US20030081528A1 - Optical system for optical pickup device, coupling lens and optical information recording/reproducing apparatus - Google Patents

Optical system for optical pickup device, coupling lens and optical information recording/reproducing apparatus Download PDF

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Publication number
US20030081528A1
US20030081528A1 US10/261,779 US26177902A US2003081528A1 US 20030081528 A1 US20030081528 A1 US 20030081528A1 US 26177902 A US26177902 A US 26177902A US 2003081528 A1 US2003081528 A1 US 2003081528A1
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United States
Prior art keywords
information recording
coupling lens
light flux
optical
optical information
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Abandoned
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US10/261,779
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English (en)
Inventor
Shinichiro Saito
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Konica Minolta Inc
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Konica Minolta Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Konica Minolta Inc filed Critical Konica Minolta Inc
Assigned to KONICA CORPORATION reassignment KONICA CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SAITO, SHINICHIRO
Publication of US20030081528A1 publication Critical patent/US20030081528A1/en
Priority to US11/144,231 priority Critical patent/US7116495B2/en
Priority to US11/734,805 priority patent/US8342936B2/en
Abandoned legal-status Critical Current

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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
    • G11B7/1376—Collimator lenses
    • 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
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1372—Lenses
    • G11B2007/13727—Compound lenses, i.e. two or more lenses co-operating to perform a function, e.g. compound objective lens including a solid immersion lens, positive and negative lenses either bonded together or with adjustable spacing

Definitions

  • the present invention relates to an optical system for an optical pickup device, a coupling lens used for the aforementioned optical system and an optical information recording/reproducing apparatus which has therein the optical system and conducts at least one of recording and reproducing of optical information.
  • an optical information recording medium capable of recording optical information has become the center of public attention.
  • energy of the spot of image formation is important.
  • establishment of a coupling lens having the positive refractive power on the light source side of the objective lens shown in FIG. 3 is more advantageous on the point of the light source energy efficiency, compared with an occasion where no coupling lens is provided.
  • the optical system magnification for the forward direction is different from that for the return direction as shown in FIG. 3, the following points are feared.
  • an object point (light source light-emitting position) and an image point (optical information recording medium image formation position) both in the forward optical system are fixed, and an object point (optical information recording medium position) and a sensor position of a photo-detector both in the return optical system are fixed. If a decline of a refractive index in the course of temperature rise is caused, it is necessary to drive the objective lens in the direction for the objective lens to part from the optical information recording medium, when excessive spherical aberration is caused on the forward optical system and when trying to form a spot satisfactorily on the optical information recording medium. In this case, however, following troubles are caused.
  • the objective lens is driven by an actuator in a way to obtain the best image point on the forward optical system, an excellent image formation spot is formed on at least on optical information recording medium.
  • an image formation magnification is changed on the forward optical system because the objective lens is driven.
  • the distance between them is constant in the same way as in the distance between a disc and a sensor. Therefore, the distance between the optical image formation point and a mechanical image formation point becomes great, causing harmful influences.
  • One of the harmful influences is that recording or reproducing is conducted as an optical pickup device under the condition which is not optically excellent image formation, because the mechanical image formation point is given priority.
  • Another harmful influence is an occurrence of a trouble that a numerical aperture of the objective lens on the light emergence side is also changed when the image formation magnification on the forward optical system is changed, and a desired spot diameter cannot be obtained on the surface of an optical information recording medium.
  • an object of the present invention is to provide an optical system for an optical pickup device wherein a plastic coupling lens is provided only on the optical path of the forward optical system, and thereby, an amount of deviation between the original image point on the return optical system and a position of the photo-detector is satisfied even in the case of temperature changes, and thus, an influence of temperature changes is eliminated, a coupling lens used for the aforementioned optical system, and an optical information recording/reproducing apparatus which has therein the optical system.
  • a plastic coupling lens having a function to cancel changes of refracting power caused by changes of the refractive index of plastic in temperature changes is used in the invention.
  • an optical system used in an optical pickup device having therein a light source with wavelength ⁇ , an optical system for forming images on an optical information recording medium from a light flux emitted from the light source, a focusing mechanism used in image formation on the optical information recording medium and a photo-detector that detects reflected light coming from the optical information recording medium in the invention, is characterized in that the optical system is composed of an objective lens and a plastic coupling lens that changes an angle of divergence of a light flux emitted from the light source, the optical system is of the structure wherein the light flux from the light source passes the objective lens and the coupling lens when forming images on the optical information recording medium, and the reflected light from the optical information recording medium does not pass through the coupling lens and passes through the objective lens when the reflected light is detected by the photo-detector, a ring-shaped zonal diffractive structure is formed on at least one surface of the coupling lens, the diffractive structure generates under-spherical aberration
  • the plastic coupling lens is arranged so that light from the light source may pass through the aforementioned optical system on the forward optical system and the reflected light may not pass through the aforementioned optical system on the return optical system, and under spherical aberration is generated by the diffractive structure provided on the coupling lens, when light is shifted to the long wavelength side. Therefore, it is possible to correct chromatic aberration caused by temperature changes on the forward optical system, and it is possible to make an amount of movement of the objective lens relative to the optical information recording medium to be less.
  • an image formation magnification on the forward optical system hardly changes, and a numerical aperture of the objective lens on the light emergence side does not change, which makes it possible to obtain a desired excellent spot diameter on the optical information recording medium.
  • an amount of deviation between an original image point and a position of a photo-detector on the return optical system can be controlled in temperature changes. Owing to this, the distance between the mechanical image formation point and the optical image formation point in the photo-detector does not become great, which makes it possible to conduct recording or reproducing under the excellent state of image formation.
  • an image formation magnification of the individual coupling lens is mostly constant even in the case of temperature changes of the optical pickup device. It is possible to make an angle of divergence of a light flux emitted from the light source to be almost constant, by making the image formation magnification to be almost constant.
  • the following expression (1) is satisfied by amount of driving ⁇ L (shifting distance) for the objective lens to be moved by the focusing mechanism so that the optimum image forming position may agree with the surface of the optical information recording medium when temperature of the optical pickup device is raised by 30° C., when a focal length of the objective lens is represented by f.
  • the image formation magnification m is defined by the following formula:
  • L image is a size or length of an formed image
  • L obj is a size or length of an object.
  • the optical system having a positive refractive power such as an objective lens of the present invention
  • a parallel light flux comes to be incident into the objective lens
  • m ⁇ 0 a divergent light flux comes to be incident into the objective lens and an inverted image is formed.
  • the above-mentioned ring-shaped zonal diffractive structure is provided on the surface on one side of the coupling lens, and a grid-like diffractive structure that splits a light flux emitted from the light source into a plurality of light fluxes is provided on the surface on the other side thereof.
  • a grid-like diffractive structure that splits a light flux emitted from the light source into a plurality of light fluxes is provided on the surface on the other side thereof.
  • the surface of the coupling lens where the grid-like diffractive structure is formed is mostly a plane surface.
  • the objective lens is made of plastic.
  • the objective lens is made to be light in weight, driving by the focusing mechanism is easy, and it is possible to contribute to downsizing of a focusing mechanism.
  • a coupling lens of the invention is a plastic coupling lens that constitutes, together with an objective lens, the optical system of the optical pickup device having therein light source with wavelength ⁇ , an optical system for forming images on an optical information recording medium from a light flux emitted from the light source, a focusing mechanism used in image formation on the optical information recording medium and a photo-detector that detects reflected light coming from the optical information recording medium, and it is characterized in that the coupling lens has a positive refracting power that changes an angle of divergence of a light flux emitted from the light source, and it is outside an optical path when the photo-detector detects reflected light coming from the optical information recording medium, a ring-shaped zonal diffractive structure is formed on at least one surface of the coupling lens, and the diffractive structure stated above generates under spherical aberration when light with a long wavelength enters.
  • this coupling lens when light is shifted to the long wavelength side in the optical system for the aforesaid optical pickup device, under spherical aberration is generated by the diffractive structure provided on the coupling lens, and therefore, it is possible to correct chromatic aberration caused by temperature changes on the forward optical system, and it is possible to make an amount of movement of the objective lens relative to the optical information recording medium to be less. Owing to this, an image formation magnification on the forward optical system hardly changes, and a numerical aperture of the objective lens on the light emergence side does not change, which makes it possible to obtain a desired excellent spot diameter on the optical information recording medium.
  • an amount of deviation between an original image point and a position of a photo-detector on the return optical system can be controlled in temperature changes. Owing to this, the distance between the mechanical image formation point and the optical image formation point in the photo-detector does not become great, which makes it possible to conduct recording or reproducing under the excellent state of image formation.
  • an image formation magnification of the individual coupling lens is almost constant even in the case of temperature changes of the optical pickup device. It is further preferable to satisfy the expressions (2), (3), (4) and (5) stated above. It is preferable that the above-mentioned ring-shaped zonal diffractive structure is provided on the surface on one side of the coupling lens, and a grid-like diffractive structure that splits a light flux emitted from the light source into a plurality of light fluxes is provided on the surface on the other side thereof. In this case, it is preferable that the surface of the coupling lens where the grid-like diffractive structure is formed is mostly a plane surface.
  • an optical information recording/reproducing apparatus of the invention having therein a light source with wavelength ⁇ , an optical system for forming images on an optical information recording medium from a light flux emitted from the light source, a focusing mechanism used in image formation on the optical information recording medium and a photo-detector that detects reflected light coming from the optical information recording medium, is characterized in that the optical system is composed of an objective lens and a plastic coupling lens having a positive refracting power that changes an angle of divergence of a light flux emitted from the light source, and it is of the structure where the light flux emitted from the light source passes through the objective lens and the coupling lens when forming images on the optical information recording medium, and it passes through the objective lens when detecting the reflected light from the optical information recording medium, and a ring-shaped zonal diffractive structure is formed on at least one surface of the coupling lens, while, the diffractive structure generates under spherical aberration when light with a long wavelength enters
  • the plastic coupling lens is arranged so that light from the light source may pass through the aforementioned optical system on the forward optical system and the reflected light may not pass through the aforementioned optical system on the return optical system, and under spherical aberration is generated by the diffractive structure provided on the coupling lens, when light is shifted to the long wavelength side. Therefore, it is possible to correct chromatic aberration caused by temperature changes on the forward optical system, and it is possible to make an amount of movement of the objective lens relative to the optical information recording medium to be less.
  • an image formation magnification on the forward optical system hardly changes, and a numerical aperture of the objective lens on the light emergence side does not change, which makes it possible to obtain a desired excellent spot diameter on the optical information recording medium.
  • an amount of deviation between an original image point and a position of a photo-detector on the return optical system can be controlled in temperature changes. Owing to this, the distance between the mechanical image formation point and the optical image formation point in the photo-detector does not become great, which makes it possible to conduct recording or reproducing under the excellent state of image formation.
  • an image formation magnification of the individual coupling lens is almost constant even in the case of temperature changes of the apparatus. It is further preferable to satisfy the expressions (1), (2), (3), (4) and (5) stated above. It is preferable that the above-mentioned ring-shaped zonal diffractive structure is provided on the surface on one side of the coupling lens, and a grid-like diffractive structure that splits a light flux emitted from the light source into a plurality of light fluxes is provided on the surface on the other side thereof, and in this case, it is preferable that the surface of the coupling lens where the grid-like diffractive structure is formed is mostly a plane surface. It is further preferable that the objective lens is made of plastic.
  • the optical information recording medium in the invention includes, for example, various types of CD such as CD, CD-R, CD-RW, CD-Video and CD-ROM, various types of DVD such as DVD, DVD-ROM, DVD-RAM, DVD-R, DVD-RW and DVD+RW, or MD.
  • Recording of information and reproducing of information in the invention respectively mean that information is recorded on the information recording surface of the optical information recording medium and that information recorded on the information recording surface is reproduced.
  • the optical system of the invention may be either one used only for recording or for reproducing, or one used for both recording and reproducing. Further, the optical system of the invention may be either one that is used to conduct recording for a certain optical information recording medium and to conduct reproducing for the other optical information recording medium, or one used to conduct recording or reproducing for a certain optical information recording medium and to conduct recording and reproducing for the other optical information recording medium. Incidentally, reproducing in this case is one including only reading of information.
  • FIG. 1 is a diagram showing schematically an optical system of the optical pickup device in the embodiment of the invention.
  • FIG. 2 is a perspective view showing a coupling lens of the optical pickup device shown in FIG. 1.
  • FIG. 3 is a diagram showing schematically a conventional optical system of the optical pickup device to which a coupling lens is added.
  • FIG. 1 is a diagram showing schematically an optical system of the optical pickup device in the embodiment of the invention
  • FIG. 2 is a perspective view showing a coupling lens of the optical pickup device shown in FIG. 1.
  • the optical pickup device in FIG. 1 has therein light source 1 that is composed of a laser semiconductor laser and has wavelength ⁇ , plastic coupling lens 2 that changes an angle of divergence of a light flux emitted from the light source 1 and has a positive refracting power, deflecting element 3 through which the rays of light emerging from the coupling lens 2 pass, objective lens 4 that makes the rays of light from the deflecting element 3 to form an image on information recording surface 10 a through a protective layer of optical information recording medium 10 , biaxial actuator 5 that drives to move the objective lens 4 both in the focusing direction and the tracking direction, and photo-detector 12 into which the reflected light from the information recording surface 10 a of the optical information recording medium 10 comes through astigmatism generating lens 11 after passing the objective lens 4 and being reflected by the deflecting element 3 , to be photo-detected.
  • light source 1 that is composed of a laser semiconductor laser and has wavelength ⁇
  • plastic coupling lens 2 that changes an angle of divergence of
  • the coupling lens 2 has therein refracting interface 2 a on which a ring-shaped zonal diffractive structure is formed on the surface of the coupling lens closer to the objective lens 4 and practical plane surface 2 b on which grid-like diffractive structure 2 c is formed on the surface of the coupling lens that is opposite to the refracting interface 2 a and is closer to the light source.
  • the refracting interface 2 a of the coupling lens is a diffractive surface on which a ring-shaped zonal diffractive structure is formed, and it is possible to correct chromatic aberration caused by temperature changes, by generating spherical aberration in the under direction when a wavelength of light entering the above-mentioned refracting interface is shifted to the long wavelength side.
  • the diffracting power of the diffractive surface provided on the coupling lens becomes strong, but in this case, there are caused harmful influences such as a decline of diffraction efficiency caused by a miniaturized pitch of diffractive ring-shaped zones and a weakness for chromatic aberration that is followed by no temperature changes. Therefore, the pitch of ring-shaped zones needs to be determined by considering the balance of the foregoing.
  • the forward optical system is composed of the coupling lens 2 , the deflecting element 3 and the objective lens 4 , and light emitted from the light source 1 is made by the forward optical system to form an image on the information recording surface 10 a of the optical information recording medium 10 .
  • the return optical system is composed of the objective lens 4 , the deflecting element 3 and the astigmatism generating lens 11 , and the reflected light from the information recording surface 10 a enters detection surface 12 a of the photo-detector 12 .
  • the coupling lens 2 is arranged so that light emitted from the light source 1 may pass through it, and the reflected light from the information recording surface 10 a may not pass through it on the return optical system, and under spherical aberration is generated by the refracting interface 2 a of the coupling lens 2 when light from the light source 1 is shifted to the long wavelength side. It is therefore possible to correct chromatic aberration caused by temperature changes on the forward optical system and to lessen an amount of movement of the objective lens 4 for optical information recording medium 10 by actuator 5 in the course of focusing.
  • the image formation magnification on the forward optical system hardly changes and a numerical aperture of the objective lens on the emergence side does not change, and a desired excellent spot diameter can be obtained on the optical information recording medium surface 10 . It is also possible to control an amount of deviation between an original image point on the return optical system and a position of a photo-detector on the return optical system and detection surface 12 a of the photo-detector 12 . Owing to this, the distance between the mechanical image formation point and the optical image formation point in the photo-detector does not become great, which makes it possible to conduct recording or reproducing under the excellent state of image formation.
  • an optical information recording/reproducing apparatus so that it may include the aforementioned optical pickup device and at least one of recording and reproducing of information may be conducted with respect to an optical information recording medium.
  • an aspheric surface formed on each of the coupling lens and the objective lens is expressed by the following expression Numeral 1, when an X-axis is in the optical axis direction, a height in the direction perpendicular to the optical axis is represented by h, and a radius of curvature of the refracting interface is represented by r, wherein, ⁇ represents a constant of the cone and Ai represents a coefficient of the aspheric surface.
  • the diffractive surface on the coupling lens is expressed by the following expression Numeral 2 with optical path difference function ⁇ b, wherein h represents a height perpendicular to the optical axis and b2i represents a coefficient of optical path difference function.
  • a unit for each of radius of curvature and spacing between surfaces is mm.
  • Table 2 shows changes of image formation magnification in temperature rise of an individual coupling lens, in comparison with an occasion where no diffractive surface is provided, which indicates that the image formation magnification does not change on the coupling lens provided with a diffractive surface in the present example even in the case of temperature change of +30° C., while, the image formation magnification is raised on the coupling lens provided with no diffractive surface.
  • the coupling lens in FIG. 1 is of the finite magnification
  • the coupling lens of the invention is not limited to this, and it may be one with infinite magnification which converts a divergent light flux into a parallel light flux. Namely, it may either be one with finite magnification such as that in FIG. 1 or be one with infinite magnification such as a collimator lens, provided that an angle of divergence of a divergent light flux emitted from the light source can be changed.
  • An optical system for the optical pickup device, a coupling lens and an optical information recording/reproducing apparatus all of the invention make it possible to eliminate influences of temperature changes by arranging a plastic coupling lens on the forward optical system alone and thereby by satisfying an amount of deviation between the original image point on the return optical system and a position of the photo-detector.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Lenses (AREA)
  • Optical Head (AREA)
  • Diffracting Gratings Or Hologram Optical Elements (AREA)
US10/261,779 2001-10-02 2002-10-02 Optical system for optical pickup device, coupling lens and optical information recording/reproducing apparatus Abandoned US20030081528A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US11/144,231 US7116495B2 (en) 2001-10-05 2005-06-02 Optical system for optical pickup device, coupling lens and optical information recording/reproducing apparatus
US11/734,805 US8342936B2 (en) 2001-10-02 2007-04-13 Slot machine and control method of game

Applications Claiming Priority (2)

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JP2001310240A JP2003114382A (ja) 2001-10-05 2001-10-05 光ピックアップ装置用光学系、カップリングレンズ及び光情報記録・再生装置
JP310240/2001 2001-10-05

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US11/144,231 Continuation US7116495B2 (en) 2001-10-05 2005-06-02 Optical system for optical pickup device, coupling lens and optical information recording/reproducing apparatus
US11/734,805 Continuation-In-Part US8342936B2 (en) 2001-10-02 2007-04-13 Slot machine and control method of game

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US11/144,231 Expired - Fee Related US7116495B2 (en) 2001-10-05 2005-06-02 Optical system for optical pickup device, coupling lens and optical information recording/reproducing apparatus

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040264349A1 (en) * 2003-06-09 2004-12-30 Konica Minolta Opto, Inc. Optical system for optical pickup apparatus, optical pickup apparatus, optical information recording and/or reproducing apparatus and aberration-correcting element for optical pickup apparatus
US20080106806A1 (en) * 2004-09-07 2008-05-08 Koninklijke Philips Electronics, N.V. Optical Device with Fresnel Structure
US20080273522A1 (en) * 2007-05-01 2008-11-06 Tao Luo Generation and detection of synchronization signal in a wireless communication system
US20090109827A1 (en) * 2007-10-24 2009-04-30 Hoya Corporation Coupling lens and optical information recording/reproducing device having the same

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5002118B2 (ja) * 2003-06-18 2012-08-15 コニカミノルタアドバンストレイヤー株式会社 光ピックアップ装置用の光学素子、及び光ピックアップ装置
US8477034B2 (en) * 2006-11-02 2013-07-02 Nec Corporation Information providing system and information providing method

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01273228A (ja) * 1988-04-25 1989-11-01 Sharp Corp 光ピックアップ装置
US5105407A (en) * 1989-01-11 1992-04-14 Kabushiki Kaisha Toshiba Optical information-processing apparatus
US5629799A (en) * 1992-07-16 1997-05-13 Asahi Kogaku Kogyo Kabushiki Kaisha Chromatic aberration correcting element and its application

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040264349A1 (en) * 2003-06-09 2004-12-30 Konica Minolta Opto, Inc. Optical system for optical pickup apparatus, optical pickup apparatus, optical information recording and/or reproducing apparatus and aberration-correcting element for optical pickup apparatus
US7515523B2 (en) 2003-06-09 2009-04-07 Konica Minolta Opto, Inc. Optical system for optical pickup apparatus, optical pickup apparatus, optical information recording and/or reproducing apparatus and aberration-correcting element for optical pickup apparatus
US20080106806A1 (en) * 2004-09-07 2008-05-08 Koninklijke Philips Electronics, N.V. Optical Device with Fresnel Structure
US20080273522A1 (en) * 2007-05-01 2008-11-06 Tao Luo Generation and detection of synchronization signal in a wireless communication system
US8649401B2 (en) 2007-05-01 2014-02-11 Qualcomm Incorporated Generation and detection of synchronization signal in a wireless communication system
US20090109827A1 (en) * 2007-10-24 2009-04-30 Hoya Corporation Coupling lens and optical information recording/reproducing device having the same
US8004955B2 (en) 2007-10-24 2011-08-23 Hoya Corporation Coupling lens and optical information recording/reproducing device having the same

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US20050226121A1 (en) 2005-10-13
JP2003114382A (ja) 2003-04-18
US7116495B2 (en) 2006-10-03

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