JP2005129204A - Optical pickup optical system, optical pickup device, and optical information recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup optical system, an optical pickup device and an optical information recording and reproducing device which have compatibility to a multiple types of optical disks, and which can compensate a spherical aberration variation resulting from an environmental temperature change in an objective optical system including a plastic lens when information recording/reproducing on a high-density optical disk is performed. <P>SOLUTION: This optical pickup optical system is provided with an aberration correction optical system which is located in an optical path between a first light source which emits a first luminous flux with a wavelength of 450 nm or less and the objective optical system, and which is made of a glass lens and a plastic lens of which the refractive power is positive. And the rate of change ΔSA/ΔT of the spherical aberration with the temperature rise in the objective optical system when information recording and/or information reproducing on a first optical disk is performed using the first luminous flux, satisfies the following formula (1). The formula (1) is expressed as ΔSA/ΔT>0. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical pickup optical system, an optical pickup device, and an optical information recording / reproducing device.

In recent years, a DVD (Digital Versatile Disc), which is rapidly spreading as an optical recording medium for video information and the like, uses a red semiconductor laser with a wavelength of 650 nm and an objective optical system with a numerical aperture (NA) of 0.65. Although 4.7 GB per unit of information can be recorded, in order to record / reproduce higher density information at a high transfer rate, there is a strong demand for higher density and larger capacity. In order to achieve higher density and larger capacity of the optical disk, it is necessary to reduce the diameter of the spot focused by the objective optical system as is well known. It is necessary to increase the numerical aperture of the system.
Regarding the shortening of the wavelength of the laser light source, a blue-violet semiconductor laser having a wavelength of 405 nm, a blue-violet SHG laser, and the like are being put into practical use. In this optical disc, information of about 15 GB per side can be recorded (hereinafter, the optical disc using the blue-violet laser light source is collectively referred to as “high density optical disc”).

In addition, regarding the increase in the NA of the objective optical system, there is a standard for an optical disk that records / reproduces information (recording and / or reproducing) by condensing a light beam from a blue-violet laser light source by an objective optical system having an NA of 0.85. The proposed optical disc can record information of about 23 GB per side of an optical disc having a diameter of 12 cm.
In a high-density optical disk using an objective optical system with NA of 0.85, coma aberration generated due to the inclination (skew) of the optical disk increases, so the protective layer is designed to be thinner than in the DVD (DVD The amount of coma with respect to skew is reduced by 0.1 mm with respect to 0.6 mm.

By the way, simply saying that information can be appropriately recorded / reproduced with respect to such a high-density optical disc cannot be said to have sufficient value as a product of an optical disc player. In light of the reality that DVDs and CDs (compact discs) on which a wide variety of information is recorded are currently being sold, it is not possible to record / reproduce information on high-density optical discs. Similarly, making it possible to appropriately record / reproduce information with respect to DVDs and CDs leads to an increase in commercial value as an optical disc player for high-density optical discs. From such a background, an optical pickup device mounted on an optical disc player for high density optical discs can record / reproduce information appropriately while maintaining compatibility with any of high density optical discs, DVDs, and CDs. It is desirable to have
Information on optical parts for high-density optical discs and optical parts for DVDs and CDs as a method for appropriately recording / reproducing information while maintaining compatibility with all high-density optical discs, DVDs and CDs Although a method of selectively switching according to the recording density of the optical disc for recording / reproducing the image is conceivable, a plurality of optical components are required, which is disadvantageous for miniaturization and increases the cost.

Therefore, in order to simplify the configuration of the optical pickup device and reduce the cost, the optical components for high-density optical discs and the optical components for DVDs and CDs should be shared in compatible optical pickup devices. It is preferable to reduce the number of optical components constituting the optical pickup device as much as possible, and it is most preferable to share the objective optical system.
Even in an objective optical system that is compatible with a plurality of types of optical disks having different recording densities, it is preferable to use a plastic lens because it is advantageous for mass production. However, since the plastic lens has a refractive index temperature change of about two orders of magnitude larger than that of the glass lens, the spherical aberration of the objective optical system including the plastic lens changes with the temperature change. Since the amount of change in spherical aberration is proportional to λ / NA ⁴ , an objective optical system including a plastic lens compatible with a plurality of types of optical discs can record / reproduce information for high-density DVDs. The spherical aberration change accompanying the temperature change at the time of performing becomes a problem.

The inventor of the present invention is an optical pickup device for a high-density optical disc that includes a light source and an objective optical system having at least one plastic lens, and an aberration correction optical system between the light source and the objective optical system. An optical pickup device having a two-group beam expander optical system was proposed (see Patent Document 1).
JP 2002-82280 A

According to the optical pickup device disclosed in Patent Document 1, it is possible to correct a spherical aberration change generated in the objective optical system with a temperature change by variably adjusting the lens interval of the beam expander optical system.
However, this optical pickup device variably adjusts the lens interval of the beam expander optical system and the spherical aberration detection means for detecting the spherical aberration change of the objective optical system due to the temperature change during recording / reproducing on the high density optical disk. And a control circuit for controlling the actuator in accordance with the detection result of the spherical aberration detector, an increase in the manufacturing cost due to an increase in the number of parts of the optical pickup device, There are problems of increasing the size and complication of the optical pickup device.

The object of the present invention is to take the above-mentioned problems into consideration, and for high-density optical disks and DVDs such as DVDs having different laser light source wavelengths, or for multiple types of optical disks such as high-density optical disks, DVDs and CDs. Thus, an optical pickup optical system that can record / reproduce information appropriately while maintaining compatibility, and is suitable for downsizing, weight reduction, cost reduction, and configuration simplification. / During playback, changes in spherical aberration that occur in objective optical systems including plastic lenses due to environmental temperature changes can be corrected without variably adjusting the lens spacing of multiple lenses that make up the optical system such as a beam expander optical system. It is an object of the present invention to provide an optical pickup optical system having a simple configuration including an aberration correction optical system that can be used.
A further object of the present invention is to provide an optical pickup device equipped with these optical pickup optical systems and an optical information recording / reproducing device equipped with this optical pickup device.

In order to solve the above problems, a first aspect of the present invention includes a first light source that emits a first light flux of 450 nm or less, a second light source that emits a second light flux in a range of 630 nm to 680 nm, Objectives for condensing at least two types of light sources having different wavelengths and light beams emitted from at least two types of light sources having different wavelengths on information recording surfaces of at least two types of optical discs having different recording densities An optical pickup optical system including an optical system and an aberration correction optical system that is disposed in an optical path between the first light source and the objective optical system and includes at least two lens groups; The objective optical system has at least one plastic lens whose refractive power in the paraxial axis is positive, and the aberration correction optical system has a glass lens and a refractive power in the paraxial which is positive. Of the at least two types of optical disks having at least one plastic lens and having different recording densities, the first optical disk is an optical disk on which information is recorded and / or reproduced by the first light flux. 1 is an optical pickup optical system in which the change rate ΔSA / ΔT of spherical aberration accompanying the temperature rise of the objective optical system satisfies the following expression (1) when recording and / or reproducing information on one optical disc.
ΔSA / ΔT> 0 (1)

If a plastic lens having a positive refractive power in the paraxial (hereinafter simply referred to as refractive power) is disposed in the aberration correction optical system, when the temperature of the optical pickup optical system rises, Since the refractive power is reduced, the degree of divergence of the marginal ray of the light beam incident on the objective optical system is reduced. This corresponds to a reduction in the magnification of the objective optical system, and the change in magnification causes the spherical aberration to change in the direction of insufficient correction in the objective optical system.
Further, in an objective optical system having a plastic lens having a positive refractive power, generally, when the temperature of the optical pickup optical system rises, the spherical aberration changes in the overcorrected direction as shown in the equation (1) (hereinafter referred to as temperature). The change in spherical aberration of the objective optical system that accompanies the change is called temperature characteristics).

Here, if the refractive power of the plastic lens in the aberration correction optical system is set appropriately, spherical aberration that changes in the overcorrection direction due to the influence of a decrease in the refractive index of the plastic lens in the objective optical system, and the aberration in the aberration correction optical system It becomes possible to cancel the spherical aberration that changes in the direction of insufficient correction due to a change in the magnification of the objective optical system due to a decrease in the refractive index of the plastic lens.
Thus, following the temperature change during recording / reproduction of the high-density optical disc, the temperature characteristic of the objective optical system is corrected by moving at least one of the lenses constituting the aberration correction optical system by the actuator. Since it is not necessary, the configuration of the compatible optical pickup device can be simplified.
However, since the refractive power of the plastic lens in the aberration correction optical system is uniquely determined depending on the temperature characteristic of the objective optical system, if the aberration correction optical system is composed only of the plastic lens, the focal length, The degree of freedom for determining the paraxial amount of the aberration correction optical system such as back focus and magnification is insufficient. On the other hand, in the invention of claim 1, since the refractive power of the glass lens that is not affected by the temperature change provided in the aberration correction optical system can be freely selected, various specifications of the aberration correction optical system can be selected. It becomes possible to cope with.

In this specification, the sign of the change rate ΔSA / ΔT of the spherical aberration of the objective optical system is positive when the spherical aberration changes in the overcorrection direction, and negative when the spherical aberration changes in the undercorrection direction. It is defined as Further, ΔSA is expressed as an RMS (Root Mean Square) value with the wavelength λ of the first light beam as a unit, and the unit of ΔSA / ΔT is λRMS / ° C.
In this specification, an optical disk using a blue-violet semiconductor laser or a blue-violet SHG laser as a light source for recording / reproducing information is generally referred to as a “high-density optical disk” and has an objective optical system of NA 0.85. In addition to a standard optical disc having a protective layer thickness of about 0.1 mm, information is recorded / reproduced by an objective optical system with an NA of 0.65. It also includes a standard optical disc of about 0.6 mm. In addition to an optical disk having such a protective layer on its information recording surface, an optical disk having a protective film with a thickness of several to several tens of nanometers on the information recording surface, and a protective layer or a protective film An optical disk having a thickness of 0 is also included. In this specification, the high-density optical disk includes a magneto-optical disk that uses a blue-violet semiconductor laser or a blue-violet SHG laser as a light source for recording / reproducing information.

Further, in this specification, DVD series optical disks such as DVD-ROM, DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW are collectively referred to as “DVD”. CD series optical disks such as CD-ROM, CD-Audio, CD-Video, CD-R, and CD-RW are collectively referred to as “CD”.
The first light flux from the first light source for recording / reproducing the high density optical disc is 450 nm or less, preferably in the range of 380 nm to 450 nm, more preferably in the range of 390 nm to 430 nm (λ1). The luminous flux is preferably emitted from the light source. Further, the second light beam from the second light source for recording / reproducing DVD is preferably a light beam that emits a wavelength (λ2) within the range of 630 nm to 680 nm, in order to record / reproduce the CD. The third light beam from the third light source is preferably a light beam that emits a wavelength (λ3) in the range of 750 nm to 800 nm.

  According to a second aspect of the present invention, in the optical pickup optical system according to the first aspect, the optical pickup optical system is disposed in an optical path between the first light source and the aberration correction optical system. And a coupling optical system that converts the divergence angle of the incident first light beam to be small and emits it, and the aberration correction optical system converts the diameter of the incident first light beam and emits it. In the panda optical system, the beam expander optical system preferably includes at least one glass lens having a negative refractive power in the paraxial axis and one plastic lens having a positive refractive power in the paraxial axis.

  According to this, even when a temperature change occurs between the coupling optical system and the beam expander optical system, the divergence degree of the light beam can be made unchanged, so that the pair of optical elements constituting the beam shaping prism can be Astigmatism can be prevented from occurring even when arranged. When enlarging the incident beam diameter, the space between the light source and the beam expander optical system can be made compact. Note that the beam expander optical system includes an apparatus that reduces the beam diameter in addition to expanding the beam diameter.

  According to a third aspect of the present invention, in the optical pickup optical system according to the second aspect, the beam expander optical system is disposed in a common optical path of the first light flux and the second light flux. It is preferable.

  According to this, the temperature characteristic can be corrected even for a DVD using the second light flux. Further, if at least one lens among a plurality of lenses constituting the beam expander optical system is movable by an actuator, spherical aberration can be corrected not only for high-density optical discs but also for recording / reproducing for DVDs. Causes of the occurrence of spherical aberration include, for example, wavelength variations due to manufacturing errors of blue-violet semiconductor lasers and red semiconductor lasers used as light sources, and focus jumps between layers during recording / reproduction with respect to multilayer discs such as two-layer discs and four-layer discs. There are thickness variations and thickness distributions due to manufacturing errors of the protective layer of the optical disk.

According to a fourth aspect of the present invention, in the optical pickup optical system according to the second aspect, the optical pickup optical system includes a beam combiner for combining the optical paths of the first light flux and the second light flux. In addition,
The coupling optical system, the glass lens whose refractive power in the paraxial axis in the beam expander optical system is negative, the beam combiner, and the plastic whose refractive power in the paraxial axis in the beam expander optical system is positive It is preferable that the lens and the objective optical system are arranged in this order from the first light source side.

  According to this, since the plastic lens in the beam expander optical system is in the common optical path of the first light beam and the second light beam, the spherical aberration is overcorrected as the temperature of the objective optical system increases during recording / reproduction of the DVD. In the case of having a temperature characteristic that changes to the above, it is possible to correct the temperature characteristic at the time of recording / reproducing with respect to the DVD. Moreover, the number of parts can be reduced by adopting a configuration in which the plastic lens also serves as a coupling optical system (more preferably, a collimating optical system) for the second light flux. Furthermore, if the plastic lens is movable by an actuator, the spherical aberration can be corrected not only when recording / reproducing with respect to a DVD, but also when recording / reproducing on a DVD.

According to a fifth aspect of the present invention, in the optical pickup optical system according to the second aspect, the optical pickup optical system includes a beam combiner for combining the optical paths of the first light flux and the second light flux. In addition,
The coupling optical system, the plastic lens having a positive refractive power in the paraxial axis in the beam expander optical system, the glass combiner, and the glass having a negative refractive power in the paraxial axis in the beam expander optical system. It is preferable that the lens and the objective optical system are arranged in this order from the first light source side.

  According to this, since the plastic lens in the beam expander optical system is in the exclusive optical path of the first light beam, the presence or absence of the beam expander optical system depends on the temperature characteristics during recording / reproduction with respect to a DVD using the second light beam. Does not affect. Accordingly, the refractive power of the plastic lens can be determined only by correcting the temperature characteristics at the time of recording / reproducing with respect to the high-density optical disk using the first light flux.

  According to a sixth aspect of the present invention, in the optical pickup optical system according to the second aspect, it is preferable that the beam expander optical system is disposed in a dedicated optical path of the first light flux.

  According to this, since the plastic lens in the beam expander optical system is in the exclusive optical path of the first light beam, the presence or absence of the beam expander optical system depends on the temperature characteristics during recording / reproduction with respect to a DVD using the second light beam. Does not affect. Accordingly, the refractive power of the plastic lens in the beam expander optical system can be determined only by correcting the temperature characteristics at the time of recording / reproducing with respect to the high-density optical disk using the first light flux.

  According to a seventh aspect of the present invention, in the optical pickup optical system according to any one of the second to sixth aspects, the coupling optical system includes at least a plastic lens having a positive refractive power in the paraxial direction. It is preferable to have one.

  According to this, the temperature characteristic can be corrected with an optical system including the coupling optical system by using a positive plastic lens of the coupling optical system. Thus, the positive refractive power necessary for correction can be distributed between the beam expander optical system and the coupling optical system, so that the degree of freedom in lens design of the beam expander optical system can be increased.

According to an eighth aspect of the present invention, in the optical pickup optical system according to the third aspect, information is recorded and / or reproduced by the first light flux among at least two types of optical disks having different recording densities. When the optical disc that performs recording is the first optical disc and the optical disc that records and / or reproduces information by the second light flux is the second optical disc,
When recording and / or reproducing information on the first optical disk, the magnification m ₁ of the objective optical system with respect to the first light flux, and when recording and / or reproducing information on the second optical disk, The magnification m _{2 of the} objective optical system with respect to the second light beam substantially matches,
Abbe number ν _{dN of} the glass lens whose refractive power in the paraxial axis in the beam expander optical system is negative, Abbe number ν _{d of} the plastic lens whose refractive power in the paraxial axis in the beam expander optical system is positive It is preferable that _dP satisfies the following formula (2).
ν _dP > ν _dN (2)

  When the beam expander optical system is designed with the first light flux, the parallel light flux is not emitted with the second light flux due to the influence of chromatic aberration caused by the difference in refractive index between the first light flux and the second light flux. When changing the disk from a density optical disk to a DVD, at least one of the plurality of lenses constituting the beam expander optical system is moved by an actuator so that the second light beam is emitted as a parallel light beam. There is a need. Therefore, as in the eighth aspect, the negative glass lens and the positive plastic lens are selected so that the Abbe number satisfies the equation (2), and the chromatic aberration between the first light beam and the second light beam is achromatic. Thus, the second light beam can be emitted as parallel light without moving the lens in the beam expander optical system by an actuator, and the control factor for recording or reproducing information by DVD can be reduced by one.

  According to a ninth aspect of the present invention, in the optical pickup optical system according to the first aspect, the aberration correcting optical system converts the divergence angle of the incident first light beam to be small and emits it. Preferably, the coupling optical system has at least one glass lens and at least one plastic lens having a positive refractive power in the paraxial axis.

  According to this, the temperature characteristic of the objective optical system is corrected to the coupling optical system for converting the divergence angle of the divergent light beam emitted from the blue-violet semiconductor laser as the first light source to be small and guiding it to the objective optical system. Therefore, the function of the aberration correction optical system can be provided, which is advantageous in reducing the number of parts, cost reduction, and size reduction of the optical pickup device.

  According to a tenth aspect of the present invention, in the optical pickup optical system according to the ninth aspect, the coupling optical system is disposed in a common optical path of the first light flux and the second light flux. It is preferable.

  According to this, since the plastic lens in the coupling optical system is in the common optical path of the first light beam and the second light beam, the spherical aberration is overcorrected as the temperature rises when the objective optical system records / reproduces the DVD. In the case of having a temperature characteristic that changes to the above, it is possible to correct the temperature characteristic at the time of recording / reproducing with respect to the DVD. In addition, if the lens constituting the coupling optical system is movable by an actuator, the spherical aberration can be corrected not only when recording / reproducing with respect to a DVD, but also when recording / reproducing the DVD.

According to an eleventh aspect of the present invention, in the optical pickup optical system according to the ninth aspect, the optical pickup optical system includes a beam combiner for combining optical paths of the first light flux and the second light flux. In addition,
The glass lens in the coupling optical system, the beam combiner, the plastic lens having a positive refractive power in the paraxial direction in the coupling optical system, and the objective optical system are arranged in this order from the first light source side. It is preferable.

  According to this, since the plastic lens in the coupling optical system is in the common optical path of the first light beam and the second light beam, the spherical aberration in the overcorrection direction as the temperature of the objective optical system increases during recording / reproduction of the DVD. When the temperature characteristic changes, the temperature characteristic at the time of recording / reproducing with respect to the DVD can be corrected. Moreover, the number of parts can be reduced by adopting a configuration in which the plastic lens also serves as a coupling optical system (more preferably, a collimating optical system) for the second light flux. Furthermore, if the plastic lens is movable by an actuator, the spherical aberration can be corrected not only when recording / reproducing with respect to a DVD, but also when recording / reproducing on a DVD.

According to a twelfth aspect of the present invention, in the optical pickup optical system according to the ninth aspect, the optical pickup optical system includes a beam combiner for combining the optical paths of the first light flux and the second light flux. Further, the glass lens in the coupling optical system has a positive refractive power in the paraxial axis,
The plastic lens having a positive refractive power at the paraxial axis in the coupling optical system, the beam combiner, the glass lens having a positive refractive power at the paraxial axis in the coupling optical system, and the objective optical system in this order. It is preferable to arrange from the first light source side.

  According to this, since the plastic lens in the coupling optical system is in the exclusive optical path of the first light beam, the presence or absence of the coupling optical system affects the temperature characteristics at the time of recording / reproducing with respect to the DVD using the second light beam. Don't give. Accordingly, the refractive power of the plastic lens can be determined only by correcting the temperature characteristics at the time of recording / reproducing with respect to the high-density optical disk using the first light flux. In addition, the number of components can be reduced by employing a configuration in which the glass lens also serves as a coupling optical system (more desirably, a collimating optical system) for the second light flux. Furthermore, if the glass lens can be moved by an actuator, the spherical aberration can be corrected not only when recording / reproducing data on a DVD but also when recording / reproducing data on a DVD.

  According to a thirteenth aspect of the present invention, in the optical pickup optical system according to the ninth aspect, the coupling optical system is disposed in a dedicated optical path of the first light flux.

  According to this, since the plastic lens in the coupling optical system is in the exclusive optical path of the first light beam, the presence or absence of the coupling optical system affects the temperature characteristics during recording / reproduction for a DVD using the second light beam. Don't give. Therefore, the refractive power of the plastic lens in the coupling optical system can be determined only by correcting the temperature characteristics at the time of recording / reproducing with respect to the high-density optical disk using the first light flux.

According to a fourteenth aspect of the present invention, in the optical pickup optical system according to the tenth aspect, information is recorded and / or reproduced by the first light flux among at least two types of optical disks having different recording densities. When the optical disc that performs recording is the first optical disc and the optical disc that records and / or reproduces information by the second light flux is the second optical disc,
When recording and / or reproducing information on the first optical disc, the magnification m ₁ of the objective optical system with respect to the first light flux, and when recording and / or reproducing information on the second optical disc, The magnification m ₂ of the objective optical system with respect to the second light beam substantially coincides, and the coupling optical system includes a glass lens having a negative refractive power in the paraxial axis and a plastic lens having a positive refractive power in the paraxial axis. Have at least one
The Abbe number ν _{dN of} the glass lens whose refractive power in the paraxial axis in the coupling optical system is negative, and the Abbe number ν _{dP of the} plastic lens whose refractive power in the paraxial axis in the coupling optical system is positive. It is preferable to satisfy the following formula (2).
ν _dP > ν _dN (2)

  When the coupling optical system is designed with the first light beam, the parallel light beam is not emitted with the second light beam due to the influence of chromatic aberration caused by the difference in refractive index between the first light beam and the second light beam, and the high density. When the disc is changed from the optical disc to the DVD, it is necessary to move the lens constituting the coupling optical system by the actuator so that the second light flux is emitted as a parallel light flux. Therefore, as in the fourteenth aspect, the coupling optical system is composed of a glass lens having a negative refractive power and a plastic lens having a positive refractive power, and each Abbe number is selected so as to satisfy Equation (2). Then, by eliminating the chromatic aberration between the first light beam and the second light beam, the second light beam can be emitted as a parallel light beam without moving the lens in the coupling optical system by an actuator. It is possible to reduce the control factor when recording or reproducing information according to.

  According to a fifteenth aspect of the present invention, in the optical pickup optical system according to any one of the ninth to fourteenth aspects, the coupling optical system causes the incident first light beam to be parallel to the optical axis. It is preferable to use a collimating optical system that converts the light into a parallel light beam and emits the light.

  According to this, by designing the coupling optical system as a collimating optical system that emits the first light beam as a parallel light beam, even if the objective optical system tracks the information when recording or reproducing information on the high-density optical disk, The point position does not move, and good tracking characteristics can be obtained.

According to a sixteenth aspect of the present invention, in the optical pickup optical system according to any one of the first to fifteenth aspects, the objective optical system includes a first plastic lens disposed in order from the light source side. A diffractive structure that diffracts at least one of the first light flux and the second light flux is formed on at least one optical surface of the first plastic lens; and the power P ₁ (mm ^-1) in the near-axis with respect to the wavelength of the first light flux of the first plastic lens, the refractive power P ₂ in the paraxial with respect to the wavelength of the first light flux of the second plastic lens (mm ^-1 It is preferable that the ratio to the following equation (3) is satisfied.
| P ₁ / P ₂ | ≦ 0.2 (3)

In order to make an objective optical system compatible with a plurality of types of optical discs having different recording densities, it is necessary to correct spherical aberration due to the difference in the thickness of the protective layer of the optical disc. In order to correct such spherical aberration, it is preferable to form a diffractive structure on the optical surface of the objective optical system. Since the diffractive structure has a large wavelength dependency in its optical characteristics, the spherical aberration due to the difference in the thickness of the protective layer of the optical disk is corrected by utilizing the difference in wavelength used for recording / reproducing information. It becomes possible.
However, when such a diffractive structure is formed on an optical surface having a large refractive power in the objective optical system, there is a problem in that the transmittance of the incident light beam is lowered due to the influence of the light beam shifting by the step portion of the diffractive structure. The decrease in transmittance due to the shifting of the light beam increases as the image-side numerical aperture increases.

  According to the sixteenth aspect, the objective optical system is composed of two plastic lenses, and the refractive power with respect to the wavelength of the first light flux of the first plastic lens disposed on the light source side is (for the second plastic lens ( By setting so as to satisfy the expression 3) and forming the diffractive structure on the optical surface of the first plastic lens, it is possible to reduce the influence of the light beam spilling due to the step portion of the diffractive structure as described above. Further, since the refractive power of the objective optical system with respect to the first light flux is exclusively given to the second plastic lens, the working distance for recording or reproducing information on an optical disk having a thick protective layer such as a CD is reduced. Largely secured.

According to a seventeenth aspect of the present invention, in the optical pickup optical system according to the sixteenth aspect, information is recorded and / or reproduced by the first light flux among at least two types of optical disks having different recording densities. When the first optical disc is the optical disc that performs
When recording and / or reproducing information on the first optical disk, the image-side numerical aperture NA _{1 of} the objective optical system, the lens thickness d _L2 on the optical axis of the second plastic lens, the second plastic lens It is preferable that the refractive power P _L2 (mm ⁻¹ ) in the paraxial with respect to the wavelength of the first light beam satisfies the following expressions (4) and (5).
NA ₁ > 0.8 (4)
0.9 <d _L2 · P _L2 <1.3 (5)

When the image-side numerical aperture NA ₁ of the objective optical system when recording / reproducing on a high-density optical disk is larger than 0.8, the refractive power of the optical surface on the light source side of the second plastic lens is very large. Therefore, in order to secure the edge thickness and facilitate the molding, it is necessary to set the lens thickness d _L2 on the optical axis of the second plastic lens large. At this time, it is preferable to set d _L2 to satisfy the formula (5) with respect to the refractive power P _{L2 with} respect to the wavelength of the first light beam, and by setting the d _L2 to be larger than the lower limit of the formula (5), Since it can be secured sufficiently, it becomes easy to mold, and by setting it smaller than the upper limit of the formula (5), it is possible to secure a sufficient working distance at the time of recording / reproducing with respect to the optical disk.

In addition, in a plastic lens, generally, the refractive power of the optical surface on the long conjugate distance side (the longer conjugate distance side) is larger than the refractive power of the optical surface on the short conjugate distance side (the shorter conjugate distance side). Spherical aberration that occurs when the temperature changes greatly occurs on the optical surface on the long conjugate distance side. However, when the numerical aperture on the short conjugate distance side (optical disc side) is not so large as in recording / reproducing for DVD, the temperature is set by setting the lens thickness larger than the refractive power of the plastic lens. It is possible to reduce spherical aberration that occurs on the optical surface on the long conjugate distance side (light source side) during the change.
As in the seventeenth aspect, by setting the lens thickness d _L2 on the optical axis of the second plastic lens to be larger than the lower limit of the equation (5), the temperature characteristics at the time of recording / reproducing with respect to the DVD can be improved. It is possible to keep the temperature characteristic at the time of recording / reproducing with respect to extremely low.
Therefore, when a plastic lens having a positive refractive power in the aberration correction optical system for correcting the temperature characteristics at the time of recording / reproducing with respect to the high-density optical disk is disposed in the common optical path of the first light beam and the second light beam. However, the influence on the temperature characteristics at the time of recording / reproducing with respect to the DVD can be made not so great.

According to an eighteenth aspect of the present invention, in the optical pickup optical system according to the seventeenth aspect, information is recorded and / or reproduced by the first light flux among at least two types of optical disks having different recording densities. When the first optical disc is the optical disc that performs
When recording and / or reproducing information with respect to the first optical disk, the image-side numerical aperture NA _{1 of} the objective optical system and the refractive power P _L2 in the paraxial with respect to the wavelength of the first light flux of the second plastic lens ( mm ⁻¹ ), the magnification m _{L2 of} the second plastic lens with respect to the wavelength of the first light beam, the wavelength λ ₁ (mm) of the first light beam, and the change rate ΔSA / of the spherical aberration accompanying the temperature rise of the objective optical system. ΔT, the sum Σ (P _i · h) of the product of the refractive power P _i in the paraxial to the wavelength of the first light flux of the plastic lens in the aberration correcting optical element and the square of the passing height h _i of the marginal ray _i ² ) preferably satisfies the following expression (6).
0.5 × 10 ⁻⁶ <k / Σ (P _i · h _i ² ) <5.5 × 10 ⁻⁶ (6)
However, k = (ΔSA / ΔT) · λ ₁ · P _L2 / (NA ₁ · (1−m _L2 )) ⁴ .
Furthermore, it is more preferable to satisfy the following expression (6 ′).
1.1 × 10 ⁻⁶ <k / Σ (P _i · h _i ² ) <3.3 × 10 ⁻⁶ (6 ′)

According to this, when the refractive power with respect to the wavelength of the first light flux of the first plastic lens disposed on the light source side is set to satisfy the expression (3) for the second plastic lens, the objective optical The temperature characteristic of the system is almost equal to the temperature characteristic of the second plastic lens.
Accordingly, the change rate ΔSA / ΔT of the spherical aberration accompanying the temperature change of the objective optical system at the time of recording / reproducing with respect to the high-density optical disc is the image side numerical aperture NA ₁ of the objective optical system and the wavelength of the first light flux of the second plastic lens. Is expressed by the following equation (7), with k as a normalization constant, based on the refractive power P _L2 (mm ⁻¹ ), the magnification m _{L2 of} the second plastic lens with respect to the wavelength of the first light flux, and the wavelength λ ₁ of the first light flux. I can do it.
ΔSA / ΔT = k · (NA ₁ · (1−m _L2 )) ⁴ / (λ ₁ · P _L2 ) (7)
However, k = (ΔSA / ΔT) · λ ₁ · P _L2 / (NA ₁ · (1−m _L2 )) ⁴ .

In this way, ΔSA / ΔT is the refractive power P _L2 of the second plastic lens with respect to the wavelength of the first light flux, the image-side numerical aperture NA, the magnification m _{L2 of} the second plastic lens with respect to the wavelength of the first light flux, and the wavelength of the first light flux. The temperature characteristic k which is a value normalized by λ ₁ takes a substantially constant value.
In order to correct the temperature characteristic k of the objective optical system by the action of the plastic lens in the aberration correction optical system, the degree of divergence of the light beam emitted from the aberration correction optical system is changed by a desired amount as the temperature changes. It is necessary to let This change in the degree of divergence, that is, the change in the defocus component of the wavefront emitted from the aberration correction optical system, causes the refractive power P _i to the wavelength of the first light flux of the plastic lens in the aberration correction optical element and the passage of the marginal ray. The change Σ (P _i · h _i ² ) of the degree of divergence necessary for correcting the temperature characteristic k is proportional to the sum Σ (P _i · h _i ² ) of the products of the squares of the height h _i. It is determined corresponding to the size of the characteristic k.

Therefore, the ratio between the temperature characteristic k and Σ (P _i · h _i ² ) takes a substantially constant value, and this ratio is set so as to satisfy the expression (6), so that recording / reproduction with respect to a high-density optical disk is performed. It is possible to satisfactorily correct the temperature characteristic k of the objective optical system at the time. If the ratio of the temperature characteristic k and Σ (P _i · h _i ² ) is set larger than the lower limit of the equation (6), the correction of the temperature characteristic k is not insufficient, and the temperature characteristic is smaller than the upper limit of the equation (6). If the ratio between k and Σ (P _i · h _i ² ) is set, the correction of the temperature characteristic k does not become excessive.
Here, the magnification m _L2 of the second plastic lens with respect to the wavelength of the first light beam is a refractive power P ₁ (mm ⁻¹ ) in the paraxial with respect to the wavelength of the first light beam of the objective optical system, and the first plastic lens. From the refractive power P _L1 (mm ⁻¹ ) in the paraxial with respect to the wavelength of the first light flux, the following formula is used.
m _L2 = P _L1 / P ₁

According to a nineteenth aspect of the present invention, in the optical pickup optical system according to the seventeenth or eighteenth aspect, in addition to the first light source and the second light source, the third light flux in the range of 750 nm to 800 nm. It is preferable to include a third light source that emits light.
In this case, it is preferable that the aberration correction optical system is disposed in a common optical path of the first light beam, the second light beam, and the third light beam. According to this, since the plastic lens in the aberration correction optical system is in the common optical path of the first light beam, the second light beam, and the third light beam, the objective optical system causes spherical aberration as the temperature rises during DVD recording / reproduction. When the temperature characteristic changes in the overcorrection direction, it becomes possible to correct the temperature characteristic at the time of recording / reproducing with respect to the DVD, and the objective optical system becomes spherical aberration as the temperature rises during recording / reproducing of the CD. Can be corrected in the recording / reproducing mode with respect to the CD. If the lens constituting the aberration correction optical system is made movable by an actuator, the spherical aberration can be corrected not only when recording / reproducing not only a high-density optical disc but also DVD and CD.
The first light source, the second light source, and the third light source are preferably packaged light source units. This is advantageous for reducing the number of parts, reducing the cost, and reducing the size.
On the other hand, in the case where the optical pickup optical system includes first to third light sources, the optical pickup optical system is disposed in an optical path between the aberration correction optical system and the objective optical system. It is preferable to further include a beam combiner for synthesizing optical paths of the light beam, the second light beam, and the third light beam.

  According to this, in the objective optical system as in the seventeenth or eighteenth aspect, in order to provide compatibility with the CD, the objective optical system uses the third light beam used for recording / reproduction as a divergent light beam. It is preferable to make it enter into. As a result, a sufficient working distance for a CD having a thick protective layer can be secured. In this case, as a configuration of the optical pickup optical system, a beam combiner for combining the optical paths of the first light flux, the second light flux, and the third light flux is provided in the optical path between the aberration correction optical system and the objective optical system. It is preferable to arrange.

  According to a twentieth aspect of the present invention, in the optical pickup optical system according to the third or tenth aspect, it is preferable that the first light source and the second light source are packaged light source units.

  According to this, when the aberration correction optical element is disposed in the common optical path of the first light beam and the second light beam, the package laser of the first light source and the second light source can be used, and the number of parts can be reduced and the cost can be reduced. This is advantageous for downsizing and downsizing.

According to the twenty-first aspect of the present invention, at least two wavelengths of the first light source that emits the first light flux of 450 nm or less and the second light source that emits the second light flux in the range of 630 nm to 680 nm are different from each other. It comprises a light source of a type and an optical pickup optical system for condensing light beams emitted from at least two types of light sources having different wavelengths on information recording surfaces of at least two types of optical discs having different recording densities. In the optical pickup device
The optical pickup optical system is disposed in an optical path between the objective optical system disposed opposite to the optical disc and the first light source and the objective optical system, and is configured by at least two lens groups. An aberration correction optical system,
The optical pickup optical system preferably includes the optical pickup optical system according to any one of the first to twentieth aspects.

  According to this, the same effect as any of the first to twentieth aspects can be obtained.

According to a twenty-second aspect of the present invention, in the optical pickup device according to the twenty-first aspect, information is recorded and / or reproduced by the first light flux among at least two types of optical disks having different recording densities. When the optical disk to be performed is the first optical disk, the optical pickup device further includes a photodetector for detecting the reflected light beam of the first light beam from the information recording surface of the optical first optical disk,
The first light beam reflected by the information recording surface of the first optical disk preferably enters the photodetector after passing through the objective optical system and all plastic lenses in the aberration correction optical system. .

  According to this, the reflected light beam from the information recording surface of the high-density optical disk passes through all the plastic lenses in the objective optical system and the aberration correction optical system, and then enters the photodetector for the high-density optical disk. In addition, it is preferable to dispose the photodetector in the optical pickup device. As a result, even when the environmental temperature changes, the conjugate relationship between the light source and the photodetector can be made unchanged, so that signal detection with the photodetector for a high-density optical disk can be performed satisfactorily.

According to a twenty-third aspect of the present invention, in the optical pickup device according to the twenty-first or twenty-second aspect, the optical pickup device drives at least one constituent lens in the aberration correction optical system in the optical axis direction. An actuator for
It is preferable that the object point position of the objective optical system with respect to the first light flux is variably adjusted in the optical axis direction by driving at least one component lens in the aberration correction optical system in the optical axis direction by the actuator. .

According to this, the lens in the aberration correction optical system can be driven in the direction of the optical axis by the actuator, so that the focus jump between layers of a multilayer disk such as a two-layer disk or a four-layer disk, a blue-violet semiconductor laser light source Therefore, it is possible to correct the spherical aberration caused by the wavelength variation due to the manufacturing error, etc., so that good recording / reproducing characteristics for the high density optical disc can be obtained.
In addition, spherical aberration caused by a focus jump between recording layers of a multi-layer disc is generated using the distance between the recording layers, the image-side numerical aperture of the objective optical system, and the recording / reproducing wavelength as parameters. Is determined by the standard of the optical disc. Accordingly, since the amount of spherical aberration that occurs at the time of focus jump is determined by the type of optical disc, the amount of movement of the movable lens in the aberration correction optical system that is required at the time of focus jump depends on the type of optical disc and the aberration correction optical system. It is uniquely determined by the specifications. That is, at the time of a focus jump between recording layers of a multi-layer disc, there is no need for spherical aberration detection means for detecting spherical aberration, and the type of optical disc and the direction of focus jump (for example, first layer → second layer, or (Second layer → first layer) is detected, and the movable lens is moved by a fixed amount in the direction determined by the result.

In addition, spherical aberration that occurs due to wavelength variations due to manufacturing errors of the blue-violet semiconductor laser light source can be achieved by adjusting the position of the movable lens in the optical pickup device manufacturing process. There is no need to correct this.
As described above, in the optical pickup device equipped with the optical pickup optical system according to the present invention, the spherical aberration change accompanying the temperature change that occurs during recording / reproducing on the high-density optical disk is automatically caused by the action of the plastic lens in the aberration correction optical system. Therefore, there is no need for a complicated control circuit for controlling the spherical aberration detector and the actuator of the movable lens according to the detection result of the spherical aberration detector, and the configuration of the optical pickup device is simplified and reduced. Cost reduction can be realized.

  According to a twenty-fourth aspect of the present invention, an optical information recording / reproducing apparatus equipped with the optical pickup device according to any one of the twenty-first to twenty-third aspects is preferable. The optical information recording / reproducing apparatus preferably has an optical disc holder that rotatably holds the optical disc. The optical information recording / reproducing apparatus in the present invention includes an optical information recording apparatus, an optical information reproducing apparatus, an optical information recording and an optical information reproducing apparatus, and an apparatus capable of recording and / or reproducing information with respect to an optical information recording medium. Point to.

  According to this, the same effect as any of the twenty-first to twenty-third aspects can be obtained.

  According to the present invention, a high-density optical disc and a DVD such as a DVD having different laser light source wavelengths, or a plurality of types of optical discs such as a high-density optical disc, a DVD, and a CD are appropriately maintained while maintaining compatibility. An optical pickup optical system that can record / reproduce information, and is suitable for downsizing, weight reduction, cost reduction, and simplification of configuration. Thus, it is possible to obtain an optical pickup optical system having a simple configuration including an aberration correction optical system capable of correcting a spherical aberration change generated in an objective optical system including a plastic lens. Further, an optical pickup device equipped with these optical pickup optical systems and an optical information recording / reproducing device equipped with this optical pickup device can be obtained.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 shows a first optical pickup apparatus PU1 that can appropriately record / reproduce information on any of a high-density optical disk HD (first optical disk), DVD (second optical disk), and CD (third optical disk). FIG. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, the numerical aperture NA1 = 0.85, and the optical specification of the DVD is the wavelength λ2 = 658 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.67. The optical specification of the CD is a wavelength λ3 = 785 nm, the protective layer PL3 has a thickness t3 = 1.2 mm, and the numerical aperture NA3 = 0. .51. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

The optical pickup device PU1 emits a 408 nm laser beam (first beam) and emits a 408 nm laser beam (first beam) when recording / reproducing information on the high-density optical disk HD. The red semiconductor laser LD2 (second light source) that emits a 658 nm laser beam (second beam) and emits a laser beam (second light beam) when the information is recorded / reproduced. On the other hand, a CD module MD3 in which an infrared semiconductor laser LD3 (third light source) that emits a 785 nm laser beam (third beam) and a photodetector PD3 are integrated when information is recorded / reproduced. , A beam expander optical system EXP as an aberration correction optical system, a single-axis actuator UAC, and each laser beam is condensed on the information recording surfaces RL1, RL2, and RL3. Objective optical system OBJ, biaxial actuator AC, first beam combiner BC1, second beam combiner BC2, third beam combiner BC3, first collimating optical system COL1, second collimating optical system COL2, It is composed of STO, sensor lens SEN and the like.
The beam expander optical system includes a glass lens (first lens EXP1) having a negative refractive power in the paraxial axis and a plastic lens (second lens EXP2) having a positive refractive power in the paraxial axis. It arrange | positions in the common optical path of a 1st light beam and a 2nd light beam.

When recording / reproducing information with respect to the high-density optical disk HD in the optical pickup device PU1, first, the blue-violet semiconductor laser LD1 is caused to emit light as illustrated by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is converted into a parallel light beam by passing through the first collimating optical system COL1, and then the first and second beam combiners BC1 and BC2, the first lens EXP1, It passes through the two lenses EXP2 and the third beam combiner BC3 in order, and becomes a spot formed on the information recording surface RL1 by the objective optical system OBJ via the protective layer PL1 of the high-density optical disc HD.
A detailed description of the objective optical system OBJ will be described later.

The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL1 passes again through the objective optical system OBJ, the third beam combiner BC3, the second lens EXP2 and the first lens EXP1 of the beam expander optical system EXP, and the second lens EXP2. The beam is branched by the beam combiner BC2, passes through the sensor lens SEN, and converges on the light receiving surface of the photodetector PD12. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD12.
When recording / reproducing information on / from a DVD, first, the red semiconductor laser LD2 is caused to emit light, as illustrated by the dotted line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is reflected by the first beam combiner BC1 and sequentially passes through the second beam combiner BC2, the first lens EXP1, the second lens EXP2, and the third beam combiner BC3. The spot is formed on the information recording surface RL2 via the protective layer PL2 of the DVD by the objective optical system OBJ.

  The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL2 passes through the objective optical system OBJ, the third beam combiner BC3, the second lens EXP2, and the first lens EXP1 again, and is branched by the second beam combiner BC2. Then, the light passes through the sensor lens SEN and converges on the light receiving surface of the photodetector PD12. And the information recorded on DVD can be read using the output signal of photodetector PD12.

When recording / reproducing information with respect to a CD, the infrared ray semiconductor laser LD3 is caused to emit light by operating the CD module MD3, as shown by the two-dot chain line in FIG. The divergent light beam emitted from the infrared semiconductor laser LD3 becomes a spot formed on the information recording surface RL3 by the objective optical system OBJ through the protective layer PL3 of the CD after being reflected by the third beam combiner BC3. . The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light flux modulated by the information pits on the information recording surface RL3 is again transmitted through the objective optical system OBJ, then reflected by the third beam combiner BC3, and converges on the light receiving surface of the photodetector PD3 of the CD module MD3. To do. And the information recorded on CD can be read using the output signal of photodetector PD3.
In the present embodiment, a package light source unit in which the blue-violet semiconductor laser LD1 and the red semiconductor laser LD2 are integrated and housed in one housing can also be used. In this case, the first beam combiner BC1 can be deleted, and for example, the second collimating optical system COL2 can be deleted.

Next, the configuration of the objective optical system OBJ will be described. The objective optical system OBJ has the same configuration in the second to fourth and sixth to ninth embodiments described later.
As shown in FIGS. 2 and 3, the objective optical system OBJ has an aspheric surface on both sides having a function of condensing the aberration correction element L1 and the laser beam transmitted through the aberration correction element L1 on the information recording surface of the optical disk. It is comprised from the condensing element L2 made. The aberration correction element L1 and the condensing element L2 are both plastic lenses, and flange portions FL1 and FL2 formed integrally with the optical function portion are formed around the respective optical function portions, and the flange portion FL1. , FL2 is integrated by fitting a part of each other.
In the present embodiment, the aberration correcting element L1 and the condensing element L2 are integrated by fitting the respective flange portions, but the aberration correcting element L1 and the condensing element L2 are integrated. For example, even if the aberration correction element L1 and the condensing element L2 are integrated via a lens frame, it is sufficient that the relative positional relationship between them is held unchanged. good.
As shown in FIG. 3A, the optical function surface S1 on the light source side of the aberration correction element L1 includes a first area AREA1 corresponding to an area up to a numerical aperture of DVD of 0.67 and a numerical aperture of DVD of 0.67. 2 to the second area AREA2 corresponding to the area of the high-density optical disk HD up to the numerical aperture 0.85, and as shown in FIG. 2 (a), a plurality of rings in which a staircase structure is formed. A staircase type diffraction structure HOE having a structure in which bands are arranged around the optical axis is formed in the first area AREA1.

In the staircase type diffraction structure HOE formed in the first area AREA1, the depth d0 per step of the staircase structure formed in each annular zone is d0 = 2 × λ1 / (n1-1) (μm). The calculated value is set, and the division number N of each annular zone is set to 5. Here, λ1 represents the wavelength of the laser beam emitted from the blue-violet semiconductor laser in units of microns (here, λ1 = 0.408 μm), and n1 is a refractive index with respect to the wavelength λ1 of the aberration correction element L1. (Here, n1 = 1.524).
When a laser beam having a wavelength of λ1 is incident on the staircase type diffractive structure HOE, an optical path difference of 2 × λ1 (μm) is generated between adjacent steps, and the laser beam having a wavelength of λ1 has a substantial phase difference. Since it is not given, it passes through without being diffracted. In the following description, a light beam that is transmitted without being substantially given a phase difference by the step-type diffraction structure is referred to as zero-order diffracted light.

  On the other hand, when a laser beam having a wavelength of λ2 (here, λ2 = 0.658 μm) emitted from the red semiconductor laser is incident on this staircase type diffractive structure HOE, d0 × (n2-1) between adjacent steps. ) −λ2 = 0.13 μm optical path difference occurs, and for one ring zone divided into five, an optical path difference of 0.13 × 5 = 0.65 μm and one wavelength of wavelength λ2 occurs. Wavefronts that have passed through adjacent annular zones overlap each other with a shift of one wavelength. That is, the light beam having the wavelength λ2 becomes diffracted light diffracted in the first-order direction by the staircase type diffraction structure HOE. Note that n2 is a refractive index with respect to the wavelength λ2 of the aberration correction element L2 (here, n2 = 1.5064). At this time, the diffraction efficiency of the first-order diffracted light of the laser beam having the wavelength λ2 is 87.5%, but the amount of light is sufficient for recording / reproducing information with respect to the DVD. In the objective optical system OBJ, the spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disk HD and the DVD is corrected by the action of the staircase type diffraction structure HOE.

In addition, when a laser beam having a wavelength of λ3 (here, λ3 = 0.785 μm) emitted from an infrared semiconductor laser is incident on this step-type diffractive structure, λ3≈2 × λ1, so that it is adjacent. An optical path difference of 1 × λ3 (μm) is generated between the steps, and the laser beam having the wavelength λ3 is transmitted without being diffracted as it is substantially not given a phase difference similarly to the laser beam having the wavelength λ1 (0 Next diffraction light). In the objective optical system OBJ, the spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disc HD and the CD is corrected by making the magnifications with respect to the wavelengths λ1 and λ3 different.
Furthermore, in the objective optical systems OBJ of the first to fourth and sixth to eighth embodiments, the optical function surface S2 on the optical disc side of the aberration correction element L1 is a DVD as shown in FIG. The third area AREA3 including the optical axis corresponding to the area within the numerical aperture 0.67, and the fourth area AREA4 corresponding to the area from the numerical aperture 0.67 of the DVD to the numerical aperture 0.85 of the high-density optical disk HD. The blazed diffraction structure DOE1 is formed in the third area AREA3, and the blazed diffraction structure DOE2 is formed in the fourth area AREA4. The blazed diffractive structures DOE1 and DOE2 are structures for correcting the chromatic aberration of the objective optical system OBJ in the blue-violet region.
In the objective optical system OBJ of the ninth embodiment, the optical function surface S2 on the optical disc side of the aberration correction element L1 is an aspheric surface having a convex shape on the optical disc side in paraxial.

In addition, in the optical pickup device in each embodiment, when recording and / or reproducing information with respect to the first optical disc, the change rate ΔSA / ΔT of the spherical aberration accompanying the temperature change of the objective optical system is expressed by the above equation (1). Designed to meet.
Accordingly, when the refractive power of the plastic lens in the aberration correction optical system is appropriately set with respect to the change rate ΔSA / ΔT of the spherical aberration accompanying the temperature change of the objective optical system OBJ, the refraction of the plastic lens in the objective optical system is achieved. Canceling spherical aberration that changes in the overcorrection direction due to the decrease in the rate and spherical aberration that changes in the direction of undercorrection due to the change in the magnification of the objective optical system due to the decrease in the refractive index of the plastic lens in the aberration correction optical system Is possible.
Accordingly, it is not necessary to correct the temperature characteristic of the objective optical system by moving the lens in the aberration correction optical system by the actuator following the temperature change during recording / reproduction of the high-density optical disc. The configuration can be simplified.

  In addition, since the refractive power of the plastic lens in the aberration correction optical system is uniquely determined depending on the temperature characteristics of the objective optical system, if the aberration correction optical system is composed only of a plastic lens, the focal length, Although the degree of freedom for determining the paraxial amount of the aberration correction optical system such as back focus and magnification is insufficient, in the optical pickup device PU1 of the present embodiment, the influence of the temperature change provided in the aberration correction optical system. Since it is possible to freely select the refractive power of the glass lens that does not receive the light, it is possible to cope with various specifications of the aberration correction optical system.

In the first to fifth embodiments, a pair of optical elements of the beam shaping prism are arranged in the optical path between the collimating optical system (COL, COL1, COL2, COL3) and the beam expander optical system EXP. In such a case, it is preferable to configure the first collimating optical system COL1 with a glass lens. As a result, the parallelism of the light beam emitted from the first collimating optical system COL1 does not change with respect to the temperature change, and astigmatism does not occur even when the temperature change occurs.
Further, in the optical pickup device PU1 in the present embodiment, since the beam expander optical system EXP is disposed in the common optical path of the first light flux and the second light flux, recording / reproduction with respect to the DVD using the second light flux is performed. The temperature characteristics can be corrected even at times. Further, by moving the first lens EXP1 of the beam expander optical system EXP by the uniaxial actuator UAC, it is possible to correct the spherical aberration not only at the time of recording / reproducing on the DVD but also at the time of recording / reproducing on the DVD.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
As shown in FIG. 4, the optical pickup device PU2 includes a blue-violet semiconductor laser LD1 that emits a first light flux, a photodetector PD1, a red semiconductor laser LD2 that emits a second light flux, and a photodetector PD2. A DVD module MD2, a CD module MD3 in which an infrared semiconductor laser LD3 emitting a third light beam and a photodetector PD3 are integrated, a beam expander optical system EXP as an aberration correction optical system, and a single-axis actuator UAC , Objective optical system OBJ, biaxial actuator AC, first beam combiner BC1, second beam combiner BC2, third beam combiner BC3, collimating optical system COL, and the like.
In the optical pickup device PU2 in the present embodiment, the collimating optical system COL, the glass lens (first lens EXP1) whose refractive power on the paraxial axis in the beam expander optical system EXP is negative, and the second beam combiner BC2. The plastic lens (second lens EXP2) having a positive refractive power in the paraxial axis in the beam expander optical system EXP and the objective optical system OBJ are arranged in this order from the blue-violet semiconductor laser LD1 side.

When recording / reproducing information with respect to the high-density optical disk HD in the optical pickup device PU2, first, the blue-violet semiconductor laser LD1 is caused to emit light as illustrated by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 passes through the first beam combiner BC1 and is converted into a parallel light beam by passing through the collimating optical system COL, and then the first lens EXP1, the second beam. The spot passes through the combiner BC2, the second lens EXP2, and the third beam combiner BC3 in order, and becomes a spot formed on the information recording surface RL1 by the objective optical system OBJ via the protective layer PL1 of the high-density optical disc HD.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL1 passes through the objective optical system OBJ, the third beam combiner BC3, the second lens EXP2, the second beam combiner BC2, the first lens EXP1, and the collimating optical system COL. The light is transmitted, branched by the first beam combiner BC1, passes through the sensor lens SEN, and converges on the light receiving surface of the photodetector PD1. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD1.

When recording / reproducing information with respect to a DVD, first, the red semiconductor laser LD2 is caused to emit light, as illustrated by the dotted line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is reflected by the second beam combiner BC2, is converted into a parallel light beam by the second lens EXP2, and then sequentially passes through the third beam combiner BC3. It becomes a spot formed on the information recording surface RL2 via the protective layer PL2 of the DVD by OBJ.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL2 passes again through the objective optical system OBJ, the third beam combiner BC3, and the second lens EXP2, and is branched by the second beam combiner BC2. Converges on the light receiving surface. Then, information recorded on the DVD can be read using the output signal of the photodetector PD2.

  When information is recorded / reproduced with respect to the CD, the infrared ray semiconductor laser LD3 is caused to emit light by operating the CD module MD3, as illustrated by the two-dot chain line in FIG. The divergent light beam emitted from the infrared semiconductor laser LD3 becomes a spot formed on the information recording surface RL3 by the objective optical system OBJ via the protective layer PL3 of the CD after being reflected by the third beam combiner BC3. . The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL3 is transmitted again through the objective optical system OBJ, is reflected by the third beam combiner BC3, and converges on the light receiving surface of the photodetector PD3 of the CD module MD3. To do. And the information recorded on CD can be read using the output signal of photodetector PD3.

  In the optical pickup device PU2 in the present embodiment, since the plastic lens (second lens EXP2) in the beam expander optical system EXP is in the common optical path of the first light flux and the second light flux, the objective optical system OBJ is DVD. When the recording / reproduction has a temperature characteristic such that the spherical aberration changes in the overcorrection direction as the temperature rises, the temperature characteristic at the time of recording / reproduction with respect to the DVD can be corrected by the action of the second lens EXP2. It becomes possible. Further, since the second lens EXP2 also serves as a collimating optical system for the second light flux, the number of parts can be reduced. Furthermore, if the plastic lens (second lens EXP2) can be moved by an actuator, the spherical aberration can be corrected not only when recording / reproducing on a DVD but also on a high-density optical disk.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
As shown in FIG. 5, in the optical pickup device PU3, a blue-violet semiconductor laser LD1, a photodetector PD1, a red semiconductor laser LD2 emitting a second light beam, and a light detector PD2 are integrated. A DVD module MD2, a CD module MD3 in which an infrared semiconductor laser LD3 emitting a third light beam and a photodetector PD3 are integrated, a beam expander optical system EXP as an aberration correction optical system, and a single-axis actuator UAC , Objective optical system OBJ, biaxial actuator AC, first beam combiner BC1, second beam combiner BC2, third beam combiner BC3, collimating optical system COL, coupling optical system CUL3, and the like.
In the optical pickup device PU3 in the present embodiment, the collimating optical system COL, the plastic lens (second lens EXP2) whose refractive power in the paraxial axis in the beam expander optical system EXP is positive, and the second beam combiner BC2. In the beam expander optical system EXP, a glass lens (first lens EXP1) whose refractive power in the paraxial axis is negative and an objective optical system OBJ are arranged in this order from the blue-violet semiconductor laser LD1 side.

When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU3, first, the blue-violet semiconductor laser LD1 is caused to emit light, as illustrated by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 passes through the first beam combiner BC1 and is converted into a parallel light beam by passing through the collimating optical system COL, and then the second lens EXP2, the second beam. The spot passes through the combiner BC2, the first lens EXP1, and the third beam combiner BC3 in order, and becomes a spot formed on the information recording surface RL1 by the objective optical system OBJ via the protective layer PL1 of the high-density optical disc HD.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL1 passes through the objective optical system OBJ, the third beam combiner BC3, the first lens EXP1, the second beam combiner BC2, the second lens EXP2, and the collimating optical system COL. The light is transmitted, branched by the first beam combiner BC1, passes through the sensor lens SEN, and converges on the light receiving surface of the photodetector PD1. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD1.

When recording / reproducing information on / from a DVD, first, the red semiconductor laser LD2 is caused to emit light, as shown by the dotted line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 passes through the coupling optical system CUL3, is reflected by the second beam combiner BC2, is converted into a parallel light beam by the first lens EXP1, and then the third beam. The spot passes through the combiner BC3 and is formed on the information recording surface RL2 via the protective layer PL2 of the DVD by the objective optical system OBJ.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL2 passes again through the objective optical system OBJ, the third beam combiner BC3, and the first lens EXP1, and is branched by the second beam combiner BC2. It passes through CUL3 and converges on the light receiving surface of the photodetector PD2. Then, information recorded on the DVD can be read using the output signal of the photodetector PD2.

When recording / reproducing information with respect to the CD, the infrared ray semiconductor laser LD3 is caused to emit light by operating the CD module MD3 as shown in FIG. The divergent light beam emitted from the infrared semiconductor laser LD3 becomes a spot formed on the information recording surface RL3 by the objective optical system OBJ through the protective layer PL3 of the CD after being reflected by the third beam combiner BC3. . The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light flux modulated by the information pits on the information recording surface RL3 is again transmitted through the objective optical system OBJ, then reflected by the third beam combiner BC3, and converges on the light receiving surface of the photodetector PD3 of the CD module MD3. To do. And the information recorded on CD can be read using the output signal of photodetector PD3.
In the optical pickup device PU3 in the present embodiment, since the plastic lens (second lens EXP2) in the beam expander optical system EXP is in the dedicated optical path of the first light flux, the presence or absence of the beam expander optical system EXP It does not affect the temperature characteristics at the time of recording / reproducing with respect to a DVD using a luminous flux. Therefore, the refractive power of the plastic lens (second lens EXP2) can be determined only by correcting the temperature characteristics during recording / reproduction with respect to the high-density optical disk using the first light flux. Furthermore, by moving the glass lens (first lens EXP1) by the uniaxial actuator UAC, the spherical aberration can be corrected not only when recording / reproducing with respect to a DVD but also with respect to a high-density optical disk.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
As shown in FIG. 6, the optical pickup device PU4 includes a high-density optical disk module MD1 in which a blue-violet semiconductor laser LD1 that emits a first light flux and a photodetector PD1 are integrated, and a red semiconductor that emits a second light flux. A DVD module MD2 in which the laser LD2 and the photodetector PD2 are integrated, a CD module MD3 in which the infrared semiconductor laser LD3 emitting the third light beam and the photodetector PD3 are integrated, and an aberration correction optical system Beam expander optical system EXP, 1-axis actuator UAC, objective optical system OBJ, 2-axis actuator AC, first beam combiner BC1, second beam combiner BC2, first collimating optical system COL1, and second collimating optical system COL2 Etc.
In the optical pickup optical system in the present embodiment, the beam expander optical system EXP is disposed in the dedicated optical path of the first light flux.

  When recording / reproducing information with respect to the high-density optical disc HD in the optical pickup device PU4, first, the blue-violet semiconductor laser LD1 is caused to emit light, as shown by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is converted into a parallel light beam by passing through the first collimating optical system, and then the first lens EXP1 (glass lens whose refractive power in the paraxial is negative), Two lenses EXP2 (a plastic lens having a positive refractive power in the paraxial axis), the first beam combiner BC1, and the second beam combiner BC2 are sequentially passed through the protective layer PL1 of the high-density optical disc HD by the objective optical system OBJ. Thus, the spots are formed on the information recording surface RL1.

  The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light flux modulated by the information pits on the information recording surface RL1 is returned to the objective optical system OBJ, the second beam combiner BC2, the first beam combiner BC1, the second lens EXP2, the first lens EXP1, and the first collimating optical system. It passes through the COL and converges on the light receiving surface of the photodetector PD1. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD1.

When recording / reproducing information with respect to a DVD, first, the red semiconductor laser LD2 is caused to emit light, as illustrated by the dotted line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is converted into a parallel light beam by passing through the second collimating optical system COL2, and then reflected by the first beam combiner BC1 and passes through the second beam combiner BC2. Then, the spot is formed on the information recording surface RL2 via the protective layer PL2 of the DVD by the objective optical system OBJ.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL2 passes again through the objective optical system OBJ and the second beam combiner BC2, is branched by the first beam combiner BC1, and passes through the second collimating optical system COL2. Thus, the light beam is converted into a convergent light beam and then converged on the light receiving surface of the photodetector PD2. Then, information recorded on the DVD can be read using the output signal of the photodetector PD2.

Further, when recording / reproducing information on / from a CD, the infrared ray semiconductor laser LD3 is caused to emit light by operating the CD module MD3, as shown by a two-dot chain line in FIG. The divergent light beam emitted from the infrared semiconductor laser LD3 becomes a spot formed on the information recording surface RL3 by the objective optical system OBJ through the protective layer PL3 of the CD after being reflected by the second beam combiner BC2. . The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL3 is transmitted again through the objective optical system OBJ, then reflected by the second beam combiner BC2, and converges on the light receiving surface of the photodetector PD3 of the CD module MD3. To do. And the information recorded on CD can be read using the output signal of photodetector PD3.
In the optical pickup device PU4 in the present embodiment, since the plastic lens (second lens EXP2) in the beam expander optical system EXP is in the optical path dedicated to the first light flux, the presence or absence of the beam expander optical system EXP It does not affect the temperature characteristics at the time of recording / reproducing for a DVD using a light beam. Therefore, the refractive power of the plastic lens (second lens EXP2) can be determined only by correcting the temperature characteristics during recording / reproduction with respect to the high-density optical disk using the first light flux.

[Fifth Embodiment]
The optical specifications of the high-density optical disk HD in the optical pickup device PU5 in the present embodiment are the wavelength λ1 = 407 nm, the thickness t1 = 0.6 mm of the protective layer PL1, and the numerical aperture NA1 = 0.67. The optical specifications are the wavelength λ2 = 655 nm, the thickness t2 of the protective layer PL2 = 0.6 mm, and the numerical aperture NA2 = 0.66. The optical specifications of the CD are the wavelength λ3 = 785 nm, and the thickness t3 of the protective layer PL3. = 1.2 mm and numerical aperture NA3 = 0.51. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.
As shown in FIG. 7, the optical pickup device PU5 includes a blue-violet semiconductor laser LD1 that emits a first light flux, a red semiconductor laser LD2 that emits a second light flux, an infrared semiconductor laser LD3 that emits a third light flux, ˜Photodetector PD123 common to the third light flux, beam expander optical system EXP as an aberration correction optical system, one-axis actuator UAC, objective optical system OBJ ′, two-axis actuator AC, first beam combiner BC1, second It comprises a beam combiner BC2, a third beam combiner BC3, a first collimating optical system COL1, a second collimating optical system COL2, a third collimating optical system COL3, and the like.
In the optical pickup optical system in the present embodiment, the beam expander optical system EXP is disposed in the common optical path of the first light beam, the second light beam, and the third light beam.

When recording / reproducing information with respect to the high-density optical disk HD in the optical pickup device PU5, first, the blue-violet semiconductor laser LD1 is caused to emit light, as shown by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is converted into a parallel light beam by passing through the first collimating optical system COL1, and then the first beam combiner BC1, the second beam combiner BC2, and the third beam. It passes through the combiner BC3, the first lens EXP1 (a glass lens having a negative refractive power in the paraxial axis), and the second lens EXP2 (a plastic lens having a positive refractive power in the paraxial axis) in order, and is increased by the objective optical system OBJ ′. It becomes a spot formed on the information recording surface RL1 via the protective layer PL1 of the density optical disk HD.
The objective optical system OBJ ′ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL1 passes again through the objective optical system OBJ ′, the second lens EXP2, and the first lens EXP1, is branched by the third beam combiner BC3, and passes through the sensor lens SEN. The light converges on the light receiving surface of the photodetector PD123. The information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD123.

When recording / reproducing information on / from a DVD, first, the red semiconductor laser LD2 is caused to emit light, as illustrated by the dotted line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is converted into a parallel light beam by passing through the second collimating optical system COL2, and then reflected by the first beam combiner BC1, and the second beam combiner BC2 and third Passes through the beam combiner BC3, the first lens EXP1, and the second lens EXP2 in this order, and becomes a spot formed on the information recording surface RL2 via the protective layer PL2 of the DVD by the objective optical system OBJ ′.
The objective optical system OBJ ′ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL2 passes again through the objective optical system OBJ ′, the second lens EXP2, and the first lens EXP1, is branched by the third beam combiner BC3, and passes through the sensor lens SEN. The light converges on the light receiving surface of the photodetector PD123. Then, information recorded on the DVD can be read using the output signal of the photodetector PD123.

When recording / reproducing information on / from a CD, first, the infrared semiconductor laser LD3 is caused to emit light, as shown by the two-dot chain line in FIG. The divergent light beam emitted from the infrared semiconductor laser LD3 is converted into a parallel light beam by passing through the third collimating optical system COL3, and then reflected by the third beam combiner BC3, and the first lens EXP1 and the second lens. It passes through EXP2 in order and becomes a spot formed on the information recording surface RL3 via the protective layer PL3 of the CD by the objective optical system OBJ ′.
The objective optical system OBJ ′ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL3 passes again through the objective optical system OBJ ′, the second lens EXP2, and the first lens EXP1, is branched by the third beam combiner BC3, and passes through the sensor lens SEN. The light converges on the light receiving surface of the photodetector PD123. And the information recorded on CD can be read using the output signal of photodetector PD123.
In the present embodiment, a package light source unit in which the red semiconductor laser LD2 and the infrared semiconductor laser LD3 are integrated and housed in one housing can be used. In this case, the second beam combiner BC2 can be deleted, and the number of collimating optical systems can be two. For example, the third collimating optical system COL3 can be deleted.
In the present embodiment, a package light source unit in which the blue-violet semiconductor laser LD1 and the red semiconductor laser LD2 are integrated and housed in one housing can also be used. In this case, the first beam combiner BC1 can be deleted, and the number of collimating optical systems can be two. For example, the second collimating optical system COL2 can be deleted.
Furthermore, in this embodiment, a package light source unit in which the blue-violet semiconductor laser LD1, the red semiconductor laser LD2, and the infrared semiconductor laser LD3 are integrated and housed in one housing can be used. In this case, the first and second beam combiners BC1 and BC2 can be deleted, and the number of collimating optical systems can be reduced to one. For example, the second and third collimating optical systems COL2 and COL3 are deleted. be able to.
Next, the configuration of the objective optical system OBJ ′ will be described. The objective optical system OBJ ′ has the same configuration in a tenth embodiment described later.

The objective optical system OBJ ′ is composed of a single plastic lens whose both surfaces are aspherical, and a blazed diffractive structure DOE3 is formed on the optical function surface S1 on the light source side. The blazed diffractive structure DOE3 is a structure for correcting spherical aberrations of the wavelengths λ1 and λ2 caused by the chromatic aberration of the plastic lens. Due to this action, the first light beam and the second light beam are respectively separated from the high-density optical disk HD. Good spots are formed on each information recording surface of the DVD. In the objective optical system OBJ ′, the spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disc HD and the CD is corrected by making the magnifications with respect to the wavelengths λ1 and λ3 different. In the fifth and tenth embodiments, the glass lens (the first lens EXP1 in the fifth embodiment and the first lens CUL1 in the tenth embodiment) in the aberration correction optical system is uniaxial. By moving the actuator UAC, the magnification of the objective optical system OBJ ′ is changed.
In the optical pickup device PU5 in the present embodiment, since the plastic lens (second lens EXP2) in the beam expander optical system EXP is in the common optical path of the first light beam, the second light beam, and the third light beam, the objective optical system When OBJ 'has a temperature characteristic such that the spherical aberration changes in the overcorrected direction as the temperature rises during recording / reproduction of DVD or CD, recording / reproduction for DVD or CD is performed by the action of the second lens EXP2. It is possible to correct the temperature characteristics of the hour. Furthermore, since the second lens EXP1 can be moved by the single-axis actuator UAC, spherical aberration can be corrected not only when recording / reproducing on DVD and CD but also on high-density optical disks.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
As shown in FIG. 8, the optical pickup device PU6 includes a light source unit LU1, a first light flux and a first light flux unit, in which a blue-violet semiconductor laser LD1 that emits a first light flux and a red semiconductor laser LD2 that emits a second light flux are integrated. Photodetector PD12 common to two light beams, infrared semiconductor laser LD3 emitting a third light beam and CD module MD3 in which the light detector PD3 is integrated, a coupling optical system CUL as an aberration correction optical system, one axis The actuator UAC, the objective optical system OBJ, the biaxial actuator AC, the first beam combiner BC1, the second beam combiner BC2, and the like.

In the sixth to tenth embodiments, the coupling optical system CUL as an aberration correction optical element is a collimating optical system that converts a divergent light beam having a wavelength λ1 emitted from the blue-violet semiconductor laser LD1 into a parallel light beam. It is.
The coupling optical system includes a glass lens (first lens CUL1) and a plastic lens (second lens CUL2) whose refractive power in the paraxial axis is positive, and is common to the first and second light beams. It is arranged in the optical path.

When recording / reproducing information with respect to the high-density optical disk HD in the optical pickup device PU6, first, the blue-violet semiconductor laser LD1 is caused to emit light, as shown by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 has a first beam combiner BC1, a first lens CUL1 (a glass lens whose refractive power in the paraxial is negative), and a second lens CUL2 (which has a positive refractive power in the paraxial). And the second beam combiner BC2 in order, and becomes a spot formed on the information recording surface RL1 by the objective optical system OBJ via the protective layer PL1 of the high-density optical disk HD.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL1 passes again through the objective optical system OBJ, the second beam combiner BC2, the second lens CUL2, and the first lens CUL1, and is branched by the first beam combiner BC1. Then, the light passes through the sensor lens SEN and converges on the light receiving surface of the photodetector PD12. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD12.
Information recording / reproduction with respect to a DVD is the same as information recording / reproduction with respect to a high-density optical disk HD, and thus description thereof is omitted.

  Further, when recording / reproducing information on / from a CD, the infrared ray semiconductor laser LD3 is caused to emit light by operating the CD module MD3, as shown by a two-dot chain line in FIG. The divergent light beam emitted from the infrared semiconductor laser LD3 becomes a spot formed on the information recording surface RL3 by the objective optical system OBJ through the protective layer PL3 of the CD after being reflected by the second beam combiner BC2. . The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL3 is transmitted again through the objective optical system OBJ, is reflected by the second beam combiner BC2, and converges on the light receiving surface of the photodetector PD3 of the CD module MD3. To do. And the information recorded on CD can be read using the output signal of photodetector PD3.

In the sixth to tenth embodiments, since the coupling optical system CUL includes a glass lens and a plastic lens having a positive refractive power, the temperature characteristics of the objective optical systems OBJ and OBJ ′ are included in the coupling optical system CUL. The function of an aberration correction optical system for correcting the above can be provided, which is advantageous in reducing the number of parts, cost reduction, and size reduction of the optical pickup device.
In the sixth to tenth embodiments, when a beam shaping element for shaping the cross-sectional shape of the laser beam emitted from the blue-violet semiconductor laser LD1 from an ellipse to a circle is used, at least one optical A beam shaping element having a cylindrical surface is preferably disposed in the optical path between the blue-violet semiconductor laser LD1 and the coupling optical system.
Further, in the optical pickup device PU6 in the present embodiment, since the coupling optical system CUL is disposed in the common optical path of the first light beam and the second light beam, the objective optical system OBJ is used for DVD recording / reproduction. When the temperature characteristic is such that the spherical aberration changes in the overcorrection direction as the temperature rises, the temperature characteristic at the time of recording / reproducing with respect to the DVD can be corrected by the action of the second lens CUL2. Further, by moving the first lens CUL1 by the uniaxial actuator UAC, it is possible to correct spherical aberration not only when recording / reproducing with respect to a DVD but also with respect to a high-density optical disc.

[Seventh Embodiment]
Next, a seventh embodiment of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
As shown in FIG. 9, the optical pickup device PU7 includes a blue-violet semiconductor laser LD1 that emits a first light flux, a red semiconductor laser LD2 that emits a second light flux, a photodetector PD12 that is common to the first light flux and the second light flux, A CD module MD3 in which an infrared semiconductor laser LD3 emitting a third light beam and a photodetector PD3 are integrated, a coupling optical system CUL as an aberration correction optical system, a single-axis actuator UAC, an objective optical system OBJ, 2 The actuator includes an axis actuator AC, a first beam combiner BC1, a second beam combiner BC2, a third beam combiner BC3, and the like.
In the optical pickup device PU7 in the present embodiment, the glass lens (first lens CUL1) whose refractive power in the paraxial axis in the coupling optical system CUL is negative, the second beam combiner BC2, and the coupling optical system CUL. A plastic lens (second lens CUL2) having a positive refractive power in the paraxial center and an objective optical system OBJ are arranged in this order from the blue-violet semiconductor laser LD1 side.

When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU7, the blue-violet semiconductor laser LD1 is first caused to emit light as shown by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 passes through the first lens CUL1, the first beam combiner BC1, and the second beam combiner BC2, and is converted into a parallel light beam by the second lens CUL2, and then the third light beam. And a spot formed on the information recording surface RL1 via the protective layer PL1 of the high-density optical disc HD by the objective optical system OBJ.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL1 passes again through the objective optical system OBJ, the third beam combiner BC3, and the second lens CUL2, and is branched by the second beam combiner BC2, and passes through the sensor lens SEN. As a result, the light converges on the light receiving surface of the photodetector PD12. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD12.

When recording / reproducing information on a DVD, first, the red semiconductor laser LD2 is caused to emit light, as shown by the dotted line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is reflected by the first beam combiner BC1, passes through the second beam combiner BC2, is converted into a parallel light beam by the second lens CUL2, and then the third beam combiner. The spot passes through BC3 and is formed on the information recording surface RL2 by the objective optical system OBJ through the protective layer PL2 of the DVD.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL2 passes again through the objective optical system OBJ, the third beam combiner BC3, and the second lens CUL2, and is branched by the second beam combiner BC2, and passes through the sensor lens SEN. As a result, it converges on the light receiving surface of the photodetector PD12. And the information recorded on DVD can be read using the output signal of photodetector PD12.

When recording / reproducing information with respect to a CD, as shown in FIG. 9, the light path is drawn by a two-dot chain line, first, the CD module MD3 is operated to emit the infrared semiconductor laser LD3. Let The divergent light beam emitted from the infrared semiconductor laser LD3 is reflected by the third beam combiner BC3 and becomes a spot formed on the information recording surface RL3 by the objective optical system OBJ via the CD protective layer PL3.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL3 again passes through the objective optical system OBJ, is branched by the third beam combiner BC3, and converges on the light receiving surface of the photodetector PD3. And the information recorded on CD can be read using the output signal of photodetector PD3.

  In the optical pickup device PU7 in the present embodiment, since the plastic lens (second lens CUL2) in the coupling optical system CUL is in the common optical path of the first light flux and the second light flux, the objective optical system OBJ is used for DVD recording. / When the reproduction has a temperature characteristic such that the spherical aberration changes in the overcorrection direction as the temperature rises during reproduction, the temperature characteristic at the time of recording / reproduction with respect to the DVD can be corrected by the action of the second lens CUL2. It becomes. Further, since the second lens CUL2 also serves as a collimating optical system for the second light flux, the number of parts can be reduced. Further, by moving the second lens by the uniaxial actuator UAC, spherical aberration can be corrected not only when recording / reproducing with respect to a DVD, but also when recording / reproducing with respect to a DVD.

[Eighth Embodiment]
Next, an eighth embodiment of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
As shown in FIG. 10, in the optical pickup device PU8, the blue-violet semiconductor laser LD1, the photodetector PD1, the red semiconductor laser LD2 that emits the second light beam, and the photodetector PD2 that emit the first light beam are integrated. A DVD module MD2, a CD module MD3 in which an infrared semiconductor laser LD3 emitting a third light beam and a photodetector PD3 are integrated, a coupling optical system CUL as an aberration correction optical system, a single-axis actuator UAC, The objective optical system OBJ, a two-axis actuator AC, a first beam combiner BC1, a second beam combiner BC2, a third beam combiner BC3, and the like are included.

In addition, the coupling optical system CUL includes a second lens CUL2 in which a glass lens having a negative paraxial refractive power, a plastic lens having a positive paraxial refractive power, and a paraxial refractive power are positive. In the optical pickup device PU8 in the present embodiment, the second lens CUL2, the second beam combiner BC2, and the coupling optical system CUL in the coupling optical system CUL are configured with the glass lens (first lens CUL1). The glass lens (first lens CUL1) in the middle and the objective optical system OBJ are arranged in this order from the blue-violet semiconductor laser LD1 side.
When recording / reproducing information with respect to the high-density optical disk HD in the optical pickup device PU8, first, the blue-violet semiconductor laser LD1 is caused to emit light, as shown by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 passes through the first beam combiner BC1, the second lens CUL2, and the second beam combiner BC2, and is converted into a parallel light beam by the first lens CUL1, and then the third light beam. And a spot formed on the information recording surface RL1 via the protective layer PL1 of the high-density optical disc HD by the objective optical system OBJ.

  The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL1 passes again through the objective optical system OBJ, the third beam combiner BC3, the first lens CUL1, the second beam combiner BC2, and the second lens CUL2 in order, 1 is split by the beam combiner BC1, passes through the sensor lens SEN, and converges on the light receiving surface of the photodetector PD1. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD1.

  When recording / reproducing information with respect to a DVD, first, the red semiconductor laser LD2 is caused to emit light, as illustrated by a dotted line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is reflected by the second beam combiner BC2, converted into a parallel light beam by the first lens CUL1, passes through the third beam combiner BC3, and is reflected by the objective optical system OBJ. It becomes a spot formed on the information recording surface RL2 via the protective layer PL2 of the DVD.

The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL2 passes again through the objective optical system OBJ, the third beam combiner BC3, and the first lens CUL1, is branched by the second beam combiner BC2, and is detected by the photodetector PD2. Converges on the light receiving surface. Then, information recorded on the DVD can be read using the output signal of the photodetector PD2.
When recording / reproducing information on / from a CD, as shown in FIG. 10, the light path is drawn by a two-dot chain line, first, the CD module MD3 is operated to emit the infrared semiconductor laser LD3. Let The divergent light beam emitted from the infrared semiconductor laser LD3 is reflected by the third beam combiner BC3 and becomes a spot formed on the information recording surface RL3 by the objective optical system OBJ via the CD protective layer PL3.

The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL2 passes again through the objective optical system OBJ, is branched by the third beam combiner BC3, and converges on the light receiving surface of the photodetector PD3. And the information recorded on CD can be read using the output signal of photodetector PD3.
In the optical pickup device PU8 in the present embodiment, since the second lens CUL2 including the plastic lens in the coupling optical system CUL is in the optical path dedicated to the first light flux, the presence or absence of the coupling optical system CUL is determined by the second light flux. This does not affect the temperature characteristics during recording / reproduction with respect to a DVD that uses DVD. Accordingly, it is possible to determine the refractive power of the plastic lens in the second lens CUL2 only in consideration of correcting the temperature characteristics at the time of recording / reproducing with respect to the high-density optical disk using the first light flux. Further, since the first lens CUL1 also serves as a collimating optical system for the second light beam, the number of parts can be reduced. Further, by moving the second lens CUL1 by the uniaxial actuator UAC, spherical aberration can be corrected not only when recording / reproducing with respect to a DVD but also with respect to a high-density optical disc.

[Ninth Embodiment]
Next, a ninth embodiment of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
As shown in FIG. 11, the optical pickup device PU9 includes a high-density optical disk module MD1 in which a blue-violet semiconductor laser LD1 that emits a first light flux and a photodetector PD1 are integrated, and a red semiconductor that emits a second light flux. A DVD module MD2 in which the laser LD2 and the photodetector PD2 are integrated, a CD module MD3 in which the infrared semiconductor laser LD3 emitting the third light beam and the photodetector PD3 are integrated, and an aberration correction optical system Coupling optical system CUL, 1-axis actuator UAC, objective optical system OBJ, 2-axis actuator AC, first beam combiner BC1, second beam combiner BC2, collimating optical system COL, and the like.
The coupling optical system CUL is disposed in a dedicated optical path for the first light flux.

When recording / reproducing information with respect to the high-density optical disk HD in the optical pickup device PU9, first, the blue-violet semiconductor laser LD1 is caused to emit light as shown by the solid line in FIG. A divergent light beam emitted from the blue-violet semiconductor laser LD1 includes a first lens CUL1 (a glass lens having a negative refractive power in the paraxial axis), a second lens CUL2 (a plastic lens having a positive refractive power in the paraxial axis), a first lens CUL1. It passes through the first beam combiner BC1 and the second beam combiner BC2, and becomes a spot formed on the information recording surface RL1 via the protective layer PL1 of the high-density optical disc HD by the objective optical system OBJ.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light flux modulated by the information pits on the information recording surface RL1 passes again through the objective optical system OBJ, the second beam combiner BC2, the first beam combiner BC1, the second lens CUL2, and the first lens CUL1 in order. It converges on the light receiving surface of the detector PD1. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD1.

When recording / reproducing information with respect to a DVD, first, the red semiconductor laser LD2 is caused to emit light, as illustrated by the dotted line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is converted into a parallel light beam by passing through the collimating optical system COL, then reflected by the first beam combiner BC1, passes through the second beam combiner BC2, and the objective. It becomes a spot formed on the information recording surface RL2 via the protective layer PL2 of the DVD by the optical system OBJ.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL2 passes again through the objective optical system OBJ and the second beam combiner BC2, is branched by the first beam combiner BC1, passes through the collimating optical system COL, and is light. It converges on the light receiving surface of the detector PD2. Then, information recorded on the DVD can be read using the output signal of the photodetector PD2.

When recording / reproducing information on / from a CD, as shown in FIG. 11, the light path is indicated by a two-dot chain line, first, the CD module MD3 is operated to emit the infrared semiconductor laser LD3. Let The divergent light beam emitted from the infrared semiconductor laser LD3 is reflected by the second beam combiner BC2, and becomes a spot formed on the information recording surface RL3 by the objective optical system OBJ via the CD protective layer PL3.
The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL3 again passes through the objective optical system OBJ, is branched by the third beam combiner BC3, and converges on the light receiving surface of the photodetector PD3. And the information recorded on CD can be read using the output signal of photodetector PD3.
In the optical pickup device PU9 in the present embodiment, since the plastic lens (second lens CUL2) in the coupling optical system CUL is in the optical path dedicated to the first light flux, the presence of the coupling optical system CUL uses the second light flux. This does not affect the temperature characteristics during recording / reproduction with respect to a DVD. Therefore, the refractive power of the plastic lens (second lens CUL2) can be determined only by correcting the temperature characteristics at the time of recording / reproducing with respect to the high-density optical disk using the first light flux.

[Tenth embodiment]
Next, a tenth embodiment of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
As shown in FIG. 12, the optical pickup device PU10 includes a blue-violet semiconductor laser LD1 that emits a first light flux, a red semiconductor laser LD2 that emits a second light flux, an infrared semiconductor laser LD3 that emits a third light flux, -Photodetector PD123 common to the third light flux, coupling optical system CUL as an aberration correction optical system, single-axis actuator UAC, objective optical system OBJ ', two-axis actuator AC, first beam combiner BC1, second beam It comprises a combiner BC2, a third beam combiner BC3, and the like.
In the optical pickup optical system in the present embodiment, the coupling optical system CUL is disposed in the common optical path of the first light flux, the second light flux, and the third light flux.

When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU10, first, the blue-violet semiconductor laser LD1 is caused to emit light as illustrated by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is a first beam combiner BC1, a second beam combiner BC2, a third beam combiner BC3, a first lens CUL1 (a glass lens having a negative refractive power in the paraxial axis). ), And sequentially passes through the second lens CUL2 (a plastic lens having a positive refractive power in the paraxial axis) and is formed on the information recording surface RL1 by the objective optical system OBJ ′ via the protective layer PL1 of the high-density optical disc HD. Become a spot.
The objective optical system OBJ ′ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL1 passes again through the objective optical system OBJ ′, the second lens CUL2, and the first lens CUL1, is branched by the third beam combiner BC3, and passes through the sensor lens SEN. The light converges on the light receiving surface of the photodetector PD123. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD1.

When recording / reproducing information with respect to a DVD, first, the red semiconductor laser LD2 is caused to emit light, as shown by the dotted line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is reflected by the first beam combiner BC1, and sequentially passes through the second beam combiner BC2, the third beam combiner BC3, the first lens CUL1, and the second lens CUL2. It becomes a spot formed on the information recording surface RL2 via the protective layer PL2 of the DVD by the objective optical system OBJ ′.
The objective optical system OBJ ′ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL2 passes again through the objective optical system OBJ ′, the second lens CUL2, and the first lens CUL1, is branched by the third beam combiner BC3, and passes through the sensor lens SEN. The light converges on the light receiving surface of the photodetector PD123. Then, information recorded on the DVD can be read using the output signal of the photodetector PD123.

When recording / reproducing information with respect to a CD, first, the infrared semiconductor laser LD3 is caused to emit light, as shown by the two-dot chain line in FIG. The divergent light beam emitted from the infrared semiconductor laser LD3 is reflected by the second beam combiner BC2, passes through the first lens CUL1 and the second lens CUL2 in order, and passes through the protective layer PL3 of the CD by the objective optical system OBJ ′. Thus, the spots are formed on the information recording surface RL3.
The objective optical system OBJ ′ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL3 passes again through the objective optical system OBJ ′, the second lens CUL2, and the first lens CUL1, is branched by the third beam combiner BC3, and passes through the sensor lens SEN. The light converges on the light receiving surface of the photodetector PD123. And the information recorded on CD can be read using the output signal of photodetector PD123.

  In the optical pickup device PU10 in the present embodiment, since the plastic lens (second lens CUL2) in the coupling optical system CUL is in the common optical path of the first light beam, the second light beam, and the third light beam, the objective optical system OBJ When the recording / reproduction of DVD or CD has a temperature characteristic such that the spherical aberration changes in the overcorrection direction as the temperature rises during recording / reproduction of DVD or CD, the second lens CUL2 acts to record / reproduce the DVD or CD. It is also possible to correct the temperature characteristics of. Further, by moving the glass lens (first lens CUL1) in the coupling optical system by the uniaxial actuator UAC, it is possible to correct the spherical aberration at the time of recording / reproducing not only for the high density optical disc but also for DVD and CD.

[Eleventh embodiment]
The optical specifications of the high-density optical disc HD in the optical pickup device PU11 in the present embodiment are the wavelength λ1 = 405 nm, the thickness t1 = 0.1 mm of the protective layer PL1, and the numerical aperture NA1 = 0.85. The optical specification is a wavelength λ2 = 655 nm, the thickness t2 of the protective layer PL2 is 0.6 mm, and the numerical aperture NA2 = 0.65. The optical specification of the CD is a wavelength λ3 = 785 nm, and the thickness t3 of the protective layer PL3. = 1.2 mm and numerical aperture NA3 = 0.45. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.
As shown in FIG. 15, in the optical pickup device PU11, a blue-violet semiconductor laser LD1 that emits a first light beam, a red semiconductor laser LD2 that emits a second light beam, and an infrared semiconductor laser LD3 that emits a third light beam are integrated. Laser light source unit LD123, photodetector PD123 common to the first to third light beams, beam expander optical system EXP as an aberration correction optical system, one-axis actuator UAC, objective optical system OBJ '', two-axis actuator AC, It consists of a beam combiner BC, a collimating optical system COL, and the like.
In the optical pickup optical system in the present embodiment, the beam expander optical system EXP is disposed in the common optical path of the first light beam, the second light beam, and the third light beam.

When recording / reproducing information with respect to the high-density optical disk HD in the optical pickup device PU11, the uniaxial actuator UAC is arranged so that the first light flux is emitted from the beam expander optical system EXP in the state of a parallel light flux. After adjusting the position of the first lens EXP1 in the optical axis direction, the blue-violet semiconductor laser LD1 is caused to emit light. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is reflected by the beam combiner BC and converted into a parallel light beam by passing through the collimating optical system COL, as shown by the solid line in FIG. , The first lens EXP1 and the second lens EXP2 are sequentially passed, the diameter of the light beam is regulated by the stop STO, and formed on the information recording surface RL1 by the objective optical system OBJ ″ via the protective layer PL1 of the high-density optical disc HD. It becomes a spot.
The objective optical system OBJ ″ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL1 passes through the objective optical system OBJ ″, the second lens EXP2, and the first lens EXP1 again, and is converted into a convergent light beam by passing through the collimating optical system COL. After that, the light passes through the beam combiner BC and the sensor lens SEN and converges on the light receiving surface of the photodetector PD123. The information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD123.

When information is recorded / reproduced with respect to the DVD, the light from the first lens EXP1 is output by the uniaxial actuator UAC so that the second light flux is emitted from the beam expander optical system EXP in the state of a parallel light flux. After adjusting the position in the axial direction, the red semiconductor laser LD2 is caused to emit light. The divergent light beam emitted from the red semiconductor laser LD2 is reflected by the beam combiner BC and converted into a substantially parallel light beam by passing through the collimating optical system COL, as depicted by the dotted line in FIG. The first lens EXP1 and the second lens EXP2 are converted into parallel light fluxes. Thereafter, the spot is formed on the information recording surface RL2 via the protective layer PL2 of the DVD by the objective optical system OBJ ″.
The objective optical system OBJ ″ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL1 passes through the objective optical system OBJ ″, the second lens EXP2, and the first lens EXP1 again, and is converted into a convergent light beam by passing through the collimating optical system COL. After that, the light passes through the beam combiner BC and the sensor lens SEN and converges on the light receiving surface of the photodetector PD123. Then, information recorded on the DVD can be read using the output signal of the photodetector PD123.

When information is recorded / reproduced with respect to the CD, the light from the first lens EXP1 is output by the uniaxial actuator UAC so that the third light beam is emitted from the beam expander optical system EXP in the state of a parallel light beam. After adjusting the position in the axial direction, the infrared semiconductor laser LD3 is caused to emit light. The divergent light beam emitted from the infrared semiconductor laser LD3 is reflected by the beam combiner BC and is converted into a substantially parallel light beam by passing through the collimating optical system COL, as depicted in the two-dot chain line in FIG. Then, the light passes through the first lens EXP1 and the second lens EXP2 and is converted into a parallel light beam. Thereafter, the spot is formed on the information recording surface RL3 via the protective layer PL3 of the CD by the objective optical system OBJ ″.
The objective optical system OBJ ″ performs focusing and tracking by a biaxial actuator AC arranged in the periphery thereof. The reflected light beam modulated by the information pits on the information recording surface RL3 passes through the objective optical system OBJ ″, the second lens EXP2, and the first lens EXP1 again, and is converted into a convergent light beam by passing through the collimating optical system COL. After that, the light passes through the beam combiner BC and the sensor lens SEN and converges on the light receiving surface of the photodetector PD123. And the information recorded on CD can be read using the output signal of photodetector PD123.

Next, the configuration of the objective optical system OBJ ″ will be described.
The objective optical system OBJ ″ has a function of condensing the aberration correction element L1 and the laser beam transmitted through the aberration correction element L1 on the information recording surface of the optical disc, as shown in a schematic configuration diagram in FIG. It is comprised from the condensing element L2 by which both surfaces were aspherical. Both the aberration correction element L1 and the condensing element L2 are plastic lenses, and the aberration correction element L1 and the condensing element L2 are integrated via a lens frame LB. As described above, the flange portions FL1 and FL2 formed integrally with the optical function portion are formed around the optical function portions of the aberration correction element L1 and the condensing element L2, and the flange portions FL1 and FL2 are formed. They may be integrated by fitting a part of them.
The optical function surface S1 on the light source side of the aberration correction element L1 includes a first area AREA1 corresponding to an area up to a numerical aperture of DVD of 0.65, and a numerical aperture of 0. A staircase that is divided into a second area AREA2 corresponding to the area up to 85 (not shown), and in which a plurality of annular zones in which a staircase structure is formed are arranged around the optical axis A type diffraction structure HOE is formed in the first area AREA1.
The stair-type diffractive structure HOE is a structure for correcting spherical aberration caused by the difference in the thickness of the protective layer between the high-density optical disk HD and the DVD, and its function and structure are the steps of the objective optical system OBJ described above. Since it is the same as the type diffraction structure HOE, a detailed description is omitted here.

  Further, in the objective optical system OBJ ″, the optical function surface S2 on the optical disc side of the aberration correction element L1 includes a third area AREA3 including an optical axis corresponding to an area within the numerical aperture 0.45 of the CD, and the CD A plurality of rings divided into a fourth area AREA4 (not shown) corresponding to an area from the numerical aperture 0.45 to the numerical aperture 0.85 of the high-density optical disc HD and having a staircase structure formed therein. A staircase type diffraction structure HOE ′ having a structure in which bands are arranged around the optical axis is formed in the third region AREA3.

In the staircase type diffraction structure HOE ′ formed in the third region AREA3, the depth d0 per step of the staircase structure formed in each annular zone is d0 = 5 × λ1 / (n1-1) (μm) The number of divisions N of each annular zone is set to 2. Here, λ1 represents the wavelength of the laser beam emitted from the blue-violet semiconductor laser in units of microns (here, λ1 = 0.405 μm), and n1 is a refractive index with respect to the wavelength λ1 of the aberration correction element L1. (Here, n1 = 1.601).
When a laser beam having a wavelength of λ1 is incident on the stepped diffractive structure HOE ′, an optical path difference of 5 × λ1 (μm) is generated between adjacent steps, and the laser beam having a wavelength of λ1 substantially has a phase difference. Is transmitted without being diffracted (0th order diffracted light)
Further, when a laser beam having a wavelength λ2 (here, λ2 = 0.655 μm) emitted from the red semiconductor laser is incident on the staircase type diffraction structure HOE ′, d0 × (n2-1) / λ3 = Since 2.98≈3, an optical path difference of 3 × λ2 (μm) occurs between adjacent stairs, and the laser beam with the wavelength λ2 is substantially given a phase difference similarly to the laser beam with the wavelength λ1. Since it is not, it is transmitted without being diffracted (0th order diffracted light). Note that n2 is a refractive index with respect to the wavelength λ2 of the aberration correction element L2 (here, n2 = 1.5407).
On the other hand, when a laser beam having a wavelength λ3 (here, λ3 = 0.785 μm) emitted from the infrared semiconductor laser is incident on the staircase type diffraction structure HOE ′, d0 × (n3-1) / λ3 Since 2.47≈2.5, the transmitted wavefront between adjacent stairs is shifted by a half wavelength, and most of the light amount of the third light beam incident on the stairs-type diffractive structure HOE ′ is ± first-order diffracted light. It is distributed to. Note that n3 is a refractive index with respect to the wavelength λ3 of the aberration correction element L1 (here, n3 = 1.5372). The annular zone pitch of the staircase type diffractive structure HOE ′ is determined so as to collect the + 1st order diffracted light of the ± 1st order diffracted light on the information recording surface RL3 of the CD. Spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disk HD and the CD is corrected.

Further, since the stair-type diffractive structure HOE is formed only within the numerical aperture NA2 of the DVD, the light beam that passes through the area outside the NA2 becomes a flare component on the information recording surface RL2 of the DVD, and the aperture limitation on the DVD is limited. It is configured to be performed automatically.
Further, since the stair-type diffractive structure HOE ′ is formed only within the numerical aperture NA3 of the CD, the light beam passing through the area outside the NA3 becomes a flare component on the information recording surface RL3 of the CD, and the aperture limit for the CD Is automatically performed.

  In the beam expander optical system EXP, the first lens EXP1 having a negative refractive power in the paraxial axis is a glass lens, and the second lens EXP2 having a positive refractive power in the paraxial axis is a plastic lens. The spherical aberration of the objective optical system OBJ ″ has a temperature dependency that changes in the overcorrection direction when the temperature rises by 30 degrees during recording / reproduction of information on the high-density optical disk HD. The refractive power of the second lens EXP2 is optimized with respect to the amount of change of the accompanying spherical aberration, and is composed of the beam expander optical system EXP and the objective optical system OBJ ″, as in the first embodiment. As a whole optical system, the spherical aberration change accompanying the temperature change is compensated.

  In the optical pickup device PU11 in the present embodiment, the plastic lens (second lens EXP2) in the beam expander optical system EXP is in the common optical path of the first light flux, the second light flux, and the third light flux. When the optical system OBJ ″ has a temperature characteristic such that the spherical aberration changes in the overcorrection direction as the temperature rises during recording / reproduction of the DVD or CD, the second lens EXP2 acts to It is also possible to correct temperature characteristics during recording / reproduction. Further, since the first lens EXP1 can be moved by the uniaxial actuator UAC, spherical aberration can be corrected not only when recording / reproducing on DVD and CD but also on high-density optical disks.

  Further, since the second lens EXP2 of the beam expander optical system EXP can be shifted in the optical axis direction by the uniaxial actuator UAC, as described above, the beam expander in a state where the light beams of the respective wavelengths are parallel light beams. The focal length of the beam expander optical system EXP can be adjusted so as to be emitted from the optical system EXP.

  In the present embodiment, the laser light source unit LD123 and the photodetector PD123 are arranged separately. However, the present invention is not limited to this, and the laser light source module in which the laser light source unit LD123 and the photodetector PD123 are integrated. May be used.

Note that it is possible to form an optical pickup by forming a diffractive structure on the optical surface of the collimating optical system COL or the beam expander optical system EXP and correcting the chromatic aberration in the blue-violet wavelength region of the objective optical system OBJ ″. This is preferable because the reliability of the recording / reproducing characteristics of the device PU11 can be improved. Thus, if it is set as the structure which correct | amends chromatic aberration with a diffraction structure, the optical system for optical pick-ups by which the chromatic aberration was correct | amended with the simple structure can be obtained.
Alternatively, instead of the above-described diffraction structure, a positive lens having a positive refractive power and an Abbe number at d-line of νd1, and an Abbe number having a negative refractive power and d-line at νd2 (νd2 <νd1). A doublet lens joined with a certain negative lens may be disposed as an element constituting at least a part of the collimating optical system COL or the beam expander optical system EXP. When the shape of the diffractive structure deviates from the design value due to a manufacturing error, the diffraction efficiency is lowered, so that the transmittance of the optical pickup optical system is lowered. However, when such a refractive doublet lens is used to correct chromatic aberration, an optical pickup optical system having high transmittance can be obtained while the optical system is corrected for chromatic aberration.

  In the present embodiment, the collimating optical system COL and the beam expander optical system EXP are arranged separately. However, the present invention is not limited to this, and the collimating optical system COL is omitted, and the laser light source unit LD123 is used. The emitted divergent light beam may be directly incident on the beam expander optical system EXP. Thereby, the number of parts of the optical pickup device PU11 can be further reduced.

  The sensor lens SEN provided in the above-described optical pickup devices PU1 to PU3, 5 to 8, 10, and 11 is for giving astigmatism to the reflected light beam from the optical disk going to the photodetector.

Further, the optical pickup devices PU1 to PU10 described above are provided with a dichroic filter DFL for restricting the opening when recording / reproducing with respect to a CD. It is integrated with the optical system and driven by a biaxial actuator AC in a direction perpendicular to the optical axis.
Although not shown, the optical pickup device shown in the first to eleventh embodiments, the rotary drive device that holds the optical disk rotatably, the control device that controls the drive of these various devices, and the like. By mounting, an optical information recording / reproducing apparatus capable of executing at least one of recording information on the optical disk and reproducing information recorded on the optical disk can be obtained.

Next, an optical system suitable as an optical pickup optical system mounted on the above-described optical pickup devices PU1 to PU11 will be described with specific numerical values.
In each embodiment, the aspherical surface of the optical surface, such as the superposition type diffractive structure (stepped diffractive structure) and the optical surface on which the diffractive structure is formed, or the optical surface on which the diffractive structure is formed, is from a plane in contact with the apex of the surface. When the deformation amount is X (mm), the height in the direction perpendicular to the optical axis is h (mm), and the radius of curvature is r (mm), the coefficients in Tables 2 to 9 shown below are the following (8 ) It is expressed by a mathematical formula substituted in the formula. Here, κ is a conic coefficient, and A _2i is an aspheric coefficient.

表２〜表１２においてNAは開口数、λ(nm)は設計波長、f(mm)は焦点距離、mは対物レンズ全系の倍率、ｔ(mm)は保護基板厚、r(mm)は曲率半径、Ｎλは設計波長に対する２５℃での屈折率、νdはｄ線におけるアッベ数を示す。

In Tables 2 to 12, NA is the numerical aperture, λ (nm) is the design wavelength, f (mm) is the focal length, m is the magnification of the entire objective lens system, t (mm) is the thickness of the protective substrate, and r (mm) is The radius of curvature, Nλ is the refractive index at 25 ° C. with respect to the design wavelength, and νd is the Abbe number at the d-line.

Further, the superposition type diffractive structure (step type diffractive structure) or the diffractive structure in each embodiment is represented by an optical path difference added to the transmitted wavefront by these structures. The optical path difference is as follows when λ is the wavelength of the incident light beam, λ _B is the manufacturing wavelength, the height in the direction perpendicular to the optical axis is h (mm), B _2j is the optical path difference function coefficient, and n is the diffraction order. It is represented by an optical path difference function φb (mm) defined by the equation (9).

Table 1 shows the values of the above formulas (1), (3), (5), and (6) in each example.

本実施例においては、近軸における屈折力が負であるガラスレンズと、近軸における屈折力が正であるプラスチックレンズとの２枚のレンズから構成されるビームエキスパンダ光学系ＥＸＰを、波長λ１と波長λ２の共通光路中に配設し、更に、ビームエキスパンダ光学系ＥＸＰと対物光学系ＯＢＪとの間の光路中に、波長λ３の光路を、波長λ１と波長λ２の光路に合成させるためのビームコンバイナを配設している。
本実施例における対物光学系ＯＢＪの球面収差は、温度が３０度上昇した場合に補正過剰方向に変化するような温度依存性を有し、これによる波面収差の変化量は、０．０５７λＲＭＳである。このような温度特性を有する対物光学系ＯＢＪにビームエキスパンダ光学系ＥＸＰを組合せることで、温度が３０度上昇した場合の波面収差の変化量を０．０１０λＲＭＳに抑えることが出来た。 Example 1 is an optical system that is optimal as an optical pickup optical system mounted on the first optical pickup device PU1, and specific numerical data thereof are shown in Table 2.

In the present embodiment, a beam expander optical system EXP composed of two lenses, a glass lens having a negative refractive power in the paraxial axis and a plastic lens having a positive refractive power in the paraxial axis, has a wavelength λ1. And in the optical path between the beam expander optical system EXP and the objective optical system OBJ, the optical path of wavelength λ3 is combined with the optical path of wavelengths λ1 and λ2. This is a beam combiner.
The spherical aberration of the objective optical system OBJ in this embodiment has a temperature dependency that changes in the overcorrection direction when the temperature rises by 30 degrees, and the change amount of the wavefront aberration due to this is 0.057λRMS. . By combining the objective optical system OBJ having such temperature characteristics with the beam expander optical system EXP, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.010λ RMS.

When calculating the amount of change in wavefront aberration when the temperature changes, only the refractive index change accompanying the temperature change of the plastic lens included in the optical system is considered, and the plastic lens of the beam expander optical system EXP The refractive index change rate of the first plastic lens (aberration correction element L1) of the objective optical system OBJ is −1.1 × 10 ⁻⁴ / ° C., and the second plastic lens (condensing element L2) of the objective optical system OBJ. The refractive index change rate was −0.9 × 10 ⁻⁴ / ° C.
Further, since the Abbe number of the glass lens and the plastic lens in the beam expander optical system is set so as to satisfy the expression (2), the wavelength λ1 and the wavelength λ2 are achromatic, so the wavelength Both λ1 and λ2 light beams are emitted as parallel light beams from the beam expander optical system.
In the present embodiment, the optical pickup optical system mounted on the fourth optical pickup device PU4 is configured such that the parallel light beam having the wavelength λ2 is incident on the objective optical system OBJ without passing through the beam expander optical system EXP. An optical system that is optimal as a system can be obtained.

本実施例においては、近軸における屈折力が負であるガラスレンズと、近軸における屈折力が正であるプラスチックレンズとの二枚からビームエキスパンダ光学系ＥＸＰを構成し、ガラスレンズとプラスチックレンズとの間の光路中に、波長λ2の光路を波長λ１の光路に合成させるためのビームコンバイナを配設している。この光学系においては、ビームエキスパンダ光学系中のプラスチックレンズは第２の光源ＬＤ２から射出された波長λ２の発散光束を平行光束に変換して対物光学系ＯＢＪに導くコリメート光学系の機能を備えている。更に、ビームエキスパンダ光学系ＥＸＰと対物光学系ＯＢＪとの間の光路中に、波長λ３の光路を波長λ１と波長λ2の光路に合成させるためのビームコンバイナを配設している。 Example 2 is an optical system that is optimal as an optical pickup optical system mounted on the second optical pickup device PU2, and specific numerical data is shown in Table 3.

In the present embodiment, the beam expander optical system EXP is composed of two pieces of a glass lens having a negative refractive power in the paraxial axis and a plastic lens having a positive refractive power in the paraxial axis. A beam combiner for synthesizing the optical path of wavelength λ2 into the optical path of wavelength λ1 is disposed in the optical path between the two. In this optical system, the plastic lens in the beam expander optical system has a function of a collimating optical system that converts a divergent light beam having a wavelength λ2 emitted from the second light source LD2 into a parallel light beam and guides it to the objective optical system OBJ. ing. Further, a beam combiner for synthesizing the optical path of wavelength λ3 into the optical path of wavelength λ1 and wavelength λ2 is disposed in the optical path between the beam expander optical system EXP and the objective optical system OBJ.

The objective optical system OBJ in the present embodiment is the same as the objective optical system OBJ in the first embodiment, and has a temperature dependency that causes the spherical aberration to change in the overcorrection direction when the temperature rises by 30 degrees. The wavefront aberration varies by 0.057λ RMS. By combining the objective optical system OBJ with the beam expander optical system EXP, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.011λ RMS.
Note that when calculating the amount of change in wavefront aberration when the temperature changes, only the refractive index change accompanying the temperature change of the plastic lens included in the optical system is considered, and the plastic lens of the beam expander optical system EXP The refractive index change rate of the first plastic lens L1 of the objective optical system OBJ is −1.1 × 10 ⁻⁴ / ° C., and the refractive index change rate of the second plastic lens L2 of the objective optical system OBJ is −0.9 ×. 10 ⁻⁴ / ° C.

本実施例においては、近軸における屈折力が正であるプラスチックレンズと、近軸における屈折力が負であるガラスレンズとの２枚からビームエキスパンダ光学系ＥＸＰを構成し、プラスチックレンズとガラスレンズとの光路中に波長λ２の光路を波長λ１の光路に合成させるためのビームコンバイナを配設している。この光学系においては第２の光源ＬＤ２から射出された波長λ２の発散光束はカップリング光学系により収斂光束に変換され、更に、ビームエキスパンダ光学系ＥＸＰ中のガラスレンズを通過することにより平行光になる。更に、ビームエキスパンダ光学系ＥＸＰと対物光学系ＯＢＪとの間の光路中に、波長λ３の光路を波長λ１と波長λ２の光路に合成させるためのビームコンバイナを配設している。 Example 3 is an optical system that is optimal as an optical pickup optical system mounted on the third optical pickup device PU3, and specific numerical data thereof are shown in Table 4.

In this embodiment, the beam expander optical system EXP is composed of two lenses, a plastic lens having a positive paraxial refractive power and a glass lens having a negative paraxial refractive power, and the plastic lens and the glass lens. And a beam combiner for synthesizing the optical path of wavelength λ2 into the optical path of wavelength λ1. In this optical system, the divergent light beam having the wavelength λ2 emitted from the second light source LD2 is converted into a convergent light beam by the coupling optical system, and further passes through the glass lens in the beam expander optical system EXP to produce parallel light. become. Further, a beam combiner for synthesizing the optical path of wavelength λ3 into the optical path of wavelength λ1 and wavelength λ2 is disposed in the optical path between the beam expander optical system EXP and the objective optical system OBJ.

The objective optical system OBJ in the present embodiment is the same as the objective optical system OBJ in the first embodiment, and has a temperature dependency that causes the spherical aberration to change in the overcorrection direction when the temperature rises by 30 degrees. The wavefront aberration varies by 0.057λ RMS. By combining the objective optical system OBJ with the beam expander optical system EXP, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.011λ RMS.
Note that when calculating the amount of change in wavefront aberration when the temperature changes, only the refractive index change accompanying the temperature change of the plastic lens included in the optical system is considered, and the plastic lens of the beam expander optical system EXP The refractive index change rate of the first plastic lens L1 of the objective optical system OBJ is −1.1 × 10 ⁻⁴ / ° C., and the refractive index change rate of the second plastic lens L2 of the objective optical system OBJ is −0.9 ×. 10 ⁻⁴ / ° C.

本実施例においては、近軸の屈折力が正であるプラスチックレンズで波長λ１のコリメート光学系ＣＯＬを構成し、波長λ１の専用光路に配設している。又、近軸の屈折力が負であるガラスレンズと、近軸の屈折力が正であるプラスチックレンズでビームエキスパンダ光学系ＥＸＰを構成し、波長λ１の専用光路に配設している。更に、ビームエキスパンダ光学系ＥＸＰと対物光学系ＯＢＪの光路中に波長λ2の光路を波長λ1の光路に合成するためのビームコンバイナと、波長λ３の光路を波長λ１と波長λ2の光路に合成するためのビームコンバイナを配設している。 Example 4 is an optical system optimal as an optical pickup optical system mounted on the fourth pickup apparatus PU4, and specific numerical data thereof are shown in Table 5.

In the present embodiment, a collimating optical system COL having a wavelength λ1 is constituted by a plastic lens having a positive paraxial refractive power, and is disposed in a dedicated optical path having a wavelength λ1. Further, the beam expander optical system EXP is composed of a glass lens having a negative paraxial refractive power and a plastic lens having a positive paraxial refractive power, and is disposed in a dedicated optical path having a wavelength λ1. Further, in the optical path of the beam expander optical system EXP and the objective optical system OBJ, a beam combiner for synthesizing the optical path of wavelength λ2 into the optical path of wavelength λ1, and the optical path of wavelength λ3 into the optical paths of wavelength λ1 and wavelength λ2. A beam combiner is provided.

The objective optical system OBJ in the present embodiment has a temperature dependency in which the spherical aberration changes in the overcorrection direction when the temperature rises by 30 degrees, whereby the wavefront aberration changes by 0.057λ RMS. By combining the objective optical system OBJ with the collimating optical system COL and the beam expander optical system EXP, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.011λRMS. In this way, by combining the collimating optical system COL formed of the plastic lens with the beam expander optical system EXP, the refractive power of the plastic lens necessary for correcting the temperature characteristics of the objective optical system OBJ is obtained. Since it is possible to assign to COL, the degree of freedom in designing the lens of the expander optical system EXP (selection of angular magnification, etc.) is increased.
When calculating the amount of change in wavefront aberration when the temperature changes, only the refractive index change accompanying the temperature change of the plastic lens included in the optical system is taken into account, and the plastic lens and beam of the collimating optical system COL are taken into account. The refractive index change rate of the plastic lens of the expander optical system EXP and the first plastic lens L1 of the objective optical system OBJ is −1.1 × 10 ⁻⁴ / ° C., and the refractive index of the second plastic lens L2 of the objective optical system OBJ. The rate of change was −0.9 × 10 ⁻⁴ / ° C.

本実施例においては、近軸における屈折力が負であるガラスレンズと、近軸における屈折力が正であるプラスチックレンズとの２枚から構成されるカップリング光学系ＣＵＬを波長λ１と波長λ２の共通光路に配置し、更にカップリング光学系ＣＵＬと対物光学系ＯＢＪとの間の光路中に、波長λ３の光路を波長λ１と波長λ２の光路に合成するためのビームコンバイナを配設している。また、波長λ１の光束を射出する発光点と、波長λ２の光束を射出する発光点とを１つの筐体に収めたパッケージ光源ユニットと、カップリング光学系ＣＵＬとの間の光路中に光ディスクの情報記録面により反射された波長λ１の光束と波長λ２の光束を光検出器へ導くためのビームコンバイナを配設している。
更に、カップリング光学系ＣＵＬ中のガラスレンズとプラスチックレンズのアッベ数を（２）式を満たすように設定することで、波長λ１と波長λ２とに対して、色消しを行っているため、波長λ１と波長λ２の光束の両方がカップリング光学系ＣＵＬから平行光束として射出される。 Example 5 is an optical system optimum as an optical pickup optical system mounted on the sixth optical pickup device PU6, and specific numerical data thereof are shown in Table 6.

In this embodiment, a coupling optical system CUL composed of two lenses, a glass lens having a negative refractive power in the paraxial axis and a plastic lens having a positive refractive power in the paraxial axis, has wavelengths λ1 and λ2. A beam combiner for combining the optical path of wavelength λ3 into the optical path of wavelengths λ1 and λ2 is disposed in the optical path between the coupling optical system CUL and the objective optical system OBJ. . In addition, the optical disk of the optical disc is coupled in the optical path between the package light source unit in which the light emitting point for emitting the light beam having the wavelength λ1 and the light emitting point for emitting the light beam having the wavelength λ2 are housed in one housing, and the coupling optical system CUL. A beam combiner is provided for guiding the light beam having the wavelength λ1 and the light beam having the wavelength λ2 reflected by the information recording surface to the photodetector.
Further, since the Abbe numbers of the glass lens and the plastic lens in the coupling optical system CUL are set so as to satisfy the expression (2), the wavelength λ1 and the wavelength λ2 are achromatic, so the wavelength Both λ1 and λ2 light beams are emitted from the coupling optical system CUL as parallel light beams.

The spherical aberration of the objective optical system OBJ in this embodiment has a temperature dependency that changes in the overcorrection direction when the temperature rises by 30 degrees, and the change amount of the wavefront aberration due to this is 0.057λRMS. . By combining the objective optical system OBJ having such temperature characteristics with the coupling optical system CUL, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.010λ RMS.
Note that when calculating the amount of change in wavefront aberration when the temperature changes, only the refractive index change associated with the temperature change of the plastic lens included in the optical system is considered, and the plastic lens of the coupling optical system CUP The refractive index change rate of the first plastic lens L1 of the objective optical system OBJ is −1.1 × 10 ⁻⁴ / ° C., and the refractive index change rate of the second plastic lens L2 of the objective optical system OBJ is −0.9 × 10. ^-4 / ° C.

本実施例においては、近軸における屈折力が正のガラスレンズと、近軸における屈折力が正であるプラスチックレンズとの２枚からカップリング光学系ＣＵＬを構成し、プラスチックレンズとガラスレンズの光路中に、波長λ２の光路を波長λ１の光路に合成するためのビームコンバイナと、光ディスクの情報記録面により反射された波長λ１と波長λ２の光束を光検出器への導くためのビームコンバイナを配設している。更に、カップリング光学系ＣＵＬと対物光学系ＯＢＪの間に、波長λ３の光路を波長λ１と波長λ２の光路に合成させるためのビームコンバイナが配設されている。 Example 6 is an optical system optimal as an optical pickup optical system mounted on the seventh optical pickup device PU7, and specific numerical data thereof are shown in Table 7.

In this embodiment, the coupling optical system CUL is composed of two lenses, ie, a glass lens having a positive paraxial refractive power and a plastic lens having a positive paraxial refractive power, and the optical path between the plastic lens and the glass lens. A beam combiner for combining the optical path of wavelength λ2 with the optical path of wavelength λ1 and a beam combiner for guiding the light beams of wavelength λ1 and wavelength λ2 reflected by the information recording surface of the optical disk to the photodetector are arranged. Has been established. Further, a beam combiner is provided between the coupling optical system CUL and the objective optical system OBJ to synthesize the optical path with the wavelength λ3 into the optical paths with the wavelength λ1 and the wavelength λ2.

The spherical aberration of the objective optical system OBJ in this embodiment has a temperature dependency that changes in the overcorrection direction when the temperature rises by 30 degrees, and the change amount of the wavefront aberration due to this is 0.057λRMS. . By combining the objective optical system OBJ having such temperature characteristics with the coupling optical system CUL, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.011λ RMS.
Note that when calculating the amount of change in wavefront aberration when the temperature changes, only the change in refractive index associated with the temperature change of the plastic lens included in the optical system is considered, and the plastic lens of the coupling optical system CUL The refractive index change rate of the first plastic lens L1 of the objective optical system OBJ is −1.1 × 10 ⁻⁴ / ° C., and the refractive index change rate of the second plastic lens L2 of the objective optical system OBJ is −0.9 × 10. ^-4 / ° C.

本実施例においては、近軸における屈折力が負のガラスレンズと、近軸における屈折力が正のプラスチックレンズとを貼り合わせた接合レンズと、近軸における屈折力が正のガラスレンズからカップリング光学系ＣＵＬを構成し、接合レンズとガラスレンズとの光路中に波長λ２の光路を波長λ１の光路に合成するためのビームコンバイナが配設されている。また、波長λ１の光源とカップリング光学系ＣＵＬの波長λ１の光路中に光ディスクで反射された波長λ１の光束を光検出器へ導くためのビームコンバイナが配設され、カップリング光学系ＣＵＬと対物光学系ＯＢＪの間に波長λ３の光路を波長λ１と波長λ２の光路に合成するためのビームコンバイナが配設されている。 Example 7 is an optical system that is optimal as an optical pickup optical system mounted on the eighth optical pickup device PU8, and specific numerical data thereof are shown in Table 8.

In this embodiment, a glass lens having a negative refractive power in the paraxial axis and a cemented lens obtained by bonding a plastic lens having a positive refractive power in the paraxial axis are coupled from the glass lens having a positive refractive power in the paraxial axis. An optical system CUL is configured, and a beam combiner for synthesizing the optical path of wavelength λ2 into the optical path of wavelength λ1 is disposed in the optical path of the cemented lens and the glass lens. In addition, a light source having wavelength λ1 and a beam combiner for guiding the light beam having wavelength λ1 reflected by the optical disk to the optical detector in the optical path having wavelength λ1 of the coupling optical system CUL are disposed. A beam combiner for synthesizing the optical path of wavelength λ3 into the optical paths of wavelength λ1 and wavelength λ2 is disposed between the optical systems OBJ.

The spherical aberration of the objective optical system OBJ in this embodiment has a temperature dependency that changes in the overcorrection direction when the temperature rises by 30 degrees, and the change amount of the wavefront aberration due to this is 0.057λRMS. . By combining the objective optical system OBJ having such temperature characteristics with the coupling optical system CUL, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.011λ RMS.
Note that when calculating the amount of change in wavefront aberration when the temperature changes, only the change in refractive index associated with the temperature change of the plastic lens included in the optical system is considered, and the plastic lens of the coupling optical system CUL The refractive index change rate of the first plastic lens L1 of the objective optical system OBJ is −1.1 × 10 ⁻⁴ / ° C., and the refractive index change rate of the second plastic lens L2 of the objective optical system OBJ is −0.9 × 10. ^-4 / ° C.

本実施例においては、波長λ１の専用光路中に、近軸の屈折力が負のガラスレンズと、近軸の屈折力が正のプラスチックレンズから成るカップリング光学系ＣＵＬを配置し、カップリング光学系ＣＵＬと対物光学系ＯＢＪの間に、波長λ２と波長λ３の光路を波長λ１の光路に合成するためのビームコンバイナがそれぞれ配設されている。
本実施例における対物光学系ＯＢＪの球面収差は、温度が３０度上昇した場合に補正過剰方向に変化するような温度依存性を有し、これによる波面収差の変化量は、０．０８５λＲＭＳである。このような温度特性を有する対物光学系ＯＢＪにカップリング光学系ＣＵＬを組合せることで、温度が３０度上昇した場合の波面収差の変化量を０．００７λＲＭＳに抑えることが出来た。 Example 8 is an optical system that is optimal as an optical pickup optical system mounted on the ninth optical pickup device PU9, and specific numerical data thereof are shown in Table 9.

In the present embodiment, a coupling optical system CUL including a glass lens having a negative paraxial refractive power and a plastic lens having a positive paraxial refractive power is arranged in a dedicated optical path having a wavelength λ1, and coupling optics is used. Between the system CUL and the objective optical system OBJ, a beam combiner for synthesizing the optical paths of the wavelengths λ2 and λ3 into the optical path of the wavelength λ1 is provided.
The spherical aberration of the objective optical system OBJ in this embodiment has a temperature dependency that changes in the overcorrection direction when the temperature rises by 30 degrees, and the change amount of the wavefront aberration due to this is 0.085λ RMS. . By combining the objective optical system OBJ having such temperature characteristics with the coupling optical system CUL, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.007λRMS.

Note that when calculating the amount of change in wavefront aberration when the temperature changes, only the change in refractive index associated with the temperature change of the plastic lens included in the optical system is considered, and the plastic lens of the coupling optical system CUL The refractive index change rate of the first plastic lens L1 of the objective optical system OBJ is −1.1 × 10 ⁻⁴ / ° C., and the refractive index change rate of the second plastic lens L2 of the objective optical system OBJ is −0.9 × 10. ^-4 / ° C.
In the first to seventh embodiments described above, spherical aberration due to a thickness error (manufacturing error, etc.) of the protective layer PL1 of the high-density optical disk HD can be obtained by moving one lens in the aberration correction optical system in the optical axis direction. In addition, it is possible to correct spherical aberration due to the wavelength change of the wavelength λ1.

近軸における屈折力が負であるガラスレンズと、近軸における屈折力が正であるプラスチックレンズとの２枚のレンズから構成されるビームエキスパンダ光学系ＥＸＰを、波長λ１、波長λ２及び波長λ３の共通光路中に配設し、更に、ビームエキスパンダ光学系中のガラスレンズとプラスチックレンズのアッベ数を（２）式を満たすように設定することで、波長λ１と波長λ２とに対して、色消しを行っているため、波長λ１と波長λ２の光束の両方がビームエキスパンダ光学系から平行光束として射出される。
本実施例における対物光学系ＯＢＪ'の球面収差は、温度が３０度上昇した場合に補正過剰方向に変化するような温度依存性を有し、これによる波面収差の変化量は、０．０２７λＲＭＳである。このような温度特性を有する対物光学系ＯＢＪ'にビームエキスパンダ光学系ＥＸＰを組合せることで、温度が３０度上昇した場合の波面収差の変化量を０．００５λＲＭＳに抑えることが出来た。
尚、温度が変化した場合の波面収差の変化量を算出する際には、光学系中に含まれるプラスチックレンズの温度変化に伴う屈折率変化のみを考慮し、ビームエキスパンダ光学系ＥＸＰのプラスチックレンズの屈折率変化率を−１．１×１０^-4／℃、対物光学系ＯＢＪ'の屈折率変化率を−０．９×１０^-4／℃とした。 Example 9 is an optical system that is optimum as an optical pickup optical system mounted on the fifth optical pickup device PU5, and specific numerical data thereof are shown in Table 10.

A beam expander optical system EXP composed of two lenses, a glass lens having a negative paraxial refractive power and a plastic lens having a positive paraxial refractive power, has a wavelength λ1, a wavelength λ2, and a wavelength λ3. Further, by setting the Abbe number of the glass lens and the plastic lens in the beam expander optical system so as to satisfy the expression (2), the wavelength λ1 and the wavelength λ2 are Since the achromatization is performed, both the light beams having the wavelengths λ1 and λ2 are emitted as parallel light beams from the beam expander optical system.
The spherical aberration of the objective optical system OBJ ′ in this embodiment has a temperature dependency that changes in the overcorrection direction when the temperature rises by 30 degrees, and the change amount of the wavefront aberration due to this is 0.027λRMS. is there. By combining the objective optical system OBJ ′ having such temperature characteristics with the beam expander optical system EXP, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.005λRMS.
When calculating the amount of change in wavefront aberration when the temperature changes, only the refractive index change accompanying the temperature change of the plastic lens included in the optical system is considered, and the plastic lens of the beam expander optical system EXP The refractive index change rate was −1.1 × 10 ⁻⁴ / ° C., and the refractive index change rate of the objective optical system OBJ ′ was −0.9 × 10 ⁻⁴ / ° C.

近軸における屈折力が負であるガラスレンズと、近軸における屈折力が正であるプラスチックレンズとの２枚のレンズから構成されるカップリング光学系ＣＵＬを、波長λ１、波長λ２及び波長λ３の共通光路中に配設し、更に、波長λ１の光束を射出する発光点、波長λ２の光束を射出する発光点と、波長λ３の光束を射出する発光点とを１つの筐体に収めたパッケージ光源ユニットと、カップリング光学系ＣＵＬとの間の光路中に光ディスクの情報記録面により反射された波長λ１、波長λ２、及び波長λ３の光束を光検出器へ導くためのビームコンバイナを配設している。
更に、カップリング光学系ＣＵＬ中のガラスレンズとプラスチックレンズのアッベ数を（２）式を満たすように設定することで、波長λ１と波長λ２とに対して、色消しを行っているため、波長λ１と波長λ２の光束の両方がカップリング光学系ＣＵＬから平行光束として射出される。 Example 10 is an optical system optimal as an optical pickup optical system mounted on the tenth optical pickup apparatus PU10, and specific numerical data thereof are shown in Table 11.

A coupling optical system CUL composed of two lenses, a glass lens having a negative paraxial refractive power and a plastic lens having a positive paraxial refractive power, has a wavelength λ1, a wavelength λ2, and a wavelength λ3. A package that is disposed in a common optical path, and further includes a light emitting point that emits a light beam having a wavelength λ1, a light emitting point that emits a light beam having a wavelength λ2, and a light emitting point that emits a light beam having a wavelength λ3. A beam combiner is provided in the optical path between the light source unit and the coupling optical system CUL to guide the light beams having the wavelengths λ1, λ2, and λ3 reflected by the information recording surface of the optical disc to the photodetector. ing.
Further, since the Abbe numbers of the glass lens and the plastic lens in the coupling optical system CUL are set so as to satisfy the expression (2), the wavelength λ1 and the wavelength λ2 are achromatic, so the wavelength Both λ1 and λ2 light beams are emitted from the coupling optical system CUL as parallel light beams.

The spherical aberration of the objective optical system OBJ ′ in this embodiment has a temperature dependency that changes in the overcorrection direction when the temperature rises by 30 degrees, and the change amount of the wavefront aberration due to this is 0.027λRMS. is there. By combining the objective optical system OBJ ′ having such temperature characteristics with the coupling optical system CUL, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.006λRMS.
When calculating the amount of change in wavefront aberration when the temperature changes, only the refractive index change accompanying the temperature change of the plastic lens included in the optical system is considered, and the plastic lens of the coupling optical system CUL is considered. The refractive index change rate was −1.1 × 10 ⁻⁴ / ° C., and the refractive index change rate of the objective optical system OBJ was −0.9 × 10 ⁻⁴ / ° C.

近軸における屈折力が負であるガラスレンズと、近軸における屈折力が正であるプラスチックレンズとの２枚のレンズから構成されるビームエキスパンダ光学系ＥＸＰを、波長λ１、波長λ２及び波長λ３の共通光路中に配設している。
更に、入射光束の波長に応じて、ビームエキスパンダ光学系ＥＸＰ中のガラスレンズ（第１レンズＥＸＰ）の光軸方向の位置を１軸アクチュエータＵＡＣにより調整することで、第１光束乃至第３光束は、何れもビームエキスパンダ光学系ＥＸＰから平行光束の状態で射出される。 Example 11 is an optimum optical system as an optical pickup optical system mounted on the eleventh optical pickup apparatus PU11, and specific numerical data thereof are shown in Table 12.

A beam expander optical system EXP composed of two lenses, a glass lens having a negative refractive power on the paraxial axis and a plastic lens having a positive refractive power on the paraxial axis, has a wavelength λ1, a wavelength λ2, and a wavelength λ3. In the common optical path.
Further, by adjusting the position of the glass lens (first lens EXP) in the beam expander optical system EXP in the optical axis direction according to the wavelength of the incident light flux by the uniaxial actuator UAC, the first to third light fluxes are adjusted. Are emitted from the beam expander optical system EXP in the form of a parallel light beam.

The spherical aberration of the objective optical system OBJ ″ in this embodiment has a temperature dependency that changes in the overcorrection direction when the temperature rises by 30 degrees during recording / reproduction of information on the high-density optical disk HD. The amount of change in wavefront aberration due to this is 0.068λRMS. By combining the objective optical system OBJ ″ having such temperature characteristics with the beam expander optical system EXP, the amount of change in wavefront aberration when the temperature rose by 30 degrees could be suppressed to 0.029λRMS.
Note that when calculating the amount of change in wavefront aberration when the temperature changes, only the refractive index change associated with the temperature change of the plastic lens included in the optical system is considered, and the plastic in the beam expander optical system EXP is taken into account. The refractive index change rate of the lens (second lens EXP2) and the refractive index change rate of the objective optical system OBJ ″ were set to −0.9 × 10 ⁻⁴ / ° C.

FIG. 13 shows the thickness change (thickness error, etc.) of the protective layer PL1 of the high-density optical disc HD by changing the distance between the glass lens and the plastic lens of the beam expander optical system EXP in the optical system of the first embodiment. On the other hand, the result of correcting the spherical aberration is shown.
Further, FIG. 14 shows the result of correcting the spherical aberration with respect to the change of the wavelength λ1 by changing the distance between the glass lens and the plastic lens of the coupling optical system CUL in the optical system of Example 5.
From these results, it can be seen that the optical systems of Examples 1 to 8 are excellent in the recording / reproducing characteristics of the double-layer disc and have sufficient tolerance with respect to the oscillation wavelength of the blue-violet semiconductor laser light source LD1.
In the above-described embodiments and examples, the optical pickup optical system and the optical pickup device that can record / reproduce with respect to the three types of optical disks of the high-density optical disk HD, DVD, and CD have been described as examples. It is easy to apply the present invention to an optical pickup optical system and an optical pickup apparatus capable of recording / reproducing on two types of optical discs, high density optical disc HD and DVD, or on two types of optical discs, high density optical disc HD and CD. Is understood.
For example, it is possible to remove the other optical system elements while leaving the optical system elements necessary for recording / reproduction of these two types of optical disks, thereby further reducing the size, weight and cost. An optical pickup optical system and an optical pickup device with a simplified configuration can be realized.

It is a principal part top view which shows the structure of an optical pick-up apparatus. It is drawing which shows the structure of an objective optical system. It is drawing which shows the structure of an aberration correction element. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a graph which shows the correction result of the spherical aberration by the thickness change of the protective layer of a high density optical disk. It is a graph which shows the correction result of spherical aberration by change of wavelength λ1. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is drawing which shows the structure of an objective optical system.

Explanation of symbols

AC actuator LD light source EXP beam expander optical system CUL coupling optical system OBJ objective lens OD optical information recording medium PU optical pickup device RL information recording surface

Claims (28)

A first light source that emits a first light beam of 450 nm or less, and a second light source that emits a second light beam in a range of 630 nm to 680 nm, at least two types of light sources having different wavelengths, and at least the wavelengths being different from each other An objective optical system for condensing light beams emitted from two types of light sources on information recording surfaces of at least two types of optical discs having different recording densities, and an optical path between the first light source and the objective optical system An optical pickup optical system that is disposed in the optical pickup optical system and includes an aberration correction optical system that includes at least two lens groups,
The objective optical system has at least one plastic lens whose refractive power in the paraxial axis is positive,
The aberration correction optical system includes at least one glass lens and a plastic lens having a positive refractive power in the paraxial axis,
Of the at least two types of optical discs having different recording densities, when the first optical disc is an optical disc that records and / or reproduces information using the first light flux,
An optical pickup characterized in that the change rate ΔSA / ΔT of the spherical aberration accompanying the temperature rise of the objective optical system satisfies the following expression (1) when recording and / or reproducing information on the first optical disc: Optical system.
ΔSA / ΔT> 0 (1) A coupling optical system that is disposed in an optical path between the first light source and the aberration correction optical system and that emits light after converting a divergence angle of the incident first light beam to be small;
The glass lens of the aberration correction optical system has a negative refractive power in the paraxial axis, and the aberration correction optical system is a beam expander optical system that changes the diameter of the incident first light beam and emits it. The optical pickup optical system according to claim 1.   The optical pickup optical system according to claim 2, wherein the beam expander optical system is disposed in a common optical path of the first light flux and the second light flux. A beam combiner for combining the optical paths of the first light flux and the second light flux;
In order from the first light source side, the coupling optical system, the glass lens of the beam expander optical system, the beam combiner, the plastic lens of the beam expander optical system, and the objective optical system are disposed. The optical pickup optical system according to claim 2. A beam combiner for combining the optical paths of the first light flux and the second light flux;
In order from the first light source side, the coupling optical system, the plastic lens of the beam expander optical system, the beam combiner, the glass lens of the beam expander optical system, and the objective optical system are disposed. The optical pickup optical system according to claim 2.   The optical pickup optical system according to claim 2, wherein the beam expander optical system is disposed in a dedicated optical path of the first light flux.   7. The optical pickup optical system according to claim 2, wherein the coupling optical system includes at least one plastic lens having a positive refractive power in the paraxial axis. Of the at least two types of optical discs having different recording densities, an optical disc that records and / or reproduces information with the first light flux is a first optical disc, and an optical disc that records and / or reproduces information with the second light flux Is the second optical disc,
The magnification m ₁ of the objective optical system with respect to the first light flux when recording or reproducing information on the first optical disc, and the second light flux when recording or reproducing information on the second optical disc. The magnification m ₂ of the objective optical system substantially matches,
The Abbe number ν _{dN of} the glass lens of the beam expander optical system and the Abbe number ν _{dP of the} plastic lens of the beam expander optical system satisfy the following expression (2). Optical pickup optical system.
ν _dP > ν _dN (2)   2. The optical pickup optical system according to claim 1, wherein the aberration correction optical system is a coupling optical system that converts the divergence angle of the incident first light beam to be small and emits the light.   The optical pickup optical system according to claim 9, wherein the coupling optical system is disposed in a common optical path of the first light flux and the second light flux. A beam combiner for combining the optical paths of the first light flux and the second light flux;
The glass lens of the coupling optical system, the beam combiner, the plastic lens of the coupling optical system, and the objective optical system are disposed in order from the first light source side. The optical pickup optical system according to 1. A beam combiner for combining the optical paths of the first light flux and the second light flux;
The glass lens of the coupling optical system has a positive refractive power in the paraxial axis,
The plastic lens of the coupling optical system, the beam combiner, the glass lens of the coupling optical system, and the objective optical system are arranged in order from the first light source side. The optical pickup optical system according to 1.   The optical pickup optical system according to claim 9, wherein the coupling optical system is disposed in a dedicated optical path of the first light flux. Of the at least two types of optical discs having different recording densities, an optical disc that records and / or reproduces information with the first light flux is a first optical disc, and an optical disc that records and / or reproduces information with the second light flux Is the second optical disc,
The magnification m ₁ of the objective optical system with respect to the first light flux when recording or reproducing information on the first optical disc, and the second light flux when recording or reproducing information on the second optical disc. The magnification m ₂ of the objective optical system substantially matches,
The glass lens of the coupling optical system has a negative refractive power in the paraxial axis,
The light according to claim 10, wherein an Abbe number ν _{dN of} the glass lens of the coupling optical system and an Abbe number ν _{dP of the} plastic lens of the coupling optical system satisfy the following expression (2). Pickup optical system.
ν _dP > ν _dN (2)   15. The collimating optical system according to claim 9, wherein the coupling optical system is a collimating optical system that converts the incident first light flux into a parallel light flux parallel to the optical axis and emits the parallel light flux. The optical pickup optical system described. The objective optical system includes a first plastic lens and a second plastic lens that are sequentially arranged from the light source side. On the at least one optical surface of the first plastic lens, the first light beam and the second optical lens are arranged. A diffractive structure for diffracting at least one of the second light beams is formed, the refractive power P ₁ (mm ⁻¹ ) of the first plastic lens with respect to the wavelength of the first light beam, and the second plastic. according to any one of claims 1 to 15 ratio of the refractive power P ₂ (mm ^-1) to satisfy the following equation (3) in the near-axis with respect to the wavelength of the first light flux of the lens Optical pickup optical system.
| P ₁ / P ₂ | ≦ 0.2 (3) Of the at least two types of optical discs having different recording densities, when the first optical disc is an optical disc that records and / or reproduces information using the first light flux,
When recording or reproducing information with respect to the first optical disk, the image-side numerical aperture NA _{1 of} the objective optical system, the lens thickness d _L2 on the optical axis of the second plastic lens, and the above-mentioned of the second plastic lens The optical pickup optical system according to claim 16, wherein refractive power P _L2 (mm ⁻¹ ) on the paraxial axis with respect to the wavelength of the first light beam satisfies the following expressions (4) and (5).
NA ₁ > 0.8 (4)
0.9 <d _L2 · P _L2 <1.3 (5) Of the at least two types of optical discs having different recording densities, when the first optical disc is an optical disc that records and / or reproduces information using the first light flux,
When recording or reproducing information with respect to the first optical disc, the refractive power P _L2 (mm ⁻⁾ in the paraxial direction with respect to the image-side numerical aperture NA _{1 of} the objective optical system and the wavelength of the first light flux of the second plastic lens. ¹ ) the magnification m _{L2 of} the second plastic lens with respect to the wavelength of the first light beam, the wavelength λ ₁ (mm) of the first light beam, and the change rate ΔSA / ΔT of spherical aberration associated with the temperature rise of the objective optical system, The sum Σ (P _i · h _i ²⁾ of the product of the refractive power P _i on the paraxial axis of the plastic lens of the aberration correction optical system with respect to the wavelength of the first light beam and the square of the passing height h _i of the marginal ray. The optical pickup optical system according to claim 17, wherein the following equation (6) is satisfied:
0.5 × 10 ⁻⁶ <k / Σ (P _i · h _i ² ) <5.5 × 10 ⁻⁶ (6)
However, k = (ΔSA / ΔT) · λ ₁ · P _L2 / (NA ₁ · (1−m _L2 )) ⁴ . The optical pickup optical system according to claim 18, wherein the following expression (6 ′) is satisfied.
1.1 × 10 ⁻⁶ <k / Σ (P _i · h _i ² ) <3.3 × 10 ⁻⁶ (6 ′)   The optical pickup optical system according to any one of claims 17 to 19, further comprising a third light source that emits a third light flux having a wavelength in a range of 750 nm to 800 nm.   21. The optical pickup optical system according to claim 20, wherein the aberration correction optical system is disposed in a common optical path of the first light beam, the second light beam, and the third light beam.   The optical pickup optical system according to claim 20 or 21, wherein the first light source, the second light source, and the third light source are packaged light source units.   A beam combiner disposed in an optical path between the aberration correction optical system and the objective optical system, for combining the optical paths of the first light flux, the second light flux, and the third light flux; 21. The optical pickup optical system according to claim 20, wherein   The optical pickup optical system according to claim 3 or 10, wherein the first light source and the second light source are packaged light source units.   An optical pickup device comprising the optical pickup optical system according to any one of claims 1 to 24. A photodetector for detecting a reflected light beam of the first light beam from the information recording surface of the first optical disc;
The first light beam reflected by the information recording surface of the first optical disc passes through the objective optical system and all the plastic lenses in the aberration correction optical system, and then enters the photodetector. The optical pickup device according to claim 25, characterized in that: An actuator for driving at least one lens in the aberration correction optical system in the optical axis direction;
The object point position of the objective optical system with respect to the first light flux is variably adjusted in the optical axis direction by driving the at least one lens in the aberration correction optical system in the optical axis direction by the actuator. An optical pickup device according to claim 25 or 26.   An optical information recording / reproducing apparatus comprising the optical pickup device according to any one of claims 25 to 27.

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