Patent Publication Number: US-10771700-B2

Title: Image blur correction apparatus, interchangeable lens, camera body, image blur correction method, and storage medium

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an image blur correction apparatus, an interchangeable lens, a camera body, an image blur correction method, and a storage medium. 
     Description of the Related Art 
     Technologies for correcting image blur caused by shake applied to an image capturing apparatus are widespread. As a method for correcting image blur, there is optical image blur correction that corrects image blur by driving a correction optical system, which is part of the optical system, in a plane perpendicular to the optical axis according to the detected shake. Also, as another method, there is image sensor shift-type image blur correction that corrects image blur by driving the image sensor in a plane perpendicular to the optical axis according to the detected shake. 
     Also, in recent years, technologies have emerged that expand the range over which image blur correction is possible, by driving these plurality of correction members in a coordinated manner, enabling correction of even large camera shake of the sort that could not be properly corrected with only one correction member. Japanese Patent Laid-Open No. 2015-194711 discloses a technology that divides an image blur correction signal into a high frequency band and a low frequency band, and performs correction of high frequency image blur with one correction member and correction of low frequency image blur with another correction member. 
     The image capturing apparatus of Japanese Patent Laid-Open No. 2015-194711 calculates the image blur correction signal based on the output of an angular velocity sensor that is mounted in an interchangeable lens, and divides the calculated image blur correction signal. The image capturing apparatus then operates the image blur correction apparatuses of the interchangeable lens and the camera body in a coordinated manner, by transmitting one of the divided image blur correction signals to the camera body via a communication unit. At this time, a phase delay occurs in the image blur correction on the camera body side due to a communication delay between the interchangeable lens and the camera body, and the image blur correction effect diminishes. As a countermeasure, a method has been proposed that involves dividing the image blur correction signal calculated by the interchangeable lens into a high frequency band and a low frequency band, transmitting the low frequency component which is less susceptible to the effect of a phase delay to the camera body, and correcting low frequency image blur with the image blur correction apparatus of the camera body. However, even if the image blur correction signal in the low frequency band is less susceptible to the effect of a phase delay, the extent to which the signal is affected will be dependent on the amount of communication delay, and thus the effect still remains depending on the magnitude of the communication delay. Accordingly, in order to reduce the effect of the communication delay, a high-speed communication cycle is required between the interchangeable lens and the camera body, which is problematic in that a high-speed CPU is required and power consumption increases due to the increased communication frequency. Also, if a cutoff frequency for dividing an image blur correction signal is not set appropriately according to the communication delay, there will be an inevitable reduction in the image blur correction effect, and thus system design is difficult. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in consideration of such circumstances, and provides a technology for reducing a correction error caused by a communication delay of a correction amount between two image blur correction apparatuses that correct image blur in a coordinated manner. 
     According to a first aspect of the present invention, there is provided an image blur correction apparatus including a communication device configured to communicate with a second image blur correction apparatus that controls a second correction member configured to correct image blur of an image capturing apparatus, the image blur correction apparatus comprising one or more processors and a memory storing a program which, when executed by the one or more processors, causes the image blur correction apparatus to function as: a detection unit configured to detect shake occurring in the image capturing apparatus; a determination unit configured to, based on the shake, determine a first correction amount and a second correction amount that are for correcting the image blur; a transmission unit configured to transmit the second correction amount to the second image blur correction apparatus via the communication device, the second image blur correction apparatus controlling the second correction member based on the second correction amount; an acquisition unit configured to acquire a correction error of the second correction member caused by a communication delay of the second correction amount in the communication device; and a control unit configured to, based on the first correction amount and the correction error, control a first correction member configured to correct image blur of the image capturing apparatus so as to reduce the correction error. 
     According to a second aspect of the present invention, there is provided an image blur correction apparatus including a communication device configured to communicate with a second image blur correction apparatus that controls a second correction member configured to correct image blur of an image capturing apparatus, the image blur correction apparatus comprising one or more processors and a memory storing a program which, when executed by the one or more processors, causes the image blur correction apparatus to function as: a detection unit configured to detect shake occurring in the image capturing apparatus; a determination unit configured to, based on the shake, determine a first correction amount for correcting the image blur; a transmission unit configured to transmit the first correction amount to the second image blur correction apparatus via the communication device, the second image blur correction apparatus controlling the second correction member based on a third correction amount obtained by subtracting the first correction amount from a second correction amount for correcting the image blur that is determined based on shake occurring in the image capturing apparatus detected by a second detection unit; an acquisition unit configured to acquire a correction error of the second correction member caused by a communication delay of the first correction amount in the communication device; and a control unit configured to, based on the first correction amount and the correction error, control a first correction member configured to correct image blur of the image capturing apparatus so as to reduce the correction error. 
     According to a third aspect of the present invention, there is provided an image blur correction method executed by an image blur correction apparatus including a communication device configured to communicate with a second image blur correction apparatus that controls a second correction member configured to correct image blur of an image capturing apparatus, the image blur correction method comprising: detecting shake occurring in the image capturing apparatus; based on the shake, determining a first correction amount and a second correction amount that are for correcting the image blur; transmitting the second correction amount to the second image blur correction apparatus via the communication device, the second image blur correction apparatus controlling the second correction member based on the second correction amount; acquiring a correction error of the second correction member caused by a communication delay of the second correction amount in the communication device; and based on the first correction amount and the correction error, controlling a first correction member configured to correct image blur of the image capturing apparatus so as to reduce the correction error. 
     According to a fourth aspect of the present invention, there is provided an image blur correction method executed by an image blur correction apparatus including a communication device configured to communicate with a second image blur correction apparatus that controls a second correction member configured to correct image blur of an image capturing apparatus, the image blur correction method comprising: detecting, by a first detector, shake occurring in the image capturing apparatus; based on the shake, determining a first correction amount for correcting the image blur; transmitting the first correction amount to the second image blur correction apparatus via the communication device, the second image blur correction apparatus controlling the second correction member based on a third correction amount obtained by subtracting the first correction amount from a second correction amount for correcting the image blur that is determined based on shake occurring in the image capturing apparatus detected by a second detector; acquiring a correction error of the second correction member caused by a communication delay of the first correction amount in the communication device; and based on the first correction amount and the correction error, controlling a first correction member configured to correct image blur of the image capturing apparatus so as to reduce the correction error. 
     According to a fifth aspect of the present invention, there is provided a non-transitory computer-readable storage medium which stores a program for causing an image blur correction apparatus to execute an image blur correction method, the image blur correction apparatus including a communication device configured to communicate with a second image blur correction apparatus that controls a second correction member configured to correct image blur of an image capturing apparatus, the image blur correction method comprising: detecting shake occurring in the image capturing apparatus; based on the shake, determining a first correction amount and a second correction amount that are for correcting the image blur; transmitting the second correction amount to the second image blur correction apparatus via the communication device, the second image blur correction apparatus controlling the second correction member based on the second correction amount; acquiring a correction error of the second correction member caused by a communication delay of the second correction amount in the communication device; and based on the first correction amount and the correction error, controlling a first correction member configured to correct image blur of the image capturing apparatus so as to reduce the correction error. 
     According to a sixth aspect of the present invention, there is provided a non-transitory computer-readable storage medium which stores a program for causing an image blur correction apparatus to execute an image blur correction method, the image blur correction apparatus including a communication device configured to communicate with a second image blur correction apparatus that controls a second correction member configured to correct image blur of an image capturing apparatus, the image blur correction method comprising: detecting, by a first detector, shake occurring in the image capturing apparatus; based on the shake, determining a first correction amount for correcting the image blur; transmitting the first correction amount to the second image blur correction apparatus via the communication device, the second image blur correction apparatus controlling the second correction member based on a third correction amount obtained by subtracting the first correction amount from a second correction amount for correcting the image blur that is determined based on shake occurring in the image capturing apparatus detected by a second detector; acquiring a correction error of the second correction member caused by a communication delay of the first correction amount in the communication device; and based on the first correction amount and the correction error, controlling a first correction member configured to correct image blur of the image capturing apparatus so as to reduce the correction error. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing the configuration of an image capturing apparatus  100  including an image blur correction apparatus. 
         FIG. 2  is a block diagram illustrating image blur correction control according to a first embodiment. 
         FIG. 3  is a block diagram illustrating an image blur correction amount calculation unit  203  in detail. 
         FIGS. 4A and 4B  are block diagrams showing an exemplary configuration of a correction amount division unit  204 . 
         FIG. 5  is a block diagram illustrating a correction error computation unit  205  in detail. 
         FIG. 6  is a graph showing frequency characteristics of a phase delay of a correction amount. 
         FIG. 7  is a graph showing a correction remainder caused by a phase delay of the correction amount. 
         FIGS. 8A to 8F  are graphs illustrating the effects that result from subtracting the correction error calculated by the correction error computation unit  205  from a first correction amount. 
         FIG. 9  is a block diagram illustrating image blur correction control according to a second embodiment. 
         FIG. 10  is a block diagram illustrating a correction error computation unit  905  in detail. 
         FIG. 11  is a block diagram illustrating image blur correction control according to a third embodiment. 
         FIG. 12  is a block diagram illustrating the correction error computation unit  205  in the third embodiment. 
         FIG. 13  is a diagram showing a way of providing a receiving buffer  1001  compatible with the second embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. Elements that are given the same reference numerals throughout all of the attached drawings represent the same or similar elements. Note that the technical scope of the present invention is defined by the claims, and is not limited by the following respective embodiments. Also, not all of the combinations of the aspects that are described in the embodiments are necessarily essential to the present invention. Also, the aspects that are described in the individual embodiments can be combined as appropriate. 
     In the following embodiments, vibration that is applied to an image capturing apparatus is referred to as “shake”, and the effect on a captured image that occurs as a result of shake applied to the image capturing apparatus is referred to as “image blur”. 
     First Embodiment 
       FIG. 1  is a block diagram showing the configuration of an image capturing apparatus  100  that includes an image blur correction apparatus. The image capturing apparatus  100  is an interchangeable-lens digital camera capable of shooting still images and moving images. However, the present embodiment is not limited to an interchangeable-lens digital camera, and the present embodiment can be applied to various types of image capturing apparatuses. 
     The image capturing apparatus  100  is constituted by an interchangeable lens  100   a  and a camera body  100   b , with the interchangeable lens  100   a  being mounted for use to the camera body  100   b . A zoom unit  101  of the interchangeable lens  100   a  includes a zoom lens that performs magnification. A zoom drive control unit  102  performs drive control of the zoom unit  101 . A diaphragm unit  103  has a function of a diaphragm. A diaphragm drive control unit  104  performs drive control of the diaphragm unit  103 . An image blur correction unit  105  is provided with an image blur correction lens such as a shift lens or the like (hereinafter, also referred to as a “correction lens” or “OIS”). An image blur correction lens is movable in a direction perpendicular to the optical axis of the image capturing apparatus  100 . An optical image blur correction control unit  106  performs drive control of the image blur correction unit  105 . A focus unit  107  includes a focus lens that performs focus adjustment and forms an object image. A focus drive control unit  108  performs drive control of the focus unit  107 . 
     A lens operation unit  109  is an operation unit that is used by a user to operate the interchangeable lens  100   a . A lens shake detection unit  110  detects the amount of shake that is applied to (that occurs in) the image capturing apparatus  100  or the interchangeable lens  100   a , and outputs a detection signal to a lens system control unit  111 . The lens system control unit  111  is provided with a CPU (central processing unit), and performs overall control of the drive control units and the correction control unit of the interchangeable lens  100   a  and controls the entire interchangeable lens  100   a . The lens system control unit  111  communicates with a camera communication control unit  127  of the camera body  100   b , via a lens communication control unit  112 . That is, in a state where the interchangeable lens  100   a  is mounted and electrically connected to the camera body  100   b , the interchangeable lens  100   a  and the camera body  100   b  communicate with each other, via the lens communication control unit  112  and the camera communication control unit  127 . 
     Next, the camera body  100   b  will be described. The camera body  100   b  is provided with a shutter unit  113 . A shutter drive control unit  114  performs drive control of the shutter unit  113 . An image capturing unit  115  is provided with an image sensor, and photoelectrically converts an optical image formed by light that has passed through each lens group and outputs an electrical signal. The image sensor of the image capturing unit  115  is movable in a direction perpendicular to the optical axis of the image capturing apparatus  100 . An image capturing surface image blur correction unit  117  is provided with an image capturing surface image blur correction unit (hereinafter, also referred to as an “image capturing surface correction unit” or “IIS”) that moves the image sensor of the image capturing unit  115  to correct image blur. An image capturing surface image blur correction control unit  116  performs drive control of the image capturing surface image blur correction unit  117 . An image capturing signal processing unit  118  converts the electrical signal output by the image capturing unit  115  into a video signal. An image signal processing unit  119  processes the video signal output by the image capturing signal processing unit  118  according to the application. For example, the image signal processing unit  119  changes a clipping position of the video signal according to the correction amount of an electronic image blur correction control unit  125 . The electronic image blur correction control unit  125  controls image blur correction by clipping images. Note that the clipping position of an image may be changed through coordinate transformation. Changing of the clipping position of an image through coordinate transformation is well-known, and thus a detailed description is omitted here, but may be performed using affine transformation, or information of one pixel may be acquired using interpolation from the information of a plurality of pixels. 
     A display unit  120  performs image display as needed, based on the signal output by the image signal processing unit  119 . A recording unit  121  stores various data such as video information. A power unit  122  supplies power to the entire apparatus according to the application. A camera operation unit  123  is an operation unit that is used by a user to operate the camera body  100   b , and outputs an operation signal to a camera system control unit  126 . A camera shake detection unit  124  detects the amount of shake that is applied to (that occurs in) the image capturing apparatus  100  or the camera body  100   b , and outputs a detection signal to the camera system control unit  126 . The camera system control unit  126  is provided with a CPU, and performs overall control of the entire camera body  100   b . The camera system control unit  126  communicates with the lens communication control unit  112  of the interchangeable lens  100   a  via the camera communication control unit  127 . That is, in a state where the interchangeable lens  100   a  is mounted and electrically connected to the camera body  100   b , the interchangeable lens  100   a  and the camera body  100   b  communicate with each other, via the lens communication control unit  112  and the camera communication control unit  127 . 
     Next, the general operations of the image capturing apparatus  100  will be described. The lens operation unit  109  and the camera operation unit  123  include an image blur correction switch with which ON/OFF of image blur correction can be selected. When a user operates the image blur correction switch to select ON, the lens system control unit  111  and the camera system control unit  126  instruct the optical image blur correction control unit  106 , the image capturing surface image blur correction control unit  116  and the electronic image blur correction control unit  125  to perform an image blur correction operation. The image blur correction control units perform control of image blur correction until an OFF instruction of the image blur correction is given. 
     Also, the camera operation unit  123  includes an image blur correction mode switch with which a first mode and a second mode can be selected in relation to image blur correction. The first mode is a mode in which image blur correction is performed through a combination of optical image blur correction and image capturing surface image blur correction. The second mode is a mode in which image blur correction is performed by using a combination of optical image blur correction, image capturing surface image blur correction, and electronic image blur correction. In the case where the first mode is selected, a wider correction angle can be realized, by performing correction through coordinating optical image blur correction and image capturing surface image blur correction, enabling large shake to be corrected. The readout position of the image capturing unit  115  is fixed, and wider angle shooting can be supported by expanding the readout range as a result. Also, in the case where the second mode is selected, the clipping range of the video signal by the image signal processing unit  119  is narrowed, but larger shake can be handled by changing the clipping position according to the amount of image blur correction. 
     The camera operation unit  123  includes a shutter release button configured such that a first switch (SW 1 ) and a second switch (SW 2 ) turn on in order according to the amount by which the shutter release button is pressed. SW 1  turns on when the user presses the shutter release button approximately halfway, and SW 2  turns on when the user presses the shutter release button all the way. As a result of SW 1  turning on, the focus drive control unit  108  drives the focus unit  107  to perform focus adjustment, and the diaphragm drive control unit  104  drives the diaphragm unit  103  to set the proper exposure. As a result of SW 2  turning on, image data obtained from the optical image exposed by the image capturing unit  115  is stored in the recording unit  121 . 
     Also, the camera operation unit  123  includes a moving image recording switch. The image capturing apparatus  100  starts moving image shooting after the moving image recording switch is pressed, and ends recording when the user presses the moving image recording switch again during recording. When the user operates the shutter release button to turn on SW 1  and SW 2  during moving image shooting, processing for acquiring and recording a still image during moving image recording is executed. Also, the camera operation unit  123  includes a playback mode selection switch with which a playback mode can be selected. In the case where the playback mode is selected through operation of the playback mode selection switch, the image capturing apparatus  100  stops the image blur correction operation. 
     Next, image blur correction control that is executed by the lens system control unit  111  and the camera system control unit  126  will be described, with reference to  FIG. 2 .  FIG. 2  is a block diagram illustrating control for driving a first image blur correction unit  211  and a second image blur correction unit  217  to perform image blur correction based on information relating to shake that is applied to the image capturing apparatus  100 . 
     In  FIG. 2 , an angular velocity sensor  201  and an A/D convertor  202  are included in the lens shake detection unit  110 . An image blur correction amount calculation unit  203 , a correction amount division unit  204 , a correction error computation unit  205  and a subtractor  206  are implemented by the lens system control unit  111 . A drive amount conversion unit  207 , a subtractor  208 , a control filter  209 , an OIS drive unit  210  and a position sensor  212  are included in the optical image blur correction control unit  106 . The first image blur correction unit  211  corresponds to the image blur correction unit  105 . A drive amount conversion unit  213 , a subtractor  214 , a control filter  215 , an IIS drive unit  216  and a position sensor  218  are included in the image capturing surface image blur correction control unit  116 . The second image blur correction unit  217  corresponds to the image capturing surface image blur correction unit  117 . 
     In the present embodiment, the image capturing apparatus  100  acquires the correction amount for image blur correction using the angular velocity sensor  201  and drives the first image blur correction unit  211 . Also, the image capturing apparatus  100  transmits the correction amount for the second image blur correction unit  217  from the interchangeable lens  100   a  to the camera body  100   b  via the lens communication control unit  112  and the camera communication control unit  127 , and drives the second image blur correction unit  217 . That is, in the image blur correction system of the present embodiment, the interchangeable lens  100   a  operates as the master and the camera body  100   b  operates as the slave. 
     The angular velocity sensor  201  detects the angular velocity of shake that is applied to the image capturing apparatus  100 , and outputs a voltage that depends on the detected angular velocity. The output voltage of the angular velocity sensor  201  is converted into digital data by the A/D convertor  202  and acquired as angular velocity data, and the angular velocity data is supplied to the image blur correction amount calculation unit  203 . The series of processing from acquisition of the angular velocity data to driving of the image blur correction units is repeatedly performed at a sufficiently high-speed cycle relative to 1 to 20 Hz, which is the frequency band of camera shake, and is repeatedly performed at a cycle of 1000 Hz, for example. 
     The image blur correction amount calculation unit  203  computes the correction amount for correcting image blur that occurs due to shake that is applied to the image capturing apparatus  100 . Note that the image capturing apparatus  100  is provided with two image blur correction units, namely, the first image blur correction unit  211  and the second image blur correction unit  217 . However, the correction amount that is calculated by the image blur correction amount calculation unit  203  is a correction amount for correcting image blur of the entire image capturing apparatus  100 , rather than a correction amount for each of the two image blur correction units. 
       FIG. 3  is a block diagram illustrating the image blur correction amount calculation unit  203  in detail. A HPF  301  (high-pass filter) is used in order to remove the DC component and the low frequency component of the angular velocity data detected by the A/D convertor  202 . Angular velocity data that has passed through the HPF  301  is converted into angular displacement data through first-order integration performed in an integrator  303 . The integration computation that is performed here is imperfect integration in order to prevent saturation, and is computed using a commonly known first-order LPF (low-pass filter). The angular displacement data calculated by the integrator  303  is supplied to a framing control unit  305  and a limiter  304 . The limiter  304  applies a restriction to the angular displacement data such that the first image blur correction unit  211  and the second image blur correction unit  217  do not hit the end of the movable range. The angular displacement data to which the restriction is applied by the limiter  304  is output as the output of the image blur correction amount calculation unit  203 , that is, the image blur correction amount of the captured image. Note that the image blur correction amount (angular displacement data) that is computed by the image blur correction amount calculation unit  203  is the total value of the correction amounts of the first image blur correction unit  211  and the second image blur correction unit  217 . Thus, the limit value that is set in the limiter  304  is the displacement amount obtained by totaling the control range of the first image blur correction unit  211  and the control range of the second image blur correction unit  217 . 
     The framing control unit  305  determines whether an operation intended by the user such as panning or tilting has been performed, and performs control to return the angular displacement data to the center. In other words, the framing control unit  305  removes the shake component caused by framing of the image capturing apparatus  100  intended by the user from the angular velocity (angular displacement data acquired with the A/D convertor  202 ) detected by the angular velocity sensor  201 . Image blur caused by camera shake can thereby be corrected, while performing framing intended by the user. Specifically, a predetermined threshold value further inside the control end of the angular displacement data provided in the limiter  304  is provided, and it is determined that panning has been performed in the case where the angular displacement data that is output by the integrator  303  exceeds the threshold value. In the case where it is determined that panning has been performed, the framing control unit  305  restricts the angular velocity data by setting a high cutoff frequency of the HPF  301  and removing much of the low frequency component. Alternatively, a configuration may be adopted in which the output of the integrator  303  returns to the center, as a result of the framing control unit  305  subtracting an offset from the angular velocity data that is input to the integrator  303 . Alternatively, the framing control unit  305  may perform control such that the output of the integrator  303  returns to the center by setting a high cutoff frequency for the LPF computation that is performed by the integrator  303 . Performing control in this way enables control to be performed such that the first image blur correction unit  211  and the second image blur correction unit  217  remain within the movable range, even in the case where shake that the user intended, such as panning or tilting, occurs. 
     Returning to  FIG. 2 , the correction amount division unit  204  determines a first correction amount that is for controlling the first image blur correction unit  211  and a second correction amount that is for controlling the second image blur correction unit  217 . Specifically, the correction amount division unit  204  divides the image blur correction amount of the entire apparatus calculated by the image blur correction amount calculation unit  203  into the first correction amount and the second correction amount. The correction amount division unit  204  outputs the first correction amount to the subtractor  206 , and outputs the second correction amount to the lens communication control unit  112  and the correction error computation unit  205 . 
       FIGS. 4A and 4B  are block diagrams showing an exemplary configuration of the correction amount division unit  204 . In  FIG. 4A , a multiplier  401  multiplies the image blur correction amount calculated by the image blur correction amount calculation unit  203  by a predetermined magnification K 1  and outputs the first correction amount. Here, K 1  is a magnification satisfying:
 
0≤ K 1≤1  (1)
 
The image blur correction amount obtained through multiplication with the predetermined magnification K 1  by the multiplier  401  is the correction amount for when performing image blur correction with the first image blur correction unit  211 . Also, a subtractor  402  calculates a second correction amount that is used when performing image blur correction with the second image blur correction unit  217 , by subtracting the first correction amount from the image blur correction amount calculated by the image blur correction amount calculation unit  203 . As a result of such an operation, the image blur correction amount calculated by the image blur correction amount calculation unit  203  is divided such that the correction amount of image blur correction of the entire apparatus is obtained when the first correction amount and the second correction amount are added together.
 
       FIG. 4A  shows an example in which the image blur correction amount is divided by a predetermined ratio, but a configuration may be adopted in which the image blur correction amount is divided by frequency band.  FIG. 4B  shows an exemplary configuration of the correction amount division unit  204  in the case of dividing the image blur correction amount by frequency band. A HPF  403  passes only the high frequency band of the image blur correction amount calculated by the image blur correction amount calculation unit  203 , and this high frequency component is calculated as the first correction amount. The subtractor  402  extracts the second correction amount (low frequency component), by subtracting the first correction amount (high frequency component) from the image blur correction amount calculated by the image blur correction amount calculation unit  203 . 
     Returning to  FIG. 2 , the correction error computation unit  205  computes the correction error of the second image blur correction unit  217  caused by the communication delay of the second correction amount in the lens communication control unit  112  and the camera communication control unit  127 . The correction error computation unit  205  will be described in detail later. 
     The subtractor  206  generates a correction amount that reduces the correction error, by subtracting the correction error output by the correction error computation unit  205  from the first correction amount output by the correction amount division unit  204 . 
     The drive amount conversion unit  207  converts the correction amount output by the subtractor  206  into a movement amount for appropriately performing image blur correction with the first image blur correction unit  211 , and outputs the movement amount as a drive target position. The position sensor  212  detects position information of the first image blur correction unit  211 . The subtractor  208  derives deviation data, by subtracting the position information of the first image blur correction unit  211  from the drive target position. The deviation data is input to the control filter  209 , where various signal processing such as gain amplification and phase correction is performed, and the obtained data is supplied to the OIS drive unit  210 . The OIS drive unit  210  drives the first image blur correction unit  211  in accordance with the output of the control filter  209 . The correction optical system thereby moves in a direction perpendicular to the optical axis. The position information of the first image blur correction unit  211  that has moved is again detected with the position sensor  212  and the next deviation data is calculated. That is, a feedback loop is formed, and the first image blur correction unit  211  is controlled such that the difference between the drive target position and the position information decreases. The correction optical system can thereby be driven so as to track the drive target position. 
     The second correction amount calculated by the correction amount division unit  204  is transmitted to the camera body  100   b  via the lens communication control unit  112  and the camera communication control unit  127 . The drive amount conversion unit  213  converts the second correction amount received from the interchangeable lens  100   a  into a movement amount for appropriately performing image blur correction with the second image blur correction unit  217 , and outputs the movement amount as a drive target position. The position sensor  218  detects the position information of the second image blur correction unit  217 . The subtractor  214  derives deviation data, by subtracting the position information of the second image blur correction unit  217  from the drive target position. The deviation data is input to the control filter  215 , where various signal processing such as gain amplification and phase correction is performed, and the obtained data is supplied to the IIS drive unit  216 . The IIS drive unit  216  drives the second image blur correction unit  217  in accordance with the output of the control filter  215 . The image capturing surface thereby moves in a direction perpendicular to the optical axis. 
     In this way, the first image blur correction unit  211  and the second image blur correction unit  217  operate in a coordinated manner so as to share correction of image blur corresponding to shake of the entire apparatus. As a result of such coordinated operation, the range over which image blur correction is possible can be expanded. 
     Here, the effect of communication of the correction amount between the interchangeable lens  100   a  and the camera body  100   b  will be described. The correction amount calculated in the interchangeable lens  100   a  is transmitted to the camera body  100   b  by communication between the interchangeable lens  100   a  and the camera body  100   b . At this time, a phase delay occurs in the control of the camera body  100   b , due to a communication delay, that is, the time period required for communication (and the time period from when communication is received until the next control of the camera body  100   b ). Here, a phase delay θ when the communication delay is given as ΔT can be calculated as follows. 
     
       
         
           
             
               
                 
                   
                     
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     As an example, when a communication delay ΔT is set to 1 ms, 2 ms and 5 ms, the phase delay θ for each frequency will, based on equation (2), have the frequency characteristics shown in  FIG. 6 . Also,  FIG. 7  shows the phase delay that occurs in the correction amount when the correction amount is given as a 10 Hz sine wave and the communication delay ΔT is given as 5 ms. Also,  FIG. 7  represents image blur that remains in the image without being corrected (hereinafter, also called “correction remainder”), when image blur correction is performed in accordance with a correction amount in which the phase delay occurs. In this way, the communication delay is a factor causing a drop in the image blur correction effect. 
     In view of this, in the present embodiment, the abovementioned correction remainder (correction error) that occurs on the slave side (second image blur correction unit  217  of the camera body  100   b ) is calculated on the master side (interchangeable lens  100   a ). The master side then performs control to cancel out the correction remainder of the slave side, by allowing for the correction error of the second image blur correction unit  217  in the correction amount of the first image blur correction unit  211 . 
       FIG. 5  is a block diagram illustrating the correction error computation unit  205  in detail. The image blur correction amount calculated by the image blur correction amount calculation unit  203  is divided into the first correction amount (master side) and the second correction amount (slave side) in the correction amount division unit  204 . The second correction amount is transmitted to the camera body  100   b . The second correction amount is also input to the correction error computation unit  205 . 
     The second correction amount input to the correction error computation unit  205  is stored in a buffer  502 . The buffer  502  is a memory that temporarily stores the second correction amount in order to add a fixed delay to the second correction amount, and has, for example, a FIFO (first in, first out) structure. A communication delay calculation unit  501  calculates the communication delay ΔT and controls the delay of the buffer  502 . As the communication delay ΔT, a delay amount measured in advance for every interchangeable lens can be stored in a computer program. Alternatively, ping communication may be performed in the initial communication when the interchangeable lens  100   a  is mounted to the camera body  100   b , and the communication delay ΔT may be calculated from the response time. A subtractor  503  subtracts the output (delayed correction amount) of the buffer  502  from the second correction amount (original correction amount that is not delayed), and outputs the obtained correction amount. This output of the subtractor  503  is a signal representing the correction remainder of the slave side. The correction remainder thus calculated is supplied to the subtractor  206  as the output of the correction error computation unit  205 . The subtractor  206  calculates the final correction amount of the first image blur correction unit  211 , by subtracting the output of the correction error computation unit  205  from the first correction amount output by the correction amount division unit  204 . 
       FIGS. 8A to 8F  are graph illustrating the effects that result from subtracting the correction error calculated by the correction error computation unit  205  from the first correction amount. The graphs represent the various signals for image blur correction control in time series, with time on the horizontal axis and displacement on the vertical axis. 
       FIG. 8A  is a graph showing the image blur correction amount of the entire apparatus that is calculated by the image blur correction amount calculation unit  203 .  FIG. 8B  shows the first correction amount generated by the correction amount division unit  204 . Here, in order to simplify the description, a method of dividing the image blur correction amount by a predetermined ratio such as shown in  FIG. 4A  is employed as the division method of the correction amount division unit  204 . K 1  is 0.5, and the amplitude of the first correction amount is calculated to be half of the amplitude of an amplitude A of the image blur correction amount calculation unit  203 .  FIG. 8C  shows the second correction amount. The second correction amount is a correction amount obtained by subtracting the first correction amount from the output of the image blur correction amount calculation unit  203 , and is calculated to be half of the amplitude A. 
       FIG. 8D  shows the situation at the time of image blur correction that is performed by the second image blur correction unit  217 , with a delay occurring due to the effect of communication of the second correction amount shown with a solid line via the lens communication control unit  112  and the camera communication control unit  127 . Thus, the correction target value (drive target value) of the second image blur correction unit  217  will be a signal whose phase is delayed. The correction remainder of the image blur correction that occurs in the case where image blur correction is performed based on a correction amount whose phase is delayed in this way appears as a waveform obtained by subtracting the drive target value of the second image blur correction unit  217  from the second correction amount, and image blur occurs in the image. 
     In view of this, in the present embodiment, the correction remainder (correction error) that occurs due to the communication delay is calculated on the master side (interchangeable lens  100   a  side). The master side then performs control to cancel out the correction error on the slave side, by allowing for the correction error in the drive target value of the first image blur correction unit  211 .  FIG. 8E  shows processing that is performed by the correction error computation unit  205 . The correction error computation unit  205  calculates a correction amount obtained by delaying the second correction amount by the communication delay ΔT (“delayed second correction amount” in  FIG. 8E ). The correction error computation unit  205  then computes the correction error, by subtracting the delayed second correction amount from the original second correction amount. As can be seen from  FIGS. 8D and 8E , this correction error that is calculated by the correction error computation unit  205  is the correction remainder in  FIG. 8E .  FIG. 8F  shows the drive target value of the first image blur correction unit  211  that is obtained by subtracting the correction error calculated by the correction error computation unit  205  from the first correction amount. 
     By performing image blur correction according to the drive target value of the first image blur correction unit  211  and the second image blur correction unit  217  calculated in this way, it becomes possible to cancel out the effect of the phase delay due to the communication delay. 
     As described above, according to the first embodiment, the interchangeable lens  100   a  divides the correction amount calculated based on the shake of the image capturing apparatus  100  into the first correction amount and the second correction amount, and transmits the second correction amount to the camera body  100   b . Also, the interchangeable lens  100   a  acquires the correction error of the second image blur correction unit  217  of the camera body  100   b , based on the communication delay of the second correction amount. The interchangeable lens  100   a  then controls the first image blur correction unit  211  based on the first correction amount and the correction error. It thereby becomes possible to reduce the correction error caused by the communication delay of the second correction amount that occurs between the interchangeable lens  100   a  and the camera body  100   b.    
     Note that, in the present embodiment, a system configuration was described in which the interchangeable lens  100   a  operates as the master and the camera body  100   b  operates as the slave. However, a system configuration can also be employed in which the camera body  100   b  operates as the master and the interchangeable lens  100   a  operate as the slave. That is, a system configuration can also be employed in which the first correction amount and the second correction amount of image blur correction are calculated using the output of the camera shake detection unit  124  of the camera body  100   b , and the second correction amount is transmitted to the interchangeable lens  100   a.    
     Second Embodiment 
     Next, a second embodiment will be described. In the present embodiment, the basic configuration of the image capturing apparatus  100  is similar to the first embodiment (refer to  FIG. 1 ). Hereinafter, the description will mainly focus on the differences from the first embodiment. 
     In the first embodiment, a configuration was described in which the first image blur correction unit  211  and the second image blur correction unit  217  perform image blur correction in a coordinated manner, by calculating the image blur correction amount of the entire image capturing apparatus using the angular velocity sensor  201  on the interchangeable lens  100   a  side and dividing the calculated correction amount. On the other hand, in the second embodiment, a configuration will be described in which the correction amount for driving the individual image blur correction units is calculated, using angular velocity sensors provided in both the interchangeable lens  100   a  and the camera body  100   b . In the case of this configuration, overcorrection occurs when the shake information detected by the individual angular velocity sensors is used directly to perform image blur correction, and correct image blur correction cannot be performed. In view of this, the interchangeable lens  100   a  transmits the image blur correction amount to the camera body  100   b , and the camera body  100   b  subtracts the image blur correction amount of the interchangeable lens  100   a  from the image blur correction amount calculated in the camera body  100   b . The camera body  100   b  controls the second image blur correction unit  217  based on the correction amount obtained by this subtraction. 
       FIG. 9  is a block diagram illustrating image blur correction control according to the second embodiment. In comparison to  FIG. 2 , the correction amount division unit  204  is omitted, and an angular velocity sensor  901 , an A/D convertor  902 , an image blur correction amount calculation unit  903  and a subtractor  904  are added. Also, a correction error computation unit  905  is provided instead of the correction error computation unit  205 . 
     In  FIG. 9 , the angular velocity sensor  901  and the A/D convertor  902  are included in the camera shake detection unit  124  of the camera body  100   b . The image blur correction amount calculation unit  903  and the subtractor  904  are implemented by the camera system control unit  126 . The correction error computation unit  905  is implemented by the lens system control unit  111 . 
     The angular velocity sensor  901  detects the angular velocity of shake that is applied to the camera body  100   b , and outputs a voltage that depends on the detected angular velocity. The output voltage of the angular velocity sensor is converted into digital data by the A/D convertor  902  and acquired as angular velocity data, and the angular velocity data is supplied to the image blur correction amount calculation unit  903 . 
     The image blur correction amount calculation unit  903  performs similar processing to the image blur correction amount calculation unit  203  described in the first embodiment. The correction amount that is calculated here is, however, the second correction amount for performing image blur correction with the second image blur correction unit  217 , and differs from the processing of the image blur correction amount calculation unit  203  in this respect. Accordingly, in relation to the image blur correction amount calculation unit  903 , a limiter value that is set in the limiter  304  of  FIG. 3  is based on the movable range of the second image blur correction unit  217 . Note that the image blur correction amount calculation unit  203  on the interchangeable lens  100   a  side calculates the first correction amount for performing image blur correction with the first image blur correction unit  211 , using the angular velocity sensor  201  on the interchangeable lens  100   a  side. 
     The subtractor  904  subtracts the first correction amount received via the lens communication control unit  112  and the camera communication control unit  127  from the second correction amount calculated by the image blur correction amount calculation unit  903 . The output of the subtractor  904  is converted by the drive amount conversion unit  213  into a drive target value for performing image blur correction with the second image blur correction unit  217 . Subtracting the first correction amount of the interchangeable lens  100   a  from the second correction amount of the camera body  100   b  in this way enables appropriate image blur correction to be performed without overcorrecting. Also, the second image blur correction unit  217  acts to correct image blur that was not corrected on the interchangeable lens  100   a  side in cases such as where the movable range of the first image blur correction unit  211  is exceeded. The range over which correction is possible can thereby be expanded. 
     However, a communication delay arises, since the first correction amount of the interchangeable lens  100   a  that is subtracted by the subtractor  904  is transmitted via the lens communication control unit  112  and the camera communication control unit  127 . Accordingly, phase delay occurs in the first correction amount of the interchangeable lens  100   a  due to the communication delay. As a result, the output of the subtractor  904  will include a correction error caused by the phase delay of the first correction amount of the interchangeable lens  100   a.    
     In view of this, in the present embodiment, the interchangeable lens  100   a  calculates the correction error caused by the phase delay of the first correction amount that is transmitted to the camera body  100   b , using the correction error computation unit  905 , and controls the first image blur correction unit  211  to cancel out the correction error. 
       FIG. 10  is a block diagram illustrating the correction error computation unit  905  in detail. The image blur correction amount (first correction amount) calculated by the image blur correction amount calculation unit  203  is transmitted to the camera body  100   b  via the lens communication control unit  112  and the camera communication control unit  127 , and is supplied to the correction error computation unit  905 . 
     The configuration and operations of the correction error computation unit  905  are substantially the same as the configuration and operations of the correction error computation unit  205  described in the first embodiment with reference to  FIG. 5 , although a subtractor  1003  is provided instead of the subtractor  503 . The subtractor  1003  subtracts the first correction amount (original correction amount that is not delayed) from the output (delayed correction amount) of the buffer  502 , and outputs the obtained correction amount. The “+” and “−” signs are reversed as compared with the subtractor  503  because the “−” sign in the subtractor  904  is given to the first correction amount transmitted to the camera body  100   b . This output of the subtractor  1003  is a signal representing the correction remainder of the slave side. The correction remainder (correction error) thus calculated is supplied to the subtractor  206  as the output of the correction error computation unit  905 . The subtractor  206  calculates the final correction amount of the first image blur correction unit  211 , by subtracting the output of the correction error computation unit  905  from the first correction amount calculated by the image blur correction amount calculation unit  203 . 
     By performing image blur correction according to the drive target value of the first image blur correction unit  211  and the second image blur correction unit  217  calculated in this way, it becomes possible to cancel out the effect of the phase delay due to the communication delay. 
     As described above, according to the second embodiment, the interchangeable lens  100   a  transmits the first correction amount calculated based on the shake of the image capturing apparatus  100  to the camera body  100   b . Also, the interchangeable lens  100   a  acquires the correction error of the second image blur correction unit  217  of the camera body  100   b , based on the communication delay of the first correction amount. The interchangeable lens  100   a  then controls the first image blur correction unit  211  based on the first correction amount and the correction error. It thereby becomes possible to reduce the correction error caused by the communication delay of the first correction amount that occurs between the interchangeable lens  100   a  and the camera body  100   b.    
     Note that, in the present embodiment, a system configuration was described in which the first correction amount of the interchangeable lens  100   a  is transmitted to the camera body  100   b , and the first correction amount is subtracted from the second correction amount calculated by the camera body  100   b . That is, in the present embodiment, a system configuration was described in which the camera body  100   b  corrects image blur that cannot be corrected by the interchangeable lens  100   a . However, a system configuration can also be employed in which the second correction amount of the camera body  100   b  is transmitted to the interchangeable lens  100   a , and the second correction amount is subtracted from the first correction amount calculated by the interchangeable lens  100   a . In this case, the processing of the correction error computation unit  905  and the subtractor  206  is executed in the camera body  100   b.    
     Third Embodiment 
     Next, a third embodiment will be described. In the present embodiment, the basic configuration of the image capturing apparatus  100  is similar to the first embodiment (refer to  FIG. 1 ). Hereinafter, the description will mainly focus on the differences from the first embodiment. 
     In the first embodiment, a configuration was described in which the first image blur correction unit  211  and the second image blur correction unit  217  are coordinated to perform image blur correction, by calculating the image blur correction amount of the entire image capturing apparatus using the angular velocity sensor  201  on the interchangeable lens  100   a  side and dividing the calculated correction amount. 
     A configuration was employed in which the correction amount for the second image blur correction unit  217  is transmitted from the interchangeable lens  100   a  to the camera body  100   b  via the lens communication control unit  112  and the camera communication control unit  127  at that time. 
     In the third embodiment, a receiving buffer  1001  is provided after the camera communication control unit  127  which is on the receiving side. 
       FIG. 11  is a block diagram illustrating image blur correction control according to the third embodiment. In comparison to  FIG. 2 , the receiving buffer  1001  is provided between the camera communication control unit  127  and the drive amount conversion unit  213 . 
     The role of the receiving buffer  1001  will be described. As described in the first embodiment, the first embodiment is sufficient in the case where a fixed communication delay occurs. On the other hand, communication between the lens communication control unit  112  and the camera communication control unit  127  is not performed solely for the purpose of image blur correction. As an example, such communication is also utilized for focusing and the like. Communication is hierarchized, and the communication delay may not be fixed due to interrupts from communication having a higher priority. In the third embodiment, the receiving buffer  1001  is provided for the purpose of handling cases where the communication delay (Δt) is not fixed for such reasons. 
     Phase delay due to communication delay was shown in equation (2) and  FIG. 7 , with the phase delay changing when the delay amount differs. In view of this, the signals received are held by the receiving buffer  1001  until the communication delay reaches a predetermined delay amount, before being sent to the drive amount conversion unit  213 . From the standpoint of the drive amount conversion unit  213 , the delay amount will be the sum total of the communication delay due to communication between the interchangeable lens and the camera body and the holding time period of the receiving buffer  1001 . That is, signals are held by the receiving buffer  1001 , so as to eliminate jitter due to the communication delay. In the first embodiment, the phase amount to be compensated changes such as shown in equation (2) and  FIG. 7  in the case where communication jitter occurs, although this problem can be solved by removing jitter with the receiving buffer  1001 . 
     In the case where communication jitter exists in  FIG. 11 , the output of the camera communication control unit  127  will contain jitter, and signals are held by the receiving buffer  1001 , such that the signals no longer have jitter after passing through the receiving buffer  1001 . 
     The setting method and preferable length of the holding time period in the receiving buffer  1001  will be described. A shorter holding time period of signals by the receiving buffer  1001  is preferable from the viewpoint of factors such as holding capacity and the stroke of the image blur correction unit. Stroke here refers to the fact when the buffer holding time period is too long, blur that occurs during a fixed time period will be corrected with only the first image blur correction unit  211 , which is disadvantageous in terms of the stroke. Because the role of the receiving buffer  1001  is to eliminate communication jitter as mentioned above, the predetermined delay amount can be determined by adding a value corresponding to the amount of jitter that is expected to occur to the communication delay amount in the case where jitter does not occur (communication delay amount in the first embodiment). This amount of jitter can be determined by estimating the communication amount of communication having a higher priority. Furthermore, the communication amount also differs depending on factors such as the operation mode of the image capturing apparatus (camera). As an example, in cases such as where the focus mode is a mode for continuous focusing, communication resulting from operations and instructions for distance measurement is frequently performed. Furthermore, in order to perform focusing at multiple points, a one-off increase in the communication amount may occur. As mentioned above, depending on the operation mode, there may be an increase in the amount of communication, and an increase in the amount of jitter. In view of this, the appropriate holding time period in the receiving buffer  1001  is preferably determined depending on the mode of the image capturing apparatus. Furthermore, because the operation mode is generally set prior to operation of the image blur correction apparatus, determination of the predetermined delay amount can be performed in advance. The holding time period of signals by the receiving buffer  1001  will be the difference between the communication delay that actually occurs and the predetermined delay amount (i.e. the time period from when the receiving buffer  1001  receives the signals until when the predetermined delay occurs). In other words, the holding time period of signals by the receiving buffer  1001  will be a value set based on expected jitter in the case where jitter does not occur. On the other hand, in the case where jitter occurs, the holding time period changes, according to the amount of jitter that has occurred. 
       FIG. 12  is a block diagram illustrating the correction error computation unit  205  in the third embodiment. The configuration is substantially the same as  FIG. 5 , although a receiving buffer delay calculation unit  1002  and an adder  1203  are provided in addition to the communication delay calculation unit  501 . Since the communication delay calculation unit  501  outputs a communication delay decided based on the interchangeable lens, a value corresponding to the amount of jitter that is expected to occur is output by the receiving buffer delay calculation unit  1002 . The amount of jitter that is expected to occur is acquired from the camera body  100   b  through communication. The communication delay that is decided based on the interchangeable lens  100   a  (communication delay when there is no jitter) and a value corresponding to the amount of jitter that is expected to occur are added together by the adder  1203 , and the predetermined delay amount is output to the buffer  502 . The correction error of the second correction unit caused by the delay of the receiving buffer can thereby be acquired, in addition to the communication delay. 
     A specific example of deriving the delay amount caused by the delay of the receiving buffer with the receiving buffer delay calculation unit  1002  will be shown. In a typical camera system, the camera body  100   b  is often the master in communication. Various settings by the user are also generally configured with the camera body  100   b . The following description envisions such a case. Settings by the user are configured via an operation unit of the camera body  100   b  having the second image blur correction unit  217 . The focus mode or the like is given as an example. The camera system control unit  126  in the camera body  100   b  determines the jitter amount that is expected to occur depending on the set mode. The smallest delay amount possible that exceeds this jitter amount is set in the receiving buffer  1001  as the value corresponding to the jitter amount that is expected to occur, and the set delay amount is notified to the lens system control unit  111  via the camera communication control unit  127  and the lens communication control unit  112 . The lens system control unit  111  need only provide the receiving buffer delay calculation unit  1002  with a value that is the same delay as the delay amount in the receiving buffer  1001 , in accordance with the notified value. 
     Description regarding the smallest delay amount possible that exceeds the jitter amount in the above description will be additionally given. In the configuration herein, as mentioned in the description of the first embodiment, acquisition of angular velocity data is performed at a sufficiently higher speed (1000 Hz, etc.) than camera shake. On the other hand, as mentioned in the Description of the Related Art herein, in order to reduce the effect of the communication delay, it is necessary to speed up the communication cycle between the interchangeable lens and the camera body, although the system load is considerable. That is, herein, communication between the lens communication control unit  112  and the camera communication control unit  127  is performed at a fixed cycle slower than acquisition of the angular velocity data. For example, 60 Hz (=16.67 ms) or the like. Here, in the case where the jitter amount is expected to be around 40 ms, communication can be performed at a three-frame (=50 ms) delay. 
     As a result of the configuration in  FIG. 12 , the final correction amount of the first image blur correction unit  211  can be calculated, such that performance deterioration of the image blur correction unit due to jitter does not occur. 
     Note that, in  FIG. 12 , a configuration is adopted in which the communication delay calculation unit  501  and the receiving buffer delay calculation unit  1002  are both provided, but a configuration may be adopted in which one of the communication delay calculation unit  501  and the receiving buffer delay calculation unit  1002  is provided. In other words, a configuration can also be adopted in which a predetermined delay amount obtained by adding a value corresponding to the jitter amount that is expected to occur to the communication delay amount that is decided based on the interchangeable lens  100   a  is acquired from the camera body  100   b  and output to the buffer  502 . 
     A way of providing the receiving buffer  1001  that is compatible with the second embodiment is shown in  FIG. 13 . In this case, the receiving buffer  1001  can be provided between the camera communication control unit  127  and the subtractor  904 . With regard to the correction error computation unit  205 , using the configuration shown in  FIG. 11  enables the final correction amount of the first image blur correction unit  211  to be calculated, such that performance deterioration of the image blur correction unit due to jitter does not occur. 
     Other Embodiments 
     The aforementioned embodiments describe configurations for performing shake detection using an angular velocity sensor, but shake detection may be performed using other configurations. For example, a configuration can be employed in which the shake amount is calculated from acceleration using an acceleration sensor or the shake amount of the apparatus is calculated by detecting motion information from image data. 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g. one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g. application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g. central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2018-004465, filed Jan. 15, 2018 and Japanese Patent Application No. 2018-238649, filed Dec. 20, 2018, which are hereby incorporated by reference herein in their entirety.