Patent Publication Number: US-11047980-B2

Title: Distance measurement device, control method for distance measurement, and control program for distance measurement

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of International Application No. PCT/JP2016/063582, filed May 2, 2016, the disclosure of which is incorporated herein by reference in its entirety. Further, this application claims priority from Japanese Patent Application No. 2015-171421 filed Aug. 31, 2015, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     A technology of the present disclosure relates to a distance measurement device, a control method for distance measurement, and a control program for distance measurement. 
     2. Description of the Related Art 
     Initially, in the present specification, distance measurement means that a distance to a subject which is a measurement target from a distance measurement device is measured. In the present specification, a captured image means an image acquired by imaging the subject by an imaging unit that images the subject. In the present specification, irradiation-position pixel coordinates mean two-dimensional coordinates as two-dimensional coordinates for specifying a position of a pixel, among pixels included in the captured image, which corresponds to an irradiation position of directional light in a real space by the distance measurement device on the assumption that distance measurement is performed by using the distance measurement device that performs the distance measurement based on a time during which the directional light (for example, laser beam) emitted by an emission unit toward the subject supposed to be a distance measurement target travels in a reciprocating motion. In the present specification, an in-image irradiation position means a position acquired as a position within the captured image, which corresponds to the irradiation position of the directional light in the real space by the distance measurement device. In other words, the in-image irradiation position means a position of a pixel, among the pixels included in the captured image, which is specified by the irradiation-position pixel coordinates. 
     In recent years, a distance measurement device provided with an imaging unit has been developed. In such a type of distance measurement device, a subject is irradiated with a laser beam, and the subject is captured in a state in which the subject is irradiated with the laser beam. The captured image acquired by imaging the subject is presented to a user, and thus, an irradiation position of the laser beam is ascertained by the user through the captured image. 
     In recent years, a distance measurement device having a function of deriving a dimension of a target within an image in a real space as in a measurement device described in JP2014-232095A has been also developed. 
     The measurement device described in JP2014-232095A includes a unit that displays an isosceles trapezoid shape of a structure having an isosceles trapezoid portion captured by the imaging unit and a unit that specifies four vertices of the displayed isosceles trapezoid shape and acquiring coordinates of the four specified vertices. The measurement device described in JP2014-232095A specifies a distance between two points on a plane including the isosceles trapezoid shape or a distance to one point on a plane from the imaging unit, acquires a shape of the structure from the coordinates of the four vertices and a focal length, and acquires a size of the structure from the specified distance. 
     Incidentally, in a case where a dimension of a target within the captured image acquired by imaging the subject by the imaging unit is derived, a plurality of pixels corresponding to a region as a deriving target in the captured image in the real space is designated by the user. The dimension of the region in the real space which is designated by the user is derived based on the distance measured by the distance measurement device. Thus, in a case where the dimension of the region in the real space specified by the plurality of designated pixels is accurately derived, it is preferable that the in-image irradiation position is derived with high accuracy and the acquired in-image irradiation position together with the distance is ascertained by the user. 
     SUMMARY OF THE INVENTION 
     However, P2014-232095A does not describe a unit that derives the in-image irradiation position with high accuracy. 
     The user designates a region as the dimension deriving target by referring to the in-image irradiation position, but the derived dimension is completely different from an actual dimension in a case where the in-image irradiation position and the irradiation position of the laser beam in the real space are positions on planes of which orientations and positions are different. 
     In a case where a colored laser beam of which an irradiation position is able to be visually perceived within a distance of about several meters from the distance measurement device is used as the laser beam, the in-image irradiation position may be visually specified and designated from the captured image depending on a diameter and/or intensity of the laser beam. However, for example, in a case where a structure separated from a building site by several tens of meters or several hundreds of meters is irradiated with the laser beam in the daytime, it is difficult to visually specify the in-image irradiation position from the captured image. A method of specifying the in-image irradiation position from a difference between the plurality of captured images acquired in a sequence of time is also considered. However, in a case where the structure separated from the building site by several tens of meters or several hundreds of meters is irradiated with the laser beam, it is difficult to specify the in-image irradiation position. In a case where the in-image irradiation position is not able to be specified, the user performs the distance measurement while the user does not recognize whether or not the subject assumed as the distance measurement target is irradiated with the laser beam. 
     The embodiment of the present invention has been made in view of such circumstances, and provides a distance measurement device, a control method for distance measurement, and a control program for distance measurement which are capable of performing distance measurement in a state in which an in-image irradiation position is in a default range within a captured image. 
     A distance measurement device according to a first aspect of the present invention comprises an imaging unit that images a subject, a measurement unit that measures a distance to the subject by emitting directional light which is light having directivity to the subject and receiving reflection light of the directional light, a change unit that is capable of changing an angle at which the directional light is emitted, a deriving unit that derives an in-image irradiation position, which corresponds to an irradiation position of the directional light onto the subject which is used in measurement performed by the measurement unit, within a captured image acquired by imaging the subject by the imaging unit based on the angle and the distance measured by the measurement unit, and a control unit that controls the measurement unit to measure the distance, and controls the deriving unit to derive the in-image irradiation position based on the distance measured by the measurement unit and the angle changed by the change unit, until the in-image irradiation position falls in a default range within the captured image in a case where the in-image irradiation position is out of the default range. 
     Therefore, according to the distance measurement device according to the first aspect of the present invention, it is possible to perform the distance measurement in a state in which the in-image irradiation position is in the default range within a captured image. 
     According to a second aspect of the present invention, in the distance measurement device according to the first aspect of the present invention, the control unit controls the measurement unit to measure the distance, controls the change unit to change the angle by driving a power source, and controls the deriving unit to derive the in-image irradiation position based on the distance measured by the measurement unit and the angle changed by the change unit, until the in-image irradiation position falls in the default range in a case where the in-image irradiation position is out of the default range. 
     Therefore, according to the distance measurement device according to the second aspect of the present invention, it is possible to reduce an effort to position the in-image irradiation position within the default range compared to a case where the angle is changed by the change unit without using the power source. 
     According to a third aspect of the present invention, in the distance measurement device according to the second aspect of the present invention, the control unit controls the power source to generate a power for causing the change unit to change the angle in a direction in which a distance between the in-image irradiation position and the default range decreases based on a positional relation between the latest in-image irradiation position and the default range. 
     Therefore, according to the distance measurement device according to the third aspect of the present invention, it is possible to position the in-image irradiation position within the default range within the captured image with high accuracy compared to a case where the power for causing the change unit to change the angle is not generated by the power source regardless of the positional relation between the latest in-image irradiation position and the default range. 
     According to a fourth aspect of the present invention, in the distance measurement device according to the first aspect of the present invention, the measurement unit includes an emission unit that emits the directional light, and the change unit includes a rotation mechanism that changes the angle by manually rotating at least the emission unit of the measurement unit. 
     Therefore, according to the distance measurement device according to the fourth aspect of the present invention, it is possible to easily reflect an intention of the user on the change of the angle at which the directional light is emitted compared to a case where the rotation mechanism for manually rotating the emission unit is not provided. 
     According to a fifth aspect of the present invention, in the distance measurement device according to any one of the first to fourth aspects of the present invention, the control unit performs the control for a period during which a plurality of captured images acquired by continuously imaging the subject by the imaging unit in a sequence of time is continuously displayed on a first display unit. 
     Therefore, according to the distance measurement device according to the fifth aspect of the present invention, it is possible to perform the distance measurement in a state in which the in-image irradiation position is in the default range within a captured image while referring to the state of the subject. 
     According to a sixth aspect of the present invention, the distance measurement device according to any one of the first to fourth aspects of the present invention further comprises: a performing unit that performs at least one of focus adjustment or exposure adjustment on the subject, and a reception unit that receives an imaging preparation instruction to cause the performing unit to start to perform at least one of the focus adjustment or the exposure adjustment before actual exposing is performed by the imaging unit. The control unit performs the control in a case where the imaging preparation instruction is received by the reception unit. 
     Therefore, according to the distance measurement device according to the sixth aspect of the present invention, it is possible to prevent the in-image irradiation position from entering a state in which the in-image irradiation position is not in the default range at the time of the actual exposing compared to a case where the control unit does not perform the control in a case where the imaging preparation instruction is received by the reception unit. 
     According to a seventh aspect of the present invention, in the distance measurement device according to any one of the first to fourth aspects of the present invention, the control unit controls the measurement unit to intermittently measure the distance, and the control unit performs the control in a case where a dissimilarity between a distance used in the deriving of the in-image irradiation position performed in a previous stage by the deriving unit and a latest distance measured by the measurement unit is equal to or greater than a threshold value. 
     Therefore, according to the distance measurement device according to the seventh aspect of the present invention, it is possible to easily to maintain the state in which the in-image irradiation position is in the default range within the captured image compared to a case where the control unit does not perform the control in a case where the dissimilarity is equal to or greater than the threshold value. 
     According to an eighth aspect of the present invention, in the distance measurement device according to any one of the first to seventh aspects of the present invention, the control unit controls a second display unit to display the captured image, and further controls such that the latest in-image irradiation position derived by the deriving unit is displayed so as to be specified in a display region of the captured image. 
     Therefore, according to the distance measurement device according to the eighth aspect of the present invention, the user can easily ascertain the latest in-image irradiation position compared to a case where the latest in-image irradiation position is not displayed so as to be specified in the display region of the captured image. 
     According to a ninth aspect of the present invention, in the distance measurement device according to any one of the first to eighth aspects of the present invention, the control unit controls a third display unit to display the captured image, and further controls such that the default range is displayed so as to be specified in a display region of the captured image. 
     Therefore, according to the distance measurement device according to the ninth aspect of the present invention, the user can easily ascertain the position of the default range in the display region of the captured image compared to a case where the default range is not displayed so as to be specified in the display region of the captured image. 
     According to a tenth aspect of the present invention, in the distance measurement device according to any one of the first to ninth aspects of the present invention, the control unit controls a first notification unit to notify that the in-image irradiation position is within the default rage in a case where the in-image irradiation position is within the default range. 
     Therefore, according to the distance measurement device according to the tenth aspect of the present invention, the user can easily recognize that the in-image irradiation position is in the default range compared to a case where the notification indicating that the in-image irradiation position is in the default range is not performed in a case where the in-image irradiation position is in the default range. 
     According to an eleventh aspect of the present invention, in the distance measurement device according to any one of the first to tenth aspects of the present invention, the control unit controls a second notification unit to notify that the in-image irradiation position is out of the default range in a case where the in-image irradiation position is out of the default range. 
     Therefore, according to the distance measurement device according to the eleventh aspect of the present invention, the user can easily recognize that the in-image irradiation position is out of the default range compared to a case where the notification indicating that the in-image irradiation position is out of the default range is not performed in a case where the in-image irradiation position is out of the default range. 
     A control method for distance measurement according to a twelfth aspect of the present invention comprises deriving an in-image irradiation position, which corresponds to an irradiation position of directional light which is light having directivity on to a subject used in measurement performed by a measurement unit that measures a distance to the subject by emitting the directional light to the subject and receiving reflection light of the directional light, within a captured image acquired by imaging the subject by an imaging unit that images the subject, based on the distance measured by the measurement unit and an angle changed by a change unit that is capable of changing the angle at which the directional light is emitted, the imaging unit, the measurement unit, and the change unit being included in a distance measurement device, and controlling the measurement unit to measure the distance and controlling the deriving unit to derive the in-image irradiation position based on the distance measured by the measurement unit and the angle changed by the change unit until the in-image irradiation position falls in a default range within a captured image in a case where the in-image irradiation position is out of the default range. 
     Therefore, according to the control method for distance measurement according to the twelfth aspect of the present invention, it is possible to perform the distance measurement in a state in which the in-image irradiation position is in the default range within a captured image. 
     A control program for distance measurement according to a thirteenth aspect of the present invention comprises deriving an in-image irradiation position, which corresponds to an irradiation position of directional light which is light having directivity on to a subject used in measurement performed by a measurement unit that measures a distance to the subject by emitting the directional light to the subject and receiving reflection light of the directional light, within a captured image acquired by imaging the subject by an imaging unit that images the subject, based on the distance measured by the measurement unit and an angle changed by a change unit that is capable of changing the angle at which the directional light is emitted, the imaging unit, the measurement unit, and the change unit being included in a distance measurement device, and controlling the measurement unit to measure the distance and controlling the deriving unit to derive the in-image irradiation position based on the distance measured by the measurement unit and the angle changed by the change unit until the in-image irradiation position falls in a default range within a captured image in a case where the in-image irradiation position is out of the default range. 
     Therefore, according to the control program for distance measurement according to the thirteenth aspect of the present invention, it is possible to perform the distance measurement in a state in which the in-image irradiation position is in the default range within a captured image. 
     According to the embodiment of the present invention, an effect capable of performing distance measurement in a state in which an in-image irradiation position is in a default range within a captured image is acquired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view showing an example of an external appearance of a distance measurement device according to first to fourth embodiments. 
         FIG. 2  is a conceptual diagram (schematic side view) showing an example of a schematic configuration of a longitudinal rotation mechanism provided in the distance measurement device according to the first to fifth embodiments. 
         FIG. 3  is a conceptual diagram (schematic front view) showing an example of a schematic configuration of a horizontal rotation mechanism provided in the distance measurement device according to the first to fifth embodiments. 
         FIG. 4  is a block diagram showing an example of a hardware configuration of main parts of the distance measurement device according to the first to third embodiments. 
         FIG. 5  is a time chart showing an example of a measurement sequence using the distance measurement device according to the first to fifth embodiments. 
         FIG. 6  is a time chart showing an example of a laser trigger, a light-emitting signal, a light-receiving signal, and a count signal required in a case where measurement using the distance measurement device according to the first to fifth embodiments is performed once. 
         FIG. 7  is a graph showing an example of a histogram (a histogram in a case where a lateral axis represents a distance (measurement value) to the subject and a longitudinal axis represents the number of times the measurement is performed) of measurement values acquired in the measurement sequence using the distance measurement device according to the first to fifth embodiments. 
         FIG. 8  is a block diagram showing an example of a hardware configuration of a main control unit included in the distance measurement device according to the first to fourth embodiments. 
         FIG. 9  is an explanatory diagram for describing a method of measuring a dimension (length) of a designated region. 
         FIG. 10  is a functional block diagram showing an example of functions of main parts realized by a CPU of the main control unit included in the distance measurement device according to the first to fourth embodiments. 
         FIG. 11  is a flowchart showing an example of a flow of a distance measurement process according to the first to fourth embodiments. 
         FIG. 12  is a flowchart subsequent to the flowchart shown in  FIG. 11 . 
         FIG. 13  is a flowchart subsequent to the flowchart shown in  FIG. 11 . 
         FIG. 14  is a conceptual diagram showing an example of a correspondence table according to the first to third embodiments. 
         FIG. 15  is an explanatory diagram for describing a parameter that influences an in-image irradiation position. 
         FIG. 16  is a screen diagram showing an example of a first intention check screen according to the first to fifth embodiments. 
         FIG. 17  is a screen diagram showing an example of a provisional measurement and provisional imaging guide screen according to the first to fifth embodiments. 
         FIG. 18  is a screen diagram showing an example of a re-performing guide screen according to the first to fifth embodiments. 
         FIG. 19  is a screen diagram showing an example of a second intention check screen according to the first to fifth embodiments. 
         FIG. 20  is a screen diagram showing an example of a screen in a state in which an actual image, a distance, and an irradiation position mark are displayed on a display unit according to the first to fifth embodiments. 
         FIG. 21  is a conceptual diagram showing an example in which a distance is in a correspondence information distance range, is out of a first correspondence information distance range, and is out of a second correspondence information distance range according to the first to fifth embodiments. 
         FIG. 22  is a screen diagram showing an example of a screen in a state in which an actual image, a distance, an irradiation position mark, and a warning and recommendation message are displayed on the display unit according to the first to fifth embodiments. 
         FIG. 23  is a flowchart showing an example of a flow of an irradiation position adjustment process according to the first embodiment. 
         FIG. 24  is a screen diagram showing an example of a live view image and a frame displayed on the display unit by performing the irradiation position adjustment process. 
         FIG. 25  is a screen diagram showing an example of a live view image, a frame, an irradiation position mark, and a message corresponding to out-of-default-range information displayed on the display unit by performing the irradiation position adjustment process. 
         FIG. 26  is a screen diagram showing an example of a live view image, a frame, an irradiation position mark, and a message corresponding to in-default-range information displayed on the display unit by performing the irradiation position adjustment process. 
         FIG. 27  is a flowchart showing an example of a flow of an irradiation position adjustment process according to the second embodiment. 
         FIG. 28  is a flowchart showing an example of a flow of an irradiation position adjustment process according to the third embodiment. 
         FIG. 29  is a flowchart showing an example of a flow of an irradiation position adjustment process according to the fourth embodiment. 
         FIG. 30  is a block diagram showing an example of a hardware configuration of main parts of the distance measurement device according to the fourth embodiment. 
         FIG. 31  is a block diagram showing an example of a hardware configuration of main parts of the distance measurement device according to the fifth embodiment. 
         FIG. 32  is a screen diagram showing an example of a screen including an actual measurement and actual imaging button, a provisional measurement and provisional imaging button, an imaging system operation mode switching button, a wide angle instruction button, a telephoto instruction button, and an irradiation position adjustment button displayed as soft keys on a display unit of a smart device according to the fifth embodiment. 
         FIG. 33  is a conceptual diagram showing an example of an aspect in which a distance measurement program and an irradiation position adjustment program are installed in the distance measurement device from a storage medium that stores a distance measurement program and an irradiation position adjustment program according to the first to fifth embodiments. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an example of an embodiment related to a technology of the present disclosure will be described with reference to the accompanying drawings. In the present embodiment, a distance between a distance measurement device and a subject as a measurement target is simply referred to as a distance for the sake of convenience in description. In the present embodiment, an angle of view (an angle of view on a subject image indicating the subject) on the subject is simply referred to as an “angle of view. 
     First Embodiment 
     For example, a distance measurement device  10 A according to the first embodiment includes a distance measurement unit  12  and an imaging device  14  as shown in  FIG. 1 . In the present embodiment, the distance measurement unit  12  and a distance measurement control unit  68  (see  FIG. 4 ) are an example of a measurement unit according to the technology of the present disclosure, and the imaging device  14  is an example of an imaging unit according to the technology of the present disclosure. 
     The imaging device  14  includes a lens unit  16  and an imaging device main body  18 , and the lens unit  16  is detachably attached to the imaging device main body  18 . 
     A hot shoe  20  is provided on a top surface of the imaging device main body  18 , and the distance measurement unit  12  is detachably attached to the hot shoe  20 . 
     The distance measurement device  10 A has a distance measurement system function of measuring a distance by emitting a laser beam for distance measurement to the distance measurement unit  12 , and an imaging system function of causing the imaging device  14  to acquire a captured image by imaging the subject. Hereinafter, the captured image acquired by imaging the subject by using the imaging device  14  by utilizing the imaging system function is simply referred to as an “image” or a “captured image” for the sake of convenience in description. 
     The distance measurement device  10 A performs one measurement sequence (see  FIG. 5 ) according to one instruction by utilizing the distance measurement system function, and ultimately outputs one distance by performing the one measurement sequence. In the present embodiment, actual measurement and provisional measurement are selectively performed by utilizing the distance measurement system function according to an instruction of a user in a distance measurement process to be described below (see  FIGS. 11 to 13 ). The actual measurement means measurement in which a distance measured by utilizing the distance measurement system function is actually used, and the provisional measurement means measurement performed in a preparation stage of increasing the accuracy of the actual measurement. 
     The distance measurement device  10 A has, as an operation mode of the imaging system function, a still image imaging mode and a video imaging mode. The still image imaging mode is an operation mode for imaging a still image, and the video imaging mode is an operation mode of imaging a motion picture. The still image imaging mode and the video imaging mode are selectively set according to an instruction of the user. 
     In the present embodiment, the actual imaging and the provisional imaging are selectively performed by utilizing the imaging system function according to an instruction of the user in the distance measurement process to be described below (see  FIGS. 11 to 13 ). The actual imaging is imaging performed in synchronization with the actual measurement, and the provisional imaging is imaging performed in synchronization with the provisional measurement. Hereinafter, for the sake of convenience in description, an image acquired through the actual imaging is referred to as an “actual captured image”, and an image acquired through the provisional imaging is referred to as a “provisional captured image”. In a case where it is not necessary to distinguish between the “actual captured image” and the “provisional captured image”, the actual captured image and the provisional captured image are referred to as an “image” or a “captured image”. Hereinafter, for the sake of convenience in description, the “actual captured image” is also referred to as an “actual image”, and the “provisional captured image” is also referred to as a “provisional image”. 
     For example, the imaging device main body  18  includes a longitudinal rotation mechanism  13  as shown in  FIG. 2 . The longitudinal rotation mechanism  13  receives a power generated by a motor  17  (see  FIG. 4 ) to be described below, and rotates the hot shoe  20  in a front-view longitudinal direction with a front end portion of the hot shoe  20  as a rotational axis. Accordingly, the hot shoe  20  to which the distance measurement unit  12  is attached is rotated by the longitudinal rotation mechanism  13  in the longitudinal direction in front view, and thus, an orientation of the distance measurement unit  12  is changed in the front-view longitudinal direction (for example, an A direction represented in  FIG. 2 ) in the front-view longitudinal direction. For the sake of convenience in description, although it has been described in the example shown in  FIG. 2  that the hot shoe  20  is rotated in the front-view longitudinal direction such that a rear end portion of the hot shoe  20  is buried within the imaging device main body  18 , the technology of the present disclosure is not limited thereto. For example, the hot shoe  20  may be rotated in the front-view longitudinal direction such that the rear end of the hot shoe  20  is pushed up from the imaging device main body  18 . Hereinafter, for the sake of convenience in description, the front-view longitudinal direction is simply referred to as a “longitudinal direction”. 
     For example, the imaging device main body  18  includes a horizontal rotation mechanism  15 , as shown in  FIG. 3 . The horizontal rotation mechanism  15  receives a power generated by a motor  19  (see  FIG. 4 ) to be described below, and rotates the hot shoe  20  in a front-view horizontal direction with a central point of the hot shoe  20  in plan view as a rotational axis. Accordingly, the hot shoe  20  to which the distance measurement unit  12  is attached is rotated by the horizontal rotation mechanism  15  in the front-view horizontal direction, and thus, an orientation of the distance measurement unit  12  is changed in the front-view horizontal direction (for example, a B direction represented in  FIG. 2 ). Hereinafter, for the sake of convenience in description, the front-view horizontal direction is simply referred to as a “horizontal direction”. 
     Hereinafter, the longitudinal rotation mechanism and the horizontal rotation mechanism are referred to as a “rotation mechanism” without being assigned the reference for the sake of convenience in description in a case where it is not necessary to distinguish between the longitudinal rotation mechanism  13  and the horizontal rotation mechanism  15 . 
     For example, the distance measurement unit  12  includes an emission unit  22 , a light receiving unit  24 , and a connector  26 , as shown in  FIG. 4 . 
     The connector  26  is able to be connected to the hot shoe  20 , and the distance measurement unit  12  is operated under the control of the imaging device main body  18  in a state in which the connector  26  is connected to the hot shoe  20 . 
     The emission unit  22  includes a laser diode (LD)  30 , a condenser lens (not shown), an object lens  32 , and an LD driver  34 . 
     The condenser lens and the object lens  32  are provided along an optical axis of a laser beam emitted by the LD  30 , and the condenser lens and the object lens  32  are arranged in order along the optical axis from the LD  30 . 
     The LD  30  emits a laser beam for distance measurement which is an example of directional light according to the technology of the present disclosure. The laser beam emitted by the LD  30  is a colored laser beam. For example, as long as the subject is separated from the emission unit  22  in a range of about several meters, an irradiation position of the laser beam is visually recognized in a real space, and is visually recognized from the captured image acquired by the imaging device  14 . 
     The condenser lens concentrates the laser beam emitted by the LD  30 , and causes the concentrated laser beam to pass. The object lens  32  faces the subject, and emits the laser beam that passes through the condenser lens to the subject. 
     The LD driver  34  is connected to the connector  26  and the LD  30 , and drives the LD  30  in order to emit the laser beam according to an instruction of the imaging device main body  18 . 
     The light receiving unit  24  includes a photodiode (PD)  36 , an object lens  38 , and a light-receiving signal processing circuit  40 . The object lens  38  is disposed on a light receiving surface of the PD  36 . After the laser beam emitted by the emission unit  22  reaches the subject, a reflection laser beam which is a laser beam reflected from the subject is incident on the object lens  38 . The object lens  38  factors the reflection laser beam to pass, and guides the reflection laser beam to the light receiving surface of the PD  36 . The PD  36  receives the reflection laser beam that passes through the object lens  38 , and outputs an analog signal corresponding to a light reception amount, as a light-receiving signal. 
     The light-receiving signal processing circuit  40  is connected to the connector  26  and the PD  36 , amplifies the light-receiving signal input from the PD  36  by an amplifier (not shown), and performs analog-to-digital (A/D) conversion on the amplified light-receiving signal. The light-receiving signal processing circuit  40  outputs the light-receiving signal digitized through the A/D conversion to the imaging device main body  18 . 
     The imaging device  14  includes mounts  42  and  44 . The mount  42  is provided at the imaging device main body  18 , and the mount  44  is provided at the lens unit  16 . The lens unit  16  is attached to the imaging device main body  18  so as to be replaceable by coupling the mount  42  to the mount  44 . 
     The lens unit  16  includes an imaging lens  50 , a zoom lens  52 , a zoom lens moving mechanism  54 , and a motor  56 . 
     Subject light which is reflected from the subject is incident on the imaging lens  50 . The imaging lens  50  factors the subject light to pass, and guides the subject light to the zoom lens  52 . 
     The zoom lens  52  is attached to the zoom lens moving mechanism  54  so as to slide along the optical axis. The motor  56  is connected to the zoom lens moving mechanism  54 . The zoom lens moving mechanism  54  receives a power of the motor  56 , and factors the zoom lens  52  to slide along an optical axis direction. 
     The motor  56  is connected to the imaging device main body  18  through the mounts  42  and  44 , and the driving of the motor is controlled according to a command from the imaging device main body  18 . In the present embodiment, a stepping motor is used as an example of the motor  56 . Accordingly, the motor  56  is operated in synchronization with a pulsed power according to a command from the imaging device main body  18 . 
     The imaging device main body  18  includes an imaging element  60 , a main control unit  62 , an image memory  64 , an image processing unit  66 , a distance measurement control unit  68 , motors  17  and  19 , motor drivers  21 ,  23 , and  72 , an imaging element driver  74 , an image signal processing circuit  76 , and a display control unit  78 . The imaging device main body  18  includes a touch panel interface (I/F)  79 , a reception I/F  80 , and a media I/F  82 . The longitudinal rotation mechanism  13 , the horizontal rotation mechanism  15 , the motors  17  and  19 , and the motor drivers  21  and  23  are examples of a change unit according to the technology of the present disclosure. For example, the change unit according to the technology of the present disclosure means a mechanism capable of changing an emission angle β to be described below. 
     The main control unit  62 , the image memory  64 , the image processing unit  66 , the distance measurement control unit  68 , the motor drivers  21 ,  23 , and  72 , the imaging element driver  74 , the image signal processing circuit  76 , and the display control unit  78  are connected to a busline  84 . The touch panel I/F  79 , the reception I/F  80 , and the media I/F  82  are also connected to the busline  84 . 
     The imaging element  60  is a complementary metal oxide semiconductor (CMOS) type image sensor, and includes a color filter (not shown). The color filter includes a G filter corresponding to green (G), an R filter corresponding to red (R), and a B filter corresponding to blue (B) which contribute to the acquisition of a brightness signal. The imaging element  60  includes a plurality of pixels (not shown) arranged in a matrix shape, and any filter of the R filter, the G filter, and the B filter included in the color filter is allocated to each pixel. 
     The subject light that passes through the zoom lens  52  is formed on an imaging surface which is the light receiving surface of the imaging element  60 , and electric charges corresponding to the light reception amount of the subject light are accumulated in the pixels of the imaging element  60 . The imaging element  60  outputs the charges accumulated in the pixels, as image signals indicating an image corresponding to a subject image acquired by forming the subject light on the imaging surface. 
     For example, the motor  17  is connected to the longitudinal rotation mechanism  13 , and the longitudinal rotation mechanism  13  receives the power of the motor  17  and rotates the hot shoe  20  in the longitudinal direction. For example, the distance measurement unit  12  is rotated in the direction of an arrow A, as shown in  FIG. 2 . The motor  19  is connected to the horizontal rotation mechanism  15 , and the horizontal rotation mechanism  15  receives the power of the motor  19  and rotates the hot shoe  20  in the horizontal direction. For example, the distance measurement unit  12  is rotated in the direction of an arrow B, as shown in  FIG. 3 . 
     The main control unit  62  controls the entire distance measurement device  10 A through the busline  84 . 
     The motor driver  21  controls the motor  17  according to an instruction of the main control unit  62 . The motor driver  23  controls the motor  19  according to an instruction of the main control unit  62 . The motors  17  and  19  are examples of a power source according to the technology of the present disclosure. 
     The motor driver  72  is connected to the motor  56  through the mounts  42  and  44 , and controls the motor  56  according to an instruction of the main control unit  62 . 
     In the present embodiment, a stepping motor is used as an example of the motors  17 ,  19 , and  56 . Accordingly, the motors  17 ,  19 , and  56  are operated in synchronization with a pulsed power according to a command from the main control unit  62 . 
     The imaging device  14  has an angle-of-view changing function. The angle-of-view changing function is a function of changing an angle of view on the subject by moving the zoom lens  52 . In the present embodiment, the angle-of-view changing function is realized by the zoom lens  52 , the zoom lens moving mechanism  54 , the motor  56 , the motor driver  72 , and the main control unit  62 . Although it has been described in the present embodiment that the optical angle-of-view changing function using the zoom lens  52  is used, the technology of the present disclosure is not limited thereto, and an electronic angle of view changing function without using the zoom lens  52  may be used. 
     The imaging element driver  74  is connected to the imaging element  60 , and supplies drive pulses to the imaging element  60  under the control of the main control unit  62 . The pixels of the imaging element  60  are driven according to the drive pulses supplied by the imaging element driver  74 . 
     The image signal processing circuit  76  is connected to the imaging element  60 , and reads image signals corresponding to one frame for every pixel out of the imaging element  60  under the control of the main control unit  62 . The image signal processing circuit  76  performs various processing tasks such as correlative double sampling processing, automatic gain adjustment, and A/D conversion on the readout image signals. The image signal processing circuit  76  outputs image signals digitized by performing various processing tasks on the image signals for every frame to the image memory  64  at a specific frame rate (for example, tens of frames/second) prescribed by an analog signal supplied from the main control unit  62 . The image memory  64  provisionally retains the image signals input from the image signal processing circuit  76 . 
     The imaging device main body  18  includes a display unit  86 , a touch panel  88 , a reception device  90 , and a memory card  92 . 
     An alarm unit and the display unit  86  which is an example of a first display unit, a second display unit, a third display unit, a first notification unit, and a second notification unit according to the technology of the present disclosure are connected to the display control unit  78 , and display various information items under the control of the display control unit  78 . The display unit  86  is realized by a liquid crystal display (LCD), for example. 
     The touch panel  88  is layered on a display screen of the display unit  86 , and senses touch using a pointer such as a finger of the user and/or a touch pen. The touch panel  88  is connected to the touch panel I/F  79 , and outputs positional information indicating a position touched by the pointer to the touch panel I/F  79 . The touch panel I/F  79  activates the touch panel  88  according to an instruction of the main control unit  62 , and outputs the positional information input from the touch panel  88  to the main control unit  62 . 
     The reception device  90  includes an actual measurement and actual imaging button  90 A, a provisional measurement and provisional imaging button  90 B, an imaging system operation mode switching button  90 C, a wide angle instruction button  90 D, a telephoto instruction button  90 E, and an irradiation position adjustment button  90 F, and receives various instructions from the user. The reception device  90  is connected to the reception I/F  80 , and the reception I/F  80  outputs an instruction content signal indicating the content of the instruction received by the reception device  90  to the main control unit  62 . 
     The actual measurement and actual imaging button  90 A is a pressing type button that receives an instruction to start the actual measurement and the actual imaging. The provisional measurement and provisional imaging button  90 B is a pressing type button that receives an instruction to start the provisional measurement and the provisional imaging. The imaging system operation mode switching button  90 C is a pressing type button that receives an instruction to switch between the still image imaging mode and the video imaging mode. 
     The wide angle instruction button  90 D is a pressing type button that receives an instruction to change the angle of view to a wide angle, and a degree of the angle of view changed to the wide angle is determined in an allowable range depending on a pressing time during which the wide angle instruction button  90 D is continuously pressed. 
     The telephoto instruction button  90 E is a pressing type button that receives an instruction to change the angle of view to an angle of a telephoto lens, and a degree of the angle of view changed to the angle of the telephoto lens is determined in an allowable range depending on a pressing time during which the telephoto instruction button  90 E is continuously pressed. 
     The irradiation position adjustment button  90 F is a pressing type button that receives an instruction to adjust an in-image irradiation position. In a case where the irradiation position adjustment button  90 F is pressed, an irradiation position adjustment process (see  FIG. 23 ) to be described below is started to be performed. 
     Hereinafter, the actual measurement and actual imaging button and the provisional measurement and provisional imaging button are referred to as a “release button” for the sake of convenience in description in a case where it is not necessary to distinguish between the actual measurement and actual imaging button  90 A and the provisional measurement and provisional imaging button  90 B. Hereinafter, the wide angle instruction button and the telephoto instruction button are referred to as an “angle-of-view instruction button” for the sake of convenience in description in a case where it is not necessary to distinguish between the wide angle instruction button  90 D and the telephoto instruction button  90 E. 
     In the distance measurement device  10 A according to the first embodiment, a manual focus mode and an auto focus mode are selectively set according to an instruction of the user through the reception device  90  in the still image imaging mode. 
     In the auto focus mode, the release button which is an example of a reception unit according to the technology of the present disclosure receives two-step pressing operations including an imaging preparation instruction state and an imaging instruction state. For example, the imaging preparation instruction state refers to a state in which the release button is pressed down from a waiting position to an intermediate position (half pressed position), and the imaging instruction state refers to a state in which the release button is pressed down to a finally pressed-down position (fully pressed position) beyond the intermediate position. 
     Hereinafter, for the sake of convenience in description, a “state in which the release button is pressed down from the waiting position to the half pressed position” is referred to as a “half pressed state”, and a “state in which the release button is pressed down from the waiting position to the fully pressed position” is referred to as a “fully pressed state”. 
     In the auto focus mode, after an imaging condition is adjusted by setting the release button to be in the half pressed state, actual exposing is subsequently performed by setting the release button to be in the fully pressed state. That is, in a case where the release button is set to be in the half pressed state before the actual exposing is performed, an automatic exposure (AE) function, and thus, exposure is adjusted. Thereafter, a focus is adjusted by performing auto-focus (AF) function, and the actual exposing is performed in a case where the release button is set to be in the fully pressed state. 
     In this example, the actual exposing refers to exposing performed in order to acquire a still image file to be described below. In the present embodiment, the exposing means exposing performed in order to acquire a live view image to be described below and exposition performed in order to acquire a motion picture image file to be described below in addition to the actual exposing. Hereinafter, for the sake of convenience in description, the exposing is simply referred to as “exposing” in a case where it is not necessary to distinguish between these exposing tasks. 
     In the present embodiment, the main control unit  62  which is an example of a performing unit according to the technology of the present disclosure performs the exposure adjustment using the AE function and the focus adjustment using the AF function. Although it has been described in the present embodiment that the exposure adjustment and the focus adjustment are performed by the main control unit  62 , the technology of the present disclosure is not limited to thereto, and the exposure adjustment or the focus adjustment may not be performed by the main control unit  62 . 
     The image processing unit  66  acquires image signals for every frame from the image memory  64  at a specific frame rate, and performs various processing tasks such as gamma correction, luminance and color difference conversion, and compression processing on the acquired image signals. 
     The image processing unit  66  outputs the image signals acquired by performing various processing tasks to the display control unit  78  for every frame at a specific frame rate. The image processing unit  66  outputs the image signals acquired by performing various processing tasks to the main control unit  62  according to a request of the main control unit  62 . 
     The display control unit  78  outputs the image signals input from the image processing unit  66  to the display unit  86  for every frame at a specific frame rate under the control of the main control unit  62 . 
     The display unit  86  displays image and character information. The display unit  86  displays the image indicated by the image signals input from the display control unit  78  at a specific frame rate, as a live view image. As the live view image, a plurality of images acquired by performing continuous imaging by the imaging device  14  in a sequence of time, that is, continuous frame images acquired by performing imaging in continuous frames is acquired, and the live view image is referred to as a live preview image. The display unit  86  also displays the still image which is a single frame image captured in a single frame. The display unit  86  also displays a playback image and/or a menu screen in addition to the live view image. 
     Although the image processing unit  66  and the display control unit  78  are realized by an application specific integrated circuit (ASIC) in the present embodiment, the technology of the present disclosure is not limited thereto. For example, the image processing unit  66  and the display control unit  78  may be realized by a field-programmable gate array (FPGA). The image processing unit  66  may be realized by a computer including a central processing unit (CPU), a read only memory (ROM), and a random access memory (RAM). The display control unit  78  may also be realized by a computer including a CPU, a ROM, and a RAM. The image processing unit  66  and the display control unit  78  may be realized by combining of a hardware configuration and a software configuration. 
     In a case where an instruction to image the still image is received by the release button in the still image imaging mode, the main control unit  62  factors the imaging element  60  to expose one frame by controlling the imaging element driver  74 . The main control unit  62  acquires the image signals acquired by exposing one frame from the image processing unit  66 , and generates the still image file having a specific still image format by performing a compression process on the acquired image signals. For example, the specific still image format refers to the Joint Photographic Experts Group (JPEG). 
     In a case where an instruction to image the motion picture is received by the release button in the video imaging mode, the main control unit  62  acquire the image signals output to the display control unit  78  in order to be used as the live view image, by the image processing unit  66  for every frame at a specific frame rate. The main control unit  62  generates a motion picture file having a specific motion picture format by performing the compression process on the image signals acquired from the image processing unit  66 . For example, the specific motion picture format refers to the Moving Picture Experts Group (MPEG). Hereinafter, the still image file and the motion picture file are referred to as the image file for the sake of convenience in description in a case where it is not necessary to distinguish between the still image file and the motion picture file. 
     The media I/F  82  is connected to the memory card  92 , and records and reads the image file in and out of the memory card  92  under the control of the main control unit  62 . The main control unit  62  performs a decompression process on the image file read out of the memory card  92  by the media I/F  82 , and displays the decompressed image file as a playback image on the display unit  86 . 
     The main control unit  62  stores distance measurement information including at least one of distance information input from the distance measurement control unit  68  or dimension information indicating a dimension derived by utilizing a dimension deriving function to be described below in association with the image file in the memory card  92  through the media I/F  82 . The distance measurement information together with the image file is read out of the memory card  92  by the main control unit  62  through the media I/F  82 . In a case where the distance information is included in the distance measurement information read out by the main control unit  62 , the distance indicated by the distance information together with the playback image which is the associated image file is displayed on the display unit  86 . In a case where the dimension information is included in the distance measurement information read out by the main control unit  62 , the dimension indicated by the dimension information together with the playback image which is the associated image file is displayed on the display unit  86 . 
     The distance measurement control unit  68  controls the distance measurement unit  12  under the control of the main control unit  62 . In the present embodiment, the distance measurement control unit  68  is realized by ASIC, but the technology of the present disclosure is not limited thereto. For example, the distance measurement control unit  68  may be realized by FPGA. The distance measurement control unit  68  may be realized by a computer including a CPU, a ROM, and a RAM. The distance measurement control unit  68  may be realized by the combination of the hardware configuration and the software configuration. 
     The hot shoe  20  is connected to the busline  84 . Under the control of the main control unit  62 , the distance measurement control unit  68  controls the emission of the laser beam from the LD  30  by controlling the LD driver  34 , and acquires light-receiving signal from the light-receiving signal processing circuit  40 . The distance measurement control unit  68  derives a distance to the subject based on a timing when the laser beam is emitted and a timing when the light-receiving signal is acquired, and outputs distance information indicating the derived distance to the main control unit  62 . 
     The measurement of the distance to the subject using the distance measurement control unit  68  will be described in more detail. 
     For example, one measurement sequence using the distance measurement device  10 A is prescribed by a voltage adjustment period, an actual measurement period, and a suspension period, as shown in  FIG. 5 . 
     The voltage adjustment period is a period during which driving voltages of the LD  30  and the PD  36  are adjusted. The actual measurement period is a period during which the distance to the subject is actually measured. For the actual measurement period, an operation for causing the LD  30  to emit the laser beam and causing the PD  36  to receive the reflection laser beam hundreds of times is repeated several hundreds of times, and the distance to the subject is derived based on the timing when the laser beam is emitted and the timing when the light-receiving signal is acquired. The suspension period is a period during which the driving of the LD  30  and the PD  36  is suspended. Thus, in one measurement sequence, the measurement of the distance to the subject is performed hundreds of times. 
     In the present embodiment, each of the voltage adjustment period, the actual measurement period, and the suspension period is hundreds of milliseconds. 
     For example, as shown in  FIG. 6 , count signals that prescribes a timing when the distance measurement control unit  68  outputs an instruction to emit the laser beam and a timing when the distance measurement control unit  68  acquires the light-receiving signal are supplied to the distance measurement control unit  68 . In the present embodiment, the count signals are generated by the main control unit  62  and are supplied to the distance measurement control unit  68 , but the present embodiment is not limited thereto. The count signals may be generated by a dedicated circuit such as a time counter connected to the busline  84 , and may be supplied to the distance measurement control unit  68 . 
     The distance measurement control unit  68  outputs a laser trigger for emitting the laser beam to the LD driver  34  in response to the count signal. The LD driver  34  drives the LD  30  to emit the laser beam in response to the laser trigger. 
     In the example shown in  FIG. 6 , a time during which the laser beam is emitted is tens of nanoseconds. A time during which the laser beam emitted to the subject far away from the emission unit  22  by several kilometers is received as the reflection laser beam by the PD  36  is “several kilometers×2/light speed”=several microseconds. Accordingly, for example, it takes a time of several microseconds as a minimum necessary time to measure the distance to the subject far away by several kilometers, as shown in  FIG. 5 . 
     In the present embodiment, for example, although a time during which the measurement is performed once is several milliseconds with consideration for a time during which the laser beam travels in a reciprocating motion as shown in  FIG. 5 , since the time during which the laser beam travels in the reciprocating motion varies depending on the distance to the subject, the measurement time per one time may varies depending on an assumed distance. 
     For example, in a case where the distance to the subject is derived based on the measurement values acquired through the measurement performed several hundreds of times in one measurement sequence, the distance measurement control unit  68  derives the distance to the subject by analyzing a histogram of the measurement values acquired through the measurement performed several hundreds of times. 
     For example, in the histogram of the measurement values acquired through the measurement performed several hundreds of times in one measurement sequence as shown in  FIG. 7 , a lateral axis represents the distance to the subject, and a longitudinal axis is the number of times the measurement is performed. The distance corresponding to the maximum value of the number of times the measurement is performed is derived as the distance measurement result by the distance measurement control unit  68 . The histogram shown in  FIG. 7  is merely an example, and the histogram may be generated based on the time during which the laser beam travels in the reciprocating motion (an elapsed time from when the laser beam is emitted to when the laser beam is received) and/or ½ of the time during which the laser beam travels in the reciprocating motion instead of the distance to the subject. 
     For example, the main control unit  62  includes the CPU  100  which is an example of a deriving unit and a control unit according to the technology of the present disclosure, as shown in  FIG. 8 . The main control unit  62  includes a primary storage unit  102  and a secondary storage unit  104 . The CPU  100  controls the entire distance measurement device  10 A. The primary storage unit  102  is a volatile memory used as a work area when various programs are executed. A RAM is used as an example of the primary storage unit  102 . The secondary storage unit  104  is a non-volatile memory that previously stores various parameters and/or control programs for controlling the activation of the distance measurement device  10 A. Electrically erasable programmable read only memory (EEPROM) and/or a flash memory are used as an example of the secondary storage unit  104 . The CPU  100 , the primary storage unit  102 , and the secondary storage unit  104  are connected to each other through the busline  84 . 
     Incidentally, the distance measurement device  10 A has the dimension deriving function. For example, as shown in  FIG. 9 , the dimension deriving function refers to a function of deriving a length L of a region in a real space included in the subject based on addresses u 1  and u 2  of the designated pixels and a distance D measured by the distance measurement device  10 A or deriving an area based on the length L. For example, the “designated pixels” refer to pixels of the imaging element  60  corresponding to two points designated by the user on the live view image. For example, the length L is derived from the following Expression (1). In Expression (1), p is a pitch between pixels included in the imaging element  60 , u 1  and u 2  are addresses of the pixels designated by the user, and f is a focal length of the imaging lens  50 . 
     
       
         
           
             
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     Expression (1) is an expression used on the assumption that a target as a dimension deriving target is captured in a state in which the target faces the imaging lens  50  in front view. Accordingly, for example, in a case where the subject including the target as the dimension deriving target is captured in a state in which the target does not face the imaging lens  50  in front view, a projection conversion process is performed. For example, the projection conversion process refers to a process of converting the captured image acquired through the imaging and/or an image of a square portion of the captured image into a facing view image based on the square image included in the captured image by using the known technology such as affine transformation. The facing view image refers to an image in a state in the subject faces the imaging lens  50  in front view. The addresses u 1  and u 2  of the pixels of the imaging element  60  are designated through the facing view image, and the length L is derived from Expression (1). 
     As stated above, it is preferable that an in-image irradiation position is derived with high accuracy and is ascertained together with the distance by the user in order to accurately derive the length L of the region in the real space based on the addresses u 1  and u 2 . The reason is that the derived length L is completely different from the actual length in a case where it is assumed that the in-image irradiation position and the irradiation position of the laser beam in the real space are positions on planes of which orientations and positions are different. 
     In a case where a colored laser beam of which an irradiation position is able to be visually perceived within a distance of about several meters from the distance measurement device  10 A is used as the laser beam, the in-image irradiation position may be visually specified and designated from the captured image depending on a diameter and/or intensity of the laser beam. However, for example, in a case where a structure separated from a building site by several tens of meters or several hundreds of meters is irradiated with the laser beam in daytime, it is difficult to visually specify the in-image irradiation position from the captured image. A method of specifying the in-image irradiation position from a difference between a plurality of captured images acquired in a sequence of time is also considered. However, in a case where the structure separated from the building site by several tens of meters or several hundreds of meters is irradiated with the laser beam, it is difficult to specify the in-image irradiation position. In a case where the in-image irradiation position is not able to be specified, the user performs the distance measurement while the user does not recognize whether or not the subject assumed as the distance measurement target is irradiated with the laser beam. 
     For example, in the distance measurement device  10 A, the secondary storage unit  104  stores a distance measurement program  106  and an irradiation position adjustment program  107 , as shown in  FIG. 8 . The irradiation position adjustment program  107  is an example of a distance measurement control program according to the technology of the present disclosure. 
     For example, the CPU  100  is operated as a deriving unit  100 A shown in  FIG. 10  by reading the distance measurement program  106  out of the secondary storage unit  104 , loading the readout distance measurement program into the primary storage unit  102 , and executing the distance measurement program  106 . 
     The deriving unit  100 A acquires the correspondence relation between an in-provisional-image irradiation position and a distance which are provisionally measured by the distance measurement unit  12  and the distance measurement control unit  68  by using the laser beam corresponding to the in-provisional-image irradiation position. The deriving unit  100 A derives an in-actual-image irradiation position, which corresponds to the irradiation position of the laser beam used in the actual measurement using the distance measurement unit  12  and the distance measurement control unit  68 , within the actual image acquired by performing the actual imaging by the imaging device  14  based on the acquired correspondence relation. The in-provisional-image irradiation position refers to a position, which corresponds to the irradiation position of the laser beam onto the subject, within a provisional image acquired by performing the provisional imaging on the subject by the imaging device  14  whenever each of a plurality of distances is provisionally measured by the distance measurement unit  12  and the distance measurement control unit  68 . 
     In the present embodiment, the irradiation-position pixel coordinates of the in-actual-image irradiation position, the in-provisional-image irradiation position, and an in-live-view-image irradiation position are derived by the CPU  100 , and the in-image irradiation position is specified from the derived irradiation-position pixel coordinates. Hereinafter, the in-actual-image irradiation position, the in-provisional-image irradiation position, and the in-live-view-image irradiation position are simply referred to as the “in-image irradiation position” in a case where it is not necessary to distinguish between the in-actual-image irradiation position and the in-provisional-image irradiation position for the sake of convenience in description. 
     The in-live-view-image irradiation position means a position, which corresponds to the irradiation position of the laser beam used in the measurement, within the live view image acquired through the imaging using the imaging device  14 . The in-live-view-image irradiation position is an example of the in-image irradiation position according to the present invention, and is derived by the same deriving method as the deriving method of the in-actual-image irradiation position described above. 
     For example, the CPU  100  is operated as the deriving unit  100 A and a control unit  100 B shown in  FIG. 10  by reading the irradiation position adjustment program  107  out of the secondary storage unit  104 , loading the readout irradiation position adjustment program into the primary storage unit  102 , and executing the irradiation position adjustment program  107 . 
     The deriving unit  100 A derives the in-live-view-image irradiation position based on the distance measured by the distance measurement unit  12  and the distance measurement control unit  68  and an emission angle β to be described below. 
     In a case where the derived in-live-view-image irradiation position is out of a default range within the live view image, the control unit  100 B performs predetermined control until the in-live-view-image irradiation position falls in the default range. The predetermined control means control for causing the distance measurement unit  12  and the distance measurement control unit  68  to measure the distance and causing the deriving unit  100 A to derive the in-live-view-image irradiation position based on the distance measured by the distance measurement unit  12  and the distance measurement control unit  68  and the emission angle β. 
     Next, the actions of the distance measurement device  10 A will be described. 
     Initially, a distance measurement process realized by executing the distance measurement program  106  in the CPU  100  in a case where a power switch of the distance measurement device  10 A is turned on will be described with reference to  FIGS. 11 to 13 . Hereinafter, a case where the live view image is displayed on the display unit  86  will be described for the sake of convenience in description. Hereinafter, the irradiation position of the laser beam onto the subject in the real space is referred to as a “real-space irradiation position” for the sake of convenience in description. 
     Although it will be described below that an in-image irradiation position in an X direction which is a front-view left-right direction for the imaging surface of the imaging element  60  included in the imaging device  14  is derived for the sake of convenience in description, an in-image irradiation position in a Y direction which is a front-view upper-lower direction for the imaging surface of the imaging element  60  included in the imaging device  14  is similarly derived. As mentioned above, the in-image irradiation positions ultimately output by deriving the in-image irradiation positions in the X direction and the Y direction are expressed by two-dimensional coordinates. 
     Hereinafter, for the sake of convenience in description, the front-view left-right direction for the imaging surface of the imaging element  60  included in the imaging device  14  is referred to as the “X direction” or a “row direction”, and the front-view upper-lower direction for the imaging surface of the imaging element  60  included in the imaging device  14  is referred to as the “Y direction” or a “column direction”. 
     In the distance measurement process shown in  FIG. 11 , the deriving unit  100 A initially determines whether or not a parameter changing factor occurs in step  200 . The parameter changing factor refers to a factor for changing parameters that influence the in-image irradiation position. 
     In the present embodiment, the parameters refer to a half angle of view α, an emission angle β, and a inter-reference-point distance d, as shown in  FIG. 15 . The half angle of view α refers to half of the angle of view on the subject captured by the imaging device  14 . The emission angle β refers to an angle at which the laser beam is emitted from the emission unit  22 . The inter-reference-point distance d refers to a distance between a first reference point P 1  prescribed for the imaging device  14  and a second base reference point P 2  prescribed for the distance measurement unit  12 . A main point of the imaging lens  50  is used as an example of the first reference point P 1 . A point previously set as an origin of coordinates capable of specifying a position of the distance measurement unit  12  in a three dimensional space is used as an example of the second reference point P 2 . Specifically, an end of front-view left and right ends of the object lens  38  or one vertex of a housing (not shown) of the distance measurement unit  12  in a case where the housing has a cuboid shape. 
     In the present embodiment, the parameter changing factor refers to, for example, replacement of the lens, the replacement of the distance measurement unit, a change in the angle of view, and a change in the emission direction. Thus, the determination result is positive in a case where at least one of the replacement of the lens, the replacement of the distance measurement unit, the change in the angle of view, and the change in the emission direction occurs in step  200 . 
     The replacement of the lens refers to the replacement of only the imaging lens  50  of the lens unit  16  and the replacement of the lens unit  16  itself. The replacement of the distance measurement unit refers to the replacement of only the object lens  32  of the distance measurement unit  12 , the replacement of only the object lens  38  of the distance measurement unit  12 , and the replacement of the distance measurement unit  12  itself. The change in the angle of view refers to a change in the angle of view by the movement of the zoom lens  52  by pressing the angle-of-view instruction button. The change in the emission direction refers to a change in the direction in which the laser beam is emitted by the emission unit  22 . 
     In a case where the parameter changing factor occurs in step  200 , the determination result is positive, and the process proceeds to step  202 . 
     For example, in step  202 , the deriving unit  100 A displays a first intention check screen  110  on the display unit  86  as shown in  FIG. 16 . Thereafter, the process proceeds to step  204 . 
     The first intention check screen  110  is a screen for checking the user&#39;s intention of whether or not to display an irradiation position mark  116  (see  FIG. 20 ) which is a mark indicating the in-actual-image irradiation position in a specifiable manner within a display region of the actual image. In the example shown in  FIG. 16 , a message of “do you display the irradiation position mark?” is displayed on the first intention check screen  110 . In the example shown in  FIG. 16 , a soft key of “yes” designated for announcing an intention to display the irradiation position mark  116  and a soft key of “no” designated for announcing an intention not to display the irradiation position mark  116  are also displayed on the first intention check screen  110 . 
     In step  204 , the deriving unit  100 A determines whether or not to display the irradiation position mark  116 . In a case where the irradiation position mark  116  is displayed in step  204 , that is, in a case where the soft key of “yes” of the first intention check screen  110  is pressed through the touch panel  88 , the determination result is positive, and the process proceeds to step  208 . In a case where the irradiation position mark  116  is not displayed in step  204 , that is, in a case where the soft key of “no” of the first intention check screen  110  is pressed through the touch panel  88 , the determination result is negative, and the process proceeds to step  290  shown in  FIG. 12 . 
     In step  290  shown in  FIG. 12 , the deriving unit  100 A determines whether or not the actual measurement and actual imaging button  90 A is turned on. In a case where the actual measurement and actual imaging button  90 A is turned on in step  290 , the determination result is positive, and the process proceeds to step  292 . 
     In step  292 , the deriving unit  100 A performs the actual measurement by controlling the distance measurement control unit  68 . The deriving unit  100 A performs the actual imaging by controlling the imaging element driver  74  and the image signal processing circuit  76 . Thereafter, the process proceeds to step  294 . 
     In step  294 , the deriving unit  100 A displays the actual image which is the image acquired by performing the actual imaging and the distance acquired by performing the actual measurement on the display unit  86 . Thereafter, the process proceeds to step  200  shown in  FIG. 11 . 
     Meanwhile, in a case where the actual measurement and actual imaging button  90 A is not turned on in step  290 , the determination result is negative, and the process proceeds to step  296 . 
     In step  296 , the deriving unit  100 A determines whether or not an end condition which is a condition in which the actual distance measurement process is ended is satisfied. For example, in the present distance measurement process, the end condition refers to a condition in which an instruction to end the actual distance measurement process is received through the touch panel  88  and/or a condition in which a predetermined time (for example, one minute) elapses after the determination result in step  290  is negative. 
     In a case where the end condition is not satisfied in step  296 , the determination result is negative, and the process proceeds to step  290 . In a case where the end condition is satisfied in step  296 , the determination result is positive, and the actual distance measurement process is ended. 
     Meanwhile, for example, the deriving unit  100 A displays a provisional measurement and provisional imaging guide screen  112  on the display unit  86  as shown in  FIG. 17  in step  208  shown in  FIG. 11 . Thereafter, the process proceeds to step  210 . 
     In the actual distance measurement process, the process is performed in any operation mode of a first operation mode in which the provisional measurement and provisional imaging is performed and a second operation mode which is an operation mode other than the first operation mode. In other words, the operation mode other than the first operation mode means an operation mode different from the first operation mode, and refers to an operation mode in which the provisional measurement and the provisional imaging are not performed. In step  208 , transition from the second operation mode to the first operation mode is displayed to the user by displaying the provisional measurement and provisional imaging guide screen  112 . In the present embodiment, the processes of step  208  to  226  correspond to the process of the first operation mode, and the processes of the steps other than step  208  to  226  correspond to the process of the second operation mode. 
     The provisional measurement and provisional imaging guide screen  112  is a screen for guiding the user information indicating that the provisional measurement and the provisional imaging are performed multiple times (for example, three times in the present embodiment) while changing the emission direction of the laser beam. In the example shown in  FIG. 17 , a message of “please, perform the provisional measurement and provisional imaging three times while changing the emission direction of the laser beam” is displayed on the provisional measurement and provisional imaging guide screen  112 . 
     In step  210 , the deriving unit  100 A determines whether or not the provisional measurement and provisional imaging button  90 B is turned on. In a case where the provisional measurement and provisional imaging button  90 B is not turned on in step  210 , the determination result is negative, and the process proceeds to step  212 . In a case where the provisional measurement and provisional imaging button  90 B is turned on in step  210 , the determination result is positive, and the process proceeds to step  214 . 
     In step  212 , the deriving unit  100 A determines whether or not the end condition is satisfied. In a case where the end condition is not satisfied in step  212 , the determination result is negative, and the process proceeds to step  210 . In a case where the end condition is satisfied in step  212 , the determination result is positive, and the actual distance measurement process is ended. 
     In step  214 , the deriving unit  100 A performs the provisional measurement by controlling the distance measurement control unit  68 . The deriving unit  100 A performs the provisional imaging by controlling the imaging element driver  74  and the image signal processing circuit  76 . Thereafter, the process proceeds to step  216 . 
     In step  216 , the deriving unit  100 A stores the provisional image which is the image acquired by performing the provisional imaging and the distance acquired by performing the provisional measurement in the primary storage unit  102 . Thereafter, the process proceeds to step  218 . 
     In step  218 , the deriving unit  100 A determines whether or not the provisional measurement and the provisional imaging are performed three times by determining whether or not the provisional measurement and provisional imaging button  90 B is turned on three times. In a case where the provisional measurement and the provisional imaging are not performed three times in step  218 , the determination result is negative, and the process proceeds to step  210 . In a case where the provisional measurement and the provisional imaging are performed three times in step  218 , the determination result is positive, and the process proceeds to step  220 . 
     Subsequently, the CPU  100  determines whether or not the relation between a plurality of provisionally measured distances (for example, three distances) is not a predetermined relation satisfying that these distances do not effectively contribute to the construction (generation) of the correspondence information to be described below used in the deriving of the in-actual-image irradiation position. That is, in step  220 , the deriving unit  100 A determines whether or not the three distances stored in the primary storage unit  102  in step  216  are effective distances. The effective distances refer to distances having the relation satisfying that the three distances stored in the primary storage unit  102  effectively contribute to the construction (generation) of correspondence information to be described below in the deriving of the in-actual-image irradiation position. For example, the relation satisfying that distances effectively contribute to the construction of the correspondence information to be described below in the deriving of the in-actual-image irradiation position means a relation satisfying that the three distances are separated from each other by a predetermined distance or more (for example, 0.3 meters or more). 
     In a case where three distances stored in the primary storage unit  102  in step  216  are not effective distances in step  220 , the determination result is negative, and the process proceeds to step  222 . In a case where the three distances stored in the primary storage unit  102  in step  216  are effective distances in step  220 , the determination result is positive, and the process proceeds to step  224 . 
     For example, in step  222 , the deriving unit  100 A displays a re-performing guide screen  114  on the display unit  86  as shown in  FIG. 18 . Thereafter, the process proceeds to step  210 . 
     The re-performing guide screen  114  is a screen for guiding the user the re-performing of the provisional measurement and the provisional imaging. In the example shown in  FIG. 18 , a message of “effective distances are not able to be measured. please, perform the provisional measurement and provisional imaging three times while changing the emission direction of the laser beam” is displayed on the re-performing guide screen  114 . 
     In step  224 , the deriving unit  100 A specifies the in-provisional-image irradiation position for every provisional image stored in the primary storage unit  102  in step  216 . Thereafter, the process proceeds to step  226 . For example, the in-provisional-image irradiation position is specified from a difference between the image acquired before the provisional measurement and the provisional imaging are performed (for example, previous frame) in the live view image and the provisional image acquired by performing the provisional imaging. The user can visually recognize the irradiation position of the laser beam from the provisional image in a case where the distance at which the provisional measurement is about several meters. In this case, the irradiation position visually recognized from the provisional image may be designated by the user through the touch panel  88 , and the designated position may be specified as the in-provisional-image irradiation position. 
     In step  226 , the deriving unit  100 A generates correspondence information which is an example of the above-described correspondence relation, and stores the generated correspondence information in the secondary storage unit  104  for every parameter changing factor. Thereafter, the process proceeds to step  228  shown in  FIG. 13 . 
     The correspondence information refers to information acquired by associating the in-provisional-image irradiation position with the distance of the distances stored in the primary storage unit  102  in step  216  which corresponds to the provisional image related to the in-provisional-image irradiation position for each in-provisional-image irradiation position specified in step  224 . 
     For example, in the present embodiment, the correspondence information is stored as a correspondence table  98  in the secondary storage unit  104 , as shown in  FIG. 14 . The correspondence table  98  is updated by storing the generated correspondence information whenever the correspondence information is generated in step  226 . In the correspondence table  98 , the correspondence information is associated with the parameter changing factor of which the occurrence is determined the in step  200 . In the example shown in  FIG. 14 , the replacement of the lens, the replacement of the distance measurement unit, the change in the angle of view, and the change in the emission direction are used as an example of the parameter changing factor. ( 1 ), ( 2 ), and ( 3 ) shown in  FIG. 14  are identification codes for identifying that these factors are parameter changing factors occurring in different timings. 
     Although three correspondence information items are associated with each of the replacement of the lens, the replacement of the distance measurement unit, and the change in the emission direction in the example shown in  FIG. 14 , the technology of the present disclosure is not limited thereto. For example, in a case where the parameter changing factor occurs once, the correspondence information items acquired by performing the provisional measurement and the provisional imaging multiple times for the parameter changing factor occurring once are associated with one parameter changing factor. For example, in a case where the provisional measurement and the provisional imaging are performed two times for the parameter changing factor occurring once, two correspondence information items are associated with one parameter changing factor. 
     In step  228 , the deriving unit  100 A determines whether or not the actual measurement and actual imaging button  90 A is turned on. In a case where the actual measurement and actual imaging button  90 A is turned on in step  228 , the determination result is positive, and the process proceeds to step  230 . In a case where the actual measurement and actual imaging button  90 A is not turned on in step  228 , the determination result is negative, and the process proceeds to step  244 . 
     In step  230 , the deriving unit  100 A performs the actual measurement by controlling the distance measurement control unit  68 . The deriving unit  100 A performs the actual imaging by controlling the imaging element driver  74  and the image signal processing circuit  76 . Thereafter, the process proceeds to step  232 . 
     In step  232 , the deriving unit  100 A determines whether or not specific correspondence information is stored in the correspondence table  98 . The specific correspondence information refers to the correspondence information of the correspondence information items acquired in the past which corresponds to the distance acquired by performing the actual measurement through the process in step  230 . 
     For example, the correspondence information items acquired in the past refer to the correspondence information items which are associated with the corresponding parameter changing factor and are stored in the correspondence table  98 . For example, the correspondence information corresponding to the distance acquired by performing the actual measurement refers to the correspondence information associated with a distance matching the distance which is acquired by performing the actual measurement within a predetermined error. For example, the predetermined error is a fixed value of ±0.1 meters, and the technology of the present disclosure is not limited thereto. The predetermined error may be a variable value changed according to an instruction of the user through the touch panel  88 . 
     In a case where the specific correspondence information is not stored in the correspondence table  98  in step  232 , the determination result is negative, and the process proceeds to step  234 . In a case where the specific correspondence information is stored in the correspondence table  98  in step  232 , the determination result is positive, and the process proceeds to step  236 . 
     In step  234 , the deriving unit  100 A derives the parameter based on the latest correspondence information of the correspondence information items which are related to the corresponding parameter changing factor and are stored in the correspondence table  98 , and associates the derived parameter with the latest correspondence information. Thereafter, the process proceeds to step  238 . For example, the “latest correspondence information” refers to the correspondence information generated lately in step  226 . The parameter derived in step  234  is an uncertain parameter in a current point of time, and varies for every parameter changing factor as represented in the following Table 1. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 parameter changing factor 
                 parameter 
               
               
                   
               
             
            
               
                 replacement of lens 
                 half angle of view α, emission angle β 
               
               
                 replacement of distance 
                 emission angle β, inter-reference-point 
               
               
                 measurement unit 
                 distance d 
               
               
                 change in angle of view 
                 half angle of view α 
               
               
                 change in emission direction 
                 emission angle β 
               
               
                   
               
            
           
         
       
     
     The number of uncertain parameters may be one to three. For example, in the example shown in Table 1, in a case where both the replacement of the distance measurement unit and the change in the angle of view are performed, the number of uncertain parameters is three such as the half angle of view α, the emission angle β, and the inter-reference-point distance d. In a case where only the replacement of the lens is performed, the number of uncertain parameters is two such as the half angle of view α and the emission angle β. In a case where only the replacement of the distance measurement unit is performed, the number of uncertain parameters is two such as the emission angle β, and the inter-reference-point distance d. In a case where only the change in the angle of view is performed, the number of uncertain parameters is one such as the half angle of view α. In a case where only the change in the emission direction is performed, the number of uncertain parameters is one such as the emission angle β. 
     For example, the parameters are derived from the following Expressions (2) to (4) in step  234 . In Expressions (2) and (3), a distance D is a distance specified from the latest correspondence information, and distances specified from the latest correspondence information are distances D 1 , D 2 , and D 3  in a case where the latest correspondence information is the correspondence information related to the change in the angle of view ( 1 ) in the example shown in  FIG. 14 . In Expression (4), “row-direction pixels of the irradiation positions” are in-image irradiation positions in a row direction, and “half of the number of row-direction pixels” is half of the number of pixels in the row direction in the imaging element  60 . For example, in the present embodiment, the half angle of view α is derived from the following Expression (5). In Expression (5), “f” is a focal length. For example, it is preferable that the focal length f substituted into Expression (5) is a focal length used in the actual imaging of step  230 . 
     
       
         
           
             
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     In step  234 , the in-provisional-image irradiation positions specified from the latest correspondence information of the correspondence information items stored in the correspondence table  98  are the “row-direction pixels of the irradiation positions”. In the example shown in  FIG. 14 , in a case where the latest correspondence information is the correspondence information related to the change in the angle of view ( 1 ), the in-provisional-image irradiation positions specified from the latest correspondence information are X 1 , X 2 , and X 3 . The distance specified from the latest correspondence information of the correspondence information items stored in the correspondence table  98  are used as the distance D in Expressions (2) and (3) for every corresponding in-provisional-image irradiation position (corresponding “row-direction pixel of the irradiation position”). The parameter closest to each of the “row-direction pixels of the irradiation positions” is derived by the deriving unit  100 A. 
     Now, an example in which a part of the correspondence table  98  shown in  FIG. 14  is used in the deriving method of the parameter will be described. For example, in a case where the correspondence information items related to the change in the angle of view ( 1 ) and the replacement of the distance measurement unit ( 1 ) which are examples of the parameter changing factor are used as the latest correspondence information items, the latest correspondence information items are distances D 1 , D 2 , D 3 , D 16 , D 17 , and D 18  and the in-provisional-image irradiation positions X 1 , X 2 , X 3 , X 16 , X 17 , and X 18 . 
     The in-provisional-image irradiation position X 1  is used as the “row-direction pixel of the irradiation position” in Expression (4), the distance D 1  is used as the distance D in Expressions (2) and (3). The in-provisional-image irradiation position X 2  is used as the “row-direction pixel of the irradiation position” in Expression (4), the distance D 2  is used as the distance D in Expressions (2) and (3). The in-provisional-image irradiation position X 3  is used as the “row-direction pixel of the irradiation position” in Expression (4), the distance D 3  is used as the distance D in Expressions (2) and (3). The in-provisional-image irradiation position X 16  is used as the “row-direction pixel of the irradiation position” in Expression (4), the distance D 16  is used as the distance D in Expressions (2) and (3). The in-provisional-image irradiation position X 17  is used as the “row-direction pixel of the irradiation position” in Expression (4), the distance D 17  is used as the distance D in Expressions (2) and (3). The in-provisional-image irradiation position X 18  is used as the “row-direction pixel of the irradiation position” in Expression (4), the distance D 18  is used as the distance D in Expressions (2) and (3). The half angle of view α, the emission angle β, and the inter-reference-point distance d closest to the in-provisional-image irradiation positions X 1 , X 2 , X 3 , X 16 , X 17 , and X 18  are derived from Expressions (2) to (4). 
     In step  236 , the deriving unit  100 A derives the parameter based on the specific correspondence information. Thereafter, the process proceeds to step  238 . The parameter derived by in step  236  is a parameter associated with the specific correspondence information, and is, for example, a parameter associated with the correspondence information by performing the process of step  234  in the past. 
     The parameter derived in step  236  may be a parameter associated with the correspondence information by performing the process of step  234  in the past, and the deriving unit  100 A may derive the parameter again by using Expressions (2) to (4) based on the specific correspondence information. 
     In step  238 , the deriving unit  100 A derives the in-actual-image irradiation position based on the parameter derived in step  234  or step  236 . Thereafter, the process proceeds to step  240 . 
     For example, the in-actual-image irradiation position is derived from Expressions (2) to (4) in step  238 . That is, the parameter derived in step  234  or step  236  is substituted into Expressions (2) to (4), and the distance is substituted as the distance D into Expressions (2) to (4) by performing the actual measurement in step  230 . Accordingly, the “row-direction pixel of the irradiation position” is derived as the in-actual-image irradiation position. 
     For example, in step  240 , the deriving unit  100 A displays the actual image, the distance, and the irradiation position mark  116  on the display unit  86  as shown in  FIG. 20 . Thereafter, the process proceeds to step  242 . 
     The actual image displayed on the display unit  86  by performing the process of step  240  is an image acquired by performing the actual imaging in step  230 . 
     The distance displayed on the display unit  86  by performing the process of step  240  is a distance acquired by performing the actual measurement in step  230 . 
     The irradiation position mark  116  displayed on the display unit  86  by performing the process of step  240  is a mark indicating the in-actual-image irradiation position derived by performing the process of step  238 . 
     In step  242 , the deriving unit  100 A determines whether or not the distance acquired by performing the actual measurement in step  230  is in a correspondence information distance range. A case where the distance acquired by performing the actual measurement in step  230  is not in the correspondence information distance range means that the distance acquired by performing the actual measurement in step  230  is out of the correspondence information distance range. 
     A case where the distance is in the correspondence information distance range means that the distance is within a range of the distance specified from the correspondence information used in step  234  or step  236 . In contrast, a case where the distance is out of the correspondence information distance range means that the distance is not in the range of the distance specified from the correspondence information used in step  234  or step  236 . The case where the distance is out of the correspondence information distance range is distinguished between a case where the distance is out of a first correspondence information distance range and a case where the distance is out of a second correspondence information distance range. 
     For example, in a case where the relation between distances D 100 , D 101 , and D 102  specified from the correspondence information used in step  234  or step  236  “D 100 &lt;D 101 &lt;D 102 ” as shown in  FIG. 21 , the case where the distance is in the correspondence information distance range and the case where the distance is out of the correspondence information distance range are defined as follows. 
     That is, in the example shown in  FIG. 21 , the case where the distance is in the correspondence information distance range corresponds to a range of the distance D 100  or more and the distance D 102  or less. The case where the distance is out of the first correspondence information distance range corresponds to a range of less than the distance D 100 . The case where the distance is out of the second correspondence information distance range corresponds to a range of more than the distance D 102 . 
     In a case the distance acquired by performing the actual measurement in step  230  is in the correspondence information distance range in step  242 , the determination result is positive, and the process proceeds to step  244 . In a case where the distance acquired by performing the actual measurement in step  230  is out of the correspondence information distance range in step  242 , the determination result is negative, and the process proceeds to step  246 . 
     For example, in step  246 , the deriving unit  100 A displays a warning and recommendation message  120  on the display unit  86  such that the alarm and recommendation message is superimposed on the actual image, as shown in  FIG. 22 . Thereafter, the process proceeds to step  248 . 
     The warning and recommendation message  120  is a message for warning the user that there is a high possibility that the laser beam will not be applied to a position in the real space which corresponds to the position of the irradiation position mark  116  and recommending the provisional measurement and the provisional imaging to the user. 
     In the example shown in  FIG. 22 , a warning message of “the irradiation position mark has low accuracy (reliability)” is included in the warning and recommendation message  120 . In the example shown in  FIG. 22 , a recommendation message of “it is recommended that the provisional measurement and the provisional imaging are performed in a range of oo meters to 44 meters” is included in the warning and recommendation message  120 . 
     The “range of oo meters to ΔΔ meters” included in the recommendation message is a range out of the first correspondence information distance range or a range out of the second correspondence information distance range. That is, in a case where the distance acquired by performing the actual measurement in step  230  is out of the first correspondence information distance range, a specific range out of the first correspondence information distance range is employed. In a case where the distance acquired by performing the actual measurement in step  230  is out of the second correspondence information distance range, a specific range out of the second correspondence information distance range is employed. 
     The specific range means a range of the distance recommended in the provisional measurement based on the relation between the distance acquired by performing the actual measurement in step  230  and the correspondence information distance range. For example, the specific range is a range which is uniquely determined from a predetermined table or calculation expression depending on a degree of deviation of the distance acquired by performing the actual measurement in step  230  from a specific value in the correspondence information distance range. The specific value in the correspondence information distance range may be a center value or an average value in the correspondence information distance range. For example, the specific range out of the first correspondence information distance range may be a range which is uniquely determined depending on a difference between the distance D 100  shown in  FIG. 21  and the distance acquired by performing the actual measurement in step  230 . For example, the specific range out of the second correspondence information distance range may be a range which is uniquely determined depending on a difference between the distance D 102  shown in  FIG. 21  and the distance acquired by performing the actual measurement in step  230 . Instead of the “specific range”, a “plurality of default distances” may be used. For example, three or more distances separated from each other at equal spaces within the specific range acquired as described above may be used as the plurality of default distances, and a plurality of distances recommended in the provisional measurement may be used. 
     For example, although the warning and recommendation message  120  is presented to the user in step  246  by being visually displayed on the display unit  86 , the technology of the present disclosure is not limited thereto. For example, the message may be presented to the user by being output as sound by a sound playback device (not shown) provided at the distance measurement device  10 A, or may be displayed through visual display and audible indication. 
     For example, in step  248 , the deriving unit  100 A displays a second intention check screen  118  on the display unit  86  as shown in  FIG. 19 . Thereafter, the process proceeds to step  250 . 
     The second intention check screen  118  is a screen for checking the user′ intention of whether or not to increase the accuracy of the irradiation position of the laser beam, that is, the accuracy of the irradiation position mark  116 . In the example shown in  FIG. 19 , a message of “do you want to increase the accuracy of the irradiation position mark?” is displayed on the second intention check screen  118 . In the example shown in  FIG. 19 , a soft key of “yes” designated for announcing an intention to increase the accuracy of the irradiation position mark  116  is displayed on the second intention check screen  118 . In the example shown in  FIG. 19 , a soft key of “no” designated for announcing an intention not to increase the accuracy of the irradiation position mark  116  is displayed on the second intention check screen  118 . 
     In step  250 , the deriving unit  100 A determines whether or not to increase the accuracy of the irradiation position mark  116 . In a case where the accuracy of the irradiation position mark  116  is increased in step  250 , that is, in a case where the soft key of “yes” of the second intention check screen  118  is pressed through the touch panel  88 , the determination result is positive, and the process proceeds to step  208 . In a case where the accuracy of the irradiation position mark  116  is not increased in step  250 , that is, in a case where the soft key of “no” of the second intention check screen  118  is pressed through the touch panel  88 , the determination result is negative, and the process proceeds to step  244 . 
     Meanwhile, in a case where the parameter changing factor does not occur in step  200  shown in  FIG. 11 , the determination result is negative, and the process proceeds to step  252 . 
     In step  252 , the deriving unit  100 A determines whether or not the correspondence information is stored in the correspondence table  98 . 
     In a case where the correspondence information is not stored in the correspondence table  98  in step  252 , the determination result is negative, and the process proceeds to step  200 . In a case where the correspondence information is stored in the correspondence table  98  in step  252 , the determination result is positive, and the process proceeds to step  228 . 
     Meanwhile, the deriving unit  100 A determines whether or not the end condition is satisfied in step  244  shown in  FIG. 13 . In a case where the end condition is not satisfied in step  244 , the determination result is negative, and the process proceeds to step  200 . In a case where the end condition is satisfied in step  244 , the determination result is positive, and the actual distance measurement process is ended. 
     Next, the irradiation position adjustment process realized by executing the irradiation position adjustment program  107  in the CPU  100  in a case where the irradiation position adjustment button  90 F is pressed in a state in which the live view image is displayed on the display unit  86  will be described with reference to  FIG. 23 . 
     Although it will be described below that the irradiation position of the laser beam in the X-direction is adjusted by operating the horizontal rotation mechanism  15  for the sake of convenience in description, the irradiation position of the laser beam in the Y direction is similarly adjusted. The adjustment of the irradiation position of the laser beam in the Y direction is realized by operating the longitudinal rotation mechanism  13 . Hereinafter, a case where the live view image is displayed on the display unit  86  at a specific frame rate will be described for the sake of convenience in description. 
     In the irradiation position adjustment process shown in  FIG. 23 , the control unit  100 B initially determines whether or not a default time comes in step  400 . For example, the default time means a time whenever the live view image is displayed in three frames. The default time is not limited to the time whenever the live view image is displayed in three frames, and the number of frames in which the live view image is displayed may not be three, or may be prescribed by a predetermined time such as 3 seconds or 5 seconds. The default time may be a time previously determined according to an instruction received through the touch panel  88 . 
     In a case where the default time comes in step  400 , the determination result is positive, and the process proceeds to step  402 . In a case where the default time does not come in step  400 , the determination result is negative, and the process proceeds to step  416 . 
     In step  402 , the control unit  100 B performs the measurement of the distance by controlling the distance measurement control unit  68 . The control unit  100 B performs the imaging by controlling the imaging element driver  74  and the image signal processing circuit  76 . Thereafter, the process proceeds to step  404 . 
     In step  404 , the control unit  100 B causes the deriving unit  100 A to derive the in-live-view-image irradiation position based on the latest parameter. Therefore, the process proceeds to step  406 . For example, the latest parameter is a parameter used in the deriving of the in-actual-image irradiation position in a case where the in-image irradiation position derived last before the process of step  404  is performed is the in-actual-image irradiation position derived by performing the process of step  238  (see  FIG. 13 ). For example, in a case where the process of step  412  to be described below after the process of previous step  404  is performed, the latest parameter is a parameter other than an emission angle β of the parameters used in the deriving of the latest in-live-view-image irradiation position and an emission angle β updated in step  412 . 
     For example, the in-live-view-image irradiation position is derived from Expressions (2) to (4) in step  404 . That is, the latest parameter is substituted into Expressions (2) to (4), and the distance acquired by performing the measurement in step  402  is substituted as the distance D into Expressions (2) to (4). Accordingly, the “row-direction pixel of the irradiation position” is derived as the in-live-view-image irradiation position. 
     For example, as shown in  FIGS. 25 and 26 , the control unit  100 B may control the display unit  86  to display an irradiation position mark  116 A which is a mark indicating the in-live-view-image irradiation position derived by performing the process of step  404  in a display region of the live view image. Therefore, according to the distance measurement device  10 A, the user can easily ascertain the latest in-live-view-image irradiation position compared to a case where the irradiation position mark  116 A is not displayed. 
     In a case where the irradiation position mark  116 A is displayed, the control unit  100 B may control the display unit  86  to display such that the irradiation position mark  116 A is turned on and off and the irradiation position mark  116  is not turned on and off in order to distinguish the irradiation position mark  116 A from the irradiation position mark  116  shown in  FIG. 20 . 
     In step  406 , the control unit  100 B determines whether or not the in-live-view-image irradiation position derived by the deriving unit  100 A by performing the process of step  404  is in the default range. For example, a case where the in-live-view-image irradiation position is in the default range means that the in-live-view-image irradiation position is present inside a circular frame  117  of which a radius from the center of the captured image is a predetermined length (for example, several millimeters in the present embodiment), as shown in  FIG. 24 . The frame  117  may be a frame surrounding a specific partial region in the display region of the captured image. Although it has been described in the present embodiment that the frame  117  is displayed in the display region of the captured image, the technology of the present disclosure is not limited thereto, and the frame  117  may not be displayed. The display and the non-display of the frame  117  performed by the display unit  86  may be selectively switched by the control unit  100 B according to an instruction received through the touch panel  88 . 
     In a case where the in-live-view-image irradiation position is out of the default range in step  406 , the determination result is negative, and the process proceeds to step  408 . 
     In step  408 , the control unit  100 B displays out-of-default-range information on the display unit  86  such that the out-of-default-range information is superimposed on the live view image. Therefore, the process proceeds to step  410 . The out-of-default-range information is information indicating that the in-live-view-image irradiation position derived by the deriving unit  100 A by performing the process of step  404  is out of the default range. 
     For example, as the out-of-default-range information, there is a message  119  of the “irradiation position of the laser beam is not present in the central portion of the image” displayed on the display unit  86 , as shown in  FIG. 25 . This message  119  is merely an example. For example, in a case where the frame  117  is displayed, a message of the “frame is not irradiated with the laser beam” may be displayed as the out-of-default-range information on the display unit  86 . For example, the message is not limited to be visually displayed on the display unit  86 , and may be audibly presented by being as sound by a sound playback device (not shown). Permanent visual display using an image forming device (not shown) may be performed, or at least two of the visual display, the audible indication, or the permanent visual display may be performed. 
     As stated above, the out-of-default-range information is displayed by the display unit  86  by performing the process of step  408 , and thus, notification indicating that the in-live-view-image irradiation position is out of the default range is presented to the user. That is, the display unit  86  is operated as the second notification unit according to the technology of the present disclosure by performing the process of step  408 . 
     In step  410 , the control unit  100 B rotates the distance measurement unit  12  to a default direction by a default rotation amount (an example of a default amount according to the technology of the present disclosure) by controlling the horizontal rotation mechanism  15  through the motor driver  23 . Thereafter, the process proceeds to step  412 . 
     For example, the default rotation amount means a constant rotation amount. For example, the default rotation amount is a rotation amount needed to change the emission angle β by a predetermined angle (for example, 3 degrees). 
     The default direction is a direction in which a distance between the in-live-view-image irradiation position derived by the deriving unit  100 A by performing the process of step  404  and the center of the frame  117  decreases. Thus, the default direction is uniquely determined from a relation between the in-live-view-image irradiation position derived by the deriving unit  100 A by performing the process of step  404  and the center of the captured image which is the center of the frame  117 . 
     In step  412 , the control unit  100 B updates the emission angle β according to the rotation direction and the rotation amount of the distance measurement unit  12  rotated by performing the process of step  410 . Thereafter, the process proceeds to step  400 . 
     In a case where the in-live-view-image irradiation position is in the default range in step  406 , the determination result is positive, and the process proceeds to step  414 . 
     In step  414 , the control unit  100 B displays in-default-range information on the display unit  86  such that the in-default-range information is superimposed on the live view image. Thereafter, the process proceeds to step  416 . The in-default-range information is information indicating that the in-live-view-image irradiation position derived by the deriving unit  100 A by performing the process of step  404  is in the default range. 
     For example, as the in-default-range information, there is a message  121  of the “irradiation position of the laser beam is present in the central portion of the image” displayed on the display unit  86 , as shown in  FIG. 26 . This message  121  is merely an example. For example, in a case where the frame  117  is displayed, a message of the “frame is irradiated with the laser beam” may be displayed as the in-default-range information on the display unit  86 . For example, the message is not limited to be visually displayed on the display unit  86 , and may be audibly presented by being output as sound by a sound playback device (not shown). Permanent visual display using an image forming device (not shown) may be performed, or at least two of the visual display, the audible indication, or the permanent visual display may be performed. 
     As mentioned above, the in-default-range information is displayed on the display unit  86  by performing the process of step  414 , and thus, notification indicating that the in-live-view-image irradiation position is in the default range is presented to the user. That is, the display unit  86  is operated by the first notification unit according to the technology of the present disclosure by performing the process of step  414 . 
     In step  416 , the control unit  100 B determines whether or not an end condition which is a condition in which an actual irradiation position adjustment process is ended is satisfied. In the actual irradiation position adjustment process, the end condition is, for example, a condition in which the irradiation position adjustment button  90 F is pressed again and/or a condition in which a predetermined time (for example, 1 minute) elapses after the performing of the actual irradiation position adjustment process is started. 
     In a case where the end condition is not satisfied in step  416 , the determination result is negative, and the process proceeds to step  400 . In a case where the end condition is satisfied in step  416 , the determination result is positive, and the actual irradiation position adjustment process is ended. 
     As described above, in the distance measurement device  10 A, in a case where the in-live-view-image irradiation position is out of the default range within the captured image (step  406 : N), the measurement performed by the distance measurement control unit  68  is performed until the in-live-view-image irradiation position is positioned within the frame  117  (step  402 ). The in-live-view-image irradiation position is derived based on the distance measured by the distance measurement control unit  68  and the latest parameter including the latest emission angle β (step  404 ). 
     Therefore, according to the distance measurement device  10 A, it is possible to perform the distance measurement in a state in which the in-live-view-image irradiation position is positioned within the frame  117 . 
     In the distance measurement device  10 A, in a case where the in-live-view-image irradiation position is out of the default range within the captured image, the measurement is performed by the distance measurement control unit  68 , and the emission angle β is changed by the rotation mechanism by driving the motors  17  and  19  until the in-live-view-image irradiation position is positioned within the frame  117 . The in-live-view-image irradiation position is derived based on the distance measured by the distance measurement control unit  68  and the latest parameter including the latest emission angle β. 
     Therefore, according to the distance measurement device  10 A, it is possible to reduce an effort to position the in-live-view-image irradiation position within the frame  117  compared to a case where the emission angle β is changed without using the motors  17  and  19  and the rotation mechanism. 
     In the distance measurement device  10 A, a power for changing the emission angle β to the default direction is generated by the motors  17  and  19  based on the positional relation between the latest in-live-view-image irradiation position and the center of the frame  117 , and thus, the emission angle β is changed (steps  410  and  412 ). 
     Therefore, according to the distance measurement device  10 A, it is possible to position the in-live-view-image irradiation position within the frame  117  with high accuracy compared to a case where the power for changing the emission angle β is not generated by the motors  17  and  19  regardless of the positional relation between the latest in-live-view-image irradiation position and the center of the frame  117 . 
     In the distance measurement device  10 A, the irradiation position adjustment process is performed for a period during which the live view image is displayed on the display unit  86 . 
     Therefore, according to the distance measurement device  10 A, it is possible to perform the distance measurement in a case where the in-live-view-image irradiation position is positioned within the frame  117  while referring to the state of the subject. 
     In the distance measurement device  10 A, the captured image is displayed as the live view image, and the frame  117  is displayed in the display region of the live view image. 
     Therefore, according to the distance measurement device  10 A, the user can easily ascertain the position of the frame  117  in the display region of the live view image compared to a case where the frame  117  is not displayed in the display region of the live view image. 
     In the distance measurement device  10 A, in a case where the in-live-view-image irradiation position is positioned within the frame  117  (step  406 : Y), the message  121  is displayed in the display region of the live view image (see  FIG. 26 ). 
     Therefore, according to the distance measurement device  10 A, the user can easily recognize that the in-live-view-image irradiation position is positioned within the frame  117  compared to a case where the notification indicating that the in-live-view-image irradiation position is positioned within the frame  117  is not presented. 
     In the distance measurement device  10 A, in a case where the in-live-view-image irradiation position is out of the frame  117  (step  406 : N), the message  119  is displayed in the display region of the live view image (see  FIG. 25 ). 
     Therefore, according to the distance measurement device  10 A, the user can easily recognize that the in-live-view-image irradiation position is positioned within the frame  117  compared to a case where the notification indicating that the in-live-view-image irradiation position is out of the frame  117  is not presented. 
     Although it has been described in the first embodiment that the control unit  100 B acquires the direction in which the distance measurement unit  12  is rotated based on the positional relation between the latest in-live-view-image irradiation position and the center of the frame  117 , the technology of the present disclosure is not limited thereto. For example, the control unit  100 B may acquire the direction in which the distance measurement unit  12  is rotated based on the positional relation between the latest in-live-view-image irradiation position and one specific point of quadrant points of the frame  117 . As stated above, the control unit  100 B may acquire the direction in which the distance measurement unit  12  is rotated based on the positional relation between the latest in-live-view-image irradiation position and the frame  117 . 
     Although it has been described in the first embodiment that the frame  117  is positioned in the central portion within the captured image, the frame  117  may be one end portion of both end portions within the captured image in a left-right direction, or may be one end of both ends within the captured image in an upper-lower direction. The position of the frame  117  may be fixed, and may be changed according to, for example, an instruction received through the touch panel  88 . The size of the frame  117  may be fixed, and may be changed according to, for example, an instruction received through the touch panel  88 . 
     Although it has been described in the first embodiment that the frame  117  has the circular shape, the technology of the present disclosure is not limited thereto, and may have, for example, a frame having another shape such as an oval shape, a square shape, or a triangular shape formed in a closed region. 
     Although it has been described in the first embodiment that the emission angle β is updated according to the rotation of the distance measurement unit  12 , the technology of the present disclosure is not limited thereto, and the inter-reference-point distance d together with the emission angle β may also be updated. For example, in a case where the inter-reference-point distance d is updated, the in-live-view-image irradiation position may be derived based on the latest parameter including the updated inter-reference-point distance d in step  404  shown in  FIG. 23 . 
     Second Embodiment 
     Although it has been described in the first embodiment that the in-live-view-image irradiation position is derived regardless of a dissimilarity between the distances before and after the measurement is performed, it will be described in a second embodiment that whether or not to derive the in-live-view-image irradiation position depending on the dissimilarity between the distances before and after the measurement is performed. In the second embodiment, since the same constituent elements as the constituent elements described in the first embodiment will be assigned the same references, the description thereof will be omitted, and only portions different from those of the first embodiment will be described. 
     A distance measurement device  10 B (see  FIGS. 1 and 4 ) according to the second embodiment is different from the distance measurement device  10 A in that an irradiation position adjustment process shown in  FIG. 27  is performed instead of the irradiation position adjustment process shown in  FIG. 23 . 
     The distance measurement device  10 B according to the second embodiment is different from the distance measurement device  10 A in that an irradiation position adjustment program  132  instead of the irradiation position adjustment program  107  is stored in the secondary storage unit  104  (see  FIG. 8 ). 
     Next, an irradiation position adjustment process which is realized as the action of the distance measurement device  10 B by performing the irradiation position adjustment program  132  in the CPU  100  will be described with reference to  FIG. 27 . The same steps as those of the flowcharts shown in  FIG. 23  will be assigned the same step numbers, and thus, the description thereof will be omitted. Hereinafter, for the sake of convenience in description, it will be described on the assumption that the process of step  238  of the distance measurement process described in the first embodiment is already performed. 
     The irradiation position adjustment process shown in  FIG. 27  is different from the irradiation position adjustment process shown in  FIG. 23  in that step  403  is provided between the step  402  and step  404 . 
     In step  403 , the control unit  100 B derives a distance dissimilarity, and determines whether or not the derived distance dissimilarity exceeds a threshold value. For example, in a case where the process of step  404  is already performed, the distance dissimilarity is a dissimilarity between the distance used in the previous deriving task of the in-live-view-image irradiation position performed by the deriving unit  100 A and the latest distance measured by performing the process of step  402 . 
     In step  403 , in a case where the process of step  404  is already performed, an absolute value of a difference between the distance used in the previous deriving task of the in-live-view-image irradiation position performed by the deriving unit  100 A and the latest distance measured by performing the process of step  402  is used as an example of the distance dissimilarity. 
     For example, in a case where the process of step  404  is not performed yet, the distance dissimilarity is a dissimilarity between the distance used in the deriving of the in-actual-image irradiation position performed by the deriving unit  100 A and the latest distance measured by performing the process of step  402 . 
     In step  403 , in a case where the process of step  404  is not performed yet, an absolute value of a difference between the distance used in the deriving of the in-actual-image irradiation position performed by the deriving unit  100 A and the latest distance measured by performing the process of step  402  is used as the example of the distance dissimilarity. 
     Although the absolute value of the difference is used as the example of the distance dissimilarity, the technology of the present disclosure is not limited thereto. For example, in a case where the process of step  404  is not performed yet, a ratio of the latest distance measured by performing the process of step  402  to the distance used in the deriving of the in-actual-image irradiation position performed by the deriving unit  100 A may be used as the distance dissimilarity. For example, in a case where the process of step  404  is already performed, a ratio of the latest distance measured by performing the process of step  402  to the distance used in the previous deriving task of the in-live-view-image irradiation position performed by the deriving unit  100 A may be used as the distance dissimilarity. 
     In a case where the distance dissimilarity exceeds the threshold value in step  403 , the determination result is positive, and the process proceeds to step  404 . In a case where the distance dissimilarity is equal to or less than the threshold value in step  403 , the determination result is negative, and the process proceeds to step  400 . 
     As described above, in the distance measurement device  10 B, the distance is Intermittently measured by performing the process of step  400  (step  402 ). In a case where the latest distance dissimilarity is equal to or greater than the threshold value (step  403 : Y), the processes subsequent to step  404  are performed. 
     Therefore, according to the distance measurement device  10 B, it is possible to easily to maintain the in-live-view-image irradiation position in the frame  117  compared to a case where the processes subsequent to step  404  are not performed in a case where the distance dissimilarity is equal to or greater than the threshold value. 
     Third Embodiment 
     Although it has been described in the second embodiment that the in-live-view-image irradiation position is able to be adjusted under the condition in which the default time comes, it will be described in a third embodiment that the in-live-view-image irradiation position is able to be adjusted under the condition in which the release button is half pressed. In the third embodiment, since the same constituent elements as the constituent elements described in the first and second embodiments will be assigned the same references, the description thereof will be omitted, and only portions different from those of the first and second embodiments will be described. 
     A distance measurement device  10 C (see  FIGS. 1 and 4 ) according to the third embodiment is different from the distance measurement device  10 B in that an irradiation position adjustment process shown in  FIG. 28  is performed instead of the irradiation position adjustment process shown in  FIG. 27 . 
     The distance measurement device  10 C according to the third embodiment is different from the distance measurement device  10 B in that an irradiation position adjustment program  134  instead of the irradiation position adjustment program  132  is stored in the secondary storage unit  104  (see  FIG. 8 ). 
     Next, an irradiation position adjustment process which is realized as the action of the distance measurement device  10 C by performing the irradiation position adjustment program  134  in the CPU  100  will be described with reference to  FIG. 28 . The same steps as those of the flowcharts shown in  FIG. 27  will be assigned the same step numbers, and thus, the description thereof will be omitted. 
     The irradiation position adjustment process shown in  FIG. 28  is different from the irradiation position adjustment process shown in  FIG. 27  in that step  450  is provided instead of step  400 . 
     In step  450 , the control unit  100 B determines whether or not the release button is in the half pressed state. In a case where the release button is in the half pressed state in step  450 , the determination result is positive, and the process proceeds to step  402 . In a case where the release button is not in the half pressed state in step  450 , the determination result is negative, and the process proceeds to step  416 . 
     As described above, in the distance measurement device  10 C, in a case where the release button is in the half pressed state (step  450 : Y), the processes subsequent to step  402  are performed. 
     Therefore, according to the distance measurement device  10 C, it is possible to prevent the in-live-view-image irradiation position from entering a state in which the in-live-view-image irradiation position is not positioned within the frame  117  at the time of the actual exposing compared to a case where the processes subsequent to step  402  are not performed in a case where the release button is in the half pressed state. 
     Fourth Embodiment 
     Although it has been described in the first to third embodiments that the distance measurement unit  12  is rotated by activating the rotation mechanism by the power generated by the motors  17  and  19 , it will be described in a fourth embodiment that the distance measurement unit  12  is manually rotated. In the fourth embodiment, since the same constituent elements as the constituent elements described in the first to third embodiments will be assigned the same references, the description thereof will be omitted, and only portions different from those of the first to third embodiments will be described. 
     For example, as shown in  FIG. 29 , a distance measurement device  10 D according to the fourth embodiment is different from the distance measurement device  10 C in that the imaging device  139  instead of the imaging device  14  is provided. The imaging device  139  is different from the imaging device  14  in that an imaging device main body  180  instead of the imaging device main body  18  is provided. The imaging device main body  180  is different from the imaging device main body  18  in that a rotary encoder  25  is provided instead of the motor  17  and the motor driver  21 . The distance measurement device  10 D according to the fourth embodiment is different from the distance measurement device  10 C in that a rotary encoder  27  is provided instead of the motor  19  and the motor driver  23 . 
     The rotary encoder  25  is connected to the longitudinal rotation mechanism  13  and the busline  84 , and detects the rotation direction and the rotation amount of the hot shoe  20  rotated by the longitudinal rotation mechanism  13 . The main control unit  62  acquires the rotation direction and the rotation amount detected by the rotary encoder  25 . The rotary encoder  27  is connected to the horizontal rotation mechanism  15  and the busline  84 , and detects the rotation direction and the rotation amount of the hot shoe  20  rotated by the horizontal rotation mechanism  15 . The main control unit  62  acquires the rotation direction and the rotation amount detected by the rotary encoder  27 . 
     A distance measurement device  10 D according to the fourth embodiment is different from the distance measurement device  10 C in that an irradiation position adjustment process shown in  FIG. 30  is performed instead of the irradiation position adjustment process shown in  FIG. 28 . 
     The distance measurement device  10 D according to the fourth embodiment is different from the distance measurement device  10 C in that an irradiation position adjustment program  136  instead of the irradiation position adjustment program  134  is stored in the secondary storage unit  104  (see  FIG. 8 ). 
     Next, an irradiation position adjustment process which is realized as the action of the distance measurement device  10 D by performing the irradiation position adjustment program  136  in the CPU  100  will be described with reference to  FIG. 30 . The same steps as those of the flowcharts shown in  FIG. 28  will be assigned the same step numbers, and thus, the description thereof will be omitted. Hereinafter, for the sake of convenience in description, it will be assumed that the distance measurement unit  12  is not rotated by the power of the motors  17  and  19 , the rotation mechanism is manually activated, and the distance measurement unit  12  is rotated according to the rotation operation of the rotation mechanism. 
     The irradiation position adjustment process shown in  FIG. 30  is different from the irradiation position adjustment process shown in  FIG. 28  in that step  460  is provided instead of step  410  and step  462  is provided instead of step  412 . 
     In step  460 , the control unit  100 B determines whether or not the distance measurement unit  12  is rotated. In a case where the distance measurement unit  12  is not rotated in step  460 , the determination result is negative, and the process proceeds to step  416 . In a case where the distance measurement unit  12  is rotated in step  460 , the determination result is positive, and the process proceeds to step  462 . 
     In step  462 , the control unit  100 B updates the emission angle β according to the rotation direction and the rotation amount of the distance measurement unit  12 . Thereafter, the process proceeds to step  450 . 
     As described above, in the distance measurement device  10 D, in a case where the distance measurement unit  12  is manually rotated and the in-live-view-image irradiation position is out of the frame  117 , the distance is measured by the distance measurement control unit  68  until the in-live-view-image irradiation position is positioned within the frame  117 . The in-live-view-image irradiation position is derived by the deriving unit  100 A based on the measured distance and the emission angle β. 
     Therefore, according to the distance measurement device  10 D, it is possible to easily reflect an intention of the user on the change of the emission angle β compared to a case where the distance measurement unit  12  is not able to be manually rotated. 
     Fifth Embodiment 
     Although it has been described in the first embodiment that the distance measurement device  10 A is realized by the distance measurement unit  12  and the imaging device  14 , a distance measurement device  10 E realized by the distance measurement unit  12 , an imaging device  140 , and a smart device  142  will be described in a fifth embodiment. 
     In the fifth embodiment, since the same constituent elements as those of the above-described embodiments will be assigned the same references, the description thereof will be omitted, and only portions different from those of the above-described embodiments will be described. Hereinafter, the distance measurement program and the irradiation position adjustment programs are referred to as the “program” for the sake of convenience in description in a case where it is not necessary to distinguish between the distance measurement program  106  and the irradiation position adjustment programs  107 ,  132 ,  134 , and  136 . Hereinafter, the irradiation position adjustment programs are referred to as the “irradiation position adjustment program” without being assigned the references for the sake of convenience in description in a case where it is not necessary to distinguish between the irradiation position adjustment programs  107 ,  132 ,  134 , and  136 . 
     For example, as shown in  FIG. 31 , the distance measurement device  10 E according to the fifth embodiment is different from the distance measurement device  10 A according to the first embodiment in that the imaging device  140  instead of the imaging device  14  is provided. The distance measurement device  10 E is different from the distance measurement device  10 A in that the smart device  142  is provided. 
     The imaging device  140  is different from the imaging device  14  in that an imaging device main body  143  instead of the imaging device main body  18  is provided. 
     The imaging device main body  143  is different from the imaging device main body  18  in that a wireless communication unit  144  and a wireless communication antenna  146  are provided. 
     The wireless communication unit  144  is connected to the busline  84  and the wireless communication antenna  146 . The main control unit  62  outputs transmission target information which is information of a target transmitted to the smart device  142  to the wireless communication unit  144 . 
     The wireless communication unit  144  transmits, as a radio wave, the transmission target information input from the main control unit  62  to the smart device  142  through the wireless communication antenna  146 . In a case where a radio wave from the smart device  142  is received by the wireless communication antenna  146 , the wireless communication unit  144  acquires a signal corresponding to the received radio wave, and outputs the acquired signal to the main control unit  62 . 
     The smart device  142  includes a CPU  148 , a primary storage unit  150 , and a secondary storage unit  152 . The CPU  148 , the primary storage unit  150 , and the secondary storage unit  152  are connected to a busline  162 . 
     The CPU  148  controls the entire distance measurement device  10 E including the smart device  142 . The primary storage unit  150  is a volatile memory used as a work area in a case where various programs are executed. A RAM is used as an example of the primary storage unit  150 . The secondary storage unit  152  is a non-volatile memory that stores various parameters or control programs for controlling the entire activation of the distance measurement device  10 E including the smart device  142 . A flash memory or an EEPROM are used as an example of the secondary storage unit  152 . 
     The smart device  142  includes a display unit  154 , a touch panel  156 , a wireless communication unit  158 , and a wireless communication antenna  160 . 
     The display unit  154  is connected to the busline  162  through a display control unit (not shown), and displays various information items under the control of the display control unit. For example, the display unit  154  is realized by a LCD. 
     The touch panel  156  is layered on a display screen of the display unit  154 , and senses touch using a pointer. The touch panel  156  is connected to the busline  162  through a touch panel I/F (not shown), and outputs positional information indicating a position touched by the pointer. The touch panel I/F activates the touch panel according to an instruction of the CPU  148 , and the touch panel I/F outputs the positional information input from the touch panel  156  to the CPU  148 . 
     The soft keys corresponding to the actual measurement and actual imaging button  90 A, the provisional measurement and provisional imaging button  90 B, the imaging system operation mode switching button  90 C, the wide angle instruction button  90 D, the telephoto instruction button  90 E, and the irradiation position adjustment button  90 F which are described above are displayed on the display unit  154 . 
     For example, as shown in  FIG. 32 , an actual measurement and actual imaging button  90 A 1  functioning as the actual measurement and actual imaging button  90 A is displayed as a soft key on the display unit  154 , and is pressed by the user through the touch panel  156 . 
     For example, a provisional measurement and provisional imaging button  90 B 1  functioning as the provisional measurement and provisional imaging button  90 B is displayed as a soft key on the display unit  154 , and is pressed by the user through the touch panel  156 . 
     For example, an imaging system operation mode switching button  90 C 1  functioning as the imaging system operation mode switching button  90 C is displayed as a soft key on the display unit  154 , and is pressed by the user through the touch panel  156 . 
     For example, a wide angle instruction button  90 D 1  functioning as the wide angle instruction button  90 D is displayed as a soft key on the display unit  154 , and is pressed by the user through the touch panel  156 . 
     For example, a telephoto instruction button  90 E 1  functioning as the telephoto instruction button  90 E is displayed as a soft key on the display unit  154 , and is pressed by the user through the touch panel  156 . 
     For example, an irradiation position adjustment button  90 F 1  functioning as the irradiation position adjustment button  90 F is displayed as a soft key on the display unit  154 , and is pressed by the user through the touch panel  156 . 
     The wireless communication unit  158  is connected to the busline  162  and the wireless communication antenna  160 . The wireless communication unit  158  transmits, as a radio wave, a signal input from the CPU  148  to the imaging device main body  143  through the wireless communication antenna  160 . In a case where a radio wave from the imaging device main body  143  is received by the wireless communication antenna  160 , the wireless communication unit  158  acquires a signal corresponding to the received radio wave, and outputs the acquired signal to the CPU  148 . Accordingly, the imaging device main body  143  is controlled by the smart device  142  by performing wireless communication with the smart device  142 . 
     The secondary storage unit  152  stores a program. The CPU  148  reads the program out of the secondary storage unit  152 , loads the readout program into the primary storage unit  150 , and executes the distance measurement program. Thus, the distance measurement process described in the first embodiment is realized. 
     The CPU  148  reads the irradiation position adjustment program out of the secondary storage unit  152 , loads the readout irradiation position adjustment program into the primary storage unit  150 , and executes the irradiation position adjustment program. Thus, the irradiation position adjustment process described in the first to fourth embodiments is realized. 
     As described above, in the distance measurement device  10 E, the correspondence information acquired by associating the in-provisional-image irradiation position with the distance which corresponds to the in-provisional-image irradiation position and is provisionally measured by using the laser beam is acquired by the CPU  148  of the smart device  142  whenever each of the plurality of distances is provisionally measured. The in-actual-image irradiation position is derived based on the acquired correspondence information by the CPU  148  of the smart device  142 . Therefore, according to the distance measurement device  10 E, it is possible to derive the in-actual-image irradiation position with high accuracy compared to a case where the actual measurement and the actual imaging are performed without performing the provisional measurement and the provisional imaging. In the distance measurement device  10 E, the CPU  148  is operated as the deriving unit  100 A and the control unit  100 B by executing the irradiation position adjustment program (see  FIG. 10 ). Therefore, according to the distance measurement device  10 E, it is possible to acquire the same effects as the effects acquired by performing the irradiation position adjustment process described in the first to fourth embodiments. 
     According to the distance measurement device  10 E, it is possible to reduce a load applied to the imaging device  140  in acquiring the effects described in the above-described embodiments compared to a case where the distance measurement process and the irradiation position adjustment process are performed by the imaging device  140 . 
     Although it has been described in the above-described embodiments that the program is read out of the secondary storage unit  104  ( 152 ), it is not necessary to store the distance measurement program in the secondary storage unit  104  ( 152 ) from the beginning. For example, as shown in  FIG. 33 , the program may be stored in an arbitrary portable storage medium  500  such as a solid state drive (SSD) or a universal serial bus (USB) memory. In this case, the program stored in the storage medium  500  is installed on the distance measurement device  10 A ( 10 B,  10 C,  10 D, or  10 E), and the installed distance measurement program is executed by the CPU  100  ( 148 ). 
     The program may be stored in a storage unit of another computer or a server device connected to the distance measurement device  10 A ( 10 B,  10 C,  10 D, or  10 E) through a communication network (not shown), or the program may be downloaded according to a request of the distance measurement device  10 A ( 10 B,  10 C,  10 D, or  10 E). In this case, the downloaded distance measurement program is executed by the CPU  100  ( 148 ). 
     Although it has been described in the above-described embodiments that various information items such as the actual image, the provisional image, the distance, the in-actual-image irradiation position, and the provisional measurement and provisional imaging guide screen  112  are displayed on the display unit  86  ( 154 ), the technology of the present disclosure is not limited thereto. For example, various information items may be displayed on a display unit of an external device used while being connected to the distance measurement device  10 A ( 10 B,  10 C,  10 D, or  10 E). A personal computer or an eyeglass type or wristwatch type wearable terminal device is used as an example of the external device. 
     Although it has been described in the above-described embodiments that various information items are visually displayed by the display unit  86  ( 154 ), the technology of the present disclosure is not limited thereto. For example, audible indication of an output of sound from a sound playback device may be audibly displayed or a permanent visual display of an output of a printed article from a printer may be performed instead of the visual display. Alternatively, at least two of the visual display, the audible indication, or the permanent visual display may be performed. 
     Although it has been described in the above-described embodiments that the first intention check screen  110 , the provisional measurement and provisional imaging guide screen  112 , the re-performing guide screen  114 , the irradiation position marks  116  and  116 A, the frame  117 , the second intention check screen  118 , and the messages  119  and  121  are displayed on the display unit  86  ( 154 ), the technology of the present disclosure is not limited thereto. For example, the first intention check screen  110 , the provisional measurement and provisional imaging guide screen  112 , the re-performing guide screen  114 , the second intention check screen  118 , and the messages  119  and  121  may be displayed on a display unit (not shown) different from the display unit  86  ( 154 ), the irradiation position marks  116  and  116 A, and the frame  117  may be displayed on the display unit  86  ( 154 ). Only at least one of the first intention check screen  110 , the provisional measurement and provisional imaging guide screen  112 , the re-performing guide screen  114 , the irradiation position marks  116  and  116 A, the frame  117 , the second intention check screen  118 , or the messages  119  and  121  may be displayed on a display unit different from the display unit  86  ( 154 ). The first intention check screen  110 , the provisional measurement and provisional imaging guide screen  112 , the re-performing guide screen  114 , the irradiation position marks  116  and  116 A, the frame  117 , the second intention check screen  118 , and the messages  119  and  121  may be individually displayed on a plurality of display units including the display unit  86  ( 154 ). 
     Although it has been described in the first embodiment that a power for changing the emission angle β by the default rotation amount is used as the power for changing the emission angle β, a rotation amount (for example, a rotation amount changed for every time) other than the default rotation amount may be used as the power for changing the emission angle β. However, it is preferable that the power for changing the emission angle β is a power for changing the emission angle β by the default rotation amount. 
     As stated above, according the distance measurement device  10 A, since the power for changing the emission angle β by the default rotation amount is generated by the motors  17  and  19 , easy control is realized compared to a case where the power for changing the emission angle β by a rotation amount other than the default rotation amount is generated by the motors  17  and  19 . 
     In the first embodiment, a default rotation amount determined such that a movement amount of the in-live-view-image irradiation position is less than an outer diameter of the frame  117  may be used. Therefore, according to the distance measurement device  10 A, it is possible to prevent the irradiation position mark  116 A from exceeding the frame  117  compared to a case where the emission angle β is changed by the default rotation amount determined such that the movement amount of the in-live-view-image irradiation position is equal to or greater than the outer diameter of the frame  117 . 
     Although it has been described in the above-described embodiments that the laser beam is used as the light for distance measurement, the technology of the present disclosure is not limited thereto. Directional light which is light having directivity may be used. For example, the measurement light may be directional light acquired by light emitting diode (LED) or a super luminescent diode (SLD). It is preferable that the directivity of the directional light is directivity having the same degree as that of the directivity of the laser beam. For example, it is preferable that the directivity of the directional light is directivity capable of being used in the distance measurement in a range of several meters to several kilometers. 
     The distance measurement process and the irradiation position adjustment process described in the above-described embodiments are merely examples. Accordingly, an unnecessary step may be removed, a new step may be added, or a process procedure may be switched without departing from the gist. The processes included in the distance measurement process may be realized by only the hardware configuration such as ASIC, or may be realized by the combination of the software configuration and the hardware configuration using the computer. 
     The disclosures of Japanese Patent Application No. 2015-171421 filed on Aug. 31, 2015 are hereby incorporated by reference in their entireties. 
     All documents, patent applications, and technical standards described in the present specification are herein incorporated by reference to the same extent as if such individual document, patent application, and technical standard were specifically and individually indicated to be herein incorporated by reference. 
     The above-described embodiments are further disclosed in the following appendix. 
     (Appendix 1) 
     A distance measurement device comprises an imaging unit that images a subject image indicating a subject, a measurement unit that measures a distance to the subject by emitting directional light which is light having directivity to the subject and receiving reflection light of the directional light, a change unit that is capable of changing an angle at which the directional light is emitted, a deriving unit that derives an in-image irradiation position, which corresponds to an irradiation position of the directional light onto the subject which is used in measurement performed by the measurement unit, within a captured image acquired by imaging the subject by the imaging unit based on the angle and the distance measured by the measurement unit, and a control unit that controls the measurement unit to measure the distance, and controls the deriving unit to derive the in-image irradiation position based on the distance measured by the measurement unit and the angle changed by the change unit, until the in-image irradiation position falls in a default range within the captured image in a case where the in-image irradiation position is out of the default range.