Imaging device and imaging method

Abstract

Provided are an imaging device and an imaging method for capturing an image in which it is possible to detect an object of interest of a subject. This imaging device comprises a camera (10), a range finder (20) that measures the distance to a wall surface (T, T2) of a tunnel (2), and a processor. The processor causes the camera (10) to execute first imaging for spatially dividing and imaging the tunnel (2) to acquire a captured image, assesses whether an object of interest can be detected from the captured image on the basis of a ranging signal of the range finder (20), and causes the camera (10) to execute second imaging, under imaging conditions different from those of the first imaging, on an imaging range of the tunnel (2) for which the assessment was made to be negative.

Description

Photographing device and photographing method

[0001] The present invention relates to an imaging device and an imaging method, and more particularly to a technique for capturing an image having a spatial resolution suitable for inspecting an object.

[0002] BACKGROUND ART In order to inspect various structures such as bridges, roads, tunnels, dams, and buildings, an image of the structure is taken using an imaging device, and the structure is inspected using the captured image.

[0003] Conventionally, when photographing a structure using this type of photographing device, a photographing support device has been proposed that supports photographing so that the photographing can be performed appropriately (Patent Document 1).

[0004] The photography support device described in Patent Document 1 acquires required pixel density information of the photographed surface of a structure required for recognizing the damage state of the structure. The photography support device also acquires photographing performance information of the photography device, distance information from the photography device to the photographed surface of the structure, and tilt angle information of the photographed surface of the structure with respect to a direction perpendicular to the photography direction of the photography device, and calculates the actual pixel density of the photographed surface of the structure based on this information.

[0005] The photographing support device then determines whether the calculated actual pixel density matches the required pixel density information and outputs the determination result.

[0006] When the photography support device determines that the actual pixel density does not conform to the required pixel density information, it outputs, as a judgment result, information to encourage the movement of the photography device (an instruction to move the photography device closer to the structure) or outputs an instruction to control the photography position and photography direction of the photography device.

[0007] International Publication No. 2017 / 126368

[0008] One embodiment of the technique of the present disclosure provides an image capturing device and an image capturing method that enable detection of an object of interest in a subject.

[0009] The invention of the first aspect is an imaging device comprising a camera, a rangefinder that measures the distance to a subject, and a processor, wherein the processor causes the camera to perform a first imaging operation in which the subject is spatially divided and an image is obtained, determines whether or not an object of interest can be detected from the captured image based on a ranging signal from the rangefinder, and causes the camera to perform a second imaging operation under different imaging conditions from the first imaging operation for the imaging range of the subject for which the determination is negative.

[0010] In the image capturing apparatus according to the second aspect of the present invention, in the first aspect, the determination is made as to whether or not the resolution of the captured image falls within an allowable range.

[0011] In the image capturing apparatus according to a third aspect of the present invention, in the second aspect, the resolution of the captured image is the spatial resolution of the captured image.

[0012] In the photographing apparatus according to a fourth aspect of the present invention, in any one of the first to third aspects, it is preferable that the subject and the camera move relatively in a first direction to photograph the subject continuously.

[0013] In the photographing apparatus according to a fifth aspect of the present invention, in the fourth aspect, it is preferable that the spatial resolution of the photographed image is the spatial resolution of the entire region of the photographed image.

[0014] In the image capturing apparatus according to the sixth aspect of the present invention, in the second aspect, the image capturing range is preferably a range for capturing a subject that has been determined not to fall within the allowable range.

[0015] In the seventh aspect of the present invention, in the fourth aspect of the photographing device, it is preferable that the first photographing is a photographing in which the spatial resolution of a first region of the photographed image falls within an acceptable range and the spatial resolution of a second region of the photographed image does not fall within the acceptable range, and the second photographing is a photographing in which the spatial resolution of the first region does not fall within the acceptable range and the spatial resolution of the second region falls within the acceptable range.

[0016] In the photographing device of the eighth aspect of the present invention, in the third aspect, it is preferable that the processor estimates the spatial resolution of the photographed image based on the photographing setting values ​​of the camera and the ranging signal of the rangefinder, and determines whether the estimated spatial resolution of the photographed image falls within an acceptable range.

[0017] In the photographing device of the ninth aspect of the present invention, in the third or eighth aspect, the processor obtains the shortest or longest distance to the subject in the photographed image based on the ranging signal of the rangefinder, and, where r_old is the distance to the subject in the first photograph, r is the shortest or longest distance, and th is a threshold that is a criterion for determining the acceptable range of spatial resolution, it is preferable that if |r - r_old| > th, the processor determines that the spatial resolution of the photographed image does not fall within the acceptable range.

[0018] In the photographing device of the tenth aspect of the present invention, in the seventh aspect, it is preferable that the first photographing is a photographing in which the focus position and focal length of the camera are adjusted for the first area, and the second photographing is a photographing in which the focus position and focal length of the camera are adjusted for the second area.

[0019] In the photographing device of the eleventh aspect of the present invention, in the seventh aspect, it is preferable that the processor causes the camera to perform a first photograph of the photographing range while the camera is moving in a first direction, and after the first photographing is completed, the camera returns to a position where it can at least photograph the photographing range again, and then causes the camera to perform a second photograph while the camera is moving in the first direction.

[0020] In the photographing device according to the twelfth aspect of the present invention, in the eleventh aspect, the processor automatically adjusts the focus position and focal length of the camera based on the distance to the subject corresponding to the second area until the camera returns to a position where it can photograph again, or outputs an instruction to the indicator prompting the user to adjust at least one of the focus position and focal length of the camera, and preferably executes the second photographing after the automatic adjustment or after the user adjusts at least one of the focus position and focal length of the camera.

[0021] A thirteenth aspect of the present invention is an imaging device in any one of the fourth, fifth, seventh, and tenth to twelfth aspects, which is provided with a positioning meter that measures the position of the camera, and when the first imaging of the imaging range is completed, the processor moves the camera in a second direction opposite to the first direction, and when it detects, based on the positioning signal of the positioning meter, that the camera has returned to a position where it can at least re-image the imaging range while moving in the second direction, the processor moves the camera again in the first direction and causes the camera to perform a second imaging of the imaging range.

[0022] A fourteenth aspect of the present invention is an imaging device in any one of the fourth, fifth, seventh, tenth to thirteenth aspects, which comprises a positioning meter that measures the position of the camera in the direction of movement, and an indicator that instructs the user on how to move the camera, and when a first image of the imaging range is completed while the camera is moving in a first direction, the processor preferably outputs an instruction to the indicator to move the camera in a second direction opposite to the first direction, and when it detects, based on the positioning signal of the positioning meter, that the camera has returned to a position where at least the imaging range can be re-imaged while moving in the second direction, it preferably outputs an instruction to the indicator to move the camera again in the first direction.

[0023] In the photographing device according to a fifteenth aspect of the present invention, in any one of the first to fourteenth aspects, it is preferable that the distance meter is a laser distance meter, and that the laser distance meter scans a subject with laser light and measures distances corresponding to the entire area of ​​the photographed image.

[0024] In the photographing device of the 16th aspect of the present invention, in any of the 7th, 10th to 12th aspects, it is preferable that the processor adjusts the focus position of the camera based on the ranging signal measured by the rangefinder, and when performing the first photograph, adjusts the focus position of the camera based on the ranging signal measured for a first region of the photographed image, and when performing the second photograph, adjusts the focus position of the camera based on the ranging signal measured for a second region of the photographed image.

[0025] A seventeenth aspect of the present invention is an imaging device in any of the first to sixteenth aspects, wherein the camera is composed of a plurality of second cameras, the plurality of second cameras are arranged in an arc shape, and the plurality of images captured by the plurality of second cameras include overlapping areas, and the processor determines, for each image captured by each of the plurality of second cameras, whether or not an object of interest can be detected from the captured image based on a ranging signal from a rangefinder, and preferably causes one or more of the plurality of second cameras that captured an image for which the determination is no to be made to perform the first and second imaging.

[0026] In an 18th aspect of the present invention, in any of the first to 17th aspects, the photographing device is preferably configured such that the camera is composed of a first camera and a second camera, the second camera is positioned in a different position from the first camera in the direction of movement and is positioned at a distance greater than the length of the camera's movement direction behind the photographing range, and the processor causes the first camera to perform the first photographing and the second camera to perform the second photographing of the photographing range.

[0027] In the photographing device according to the 19th aspect of the present invention, in any of the 7th, 10th to 12th, and 16th aspects, the processor preferably performs panoramic synthesis of the photographed images, and the photographed images used for the panoramic synthesis of the photographed range are images of a first area among the images photographed by the first photographing and images of a second area among the images photographed by the second photographing.

[0028] The invention of the twentieth aspect is a photographing method for a photographing device comprising a camera, a rangefinder that measures the distance to a subject, and a processor, in which the processor executes the following steps: having the camera execute a first photographing operation in which the subject is photographed in spatially divided portions to obtain a photographed image; determining whether or not an object of interest can be detected from the photographed image based on a ranging signal from the rangefinder; and having the camera execute a second photographing operation under photographing conditions different from those of the first photographing operation for a photographing range of the subject for which the determination is negative.

[0029] FIG. 1 is a diagram showing how a camera mounted on a moving object moving along the longitudinal direction of the object continuously captures images of the object while the moving object is moving. FIG. 2 is a diagram showing the state where the camera has moved from the image capture position shown in FIG. 1 to the next image capture position. FIG. 3 is a diagram showing the state where the camera has moved from the image capture position shown in FIG. 2 to the next image capture position. FIG. 4 is a diagram showing the state where the camera has moved from the image capture position shown in FIG. 3 to the next image capture position. FIG. 5 is a diagram showing the state where the camera has moved from the image capture position shown in FIG. 4 to the next image capture position. FIG. 6 is a diagram showing the state where the camera is in the same image capture position as shown in FIG. 5, but the camera's image capture conditions have been reset. FIG. 7 is a diagram showing the state where the camera has returned to a predetermined position from the image capture position shown in FIG. 6. FIG. 8 is a diagram showing the positional relationship between the camera and the range finder, the image capture range, etc. of the camera. FIG. 9 is another diagram showing the positional relationship between the camera and the range finder, the image capture range, etc. of the camera. FIG. 10 is a diagram showing the positional relationship of each part when a position finder is mounted on a dolly. FIG. 11 is a configuration diagram showing a first embodiment of an image capture device according to the present invention. FIG. 12 is a block diagram showing an embodiment of the hardware configuration of the control device shown in FIG. 11. FIG. 13 is a timing chart showing an example of the photographing operation by the photographing device of the first embodiment. FIG. 14 is a diagram showing another embodiment of a camera. FIG. 15 is a structural diagram showing a second embodiment of the photographing device according to the present invention. FIG. 16 is a structural diagram of the main parts of a third embodiment of the photographing device according to the present invention. FIG. 17 is a diagram showing a part of a flowchart showing an embodiment of the photographing method according to the present invention. FIG. 18 is a diagram continuing from the flowchart shown in FIG. 17. FIG. 19 is a diagram continuing from the flowchart shown in FIG. 17. FIG. 20 is a diagram showing an example of a photographed image of a portion of a tunnel where the diameter changes significantly.

[0030] Hereinafter, preferred embodiments of the photographing device and photographing method according to the present invention will be described with reference to the accompanying drawings.

[0031] [Outline of the Present Invention] The outline of the present invention will be described with reference to FIGS. 1 to 7. FIG.

[0032] Figures 1 to 7 each show how a subject is continuously photographed while the moving body is moving by a camera mounted on the moving body that moves along the longitudinal direction of the subject, and the positions of the moving body (camera) relative to the subject are different.

[0033] In this example, the subject is a railway tunnel 2, and the moving object is a carriage 50 running on the railway rails.

[0034] The dolly 50 is equipped with a camera 10, a range finder 20, and a control device (not shown).

[0035] The trolley 50 may be a self-propelled trolley that is controlled to move in a first direction (forward), stop, and a second direction (backward) along a rail in response to commands from a control device, or it may be a trolley that can be moved and operated manually.

[0036] The camera 10 is a camera whose focus position and focal length can be adjusted, and takes still images at set intervals while the cart 50 is traveling, or takes still images every set distance traveled, or takes videos. As a result, the camera 10, which moves relatively to the tunnel 2, takes spatially divided images of the tunnel 2.

[0037] When still images are captured sequentially, the interval of the camera 10 is set so that the captured images before and after each other include overlapping areas.

[0038] The distance measuring device 20 is provided at a position a distance s ahead of the camera 10 (in the forward direction of the carriage 50), and measures the distance R to the tunnel 2 at that position.

[0039] In this example, a LiDAR (Light Detection and Ranging), which is a type of laser rangefinder that uses laser light to measure the distance to the surface of a subject, is used as the rangefinder 20. Examples of LiDAR include FMCW (Frequency Modulated Continuous Wave) LiDAR and TOF (Time of Flight) LiDAR. Furthermore, the rangefinder 20 is not limited to LiDAR, and may be a laser radar three-dimensional shape measurement device as described in Japanese Patent Laid-Open Publication No. 9-297014, or a measurement device using a light-section method that uses an imaging device and a slit laser light projector as described in Japanese Patent Laid-Open Publication No. 2021-2016-31249, and the type of rangefinder is not important.

[0040] The distance measuring device 20 rotates the laser light emitted from the measurement head to scan the laser light on the wall surface, and measures the distance between the measurement head and the position on the wall surface of the tunnel 2 where the laser light is irradiated.

[0041] Furthermore, it is preferable that the distance meter 20 converts the measured distance into a distance in the same direction as the optical axis of the camera 10 based on the angle between the optical axis of the camera 10 and the laser light. Alternatively, the distance meter 20 may irradiate the laser light in the same direction as the optical axis of the camera 10 without rotating the laser light, and may measure the distance to the wall of the tunnel 2 in real time while the cart 50 is moving.

[0042] Furthermore, the distance meter 20 is disposed a distance s ahead of the camera 10, but the position (distance s) of the distance meter 20 can be set arbitrarily, and for example, the distance s may be set to zero. The distance meter 20 is preferably disposed in a position close to the camera 10 as long as it does not interfere with distance measurement.

[0043] 1 , the camera 10 captures an image of the wall surface T1 of the tunnel 2. In this case, the focus position and focal length of the camera 10 are adjusted so that the spatial resolution of the captured image of the wall surface T1 falls within an allowable range. The allowable range of spatial resolution is determined by the spatial resolution required for inspecting the damage state of the surface of the structure (in this example, the wall surface of the tunnel 2), and differs depending on, for example, whether it is required to detect cracks in the wall surface of the tunnel 2 that are 0.2 mm or wider or whether it is required to detect cracks that are 1.0 mm or wider.

[0044] Furthermore, it is preferable that the focal length of the camera 10 is short within the range in which the spatial resolution is within the allowable range, because this allows a larger area of ​​the tunnel 2 wall surface to be photographed in one shot, and the wall surface to be photographed efficiently.

[0045] In Figure 1, D1 is the shooting distance of camera 10 (the distance in the optical axis direction between camera 10 and wall surface T1), and R1 is the distance to wall surface T1 in the same direction as the optical axis of camera 10 measured by rangefinder 20.

[0046] FIG. 2 is a diagram showing a state in which the camera has moved from the photographing position shown in FIG. 1 to the next photographing position.

[0047] That is, the camera 10 shown in FIG. 2 is a fixed distance forward from the camera 10 shown in FIG. 1 . When the camera 10 takes images at fixed time intervals, the "fixed distance" is determined by the speed of the cart 50 and the fixed time interval. When the examiner (user) manually pushes the cart 50 forward, the speed of the cart 50 corresponds to the user's walking speed. Also, when the camera 10 repeatedly takes a still image each time the cart 50 advances a preset distance, the "fixed distance" is a preset distance. In this case, the position of the cart 50 is measured by a positioning meter, and each time it is detected that the cart 50 has advanced a preset distance (fixed distance) based on the positioning data from the positioning meter, a shooting instruction is given to the camera 10 to perform shooting.

[0048] Furthermore, it is preferable that the "certain distance" be determined so as to include an area where the images captured one after the other overlap. The overlapping area of ​​the images is the area used when combining the images into a panorama. Since the images of the wall of the tunnel 2 have few areas that can be used as feature points for panorama composition, it is preferable that the overlapping area be sufficiently large.

[0049] 2, the camera 10 photographs a wall surface T1 at a photographing distance D1 as in the case of FIG. 1, but the distance finder 20 measures a distance R2 to a wall surface T2 that is farther away than the wall surface T1.

[0050] In the case of the photographing position shown in Fig. 2, the camera 10 photographs only the wall surface T1, and does not photograph the wall surface T2. Also, in Fig. 2, "a" denotes the boundary position between the wall surface T1 and the wall surface T2. This boundary position "a" can be obtained from a positioning device that measures the position of the cart 50, as will be described later. Furthermore, the boundary between the wall surface T1 and the wall surface T2 is not limited to the case where it changes stepwise as shown in Fig. 2, but also includes the case where it changes continuously with an inclined surface from the wall surface T1 to the wall surface T2.

[0051] FIG. 3 is a diagram showing a state in which the camera has moved from the photographing position shown in FIG. 2 to the next photographing position.

[0052] The imaging range of the camera 10 at the imaging position shown in Figure 3 includes wall surface T1 and wall surface T2. In this example, the camera 10 repeatedly captures images with the focus position and focal length adjusted for wall surface T1. Therefore, the spatial resolution of wall surface T1 included in the captured image is within the allowable range, but the spatial resolution of wall surface T2 included in the captured image is not within the allowable range. In other words, in this example, wall surface T2 is separated from wall surface T1 by a distance such that the spatial resolution of wall surface T2 will not fall within the allowable range unless the focus position and focal length of the camera 10 are readjusted.

[0053] FIG. 4 is a diagram showing a state in which the camera has moved from the photographing position shown in FIG. 3 to the next photographing position.

[0054] 4 does not include wall surface T1, but does include the boundary wall surface between wall surface T1 and wall surface T2. In this case, the boundary wall surface between wall surface T1 and wall surface T2 in the captured image does not face camera 10 directly, so it can be determined that the spatial resolution of the region corresponding to the boundary wall surface does not fall within the allowable range. As a result, the spatial resolution of the entire region of the captured image does not fall within the allowable range.

[0055] FIG. 5 is a diagram showing a state in which the camera has moved from the photographing position shown in FIG. 4 to the next photographing position.

[0056] The imaging range of the camera 10 shown in Fig. 5 includes only the wall surface T2. Therefore, in this case, the spatial resolution of the entire area of ​​the captured image does not fall within the allowable range, as in the case of Fig. 4.

[0057] FIG. 6 shows a state where the camera is in the same shooting position as the camera 10 shown in FIG. 5, but the shooting conditions of the camera have been reset.

[0058] In one embodiment of the present invention, the dolly 50 is temporarily stopped when the camera 10 reaches the position shown in Fig. 6. In this example, the camera 10 is stopped at a position where it captures only the wall surface T2.

[0059] During the pause, the focus position of the camera 10 is adjusted so that the in-focus position of the camera 10 is the wall surface T2, and the focal length of the camera 10 is adjusted so that the photographing angle of view becomes narrow.

[0060] In this example, wall surface T2 is farther away than wall surface T1, and as a result, the spatial resolution of wall surface T2 does not fall within the allowable range. Therefore, in order to capture an image of wall surface T2 with high spatial resolution, it is necessary to increase the number of pixels of the image sensor of camera 10 per unit length of wall surface T2 (to increase the resolution of the captured image) by increasing the focal length of the lens of camera 10 and narrowing the shooting angle of view.

[0061] The focal length of the lens 11 of the camera 10 can be adjusted to the calculated focal length by, for example, calculating the optimal focal length of the camera 10 that satisfies the required spatial resolution using a formula based on the shooting distance of the subject, the performance of the camera 10 (image sensor size, number of pixels, lens performance, etc.), the required spatial resolution, etc. Alternatively, when using a lookup table in which the relationship between the shooting distance of the subject and the optimal focal length is registered and adjusting the focal length of the camera 10, it is possible to read the corresponding focal length from the lookup table based on the shooting distance of the subject and adjust the focal length to the read focal length. The focal length of the camera 10 may be adjusted automatically using an electric motor or manually by operating a zoom ring or the like.

[0062] The focus position of the lens of the camera 10 can be adjusted automatically using the distance measurement signal (distance measurement data) from the distance finder 20, by using the autofocus function of the camera 10, or manually by operating a focus ring, etc. Since the focus position and focal length of the camera 10 are adjusted while the dolly 50 is temporarily stopped, the adjustment can be performed with high precision.

[0063] 6, R2 is the distance to wall T2 in the same direction as the optical axis of camera 10 measured by rangefinder 20. C2 indicates half the width of the shooting range at the same distance as wall T1 after the focal length of the lens of camera 10 has been adjusted according to the distance to wall T2.

[0064] In one embodiment of the present invention, the dolly 50 is temporarily stopped at the photographing position shown in Fig. 6, and the focus position and focal length of the camera 10 are adjusted relative to the wall surface T2. Thereafter, the dolly 50 is caused to travel in the direction opposite to the forward direction (rearward direction) and returned to a position where the camera 10 can photograph the wall surface T1, as shown in Fig. 7.

[0065] FIG. 7 is a diagram showing a state in which the camera has returned to a predetermined position from the photographing position shown in FIG.

[0066] As shown in Fig. 7, the optical axis (image capture position) of camera 10 is located a distance C2 behind (to the left in Fig. 7) the boundary position a between wall surface T1 and wall surface T2. When camera 10 returns to this position, it captures only wall surface T1.

[0067] Note that the focus position of the camera 10 is adjusted to focus on the wall surface T2, so the image of the wall surface T1 captured by the camera 10 at the shooting position shown in Fig. 7 is out of focus. That is, it is considered that the spatial resolution of the wall surface T1 included in the image captured at the shooting position shown in Fig. 7 exceeds the allowable range.

[0068] Thereafter, the cart 50 starts moving forward again, and the camera 10 also starts capturing images. When the capturing range of the camera 10 includes the wall surfaces T1 and T2, the spatial resolution of the area in the captured image corresponding to the wall surface T2 falls within the allowable range. Also, when the camera 10 captures an image of only the wall surface T2, the spatial resolution of the wall surface T2 in the captured image falls within the allowable range. This is because the focus position and focal length of the camera 10 have been adjusted in advance with respect to the wall surface T2.

[0069] FIG. 8 is a diagram showing the positional relationship between the camera and the distance measuring device, the photographing range of the camera, etc.

[0070] 8, the focal length of the lens 11 of the camera 10 is represented by f1, the width of the image sensor 12 is represented by W, and the shooting distance of the wall surface T1 is represented by D1. Furthermore, C1 is an index indicating how far away the camera 10 can shoot from the position corresponding to the center of the captured image of the wall surface T1, and corresponds to half the width of the wall surface T1 photographed by the camera 10.

[0071] The following equation is established from the geometric relationship between the focal length f1 of the lens 11 of the camera 10, the width W of the image sensor 12, the photographing distance D1 of the wall surface T1, and the length C1 of the half width of the wall surface T1 photographed by the camera 10: [Equation 1] C1:D1=W / 2:f1

[0072] By modifying the above formula (1), C1 can be expressed by the following formula: (2) C1 = D1 × (W / 2) × 1 / f1 = (R1 - f1 - m) × (W / 2) × 1 / f1

[0073] Here, the shooting distance D1 can be expressed as D1=R1-f1-m, where R1 is the distance measured by the range finder 20 and m is the distance in the optical axis direction of the lens 11 between the range finder 20 and the image sensor 12.

[0074] The spatial resolution is evaluated by the number of light and dark line pairs that can be resolved per 1 mm in length. Since the number of pixels of the image sensor 12 is determined by the performance of the camera 10, the shorter C1 is, the higher the spatial resolution is.

[0075] FIG. 9 is another diagram showing the positional relationship between the camera and the range finder, the shooting range of the camera, etc. In particular, the focal length of the camera shown in FIG. 9 is adjusted to be longer than the focal length of the camera shown in FIG. 8.

[0076] 9, if the focal length of the lens 11 of the camera 10 is f2, the width of the image sensor 12 is W, and the shooting distance of the wall surface T1 is D2, then similar to equation (2), the length C2 of half the width of the shooting range of the wall surface T1 photographed by the camera 10 after focus adjustment can be calculated by the following equation: [Equation 3] C2 = D2 W / (2f2) = (R1 - f2 - m) × (W / 2) × 1 / f2

[0077] FIG. 10 is a diagram showing the positional relationship of each part when the positioning device is mounted on a cart.

[0078] In Figure 10, the position meter 30 can use, for example, a rotary encoder that measures the position of the trolley 50 by accumulating pulse signals generated in response to the rotation of the wheels of the trolley 50 from the positioning start position and converting the accumulated value into distance.

[0079] As shown in Figure 10, if the distance (interval) between the distance meter 20 and the position meter 30 in the traveling direction of the carriage 50 is q, the position of the distance meter 20 is at the boundary position a between the wall surface T1 and the wall surface T2, and the position measured by the position meter 30 is p, the boundary position a can be expressed by the following equation: [Equation 4] a = p + q

[0080] The positioning position (photographing position) of the camera 10 in the traveling direction can also be determined from the positioning position p measured by the positioning meter 30. It is preferable that the camera 10 adds, as auxiliary information of the photographed image, information indicating the photographing position determined from the positioning position p measured by the positioning meter 30. The information indicating the photographing position can be used when sequentially photographed images are combined into a panorama.

[0081] [First Embodiment of Imaging Apparatus] FIG. 11 is a diagram showing the configuration of a first embodiment of an imaging apparatus according to the present invention.

[0082] The photographing device 1-1 of the first embodiment shown in FIG. 11 comprises the camera 10, the distance measuring device 20, the position measuring device 30, and the control device 40 shown in FIG.

[0083] The control device 40 inputs ranging data indicating the distance to the wall of the tunnel 2 measured by the range finder 20, and a positioning signal (positioning data) indicating the position p of the cart 50 in the traveling direction measured by the position meter 30, and causes the camera 10 to perform shooting operations and set shooting conditions, etc.

[0084] FIG. 12 is a block diagram showing an embodiment of the hardware configuration of the control device shown in FIG.

[0085] 12 is configured by a personal computer, a workstation, or the like, and includes a processor 41, a memory 42, an operation unit 43, a display 44, a speaker 45, and an input / output interface 46. Since the control device 40 is mounted on a dolly 50 together with the camera 10 and the like and can be moved, a laptop computer is suitable.

[0086] The processor 41 is composed of a CPU (Central Processing Unit) and the like, and controls all parts of the control device 40 and also controls the camera 10. Details of the various processes performed by the processor 41 will be described later.

[0087] The memory 42 includes a flash memory, a read-only memory (ROM), a random access memory (RAM), a hard disk drive, etc. The flash memory, ROM, or hard disk drive is a non-volatile memory that stores an operating system, various programs including a program for executing the imaging method according to the present invention, etc. The non-volatile memory, such as the flash memory or hard disk drive, also stores imaging performance information of the camera 10, information indicating the positional relationship between the camera 10, the rangefinder 20, and the position meter 30 mounted on the dolly 50, etc.

[0088] The RAM functions as a work area for processing by the processor 41. It also temporarily stores various programs stored in flash memory or the like, data used for arithmetic processing, etc. The processor 41 may have a part of the memory 42 (RAM) built in.

[0089] The operation unit 43, the display 44, and the speaker 45 are used as a user interface. When the control device 40 is configured by a notebook computer, the operation unit 43 is the notebook computer's keyboard, touchpad, mouse, etc. The display 44 displays an operation screen and notifies the user of necessary information by text information, etc., and the speaker 45 notifies the user of necessary information by voice.

[0090] The input / output interface 46 includes a connection unit connectable to an external device, a communication unit connectable to a network, etc. As the connection unit connectable to an external device, a Universal Serial Bus (USB), a High-Definition Multimedia Interface (HDMI) (HDMI is a registered trademark), etc. can be applied.

[0091] In this example, the camera 10, the rangefinder 20, and the positioning meter 30 are connected to the input / output interface 46, and the processor 41 acquires ranging data and positioning data from the rangefinder 20 and the positioning meter 30 via the input / output interface 46, and causes the camera 10 to perform shooting operations and set shooting conditions, or provides the user with necessary information via indicators (display 44 and speaker 45).

[0092] <Photographing Operation by Photographing Device> FIG. 13 is a timing chart showing an example of a photographing operation by the photographing device of the first embodiment.

[0093] In the case of the image capturing device 1-1 of the first embodiment, a user manually pushes a cart 50 on a railroad track to move it forward at a constant speed, and the user manually adjusts the focus position and focal length of the lens 11 of the camera 10. The "constant speed" is the speed at which the user manually pushes the cart 50, and is therefore determined by the user's walking speed.

[0094] FIG. 13A is a diagram schematically showing the photographing position and photographing range of the camera 10 shown in FIGS.

[0095] In FIG. 13A, when the camera 10 receives an instruction to start shooting from the control device 40 (processor 41), it continues to shoot still images at regular intervals until it receives an instruction to pause shooting or stop shooting.

[0096] 13, the distance traveled by the moving cart 50 (camera 10) during a fixed time interval corresponds to the length C1 of half the width of the imaging range of the wall surface T1 captured by the camera 10. Therefore, the images captured before and after each imaging position are captured with an overlap rate of 50% or more.

[0097] Although there is variation in the speed at which the user walks while pushing the dolly 50, the distance traveled by the dolly 50 over a fixed time interval can be kept approximately constant. Furthermore, when a still image is captured each time the dolly 50 moves a fixed distance forward, the processor 41 can determine, based on the positioning data from the positioning meter 30, whether the dolly 50 has advanced a fixed distance from the previous image capture position, and issue an instruction to capture a still image.

[0098] FIG. 13B is an image diagram of five photographed images Ia to Ie photographed at each photographing position.

[0099] When the cart 50 moves forward (from left to right in Figure 13), the range finder 20 measures the distance to the wall surface a distance s ahead of the position of the camera 10 (see Figure 1), so the processor 41 can obtain the distance to the wall surface corresponding to the image captured by the camera 10 based on the range measurement data from the range finder 20.

[0100] If the distance R2 to the wall surface corresponding to the current captured image changes from the distance R1 to the wall surface corresponding to the previously captured image by more than the threshold th, which is the criterion for determining the tolerance (|R2-R1|≧th), the spatial resolution of the current captured image will not fall within the tolerance range, and it is therefore necessary to change the previous capturing conditions of camera 10 (the focus position and focal length of the lens of camera 10). Note that in this example, the absolute value of the difference in distance between wall surface T1 and wall surface T2 (|R2-R1|) is more than the threshold th.

[0101] Furthermore, when it is detected that the change in distance is greater than or equal to the threshold, the image captured by camera 10 may be one in which only wall surface T1 is captured (Figure 2), one in which wall surfaces T1 and T2 are captured (Figure 3), one in which the wall surface at boundary position a between wall surfaces T1 and T2 and wall surface T2 are captured (Figure 4), or one in which only wall surface T2 is captured (Figure 5).

[0102] Because the focus position and focal length of the camera 10 are adjusted with respect to the wall surface T1, the wall surface T2 cannot be clearly captured. The shaded areas in each of the captured images Ia to Ie shown schematically in FIG. 13B do not correspond to the wall surface T1 and are therefore not clearly captured. That is, the captured images Ia and Ib capture only the wall surface T1, so they are clearly captured, and the spatial resolution of the captured images Ia and Ib is within the acceptable range. On the other hand, the captured image Ic captures the wall surfaces T1 and T2 before and after the boundary position a, but the area corresponding to the wall surface T2 is not clearly captured. Furthermore, the wall surface T1 is not captured in the captured images Id and Ie, and the captured images Id to Ie do not capture the entire area clearly.

[0103] Therefore, when the trolley 50 reaches the shooting position where the camera 10 captures an image Ie of only the wall surface T2 (the shooting position where the wall surface T1 is no longer captured), the processor 41 outputs an instruction to the indicator (display 44 and / or speaker 45) to stop the trolley 50 and temporarily suspends subsequent shooting.

[0104] Based on the ranging data measured by the rangefinder 20, the processor 41 can detect whether the image captured by the camera 10 includes the area of ​​wall surface T1 and the area of ​​wall surface T2 before and after the boundary position a.

[0105] When the processor 41 detects that the image captured by the camera 10 includes the areas of the wall surface T1 and the wall surface T2 before and after the boundary position a, as shown in Fig. 5, when the image capturing position of the camera 10 subsequently reaches an image capturing position that is moved from the boundary position a by a width C1 or more that is half the image capturing range of the wall surface T1, the processor 41 outputs a command to the display 44 and the speaker 45 to stop the cart 50. This is because the wall surface T1 will not be included in the image captured at an image capturing position that is moved by the width C1 or more from the boundary position a.

[0106] Furthermore, as shown in Figure 5, if the position of the rangefinder 20 is located a distance s ahead of the shooting position of the camera 10, and the position of the rangefinder 20 relative to the boundary position a is (a + M), then the image captured at the shooting position where M ≥ s + C1 will no longer include the wall surface T1.

[0107] When the processor 41 determines that the wall surface T1 is not included in the captured image as described above, it outputs a command to the display 44 to display text such as "Please stop the cart," and outputs a command to the speaker 45 to generate a sound to notify the driver that the cart 50 has stopped.

[0108] When the user is notified by the display 44 and the speaker 45 that the cart 50 is to be stopped, the user immediately stops the cart 50. Note that the cart 50 may have moved forward further than when the processor 41 output the stop command due to a delay in the user's operation to stop the cart 50.

[0109] Next, the processor 41 outputs a command to the indicator (display 44, speaker 45) to prompt adjustment of the focus position and focal length of the camera 10 so that the spatial resolution of the area corresponding to the wall surface T2 in the captured image falls within an acceptable range while the cart 50 is stopped.

[0110] In accordance with the command to adjust the focus position and focal length of camera 10, the user manually operates the focus ring of camera 10 to adjust the focus position of camera 10 while viewing a live view image or the like captured by camera 10, and also manually operates the zoom ring to adjust the focal length of camera 10. It is preferable that processor 41 display information indicating the optimal focal length of camera 10 for the distance to wall surface T2 on display 44. The focus position during the stopped period of camera 10 may be automatically adjusted based on the distance to wall surface T2 measured by rangefinder 20, or may be adjusted by an autofocus function provided in camera 10.

[0111] When the user has finished adjusting the focus position and focal length of the camera 10 (see FIG. 6), the processor 41 outputs to the display 44 a command to return the dolly 50.

[0112] FIG. 13C is a diagram showing the traveling directions of the carriage 50, including forward and backward movement.

[0113] It is preferable that the processor 41 outputs distance information indicating the difference between the current position of the camera 10 and position (a-C2) to the display 44 based on the positioning data from the positioning meter 30 so that the shooting position of the camera 10 becomes position (a-C2).

[0114] In this case, the user simply moves the cart 50 back so that the distance information displayed on the display 44 becomes zero. When the distance information becomes zero, the position of the camera 10 becomes a position (a-C2) where a specific shooting range can be re-photographed, as shown in FIG. 7.

[0115] When the user returns the cart 50 so that the camera 10 is positioned to a position (a-C2) where a specific shooting range can be re-photographed, the processor 41 resumes shooting by the camera 10, and the user again moves the cart 50 forward.

[0116] Furthermore, as mentioned above, when the camera 10 returns to the shooting position (a-C2), the image captured at this shooting position (a-C2) will be blurry because the focus position of the camera 10 is not aligned with the wall surface T1.

[0117] Thereafter, when the cart 50 moves forward and the wall surface T2 is photographed by the camera 10, the focus position and focal length of the camera 10 are adjusted with respect to the wall surface T2, so that the camera 10 can immediately photograph the wall surface T2 clearly, and the spatial resolution of the wall surface T2 in the photographed image can be kept within an acceptable range.

[0118] According to the first embodiment, the processor 41 determines whether the spatial resolution of the captured image falls within an acceptable range based on the ranging signal of the rangefinder 20, and if it determines that it does not fall within the acceptable range, it causes the camera 10 to perform a second photograph (photographing in which the shooting conditions are set for wall surface T2) with different shooting conditions from the first photograph (photographing in which the shooting conditions are set for wall surface T1) for a specific shooting range of the wall surface that is determined to not fall within the acceptable range (the shooting range in which the shooting position of the camera 10 is returned and photographed again).

[0119] In this case, the first photograph is one in which the spatial resolution of the area (first area) of the photographed image corresponding to wall surface T1 falls within the acceptable range, but the spatial resolution of the area (second area) of the photographed image corresponding to wall surface T2 does not fall within the acceptable range, while the second photograph is one in which the spatial resolution of the first area of ​​the photographed image corresponding to wall surface T1 does not fall within the acceptable range, but the spatial resolution of the second area of ​​the photographed image corresponding to wall surface T2 falls within the acceptable range.

[0120] As a result, the wall surfaces T1 and T2 for which the absolute value of the difference in distance between the wall surfaces T1 and T2 (|R2-R1|) is equal to or greater than the threshold value th become the objects of photography, and in a specific photography range in which at least the wall surfaces T1 and T2 are photographed simultaneously, two photography sessions, a first photography session and a second photography session, are performed under different photography conditions. As a result, the wall surfaces T1 and T2 are always clearly photographed in one of the two photographed images including the same wall surface T1 and the two photographed images including the same wall surface T2 that are photographed twice.

[0121] When the photographing of the tunnel 2 is completed, or during the photographing, the processor 41 performs panoramic composition using the photographed images before and after in the direction of movement of the camera 10. Panoramic composition can be performed by extracting multiple feature points from the overlapping areas of the previous and next photographed images, and aligning the previous and next photographed images so that the extracted multiple feature points match. If information indicating the photographing position obtained from the positioning data of the positioning meter 30 is added as auxiliary information for each photographed image, it is preferable to roughly align the previous and next photographed images using the information indicating the photographing position, and then extract multiple feature points to perform highly accurate alignment.

[0122] In addition, in a specific shooting range where wall surfaces T1 and T2 are photographed simultaneously, two shootings, a first shooting and a second shooting, are performed under different shooting conditions, and two photographed images of the same wall surfaces T1 and T2 are obtained, but it is preferable that the processor 41 uses only the image of the area of ​​the two photographed images that is clearly photographed as the photographed image to be used for panoramic synthesis. Furthermore, even if there is a discontinuous portion such as boundary position a between wall surfaces T1 and T2, the previous and next photographed images can be properly aligned by using information indicating the photographing position.

[0123] The photographing operation by the photographing device 1-1 has been described as occurring when the trolley 50 moves forward and transitions from photographing wall surface T1 to photographing wall surface T2, which is farther away than wall surface T1. However, the same photographing operation as described above is also performed when the trolley 50 moves forward and transitions from photographing wall surface T2 to photographing wall surface T1 (or a wall surface closer than wall surface T2).

[0124] In addition, in this example, the processor 41 detects whether the absolute value of the difference in distance between wall surface T1 and wall surface T2 (|R2-R1|) is greater than or equal to a threshold value th, and thereby determines whether an object of interest (for example, a crack with a desired crack width) can be detected from the captured image.However, without being limited to this, the processor 41 may estimate (calculate) the spatial resolution of the captured image based on the current focal length of the camera 10, the shooting settings of the camera 10 (size of the image sensor, number of pixels), etc., and the ranging signal of the rangefinder 20, and determine whether the calculated spatial resolution is within an acceptable range, thereby determining whether an object of interest can be detected from the captured image.

[0125] FIG. 14 shows another embodiment of the camera.

[0126] 14 is composed of multiple (five) second cameras 10a to 10e. The five second cameras 10a to 10e are arranged in an arc equidistant from a reference position (center) O of the camera mounting member 14.

[0127] The camera mounting member 14, to which the second cameras 10a to 10e shown in Figure 14 are attached, is attached to a dolly 50. The optical axes of the five second cameras 10a to 10e are arranged radially from the center O of the camera mounting member 14, each with a different shooting direction, and the second cameras 10a to 10e simultaneously capture images of the inner circumferential surface of the tunnel. It is preferable to position the second cameras 10a to 10e so that adjacent images among the multiple images captured by the second cameras 10a to 10e have overlapping areas.

[0128] In this way, when a plurality of second cameras 10a to 10e are mounted on the carriage 50, it is preferable that the distance measuring device 20 measures the distance in all directions around the tunnel by rotating the laser light.

[0129] When the inner periphery of the tunnel is photographed by multiple second cameras 10a to 10e, the distance to the wall in the photographed image changes by more than a threshold value for some cameras, and the distance does not change for others. In this case, if the distance to the wall in the photographed image changes by more than the threshold value for even one camera, the carriage 50 stops (changes the photographing conditions) → moves backward → stops → moves forward (resumes photographing) as described above. However, for cameras whose distance to the wall in the photographed image does not change by more than the threshold value, there is no need to change the photographing conditions or photograph the same photographing range twice.

[0130] [Second Embodiment of Imaging Apparatus] FIG. 15 is a diagram showing the configuration of a second embodiment of an imaging apparatus according to the present invention.

[0131] The image capturing device 1-2 of the second embodiment shown in Fig. 15 is composed of the camera 10, rangefinder 20, position meter 30, control device 40, and dolly 50 shown in Fig. 10. Note that parts common to the image capturing device 1-1 of the first embodiment shown in Fig. 11 are given the same reference numerals, and detailed description thereof will be omitted.

[0132] In the case of the imaging device 1-1 of the first embodiment, the user manually pushes the cart 50 along the rails of the railway, but in the case of the imaging device 1-2 of the second embodiment, the cart 50 is self-propelled, and the control device 40 (processor 41) controls the movement of the cart 50 (forward, stop, backward, movement speed, etc.), which is different from the first embodiment.

[0133] The processor 41 of the control device 40 shown in Figure 15 outputs a movement command to the carriage 50 in Figure 13 to move the carriage 50 in the forward direction (from left to right in Figure 13) at a constant speed, thereby moving the carriage 50.

[0134] The processor 41 also instructs the camera 10 to start shooting and causes the camera 10 to perform interval shooting at fixed time intervals. By controlling the movement of the dolly 50 and the interval shooting by the camera 10, images Ia to Ie are taken at each shooting position (FIG. 13B).

[0135] In this case, since the focus position and focal length of the camera 10 are adjusted with respect to the wall surface T1, when the processor 41 detects that the trolley 50 has reached the shooting position where the camera 10 has captured an image Ie of only the wall surface T2 (the shooting position where the wall surface T1 is no longer captured), the processor 41 outputs an instruction to the trolley 50 to stop the trolley 50, causing the trolley 50 to stop.

[0136] The processor 41 automatically adjusts the focus position and focal length of the camera 10 so that the spatial resolution for the wall surface T2 falls within an allowable range while the cart 50 is stopped. The processor 41 may automatically adjust the focus position of the camera 10 to a focus position that corresponds to the distance to the wall surface T2 measured by the rangefinder 20, or may enable an autofocus function of the camera 10 to perform the automatic adjustment.

[0137] In addition, the processor 41 can read out from the lookup table a focal length that has been registered in advance corresponding to the shooting distance of the subject based on the shooting distance of the subject (the distance to the wall T2 measured by the rangefinder 20), and automatically adjust the focal length of the camera 10 to the read focal length.

[0138] When the processor 41 finishes adjusting the focus position and focal length of the camera 10 relative to the wall surface T2 during the stopped period of the trolley 50, it outputs a command to the trolley 50 to move the stopped trolley 50 in the backward direction (to the left in Figure 13), causing the trolley 50 to move backward.

[0139] The processor 41 determines whether the current position of the camera 10 has reached position (a-C2) based on the positioning data from the positioning meter 30 while the cart 50 is moving backward, and when it detects that the current position of the camera 10 has reached position (a-C2), it stops the cart 50 (see Figure 13 (C)).

[0140] Thereafter, the processor 41 moves the dolly 50 forward again and resumes shooting with the camera 10 including the shooting position (a-C2) of the camera 10.

[0141] Furthermore, the image captured at the shooting position (a-C2) will be blurry because the focus position of the camera 10 is not aligned with the wall surface T1. However, when the cart 50 then moves forward and the camera 10 captures the image of the wall surface T2, the focus position and focal length of the camera 10 have been adjusted with respect to the wall surface T2, so the wall surface T2 can be captured clearly and the spatial resolution of the wall surface T2 can be within an acceptable range.

[0142] According to the second embodiment, as in the first embodiment, in a specific shooting range where at least wall surface T1 and wall surface T2 are photographed simultaneously, two shots are taken: a first shot in which the spatial resolution of wall surface T1 falls within the acceptable range, and a second shot in which the spatial resolution of wall surface T2 falls within the acceptable range.As a result, it is possible to obtain images in which the spatial resolution falls within the acceptable range, even for wall surfaces T1 and T2 before and after the boundary position between wall surface T1 and wall surface T2.

[0143] In the second embodiment, the adjustment of the focus position and focal length of the camera 10 is performed while the dolly 50 is stopped, but the adjustment may be performed at least until the dolly 50 is returned and image capture is resumed. Furthermore, the adjustment of the focus position and focal length of the camera 10 while the dolly 50 is stopped is performed automatically, but at least one of the adjustment of the focus position and focal length of the camera 10 may be performed by the user manually operating the camera 10.

[0144] 16 is a configuration diagram of the main parts of a third embodiment of the imaging device according to the present invention. Note that parts common to the imaging device 1-1 of the first embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted.

[0145] The photographing device of the third embodiment shown in Figure 16 differs from the photographing devices of the first and second embodiments in that it photographs the subject by moving the dolly only in the forward direction, and returns the dolly to its original position and photographs the subject again.

[0146] Therefore, the imaging device of the third embodiment shown in Figure 16 uses two carts 50A and 50B, each of which is equipped with a first camera (camera 10A) and a second camera (camera 10B).

[0147] The carriages 50A and 50B are connected by a connecting rod 52, and the cameras 10A and 10B are arranged at different positions in the moving directions of the carriages 50A and 50B with a fixed distance therebetween.

[0148] When a specific imaging range is defined as the range of imaging positions where the front camera 10A can simultaneously capture images of wall surface T1 and wall surface T2, cameras 10A and 10B are disposed at an interval equal to or greater than the length of the specific imaging range (the length in the direction of movement of cart 50A). That is, camera 10B is disposed at a position rearward of camera 10A by the length of the specific imaging range. For example, when camera 10A moves forward from boundary position a between wall surface T1 and wall surface T2 and initially reaches an imaging position where wall surface T1 is not imaged, camera 10B is disposed rearward of camera 10A so that it will be positioned to image only wall surface T1.

[0149] The processor 41 of the control device 40 constituting the photographing device of the third embodiment causes the camera 10A to perform interval photographing while the carriages 50A and 50B are moving forward. That is, the processor 41 causes the camera 10A to perform photographing according to the photographing conditions currently set for the camera 10A (the focus position and focal length of the camera 10A), regardless of the distance between the wall surfaces T1 and T2.

[0150] On the other hand, the processor 41 normally stops the camera 10B from taking pictures, but when certain conditions are met, it adjusts the focus position and focal length of the camera 10B and starts interval photography with the camera 10B.

[0151] In this example, when the processor 41 detects based on the ranging data from the rangefinder 20 that the camera 10A has photographed only the wall surface T1 and then reached a shooting position where it can simultaneously photograph the wall surfaces T1 and T2, the processor 41 adjusts the focus position and focal length of the camera 10B so that the spatial resolution of the wall surface T2 is within the allowable range, and starts interval shooting by the camera 10B.

[0152] When camera 10B starts taking pictures, the focus position and focal length are adjusted relative to wall surface T2, so the image of wall surface T1 taken by camera 10B is blurry and the spatial resolution of wall surface T1 exceeds the allowable range.

[0153] Thereafter, when the carts 50A and 50B move forward and the camera 10B begins to photograph the wall surface T2, the spatial resolution of the portion of the image photographed by the camera 10B corresponding to the wall surface T2 falls within the allowable range because the focus position and focal length of the camera 10B have been adjusted with respect to the wall surface T2.

[0154] On the other hand, when the processor 41 detects based on the ranging data from the rangefinder 20 that the camera 10A is photographing only the wall surface T2, it adjusts the focus position and focal length of the camera 10A so that the spatial resolution of the wall surface T2 falls within the allowable range.

[0155] When the carts 50A and 50B continue to move forward and the camera 10B captures only the wall surface T2 and the capture range of the camera 10A, whose focus position and focal length have been adjusted for the wall surface T2, is detected from the relationship between the current capture position of the camera 10B and the past capture positions of the camera 10A, the processor 41 stops the camera 10B from capturing the wall surface T2. This is because there is no need to capture the wall surface T2 in the same position with the two cameras 10A and 10B.

[0156] In the third embodiment, the dollies 50A and 50B are not stopped even while the focus positions and focal lengths of the cameras 10A and 10B are being adjusted, but the processor 41 only needs to use images captured after the time required for the adjustment (after the adjustment is completed). Alternatively, a single dolly may be used instead of the two dollies 50A and 50B. In this case, the length of the single dolly may be set to the same length as the combined length of the two dollies 50A and 50B.

[0157] [Photographing Method] FIGS. 17 to 19 are flowcharts showing embodiments of the photographing method according to the present invention.

[0158] The photographing method shown in FIGS. 17 to 19 is a method performed by the processor 41 of the control device 40 shown in FIG.

[0159] In FIG. 17, the processor 41 acquires the distance r to the wall of the tunnel measured by the distance measuring device 20, and registers this distance r as the distance R1 (R1=r) (step S10).

[0160] Next, the processor 41 adjusts the focal length of the lens 11 of the camera 10 to a focal length f1 corresponding to R1 (step S12). Note that a lookup table is stored in the memory 42, which registers the relationship between the shooting distance of the subject and the optimal focal length for which the spatial resolution of the subject falls within an allowable range for that shooting distance. The processor 41 reads the focal length f1 corresponding to the distance R1 from the lookup table, and adjusts the focal length of the lens 11 to the read focal length f1. The processor 41 may also display the read focal length f1 on the display 44, allowing the user to manually adjust the focal length of the lens 11 in accordance with the focal length f1 displayed on the display 44.

[0161] Next, the processor 41 calculates half the width C1 of the imaging range of the wall surface based on the distance R1 and the focal length f1 using the above-mentioned [Equation 2] (step S14). Note that in [Equation 2], W is the size of the image sensor 12 of the camera 10 as shown in Figure 8, and m is the distance in the optical axis direction of the lens 11 between the rangefinder 20 and the image sensor 12, both of which are fixed values.

[0162] Next, the processor 41 starts measuring the position of the cart 50 (the shooting position of the camera 10) using the position meter 30 (step S16). The processor 41 also registers the distance r measured in step S10 as distance r_old (step S18). Furthermore, the processor 41 controls the focus position of the lens 11 of the camera 10 so that the focus position of the lens 11 is on the wall surface of the shooting target (step S20).

[0163] Next, the processor 41 starts capturing images using the camera 10 whose focus position and focal length have been adjusted (step S22). The camera 10, which has been instructed to start capturing images, captures still images at regular time intervals, or captures still images every set distance traveled, or captures video.

[0164] Furthermore, when the processor 41 starts capturing images using the camera 10, it moves the dolly 50 forward (step S24) as shown in Fig. 18. If the dolly 50 is not self-propelled, the user manually pushes the dolly 50 forward.

[0165] The processor 41 determines whether the dolly 50 has reached the image capture end position based on the positioning data of the dolly 50 (step S26). If the image capture end position has been reached (if "Yes"), the photographing using this photographing method is terminated (step S44). On the other hand, if the image capture end position has not been reached (if "No"), the distance to the wall surface is measured using the range finder 20, and the measured distance is set as the distance r (step S28).

[0166] The processor 41 determines whether the absolute value of the difference (|r - r_old|) between the distance r measured in step S28 and the distance r_old registered in step S18 exceeds a threshold th (|r - r_old| > th) (step S30). If it determines that the threshold th is not exceeded (in the case of "No"), the process returns to step S24. In other words, if the threshold th is not exceeded, it determines that the spatial resolution of the wall surface corresponding to the captured image captured using the current focus position and focal length of the camera 10 is within the allowable range, and the forward movement of the cart 50 and the capture of the wall surface continue.

[0167] In other words, if the distance r is the shortest or longest distance to the wall in the captured image measured based on the ranging signal of the rangefinder 20, and the absolute value of the difference (|r - r_old|) between the distance r and the distance r_old to the wall to which the focus position and focal length of the camera 10 have been adjusted relative to the wall currently being photographed exceeds the threshold value th, the processor 41 can determine that the spatial resolution of the captured image does not fall within the acceptable range.

[0168] On the other hand, if it is determined in step S30 that the threshold value th is exceeded (if "Yes"), the processor 41 registers the distance r measured in step S28 as the distance R2 (step S32).

[0169] Next, based on the positioning data p from the positioning meter 30, the processor 41 determines the change point of the wall surface where the distance has changed by exceeding the threshold th (for example, the boundary position a between the wall surfaces T1 and T2 shown in Figure 10) using the above-mentioned [Equation 4] and registers it as a marking point (step S34).

[0170] The processor 41 moves the cart 50 in the forward direction (step S36), and calculates the distance M by subtracting the position of the registered marking point a from the position of the positioning data b, assuming that the positioning data from the positioning meter 30 is b (step S38).

[0171] The processor 41 determines whether the distance M (M=b-a) calculated in step S52 satisfies M≧s+C1 (step S40). As shown in FIG. 5, the wall surface T1 is not included in the image captured at the photographing position that satisfies M≧s+C1.

[0172] If the processor 41 determines in step S40 that M≧s+C1 is not satisfied (in the case of “No”), the process proceeds to step S36. In this case, the captured image includes a portion corresponding to the wall surface T1, and the cart 50 needs to be further moved forward.

[0173] On the other hand, if the processor 41 determines in step S54 that M≧s+C1 is satisfied (if "Yes"), it stops the carriage 50 (step S42).

[0174] When the cart 50 stops, the processor 41 reads out the focal length f2 corresponding to the distance R2 registered in step S46 from the lookup table, and adjusts the focal length of the lens 11 of the camera 10 to the read focal length f2, as shown in Figure 19 (step S46).

[0175] Next, the processor 41 calculates the width C2 based on the distance R2 and the focal length f2 using the above-mentioned formula 3 (step S48). The width C2 is half the width of the shooting range at the same distance to the wall T1 after the focal length of the lens 11 of the camera 10 is adjusted to the focal length f2 corresponding to the distance R2 to the wall T2.

[0176] The processor 41 also controls the focus position of the lens 11 of the camera 10 so that the focus position of the lens 11 is on the wall surface T2 at the distance R2 (step S50).

[0177] When the focus position and focal length of the camera 10 are adjusted in accordance with the distance R2 to the wall surface T2 while the cart 50 is stopped, the processor 41 moves the cart 50 backward (returns) so that the position of the camera 10 is at position (a-C2). When the position of the camera 10 is at position (a-C2), the camera 10 at that position (a-C2) captures only the wall surface T1 as shown in Fig. 7, but the focus position of the camera 10 has been adjusted to the wall surface T2, so the camera 10 is not in focus on the wall surface T1.

[0178] Next, the processor 41 registers the distance R2 as the distance r_old (step S54), and moves the carriage 50 forward again (step S56).

[0179] Next, the processor 41 determines whether the position of the rangefinder 20 has progressed beyond the registered marking point a (step S58), and if not, transitions to step S56, and if it has progressed, transitions to step S26 shown in Figure 18.

[0180] If it is determined in step S26 that the photographing end position has not been reached, the processes from step S28 to step S58 are repeated again.

[0181] The photographing method shown in the flowcharts of FIGS. 17 to 19 is one embodiment of the photographing method according to the present invention, and the present invention is not limited to the photographing method shown in the flowcharts of FIGS.

[0182] FIG. 20 is a diagram showing an example of a captured image of a portion of a tunnel where the diameter changes significantly.

[0183] The captured images shown in FIGS. 20A and 20B include portions corresponding to wall surfaces T1 and T2, which are at different distances.

[0184] 20A and 20B, A indicates a crack on the wall surface T1, B indicates a crack on the wall surface T2, and K indicates a boundary portion between the wall surface T1 and the wall surface T2.

[0185] The captured image shown in Figure 20 (A) was captured with the camera's focus position and focal length adjusted to correspond to the wall surface T1 in the foreground. The image is focused on the wall surface T1 in the foreground, and crack A on wall surface T1 is clearly depicted, but the image is not focused on the wall surface T2 in the background, and crack B on wall surface T2 has insufficient resolution and is unclear.

[0186] On the other hand, the captured image shown in Figure 20 (B) was captured with the focus position and focal length of the camera 10 adjusted to correspond to the rear wall surface T2, and the crack B on the rear wall surface T2 is clearly depicted, but the front wall surface T1 is not in focus, and the resolution of the crack A on the wall surface T1 is insufficient and unclear.

[0187] In a section where the diameter of the tunnel changes significantly, it is difficult to focus on the front wall T1 and the back wall T2 in a single shot and maintain the resolution to depict fine details.

[0188] Therefore, when photographing at a photographing position (photographing range) where the front wall surface T1 and the back wall surface T2 are photographed simultaneously as shown in Figures 20(A) and (B), the focus position and focal length are adjusted for the front wall surface T1 to photograph (first photographing), as in the photographed image shown in Figure 20(A), and the focus position and focal length are adjusted for the back wall surface T2 to photograph (second photographing), as in the photographed image shown in Figure 20(B).

[0189] Furthermore, when attempting to capture images that maintain resolution in accordance with changes in subject distance, taking multiple images at different focal lengths each time the camera moves to each shooting location would require an enormous amount of time and number of images, raising concerns that this would result in extremely low work efficiency.

[0190] The present invention performs photography using distance information about the subject, and by continuing photography and movement while maintaining the focus position and focal length when there is no change in the shape of the tunnel, such as the diameter of the tunnel, and controlling the focus position and focal length when there is a change exceeding a threshold, it is possible to achieve accurate photography without waste. In this case, in areas where the shape changes, such as the diameter of the tunnel, subjects with different photography distances are included in the photographed image, so by changing the photography conditions and taking photographs repeatedly, it is possible to inspect without omissions.

[0191] In addition, by utilizing positioning information, it becomes possible to take photographs repeatedly with high reproducibility, and even when photographing the same location by changing the focal length or focus position, this can be done efficiently and accurately.

[0192] [Others] In this embodiment, the case of photographing a railway tunnel has been described, but the subject is not limited to a railway tunnel, and the present invention can be applied to any subject, such as a road tunnel, as long as the subject is photographed while the camera is moving along the subject.

[0193] In this embodiment, the hardware structure of a processing unit that executes various processes, such as a CPU (Central Processing Unit), is the following various processors: The various processors include a CPU, which is a general-purpose processor that executes software (programs) to function as various processing units, a programmable logic device (PLD), such as an FPGA (Field Programmable Gate Array), whose circuit configuration can be changed after manufacture, and a dedicated electrical circuit, such as an ASIC (Application Specific Integrated Circuit), which is a processor with a circuit configuration designed specifically for executing specific processes.

[0194] A single processing unit may be configured with one of these various processors, or may be configured with two or more processors of the same or different types (e.g., multiple FPGAs, or a combination of a CPU and an FPGA). Multiple processing units may also be configured with a single processor. Examples of multiple processing units configured with a single processor include: a first configuration, as typified by client or server computers, in which a single processor is configured with a combination of one or more CPUs and software, and this processor functions as multiple processing units; and a second configuration, as typified by system-on-chip (SoC), in which a processor is used to realize the functions of an entire system including multiple processing units on a single IC (Integrated Circuit) chip. In this way, the various processing units are configured with one or more of the above-mentioned various processors as a hardware structure.

[0195] Furthermore, the hardware structure of these various processors is, more specifically, an electric circuit made up of a combination of circuit elements such as semiconductor elements.

[0196] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention.

[0197] 1-1...Photographing device 1-2...Photographing device 2...Tunnel 10, 10A, 10B...Camera 10a to 10e...Second camera 11...Lens 12...Image pickup element 14...Camera mounting member 17...International Publication No. 20 20...Range finder 30...Position meter 40...Control device 41...Processor 42...Memory 43...Operation unit 44...Display 45...Speaker 46...Input / output interface 50, 50A, 50B...Cart 52...Connecting rod S10 to S58...Steps

Claims

1. An imaging device comprising a camera, a range finder that measures the distance to a subject, and a processor, wherein the processor causes the camera to execute a first imaging operation in which the subject is spatially divided and photographed to obtain a photographed image, determines whether or not an object of interest is detectable from the photographed image based on a ranging signal from the range finder, and causes the camera to execute a second imaging operation under different imaging conditions from the first imaging operation for the photographed range of the subject for which the determination is no.

2. The photographing device according to claim 1, wherein the determination is whether or not the resolution of the photographed image falls within an acceptable range.

3. The imaging device according to claim 2, wherein the resolution of the captured image is a spatial resolution of the captured image.

4. The photographing device according to claim 3, wherein the subject and the camera move relatively in a first direction to continuously photograph the subject.

5. The imaging device according to claim 4, wherein the spatial resolution of the captured image is the spatial resolution of the entire area of ​​the captured image.

6. The photographing device according to claim 2, wherein the photographing range is a photographing range of the subject that is determined to be outside the allowable range.

7. The photographing device of claim 4, wherein the first photographing is a photographing in which the spatial resolution of a first region of the photographed image falls within an acceptable range and the spatial resolution of a second region of the photographed image does not fall within an acceptable range, and the second photographing is a photographing in which the spatial resolution of the first region does not fall within the acceptable range and the spatial resolution of the second region falls within the acceptable range.

8. The photographing device according to claim 3, wherein the processor estimates the spatial resolution of the photographed image based on the photographing settings of the camera and the ranging signal of the rangefinder, and determines whether the estimated spatial resolution of the photographed image falls within the allowable range.

9. The photographing device described in claim 3, wherein the processor obtains the shortest or longest distance to the subject in the captured image based on the ranging signal of the rangefinder, and determines that the spatial resolution of the captured image does not fall within the acceptable range if |r - r_old| > th, where r_old is the distance to the subject in the first photograph, r is the shortest or longest distance, and th is a threshold that is a criterion for determining the acceptable range of the spatial resolution.

10. The photographing device of claim 7, wherein the first photograph is a photograph in which the focus position and focal length of the camera are adjusted for the first area, and the second photograph is a photograph in which the focus position and focal length of the camera are adjusted for the second area.

11. The photographing device described in claim 7, wherein the processor causes the camera to perform the first photographing of the shooting range while the camera is moving in the first direction, and after the first photographing is completed and the camera returns to a position where it can at least photograph the shooting range again, causes the camera to perform the second photographing while the camera is moving in the first direction.

12. The photographing device described in claim 11, wherein the processor automatically adjusts the focus position and focal length of the camera based on the distance to the subject corresponding to the second area while the camera is returning to a position where it can take another photograph, or outputs an instruction to an indicator to prompt a user to adjust at least one of the focus position and focal length of the camera, and executes the second photographing after the automatic adjustment or after the user adjusts at least one of the focus position and focal length of the camera.

13. The photographing device according to claim 4, further comprising a positioning meter that measures the position of the camera, wherein the processor, when the first photographing of the shooting range is completed, moves the camera in a second direction opposite to the first direction, and, when it detects based on the positioning signal of the positioning meter that the camera has returned to a position where at least the shooting range can be photographed again while moving in the second direction, moves the camera again in the first direction and causes the camera to perform the second photographing of the shooting range.

14. The photographing device of claim 4, further comprising: a positioning meter that measures the position of the camera in the direction of movement; and an indicator that instructs the user on how to move the camera, wherein the processor outputs an instruction to the indicator to move the camera in a second direction opposite to the first direction when the first photographing of the shooting range is completed while the camera is moving in the first direction, and outputs an instruction to the indicator to move the camera in the first direction again when it detects, based on the positioning signal of the positioning meter, that the camera has returned to at least a position where it can photograph the shooting range again while moving in the second direction.

15. The photographing device according to any one of claims 1 to 14, wherein the distance finder is a laser distance finder that scans the subject with a laser beam and measures the distance corresponding to the entire area of ​​the photographed image.

16. The photographing device described in claim 7, wherein the processor adjusts the focus position of the camera based on the distance measurement signal measured by the rangefinder, and when performing the first photographing, adjusts the focus position of the camera based on the distance measurement signal measured for the first area of ​​the photographed image, and when performing the second photographing, adjusts the focus position of the camera based on the distance measurement signal measured for the second area of ​​the photographed image.

17. The photographing device of claim 1, wherein the camera is composed of a plurality of second cameras, the plurality of second cameras are arranged in an arc shape, the plurality of captured images taken by the plurality of second cameras include overlapping areas, and the processor determines, for each captured image taken by each of the plurality of second cameras, whether or not an object of interest can be detected from the captured image based on the distance measurement signal of the distance measurer, and for one or more of the plurality of second cameras that captured an image for which the determination is no, causes the first photographing and the second photographing to be performed.

18. The photographing device of claim 1, wherein the camera is composed of a first camera and a second camera, the second camera is positioned in a position different in a moving direction from the first camera and at a position at least the length behind the shooting range in the moving direction of the camera, and the processor causes the first camera to perform the first photographing and causes the second camera to perform the second photographing of the shooting range.

19. The photographing device according to claim 7, wherein the processor performs a panoramic synthesis of the captured images, and the captured images used for the panoramic synthesis of the shooting range are an image of the first area among the captured images obtained by the first photographing and an image of the second area among the captured images obtained by the second photographing.

20. A photographing method for an imaging device equipped with a camera, a rangefinder that measures the distance to a subject, and a processor, the method comprising the steps of: having the camera perform a first photographing operation in which the subject is photographed in a spatially divided manner to obtain a photographed image; determining whether or not an object of interest is detectable from the photographed image based on a distance measurement signal from the rangefinder; and having the camera perform a second photographing operation under photographing conditions different from those of the first photographing operation for a photographing range of the subject for which the determination is no.