JP2009109888A - Image pickup apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely specify the reference position of the lens unit by accurately sensing the movement starting time of a lens unit. <P>SOLUTION: The apparatus is provided with a leaf spring 11 for applying downward bias to a lens unit 12, the lens unit 12 composing an imaging optical system for taking in an optical image of an object, a moving part 13 for pressing upward the lens unit 12 for moving upward the lens unit 12, a distortion sensor 14 mounted on the leaf spring 11 for sensing distortion of the leaf spring 11, and a judging part 41 for judging the time of change of the voltage output form the distortion sensor 14 as the movement starting time of the lens unit 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a driving technology for a lens unit that constitutes an imaging optical system that is suitably mounted on, for example, a mobile phone with a camera.

  In recent years, mobile phones with cameras have been improved in functionality such as an auto-focus type instead of a fixed-focus type, and an optical zoom instead of or in addition to a digital zoom. Along with this, there is a demand for a technique for accurately positioning the lens unit constituting the imaging optical system.

  Since it is difficult to mount a position sensor for detecting the moving position of the lens unit due to restrictions on installation space in a camera-equipped mobile phone, the lens unit is positioned based on a predetermined reference position on the optical axis. It has been common.

Further, as a prior art related to the present invention, Patent Document 1 discloses a technique for measuring a characteristic value in the vicinity of a wafer surface, and a probe that is in contact with a wafer based on a strain amount of a strain sensor fixed to a leaf spring. Has been disclosed (see paragraph [0031], etc.).
JP 2003-142536 A

  However, in the conventional camera-equipped mobile phone, the reference position of the lens unit is determined based on the timing at which the drive start signal is output to the actuator that moves the lens unit. There is a time lag from when the drive start signal is output to the actuator until the lens unit actually starts to move, and this time lag varies among the objects. Therefore, the conventional camera-equipped mobile phone has a problem that the reference position cannot be specified with high accuracy.

  The technique of Patent Document 1 detects the probe pressure based on the strain amount of the strain sensor fixed to the leaf spring, and does not detect the probe position. The challenges are also very different.

  An object of the present invention is to provide an imaging apparatus that can accurately detect the start of movement of a lens unit and accurately specify the reference position of the lens unit.

  An image pickup apparatus according to the present invention includes a lens unit, an elastic member that applies a bias force in the optical axis direction to the lens unit, and the lens unit is pressed in a reverse bias direction against the bias force. A moving unit that moves, a driving unit that drives the moving unit, a strain sensor attached to the elastic member, and a determination unit that determines when the output of the strain sensor has changed as the start of movement of the lens unit It is provided with these.

  According to this configuration, when the output of the strain sensor attached to the elastic member is changed, it is determined as the start of movement of the lens unit. Therefore, the start of movement of the lens unit is accurately detected, and the position sensor is not used. However, the reference position of the lens unit can be specified with high accuracy. That is, even if the moving unit starts pressing the lens unit in the reverse bias direction, the lens unit cannot move immediately, and there is a time lag between when the moving unit starts pressing and when the lens unit actually starts moving. However, in this configuration, when the lens unit actually starts to move is determined as the start of lens unit movement, the time when the drive start signal is output to the actuator as in the conventional case is determined. It is possible to detect the start of movement of the lens unit with higher accuracy than when starting the movement.

  The elastic member is preferably a parallel leaf spring. According to this configuration, since the elastic member is configured by the parallel leaf spring, it is possible to apply a bias force to the lens unit while securing an installation space for the imaging device.

  Moreover, it is preferable that the said elastic member has a bending part, and the said strain sensor is attached to the said bending part. According to this configuration, since the strain sensor is attached to the bent portion where the change of the elastic member first appears when the lens unit moves, the start of movement of the lens unit can be detected with higher accuracy.

  Further, the strain sensor is preferably an electromechanical conversion element attached or vapor-deposited on the elastic member or a strain gauge attached or vapor-deposited on the elastic member.

  According to this configuration, since the strain sensor is configured by an electromechanical transducer or a strain gauge, it is possible to accurately detect the strain of the elastic member while securing the installation space for the imaging device. Further, since the strain gauge or the electromechanical conversion element is attached to the elastic member by vapor deposition or pasting, the strain gauge or the electromechanical conversion element can be easily and firmly attached to the bent portion of the elastic member.

  In addition, the position of the lens unit when the output of the distortion sensor changes is set as a reference position, and imaging of the lens unit is started at a position where the lens unit is moved a predetermined distance from the reference position in the reverse bias direction. It is preferable to further include a setting unit that sets the reference position. According to this configuration, since the imaging start reference position is determined based on the reference position that is the position where the lens unit actually starts to move, the imaging start reference position is accurately determined regardless of variations among the individual imaging devices. be able to.

  The imaging start reference position is preferably an optical infinite equivalent position. According to this configuration, since the imaging start reference position is set to the optical infinity-equivalent position, the optical infinity-equivalent position can be determined with high accuracy regardless of the variation among the individual imaging devices.

  Further, it is preferable that the setting unit sets a position where the lens unit is moved a predetermined distance from the reference position in the reverse bias direction as an upper limit position of the movable range of the lens unit. According to this configuration, since the upper limit position of the movable range of the lens unit is determined based on the reference position, the upper limit position can be determined with high accuracy regardless of the variation among the individual imaging devices.

  In addition, it is preferable that a position obtained by moving the lens unit by a predetermined distance in the reverse bias direction from the imaging start position is set as a lower limit position of the movable range. According to this configuration, since the lower limit position of the movement range of the lens unit is determined with reference to the reference position, the lower limit position can be accurately determined regardless of the variation among the individual imaging devices.

  According to the present invention, since the time when the lens unit actually starts moving is detected as the time when the lens unit starts moving, the time when the lens unit starts moving is accurately determined, and the reference can be obtained without using a position sensor. The position can be specified with high accuracy.

  Hereinafter, an imaging device according to an embodiment of the present invention will be described. FIG. 1 is an external configuration diagram of a camera-equipped mobile phone 70 as an example of an imaging apparatus. FIG. 1A is a perspective view showing a front surface (operation surface) of the camera-equipped mobile phone 70, and FIG. FIG. The camera-equipped cellular phone 70 has a foldable structure in which a first casing 71 and a second casing 72 are connected by a hinge 73 as shown in FIG. An LCD (Liquid Crystal Display) 74 as a display unit for various information is provided on the front surface of the first housing 71, and a key input unit 75 is provided on the front surface of the second housing 71. . Further, as shown in FIG. 1B, a camera unit OP including the lens driving mechanism 10 is built in the back surface of the first housing 71 so that the objective lens is exposed.

  In addition to various dial buttons for operating the mobile phone function, the key input unit 75 includes a mode setting button for starting a shooting mode, switching between still image shooting and moving image shooting, and a camera unit OP. A zoom button for controlling the optical zoom (magnification) operation of the lens driving mechanism 10 and a shutter button for executing a photographing operation are included.

  FIG. 2 is a block diagram showing an electrical configuration of the camera-equipped mobile phone 70. The camera-equipped mobile phone 70 includes a lens driving mechanism 10, a timing generator (TG) 31, an analog front end (AFE) 32, an image processing unit 33, an image memory 34, an amplifier (AMP) 35, a display unit 36, and an image recording unit 37. , A drive voltage generation unit 38 (an example of a drive unit), and a control unit 40.

  The lens driving mechanism 10 includes a leaf spring 11 (an example of an elastic member) that applies a biasing force to the lens unit 12 in a bias direction (downward) that is a downward direction parallel to the optical axis direction, and an optical image of the subject. The lens unit 12 constituting the imaging optical system to be incorporated, the moving unit 13 that moves the lens unit 12 upward by pressing the lens unit 12 in the reverse bias direction (upward) against the bias force, and the leaf spring 11 A strain sensor 14 that is attached and detects the strain of the leaf spring 11; an imaging unit 15 that receives an optical image taken by the lens unit 12 and obtains an image signal; and a holding unit 16 that holds the imaging unit 15; And a housing 17.

  The leaf spring 11 includes a pair of leaf springs 11 and 11 attached to the top and bottom of the lens unit 12. FIG. 3 shows a plan view of the leaf springs 11 and 11. The leaf springs 11 and 11 are made of a flat plate-like metal member having a quadrangular shape when viewed from above, and include an outer frame portion 112, a ring portion 113, and an arm portion 114.

  The outer frame portion 112 is composed of a substantially rectangular frame-shaped member, the outer edge is attached to the inner wall of the housing 17, and the four arm portions 114 are extended from the four vertices of the rectangular inner edge, It is connected to a ring portion 113 located in the center via four arm portions 114. A hole for guiding the optical image of the subject to the imaging unit 15 is formed in the center of the ring unit 113. The arm portion 114 is warped upward with respect to the ring portion 113, whereby the connecting portion between the ring portion 113 and the arm portion 114 is bent to form a bent portion 111. The leaf springs 11 and 11 sandwich the lens unit 12 in the vertical direction and bias the lens unit 12 downward to give a bias force.

  The lens unit 12 has a lens group 121 composed of a plurality of lenses arranged in the optical axis direction, a cylindrical shape with upper and lower surfaces opened to guide an optical image to the imaging unit 15, and a housing 122 that covers the lens group 121. And a diaphragm, a shutter, etc. (not shown). The lens unit 12 is pressed upward by the moving unit 13, slides upward against the biasing force of the plate springs 11, 11, and when the upward pressing by the moving unit 13 disappears, the plate spring 11 , 11 to slide downward and return to the home position.

  The moving unit 13 includes a lever 131 and an SMA (Sharp Memory Alloy) actuator 132. The lever 131 has an upper end 131 a attached to the back surface of the upper leaf spring 11 and a lower end 131 b attached to the right end of the SMA actuator 132. The SMA actuator 132 is disposed between the lower leaf spring 11 and the imaging unit 15, generates heat when energized, and recovers to a previously stored shape when the temperature exceeds the transformation temperature. Here, the SMA actuator 132 is deformed so as to draw the lower end 131b into the center in the left-right direction. As a result, the lever 131 rotates clockwise with the upper end of the holding portion 16 as a fulcrum 161, pushes the upper leaf spring 11 upward, and moves the lens unit 12 upward.

  The strain sensor 14 is attached to the bent portion 111 on the upper surface of the upper leaf spring 11. Here, the strain sensor 14 may be attached to the leaf spring 11 by transfer, or may be deposited on the leaf spring 11 using a technique such as sputtering. As the strain sensor 14, a strain gauge made of a piezoelectric element may be employed, or an electromechanical conversion element such as a piezoelectric element may be employed.

  4A and 4B are enlarged views of the bent portion 111, in which FIG. 4A shows the leaf spring 11 before deformation, and FIG. 4B shows the leaf spring 11 after deformation. As can be seen from a comparison between FIGS. 4A and 4B, when the leaf spring 11 is pressed upward by the lever 131, the bending portion 111 is deformed so that the bending angle θ is widened.

  Therefore, a voltage corresponding to the difference between the strain amount on the upper surface side (inner diameter side) and the strain amount on the lower surface side (outer side) of the strain sensor 14 is generated, and the deformation of the leaf spring 11 can be detected. Specifically, the strain sensor 14 outputs a voltage corresponding to the difference between the strain amount on the inner diameter side and the strain amount on the outer shape side to the control unit 40 via the AMP 35.

  Here, when the leaf spring 11 starts to be deformed, the influence first appears in the bent portion 111. Therefore, by attaching the strain sensor 14 to the bent portion 111, it is possible to quickly detect the start of the deformation of the leaf spring 11. It becomes. In FIG. 2, the strain sensor 14 is attached to the upper surface of the leaf spring 11, but may be attached to the lower surface. Two or more strain sensors 14 may be provided in the bent portion 111, or one or more strain sensors 14 may be attached to the lower leaf spring 11. In this case, the control unit 40 may determine that the leaf spring 11 has started to deform when the output of any one of the strain sensors 14 changes. By doing so, the start of the change of the leaf spring 11 can be detected more accurately. In the lower leaf spring 11, the strain sensor 14 is preferably attached to the bent portion 111 on the back surface.

  The imaging unit 15 includes a sealing unit 151 attached to the SMA actuator 132 side and an imaging element 152 attached to the lower side of the sealing unit 151. For example, an IR cut filter is attached to the surface of the sealing unit 151, and the imaging element 152 is sealed in a recess formed by the inner side wall and the bottom surface 18 of the holding unit 16. The image sensor 152 is configured by an image sensor such as a CMOS image sensor or a CCD image sensor, and receives an optical image captured by the lens unit 12 via the sealing unit 151. The holding unit 16 includes a pair of left and right holding units 16 and 16 attached to the bottom surface 18. The left holding unit 16 holds the SMA actuator 132 on the upper surface. The right holding part 16 includes a standing part 162. The standing portion 162 penetrates and holds the SMA actuator 132, and the upper surface serves as a fulcrum 161 of the lever 131. The housing 17 has, for example, a rectangular parallelepiped shape, and an upper center portion is opened to capture an optical image.

  The timing generator (TG) 31 controls a photographing operation (charge accumulation based on exposure, reading of accumulated charge, etc.) by the image sensor 152. Specifically, the TG 31 generates a predetermined timing pulse (vertical transfer pulse, horizontal transfer pulse, charge sweeping pulse, etc.) based on the reference clock output from the control unit 40, and outputs it to the image sensor 152 for imaging. The imaging operation of the element 152 is controlled. The TG 31 controls the A / D conversion operation and the like by generating a predetermined timing pulse and outputting it to the analog front end (AFE) 32.

  The AFE 32 performs predetermined signal processing on the image signal output from the image sensor 152 (analog signal group received by each pixel of the CCD area sensor), converts the image signal into a digital signal, and outputs the digital signal to the image processing unit 33. The AFE 32 includes a correlated double sampling circuit for reducing reset noise included in the analog image signal voltage, an auto gain control circuit for correcting the level of the analog image signal, a clamp circuit for fixing a potential indicating a black level, and an analog R , G, B image signals are converted to, for example, 14-bit image signals.

  The image processing unit 33 performs predetermined signal processing on the image signal output from the AFE 32. The predetermined image processing includes black level correction, white balance correction, color complementation, gamma correction, and the like. Note that the image processing unit 33 temporarily writes the captured image signal in the image memory 34 in synchronization with the reading of the image sensor 152, and thereafter accesses the image memory 34 to perform image processing on the captured image signal.

  The image memory 34 is composed of, for example, a RAM, temporarily stores image signals and the like, and is used as a work area for the control unit 40 and the image processing unit 33. The AMP 35 amplifies the voltage level output from the strain sensor 14 to a level preferable for the control unit 40 to handle.

  The display unit 36 corresponds to the LCD 74 shown in FIG. 1A and displays a captured image, a live view image before imaging, and the like. The image recording unit 37 includes a memory card or the like, and stores the image data that has been subjected to image processing by the image processing unit 33. The drive voltage generator 38 generates a drive voltage for energizing and heating the SMA actuator 132 under the control of the controller 40.

  The control unit 40 is composed of a microcomputer such as a CPU (Central Processing Unit), controls the whole or a part of the camera-equipped mobile phone 70, and includes a determination unit 41 and a setting unit 42. The determination unit 41 determines the time when the voltage output from the strain sensor 14 is changed as the start of movement of the lens unit 12. Specifically, the determination unit 41 determines the time when the change rate of the voltage output from the strain sensor 14 has changed from 0 as the start of movement of the lens unit 12.

  The setting unit 42 sets the position of the lens unit 12 when the voltage output from the strain sensor 14 is changed by the determination unit 41 as the reference position P1. FIG. 5 is an explanatory diagram of each position set by the setting unit 42. Here, the setting unit 42 may set the reference position P1 by storing, for example, the voltage output from the drive voltage generation unit 38 at the reference position P1 as the reference voltage value Vref.

  The setting unit 42 sets a position where the lens unit 12 is moved upward by a predetermined distance L1 with the reference position P1 as a reference as an imaging start reference position P2 of the lens unit 12. In the present embodiment, the setting unit 42 sets the imaging start reference position P2 as the optical infinite equivalent position P∞. Here, for example, the setting unit 42 stores in advance a relative voltage value Vα indicating how much voltage can be applied to the reference voltage value Vref to move the lens unit 12 to the optical infinite equivalent position P∞. By storing Vref + Vα, the optical infinite equivalent position P∞ may be set. The distance L1 for determining the optical infinite equivalent position P∞ is a preferable distance from the reference position P1 as the optical infinite equivalent position P∞, and an experimentally obtained distance can be adopted.

  Further, the setting unit 42 sets a position where the lens unit 12 is moved upward by a predetermined distance L2 from the reference position P1 as the upper limit position P3 of the movable range of the lens unit 12. Here, the setting unit 42 stores in advance a relative voltage value Vβ indicating, for example, how much voltage is applied from the reference voltage value Vref to move the lens unit 12 to the upper limit position P3, and Vref + Vβ is set as Vref + Vβ. By storing, the upper limit position P3 may be set. The distance L2 may be an experimentally obtained distance that is based on the reference position P1 so that the upper surface of the lens unit 12 does not collide with the housing 17.

  In addition, the setting unit 42 sets a position separated from the reference position P1 by a predetermined distance L3 upward as the lower limit position P4 of the movable range. Here, for example, the setting unit 42 stores in advance a relative voltage value Vγ indicating how much voltage can be applied from the reference voltage value Vref to move the lens unit 12 to the lower limit position P4, and Vref + Vγ. May be stored to set the lower limit position P4. Note that the distance L3 is a position that is preferable as the lower limit position P4 with respect to the reference position P1, and an experimentally obtained distance can be adopted. In the present embodiment, the lower limit position P4 is located between the reference position P1 and the optical infinite equivalent position P∞.

  Next, the operation of the control unit 40 will be described. FIG. 6 is a flowchart showing the operation of the control unit 40. Note that this flowchart may be executed when the imaging apparatus is turned on, for example, every time the power is turned on a predetermined number of times, or may be executed only once at the time of factory shipment. First, in step S <b> 1, the control unit 40 outputs a drive start signal to the drive voltage generation unit 38. In step S <b> 2, the drive voltage generation unit 38 starts applying a voltage to the SMA actuator 132 under the control of the control unit 40. In step S <b> 3, the drive voltage generation unit 38 starts increasing the voltage under the control of the control unit 40. In step S4, the determination unit 41 determines whether or not the voltage of the strain sensor 14 has changed. If the voltage has not changed (NO in step S4), the determination unit 41 further determines that the movement of the lens unit 12 has not started. The voltage is increased with a predetermined resolution (step S5), and the process returns to step S4.

  On the other hand, when the voltage of the strain sensor 14 has changed (YES in step S4), the determination unit 41 stops the voltage increase by the drive voltage generation unit 38 (step S6). In step S <b> 7, the setting unit 42 stores a reference voltage value Vref that is a voltage value from the drive voltage generation unit 38 when the determination unit 41 detects the distortion of the distortion sensor 14, so that the reference of the lens unit 12 is stored. A position P1 is set. That is, the determination unit 41 increases the output to the SMA actuator 132 with a predetermined resolution, and when the voltage of the strain sensor 14 changes and the change of the leaf spring 11 is detected by the strain sensor 14, the lens unit 12. Is determined to have started moving, and the position of the lens unit 12 at that time is set as the reference position P1.

  FIG. 7A is a graph showing the relationship between the voltage applied to the SMA actuator 132 and time, and FIG. 7B is a graph showing the voltage (sensor output) from the strain sensor 14. At time t1, the drive voltage generator 38 starts increasing the voltage applied to the SMA actuator 132. As a result, the SMA actuator 132 is energized and the temperature rises, and when it reaches the transformation temperature, the deformation to the memory shape is started. As a result, the lower end 131b of the lever 131 is pulled leftward as shown in FIG. 2 by the SMA actuator 132, rotates clockwise around the fulcrum 161 as a fulcrum, and presses the leaf spring 11 upward. When the force pressing the leaf spring 11 overcomes the bias force, the leaf spring 11 pushes the lens unit 12 upward. Accordingly, as shown in FIG. 7B, at time t2, the voltage of the strain sensor 14 changes, and the determination unit 41 determines that the lens unit 12 has started moving.

  FIG. 8 is a flowchart showing the operation when the lens unit 12 moves to the optical infinite equivalent position P∞. First, in step S11, the setting unit 42 sets a reference position P1. The setting of the reference position P1 has been described with reference to FIG. In step S12, the drive voltage generation unit 38 increases the voltage from Vref to Vref + Vα at a predetermined increase rate under the control of the control unit 40. Thereby, the lens unit 12 slides upward. Next, when the output voltage becomes Vref + Vα under the control of the control unit 40, the drive voltage generation unit 38 stops the voltage increase and causes the lens unit 12 to wait at the optical infinite equivalent position P∞ (step S13). ). Thereby, the control unit 40 can move the lens unit 12 to the optical infinite equivalent position P∞ without using a position sensor.

  FIG. 9 shows a graph when the lens unit 12 is moved from the reference position P1 to the optical infinite equivalent position P∞, (a) shows the voltage applied to the SMA actuator 132, and (b) shows from the strain sensor 14. (C) shows the position of the lens unit 12. The drive voltage generation unit 38 increases the voltage applied to the SMA actuator 132 at a predetermined increase rate under the control of the control unit 40, and when the determination unit 41 detects the start of movement of the lens unit 12 ( At time t2), the voltage increase is once stopped, and at time t2 ′, the voltage increase is started again. Accordingly, the voltage from the strain sensor 14 increases at time t2 ′ as shown in FIG. 9B, and the lens unit 12 moves upward at time t2 ′ as shown in FIG. 9C. It can be seen that the movement has started.

  Then, when the voltage is increased at a predetermined rate from time t2 ′ and the voltage output from the drive voltage generation unit 38 reaches time t3 when Vref + Vα is reached, the lens unit 12 has reached the optical infinite equivalent position P∞. The drive voltage generator 38 stops increasing the voltage as shown in FIG. Accordingly, the signal output from the strain sensor 14 becomes constant as shown in FIG. 9B, and the lens unit 12 stands by at the optical infinite equivalent position P∞ as shown in FIG. 9C.

  As described above, according to the imaging apparatus according to the present embodiment, since the strain of the leaf spring 11 is detected by the strain sensor 14 attached to the leaf spring 11, the lens unit 12 actually starts moving. Can be detected when the movement of the lens unit 12 starts, and the reference position P1 of the lens unit 12 can be accurately identified without using a position sensor.

  In the above embodiment, the lens drive mechanism 10 is configured to move the lens unit 12 upward by the lever 131. However, the present invention is not limited to this, and for example, a lens drive mechanism as shown in FIG. 10a may be adopted.

  FIG. 10 is a cross-sectional view showing the lens driving mechanism 10a. In FIG. 10, the electrical connection relationship with various blocks such as the control unit 40 is the same as that in FIG.

  The lens driving mechanism 10a is characterized in that the moving unit 13 includes a coil 133 and a permanent magnet 134, and moves the lens unit 12 upward based on the same principle as that of the voice coil motor. The coil 133 is wound with a predetermined number of turns along the circumferential surface of the housing 122 of the lens unit 12. The permanent magnet 134 is composed of, for example, a pair of permanent magnets 134 and 134 attached to the inner wall of the housing 17, and generates a magnetic field in a direction perpendicular to the optical axis direction. Then, when a current is supplied to the coil 133 from the drive voltage generator 38 shown in FIG. 2 under the control of the control unit 40, the coil 133 receives a force in the upward direction according to the Fleming left-hand rule, and the lens unit 12 is moved upward. Slide in the direction.

  In the present invention, a lens driving mechanism 10b shown in FIG. 11 may be adopted instead of the lens driving mechanism 10a shown in FIG. The lens driving mechanism 10 b is characterized in that the moving unit 13 is configured by a polymer actuator 135.

  The polymer actuator 135 is attached between the lower leaf spring 11 and the holding portion 16. Here, on the back surface of the leaf spring 11, for example, one cylindrical polymer actuator 135 that extends along the outer periphery of the bottom surface of the housing 122 is attached between the leaf spring 11 and the holding portion 16 to move the lens unit 12. The plurality of polymer actuators 135 may be spot-attached between the leaf spring 11 and the holding portion 16 so that the total volume of the polymer actuators 135 is reduced.

  When the voltage from the drive voltage generation unit 38 is applied under the control of the control unit 40, the polymer actuator 135 expands in the vertical direction with a magnitude corresponding to the level of the applied voltage. Move up. The actuator for driving the lens is not limited to the motor and polymer actuator as described above, and various actuators can be used.

  The imaging device according to the present invention may be applied to a digital still camera, a digital video camera, a personal digital assistant (PDA), or the like having a built-in photographing lens unit in addition to the camera-equipped cellular phone 70 described above. .

  Moreover, in the said embodiment, although the moving part 13 was controlled by the voltage, it is not limited to this, You may control by an electric current. In this case, the drive voltage generation unit 38 may be configured by a constant current circuit that can vary the current value under the control of the control unit 40.

  In the above-described embodiment, the lower limit position P4 to the upper limit position P3 shown in FIG. 5 are the movable range of the lens unit 12, but the present invention is not limited to this, and the reference position P1 to the upper limit position P3 may be the movable range. Good.

It is an external appearance block diagram of the mobile phone with a camera as an example of an imaging device. It is a block diagram which shows the electrical constitution of the mobile phone with a camera. The top view of a leaf | plate spring is shown. It is an enlarged view of a bending part. It is explanatory drawing of each position which a setting part sets. It is a flowchart which shows operation | movement of a control part. (A) is the graph which showed the relationship between the voltage applied to a SMA actuator, and time, (b) is the graph which showed the signal output from a distortion sensor. It is a flowchart which shows the operation | movement at the time of the lens unit 12 moving to the optical infinite equivalent position P∞. The graph at the time of moving a lens unit from a reference position to an optical infinite equivalent position is shown. It is sectional drawing which showed another example of the lens drive mechanism. It is sectional drawing which showed another example of the lens drive mechanism.

Explanation of symbols

10, 10a, 10b Lens drive mechanism 11 Leaf spring 12 Lens unit 13 Moving unit 14 Strain sensor 15 Imaging unit 40 Control unit 41 Determination unit 42 Setting unit 70 Mobile phone with camera 111 Bending unit 131 Lever 132 SMA actuator 133 Coil 134 Permanent magnet 135 Polymer actuator P∞ Optical infinite equivalent position P1 Reference position P2 Imaging start reference position P3 Upper limit position P4 Lower limit position

Claims (8)

A lens unit;
An elastic member for applying a bias force in the optical axis direction to the lens unit;
A moving unit that moves the lens unit by pressing the lens unit in a reverse bias direction against the bias force;
A drive unit for driving the moving unit;
A strain sensor attached to the elastic member;
An image pickup apparatus comprising: a determination unit that determines a time when the output of the strain sensor changes as a time when the lens unit starts moving.   The imaging apparatus according to claim 1, wherein the elastic member is a parallel leaf spring. The elastic member has a bent portion;
The imaging apparatus according to claim 1, wherein the strain sensor is attached to the bent portion.   4. The strain sensor according to claim 1, wherein the strain sensor is an electromechanical conversion element attached or vapor-deposited on the elastic member or a strain gauge attached or vapor-deposited on the elastic member. Imaging device.   The position of the lens unit when the output of the strain sensor changes is set as a reference position, and the position where the lens unit is moved a predetermined distance in the reverse bias direction from the reference position is the imaging start reference position of the lens unit The imaging apparatus according to claim 1, further comprising: a setting unit that sets as follows.   The imaging apparatus according to claim 5, wherein the imaging start reference position is an optical infinite equivalent position.   The said setting part sets the position which moved the said lens unit the predetermined distance from the said reference position to the said reverse bias direction as an upper limit position of the movable range of the said lens unit, The said Claim 5 or 6 characterized by the above-mentioned. Imaging device.   The said setting part sets the position which moved the said lens unit the predetermined distance from the said imaging start position to the said reverse bias direction as a lower limit position of the said movable range, The said any one of Claims 5-7 characterized by the above-mentioned. The imaging device described.

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