Complex workpiece cavity hole inner wall surface high-resolution imaging method and system

Abstract

The invention discloses a high-resolution imaging method and system for the surface of the inner wall of a cavity hole of a complex workpiece. The imaging system extends into the workpiece cavity hole at a constant speed along the centroid axis direction of the workpiece cavity hole, and acquires images at a preset frame rate to obtain a plurality of frames of cavity hole inner wall images; extracting the plurality of frames of cavity hole inner wall images to obtain an annular scanning area of each frame of cavity hole inner wall image; expanding the annular scanning area in each frame of cavity hole inner wall image through coordinate mapping to obtain a rectangular expanded view of the annular scanning area in each frame of cavity hole inner wall image; and splicing the rectangular expanded images of the annular scanning areas in the cavity hole inner wall images according to an acquisition sequence to obtain a panoramic expanded image of the cavity hole inner wall of the workpiece. According to the invention, a high-resolution panoramic unfolded image of the inner wall surface can be obtained, and the method is suitable for visual detection of the inner wall surfaces of workpiece cavity holes with various complex section shapes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of machine vision, in particular to a high-resolution imaging method and system for the inner wall surface of a complex workpiece cavity. BACKGROUND

[0002] In the production of workpieces, the manufacturing quality of the inner wall surface of the cavity directly affects the performance, reliability and service life of the workpiece. Traditional inner wall surface quality detection usually relies on manual naked eye visual inspection or visual inspection with an endoscopic camera, which has problems such as high cost, low efficiency, poor consistency, and inability to meet the needs of large-scale automated production. The application of ordinary industrial cameras to the imaging of the inner wall surface of the workpiece cavity has great limitations: ordinary line array scanning cameras are usually difficult to enter the inside of the workpiece cavity due to their large size, and their working range is limited, making it difficult to scan and collect inner wall surface images; and ordinary area array cameras are difficult to obtain complete high-resolution images of the inner wall surface of a narrow and long cavity through a single frame image due to the limitation of the pixel array and field of view. In addition, the space inside the workpiece cavity is narrow, making it difficult to arrange and adjust the light source. Ordinary light sources often have difficulty in uniformly illuminating the entire inner wall surface, resulting in poor lighting conditions such as local high reflectivity and local shadows, thereby affecting the quality of the final image.

[0003] Invention patent No. CN101109716A proposes an optical detection method for the inner surface of a hole, which forms a complete image by polar coordinate mapping and splicing multiple images. The limitation of this method is that it can only be used for cylindrical bores, and image splicing relies on the texture of the inner bore, which cannot be used for non-textured surfaces or non-cylindrical bores. Invention patent No. CN118500252A proposes a method of using a laser to detect the inner wall, which constructs a three-dimensional data graph by splicing the circular ring illuminated by the laser. The limitation of this method is that it can only be applied to cylindrical bores, and can only detect geometric shape changes, which cannot meet the high-resolution visual imaging needs of the inner bore surface quality. SUMMARY

[0004] To solve the problems in the background art, the present application provides a high-resolution scanning imaging method and system suitable for the inner wall surface of a narrow and long cavity with a complex cross-sectional shape, which realizes visual data acquisition and panoramic viewing imaging of the inner wall surface of the cavity by constructing a special image acquisition system, optimizing the working parameters of the imaging system, scanning and collecting inner wall surface videos, and extracting the scanning area for geometric transformation and image splicing.

[0005] The technical solution adopted by the present application is as follows: The present application comprises the following steps: S1, the imaging system uniformly enters the workpiece cavity along the workpiece cavity center axis direction at a preset frame rate to acquire images and obtain a plurality of cavity inner wall images; S2, respectively extracting a plurality of frames of inner wall images of the chamber hole to obtain a ring scanning area of each frame of inner wall image of the chamber hole; S3, unfolding the ring scanning area in each frame of inner wall image of the chamber hole through coordinate mapping to obtain a rectangular unfolded image of the ring scanning area in each frame of inner wall image of the chamber hole; S4, splicing the rectangular unfolded images of the ring scanning area in each frame of inner wall image of the chamber hole according to the collection sequence to obtain a panoramic unfolded image of the inner wall of the workpiece chamber hole.

[0006] The ring scanning area is an inner wall surface image of a preset depth section in the inner wall surface scanning section of each frame of image, and the ring scanning area is composed of a plurality of closed boundary lines with a common center.

[0007] The S3 specifically includes the following steps for each frame of inner wall image of the chamber hole: S3.1, determining the size of the rectangular unfolded image according to the outer boundary circumference of the ring scanning area and the distance between the inner boundary and the outer boundary; S3.2, establishing a geometric mapping relationship between the ring scanning area and the rectangular unfolded image according to the size of the rectangular unfolded image and the ring scanning area; S3.3, reversely mapping the pixel points of the rectangular unfolded image to the ring scanning area according to the geometric mapping relationship between the ring scanning area and the rectangular unfolded image, and then filling the pixel values of the rectangular unfolded image by using interpolation calculation to obtain the rectangular unfolded image of the ring scanning area.

[0008] In the S3.1, the width of the rectangular unfolded image is equal to the outer boundary circumference of the ring scanning area, and the length of the rectangular unfolded image is equal to the maximum radial distance between the inner boundary and the outer boundary of the ring scanning area in all radial directions.

[0009] The S3.3 specifically includes the following steps for all pixel points of the rectangular unfolded image: 1) obtaining the coordinates of the current pixel point of the rectangular unfolded image and substituting them into the geometric mapping relationship between the ring scanning area and the rectangular unfolded image to obtain the corresponding coordinates of the current pixel point in the ring scanning area; 2) calculating the pixel value of the corresponding coordinates of the current pixel point in the ring scanning area by using an interpolation method according to the corresponding coordinates of the current pixel point in the ring scanning area; 3) assigning the pixel value of the corresponding coordinates of the ring scanning area to the pixel value of the current pixel point of the rectangular unfolded image.

[0010] In the step S1, the imaging system moves into the workpiece chamber hole at a uniform speed along the workpiece chamber hole center axis, and the movement speed of the imaging system is set according to the following formula: wherein, where f is the frame rate of image acquisition, n is the number of rows after the annular scanning area of each frame of image is developed into a rectangle, and p is the imaging resolution of the inner wall scanning section in the axial direction.

[0011] The present application adopts a high-resolution imaging system for the inner wall surface of a complex workpiece cavity, which comprises a stepping motor, a guide rail, a camera and an annular light source.

[0012] The present application further comprises an image processing module, which is electrically connected to the camera and used to process the images of the inner wall surface of the workpiece cavity collected by the camera to obtain a panoramic developed image of the inner wall surface of the workpiece cavity.

[0013] In the workpiece cavity, the cavity boundary profiles in all cavity cross sections perpendicular to the axial direction of the workpiece cavity are the same, and the centers of all cavity cross sections are located on the same vertical axis.

[0014] The present application has the following advantages: 1. High-resolution imaging of the inner wall surface of a complex cross-sectional shape: By optimizing the working parameters of the imaging system, the present application can efficiently collect high-resolution images of the inner wall surface of the workpiece cavity, capturing tiny details, and is particularly suitable for detailed panoramic scanning of the inner wall surface of a long and narrow cavity with a complex cross-sectional shape.

[0015] 2. Efficient image stitching and 360-degree panoramic scanning: By using geometric transformation and image stitching technology, the present application can seamlessly stitch multiple local images into a complete inner wall surface image, avoiding the problems of incomplete image stitching and discontinuity in the existing scanning methods. At the same time, the 360-degree panoramic scanning image can more intuitively visualize the texture of the inner wall surface of the cavity, facilitating subsequent quality inspection and defect analysis.

[0016] 3. High image quality stability: By precisely controlling the scanning motion and multi-channel light source, the present application can avoid common problems such as uneven lighting, overexposure or underexposure, improve the consistency and stability of the imaging quality of cavities with different cross-sectional shapes and different depth scanning sections, and meet the demand for high-quality imaging in automated detection.

[0017] 4. Strong adaptability and high flexibility: According to the three-dimensional structure and size of the workpiece cavity to be measured, the present application optimizes the working parameters of the imaging system, continuously scans and collects videos, and synthesizes panoramic scanning images through post-processing algorithms, which can adapt to the imaging of the inner wall surface of various complex cross-sectional shape cavities.

[0018] In summary, the present application can overcome the shortcomings of traditional imaging equipment in imaging the inner wall surface of a long and narrow cavity by designing a mechanical movement device with precise fit, a multi-channel light source, a surface array camera and an endoscope lens, and is suitable for cavities with complex cross-sectional shapes and no obvious surface texture, thereby realizing high-resolution panoramic imaging of the inner wall surface of a workpiece cavity and meeting the needs of efficient quality detection based on vision in industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The main step flow chart of high-resolution scanning and imaging of the inner wall surface of a workpiece cavity; Figure 2 The schematic diagram of the front-end hardware device of the image acquisition system shows the structure, layout and scanning movement mode of the camera, lens, light source and workpiece, Figure 2 (A) is an acquisition device based on an endoscopic wide-angle lens, Figure 2 (B) is an acquisition device based on a 360-degree panoramic lens; Figure 3 The schematic diagram of the annular scanning area corresponding to various complex cross-sectional shape workpiece cavities, Figure 4 The panoramic panoramic unfolded image of the inner wall surface obtained after geometric transformation and splicing of the annular scanning area, Figure 4 (A) is a schematic diagram of a circular cross-sectional cavity, Figure 4 (B) is a schematic diagram of a square cross-sectional cavity; Figure 5 A single frame image of the inner wall surface of a metal workpiece cavity, Figure 6 A panoramic panoramic unfolded image of the inner wall surface of a metal workpiece cavity. DETAILED DESCRIPTION

[0020] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0021] The system and method of the present application will be described in more detail below in combination with the drawings.

[0022] As shown in the drawings, Figure 1 The method of the present embodiment comprises the following steps: S1, the imaging system uniformly and linearly extends into the workpiece cavity along the workpiece cavity center axis direction at a preset frame rate, and acquires images to obtain a plurality of cavity inner wall images; S2, the annular scanning area of each cavity inner wall image is extracted to obtain a plurality of cavity inner wall images; Specifically, based on the projection shape of the cross-sectional boundary line of the inner wall surface of the workpiece cavity onto the camera target surface, a suitable annular scanning area is determined to ensure that the spatial resolution within the annular area meets the requirements and the image is clear. In fact, this annular area corresponds precisely to the inner wall surface image at a certain depth. Typically, the outer boundary of the annular area corresponds to the inner wall cross-sectional boundary line near the lens, and the inner boundary corresponds to the inner wall cross-sectional boundary line far from the lens. With the inner wall cross-sectional shape remaining essentially unchanged, the annular area consists of a series of similarly shaped closed boundary lines sharing a common centroid.

[0023] like Figure 3 As shown, for any line connecting in any direction, the length from the centroid to the outer boundary is... Length to inner boundary proportion Constant. Choosing a larger diameter annular region can improve the resolution of the scanned image, ensuring that the details of the inner wall are fully displayed. At the same time, the diameter of the annular region directly affects the size of the image output ROI window, thus limiting the maximum acquisition frame rate and scanning speed. Therefore, the selection of the annular region needs to comprehensively consider image resolution and acquisition efficiency, and be optimized and balanced according to the specific application.

[0024] S3. Expand the annular scanning region in each frame of cavity inner wall image through coordinate mapping to obtain a rectangular unfolded diagram of the annular scanning region in each frame of cavity inner wall image. Specifically, the annular scanning area is unfolded into a rectangular image, equivalent to the image seen by viewing the inner wall of the cavity 360 degrees along its centroidal axis. This unfolding process is achieved through the following geometric transformation: the annular scanning area... Each concentric and similar inner wall cross-sectional boundary line is straightened into a row of pixels to form a single line. The line width is The pixels. A polar coordinate system is established for the annular scan area with the centroid as the origin. Equal-interval sampling was performed on the outer boundary of the annular region (total... (Number of pixels), sampling is performed at equal intervals on each radius of the line connecting the origin and the outer boundary sampling points (total number of pixels). (pixels), obtain pixel values ​​at non-integer positions through image interpolation, and then map them to the rectangular unfolded image. On whole pixel grid points.

[0025] S4. Stitch together the rectangular unfolded images of the annular scanning area in each frame of the cavity inner wall image according to the acquisition order to obtain a panoramic unfolded image of the workpiece cavity inner wall.

[0026] like Figure 4 Specifically, the rectangular unfolded images of the circular scan areas of each frame are seamlessly stitched together in the order of acquisition to obtain a complete scan image of the inner wall surface. The row width of the stitched image is... , the column height is . When the number of rows collected per frame , the imaging consistency between different rows is best, similar to the ordinary linear array camera imaging, 1 row of image is collected each time scanning.

[0027] As shown in Figure 5 and Figure 6 , Figure 5 is a single frame image collected, the area composed of white solid lines and dashed lines is the selected annular scanning area, wherein the white solid line is the outer ring, and the white dashed line is the inner ring, Figure 6 is the scanning and synthesized inner wall surface panoramic ring view development image.

[0028] The size of the spliced image is determined by the development image of the annular scanning area. Specifically, the row width of the spliced image is equal to the width of the development image , and the width of the spliced image remains the same, ensuring seamless connection of the entire workpiece cavity hole inner wall surface image. The column height of the image is the number of pixels corresponding to the cavity hole depth at the set spatial resolution, which is determined by the camera frame rate , the number of rows collected per frame and the scanning time . The final spliced development image has a height of .

[0029] In particular, when , the splicing effect is best, because there is no image overlap at this time, and the spliced image is natural and seamless, similar to the single row scanning imaging of the conventional linear array camera. When , the motion speed of scanning and collecting can be improved , and the scanning imaging time is shortened.

[0030] The annular scanning area is the inner wall surface scanning section of each frame image, corresponding to the inner wall surface image of a certain depth section, and under the condition that the inner wall cross-sectional shape is basically unchanged, the annular area is composed of a series of similar shape closed boundary lines with a common center.

[0031] The panoramic development image is a rectangular development image containing the complete scanning height of the inner wall.

[0032] S3 is specifically as follows: S3.1, determining the size of the rectangular development image according to the outer boundary circumference of the annular scanning area and the distance between the inner boundary and the outer boundary; Specifically, the concentric and similar closed boundary lines of the annular scanning area are respectively straightened to form row width is pixels. The width of the unwrapped image is the outer ring circumference, and the height is the maximum distance difference to the image center (i.e. the maximum value).

[0033] Specifically, a polar coordinate system is established with the centroid as the coordinate origin for the annular region , and the outer ring curve is assumed to have an analytical expression , which can be a piecewise function, and the curve is a closed curve. The inner ring curve has an analytical expression , where for any , the proportional coefficient is a constant, , and the value range is .

[0034] The circumference of the outer ring boundary line is calculated, and the width of the unwrapped image is the boundary line circumference, i.e. . The unwrapped image height of each frame (the number of rows collected per frame) is the maximum value of the distance difference between the inner and outer rings to the image center, i.e. . The points on the outer ring are evenly spaced, and the line segment is equally divided, and points are selected at equal intervals on it.

[0035] In particular, when the number of collected rows , the outer ring circumference is equal to the inner ring circumference, and only a single closed curve is taken for each frame, and the corresponding row of data is unwrapped. It is equivalent to that only one inner wall section boundary ring line data is scanned and collected for each frame of image.

[0036] S3.2, according to the size of the rectangular unwrapped image and the annular scanning region, a geometric mapping relationship between the annular scanning region and the rectangular unwrapped image is established; Specifically, the points on the outer ring are evenly spaced , connected to the image center , and intersected with the inner ring , and points are selected on the line segment . Specifically, when the number of collected rows , the two points coincide, and only one image point is taken; when the number of collected rows , only two image points are taken; when , additional points need to be selected within the line segment , at this time the angle is constant, and the radial length of the th point is .

[0037] The embodiments take a standard circle and a square ring as examples, as shown in Figure 4 , wherein (A) is a schematic diagram of a circular cross-section cavity hole, and (B) is a schematic diagram of a square cross-section cavity hole. It is assumed that the image center position is , the pixel points in the unfolded diagram are represented by coordinates , and the polar coordinates in the ring diagram correspond thereto.

[0038] For a circle, as shown in Figure 4 (A), the outer ring analytical expression is , the inner ring analytical expression is , the width of the unfolded diagram is , and the mapping relationship is as follows: wherein , the outer ring radius is , the inner ring radius is , .

[0039] For a square ring, as shown in Figure 4 (B), the outer ring analytical expression is: the inner ring analytical expression is the width of the unfolded diagram is , and the mapping relationship is the same as formula (7), wherein , the outer ring side length is , the inner ring side length is , .

[0040] S3.3, according to the geometric mapping relationship between the ring scanning area and the rectangular unfolded diagram, the pixel points of the rectangular unfolded diagram are reversely mapped to the ring scanning area, and then interpolation calculation is adopted to fill the pixel values of the rectangular unfolded diagram, so as to obtain the rectangular unfolded diagram of the ring scanning area.

[0041] Specifically, the number of pixel points in the unfolded diagram is usually much more than the number of pixel points in the ring area. In the mapping process, in order to avoid the generation of an unfilled pixel area in the unfolded diagram, the corresponding pixel points in the ring diagram are reversely mapped and located through the unfolded diagram coordinates, and then the gray values of the adjacent pixels are calculated by interpolation. The pixel value at the accurate position is calculated by using the interpolation method, and this method ensures the smooth transition of the unfolded diagram pixels and the consistency of the visual effect.

[0042] The width of the rectangular unfolded diagram in S3.1 is equal to the outer boundary circumference of the ring scanning area, and the length of the rectangular unfolded diagram is equal to the maximum radial distance between the inner boundary and the outer boundary of the ring scanning area in all radial directions.

[0043] S3.3 is specifically for all pixel points of the rectangular unwrapping map respectively performing the following steps: 1) obtaining the coordinates of the current pixel point of the rectangular unwrapping map, substituting the coordinates into the geometric mapping relationship between the annular scanning area and the rectangular unwrapping map, and obtaining the corresponding coordinates of the current pixel point in the annular scanning area; 2) according to the corresponding coordinates of the current pixel point in the annular scanning area, the pixel value of the corresponding coordinates of the current pixel point in the annular scanning area is calculated by using an interpolation method; 3) the pixel value of the corresponding coordinates of the annular scanning area is assigned to the pixel value of the current pixel point of the rectangular unwrapping map.

[0044] A high-resolution imaging system for the inner wall surface of a complex workpiece cavity hole includes a stepping motor, a guide rail, a camera, and a ring light source. The imaging system is arranged above the workpiece. The output end of the stepping motor is fixedly connected to the upper surface of the sliding block of the guide rail, and is used to drive the camera to uniformly and linearly extend into the workpiece cavity hole along the center axis direction of the workpiece cavity hole. The lower surface of the sliding block of the guide rail is provided with the camera, which is arranged towards the workpiece cavity hole and is used to collect the image of the inner wall of the workpiece cavity hole. The ring light source is installed on the camera and is coaxially arranged with the camera.

[0045] It also includes a camera control module and an image processing module, which are electrically connected to the camera and are used to process the image of the inner wall of the workpiece cavity hole collected by the camera to obtain a panoramic unwrapping image of the inner wall of the workpiece cavity hole. The camera control module and the stepping motor are electrically connected, and are used to control the speed of the camera extending into the workpiece cavity hole.

[0046] In the workpiece cavity hole, the cavity boundary profile in all cross sections perpendicular to the axial direction of the workpiece cavity hole is the same, and the centers of all cross sections are located on the same vertical axis.

[0047] The imaging system drives the camera, lens and light source to rise and fall synchronously by using a single-axis linear guide rail. The guide rail is controlled by a precision stepping motor, and the driving precision directly affects the imaging quality. The workpiece is placed directly below the lens, and the opening of the cavity to be measured is vertically upward. The inner wall surface of the cavity is allowed to have a slight three-dimensional structure (protrusion or depression), but the cross section is basically unchanged, and the geometric center (center) is on the vertical line in the same vertical direction. The optical axis of the camera is perpendicular to the cross section of the cavity to be measured and coincides with the center axis of the cross section of the inner wall of the cavity.

[0048] The camera of the embodiment adopts an industrial area array camera, and the target surface resolution meets the resolution requirement of the inner wall surface visual detection of the cavity to be measured. According to the application requirement, a color or gray camera can be selected. A suitable internal inspection lens is selected for the lens, including an endoscopic wide-angle lens or a 360-degree ring-view lens, etc., to ensure that a clear and complete inner wall surface image can be collected.

[0049] Figure 2 The front-end hardware device of the image acquisition system is illustrated, showing the structure, layout and scanning motion mode of the camera, lens, light source and workpiece. According to the three-dimensional geometric structure and size of the cavity to be measured, a suitable internal inspection lens can be selected. Figure 2 (A) illustrates the acquisition device based on an endoscopic wide-angle lens, which is suitable for exploring the inside of a workpiece cavity with a very small entrance diameter. All the inner wall surfaces in the field of view in front of the lens will be projected and imaged as a circle on the camera target surface, but only the part of the inner wall close to the lens can be in focus and the closer to the lens, the higher the imaging resolution. Figure 2 (B) illustrates the acquisition device based on a 360-degree ring-view lens, which is suitable for exploring the inside of a workpiece cavity with a larger entrance diameter. Only the part of the inner wall surface close to the lens can be imaged, projected and imaged as a ring-shaped area, and the resolution is usually larger than that of the endoscopic wide-angle lens.

[0050] The ring-shaped light source can be replaced by a multi-channel light source to ensure uniform illumination of the inner wall surface of the workpiece cavity and avoid local over-brightness or over-darkness. The multi-channel light source is divided into external light source and internal light source. The external light source is located outside the cavity, and the three-dimensional geometric structure and size of the workpiece cavity to be measured are combined to design a bowl-shaped dome light source or a ring-shaped light source of appropriate size to provide basic illumination for the inside of the cavity. The internal light source is located on the lens and enters the cavity during scanning and imaging to provide local supplementary illumination.

[0051] As shown in Figure 2 (A), the external light source includes a ring-shaped light source, a multi-angle ring-view light source, and the internal light source is introduced from the side of the tail of the endoscopic lens and emitted from the front end of the lens. As shown in Figure 2 (B), the 360-degree ring-view lens is equipped with a multi-angle time-sharing stroboscopic light source, which illuminates a part of the inner wall in the field of view of the lens, and an external light source can also be provided.

[0052] The imaging system collects the cavity wall image according to the following steps: (1) Set the camera image output ROI window Adjust the size and position of the ROI (Region of Interest) window of each frame of image output of the area array camera to ensure that it can completely contain the image corresponding to the scanned section of the inner wall surface, i.e. the ring-shaped scanning area. At the same time, try to reduce the size of the ROI window to reduce the amount of data to be transmitted for each frame of image and improve the maximum acquisition frame rate available during scanning.

[0053] (2) Set the camera acquisition frame rate To improve the spatial resolution of scanning imaging, the camera acquisition frame rate should be as high as possible. But the maximum available acquisition frame rate is mainly limited by the image data transmission speed between the camera and the computer. The acquisition time interval of adjacent image frames should be greater than the transmission time of the data in the ROI window of each image output, otherwise the data transmission will lose frames. According to the image data transmission bandwidth between the camera and the computer and the amount of data in the camera image output ROI window, the image data transmission time of each frame is determined, and the camera acquisition frame rate is set .

[0054] (3) Set the scanning speed of the camera The stepping motor drives the camera to enter the workpiece cavity hole at a constant speed along the axis direction of the workpiece cavity hole. Under the drive of the mechanical motion device, the camera and the lens move at a constant speed along the optical axis direction. The motion speed (unit: m / s) is set according to the following formula: is the image acquisition frame rate, is the number of rows after the annular scanning area of each frame of image is unfolded into a rectangle (i.e. the number of pixels corresponding to the inner wall scanning section in the axis direction of each frame of image), is the imaging resolution of the inner wall scanning section in the axis direction (unit: pixels / m).

[0055] (4) Set the exposure time of the camera The relative motion between the camera and the workpiece during scanning and acquisition may cause motion blur of the image. We set the exposure time of the camera according to the following formula to control the length of the motion blur so that it does not exceed 2 pixels: After the exposure time is determined, the aperture size and the light source brightness are adjusted to make each frame of image obtain appropriate exposure and moderate brightness.

[0056] (5) Set the scanning and acquisition time According to the depth of the workpiece cavity hole to be measured , the total scanning and acquisition time of the camera motion is determined using the following formula: (6) Scan and acquire the video of the inner wall surface of the cavity hole After the working parameters of the imaging system are set according to the above steps (1)-(5), the computer first controls the mechanical device to move to the scanning starting position, and then starts the scanning and continuously acquires the images of the inner wall surface of the cavity hole. During the scanning process, the lens moves along the optical axis direction at a speed​ Uniform linear motion, the camera at a frame rate Continuously collect images.

[0057] Subsequently, the annular region corresponding to the scanning section is extracted from each frame image of the cavity hole inner wall surface video, unfolded into a 360-degree panoramic view effect rectangular region through geometric transformation, sequentially spliced according to the collection order of the image frames, and the panoramic scanning image of the inner wall surface is generated.

[0058] The above is only the technical idea of the present application, and cannot be used to limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A high-resolution imaging method for the inner wall surface of a complex workpiece cavity, characterized in that, The method comprises the following steps: S1, the imaging system uniformly enters the workpiece cavity hole along the cavity hole center axis direction, and acquires images at a preset frame rate to obtain a plurality of cavity hole inner wall images; S2, the plurality of cavity hole inner wall images are extracted to obtain a ring scanning area of each cavity hole inner wall image; S3, the ring scanning area in each cavity hole inner wall image is unfolded through coordinate mapping to obtain a rectangular unfolded image of the ring scanning area in each cavity hole inner wall image; S4, the rectangular unfolded images of the ring scanning areas in each cavity hole inner wall image are spliced according to the acquisition sequence to obtain a panoramic unfolded image of the workpiece cavity hole inner wall.

2. The high-resolution imaging method for the inner wall surface of a complex workpiece cavity according to claim 1, characterized in that: The ring scanning area is an inner wall surface image of a preset depth section in the inner wall surface scanning section of each image, and the ring scanning area is composed of a plurality of closed boundary lines with a common center.

3. The method of claim 1, wherein the method further comprises: S3 specifically comprises the following steps for the ring scanning area in each cavity hole inner wall image: S3.1, the size of the rectangular unfolded image is determined according to the outer boundary circumference of the ring scanning area and the distance between the inner boundary and the outer boundary; S3.2, a geometric mapping relationship between the ring scanning area and the rectangular unfolded image is established according to the size of the rectangular unfolded image and the ring scanning area; S3.3, the pixel points of the rectangular unfolded image are reversely mapped to the ring scanning area according to the geometric mapping relationship between the ring scanning area and the rectangular unfolded image, and then the pixel values of the rectangular unfolded image are filled by using interpolation calculation to obtain the rectangular unfolded image of the ring scanning area.

4. The method of claim 3, wherein: In S3.1, the width of the rectangular unfolded image is equal to the outer boundary circumference of the ring scanning area, and the length of the rectangular unfolded image is equal to the maximum radial distance between the inner boundary and the outer boundary of the ring scanning area in all radial directions.

5. The high-resolution imaging method for the inner wall surface of a complex workpiece cavity according to claim 3, characterized in that: S3.3 specifically comprises the following steps for all pixel points of the rectangular unfolded image: 1) the coordinates of the current pixel point of the rectangular unfolded image are obtained, and the coordinates are substituted into the geometric mapping relationship between the ring scanning area and the rectangular unfolded image to obtain the corresponding coordinates of the current pixel point in the ring scanning area; 2) the pixel value of the corresponding coordinates of the current pixel point in the ring scanning area is calculated by using the interpolation method according to the corresponding coordinates of the current pixel point in the ring scanning area; 3) the pixel value of the corresponding coordinates of the ring scanning area is assigned to the pixel value of the current pixel point of the rectangular unfolded image.

6. The high-resolution imaging method for the inner wall surface of a complex workpiece cavity according to claim 1, characterized in that: In the process of the imaging system uniformly entering the workpiece cavity hole along the cavity hole center axis direction in step S1, the movement speed of the imaging system is set according to the following formula: wherein, wherein v denotes the motion velocity of the imaging system, f is the image acquisition frame rate, n is the number of lines after the annular scanning region of each image is unfolded into a rectangle, and p is the imaging resolution of the inner wall scanning section in the axial direction.

7. A high resolution imaging system for the inner wall surface of a complex workpiece bore suitable for use in the method of any one of claims 1-6, characterized by: It comprises a stepping motor, a guide rail, a camera and a ring light source. The imaging system is arranged above the workpiece. The output end of the stepping motor is fixedly connected to the upper surface of the sliding block of the guide rail, and is used to drive the camera to uniformly and linearly enter the workpiece cavity hole along the cavity hole axis direction. The lower surface of the sliding block of the guide rail is provided with the camera, and the camera is arranged towards the workpiece cavity hole, and is used to acquire the workpiece cavity hole inner wall image. The ring light source is installed on the camera and is coaxially arranged with the camera.

8. The high resolution imaging system for the interior wall surface of a complex workpiece cavity according to claim 7, wherein: It further comprises an image processing module, and the camera and the image processing module are electrically connected, and are used to process the workpiece cavity hole inner wall image acquired by the camera to obtain the panoramic unfolded image of the workpiece cavity hole inner wall.

9. The high resolution imaging system for the interior wall surface of a complex workpiece cavity according to claim 7, wherein: In the workpiece cavity, all cavity cross sections perpendicular to the workpiece cavity axis have the same cavity boundary profile, and the centroids of all cavity cross sections are located on the same vertical axis.

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