Abstract:
Disclosed herein is a lens driving mechanism which can achieve simplification of the mechanism and provision of appropriate control relating to correction against a shake. The lens driving mechanism includes a piezoelectric element deformed when energized for applying driving force to the movable block, and a charge amount sensor for detecting the amount of charge accumulated in the piezoelectric element. The amount of electric current to be supplied to the piezoelectric element is determined based on external force, acting upon the movable block, estimated based on a difference between the amount of charge injected into or discharged from the piezoelectric element and the amount of charge accumulated in the piezoelectric element and detected by the charge amount sensor when the movable block is moved in the direction perpendicular to the optical axis.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]     The present invention contains subject matter related to Japanese Patent Application JP 2005-092157 filed in the Japanese Patent Office on Mar. 28, 2005, the entire contents of which being incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     This invention relates to a lens driving mechanism, a lens unit and an image pickup device.  
         [0003]     A lens unit wherein an image pickup optical system including a movable lens and a lens driving mechanism for moving the movable lens are disposed in a lens barrel is incorporated not only in video cameras and still cameras but also in various image pickup devices of portable telephone sets and like devices. The movable lens cooperates with a lens holder which holds the movable lens thereon to form a movable block. The movable block is moved by the lens driving mechanism in a direction perpendicularly to the optical axis to perform correction against a shake.  
         [0004]     One of such lens driving mechanisms as described above uses a linear actuator formed from a driving coil, a driving magnet and so forth as disclosed, for example, in Japanese Patent Laid-open No. 2000-66257.  
       SUMMARY OF THE INVENTION  
       [0005]     However, since, in such an image pickup device in related art as described above, a linear actuator formed form a driving coil, a driving magnet and so forth is used for the lens driving mechanism, the image pickup device has a problem in that it requires a complicated structure and an increased arrangement space due to the arrangement of the driving coil, driving magnet and so forth, resulting in increase of the scale of the image pickup device.  
         [0006]     Further, the image pickup device in related art described above has a problem also in that the number of parts is great and the mechanism is complicated because it includes not only an acceleration sensor for detecting a shake but also an MR (Magneto Resistance) sensor and so forth for detecting position of a movable block.  
         [0007]     Further, the amount of shaking of the movable block is calculated based on an output value detected by a detection section such as an acceleration sensor, and the movable block is moved in a direction perpendicular to the optical axis by a shake correction amount corresponding to the amount of shaking by the lens driving mechanism. Therefore, open loop control is used for the control for moving the movable block by the shake correction amount based on the amount of shaking. Accordingly, since the control does not have a real time responsibility, for example, if self-excided vibration occurs with the lens driving mechanism or in a like case, there is the possibility that correction against a shake may not be performed appropriately.  
         [0008]     It is desirable to provide a lens driving mechanism, a lens unit and an image pickup device which can achieve simplification of the mechanism and provision of appropriate control relating to correction against a shake.  
         [0009]     According to the present invention, the amount of charge accumulated in a piezoelectric element for moving a movable block is detected and an energization amount for the piezoelectric element is determined based on the detected charge amount.  
         [0010]     In particular, according to an embodiment of the present invention, there is provided a lens driving mechanism for moving a movable block including a movable lens in a direction perpendicular to an optical axis of the movable lens to perform correction against a shake, including a piezoelectric element deformed when energized for applying driving force to the movable block, and a charge amount sensor for detecting the amount of charge accumulated in the piezoelectric element, wherein the amount of electric current to be supplied to the piezoelectric element is determined based on external force, acting upon the movable block, estimated based on a difference between the amount of charge injected into or discharged from the piezoelectric element and the amount of charge accumulated in the piezoelectric element and detected by the charge amount sensor when the movable block is moved in the direction perpendicular to the optical axis.  
         [0011]     In the lens driving mechanism, the piezoelectric element is energized in response to the deformation state of the piezoelectric element caused by the displacement of the movable block acted upon by external force.  
         [0012]     Accordingly, with the lens driving mechanism, simplification and miniaturization of the mechanism can be anticipated and closed loop control can be achieved readily, and besides control relating to correction against a shake can be achieved appropriately.  
         [0013]     According to another embodiment of the present invention, there is provided a lens unit including a movable block including a movable lens, and a lens driving mechanism for moving the movable block in a direction perpendicular to an optical axis of the movable lens to perform correction against a shake, wherein the lens driving mechanism including a piezoelectric element deformed when energized for applying driving force to the movable block and a charge amount sensor for detecting the amount of charge accumulated in the piezoelectric element, wherein the amount of electric current to be supplied to the piezoelectric element is determined based on external force, acting upon the movable block, estimated based on a difference between the amount of charge injected into or discharged from the piezoelectric element and the amount of charge accumulated in the piezoelectric element and detected by the charge amount sensor when the movable block is moved in the direction perpendicular to the optical axis.  
         [0014]     In the lens unit, the piezoelectric element is energized in response to the deformation state of the piezoelectric element caused by the displacement of the movable block acted upon by external force.  
         [0015]     Accordingly, with the lens unit, simplification and miniaturization of the mechanism can be anticipated and closed loop control can be achieved readily, and besides control relating to correction against a shake can be achieved appropriately.  
         [0016]     According to a further embodiment of the present invention, there is provided an image pickup device including a movable block including a movable lens, and a lens driving mechanism for moving the movable block in a direction perpendicular to an optical axis of the movable lens to perform correction against a shake, an image pickup optical system, and an image pickup element for converting an image formed by the image pickup optical system into an electric signal, wherein the lens driving mechanism including a piezoelectric element deformed when energized for applying driving force to the movable block and a charge amount sensor for detecting the amount of charge accumulated in the piezoelectric element, wherein the amount of electric current to be supplied to the piezoelectric element is determined based on external force, acting upon the movable block, estimated based on a difference between the amount of charge injected into or discharged from the piezoelectric element and the amount of charge accumulated in the piezoelectric element and detected by the charge amount sensor when the movable block is moved in the direction perpendicular to the optical axis.  
         [0017]     In the image pickup device, the piezoelectric element is energized in response to the deformation state of the piezoelectric element caused by the displacement of the movable block acted upon by external force.  
         [0018]     Accordingly, with the image pickup device, simplification and miniaturization of the mechanism can be anticipated and closed loop control can be achieved readily, and besides control relating to correction against a shake can be achieved appropriately.  
         [0019]     The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements denoted by like reference symbols. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a block diagram showing a general configuration of an image pickup device to which the present invention is applied;  
         [0021]      FIG. 2  is an enlarged schematic front elevational view, partly in section, showing a piezoelectric element before it is deformed together with a movable block of the image pickup device;  
         [0022]      FIG. 3  is a graph illustrating a relationship between the displacement amount of the piezoelectric element and the charge amount detected by a charge amount sensor of the image pickup device;  
         [0023]      FIG. 4  is an enlarged schematic front elevational view, partly in section, showing the piezoelectric element after it is deformed and the movable block is moved in an X direction together with the movable block; and  
         [0024]      FIG. 5  is an enlarged schematic front elevational view, partly in section, showing the piezoelectric element after it is deformed and the movable block is moved in a Y direction together with the movable block. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     Although the present invention can be applied to various image pickup device which have a moving picture image pickup function or a still picture image pickup function such as portable telephone sets, video cameras and still cameras and also to various lens units and lens driving mechanisms used in such image pickup device, a general configuration of an image pickup device to which the present invention is described first with reference to  FIG. 1 .  
         [0026]     The image pickup device  1  includes a camera block  2 , a camera DSP (Digital Signal Processor)  3 , an SDRAM (Synchronous Dynamic Random Access Memory)  4 , a medium interface (I/F)  5 , a control block  6 , an operation section  7 , an LCD (Liquid Crystal Display) unit  8  and an external interface (I/F)  9 . A recording medium  100  can be removably loaded into the external interface  9 .  
         [0027]     For the recording medium  100 , various media can be used including memory cards in which a semiconductor memory is incorporated and disk-type recording media such as a recordable DVD (Digital Versatile Disk) and a recordable CD (Compact Disk).  
         [0028]     The camera block  2  includes a movable block  10 , an image pickup device  11  such as a CCD (Charge Coupled Device) image pickup device, an A/D conversion circuit  12 , a first driver  13 , a second driver  14  and a timing generation circuit  15 .  
         [0029]     The movable block  10  includes a movable lens  16  such as, for example, a focusing lens and a zoom lens, and a lens holder  17  for holding the movable lens  16  thereon as particularly shown in  FIG. 2 .  
         [0030]     Referring to  FIG. 2 , the lens holder  17  includes, for example, a lens holding member  18 , a movable base  19  and a support base  20 .  
         [0031]     The movable lens  16  is attached to and held by the lens holding member  18 , and a pair of arm portions  18   a  are provided on the lens holding member  18  such that they project leftwardly and rightwardly. Further, a projection  18   b  is provided on the lens holding member  18  such that it projects, for example, downwardly, and an upwardly and downwardly elongated support hole  18   c  is formed in the projection  18   b.    
         [0032]     A pair of arm portions  19   a  are provided on the movable base  19  such that they project, for example, upwardly and downwardly. Further, a projection  19   b  is provided on the lens holding member  18  such that it projects, for example, rightwardly, and a leftwardly and rightwardly elongated sliding hole  19   c  is formed in the projection  19   b . A pair of support shafts  21  are provided on the movable base  19  and extend leftwardly and rightwardly, and the arm portions  18   a  of the lens holding member  18  are supported for sliding movement on the support shafts  21 . Accordingly, the lens holding member  18  can be moved in the leftward and rightward directions (X direction in  FIG. 2 ) with respect to the movable base  19 .  
         [0033]     A pair of sliding shafts  22  are provided on the support base  20  such that they extend upwardly and downwardly, and the arm portions  19   a  of the movable base  19  are supported for sliding movement on the sliding shafts  22 . Accordingly, the movable base  19  can be moved in the upward and downward directions (Y direction in  FIG. 2 ) with respect to the support base  20 . When the movable base  19  is moved in the Y direction with respect to the support base  20 , also the lens holding member  18  is moved in the Y direction integrally with the movable base  19 .  
         [0034]     A pair of bearing portions  20   a  are provided on the support base  20  such that they individually project outwardly and are supported for sliding movement on a pair of guide shafts  23  which extend in the direction of the optical axis. The support base  20  can be moved in the direction of the optical axis under the guidance of the  23 , and when the support base  20  is moved in the direction of the optical axis, also the lens holding member  18  and the movable base  19  are moved in the direction of the optical axis integrally with the support base  20 .  
         [0035]     Referring back to  FIG. 1 , the image pickup device  11  operates in response a driving signal from the second driver  14  and fetches an image of a subject fetched through the movable lens  16 . Then, the image pickup device  11  signals the fetched image (image information) of the subject as an electric signal to the A/D conversion circuit  12  in response to a timing signal outputted from the timing generation circuit  15  which is controlled by the control block  6 .  
         [0036]     It is to be noted that the image pickup device  11  is not limited to a CCD device, but some other device such as, for example, a CMOS (Complementary Metal-Oxide Semiconductor) device can be used as the image pickup device  11 .  
         [0037]     The AID conversion circuit  12  performs a CDS (Correlated Double Sampling) process for the image information as the inputted electric signal to maintain a good S/N ratio and performs an AGC (Automatic Gain Control) process to control the gain. The A/D conversion circuit  12  further performs an A/D (Analog/Digital) conversion process to produce image data in the form of a digital signal.  
         [0038]     The first driver  13  signals a driving signal to a piezoelectric element hereinafter described in accordance with an instruction of a CPU hereinafter described of the control block  6 .  
         [0039]     The second driver  14  signals a driving signal to the image pickup device  11  based on a timing signal outputted from the timing generation circuit  15 .  
         [0040]     The timing generation circuit  15  generates a timing signal for providing a predetermined timing under the control of the control block  6 .  
         [0041]     The camera block  2  includes a pair of piezoelectric elements  24  and  25  which function as driving sections for moving the movable block  10 , for example, in the XY directions perpendicular to an optical axis (refer to  FIG. 2 ). In particular, the piezoelectric element  24  functions as a driving section for moving the movable block  10 , for example, in the X direction and the piezoelectric element  25  functions as a driving section for moving the movable block  10 , for example, in the Y direction.  
         [0042]     Each of the piezoelectric elements  24  and  25  is deformed in a substantially fixed radius of curvature when it is energized. At this time, charge is accumulated into the piezoelectric element  24  or  25 . Each of the piezoelectric elements  24  and  25  is secured at an end portion thereof to a fixed member  26  or  27  and is deformed in a direction corresponding to the X or Y direction. It is to be noted that the fixed members  26  and  27  may be disposed on the support base  20 . Alternatively, the fixed member  26  may be disposed on the movable base  19  while the fixed member  27  is disposed on the support base  20 .  
         [0043]     While piezoelectric elements are roughly classified into the bimorph type and the unimorph type, for example, a bimorph type piezoelectric element is used as the piezoelectric elements  24  and  25  of the camera block  2 . It is to be noted, however, that the piezoelectric elements  24  and  25  may alternatively be of the unimorph type.  
         [0044]     Referring to  FIG. 2 , engaging pins  28  and  29  are attached to the other end portions of the piezoelectric elements  24  and  25 , respectively. The engaging pins  28  and  29  are supported for sliding movement in the support hole  18   c  of the lens holding member  18  and the sliding hole l 9   c  of the movable base  19 , respectively.  
         [0045]     A charge amount sensor  30  is provided on the camera block  2 . The charge sensor  30  detects the amount of charge accumulated in each of the piezoelectric elements  24  and  25  and is incorporated, for example, in a detection circuit not shown. An output of the charge amount sensor  30  is inputted to a CPU of the control block  6  hereinafter described.  
         [0046]     The camera DSP  3  performs signal processing for image data inputted thereto from the A/D conversion circuit  12  such as AF (Automatic Focusing), AE (Automatic Exposure) and AWB (Auto White Balancing). Image data for which the signal processing such as AF, AE and AWB has been performed are compressed by a predetermined method and outputted to the recording medium  100  through the control block  6  so that they are recorded as a file on the recording medium  100 .  
         [0047]     The camera DSP  3  includes an SDRAM controller  31  and performs writing and reading of data at a high speed into and from the SDRAM  4  in accordance with an instruction of the SDRAM controller  31 .  
         [0048]     The control block  6  is a microcomputer formed from a CPU (Central Processing Unit)  32 , a RAM (Random Access Memory)  33 , a flash ROM (Read Only Memory)  34 , a clock circuit  35  and other circuits connected to each other through a system bus  36 . The control block  6  has a function of controlling the components of the image pickup device  1 .  
         [0049]     The CPU  32  signals an instruction signal to the first driver  13  and signals an instruction signal to the second driver  14  and so fourth through the timing generation circuit  15  so that the components may operate. The CPU  32  receives information of the amounts of charge accumulated in the piezoelectric elements  24  and  25  and detected by the charge amount sensor  30  as an input thereto and outputs an instruction signal to the first driver based on the received information of the charge amounts.  
         [0050]      FIG. 3  illustrates a relationship between the amount of displacement (deformation amounts) of the piezoelectric elements  24  and  25  and the amount of charge detected by the charge amount sensor  30 .  
         [0051]     As seen from  FIG. 3 , the displacement amount of the piezoelectric elements  24  and  25  has a proportional relationship to the charge amount accumulated in the piezoelectric elements  24  and  25 . Further, the piezoelectric elements  24  and  25  have a characteristic that, if the piezoelectric elements  24  and  25  are deformed by the accumulated charge amount, then charge of an amount which increases in proportion to the deformation amount is accumulated.  
         [0052]     Accordingly, if the charge amount accumulated in each of the piezoelectric elements  24  and  25  is detected and the amount of charge injected into or discharged from the piezoelectric element  24  or  25  in response to the driving voltage applied to the piezoelectric element  24  or  25  is subtracted from the detected charge amount, then the amount of charge accumulated in the piezoelectric element  24  or  25  by external force can be calculated. It is to be noted that, if a driving voltage higher than a driving voltage which has been applied to the piezoelectric element  24  or  25  is applied, then charge is injected into the piezoelectric element  24  or  25 , but if a driving voltage lower than a voltage which has been applied to the piezoelectric element  24  or  25  is applied, then charge is discharged from the piezoelectric element  24  or  25 .  
         [0053]     In this manner, where the piezoelectric elements  24  and  25  are used, the magnitude of external force applied to the movable block  10  by inertial force when shaking of the image pickup device  1  by hand occurs, that is, the amount of shaking of the image pickup device  1 , can be estimated by detecting the charge amounts accumulated in the piezoelectric elements  24  and  25  which are deformed by displacement of the movable block  10 . Accordingly, the piezoelectric elements  24  and  25  function not only as a driving section for moving the movable block  10  in the XY directions but also as a shaking detection section for detecting an amount of shaking which occurs with the movable block  10 .  
         [0054]     In the image pickup device  1 , a relationship between the “difference between the charge amount injected into or discharged from the piezoelectric elements  24  and  25  and the charge amount accumulated in the piezoelectric elements  24  and  25  and detected by the charge amount sensor  30 ” and the “amount of shaking estimated to occur with the movable block  10 ” is stored as map information in the flash ROM  34  or the like in advance. Accordingly, upon image pickup by the image pickup device  1 , the amounts of charge accumulated in the piezoelectric elements  24  and  25  are detected continually by the charge amount sensor  30 , and results of the detection are inputted as information of the charge amounts to the CPU  32 . At this time, the map information described above is read out, and an instruction signal corresponding to a correction amount to be used for correction of the amount of shaking occurring with the movable block  10  is outputted from the CPU  32  to the first driver  13 . Consequently, driving signals are outputted from the first driver  13  to the piezoelectric elements  24  and  25  in accordance with the instruction of the CPU  32  to apply necessary driving voltages to the piezoelectric elements  24  and  25 .  
         [0055]     The RAM  33  is used principally as a working area for temporarily storing intermediate results of processing and so forth.  
         [0056]     The flash ROM  34  stores therein various programs to be executed by the CPU  32 , data necessary for processes of the CPU  32  and so forth.  
         [0057]     The clock circuit  35  outputs the year, month and day at present, the day of the week at present, the hour at present, the date and hour of image pickup and so forth.  
         [0058]     The operation section  7  includes a touch panel, control keys and so forth provided on a housing of the image pickup device  1 . A signal corresponding to an operation of the operation section  7  is inputted to the CPU  32 , and instruction signals are signaled from the CPU  32  to pertaining components of the image pickup device  1  based on the signal inputted thereto from the operation section  7 .  
         [0059]     The LCD unit  8  is provided, for example, on the housing and controlled by an LCD controller  37  connected to the system bus  36 . The LCD unit  8  displays thereon various kinds of information such as image data based on a driving signal from the LCD controller  37 .  
         [0060]     The external interface  9  is connected to the system bus  36 . The image pickup device  1  is connected to an external apparatus  200  such as, for example, an external personal computer through the external interface  9  such that it can receive image data from the personal computer and records the image data on the recording medium  100  or output image data recorded on the recording medium  100  to the personal computer or the like. It is to be noted that the recording medium  100  is connected to the control block  6  through the medium interface  5  connected to the system bus  36 .  
         [0061]     Further, where the external apparatus  200 , for example, a communication module, is connected to the external interface  9 , it is possible to connect the image pickup device  1  to a network such as, for example, the Internet and acquire various image data or other information through the network and record the data and/or information on the recording medium  100  or transmit data recorded on the recording medium  100  to an opposite party of communication through the network.  
         [0062]     It is to be noted that it is possible to provide the external interface  9  as an interface for wire communication such as an IEEE (Institute of Electrical and Electronics Engineers)  1394  interface or a USB (Universal Serial Bus) interface or as an interface for wireless communication which makes use of light or radio waves.  
         [0063]     Meanwhile, image data recorded on the recording medium  100  are read out from the recording medium  100  in response to an operation signal based on an operation of the operation section  7  performed by the user and signaled to the camera DSP  3  through the medium interface  5 .  
         [0064]     The camera DSP  3  performs a decompression process for image data in a compressed form read out from the recording medium  100  and inputted thereto and signals the decompressed image data to the LCD controller  37  through the system bus  36 . The LCD controller  37  signals an image signal based on the received image data to the LCD unit  8 . The LCD unit  8  displays an image thereon based on the received image signal.  
         [0065]     In the image pickup device  1  having such a configuration as described above, the piezoelectric elements  24  and  25 , engaging pines  28  and  29  and charge amount sensor  30  are components of a lens driving mechanism for controlling the movement of the movable block  10 , and the lens driving mechanism and the movable block  10  are components of a lens unit  39  (refer to  FIG. 1 ).  
         [0066]     In the image pickup device  1 , if a driving signal is outputted from the first driver  13  to the piezoelectric elements  24  and  25  in accordance with an instruction from the CPU  32 , then a driving voltage is applied from a power supply circuit not shown to the piezoelectric elements  24  and  25  as described hereinabove.  
         [0067]     When the driving voltage is applied to the piezoelectric elements  24  and  25 , the piezoelectric elements  24  and  25  are deformed, and the movable block  10  is moved in the XY directions to perform a shaking correction operation (refer to  FIGS. 4 and 5 ). Thereupon, the engaging pins  28  and  29  attached to the piezoelectric elements  24  and  25  slidably move in the support hole  19   c  of the lens holding member  19  and the sliding hole  20   c  of the movable base  20 , respectively.  
         [0068]     Since the piezoelectric elements  24  and  25  are used for the lens driving mechanism  38  in the image pickup device  1  as described above, simplification of the mechanism and reduction of the arrangement space can be achieved, and consequently, miniaturization can be anticipated.  
         [0069]     Further, since the piezoelectric elements  24  and  25  are used commonly for the driving section for moving the movable block  10  and the detection section for detecting the shaking amount appearing with the movable block  10 , closed loop control (feedback control) can be achieved readily and correction against a shake can be performed on the real time basis. Therefore, control relating to the correction against a shake can be performed appropriately.  
         [0070]     It is to be noted that, while the movable block  10  in the image pickup device  1  described hereinabove is moved in the XY directions to perform correction against a shake, it is otherwise possible to perform correction against a shake only with regard to one of the X direction and the Y direction. In this instance, it is only necessary to use a corresponding one of the piezoelectric elements  24  and  25 .  
         [0071]     Further, while, in the image pickup device  1  described hereinabove, the movable block  10  having a zoom lens or a focusing lens which is used in the direction of the optical axis is moved in a direction perpendicular to the optical axis to perform correction against a shake, it is possible otherwise to use a lens for exclusive use which can be moved only in a direction perpendicular to the optical axis without moving in the direction of the optical axis as the lens for correction against a shake. The lens for correction against a shake in this instance need not be supported on the guide shafts  23 .  
         [0072]     It is to be noted that the upward and downward directions in the foregoing description are merely for the convenience of description and the application of the present invention is not restricted by the directions.  
         [0073]     While a preferred embodiment of the present invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.