Imaging system, appearance inspection system, and image acquisition method

Abstract

This imaging system includes: a camera that images a subject moving on a conveyance path; a sensor that measures a physical quantity for calculating the movement amount of the subject without coming into contact with either of a conveyance mechanism of the conveyance path and the subject; and an imaging control unit that calculates the movement amount on the basis of the physical quantity and determines imaging timing by the camera on the basis of the movement amount.

Description

Photography system, visual inspection system, and image acquisition method

[0001] The present invention relates to an imaging system that images an object traveling on a transport path, an appearance inspection system that uses the imaging system, and a method for acquiring an image of the object.

[0002] Conventionally, there has been known an appearance inspection device that irradiates an object to be inspected as it travels along a transport path with illumination light, photographs the object with a camera, and inspects the object based on the image of the object (for example, Patent Documents 1 and 2).

[0003] In such visual inspection devices, an object being transported in a fixed direction is photographed by a line sensor camera, so unless the transport speed (transport distance) and the interval between photographs taken by the camera (scan rate) are appropriate, images suitable for inspection cannot be obtained. For this reason, it is necessary to synchronize the transport speed of the object being inspected with the scan rate of the camera.

[0004] As a method for synchronizing the transport speed of the inspection object with the scan rate of the camera, a rotary encoder is attached to the rotating shaft of the transport mechanism, and the timing of photographing by the camera is determined based on the output signal (pulse) of the rotary encoder (by inputting a trigger signal to the camera) as has been known for some time (see, for example, Non-Patent Documents 1 and 2). Fig. 8 shows a schematic diagram for explaining an appearance inspection system 9 employing such a conventional photographing system.

[0005] 8 shows an outline of an appearance inspection system 9 that photographs a sheet-like inspection object T with a camera 99 while transporting the object, and then inspects the object T for defects (foreign matter contamination, scratches, dirt, etc.) based on the photographed images. The inspection object T is a sheet-like article that is unwound from a roll by a feed roll 41, and is transported in the direction of the white arrow in the figure by a dancer roll DR and multiple transport rolls R, and is wound up on a take-up roll 42.

[0006] The camera 99 is, for example, a line sensor camera, and is equipped with a plurality of image pickup elements arranged in a line in a direction perpendicular to the sheet conveyance direction. The inspection object T is photographed by the camera 99 in an imaging area P during conveyance, and the photographed image is output to the inspection device 92, where inspection is automatically performed based on inspection standards set in advance. Here, since the inspection object T is always conveyed in the direction indicated by the white arrow, if the timing of movement in the conveyance direction and the timing of photographing by the camera 99 do not match, problems such as missing parts in the photographed image or overlapping photographs resulting in the image being stretched will occur.

[0007] For this reason, in the appearance inspection system 9, a rotary encoder 91 is installed on the shaft of a measuring roll 90, which is one of the transport rolls. The rotary encoder 91 measures the rotation speed of the measuring roll 90 and transmits an output signal to an inspection device 92. The inspection device 92 calculates the transport speed of the inspection object T based on the output of the rotary encoder 91, determines the timing of photographing by a camera 99 so as to synchronize with this, and outputs that signal to the camera 99. With such a system, it is possible to synchronize the transport speed of the inspection object T with the timing of photographing, thereby acquiring images suitable for inspection.

[0008] JP 2015-172519 A JP 2016-109495 A

[0009] Okabe Machinery Co., Ltd., "When using a line scan camera, synchronization with the transport system is essential," [online], Image Inspection.COM, [Retrieved August 5, 2024], Internet <URL: https: / / gazou-kensa.com / camera / 136 / > Futec Co., Ltd., "Plain surface inspection device," [online], [Retrieved August 5, 2024], Internet <URL: https: / / www.futec.co.jp / products / surface>

[0010] However, in reality, due to constraints on the transport route along which the object to be inspected is transported (for example, a product manufacturing line), it is often difficult to determine the installation location of the rotary encoder and to match its specifications (such as the number of pulses required for the diameter of the roll on which the encoder is attached), and it is often not easy to introduce an imaging system.

[0011] Furthermore, various factors, such as slippage in the roll on which the rotary encoder is installed, or the occurrence of slack or tension during transport of a sheet-like object to be inspected, which can cause a mismatch between the amount of movement of the object and the timing of the trigger signal to the line sensor camera, can cause a mismatch. In such cases, an appropriate image cannot be acquired, resulting in reduced inspection accuracy. In particular, when using a TDI camera equipped with a TDI (Time Delay Integration) sensor, inspection can be performed using higher-quality images than with a conventional line sensor camera. However, if the timing of the transport of the object to be inspected and the timing of the image capture are not perfectly synchronized, the image will be blurred and inspection will be impossible. Therefore, stricter tracking of the transport is required than when using a conventional line sensor camera.

[0012] The present invention has been made in consideration of the above-described situation, and aims to provide a technology for a photography system that photographs a subject moving on a transport path, which reduces restrictions on installation on the transport path and can eliminate errors in synchronization between the transport of the subject and the timing of photography.

[0013] In order to achieve the above object, the present invention employs the following configuration: an imaging system having a camera that captures an image of a subject moving on a transport path, a sensor that measures a physical quantity for calculating the amount of movement of the subject without contacting either the transport mechanism that constitutes the transport path or the subject, and an imaging control unit that calculates the amount of movement based on the physical quantity and determines the timing of imaging by the camera based on the amount of movement.

[0014] Here, the sensor may be any sensor that outputs a signal capable of measuring a physical quantity for calculating the movement amount of the subject, and may be, for example, a sensor that measures the "conveying speed," "acceleration," or "position (distance)" of the subject. More specifically, for example, a laser Doppler velocimeter or the like may be used, but this is not necessarily limited to this, and a sensor that measures a physical quantity other than speed may also be used, and the velocimeter may be one that uses radio waves or ultrasonic waves. Furthermore, the conveying path may be, for example, a manufacturing line for the product that is the subject.

[0015] With this configuration, the sensor can calculate the movement of the subject without contacting either the transport mechanism or the subject, significantly reducing restrictions on sensor installation location and the effort required to match specifications with the transport mechanism. This allows the imaging system to be easily retrofitted to existing transport routes, such as those on product manufacturing lines. Furthermore, the increased flexibility in sensor installation allows the sensor to be installed so that it measures at (or near) the camera's imaging position, minimizing the discrepancy between the actual movement of the subject and the camera's imaging trigger, which is determined based on the sensor output.

[0016] Furthermore, the camera may be a TDI camera having a plurality of line sensors having a longitudinal direction intersecting with the conveying direction of the subject, and the photographing control unit may determine the photographing timing of the TDI camera so that each of the plurality of line sensors sequentially photographs the same location of the subject in accordance with the movement of the subject. Note that "intersect" here does not only refer to something that is completely perpendicular, but also includes an intersection that is close to being perpendicular.

[0017] In other words, the camera is equipped with a plurality of line sensors having their longitudinal direction perpendicular to the conveying direction of the subject, and is configured to acquire an image by sequentially accumulating the outputs of each line sensor lined up in the conveying direction at each photographing timing determined by the trigger generating means, and the photographing control unit may determine the photographing timing so that such a plurality of line sensors photograph the same location on the subject.

[0018] By using such a high-performance camera, clear images can be obtained, and when the image is used to inspect the object (i.e., the object under inspection), foreign objects and defects of a few microns in size can be detected. When photographing using a TDI camera, the timing of photographing the object must be perfectly synchronized with the transport of the object, otherwise the quality of the photographed image will be significantly affected. Therefore, stricter tracking of the photographing trigger with the transport is required than when using a normal line sensor camera. In this regard, the present invention is suitable for inspection using a TDI camera because it can minimize the difference between the amount of movement of the transported object and the timing of photographing by the camera.

[0019] The camera and the sensor may also be configured as an integrated unit. Such a configuration allows for easy installation of the present photography system. A unit may also be configured with a trigger signal generating unit that determines the timing of photography by the camera based on the measurement results of the sensor. With such a configuration, the present photography system can be installed simply by installing the unit. However, the trigger signal may also be generated by a separate device (such as an information processing terminal). That is, a separate device may receive the output from the sensor, generate a trigger signal based on the output, and then transmit the trigger signal to the camera in the unit, thereby determining the timing of photography by the camera.

[0020] In addition, the sensor may be a sensor that performs measurements by irradiating a laser, and the camera and the sensor may be positioned in the unit so that the focus of the camera on the subject coincides with the focus of the laser irradiation light.

[0021] Note that "matching" here does not necessarily mean an exact match, but also includes a close enough match that it can be considered a match. This configuration reduces the effort required to align the focal points of the camera and sensor on-site when installing them. Furthermore, because the laser (illuminated light) and its reflected light are visible, the position where the light beam converges most closely on the transported object (i.e., the focal point) can be found by moving the unit while illuminating the laser on the transported object, and the installation position of the unit where the camera and laser Doppler velocimeter are in focus can be easily determined.

[0022] Furthermore, the position where the sensor measures the physical quantity may be set upstream of the camera's imaging position on the conveying path. For example, if a non-contact speed sensor that measures the speed of a moving object using the Doppler effect is used as the sensor, a delay of microseconds occurs between detecting a reflected wave to calculate the speed and inputting an imaging trigger based on the speed to the camera. Although this delay is essentially negligible, if the speed measurement position cannot be aligned with the camera's imaging position in the conveying direction, it is preferable that the speed measurement position be upstream of the camera's imaging position rather than downstream.

[0023] Furthermore, the subject may be a sheet-like object, and the sensor may be located opposite the camera across the subject. When the transported object is a sheet-like object, for example, during inspection, the sheet-like object itself is transported by being unwound from one end of the transport path and wound up at the other end. In this case, when the front side of the sheet is photographed with a camera, it is also possible to perform non-contact measurements on the back side of the sheet. Therefore, even if it is not possible to position the sensor on the front side so as to perform measurements at the same position as the camera's photographing position, by positioning the sensor on the back side so as to perform measurements at a position opposite the camera (i.e., the same position as the photographing location in the transport direction), it is possible to accurately synchronize the movement of the subject with the timing of the camera's photographing.

[0024] The photographing system may further include an image generating unit that generates a composite image based on the images photographed by the camera, and an image display unit that displays the composite image.

[0025] The present invention can also be understood as an appearance inspection system having the above-described photographing system and an inspection device that inspects the subject based on the photographed image of the subject.

[0026] The present invention can also be understood as an image acquisition method as follows: That is, a method for acquiring an image of a subject, comprising: measuring the amount of movement of a subject moving on a transport path without contacting either a transport mechanism constituting the transport path or the subject; determining the timing for photographing the subject based on the amount of movement; and photographing the subject moving on the transport path with a camera in accordance with the determined timing.

[0027] The present invention can be achieved by combining the above-described configurations and processes as long as no technical contradiction occurs.

[0028] According to the present invention, in a photography system that photographs a subject moving on a transport path, it is possible to provide technology that reduces restrictions on installation on the transport path and suppresses errors in synchronization between the transport of the subject and the timing of photography.

[0029] FIG. 1 is a schematic diagram showing the configuration of a visual inspection system according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram showing an outline of the structure of a TDI camera according to the first embodiment. FIG. 3 is a block diagram showing the hardware configuration of an information processing device according to the first embodiment of the present invention. FIG. 4 is a flowchart showing an example of the flow of processing executed in the visual inspection system according to the first embodiment of the present invention. FIG. 5 is a schematic diagram showing the configuration of a visual inspection management system according to a second embodiment of the present invention. FIG. 6 is a schematic diagram showing the configuration of a modified example of the visual inspection management system according to the second embodiment. FIG. 7 is a flowchart showing another example of the flow of processing executed in the visual inspection system according to the first embodiment of the present invention. FIG. 8 is a schematic diagram showing the configuration of a conventional visual inspection system.

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0031] <Application Example> The present invention can be applied to, for example, an appearance inspection system 1 as shown in Fig. 1. Fig. 1 is a schematic diagram showing the overall configuration of the appearance inspection system 1 according to this application example. The appearance inspection system 1 has an imaging system 30 including an imaging unit 10 and an information processing device 20, a transport mechanism including a payout roll 41, a dancer roll DR, multiple transport rolls R, and a take-up roll 42, and an illumination means (not shown). A transport path for the inspection object T is formed by the transport mechanism.

[0032] The photographing unit 10 is an integrated unit of a laser Doppler velocimeter 11 and a TDI camera 12. The laser Doppler velocimeter 11 irradiates a measurement target (moving object) with laser light and receives the reflected light, and measures the moving speed of the measurement target without contacting it by utilizing the Doppler effect. Note that the laser Doppler velocimeter 11 is a well-known technology, so a detailed description thereof will be omitted.

[0033] Fig. 2 is a schematic diagram illustrating an outline of the configuration of the TDI camera 12. As shown in Fig. 2, the TDI camera 12 is configured such that a plurality of rows of line sensors 121, each having a longitudinal direction perpendicular to the conveyance direction of the object T (the direction indicated by the white arrow in Fig. 2), are arranged in the conveyance direction of the object T so as to be able to capture an image of the entire width direction of the object T. Note that Fig. 2 schematically shows three rows of line sensors 121, but in reality, the TDI camera 12 according to this embodiment is equipped with a greater number of line sensors 121 (for example, 64 rows).

[0034] Such a TDI camera 12 can acquire a clear, high-quality image of the object to be inspected T by sequentially accumulating the outputs of the line sensors 121 in the traveling direction in accordance with the movement of the object to be inspected T. On the other hand, even if there is even a slight mismatch between the amount of movement of the object to be inspected T and the timing of photographing (accumulation of the outputs of the line sensors 121), the image acquired by the TDI camera 12 will be vertically long and blurry.

[0035] Incidentally, even when photographing with not only a TDI camera but also a normal line sensor camera, a rotary encoder has been installed on the shaft of one of the transport rolls R to determine the amount of movement of the object in order to synchronize the timing of photographing with the movement of the object. The rotary encoder is in physical contact with the drive shaft of the transport roll R and generates pulses at a constant pace in accordance with the rotation. However, the object to be inspected may become loose or tense during transport, causing the amount of movement to be inconsistent and slippage to occur on the transport rolls R. Therefore, the actual amount of movement of the object to be inspected often does not match the pulses of the rotary encoder, and it is difficult to say that the measurement accuracy is sufficiently high.

[0036] In this regard, in the imaging unit 10 according to this application example, the laser Doppler velocimeter 11, which is a non-contact velocity sensor, measures the velocity of the object T in the imaging area P of the TDI camera 12, so that it is possible to accurately measure the moving velocity of the object T without being affected by slippage of the transport rolls or slack or tension of the object T. Then, an accurate amount of movement is calculated based on the measured moving velocity, and the imaging timing of each of the multiple line sensors 121 of the TDI camera 12 is determined, so that the movement of the object T and the imaging timing of each line sensor 121 of the TDI camera 12 can be precisely synchronized.

[0037] Furthermore, even if a rotary encoder was previously installed, there were many restrictions on where it could be installed, and it was often difficult to select the equipment and match specifications (settings), such as determining how many pulses should be output based on the diameter of the transport roll on which the encoder was attached.

[0038] In contrast, in the photographing unit 10 according to this application example, the TDI camera 12 and the laser Doppler velocimeter 11 are integrated, so there is no need to worry about installing sensors, and the hassle of introducing the photographing system 30 to the conveying line can be eliminated.

[0039] <Embodiment 1> Next, an embodiment of the present invention will be described in more detail with reference to the drawings. The appearance inspection system 1 according to this embodiment has the same configuration as that described in the application example using FIG. 1. That is, the appearance inspection system 1 includes an imaging system 30, a transport mechanism (a feed roll 41, a dancer roll DR, multiple transport rolls R, and a take-up roll 42), and an illumination means (not shown). Note that detailed description of the configuration already described in the application example will be omitted.

[0040] The inspection object T in this embodiment is a sheet-like article such as paper or film, and is set on the payout roll 41 in a rolled state. It is continuously transported by a transport mechanism in the direction indicated by the white arrow to the take-up roll 42. The object T is then photographed by the TDI camera 12 in an imaging area P during transport. More specifically, the dancer roll DR moves up and down as indicated by the black arrow in Figure 1, and the inspection object T is paid out from the payout roll 41, and is sequentially sent by each transport roll R in the transport direction indicated by the white arrow in the figure, and is finally taken up by the take-up roll 42.

[0041] The photographing unit 10 is configured so that the focal point of the TDI camera 12 on the object to be inspected T coincides with the focal point of the light emitted by the laser Doppler velocimeter 11. For example, if the focal distance of the TDI camera 12 is 200 mm from the lens and the focal distance of the laser Doppler velocimeter 11 is 40 mm from the laser light emitting element, the laser Doppler velocimeter 11 is configured to protrude from the lens of the TDI camera 12 to fill the difference of 160 mm.

[0042] Although not shown, the photographing unit 10 is also provided with a calculation processing unit that determines the timing of photographing by the TDI camera 12 based on the measurement values ​​of the laser Doppler velocimeter 11. Therefore, the photographing unit 10 alone can determine the timing of photographing by the TDI camera 12. That is, in this embodiment, the photographing unit 10 is configured to also function as a photographing control unit.

[0043] The photographing unit 10 is installed above the transport mechanism so as to be able to photograph the entire width of the surface of the inspection object T from above along the transport path. In addition, although not shown, a lighting means is provided to illuminate the photographing area P.

[0044] The information processing device 20 can be, for example, a general-purpose computer, and acquires image data of the inspection object T by receiving signals output by the sensor elements of the TDI camera 12, synthesizes the image data to generate a composite image of the subject, and inspects the inspection object T based on the composite image and pre-stored inspection criteria. That is, the information processing device 20 functions as an inspection device.

[0045] The generation of the composite image includes both the sequential accumulation of brightness values ​​of the same location on the object T by a plurality of line sensors provided in the TDI camera 12, and the stitching together of images of the object T moving in the traveling direction, in chronological order of the images taken. The information processing device 20 also includes a display device 24a as one of the output IFs 24 described later, and can display the composite image on the display device 24a.

[0046] Fig. 3 is a block diagram showing an outline of the hardware configuration of the information processing device 20. As shown in Fig. 3, the hardware configuration of the information processing device 20 includes, as components, a processor 21, a memory 22, an input interface (IF) 23, an output IF 24, and a communication IF 25, which are interconnected by a connection bus 29.

[0047] The processor 21 may be any arithmetic processing device such as a CPU (Central Processing Unit), an MPU (Micro-Processing Unit), or a DSP (Digital Signal Processor).

[0048] Although not shown, the memory 22 includes a main storage device such as a flash memory, a RAM (Random Access Memory), or a ROM (Read Only Memory), and an auxiliary storage device such as an SSD (Solid State Drive), an EPROM (Erasable Programmable ROM), a flash memory, a USB memory, or an SD (Secure Digital) memory card. The memory 22 stores information such as programs executed by the processor 21, data processed by the processor 21, image data captured by the TDI camera 12, and inspection criteria (inspection items, thresholds) used for inspection.

[0049] The processor 21 executes a program stored in the memory 22, thereby controlling each component of the information processing device 20, thereby realizing each functional unit that fulfills a predetermined purpose. For example, in this embodiment, the functional unit of the image generation unit is realized by the information processing device 20. Furthermore, as in other embodiments described below, the functional unit of the imaging control unit may be realized by the arithmetic processing device. In other words, it is also possible for the arithmetic processing device to determine the timing of imaging by the TDI camera 12.

[0050] Examples of the input IF 23 include various input devices such as a keyboard, mouse, camera, and microphone. Examples of the output IF 24 include various output devices such as a display, speaker, and printer. A touch panel display can also be used as a configuration that serves as both the input IF 23 and the output IF. The communication IF 25 is connected to communicate with the photographing unit 10 and may also have an appropriate configuration for connecting to other external devices.

[0051] A series of steps for acquiring images of the inspection object T using the visual inspection system 1 will be described with reference to the flowchart in Fig. 4. As shown in Fig. 4, when the sheet-like inspection object T is transported along the transport path, the laser Doppler velocimeter 11 measures the moving speed of the inspection object T, and the amount of movement of the inspection object T is calculated based on this (S1). Then, based on the amount of movement calculated in step S1, an arithmetic processing unit (not shown) of the photographing unit 10 determines the timing of photographing by the TDI camera 12 (S2). Subsequently, the TDI camera 12 performs photographing using each sensor element in accordance with the photographing timing determined in step S2 (S3), and the photographed data is transmitted to the information processing device 20 (S4).

[0052] Note that steps S1 to S4 are repeated until the transportation of the entire inspection object T is completed (branch of NO in S5). Then, when the transportation of the entire inspection object T is completed (branch of YES in S5), the information processing device 20 synthesizes the photographed data to generate a composite image (S6), and inspects the inspection object T (detects defects) based on the composite image and predetermined inspection criteria stored in advance in the information processing device (S7), and the series of processes is completed.

[0053] The above processing procedure is an example, and the generation and inspection of the composite image may be performed at any timing before the completion of the transport of the entire inspection object T. Also, the process may include a step of displaying the composite image, inspection results, etc. on the display device 24a.

[0054] According to the appearance inspection system 1 configured as described above, the photographing unit 10 is configured so that the focal point of the TDI camera 12 and the focal point of the light emitted by the laser Doppler velocimeter 11 are aligned, which eliminates the need to align the focal points of the TDI camera 12 and the laser Doppler velocimeter 11 on-site when introducing the photographing system 30 into the transport path of the object under inspection T. Furthermore, because the light emitted from the laser Doppler velocimeter 11 and its reflected light are visible, the position on the object under inspection T where the light rays converge most (i.e., the focal point) can be found by moving the photographing unit 10, which is an integrated camera and velocity sensor, while irradiating the laser onto the object under inspection T, and this makes it possible to easily determine the installation position of the photographing unit 10.

[0055] <Embodiment 2> Next, another embodiment of the present invention will be described with reference to Fig. 5. A visual inspection system 2 according to this embodiment has a configuration generally similar to that of the visual inspection system 1 of embodiment 1. In the following, the same reference numerals are used for components already described in embodiment 1, and repeated description will be omitted. Fig. 5 is a schematic diagram showing the general configuration of the visual inspection system 2 according to this embodiment.

[0056] 5 , in the appearance inspection system 2 according to this embodiment, the TDI camera 12 and the laser Doppler velocimeter 11 are configured as separate entities, and the laser Doppler velocimeter 11 is disposed opposite the TDI camera 12 with the object to be inspected T in between. In other words, the laser Doppler velocimeter 11 irradiates a laser onto the back side of the photographing area P photographed by the TDI camera 12. In this embodiment, the TDI camera 12, the laser Doppler velocimeter 11, and the information processing device 20 form an photographing system 30.

[0057] The measurement values ​​measured by the laser Doppler velocimeter 11 are transmitted to the information processing device 20, which calculates the amount of movement of the object T based on the measurement values ​​and generates a trigger signal that determines the timing of imaging by the TDI camera 12 based on the amount of movement. That is, in this embodiment, the information processing device 20 (processor 21) corresponds to the imaging control unit. The trigger signal generated by the information processing device 20 is transmitted to the TDI camera 12, and imaging is performed in synchronization with the movement of the object T based on this trigger signal.

[0058] According to the appearance inspection system 2 of the present embodiment as described above, even if it is not possible to arrange the laser Doppler velocimeter 11 so as to measure the speed at the same location on the front side of the object T as the shooting area P of the TDI camera 12 due to restrictions on the installation location or the like, by arranging a speed sensor so as to measure the speed at a position opposite the TDI camera 12 on the back side (i.e., the same position in the conveying direction as the shooting area P), it is possible to accurately synchronize the conveying speed of the object and the timing of the camera's shooting.

[0059] <Modification> In the above-described appearance inspection system 2, the laser Doppler velocimeter 11 is disposed in a position facing the TDI camera 12 across the object to be inspected T, but there are no particular restrictions on the location of the laser Doppler velocimeter 11. Fig. 6 shows a schematic diagram of an appearance inspection system 3 according to a modification in which the location of the laser Doppler velocimeter 11 is changed.

[0060] As shown in FIG. 6, in the appearance inspection system 3 according to this modified example, the laser Doppler velocimeter 11 is configured to measure the moving speed of the inspection object T on the upstream side of the line from the photographing area P of the TDI camera 12.

[0061] When a non-contact speed sensor that measures the speed of a moving object using the Doppler effect is used, a delay of the order of microseconds occurs between detecting the reflected wave to calculate the speed and inputting the imaging trigger based on this to the TDI camera 12. Although this delay is practically negligible, if the position where the speed measurement is performed cannot be made to coincide with the imaging area P, it is preferable that the position where the speed measurement is performed is upstream of the imaging area P rather than downstream.

[0062] <Others> The above-described embodiments are merely illustrative of the present invention, and the present invention is not limited to the specific embodiments described above. The present invention can be modified in various ways other than the above examples within the scope of its technical concept.

[0063] For example, in the second embodiment and its modified example, the information processing device 20 generates a trigger signal indicating the timing of photographing, but the laser Doppler velocimeter 11 may have a function to generate such a trigger signal. In that case, the trigger signal may be transmitted directly to the TDI camera 12 without going through the information processing device 20.

[0064] Furthermore, in the above embodiment, the information processing device 20 is configured to include an image generating section, but the photographing unit 10 may accumulate photographic data and generate a composite image.

[0065] Furthermore, although the above embodiment employs the TDI camera 12 as the imaging means, the present invention can also be applied to imaging systems using other cameras. When using a TDI camera, it is particularly strict to synchronize the timing of imaging with the movement of the subject, but there is also the advantage that a general line sensor camera can accurately synchronize the timing of imaging with the movement of the subject.

[0066] In the above embodiment, the laser Doppler velocimeter 11 is used as the sensor for calculating the amount of movement of the subject, but the sensor is not limited to a velocimeter as long as it can calculate the amount of movement of the subject in a non-contact manner. Furthermore, a sensor that measures acceleration or position to calculate the amount of movement of the subject using, for example, radio waves or ultrasonic waves instead of light can also be used.

[0067] Furthermore, in the above embodiment, an example of offline inspection has been described in which a composite image is generated and inspection is performed after the transportation of the inspection object T has been completed, but the inspection of the inspection object T may also be performed by inline inspection as shown in Fig. 7. An example of the processing flow when inline inspection is performed will be described below with reference to Fig. 7. Note that the processing from step S1 to step S4 is the same as that described in the embodiment, and therefore description thereof will be omitted.

[0068] After the photographic data is transmitted to the information processing device 20 in step S4, the information processing device 20 determines whether a predetermined amount of photographic data has been transmitted (S11), rather than whether the transport has been completed. If it is determined that the predetermined amount of photographic data has not been transmitted, the process returns to step S1 and the subsequent processes are repeated (NO branch in step S11).

[0069] On the other hand, if it is determined in step S11 that the predetermined amount of photographed data has been transmitted, the information processing device 20 generates a composite image from the predetermined amount of data (S12). That is, a composite image showing a portion of the object T to be inspected corresponding to the predetermined amount of photographed data is generated. Then, based on the composite image synthesized in step S12 and predetermined inspection criteria previously stored in the information processing device 20, inspection of the portion of the object T to be inspected is performed (S13).

[0070] Next, the information processing device 20 determines whether or not the transport of the entire object to be inspected T has been completed (S14). If it is determined that the transport of the object to be inspected T has not been completed (NO at the branch of S14), the information processing device 20 returns to step S1 and repeats the subsequent processes. On the other hand, if it is determined in step S14 that the transport of the object to be inspected T has been completed (YES at the branch of step S14), the series of processes ends. According to such in-line inspection, the transport and photography of the object to be inspected T are performed in parallel with the inspection, so that the inspection of the object to be inspected T can be completed soon after the transport of the object to be inspected T has been completed.

[0071] In addition, although the above embodiment has been described as an example of an image capturing system that captures a sheet-like object as a subject, the object is not limited to a sheet-like object. For example, the present invention can be applied to an image capturing system that captures products, fruits and vegetables, etc., transported on a belt conveyor.

[0072] <Supplementary Note 1> An imaging system (30) comprising: a camera (12) that images an object (T) moving on a conveying path; a sensor (11) that measures a physical quantity for calculating a movement amount of the object without contacting either a conveying mechanism that constitutes the conveying path or the object; and an imaging control unit (20) that calculates the movement amount based on the physical quantity and determines the timing of imaging by the camera based on the movement amount.

[0073] <Supplementary Note 2> The photographing system (30) described in Supplementary Note 1, wherein the camera (12) is a TDI camera having a plurality of line sensors in a conveying direction, the line sensors having a longitudinal direction in a direction intersecting with the conveying direction of the subject, and the photographing control unit determines a photographing timing by the TDI camera such that each of the plurality of line sensors sequentially photographs the same location of the subject in accordance with the movement of the subject.

[0074] <Supplementary Note 3> The photographing system (30) according to Supplementary Note 1, wherein the camera (12) and the sensor (11) are configured as an integrated unit (10).

[0075] <Supplementary Note 4> The photographing system (30) according to Supplementary Note 3, wherein the sensor is a sensor that performs measurements by irradiating a laser, and the camera and the sensor are arranged in the unit so that the focal point of the camera and the focal point of the laser irradiation light with respect to the subject coincide with each other.

[0076] <Supplementary Note 5> The photographing system (30) according to Supplementary Note 1, wherein a position where the sensor (11) measures the physical quantity is set upstream of a photographing position (P) of the camera (12) on the conveying path.

[0077] <Supplementary Note 6> The photographing system (30) according to Supplementary Note 1, wherein the subject (T) is a sheet-like article, and the sensor (11) is provided at a position facing the camera (12) with the subject in between.

[0078] <Supplementary Note 7> The photographing system according to Supplementary Note 1, further comprising: an image generating unit (20) that generates a composite image based on images photographed by the camera; and an image display unit (24a) that displays the composite image.

[0079] <Supplementary Note 8> An appearance inspection system (1, 2, 3) comprising: an imaging system (30) according to any one of Supplementary Notes 1 to 7; and an inspection device that inspects the subject based on a captured image of the subject.

[0080] <Supplementary Note 9> A method for acquiring an image of a subject, comprising: measuring an amount of movement of a subject moving on a transport path without contacting either a transport mechanism constituting the transport path or the subject (S1); determining a timing for photographing the subject based on the amount of movement (S2); and photographing the subject moving on the transport path with a camera in accordance with the determined timing (S3).

[0081] REFERENCE SIGNS LIST 10: Imaging unit 11: Laser Doppler velocimeter 12: TDI camera 121: Line sensor 20: Information processing device 24a: Image display unit 30: Imaging system 41: Feeding roll 42: Winding roll 90: Measurement roll 91: Rotary encoder 92: Inspection device 99: Camera P: Imaging area R: Transport roll DR: Dancer roll T: Inspected object

Claims

1. An imaging system comprising: a camera that captures an image of an object moving on a transport path; a sensor that measures a physical quantity for calculating the amount of movement of the object without contacting either the object or a transport mechanism that constitutes the transport path; and an imaging control unit that calculates the amount of movement based on the physical quantity and determines the timing of imaging by the camera based on the amount of movement.

2. The photographing system according to claim 1, wherein the camera is a TDI camera having a plurality of line sensors in the transport direction, each line sensor having its longitudinal direction intersecting the transport direction of the subject, and the photographing control unit determines the photographing timing of the TDI camera so that each of the plurality of line sensors sequentially photographs the same location of the subject in accordance with the movement of the subject.

3. The photographing system according to claim 1, wherein the camera and the sensor are configured as an integrated unit.

4. The photography system according to claim 3, wherein the sensor is a sensor that performs measurements by irradiating a laser, and the camera and the sensor are arranged in the unit so that the focus of the camera on the subject coincides with the focus of the laser irradiation light.

5. The imaging system according to claim 1, wherein the position where the sensor measures the physical quantity is set upstream of the imaging position of the camera on the conveying path.

6. The photographing system according to claim 1, wherein the subject is a sheet-like article, and the sensor is provided at a position facing the camera across the subject.

7. The photographing system according to claim 1, further comprising: an image generating unit that generates a composite image based on images photographed by the camera; and an image display unit that displays the composite image.

8. An appearance inspection system comprising: the photographing system according to any one of claims 1 to 7; and an inspection device that inspects the subject based on a photographed image of the subject.

9. A method for acquiring an image of a subject, comprising: measuring the amount of movement of a subject moving on a transport path without contacting either a transport mechanism constituting the transport path or the subject; determining the timing for photographing the subject based on the amount of movement; and photographing the subject moving on the transport path with a camera in accordance with the determined timing.

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