A method and apparatus for stitching back-illuminated images from a stator annular aperture.

Abstract

This invention relates to a method for stitching backlit images of a stator annular aperture, comprising: focusing an industrial camera on the stator annular aperture; determining the required number of local backlit images and planning the acquisition position for each local backlit image; acquiring each local backlit image using the industrial camera according to the planned acquisition position; determining the corresponding image stitching matrix according to the selected image stitching method; and generating a panoramic backlit image of the stator annular aperture based on the image stitching matrix. This invention also relates to a stitching device for backlit images of a stator annular aperture. The purpose of this method and device for stitching backlit images of a stator annular aperture is to solve the problem of difficulty in stitching backlit images of apertures.

Description

Technical Field

[0001] This invention relates to the field of aero-engine blade aperture detection technology, specifically to a method and apparatus for stitching back-illuminated images of stator ring blade apertures. Background Technology

[0002] In many industrial fields such as aviation, aerospace, and nuclear energy, many important equipment components are designed with irregular hole features, such as the blade-shaped holes on the stator ring of an aero-engine and the irregular holes on the support plate of the nuclear island. While striving to improve the overall performance of the equipment, this has also brought about the processing and inspection challenges of such irregular hole features.

[0003] In small and medium-sized aero-engines, the stator ring is a key component in parts such as the inlet casing, low-pressure compressor, and rectifier turbine guide vanes. Numerous airfoil holes for mounting blades are evenly distributed on its cylindrical wall. There are hundreds of these airfoil holes throughout the engine, with complex shapes and diverse specifications. Currently, because these airfoil holes are non-standard features and located on the stator ring wall, there are almost no effective means to inspect their form and position parameters. On the production floor, operators can only roughly judge the quality of the machined airfoil holes by looking at standard airfoil samples, without obtaining other form and position parameters. This manual inspection method is not only inefficient and labor-intensive, but also cannot complete all effective inspection work, nor can it obtain objective, accurate, and specific inspection data. In recent years, with the rapid development of measurement technology and related disciplines, machine vision measurement based on image technology has been widely applied in various fields of the aerospace industry as a high-tech application. Visual measurement uses images as a means of acquiring information and applies machine vision technology to the measurement and positioning of geometric dimensions. It not only has the advantages of non-contact measurement technology, but also has unique advantages such as low cost, simple operation, high mobility and flexibility, and strong real-time performance. Therefore, it is widely used in industrial sites and has now become an important part of non-contact measurement in industrial sites.

[0004] In the visual measurement of airfoils, since the airfoils are fully through holes distributed on the stator ring wall, backlighting can be used to acquire the original image of the airfoils. However, due to limitations in the resolution and field of view of the imaging device in the system, for larger airfoils, a complete backlit image cannot be obtained in a single imaging operation. It is necessary to sequentially acquire multiple local images with overlapping areas, and then synthesize a panoramic image of the airfoil using image stitching technology for subsequent image processing and measurement analysis. This approach of high-precision measurement with a small field of view combined with local stitching is an effective method for visual measurement of large-sized mechanical parts, and image stitching is one of the key technologies involved.

[0005] Image stitching is a technique that spatially matches and aligns multiple sequences of images with overlapping areas (acquired at different times, from different viewpoints, or by different sensors), then resamples and synthesizes them to form a complete and clear panoramic image containing information from each sequence of images, offering a wide field of view. Image stitching allows for the acquisition of images of the object under test with a large field of view without reducing image resolution. This overcomes the field-of-view limitations of traditional industrial cameras and other imaging devices, enabling both the overall picture and local details of the object under test to be captured. Therefore, it has broad application prospects in the field of machine vision measurement.

[0006] Currently, there are two main image stitching methods: template matching-based stitching and feature matching-based stitching. Both methods require first setting or extracting templates or features from a reference image, and then searching and registering the templates and features in the image to be stitched to generate a projection transformation matrix, thereby achieving image stitching. However, the outline shape of the stator ring leaf-shaped aperture is similar to the cross-sectional shape of a blade, composed of multiple smoothly connected and gently transitioning arc segments with different parameters. Furthermore, the backlit image of the leaf-shaped aperture exhibits a "black and white" grayscale characteristic, resulting in a lack of rich grayscale information in the obtained backlit image of the leaf-shaped aperture. It almost entirely lacks features such as corners, straight edges, and textures, making the information and elements applicable to image matching extremely scarce. These factors pose significant challenges to the setting, extraction, searching, and registration of templates and features during the image stitching process, and are highly prone to mismatching or stitching misalignment, leading to errors or failures in the backlit image stitching of the leaf-shaped aperture, adversely affecting the visual measurement task of the leaf-shaped aperture.

[0007] Therefore, the inventors provide a method and apparatus for stitching backlit images of a stator ring-shaped aperture. Summary of the Invention

[0008] (1) Technical problems to be solved

[0009] This invention provides a method and apparatus for stitching back-illuminated images of a stator ring-shaped aperture, solving the technical problem of the difficulty in stitching back-illuminated images of an aperture.

[0010] (2) Technical solution

[0011] This invention provides a method for stitching back-illuminated images of a stator annular aperture, comprising the following steps:

[0012] Focus the industrial camera on the stator ring-shaped aperture;

[0013] Determine the number of local backlit images required and plan the acquisition location for each local backlit image;

[0014] Based on the planned acquisition locations, the industrial camera is used to acquire each local backlit image;

[0015] Determine the corresponding image stitching matrix based on the selected image stitching method;

[0016] Based on the image stitching matrix, a panoramic backlighting image of the stator annular aperture is generated.

[0017] Furthermore, focusing the industrial camera on the stator ring-shaped aperture specifically includes the following steps:

[0018] The X, Y, and Z axes of the three-coordinate motion device are controlled to drive the industrial camera to move, so that the stator annular aperture enters the field of view of the industrial camera;

[0019] The industrial camera's front-to-back distance is adjusted by a focusing function and X-axis movement, enabling it to automatically focus on the stator ring-shaped aperture.

[0020] Furthermore, determining the required number of local backlit images and planning the acquisition location for each local backlit image specifically includes the following steps:

[0021] The required number of local backlit images is calculated based on the minimum circumscribed rectangle size of the stator annular aperture and the imaging field of view of the industrial camera.

[0022] Based on the number of locally backlit images and the first and second preset values, the coordinate positions for acquiring each locally backlit image are planned in the host computer software; wherein,

[0023] The first setting value is the Z-axis coordinate interval between adjacent local backlit images, and the second setting value is the Y-axis coordinate interval between adjacent local backlit images.

[0024] Furthermore, the step of calculating the required number of locally backlit images based on the minimum circumscribed rectangle size of the stator annular aperture and the imaging field of view of the industrial camera specifically includes the following steps:

[0025] Set the minimum overlap length of adjacent local backlit images in the v direction to l. h The minimum overlap length in the u direction is l. w ;

[0026] Determine h a w is the distance between the upper edge of the leaf-shaped aperture and the upper edge of the image. a h is the distance between the right edge of the leaf-shaped aperture and the right edge of the image. b w is the distance between the lower edge of the leaf-shaped aperture and the lower edge of the image. bThis is the distance between the left edge of the leaf-shaped aperture and the left edge of the image.

[0027] Based on the height and width dimensions of the minimum circumscribed rectangle of the stator annular aperture, the height and width dimensions of the imaging field of view of the industrial camera, and the first set value, the second set value, and h a w a h b w b The number of longitudinal local backlighting images and the number of lateral local backlighting images required to obtain the panoramic backlighting image of the stator annular aperture;

[0028] The maximum value between the number of longitudinal local backlit images and the number of transverse local backlit images is taken as the number of local backlit images.

[0029] Furthermore, the acquisition of each locally backlit image using the industrial camera specifically involves:

[0030] The three-coordinate motion device is controlled to move the industrial camera to each coordinate position in turn, and to collect the corresponding local backlit images.

[0031] Furthermore, the image stitching matrix includes a first image stitching matrix and a second image stitching matrix; wherein, the first image stitching matrix is ​​a local image I. i With local image I i+1 The relative positional relationship between them, the second image stitching matrix is ​​a local image I i The relative positional relationship between the local image I1 and the local image I1.

[0032] Further, generating the panoramic back-illuminated image of the stator annular aperture based on the image stitching matrix specifically involves:

[0033] Based on the calculated image stitching matrix, each local backlit image is stitched together to form a panoramic backlit image of the stator annular aperture.

[0034] Furthermore, the step of focusing the industrial camera before the stator annular aperture also includes:

[0035] The stator ring is clamped in the stator ring fixture, and mechanical adjustment is used to align the geometric axis of the stator ring with the rotation axis of the rotary table; and,

[0036] Controlling the rotation of the rotary table changes the angular position of the stator ring, so that the stator ring leaf-shaped hole faces the industrial camera and its stacking axis direction is parallel to the X-axis direction.

[0037] Furthermore, each locally backlit image is obtained through precise linear coordinate motion.

[0038] The present invention also provides a stitching device for back-illuminated images of a stator annular aperture, comprising:

[0039] The camera focusing unit is used to focus the industrial camera on the stator ring-shaped aperture;

[0040] The location planning unit is used to determine the number of local backlit images required and plan the acquisition location for each local backlit image;

[0041] An image acquisition unit is used to acquire each local backlit image based on the planned acquisition position using the industrial camera.

[0042] The matrix selection unit is used to determine the corresponding image stitching matrix based on the selected image stitching method.

[0043] The image generation unit is used to generate a panoramic backlighting image of the stator annular aperture based on the image stitching matrix.

[0044] (3) Beneficial effects

[0045] In summary, this invention acquires multiple local backlit images of the tested leaf-shaped aperture based on precise linear coordinate motion and control. Then, based on the precise relative positional relationship between these local backlit images, an image stitching matrix is ​​calculated, enabling the acquisition of a panoramic backlit image of the leaf-shaped aperture. This method overcomes the shortcomings and deficiencies of conventional image stitching methods such as template matching and feature matching. Furthermore, it boasts advantages such as low computational cost, fast processing speed, good stitching results, and no requirements regarding overlapping image areas. It can also be extended to acquire panoramic backlit images of other irregular aperture features. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the stator ring-shaped aperture structure;

[0048] Figure 2 This is a schematic flowchart of a method for stitching back-illuminated images of a stator annular aperture provided in an embodiment of the present invention;

[0049] Figure 3This is a schematic diagram of the structure of the multi-axis visual coordinate measuring device for implementing the present invention, provided in an embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of the minimum circumscribed rectangle of a leaf-shaped aperture and the imaging field of view of an industrial camera, provided in an embodiment of the present invention.

[0051] Figure 5 This is a calculation diagram of an image stitching process provided in an embodiment of the present invention;

[0052] Figure 6 This is a partial backlit image of a leaf-shaped aperture provided in an embodiment of the present invention;

[0053] Figure 7 This is a partial backlit image of another leaf-shaped aperture provided in an embodiment of the present invention;

[0054] Figure 8 This is a partial backlit image of another leaf-shaped aperture provided in an embodiment of the present invention;

[0055] Figure 9 This is a spliced ​​panoramic backlit image of a leaf-shaped aperture provided in an embodiment of the present invention.

[0056] In the picture:

[0057] 1-Stator ring; 2-Airfoil-shaped aperture; 3-Airfoil-shaped aperture multi-axis vision coordinate measuring device; 31-Industrial camera; 32-Backlight source; 33-Stator ring clamp; 34-Rotary table; 35-Base; 36-Three-coordinate motion device; 4-Industrial camera object-side focal plane imaging field of view. Detailed Implementation

[0058] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments, and any modifications, substitutions and improvements to the parts, components and connection methods are covered without departing from the spirit of the present invention.

[0059] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0060] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0061] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "install" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0062] Figure 1 This is a flowchart illustrating a method for stitching back-illuminated images of a stator annular aperture according to an embodiment of the present invention. The method may include the following steps:

[0063] S100, Focus the industrial camera on the stator ring-shaped aperture;

[0064] S200. Determine the number of local backlit images required and plan the acquisition location for each local backlit image;

[0065] S300: Based on the planned acquisition locations, use an industrial camera to acquire each local backlit image;

[0066] S400. Determine the corresponding image stitching matrix according to the selected image stitching method;

[0067] S500: Based on the image stitching matrix, generate a panoramic backlighting image of the stator ring-shaped aperture.

[0068] In the above implementation, the required number of local backlighting images is calculated based on the minimum circumscribed rectangle size of the leaf-shaped aperture and the imaging field of view of the industrial camera, and the acquisition position is planned. Then, multiple local backlighting images of the measured leaf-shaped aperture are acquired based on precise linear coordinate motion and control.

[0069] Two forms of image stitching matrices are proposed to describe the relative positional relationship between local backlit images to be stitched. The parameters in the image stitching matrix can be calculated through precise coordinate motion and calibrated pixel size equivalents. The algorithm is simple and has low computational cost.

[0070] The method is based on a multi-axis visual coordinate measurement device 3 for leaf-shaped apertures, such as... Figure 3 As shown, it includes an industrial camera 31, a backlight source 32, a stator ring clamp 33, a rotary table 34, a base 35, and a three-coordinate motion device 36. The multi-axis vision coordinate measuring device 3 for leaf-shaped holes has four coordinate axes: three linear coordinate axes X, Y, and Z, and one rotary coordinate axis C. The three linear coordinate axes X, Y, and Z are integrated together and implemented by the three-coordinate motion device 36, while the rotary coordinate axis C is arranged separately and implemented by the rotary table 34.

[0071] Furthermore, the coordinate measuring machine 36 is mounted on the base 35, located at the rear end of the table surface of the base 35. It can generate linear motion in the X, Y, and Z directions, which are perpendicular to each other. Each linear coordinate axis is equipped with a high-precision grating ruler, thereby ensuring the precise motion control and positioning accuracy of each linear coordinate axis. The industrial camera 31 is mounted on the Z-axis support plate of the coordinate measuring machine 36. Through mechanical adjustment, its imaging optical axis is made parallel to the X-axis direction of the coordinate measuring machine 36. The industrial camera 31 can move independently or in conjunction along the X, Y, and Z axes, and achieve precise positioning of any point in the measurement space. The rotary table 34 is fixed on the base 35, located at the front end of the table surface of the base 35, and positioned at the middle position of the Y-axis travel of the coordinate measuring machine 36. The table surface and rotation axis of the rotary table 34 are mechanically adjusted so that the table surface is in a horizontal position and its rotation axis is in a vertical position. The stator ring clamp 33 is mounted on the table surface of the rotary table 34, and the stator ring 1 (e.g., Figure 1 (As shown) It is clamped in the stator ring clamp 33. The backlight source 32 is cylindrical in shape and is installed in the center of the stator ring clamp 33. The backlight source 32 and the industrial camera 31 are located on the front and rear sides of the leaf-shaped aperture 2, respectively. The uniform and stable light emitted by the backlight source 32 shines from the back of the leaf-shaped aperture 2 and illuminates the leaf-shaped aperture 2. Then it enters the lens of the industrial camera 31 and is imaged on its photosensitive surface to form a backlight image of the leaf-shaped aperture 2.

[0072] Furthermore, in order to ensure the accuracy and quality of the back-illuminated image stitching of the leaf-shaped aperture 2, the spatial motion and positioning accuracy of the three-coordinate motion device 36 is required to be better than 0.5·K, where K is the pixel size equivalent on the object-side focal plane imaging field of view 4 of the industrial camera, which is obtained through calibration and is in mm / pixel.

[0073] As an optional implementation, step S100, focusing the industrial camera on the stator ring-shaped aperture, specifically includes the following steps:

[0074] S101. Control the X, Y and Z axes of the three-coordinate motion device to drive the industrial camera to move, so that the stator ring-shaped hole enters the field of view of the industrial camera.

[0075] S102. Adjust the front and rear distance of the industrial camera through the focusing function and the movement of the X-axis to make it automatically focus on the stator ring-shaped aperture.

[0076] Specifically, the X, Y, and Z axes of the three-coordinate motion device 36 are controlled to drive the industrial camera 31 to move, so that the leaf-shaped aperture 2 enters the field of view of the industrial camera 31. The front and rear distance of the industrial camera 31 is adjusted by the focusing function and the movement of the X axis, so that it automatically focuses on the leaf-shaped aperture 2. At this time, the leaf-shaped aperture 2 is on the object-side focal plane of the industrial camera 31, and the clearest and most contrasting backlit image can be captured.

[0077] As an optional implementation, step S200, determining the required number of local backlit images and planning the acquisition location for each local backlit image, specifically includes the following steps:

[0078] S201. Calculate the required number of local backlighting images based on the minimum circumscribed rectangle size of the stator ring-shaped aperture and the imaging field of view of the industrial camera.

[0079] S202. Based on the number of local backlit images and the first and second set values, the coordinate positions for acquiring each local backlit image are planned in the host computer software; wherein,

[0080] The first setting is the Z-axis coordinate interval between adjacent local backlit images, and the second setting is the Y-axis coordinate interval between adjacent local backlit images.

[0081] Specifically, this step includes two parts: calculating the number of required local images and planning the acquisition locations for each local image.

[0082] When acquiring local images of the leaf-shaped aperture 2, the movement of the industrial camera 31 along both the Z and Y axes is set to equal intervals. The Z-axis coordinate interval between adjacent local images is set to h, and the Y-axis coordinate interval is set to w. Based on actual needs, the minimum overlap length of adjacent local images in the v direction is set to l. h (0≤l h ≤H), while the minimum overlap length in the u direction is l. w (0≤l w ≤W). Additionally, a certain edge distance h can be set. a w a h b and w b This ensures that the leaf-shaped hole 2 in the image is kept at a certain distance from the image edge, facilitating subsequent edge extraction. Where h a w is the distance between the upper edge of the leaf-shaped aperture 2 and the upper edge of the image. ah is the distance between the right edge of the leaf-shaped aperture 2 and the right edge of the image. b w is the distance between the lower edge of the leaf-shaped aperture 2 and the lower edge of the image. b This is the distance between the left edge of leaf-shaped hole 2 and the left edge of the image.

[0083] according to Figure 5 The values ​​of h and w are subject to the following constraints:

[0084] 0≤h≤Hl h (1)

[0085] 0≤w≤Wl w (2)

[0086] As an optional implementation, in step S201, the required number of local backlit images is calculated based on the minimum circumscribed rectangle size of the stator annular aperture and the imaging field of view of the industrial camera. This specifically includes the following steps:

[0087] S2011. Set the minimum overlap length of adjacent local backlit images in the v direction to l. h The minimum overlap length in the u direction is l. w ;

[0088] S2012, Determine h a w is the distance between the upper edge of the leaf-shaped aperture and the upper edge of the image. a h is the distance between the right edge of the leaf-shaped aperture and the right edge of the image. b w is the distance between the lower edge of the leaf-shaped aperture and the lower edge of the image. b This is the distance between the left edge of the leaf-shaped aperture and the left edge of the image.

[0089] S2013, based on the height and width dimensions of the minimum circumscribed rectangle of the stator annular aperture, the height and width dimensions of the imaging field of view of the industrial camera, and the first set value, the second set value, and h. a w a h b w b The number of longitudinal local backlighting images and the number of lateral local backlighting images required to obtain a panoramic backlighting image of the stator annular aperture;

[0090] S2014. Take the maximum value between the number of longitudinal local backlit images and the number of transverse local backlit images as the number of local backlit images.

[0091] Specifically, based on the theoretical profile data of the leaf-shaped hole 2, the height dimension L of its minimum circumscribed rectangle is determined. H and width dimension L WThe height H and width W of the focal plane imaging field of view 4 of an industrial camera are determined according to... Figure 4 and Figure 5 From the geometric relationships, we can obtain:

[0092] (N H -1)·h+H=h a +L H +h b (3)

[0093] (N W -1)·w+W=w a +L W +w b (4)

[0094] In equations (3) and (4), N H and N W The vertical and horizontal local images required to obtain the panoramic backlit image of the leaf-shaped aperture 2 are respectively calculated using equations (3) and (4), yielding the expressions for h and w as follows:

[0095]

[0096]

[0097] By combining equations (1) and (5), and equations (2) and (6), we can obtain:

[0098]

[0099]

[0100] Furthermore, take

[0101]

[0102]

[0103] In equations (9) and (10), h a h b w a w b L H L W The units for H and W are all mm; ceiling(x) is the ceiling function, which represents rounding up the real number x. Therefore, according to N H and N W Furthermore, the maximum value of the two is taken as the number of local images N required to obtain the panoramic backlit image of the leaf-shaped aperture 2, as shown in the following formula:

[0104] N = max{NH N W} (11)

[0105] As an optional implementation, in step S300, each local backlit image is acquired using an industrial camera, specifically as follows:

[0106] The three-coordinate motion device is controlled to move the industrial camera to each coordinate position in turn, and the corresponding local backlit images are collected.

[0107] Specifically, based on the number N of local images required to acquire the panoramic backlighting image of the leaf-shaped aperture 2, and the set h and w, the coordinate positions (X1, Y1, Z1), (X2, Y2, Z2), ..., (X...) of each local image are planned in the host computer software. N ,Y N Z N The system controls the three-coordinate motion device 36 to drive the industrial camera (31) to move to each coordinate position successively, and acquires the corresponding local images I. i (i = 1, 2, ..., N).

[0108] As an optional implementation, in step S400, the image stitching matrix includes a first image stitching matrix and a second image stitching matrix; wherein, the first image stitching matrix is ​​a local image I. i With local image I i+1 The relative positional relationship between them, the second image stitching matrix is ​​the local image I i The relative positional relationship between the local image I1 and the local image I1.

[0109] Specifically, depending on the selected image stitching method, two different forms of image stitching matrices can be used, M i Or P i (i = 1, 2, ..., N-1). Due to the local images I... i All were obtained through precise linear coordinate motion, thus each local image I i If there is only a translation relationship and no rotation relationship between the images, then the image stitching matrix M... i Or P i The format is as follows:

[0110] M i or

[0111] In equation (12), t vi t represents the pixel translation amount in the v direction. ui This represents the pixel translation amount in the u direction, with the unit being pixels.

[0112] Image stitching matrix M iDescribes local image I i With local image I i+1 The relative positional relationship between them, that is, when stitched into a panoramic backlit image, the local image I i+1 Relative to local image I i The pixel translation amounts in the v and u directions are used to realize the local image I. i With local image I i+1 The splicing between them. In M i In the middle, t vi and t ui The calculation formula is as follows:

[0113]

[0114] Image stitching matrix P i Describes local image I i The relative positional relationship between local image I1 and the local image I2 when stitched together to form a panoramic backlit image. i The pixel translations relative to the local image I1 in the v and u directions are used to realize the local image I. i The stitching between the local image I1 and the image I1.

[0115] In P i In the middle, t vi and t ui The calculation formula is as follows:

[0116]

[0117] As an optional implementation, in step S500, a panoramic backlighting image of the stator annular aperture is generated based on the image stitching matrix, specifically as follows:

[0118] Based on the calculated image stitching matrix, each local backlit image is stitched together to form a panoramic backlit image of the stator ring-shaped aperture.

[0119] As an optional implementation, in step S100, before focusing the industrial camera on the stator annular aperture, the method further includes:

[0120] The stator ring is clamped in the stator ring fixture, and mechanical adjustment is used to align the geometric axis of the stator ring with the rotation axis of the rotary table; and,

[0121] Controlling the rotation of the rotary table changes the angular position of the stator ring, making the stator ring's leaf-shaped hole face the industrial camera and its stacking axis direction parallel to the X-axis direction.

[0122] Specifically, the stator ring is clamped in the stator ring fixture, and the geometric axis of the stator ring is aligned with the rotation axis of the rotary table through mechanical adjustment; then the rotation of the rotary table is controlled to change the angular position of the stator ring, so that the leaf-shaped hole faces the industrial camera and its stacking axis is parallel to the X-axis, and the backlight source is turned on for backlighting.

[0123] As an alternative implementation, each locally backlit image is obtained through precise linear coordinate motion.

[0124] This invention also provides a stitching device for back-illuminated images of a stator annular aperture, the device comprising:

[0125] The camera focusing unit is used to focus the industrial camera on the stator ring-shaped aperture;

[0126] The location planning unit is used to determine the number of local backlit images required and plan the acquisition location for each local backlit image;

[0127] The image acquisition unit is used to acquire each local backlit image based on the planned acquisition position using an industrial camera;

[0128] The matrix selection unit is used to determine the corresponding image stitching matrix based on the selected image stitching method.

[0129] The image generation unit is used to generate a panoramic backlighting image of the stator ring-shaped aperture based on the image stitching matrix.

[0130] Example 1

[0131] The multi-axis visual coordinate measuring device for leaf-shaped apertures upon which this invention is based has a travel of 500mm for each of the three linear coordinate axes X, Y, and Z, a spatial positioning accuracy of ≤5μm, a rotation range of 0° to 360° for the rotary coordinate axis C, and an industrial camera object-side focal plane imaging field of view of H = 15mm, W = 20mm, and a pixel size equivalent K = 0.01mm / pixel.

[0132] Taking the airfoil-shaped aperture on a certain stage stator ring of a certain type of aero-engine as the object of measurement, the minimum circumscribed rectangle dimension of the airfoil-shaped aperture is: L W =25mm, L H =35mm. Set edge distance h a w a h b and w b Both are 1.5mm, and the minimum overlap length of adjacent local images in the v direction is set to l. h =3mm, while the minimum overlap length in the u direction is l w =4mm.

[0133] Based on equations (1) and (2), we can obtain:

[0134] 0≤h≤12

[0135] 0≤w≤16

[0136] According to equations (9) and (10), we can obtain:

[0137] N H =3

[0138] N W =2

[0139] Therefore, according to equation (11), the required number of local images N is:

[0140] N=3

[0141] Therefore, let N H =N=3, N W =N=3, substituting the two into equations (5) and (6) respectively, we get:

[0142] h = 11.5

[0143] w=4

[0144] Based on the values ​​of N, h, and w, the coordinate positions for acquiring each local image are planned in the host computer software. The three-coordinate motion device is then controlled to move the industrial camera to each coordinate position sequentially, acquiring the corresponding local images I1, I2, and I3, as follows: Figure 6-8 As shown.

[0145] According to equation (14), the parameters in the image stitching matrices P1 and P2 can be calculated to obtain...

[0146]

[0147] Based on image stitching matrices P1 and P2, local images I1, I2, and I3 are stitched together one by one to ultimately form a panoramic backlit image of the tested aperture, as shown below. Figure 9 As shown.

[0148] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0149] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A method for stitching back-illuminated images of a stator annular aperture, characterized in that, The method includes the following steps: Focus the industrial camera on the stator ring-shaped aperture; Determine the number of local backlit images required and plan the acquisition location for each local backlit image; Based on the planned acquisition locations, the industrial camera is used to acquire each local backlit image; Determine the corresponding image stitching matrix based on the selected image stitching method; Based on the image stitching matrix, a panoramic backlighting image of the stator annular aperture is generated; The process of determining the required number of local backlit images and planning the acquisition location for each local backlit image specifically includes the following steps: The required number of local backlit images is calculated based on the minimum circumscribed rectangle size of the stator annular aperture and the imaging field of view of the industrial camera. Based on the number of locally backlit images and the first and second preset values, the coordinate positions for acquiring each locally backlit image are planned in the host computer software; wherein, The first setting value is the distance between adjacent local backlit images. Z The axis coordinate interval value, the second set value is the interval between adjacent local backlit images. Y Axis coordinate interval values; The step of calculating the required number of locally backlit images based on the minimum circumscribed rectangle size of the stator annular aperture and the imaging field of view of the industrial camera specifically includes the following steps: Set adjacent local backlighting images v The minimum overlap length in the direction is l h ,exist u The minimum overlap length in the direction is l w ; Sure h a This is the distance between the upper edge of the leaf-shaped aperture and the upper edge of the image. w a This is the distance between the right edge of the leaf-shaped aperture and the right edge of the image. h b This is the distance between the lower edge of the leaf-shaped aperture and the lower edge of the image. w b This is the distance between the left edge of the leaf-shaped aperture and the left edge of the image. Based on the height and width dimensions of the minimum circumscribed rectangle of the stator annular aperture, the height and width dimensions of the imaging field of view of the industrial camera, and the first and second set values, h a , w a , h b , w b The number of longitudinal local backlighting images and the number of lateral local backlighting images required to obtain the panoramic backlighting image of the stator annular aperture; The maximum value between the number of longitudinal local backlit images and the number of transverse local backlit images is taken as the number of local backlit images.

2. The method for stitching back-illuminated images of a stator annular aperture according to claim 1, characterized in that, The step of focusing the industrial camera onto the stator ring-shaped aperture specifically includes the following steps: Controlling the three-coordinate motion device X , Y and Z The shaft drives the industrial camera to move, causing the stator annular aperture to enter the field of view of the industrial camera; Through focus function and X The movement of the shaft adjusts the front-to-back distance of the industrial camera, enabling it to automatically focus on the stator ring-shaped aperture.

3. The method for stitching back-illuminated images of a stator annular aperture according to claim 1, characterized in that, The process of acquiring each locally backlit image using the industrial camera specifically involves: The three-coordinate motion device is controlled to move the industrial camera to each coordinate position in turn, and to collect the corresponding local backlit images.

4. The method for stitching back-illuminated images of a stator annular aperture according to claim 1, characterized in that, The image stitching matrix includes a first image stitching matrix and a second image stitching matrix; wherein, the first image stitching matrix is ​​a local image. I i With local images I i+1 The relative positional relationships between them, the second image stitching matrix is ​​a local image I i With local images I The relative positional relationship between 1.

5. The method for stitching back-illuminated images of a stator annular aperture according to claim 1, characterized in that, The step of generating a panoramic backlighting image of the stator annular aperture based on the image stitching matrix specifically involves: Based on the calculated image stitching matrix, each local backlit image is stitched together to form a panoramic backlit image of the stator annular aperture.

6. The method for stitching back-illuminated images of a stator annular aperture according to claim 1, characterized in that, The step of focusing the industrial camera on the stator annular aperture also includes: The stator ring is clamped in the stator ring fixture, and mechanical adjustment is used to align the geometric axis of the stator ring with the rotation axis of the rotary table; and, Controlling the rotation of the rotary table changes the angular position of the stator ring, causing the stator ring's leaf-shaped hole to face the industrial camera and aligning its stacking axis with... X The axes are parallel.

7. The method for stitching back-illuminated images of a stator annular aperture according to claim 1, characterized in that, Each partially backlit image was obtained through precise linear coordinate motion.

8. An apparatus for stitching images using the back-illuminated image stitching method of the stator annular aperture as described in claim 1, characterized in that, include: The camera focusing unit is used to focus the industrial camera on the stator ring-shaped aperture; The location planning unit is used to determine the number of local backlit images required and plan the acquisition location for each local backlit image; An image acquisition unit is used to acquire each local backlit image based on the planned acquisition position using the industrial camera. The matrix selection unit is used to determine the corresponding image stitching matrix based on the selected image stitching method. The image generation unit is used to generate a panoramic backlighting image of the stator annular aperture based on the image stitching matrix.

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