United States Patent [19J
`Mohri et al.
`
`[54] OBJECT LENS DRIVING DEVICE
`
`[75]
`
`Inventors: Masanari Mohri, Hyogo; Hitoshi
`Fujii, Osaka; Kanji Wakabayashi;
`Hiroshi Yamamoto, both of Kyoto;
`Teruyuki Thkizawa; Thkeo Santo, both
`of Osaka, all of Japan
`
`[73] Assignee: Matsushita Electric Industrial Co.,
`Ltd., Osaka, Japan
`
`[21] Appl. No.: 09/342,585
`
`[22] Filed:
`
`Jun. 29, 1999
`
`[30]
`
`Foreign Application Priority Data
`
`[.TP]
`[JP]
`
`Japan .................................. 10-188650
`Japan .................................. 10-298051
`
`Jul. 3, 1998
`Oct. 20, 1998
`Int. Cl.7
`•••••••••••••••••••••••.......... G02B 7/02; GllB 7/00
`[51]
`[52] U.S. Cl ........................... 359/824; 359/813; 359/814;
`369/44.15
`[58] Field of Search ..................................... 359/811, 813,
`359/814, 819, 823, 824; 369/44.15, 44.16
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,773,055
`5,446,721
`5,905,255
`6,016,292
`
`9/1988 Gijzen et a!. ........................ 369/44.16
`8/1995 Sekimoto et a!. ...................... 369/247
`5/1999 Wakabayashi et a!. .............. 250/201.5
`1/2000 Lee ....................................... 369/44.15
`
`FOREIGN PATENT DOCUMENTS
`
`58-88841
`60-142822
`61-187134
`62-33345
`62-33346
`
`5/1983
`9/1985
`8/1986
`2/1987
`2/1987
`
`Japan .
`Japan .
`Japan .
`Japan .
`Japan .
`
`150
`
`f
`
`100
`(
`)
`
`10
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006134058A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,134,058
`Oct. 17, 2000
`
`62-119742
`64-82341
`2-23536
`4-103042
`4-366429
`5-10249
`5-16647
`6-68844
`9-22537
`
`6/1987
`3/1989
`1/1990
`4/1992
`12/1992
`3/1993
`5/1993
`8/1994
`1/1997
`
`Japan.
`Japan.
`Japan.
`Japan.
`Japan.
`Japan.
`Japan.
`Japan.
`Japan.
`
`Primary Examiner-Georgia Epps
`Assistant Examiner-Saud Seyrafi
`Attorney, Agent, or Firm--Ratner & Prestia
`
`[57]
`
`ABSTRACT
`
`An object lens driving device of the present invention
`includes a movable section, supporting sections for support(cid:173)
`ing the movable section and a base for holding the support(cid:173)
`ing sections. The movable section includes an object lens for
`recording and/or reproducing optical information to and/or
`from a disk-shaped recording medium, a lens holder for
`holding the object lens and at least four permanent magnets
`adhered to the lens holder. The supporting sections include
`at least four metal wires substantially parallel to each other,
`each wire having a first end fixed to the lens holder and a
`second end connected to the base, and elastic deformable
`elements connected to the base and having connecting
`sections thereof connected to the second end of each respec(cid:173)
`tive metal wire. The base includes yokes fixed to the base
`and facing the respective permanent magnets, focusing coils
`wound around the respective yokes, wound axes of the
`focusing coils being oriented in a direction of an optical axis
`of the object lens, and tracking coils wound around the
`respective yokes, wound axes of the tracking coils being
`oriented in a direction perpendicular to the wound axes of
`the focusing coils.
`
`15 Claims, 17 Drawing Sheets
`
`LG Electronics, Inc. et al.
`EXHIBIT 1006
`IPR Petition for
`U.S. Patent No. 6,785,065
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 1 of 17
`
`6,134,058
`
`FIG. 1A
`
`150
`
`I
`
`100 j
`
`10
`
`160
`
`j
`
`sa
`
`FIG. 1 B
`6a
`
`+Tb 6b
`
`sr'\~~
`
`""""\\11111:«:
`
`7b
`
`+Fd
`
`6d
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 2 of 17
`
`6,134,058
`
`FIG.2A
`
`Fo
`~
`Y axis
`I
`~ Rt
`'R+
`-Foa•
`f
`'""+Fob
`3b
`~~
`
`150
`
`j
`
`-Foe~
`4
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 3 of 17
`
`6,134,058
`
`FIG.2B
`
`Fo
`z ~ I
`
`/150
`
`4
`
`4
`
`FIG.2C
`
`/150
`
`~~-·4
`
`FIG.2D
`
`/150
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 4 of 17
`
`6,134,058
`
`FIG.3A
`
`+Foa
`~
`+Fob
`t ~~
`
`3b
`
`150
`
`/
`
`..
`
`2
`/
`Tt
`-q"
`,P +
`X axis
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 5 of 17
`
`6,134,058
`
`/150
`
`X
`
`- - -
`
`-. +Mt
`
`X
`
`-Mt
`_ _L
`
`FIG.3B
`10'\
`
`4A
`
`4A
`
`1 Oa
`
`4
`
`1 Oa
`
`4
`
`FIG.3C
`10\
`
`4A ---..~~\--
`
`4
`
`4A
`
`1 Oa
`
`FIG. 3D
`
`10a
`
`4
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 6 of 17
`
`6,134,058
`
`FIG.4A
`
`Focusing coil driving circuit
`
`FIG.4B
`
`Focusing coil driving circuit
`
`7a
`
`7b
`
`7c
`
`7a
`
`7b
`
`7c
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 7 of 17
`
`6,134,058
`
`FIG.4C
`
`Focusing coil driving circuit
`
`7a
`
`7b
`
`7c
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 8 of 17
`
`6,134,058
`
`FIG. SA
`
`Focusing coil driving circuit
`
`11
`
`FIG.5B
`
`Radial tilt drive
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 9 of 17
`
`6,134,058
`
`FIG.5C
`
`Tangential tilt drive
`
`1 1
`
`7a
`
`7b
`
`-------7c
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 10 of 17
`
`6,134,058
`
`FIG. 6A
`
`I ... Dd
`Tw
`1
`....----~: :...__Gd
`
`,_I
`1
`
`4
`
`/200
`
`150
`
`Sb
`
`10
`
`8a
`
`j ~I 1-
`1 _Gc
`' - - - / -+-I
`I
`I
`I
`T
`w
`1 1 De
`"""'I
`I"'""
`
`4
`
`1
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 11 of 17
`
`6,134,058
`
`FIG.6B
`IE Dd
`30' I
`Tw
`1
`1
`I.., Gd
`.----~ ~ 1
`1~. '~
`
`Uc,Ud
`
`1
`
`5d
`
`8b
`
`10
`
`/300
`
`150
`
`4
`
`5b
`
`Sa
`
`I
`
`-+ 1
`
`I
`1 E Da
`I
`I
`1 1 Ga
`.... I I"""
`
`1
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 12 of 17
`
`6,134,058
`
`co
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 13 of 17
`
`6,134,058
`
`FIG.B
`
`4a t +Fo
`11 a 1
`
`1
`
`-Tr ' 3a
`
`'
`
`2
`
`I t -Fo
`
`12
`
`8
`
`400
`
`5
`
`4c
`___/450
`
`'(S
`
`4d
`~ +Tt
`,..........._+Tr
`11b
`,
`-Tt
`6b
`
`J460
`
`7a
`
`7b
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 14 of 17
`
`6,134,058
`
`FIG. 9A
`
`±Tt
`
`10a, 10b
`
`FIG.9B
`
`±Tt
`
`1
`
`1 Oa, 1 Ob
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 15 of 17
`
`6,134,058
`
`FIG.10
`
`11 a
`
`I
`
`t +Fo
`I
`
`I
`
`I
`
`I
`
`'
`
`I
`I
`l-F:\
`
`1
`
`+Tt
`
`~, +Tk
`~
`-Tt
`
`13b
`
`450
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 16 of 17
`
`6,134,058
`
`500
`
`)
`
`FIG.11
`
`108
`
`550
`
`105d107d
`)
`103b
`101
`102
`~Mr};;rr
`
`/
`
`103a
`105b
`
`107b
`
`109
`
`107a
`
`PRIOR ART
`
`

`
`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 17 of 17
`
`6,134,058
`
`FIG. 12
`
`Fo
`t Direction
`1 of. optical 550
`laXIS
`/
`
`Fo
`~+
`j Z axis
`Tt
`+
`
`I
`
`Tangential
`direction Rt
`Y axi?''~ +
`-
`I
`'~
`' Go
`
`I
`
`+
`Tr X axis I
`I t-
`
`

`
`6,134,058
`
`1
`OBJECT LENS DRIVING DEVICE
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to an object lens driving
`device used in an optical information recording and/or
`reproduction apparatus for recording information to and/or
`reproducing information from a disk-shaped recording
`medium.
`2. Description of the Related Art
`If a disk-shaped recording medium (hereinafter, simply
`referred to as "disk") is warped, the distance between the
`surface of the recording medium and an object lens of the
`object lens driving device varies as the recording medium 15
`rotates, resulting in a focusing error. If the rotation of the
`recording medium is off-center, a tracking error occurs. In
`order to prevent a focusing or tracking error, an object lens
`driving device controls the object lens to be driven in two
`directions, namely, along the optical axis of the object lens 20
`which is vertical to the surface of the recording medium
`(focusing direction) and along the direction parallel to the
`surface of the recording medium (tracking direction).
`In the optical information recording and/or reproduction
`apparatus incorporating the object lens driving device as 25
`described above, a relative tilt of the optical axis of the
`object lens to the surface of a disk (hereinafter, simply
`referred to as "tilt") may occur besides the focusing error
`and the tracking error. The tilt is responsible for optical
`aberration which deteriorates signals during recording and 30
`reproduction.
`Some conventional optical information recording and/or
`reproduction apparatus have been proposed for solving the
`above problems. For example, Japanese Laid-Open Publi(cid:173)
`cation No. 9-22537 discloses that the tilt is corrected by 35
`providing at least one permanent magnet adhered to a
`movable section and at least two focusing coils attached on
`a base and regulating currents flowing through the coils.
`Such a conventional optical information recording and/or
`reproduction apparatus will be described below with refer(cid:173)
`ence to the accompanying drawings. FIG. 11 is a perspective
`view of a structure of the conventional optical information
`recording and/or reproduction apparatus 500. FIG. 12 is a
`diagram for explaining the definitions of the reference
`symbols of the present specification.
`Referring to FIG. 11, the apparatus 500 includes an object
`lens 101, a lens holder 102 for holding the object lens 101,
`permanent magnets 103a and 103b adhered to the lens
`holder 102, suspension wires 104, opposed yokes 50
`105a-105d, tracking coils 106a-106d, focusing coils
`107a-107d, a suspension holder 108, and a fixation base
`109. The object lens 101, the lens holder 102, and the
`permanent magnets 103a and 103b constitute a movable
`section 550. A first end of each suspension wire 104 is 55
`attached to the movable section 550 while one end of each
`suspension wire 104 is attached to the suspension holder
`108.
`Referring to FIG. 12, moving directions of the movable
`section 550 are defined. In FIG. 12, Fo indicates a focusing
`direction parallel to an optical axis; Tr a tracking direction
`perpendicular to the direction Fo; Rt a radial tilt which is a
`tilt around the axis of a tangential direction; and Tt a
`tangential tilt which is a tilt around the axis of the tracking
`direction.
`Now the operation of the conventional object lens driving
`apparatus 500 will be described with reference to FIG. 11.
`
`2
`The movable section 550 is driven toward the tracking
`direction Tr by electromagnetic forces generated by electric
`currents through the tracking coils 106a-106d traversing in
`a direction perpendicular to the magnetic flux of the perma-
`5 nent magnets 103a and 103b. Since the tracking coils
`106a-106d are fixed on the base 109, the movable section
`550 performs its relative substantially translational move(cid:173)
`ment.
`The movable section 550 is also driven toward the focus-
`10 ing direction Fo by electromagnetic forces generated by
`electric currents through the focusing coils 107a-107d tra(cid:173)
`versing in a direction perpendicular to the magnetic flux of
`the permanent magnets 103a and 103b, performing its
`substantially translational movement.
`Furthermore, the movable section 550 is driven along the
`direction of the radial tilt Rt by the moment Mr of a force
`around the Y axis produced by applying to the movable
`section 550 a driving force in the direction Fo by the
`focusing coils 107a and 107c and a driving force in the
`direction Fo, but in the opposite direction, by the focusing
`coils 107b and 107d. According to this, it is possible to
`correct the radial tilt.
`To enhance the recording capacity of an optical informa(cid:173)
`tion recording and/or reproduction apparatus using disks, a
`condensed light spot used for recording and reproducing
`information to and from the disk has been increasingly made
`narrower by adopting an object lens having a higher aperture
`ratio. In this case, the optical aberration caused by the
`relative tilt of the optical axis of the object lens to the surface
`of the disk increases in proportion to the third power of the
`aperture ratio. To obtain satisfactory recording and repro-
`duction signals, it is therefore required to correct the tilt of
`the optical axis of the object lens to the disk.
`Although the above-described structure makes it possible
`to correct a tilt in a radial direction caused by the warp of a
`disk and the like, so-called radial tilt, it is difficult to correct
`a tilt in a tangential direction caused by the bend of a disk,
`so-called tangential tilt.
`The present invention is provided to solve the above
`problems with the conventional object lens driving device.
`
`40
`
`SUMMARY OF THE INVENTION
`
`45
`
`According to one aspect of the present invention, an
`object lens driving device includes a movable section,
`supporting sections for supporting the movable section and
`a base for holding the supporting sections. The movable
`section includes an object lens for recording and/or repro(cid:173)
`ducing optical information to and/or from a disk-shaped
`recording medium, a lens holder for holding the object lens
`and at least four permanent magnets adhered to the lens
`holder. The supporting sections include at least four metal
`wires substantially parallel to each other, each wire having
`a first end fixed to the lens holder and a second end
`connected to the base, and elastic deformable elements
`connected to the base and having connecting sections
`thereof connected to the second end of each respective metal
`wire. The base includes yokes fixed to the base and facing
`the respective permanent magnets, focusing coils wound
`60 around the respective yokes, wound axes of the focusing
`coils being oriented in a direction of an optical axis of the
`object lens, and tracking coils wound around the respective
`yokes, wound axes of the tracking coils being oriented in a
`direction perpendicular to the wound axes of the focusing
`65 coils.
`In one embodiment of the present invention, the object
`lens driving further includes a control section for applying
`
`

`
`6,134,058
`
`4
`In another embodiment of the present invention, the
`elastic deformable element is hinge-shaped.
`In still another embodiment of the present invention, the
`elastic deformable element has a pivotal axis and deforms by
`twisting around the pivotal axis so that the main body of the
`lens holder pivots in a tangential tilt direction. The elastic
`deformable element is provided so that the pivotal axis
`passes through a center of mass of the movable section.
`In still another embodiment of the present invention, the
`elastic deformable element has a pivotal axis and deforms by
`twisting around a pivotal axis so that the main body of the
`lens holder pivots in a tangential tilt direction. The elastic
`deformable element is provided so that the pivotal axis
`passes through a principal point of the object lens.
`In still another embodiment of the present invention, the
`elastic deformable element includes a fiat spring that has a
`pivotal axis and deforms by twisting around the pivotal axis
`so that the main body of the lens holder pivots in a tangential
`tilt direction, and the fiat spring is covered with a damping
`material.
`In still another embodiment of the present invention, a
`returning force generated by a pivotal movement of the
`elastic deformable element is greater than at least a magnetic
`force of attraction around the pivotal axis generated between
`the yoke and the permanent magnet.
`Thus, the invention described herein makes possible the
`advantages of (1) providing an object lens driving device
`which can correct positions of a movable section with
`30 respect to a disk in a tangential tilt direction, as well as a
`focusing direction, a tracking direction and a radial tilt
`direction; and (2) providing an object lens driving device
`which has optimal drive characteristics by providing design
`freedom of a spring constant defining sensitivity in a low-
`35 frequency region (first-order resonant frequency region) for
`tangential tilt correction.
`These and other advantages of the present invention will
`become apparent to those skilled in the art upon reading and
`understanding the following detailed description with refer-
`40 ence to the accompanying figures.
`
`20
`
`15
`
`3
`electric currents to the respective focusing coils, in which
`the control section switches directions of the electric cur(cid:173)
`rents to drive the lens holder in a focusing direction, a radial
`tilt direction and a tangential tilt direction.
`In another embodiment of the present invention, the 5
`elastic deformable elements are board-shaped or rod-shaped
`and the connecting sections are elastic-deformable so that
`the second end of each respective metal wire can displace
`along an axial direction of the metal wire.
`In still another embodiment of the present invention, the 10
`yokes are provided to face the respective permanent magnets
`along the axial direction of the metal wire. The yokes and the
`permanent magnets are provided so that forces of tension act
`on the metal wires. The forces of tension are generated by
`the addition of magnetic forces of attraction between the
`yokes and the permanent magnets.
`In still another embodiment of the present invention,
`distances between the yokes and the permanent magnets are
`provided so that forces of tension act on the metal wires.
`In still another embodiment of the present invention,
`thicknesses of the yokes along the axial direction of the
`metal wire are provided so that forces of tension act on the
`metal wires.
`In still another embodiment of the present invention,
`spring forces necessary for the connecting sections to 25
`deform along axial directions of the respective metal wires
`are greater than at least the respective magnetic forces of
`attraction.
`In still another embodiment of the present invention, the
`lens holder includes relaying elements, the first end of the
`metal wire being connected to each relaying element, a main
`body of the lens holder for holding the object lens and elastic
`deformable elements for interconnecting the main body of
`the lens holder and the relaying elements, deforming so that
`the main body of the lens holder pivots in a tangential tilt
`direction.
`According to another aspect of the present invention, an
`object lens driving device includes a movable section,
`supporting sections for supporting the movable section and
`a base for holding the supporting sections. The movable
`section includes an object lens for recording and/or repro(cid:173)
`ducing optical information to and/or from a disk-shaped
`recording medium, a lens holder for holding the object lens
`and at least two permanent magnets adhered to the lens
`holder. The supporting sections include at least four metal 45
`wires substantially parallel to each other, each wire having
`a first end fixed to the lens holder and a second end
`connected to the base. The base includes yokes fixed to the
`base and facing the respective permanent magnets, focusing
`coils wound around the respective yokes, wound axes of the
`focusing coils being oriented in a direction of an optical axis
`of the object lens, and tracking coils wound around the
`respective yokes, wound axes of the tracking coils being
`oriented in a direction perpendicular to the wound axes of
`the focusing coils. The lens holder includes relaying 55
`elements, the first end of the metal wire being connected to
`each relaying element, a main body of the lens holder for
`holding the object lens and elastic deformable elements for
`interconnecting the main body of the lens holder and the
`relaying elements, deforming so that the main body of the 60
`lens holder pivots in a tangential tilt direction.
`In one embodiment of the present invention, the elastic
`deformable element includes a fiat spring that has a pivotal
`axis and deforms by twisting around the pivotal axis so that
`the main body of the lens holder pivots in a tangential tilt 65
`direction, the fiat spring having L-shaped or +-shaped cross(cid:173)
`section thereof.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1A is a perspective view illustrating a portion of a
`structure of an object lens driving device according to
`Example 1 of the present invention.
`FIG. 1B is a perspective view illustrating another portion
`of a structure of an object lens driving device according to
`Example 1 of the present invention.
`FIG. 2A is a schematic diagram illustrating a radial tilt
`50 movement in Example 1 of the present invention.
`FIG. 2B is a side view illustrating a radial tilt movement
`in Example 1 of the present invention.
`FIG. 2C is a side view illustrating a radial tilt movement
`in a direction +Rt in Example 1 of the present invention.
`FIG. 2D is a side view illustrating a radial tilt movement
`in a direction -Rt in Example 1 of the present invention.
`FIG. 3A is a schematic diagram illustrating a tangential
`tilt movement in Example 1 of the present invention.
`FIG. 3B is a side view illustrating a tangential tilt move(cid:173)
`ment in Example 1 of the present invention.
`FIG. 3C is a side view illustrating a tangential tilt move(cid:173)
`ment in a direction +Tt in Example 1 of the present inven(cid:173)
`tion.
`FIG. 3D is a side view illustrating a tangential tilt move(cid:173)
`ment in a direction -Tt in Example 1 of the present inven(cid:173)
`tion.
`
`

`
`6,134,058
`
`5
`FIG. 4Ais a schematic diagram illustrating connections of
`focusing coils and directions of electric currents for a drive
`in a focusing direction Fo in Example 4 of the present
`invention.
`FIG. 4B is a schematic diagram illustrating connections of
`focusing coils and directions of electric currents for a drive
`in a radial direction Rt in Example 4 of the present invention.
`FIG. 4C is a schematic diagram illustrating connections of
`focusing coils and directions of electric currents for a drive
`in a tangential direction Tt in Example 4 of the present
`invention.
`FIG. SA is a schematic diagram illustrating directions of
`electric currents for a drive in a focusing direction Fo in
`Example 4 of the present invention.
`FIG. 5B is a schematic diagram illustrating directions of
`electric currents for a drive in a radial direction Rt in
`Example 4 of the present invention.
`FIG. 5C is a schematic diagram illustrating directions of
`electric currents for a drive in a tangential direction Tt in 20
`Example 4 of the present invention.
`FIG. 6A is a schematic diagram illustrating a structure of
`an object lens driving device according to Example 2 of the
`present invention.
`FIG. 6B is a schematic diagram illustrating a structure of 25
`an object lens driving device according to Example 3 of the
`present invention.
`FIG. 7 is a perspective view illustrating a structure of an
`object lens driving device according to Example 4 of the 30
`present invention.
`FIG. 8 is an exploded perspective view illustrating a
`definition of drive directions in Example 4 of the present
`invention.
`FIG. 9 is an exemplary diagram illustrating rotation
`around a rotational axis for a tangential drive according to
`Example 4 of the present invention.
`FIG. 10 is a schematic diagram illustrating an object lens
`driving device employing hinges as elastic deformable ele(cid:173)
`ments according to Example 4 of the present invention.
`FIG. 11 is a perspective view illustrating a structure of an
`object lens driving device in the prior art.
`FIG. 12 is a diagram for explaining definitions of refer(cid:173)
`ence symbols in the present specification.
`
`6
`direction; ±Fa-±Fd directions of electric current through the
`focusing coils 7a-7d, respectively; and ±Ta-±Td directions
`of electric currents through the tracking coils 6a-6d, respec(cid:173)
`tively. Note that the above directions of electric currents
`5 having negative signs are not shown. The Tr to Tt directions
`have been previously defined with reference to FIG. 12.
`The object lens 1, the lens holder 2, and the permanent
`magnets 3a-3d constitute a movable section 150. A first end
`of each suspension wire 4 is attached to the movable section
`10 150 while a second end of each suspension wire 4 is attached
`to the tilt spring 10. The tilt spring 10 is further fixed to the
`fixation base 9 via the suspension holder 8. The movable
`section 150 is driven by electromagnetic forces generated by
`interaction of magnetic fields of the permanent magnets
`3a-3d adhered thereto and electric currents past through the
`15 tracking coils 6a-6d and the focusing coils 7a-7d made by
`winding wire around the yokes 5a-5d fixed to the fixation
`base 9.
`Next, the movement and driving of the movable section
`150 will be described with reference to FIGS. lA and lB. As
`shown in FIGS. lA and lB, the movable section 150 is
`supported by the four suspension wires 4 so that it can
`perform translational movements in the Fo and Tr directions.
`Each direction is defined in FIG. 12.
`The force of driving the movable section 150 toward the
`focusing direction +Fo is generated by electric currents
`flowing through the focusing coils 7 a-7 d toward the direc-
`tions +Fa, +Fb, +Fe and +Fd, respectively. Then, the mov(cid:173)
`able section 150 translationally moves toward the focusing
`direction +Fo. The force of driving the movable section 150
`toward the tracking direction + Tr is generated by electric
`currents flowing through the focusing coils 6a-6d toward
`the directions + Ta, + Tb, + Tc and + Td, respectively. Then,
`the movable section 150 translationally moves toward the
`35 direction + Tr.
`Next, the driving and supporting of the movable section
`150 in the radial tilt direction Rt will be described with
`reference to FIGS. 2A-2D. FIG. 2A is a partial perspective
`view illustrating the movable section 150, the suspension
`40 wires 4 and the tilt spring 10. FIGS. 2B-2D are side views
`of the movable section 150 as seen in the direction of an
`arrow VR of FIG. 2A.
`In FIGS. 2A-2D, reference symbol Y indicates theY axis
`defined in FIG. 12; r indicates the distance between theY
`45 axis and the center of the suspension wire 4; ±Mr the
`moment of a force around the Y axis acting on the movable
`section 150; 4' positions of the suspension wires 4 after they
`have been driven toward the radial tilt direction Rt; and
`±Foa-Fod driving forces acting on the movable section 150.
`In FIG. 2A, the driving forces -Foa, +Fob, -Foe and +Fod
`are produced by electric currents flowing through the focus(cid:173)
`ing coils 7a-7d of FIGS. lA and lB in the directions -Fa,
`+Fb, -Fe and +Fd, respectively. Movements of the movable
`section 150 in the radial tilt direction when the driving forces
`55 -Foa, +Fob, -Foe and +Fod act on the movable section 150
`will be described with reference to FIGS. 2B-2D. FIG. 2B
`illustrates a state (initial state) of the movable section 150
`when no driving force acts thereon. FIGS. 2C and 2D
`illustrate states of the movable section 150 with radial tilts
`60 Rt.
`As shown in FIG. 2C, the addition of the driving forces
`-Foa, +Fob, -Foe and +Fod acts on the movable section 150
`as the moment of the force +Mr around the Y axis. The
`moment of the force +Mr makes each suspension wire 4
`twisted in such a way that the end of the suspension wire 4
`attached to the movable section 150 follows along a circle
`with the radius r.
`
`50
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Examples of the present invention will be described
`below with reference to the accompanying drawings.
`
`EXAMPLE 1
`
`FIGS. lA and lB are perspective views of an object lens
`driving device 100 according to Example 1 of the present
`invention. FIGS. 2A-2D are schematic diagrams illustrating
`radial tilt movements of a movable section. FIGS. 3A-3D
`are schematic diagrams illustrating tangential tilt move(cid:173)
`ments of the movable section.
`Referring to FIGS. lA and lB, the device 100 includes an
`object lens 1, a lens holder 2 for holding the object lens 1,
`permanent magnets 3a-3d adhered to the lens holder 2,
`suspension wires 4, opposed yokes 5a-5d, tracking coils
`6a-6d, focusing coils 7a-7d, a suspension holder 8, a
`fixation base 9, and a tilt spring 10. Reference symbols
`Ha-Hd indicate directions of magnetization of the perma- 65
`nent magnets 3a-3d; Tr a tracking direction; Fo a focusing
`direction; Rt a radial tilt direction: Tt a tangential tilt
`
`

`
`6,134,058
`
`8
`elastic supporting element and the suspension wires 4 are
`combined into an integral unit, thereby obtaining the same
`functions and effects. Furthermore, when the rod-like elastic
`supporting element and the suspension wires 4 are
`integrated, the tilt spring 10 effectively becomes unneces(cid:173)
`sary.
`FIGS. 4A-4C are schematic diagrams illustrating the
`directions of electric currents through the focusing coils
`7a-7d and the connections between the focusing coils 7a-7d
`10 and a focusing coil driving circuit 11. Referring to FIGS.
`4A-4C, the focusing coil driving circuit 11 controls the
`directions and amounts of electric currents through the
`focusing coils 7a-7d, respectively.
`FIG. 4A illustrates directions of electric currents through
`the focusing coils 7 a-7 d for driving the movable section 150
`toward the focusing direction Fo. FIG. 4B illustrates direc(cid:173)
`tions of electric currents through the focusing coils 7a-7d
`for driving the movable section 150 toward the radial tilt
`direction Rt. FIG. 4C illustrates directions of electric cur-
`20 rents through the focusing coils 7a-7d for driving the
`movable section 150 toward the tangential tilt direction Tt.
`The focusing coils 7a-7d and the focusing coil driving
`circuit 11 are connected as shown in FIGS. 4A-4C. This
`connection is such that when the movable section 150 is
`25 driven toward the focusing direction Fo, electric currents
`flow through the focusing coils 7 a-7 d as if the focusing coils
`7a-7d are connected as shown in FIG. SA
`When the movable section 150 is driven toward the radial
`tilt direction Rt, electric currents flow through the focusing
`coils 7a-7d as if the focusing coils 7a-7d are connected as
`shown in FIG. 5B. The direction of electric currents through
`the focusing coils 7a and 7c is opposite to that through the
`focusing coils 7b and 7d.
`When the movable section 150 is driven toward the
`tangential tilt direction Tt, electric currents flow through the
`focusing coils 7a-7d as if the focusing coils 7a-7d are
`connected as shown in FIG. 5C. The direction of electric
`currents through the focusing coils 7a and 7b is opposite to
`that through the focusing coils 7c and 7d.
`It should be noted that the amounts of driving currents
`through the focusing coils 7a-7d may be changed based on
`focusing error signals or tracking error signals, thereby
`obtaining satisfactory control features.
`
`30
`
`7
`FIG. 2D illustrates the movable section 150 driven by the
`moment of the force -Mr in a direction opposite to the
`moment of the force +Mr of FIG. 2C. The moment of the
`force -Mr is produced by electric currents flowing through
`the focusing coils 7a-7d in the opposite directions to those 5
`in the case of FIG. 2C.
`As described above, the movable section 150 is supported
`by the deformable suspension wires 4 so that the movable
`section 150 can be driven in the radial direction Rt by
`controlling the directions of flow of electric currents through
`the focusing coils 7a-7d.
`Next, the driving and supporting of the movable direction
`150 in the tangential tilt direction Tt will be described with
`reference to FIGS. 3A-3D. FIG. 3A is a partial perspective
`view illustrating the movable section 150, the suspension 15
`wires 4 and the tilt spring 10. FIGS. 3B-3D are side views
`of the movable section 150 as seen in the direction of an
`arrow Vt of FIG. 3A.
`In FIGS. 3A-3D, reference numeral lOa indicates pivotal
`axes of the deformable tilt spring 10; 4A fixation sections of
`the suspension wires 4 at which a second end of each
`suspension wire 4 is fixed to the tilt spring 10; X the X axis
`defined in FIG. 6; ±Mt the moment of a force around the X
`axis acting on the movable section 150; and ±Foa-±Fod
`driving forces acting on the movable section 150.
`In FIG. 3A, the driving forces +Faa, +Fob, -Foe and -Fad
`are produced by electric currents flowing through the focus(cid:173)
`ing coils 7a-7d of FIGS. lA and lB in the directions +Fa,
`+Fb, -Fe and -Fd, respectively. Movements of the movable
`section 150 in the tangential tilt direction when the driving
`forces +Foa, +Fob, -Foe and -Fod act on the movable
`section 150 will be described with reference to FIGS.
`3B-3D.
`FIG. 3B illustrates a state (initial state) of the movable 35
`section 150 when no driving force acts thereon. FIGS. 3C
`and 3D illustrate states of the movable section 150 with the
`tangential tilts Tt. As described in FIG. 3C, the addition of
`the driving forces +Foa, +Fob, -Foe and -Fod acts on the
`movable section 150 as the moment of the force +Mt around 40
`the X axis. The moment of the force +Mt acts on each
`suspension wire 4 as a buckling force of tension and
`compression. As shown in FIGS. 3C and 3D, the tilt spring
`10 Is deformed around the pivotal axes lOa.
`The fixation section 4A of the suspension wire 4 is 45
`displaced in the tension or compression direction by the
`deformation of the tilt spring 10. Thus, the movable section
`150 can move along the tangential tilt direction Tt in
`proportion to the amount of the displacement of the fixation
`section 4A.
`As described above, according to Example 1, the driving
`means are d