JP7075965B2 - Defect inspection system, defect inspection method and aircraft - Google Patents

Description

Embodiments of the present invention relate to defect inspection systems, defect inspection methods and aircraft.

Conventionally, as non-destructive inspection (NDI: Non Destructive Inspection), traction flaw detection inspection (ET: Eddy Current Testing), ultrasonic flaw detection inspection (UT: Ultrasonic Testing), penetrant inspection (PT: Penetrant Testing), etc. Are known. Further, in recent years, a flaw detection inspection method using an optical fiber sensor is also known (see, for example, Patent Documents 1 to 4).

Specific examples of inspection methods using optical fiber sensors include fiber reinforced plastics made of resin such as glass fiber reinforced plastics (GFRP: Glass Fiber Reinforced Plastics) and carbon fiber reinforced plastics (CFRP: Carbon Fiber Reinforced Plastics). A technique of embedding an optical fiber in a composite material (FRP: Fiber Reinforced Plastics) to detect the position of damage or breakage has also been proposed (see, for example, Patent Documents 5 and 6). In addition, NDI has also been proposed to evaluate abnormalities such as wrinkles (wrinkles of fibers) that may occur in a composite material by photographing infrared thermography (see, for example, Patent Document 7).

Japanese Unexamined Patent Publication No. 2000-146746 Japanese Unexamined Patent Publication No. 2005-321223 Japanese Unexamined Patent Publication No. 2005-208000 Japanese Unexamined Patent Publication No. 61-155802 Japanese Unexamined Patent Publication No. 09-273906 Japanese Unexamined Patent Publication No. 08-054343 Japanese Unexamined Patent Publication No. 2017-129560

An object of the present invention is to enable non-destructive and easy detection of defects in a structure.

The defect inspection system according to the embodiment of the present invention is a defect inspection system for determining whether or not a crack has occurred in an inspection target area in an aircraft structure composed of at least one of a composite material and a metal, and has a wavelength of 380 nm to 780 nm. It has a light source that emits visible light and an optical path of the visible light that is arranged in the inspection target area and is made of a polymer optical waveguide or an optical fiber having a thickness of micron order, and a crack is formed in the inspection target area. In order to determine whether or not the optical path is generated, the optical detector is used without being connected to the optical path, and when a crack occurs in the inspection target area, the optical path bends at the position where the crack occurs, and the optical path is bent. Whether or not a crack has occurred in the inspection target area by utilizing the phenomenon that the amount of visible light leaking from the optical path increases to the extent that it can be determined by the inspector's visual inspection or the image taken by an optical camera due to the bending of the optical path. Is made possible.
Further, the defect inspection system according to the embodiment of the present invention is connected to an optical path arranged in an area to be inspected for defects in a structure composed of at least one of a composite material and a metal, and is connected to one end of the optical path, and the light is transmitted to the optical path. It has a light source that emits light and a reflecting mirror connected to another end of the optical path, and an optical detector is connected to the optical path in order to determine whether or not a defect has occurred in the inspection target area. It is used without being used.

Further, the aircraft according to the embodiment of the present invention is provided with the above-mentioned defect inspection system.

Further, the defect inspection method according to the embodiment of the present invention is to determine whether or not a defect has occurred in the inspection target area by using the defect inspection system described above.

Further, the defect inspection method according to the embodiment of the present invention is a defect inspection method for determining whether or not a crack has occurred in an inspection target area in an aircraft structure composed of at least one of a composite material and a metal. The crack occurred in the step of emitting visible light having a wavelength of 380 nm to 780 nm in an optical path composed of a polymer optical waveguide or an optical fiber having a thickness of micron order, and when a crack occurred in the inspection target area. A phenomenon in which the optical path bends at a position, and the amount of visible light leaking from the optical path increases to the extent that it can be determined visually by an inspector or photographed by an optical camera during propagation of the visible light due to the bending of the optical path. It has a step of determining whether or not a crack has occurred in the inspection target area by the inspector's visual inspection or an optical camera image without connecting an optical detector to the end of the optical path. be.
Further, in the defect inspection method according to the embodiment of the present invention, a light source is connected to one end of an optical path arranged in an area to be inspected for defects in a structure composed of at least one of a composite material and a metal, while another optical path is connected. When a reflector is connected to the end and light is emitted from the light source to the optical path, and when a defect occurs in the inspection target area, the optical path bends at the position where the defect occurs, and the optical path bends. Whether or not a defect has occurred in the inspection target area by utilizing the increase in the amount of visible light leaking from the optical path or the amount of infrared rays emitted from the optical path during the propagation of the light is determined by the optical path. It has a step of determining without connecting an optical detector to the end of the light detector.

The block diagram of the defect inspection system which concerns on 1st Embodiment of this invention. The figure which shows the arrangement example of the optical path shown in FIG. FIG. 3 is a cross-sectional view showing a state of an optical path when a crack is generated in the structure shown in FIG. The figure which shows another arrangement example of the optical path shown in FIG. The block diagram of the defect inspection system which concerns on 2nd Embodiment of this invention. The figure which shows another arrangement example of the optical path shown in FIG. The block diagram of the defect inspection system which concerns on 3rd Embodiment of this invention. The figure which shows another arrangement example of the optical path shown in FIG. 7. (A), (B), and (C) are diagrams showing an example in which a plurality of defects occur in a structure in which a plurality of optical paths are arranged in a quadrangular grid pattern as shown in FIG. The block diagram of the defect inspection system which concerns on 4th Embodiment of this invention.

The defect inspection system, the defect inspection method, and the aircraft according to the embodiment of the present invention will be described with reference to the accompanying drawings.

(First Embodiment)
(Configuration and function)
FIG. 1 is a block diagram of a defect inspection system according to the first embodiment of the present invention.

The defect inspection system 1 is a system for inspecting the presence or absence of defects such as cracks, damage, and peeling. Any structure 2 can be a defect inspection target by the defect inspection system 1. For example, when the structure 2 constituting the aircraft is a defect inspection target, the defect inspection system 1 can be provided in the aircraft. That is, the defect inspection target area can be set in the aircraft structure, and it can be determined whether or not the defect has occurred in the aircraft structure. The material of the structure 2 is also arbitrary. For example, a structure 2 made of at least one of a metal and a composite material is inspected for defects by a defect inspection system 1, such as a structure made of a metal, a structure made of a composite material, or a structure obtained by superimposing a metal and a composite material. Can be targeted.

The defect inspection system 1 can be composed of a light source 3 that emits visible light such as a laser beam, an optical path 4 for the laser beam, an optical camera 5, an image analysis unit 6, an input device 7, and a display 8. When the inspector visually determines the presence or absence of a defect in the inspection target area, the optical camera 5, the image analysis unit 6, the input device 7, and the display 8 may be omitted. Further, although the case where the laser light is mainly emitted from the light source 3 will be described below as an example, visible light other than the laser light may be emitted from the light source 3.

FIG. 2 is a diagram showing an arrangement example of the optical path 4 shown in FIG.

At least one optical path 4 is arranged in the inspection target area of the defect D in the structure 2. FIG. 2 shows an example in which a plurality of optical paths 4 are arranged in parallel so as to cross an inspection target area of a defect D on the surface of the structure 2.

Examples of the optical element for forming the optical path 4 include an optical fiber and an optical waveguide. In a broad sense, an optical fiber is a kind of optical waveguide. Typical examples of optical waveguides in a narrow sense include inorganic optical waveguides such as glass optical waveguides and polymer optical waveguides. The polymer optical waveguide is originally an optical element for a printed substrate using an optical signal, and is also called an organic optical waveguide, a plastic optical waveguide, a polymer optical wiring, a polymer optical circuit, or the like.

The polymer optical wave guide has a core layer formed inside the clad layer, and the core layer can be formed of a polymer material, while the clad layer can be formed of a resin sheet or the like. The features of the polymer optical waveguide are that there is no light loss in the direction perpendicular to the length direction, that it is easy to process, that it is possible to increase the density, and that it is easy to mount.

The optical camera 5 is arranged at a position where it is possible to take a visible light image of the inspection target area of the defect D including the optical path 4 during the propagation of the laser beam. Therefore, the optical camera 5 can acquire a two-dimensional optical image of the inspection target area including the optical path 4.

FIG. 3 is a cross-sectional view showing a state of the optical path 4 when a crack is generated in the structure 2 shown in FIG.

The optical path 4 of the laser beam can be composed of an optical waveguide 12 such as an optical fiber or a polymer optical waveguide in which a core layer 11 is formed inside the clad layer 10. The optical waveguide 12 can be adhered to the surface of the structure 2 with the adhesive 13. After painting the surface of the structure 2 or performing surface treatment, the optical waveguide 12 may be adhered to the surface of the coating film or the surface treatment layer with an adhesive 13. Alternatively, conversely, the outside of the optical waveguide 12 may be painted.

When a defect D such as a crack occurs on the surface of the structure 2, the optical waveguide 12 forming the optical path 4 of the laser beam bends at the position where the defect D occurs as shown in FIG. That is, the clad layer 10 of the optical waveguide 12 is deformed. Further, not limited to the example shown in FIG. 3, when the optical waveguide 12 itself is damaged due to a collision of an object or the like, the optical waveguide 12 is deformed and the optical path 4 is bent. As a result, a part of the laser beam is reflected and refracted by the bent optical waveguide 12, and visible light leaks from the optical waveguide 12. That is, light having a wavelength of 380 nm to 780 nm passes through the deformed clad layer 10 and leaks to the outside of the optical waveguide 12. Therefore, the amount of visible light leaking from the optical waveguide 12 existing at the position where the defect D is generated increases.

Therefore, it is possible to determine whether or not the defect D is generated in the inspection target area based on the amount of visible light leaking from the optical waveguide 12 forming the optical path 4 of the laser light. That is, when a defect D occurs in the inspection target area of the defect D, the optical path 4 bends at the position where the defect D occurs, and the amount of visible light leaking from the optical path 4 increases due to the bending of the optical path 4. Can be used to determine whether or not a defect D has occurred in the inspection target area.

Therefore, in order to determine whether or not a defect D has occurred in the inspection target area, a light source 3 for emitting a laser beam to the optical waveguide 12 forming the optical path 4 is required, but the light source 3 is emitted from the optical waveguide 12. No photodetector is required to detect the laser beam. Therefore, the defect inspection system 1 can be used without connecting the photodetector to the optical path 4. That is, it is possible to determine whether or not a defect D has occurred in the inspection target area without directly or indirectly connecting the photodetector to the end of the optical path 4.

Most simply, an inspector who is a user of the defect inspection system 1 can visually check the optical path 4 to determine whether or not a defect D has occurred in the inspection target area. Further, if the optical camera 5 is installed so that the inspection target area and the optical path 4 can be photographed as illustrated in FIG. 1, the inspection target area and the optical path 4 are photographed by the optical camera 5 based on a visible light image. It is also possible to determine whether or not the defect D has occurred. That is, by visually observing the visible light image obtained by taking an image with the optical camera 5, it is possible to determine whether or not the defect D is generated in the inspection target area. Therefore, it is possible to inspect the presence or absence of the defect D by setting a portion that cannot be directly seen by the inspector in the inspection target area.

Further, regardless of whether or not the inspector can directly see the visible light image, if the optical camera 5 captures a visible light image of the inspection target area including the optical path 4 such as the optical waveguide 12, the inspection target can be inspected at a desired time and place. Not only is it possible to inspect the presence and location of defects D in the area, but visible light images can also be stored as inspection records. That is, if a singular point or region having a relatively large amount of visible light is observed in the visible light image captured by the optical camera 5, the singular point or region represents the position or range of the defect D. .. That is, it is possible to save an inspection record that visualizes the position and range of the defect D by taking a visible light image in the inspection target area.

In order to be able to detect the defect D with high accuracy, it is important that the defect D causes the leakage of visible light due to the refraction of the laser light to the extent that it can be observed. For that purpose, it is preferable to configure the optical path 4 with an optical waveguide 12 that is easily deformed. Examples of the optical waveguide 12 that is easily deformed under the influence of the defect D include a polymer optical waveguide and a thin optical fiber having a thickness on the order of microns. Therefore, it is desirable to form the optical path 4 with a polymer optical waveguide or a thin optical fiber having a thickness of micron order.

On the other hand, the presence or absence of the defect D can be determined by visually observing a visible light image of the inspection target area including the optical path 4 or the inspection target area including the optical path 4. Therefore, it is appropriate to use a visible light laser as the laser light.

Further, if the number and length of the optical waveguides 12 are increased, it becomes possible to inspect the defect D in a wider inspection target area, and if the density of the optical waveguides 12 is increased, the defect inspection can be performed. Spatial resolution can be improved.

In the example shown in FIG. 1, a plurality of optical waveguides 12 are arranged in parallel with the inspection target area of the defect D. Therefore, it is possible to inspect defects at the portion crossed by each optical waveguide 12. Of course, a plurality of optical waveguides 12 may be arranged non-parallel. Further, depending on the shape of the structure 2, the optical waveguide 12 may be branched, merged or crossed.

In particular, if the optical path 4 is formed by a polymer optical waveguide capable of increasing the density as described above, it is possible to arrange a plurality of optical paths 4 at a pitch of 1 mm or less (μm order). Further, even when it is unavoidable to cross the optical paths 4, unlike the optical fiber, the optical paths 4 can be formed without overlapping the polymer optical waveguides. Therefore, if a polymer optical waveguide is used to form the optical path 4, it is possible to avoid unevenness that occurs when optical fibers are crossed.

Moreover, as described above, the polymer optical waveguide is easy to construct. For example, a plurality of optical paths 4 can be easily arranged on the surface of the structure 2 by simply attaching a resin sheet having a plurality of polymer optical waveguides formed as the plurality of optical paths 4 to the surface of the structure 2 with an adhesive 13. Can be done.

Therefore, when the intersection of the optical paths 4 is unavoidable, the polymer optical waveguide can be formed by intersecting in one resin sheet. Then, it is possible to reduce the variation in the distance between the polymer optical waveguides arranged so as to intersect with each other and the surface of the structure 2. Further, if a film adhesive is used as the adhesive 13 for attaching the optical waveguide 12 to the surface of the structure 2, regardless of whether or not the optical paths 4 are crossed, the optical waveguide 12 is optical as compared with the case where a liquid adhesive or the like is used. The distance between the waveguide 12 and the surface of the structure 2 can be made more uniform. As a result, the detectability of the defect D can be further improved.

FIG. 4 is a diagram showing another arrangement example of the optical path 4 shown in FIG.

As shown in FIG. 4, the optical waveguide 12 may be arranged in a meandering manner by smoothly curving a part or all of the optical waveguide 12. In the example shown in FIG. 4, the shape of the optical waveguide 12 is a shape in which smoothly curved curved portions and straight portions are alternately connected.

When a part or all of the optical waveguide 12 is smoothly curved as illustrated in FIG. 4, the optical waveguide 12 can be provided at a high density in the inspection target area of the defect D without crossing the optical waveguide 12. Alternatively, the branching of the optical waveguide 12 can be eliminated. Further, if the number of optical waveguides 12 to which the laser beam should be incident is one, the number of light sources 3 can be one. In addition, by arranging the optical waveguide 12 in a spiral shape, the optical waveguide 12 can be provided at a high density in the inspection target area of the defect D without crossing the optical waveguide 12.

As illustrated in FIG. 1 or FIG. 4, a plurality of optical waveguides 12 or curved optical waveguides 12 can be two-dimensionally arranged so as to cross a plurality of different positions in the biaxial directions of the vertical axis and the horizontal axis. .. Then, the inspection target area of the defect D can be inspected as a two-dimensional area, and the position of the defect D can be inspected as a two-dimensional position. Of course, if the inspection target area of the defect D is a narrow portion, one optical waveguide 12 is arranged linearly or curved with a small curvature, and the position of the defect D is arranged on the linear axis or the curved axis. It may be possible to inspect it as a one-dimensional position.

The two-dimensional image of the surface of the structure 2 taken by the optical camera 5 can be displayed on the display 8. As a result, a user such as an inspector can confirm the presence / absence and position of the defect D by visually observing the visible light image displayed on the display 8. For example, when the structure 2 constituting the aircraft is to be inspected for the defect D, the dent and the resin crack due to the impact damage of the metal or the composite material due to the collision of birds, stones or hail, and the resin due to the peeling of the composite material. It is possible to confirm the presence / absence and position of defects D such as cracks, cracks due to fatigue of the composite material or metal, and deformation or cracks of the composite material or metal due to a large local load exceeding the limit load.

The presence / absence and position of the defect D can be automatically detected. When the presence / absence and the position of the defect D are automatically detected, an image analysis unit 6 is provided on the output side of the optical camera 5. Therefore, when the user performs the detection of the presence / absence and the position of the defect D only by visual inspection of the visible light image displayed on the display 8, or the visible light image taken by the optical camera 5 is taken into another image analysis system to obtain an image. When the presence / absence and the position of the defect D are detected by performing the analysis, the image analysis unit 6 may be omitted.

The image analysis unit 6 is provided with a function of automatically determining the presence / absence and position of the defect D in the inspection target area of the defect D by image processing such as detection processing of a singular point for a visible light image and threshold processing. The image analysis unit 6 having such an image processing function can be configured by an electronic circuit such as a computer in which an image processing program is read.

The amount of visible light leaking from the optical path 4 arranged in the portion where the defect D is generated is larger than the amount of visible light leaking from the portion where the defect D is not generated. Therefore, the singular point or region corresponding to the defect D may be detected by comparing the pixel values of the image data captured by the optical camera 5 into the image analysis unit 6 or by comparing the pixel values with the reference values. As a specific example, a threshold process in which the pixel value of the image data captured in the image analysis unit 6 is compared with the average value or the reference value of the pixel values, and if the difference or ratio exceeds the threshold value, it is determined that the defect D exists. The determination process including the above can be performed.

As another specific example, the change in the amount of visible light leaking from the optical path 4 arranged in the inspection target area of the defect D, that is, the change in the pixel value of the visible light image captured in the image analysis unit 6 is compared with the reference value. May detect a singular point or region representing the position where the defect D exists. Specifically, a determination process including a threshold value process for comparing the visible light image to be detected for the defect D with the reference image and determining that the defect D exists when the difference or ratio of the pixel values exceeds the threshold value is performed. It can be carried out.

The optical camera 5 is used during the period in which the laser beam is propagating in the optical path 4 in a state where it is confirmed that the defect D does not exist in the reference image to be compared with the visible light image to be detected by the defect D. A visible light image in the inspection target area of the photographed defect D can be used. Alternatively, during the period in which the laser beam is propagating in the optical path in the inspection target area of another structure in which the presence of the defect D is confirmed and the structure of the inspection target area and the arrangement pattern of the optical path are the same. A visible light image taken by an optical camera may be used as a reference image.

Even when the user detects the defect D by visual inspection of the visible light image displayed on the display 8 or the optical path 4, the presence or absence of the defect D can be determined by comparing with the same reference image.

Not only the visible light image taken by the optical camera 5 but also the automatic inspection result of the defect D by the image analysis unit 6 can be displayed on the display 8. For example, when the defect D is detected by the image analysis of the visible light image by the image analysis unit 6, the position of the defect D can be highlighted on the visible light image by coloring or the like.

The input device 7 is a device for inputting necessary instruction information to the defect inspection system 1 by the user. For example, it is possible to instruct the emission of the laser beam from the light source 3 and the start of image analysis in the image analysis unit 6 by operating the input device 7.

The defect inspection system 1 and the defect inspection method as described above are such that the presence / absence and the position of the defect D are inspected by utilizing the fact that visible light leaks from the optical path 4 of the laser beam arranged in the portion where the defect D exists. It is the one that was made.

(effect)
According to the defect inspection system 1 and the defect inspection method, non-destructive inspection using a laser beam can be easily performed only by arranging the light source 3 and the optical path 4 without using a photodetector. In particular, even in a part where it is difficult to install a photodetector or a part where it is difficult to install sensors for other non-destructive inspection, if the inspection target area of the defect D can be observed, the defect D The presence or absence can be inspected. For example, even if the structural component is difficult for the inspector to access, the presence or absence of the defect D can be inspected by taking a visible light image of the inspection target area with the optical camera 5 from a distant position.

In addition, the presence / absence, position, scale, etc. of defects D such as cracks can be visually detected. Therefore, the inspection labor and the inspection time can be reduced as compared with the conventional non-destructive inspection method.

Further, when the inspection target of the defect D is inside the structure constituting the aircraft, the optical camera 5, the image analysis unit 6, the input device 7, the display 8, and the like can be mounted on the aircraft. Then, it becomes possible to detect the defect D such as a crack during the flight of the aircraft. That is, it is possible to determine whether or not a defect D is generated in the inspection target area based on the visible light image obtained by photographing the optical path 4 with the optical camera 5 during the flight of the aircraft provided with the aircraft structure. .. In this case, when the defect D is detected, the flight safety can be improved by taking measures such as changing the flight conditions.

On the other hand, if the aircraft is not flying, whether or not the defect D is generated in the inspection target area based on the visible light image obtained by photographing the optical path 4 with the optical camera 5 or by visually observing the optical path 4. Can be determined. Therefore, when a defect D such as a crack is detected during the flight of an aircraft, a detailed inspection of the defect D can be performed at the time of ground inspection.

On the other hand, even when the optical camera 5 for photographing the inspection target area of the defect D cannot be mounted on the aircraft, such as when the inspection target of the defect D is the surface of the aircraft body, during the inspection on the ground. By bringing the optical camera 5, it is possible to easily inspect the presence or absence of the defect D. In particular, if a sheet on which a polymer optical waveguide is printed at high density is attached and an image is taken with the optical camera 5, a non-destructive inspection can be easily performed on a desired portion of the aircraft body surface.

(Second embodiment)
FIG. 5 is a block diagram of a defect inspection system according to a second embodiment of the present invention.

In the defect inspection system 1A according to the second embodiment shown in FIG. 5, visible light other than laser light is emitted from the light source 3, and the light source 3 is connected to one end of the optical path 4, while another optical path 4 is connected. The point that the reflector 20 is connected to the end portion is different from the defect inspection system 1 in the first embodiment. Since the other configurations and operations of the defect inspection system 1A in the second embodiment are not substantially different from those of the defect inspection system 1 in the first embodiment, the optical camera 5, the image analysis unit 6, the input device 7, and the display The illustration of No. 8 is omitted, and the same or corresponding configurations are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 5, the reflector 20 can be connected to the end of the optical path 4 on the side not connected to the light source 3, that is, the end on the light emitting side. Then, the light is reflected by the reflecting mirror 20, and the reflected light also passes through the inspection target area of the defect D. Therefore, in the portion where the defect D exists, the light leaks not only by the refraction of the light emitted from the light source 3 but also by the refraction of the reflected light reflected by the reflecting mirror 20. Therefore, the amount of visible light leaking from the portion where the defect D exists can be amplified. As a result, the detection sensitivity of the defect D can be improved. If laser light is used as visible light, the laser output becomes unstable due to the reflected light of the laser light, so it is realistic to use visible light other than laser light.

FIG. 6 is a diagram showing another arrangement example of the optical path 4 shown in FIG.

Even when the optical waveguide 12 is arranged in a zigzag manner as shown in FIG. 6, the reflecting mirror 20 can be connected to the other end of the optical waveguide 12. Of course, the same applies when the optical waveguide 12 is arranged in a spiral shape.

According to the above-mentioned second embodiment, in addition to the same effect as that of the first embodiment, the effect that the detection sensitivity of the defect D can be improved can be obtained.

(Third embodiment)
FIG. 7 is a block diagram of a defect inspection system according to a third embodiment of the present invention.

In the defect inspection system 1B according to the third embodiment shown in FIG. 7, the method of arranging the optical path 4 and the point that the photodetector 30 and the signal processing unit 31 are connected to the end of the optical path 4 are the first embodiments. It is different from the defect inspection system 1 in. Since the other configurations and operations of the defect inspection system 1B in the third embodiment are not substantially different from those of the defect inspection system 1 in the first embodiment, the optical camera 5, the image analysis unit 6, the input device 7, and the display The illustration of No. 8 is omitted, and the same or corresponding configurations are designated by the same reference numerals and the description thereof will be omitted.

In the defect inspection system 1B in the third embodiment, the optical paths 4 composed of the optical waveguide 12 are arranged in a grid pattern. A light source 3 is connected to one end of one optical path 4, while a photodetector 30 is connected to the other end. Therefore, the laser light propagating in each optical path 4 can be detected by the photodetector 30.

A signal processing unit 31 is connected to the output side of the photodetector 30. The signal processing unit 31 can also be configured by an electronic circuit such as a computer in which a signal processing program is read. The signal processing unit 31 is provided with a function of identifying the position of the defect D based on the detection signal of the light detected by the photodetector 30. Therefore, not only the image analysis unit 6 but also the signal processing unit 31 can automatically inspect the defect D. That is, the inspection of the defect D based on the visible light image taken by the optical camera 5 and the inspection of the defect D based on the optical signal can be used in combination.

As described in the first embodiment, the optical path 4 crossing the defect D bends. As a result, the intensity of the laser beam propagating in the optical path 4 that crosses the defect D is reduced. Therefore, if the signal processing unit 31 detects a change in the intensity of the laser beam propagating through each optical path 4, the optical path 4 that crosses the defect D can be specified. That is, an optical path 4 in which the intensity of the laser beam detected by the light detector 30 is reduced by exceeding a threshold value from the intensity of the laser beam output from the light source 3 can be determined as an optical path 4 crossing the defect D.

Then, the intensity of the laser beam is reduced, and the position and size of the defect D can be specified by specifying the plurality of optical paths 4 that intersect with each other. As a specific example, if the optical paths 4 are arranged in a grid pattern in a two-dimensional region whose positions are defined by the X-axis and the Y-axis that are orthogonal to each other as shown in FIG. 7, the positions X1 and X2 are different in the X-axis direction. , A plurality of optical paths 4 located at X3 and parallel to the Y axis, and a plurality of optical paths 4 located at different positions Y1, Y2, and Y3 in the Y-axis direction and parallel to the X axis are arranged.

In this case, only the intensity of the laser beam propagating in the optical path 4 at the position X2 in the X-axis direction and parallel to the Y axis and the intensity of the laser beam propagating in the optical path 4 at the position Y2 in the Y-axis direction and parallel to the X axis. If is reduced, the defect D is surrounded by a position (X1, Y1), a position (X3, Y1), a position (X3, Y3) and a position (X1, Y3) represented by the X and Y coordinates. It will be in the range. Further, if the intensity of the laser beam propagating through the plurality of optical paths 4 arranged in parallel is reduced, it means that the size of the defect D is a size straddling the plurality of optical paths 4 arranged in parallel.

By crossing the plurality of optical paths 4 in this way, it is possible to specify the position and size of the defect D by detecting a decrease in the amount of light of the laser beam. In particular, since the polymer optical waveguides can be arranged at 1 mm intervals, if the polymer optical waveguides are arranged in a grid pattern at 1 mm intervals, the position and size of the defect D can be specified with an accuracy of 1 mm.

FIG. 8 is a diagram showing another arrangement example of the optical path 4 shown in FIG. 7.

As shown in FIG. 8, a plurality of optical paths 4 may be arranged so as to be parallel to each other in three directions. In this case, there will be a plurality of optical paths 4 that intersect at an angle other than 90 degrees. By arranging the plurality of optical paths 4 in parallel in three or more different directions, it is possible to detect each of the plurality of defects D even if they occur at different positions.

9 (A), (B), and (C) are diagrams showing an example in which a plurality of defects D occur in the structure 2 in which a plurality of optical paths 4 are arranged in a quadrangular grid pattern as shown in FIG. be.

As shown in FIG. 9A, a defect inspection system 1B is configured by arranging a plurality of parallel optical paths 4 orthogonally in a quadrangular grid pattern and connecting a light source 3 and a photodetector 30 to each optical path 4. Can be done. However, for example, as shown in FIG. 9A, when the laser beam propagating in a plurality of optical paths 4 that are not adjacent in the same direction is lost due to the defect D, the intersection position of the optical paths 4 where the laser beam is lost is lost. Is in multiple places. Therefore, the position of the defect D cannot be specified. Specifically, if there is a loss of laser light as illustrated in FIG. 9 (A), is there a defect D in the two regions shown in FIG. 9 (B), or is there a defect D in FIG. 9? It is not possible to identify whether the defect D has occurred in the two regions shown in (C).

On the other hand, as shown in FIG. 8, if three or more coordinate axes are defined and the position of the defect D is specified by the three or more coordinates, it is possible to identify a plurality of defects D generated at different positions. It will be possible. More specifically, the surface of the structure 2 is a plurality of optical paths 4 for propagating laser light in a plurality of directions different from each other in three or more directions, and having a plurality of optical paths 2 having at least two optical paths 2 in one direction. A light source 3 for incidenting a laser beam is connected to each one end of a plurality of optical paths 4, while a laser beam emitted from each other end of the plurality of optical paths 4 is detected at each other end of the plurality of optical paths 4. By connecting the optical detector 30, it is possible to identify each of the plurality of defects D.

In the example shown in FIG. 8, the position of the defect D can be specified by three axes intersecting at 60 degrees. Therefore, when the intensities of the laser beams emitted from the three optical paths 4 are reduced, the region including each part of the three optical paths 4 can be specified as the position where the defect D is generated.

As described in the first embodiment, the loss of the laser beam also occurs in the portion where the optical paths 4 intersect. Therefore, it is desirable to arrange the optical paths 4 so that the three or more optical paths 4 do not intersect at one place regardless of the angle at which the optical paths 4 intersect, from the viewpoint of reducing unnecessary laser light loss.

In addition to the above, functions for performing filter processing for removing noise from the detection signal output from the optical detector 30, average processing, envelope detection processing, frequency analysis processing such as Fourier transform and weavelet conversion, and the like. Can be provided in the signal processing unit 31 as needed. This makes it possible to detect a decrease in the detection signal of the laser beam with higher accuracy.

According to the above-mentioned third embodiment, in addition to the same effect as that of the first embodiment, it is possible to obtain the effect that the detection of the defect D based on the intensity of the laser beam propagating in the optical path 4 can be used together. Therefore, it is possible to reduce the occurrence of erroneous detection of the defect D.

In particular, when the optical paths 4 are arranged in a quadrangular grid pattern, it may be difficult to identify the positions of the plurality of defects D. The position of the defect D can be specified. Therefore, the defect D is automatically detected based on the intensity of the laser beam propagating through the optical paths 4 arranged in a grid pattern, and the visible light captured by the optical camera 5 when there are a plurality of candidate positions for the defect D. The defect D may be inspected based on the image.

(Fourth Embodiment)
FIG. 10 is a block diagram of a defect inspection system according to a fourth embodiment of the present invention.

In the defect inspection system 1C according to the fourth embodiment shown in FIG. 10, infrared rays (IR: Infrared ray) are used instead of visible light to determine whether or not a defect has occurred in the inspection target area. The above points are different from the defect inspection systems 1, 1A and 1B in the other embodiments. Since the other configurations and operations of the defect inspection system 1C in the fourth embodiment are not substantially different from those of the defect inspection systems 1, 1A and 1B in the other embodiments, the defect inspection system 1 and the defect inspection system 1 in the first embodiment are used. Only the differences between are described.

In the defect inspection system 1C according to the fourth embodiment, an infrared camera 40 is provided instead of the optical camera 5 in order to determine the presence or absence of defects in the inspection target area by using infrared rays. The infrared camera 40 is an infrared temperature sensor that captures a two-dimensional infrared image showing the temperature distribution of the inspection target area. Infrared images showing the temperature distribution are also called thermography. Infrared rays have a wavelength of 780 nm to 1 mm and cannot be visually recognized. Therefore, the defect inspection system 1C includes an image analysis unit 6, an input device 7, and a display 8 in addition to the infrared camera 40.

As illustrated in FIG. 3, when a defect D such as a crack or damage occurs on the surface of the structure 2, the optical waveguide 12 forming the optical path 4 of the laser beam bends as described above. Therefore, the optical waveguide 12 is deformed and the optical path 4 is narrowed or blocked. As a result, the amount of loss of laser light in the portion of the optical waveguide 12 in which the optical path 4 is narrowed or the portion of the optical waveguide 12 in which the optical path 4 is blocked is increased as compared with the other portions, and the amount of decrease in the energy of the laser beam is different. It is relatively more than the part of.

Then, since the energy reduction of the laser beam becomes heat energy and generates heat, the temperature in the portion of the optical waveguide 12 crossing the defect D becomes relatively higher than the temperature in the portion of the other optical waveguide 12. That is, the temperature of the optical waveguide 12 forming the optical path 4 that crosses the defect D rises locally.

Therefore, if an infrared image of the inspection target area including the optical waveguide 12 is taken with the infrared camera 40, the presence / absence and position of the defect D can be detected based on the infrared image. That is, if a singular point having a relatively high temperature is observed in the infrared image, the singular point represents the position of the defect D. That is, the position of the defect D can be visualized by taking an infrared image.

Even when the presence or absence and the position of the defect D are detected by using the infrared image, the laser beam is used by the defect D in order to detect the defect D with high accuracy as in the case of using the visible light image. It is important that the loss due to refraction and local temperature changes occur to the extent that they can be observed. Therefore, it is preferable that the optical path 4 is composed of a easily deformable optical waveguide 12 such as a polymer optical waveguide or a thin optical fiber having a thickness of micron order.

If a two-dimensional infrared image on the surface of the structure 2 taken by the infrared camera 40 is displayed on the display 8, a user such as an inspector can visually check the infrared image displayed on the display 8 to display the defect D. It is possible to confirm the presence or absence and the position of. On the other hand, the image analysis unit 6 may automatically determine the presence / absence and position of the defect D in the inspection target area. In that case, the presence / absence and position of the defect D in the inspection target area can be automatically determined by the detection process of the singular point of the infrared image.

The amount of temperature increase of the optical path 4 arranged in the portion where the defect D is generated is larger than the amount of temperature increase of the optical path 4 arranged in the portion where the defect D is not generated. Therefore, the singular point corresponding to the defect D may be detected by comparing the pixel values of the infrared image with each other or comparing the pixel value with the reference value. As a specific example, it is possible to perform a determination process including a threshold value process for comparing the pixel value of an infrared image with an average value or a reference value of the pixel values and determining that a defect D exists when the difference or ratio exceeds the threshold value. can.

However, when the surface of the structure 2 itself has a temperature distribution, infrared rays having an intensity distribution corresponding to the temperature distribution are also emitted from the surface of the structure 2. Therefore, the singularity may be detected by comparing the temperature change in the inspection target area of the defect D, that is, the change in the pixel value of the infrared image with the reference value. That is, a determination process including a threshold value process in which the infrared image for which the singular point corresponding to the defect D is to be detected is compared with the reference image, and the defect D is determined to exist when the difference or ratio of the pixel values exceeds the threshold value. It can be performed.

In the reference image to be compared with the infrared image to be detected of the singular point, there is no infrared image or defect D in the inspection target area of the defect D taken during the period when the laser beam does not propagate in the optical path 4. It is possible to use an infrared image in the inspection target area of the defect D taken during the period when the laser beam is propagating in the optical path 4 in the state where it is confirmed.

In the defect inspection system 1C according to the fourth embodiment as described above, in the optical path 4 of the laser beam arranged in the portion where the defect D exists, the optical path 4 radiates from the optical path 4 together with the amount of temperature rise due to the bending of the optical path 4 and the loss of the laser beam. Utilizing the increase in the amount of infrared rays generated, the presence / absence and position of a defect D can be detected by taking an infrared image. In other words, the defect inspection system 1C in the fourth embodiment determines whether or not a defect has occurred in the inspection target area based on the amount of infrared rays emitted from the optical path 4 during the propagation of the laser beam. ..

Therefore, even in the defect inspection system 1C according to the fourth embodiment, non-destructive inspection using a laser beam can be easily performed only by arranging the light source 3 and the optical path 4 without using a photodetector. Further, when the inspection target of the defect D is inside the structure constituting the aircraft, by mounting the defect inspection system 1C on the aircraft, the defect D can be found in the inspection target area even during the flight of the aircraft. It can be determined whether or not it has occurred.

(Other embodiments)
Although the specific embodiments have been described above, the described embodiments are merely examples and do not limit the scope of the invention. The novel methods and devices described herein can be embodied in a variety of other modes. In addition, various omissions, substitutions and changes may be made in the methods and modes of the apparatus described herein without departing from the gist of the invention. The appended claims and their equivalents include such various modalities and variations as embraced in the scope and gist of the invention.

1, 1A, 1B, 1C Defect inspection system 2 Structure 3 Light source 4 Optical path 5 Optical camera 6 Image analysis unit 7 Input device 8 Display 10 Clad layer 11 Core layer 12 Optical waveguide 13 Adhesive 20 Reflector 30 Photodetector 31 Signal Processing unit 40 Infrared camera D Defect

Claims (7)

A defect inspection system that determines whether or not a crack has occurred in the inspection target area of an aircraft structure consisting of at least one of a composite material and a metal.
A light source that emits visible light with a wavelength of 380 nm to 780 nm ,
With the visible light path arranged in the inspection area and made of a polymer optical waveguide or an optical fiber having a thickness of micron order .
In order to determine whether or not a crack has occurred in the inspection target area, a photodetector is not connected to the optical path and is used.
When a crack occurs in the inspection target area, the optical path bends at the position where the crack occurs, and the amount of visible light leaking from the optical path due to the bending of the optical path is visually measured by an inspector or photographed by an optical camera. A defect inspection system that can determine whether or not a crack has occurred in the inspection target area by utilizing the phenomenon that the number increases to the extent that it can be determined by. An optical path located in a defect inspection area in a structure consisting of at least one of a composite and a metal,
A light source connected to one end of the optical path and emitting light to the optical path,
With a reflector connected to another end of the optical path,
Have,
A defect inspection system used without a photodetector connected to the optical path to determine whether or not a defect has occurred in the inspection target area. An aircraft provided with the defect inspection system according to claim 1 or 2 . A defect inspection method for determining whether or not a crack has occurred in the inspection target area using the defect inspection system according to claim 1 or 2 . In a defect inspection method for determining whether or not a crack has occurred in an inspection target area in an aircraft structure composed of at least one of a composite material and a metal.
A step of emitting visible light having a wavelength of 380 nm to 780 nm into an optical path composed of a polymer optical waveguide or an optical fiber having a thickness of micron order, which is arranged in the inspection target area.
When a crack occurs in the inspection target area, the optical path bends at the position where the crack occurs, and the amount of visible light leaking from the optical path during propagation of the visible light due to the bending of the optical path is an inspector. An inspector without connecting an optical detector to the end of the optical path can determine whether or not a crack has occurred in the inspection target area by utilizing the phenomenon that the amount increases to the extent that it can be determined visually or by taking an image of an optical camera. Steps to be judged visually or by shooting with an optical camera ,
Defect inspection method with. A light source is connected to one end of an optical path arranged in an area to be inspected for defects in a structure composed of at least one of a composite material and a metal, while a reflecting mirror is connected to another end of the optical path, and the light source is connected to the optical path. And the step of emitting light to
When a defect occurs in the inspection target area, the optical path bends at the position where the defect occurs, and the amount of visible light leaking from the optical path during propagation of the light due to the bending of the optical path or from the optical path. A step of determining whether or not a defect has occurred in the inspection target area by utilizing the increase in the amount of infrared rays emitted, without connecting an optical detector to the end of the optical path, and
Defect inspection method with. During the flight of an aircraft equipped with the aircraft structure, it is determined whether or not a crack has occurred in the inspection target area based on an image obtained by photographing the optical path with an optical camera, while the aircraft flies. A claim for determining whether or not a crack has occurred in the inspection target area based on an image obtained by photographing the optical path with an optical camera or by visually observing visible light leaking from the optical path. 5 Defect inspection method.

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