WO2011040135A1 - 金型の加工方法、金型、対物レンズ及び光ピックアップ装置 - Google Patents
金型の加工方法、金型、対物レンズ及び光ピックアップ装置 Download PDFInfo
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- WO2011040135A1 WO2011040135A1 PCT/JP2010/063860 JP2010063860W WO2011040135A1 WO 2011040135 A1 WO2011040135 A1 WO 2011040135A1 JP 2010063860 W JP2010063860 W JP 2010063860W WO 2011040135 A1 WO2011040135 A1 WO 2011040135A1
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- Prior art keywords
- objective lens
- axis
- optical
- edge
- mold
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1372—Lenses
- G11B7/1374—Objective lenses
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23B—TURNING; BORING
- B23B1/00—Methods for turning or working essentially requiring the use of turning-machines; Use of auxiliary equipment in connection with such methods
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23B—TURNING; BORING
- B23B27/00—Tools for turning or boring machines; Tools of a similar kind in general; Accessories therefor
- B23B27/005—Geometry of the chip-forming or the clearance planes, e.g. tool angles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23B—TURNING; BORING
- B23B27/00—Tools for turning or boring machines; Tools of a similar kind in general; Accessories therefor
- B23B27/06—Profile cutting tools, i.e. forming-tools
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00009—Production of simple or compound lenses
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00009—Production of simple or compound lenses
- B29D11/0048—Moulds for lenses
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1876—Diffractive Fresnel lenses; Zone plates; Kinoforms
- G02B5/189—Structurally combined with optical elements not having diffractive power
- G02B5/1895—Structurally combined with optical elements not having diffractive power such optical elements having dioptric power
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1353—Diffractive elements, e.g. holograms or gratings
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/42—Moulds or cores; Details thereof or accessories therefor characterised by the shape of the moulding surface, e.g. ribs or grooves
- B29C33/424—Moulding surfaces provided with means for marking or patterning
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
- G11B2007/0006—Recording, reproducing or erasing systems characterised by the structure or type of the carrier adapted for scanning different types of carrier, e.g. CD & DVD
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
- G11B7/13922—Means for controlling the beam wavefront, e.g. for correction of aberration passive
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/22—Apparatus or processes for the manufacture of optical heads, e.g. assembly
Definitions
- the present invention relates to a mold processing method, a mold, an objective lens, and an optical pickup device.
- a light capable of recording and / or reproducing information (hereinafter referred to as “recording / reproducing”) on a high-density optical disk using a blue-violet semiconductor laser having a wavelength of about 400 nm.
- Recording / reproducing a light capable of recording and / or reproducing information (hereinafter referred to as “recording / reproducing”) on a high-density optical disk using a blue-violet semiconductor laser having a wavelength of about 400 nm.
- Pickup devices have been developed and are already on the market.
- BD Blu-ray Disc
- DVD NA 0.6, light source wavelength 650 nm, storage capacity
- Information of 25 GB per layer can be recorded on an optical disc having a diameter of 12 cm, which is the same size as 4.7 GB).
- the value as a product of an optical disc player / recorder cannot be said to be sufficient simply by saying that information can be appropriately recorded / reproduced on such a high-density optical disc.
- DVDs and CDs compact discs
- making it possible to appropriately record / reproduce information on DVDs and CDs leads to an increase in commercial value as an optical disc player / recorder for high-density optical discs.
- an optical pickup device mounted on an optical disc player / recorder for high density optical discs can appropriately receive information while maintaining compatibility with both high density optical discs, DVDs, and even CDs. It is desired to have a performance capable of recording / reproducing.
- optical systems for high-density optical discs and optical systems for DVDs and CDs are used.
- a method of selectively switching the system to and from the recording density of an optical disk for recording / reproducing information is conceivable, but a plurality of optical systems are required, which is disadvantageous for miniaturization and increases the cost.
- the optical system for high-density optical discs and the optical system for DVDs and CDs must 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. In addition, it is most advantageous for miniaturization and cost reduction of the configuration of the optical pickup device to make the objective optical element arranged facing the optical disc as common as possible.
- Patent Document 1 light beams having three different wavelengths are condensed on information recording surfaces of high-density optical discs, DVDs, and CDs using a common objective lens, and the information is compatible with them.
- An optical pickup device for recording and / or reproducing is described.
- the objective lens shown in Patent Document 1 uses an optical path difference providing structure called a multi-level structure as an optical surface in order to appropriately collect light beams having three different wavelengths on information recording surfaces of high-density optical discs, DVDs, and CDs. May have.
- the multi-level structure is a fine structure having a narrow groove shape and a deep groove shape, a corresponding fine structure must be formed on the transfer surface of the mold for transferring and molding the objective lens. Even if a sharp sword tool is used, there is a risk that tool interference will occur in the mold material. Therefore, in order to avoid this tool interference, it is necessary to perform cutting while turning the sword tool, and an expensive multi-axis machine is required, which increases the cost of the mold.
- the present invention provides, for example, a mold processing method capable of processing a mold for forming an objective lens for an optical pickup device having a multi-level structure at a low cost, a mold processed by the mold, and a mold formed by such a mold. It is an object of the present invention to provide an objective lens and an optical pickup device using the objective lens.
- the mold processing method according to claim 1 is used in common in an optical pickup device that can use different optical disks interchangeably, and forms a multi-level structure on a curved surface so as to condense a light beam on an information recording surface of each optical disk.
- a mold processing method for forming an objective lens While rotating the mold around the axis, A first linear edge, a second linear edge extending in a direction intersecting at an acute angle with respect to the first edge, an end of the first edge, and the first edge
- a tool having a rake face contoured from a third edge connecting the end of the second edge, and at least one of the first edge and the second edge with respect to the axis.
- the transfer surface of the objective lens is cut in a tilted state.
- the surface extending in the optical axis direction in the multilevel structure of the objective lens is formed in parallel to the optical axis in order to increase the light use efficiency.
- a sharp blade with a sharp point is used in order to form all the transfer surfaces of the mold for transferring the surface extending in the optical axis direction in the multi-level structure with high accuracy and parallel to the optical axis. Even so, there is a risk of tool interference in the mold material, so to avoid tool interference, you must perform cutting while turning the blade tip tool, requiring an expensive multi-axis machine. This increases the cost of the mold.
- the axis and the axis intersect.
- the mold can be processed using an inexpensive processing machine such as a biaxial processing machine while ensuring the optical performance of the objective lens.
- the surface of the mold for transferring and molding the multi-level structure is inclined with respect to the axis, there is an advantage that it is easy to release the mold.
- the tool and the mold are likely to interfere with each other in a place where a curved surface such as the periphery of the objective lens is tight.
- the invention also has the advantage that interference between the tool and the mold can be prevented.
- the die machining method according to the first aspect, wherein the tool is tilted at least one of the first edge and the second edge with respect to the axis.
- the transfer surface of the objective lens is cut by moving only in the axial direction and in a direction crossing the axial line.
- the die processing method according to the second aspect wherein the first edge portion and the second edge portion closer to the axis line and the axis line. Processing is performed in a state where the inclination angle ⁇ 1 is larger than the inclination angle ⁇ 2 between the far edge and the axis.
- a metal mold machining method according to the third aspect of the present invention, wherein the following expression is satisfied. 15 ° ⁇ ⁇ 1 ⁇ 35 ° (1) 0 ° ⁇ ⁇ 2 ⁇ 15 ° (2)
- a metal mold machining method according to the fourth aspect, wherein the following expression is satisfied. 1 ° ⁇ ⁇ 2 ⁇ 15 ° (3)
- the mold processing method is the invention according to claim 1 or 2, wherein the edge portion closer to the axis line and the axis line among the first edge portion and the second edge portion. The processing is performed in a state where the inclination angle ⁇ 1 is equal to or substantially equal to the inclination angle ⁇ 2 between the far edge and the axis.
- a die machining method according to the sixth aspect of the invention, wherein the following equation is satisfied. 10 ° ⁇ ⁇ 1 ⁇ 20 ° (4)
- a die machining method according to any one of the first to seventh aspects, wherein the cutting is performed while moving the tool so as to approach the axis.
- a mold machining method is the invention according to any one of claims 3 to 5, wherein the mold is preceded by an edge having an inclination angle ⁇ 1 with respect to the axis. Cutting is performed while moving in a direction intersecting the axis so as to cut the material.
- the tool is a sword tip bite.
- the mold processing method according to claim 11 is the invention according to any one of claims 1 to 10, wherein a blaze structure is formed on the curved surface of the objective lens in addition to the multi-level structure. It is characterized by that.
- a mold machining method is the invention according to any one of the first to eleventh aspects, wherein the axial thickness of the objective lens is d (mm) and the focal length of the objective lens is f (mm). ), The following expression is satisfied. 0.9 ⁇ d / f ⁇ 1.6 (5)
- a mold according to a thirteenth aspect is characterized by being formed by the mold processing method according to any one of the first to twelfth aspects.
- the objective lens according to claim 14 is used in common in an optical pickup apparatus that can use different optical disks interchangeably, and is formed with a multi-level structure on a curved surface so as to collect a light beam on an information recording surface of each optical disk.
- An objective lens, At least a part of the surface extending in the optical axis direction in the multilevel structure is inclined with respect to the optical axis.
- the surface extending in the optical axis direction in the multilevel structure of the objective lens is formed in parallel to the optical axis in order to increase the light use efficiency.
- a sharp blade with a sharp point is used in order to form all the transfer surfaces of the mold for transferring the surface extending in the optical axis direction in the multi-level structure with high accuracy and parallel to the optical axis. Even so, there is a risk of tool interference in the mold material, so to avoid tool interference, you must perform cutting while turning the blade tip tool, requiring an expensive multi-axis machine. This increases the cost of the mold.
- the objective lens for a high-density optical disk has a high NA
- the radius of curvature of the optical surface is relatively small, so that the problem of byte interference becomes more serious.
- the mold in the state where the edge of the rake face in the tool for cutting the mold is intentionally inclined with respect to the axis, the mold is cut while moving only in the axial direction and the direction intersecting the axis. Because it becomes possible to process, molds can be processed using an inexpensive processing machine such as a biaxial processing machine, and an objective lens can be manufactured at low cost using such a mold. it can.
- the surface along the optical axis of the multi-level structure is inclined with respect to the optical axis, it is easy to release after molding, and there is an advantage that light quantity loss based on manufacturing errors can be reduced.
- the tool and the mold are likely to interfere with each other in a place where a curved surface such as the periphery of the objective lens is tight.
- the invention also has the advantage that interference between the tool and the mold can be prevented.
- the objective lens according to claim 14 is the invention according to claim 13, wherein when the cross section of the objective lens in the optical axis direction is taken, a surface closer to the optical axis among the opposingly extending surfaces;
- the tilt angle ⁇ 1 ′ with respect to the optical axis is characterized by being larger than the tilt angle ⁇ 2 ′ between the far surface and the optical axis.
- the surface away from the optical axis among the two surfaces extending in the optical axis direction and facing each other is tilted with respect to the optical axis, thereby causing a loss of light amount.
- the light amount loss does not increase even if the surface is close to the optical axis. Therefore, in one basic structure of the multi-level structure, a surface close to the optical axis among two surfaces extending in the optical axis direction and facing each other is inclined with respect to the optical axis and separated from the optical axis.
- the surface parallel to the optical axis As much as possible, it can be processed with a simple processing machine such as a two-axis processing machine without increasing the loss of light, reducing costs and making it easier to take out the lens from the mold. This is preferable because the effects of the present invention can be enjoyed.
- the objective lens according to claim 15 extends in the optical axis direction in one step unit of the multi-level structure when the cross section in the optical axis direction of the objective lens is taken in the invention according to claim 14.
- the tilt angle ⁇ 1 ′ between the two surfaces facing each other and the surface closer to the optical axis and the optical axis is larger than the tilt angle ⁇ 2 ′ between the surface far from the optical axis and the optical axis. It is characterized by.
- the objective lens described in claim 16 is characterized in that, in the invention described in claim 15, the following expression is satisfied. 15 ° ⁇ ⁇ 1 ′ ⁇ 35 ° (6) 0 ° ⁇ ⁇ 2 ′ ⁇ 15 ° (7)
- the objective lens described in claim 17 is characterized in that, in the invention described in claim 16, the following expression is satisfied. 1 ° ⁇ ⁇ 2 ′ ⁇ 15 ° (8)
- the objective lens according to claim 18 extends in the optical axis direction in one step unit of the multi-level structure when the cross section in the optical axis direction of the objective lens is taken in the invention according to claim 14.
- the tilt angle ⁇ 1 ′ between the two surfaces facing each other and the surface closer to the optical axis and the optical axis is equal to or substantially equal to the tilt angle ⁇ 2 ′ between the surface far from the optical axis and the optical axis. It is characterized by being equal.
- the objective lens described in claim 19 is characterized in that, in the invention described in claim 18, the following expression is satisfied. 10 ° ⁇ ⁇ 1 ′ ⁇ 20 ° (9)
- the objective lens according to claim 20 is characterized in that, in the invention according to any one of claims 14 to 19, a blaze structure is formed on the curved surface of the objective lens in addition to the multi-level structure.
- the objective lens according to claim 21 is the invention according to any one of claims 14 to 20, wherein the axial thickness of the objective lens is d (mm) and the focal length of the objective lens is f (mm). Sometimes, the following formula is satisfied. 0.9 ⁇ d / f ⁇ 1.6 (5)
- An optical pickup device uses the objective lens according to any one of the fourteenth to twenty-first aspects.
- FIG. 1 is a schematic view showing an example of a rake face shape of a cutting tool.
- the cutting face SP of the cutting tool shown in FIG. 1A includes a first linear edge E1, a second linear edge E2 extending in a direction intersecting at an acute angle, and a first edge E2.
- the tip is contoured by an arcuate third edge E3 connecting the end of the edge E1 and the end of the second edge E2.
- those having a radius r of the third edge E3 of 0.5 ⁇ m to 5.0 ⁇ m are called sword tips and those having the radius r of 5.0 ⁇ m or more are called R tools.
- 1B includes a linear first edge E1, a linear second edge E2 extending parallel to the first edge E1, and a first edge.
- the tip is contoured by a third edge E3 orthogonal to E1 and the second edge E2, and such a cutting tool is called a flat cutting tool and distinguished from a sword cutting tool or an R cutting tool.
- a sword-tip tool by using a sword-tip tool, the radius of the back corner of the fine groove shape that transfers the multi-level structure can be kept small, and the light utilization efficiency of the objective lens molded using such a mold is further increased. be able to.
- R bytes can be used depending on the application.
- the cutting tool When the cutting tool is moved while moving in the direction intersecting the axis so that the edge having the inclination angle ⁇ 1 with respect to the axis is leading and cutting the material of the mold, the load on the tool is reduced. This is preferable because the tool life is extended.
- the optical pickup device has at least three light sources: a first light source, a second light source, and a third light source. Furthermore, the optical pickup device of the present invention condenses the first light flux on the information recording surface of the first optical disc, condenses the second light flux on the information recording surface of the second optical disc, and causes the third light flux to be third. It has a condensing optical system for condensing on the information recording surface of the optical disc.
- the optical pickup device of the present invention includes a light receiving element that receives a reflected light beam from the information recording surface of the first optical disc, the second optical disc, or the third optical disc.
- the first optical disc has a protective substrate having a thickness t1 and an information recording surface.
- the second optical disc has a protective substrate having a thickness t2 (t1 ⁇ t2) and an information recording surface.
- the third optical disc has a protective substrate having a thickness t3 (t2 ⁇ t3) and an information recording surface.
- the first optical disc is preferably a BD
- the second optical disc is a DVD
- the third optical disc is preferably a CD, but is not limited thereto.
- the first optical disc, the second optical disc, or the third optical disc may be a multi-layer optical disc having a plurality of information recording surfaces.
- BD means that information is recorded / reproduced by a light beam having a wavelength of about 390 to 415 nm and an objective lens having an NA of about 0.8 to 0.9, and the thickness of the protective substrate is 0.05 to 0.00 mm.
- It is a generic term for a BD series optical disc of about 125 mm, and includes a BD having only a single information recording layer, a BD having two information recording layers, and the like.
- DVD is a general term for DVD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.60 to 0.67 and the thickness of the protective substrate is about 0.6 mm.
- CD is a general term for CD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.45 to 0.51 and the thickness of the protective substrate is about 1.2 mm.
- CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW and the like As for the recording density, the recording density of BD is the highest, followed by the order of DVD and CD.
- the thickness of the protective substrate referred to here is the thickness of the protective substrate provided on the surface of the optical disk. That is, the thickness of the protective substrate from the optical disc surface to the information recording surface closest to the surface.
- the first light source, the second light source, and the third light source are preferably laser light sources.
- the laser light source a semiconductor laser, a silicon laser, or the like can be preferably used.
- the first wavelength ⁇ 1 of the first light beam emitted from the first light source is shorter than the second wavelength ⁇ 2 of the second light beam emitted from the second light source, and the second wavelength ⁇ 2 is the third wavelength emitted from the third light source. It is shorter than the third wavelength ⁇ 3 of the light beam.
- the first wavelength ⁇ 1 of the first light source is preferably 350 nm or more and 440 nm or less, more preferably 390 nm.
- the second wavelength ⁇ 2 of the second light source is preferably 570 nm or more and 680 nm or less, more preferably 630 nm or more and 670 nm or less, and the third wavelength ⁇ 3 of the third light source is preferably 415 nm or less. It is 750 nm or more and 880 nm or less, More preferably, it is 760 nm or more and 820 nm or less.
- the first light source, the second light source, and the third light source may be unitized.
- the unitization means that the first light source and the second light source are fixedly housed in one package, for example.
- a light receiving element to be described later may be packaged.
- a photodetector such as a photodiode is preferably used.
- Light reflected on the information recording surface of the optical disc enters the light receiving element, and a read signal of information recorded on each optical disc is obtained using the output signal. Furthermore, it detects the change in the light amount due to the spot shape change and position change on the light receiving element, performs focus detection and track detection, and based on this detection, the objective lens can be moved for focusing and tracking I can do it.
- the light receiving element may comprise a plurality of photodetectors.
- the light receiving element may have a main photodetector and a sub photodetector.
- two sub photodetectors are provided on both sides of a photodetector that receives main light used for recording and reproducing information, and the sub light for tracking adjustment is received by the two sub photodetectors. It is good also as a simple light receiving element.
- the light receiving element may have a plurality of light receiving elements corresponding to the respective light sources.
- the condensing optical system has an objective lens.
- the condensing optical system preferably has a coupling lens such as a collimator in addition to the objective lens.
- the coupling lens is a single lens or a lens group that is disposed between the objective lens and the light source and changes the divergence angle of the light beam.
- the collimator is a type of coupling lens, and is a lens that emits light incident on the collimator as parallel light.
- the objective lens refers to an optical system that is disposed at a position facing the optical disk in the optical pickup device and has a function of condensing the light beam emitted from the light source onto the information recording surface of the optical disk.
- the objective lens is preferably a single lens.
- the objective lens may be a glass lens or a plastic lens, or an optical path difference providing structure is provided on the glass lens with a photo-curing resin, a UV-curing resin, or a thermosetting resin.
- a hybrid lens may also be used.
- the objective lens preferably has a refractive surface that is aspheric.
- the base surface on which the optical path difference providing structure is provided is preferably an aspherical surface.
- the objective lens is a glass lens
- a glass material having a glass transition point Tg of 450 ° C. or lower more preferably 400 ° C. or lower.
- a glass material having a glass transition point Tg of 450 ° C. or lower molding at a relatively low temperature becomes possible, so that the life of the mold can be extended.
- Examples of such a glass material having a low glass transition point Tg include K-PG325 and K-PG375 (both product names) manufactured by Sumita Optical Glass Co., Ltd.
- the specific gravity of the glass lens is generally larger than that of the resin lens, if the objective lens is a glass lens, the weight increases and a load is imposed on the actuator that drives the objective lens. Therefore, when the objective lens is a glass lens, it is preferable to use a glass material having a small specific gravity.
- the specific gravity is preferably 4.0 or less, more preferably the specific gravity is 3.0 or less.
- the objective lens is a plastic lens
- an alicyclic hydrocarbon polymer material such as a cyclic olefin resin material.
- the resin material has a refractive index of 1.54 to 1.60 at a temperature of 25 ° C. with respect to a wavelength of 405 nm, and a wavelength of 405 nm according to a temperature change within a temperature range of ⁇ 5 ° C. to 70 ° C.
- the coupling lens is preferably a plastic lens.
- the Abbe number of the material constituting the objective lens is preferably 50 or more.
- the objective lens is further described below. It is preferable that at least one optical surface of the objective lens has at least a central region, an intermediate region around the central region, and a peripheral region around the intermediate region.
- the central region is preferably a region including the optical axis of the objective lens, but a minute region including the optical axis may be an unused region or a special purpose region, and the periphery thereof may be the central region.
- the central region, the intermediate region, and the peripheral region are preferably provided on the same optical surface. As shown in FIG. 2, the central region CN, the intermediate region MD, and the peripheral region OT are preferably provided concentrically around the optical axis on the same optical surface.
- a first optical path difference providing structure is provided in the central region of the objective lens, and a second optical path difference providing structure is provided in the intermediate region.
- the peripheral region may be a refractive surface, or a third optical path difference providing structure may be provided in the peripheral region.
- the central region, the intermediate region, and the peripheral region are preferably adjacent to each other, but there may be a slight gap between them.
- the central area of the objective lens is preferably a shared area of the first, second, and third optical disks used for recording / reproduction of the first optical disk, the second optical disk, and the third optical disk. That is, the objective lens condenses the first light flux that passes through the central area so that information can be recorded / reproduced on the information recording surface of the first optical disc, and the second light flux that passes through the central area becomes the second light flux. Information is recorded and / or reproduced on the information recording surface of the optical disc so that information can be recorded and / or reproduced, and the third light beam passing through the central area can be recorded / reproduced on the information recording surface of the third optical disc. It is preferable that the light is condensed.
- the first optical path difference providing structure provided in the central region has the thickness t1 of the protective substrate of the first optical disc and the second optical disc with respect to the first and second light fluxes passing through the first optical path difference providing structure. It is preferable to correct spherical aberration generated due to the difference in the thickness t2 of the protective substrate / spherical aberration generated due to the difference between the wavelengths of the first light flux and the second light flux. Further, the first optical path difference providing structure has a thickness t1 of the protective substrate of the first optical disc and a thickness of the protective substrate of the third optical disc with respect to the first light beam and the third light beam that have passed through the first optical path difference providing structure. It is preferable to correct the spherical aberration that occurs due to the difference between t3 and the spherical aberration that occurs due to the difference between the wavelengths of the first and third light beams.
- the intermediate region of the objective lens is preferably a first and second optical disc shared region that is used for recording / reproduction of the first optical disc and the second optical disc and not used for recording / reproduction of the third optical disc. That is, the objective lens condenses the first light flux that passes through the intermediate area so that information can be recorded / reproduced on the information recording surface of the first optical disc, and the second light flux that passes through the intermediate area becomes the second light flux. It is preferable to collect light so that information can be recorded / reproduced on the information recording surface of the optical disc. On the other hand, it is preferable that the third light flux passing through the intermediate region is not condensed so that information can be recorded / reproduced on the information recording surface of the third optical disc.
- the third light flux passing through the intermediate region of the objective lens preferably forms a flare on the information recording surface of the third optical disc.
- the light amount density is high in the order from the optical axis side (or the center of the spot) to the outside. It is preferable to have a spot central portion SCN, a spot intermediate portion SMD having a light intensity density lower than that of the spot central portion, and a spot peripheral portion SOT having a light intensity density higher than that of the spot intermediate portion and lower than that of the spot central portion.
- the center portion of the spot is used for recording / reproduction of information on the optical disc, and the middle portion of the spot and the peripheral portion of the spot are not used for recording / reproduction of information on the optical disc.
- this spot peripheral part is called flare.
- the spot peripheral part may be called a flare.
- the third light flux that has passed through the intermediate region of the objective lens preferably forms a spot peripheral portion on the information recording surface of the third optical disc.
- the peripheral area of the objective lens is preferably an area dedicated to the first optical disc that is used for recording / reproduction of the first optical disc and not used for recording / reproduction of the second optical disc and the third optical disc. That is, it is preferable that the objective lens condenses the first light flux passing through the peripheral region so that information can be recorded / reproduced on the information recording surface of the first optical disc.
- the second light flux that passes through the peripheral area is not condensed so that information can be recorded / reproduced on the information recording surface of the second optical disc, and the third light flux that passes through the peripheral area does not converge. It is preferable that the light is not condensed so that information can be recorded / reproduced on the information recording surface.
- the second light flux and the third light flux that pass through the peripheral area of the objective lens preferably form a flare on the information recording surfaces of the second optical disc and the third optical disc. That is, it is preferable that the second light flux and the third light flux that have passed through the peripheral area of the objective lens form a spot peripheral portion on the information recording surfaces of the second optical disc and the third optical disc.
- the first optical path difference providing structure is preferably provided in a region of 70% or more of the area of the central region of the objective lens, and more preferably 90% or more. More preferably, the first optical path difference providing structure is provided on the entire surface of the central region.
- the second optical path difference providing structure is preferably provided in a region of 70% or more of the area of the intermediate region of the objective lens, and more preferably 90% or more. More preferably, the second optical path difference providing structure is provided on the entire surface of the intermediate region.
- the third optical path difference providing structure is preferably provided in a region of 70% or more of the area of the peripheral region of the objective lens, and more preferably 90% or more. More preferably, the third optical path difference providing structure is provided on the entire surface of the peripheral region.
- optical path difference providing structure referred to in this specification is a general term for structures that add an optical path difference to an incident light beam.
- the optical path difference providing structure also includes a phase difference providing structure for providing a phase difference.
- the phase difference providing structure includes a diffractive structure.
- the optical path difference providing structure of the present invention is preferably a diffractive structure.
- the optical path difference providing structure has a step, preferably a plurality of steps. This step adds an optical path difference and / or phase difference to the incident light flux.
- the optical path difference added by the optical path difference providing structure may be an integer multiple of the wavelength of the incident light beam or a non-integer multiple of the wavelength of the incident light beam.
- the steps may be arranged with a periodic interval in the direction perpendicular to the optical axis, or may be arranged with a non-periodic interval in the direction perpendicular to the optical axis.
- the objective lens provided with the optical path difference providing structure is a single aspherical lens
- the incident angle of the light flux to the objective lens differs depending on the height from the optical axis.
- Each will be slightly different.
- the objective lens is a single-lens aspherical convex lens, even if it is an optical path difference providing structure that provides the same optical path difference, generally the distance from the optical axis tends to increase.
- the diffractive structure referred to in this specification is a general term for structures that have a step and have a function of converging or diverging a light beam by diffraction.
- a plurality of unit shapes are arranged around the optical axis, and a light beam is incident on each unit shape, and the wavefront of the transmitted light is shifted between adjacent annular zones, resulting in new It includes a structure that converges or diverges light by forming a simple wavefront.
- the diffractive structure preferably has a plurality of steps, and the steps may be arranged with a periodic interval in the direction perpendicular to the optical axis, or may be arranged with a non-periodic interval in the direction perpendicular to the optical axis.
- the objective lens provided with the diffractive structure is a single aspherical lens
- the incident angle of the light beam to the objective lens differs depending on the height from the optical axis, so the step amount of the diffractive structure is slightly different for each annular zone. It will be.
- the objective lens is a single aspherical convex lens, even if it is a diffractive structure that generates diffracted light of the same diffraction order, generally, the distance from the optical axis tends to increase.
- the optical path difference providing structure has a plurality of concentric annular zones with the optical axis as the center.
- the optical path difference providing structure can generally have various cross-sectional shapes (cross-sectional shapes on the plane including the optical axis), and the cross-sectional shape including the optical axis is roughly divided into a blaze structure and a multi-level (step type) structure. Is done.
- the blaze structure means that the cross-sectional shape including the optical axis of the objective lens having the optical path difference providing structure is a sawtooth shape, as shown in FIGS. 4 (a) and 4 (b).
- FIG. 4 shows an example in which the upper side is the light source side and the lower side is the optical disc side, and the optical path difference providing structure is formed on a plane as a mother aspheric surface for easy understanding. It is formed on an optical surface that is a curved surface of a lens.
- the length in the direction perpendicular to the optical axis of one blaze unit is called a pitch P.
- the length of the step in the direction along the optical axis of the blaze is referred to as a step amount B. (See FIG. 4 (a)).
- the multi-level structure has a cross-sectional shape including an optical axis of an objective lens having an optical path difference providing structure having a small step shape (referred to as a step unit). ).
- V level means an annular surface (hereinafter also referred to as a terrace surface) corresponding to (or facing) the vertical direction of the optical axis in one step unit of a multi-level structure. In other words, it is divided by V steps and divided into V ring zones.
- a multi-level structure having three or more levels has a small step and a large step.
- the optical path difference providing structure shown in FIG. 4C is called a five-level multilevel structure
- the optical path difference providing structure shown in FIG. 4D is called a two-level multilevel structure (also called a binary structure).
- a two-level multi-level structure is described below.
- the cross-sectional shape of the plurality of annular zones including a plurality of concentric annular zones around the optical axis and including the optical axis of the objective lens is adjacent to the side surfaces Pa and Pb extending in the optical axis direction.
- the light source side terrace surface Pc for connecting the light source side ends of the side surfaces Pa and Pb and the optical disk side terrace surface Pd for connecting the optical disk side ends of the adjacent side surfaces Pa and Pb are formed.
- the side terrace surface Pd is alternately arranged along the direction intersecting the optical axis. Note that at least one of the side surfaces Pa and Pb along the optical axis may be entirely inclined with respect to the optical axis, but as shown in FIG. 4E, a part of the side surface Pa (or Pb). It may be tilted with respect to the optical axis only (the multilevel structure in FIG. 4C is also the same).
- the length in the direction perpendicular to the optical axis of one step unit is called a pitch P.
- the length of the step in the direction parallel to the optical axis of the staircase is referred to as step amounts B1 and B2.
- step amounts B1 and B2 In the case of a multi-level structure of three or more levels, there is a large step amount B1 and a small step amount B2 (see FIG. 4C).
- the small step amount B2 is desirably 10 ⁇ m or less, and the step width W is desirably 6 ⁇ m or less.
- the optical path difference providing structure is preferably a structure in which a certain unit shape is periodically repeated.
- unit shape is periodically repeated” naturally includes shapes in which the same shape is repeated in the same cycle.
- the unit shape that is one unit of the cycle has regularity, and the shape in which the cycle gradually increases or decreases gradually is also included in the “unit shape is periodically repeated”.
- the sawtooth shape as a unit shape is repeated. As shown in FIG. 4 (a), the same sawtooth shape may be repeated, and as shown in FIG. 4 (b), the shape of the sawtooth shape gradually increases as it moves away from the optical axis. A shape in which the pitch becomes longer or a shape in which the pitch becomes shorter may be used.
- the blazed structure has a step opposite to the optical axis (center) side, and in other areas, the blazed structure has a step toward the optical axis (center).
- the optical path difference providing structure has a multi-level structure
- the first optical path difference providing structure provided in the central region is an aspect including only a single basic structure.
- a single substructure is a multilevel structure. Further preferable conditions of this embodiment will be described in detail below.
- the basic structure which is a multi-level structure makes the X-order diffracted light amount of the first light beam passing through the basic structure larger than any other order diffracted light amount, and the Y-order diffracted light amount of the second light beam passing through the basic structure. Is made larger than any other order of the diffracted light quantity, and the Z-order diffracted light quantity of the third light beam that has passed through the basic structure is made larger than any other order of diffracted light quantity.
- any one of X, Y, and Z is preferably a positive diffraction order, and the rest are preferably negative diffraction orders.
- Examples of preferable combinations of (X, Y, Z) include (1, -1, -2), (1, -2, -3) or (1, -3, -4). Particularly preferred is (1, -1, -2) or (1, -2, -3).
- an objective lens that not only enables compatibility of three types of optical discs such as BD / DVD / CD, but can maintain high light utilization efficiency particularly for BD is provided. It becomes possible. For example, it is possible to provide an objective lens having a diffraction efficiency of 80% or more for the wavelength ⁇ 1. Furthermore, an objective lens having a diffraction efficiency of 90% or more for the wavelength ⁇ 1 can be provided.
- X, Y, and Z are 1, ⁇ 1, and ⁇ 2, respectively, and X, Y, and Z are 1, ⁇ 2, and ⁇ 3, respectively. And can be expressed as follows:
- the step amount B2 in the optical axis direction of the small step in the multilevel structure is a step amount that gives an optical path difference of 1.23 ⁇ 1 with respect to the first wavelength ⁇ 1.
- the step amount B2 of the small step of the multilevel structure in this case preferably satisfies the following conditional expression. 0.6 ⁇ (1.23 ⁇ ⁇ 1 / (n-1)) ⁇ B2 ⁇ 1.5 ⁇ (1.23 ⁇ ⁇ 1 / (n-1)) (10)
- X, Y, and Z are 1, -2, and -3, respectively
- a 7-level multilevel structure is preferable.
- the step amount B2 in the optical axis direction of the small step in the multilevel structure is a step amount that gives an optical path difference of 1.16 ⁇ 1 to the first wavelength ⁇ 1.
- the step amount B2 of the small step of the multilevel structure in this case preferably satisfies the following conditional expression. 0.6 ⁇ (1.16 ⁇ ⁇ 1 / (n-1)) ⁇ B2 ⁇ 1.5 ⁇ (1.16 ⁇ ⁇ 1 / (n-1)) (11)
- the second optical path difference providing structure in this aspect is a structure having at least a basic structure.
- This basic structure is a multi-level structure in which the Nth-order diffracted light quantity of the first light flux that has passed through the basic structure is made larger than any other order diffracted light quantity, and the Oth order of the second light flux that has passed through the basic structure. Is made larger than any other order of diffracted light, and the P-order diffracted light of the third light beam that has passed through the basic structure is made larger than any other order of diffracted light.
- (N, O, P) (0, ⁇ 1, ⁇ 1).
- the basic structure is a three-level multi-level structure, and the step amount in the optical axis direction of the small step in the multi-level structure gives an optical path difference of 1.02 ⁇ 1 to the first wavelength ⁇ 1. It is preferable that
- the third optical path difference providing structure is preferably provided in order to reduce a change in spherical aberration due to a temperature change.
- the third optical path difference providing structure is preferably composed of a single basic structure that is a blaze structure, regardless of the first optical path difference providing structure and the second optical path difference providing structure.
- This basic structure is a blazed structure in which the first-order diffracted light quantity of the first light beam that has passed through the basic structure is made larger than any other order diffracted light quantity, and the R-order of the second light flux that has passed through the basic structure. Is made larger than any other order of diffracted light, and the S order diffracted light of the third light flux that has passed through the basic structure is made larger than any other order of diffracted light.
- the above is a description of a preferred example of the first optical path difference providing structure, the second optical path difference providing structure, and the third optical path difference providing structure.
- both the blaze structure and the multilevel structure are formed on one optical surface of the objective lens.
- the effect of the present invention is more remarkable, which is preferable.
- Having a blaze structure and a multi-level structure means that the blaze structure and the multi-bell structure overlap each other in the same optical surface even when the blaze structure and the multi-level structure are overlapped at the same position. If not, it is included.
- a certain optical surface has only a multi-level structure and does not have a blaze structure, it is possible to cut even with a flat tip tool, so there may be an option of processing with a biaxial processing machine having a flat tip tool,
- a flat point tool cannot be used, and it is limited to a sword tip tool or an R tool. Accordingly, it is very important to make the side surfaces oblique in order to enable processing with a biaxial processing machine.
- FIG. 5 is a cross-sectional view showing a mold M cut by the sword tip tool SB and an objective lens OBJ formed by, for example, injection molding a resin into the mold M.
- the rotation axis of the material of the mold M is RX
- the optical axis of the objective lens OBJ is OX.
- the material of the mold M rotated around the rotation axis RX is relative to the Z-axis direction (parallel to the rotation axis RX) and the X-axis direction (perpendicular to the rotation axis RX) without rotating the blade tip tool SB within the paper surface.
- the groove shape corresponding to the multilevel structure shown in FIG. 4C is cut into the aspherical curved concave portion CV.
- the angle between the first edge E1 of the sword tip SB close to the rotation axis RX and the rotation axis RX is ⁇ 1, and the second edge E2 of the sword tip SB far from the rotation axis RX and the rotation axis RX
- the angle is set to ⁇ 2
- the groove shape of the mold M is processed as shown in FIG. 5, but in one groove shape, the surface extending along the direction of the rotation axis RX and close to the rotation axis RX is the outer surface SP1.
- a surface extending along the direction of the axis RX and far from the rotation axis RX is defined as an inner surface SP2.
- the angle between the outer surface SP1 and the rotation axis RX is ⁇ 1
- the angle between the inner surface SP2 and the rotation axis RX is ⁇ 2
- the following relationship holds. 15 ° ⁇ ⁇ 1 ⁇ 35 ° (1) 0 ° ⁇ ⁇ 2 ⁇ 15 ° (2)
- the objective lens OBJ shown in FIG. 5 is transferred and formed together with the annular structure corresponding to the groove shape.
- the side surface extending in the optical axis OX direction and close to the optical axis OX is Pa, extending in the optical axis OX direction, and far from the optical axis OX.
- the side be Pb.
- the angle between the side surface Pa of the annular zone structure and the optical axis OX is ⁇ 1 ′ and the angle between the side surface Pb and the optical axis OX is ⁇ 2 ′, it is preferable that the following relationship is established.
- the side surface Pb Since the shadow effect on the side surface Pa exists even when the side surface Pa is parallel to the optical axis, the problem of light loss caused by tilting the side surface Pa with respect to the optical axis does not change much.
- the side surface Pb since the shadow effect on the side surface Pb hardly exists when the side surface Pb is parallel to the optical axis, the side surface Pb is not inclined with respect to the optical axis, or even if it is inclined, it can be made as small as possible. This is preferable in terms of reducing light loss. Therefore, it is preferable that ⁇ 2 ′ ⁇ ⁇ 1 ′, and more preferably satisfy the expressions (6) and (7). If the expressions (6) and (7) are satisfied, the expressions (1) and (2) are satisfied.
- ⁇ 2 ′ is preferably 0 ° or more and 5 ° or less from the viewpoint of reducing the light amount loss as much as possible. In order to reduce the light amount loss as much as possible, it is preferable that ⁇ 2 ′ is 0 °. To reduce the light amount loss as much as possible, in order to make it easy to remove the objective lens from the mold, it is larger than 0 ° and 5 °. Or less (more preferably 3 ° or less).
- the loss of the luminous flux is substantially constant when ⁇ 1 ′ is between 0 ° and 35 °, and the loss increases when it exceeds 35 °. Therefore, 0 ° ⁇ ⁇ 1 ′ ⁇ 35 ° is desirable from the viewpoint of light utilization efficiency. Further, when considering the edge of the sword cutting tool, the edge of the R tool, the inclination angle of the tool, 15 ° ⁇ ⁇ 1 ′ ⁇ 35 ° is a desirable range.
- ⁇ 2 ′ will be described.
- ⁇ 2 ′ is 0 °, that is, when the side surface far from the optical axis is parallel to the optical axis, there is no shadow effect and there is no light loss.
- FIG. 20 when the side surface far from the optical axis is inclined with respect to the optical axis, the gray region cannot use the light flux due to the shadow effect. That is, it can be seen that the adverse effect on the light loss increases when the side surface far from the optical axis is inclined with respect to the optical axis. Therefore, it is preferable that the side surface far from the optical axis be as close to the optical axis as possible.
- ⁇ 2 ′ may be equal to or substantially equal to ⁇ 1 ′ when it is not necessary to be concerned about the loss of light amount or depending on the shape of the multilevel structure. “Substantially equal” means that the difference between ⁇ 2 ′ and ⁇ 1 ′ is 5 ° or less. In such a case, it is preferable to satisfy the following formula. Note that when the expression (9) is satisfied, the expression (4) is satisfied. 10 ° ⁇ ⁇ 1 ′ ⁇ 20 ° (9)
- a biaxial processing machine having a die shape corresponding to the lens shape having the optical path difference providing structure and a cutting tool such as a sword tip tool (an example is shown in FIG. 7). (An example is shown in FIG. 8) and the like, and the molten material is put into the mold after cutting, and after cooling and solidifying the material, the lens is taken out from the mold to mold the lens. It is common to do.
- the corner of the optical path difference providing structure preferably has a curvature.
- the objective lens preferably satisfies the following conditional expression (5). 0.9 ⁇ d / f ⁇ 1.6 (5)
- d represents the thickness (mm) on the optical axis of the objective lens
- f represents the focal length of the objective lens in the first light flux. Note that f preferably represents the focal length at the shortest wavelength among the used wavelengths.
- conditional expression (5) results in a thick objective lens with a thick on-axis objective lens, so that the working distance during CD recording / playback tends to be short.
- die processing method which can process the metal mold
- FIG.7 (a) is a perspective view which shows the cutting edge, ie, bite, of a diamond tool
- FIG.7 (b) is an enlarged view which shows the front-end
- FIG. 1 is a schematic configuration diagram of an optical pickup device 1.
- FIG. It is a figure which expands and shows an example of the diffraction structure of the objective lens concerning this invention. It is a figure which expands and shows another example of the diffraction structure of the objective lens concerning this invention.
- FIG. 6 is an enlarged cross-sectional view when a light beam is incident on a multi-level structure in which ⁇ 1 ′ is a value between 0 ° and 35 °.
- FIG. 6 is an enlarged cross-sectional view when a light beam is incident on a multilevel structure having a large value of ⁇ 2 ′.
- FIG.7 (a) is a perspective view which shows the cutting edge, ie, bite, of a diamond tool
- FIG.7 (b) is an enlarged view which shows the front-end
- a sword tip SB of a diamond tool is brazed to a shank S as shown in the figure, and has a rake face SP that faces the rotational direction of a die to be cut.
- the tip portion of the rake face SP includes a linear first edge E1, a linear second edge E2 extending in a direction intersecting the first edge E1 at an acute angle, and an edge It is contoured from the arcuate third edge portion E3 connecting the end portions on the front end side of the portions E1 and E2.
- the radius r of the third edge E3 is set to 5 ⁇ m or less, preferably 2.5 ⁇ m or less, but it is preferable to set the radius r to 0.5 ⁇ m or more to ensure the life.
- FIG. 8 is a perspective view of a biaxial processing machine MC2 used for machining the mold.
- an X-axis stage XST movable in the X-axis direction and a Z-axis stage ZST movable in the Z-axis direction orthogonal to the X-axis direction are placed on a base BSE installed on a surface plate (not shown). And are arranged.
- the blade tip SB is held with the third edge E3 (FIG. 7B) facing the mold material MM so as to move in the X-axis direction together with the X-axis stage XST. It has become.
- a rotation drive unit RD is held on the Z-axis stage ZST and moves in the Z-axis direction together with the Z-axis stage ZST.
- the rotation drive unit RD holds the mold material MM and rotates it around an axis RX extending in the Z-axis direction.
- the rotation direction of the mold is clockwise, but it may be rotated counterclockwise.
- the die material MM is brought relatively close to the sword tip SB by the Z-axis stage ZST, and the tip of the sword tip SB is placed on the outer side in the direction perpendicular to the axis of the transfer surface to be cut. Position. After that, while rotating the mold material MM around the axis RX by the rotation drive unit RD, as indicated by an arrow in FIG. 9, the Z-axis stage ZST is driven so that the tip of the sword tip bit SB is made of the mold material MM. Advance inward and cut.
- the drive of the Z-axis stage ZST is interrupted, and instead the X-axis stage XST is driven to advance the blade tip tool SB so as to approach the axis line RX, and the groove at the first edge E1. Cut the bottom of the shape.
- the drive of the X-axis stage XST is interrupted, and instead, the Z-axis stage ZST is driven so that the sword tip bite SB is separated from the mold MM until the first step amount is reached.
- the driving of the Z-axis stage ZST is interrupted, and instead, the X-axis stage XST is driven to advance the sword tip bite SB so as to approach the axis line RX. To cut.
- the groove shape corresponding to the multilevel structure shown in FIG. 9 can be cut.
- the inner side surface SP2 facing the axis line RX is inclined by ⁇ 2 with respect to the axis line RX, but the outer side surface SP1 facing it is the axis line It is inclined by ⁇ 1 with respect to RX.
- ⁇ 2 is 0 ° is shown.
- FIG. 2 a groove-shaped cutting example 2 corresponding to the multilevel structure as shown in FIG. Referring to FIG.
- the angle between the first edge E1 of the sword tip SB close to the rotation axis RX and the rotation axis RX is ⁇ 1, and the second edge E2 of the sword tip SB far from the rotation axis RX
- the die material MM is brought relatively close to the sword tip SB by the Z-axis stage ZST, and the tip of the sword tip SB is placed on the outer side in the direction orthogonal to the axis of the transfer surface to be cut. Position.
- the Z-axis stage ZST is driven so that the tip of the sword tip bit SB is made of the mold material MM. Advance inward and cut. After cutting to the required position, the drive of the Z-axis stage ZST is interrupted, and instead the X-axis stage XST is driven to advance the blade tip tool SB so as to approach the axis line RX, and the groove at the first edge E1. Cut the bottom of the shape.
- the drive of the X-axis stage XST is interrupted, and instead, the Z-axis stage ZST is driven so that the sword tip bite SB is separated from the mold MM until the first step amount is reached.
- the driving of the Z-axis stage ZST is interrupted, and instead, the X-axis stage XST is driven to advance the sword tip bite SB so as to approach the axis line RX. To cut.
- the groove shape corresponding to the multilevel structure shown in FIG. 10 can be cut.
- the die material MM is relatively brought close to the sword tip SB by the Z-axis stage ZST, and the tip of the sword tip SB is placed on the outer side in the direction orthogonal to the axis of the transfer surface to be cut. Position. After that, while rotating the mold material MM around the axis RX by the rotation drive unit RD, as indicated by an arrow in FIG. 11, the Z-axis stage ZST is driven and the tip of the sword tip bit SB is moved to the mold material MM. Advance inward and cut by the amount of the step.
- the drive of the Z-axis stage ZST is interrupted, and instead the X-axis stage XST is driven to advance the blade tip tool SB so as to approach the axis line RX, and the groove at the first edge E1. Cut the bottom of the shape.
- the drive of the X-axis stage XST is interrupted, and instead the Z-axis stage ZST is driven so that the sword tip bit SB is separated from the mold MM by the step amount, and then the Z-axis stage ZST
- the driving is interrupted, and instead the X-axis stage XST is driven, the sword tip bite SB is moved to a predetermined position so as to approach the axis RX, and then the driving of the X-axis stage XST is interrupted and the Z-axis stage ZST is driven.
- the tip of the sword tip cutting tool SB is advanced inward of the die material MM and cut by the step amount.
- the angle between the first edge E1 of the sword tip SB close to the rotation axis RX and the rotation axis RX is ⁇ 1, and the second edge E2 of the sword tip SB far from the rotation axis RX
- the die material MM is brought relatively close to the sword tip SB by the Z-axis stage ZST, and the tip of the sword tip SB is placed on the outer side in the direction orthogonal to the axis of the transfer surface to be cut. Position.
- the Z-axis stage ZST is driven so that the tip of the sword tip bit SB is made of the mold material MM. Advance inward and cut by the amount of the step. After cutting to the required position, the drive of the Z-axis stage ZST is interrupted, and instead the X-axis stage XST is driven to advance the blade tip tool SB so as to approach the axis line RX, and the groove at the first edge E1. Cut the bottom of the shape.
- the drive of the X-axis stage XST is interrupted, and instead the Z-axis stage ZST is driven so that the sword tip bit SB is separated from the mold MM by the step amount, and then the Z-axis stage ZST
- the driving is interrupted, and instead the X-axis stage XST is driven, the sword tip bite SB is moved to a predetermined position so as to approach the axis RX, and then the driving of the X-axis stage XST is interrupted and the Z-axis stage ZST is driven.
- the tip of the sword tip cutting tool SB is advanced inward of the die material MM and cut by the step amount.
- the objective lens mold can be formed by cutting in this manner.
- An objective lens can be formed by injection molding a resin using such a mold (see FIG. 5).
- FIG. 13 includes an objective lens that is transferred from a mold formed by the above-described processing method, and can appropriately record and / or reproduce information on BD, DVD, and CD, which are different optical disks. It is a figure which shows schematically the structure of optical pick-up apparatus PU1 of this Embodiment which can be performed. Such an optical pickup device PU1 can be mounted on an optical information recording / reproducing device.
- the first optical disc is a BD
- the second optical disc is a DVD
- the third optical disc is a CD.
- the present invention is not limited to the present embodiment.
- the light beam condensed by the central region, the intermediate region, and the peripheral region of the objective lens OBJ becomes a spot formed on the information recording surface RL1 of the BD through the protective substrate PL1 having a thickness of 0.1 mm. .
- the reflected light beam modulated by the information pits on the information recording surface RL1 is again transmitted through the objective lens OBJ and a diaphragm (not shown), and then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP, and by the collimating lens COL.
- a converged light beam is reflected by the polarization beam splitter BS, and converges on the light receiving surface of the light receiving element PD via the sensor lens SEN. Then, by using the output signal of the light receiving element PD to focus or track the objective lens OBJ by the biaxial actuator AC1, information recorded on the BD can be read.
- the spherical aberration generated due to the wavelength fluctuation or different information recording layers is changed in magnification. Correction can be made by changing the divergence angle or convergence angle of the light beam incident on the objective optical element OL by changing the collimating lens COL as means in the optical axis direction.
- the / 4 wavelength plate QWP converts the linearly polarized light into circularly polarized light and enters the objective lens OBJ.
- the light beam condensed by the central region and the intermediate region of the objective lens OBJ (the light beam that has passed through the peripheral region is flared and forms a spot peripheral portion) is passed through the protective substrate PL2 having a thickness of 0.6 mm.
- the spot is formed on the information recording surface RL2 of the DVD and forms the center of the spot.
- the reflected light flux modulated by the information pits on the information recording surface RL2 is again transmitted through the objective lens OBJ, then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP, and converted into a convergent light flux by the collimating lens COL,
- the light is reflected by the polarization beam splitter BS and converges on the light receiving surface of the light receiving element PD via the sensor lens SEN.
- the information recorded on DVD can be read using the output signal of light receiving element PD.
- the linearly polarized light is converted into circularly polarized light by the ⁇ / 4 wavelength plate QWP, and is incident on the objective lens OBJ.
- the light beam condensed by the central region of the objective lens OBJ (the light beam that has passed through the intermediate region and the peripheral region is flared and forms a spot peripheral part) is passed through the protective substrate PL3 having a thickness of 1.2 mm.
- the spot is formed on the information recording surface RL3 of the CD.
- the reflected light beam modulated by the information pits on the information recording surface RL3 passes through the objective lens OBJ again, is converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wave plate QWP, and is converged by the collimating lens COL, The light is reflected by the polarization beam splitter BS and converges on the light receiving surface of the light receiving element PD via the sensor lens SEN. And the information recorded on CD can be read using the output signal of light receiving element PD.
- FIG. 14 is a simplified diagram of an example of a combination of a multilevel structure and a blazed structure of an objective lens according to the present invention
- FIG. 15 is another example of a combination of a multilevel structure and a blazed structure of an objective lens according to the present invention.
- it is a simplified view, it is shown formed on a parallel plate so that the shape in such a structure can be easily understood. Actually, it is further combined with an aspherical shape.
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Abstract
Description
金型を軸線回りに回転させながら、
直線状の第1の縁部と、前記第1の縁部に対して鋭角で交差する方向に延在する直線状の第2の縁部と、前記第1の縁部の端部と前記第2の縁部の端部とを結ぶ第3の縁部とから輪郭づけられたすくい面を有する工具を、前記第1の縁部と前記第2の縁部のうち少なくとも一方を前記軸線に対して傾けた状態で、前記対物レンズの転写面を切削加工することを特徴とする。
15°≦θ1≦35° (1)
0°≦θ2≦15° (2)
請求項5に記載の金型の加工方法は、請求項4に記載の発明において、以下の式を満たすことを特徴とする。
1°≦θ2≦15° (3)
請求項6に記載の金型の加工方法は、請求項1又は2に記載の発明において、前記第1の縁部と前記第2の縁部のうち前記軸線に近い方の縁部と前記軸線との傾き角θ1を、遠い方の縁部と前記軸線との傾き角θ2と等しく又は略等しくした状態で加工を行うことを特徴とする。
10°≦θ1≦20° (4)
請求項8に記載の金型の加工方法は、請求項1~7のいずれかに記載の発明において、前記工具を前記軸線に接近するように移動しながら切削加工を行うことを特徴とする。
0.9≦d/f≦1.6 (5)
請求項13に記載の金型は、請求項1~12のいずれかに記載の金型の加工方法によって形成されたことを特徴する。
前記マルチレベル構造における光軸方向に延在する面のうち少なくとも一部は、光軸に対して傾いていることを特徴とする。
15°≦θ1’≦35° (6)
0°≦θ2’≦15° (7)
請求項17に記載の対物レンズは、請求項16に記載の発明において、以下の式を満たすことを特徴とする。
1°≦θ2’≦15° (8)
請求項18に記載の対物レンズは、請求項14に記載の発明において、前記対物レンズの光軸方向断面をとったとき、前記マルチレベル構造の一つの階段単位において、光軸方向に延在しており互いに対向している2つの面のうち光軸に近い方の面と光軸との傾き角θ1’は、光軸から遠い方の面と光軸との傾き角θ2’と等しく又は略等しくなっていることを特徴とする。
10°≦θ1’≦20° (9)
請求項20に記載の対物レンズは、請求項14~19のいずれかに記載の発明において、前記対物レンズの曲面上には、前記マルチレベル構造に加えてブレーズ構造が形成されていることを特徴とする。
0.9≦d/f≦1.6 (5)
請求項22に記載の光ピックアップ装置は、請求項14~21のいずれかに記載の対物レンズを用いたことを特徴する。
0.5mm≦t2≦0.7mm
1.0mm≦t3≦1.3mm
本明細書において、第1光源、第2光源、第3光源は、好ましくはレーザ光源である。レーザ光源としては、好ましくは半導体レーザ、シリコンレーザ等を用いることが出来る。第1光源から出射される第1光束の第1波長λ1は、第2光源から出射される第2光束の第2波長λ2より短く、第2波長λ2は、第3光源から出射される第3光束の第3波長λ3より短い。
0.6・(1.23・λ1/(n-1))<B2<1.5・(1.23・λ1/(n-1)) (10)
X、Y、Zが、それぞれ、1、-2、-3である場合は、7レベルのマルチレベル構造であることが好ましい。また、マルチレベル構造の小さい段差の光軸方向の段差量B2が、第1の波長λ1に対して1.16λ1の光路差を与える段差量であることが好ましい。
0.6・(1.16・λ1/(n-1))<B2<1.5・(1.16・λ1/(n-1)) (11)
次に、例えば中間領域に設けられる第2光路差付与構造について以下に詳述する。本態様における第2光路差付与構造は、少なくとも基礎構造を有する構造である。
15°≦θ1≦35° (1)
0°≦θ2≦15° (2)
これにより、金型Mの溝形状は図5に示すように加工されるが、1つの溝形状において、回転軸線RX方向に沿って延在し且つ回転軸線RXに近い面を外側面SP1、回転軸線RX方向に沿って延在し且つ回転軸線RXから遠い面を内側面SP2とする。ここで、外側面SP1と回転軸線RXとの角度をθ1とし、内側面SP2と回転軸線RXとの角度をθ2としたときに、以下の関係が成立すると好ましい。
15°≦θ1≦35° (1)
0°≦θ2≦15° (2)
かかる金型Mにより、図5に示す対物レンズOBJが溝形状に対応する輪帯構造と共に転写形成される。光路差付与構造の1つの階段単位において、対向する2面のうち、光軸OX方向に延在し且つ光軸OXに近い側面をPa、光軸OX方向に延在し且つ光軸OXから遠い側面をPbとする。ここで、輪帯構造の側面Paと光軸OXとの角度をθ1’とし、側面Pbと光軸OXとの角度をθ2’としたときに、以下の関係が成立すると好ましい。
15°≦θ1’≦35° (6)
0°≦θ2’≦15° (7)
このような対物レンズOBJに、図6に示すように略平行光を入射させると、側面Paに交差するテラス面Pcに入射した光束のうち、側面Paとの交点近傍の領域から対物レンズOBJ内に入射した光束は、側面Paから出射してしまうので、光ディスクの情報記録面に集光する光束として有効に用いられない。一方、側面Pbから対物レンズOBJ内に入射した光束も、光ディスクの情報記録面に集光する光束として有効に用いることは困難である。これを「影の効果」と呼ぶ。側面Paにおける影の効果は、側面Paが光軸に平行である場合であっても、存在するため、側面Paを光軸に対して傾けることによる光量ロスの問題はあまり変わらない。一方で、側面Pbにおける影の効果は、側面Pbが光軸に平行である場合は、殆ど存在しないため、側面Pbを光軸に対して傾けないか、傾けても出来るだけ小さくすることが、光量ロスを低減するという意味で好ましい。よって、θ2’≦θ1’であることが好ましく、より好ましくは(6)、(7)式を満たすことである。尚、(6)、(7)式を満たすと、(1)、(2)式が満たされることとなる。また、θ2’は、光量ロスを出来るだけ減らすと言う観点からは0°以上、5°以下であることが好ましい。光量ロスを限りなく減らすためには、θ2’が0°であることが好ましく、光量ロスを出来るだけ減らしながらも、金型から対物レンズを抜けやすくするためには、0°より大きく、5°以下(より好ましくは3°以下)であることが好ましい。
1°≦θ2’≦15° (8)
上記の点について、更に詳細に説明する。先ず、θ1’について説明する。図16に示すように、θ1’が0°である場合、即ち光軸に近い側の側面が光軸に平行な場合であっても、図16におけるグレーの領域は影の効果によって、光束を利用できず、光量ロスとなることは避けられない。次に、図17に示すように、光軸に近い側の側面が光軸に対して傾き、θ1’が35°となる場合も、グレーの領域は影の効果によって光束を利用できないが、この影の効果は、図16に示すように、側面が光軸に平行な場合も存在しているため、光量ロスが特に増えるわけではない。従って、光軸に近い側の側面を光軸に対して傾けても、光量ロスにおいて悪影響が増えないことがわかる。また、θ1’が0°~35°の間の角度である図18に示すような場合であっても、同様にグレーの領域は影の効果によって光束を利用出来ないが、光量ロスが特に増えるわけではない。従って、θ1’は0°~35°の間では光束の損失はほぼ一定であり、35°を超えると損失が増大するため、光利用効率の観点では0°≦θ1’≦35°が望ましい。さらに、剣先バイトやRバイトの縁部やバイトの傾け角等を考慮すると、15°≦θ1’≦35°が望ましい範囲となる。
10°≦θ1’≦20° (9)
光路差付与構造を有する対物レンズを成形する際は、当該光路差付与構造を有するレンズ形状に対応する金型形状を、剣先バイト(図7に一例を示す)等のバイトを有する二軸加工機(図8に一例を示す)等を用いて切削し、切削した後の金型内に溶融した材料を入れ、冷却し材料が固化した後、当該金型からレンズを取り出すことで、レンズを成形するのが一般的である。
0.9≦d/f≦1.6 (5)
但し、dは、対物レンズの光軸上の厚さ(mm)を表し、fは、第1光束における対物レンズの焦点距離を表す。なお、fは、好ましくは、使用波長のうち最も短い波長における焦点距離を表す。
(切削加工例1)
次に、2軸加工機MC2を用いた金型の加工について説明する。まず、図4(c)に示すようなマルチレベル構造に対応した溝形状の切削加工例1について説明するが、ここでは説明を容易とすべく、平行平板上に加工する例を示す。図5を参照して、回転軸線RXに近い剣先バイトSBの第1の縁部E1と、回転軸線RXとの角度をθ1とし、回転軸線RXから遠い剣先バイトSBの第2の縁部E2と、回転軸線RXとの角度をθ2としたときに、以下の関係になるように、剣先バイトSBをX軸ステージXST上に固定する。
15°≦θ1≦35° (1)
0°≦θ2≦15°(但し、1°≦θ2であると良い) (2)
次いで、図9に示すように、Z軸ステージZSTにより剣先バイトSBに対して金型の素材MMを相対的に接近させ、切削しようとする転写面の軸線直交方向外側に剣先バイトSBの先端を位置させる。その後、回転駆動部RDにより金型の素材MMを軸線RX回りに回転させながら、図9に矢印で示すように、Z軸ステージZSTを駆動して剣先バイトSBの先を金型の素材MMの内方に進行させて切削する。必要な位置まで切削したら、Z軸ステージZSTの駆動を中断し、代わりにX軸ステージXSTを駆動して、剣先バイトSBを軸線RXに接近するように進行させて第1の縁部E1で溝形状の最底部を切削する。必要な位置まで切削したら、X軸ステージXSTの駆動を中断し、代わりにZ軸ステージZSTを駆動して、1段目の段差量になるまで剣先バイトSBを金型MMから離すようにし、その後、Z軸ステージZSTの駆動を中断し、代わりにX軸ステージXSTを駆動して、剣先バイトSBを軸線RXに接近するように進行させて第1の縁部E1で、1段目の段差部を切削する。以上を繰り返すことで、図9に示すマルチレベル構造に対応した溝形状を切削できる。切削加工例1の場合、軸線RX方向に延在する溝形状の側面のうち、軸線RXを向いた内側面SP2は軸線RXに対してθ2だけ傾いているが、それに対向する外側面SP1は軸線RXに対してθ1だけ傾いている。(図9においては、θ2が0°である例を示している。)
(切削加工例2)
次に、図4(c)に示すようなマルチレベル構造に対応した溝形状の切削加工例2について説明する。図5を参照して、回転軸線RXに近い剣先バイトSBの第1の縁部E1と、回転軸線RXとの角度をθ1とし、回転軸線RXから遠い剣先バイトSBの第2の縁部E2と、回転軸線RXとの角度をθ2としたときに、以下の関係になるように、剣先バイトSBをX軸ステージXST上に固定する。
10°≦θ1≦20° (4)
θ1=θ2
次いで、図10に示すように、Z軸ステージZSTにより剣先バイトSBに対して金型の素材MMを相対的に接近させ、切削しようとする転写面の軸線直交方向外側に剣先バイトSBの先端を位置させる。その後、回転駆動部RDにより金型の素材MMを軸線RX回りに回転させながら、図10に矢印で示すように、Z軸ステージZSTを駆動して剣先バイトSBの先を金型の素材MMの内方に進行させて切削する。必要な位置まで切削したら、Z軸ステージZSTの駆動を中断し、代わりにX軸ステージXSTを駆動して、剣先バイトSBを軸線RXに接近するように進行させて第1の縁部E1で溝形状の最底部を切削する。必要な位置まで切削したら、X軸ステージXSTの駆動を中断し、代わりにZ軸ステージZSTを駆動して、1段目の段差量になるまで剣先バイトSBを金型MMから離すようにし、その後、Z軸ステージZSTの駆動を中断し、代わりにX軸ステージXSTを駆動して、剣先バイトSBを軸線RXに接近するように進行させて第1の縁部E1で、1段目の段差部を切削する。以上を繰り返すことで、図10に示すマルチレベル構造に対応した溝形状を切削できる。切削加工例2の場合、軸線RX方向に延在する溝形状の側面のうち、軸線RXを向いた内側面SP2と、それに対向する外側面SP1は、それぞれ軸線RXに対して逆方向に同じ角度(θ1=θ2)だけ傾いている。
(切削加工例3)
次に、図4(d)に示すようなマルチレベル構造に対応した溝形状の切削加工例3について説明する。図5を参照して、回転軸線RXに近い剣先バイトSBの第1の縁部E1と、回転軸線RXとの角度をθ1とし、回転軸線RXから遠い剣先バイトSBの第2の縁部E2と、回転軸線RXとの角度をθ2としたときに、以下の関係になるように、剣先バイトSBをX軸ステージXST上に固定する。
15°≦θ1≦35° (1)
0°≦θ2≦15°(但し、1°≦θ2であると良い) (2)
次いで、図11に示すように、Z軸ステージZSTにより剣先バイトSBに対して金型の素材MMを相対的に接近させ、切削しようとする転写面の軸線直交方向外側に剣先バイトSBの先端を位置させる。その後、回転駆動部RDにより金型の素材MMを軸線RX回りに回転させながら、図11に矢印で示すように、Z軸ステージZSTを駆動して剣先バイトSBの先を金型の素材MMの内方に進行させて段差量分だけ切削する。必要な位置まで切削したら、Z軸ステージZSTの駆動を中断し、代わりにX軸ステージXSTを駆動して、剣先バイトSBを軸線RXに接近するように進行させて第1の縁部E1で溝形状の底部を切削する。必要な位置まで切削したら、X軸ステージXSTの駆動を中断し、代わりにZ軸ステージZSTを駆動して段差量分だけ剣先バイトSBを金型MMから離すようにし、その後、Z軸ステージZSTの駆動を中断し、代わりにX軸ステージXSTを駆動し、剣先バイトSBを軸線RXに接近するように所定の位置まで移動させ、その後X軸ステージXSTの駆動を中断し、Z軸ステージZSTを駆動して剣先バイトSBの先を金型の素材MMの内方に進行させて段差量分だけ切削する。以上を繰り返すことで、図11に示すマルチレベル構造に対応した溝形状を切削できる。切削加工例3の場合、軸線RX方向に延在する溝形状の側面のうち、軸線RXを向いた内側面SP2は軸線RXに対してθ1だけ傾いているが、それに対向する外側面SP1は軸線RXに対してθ2だけ傾いている。(図9においては、θ1が0°である例を示している。)
(切削加工例4)
次に、図4(d)に示すようなマルチレベル構造に対応した溝形状の切削加工例4について説明する。図5を参照して、回転軸線RXに近い剣先バイトSBの第1の縁部E1と、回転軸線RXとの角度をθ1とし、回転軸線RXから遠い剣先バイトSBの第2の縁部E2と、回転軸線RXとの角度をθ2としたときに、以下の関係になるように、剣先バイトSBをX軸ステージXST上に固定する。
10°≦θ1≦20° (4)
θ1=θ2
次いで、図12に示すように、Z軸ステージZSTにより剣先バイトSBに対して金型の素材MMを相対的に接近させ、切削しようとする転写面の軸線直交方向外側に剣先バイトSBの先端を位置させる。その後、回転駆動部RDにより金型の素材MMを軸線RX回りに回転させながら、図12に矢印で示すように、Z軸ステージZSTを駆動して剣先バイトSBの先を金型の素材MMの内方に進行させて段差量分だけ切削する。必要な位置まで切削したら、Z軸ステージZSTの駆動を中断し、代わりにX軸ステージXSTを駆動して、剣先バイトSBを軸線RXに接近するように進行させて第1の縁部E1で溝形状の底部を切削する。必要な位置まで切削したら、X軸ステージXSTの駆動を中断し、代わりにZ軸ステージZSTを駆動して段差量分だけ剣先バイトSBを金型MMから離すようにし、その後、Z軸ステージZSTの駆動を中断し、代わりにX軸ステージXSTを駆動し、剣先バイトSBを軸線RXに接近するように所定の位置まで移動させ、その後X軸ステージXSTの駆動を中断し、Z軸ステージZSTを駆動して剣先バイトSBの先を金型の素材MMの内方に進行させて段差量分だけ切削する。以上を繰り返すことで、図12に示すマルチレベル構造に対応した溝形状を切削できる。切削加工例4の場合、軸線RX方向に延在する溝形状の側面のうち、軸線RXを向いた内側面SP2と、それに対向する外側面SP1は、それぞれ軸線RXに対して逆方向に同じ角度(θ1=θ2)だけ傾いている。
BSE ベース
BS 偏光ビームスプリッタ
CN 中央領域
COL コリメートレンズ
DP ダイクロイックプリズム
E1 第1の縁部
E2 第2の縁部
E3 第3の縁部
SP2 内側面
LD1 半導体レーザ
LD2 半導体レーザ
LD3 半導体レーザ
LDP レーザユニット
M 金型
MC2 2軸加工機
MD 中間領域
MM 金型の素材
OBJ 対物レンズ
SP1 外側面
OT 周辺領域
OX 光軸
PD 受光素子
PL1~PL3 保護基板
PU1 光ピックアップ装置
Pa 側面
Pb 側面
Pc 光源側テラス面
Pd 光ディスク側テラス面
QWP λ/4波長板
RD 回転駆動部
RL1~RL4 情報記録面
RX 回転軸線
S シャンク
SB 剣先バイト
SCN スポット中心部
SEN センサレンズ
SMD スポット中間部
SOT スポット周辺部
XST X軸ステージ
ZST Z軸ステージ
Claims (22)
- 異なる光ディスクを互換使用可能な光ピックアップ装置において共通に用いられ各光ディスクの情報記録面に光束を集光するべく、曲面上にマルチレベル構造を形成してなる対物レンズを成形するための金型の加工方法であって、
金型を軸線回りに回転させながら、
直線状の第1の縁部と、前記第1の縁部に対して鋭角で交差する方向に延在する直線状の第2の縁部と、前記第1の縁部の端部と前記第2の縁部の端部とを結ぶ第3の縁部とから輪郭づけられたすくい面を有する工具を、前記第1の縁部と前記第2の縁部のうち少なくとも一方を前記軸線に対して傾けた状態で、前記対物レンズの転写面を切削加工することを特徴とする金型の加工方法。 - 前記工具を、前記第1の縁部と前記第2の縁部のうち少なくとも一方を前記軸線に対して傾けた状態で、前記軸線方向および前記軸線に交差する方向にのみ移動させ、前記対物レンズの転写面を切削加工することを特徴とする請求項1に記載の金型の加工方法。
- 前記第1の縁部と前記第2の縁部のうち前記軸線に近い方の縁部と前記軸線との傾き角θ1を、遠い方の縁部と前記軸線との傾き角θ2よりも大きくした状態で加工を行うことを特徴とする請求項1又は2に記載の金型の加工方法。
- 以下の式を満たすことを特徴とする請求項3に記載の金型の加工方法。
15°≦θ1≦35° (1)
0°≦θ2≦15° (2) - 以下の式を満たすことを特徴とする請求項4に記載の金型の加工方法。
1°≦θ2≦15° (3) - 前記第1の縁部と前記第2の縁部のうち前記軸線に近い方の縁部と前記軸線との傾き角θ1を、遠い方の縁部と前記軸線との傾き角θ2と等しく又は略等しくした状態で加工を行うことを特徴とする請求項1又は2に記載の金型の加工方法。
- 以下の式を満たすことを特徴とする請求項6に記載の金型の加工方法。
10°≦θ1≦20° (4) - 前記工具を前記軸線に接近するように移動しながら切削加工を行うことを特徴とする請求項1~7のいずれかに記載の金型の加工方法。
- 前記工具を、前記軸線に対して傾き角θ1を有する縁部が先行して前記金型の素材を切削するように、前記軸線に交差する方向に移動しながら切削加工を行うことを特徴とする請求項3~5のいずれかに記載の金型の加工方法。
- 前記工具は剣先バイトであることを特徴とする請求項1~9のいずれかに記載の金型の加工方法。
- 前記対物レンズの曲面上には、前記マルチレベル構造に加えてブレーズ構造が形成されていることを特徴とする請求項1~10のいずれかに記載の金型の加工方法。
- 前記対物レンズの軸上厚をd(mm)、前記対物レンズの焦点距離をf(mm)としたときに、以下の式を満たすことを特徴とする請求項1~11のいずれかに記載の金型の加工方法。
0.9≦d/f≦1.6 (5) - 請求項1~12のいずれかに記載の金型の加工方法によって形成されたことを特徴とする金型。
- 異なる光ディスクを互換使用可能な光ピックアップ装置において共通に用いられ各光ディスクの情報記録面に光束を集光するべく、曲面上にマルチレベル構造を形成してなる対物レンズであって、
前記マルチレベル構造における光軸方向に延在する面のうち少なくとも一部は、光軸に対して傾いていることを特徴とする対物レンズ。 - 前記対物レンズの光軸方向断面をとったとき、前記マルチレベル構造の一つの階段単位において、光軸方向に延在しており互いに対向している2つの面のうち光軸に近い方の面と光軸との傾き角θ1’は、光軸から遠い方の面と光軸との傾き角θ2’よりも大きくなっていることを特徴とする請求項14に記載の対物レンズ。
- 以下の式を満たすことを特徴とする請求項15に記載の対物レンズ。
15°≦θ1’≦35° (6)
0°≦θ2’≦15° (7) - 以下の式を満たすことを特徴とする請求項16に記載の対物レンズ。
1°≦θ2’≦15° (8) - 前記対物レンズの光軸方向断面をとったとき、前記マルチレベル構造の一つの階段単位において、光軸方向に延在しており互いに対向している2つの面のうち光軸に近い方の面と光軸との傾き角θ1’は、光軸から遠い方の面と光軸との傾き角θ2’と等しく又は略等しくなっていることを特徴とする請求項14に記載の対物レンズ。
- 以下の式を満たすことを特徴とする請求項18に記載の対物レンズ。
10°≦θ1’≦20° (9) - 前記対物レンズの曲面上には、前記マルチレベル構造に加えてブレーズ構造が形成されていることを特徴とする請求項14~19のいずれかに記載の対物レンズ。
- 前記対物レンズの軸上厚をd(mm)、前記対物レンズの焦点距離をf(mm)としたときに、以下の式を満たすことを特徴とする請求項14~20のいずれかに記載の対物レンズ。
0.9≦d/f≦1.6 (5) - 請求項14~21のいずれかに記載の対物レンズを用いたことを特徴とする光ピックアップ装置。
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JP2015511893A (ja) * | 2012-01-17 | 2015-04-23 | 三井化学株式会社 | 表面起伏を有する可撓性膜および電気活性光学系におけるその使用 |
JP2018013678A (ja) * | 2016-07-22 | 2018-01-25 | 大日本印刷株式会社 | 回折光学素子、光照射装置、回折光学素子の製造方法 |
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