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`
`US006552990B1
`
`(12) United States Patent
`Kajiyama et al.
`
`(10) Patent No.: US 6,552,990 B1
`(45) Date of Patent: Apr. 22, 2003
`
`(54) OPTICAL HEAD FOR TWO DIFFERENT
`DISK THICKNESSES WITH A LIGHT BEAM
`DIAMETER CONTROL DEVICE
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`
`0 610 055 A2 8/1994
`12/1996
`0 747 893 A2
`
`(75) Inventors:
`
`Seiji Kajiyama, Ibi-gun (JP); Yoichi
`Tsuchlya, Hashima (JP); Masato
`Yamada, Inuyama OP); Yasuyuki
`Kanou, Hashima (JP); Shuichi Ichiura,
`Hashima (JP)
`
`(73)
`
`Assignee: Sanyo Electric Co., Ltd., Mofiguchi
`(Je)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21)
`
`Appl. No.:
`
`09/180,301
`
`(22)
`
`PCT Filed:
`
`Sep. 29, 1997
`
`(86)
`
`PCT No.:
`
`PCT/JP97/03482
`
`§ 371 (c)(1),
`(2), (4) Date: Nov. 5, 1998
`
`(87) PCT Pub. No.: WO98/19303
`
`PCT Pub. Date: May 7, 1998
`
`(30) Foreign Application Priority Data
`
`Oct. 31, 1996 (JP) ............................................. 8-290721
`
`Int. CI.7 .................................................. GlIB 7/00
`(51)
`(52) U.S. CI ................................ 369/112.06; 369/44.14;
`369/94; 369/44.37
`(58) Field of Search ........................... 369/44.23, 44.37,
`369/112, 118, 103, 109, 94, 44.14, 53.2,
`112.06, 112.01, 44.15, 44.24, 44.16, 112.08,
`112.24
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,343,332 A 8/1994 Oono et al .................. 359/837
`5,638~353 A * 6/1997 Takahashi ................... 369/112
`
`(List continued on next page.)
`
`OTHER PUBLICATIONS
`
`Supplementary European Search Report dated Apr. 17,
`2001.
`Office Action of corresponding Japanese Patent Application
`with English translation.
`
`Primary Examiner--William Korzuch
`Assistant Examiner---KJm-Kwok Chu
`(74) Attorney, Agent, or Firm---Armstrong, Westerman &
`Hattori, LLP
`
`(57)
`
`ABSTRACT
`
`An optical pickup device which includes a semiconductor
`laser selectively generating a laser beam with a wavelength
`of 635 nm, a laser beam with a wavelength of 780 nm, and
`an optical device having a central region in which a holo-
`gram is formed and a peripheral region in which a diffraction
`grating is formed. In particular, the optical device is
`arranged immediately below an objective lens, and the
`central region allows transmission of the laser beam with the
`wavelength of 635 nm without any diffraction but increases
`the diameter of the teaser beam to the wavelength of 780 nm
`by diffraction. On the other hand, peripheral region allows
`transmission of the laser beam with the wavelength of 635
`nm without any diffraction, but substantially shields the laser
`beam with the wavelength of 780 nm by diffraction. Thus,
`each laser beam with the wavelength 635 nm is transmitted
`through objective lens and focused on a signal recording
`surface of a DVD. The periphery of the laser beam with the
`wavelength of 780 nm is significantly difl~racted by periph-
`eral region of optical device and only the central portion of
`the laser beam enters objective lens while increasing its
`diameter. Thus, the laser beam with the wavelength of 780
`nm is focused on a signal recording surface of a CD-R or a
`CD-ROM. Therefore, the optical pickup device is capable of
`compatibly reproducing the DVD, CD-R and CD-ROM.
`
`(List continued on next page.)
`
`1 Claim, 36 Drawing Sheets
`
`? ?
`
`7_.?/
`
`/I I\ I\
`
`4
`
`lb-i ~L-~ i- la
`
`Lk
`
`LG Electronics, Inc. et al.
`EXHIBIT 1020
`IPR Petition for
`U.S. Patent No. RE43,106
`
`

`
`US 6,552,990 B1
`Page 2
`
`U.S. PATENT
`
`DOCUMENTS
`
`6,049,518 A * 4/2000 Tsuehiya et al ............. 369/118
`
`5,665,957 A * 9/1997
`5,696,750 A
`* 12/1997
`5,703,856 A
`12/1997
`* 1/1998
`5,708,641 A
`5,734,637 A
`* 3/1998
`* 5/1998
`5,748,603 A
`* 7/1998
`5,777,973 A
`* 7/1999
`5,923,636 A
`* 7/1999
`5,930,214 A
`* 7/1999
`5,930,219 A
`* 8/1999
`5,940,227 A
`* 8/1999
`5,940,360 A
`
`Lee et al .................... 369/118
`Katayama ................... 369/112
`Hayashi et al. ............ 369/53.2
`Choi et al. .................. 369/112
`Ootaki et al ................ 369/112
`Kim et al ................... 369/112
`Yoo et al .................... 369/109
`Haruguchi et al .......... 369/112
`Kasahara et al ....... 369/112.24
`Kim ........................... 369/109
`Haruguchi et al ....... 369/44.15
`Choi .......................... 369/112
`
`FOREIGN PATENT DOCUMENTS
`
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`
`63184935 A
`02079483 A
`5-303766
`7-98431
`8-55363
`8-321065
`9-54973
`09306018 A
`
`7/1988
`3/1990
`11/1993
`4/1995
`2/1996
`12/1.996
`2/1997
`11/1997
`
`* cited by examiner
`
`

`
`U.S. Patent Apr. 22, 2003 Sheet 1 of 36
`
`US 6,552,990 B1
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`U.S. Patent
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`Apr. 22, 2003 Sheet 2 of 36
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`US 6,552,990 B1
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`FIG. 2
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`U.S. Patent
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`Apr. 22, 2003 Sheet 3 of 36
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`Apr. 22, 2003 Sheet 4 of 36
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`US 6,552,990 B1
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`U.S. Patent
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`Apr. 22, 2003 Sheet 5 of 36
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`US 6,552,990 B1
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`U.S. Patent Apr. 22, 2003 Sheet 7 of 36
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`US 6,552,990 B1
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`FIG. 8
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`U.S. Patent
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`Apr. 22, 2003 Sheet 8 of 36
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`US 6,552,990 B1
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`FIG. 9
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`U.S. Patent Apr. 22, 2003 Sheet 9 of 36
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`U.S. Patent Apr. 22, 2003 Sheet 10 of 36
`
`US 6,552,990 B1
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`FIG. 11
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`U.S. Patent Apr. 22, 2003 Sheet 11 of 36
`
`US 6,552,990 B1
`
`FIG. 13
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`U.S. Patent Apr. 22, 2003 Sheet 12 of 36
`
`US 6,552,990 B1
`
`FIG. 15
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`U.S. Patent Apr. 22, 2003 Sheet 13 of 36
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`US 6,552,990 B1
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`U.S. Patent Apr. 22, 2003 Sheet 14 of 36
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`U.S. Patent Apr. 22, 2003 Sheet 15 of 36
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`U.S. Patent Apr. 22, 2003 Sheet 16 of 36
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`Apr. 22, 2003 Sheet 17 of 36
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`U.S. Patent Apr. 22, 2003 Sheet 18 of 36
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`US 6,552,990 B1
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`FIG. 23
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`Apr. 22, 2003 Sheet 19 of 36
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`US 6,552,990 B1
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`FIG. 25
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`Apr. 22, 2003
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`Sheet 23 of 36
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`US 6,552,990 B1
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`U.S. Patent Apr. 22, 2003 Sheet 25 of 36
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`U.S. Patent Apr. 22, 2003
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`Sheet 26 of 36
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`US 6,552,990 B1
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`FIG. 36
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`U.S. Patent Apr. 22, 2003 Sheet 28 of 36
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`US 6,552,990 B1
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`FIG. 40A
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`U.S. Patent
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`Apr. 22, 2003 Sheet 29 of 36
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`FIG. 42
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`U.S. Patent Apr. 22, 2003 Sheet 30 of 36
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`U.S. Patent Apr. 22, 2003
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`Sheet 31 of 36
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`US 6,552,990 B1
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`FIG. 45
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`U.S. Patent Apr. 22, 2003 Sheet 32 of 36
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`US 6,552,990 B1
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`FIG. 48
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`U.S. Patent Apr. 22, 2003 Sheet 33 of 36
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`US 6,552,990 B1
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`U.S. Patent
`
`Apr. 22, 2003 Sheet 34 of 36
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`US 6,552,990 B1
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`FIG. 50
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`U.S. Patent Apr. 22, 2003 Sheet 35 of 36
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`US 6,552,990 B1
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`FIG. 51A
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`U.S. Patent Apr. 22, 2003 Sheet 36 of 36
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`US 6,552,990 B1
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`FIG. 52A
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`
`!
`id ib le
`
`\
`1 43
`
`

`
`US 6,552,990 B1
`1 2
`substrates of different thicknesses, it cannot reproduce the
`OPTICAL HEAD FOR TWO DIFFERENT
`CD-R as a laser beam with a wavelength of 635 nm is
`DISK THICKNESSES WITH A LIGHT BEAM
`DIAMETER CONTROL DEVICE
`employed. The reason is as follows.
`
`TECHNICAL FIELD
`
`The present invention relates to optical pickup devices
`and, more specifically, to an optical pickup device perform-
`ing recording and/or reproducing for a digital video disk (a
`DVD) and a compact disk (a CD).
`
`TECHNICAL BACKGROUND
`
`An optical disk with a thickness of about 1.2 mm, such as
`a CD-ROM (Compact Disk-Read Only Memory), has been
`provided for reading information using a semiconductor
`laser. In this type of optical disk, by performing focusing
`servo control and tracking servo control for an objective lens
`for pickup, a pit string of a signal recording surface is
`irradiated with laser beam to reproduce a signal. Recently,
`such optical disks are increasingly becoming higher in
`density for recording an animation lasting for a long period
`of time.
`For example, a DVD standard has been proposed for
`recording information of 4.7 G bytes on one side of the
`optical disk having a diameter of 12 cm, which is the same
`as that of the CD-ROM. A transparent substrate of the DVD
`has a thickness of about 0.6 mm. A single DVD, which has
`two such transparent substrates applied to each other back to
`back, can record information of 9.4 G bytes. Further, as a
`write-once optical disk having the same diameter, thickness
`of substrate and recording density as those for the CD-ROM,
`there exists a CD-R (Compact Disk-Recordable).
`Since three different types of optical disks, including the
`DVD, the CD-ROM and the CD-R, would exist in the same
`apparatus in the near future, a device capable of compatibly
`reproducing these three different types of optical disks is
`required. The DVD and the CD-ROM or the CD-R,
`however, cannot be reproduced by a single optical pickup
`device because of the difference in thicknesses of the trans-
`parent substrates.
`Then, in Japanese Patent Laying-Open No. 5-303766, an
`apparatus has been proposed which allows reproduction of
`a high density optical disk having a thin transparent sub-
`strate with a thickness of 0.6 mm and a standard density
`optical disk having a standard transparent substrate with a
`thickness of 1.2 mm by using a single optical pickup device.
`In the apparatus, an objective lens with a numerical aperture
`of 0.6 is employed which has been designed to reproduce the
`high density optical disk by a laser beam with a short
`wavelength. When the standard density optical disk is to be
`reproduced, an aspherical optical device is inserted on the
`side of a light source of the objective lens which is provided
`with an aperture for shielding the periphery of laser beam to
`decrease an effective numerical aperture of the objective
`lens.
`Moreover, to change the effective numerical aperture of
`an objective lens selectively shielding the periphery of laser
`beam emitted from a semiconductor laser to collect laser
`beam, an apparatus has been disclosed in Japanese Patent
`Laying-Open No. 8-321065 which is provided with a liquid
`crystal selectively rotating the plane of polarization of laser
`beam and a polarizing plate allowing transmission of only
`laser beam which is polarized in a specific direction, and
`which can compatibly reproduce optical disks having sub-
`strates with different thicknesses. While the apparatus can
`compatibly reproduce the DVD and the CD-ROM having
`
`5 FIG. I is a diagram showing a relation between a pit depth
`and intensity of reflected light for every laser beam with a
`different wavelength. As shown in FIG. 1, when the laser
`beam with a wavelength of 635 nm is employed, the
`intensity of reflected light is the highest with the pit depth of
`10 about 105 nm. On the other hand, when laser beam with a
`
`wavelength of 780 nm is employed, the intensity of reflected
`light is the highest with the pit depth of about 125 nm. In the
`case of the CD-R, reflectance significantly changes with the
`
`15 wavelength of laser beam as organic dye is used for a
`recording film and a sufficient intensity of reflected light
`cannot be obtained using a single-wavelength laser with a
`wavelength of 635 nm. Thus, the CD-R cannot be suitably
`reproduced. Therefore, a two wavelengths to beam laser is
`2o required for the optical pickup device capable of compatibly
`
`reproducing the DVD and the CD-R or the CD-ROM. When
`laser beam with a wavelength of 430 nm would be employed
`due to the trend of shorter wavelength in the near future,
`such a two wavelengths to beam laser would be even more
`highly required.
`
`Therefore, it is an object of the present invention to
`provide an optical pickup device capable of performing
`recording and/or reproducing for optical disks having sub-
`strates with different thicknesses by using a laser beam with
`two different wavelengths.
`
`DISC’LOSURE OF THE INVENTION
`
`25
`
`3o
`
`35
`
`According to the present invention, an optical pickup
`device performing recording and/or reproducing for a first
`optical disk having a first transparent substrate and a second
`optical disk having a second transparent substrate with a
`4o thickness which is smaller than that of the first transparent
`
`substrate includes an objective lens, a laser beam generating
`means and an optical device. The objective lens is arranged
`opposite to the first or second optical disk. The laser beam
`
`45 generating means ,selectively generates a first laser beam
`with a first wavelength and a second laser beam with a
`second wavelength which is different from the first wave-
`length. The optical device includes: a central region
`arranged between the objective lens and the laser beam
`50 generating means, allowing transmission of the first laser
`beam without any change and increasing the diameter of the
`second laser beam by diffraction; and a peripheral region
`allowing transmission of the first laser beam without any
`change and substantially shielding the second laser beam by
`55 diffraction or absorption.
`
`Preferably, a hologram is formed in the central region of
`the optical device.
`
`6o
`
`More preferably, the hologram includes a plurality of
`annular convex portions each having four steps and coaxi-
`ally formed, where a height hl of each step is determined in
`accordance with the following expressions (1) to (5).
`
`

`
`US 6,552,990 B1
`
`4
`body is supported between the two guide shafts and the
`objective lens accommodates the optical device, the semi-
`conductor laser and the rising mirror. An optical axis of the
`laser beam entering the rising mirror is angled with respect
`5 to a perpendicular relative to the two guide shafts to form an
`acute angle.
`More preferably, a line passing emittance openings of the
`first and second laser chips is angled with respect to the main
`surface of the first or second optical disk to form an acute
`(3) 10 angle which is equal to the above mentioned acute angle.
`Preferably, the optical pickup device further includes a
`collimator lens arranged between the optical device and the
`semiconductor laser. The first laser chip is spaced by a first
`distance from the collimator lens such that the first laser
`a5 beam transmitted through the collimator lens is collimated.
`The second laser chip is spaced by a second distance, which
`is different from the first distance, from the collimator lens
`such that the second laser beam transmitted through the
`collimator lens is collimated.
`2o Preferably, the semiconductor laser further includes an
`
`C4)
`
`(5)
`
`optical waveguide. The optical waveguide includes a first
`incident opening facing the emittance opening of the first
`laser chip, a second incident opening facing the emittance
`opening of the second laser chip and an emittance opening
`25 communicating with the first and second incident openings.
`
`3
`-continued
`
`T
`if0~x_-<~
`
`¢(x) = 0
`
`T T
`if ~__.x__.~
`
`~b(x) = -~-(n-no)hi = ~bo(COnStant)
`
`4g
`T 3
`if ~ _-<x_~ gT (cid:128),(x) = -~(n-no)hl =2~0
`
`3 Or
`if ~’l"<-x~_T ck(x)=---~(n-no)hl=3q~o
`
`if m=0
`
`1
`= -~1(1 + COS¢(x) + COS2¢(x) + COS30(x))2 +
`
`(SINe(x) + SIN24,(x) + SIN3¢,(x))2}
`
`if m = -1
`
`1
`= ~f~2 {(1 - cos¢(x) - cos2(cid:128),(x) + cos3(cid:128)(x) -
`
`SINO(x) + SIN2C,(x) + SIN3¢(x))-~ +
`
`(1 + COS¢,(x) - COS2¢(x) - COS3¢(x) -
`
`SIN~b(x) - SIN2¢(x) + SIN3¢(x))z}
`
`if m=l
`
`I
`= ~-~nz ~(1 - cos¢,(x) - cos2¢,(x) + cos3¢(x) -
`
`SIN~b(x) + SIN24b(x) + SIN3~b(x))2+
`
`(1 + COS¢(x) - COS2(cid:128),(x) - COS3(cid:128)(x) +
`
`SINqS(x) + SIN2~b(x) + SIN3~b(x))2}
`
`Here, "qm is ruth order diffraction efficiency, d~(x) is a
`function of phase difference defined by expression (2), T is
`a period of the function of phase difference, A(x) is
`transmittance, L is the first, or second wavelength, n is
`refractive index of the annular convex portion, no is refrac-
`tive index of the periphery of the annular convex portion and
`q~o is a constant.
`Preferably, a refraction grating is formed in the peripheral
`region of the optical device.
`More preferably, the diffraction grating has varying grat-
`ing constants.
`Preferably, the laser beam generating means polarizes the
`first laser beam in a first direction and the second laser beam
`in a second direction which is different from the first
`direction, in the peripheral region of the optical device, a
`polarizing filter is formed having a polarizing direction
`which is perpendicular to the second direction.
`Preferably, a polarizing glass is formed in the peripheral
`region of the optical device which absorbs the laser beam
`with the second wavelength.
`Preferably, the laser beam generating means is a semi-
`conductor laser including a package and first and second
`laser chips. The first lair chip is arranged within the
`package and oscillates the first laser beam. The second laser
`beam is arranged within the package and oscillates the
`second laser beam.
`More preferably, the optical pickup device moves along
`two parallel guide shafts provided in a radial direction of the
`first or second optical disk, and includes a rising mirror and
`a body. The rising mirror is arranged immediately below the
`objective lens and the optical device, and reflects the first or
`second laser beam directed from the semiconductor laser in
`a direction which is parallel to the main surface of the first
`or second optical disk in a direction which is perpendicular
`to the main surface of the first or second optical disk. The
`
`35
`
`Preferably, the first and second lair chips are arranged
`such that one sides thereof are adjacent to each other. The
`distances between the emittance openings of the first and
`second laser chips and the one sides are respectively shorter
`30 than the distances between the emittance openings and the
`other sides opposite to the one sides.
`Preferably, the semiconductor laser further includes a
`photodetector arranged on the side opposite to the side of
`emittance of the first and second laser chips for monitoring
`both the first and second laser beams leaked from the first
`and second laser chips.
`Preferably, the semiconductor laser further includes first
`to fourth terminals. The first terminal is connected to one
`electrodes of the first and second laser chips and the pho-
`todetector. The second terminal is connected to the other
`terminal of the second laser chip. The third terminal is
`connected to the other electrode of the second laser chip. The
`fourth terminal is connected to the other electrode of the
`
`4o
`
`45 photodetector.
`Preferably, the first wavelength is between 620 nm and
`
`tOOl./ LILLI ~tllH tll~ ;~G~t, JLIIJ W~.V~;l~ll~ttl 1~ O~LW~IJ ILl.) lllll an
`795 rim.
`Preferably, the objective lens is adapted to the first optical
`5o disk and has a numerical aperture of between 0.55 and 0.65.
`Preferably, the objective lens has an effective numerical
`aperture of between 0.40 and 0.50 upon incidence of the
`second laser beam.
`Thus, in recording and/or reproducing of the first optical
`55 disk, the first laser beam is transmitted through the optical
`device without any change and focused on a signal recording
`surface of the first optical disk by the objective lens. On the
`other hand, in recording and/or reproducing of the second
`optical disk, the periphery of the second laser beam is
`60 substantially shielded by the peripheral region of the optical
`device and the diameter of the central portion of the second
`laser beam is increased by the central region of the optical
`device, so that the second laser beam is focused on the signal
`recording surface of the second optical disk by the objective
`65 lens. Thus, the optical pickup device is capable of perform-
`ing recording and/or reproducing for the first and second
`optical disks having substrates with different thicknesses.
`
`

`
`5
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`US 6,552,990 B1
`
`FIG. I is a diagram showing a relation between a pit depth
`of an optical disk and intensity of light reflected therefrom
`for every laser beam with a different wavelength.
`FIG. 2 is a diagram showing a structure of an optical
`pickup device in accordance with an embodiment of the
`present invention.
`FIG. 3 is a block diagram showing an overall arrangement
`of an optical disk reproducing apparatus including the 10
`optical pickup device shown in FIG. 1.
`FIG. 4 is a top view showing a structure of a semicon-
`ductor laser shown in FIG. 2.
`FIG. 5 is a top view of an optical device shown in FIG.
`2. is
`FIG. 6 is a cross sectional view of the optical device
`shown in FIG. 5.
`FIG. 7 is a diagram showing an optical path when a laser
`beam with a wavelength of 635 nm enters the optical device
`shown in FIGS. 5 and 6.
`FIGS. 8 to 12 are diagrams showing optical paths when a
`laser beam with a wavelength of 780 nm enters the optical
`device shown in FIGS. 5 and 6.
`FIG. 13 is a cross sectional view showing in enlargement 25
`a central region of the optical device shown in FIG. 6.
`FIG. 14 is a diagram showing a function of phase differ-
`ence used for determining a height of each step of annular
`convex portions in a hologram shown in FIG. 13.
`FIG. 15 is a diagram showing a relation between a height
`of each step of annular convex portions in the hologram and
`Oth and _+ first order diffraction efficiencies for the laser
`beam with the wavelength of 635 nm.
`FIG. 16 is a diagram showing a relation between a height
`of each step of annular convex portions in the hologram and
`0th and -+ first order diffraction efficiencies for the laser
`beam with the wavelength of 780 nm.
`FIG. 17 is a diagram collectively showing the diffraction
`efficiencies shown in FIGS. 15 and 16 for determining the
`height of each step of annular convex portions.
`FIG. 18 is a diagram showing an optical path of the laser
`beam with the wavelength of 635 nm in reproducing a DVD
`by the optical pickup device shown in FIG. 2.
`FIG. 19 is a diagram showing an optical path of the laser
`beam with the wavelength of 780 nm in reproducing a CD-R
`or a CD-ROM by the optical pickup device shown in FIG.
`2.
`
`5
`
`20
`
`6
`FIG. 38 is a diagram showing an optical system of the
`optical pickup device according to an embodiment of the
`present invention.
`
`FIG. 39 is a diagram showing a relation between a focal
`length and a wavelength of a collimator lens shown in FIG.
`38.
`
`FIG. 40A is a diagram showing an optical path when the
`laser beam with the wavelength of 635 nm enters the
`collimator lens, and FIG. 40B is a diagram showing an
`optical path when the laser beam with the wavelength of 780
`nm enters the collimator lens.
`
`FIG. 41A is a diagram showing a modification of the
`semiconductor laser with an optical path when the laser
`beam with the wavelength of 635 nm enters the collimator
`lens, and FIG. 41B is a diagram showing an optical path
`when the laser beam with the wavelength of 780 nm enters
`the collimator lens from the semiconductor laser shown in
`FIG. 41A.
`
`FIG. 42 is a diagram showing a modification of the
`semiconductor laser with an optical system of the optical
`pickup device.
`
`FIG. 43 is a diagram showing a structure of the semicon-
`ductor laser shown in FIG. 42.
`
`FIG. 44A is a side view showing a modification of the
`semiconductor laser, and FIG. 44B is a top view of the
`semiconductor laser shown in FIG. 44A.
`
`FIG. 45 is a diagram showing an arrangement of two laser
`3o chips in the semiconductor laser.
`
`FIG. 46 is a diagram showing a modification of the two
`laser chips in the semiconductor laser.
`
`FIG. 47 is a diagram showing another modification of the
`
`35 two laser chips in the semiconductor laser.
`FIG. 48 is a partially cutaway perspective view showing
`still another modification of the semiconductor laser.
`
`FIG. 49A is a circuit diagram of the semiconductor laser
`shown in FIG. 48, and FIGS. 49B to 49D are another circuit
`4o diagrams.
`
`FIG. 50 is a diagram showing the optical system of the
`optical pickup device in accordance with an embodiment of
`the present invention.
`
`FIG. 51A is a top view of the optical pickup device, and
`FIG. 51B is a cross sectional view showing the optical
`pickup device in FIG. 51A.
`
`45
`
`FIG. 20 is a diagram showing one modification of the
`optical device shown in FIG. 6.
`FIGS. 21 to 28 are cross ,sectional views showing another
`modifications of the optical device.
`FIG. 29 is a top view showing still another modification
`of the optical device.
`FIGS. 30 to 33 are diagrams showing optical paths when 55
`the laser beam with the wavelength of 780 nm enters the
`optical device shown in FIG. 29.
`FIG. 34 is a top view showing still another modification
`of the optical device.
`FIG. 35 is a diagram showing a polarizing direction of a 60
`polarizing filter formed in the peripheral region shown in
`FIG. 34.
`FIG. 36 is a top view showing still another modification
`of the optical device.
`FIG. 37 is a diagram partially showing in enlargement a
`polarizing glass in the peripheral region of the optical device
`shown in FIG. 36.
`
`FIG. 52A is a top view showing a modification of the
`optical pickup device, and FIG. 52B is a cross sectional view
`5o showing the optical pickup device in FIG. 52A.
`
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`
`The embodiments of the present invention will now be
`described in detail with reference to the drawings. It is noted
`that the same or corresponding portions in the drawings have
`the same reference numerals and the description thereof will
`not be repeated here.
`
`Standard and Reproducing Condition for Subject
`Optical Disk
`
`The following table shows a rated value and a reproduc-
`6s ing condition for a CD-ROM, a CD-R and a DVD, which are
`compatibly reproduced by an optical pickup device accord-
`ing to an embodiment of the pre~nt invention.
`
`

`
`US 6,552,990 B1
`
`TABLE
`
`’I~oe
`
`CD-ROM
`
`CD-R
`
`DVD
`
`Rated Value
`
`Substmte
`Thickness on
`Reading Side
`Minimum Pit
`Length
`Track Pitch
`
`Reflectance
`
`Reproducing
`Condition
`
`1.2 mm
`(1.1-1,3 ram)
`
`1.2 mm
`(1.1-1.3 ram)
`
`0.6 mm
`(0.55~0.65 mm)
`
`0.90 Itm
`0.90 ,urn
`(0.8-1.0 ,urn)
`(0.8-1.0 Inn)
`1.6/nn
`1.6/an
`(3..5-1.7 pm)
`(1.5-1.7/an)
`At least 60-70% At least 60-70%
`
`0.40 l#m
`(0.3--o5 ,~)
`0.74 ,urn
`(0.73--0.75/tin)
`At least 20~40%
`7O%
`
`Spot Diameter 1.5/.tin
`(1.4-,1.6 inn)
`0.45
`(0.40--0.50)
`780
`(765-795)
`
`Numerical
`aperture
`Wavelength
`
`1.5 ,urn
`(1.4,,-1.6 ,urn)
`0.45
`(0.40-0.50)
`780
`(765-795)
`
`0.9/tin
`(0.85-0.95 #m)
`0.60
`(0.55-0.65)
`635
`(620-680)
`
`As shown in the table, for the CD-ROM, a thickness of a
`substrate is 1.2 (with tolerance of z0.1)mm, a minimum pit
`length is 0.90 (with tolerance of ±0.1)jum, a track pitch is 1.6
`(with tolerance of ±0.1)/ma and a reflectance is at least 60%
`to 70% for a laser beam with a wavelength of 780 nm.
`Further, a spot diameter of the laser beam during reproduc-
`tion is 1.5 (with tolerance of __0.1)/xm, a numerical aperture
`of an objective lens is 0.45 (with tolerance of ±0.05) and a
`wavelength of the laser beam is 780 (with tolerance of
`±15)nm. The CD-R has the same thickness of substrate,
`minimum pit length, track pitch, reflectance, spot diameter
`during reproduction, numerical aperture of objective lens
`and wavelength of laser beam as those for the above
`mentioned CD-ROM.
`On the other hand, for the DVD, a thickness of substrate
`is 0.6 (with tolerance of ±0.05)mm, a minimum pit length is
`0.40 (with tolerance of __.0.1)knn, a track pitch is 0.74 (with
`tolerance of _0.0)/.tm and a reflectance is at least 70% (in the
`case of one layer DVD) or at least 20% to 40% (in the case
`of two layered DVD) fora laser beam with a wavelength of
`635 nm. Further, a spot diameter of the laser beam during
`reproduction is 0.9 (with tolerance of _+0.5)ban, a numerical
`aperture of an objective lens is 0.60 (with tolerance of ±0.05)
`and a wavelength of the laser beam is 635 (with tolerance of
`620 to 680)nm.
`
`Structure of Optical Pickup Device
`
`Referring to FIG. 2, an optical pickup device 10 according
`to an embodiment of the present invention includes: an
`objective lens 7 arranged opposite to an optical disk; a
`semiconductor laser 1 selectively generating laser beams
`with wavelengths of 635 (with tolerance of ±15)nm and 780
`(with tolerance of ±15)nm; an optical device 5 arranged
`immediately below objective lens 7; an actuator 6 holding
`both objective lens 7 and optical device 5; a mirror 4
`arranged immediately below objective lens 7 and optical
`device 5 for reflecting a laser beam directed from semicon-
`ductor laser 1 in a direction parallel to a main surface of the
`optical disk in a direction perpendicular to the main surface
`of the optical disk; a half