WO2011093165A1 - Lentille d'objectif et dispositif d'acquisition optique - Google Patents

Lentille d'objectif et dispositif d'acquisition optique Download PDF

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Publication number
WO2011093165A1
WO2011093165A1 PCT/JP2011/050705 JP2011050705W WO2011093165A1 WO 2011093165 A1 WO2011093165 A1 WO 2011093165A1 JP 2011050705 W JP2011050705 W JP 2011050705W WO 2011093165 A1 WO2011093165 A1 WO 2011093165A1
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WIPO (PCT)
Prior art keywords
objective lens
resin
optical
pickup device
less
Prior art date
Application number
PCT/JP2011/050705
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English (en)
Japanese (ja)
Inventor
省吾 山本
Original Assignee
コニカミノルタオプト株式会社
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Publication date
Application filed by コニカミノルタオプト株式会社 filed Critical コニカミノルタオプト株式会社
Priority to JP2011551807A priority Critical patent/JPWO2011093165A1/ja
Publication of WO2011093165A1 publication Critical patent/WO2011093165A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F232/00—Copolymers of cyclic compounds containing no unsaturated aliphatic radicals in a side chain, and having one or more carbon-to-carbon double bonds in a carbocyclic ring system

Definitions

  • the present invention relates to an objective lens, and more particularly to an objective lens having an NA of 0.75 or more and an optical pickup device that are suitable for use in an optical pickup device.
  • a high-density optical disk system capable of recording and / or reproducing information (hereinafter, “recording and / or reproduction” is referred to as “recording / reproduction”) using a blue-violet semiconductor laser having a wavelength of about 400 nm is already on the market. Yes.
  • BD Blu-ray Disc
  • DVD DVD (NA 0.6, light source wavelength 650 nm, storage capacity 4.7 GB) It is possible to record information of 23 to 27 GB per layer on an optical disk having a diameter of 12 cm which is the same size as the above.
  • Patent Document 1 discloses a technique for manufacturing a resin lens by so-called injection molding in which a cavity corresponding to a lens is formed by a mold, and a molten resin is poured into the cavity from a resin inlet called a gate to form a lens. Is disclosed.
  • the axial lens thickness is relatively thin with respect to the flange thickness because of NA of about 0.6, and the injection molding technique disclosed in Patent Document 1 is used. Manufacturing is possible.
  • NA is 0.75 or more
  • the axial lens thickness becomes relatively thick with respect to the flange thickness and becomes nearly hemispherical, and the total amount of resin injected into the cavity Will increase.
  • the gate seals before the pressure is sufficiently transmitted to the maximum wall thickness in the cavity, and the air in the cavity cannot be pushed out.
  • the problem is that a desired optical surface cannot be obtained due to the accumulation of the resin and the shrinkage of the resin accompanying the temperature decrease.
  • the gate can also be increased, so that the pressure can be sufficiently transmitted, but there is a problem in that the mass increases which is disadvantageous for the tracking and focusing control of the objective lens. Arise.
  • the thickness of the axial lens is increased as the flange thickness is increased as a whole, there arises a problem that the working distance for avoiding the interference with the optical disc is reduced.
  • the present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide an objective lens and an optical pickup device that can suppress problems during molding in a high NA lens.
  • the objective lens according to claim 1 is an objective lens used in an optical pickup device that records and / or reproduces information by condensing a light beam having a wavelength of 500 nm or less on an information recording surface of an optical disc.
  • the NA of the objective lens is 0.75 or more and 0.9 or less, satisfies the following formula, and is formed of a resin having an MFR of 10 (g / 10 min) or more and 70 (g / 10 min) or less. It is characterized by. 0.9 ⁇ d / f ⁇ 1.2 (1)
  • d (mm) represents the on-axis lens thickness of the objective lens
  • f (mm) represents the focal length of the objective lens in a light beam having a wavelength of 500 nm or less.
  • the objective lens of the present invention is formed from a resin having an MFR of 10 (g / 10 min) to 70 (g / 10 min), for example, the NA of the objective lens is 0.75 or more, and (1) Even if it has a shape that satisfies the equation, the gate solidifies before the resin flowing from the gate during molding fills up to the maximum thickness of the mold (usually near the optical axis of the objective lens). Can be suppressed. As a result, the resin is effectively filled up to the maximum thickness portion, and the shrinkage can be compensated for by sufficiently transmitting the pressure, and a highly accurate optical surface can be transferred and molded.
  • MFR means a melt flow rate (Melt flow rate), and a certain amount of synthetic resin is heated and pressurized at a predetermined temperature (eg, 260 ° C.) in a cylindrical container heated by a heater.
  • a predetermined temperature eg, 260 ° C.
  • the test machine uses an extrusion plastometer defined by JIS K6760, and the measurement method is defined by JIS K7210.
  • the objective lens according to claim 2 is the following formula in the invention according to claim 1, 0.9 ⁇ d / f ⁇ 1.1 (1 ′) It is characterized by satisfying.
  • the objective lens described in claim 3 is characterized in that, in the invention described in claim 1 or 2, the resin is a cycloolefin resin.
  • Preferred examples of such a resin include ZEONEX manufactured by Nippon Zeon, APEL manufactured by Mitsui Chemicals, TOPAS ADVANCED, TOPAS manufactured by POLYMERS, and ARTON manufactured by JSR.
  • the MFR of the resin is preferably 20 or more and 55 or less, more preferably 30 or more and 50 or less.
  • the objective lens according to any one of the first to third aspects, wherein the objective lens has a flange portion around an optical surface, and the minimum thickness of the flange portion is t (mm). ) 5.0 ⁇ d / t ⁇ 8.0 (2) It is characterized by satisfying.
  • the present invention is particularly effective for an objective lens having such a shape.
  • An optical pickup device includes a light source that emits a light beam having a wavelength of at least 500 nm, a condensing optical system including the objective lens according to any one of the first to fourth aspects, a photodetector, The objective lens is characterized in that the optical surface with the smaller radius of curvature is arranged toward the light source side.
  • the condensing optical system may be composed of only an objective lens, or may have a coupling lens such as a collimator in addition to the objective lens.
  • 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 a light beam emitted from the light source onto the information recording surface of the optical disk.
  • the objective lens is preferably a single lens.
  • an optical path difference providing structure may be formed integrally with the objective lens.
  • 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 optical pickup device uses a light source (for example, a semiconductor laser) having a wavelength of at least 500 nm or less (preferably 350 nm or more and 450 nm or less).
  • the objective lens has an image-side numerical aperture of 0.75 to 0.9.
  • the objective lens preferably has an optical surface and a flange portion.
  • the flange portion refers to a portion used to hold the objective lens, having an annular portion extending in a direction substantially orthogonal to the optical axis around the optical surface.
  • the objective lens satisfies the following conditional expression (1). 0.9 ⁇ d / f ⁇ 1.2 (1)
  • d (mm) represents the axial lens thickness of the objective lens
  • f (mm) represents the focal length of the objective lens in a light beam having a wavelength of 500 nm or less.
  • conditional expression (1) it is possible to ensure a long working distance while suppressing the generation of astigmatism and decentration coma. In order to secure a longer working distance, it is preferable to satisfy the conditional expression (1 ′).
  • FIG. 1 is a diagram showing a process of molding a lens having an NA of 0.85 used for an optical pickup device for BD using a molding die.
  • FIG. 2 is an enlarged view of the molding die according to the present embodiment, and shows a state during molding.
  • FIG. 3 is an enlarged view of a molding die according to a comparative example, and similarly shows a state during molding.
  • the molding die includes a first die 10 and a second die 20, and a plurality of cavities are formed in a state where both are clamped.
  • the cavity shape in FIG. 1 is schematic. Since a general optical pickup device is sufficient, it is omitted here.
  • the first mold 10 is a first optical transfer for transferring and forming the first optical surface of the objective lens (the light source side when attached to the optical pickup device).
  • the first mold 10 is formed with a gate portion (inlet channel) GT so as to be connected to the first flange portion transfer surface 11b.
  • the second mold 20 continues to the second optical transfer surface 21a for transferring and forming the second optical surface of the objective lens (on the optical disc side when attached to the optical pickup device) and the periphery thereof.
  • a second flange portion transfer surface 21b for transferring and forming the optical disc side surface of the flange portion is provided.
  • the shapes of the first mold 10 and the second mold 20 are the same as those in the present embodiment.
  • the first mold 10 is set so as to face the second mold 20. Further, by heating the first mold 10 and the second mold 20 with a heater (not shown), the optical transfer surfaces 11a and 21a are heated to a predetermined temperature.
  • the first mold 10 is relatively approached and brought into close contact with the second mold 20, and the mold is clamped with a predetermined holding pressure.
  • a resin heated to a higher temperature than the mold temperature is supplied in a state of being pressurized to an arbitrary pressure through the runner LN and the gate part GT from the nozzle (see FIG. 1C).
  • the fluidity of the resin PL ′ is worse than that of the resin PL having an MFR of 10 or more and 70 or less. For this reason, resin begins to be filled in the cavity as in the initial state shown in FIG. 3A, but in the intermediate state shown in FIG. 3B, a sufficient amount of resin PL ′ is filled in the cavity. Before the resin is cooled, the fluidity deteriorates as the resin cools in the vicinity of the gate part GT having a relatively small opening area, and the pressure is not gradually transmitted through the gate part GT because a part of the resin starts to solidify. . In the final state shown in FIG.
  • the pressure on the runner LN side is not effectively transmitted to the resin PL ′ in the cavity, and thereby the maximum thickness portion of the transfer surface 10a of the first mold 10 having a small curvature radius.
  • the resin PL ′ does not adhere to the vicinity, and molding defects may occur, and a highly accurate optical surface may not be obtained.
  • the fluidity of the resin PL ′′ is better than that of the resin PL having an MFR of 10 to 70.
  • the fluidity is too good, it immediately scatters into the cavity immediately after passing through the gate GT, and directly solidifies by hitting the transfer surface 10a of the first mold 10 having a small curvature radius. There is a problem that unevenness occurs on the surface, resulting in poor appearance.
  • the resin PL having an MFR of 10 (g / 10 min) to 70 (g / 10 min) since the resin PL having an MFR of 10 (g / 10 min) to 70 (g / 10 min) is used, the fluidity of the resin PL is maintained to some extent even when the temperature is lowered. Is done. Accordingly, from the initial state shown in FIG. 2 (a) to the final state shown in FIG. 2 (c) through the intermediate state shown in FIG. 2 (b), a sufficient amount of resin PL is filled in the cavity. Since the solidification in the vicinity of the gate part GT can be suppressed, the pressure on the runner LN side is effectively transmitted to the resin PL in the cavity, and thereby the vicinity of the maximum thickness part of the transfer surface 10a of the first mold 10 having a small curvature radius. Resin PL adheres. In addition, since poor appearance caused by fluidity is too good, a highly accurate optical surface can be obtained.
  • the resin is cooled by waiting for a predetermined time until the molten resin is solidified in a state where the shapes of the transfer surfaces 11a, 11b, 21a, and 21b are transferred.
  • FIG. 4 is a view of the objective lens OBJ formed by the molding die shown in FIGS. 1 and 2, viewed from the optical axis direction
  • FIG. 5 is a view of the objective lens OBJ viewed from the direction orthogonal to the optical axis.
  • the first optical surface S1 transferred and molded by the first optical transfer surface 11a and the second optical transfer surface 21a have a radius of curvature larger than that of the first optical surface S1. It has a second optical surface S2 that has been transfer-molded, and a flange portion FL that has been transfer-molded by the first flange portion transfer surface 11b and the second flange portion transfer surface 21b.
  • the axial lens thickness of the objective lens OBJ is d (mm)
  • the focal length of the objective lens OBJ in a light beam having a wavelength of 500 nm or less is f (mm)
  • the flange portion FL thin flange portion FT of the objective lens OBJ.
  • the wall thickness of t (mm) 0.9 ⁇ d / f ⁇ 1.2 (1) 5.0 ⁇ d / t ⁇ 8.0 (2) Meet.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Optical Head (AREA)

Abstract

L'invention concerne une lentille d'objectif capable de supprimer les défauts au moment de la formation dans une lentille ayant un NA élevé, et un dispositif d'acquisition optique. La lentille utilise une résine (PL) ayant un MFR supérieur ou égal à 10 (g/10 min) et inférieur ou égal à 70 (g/10 min) et donc, de l'état initial représenté dans la figure 2(a) à l'état final représenté dans la figure 2(b), la solidification de la résine (PL) à proximité de la partie grille (GT) est supprimée, la pression d'un côté de coulisseau (LN) est transférée vers la résine (PL) dans une cavité et, en conséquence, la résine (PL) est moulée de façon à atteindre un point proche de l'épaississement maximal d'un plan de transfert (10a) d'un premier moule (10) ayant un rayon de courbure réduit. Il est ainsi possible d'acquérir une surface optique d'une grande précision.
PCT/JP2011/050705 2010-01-29 2011-01-18 Lentille d'objectif et dispositif d'acquisition optique WO2011093165A1 (fr)

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Application Number Priority Date Filing Date Title
JP2011551807A JPWO2011093165A1 (ja) 2010-01-29 2011-01-18 対物レンズ及び光ピックアップ装置

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2010018669 2010-01-29
JP2010-018669 2010-01-29

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WO2011093165A1 true WO2011093165A1 (fr) 2011-08-04

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001235677A (ja) * 2000-02-24 2001-08-31 Konica Corp 対物レンズ及びｄｖｄ／ｃｄ互換光ピックアップ装置
JP2004197067A (ja) * 2002-10-23 2004-07-15 Konica Minolta Holdings Inc 環状オレフィン樹脂、プラスチック製光学素子及び光ピックアップ装置
WO2006112434A1 (fr) * 2005-04-18 2006-10-26 Mitsui Chemicals, Inc. Composition de resine et composant optique
JP2007154072A (ja) * 2005-12-06 2007-06-21 Mitsubishi Rayon Co Ltd 光学用共重合体及びそれからなる成形体
JP2007179720A (ja) * 2005-11-29 2007-07-12 Konica Minolta Opto Inc 光ピックアップ装置用の対物レンズ、光ピックアップ装置用の対物レンズユニット及び光ピックアップ装置
JP2009211795A (ja) * 2008-02-06 2009-09-17 Panasonic Corp 対物レンズおよび光ピックアップ装置

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001235677A (ja) * 2000-02-24 2001-08-31 Konica Corp 対物レンズ及びｄｖｄ／ｃｄ互換光ピックアップ装置
JP2004197067A (ja) * 2002-10-23 2004-07-15 Konica Minolta Holdings Inc 環状オレフィン樹脂、プラスチック製光学素子及び光ピックアップ装置
WO2006112434A1 (fr) * 2005-04-18 2006-10-26 Mitsui Chemicals, Inc. Composition de resine et composant optique
JP2007179720A (ja) * 2005-11-29 2007-07-12 Konica Minolta Opto Inc 光ピックアップ装置用の対物レンズ、光ピックアップ装置用の対物レンズユニット及び光ピックアップ装置
JP2007154072A (ja) * 2005-12-06 2007-06-21 Mitsubishi Rayon Co Ltd 光学用共重合体及びそれからなる成形体
JP2009211795A (ja) * 2008-02-06 2009-09-17 Panasonic Corp 対物レンズおよび光ピックアップ装置

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