Patent Publication Number: US-11050941-B2

Title: Camera device and manufacturing system for selective outputting of images based on rotational position of the camera device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2019-103209 filed on May 31, 2019, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a camera device for imaging a subject and a manufacturing system. 
     BACKGROUND ART 
     A imaging element is known that is employed in a manufacturing system such as a factory line and is equipped with an imaging unit for imaging a work passing through an imaging range being conveyed by a conveying machine, an illumination unit for illuminating the work passing through the imaging range with light, and a control unit for controlling the imaging unit and the illumination unit (refer to Patent document 1, for example). This imaging element is equipped with a first illumination unit having an opening and a second illumination unit having an opening that is smaller than the opening of the first illumination unit. The imaging element captures a moving work by executing a first imaging process of acquiring an image including a portion formed by reflection light coining from a mark provided in the work from an image taken by turning on only the second illumination unit and a second imaging process of acquiring an image including the work from an image taken by turning on only the first illumination unit on the basis of a result of the first imaging process. 
     CITATION LIST 
     Patent Literature 
     Patent document 1: JP-A-2017-76169 
     SUMMARY OF INVENTION 
     However, the imaging element disclosed in above Patent document 1 is large in size because it is equipped with the plural illumination units. Furthermore, in the above imaging element, since the imaging unit has a high shutter speed, a large number of images are taken, image processing takes long time, and a heavy computation load occurs. As a result, a manufacturing system using such an imaging element may suffer a problem that a cycle time is made long (e.g., a line operation speed is made slow). 
     The concept of the present disclosure has been made in view of the above circumstances and an object of the disclosure is therefore to provide a camera device and a manufacturing system capable of performing image processing efficiently and acquiring a clear image simply in a short time and thereby increasing the production efficiency. 
     This disclosure provides a camera device including at least one imaging unit which captures a subject; a rotary motor which rotates the imaging unit at a prescribed rotation speed; an output unit which outputs images captured by the imaging unit; and a body which incorporates the imaging unit, the rotary motor, and the output unit. The output unit outputs at least one image, among the images, captured at an imaging position where the imaging unit and the subject are approximately parallel with each other. 
     The disclosure also provides a manufacturing system including a camera for imaging a subject and an image processing device which is communicably connected to the camera. The camera transmits at least one image taken at an imaging position where the subject and at least one imaging unit being rotated at a prescribed rotation speed are approximately parallel with each other; and the image processing device analyzes a state of the subject on the basis of the at least one image received from the camera and outputs an analysis result. 
     The disclosure makes it possible to acquire a clear image simply in a short time and thereby increase the production efficiency. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing an example inspection device according to a first embodiment. 
         FIG. 2  is a perspective view showing an E-E cross section of an inspection cart shown in  FIG. 1 . 
         FIG. 3  is an E-E sectional view of the inspection cart shown in  FIG. 1 . 
         FIG. 4  is a side view showing an example appearance of a camera unit. 
         FIG. 5  is an F-F sectional view of the camera unit shown in  FIG. 4 . 
         FIG. 6  is a perspective view showing an example rotation direction of a drum. 
         FIG. 7  is a perspective view showing an example appearance of the camera unit. 
         FIG. 8  is a perspective view showing an example internal structure of a camera head. 
         FIG. 9  is a side view showing the example internal structure of the camera head. 
         FIG. 10  is a block diagram showing an example internal configuration of a manufacturing system according to the first embodiment. 
         FIG. 11  is a diagram showing an imaging example of subject captured by the camera head. 
         FIG. 12  is a diagram showing an example of how the angle of view of the camera head varies as it moves in a time taken by imaging. 
         FIG. 13  is a flowchart showing an example operation procedure of a camera control unit according to the first embodiment. 
         FIG. 14  is a schematic view of an example manufacturing system including a camera unit according to a first modification of the first embodiment. 
         FIG. 15  is a block diagram showing an example internal configuration of the manufacturing system according to the first modification of the first embodiment. 
         FIG. 16  is a flowchart showing an example operation procedure of the manufacturing system according to the first modification of the first embodiment. 
         FIG. 17  is a perspective view showing an example appearance of a drum according to a second embodiment. 
         FIG. 18  is a sectional view showing an example arrangement of four camera heads provided in the drum. 
         FIG. 19  is a diagram showing imaging examples captured by the four camera heads. 
         FIG. 20  is a diagram showing an imaging example captured by a single camera head. 
         FIG. 21  is a diagram showing an example internal configuration of a camera unit according to a first modification of the second embodiment. 
         FIG. 22  is a diagram showing an example internal configuration of a camera unit according to a second modification of the second embodiment. 
         FIG. 23  is a diagram showing an example internal configuration of a camera unit according to a third modification of the second embodiment. 
         FIG. 24  is a diagram showing an example internal configuration of a camera unit according to a fourth modification of the second embodiment. 
         FIG. 25  is a perspective view showing an example appearance of a camera unit according to a third embodiment. 
         FIG. 26  is a view showing an example of imaging by the camera unit according to the third embodiment. 
         FIG. 27  is a diagram showing an example of how the camera unit according to the third embodiment captures a subject. 
         FIG. 28  is a perspective view showing an example appearance of a camera unit according to a fourth embodiment. 
         FIG. 29  is a perspective view showing an example internal mechanism of a drum of the camera unit according to the fourth embodiment. 
         FIG. 30  is a diagram showing an example operation of a first gear and a second gear. 
         FIG. 31  is a diagram showing an example of how a subject is captured by the camera unit according to the fourth embodiment. 
         FIG. 32  is another diagram showing the example of how the subject is captured by the camera unit according to the fourth embodiment. 
         FIG. 33  is a perspective view showing an example appearance of a camera according to a fifth embodiment. 
         FIG. 34  is a perspective view showing an example appearance of the camera unit as viewed from obliquely below in  FIG. 33 . 
         FIG. 35  is a front view showing an example drive mechanism of the camera unit as viewed from an arrowed line H-H in  FIG. 33 . 
         FIG. 36  is a perspective view showing the example drive mechanism of the camera unit as viewed from the arrowed line H-H in  FIG. 33 . 
         FIG. 37  is a diagram for description of an example imaging operation of the camera unit according to the fifth embodiment. 
         FIG. 38  is a flowchart showing an example operation procedure of a manufacturing system according to the fifth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Background of Conception of First Embodiment 
     Patent document 1 discloses an imaging element that is employed in a manufacturing system such as a factory line and obtains an image of a subject (work) having a marker that reflects light shining on it by imaging the subject having the marker by illuminating the subject passing through an imaging range with light. An imaging unit of this imaging element has a high shutter speed. This imaging element can image many subjects being conveyed by a conveying machine and performs image processing on them. However, in the imaging element, because of a large number of images to be subjected to the image processing, a long time is taken to perform the image processing, that is, the imaging element suffers a heavy computation load. As a result, a manufacturing system using such an imaging element may suffer a problem that a cycle time is made long (e.g., a line operation speed is made slow). 
     The concept of the present disclosure has been made in view of the above circumstances and an object of the disclosure is therefore to provide a camera device and a manufacturing system capable of performing image processing efficiently and acquiring a clear image simply in a short time and thereby increasing the production efficiency. 
     Camera devices and manufacturing systems according to specific embodiments of the disclosure will be hereinafter described in detail by referring to the drawings when necessary. However, unnecessarily detailed descriptions may be avoided. For example, already well-known items may be refrained from being described in detail and constituent elements having substantially the same ones already described may be refrained from being described redundantly. This is to prevent the following description from becoming unnecessarily redundant and thereby facilitate its understanding by those skilled in the art. The following description and the accompanying drawings are provided to allow those skilled in the art to understand this disclosure sufficiently and they are not intended to restrict the subject matter described in the claims. 
     First Embodiment 
       FIG. 1  is a perspective view of an example inspection device according to a first embodiment. A manufacturing system according to the first embodiment is configured so as to include an inspection cart  10  which is the example inspection device. The inspection cart  10  is equipped with a camera unit  30  as an example camera device and moves on a rail  80 . 
     The inspection cart  10  can move freely along the rail  80  which extends straightly. The rail  80  may be a running lane. For example, the rail may be an inspection lane installed alongside a factory line, a conveyance lane dedicated to loads, a lane of a road, a railroad, or the like. The rail is not limited to a straight one, that is, may be curved. The rail  80  is laid in the longitudinal direction of the lane at its center. 
     The inspection cart  10  performs inspection while imaging the rail  80  or subjects Wk (e.g., works) disposed on the rail  80  while moving on the rail  80 . Equipped with a drive device inside, the inspection cart  10  is a self-propelled cart that runs by driving wheels. The inspection cart  10  may be a cart that runs by driving wheels that are kept in contact with the rail  80  by sandwiching the rail  80  from both sides. Alternatively, the inspection cart  10  may be moved being driven by an external drive device. 
     The inspection cart  10  inspects states of the rail  80  (e.g., finds presence/absence of a scratch, a deteriorated portion, or a damaged portion formed on the rail  80 ). The inspection cart  10  has an approximately box-shaped case  10   z . Devices necessary for inspection of the rail  80  are provided inside the case  10   z . It goes without saying that the shape of the case  10   z  is not limited to a box-like shape as mentioned above. 
       FIG. 2  is a perspective view showing an E-E cross section of the inspection cart  10  shown in  FIG. 1 .  FIG. 3  is an E-E sectional view of the inspection cart  10  shown in  FIG. 1 . The inspection cart  10  is connected to a camera control unit  50  so as to be able to communicate with it and is configured so as to include, inside the case  10   z , a camera unit  30 , an encoder  60 , wheels  65 , etc. 
     Directions as coordinate axes are defined as follows. The X direction is defined as a movement direction of the inspection cart  10  (may be the camera unit  30  or the subjects Wk). The Y direction is defined as a direction that is perpendicular to the X direction in a surface that is captured by the camera unit  30 . The Z direction is a direction that is perpendicular to the surface that is captured by the camera unit  30 . Coordinate axes will be defined in similar manners in following embodiments. 
     A camera control unit  50  as an example image processing device, which serves to control the camera unit  30 , is configured using, for example, a CPU (central processing unit). an MPU (micro processing unit), or a DSP (digital signal processor). The camera control unit  50  generates, at a prescribed frame rate (e.g., 60 fps or 120 fps), data (frames) of an image taken in the form of RGB (red, green, and blue) signals, YUV (luminance and color differences) signals, or the like that can be recognized by humans by performing prescribed signal processing on an image signal received from the camera unit  30 . The camera control unit  50  performs image processing on the basis of a received image, taken by the camera unit  30 , of a surface of the rail  80  or subjects Wk (e.g., works) disposed on the rail  80 . The camera control unit  50  judges whether an abnormality exists in the rail  80  or a subject Wk (e.g., a scratch, a deteriorated portion, or a damaged portion formed on a surface) and outputs a judgment result. 
     The encoder  60  is an encoder for detection of a speed that detects a rotational position of a rotation axis of one wheel  65  of the inspection cart  10  and detects a speed of the inspection cart  10  on the basis of the number of revolutions per unit time. The encoder  60  can also detect a position of the inspection cart  10  corresponding to a pre-specified distance of the rail  80  on the basis of a rotational position of the rotation axis of the wheel  65 . The encoder  60  may be either an absolute encoder capable of detecting an absolute rotational position or an incremental rotary encoder capable of detecting a relative rotational position. The camera unit  30  may be equipped with a speed sensor in place of the encoder  60 . 
       FIG. 4  is a side view showing an example appearance of the camera unit  30 .  FIG. 5  is an F-F sectional view of the camera unit  30  shown in  FIG. 4 . The camera unit  30  is configured in such a manner that a drum  31 , a wireless power reception unit  32 , and a wireless power supply unit  34  are laid on one on another coaxially. 
     In a side wall (circumferential wall) pf the drum  31 , openings are formed. A camera head  35  is disposed in the opening of the drum  31 . A camera head  35  is disposed in the opening of the drum  31 . The camera head  35  is disposed so as to be able to capture the rail  80  or the subject Wk through the opening formed in the circumferential wall of the drum  31 . The camera head  35  captures the subject Wk at a high shutter speed. 
     The wireless power reception unit  32  has a recess which is a recessed central portion. On the other hand, the wireless power supply unit  34  has a projection which is a projected central portion. The projection of the wireless power supply unit  34  is fitted in the recess of the wireless power reception unit  32 , whereby wireless power supply to each of an illumination unit  33 , the camera head  35 , and a rotary motor  37  is made possible. The thickness of the camera unit  30  can be reduced because the wireless power reception unit  32  and the wireless power supply unit  34  have the above structures. The wireless power reception unit  32  and the wireless power supply unit  34  transmit and receive signals such as a drive signal for the drum  31  and an image signal of the camera head  35 . Having the above configuration, the camera unit  30  employed in the first embodiment prevents a harness  43  (see  FIGS. 8 and 9 ) for electrical connection of the camera head  35  and power-supply-side members from being twisted by rotation of the drum  31 . 
       FIG. 6  is a perspective view showing an example rotation direction of the drum  31 . The drum  31  employed in the first embodiment may be shaped like either a circular ring having a central hole or a cylinder having flat side surfaces. The drum  31  can rotate around its rotation axis with respect to the wireless power reception unit  32  and the wireless power supply unit  34 . A drive mechanism for rotating the drum  31  may be provided either inside or outside the camera unit  30 . For example, the drum  31  may be connected to the shaft of a motor (not shown) directly or via gears and driven rotationally as the motor rotates. Alternatively, the drum  31  may either be in contact with a member vibrated by ultrasonic waves and driven rotationally by vibration produced by an ultrasonic motor or be formed as a rotor of a motor and driven rotationally by its stator. 
     Although a case that the drum  31  in the first embodiment will be described as one that is rotated in one direction, the drum  31  may be one that is rotated in the normal direction and the reverse direction repeatedly. 
       FIG. 7  is a perspective view showing an example appearance of a camera unit  30 A. The camera unit  30 A shown in  FIG. 7  is configured in such a manner as to include the illumination unit  33  in an integrated component in addition to the camera unit  30 . Alternatively, the illumination unit  33  may be provided on the inspection cart  10  so as to be able to illuminate an imaging range of the camera head  35 . 
     The lighting unit  33  is formed in a substantially rectangular plate shape, and illuminates an imaging range of the camera head  35 . The illumination unit  33  provides LED (light-emitting diode) illumination, IR (infrared) illumination, or the like. The illumination unit  33  illuminates a subject to be captured by the camera head  35 . The illumination unit  33  is not limited to the case of providing LED illumination or IR illumination and may employ an EL (electroluminescence) device, a fluorescent lamp, a white lamp, a halogen lamp, a xenon lamp, or the like. 
     The wireless power reception unit  32  and the wireless power supply unit  34  of the camera unit  30 A shown in  FIG. 7  transmit and receive signals such as a drive signal for the drum  31  and an image signal of the camera head  35  by wireless power supply. Having this configuration, the camera unit  30 A prevents a harness of the camera head from being twisted by rotation of the drum  31 . The wireless power supply method may be any of an electromagnetic coupling method, a magnetic resonance method, and an electromagnetic induction method. 
       FIG. 8  is a perspective view showing an example internal structure of the camera head  35 .  FIG. 9  is a side view showing the example internal structure of the camera head  35 . The camera head  35  as an example imaging unit is housed in a lens barrel (not shown) and is configured so as to include an imaging lens  41 , an imaging element  42 , and a harness  43 . The camera head  35  shown in  FIGS. 8 and 9  has an air layer between the imaging lens  41  and the imaging element  42 , whereby the focal length is adjusted. The camera head  35  is not limited to a visible light camera, and may be an infrared camera that can emit near infrared light and receive resulting reflection light to enable imaging, for example, during the nighttime or in a dark place. 
     The imaging lens  41  focuses light coming from outside the camera unit  30  (camera head  35 ) through an opening of the drum  31  and images it on a prescribed imaging surface of an image sensor (imaging element  42 ). The imaging lens  41  may be either a fixed lens having a constant focal length or a zoom lens whose focal length is adjustable. 
     The imaging element  42  is a solid-state imaging element such as a CCD (charge-coupled device) or a CMOS (complementary metal-oxide semiconductor) sensor. The imaging element  42  converts the focused and imaged optical image into an electrical signal and outputs a resulting video signal. 
     The harness  43  connects the camera head  35  and the wireless power reception unit  32  to each other electrically. The harness  43  supplies power to the camera head  35  and transmits various signals such as a control signal and a video signal (image taken) to and from the imaging element  42 . The harness  43  may be either plural signal lines or a flexible wiring board (FPC: flexible printed circuits). 
       FIG. 10  is a block diagram showing an example internal configuration of a manufacturing system according to the first embodiment. The manufacturing system according to the first embodiment is configured so as to include the inspection cart  10  as an inspection device and a camera control unit  50 . Units and components relating to control such as wheels for driving the inspection cart  10  are omitted in  FIG. 10 . 
     The inspection cart  10  incorporates a camera unit  30  for imaging an inspection subject, that is, a rail  80  or a subject Wk on the rail  80 . The inspection cart  10  is configured so as to include an encoder  60  and the camera unit  30 . The inspection cart  10  may further be equipped with a Hall element capable of detecting a current position of the inspection cart  10  in a movement range (i.e., inspection range), set in advance by a user, of the rail  80 . 
     The encoder  60  detects a movement speed of the inspection cart  10  and transmits it to the camera control unit  50 . 
     The camera unit  30  is installed in the inspection cart  10  in such a manner as to be able to capture the rail  80  or subjects Wk on the rail  80  by means of the camera head  35 . Although the camera unit  30  employed in the first embodiment is movable being mounted in the inspection cart  10 , the concept of the disclosure is not limited to this case. For example, the camera unit  30  may be equipped with a motor as a moving means for imaging rail  80  or subjects Wk on the rail  80 . The camera unit  30  is configured so as to include a rotary motor  37 , a power supply unit  40 , an imaging lens  41 , and an imaging element  42 . 
     The rotary motor  37  rotationally drives the camera unit  30  at a prescribed rotation speed around the rotation axis shown in  FIGS. 6 and 7 . A rotation speed of e rotary motor  37  is calculated and set by the camera control unit  50 . 
     The power supply unit  40  is configured so as to include a wireless power reception unit  32  and a wireless power supply unit  34 . The power supply unit  40  supplies power to an illumination unit  33  (not shown), the camera head  35 , the rotary motor  37 , etc. 
     The camera control unit  50  controls the inspection cart  10  and the camera unit and acquires an image taken (image signal) from the camera unit  30 . The camera control unit  50  is configured so as to include a motor control unit  51 , a camera control unit  52 , an LED control unit  53 , and a power source unit  54 . 
     The motor control unit  51  transmits a control signal for controlling the movement speed of the inspection cart  10  to a motor (not shown) for driving the inspection cart  10 . The motor control unit  51  receives detected speed information of the inspection cart  10  from the encoder  60 . The motor control unit  51  compares the received speed information with a movement speed indicated by the transmitted control signal and manages the movement speed of the inspection cart  10 . The motor control unit  51  may transmit a control signal that is set by the user. 
     The motor control unit  51  transmits a control signal for controlling the rotation speed of the camera unit  30  to the rotary motor  37 . As for the motor control unit  51 , a frame rate of the camera head  35  and a distance between the camera head  35  and a subject Wk are set by the user in advance. The motor control unit  51  calculates a rotation speed of the rotary motor  37  so that the relative speed between the camera head  35  and the subject Wk becomes equal to 0 on the basis of these set values, a movement direction and speed of the inspection cart  10 , and a movement direction and speed of the subject Wk. The motor control unit  51  transmits a control signal generated on the basis of the calculated rotation speed to the rotary motor  37 . 
     The camera control unit  52  controls the shutter speed, the imaging start timing, and the imaging end timing of the camera head  35 . The camera control unit  52  receives an image signal of an image taken by the camera head  35 . The camera control unit  52  performs image processing on the basis of an image taken (image signal) received from the camera unit  30 . The camera control unit  52  judges whether a portion of the rail  80  or a subject Wk existing in an image taken has an abnormality (e.g., scratch, fatigue, or foreign substance) and outputs a judgment result. 
     The camera control unit  50  may measure a current position of the inspection cart  10  on the basis of movement information received from the encoder  60  and a movement range (e.g., inspection range) that was set by the user in advance. Where the inspection cart  10  is equipped with a component such as a Hall element capable of detecting current position information, the camera control unit  50  may estimate a current position of the inspection cart  10  on the basis of this position information. Where the position of subjects Wk is fixed, the camera control unit  50  may control the imaging timing of the camera head  35  (i.e., an image to be received) on the basis of a current position of the inspection cart  10  measured or estimated on the basis of a movement range or position information. 
     The LED control unit  53  controls an illumination unit  33  provided in or for the inspection cart  10  or the camera head  35 . 
     When turned on by the user, the power source unit  54  supplies power to the individual units and components of the camera control unit  50  and the camera unit  30 . 
       FIG. 11  is a diagram showing an example of how a subject Wk is captured by the camera head  35 . In the example of imaging shown in  FIG. 11 , the inspection cart  10  is moving straightly in a direction MV 1 . The camera unit  30  is rotating in a direction MM 1  around the rotation axis of the drum  31 . A position Oj (described later) on the subject Wk being captured by the camera head  35  is a position at which the camera head  35  is focused. As the inspection cart  10  moves and the camera unit  30  rotates, the camera head  35  is moved so as to form a trace that is shaped like a cycloid curve. The inspection cart  10  is omitted in  FIG. 11  to describe positional relationships between the drum  31 , the subject Wk, and the camera head  35  that is imaging the subject Wk. 
     The imaging lens  41  of the camera head  35  focuses, with a prescribed angle of view Ar, light coming from the subject Wk and forms an optical image of the subject Wk located at the position Oj on the imaging surface of the imaging element  42 . The camera unit  30  starts transmitting an image of the subject Wk to the camera control unit  50  when or immediately before the relative speed between the camera head  35  and the subject Wk becomes equal to 0. A time during which the camera unit  30  transmits images of the subject Wk to the camera control unit  50  is from immediately before the above-mentioned relative speed becomes equal to 0 to a time when it can no longer be regarded as being equal to 0. That is, images transmitted from the camera head  35  are ones that are taken while the camera head  35  can be regarded as being parallel with the subject Wk (in other words, the relative speed between the camera head  35  and the subject Wk is approximately equal to 0). 
     The camera head  35  may transmit images taken according to a signal indicating imaging timing received from the camera control unit  50 . 
     The subject Wk shown in  FIG. 11  may be one other than the rail  80  along which the inspection cart  10  can move, such as a work that is conveyed by a belt conveyor (described later). That is, the movement speed of the subject Wk need not be equal to 0. 
       FIG. 12  is a diagram showing an example of how the angle of view of the camera head  35  varies as it moves in a time taken by imaging. Referring to  FIG. 12 , the inspection cart  10  (not shown) moves in a direction MV 1 . In  FIG. 12 , as in  FIG. 11 , The inspection cart  10  and the rail  80  are omitted to describe positional relationships between the drum  31 , the subject Wk, and the camera head  35  that is imaging the subject Wk. 
     A locus of a point at which the camera head  35  is focused (i.e., a position Oj that is located on the subject Wk when the relative speed between the camera head  35  and the subject Wk is equal to 0) is what is called a cycloid curve. The camera head  35  becomes parallel with the subject Wk on the rail  80  (the relative speed between them becomes approximately equal to 0) at time t 0  when the camera head  35  is located at the lowest position of its locus. The camera head  35  transmits, to the camera control unit  50 , images from an image taken at time t 0  or a time immediately before time t 0  when imaging is started to an image taken at time t 2 . 
     At time t 0 , the camera head  35  is in a state that its speed relative to the subject Wk is equal to 0. The camera unit  30  transmits an image of the subject Wk taken at time t 0  to the camera control unit  50 . At this time point, the position Oj on the subject Wk is located at the center of an angle of view Ag 0 . At time t 1 , the camera head  35  is in a state that its speed relative to the subject Wk is approximately equal to 0. The camera unit  30  transmits an image of the subject Wk taken at time t 1  to the camera control unit  50 . At this time point, the position Oj on the subject Wk is located at the center of an angle of view Ag 1 . At time t 2 , the camera head  35  is in a state that its speed relative to the subject Wk is approximately equal to 0. The camera unit  30  transmits an image of the subject Wk taken at time t 2  to the camera control unit  50 . At this time point, the position Oj on the subject Wk is located at the center of an angle of view Ag 2 . After time t 2 , the transmission of an image of the subject Wk is not transmitted. 
     As described above, the camera head  35  which is incorporated in the inspection cart  10  starts imaging at time t 0  and finishes the imaging at time t 2 . The camera head  35  moves by a distance ΔL in the direction MV 1  from time t 0  to time t 2 . During that time, the position Oj where the camera head  35  is focused (i.e., the position on the subject Wk in the angle of view of the imaging by the camera head  35 ) does not vary irrespective of the movement distance ΔL of the camera head  35 , that is, the position Oj which is located in the angles of view corresponding to images taken at times t 0 , t 1 , and t 2  does not vary. The relative speed between the subject Wk and the camera head  35  is kept approximately equal to 0 from time t 0  to time t 2 . Peripheral portions of an image taken by the camera head  35  are distorted because the movement distance of the camera head  35  itself is long. 
     The relative speed between the camera head  35  and the subject Wk is kept equal to 0 or can be regarded as being kept approximately equal to 0 from time t 0  to time t 2 . The time during which the relative speed can be regarded as being kept approximately equal to 0 is a time slot during which images can be taken that allow the camera control unit  50  to perform image processing on them and image analysis for, for example, detection of an abnormality of the subject Wk. The time from time t 0  to time t 2  varies depending on the movement speed of the inspection cart  10 , the rotation speed of the camera head  35 , the movement speed of the subject Wk, the imaging distance between the camera head  35  and the subject Wk, etc. Thus, the time from time t 0  to time t 2  may be either set automatically by the camera control unit  50  on the basis of the above values or set by the user. 
       FIG. 13  is a flowchart showing an example operation procedure of the camera control unit  50  employed in the first embodiment. The example operation procedure of the camera control unit  50  shown in  FIG. 13  is directed to the example of imaging shown in  FIG. 11 . In the example operation procedure shown in  FIG. 13 , the subject Wk shown in  FIG. 11  does not move, that is, its movement speed is equal to 0. 
     At step S 1 , the motor control unit  51  receives and acquires speed information of the inspection cart  10  from the encoder  60 . For example, the speed information of the inspection cart  10  is a movement speed V (km/h) of the inspection cart  10 . 
     At step S 2 , the motor control unit  51  calculates a rotation speed of the rotary motor  37 , that is, the number of revolutions per unit time of the drum  31 , on the basis of the received speed information according to Equation (1). A method for calculating a rotation speed R of the rotary motor  37  will be described below. 
     A rotation speed R (rps) of the rotary motor  37  is calculated according to Equation (1) so that the relative speed between the camera head  35  which moves at the movement speed V together with the inspection cart  10  and the subject Wk (or rail  80 ). That is, Equation (1) is an equation for calculating a rotation speed R of the rotary motor  37  that makes equal to 0 the relative speed between the movement speed (in the X direction) of the surface of the subject Wk to be captured by the camera head  35  and the movement speed of the camera head  35  of the inspection cart  10  at a position where the subject Wk and the camera head  35  are parallel with and closest to each other. A distance r 1  (mm) between the camera head  35  and the subject Wk and a radius r 2  (mm) of rotation of the camera head  35  (i.e., the radius of the drum  31 ,  31 A) may be set by the user in advance. 
     
       
         
           
             
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                             1 
                           
                           + 
                           
                             r 
                             2 
                           
                         
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     Using Equation (1), a rotation speed R (rps) of the camera head  35  shown in  FIG. 11  can be calculated to be 52 (rps) when, for example, V=70 km/h (19.4 m/s), r 1 =30 mm, and r 2 =30 mm. The movement sped of the subject Wk shown in  FIG. 11  is equal to 0. Thus, where the subject Wk is moved, it is necessary to calculate a rotation speed R (rps) of the rotary motor  37  further on the basis of a movement direction of the subject Wk, a movement direction of the inspection cart  10 , and a rotation direction of the camera head  35 . 
     At step S 3 , the motor control unit  51  generates a control signal to be used for rotating the rotary motor  37  on the basis of the calculated rotation speed R and transmits the generated control signal to the rotary motor  37 . The rotary motor  37  is driven rotationally at the rotation speed R on the basis of the received control signal. 
     At step S 4 , the camera control unit  52  detects, as an exposure start position (exposure start timing), timing at which the relative speed between the camera head  35  and the subject Wk becomes equal to 0, that is, a position where the camera head  35  and the subject Wk becomes parallel with each other. Although the term “exposure start position” is used above, it is noted that the imaging element  42  continues to receive light coming from the subject Wk (optical image) and output an image signal after an inspection start manipulation was made by the user. 
     Upon detecting an exposure start position at step S 4 , at step S 5  the camera control unit  52  receives an image signal that is transmitted from the imaging element  42 . 
     At step S 6 , the camera control unit  50  judges whether the inspection cart  10  has completed a prescribed imaging process that was set by the user. For example, the camera control unit  50  may finish the imaging either when the inspection cart  10  has passed an inspection interval set by the user or when an inspection finishing manipulation is made by the user. 
     If judging that the imaging has not been completed yet (S 6 : no), the camera control unit  50  returns to step S 1 . 
     On the other hand, if judging that the imaging has been completed (S 6 : yes), the camera control unit  50  finishes the inspection process. 
     As described above, while the inspection cart  10  employed in the first embodiment runs along the rail  80 , the camera head  35  which is disposed in the circumferential surface of the rotating drum  31  captures the rail  80  and the subject Wk on the rail  80  continuously at an imaging position where the camera head  35  is approximately parallel with the rail  80  or the subject Wk on the rail  80 . That is, timing at which the imaging element  42  starts to be exposed to light (in other words, timing at which the imaging element  42  starts transmitting data of an image taken to the camera control unit  50 ) is timing at which the relative speed between the movement speed of the subject Wk to be captured by the camera head  35  and that of the camera head  35  becomes equal to 0. Since in this state the rail  80  or the subject Wk on the rail  80  is stopped relative to the camera head  35 , a blur of the rail  80  or the subject Wk on the rail  80  existing in an image taken by the imaging element  42  can be made small. As a result, the camera head  35  can produce a clear image of the rail  80  or the subject Wk even if the inspection cart  10  is moving along the rail  80  at high speed. 
     Thus, the camera control unit  50  can detect (make a judgment about) an abnormality (e.g., a scratch, a deteriorated portion, or a damaged portion formed on its surface) of the rail  80  or the subject Wk in a shorter time on the basis of data of images taken. 
     Although in the above-described manufacturing system according to the embodiment the camera control unit  50  has functions of an image processing device, an image processing device may be provided separately from the camera control unit  50 . In this case, the image processing device performs analysis about presence/absence of an abnormality (e.g., a scratch, a deteriorated portion, or a damaged portion formed on its surface) of the rail  80  or the subject Wk by doing image analysis on data of images taken that are received from the camera control unit  50  and outputs an analysis result to a monitor, an alarm lamp, or the like. 
     First Modification of First Embodiment 
     The manufacturing system according to the first embodiment is such that the inspection cart  10  captures a subject Wk while the inspection cart  10  is moving. A manufacturing system  100 A according to a first modification of the first embodiment will be described below in which a camera unit  30 A captures each of plural subjects Wk that are moving. In the first modification of the first embodiment, the same constituent elements as in the first embodiment will be given the same reference symbols and will not be described in detail. 
       FIG. 14  is a rough view of an example manufacturing system  1004  that includes a camera unit  30 A according to the first modification of the first embodiment. In the manufacturing system  100 A according to the first modification of the first embodiment, the camera unit  30 A that is installed fixedly captures subjects Wk moving at a constant speed. The subjects Wk may be moved either being conveyed by a conveying machine such as a belt conveyor  110  (see  FIG. 14 ) or being driven by moving means provided in themselves. The manufacturing system  100 A is configured so as to include the camera unit  30 A and a camera control unit  50 A. The camera head  35  is configured similarly to the camera unit  30  employed in the first embodiment and is disposed in the circumferential surface of a drum  31  which is rotated. 
     The camera unit  30 A according to the first modification of the first embodiment captures each of the plural subjects Wk being conveyed by a belt conveyor  110 . Like the camera unit  30  or  30 A according to the first embodiment, the camera unit  30 A captures each subject Wk with such timing that the relative speed between the camera head  35  and the subject Wk becomes equal to 0 (in other words, the camera head  35  and the subject Wk become approximately parallel with each other). 
     Imaging targets of the camera unit  30 A according to the first modification of the first embodiment are not limited to plural subjects Wk that are conveyed at a constant speed so as to be arranged at the same interval as shown in  FIG. 14 . Where the plural subjects Wk are neither arranged at the same interval nor conveyed at a constant speed, the camera control unit  50 A may be configured so as to be able to capture the subjects Wk by calculating a movement speed of each subject Wk on the basis of a variation of the position of the subject Wk detected by a Hall element (not shown) or a variation of the position of the subject Wk existing in at least two images (frames) taken immediately before and rotating the rotary motor  37  according to the calculated movement speed. 
       FIG. 15  is a block diagram showing an example internal configuration of the manufacturing system  100 A according to the first modification of the first embodiment. The manufacturing system  100 A is configured so as to include the camera unit  30 A and a camera control unit  50 A. 
     The camera unit  30 A is configured so as to include a work speed detection sensor  45  in addition to the imaging lens  41 , the imaging element  42 , the rotary motor  37 , and the power supply unit  40  which were described in the first embodiment. The imaging lens  41 , the imaging element  42 , the rotary motor  37 , and the power supply unit  40  will not be described in detail because they have the same functions and operate in the same manners as in the first embodiment. 
     The work speed detection sensor  45  detects a movement speed of each of the subjects (works) Wk being conveyed by the belt conveyor  110 . The work speed detection sensor  45  is, for example, a Hall element, which detects a position of each of the subjects Wk on the basis of a magnetic field variation caused by a magnet attached to the subject Wk. The work speed detection sensor  45  detects a movement speed of each of the subjects Wk on the basis of detected positions of the respective subjects Wk. 
     Alternatively, the work speed detection sensor  45  may be a fixed-point camera. The fixed-point camera detects a movement speed of each of the subjects (works) Wk by measuring a position variation of the subject Wk existing in at least two images (frames) taken by performing image analysis on the at least two images. In this case, a movement speed of each of the subjects Wk can be detected easily without using additional electronic device such as a Hall element. 
     The work speed detection sensor  45  transmits the detected movement speed information of each of the subjects (works) Wk to the camera control unit  50 A. The camera control unit  50 A may calculate a rotation speed R of the rotary motor  37  adaptively on the basis of the received movement speed of each subject Wk. The camera control unit  50 A transmits the calculated rotation speed R to the camera unit  30 A. As a result, the camera unit  30 A can change the rotation speed R when necessary according to a movement speed of a subject Wk and hence can capture the subject Wk in a state that the relative speed between the camera head  35  and the subject Wk is made approximately equal to 0. 
     Imaging targets of the camera unit  30 A according to the first modification of the first embodiment are not limited to plural subjects Wk that are conveyed being arranged at the same interval as shown in  FIG. 14 . Thus, the camera unit  30 A may have such an angle of view that plural subjects Wk exist in one image taken. 
     The camera control unit  504  is configured so as to include a motor control unit  51 A, a camera control unit  52 , an LED control unit  53 , and a power source unit  54 . The motor control unit  51 A calculates a rotation speed R of the rotary motor  37  on the basis of received speed information of a subject Wk and generates a control signal for controlling the rotary motor  37 . 
     The camera control unit  50 A may have an external input interface and receive a conveyance speed of the belt conveyor  110  via the external input interface. In this case, the camera control unit  50 A may infer that a movement speed of the subjects Wk is equal to that of the belt conveyor  110 : the work speed detection sensor  45  can be omitted. 
     An operation procedure of the manufacturing system  100 A shown in  FIGS. 14 and 15  will be described with reference to  FIG. 16 .  FIG. 16  is a flowchart showing an example operation procedure of the manufacturing system  100 A according to the first modification of the first embodiment. 
     At step S 1 A, the motor control unit  51 A receives and acquires speed information of a subject Wk from the work speed detection sensor  45 . For example, the speed information may be a conveyance speed that is set for the belt conveyor  110 . 
     At step S 2 A, the motor control unit  51 A calculates a rotation speed R of the rotary motor  37 , that is, the number of revolutions per unit time of the drum  31 , on the basis of the received speed information according to Equation (2). The movement speed V A  (m/s) in Equation (2) is the movement speed of the subject Wk. 
     
       
         
           
             
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     Equation (2) is an equation for calculating a rotation speed R of the rotary motor  37  that makes equal to 0 the relative speed between the movement speed (in the X direction) V A  of the surface of the subject Wk to be captured by the camera head  35  and the movement speed of the camera head  35  at a position where the camera head  35  is closest to the moving subject Wk (i.e., a position where the camera head  35  and the subject Wk are parallel with each other). 
     At step S 3 A, the motor control unit  51 A generates a control signal to be used for rotating the rotary motor  37  on the basis of the calculated rotation speed R and transmits the generated control signal to the rotary motor  37 . The rotary motor  37  is driven rotationally at the rotation speed R on the basis of the received control signal. 
     Steps S 4  to S 6  will not be described in detail because they are the same as in the operation procedure of the manufacturing system according to the first embodiment. 
     As described above, in the manufacturing system  100 A according to the first modification of the first embodiment, plural subjects Wk being conveyed by the belt conveyor  110  are captured by the camera head  35  continuously. Timing at which the imaging element  42  starts to be exposed to light (in other words, timing at which data of an image taken is transmitted to the camera control unit  50 A) is timing at which the relative speed between the movement speed of each subject Wk to be captured by the camera head  35  and that of the camera head  35  of the inspection cart  10  becomes equal to 0. Since in this state the subject Wk on the belt conveyor  110  is stopped relative to the camera head  35 , a blur of the subject Wk existing in an image taken by the imaging element  42  can be made small. As a result, the camera head  35  can produce a clear image of the subject Wk even if the belt conveyor  110  is conveying the subject Wk at a conveyance speed that is higher than a conventional conveyance speed. 
     Thus, the camera control unit  50 A can detect (make a judgment about) an abnormality (e.g., a scratch, a deteriorated portion, or a damaged portion formed on its surface) of each subject Wk in a shorter time on the basis of data of images taken. 
     Second Embodiment 
     The camera unit  30  according to the first embodiment has one camera head  35  which is disposed in the circumferential surface of the drum  31 . Provided with only one camera head  35 , the camera unit  30  according to the first embodiment is restricted in the imaging-possible angle of view and the imaging timing. Since it is preferable that a subject Wk be captured so as to included in the angle of view in its entirety, it is difficult to shorten the imaging distance between the camera head  35  and the subject Wk. In the camera unit  30  according to the first embodiment, the resolution of an image taken is low because it employs the same kind of illumination (illumination unit  33 ) as in conventional cases to prevent its size increase. Furthermore, in the camera unit  30  according to the first embodiment, since the camera head  35  performs imaging while rotating, peripheral portions of an image taken may be distorted more than its central portion. 
     In view of the above, in a camera unit  309  according to a second embodiment, plural camera heads are provided in the peripheral surface of a drum  31 A. In the camera unit  30 B according to the second embodiment, since the number of camera heads is increased, the number of timings at which the relative speed between a camera head and a subject Wk is made equal to 0 (i.e., a camera head and a subject Wk become parallel with each other) can be increased. In this manner, in the camera unit  30 B according to the second embodiment, the number of images taken to be transmitted to the camera control unit  50  for each subject Wk can be increased. Furthermore, since the increase in the number of images taken makes it unnecessary to capture each subject Wk in such a manner that it is included in an angle of view, it becomes possible to capture each subject Wk from a position closer to it. Still further, in the camera control unit  50  according to the second embodiment, since the resolution of an image taken of one subject Wk can be increased by adding its plural images pixel by pixel, data of an image taken can be generated in which peripheral portions are reduced in distortion. 
     The camera unit  30 B according to the second embodiment can be applied to both of the case that the camera unit  30 B performs imaging while being moved by the inspection cart  10  or the like (first embodiment) and the case that the camera unit  30 B is fixed and subjects Wk are moved (first modification of the first embodiment). 
     In the following description of the second embodiment, constituent elements having the same ones in the first embodiment or the first modification of the first embodiment will be given the same reference symbols as the latter and will not be described in detail. 
     The drum  31 A employed in the second embodiment will be described below with reference to  FIGS. 17 and 18 .  FIG. 17  is a perspective view showing an example appearance of the drum  31 A employed in the second embodiment.  FIG. 18  is a sectional view showing an example arrangement of four camera heads  35 A,  35 B,  35 C, and  35 D provided in the drum  31 A. Although in this example the four camera heads  35 A,  35 B,  35 C, and  35 D are disposed in the circumferential surface of the drum  31 A, it goes without saying that the number of camera heads is not limited to four and may be two or larger than two. 
     Four openings are formed in the circumferential surface of the drum  31 A at intervals of 90°. The four openings are openings that allow the imaging elements  42  of the four camera heads  35 A,  35 B,  35 C, and  35 D to capture subjects Wk, respectively. Each of the four openings may be fitted with a transparent member. Each of the four camera heads  35 A,  35 B,  35 C, and  35 D has the same configuration as the camera head  35  employed in the first embodiment and the first modification of the first embodiment. 
       FIG. 19  is a diagram showing an example of how the four camera heads  35 A,  35 B,  35 C, and  35 D perform imaging. In the camera unit  30 B shown in  FIG. 19 , each of the four camera heads  35 A,  35 B,  35 C, and  35 D captures subjects TgA and TgB as the drum  314  is moved in a direction MV 2  while being rotated in a direction MM 2 . 
     The four camera heads  35 A,  35 B,  35 C, and  35 D have respective angles of view Ag 21 , Ag 22 , Ag 23 , and Ag 24 . The four camera heads  35 A,  35 B,  35 C, and  35 D capture the subjects TgA and TgB in such a manner their angles of view Ag 21 , Ag 22 , Ag 23 , and Ag 24  overlap with each other and each of the subjects TgA and TgB is captured by plural ones of the camera heads  35 A,  35 B,  35 C, and  35 D. In the camera unit  30 B shown in  FIG. 19 , the angle of view Ag 21  of the camera head  354  and the angle of view Ag 22  of the camera head  35 B cover the subject TgA. The angle of view Ag 22  of the camera head  35 B, the angle of view Ag 23  of the camera head  35 C, and the angle of view Ag 24  of the camera head  35 D cover the subject TgB. 
     With the above measure, in the camera unit  30 B, even if the angle of view of a camera head facing the subject side (e.g., the angle of view Ag 21  of the camera head  35 A) does not fully cover the subject TgA, the angle of view of the camera head that faces the subject side next (e.g., the angle of view Ag 22  of the camera head  35 B) also covers the subject TgA. In this manner, in the camera unit  30 B, each of the plural subjects TgA and TgB can be captured in such a manner that corresponding ones of the plural camera heads  35 A to  35 D are brought close to it. The distance from the camera head  35  to the subject (distance to subject) is set at 40 mm, for example. The camera control unit  50  can perform pixel-by-pixel addition in peripheral portions of plural images taken of one subject because the peripheral portions can overlap with each other. As a result, the camera control unit  50  can increase the resolution of peripheral portions of each image taken. 
       FIG. 20  is a diagram showing an example of imaging by a single camera head  35 . The camera unit  30  shown in  FIG. 20  has one camera head  35  like the camera unit  30  according to the first embodiment does. In the camera unit  30  shown in  FIG. 20 , the camera head  35  captures each of subjects TgA and TgB as the drum  31  is moved in a direction MV 2  while being rotated in a direction MM 2 . 
     As shown in  FIG. 20 , the camera unit  30  having the single camera head  35  should preferably capture subjects TgA and TgB in such a manner that its angle of view covers each of the subjects TgA and TgB fully, even preferably in such a manner that each of the subjects TgA and TgB is located at a central portion of the angle of view. In this case, the camera head  35  is disposed at a position that is far from the subjects Tg and captures each of the subjects TgA and TgB in such a manner that it is covered by the angle of view. For example, to allow the camera head  35  to capture each of the subjects TgA and TgB in the same manner as in the case where the four camera heads  35 A to  35 D are provided, the distance from the camera head  35  to each of the subjects TgA and TgB (distance to subject) needs to be set two times as long as a distance of the case that the four camera heads  35 A to  35 D are provided. More specifically, where the camera head  35  performs high-speed imaging under conditions that the frame rate is 120 (fps), the diagonal angle of view is 120°, and the movement speed is 100 km/h, an imaging interval to the next frame is equal to 277.8 mm. Thus, a distance of about 80 mm is necessary between the camera head  35  and each of the subjects TgA and TgB. 
     On the other hand, in the camera unit  30 B according to the second embodiment, the four camera heads  35 A to  35 D are disposed in the peripheral surface of the drum  31 A at intervals of 90°. Thus, each of the four camera heads  35 A to  35 D can capture each subject Tg from a closer position. As a result, in performing high-speed imaging on each subject Tg, the resolution of an image taken by the camera unit  30 B according to the second embodiment can be made higher. Furthermore, in the camera unit  30 B according to the second embodiment, imaging is performed so that peripheral portions of images taken overlap with each other and pixel-by-pixel addition is performed in the overlap, whereby distortion of the images can be suppressed and the peripheral portions of the images can be increased in resolution. 
     First Modification of Second Embodiment 
       FIG. 21  is a diagram showing an example internal configuration of a camera unit  30 C according to a first modification of the second embodiment. In the camera unit  30 C, four openings are formed in the peripheral surface of a drum  31 B. Each of the four openings is formed at a position that is deviated by a distance B from one of two lines (indicated by chain lines in  FIG. 21 ) that divide the camera unit  30 C into four equal parts. Four camera heads  35 E,  35 F,  35 G, and  35 H are disposed like the blades of a windmill at positions that are deviated by a distance B from the two lines that divide the camera unit  30 C into four equal parts. With this structure, the four camera heads  35 E to  35 H and four imaging elements  42 E,  42 F,  42 G, and  42 H can be located at positions that are closer to the rotation axis of the camera unit  30 C than in the camera unit  30 B shown in  FIG. 18  having the four camera heads  35 A to  35 D. 
     As a result, the size (diameter) of the camera unit  30 C according to the first modification of the second embodiment can be made smaller. Furthermore, in the camera unit  30 C, since the four camera heads  35 E to  35 H are deviated by the distance B from the above two lines passing through the rotation axis, the degree of distortion in peripheral portions of each image taken can be lowered (refer to paragraph 0053). 
     Second Modification of Second Embodiment 
       FIG. 22  is a diagram showing an example internal configuration of a camera unit  30 D according to a second modification of the second embodiment. In the camera unit  30 D, four openings are formed in the peripheral surface of a drum  31 C at intervals of an angle 90°. Two camera heads  35 I and  35 K are disposed in such a manner that they are opposed to each other and their center lines coincide with one of two lines that divide the camera unit  30 D into four equal parts. Likewise, two imaging units  42 I and  42 K are disposed in such a manner that they are opposed to each other and their center lines coincide with the one of the two lines that divide the camera unit  30 D into four equal parts. A camera head  35 J and an imaging element  42 J are arranged parallel with and directed oppositely to the camera head  35 K and the imaging element  42 K. A camera head  35 L and an imaging element  42 L are arranged parallel with and directed oppositely to the camera head  35 I and the imaging element  42 I. 
     The camera head  35 J has an imaging lens  41 J for focusing light reflected by a mirror  46 J which reflects light coming from an opening  44 J by 90° and the imaging element  42 J for converting an optical image formed by the imaging lens  41 J into an image signal. Likewise, the camera head  35 L has an imaging lens  41 L for focusing light reflected by a mirror  46 L which reflects light coming from an opening  44 L by 90° and the imaging element  42 L for converting an optical image formed by the imaging lens  41 L into an image signal. Each of the four openings may be fitted with a transparent member. 
     In the camera unit  30 D according to the second modification of the second embodiment, the optical axes of the four imaging elements  42 I to  42 L are arranged parallel with each other because of the intervention of the two mirrors  46 J and  46 L. With this measure, in camera unit  30 D according to the second modification of the second embodiment, the four camera heads  35 I to  35 L can be disposed closer to the rotation axis of the camera unit  30 D than the four camera heads  35 A to  35 D of the camera unit  30 B shown in  FIG. 18  are to its rotation axis. 
     Where a camera unit is equipped with mirrors, an improvement may be made so that the number of images is increased that are taken with a subject located at the center of the angle of view of imaging by rotating each mirror by a very small angle according to a rotation speed of the camera unit and thereby changing the center line of imaging in which the subject is located right in front of the camera head. Each mirror provided in a camera unit is not limited to a planar mirror; for example, a prism may be provided instead of the planar mirror to enable selection of an input wavelength. 
     As such, the size (diameter) of the camera unit  30 D according to the second modification of the second embodiment can be made smaller. 
     Third Modification of Second Embodiment 
       FIG. 23  is a diagram showing an example internal configuration of a camera unit  30 E according to a third modification of the second embodiment. The camera unit  30 E is equipped with two drums  31 D 1  and  31 D 2  and is thus about two times as thick as in the case where the drum  31  or  31 B is employed. 
     In the drum  31 D 1 , four camera heads  35 M,  35 N, . . . are formed in its circumferential surface at the same intervals. In the drum  31 D 2 , four camera heads  35 O,  35 P, are formed in its circumferential surface at the same intervals. The four camera heads  35 M,  35 N, . . . and the four camera heads  35 O,  35 P, . . . are deviated so as not to be located at the same positions in the circumferential direction of the drums  31 D 1  and  31 D 2  (i.e., in the rotation direction of the camera unit  30 E). 
     Although in the example shown in  FIG. 23  the four camera heads  35 M,  35 N, . . . are deviated from the four respective camera heads  35 O,  35 P, by 45° (staggered arrangement), the manner of deviation is not limited to this; the camera heads  35 M,  35 N, . . . may be deviated from the respective camera heads  35 O,  35 P, . . . by 20° or 30°. The number of camera heads provided in each of the drums  31 D 1  and  31 D 2  is not limited to four and may be two, for example. Furthermore, the numbers of camera heads provided in the respective drums  31 D 1  and  31 D 2  need not always be identical. 
     As described above, in the camera unit  30 E according to the third modification of the second embodiment, since the camera heads are arranged in two levels, the number of camera heads can be increased without increasing the diameter of the camera unit  30 E. In the camera unit  30 E according to the third modification of the second embodiment, the degree of freedom of arrangement of camera units can be increased. Thus, the camera unit  30 E can capture subjects reliably by virtue of an increased number of camera heads even in the case where the camera heads capture the subjects while the camera unit  30 E is moving or rotating at high speed. Furthermore, in the camera unit  30 E, the number of images taken by plural respective camera heads can be increased and, at the same time, the number of overlaps between the ranges of angles of view can be increased. As a result, the camera control unit  50  can increase the resolution of peripheral portions of each image corresponding to peripheral portions of the range of each angle of view by performing addition on a pixel-by-pixel basis. 
     Fourth Modification of Second Embodiment 
       FIG. 24  is a diagram showing an example internal configuration of a camera unit  30 F according to a fourth modification of the second embodiment. As in the camera unit  30 E according to the third modification of the second embodiment, a drum  31 E of the camera unit  30 F according to the fourth modification of the second embodiment is about two times as thick as the drums  31  and  31 B. In the camera unit  30 F, four camera heads  35 Q,  35 R, . . . are formed in a lower part of the circumferential surface of the drum  31 E and four camera heads  35 S,  35 T, . . . are formed in an upper part of the circumferential surface of the drum  31 E. The four camera heads  35 Q,  35 R, . . . and the four camera heads  35 S,  35 T, . . . are formed at the same positions in the circumferential direction (i.e., the rotation direction of the camera unit  30 F), respectively. 
     As described above, in the camera unit  30 F according to the fourth modification of the second embodiment, since the camera heads are arranged in two levels, the number of camera heads can be increased without increasing the diameter of the camera unit  30 F. In the camera unit  30 F according to the fourth modification of the second embodiment, the degree of freedom of arrangement of camera units can be increased. Thus, the camera unit  30 F can capture subjects reliably by virtue of an increased number of camera heads even in the case where the camera heads capture the subjects while the camera unit  30 F is moving or rotating at high speed. Furthermore, in the camera unit  30 F, the number of images taken by plural respective camera heads can be increased and, at the same time, the number of overlaps between the ranges of angles of view can be increased. As a result, the camera control unit  50  can increase the resolution of peripheral portions of each image corresponding to peripheral portions of the range of each angle of view by performing addition on a pixel-by-pixel basis. 
     Third Embodiment 
     In the first and second embodiments, the camera heads are disposed in the peripheral surface of the drum. In a third embodiment, a camera head is disposed in a side surface of the drum. The third embodiment is directed to a case that the camera head captures a subject while being moved. In the following description of the camera device according to the third embodiment, constituent elements having the same ones in the first or second embodiment will be given the same reference symbols as the latter and will not be described in detail. 
       FIG. 25  is a perspective view showing an example appearance of the camera unit  30 G according to the third embodiment. In the camera unit  30 G according to the third embodiment, a camera head  35 U is disposed in an opening formed in a side surface of a ring-shaped drum  31 G. The optical axis of the camera head  35 U is parallel with the rotation axis of the drum  31 G. The camera head  35 U is rotated in a direction MM 3  around the rotation axis. 
       FIG. 26  is a view showing an example manner of imaging by the camera unit  30 G. A subject TgC is suspended on a rail  180 . The camera unit  30 G is disposed under the rail  180  and captures the subject TgC from under the subject TgC as the camera unit  30 G is moved at a prescribed speed in a direction MV 3  alongside the rail  180  while being rotated in the direction MM 3  of the drum  31 G. The camera head  35 U is rotated around the rotation axis of the drum  31 G. Although the camera unit  30 G shown in  FIG. 26  is moved by an inspection cart  10 , the inspection cart  10  is omitted in  FIG. 26  to simplify the description. Where the subject TgC is moved, it may be conveyed by the rail  180  serving as part of a conveying machine. 
     The positional relationship between the camera unit  30 G and the subject TgC may be opposite to that shown in  FIG. 26 . That is, the camera unit  30 G may be suspended on the rail  180  and capture the subject TgC disposed under the camera unit  30 G. 
       FIG. 27  is a diagram showing an example of how the camera unit  30 G according to the third embodiment captures the subject TgC. The drum  31 G shown in  FIG. 27  is moved in the direction MV 3 . The camera unit  30 G according to the third embodiment transmits, to the camera control unit  50 , an image of the subject TgC that was taken while being moved in the X direction by a movement distance ΔL 1 . 
     The camera head  35 U employed in the third embodiment is moved while being rotated so as to form, with respect to the subject TgC, a trace that is shaped like a cycloid curve. That is, the subject TgC is captured so that its locus in plural images taken with respective view ranges likewise becomes a cycloid curve.  FIG. 27  shows a view range Ag 31  of the camera head  35 U and a corresponding position of the subject TgC at timing of a start of exposure as well as a view range Ag 32  of the camera head  35 U and the corresponding position of the subject TgC at timing of an end of the exposure. 
     At the timing of the start of exposure, the relative speed between the X component of the rotation speed of the camera head  35 U and the movement speed of the camera head  35 U is made equal to zero. The time during which the relative speed between the camera head  35 U and the subject TgC is kept equal to 0 is long because the camera head  35 U is disposed so that its optical axis is parallel with the rotation axis of the drum  31 G and hence the position variation of the subject TgC moving relative to the view range is made smaller. 
     As a result, the camera unit  30 G according to the third embodiment can capture the subject TgC for a longer time. That is, the camera control unit  50  employed in the third embodiment can receive more images for the single subject TgC and the variation of the position of the single subject TgC with respect to the center of a view range is made smaller. Thus, the camera control unit  50  can generate data of clearer images taken. Furthermore, capable of receiving many images taken that are suitable for addition for image quality improvement, the resolution corresponding to a peripheral portion of a view range can be made higher. 
     Embodiment 4 
     In a fourth embodiment, a camera head  35 W is disposed in the circumferential surface of a drum  31 H and performs imaging being always directed to one direction (i.e., the direction of a subject TgD) while the drum  31 H is moved (rotation is caused in the drum  31 H). In the following description of a camera unit  34 H according to the fourth embodiment, constituent elements having the same ones in the control unit  30  or  30 A according to the first embodiment will be given the same reference symbols as the latter and will not be described in detail. 
       FIG. 28  is a perspective view showing an example appearance of the camera unit  34 H according to the fourth embodiment. The camera unit  34 H has a drum  31 H which is thicker than the drum  31  employed in the first embodiment. The circumferential surface of the drum  31 H is formed with an opening that allows a camera head  35 W to capture a subject TgD. 
       FIG. 29  is a perspective view showing an example internal mechanism of the drum  31 H.  FIG. 30  is a diagram showing an example operation of a first gear  131  and a second gear  132 . The drum  31 H is equipped with a gear mechanism  130  which has the first gear  131  and the second gear  132 . 
     The first gear  131  is supported pivotally by a rotary motor  37 , for example, and is driven rotationally in a direction MM 4   a  at a rotation speed R. The first gear  131  is in mesh with the second gear  132  with a speed reduction ratio 1 and transmits rotational power to the second gear  132 . 
     The second gear  132  supports the camera head  35 W pivotally. The second gear  132  is rotated in a direction MM 4   b  by the rotational power transmitted from the first gear  131  (speed reduction ratio: 1). That is, the second gear  132  is in mesh with the first gear  131  and rotates on its axis while circling around the first gear  131 . Thus, the camera head  35 W which is supported by the second gear  132  pivotally can perform imaging in such a manner as to be always directed in the same direction (−Z direction in  FIG. 30 ). 
       FIG. 31  is a diagram showing an example of how a subject TgD is captured by the camera unit  30 H according to the fourth embodiment. As described above with reference to  FIGS. 29 and 30 , the camera head  35 W and its angle of view Ag 40  are always directed toward the subject TgD (i.e., in the −Z direction). 
     The camera head  35 W according to the fourth embodiment is controlled by the camera control unit  50  in such a manner that rotation is caused in the drum  31 H at a rotation speed that makes approximately equal to 0 the relative speed between a movement speed (in the X direction) of the subject TgD and a movement speed of the camera head  35 W at a position where the distance between the camera head  35 W and the subject TgD is smallest. With this measure, the camera head  35 W can capture the subject TgD by starting exposure at such timing that the distance to the subject TgD becomes smallest (i.e., the imaging distance to the subject TgD becomes smallest). 
       FIG. 32  is another diagram showing an example of how the subject TgD is captured by the camera unit  30 H according to the fourth embodiment. The camera unit  30 H is moved in a direction MV 4 . The camera head  35 W employed in the fourth embodiment starts exposure from a position where the distance between the camera head  35 W and the subject TgD is smallest (in other words, starts transmission of an image taken to the camera control unit  50 ). An angle of view Ag 42  of the camera head  35 W at timing when the relative speed between the camera head  35 W and the subject TgD can be regarded as being equal to 0 is made larger than an angle of view Ag 41  at timing when the relative speed between the camera head  35 W and the subject TgD is equal to 0 according to a movement distance of the camera head  35 W in the Z direction per an imaging time of the camera head  35 W. 
     As described above, in the camera unit  30 H according to the fourth embodiment, since the camera head  35 W performs imaging being always directed toward the subject TgD, the variation, from the center of the angle of view, of the position of the subject TgD in each of plural images taken that are transmitted to the camera control unit  50  is much smaller than in the other embodiments. As a result, in the camera unit  30 H according to the fourth embodiment, the deviation of the imaging position of the subject TgD of each of plural images taken that are transmitted to the camera control unit  50  can be made small and data of images taken that are high in resolution in peripheral portions of an angle of view can be generated by performing pixel-by-pixel addition using many images. Furthermore, by performing pixel-by-pixel addition, the camera control unit  50  can suppress distortion of an image due to a difference in distance between a peripheral portion of a subject-side view range and a peripheral portion of a camera-side view range that occurs when the subject TgD is captured obliquely. 
     Fifth Embodiment 
     In the above-described camera units according to the first to fourth embodiments, a subject can be captured by making the relative speed between the camera head and a subject approximately equal to 0 by rotating the drum (or causing rotation in the drum). In a camera unit according to a fifth embodiment to be described below, a piston mechanism is provided and a subject is captured in such a manner that the relative speed between the camera head and the subject is made approximately equal to 0 by driving the piston mechanism. 
     In the following description of the camera unit according to the fifth embodiment, constituent elements having the same ones in the third embodiment will be given the same reference symbols as the latter and will not be described in detail. The camera unit  30 J according to the fifth embodiment can be applied to not only a case of a moving subject TgE but also a case that the camera unit  30 J performs imaging while being moved. 
     The configuration and a moving mechanism of the camera unit  30 J according to the fifth embodiment with reference to  FIGS. 33 to 36 .  FIG. 33  is a perspective view showing an example appearance of the camera unit  30 J according to the fifth embodiment.  FIG. 34  is a perspective view showing an example appearance of the camera unit  30 J as viewed from below in  FIG. 33 .  FIG. 35  is a front view showing an example drive mechanism of the camera unit  30 J as viewed from an arrowed line H-H in  FIG. 33 .  FIG. 36  is a perspective view showing the example drive mechanism of the camera unit  30 J as viewed from the arrowed line H-H in  FIG. 33 . 
     The camera unit  30 J is configured so as to have two guide plates  151  and  161 , a drive shaft  152 , two cams  153  and  163 , two connecting rods  154 , and  164 , two bearings  155   z  and  165   z , two sensors  158  and  168 , and two camera heads  35 Z and  35 V. In the camera unit  30 J, rotational drive power of a rotary motor  37  is transmitted to the two cams  153  and  163  by the drive shaft  152  to rotate them. Rotational drive power of the two cams  153  and  163  is transmitted to the two connecting rods  154 , and  164 , whereby the two camera heads  35 Z and  35 V which are provided on the side of one end portions of the connecting rods  154 , and  164  are reciprocated, respectively. That is, the camera unit  30 J is equipped with a piston mechanism  150  for reciprocating the camera head  35 Z and a piston mechanism  160  for reciprocating the camera head  35 V. The two piston mechanisms  150  and  160  are disposed adjacent to each other. 
     The piston mechanism  150  has the guide plate  151  which is approximately shaped like an ellipse. A hole  151   z  is formed through the guide plate  151  so as to extend in its longitudinal direction. The piston mechanism  160  has the guide plate  161  which is approximately shaped like an ellipse. A hole  161   z  is formed through the guide plate  161  so as to extend in its longitudinal direction. 
     Two circular-disc-shaped cams  153  and  163  facing the confronting surfaces of the guide plates  151  and  161  are supported rotatably by the guide plates  151  and  161 , respectively. 
     Rotational drive power of a rotary motor (not shown) is transmitted to the drive shaft  152 , whereby the two cams  153  and  163  which are connected to the drive shaft  152  are rotated. The cam  153  is provided with, at one point in the circumferential direction, an engagement portion  153   z  that is engaged with the other end portion of the connecting rod  154 . The cam  163  is provided with, at one point in the circumferential direction, an engagement portion  163   z  that is engaged with the other end portion of the connecting rod  164 . 
     The one end portion of the connecting rod  154  is provided with a head portion  155 , and the one end portion of the connecting rod  164  is provided with a head portion  165 . 
     The head portion  155  has the bearing  155   z  that is inserted slidably in the longitudinal hole  151   z  of the guide plate  151 . Likewise, the head portion  165  has the bearing  165   z  that is inserted slidably in the longitudinal hole  161   z  of the guide plate  161 . The camera heads  35 Z and  35 V are attached to the respective head portions  155  and  165 . 
     In the piston mechanism  150 , when the drive shaft  152  is rotated being driven rotationally by the rotary motor, rotational drive power of the rotary motor is transmitted to the cam  153 , whereby the cam  153  is rotated. The connecting rod  154  which is connected to the engagement portion  153   z  of the cam  153  advances and retreats in the X direction as the cam  153  is rotated. The camera head  35 Z which is attached to the head portion  155  which is moved in link with the connecting rod  154  advances and retreats in the X direction as the cam  153  is rotated. The sensor  158  capable of detecting an imaging start position (i.e., exposure start timing) is provided at the cam- 153 -side end of the longitudinal hole  151   z . A Hall element or a proximity switch, for example, is used as the sensor  158  and detects approach of, for example, a magnet attached to the end portion of the connecting rod  154 . 
     Likewise, the piston mechanism  160 , when the drive shaft  152  is rotated being driven rotationally by the rotary motor, rotational drive power of the rotary motor is transmitted to the cam  163 , whereby the cam  163  is rotated. The connecting rod  164  which is connected to the engagement portion  163   z  of the cam  163  advances and retreats in the X direction as the cam  163  is rotated. The camera head  35 V which is attached to the head portion  165  which is moved in link with the connecting rod  164  advances and retreats in the X direction as the cam  163  is rotated. The sensor  168  capable of detecting an imaging start position (i.e., exposure start timing) is provided at the cam- 163 -side end of the longitudinal hole  161   z . A Hall element or a proximity switch, for example, is used as the sensor  168  and detects approach of, for example, a magnet attached to the end portion of the connecting rod  164 . 
       FIG. 37  is a diagram for description of an example imaging operation of the camera unit  30 J according to the fifth embodiment. In the camera unit  30 J according to the fifth embodiment, the two piston mechanisms  150  and  160  cause the camera heads  35 Z and  35 V to advance and retreat alternately in the X direction which is the same as a movement direction MVS of subjects TgF. In the camera unit  30 J according to the fifth embodiment shown in  FIG. 37 , the camera head  35 Z captures plural subjects TgF. In  FIG. 37 , the two guide plates  151  and  161  are omitted to simplify the description. 
     The camera head  35 Z starts exposure (i.e., starts transmitting an image taken to the camera control unit  50 ) as soon as the rear end of the connecting rod  154  is detected by the sensor  158  (i.e., an imaging start position is detected). Timing at which the relative speed between the camera head  35 Z and a subject TgF becomes 0 is timing at which the distance between camera head  35 Z and the subject TgF becomes smallest. When the connecting rod  154  reaches the end that is opposite to the sensor  158 , the camera head  35 Z stops the imaging (i.e., transmission of an image taken to the camera control unit  50  is stopped). 
     At timing when the camera head  35 Z stops imaging, an imaging start position is detected is detected by the sensor  168  and the camera head  35 V starts exposure (i.e., starts transmitting an image taken to the camera control unit  50 ). Timing at which the relative speed between the camera head  35 V and the next subject (not shown) becomes approximately equal to 0 is timing at which the distance between camera head  35 V and the next subject becomes smallest. When the connecting rod  164  reaches the end that is opposite to the sensor  168 , the camera head  35 V stops the imaging (i.e., transmission of an image taken to the camera control unit  50  is stopped). 
     Where the camera unit  30 J moves in the direction MV 5  and plural subjects are stopped, each of the two camera heads  35 Z and  35 V captures a subject while moving in the −X direction. In this case, the relative speed between each of the two camera heads  35 Z and  35 V and a subject becomes approximately equal to 0 at timing when the distance between the camera head  35 Z or  35 V and the subject becomes smallest. 
     The same operation as described above is performed repeatedly. In the camera unit  30 J according to the fifth embodiment, the relative speed between each of the camera heads  35 Z and  35 V and a subject TgF becomes approximately equal to 0 at timing when the two engagement portions  153   z  and  163   z  reach a position P 1 . At this time, a rotation speed of the rotary motor  37  is calculated on the basis of a movement speed of the subject TgF, a movement speed of the camera unit  30 J, and movement speeds of the two camera heads  35 Z and  35 V so that the relative speed between each of the camera heads  35 Z and  35 V and the subject TgF becomes approximately equal to 0. 
     In the camera unit  30 J according to the fifth embodiment, angles of view of the camera heads  35 Z and  35 V overlap with each other because the piston mechanisms  150  and  160  are adjacent to each other and the camera heads  35 Z and  35 V are located close to each other. 
       FIG. 38  is a flowchart showing an example operation procedure of a manufacturing system according to the fifth embodiment. A description will be made with reference to  FIG. 18  with an assumption that subjects TgF are moving subjects. 
     At step S 1 B, the motor control unit  51 A receives and acquires speed information of subjects TgF from the work speed detection sensor  45 . Where the camera unit  30 J is moved, the motor control unit  51 A receives movement speed information of the camera unit  30 J. 
     At step S 2 B, the motor control unit  51 A calculates, on the basis of the received speed information of the subjects TgF, a rotation speed R of the rotary motor  37  for causing the cams  153  and  163  to be driven rotationally so that relative speed between each of the two camera heads  35 Z and  35 V and a subject TgF becomes equal to 0. 
     At step S 3 B, the motor control unit  51 A generates a control signal to be used for rotating the rotary motor  37  on the basis of the calculated rotation speed R and transmits the generated control signal to the rotary motor  37 . The rotary motor  37  is driven rotationally at the rotation speed R on the basis of the received control signal. 
     At step S 4 B, the camera control unit  52  detects timing when the camera head  35 Z or  35 V is to start imaging on the basis of detection information of each of the two sensors  158  and  168 . 
     If at step S 4 B the camera control unit  52  detects timing when the camera head  35 Z is to start imaging on the basis of detection information of each of the two sensors  158  and  168  (S 4 B: camera head  1  on), at step S 5 B the camera control unit  52  starts reception of images taken by the camera head  35 Z. 
     If at step S 4 B the camera control unit  52  detects timing when the camera head  35 V is to start imaging on the basis of detection information of each of the two sensors  158  and  168  (S 4 B: camera head  2  on), at step S 6 B the camera control unit  52  starts reception of images taken by the camera head  35 V. 
     At step S 7 B, the camera control unit  50 A judges whether the camera unit  30 J has completed a prescribed imaging process that was set by the user. For example, the camera control unit  50 A may finish the imaging either when an inspection interval set by the user has passed or when an inspection finishing manipulation is made by the user. 
     If judging that the imaging has not been completed yet (S 7 B: no), the camera control unit  50 A returns to step S 1 B. 
     On the other hand, if judging that the imaging has been completed (S 7 B: yes), the camera control unit  50 A finishes the inspection process. 
     As described above, the camera unit  30 J according to the fifth embodiment in which the camera head  35 Z and the camera head  35 V advance and retreat alternately, plural subjects TgF can be captured successively. As a result, the camera control unit  50 A can suppress image blurring in a direction opposite to the movement direction of the subjects TgF. 
     Although the various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not restricted to those embodiments. It is apparent that those skilled in the art would be able to conceive various changes and modifications without departing from the scope of the claims, and they should naturally be construed as belonging to the technical scope of the disclosure. 
     For example, although the camera unit  30 A of the manufacturing system  100 A according to the first modification of the first embodiment is installed fixedly whereas the plural subjects Wk are conveyed by the belt conveyor  110 , the camera unit  30 A may be installed on the inspection vehicle  10  and capture each of the subjects Wk while moving. As a result, the manufacturing system  1004  can be increased in imaging speed. 
     As described above, the camera unit  30  (camera device) is equipped with the at least one camera head  35  (imaging unit) which captures the rail  80  (subject), the rotary motor  37  (rotary motor) which rotates the camera head  35  at a prescribed rotation speed a harness  43  (output unit) which outputs images taken by the camera head  35 , the drum  31  (body) which incorporates the camera head  35 , the rotary motor  37 , and the harness  43 . The harness  43  outputs at least one image, among the images, taken at an imaging position where the camera head  35  and a surface of the rail  80  are approximately parallel with each other. With the above configuration, the camera unit  30  can produce a clear image by imaging the rail  80  (subject) can acquire a clear image simply in a short time and hence increase the production efficiency. 
     The camera head  35  is installed so as to be capable of imaging in a direction that is perpendicular to a rotation axis of the drum  31 . This makes it possible to produce a clear image by imaging the rail  80  (subject) consecutively. 
     The camera head  35  is installed so as to be capable of imaging in a direction that is parallel with a rotation axis of the drum  31 . With this measure, the camera head  35  can capture the subject in such a state that the angle of view deviation from the center in an imaging duration is small, whereby image blurring can be suppressed. 
     The four camera heads  35 A,  35 B,  35 C, and  35 D (plural imaging units) are disposed in the same circumferential surface that is perpendicular to the rotation axis of the drum  31 . With this measure, each camera head  35  can capture the subject from a position that is close to the subject. Furthermore, the resolution of images taken can be increased when the camera head  35  captures a subject that is moving at a high speed. Still further, the distortion of each image can be suppressed because peripheral portions of each image are taken so as to overlap with each other, whereby the resolution of overlap portions of each image can be increased. 
     The camera unit  30 D is further equipped with the at least one mirror  46 J and  46 L and at least one opening  44 J through which light coming from the imaging position passes to shine on the mirrors  46 J and  46 L. Among the four camera heads  35 I,  35 J,  35 K, and  35 L, each the camera heads  35 J and  35 L (at least one imaging unit) captures a subject on the basis of light reflected by the mirror  46 J or  46 L. As a result, with the intervention of the mirrors  46 J and  46 L, the four imaging elements are arranged so that their optical axes are arranged parallel with each other. Furthermore, the four camera heads  35 I,  35 J,  35 K, and  35 L are disposed close to each other near the center of the drum  31 C, In a central portion of the drum  31 C, a small empty space remains and the two image devices and the two mirror  46 J or  46 L are arranged densely. This configuration accelerates miniaturization of the camera unit  30 D. 
     The camera unit  30 H is further equipped with the first gear  131  which is coupled with the rotary motor  37  and transmits rotational power of the rotary motor  37  and the second gear  132  which is coupled with the first gear  131  and transmits rotational power from the first gear  131  to the camera head  35 W. The camera head  35 W is rotated via the first gear  131  and the second gear  132  so that its imaging direction always coincides with a direction at the imaging position. With this measure, a subject can be captured without blurring of the camera head  35 W. Furthermore, a subject can be captured from right above from a start to an end of imaging. As a result, the number of images can be increased that can be captured squarely and a high-resolution image can be obtained by pixel-by-pixel addition using many images taken. 
     The camera unit  30 J is further equipped with two connecting rods  154  and  164  each of which has a camera head  35 Z or  35 V on the side of its one end, two cams  153  and  163  connected to the other ends of the connecting rods  154  and  164 , respectively; and a drive shaft  152  which is connected to the rotary motor  37  and transmits rotational power of the rotary motor  37  to the two cams  153  and  163 . The camera heads  35 Z and  35 V capture the subject alternately. With this measure, since the two camera heads  35 Z and  35 V advance and retreat alternately, one of them is moved in the same direction as a subject is. One of the camera heads  35 Z and  35 V can capture a subject at timing when the relative speed between a movement speed of the subject and a movement speed of the one camera head  35 Z or  35 V is made equal to 0. 
     The camera unit  30 A is further equipped with the subject speed detection sensor  45  (subject speed detection unit) which detects a movement speed of the work Wk (subject) on the basis of images taken. With this measure, a speed of a work can be detected easily without using an additional electronic component by performing image analysis on the images taken. 
     The motor control unit  51  calculates and sets a rotation speed of the rotary motor  37  that makes a relative speed between the camera head  35  and the subject located at the imaging position equal to 0. With this measure, the camera head  35  can capture a subject in a state that the subject is stationary relative to the camera head  35 . This makes it possible to suppress image blurring in the direction opposite to the moving direction that is prone to occur when the camera head  35  captures a moving subject. 
     In the manufacturing system  100 , the camera unit  30  (camera) which is installed in an inspection cart  10  captures a subject such as the rail  80 . The inspection cart  10  and the image processing device are connected to each other by a wired or wireless network so as to be able to communicate with each other. The camera unit  30  transmits at least one image taken at an imaging position where the subject and the camera head  35  being rotated at a rotation speed R (prescribed rotation speed) of the rotary motor  37  are approximately parallel with each other. The image processing device analyzes a state of the subject on the basis of the received at least one image and outputs an analysis result. This configuration increases the production efficiency. 
     The manufacturing system  100  is equipped with the inspection cart  10  (conveying device) which moves the camera unit  30  at a prescribed movement speed. The motor control unit  51 A calculates and sets, for the rotary motor  37 , a rotation speed that makes a relative speed between the camera head  135  and the subject located at the imaging position equal to 0 on the basis of the movement speed of the inspection cart  10 . With this measure, the camera head  135  can capture a subject in a state that the subject is stationary relative to the camera head  35 . This makes it possible to suppress image blurring in the direction opposite to the moving direction that is prone to occur when the camera head  35  captures a moving subject. 
     Although the various embodiments have been described above with reference to the drawings, the present disclosure is not restricted to those embodiments. It is apparent that those skilled in the art would be able to conceive various changes, modifications, replacements, additions, deletions, and equivalents without departing from the scope of the claims, and they should naturally be construed as belonging to the technical scope of the disclosure. Furthermore, constituent elements of some of the above-described various embodiments may be combined in a desired manner without departing from the spirit and scope of the disclosure. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure is useful in providing camera devices and manufacturing systems capable of acquiring a clear image simply in a short time and thereby increasing the production efficiency.