface) is S1, and the optical disk side optical surface (second optical surface) is S2. In FIG. 8, when a light beam is incident on the objective lens section OL, the outer edge radius of the light beam incident on the optical surface S1 is the effective radius φ1 of the first optical surface, and the outer edge radius of the light beam emitted from the optical surface S2 is the first radius. The effective radius φ2 of the optical surface 2 and the optical axis direction distance from the surface vertex P1 of the optical surface S1 to the outer edge of the light beam incident on the optical surface S1 are defined as the sag amount SAG1 of the first optical surface, and the surface of the optical surface S2 The distance in the optical axis direction from the vertex P2 to the outer edge of the light beam emitted from the optical surface S2 is defined as the sag amount SAG2 of the second optical surface. However, the sag amount is positive in the direction from the light source toward the optical disk. Therefore, in the example shown in FIG. 8, SAG1 has a positive value and SAG2 has a negative value.

The lens unit for an optical pickup device according to claim 25 is the lens unit according to any one of claims 6 to 11, wherein the first objective lens portions are opposed to each other. And the second objective lens portion has a first optical surface and a second optical surface that face each other, and the first objective lens portion and the second optical surface. The first optical surface of the objective lens unit has a larger curvature than the second optical surface of the first objective lens unit and the second objective lens unit, and the first optical information recording medium is a DVD. The two-optical information recording medium is a CD and satisfies the following conditional expression.
1.1 ≦ {(Φ11 / SAG11) × (Φ12 / SAG12)} / {(Φ21 / SAG21) × (Φ22 / SAG22)} ≦ 1.6 (12)
Φ11 (mm): effective radius of the first optical surface of the first objective lens portion Φ12 (mm): effective radius of the second optical surface of the first objective lens portion Φ21 (mm): the above Effective radius Φ22 (mm) of the first optical surface of the second objective lens unit: Effective radius SAG11 (mm) of the second optical surface of the second objective lens unit: the first objective lens unit Sag amount SAG12 (mm) of the first optical surface: Sag amount SAG21 (mm) of the second optical surface of the first objective lens unit: The first optical of the second objective lens unit Surface sag amount SAG22 (mm): Sag amount of the second optical surface of the second objective lens unit. Thereby, coma aberration can be suppressed and image height characteristics can be improved.

The lens unit for an optical pickup device according to claim 26, in the invention according to any one of claims 12 to 17, wherein the first objective lens portions are opposed to each other. And the second objective lens portion has a first optical surface and a second optical surface facing each other, and the first objective lens portion and the second optical surface. The first optical surface of the objective lens unit has a larger curvature than the second optical surface of the first objective lens unit and the second objective lens unit, and the first optical information recording medium is a BD. The second optical information recording medium is HD, and satisfies the following conditional expression.
1.0 ≦ {(Φ11 / SAG11) × (Φ12 / SAG12)} / {(Φ21 / SAG21) × (Φ22 / SAG22)} ≦ 1.2 (13)
Φ11 (mm): effective radius of the first optical surface of the first objective lens portion Φ12 (mm): effective radius of the second optical surface of the first objective lens portion Φ21 (mm): the above Effective radius Φ22 (mm) of the first optical surface of the second objective lens unit: Effective radius SAG11 (mm) of the second optical surface of the second objective lens unit: the first objective lens unit Sag amount SAG12 (mm) of the first optical surface: Sag amount SAG21 (mm) of the second optical surface of the first objective lens unit: The first optical of the second objective lens unit Surface sag amount SAG22 (mm): Sag amount of the second optical surface of the second objective lens unit. Thereby, coma aberration can be suppressed and image height characteristics can be improved.

  According to the invention described in claims 24 to 26, when any one of the expressions (11) to (13) is satisfied, the sine condition is satisfied, the coma is suppressed, and the image height is suppressed. It is possible to improve the characteristics.

  The optical pickup device according to claim 27 uses the lens unit for an optical pickup device according to any one of claims 1 to 26.

  ADVANTAGE OF THE INVENTION According to this invention, the lens unit for optical pick-up apparatuses and the optical pick-up apparatus which can reduce the burden of an actuator and can perform a highly accurate operation | movement can be provided.

It is a figure which shows schematic structure of optical pick-up apparatus PU1. It is sectional drawing of the lens unit used by this Embodiment, and has shown (a) at the time of DVD use, and (b) at the time of CD use. It is a figure which shows the example of the lens unit which engages and forms the 1st objective lens part and the 2nd objective lens part integrally. 2 is a cross-sectional view of an objective lens unit for DVD (a) and an objective lens unit for CD (b) according to Example 1. FIG. FIG. 7 is a cross-sectional view of a DVD objective lens section (a) and a CD objective lens section (b) according to Example 4; It is sectional drawing of the objective-lens part (a) for DVD concerning Example 11, and the objective-lens part (b) for CD. FIG. 16 is a cross-sectional view of a DVD objective lens section (a) and a CD objective lens section (b) according to Example 16; It is sectional drawing of an objective lens part.

Explanation of symbols

AC1 2-axis actuator AC2 1-axis actuator BS beam splitter COL1 first collimator COL2 second collimator HL1 first hologram laser HL2 second hologram laser OL1 first objective lens section OL2 second objective lens section PL1 protective substrate PL2 protection Substrate PU1 Optical pickup device RL1 Information recording surface RL2 Information recording surface

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiment, a case where the first optical information recording medium is a DVD and the second optical information recording medium is a CD will be described. The optical pickup device PU1 according to the present embodiment can be incorporated in an optical disk drive device. FIG. 1 is a diagram showing a schematic configuration of the optical pickup device PU1.

  The optical pickup device PU1 is a light emitting unit in which a first light source that emits a laser light beam (first light beam) of λ1 = 655 nm and a photodetector are emitted when information is recorded / reproduced on a DVD. A first hologram laser HL1 that is a light source unit-integrated light source unit and a second light source that emits a laser beam (second beam) of λ2 = 785 nm that is emitted when information is recorded / reproduced with respect to a CD. And a second hologram laser HL2 which is a light source unit / light receiving unit integrated light source unit integrated with a photodetector.

  Further, the lens unit OE held by the holding member H has a first objective lens portion OL1 and a second objective lens portion OL2 each having only an optical surface of an aspherical refractive surface, as shown in FIG. As described above, the working distance WD1 of the first objective lens portion OL1 (the distance between the second optical surface S2 on the optical disc side of the first objective lens portion OL1 and the DVD) is the working distance WD2 of the second objective lens portion OL2. (The distance between the second optical surface S2 on the optical disc side of the second objective lens section OL2 and the CD) is substantially equal. Further, as shown in FIGS. 2A and 2B, in the lens unit OE, the surface vertex P12 of the second optical surface of the first objective lens section OL1 and the second of the second objective lens section OL2 are used. The height of the surface vertex P22 of the optical surface in the optical axis direction is equal.

  When recording / reproducing information with respect to the DVD in the optical pickup device PU1, the holding member H is moved to the position shown in FIG. 1, the first objective lens portion OL1 is inserted into the optical path, and the first The first light source of the hologram laser HL1 is caused to emit light. The divergent light beam emitted from the first light source is converted into a parallel light beam by the first collimator COL1, as shown by the solid line in FIG. 1, passes through the beam splitter BS, and the first objective lens unit. After entering the OL 1 in the state of parallel light, it becomes a spot formed on the information recording surface RL 1 via the protective substrate PL 1 of the DVD. The lens unit OE having the first objective lens portion OL1 is driven together with the holding member H by the biaxial actuator AC1 to perform focusing and tracking.

  The reflected light beam modulated by the information pits on the information recording surface RL1 is again transmitted through the first objective lens section OL1, the beam splitter BS, and the first collimator COL1, and then enters the photodetector of the first hologram laser HL1. . And the information recorded on DVD can be read using the output signal of a photodetector.

  When recording / reproducing information with respect to the CD in the optical pickup device PU1, the holding member H is moved from the position shown in FIG. 1, the second objective lens portion OL2 is inserted into the optical path, and the second The second light source of the hologram laser HL2 is caused to emit light. The divergent light beam emitted from the second light source is converted into a parallel light beam by the second collimator COL2 and reflected by the beam splitter BS as depicted by the dotted line in FIG. 1, and the second objective lens unit. After entering the OL2 in the state of parallel light, it becomes a spot formed on the information recording surface RL2 via the CD protective substrate PL2. The lens unit OE having the second objective lens section OL2 is driven together with the holding member H by the biaxial actuator AC1 to perform focusing and tracking.

The reflected light beam modulated by the information pits on the information recording surface RL2 again passes through the second objective lens section OL2, is reflected by the beam splitter BS, passes through the second collimator COL2, and then passes through the second hologram laser HL2. The light enters the photodetector. And the information recorded on CD can be read using the output signal of a photodetector. In addition to this, the objective lens unit capable of forming a focused spot on any of the four types of optical disks of BD, HD, DVD, and CD can be arbitrarily combined in the lens knit.
(Example)
Hereinafter, an example suitable as the above-described lens unit will be described. The following objective lens portions are all dedicated lenses, have an aspherical refracting surface, and do not have an optical path difference providing structure.

  First, Table 1 and Table 2 show lens data of the second objective lens unit for CD and the first objective lens unit for DVD, as in the above-described embodiment. In this embodiment, all the light beams are incident on the objective lens unit as parallel light beams, and the conditions under which CDs and DVDs can be recorded / reproduced are examined. According to Tables 1 and 2, the working distances WD1 and WD2 in the first objective lens part and the second objective lens part are set to the same value, and the working distance WD is in the range of 0.1 to 1.0 (mm). When changed, f2 / f1 is 1.011 to 1.460, d2 / f2 is 0.344 to 0.641, d1 / f1 is 0.435 to 1.171, and NA2 / f2 Is 0.219 to 0.408, and NA1 / f1 is 0.283 to 0.761. A sectional view of the objective lens portion for DVD according to Example 1 (WD = 0.1 mm) shown in Table 1 is shown in FIG. 4A, and a sectional view of the objective lens portion for CD is shown in FIG. 4B. . FIG. 5A shows a sectional view of an objective lens portion for DVD according to Example 4 (WD = 0.3 mm) shown in Table 1, and FIG. 5B shows a sectional view of an objective lens portion for CD. FIG. 6A shows a sectional view of the objective lens portion for DVD according to Example 11 (WD = 0.5 mm) shown in Table 2, and FIG. 6B shows a sectional view of the objective lens portion for CD. . FIG. 7A shows a cross-sectional view of the objective lens portion for DVD according to Example 16 (WD = 1.0 mm) shown in Table 2, and FIG. 7B shows a cross-sectional view of the objective lens portion for CD. . In each figure, the parallel plane behind the objective lens portion is a protective substrate.

  Next, Tables 3 and 4 show lens data of another example of the second objective lens unit for CD and the first objective lens unit for DVD. In this embodiment, the on-axis thicknesses d1 and d2 of the objective lens portion are changed from the examples in Tables 1 and 2 for examination. Also in this embodiment, all the light beams are incident on the objective lens unit as parallel light beams, and the conditions under which CDs and DVDs can be recorded / reproduced are examined. According to Tables 3 and 4, the working distances WD1 and WD2 in the first objective lens unit and the second objective lens unit are set to the same value, and the working distance is changed in a range of 0.2 to 1.5 (mm). F2 / f1 is 1.071 to 1.275, d2 / f2 is 0.343 to 0.589, d1 / f1 is 0.503 to 0.971, and NA2 / f2 is It is 0.182 to 0.376, and NA1 / f1 is 0.249 to 0.587. However, although there is an example where the values of WD1 and WD2 are not the same, 0.9 · WD1 ≦ WD2 ≦ 1.1 · WD1 is satisfied and is within the scope of the present invention.

  Table 5 shows results of extracting three examples from the examples shown in Tables 3 and 4 and examining conditions that satisfy the sine condition. Three extracted examples are those having the working distance WD = 0.3 shown in Table 3, WD = 0.5 and f2 / f1 = 1.275, and WD = 1.5 shown in Table 4. Is. According to Table 5, when the working distances WD1 and WD2 in the first objective lens unit and the second objective lens unit are set to the same value and the working distance WD is changed within a range of 0.3 to 1.5 (mm) Further, the effective radius Φ11 of the first optical surface of the first objective lens unit is 0.783 to 1.697, and the effective radius Φ12 of the second optical surface of the first objective lens unit is 0.583 to The effective radius Φ21 of the first optical surface of the second objective lens portion is 0.741 to 1.423, and the effective radius Φ22 of the second optical surface of the second objective lens portion is 1.614. 0.626 to 1.348. The sag amount SAG11 of the first optical surface of the first objective lens unit is 0.417 to 1.048, and the sag amount SAG12 of the second optical surface of the first objective lens unit is -0.086. The sag amount SAG21 of the first optical surface of the second objective lens unit is 0.291 to 0.627, and the sag amount of the second optical surface of the second objective lens unit is SAG22 is -0.084 to -0.064. Therefore, the value of {(Φ11 / SAG11) × (Φ12 / SAG12)} / {(Φ21 / SAG21) × (Φ22 / SAG22)} is 1.199 to 1.524.

For one of the examples shown in Table 3 (WD = 0.51 (DVD), 0.48 (CD), f1 = 1.308 mm, f2 = 1.667 mm), lens data indicating the shape of the objective lens portion is shown. Table 6 shows. The optical surface of each objective lens portion is formed as an aspherical surface that is symmetric about the optical axis and is defined by a mathematical expression in which the coefficients shown in Table 6 are substituted into Expression (X). In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻³ ) is expressed using E (for example, 2.5 × E−3).
z = (y ² / R) / [1 + √ {1− (κ + 1) (y / R) ² }] + A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰ + A ₁₂ y ¹² + A ₁₄ y ¹⁴ + A ₁₆ y ¹⁶ + A ₁₈ y ¹⁸ + A ₂₀ y ²⁰ (X)
However,
z: Aspherical shape (distance in the direction along the optical axis from the plane that contacts the apex of the aspherical surface)
y: Distance from optical axis R: Radius of curvature κ: Conic coefficient A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ , A ₁₄ , A ₁₆ , A ₁₈ , A ₂₀ : Aspheric coefficient

  Table 7 shows lens data of the second objective lens unit for HD and the first objective lens unit for BD. Also in this embodiment, all the light beams are incident on the objective lens unit as parallel light beams, and the conditions under which HD and BD can be recorded / reproduced are examined. According to Table 7, when the working distances WD1 and WD2 in the first objective lens unit and the second objective lens unit are set to the same value, and the working distance WD is changed within a range of 0.1 to 1.0 (mm). Further, f2 / f1 is 0.778 to 1.221, d2 / f2 is 0.695 to 1.100, d1 / f1 is 1.153 to 1.434, and NA2 / f2 is 0.8. 248 to 0.748, and NA1 / f1 is 0.360 to 0.847.

  Table 8 shows results of extracting three examples from the examples shown in Table 7 and examining conditions that satisfy the sine condition. The three extracted examples are those having the working distance WD = 0.3 shown in Table 7, f2 / f1 = 1.214 with WD = 0.5, and f2 / f1 = 1. 111. According to Table 8, when the working distances WD1 and WD2 in the first objective lens part and the second objective lens part are set to the same value, and the working distance WD is changed within a range of 0.3 to 0.8 (mm) The effective radius Φ11 of the first optical surface of the first objective lens unit is 1.100 to 2.000, and the effective radius Φ12 of the second optical surface of the first objective lens unit is 0.684 to 1.458, the effective radius Φ21 of the first optical surface of the second objective lens portion is 1.000 to 1.700, and the effective radius Φ22 of the second optical surface of the second objective lens portion is 0.582 to 1.007. The sag amount SAG11 of the first optical surface of the first objective lens unit is 0.942 to 1.762, and the sag amount SAG12 of the second optical surface of the first objective lens unit is -0.086. The sag amount SAG21 of the first optical surface of the second objective lens unit is 0.514 to 0.890, and the sag amount of the second optical surface of the second objective lens unit is SAG22 is -0.095 to -0.059. Therefore, the value of {(Φ11 / SAG11) × (Φ12 / SAG12)} / {(Φ21 / SAG21) × (Φ22 / SAG22)} is 1.052 to 1.153.

  Table 9 shows lens data indicating the shape of the objective lens portion for one of the examples in Table 7 (WD = 0.56, f1 = 1.664 mm, f2 = 2.153 mm). The optical surface of each objective lens portion is formed as an aspherical surface that is axisymmetric about the optical axis and is defined by a mathematical formula in which the coefficient shown in Table 9 is substituted into the above-described formula (X).

  Table 10 shows lens data of the second objective lens unit for DVD and the first objective lens unit for BD. Also in this embodiment, all the light beams are incident on the objective lens unit as parallel light beams, and the conditions under which DVD / BD can be recorded / reproduced are examined. According to Table 10, when the working distances WD1 and WD2 in the first objective lens unit and the second objective lens unit are set to the same value and the working distance WD is changed in the range of 0.2 to 1.0 (mm) F2 / f1 is 0.794 to 1.017, d2 / f2 is 0.705 to 0.981, d1 / f1 is 1.153 to 1.434, and NA2 / f2 is 0. 284 to 0.637, and NA1 / f1 is 0.362 to 0.847.

  Next, Table 11 shows lens data of the second objective lens unit for DVD and the first objective lens unit for HD. Also in this embodiment, all the light beams are incident on the objective lens unit as parallel light beams, and the conditions under which DVD / HD can be recorded / reproduced are examined. According to Table 11, when the working distances WD1 and WD2 in the first objective lens part and the second objective lens part are set to the same value, and the working distance WD is changed in the range of 0.2 to 1.3 (mm) F2 / f1 is 0.961 to 1.022, d2 / f2 is 0.503 to 0.971, d1 / f1 is 0.517 to 1.039, and NA2 / f2 is 0. 279 to 0.587, and NA1 / f1 is 0.277 to 0.564.

  Table 12 shows lens data of the second objective lens unit for CD and the first objective lens unit for HD. Also in this embodiment, all the light beams are incident on the objective lens unit as a parallel light beam, and the conditions under which CD and HD can be recorded / reproduced are examined. According to Table 12, when the working distances WD1 and WD2 in the first objective lens unit and the second objective lens unit are set to the same value, and the working distance WD is changed in the range of 0.2 to 1.5 (mm) F2 / f1 is 1.070 to 1.236, d2 / f2 is 0.343 to 0.589, d1 / f1 is 0.503 to 1.039, and NA2 / f2 is 0.00. 182-0.376, and NA1 / f1 is 0.249-0.564.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be appropriately changed or improved.

Claims (27)

A single or a plurality of light sources, and a lens unit in which a first objective lens unit and a second objective lens unit are integrally formed, and a light beam from the light source is transmitted through the first objective lens unit. By focusing the light on the information recording surface of the first optical information recording medium having the protective substrate thickness t1, information can be recorded and / or reproduced on the information recording surface, and the light flux from the light source Can be recorded on and / or reproduced from the information recording surface by focusing the light onto the information recording surface of the second optical information recording medium having the protective substrate thickness t2 through the second objective lens unit. A lens unit for an optical pickup device,
The required numerical aperture NA1 of the first optical information recording medium is larger than the required numerical aperture NA2 of the second optical information recording medium, or the wavelength λ1 of the light beam incident on the first objective lens unit is A lens unit for an optical pickup device characterized by satisfying the following expression when shorter than a wavelength λ2 of a light beam incident on the second objective lens portion.
0.1 ≤ WD1 ≤ 1.5 (1)
0.1 ≦ WD2 ≦ 1.5 (2)
0.9 · WD1 ≤ WD2 ≤ 1.1 · WD1 (3)
0.76 ≦ f2 / f1 ≦ 1.46 (4)
However, WD1 (mm): the first optical information recording medium side in the first objective lens portion when a condensing spot is formed to record and / or reproduce information on the first optical information recording medium The distance WD2 (mm) from the surface vertex of the first optical information recording medium to the surface of the first optical information recording medium: when a focused spot is formed to perform information recording and / or reproduction on the second optical information recording medium, Distance f1 (mm) from the surface vertex of the second optical information recording medium side to the surface of the second optical information recording medium in the second objective lens unit: the first objective lens unit with a light beam having a wavelength λ1 Focal length f2 (mm): focal length of the second objective lens unit with a light beam having a wavelength λ2. The lens unit for an optical pickup device according to claim 1, wherein the following expression is satisfied.
0.43 ≦ d1 / f1 ≦ 1.45 (5)
Where d1 (mm): axial thickness of the first objective lens portion The lens unit for an optical pickup device according to claim 1 or 2, wherein the following expression is satisfied.
0.34 ≦ d2 / f2 ≦ 1.10 (6)
Where d2 (mm): axial thickness of the second objective lens portion The lens unit for an optical pickup device according to any one of claims 1 to 3, wherein the following expression is satisfied.
0.24 ≦ NA1 / f1 ≦ 0.85 (7) The lens unit for an optical pickup device according to any one of claims 1 to 4, wherein the following expression is satisfied.
0.18 ≦ NA2 / f2 ≦ 0.75 (8) The first optical information recording medium is a DVD, and the second optical information recording medium is a CD;
The lens unit for an optical pickup device according to any one of claims 1 to 5, wherein the following expression is satisfied.
0.3 ≦ WD1 ≦ 1.5 (1 ^* )
0.3 ≦ WD2 ≦ 1.5 (2 ^* )
1.01 ≦ f2 / f1 ≦ 1.29 (4 ^* ) The lens unit for an optical pickup device according to claim 6, wherein the following expression is satisfied.
0.4 ≦ WD1 ≦ 1.0 (1 ^** )
0.4 ≤ WD2 ≤ 1.0 (2 ^** )
1.01 ≦ f2 / f1 ≦ 1.29 (4 ^** ) The lens unit for an optical pickup device according to claim 6 or 7, wherein the following expression is satisfied.
0.43 ≦ d1 / f1 ≦ 1.18 (5 ^* )
Where d1 (mm): axial thickness of the first objective lens unit The lens unit for an optical pickup device according to any one of claims 6 to 8, wherein the following expression is satisfied.
0.34 ≦ d2 / f2 ≦ 0.65 (6 ^* )
Where d2 (mm): axial thickness of the second objective lens section The lens unit for an optical pickup device according to any one of claims 6 to 9, wherein the following expression is satisfied.
0.24 ≦ NA1 / f1 ≦ 0.77 (7 ^* ) The lens unit for an optical pickup device according to any one of claims 6 to 10, wherein the following expression is satisfied.
0.18 ≦ NA2 / f2 ≦ 0.41 (8 ^* ) The first optical information recording medium is a BD; the second optical information recording medium is an HD;
The lens unit for an optical pickup device according to any one of claims 1 to 5, wherein the following expression is satisfied.
0.1 ≤ WD1 ≤ 1.0 (1 ^*** )
0.1 ≤ WD2 ≤ 1.0 (2 ^*** )
0.77 ≦ f2 / f1 ≦ 1.23 (4 ^*** ) The lens unit for an optical pickup device according to claim 12, wherein the following expression is satisfied.
0.5 ≤ WD1 ≤ 0.8 (1 ^*** )
0.5 ≤ WD2 ≤ 0.8 (2 ^*** )
0.77 ≦ f2 / f1 ≦ 1.23 (4 ^*** ) The lens unit for an optical pickup device according to claim 12 or 13, wherein the following expression is satisfied.
1.15 ≦ d1 / f1 ≦ 1.44 (5 ^** )
Where d1 (mm): axial thickness of the first objective lens portion The lens unit for an optical pickup device according to any one of claims 12 to 14, wherein the following expression is satisfied.
0.69 ≦ d2 / f2 ≦ 1.20 (6 ^** )
Where d2 (mm): axial thickness of the second objective lens portion The lens unit for an optical pickup device according to any one of claims 12 to 15, wherein the following expression is satisfied.
0.35 ≦ NA1 / f1 ≦ 0.85 (7 ^** ) The lens unit for an optical pickup device according to any one of claims 12 to 16, wherein the following expression is satisfied.
0.24 ≦ NA2 / f2 ≦ 0.75 (8 ^** ) The lens unit for an optical pickup device according to any one of claims 1 to 17, wherein the following expression is satisfied.
−0.02 <m1 <0.02 (9)
−0.02 <m2 <0.02 (10)
Where m1: magnification of the light beam emitted from the light source and incident on the first objective lens unit m2: magnification of the light beam emitted from the light source and incident on the second objective lens unit   19. At least one of the first objective lens part and the second objective lens part has only an aspherical refracting optical surface, according to any one of claims 1 to 18. A lens unit for the optical pickup device described.   20. The lens unit for an optical pickup device according to claim 19, wherein both the first objective lens portion and the second objective lens portion have only an aspherical refracting optical surface. .   21. The light according to any one of claims 1 to 20, wherein the first objective lens portion and the second objective lens portion are integrally formed by integral molding. Lens unit for pickup device.   21. The light according to claim 1, wherein the first objective lens part and the second objective lens part are integrally formed by engaging with each other. Lens unit for pickup device. The first objective lens unit has a first optical surface and a second optical surface facing each other, and the second objective lens unit has a first optical surface and a second optical surface facing each other. The first optical surfaces of the first objective lens unit and the second objective lens unit have a curvature that is greater than the second optical surfaces of the first objective lens unit and the second objective lens unit. big,
The height in the optical axis direction of the surface vertex of the second optical surface of the first objective lens portion and the surface vertex of the second optical surface of the second objective lens portion are equal. A lens unit for an optical pickup device according to any one of claims 1 to 22. The first objective lens unit has a first optical surface and a second optical surface facing each other, and the second objective lens unit has a first optical surface and a second optical surface facing each other. The first optical surfaces of the first objective lens unit and the second objective lens unit have a curvature that is greater than the second optical surfaces of the first objective lens unit and the second objective lens unit. The lens unit for an optical pickup device according to any one of claims 1 to 23, which is large and satisfies the following conditional expression.
1.0 ≦ {(Φ11 / SAG11) × (Φ12 / SAG12)} / {(Φ21 / SAG21) × (Φ22 / SAG22)} ≦ 1.6 (11)
Φ11 (mm): effective radius of the first optical surface of the first objective lens portion Φ12 (mm): effective radius of the second optical surface of the first objective lens portion Φ21 (mm): the above Effective radius Φ22 (mm) of the first optical surface of the second objective lens unit: Effective radius SAG11 (mm) of the second optical surface of the second objective lens unit: the first objective lens unit Sag amount SAG12 (mm) of the first optical surface: Sag amount SAG21 (mm) of the second optical surface of the first objective lens unit: The first optical of the second objective lens unit Surface sag amount SAG22 (mm): Sag amount of the second optical surface of the second objective lens unit The first objective lens unit has a first optical surface and a second optical surface facing each other, and the second objective lens unit has a first optical surface and a second optical surface facing each other. The first optical surfaces of the first objective lens unit and the second objective lens unit have a curvature that is greater than the second optical surfaces of the first objective lens unit and the second objective lens unit. The first optical information recording medium is a DVD, and the two optical information recording medium is a CD, which satisfies the following conditional expression: A lens unit for the optical pickup device described.
1.1 ≦ {(Φ11 / SAG11) × (Φ12 / SAG12)} / {(Φ21 / SAG21) × (Φ22 / SAG22)} ≦ 1.6 (12)
Φ11 (mm): effective radius of the first optical surface of the first objective lens portion Φ12 (mm): effective radius of the second optical surface of the first objective lens portion Φ21 (mm): the above Effective radius Φ22 (mm) of the first optical surface of the second objective lens unit: Effective radius SAG11 (mm) of the second optical surface of the second objective lens unit: the first objective lens unit Sag amount SAG12 (mm) of the first optical surface: Sag amount SAG21 (mm) of the second optical surface of the first objective lens unit: The first optical of the second objective lens unit Surface sag amount SAG22 (mm): Sag amount of the second optical surface of the second objective lens unit The first objective lens unit has a first optical surface and a second optical surface facing each other, and the second objective lens unit has a first optical surface and a second optical surface facing each other. The first optical surfaces of the first objective lens unit and the second objective lens unit have a curvature that is greater than the second optical surfaces of the first objective lens unit and the second objective lens unit. The first optical information recording medium is a BD, the second optical information recording medium is an HD, and satisfies the following conditional expression: Any one of claims 12 to 17 A lens unit for the optical pickup device described in 1.
1.0 ≦ {(Φ11 / SAG11) × (Φ12 / SAG12)} / {(Φ21 / SAG21) × (Φ22 / SAG22)} ≦ 1.2 (13)
Φ11 (mm): effective radius of the first optical surface of the first objective lens portion Φ12 (mm): effective radius of the second optical surface of the first objective lens portion Φ21 (mm): the above Effective radius Φ22 (mm) of the first optical surface of the second objective lens unit: Effective radius SAG11 (mm) of the second optical surface of the second objective lens unit: the first objective lens unit Sag amount SAG12 (mm) of the first optical surface: Sag amount SAG21 (mm) of the second optical surface of the first objective lens unit: The first optical of the second objective lens unit Surface sag amount SAG22 (mm): Sag amount of the second optical surface of the second objective lens unit An optical pickup device using the lens unit for an optical pickup device according to any one of claims 1 to 26.