c12) United States Patent
`Song et al.
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006785065Bl
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6, 785,065 Bl
`Aug. 31, 2004
`
`(54) OPTICAL PICKUP ACTUATOR DRIVING
`METHOD AND APPARATUS THEREFOR
`
`(75)
`
`Inventors: Byung-youn Song, Gyeonggi-do (KR);
`Kyung-sik Shin, Gyeonggi-do (KR)
`
`(73) Assignee: Samsung Electronics Co., Ltd.,
`Suwon-si (KR)
`
`( * ) 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.: 10/772,339
`
`(22) Filed:
`
`Feb. 6, 2004
`
`Related U.S. Application Data
`
`(63) Continuation of application No. 10/173,958, filed on Jun.
`19, 2002, now Pat. No. 6,721,110.
`
`(30)
`
`Foreign Application Priority Data
`
`Jun. 19, 2001
`
`(KR) ........................................ 2001-34687
`
`Int. Cl.7
`.................................................. G028 7/02
`(51)
`(52) U.S. Cl ...................... 359/814; 359/824; 369/44.15
`(58) Field of Search ................................. 359/814, 824,
`359/813, 811; 369/44.15
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,479,051 A
`
`10/1984 Musha
`
`5/1993 Ikegame eta!.
`5,208,703 A
`9/1997 Matsui
`5,663,840 A
`6,580,569 B2 * 6/2003 Choi eta!. .................. 359/814
`6,639,744 B2 * 10/2003 Ohno ......................... 359/824
`* cited by examiner
`
`Primary Examiner-Hung X. Dang
`(74) Attorney, Agent, or Firm-8taas & Halsey, LLP
`
`(57)
`
`ABSTRACT
`
`An optical pickup actuator includes a bobbin. At least one
`focus coil and at least one track coil are arranged at both
`sides of the bobbin to secure the remaining sides of the
`bobbin. The optical pickup actuator can drive an optical
`pickup in a focus direction, a track direction, and a tilt
`direction. The focus coil is also used as the tilt coil. An
`optical pickup actuator is driven by arranging a bobbin on a
`base of the optical pickup actuator so as to be moved by
`support members, installing at least one focus and tilt coil to
`drive the bobbin in focus and tilt directions and at least one
`track coil to drive the bobbin in a track direction at opposite
`side surfaces of the bobbin, arranging magnets to face
`corresponding sides of the opposite side surfaces of the
`bobbin, and dividing the focus and tilt coils into at least two
`sets of coils and applying an input signal to each of the sets.
`Since driving in the focus direction and the tilt direction can
`be controlled together by a single coil, the number of the
`support members can be reduced and the defective ratio can
`be lowered. Accordingly, the three axes driving and the four
`axes driving can be stably implemented.
`
`10 Claims, 8 Drawing Sheets
`
`LG Electronics, Inc. et al.
`EXHIBIT 1001
`IPR Petition for
`U.S. Patent No. 6,785,065
`
`

`
`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 1 of 8
`
`US 6, 785,065 Bl
`
`FIG. 1 (PRIOR ART)
`
`100
`
`M
`
`~.-
`
`... ~1 ...
`
`120
`
`05
`
`.·· .-;
`.. ,._~· .: ..
`... ~ .
`..
`... ~ .. ,/
`119-f--h;
`~· .. ,.
`, ......... -
`.....
`.. -
`:-=.:~i:
`
`~ ":•.:,•"!
`
`12c(
`
`109
`
`118
`
`11 7
`
`

`
`U.S. Patent
`
`Aug. 31,2004
`
`Sheet 2 of 8
`
`US 6, 785,065 Bl
`
`FIG. 2A (PRIOR ART)
`
`110 t 107a
`
`117
`
`112
`
`Ft BLI
`F11 BLI
`
`FIG. 28 (PRIOR ART)
`
`107b
`
`119
`
`115
`
`

`
`U.S. Patent
`
`Aug. 31,2004
`
`Sheet 3 of 8
`
`US 6, 785,065 Bl
`
`FIG. 3
`
`15
`
`F
`
`Tir
`
`15b
`
`

`
`U.S. Patent
`
`Aug. 31,2004
`
`Sheet 4 of 8
`
`US 6, 785,065 Bl
`
`FIG. 4
`
`r
`
`1--
`r-
`
`25-
`22-
`F
`
`T C2-
`
`CA F
`1 5a
`
`27
`
`I
`
`r":
`
`~·
`
`~
`~~ I
`~~ I
`~ .
`i.'i ~ !if
`~~
`~i
`~..,
`·t~
`l't·
`~li!
`,_.
`
`-
`
`1--
`
`0
`
`15b
`
`30 15
`I
`
`14
`
`-
`
`2225
`
`-+-
`
`~ ~~
`
`,;:. v
`~ "'":~
`··.9 0 ~~ ,.. ..
`~~ !~. a
`~
`~ ...
`..... u
`~ l>·'i:
`m
`' 12
`
`- 1-.
`
`I
`
`....__
`
`I I
`
`10 30
`
`r-
`
`.._
`
`-FC1
`-TC1
`-FC3
`
`FIG. 5
`
`22b
`
`TC1 (TC2)
`
`s
`
`22a
`
`22
`
`/
`-~11
`
`Ff3
`
`I
`I
`I
`
`I l I I
`
`I
`
`,--l-~
`
`I
`
`N
`
`s
`
`22d
`
`22n
`
`

`
`U.S. Patent
`
`Aug. 31,2004
`
`Sheet 5 of 8
`
`US 6, 785,065 Bl
`
`FIG. 6
`
`22b
`
`22
`
`20
`
`N
`
`22a
`
`23
`
`22c
`
`FC3(FC4)
`
`22d
`
`

`
`U.S. Patent
`
`Aug. 31,2004
`
`Sheet 6 of 8
`
`US 6, 785,065 Bl
`
`FIG. 7A
`
`5r---~--~----r---,---~----~--~--~--~r-~
`
`0
`
`-5~--~--~--~------------~--~----~--~--~
`10
`9
`7
`6
`2
`3
`1
`5
`0
`8
`4
`
`FIG. 7B
`
`5r---,---~---,----~--~---.---,----~--~---,
`
`0
`
`-5~--~--~----~--~--_.----~--~--~----~--~
`1
`7
`8
`5
`10
`4
`3
`2
`9
`6
`0
`
`FIG. 7C
`
`0
`
`-5~--~--~--~----~--~--~--~----~--~--~
`0
`1
`2
`3
`4
`5
`6
`7
`B
`9
`10
`
`

`
`U.S. Patent
`
`Aug. 31,2004
`
`Sheet 7 of 8
`
`US 6, 785,065 Bl
`
`FIG. BA
`
`0
`
`-5~------~--~----~--~--~--~----~--~--~
`4
`7
`10
`0
`1
`3
`8
`5
`2
`6
`9
`
`FIG. BB
`
`0
`
`-5~--~--_.--~~--~--~--~--~~--~--~--~
`4
`10
`7
`2
`6
`8
`5
`1
`3
`9
`0
`
`FIG. BC
`
`0
`
`-sh---~----._---4----~--~----._--~----~--~--~
`0
`1
`2
`3
`4
`5
`6
`7
`8
`9
`10
`
`

`
`U.S. Patent
`
`Aug. 31,2004
`
`Sheet 8 of 8
`
`US 6, 785,065 Bl
`
`FIG. 9
`
`FOCUS SS~ OUTPUT
`~----~---+--------~~
`FOOJS Sl1l'W. OUlPUT
`
`RESULT
`
`FOC1JS S1GtW.INPUT
`
`TilT RIGHT SOOI.INPUT
`
`liLT lEFT SIGNAL INPUT
`
`

`
`US 6, 785,065 B 1
`
`1
`OPTICAL PICKUP ACTUATOR DRIVING
`METHOD AND APPARATUS THEREFOR
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a continuation of U.S. patent applica(cid:173)
`tion Ser. No. 10/173,958, filed Jun. 19, 2002 now U.S. Pat.
`No. 6,721,110, and claims the benefit of Korean Patent
`Application No. 2001-34687 filed on Jun. 19, 2001, in the
`Korean Industrial Property Office, the disclosures of which
`are incorporated herein by reference.
`
`BACKGROUND OF THE INVENTION
`
`5
`
`2
`where the focus coils 110 and the tilt coils 112 are not
`arranged, and first and second magnets 117 and 119 installed
`on the base 100 to face the focus coils 110, the tilt coils 112,
`and the track coils 115 with corresponding predetermined
`intervals therebetween. Outer yokes 118 and 120 which fix
`the first and second magnets 117 and 119 are installed on the
`base 100. Inner yokes 122 are installed on the base 100 at
`corresponding positions facing the first magnets 117 to guide
`the bobbin 107. The outer yokes 118 and 120 and the inner
`10 yokes 122 guide a path of magnetism generated by the first
`and second magnets 117 and 119 to direct the bobbin 107 to
`a desired location.
`Each of the wires 109 has one end soldered to a corre(cid:173)
`sponding area of both the opposite and other side surfaces of
`15 the bobbin 107 and the other end connected to the holder
`103, and is electrically connected to a circuit portion (not
`shown) which applies current to the magnetic driving por(cid:173)
`tion.
`FIG. 2A shows an example of the polarity of the first
`magnet 117 and the direction of current I to disclose the
`relationship of forces by the interaction between the focus
`coil 110 and the tilt coil 112, and the first magnet 117
`corresponding thereto. Here, the focus coil 110 provided at
`each of the opposite side surfaces 107a of the four side
`25 surfaces of the bobbin 107 receives a force F1 by Fleming's
`left hand rule so that the bobbin 107 is moved in the focus
`direction L. Where the direction of the current I changes to
`the opposite, the focus coil 110 receives a force in the
`opposite direction L'.
`The tilt coil112 is provided at both opposite side surfaces
`107a of the bobbin 107, forms a couple with the correspond-
`ing focus coil110, and interacts with the corresponding first
`magnet 117. Here, where the same currents flowing in the
`opposite directions are applied to the tilt coils 112, the forces
`F,; received by the both tilt coils 112 become opposite so as
`to drive the optical pickup in the tilt direction, in particular,
`in the radial tilt direction (N).
`FIG. 2B shows an example of the polarity of the second
`40 magnet 119 and the direction of current I to disclose the
`relationship of forces by the interaction between the track
`coil115 and the second magnet 119 corresponding thereto.
`The direction and magnitude of forces between a magnet
`and a coil is determined by Fleming's left hand rule. Thus,
`45 the track coil115 provided at each of the other side surfaces
`107b of the four side surfaces of the bobbin 107, where the
`focus coils 110 and the tilt coils 112 are not arranged,
`receives the force F, in the track direction by the second
`magnet 119 so as to move the bobbin 107 in the track
`50 direction M. Here, where the direction of current I changes
`to the opposite, the track coil 115 receives a force in the
`opposite direction M'.
`Typically, six wires 109 of the optical pickup actuator are
`provided to drive the bobbin 107 in the focus direction, the
`55 track direction, and the tilt direction. But, more wires may
`be needed for a four axes driving actuator.
`However, since the optical pickup actuator is very small,
`where all four side surfaces of the bobbin 107 are used to
`install the focus coils 110, the track coils 115, or the tilt coils
`112, a sufficient space may not be present to install the wires
`109. In addition, when the number of the wires 109
`increases, it is very difficult to attach the additional wire(s)
`in such a small space. Accordingly, the defective ratio of the
`conventional optical pickup actuators increases.
`Also, when coils are arranged using all four side surfaces
`of the bobbin 107, wiring of the coils is complicated.
`Furthermore, since a magnet is provided at each of the focus
`
`35
`
`1. Field of the Invention
`The present invention relates to an apparatus and a
`method of driving an optical pickup actuator, and more
`particularly, to an apparatus and a method of driving an
`optical pickup actuator in which a focus coil, a track coil,
`and a tilt coil which drive an optical pickup in a focus 20
`direction, a track direction, and a tilt direction, respectively,
`are provided at both sides of a bobbin to secure the remain(cid:173)
`ing sides of the bobbin, and the focus coil is also used as the
`tilt coil.
`2. Description of the Related Art
`In general, optical pickups are adopted in optical
`recording/reproducing apparatuses. An optical pickup per(cid:173)
`forms recording and/or reproduction of information with
`respect to a recording medium, such as an optical disk,
`placed on a turntable in a non-contact manner while moving 30
`in a radial direction of the optical disk.
`The optical pickup includes an objective lens which forms
`a light spot on the optical disk by focusing light emitted from
`a light source, and an actuator which controls the objective
`lens in a track direction, a focus direction, and a tilt direction
`so as to accurately place the light spot formed by the
`objective lens on the optical disk.
`The optical pickup actuator includes a double axes driving
`actuator which drives the optical pickup in the track direc(cid:173)
`tion and the focus direction. Recently, to perform a high
`density recording, the N/A of the objective lens has been
`increased and the wavelength of a laser has been decreased.
`However, a margin in tilt of the optical pickup actuator
`decreases in response to increase of the N/ A and decrease of
`the wavelength. To compensate for the reduced tilt margin,
`three axes or four axes driving actuators capable of driving
`an optical pickup in the tilt direction are needed in addition
`to the existing double axes driving actuator. The three axes
`driving refers to driving in the focus direction, the track
`direction, and the tilt direction. The four axes driving refers
`to driving in the focus direction, the track direction, a tilt
`radial direction, and a tilt tangential direction. Referring to
`FIG. 1, the focus direction, the track direction, the tilt radial
`direction, and the tilt tangential direction are indicated by
`L-L', M-M', N, and 0, respectively.
`FIG. 1 shows a conventional optical pickup actuator
`which includes a base 100, a holder 103 fixed to the base
`100, a bobbin 107 where an objective lens 105 is mounted,
`wires 109 which connect the bobbin 107 to the holder 103, 60
`and a magnetic driving portion (described below) which
`moves the bobbin 107 in the track direction, the focus
`direction, or the tilt direction.
`The magnetic driving portion includes a couple of a focus
`coil110 and a tilt coil112 (see FIG. 2A) provided at each 65
`of the opposite side surfaces 107a of the bobbin 107, a track
`coil 115 arranged at each of the other side surfaces 107b
`
`

`
`US 6, 785,065 B 1
`
`4
`The support member may be arranged at other opposite
`side surfaces of the bobbin, wherein the focus and tilt coils
`and the track coils are not arranged on the other opposite
`side surfaces of the bobbin.
`To achieve the above and other objects according to
`another embodiment of the present invention, there is pro(cid:173)
`vided a method of driving an optical pickup actuator having
`a bobbin, a support member, focus and tilt coils, track coils,
`and magnets, the method comprising arranging the bobbin
`10 on a base of the optical pickup actuator so as to be moved
`by the support member, installing at least one focus and tilt
`coil to drive the bobbin in focus and tilt directions and at
`least one track coil to drive the bobbin in a track direction
`at each of opposite side surfaces of the bobbin, arranging the
`magnet to face the respective focus and tilt coils and the
`track coils, and independently inputting a signal to each
`focus and tilt coil.
`The same input signal may be input to at least one of the
`focus and tilt coils to drive the bobbin in the focus direction.
`A different input signal may be applied to at least one of
`the focus and tilt coils to drive the bobbin in the tilt direction.
`The installation of at least one focus and tilt coil may
`comprise arranging first and third focus and tilt coils on one
`side of the opposite side surfaces of the bobbin, and arrang(cid:173)
`ing second and fourth focus and tilt coils on the other side
`of the opposite side surfaces of the bobbin. The applying of
`the input signal may comprise inputting first and second
`input signals to respective first and second set coils, wherein
`30 each of the first and second set coils is formed of a selected
`couple of the first through fourth focus and tilt coils.
`
`3
`coilllO, the tilt coil112, and the track coil115, the number
`of parts constituting the optical pickup actuator increases,
`decreasing the productivity. Additionally, interference with a
`spindle motor (not shown), which rotates a disc, is generated
`by the first magnet 117 arranged at the opposite side surfaces 5
`(left and right sides) of the bobbin 107. Therefore, the
`spindle motor is not accurately controlled.
`SUMMARY OF THE INVENTION
`Accordingly, it is an object of the present invention to
`provide an apparatus and a method of driving an optical
`pickup actuator in which a focus and tilt coil and a track coil
`which drive an objective lens in the focus direction, the track
`direction, and the tilt direction are arranged at both side
`surfaces of a bobbin so as to secure a sufficient space
`provided at the other side surfaces of the bobbin, wherein 15
`driving in the focus direction and the tilt direction can be
`controlled together by a single coil.
`Additional objects and advantages of the invention will be
`set forth in part in the description which follows and, in part,
`will be obvious from the description, or may be learned by 20
`practice of the invention.
`To achieve the above and other objects of the present
`invention, there is provided a method of driving an optical
`pickup actuator having a bobbin, a support member, focus
`and tilt coils, track coils, and magnets, the method compris- 25
`ing arranging the bobbin on a base of the optical pickup
`actuator so as to be moved by the support member, installing
`at least one focus and tilt coil to drive the bobbin in focus
`and tilt directions and at least one track coil to drive the
`bobbin in a track direction at each of opposite side surfaces
`of the bobbin, arranging the magnets to face the respective
`focus and tilt coils and the track coils, and dividing the focus
`and tilt coils into at least two sets of coils and applying an
`input signal to each of the sets.
`According to an aspect of the present invention, the 35
`installation of at least one focus and tilt coil comprises
`arranging first and third focus and tilt coils on one side of the
`opposite side surfaces of the bobbin, and arranging second
`and fourth focus and tilt coils on the other side of the
`opposite side surfaces of the bobbin. The applying of the
`input signal comprises inputting first and second input
`signals to respective first and second set coils, wherein each
`of the first and second set coils is formed by a coupling of
`two of the first through fourth focus and tilt coils.
`The first set coil may be formed of the first and third focus
`and tilt coils and the second set coil may be formed of the
`second and fourth focus and tilt coils. Alternatively, the first
`set coil may be formed of the first and second focus and tilt
`coils and the second set coil may be formed of the third and 50
`fourth focus and tilt coils.
`The first and second input signals may be the same input
`signal to drive the bobbin in the focus direction.
`Alternatively, the first and second input signals may have
`different phases. On the other hand, each of the first and 55
`second input signals may comprise a sum signal of a focus
`signal and a corresponding tilt signal having a phase differ(cid:173)
`ent from that of the focus signal.
`Each of the magnets may have four polarizations.
`Alternatively, each of the magnets may comprise first mag- 60
`net and second magnet parts, each part having two polar(cid:173)
`izations.
`The method of driving the optical pickup actuator further
`includes inputting another input signal to each of the track
`coils independent of the focus and tilt coils.
`At least one of the focus and tilt coils and the tracks may
`be formed of a fine pattern coil.
`
`65
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`These and other objects and advantages of the present
`invention will become apparent and more readily appreci(cid:173)
`ated from the following description of the embodiments,
`taken in conjunction with the accompanying drawings of
`which:
`FIG. 1 is a plane view of a conventional optical pickup
`40 actuator;
`FIGS. 2A and 2B are views illustrating the relationship
`between a magnet and coil of the optical pickup actuator of
`FIG. 1;
`FIG. 3 is an exploded perspective view of an optical
`45 actuator according to an embodiment of the present inven-
`tion;
`FIG. 4 is a plan view of the optical pickup actuator shown
`in FIG. 3;
`FIG. 5 is a view illustrating the relationship and arrange(cid:173)
`ment of a magnet and coil of the optical pickup actuator
`shown in FIG. 3;
`FIG. 6 is a view illustrating the relationship of forces
`acting between a magnet and a fine pattern coil of an optical
`pickup actuator according to the present invention;
`FIGS. 7A through 7C and FIGS. SA through 8C are
`graphs illustrating waveforms of input signals to implement
`a method of driving an optical pickup actuator according to
`the present invention; and
`FIG. 9 is a circuit diagram to implement a method of
`driving an optical pickup actuator according to the present
`invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`Reference will now be made in detail to the embodiments
`of the present invention, examples of which are illustrated in
`
`

`
`US 6, 785,065 B 1
`
`15
`
`20
`
`25
`
`5
`the accompanying drawings, wherein like reference numer(cid:173)
`als refer to the like elements throughout. The embodiments
`are described below in order to explain the present invention
`by referring to the figures.
`To describe a method of driving an optical pickup actuator
`according to the present invention, an optical pickup actua(cid:173)
`tor to which the present invention is adopted is described as
`follows.
`FIGS. 3 and 4 show an optical pickup actuator according
`to an embodiment of the present invention. The optical
`pickup actuator includes a base 10, a holder 12 provided at
`one side of the base 10, a bobbin 15 on which an objective
`lens 14 is mounted, and a magnetic driving portion
`(described below) which drives the bobbin 14 in a focus
`direction, a tilt direction, and a track direction.
`The magnetic driving portion includes at least one focus
`and tilt coil and at least one track coil provided at each of
`opposite side surfaces 15a of the bobbin 15, and a magnet
`22 installed to face each combination of the focus and tilt
`coil and the track coil provided on each of the opposite side
`surfaces. For example, the focus and tilt coils may include
`first, second, third, and fourth focus and tilt coils FC1, FC2,
`FC3, and FC4 and the track coils may include first and
`second track coils TC1 and TC2 each of which is provided
`at the corresponding opposite side surfaces of the bobbin 15,
`as shown in FIG. 4. Here, the first through fourth focus and
`tilt coils FC1, FC2, FC3, and FC4 and the first and second
`track coils TC1 and TC2 are all arranged at the opposite side
`surfaces 15a of the bobbin 15. A support member 30 is
`arranged at each of the other opposite side surfaces 15b of
`the bobbin (where the focus and tilt coils FC1-FC4 and the
`tracks coils TC1-TC2 are not arranged). The support mem(cid:173)
`bers 30 movably supports the bobbin 15 and simultaneously
`applies current to the first through fourth focus and tilt coils
`FC1, FC2, FC3, and FC4 and the first and second track coils
`TC1 and TC2. The support members 30 may be wires or leaf
`springs.
`In the optical pickup actuator having the above structure,
`the first through fourth focus and tilt coils FC1, FC2, FC3,
`and FC4 are controlled to drive the object lens 14 both in the
`focus direction and the tilt direction.
`FIG. 5 shows that the magnet 22 may be divided into four
`sections. That is, the magnet 22 is divided into four sections
`in which N poles and S poles are appropriately distributed. 45
`For the convenience of explanation, the divided magnet 22
`includes a first divided pole 22a, a second divided pole 22b,
`a third divided pole 22c, and a fourth divided pole 22d. The
`first divided pole 22a is an N pole, a second divided pole 22b
`is an S pole, a third divided pole 22c is an N pole, and a 50
`fourth divided pole 22d is an S pole. The focus and tilt coils
`FC1, FC2, FC3, and FC4 and the track coils TC1 and TC2
`are arranged corresponding to the respective polarization
`22a, 22b, 22c, and 22d of the magnet 22.
`For example, each of the track coils TC1 and TC2 is 55
`arranged to face both of the first and second polarization 22a
`and 22b of the magnet 22, as shown in FIG. 5. A couple of
`the first and third focus and tilt coils FC1 and FC3 are
`provided at the one side surface of the opposite side surfaces
`15a of the bobbin 15 and the other couple of the second and
`fourth focus and tilt coils FC2 and FC4 are provided at the
`other side surface of the opposite side surfaces 15a of the
`bobbin 15. The first or second focus and tilt coil FC1 or FC2
`can be arranged to face both of the second and third
`polarization 22b and 22c while the third or fourth focus and
`tilt coil FC3 or FC4 can be arranged to face both of the first
`and fourth polarization 22a and 22d.
`
`6
`Alternatively, the magnet 22 may be a magnet having two
`polarizations. For example, a set of two magnets each
`having two polarizations can be arranged to be separated by
`a predetermined distance from each other to face the focus
`5 and tilt coils FC1, FC2, FC3, and FC4 and the track coils
`TC1 and TC2.
`Here, the focus and tilt coils FC1, FC2, FC3, and FC4 and
`the track coils TC1 and TC2 can be winding coils. Also, as
`shown in FIG. 6, at least one of the focus and tilt coils and
`10 the track coils can be a fine pattern coil20. The fine pattern
`coil 20 is manufactured by patterning a coil shape on a film
`and can be very useful in installation of a coil in a small
`space.
`Although the magnet 22 can have four polarizations,
`which are divided symmetrically, to secure effective areas of
`the track coils TC1 and TC2, the first and second polariza(cid:173)
`tions 22a and 22b corresponding to the track coils TC1 and
`TC2 can be divided to have areas greater than those of the
`third and fourth polarizations 22c and 22d. That is, since the
`focus and tilt coils FC1, FC2, FC3, and FC4 use all of the
`first through fourth polarization 22a, 22b, 22c, and 22d
`while the track coils TC1 and TC2 use only the first and
`second polarization 22a and 22b, each of the areas of the
`polarization can be adjusted to balance with respect to the
`focus and tilt coils FC1, FC2, FC3, and FC4.
`Also, a neutral zone 22n can be arranged between the
`respective polarizations 22a, 22b, 22c, and 22d of the
`magnet 22. The neutral zone 22n is provided at a boundary
`portion between the respective polarizations to prevent
`lowering of the overall lines of a magnetic force as the lines
`of the magnetic force are offset at a boundary area where the
`magnetic poles are opposite.
`Referring back to FIGS. 3 and 4, outer yokes 25 and inner
`yokes 27 may be further provided to guide lines of a
`magnetic force generated by the magnets 22 in a desired
`direction.
`A method of driving an optical pickup actuator having the
`structure above is described below. That is, at least one ofthe
`focus and tilt coils FC1, FC2, FC3, and FC4 and one of the
`40 track coils TC1 and TC2 are arranged at both side surfaces
`15a of the bobbin 15. The focus and tilt coils are divided into
`at least two sets to receive first and second input signals.
`For example, FIGS. 7Aand SA show that where first and
`second input signals are focus signals in the same direction,
`the bobbin 15 moves in the focus direction F. That is, in the
`case in which the first and second focus and tilt coils FC1
`and FC2 constitute a first set coil and the third and fourth
`focus and tilt coils FC3 and FC4 constitute a second set coil,
`where the same signal is applied to both of the first and
`second set coils, the first through fourth focus and tilt coils
`FC1, FC2, FC3, and FC4 receive the same forces in the
`upward or downward direction by the interaction with the
`magnets 22. Thus, the bobbin 15 can be driven in the focus
`direction F.
`In contrast, where the first and second input signals
`different from each other are input to the first and second
`focus and tilt coils FC1 and FC2 and the third and fourth
`focus and tilt coils FC3 and FC4, the focus and tilt coils
`receive forces in the upward or downward direction that are
`60 opposite to each other at the left and right sides. Here, for
`example, the first input signal, as shown in FIG. 7B, is input
`to the first and second focus and tilt coils FC1 and FC2, and
`the second input signal, as shown in FIG. 8B, having a phase
`different from that of the first input signal is input to the third
`65 and fourth focus and tilt coils FC3 and FC4. Accordingly,
`driving of the bobbin 15 in a tilt radial direction Tir can be
`controlled.
`
`30
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`35
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`

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`US 6, 785,065 B 1
`
`7
`Furthermore, an input signal may be input to each of the
`tracks coils TC1 and TC2, independent of the focus and tilt
`coils FC1-FC4, to drive the bobbin 15 in the track direction
`T.
`
`As describe above, by having the first and second focus 5
`and tilt coils FC1 and FC2 and the third and fourth focus and
`tilt coils FC3 and FC4 as the first set coil and the second set
`coil, respectively, and having the first and second track coils
`TC1 and TC2, driving of the bobbin 15 along three axes of
`the focus direction F, the track direction T, and the radial tilt
`direction Tir is possible. FIG. 9 shows a circuit diagram for
`the above case.
`Alternatively, the first and third focus and tilt coils FC1
`and FC3 of the first through fourth focus and tilt coils FC1,
`FC2, FC3, and FC4 may form a first set coil and the second
`and fourth focus and tilt coils FC2 and FC4 may form a
`second set coil. Here, where first and second input signals
`having phases different from each other are input to the first
`set coil and the second set coil, respectively, driving of the
`bobbin 15 in a tangential tilt direction Tit is possible.
`In addition to the above method of independently con(cid:173)
`trolling the driving of the bobbin 15 in the focus direction
`and the tilt direction, the driving of the bobbin 15 in the
`focus and tilt directions can be simultaneously controlled by
`applying a sum signal of the first and second input signals
`for driving in the tilt direction as a signal for driving in the
`focus direction. That is, a sum signal (FIG. 7C) of the focus
`driving signal (FIG. 7A) and the first input signal (FIG. 7B)
`for driving in the tilt direction is input to the first set coil. A
`sum signal (FIG. SC) of the focus driving signal (FIG. SA)
`and the second input signal (FIG. 7C) for driving in the tilt
`direction is input to the second set coil. Thus, driving in the
`focus direction F, and the tilt radial direction Tir or the
`tangential tilt direction Tit can be controlled simultaneously.
`Here, the first set coil is formed of the first and second
`focus and tilt coils FC1 and FC2 and the second set coil is
`formed of the third and fourth focus and tilt coils FC3 and
`FC4. By doing so, the driving in the focus direction F and
`the driving in the radial tilt direction Tir can be controlled
`together. Alternatively, the first set coil can be formed of the
`first and third focus and tilt coils FC1 and FC3 and the
`second set coil is formed of the second and fourth focus and
`tilt coils FC2 and FC4. By doing so, the driving in the focus
`direction F and the driving in the tangential tilt direction Tit 45
`can be controlled together.
`The present invention further provides a method of inde(cid:173)
`pendently applying a signal to each of the first through
`fourth focus and tilt coils FC1, FC2, FC3, and FC4. That is,
`where the focus signal (see FIGS. 7 A and SA) is identically 50
`applied to the first through fourth focus and tilt coils FC1,
`FC2, FC3 and FC4, the bobbin 15 move up and down and
`is driven in the focus direction F.
`In contrast, the driving in the tilt radial direction Tir and
`the driving in the tilt tangential direction Tit can be con- 55
`trolled by selectively inputting an input signal to each of the
`first through fourth focus and tilt coils FC1, FC2, FC3, and
`FC4. For example, the first and second focus and tilt coils
`FC1 and FC2 of the first through fourth focus and tilt coils
`FC1, FC2, FC3, and FC4 can form a first set, and the third 60
`and fourth focus and tilt coils FC1 and FC3 can form a
`second set. Alternatively, the first and third focus and tilt
`coils FC1 and FC3 can form a first set, and the second and
`fourth focus and tilt coils FC2 and FC4 can form a second
`~.
`Here, by inputting a predetermined first input signal (FIG.
`7B) to the first set and the second input signal (FIG. SB)
`
`8
`having a phase different from that of the first input signal to
`the second set, the driving in the tilt radial direction Tir and
`in the tilt tangential direction Tit can be selectively con(cid:173)
`trolled.
`Furthermore, a sum signal of the focus signal and the first
`or second input signal for tilt driving can be selectively input
`to the first through fourth focus and tilt coils FC1, FC2, FC3,
`and FC4. By doing so, driving in the focus direction, and
`driving in the radial tilt direction Tir or in the tangential tilt
`10 direction Tit can be controlled together.
`On the other hand, the track coils TC1 and TC2 can move
`the bobbin 15 in the track direction T by interacting with the
`first divided pole 22a and the second divided pole 22b. Thus,
`four axes driving in the focus direction F, the track direction
`15 T, the radial tilt direction Tir, and the tangential tilt direction
`Tit is possible.
`It is understood that the arrangement of the polarization of
`the magnets 22 and the coils FC1-FC4 and TC1-TC2 can be
`modified without departing from the principles and spirit of
`20 the present invention.
`As described above, since focus and tilt coils and track
`coils are provided at opposite side surfaces of a bobbin to
`secure a free space at the other opposite side surfaces of the
`bobbin, driving in a focus direction and in a tilt direction can
`25 be controlled together by a single coil. Therefore, a support
`member can be easily installed at the other opposite side
`surfaces of the bobbin and the number of the support
`members can be reduced. Accordingly, the defective ratio
`can be lowered and the three axes driving and the four axes
`30 driving can be stably implemented.
`Although a few embodiments of the present invention
`have been shown and described it will be appreciated by
`those skilled in the art that cha