JP2012002982A - Lens drive unit, imaging apparatus, and portable terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens drive unit surely capable of moving an imaging lens with a simple configuration and without any subtle balance setting with respect to an energizing force of an energizing member; an imaging apparatus having the lens drive unit; and a portable terminal having the imaging apparatus.SOLUTION: The lens drive unit includes: an imaging lens for guiding subject light; an energizing member for energizing the imaging lens in a direction of the optical axis; a piezoelectric element formed into a plate shape and arranged to elongate in a direction perpendicular to the optical axis of the imaging lens when a potential difference is applied between the front and the back; and a blocking member blocking the elongation of the piezoelectric element. When the piezoelectric element is elongated, the lens drive unit bends the piezoelectric element in the direction of the optical axis by blocking the elongation thereof with the blocking member, and moves the imaging lens at the bent portion in the direction of the optical axis against the energizing force of the energizing member.

Description

  The present invention relates to a lens driving device using a piezoelectric element, an imaging device including the lens driving device, and a portable terminal including the imaging device.

  Conventionally, a small and thin imaging device is mounted on a portable terminal such as a cellular phone, and it is possible to transmit not only shooting but also audio information as well as image information to a remote place. . Some of such imaging devices include a lens driving device for moving the imaging lens along the optical axis so as to enable autofocus imaging.

  As an actuator for driving a lens of such a small and thin imaging device, an actuator using a shape memory alloy or a piezoelectric element is known (for example, see Patent Document 1).

JP 2010-85798 A

  Since the lens driving device described in Patent Document 1 uses a plate-like actuator, the imaging device can be made thin.

  However, it is a cantilever structure in which one end portion of the piezoelectric element is fixed and the other end portion is a free end (driving portion) while urging the imaging lens in a predetermined direction, and deformation of the free end is used. The imaging lens is moved, and the piezoelectric element has a deformed shape different from the deformed shape of the free end when there is no biasing force. Specifically, if the urging force is too strong, the amount of movement of the lens group is insufficient even if the urging force is deformed, and if the urging force is too weak, there is a problem in the posture difference that the lens group moves depending on the posture. That is, the balance setting between the deformed shape of the piezoelectric element and the urging force of the urging member becomes very delicate.

  In view of the above problems, an object of the present invention is to provide a lens driving device that can move an imaging lens reliably with a simple configuration and does not require delicate balance setting with a biasing force of a biasing member. An object of the present invention is to provide an imaging device including a driving device and a portable terminal including the imaging device.

  The above object is achieved by the following configuration.

  (1) An imaging lens that guides subject light, an urging member that urges the imaging lens in the optical axis direction, and a plate-like shape that is orthogonal to the optical axis of the imaging lens when a potential difference is applied between the front and back surfaces. A piezoelectric element disposed so as to extend in the direction of extending, and a blocking member that prevents the piezoelectric element from extending, and when the piezoelectric element expands, the blocking member prevents the expansion by A lens driving device characterized in that a piezoelectric element is bent in the optical axis direction, and the imaging lens is moved in the optical axis direction against the biasing force of the biasing member at the curved portion.

  (2) The lens driving device according to (1), wherein the piezoelectric element is formed of a translucent member and is disposed across a light beam path of the imaging lens.

  (3) The lens driving device according to (1), wherein the piezoelectric element is formed of a light-shielding member and has an opening at a portion corresponding to a light beam path of the imaging lens.

  (4) An imaging apparatus comprising: an imaging element that photoelectrically converts subject light guided to the imaging lens; and the lens driving device according to any one of (1) to (3).

  (5) A portable terminal comprising the imaging device according to (4).

  According to the present invention, it is possible to provide a lens driving device that can move the imaging lens reliably with a simple configuration and does not require delicate balance setting with the biasing force of the biasing member. It is possible to provide an imaging device provided with a portable terminal equipped with the imaging device.

It is a perspective view of the imaging device concerning a 1st embodiment. It is the figure which showed typically the cross section containing the optical axis of the imaging lens of the imaging device which concerns on 1st Embodiment (AA cross section shown in FIG. 1). It is a schematic diagram which shows the piezoelectric element which concerns on 1st Embodiment. It is sectional drawing which shows the state of a piezoelectric element and the imaging lens at the time of potential difference provision to a piezoelectric element. It is a perspective view of the imaging device concerning a 2nd embodiment. It is the figure which showed typically the cross section containing the optical axis of the imaging lens of the imaging device which concerns on 2nd Embodiment (BB cross section shown in FIG. 5). It is a schematic diagram which shows the piezoelectric element which concerns on 2nd Embodiment. It is an external view of the mobile telephone which is an example of the portable terminal provided with the imaging device which concerns on this Embodiment. It is a figure which shows an example of the control block of a mobile telephone.

  Hereinafter, the present invention will be described with reference to embodiments, but the present invention is not limited thereto.

(First embodiment)
FIG. 1 is a perspective view of an imaging apparatus 50 according to the first embodiment.

  As illustrated in FIG. 1, the imaging device 50 includes an imaging lens 10 that forms a subject image on a photoelectric conversion unit of the imaging element, a casing 53 including a light shielding member, an imaging element cover 55 that includes the imaging element, A support substrate 52a for holding the image sensor and a flexible printed circuit board 52b having an external connection terminal (also referred to as an external connection terminal) 54 for transmitting and receiving the electrical signal are integrally formed.

  FIG. 2 is a diagram schematically showing a cross section including the optical axis O of the imaging lens of the imaging apparatus 50 according to the first embodiment (cross section AA shown in FIG. 1).

  In FIG. 2, reference numeral 51 denotes an image sensor, in which pixels (photoelectric conversion elements) are two-dimensionally arranged at the center of the light receiving side surface, and a signal processing circuit is formed around the pixels.

  A large number of pads (not shown) are provided in the vicinity of the outer edge of the light receiving side surface of the image sensor 51, and are connected to the support substrate 52 a via bonding wires W. The image sensor 51 converts the signal charge from the photoelectric conversion unit into an image signal such as a digital YUV signal, and outputs the image signal to a predetermined circuit on the support substrate 52a via the bonding wire W.

  As the image sensor 51, a CMOS image sensor or a CCD image sensor is used.

  One end of the substrate 52 is connected to the other surface of the support substrate 52a (the surface opposite to the image sensor 51) of the hard support substrate 52a that supports the image sensor 51 and the housing 53 on one surface. It is comprised with the flexible printed circuit board 52b. The support substrate 52a is provided with a large number of signal transmission pads on both the front and back surfaces, and is connected to the imaging device 51 via bonding wires W on one surface and to the flexible printed circuit board 52b on the other surface. .

  As shown in FIG. 1, the flexible printed board 52b has one end connected to the support board 52a. Further, the support substrate 52a and an external circuit (not shown) (for example, a control circuit included in a host device on which the imaging device is mounted) are connected via an external connection terminal 54 provided at the other end. Via this external connection terminal 54, it is possible to receive a voltage and a clock signal for driving the image sensor 51 from an external circuit, and to output a digital YUV signal to the external circuit. Further, the flexible printed circuit board 52b has flexibility and an intermediate portion is deformed to give a degree of freedom to the orientation and arrangement of the external connection terminals 54 with respect to the support board 52a.

  The support substrate 52a is provided with an image sensor cover 55 made of a light-shielding material that encloses the image sensor 51, and a cover glass 56 is fixed to the opening. The imaging element cover 55 and the cylindrical casing 53 are fixed, and a cylindrical lens frame 57 that holds the imaging lens 10 is disposed in the casing 53 so as to be movable in the optical axis direction. The lens frame 57 is biased toward the image sensor 51 by a coil spring 58 that is a biasing member.

  A piezoelectric element 60 is disposed between the image sensor cover 55 and the lens frame 57 in the housing 53. The piezoelectric element 60 is formed in a plate shape, and is incorporated so that the extending direction when a potential difference is applied between the front and back surfaces is a direction orthogonal to the optical axis O of the imaging lens 10. The piezoelectric element 60 is formed of a light-transmitting member, is fitted into the inner diameter of the housing 53 and is formed in a substantially circular shape, and is disposed across the light beam path of the imaging lens 10. The piezoelectric element 60 has transparent electrodes formed on the imaging lens side surface and the imaging element side surface, respectively, and a constant voltage circuit (not shown) is provided so that a potential difference can be applied to the transparent electrode. Is connected.

  Although not shown, a filter or coating for cutting infrared light is provided on either the surface of the imaging lens 10 closest to the subject to the surface of the cover glass 56 facing the imaging lens 10.

  FIG. 3 is a schematic diagram showing the piezoelectric element 60 according to the first embodiment. 3A is a cross-sectional view of the piezoelectric element 60 cut along a plane including the optical axis O, and FIGS. 3B and 3C are front views as viewed from the optical axis O direction.

  A piezoelectric element 60 shown in FIG. 3A is obtained by forming transparent electrodes 62 on both surfaces of a translucent organic piezoelectric body 61.

  The organic piezoelectric body 61 is described in JP-A-8-36917, JP-A-2005-213376, JP-A-2003-28283, JP-A-2006-49418, JP-A-2009-267528, and the like. Polyvinylidene fluoride (PVDF), vinylidene fluoride-trifluoroethylene (VDF / TrFE) copolymer, vinylidene fluoride tetrafluoroethylene (VDF-TeFE) copolymer, vinylidene cyanide-vinyl acetate copolymer, Nylon-11, PZT-vinylidene fluoride copolymer, PZT-polyoxymethylene, or the like that develops piezoelectricity by applying a DC electric field called poling treatment to the film and aligning the dipoles in one direction, (Polyglutarate γ-benzyl), poly (glutarate γ-methyl) Examples thereof include a peptide, a cellulose derivative such as cellulose acetate and cyanoethyl cellulose, and an optically active polymer such as polylactic acid, polypropylene oxide, and poly (β-hydroxybutyric acid) that exhibits piezoelectricity by mechanical stretching.

  In addition, a polylactic acid resin (polylactic acid, a copolymer of a polyfunctional compound copolymerizable with lactic acid and a mixture thereof), a diisocyanate compound, or a diisocyanate compound and a diamine compound are combined with an inorganic compound. Polymer piezoelectric material obtained by connecting and cross-linking by a cross-linking agent under the application of an electric field using urea resin such as prepolymer as a raw material monomer, fullerenol-introduced polyurethane elastomer, and bifunctional polar cross-linking agent A known organic piezoelectric substance can be used.

  Examples of the transparent electrode 62 include inorganic oxides such as tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), aluminum-doped tin oxide, and indium-doped zinc oxide (IZO). A conductive polymer typified by a sputtering method or polystyrene sulfonate-doped polyethylene dioxythiophene (PEDOT / PSS) is formed using various wet coating methods.

  For example, a constant voltage circuit as shown in FIG. 3A is connected to the transparent electrode 62 formed on the translucent organic piezoelectric body 61 so that a potential difference can be applied between the front and back sides. 3A, VIN is a DC power supply, Tr is a transistor, r1 and r2 are resistors, C is a capacitor, CM is a comparator, and 70 is a reference voltage generation circuit. In the example shown in FIG. 3A, a voltage is applied to one surface and the other surface is grounded (0 V) to apply a potential difference. However, a positive voltage is applied to one surface. Then, a potential difference may be applied by applying a negative voltage to the other surface.

  The piezoelectric element 60 used in the lens driving device according to the first embodiment shown in FIG. 3 extends in a plane as shown by a broken line when a potential difference is applied to a transparent electrode in a free state. Is. As a form of extension, one extending in a predetermined direction as shown in FIG. 3B or one extending in all directions as shown in FIG. 3C can be used. The piezoelectric element 60 is incorporated in the casing 53 of the imaging device 50 shown in FIG. 2 so that the extending direction is perpendicular to the optical axis O.

  FIG. 4 is a cross-sectional view showing the state of the piezoelectric element 60 and the imaging lens 10 when a potential difference is applied to the piezoelectric element 60. 4A shows a state when no potential difference is applied to the piezoelectric element 60 as in FIG. 2, and FIG. 4B shows a state when a potential difference is applied to the piezoelectric element 60.

  When a potential difference is not applied to the piezoelectric element 60, as shown in FIG. 4A, the piezoelectric element 60 is not elongated, is fitted into the inner diameter of a substantially circular and cylindrical casing 53, and is approximately It is a flat state. At this time, the cylindrical lens frame 57 is urged in the direction of the image sensor 51 by the urging force of the coil spring 58, and becomes a position on the image sensor 51 side by contact of the stopper 57s with the housing 53 in the optical axis direction. Yes. The position of the imaging lens 10 at this time is, for example, a position that focuses on a predetermined distance between the hyperfocal distance, infinity, and the hyperfocal distance and infinity.

  When a potential difference is applied to the piezoelectric element 60, the piezoelectric element 60 expands as shown in FIG. 3, but since it is fitted to the inner diameter of the casing 53, the planar extension in the direction perpendicular to the optical axis O is not the casing. 53. For this reason, there is no escape space for the extension amount, and the piezoelectric element 60 is curved as shown in FIG. Due to this bending, the lens frame 57 is moved against the urging force of the coil spring 58, and becomes a position on the subject side by contact of the stopper 57s with the housing 53 in the optical axis direction. At this time, the position of the imaging lens 10 is a position that focuses on a close distance.

  In other words, the imaging apparatus according to the first embodiment has a piezoelectric element formed of a translucent member, has a large area that crosses the light path of the imaging lens, and extends in a direction perpendicular to the optical axis of the imaging lens. Provided with a lens driving device that is arranged so as to extend, and is configured to bend in the optical axis direction by blocking the extension direction with a blocking member and move the lens frame in the optical axis direction at the curved portion. It is a thing.

  Accordingly, not only can a large deformation amount of the piezoelectric element having a large area be used, but also a cantilever structure is not required, so that the driving force for moving the lens frame due to deformation during bending can be sufficient. Accordingly, it is possible to provide a lens driving device that can move the imaging lens reliably with a simple configuration without requiring a delicate balance setting with the biasing force of the biasing member.

  In this example, the housing 53 corresponds to a blocking member that prevents the piezoelectric element 60 from extending. However, the present invention is not limited to this, and a blocking member may be provided exclusively or other members. You may comprise so that it may be performed.

  Further, in the present application, “having translucency” and “transparent” indicate that the transmittance in the visible light region (wavelength 400 nm to 700 nm) is 50% or more.

(Second Embodiment)
FIG. 5 is a perspective view of the imaging apparatus 50 according to the second embodiment.

  The imaging device 50 shown in FIG. 5 is different from the imaging device 50 shown in FIG. 1 in that the housing 53 has a prismatic inner shape and a mirror frame (not shown) is included in the housing 53, and the light It can be moved in the direction of the axis O.

  FIG. 6 is a diagram schematically showing a cross section including the optical axis O of the imaging lens of the imaging device 50 according to the second embodiment (cross section BB shown in FIG. 5). Regarding the cross section of the imaging device 50 shown in FIG. 6, only the parts different from those shown in FIG. 2 will be described.

  A piezoelectric element 60 is incorporated at the same position as in FIG. 2 in the imaging device 50 shown in FIG. 6, but the outer shape of the piezoelectric element 60 is formed in a substantially rectangular shape, and the imaging lens 10 is further configured. An opening 60k is formed in a portion corresponding to the light beam path.

  FIG. 7 is a schematic diagram showing a piezoelectric element 60 according to the second embodiment. FIG. 7A is a cross-sectional view of the piezoelectric element 60 cut along a plane including the optical axis, and FIGS. 7B and 7C are front views as seen from the direction of the optical axis O. FIG. These are figures which show a deformation | transformation state when expansion | extension is blocked | prevented by two opposing sides at the time of expansion | extension.

  As shown in FIG. 7A, the piezoelectric element 60 has electrodes 62 formed on both surfaces of an organic piezoelectric body 61. For example, a constant voltage circuit as shown in FIG. 3A is connected to the electrode 62 formed on the organic piezoelectric body 61 so that a potential difference can be applied between the front and back sides. As a form of extension, when a potential difference is applied to the electrode 62 in a free state, as shown by a broken line in FIG. 7B, it extends in a plane so that the interval between two opposing sides is widened. Alternatively, as shown by a broken line in FIG. 7C, one that extends in a plane in all directions can be used.

  In the case of the piezoelectric element 60 that extends as shown by the broken line in FIG. 7B, the piezoelectric element 60 is fitted to the inner shape of the housing 53 at least in the extending direction without applying a potential difference. The outer shape of 60 is formed in a substantially rectangular shape. Further, an opening 60k is formed at a portion corresponding to the light path of the imaging lens 10. The piezoelectric element 60 is incorporated in the casing 53 of the imaging device 50 shown in FIG. 6 so that the extending direction is perpendicular to the optical axis O.

  When the piezoelectric element 60 shown in FIG. 7B is incorporated in the imaging device 50 and a potential difference is applied between the front and back electrodes, the piezoelectric element 60 expands so that the interval between two opposing sides widens. Since the extension is prevented by the casing 53 at both ends in the direction, it bends as shown in FIG. Due to this bending, the lens frame 57 can be moved against the urging force of the coil spring 58 in the same manner as shown in FIG.

  In the case of the piezoelectric element 60 extending as shown by the broken line in FIG. 7C, the piezoelectric element 60 is fitted with the inner shape of the housing 53 only in two opposing sides in a state where no potential difference is applied. The other two opposite sides are formed with a gap with respect to the inner shape of the housing 53 so that the extension is not prevented even if it is extended. Similarly, in the casing 53 of the imaging device 50 shown in FIG. 6, the extension direction is incorporated so as to be a direction orthogonal to the optical axis O.

  When the piezoelectric element 60 shown in FIG. 7C is incorporated in the imaging device 50 and a potential difference is applied between the front and back electrodes, the piezoelectric element 60 expands in all directions, but only two opposing sides expand. Since it is blocked, it bends as shown in FIG. Due to this bending, the lens frame 57 can be moved against the urging force of the coil spring 58 in the same manner as shown in FIG.

  In the second embodiment as well, the lens frame 57 is moved against the urging force of the coil spring 58 in the same manner as shown in FIG.

  As described above, the part corresponding to the light path of the imaging lens 10 is opened, and is arranged so as to extend in the direction perpendicular to the optical axis of the imaging lens. When the extension is extended, the extension direction is blocked by the blocking member. Thus, the lens driving device configured to bend in the optical axis direction and move the lens frame in the optical axis direction at the curved portion can achieve the same effect as described above. In this example as well, the housing 53 corresponds to a blocking member that prevents the piezoelectric element 60 from extending, but the present invention is not limited to this, and a blocking member may be provided exclusively or other members may be used. You may comprise as follows.

  In the case of a piezoelectric element that expands as shown in FIG. 7B, it is preferable to set the expansion direction when a potential difference is applied to the long side direction of the image sensor (long side direction of the opening). By setting in this way, the width H in the direction orthogonal to the extending direction can be increased, and the driving force for moving the lens frame due to deformation during bending can be increased.

  Further, in the case of a piezoelectric element that extends as shown in FIG. 7C, it is preferable to set so as to block the side indicated by L in the figure. By setting in this way, it is possible to increase the driving force for moving the lens frame due to deformation during bending.

  In addition, regarding the piezoelectric element 60 in the second embodiment, the organic piezoelectric body 61 and the electrode 62 may or may not have translucency, but it is more preferable to have light shielding properties. By having the light shielding property, the opening 60k serves as a diaphragm that shields unnecessary light, and the piezoelectric element 60 can be used both as an actuator and a diaphragm.

  In the first embodiment described above, a piezoelectric element having a circular outer shape is used, and in the second embodiment, a piezoelectric element having a rectangular outer shape is used. However, the present invention is not limited to this. Not. An elliptical or rectangular piezoelectric element may be used in the first embodiment, or a circular or elliptical piezoelectric element may be used in the second embodiment.

  In the first embodiment and the second embodiment described above, the mirror frame is biased in the direction of the image sensor by the biasing member, and the mirror resists the biasing force due to the bending of the piezoelectric element. Although the description has been made with the configuration in which the frame is moved in the subject direction, the present invention is not limited to this, and the lens frame is biased in the subject direction by a biasing member, and the lens frame is moved in the image sensor direction by the bending of the piezoelectric element. It is good also as a structure to which it moves.

  Further, in the first embodiment and the second embodiment described above, the example has been described in which the imaging lens is stopped at a position where the imaging lens is focused at two locations, that is, a long distance and a close distance. In addition, a configuration in which the stopper 57s is stopped at a position between the two positions where the stopper 57s does not contact the casing 53 and stopped at three or more positions is also possible.

  In this case, for example, a LUT (Look Up Table) that associates the potential difference with the bending amount of the piezoelectric element (the amount of movement of the imaging lens) is provided in advance, and the control signal shown in FIG. This can be done by inputting based on the LUT.

  FIG. 8 is an external view of a mobile phone 100 that is an example of a mobile terminal including the imaging device 50 according to the present embodiment.

  In the mobile phone 100 shown in the figure, an upper casing 71 as a case having display screens D1 and D2 and a lower casing 72 having an operation button 70 as an input unit are connected via a hinge 73. Yes. The imaging device 50 is built below the display screen D <b> 2 in the upper casing 71, and is arranged so that the imaging device 50 can capture light from the outer surface side of the upper casing 71.

  Note that the position of the imaging device may be disposed above or on the side of the display screen D2 in the upper casing 71. Of course, the mobile phone is not limited to a folding type.

  FIG. 9 is a diagram illustrating an example of a control block of the mobile phone 100.

  As shown in the figure, the imaging device 50 is connected to the control unit 101 of the mobile phone 100 via the flexible printed circuit board 52b, and outputs image signals such as luminance signals and color difference signals to the control unit 101.

  On the other hand, the mobile phone 100 controls each unit in an integrated manner, and executes a control unit (CPU) 101 that executes a program corresponding to each process, an operation button 70 that is an input unit for inputting a number and the like, Display screens D1 and D2 for displaying predetermined data and captured images, a wireless communication unit 80 for realizing various information communications with an external server, a system program for mobile phone 100, various processing programs, and a terminal A storage unit (ROM) 91 that stores necessary data such as an ID, and various processing programs and data executed by the control unit 101 or processing data, image data from the imaging device 50, and the like are temporarily stored. Or a temporary storage unit (RAM) 92 used as a work area.

  The image signal input from the imaging device 50 is subjected to predetermined processing and then stored in the nonvolatile storage unit (flash memory) 93 by the control unit 101 of the mobile phone 100 or the display screens D1 and D2. In addition, the image information is transmitted to the outside as image information via the wireless communication unit 80. Although not shown, the mobile phone 100 includes a microphone and a speaker for inputting and outputting audio.

DESCRIPTION OF SYMBOLS 10 Imaging lens 50 Imaging device 51 Imaging element 52 Board | substrate 53 Housing | casing 54 External connection terminal 55 Imaging element cover 56 Cover glass 57 Frame 57s Stopper 58 Coil spring 60 Piezoelectric element 62 Electrode 60k Opening part (piezoelectric element)
100 Mobile phone O Optical axis W Bonding wire

Claims (5)

An imaging lens that guides the subject light;
A biasing member that biases the imaging lens in the optical axis direction;
A piezoelectric element formed in a plate shape and arranged to extend in a direction perpendicular to the optical axis of the imaging lens when a potential difference is applied between the front and back surfaces;
A blocking member for blocking expansion of the piezoelectric element,
When the piezoelectric element expands, the blocking member prevents the expansion by bending the piezoelectric element in the optical axis direction, and the imaging lens resists the biasing force of the biasing member at the curved portion. Is moved in the direction of the optical axis.   The lens driving device according to claim 1, wherein the piezoelectric element is formed of a translucent member and is disposed across a light beam path of the imaging lens.   The lens driving device according to claim 1, wherein the piezoelectric element is formed of a light-shielding member and has an opening at a portion corresponding to a light beam path of the imaging lens. An image sensor that photoelectrically converts subject light guided to the imaging lens;
An imaging device comprising: the lens driving device according to claim 1.   A portable terminal comprising the imaging device according to claim 4.

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