Railway tunnel construction crack detection method based on machine vision

Abstract

The invention relates to a railway tunnel construction crack detection method based on machine vision, which is applied to the field of tunnel detection, and comprises the following steps: marking a crack by using the flight coordinate of an inspection unmanned aerial vehicle body on the basis of the existing unmanned aerial vehicle detection, and then controlling the inspection unmanned aerial vehicle body to approach and confirm; then, the marking bomb is ejected to the crack in a manual control mode, so that visual marking is carried out, researchers can know crack information through data and can rapidly and accurately find the crack through marking to carry out field research and analysis, and therefore the detection efficiency and accuracy are effectively improved; in addition, the method can effectively avoid defects of inspection robots for top lining detection in the prior art, and effectively reduce interference of factors such as distance, dust and vibration.

Description

Technical Field

[0001] The present invention relates to a railway tunnel construction crack detection method based on machine vision, and in particular to a railway tunnel construction crack detection method based on machine vision applied in the field of tunnel detection. Background Art

[0002] Railway tunnel crack detection based on machine vision is an important technology in the current railway engineering field. It uses machine vision systems to quickly and accurately detect cracks in tunnel linings to improve the safety and stability of tunnel structures. Currently, most detection methods are implemented using inspection robots and drones, which can effectively reduce the impact of human factors, but inspection robots are not very effective in detecting linings above tunnels.

[0003] In order to solve the problem of detecting cracks in tunnel linings, a certain detection method on the market adopts the design of three-dimensional reconstruction model, which has a certain market share.

[0004] The specification of Chinese patent CN118674679A discloses a method, system, storage medium and inspection robot for detecting cracks in tunnel lining, which comprises: performing tunnel lining crack detection on the visual image of any grid area of ​​the tunnel to be detected, obtaining crack feature information of any grid area, and performing three-dimensional reconstruction on the point cloud data of any grid area to obtain a three-dimensional reconstruction model of any grid area; based on the crack feature information of any grid area and the three-dimensional reconstruction model, determining the location information of the tunnel lining cracks in any grid area. The present invention can improve the accuracy of tunnel lining crack detection and the efficiency of tunnel lining crack detection.

[0005] Although the above patent can perform a three-dimensional reconstruction model of any grid area of ​​the tunnel lining to determine the location information of the cracks, it requires high data processing capabilities and the method is relatively complicated. In addition, when the inspection robot inspects the lining on the top of the tunnel, it is easily affected by distance, light and dust, thereby reducing the accuracy of the detection. Summary of the invention

[0006] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is to detect cracks in the lining above the tunnel.

[0007] To solve the above problems, the present invention provides a method for detecting cracks in railway tunnel construction based on machine vision, comprising the following detection steps: S1. Preliminary preparation: debug the flight indicators of the inspection drone used to detect cracks to ensure that the inspection drone can fly safely and smoothly, and then connect the inspection drone to the data and network transmission routes of the background processing system and control system to ensure stable data transmission and remote control flight network connection; S2, crack detection: let the inspection drone fly automatically at a low and uniform speed in the middle of the railway tunnel. The inspection drone uses its own multiple high-definition cameras to continuously take pictures of the tunnel lining to obtain images. While the multiple high-definition cameras are taking pictures, the inspection drone embeds the flight coordinates into the image information. Then, the inspection drone transmits the acquired images to the background processing system while flying. S3. Crack marking: The background processing system performs image comparison and analysis. Once the existence of cracks is detected, the background processing system immediately sends the coordinate information on the image to the inspection drone body, causing the inspection drone body to stop moving and fly back to the coordinate position sent by the background processing system, so as to take close-up photos and obtain clearer crack images to avoid misjudgment. When the inspection drone body takes close-up photos, it maintains a safe distance from the lining to prevent the wings from hitting the lining.

[0008] In the above-mentioned railway tunnel construction crack detection method based on machine vision, a drone is used to inspect the tunnel top lining, and the cracks are marked by relying on the drone's own flight coordinates, which effectively improves the detection efficiency.

[0009] As a further improvement of the present application, the upper side wall of the inspection drone body is fixedly connected to a detection seat through a bracket, and the upper side wall of the detection seat is fixedly connected to a fan-shaped seat, on which a plurality of equally spaced and surrounding high-definition cameras are installed, and an image preprocessor electrically connected to the high-definition camera is installed at the bottom of the inspection drone body, the fan-shaped seat is located on the left side of the high-definition camera and has an aiming adjustment slot, and the side wall of the detection seat below the aiming adjustment slot has a yield slot, and a turntable is rotatably connected to the side wall of the aiming adjustment slot, and the yield slot A driving motor connected to the turntable at the output end is installed in the slot, a launch tube is fixedly connected to the upper end of the turntable, and a solenoid valve is fixedly embedded at the bottom of the launch tube, an launch seat is slidably connected to the inner wall of the launch tube, and a buffer pad is connected between the lower end of the launch seat and the bottom of the launch tube, a high-pressure gas tank is inserted into the side wall of the detection seat, and a gas tank connecting valve threadedly connected to the high-pressure gas tank is fixedly embedded on the inner wall of the detection seat, the solenoid valve and the gas tank connecting valve are connected by a high-pressure hose, and a laser indicator is fixedly connected to the ejection tube at one side of its bullet outlet. A driving cavity is provided on the inner wall of the detection seat near the aiming and adjusting groove, and a loading tube extending to the top of the aiming and adjusting groove is rotatably connected in the driving cavity, a gear plate is fixedly sleeved on the outer wall of the loading tube located inside the driving cavity, and a driving motor connected with the gear plate at the output end is installed in the driving cavity, an electric push rod is installed at the bottom of the driving cavity just below the loading tube, and the output end of the electric push rod is connected with a push pad slidably connected to the inner wall of the loading tube, a plurality of marking bullets are placed in the space above the push pad of the loading tube, an inclined filling tube is connected to the upper side wall of the loading tube, and the lower end outlet of the filling tube is located just above the ejection tube, and a replenishing cover is rotatably connected to the upper opening of the loading tube, while the background processing system marks the cracks by relying on the flight coordinates of the inspection drone body, and also takes close photos of the cracks for confirmation by manually controlling the inspection drone body, and drives the turntable to adjust the ejection tube to aim at the cracks through the control system, and ejects the marking bullets onto the cracks by relying on high-pressure gas, so as to realize visual marking of the cracks, which is convenient for researchers to find the cracks quickly and accurately, and effectively improves work efficiency.

[0010] As a further improvement of the present application, a groove is provided on the inner wall of the buffer pad, and an elastic reset belt is fixedly connected between the bottom of the groove and the lower side wall of the ejection seat. When the high-pressure gas ejects the ejection seat, the elastic reset belt is stretched. When the marking bullet is ejected, the elastic force of the elastic reset belt can pull the ejection seat back, thereby realizing automatic reset of the ejection seat and preparing for the next launch.

[0011] As a further improvement of the present application, the aiming adjustment slot is located on the side walls on both sides of the ejection tube and is slidably connected with a telescopic accordion dust cover, and the telescopic accordion dust covers on both sides are simultaneously against the side walls of the ejection tube, and the telescopic accordion dust covers play a dust-proof role. When the ejection tube rotates, the telescopic accordion dust covers on both sides move with the ejection tube and are stretched or compressed, which can effectively prevent dust from entering the aiming adjustment slot and saves the trouble of later cleaning.

[0012] As another improvement of the present application, the marking bullet includes a brittle wrapped shell, and the interior of the brittle wrapped shell is wrapped with fluorescent pigment powder. The brittle wrapped shell immediately breaks after hitting the lining, so that the fluorescent pigment powder is released to mark the crack.

[0013] As another improvement of the present application, a crack marking method for inspecting a drone body includes the following steps: N1. After the background processing system sends a command to let the inspection drone return to the coordinate position where the crack is detected, the background processing system manually controls the inspection drone to approach the crack, takes photos again to confirm that it is a crack, and then drives the turntable through the control system to drive the ejection tube to rotate and aim at the crack. Then, the solenoid valve is opened to allow the high-pressure gas stored in the high-pressure gas storage tank to instantly enter the ejection tube, and the marker is ejected using high pressure, so that the marker is ejected onto the crack to mark it, making it easier for researchers to find it quickly. N2. After marking the crack with the marking bullet, the background processing system allows the inspection drone to continue to fly forward along the original detection path. The control system restores the ejection tube to a vertical state and then drives the loading tube to rotate so that the loading tube rotates to the top of the ejection tube. The control system then starts the electric push rod, which rises upward. The push pad pushes the marking bullet upward, and the top marking bullet rolls down the loading tube into the ejection tube, thereby completing the reloading and facilitating the next crack marking. Finally, the loading tube is rotated 90° and is in standby mode to prevent the loading tube from hindering the rotation of the ejection tube.

[0014] To sum up, based on the existing drone detection, this method uses the flight coordinates of the inspection drone body to first mark the cracks, then controls the inspection drone body to approach for confirmation, and then manually ejects the marking bullet onto the crack for visual marking. In this way, researchers can not only know the crack information through data, but also quickly and accurately find the cracks through marking for on-site research and analysis, thereby effectively improving the detection efficiency and accuracy. In addition, this method can effectively avoid the defects of the inspection robot in the existing technology in the top lining detection, and effectively reduce the interference of factors such as distance, dust and vibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1This is a method flow chart of the first implementation mode of this application; Figure 2 This is a working pictogram of the inspection drone of the first embodiment of the present application when detecting cracks; Figure 3 This is a working pictogram of the inspection drone of the second embodiment of the present application when performing crack marking; Figure 4 This is a stereoscopic image of the inspection drone according to the first embodiment of the present application; Figure 5 This is a three-dimensional diagram of the detection base according to the first embodiment of the present application; Figure 6 This is a cross-sectional view of a loading tube according to a second embodiment of the present application; Figure 7 This is a cross-sectional view of the ejection tube according to the second embodiment of the present application; Figure 8 This is a state diagram of the catapult tube of the second embodiment of the present application during launching; Fig. 9 This is a cross-sectional view of a marking bullet according to a second embodiment of the present application; Fig.10 This is a diagram showing the connection relationship between the ejection tube and the telescopic accordion dust cover of the second embodiment of the present application.

[0016] Description of the numbers in the figure: 1 Inspection UAV body, 2 detection seat, 201 give way slot, 202 drive cavity, 3 fan-shaped seat, 4 high-definition camera, 5 aiming adjustment slot, 6 turntable, 7 ejection tube, 8 solenoid valve, 9 ejection seat, 10 buffer pad, 11 elastic reset belt, 12 high-pressure gas tank, 13 gas tank connecting valve, 14 laser indicator, 15 image preprocessor, 16 loading tube, 17 marking bullet, 1701 brittle wrapped shell, 1702 fluorescent pigment powder, 18 gear plate, 19 electric push rod, 20 bullet push pad, 21 filling tube, 22 bullet replenishment cover, 23 telescopic accordion dust cover. DETAILED DESCRIPTION

[0017] Two implementation modes of the present application are described in detail below with reference to the accompanying drawings.

[0018] The first implementation method: Figure 1 , 2 It is shown that the following detection steps are included: S1. Preliminary preparation: debug the flight indicators of the inspection drone 1 used for crack detection to ensure that the inspection drone 1 can fly safely and smoothly, and then connect the inspection drone 1 with the data and network transmission routes of the background processing system and control system to ensure stable data transmission and remote control flight network connection; S2, crack detection: let the inspection drone body 1 automatically fly at a low and uniform speed in the middle of the railway tunnel. The inspection drone body 1 uses multiple high-definition cameras 4 carried by it to continuously take pictures of the tunnel lining to obtain images. While the multiple high-definition cameras 4 are taking pictures, the inspection drone body 1 embeds the flight coordinates into the image information. Then, the inspection drone body 1 transmits the obtained images to the background processing system while flying; S3. Crack marking: The background processing system performs image comparison and analysis. Once the existence of cracks is detected, the background processing system immediately sends the coordinate information on the image to the inspection drone body 1, so that the inspection drone body 1 stops moving and flies back to the coordinate position sent by the background processing system, so as to take close-up photos and obtain clearer crack images to avoid misjudgment. When the inspection drone body 1 takes close-up photos, it maintains a safe distance from the lining to prevent the wing from hitting the lining.

[0019] The second implementation method: Figure 4 , 5 , 7, 8 and Fig.10It is shown that the upper side wall of the inspection drone body 1 is fixedly connected to the detection seat 2 through a bracket, and the upper side wall of the detection seat 2 is fixedly connected to the fan-shaped seat 3, and a plurality of high-definition cameras 4 (the specific model is selected according to actual needs and is not described in detail here) are installed on the fan-shaped seat 3 and are distributed around at equal intervals, and an image preprocessor 15 (the specific connection structure and working principle are well-known technologies for technicians in the relevant field and are not described in detail here) electrically connected to the high-definition camera 4 is installed at the bottom of the inspection drone body 1, and an aiming adjustment slot 5 is provided on the left side of the high-definition camera 4, and a clearance slot 201 is provided on the side wall of the detection seat 2 below the aiming adjustment slot 5, a turntable 6 is rotatably connected to the side wall of the aiming adjustment slot 5, and a driving motor connected to the turntable 6 at the output end is installed in the clearance slot 201, and a catapult tube 7 is fixedly connected to the upper end of the turntable 6, and a telescopic accordion dust cover 23 is slidably connected to the side walls of the aiming adjustment slot 5 on both sides of the catapult tube 7, and the telescopic accordion dust cover 23 on both sides is simultaneously connected to the catapult. The side walls of the ejection tube 7 are against each other, and the telescopic accordion dust cover 23 plays a role in dust prevention. When the ejection tube 7 rotates, the telescopic accordion dust covers 23 on both sides move with the ejection tube 7 and are stretched or compressed, which can effectively prevent dust from entering the aiming adjustment slot 5, eliminating the trouble of later cleaning. The bottom of the ejection tube 7 is fixedly inlaid with an electromagnetic valve 8 (the specific model is selected according to actual needs and is not described in detail here), and the inner wall of the ejection tube 7 is slidably connected with the ejection seat 9, and the lower end of the ejection seat 9 is in contact with the ejection tube 7. A buffer pad 10 is connected between the bottom, and a groove is provided on the inner wall of the buffer pad 10, and an elastic reset belt 11 (rubber material is preferably selected, and other materials can also be selected according to actual needs) is fixedly connected between the bottom of the groove and the lower end side wall of the ejection seat 9. When the high-pressure gas ejects the ejection seat 9, the elastic reset belt 11 is stretched. When the marking bullet 17 is ejected, the elastic force of the elastic reset belt 11 can pull the ejection seat 9 back again, thereby realizing the automatic reset of the ejection seat 9 and preparing for the next launch; Figure 5 , 6 and Fig. 9As shown, a high-pressure gas tank 12 is inserted into the side wall of the detection seat 2, and a gas tank connecting valve 13 threadedly connected to the high-pressure gas tank 12 is fixedly inlaid on the inner wall of the detection seat 2 (the specific connection structure and working principle refer to the anti-drowning life-saving bracelet in the prior art, which will not be described in detail here), the solenoid valve 8 and the gas tank connecting valve 13 are connected by a high-pressure hose, and the ejection tube 7 is located on one side of its ejection port. A laser indicator 14 is also fixedly connected, and the laser indicator 14 mainly serves to calibrate the ejection tube 7 to ensure that the marking bullet 17 fired by the ejection tube 7 can accurately hit the crack. The detection seat 2 is close to the aiming The inner wall of the aiming adjustment slot 5 is provided with a driving chamber 202, and a loading tube 16 extending to the top of the aiming adjustment slot 5 is rotatably connected in the driving chamber 202, and a gear plate 18 is fixedly sleeved on the outer wall of the loading tube 16 located inside the driving chamber 202, and a driving motor connected to the gear plate 18 at the output end is installed in the driving chamber 202 (the specific model is selected according to actual needs, and the driving motor and the gear plate 18 are preferably connected in a worm gear, and other connection methods can also be selected according to actual needs, which will not be described in detail here), and the driving chamber 202 is located at the bottom installation just below the loading tube 16 There is an electric push rod 19 (the specific model is selected according to actual needs and will not be described in detail here), and the output end of the electric push rod 19 is connected to a push pad 20 that is slidably connected to the inner wall of the loading tube 16. The loading tube 16 is located in a space above the push pad 20. A plurality of marking bullets 17 are placed. The marking bullet 17 includes a brittle wrapped shell 1701, and the interior of the brittle wrapped shell 1701 is wrapped with fluorescent pigment powder 1702. The brittle wrapped shell 1701 immediately breaks after hitting the lining, so that the fluorescent pigment powder 1702 is released to mark the cracks. The upper side wall of the loading tube 16 It is connected with an inclined bullet-filling tube 21, and the lower end outlet of the bullet-filling tube 21 is located just above the ejection tube 7. The upper end opening of the bullet-filling tube 16 is also rotatably connected with an ammunition-filling cover 22. The background processing system not only marks the cracks by relying on the flight coordinates of the inspection drone body 1, but also manually controls the inspection drone body 1 to take close photos of the cracks for confirmation, and drives the turntable 6 through the control system to adjust the ejection tube 7 to aim at the cracks, and relies on high-pressure gas to eject the marking bullet 17 onto the cracks, so as to realize visual marking of the cracks, which is convenient for researchers to find the cracks quickly and accurately, and effectively improve work efficiency; Figure 3 , 6 , 7 and Figure 8 As shown, the crack marking method of the inspection drone body 1 includes the following steps: N1. After the background processing system sends a command to let the inspection drone body 1 return to the coordinate position where the crack is detected, the background processing system manually controls the inspection drone body 1 to approach the crack, takes photos again to confirm that it is a crack, and then drives the turntable 6 through the control system to drive the ejection tube 7 to rotate and aim at the crack, and then opens the solenoid valve 8 to allow the high-pressure gas stored in the high-pressure gas storage tank 12 to instantly enter the ejection tube 7, and uses the high pressure to eject the marking bullet 17, so that the marking bullet 17 is shot onto the crack to mark it, so that researchers can find it quickly; N2. After marking the crack with the marking bullet 17, the background processing system allows the inspection drone body 1 to continue to fly forward along the original detection path, the control system restores the ejection tube 7 to a vertical state, and then drives the loading tube 16 to rotate, so that the loading tube 21 rotates to the top of the ejection tube 7. The control system then starts the electric push rod 19, the electric push rod 19 rises upward, and the push pad 20 pushes the marking bullet 17 upward. The topmost marking bullet 17 rolls down the loading tube 21 into the ejection tube 7, thereby completing the reloading, which is convenient for the next crack marking. Finally, the loading tube 16 is rotated 90° and is in a standby state to prevent the loading tube 21 from hindering the rotation of the ejection tube 7.

[0020] In view of current practical needs, the above-mentioned implementation mode adopted in this application is not limited to the scope of protection. Various changes made within the knowledge scope of technical personnel in this field without departing from the concept of this application still fall within the scope of protection of the present invention.

Claims

1. A method for detecting cracks in railway tunnel construction based on machine vision, characterized in that: The following detection steps are included: S1. Preliminary preparation: Debug the flight parameters of the inspection drone body (1) used for crack detection to ensure that the inspection drone body (1) can fly safely and smoothly, and then connect the inspection drone body (1) with the data and network transmission routes of the background processing system and the control system to ensure stable data transmission and remote control flight network connection; S2, crack detection: the inspection drone body (1) automatically flies at a low and uniform speed in the middle of the railway tunnel, and the inspection drone body (1) continuously takes pictures of the tunnel lining with the multiple high-definition cameras (4) carried by it to obtain images. While the multiple high-definition cameras (4) are taking pictures, the inspection drone body (1) embeds the flight coordinates into the image information, and then the inspection drone body (1) transmits the obtained images to the background processing system while flying; S3, crack marking: the background processing system performs image comparison and analysis. Once the existence of cracks is detected, the background processing system immediately sends the coordinate information on the image to the inspection drone body (1), so that the inspection drone body (1) stops moving forward and flies back to the coordinate position sent by the background processing system, so as to take close-up photos and obtain clearer crack images to avoid misjudgment. When taking close-up photos, the inspection drone body (1) maintains a sufficient safe distance from the lining to prevent the wings from hitting the lining; The upper side wall of the inspection drone body (1) is fixedly connected to a detection seat (2) via a bracket, and the upper side wall of the detection seat (2) is fixedly connected to a fan-shaped seat (3), a plurality of high-definition cameras (4) are installed on the fan-shaped seat (3) and are distributed around the inspection drone body (1). An image preprocessor (15) electrically connected to the high-definition camera (4) is installed at the bottom of the inspection drone body (1), an aiming adjustment slot (5) is provided on the fan-shaped seat (3) on the left side of the high-definition camera (4), and a clearance slot (201) is provided on the side wall of the detection seat (2) below the aiming adjustment slot (5). A turntable (6) is rotatably connected to the side wall of the adjustment groove (5), and a driving motor whose output end is connected to the turntable (6) is installed in the clearance groove (201); an ejection tube (7) is fixedly connected to the upper end of the turntable (6), and a solenoid valve (8) is fixedly embedded in the bottom of the ejection tube (7); an ejection seat (9) is slidably connected to the inner wall of the ejection tube (7), and a buffer pad (10) is connected between the lower end of the ejection seat (9) and the bottom of the ejection tube (7); a high-pressure gas tank (12) is inserted into the side wall of the detection seat (2), and a solenoid valve (8) is fixedly embedded in the inner wall of the detection seat (2) and is threadedly connected to the high-pressure gas tank (12). The gas tank connecting valve (13) is connected to the solenoid valve (8) and the gas tank connecting valve (13) via a high-pressure hose. The ejection tube (7) is also fixedly connected to a laser indicator (14) on one side of the ejection port thereof. The detection seat (2) is provided with a driving cavity (202) on the inner wall close to the aiming adjustment groove (5). A loading tube (16) extending to the upper side of the aiming adjustment groove (5) is rotatably connected in the driving cavity (202). A gear plate (18) is fixedly sleeved on the outer wall of the loading tube (16) located inside the driving cavity (202). An output end and the gear plate (18) are installed in the driving cavity (202). ) connected to a driving motor, the driving chamber (202) being located at the bottom of the loading tube (16) and being equipped with an electric push rod (19), and the output end of the electric push rod (19) being connected to a bullet pushing pad (20) which is slidably connected to the inner wall of the loading tube (16), a plurality of marking bullets (17) being placed in a space above the bullet pushing pad (20) of the loading tube (16), the upper side wall of the loading tube (16) being connected to an inclined bullet filling tube (21), and the lower end outlet of the bullet filling tube (21) being located just above the ejection tube (7), and a bullet replenishing cover (22) being rotatably connected to the upper end opening of the loading tube (16); The crack marking method of the inspection drone body (1) comprises the following steps: N1. After the background processing system sends a command to the inspection drone body (1) to return to the coordinate position where the crack is detected, the background processing system manually controls the inspection drone body (1) to approach the crack, takes photos again to confirm that it is a crack, and then drives the turntable (6) through the control system to drive the ejection tube (7) to rotate and aim at the crack, and then opens the solenoid valve (8) to allow the high-pressure gas stored in the high-pressure gas storage tank (12) to instantly enter the ejection tube (7), and uses the high pressure to eject the marking bullet (17), so that the marking bullet (17) is shot onto the crack to mark it, so that researchers can quickly find it; N2. After the crack is marked with the marking bullet (17), the background processing system allows the inspection drone body (1) to continue to fly forward along the original inspection path. The control system allows the ejection tube (7) to return to a vertical state, and then drives the loading tube (16) to rotate, so that the loading tube (21) rotates to the top of the ejection tube (7). The control system then starts the electric push rod (19), the electric push rod (19) rises upward, and the push pad (20) pushes the marking bullet (17) upward. The topmost marking bullet (17) rolls down the loading tube (21) into the ejection tube (7), thereby completing the reloading, which is convenient for the next crack marking. Finally, the loading tube (16) is rotated 90 degrees to be in a standby state to prevent the loading tube (21) from hindering the rotation of the ejection tube (7).

2. The method for detecting cracks in railway tunnel construction based on machine vision according to claim 1, characterized in that: The inner wall of the buffer pad (10) is provided with a groove, and an elastic reset belt (11) is fixedly connected between the bottom of the groove and the lower end side wall of the ejection seat (9).

3. The method for detecting cracks in railway tunnel construction based on machine vision according to claim 1, characterized in that: The aiming adjustment slot (5) is slidably connected to the side walls on both sides of the ejection tube (7) with telescopic accordion dust covers (23), and the telescopic accordion dust covers (23) on both sides abut against the side walls of the ejection tube (7) at the same time.

4. The method for detecting cracks in railway tunnel construction based on machine vision according to claim 1, characterized in that: The marking bullet (17) comprises a brittle wrapped cartridge case (1701), and the interior of the brittle wrapped cartridge case (1701) is wrapped with fluorescent pigment powder (1702).

Images