CA3158259A1

CA3158259A1 - Borescope

Info

Publication number: CA3158259A1
Application number: CA3158259A
Authority: CA
Inventors: Jan Oke Peters; Michael Thies; Thomas Ruegg; Soren Wedow; Sven Rasche; Jens-Peter Tuppatsch; Sonke Bahr; Lukas BATH; Thorsten Schuppstuhl; Tarek Mostafa; Oliver Neumann
Original assignee: Bath Lukas; Mostafa Tarek; Ruegg Thomas; Schuppstuhl Thorsten; Tuppatsch Jens Peter; Wedow Soren; Lufthansa Technik AG
Current assignee: Lufthansa Technik AG
Priority date: 2019-11-15
Filing date: 2020-11-13
Publication date: 2021-05-20
Also published as: WO2021094533A2; WO2021094533A3; JP2023501674A; DE102019130949A1; CN114945849A; US20220404291A1; EP4058836A2

Abstract

The invention relates to a borescope (1), in particular for the borescopy of fuel chambers (58) of aircraft engines (50), and to an assembly (31) comprising a borescope (1). The borescope (1) comprises an electronic image capturing unit (20) with at least one image capturing sensor (22, 23) with a receiving cone at a first end (4) of a shaft (3) which has a shaft axis (3') and through which data and supply lines (21) for the image capturing unit (20) are guided. The image capturing unit (20) is arranged on a rotary head (10) which is rotatably secured to the first end (4) about the shaft axis (3') such that the axis (22', 23') of the receiving cone is not parallel to the shaft axis (3') on the first end (4) and a panoramic image can be captured by rotating the rotary head (10). The assembly (30) comprises a borescope (1) according to the invention and a control and analysis unit (31) which is designed to control the rotational movement of the rotary head (10) and the image capturing unit (20) and to combine the image data captured by the at least one image capturing sensor (22, 23) in order to form a panoramic image.

Description

-1.
BORESCOPE
The invention relates to a borescope, in particular for the borescopy of the combustion chambers of aircraft engines, and to an assembly comprising a borescope.
In tne prior art, it is known to use borescopes for tne inspection of industrial devices in areas which are not immediately visible. :he borescopes can be inserted into the areas in question through small openings and, either directly or via an optical unit or via a display of a video image captured by suitable sensors on the borescope tip - also called a video borescope - offer an insight into areas tnat are otherwise not visible.
Borescopy is used, for example, during tne inspection of aircraft engines, in order to obtain an insight into the interior of the engine, without having to take it apart with a great deal of effort for the purpose. Here, at least for individual areas of the aircraft engine, such as, for example, tne combustion cnamber, it is required or at least desirable to analyze and to document tne area completely.
At the current time, for the borescopy of the interior of the combustion chamber, use is made of a video borescope with a flexible shaft, which is guided manually througn tne combustion cnamber. For this purpose, tne flexible borescope is guided along the complete inner circumference of the combustion chamber and then drawn out slowly. During the withdrawal, the images captured by the borescope are recorded. In the process, it is attempted to ensure that the complete circumference of the usually ring-is:Japed combustion chamber is captured.
If a possible problem location in the combustion chamber is identified, manual 3D capture of the corresponding point with separate 3D borescopes that are suitable for the purpose can then be carried out.

-2-Because of the manual guidance of the borescope with a flexible shaft, complete and reproducible documentation of the condition of a combustion chamber is, however, barely possible. In addition, in particular tfie subsequent 3D capture of possible problem locations is very complicated and time-consuming.
It is an object of the present invention to devise a borescope with which the inspection of industrial devices, in particular of the combustion chambers of aircraft engines, can be simplified and improved.
:his object is achieved by a borescope as claimed in the main claim and by an assembly as claimed in tfie subordinate claim 12. Advantageous developments are the subject-matter of the dependent claims.
Accordingly, the invention relates to a borescope, in particular for the borescopy of tfie combustion cfiambers of aircraft engines, comprising an electronic image capturing unit witfi at least one image capturing sensor with a receiving cone at a first end of a shaft wfiicfi fias a shaft axis and through which data and supply lines for the image capturing unit are led, wherein the image capturing unit is arranged on a rotary head which is secured to the first end so as to be rotatable about tfie shaft axis such that tfie axis of the receiving cone is not parallel to tfie sfiaft axis at the first end and a panoramic image can be captured by rotating tne rotary head.
Furthermore, the invention relates to an assembly comprising a borescope as claimed in one of the preceding claims and a control and evaluation unit, which is designed to control the rotational movement of the rotary head and tfie image capturing unit and to combine the .3.
image data captured by tfie at least one image capturing sensor into a panoramic image.
The invention has recognized that, for the borescopy of industrial devices, in particular tfie combustion cfiambers of aircraft engines, it is advantageous if tfie borescope used is designed to create panoramic images - i.e. a 360 panoramic image. Once the borescope has been moved to a desired position, according to the invention the panoramic image can be created without changing the position or location of the borescope shaft.
:o this end, provision is made for tfie at least one image sensor of the image capturing unit to be arranged on a rotary fiead which can be rotated about the shaft axis.
Here "shaft axis" designates the longitudinal axis or axis of symmetry of the shaft. If the shaft axis does not extend linearly (for example in the case of a curved shaft) and/or if it is variable (for example in the case of a flexible shaft), the focus is on tfiat part of tfie shaft axis immediately at the first end of the sfiaft on which the rotary head is arranged as an axis of rotation for the rotary fiead.
The rotary range of the rotary head can be less than or equal to 3600. By means of an appropriate limitation of the rotary range, it is possible to prevent tfie data and supply lines possibly led out of the shaft as far as tfie rotary fiead from twisting or winding up during any rotation of the rotary head. Since it is simultaneously sufficient for the creation of a panoramic imace if the entire 360 range is actually captured by the receiving cone of the image capturing unit, a rotary range of less than 360 may also be sufficient, since the receiving cone regularly has an extent in tfie plane perpendicular to tfie axis of rotation of the rotary fiead, so that a complete panoramic image can nevertfieless be created.

The rotary head preferably has an internal gear, in which a pinion driven by a drive unit secured so as to be stationary and eccentric with respect to the shaft axis engages. As a result of tfie eccentric arrangement of tfie drive unit with respect to the sfiaft, tfie guidance of the data and supply lines on the sfiaft into tfie rotary head can be simplified. :he drive unit can be an electric motor, preferably a stepper motor, the supply and control lines of which can likewise be led through the shaft.
The rotary head preferably comprises a co-rotating cylindrical fiousing fiaving at least one transparent window, in which the image capturing unit is arranged in such a way tfiat tfie receiving cone of eacfi image capturing sensor is respectively aimed through a transparent window. The image capturing unit is protected by the housing while, because of the co-rotating window provided therein, no restriction is to be expected with regard to the image capture at any desired angular positions of tfie rotary fiead.
Alternatively, a cylindrical housing tfiat is stationary at the first end with respect to the shaft axis, surrounds the rotary head and has at least one transparent ring segment can be provided, wherein the receiving cone of each image capturing unit is respectively aimed tfirougfi a transparent ring segment, wfierein, for eacn individual image capturing sensor (respectively) a separate ring segment can be provided and/or the receiving cone of a plurality of image capturing sensors can be aimed through a common ring segment. In this case, although the housing is stationary, because of the at least one ring segment, the image capture by the image capturing sensor is not impaired in any angular position of the rotary -lead.

.5.
In both cases, the housing has a cylindrical shape. :he housing can thus be viewed as a rigid continuation of the shaft, with which in particular the insertion of the borescope according to the invention into a borescope opening is simply possible. The external diameter of tfie housing can preferably correspond approximately to tfie external diameter of the shaft.
The housing - in both the aforementioned embodiments -is preferably encapsulated in a liquid-tight manner. The borescope can also be used for liquid-filled cavities without the image capturing unit or other components of the borescope in the area of its tip coming into direct contact witfi tfie liquid and being damaged as a result.
It is preferred for the image capturing unit to comprise at least two image capturing sensors spaced apart from one another, preferably in the direction of the shaft axis, having receiving cones at least partly intersecting and/or aimed parallel to each other for determining 3D
information by means of triangulation. Since the two image capturing sensors of tfie pair spaced apart from each other capture a common image section, with tfie aid of triangulation it is possible to determine 3D
information about the spacing of the image points received by the two image capturing sensors, which can be combined later to form a 3D model of the borescoped area. Suitable triangulation metfiods are known from tfie prior art.
It is preferred for the image capturing sensors of a pair provided for the triangulation to be arranged with a center spacing of 15 mm to 25 mm, preferably of 17 mm to 22 mm, more preferably of about 20 mm. Alternatively, a center spacing of 5 mm to 15 mm, preferably 7 mm to 12 mm, more preferably 10 mm to 11 mm is preferred. "Center spacing" designates tfie spacing of the two sensor centers relative to each other. Inc accuracy of tne determination of the 3D data with the aid of triangulation depends on the spacing of the two image capturing units, the limited available installation space and optical distortions because of the regularly only small spacing of the capture plane from tne image capturing unit being limiting factors. The aforementioned spacings have proved to be advantageous in particular for tne use of the borescope according to the invention for the inspection of aircraft engines.
The image capturing sensors can be arranged and/or configured in sucn a way tat tne receiving cone of one or two image capturing sensors provided for the capture of 3D information is/are arranged witn a predefined viewing angle to the longitudinal axis of the image capturing unit. If this viewing angle is 900, areas at the side of the image capturing unit can be captured. By means of a different selection of the viewing angle differing from 90 , areas located in front in the insertion direction of the baroscope (angular range of 300 - 90 ) or areas located further back (angular range 90 - 150 ) can be captured. However, it is also possible to provide a plurality of image capturing sensors or pairs of image capturing sensors provided for trianculation, which each have different viewing angles, an a single borescape. In particular, two pairs of image capturing sensors can be provided, wherein the receiving cones of the two image capturing sensors of one pair can be aimed at a different viewing angle witn respect to the shaft axis than the receiving cones of the two image capturing sensors of the other pair.
The image capturing unit can comprise at least one image capturing sensor for capturing color images. The color images captured by this at least one image capturing sensor can be used directly as a panoramic image.

However, it is also possible for an item of 3D information determined on the basis of gray-value images captured by one pair of image capturing sensors to be supplemented with the color information from a color image capturing sensor, in order thus to obtain color 3D information or a color 3D model. :he use of gray-value image capturing sensors for determining 3D information may be advantageous because of tne higher resolution as compared with color image capturing sensors of an identical sensor size.
The image capturing sensors are preferably CCD sensors or CMOS sensors, preferably with a global snutter. :he image capturing sensors preferably nave a resolution of 400 x 400 pixels to 2400 x 2400 pixels, an image repetition rate of up to 240 frames per second and/or an angle of field of 30 to 120 , preferably 35 to 65 , more preferably of 400, 50 or 60 , in each case 5 , preferably in each case 3 . By using appropriate image capturing sensors, continuous capture of image information is in particular also possible.
It is preferred if at least one light source, preferably an LED, is arranged on the rotary head to illuminate the capture area. As a result of arranging the light source directly on the rotary head, good illumination and lighting of the capture area can be ensured, irrespective of tne angular position of the rotary nead. The at least one lignt source can emit visible light and/or infrared radiation, depending on the wavelengtn range for wnicn the image capturing sensors are designed. It is of course also possible to provide a plurality of different light sources, for example one for the visible and one for the infrared range. The use of LEDs as light sources is particularly preferred because of tne low development of heat and tne low energy consumption.

:he shaft of the borescope can be rigid, semi-flexible or flexible. If the shaft is flexible, the borescope can, for example, be led through a guide tube. The guide tube can be part of the borescope or of a separate guide device. Via the guide tube, tfie fundamental position of the baroscope or its image capturing unit in tfie interior of tfie area to be borescoped can be defined. The shaft can also be provided witfi control cables, wfiich permit control of the shaft. However, it is also possible to guide the borescope having a flexible shaft loosely throuch an area to be recorded and to create the desired recordings in particular during the withdrawal of the borescope.
In tfie assembly according to the invention, a control and evaluation unit connected to the borescope according to the invention is provided, with which the rotational movement of the rotary head and the at least one image capturing unit is controlled and with which the individual images captured by the at least one image capturing sensor can be combined into a panoramic image.
:he assembly can be designed for continuous capture by the image capturing sensors during rotation of the rotary head. In other words, in a short sequence - as a rule predefined only by the speed of the image capturing sensors - images are captured as the rotary fiead rotates.
Appropriate continuous capture permits a fiigfi quality in the panoramic image assembled on the basis of these images.
Alternatively, it is possible that the assembly is designed to capture individual images by the image capturing unit at angular positions reached one after another during rotation of tfie rotary head. Inc angular positions should be chosen such that the individual images can continue to be combined into a panoramic image. As compared witn continuous capture by tne image capturing sensors, the quantity of data to be processed is smaller in this alternative.
The control and evaluation unit is preferably designed to combine two partly overlapping panoramic images. By combining overlapping panoramic images, an enlarged panoramic image can be created. :he control and evaluation unit can also be used to control the change in the position of the rotary head, from each of which a panoramic image is to be captured. Suitable controllable guide devices for this purpose are known in the prior art.
:he combining of individual images into panoramic images or of individual panoramic images into an enlarged panoramic image comprises the combining of the associated 3D information, if this has been determined by the borescope or by the control and evaluation unit. In this way, a 3D model of the borescoped area is produced.
:he invention will be described by way of example by using advantageous embodiments with reference to tne appended drawings, in which:
Figure 1 shows a schematic illustration of the borescope tip of a first exemplary embodiment of the borescope according to tne invention;
Figure 2 snows a scnematic illustration of the borescope tip of a second exemplary embodiment of a borescope according to the invention; and Figure 3 shows a schematic illustration of an assembly according to the invention comprising a borescope according to figure 1 or 2.

Figure 1 shows, scnematically, tne tip 2 of a borescope 1, which tip is inserted into the areas to be examined.
The 3orescope 1 comprises a flexible shaft 3, controllable via control cables, which is merely indicated in figure 1. At the first end 4 of tne snaft 2, close to tne tip, tnere is arranged a rotary nead 10, which is mounted via a bearing 11 such tnat it can rotate about the shaft axis 3'. The snaft axis 3' is designated the axis of symmetry of the shaft 3, wherein the axis of rotation 10' of the rotary head 10 coincides with the shaft axis 3' directly at the first end 4 of the shaft

3, so that the remaining instantaneous shape of the flexible shaft 3 does not matter. If tne shaft axis 3' is mentioned below, the part of tne shaft axis 3' directly adjacent to tne first end 4 of tne snaft 3 is meant.
On the bearing 11, a stepper motor is secured in a fixed location with respect to the shaft 3 and its shaft axis 3' as a drive unit 12. The drive unit 12 is arranged eccentrically relative to tne shaft 3, so tnat sufficient space remains for data and supply lines 21 to be led througn from the shaft 3 into tne rotary head 10. The drive unit 12 is connected to control and supply cables 13, which are likewise led through the shaft 3 and via which the drive unit 12 can be controlled.
The drive unit 12 engages witn a pinion 14 in an internal gear 15 on tne rotary head 10 (botn illustrated only schematically), and can tnus rotate tne rotary nead 10 about its axis of rotation 10' and tne snaft axis 3'. The range of rotation of the rotary head 10 is limited by suitable stops to about 280 , in order to prevent the data and supply lines 21 butting against the possibly heat-developing drive unit 12 or twisting.

:he rotary head 10 comprises a co-rotating cylindrical housing 16 with a transparent window 17. The housing 16 is encapsulated in a liquid-tight manner.
Arranged in the interior of tne rotary nead 10 or its housing 16 is an image capturing unit 20, which is attached to tne data and supply lines 21.
The image capturing unit 20 comprises two gray-value image capturing sensors 22 which are spaced apart from one another and the receiving cones of which intersect in such a way that 3D information for the overlapping area can be derived from tne images from the two image capturing sensors 22 by triangulation. Furtnermore, a color image capturing sensor 23 is provided, which likewise captures the overlapping area of the two other image capturing sensors 22. The color image information from the image capturing sensor 23 can be used to enhance the 3D information obtained via the two other image capturing sensors 22 witn color information. Appropriate methods for tnis purpose are known in the prior art.
:he image capturing unit 20 also comprises two LEDs as light sources 24, with which the capture area of the individual image capturing sensors 22, 23 can be adequately lit.
:he image capturing unit 20 is arranged within the housing 16 of the rotary head 10 such tnat botn tne image capturing sensors 22, 23 capture the surroundings tnrougn the transparent window 17, and also the light sources 24 can illuminate the surroundings through the transparent window 17.
:he image capturing sensors 22, 23 are also arranged sucn that tneir receiving cones or tneir receiving axes 22', 23' are oriented at a predefined viewing angle of 900 with respect to tfie snaft axis 3' and the axis of rotation 10'.
Since the image capturing unit 20 is fixed in its location with respect to the housing 16 and is tfius rotatable about tfie axis of rotation 10' by 280 , tfie result, together with the receiving areas of tfie image capturing sensors 22, 23, is the possibility of an annular 360 panorama solely as a result of rotation of the rotary head 10. The image data and 3D information captured by the image capturing sensors 22, 23 can be combined appropriately into a panoramic image.
In figure 2, an alternative exemplary embodiment of a baroscope 1 is snown, wfierein there is broad agreement with the exemplary embodiment from figure 1. In the following, only the differences of the alternative exemplary embodiment will therefore be discussed and otherwise reference will be made to the above explanations.
In the exemplary embodiment according to figure 2, the housing 16 is designed to be fixed witn respect to the shaft 3, and the parts of the rotary head 10 that are rotatable about the axis of rotation 10' comprise the image capturing unit 20 already fixed to a holder 18 of the internal gear 15 within tfie housing 16. The non-visible bearing is provided between the internal gear 15 and tne inner wall of tfie housing 16. :he first end 4 of the shaft 3 is inserted into tfie housing 16 and firmly connected thereto.
In order that the image capturing sensors 22, 23 of the image capturing unit 20 projecting from the holder 18 can capture tfie surroundings in every angular position to which the drive unit 12 can be driven, tfie nousing nas a completely transparent ring segment 17'. The ring segment 17' is connected to the remaining non-transparent parts of the housing 16 in such a way that the housing 16 is liquid-tight as a whole; the rotary head 10 is therefore encapsulated in a liquid-tight manner.
Figure 3 shows, scnematically, a section througn a two-shaft engine 50 in wnicn the fan 51 and the low-pressure compressor 52 are rotationally connected via a first shaft 53 to the low-pressure turbine 54, while the high-pressure compressor 55 is rotationally connected via a second shaft 56 to the high-pressure turbine 57. The annular combustion chamber 58 is arranged between the high-pressure compressor 55 and the nigh-pressure turbine 57.
In addition to a borescope 1, which is designed according to one of figures 1 or 2 and consequently comprises a rotary head 10, the assembly 30 comprises a control and evaluation unit 31. Since the control and evaluation unit 31 also comprises tne actuators for tne control cables of the controllable snaft 3, it is secured directly to the engine 50 in tne area of a baroscope opening 59, througn wnicn the borescope 1 is inserted into tne combustion chamber 58.
The control and evaluation unit 31 is connected to the image capturing unit 20 and tfie drive unit 12 via the data, control and supply lines 14, 21 running in the shaft 3 of tne borescope 1 (cf. Figures 1 and 2). Since the control and evaluation unit 31 can, moreover, control the shaft 3 via its control cables, completely automatic 3D capture of the combustion chamber 58 is possible.
For this purpose, the control and evaluation unit 31 controls tne control cables of the snaft 3 such that predefined positions witnin the combustion cnamber 58 can be approacned by tne rotary :lead 10 one after anotner.

At each of tnese positions, by rotating the rotary head and simultaneously capturing the surroundings by means of the image sensors 22, 23, 3D information and color information is then collected, which is then combined by the control and evaluation unit 31 into color 3D
panoramic images by using known triangulation and sampling methods. The imaging sensors 22, 23 are able to capture images continuously as tne rotary :lead 10 rotates, or individual images are captured only at specific angular positions of the rotary head 10. In both cases, the image information can be combined into color panoramic images comprising 3D information.
:he overlapping color 3D panoramic images captured at the various points can then be combined further into a 3D
model of the interior of the combustion chamber 58, which can then be assessed and analyzed at a user terminal (not illustrated).

Claims

Patent claims

1. A boresope (1), in particular for the borescopy of the combustion chambers (58) of aircraft engines (50), comprising an electronic image capturing unit (20) with at least one image capturing sensor (22, 23) with a receiving cone at a first end (4) of a snaft (3) wnicn has a shaft axis (3') and tnrougn whicn data and supply lines (21) for the image capturing unit (20) are led, characterized in that the image capturing unit (20) is arranged on a rotary head (10) which is secured to the first end (4) so as to be rotatable about the sfiaft axis (3) sucfi tfiat tfie axis (22', 23') of tne receiving cone is not parallel to the shaft axis (3') at tne first end (4) and a panoramic image can be captured by rotating tne rotary head (10).

2. The borescope as claimed in claim 1, characterized in that the rotary range of the rotary head (10) is less than or equal to 360 .

3. The borescope as claimed in one of the preceding claims, characterized in that the rotary head (10) has an internal gear (15), in which a pinion (14) driven by a drive unit (12) fixed so as to be stationary and eccentric witn respect to tne shaft axis engages.

4. The borescope as claimed in one of the preceding claims, characterized in that the rotary nead (10) comprises a co-rotating cylindrical housing (16) having at least one transparent window (17), in which the image capturing unit is arranged in such a way that the receiving cone of each image capturing sensor (22, 23) is respectively aimed tsrough a transparent window (17).

5. The borescope as claimed in one of claims 1 to 3, characterized in that a cylindrical housing (16) that is stationary at tne first end (4) with respect to tne snaft axis (3'), surrounds tne rotary :lead (10) and has at least one transparent ring segment (17') is provided, wherein the receiving cone of each image capturing unit (22, 23) is respectively aimed through a transparent ring segment (17').

6. The borescope as claimed in claim 4 or 5, characterized in that the housing (16) is encapsulated in a liquid-tight manner.

7. The borescope as claimed in one of the preceding claims, characterized in that the image capturing unit (20) comprises at least two image capturing sensors (22) spaced apart from one another, having receiving cones at least partly intersecting and/or aimed parallel to each other for determining 3D information by means of triangulation.

8. The borescope as claimed in one of the preceding claims, characterized in that the at least one image capturing sensor (22, 23) is/are arranced and/or configured such that the receiving cone/s of an image capturing sensor (23) or of a pair of image capturing sensors (22) provided for the capture of 3D
information is/are orientec at a predefined viewing angle with respect to tne snaft axis (3') at tne first end (4).

9.
The borescope as claimed in one of the preceding claims, characterized in that the image capturing unit (22) of at least one image capturing sensor (23) is designed to capture color images.

10. Me borescope as claimed in one of the preceding claims, characterized in that at least one light source (24), preferably an LED, is provided on the rotary head (10) to illuminate the capture area.

11. Me borescope as claimed in one of the preceding claims, characterized in that the shaft (3) is configured as a flexible shaft.

12. An assembly (30) comprising a borescope (1) as claimed in one of tne preceding claims and a control and evaluation unit (31), wnich is designed to control the rotational movement of tne rotary head (10) and tne image capturing unit (20) and to combine the image data captured by the at least one image capturing sensor (22, 23) into a panoramic image.

13. Me assembly as claimed in claim 12, characterized in that the assembly (31) is designed for continuous capture by the image capturing unit (20) during rotation of the rotary head (10).

14. The assembly as claimed in claim 12, characterized in that the assembly (31) is designed to capture individual images by the image capturing unit (20) at angular positions reacned one after another by rotation of tne rotary head (10).

15. The assembly as claimed in one of claims 12 to 14, characterized in that the control and evaluation unit (31) is designed to combine two partly overlapping panoramic images.