Abstract:
A drive control circuit executes a cycle at least once while a first movable part moves one pitch of an electrode of a plurality of groups of electrodes, the cycle including a first operation for attracting the first movable part to a driving electrode substrate, a second operation for attracting the first movable part and a second movable part to stripe electrodes, a third operation for attracting the second movable part to the driving electrode substrate, and a fourth operation for attracting the first and second movable parts to the stripe electrodes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-287361, filed Sep. 30, 2002, the entire contents of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a zoom lens unit and a method of driving the same for driving lenses using an electrostatic actuator, and more particularly, to a zoom lens unit and a method of driving the same capable of separately controlling a plurality of movable parts.  
           [0004]    2. Description of the Related Art  
           [0005]    In recent years, assembling a camera unit having a zoom function in mobile equipment such as mobile phones has been examined. In such a camera unit, the focal point is adjusted by driving lenses, and an image is finally formed on a sensor. Electrostatic actuators may be used as a drive source for driving the lenses along the optical axis.  
           [0006]    The zoom lens unit adjusts the zoom magnification by driving a plurality of lenses. The electrostatic actuator includes, for example, a stationary part, a first movable part, and a second movable part, and each of the first and second movable parts holds a lens.  
           [0007]    The stationary part includes a driving electrode substrate and a holding electrode substrate attached to the upper and lower inner walls of a stationary part frame in FIG. 1. Further, the first and second movable parts are disposed such that they can be reciprocated in the axial direction of the lenses with a gap of several microns between the pair of electrode substrates.  
           [0008]    In the zoom lens unit configured as described above, the first and second movable parts can be driven by an electrostatic force by supplying a voltage to the electrodes of the pair of electrode substrates of the stationary part in a predetermined sequence using a switching circuit.  
           [0009]    The zoom lens unit described above has the following problems. That is, when the common electrode substrates are used with respect to the plurality of movable parts, the plurality of movable parts can be driven only separately, respectively, because one of the movable parts is driven by supplying the voltage to the driving electrode substrate in the predetermined sequence while holding the other of the movable parts by the holding electrode substrate.  
           [0010]    In the zoom lens unit, the respective lenses must trace a zoom curve based on predetermined lens design to vary the zoom magnification. When the zoom curve is traced, it is not preferable to separately drive the respective groups of lenses. This is because when the lenses are driven separately, the zoom magnification is not continuously varied at a constant speed and is changed intermittently, and the user gets the impression that the image is irregularly output onto a screen and it is difficult to view the image.  
           [0011]    When, for example, a second group of lenses acts to vary the zoom magnification and a first group of lenses acts to adjust the focal point, the zoom curve is traced in such a sequence that the magnification is varied by moving the second group of lenses first and then focusing is executed by driving the first group of lenses, thereby the magnification is varied intermittently.  
           [0012]    To prevent the above problem, the plurality of movable parts must be simultaneously driven in the same direction or in an opposite direction. However, to drive the plurality of movable parts independently, as many stationary parts as movable parts are required, which increases the volume of an actuator unit with an increase in its size. Note that there is a configuration by which the plurality of movable parts are driven independently by devising the disposition of the electrodes of the stationary part. In the configuration, however, a driving force may be in short supply.  
           [0013]    Further, when a plurality of movable parts are provided in other drive systems (for example, an electromagnetic device and a piezoelectric device), as many stationary parts as the movable parts are necessary, thereby the volume of the actuator unit is increased with an increase in its size.  
           [0014]    In contrast, when the plurality of movable parts are simultaneously driven using a cam mechanism and the like, it is difficult to drive the movable parts separately. Thus, it is difficult to adjust the focal point and to cope with a change of the focal point due to a change of temperature in an external environment which are required to a lens unit. In this case, a significant burden is placed on the selection of a lens material and on the optical design of lenses.  
         BRIEF SUMMARY OF THE INVENTION  
         [0015]    An object of the present invention is to drive a plurality of movable parts simultaneously in the same direction or in an opposite direction even if electrode substrates on a stationary part side are commonly used.  
           [0016]    A zoom lens unit of the present invention for forming a subject image on an image pick-up device comprises a stationary part,first and second movable parts to reciprocate in predetermined directions by being guided by the stationary part, each movable part having electrodes formed on surfaces and supporting a lens, at least one of the electrodes being one used to hold the movable part, wherein the stationary part comprises a driving electrode substrate having a plurality of groups of electrodes formed thereon in a predetermined direction at a constant pitch to drive the first and second movable parts, a holding electrode unit having a pair of electrodes corresponding to the electrodes of the first and second movable parts to selectively attract and hold the first and second movable parts, and a drive control circuit for sequentially energizing the groups of the electrodes of the driving electrode substrate as well as for selectively energizing the electrodes of the holding electrode unit, wherein the drive control circuit executes a cycle at least once while at least one of the first and second movable parts moves one pitch of an electrode of the plurality of groups of the electrodes when the first and second movable parts are moved in a different direction, wherein the cycle comprises a first operation for simultaneously grounding the electrodes of the first movable part and the electrodes of the holding electrode unit corresponding to the electrodes as well as attracting the first movable part to the driving electrode substrate by energizing one group of the electrodes of the plurality of groups of the electrodes, a second operation executed just after the first operation to energize ones of the holding electrodes and the electrodes such that the first and second movable parts are attracted to the pair of electrodes of the holding electrode unit, a third operation executed just after the second operation to simultaneously ground the electrodes of the second movable part and the electrodes of the holding electrode unit corresponding to the electrodes as well as to attract the second movable part to the driving electrode substrate by energizing at least one group of the electrodes of the plurality of groups of the electrodes, and a fourth operation executed just after the third operation to energize ones of the holding electrodes and the electrodes such that the first and second movable parts are attracted to the pair of electrodes of the holding electrode unit.  
           [0017]    A method of driving a zoom lens unit of the present invention for executing a zoom operation by driving a first movable part and a second movable part, which are disposed so as to reciprocate in predetermined directions by being guided by a stationary part and each of which holds a lens, in a different direction such that a subject image is formed on an image pick-up device, the method comprising the step of executing a cycle at least once while at least one of the first movable part and the second movable part moves one pitch of an electrode of a plurality of groups of electrodes, wherein the cycle comprises a first step for simultaneously grounding the electrodes of the first movable part and the electrodes of a holding electrode unit corresponding to the electrodes as well as attracting the first movable part to a driving electrode substrate by energizing one group of the electrodes of the plurality of groups of the electrodes, a second step executed just after the first step to energize the holding electrodes and the electrodes such that the first and second movable parts are attracted to a pair of electrodes of the holding electrode unit, a third step executed just after the second step to simultaneously ground the electrodes of the second movable part and the electrodes of the holding electrode unit corresponding to the electrodes as well as to attract the second movable part to the driving electrode substrate by energizing one group of the electrodes of the plurality of groups of the electrodes, and a fourth step executed just after the third step to energize ones of the holding electrodes and the electrodes such that the first and second movable parts are attracted to the pair of electrodes of the holding electrode unit, and the stationary part comprises the driving electrode substrate having the plurality of groups of the electrodes formed thereon in a predetermined direction at a constant pitch to drive the first and second movable parts, and the holding electrode unit having the pair of electrodes corresponding to the electrodes of the first and second movable parts to selectively attract and hold the first and second movable parts. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0018]    [0018]FIG. 1 is a perspective view, partly notched, of an image pick-up apparatus according to an embodiment of the present invention;  
         [0019]    [0019]FIG. 2 is an exploded perspective view of the image pick-up apparatus;  
         [0020]    [0020]FIG. 3A is a plan view schematically showing a driving electrode substrate incorporated in the image pick-up apparatus;  
         [0021]    [0021]FIG. 3B is a plan view schematically showing a holding electrode substrate incorporated in the image pick-up apparatus;  
         [0022]    [0022]FIG. 4 is a sectional view schematically showing the relationship between a stationary part and movable parts incorporated in the image pick-up apparatus;  
         [0023]    [0023]FIG. 5 is a view explaining the driving patterns in an operation mode M 1  of the image pick-up apparatus;  
         [0024]    [0024]FIG. 6 is a view explaining the driving patterns in an operation mode M 2  of the image pick-up apparatus;  
         [0025]    [0025]FIG. 7 is a view explaining the driving patterns in an operation mode M 3  of the image pick-up apparatus;  
         [0026]    [0026]FIG. 8 is a view explaining the driving patterns in an operation mode M 4  of the image pick-up apparatus;  
         [0027]    [0027]FIG. 9 is a view explaining the driving patterns in an operation mode M 5  of the image pick-up apparatus;  
         [0028]    [0028]FIG. 10 is a view explaining the driving patterns in an operation mode M 6  of the image pick-up apparatus;  
         [0029]    [0029]FIG. 11 is a view explaining the driving patterns in an operation mode M 7  of the image pick-up apparatus; and  
         [0030]    [0030]FIG. 12 is a view explaining the driving patterns in an operation mode M 8  of the image pick-up apparatus. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    [0031]FIG. 1 is a perspective view, partly notched, of an image pick-up apparatus  10  according to a first embodiment of the present invention, FIG. 2 is an exploded perspective view showing the image pick-up apparatus  10 , FIG. 3A is a plan view schematically showing a driving electrode substrate, FIG. 3B is a plan view schematically showing a holding electrode substrate, and FIG. 4 is a longitudinal sectional view schematically showing a zoom lens unit  30 . In these figures, arrows X, Y and Z shows three directions intersecting with each other, and in particular, the arrow X shows the moving direction of first and second movable parts  50  and  60 . Further, FIGS.  5  to  8  are views explaining a drive control method when only one of the movable parts is driven, and FIGS.  9  to  12  are views explaining drive patterns when the two movable parts are driven simultaneously.  
         [0032]    The image pick-up apparatus  10  includes an image pick-up device unit  20  and a zoom lens unit  30 . The image pick-up device unit  20  includes a substrate  21 , a sensor  22  such as a CCD or the like and a control electronic part  23  each disposed on the substrate  21 . The electronic part  23  has an drive control circuit  24  incorporated therein.  
         [0033]    The zoom lens unit  30  includes a cylindrical cover  31 , a stationary part  40 , the first movable part  50 , and the second movable part  60 . The first and second movable parts  50  and  60  are inserted into a stationary part frame  41  (which will be described later) such that they can move in an optical direction C while separating from each other.  
         [0034]    The stationary part  40  includes the stationary part frame  41  composed of a hollow frame member having a passing-though portion and being formed in a cuboid shape. The stationary part frame  41  has an upper inner surface  41   a , a lower inner surface  41   b , and side inner surfaces  41   c  and  41   d , and a driving electrode substrate  42  for driving the first and second movable parts  50  and  60  is attached to the upper inner surface  41   a . Further, a holding electrode substrate  43  for holding the first and second movable parts  50  and  60  at their positions is attached to the lower inner surface  41   b.    
         [0035]    As shown in FIG. 3A, the driving electrode substrate  42  is made by forming a desired pattern on the surface of a glass sheet, and a plurality of groups of driving electrodes  42   a  to  42   d , each of which extends in the Y-direction perpendicular to the moving direction X, are disposed in parallel with each other on the glass sheet. Note that the respective electrodes have a width of about 20 μm and intervals between the electrodes are 20 μm and the respective electrodes are disposed at a pitch of about 40 μm.  
         [0036]    The driving electrodes  42   a  to  42   d  are connected to the drive control circuit  24  of the electronic part  23  and driven in response to control voltage signals applied thereto from the drive control circuit  24 . That is, the voltage signals are applied independently to the driving electrodes  42   a  to  42   d  of the respective groups. When, for example, a voltage is applied to the driving electrodes  42   a , the voltage signal is applied to the convex portions corresponding to the driving electrodes  42   a  of all the groups on the driving electrode substrate  42 . The driving electrodes  42   a  correspond to a channel 1 (ch1), the driving electrodes  42   b  correspond to a channel 2 (ch2), the driving electrodes  42   c  correspond to a channel 3 (ch3), and the driving electrodes  42   d  correspond to a channel 4 (ch4).  
         [0037]    As shown in FIG. 3B, the holding electrode substrate  43  is made by forming a desired pattern on the surface of a glass sheet, and stripe electrodes  43   a , which correspond to the first movable part electrodes  53  (which will be described later) of the first movable part  50 , and stripe electrodes  43   b , which correspond to the second movable part electrodes  63  (which will be described later) of the second movable part  60 , are formed parallel to each other on the glass sheet. The second movable part stripe electrodes  43   b  correspond to a channel 5 (ch5), and the first movable part stripe electrodes  43   a  correspond to a channel 6 (ch6). Further, these stripe electrodes  43   a  and  43   b  are disposed electrically independently so that the first and second movable parts  50  and  60  can be controlled independently.  
         [0038]    The first movable part  50  includes an approximately cuboid support member  51  formed of a conductive member having a hollow portion. A movable part side driving electrode  52  is formed on the upper surface of the support member  51 , and a first movable part electrode  53  is formed on the lower surface thereof. Further, a lens  54  is fixed in the hollow portion.  
         [0039]    The movable part side driving electrode  52  has a plurality of projecting stripes extending thereon, the projecting stripes being formed by etching so as to be orthogonal to the moving direction X of the first movable part  50 , thereby concave portions and convex portions are formed by the plurality of stripes in parallel with each other in the moving direction X. The intervals between the concave portions and the convex portions are set to about 40 μm, and the convex portions have a height of about 10 μm from the surface in the concave portions. The height is set to at least 10 μm and may be larger than 10 μm. That is, the end surface of each convex portion of the movable part side driving electrode  52  has a width equal to the width of the two electrodes  42   a  and  42   b  of the driving electrode substrate  42 , the bottom surface of each concave portion of the movable part side driving electrode  52  has a width equal to the width of the two electrodes  42   c  and  42   d , and the concave portions and the convex portions of the movable part side driving electrode  52  are disposed at a pitch of about 80 μm.  
         [0040]    The first movable part electrode  53  is extended in the moving direction of the first movable part  50 , and a plurality of projecting stripes are formed by etching in the first movable part electrode  53  so that they are disposed in parallel with each other in the Y-direction. The first movable part electrode  53  corresponds to a seven channel 7 (ch7).  
         [0041]    The second movable part  60  includes an approximately cuboid support member  61  formed of a conductive member having a hollow portion. A movable part side driving electrode  62  is formed on the upper surface of the support member  61 , and a second movable part electrode  63  is formed on the lower surface thereof. Further, a lens  64  is fixed in the hollow portion.  
         [0042]    The movable part side driving electrode  62  has a plurality of projecting stripes extending thereon, the projecting stripes being formed by etching so as to be orthogonal to the moving direction X of the second movable part  60 , thereby concave portions and convex portions are formed by the plurality of stripes parallel to each other in the moving direction X. The intervals between the concave portions and the convex portions are set to about 40 μm, and the convex portions have a height of about 10 μm from the surface in the concave portions. The height is set to at least 10 μm and may be larger than 10 μm. That is, the end surface of each convex portion of the movable part side driving electrode  62  has a width equal to the width of the two electrodes  42   a  and  42   b  of the driving electrode substrate  42 , the bottom surface of each concave portion of the movable part side driving electrode  62  has a width equal to the width of the two electrodes  42   c  and  42   d , and the concave portions and the convex portions of the movable part side driving electrode  62  are disposed at a pitch of about 80 μm.  
         [0043]    The second movable part electrode  63  is extended in the moving direction of the first movable part  50 , and a plurality of projecting stripes are formed in the second movable part electrode  63  by etching so as to be disposed parallel to each other in the Y-direction.  
         [0044]    Further, a lens system composed of both the lenses  54  and  64  is zoomed between a wide side and a telescopic side by changing the positions of the lens  54  of the first movable part  50  and the lens  64  of the second movable part  60 , and a subject is focused according to a zoomed focal length.  
         [0045]    In the image pick-up apparatus  10  configured as described above, the first and second movable parts  50  and  60  are driven as described below. That is, the first and second movable parts  50  and  60  are driven in a total of eight operation modes, i.e., one group separate drive modes (operation modes M 1  to M 4 ) in which only one of the movable parts are driven and both group separate drive modes (operation modes M 5  to M 8 ) in which both movable parts are simultaneously driven.  
         [0046]    In the “operation mode M 1 ”, the first movable part  50  is moved to the sensor  22  side, and the second movable part  60  is fixed. In the “operation mode M 2 ”, the first movable part  50  is fixed, and the second movable part  60  is moved to the sensor  22  side. In the “operation mode M 3 ”, the first movable part  50  is fixed, and the second movable part  60  is moved to a subject side. In the “operation mode M 4 ”, the first movable part  50  is moved to the subject side, and the second movable part  60  is fixed.  
         [0047]    In the “operation mode M 5 ”, the first and second movable parts  50  and  60  are moved to the sensor  22  side. In the “operation mode M 6 ”, the first movable part  50  is moved to the sensor  22  side, and the second movable part  60  is moved to the subject side. In the “operation mode M 7 ”, the first movable part  50  is moved to the subject side, and the second movable part  60  is moved to the sensor  22  side. In the “operation mode M 8 ”, the first and second movable parts  50  and  60  are moved to the subject side.  
         [0048]    The eight operation modes M 1  to M 8  will be explained using FIGS.  5  to  12 , respectively. In the explanation, “H” means to set a potential at a high level by energization, and “GND” means to set to the potential to zero by grounding. In the figures, the former is shown by “H”, and the latter is shown by a blank.  
         [0049]    [0049]FIG. 5 is a view explaining the driving patterns in the operation mode M 1 . The operation mode M 1  is a driving method of moving the first movable part  50  to the sensor  22  side and fixing the second movable part  60 . Note that the operation mode M 1  is roughly composed of four operating sections 1 to 4, and each of the four operating sections includes four energizing patterns α to δ.  
         [0050]    (1) Section 1 (Attraction Phase of First Movable Part: AB Phase, Attraction Phase of Second Movable Part: AB Phase)  
         [0051]    In the energizing pattern α, the first movable part electrode  53  is set to GND, and the second movable part electrode  63  is set to H. Further, the potential of the first and second movable part stripe electrodes  43   a  and  43   b  is set to GND. With the above operations, the second movable part electrodes  63  are attracted to the second movable part stripe electrodes  43   b , and the second movable part  60  is held at its position. In contrast, the driving electrodes  42   a  and  42   b  are set to H. With this operation, the movable part side driving electrode  52  in the vicinity of the driving electrodes  42   a  and  42   b  is attracted to the driving electrodes  42   a  and  42   b  by electrostatic force, thereby the movable part side driving electrode  52  is attracted to the driving electrodes  42   a  and  42   b . Accordingly, only the first movable part  50  is moved to the driving electrode substrate  42  side.  
         [0052]    Next, in the energizing pattern β, the first movable part electrode  53  is set to GND, and the second movable part electrode  63  is set to H. Further, the potential of the first movable part stripe electrodes  43   a  are set to H, and the potential of the second movable part stripe electrodes  43   b  is set to GND. In contrast, the potential of the driving electrodes  42   b  is set to a high level (H). With the above operations, the first movable part electrode  53  is attracted to the first movable part stripe electrodes  43   a , and the first movable part  50  is moved to the holding electrode substrate  43  side. Note that since the second movable part electrode  63  is attracted to the second movable part stripe electrodes  43   b , the second movable part  60  remains held on the holding electrode substrate  43  side.  
         [0053]    Next, in the energizing pattern γ, the first movable part electrode  53  is set to H, and the second movable part electrode  63  is set to GND. Further, the first and second movable part stripe electrodes  43   a  and  43   b  are set to H. With the above operations, the second movable part electrodes  63  are attracted to the second movable part stripe electrodes  43   b , and the second movable part  60  is held at its position. In contrast, the driving electrodes  42   c  and  42   d  are set to H. With this operation, the movable part side driving electrode  52  in the vicinity of the driving electrodes  42   c  and  42   d  is attracted to the driving electrodes  42   c  and  42   d  by electrostatic force, thereby the movable part side driving electrode  52  is attracted to the driving electrodes  42   c  and  42   d . Accordingly, only the first movable part  50  is moved to the driving electrode substrate  42  side.  
         [0054]    Next, in the energizing pattern δ, the first movable part electrode  53  is set to H, and the second movable part electrode  63  is set to GND. Further, the first movable part stripe electrodes  43   a  are set to GND, and the second movable part stripe electrodes  43   b  are set to H. In contrast, the driving electrodes  42   a ,  42   c  and  42   d  are set to H.  
         [0055]    With the above operations, the first movable part electrode  53  is attracted to the first movable part stripe electrodes  43   a , and the first movable part  50  is moved to the holding electrode substrate  43  side. Note that since the second movable part electrode  63  is attracted to the second movable part stripe electrodes  43   b , the second movable part  60  remains held on the holding electrode substrate  43  side.  
         [0056]    Repeating the energizing patterns α to δ a plurality of times moves the first movable part  50  to the AB phase side and causes the second movable part  60  to stay in the AB phase.  
         [0057]    (2) Section 2 (Attraction Phase of First Movable Part: BC Phase, Attraction Phase of Second Movable Part: AB Phase)  
         [0058]    Similarly to section 1, the driving electrodes  42   a  to  42   d , the first movable part electrode  53 , the second movable part electrode  63 , the first movable part stripe electrodes  43   a , and the second movable part stripe electrodes  43   b  are controlled by the energizing patterns α to δ.  
         [0059]    Repeating the energizing patterns α to δ shown in FIG. 5 a plurality of times in the section 2 moves the first movable part  50  to the BC phase side and causes the second movable part  60  to stay in the AB phase.  
         [0060]    (3) Section 3 (Attraction Phase of First Movable Part: CD Phase, Attraction Phase of Second Movable Part: AB Phase)  
         [0061]    Similarly to section 1, the driving electrodes  42   a  to  42   d , the first movable part electrode  53 , the second movable part electrode  63 , the first movable part stripe electrodes  43   a , and the second movable part stripe electrodes  43   b  are controlled by the energizing patterns α to δ.  
         [0062]    Repeating the energizing patterns α to δ shown in FIG. 5 a plurality of times in section 3 moves the first movable part  50  to the CD phase side and causes the second movable part  60  to stay in the AB phase.  
         [0063]    (4) Section 4 (Attraction Phase of First Movable Part: DA Phase, Attraction Phase of Second Movable Part: AB Phase)  
         [0064]    Similarly to section 1, the driving electrodes  42   a  to  42   d , the first movable part electrode  53 , the second movable part electrode  63 , the first movable part stripe electrodes  43   a , and the second movable part stripe electrodes  43   b  are controlled by the energizing patterns α to δ.  
         [0065]    Repeating the energizing patterns α to δ shown in FIG. 5 a plurality of times in the section 4 moves the first movable part  50  to the DA phase side and causes the second movable part  60  to stay in the AB phase.  
         [0066]    The first movable part  50  is moved to the sensor  22  side by executing the operations (1) to (4) described above. It is possible to move only the first movable part  50  to a desired position by repeating these operations.  
         [0067]    [0067]FIG. 6 is a view explaining the driving patterns in the operation mode M 2 . The operation mode M 2  is a driving method of fixing the first movable part  50  and moving the second movable part  60  to the sensor  22  side. In the operation mode M 2 , it is possible to move only the second movable part  60  to a desired position by executing energization according to the driving patterns shown in FIG. 6.  
         [0068]    [0068]FIG. 7 is a view explaining the driving patterns in the operation mode M 3 . The operation mode M 3  is a driving method of fixing the first movable part  50  and moving the second movable part  60  to the subject side. In the operation mode M 3 , it is possible to move only the second movable part  60  to a desired position by executing energization according to the driving patterns shown in FIG. 7.  
         [0069]    [0069]FIG. 8 is a view explaining the driving patterns in the operation mode M 4 . The operation mode M 4  is a driving method of moving the first movable part  50  to the subject side and fixing the second movable part  60 . In the operation mode M 4 , it is possible to move only the first movable part  50  to a desired position by executing energization according to the driving patterns shown in FIG. 8.  
         [0070]    [0070]FIG. 9 is a view explaining the driving patterns in the operation mode M 5 . The operation mode M 5  is a driving method of moving the first and second movable parts  50  and  60  to the sensor  22  side. Note that the driving mode M 5  is roughly composed of four operating sections 1 to 4, and each of the four operating sections includes four energizing patterns α to δ.  
         [0071]    (1) Section 1 (Attraction Phase of First Movable Part: AB Phase, Attraction Phase of Second Movable Part: AB Phase)  
         [0072]    In the energizing pattern α, the first and second movable part electrodes  53  and  63  are set to GND. Further, the first and second movable part stripe electrodes  43   a  and  43   b  are set to GND.  
         [0073]    In contrast, the driving electrodes  42   a  and  42   b  are set to H. With the above operations, the movable part side driving electrodes  52  and  62  in the vicinity of the driving electrodes  42   a  and  42   b  is attracted to the driving electrodes  42   a  and  42   b  by electrostatic force, thereby the movable part side driving electrode  52  is attracted to the driving electrodes  42   a  and  42   b . Accordingly, the first and second movable parts  50  and  60  are moved to the driving electrode substrate  42  side.  
         [0074]    Next, in the energizing pattern β, the first and second movable part electrodes  53  and  63  are set to GND. Further, the first and second movable part stripe electrodes  43   a  and  43   b  are set to H. In contrast, the driving electrodes  42   b  are set to H. With the above operations, the first movable part electrode  53  is attracted to the first movable part stripe electrodes  43   a , the second movable part electrode  63  is attracted to the second movable part stripe electrodes  43   b , and the first and second movable parts  50  and  60  are moved to the holding electrode substrate  43  side.  
         [0075]    Next, in the energizing pattern γ, the first and second movable part electrodes  53  and  63  of the first and second movable parts  50  and  60  are set to H. Further, the first and second movable part stripe electrodes  43   a  and  43   b  are set to H. In contrast, the driving electrodes  42   c  and  42   d  are set to H. With the above operations, the movable part side driving electrodes  52  and  62  in the vicinity of the driving electrodes  42   c  and  42   d  are attracted to the driving electrodes  42   c  and  42   d  by electrostatic force, thereby the movable part side driving electrode  52  is attracted to the driving electrodes  42   c  and  42   d . Accordingly, the first and second movable parts  50  and  60  are moved to the driving electrode substrate  42  side.  
         [0076]    Next, in the energizing pattern δ, the first and second movable part electrodes  53  and  63  of the first and second movable parts  50  and  60  are set to H. Further, the first movable part stripe electrodes  43   a  are set to H, and the second movable part stripe electrodes  43   b  are set to GND. In contrast, the driving electrodes  42   a ,  42   c  and  42   d  are set to H. With the above operations, the first movable part electrode  53  is attracted to the first movable part stripe electrodes  43   a , the second movable part electrode  63  is attracted to the second movable part stripe electrodes  43   b , and the first and second movable parts  50  and  60  are moved to the holding electrode substrate  43  side.  
         [0077]    (2) Section 2 (Attraction Phase of First Movable Part: BC Phase, Attraction Phase of Second Movable Part: BC Phase)  
         [0078]    Similarly to section 1, the driving electrodes  42   a  to  42   d , the first movable part electrode  53 , the second movable part electrode  63 , the first movable part stripe electrodes  43   a , and the second movable part stripe electrodes  43   b  are controlled by the energizing patterns α to δ.  
         [0079]    Repeating the energizing patterns α to δ shown in FIG. 9 a plurality of times in the section 2 moves the first and second movable parts  50  and  60  to the BC phase side.  
         [0080]    (3) Section 3 (Attraction Phase of First Movable Part: CD Phase, Attraction Phase of Second Movable Part: CD Phase)  
         [0081]    Similarly to section 1, the driving electrodes  42   a  to  42   d , the first movable part electrode  53 , the second movable part electrode  63 , the first movable part stripe electrodes  43   a , and the second movable part stripe electrodes  43   b  are controlled by the energizing patterns α to δ.  
         [0082]    Repeating the energizing patterns α to δ shown in FIG. 9 a plurality of times in the section 3 moves the first and second movable parts  50  and  60  to the CD phase side.  
         [0083]    (4) Section 4 (Attraction Phase of First Movable Part: DA Phase, Attraction Phase of Second Movable Part: DA Phase)  
         [0084]    Similarly to section 1, the driving electrodes  42   a  to  42   d , the first movable part electrode  53 , the second movable part electrode  63 , the first movable part stripe electrodes  43   a , and the second movable part stripe electrodes  43   b  are controlled by the energizing patterns α to δ.  
         [0085]    Repeating the energizing patterns α to δ shown in FIG. 9 a plurality of times in the section 4 moves the first and second movable parts  50  and  60  to the DA phase side.  
         [0086]    It is possible to move the first and second movable parts  50  and  60  to the sensor  22  side by executing the operations (1) to (4) described above.  
         [0087]    [0087]FIG. 10 is a view explaining the driving patterns in the operation mode M 6 . The driving mode M 6  is a driving method of moving the first movable part  50  to the sensor  22  side and moving the second movable part  60  to the subject side. Note that the driving mode M 6  is roughly composed of four operating sections 1 to 4, and each of the four operating sections includes four energizing patterns α to δ.  
         [0088]    (1) Section 1 (Attraction Phase of First Movable Part: AB Phase, Attraction Phase of Second Movable Part: AB Phase)  
         [0089]    In the energizing pattern α, the first and second movable part electrodes  53  and  63  are set to GND. Further, the first and second movable part stripe electrodes  43   a  and  43   b  are set to GND. In contrast, the driving electrodes  42   a  and  42   b  are set to H. With the above operations, the movable part side driving electrodes  52  and  62  in the vicinity of the driving electrodes  42   a  and  42   b  are attracted to the driving electrodes  42   a  and  42   b  by electrostatic force, thereby the movable part side driving electrode  52  is attracted to the driving electrodes  42   a  and  42   b . Accordingly, the first and second movable parts  50  and  60  are moved to the driving electrode substrate  42  side.  
         [0090]    Next, in the energizing pattern β, the first movable part electrode  53  is set to GND, and the second movable part electrode  63  is set to H. Further, the first movable part stripe electrodes  43   a  are set to H, and the second movable part stripe electrodes  43   b  are set to GND. In contrast, the driving electrodes  42   b  and  42   c  are set to H. With the above operations, the first movable part electrode  53  is attracted to the first movable part stripe electrodes  43   a , the second movable part electrode  63  is attracted to the second movable part stripe electrodes  43   b , and the first and second movable parts  50  and  60  are moved to the holding electrode substrate  43  side.  
         [0091]    Next, in the energizing pattern γ, the first and second movable part electrodes  53  and  63  are set to H. Further, the first and second movable part stripe electrodes  43   a  and  43   b  are set to H. In contrast, the driving electrodes  42   c  and  42   d  are set to H. With the above operations, the movable part side driving electrodes  52  and  62  in the vicinity of the driving electrodes  42   c  and  42   d  are attracted to the driving electrodes  42   c  and  42   d  by electrostatic force, thereby the movable part side driving electrode  52  is attracted to the driving electrodes  42   c  and  42   d . Accordingly, the first and second movable parts  50  and  60  are moved to the driving electrode substrate  42  side.  
         [0092]    Next, in the energizing pattern δ, the first movable part electrode  53  of the first movable part  50  is set to GND, and the second movable part electrode  63  of the second movable part  60  is set to H. Further, the first movable part stripe electrodes  43   a  are set to GND, and the second movable part stripe electrodes  43   b  are set to H. In contrast, the driving electrodes  42   a  and  42   d  are set to H. With the above operations, the first movable part electrode  53  is attracted to the first movable part stripe electrodes  43   a , the second movable part electrode  63  is attracted to the second movable part stripe electrodes  43   b , and the first and second movable parts  50  and  60  are moved to the holding electrode substrate  43  side.  
         [0093]    (2) Section 2 (Attraction Phase of First Movable Part: BC Phase, Attraction Phase of Second Movable Part: DA Phase)  
         [0094]    In the energizing pattern α, the first movable part electrode  53  is set to GND, and the second movable part electrode  63  is set to H. Further, the first movable part stripe electrodes  43   a  are set to GND, and the second movable part stripe electrodes  43   b  are set to H. In contrast, the driving electrodes  42   b  and  42   c  are set to H. With the above operations, the movable part side driving electrode  52  in the vicinity of the driving electrodes  42   a  and  42   b  is attracted to the driving electrodes  42   a  and  42   b  by electrostatic force, thereby the movable part side driving electrode  52  is attracted to the driving electrodes  42   a  and  42   b . Accordingly, only the first movable part  50  is moved to the driving electrode substrate  42  side.  
         [0095]    Next, in the energizing pattern β, the first and second movable part electrodes  53  and  63  are set to GND. Further, the first and second movable part stripe electrodes  43   a  and  43   b  are set to H. In contrast, the driving electrodes  42   c  and  42   d  are set to H. With the above operations, the first movable part electrode  53  is attracted to the first movable part stripe electrodes  43   a , the second movable part electrode  63  is attracted to the second movable part stripe electrodes  43   b , and the first and second movable parts  50  and  60  are moved to the holding electrode substrate  43  side.  
         [0096]    Next, in the energizing pattern γ, the first movable part electrode  53  is set to H, and the second movable part electrode  63  is set to GND. Further, the first movable part stripe electrodes  43   a  are set to H, and the second movable part stripe electrodes  43   b  are set to GND. In contrast, the driving electrodes  42   a  and  42   d  are set to H. With the above operations, the movable part side driving electrode  62  in the vicinity of the driving electrodes  42   c  and  42   d  are attracted to the driving electrodes  42   c  and  42   d  by electrostatic force, thereby the movable part side driving electrode  52  is attracted to the driving electrodes  42   c  and  42   d . Accordingly, only the second movable part  60  is moved to the driving electrode substrate  42  side.  
         [0097]    Next, in the energizing pattern δ, the first and second movable part electrodes  53  and  63  are set to H. Further, the first and second movable part stripe electrodes  43   a  and  43   b  are set to GND. In contrast, the driving electrodes  42   a  and  42   b  are set to H. With the above operations, the first movable part electrode  53  is attracted to the first movable part stripe electrodes  43   a , the second movable part electrode  63  is attracted to the second movable part stripe electrodes  43   b , and the first and second movable parts  50  and  60  are moved to the holding electrode substrate  43  side.  
         [0098]    Repeating the energizing patterns α to δ shown in FIG. 10 a plurality of times in section 2 moves the first movable part  50  to the BC phase side, and the second movable part  60  is moved to the DA phase side.  
         [0099]    (3) Section 3 (Attraction Phase of First Movable Part: CD Phase, Attraction Phase of Second Movable Part: CD Phase)  
         [0100]    Similarly to section 1, the driving electrodes  42   a  to  42   d , the first movable part electrode  53 , the second movable part electrode  63 , the first movable part stripe electrodes  43   a , and the second movable part stripe electrodes  43   b  are controlled by the energizing patterns α to δ.  
         [0101]    Repeating the energizing patterns α to δ shown in FIG. 9 a plurality of times in the section 3 moves the first and second movable parts  50  and  60  to the CD phase side.  
         [0102]    (4) Section 4 (Attraction Phase of First Movable Part: DA Phase, Attraction Phase of Second Movable Part: BC Phase)  
         [0103]    Similarly to section 1, the driving electrodes  42   a  to  42   d , the first movable part electrode  53 , the second movable part electrode  63 , the first movable part stripe electrodes  43   a , and the second movable part stripe electrodes  43   b  are controlled by the energizing patterns α to δ.  
         [0104]    Repeating the energizing patterns α to δ shown in FIG. 9 a plurality of times in section 4 moves the first movable part  50  to the DA phase side, and the second movable part  60  is moved to the BC phase side.  
         [0105]    It is possible to move the first movable part  50  to the sensor  22  side and to move the second movable part  60  to the subject side by executing the operations (1) to (4) described above. In the operation mode M 6 , it is possible to move the first and second movable parts  50  and  60  to a desired position, respectively by executing energization according to the driving patterns shown in FIG. 10.  
         [0106]    [0106]FIG. 11 is a view explaining the driving patterns in the operation mode M 7 . The driving mode M 7  is a driving method of moving the first movable part  50  to the subject side and moving the second movable part  60  to the sensor  22  side. In the operation mode M 7 , it is possible to move the first and second movable parts  50  and  60  to a desired position, respectively by executing energization according to the driving patterns shown in FIG. 11.  
         [0107]    [0107]FIG. 12 is a view explaining the driving patterns in the operation mode M 8 . The driving mode M 8  is a driving method of moving the first and second movable parts  50  and  60  to the subject side. In the operation mode M 8 , it is possible to move the first and second movable parts  50  and  60  to a desired position, respectively by executing energization according to the driving patterns shown in FIG. 12.  
         [0108]    As described above, in the image pick-up apparatus  10  according to the embodiment, even if the driving electrode substrate  42  and the holding electrode substrate  43  on the stationary part are commonly used, it is possible to simultaneously move the first and second movable parts  50  and  60  in the same direction or in an opposite direction. That is, since the two lenses can be moved simultaneously, the zoom magnification can be continuously varied at a constant speed, which provides the user with the smooth and natural impression of an output image on a screen.  
         [0109]    Further, only one set of the stationary part is needed, the volume of an actuator unit is not increased and thus the size thereof is not increased. Further, since the electrodes are disposed in a manner entirely similar to a conventional manner, a driving force is not in short supply.  
         [0110]    Further, since a cam mechanism and the like are not used, it is easy to adjust a focal point and to cope with a change of the focal point due to a change of temperature in an external environment which are required to a zoom lens unit. Accordingly, a degree of freedom is increased in the selection of a lens material and in the optical design of lenses.  
         [0111]    Note that the present invention is by no means limited to the above embodiment. While the example described above has been explained as to the two movable parts, the zoom lens unit may include three movable parts. In addition, it goes without saying that various modifications can be made within the range which does not depart from the gist of the present invention.  
         [0112]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.