Method for image acquisition of a transparent tubular workpiece

Abstract

The present application is suitable for product quality detection field, disclose transparent tubular workpiece image acquisition method, it includes: initialization transparent tubular workpiece's position, make transparent tubular workpiece be located in the imaging range outside of image sensing acquisition element;Control transparent tubular workpiece to set speed and direction straight line motion and rotation motion are carried out simultaneously, when transparent tubular workpiece is in the uniform velocity motion state, with the frequency of acquisition to micro mirror array sends trigger signal, will focal plane in turn align transparent tubular workpiece's upper and lower pipe wall;Receive the zoom completion signal that micro mirror array feedback, trigger image sensing acquisition element to gather the image of corresponding position, get multiple initial images, and carry out numbering and correction, obtain correction image;Based on the image splicing rule of prearranged all correction image is spliced, obtain transparent tubular workpiece image, this method can satisfy the demand of fast completion transparent tubular workpiece's image acquisition work when detecting defect, improve the efficiency and precision of defect inspection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of product quality detection, and in particular to a transparent tubular workpiece image acquisition method. BACKGROUND

[0002] In the fields of precision manufacturing, medical devices, optical fiber communication (such as microstructured optical fiber), etc., ultra-fine hollow quartz glass tube as a kind of key basic element, its quality requirement is extremely strict. For the quartz glass tube with an outer diameter of 2.4 mm, an inner diameter of 1.6 mm and a wall thickness of only 0.4 mm, any tiny defect, such as inner wall scratch, surface crack, uneven wall thickness, internal contamination or bubble, etc., may directly affect its mechanical strength, optical performance or fluid passability, resulting in unqualified final product quality detection. The inner and outer defect image detection of ultra-fine hollow glass tube needs to complete the full-size defect detection of the inner and outer walls of the hollow quartz glass tube, which is a complex image detection system problem. The detection methods commonly implemented by the industry at present mostly adopt optical detection (microscope observation) and manual sampling inspection, which are low in efficiency and high in missed detection rate. There is also an automatic scheme of image acquisition using line scan camera and single-axis motion platform, but the cost is high, the time consumption of completing full-size image acquisition in the defect detection process is long, and it is difficult to meet the high-precision and high-efficiency requirements of ultra-fine hollow glass tube defect detection in high-end industrial fields.

[0003] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0004] The purpose of the present application is to provide a transparent tubular workpiece image acquisition method, which aims to solve the technical problem of long time consumption in collecting panoramic images of the inner wall of transparent workpiece in defect detection in the prior art, which is not conducive to improving the efficiency of defect inspection.

[0005] To achieve the above-mentioned purpose, the scheme provided by the present application is:

[0006] The application discloses a transparent tubular workpiece image acquisition method, which comprises the following steps: initializing the position of the transparent tubular workpiece, so that the transparent tubular workpiece is located outside the imaging range of an image sensing acquisition element; acquiring an acquisition frequency; controlling the transparent tubular workpiece to simultaneously perform linear motion and rotary motion at a set speed and direction; when the transparent tubular workpiece is in a uniform motion state, sending a trigger signal to a micromirror array at the acquisition frequency to trigger the micromirror array to perform fast double zooming operation, so that the focal plane is sequentially aligned with the upper tube wall and the lower tube wall of the transparent tubular workpiece until the transparent tubular workpiece completes a preset stroke; receiving a zooming completion signal fed back by the micromirror array and sending an acquisition signal to the image sensing acquisition element to trigger the image sensing acquisition element to acquire images at corresponding positions, thereby obtaining a plurality of initial images; acquiring the image acquisition trigger number corresponding to each initial image, and numbering the initial images based on the image acquisition trigger number and the focal plane position, thereby obtaining numbered images; for each numbered image, using an offset angle mean value obtained through pre-calibration to correct the numbered image, thereby obtaining a corrected image; and acquiring a preset image splicing rule and splicing all the corrected images based on the preset image splicing rule, thereby obtaining a transparent tubular workpiece image.

[0007] Preferably, the acquisition frequency is determined by the light transmission range of the transparent tubular workpiece and the time for the transparent tubular workpiece to rotate 360°, the light transmission range is defined as d°, the time for the transparent tubular workpiece to rotate 360° is 1 s, and the acquisition frequency is equal to 360÷d, which is in Hz.

[0008] Preferably, the acquisition frequency is defined as f, the number of image acquisition triggers triggered in the time for the transparent tubular workpiece to rotate 360° is 2f, and the number of image acquisition triggers triggered in the time for the transparent tubular workpiece to rotate 180° is f.

[0009] Preferably, for each numbered image, the offset angle mean value obtained through pre-calibration is used to correct the numbered image, thereby obtaining a corrected image, which comprises the following steps: for each numbered image, an algorithm consistent with image affine transformation is adopted to perform geometric adjustment on the numbered image by taking the offset angle mean value as a correction parameter, thereby obtaining a corrected image.

[0010] Preferably, the preset image splicing rule comprises a splicing period, a sequence adjustment rule and a splicing direction.

[0011] Preferably, the splicing period is a 180° rotation period, the sequence adjustment rule is a combination of trigger number increment and upper and lower tube wall alternation, and the splicing direction is a combination of the circumferential direction and the length direction.

[0012] Preferably, the preset image stitching rule is acquired, and all the corrected images are stitched based on the preset image stitching rule to obtain the transparent tubular workpiece image, and specifically includes: the corrected images are sorted according to the number, and the sorting logic is: taking a rotation period as a grouping unit, and arranging the upper and lower tube walls alternately in each group according to the increasing trigger number; and the sorted corrected images are stitched at the pixel level in the order of the circumferential direction first and then the length direction to obtain the transparent tubular workpiece image.

[0013] The transparent tubular workpiece image acquisition method provided by the application only sends a trigger signal to the micromirror array at a set frequency when both motions reach a stable uniform speed, cooperates with the fast double zoom operation of the micromirror array to align the upper and lower tube walls in turn, realizes deep matching of the motion state and the acquisition rhythm, ensures that there is no omission and no overlap in acquisition, moreover, adopts zoom to complete the linkage mechanism of feedback-acquisition start, eliminates the problem of virtual focus acquisition, guarantees the definition of the initial image, at the same time, establishes a traceable identification for each image through the numbering rule of the acquisition trigger number-focal plane position, avoids confusion in batch processing, and corrects the numbered images by relying on the pre-marked mean value of the offset angle and combining the image affine transformation algorithm to accurately eliminate the coordinate system deviation, in addition, combining the preset image stitching rule, realizes continuous coverage of 0°~360° in the circumferential direction and error-free connection in the length direction, and outputs the complete image of the full surface form of the transparent tubular workpiece, so as to meet the demand of quickly completing the image acquisition of the transparent tubular workpiece in defect detection, and provide high-quality and reliable image input for the defect detection system, thereby improving the efficiency and precision of defect inspection. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only show some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from the structures shown in the drawings without creative labor.

[0015] Figure 1 is a flow chart of the transparent tubular workpiece image acquisition method provided by the embodiment of the application;

[0016] Figure 2 is an image stitching schematic diagram of the embodiment of the application;

[0017] Figure 3 is the initial image and the stitched image of 0 degrees-90 degrees completed by the transparent tubular workpiece image acquisition system provided by the embodiment of the application;

[0018] Figure 4 is a structural schematic diagram of the transparent tubular workpiece image acquisition system provided by the embodiment of the application.

[0019] Explanation of icon numbers:

[0020] 10. Imaging unit; 11. Double telecentric lens; 12. Micromirror array; 13. Image sensing and acquisition element; 14. Semi-reflective mirror; 15. Polarizer; 16. Quarter wave plate; 20. Trigger and motion control unit; 21. Drive device; 211. Linear motion platform; 212. Linear drive; 213. Rotary drive; 22. Controller; 30. Illumination unit; 31. Telecentric light source; 32. Light source fixing bracket; 100. Transparent tubular workpiece under test. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0023] It should also be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component present. When a component is described as "connected to" another component, it can be directly connected to the other component or there may be an intervening component present.

[0024] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0025] like Figures 1 to 3 As shown, this is an embodiment of the transparent tubular workpiece image acquisition method of the present invention, which is based on a transparent tubular workpiece image acquisition system, which includes a micromirror array 12 and an image sensing acquisition element 13.

[0026] Referring to Figures 1-3 The transparent tubular workpiece image acquisition method of the embodiment of the present application comprises:

[0027] S101, initializing the position of the transparent tubular workpiece, so that the transparent tubular workpiece is located outside the imaging range of the image sensing acquisition element 13;

[0028] S102, acquiring an acquisition frequency, controlling the transparent tubular workpiece to perform linear motion and rotational motion at a set speed and direction at the same time, and when the transparent tubular workpiece is in a uniform motion state, sending a trigger signal to the micromirror array 12 at the acquisition frequency to trigger the micromirror array 12 to perform fast double zoom operation, so that the focal plane is sequentially aligned with the upper and lower tube walls of the transparent tubular workpiece, until the transparent tubular workpiece completes the preset stroke;

[0029] S103, receiving the zoom completion signal fed back by the micromirror array 12, and sending an acquisition signal to the image sensing acquisition element 13 to trigger the image sensing acquisition element 13 to acquire the image at the corresponding position, to obtain a plurality of initial images;

[0030] S104, acquiring the image acquisition trigger number corresponding to each initial image, and numbering the initial images based on the image acquisition trigger number and the focal plane position, to obtain numbered images;

[0031] S105, for each numbered image, using the offset angle mean value obtained by pre-calibration to correct the numbered image, to obtain a corrected image;

[0032] S106, acquiring a preset image splicing rule, and splicing all the corrected images based on the preset image splicing rule, to obtain a transparent tubular workpiece image.

[0033] The transparent tubular workpiece of the embodiment can be a quartz glass tube. The full-size image acquisition of the quartz glass tube refers to the image acquisition of the entire length and the entire angle (360 degrees) of a glass tube.

[0034] The transparent tubular workpiece image acquisition method of the embodiment provides a quality reliable transparent tubular workpiece image for the defect detection system, so as to improve the detection accuracy.

[0035] In the embodiment, in step S101, the initialized position is used as the starting point of motion, to ensure that the transparent tubular workpiece has enough distance to accelerate to a stable uniform speed state after starting, and then enters the imaging range to complete the acquisition, to guarantee the consistency of the full-stroke image quality.

[0036] In the embodiment, the image sensing acquisition element 13 is a CMOS image sensor.

[0037] In the embodiment, in step S102, the acquisition frequency is determined by the light transmission range of the transparent tubular workpiece and the time for the transparent tubular workpiece to rotate 360°, the light transmission range is defined as d°, the time for the transparent tubular workpiece to rotate 360° is 1s, then the acquisition frequency = 360 ÷ d, the unit is Hz, for example, the light transmission range is 90°, then the acquisition frequency is 4.

[0038] In the embodiment, the acquisition frequency is defined as f, then the acquisition trigger times triggered by the transparent tubular workpiece per 360° rotation are 2f, the acquisition trigger times triggered by the transparent tubular workpiece per 180° rotation are f.

[0039] In the embodiment, the linear encoder (such as grating ruler, magnetic grating ruler) is used to acquire the position coordinates or displacement increments of the transparent tubular workpiece in the linear motion, and the rotary encoder (such as photoelectric encoder, magnetic encoder) is used to acquire the rotation angle or rotation speed data, and the data acquired is used to determine whether the transparent tubular workpiece is in the uniform motion state.

[0040] If the speed deviation of the linear and rotary motion does not exceed the threshold value within 100ms, and there is no obvious jitter (determined by the feedback data without mutation), it is determined that the transparent tubular workpiece is in the uniform motion state, otherwise it is determined that it is not in the uniform motion state.

[0041] In the embodiment, in step S103, after the micro-mirror array 12 receives the trigger signal, the fast double zoom operation is immediately performed, the focal plane is first aligned with the upper tube wall of the transparent tubular workpiece, and then switched to the lower tube wall of the transparent tubular workpiece after completion, covering the two target tube walls in turn, and the micro-mirror array sends a zoom completion signal to the controller 22 every time the focal plane switching is completed.

[0042] For example, when the micro-mirror array 12 aligns the focal plane with the upper tube wall of the transparent tubular workpiece, the feedback zoom completion signal is fed back to the controller 22, the controller 22 receives the zoom completion signal fed back by the micro-mirror array 12, sends an acquisition signal to the image sensing acquisition element 13, the image sensing acquisition element 13 receives the acquisition signal sent by the controller 22, and acquires the image.

[0043] In the embodiment, one single trigger signal corresponds to two zooms, the two zooms correspond to two zoom completion signals, the two zoom completion signals correspond to two acquisition instructions, and the two acquisition instructions correspond to two initial images (upper tube wall image and lower tube wall image), that is, the micromirror array 12 receives one single trigger signal, performs the first zoom, sends the first zoom completion signal, the controller 22 sends the first acquisition instruction, the image sensing and collecting element 13 collects the first initial image (upper tube wall image), the micromirror array 12 performs the second zoom, sends the second zoom completion signal, the controller 22 sends the second acquisition instruction, and the image sensing and collecting element 13 collects the second initial image (lower tube wall image). After the full stroke collection is completed, a plurality of initial images are accumulated, and the number of initial images is twice the number of acquisition triggers.

[0044] In step S104, the initial images are numbered based on the image acquisition trigger number and the focal plane position to obtain numbered images, that is, all initial images are uniquely numbered according to a double-dimension identification rule, and the numbering format is: image acquisition trigger number-focal plane position.

[0045] The image acquisition trigger number refers to the cumulative number of trigger signals sent by the controller, which is related to the acquisition frequency, for example, the first trigger is recorded as 1, the second trigger is recorded as 2, and so on. The focal plane position is used to distinguish the tube wall corresponding to the image, and the upper wall image is recorded as upper, and the lower tube wall image is recorded as lower. For example, the upper wall image corresponding to the third trigger signal is numbered as “3-upper”, and the lower wall image is numbered as “3-lower”.

[0046] In the embodiment, the trigger timing, focal plane position, and image tracing relationship can be established, and in subsequent correction and splicing, the corresponding acquisition scene (when the trigger is triggered, which face of the tube wall corresponds) of the image can be quickly located through the number, the number of images collected in the full stroke collection is large, for example, 200 initial images are obtained by 100 acquisition triggers, and the number can clearly distinguish the uniqueness of each image, and provide order guarantee for batch processing (correction and splicing).

[0047] Please refer to Figure 4As shown, in the present embodiment, in step S105, the transparent tubular workpiece image acquisition system comprises an imaging unit 10, a trigger and motion control unit 20, and an illumination unit 30. The trigger and motion control unit 20 comprises a driving device 21 for carrying and driving the measured transparent tubular workpiece 100 to move horizontally and rotate, and a controller 22. The imaging unit 10 comprises a double telecentric lens 11, the above-mentioned micro-mirror array 12, the above-mentioned image sensing acquisition element 13, and a half mirror 14. The driving device 21 and the micro-mirror array 12 are respectively connected with the controller 22. The illumination unit 30 comprises a telecentric light source 31 arranged directly below the double telecentric lens 11 and below the measured transparent tubular workpiece 100. The parallel light source emitted by the telecentric light source 31 is vertically irradiated to the measured transparent tubular workpiece 100. The parallel light source passes through the measured transparent tubular workpiece 100, enters the double telecentric lens 11 after three times of refraction, and is filtered and calibrated by the double telecentric lens 11. After being transmitted by the half mirror 14, the light enters the micro-mirror array 12. The micro-mirror array 12 receives the trigger signal of the controller 22, and adjusts the light direction to be aligned with the imaging focal plane of the upper tube wall and the imaging focal plane of the lower tube wall of the measured transparent tubular workpiece 100 in sequence. The light reflected by the micro-mirror array 12 is reflected to the image sensing acquisition element 13 through the half mirror 14, and is converted into a digital image signal by the image sensing acquisition element 13.

[0048] In the present embodiment, the imaging unit 10 further comprises a polarizer 15 and a 1 / 4 wave plate 16. The polarizer 15 is arranged between the double telecentric lens 11 and the half mirror 14. The 1 / 4 wave plate 16 is arranged between the half mirror 14 and the micro-mirror array 12. After being filtered and calibrated by the double telecentric lens 11, the light is filtered by the polarizer 15 to be polarized light with only one polarization direction, enters the half mirror 14, and is transmitted by the polarizer 15 to enter the 1 / 4 wave plate 16. After adjusting the incident polarization angle, the 1 / 4 wave plate 16 enters the micro-mirror array. The micro-mirror array 12 receives the trigger signal of the controller 22, and adjusts the light direction to be aligned with the imaging focal plane of the upper tube wall and the imaging focal plane of the lower tube wall of the measured transparent tubular workpiece 100 in sequence. The light reflected by the micro-mirror array 12 enters the half mirror 14 after the polarization angle is adjusted again by the 1 / 4 wave plate 16. At this time, the half mirror 14 only allows the polarized light to be reflected, so that the light is finally projected to the image sensing acquisition element 13, and is converted into a digital image signal by the image sensing acquisition element 13. The polarizer 15 can filter out the chaotic polarized light (such as the surface diffuse reflection light and the internal multiple scattering light) generated by the refraction / reflection of the transparent tubular workpiece, and only keep the single polarized light propagating along the target direction, thereby reducing the interference of stray light on imaging from the source. In combination with the adjustment of the polarization angle by the 1 / 4 wave plate 16, the polarization state disorder light caused by the characteristics of the transparent material can be further weakened, so as to avoid the image from appearing halo, fog, or detail blur.

[0049] Furthermore, the driving device 21 includes a linear motion platform 211, a linear drive component 212, and a rotary drive component 213. The linear drive component 212 is connected to the linear motion platform 211 and is used to drive the linear motion platform 211 to move the transparent tubular workpiece 100 under test in a horizontal linear motion. The rotary drive component 213 is mounted on the linear motion platform 211 and is used to drive the transparent tubular workpiece 100 under test to rotate. The combined drive of linear motion and rotary motion can basically drive the transparent tubular workpiece 100 under test to achieve all-round imaging without blind spots, avoiding missing tube wall defects. Moreover, the driving device 21 has a clear division of labor, more precise motion control, and is suitable for the detection of transparent tubular workpieces of different lengths and specifications.

[0050] Understandably, in this embodiment, the linear drive 212 can be a linear motor, the rotary drive 213 can be a rotary motor, and a gripper (not shown) is installed at the end of the rotary motor shaft. The gripper holds the transparent tubular workpiece 100 to be tested. The gripper gripping position does not exceed 5mm, and the gripping force of the gripper will not damage the transparent tubular workpiece 100 to be tested.

[0051] Specifically, the calibration method for the offset angle includes: placing the dot array calibration plate on a linear motion platform and driving the linear motion platform to move the dot array calibration plate to one side of the field of view of the imaging unit 10; moving the linear motion platform at a fixed distance, acquiring an image of the dot array calibration plate through the imaging unit 10 each time the platform moves, obtaining multiple images of the dot array calibration plate, each image of the dot array calibration plate including multiple dots; calculating the offset angle of each group of corresponding dots in two adjacent images of the dot array calibration plate; calculating the average value of all offset angles, obtaining the mean offset angle, and completing the calibration.

[0052] It should be noted that since the image acquisition system uses a dual telecentric imaging lens, the calibration can be simplified to the calibration of the system's vertical rotation angle.

[0053] In this embodiment, calculating the center offset angle of each group of corresponding dots in two adjacent dot array calibration plate images specifically includes: calculating the ratio of the center of the dots in the later dot array calibration plate image to the center of the corresponding dots in the previous dot array calibration plate image. Directional offset and Directional offset; based on Directional offset and The directional offset is calculated to obtain the offset angle of each dot center in the subsequent dot array calibration plate image compared to the corresponding dot center in the previous dot array calibration plate image; the average value of all offset angles is calculated to obtain the average offset angle, thus completing the calibration.

[0054] In this embodiment, it is assumed that The direction refers to the moving direction of the linear motion platform, The direction refers to the direction perpendicular to the direction of the linear motion platform, and the pixel resolution of the image collected by the imaging unit 10 is , the fixed distance is , and a total of times of movement is performed, so a total of images of the circular dot array calibration board are shot, each of which includes circular dots , and the center of each circular dot is , so that:

[0055]

[0056]

[0057]

[0058]

[0059] In the formula, represents the offset of the center of the th circular dot in the th image in the direction, represents the offset of the center of the th circular dot in the th image in the direction, represents the coordinate of the center of the th circular dot in the th image in the direction, represents the coordinate of the center of the th circular dot in the th image in the direction, represents the offset angle of the center of the th circular dot in the th image and the corresponding center of the circular dot in the th image, represents the mean offset angle, that is, the mean value of all offset angles, which eliminates random errors.

[0060] It can be understood that the above formula is used to calculate the offset (in pixels) of a single circular dot in the moving direction of the displacement table (the direction): the fixed distance is moved by s um, and the image resolution is u um, so s / u obtains the offset of a single circular dot in the moving direction of the displacement table (the direction) in pixels.

[0061] It can be understood that the core principle of the calibration method is: using the characteristics of the double telecentric lens 11 to simplify the calibration dimension, collecting multiple groups of images through the straight line motion of the circular dot array calibration board, calculating the offset angle of the corresponding circular dots in the adjacent images and taking the average value, and realizing the accurate calibration of the vertical direction rotation angle of the system. Specifically embodied as:

[0062] The center position deviation of the same circular dot in the adjacent two images is caused by the vertical rotation angle of the system. By calculating the direction (the direction of the platform motion) and direction (the vertical direction of the platform) offset of the circular dot center of the latter image relative to the former image, the offset angle of a single circular dot is calculated according to the geometric relationship, and the accidental error is offset through the average processing of multiple groups of circular dot data.

[0063] The average value of all the calculated offset angles is taken to obtain the calibration result of the vertical direction rotation angle of the image acquisition system. The average value can more accurately reflect the actual deviation of the system, ensure the geometric accuracy of the image acquisition after calibration, and provide calibration basis for the accurate imaging of the measured transparent tubular workpiece 100. The characteristics of the double telecentric lens 11 simplify the calibration to vertical direction rotation angle calibration, and multiple images are collected by moving the circular dot array calibration board with the straight line motion platform at a fixed distance. The 、 direction offset angle of the corresponding circular dots in the adjacent images is calculated and the average value is taken, which not only simplifies the calibration process and reduces the operation complexity, but also effectively offsets the accidental error and ensures the calibration accuracy.

[0064] In this embodiment, for each numbered image, an algorithm consistent with image affine transformation is used, and the average value of the offset angle is used as the correction parameter to perform geometric adjustment such as rotation and translation on the numbered image, so as to eliminate the image tilt and position deviation caused by the coordinate system deviation. The adjusted image is the corrected image, and its geometric shape and position are completely matched with the actual pipe wall shape of the workpiece. Even if there is a slight installation deviation of the imaging unit 10 and the trigger and motion control unit 20, the coordinate systems of all images can be ensured to be the same through correction. Moreover, if not corrected, the images collected at different trigger times will have splicing gaps or overlaps due to the coordinate system deviation, and the corrected images can ensure pixel-level alignment when splicing.

[0065] In this embodiment, in step S106, the preset image stitching rules include a stitching period, a sequence adjustment rule, and a stitching direction. The stitching period is a 180° rotation period, the sequence adjustment rule is an increasing trigger number combined with alternating upper and lower tube walls, and the stitching direction is a combination of the circumferential direction and the length direction. The preset image stitching rules are obtained, and all corrected images are stitched together based on these rules to obtain a transparent tubular workpiece image. Specifically, this includes: sorting the corrected images by number, with the sorting logic being: using the rotation period as a grouping unit, and within each group arranged by an increasing trigger number combined with alternating upper and lower tube walls; and stitching the sorted corrected images pixel-level according to the order of circumferential direction first, then length direction, to obtain a transparent tubular workpiece image.

[0066] In this embodiment, the length direction refers to the distance from the start point to the end point of the journey.

[0067] In this embodiment, the acquisition method only covers a local area of ​​the tube wall (a 90° area between the upper and lower tube walls) in a single acquisition. By stitching and integrating all corrected images, a single image is equivalent to the entire surface of the transparent tubular workpiece. For example, let the controller acquisition frequency be... (4Hz), meaning the controller triggers every 360°. =4 times, image acquisition triggered =8 times; controller triggers every 180° =2 times, image acquisition triggered =4 times. At this time, the tube wall is divided into 4 arc surfaces. The images collected from each arc surface are sequentially spliced ​​according to the increasing trigger number and the alternation of the upper and lower walls to form a complete image covering the entire circumference and length of the transparent tubular workpiece. The splicing sequence is arranged alternately according to the increasing trigger number and the alternation of the upper and lower walls. It starts with the upper pipe wall image of the kth trigger (k from 1 to f), i.e., "k-up". The upper pipe wall image is recorded as "k+(t-1)×f / 2-up", where t increases by odd numbers. The lower pipe wall image is recorded as "k+(t-1)×f / 2-down", where t increases by even numbers. This alternation is arranged to obtain "k-up→(k+1*f / 2)-down→(k+2*f / 2)-up→…→(k+(t-1)*f / 2)-down". This ensures that the upper and lower pipe wall images are continuous in the circumferential direction after flipping. The continuity of the two directions must be ensured simultaneously during splicing. The circumferential direction is connected in the order of 0°~360°. The length direction is arranged in the order from the starting point to the end point of the straight movement of the transparent tubular workpiece. Finally, a complete image covering the entire circumference and length of the transparent tubular workpiece is formed.

[0068] In this embodiment, f is a non-zero even number.

[0069] For example, the splicing sequence is:

[0070] 1-up, (1+ ) - up, (1 ) - up, (1 ) - up, (1 ) - up, (1 ) - up

[0071] 2 - up, (2 ) - up, (2 ) - up, (2 ) - up, (2 ) - up, (2 ) - up

[0072] …,

[0073] ) - up, (3 + ) - up, (3 + ) - up, (3 + ) - up, (3 + ) - up, (3 + ) - up.

[0074] With the light range of the transparent tubular workpiece being 90 degrees, the image field range being 6.4mm, and the design magnification being 1 times, the parameters of the transparent tubular workpiece image acquisition system are taken as an example, the speed of the rotary driving member 213 is 360° / s, the speed of the linear driving member 212 is 12.88mm / s, the controller triggering frequency is 4Hz, i.e., f=4, the acquisition image part splicing diagram is shown as Figure 2 , and Figure 3 The initial image and the spliced image from 0 degrees to 90 degrees completed by the transparent tubular workpiece image acquisition system are exemplarily given.

[0075] It should be noted that Figure 2 is only a part of the example, the acquisition image is not terminated at 8, and the ellipsis omits the subsequent acquisition number, for example, after 7 - down, the subsequent 9 - up, 11 - down, 13 - up, etc. are omitted, and the specific number depends on the tube length of the transparent tubular workpiece.

[0076] As Figure 2As shown, assuming that the transparent tubular workpiece is divided into an arc surface every 90 degrees, and each arc surface is named as the first arc surface, the second arc surface, the third arc surface and the fourth arc surface, assuming that when the transparent tubular workpiece is in a uniform motion state, the first trigger signal is sent to the micromirror array, and the first arc surface is just in the collection range of the image sensing collection element, at this time, the collected upper tube wall image is the image of the first arc surface, named as 1-upper, and the collected lower tube wall image is the image of the third arc surface, named as 1-lower, at the same time, the transparent tubular workpiece keeps straight line motion and rotation motion at the set speed and direction, when the second trigger signal is sent to the micromirror array, the transparent tubular workpiece rotates 90 degrees compared with the position at the first trigger signal, the second arc surface is in the collection range of the image sensing collection element, then the collected upper tube wall image is the image of the second arc surface, named as 2-upper, and the collected lower tube wall image is the image of the fourth arc surface, named as 2-lower, when the third trigger signal is sent to the micromirror array, the transparent tubular workpiece rotates 270 degrees compared with the position at the first trigger signal, then the collected upper tube wall image is the image of the third arc surface, named as 3-upper, and the collected lower tube wall image is the image of the first arc surface, named as 3-lower, when the fourth trigger signal is sent to the micromirror array, the transparent tubular workpiece rotates 360 degrees compared with the position at the first trigger signal, then the collected upper tube wall image is the image of the fourth arc surface, named as 4-upper, and the collected lower tube wall image is the image of the second arc surface, named as 4-lower. Because the collection frequency, the motion speed and the image fov match, when 3-lower is collected, the straight line motion ensures that 1-upper and 3-lower are just different by an image fov distance, therefore, when the images corresponding to the first arc surface are sequentially spliced, 1-upper and 3-lower are sequentially spliced, by analogy, when the images corresponding to the second arc surface are sequentially spliced, 2-upper and 4-lower are sequentially spliced, when the images corresponding to the third arc surface are sequentially spliced, 1-lower and 3-upper are sequentially spliced, and when the images corresponding to the fourth arc surface are sequentially spliced, 2-lower and 4-upper are sequentially spliced.

[0077] The image FOV matching refers to that the field of view (FOV) of two or more images reaches a preset consistency or complementary adaptation relationship in the spatial range, coverage area and scaling ratio, and the core is to ensure that the observation range of multiple images meets the requirements of subsequent processing (such as splicing, comparison and fusion).

[0078] The transparent tubular workpiece image acquisition method of the embodiment only sends a trigger signal to the micromirror array at a set frequency when both motions reach a stable uniform speed state, cooperates with the fast double zoom operation of the micromirror array to align the upper and lower tube walls in turn, realizes the deep matching of the motion state and the acquisition rhythm, ensures that there is no omission and no overlap in the acquisition, moreover, adopts the zoom to complete the linkage mechanism of feedback-acquisition start, eliminates the problem of false focus acquisition, guarantees the clarity of the initial image, at the same time, through the numbering rule of the acquisition trigger number-focal plane position, a traceable identification is established for each image, batch processing confusion is avoided, and relying on the pre-marked mean value of the offset angle, combined with the image affine transformation algorithm, the numbered image is corrected to accurately eliminate the coordinate system deviation, in addition, combined with the preset image splicing rule, the continuous coverage of 0°~360° in the circumferential direction and the error-free connection in the length direction are realized, and the complete image of the full surface morphology of the transparent tubular workpiece is output, so that the demand of quickly completing the image acquisition work of the transparent tubular workpiece in the defect detection can be met, and high-quality and reliable image input is provided for the defect detection system, so that the efficiency and precision of the defect inspection can be improved.

[0079] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made under the inventive concept of the present application, using the content of the present application specification and drawings, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A method of image acquisition of a transparent tubular workpiece, characterized in that, The transparent tubular workpiece image acquisition method is realized based on a transparent tubular workpiece image acquisition system, the transparent tubular workpiece image acquisition system comprises a micromirror array and an image sensing acquisition element, and the transparent tubular workpiece image acquisition method comprises the following steps: initializing the position of the transparent tubular workpiece, so that the transparent tubular workpiece is located outside the imaging range of the image sensing acquisition element; acquiring an acquisition frequency, controlling the transparent tubular workpiece to perform linear motion and rotational motion at a set speed and direction at the same time, and when the transparent tubular workpiece is in a uniform motion state, sending a trigger signal to the micromirror array at the acquisition frequency to trigger the micromirror array to perform fast double zoom operation, so that the focal plane is sequentially aligned with the upper and lower tube walls of the transparent tubular workpiece until the transparent tubular workpiece completes a preset stroke; receiving a zoom completion signal fed back by the micromirror array, and sending an acquisition signal to the image sensing acquisition element to trigger the image sensing acquisition element to acquire images of corresponding positions to obtain a plurality of initial images; acquiring an image acquisition trigger number corresponding to each initial image, and numbering the initial images based on the image acquisition trigger number and the focal plane position to obtain numbered images; for each numbered image, using an offset angle mean value obtained through pre-calibration to correct the numbered image to obtain a corrected image; acquiring a preset image splicing rule, and splicing all the corrected images based on the preset image splicing rule to obtain a transparent tubular workpiece image.

2. The transparent tubular workpiece image acquisition method of claim 1, wherein, The acquisition frequency is determined by the light transmission range of the transparent tubular workpiece and the time for the transparent tubular workpiece to rotate 360°, the light transmission range is defined as d°, the time for the transparent tubular workpiece to rotate 360° is 1s, and then the acquisition frequency = 360 ÷ d, with the unit of Hz.

3. The transparent tubular workpiece image acquisition method of claim 2 wherein, Defining the acquisition frequency as f, the number of image acquisition triggers triggered in the time for the transparent tubular workpiece to rotate 360° is 2f, and the number of image acquisition triggers triggered in the time for the transparent tubular workpiece to rotate 180° is f.

4. The transparent tubular workpiece image acquisition method of claim 1 wherein, For each numbered image, using an offset angle mean value obtained through pre-calibration to correct the numbered image to obtain a corrected image, comprising: for each numbered image, using an algorithm consistent with image affine transformation, taking the offset angle mean value as a correction parameter, and performing geometric adjustment on the numbered image to obtain a corrected image.

5. The transparent tubular workpiece image acquisition method of claim 1 wherein, The preset image splicing rule comprises a splicing period, a sequence adjustment rule and a splicing direction.

6. The transparent tubular workpiece image acquisition method of claim 5 wherein, The splicing period is a 180° rotation period, the sequence adjustment rule is an incremental combination of the upper and lower tube walls, and the splicing direction is a circumferential direction combination of a length direction.

7. The transparent tubular workpiece image acquisition method of claim 5 wherein, The acquisition of the preset image splicing rule and the splicing of all the corrected images based on the preset image splicing rule to obtain a transparent tubular workpiece image specifically comprises: sorting the corrected images according to the number, and the sorting logic is: taking a rotation period as a grouping unit, and arranging the images in each group in an incremental combination of the trigger number and the upper and lower tube walls alternately; performing pixel-level splicing on the sorted corrected images in the order of the circumferential direction first and then the length direction to obtain a transparent tubular workpiece image.

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