Patent Publication Number: US-8994298-B2

Title: Movement control apparatus, movement control method, and movement control circuit

Description:
TECHNICAL FIELD 
     The present invention relates to a movement control apparatus, a movement control method and a movement control circuit for allowing a driven body to perform reciprocating movement, and more particularly to a movement control apparatus, a movement control method and a movement control circuit for allowing an optical element such as a lens and an imaging element to perform reciprocating movement in an optical axis direction in order to extend depth of field upon capturing a moving image or a still image of an object using a camera. 
     BACKGROUND ART 
     An available method for implementing extended depth of field (hereafter EDOF) is to convolute images uniformly focusing in the depth direction by moving a focal lens or an imaging element during an exposure time, and perform image restoration processing using a blur pattern which is obtained in advance by measurement or simulation, to thereby obtain an EDOF image (Non-patent Document 1). 
     A primary application example of the EDOF technology is for imaging with a microscope. In this application, the EDOF technology is known to be rational because the image restoration processing method after exposure, using a single blur pattern, can be applied if a way of moving a focus lens or an imaging element is controlled such that the blur of an image always becomes uniform (Patent Document 1). 
     In the application example however, focus must be controlled upon driving the focus lens or the imaging element, so that the imaging surface moves at a constant velocity (Non-patent Document 1). 
     Therefore the movement pattern is demanded to have a constant velocity from the rear side focusing end position to the front side focusing position, or in the opposite direction thereof. 
     Another application example of EDOF technology is downsizing a camera installed in a portable telephone or the like. In other words, using the EDOF effect, an all focused image (an image in which all objects are focused) can be obtained without including an auto focus mechanism. 
     Another application example of EDOF technology is an application to a standard digital still camera and digital video camera. As a recent trend in digital still cameras and digital video cameras, simpler image capturing with less error is demanded, and EDOF technology is expected as a technology that can implement an all focused image, which is image capturing without focusing error. 
     In order to apply the EDOF method to a digital still camera and a digital video camera like this, continuous image capturing without generating a delay between frames is demanded upon capturing moving images, therefore it is known that reciprocating movement as shown in  FIG. 14  is performed when capturing a moving image, assigning one video frame respectively to the advance movement and return movement of a focus lens or an imaging element, whereby EDOF moving image capturing is enabled. 
     However a displacement pattern of a focus lens or a displacement pattern of an imaging element shown in  FIG. 14  includes a return movement at an acute angle at a closest end or most distant end from the object. In order to implement this return movement at an acute angle, a large thrust must be generated momentarily in an actuator for driving the imaging element or the focus lens. In terms of downsizing and conserving power of an apparatus, the reciprocating movement control that generates such a large thrust is not practical for a portable digital still camera or digital video camera. Furthermore this kind of reciprocating movement control momentarily generates a large thrust, and suddenly inverts the velocity, hence the driving mechanism quickly wears out, and vibration and noise during driving are large, which is not acceptable in terms of quality. 
     Available conventional movement control apparatuses which reciprocate an optical element such as a focus lens or an imaging element in the optical axis direction, which may be possible to be used to implement EDOF for capturing a moving image or a still image of an object, are the movement control apparatuses disclosed in Patent Document 2 and Patent Document 3. 
     According to the technology disclosed in Patent Document 2, as illustrated in  FIG. 15 , a stator  113  constituted by a yoke  116  facing an outer surface of a cylindrical permanent magnet via a space, and a movable element  127  which has a driving coil  129  that can slide in the axis direction with respect to the stator  113 , are disposed, an air-core coil  132 , as a sensor coil, is disposed outside the yoke  116 , and a permanent magnet  128 , which displaces in the air-core  132  as the movable element  127  displaces, is installed in the movable element  127 . Since the electromagnetic induction function to the air-core coil  132  by the driving coil  129  is magnetically shielded by the yoke  116  located therebetween, only an electromotive force in accordance with the displacement velocity of the permanent magnet  128  interlocking with the movable element  127 , which is only a velocity signal, is generated in the air-core coil  132 . The position of the movable element  127  is controlled by the position detection voltage of a position sensor  161 , and by damping the movable element  127  using the velocity signal, which is the output of the air-core coil  132 , response can be improved without generating hunching. 
     According to the technology disclosed in Patent Document 3, as illustrated in  FIG. 16 , a focus lens  110  is driven in the optical axis direction by an actuator that is constituted by a driving coil  135  and a magnet  134  and is disposed coaxially around the optical axis of the focus lens  110 , and position control is performed using a position signal of a position sensor that is constituted by an inclined magnet  139 , of which magnetic flux changes as the focus lens  110  moves, and a Hall element, and a velocity signal of a moving velocity detection coil  137  of the focus lens  110 . Since the velocity detection coil  137  is wound around a bobbin  131  on which the driving coil  135  is wound, a magnet for a sensor can be used for driving as well, which allows decreasing a number of components, decreasing weight and decreasing cost. 
     In order to extend the depth of field, the optical element is moved at a constant velocity for the amount of a focal distance which corresponds to the depth of field to be extended. For this purpose, a moving pattern of the optical element is generated, and high-speed positioning control is performed on the optical element in accordance with the target position of the pattern. 
     In the case of the actuator having a conventional configuration, however, the positioning of the focus lens is controlled basically by feeding back the position signal outputted by the position sensor to the control circuit. Therefore the moving distance of the focus lens is long, and the focus lens must be moved at a constant velocity. As a result, the position detection range of the lens is long, that is, an entire operation range in the movable area, and a position sensor which excels in position detection accuracy and linearity is required. Furthermore, a velocity sensor to obtain a velocity signal, for damping the movable element upon positioning the actuator so that vibration is not generated, is required. This makes the apparatus large and expensive.
     Patent Document 1: Japanese Patent Application Laid-Open No. H5-313068   Patent Document 2: Japanese Patent Application Laid-Open No. H1-206861   Patent Document 3: Japanese Patent Application Laid-Open No. H4-119306   Non-patent Document 1: H. Nagahara, S. Kuthirummal, C. Zhou and S. Nayar: “Flexible Depth of Field Photography”, European Conference on Computer Vision (ECCV), October 16th, Morning Session 2: Computational Photography (2008)   

     SUMMARY OF THE INVENTION 
     With the foregoing in view, it is an object of the present invention to provide a movement control apparatus, a movement control method, and a movement control circuit which is able to cause a driven body to perform good reciprocating movement at low cost. 
     A movement control apparatus according to an aspect of the present invention comprises: an actuator that includes a permanent magnet and a driving coil facing the permanent magnet via a predetermined air gap, and causes a driven body connected to the driving coil to perform reciprocating movement; a signal generation unit that generates a velocity command signal which indicates a target velocity of the driven body; a driving unit that supplies electric current corresponding to an inputted driving signal to the driving coil of the actuator; a voltage detection unit that detects induced voltage generated in the driving coil with electric current supplied by the driving unit, and outputs a voltage signal corresponding to the detected induced voltage; a signal correction unit that corrects, based on the driving signal and the voltage signal outputted from the voltage detection unit, the voltage signal to adjust a shift of a resistance value from a predetermined reference resistance value of the driving coil, thereby generating a velocity signal; and a control unit that generates the driving signal based on the velocity command signal generated by the signal generation unit and the velocity signal generated by the signal correction unit, and outputs the driving signal to the driving unit. 
     A movement control method according to an aspect of the present invention is a movement control method of a driven body in a movement control apparatus including an actuator that has a permanent magnet and a driving coil facing the permanent magnet via a predetermined air gap, and causes the driven body connected to the driving coil to perform reciprocating movement, comprises: a first step of generating a velocity command signal that indicates a target velocity of the driven body; a second step of supplying electric current to the driving coil of the actuator, the electric current corresponding to a driving signal for causing the driven body to perform reciprocating movement; a third step of detecting induced voltage generated in the driving coil with electric current supplied to the driving coil in the second step, and outputting a voltage signal corresponding to the induced voltage; a fourth step of correcting, based on the driving signal and the voltage signal outputted in the third step, the voltage signal to adjust a shift of a resistance value from a predetermined reference resistance value of the driving coil, thereby generating a velocity signal; and a fifth step of generating the driving signal based on the velocity command signal generated in the first step and the velocity signal generated in the fourth step. 
     A movement control circuit according to an aspect of the present invention is a movement control circuit that controls an actuator which has a permanent magnet and a driving coil facing the permanent magnet via a predetermined air gap and which causes a driven body connected to the driving coil to perform reciprocating movement, comprises: a signal generation circuit that generates a velocity command signal which indicates a target velocity of the driven body; a driving circuit that supplies electric current corresponding to an inputted driving signal to the driving coil of the actuator; a voltage detection circuit that detects induced voltage generated in the driving coil with electric current supplied by the driving circuit, and outputs a voltage signal corresponding to the detected induced voltage; a signal correction circuit that corrects, based on the driving signal and the voltage signal outputted from the voltage detection circuit, the voltage signal to adjust a shift of a resistance value from a predetermined reference resistance value of the driving coil, thereby generating a velocity signal; and a control circuit that generates the driving signal based on the velocity command signal generated by the signal generation circuit and the velocity signal generated by the signal correction circuit, and outputs the driving signal to the driving circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram depicting a functional configuration of a movement control apparatus according to an embodiment of the present invention. 
         FIG. 2  is a circuit diagram depicting an internal configuration of an induced voltage detector constituting the movement control apparatus according to an embodiment of the present invention. 
         FIG. 3  is a block diagram depicting an internal configuration of a signal correction unit constituting the movement control apparatus according to an embodiment of the present invention. 
         FIGS. 4A to 4E  are time waveform diagrams depicting simulation results, which describe operation of a correction signal generator constituting the movement control apparatus according to an embodiment of the present invention. 
         FIGS. 5A to 5C  are time waveform diagrams depicting simulation results, which describe operation of a signal correction unit constituting the movement control apparatus according to an embodiment of the present invention. 
         FIG. 6  is a flow chart depicting an operation to adjust amplitude of reciprocating movement, out of the functions of a velocity command generator constituting the movement control apparatus according to an embodiment of the present invention. 
         FIGS. 7A and 7B  are time waveform diagrams depicting simulation results, which describe operation to adjust amplitude of the velocity command generator constituting the movement control apparatus according to an embodiment of the present invention. 
         FIG. 8  is a flow chart depicting an operation to adjust a cycle of reciprocating movement, out of the functions of the velocity command generator constituting the movement control apparatus according to an embodiment of the present invention. 
         FIGS. 9A and 9B  are time waveform diagrams depicting simulation results, which describe operation to adjust a cycle of the velocity command generator constituting the movement control apparatus according to an embodiment of the present invention. 
         FIGS. 10A to 10D  are time waveform diagrams depicting simulation results, which describe simultaneous operation of amplitude adjustment and cycle adjustment of the velocity command generator constituting the movement control apparatus according to an embodiment of the present invention. 
         FIGS. 11A to 11E  are time waveform diagrams depicting simulation results, which describe operation in a stationary state of the reciprocating movement by the movement control apparatus according to an embodiment of the present invention. 
         FIG. 12  is a block diagram depicting another example of the internal configuration of the signal correction unit. 
         FIG. 13  is a block diagram depicting still another example of the internal configuration of the signal correction unit. 
         FIG. 14  is a pattern diagram depicting an example of a conventional displacement pattern of a focus lens or an imaging element upon capturing a moving image. 
         FIG. 15  is a diagram depicting an example of a configuration of a conventional movement control apparatus. 
         FIG. 16  is a diagram depicting another example of a configuration of a conventional movement control apparatus. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will now be described with reference to the drawings. 
       FIG. 1  is a block diagram depicting a functional configuration of a movement control apparatus according to an embodiment of the present invention. The movement control apparatus shown in  FIG. 1  has an actuator  1 , a first edge detection sensor  2 , a second edge detection sensor  3 , a driving unit  4 , an induced voltage detector  5 , a signal correction unit  6 , a velocity controller  7  and a velocity command generator  8 . 
     In  FIG. 1 , the actuator  1  has a stator  11  and a driving coil  12 . The stator  11  has yokes  13  which face each other via a cylindrical air gap, and a cylindrical permanent magnet  14  is secured on at least one of the yokes corresponding to the air gap portion. The permanent magnet  14  is disposed on a surface of the yoke  13  so as to face the driving coil  12 . The driving coil  12  is movably supported by a support mechanism (not illustrated) maintaining a predetermined air gap from the permanent magnet  14 . The driving coil  12  receives thrust by interaction of a magnetic flux generated by the permanent magnet  14  disposed on the stator  11 , and a magnetic field generated by electric current that flows through the driving coil  12 . 
     A driven body  9  (a focus lens for example in this embodiment) is connected to the driving coil  12 , and performs reciprocating movement in an optical axis direction (horizontal direction indicated by arrows in  FIG. 1 ) according to the movement of the driving coil  12 . The first edge detection sensor  2  and the second edge detection sensor  3  determine a movement range of the driven body  9 , such as a focus lens, which performs reciprocating movement in the optical axis direction according to the movement of the driving coil  12 . The first edge detection sensor  2  is disposed so as to face a movable portion of the actuator  1 , detects one edge position AU of the movement range of the driven body  9 , which is driven by the actuator  1 , and outputs a first edge position signal X 1 . The second edge detection sensor  3  is disposed so as to face the movable portion of the actuator  1 , detects the other edge position AL of the movement range of the driven body  9 , which is driven by the actuator  1 , and outputs a second edge position signal X 2 . The movable portion includes the driving coil  12  and the driven body  9 . The first edge detection sensor  2  and the second edge detection sensor  3  are disposed so as to face the driving coil  12  for example, and detects both the edge positions AU and AL of the movement range of the driven body  9  by detecting the driving coil  12  which performs reciprocating movement. The first edge detection sensor  2  and the second edge detection sensor  3  may be disposed so as to face the driven body  9 , so that the driven body  9  is detected by the first edge detection sensor  2  and the second edge detection sensor  3 . For the first edge detection sensor  2  and the second edge detection sensor  3 , an MR (Magneto-Resistance) sensor, a photo-reflector or a photo-interruptor can be used among others. 
     The induced voltage detector  5  detects induced voltage Ea to be generated on the driving coil  12 , from the voltage on both edges of the driving coil  12 , and outputs a voltage signal Ed. The signal correction unit  6  generates a velocity signal Vc that indicates movement velocity of the movable portion (that is, the driven body  9 ) of the actuator  1 , from the driving signal U that is input to the driving unit  4  and the voltage signal Ed that is output from the induced voltage detector  5 , and outputs the velocity signal Vc to the velocity controller  7 . 
     The velocity controller  7  generates a velocity error signal e which indicates a difference between the target velocity command Vref and the velocity signal Vc, performs amplification and integration compensation computation on the velocity error signal e, and then generates a driving signal U. 
     When the first edge detection sensor  2  and the second edge detection sensor  3  detect positions AU and AL on both edges of the movement range of the driven body  9 , which is driven by the actuator  1 , the velocity command generator  8  generates the target velocity command Vref and a detection window signal W (described later) from the first edge position signal X 1  and the second edge position signal X 2  outputted from the sensors  2  and  3  respectively. The velocity command generator  8  outputs the target velocity command Vref to the velocity controller  7 , and at the same time outputs the detection window signal W to the signal correction unit  6 . The driving unit  4  supplies driving current Ia to the driving coil  12  in accordance with the inputted driving signal U, and causes the driving coil  12  to perform reciprocating movement. The driven body  9 , such as a focus lens, connected to the driving coil  12 , performs reciprocating movement in the movement range, which is determined by the first edge position signal X 1  and the second edge position signal X 2 , in the optical axis direction (horizontal direction indicated by arrows in  FIG. 1 ). 
     In this movement control apparatus, the voltage signal Ed corresponding to the induced voltage Ea of the driving coil  12  of the actuator  1  is not directly input to the velocity controller  7 , but the voltage signal Ed is adjusted so as to correct a shift of the resistance value from a reference value (e.g. nominal resistance value) of a coil resistance of the driving coil  12  of the actuator  1 , whereby an accurate velocity signal Vc is generated, and the generated velocity signal Vc is input to the velocity controller  7 . Therefore even if the resistance value of the driving coil  12  of the actuator  1  disperses or the resistance value fluctuates due to a temperature rise while power is applied to the driving coil  12 , the induced voltage Ea, which is generated in the driving coil  12  along with driving by the actuator  1 , can be accurately determined and used as the velocity signal Vc. 
       FIG. 2  is a known circuit diagram depicting an internal configuration of the induced voltage detector  5  constituting the movement control apparatus according to the embodiment of the present invention. 
     In  FIG. 2 , the induced voltage detection unit  5  comprises amplifiers  21  and  22 , and resistors  23 ,  24 ,  25 ,  26 ,  27 ,  28  and  29 . The resistor  23  is a current detection resistor Rs, and converts driving current Ia supplied to the driving coil  12  into a voltage value. The resistance values of the resistors  24  and  25  are r 1  and r 2  respectively, the resistance values of the resistors  26  and  27  are both r 3 , and the resistance values of the resistors  28  and  29  are both r 4 . 
     Voltage Va generated on both ends of the driving coil  12  is given by
 
 Va=Ea+Ra×Ia   (Expression 1).
 
Here Ea denotes induced voltage generated on both ends of the driving coil  12  when the actuators  1  causes the driven body  9  to perform reciprocating movement, Ra denotes a coil resistance of the driving coil  12 , and Ia denotes electric current flowing through the driving coil  12 . The drop in voltage due to coil inductance, out of the drop in voltage generated by the driving current Ia flowing through the driving coil  12 , is sufficiently small compared with the drop in voltage due to coil resistance, hence only a drop in voltage due to coil resistance is considered, and a drop in voltage due to coil inductance is omitted.
 
     Output of the amplifier  21  V 1  is given by
 
 V 1 =Rs×Ia ×(1+ r 2/ r 1)+ VC   (Expression 2).
 
Here VC denotes potential of a terminal TC in  FIG. 2 .
 
     Potential VA of a terminal TA in  FIG. 2  is given by
 
 VA=Va+Rs×Ia+VC   (Expression 3).
 
The amplifier  22  and the resistors  26 ,  27 ,  28  and  29  constitute an error amplifier of which amplification factor is r 4 /r 3 . The voltage signal Ed of the amplifier  22 , which is output of the induced voltage detector  5 , is given by
 
 Ed =( VA−V 1)× r 4/ r 3  (Expression 4).
 
For simplification, the resistors  26 ,  27 ,  28  and  29  are selected so that (Expression 5) is established.
 
 r 3= r 4  (Expression 5)
 
Then (Expression 1), (Expression 2) and (Expression 3) are substituted for (Expression 4), the expression is simplified, and then the voltage signal Ed outputted by the amplifier  22  is given by
 
 Ed=Va−Rs×r 2/ r 1× Ia=Ea +( Ra−Ran )× Ia   (Expression 6).
 
The amplifier  21  and the resistors  23 ,  24  and  25  constitute a bridge circuit, and in (Expression 6),
 
 Ran=Rs×r 2/ r 1  (Expression 7).
 
Where Ran is a nominal resistance value of the driving coil  12 .
 
If a ratio of r 2  and r 1  is set so that
 
 Ra=Ran   (Expression 8)
 
is established, then because (Expression 6), (Expression 7) and (Expression 8), the voltage signal Ed outputted by the amplifier  22  is given by
 
 Ed=Ea   (Expression 9).
 
In other words, when the actuator  1  causes the driven body  9  to perform reciprocating movement, the induced voltage detector  5  in  FIG. 2  can accurately detect the induced voltage Ea generated at both ends of the driving coil  12 , and output the obtained voltage signal Ed as the velocity signal Vc.
 
     On the other hand, the resistance value Ra of the driving coil  12  of the actuator  1  may vary depending on the driving coil. The resistance value Ra may also fluctuate by a temperature rise due to heating of the driving coil  12  when the driving current Ia flows through the driving coil  12 . In such a case, the induced voltage detector  5  cannot accurately detect the induced voltage Ea generated on both ends of the driving coil  12 , because of the error of the resistance value Ra (shift from the nominal resistance value Ran) of the driving coil  12 , and if the obtained voltage signal Ed is used as the velocity signal Vc, the velocity control system becomes unstable. 
     With the foregoing in view, it is an object of the present invention to accurately detect movement velocity of the driven body  9 , which is driven by the actuator  1 , using the induced voltage detector  5 , even if the resistance value Ra of the driving coil  12  of the actuator  1  is shifted from the nominal resistance value Ran, so as to control the velocity of the driven body  9  (e.g. focus lens), with respect to the target velocity command Vref, at high accuracy and stability. 
       FIG. 3  is a block diagram depicting an internal configuration of the signal correction unit  6  according to an embodiment of the present invention shown in  FIG. 1 . As  FIG. 3  shows, the signal correction unit  6  has a multiplier  31 , a switch  32 , a correction signal generator  33 , a multiplier  34  and a subtractor  35 . 
     In  FIG. 3 , a driving signal U is inputted from the velocity controller  7  to the multiplier  31 . The multiplier  31  multiplies the driving signal U by gm. The multiplication coefficient gm is preset such that gm×U=Ia is established. The signal gm×U (=Ia) outputted from the multiplier  31  is input to the correction signal generator  33  via the switch  32 , which switches according to a detection window signal W described later. The signal gm×U (=Ia) outputted from the multiplier  31  is input to the multiplier  34 . 
     The correction signal generator  33  is constituted by a computing unit  36  and an integrator  37 , and generates a correction signal ΔR, and outputs this signal to the multiplier  34 . The signal gm×U (=Ia) and the velocity signal Vc, which is an output of the signal correction unit  6 , are input to the computing unit  36  included in the correction signal generator  33 . The computing unit  36  generates an error signal P from the signal gm×U (=Ia) and the velocity signal Vc. The integrator  37  generates the correction signal ΔR by integrating the error signal P. The multiplier  34  multiplies the signal gm×U (=Ia) generated by the multiplier  31  multiplying the drive signal U by gm, and the correction signal ΔR from the correction signal generator  33 , and outputs the generated multiplication result to the subtractor  35 . The subtractor  35  subtracts the multiplication result ΔR×gm×U (=ΔR×Ia) of the signal gm×U (=Ia), generated by multiplying the driving signal U by gm, and the correction signal ΔR, from the voltage signal Ed outputted by the induced voltage detector  5 , whereby the velocity signal Vc is generated. 
     Therefore the velocity signal Vc is given by (Expression 10).
 
 Vc=Ed−ΔR×gm×U=Ea +( Ra−Ran−ΔR )× Ia   (Expression 10)
 
     In (Expression 10), if the correction signal ΔR is the same as the difference between the coil resistance value Ra of the driving coil  12  and the nominal resistance value Ran thereof, that is if (Expression 11) is established,
 
Δ R=Ra−Ran   (Expression 11)
 
then the velocity signal Vc given by (Expression 10) is equal to the induced voltage Ea of the driving coil  12 . Therefore even if the resistance value Ra of the driving coil  12  of the actuator  1  is different from the nominal resistance value Ran, the velocity signal Vc, which is an output of the signal correction unit  6 , can accurately represent the movement velocity of the driven body  9  which is driven by the actuator  1 . As a result, feedback control can be favorably performed based on the induced voltage Ea of the driving coil  12  detected by the induced voltage detector  5 , and the velocity control system of the driven body  9  (e.g. focus lens) with respect to the target velocity command Vref can be stabilized.
 
     Operation of the correction signal generator  33  according to an embodiment of the present invention shown in  FIG. 3  which performs this signal processing will be described in detail with reference to the drawings. 
     Operation of resistance correction will be described first. In other words, a correction operation will be described, which is for generating the correction signal ΔR considering the resistance error (Ra−Ran) given by (Expression 11), so as to accurately determine the induced voltage Ea, which is generated in the driving coil  12  due to the reciprocating movement of the driven body  9  which is driven by the actuator  1 . 
       FIGS. 4A to 4E  are time waveform diagrams depicting simulation results, which describe operation of the correction signal generator  33  constituting the movement control apparatus according to the present invention. 
       FIG. 4A  indicates the induced voltage Ea when the driving coil  12  included in the actuator  1  performs reciprocating movement.  FIG. 4B  indicates the driving current Ia supplied to the driving coil  12 . It is assumed that there is no load resistance, such as bearing friction and elastic force, applied to the actuator  1  when the driving coil  12 , supported by the support mechanism, performs reciprocating movement. 
     Therefore as the driving current Ia supplied to the driving coil  12 , high electric current is needed upon inverting the moving direction of the driven body  9  which has inertia, and no electric current is needed when the driven body  9  is moving at a constant velocity. In other words, the driving current Ia is highest at a point where the induced voltage Ea, which is induced in proportion to the movement velocity, crosses zero.  FIG. 4C  indicates a detection window signal W generated by the velocity command generator  8 . 
     The signal gm×U (=Ia) and the velocity signal Vc given by (Expression 10) are input to the computing unit  36  included in the correction signal generator  33  via the switch  32 , which is switched according to the detection window signal W shown in  FIG. 4C . The computing unit  36  multiplies the signal gm×U (=Ia) by the velocity signal Vc, performs time-integration on the multiplication result, and generates the error signal P. 
     The error signal P is given by (Expression 12), where (Expression 10) is substituted. 
     
       
         
           
             
               
                 
                   
                     
                       
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       FIG. 4D  indicates a time waveform of a term to be integrated (Ea×Ia) in the first term at the right hand side of (Expression 12). 
     When the velocity of the driven body  9  is inverted (that is, when the moving direction is inverted), the induced voltage Ea crosses zero, therefore as  FIG. 4D  indicates, the term to be integrated (Ea×Ia) has a point-symmetrical waveform of which center is zero. Hence the value of the first term at the right hand side of (Expression 12) after performing time-integration on the waveform of  FIG. 4D  is zero. 
       FIG. 4E  indicates a time waveform of a term to be integrated (Ra−Ran−ΔR) Ia 2  in the second term at the right hand side of (Expression 12). 
     In  FIG. 4E , the waveform  41  indicates a time waveform which the value of (Ra−Ran−ΔR) is 20% of the value of Ran, the waveform  42  indicates a time waveform when the value of (Ra−Ran−ΔR) is −20% of the value of Ran, and the waveform  43  indicates a time waveform when the value of (Ra−Ran−ΔR) is zero. In other words, if (Expression 12) is calculated, the first term at the right hand side of (Expression 12) always becomes zero, so the error signal P has a negative value if ΔR&gt;(Ra−Ran), the error signal P has a positive value if ΔR&lt;(Ra−Ran), and the error signal P has a value zero if ΔR=(Ra−Ran). 
     The signal gm×U (=Ia) and the velocity signal Vc are input to the computing unit  36 , and the computing unit  36  generates the error signal P using (Expression 12), and the integrator  37  generates the correction signal ΔR by integrating the error signal P. The error signal P generated by the computing unit  36 , included in the correction signal generator  33 , is output to the integrator  37 , hence the integrator  37  integrates the error signal P until the error signal P becomes zero. Time when the error signal P to be inputted to the integrator  37  becomes zero is the time when the correction signal ΔR, generated by the integrator  37 , becomes equal to an actual resistance error dR (=Ra−Ran) between the coil resistance value Ra of the driving coil  12  and the nominal resistance value Ran. Then the relationship of (Expression 11) is established, and therefore (Expression 13) is established.
 
 Vc=Ea   (Expression 13)
 
     As a consequence, the velocity signal Vc outputted by the signal correction unit  6  becomes equal to the induced voltage Ea generated in the driving coil  12  upon driving by the actuator  1 . 
       FIGS. 5A to 5C  are time waveform diagrams depicting simulation results, which describe operation of the signal correction unit  6 . 
     An assumed condition is that the coil resistance value Ra of the driving coil  12  is different from the nominal resistance value Ran, and the resistance error dR (=Ra−Ran) is +20% of the value of Ran. 
       FIG. 5A  indicates a time waveform of the correction signal ΔR generated by the integrator  37  in  FIG. 3 . The value of the correction signal ΔR is updated every time the detection window signal W is output and the switch  32  is turned ON, and is converged into 20% of the value of Ran. As  FIG. 5A  indicates, after the driven body  9 , which is driven by the actuator  1 , reciprocates five times, the value of the correction signal ΔR is converged to the correction signal ΔR having a constant value (=20%) according to the resistance error dR, which shows that the velocity signal Vc is adjusted at high-speed and at high precision. 
       FIG. 5B  indicates a waveform of the voltage signal Ed that is input from the induced voltage detector  5  to the signal correction unit  6 , and  FIG. 5C  indicates a waveform of the velocity signal Vc which is generated via the correction signal generator  33 , the multiplier  34  and the subtractor  35  in  FIG. 3 . If there is a resistance error dR (=Ra−Ran) between the coil resistance value Ra of the driving coil  12  and the nominal resistance value Ran, not only the induced voltage Ea that is generated on the driving coil  12  by the reciprocating movement of the driven body  9  which is driven by the actuator  1 , but also a drop in voltage (dR×Ia), due to the resistance error dR and the driving current Ia, is included in the waveform of the voltage signal Ed in  FIG. 5B  (see (Expression 10)). Whereas the waveform of the velocity signal Vc in  FIG. 5C  does not include the drop in voltage (dR×Ia) due to the resistance error dR, but includes only the induced voltage Ea, since the drop in voltage (dR×Ia), generated due to the resistance error dR, is corrected with the drop in voltage (ΔR×Ia) using the correction signal ΔR. 
     As described above, even if the resistance value Ra of the driving coil  12  of the actuator  1  disperses and is shifted from the nominal resistance value Ran, or even if the resistance value Ra of the driving coil  12  changes due to a rise in temperature due to applying power, the induced voltage detector  5  and the signal correction unit  6  can accurately detect the movement velocity Vc of the driven body  9  which is driven by the actuator  1 , the velocity of the driven body  9  (e.g. focus lens) with respect to the target velocity command Vref can be controlled at high precision and the driven body  9  can be stably operated. In this embodiment, the velocity command generator  8  corresponds to an example of a signal generation unit, the driving unit  4  corresponds to an example of a driving unit, the induced voltage detector  5  corresponds to an example of a voltage detection unit, the signal correction unit  6  corresponds to an example of a signal correction unit, the velocity controller  7  corresponds to an example of a control unit, the correction signal generator  33  corresponds to an example of a correction signal generation unit, the multiplier  34  corresponds to an example of a multiplication unit, the subtractor  35  corresponds to an example of a velocity signal generation unit, the multiplier  31  corresponds to an example of a multiplying unit, the computing unit  36  corresponds to an example of an error signal generation unit, the integrator  37  corresponds to an example of an integration unit, the first edge detection sensor  2  corresponds to an example of a first edge detection unit, the second edge detection sensor  3  corresponds to an example of a second edge detection unit, the switch  32  corresponds to an example of an input prohibition unit, and the target velocity command Vref corresponds to an example of a velocity command signal. 
     In the above example, the value of the correction signal ΔR is updated every time the velocity of the driven body  9 , which is driven by the actuator  1 , is inverted (that is, the moving direction is inverted). In other words, every time the velocity command generator  8  generates the detection window signal W, the value of the correction signal ΔR is updated. The present invention, however, is not limited to this. Instead of updating the value of the correction signal ΔR every time the velocity of the driven body  9  is inverted, the correction signal ΔR may be determined every time the velocity of the driven body  9  is inverted, so that a mean value of the correction signal ΔR is determined each time the velocity is inverted for a plurality of times, and the value of the correction signal ΔR is updated by this mean value. In other words, the value of the correction signal ΔR may be updated every time the detection window signal W is generated for a plurality of times by the velocity command generator  8 . 
     Central to this embodiment of the present invention is that the level of the driving current Ia, which is supplied to the driving coil  12 , becomes the maximum, and the induced voltage Ea, induced on the driving coil  12 , crosses zero in the inversion period of the moving velocity (that is, the inversion period of the moving direction thereof) of the driven body  9 , which performs reciprocating movement by the actuator  1 . By using the velocity inversion period of the driven body  9 , which is driven by the actuator  1 , for the resistance correction period to accurately detect the induced voltage Ea, the influence of dispersion of the resistance and resistance-temperature characteristic of the driving coil  12  is eliminated, and the control system is stabilized while driving the driven body  9  by the actuator  1 . In the inversion period of the moving velocity of the driven body  9  which is driven by the actuator  1 , resistance that makes the control system unstable is sequentially corrected, and periods other than the inversion period of the moving velocity of the driven body  9  which is driven by the actuator  1 , the detected induced voltage Ea is used as the velocity signal Vc, whereby the velocity of the driven body  9  can be controlled by the actuator  1  at high accuracy and stably, without installing a special velocity sensor, a velocity detection coil or the like. 
     Now the operation of the velocity command generator  8  in  FIG. 1  will be described. 
     The first edge detection sensor  2  and the second edge detection sensor  3  detect both edges of the movement range of the driven body  9  which is driven by the actuator  1 . The velocity command generator  8  generates the target velocity command Vref and the detection window signal W from the first edge position signal X 1  and the second edge position signal X 2  which sensors  2  and  3  output respectively. The velocity command generator  8  outputs the target velocity command Vref to the velocity controller  7 , and at the same time outputs the detection window signal W to the signal correction unit  6 . The velocity command generator  8  functions to output the target velocity command Vref to the velocity controller  7  so that the amplitude of the driven body  9 , which performs reciprocating movement by the actuator  1 , and the cycle of the reciprocating movement become predetermined values respectively. 
       FIG. 6  is a flow chart depicting an operation to adjust the amplitude of the reciprocating movement, out of the functions of the velocity command generator  8 . 
     In step S 1  in  FIG. 6 , zero is stored first as the initial values for the first position correction signal SU and the second position correction signal SL, to indicate the velocity inversion operation start position respectively. A constant value REF is stored for the target velocity command Vref. 
     In step S 2 , it is determined whether the first edge position signal X 1  outputted from the first edge detection sensor  2  satisfies (Expression 14), and if (Expression 14) is not satisfied, the determination processing in step S 2  is repeated.
 
 X 1&gt; AU−SU   (Expression 14)
 
     Here AU denotes one edge position of the movement range of the driven body  9  which is driven by the actuator  1 . 
     If the first edge detection sensor  2  detects one edge position AU of the movement range of the driven body  9  and (Expression 14) is satisfied in step S 2  (YES in step S 2 ), processing moves to step S 3 . In step S 3 , the detection window signal W to be outputted to the signal correction unit  6  is set to “1”, the detection window signal W is turned ON, the switch  32  is turned ON, and processing moves to step S 4 . 
     In step S 4  and step S 5 , a value dr is sequentially decremented from the value of the target velocity command Vref, so that the value of the target velocity command Vref changes from the constant value REF to zero within a predetermined time τ, whereby a velocity profile is generated. In step S 5 , it is determined whether the predetermined time τ has elapsed since the first edge position signal X 1  of the first edge detection sensor  2  satisfies (Expression 14) in step S 2 . If the predetermined time τ has not elapsed (NO in step S 5 ), processing returns to step S 4 , and if the predetermined time τ has elapsed (YES in step S 5 ), processing moves to step S 6 . When the predetermined time τ has elapsed, the value of the target velocity command Vref is zero, and the moving distance of the driven body  9  which is driven by the actuator  1 , is at the maximum on the side where the first edge detection sensor  2  exists. 
     In step S 6 , an error between the first edge position signal X 1  of the first edge detection sensor  2  read in step S 2  and one edge position AU of the target movement range is calculated, and the value (X 1 −AU) is stored in a variable ΔA. Then processing moves to step S 7  and step S 8 . In step S 7  and step S 8 , the value dr is sequentially decremented from the value of the target velocity command Vref so that the value of the target velocity command Vref changes from zero to a constant value REF within the predetermined time τ, whereby a velocity profile described later is generated. In step S 8 , it is determined whether the predetermined time τ has elapsed since the value of the target velocity command Vref became zero. If the predetermined time τ has not elapsed (NO in step S 8 ), processing returns to step S 7 , and if the predetermined time τ has elapsed (YES in step S 8 ), processing moves to step S 9 . When the predetermined time τ has elapsed, the value of the target velocity command Vref is a value −REF, and switching of the moving direction of the driven body  9 , which is driven by the actuator  1 , is completed, and processing moves to step S 9 . Thus in step S 4  and step S 7 , the value dr is sequentially decremented from the value of the target velocity command Vref. In other words, each time step S 4  or step S 7  is executed, the target velocity command Vref always decreases without maintaining a same value, that is, strictly monotone decreasing is performed. 
     In step S 9 , the detection window signal W to be outputted to the signal correction unit  6  is returned to “0”, the detection window signal W is turned OFF, the switch  32  is turned OFF, and processing moves to step S 10 . In step S 10 , the variable ΔA stored in step S 6  is multiplied by a constant coefficient K, and is sequentially added to the first position correction signal SU. In other words, the addition is sequentially performed by computing (SU+K×ΔA), and the result is stored in the first position correction signal SU. 
     In the above step S 2  to step S 10 , a series of processings is executed for the actuator  1  to cause the driven body  9  to perform the reciprocating movement, where one edge position AU of the movement range of the driven body  9  is detected by the first edge sensor  2 , and the sign of the target velocity command Vref is inverted. By this series of processings, when the driven body  9 , which is driven by the actuator  1 , is moving in the direction to the first edge detection sensor  2 , the moving direction is smoothly inverted at a return point in the edge position AU, and the detection window signal W, to indicate the decelerating or accelerating period including this directional inversion, is generated. The detection window signal W is output to the signal correction unit  6 . An ON period of the detection window signal W (that is, ON period of the switch  32 ) is used as a driving coil resistance correction period to accurately detect the induced voltage Ea induced in the driving coil  12 . 
     In the next step S 11  to step S 19 , a series of processings is executed for the actuator  1  to cause the driven body  9  to perform the reciprocating movement, to detect the other edge position AL of the movement range of the driven body  9  by the second edge detection sensor  3 , and to invert the value of the target velocity command Vref from the value −REF to the value REF. By this series of processings, when the driven body  9 , which is driven by the actuator  1 , is moving in the direction to the second edge detection sensor  3 , the moving direction is smoothly inverted at a return point in the edge position AL, and the detection window signal W, to indicate the directional inversion period, is generated. 
     The processings in step S 11  to step S 19  is the same as the processings in step S 2  to step S 10 , only the sensor to detect the edge of the movement range of the driven body  9 , which is driven by the actuator  1 , is the second edge detection sensor  3  instead of the first edge detection sensor  2 , and the second edge position signal X 2  is used instead of the first edge position signal X 1 . (Redundant description on a processing in step S 11  to step S 19  in  FIG. 6  is omitted if the processing has the same function as a processing in step S 2  to step S 10 .) 
     In step S 11 , the second edge detection sensor  3  detects the other edge position AL of the movement range, and the processing in step S 11  is repeated until (Expression 15) is established.
 
 X 2&lt; AL+SL   (Expression 15)
 
     Here AL denotes the other edge position of the movement range of the driven body  9  which is driven by the actuator  1 . 
     If the second edge detection sensor  3  detects the other edge position AL of the movement range of the driven body  9  and (Expression 15) is satisfied in step S 11  (YES in step S 11 ), processing moves to step S 12 . In step S 12 , the detection window signal W to be outputted to the signal correction unit  6  is set to “1”, the detection window signal W is turned ON, the switch  32  is turned ON, and processing moves to step S 13 . 
     In step S 13  and step S 14 , a value dr is sequentially incremented from the value of the target velocity command Vref so that the value of the target velocity command Vref changes from the constant value −REF to zero within the predetermined time τ, whereby a velocity profile is generated. In step S 14 , it is determined whether the predetermined time τ has elapsed since the second edge position signal X 2  of the second edge detection sensor  3  satisfies (Expression 15) in step S 11 . If the predetermined time τ has not elapsed (NO in step S 14 ), processing returns to step S 13 , and if the predetermined time τ has elapsed (YES in step S 14 ), processing moves to step S 15 . When the predetermined time τ has elapsed, the value of the target velocity command Vref is zero, and the moving distance of the driven body  9 , which is driven by the actuator  1 , is at the maximum on the side where the second edge detection sensor  3  exists. 
     In step S 15 , an error between the second edge position signal X 2  of the second edge detection sensor  3  read in step S 11  and the other edge position AL of the target movement range is calculated, and the value (X 2 −AL) is stored in a variable ΔB. The processing moves to step S 16  and step S 17 . In step S 16  and step S 17 , the value dr is sequentially incremented from the value of the target velocity command Vref so that the value of the target velocity command Vref changes from zero to the constant value REF within the predetermined time τ, whereby a velocity profile described later is generated. In step S 17 , it is determined whether the predetermined time τ has elapsed since the value of the target velocity command Verf becomes zero. If the predetermined time τ has not elapsed (NO in step S 17 ), processing returns to step S 16 , and if the predetermined time τ has elapsed (YES in step S 17 ), processing moves to step S 18 . When the predetermined time τ has elapsed, the value of the target velocity command Vref is the constant value REF, and switching of the moving direction of the driven body  9 , which is driven by the actuator  1 , is completed, and processing moves to step S 18 . Thus in step S 13  and step S 16 , the value dr is sequentially incremented from the value of the target velocity command Vref. In other words, each time step S 13  or step S 16  is executed, the target velocity command Vref always increases without maintaining a same value, that is, strictly monotone increasing is performed. 
     In step S 18 , the detection window signal W to be outputted to the signal correction unit  6  is returned to “0”, the detection window signal W is turned OFF, the switch  32  is turned OFF, and processing moves to step S 19 . In step S 19 , the variable ΔB stored in step S 15  is multiplied by a constant coefficient K, and is sequentially added to the second position correction signal SL. In other words, the addition is sequentially performed by computing (SL+K×ΔB), and the result is stored in the second position correction signal SL. 
     In the above step S 11  to step S 19 , a series of processings is executed for the actuator  1  to cause the driven body  9  to perform the reciprocating movement, where the other edge position AL of the movement range of the driven body  9  is detected by the second edge detection sensor  3 , and the sign of the target velocity command Vref is inverted. By this series of processings, when the driven body  9 , which is driven by the actuator  1 , is moving in the direction to the second edge detection sensor  3 , the moving direction is smoothly inverted at a return point in the edge position AL, and the detection window signal W, to indicate the directional inversion period, is generated. The detection window signal W is output to the signal correction unit  6 . An ON period of the detection window signal W (that is, the ON period of the switch  32 ) is used as the driving coil resistance correction period to accurately detect the induced voltage Ea induced in the driving coil  12 . In this embodiment, the constant value REF corresponds to an example of a target value. 
     The operation to adjust the amplitude of the reciprocating movement of the velocity command generator  8  that performs the above signal processing will be described in detail with reference to the drawings.  FIGS. 7A and 7B  are time waveform diagrams depicting an operation to adjust the amplitude of the reciprocating movement of the velocity command generator  8 . 
     In  FIGS. 7A and 7B ,  FIG. 7A  shows a position of the driven body  9  which is driven by the actuator  1 . A position (AU−SU) and a position (AL+SL) in  FIG. 7A  indicate the velocity inversion operation start positions where the driven body  9 , which is driven by the actuator  1 , starts the velocity inversion operation. 
     The first position correction signal SU is vertically corrected in  FIG. 7A  in step S 3  to step S 10  in  FIG. 6 , so that the first edge position signal X 1  detected by the first edge detection sensor  2  in step S 2  in  FIG. 6  matches the one edge position AU, that is, so that the position of the driven body  9 , which is driven by the actuator  1 , has the maximum value. In the same way, the second position correction signal SL is vertically corrected in  FIG. 7A  in step S 12  to step S 19  in  FIG. 6 , so that the second edge position signal X 2  detected by the second edge detection sensor  3  in the step S 11  in  FIG. 6  matches the other edge position AL, that is, so that the position of the driven body  9 , which is driven by the actuator  1 , has the minimum value. 
       FIG. 7B  indicates the target velocity command Vref that is inputted to the velocity controller  7  for controlling the velocity of the driven body  9  which is driven by the actuator  1 . 
     Operation of the velocity inversion (that is, the inversion of the moving direction) of the driven body  9 , which is driven by the actuator  1 , is started at the point of the position (AU−SU) and the position (AL+SL) in  FIG. 7A , the value of the target velocity command Vref becomes zero when the predetermined time τ elapsed, and the operation of the velocity inversion is completed when the time 2τ elapsed from the start of the operation of the velocity inversion. As  FIG. 7B  indicates, the target velocity command Vref has a velocity profile in a trapezoidal waveform. Therefore the position of the driven body  9 , which is driven by the actuator  1 , in  FIG. 7A  changes smoothly when the velocity inverts. As a result, the actuator  1  can implement driving with less vibration and noise. 
     As described above, in the velocity command generator  8  in  FIG. 1 , errors in one edge position AU and the other edge position AL of the movement range of the driven body  9 , obtained in step S 6  and step S 15  in  FIG. 6 , are sequentially added, and the first position correction signal SU and the second position correction signal SL are generated, and the timing to switch the moving direction is adjusted in step S 10  and step S 19 . Therefore the driven body  9 , which is driven by the actuator  1 , performs reciprocating movement between the edge position AU and the edge position AL. 
       FIG. 8  is a flow chart depicting an operation to adjust a cycle of reciprocating movement, out of the operations of the velocity command generator  8 . 
     In  FIG. 8 , as an initial value, the value REF is stored in the target velocity command Vref in step S 21  in order to prepare for adjusting the cycle. 
     In step S 22 , the cycle T, from the first edge detection sensor  2  detecting one edge position AU to the first edge detection sensor  2  detecting the edge position AU again, is measured. 
     In step S 23 , an error between the cycle T read in step S 22  and the target cycle To, that is (T−To), is calculated, and the value (T−To) is stored in a variable ΔT. Then processing moves to step S 24 . In step S 24 , the variable ΔT stored in step S 23  is multiplied by a constant coefficient G, and the result is sequentially added to the target velocity command Vref. In other words, the computation (Vref+G×ΔT) is sequentially performed, and the result is stored in the target velocity command Vref. 
     After the processing in step S 24  is executed, processing returns to step S 22 , and the operation in step S 22  to step S 24  is repeatedly executed. 
     The operation to adjust a cycle of the reciprocating movement of the velocity command generator  8  that performs the above signal processing will be described in detail with reference to the drawings.  FIGS. 9A and 9B  are timing waveform diagrams depicting an operation to adjust a cycle of the reciprocating movement of the velocity command generator  8 . 
     In  FIGS. 9A and 9B ,  FIG. 9A  indicates a position of the driven body  9 , which is driven by the actuator  1 . The driven body  9  performs reciprocating movement between one edge position AU and the other edge position AL. The first edge position signal X 1  detected by the first edge detection sensor  2  in step S 2  in  FIG. 6  matches the one edge position AU, and the second edge position signal X 2  detected by the second edge detection sensor  3  in step S 11  in  FIG. 6  matches the other edge position AL. Therefore the cycle T, from the second edge detection sensor  3  detecting the other edge position AL to the second edge detection sensor  3  detecting the other edge position AL again, is measured, for example, and the value REF is adjusted so that this cycle T becomes the target cycle To. 
     In other words, as the broken line in  FIG. 9B  indicates, if the cycle error ΔT obtained in step S 23  in  FIG. 8  is a positive value and the reciprocating cycle T of the driven body  9 , which is driven by the actuator  1 , is longer than the target cycle To, the movement velocity of the driven body  9  is increased by increasing the target velocity Vref, and as a result, the reciprocating cycle T decreases. Whereas if the cycle error ΔT obtained in step S 23  is a negative value and the reciprocating cycle T of the driven body  9 , which is driven by the actuator  1 , is shorter than the target cycle To, the movement velocity of the driven body  9  is decreased by decreasing the target velocity Vref, and as a result, the reciprocating cycle T increases. When the reciprocating cycle T of the driven body  9 , which is driven by the actuator  1 , matches the target cycle To, the cycle error ΔT obtained in step S 23  is zero, and the value of the target velocity command Vref does not change any more even if the computation in step S 24  is repeated. 
     As described above, in the velocity command generator  8  in  FIG. 1 , the cycle error ΔT obtained in step S 23  in  FIG. 8  between the reciprocating cycle T of the driven body  9 , which is driven by the actuator  1 , and the target cycle To, is sequentially added in step S 24  to generate the target velocity command Vref, and the movement velocity of the driven body  9  is adjusted. Therefore in the end, the driven body  9 , which is driven by the actuator  1 , performs the reciprocating movement between one edge position AU and the other edge position AL at the target cycle To. 
     In the flow chart depicting the operation to adjust the cycle of the reciprocating movement in  FIG. 8 , the cycle from the first edge detection sensor  2  detecting one edge position AU to the first edge detection sensor  2  detecting this one edge position AU again is measured in step S 22  in  FIG. 8 , but the present invention is not limited to this configuration. Instead the cycle from the second edge detection sensor  3  detecting the other edge position AL to the second edge detection sensor  3  detecting this other edge position AL again may be measured. Furthermore, a half cycle from the first edge detection sensor  2  detecting one edge position AU to the second edge detection sensor  3  detecting the other edge position AL, where the driven body  9 , which is driven by the actuator  1 , moves one way, may be measured using both the first edge detection sensor  2  and the second edge detection sensor  3 , then double the measured value may be used as the cycle. 
       FIGS. 10A to 10D  are time waveform diagrams depicting simulation results, which describe the simultaneous operation of the amplitude adjustment and the cycle adjustment of the velocity command generator  8  constituting the movement control apparatus according to this embodiment of the present invention. In other words, the time waveform diagrams in  FIGS. 10A to 10D  are simulation results for describing operation in the transient state when the operation flow to adjust the amplitude in  FIG. 6  and the operation flow to adjust the cycle in  FIG. 8  are simultaneously performed, so that the amplitude and the cycle of the driven body  9 , which performs the reciprocating movement, can be set to predetermined values respectively by the velocity command generator  8  in  FIG. 1 . 
     In  FIGS. 10A to 10D , the waveform  51  in  FIG. 10A  indicates a time waveform of a position of the driven body  9 , which is driven by the actuator  1 , the waveform  52  indicates a velocity inverting operation start position (AU−SU) of the driven body  9 , which is detected by the first edge detection sensor  2 , and the waveform  53  indicates a velocity inverting operation start position (AL+SL) of the driven body  9 , which is detected by the second edge detection sensor  3 .  FIG. 10B  indicates a time waveform of the movement velocity of the driven body  9 , which is driven by the actuator  1 . It is shown that the velocity inverting operation start positions (AU−SU) and (AL+SL) of the driven body  9 , indicated by the waveforms  52  and  53 , are adjusted as time elapses, and reach the stationary state after the driven body  9  performs reciprocating operation ten times. 
       FIG. 10C  indicates a time waveform of the amplitude of the driven body  9 , which is driven by the actuator  1 , and  FIG. 10D  indicates a time waveform of the cycle of the driven body  9 , which is driven by the actuator  1 . As  FIGS. 10A to 10D  show, even if the amplitude adjustment function and the cycle adjustment function of the velocity command generator  8  constituting the movement control apparatus according to this embodiment of the present invention are simultaneously operated, the driven body  9 , which performs the reciprocating movement by the actuator  1 , reaches the stationary state after performing the reciprocating movement about ten times, demonstrating a good stabilizing characteristic. 
     In the simulation in  FIGS. 10A to 10D , zero is stored in the first position correction signal SU and the second position correction signal SL respectively as initial values, when the driven body  9 , which is driven by the actuator  1 , starts reciprocating movement (step S 1  in  FIG. 6 ), but the present invention is not limited to this. Instead the values of the first position correction signal SU and the second position correction signal SL, when the reciprocating movement of the driven body  9  reaches the stationary state, may be stored in a memory included in the velocity command generator  8 , for example, so that the values stored in the memory are used as the initial values when the driven body  9  starts the reciprocating movement again. According to this embodiment, stable reciprocating movement can be implemented without generating the transient state shown in  FIGS. 10A to 10D . 
       FIGS. 11A to 11E  are time waveform diagrams depicting simulation results, which describe operation in a stationary state of the reciprocating movement of the driven body  9  by the movement control apparatus according to the embodiment of the present invention. 
     In  FIGS. 11A to 11E ,  FIG. 11A  indicates the time waveform of a position of the driven body  9 , which is driven by the actuator  1 . As  FIG. 11A  shows, the driven body  9 , which is driven by the actuator  1 , performs the reciprocating movement with the amplitude (AU−AL) and the cycle To between the maximum edge position AU and the minimum edge position AL.  FIG. 11B  indicates the time waveform of the movement velocity of the driven body  9 , which is driven by the actuator  1 . In the actuator  1 , a velocity profile control is performed to form a trapezoidal waveform. Therefore the moving direction of the driven body  9  is smoothly inverted at the return points in the edge position AU and the edge position AL, and the driven body  9  moves at a velocity that is constant with a constant value REF until the direction is inverted next, and this reciprocating movement is repeated. 
       FIG. 11C  is a time waveform of the voltage signal Ed which is outputted from the induced voltage detector  5 ,  FIG. 11D  indicates a time waveform of the velocity signal Vc which is outputted from the signal correction unit  6 , and  FIG. 11E  indicates a time waveform of the drive current Ia which is supplied to the driving coil  12 . In the simulation in  FIGS. 11A to 11E , it is assumed that the coil resistance value Ra of the driving coil  12  is a value different from the nominal resistance value Ran, and the resistance error dR (=Ra−Ran) is 20%. It is also assumed that there is no load resistance, such as bearing friction and elastic force, applied to the actuator  1  when the driving coil  12 , supported by the supporting mechanism, performs reciprocating movement. 
     If the resistance error dR exists, the waveform of the voltage signal Ed in  FIG. 11C  includes, not only the induced voltage Ea generated in the driving coil  12  due to the reciprocating movement of the driven body  9 , which is driven by the actuator  1 , but also a drop in voltage (dR×Ia) due to the resistance error dR and the driving current Ia. 
     Whereas the waveform of the velocity signal Vc in  FIG. 11D  does not include the drop in voltage (dR×Ia) due to the resistance error dR, since the drop in voltage (dR×Ia), generated due to the resistance error dR, is corrected by the drop in voltage (ΔR×Ia) using the correction signal ΔR of the signal correction unit  6 , but includes only the induced voltage Ea. 
     According to the movement control apparatus and the movement control method of the embodiment of the present invention, the level of the driving current Ia, which is supplied to the driving coil  12 , becomes the maximum in the inversion period of the movement velocity (that is, the inversion period of the moving direction) of the driven body  9 , which performs reciprocating movement by the actuator  1  ( FIG. 11E ), and the velocity inversion period 2τ of the driven body  9  is used for the resistance correction period for accurately detecting the induced voltage Ea. Thereby the influence of the dispersion of resistance and resistance temperature characteristic of the driving coil  12  is eliminated using the induced voltage detector  5  and the signal correction unit  6 , while the actuator  1  is driving the driven body  9 , so that the control system is stabilized. 
     Further, according to the movement control apparatus of the embodiment of the present invention, the coil resistance value of the driving coil  12 , to be a factor of making the control system unstable, is sequentially corrected in the inversion period 2τ of the movement velocity of the driven body  9 , which is driven by the actuator  1 , while in the periods other than the inversion period 2τ of the movement velocity of the driven body  9 , which is driven by the actuator  1 , the induced voltage Ea detected by the induced voltage detector  5  and the signal correction unit  6  is used as the velocity signal Vc. Thereby the movement velocity Vc of the driven body  9 , which is driven by the actuator  1 , can be accurately detected ( FIG. 11D ). Therefore the velocity of the driven body  9  (e.g. an optical element such as a focus lens and an imaging element), with respect to the target velocity command Vref, can be controlled at high accuracy and the driven body  9  can be stably operated without installing a special velocity sensor, velocity detection coil or the like. 
     Further, according to the movement control apparatus and the movement control method of the embodiment of the present invention, the target velocity command Vref has a velocity profile in a trapezoidal waveform ( FIG. 11B ). Therefore the position of the driven body  9 , which is driven by the actuator  1 , smoothly changes when the velocity is inverted (that is, when the moving direction is inverted) ( FIG. 11A ). As a result, the actuator  1  can implement driving with less vibration and less noise. 
     Furthermore, according to the movement control apparatus of the embodiment of the present invention, the driven body  9  is an optical element such as a focus lens and an imaging element. Therefore the optical element, which is the driven body  9 , can perform reciprocating movement at a constant high velocity during the exposure time throughout the focal length that corresponds to the extended depth of field. 
     In the above embodiment, the multiplier  34  of the signal correction unit  6  uses the correction signal ΔR which is outputted from the integrator  37  of the correction signal generator  33  after the driven body  9 , which is driven by the actuator  1 , starts the reciprocating movement, but the present invention is not limited to this. 
       FIG. 12  is a block diagram depicting another example of the configuration of the signal correction unit. The signal correction unit  6   a  shown in  FIG. 12  has a non-volatile memory circuit  38  in addition to each composing element of the signal correction unit  6  in  FIG. 3 . In the signal correction unit  6   a  shown in  FIG. 12 , the integrator  37  of the correction signal generator  33  outputs the correction signal ΔR not to the multiplier  34 , but to the non-volatile memory circuit  38 . 
     The non-volatile memory circuit  38  stores the correction signal ΔR outputted from the integrator  37 , before the actuator  1  stops the reciprocating movement of the driven body  9 . When the actuator  1  starts the reciprocating movement of the driven body  9 , the non-volatile memory circuit  38  outputs the stored correction signal ΔR to the multiplier  34  as the initial value of the correction signal ΔR. After the actuator  1  starts the reciprocating movement of the driven body  9 , the non-volatile memory circuit  38  directly outputs the correction signal ΔR outputted from the integrator  37  to the multiplier  34 . In the configuration shown in  FIG. 12 , the non-volatile memory circuit  38  corresponds to an example of a non-volatile memory. 
     According to the embodiment shown in  FIG. 12 , the correction signal ΔR obtained in the previous reciprocating movement of the driven body  9  is used as the initial value of the correction signal ΔR in the current reciprocating movement of the driven body  9 . Therefore, compared with the above-described embodiment, the driven body  9  can perform the reciprocating movement more stably from the start of the movement. 
     According to the embodiment shown in  FIG. 12 , the non-volatile memory circuit  38  stores the correction signal ΔR outputted from the integrator  37  before the actuator  1  stops the reciprocating movement of the driven body  9 , but the present invention is not limited to this, and may store a different value as the initial value. For example, in  FIG. 1 , before the actuator  1  starts the reciprocating movement of the driven body  9 , the velocity controller  7  causes the driving unit  4  to supply the electric current, having the predetermined reference current value I 0 , to the driving coil  12 , and causes the induced voltage detector  5  to detect the voltage value V 0 , which is generated on both ends of the driving coil  12  in a state where the driving coil  12  of the actuator  1  is contacted to a right edge  13   a  of the yoke  13  and stopped. The right edge  13   a  of the yoke  13  is disposed outside the movement range of the driving coil  12  when the driven body  9  performs the reciprocating movement. 
     Then the signal correction unit  6   a  calculates the resistance value Ra=V 0 /I 0  of the driving coil  12  based on the reference current value I 0  and the detected voltage value V 0 , and calculates the shift from the nominal resistance value Ran as the resistance error dR=(Ra−Ran)=(V 0 /I 0 −Ran). The signal correction unit  6   a  stores the calculated resistance error dR=(V 0 /I 0 −Ran) in the non-volatile memory circuit  38  as the initial value of the correction signal ΔR. When the driven body  9  starts the reciprocating movement, the signal correction unit  6   a  uses the resistance error stored in the non-volatile memory circuit  38  as the initial value of the correction signal ΔR. In this embodiment, the driving coil  12  and the driven body  9  correspond to an example of a movable portion, and the right edge  13   a  of the yoke  13  corresponds to an example of a wall unit. In this embodiment as well, the driven body  9  can perform the reciprocating movement even more stably from the start of the movement. 
     According to the above embodiment, the signal correction unit  6  has the switch  32 , and turns the switch  32  ON when the detection window signal W is “1”, that is ON, so as to input the signal gm×U (=Ia) from the multiplier  31  to the computing unit  36  of the correction signal generator  33 , but the present invention is not limited to this, and may not include the switch  32 . 
       FIG. 13  is a block diagram depicting still another example of the configuration of the signal correction unit. A signal correction unit  6   b  shown in  FIG. 13  is the same as the signal correction unit  6  shown in  FIG. 3 , except that the switch  32  is not included. Therefore regardless the detection window signal W, the signal gm×U (=Ia) is always inputted from the multiplier  31  to the computing unit  36  of the correction signal generator  33 . If the detection window signal W is “0”, that is OFF, the induced voltage Ea of the driving coil  12  is constant and the driving current Ia=0, as shown in  FIGS. 4A to 4E . Therefore the multiplication result outputted from the multiplier  34  is ΔR×Ia=0. As a result, the driven body  9  can also be driven well in the embodiment of  FIG. 13 . But the configuration of turning off the switch  32  when the detection window signal W is OFF, as in the case of the signal correction unit  6  shown in  FIG. 3 , is preferable, since disturbance of the velocity signal Vc is less. 
     In the above embodiment, the driven body  9  is an optical element such as a focus lens, as an example, but the present invention is not limited to this. For example, the driven body  9  can be a print head which is used for a printing apparatus, such as a plotter and a printer, or a moving member which performs reciprocating movement in linear actuator used in the industrial apparatus field, including robots. 
     The above-described embodiments primarily include the invention having the following configuration. 
     A movement control apparatus according to an aspect of the present invention comprises: an actuator that includes a permanent magnet and a driving coil facing the permanent magnet via a predetermined air gap, and causes a driven body connected to the driving coil to perform reciprocating movement; a signal generation unit that generates a velocity command signal which indicates a target velocity of the driven body; a driving unit that supplies electric current corresponding to an inputted driving signal to the driving coil of the actuator; a voltage detection unit that detects induced voltage generated in the driving coil with electric current supplied by the driving unit, and outputs a voltage signal corresponding to the detected induced voltage; a signal correction unit that corrects, based on the driving signal and the voltage signal outputted from the voltage detection unit, the voltage signal to adjust a shift of a resistance value from a predetermined reference resistance value of the driving coil, thereby generating a velocity signal; and a control unit that generates the driving signal based on the velocity command signal generated by the signal generation unit and the velocity signal generated by the signal correction unit, and outputs the driving signal to the driving unit. 
     According to this configuration, an actuator includes a permanent magnet and a driving coil facing the permanent magnet via a predetermined air gap, and causes a driven body connected to the driving coil to perform reciprocating movement. A signal generation unit generates a velocity command signal which indicates a target velocity of the driven body. A driving unit supplies electric current corresponding to an inputted driving signal to the driving coil of the actuator. A voltage detection unit detects induced voltage generated in the driving coil with electric current supplied by the driving unit, and outputs a voltage signal corresponding to the detected induced voltage. A signal correction unit corrects, based on the driving signal and the voltage signal outputted from the voltage detection unit, the voltage signal to adjust a shift of a resistance value from a predetermined reference resistance value of the driving coil, thereby generating a velocity signal. A control unit generates the driving signal based on the velocity command signal generated by the signal generation unit and the velocity signal generated by the signal correction unit, and outputs the driving signal to the driving unit. 
     Thus the voltage signal corresponding to the induced voltage induced in the driving coil is corrected to adjust the shift of the resistance value from the reference resistance value of the driving coil, whereby the velocity signal is generated, the driving signal is generated based on the velocity command signal and the velocity signal, the electric current corresponding to the driving signal is supplied to the driving coil, and the driven body is driven. Therefore a velocity detection coil need not be especially installed for detecting the velocity of the driven body, which is driven by the actuator. As a result, even if the resistance value of the driving coil is shifted from the reference resistance value, the driven body can favorably perform the reciprocating movement at low cost. 
     In this movement control apparatus, it is preferable that the signal correction unit includes: a correction signal generation unit that generates a correction signal which corresponds to a shift of the resistance value from the reference resistance value of the driving coil, based on an electric current signal which corresponds to the driving signal, and the velocity signal; a multiplication unit that multiplies the correction signal generated by the correction signal generation unit by the electric current signal that corresponds to the driving signal, and outputs a multiplication result obtained by the multiplication; and a velocity signal generation unit that generates the velocity signal from the multiplication result outputted from the multiplication unit and the voltage signal outputted from the voltage detection unit. 
     According to this configuration, a correction signal generation unit included in the signal correction unit generates a correction signal which corresponds to a shift of the resistance value from the reference resistance value of the driving coil, based on an electric current signal which corresponds to the driving signal, and the velocity signal. A multiplication unit included in the signal correction unit multiplies the correction signal generated by the correction signal generation unit by the electric current signal that corresponds to the driving signal, and outputs the multiplication result obtained by the multiplication. A velocity signal generation unit included in the signal correction unit generates the velocity signal from the multiplication result outputted from the multiplication unit and the voltage signal outputted from the voltage detection unit. Thus the velocity signal is generated by the multiplication result of the correction signal which corresponds to the shift of the resistance value from the reference resistance value of the driving coil and the electric current signal which corresponds to the driving signal, and the voltage signal. And the driving signal is generated based on the generated velocity signal and the velocity command signal. As a result, even if the resistance value of the driving coil is shifted from the reference resistance value, the actuator can cause the driven body to perform the reciprocating movement favorably. 
     In the movement control apparatus, it is preferable that the signal correction unit further includes a multiplying unit that multiplies the driving signal by a predetermined multiplication coefficient to generate the electric current signal, wherein the correction signal generation unit includes: an error signal generation unit that multiplies the electric current signal by the velocity signal, and performs time integration on a multiplication result obtained by the multiplication to generate an error signal which indicates a shift of the resistance value from the reference resistance value of the driving coil; and an integration unit that integrates the error signal generated by the error signal generation unit to generate the correction signal, and wherein the velocity signal generation unit subtracts the multiplication result outputted from the multiplication unit, from the voltage signal outputted from the voltage detection unit, and generates a subtraction result obtained by the subtraction as the velocity signal. 
     According to this configuration, a multiplying unit included in the signal correction unit multiplies the driving signal by a predetermined multiplication coefficient to generate the electric current signal. An error signal generation unit included in the correction signal generation unit multiplies the electric current signal by the velocity signal, and performs time integration on a multiplication result obtained by the multiplication to generate an error signal which indicates a shift of the resistance value from the reference resistance value of the driving coil. An integration unit included in the correction signal generation unit integrates the error signal generated by the error signal generation unit to generate the correction signal. The velocity signal generation unit subtracts the multiplication result outputted from the multiplication unit, from the voltage signal outputted from the voltage detection unit, and generates a subtraction result obtained by the subtraction as the velocity signal. Thus the multiplication result of multiplying the current signal, which is generated by multiplying the driving signal by the multiplication coefficient, and the velocity signal, is time-integrated, and the error signal is generated. Therefore an error signal, which favorably indicates the shift of the resistance value from the reference resistance value of the driving coil, can be generated. Since the correction signal is generated by integrating this error signal, the correction signal can be favorably generated. As a result, even if the resistance value of the driving coil is shifted from the reference resistance value, the actuator can cause the driven body to perform reciprocating movement favorably. 
     It is preferable that this movement control apparatus further comprises: a first edge detection unit that detects one edge position of a movement range of the driven body to output a first edge position signal; and a second edge detection unit that detects the other edge position of the movement range of the driven body to output a second edge position signal, wherein the signal generation unit generates a detection window signal based on the first edge position signal outputted from the first edge detection unit and the second edge position signal outputted from the second edge detection unit, and the signal correction unit further includes an input prohibition unit that prohibits input of the driving signal to the correction signal generation unit during a period when the signal generation unit does not generate the detection window signal. 
     According to this configuration, a first edge detection unit detects one edge position of a movement range of the driven body to output a first edge position signal. A second edge detection unit detects the other edge position of the movement range of the driven body to output a second edge position signal. The signal generation unit generates a detection window signal based on the first edge position signal outputted from the first edge detection unit, and the second edge position signal outputted from the second edge detection unit. An input prohibition unit included in the signal correction unit prohibits input of the driving signal to the correction signal generation unit during a period when the signal generation unit does not generate the detection window signal. Therefore the velocity signal is generated only during a period when the detection window signal is generated. As a result, the velocity signal can be generated at an appropriate timing by appropriately setting the period when the detection window signal is generated. 
     It is preferable that the movement control apparatus further comprises: a first edge detection unit that detects one edge position of a movement range of the driven body to output a first edge position signal; and a second edge detection unit that detects the other edge position of the movement range of the driven body to output a second edge position signal, wherein the signal generation unit generates a detection window signal based on the first edge position signal outputted from the first edge detection unit and the second edge position signal outputted from the second edge detection unit, and the signal correction unit is configured to generate the velocity signal each time the signal generation unit generates the detection window signal. 
     According to this configuration, a first edge detection unit detects one edge position of a movement range of the driven body to output a first edge position signal. A second edge detection unit detects the other edge position of the movement range of the driven body to output a second edge position signal. The signal generation unit generates a detection window signal based on the first edge position signal outputted from the first edge detection unit, and the second edge position signal outputted from the second edge detection unit. The signal correction unit is configured to generate the velocity signal each time the signal generation unit generates the detection window signal. Therefore the velocity signal is generated at a same frequency as the generation frequency of the detection window signal. As a result, the velocity signal can be generated at an appropriate frequency by setting the generation frequency of the detection window signal appropriately. 
     It is preferable that the movement control apparatus further comprises: a first edge detection unit that detects one edge position of a movement range of the driven body to output a first edge position signal; and a second edge detection unit that detects the other edge position of the movement range of the driven body to output a second edge position signal, wherein the signal generation unit generates a detection window signal based on the first edge position signal outputted from the first edge detection unit and the second edge position signal outputted from the second edge detection unit, and the signal correction unit is configured to generate the velocity signal each time the signal generation unit generates the detection window signal for a plurality of times. 
     According to this configuration, a first edge detection unit detects one edge position of a movement range of the driven body to output a first edge position signal. A second edge detection unit detects the other edge position of the movement range of the driven body to output a second edge position signal. The signal generation unit generates a detection window signal based on the first edge position signal outputted from the first edge detection unit and the second edge position signal outputted from the second edge detection unit. The signal correction unit is configured to generate the velocity signal each time the signal generation unit generates the detection window signal for a plurality of times. Therefore the velocity signal can be generated at a required frequency by appropriately setting the generation frequency of the velocity signal to be a frequency less than the generation frequency of the detection window signal. 
     In this movement control apparatus, it is preferable that the signal generation unit is configured to generate the detection window signal during a period including a timing of inversion of the velocity of the driven body, which performs reciprocating movement by the actuator. 
     According to this configuration, the signal generation unit is configured to generate the detection window signal during a period including a timing of inversion of the velocity of the driven body, which performs reciprocating movement by the actuator. Therefore the detection window signal can be generated during the period including the period when the velocity of the driven body is changing. 
     In this movement control apparatus, it is preferable that the signal generation unit is configured to generate the detection window signal during a period from a start of deceleration of the driven body, which performs reciprocating movement by the actuator, to an end of acceleration after an inversion of the velocity. 
     According to this configuration, the signal generation unit is configured to generate the detection window signal during a period from a start of deceleration of the driven body, which performs reciprocating movement by the actuator, to an end of acceleration after an inversion of the velocity. Therefore the detection window signal can be generated during the period when the driven body is decelerating or accelerating, which is other than the period when the driven body is moving at a constant velocity. 
     In the movement control apparatus, it is preferable that the signal generation unit is configured to adjust a velocity inverting operation start position of the velocity command signal respectively in a direction for the driven body to move toward the one edge position, and in a direction for the driven body to move toward the other edge position, to cause the first edge detection unit to output the first edge position signal at a timing when the movement velocity of the driven body is inverted at the one edge position of the movement range of the driven body, and to cause the second edge detection unit to output the second edge position signal at a timing when the movement velocity of the driven body is inverted at the other edge position of the movement range of the driven body. 
     According to this configuration, the signal generation unit is configured to adjust a velocity inverting operation start position of the velocity command signal respectively in a direction for the driven body to move toward the one edge position, and in a direction for the driven body to move toward the other edge position, to cause the first edge detection unit to output the first edge position signal at a timing when the movement velocity of the driven body is inverted at the one edge position of the movement range of the driven body, and to cause the second edge detection unit to output the second edge position signal at a timing when the movement velocity of the driven body is inverted at the other edge position of the movement range of the driven body. Therefore the movement range of the driven body can with certainty be in the range between the output position of the first edge position signal and the output position of the second edge position signal. 
     In this movement control apparatus, it is preferable that the signal generation unit is configured to measure a cycle of the driven body that performs reciprocating movement using at least one of the first edge position signal outputted from the first edge detection unit and the second edge position signal outputted from the second edge detection unit, and to adjust a level of the velocity command signal to mach the measured cycle to a predetermined target cycle. 
     According to this configuration, the signal generation unit is configured to measure a cycle of the driven body that performs reciprocating movement using at least one of the first edge position signal outputted from the first edge detection unit and the second edge position signal outputted from the second edge detection unit, and to adjust the level of the velocity command signal to mach the measured cycle to a predetermined target cycle. Therefore the driven body can with certainty perform the reciprocating movement in the target cycle. 
     In this movement control apparatus, it is preferable that the signal generation unit is configured to generate the velocity command signal to maintain a value of the velocity command signal at a predetermined target value which is positive until the first edge position signal or the second edge position signal is outputted, to gradually decrease the value of the velocity command signal from an output timing of the first edge position signal or the second edge position signal to become zero when a predetermined time elapses, and to further gradually decrease the value of the velocity command signal from the timing when the predetermined time elapses to become the target value which is negative when the predetermined time elapses. 
     According to this configuration, the signal generation unit is configured to generate the velocity command signal to maintain a value of the velocity command signal at a predetermined target value which is positive until the first edge position signal or the second edge position signal is outputted, to gradually decrease the value of the velocity command signal from an output timing of the first edge position signal or the second edge position signal to become zero when a predetermined time elapses, and to further gradually decrease the value of the velocity command signal from the timing when the predetermined time elapses to become the target value which is negative when the predetermined time elapses. Therefore the velocity of the driven body can be smoothly inverted. 
     It is preferable that this movement control apparatus further comprises a wall unit that is disposed outside a movement range of a movable portion when the driven body performs reciprocating movement, wherein the movable portion of the actuator includes the driven body and the driving coil, the control unit causes the driving unit to supply electric current having a predetermined reference current value to the driving coil, and causes the voltage detection unit to detect a voltage value generated between both ends of the driving coil in a state of the movable portion of the actuator being contacted to the wall unit and stopped, before the actuator starts the reciprocating movement of the driven body, and the signal correction unit is configured to calculate, based on the reference current value and the detected voltage value, a shift of the resistance value from the reference resistance value of the driving coil as a resistance error, and to use the calculated resistance error as an initial value of the correction signal when the actuator starts the reciprocating movement of the driven body. 
     According to this configuration, a wall unit is disposed outside a movement range of a movable portion when the driven body performs reciprocating movement. The movable portion of the actuator includes the driven body and the driving coil. The control unit causes the driving unit to supply electric current having a predetermined reference current value to the driving coil, and causes the voltage detection unit to detect a voltage value generated between both ends of the driving coil in a state of the movable portion of the actuator being contacted to the wall unit and stopped, before the actuator starts the reciprocating movement of the driven body. The signal correction unit is configured to calculate, based on the reference current value and the detected voltage values, a shift of the resistance value from the reference resistance value of the driving coil as a resistance error, and to use the calculated resistance error as an initial value of the correction signal when the actuator starts the reciprocating movement of the driven body. Therefore the velocity signal can be favorably calculated from the start of the driving of the actuator. As a result, time required to stabilize the reciprocating movement of the driven body can be decreased. 
     It is preferable that this movement control apparatus further comprises a non-volatile memory, wherein the signal correction unit is configured to store the correction signal generated by the correction signal generation unit in the non-volatile memory before the actuator stops the reciprocating movement of the driven body, and to use the correction signal stored in the non-volatile memory as an initial value of the correction signal when the actuator starts the reciprocating movement of the driven body next time. 
     According to this configuration, the movement control apparatus further comprises a non-volatile memory. The signal correction unit is configured to store the correction signal generated by the correction signal generation unit in the non-volatile memory before the actuator stops the reciprocating movement of the driven body, and to use the correction signal stored in the non-volatile memory as an initial value of the correction signal when the actuator starts the reciprocating movement of the driven body next time. Therefore the velocity signal can be favorably calculated from the start of the driving of the actuator. As a result, time required to stabilize the reciprocating movement of the driven body can be decreased. 
     A movement control method according to an aspect of the present invention is a movement control method of a driven body in a movement control apparatus including an actuator that has a permanent magnet and a driving coil facing the permanent magnet via a predetermined air gap, and causes the driven body connected to the driving coil to perform reciprocating movement, comprises: a first step of generating a velocity command signal that indicates a target velocity of the driven body; a second step of supplying electric current to the driving coil of the actuator, the electric current corresponding to a driving signal for causing the driven body to perform reciprocating movement; a third step of detecting induced voltage generated in the driving coil with electric current supplied to the driving coil in the second step, and outputting a voltage signal corresponding to the induced voltage; a fourth step of correcting, based on the driving signal and the voltage signal outputted in the third step, the voltage signal to adjust a shift of a resistance value from a predetermined reference resistance value of the driving coil, thereby generating a velocity signal; and a fifth step of generating the driving signal based on the velocity command signal generated in the first step and the velocity signal generated in the fourth step. 
     According to this configuration, in a first step, a velocity command signal that indicates a target velocity of the driven body is generated. In a second step, electric current corresponding to a driving signal for causing the driven body to perform reciprocating movement is supplied to the driving coil of the actuator. In a third step, induced voltage generated in the driving coil with electric current supplied to the driving coil in the second step is detected, and a voltage signal corresponding to the induced voltage is outputted. In a fourth step, based on the driving signal and the voltage signal outputted in the third step, the voltage signal is corrected to adjust a shift of a resistance value from a predetermined reference resistance value of the driving coil, whereby a velocity signal is generated. In a fifth step, the driving signal is generated based on the velocity command signal generated in the first step and the velocity signal generated in the fourth step. 
     Thus the voltage signal corresponding to the induced voltage induced in the driving coil is corrected to adjust the shift of the resistance value from the reference resistance value of the driving coil, whereby the velocity signal is generated, the driving signal is generated based on the velocity command signal and the velocity signal, the electric current corresponding to the driving signal is supplied to the driving coil, and the driven body is driven. Therefore a velocity detection coil need not be especially installed for detecting the velocity of the driven body, which is driven by the actuator. As a result, even if the resistance value of the driving coil is shifted from the reference resistance value, the driven body can favorably perform the reciprocating movement at low cost. 
     It is preferable that this movement control method further comprises: a sixth step of detecting one edge position of a movement range of the driven body to output a first edge position signal; and a seventh step of detecting the other edge position of the movement range of the driven body to output a second edge position signal, wherein the first step is a step of adjusting a velocity inverting operation start position of the velocity command signal respectively in a direction for the driven body to move toward the one edge position, and in a direction for the driven body to move toward the other edge position, to output the first edge position signal in the sixth step at a timing when a moving direction of the driven body is inverted at the one edge position of the movement range of the driven body, and to output the second edge position signal in the seventh step at a timing when the moving direction of the driven body is inverted at the other edge position of the movement range of the driven body. 
     According to this configuration, in a sixth step, one edge position of a movement range of the driven body is detected, whereby a first edge position signal is outputted. In a seventh step, the other edge position of the movement range of the driven body is detected, whereby a second edge position signal is outputted. The first step is a step of adjusting a velocity inverting operation start position of the velocity command signal respectively in a direction for the driven body to move toward the one edge position, and in a direction for the driven body to move toward the other edge position, to output the first edge position signal in the sixth step at a timing when a moving direction of the driven body is inverted at the one edge position of the movement range of the driven body, and to output the second edge position signal in the seventh step at a timing when the moving direction of the driven body is inverted at the other edge position of the movement range of the driven body. Therefore the movement range of the driven body can with certainty be between the output position of the first edge position signal and the output position of the second edge position signal. 
     It is preferable that this movement control method further comprises: a sixth step of detecting one edge position of a movement range of the driven body to output a first edge position signal; and a seventh step of detecting the other edge position of the movement range of the driven body to output a second edge position signal, wherein the first step is a step of measuring a cycle of the driven body that performs reciprocating movement using at least one of the first edge position signal outputted in the sixth step and the second edge position signal outputted in the seventh step, and adjusting a level of the velocity command signal to mach the measured cycle to a predetermined target cycle. 
     According to this configuration, in a sixth step, one edge position of a movement range of the driven body is detected, whereby a first edge position signal is outputted. In a seventh step, the other edge position of the movement range of the drive body is detected, whereby a second edge position signal is outputted. The first step is a step of measuring a cycle of the driven body that performs reciprocating movement using at least one of the first edge position signal outputted in the sixth step and the second edge position signal outputted in the seventh step, and adjusting a level of the velocity command signal to mach the measured cycle to a predetermined target cycle. Therefore the driven body can with certainty perform the reciprocating movement in the target cycle. 
     A movement control circuit according to an aspect of the present invention is a movement control circuit that controls an actuator which has a permanent magnet and a driving coil facing the permanent magnet via a predetermined air gap and which causes a driven body connected to the driving coil to perform reciprocating movement, comprises: a signal generation circuit that generates a velocity command signal which indicates a target velocity of the driven body; a driving circuit that supplies electric current corresponding to an inputted driving signal to the driving coil of the actuator; a voltage detection circuit that detects induced voltage generated in the driving coil with electric current supplied by the driving circuit, and outputs a voltage signal corresponding to the detected induced voltage; a signal correction circuit that corrects, based on the driving signal and the voltage signal outputted from the voltage detection circuit, the voltage signal to adjust a shift of a resistance value from a predetermined reference resistance value of the driving coil, thereby generating a velocity signal; and a control circuit that generates the driving signal based on the velocity command signal generated by the signal generation circuit and the velocity signal generated by the signal correction circuit, and outputs the driving signal to the driving circuit. 
     According to this configuration, a signal generation circuit generates a velocity command signal which indicates a target velocity of the driven body. A driving circuit supplies electric current corresponding to an inputted driving signal to the driving coil of the actuator. A voltage detection circuit detects induced voltage generated in the driving coil with electric current supplied by the driving circuit, and outputs a voltage signal corresponding to the detected induced voltage. A signal correction circuit corrects, based on the driving signal and the voltage signal outputted from the voltage detection circuit, the voltage signal to adjust a shift of a resistance value from a predetermined reference resistance value of the driving coil, thereby generating a velocity signal. A control circuit generates the driving signal based on the velocity command signal generated by the signal generation circuit and the velocity signal generated by the signal correction circuit, and outputs the driving signal to the driving circuit. 
     Thus the voltage signal corresponding to the induced voltage induced in the driving coil is corrected to adjust the shift of the resistance value from the reference resistance value of the driving coil, whereby the velocity signal is generated, the driving signal is generated based on the velocity command signal and the velocity signal, the electric current corresponding to the driving signal is supplied to the driving coil, and the driven body is driven. Therefore a velocity detection coil need not be especially installed for detecting the velocity of the driven body, which is driven by the actuator. As a result, even if the resistance value of the driving coil is shifted from the reference resistance value, the driven body can favorably perform the reciprocating movement at low cost. 
     According to the movement control apparatus, the movement control method and the movement control circuit of the present invention, the velocity signal is generated using the induced voltage which is induced in the driving coil when the driven body, which is driven by the actuator, performs the reciprocating movement. Detection of the induced voltage is influenced by the dispersion of resistance and the resistance temperature characteristic of the driving coil, but the voltage signal corresponding to the induced voltage is corrected to adjust the shift of the resistance value from the reference resistance value of the driving coil, whereby the velocity signal is generated. Therefore the driven body can favorably perform the reciprocating movement. Furthermore, there is no need to install a separate velocity detection coil to detect velocity of the driven body, hence a number of components of the movement control apparatus can be decreased, weight thereof can be lighter, and cost reduction is implemented. 
     INDUSTRIAL APPLICABILITY 
     The movement control apparatus, the movement control method and the movement control circuit according to the present invention have a function to generate the velocity signal using the induced voltage that is induced in the driving coil, to eliminate the influence of the dispersion of the resistance and the resistance temperature characteristic of the driving coil while driving the driven body by the actuator, and to control the velocity of the driven body. Therefore the present invention is useful for a movement control apparatus and the like that cause a lens or an imaging element to perform reciprocating movement in the optical axis direction in order to extend the depth of focus in capturing a moving image or a still image of an object using a camera. The present invention can also be applied to a printing apparatus such as a plotter and a printer, and a linear actuator used in the industrial apparatus field including robots, and can demonstrate an effect similar to that described above.