Abstract:
An image capturing apparatus includes a main body and a rotatable image capturing unit. The main body includes a spherical portion having at least three support points. The rotatable image capturing unit includes an image capturing optical system, and is configured to rotationally move while being supported by the support points. In the rotatable image capturing unit, a gravitational point is located so as to overlap a center of gravity of a polygonal plane formed by connecting the support points and present on a side closer to an image sensor the polygonal plane in a direction perpendicular to the polygonal plane.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2013-136289, filed Jun. 28, 2013, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image capturing apparatus. 
     2. Description of the Related Art 
     A method of acquiring an image including objects in all directions has conventionally been proposed. An image including objects in all directions can be acquired by, for example, repeating shooting while rotating an image capturing apparatus held by a user through 360°. More specifically, the user can create an image including objects in all directions by combining photos acquired by this method. In this method, a time lag occurs between the photo at the start of shooting and the photo at the end of shooting. 
     Jpn. Pat. Appln. KOKAI Publication No. 2003-244511 proposes an image capturing apparatus including a plurality of image capturing apparatuses arranged so as to make a plurality of optical axes face in radial directions, a release button configured to simultaneously release the plurality of image capturing apparatuses, and a composition processing unit configured to combine a plurality of images acquired by the plurality of image capturing apparatuses. This image capturing apparatus also includes a level, and an LCD monitor capable of displaying the image of an arbitrary one of the plurality of fixed focus digital cameras. Using the level and the LCD monitor, the user can make the image capturing apparatus level while viewing the LCD monitor. The image capturing apparatus having the above-described functional arrangement can simultaneously shoot objects in all directions while keeping the image capturing apparatus level, and automatically create a panoramic image. 
     There also exists a method of shooting all directions in the angle of view by using a wide-field lens such as a fisheye lens facing the zenith. To keep the optical axis of the wide-field lens almost facing the zenith, the user needs to frequently adjust the tilt of the image capturing apparatus including the wide-field lens. 
     BRIEF SUMMARY OF THE INVENTION 
     An image capturing apparatus according to a first aspect of the invention comprises: a main body including a spherical portion having at least three support points; and a rotatable image capturing unit including an image capturing optical system for shooting an object and acquiring image data, the rotatable image capturing unit being configured to rotationally move while being supported by the support points, in which a gravitational point is located so as to overlap a center of gravity of a polygonal plane formed by connecting the support points and present on a side closer to an image sensor than the polygonal plane in a direction perpendicular to the polygonal plane. 
     An image capturing apparatus according to a first aspect of the invention comprises: a main body including a spherical portion having at least three support points; a rotatable image capturing unit incorporating an image capturing optical system for shooting an object and acquiring image data, in which an optical axis of the image capturing optical system is located so as to overlap a center of gravity of a polygonal plane formed by connecting the support points; and an autonomous moving unit configured to rotationally move the rotatable image capturing unit kept supported by the support points and to make the optical axis of the image capturing optical system face a zenith. 
     Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a block diagram showing the arrangement of an image capturing apparatus according to an embodiment of the present invention; 
         FIG. 2  is a plan view showing an example of the arrangement of a rotatable image capturing unit  1   d;    
         FIG. 3  is a front view for explaining details of the image capturing apparatus; 
         FIG. 4A  is a view showing a state in which a user shoots an object by the right hand; 
         FIG. 4B  is a view showing a state in which a user performs self portrait photography by the left hand; 
         FIG. 4C  is a view showing a state in which a user shoots the zenith direction using an image capturing apparatus including a fisheye lens; 
         FIG. 5A  is a view showing an example of omnidirectional shooting; 
         FIG. 5B  is a view showing a circular image obtained by omnidirectional shooting; 
         FIG. 5C  is a view showing a panoramic image obtained by processing the circular image; 
         FIG. 6A  is a flowchart for explaining the operation of the image capturing apparatus; 
         FIG. 6B  is a flowchart for explaining the operation of the image capturing apparatus; 
         FIG. 7A  is a view showing an example in which a general image capturing apparatus is manipulated by the right hand; 
         FIG. 7B  is a view showing an example in which a general image capturing apparatus is manipulated by the left hand; 
         FIG. 8  is a flowchart for explaining details of left-hand grip determination; 
         FIG. 9A  is a view showing the first example of performing a touch manipulation by the left hand while gripping the image capturing apparatus by the left hand; 
         FIG. 9B  is a view showing the second example of performing a touch manipulation by the left hand while gripping the image capturing apparatus by the left hand; 
         FIG. 10A  is a view for explaining an example of the operation of the unlocked rotatable image capturing unit; 
         FIG. 10B  is a view for explaining another example of the operation of the unlocked rotatable image capturing unit; 
         FIG. 11A  is a view showing an example of objects easy to shoot; 
         FIG. 11B  is a view showing a shooting result obtained by shooting the objects easy to shoot; 
         FIG. 11C  is a view showing a state in which an object difficult to shoot is irradiated with guide light; 
         FIG. 11D  is a view showing a shooting result obtained by shooting the object difficult to shoot while irradiating it with guide light; 
         FIG. 12  is a flowchart for explaining an operation of determining a left-hand manipulation; 
         FIG. 13A  is a view showing an example of a manipulation of simultaneously touching two portions of a touch panel by the left hand; 
         FIG. 13B  is a view showing an example of a manipulation of touching one portion of the touch panel by the left hand, and the like; 
         FIG. 13C  is a view showing an example of performing a slide manipulation on the touch panel by the left hand; 
         FIG. 14A  is a view showing an example in which a user in a canoe performs self-portrait photography; 
         FIG. 14B  is a view showing an example in which the gravitational direction at the time of shooting matches the gravitational direction of image data; 
         FIG. 14C  is a view showing an example in which the gravitational direction at the time of shooting does not match the gravitational direction of image data; 
         FIG. 15A  is a view showing an example in which image data whose gravitational direction does not match the gravitational direction of the image capturing apparatus is tilted in the gravitational direction of the image data; 
         FIG. 15B  is a view showing a composition procedure of tilting image data; 
         FIG. 16A  is a view showing image data tilted for composition; 
         FIG. 16B  is a view showing horizontal image data for composition; 
         FIG. 16C  is a view showing an example in which the tilted image data and the horizontal image data are composed; 
         FIG. 17A  is a view showing portions where portions unnecessary for composition are deleted; 
         FIG. 17B  is a view showing image data after deletion in composition is performed; 
         FIG. 18A  is a view showing deletion of unnecessary portions near ends in composition; 
         FIG. 18B  is a view showing composite image data; 
         FIG. 19  is a flowchart for explaining details of image data composition; 
         FIG. 20  is a view showing an example of the arrangement of an image capturing apparatus according to the first modification of an embodiment of the present invention; 
         FIG. 21  is a view showing an example of the arrangement of an image capturing apparatus according to the second modification of an embodiment of the present invention; 
         FIG. 22A  is a view for explaining the operation of a voice coil motor; 
         FIG. 22B  is a view for explaining voice coil motors attached to a rotatable image capturing unit; and 
         FIG. 23  is a flowchart for explaining an example of the operation of the image capturing apparatus according to the second modification. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
     The first embodiment of the present invention will now be described with reference to  FIGS. 1, 2, 3, 4A, 4B, 4C, 5A, 5B, 5C, 6A, 6B, 7A, 7B, 8, 9A, 9B, 10A, 10B, 11A, 11B, 11C ,  11 D,  12 ,  13 A,  13 B,  13 C,  14 A,  14 B,  14 C,  15 A,  15 B,  16 A,  16 B,  16 C,  17 A,  17 B,  18 A,  18 B, and  19 . An example of the arrangement of an image capturing apparatus  12  according to the first embodiment of the present invention will be described with reference to  FIG. 1 . The image capturing apparatus  12  includes a rotatable image capturing unit  1   d  configured to make the optical axis of a lens face the zenith, and a main body  10  that holds the rotatable image capturing unit  1   d.    
     The rotatable image capturing unit  1   d  has a spherical shape, and includes an image capturing optical system  1   a , an image capturing unit  1   b , and a communication unit  1   c . The image capturing optical system  1   a  includes a plurality of lenses functioning as a fisheye lens, and captures light in a wide field around the optical axis. The image capturing unit  1   b  converts the light captured by the image capturing optical system  1   a  into a digital signal (image data). The communication unit  1   c  transmits the image data to the main body  10  by performing wired or wireless communication with the main body  10 . 
     The main body  10  holds the rotatable image capturing unit  1   d , and includes an auxiliary light-emitting unit  7 , a control unit  2 , a display unit  3   b , a recording unit  4 , a touch panel  3   a , a manipulation determination unit  6 , an electronic flash  5 , a posture determination unit  9 , and an external communication unit  11 . 
     The auxiliary light-emitting unit  7  emits guide light. The guide light is, for example, a laser beam. The guide light is used to cause the user to confirm that a predetermined object exists in the angle of view. 
     The control unit  2  includes a face detection unit  2   a , an image processing unit  2   b , a display control unit  2   c , an image composition unit  2   e , and an auxiliary light control unit  2   f . The face detection unit  2   a  detects a face from image data. The image processing unit  2   b  performs white balance correction, gamma correction, and the like. The display control unit  2   c  causes the display unit  3   b  to display an image based on image data processed by the image processing unit  2   b . The image composition unit  2   e  calculates corresponding pixel values of two pieces of image data and outputs one piece of composite image data. The image composition unit  2   e  performs correction of the tilt of image data and trimming of image data. The auxiliary light control unit  2   f  controls light emission of the auxiliary light-emitting unit  7 . The auxiliary light control unit  2   f  controls guide light irradiation. The auxiliary light-emitting unit  7  projects guide light to, for example, an object at an end of the angle of view. The user can know the range of the angle of view by the guide light projected to the end of the angle of view. 
     The display unit  3   b  is, for example, a liquid crystal display or an organic EL, and displays an image under the control of the display control unit  2   c . The recording unit  4  is, for example, a ROM, and records image data. The touch panel  3   a  detects a touched position, and inputs an electrical signal according to the touched position to the control unit  2 . The manipulation determination unit  6  is, for example, a button configured to detect pressing and output a predetermined signal, for example, a release button. The release button is arranged at a position of the main body  10  easy for the user to manipulate by the right hand. The electronic flash  5  emits light when, for example, the luminance of an object is low. The posture determination unit  9  includes, for example, 3-axes acceleration sensors, and determines a change in the posture of the image capturing apparatus  12 . The external communication unit  11  transmits data to an external terminal via wired communication or wireless communication by Wi-Fi or the like. 
     An example of the structure of the rotatable image capturing unit  1   d  and its peripheral portion will be described with reference to the plan view of  FIG. 2 . The rotatable image capturing unit  1   d  is held by a semispherical fixed frame  403  provided in the main body  10 . An axis A passes through the center of the semispherical fixed frame  403 . 
     The fixed frame  403  includes a rotation regulation portion  404  and balls  111 . The rotation regulation portion  404  projects from the fixed frame  403 , and is formed into an annular shape about the axis A. Support points  405  support the rotatable image capturing unit  1   d.    
     A rotation regulation pin  402  is formed on the outer surface of the rotatable image capturing unit  1   d . The rotation regulation pin  402  rotationally moves inside the rotatable image capturing unit  1   d  as the rotatable image capturing unit  1   d  rotationally moves. The rotatable image capturing unit  1   d  is limited by the rotation regulation pin  402  and the rotation regulation portion  404  so as to rotationally move inside the rotation regulation portion  404  on the fixed frame  403 . That is, the range of the rotational movement is limited so the main body  10  does not hide a fisheye lens  120 . 
     The balls  111  are provided at the three support points  405  on the fixed frame  403 . The balls  111  intervene between the fixed frame  403  and the rotatable image capturing unit  1   d . The rotatable image capturing unit  1   d  is smoothly rotationally moved by the balls  111 . 
     A component such as the ball  111  configured to smoothly rotate the rotatable image capturing unit  1   d  will be referred to as a rotation promoting portion. The rotation promoting portion is not limited to a rolling element such as a ball, and may be configured to slidably move surfaces against each other. A lubricant such as grease may be used for the rotation promoting portion to facilitate the operation. 
     With the above-described arrangement, the fixed frame  403  can rotatably support the rotatable image capturing unit  1   d  via the balls  111 . 
       FIG. 3  is a sectional view of the image capturing apparatus  12  taken along a line B-B in  FIG. 2 . A detailed example of the arrangement of the image capturing apparatus  12  will be described with reference to  FIG. 3 . The rotatable image capturing unit  1   d  specifically includes the image capturing optical system  1   a , an image sensor  101   b , an A/D conversion circuit  101   c , a support portion  101   d , a weight  101   f , and a connector  104   a.    
     The image capturing optical system  1   a  includes the fisheye lens  120 , and a low-pass filter  101   e . The fisheye lens  120  captures light in a wide field, and forms an image on the light-receiving surface (not shown) of the image sensor  101   b . The low-pass filter  101   e  removes high-frequency noise from the light that has entered from the fisheye lens  120 . 
     The image sensor  101   b  converts an object image based on the light that has entered from the fisheye lens  120  into an electrical signal. The A/D conversion circuit  101   c  converts the electrical signal into a digital signal (image data). The support portion  101   d  fixes the fisheye lens  120  in the rotatable image capturing unit  1   d . A board  108  is a printed board configured to incorporate electronic components such as an image processing IC  102   a . The connector  104   a  connects the board  108  and a flexible printed board  104   b  to each other. Note that the image circle of the image capturing optical system  1   a  is set to be smaller than the image capturing range of the image sensor  101   b.    
     The weight  101   f  is arranged such that the optical axis of the fisheye lens  120  faces the zenith. The image capturing optical system  1   a  rotationally moves such that the weight  101   f  makes its optical axis face the zenith independently of the tilt of the main body  10 . Note that the weight  101   f  is preferably made of a high-density material such as tungsten. 
     The main body  10  specifically includes the flexible printed board  104   b , a connector  104   e , a flexible printed board case  104   c , a board  119 , the image processing IC  102   a , a display control IC  102   b , the display unit  3   b , a lock mechanism  106 , the memory card  4 , a battery  109 , a power supply circuit  110 , a grip portion  125 , and a main capacitor  107 . 
     The flexible printed board  104   b  is a flexible board on which wiring configured to transfer image data from the A/D conversion circuit  101   c  to the image processing IC  102   a  and the display control IC  102   b  is printed. The flexible printed board  104   b  is so short as not to impede the rotational movement of the rotatable image capturing unit  1   d.    
     The flexible printed board case  104   c  is a case configured to prevent the flexible printed board  104   b  from coming into contact with other components. The flexible printed board case  104   c  has sufficient capacity to store the flexible printed board  104   b.    
     The connector  104   e  connects the flexible printed board  104   b  and the board  119 . The board  119  is a printed board configured to incorporate electronic components such as the image processing IC  102   a.    
     The image processing IC  102   a  corresponds to the image processing unit  2   b , and performs image processing such as white balance correction and gamma correction for image data. The display control IC  102   b  corresponds to the display control unit  2   c , and displays an image on the display unit  3   b.    
     The lock mechanism  106  locks a lock pin provided on it and a concave portion formed in the rotatable image capturing unit  1   d . The lock mechanism  106  displaces the lock pin between a state in which the concave portion is locked and a state in which the concave portion is unlocked. When the concave portion is locked by the lock pin, the rotatable image capturing unit  1   d  is locked by the main body  10 . The concave portion and the distal end of the lock pin have, for example, a non-rotational symmetric shape (for example, triangular pyramidal shape) with respect to the axis of the lock pin. When the concave portion and the distal end of the lock pin have a non-rotational symmetric shape, rotation of the lock pin is regulated, and the rotatable image capturing unit  1   d  is locked by the main body  10  more firmly. The mechanism for locking the rotatable image capturing unit  1   d  and the main body  10  is not limited to the lock mechanism  106 , and may be a magnet, a cord, or a spring. The mechanism for locking the rotatable image capturing unit  1   d  and the main body  10  will be referred to as a rotation limiting mechanism. Note that upon determining that the image capturing apparatus  12  is facing the zenith for a predetermined time or more, the image capturing apparatus  12  can cancel lock of the lock mechanism, rotationally move the rotatable image capturing unit  1   d , and make it face the zenith. 
     The memory card  4  stores image data. The battery  109  applies a voltage to the power supply circuit  110 . The power supply circuit  110  operates the image capturing apparatus  12  by controlling the voltage obtained from the battery  109 . The grip portion  125  is an auxiliary member formed outside the main body  10 , which is provided to cause the user to stably hold the image capturing apparatus. The main capacitor  107  performs charging to cause the electronic flash  5  to emit light. 
     Shooting examples according to the purpose or situation of shooting will be described here with reference to  FIGS. 4A, 4B, and 4C . In the shooting example shown in  FIG. 4A , the user performs a release manipulation by the right hand while viewing the display unit  3   b . In the shooting example shown in  FIG. 4B , the user performs self-portrait photography by the left hand. In the self-portrait photography, the user does not confirm the angle of view. In the shooting example shown in  FIG. 4C , the user performs omnidirectional shooting by making the optical axis of the image capturing apparatus including the fisheye lens  120  face the zenith. 
     An example in which the user performs omnidirectional shooting using the image capturing apparatus including the fisheye lens  120  will be described with reference to  FIGS. 5A, 5B, and 5C . In the shooting example shown in  FIG. 5A , the user on the left side is shooting three objects including the user herself. When making the optical axis of the fisheye lens  120  face the zenith, the user can shoot the image including the three objects shown in  FIG. 5A . The image acquired by this shooting is a circular image including the three objects, as shown in  FIG. 5B . The circular image may be generated as a panoramic image by processing using a PC or the like, as shown in  FIG. 5C . In the shooting example shown in  FIG. 5A , it is difficult for the user to shoot while confirming the angle of view of the image capturing apparatus. Hence, the three objects may be excluded from the image. However, it is difficult for the user to make the optical axis of the image capturing apparatus including the fisheye lens face the zenith. For example, it is difficult for the user to keep the image capturing apparatus level. 
     An example of the operation of the image capturing apparatus  12  will be described here with reference to the flowchart of  FIGS. 6A and 6B . The control unit  2  determines whether a shooting mode is selected (step S 100 ). Upon determining that a shooting mode is not selected (NO in step S 100 ), the control unit  2  selects a reproduction mode. Upon determining that a shooting mode is selected (YES in step S 100 ), the control unit  2  determines whether the optical axis of the rotatable image capturing unit  1   d  faces the zenith (step S 101 ). Upon determining that the optical axis of the rotatable image capturing unit  1   d  faces the zenith (YES in step S 101 ), the control unit  2  causes the process to advance to step S 109 . Upon determining that the optical axis of the rotatable image capturing unit  1   d  does not face the zenith (NO in step S 101 ), the control unit  2  causes the lock mechanism  106  to lock the rotatable image capturing unit  1   d  (step S 102 ). After step S 102 , the control unit  2  determines whether the user grips the image capturing apparatus  12  by the left hand (step S 103 ). 
     The image capturing apparatus  12  according to this embodiment has an arrangement example that allows shooting by the left hand or right hand. Situations where the user grips the image capturing apparatus  12  by one hand will be described with reference to  FIGS. 7A and 7B . In  FIGS. 7A and 7B , the user shoots while rock-climbing. Referring to  FIG. 7A , the user is holding on to the cliff by the left hand and is going to press the release button (not shown) of the image capturing apparatus  12  by the right hand. The manipulation determination unit  6  is configured to be capable of operating by the right hand. The user can easily shoot by the right hand. Referring to  FIG. 7B , the user is holding on to the cliff by the right hand and is going to press the release button of the image capturing apparatus  12  by the left hand. In general, however, the release button of the image capturing apparatus is arranged at a position hard to manipulate by the left hand. That is, it is difficult for the user to press the release button by the left hand. 
     The image capturing apparatus  12  can determine that it is gripped by the left hand. An example of this determination will be described with reference to the flowchart of  FIG. 8 . Examples of detection of grip by the left hand will be described with reference to  FIGS. 9A and 9B . 
     The control unit  2  determines whether the image capturing apparatus  12  remains level (step S 201 ). Upon determining that the image capturing apparatus  12  remains level (YES in step S 201 ), the control unit  2  starts detecting the touch position on the touch panel  3   a  (step S 202 ). Upon determining that the image capturing apparatus  12  does not remain level, that is, tilts (NO in step S 201 ), the control unit  2  clears a left-hand grip flag to 0 (step S 206 ). The left-hand grip flag is a flag representing that the user is gripping the image capturing apparatus  12  by the left hand. When the left-hand grip flag is 0, the image capturing apparatus  12  is not gripped by the left hand. On the other hand, when the left-hand grip flag is 1, the user is gripping the image capturing apparatus  12  by the left hand. Hence, after step S 206 , the control unit  2  determines in the left-hand grip determination (step S 103 ) that the user does not grasp the image capturing apparatus  12  by the left hand. 
     After step S 202 , the control unit  2  determines whether a triangular touch portion of the touch panel  3   a  shown in  FIG. 9A  is touched. The triangular touch portion is a portion where the user&#39;s left palm contacts when the user grasps the image capturing apparatus  12  by the left hand (step S 203 ). Upon determining that the triangular touch portion is touched (YES in step S 203 ), the control unit  2  sets the flag representing that the image capturing apparatus  12  is gripped by the left hand to 1 (step S 204 ). At this time, the control unit  2  determines that the user grasps the image capturing apparatus  12  by the left hand. Upon determining that the triangular touch portion is not touched (NO in step S 203 ), the control unit  2  determines whether simultaneous touches in two touch portions on the touch panel  3   a  shown in  FIG. 9B  are detected when the user grasps the image capturing apparatus  12  by the left hand in another form (step S 205 ). Upon determining that simultaneous touches in two touch portions on the touch panel  3   a  are detected (YES in step S 205 ), the control unit  2  sets the left-hand grip flag to 1 (step S 204 ). Upon determining that simultaneous touches in two touch portions on the touch panel  3   a  are not detected (NO in step S 205 ), the control unit  2  clears the left-hand grip flag to 0 (step S 206 ). 
     Referring to  FIGS. 6A and 6B , upon determining that the image capturing apparatus  12  is not gripped by the left hand (NO in step S 103 ), that is, upon determining that the image capturing apparatus  12  is gripped by the right hand, the control unit  2  determines whether the duration of the optical axis horizontal state is shorter than a predetermined time (step S 104 ). Upon determining that the duration of the horizontal state is not shorter than the predetermined time (NO in step S 104 ), the control unit  2  causes the display unit  3   b  to display a live view, and detects the face of an object (step S 105 ). The control unit  2  determines whether the release button or the touch panel  3   a  is manipulated, that is, whether a release manipulation is performed (step S 106 ). Upon determining that the release button or the touch panel  3   a  is not manipulated, the process advances to step S 108 . Upon determining that the release button or the touch panel  3   a  is manipulated (YES in step S 106 ), the control unit  2  adjusts the focus and exposure for the touch position on the touch panel  3   a  or a face portion detected as the result of face detection, performs shooting, and records image data obtained by the shooting in the recording unit  4  (step S 107 ). After the image data is recorded in the recording unit  4 , the control unit  2  determines whether to power off the image capturing apparatus  12 . Upon determining to power off (YES in step S 108 ), the processing ends. Upon determining not to power off (NO in step S 108 ), the process returns to step S 100 . 
     Upon determining that the optical axis faces the zenith (YES in step S 101 ), the control unit  2  determines whether a predetermined time has elapsed in a state in which the optical axis faces the zenith (step S 109 ). Upon determining that the predetermined time has elapsed in a state in which the optical axis faces the zenith (YES in step S 109 ), the control unit  2  causes the lock mechanism  106  to unlock the rotatable image capturing unit  1   d  (step S 110 ). When unlocked by the lock mechanism  106 , the optical axis of the rotatable image capturing unit  1   d  faces the zenith independently of the tilt of the main body  10 . 
     The operation of the rotatable image capturing unit  1   d  after being unlocked by the lock mechanism  106  will be described here with reference to  FIGS. 10A and 10B . The lock mechanism  106  locks the rotatable image capturing unit  1   d  when the image capturing apparatus  12  is not facing the zenith. At this time, the optical axis of the image capturing optical system  1   a  provided in the rotatable image capturing unit  1   d  faces the direction of the main body  10 . On the other hand, when the predetermined time has elapsed in a state in which the image capturing apparatus  12  faces the zenith (YES in step S 109 ), the lock mechanism  106  unlocks the rotatable image capturing unit  1   d  (step S 110 ). The position of a center g of gravity of the rotatable image capturing unit  1   d  is set to make the optical axis face the zenith. For this reason, the optical axis of the image capturing optical system  1   a  provided in the rotatable image capturing unit  1   d  faces the zenith independently of the tilt of the main body  10 , as shown in  FIGS. 10A and 10B . 
     Upon determining that the time during which the optical axis faces the zenith is shorter than the predetermined time (NO in step S 109 ), the control unit  2  locks the rotatable image capturing unit  1   d  using the lock mechanism  106  (step S 111 ). If the rotatable image capturing unit  1   d  is already locked, the control unit  2  causes the lock mechanism  106  to maintain the lock of the rotatable image capturing unit  1   d.    
     After step S 111 , the control unit  2  clears the left-hand grip flag to 0 (step S 112 ). That is, when omnidirectional shooting is to be performed, the left-hand grip flag is cleared to 0. 
     Upon determining that the image capturing apparatus  12  is gripped by the left hand (YES in step S 103 ), after clearing the left-hand grip flag to 0 (step S 112 ), or upon determining that the horizontal state duration is shorter than the predetermined time (YES in step S 104 ), the control unit  2  causes the display unit  3   b  to display a live view, and detects the face of an object (step S 114 ). After that, the control unit  2  determines whether a face is detected from the image data (step S 115 ). Upon determining that a face is detected from the image data (YES in step S 115 ), the control unit  2  causes the auxiliary light-emitting unit  7  to irradiate a predetermined region in the angle of view with guide light (step S 118 ). 
     The effect of guide light will be described here with reference to  FIGS. 11A, 11B, 11C, and 11D . By seeing the guide light that irradiates an object, the user can know various kinds of information concerning shooting. An object is irradiated with the guide light to notify the user that, for example, the object exists in the angle of view. 
     In  FIG. 11A , the user shoots standing objects. In  FIG. 11B , the objects are included in the image. In the shooting situation shown in  FIG. 11A , the user can easily acquire the image including the objects in the angle of view, as shown in  FIG. 11B , by shooting the objects. 
     On the other hand, in  FIG. 11C , the user shoots a moving object.  FIG. 11D  shows an image in which the object is irradiated with guide light P. In the shooting situation shown in  FIG. 11C , it is difficult for the user to shoot at the instant the moving object is included in the angle of view. 
     After detecting the face of an object, the image capturing apparatus  12  irradiates the body of the object with the guide light. The guide light irradiates the object when it is included in the angle of view. Hence, without seeing a live view, the user can shoot at the instant the object is included in the angle of view. 
     Upon determining that the face detection unit  2   a  does not detect the face of an object (NO in step S 115 ), the control unit  2  determines whether the distance between the object and the image capturing apparatus  12  is shorter than a predetermined distance (step S 116 ). Upon determining that the distance between the object and the image capturing apparatus  12  is shorter than the predetermined distance (YES in step S 116 ), the control unit  2  causes the auxiliary light-emitting unit  7  to emit light and irradiate the object with blinking guide light, thereby notifying the user that the object does not fit in the angle of view. 
     Note that the guide light irradiation position may be changed in accordance with the application purpose of the guide light. For example, the guide light irradiation positions may be positions corresponding to two ends of the angle of view. Without seeing the display unit  3   b , the user can confirm the angle of view or the position of the user in the angle of view by confirming the guide light irradiating the two ends of the angle of view. 
     After irradiating the object with the guide light (step S 118 ) or after irradiating the object with blinking guide light (step S 117 ), the control unit  2  determines whether the gravitational direction of the image capturing apparatus  12  matches the gravitational direction of the image data obtained for the live view (step S 119 ). 
     Upon determining that the gravitational direction of the image capturing apparatus  12  matches the gravitational direction of the image data obtained for the live view (YES in step S 119 ), the control unit  2  temporarily stores the image data (step S 120 ). The temporarily stored image data is used for image composition. The temporarily stored image data will be referred to as horizontal image data. 
     After step S 120 , the control unit  2  determines whether the optical axis of the image capturing optical system  1   a  faces the zenith (step S 121 ). Upon determining that the image data of the image capturing optical system  1   a  faces the zenith (YES in step S 121 ), the control unit  2  determines whether the user is to execute omnidirectional shooting (step S 125 ). Upon determining not to execute omnidirectional shooting (NO in step S 125 ), the control unit  2  determines whether to power off the image capturing apparatus (step S 108 ). 
     After step S 121 , upon determining that the optical axis of the image capturing optical system  1   a  does not face the zenith (NO in step S 121 ), the control unit  2  determines whether the left-hand grip flag is set to 1 (step S 122 ). Upon determining that the left-hand grip flag is set to 1, that is, upon determining that the image capturing apparatus  12  is gripped by the left hand (YES in step S 122 ), the control unit  2  determines whether a release manipulation by the user&#39;s left hand is performed (step S 124 ). 
     The determination of the release manipulation by the left hand (step S 124 ) will be described here with reference to the flowchart of  FIG. 12  and  FIGS. 13A, 13B, and 13C . Referring to  FIG. 12 , the control unit  2  determines whether it is determined in the left-hand grip determination (step S 103 ) that simultaneous touches in two portions on the touch panel  3   a  are detected (step S 211 ). Upon determining that simultaneous touches in two portions on the touch panel  3   a  are detected (YES in step S 211 ), the control unit  2  provides touch portions shown in  FIG. 13A , which can perform a release manipulation by detecting simultaneous touches in two portions (step S 212 ). Upon determining that simultaneous touches in two portions on the touch panel  3   a  are not detected (NO in step S 211 ), the control unit  2  provides touch portions shown in  FIG. 13B , which allow the user to perform a release manipulation and the like by touching one touch portion with a finger or sliding a finger on the touch panel  3   a  (step S 213 ). After providing the touch portions on the touch panel  3   a , the control unit  2  determines whether the touch panel  3   a  is manipulated (step S 214 ). Upon determining that a manipulation of pressing the touch panel  3   a  with a finger or sliding a finger, as shown in  FIG. 13C , is performed (YES in step S 214 ), the control unit  2  determines whether the manipulation is a release manipulation (step S 217 ). Upon determining that the manipulation is a release manipulation (YES in step S 217 ), the control unit  2  determines that the release manipulation by the user&#39;s left hand is performed. Upon determining that the manipulation is not a release manipulation (NO in step S 217 ), the control unit  2  performs control according to the contents of the manipulation such as zooming or exposure correction (step S 216 ). The control unit  2  determines that the release manipulation by the user&#39;s left hand is not performed. Upon determining that a touch manipulation such as pressing or sliding is not performed (NO in step S 214 ), the control unit  2  determines that the release manipulation by the user&#39;s left hand is not performed. At this time, the process advances to step S 108 . 
     Upon determining that the left-hand grip flag is not 1 (NO in step S 122 ), that is, when the user grasps the image capturing apparatus  12  by the right hand, the control unit  2  determines whether a release manipulation is performed (step S 123 ). 
     Upon determining that a release manipulation is performed (YES in step S 124  or YES in step S 123 ), the control unit  2  turns out guide light and performs shooting (step S 126 ). Upon turning out guide light and performing shooting (step S 126 ), the control unit  2  determines whether it is necessary and possible to composite image data obtained by temporary storage and image data obtained by shooting (step S 127 ). Note that a situation where composition is necessary is a situation where the gravitational direction at the time of shooting does not match the gravitational direction of image data. A situation where composition is possible is a situation where, for example, image data usable for composition is included in the temporarily stored image data group. Upon determining that it is necessary and possible to composite temporarily stored image data (step S 120 ) and image data obtained by shooting (YES in step S 127 ), the control unit  2  composites the two pieces of image data (step S 128 ). The control unit  2  records the composite image data obtained by composition in the recording unit  4  (step S 129 ). 
     A situation where image data composition is necessary and an operation of compositing image data will be described here in detail with reference to  FIGS. 14A, 14B, 14C, 15A, 15B, 16A, 16B, 16C, 17A, 17B, 18A, 18B, and 19 .  FIG. 14A  illustrates a situation where the user in a canoe shoots herself as an example of a situation where image data composition is necessary. As shown in  FIG. 14A , the user in the canoe holds the paddle by the right hand, and therefore performs the release manipulation and the like of the image capturing apparatus by the left hand. In an ideal shooting result in the situation of  FIG. 14A , the gravitational direction at the time of shooting matches the gravitational direction of the image data, as shown in  FIG. 14B . However, since the situation is unstable, as described above, a shooting result in which the gravitational direction at the time of shooting does not match the gravitational direction of the image data, as shown in  FIG. 14C , is often obtained. 
     The image capturing apparatus  12  according to an embodiment of the present invention composites image data using the image composition unit  2   e  so as to change the image data obtained at the time of shooting in which the gravitational direction at the time of shooting does not match the gravitational direction of the image data to image data in which the gravitational direction at the time of shooting matches the gravitational direction of the image data. 
     An operation of compositing image data will be described with reference to  FIGS. 15A, 15B, 16A, 16B, 16C, 17A, 17B, 18A, and 18B  and the flowchart of  FIG. 19 . Upon determining that it is necessary and possible to composite image data (YES in step S 127 ), the control unit  2  matches the gravitational direction (G in  FIG. 14C ) of image data obtained at the time of shooting with the gravitational direction (for example, downward direction) at the time of shooting, for example, tilts the image data shown in  FIG. 15A , in which the gravitational direction of the image data is different from the gravitational direction at the time of shooting, in a manner as shown in  FIG. 15B  (step S 301 ). Next, the control unit  2  composite tilted shot image data I1 shown in  FIG. 16A  and temporarily recorded horizontal image data I2 shown in  FIG. 16B  such that the degree of matching between the shot image data I1 and the horizontal image data I2 is maximized, thereby obtaining composite image data I3 shown in  FIG. 16C  (step S 302 ). Composition of the image data is performed such that, for example, the positions of person region S match, as shown in  FIG. 16C . After compositing the image data, the control unit  2  deletes a horizontal image data portion existing in the overlap portion between the horizontal image data and the shot image data, as shown in  FIG. 17A  (step S 303 ). For example, as shown in  FIG. 17B , when the horizontal image data of the person portion S is deleted, only the shot image data remains for the person portion S. As shown in  FIG. 18A , the control unit  2  extracts the composite image data into a rectangular shape (step S 304 ). For example, in  FIG. 18B , the portion indicated by the broken line is deleted, and final composite image data is obtained. After that, the processing of  FIG. 19  ends. 
     Upon determining that composition is unnecessary or impossible (NO in step S 127 ), the control unit  2  records the shot image data I1 (step S 130 ). After step S 130 , the process advances to step S 108 . 
     As described above, according to this embodiment, the image capturing apparatus  12  can make the optical axis of the image capturing optical system  1   a  provided in the rotatable image capturing unit  1   d  face the zenith independently of the tilt of the main body  10 . When omnidirectional shooting is not performed, the image capturing apparatus  12  locks the rotatable image capturing unit  1   d  by the lock mechanism  106 . This lock prevents the rotatable image capturing unit  1   d  from rotationally moving in accordance with the direction of gravity at the time of shooting, except in omnidirectional shooting. 
     In a situation where it is difficult for the user to confirm an object in the angle of view, the image capturing apparatus  12  projects guide light from the auxiliary light-emitting unit  7  to the object. This guide light projection is done to notify the user that, the object fits in the angle of view. In a situation where the user shoots while grasping the image capturing apparatus  12  by the left hand, a touch portion used for a manipulation by the left hand is provided on the touch panel  3   a . The user can manipulate the image capturing apparatus  12  by only the left hand by touching the touch portion. In addition, when the gravitational direction of image data does not match the gravitational direction at the time of shooting, the image capturing apparatus  12  can match the gravitational direction of image data with the gravitational direction at the time of shooting by composition processing. 
     First Modification 
     The first modification of the first embodiment will be described below with reference to  FIG. 20 .  FIG. 20  shows a modification of the image capturing apparatus according to the first embodiment. An arrangement example according to the first modification includes an arrangement example different from the communication method between the rotatable image capturing unit  1   d  and the main body  10  according to the first embodiment and the charging method according to the first embodiment. Note that the same reference numerals as in the arrangement example described in the first embodiment denote the same parts, and a description thereof will be omitted. An operation example according to the first modification is the same as that of the first embodiment, and a description of the first modification will be omitted. 
     The main body  10  of the image capturing apparatus  12  according to the first modification includes the power supply circuit  110 , a noncontact charge control unit  112 , and a coil  113 . The noncontact charge control unit  112  controls wireless power supply between the coil  113  on the main body side and a coil  118  on the rotatable image capturing unit side. For example, Qi® is used as the wireless power supply method. The power supply circuit  110  supplies a current to the coil  113 . The coil  113  supplies power to the coil  118  on the side of the rotatable image capturing unit  1   d.    
     The rotatable image capturing unit  1   d  includes an image processing IC  115 , a wireless communication IC  114 , a shield  117 , and the coil  118 . The image processing IC  115  further performs compression of image data. The amount of image data compressed by the image processing IC  115  is smaller than that before compression. The wireless communication IC  114  transmits the compressed image data to the side of the main body  10 . Since compressed image data is transmitted, image data communication speeds up. The wireless communication IC  114  wirelessly transfers the image data compressed by the image processing IC  115  to a wireless communication IC  116  on the main body side. The amount of image data compressed by the image processing IC  115  is smaller than that before compression. For this reason, the wireless communication IC  114  can transmit the image data to the side of the main body  10  in a shorter time. The shield  117  suppresses electromagnetic noise generated in the wireless communication IC  114  and the like from mixing into an analog signal from the image sensor  101   b . The coil  118  supplies power to the image processing IC  115  and the like. 
     As described above, the image capturing apparatus  12  according to the modification of an embodiment of the present invention can compress image data acquired by the rotatable image capturing unit  1   d  and transmit the compressed image data to the main body  10  by wireless communication. The image capturing apparatus  12  can wirelessly supply power from the main body  10  to the rotatable image capturing unit  1   d.    
     Second Modification 
     The second modification of the image capturing apparatus according to an embodiment of the present invention will be described with reference to  FIG. 21 . The image capturing apparatus  12  according to the second modification can rotationally move the rotatable image capturing unit  1   d  by a method different from the first embodiment. Note that the same reference numerals as in the arrangement example described in the first embodiment denote the same parts, and a description thereof will be omitted. 
     The rotatable image capturing unit  1   d  includes a magnet  123  for voice coil motor, and a spring  122 . When a current is supplied to a coil  124  for voice coil motor, the magnetic field generated by the magnet  123  for voice coil motor changes, and the voice coil motor generates a force in accordance with the change. The magnet  123  for voice coil motor and the coil  124  for voice coil motor will be referred to as a pair of voice coil motors hereinafter. The spring  122  has a function of limiting the moving range of the rotatable image capturing unit  1   d  to a range capable of omnidirectional shooting. The component having the function of limiting the moving range of the rotatable image capturing unit  1   d  to the range capable of omnidirectional shooting will be referred to as a rotation limiting mechanism. 
     The main body  10  includes a magnetic sensor  126 , and a position control driver  121 . The magnetic sensor  126  detects a change in the magnetic intensity concerning the voice coil motors. The position control driver  121  receives the detection result of the change in the magnetic intensity of the voice coil motors from the magnetic sensor  126 , calculates the orientation of the rotatable image capturing unit  1   d , and drives the voice coil motors in accordance with the orientation. 
     The voice coil motors will be described here in more detail with reference to  FIGS. 22A and 22B .  FIG. 22A  is a view for explaining the operation of a single voice coil motor. The voice coil motor energizes the coil  124  for voice coil motor within the magnetic field of the magnet  123  for voice coil motor to generate a force. The force generated by the voice coil motor shown in  FIG. 22A  is unidirectional. Hence, to freely rotationally move the rotatable image capturing unit  1   d , a plurality of voice coil motors are used, as shown in  FIG. 22B . 
     In the second modification, the rotatable image capturing unit  1   d  can be made to freely rotate by the voice coil motors and the position control driver  121 . The mechanism for making the rotatable image capturing unit  1   d  freely rotate need not always be a voice coil motor, and may be, for example, a spring or an elastic member. The mechanism for making the rotatable image capturing unit  1   d  freely rotate will be referred to as an autonomous moving unit. 
     The operation of the image capturing apparatus shown in  FIG. 21  will be described here with reference to the flowchart of  FIG. 23 . A description of the same steps as in the flowchart of  FIG. 6  will be omitted. Step S 102  of the first embodiment is replaced with steps S 131  and S 133  of the second modification, as shown in  FIG. 23 . Step S 110  of the first embodiment is replaced with step S 132  of the second modification, as shown in  FIG. 23 . Referring to  FIG. 23 , upon determining that a predetermined time has elapsed in a state in which the optical axis faces the zenith (YES in step S 109 ), the control unit  2  causes the lock mechanism  106  to unlock the rotatable image capturing unit  1   d , and instructs the position control driver  121  to drive the voice coil motors. The position control driver  121  calculates the orientation of the rotatable image capturing unit  1   d  from the magnetic intensity detected by the magnetic sensor  126 , and drives the voice coil motors based on the orientation such that the optical axis of the image capturing optical system  1   a  faces the zenith (step S 132 ). Upon determining that the predetermined time has not elapsed in a state in which the optical axis faces the zenith (NO in step S 109 ), the control unit  2  locks the rotatable image capturing unit  1   d  using the lock mechanism  106  (step S 111 ). 
     Upon determining that the optical axis does not face the zenith (NO in step S 101 ), the control unit  2  determines whether the rotatable image capturing unit  1   d  is locked by the lock mechanism  106  (step S 131 ). Upon determining that the rotatable image capturing unit  1   d  is not locked by the lock mechanism  106  (NO in step S 131 ), the control unit  2  causes the position control driver  121  to adjust the position of the rotatable image capturing unit  1   d , and then causes the lock mechanism  106  to lock the rotatable image capturing unit  1   d . After that, the control unit  2  determines whether the user grips the image capturing apparatus  12  by the left hand (step S 103 ). Upon determining that the rotatable image capturing unit  1   d  is locked by the lock mechanism  106  (YES in step S 131 ), the control unit  2  advances the process to determine whether the user grips the image capturing apparatus  12  by the left hand (step S 103 ). 
     As described above, the image capturing apparatus  12  according to the second modification of an embodiment of the present invention includes a pair of voice coil motors in the main body  10  and the rotatable image capturing unit  1   d . The image capturing apparatus  12  can adjust the orientation of the rotatable image capturing unit  1   d  without using the weight  101   f  by driving the pair of voice coil motors. 
     The rotatable image capturing unit  1   d  of the image capturing apparatus  12  has been described as a portable device such as an image capturing apparatus that is used while being gripped by a user&#39;s hand. However, the rotatable image capturing unit  1   d  may be incorporated as part of a helmet or glasses. The rotatable image capturing unit  1   d  may be incorporated in a wearable device. The rotatable image capturing unit  1   d  may be attached to a fixed device such as a bicycle, a motorcycle, a vehicle, a boat, a balloon, or a kite. A device with the rotatable image capturing unit  1   d  attached to a balloon or a kite is usable to shoot the earth&#39;s surface by making the optical axis of the image capturing optical system  1   a  of the rotatable image capturing unit  1   d  face the gravitational direction. The orientation of the optical axis of the image capturing optical system  1   a  is controlled by the attachment position of the weight  101   f  or the voice coil motors. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.