JP2006260746A - Optical pickup optical system, optical pickup device, optical disk recording/reproducing device and relay lens group - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly record/reproduce information in a different high-density disk by using a short-wavelength luminous flux. <P>SOLUTION: The optical pickup optical system includes a relay lens group REL having a plurality of lens groups including a movable lens group, and an objective lens OL. The relay lens group REL emits a luminous flux so that magnification of the objective lens OL is lager than -1/100 and smaller than 1/50 when recording/reproducing is performed in a first optical disk, and emits a dispersed light to the objective lens OL when recording/reproducing is performed in a second optical disk. Regarding the movable lens group, a moving amount δ[mm] from the position of the movable lens when the recording/reproducing is performed in the first optical disk to the position of the movable lens group when the recording/reproducing is performed in the second optical disk satisfies 7.5≤(NA<SB>1</SB>×δ)/(t<SB>2</SB>-t<SB>1</SB>)≤22. NA1 is a numerical aperture of the objective lens OL when the recording/reproducing is performed in the first optical disk. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup optical system, an optical pickup device, an optical disc recording / reproducing device, and a relay lens group, and in particular, performs at least one of information recording and reproducing operations so as to be compatible with different types of optical information recording media. The present invention relates to an optical pickup optical system, an optical pickup device, an optical disc recording / reproducing device, and a relay lens group that can be performed.

In recent years, with the practical use of short-wavelength red semiconductor lasers, large-capacity information can be recorded while maintaining the same size as a CD (Compact Disc), which is a conventional optical disc (also referred to as an optical information recording medium). DVD (Digital Versatile Disc), which is a high-density optical disc, has been commercialized.
Recently, a next-generation optical disc capable of recording a larger amount of information has been developed. A condensing optical system in an optical pickup device using such a next-generation optical disc as a medium is used to increase the density of recorded signals. high density in order to reproduce the record signal, to reduce the diameter of the spot Bok that converged on the information recording surface through the objective optical system is required. For this reason, it is required to shorten the wavelength of the laser as a light source, and specifically, a blue-violet semiconductor laser having a wavelength of about 400 nm is expected to be put into practical use.

Using a blue-violet semiconductor laser of about this wavelength 400 nm, a next-generation optical disc for recording and / or reproducing operation of the information, the so-called high density optical disc, HD DVD (High Definition DVD: hereinafter, HD called.) Or Blu-ray Disc (hereinafter referred to as BD).
) And the like. Among, HD is the numerical aperture NA is 0.67, the light source wavelength 405 nm, thickness of the protective layer is designed to 0.6 mm, the optical disc of the same diameter 12cm and DVD, 15～20GB per side Can be recorded. On the other hand, the BD is designed with a numerical aperture NA of 0.85, a light source wavelength of 405 nm, a protective layer (also referred to as a protective substrate or a protective film) having a thickness of 0.1 mm, and an optical disk having a diameter of 12 cm. It is possible to record information of 20 to 30 GB per side.

  However, at the present stage, two types of high-density optical disc standards have been determined, and software with various information recorded on both high-density optical discs is planned to be sold. Then, just being able to appropriately record and reproduce information on only one type of high-density optical disc is very inconvenient and does not fully function as an optical pickup device. There was a problem.

  Therefore, as an objective optical system capable of performing information recording operation and the like interchangeably with optical discs having different thicknesses of the protective layer and light source wavelengths, the wavelength dependence of spherical aberration generated by the diffractive structure is utilized. An objective optical system that corrects spherical aberration due to the thickness of the protective layer has been developed (see, for example, Patent Document 1).

In addition, as an objective optical system capable of performing information recording operation and the like interchangeably with optical discs having different protective layer thicknesses and the same light source wavelengths, an annular zone having a small step in the optical surface is provided. formed, condensing positions of the light beam passing through the ring-shaped zone by utilizing the fact that dependent on the thickness of the protective layer, an objective optical system for correcting a spherical aberration caused by the thickness of the protective layer have been developed (For example, refer to Patent Document 2).
JP 2001-195769 A JP-A-11-96585

  However, when performing BD and recording operations of compatibly information to HD, unlike both the protective layer thickness of each other, the light source wavelength is the same. Therefore, when the objective optical system of Patent Document 1 described above is applied as it is, spherical aberration caused by the protective layer thickness using diffractive action due to the fact that the light source wavelengths are the same in BD and HD. It has arisen problem that it is difficult to correct.

  On the other hand, when the objective optical system described in Patent Document 2 described above is applied as it is, the amount of spherical aberration generated with the difference in the protective layer thickness is large in BD and HD in which the objective optical system has a high numerical aperture. As a result, there is a problem that it is difficult to correct spherical aberration to the extent that it can withstand actual use.

  Also, when performing an information recording operation or the like compatible with BD and HD, BD and HD have different numerical apertures. Therefore, this is known as a technique for controlling the numerical aperture of an objective optical system according to the light source wavelength. Even if a technology using the wavelength dependence of a certain diffraction action or a technology using a wavelength selective filter having a wavelength dependence of transmittance is difficult to apply to BD and HD having the same light source wavelength. There is also a problem such as.

  The present invention has been made in view of the above points, and an optical pickup optical system and an optical pickup capable of appropriately performing information recording and reproducing operations on different high-density disks using a light beam with a short wavelength. It is an object to provide an apparatus, an optical disc recording / reproducing apparatus, and a relay lens group.

In order to solve the above problems, the invention described in claim 1
For the second optical disc having a second protective substrate having a thickness of t ₁ the first optical disk and the thickness having a first protective substrate _{[mm] t 2 [mm]} (t 1 <t 2), emitted from the light source In an optical pickup optical system used in an optical pickup device that reproduces and / or records information using a luminous flux
A relay lens group having a plurality of lens groups including at least one movable lens group movable along the optical axis direction;
An objective lens for condensing the light flux emitted from the light source on the information recording surface of the first optical disc or the second optical disc via the relay lens group;
When performing reproduction and / or recording on the first optical disc, the relay lens group emits a light beam so that a magnification of the objective lens is greater than −1/100 and smaller than 1/50, 2 When reproducing and / or recording on an optical disc, divergent light is emitted to the objective lens,
For at least one of said movable lens group, the position of the movable lens group when performing the reproduction from the position of the movable lens group of the second optical disk and / or recording in the case where the reproducing and / or recording of the first optical disk The movement amount δ [mm] up to the above satisfies the following conditional expression.
7.5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22
However, NA ₁ is the numerical aperture of the objective lens when reproducing and / or recording on the first optical disk.

Here, when the relay lens group has a plurality of movable lens groups, it is sufficient that at least one movable lens group satisfies the above conditional expression. Further, in this invention, when the reproducing and / or recording on the first optical disk, it is preferable that the magnification of the objective lens is 0, i.e., parallel light is incident on the objective lens. Further, in the optical path of the optical pickup device, it is preferable that the lens group disposed next to the objective lens (on the light source side) is a relay lens group. Further, when reproducing and / or recording on the second optical disk, it is preferable that the light beam is incident on the objective lens so that the magnification of the objective lens is −1/5 or more and −1/30 or less. More preferably, the magnification of the objective lens is −1/10 or more and −1/30 or less. The relay lens group preferably has at least one fixed lens group.

According to a second aspect of the present invention, in the optical pickup optical system according to the first aspect,
The thickness of the first and second protective substrates is characterized Mitsurusu that the following equation.
0.06 [mm] ≦ t ₁ ≦ 0.11 [mm]
0.54 [mm] ≦ t ₂ ≦ 0.62 [mm]
Here, the first optical disc BD, the second optical disk preferably used HD or DVD.

The invention according to claim 3 is the optical pickup optical system according to claim 1 or 2,
Wherein the plurality of lens groups in order from a side closer to the objective lens, and a positive first lens group having a second lens unit and the negative refractive power having a refractive power,
The first lens group is the movable lens group.

According to a fourth aspect of the present invention, in the optical pickup optical system according to the third aspect,
The first lens group includes only a single lenses having a negative refractive power,
The relay lens group is characterized by Mitsurusu the following equation.
−3.5 ≦ p ₁ / p ₂ ≦ −1.8
However, p ₁ is the refractive power of the first lens group, p ₂ is the refractive power of the second lens group.

According to a fifth aspect of the invention, the optical pickup optical system according to claim 3 or claim 4,
The second lens group includes a single lens, and the single lens has a first optical surface on the first lens group side and a second optical surface on the objective lens side, and the second optical surface is a convex surface. It is characterized by that.

According to a sixth aspect of the present invention, in the optical pickup optical system according to any one of the third to fifth aspects,
The numerical aperture NA ₁ of the objective lens is a 0.8 or more,
The relay lens group includes a lens formed of a plastic having a water absorption rate of 0.1% or less.

The invention according to claim 7 is the optical pickup optical system according to claim 6,
The second lens group includes a single lens made of plastic having a water absorption rate of 0.1% or less.

The invention according to claim 8 is the optical pickup optical system according to claim 7,
The second lens group is movable in a direction perpendicular to the optical axis.

The invention of claim 9, wherein, in the optical pickup system according to claim 1 or claim 2,
Wherein the plurality of lens groups in order from a side closer to the objective lens, a third lens group having positive refractive power, a second lens group having negative refractive power, the first lens having a positive refractive power A group of
The first lens group and the second lens group are the movable lens group.

  Here, it is preferable that the second lens group satisfies the conditional expression according to claim 1, the first lens group may or may not satisfy the conditional expression. Moreover, it is preferable that the movement amount of the second lens group is larger than the movement amount of the first lens group.

The invention according to claim 10 is the optical pickup optical system according to claim 9,
With respect to the second lens group, the position of the second lens group when reproducing and / or recording the second optical disk from the position of the second lens group when reproducing and / or recording the first optical disk The movement amount δ [mm] up to the above satisfies the following conditional expression.
8 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 15

  The first lens group may or may not satisfy this conditional expression. In addition, the movement amount of the second lens group is preferably larger than the movement amount of the first lens group.

The invention of claim 11, wherein, in the optical pickup system according to claim 9 or claim 10,
The relay lens group, and wherein the Mitsurusu the following equation.
0.7 ≦ p ₁ / p ₃ ≦ 1.6
−5 ≦ p ₂ / p ₃ ≦ −3.7
Here, p ₁ is the refractive power of the first lens group, p ₂ is the refractive power of the second lens group, and p ₃ is the refractive power of the third lens group.

The invention according to claim 12 is the optical pickup optical system according to any one of claims 9 to 11,
The third lens group comprises a single lens, and the single lens has a first optical surface on the second lens group side and a second optical surface on the objective lens side, and the second optical surface is a convex surface. It is characterized by.

The invention according to claim 13 is the optical pickup optical system according to any one of claims 9 to 12,
The second lens group includes a single lens, and the single lens has a first optical surface on the first lens group side and a second optical surface on the third lens group side, and the first optical surface is a concave surface. It is characterized by being.

The invention according to claim 14 is the optical pickup optical system according to any one of claims 9 to 13,
The numerical aperture NA ₁ of the objective lens is 0.8 or more,
The relay lens group includes a lens formed of a plastic having a water absorption rate of 0.1% or less.

The invention according to claim 15 is the optical pickup optical system according to claim 14,
The third lens group is composed of a single lens made of plastic having a water absorption rate of 0.1% or less.

The invention according to claim 16 is the optical pickup optical system according to any one of claims 1 to 15,
It is characterized by satisfying the following formula.
0.95 ≦ NA ₁ · TF ₁ / (NA ₂ · TF ₂ ) ≦ 1.05
However, TF ₁ is the combined focal length of the relay lens group and the objective lens when performing the recording or reproducing operation on the first optical disk, and TF ₂ is the relay when performing the recording or reproducing operation on the second optical disk. The combined focal length NA ₂ of the lens group and the objective lens is the numerical aperture of the objective lens when performing recording or reproducing operation on the second optical disc.

The invention according to claim 17 is the optical pickup optical system according to any one of claims 1 to 16,
When diverging light or convergent light is incident on the objective lens, among the plurality of lens groups, a lens group disposed on the vicinity side of the objective lens and the objective lens moving in a direction perpendicular to the optical axis; It is possible to move in the opposite direction.

The invention according to claim 18 is the optical pickup optical system according to claim 17,
Wherein when recording or reproducing operation in the first optical disk, the incident parallel light or substantially parallel light to the objective lens, when recording or reproducing operation on the second optical disk, diverging light to the objective lens Is incident, moves the objective lens in a direction orthogonal to the optical axis, and out of the lens groups constituting the relay lens group, the lens group disposed near the objective lens is opposite to the objective lens. It is characterized by moving in the direction.

The invention according to claim 19 is the optical pickup optical system according to any one of claims 1 to 18,
It is characterized by satisfying the following formula.
0.6 ≦ TO / TR ≦ 1.5
Where TO is the absolute value of the amount of movement of the objective lens in the direction orthogonal to the optical axis during tracking, and TR is the direction in the direction orthogonal to the optical axis of at least one of the relay lens groups during tracking. This is the absolute value of the movement amount.

The invention of claim 20, wherein, in the optical pickup system according to claim 17 or claim 18,
Among the plurality of lens groups, a lens group disposed closest to the objective lens is a lens formed of plastic having a water absorption of 0.1% or less and a specific gravity of 1.5 or less. It is characterized by comprising.

The invention according to claim 21 is the optical pickup optical system according to any one of claims 1 to 20,
The objective lens is characterized in that it consists of two lenses.

The invention according to claim 22 is the optical pickup optical system according to claim 21,
Of the two lenses, a lens disposed on the far side of the optical disk has a phase structure.
The “phase structure” here includes both a phase difference providing structure including a diffractive structure and an optical path difference providing structure.

The invention of claim 23, wherein, in the optical pickup system according to claim 21 or claim 22,
It is characterized by satisfying the following formula.
0.05 ≦ PO ₁ / PO ₂ ≦ 0.2
However, PO ₁ is one of the two lenses, the refractive power of the lens arranged near the side of the relay lens group, PO ₂ is one of the two lenses, it is disposed distally of the relay lens group The refractive power of the lens.

The invention according to claim 24 is the optical pickup optical system according to any one of claims 1 to 23, wherein:
The optical pickup optical system has a collimator lens,
The collimator lens is an optical path of the light beam emitted from the light source, characterized in that it is located away from the objective lens than the relay lens group. That is, as shown in FIG. 1, it is preferable that a relay lens group is provided between the collimator lens and the objective lens. Here, the "collimator lens" is intended to refer to a fixed lens or a fixed lens group and emits the parallel light flux emitted incident.

According to a twenty-fifth aspect of the present invention, in the optical pickup optical system according to any one of the first to twenty-fourth aspects,
The optical pickup device performs reproduction and / or recording of the first optical disc and the second optical disc using the same light beam.
For example, a combination in which the first optical disc is BD and the second optical disc is HD DVD is included in the present invention.

The invention according to claim 26 is the optical pickup optical system according to any one of claims 1 to 24, wherein:
The optical pickup device is characterized in that reproduction and / or recording of the first optical disc and the second optical disc is performed using light beams having different wavelengths.
For example, a combination in which the first optical disk is BD and the second optical disk is DVD, a combination in which the first optical disk is BD and the second optical disk is CD, a combination in which the first optical disk is HD, and the second optical disk is CD Included in the invention.

According to a twenty-seventh aspect of the present invention, in the optical pickup optical system according to any one of the first to twenty-sixth aspects,
The following formula is satisfied.
r ₁ × 0.8 <r ₂ <r ₁ × 1.2
Here, r ₁ is the entrance pupil diameter of the relay lens group when reproducing and / or recording the first optical disk, and r ₂ is incident of the relay lens when reproducing and / or recording the second optical disk. The pupil diameter.
Preferably, r ₁ × 0.9 <r ₂ <r ₁ × 1.1 is satisfied. More preferably, r ₁
A _{× 0.95 <r 2 <r 1} × 1.05, and most preferably r ₂ = r _1.

The invention according to claim 28 provides
The thickness t ₁ the second optical disk having a second protective layer of the first optical disk and the thickness having a first protective layer of _{[mm] t 2 [mm]} (t 1 <t 2), using a light beam In an optical pickup device for reproducing and / or recording information,
A light source that emits the luminous flux, and an optical pickup optical system;
The optical pickup optical system is
A relay lens group having a plurality of lens groups including at least one movable lens group movable along the optical axis direction;
Through said relay lens group, and a objective lens for converging the light flux emitted from the light source on the information recording surface of the first optical disc or the second optical disc,
When performing reproduction and / or recording on the first optical disc, the relay lens group emits a light beam so that a magnification of the objective lens is greater than −1/100 and smaller than 1/50, 2 When reproducing and / or recording on an optical disc, divergent light is emitted to the objective lens,
For at least one of said movable lens group, the position of the movable lens group when performing the reproduction from the position of the movable lens group of the second optical disk and / or recording in the case where the reproducing and / or recording of the first optical disk The movement amount δ [mm] up to the above satisfies the following conditional expression.
7.5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22
However, NA ₁ is the numerical aperture of the objective lens when reproducing and / or recording on the first optical disk.

The invention according to claim 29 provides
A light beam is used for a first optical disc having a first protective layer having a thickness of t ₁ [mm] and a second optical disc having a second protective layer having a thickness of t ₂ [mm] (t ₁ <t ₂ ). In an optical disc recording / reproducing apparatus having an optical pickup device for reproducing and / or recording information,
The optical pickup device includes a light source that emits the light beam, and an optical pickup optical system,
The optical pickup optical system is
A relay lens group having a plurality of lens groups including at least one movable lens group movable along the optical axis direction;
An objective lens that focuses the light beam emitted from the light source on the information recording surface of the first optical disc or the second optical disc via the relay lens group;
When performing reproduction and / or recording on the first optical disc, the relay lens group emits a light beam so that a magnification of the objective lens is greater than −1/100 and smaller than 1/50, 2 When reproducing and / or recording on an optical disc, divergent light is emitted to the objective lens,
For at least one of said movable lens group, the position of the movable lens group when performing the reproduction from the position of the movable lens group of the second optical disk and / or recording in the case where the reproducing and / or recording of the first optical disk The movement amount δ [mm] up to the above satisfies the following conditional expression.
7.5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22
Here, NA1 is the numerical aperture of the objective lens when reproducing and / or recording on the first optical disc.

The invention according to claim 30 provides
The light source is emitted from the light source to the first optical disc having the first protective layer having a thickness of t ₁ [mm] and the second optical disc having the second protective layer having a thickness of t ₂ [mm] (t ₁ <t ₂ ). In a relay lens group used in an optical pickup optical system of an optical pickup device that reproduces and / or records information using a luminous flux,
And said light source is arranged between the said light beam emitted from the light source first optical disc or the objective lens for condensing onto the information recording surface of the second optical disk,
Having a plurality of lens groups including at least one movable lens group movable along the optical axis direction,
When performing reproduction and / or recording on the first optical disk, a light beam is emitted so that the magnification of the objective lens is greater than −1/100 and smaller than 1/50, and reproduction and / or reproduction is performed on the second optical disk. Or, when recording, emit divergent light to the objective lens,
For at least one of said movable lens group, the position of the movable lens group when performing the reproduction from the position of the movable lens group of the second optical disk and / or recording in the case where the reproducing and / or recording of the first optical disk The movement amount δ [mm] up to the above satisfies the following conditional expression.
7.5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22
However, NA ₁ is the numerical aperture of the objective lens when reproducing and / or recording on the first optical disk.

The present invention can be also be a following mode.
First, the first aspect of the present invention will be described below. An optical pickup system according to the present embodiment is the optical pickup optical system provided in the optical pickup apparatus for recording and / or reproducing operation the thickness of the protective substrate is a plurality of different optical disks, a plurality of lens groups, A relay lens group including a movable lens group in which at least one of the plurality of lens groups is movable along the optical axis direction, and a predetermined wavelength emitted from the light source via the relay lens group comprising an objective lens for converging the light having the relay lens group, when the recording or reproducing operation on an optical disk having a first protective substrate thickness is substantially parallel or slightly relative to the objective lens when the light beam converges and emits, for recording or reproducing operation on the first protective optical disc having a substrate second protective substrate thickness thickness dimension greater than the thickness When the recording or reproducing operation is performed on the optical disk having the first protective substrate thickness, the movement amount δ from the position of the movable lens group is moved so as to satisfy the following conditional expression (1), and the objective lens is moved. And diverging light is emitted.
_{7.5 ≦ (NA 1 · δ)} / (t 2 -t 1) ≦ 22 ......... (1)
Where NA ₁ is the numerical aperture of the objective lens when performing recording or reproducing operation on the optical disk having the first protective substrate thickness, t ₁ is the first protective substrate thickness, and t ₂ is the second protective substrate. It is thick.

Here, “substantially parallel or slightly convergent” in the above means that the magnification of the objective lens is greater than −1/100 and greater than 1/50. Further, when there are a plurality of movable lens groups, it is sufficient that at least one movable lens group satisfies the conditional expression (1). Further, when reproducing and / or recording on the second optical disk, it is preferable that the light beam enters the objective lens so that the magnification of the objective lens is not less than −1/5 and not more than −1/30. More preferably, the magnification of the objective lens is −1/10 or more and −1/30 or less. The relay lens group preferably includes at least one fixed lens group.

  According to the first aspect, when an objective lens in which spherical aberration is corrected in a state where a light beam substantially parallel or slightly converged with the objective lens is emitted to the optical disk having the first protective substrate thickness is used. The spherical aberration generated in the optical disk having the second protective substrate thickness by moving at least one lens group of the relay lens group and changing the use magnification of the objective lens so that divergent light is emitted to the objective lens Can be corrected. At this time, by making sure that the lower limit of conditional expression (1) is not exceeded, it is possible to reduce aberrations that occur when the relay lens is decentered and to generate good spots on the recording surface. As a result, at least one of a good recording signal and reproduction signal can be obtained. In general, since the amount of movement of the actuator is proportional to the eccentricity accuracy, it is possible to prevent the amount of movement of the movable lens from becoming excessive by not exceeding the upper limit value of the conditional expression (1). possible and will, thereby, across the actuator load is reduced, with reduction in the amount of eccentricity due to the movement, it can be miniaturized.

An optical pickup optical system according to a second aspect of the present invention is the optical pickup optical system according to the first aspect, wherein the thicknesses of the first and second protective substrates are the following conditional expressions (2) and (3): It is characterized by satisfying each.
0.06 ≦ t ₁ ≦ 0.11 (2)
0.54 ≦ t ₂ ≦ 0.62 (3)
t ₁ is the thickness of the first protective substrate, and t ₂ is the thickness of the second protective substrate. The conditional expression (2) By Mitsurusu, is suitable to BD and multilayer BD. Further, the conditional expression (3) By Mitsurusu, is suitable to HD and multilayer HD.

An optical pickup optical system according to a third aspect is the optical pickup optical system according to the first or second aspect, wherein the relay lens group has a negative refractive power from a distance of the objective lens. lens group, the second sequential disposed a lens group having positive refractive power, when recording or reproducing operation to the optical disc having a thickness different protective substrate, wherein the first lens group is a said movable lens groups , the amount of movement of the first lens group δ is equal to or following conditional expression (4) Mitsurusu.
_{7.5 ≦ (NA 1 · δ)} / (t 2 -t 1) ≦ 22 ......... (4)
Where NA ₁ is the numerical aperture of the objective lens when performing recording or reproducing operation on the optical disk having the first protective substrate thickness, t ₁ is the first protective substrate thickness, and t ₂ is the second protective substrate. It is thick.

  According to the third aspect, with a simple configuration, a recording operation or the like with respect to optical discs having different protective substrate thicknesses is performed satisfactorily, so that the relay lens does not fall below the lower limit value of the conditional expression (4). It is possible to reduce the aberration caused by decentering and generate a good spot on the recording surface, whereby a good recording signal and the like can be obtained. In addition, by not exceeding the upper limit value of the conditional expression (4), it is possible to prevent the amount of movement of the movable lens from becoming excessive, thereby reducing the load on the actuator and moving the movable lens. As well as reducing the amount of eccentricity associated with the device, the device can be miniaturized.

  Furthermore, by arranging a stop on the farthest surface opposite to the objective lens of the relay lens that satisfies the conditional expression (4), a light beam that obtains the required numerical aperture of the objective lens without providing an aperture limiting member is provided. The light can be emitted to the objective lens.

An optical pickup optical system according to a fourth aspect is the optical pickup optical system according to the third aspect, wherein the first lens group includes only a single lens having negative refractive power, and the relay lens group Satisfies the following conditional expression (5).
−3.5 ≦ p ₁ / p ₂ ≦ −1.8 (5)
Here, p ₁ is the refractive power of the first lens group, and p ₂ is the refractive power of the second lens group.

  According to the fourth aspect, the movable lens group composed of a single lens having a negative refractive index is reduced in weight, and the load applied to the actuator for movement can be reduced. The optical pickup optical system and the optical disk drive device can be reduced in size. Further, by satisfying the conditional expression (5), it is possible to reduce the eccentricity sensitivity and prevent the movement amount of the lens unit from becoming excessive.

Further, the conditional expression (4) and (5) By Mitsurusu, necessary numerical aperture NA _1, of the objective lens necessary for conducting recording operation or the like on an optical disk having a protective substrate thickness of the first and 2 NA _Since the entrance pupil diameter obtained by combining the relay lens for obtaining ₂ and the objective lens (for example, the entrance pupil diameter for L _{1 in} the example of FIG. 1) can be made substantially the same, the light beam emitted from the semiconductor laser and collimated by the collimator Can be guided onto the recording surface without waste, and an optical pickup optical system with high light utilization efficiency can be obtained. Here, “substantially identical” means that when the entrance pupil diameter at NA ₁ is r ₁ and the entrance pupil diameter of the difference between NA ₂ is r ₂ , r ₂ is larger than 80% of r _1. , Say less than 120%. More preferably, r ₂ is greater than 90% of the _{r 1,} is less than 110%. More preferably, r ₂ 2 is greater than 95% of the r _1, is less than 105%. Most preferably, r ₂ is equal to r ₁ as shown in FIG.

  An optical pickup optical system according to a fifth aspect is the optical pickup optical system according to the third or fourth aspect, wherein the second lens group has a convex surface on the side facing the objective lens. It consists of a single lens. According to the fifth aspect, the distance from the first lens group to the second lens group in the relay lens group is shortened, and the aberration generated in the relay lens group is reduced by reducing the refractive power of each lens group. Thus, it is possible to suppress aberration deterioration due to decentration.

Optical pickup system according to a sixth aspect is the optical pickup system of the third to fifth embodiments, the numerical aperture NA ₁ of the objective lens, a 0.8 or more, the relay lens group the water absorption, characterized in that it comprises a lens formed by more than 0.1% of the plastic. According to the sixth aspect, it is possible to reduce the size of the actuator by reducing the weight of the relay lens group. In addition, it is possible to suppress aberrations caused by fluctuations in water absorption due to changes in the environmental humidity of plastics, and to perform good recording operations and the like even on high-density optical disks using a high numerical aperture with NA of 0.8 or more. .

  An optical pickup optical system according to a seventh aspect is the optical pickup optical system according to the sixth aspect, wherein the second lens group is a single lens formed of a plastic having a water absorption rate of 0.1% or less. It is characterized by becoming. According to the seventh aspect, in the relay lens group, the second lens group disposed closest to the object side is a single lens made of plastic, thereby reducing the weight of the device and reducing the manufacturing cost. be able to. Further, in the relay lens group, the lens disposed closest to the objective lens has a high marginal ray height, that is, a large luminous flux diameter, so that the refractive index change due to moisture absorption of plastic caused by environmental humidity change, Although it is easily affected by the refractive index distribution, it is possible to sufficiently reduce these effects by using a lens made of a plastic having a water absorption of 0.1% or less.

  An optical pickup optical system according to an eighth aspect is the optical pickup optical system according to the seventh aspect, wherein the second lens group is movable in a direction perpendicular to the optical axis. According to the eighth aspect, by configuring the second lens group to be movable in the direction perpendicular to the optical axis, it is possible to reduce coma aberration that occurs during tracking of the objective lens.

Optical pickup system according to a ninth aspect is the optical pickup system of the first or second aspect, the relay lens group, from a distance of the objective lens, the first having a positive refractive power lens group, a second lens group having negative refractive power, a third lens sequentially arranged group having positive refractive power, when recording or reproducing operation to the optical disc having a thickness different protective substrate, the The first and second lens groups are the movable lens group, and the movement amount δ of the second lens group satisfies the following conditional expression (6).
_{8 ≦ (NA 1 · δ)} / (t 2 -t 1) ≦ 15 ......... (6)
NA ₁ is the numerical aperture of the objective lens when performing recording or reproducing operation on the optical disk having the first protective substrate thickness, t ₁ is the first protective substrate thickness, and t ₂ is the second protective substrate thickness. is there. Incidentally, if only meet the second lens group Conditional expression (6), the first lens group may be satisfying the condition expression (1) or (6), may not meet .

  According to the ninth aspect, when the optical disk having the first protective substrate thickness and the optical disk having the second protective substrate thickness are used, the movement amount is smaller than that of the relay lens group having the two-group configuration. The entrance pupil diameter in the combined system of the relay lens and the objective lens can be made substantially the same. Further, by making sure that the lower limit value of conditional expression (6) is not exceeded, it is possible to prevent the aberration fluctuations at the time of decentering of the relay lens group from becoming excessive. Also, by not exceed the upper limit, it is possible to reduce the burden of reducing the amount of movement of the movable lens groups, across the actuator.

Optical pickup system according to a tenth aspect is the optical pickup system of the ninth mode of the relay lens group, characterized in Mitsurusu that the following conditional expression (7) and (8).
_{0.7 ≦ p 1 / p 3 ≦} 1.6 ......... (7)
−5 ≦ p ₂ / p ₃ ≦ −3.7 (8)
p ₁ is the refractive power of the first lens group, p ₂ is the refractive power of the second lens group, and p ₃ is the refractive power of the third lens group.

  According to the tenth aspect, the structure of the ninth aspect can be realized with a simple structure. In addition, by preventing the lower limit of conditional expression (7) from being exceeded, it is possible to prevent the amount of movement of the relay lens group from becoming excessive, and to maintain the entrance pupil diameter in the above-described combining system constant. Can do. On the other hand, by making sure that the upper limit value of conditional expression (7) is not exceeded, various aberrations can be corrected satisfactorily and the occurrence of aberrations when the first lens group is decentered can be suppressed. Furthermore, by making sure that the lower limit of conditional expression (8) is not exceeded, various aberrations can be corrected well, and the occurrence of aberrations when the first lens group is decentered can be suppressed. Furthermore, by not exceeding the upper limit value of the conditional expression (8), it is possible to prevent the amount of movement of the relay lens group from becoming excessive and to reduce the load applied to the actuator.

  An optical pickup optical system according to an eleventh aspect is the optical pickup optical system according to the ninth or tenth aspect, wherein the third lens group has a convex surface on the side facing the objective lens. It is characterized by comprising a single lens. According to the eleventh aspect, with even a small number of lenses to satisfactorily correct aberrations, it is possible to shorten the overall length of the relay lens group.

  An optical pickup optical system according to a twelfth aspect is the optical pickup optical system according to the ninth to eleventh aspects, wherein the second lens group has a concave surface on the side opposite to the side facing the objective lens. It consists of a formed single lens. According to the twelfth aspect, it is possible to suppress the occurrence of aberrations at the time of decentering and to reduce the movement amount of the lens.

Optical pickup system according to a thirteenth aspect is the optical pickup system of the ninth to twelfth aspects, the numerical aperture NA ₁ of the objective lens, a 0.8 or more, the relay lens group Includes a lens formed of a plastic having a water absorption rate of 0.1% or less. According to the thirteenth aspect, the actuator can be miniaturized by reducing the weight of the relay lens group. In addition, aberrations caused by fluctuations in water absorption due to changes in environmental humidity of plastics are reduced, and good recording operations and the like can be performed even on high-density optical disks using a high numerical aperture with NA of 0.8 or more. it can.

  An optical pickup optical system according to a fourteenth aspect is the optical pickup optical system according to the thirteenth aspect, wherein the third lens group is formed of a plastic having a water absorption rate of 0.1% or less. It is characterized by comprising. According to the fourteenth aspect, the third lens group disposed on the most object side in the relay lens group is a single lens made of plastic, thereby reducing the weight of the apparatus and reducing the manufacturing cost. . In addition, since the lens disposed closest to the objective lens in the relay lens group has a high marginal ray height, that is, a large luminous flux diameter, the refractive index changes due to the moisture absorption of the plastic due to environmental changes, and the refractive index distribution. becomes susceptible to the influence, water absorption by configuring a lens which is formed by more than 0.1% of the plastic, it is possible to mitigate these effects sufficiently.

An optical pickup optical system according to a fifteenth aspect is the optical pickup optical system according to the first or second aspect, wherein the relay lens is used when a recording or reproducing operation is performed on an optical disk having the first protective substrate thickness. the numerical aperture of the combined focal length and the objective lens of the the group objective lens, the combined focal length of the relay lens group and the objective lens when recording or reproducing operation on the second protective optical disc having a substrate thickness and The numerical aperture of the objective lens satisfies the following conditional expression (9).
0.95 ≦ NA ₁ · TF ₁ / (NA ₂ · TF ₂ ) ≦ 1.05 (9)
TF ₁ is recorded has a combined focal length, NA ₁ is the thickness of the first protective substrate of the relay lens and the objective lens when recording or reproducing operation on an optical disk having a thickness of the first protective substrate or The numerical aperture of the objective lens when performing the reproducing operation, TF ₂ is the combined focal length of the relay lens group and the objective lens when performing the recording or reproducing operation on the optical disk having the second protective substrate thickness, NA ₂ is the numerical aperture of the objective lens when performing a recording or reproducing operation on an optical disk having the second protective substrate thickness. According to the fifteenth aspect of the invention, by designing to satisfy the conditional expression (9), the entrance pupil diameters in the relay lens group and the objective lens combining system can be made substantially the same. As a result, an optical pickup optical system with high light utilization efficiency can be obtained.

  An optical pickup optical system according to a sixteenth aspect is the optical pickup optical system according to the first or second aspect, wherein when the relay lens group has a finite magnification of the objective lens, the relay lens group Among the constituting lens groups, a lens group disposed on the vicinity side of the objective lens is characterized in that it can move in the direction opposite to the objective lens that moves in a direction orthogonal to the optical axis. According to the sixteenth aspect, even when coma occurs when the objective lens is tracked, the coma can be favorably corrected.

  An optical pickup optical system according to a seventeenth aspect is the optical pickup optical system according to the sixteenth aspect, wherein the objective lens performs a recording or reproducing operation on an optical disc having the first protective substrate thickness. When the objective lens has a magnification of approximately zero and recording or reproduction is performed on the optical disk having the second protective substrate thickness, the objective lens has a negative finite value and the objective lens has a negative finite value. Moving the lens in a direction orthogonal to the optical axis, and moving the lens group disposed on the vicinity side of the objective lens among the lens groups constituting the relay lens group in a direction opposite to the objective lens. Features. According to the seventeenth aspect, when the optical disk having the first protective substrate thickness that is most susceptible to the error is used, the optical disk having the second protective substrate thickness can be prevented by tracking the objective lens to prevent the occurrence of aberration. At the time of use, the coma aberration generated by the tracking of the objective lens can be favorably corrected by moving the relay lens group in the direction opposite to the tracking movement direction of the objective lens.

An optical pickup optical system according to an eighteenth aspect is the optical pickup optical system according to the first or second aspect, wherein the absolute value of the amount of movement in the direction orthogonal to the optical axis during tracking of the objective lens and the above The absolute value of the amount of movement of the relay lens group in the direction orthogonal to the optical axis satisfies the following conditional expression (10).
0.6 ≦ TO / TR ≦ 1.5 (10)
TO is the absolute value of the movement amount in the direction perpendicular to the optical axis at the time of tracking of the objective lens, TR is the absolute value of the movement amount in the direction perpendicular to the optical axis of the relay lens group. According to the eighteenth aspect, coma generated by tracking can be corrected satisfactorily. Further, by making sure that the lower limit of conditional expression (10) is not exceeded, it is possible to prevent excessive correction for coma aberration and to reduce residual aberration. In addition, by preventing the upper limit of conditional expression (10) from being exceeded, it is possible to prevent the correction for coma from being insufficient.

Optical pickup system according to a nineteenth aspect is the optical pickup system of the 16th to 18th aspects, the relay lens group is disposed closest to the objective lens in the relay lens group The lens group is made of a lens made of plastic having a water absorption of 0.1% or less and a specific gravity of 1.5 or less. According to the nineteenth aspect, it is possible to reduce the weight of the relay lens group and reduce the manufacturing cost, whereby the load applied to the actuator that moves the relay lens group for correcting coma generated by tracking is reduced. And can be driven at high speed following the objective lens. In addition, since the lens disposed closest to the objective lens side of the relay lens has a high marginal ray height, that is, a large luminous flux diameter, the refractive index change due to plastic moisture absorption caused by environmental changes, or the refractive index distribution. However, these effects can be sufficiently reduced by using a plastic having a water absorption rate of 0.1% or less.

  An optical pickup optical system according to a twentieth aspect is the optical pickup optical system according to the first or second aspect, wherein the objective lens includes two lenses. According to the twentieth aspect, since the objective lens has a two-group configuration, the lens surface is increased, the degree of freedom in design is increased, and the amount of bending of the light beam on each lens surface is dispersed, thereby each lens. it can be reduced generation amount of the aberration in the plane. In addition, since the spherical aberration fluctuates due to the change in the magnification of use of the objective lens, it is possible to correct the spherical aberration in the optical disk having a different protective substrate thickness by changing the magnification of use, but the numerical aperture of the objective lens is large. As a result, a fifth or higher order spherical aberration that cannot be corrected by changing the magnification used is generated. Therefore, by forming the objective lens in a two-group configuration, it is possible to suppress the occurrence of aberrations on each surface as described above, and thereby a good spot can be generated on the recording surface.

  An optical pickup optical system according to a twenty-first aspect is the optical pickup optical system according to the twentieth aspect, wherein the objective lens is disposed on the far side of the optical disc among the two lenses constituting the objective lens. lenses are characterized by having a phase structure. According to the twenty-first aspect, when performing a recording operation or the like on an optical disc using a different wavelength, it becomes possible to make a difference in the function of the phase structure according to the wavelength. However, the aberration can be corrected satisfactorily. The “phase structure” here includes both a phase difference providing structure including a diffraction structure and an optical path difference providing structure.

An optical pickup optical system according to an embodiment of the 22 is an optical pickup optical system of the 20 or 21 aspect of the objective lens, one of the two lenses constituting the objective lens, the relay lens group power and the refractive power of the lens disposed on the far side of the relay lens group disposed lenses near side and wherein the Mitsurusu the following conditional expression (11) of.
_{0.05 ≦ PO 1 / PO 2 ≦} 0.2 ......... (11)
PO ₁ is the refractive power of the lens arranged near the side of the relay lens group, PO ₂ is the refractive power of the lens disposed on the far side of the relay lens group. According to an aspect of the 22, it is possible to suppress the occurrence of high order spherical aberration mentioned above. Further, by preventing the lower limit value of the conditional expression (11) from being lower than the upper limit of the conditional expression (11), it is possible to suppress the occurrence of higher-order spherical aberration and to prevent the objective expression from exceeding the upper limit of the conditional expression (11). It is possible to increase the working distance of the lens, that is, the distance from the surface closest to the disc of the objective lens to the disc surface.

  A twenty-third aspect is an optical disk drive device, comprising: the optical pickup optical system according to any one of the first to twenty-second aspects; a light source that emits light having a predetermined wavelength; and a light receiving element. It is characterized by that.

  24th aspect, in the relay lens, characterized by being used from the first embodiment in any of the optical pickup optical system of the 22nd aspect of the.

  In this specification, the “objective lens” is an optical system that is disposed at a position facing the optical disk in the optical pickup device and has a function of condensing the light beam emitted from the light source on the information recording surface of the optical disk. An optical system that can be shifted at least in the direction of the optical axis by an actuator. In the present specification, the “objective lens” may be a single lens or a plurality of lenses. It is assumed that the objective lens is not included in the relay lens group in this specification.

  In this specification, the numerical aperture NA on the optical information recording medium side (image side) of the objective lens is the optical position of the objective lens closest to the optical information recording medium when the objective lens has a plurality of lenses. It refers to the numerical aperture NA of the surface. In addition, the numerical aperture (NA) or the required numerical aperture in this specification refers to the numerical aperture defined by the standard of each optical information recording medium, or the light source used for each optical information recording medium. The numerical aperture of an objective optical system having a diffraction limited performance capable of obtaining a spot diameter necessary for performing an information recording or reproducing operation according to the wavelength of.

  In the present specification, the lens group means a single lens in the case of a fixed lens group or a plurality of lenses in contact with each other, and in the case of a movable lens group, a single lens that moves in the optical axis direction. refers to the plurality of lenses of the same motion in the optical axis direction.

The optical disk in the present specification includes a high-density optical information recording medium (high-density optical disk), DVD, CD, and the like, but is not limited thereto. The recording density is highest for high-density optical discs, and then decreases sequentially for DVD and CD.

  As a high-density optical information recording medium (high-density optical disk), 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 performing an information recording operation or reproducing operation. For example, a standard optical disc (for example, BD) in which an information recording operation or the like is performed by an objective optical system having an NA of 0.85, and a protective layer has a thickness of about 0.1 mm, or an NA of 0.1. Information recording operation or the like is performed by an objective optical system in the range of 65 to 0.67, and a standard optical disc (for example, HD) having a protective layer thickness of about 0.6 mm is also included. Blu-ray disc (BD) and HD DVD (HD) as well as magneto-optical discs, optical discs having a protective film with a thickness of several to several tens of nanometers on the information recording surface, the thickness of protective layers or protective films optical disc Sagazero is also included in the high-density optical disk.

  DVD is a general term for DVD optical discs such as DVD-ROM, DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW, and CD is CD- A general term for optical disks of CD series such as ROM, CD-Audio, CD-Video, CD-R, CD-RW and the like.

According to the invention described in claim 1,28～30 objective the spherical aberration is corrected in a state of emitting a light beam substantially parallel or slightly convergent and the objective lens for the first optical disk having a first protective substrate when using a lens, by moving at least one lens group of the group relay lens, that the divergent light on the objective lens to change the lateral magnification of the objective lens so as to emit, first having a second protective substrate 2 Spherical aberration occurring in the optical disc can be corrected.
At this time, by making sure that the lower limit of conditional expression (1) is not exceeded, it is possible to reduce aberrations that occur when the relay lens is decentered and to generate good spots on the recording surface. As a result, at least one of a good recording signal and reproduction signal can be obtained. In general, since the amount of movement of the actuator is proportional to the eccentricity accuracy, it is possible to prevent the amount of movement of the movable lens from becoming excessive by not exceeding the upper limit value of the conditional expression (1). As a result, the load on the actuator is reduced, and the amount of eccentricity accompanying the movement can be reduced, and the apparatus can be downsized.

  According to the invention described in claim 2, by satisfying the conditional expression (2), it is suitable for a BD capable of recording on a BD and a multilayer. Further, by satisfying the conditional expression (3), it is suitable for HD and HD capable of recording on multiple layers.

According to the third aspect of the present invention, the recording operation and the like with respect to the optical disks having different protective substrate thicknesses can be satisfactorily performed with a simple configuration.
Moreover, in order to obtain the necessary numerical apertures NA ₁ and NA ₂ of the objective lens necessary for performing a recording operation or the like on the optical disc having the first and second protective substrate thicknesses by satisfying the conditional expression (1). The entrance pupil diameter of the combined relay lens and objective lens is almost the same, so it is possible to guide the light beam collimated by the collimator onto the recording surface without any waste, thereby improving light utilization efficiency. High optical pickup optical system can be obtained. When the entrance pupil diameters are different, the light beam is blocked by an aperture limiting member such as a liquid crystal shutter that limits the aperture of the objective lens when performing a recording operation or the like on one of the optical disks, and the amount of light is lost.
Further, by arranging the stop on the farthest surface opposite to the objective lens of the relay lens satisfying the conditional expression (1), the necessary numerical aperture of the objective lens can be obtained without providing the aperture limiting member described above. The light beam can be emitted to the objective lens.

According to the invention described in claim 4, the movable lens group composed of a single lens having a negative refractive index is reduced in weight, and the load applied to the actuator for movement can be reduced, so that the actuator can be downsized. thereby, it is possible to reduce the size of the optical pickup system and an optical disk recording and reproducing apparatus.
Further, by satisfying the conditional expression (5), it is possible to reduce the eccentricity sensitivity and prevent the movement amount of the lens unit from becoming excessive.

  According to the fifth aspect of the present invention, the distance from the first lens group to the second lens group in the relay lens group is shortened, and the refractive power of each lens group is reduced, thereby generating in the relay lens group. It is possible to reduce aberration and suppress aberration deterioration due to eccentricity.

  According to the invention described in claim 6, the actuator can be reduced in size by reducing the weight of the relay lens group. In addition, it is possible to suppress aberrations caused by fluctuations in water absorption due to changes in the environmental humidity of plastics, and to perform good recording operations and the like even on high-density optical disks using a high numerical aperture with NA of 0.8 or more. .

  According to the invention described in claim 7, in the relay lens group, the second lens group disposed closest to the object side is a single lens formed of plastic, thereby reducing the weight of the device and the manufacturing cost. Reduction can be achieved. Further, in the relay lens group, the lens disposed closest to the objective lens has a high marginal ray height, that is, a large luminous flux diameter, so that the refractive index change due to moisture absorption of plastic caused by environmental humidity change, Although it is easily affected by the refractive index distribution, it is possible to sufficiently reduce these effects by using a lens made of a plastic having a water absorption of 0.1% or less.

  According to the eighth aspect of the invention, the second lens group can be moved in the direction perpendicular to the optical axis, so that the coma aberration generated during tracking of the objective lens can be reduced. it can.

  According to the ninth aspect of the present invention, when the first optical disk having the first protective substrate is used and the second optical disk having the second protective substrate is used, the movement amount is smaller than that of the relay lens group having the two-group structure. The entrance pupil diameters in the combined system of the relay lens and the objective lens in FIG.

  According to the tenth aspect of the present invention, it is possible to prevent the aberration fluctuation at the time of decentering of the relay lens group from becoming excessive by preventing the lower limit of the conditional expression (6) from being exceeded. Further, by not exceeding the upper limit value, it is possible to reduce the amount of movement of the movable lens group and to reduce the burden on the actuator.

According to the invention described in claim 11, the configuration described in claim 9 or 10 can be realized with a simple configuration. In addition, by preventing the lower limit of conditional expression (7) from being exceeded, it is possible to prevent the amount of movement of the relay lens group from becoming excessive, and to maintain the entrance pupil diameter in the above-described combining system constant. Can do. On the other hand, by making sure that the upper limit value of conditional expression (7) is not exceeded, various aberrations can be corrected satisfactorily and the occurrence of aberrations when the first lens group is decentered can be suppressed.
Furthermore, by so as not to fall below the lower limit of Condition (8), as well as satisfactorily correct the aberrations, it is possible to suppress the occurrence of aberrations when eccentricity of the first lens group. Furthermore, by not exceed the upper limit of the condition (8), with the amount of movement of the relay lens group is prevented from becoming excessively large, it is possible to reduce the across the actuator load.

  According to the invention described in claim 12, with even a small number of lenses to satisfactorily correct aberrations, it is possible to shorten the overall length of the relay lens group.

  According to the invention described in claim 13, it is possible as well as suppress the occurrence of aberrations during eccentric, a reduction in the movement amount of the lens.

  According to the fourteenth aspect of the present invention, the actuator can be miniaturized by reducing the weight of the relay lens group. In addition, aberrations caused by fluctuations in water absorption due to changes in environmental humidity of plastics are reduced, and good recording operations and the like can be performed even on high-density optical disks using a high numerical aperture with NA of 0.8 or more. it can.

  According to the fifteenth aspect of the present invention, the third lens group disposed on the most object side in the relay lens group is a single lens made of plastic, thereby reducing the weight of the device and reducing the manufacturing cost. be able to. In addition, since the lens disposed closest to the objective lens in the relay lens group has a high marginal ray height, that is, a large luminous flux diameter, the refractive index changes due to the moisture absorption of the plastic due to environmental changes, and the refractive index distribution. becomes susceptible to the influence, water absorption by configuring a lens formed by more than 0.1% of the plastic, it is possible to mitigate these effects sufficiently.

  According to the invention described in claim 16, by designing so as to satisfy the conditional expression (9), the entrance pupil diameters in the relay lens group and the synthesis system of the objective lens can be made substantially the same, This makes it possible to obtain a high light use efficiency optical pickup system.

  According to the invention described in claim 17, even when the coma aberration occurs when the tracking of the objective lens, it is possible to satisfactorily correct comatic aberration.

  According to the eighteenth aspect of the invention, when the first optical disc having the first protective substrate that is most susceptible to the error is used, the occurrence of aberration is prevented by tracking the objective lens, and the second protective substrate is provided. When the second optical disk is used, the coma aberration generated by the tracking of the objective lens can be favorably corrected by moving the relay lens group in the direction opposite to the tracking movement direction of the objective lens.

  According to the nineteenth aspect, coma generated by tracking can be corrected satisfactorily. Further, by making sure that the lower limit of conditional expression (10) is not exceeded, it is possible to prevent excessive correction for coma aberration and to reduce residual aberration. Also, by not exceed the upper limit of the condition (10), it is possible to prevent a shortage of correction for coma.

  According to the invention of claim 20, it is possible to reduce the weight of the relay lens group and reduce the manufacturing cost, and thereby an actuator that moves the relay lens group for correcting coma generated by tracking. Can be driven at high speed following the objective lens. In addition, since the lens disposed closest to the objective lens side of the relay lens has a high marginal ray height, that is, a large luminous flux diameter, the refractive index change due to plastic moisture absorption caused by environmental changes, or the refractive index distribution. becomes susceptible to the influence, water absorption by constituting less than 0.1% of the plastic, it is possible to mitigate these effects sufficiently.

According to the twenty-first aspect of the present invention, by forming the objective lens in a two-group configuration, the lens surface is increased, the degree of freedom in design is increased, and the amount of bending of the light beam on each lens surface is dispersed. , it is possible to reduce the generation amount of the aberration in the lens surfaces.
Further, in order to change the spherical aberration by changing the use ratio of the objective lens, by changing the use ratio, although it is possible to correct spherical aberration in the optical disc having a thickness different protective substrate, a large numerical aperture of the objective lens As a result, a fifth or higher order spherical aberration that cannot be corrected by changing the magnification used is generated. Therefore, by the two groups constituting the objective lens, it is possible to achieve suppression of the aberration generation in each surface as described above, thereby, it is possible to generate a good spot on the recording surface.

  According to the invention described in claim 22, when performing a recording operation or the like on an optical disk using different wavelengths, it is possible to make a difference in the function of the phase structure depending on the wavelength, and thereby, more types of even for an optical disc, it is possible to satisfactorily correct the aberrations

  According to the twenty-third aspect of the present invention, it is possible to suppress the occurrence of the high-order spherical aberration described above. Further, by preventing the lower limit value of the conditional expression (11) from being lower than the upper limit of the conditional expression (11), it is possible to suppress the occurrence of higher-order spherical aberration and to prevent the objective expression from exceeding the upper limit of the conditional expression (11). It is possible to increase the working distance of the lens, that is, the distance from the surface closest to the disc of the objective lens to the disc surface.

  According to the twenty-fourth aspect of the present invention, parallel light or substantially parallel light can be incident on the relay lens group, so that the magnification change by the relay lens group can be easily and stably performed.

  According to the twenty-fifth aspect of the present invention, when recording / reproducing of optical disks having different protective substrate thicknesses is performed with the same light beam, spherical aberration that cannot be corrected by an optical element such as a diffractive optical element can be corrected. be able to.

  According to the twenty-seventh aspect of the present invention, since the entrance pupil diameters of the light beams are substantially the same in recording and reproduction of different optical disks, it is possible to reduce the loss of light amount and increase the light beam utilization efficiency.

The best mode for carrying out the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.
First, an optical pickup optical system and an optical pickup device in this embodiment will be described with reference to FIG.

As shown in FIG. 1 and FIG. 16, the optical pickup apparatus PU1 in the present embodiment, B
When recording operation of information with respect to D and HD, blue-violet semiconductor laser LD is provided a light source that emits a blue-violet laser light flux of wavelength of 405 nm. That is, in this embodiment, the same light source is used for different disks. However, a plurality of light sources having different wavelengths may be used for different disks.

  The optical axis of the blue-violet light emitted from the blue violet semiconductor laser LD, substantially square splitter PS is provided. In the optical axis direction of the light split by the splitter PS, the collimator CL, the relay lens group REL including the first lens group L1 and the second lens group L2, the liquid crystal shutter LQS, the quarter wavelength plate QWP, the objective The lenses OL are sequentially arranged, and an optical information recording medium BD or HD is arranged at a position facing the quarter wavelength plate QWP with the objective lens OL interposed therebetween.

Here, the objective lens OL may be composed of only a single lens, or may be composed of two or more lenses. When the objective lens OL is composed of two or more lenses, the lens farthest from BD and HD preferably has a phase structure. Further, when the objective lens OL consists of two lenses, the refractive power PO ₁ a lens disposed near the side of the relay lens group REL, the refractive power PO ₂ of disposed lenses to the far side It is preferable that the following conditional expression (11) is satisfied.
_{0.05 ≦ PO 1 / PO 2 ≦} 0.2 ......... (11)

  The second lens unit L2 is composed of a single lens. This single lens has an optical surface on the first lens unit L1 side and an optical surface on the objective lens OL side, and the optical surface on the objective lens OL side is formed in a substantially convex shape. The single lens constituting the second lens unit L2 is made of plastic having a water absorption rate of 0.1% or less and a specific gravity of 1.5 or less, and has a positive refractive power.

Further, the first lens unit L1 has a negative refractive power, the refractive power p ₁ such first lens unit L1, the refractive power p ₂ of the second lens unit L2, the following conditional expression ( Satisfies 5).
−3.5 ≦ p ₁ / p ₂ ≦ −1.8 (5)

The thickness dimension t ₁ of the protective substrate having the BD in the present embodiment, the following conditional expression (2)
Is to meet.
_{0.06 ≦ t 1 ≦ 0.11 [mm} ] ......... (2)
Furthermore, the thickness dimension t ₂ of the protective substrate of the HD in this embodiment is expressed by the following conditional expression (3
).
_{0.54 ≦ t 2 ≦ 0.62 [mm} ] ......... (3)

  On the other hand, on the side facing the collimator CL across the splitter PS, there is a sensor lens SEN for adding astigmatism to the reflected light beam from the information recording surface RL1, and for BD and HD for detecting the reflected light beam. and a photodetector PD are sequentially arranged.

  A blue-violet semiconductor laser LD is used as the light source in the present embodiment, but is not particularly limited as long as it can emit light having a desired short wavelength. An SHG laser or the like is applicable.

  Further, the first lens group L1 and the second lens group L2 in the relay lens group REL described above are respectively provided with uniaxial actuators AC2 and AC3, and are parallel when performing a recording operation or the like on the BD. The distance between the first lens unit L1 and the second lens unit L2 is set by the uniaxial actuator AC2 so that the light beam is emitted, that is, the magnification of the objective lens OL is larger than −1/100 and smaller than 1/50. It comes to optimize.

  On the other hand, when a recording operation or the like is performed on the HD, the interval between the first lens unit L1 and the second lens group L2 is smaller than the interval when the recording operation or the like is performed on the BD so as to emit a divergent light beam. It is adapted to optimize by uniaxial actuator AC2 so.

Here, the numerical aperture NA ₁ of the combined focal length TF ₁ and the objective lens OL of the relay lens group REL and the objective lens OL in performing the recording operation or the like to BD, the relay lens group when performing the recording operation or the like on the HD The combined focal length TF ₂ of REL and objective lens OL and the numerical aperture N of objective lens OL
A ₂ satisfies the following conditional expression (9).
0.95 ≦ NA ₁ · TF ₁ / (NA ₂ · TF ₂ ) ≦ 1.05 (9)

  Further, when performing a recording operation or the like on the HD, when the second lens unit L2 is tracked in the direction orthogonal to the optical axis by the uniaxial actuator AC3, in the direction opposite to the objective lens OL, more specifically, the objective lens The movement is made in the direction opposite to the movement direction of the OL.

Here, the absolute value TO of the amount of movement in the direction orthogonal to the optical axis during tracking of the objective lens OL and the absolute value TR of the amount of movement in the direction orthogonal to the optical axis of the relay lens group REL are as follows: Formula (10) is satisfied.
0.6 ≦ TO / TR ≦ 1.5 (10)

  Further, the above-described uniaxial actuators AC2 and AC3 are adapted to support BDs capable of recording on multiple layers. More specifically, in order to access information recording layers of different depths in the same BD, the distance between the first lens unit L1 and the second lens unit L2 is optimized by a uniaxial actuator, that is, By changing the magnification of the objective lens OL, spherical aberration that occurs when performing a so-called focus jump that displaces the objective lens OL in the optical axis direction is corrected.

Here, the numerical aperture NA1 of the objective lens OL when performing a recording operation or the like on the BD is 0.8 or more, and the movement amount δ of the first lens unit L1 that moves according to the recording operation or the like is expressed by the following conditional expression: (4) is satisfied.
7.5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22 (4)
However, t ₁ is the thickness of the protective substrate having the BD, t ₂ is the thickness of the protective substrate having the HD.

Further, an entrance pupil diameter r ₁ of the relay lens group REL when performing a recording operation or the like on the BD and an entrance pupil diameter r ₂ of the relay lens group REL when performing a recording operation or the like on the HD are the following conditional expressions (14 ).
r ₁ × 0.8 <r ₂ <r ₁ × 1.2 ……… (14)

  Incidentally, by using the uniaxial actuator AC2, AC3 described above, similarly to the BD, may be configured to correspond to the possible recording HD respect multilayer. In this case, the optical pickup device PU1 includes a recording layer discriminating unit for discriminating which recording layer is the information recording layer on which the objective lens OL is focused.

  Further, the optical pickup device PU1 described above determines the type (for example, BD or HD) of the optical disk accommodated in the disk tray (not shown), and controls to move the first lens unit L1 to the optimum position. Means are provided.

Note that the relay lens group REL in the present embodiment is a first lens from a distance from the objective lens OL.
The lens group L1 and the second lens group L2 have a two-group configuration in which the lens group L1 and the second lens group L2 are sequentially arranged, but are not particularly limited. For example, the side facing the second lens group L2 with the first lens group L1 interposed therebetween, Alternatively, a three-group configuration in which a third lens group having a positive refractive power is added to the second lens group L2 on the side opposite to the first lens group L1. In this case, also in the third lens group, similarly to the first lens group L1 and the second lens group L2 described above, a uniaxial actuator is provided so as to optimize the interval between the adjacent first lens groups L1. It has become.

  In the case of the relay lens group having the three-group configuration described above, the second lens group L2 is composed of a single lens having a substantially concave surface on the side opposite to the side facing the objective lens. one surface of the opposing side is composed of a single lens having a substantially convex shape. The single lens constituting the third lens group is made of plastic having a water absorption rate of 0.1% or less and a specific gravity of 1.5 or less.

The refractive power p ₃ of the third lens unit L3, the refractive power p ₂ refractive power p ₁ and the second lens unit L2 in the first lens unit L1 described above, the following conditional expressions (7) and (8 ).
0.7 ≦ p ₁ / p ₃ ≦ 1.6 (7)
−5 ≦ p ₂ / p ₃ ≦ −3.7 (8)

The numerical aperture NA1 of the objective lens OL when performing a recording operation or the like on the BD is 0.8 or more, and the movement amount δ of the first lens unit L1 that moves according to the recording operation or the like is expressed by the following conditional expression ( 6) is satisfied.
_{8 ≦ (NA 1 · δ)} / (t 2 -t 1) ≦ 15 ......... (6)
However, t ₁ is the thickness of the protective substrate having the BD, t ₂ is the thickness of the protective substrate having the HD.

Further, similar to the two-group relay lens group REL described above, the combined focal length TF ₁ of the relay lens group REL and the objective lens OL when performing a recording operation or the like on the BD and the objective lens OL.
And the numerical aperture NA ₁ of the relay lens group REL and the objective lens OL in performing the recording operation or the like on the HD
And the combined focal length TF ₂ and the numerical aperture NA ₂ of the objective lens OL satisfy the following conditional expression (9).
0.95 ≦ NA ₁ · TF ₁ / (NA ₂ · TF ₂ ) ≦ 1.05 (9)

Further, as in the case of the relay lens group REL having the two-group configuration described above, in the case where a recording operation or the like is performed on the HD, when the third lens group L3 is tracked in the direction orthogonal to the optical axis by the single-axis actuator, The lens is moved in the opposite direction to the lens OL. Here, the absolute value TO of the amount of movement in the direction orthogonal to the optical axis during tracking of the objective lens OL and the absolute value TR of the amount of movement in the direction orthogonal to the optical axis of the relay lens group REL are as follows: Formula (10) is satisfied.
0.6 ≦ TO / TR ≦ 1.5 (10)

Furthermore, like the relay lens group REL of 2-group configuration as described above, the entrance pupil diameter r ₁ of the relay lens group REL in performing the recording operation or the like to BD, the relay lens group REL in performing the recording operation or the like on the HD and the entrance pupil diameter r ₂ is made following conditional expression (14) to Mitsurusu so.
_{r 1 × 0.8 <r 2 <} r 1 × 1.2 ......... (14)

  The optical pickup device PU1 described above can be incorporated in an optical disk drive device.

Next, the operation of the optical pickup optical system and the optical pickup device PU1 will be described.
Optical pickup system and an optical pickup apparatus PU1 in the present embodiment, by the type of the optical disc, i.e., to the different operations depending on the size of the thickness dimension having a protective substrate, in the following, the first protective substrate thickness PL1 and Details of the operation mode for the optical disk having the second protective substrate thickness PL2 will be described.

First, the operation of the optical pickup device 1 for the BD, that is, the optical disc having the first protective substrate thickness PL1 will be described.
Light is emitted from the blue-violet semiconductor laser LD at the time of information recording operation on the optical disc having the first protective substrate thickness PL1 or at the time of reproducing information recorded on the optical disc having the first protective substrate thickness PL1. The emitted light is reflected by the splitter PS, is a parallel light by the collimator CL. Then, the light passes through the relay lens group REL, the liquid crystal shutter LQS, the quarter-wave plate QWP, and the objective lens OL (light beam LA1) to form a condensing spot on the recording surface RL1 of the optical disc having the first protective substrate thickness PL1. . At this time, the interval between the first lens group L1 and the second lens group L2 constituting the relay lens group REL is optimized by the uniaxial actuator AC2, and a parallel light beam is emitted.

  Light that formed the concentrated light spot is modulated by the information pit on the recording surface RL1 of the optical disc having a first protective substrate thickness PL1, is reflected by the recording surface RL1. The reflected light passes through the objective lens OL, the quarter-wave plate QWP, the liquid crystal shutter LQS, the relay lens group REL, and the splitter PS, and then passes through the sensor lens SEN to give astigmatism. Light is received by the detector PD. Thereafter, such an operation is repeatedly performed, and the information recording operation on the optical disc having the first protective substrate thickness PL1 and the reproducing operation of information recorded on the optical disc having the first protective substrate thickness PL1 are completed.

Next, the operation of the optical pickup device PU1 for HD, that is, an optical disc having the second protective substrate thickness PL2 will be described.
Light is emitted from the blue-violet semiconductor laser LD at the time of information recording operation on the optical disc having the second protective substrate thickness PL2 or at the time of reproducing information recorded on the optical disc having the second protective substrate thickness PL2. The emitted light is reflected by the splitter PS, is a parallel light by the collimator CL. Then, the light passes through the relay lens group REL, the liquid crystal shutter LQS, the quarter wavelength plate QWP, and the objective lens OL (light ray LA2), and forms a condensing spot on the recording surface RL2 of the optical disc having the second protective substrate thickness PL2. . At this time, the 1-axis actuator AC2, a first lens unit L1 distance between the second lens unit L2 are optimized so as to be smaller than the operation for the BD that constitute the relay lens group REL, divergent light flux emitted Is done.

  The light that forms the focused spot is modulated by the information pits on the recording surface RL2 of the optical disc having the second protective substrate thickness PL2, and is reflected by the recording surface RL2. The reflected light passes through the objective lens OL, the quarter-wave plate QWP, the liquid crystal shutter LQS, the relay lens group REL, and the splitter PS, and then passes through the sensor lens SEN to give astigmatism. Light is received by the detector PD. Thereafter, such an operation is repeatedly performed, and the recording operation of information on the optical disc having the second protective substrate thickness PL2 and the reproducing operation of information recorded on the optical disc having the second protective substrate thickness PL2 are completed.

As shown in FIG. 16, a relay for obtaining the necessary numerical apertures NA ₁ and NA ₂ of the objective lens necessary for performing recording operation on the first and second optical disks having the first and second protective substrates. The entrance pupil diameter obtained by combining the lens and the objective lens is preferably substantially the same.

Next, examples of the optical pickup optical system and the optical pickup device PU1 will be described.
First, items common to the embodiments will be described. The optical disk (BD) having the first type protective substrate thickness PL1 in Example 1 to Example 7 has a wavelength λ ₁ = 405 nm.
, The thickness t ₁ = 0.1 mm of the protective substrate is set to a first numerical aperture NA ₁ = 0.85, the optical disk having a second type protective substrate thickness PL2 (HD), the wavelength lambda ₁ = 405 nm, the thickness t ₂ = 0.6 mm of the protective substrate, a second numerical aperture NA ₂ = 0.65, is set to a focal length f = 2.2 mm of the objective lens OL. In all the embodiments, when recording and / or reproducing BD, parallel light is incident on the objective lens, and when recording and / or reproducing HD is performed, divergent light is incident on the objective lens. Yes.

Therefore, the optical pickup optical system and the optical pickup apparatus PU1 in the first to seventh embodiments have 0.06 ≦ t ₁ ≦ 0.11 in the equation (2) and 0.54 ≦ in the equation (3).
Each of t ₂ ≦ 0.62 is satisfied. The value of NA ₁ · TF ₁ / (NA ₂ · TF ₂ ) is
1.0, which satisfies 0.95 ≦ NA ₁ · TF ₁ / (NA ₂ · TF ₂ ) ≦ 1.05 in the formula (9).

  Further, the lenses constituting the relay lens group REL in Examples 1 to 7 are all formed of a polyolefin plastic such as Zeonex (manufactured by Nippon Zeon Co., Ltd.), and the water absorption of the polyolefin plastic is almost 0. %.

Next, details of each embodiment will be described.
First, Example 1 will be described.
As shown in FIGS. 2 and 3, the relay lens group REL in this embodiment, chromatic a first lens group having a negative refractive power, a 2-group configuration consisting of a second lens group having positive refractive power is doing.

Next, the data of each lens and the aspheric surface data in this embodiment are shown in the following Tables 1 and 2, respectively, and the optical disc having the first type protective substrate thickness PL1 and the second type protective substrate thickness PL2 in Table 1. Table 3 below shows the values of dn and aperture.

Here, “OBJ” in the table indicates an object position. Since the light emitted from the semiconductor laser LD is collimated into parallel light by the collimator CL, the object is at infinity. . Symbols r, d, n (405), and nd in the table indicate a radius of curvature, a surface interval, a refractive index at a wavelength of 405 nm, and a refractive index at a d-line (587 nm), respectively. Further, an aperture limiting member such as a liquid crystal shutter is provided on the surface of the objective lens OL on the surface on which the letters “aperture” in the surface number are written.

Here, K in the table represents a conic constant, and A2I (I is 2, 3, 4,...) Represents an aspheric coefficient.
Incidentally, the non-spherical shape, the optical axis direction to the z-axis, coordinate x axis orthogonal two in a direction perpendicular to the optical axis, taking the y-axis, the point on the aspherical surface coordinates (x, y, z) is determined so as to satisfy the following conditional expressions (12) and (13).

………（１２）

......... (12)

  Here, x (h) is an axis in the optical axis direction (the light traveling direction is positive), K is a conic constant, A2I (I is 2, 3, 4,...) Is an aspheric coefficient, and h (nm ) is the direction perpendicular to the optical axis height, r is a radius of curvature.

………（１３）

……… (13)

As a result, the value of (NA ₁ · δ) / (t ₂ −t ₁ ) is 9.4, and the above formulas (1) and (
4) 7.5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22 is satisfied.

Further, the value of p ₁ / p ₂ is −2.05, which satisfies −3.5 ≦ p ₁ / p ₂ ≦ −1.8 in the above formula (5).

Next, Example 2 will be described.
As shown in FIGS. 4 and 5, the relay lens group REL in this embodiment includes a first lens group having a negative refractive power and a second lens group having a positive refractive power, as in the first embodiment. Has a two-group configuration.

  The data of each lens and the aspheric surface data in this embodiment are shown in the following Tables 4 and 5, respectively. The dn of the optical disk having the first type protective substrate thickness PL1 and the second type protective substrate thickness PL2 in Table 4 is shown. the value of the aperture value, shown in table 6 below.

As a result, the value of (NA ₁ · δ) / (t ₂ -t ₁ ) is 13.6, and 7.5 ≦ (NA ₁ · δ) / (t in the above formulas (1) and (4). ₂ −t ₁ ) ≦ 22.

Further, the value of p ₁ / p ₂ is −2.86, which satisfies −3.5 ≦ p ₁ / p ₂ ≦ −1.8 in the above formula (5).

Next, Example 3 will be described.
As shown in FIGS. 6 and 7, the relay lens group REL in this embodiment, as in Embodiment 1 and Embodiment 2 includes a first lens group having negative refractive power, positive refractive power It has a two-group configuration consisting of a second lens group.

  The data of each lens and the aspheric surface data in this example are shown in Table 7 and Table 8 below, respectively, and dn of the optical disc having the first type protective substrate thickness PL1 and the second type protective substrate thickness PL2 in Table 7 is shown. The values and aperture values are shown in Table 9 below.

As a result, the value of (NA ₁ · δ) / (t ₂ −t ₁ ) is 20.4, and 7.5 ≦ (NA ₁ · δ) / (t in the above formulas (1) and (4). ₂ −t ₁ ) ≦ 22.

Further, the value of p ₁ / p ₂ is −3.0, which satisfies −3.5 ≦ p ₁ / p ₂ ≦ −1.0 in the formula (5).

Next, Example 4 will be described.
As shown in FIGS. 8 and 9, the relay lens group REL in this example is similar to the first example, the second example, and the third example, and the first lens group having a negative refractive power is positive. and a two-group configuration consisting of a second lens group having a refractive power. Further, the optical pickup optical system in the present embodiment moves the second lens group in accordance with the tracking of the objective lens when performing a recording operation or the like on the optical disc having the second type protective substrate thickness PL2, and thereby performs tracking tracking. It is configured to correct aberrations.

  The data of each lens and the aspheric surface data in this example are shown in Table 10 and Table 11 below, respectively, and dn of the optical disc having the first type protective substrate thickness PL1 and the second type protective substrate thickness PL2 in Table 10 is shown. The values and aperture values are shown in Table 12 below.

As a result, the value of (NA ₁ · δ) / (t ₂ −t ₁ ) is 20.4, and 7.5 ≦ (NA ₁ · δ) / (t in the above formulas (1) and (4). ₂ −t ₁ ) ≦ 22.

Further, the value of p ₁ / p ₂ is −3.29, which satisfies −3.5 ≦ p ₁ / p ₂ ≦ −1.8 in the above formula (5).

  Furthermore, the value of TO / TR is 0.78, which satisfies 0.6 ≦ TO / TR ≦ 1.5 in the above formula (10).

Next, Example 5 will be described.
As shown in FIGS. 10 and 11, relay lens group REL in this embodiment, the Example 1, Example 2, as in Example 3 and Example 4, the first lens group having negative refractive power And a second lens group having a positive refractive power. Also, the optical pickup optical system in the present embodiment, like the fourth embodiment, uses the second lens group according to the tracking of the objective lens when performing a recording operation or the like on the optical disc having the second type protective substrate thickness PL2. So that the tracking coma is corrected.

  The data of each lens and the aspherical surface data in this example are shown in Table 13 and Table 14 below, respectively, and dn of the optical disk having the first type protective substrate thickness PL1 and the second type protective substrate thickness PL2 in Table 13 is shown. the value of the aperture value, shown in table 15.

As a result, the value of _{(NA 1 · δ) / (} t 2 -t 1) is 11.9, the formula (1) and (4) of _{7.5 ≦ (NA 1 · δ)} / (t ₂ −t ₁ ) ≦ 22.

Further, the value of p ₁ / p ₂ is −2.56, which satisfies −3.5 ≦ p ₁ / p ₂ ≦ −1.8 in the formula (5).

  Furthermore, the value of TO / TR is 1.33, which satisfies 0.6 ≦ TO / TR ≦ 1.5 in the above formula (10).

Next, Example 6 will be described.
As shown in FIGS. 12 and 13, the relay lens group REL in this embodiment has a negative refractive power, the first lens group L1, the second lens group L2 having a positive refractive power, and a positive refractive power. The third lens unit L3 has a three-group configuration.

  The data of each lens and the aspheric surface data in this example are shown in Table 16 and Table 17 below, respectively, and dn of the optical disc having the first type protective substrate thickness PL1 and the second type protective substrate thickness PL2 in Table 16 is shown. The values and aperture values are shown in Table 18 below.

As a result, the value of (NA ₁ · δ) / (t ₂ −t ₁ ) is 9.35, which is 7 in the formula (1).
. 5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22 and 8 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 15 in the above formula (6) are satisfied.

Furthermore, the value of p ₁ / p ₃ and p ₂ / p ₃ is 1.42, a -4.14, and _{-0.7 ≦ p 1 / p 3 ≦} 1.6 in the formula (7) In addition, −5 ≦ p ₂ / p ₃ ≦ −3.7 of the formula (8) is satisfied.

Next, Example 7 will be described.
As shown in FIGS. 14 and 15, the relay lens group REL in the present embodiment includes a first lens group L1 having a negative refractive power, a second lens group L2 having a positive refractive power, and a positive refractive power. And a third lens unit L3 having a third lens unit L3. In addition, the optical pickup optical system and the optical pickup device PU1 in this embodiment perform the recording operation or the like on the optical disk having the second type protective substrate thickness PL2, and set the third lens unit L3 according to the tracking operation of the objective lens. It is configured to move and correct the coma aberration of the tracking operation.

  The data of each lens and the aspheric surface data in this example are shown in Table 19 and Table 20 below, respectively, and dn of the optical disc having the first type protective substrate thickness PL1 and the second type protective substrate thickness PL2 in Table 19 is shown. The values and aperture values are shown in Table 21 below.

As a result, the value of (NA ₁ · δ) / (t ₂ −t ₁ ) is 13.6, which is 7 in the formula (1).
. 5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22 and 8 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 15 in the above formula (6) are satisfied.

Furthermore, the value of p ₁ / p ₃ and p ₂ / p ₃ is 0.84, a -4.39, and _{-0.7 ≦ p 1 / p 3 ≦} 1.6 in the formula (7) In addition, −5 ≦ p ₂ / p ₃ ≦ −3.7 of the formula (8) is satisfied.

  Further, the value of TO / TR is 1.15, which satisfies 0.6 ≦ TO / TR ≦ 1.5 in the above formula (10).

  As described above, according to the optical pickup optical system and the optical pickup device PU1 in the present embodiment, a spherical surface in a state in which a light beam that is substantially parallel to or slightly converges with the objective lens OL is emitted to a BD having the first type protective substrate thickness PL1. When the objective lens OL with corrected aberration is used, at least one lens group of the relay lens group REL is moved to change the use magnification of the objective lens OL so that divergent light is emitted to the objective lens OL. Thus, it is possible to correct the spherical aberration that occurs in the HD having the second type protective substrate thickness PL2.

  At this time, by making sure that the lower limit of conditional expression (1) is not exceeded, aberrations that occur when the relay lens group REL is decentered can be reduced, and a good spot can be generated on the recording surface. This makes it possible to obtain at least one of a good recording signal and reproduction signal. In general, since the movement amount of the single-axis actuators AC2 and AC3 is proportional to the eccentricity accuracy, the movement amount of the movable lens becomes excessive if the upper limit value of the conditional expression (1) is not exceeded. As a result, the load on the single-axis actuators AC2 and AC3 is reduced, and the amount of eccentricity accompanying the movement can be reduced, and the optical pickup apparatus PU1 can be downsized.

It is a schematic diagram showing the internal structure of the optical pickup device. It is sectional drawing which shows the aspect at the time of use of the optical disk which has 1st type protective substrate thickness in 1st Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has the 2nd kind protective substrate thickness in 1st Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has 1st type protection board thickness in 2nd Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has the 2nd kind protective substrate thickness in 2nd Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has the 1st type protection board thickness in 3rd Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has the 2nd kind protective substrate thickness in 3rd Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has 1st type protection board thickness in 4th Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has the 2nd kind protective substrate thickness in 4th Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has 1st type protection board thickness in 5th Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has the 2nd kind protective substrate thickness in 5th Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has 1st type protection board thickness in 6th Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has the 2nd kind protective substrate thickness in 6th Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has 1st type protection board thickness in 7th Example. It is sectional drawing which shows the aspect at the time of use of the optical disk which has the 2nd kind protective substrate thickness in 7th Example. It is the schematic which shows the internal structure of another Example of an optical pick-up apparatus.

Explanation of symbols

PU1 Optical pickup device AC1 3-axis actuator AC2, AC3 1-axis actuator REL Relay lens group L1 First lens group L2 Second lens group LD Blue-violet semiconductor laser OL Objective lens PD Photodetector PL1 First type protective substrate thickness PL2 Second Seed protection board thickness

Claims (30)

For the second optical disc having a second protective substrate having a thickness of t ₁ the first optical disk and the thickness having a first protective substrate _{[mm] t 2 [mm]} (t 1 <t 2), emitted from the light source In an optical pickup optical system used in an optical pickup device that reproduces and / or records information using a luminous flux
A relay lens group having a plurality of lens groups including at least one movable lens group movable along the optical axis direction;
An objective lens for condensing the light flux emitted from the light source on the information recording surface of the first optical disc or the second optical disc via the relay lens group;
When performing reproduction and / or recording on the first optical disc, the relay lens group emits a light beam so that a magnification of the objective lens is greater than −1/100 and smaller than 1/50, 2 when the reproducing and / or recording on an optical disk, and emits divergent light to the objective lens,
For at least one of said movable lens group, the position of the movable lens group when performing the reproduction from the position of the movable lens group of the second optical disk and / or recording in the case where the reproducing and / or recording of the first optical disk An optical pickup optical system characterized in that the amount of movement δ [mm] up to
7.5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22
However, NA ₁ is the numerical aperture of the objective lens when reproducing and / or recording on the first optical disk. The optical pickup optical system according to claim 1, wherein the thicknesses of the first and second protective substrates satisfy the following expression.
0.06 [mm] ≦ t ₁ ≦ 0.11 [mm]
0.54 [mm] ≦ t ₂ ≦ 0.62 [mm] The plurality of lens groups, in order from the side closer to the objective lens, includes a second lens group having a positive refractive power and a first lens group having a negative refractive power,
The optical pickup optical system according to claim 1, wherein the first lens group is the movable lens group. The first lens group comprises only a single lens having negative refractive power,
The optical pickup optical system according to claim 3, wherein the relay lens group satisfies the following expression.
−3.5 ≦ p ₁ / p ₂ ≦ −1.8
However, p ₁ is the refractive power of the first lens group, p ₂ is the refractive power of the second lens group.   The second lens group includes a single lens, and the single lens has a first optical surface on the first lens group side and a second optical surface on the objective lens side, and the second optical surface is a convex surface. The optical pickup optical system according to claim 3 or 4, wherein The numerical aperture NA ₁ of the objective lens is a 0.8 or more,
The optical pickup optical system according to any one of claims 3 to 5, wherein the relay lens group includes a lens made of a plastic having a water absorption rate of 0.1% or less.   The optical pickup optical system according to claim 6, wherein the second lens group includes a single lens made of plastic having a water absorption rate of 0.1% or less.   The optical pickup optical system according to claim 7, wherein the second lens group is movable in a direction perpendicular to the optical axis. Wherein the plurality of lens groups in order from a side closer to the objective lens, a third lens group having positive refractive power, a second lens group having negative refractive power, the first lens having a positive refractive power A group of
The optical pickup optical system according to claim 1, wherein the first lens group and the second lens group are the movable lens group. With respect to the second lens group, the position of the second lens group when reproducing and / or recording the second optical disk from the position of the second lens group when reproducing and / or recording the first optical disk The optical pickup optical system according to claim 9, wherein the amount of movement δ [mm] up to satisfies the following conditional expression.
8 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 15 The optical pickup optical system according to claim 9 or 10, wherein the relay lens group satisfies the following expression.
0.7 ≦ p ₁ / p ₃ ≦ 1.6
−5 ≦ p ₂ / p ₃ ≦ −3.7
Here, p ₁ is the refractive power of the first lens group, p ₂ is the refractive power of the second lens group, and p ₃ is the refractive power of the third lens group.   The third lens group comprises a single lens, and the single lens has a first optical surface on the second lens group side and a second optical surface on the objective lens side, and the second optical surface is a convex surface. The optical pickup optical system according to any one of claims 9 to 11, wherein:   The second lens group includes a single lens, and the single lens has a first optical surface on the first lens group side and a second optical surface on the third lens group side, and the first optical surface is a concave surface. The optical pickup optical system according to any one of claims 9 to 12, wherein the optical pickup optical system is provided. The numerical aperture NA ₁ of the objective lens is 0.8 or more,
The optical pickup optical system according to any one of claims 9 to 13, wherein the relay lens group includes a lens formed of a plastic having a water absorption rate of 0.1% or less.   15. The optical pickup optical system according to claim 14, wherein the third lens group comprises a single lens made of plastic having a water absorption rate of 0.1% or less. The optical pickup optical system according to claim 1, wherein the following expression is satisfied.
0.95 ≦ NA ₁ · TF ₁ / (NA ₂ · TF ₂ ) ≦ 1.05
However, TF ₁ is the combined focal length of the relay lens group and the objective lens when performing the recording or reproducing operation on the first optical disk, and TF ₂ is the relay when performing the recording or reproducing operation on the second optical disk. The combined focal length NA ₂ of the lens group and the objective lens is the numerical aperture of the objective lens when performing recording or reproducing operation on the second optical disc. When diverging light or convergent light is incident on the objective lens,
The lens group disposed near the objective lens among the plurality of lens groups is movable in a direction opposite to the objective lens moving in a direction orthogonal to the optical axis. The optical pickup optical system according to any one of claims 1 to 16.   When performing recording or reproducing operation on the first optical disk, parallel light or substantially parallel light is incident on the objective lens, and when performing recording or reproducing operation on the second optical disk, divergent light is incident on the objective lens. Is incident, moves the objective lens in a direction orthogonal to the optical axis, and out of the lens groups constituting the relay lens group, the lens group disposed near the objective lens is opposite to the objective lens. The optical pickup optical system according to claim 17, wherein the optical pickup optical system is moved in a direction. The optical pickup optical system according to claim 1, wherein the following expression is satisfied.
0.6 ≦ TO / TR ≦ 1.5
Where TO is the absolute value of the amount of movement of the objective lens in the direction orthogonal to the optical axis during tracking, and TR is the direction in the direction orthogonal to the optical axis of at least one of the relay lens groups during tracking. This is the absolute value of the movement amount.   Among the plurality of lens groups, a lens group disposed closest to the objective lens is a lens formed of plastic having a water absorption of 0.1% or less and a specific gravity of 1.5 or less. The optical pickup optical system according to claim 17 or 18, characterized by comprising:   The optical pickup optical system according to any one of claims 1 to 20, wherein the objective lens includes two lenses.   The optical pickup optical system according to claim 21, wherein, of the two lenses, a lens disposed on a far side of the optical disk has a phase structure. The optical pickup optical system according to claim 21 or 22, wherein the following expression is satisfied.
0.05 ≦ PO ₁ / PO ₂ ≦ 0.2
However, PO ₁ is one of the two lenses, the refractive power of the lens arranged near the side of the relay lens group, PO ₂ is one of the two lenses, it is disposed distally of the relay lens group The refractive power of the lens. The optical pickup optical system has a collimator lens,
24. The collimator lens is disposed in a light path of the light beam emitted from the light source and is further away from the objective lens than the relay lens group. The optical pickup optical system according to any one of the above.   The light according to any one of claims 1 to 24, wherein the optical pickup device performs reproduction and / or recording of the first optical disc and the second optical disc using the same light flux. Pickup optical system.   25. The optical pickup device performs reproduction and / or recording of the first optical disc and the second optical disc using light beams having different wavelengths. Optical pickup optical system. 27. The optical pickup optical system according to claim 1, wherein the following expression is satisfied.
r ₁ × 0.8 <r ₂ <r ₁ × 1.2
Here, r ₁ is the entrance pupil diameter of the relay lens group when reproducing and / or recording the first optical disk, and r ₂ is incident of the relay lens when reproducing and / or recording the second optical disk. The pupil diameter. The thickness t ₁ the second optical disk having a second protective layer of the first optical disk and the thickness having a first protective layer of _{[mm] t 2 [mm]} (t 1 <t 2), using a light beam In an optical pickup device for reproducing and / or recording information,
A light source that emits the luminous flux, and an optical pickup optical system;
The optical pickup optical system is
A relay lens group having a plurality of lens groups including at least one movable lens group movable along the optical axis direction;
Through said relay lens group, and a objective lens for converging the light flux emitted from the light source on the information recording surface of the first optical disc or the second optical disc,
When performing reproduction and / or recording on the first optical disc, the relay lens group emits a light beam so that a magnification of the objective lens is greater than −1/100 and smaller than 1/50, 2 When reproducing and / or recording on an optical disc, divergent light is emitted to the objective lens,
With respect to at least one movable lens group, the position of the movable lens group when reproducing and / or recording the second optical disk from the position of the movable lens group when reproducing and / or recording the first optical disk An optical pickup device characterized in that the movement amount δ [mm] up to satisfies the following conditional expression:
7.5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22
However, NA ₁ is the numerical aperture of the objective lens when reproducing and / or recording on the first optical disk. A light beam is used for a first optical disc having a first protective layer having a thickness of t ₁ [mm] and a second optical disc having a second protective layer having a thickness of t ₂ [mm] (t ₁ <t ₂ ). In an optical disc recording / reproducing apparatus having an optical pickup device for reproducing and / or recording information,
The optical pickup device includes a light source that emits the light beam, and an optical pickup optical system,
The optical pickup optical system is
A relay lens group having a plurality of lens groups including at least one movable lens group movable along the optical axis direction;
Through said relay lens group, and a objective lens for converging the light flux emitted from the light source on the information recording surface of the first optical disc or the second optical disc,
When performing reproduction and / or recording on the first optical disc, the relay lens group emits a light beam so that a magnification of the objective lens is greater than −1/100 and smaller than 1/50, 2 When reproducing and / or recording on an optical disc, divergent light is emitted to the objective lens,
With respect to at least one movable lens group, the position of the movable lens group when reproducing and / or recording the second optical disk from the position of the movable lens group when reproducing and / or recording the first optical disk An optical disc recording / reproducing apparatus characterized in that the movement amount δ [mm] up to
7.5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22
Here, NA1 is the numerical aperture of the objective lens when reproducing and / or recording on the first optical disc. The light source is emitted from the light source to the first optical disc having the first protective layer having a thickness of t ₁ [mm] and the second optical disc having the second protective layer having a thickness of t ₂ [mm] (t ₁ <t ₂ ). In a relay lens group used in an optical pickup optical system of an optical pickup device that reproduces and / or records information using a luminous flux,
And said light source is arranged between the said light beam emitted from the light source first optical disc or the objective lens for condensing onto the information recording surface of the second optical disk,
Having a plurality of lens groups including at least one movable lens group movable along the optical axis direction,
When performing reproduction and / or recording on the first optical disk, a light beam is emitted so that the magnification of the objective lens is greater than −1/100 and smaller than 1/50, and reproduction and / or reproduction is performed on the second optical disk. Or, when recording, emit divergent light to the objective lens,
With respect to at least one movable lens group, the position of the movable lens group when reproducing and / or recording the second optical disk from the position of the movable lens group when reproducing and / or recording the first optical disk A relay lens group in which the amount of movement δ [mm] up to satisfies the following conditional expression:
7.5 ≦ (NA ₁ · δ) / (t ₂ −t ₁ ) ≦ 22
However, NA ₁ is the numerical aperture of the objective lens when reproducing and / or recording on the first optical disk.

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