Patent Publication Number: US-9407804-B2

Title: Method, apparatus, and non-transitory medium for generating a synthetic image from a series of captured images

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. JP 2009-264616 filed in the Japanese Patent Office on Nov. 20, 2009, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image processing apparatus, and more particularly, to an image processing apparatus and an image processing method for processing a plurality of images which continues in a time-series manner, and a program for allowing the method to be executed on a computer. 
     2. Description of the Related Art 
     In recent years, image capturing apparatuses are widely used such as a digital still camera, a digital video camera (for example, integrated camera recorder) or the like which generates image data by imaging objects such as people and records the generated image data as contents such as image files, moving image files or the like. Further, recording of images of sport, for example, golf, baseball or the like, as contents is widely used such an image capturing apparatus. The contents (for example, moving image contents) recorded in this way can be used, for example, for checking actions in sport (for example, a golf swing or batting (baseball)). 
     For example, in the case of confirming a sport action (for example, a golf swing or batting (baseball)), there has been proposed a synthetic image generation method which generates an image representing motion transitions as a synthetic image so that the motion transitions can be easily grasped. For example, there is proposed an image capturing apparatus which selects a plurality of images from images which are continuously shot at predetermined intervals and generates a synthetic image using the selected plurality of images (refer to Japanese Unexamined Patent Application Publication No. 2009-44573 (FIG. 9), for example). 
     SUMMARY OF THE INVENTION 
     According to the above-described related art, it is possible to generate a synthetic image representing motion transitions of a person performing a golf swing, for example. 
     In this respect, for example, since the motion of a golf swing or batting (baseball) is performed in a relatively short time, when generating a synthetic image representing motion transitions, it is important to appropriately select images forming the synthetic target image. However, in the above-described related art, a range for selection of a plurality of images to be used for generating the synthetic image is determined with reference to the time of a start manipulation by a user. Thus, for example, in a case where the user is not accustomed to photographing or is a beginner, it may be difficult to appropriately perform the start manipulation with respect to the golf swing or batting (baseball) which are performed in a relatively short time. 
     Accordingly, for example, when selecting images representing the motion transitions of the golf swing or batting (baseball), it is important to select images included in an appropriate range. 
     Accordingly, it is desirable to provide a technique which can appropriately select images representing the transitions of a specific motion performed by a target object. 
     According to an embodiment of the present invention, there are provided an image processing apparatus including: a specific sound detecting section which detects a specific sound generated during motion in a specific motion performed by a target object included in an image group including a plurality of images which continues in a time-series manner; a valid sound range setting section which sets, as a valid sound range, a range in the time axis for determination of whether the specific sound detected by the specific sound detecting section is valid on the basis of a user manipulation; and a selecting section which selects a predetermined number of motion transition images representing transitions of the specific motion from a selection range of the image group in the time axis, with reference to a detection position of the specific sound in the time axis, in a case where the specific sound is detected in the set valid sound range, an image processing method and a program for allowing the method to be executed on a computer. Accordingly, it is possible to set the valid sound range on the basis of the user manipulation, and to select the predetermined number of motion transition images from the selection range, with reference to the detection position of the specific sound, in the case where the specific sound is detected in the set valid sound range. 
     In this embodiment, the user manipulation may be a specific manipulation received when the specific motion is terminated or a timer setting manipulation for such a setting that a termination time of the specific motion becomes a termination time of a time counter, and the valid sound range setting section may set the valid sound range with reference to a position in the time axis where the specific manipulation is received in a case where the user manipulation is the specific manipulation, and may set the valid sound range with reference to the termination time of the time counter by means of the timer setting manipulation in a case where the user manipulation is the timer setting manipulation. Accordingly, it is possible to set the valid sound range with reference to the position where the specific manipulation is received in the case where the user manipulation is the specific manipulation, and to set the valid sound range with reference to the termination time of the time counter by means of the timer setting manipulation in the case where the user manipulation is the timer setting manipulation. 
     In this embodiment, the valid sound range setting section may narrow the valid sound range set in the case where the user manipulation is the specific manipulation compared with the valid sound range set in the case where the user manipulation is the timer setting manipulation. Accordingly, it is possible to narrow the valid sound range set in the case where the user manipulation is the specific manipulation compared with the valid sound range set in the case where the user manipulation is the timer setting manipulation. 
     In this embodiment, the apparatus may further include a determining section which determines, as the selection range, a predetermined range before and after the detection position, in the time axis, of the specific sound detected in the set valid sound range, and the selecting section may select the motion transition images in the determined selection range. Accordingly, it is possible to determine, as the selection range, the predetermined range before and after the detection position of the specific sound detected in the set valid sound range, and to select the motion transition images in the determined selection range. 
     In this embodiment, the apparatus may further include: an object distance calculating section which calculates a distance to the target object; and a delay time calculating section which calculates a delay time of the detected specific sound on the basis of the calculated distance, and the selecting section may correct the detection position of the detected specific sound in the time axis on the basis of the calculated delay time and selects the motion transition images from the selection range, with reference to the corrected detection position, in a case where the corrected detection position exists in the set valid sound range. Accordingly, it is possible to calculate the distance to the target object, calculate the delay time of the detected specific sound on the basis of the calculated distance, correct the detection position of the detected specific sound on the basis of the calculated delay time, and select the motion transition images from the selection range, with reference to the corrected detection position, in the case where the corrected detection position exists in the set valid sound range. 
     In this embodiment, the selecting section may compress a selection interval in a range narrower than the selection range having, as a central position, the detection position of the specific sound in the time axis compared with other selection intervals, with respect to the selection interval of the motion transition images in the selection range. Accordingly, it is possible to compress the selection interval in the range narrower than the selection range having, as the central position, the detection position of the specific sound, compared with the other selection intervals, with respect to the selection interval of the motion transition images in the selection range. 
     In this embodiment, the apparatus may further include a synthetic image generating section which generates a synthetic image representing the motion transitions of the target object by arranging and synthesizing the plurality of selected motion transition images in a time-series manner. Accordingly, it is possible to arrange and synthesize the plurality of selected motion transition images in a time-series manner, to thereby generate the synthetic image representing the motion transitions of the target object. 
     In this embodiment, the apparatus may further include: a storing section which stores the specific sounds and the valid sound ranges relating to a plurality of types of specific motions; a manipulation receiving section which receives a designating manipulation for designating a desired specific motion from among the plurality of types of specific motions in which the specific sounds and the valid sound ranges are stored. Here, the specific sound detecting section may detect the specific sound relating to the designated specific motion, and the valid sound range setting section may set the valid sound range relating to the designated specific motion on the basis of the user manipulation. Accordingly, when the designating manipulation for designating the desired specific motion from among the plurality of types of specific motions is received, it is possible to detect the specific sound relating to the designated specific motion, and to set the valid sound range relating to the designated specific motion on the basis of the user manipulation. 
     In this embodiment, the valid sound range setting section may set the valid sound range on the basis of a user manipulation relating to an image capturing operation when the image group is generated. 
     According to another embodiment of the present invention, there are provided an image processing apparatus including: a specific sound detecting section which detects a specific sound generated during motion in a specific motion performed by a target object included in an image group including a plurality of images which continue in a time-series manner; a specific change detecting section which detects a specific change in the time axis between the respective images forming the image group; a valid sound range setting section which sets, as a valid sound range, a range in the time axis for determination of whether the specific sound detected by the specific sound detecting section is valid on the basis of a position in the time axis in which the specific change is detected; and a selecting section which selects a predetermined number of motion transition images representing transitions of the specific motion from a selection range of the image group in the time axis, with reference to a detection position of the specific sound in the time axis, in a case where the specific sound is detected in the set valid sound range, an image processing method and a program for allowing the method to be executed on a computer. Accordingly, it is possible to set the valid sound range on the basis of the position in which the specific change is detected, and to select the predetermined number of motion transition images from the selection range, with reference to the detection position of the specific sound, in the case where the specific sound is detected in the set valid sound range. 
     In this embodiment, the specific change detecting section may detect the specific change using at least one of a characteristic amount extracted from each image forming the image group and a characteristic amount extracted on the basis of a sound relating to each image forming the image group. Accordingly, it is possible to detect the specific change using at least one of the characteristic amount extracted from each image forming the image group and the characteristic amount extracted on the basis of the sound relating to each image forming the image group. 
     According to the embodiments of the present invention, it is possible to appropriately select the images representing the transitions of the specific motion performed by the target object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an example of a functional configuration of an image capturing apparatus according to a first embodiment of the present invention. 
         FIG. 2  is a block diagram illustrating an example of a functional configuration of a selecting section and a layer processing section according to a second embodiment of the present invention. 
         FIGS. 3A, 3B and 3C  are diagrams schematically illustrating the positional relation between an image capturing apparatus and a person who is an image capturing target, and the relation between moving images generated from the positional relation, according to a first embodiment of the present invention. 
         FIGS. 4A and 4B  are diagrams illustrating an example of synthesis target images selected by a synthesis target image selecting section and a synthetic image generated by a layer processing section, according to a first embodiment of the present invention. 
         FIGS. 5A, 5B and 5C  are diagrams schematically illustrating a setting method of a valid sound range by a valid sound range setting section and a determination method of a synthesis target image selection range by a synthesis target image selection range determining section, according to a first embodiment of the present invention. 
         FIGS. 6A and 6B  are diagrams illustrating an example of transitions of a display screen displayed on a display section according to a first embodiment of the present invention. 
         FIGS. 7A, 7B and 7C  are diagrams schematically illustrating a setting method of a valid sound range by a valid sound range setting section and a determination method of a synthesis target image selection range by a synthesis target image selection range determining section, according to a first embodiment of the present invention. 
         FIGS. 8A, 8B, 8C and 8D  are diagrams schematically illustrating an example of a flow of a selection process of synthesis target images by a selecting section and a generation process of a synthetic image by a layer processing section, according to a first embodiment of the present invention. 
         FIGS. 9A and 9B  are diagrams schematically illustrating a separation method of synthesis target images by a layer separating section according to a first embodiment of the present invention. 
         FIGS. 10A, 10B and 10C  are diagrams schematically illustrating an image which is a target of a modification process by a layer modifying section and an image which is modified by the layer modifying apparatus, according to a first embodiment of the present invention. 
         FIGS. 11A and 11B  are diagrams schematically illustrating a synthesis method by a layer synthesizing section according to a first embodiment of the present invention. 
         FIGS. 12A and 12B  are diagrams schematically illustrating a synthesis method of synthesis target images by a layer synthesizing section according to a first embodiment of the present invention. 
         FIG. 13  is a diagram illustrating an example of a synthetic image generated by a layer processing section according to a first embodiment of the present invention. 
         FIG. 14  is a flowchart illustrating an example of a process procedure of a synthetic image generation process by an image capturing apparatus according to a first embodiment of the present invention. 
         FIG. 15  is a flowchart illustrating an example of a process procedure of a synthetic image generation process by an image capturing apparatus according to a first embodiment of the present invention. 
         FIGS. 16A and 16B  are diagrams illustrating the distance between an image capturing apparatus and a target object, and the relation between a generation position of an impact sound and an arrival position thereof, according to a second embodiment of the present invention. 
         FIG. 17  is a block diagram illustrating an example of a functional configuration of an image capturing apparatus according to a second embodiment of the present invention. 
         FIGS. 18A and 18B  are diagrams schematically illustrating an image capturing range which is an image capturing target by an image capturing section and a captured image displayed on a display section, according to a second embodiment of the present invention. 
         FIG. 19  is a top view schematically illustrating the positional relation between an image capturing range which is an image capturing target by an image capturing section and a captured image displayed on a display section, according to a second embodiment of the present invention. 
         FIGS. 20A and 20B  are diagrams schematically illustrating a setting method of a valid sound range by a valid sound range setting section and a determination method of a synthesis target image selection range by a synthesis target image selection range determining section, according to a second embodiment of the present invention. 
         FIG. 21  is a diagram illustrating a display example in a display section according to a second embodiment of the present invention. 
         FIG. 22  is a flowchart illustrating an example of a process procedure of a synthetic image generation process by an image capturing apparatus according to a second embodiment of the present invention. 
         FIG. 23  is a block diagram illustrating an example of a functional configuration of an image capturing apparatus according to a third embodiment of the present invention. 
         FIG. 24  is a diagram illustrating an example of stored contents of a target object information storing section according to a third embodiment of the present invention. 
         FIG. 25  is a diagram illustrating a display example (display screen) of a display section according to a third embodiment of the present invention. 
         FIGS. 26A and 26B  are diagrams illustrating an example of a synthetic image generated by a layer processing section according to a third embodiment of the present invention. 
         FIG. 27  is a block diagram illustrating an example of a functional configuration of an image processing apparatus according to a fourth embodiment of the present invention. 
         FIG. 28  is a diagram illustrating an example of stored contents of a target object information storing section according to a fourth embodiment of the present invention. 
         FIGS. 29A and 29B  are diagrams schematically illustrating a setting method of a valid sound range by a valid sound range setting section and a determination method of a synthesis target image selection range by a synthesis target image selection range determining section, according to a fourth embodiment of the present invention. 
         FIGS. 30A and 30B  are diagrams schematically illustrating a setting method of a valid sound range by a valid sound range setting section and a determination method of a synthesis target image selection range by a synthesis target image selection range determining section, according to a fourth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments for carrying out the present invention will be described in the following order. 
     1. First embodiment (synthetic image generation control: an example of setting a valid sound range on the basis of user manipulation) 
     2. Second embodiment (synthetic image generation control: an example of calculating an object distance and correcting an impact sound detecting position) 
     3. Third embodiment (synthetic image generation control: an example of designating a desired object from a plurality of objects and generating a synthetic image relating to the object) 
     4. Fourth embodiment (synthetic image generation control: an example of generating a synthetic image in recorded image contents) 
     1. First Embodiment 
     [Configuration Example of Image Capturing Apparatus] 
       FIG. 1  is a block diagram illustrating an example of a functional configuration of an image capturing apparatus  100  according to a first embodiment of the present invention. The image capturing apparatus  100  includes an image capturing section  111 , an object information generating section  120 , a captured image retaining section  115 , a sound input section  131 , a specific sound detecting section  132 , a manipulation receiving section  140 , and a timer setting section  150 . Further, the image capturing apparatus  100  includes a valid sound range setting section  160 , a selecting section  170 , a layer processing section  180 , a synthetic image retaining section  185 , a display control section  190 , a display section  191 , and a synthetic image storing section  200 . For example, the image capturing apparatus  100  can be realized by a digital video camera which can image an object to generate a captured image (image data), extract each characteristic amount for the image data by image analysis, and perform a variety of image processes using each of the extracted characteristic amounts. Further, the image capturing apparatus  100  is an example of image processing apparatuses disclosed in the claims. 
     The image capturing section  111  includes an image capturing element (for example, an image capturing element  112  shown in  FIG. 19 ) which transforms light of an object incident through a lens (not shown) into an electric signal, and a signal processing section (not shown) which processes an output signal of the image capturing element to generate a captured image (image data). That is, in the image capturing section  111 , an optical image of the object incident through the lens is formed on an imaging surface of the image capturing element, the image capturing element performs an image capturing operation in this state, and the signal processing section performs a signal process for the imaging signal, and thus, the captured image is generated. The captured image is generated on the basis of start instruction information of the image capturing operation output from the manipulation receiving section  140  or the timer setting section  150 . Further, the generated captured image is supplied to and retained in the captured image retaining section  115 . In addition, the generated captured image is supplied to the display control section  190  and then is displayed on the display section  191 . Further, the generated captured image, and the position and focusing position of each lens (for example, a focus lens and a zoom lens) at the time of generation of the captured image are supplied to the object information generating section  120 . 
     The captured image retaining section  115  is a ring buffer for retaining the captured image generated by the image capturing section  111  for a predetermined time, and supplies the retained captured image to the selecting section  170 . Further, the captured image retaining section  115  retains the object information generated by the object information generating section  120  in relation to the captured image generated by the image capturing section  111 . Here, the predetermined time when the captured image is retained in the captured image retaining section  115  can be 3 to 10 seconds, for example. That is, the latest captured image generated by the image capturing section  111  and the object information generated by the object information generating section  120  are retained for 3 to 10 seconds in the captured image retaining section  115 . 
     The object information generating section  120  generates object information relating to the captured image, on the basis of the captured image generated by the image capturing section  111  and each piece of information (for example, the position and focusing position of the lens) at the time of generation of the captured image. Further, the object information generating section  120  supplies the generated object information to the captured image retaining section  115  and allows it to be retained therein. The object information is information for discerning a target object region and a background region thereof from objects included in the captured image generated by the image capturing section  111 , for example. As the object information, for example, a depth map is generated. Here, the depth map is data indicating the distance (object distance) from an image capturing position (for example, a position of the image capturing apparatus  100 ) to the object included in the captured image. As a technique of generating the depth map, for example, a technique such as TOF (time of flight), depth from defocus or the like may be used. For example, the TOF technique is a technique for calculating a distance to an object on the basis of the delay time during which light emitted from a light source is reflected from the object and reaches a sensor and the speed of the light. 
     The sound input section  131  obtains a sound around the image capturing apparatus  100 , and outputs the obtained sound (sound data) to the specific sound detecting section  132 . The sound input section  131  is realized by a plurality of microphones or the like, for example. 
     The specific sound detecting section  132  detects a specific sound on the basis of the sound output from the sound input section  131  and, in a case where the specific sound is detected, outputs this to the selecting section  170 . In the first embodiment of the present invention is exemplified a case where a sound (impact sound) generated at the moment that a golf club comes in contact with a golf ball during a golf swing is a specific sound. For example, the specific sound detecting section  132  stores a characteristic amount relating to a specific sound as specific sound identification information (reference data) in advance. Then, the specific sound detecting section  132  extracts the characteristic amount from the sound output from the sound input section  131  and compares the extracted characteristic amount and the specific sound identification information to calculate the similarity. In a case where the calculated similarity exceeds a threshold, the specific sound detecting section  132  determines that the sound output from the sound input section  131  is the specific sound. Specifically, the sound data output from the sound input section  131  is sampled by an AD (Analog to Digital) conversion process, and is converted into digital data. Further, a process such as a frequency analysis is performed for the digital data at an appropriate time interval, so that the digital data is converted into a parameter indicating a spectrum or other acoustic characteristics of the sound. Thus, the time-series characteristic amount for the sound is extracted. Further, a matching process with the extracted time-series characteristic amount is performed using the retained reference data, and then the sound recognition result is output as the result of the matching process. The sound analysis and recognition may be performed using various other existing methods. 
     The manipulation receiving section  140  receives manipulation contents manipulated by a user, and outputs a manipulation signal based on the received manipulation contents to the image capturing section  111 , the timer setting section  150 , the valid sound range setting section  160  and the display control section  190 . For example, when receiving a synthetic image recording mode setting manipulation which instructs setting of a synthetic image recording mode for generating the synthetic image, the manipulation receiving section  140  outputs a control signal for instructing a start of the image capturing operation to the image capturing section  111 . Then, the manipulation receiving section  140  outputs a control signal for instructing a display start of the captured image to the display control section  190 . The setting manipulation of the synthetic image recording mode is performed by a pressing manipulation of a setting button of the synthetic image recording mode, for example. Further, for example, when receiving a synthetic image recording mode release manipulation for instructing a release of the synthetic image recording mode, the manipulation receiving section  140  outputs a control signal for stopping the image capturing operation to the image capturing section  111 . The synthetic image recording mode release manipulation is performed by a release button of the synthetic image recording mode, for example. Further, for example, when receiving a recording instruction manipulation of the synthetic image in a case where the synthetic image recording mode is set, the manipulation receiving section  140  outputs a control signal indicating that the recording instruction manipulation of the synthetic image is received to the valid sound range setting section  160 . Then, the manipulation receiving section  140  outputs the control signal for stopping the image capturing operation to the image capturing section  111 . The recording instruction manipulation of the synthetic image is performed by a video recording button (REC button), for example. Further, for example, when receiving a timer setting manipulation for performing the image capturing operation in the synthetic image recording mode by a timer setting, the manipulation receiving section  140  outputs a control signal for instructing the timer setting to the timer setting section  150 . The timer setting manipulation is performed by a timer setting button, for example. Further, when the timer setting button is pressed, the setting manipulation of a counter value (for example, a setting of 8 to 17 seconds) may be performed. These manipulations may be input using a manipulation member such as buttons which are provided on the image capturing apparatus  100 , and may be performed by wireless communication through a remote controller manipulation or the like. 
     The timer setting section  150  sets a timer (for example, a self timer function) for performing the image capturing operation in the synthetic image recording mode. Specifically, if the timer setting manipulation is received by the manipulation receiving section  140 , the timer setting section  150  outputs the control signal for instructing the start of the image capturing operation to the image capturing section  111 . Further, the timer setting section  150  outputs the control signal for instructing the display start of the captured image and the count value due to the timer setting to the display control section  190 . In addition, after the display start of the count value, the timer setting section  150  sequentially outputs the count values according to the set contents to the display control section  190 . Thus, as shown in  FIGS. 6A and 6B , the captured image generated by the image capturing section  111  is displayed on the display section  191 , and the count value is overlapped and displayed on the captured image. For example, a count value which is counted up one by one for every second is displayed on the display section  191 . Further, in a case where the count value of the set timer is “zero”, the timer setting section  150  outputs a control signal indicating the fact to the valid sound range setting section  160 . Further, the timer setting section  150  outputs the control signal for stopping the image capturing operation to the image capturing section  111 . 
     In a case where the synthetic image recording mode is set, the valid sound range setting section  160  sets a valid sound range for determining whether a specific sound detected by the specific sound detecting section  132  is valid or not. Further, the valid sound range setting section  160  outputs information about the set valid sound range (the valid sound range and the position in the time axis which serves as a reference at the time of setting the range) to the selecting section  170 . Specifically, in a case where the recording instruction manipulation of the synthetic image is received by the manipulation receiving section  140 , or in a case where the count value of the timer set by the timer setting section  150  becomes “zero”, the valid sound range setting section  160  sets the valid sound range. Here, in a case where the recording instruction manipulation of the synthetic image is received by the manipulation receiving section  140 , the position in the time axis in which the recording instruction manipulation of the synthetic image is received becomes the reference position. Further, the count value of the timer set by the timer setting section  150  becomes “zero”, the position in the time axis in which the count value becomes “zero” becomes the reference position. These setting methods of the valid sound range will be described in detail with reference to  FIGS. 5A to 7C  and so on. 
     The selecting section  170  selects synthesis target images used in the generation process of the synthetic image by means of the layer processing section  180 , from the captured images retained in the captured image retaining section  115 . Further, the selecting section  170  outputs information about the selected synthesis target images (for example, the synthesis target images, object information about these images, and coordinates used in the generation process of the synthetic image) to the layer processing section  180 . An internal configuration of the selecting section  170  will be described in detail with reference to  FIG. 2 . Further, the synthesis target images are an example of motion transition images disclosed in the claims. 
     The layer processing section  180  generates the synthetic image using the synthesis target images selected by the selecting section  170  and then stores the generated synthetic image in the synthetic image storing section  200 . An internal configuration of the layer processing section  180  will be described in detail with reference to  FIG. 2 . Further, the layer processing section  180  is an example of a synthetic image generating section disclosed in the claims. 
     The synthetic image retaining section  185  retains the synthetic image (history image) during the synthesis process at the time of the generation process of the synthetic image by means of the layer processing section  180 , and supplies the retained synthetic image to the layer processing section  180 . The synthetic image retaining section  185  will be described in detail with reference to  FIG. 2 . 
     The display control section  190  displays the synthetic image stored in the synthetic image storing section  200  or the captured image output from the image capturing section  111  on the display section  191 , according to the manipulation input received by the manipulation receiving section  140 . Further, the display control section  190  overlaps the count value of the timer set by the timer setting section  150  with the captured image to be displayed on the display section  191 . 
     The display section  191  displays each image under the control of the display control section  190 . 
     The synthetic image storing section  200  stores the synthetic image generated by the layer processing section  180  and supplies the stored synthetic image to the display control section  190 . 
       FIG. 2  is a block diagram illustrating an example of a functional configuration of the selecting section  170  and the layer processing section  180  according to a second embodiment of the present invention. The selecting section  170  includes the synthesis target image selection range determining section  171 , the synthesis target image selecting section  172 , a coordinate calculating section  173 , and a counter section  174 . Further, the layer processing section  180  includes the layer separating section  181 , the layer modifying section  182  and a layer synthesizing section  183 . 
     The synthesis target image selection range determining section  171  determines a range (synthesis target image selection range) for selecting the synthesis target images used in the generation process of the synthetic image by means of the layer processing section  180 , among the captured images retained in the captured image retaining section  115 . Specifically, the synthesis target image selection range determining section  171  determines the synthesis target image selection range, on the basis of, the detection position (position in the time axis) of the specific sound detected by the specific sound detecting section  132  and the valid sound range set by the valid sound range setting section  160 . For example, the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the detection position of the specific sound, in a case where the detection position of the specific sound is included in the valid sound range. On the other hand, the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the position in the time axis which becomes the reference at the time of setting the valid sound range, in a case where the detection position of the specific sound is not included in the valid sound range. Here, in a case where the recording instruction manipulation of the synthetic image is received by the manipulation receiving section  140 , the position in the time axis in which the recording instruction manipulation of the synthetic image is received becomes the reference position. Further, in a case where the count value of the timer set by the timer setting section  150  becomes “zero”, the position in the time axis in which the count value becomes “zero” becomes the reference position. Further, the synthesis target image selection range determining section  171  outputs the information about the determined synthesis target image selection range (for example, the synthesis target image selection range and object information about images included in this range) to the synthesis target image selecting section  172 . The synthesis target image selection range determining section  171  is an example of a determining section disclosed in the claims. 
     The synthesis target image selecting section  172  selects the synthesis target images used in the generation process of the synthetic image by means of the layer processing section  180  from the respective images included in the synthesis target image selection range determined by the synthesis target image selection range determining section  171 . For example, the synthesis target image selecting section  172  selects images at a predetermined time interval as the synthesis target images from the respective images (captured images retained in the captured image retaining section  115 ) included in the synthesis target image selection range determined by the synthesis target image selection range determining section  171 . Further, for example, the synthesis target images may be selected to have an interval suitable for visualizing the motion transitions of the target object. Further, the synthesis target image selecting section  172  outputs the information about the selected synthesis target images (for example, the synthesis target images, object information about these images) to the coordinate calculating section  173  and the layer separating section  181 . 
     The coordinate calculating section  173  calculates coordinates used in the generation process of the synthetic image by the layer processing section  180 , with respect to each synthesis target image output from the synthesis target image selecting section  172 , and outputs the calculated coordinates to the layer modifying section  182 . In this coordinate calculation, a pixel position to be synthesized with the synthetic image relating to the synthesis target image which is the calculation target is calculated. That is, in this coordinate calculation, a pixel range (for example, a range including F 0  and F 10  shown in  FIG. 8D ) is calculated corresponding to the synthesis target images which are the calculation target among a synthetic image which is finally generated (for example, a synthetic image  402  shown in  FIG. 8D ). 
     The counter section  174  supplies a value of the counter (impact sound detection counter) used at the time of the synthesis target image selection range determination by the synthesis target image selection range determining section  171  to the synthesis target image selection range determining section  171 . Here, the counter section  174  continuously increases the impact sound detection counter. Further, in a case where the fact that the specific sound is detected from the specific sound detecting section  132  is output to the synthesis target image selection range determining section  171 , the value of the impact sound detection counter is reset to “zero” by the synthesis target image selection range determining section  171 . Similarly, after the reset, the counter section  174  also continuously increases the impact sound detection counter. Further, the synthesis target image selection range determining section  171  estimates the impact sound detection position using the value of the impact sound detection counter at the time of the determination of the synthesis target image selection range. That is, at the time of the determination of the synthesis target image selection range, a position (preceding position in the time axis) preceding by the value of impact sound detection counter than the determination time is estimated as the impact sound detection position. 
     The layer separating section  181  performs layer separation using corresponding object information, for the synthesis target images selected by the synthesis target image selecting section  172 . Here, the term “layer” refers to each image obtained by separating the target object section and the background section for one image (frame). Further, the layer separating section  181  outputs each separated layer image to the layer modifying section  182 . 
     The layer modifying section  182  performs a variety of modifying processes for generating the respective layer images output from the layer separating section  181  as the synthetic image, using the coordinates calculated by the coordinate calculating section  173 . As this modifying process, geometric arithmetic processes such as cutout, scaling, rotation and coordinate movement are performed. For example, the scaling has its process contents determined according to the number of synthesis target images, the size of the synthetic image, or the like. Further, as the modifying process, image processing such as emphasis on a motion portion of the target object may be performed. In addition, the layer modifying section  182  outputs the layer image which is processed to the layer synthesizing section  183 . 
     The layer synthesizing section  183  performs an image synthesis process for the layer image output from the layer modifying section  182 , and stores the generated synthetic image to the synthetic image storing section  200 . Specifically, the layer synthesizing section  183  synthesizes the respective layer images so that the layer image output from the layer modifying section  182  is arranged in a corresponding pixel range. Further, the layer synthesizing section  183  synthesizes the layer images which are immediately before the synthesis targets, and then sequentially retain the synthetic images (history images) in the synthetic image retaining section  185 . Further, when performing the synthesis process of the layer images which become the next synthesis target, the layer synthesizing section  183  obtains, from the synthetic image retaining section  185 , the synthetic images (history images) retained in the synthetic image retaining section  185 , and uses them in the synthesis process. 
     The synthetic image retaining section  185  sequentially retains the synthetic images (history images) generated by the layer synthesizing section  183 , and supplies the retained synthetic images to the layer synthesizing section  183 . That is, the synthetic images generated by the layer synthesizing section  183  are sequentially updated and retained in the synthetic image retaining section  185 . 
     [Example of Transitions of Synthetic Image Generation Process] 
     Next, an example of transitions of the generation process in a case where the synthetic image is generated will be briefly described. 
       FIGS. 3A to 3C  are diagrams schematically illustrating the positional relation of the image capturing apparatus  100  and a person  300  who is the image capturing target and the relation of moving images generated in this positional relation, according to the first embodiment of the present invention. 
       FIG. 3A  schematically illustrates the positional relation between the image capturing apparatus  100  and the person  300  who is the image capturing target with respect to the image capturing apparatus  100 . The person  300 , for example, has a practice swing of a golf club  301  in a golf practice range. As the person  300  swings the golf club  301  from a posture shown in  FIG. 3A , the person  300  hits the golf ball  302  with the golf club  301  to drive the golf ball  302  in a desired direction. 
       FIG. 3B  schematically illustrates a moving image  310  generated by the image capturing section  111  in a rectangular shape. Further, in  FIG. 3B , in the rectangular shape corresponding to the moving image  310 , some frames (images  311  to  313  and the like) among frames for forming the moving image  310  are arranged along a time axis. Further, the moving image  310  is a moving image obtained by imaging the appearance of the golf practice swing of the person  300  by the image capturing apparatus  100  in a state shown in  FIG. 3A . Here, the image  311  is an image obtained by imaging a state where the person  300  is ready for the golf swing, and the image  312  is an image obtained by imaging a state where the person  300  views a direction where the golf ball  302  flies after the golf swing is finished. Further, the image  313  is an image obtained by imaging a state of the moment when the golf club  301  comes in contact with the golf ball  302  when the person  300  performs a golf swing. Here, when the person  300  performs the golf swing, a specific sound (impact sound) is generated at the moment when the golf club  301  comes in contact with the golf ball  302 . The position in the moving image  310  in which the impact sound is generated is represented as an impact sound generation position  315 . 
     In a case where the synthetic image indicating the transitions of the golf swing of the person  300  is generated using the moving image  310  thus generated, for example, a predetermined range (synthesis target image selection range) for selecting the synthesis target images is selected. The synthesis target image selection range is a range in which a series of motion transitions, for example, from the start of the golf swing to the end thereof is included. Further, in the predetermined range, the images which are the synthesis targets are selected and synthesized. This synthesis example is shown in  FIG. 4B . 
     For example, as shown in  FIG. 3B , a synthesis target image selection range  320  is determined in the moving image  310 , and frames which satisfy a predetermined condition are determined as the synthesis target images, among respective frames included in the synthesis target image selection range  320 . 
     In  FIG. 3C , some frames (images  321  to  326 ) among the respective frames included in the synthesis target image selection range  320  determined in the moving image  310  shown in  FIG. 3B  are arranged along the time axis. Here, the moving image  321  is an image captured when the person  300  starts the golf swing, and the image  326  is an image captured when the person  300  finishes the golf swing. Further, the image  323  is an image corresponding to the image  313  shown in  FIG. 3B . In addition, the images  322 ,  324  and  325  are images obtained by sequentially imaging the motion transitions of the person  300  who performs the golf swing in a time-series manner, between the images  321  and  326 . 
       FIGS. 4A and 4B  are diagrams illustrating an example of the synthesis target images selected by the synthesis target image selecting section  172  and the synthetic image generated by a layer processing section  180 , according to the first embodiment of the present invention. In  FIG. 4A, 24  images selected as the synthesis target images among the respective frames included in the synthesis target image selection range  320  in the moving image  310  shown in  FIG. 3B  are arranged in a time-series manner. Images including the same object as the images  321  to  326  shown in  FIG. 3C  among the  24  images shown in  FIG. 4A  are given the same reference numbers. Here, as the selection method of the synthesis target images, for example, a selection method for selecting frames at a predetermined interval as the synthesis target images may be used. Further, for example, it may be considered that the motion transitions around the time when the golf ball  301  comes in contact with the golf ball  302  are minutely confirmed in some cases. In this case, an interval of the neighboring images of the image (for example, the image  323 ) when the impact sound is generated may be closer than other intervals to select the synthesis target images. 
       FIG. 4B  schematically illustrates the synthetic image  330  generated by the layer processing section  180 . In this way, the synthesis target image selection range in which the motion transitions from the start of the golf swing of the person  300  to the end thereof are included is determined and the synthesis target images are selected in the synthesis target image selection range for synthesis. Thus, the synthetic image indicating the motion transitions of the golf swing of the person  300  can be generated. 
     As described above, in a case where the synthetic image is generated from the moving image  310 , it is important to appropriately select the synthesis target image selection range for selection of the synthesis target images. However, since the golf swing is performed in a relatively short time, it may be difficult to appropriately select the synthesis target image selection range from the moving image  310 . That is, it may be difficult to select the synthesis target image selection range from the moving image  310  including images ranging from an image including a state before the start of the golf swing of the person  300  to an image including a state after the end of the golf swing. 
     Here, as described above, the impact sound is generated in the middle of the golf swing. In this way, since the impact sound is frequently generated in a predetermined position during the golf swing, the synthesis target image selection range may be selected on the basis of the impact sound. However, in a case where the person  300  practices at a golf practice range where there are a lot of other people, it is highly likely that the impact sound is generated by the golf swing of a person other than the person  300  as the person  300  gets ready for a golf swing or the like. That is, in a case where an instant motion relating to sport causing the impact sound is appropriately recorded, if the detected impact sound is always valid, it is highly likely to mistakenly detect an impact sound from a person other than a detection target. For this reason, in a case where the synthetic image relating to the person  300  is generated, it is important to appropriately detect the impact sound generated by the golf swing of the person  300  when the synthesis target image selection range is selected on the basis of the impact sound. Thus, in the first embodiment of the present invention, an example that a valid sound range is provided in which only adjacent timing around a photographing trigger based on the user manipulation is valid is set to reduce the false detection of the impact sound. The synthesis target image selection range is set using only the impact sound detected in the valid sound range, to thereby select appropriate synthesis target images. 
     [Determination Example of Synthesis Target Image Selection Range Based on Video Recording Button Manipulation] 
       FIGS. 5A, 5B and 5C  are diagrams schematically illustrating a setting method of a valid sound range by the valid sound range setting section  160  and a determination method of a synthesis target image selection range by the synthesis target image selection range determining section  171 , according to the first embodiment of the present invention. 
       FIG. 5A  schematically illustrates a moving image  350  generated by the image capturing section  111  in a rectangular shape. Further, in a similar way to the example shown in  FIG. 3B , the moving image  350  is a moving image obtained by imaging the appearance of a golf practice swing of a person (for example, Koda Goro) by the image capturing apparatus  100 . Here, it is assumed that Koda Goro asks his friend (for example, Otogawa Rokuro) to photograph his golf swing. In this case, Otogawa Rokuro holds the image capturing apparatus  100  with his hands with an optical axis direction thereof being toward Koda Goro, and presses a setting button of a synthetic image recording mode. If the press manipulation is received by the manipulation receiving section  140 , captured images are generated by the image capturing section  111 , and the generated captured images are sequentially retained in the imaging image retaining section  115 . Further, the display control section  190  sequentially displays the generated captured images (so-called through images) on the display section  191 . In this way, in a state where Otogawa Rokuro performs photographing using the image capturing apparatus  100  in which the synthetic image recording mode is set, Koda Goro performs a golf swing. Right after Koda Goro finishes the golf swing, Otogawa Rokuro rapidly presses the video recording button. If the press manipulation is received by the manipulation receiving section  140 , the valid sound range setting section  160  sets the valid sound range. 
     For example, it is assumed that a position (position in the time axis) where the video recording button is pressed by Otogawa Rokuro is a press position (video recording button press position  351 ) of the video recording button in the time axis of the moving image  350  shown in  FIG. 5A . In this case, the valid sound range setting section  160  sets a valid sound range  352  on the basis of the video recording button press position  351 . Specifically, the valid sound range setting section  160  sets a range which precedes the video recording button press position  351  by a time L 1  in the time axis, as the valid sound range  352 . In this example, since the pressing (photographing trigger) of the video recording button may be generated after the end of a series of golf swing motions, the generation position of the impact sound may exist before the timing of the photographing trigger. Accordingly, this example is an example in which the valid sound range is set before the pressing of the video recording button. 
     Here, the time L 1  can be 1.0 second, for example. The synthesis target image selection range is determined on the basis of the impact sound detected in the valid sound range set in this way. The determination method of the synthesis target image selection range will be described with reference to  FIG. 5B . Further, in a case where the impact sound is not detected in the valid sound range set in this way, the synthesis target image selection range is determined on the basis of the video recording button press position  351 . The determination method of the synthesis target image selection range will be described with reference to  FIG. 5C . 
       FIG. 5B  schematically illustrates a determination method of the synthesis target image selection range in a case where the impact sound is detected in the valid sound range  352  set by the valid sound range setting section  160 . In  FIG. 5B , the position (position in the time axis) where the impact sound is detected by the specific sound detecting section  132  is represented as an impact sound detection position  353 . As shown in  FIG. 5B , in the case where the impact sound is detected in the valid sound range  352  set by the valid sound range setting section  160 , the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the impact sound detection position  353 . That is, the synthesis target image selection range determining section  171  determines a predetermined range before and after the impact sound detection position  353  in the time axis with reference to the impact sound detection position  353 , as the synthesis target image selection range  354 . Specifically, the synthesis target image selection range determining section  171  determines a range L 4 , which includes a range which precedes the impact sound detection position  353  by a time L 2  and a range which exceeds the impact sound detection position  353  by a time L 3 , in the time axis, as a synthesis target image selection range  354 . 
     Here, in consideration of the rotation speed of the golf club, the time during a golf swing after the golf club comes in contact with the golf ball is shorter than the time before the golf club comes in contact with the golf ball. That is, the time during a golf swing after the impact sound is generated is shorter than the time before the impact sound is generated. Thus, the synthesis target image selection range  354  is determined so that the time L 2  before the impact sound detection position  353  is longer than the time L 3  thereafter. For example, the time L 2  can be 1.5 seconds and the time L 3  can be 0.5 seconds. In this way, as the synthesis target image selection range is determined on the basis of the impact sound detected in the valid sound range, an appropriate synthesis target image selection range can be determined. 
     Here, it is assumed that an impact sound is detected in positions (for example, positions indicated by arrows  358  and  359  shown in  FIG. 5B ) other than the valid sound range  352  set by the valid sound range setting section  160 . In a case where the impact sound is detected in the positions other than the valid sound range  352 , the impact sound is not used for determination of the synthesis target image selection range. In a case where the impact sound is not used, as shown in  FIG. 5C , the synthesis target image selection range can be determined on the basis of the press position of the video recording button. Further, in a case where the impact sound is detected in the positions other than the valid sound range  352 , the impact sound is not used for determination of the synthesis target image selection range, but may be used for the generation process of the next synthetic image. 
       FIG. 5C  schematically illustrates a determination method of the synthesis target image selection range in a case where the impact sound is not detected in the valid sound range  352  set by the valid sound range setting section  160 . In  FIG. 5C , in a similar way to the case of  FIG. 5A , a position where the video recording button is pressed is represented as the video recording button press position  351 . As shown in  FIG. 5C , in a case where the impact sound is not detected in the valid sound range  352 , the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the video recording button press position  351 . That is, the synthesis target image selection range determining section  171  determines a predetermined range before the video recording button press position  351  in the time axis with reference to the video recording button press position  351 , as a synthesis target image selection range  355 . Specifically, the synthesis target image selection range determining section  171  determines a range which precedes the impact sound detection position  353  by a time L 7  (L 5 +L 6 ) in the time axis, as the synthesis target image selection range  355 . In this way, in a case where the impact sound is not detected in the valid sound range  352 , a position, which precedes the press position of the video recording button by a time L 6  in the time axis, is considered as the impact sound detection position to determine the synthesis target image selection range  355 . That is, the times L 5  and L 6  correspond to the times L 2  and L 3  shown in  FIG. 5B . Here, for example, in a similar way to the case of  FIG. 5B , the time L 7  can be 2.0 seconds. That is, the time L 5  is 1.5 seconds and the time L 6  is 0.5 seconds. However, in a case where the synthesis target image selection range is determined on the basis of the video recording button press position, since the synthesis target image selection range is determined on the basis of the user manipulation, accuracy may be decreased compared with the synthesis target image selection range  354  shown in  FIG. 5B . Thus, in a case where the synthesis target image selection range is determined on the basis of the video recording button press position, for example, the time L 7  may be longer than the time L 4  to determine the synthesis target image selection range. 
     Further, these times L 1  to L 7  may be changed by the user manipulation. 
     [Determination Example of Synthesis Target Image Selection Range Based on Timer] 
       FIGS. 6A and 6B  are diagrams illustrating an example of transitions of a display screen displayed on the display section  191  according to the first embodiment of the present invention.  FIG. 6A  illustrates a display example (display screen  370 ) in which a count value “17” ( 372 ) of a timer set by the timer setting section  150  is overlapped with an image generated by the image capturing section  111  before the start of the golf swing of the person  300 .  FIG. 6B  illustrates a display example (display screen  371 ) in which a count value “0” ( 373 ) of the timer set by the timer setting section  150  is overlapped with an image generated by the image capturing section  111  at the end of the golf swing of the person  300 . 
     In this example, it is assumed that the person  300  (for example, Koda Goro) photographs his appearance of golf practice swing by himself. In this case, for example, Koda Goro who is practicing installs the image capturing apparatus  100  so that the optical axis direction thereof is directed toward himself, as shown in  FIG. 3A , and then presses a timer setting button. Through this press manipulation, captured images are generated by the image capturing section  111 , and the display control section  190  displays the generated captured images (so-called through images) on the display section  191 . Further, the timer setting section  150  sets the timer through the press manipulation of the timer setting button, and the display control section  190  overlaps the count value (for example, 17 seconds) corresponding to the set contents with the through images to be displayed on the display section  191 . For example, as shown in  FIG. 6A , after the press of the timer setting button, the display screen  370  is displayed in which the count value “17” ( 372 ) of the timer set by the timer setting section  150  is overlapped with the captured image including the person  300  who is ready for the golf swing. Thereafter, similarly, a display screen in which the count values (for example, values decreased from 17 seconds at intervals of one second) of the timer are overlapped with the captured image including the person  300  is displayed on the display section  191 . The person  300  performs the golf swing so that the golf swing is terminated around the time when the count value of the timer becomes “0” while viewing the display screen displayed on the display section  191  in this way. Further, in a case where the count value of the timer is “0”, the valid sound range setting section  160  sets the valid sound range. Then, the imaging motion is stopped after a predetermined time. The setting method of the valid sound range will be described in detail with reference to  FIGS. 7A, 7B and 7C . 
     As the timer setting is performed as described above, for example, even in a case where a friend does not perform photographing, the person  300  can easily photograph the appearance of the golf swing of his own. 
       FIGS. 7A, 7B and 7C  are diagrams schematically illustrating a setting method of a valid sound range by the valid sound range setting section  160  and a determination method of the synthesis target image selection range by the synthesis target image selection range determining section  171 , according to the first embodiment of the present invention. Here, the first embodiment provides an example in which the valid sound range is set on the basis of the timer set by the timer setting section  150 . 
       FIG. 7A  schematically illustrates a moving image  380  generated by the image capturing section  111  in a rectangular shape. In a similar way to the example shown in  FIG. 3B , the moving image  380  is a moving image obtained by imaging the appearance of a golf practice swing of a person (for example, Koda Goro) by the image capturing apparatus  100 . For example, as shown in  FIGS. 6A and 6B , in a case where the person  300  (for example, Koda Goro) photographs his appearance of golf practice swing by himself, it is assumed that the count value of the timer set by the timer setting section  150  is “0”. In this case, as described above, the valid sound range setting section  160  sets the valid sound range. 
     For example, it is assumed that a position in which the count value of the timer set by the timer setting section  150  is “0” is a position of the time counter “0” in the time axis of the moving image  380  shown in  FIG. 7A  (time counter “0” position  381 ). In this case, the valid sound range setting section  160  sets the valid sound range  382  on the basis of the time counter “0” position  381 . Specifically, the valid sound range setting section  160  sets a predetermined range before and after the time counter “0” position  381  in the time axis with reference to the time counter “0” position  381 , as the valid sound range  382 . For example, the valid sound range setting section  160  sets a range L 13 , which includes a range which precedes the time counter “0” position  381  by a time L 11  and a range which exceeds the time counter “0” position  381  by a time L 12 , in the time axis, as the valid sound range  382 . 
     Here, it may be difficult for the person  300  to perform the golf swing so as to terminate the series of golf swing motions at the timing of the time counter “0”. Thus, in this example, the instant when the impact sound is generated may correspond to the position of the time counter “0”, and the valid sound range is set to cover a range before and after the position of the time counter “0”. In this way, a case where the valid sound range is set on the basis of the press position of the video recording button and a case where the valid sound range is set on the basis of the position of the time counter “0” can have different set contents. As the valid sound range is set according to a plurality of photographing trigger characteristics, it is possible to reduce the risk that sounds other than the impact sound to be detected are mistakenly detected. 
     In this respect, the time L 11  can be 0.5 seconds and the time L 12  can be 0.5 seconds, for example. That is, the time L 13  of the valid sound range  382  can be 1.0 second, for example. The person  300  performs the golf swing so that the golf swing is terminated around the time when the count value of the timer becomes “0” while viewing the display screen displayed on the display section  191 . For this reason, compared with the case where the valid sound range is set on the basis of the position where the video recording button is pressed, accuracy may be reduced. Accordingly, the valid sound range based on the timer setting manipulation may be relatively wider than the valid sound range based on the video recording button press manipulation. That is, the valid sound range based on the video recording button press manipulation may be narrower than the valid sound range based on the timer setting manipulation. The synthesis target image selection range is determined on the basis of the impact sound detected in the valid sound range set in this way. The determination method of the synthesis target image selection range will be described with reference to  FIG. 7B . Further, in a case where the impact sound is not detected in the valid sound range set in this way, the synthesis target image selection range is determined on the basis of the time counter “0” position  381 . The determination method of the synthesis target image selection range will be described with reference to  FIG. 7C . 
       FIG. 7B  schematically illustrates the determination method of the synthesis target image selection range in a case where the impact sound is detected in the valid sound range  382  set by the valid sound range setting section  160 . In  FIG. 7B , a position (position in the time axis) in which the impact sound is detected by the specific sound detecting section  132  is represented as the impact sound detection position  383 . As shown in  FIG. 7B , in a case where the impact sound is detected in the valid sound range  382  set by the valid sound range setting section  160 , the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the impact sound detection position  383 . That is, the synthesis target image selection range determining section  171  determines a predetermined range before and after the impact sound detection position  383  in the time axis with reference to the impact sound detection position  383 , as the synthetic target image selection range  384 . Specifically, a range L 16 , which includes a range which precedes the impact sound detection position  383  by a time L 14  and a range which exceeds the impact sound detection position  383  by a time L 15 , in the time axis, is determined as the synthetic target image selection range  384 . 
     Here, as described above, the time during a golf swing after the golf club comes in contact with the golf ball is shorter than the time before the golf club comes in contact with the golf ball. Thus, the synthesis target image selection range  384  is determined so that the time L 14  before the impact sound detection position  383  is longer than the time L 15  thereafter. For example, the time L 14  can be 1.5 seconds and the time L 15  can be 0.5 seconds. In this way, as the synthesis target image selection range is determined on the basis of the impact sound detected in the valid sound range, an appropriate synthesis target image selection range can be determined. 
     It is assumed that the impact sound is detected in positions (for example, positions indicated by arrows  388  and  389  in  FIG. 7B ) other than the valid sound range  382  set by the valid sound range setting section  160 . In a case where the impact sound is detected in the positions other than the valid sound range  382  in this way, the impact sound is not used for determination of the synthesis target image selection range, in a similar way to the example shown in  FIG. 5B . In a case where the impact sound is not used, as shown in  FIG. 7C , the synthesis target image selection range can be determined on the basis of the time counter “0” position. Further, in a case where the impact sound is detected in the positions other than the valid sound range  382 , the impact sound is not used for determination of the synthesis target image selection range, but may be used for a generation process of the next synthetic image. 
       FIG. 7C  schematically illustrates the determination method of the synthesis target image selection range in a case where the impact sound is not detected in the valid sound range  382  set by the valid sound range setting section  160 . In  FIG. 7C , the position in which the count value of the timer set by the timer setting section  150  is “0” is represented as the time counter “0” position  381 , in a similar way to the example of  FIG. 7A . As shown in  FIG. 7C , in a case where the impact sound is not detected in the valid sound range  382 , the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the time counter “0” position  381 . That is, the synthesis target image selection range determining section  171  determines a predetermined range before and after the time counter “0” position  381  in the time axis with reference to the time counter “0” position  381 , as a synthesis target image selection range  385 . Specifically, the valid sound range setting section  160  sets a range L 19 , which includes a range which precedes the time counter “0” position  381  by a time L 17  and a range which exceeds the time counter “0” position  381  by a time L 18 , in the time axis, as the synthesis target image selection range  385 . 
     Here, the person  300  performs the golf swing so that the golf swing is terminated around the time when the count value of the timer becomes “0” while viewing the display screen displayed on the display section  191 . For this reason, as shown in  FIG. 5C , compared with the case where the synthesis target image selection range is determined on the basis of the position where the video recording button is pressed, accuracy may be reduced. Accordingly, in a case where the impact sound is not detected in the valid sound range  382 , a position where the count value of the timer is “0” (timer counter “0” position  381 ) in the time axis is considered as the impact sound detection position to determine the synthesis target image selection range  385 . 
     Further, the times L 17  and L 18  correspond to the times L 14  and L 15  shown in  FIG. 7B . Further, for example, the time L 17  is 1.5 seconds and the time L 18  is 0.5 seconds, in a similar way to the example of  FIG. 7B . As described above, in a case where the synthesis target image selection range is determined on the basis of the position where the count value of the timer is “0”, the synthesis target image selection range is determined on the basis of an action due to a sense of the user. For this reason, accuracy may be reduced, compared with the synthesis target image selection range  384  shown in  FIG. 7B . Thus, in a case where the synthesis target image selection range is determined on the basis of the position where the count value of the timer is “0”, for example, the time L 19  may be longer than the time L 16  to determine the synthesis target image selection range. 
     Further, the respective times L 11  to L 19  may be changed by the user manipulation. 
     [Generation Example of Synthetic Image] 
     Next, an example of generating a synthetic image will be described in detail with reference to the drawings, using each frame included in the determined synthesis target image selection range. In the first embodiment of the present invention, a case where a synthetic image of a still image is generated will be described as an example. 
       FIGS. 8A, 8B, 8C and 8D  are diagrams schematically illustrating an example of a flow of a selection process of synthesis target images by the selecting section  170  and a generation process of a synthetic image by the layer processing section  180 , according to the first embodiment of the present invention. 
       FIG. 8A  schematically illustrates a moving image  400  generated by the image capturing section  111  and a synthesis target image selection range  401  determined by the synthesis target image selection range determining section  171  in the moving image  400 . The moving image  400  is a moving image obtained by imaging the appearance of a golf practice swing of a person by the image capturing apparatus  100 , in a similar way to the example shown in  FIG. 3B  or the like. Further, it is assumed that the synthesis target image selection range  401  is a synthesis target image selection range determined by the synthesis target image selection range determining section  171 , in a similar way to the examples shown in  FIGS. 5B and 5C  and  FIGS. 7B and 7C . 
       FIG. 8B  schematically illustrates respective frames included in the synthesis target image selection range  401  in the moving image  400 . In  FIG. 8B , the respective frames included in the synthesis target image selection range  401  are shown in a rectangular shape. Here, F 1  to F 90  indicating the respective frames are given in the rectangular shape. 
     The synthesis target image selecting section  172  selects synthesis target images on the basis of a predetermined condition, from the respective frames included in the synthesis target image selection range  401 . For example, the synthesis target image selecting section  172  selects frames at a predetermined interval (for example, 10-frame interval) among the frames F 1  to F 90 , as the synthesis target images. In this case, for example, intervals of frames included in a predetermined range (for example, 0.05 seconds) around a position where the impact sound is detected may be closer than other intervals, to be selected. Accordingly, the synthetic image can be generated using the images selected around motion transitions to be observed. The synthesis target images selected in this way are shown in  FIG. 8C . In this example, for simplicity of the description, a relatively small number of frames are exemplified. 
       FIG. 8C  schematically illustrates a plurality of synthesis target images (frames F 0 , F 10  and the like) selected as the synthesis target image, from the respective frames included in the synthesis target image selection range  401 . In  FIG. 8C , the synthesis target images are shown in a rectangular shape. Here, F 0 , F 10  or the like indicating each synthesis target image is given in the rectangular shape. In this example, for simplicity of the description, a relatively small number of frames (for example, 10 frames) are exemplified. 
       FIG. 8D  schematically illustrates a synthetic image  402  generated by the synthesis target images (the plurality of frames F 0 , F 10  and the like). In  FIG. 8D , the synthesis target images are shown in a rectangular shape, in a similar way to the example of  FIG. 8C . Here, F 1 , F 10  or the like indicating each synthesis target image is given in the rectangular shape. 
     The layer processing section  180  synthesizes the synthesis target images (frames F 0 , F 10  and the like) selected by the synthesis target image selecting section  172  through a modifying process, to thereby generate a synthetic image. For example, the layer processing section  180  performs the modifying process (for example, cutout of opposite ends) for synthesis with respect to ten synthesis target images selected by the synthesis target image selection range determining section  171 , to thereby synthesize the synthesis target images after modification in a time-series manner. For example, the layer processing section  180  synthesizes five synthesis target images (F 0 , F 10 , F 20 , F 30  and F 40 ) to be arranged in a time-series manner from an upper left end part, and synthesis five synthesis target images (F 50 , F 60 , F 70 , F 80  and F 90 ) to be arranged in a time-series manner from a lower left end part. The synthesis positions of the synthesis target images are determined on the basis of the calculation result by the coordinate calculating section  173 . Accordingly, as shown in  FIG. 4B , the synthetic image indicating the motion transitions of the person who practices the golf swing is generated. 
     In  FIGS. 8A, 8B, 8C and 8D , the example in which the image synthesis is easily performed (example in which the image synthesis is performed after the cutout of the opposite ends of the synthesis target image) has been described. Hereinafter, an example in which the synthesis target images are separated into a target object layer and a background layer to generate a synthetic image will be described. 
     [Layer Separation Example of Synthesis Target Images] 
       FIGS. 9A and 9B  are diagrams schematically illustrating a separation method of synthesis target images by the layer separating section  181  according to the first embodiment of the present invention. In this example, the synthesis target images selected by the synthesis target image selecting section  172  are separated into two layers on the basis of the object information generated by the object information generating section  120 . 
       FIG. 9A  illustrates the synthesis target image  410  and an object information  412  generated for the synthesis target image  410 . The synthesis target image  410  is an image including a person  411 . Further, as the object information generated by the object information generating section  120 , for example, information indicating that “1” is given to pixels corresponding to a target object region and “0” is given to pixels corresponding to a region (for example, background region) other than the target object is generated. In  FIG. 9A , a region (target object region) corresponding to the person  411  is a white region  413  and the region (background region) other than the person  411  is a black region, to thereby schematically illustrate the object information  412 . 
     As described above, in the captured image retaining section  115 , the captured images generated by the image capturing section  111  are sequentially retained, and the object information generated by the object information generating section  120  is retained in relation to the captured images. Further, the synthesis target image selecting section  172  outputs the selected synthesis target images and the object information generated for the synthesis target images to the layer separating section  181 . Then, the layer separating section  181  separates the synthesis target images output from the synthesis target image selecting section  172  into two layers, using the corresponding object information. 
       FIG. 9B  illustrates a target object layer  420  separated by the layer separating section  181  and a background layer  422 . The target object layer  420  is an image obtained by extracting the target object region (that is, a pixel region which is given “1” as the object information  412 ) in the synthesis target image  410  shown in  FIG. 9A . That is, a region  421  corresponding to the person  411  included in the synthesis target image  410  is extracted. Further, the background layer  422  is an image obtained by extracting the background region (that is, a pixel region which is given “0” as the object information  412 ) in the synthesis target image  410  shown in  FIG. 9A . That is, a region is extracted (region other than a region  423 ) corresponding to the region (background region) other than the person  411  included in the synthesis target image  410 . 
     A variety of modifying processes is performed by the layer modifying section  182 , for the respective layer images separated in this way. This modification example will be described in detail with reference to  FIGS. 10A to 10C . 
     [Modification Example of Synthesis Target Images] 
       FIGS. 10A, 10B and 10C  are diagrams schematically illustrating an image which is a target of a modification process by the layer modifying section  182  and an image which is modified by the layer modifying apparatus  182 , according to the first embodiment of the present invention. Here, a case where a synthetic image is generated for sport performed in a standing posture such as golf will be described as an example. Further, in  FIGS. 10A, 10B and 10C , for simplicity of the description, a case where the modifying process is performed using a synthesis target image of a state before layer separation is shown as an example. 
       FIG. 10A  illustrates a synthesis target image  430  before modification by means of the layer modifying section  182 . Further,  FIGS. 10B and 10C  illustrate synthesis target images  432  and  433  after modification by means of the layer modifying section  182 . A person  431  who performs the golf swing is included in the synthesis target images  430 ,  432  and  433 . 
     The synthesis target image  430  shown in  FIG. 10A  has an image size of a width W 1  and a height H 1 , for example. For example, the image size of the synthesis target image  430  can be the VGA size (640 pixels×480 pixels). That is, the width W 1  can be 640, and the height H 1  can be 480. 
     The synthesis target image  432  shown in  FIG. 10B  is an image corresponding to a transition motion valid region in the synthesis target image  430  shown in  FIG. 10A , and for example, has an image size of a width W 2  and a height H 2 . Here, the transition motion valid region is a region for cutting out the target object from objects included in the synthesis target image before modification. For example, the image size of the synthesis target image  432  can be 320 pixels×480 pixels. That is, the width W 2  can be 320, and the height H 2  can be 480. 
     The synthesis target image  433  shown in  FIG. 10C  is an image corresponding to a remaining background region in the synthesis target image  430  shown in  FIG. 10A , and for example, has an image size of a width W 3  and a height H 3 . The remaining background region is a region which is used as a background image in the synthesis process. For example, the image size of the synthesis target image  433  can be 160 pixels×480 pixels. That is, the width W 3  can be 160, and the height H 3  can be 480. 
     It is assumed that a central position between the transition motion valid region and the remaining background region coincides with a central position of the synthesis target image. Further, the size (W 2 ×H 2 ) of the transition motion valid region and the size (W 3 ×H 3 ) of the remaining background region may be the same in their sizes (at least one of the width and height) according to the transition direction of the target object. For example, the transition direction of the target object is a direction in which the images proceed in a temporal manner when the images are represented as motion transition images. 
     For example, in a case where a synthetic image is generated for motion transitions of sport performed in a standing posture such as golf, as shown in  FIG. 4B , it is likely that each target object image is transited in a transverse direction. For this reason, as shown in  FIGS. 10B and 10C , it may be preferable that the heights H 2  and H 3  of the transition motion valid region and the remaining background region are the same as the height H 1  of the synthesis target image. On the other hand, in a case where a synthetic image is generated for motion transitions of sport performed in a horizontal direction state, each target object image may be transited in a longitudinal direction. In this case, it may be preferable that the widths W 2  and W 3  of the transition motion valid region and the remaining background region are the same as the width W 1  of the synthesis target image. For example, in a case where ground work or the like in judo becomes a target object, it is likely that the motion transitions are performed in a longitudinal direction. 
       FIGS. 10A, 10B and 10C  shows an example, in which it is preferable to perform appropriate setting for the width and the height of the transition motion valid region and the remaining background region according to the size or motion of the object, so as to cut out the image as an image used for the synthesis process. 
     [Image Synthesis Example] 
       FIGS. 11A and 11B  are diagrams schematically illustrating a synthesis method by the layer synthesizing section  183  according to the first embodiment of the present invention. Here, this embodiment provides an example in which a synthesis process is performed for two synthesis target images which continues in a time-series manner. 
       FIG. 11A  schematically illustrates synthesis target images (two synthesis target images which continue in a time-series manner) separated by the layer separating section  181  and modified by the layer modifying section  182 . As described above, the synthesis target images are separated into a target object layer and a background layer by the layer separating section  181 . Further, the layer modifying section  182  performs a modification process for the target object layer and the background layer separated by the layer separating section  181 . In this way, as the separation and modification are performed for two synthesis target images which continue in a time-series manner, as shown in  FIG. 11A , four layers (a first priority image  441  to a fourth priority image  444 ) are generated. 
     It is assumed that the first priority image  441  is a target object layer of a synthesis target image which comes later in the time axis, and the third priority image  443  is a background layer of the synthesis target image. Further, it is assumed that the second priority image  442  is a target object layer of a synthesis target image which comes earlier in the time axis, and the fourth priority image  444  is a background layer of the synthesis target image. Furthermore, in a case where these images are synthesized, the synthesis is performed so that an image having a higher priority is overwritten. 
       FIG. 11B  illustrates a synthetic image  450  generated on the basis of the priority of the respective layer images. That is, the layer synthesizing section  183  synthesizes four layers (the first priority image  441  to the fourth priority image  444 ) on the basis of the priority, to thereby generate the synthetic image  450 . The synthetic image  450  is an image obtained by synthesizing a person image  445  included in the first priority image  441  and a person image  446  included in the second priority image  442  to be overwritten on the background region synthesized by the third priority image  443  and the fourth priority image  444 . In this case, the third priority image  443  is synthesized to be overwritten on the fourth priority image  444 . Further, the person image  445  included in the first priority image is synthesized to be overwritten on the person image  446  included in the second priority image  442 . 
     As shown in  FIGS. 12A and 12B , in a case where three or more synthesis target images are sequentially synthesized to generate a synthetic image, the synthesis target images are sequentially synthesized in a time-series manner, to thereby generate the synthetic image. Further, a synthesis target image which comes earlier in the time axis among two synthesis target images which continue in a time-series manner is retained in the synthetic image retaining section  185 , until a synthesis process time of a synthesis target image which comes later. 
       FIGS. 12A and 12B  are diagrams schematically illustrating a synthesis method of synthesis target images by means of the layer synthesizing section  183  according to the first embodiment of the present invention. Here, a synthesis example of the synthesis target images until a synthetic image  460  shown in  FIG. 12B  is generated is shown. 
       FIG. 12A  illustrates a synthesis state at a certain time point until the synthetic image  460  shown in  FIG. 12B  is generated. For example, it is assumed that the state shown in  FIG. 12A  is a state at a time point when the synthesis process is performed for a synthesis target image  462  (two layer images). That is,  FIG. 12A  shows a transition motion valid region E 10  corresponding to the synthetic target image  462 , and a synthetic image  461  in which the synthesis process is performed for a synthesis target image  463  which comes right before. In this example, the respective layer images which become the synthesis targets right before are retained in the synthetic image retaining section  185 . 
     Here, in a region E 11  in the synthesis target image  462 , there is no overlapped region between the adjacent synthesis target image  463  and the synthesis target image  462 . For this reason, in a case where the synthesis target image  462  is synthesized with the synthetic image  461 , with respect to the region E 11  in the synthesis target image  462 , pixels of the transition motion valid region of the synthesis target image  462  are synthesized to be overwritten on the synthetic image  461  as a new synthetic image as they are. 
     However, a region E 12  in the synthesis target image  462  is overlapped with a part of the adjacent synthesis target image  463 . Thus, as shown in  FIGS. 11A and 11B , the respective layer images are synthesized in the region E 12  in the synthesis target image  462  according to the priority. 
     That is, the layer synthesizing section  183  synthesizes the respective layer images according to the priority for the region E 12 , using the respective layer images of the synthesis target image  462  which is a current synthesis target and the adjacent synthesis target image  463  retained in the synthetic image retaining section  185 . Through such a synthesis, a synthetic image of a region E 11 +E 12  is generated from the synthesis target images  462  and  463 . Further, the layer synthesizing section  183  synthesizes the synthetic image of the region E 11 +E 12  generated in this way to be overwritten, with the synthetic image (synthetic image synthesized with the adjacent synthesis target image  463 ) retained in the synthetic image retaining section  185 . That is, the layer synthesizing section  183  performs the process of pasting the synthetic image of the region E 11 +E 12  generated by such a synthesis in a region E 1  corresponding to the synthetic images retained in the synthetic image retaining section  185 . 
     Further, the synthesis target image  462  (two layer images) which becomes the current synthesis target and the synthetic image generated by the current synthesis process are retained in the synthetic image retaining section  185  and are used for the next synthesis process. An example of the synthetic image generated in this way is shown in  FIG. 12B . 
     In this way, as the respective layer images are synthesized according to the priority, with respect to a region (for example, region E 12 ) which is overlapped between continuous images in the synthesis process, the synthetic image can be generated without damaging a part of the target object. Thus, in a case where the synthetic image is generated using a plurality of synthesis target images, it is also possible to generate the motion transition images capable of appropriately expressing motions of the target object. 
     In this way, the synthetic image  460  generated by the layer synthesizing section  183  is stored in a synthetic image storing section  200 . Further, for example, the synthetic image  460  is displayed on the display section  191  according to the user manipulation. Further, for example, whenever the synthetic image is generated by the layer synthesizing section  183 , it may be automatically displayed on the display section  191 .  FIG. 13  illustrates an example of the synthetic image generated in this way. 
     [Synthetic Image Example] 
       FIG. 13  is a diagram illustrating an example of a synthetic image generated by the layer processing section  180  according to the first embodiment of the present invention. A synthetic image  470  shown in  FIG. 13  indicates motion transitions of a person who practices a golf swing. In the synthetic image  470 , a region indicated by an arrow  471  is a region including an image corresponding to a position where an impact sound is generated. 
     [Operation Example of Image Capturing Apparatus] 
       FIG. 14  is a flowchart illustrating an example of a process procedure of a synthetic image generation process by means of the image capturing apparatus  100  according to the first embodiment of the present invention. 
     Firstly, it is determined whether a setting manipulation of a synthetic image recording mode is performed (step S 901 ). For example, it is determined whether a press manipulation of a setting button of the synthetic image recording mode or a timer setting button is performed. In a case where the setting manipulation of the synthetic image recording mode is not performed (step S 901 ), monitoring is continued until the setting manipulation of the synthetic image recording mode is performed. In a case where the setting manipulation of the synthetic image recording mode is performed (step S 901 ), the image capturing section  111  performs the generation process of the captured image (step S 902 ), and the generated captured image is retained in the captured image retaining section  115  (step S 903 ). That is, the buffering process is performed. 
     Subsequently, it is determined whether the press manipulation of the video recording button is performed (step S 904 ). In a case where the press manipulation of the video recording button is performed, the valid sound range setting section  160  sets the valid sound range on the basis of the press position (step S 905 ). For example, as shown in  FIG. 5A , the valid sound range  352  is set on the basis of the video recording button press position  351 . On the other hand, in a case where the press manipulation of the video recording button is not performed (step S 904 ), it is determined whether the count value of the timer set by the timer setting section  150  is “0” (step S 906 ). In a case where the count value of the timer is “0” (step S 906 ), the valid sound range setting section  160  sets the valid sound range on the basis of the position where the count value of the timer is “0” (step S 907 ). For example, as shown in  FIG. 7A , the valid sound range  382  is set on the basis of the time counter “0” position  381 . Further, in a case where the count value of the timer is not “0”, or the timer setting is not performed by the timer setting section  150  (step S 906 ), the procedure returns to step S 902 . Steps S 904  to S 907  represent an example of a valid sound range setting procedure disclosed in the claims. 
     Next, the buffering termination process is performed (step S 908 ), and it is determined whether the impact sound is detected in the set valid sound range (step S 909 ). In a case where the impact sound is detected in the set valid sound range (step S 909 ), the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the position where the impact sound is detected (step S 910 ). For example, as shown in  FIG. 5C , the synthesis target image selection range  355  is determined on the basis of the impact sound detection position  353 . Further, for example, as shown in  FIG. 7C , the synthesis target image selection range  385  is determined on the basis of the impact sound detection position  383 . Steps S 909  and S 910  represent an example of a selection procedure disclosed in the claims. 
     Further, in a case where the impact sound is not detected in the set valid sound range (step S 909 ), the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the position which is a reference when the valid sound range is set (step S 911 ). That is, in a case where the valid sound range is set on the basis of the press position of the video recording button, the synthesis target image selection range is determined on the basis of the press position. For example, as shown in  FIG. 5C , the synthesis target image selection range  355  is determined on the basis of the video recording button press position  351 . On the other hand, in a case where the valid sound range is set on the basis of the position where the count value of the timer is “0”, the synthesis target image selection range is determined on the basis of the position. For example, as shown in  FIG. 7C , the synthesis target image selection range  385  is determined on the basis of the time counter “0” position  381 . 
     Subsequently, the synthesis target image selecting section  172  selects synthesis target images from the respective images included in the determined synthesis target image selection range (step S 912 ). Then, the generation process of the synthetic image is performed using the selected synthesis target images (step S 913 ). 
     Next, it is determined whether a release manipulation of the synthetic image recording mode is performed (step S 194 ). In a case where the release manipulation of the synthetic image recording mode is not performed, the procedure returns to step S 902 , and the image synthesis process relating to the next synthetic image is subsequently performed. On the other hand, in a case where the release manipulation of the synthetic image recording mode is performed (step S 914 ), the operation of the synthetic image generation process is terminated. 
     In this way, in the first embodiment of the present invention, a time span in which an impact sound which becomes the detection target can exist is set as the valid sound range, and thus, it is possible to reduce false detection of sounds other than the impact sound which becomes the detection target. Thus, in a case where a synthetic image using an extremely fast motion causing the impact sound such as a golf swing as a target is generated, it is possible to detect the generation position of the impact sound with a high degree of accuracy. Further, it is possible to generate the synthetic image with the emphasis around the accurate generation position of the impact sound, and to generate the synthetic image having a high visibility. In this case, since a manual work of the user is unnecessary for the detection of the generation position of the impact sound, it is possible to reduce user&#39;s inconvenience. 
     Further, as described above, it may be determined whether the synthetic image is generated according to whether the impact sound is detected in the valid sound range. This example is shown in  FIG. 15 . 
       FIG. 15  is a flowchart illustrating an example of a process procedure of the synthetic image generation process by means of the image capturing apparatus  100  according to the first embodiment of the present invention. This example is a modified example of the process procedure of the synthetic image generation process shown in  FIG. 14 , in which step S 911  is omitted. Thus, the same reference numerals are given to the same process steps as shown in  FIG. 14 , and description thereof will be omitted. 
     It is determined whether the impact sound is detected in the valid sound range set in step S 905  or S 907  (step S 909 ). In a case where the impact sound is not detected in the set valid sound range (step S 909 ), the procedure goes to step S 914 . That is, in a case where the impact sound is not detected in the set valid sound range, the generation process of the synthetic image is performed using the press position of the next video recording button, or the position where the count value of the timer is “0”, without generating the synthetic image. That is, the selecting section  170  performs a control, in a case where the impact sound is detected in the valid sound range, so that the synthetic image using the specific sound is generated in the layer processing section  180 , and performs a control so that the synthetic image is not generated in the layer processing section  180  in a case where the impact sound is not detected in the valid sound range. 
     In this way, in a case where the impact sound is not able to be detected in the valid sound range, it is possible to reduce a loss of a photographing chance for the user, by returning to the next photographable state without generating the synthetic image. Further, since the synthetic image can be generated using the accurate impact sound, it is possible to generate an appropriate synthetic image. 
     As the synthetic image is generated in this way, even a beginner who is not accustomed to the handling of the image capturing apparatus can easily generate an appropriate synthetic image. 
     In a case where the captured images generated by the image capturing section  111  are recorded as image contents (for example, a moving image file or continuous still image file), the impact sound detection position may be recorded as metadata of frame. Thus, for example, in a case where a list of the image contents is displayed, the frame corresponding to the impact sound detection position can be used as a representative thumbnail. 
     2. Second Embodiment 
     In the first embodiment of the present invention, the case where the distance between the image capturing apparatus and the target object (person who practices the golf swing) is relatively short has been described by way of example. However, the image capturing apparatus may be located in a position where the distance from the target object is relatively long and may photograph the target object by means of a zoom function of the image capturing apparatus. In such a case where the distance between the image capturing apparatus and the target object is relatively long, the time until the impact sound reaches the image capturing apparatus becomes long according to the length of the distance. In this case, a delay occurs between the time when the impact sound is generated and the time when the impact sound reaches the image capturing apparatus. Thus, the second embodiment of the present invention provides an example in which the detection position of the impact sound in the time axis is corrected, in a case where the distance between the image capturing apparatus and the target object is relatively long, according to the length of the distance. 
       FIGS. 16A and 16B  are diagrams illustrating the distance between an image capturing apparatus  500  and a target object and the relation between a generation position of an impact sound and an arrival position thereof, according to the second embodiment of the present invention.  FIG. 16A  schematically illustrates the positional relation between the image capturing apparatus  500  and a person  540  who becomes an image capturing target by the image capturing apparatus  500 . Here, the distance between the image capturing apparatus  500  and the person  540  is referred to as a distance d. The relation between the image capturing apparatus  500  and the person  540  is approximately the same as the example shown in  FIG. 3A , except that the distance d is different, and thus, description thereof will be omitted. 
       FIG. 16B  schematically illustrates the relation between respective images forming a moving image generated by the image capturing section  111  shown in  FIG. 17  and motion transitions of the person  540 . An image group  550  represents the motion transitions of the person  540  in a state shown in  FIG. 16A , in which respective images forming the image group  550  are arranged in the time axis. An image group  560  represents the respective images forming the moving image generated by the image capturing section  111  in the state shown in  FIG. 16A , in which the respective images forming the image group  560  are arranged in the time axis. Here, the position (position in the time axis) where the impact sound is generated by the golf swing of the person  540  is represented as an impact sound generation position  555 . 
     In this respect, the speed of sound in air is about  340 m/sec. Thus, in a case where the distance d between the image capturing apparatus  500  and the person  540  is relatively long, the time until the impact sound reaches the image capturing apparatus  500  becomes long, and thus, a delay occurs between the time when the impact sound is generated and the time when the impact sound is input to the image capturing apparatus  500 . 
     For example, it is assumed that the position of an image  551  among the images forming the image group  550  shown in  FIG. 16B  is the impact sound generation position  555 . In this case, for example, in a case where the distance d is relatively short (several meters, for example), as indicated by an arrow  552 , the image  551  corresponding to the position where the impact sound is generated and an image  561  generated when the impact sound is input to the image capturing apparatus  500  are approximately the same each other. On the other hand, in the case where the distance d is relatively long (340 m or longer, for example), as indicated by an arrow  553 , the image  551  corresponding to the position where the impact sound is generated and an image  562  generated when the impact sound is input to the image capturing apparatus  500  are different from each other, thereby causing a delay. In this respect, even in the case where the distance d is relatively long, it is likely that an image on a display screen displayed on the display section  191  is viewed at approximately the same angle of view as in the case where the distance d is relatively short. For this reason, it may be difficult to correct the delay of the impact sound by a manual manipulation of a user. Thus, hereinafter, an example in which the delay of the impact sound generated according to the distance between the image capturing apparatus and the target object is corrected is shown. 
     [Configuration Example of Image Capturing Apparatus] 
       FIG. 17  is a block diagram illustrating an example of a functional configuration of an image capturing apparatus  500  according to the second embodiment of the present invention. The image capturing apparatus  500  is different from the image capturing apparatus  100  shown in  FIG. 1  in that an object distance calculating section  510  is added, and a selecting section  520  is installed instead of the selecting section  170 . The configuration other than these components is approximately the same as in the image capturing apparatus  100 . Thus, the same reference numerals are given to common components, and description of a part thereof will be omitted. 
     The object distance calculating section  510  calculates distance (object distance) from the object included in the captured image generated by the image capturing section  111 , and outputs the calculated object distance to the selecting section  520 . For example, the object distance calculating section  510  detects a face of the person included in the captured image generated by the image capturing section  111 , and calculates the object distance of the target object, using the detected face and the imaging information (for example, position of each lens and focus position) at the time of generation of the captured image. For example, a face detection method (for example, see Japanese Unexamined Patent Application Publication No. 2004-133637) through matching of a template in which luminance distribution information of the face is recorded and a content image can be used as the detection method of the face included in the captured image. Further, a face detection method based on a characteristic amount of a flesh-colored portion or a human face included in the captured image can be used. Through such a face detection method, the position and size of the person&#39;s face in the captured image can be calculated. 
     The selecting section  520  estimates the delay time of the impact sound on the basis of the object distance output from the object distance calculating section  510 , and selects the synthesis target images in consideration of the delay time. Specifically, the synthesis target image selection range determining section  171  (shown in  FIG. 2 ) of the selecting section  520  corrects the detection position (position in the time axis) of the specific sound detected by the specific sound detecting section  132 , on the basis of the object distance output from the object distance calculating section  510 . Further, the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the position after correction (corrected position) and the valid sound range set by the valid sound range setting section  160 . The synthesis target image selection range determining section  171  is an example of a delay time calculating section disclosed in the claims. 
     [Calculation Example of Object Distance] 
     Next, a distance calculation method for calculating the distance between the image capturing apparatus  500  and the target object will be described in detail with reference to the drawings. Here, the distance calculation method for estimating the distance between the image capturing apparatus  500  and the face using the size (reference value) of an ordinary human face will be described. 
       FIGS. 18A and 18B  are diagrams schematically illustrating an image capturing range which is an image capturing target by the image capturing section  111  and the captured image displayed on a display section  191 , according to the second embodiment of the present invention.  FIG. 18A  is a diagram schematically illustrating an image capturing range  570  in a case where a person  571  against a golf range is imaged, and  FIG. 18B  is a diagram illustrating a display example of the display section  191  for a captured image  575  corresponding to the image capturing range  570  shown in  FIG. 18A . 
     For example, as shown in  FIG. 18A , in a case where the person  571  is imaged against the golf range as an object, a range (image capturing range  570 ) where the person  571  is imaged is determined according to the position of the image capturing apparatus  500 , the position of a zoom lens or the like. Further, as shown in  FIG. 18B , light incident from the object included in the image capturing range  570  is converted into an captured image by the image capturing section  111 , and the captured image (so-called through image) is displayed on the display section  191 . 
     Here, the width of the image capturing apparatus  500  in the left and right direction is represented as an image capturing range width Wa, and the width of a face  572  of the person  571  included in the image capturing range  570  in the left and right direction is represented as a face width Wref, in the image capturing range  570  shown in  FIG. 18A . The face width Wref corresponds to the size of an ordinary human face, not the actual face width of the person  571 . Further, the width in the left and right direction of the captured image  575  shown in  FIG. 18B  is represented as an image width Ww, and the width of a face  577  of a person  576  included in the captured image  575  in the left and right direction is represented as a face image width Wf. In this case, the ratio of the image capturing range width Wa to the face width Wref is generally the same as ratio of the image width Ww to the face image width Wf. 
       FIG. 19  is a top view schematically illustrating the positional relation between an image capturing range which is an image capturing target by the image capturing section  111  and a captured image displayed on the display section  191 , according to the second embodiment of the present invention. In an example shown  FIG. 19 , the positional relation between the person  571  shown in  FIG. 18A  and an image capturing element  112  and the display section  191  provided in the image capturing apparatus  500  is schematically shown. As shown in  FIG. 19 , the distance from the image capturing apparatus  500  to the face  572  is represented as an object distance Df; the focus distance in the image capturing apparatus  500  is represented as a focus distance f; and the width of the image capturing element  112  is represented as an image capturing element width Wi. The image capturing range width Wa and the face width Wref are the same as those shown in  FIG. 18A . 
     As shown in  FIG. 19 , if the light incident from the object included in the image capturing range  570  enters the image capturing element  112 , the captured image corresponding to the object included in the image capturing range  570  is generated, and then the generated captured image  575  is displayed on the display section  191 . Further, the width of the face on the image capturing element  112  in a case where the light incident from the face  572  of the person  571  enters the image capturing element  112  is a face width Wb on the image capturing element. 
     Here, the following two equations are established from the proportional relation with parallel lines.
 
 Df/W ref= f/Wb    Equation 1
 
 Wf/Ww=Wb/Wi    Equation 2
 
     Here, the equation 1 is changed into Df=f×Wref/Wb, and the equation 2 is changed into Wb=Wf×Wi/Ww. Then, Wb=Wf×Wi/Ww obtained by changing the equation 2 is replaced with the equation 1, to thereby calculate the following equation 3. This equation 3 is calculated on the basis of a basic physical law of a lens.
 
 Df=W ref×( f/Wi )×( Ww/Wf )   Equation 3
 
     Here, Wi (image capturing element width) and Ww (image width) are constant numbers, and the size of an ordinary human face is used as Wref. In this case, as Wf (face image width) is detected, it is possible to calculate Df (estimation distance to the face) using the equation 3. 
     For example, as shown in  FIG. 18A , in a case where the face  572  of one person is included in the image capturing range  570 , the face  577  is detected from the captured image  575  corresponding to the image capturing range  570  by the object distance calculating section  510 . In this way, in a case where the face is detected, the object distance calculating section  510  calculates the object distance Df using the width (face image width) of the detected face on the basis of the equation 3. 
     The second embodiment of the present invention provides an example in which the object distance is calculated using one reference value as the ordinary human face size. Here, the person who becomes the image capturing target may have different face sizes according to the person&#39;s attributes (for example, age and gender). For example, in a case where a child face is compared with an adult face, the face sizes may be different from each other. Further, in a case where a female face is compared with a male face, the face sizes may be different from each other. Thus, a plurality of reference values according to the person&#39;s attributes may be retained in the object distance calculating section  510 . Then, the object distance calculating section  510  may detect the attributes for the face detected from the captured image, and the object distance calculating section  510  may calculate the distance d using the reference value according to the attributes. In order to detect the attributes, for example, a detection method in which the respective attributes are detected by a weak learner using difference values of luminance between two points in the face image can be used (for example, see Japanese Unexamined Patent Application Publication No. 2009-118009). 
     [Correction Example of Delay Time] 
       FIGS. 20A and 20B  are diagrams schematically illustrating a setting method of a valid sound range by means of the valid sound range setting section  160  and a determination method of a synthesis target image selection range by means of the synthesis target image selection range determining section  171 , according to the second embodiment of the present invention. Since this example is a modified example of  FIGS. 5A and 5B , description of a part of common components will be omitted. 
       FIG. 20A  schematically illustrates a moving image  580  generated by the image capturing section  111  in a rectangular shape. Further, it is assumed that the position where the video recording button is pressed is the press position (video recording button press position  581 ) of the video recording button in the time axis of the moving image  580  shown in  FIG. 20A . In this case, the valid sound range setting section  160  sets a valid sound range  582  on the basis of the video recording button press position  581 . Specifically, the valid sound range setting section  160  sets a range, which precedes the video recording button press position  581  by a time L 21  in the time axis, as the valid sound range  582 . Here, for example, the time L 21  can be 1.0 second, in a similar way to the time L 1  shown in  FIG. 5A . Further, the time L 21  may be longer than the time L 1 , and may be changed according to the size of the object distance calculated by the object distance calculating section  510 . 
       FIG. 20B  schematically illustrates a determination method of the synthesis target image selection range in a case where the impact sound is detected in the valid sound range  582  set by the valid sound range setting section  160 . In  FIG. 20B , the position (position in the time axis) where the impact sound is detected by the specific sound detecting section  132  is represented as an impact sound detection position  583 . 
     In the second embodiment of the present invention, before determination of whether the impact sound is detected in the valid sound range  582 , the synthesis target image selection range determining section  171  estimates the delay time of the sound on the basis of the object distance d(m) estimated by the object distance calculating section  510 . Specifically, the synthesis target image selection range determining section  171  estimates the delay time of the sound on the basis of the object distance d(m) estimated by the object distance calculating section  510 . As described above, since the speed of sound is 340 (m/s), the time×(sec) until the impact sound reaches the image capturing apparatus  500  can be calculated using the following equation 4.
 
 x=d/ 340   Equation 4
 
     The synthesis target image selection range determining section  171  moves the impact sound detection position  583  in the time axis by the time x calculated using the equation 4. The position after the movement is represented as a correction position  584 . 
     Subsequently, the synthesis target image selection range determining section  171  determines whether the correction position  584  is included in the valid sound range  582  set by the valid sound range setting section  160 . As shown in  FIG. 20B , in a case where the correction position  584  is included in the valid sound range  582  set by the valid sound range setting section  160 , the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the correction position  584 . That is, the synthesis target image selection range determining section  171  determines a predetermined range before and after the correction position  584  in the time axis with reference to the correction position  584 , as a synthesis target image selection range  585 . Specifically, the synthesis target image selection range determining section  171  determines a range L 24 , which includes a range which precedes the correction position  584  by a time L 22  and a range which exceeds the correction position  584  by a time L 23  in the time axis, as the synthesis target image selection range  585 . 
     Here, the times L 22  to L 24  may be the same values as the times L 2  to L 4  shown in  FIG. 5B , for example. Further, the time L 24  may be longer than the time L 4 , and may be changed according to the size of the object distance calculated by the object distance calculating section  510 . 
     Further, for example, in a case where the distance between the image capturing apparatus  500  and the person  540  is relatively distant, a timer setting can be performed by a remote controller manipulation. Thus, in a case where the valid sound range is set on the basis of the count value of the timer set by the timer setting section  150  and the synthesis target image selection range is determined using the valid sound range, similarly, the delay time of the sound may be estimated and the correction may be performed on the basis of the delay time. 
     In this way, even in the case where the distance between the image capturing apparatus  500  and the person  540  is relatively distant, the detection position of the impact sound is corrected to determine the synthesis target image selection range on the basis of the position after correction. Thus, it is possible to determine an appropriate synthesis target image selection range. 
     Here, the correction position may not exist in the valid sound range  582  set by the valid sound range setting section  160 . In this case, in a similar way to the example in  FIG. 5C , the impact sound is not used. Further, in a case where the impact sound is not used, as shown in  FIG. 5C , the synthesis target image selection range can be determined on the basis of the press position of the video recording button. 
     In  FIGS. 18A, 18B  and  FIG. 19 , an example where the object distance is calculated using the size of the person&#39;s face is shown, but as shown in  FIG. 21 , the object distance may be calculated by the size of portions other than the face. 
     [Calculation Example of Object Distance] 
       FIG. 21  is a diagram illustrating a display example in the display section  191  according to the second embodiment of the present invention. Manipulation support images  592  and  593  for arranging a person  591  who performs a golf swing in an appropriate position are displayed to be overlapped on a captured image, in a display screen  590  shown in  FIG. 21 . This example is a modified example of the calculation method of the object distance shown in  FIGS. 18A and 18B  and  FIG. 19 , and is an example in which the object distance is calculated on the basis of the size (length in the vertical direction) of a region occupied by the object in the display screen  590 . 
     The manipulation support images  592  and  593  represent recommendation regions in which the person  591  who performs the golf swing is to be arranged in the display screen  590 . The manipulation support image  592  is indicated by a black line in the display screen  590  and represents the recommendation region of the person  591  who performs the golf swing in the left and right direction. Further, the manipulation support image  593  is indicated by a dotted black frame in the display screen  590  and represents the recommendation region of the person  591  who performs the golf swing in the up and down direction. Here, the recommendation region in the up and down direction specified by the manipulation support image  593  can be a value H 11  of a predetermined ratio (for example, 70%) of the length of the display screen  590  in the vertical direction. 
     For example, in a case where photographing is performed by setting the synthetic image recording mode using the image capturing apparatus  500 , a photographer confirms the manipulation support images  592  and  593  included in the display screen  590  and performs an adjustment so that the person of the target object is included in the manipulation support images  592  and  593 . Further, in a case where a zoom manipulation or the like is performed, similarly, the photographer performs an adjustment so that the person of the target object is included in the manipulation support images  592  and  593 . 
     In this way, by applying the object distance calculation method for calculating the object distance on the basis of the reference value relating to the face as described above and the size of the face included in the captured image, it is possible to calculate the object distance. That is, since the size of the person included in the captured image can be the predetermined value H 11  in the example shown in  FIG. 21 , the object distance can be calculated on the basis of the reference value (for example, 170 cm) relating to an ordinary height of the person who plays golf and the predetermined value H 11 . 
     In the examples shown in  FIGS. 18A, 18B ,  FIG. 19 , and  FIG. 21 , the object distance is calculated using the size of each portion of the person, but other object distance calculation methods may be used. For example, a depth map relating to the captured image may be generated and the object distance may be calculated using the depth map. Further, a distance measurement sensor may be installed in the image capturing apparatus  500  and the object distance measured by the distance measurement sensor may be used. Furthermore, the object distance may be calculated using focus position information. 
     Further, any one of the object distance calculation method using the focus position information and the object distance calculation method using the zoom position information may be selected for use according to photographing situations. For example, in a case where a focus is formed in a zoom position of a wide edge, it is likely that the focus position information has a higher accuracy than the zoom position information. For this reason, in a case where the focus is formed in the zoom position of the wide edge, the object distance calculation method using the focus position information can be selected. Further, the object distance may be estimated by a specific method, and it may be determined whether to use the estimation result or to perform re-estimation by other methods with reference to the estimation result. 
     [Operation Example of Image Capturing Apparatus] 
       FIG. 22  is a flowchart illustrating an example of a process procedure of a synthetic image generation process by means of the image capturing apparatus  500  according to the second embodiment of the present invention. This example is a modified example of the process procedure of the synthetic image generation process shown in  FIG. 14 , in which step S 921  is added and a process procedure of steps S 922  and S 923  is performed instead of step S 910 . Thus, the same reference numerals are given to the same process procedure as shown in  FIG. 14 , and description thereof will be omitted. 
     After a buffering termination process is performed (step S 908 ), the object distance calculating section  510  calculates the object distance (step S 921 ). 
     Further, in a case where the impact sound is detected in the set valid sound range (step S 909 ), the synthesis target image selection range determining section  171  corrects the impact sound detection position on the basis of the calculated object distance (step S 922 ). Specifically, the synthesis target image selection range determining section  171  calculates the delay time on the basis of the object distance, and subtracts the count value supplied from the counter section  174  by the calculated delay time to calculate a correction value. Then, the synthesis target image selection range determining section  171  specifies a position after correction of the impact sound detection position on the basis of the correction value. For example, as shown in  FIG. 20B , the impact sound detection position  583  is moved by the correction value x to calculate the correction position  584 . 
     Subsequently, the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the position after correction (correction position) (step S 923 ). For example, as shown in  FIG. 20B , the synthesis target image selection range  585  is determined on the basis of the correction position  584 . 
     In this way, according to the second embodiment of the present invention, it is possible to detect the generation position of the impact sound with a high accuracy, without relying on the change in the distance between the image capturing apparatus  500  and the target object due to the zoom manipulation. Thus, it is possible to generate the synthetic image having a high visibility, without relying on the change in the distance between the image capturing apparatus  500  and the target object due to the zoom manipulation. Further, since the manual work of the user is unnecessary, it is possible to reduce the user&#39;s inconvenience. 
     Further, for example, in a case where the captured images generated by the image capturing section  111  are recorded as the image contents, when the metadata is recorded in relation to the image contents, it is possible to record the impact sound detection position after correction. Thus, since the impact sound detection position after correction can be used in a case where the image file is reproduced, it is possible to detect the correct generation position of the impact sound. Further, for example, in a case where a list of the image contents is displayed, a frame corresponding to the impact sound detection position after correction can be used as a representative thumbnail. 
     3. Third Embodiment 
     The first and second embodiments of the present invention mainly provide the examples in which the motion transitions of the person who performs the golf swing are generated as the synthetic image. Here, for example, in the case of sport other than golf such as a ball hitting game or an object collision game, a characteristic sound is generated at the moment when a player hits a ball or objects collide with each other. Further, for example, in the case of fireworks, an explosion sound is generated at a splendidly exploding moment. As the synthesis target image selection range is determined using these specific sounds, an appropriate synthetic image can be generated. In this respect, the third embodiment of the present invention provides an example in which such a synthetic image is easily generated according to the user&#39;s preference. 
     [Configuration Example of Image Capturing Apparatus] 
       FIG. 23  is a block diagram illustrating an example of a functional configuration of an image capturing apparatus  600  according to the third embodiment of the present invention. The image capturing apparatus  600  is different from the image capturing apparatus  500  shown in  FIG. 17  in that a target object information storing section  610  is added and a part of other components are modified. That is, the image capturing apparatus  600  is provided with a specific sound detecting section  620 , a valid sound range setting section  630  and a selecting section  640 , instead of the specific detecting section  132 , the valid sound range setting section  160  and the selecting section  520  in the image capturing apparatus  500 . The configuration other than these components is approximately the same as the image capturing apparatus  500 . Thus, the same reference numerals are given to common components, and description of a part thereof will be omitted. 
     Hereinafter, an example of conditions (a first condition and a second condition, for example) of a specific motion (for example, sport or the like) suitable for the selection process of the synthesis target image according to the embodiments of the present invention will be described. The first condition is that a body portion of a target object basically exists in the same position throughout overall motions. Further, the second condition is that a rapid motion involving an impact sound exists among a series of motions. As an example of sport, other than golf, satisfying these conditions, batting of baseball, a tennis serve, breaking of roof tiles or the like can be exemplified. Further, an object such as fireworks, other than sport, can be exemplified. Thus, the third embodiment of the present invention provides an example in which such an object or sport becomes a target object. 
     The target object information storing section  610  stores information about specific sounds and valid sound ranges with respect to specific motions of a plurality of types of target objects, and supplies the respective stored information to the specific sound detecting section  620 , the valid sound range setting section  630  and the selecting section  640 . The stored contents of the target object information storing section  610  will be described in detail with reference to  FIG. 24 . The target object information storing section  610  is an example of a storing section disclosed in the claims. 
     The specific sound detecting section  620  detects a specific sound on the basis of sounds output from the sound input section  131 , and outputs, in a case where the specific sound is detected, the fact to the selecting section  640 . Further, the specific sound detecting section  620  detects a sound of a specific value or higher relating to tennis (service) and roof tile breaking. In this respect, the third embodiment of the present invention provides an example in which each impact sound shown in an impact sound  611  in  FIG. 24 , in addition to an impact sound relating to the golf swing, becomes a specific sound. For example, in baseball (batting) and tennis (service), a sound generated at the moment when a bat or a racket comes in contact with a ball in motion becomes the impact sound. Further, for example, in roof tile breaking, a sound generated at the moment when a hand comes in contact with roof tiles in motion becomes the impact sound. In addition, in fireworks, a sound generated at the moment when fireworks explode in the sky becomes the impact sound. In order to detect these sounds, the specific sound detection method according to the first embodiment of the present invention can be used. 
     Further, the specific sound detecting section  620 , the valid sound range setting section  630  and the selecting section  640  acquires target object information on a specific motion designated by a user manipulation from the target object information storing section  610 , among the specific motions of the plurality of types of target objects. Then, the specific sound detecting section  620 , the valid sound range setting section  630  and the selecting section  640  perform respective processes using the acquired target object information. In these respective processes, this example is approximately the same as the examples shown in the first and second embodiments of the present invention except that the value of the impact sound and the valid sound range or the like is different, and thus description thereof will be omitted. 
     [Storage Example of Target Object Information Storing Section] 
       FIG. 24  is a diagram illustrating an example of the stored contents of the target object information storing section  610  according to the third embodiment of the present invention. In the target object information storing section  610  are stored the impact sound  611 , a high speed motion range  612 , a valid sound range  613  and a synthesis target image selection range  614 . 
     Specific sound identification information (reference data) for detecting a specific sound (impact sound) by the specific sound detecting section  620  is stored in the impact sound  611 . The impact sound  611  shown in  FIG. 24  discloses only words indicating a corresponding specific sound. 
     In the high speed motion range  612  is stored a range with intervals closer than other intervals for selection of synthesis target images, in the synthesis target image selection range. For example, in a case where the specific motion due to the target object is baseball (batting), it may be considered that the motion transitions around the moment when a baseball bat comes in contact with a ball are minutely confirmed. Thus, in the synthesis target image selection range, a high speed motion range in which intervals of the images around the moment may be closer than other intervals for selection of the synthesis target images is set. In this high speed motion range, a predetermined range around the impact sound is set, for example. 
     The valid sound range  613  stores the valid sound range which becomes the setting target by the valid sound range setting section  630 . The third embodiment of the present invention provides an example in which the press manipulation of the video recording button is used as the photographing trigger. In a similar way to the examples shown in the first and second embodiments of the present invention, in the golf and baseball (batting), the photographing trigger may be generated after the motion which is the target is terminated. In the case of the fireworks, the photographing trigger may be generated at the moment when fireworks are exploded in the sky. Further, in a similar way to the examples shown in the first and second embodiments of the present invention, in the golf, baseball (batting) and fireworks, a specific range before the photographing trigger may be set as the valid sound range. 
     In addition, in the case of tennis (service), the photographing trigger may be generated at the moment when a player turns up for a predetermined time. In the roof tile breaking, the photographing trigger may be generated at the moment when the face of a person who breaks the roof tiles is full of fighting spirit. Further, in the tennis (service) and roof tile breaking, a specific range before a sound of a specific value or higher is initially detected from the photographing trigger can be set as the valid sound range. In this way, in the case of the tennis (service) and roof tile breaking, a rear edge of the valid sound range is set corresponding to the time when the sound of the specific value or higher is detected. However, in a case where the sound is not detected over a predetermined time, the sound detection may become invalid, and then a new valid sound range may be set. For this new valid sound range, the photographing trigger is newly generated. Accordingly, it is possible to reduce a false detection of an impact sound. In this respect, the sound of the specific value or higher in the tennis (service) and roof tile breaking is detected by the specific sound detecting section  620 . 
     In the synthesis target image selection range  614  is stored a synthesis target image selection range determined by the synthesis target image selection range determining section  171 . The third embodiment of the present invention provides an example in which a specific range with reference to the impact sound detected in the valid sound range is set as the synthesis target image selection range. 
     [Display Example of Designation Screen of Target Object] 
       FIG. 25  is a diagram illustrating a display example of (display screen  660 ) of the display section  191  according to the third embodiment of the present invention. The display screen  660  is provided with a golf (swing) button  661 , a baseball (batting) button  662 , a tennis (service) button  663 , a roof tile breaking button  664  and a firework button  665 . Further, the display screen  660  is provided with a return button  666  and a determination button  667 . 
     The golf (swing) button  661 , the baseball (batting) button  662 , the tennis (service) button  663 , the roof tile breaking button  664  and the firework button  665  are pressed to designate the sport type which is a target when a synthetic image is generated for motion transitions. For example, in a case where the display section  191  is made of a touch panel, the designation can be performed by a press manipulation of a desired button. 
     The determination button  667  is pressed to determine the designation after the press manipulation for designating the sport type which is the target of the synthetic image. Through this press, the synthesis target image recording mode is set. 
     The return button  666  is pressed to return to the display screen displayed right before, for example. 
     For example, in the display screen  660 , in a case where a desired button (for example, the tennis (service) button  663 ) is pressed and the determination button  667  is pressed, a manipulation signal indicating the fact is output from the manipulation receiving section  140  to the respective sections. Then, the specific sound detecting section  620 , the valid sound range setting section  630  and the selecting section  640  acquire target object information (target object information about the tennis (service), for example) of the designated sport type from the target object information storing section  610 . Then, the specific sound detecting section  620 , the valid sound range setting section  630  and the selecting section  640  perform the respective processes using the acquired target object information. 
     [Synthetic Image Example] 
       FIGS. 26A and 26B  are diagrams illustrating an example of a synthetic image generated by the layer processing section  180  according to the third embodiment of the present invention. 
       FIG. 26A  illustrates a synthetic image  671  in a case where a person who performs baseball batting is imaged. That is, the synthetic image  671  is a synthetic image generated using a moving image obtained by the image capturing operation started after the baseball (batting) button  662  shown in  FIG. 25  is pressed and the determination button  667  is pressed. 
       FIG. 26B  illustrates a synthetic image  672  in a case where a person who performs tennis service is imaged. That is, the synthetic image  672  is a synthetic image generated using a moving image obtained by the image capturing operation started after the tennis (service) button  663  shown in  FIG. 25  is pressed and the determination button  667  is pressed. 
     In this way, during specific motions other than a golf swing, a time span in which an impact sound which becomes the detection target can exist is set as the valid sound range, and thus, it is possible to reduce a false detection of sounds other than the impact sound which becomes the detection target. Thus, in a case where a synthetic image using an extremely fast motion causing the impact sound as a target is generated, it is possible to detect the generation position of the impact sound with a high degree of accuracy. Further, it is possible to generate the synthetic image with the emphasis around the accurate generation position of the impact sound, and to generate the synthetic image having a high visibility. In this case, since a manual work of the user is unnecessary for the detection of the generation position of the impact sound, it is possible to reduce user&#39;s inconvenience. As the synthetic image is generated in this way, even a beginner who is not accustomed to the handling of the image capturing apparatus can easily generate an appropriate synthetic image according to the user&#39;s preference. 
     4. Fourth Embodiment 
     The first to third embodiments of the present invention provide the examples in which the image capturing operation is performed by the image capturing apparatus and the synthetic image is generated using the impact sound generated at the time of the image capturing operation. Here, in the case of generating the synthetic image for the contents (for example, moving image contents) recorded by the image capturing apparatus, the synthetic image may be generated using the impact sound included in the contents. Further, for example, in the case of a golf game, a characteristic sound may be generated other than the impact sound, such as a great cheer of spectators after a golf swing. For this reason, the valid sound range may be set using the characteristic sound as a trigger, instead of the press manipulation of the video recording button or the timer setting. Thus, the fourth embodiment of the present invention provides an example in which the valid sound range is set using the characteristic sound instead of the press manipulation of the video recording button or the timer setting, and the synthetic image is generated for the moving image contents recorded by the image capturing apparatus. 
     [Configuration Example of Image Processing Apparatus] 
       FIG. 27  is a block diagram illustrating an example of a functional configuration of an image processing apparatus  700  according to the fourth embodiment of the present invention. The image processing apparatus  700  is different from the image capturing apparatus  600  shown in  FIG. 23  in that the sound input section  131  and the timer setting section  150  are omitted and some other components are modified. That is, the image capturing apparatus  700  is provided with a target object information storing section  710 , an input section  720  and an object information generating section  730 , instead of the target object information storing section  610 , the image capturing section  111  and the object information generating section  120  in the image capturing apparatus  600 . Further, the image capturing apparatus  700  is provided with a specific sound detecting section  740 , a valid sound range setting section  750  and a selecting section  760 , instead of a specific sound detecting section  620 , the valid sound range setting section  630  and the selecting section  640  in the image capturing apparatus  600 . The configuration other then these components is approximately the same as in the image capturing apparatus  600 . Thus, the same reference numerals are given to common components, and description of a part thereof will be omitted. 
     The target object information storing section  710  stores information about specific sounds or valid sound ranges for specific motions of a plurality of types of target objects, and supplies the respective stored information to the specific sound detecting section  740 , the valid sound range setting section  750  and the selecting section  760 . The storing contents of the target object information storing section  710  will be described in detail with reference to  FIG. 28 . 
     The input section  720  is an input section, through which the image contents (for example, moving image files) recorded by the image capturing apparatus such as a digital video camera are input. It is assumed that the image contents are contents in which metadata (for example, sound information, zoom information or focus position information) relating to respective frames at the time of the image capturing operation of moving images or continuous still images is recorded in relation to the respective frames, for example. The input section  720  supplies respective images (frames) for forming the input image contents to the captured image retaining section  115 , the display control section  190  and the specific sound detecting section  740 , at a predetermined interval. Further, the input section  720  outputs the respective images for forming the input image contents and attribute information (for example, lens position and focus position) about the images to the object distance calculating section  510  and the object information generating section  730 . 
     The object information generating section  730  generates object information about the respective images on the basis of the respective images supplied from the input section  720  and the attribute information about the images. Further, the object information generating section  730  supplies the generated object information to the captured image retaining section  115  to retain the object information therein, and also supplies the object information to the valid sound range setting section  750  and the selecting section  760 . As the object information, for example, information for detecting a specific change in the time axis between the respective images is generated, in addition to information for discerning a region of the target object and a background region thereof. For example, a face included in the image is detected, and attribute information about an expression, direction or the like of the face is generated. For example, an attribute such as delight, anger, sorrow or expression of pleasure, strain, face direction, mouth expression (opening/closing), eye expression (for example, wink) or the like may be detected, and the attribute information may be generated on the basis of the detection result. As the attribute detection method, for example, an identification method based on the characteristic amount extracted from the face image relating to the attribute which becomes the detection target can be used. That is, the characteristic amount extracted from the face image relating to the attribute which becomes the detection target is stored in advance as an identification dictionary. Further, the characteristic amount is extracted from the face image including the detected face, and the extracted characteristic amount is compared with the characteristic amount included in the identification dictionary, to thereby calculate the similarity between these characteristic amounts. In addition, in a case where the calculated similarity exceeds a threshold value, it is determined that the detected face is an attribute corresponding to the identification dictionary which becomes the calculation target of the similarity which exceeds the threshold value. Furthermore, for example, the above-described attribute detection method may be used (for example, refer to Japanese Unexamined Patent Application Publication No. 2009-118009). 
     The valid sound range setting section  750  detects a specific change in the time axis between the respective images, on the basis of the attribute information generated in this way. As this specific change, for example, a face change can be detected. For example, the change in expression at the time of delight, anger, sorrow, pleasure or strain, the change in the face direction, for example, in a case where the face direction is changed to the front side from below, the change at the time of opening or closing the mouth, or the change in eyes at the time of wink can be detected as a face change. Further, a case where the person&#39;s face comes on the screen or the person&#39;s face goes out of the screen may be detected as the specific change in the time axis between the respective images. Further, as information for detecting the specific change in the time axis between the respective images, brightness information indicating the brightness of the entire image and luminance value distribution information indicating a distribution state of luminance values in the image may be generated. Then, a specific change in the information may be detected as the specific change in the time axis between the respective images. 
     The specific sound detecting section  740  detects the specific sound on the basis of the sound included in the image contents supplied from the input section  720 , and then outputs, in a case where the specific sound is detected, the fact to the valid sound range setting section  750  and the selecting section  760 . The impact sound which becomes the detection target by the specific sound detecting section  740  is the same as in the third embodiment of the present invention. Further, in the fourth embodiment of the present invention, when the specific change in the time axis between the respective images is detected, the specific sound detected by the specific sound detecting section  740  is used. For example, great cheers (wild applauses) of spectators in a case where a golf or baseball game is held, or a shout at the moment when fighting spirit is put into roof tile breaking is detected as the specific sound. Further, for example, a whistling sound of a piper or a splash sound of the water (for example, in a case where the target object relates to the water) may be detected as the specific sound. Further, the valid sound range setting section  750  detects the change in the specific sound as the specific change in the time axis between the respective images. For example, the time when the great cheers are detected from a state where the sound barely exists, or the time when the sound barely exists from the state where the great cheers are detected, can be detected as the specific change in the time axis between the respective images. As the specific sound detection method, the specific sound detection method shown in the first embodiment of the present invention can be applied. That is, the valid sound range setting section  750  can detect the specific change using at least one of the characteristic amount extracted from the respective images and the characteristic amount extracted on the basis of the sound in relation to the respective images. The valid sound range setting section  750  is an example of a specific change detecting section disclosed in the claims. 
     The specific sound detecting section  740 , the valid sound range setting section  750  and the selecting section  760  acquire target object information about the specific motion designated by the user manipulation among the specific motions of the plurality of types of target objects, from the target object information storing section  710 . Further, the specific sound detecting section  740 , the valid sound range setting section  750  and the selecting section  760  perform the respective processes using the acquired target object information. The respective processes are approximately the same as the examples as shown in the first to third embodiments of the present invention, except that the trigger when the impact sound is set, the impact sound, the value of the valid sound range and the like are different, and thus, description thereof will be omitted. 
     [Storage Example of Target Object Information Storing Section] 
       FIG. 28  is a diagram illustrating an example of stored contents of the target object information storing section  710  according to the fourth embodiment of the present invention. In the target object information storing section  710  are stored an impact sound  711 , a high speed motion range  712 , a trigger  713  for determining a valid sound range, a valid sound range  714  and a synthesis target image selection range  715 . The impact sound  711 , the high speed motion range  712  and the synthesis target image selection range  715  are approximately the same as the impact sound  611 , the high speed motion range  612  and the synthesis target image selection range  614  shown in  FIG. 24 , and thus, description thereof will be omitted. 
     The trigger  713  for determining the valid sound range stores a trigger when the valid sound range is set by the valid sound range setting section  750 . For example, in the case of golf and baseball (batting), the trigger may be generated at the moment when the great cheer of spectators is detected in the contents input from the input section  720 . The detection of the great cheer of spectators is performed by the valid sound range setting section  750  on the basis of the specific sound detected by the specific sound detecting section  740 . Further, in the case of fireworks, the trigger may be generated at the moment when a dark state in the screen is transited to a bright state in the contents input from the input section  720 . The detection of the moment when the dark state in the screen is transited to the bright state is performed by the valid sound range setting section  750 , on the basis of the attribute information generated by the object information generating section  730 . Further, in the case of tennis (service), the trigger may be generated at the moment when a player turns up for a predetermined time in the contents input from the input section  720 . The detection of the moment when the player turns up for the predetermined time is performed by the valid sound range setting section  750 , on the basis of the attribute information generated by the object information generating section  730 . Further, in the case of roof tile breaking, the trigger may be generated at the moment when the face of a person who performs roof tile breaking is full of fighting spirit in the contents input from the input section  720 . The detection of the moment when the face of a person who performs roof tile breaking is full of fighting spirit is performed by the valid sound range setting section  750 , on the basis of the attribute information generated by the object information generating section  730  or the specific sound detected by the specific sound detecting section  740 . 
     The valid sound range  714  stores the valid sound range which becomes the setting target by the valid sound range setting section  750 . The fourth embodiment of the present invention provides an example in which the detection time of the specific change stored in the trigger  713  for determining the valid sound range is the trigger of the valid sound range. This valid sound range is approximately the same as the valid sound range  613  shown in  FIG. 24 , except that the detection time of the specific change stored in the trigger  713  for determining the valid sound range is the trigger of the valid sound range, and thus, description thereof will be omitted. 
     [Determination Example of Synthesis Target Image Selection Range] 
       FIGS. 29A and 29B  are diagrams schematically illustrating a setting method of a valid sound range by means of the valid sound range setting section  750  and a determination method of a synthesis target image selection range by means of the synthesis target image selection range determining section  171 , according to the fourth embodiment of the present invention. This is an example in which the synthesis target image selection range is determined in a case where the baseball (batting) shown in  FIG. 28  is designated. Further, this example is a modified example in  FIGS. 5A and 5B , and thus, description of a part of common components will be omitted. 
       FIG. 29A  schematically illustrates a moving image  800  input through the input section  720  in a rectangular shape. The moving image  800  is a moving image in which the appearance of a baseball game is recorded, for example. Further, in respective images for forming the moving image  800 , the position where the great cheer of spectators is detected by the specific sound detecting section  740  is represented as a great cheer detecting position  801  in the time axis of the moving image  800  shown in  FIG. 29A . In this case, the valid sound range setting section  750  sets a valid sound range  802  on the basis of the great cheer detection position  801 . Specifically, the valid sound range setting section  750  sets a range, which precedes the great cheer detection position  801  by a time L 31  in the time axis, as the valid sound range  802 . Here, the time L 31  can be 1.0 second, in a similar way to the time L 1  shown in  FIG. 5A , for example. Further, the time L 31  may be longer than the time L 1 . 
     For example, it is considered that a generation position of the impact sound when a player has a great shot in a golf tournament occurs prior to the great cheer of spectators. Thus, the valid sound range is set (in a preceding position in the time axis) prior to the great cheer of spectators, thereby making it possible to appropriately detect the impact sound. 
       FIG. 29B  schematically illustrates a determination method of the synthesis target image selection range in a case where the impact sound is detected in the valid sound range  802  set by the valid sound range setting section  750 . In  FIG. 29B , the position (position in the time axis) where the impact sound is detected by the specific sound detecting section  740  is represented as an impact sound detection position  803 . 
     For example, the synthesis target image selection range determining section  171  determines whether the impact sound detection position  803  is included in the valid sound range  802  set by the valid sound range setting section  750 . As shown in  FIG. 29B , in a case where the impact sound detection position  803  is included in the valid sound range  802 , the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the impact sound detection position  803 . That is, the synthesis target image selection range determining section  171  determines a specific range before and after the impact sound detection position  803  in the time axis with reference to the impact sound detection position  803  as a synthesis target image selection range  804 . Specifically, a range L 34 , which includes a range which precedes with reference to the impact sound detection position  803  by a time L 32  in the time axis and a range which exceeds the impact sound detection position  803  by a time L 33 , is determined as the synthesis target image selection range  804 . 
     Here, the times L 32  to L 34  may be the same values as the times L 2  to L 4  shown in  FIG. 5B , for example. Further, the time L 34  may be longer than the time L 4 . 
       FIGS. 30A and 30B  are diagrams schematically illustrating a setting method of a valid sound range by means of the valid sound range setting section  750  and a determination method of a synthesis target image selection range by means of the synthesis target image selection range determining section  171 , according to the fourth embodiment of the present invention. This is an example in which the synthesis target image selection range is determined in a case where the tennis (service) in  FIG. 28  is designated. Further, this example is a modified example shown in  FIGS. 5A and 5B , and thus, description of a part of common components will be omitted. 
       FIG. 30A  schematically illustrates a moving image  810  input through the input section  720  in a rectangular shape. The moving image  810  is a moving image in which the appearance of a tennis game is recorded, for example. Further, in respective images for forming the moving image  810 , the position where it is detected by the object information generating section  730  that a face of a tennis player turns up for a predetermined time or longer is represented as a face turn-up state detection position  811  of the moving image  800  in the time axis. Further, the position (position in the time axis) where a sound of a specific value or higher is detected by the specific sound detecting section  740  is represented as a sound detection position  812  of a specific value or higher. In this case, the valid sound range setting section  750  sets a valid sound range  813  on the basis of the face turn-up state detection position  811  and the sound detection position  812  of the specific value or higher. Specifically, the valid sound range setting section  750  sets the valid sound range  813  (time L 41 ) in the time axis with reference to the face turn-up state detection position  811  and the sound detection position  812  of the specific value or higher. Here, the time L 41  is a range where the face turn-up state detection position  811  is a start point and the sound detection position  812  of the specific value or higher is an end point, for example. 
     In this respect, in the end point of the valid sound range relating to tennis (service), the detection of the sound of the specific value or higher is a setting condition. Here, in a case where the sound of the specific value or higher is not detected from the start point of the valid sound range for a predetermined time or longer, the valid sound range setting section  750  makes invalid the valid sound range relating to the start point, and may wait for a new trigger for determining the valid sound range. Thus, a false detection of the impact sound can be reduced. Further, the end point of the valid sound range relating to the roof tile breaking can be similarly applied. 
       FIG. 30B  schematically illustrates a determination method of a synthesis target image selection range in a case where the impact sound is detected in the valid sound range  813  set by the valid sound range setting section  750 . In  FIG. 30B , the position (position in the time axis) where the impact sound is detected by the specific sound detecting section  740  is represented as an impact sound detection position  814 . 
     For example, the synthesis target image selection range determining section  171  determines whether the impact sound detection position  814  is included in the valid sound range  813  set by the valid sound range setting section  750 . As shown in  FIG. 30B , in a case where the impact sound detection position  814  is included in the valid sound range  813 , the synthesis target image selection range determining section  171  determines the synthesis target image selection range on the basis of the impact sound detection position  814 . That is, the synthesis target image selection range determining section  171  determines a specific range before and after the impact sound detection position  814  in the time axis with reference to the impact sound detection position  814  as a synthesis target image selection range  815 . Specifically, a range L 44 , which includes a range which precedes the impact sound detection position  814  by a time L 42  in the time axis and a range which exceeds the impact sound detection position  814  by a time L 43 , is determined as the synthesis target image selection range  815 . 
     Here, as shown in  FIG. 28 , the time L 42  can be 2.5 seconds, for example; and the time L 43  can be 0.5 seconds, for example. That is, the time L 44  can be 3.0 seconds. The setting contents of the times L 42  to L 44  may be changed according to user&#39;s preference. 
     Further, in the examples shown in  FIGS. 29A, 29B  and  FIGS. 30A and 30B , before determination of whether the impact sound is detected in the valid sound range as shown in the second embodiment of the present invention, the delay time of the sound may be estimated, and the impact sound detection position may be corrected on the basis of the estimation result. In this way, the detection position of the impact sound is corrected, thereby making it possible to determine the synthesis target image selection range on the basis of the position after correction. Further, in the specific sound (for example, great cheer of spectators) which is the trigger of the valid sound range, the sound delay time may be estimated, and the detection position may be corrected on the basis of the estimation result. For example, in a case where the specific sound is the great cheer of spectators, the object distance to the background of the target object is calculated using metadata (for example, zoom information or focus position information) relating to respective frames, and the delay time of the great cheer of spectators can be estimated on the basis of the object distance. Thus, even in the moving image contents in which the target object which is relatively distant becomes an image capturing target by a zoom function, an appropriate synthesis target image selection range can be also determined. 
     Further, in the examples shown in  FIGS. 29A and 29B  and  FIGS. 30A and 30B , the impact sound may not be detected in the valid sound range set by the valid sound range setting section  750 . In this case, a synthetic image is not generated using the impact sound, and the next synthetic image process may be performed. 
     In this way, with respect to the image contents recorded by the image capturing apparatus such as a digital video camera or the like, the valid sound range can be set using the specific change in the time axis between the respective images. Thus, in a case where the synthetic image in which an extremely fast motion causing the impact sound is a target is generated, it is possible to detect the generation position of the impact sound without pressing the video recording button or the like with a high level of accuracy. Further, it is possible to generate the synthetic image with the emphasis around the accurate generation position of the impact sound, and to generate the synthetic image having high visibility. Further, since manual work of the user is also unnecessary for the detection of the generation position of the impact sound, it is possible to reduce inconvenience for the user. As the synthetic image is generated in this way, even a beginner who is not accustomed to the handling of the image capturing apparatus can easily generate an appropriate synthetic image according to the user&#39;s preference. 
     The setting method for setting the valid sound range using the specific change in the time axis between the respective images may be employed to the image capturing apparatus shown in the first to the third embodiments of the present invention. 
     Further, in the embodiments of the present invention, the synthesis target images selected by the synthesis target image selecting section  172  are used for the generation process of the synthetic image as the still image. Here, for example, the selected synthesis target images may be used for the synthetic image generation process in which the process of generating the synthetic image is displayed as a moving image. Further, the selected synthesis target images may be used as the synthesis targets, and also, may be used as a plurality of images (for example, images used in a slide-show) indicating transitions of the specific motion. 
     The present embodiments can be applied to image processing apparatuses such as a mobile phone with an imaging function, personal computer, video system, editing apparatus or the like. Further, the process procedures in the present embodiments of the present invention may be also provided in a process program. 
     The embodiments of the present invention exemplify examples for realizing the present invention. Here, as obviously seen in the embodiments of the present invention, the disclosures in the embodiments of the present invention correspond to the disclosures in the claims, respectively. Similarly, the disclosures in the claims correspond to the disclosures in the embodiments of the present invention having the same reference numerals, respectively. Here, the present invention is not limited to the embodiments, may be variously modified within the range without departing from the spirit of the present invention. 
     Further, the process procedures described in the embodiments of the present invention may be provided as a method having the series of procedures. Further, the process procedures may be provided as a program for allowing the series of procedures to be executed on a computer and a recording medium which records the program. A CD (Compact Disc), MD (MiniDisc), DVD (Digital Versatile Disc), memory card, Blu-ray Disc (registered trademark) or the like may be used as this recording medium. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.