Sewer pipe inspection device and method for inspecting sewer pipes

Abstract

A sewer pipe inspection device (10), which has a device for determining the diameter, comprising a bracket (20) and a camera (30) pivotable about a first angle (α) relative to this bracket (20), and a point light source (40) attached to the bracket (20), which emits in a pivot plane of the camera (30) at a second angle (β) to a feed axis (F) of the sewer pipe inspection device (10) and which is mounted at a distance (α) from the camera (30), characterized in that the measuring and control circuit (50), for automatically determining the position of a light point (L) emitted by the point light source (40) and reflected from an inner wall of a sewer pipe in an image (P) captured by the camera (30), is designed such that an analog video signal (S) from the camera (30) is evaluated to determine this position, and that the measuring and control circuit (50) is further designed to based on the position of the light point (L) in the image (P), the camera (30) is automatically tilted by the first angle (α) so that the light point (L) is centered in this image (P), to capture the first angle (α) and to determine the diameter based on this first angle (α).

Description

[0001] The present invention relates to a sewer pipe inspection device according to the preamble of claim 1 and a method for inspecting sewer pipes according to the preamble of claim 7.

[0002] German patent DE 196 51 433 C1 shows a camera tube carriage with a chassis, a housing, a bracket rotatable to the housing by a defined angle γ, a camera mounted on the bracket so as to be pivotable to it by a first angle α, and a point light source placed on the bracket and emitting light in the plane of rotation of the camera at a second angle β to the axis of rotation of the bracket.

[0003] To determine the height h, i.e. the distance between the axis of rotation of the mount and the pipe wall, the remotely controlled camera is swivelled by an operator until the optical axis of the camera points to the light point, i.e. the light point appears in the middle of the monitor image observed by the operator.

[0004] The distance between the pipe wall and the axis of rotation of the bracket is then calculated as follows: h=a∗tan α*tan βtan α+tan β, where α represents the distance between the imaginary intersection point of the point light ray with the axis of rotation of the mount and the intersection point of the camera's pan axis with the axis of rotation of the mount; thus, like the angle α, it is a fixed value. The angle β is the angle formed by the optical axis of the camera with the axis of rotation of the mount after the mount has been panned onto the point light.

[0005] To determine the diameter of a circular tube, the holder must be rotated 180° and the process repeated; the diameter is then the sum of the measurements. To measure non-circular tubes, multiple measurements (at least three) are required.

[0006] With simple sewer pipe inspection devices, however, the camera movements often cannot be controlled precisely enough due to the operating elements. This leads to measurement inaccuracies that significantly reduce the reliability of the method, or at the very least make the device cumbersome and difficult to use. Furthermore, the video display on these devices is often designed in such a way that a crosshair cannot be easily superimposed. In addition, basic devices lack a processing unit that would allow for comprehensive data analysis.

[0007] DE 203 08 761 U1 discloses a sewer inspection vehicle for inspecting sewer pipes, in which a light source is arranged in a marking plane perpendicular to the longitudinal axis of the vehicle, and a camera is positioned such that the marking plane lies within its field of view. Furthermore, the sewer inspection vehicle has two marking heads spaced apart from each other and arranged in the marking plane at a defined distance. In the camera's video image, the marking heads and the light reflections of the light source on the sewer pipe wall are marked, and software compares the marked distances with the distance between the marking heads. This method thus requires complex image analysis, and the length comparison carries the risk of inaccuracies.

[0008] The object of the present invention is to enable a simple, yet accurate and reliable determination of the diameter of a sewer pipe automatically, even with simple sewer pipe inspection devices that do not allow sensitive manual control of the camera and / or do not have a computing unit for data evaluation.

[0009] This problem is solved according to the invention by a sewer pipe inspection device with the features specified in claim 1 and a method with the features specified in claim 6. Advantageous embodiments of the invention will become apparent from the dependent claims, the following description, and the drawings.

[0010] The sewer pipe inspection device according to the invention includes a device for determining the diameter of the sewer pipe. This device comprises a swiveling camera, which is swiveling at a first angle α relative to a bracket transverse to the longitudinal axis of the bracket or to the feed axis of the sewer pipe inspection device. Such swiveling cameras are common in sewer pipe inspection devices to allow viewing of the pipe wall and, optionally, also in the feed direction. Furthermore, the bracket can be rotatable about its longitudinal axis or the feed axis of the sewer pipe inspection device to allow viewing of the pipe wall over a 360° angle. For diameter determination, a point light source is also provided, which is inclined at a second angle β relative to the longitudinal axis of the bracket or the feed axis of the sewer pipe inspection device, so that it shines towards the pipe wall.This second angle β is preferably a fixed angle, but can also be an adjustable angle, in which case the angle can be determined in a suitable manner. The point light source is arranged at a defined distance from the camera. Furthermore, a measuring and control circuit is provided which, based on the first and second angles and the distance between the camera and the point light source, can determine the distance of the inner wall of the sewer pipe from the support and, based on this distance, the pipe diameter. The pipe diameter can be determined by several distance measurements or by knowing the distance of the support's central axis from the underside of the sewer pipe.

[0011] As an alternative to angle measurement, the first angle α, i.e., the camera's pan angle, can be adjusted via a stepper or servo motor, allowing the desired pan angle to be detected directly above the actuator. The detected angle α is then fed to the measuring and control circuitry for calculating the diameter or distance.

[0012] According to the invention, the measuring and control circuit is designed to detect the first angle α, i.e., the swivel angle of the camera, in order to then determine the distance or diameter on the basis of this angle.

[0013] The sewer pipe inspection device according to the invention comprises a measuring and control circuit designed to automatically determine the position of a light point emitted by the point light source and reflected from the inner wall of a sewer pipe within an image captured by the camera. To determine this position, an analog video signal from the camera is evaluated. Furthermore, the measuring and control circuit is designed to automatically pan the camera based on the position of the light point in the image so that the light point is centered within the image. Thus, as in the prior art, a light point is used to measure the sewer pipe diameter. However, the solution according to the invention provides for its surprisingly simple detection and subsequent centering within the camera image, enabling complete automation of the entire measurement process.The second angle β, at which the point light source emits light, does not need to be fixed; the light source can also be mounted in a pivotable manner. However, the device according to the invention can be designed more simply by fixedly orienting the point light source. It is only important that the second angle β is known, as it is used to calculate the inner diameter of the pipe. Determining the respective emission angle β, swivel angle α of the camera, and, if applicable, rotation angle γ of the mount with respect to the feed axis is carried out in the usual way, e.g., by using a potentiometer or an angle encoder mounted on the respective axes.

[0014] The position of the light point in the analog video image or video signal can be determined, for example, by adding up the lines that were traversed before it appeared in the image. No additional processing unit, such as a PC, is required for this. However, a particularly simple, accurate, and reliable determination of the light point's position in the camera image is possible if the measuring and control circuit is designed to determine the light point's position from the propagation time of the analog video signal during the line-by-line construction of the image captured by the camera. This requires only simple electronic circuits, which also do not require any additional processing unit. To measure a sewer pipe diameter, only the required light point in the camera image needs to be automatically determined, automatically centered in the image by panning the camera, and, if necessary, adjusted.The required measuring points are reached by swiveling the camera around the feed axis. No operator intervention is required during the entire measurement process.

[0015] Preferably, the detection of the light point in the camera image is made possible by the measuring and control circuit being designed to switch off a light source mounted on the sewer pipe inspection device before the position of the light point emitted by the point light source is determined. This makes the light point stand out clearly from its (co-)captured dark background, and its signal is easily detectable in the camera's analog video signal. The light source does not necessarily have to be attached to the mounting of the sewer pipe inspection device, but can also be mounted elsewhere on the housing of a sewer pipe inspection device in a known manner or be designed as a separate light source. The only important thing is that such a light source is switched off before the measurement of the sewer pipe diameter according to the invention in order to achieve the aforementioned advantages.This is because the image captured by the camera then consists only of the laser point itself. Even further improved detectability of the light point is possible if the point light source is a laser light source.

[0016] A further advantage of the sewer pipe inspection device according to the invention is that it can be designed as either a mobile or a pushable sewer pipe inspection device. This allows for flexible use depending on the diameter of the sewer pipe to be inspected. A mobile device has wheels that allow it to be moved within the sewer pipe, while a pushable device has a push camera that can be advanced within the sewer pipe using a push rod. With the latter type of camera, the camera head itself is generally rotatable about the longitudinal axis or thrust axis and can be angled relative to it so that it views the pipe wall.

[0017] According to the invention, the problem is also solved by a method for inspecting sewer pipes with the sewer pipe inspection device described above, having the features specified in claim 6.

[0018] The system then analyzes an analog video signal from the camera to determine the position of the light point within the image captured by the camera. Based on this position, the camera is automatically panned to center the light point in the image. This allows for the simple automation of the entire measurement process, eliminating the need for manual operation of the device during the measurement. Consequently, the accuracy and reliability of the measurement are increased. After panning the camera, its angle α relative to the feed axis is determined. Based on the known beam angle β of the point light source and the distance α between the point light source and the camera, the distance of the pipe wall from the feed axis is calculated.

[0019] While it is theoretically possible to determine the position of the light point by adding up the lines traversed before its appearance in the image, the most accurate and reliable method is to determine the light point's position from the propagation time of the analog video signal during the line-by-line construction of the captured image. Due to its surprising simplicity, this method can also be easily automated. By rotating the holder around the feed axis by a defined angle γ and repeatedly centering the light point in the camera image, pipe diameter determination can be performed automatically without any further operation.

[0020] It is advantageous to switch off the lighting of the sewer pipe inspection device before determining the position of the light point in the image, because this makes it very easy to detect the occurrence of the point in the analog video signal of the camera, since the light point then represents the only image information in the form of a bright point in the otherwise dark image.

[0021] The present invention is explained in more detail below with reference to an exemplary embodiment and the accompanying figures. Identical or equivalently functioning parts are designated with the same reference numerals. The figures show: Fig. 1A a schematic side view of a sewer pipe inspection device according to the invention, which is designed to be mobile, Fig. 1B a non-circular cross-section of a sewer pipe in which various distance measurements are applied starting from the sewer pipe inspection device according to the invention, Fig. 2A a schematic top view of a first image captured by the camera of the sewer pipe inspection device according to the invention, in which a point of light is depicted after a first transit time of the video signal, and Fig. 2B a schematic top view of a second image captured by the camera of the sewer pipe inspection device according to the invention, in which a point of light is depicted after a second transit time of the video signal.

[0022] Fig. Figure 1A shows a schematic side view of a sewer pipe inspection device 10 according to the invention, which is designed to be mobile. The device has a mount 20 rotatable about a feed axis F by an angle α and a camera 30 pivotable about an axis intersecting the feed axis F of the mount 20 by an angle α. A point light source 40 in the form of a laser light source is mounted on the mount 20, which projects a point light beam 41 onto the wall of the pipe to be measured in the pivot plane of the camera 30 at an angle α to the feed axis F (axis of rotation) of the mount 20. The distance α between the imaginary intersection of the point light beam 41 with the feed axis F of the mount 20 and the intersection of the pivot axis of the camera 30 with the axis of rotation of the mount 20 is known.

[0023] To determine the height h, i.e., the distance between the feed axis F of the bracket 20 and the pipe wall, the camera 30 is automatically pivoted by means of a measuring and control circuit 50 so that its optical axis points towards the light point L, thus centering it in the image P captured by the camera 30. The angle α by which the camera 30 is pivoted is recorded and fed to the measuring and control circuit 30 for evaluation. To improve the determination of the light point L in the image P, the usual illumination of the camera's field of view is switched off before the measurement. The distance h of a sewer pipe wall 60 from the feed axis F of the bracket 20 is then calculated in the known manner using the equation mentioned above.

[0024] The light point L in the image P of camera 30 is of particular importance, because according to the invention an analog video signal S is used for this purpose (see Fig. 2) The camera 30 is accessed and its transit time Δt until the appearance of the light point L is measured. Since the illumination was switched off beforehand, the light point P represents the only easily detectable image information in the otherwise dark image. From the transit time, the exact position of the light point P within the image P captured by the camera 30 can be determined. Because this is possible with a simple circuit, an additional processing unit such as a PC is not required. At the same time, the measurement process can be fully automated, thus significantly simplifying the handling of the device 10, avoiding operator error, and enabling faster measurement.

[0025] In this example, the device 10 is equipped with a chassis 70 to which the bracket 20 is rotatably attached. The resulting sewer pipe inspection device 80 is particularly suitable for inspecting the walls 60 of larger diameter sewer pipes. However, for inspecting smaller pipes, it is also possible to design the device 10 to be movable.

[0026] To determine the diameter of a circular tube, the holder 20 is rotated by 180° and the measurement process repeated, which can also be automated. The diameter is then calculated as the sum of the two measurements; in practice, however, at least three measurements will regularly be taken at different angles, as it cannot be guaranteed that the device 10 is located exactly in the center of the tube. Overall, this results in a fully automated diameter determination of the tube, which is equally accurate, reliable, and can be performed virtually 'at the push of a button'.

[0027] To measure non-round pipes, a plurality of measurements, i.e. at least three, must be taken, as described in Fig. Figure 1B shows a non-circular cross-section of a sewer pipe in which various distance measurements h1, h2, and h3 are plotted, starting from the sewer pipe inspection device according to the invention (the position of the bracket 20 is indicated). The rotation angle γ of the bracket 20 together with the camera 30 and the laser light source 40 is shown relative to the horizontal H. The algorithms for determining the internal profile of the pipe from the measurements are known to those skilled in the art. The determination of the respective swivel angle α of the camera 30 and the rotation angle γ of the bracket 20 is carried out in the usual manner, e.g., by a potentiometer mounted on the respective axes or by an angle encoder.

[0028] The Fig. Figure 2A shows a schematic top view of a first image P, which was captured by the camera 20 of the sewer pipe inspection device 10 according to the invention, and in which a light point L is depicted after a first transit time Δ1 of the video signal S. From this transit time Δ1, the position of the light point L is determined using the measuring and control circuit 50; here, it is horizontally centered but vertically shifted upwards. The camera 30 is subsequently panned in direction C until the light point L is centered in the image P, and the panning angle α is recorded.

[0029] The Fig.Figure 2B shows a schematic top view of a second image P, which was captured by the camera 30 of the sewer pipe inspection device 10 according to the invention, and in which a light point L is depicted after a second transit time Δt2 of the video signal S. This light point L is now shifted horizontally to the left and vertically upwards in image P, which can occur, for example, if the light beam 41 is reflected out of the panning plane of the camera 30 by irregularities in the sewer pipe wall 60. With the aid of the measuring and control circuit 50, the camera 30 is then panned in the direction of C so that the light point L is at least vertically centered in image P.

[0030] The result is a sewer pipe inspection device that allows for fully automatic and reliably accurate diameter determination of sewer pipes using simple means. Reference symbol list 10 sewer pipe inspection device 20 brackets 30 Camera 40 Point light source 41 Light beam 50 Measuring and control circuit 60 sewer pipe wall 70 Chassis of the sewer pipe inspection device 80 Sewer pipe inspection device α Distance point light source / camera P Image of the camera C Centering direction F Feed axis, rotation axis of the holder H Horizontal plane h1, h2, h3 Distance between inner wall of the sewer pipe / axis of rotation of the bracket L Light point S video signal α Angle optical axis camera / rotation axis F of the mount β Angle of emission direction Point light source / axis of rotation F of the bracket γ Rotation angle of the feed axis F Δt1, Δt2 propagation time of the video signal

Claims

[1] Sewer pipe inspection device (10), which has a device for determining the diameter, with a bracket (20) and a camera (30) which can be pivoted about a first angle (α) relative to this bracket (20), and with a point light source (40) attached to the bracket (20), which emits in a pivot plane of the camera (30) at a second angle (β) to a feed axis (F) of the sewer pipe inspection device (10) and which is mounted at a distance (α) from the camera (30), characterized by , that the measuring and control circuit (50) for automatically determining the position of a light point (L) emitted by the point light source (40) and reflected by the inner wall of a duct pipe in an image (P) captured by the camera (30) is designed such that an analog video signal (S) from the camera (30) is evaluated to determine this position, and that the measuring and control circuit (50) is further designed to based on the position of the light point (L) in the image (P), the camera (30) is automatically tilted by the first angle (α) so that the light point (L) is centered in this image (P), to capture the first angle (α) and to determine the diameter based on this first angle (α). [2] Sewer pipe inspection device (10) according to claim 1, characterized by , that the measuring and control circuit (50) is designed to determine the position of the light spot (L) from a transit time Δt of the analog video signal (S) during the line-shaped construction of the image (P) captured by the camera (30). [3] Sewer pipe inspection device (10) according to one of the preceding claims, characterized by , that the measuring and control circuit (50) is designed to switch off a light mounted on the sewer pipe inspection device (10) before the position of the light spot (L) emitted by the point light source (40) is determined. [4] Sewer pipe inspection device (10) according to one of the preceding claims, characterized by , that the point light source (40) is designed as a laser light source. [5] Sewer pipe inspection device (10) according to one of the preceding claims, characterized by , that it is designed as a mobile or pushable sewer pipe inspection device (80). [6] Method for inspecting sewer pipes using a sewer pipe inspection device (10) according to one of the preceding claims, wherein the point light source (40) emits a light beam (41) which is reflected by an inner wall of a sewer pipe and is detected by the camera (30), characterized by, that by evaluating an analog video signal (S) of the camera (30) a position of the light point (L) in the image (P) captured by the camera (30) is determined, and based on this position of the light point (L) in the image (P) the camera (30) is automatically panned so that the light point (L) is centered in this image (P). [7] Method according to claim 6, characterized by , that the position of the light point (L) is determined from the transit time of the analog video signal (S) during the line-shaped construction of the captured image (P). [8] Method according to claim 6 or 7, characterized by , that the holder (20) is rotated by a defined angle (γ) about the feed axis (F) and the centering of the light point (L) in the image (P) of the camera (30) is repeated. [9] Method according to one of the claims 6 to 8, characterized by, that the lighting of the sewer pipe inspection device (10) is switched off before the position of the light point (L) in the image (P) is determined.

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