Measuring device for measuring surface profiles in cavities

Abstract

Measuring device (1) for surface profile measurement in cavities and tubes consisting of a ring light source (2), a camera (3), a transparent tube (6), and at least one deflection module, characterized in that a) the ring light source (2) emits a narrow line in a ring shape, b) the ring light source (2), the image plane of the camera (3) and the at least one deflection module are located in the transparent tube (6), c) Ring light source (2), deflection modules and camera (3) have their beam path on a common axis (5). d) the deflection module consists of a transparent ring (12) with bevelled ends and is located in the beam of the ring light source (2). e) the deflection module deflects the beam of the ring light source (2) almost radially towards the surface to be measured. f) the beam of the ring light source (2) points in the direction of the camera (3) and the deflection module is located in between, or the beam of the ring light source (2) with deflection module points away from the camera (3). g) the transparent tube (6) is simultaneously the housing of the measuring device (1) and fastening for the ring light source (2), deflection module and camera (3). h) the cavity surface is calculated by triangulation.

Description

[0001] A measuring device (1) for measuring internal geometry and surface profiles in interior spaces, cavities, and tubes is described. The measuring device (1) allows for non-contact measurements of both the interior geometry and the profile of internal surfaces.

[0002] In the prior art, measurements are generally dispensed with and assessment is performed by optical inspection, e.g., with an endoscope. Measurements are performed by mechanically scanning the surface. Patent application DE 103 17 488 A1 describes a device for examining surfaces in confined spaces under the name Technoscope. A pivoting arm is attached to the end of an insertable shaft. This allows the surface to be scanned and the surface texture to be calculated using the geometric data from the shaft and pivoting arm. A similar technoscope is also described in patent application DE 38 23 554 A1. Here, the shaft has a measuring attachment for determining the depth of damage. Several works have appeared under the title of cavity inspection. Measurements are performed using image processing.

[0003] Such scanning methods are complex and inaccurate. Fine surface structures, such as cracks, are difficult or impossible to detect.

[0004] Published patent application WO 2012 / 059 253 A1 describes a method using an endoscope. A pattern is projected through the endoscope onto the object to be viewed, and the image projected onto the object is captured with the endoscope's camera. Triangulation methods can be used to determine the size of an object within the cavity. Due to the limited angular relationships between the projector and camera in the endoscope, profile measurement of the cavity's surfaces is not possible. The projection is not radial to the surface being measured. Furthermore, the light conditions of the projected image are weaker than with direct illumination, which can lead to problems with weakly reflective surfaces.

[0005] The present invention eliminates the need for an endoscope, and the light can reach the object surface at the required angles, preferably radially. Therefore, the present invention is particularly suitable for measuring the surfaces of cavities and their profiles. Both small-diameter cavities and larger cavities can be measured with it.

[0006] Patent CN 104 568 983 B describes a measuring system for measuring tubes. The system consists of a ring laser, a deflection prism, and a camera. However, as with all known patent applications, not all components of the measuring device are located in and attached to a transparent tube. This does not allow for a compact design, and the measuring device is therefore not intended for small cavities. Furthermore, the transparent tube is only in front of the line laser and deflection prism. The camera is located outside the transparent tube. Because not all components are located in the transparent tube, the measuring instrument is larger. This instrument is therefore not suitable for cavities with small openings or narrow bores. The 90° deflection of the laser beam is achieved by a mirrored prism. Total internal reflection is not used, which is significantly more economical.

[0007] The published patent application DE 10 2009 043 523 A1 describes an endoscope with a projection light source. The projection unit and imaging unit are integrated into one endoscope. The projection unit is not a ring light source with a narrow ring-shaped line and direct light, such as a ring laser. The rays of the projection light source are not deflected radially toward the surface to be measured. Projection light sources are less luminous than direct light sources. The surface of the entire circumference of a cavity cannot be measured in a single step.

[0008] The published patent application DE 10 2011 016 852 A1 describes a light guide with a conical deflection prism, but not in conjunction with a ring light source and for surface profile measurement of cavities.

[0009] The measuring device (1) of the present invention consists of a ring light source (2), which can be a ring laser, and a camera (3). The ring light source (2) is a light source that emits a ring-shaped beam (4) with a narrow line width. A ring light source (2) can be particularly advantageously implemented with a laser. The ring light source (2) and camera (3) have their beam path on a common optical axis (5). The ring light source (2) and camera (3) are positioned in a transparent tube (6). This transparent tube (6) simultaneously serves as a holder and housing for the measuring device (1). During the measurement, the transparent tube (6) with the ring light source (2) and camera (3) is inserted into the cavity of the measuring object (7), the interior space, or the tube to be measured. The ring light source (2) radiates a narrow circular line onto a deflection module that directs the light radially through the transparent tube (6) onto the inner wall of the measuring object (7).The light (30) of the ring light source (2) diffusely reflected from the inner wall of the measuring object (7) is recorded by the camera (3). Using the geometric data, distance between the ring light source (2) and camera (3), the angular relationships, and the camera data, the surface profile, the distance to the surface of the measuring object (7), and the diameter of a tubular measuring object (7) are calculated by triangulation. Further profile data, such as the profile depth, as well as angles, radii, and areas of the profile can be measured. The transparent tube (6) can be made of glass or other transparent materials, such as transparent plastic, e.g., PMMA or PC. The diameter of the transparent tube (6) is kept as small as possible and depends on the size of the ring light source (2) and camera (3). With the current state of the art, a smallest inner diameter of 3 mm should be possible.

[0010] Light deflection modules are required to radially radiate the light from the ring light source (2) and to measure the reflected light from the walls of the measurement object (7) at small angles with the camera (3). The light deflection modules can be implemented in various ways: The first option is to place a conical mirror (8) in front of the ring light source (2) or the camera (3). In the conical mirror (8), the outer surface of the cone is mirrored. The conical mirror (8) is positioned so that the center of the cone lies on the common optical axis (5) and the cone apex points towards the ring light source (2) or camera (3). If the angle of the cone apex is a right angle of 90°, the rays from the ring light source (2) are deflected perpendicular to the common optical axis (5). In certain cases, a deflection of less than or greater than 90° is useful.Instead of the conical mirror (8), a truncated cone-shaped mirror with a mirrored outer surface can also be used, since the cone tip is generally inactive. A second option for the light deflection modules is the use of a rod prism (9). The rod prism (9) consists of a short, round light guide rod (10) made of transparent material, which has a flat surface on one side and a prism (11) on the opposite side. The prism (11) is designed as an inverted cone that is incorporated into the material. The light is deflected radially by total internal reflection. A third option for radial deflection exists for the ring light source (2). The light from the ring light source (2) is coupled into a transparent ring (12) on one side. On the other side, the transparent ring (12) is beveled so that the ring becomes linearly shorter from the outside to the inside. Here, too, the light is emitted radially by total internal reflection.This transparent ring (12) can be very short and integrated as a miniature component directly into the ring light source (2). This is particularly advantageous for a ring laser. This results in a radial, ring-shaped laser. The various deflection module options can be combined in various ways.

[0011] To obtain an accurate metric measurement, the measuring device (1) must be calibrated using a calibration standard (13). The calibration standard (13) preferably has a regular profile (14) on the inside of a ring.

[0012] To suppress extraneous light, a filter (15) tuned to the spectral emission of the ring light source (2) can be mounted in front of the camera (3). This is particularly advantageous when the ring light source (2) is a narrowband ring laser.

[0013] Moving the measuring device (1) inside a tube or a pipe produces a three-dimensional scan of the interior or surface of the tube. An insertion aid can be used to move the measuring device (1) inside a tube. This can be an extension of the transparent tube (6). A scale attached to the transparent tube (6) indicates the position of the measurement in the tube. The measuring device (1) can be moved manually or by a defined drive.

[0014] The camera (3) is advantageously placed on the side with the insertion aid so that the power and data lines (16) of the camera (3) do not interfere with the measurement result. The ring light source (2) can be installed in various ways. If the ring light source (2) shines towards the camera (3), the conical mirror (8) is located between the camera (3) and the ring light source (2). In this case, the ring light source (2) is powered by a built-in rechargeable battery (17) or battery (18). If the ring light source (2) shines away from the camera (3), the conical mirror (8) for the ring light source (2) is located in front of the ring light source (2) at the end of the transparent tube (6). In this case, the power supply can be provided in various ways. One possibility is via a built-in rechargeable battery (17) or battery (18). With this setup, the measuring device (1) must be removed when changing or charging the battery.Another possibility is inductive coupling using a coil (19) around the camera (3) and a second coil (19) around the ring light source (2). This is possible with this setup due to the short distance between the camera (3) and the ring light source (2). The setup enables the measurement of the end wall (20) of the measurement object (7) up to the end of the tube. The transition from the tube to the end wall (20) can also be measured. If the ring light source (2) has a battery (17) for power supply and a coil (19), the battery (17) can be inductively charged with an external charger (21) which also contains a coil (19). This arrangement has the advantage that the two coils (19) can be located close to one another.

[0015] The advantage of the invention is a compact design that allows the profile of internal surfaces in confined spaces to be measured with great accuracy using a ring light source (2) and camera (3). The non-contact method also allows sensitive surfaces to be measured. By attaching it to a mobile system, it can be used to measure pipe systems and precisely measure the size of damaged areas. Corrosion on pipes can be determined metrologically. Changes in internal pipe diameters can be measured. If the measurements are taken at different time intervals, changes over time can be determined. In this way, for example, changes in tunnel walls in mines can be recorded. Another area of ​​application is the measurement of diameters and surfaces of boreholes as well as measurements of threaded bores.

[0016] In a special embodiment, the measuring instrument (1) can be mounted on a remote-controlled or wired vehicle (22) with an autonomous or wired power supply (23), a radio device (24) or cable for transmitting the camera data, and a device for determining position or distance. Such a measuring system (25) is particularly suitable for inspecting and measuring pipe or pipeline systems (26). Explanation of the invention based on drawings Fig. Figure 1 shows the basic structure of the measuring device (1). A camera (3) with electronics (27) is located in a transparent tube (6), which also serves as a holder and housing for the measuring device (1). The camera (3) is attached and centered in the transparent tube (6) with a holder (28). The holder (28) can be glued or screwed into the transparent tube (6). Opposite the camera (3) is the ring light source (2), preferably a ring laser with a power supply in the form of a rechargeable battery (17) or battery (18). The ring light source (2), rechargeable battery (17), or battery (18) are connected to the transparent tube (6) with a holder (28). The ring-shaped beam (4) of the ring light source (2) falls on the conical mirror (8), which is attached and centered in the transparent tube (6) with another holder (28). In this case, the conical mirror (8) has a right angle at the cone tip.The camera (3), ring light source (2), and conical mirror (8) lie on a common optical axis (5). The conical mirror (8) deflects the ring-shaped beam (4) of the ring light source (2) radially to the common optical axis (5). The radial beam (29) strikes the inner wall of the measuring object (7). The camera (3) measures the light (30) of the ring light source (2) diffusely reflected from the inner wall of the measuring object (7). The camera (3) and the radial beam (29) are at a fixed, defined distance. From the distance and the angular relationship (31) determined by the camera measurement, the radius and surface profile can be calculated by triangulation. The small offset of the diffusely reflected light (30) due to refraction on the walls of the transparent tube (6) can be calculated out. Fig. Figure 2 shows the ring light source (2), which emits a ring-shaped beam (4). A light ring (33) is created on a ground glass screen (32). The line width of the light ring (33) should be as small as possible. Using a ring laser as the ring light source (2), the steel profile shown can be directly generated as a light ring (33). Fig. 3 shows the structure as in Fig. 1 but with an additional conical mirror (34) in front of the camera (3). The light (30) diffusely reflected from the walls of the measuring object (7) is guided to the camera (3) via the conical mirror (34) in front of the camera (3). This allows the central area of ​​the camera (3) to be used. The conical mirror (34) in front of the camera (3) and the conical mirror (8) in front of the ring light source (2) have a common holder (28), so that the camera (3), ring light source (2), conical mirror (8) in front of the ring light source (2) and conical mirror (34) in front of the camera (3) have a common axis (5). Fig. Figure 4 shows another variant of the measuring device (1). Here, the recording direction of the camera (3) and the radiation of the ring light source (2) are in the same direction. The conical mirror (8) is attached to the end of the transparent tube (6) with a holder (28). The ring light source (2) located behind it radiates onto the conical mirror (8) and thus radially (29). The ring light source (2) is attached to the transparent tube (6) with a holder (28) and is powered by a battery or rechargeable battery (17). The digital camera (3) is located behind the ring light source (2) and records the diffusely reflected light (30) from the wall of the measuring object (7) at a large angle. This arrangement has the advantage that, with a tube end wall (20) or a tube end, measurements can be taken close to the end area. The disadvantage of this arrangement is that the measuring device (1) must be disassembled when changing the battery or recharging the battery.The figure also shows the common optical axis (5) and the electronics of the camera (27). Fig. 5 shows another variant of Fig. 4. The conical mirror (8) has an angle (35) greater than 45°. This enables annular radiation (36) and thus measurement in the corners of the tube end (37). This arrangement enables measurement of the profile surface up to the end of the tube. The transition (37) to the end wall (20) can also be measured. Fig. 6 shows a variant of Fig. 4 and Fig. 5 without the disadvantage of disassembling the measuring device (1) when changing or charging the battery. In this setup, a coil (19) is located around the ring light source (2) and around the camera (3). Since the distance between the camera (3) and the ring light source (2) is small, an inductive current transfer from the camera coil (19) to the ring light source coil (19) is possible. Otherwise, the setup and the designations are as in Fig. 4 or Fig. 5. Fig. Figure 7 shows an alternative to the conical mirrors (8). The conical mirror (8) is replaced by a transparent, round light guide rod (10), which is attached to the ring light source (2) or the camera (3) with a flat surface. On the opposite side, the light guide rod (10) has a prism (11). The prism (11) is designed as an inverted cone. The surfaces of the light guide rod (10) are polished. The beam is deflected to the outer walls by total internal reflection. Fig. Figure 7a shows the arrangement for the ring light source (2). Here, the prism (11) preferably has an angle of 45° for radial emission (29). The light guide rod (10) covers the exit area of ​​the ring light source (2). It can be attached by a lateral projection on the ring light source (2). The annular beam (4) of the ring light source (2) is coupled into the flat side of the light guide rod (10) and deflected, preferably radially outward, by total internal reflection at the prism (11). Fig. Figure 7b shows the arrangement for the camera (3). The light guide rod (10) is mounted on the lens of the camera (3). The angle of the prism (11) is greater than 45° in this case. The light guide rod (10) can be glued to the lens of the camera (3) using optical adhesive, or it can be attached as with the ring light source (2). The light path (38) leads from the measurement object (7) (not shown here) to the prism (11) of the light guide rod (10) and is deflected by total internal reflection to the central area of ​​the camera (3). Also shown in Fig. 7a and Fig. 7b. the common optical axis (5), the transparent tube (6), mounts (28) and the camera electronics (27). Fig. Figure 8 shows the detail of the coupling of light from the ring light source (2) with an annular beam (4) into the flat end of a transparent ring (12) and the radial coupling out at the other end of the tube via 45° slopes. The light path (38) is shown. The optical axis (5) is also shown. Fig. 9 shows an application of the Fig. 8 shown coupling of light from the ring light source (2) into a transparent ring (12) combined with a light guide rod (10) in front of the camera (3). Fig. Figure 10 shows another version of the measuring instrument (1) with the option of externally charging the battery (17) of the ring light source (2). A coil (19) is mounted around the ring light source (2), located as close as possible to the transparent tube (6). A charger (21) has a cylindrical opening (40) into which the measuring instrument (1) can be inserted. A coil (19) is also located around the cylindrical opening (40) in the charger (21). This allows the internal battery (17) to be inductively charged with the charger (21). The other versions of the measuring instrument (1) in this figure correspond to the versions shown in the previous figures, in particular with the Fig. 7 details shown. Fig. Figure 11 shows a possible calibration standard (13). A regular calibration profile (14) is applied to the inside of a calibration ring (39). In the case shown, these are defined and measured equidistant prisms. By measuring this ring with the measuring instrument (1), a metric calibration of the measuring instrument is possible. Fig. Figure 12 shows a specific application of the measuring instrument. In this specific application, the measuring instrument (1) can be mounted on a remote-controlled vehicle (22) with a drive system (41). This remote-controlled vehicle (22) can be equipped with an autonomous power supply (23), a radio device (24) for transmitting the camera data, and a device for determining position or distance (42). Such a measuring system (25) is particularly suitable for inspecting and measuring pipe or pipeline systems (26). Designations internal geometry measurement 1 measuring device 2 ring light source . 3 Camera 4 annular beam 5 Optical axis 6 Transparent tube 7 Measurement object 8 conical mirrors 9 Rod prism 10 light guide rod 11 Prism 12 transparent rings 13 Calibration standard 14 regular profile 15 filters 16 supply and data lines 17 Battery 18 Battery 19 coil 20 End wall 21 external charger 22 wired vehicle 23 wired power supply 24 radio equipment 25 measuring system 26 piping systems 27 Electronics 28 Bracket 29 radial beam 30 diffusely reflected light 31 Angle relationship 32 focusing screen 33 Light ring 34 conical mirrors 35 angles 36 annular radiation 37 tube termination 38 Light path 39 Calibration ring

Claims

[1] Measuring device (1) for surface profile measurement in cavities and tubes consisting of a ring light source (2), a camera (3), a transparent tube (6), and at least one deflection module, characterized by , that a) the ring light source (2) emits a narrow line in a ring shape, b) the ring light source (2), the image plane of the camera (3) and the at least one deflection module are located in the transparent tube (6), c) Ring light source (2), deflection modules and camera (3) have their beam path on a common axis (5). d) the deflection module consists of a transparent ring (12) with bevelled ends and is located in the beam of the ring light source (2). e) the deflection module deflects the beam of the ring light source (2) almost radially towards the surface to be measured. f) the beam of the ring light source (2) points in the direction of the camera (3) and the deflection module is located in between, or the beam of the ring light source (2) with deflection module points away from the camera (3). g) the transparent tube (6) is simultaneously the housing of the measuring device (1) and fastening for the ring light source (2), deflection module and camera (3). h) the cavity surface is calculated by triangulation. [2] Measuring device (1) according to claim 1, characterized by that the ring light source (2) is a ring laser. [3] Measuring device (1) according to claim 1, characterized by that the transparent tube (6) is a glass tube. [4] Measuring device (1) according to claim 1, characterized by that the transparent tube (6) is a tube made of transparent plastic. [5] Measuring device (1) according to claim 1, characterized by that the transparent tube (6) is an optical fiber. [6] Measuring device (1) according to claim 1, characterized bythat the deflection module is a conical mirror (8) with mirrored lateral surfaces. [7] Measuring device (1) according to claim 1, characterized by The deflection module is a light guide rod (10) made of transparent material with a flat side and a prism (11) on the opposite side. The prism (11) is designed as an inverted cone that is incorporated into the material. [8] Measuring device (1) according to claim 1, characterized by that a second deflection module is located in front of the camera (3) and directs the light from the measuring object (7) at small angles to the camera (3). [9] Measuring device (1) according to claim 1 and 2, characterized by that the ring light source (2) is equipped with a battery or rechargeable battery. [10] Measuring device (1) according to claim 1 and 2, characterized by The ring light source (2) is powered by induction. A coil (19) is located around the camera lens (3) and the light source housing. [11] Measuring device (1) according to claim 1 and 2, characterized by The battery (17) of the ring light source (2) is charged inductively using a charger (21). A coil (19) is located in the charger (21) and around the ring light source (2). [12] Measuring device (1) according to one of claims 1 and 8, characterized by that the calibration is carried out using a ring as a calibration standard (13) with a regular calibration profile (14). [13] Measuring device (1) according to one of claims 1, 8 and 12, characterized by that a filter (15) for suppressing extraneous light is mounted in front of the camera (3). [14] Measuring device (1) according to one of claims 1, 8, 12 and 13, characterized by that the measuring device (1) mounted on a vehicle forms a measuring system (25) for inspecting and measuring pipe and pipeline systems (26).

Images