c12) United States Patent
`Akanuma et al.
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006343053Bl
`US 6,343,053 Bl
`Jan.29,2002
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) OBJECTIVE LENS DRIVING APPARATUS
`FOR DRIVING AN OBJECTIVE LENS OF AN
`OPTICAL DISK DRIVE
`
`(75)
`
`Inventors: Goichi Akanuma, Tokyo; Hiroshi
`Koide, Kanagawa, both of (JP)
`
`(73) Assignee: Ricoh Company, Ltd., Tokyo (JP)
`
`( * ) 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.: 09/382,585
`
`(22) Filed:
`
`Aug. 25, 1999
`
`(30)
`
`Foreign Application Priority Data
`
`(JP) ........................................... 10-243873
`Aug. 28, 1998
`(JP) ........................................... 10-317517
`Nov. 9, 1998
`(JP) ........................................... 10-364609
`Dec. 22, 1998
`May 21, 1999
`(JP) .. ... ... . .. ..... .. . ... ... .. ....... .. ....... 11-142300
`Int. Cl.7
`••...................•.•.•.•.•.••.•.•..••......... GUB 7/U
`(51)
`(52) U.S. Cl. ................................. 369/44.14; 369/44.11;
`359/814
`(58) Field of Search ........................... 369/44.11, 44.12,
`369/44.14, 44.15, 44.22, 44.28, 47.1, 53.1,
`112.D1; 59/814, 824
`
`(56)
`
`References Cited
`
`U.S. PAJENT DOCUMENTS
`5,388,086 A * 2/1995 Yamasaki et al. ........ 369/44.14
`
`5,566,149 A * 10/1996 Song ....................... 369/44.15
`
`FOREIGN PAJENT DOCUMENTS
`
`JP
`8-221776
`JP
`9-180207
`* cited by examiner
`
`8/1996
`7/1997
`
`Primary Examiner-Muhammad Edun
`(74) Attorney, Agent, or Firm--Dickstein Shapiro Morin &
`Oshinsky LLP
`
`(57)
`
`ABSTRACT
`
`An objective lens driving apparatus having a focusing coil
`and a tracking coil arranged in a parallel relationship with a
`thin, fiat shape so that both the focusing coil and the tracking
`coil can be moved by a single fiat magnet. An objective lens
`supporting member supports the objective lens, and is mov(cid:173)
`ably supported on a stationary member. A drive motor is
`provided at least one side of the objective lens supporting
`member. A yoke is fixed to the stationary member, and a
`drive magnet is mounted to the yoke. The drive magnet has
`a fiat surface parallel to both the focusing direction and the
`tracking direction, the fiat surface having four single-pole
`areas each of which is magnetized in a direction perpen(cid:173)
`dicular to the fiat surface. A drive coil assembly including
`the focusing coil and the tracking coil is mounted on the
`objective lens supporting member. The drive magnet assem(cid:173)
`bly has a fiat shape so that the drive coil assembly faces the
`fiat surface of the drive magnet in parallel relationship with
`a small air gap therebetween.
`
`15 Claims, 20 Drawing Sheets
`
`29
`
`21
`
`20
`16
`
`29
`
`30
`
`26
`
`15
`
`15
`
`LG Electronics, Inc. et al.
`EXHIBIT 1002
`IPR Petition for
`U.S. Patent No. 6,785,065
`
`

`
`U.S. Patent
`
`Jan.29,2002
`
`Sheet 1 of 20
`
`US 6,343,053 Bl
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`
`U.S. Patent
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`Jan. 29, 2002
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`Sheet 2 of 20
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`US 6,343,053 Bl
`
`FIG.2 PRIOR ART
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`6
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`FIG.3 PRIOR ART
`
`4
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`9b 6
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`

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`U.S. Patent
`
`Jan. 29, 2002
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`Sheet 3 of 20
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`US 6,343,053 Bl
`
`FIG.4 PRIOR ART
`
`CENTER OF
`AREA RECEIVING
`DRIVE FORCE
`(=CENTER AXIS
`OF MAGNET)
`
`I
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`
`U.S. Patent
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`Jan.29,2002
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`Sheet 4 of 20
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`US 6,343,053 Bl
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`FIG.5A
`29
`21
`
`25
`26
`
`FIG.5B
`
`20
`16
`
`28
`
`30
`
`25
`
`15
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`15
`
`FIG.6
`
`26
`
`~KING
`
`l FOCUSING
`
`

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`U.S. Patent
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`Jan. 29, 2002
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`Sheet 5 of 20
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`US 6,343,053 Bl
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`FIG.?A
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`FIG.?B
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`29
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`21
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`25
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`30
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`13
`
`15
`
`

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`U.S. Patent
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`Jan.29,2002
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`Sheet 6 of 20
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`US 6,343,053 Bl
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`FIG.8
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`26
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`32
`
`~KING
`
`b
`
`t FOCUSING
`
`

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`U.S. Patent
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`Jan. 29,2002
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`Sheet 7 of 20
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`US 6,343,053 Bl
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`FIG.9A
`
`FIG.9B
`
`13
`
`30
`
`@
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`15
`
`22
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`15
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`

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`U.S. Patent
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`Jan.29,2002
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`Sheet 8 of 20
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`US 6,343,053 Bl
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`FIG.1 OA
`42
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`FIG.1 08
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`38
`44
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`54
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`36
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`36
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`

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`U.S. Patent
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`Jan.29,2002
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`Sheet 9 of20
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`US 6,343,053 Bl
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`FIG.11
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`48
`
`TRACKING
`
`a
`1 FOCUSING
`
`FIG.12
`
`52
`
`52
`
`

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`U.S. Patent
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`Jan. 29, 2002
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`Sheet 10 of 20
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`US 6,343,053 Bl
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`FIG.13
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`52
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`52
`
`

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`U.S. Patent
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`Jan. 29, 2002
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`Sheet 11 of 20
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`US 6,343,053 Bl
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`FIG.14
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`56
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`46
`
`... ... ... .........
`
`52
`
`... ...
`................
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`52
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`

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`U.S. Patent
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`Jan. 29, 2002
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`Sheet 12 of 20
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`US 6,343,053 Bl
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`FIG.15A
`
`FIG.15B
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`37
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`37 54
`
`34
`
`36
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`

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`U.S. Patent
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`Jan. 29, 2002
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`Sheet 13 of 20
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`US 6,343,053 Bl
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`FIG.16
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`58
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`

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`U.S. Patent
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`Jan. 29,2002
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`Sheet 14 of 20
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`US 6,343,053 Bl
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`FIG.17A
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`48
`
`48
`
`

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`U.S. Patent
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`Jan. 29, 2002
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`Sheet 15 of 20
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`US 6,343,053 Bl
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`FIG.18A
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`FIG.18B
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`43
`
`37
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`35
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`54
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`36
`
`36
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`

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`U.S. Patent
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`Jan. 29, 2002
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`Sheet 16 of 20
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`US 6,343,053 Bl
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`FIG.19A
`
`FIG.19B
`
`30
`
`19
`
`15
`
`60
`
`@
`
`15
`
`FIG.19C
`61a 60a
`~+-+....,....::;.., c~71
`
`63
`60d
`eoc a
`61 60b
`61b
`
`

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`U.S. Patent
`
`Jan. 29,2002
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`Sheet 17 of 20
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`US 6,343,053 Bl
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`FIG.20
`
`71
`)
`60a
`~FOCUSING
`y
`
`60c
`
`70 \
`
`62b
`62
`
`a
`
`TRACKING
`
`61b
`
`63a
`
`63
`
`

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`U.S. Patent
`
`Jan. 29, 2002
`
`Sheet 18 of 20
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`US 6,343,053 Bl
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`FIG.21A
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`FIG.21 B
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`25
`
`15
`
`15
`
`

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`U.S. Patent
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`Jan. 29, 2002
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`Sheet 19 of 20
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`US 6,343,053 Bl
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`FIG.22
`
`70
`
`\
`
`62
`
`y
`
`83
`
`c 61b 61
`82a
`
`63
`
`82b
`
`82d
`
`

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`U.S. Patent
`
`Jan. 29,2002
`
`Sheet 20 of 20
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`US 6,343,053 Bl
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`FIG.23A
`
`FIG.23B
`
`24
`
`83
`82
`
`13
`
`_ _. 22
`
`82
`62
`60
`25
`16
`
`@
`
`30
`
`81
`
`63
`
`16
`
`

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`US 6,343,053 Bl
`
`1
`OBJECTIVE LENS DRIVING APPARATUS
`FOR DRIVING AN OBJECTIVE LENS OF AN
`OPTICAL DISK DRIVE
`
`15
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention generally relates to an objective
`lens driving apparatus of an optical disk drive and, more
`particularly, to an objective lens driving apparatus having an
`actuator for moving an objective lens in a focusing direction 10
`and a tracking direction.
`2. Description of the Related Art
`FIGS. 1A and 1B show a first example of a conventional
`objective lens driving apparatus. In the objective lens driv-
`ing apparatus shown in FIGS. 1A and 1B, an objective lens
`1 is supported by an objective lens supporting member 2 that
`is elastically supported by four wire springs 4 extending
`from a stationary member 3. A focusing coilS and a tracking
`coil 6, which are wound in directions perpendicular to each
`other, are provided around the objective lens supporting
`member 2. An end of each of the wire springs 4 is soldered
`to a base board 7 at a soldered portion Sa. The opposite end
`of each of the wire springs 4 is soldered to a respective one
`of the focusing coil S and the tracking coil 6 at a soldered
`portion Sb. Accordingly, the wire springs 4 serve as con(cid:173)
`ductive wires to provide an electrical connection to the
`focusing coilS and the tracking coil 6. Magnets 10 are fixed
`to yokes 9 so that the objective lens supporting member 2 is
`interposed between the magnets 10. A light beam having an
`optical axis indicated by a chain line 12 is deflected by a
`prism 11, and enters the objective lens 1.
`In the above-mentioned structure, the objective lens 1 is
`moved in a focusing direction indicated by an arrow Z and
`a tracking direction indicated by an arrow Y by moving the 35
`objective lens supporting member 2 by providing control
`currents to the focusing coil S and the tracking coil 6.
`A description will now be given, with reference to FIG. 2,
`of a second example of the conventional objective lens
`driving apparatus. FIG. 2 is a perspective view of the second 40
`example of the conventional objective lens driving appara(cid:173)
`tus. In FIG. 2, parts that are the same as the parts shown in
`FIGS. 1Aand 1B are given the same reference numerals, and
`descriptions thereof will be omitted.
`In the objective lens driving apparatus shown in FIG. 2, 45
`each of the two magnets 10 is fixed to a respective one of
`yokes 9a. The focusing coil S and the tracking coil 6 are
`situated around the objective lens supporting member 2. An
`additional yoke 9b is provided near a respective one of the
`yokes 9a so that the focusing coil S and the tracking coil 6 50
`are interposed between the yokes 9a and 9b. Accordingly, a
`closed magnetic circuit is formed by each of the magnets 10
`and a respective pair of the yokes 9a and 9b. Thus, similar
`to the first example, the objective lens 1 is movable in a
`focusing direction indicated by an arrow Z and a tracking 55
`direction indicated by an arrow Y by moving the objective
`lens supporting member 2 by providing control currents to
`the focusing coil S and the tracking coil 6.
`In the above-mentioned first and second examples of the
`conventional objective lens driving apparatus, the prism 11 60
`must be situated under the objective lens supporting member
`2 as shown in FIG. 1B since the focusing coil S and the
`tracking coil 6 are present. Thus, there is a problem in that
`a thickness of the entire apparatus is increased due to the
`arrangement of the prism 11.
`Additionally, Japanese Laid-Open Patent Application
`No.9-180207 discloses a third example of the conventional
`
`2
`objective lens driving apparatus. In this objective lens driv(cid:173)
`ing apparatus, a deflection mirror is provided inside the
`objective lens supporting member 2 so that the deflection
`mirror is movable together with the objective lens 1.
`5 Thereby, a light beam is prevented from being offset when
`the objective lens supporting member 2 is moved in the
`tracking direction.
`It is considered to adopt a structure shown in FIG. 3 in
`which structure a driving motor having a closed magnetic
`circuit similar to the above-mentioned second example is
`applied to the structure disclosed in Japanese Laid-Open
`Patent Application No.9-180207. However, in such a case,
`there is a problem in that the objective lens supporting
`member 2 is tilted due to a torque generated by an offset
`between a center of driving force exerted on the focusing
`coil S and the center of gravity of a movable part including
`the focusing coil S as shown in FIG. 4.
`Additionally, since the tracking force is generated by the
`tracking coil 6 in which a current flows in the focusing
`direction, there is a problem in that a sufficient drive force
`cannot be obtained.
`Further, the above-mentioned Japanese Laid-Open Patent
`Application No.9-180207 discloses another embodiment in
`which an actuator for tracking is formed by a magnetic
`circuit different from a magnetic circuit of an actuator for
`focusing. Such a structure has a problem in that an assem(cid:173)
`bling operation is complex and a manufacturing cost is
`increased.
`
`20
`
`25
`
`30
`
`65
`
`SUMMARY OF THE INVENTION
`
`It is a general object of the present invention to provide an
`improved and useful objective lens driving apparatus m
`which the above-mentioned problems are eliminated.
`A more specific object of the present invention is to
`provide an objective lens driving apparatus in which a
`focusing coil and a tracking coil can be arranged in a parallel
`relationship with a thin, fiat shape so that both the focusing
`coil and the tracking coil can be moved by a single fiat
`magnet.
`Another object of the present invention is to provide an
`objective lens driving apparatus in which a movable part
`including a focusing coil is prevented from being tilted.
`A further object of the present invention is to provide an
`objective lens driving apparatus in which drive forces gen(cid:173)
`erated by a focusing coil and a tracking coil are increased by
`forming a closed magnetic circuit.
`In order to achieve the above-mentioned objects, there is
`provided according to the present invention an objective lens
`driving apparatus for moving an objective lens in a focus(cid:173)
`sing direction and a tracking direction relative to an optical
`disk, the objective lens driving apparatus comprising:
`an objective lens supporting member supporting the
`objective lens, the objective lens supporting member being
`movably supported on a stationary member; and
`a drive motor provided at least one side of the objective
`lens supporting member, the drive motor comprising:
`a yoke fixed to the stationary member;
`a drive magnet mounted to the yoke and having a fiat
`surface parallel to both the focusing direction and the
`tracking direction, the fiat surface having four single-pole
`areas each of which is magnetized in a direction perpen(cid:173)
`dicular to the fiat surface; and
`a drive coil assembly mounted on the objective lens
`supporting member and including a focusing coil and a
`tracking coil, the drive coil assembly having a fiat shape so
`
`

`
`US 6,343,053 Bl
`
`3
`that the drive coil assembly faces the fiat surface of the drive
`magnet in parallel relationship with a small air gap therebe(cid:173)
`tween.
`According to the above-mentioned invention, the drive
`motor is formed by the combination of the drive magnet
`having a surface divided into four magnetization areas and
`the drive coil assembly having a fiat shape. The drive magnet
`generates magnetic fields in different directions in the vicin-
`ity of the fiat surface. Accordingly, both the focusing coil
`and the tracking coil can be positioned in the vicinity of the
`drive magnet and parallel to the fiat surface so that both the
`focusing coil and the tracking coil generate a drive force by
`being subjected to the magnetic fields in the vicinity of the
`drive magnet. Thus, the drive motor can be formed in a fiat
`shape. Since the focusing coil does not surround the objec(cid:173)
`tive lens supporting member, a light beam can be introduced
`into an optical system provided within the objective lens
`supporting member in the tracking direction. Additionally,
`the entire focusing coil can be subjected to the magnetic field
`generated by the drive magnet, a focusing force is generated
`uniformly in the entire focusing coil. Thereby, it can be
`assumed that the focusing force is exerted on the center of
`gravity of the focusing coil. Thus, the objective lens sup(cid:173)
`porting member to which the focusing coil is mounted is
`prevented from being tilted due to an offset between the
`center of gravity of the focusing coil and the center of the
`area which receives the focusing force.
`In the objective lens driving apparatus according to the
`present invention, the drive motor may further comprise an
`additional yoke fixed to the stationary member and an
`additional drive magnet mounted to the additional yoke, the
`additional drive magnet having the same magnetization
`structure as the drive magnet, the additional drive magnet
`being positioned adjacent to the drive magnet so that the
`drive coil assembly is interposed therebetween and a closed
`magnetic circuit is formed by a combination of the yoke, the
`drive magnet, the additional drive magnet and the additional
`yoke.
`According to this invention, the drive coil assembly is
`interposed between the two drive magnets that are mounted
`on the respective yokes. That is, the drive coil assembly is
`positioned in a closed magnetic circuit. In such a closed
`magnetic circuit, a high, uniform magnetic flux density can
`be obtained. Thus, the drive motor can effectively generate
`both a focusing force and a tracking force.
`According to one embodiment of the present invention,
`the single-pole areas of the drive magnet are defined by a
`first line extending in a focusing direction and a second line
`perpendicular to the first line and extending in the tracking
`direction, each of the single-pole areas is magnetized in a
`direction opposite to a direction of magnetization of adjacent
`ones of the single-pole magnets;
`the focusing coil including a first focusing coil and a
`second focusing coil, the first focusing coil being positioned
`on one side of the first line and extending over the second
`line, the second focusing coil being positioned on the other
`side of the first line and extending over the second line; and
`the tracking coil including a first tracking coil and a
`second tracking coil, the first tracking coil being positioned
`on one side of the second line and extending over the first
`line, the second tracking coil being positioned on the other
`side of the second line and extending over the first line.
`Additionally, according to another embodiment of the
`present invention, the single-pole areas of the drive magnet
`includes a first single-pole area, a second single-pole area, a
`third single pole area and a fourth single pole area defined
`
`10
`
`4
`by a first line extending in the focusing direction and a
`second line extending in the tracking direction, the first and
`second single-pole areas being positioned on one side of the
`first line and the third and fourth single-pole areas being
`5 positioned on the other side of the first line, the first and
`fourth single-pole areas being positioned on one side of the
`second line and the second and third single-pole areas being
`positioned on the other side of the second line, each of the
`single-pole areas being magnetized in a direction opposite to
`a direction of magnetization of adjacent ones of the single(cid:173)
`pole areas;
`the focusing coil includes a first focusing coil and a
`second focusing coil, the first focusing coil being positioned
`on one side of the first line and extending over the second
`15 line so that a half portion overlaps the first single-pole area
`and the other half portion overlaps the second single-pole
`area, the second focusing coil being positioned on the other
`side of the first line and extending over the second line so
`that a half portion overlaps the third single-pole area and the
`20 other half portion overlaps the fourth single-pole area; and
`the tracking coil includes a first tracking coil, a second
`tracking coil and four third tracking coils, the first tracking
`coil being positioned on one side of the second line and
`extending over the first line so that a half portion overlaps
`25 the first single-pole area and the other half portion overlaps
`the fourth single-pole area, the second tracking coil being
`positioned on the other side of the second line and extending
`over the first line so that a half portion overlaps the second
`single-pole area and the other half portion overlaps the third
`30 single-pole area, a first one of the third tracking coils being
`positioned on one side of the first tracking coil so that at
`most a half portion of the first one of the third tracking coils
`overlaps the first single-pole area, a fourth one of the third
`tracking coils being positioned on the other side of the first
`35 tracking coil so that at most a half portion of the second one
`of the third tracking coils overlaps the fourth single-pole
`area, a second one of the third tracking coils being posi(cid:173)
`tioned on one side of the second tracking coil so that at most
`a half portion of the second one of the third tracking coils
`40 overlaps the second single-pole area, a third one of the third
`tracking coils being positioned on the other side of the
`second tracking coil so that at most a half portion of the third
`one of the third tracking coils overlaps the third single-pole
`area.
`Further, according to one embodiment of the present
`invention, the single-pole areas of the drive magnet includes
`a first single-pole area, a second single-pole area, a third
`single pole area and a fourth single pole area that are defined
`by a first line extending in the focusing direction, a second
`50 line parallel to the first line and a third line extending in the
`tracking direction between the first line and the second line,
`the first single-pole area being positioned on one side of the
`third line and between the first line and the second line, the
`second single-pole area being positioned on the other side of
`55 the third line between the first line and the second line, the
`third single-pole area being positioned on a side of the first
`line which side is opposite to a side on which the first and
`second single-pole areas are positioned, the fourth single(cid:173)
`pole area being positioned on a side of the second line which
`60 side is opposite to a side on which the first and second
`single-pole areas are positioned, the first single-pole area
`being magnetized in a direction opposite to a direction of
`magnetization of the second single-pole area;
`the focusing coil is positioned between the first line and
`65 the second line and extends over the third line so that a half
`portion overlaps the first single-pole area and the other half
`portion overlaps the second single-pole area; and
`
`45
`
`

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`US 6,343,053 Bl
`
`5
`the tracking coil includes a first tracking coil and a second
`tracking coil, the first tracking coil being positioned on one
`side of the focusing coil so that at most a half portion
`overlaps the third single-pole area, the second tracking coil
`being positioned on the other side of the focusing coil so that 5
`at most a half portion overlaps the fourth single-pole area.
`Other objects, features and advantages of the present
`invention will become more apparent from the following
`detailed description when read in conjunction with the
`accompanied drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`15
`
`6
`invention; FIG. lSB is a side view of the objective lens
`driving apparatus shown in FIG. lSA;
`FIG. 16 is an illustration for explaining a relationship
`between a magnet, a focusing coil and a tracking coil
`provided in the objective lens driving apparatus shown in
`FIGS. lSA and lSB;
`FIG. 17Ais a variation of a drive coil assembly provided
`in the objective lens driving apparatus shown in FIGS. lSA
`and lSB; FIG. 17B is another variation of the objective lens
`10 driving apparatus shown in FIGS. lSA and lSB;
`FIG. 18A is a plan view of the objective lens driving
`apparatus according to a sixth embodiment of the present
`invention; FIG. 18B is a side view of the objective lens
`driving apparatus shown in FIG. 18A;
`FIG. 19A is a plan view of an objective lens driving
`apparatus according to a seventh embodiment of the present
`invention; FIG. 19B is a side view of the objective lens
`driving apparatus shown in FIG. 19A; FIG. 19C is a front
`view of a motor part of the objective lens driving apparatus
`shown in FIGS. 19A and 19B;
`FIG. 20 is an illustration for explaining a relationship
`between a magnet, a focusing coil and a tracking coil
`provided in the objective lens driving apparatus shown in
`25 FIGS. 19A and 19B;
`FIG. 21A is a plan view of an objective lens driving
`apparatus according to an eighth embodiment of the present
`invention; FIG. 21B is a side view of the objective lens
`driving apparatus shown in FIG. 21A;
`FIG. 22 is an illustration for explaining a relationship
`between a magnet, a focusing coil and a tracking coil
`provided in the objective lens driving apparatus shown in
`FIGS. 21A and 21B; and
`FIG. 23A is a plan view of an objective lens driving
`35 apparatus according to a ninth embodiment of the present
`invention; FIG. 23B is a side view of the objective lens
`driving apparatus shown in FIG. 23A.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`A description will now be given, with reference to FIGS.
`SA, SB and 6, of an objective lens driving apparatus accord(cid:173)
`ing to a first embodiment of the present invention. FIG. SA
`is a plan view of the objective lens driving apparatus
`45 according to the first embodiment of the present invention.
`FIG. SB is a side view of the objective lens driving apparatus
`shown in FIG. SA FIG. 6 is an illustration for explaining a
`relationship between a magnet, a focusing coil and a track(cid:173)
`ing coil provided in the objective lens driving apparatus
`50 shown in FIGS. SA and SB.
`In the objective lens driving apparatus according to the
`first embodiment of the present invention, an objective lens
`13 is supported by an objective lens supporting member 14
`that is elastically supported by four wire springs 16 extend-
`55 ing from a stem lS. The objective lens supporting member
`14 has a generally box-like shape so that an inner apace 17
`is formed. The objective lens 13 is mounted on a bottom wall
`18 of the objective lens supporting member 14. An opening
`19 is formed on the bottom wall 18 so that a light beam
`60 enters the objective lens 13 by passing through the opening
`19. The objective lens supporting member 14 has side walls
`20 on opposite sides in an extending direction of the wire
`springs 16. Each of the side walls 20 serves as a base boards
`to which a drive coil assembly 21 is mounted. A structure of
`65 the drive coil assembly 21 will be described later.
`A notch (not shown in the figure) is formed on one of the
`side walls of the objective lens supporting member 14 so as
`
`20
`
`30
`
`FIG. lAis a plan view of a first example of a conventional
`objective lens driving apparatus; FIG. lB is a side view of
`the first example of the conventional objective lens driving
`apparatus;
`FIG. 2 is a perspective view of a second example of the
`conventional objective lens driving apparatus;
`FIG. 3 is an illustration of an objective lens driving
`apparatus provided with a deflection mirror inside a movable
`part;
`FIG. 4 is an illustration showing a positional relationship
`between a drive magnet and a focusing coil in the conven(cid:173)
`tional objective lens driving apparatus;
`FIG. SA is a plan view of an objective lens driving
`apparatus according to a first embodiment of the present
`invention; FIG. SB is a side view of the objective lens
`driving apparatus shown in FIG. SA;
`FIG. 6 is an illustration for explaining a relationship
`between a magnet, a focusing coil and a tracking coil
`provided in the objective lens driving apparatus shown in
`FIGS. SA and SB;
`FIG. 7A is a plan view of an objective lens driving
`apparatus according to a second embodiment of the present
`invention; FIG. 7B is a side view of the objective lens
`driving apparatus shown in FIG. 7A;
`FIG. 8 is an illustration for explaining a relationship
`between a magnet, a focusing coil and a tracking coil 40
`provided in the objective lens driving apparatus shown in
`FIGS. 7A and 7B;
`FIG. 9A is a plan view of an objective lens driving
`apparatus according to a third embodiment of the present
`invention; FIG. 9B is a side view of the objective lens
`driving apparatus shown in FIG. 9A;
`FIG. lOA is a plan view of an objective lens driving
`apparatus according to a fourth embodiment of the present
`invention. FIG. lOB is a side view of the objective lens
`driving apparatus shown in FIG. lOA;
`FIG. 11 is an illustration for explaining a relationship
`between a magnet, a focusing coil and a tracking coil
`provided in the objective lens driving apparatus shown in
`FIGS. lOA and lOB;
`FIG. 12 is an illustration for explaining a relationship
`between a magnet, a focusing coil and a tracking coil
`provided in the objective lens driving apparatus shown in
`FIGS. lOA and lOB;
`FIG. 13 is a perspective view of a variation of a drive
`motor provided in the objective lens driving apparatus
`shown in FIGS. lOA and lOB;
`FIG. 14 is a perspective view of another variation of the
`drive motor provided in the objective lens driving apparatus
`shown in FIGS. lOA and lOB;
`FIG. lSA is a plan view of an objective lens driving
`apparatus according to a fifth embodiment of the present
`
`

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`US 6,343,053 Bl
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`10
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`7
`to pass a light beam having an optical axis 22. A movable
`deflection mirror 23 is provided within the inner space 17 so
`that the deflection mirror 23 deflects the light beam toward
`a deflection prism 24 which is also provided within the inner
`space 17. The light beam is deflected by the deflection prism 5
`24 and incident on the objective lens 13. It should be noted
`that one of the wire springs 16, which one is located on the
`side of the side wall provided with the notch and remote
`from the objective lens 13, is offset in an extending direction
`of the spring wires 16 so that the one of the wire springs 16
`does not interfere with the light beam passing through the
`notch.
`A yoke (magnetic material) 25 and a drive magnet 26 are
`provided on each side of the side walls 20 so that the drive
`magnet 26 faces the drive coil assembly 21 with a small air 15
`gap therebetween. The drive magnet 26 is magnetized so
`that a surface of the drive magnet 26 is divided into four
`single-pole areas by magnetization boundary lines "a" and
`"b" as shown in FIG. 6. Directions of magnetization of the
`drive magnet 26 are perpendicular to each of a focusing
`direction and a tracking direction so that the direction of
`magnetization of each of the four single-pole areas 1s
`opposite to adjacent ones of the single-pole areas.
`As mentioned above, the drive coil assembly 21 is
`mounted to the objective lens supporting member 14. The 25
`drive coil assembly 21 comprises two focussing coils 27 and
`two tracking coils 28. One of the focusing coils 27 is
`provided on one side of the magnetization boundary line "a"
`and the other is provided on the opposite side of the
`magnetization boundary line "a". Accordingly, each of the 30
`focusing coils 27 extends over the magnetization boundary
`line "b". On the other hand, one of the tracking coils 28 is
`provided on one side of the magnetization boundary line "b"
`and the other is provided on the opposite side of the
`magnetization boundary line "b". Accordingly, each of the 35
`tracking coils 28 extends over the magnetization boundary
`line "a". A drive motor (actuator) 29 is formed by the
`focussing coils 27, the tracking coils 28 and the drive
`magnet 26. It should be noted that an optical recording
`medium 30 such as an optical disk is located near the 40
`objective lens 13.
`In the above-mentioned structure, a drive force is gener(cid:173)
`ated by providing a current to the focusing coils 27 and/or
`the tracking coils 18 due to magnetic fields generated by the
`drive magnet 26. Accordingly, the objective lens supporting
`member 14 including the objective lens 13 is movable in the
`focusing direction and/or the tracking direction.
`Additionally, if currents are separately provided to each of
`the focusing coils 27, the objective lens 13 can be tilted with
`respect to a recording surface of the optical recording 50
`medium 30 so as to adjust an incident angle of the light beam
`on the optical recording medium 30. Further, if currents are
`individually provided to each of the tracking coils 28, the
`objective lens 13 can be tilted with respect to a recording
`surface of the optical recording medium 30 so as to adjust an 55
`incident angle of the light beam on the optical recording
`medium 30. In such a case, additional lead wires must be
`connected to the focusing coils 27 or the tracking coils 28 so
`as to achieve electrical connection. Thus, a number of wire
`springs 16, which serve as lead wires for electrical 60
`connection, may be increased, or each of the wire springs 16
`may be formed by a plurality of core wires.
`In the above-mentioned structure, the movable deflection
`mirror 23 and the deflection prism 24 are provided within the
`inner space 17. Thereby, a thickness and a size of the entire 65
`apparatus can be reduced even if the focusing coils 27 and
`the tracking coils 28 occupy relatively large areas.
`
`20
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`45
`
`8
`A description will now be given, with reference to FIGS.
`7A, 7B and 8, of an objective lens driving apparatus accord(cid:173)
`ing to a second embodiment of the present invention. FIG.
`7 A is a plan view of the objective lens driving apparatus
`according to the second embodiment of the present inven(cid:173)
`tion. FIG. 7B is a side view of the objective lens driving
`apparatus shown in FIG. 7A. FIG. 8 is an illustration for
`explaining a relationship between a magnet, a focusing coil
`and a tracking coil provided in the objective lens driving
`apparatus shown in FIGS. 7 A and 7B. In FIGS. 7 A, 7B and
`8, parts that are the same as the parts shown in FIGS. SA, 5B
`and 6 are given the same reference numerals, and descrip(cid:173)
`tions thereof will be omitted.
`In the present embodiment, the objective lens supporting
`member 14 is enlarged so as to form a space 31 on each side
`of the inner space 17. That is, an additional wall is formed
`inside each of the side walls 20. The drive coil assembly 21
`is embedded in each of the side walls 20. The drive magnet
`26 mounted on the yoke 25 is provided so as to face the dr