JP2008276091A - Drive unit and mobile module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit and mobile module for moving a part to be driven with a shape memory alloy as a driving source, which is capable of driving at a high speed regardless of an environmental temperature and a position of the part to be driven. <P>SOLUTION: In the drive unit and mobile module for moving the part to be driven with the shape memory alloy as the driving source, a timing when the part to be driven is moved is controlled on the basis of a movement target position of the part to be driven and a stabilization time corresponding to this position, which is required for stopping in the position of the part to be driven, so that the part to be driven can be moved in the shortest driving time. Thus the drive unit and mobile module can be driven at a high speed regardless of an environmental temperature and the position of the part to be driven. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drive unit and a movable module, and more particularly to a drive unit and a movable module using a shape memory alloy as a drive source.

  In recent years, digital camera functions have come to be standard-installed in personal devices typified by mobile phones, and accordingly, there has been an increasing demand for smaller and lighter camera modules. On the other hand, camera modules used for personal devices and the like are also strongly demanded to have high functions such as an autofocus function and a camera shake correction function.

  For example, taking autofocus as an example, release timing is important when shooting with personal devices, since snapshot-like shooting is overwhelming, and in order to minimize the release time lag, autofocus speedup is important. Required. The same applies to camera shake correction.

  Therefore, when it is determined that the movement of the focus adjustment lens cannot be completed within the movement period based on the maximum drive speed and drive delay time of the focus adjustment lens, the focus adjustment is performed up to the amount that the focus adjustment lens can move within the movement period. A method has been proposed in which the autofocus function is properly functioned by maximizing the performance of the lens unit by reducing the driving amount of the lens for use (see, for example, Patent Document 1).

  On the other hand, an actuator for driving an optical system and a mechanical mechanism is indispensable for enhancing the functionality of a camera module used in personal equipment, etc., and an actuator for enhancing the function while satisfying the demand for a reduction in size and weight. It has been demanded.

Under such circumstances, an actuator using a shape memory alloy is attracting attention as an actuator for achieving high functionality while satisfying the demand for reduction in size and weight. Shape memory alloy is an alloy that has the property of recovering to its original shape by martensitic transformation when it is deformed below a certain temperature and heated above that temperature, as typified by an alloy of titanium and nickel. By using this property, the shape memory alloy can be heated to operate as an actuator.
JP 2005-277765 A

  However, in the method proposed in Patent Document 1, the focusing range using the autofocus function is narrowed to limit the shooting range, and thus the problem of speeding up autofocus cannot be solved.

  The present invention has been made in view of the above circumstances, and in a drive unit and a movable module that move a driven part using a shape memory alloy as a driving source, high-speed driving is possible regardless of the environmental temperature and the position of the driven part. An object is to provide a drive unit and a movable module.

  The object of the present invention can be achieved by the following constitution.

1. A biasing member that biases the driven part in one direction;
A shape memory alloy configured to move the driven part in a direction different from the direction of the urging force of the urging member by being energized;
In a drive unit comprising a shape memory alloy drive unit for controlling energization to the shape memory alloy,
The shape memory alloy driving unit is
A drive unit for energizing the shape memory alloy;
A shape memory alloy resistance value calculation unit that calculates a resistance value of the shape memory alloy when energized by the drive unit;
A storage unit that stores a stable time corresponding to a position where the driven unit is moved until the driven unit stops at the position;
The movement of the driven part is controlled based on the resistance value of the shape memory alloy calculated by the shape memory alloy resistance value calculating part, and the position where the driven part is moved is stored in the storage part. A drive unit comprising: a control unit that controls a timing for moving the driven unit based on a stabilization time corresponding to a position where the driven unit is moved.

  2. 2. The drive unit according to 1, wherein when the driven unit is moved stepwise, the control unit moves the driven unit to the next stage after the stabilization time corresponding to the position of the driven unit has elapsed.

  3. The drive unit according to 1 or 2, wherein the storage unit stores a stable time corresponding to the position of the driven unit for each ambient temperature around the shape memory alloy.

4). A driven part;
A movable module comprising the drive unit according to any one of 1 to 3.

  5. 5. The movable module according to 4, wherein the driven part is an imaging optical system that constitutes an imaging apparatus.

  6). 5. The movable module according to 4, wherein the driven part is a shutter blade constituting a shutter unit.

  7. 5. The movable module according to 4, wherein the driven part is a correction lens constituting a camera shake correction unit.

  According to the present invention, in the drive unit and the movable module that move the driven part using the shape memory alloy as the driving source, the position where the driven part is moved and the driven part corresponding to the position are stopped at that position. By controlling the timing of moving the driven part based on the stabilization time until the driven part can be moved in the shortest driving time, high speed is achieved regardless of the environmental temperature and the position of the driven part. A drive unit and a movable module that can be driven can be provided.

  Hereinafter, the present invention will be described based on the illustrated embodiment, but the present invention is not limited to the embodiment. In the drawings, the same or equivalent parts are denoted by the same reference numerals, and redundant description is omitted.

  First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing an example of an imaging apparatus according to the first embodiment of the present invention.

  In FIG. 1, an imaging apparatus 10 is a camera module built in, for example, a mobile phone, and includes an imaging optical system 201, an autofocus (hereinafter referred to as AF) mechanism 100, a camera circuit 300, and the like. The camera circuit 300 includes an imaging element 301, an imaging unit 320, a control unit 310, a storage unit 340, an SMA driving unit 330, and the like. The imaging device 10 is a movable module in the present invention, and the AF mechanism 100 and the camera circuit 300 function as a drive unit in the present invention.

  The imaging optical system 201 forms an optical image of a subject on the imaging surface of the image sensor 301. The AF mechanism 100 performs focus adjustment by moving the imaging optical system 201 in the direction of the optical axis 203. The AF mechanism 100 includes a wire-shaped shape memory alloy (hereinafter referred to as SMA) as a drive source for moving the imaging optical system 201. The AF mechanism 100 will be described in detail after FIG.

  The optical image of the subject imaged on the imaging surface of the imaging element 301 is photoelectrically converted by the imaging element 301 and converted into digitized image data by the imaging unit 320. The image data before photographing is displayed as a moving image as a preview image on the display unit 999 via the control unit 310. In addition, the image data after shooting is stored in the storage unit 340 configured by a memory or the like via the control unit 310 and is appropriately displayed on the display unit 999 as a shot image. The display unit 999 is, for example, a liquid crystal display screen of a mobile phone.

  The imaging unit 320 obtains the above-described image data by controlling the operation of the imaging element 301. In addition, the imaging unit 320 cooperates with the control unit 310 and image data of pixels (hereinafter referred to as AF pixels) in a partial area (hereinafter referred to as AF area) on the imaging surface of the imaging element 301. Is used to detect focus information (hereinafter referred to as AF data AFD).

  The SMA driving unit 330 controls the driving of the AF mechanism 100 by controlling energization to the SMA, and moves the imaging optical system 201 in the direction of the optical axis 203, thereby adjusting the focus of the imaging optical system 201. The SMA driving unit 330 will be described in detail with reference to FIG. The focus detection and focus adjustment described above are collectively referred to as an AF operation.

  The control unit 310 includes, for example, a microcomputer, and controls the entire operation of the imaging apparatus 10 including the imaging operation by the imaging element 301 and the imaging unit 320 described above and the AF operation. The control unit 310 may be a microcomputer that controls a device in which the imaging apparatus 10 such as a mobile phone is incorporated.

  Next, the configuration and operation of the AF mechanism 100 described above will be described with reference to FIGS. FIG. 2 is a schematic diagram showing an example of the configuration and operation of the main part of the AF mechanism 100. FIG. 2A shows the AF mechanism 100 along the AA ′ plane perpendicular to the optical axis 203 in FIG. FIGS. 2B and 2C are side views of the AF mechanism 100 viewed from the B direction in FIG. 2A.

  In FIG. 2, the AF mechanism 100 includes a base plate 101, a top plate 103, an SMA support unit 105, a lens barrel 111, a lens driving frame 113, an SMA 151, a tension guide 153, an SMA fixing unit 155, an urging spring 131, and a driving arm 121. And a displacement input unit 123 and the like. The imaging optical system 201 is fixed inside the lens barrel 111. In this example, the image sensor 301 is disposed on the base plate 101, but this is not essential, and may be disposed at the imaging position of the image capturing optical system 201.

  In FIG. 2A, the SMA 151 has a wire shape with a wire diameter of about several tens of μm, for example, and is extended between two displacement input portions 123 and a tension guide 153 attached to the drive arm 121. Both ends of the SMA 151 are fixed to the SMA support portion 105 by a fixing method such as caulking by two SMA fixing portions 155 that also serve as electrodes while being pulled with a predetermined tension.

  Two beams 131a of the lens drive frame 113 are placed on the two flat portions 121a of the drive arm 121, respectively, and the movement of the flat portion 121a of the drive arm 121 is transmitted to the lens drive frame 113. It has a configuration. Note that the circumferential portion 113b of the lens drive frame 113 is urged from the front side of the paper surface of FIG. 2A by the urging spring 131 toward the back side of the paper surface. 113 a is pressed against the flat portion 121 a of the drive arm 121.

  FIG. 2B shows a state where no current is supplied to the SMA 151. The lens barrel 111 and the lens driving frame 113 are integrated by, for example, adhesion, and are urged downward from above the paper surface in the direction of the optical axis 203 by the urging spring 131 which is an urging member in the present invention. It is pressed to the 101 side. The driving arm 121 is also urged downward from above in the direction of the optical axis 203 by the urging spring 131 through the two flat portions 121a and the two beams 131a of the lens driving frame 113.

  FIG. 2C shows a state where a current is supplied to the SMA 151. The drive arm 121 has a so-called pantograph structure. When a current is passed through the SMA 151, the length of the SMA 151 contracts, and the contraction force acts on the two displacement input parts 123 to compress the drive arm 121. Force Fx.

  Due to the compressive force Fx, the driving arm 121 resists the biasing force Fz by the biasing spring 131 described above, and the lens barrel 111 and the lens driving frame 113 via the two flat portions 121a and the two beams 131a. Is pushed up from below in the direction of the optical axis 203. As a result, the imaging optical system 201 is extended from the bottom to the top in the direction of the optical axis 203, that is, from the infinity side to the nearest side.

  As described above, the SMA 151 and the biasing spring 131 function as an actuator that drives the imaging optical system 201 via the lens barrel 111, the lens driving frame 113, and the driving arm 121. Here, the imaging optical system 201 is a driven portion in the present invention.

  Here, the relationship between the SMA 151 and the driving arm 121 will be described with reference to FIGS. 3A and 3B are schematic diagrams for explaining the relationship between the SMA 151 and the drive arm 121. FIG. 3A shows the operation of the SMA 151, and FIG. 3B shows the operation of the drive arm 121.

  In FIG. 3A, it is assumed that the SMA 151 contracts from the state of the length Ls1 to the state of the length Ls2. The SMA 151 cannot move between both end portions fixed by the SMA fixing portion 155 and the central portion laid over the tension guide 153. Therefore, the change in the length of the SMA 151 becomes a change X in the positions of the portions 151a and 151b where the SMA 151 is in contact with the displacement input unit 123 of the drive arm 121. The position change X causes the compression force described above to be applied to the displacement input unit 123. Fx is added.

  3B, when the two displacement input portions 123 of the drive arm 121 receive the compression force Fx and are pushed inward by X in the pantograph shape, the drive arm 121 is deformed, and the flat portion of the drive arm 121 is deformed. 121a is pushed up by the amount of movement Z from the bottom to the top of FIG. 3B against the biasing force Fz by the biasing spring 131.

  FIG. 4 is a schematic graph showing the relationship between the movement amount Z of the drive arm 121, that is, the feed amount Z of the imaging optical system 201, and the characteristics of the SMA 151. FIG. 4A shows the feed amount Z and the SMA 151. 4B shows the relationship between the length Lsma of the SMA 151 and the resistance value Rsma, and FIG. 4C shows the relationship between the feed amount Z and the resistance value Rsma of the SMA 151.

  In FIG. 4A, the moving amount Z of the driving arm 121, that is, the feeding amount Z of the imaging optical system 201 and the length Lsma of the SMA 151 are one-to-one although they are non-linear regardless of the ambient temperature Ta around the SMA 151. There is a relationship. The length SMA of the SMA 151 when no driving current is supplied to the SMA 151 is set to Lsma = L0, and the feed amount Z at this time is set to Z0. When the drive current is supplied to the SMA 151 and the SMA 151 generates heat, the length Lsma of the SMA 151 is shortened and, as shown in FIG. 3, the drive arm 121 is pushed up by the compression force Fx of the SMA 151. Until the length Lsma = Lhp, the amount of biasing force Fz of the biasing spring 131 is larger, so that the feed amount Z remains Z0.

  When the drive current further increases and the length Lsma of the SMA 151 becomes Lsma ≦ Lhp, the compression force Fx by the SMA 151 becomes larger than the urging force Fz of the urging spring 131 and the drive arm 121 starts to be pushed up. The feed amount Z = Zinf for focusing the imaging optical system 201 to infinity is set, and the length SMA 151 at this time is set to Lsma = Linf. Further, the feeding amount Z = Znt for focusing the imaging optical system 201 to the closest distance is set, and the length SMA 151 at this time is set to Lsma = Lnt. A region from the feed amount Z = Z0 to Z = Zinf is a region where the imaging optical system 201 cannot focus (hereinafter referred to as an over-infinite region).

  In FIG. 4B, the resistance value Rsma = R0 of the SMA 151 when the driving current is not applied to the SMA 151, that is, when the length SMA of the SMA 151 is L0. When a drive current is applied to the SMA 151, the SMA 151 generates heat due to Joule heat caused by its own resistance value Rsma, and the temperature Tsma of the SMA 151 rises. In the case of the SMA 151 alone, when the temperature Tsma of the SMA 151 rises and the length Lsma of the SMA 151 starts to decrease, the resistance value Rsma of the SMA 151 increases first, and when the length SMA 151 becomes shorter than a certain length, the resistance value Rsma of the SMA 151 decreases. Turn.

  However, in the system in which the urging force Fz is always applied to the SMA 151 by the urging spring 131 as in the AF mechanism 100, the above-described reversal phenomenon of the resistance value Rsma of the SMA 151 is hardly seen, and the length Lsma of the SMA 151 and the resistance It is known that there is a one-to-one relationship with the value Rsma, regardless of the ambient temperature Ta around the SMA 151, although it is non-linear.

  The resistance value Rsma = Rhp of the SMA 151 when the length Lsma = Lhp of the SMA 151 is assumed. Similarly, the resistance value Rsma = Rinf at the length Lsma = Linf of the SMA 151 for focusing the imaging optical system 201 to infinity, and the length Lnt of the SMA 151 for focusing the imaging optical system 201 to the closest distance Resistance value Rsma = Rnt.

  In FIG. 4C, from the relationship described in FIGS. 4A and 4B, the ambient temperature around the SMA 151 is also between the feed amount Z of the imaging optical system 201 and the resistance value Rsma of the SMA 151. Regardless of Ta, a one-to-one relationship is established although it is non-linear. When the SMA 151 is energized and generates heat, the resistance value Rsma of the SMA 151 decreases, the length Lsma decreases, and the feed amount Z increases. That is, the imaging optical system 201 moves from the infinity side to the closest distance side. Will be paid out. When the resistance value Rsma of the SMA 151 is between Rmax and Rhp, the urging force Fz by the urging spring is larger than the compression force Fx by the SMA 151, so that the feed amount Z remains Z0.

  The resistance value Rsma = Rhp to Rinf of the SMA 151 is in a state where the imaging optical system 201 is in an infinite range where focusing cannot be performed, and the focusing of the imaging optical system 201 is between Rsma = Rinf and Rnt. It is an area. The region of Rsma> Rnt is a region that is in focus closer to the closest distance than the closest distance. However, in this region, generally, sufficient optical performance cannot be obtained due to aberration of the imaging optical system 201, peripheral light amount, and the like. .

  As shown in FIG. 4C, the movement amount of the drive arm 121, that is, the feed amount Z of the imaging optical system 201 and the resistance value Rsma of the SMA 151 are non-linear regardless of the ambient temperature Ta around the SMA 151. A one-to-one relationship is established. That is, by controlling the resistance value of the SMA 151 to be a predetermined resistance value, it is possible to control the in-focus position of the imaging optical system 201 regardless of the ambient temperature Ta around the SMA 151.

  FIG. 5 is a diagram showing the relationship between the feed amount Z of the imaging optical system 201 and the target resistance value Rsma of the SMA 151. FIG. 5A shows the feed amount Z and the target resistance value Rsma shown in FIG. FIG. 5B is an example of a feeding position table ZT showing the relationship of FIG. 5A. FIG. 5B is a graph obtained by enlarging a part between Rsma = Rinf and Rnt.

  In the first embodiment, it is assumed that the focusing operation of the imaging optical system 201 is performed by so-called step driving in which the imaging optical system 201 is extended at equal intervals. Here, an AF step number n (n is 0 (zero) or a positive integer) is introduced as a parameter indicating the feeding position of the imaging optical system 201 during step driving. A target when the resistance value Rsma of the SMA 151 is controlled so that the feeding position of the imaging optical system 201 when the AF step number is n is Z (n) and the imaging optical system 201 is moved to the feeding position Z (n). The resistance value is Rtg (n).

  When the relationship between the feed amount Z shown in FIG. 4C and the feed position Z (n) described above is arranged, the feed position Z (0) at the AF step number n = 0 (zero) has a current flowing through the SMA 151. The initial position Z0 is not energized. Similarly, the feeding position Z (1) at the AF step number n = 1 is the infinity position Zinf for focusing the imaging optical system 201 to infinity, and the feeding position Z (nt) at the AF step number n = nt. Is the closest position Znt that focuses the imaging optical system 201 to the closest distance.

  In FIG. 5A, assuming that the imaging optical system 201 is extended in units of equally-spaced movement width ΔZ, for example, each of the imaging optical systems 201 at the time of AF step number n = k−2, k−1, k, k + 1. Let position Z (n) be Z (k−2), Z (k−1), Z (k) and Z (k + 1). At this time, when the imaging optical system 201 is extended by energizing the SMA 151 with the drive current Is (n) and increasing the temperature Tsma of the SMA 151, it corresponds to each extension position Z (n) of the imaging optical system 201. The target resistance value Rtg (n) of the SMA 151 is Rtg (k−2), Rtg (k−1), Rtg (k), and Rtg (k + 1), respectively. As described with reference to FIG. There is a one-to-one relationship, although it is non-linear, regardless of the ambient temperature Ta.

  In FIG. 5B, the feeding position table ZT includes the AF step number n, the target resistance value Rtg (n) of the SMA 151 when the imaging optical system 201 corresponding to the AF step number n is moved to each feeding position Z (n), and The SMA 151 includes a reference SMA drive current value Is (n) for setting the resistance value Rs (n) of the SMA 151 to the target resistance value Rtg (n).

  When n = 1, that is, the target resistance value Rtg (1) = Rinf when the imaging optical system 201 is focused to infinity, the SMA drive current value Is (1) = Iinf, and n = nt, that is, the imaging optical system 201 is recently The target resistance value Rtg (nt) = Rnt when focusing on the contact distance, and the SMA drive current value Is (nt) = Int. Similarly, n = k, that is, the target resistance value when moving the imaging optical system 201 to the extended position Z (k) is Rtg (k), and the SMA drive current value is Is (k).

  However, since the imaging optical system 201 has a depth of field that depends on its focal length and aperture value, for example, the infinity position Zinf is closer to the imaging optical system 201 from the infinity by the depth of field. The corresponding resistance value Rinf may be set to a lower resistance value corresponding to the depth of field. Similarly, the closest position Znt may be focused at a distance far from the closest distance by the depth of field, and the corresponding resistance value Rnt may be set to a resistance value that is higher by an amount corresponding to the depth of field. .

  Here, the feeding position table ZT stores, for example, a target resistance value Rtg (n) calculated at the time of focus adjustment of the imaging optical system 201 and an SMA drive current value Is (n) used at that time. Created with. The feeding position table ZT is provided, for example, in the storage unit 340 of FIG. 1 and is used in the flowcharts shown in FIGS. 11 and 15.

  The example of the feeding position table ZT described above is composed of the resistance value Rs (n) of the SMA 151 and a reference SMA drive current value Is (n) for making it the target resistance value Rtg (n). For example, the resistance value Rs (n) of the SMA 151 and a reference SMA drive voltage value Vs (n) for making the target resistance value Rtg (n) may be used. .

  Next, a method for detecting the resistance value Rs (n) of the SMA 151 will be described with reference to FIG. FIG. 6 is a block diagram illustrating an example of a circuit configuration of the SMA driving unit 330.

  In FIG. 6, the SMA drive unit 330 includes a drive unit 331, an SMA resistance value calculation unit 333, a comparison unit 335, a drive amount calculation unit 337, a reference resistor 339, and the like. The operation of the SMA driving unit 330 is controlled by the control unit 310.

  First, an approximate value of the SMA drive current Is (n) stored in the feed position table ZT of FIG. 5B on the storage unit 340 is transmitted to the drive unit 331 via the control unit 310, and the SMA drive is performed. The current Is (n) is energized to the SMA 151 via the reference resistor 339 by the driving unit 331. As described above, the drive voltage may be controlled using the approximate SMA drive voltage value Vs (n).

  The SMA resistance value calculation unit 333 receives the potentials Vd and Vsma at both ends of the reference resistor 339, and the current resistance value Rs (n) of the SMA 151 is calculated from the potentials Vd and Vsma according to (Expression 1) described later. The

  The current resistance value Rs (n) calculated by the SMA resistance value calculation unit 333 is input to one input of the comparison unit 335, and the feeding position in FIG. 5B is input to the other input via the control unit 310. The target resistance value Rtg (n) stored in the table ZT is input and compared. The comparison result of the comparison unit 335 is input to the drive amount calculation unit 337, and the drive amount of the SMA 151 (in this example, the drive unit 331) is calculated from the current resistance value Rs (n) and the target resistance value Rtg (n) of the SMA 151. The control value of the drive current Is (n) is calculated and fed back to the drive unit 331.

Here, the current resistance value Rs (n) of the SMA 151 is obtained. First, if the resistance value of the reference resistor 339 is Rd, the potential (Vd−Vsma) at both ends of the reference resistor 339 is
Vd−Vsma = Is (n) × Rd
From this, the current SMA drive current Is (n) is
Is (n) = (Vd−Vsma) / Rd
The potential at the lower end of the reference resistor 339, that is, the potential Vsma at the upper end of the SMA 151 is
Vsma = Is (n) × Rs (n)
Therefore, the current resistance value Rs (n) of the SMA 151 is
Rs (n) = Vsma / Is (n)
= (Vsma / (Vd−Vsma)) × Rd (1 formula)
It becomes. Since the resistance value Rd of the reference resistor 339 is known, the current resistance value Rs (n) of the SMA 151 can be obtained by measuring the potentials Vd and Vsma at both ends of the reference resistor 339.

  Subsequently, the operation of the imaging apparatus 10 according to the first embodiment will be described with reference to FIGS. FIG. 7 is a main routine of a flowchart showing an operation flow of the imaging apparatus 10.

  In FIG. 7, when an operation for photographing is performed in step S101, for example, the user sets the mobile phone in the camera mode, the power of the imaging device 10 is turned on in step S103, and step S200 “status detection subroutine” is performed. ”Is executed, and a state related to the SMA 151 such as a defect such as a disconnection or a short circuit of the SMA 151 and the detection of the environmental temperature Ta in the vicinity of the SMA 151 is confirmed (state detection step). Step S200 “status detection subroutine” will be described with reference to FIG.

  Next, step S300 “lens infinity position setting subroutine” is executed, the imaging optical system 201 is set to the infinity position (lens infinity position setting step), and imaging with the imaging device 10 is started in step S111. Thus, display of the preview image on the display unit 999 is started (preview process). The preview image displayed here is an image focused at infinity. Step S300 “lens infinite position setting subroutine” will be described with reference to FIG.

  In step S113, it is confirmed whether or not the release switch is turned on by the user. It waits in step S113 until the release switch is turned on (release detection step). When the release switch is turned on (step S113; Yes), step S400 “AF subroutine” is executed, and the imaging optical system 201 is moved to the in-focus position on the subject (AF process). Step S400 “AF subroutine” will be described with reference to FIG.

  Photographing is performed in step S121 (imaging process), the captured image data is stored in the storage unit 340 (image data storage process), and in step S123, the captured image is appropriately displayed on the display unit 999 ( Image display process). In step S125, it is confirmed whether or not to end the shooting (shooting end confirmation step). If the photographing is not finished (step S125; No), the process returns to step S200 “status detection subroutine” to check the status of the SMA 151, and thereafter the above-described operation is repeated.

  When the photographing is finished (step S125; Yes), the power of the imaging device 10 is turned off in step S131, and the series of operations is finished. The operation of the imaging apparatus 10 described above is controlled by the control unit 310.

  FIG. 8 is a flowchart showing step S200 “status detection subroutine” of FIG.

  In FIG. 8, in step S201, the AF step number n indicating the feed position of the imaging optical system 201 is set to “0 (zero)” indicating the initial position (initial position parameter setting step). In step S203, the SMA 151 is energized with a predetermined initial current Is (0) stored in advance in the storage unit 340 (initial current energization step). The initial current Is (0) is a current value of about several mA, for example. By supplying the initial current Is (0), the temperature Tsma of the SMA 151 becomes higher than the ambient temperature Ta around the SMA 151. For example, the focus controller of the imaging optical system 201 detects an increase value ΔTsma of the temperature Tsma of the SMA 151. It is sufficient to detect the increase value ΔTsma of the temperature Tsma at the time of focus adjustment, store it in the storage unit 340, and correct that amount.

  In step S205, the initial resistance value Rs (0) of the SMA 151 is detected by the SMA resistance value calculation unit 333 using the above-described (1 expression) (initial resistance value calculation step). Here, Rs (0) is the resistance value R0 of the SMA 151 when no drive current is applied to the SMA 151 of FIG. The energization time of the predetermined initial current Is (0) may be a time necessary for detecting the initial resistance value Rs (0) of the SMA 151 in step S205.

  Although details will be described later with reference to FIG. 10A, the initial resistance value Rs (0) when the drive current Is (n) is not applied to the SMA 151 has a one-to-one correspondence with the ambient temperature Ta around the SMA 151. is there. Accordingly, it is assumed that the initial resistance value Rs (0) of the SMA 151 detected by applying the initial current Is (0) corresponds to the temperature increase value ΔTsma caused by the ambient temperature Ta around the SMA 151 + the initial current Is (0). Good.

  Subsequently, step S600 “SMA disconnection detection subroutine” is executed to check whether or not there is a malfunction such as disconnection or short circuit of the SMA 151 (SMA disconnection detection step). Step S600 “SMA disconnection detection subroutine” will be described with reference to FIG. When the state of the SMA 151 is normal, in step S207, based on the resistance value Rs (0) of the SMA 151 detected in step S205, the control unit 310 performs an environmental temperature table described later with reference to FIG. The environmental temperature Ta is read from the TaT, or the environmental temperature Ta is calculated from the value of the environmental temperature table TaT (environment temperature calculating step).

  In step S209, the temperature increase value ΔTsma caused by the initial current Is (0) stored in the storage unit 340 by the control unit 310 is read from the environmental temperature table TaT read in step S207 or calculated. Subtracted (environmental temperature correction step). As a result, the temperature rise of the SMA 151 due to the initial current Is (0) can be corrected, and the true environmental temperature Ta can be obtained. Subsequently, the process returns to step S200 of FIG.

  Alternatively, in step S203, if the initial current Is (0) is set to a very small current that does not generate much heat from the SMA 151 itself, the temperature Tsma of the SMA 151 matches the ambient temperature Ta around the SMA 151. Correction of the temperature increase value ΔTsma by the current Is (0) is not necessary, and step S209 can be omitted.

  In this case, since the initial current Is (0) is a very small current, the potentials Vd and Vsma at both ends of the reference resistor 339 are very small. Therefore, the detection gain of the SMA resistance value calculation unit 333 is increased to increase the detection accuracy. It is desirable to consider such as improving Here, the control unit 310 functions as a state detection unit, a disconnection detection unit, a temperature detection unit, and a temperature correction unit in the present invention.

  It should be noted that the detection of the environmental temperature Ta by the step S200 “state detection subroutine” is desirably executed every time shooting is performed in order to be used for correcting the temperature characteristics of the imaging device 10. However, for example, when the environmental temperature does not change greatly between the shootings, such as continuous shooting for continuously shooting a plurality of images, the environmental temperature Ta may be detected immediately before the first shooting is performed. .

  FIG. 9 is a flowchart showing step S600 “SMA disconnection detection subroutine” of FIG. Here, prior to the calculation of the environmental temperature Ta in step S207 of FIG. 8, an abnormality in resistance value due to disconnection or short circuit of the SMA 151 is confirmed.

  In FIG. 9, in step S601, it is confirmed whether or not the initial resistance value Rs (0) of the SMA 151 detected in step S205 in FIG. 8 is smaller than a predetermined resistance value R1. If the initial resistance value Rs (0) of the SMA 151 is greater than or equal to the predetermined resistance value R1 (step S601; No), it is determined that the SMA 151 is disconnected, and an SMA disconnection flag is set in step S651. For example, the SMA 151 is prohibited from being energized, and the process proceeds to an “abnormal processing routine” for performing processing in the event of an abnormality such as displaying a warning for an abnormal state or notifying with a warning sound. Details of the “abnormal processing routine” are omitted.

  If the initial resistance value Rs (0) of the SMA 151 is smaller than the predetermined resistance value R1 (step S601; Yes), whether or not the initial resistance value Rs (0) of the SMA 151 is larger than the predetermined resistance value R2 in step S611. Is confirmed. If the initial resistance value Rs (0) of the SMA 151 is smaller than or equal to the predetermined resistance value R2 (step S611; No), it is determined that the SMA 151 is short-circuited or the leakage current is large, and AF is performed in step S631. A disabled flag is set and, for example, the process shifts to a “lens position fixing routine” for performing processing such as moving the imaging optical system 201 to a predetermined fixed position (for example, a normal focus position focusing on a distance of several meters) by mechanical means. To do. Details of the “lens position fixing routine” are omitted.

  When the initial resistance value Rs (0) of the SMA 151 is larger than the predetermined resistance value R2 (step S611; Yes), an SMA normal flag is set in step S621, and the process returns to step S600 in FIG.

  The predetermined resistance values R1 and R2 described above are a slightly higher resistance value and a slightly lower resistance value than the range of resistance values that the SMA 151 can take. For example, when the resistance value that the SMA 151 can take is 30Ω to 35Ω, R1 = 50Ω and R2 = 20Ω may be set.

  FIG. 10 is a diagram showing the relationship between the initial resistance value Rs (0) of the SMA 151 and the ambient temperature Ta around the SMA 151. FIG. 10 (a) shows the relationship between the initial resistance value Rs (0) and the ambient temperature Ta. FIG. 10B shows an example of the environmental temperature table TaT.

  The initial length Ls (0) when the SMA 151 is not energized and the initial resistance value Rs (0) are maintained around the SMA 151 while maintaining the one-to-one relationship shown in FIG. It is known to change depending on the environmental temperature Ta. Therefore, a one-to-one relationship is established between the environmental temperature Ta and the initial resistance value Rs (0). An example of this relationship is the graph shown in FIG. Here, the environmental temperature Ta is taken on the horizontal axis and the initial resistance value Rs (0) is taken on the vertical axis, and the relationship between the environmental temperature Ta and the initial resistance value Rs (0) is shown.

  The initial resistance value Rs (0) (30Ω in this example) at the maximum value of the environmental temperature Ta (+ 60 ° C. in this example) is larger than the infinity position resistance value Rinf corresponding to the infinity position of the imaging optical system 201. Need to be set to When this relationship is reversed, near the maximum value of the environmental temperature Ta, the SMA 151 is not energized with the SMA drive current Is (n), and the imaging optical system 201 passes through the infinity position Zinf and reaches a position where it is focused on a finite distance. Because it will move. The reason why the over infinite region is provided in the first embodiment is as described above.

  10B, the environmental temperature table TaT is a table showing the relationship shown in the graph of FIG. 10A. The initial resistance value Rs (0) of the SMA 151 and the environmental temperature Ta around the SMA 151 corresponding to the initial resistance value Rs (0). Is a conversion table consisting of In this example, the range of the table is, for example, from −20 ° C. to + 60 ° C., which is the guaranteed operating temperature range of the imaging device 10, and the initial resistance value Rs (0) therebetween is equally spaced (for example, 35Ω to 30Ω is 1Ω spaced). The ambient temperature Ta corresponding to each initial resistance value Rs (0) is tabulated. What is necessary is just to determine the division | segmentation space | interval of a table in consideration of the detection accuracy of the required environmental temperature Ta.

  Alternatively, when an initial resistance value Rs (0) that does not exist in the environmental temperature table TaT is detected in step S205 in FIG. 8, in step S207 in FIG. 8, for example, the detected initial resistance value that exists in the environmental temperature table TaT. The ambient temperature Ta around the SMA 151 may be calculated by a method such as proportional distribution from the initial resistance values Rs (0) above and below Rs (0). Further, instead of the environmental temperature table TaT, a conversion formula for converting the initial resistance value Rs (0) into the environmental temperature Ta may be stored.

  In FIG. 11, in step S301, the AF step number n indicating the extended position of the imaging optical system 201 is set to “1” indicating the infinity position (infinity position parameter setting step). In step S303, the infinity position resistance value Rinf of the SMA 151 corresponding to the feeding position Z (1) = Zinf when the imaging optical system 201 is focused at infinity from the feeding position table ZT of FIG. The reference SMA drive current value Iinf for the resistance value of the SMA 151 to become the infinite position resistance value Rinf is read (infinite position resistance value reading step).

  In step S305, the target resistance value Rtg (n) that is a control target in the following control is set to the infinity position resistance value Rinf read in step S303 (infinity position target resistance value setting step), and in step S307. , The drive current Is (n) of the SMA 151 is set to the reference SMA drive current value Iinf read in step S303 (infinity position drive current value setting step).

  Subsequently, Step S500 “Lens Drive Subroutine” is executed to control the drive current Is (n) supplied to the SMA 151 so that the resistance value Rs (n) of the SMA 151 becomes the infinite position resistance value Rinf. Thus, the imaging optical system 201 is moved to the infinity position Zinf (imaging optical system infinity position setting step), and the process returns to step S300 in FIG. Step S500 “lens driving subroutine” will be described with reference to FIG.

  FIG. 12 is a flowchart showing step S500 “lens drive subroutine” in FIG. 11 and FIG. 15 described later.

  In FIG. 12, in step S501, the stable time tst (n) is read from the stable time table STT based on the AF step number n indicating the feeding position of the imaging optical system 201 and the ambient temperature Ta around the SMA 151 (read stable time). Process). The environmental temperature Ta is accurately detected by detecting the initial resistance value Rs (0) of the SMA 151 in step S200 “state detection subroutine” of FIG.

  As described above, the stabilization time tst (n) is the feeding position Z (n) of the imaging optical system 201 when the imaging optical system 201 is moved from the position of the AF step number n-1 to the position of the AF step number n. ) Is the time required to stabilize. The stable time tst (n) and the stable time table STT will be described later with reference to FIGS.

  In step S503, the stable time tst (n) read in step S501 is set in the timer TM (n). In step S505, a predetermined time t1 necessary for executing any one of the three processes from step S507 to step S551 is subtracted from the timer TM (n).

  In step S507, the drive current Is (n) is supplied to the SMA 151, whereby the SMA 151 generates heat (drive current supply process). In step S509, the resistance value Rs (n) of the SMA 151 is the above-described circuit in FIG. (Resistance value detection step). In step S511, it is confirmed whether or not the resistance value Rs (n) of the SMA 151 detected in step S509 is larger than a value (Rtg (n) −Rp) that is smaller than the target resistance value Rtg (n) by the allowable error Rp. The

  If it is larger (step S511; Yes), in step S513, whether or not the resistance value Rs (n) of the SMA 151 is smaller than a value (Rtg (n) + Rp) greater than the target resistance value Rtg (n) by the tolerance Rp. It is confirmed. If the resistance value Rs (n) of the SMA 151 is within the range of the target resistance value Rtg (n) ± allowable error Rp (step S513; Yes), the resistance value Rs (n) of the SMA 151 reaches the target value. In step S521, the value of the driving current Is (n) of the SMA 151 is fixed, and the process proceeds to step S551.

  If the resistance value Rs (n) of the SMA 151 is greater than the value (Rtg (n) + Rp) that is greater than the target resistance value Rtg (n) (Rtg (n) + Rp) in step S513 (step S513; No), the temperature of the SMA 151 is low. In step S531, in order to increase the temperature of the SMA 151, the driving current Is (n) of the SMA 151 is set larger than the current value by a predetermined value Ist, and the process proceeds to step S551.

  When the resistance value Rs (n) of the SMA 151 is smaller than the value (Rtg (n) −Rp) that is smaller than the target resistance value Rtg (n) by the allowable error Rp (step S511; No), it is determined that the temperature of the SMA 151 is too high. In step S541, in order to lower the temperature of the SMA 151, the drive current Is (n) of the SMA 151 is set smaller than the current value by a predetermined value Ist, and the process proceeds to step S551.

  In step S551, it is confirmed whether the timer TM (n) has become 0 (zero) or less, that is, whether the stable time tst (n) has elapsed since the timer TM (n) was set in step S503. When the time has elapsed (step S551; Yes), the process returns to step S500 in FIGS.

  If the stabilization time tst (n) has not elapsed (step S551; No), the process returns to step S505, and the operations of steps S505 to S551 are continued until the stabilization time tst (n) has elapsed.

  Here, steps S511 and S513 are resistance value determination steps, and steps S531 and S541 are drive current feedback steps.

  In steps S531 and S541, the method of controlling the drive current Is (n) of the SMA 151 stepwise by increasing or decreasing the predetermined value Ist is shown. However, the current resistance value Rs of the SMA in the comparison unit 335 of FIG. Based on the comparison result between (n) and the target resistance value Rtg (n), the drive amount calculation unit 337 calculates a change value of the drive current Is (n) of the SMA 151, and based on the calculation result, the drive current Is of the SMA 151. (N) may be controlled.

  FIG. 13 is a schematic diagram for explaining the above-described stable time tst (n). FIG. 13A shows a driving waveform and a moving waveform of the imaging optical system 201 when the imaging optical system 201 is extended by step driving. FIG. 13B is a comparison diagram of the time required for driving when step driving is performed at regular intervals and when step driving is performed after the stable time shown in FIG. 12 has elapsed.

  In FIG. 13A, the drive waveform DP is energized to the imaging optical system 201, and the position Z (k) of the AF step number n = k−1 from the position Z (k−2) of the AF step number n = k−2. In the case of moving to -1), the imaging optical system 201 actually moves like a movement waveform MW due to mechanical response delay, bounce, or the like. The time tst (n) until the response delay, bounce, etc. converge and the position of the imaging optical system 201 is stabilized is defined as a stable time. The stabilization time tst (n) varies depending on the current position Z (n) of the imaging optical system 201, the environmental temperature Ta, and the like. Therefore, when step driving is performed at regular intervals Δt, the constant interval Δt is set to a value equal to or longer than the longest stable time + time ts400 required for step S400 “AF subroutine” in FIG. Therefore, it takes time to move the imaging optical system 201 to the in-focus position.

  In FIG. 13B, as shown in FIG. 12, each position of the step driving of the imaging optical system 201 in the case where the above-described step driving is performed at regular intervals Δt (solid drive waveform DP in the figure). In step S400 “AF subroutine” in FIG. 7 after the stabilization time tst (n) elapses in FIG. 7, the next step drive is performed immediately (the drive waveform DPst in the dashed line in FIG. 7). For example, while the imaging optical system 201 is moved from the position Z (k−2) with the AF step number n = k−2 to the position Z (k + 1) with the AF step number n = k + 1, the time required for driving for the time tsh is reduced. It can be shortened.

  FIG. 14 is a diagram illustrating an example of the stable time table STT. As described with reference to FIG. 13, the stabilization time tst (n) varies depending on the current position Z (n) of the imaging optical system 201, the environmental temperature Ta, and the like. Therefore, the stable time table STT is composed of the AF step number n set for each environmental temperature Ta and the stable time tst (n) at that position.

  In this example, as in FIG. 10, for example, the range of the guaranteed operating temperature range of −20 ° C. to + 60 ° C. of the imaging apparatus 10 is taken as the table range, and the environmental temperature Ta between them is equally spaced (for example, every 10 ° C.) The table is divided, and the number of AF steps n and the corresponding stable time tst (n) are tabulated for each environmental temperature Ta. The division width of the environmental temperature Ta may be determined in consideration of the accuracy required for the stable time tst (n).

  When the environmental temperature Ta is not in the stable time table STT, the stable time tst (n) may be calculated from the stable time table STT by proportional distribution or the like, or the nearest stable temperature table of the environmental temperature Ta STT may be used. The stable time table STT is used in FIG.

  FIG. 15 is a flowchart showing step S400 “AF subroutine” of FIG. In the AF operation performed in this subroutine, a so-called hill-climbing method is used instead of separately providing a sensor dedicated to the AF operation. The hill-climbing method is a method in which the contrast of an image is detected while moving the imaging optical system 201 from the infinity side to the closest side in steps at substantially equal intervals, and a position where the contrast is maximum, that is, a focus position is searched. It is.

  The AF data AFD (n) indicating the focus information shown in FIG. 1, here, the contrast of the image, is normally defined as the sum of image data differences between adjacent AF pixels in the AF area on the image sensor 301. Of course, it may be obtained by other methods such as a sum of differences of image data of all pixels of the image sensor 301.

  In FIG. 15, in step S401, step S300 “lens infinity position setting subroutine” in FIG. 7 is executed, and the imaging optical system 201 is set to the infinity position (AF step number n = 1). AF data AFD (1) at the position is acquired (infinity AF data acquisition step).

  In step S411, “1” is added to the AF step number n (parameter changing step), and in step S413, the AF step number n from the feed position table ZT described with reference to FIG. The target resistance value Rtg (n) corresponding to the reference SMA drive current value Is (n) is read (target resistance value reading step). Subsequently, step S500 “lens drive subroutine” of FIG. 12 is executed, and the imaging optical system 201 is advanced one step from the infinity side to the closest side (imaging optical system extension step).

  Here, in step S413, the target resistance value Rtg (n) and the reference SMA drive current value Is (n) are read from the feeding position table ZT. However, as described with reference to FIG. 12, in step S500 “lens drive subroutine”, depending on the difference between the current resistance value Rs (n) of the SMA and the target resistance value Rtg (n) in the comparison unit 335 in FIG. The drive amount calculation unit 337 calculates a change value of the drive current Is (n) of the SMA 151, and controls the drive current Is (n) of the SMA 151 based on the calculated change value of the drive current Is (n). Also good.

  In this case, it is not necessary to read out the reference SMA drive current value Is (n), and the feed position table ZT moves the AF step number n and the imaging optical system 201 corresponding thereto to each feed position Z (n). And the target resistance value Rtg (n) of the SMA 151 at the time.

  In step S421, AF data AFD (n) indicating the contrast of the image is acquired (AF data acquisition step). In step S423, the AF data AFD (n) acquired in step S421 is one step before the imaging optical system 201. Whether it is smaller than the AF data AFD (n-1) at the position (AF data comparison step).

  When the AF data AFD (n) is equal to or larger than the AF data AFD (n−1) (step S423; No), the process returns to step S411, and “1” is added to the AF step number n. The imaging optical system is such that the AF data AFD (n) is smaller than the AF data AFD (n−1), that is, the mountain climbs step by step until it passes the in-focus position of the imaging optical system 201 where the contrast of the image is maximum. The system 201 is extended step by step from the infinity side to the nearest side, and the operation of acquiring the AF data AFD (n) and comparing it with the AF data AFD (n−1) is repeated.

  When the AF data AFD (n) is smaller than the AF data AFD (n−1) (step S423; Yes), it is determined that the imaging optical system 201 has passed the in-focus position, and after step S431, the imaging optical system 201 is changed. The operation of returning to the in-focus position is performed.

  In the conventional AF operation, when the imaging optical system 201 passes the in-focus position, the imaging optical system 201 is temporarily moved from the in-focus position to the initial position Z in order to correct backlash caused by gears, cams, and the like. Generally, after moving in to the (0) side, it is moved again to the feeding position Z (n−1) which is the in-focus position. In this method, since it takes in once and then takes out again, it takes time to move the imaging optical system 201.

  However, in the first embodiment, since it is possible to return from the feeding position Z (n) of the imaging optical system 201 to the feeding position Z (n−1) that is the in-focus position, the imaging optical system 201 can The time required for movement is very short.

  However, like the backlash in the drive mechanism using the conventional gear or cam, the AF mechanism 100 described in FIGS. 2 to 4 includes the case where the imaging optical system 201 is extended from the infinity side to the closest side, There is a hysteresis in the relationship between the target resistance value Rtg (n) of the SMA 151 and the feeding position Z (n) of the imaging optical system 201 when moving from the closest side to the infinity side. The hysteresis will be described later with reference to FIG.

  Therefore, even if control is performed so that the resistance value Rs (n) of the SMA 151 becomes the target resistance value Rtg (n−1) of the SMA 151 one step before in the step S500 “lens driving subroutine” of FIG. The system 201 cannot be returned to the in-focus position.

  Therefore, in step S431, based on the target resistance value Rtg (n-1) of the SMA 151 one step before and the ambient temperature Ta around the SMA 151, the resistance correction value Rcor (n- 1) and the current correction value Icor (n-1) are read out (hysteresis correction value reading step). The environmental temperature Ta is accurately detected by detecting the initial resistance value Rs (0) of the SMA 151 in step S200 “state detection subroutine” of FIG. Here, the resistance correction value Rcor (n−1) is a hysteresis correction value in the present invention.

  In step S433, the target resistance value Rtg (n) of SMA 151 is set to Rs (n-1) + Rcor (n-1) (target resistance value correcting step). In step S435, the driving current Is (n) of SMA 151 = Is (n-1) -Icor (n-1) is set (drive current correction step). Subsequently, Step S500 “Lens Drive Subroutine” in FIG. 12 is executed, and the imaging optical system 201 is returned to the in-focus position in consideration of the hysteresis (imaging optical system loading process), and Step S400 in FIG. 7 is performed. Return to.

  Here, the resistance correction value Rcor (n−1) and the current correction value Icor (n−1) are read from the hysteresis correction table HCT in step S431, and the target resistance value Rtg (n) = Rs (n) of the SMA 151 is read in step S433. −1) + Rcor (n−1), and in step S435, the driving current Is (n) = Is (n−1) −Icor (n−1) of the SMA 151 is corrected.

  However, as described with reference to FIG. 12, in step S500 “lens drive subroutine”, depending on the difference between the current resistance value Rs (n) of the SMA and the target resistance value Rtg (n) in the comparison unit 335 in FIG. The drive amount calculation unit 337 calculates a change value of the drive current Is (n) of the SMA 151, and controls the drive current Is (n) of the SMA 151 based on the calculated change value of the drive current Is (n). Also good.

  In this case, only the resistance correction value Rcor (n−1) is necessary, and it is not necessary to read out the current correction value Icor (n−1). The hysteresis correction table HCT described later is an AF at each environmental temperature Ta. What is necessary is just to be comprised by the number n of steps and the correction | amendment resistance value Rcor (n-1) corresponding to it. Step S435 is also unnecessary.

  FIG. 16 is a schematic diagram for explaining the hysteresis between the target resistance value Rtg (n) of the SMA 151 and the feeding position Z (n) of the imaging optical system 201 when the imaging optical system 201 is drawn out and when it is drawn. The graph shows the relationship between the target resistance value Rtg (n) of the SMA 151 that is a control target in the AF operation and the position Z (n) of the imaging optical system 201.

  In FIG. 16, in the first embodiment, when the drive current Is (n) is supplied to the SMA 151 and the SMA 151 generates heat and contracts, the imaging optical system 201 is extended from the infinity side to the nearest side. It is. The relationship between the target resistance value Rtg (n) of the SMA 151 at the time of extension and the extension position Z (n) of the imaging optical system 201 draws a locus FW in the drawing. Here, the imaging optical system 201 is moved from the position Z (k−1) with the AF step number n = k−1 to the position Z (k) with the AF step number n = k. In step S423 in FIG. If it is determined that the data AFD (k) is smaller than the AF data AFD (k−1), the imaging optical system 201 needs to be moved from the position Z (k) to the position Z (k−1) that is the in-focus position. There is.

  At this time, the target resistance value Rtg (n) of the SMA 151 when the imaging optical system 201 is retracted and the position Z (n) of the imaging optical system 201 due to hysteresis mainly due to mechanical factors such as distortion of the drive arm 121 shown in FIG. ) Draws a trajectory BW that is different from that during feeding.

  Therefore, in order to move the imaging optical system 201 from the position Z (k) to the position Z (k−1), the target resistance value Rtg (n) of the SMA 151 is set to the target resistance when the position Z (k−1) is extended. The resistance correction value Rcor (k−1) needs to be larger than the value Rtg (k−1). Therefore, the SMA drive current value Is (n) at that time also needs to be set smaller than the SMA drive current value Is (k−1) at the time of feeding by the current correction value Icor (k−1). Further, since the hysteresis described above also depends on the linear expansion coefficient and the like of each component constituting the AF mechanism 100, it also depends on the environmental temperature Ta.

  FIG. 17 is a diagram illustrating an example of the hysteresis correction table HCT.

  In FIG. 17, a hysteresis correction table HCT is a correction table for correcting hysteresis when the imaging optical system 201 is extended as described in FIG. 16, and the number of AF steps n at each ambient temperature Ta and resistance correction. It is composed of a value Rcor (n) and a current correction value Icor (n). The hysteresis correction table HCT is stored, for example, in the storage unit 340 of FIG.

  In this example, as in FIG. 10 and FIG. 14, for example, the operation guaranteed temperature range of the imaging apparatus 10 is −20 ° C. to + 60 ° C. The AF step number n, the resistance correction value Rcor (n), and the current correction value Icor (n) corresponding thereto are tabulated for each environmental temperature Ta. The division width of the environmental temperature Ta may be determined in consideration of the allowable width of hysteresis and the like. The hysteresis correction table HCT is used in FIG.

  As described above, according to the difference between the current resistance value Rs (n) of the SMA and the target resistance value Rtg (n) in the comparison unit 335 in FIG. 6, the drive amount calculation unit 337 drives the drive current Is ( When the change value of n) is calculated and the drive current Is (n) of the SMA 151 is controlled based on the calculated change value of the drive current Is (n), the current correction value Icor ( n) is not necessary.

  According to the first embodiment described above, the state of the SMA 151, that is, the disconnection, is detected by supplying a predetermined initial current Is (0) to the SMA 151 and detecting the initial resistance value Rs (0) of the SMA 151. Therefore, the abnormal operation of the imaging device 10 can be prevented. Further, depending on the state, for example, by forcibly setting the imaging optical system to the normal focus position, it is possible to perform imaging even if there is an abnormality in the SMA 151.

  In addition, a temperature detection circuit that detects a temperature using a temperature sensor such as a thermistor and a temperature sensor by supplying a predetermined initial current Is (0) to the SMA 151 and detecting an initial resistance value Rs (0) of the SMA 151; Therefore, the ambient temperature Ta around the SMA 151 can be detected, and the ambient temperature Ta can be used for correcting the temperature characteristics of the AF operation of the imaging device 10 to be described later. It can contribute to image quality, cost reduction, and space saving.

  Further, according to the first embodiment described above, the drive current Is (n) supplied to the SMA 151 is controlled so that the resistance value Rs (n) of the SMA 151 becomes the infinite position resistance value Rinf. Thus, when the image data is displayed as a preview, the image pickup optical system 201 can be accurately moved to the infinity position Z0. Therefore, a sensor and a detection circuit for detecting the feeding position of the image pickup optical system 201 are provided separately. Therefore, it is possible to contribute to high image quality, cost reduction, and space saving of the imaging apparatus 10.

  Furthermore, by moving the imaging optical system 201 to the infinity position Z0, it is possible to display a moving image focused at infinity at the time of preview. Therefore, an imaging device that is easy to use when determining a composition for shooting, etc. 10 can be provided to the user. Furthermore, since the SMA 151 is preheated by supplying the drive current Is (n) to the SMA 151, the drive responsiveness of the imaging optical system 201 in the subsequent step S400 “AF subroutine” is improved. A user-friendly imaging device 10 can be provided to the user.

  In addition, according to the first embodiment described above, when the imaging optical system 201 is step-driven, the movement of the imaging optical system 201 is actually completed after the drive waveform is input, and the position is The stabilization time tst (n) until the image stabilization becomes stable is prepared as the stabilization time table STT, and the “AF subroutine” is executed after the stabilization time tst (n) at each step drive position of the imaging optical system 201 has elapsed. By performing the next step drive immediately, the time required to move the imaging optical system 201 to the in-focus position is shortened compared to the case where the conventional step drive is performed at regular intervals Δt. Therefore, the user-friendly imaging device 10 can be provided to the user.

  Further, according to the first embodiment described above, the resistance correction value Rcor (n) is calculated for each environmental temperature Ta in order to correct the hysteresis between when the imaging optical system 201 is extended and when it is retracted. The current correction value Icor (n) and the hysteresis correction table HCT are prepared as necessary. The environmental temperature Ta can be accurately known by detecting the initial resistance value Rs (0) of the SMA 151 in step S200 “state detection subroutine” of FIG.

  When the imaging optical system 201 is returned from the position after passing the focus position to the focus position, the target resistance value Rtg (n) of the SMA 151 and, if necessary, the SMA drive current value Is (n) are hysteresis. Correction is performed using the resistance correction value Rcor (n) and the current correction value Icor (n) of the correction table HCT. By doing so, the imaging optical system 201 can be returned to the in-focus position from the position that has passed through the in-focus position at a stroke, and thus it is necessary to return the imaging optical system 201 to the initial position Z (0) once as in the prior art. In addition, since the time required to move the imaging optical system 201 to the in-focus position can be shortened, the user-friendly imaging device 10 can be provided to the user.

  Next, a second embodiment of the present invention will be described with reference to FIGS. 18A and 18B are schematic views of the shutter unit according to the second embodiment of the present invention. FIG. 18A shows a state where the shutter is closed, and FIG. 18B shows a state where the shutter is fully opened. In the present embodiment, the shutter unit includes a coil spring-like SMA as a driving source of the shutter blades.

  In FIG. 18, the shutter unit 400 includes shutter blades 401 and 402, rotating shafts 401a and 402a, a connecting pin 403, an SMA 404, an urging spring 405, a shutter base plate 406, an SMA drive control unit 410, and the like. The shutter base plate 406 is provided with a shutter opening 406a.

  Here, the SMA drive control unit 410 functions as a drive unit, a shape memory alloy resistance value calculation unit, a temperature detection unit, a storage unit, and a temperature correction unit in the present invention. The shutter unit 400 includes the movable module according to the present invention, the rotation shafts 401a and 402a, the connecting pin 403, the SMA 404, the urging spring 405, the shutter base plate 406, and the SMA drive control unit 410. Reference numeral 402 denotes a driven portion in the present invention.

  In FIG. 18A, shutter blades 401 and 402 are supported so as to be rotatable about rotation shafts 401a and 402a, respectively, and are connected to each other by a connecting pin 403. The SMA 404 and the biasing spring 405 are connected between the shutter blade 402 and the shutter base plate 406 so that the acting directions of the forces are opposite to each other. The SMA 404 and the biasing spring 405 function as an actuator that drives the shutter blade 402.

  When the SMA 404 is energized by the SMA drive control unit 410 and the SMA 404 contracts, the shutter blade 401 rotates counterclockwise around the rotation shaft 401a against the urging force of the urging spring 405, The shutter blade 402 connected by the connecting pin 403 also rotates in the clockwise direction in the drawing around the rotation shaft 402a. Accordingly, when the shutter is opened and the shutter is fully opened, the state shown in FIG.

  When the power supply to the SMA 404 is interrupted and the contraction force of the SMA disappears, the urging force of the urging spring 405 causes the shutter blade 401 to rotate clockwise around the rotation shaft 401 a and be connected by the connecting pin 403. The shutter blades 402 are also rotated counterclockwise around the rotation shaft 402a in conjunction with the shutter blades 402. This closes the shutter and returns to the state of FIG. The above-described operation is driven and controlled by the SMA drive control unit 410.

  FIG. 19 is a flowchart showing an example of an operation flow when the shutter unit 400 according to the second embodiment is used in a digital camera.

  In FIG. 19, when the power of the digital camera is turned on in step S701, the initial resistance value Rs (0) of SMA is detected in step S703, as in step S200 “state detection subroutine” of FIG. 8 in the first embodiment. ) Is measured by the method of calculating (state detection step). The measured ambient temperature Ta is used for subsequent operations of the shutter unit 400, for example, when correcting the temperature dependence of hysteresis when the shutter blades 401 and 402 are moved to the reference position immediately before the opening in step S715 to be described later. Used to contribute to high performance of the shutter.

  Subsequently, in step S705, the SMA 404 is energized to fully open the shutter blades 401 and 402, and in step S707, a preview operation is started (preview process). In the case of a digital camera, unlike the case of the mobile phone in the first embodiment, the AF operation is generally performed during preview. When the shutter button is pressed halfway by the user in step S709 and the AF switch is turned on, AF operation and photometry (AE) operation are performed in step S711, and the position and exposure value of the taking lens are fixed (AF / AE lock process).

  In step S713, it is confirmed whether or not the shutter button is fully pressed by the user and the release switch is turned on (release detection step). It waits in step S713 until the release switch is turned on. When the release switch is turned on (step S713; Yes), the shutter is temporarily closed in step S715. However, here, energization to the SMA 404 is not turned off and the shutter blades 401 and 402 are not returned to the initial positions, but are moved to the reference position immediately before the opening (shutter blade reference position setting step).

  The movement of the shutter blades 401 and 402 to the reference position immediately before the opening is performed in the same way as the “lens infinite position setting subroutine” in FIG. 11 of the first embodiment, when the resistance value Rs (1) of the SMA is the reference immediately before the opening. This is performed by controlling the SMA drive current Is (n) so as to be the target resistance value Rtg (1) of the position. Further, the target resistance value Rtg (1) at the reference position immediately before the opening is similar to the operation in the direction in which the shutter blades 401 and 402 are opened and the shutter blade 401, as in FIG. 15 “AF subroutine” of the first embodiment. And the hysteresis with respect to the movement in the direction of closing 402 are determined.

  In step S717, the shutter is opened again to the aperture value determined from the exposure value determined in step S711, and in step S719, shooting is performed for the exposure time determined from the exposure value determined in step S711, and step S721 is performed. Thus, the energization to the SMA 404 is turned off, and the shutter blades 401 and 402 are returned to the initial positions. Here, steps S717, S719, and S721 are photographing steps.

  In step S723, it is confirmed whether or not to end shooting (shooting end confirmation step). If the photographing is not finished (step S723; No), the process returns to step S703, the environmental temperature Ta is measured, and the above-described operation is repeated thereafter.

  When the photographing is to be ended (step S723; Yes), the digital camera is turned off in step S725, and the series of operations is ended.

  As described above, according to the second embodiment, a predetermined initial current Is (0) is supplied to the SMA 404 and the initial resistance value Rs (0) of the SMA 404 is detected. Since it is possible to detect the ambient temperature Ta around the SMA 404 without separately providing a temperature sensor and a temperature detection circuit that detects the temperature using the temperature sensor, the shutter unit 400 has high performance, cost reduction, and space saving. It can contribute to the conversion.

  Further, when the release switch is turned on by the user and the shutter is once closed, the SMA 404 drive current Is () is set so that the resistance value Rs (1) of the SMA 404 becomes the target resistance value Rtg (1) of the reference position immediately before the shutter opening. By controlling n), the shutter blades 401 and 402 can be accurately closed to the reference position immediately before the opening without separately providing a sensor or a detection circuit for detecting the positions of the shutter blades 401 and 402. The release time lag until the shutter is re-opened in step S717 can be eliminated, contributing to higher performance, cost reduction, and space saving of the shutter unit 400.

  Further, since the driving current Is (n) is supplied to the SMA 404 and the SMA 404 is preheated, the responsiveness when the shutter is re-opened in the subsequent step S717 is improved. Can be provided.

  In addition, the shutter blades 401 and 402 are adjusted by correcting the hysteresis of the target resistance value Rtg (1) indicating the reference position immediately before the shutter opening at the time of opening and closing the shutter using the resistance correction value Rcor (n). Since the reference position immediately before the shutter opening can be returned from the fully opened position at once, the release time lag can be eliminated, and the user-friendly shutter unit 400 can be provided.

  Next, a third embodiment of the present invention will be described with reference to FIGS. 20A and 20B are schematic diagrams of a camera shake correction unit according to the third embodiment of the present invention. FIG. 20A shows a state where camera shake correction is not performed, and FIG. 20B shows a camera shake correction performed. Indicates the state. Although the third embodiment exemplifies a method of performing camera shake correction by moving a correction lens incorporated in a photographing optical system and including a wire-like SMA as a drive source, for example, a method of moving an image sensor Even so, it is the same.

  20, the camera shake correction unit 500 includes a base 510, a guide rod 501, a correction lens 502, a holding frame 503, an SMA 507, an urging spring 508, an SMA drive control unit 520, and the like. Here, the SMA drive control unit 520 functions as a drive unit, a shape memory alloy resistance value calculation unit, a temperature detection unit, a storage unit, and a temperature correction unit in the present invention. In addition, the camera shake correction unit 500 is the movable module, base 510, guide rod 501, holding frame 503, SMA 507, urging spring 508, and SMA drive control unit 520 in the present invention, the drive unit in the present invention, and the correction lens 502 in the present invention. Driven part.

  FIG. 20A shows a state where energization to the SMA 507 is stopped. In FIG. 20A, the slide portion 503 a of the holding frame 503 that holds the correction lens 502 is slidably engaged with a guide rod 501 fixed to the base 510. An SMA 507 and a biasing spring 508 are connected between the slide portion 503a and the base 510 so that the acting directions of the forces are opposite to each other. Since energization to the SMA 507 is stopped, the holding frame 503, that is, the correction lens 502 is pulled downward in the figure by the urging force of the urging spring 508, and stops at the SMA energization off position P0 (zero) which is the initial position. ing.

  FIG. 20B shows a state in which the standby current Is (1) is supplied to the SMA 507 and the correction lens 502 is moved to the optical axis center position (centering position) of the photographing optical system. In FIG. 20B, the standby current Is (1) is energized and controlled so that the resistance value Rs (1) of the SMA 507 becomes the target resistance value Rtg (1) of the centering position that is the reference position. When contracted, the holding frame 503, that is, the correction lens 502 moves upward in the figure along the guide rod 501 against the biasing force of the biasing spring 508, and stops at the centering position P1.

  By controlling the drive current Is (n) while monitoring the resistance value Rs (n) of the SMA 507 from the centering position P1, the position of the correction lens 502 can be moved to an arbitrary camera shake correction position. At this time, it is necessary to correct the hysteresis between the case of moving from the bottom to the top and the case of moving from the top to the bottom. Furthermore, since the time required for the movement varies depending on the position of the correction lens 502 in the vertical direction, it is necessary to set a stable time for minimizing the movement time, as in FIG. 12 in the first embodiment.

  In order to simplify the explanation, the camera shake correction unit 500 in the uniaxial direction only in the vertical direction in the figure is illustrated here. However, the camera shake correction unit having the same mechanism as that of the present example so that the movement directions are orthogonal to each other. By stacking 500, it is possible to realize a camera shake correction unit in the biaxial direction.

  FIG. 21 is a flowchart showing an example of an operation flow when the camera shake correction unit 500 according to the third embodiment is used in an imaging apparatus such as a digital camera or a mobile phone camera unit. Here, only the flow of operations related to camera shake correction is shown, and AF and exposure control are omitted.

  In FIG. 21, when the power of the imaging apparatus is turned on in step S801, in step S803, step S200 “state detection subroutine” in FIG. 8 in the first embodiment and step in FIG. 19 in the second embodiment are performed. Similarly to S703, the environmental temperature Ta is measured by the method of calculating the initial resistance value Rs (0) of SMA (state detection step). The measured ambient temperature Ta is used for the subsequent operations of the camera shake correction unit 500, for example, when correcting the temperature dependency of hysteresis or moving time when the correction lens 502 is moved to the camera shake correction position in step S811 described later. It is used and contributes to high performance of the image stabilization unit 500.

  Subsequently, in step S805, the standby current Is (1) is energized and controlled in the SMA 507 so that the reference position resistance value Rs (1) of the SMA 507 becomes the target resistance value Rtg (1) of the centering position that is the reference position. Thus, the correction lens 502 is moved from the SMA energization off position P0 (zero) to the centering position P1 (correction lens centering step). In step S807, a preview operation is started (preview process). In step S809, it is confirmed whether or not the shutter button is fully pressed and the release switch is turned on (release detection step). It waits in step S809 until the release switch is turned on.

  When the release switch is turned on (step S809; Yes), in step S811, the resistance value Rs (n) of the SMA 507 corresponds to the movement amount of the correction lens 502 calculated by a camera shake correction amount calculation unit (not shown). Shooting is performed and image data is generated while correcting the camera shake by controlling the drive current Is (n) of the SMA 507 so as to be equal to the resistance value Rtg (n) (camera correction correcting imaging step).

  In step S813, it is confirmed whether or not to end shooting (shooting end confirmation step). If the photographing is not finished (step S813; No), the process returns to step S803 to measure the environmental temperature Ta, and thereafter the above-described operation is repeated. When photographing is to be ended (step S813; Yes), the power of the imaging device is turned off in step S815, and a series of operations is ended.

  As described above, according to the third embodiment, the SMA 507 is energized with a predetermined initial current Is (0) and the initial resistance value Rs (0) of the SMA 507 is detected. Since the ambient temperature Ta around the SMA 507 can be detected without separately providing a temperature sensor and a temperature detection circuit that detects the temperature using the temperature sensor, the camera shake correction unit 500 is improved in performance, cost, and saving. It can contribute to space.

  Further, energization control of the standby current Is (1) is performed so that the reference position resistance value Rs (1) of the SMA 507 becomes the target resistance value Rtg (1) of the centering position, and the correction lens 502 is moved to the SMA energization off position P0 (zero). ) To the centering position P1, the correction lens 502 can be moved to the centering position P1 without separately providing a sensor or a detection circuit for detecting the position of the correction lens 502. It is possible to contribute to high performance of 500, cost reduction, and space saving.

  Furthermore, the hysteresis of the target resistance value Rtg (n) of the MA 507 between the case where the correction lens 502 is moved from the bottom to the top in the figure and the case where the correction lens 502 is moved from the top to the bottom is shown as the resistance correction value Rcor (n ), The correction lens 502 can be quickly moved to the target position, so that the camera shake correction unit 500 with high responsiveness can be provided.

  In addition, when the correction lens 502 is moved for camera shake correction, the time required for the movement varies depending on the position of the correction lens 502, so that the movement time is minimized as in FIG. 12 in the first embodiment. By setting the stabilization time for this and moving the correction lens 502 while waiting for the shortest stabilization time, the correction lens 502 can be quickly moved to the target position, so that the camera shake correction unit 500 with high responsiveness is provided. can do.

  As described above, according to the present invention, in the drive unit and the movable module that move the driven part using the shape memory alloy as the driving source, the position where the driven part is moved and the driven corresponding to the position. By controlling the timing of moving the driven part based on the stable time until the part stops at that position, the driven part can be moved in the shortest driving time. It is possible to provide a drive unit and a movable module that can be driven at a high speed regardless of the position of the drive unit.

  The detailed configuration and detailed operation of each component constituting the drive unit according to the present invention can be changed as appropriate without departing from the spirit of the present invention.

It is a block diagram showing an example of an imaging device in a 1st embodiment of the present invention. It is a schematic diagram which shows an example of the main structures of AF mechanism. It is a schematic diagram for demonstrating the relationship between SMA and a drive arm. It is a typical graph which shows the relationship between the feed amount of an imaging optical system, and the characteristic of SMA. It is a figure which shows the relationship between the drawing | feeding-out amount of an imaging optical system, and the resistance value of SMA. It is a block diagram which shows an example of the circuit structure of an SMA drive part. It is the main routine of the flowchart which shows the flow of operation | movement of an imaging device. It is a flowchart which shows step S200 "state detection subroutine" of FIG. It is a flowchart which shows step S600 "SMA state detection subroutine" of FIG. It is a figure which shows one example of an environmental temperature table. It is a flowchart which shows step S300 "lens infinity position setting subroutine" of FIG. It is a flowchart which shows step S500 "lens drive subroutine" of FIG. 11 and FIG. It is a schematic diagram for demonstrating stabilization time. It is a figure which shows an example of a stable time table. It is a flowchart which shows step S400 "AF subroutine" of FIG. It is a typical graph for demonstrating the hysteresis of the extended position and the target resistance value of SMA in the case where it draws out an imaging optical system, and the case where it draws in. It is a figure which shows one example of a hysteresis correction table. It is a schematic diagram of the shutter unit in the 2nd Embodiment of this invention. It is a flowchart which shows an example of the flow of operation | movement when using a shutter unit for a digital camera. It is a schematic diagram of the camera-shake correction unit in the third embodiment of the present invention. It is a flowchart which shows an example of the flow of operation | movement when using a camera shake correction unit for an imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Imaging device 100 Autofocus (AF) mechanism 101 Base plate 103 Top plate 105 SMA support part 111 Lens barrel 113 Lens drive frame 121 Drive arm 123 Displacement input part 131 Energizing spring 151 SMA
153 Tension guide 155 SMA fixing unit 201 Imaging optical system 203 Optical axis 300 Camera circuit 301 Imaging element 310 Control unit 320 Imaging unit 330 SMA drive unit 331 Drive unit 333 SMA resistance value calculation unit 335 Comparison unit 337 Drive amount calculation unit 339 Reference resistance 340 storage unit Rsma (SMA) resistance value Lsma (SMA) length Z (drive arm) movement amount Rs (n) (current SMA) resistance value Rtg (n) target resistance value Is (SMA) n) Drive current value (of SMA) 400 Shutter unit 401 Shutter blade 401a Rotating shaft 402 Shutter blade 402a Rotating shaft 403 Connecting pin 404 SMA
405 Biasing spring 406 Shutter base plate 406a Shutter opening 410 SMA driving unit 500 Camera shake correction unit 501 Guide rod 502 Correction lens 503 Holding frame 507 SMA
508 Biasing spring 510 Base 520 SMA drive unit

Claims (7)

A biasing member that biases the driven part in one direction;
A shape memory alloy configured to move the driven part in a direction different from the direction of the urging force of the urging member by being energized;
In a drive unit comprising a shape memory alloy drive unit for controlling energization to the shape memory alloy,
The shape memory alloy driving unit is
A drive unit for energizing the shape memory alloy;
A shape memory alloy resistance value calculation unit that calculates a resistance value of the shape memory alloy when energized by the drive unit;
A storage unit that stores a stable time corresponding to a position where the driven unit is moved until the driven unit stops at the position;
The movement of the driven part is controlled based on the resistance value of the shape memory alloy calculated by the shape memory alloy resistance value calculating part, and the position where the driven part is moved is stored in the storage part. A drive unit comprising: a control unit that controls a timing for moving the driven unit based on a stabilization time corresponding to a position where the driven unit is moved. 2. The drive according to claim 1, wherein when the driven unit is moved stepwise, the control unit moves the driven unit to the next stage after the stabilization time corresponding to the position of the driven unit. unit. The drive unit according to claim 1, wherein the storage unit stores a stable time corresponding to the position of the driven unit for each ambient temperature around the shape memory alloy. A driven part;
A movable module comprising the drive unit according to any one of claims 1 to 3. The movable module according to claim 4, wherein the driven unit is an imaging optical system constituting an imaging apparatus. The movable module according to claim 4, wherein the driven part is a shutter blade constituting a shutter unit. The movable module according to claim 4, wherein the driven portion is a correction lens constituting a camera shake correction unit.

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