JP2008256800A - Camera module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a camera module which can correctly displace a moving body and can be miniaturized. <P>SOLUTION: In the camera module, the image of an object is formed on an image sensor 2 through an optical system 1 including a lens 1A. In the camera module, the optical system 1 is connected to the moving body 20 through a connection member 21. An actuator 6 is electrically controlled to be displaced. Thus, the moving body 20 is moved in the direction of an arrow R2 and the relative distance between the optical system 1 and the image sensor 2 is changed according to the movement of the moving body. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a camera module, and more particularly to a camera module including an actuator using a piezoelectric element.

  In recent years, there are many products in which camera functions are incorporated in devices such as mobile phones. These products are usually equipped with parts called camera modules. The camera module includes an image pickup device such as a CCD (Charge Coupled Devices) for image pickup, an optical system including a lens for forming an image on the image pickup device, a housing for supporting and protecting these, and the like. .

  Conventional products employ a pan-focus camera module that does not require focus control of captured images. However, recently, in response to the increase in the number of pixels of the image sensor and the improvement of the imaging performance, it has become necessary to perform focus control of the captured image in the camera module. When focus control is performed, a part or all of the optical system in the camera module needs to be configured to be displaceable.

  In order to displace the lens, a drive source (actuator) is required. In camera focus control, there are many technologies related to actuators already installed in film cameras, digital still cameras, and the like. For mobile phones, the size required for the camera module is so small that it cannot be compared with a normal camera. That is, a large-sized actuator cannot be mounted on a mobile phone, and a special small actuator is required.

As an actuator used in terms of small size, an actuator using a piezoelectric element can be cited. In addition, as a prior art about the actuator using a piezoelectric element, there exist some which are disclosed by patent document 1 (Unexamined-Japanese-Patent No. 2006-189648), for example. The gazette discloses a technique for displacing a moving body using the stretchability of a piezoelectric element. More specifically, a driving voltage is applied to the piezoelectric element to electrically expand and contract to vibrate the driving member fixed to the piezoelectric element, and thereby, between the driving member and the moving body frictionally engaged. A technique for displacing a moving body using a frictional relationship is disclosed.
JP 2006-189648 A

  Mobile phones, which are one of the devices on which the above-described camera modules are mounted, have recently become multifunctional, and it is becoming increasingly difficult to secure the space for each component in the mobile phone. In addition, there is a strong demand from users for further miniaturization and thinning of mobile phones, which has spurred downsizing of components used. Such a situation is no exception in the camera module.

  On the other hand, the image sensor, the optical system, the lens driving actuator, and the housing, which are components constituting the above-described camera module, are essential components, and can be omitted even if they can be miniaturized by contrivance.

  In Patent Document 1, as described above, a drive system using a piezoelectric element is described. However, in this system, a position sensor is provided to know the position of a moving body. This is because, when a frictionally engaged moving body (and an optical system fixed to the moving body) is moved with a frictional force, the frictional force fluctuates due to a secular change of the friction member, etc. Variations occur in the amount of displacement of the moving body. In the technique disclosed in Patent Document 1, in order to displace the moving body to a target position, the camera module requires a position sensor that detects the amount of displacement of the moving body for this reason. . When the position sensor is provided, the displacement amount relative to the input to the piezoelectric element can be grasped even when the displacement amount of the moving body decreases due to the secular change of the friction member, etc., so the input amount of electric power to the piezoelectric element is controlled. As a result, a decrease in the driving speed of the moving body can be reduced. That is, the moving body can be accurately displaced.

  However, the above system requires a position sensor, a board and connectors for energizing the sensor, a support member for supporting these, and the like. This has hindered miniaturization of the camera module.

  The present invention has been conceived in view of such circumstances, and an object of the present invention is to provide a camera module capable of accurately displacing a moving body and miniaturizing.

  A camera module according to the present invention is a camera module that forms an image input through a lens with an imaging device, and is frictionally engaged with a drive unit that is displaced by electrical control and the drive unit. Electrically controlling the moving unit, a connecting unit that connects the lens or the image sensor and the moving unit, a focus evaluation unit that evaluates a focus of an image formed by the image sensor, and the drive unit. Accordingly, the focus evaluation unit evaluates the focus while changing the relative distance between the lens and the image sensor, and thereby the image focused on the image formed by the image sensor and the image sensor A focus control means for executing focus control for determining a relative position of the camera and a history information for storing the history information related to the focus control. Storage means, and control mode relation storage means for storing the relationship between the history information and the control mode for the drive unit, wherein the focus control unit is selected from the control modes stored in the control mode relation storage unit. The drive unit is electrically controlled according to a control mode corresponding to history information stored in the history storage means.

  In the camera module according to the aspect of the invention, it is preferable that the history information is information serving as an index of wear of the friction engagement portion of the moving unit and the driving unit.

  In the camera module of the present invention, it is preferable that the history information is information on a time required for one focus control.

  In the camera module according to the aspect of the invention, it is preferable that the history information is information on an accumulated time spent for the focus control.

  In the camera module according to the aspect of the invention, it is preferable that the history information is information on a cumulative number of times the focus control is performed.

  In the camera module according to the aspect of the invention, it is preferable that the history information is information on an accumulated time during which the drive unit is electrically controlled.

  In the camera module according to the aspect of the invention, it is preferable that the history information is information on a cumulative number of times that the drive unit is electrically controlled.

  In the camera module of the present invention, it is preferable that the control mode specifies a value of a voltage input to the driving unit.

  In the camera module of the present invention, it is preferable that the control mode specifies a speed at which a value of a voltage input to the driving unit is changed.

  In the camera module of the present invention, it is preferable that the control mode specifies a frequency of a voltage input to the driving unit.

  In the camera module of the present invention, it is preferable that the control mode is a mode of adjusting a frictional force of a friction engagement portion between the driving unit and the moving unit.

  The focus control unit electrically controls the drive unit according to the control mode corresponding to the history information stored in the history storage unit from among the control modes stored in the control mode relationship storage unit. Even if a sensor for detection is not provided, the position of the moving unit can be accurately displaced based on the history.

  Therefore, in the camera module, the moving body can be accurately displaced, and the sensor for detecting the position of the moving body can be omitted, so that the size can be reduced.

  FIG. 1 is a diagram schematically showing a schematic configuration of a camera module according to an embodiment of the present invention, and FIG. 2 is a control block diagram of the camera module.

  1 and 2, the camera module 10 mainly includes an optical system 1, an image sensor 2, a moving body 20, and an actuator 6 that drives the moving body 20. The optical system 1 is an element for forming a subject image on the image sensor 2, and includes elements provided in a general optical system, such as a lens 1A, a mirror (not shown), and members that support these. Including. The imaging device 2 is an element that receives an image formed by the optical system 1 and is configured by an image sensor using a CCD or a CMOS (Complementary Metal Oxide Semiconductor), for example. The optical system 1 and the image sensor 2 are accommodated in a housing 7.

  In the camera module 10 of the present embodiment, the relative position of the optical system 1 with respect to the image sensor 2 is changed by the actuator 6 in order to form a subject image on the image sensor 2. The actuator 6 is constituted by a small actuator using a piezoelectric element, for example. The actuator 6 and the optical system 1 are connected by a connecting member 21.

  It is necessary to determine whether the image obtained by the image sensor 2 is focused on the subject (whether it is in focus). If the photographer can operate the focus adjustment portion of the camera module 10, the photographer may adjust the focus while determining the in-focus state. However, when the determination is made on the camera module 10 side, some means for evaluating whether or not the camera module 10 is in focus is required.

  In the present embodiment, the focus evaluation unit 3 evaluates whether or not the subject is in focus. Note that how the focus evaluation unit 3 evaluates whether or not it is in focus will be described later.

  The actuator control unit 4 controls the movement of the actuator 6 (which drives the optical system 1) based on information regarding whether or not the focus evaluation unit 3 has focused.

  The drive unit 5 is a part that electrically drives the actuator 6 based on information from the actuator control unit 4.

  The history storage unit 8 stores a result related to the focus control in the past focus control. Further, in the control mode relation storage unit 9, a relationship between history information (for example, average focus control time) related to focus control and a control mode for the actuator 6 (for example, amplitude of voltage input to the actuator 6) as described later. Information for identifying is stored.

FIG. 3 schematically shows a hardware configuration of the camera module 10.
The camera module 10 includes a CPU (Central Processing Unit) 91 that controls the overall operation of the camera module 10 described above, a main storage device 92 including a semiconductor memory, and a RAM (Random Access Memory) 94 that functions as a work area for the CPU 91. In addition, an actuator driving unit 95 that controls input of a voltage to the actuator 6 as will be described later, and an external I / F (external interface) 96 that is an interface with a device main body on which the camera module 10 is mounted. The external I / F 96 also reads and writes information to and from external media such as an SD memory card (Secure Digital memory card). The CPU 91 controls the operation of the camera module 10 by executing a program stored in the main storage device 92 (and / or an external medium). In FIG. 22, the focus evaluation unit 3 and the actuator control unit 4 are configured by a CPU 91, the drive unit 5 is configured by an actuator drive unit 95, and the history storage unit 8 is configured by a main storage device 92. In the camera module 10, image data imaged on the image sensor 2 is continuously input to the CPU 91 as a finder image, and further, for example, a shutter button input via the external I / F 96 is operated. In response to the information to that effect, the image data is stored as a captured image in the main storage device 92 (and / or an external medium).

  The actuator 6 uses a bimorph piezoelectric element. Here, the configuration of the actuator 6 will be described in detail with reference to FIGS.

  4 and 5 show an example of the configuration of the bimorph piezoelectric element. An electrode 11 and an electrode 13 are provided on each of the main surface and the back surface of the plate-like piezoelectric element 12. When the voltage + V is applied, the piezoelectric element 12 is subjected to polarization treatment so as to contract as indicated by an arrow in FIG. Therefore, as shown in FIG. 5, when a voltage (−V) opposite to that applied in FIG. 4 is applied to the piezoelectric element 12 as shown in FIG. Stretch to.

  FIG. 6 shows a state in which two piezoelectric elements as shown in FIG. 4 or 5 are fixed to the stationary object 14 while being overlapped via the core member 17. In FIG. 6, the same voltage is applied to the electrode 11 provided on the upper piezoelectric element 12 and the electrode 13 provided on the lower piezoelectric element 12, and the voltage is provided on the upper piezoelectric element 12. The state where the voltage of the same potential is applied to the electrode 13 provided and the electrode 11 provided on the lower piezoelectric element 12 is shown. In this state, when an AC voltage is applied from the power supply, when one piezoelectric element 12 (upper or lower) contracts, the other piezoelectric element 12 expands. As a result, as indicated by a double-headed arrow R12 in the figure, one end of the core member 17 (the right end in FIG. 6) is moved up and down, that is, in the state shown in FIG. 7 (B) is displaced so as to alternate with the state shown in FIG.

  FIG. 8 shows an example of the configuration of the actuator 6 using such behavior when a voltage is applied to the electrodes 11 and 13 of the piezoelectric element 12.

  In the actuator 6 shown in FIG. 8, two sets of bimorph actuators 100 and 200 are disposed at both ends of the link member 16. The link member 16 is an elastic body, and both ends thereof are fixed to the stationary object 14, and a drive unit 15 is attached to the center thereof. In the actuator 6 shown in FIG. 8, the link material 16 is commonly used as the core material of the two bimorph actuators 100 and 200, but this is not always necessary.

  The electrodes 11 and 13 of each piezoelectric element 12 are connected as shown in FIG. An input voltage to the bimorph actuator 100 is a voltage V1, and an input voltage to the bimorph actuator 200 is an input V2. When the voltages V1 and V2 are changed with respect to time as shown in FIG. 9, the bimorph actuators 100 and 200 in FIG. 8 are displaced in opposite phases. FIG. 10 shows a state where the bimorph actuator 100 and the bimorph actuator 200 are displaced in opposite phases.

  With reference to FIG. 10, in this state, in the actuator 6, the link member 16 is deformed into an N shape because the bimorph actuator 100 and the bimorph actuator 200 are displaced in different phases. In FIG. 10, solid arrows and broken arrows indicating the displacement of the bimorph actuator 100, the bimorph actuator 200, the driving unit 15, and the moving body 20 are shown. 9, each part of the actuator 6 is displaced in the direction indicated by the solid line in FIG. Further, in the period indicated as “recovery” in FIG. 9, each part of the actuator 6 is displaced in the direction indicated by the broken line in FIG. 10. That is, when a voltage is input to the actuator 6 once in a manner shown by “outgoing” and “returning” in FIG. 9, the displacement shown by the solid line in FIG. The displacement indicated by the broken line is realized. In FIG. 9, one set of “when going” and “when returning” is shown as “1 step”. The actuator 6 repeats the displacement in the solid line direction and the displacement in the broken line direction in FIG. 10 by repeating the input mode of the “forward” and “return” voltages in FIG. Thereby, the drive part 15 reciprocates so that the displacement of a continuous line direction and the displacement of a broken line direction may be repeated.

  FIG. 10 is a diagram illustrating a state in which the actuator 6 has been displaced from the state illustrated in FIG. On the other hand, FIG. 11 shows a state in which the actuator 6 is displaced during the “return time” period.

  Then, as shown by an arrow R <b> 1 in FIG. 10, the moving body 20 is arranged so as to be frictionally engaged with the drive unit 15 of the actuator 6, and accordingly, with the displacement of the drive unit 15. , Move in the left-right direction (in the direction indicated by arrows R21, R22 of the moving body 20 in FIG. 10).

  Note that the lengths of the arrow R21 and the arrow R22 in FIG. 10 are different because the displacement amount in each direction of the moving body 20 differs when a voltage is input to the actuator 6 in the manner shown in FIG. Means. Here, it is assumed that the arrow R21 corresponds to the displacement of the moving body 20 at the time of going in FIG. 9, and the arrow R22 corresponds to the displacement of the moving body 20 at the time of returning in FIG. In the following, the reason why the displacement amount of the moving body 20 is different between the forward time and the backward time (while the displacement amount of the drive unit 15 is the same) will be described.

  A moving body 20 is disposed above the drive unit 15, and the moving body 20 is pressurized so as to be frictionally engaged with the drive unit 15. As shown in FIG. 9, the moving body 20 can be moved in the left-right direction by making the forward period and the backward period different.

  That is, the amount of displacement of the drive unit 15 is the same between the forward time and the backward time, but the time required for the displacement is different, so the speed of the drive unit 15 is different between the forward time and the backward time. When a voltage is applied as shown in FIG. 9, the speed in the forward direction is slower than that in the reverse direction. Therefore, the acceleration of the drive unit 15 is smaller in the forward period than in the reverse period, and the force applied to the drive unit 15 is also weakened. The moving body 20 can be displaced from the relationship between the driving force of the driving unit 15 during the reciprocation and the frictional force between the moving body 20 and the driving unit 15.

  When the driving force of the driving unit 15 is smaller than the frictional force between the moving body 20 and the driving unit 15 at the time of traveling, the moving body 20 moves rightward in synchronization with the movement of the driving unit 15.

  Further, when the driving force of the driving unit 15 is larger than the static frictional force between the moving body 20 and the driving unit 15 at the time of recovery, the moving body 20 looks like sliding with respect to the movement of the driving unit 15. Although it moves slightly to the left, the amount of displacement at this time is smaller than the amount of displacement in the past.

  FIG. 12 is a diagram showing displacement of the moving body 20 when the AC voltage shown in FIG. 9 is repeatedly applied to the actuator 6. The moving body 20 moves to the right while repeating the forward displacement and the backward displacement. If the forward and return times are combined into one step, the movement amount that the moving body 20 moves in one step is the difference between the displacement amount in the forward time and the displacement amount in the backward time.

  In the present embodiment, since the moving body 20 and the optical system 1 are coupled by the connecting member 21, the optical system 1 can be driven if a voltage is input to the actuator 6. In addition, when moving the mobile body 20 in the direction opposite to the “moving direction in the past” described with reference to FIGS. 9 and 10, the time for changing the input voltage described with reference to FIG. May be reversed between the “outgoing” period and the “returning” period.

  Next, focus evaluation on an image formed on the image sensor 2 in the camera module 10 of the present embodiment will be described.

  As illustrated in FIG. 13, when the imaging device 500 in which the camera module 10 is mounted captures a subject S that exists in the field of view A <b> 1 of the imaging device 500, an image of the subject F is captured on the imaging device 2. Imaged. In the camera module 10, focus evaluation on an image formed on the image sensor 2 is performed based on a brightness histogram of the image.

  14A and 14B are brightness histograms of image data input from the image sensor 2 to the CPU 91, respectively. FIG. 14A is an example of a brightness histogram in a focused state, and FIG. 14B is an example of a brightness histogram in a out of focus state. In the brightness histograms shown in FIGS. 14A and 14B, the horizontal axis defines the pixel brightness and the vertical axis defines the pixel frequency.

  In the camera module 10, the frequency Mo for determining the focus evaluation is set in advance for the brightness histogram. Note that the value Mo is appropriately set based on a general technique in focus evaluation and identification of the image sensor 2 and is stored in the main storage device 92, for example.

  In the brightness histogram curves shown in FIGS. 14A and 14B, the maximum value in the range of brightness (image brightness) having a frequency equal to or higher than Mo is set as the focus evaluation value C. Here, Co is set as the evaluation value C obtained based on the brightness histogram of the focused image in FIG. 14A, and based on FIG. 14B, which is the brightness histogram of the focused image. The evaluation value C obtained in this way is defined as Co.

  In general, an in-focus image has a high contrast, and an image that is out of focus in the same image has a low contrast. This is because the lightness of the image that is not in focus is a medium value overall. That is, Co> Cx.

  FIG. 15 shows the relationship between the optical system-image sensor distance (the distance between the optical system 1 and the image sensor 2) and the focus evaluation value C. If the captured image is focused at the optical system-imaging element distance Fo, the focus evaluation value at that point is maximized, and the value is considered to be Co. In the description with reference to FIG. 14A and FIG. 15, the brightness histogram is created for the pixels of the entire captured image, but the same result can be obtained by performing similar processing on a part of the captured image.

  Here, a description will be given with reference to FIG. 16 which is a flowchart of a focus control process executed to adjust the focus in the camera module 10.

  When photographing, it is necessary to first move the position of the optical system to the reference position. Therefore, in the focus control process, first, in step S1, the CPU 91 moves the optical system 1 to a predetermined reference position (initial position). This movement is assumed, for example, in the MAX position where the optical system 1 is the maximum movement position (a position farthest from the initial position where the optical system 1 can be moved by the moving body 20 in the housing 7). This is realized by giving the actuator 6 a drive amount (electric power) necessary for moving from the position to the initial position.

  If the optical system 1 is present at a position other than the MAX position at the time when step S1 is executed, the actuator 6 is driven even after the optical system 1 returns to the initial position (the voltage is changed). Will be input). However, the actuator 6 drives the moving body 20 (that is, the optical system 1 coupled thereto) by the frictional force between the driving unit 15 and the moving body 20. Further, the camera module 10 is provided with a mechanism for supporting the optical system 1 so that it does not move further from the initial position even if the movable body 20 is further driven after the optical system 1 returns to the initial position. . Thus, as described above, even if an excessive voltage is input to the actuator 6 (even after the optical system 1 returns to the initial position), the drive unit 15 simply slides on the moving body 20. The camera module 10 (for example, the optical system 1) is not damaged.

As described above, in the camera module 10, the optical system 1 is configured to be movable from the initial position to the MAX position, which is the maximum movement position set by design, when the moving body 20 is driven. Yes. As shown in FIG. 17, the horizontal axis is the driving amount (= step number) of the actuator 6 that moves the optical system 1 and the vertical axis is the position of the optical system 1. The position changes from the initial position F ₁ to the MAX position via the positions F ₂ and F ₃ . In FIG. 17, the position of the optical system 1 when in focus is shown as a focus position Ff. When the optical system 1 is specified by the focus position _Ff , the distance between the optical system 1 and the image sensor 2 is the optical system-image sensor distance Fo (or a value close thereto) in FIG.

In the present embodiment, the optical system 1 is gradually moved, and focus evaluation is performed each time the optical system 1 is moved. Prior to the movement, first, in step S2, the CPU 91 calculates the evaluation value C1 at the initial position F1 based on the image input from the image pickup device 2 at that time, as shown in FIG. In order to generate such a graph, the evaluation value C ₁ is stored in the RAM 94.

Next, the CPU 91 inputs an appropriate voltage to the actuator 6 to move the optical system 1 by a predetermined displacement amount L (step S3), and calculates an evaluation value C _n at the position F _n and the evaluation. The value is stored in the RAM 94 (step S4).

Next, in step S5, the CPU 91 compares the evaluation value (C _n ) stored in the RAM 94 in the previous step S4 with the evaluation value (C _n−1 ) stored in the previous round. For example, if you are moved in the previous step S4 from the initial position F1 only in the moving position F2 L _{C 2} is stored in the RAM 94, in step S5, the _{C 1} and _{C 2} are compared. As a result of the comparison, if the CPU 91 determines that C _n−1 ≦ C _n , the CPU 91 returns the process to step S3, and if it determines that C _n−1 > C _n , the CPU 91 advances the process to step S6.

As can be understood from FIG. 15, while C _n−1 ≦ C _n, it is considered that C _n has not yet reached the focus point, and if C _n−1 > C _n , It is considered that the focus point has been reached (passed through the focus point). The process of step S5 is a process performed based on such an idea.

In step S6, the CPU 91 moves the optical system 1 to the position F _n-1 when C _n-1 is stored, and ends the focus control process.

  For the predetermined displacement amount L, which is a unit for moving the optical system 1, an arbitrary value may be set based on the size of the optical system 1 or the like.

Next, the movement of the optical system 1 when focus control is performed will be described.
In the camera module 10, as described with reference to FIG. 1, the optical system 1 is connected to the moving body 20 frictionally engaged with the actuator 6 by the connecting member 21. Thereby, the optical system 1 can move so as to change the distance from the image sensor 2 as the moving body 20 moves.

  When focus control is performed, as described above, the position of the optical system 1 is gradually moved from the initial position (for example, closer to the image sensor 2), and the optical system 1 is moved by a predetermined displacement amount L. Therefore, every time a voltage is input to the actuator 6, the focus is evaluated.

  However, even if a voltage is input to the actuator 6 so that the optical system 1 moves by the predetermined displacement amount L, the optical system 1 does not necessarily move by the predetermined displacement amount L actually. The reason is that the actuator 6 moves the frictionally engaged moving body 20 with a frictional force, so that the frictional force fluctuates due to the secular change of the frictional member (the part where both frictional engagements are performed). This is because the moving amount of the moving body 20 with respect to voltage input varies. In addition, as a secular change, the fall of the frictional force by degradation or wear of a friction member is mentioned.

  In the present embodiment, in order to detect how much the friction force is reduced at the engagement site, for example, the time required for one focus control is detected. This is because when the frictional force is reduced, even if a voltage is input to the actuator in the same pattern for the same time, the amount of movement of the moving body 20 by the actuator 6 decreases, and thus, until the control ends (the optical system 1 at the focus position). This is due to the fact that it takes a long time to reach.

  However, the distance that the optical system 1 needs to move in the focus control is the distance (positional relationship) between the imaging device on which the camera module 10 is mounted and the subject (other than the decrease in the frictional force) and the like. Therefore, even if there is no change in the frictional force, the actuator drive time (that is, the time required for focus control; hereinafter also referred to as focus control time) changes.

  For this reason, it is impossible to determine the decrease in the frictional force with one focus control time. In order to avoid this problem, for example, a decrease in the frictional force of the actuator is determined as an average focus control time using an average value of several times of past focus control times. In this way, there is a low possibility that the user will make a judgment error even if the distance to the subject to be photographed is different for each photographing.

  The focus control time can be counted, for example, by counting the number of clocks of the CPU 91 from the start to the end of the focus control process. This count number may be stored in the history storage unit 8 as the focus control time. To obtain the average focus control time, for example, to obtain the average of the past 10 focus control times, 10 history storage areas are prepared in the history storage unit 8, and the latest 10 focus control times are prepared. Store time. Then, when the focus control is performed next time, based on the time required for the current focus control process and the average value of the latest ten focus control times stored in the history storage unit 8, A reduction amount of the frictional force at the engagement portion is determined.

  As a method of reducing a decrease in the amount of movement of the moving body 20 due to a decrease in frictional force, there is a method of increasing the amplitude of the input voltage applied to the actuator 6. From the fact that the displacement of the bimorph actuator is proportional to the input voltage, the amount of displacement of the drive unit 15 (in the direction indicated by the solid line or broken line arrow in FIG. 10) can be increased by increasing the amplitude of the input voltage. . If the displacement amount of the drive unit 15 can be increased, the distance that can be frictionally driven with respect to the moving body 20 is increased, and the moving amount of the moving body 20 per step can be increased. Thereby, the fall of the movement amount by the fall of frictional force can be reduced.

  When the amplitude of the voltage input to the actuator 6 is controlled, if the relationship of the friction force with respect to the average focus control time is as shown in FIG. 18, it is possible to reduce the decrease in the moving amount of the moving body 20 due to the friction force reduction. The relationship of the input voltage amplitude (the amplitude of the voltage input to the actuator 6) with respect to the average focus control time may be set as shown in FIG.

  Further, in the case of controlling the amplitude of the input voltage applied to the actuator, when the relationship of the friction force with respect to the average focus control time is as shown in FIG. 18, in order to reduce the decrease in the moving amount of the moving body 20 due to the friction force reduction, FIG. As shown in FIG. 20, the input voltage amplitude may be changed stepwise for a certain average focus control time range.

  FIG. 18 is a diagram schematically showing the relationship between the average focus control time and the friction force, and is not a specific measurement result of the friction force. However, in the camera module, the relationship as shown in FIG. 18 is stored in the history storage unit 8 or the like in advance, and by calculating the average focus control time, the CPU 91 stores the calculated value and the relationship stored. It is possible to predict how much the frictional force of the engagement portion is reduced by referring to FIG.

  In addition, as another method for reducing a decrease in the amount of movement of the moving body 20 due to a decrease in frictional force, a method of reducing the recovery period within one cycle (in one step) of the input voltage shown in FIG. There is. As described above, this controls the expansion / contraction speed of the piezoelectric element 12. That is, the speed of the drive unit 15 when going and returning is controlled.

  Specifically, by reducing the recovery period, the moving speed of the drive unit 15 at the time of recovery increases, and thereby the acceleration applied to the drive unit 15 increases, so that the drive unit 15 slides the moving body 20. However, the time for the force to move in the reverse direction is reduced. For this reason, the distance that the moving body 20 moves in the backward direction within one step is reduced. Accordingly, the moving amount of the moving body 20 in the forward direction within one step increases. Thereby, the fall of the movement amount by the fall of frictional force can be reduced. When controlling the period of reciprocation given to the actuator 6, assuming that the ratio between the forward times with respect to the return period is “outgoing period rate”, if the relationship of the friction force to the average focus control time is as shown in FIG. In order to reduce the decrease in the moving amount of the moving body due to the reduction, the relationship of the forward period rate with respect to the average focus control time may be set as shown in FIG. 19, or a constant average focus control time as shown in FIG. The forward period rate may be changed stepwise with respect to the range.

  Further, in the present embodiment, as another method for reducing a decrease in the amount of movement of the moving body 20 due to a decrease in the frictional force at the engagement site, a method of increasing the frequency of the input voltage applied to the actuator 6 is also conceivable. By increasing the frequency of the input voltage, the driving amount of the driving unit 15 per unit time (the amount of electric power input to the actuator 6) can be increased, whereby the moving amount of the moving body 20 can be increased. Accordingly, it is possible to reduce a decrease in the amount of movement due to a decrease in frictional force. When controlling the frequency of the voltage input to the actuator 6, assuming that the relationship of the frictional force with respect to the average focus control time is as shown in FIG. 18, in order to reduce the decrease in the moving amount of the moving body 20 due to the reduction of the frictional force, The relationship between the input voltage frequency and the average focus control time may be set as shown in FIG. Alternatively, as shown in FIG. 20, the input voltage frequency may be changed stepwise within a certain average focus control time range.

  In addition, as another method for reducing a decrease in the amount of movement of the moving body 20 due to a decrease in the frictional force at the engagement portion in the present embodiment, the frictional force between the drive unit 15 of the actuator 6 and the moving body 20 is increased. There is a method. FIG. 21 shows an example of a modification of the camera module 10 for increasing the frictional force.

  In the modification shown in FIG. 21, a mechanism for pressing the actuator 6 toward the moving body 20 is added to the camera module shown in FIG. Specifically, the pressurizing piezoelectric element 22 attached to the pressurizing piezoelectric element fixing member 23 is attached to the actuator 6 on the side opposite to the side facing the moving body 20. It is desirable that the pressurizing piezoelectric element fixing member 23 is connected to a member supporting the moving body 20. The pressurizing piezoelectric element 22 is arranged so that the actuator 6 expands and contracts in a direction toward the moving body 20 (a direction indicated by a double-headed arrow R4) when a voltage is supplied from a power source (power source 90) (not shown). When a voltage is applied to the pressurizing piezoelectric element 22 so as to extend in the direction of the double arrow R4, the actuator 6 is pressed against the moving body 20. Actually, the drive unit 15 of the actuator 6 is pressed against the moving body 20. That is, when a voltage is applied so that the pressurizing piezoelectric element 22 extends in the direction of the moving body 15, the frictional force between the driving unit 15 and the moving body 20 increases. Thereby, the fall of the movement amount by the fall of frictional force can be reduced. When the CPU 91 controls the input voltage applied to the pressurizing piezoelectric element 22, the amount of expansion / contraction of the pressurizing piezoelectric element 22 is proportional to the value of the applied voltage, so the relationship of the friction force with respect to the average focus control time is as shown in FIG. Assuming that there is a reduction in the amount of movement of the moving body 20 due to the reduction in frictional force, the relationship between the value of the input voltage applied to the pressurizing piezoelectric element 22 with respect to the average focus control time is set as shown in FIG. Good (however, the input voltage applied in the direction in which the pressurizing piezoelectric element 22 extends is positive), or the input voltage applied to the pressurizing piezoelectric element 22 over a certain average focus control time range as shown in FIG. It may be changed in stages.

  In the camera module 10 described above, information for specifying the relationship as described with reference to FIGS. 19 to 20 is stored in the control mode relationship storage unit 9.

[Other variations]
In the camera module 10, the CPU 91 detects, for example, how much the friction force is reduced between the actuator 6 and the moving body 20. Count) or accumulated focus control time (time when the focus control process is executed) is counted, and it is possible to determine how much the friction force is reduced based on the counted value. This is related to the fact that the focus control is accompanied by the operation of the actuator 6, and when the number of times of focus control or the control time increases, the time for the engagement portion of the drive unit 15 and the moving body 20 to friction increases. This is because it is considered that the wear progresses and the frictional force decreases.

  A method similar to that described with reference to FIGS. 18 to 20 may be applied as a method for reducing a decrease in driving force due to a decrease in frictional force. That is, the same effect can be obtained by replacing each horizontal axis in FIGS. 18 to 20 with the cumulative number of times of focus control or the cumulative control time.

  That is, in the focus control process, the CPU 91 changes the input voltage amplitude, the forward period rate, the frequency (of the input voltage), or the input voltage to the pressurizing piezoelectric element 22 in FIG. 19 or FIG. Based on the relationship, the value is changed to a value corresponding to the current focus control cumulative number (or cumulative control time).

  In order to count the cumulative focus control count, the CPU 91 adds “+1” to the count value stored in the history storage unit 8 every time focus control is performed.

  In order to count the cumulative focus control time, the CPU 91 adds the time from the start to the end of the process to the history storage unit 8 when executing the focus control process. The time can be the number of clocks of the CPU 91, for example. Then, when the actuator is driven next, the value in the history storage unit 8 is referred to, and the input voltage to the actuator 6 is controlled based on the result.

[About other modifications]
In addition, the CPU 91 detects, for example, how many times the frictional force is reduced in the engagement portion between the actuator 6 of the camera module 10 and the moving body 20, for example, the cumulative number of driving or the cumulative driving of the driving unit 15 of the actuator 6. You can guess by counting time. This is because when the number of times of driving of the driving unit or the driving time increases, the frictional force decreases due to wear of the contact portion of the driving unit 15 and the moving body 20.

  A method similar to that described with reference to FIGS. 18 to 20 may be applied as a method for reducing a decrease in driving force due to a decrease in frictional force. That is, the same effect can be obtained by replacing each horizontal axis in FIGS. 18 to 20 with the drive unit cumulative drive count or the cumulative drive time.

  In order to count the drive unit cumulative drive count or cumulative drive time, the drive amount (= number of steps) or drive time given to the actuator 6 may be counted cumulatively, and each time the actuator 6 is driven, the step driven at that time The number or driving time is added to the history storage unit. Then, when the actuator is driven next, the value in the history storage unit is referred to, and the input voltage to the actuator may be controlled based on the result.

  As described above, in the camera module 10 described above, the focus is adjusted by displacing the optical system 1 with respect to the image sensor 2. However, as shown in FIG. 22, the image sensor 2 is displaced with respect to the optical system 1. May be. In this case, instead of the optical system 1, the imaging element 2 is connected to the moving body 20 and the connecting member 21. Specific control contents can be dealt with by appropriately replacing “optical system 1” in the above description with “imaging device 2”.

  In the above-described embodiment, an example in which a piezoelectric element is used as the actuator 6 has been described and described. However, if the displacement of the driving unit 15 can be electrically controlled similarly, a device other than the piezoelectric element is used. You can do the same thing with.

  Further, as a method of reducing the driving force decrease due to the decrease in the frictional force, the input voltage amplitude to the actuator 6 is increased, the displacement speed of the driving unit 15 of the actuator 6 is controlled, and the signal frequency for driving the actuator 6 is increased. Each method of controlling the frictional force between the driving unit 15 of the actuator 6 and the moving body 20 has been described above. However, when these methods are executed without a decrease in the frictional force being estimated, Will cause problems. The reason is that the execution of these methods increases the minimum resolution of the focus control and causes a decrease in focus accuracy. The amount by which the moving body 20 is displaced in one step of driving the actuator 6 is the minimum resolution of the focus control process. Therefore, in the present embodiment, it is preferable that each method is executed only when a decrease in the frictional force of the engagement portion is detected.

  Further, in the present embodiment described above, the camera module 10 has been described as being incorporated in another device. However, the camera module 10 functions as a single imaging device like the imaging device 500. It may be configured. That is, for example, as shown in FIG. 23, the camera module 10 further includes an input unit 97 that accepts external operation content, so that the camera module 10 functions alone as an imaging device rather than being incorporated into another device. It may be configured as follows.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows typically schematic structure of the camera module which is one embodiment of this invention. It is a control block diagram of the camera module of FIG. It is a figure which shows typically the hardware constitutions of the camera module of FIG. It is a figure which shows an example of a structure of a bimorph piezoelectric element. It is a figure which shows an example of a structure of a bimorph piezoelectric element. It is a figure which shows the state by which the piezoelectric element of FIG. 4 or FIG. 5 was fixed to the stationary object. It is a figure for demonstrating the behavior when a voltage is applied to the piezoelectric element of FIG. It is a figure which shows typically the structure of an example of the actuator utilized with the camera module of this Embodiment. It is a figure which shows the change of the voltage input into two bimorph actuators shown by FIG. FIG. 10 is a diagram illustrating a state in which the forward voltage of FIG. 9 is input to the actuator illustrated in FIG. 8. FIG. 10 is a diagram illustrating a state in which the voltage at the time of return in FIG. 9 of the actuator illustrated in FIG. 8 is input. It is a figure which shows the change of the displacement amount of a drive part and a moving body when a voltage is input into an actuator as FIG. 9 showed. It is a figure which shows typically the state which image | photographs a to-be-photographed object with the imaging device carrying the camera module of FIG. It is a figure which shows an example of the brightness histogram about the image imaged in the image pick-up element of the camera module of FIG. The relationship between the optical system-image sensor distance and the focus evaluation value in the camera module of FIG. 1 is shown. It is a flowchart of the focus control process performed in the camera module of FIG. It is a figure which shows the relationship between the step number which drives an actuator, and the position of an optical system in the camera module of FIG. It is a figure which shows an example of the relationship of the frictional force with respect to the average focus control time in the camera module of FIG. FIG. 2 is a diagram illustrating an example of a relationship between various values such as an input voltage amplitude with respect to an average focus control time in the camera module of FIG. 1. FIG. 10 is a diagram illustrating another example of the relationship between various values such as input voltage amplitude with respect to the average focus control time in the camera module of FIG. 1. It is a figure which shows the modification of the camera module of FIG. It is a figure which shows the modification of the control block diagram of FIG. It is a figure which shows typically the hardware constitutions of one Embodiment of the imaging device of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Optical system, 1A lens, 2 Image pick-up element, 3 Focus evaluation part, 4 Actuator control part, 5 Drive part, 6 Actuator, 7 Case, 9 Control aspect relationship memory | storage part, 10 Camera module, 11, 13 Electrode, 12 Piezoelectric Element, 14 Stationary object, 15 Drive unit, 16 Link member, 17 Core material, 20 Moving body, 21 Connecting member, 22 Pressurizing piezoelectric element, 23 Pressurizing piezoelectric element fixing member, 91 CPU, 92 Main memory, 94 RAM , 95 Actuator drive unit, 96 External I / F, 97 Input unit, 100, 200 Bimorph actuator.

Claims (11)

In a camera module that forms an image input through a lens with an image sensor,
A drive unit that is displaced by being electrically controlled; and
A moving part frictionally engaged with the driving part;
A connecting part for connecting the lens or the image sensor and the moving part;
Focus evaluation means for evaluating the focus of an image formed by the image sensor;
The focus evaluation means evaluates the focus while changing the relative distance between the lens and the image sensor by electrically controlling the drive unit, and thereby the image formed on the image sensor is changed. A focus control means for performing focus control for determining a relative position between the lens and the image sensor in focus;
History storage means for storing history information related to the focus control;
Control mode relationship storage means for storing a relationship between the history information and a control mode for the drive unit;
The focus control unit electrically controls the drive unit according to a control mode corresponding to history information stored in the history storage unit from among control modes stored in the control mode relationship storage unit. module.   The camera module according to claim 1, wherein the history information is information serving as an index of wear of a friction engagement portion between the moving unit and the driving unit.   The camera module according to claim 1, wherein the history information is information of a time required for one focus control.   The camera module according to claim 1, wherein the history information is information on an accumulated time spent for the focus control.   The camera module according to claim 1, wherein the history information is information on a cumulative number of times the focus control has been performed.   The camera module according to claim 1, wherein the history information is information of an accumulated time during which the drive unit is electrically controlled.   The camera module according to claim 1, wherein the history information is information on a cumulative number of times that the drive unit is electrically controlled.   The camera module according to claim 1, wherein the control mode specifies a value of a voltage input to the drive unit.   The camera module according to claim 1, wherein the control mode specifies a speed at which a value of a voltage input to the driving unit is changed.   The camera module according to claim 1, wherein the control mode specifies a frequency of a voltage input to the drive unit.   The camera module according to any one of claims 1 to 7, wherein the control mode is a mode of adjusting a frictional force of a friction engagement portion between the driving unit and the moving unit.

Images