Scanning sampling method and device

Abstract

The invention provides a scanning sampling method and device. The method provided by the invention comprises the following steps: determining a motion path penetrating through a single scanning area of a linear array detector, wherein the maximum width of the scanning area is smaller than the size of a to-be-scanned workpiece; according to the fan-beam included angle of the linear array detector, determining a single rotation angle interval of the rotary table; the rotary table moves back and forth along a motion path, the linear array detector collects a scanning image of a workpiece in single motion, and the scanning image at least comprises a first direction image and a second direction image which are along the motion path of the rotary table but are opposite in direction; before single-time movement, based on the single-time rotation angle interval and the current rotation angle of the rotary table, the rotary value of the rotary table is calculated, and the rotary table is driven to rotate; and splicing the scanned images acquired at adjacent time to obtain complete projection data. According to the scanning and sampling method provided by the invention, the large-size workpiece can be completely scanned, and meanwhile, the scanning precision and the reconstructed image quality are improved.

Description

Technical Field

[0001] This application relates to the field of digital scanning imaging technology for nondestructive testing, and in particular to a scanning sampling method and apparatus. Background Technology

[0002] Scanning sampling systems typically consist of an accelerometer, a linear array detector, and a motion mechanism. The detector receives rays that penetrate the workpiece to obtain projection data. To cover larger workpieces, linear array detectors generally employ a multi-channel arrangement. However, as the number of channels increases, the difficulty in ensuring crystal consistency, controlling electrical noise, designing readout links, and synchronous acquisition significantly increases, leading to higher manufacturing costs. Furthermore, limitations imposed by crystal processing technology, array structure, and heat dissipation restrict the channel spacing, limiting the spatial sampling density of the detector. Larger channel spacing not only constrains the size range of detectable workpieces but also results in insufficient projection data resolution, affecting the quality of the final reconstructed image. Therefore, improving the system's coverage of large workpieces and enhancing the consistency and quality of the projected image within a limited number of channels and a fixed channel spacing is a pressing technical challenge in this field. Summary of the Invention

[0003] In view of this, this application provides a scanning sampling method and apparatus to solve the problems of insufficient coverage of large-sized workpieces and degraded projection data quality in existing scanning sampling systems.

[0004] Specifically, this application is implemented through the following technical solution:

[0005] A first aspect of this application provides a scanning sampling method, the method comprising:

[0006] Determine the motion path through a single scan area of ​​the linear array detector, wherein the maximum width of the single scan area is smaller than the size of the workpiece to be scanned;

[0007] Determine the fan beam angle of the linear array detector, and determine the single rotation angle interval of the turntable based on the fan beam angle;

[0008] The turntable moves back and forth along the motion path. The linear array detector acquires a scanned image of the workpiece above the turntable during a single motion. Depending on the direction of the turntable's motion, the scanned image includes at least a first-direction image and a second-direction image. The first and second directions are parallel and opposite in direction. Before a single motion, the rotation value of the turntable is calculated based on the single rotation angle interval and the current rotation angle of the turntable. The turntable rotates by the angle corresponding to the rotation value.

[0009] By stitching together at least one first-direction image and at least one second-direction image acquired at adjacent acquisition times, complete projection data of the workpiece is obtained.

[0010] A second aspect of this application provides a scanning sampling device, the device comprising a determining module, a processing module, and a stitching module; wherein...

[0011] The determining module is used to determine the motion path through a single scan area of ​​the linear array detector, wherein the maximum width of the single scan area is smaller than the size of the workpiece to be scanned.

[0012] The determining module is used to determine the fan beam angle of the linear array detector and determine the single rotation angle interval of the turntable based on the fan beam angle.

[0013] The processing module is used to make the turntable move back and forth according to the motion path. The linear array detector acquires a scan image of the workpiece above the turntable in a single motion. The scan image includes at least a first direction image and a second direction image depending on the motion direction of the turntable. The first direction and the second direction are parallel and opposite in direction. Before a single motion, the rotation value of the turntable is calculated based on the single rotation angle interval and the current rotation angle of the turntable. The turntable rotates by the angle corresponding to the rotation value.

[0014] The stitching module is used to stitch together at least one first-direction image and at least one second-direction image acquired at adjacent acquisition times to obtain complete projection data of the workpiece.

[0015] The scanning sampling method and apparatus provided in this application, under the constraint of limited linear array detector size, achieve complete projection data acquisition of large-sized workpieces through scanning path planning and multiple round-trip scanning strategies of the linear array detector, combined with subsequent image alignment and stitching processing. First, the motion path through the single-scan area of ​​the linear array detector is determined, ensuring that the maximum width of the single-scan area is less than the size of the workpiece to be scanned, thereby guaranteeing that the scanning area can controllably cover and move across the object's surface. Then, the single-rotation angle interval of the turntable is determined based on the fan beam angle of the linear array detector, ensuring that the coverage angle of each round-trip scan meets the continuous acquisition requirements, thus providing a reliable angular basis for subsequent projection stitching. During the scanning process, the turntable moves back and forth according to the motion path, and the linear array detector acquires the corresponding scan image in each unidirectional movement. Depending on the turntable's movement direction, the scan image includes at least a first-direction image and a second-direction image, with the two directions being opposite. Before starting a single scan, a rotation value is calculated based on the current rotation angle and a preset single-rotation angle interval, causing the turntable to rotate to the target angle before scanning, ensuring continuous image coverage within the angular domain. Finally, the scanned images acquired at adjacent times are stitched together according to their temporal order and spatial correspondence to obtain the complete projection data of the workpiece. This method can achieve complete projection acquisition of large-sized workpieces by means of the movement of a turntable, even when the number of detector channels is limited and the field of view is restricted in a single scan. In addition, by setting the movement speed of the turntable, higher scanning image accuracy can be obtained, significantly improving the adaptability of the scanning sampling system to large-sized workpieces and the imaging quality. Attached Figure Description

[0016] Figure 1 A flowchart of Embodiment 1 of the scanning sampling method provided in this application;

[0017] Figure 2 This is a schematic diagram of a scanning sampling device shown in an exemplary embodiment of this application;

[0018] Figure 3 A general timing diagram illustrating a synchronous scanning method as shown in an exemplary embodiment of this application;

[0019] Figure 4 This is a schematic diagram illustrating the sampling interval of different channels of a linear array detector, as shown in an exemplary embodiment of this application.

[0020] Figure 5 This is a schematic diagram illustrating the scanning image rotation process of an exemplary embodiment of this application;

[0021] Figure 6 This is a schematic diagram of scanned image stitching shown in an exemplary embodiment of this application;

[0022] Figure 7This is a schematic diagram of the structure of a first embodiment of the scanning sampling device provided in this application. Detailed Implementation

[0023] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0024] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0025] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0026] The following specific embodiments are given to illustrate the technical solution of this application in detail.

[0027] Figure 1 This is a flowchart of an embodiment of the scanning sampling method provided in this application. Please refer to... Figure 1 The method provided in this embodiment may include:

[0028] S101. Determine the motion path through the single-scan area of ​​the linear array detector, wherein the maximum width of the single-scan area is less than the size of the workpiece to be scanned.

[0029] Figure 2 This is a schematic diagram of a scanning sampling device shown in an exemplary embodiment of this application. Please refer to... Figure 2 , Figure 2 (a) illustrates the structure of the scanning sampling device provided in this embodiment. The device includes hardware units such as an accelerator, a linear array detector, and a turntable. The accelerator is used to emit a pulsed X-ray beam to the workpiece to be scanned. The linear array detector is set in the direction of the accelerator's emission and is used to receive the X-rays after exposure. The turntable is used to carry and drive the workpiece to perform horizontal reciprocating motion, and can also perform rotation at a specified angle according to control commands.

[0030] Specifically, during scanning, the workpiece is placed on a turntable, which moves horizontally back and forth along a preset path. The accelerator continuously emits pulsed X-rays during this motion, while a linear array detector simultaneously acquires projection data. Since the effective width of the linear array detector is limited, this application designs the workpiece's reciprocating motion path relative to the detector, combined with a segmented rotation method for the turntable, to ensure that a single scan covers all areas of the workpiece at different angles. Finally, complete projection data of the workpiece is obtained through image stitching.

[0031] Specifically, when determining the motion path of a single scan area, it is first necessary to determine the fan-shaped coverage range of the accelerator beam on the scanning plane based on the accelerator's beam width and divergence angle, thus obtaining the outermost boundary of the image that the beam can image. Then, combining the projection positions of each channel of the linear array detector in the plane, the overall detectable area of ​​the linear array detector is determined, and this is superimposed with the accelerator beam range to obtain the actual imageable effective fan-shaped area. Based on this, the position of the central beam corresponding to the central channel of the linear array detector is determined. Using this central beam as a reference direction, a horizontal straight line is drawn vertically to serve as the single scan motion path for the workpiece. When the workpiece moves back and forth along this horizontal path, the relative position of the beam and the workpiece during sampling is ensured to be stable and highly repeatable, thereby improving scanning accuracy.

[0032] It should be noted that the direction of motion of the workpiece is perpendicular to the central beam of the accelerator, which ensures that the relative position of the beam and the workpiece is accurate and highly repeatable during each sampling, thereby reducing the projection geometric error caused by deviation of the motion direction and improving the scanning accuracy and the quality of the reconstructed image.

[0033] It should be noted that, in order to achieve scanning of large-sized workpieces, this embodiment limits the single-scan area to a local range that the linear array detector can cover under fixed geometric conditions, and constrains the maximum width of this single-scan area to be less than the overall lateral dimension of the workpiece. To ensure that the workpiece completely enters from outside the ray coverage area and completely exits it, each channel on the detector can scan the entire range of the workpiece. In other words, a single left-to-right scan scans a portion of the entire workpiece's angle (i.e., the detector's fan beam angle), thereby achieving sequential scanning of different angles through the workpiece's reciprocating motion.

[0034] S102. Determine the fan beam angle of the linear array detector, and determine the single rotation angle interval of the turntable based on the fan beam angle.

[0035] Specifically, the fan beam angle of the linear array detector is obtained, and this fan beam angle is used as the effective angular coverage range for a single scan. Furthermore, the rotation angle interval of the turntable between two adjacent scans is set according to this angular coverage range, so that the turntable completes sampling of the full angular range in a preset angular step during successive scans.

[0036] Optionally, in one possible implementation, determining the fan beam angle of the linear array detector and determining the single rotation angle interval of the turntable based on the fan beam angle further includes:

[0037] (1) Obtain the number of channels of the linear array detector and the angle between each channel, and calculate the fan beam angle based on the number of channels and the angle value.

[0038] Specifically, the total number of channels n of the linear array detector and the fixed angle α between adjacent channels are obtained. The geometric arrangement of each channel can be obtained from device calibration data or detector design parameters. When the linear array detector has an equiangular arrangement, the angle between the ray directions of adjacent channels remains constant; therefore, the fan beam angle of the linear array detector can be directly calculated based on the number of channels and the angle values. .

[0039] (2) Determine the single rotation angle interval of the turntable according to the fan beam angle, wherein the single rotation angle interval is less than or equal to the fan beam angle.

[0040] Specifically, after obtaining the fan beam angle β, the single rotation angle interval of the turntable is further determined. In a specific implementation, the single rotation angle interval can be set to any positive value less than or equal to the fan beam angle, based on the angle coverage required for image acquisition, to ensure that the projection data of two adjacent scans have sufficient angle difference and meet the reconstruction requirements. Preferably, the single rotation angle interval can be set to be less than the fan beam angle to ensure that there is an overlapping area between two adjacent scan images, thereby improving the continuity in the angular dimension when stitching adjacent scan images. The single rotation angle interval can be set according to the scanning accuracy, imaging resolution, and system kinematic constraints. For example, the optimal interval value can be selected through experimental calibration based on the detector fan beam coverage and the angle sampling density requirements of the reconstruction algorithm, so that the scan position after two consecutive rotations will not have excessively sparse projection angles, nor will it cause an efficiency decrease due to excessive repeated acquisition.

[0041] S103. The turntable moves back and forth along the motion path. The linear array detector acquires a scanned image of the workpiece above the turntable in a single motion. Depending on the direction of motion of the turntable, the scanned image includes at least a first direction image and a second direction image. The first direction and the second direction are parallel and opposite in direction. Before a single motion, the rotation value of the turntable is calculated based on the single rotation angle interval and the current rotation angle of the turntable. The turntable rotates by the angle corresponding to the rotation value.

[0042] Specifically, the turntable reciprocates along a preset path on a horizontal axis. During each uniform rotation of the turntable, the linear array detector synchronously receives pulsed X-rays emitted by the accelerator, acquiring a localized projection scan image. Then, the turntable rotates according to the calculated rotation value, and repeats the reciprocating motion along the preset path until the cumulative scanning angle reaches at least 180°, thereby obtaining scan images in all first or second directions. Please refer to [reference needed]. Figure 2 (a) where the first direction is the turntable moving from left to right, and the second direction is the turntable moving from right to left. Multiple scanned images in the first and second directions provide continuous data segments for subsequent projection stitching. The specific implementation steps are as follows:

[0043] (1) Control the accelerator beam output and achieve a stable beam output state.

[0044] Specifically, the beam dose rate of the accelerator will fluctuate in the short period after startup. To ensure the stability of the acquired images, the motion scanning phase of the turntable should only be started after the accelerator dose rate reaches a stable value.

[0045] Optionally, in one possible implementation, before the turntable reciprocates along the motion path, the method further includes:

[0046] (A) The scanning sampling method uses an accelerator as a radiation source, controls the accelerator to enter the preheating beam output stage, and detects the rate of change of the output beam dose of the accelerator within a preset time window until the rate of change is lower than a preset threshold.

[0047] Specifically, during the preheating and beam-out phase, the control system starts the accelerator and continuously monitors the accelerator output dose within a preset time window. The rate of change of dose per unit time is measured and compared with a preset threshold. When the rate of change is less than the preset threshold, the accelerator is determined to be in a stable beam-out state. In this embodiment, the accelerator reaches a stable beam-out state within 7 seconds of startup. Accelerators at different energy levels may have different stable dose rates, but the stabilization condition can be detected using this method, ensuring a consistent radiation dose at each sampling point during the scanning process and avoiding uneven image brightness or signal-to-noise ratio due to dose fluctuations. When the rate of change of the accelerator output dose is lower than the set stabilization threshold for multiple consecutive sampling periods, the accelerator is confirmed to have entered a stable beam-out state. The stabilization threshold characterizes the allowable range of dose fluctuation per unit time and can be set according to the accelerator model, beam characteristics, or image quality requirements. The duration of the continuous sampling period can also be determined according to system requirements to ensure that the accelerator's beam output remains stable within a certain time range. The accelerator stabilizes the output beam to ensure that the dose received at each sampling point is consistent during the scanning process, thereby avoiding uneven image brightness or signal-to-noise ratio caused by dose fluctuations, which would affect the quality of the final reconstructed image.

[0048] (B) Keep the accelerator continuously emitting beams until all the scan images have been acquired.

[0049] Specifically, the accelerator continues to emit beams until all scanned images are acquired, to ensure that scanned data from different angles and channels are comparable and consistent, and to avoid data distortion or acquisition deviation caused by beam interruption or fluctuation.

[0050] (2) Control the turntable to move back and forth along the preset path, and the linear array detector synchronously acquires the scan image of the workpiece above the turntable.

[0051] Specifically, after the accelerator beam dose rate stabilizes, the turntable first rotates to the initial starting position of the scan to begin the first round-trip scan. For each subsequent round-trip scan, the turntable adjusts its angle based on the rotation value calculated from the previous scan before starting horizontal movement to ensure the correct starting position for each scan. During the scanning process, to maintain a constant final sampling interval, in this embodiment, the turntable must reach a set uniform speed before entering the fan beam coverage area. Uniform speed ensures equidistant displacement of the workpiece during scanning, thereby guaranteeing a uniform spatial sampling distribution. Simultaneously, it avoids geometric distortions such as stretching and compression of the projected image caused by instantaneous speed fluctuations.

[0052] It should be noted that the uniform speed V can be reasonably set according to the acquisition accuracy required in the actual scenario. By adjusting the speed, the sampling interval can be controlled, thereby improving the spatial resolution and imaging accuracy of the scanning sampling.

[0053] Furthermore, after the turntable reaches the end position, it decelerates and stops, and then performs a rotation based on the rotation value calculated before scanning. After the rotation is completed, the turntable starts to move horizontally again in the opposite direction (from right to left) to complete one round-trip scan.

[0054] Furthermore, the aforementioned reciprocating scans are repeated continuously until the total angle of the turntable rotation reaches 180°, to meet the basic requirements of CT reconstruction for parallel beam scan data. For data exceeding 180°, symmetrical folding / mirroring and redundant angle reconstruction can be performed. In this embodiment, scan image data exceeding 180° during the scanning process are discarded to ensure that CT reconstruction uses only effective scan images from 0 to 180°, thus ensuring the accuracy and integrity of the reconstructed images.

[0055] (3) During the uniform motion of the turntable, the linear array detector synchronously acquires scanning images.

[0056] Specifically, the linear array detector begins to collect data once the turntable reaches a constant speed, and stops collecting data once the turntable stops moving.

[0057] Furthermore, in one possible implementation, the scanning sampling device also includes a motion control unit. A position detection unit with a grating ruler is mounted on the horizontal motion axis of the turntable. This grating ruler precisely monitors the turntable's movement and can output pulse signals to the motion control unit, achieving synchronization with the accelerator beam output and the linear array detector's data acquisition. Specifically, after the turntable reaches a constant speed, the motion control unit sets the POS signal to 1, indicating the start of the scanning interval, and the linear array detector begins acquisition. The grating ruler pulses trigger the accelerator to continuously output beams at the synchronization frequency f, and also trigger the linear array detector's synchronous sampling. When the turntable reaches the end of the path, the POS signal is set to 0, and the linear array detector stops acquiring data. At this point, the linear array detector completes one scan sampling cycle. After the turntable rotates according to the specified rotation value, it starts moving again, and the linear array detector performs synchronous acquisition again using the same method, obtaining a set of scan images of the round-trip path.

[0058] Figure 3 This is a general timing diagram illustrating a synchronous scanning method as shown in an exemplary embodiment of this application. Please refer to... Figure 3 , Figure 3 Showing Figure 3 The timing relationship between accelerator beam output, turntable rotation, turntable horizontal movement, and the sampling state of the linear array detector is shown. Figure 3The demonstration showed that after the accelerator begins to stabilize and emit its beam, the turntable starts moving along the horizontal axis from its initial position. Before entering the fan-beam coverage area, the turntable needs to reach a constant speed, and simultaneously, the linear array detector starts sampling and acquiring scan images. After the turntable reaches its final position and stops, its rotation axis is adjusted by a preset rotation value. The turntable then begins to move at a constant speed again in the opposite direction, and the linear array detector continues to sample synchronously. This entire process is repeated until the required total rotation angle is achieved, realizing a complete scan covering a 180° angle.

[0059] Furthermore, since the linear array detector continues to acquire data before and after the workpiece enters the effective imaging range, unobstructed background imaging regions, i.e., empty scan regions, are formed at both ends of each single scan path. These empty scan regions appear as regular rectangular strips at the top and bottom of the final scan image. Their horizontal width is equal to the detector's effective imaging width, and their vertical height is calculated from the length of the empty scan regions reserved at the start and end points of the scan. The empty scan regions not only ensure sufficient background sampling for flat field correction, dark field estimation, and fixed pattern noise subtraction, but also help determine the moment the workpiece enters / leaves the field of view, improve the stitching consistency of multi-segment scans, achieve global uniformity of imaging brightness, and provide a reliable background reference for subsequent geometric correction, noise modeling, and motion compensation. Therefore, they are an indispensable component for ensuring high-quality reconstructed images. The specific steps for setting up the empty scan regions are as follows:

[0060] (1) Calculate the minimum scanning length of the empty scanning area based on the parameters of the detector, the speed of the turntable movement and the imaging accuracy requirements.

[0061] Specifically, the detector's field of view and frame rate are obtained. The field of view and frame rate are inherent parameters of the detector and can be directly obtained from the equipment specifications. The frame rate is the frequency (fps) at which the hardware can output images. Next, the number of pixels required for background modeling is calculated based on the actual scene's imaging accuracy requirements. This number of pixels refers to the necessary sampling amount used to estimate the detector's background response, such as dark current, fixed pattern noise, and the grayscale baseline when no object is transmitted. This part is mainly used for background subtraction, noise modeling, and flat-field correction. Generally, this value is determined by the system's own correction requirements. A typical value is 100–500 pixels, which can be determined through noise statistical derivation, background stability judgment, or preset based on engineering experience; no specific limit is imposed here.

[0062] Furthermore, based on the detector's field of view size, detector frame rate, number of pixels required for background modeling, and turntable speed, the minimum scan length required before the workpiece enters and after it leaves the detector's effective imaging range is calculated. In this embodiment, the workpiece is treated the same before and after entering the detector's effective imaging range; that is, the minimum scan length for the empty scan area is the same. The calculation formula is as follows:

[0063]

[0064]

[0065] in, The pixels needed to model the background. The speed of the turntable movement. For detector frame rate, The minimum scan length for the empty scan area. For detector pixel size, This represents the minimum height of the empty scan area in the scanned image.

[0066] (2) Control the start and end points of the scan based on the minimum scan length of the empty scan area.

[0067] Specifically, based on the nominal imaging position of the workpiece center relative to the detector's field of view, at least [amount missing] are reserved on both the front and rear sides of the scanning direction. The motion path is determined by using the reserved starting position as the scanning start point and the reserved ending position as the scanning end point.

[0068] Specifically, before / after the turntable enters the detector's field of view in the scanning direction, it is necessary to ensure that the detector can acquire continuous data. Frame background data, therefore the scan start / end point are set to:

[0069]

[0070]

[0071] in, The actual width of the workpiece in the scanning direction. This is the reference position corresponding to the center of the workpiece in the center of the detector's field of view. During actual scanning... Exercise Within the motion range before the workpiece enters and the motion range after the workpiece leaves, the detector collects background data that is unobstructed by any object.

[0072] Please continue to refer to Figure 2 , Figure 2(b) shows a scanned image obtained from a single sampling by the linear array detector. The horizontal axis represents the detector channel, and the vertical axis represents the number of samplings. A blank area is visible at the top of the image, which corresponds to... Figure 2 (a) The sampling stage before the turntable reaches position a. At this time, the workpiece has not yet entered the fan beam coverage area, so the linear array detector does not detect workpiece information. There is also a blank area at the bottom of the image. This area corresponds to the sampling stage after the turntable moves to position c, that is, the workpiece has completely left the coverage area of ​​the linear array detector channel n, and the linear array detector collects blank data.

[0073] Please continue to refer to Figure 2 , Figure 2 (c) illustrates the blank data collected by the linear array detector when the turntable is not yet within the fan beam coverage area and when it has already left the fan beam coverage area. In the figure, the blank data collected when the turntable is not yet within the fan beam coverage area is marked as the top blank area. The position of the turntable at this time is also marked in the figure to visually show that the workpiece has not yet entered the detector's field of view. After the turntable completes one scan, when the workpiece has completely left the fan beam coverage area, the blank data collected by the linear array detector is marked as the bottom blank area. Figure 2 The position of the turntable at this time is also marked in (c). Figure 2 The annotation in (c) clearly shows the relationship between the blank data and the position of the turntable.

[0074] Optionally, in one possible implementation, the turntable reciprocates along the motion path, and the linear array detector acquires a scanned image of the workpiece above the turntable in a single motion. The scanned image, depending on the direction of the turntable's motion, includes at least a first-direction image and a second-direction image; including:

[0075] (1) Control the turntable to move at a constant speed from the starting point to the end point of the motion path. When the turntable is at the starting point, the linear array detector starts to collect images and stops collecting images when the turntable reaches the end point. The resulting scanned image is recorded as the first direction image.

[0076] Specifically, the turntable maintains a constant speed throughout the entire horizontal movement, allowing the linear array detector to continuously collect projection data for each row as it moves from the starting point to the end point along the movement path, thus forming a complete first-direction scan image sequence.

[0077] (2) Control the turntable to move at a constant speed from the end point of the motion path to the starting point. When the turntable is at the end point, the linear array detector starts to collect images and stops collecting images when the turntable reaches the starting point. The resulting scanned image is recorded as the second direction image.

[0078] Specifically, while maintaining a constant speed, the turntable allows the linear array detector to continuously collect projection data for each row as it moves from the end point to the starting point along the motion path, thus forming a complete second-direction scanning image sequence.

[0079] Please continue to refer to Figure 2 , Figure 2 (a) illustrates the sampling process of the linear array detector as the turntable moves the workpiece at a constant speed from the starting point to the end point. When the turntable moves to position a, the linear array detector channel 1 scans the workpiece first, then channel 2, and so on. When the turntable moves to position b, the workpiece leaves channel 1; when the turntable continues to move towards the end point to position c, the workpiece leaves the linear array detector channel n, completing one scan.

[0080] S104. At least one first-direction image and at least one second-direction image acquired at adjacent acquisition times are stitched together to obtain complete projection data of the workpiece.

[0081] Specifically, before stitching, the acquired scanned image sequence can be preprocessed, including: time alignment of the images according to the turntable movement time or sampling sequence to ensure that the spatial positions corresponding to each scanned image are consistent; interpolation processing to compensate for possible displacement errors in cases of uneven sampling intervals; and orientation standardization of the images obtained from the second direction scan to make them consistent with the orientation of the images from the first direction. After completing the above preprocessing, the scanned images acquired at adjacent times are stitched together in the scanning order to form a complete projection data sequence covering the entire workpiece.

[0082] Optionally, in one possible implementation, before stitching together at least one first-direction image and at least one second-direction image acquired at adjacent acquisition times, the method further includes:

[0083] (1) Obtain the parameters of the linear array detector and the turntable motion data, wherein the turntable motion data includes at least the turntable motion speed.

[0084] Specifically, the parameters of the linear array detector include the sampling frequency and the equivalent projection distance of each channel in the scanning direction. The equivalent projection distance refers to the actual spatial coverage length of each channel of the linear array detector in the scanning direction. The turntable motion data includes at least the speed of the turntable during the scanning process, which reflects the movement of the workpiece relative to the detector. The speed of the turntable can be acquired in real time by a position detection unit installed on the horizontal motion axis of the turntable, such as a grating ruler or encoder.

[0085] (2) Based on the parameters and turntable motion data, the scanned image is time-aligned to obtain the aligned scanned image.

[0086] Specifically, when the linear array detector is fixed and the workpiece moves at a uniform speed, the scanning times of different detector channels at the same physical location have a deterministic order. To ensure that the data from each channel corresponds to the same instantaneous physical cross-section, it is necessary to calculate and correct the time offset of each channel relative to the reference channel, and map the sampling sequence of each channel to a unified time reference. After time alignment, the projected data corresponding to different channels will represent the same physical cross-section, which helps to eliminate tilted trajectories in the scanned image and provides a consistent time / space reference for subsequent spacing unification and stitching.

[0087] Optionally, in one possible implementation, the step of performing time alignment on the scanned image based on the parameters and turntable motion data to obtain an aligned scanned image includes:

[0088] (A) Calculate the time offset of each channel relative to the reference channel based on the equivalent projection distance and the turntable movement speed.

[0089] Specifically, when performing time alignment on scanned images, a reference channel needs to be selected as a baseline to map data from other channels to the same time baseline, achieving spatial consistency. Further, the actual spacing between each channel of the linear array detector in the horizontal scanning direction is calculated. This calculation determines the time advance or lag of each channel relative to the reference channel at the start of the scan, i.e., the time offset of each channel relative to the reference channel, providing a basis for subsequent sample offsetting and data mapping.

[0090] (B) Calculate the sample offset of each channel based on the time offset and the sampling frequency.

[0091] Specifically, the time offset of each channel is converted into the number of sample rows that need to be moved in the sampling sequence, i.e., the sample offset. That is, through the channel... Time offset and sampling frequency Multiplying by each other yields the sample offset. Each channel is based on the calculated sample offset. Perform vertical translation of the image, where The value can be a non-integer. To ensure accuracy, the non-integer row offset can be compensated by interpolation to align it with the center channel.

[0092] (C) Based on the sample offset, map the sampled data of each channel to a unified target time base.

[0093] Specifically, the sampled data for each channel is vertically shifted according to the calculated sample offset, so that all channels are aligned in the same row and correspond to the same physical cross-section. After mapping, the tilted trajectory originally caused by the different scanning times of each channel is corrected, aligning the data of all channels in space and generating an aligned scan image.

[0094] Optionally, in one possible implementation, calculating the time offset of each channel relative to the reference channel based on the equivalent projection distance and the motion speed includes:

[0095] (A) Select one channel as a reference channel and calculate the difference in the equivalent projection distance between each channel and the reference channel.

[0096] Specifically, the reference channel can usually be selected as needed, such as the middle channel, the channel with the highest sampling accuracy, or any channel chosen as the alignment reference based on the specific scanning task; no limitation is made here. In this embodiment, to ensure the balance of the left and right channels and facilitate calculation, the center channel of the linear array detector is used as the reference channel for channel calculation. Equivalent projection distance from the center channel in the horizontal scanning direction Its mathematical expression is as follows:

[0097]

[0098]

[0099] in, The distance between detector channels. Channel number, This is a reference channel number; in this embodiment, the reference is typically the center channel. The angle between the fan beams of the linear array detector channels. For channel The angle between the direction of the ray and the direction of the scanning motion. For channel The difference in equivalent projected distance relative to the reference channel.

[0100] (B) Calculate the time offset based on the difference in the equivalent projected distance and the turntable movement speed.

[0101] Specifically, during the imaging process of the linear array detector, the turntable moves at a constant speed. When the workpiece is driven to move relative to the linear array detector, the time offset of each channel relative to the reference channel can be obtained by dividing the difference in their equivalent projected distances by the movement speed. That is:

[0102]

[0103] in, For channel The lead or lag relative to the reference channel. For channel The difference in equivalent projected distance between the reference channel and the reference channel in the scanning direction. The constant velocity of the turntable is used for calculation. This calculation yields the time offset of all channels at the start of the scan, providing a basis for subsequently converting the time offset into a sampling offset.

[0104] (3) Based on the parameters and turntable motion data, the sampling interval of each channel in the aligned scan image is unified to the same spacing to obtain a uniform spacing scan image.

[0105] Specifically, for the time-aligned scanned image, the sampling points of each channel are unified to the same equivalent spacing according to their spatial location to eliminate spatial non-uniformity caused by differences in detector geometric projection or discretization of sampling index. Specifically, the target sampling spacing is determined based on the sampling frequency and the constant speed of the turntable. Subsequently, for each channel's time-aligned sampling sequence, the projection value at the reference position is estimated based on its corresponding spatial coordinate mapping relationship, i.e., the actual spatial position of each sampling point in the scanning direction, thereby achieving alignment of the projection rows. The specific steps are as follows:

[0106] (A) Calculate the original sampling interval of each channel based on the sampling frequency of the linear array detector and the speed of the turntable.

[0107] Specifically, let the total number of channels of the linear array detector be... The turntable moves at a constant speed of _____. The sampling frequency is The sampling interval of the central channel is For any channel The angle between it and the central passage is Then the original sampling interval of this channel in the scanning direction is Using this formula, the original sampling interval of all channels in the scanning direction can be obtained. .

[0108] (B) Select a reference channel based on the original sampling interval, and determine the sampling interval corresponding to the reference channel as the target sampling interval.

[0109] Specifically, to ensure equidistant sampling of each channel in space, a reference channel can be selected based on the principles of system geometric stability and sampling consistency. Common reference channels include the center channel aligned with the accelerator's central beam, the channel with the highest signal-to-noise ratio, or the channel with the smallest geometric distortion determined through calibration. Because the center channel corresponds to the system's optical axis, its sampling interval is closest to the theoretical geometric model, which can reduce subsequent geometric correction errors. In this embodiment, the center channel is selected as the reference channel. Subsequently, the actual sampling interval of this reference channel in the original image is calculated. The target sampling interval can be set as the target sampling interval, or a uniform target sampling interval can be preset according to specific scanning accuracy requirements. In a preferred embodiment, this application uses the sampling interval of the reference channel as the target sampling interval. This ensures that the standardized coordinate system is consistent with the actual geometric features of the reference channel, thereby improving the spatial consistency and geometric accuracy of subsequent cutting, splicing and reconstruction processes.

[0110] (C) Based on the target sampling interval, the sampling interval of each channel is unified to the same interval.

[0111] Specifically, for each channel, its original sampling interval is... Mapped to target sampling interval .because and Generally, the sampling points are not completely equal, requiring interpolation methods such as linear interpolation or higher-order interpolation to resample or adjust the data, ensuring uniform spacing of sampling points across channels in the scanning direction. This is not limited here. In this application, to unify the spatial spacing of sampling points across channels, linear interpolation is used. Based on the original sampling points' positions in the scanning direction, they are mapped to equidistant target positions, and the grayscale or measured value of the insertion points is calculated using linear interpolation. This results in a uniformly spaced scanned image, facilitating subsequent stitching and angle sorting.

[0112] Figure 4 This is a schematic diagram illustrating the sampling intervals of different channels of a linear array detector, as shown in an exemplary embodiment of this application. Please refer to... Figure 4 , Figure 4 This demonstrates that the sampling interval is different for each detector channel. The detector channel corresponding to the central beam is n / 2, and its sampling interval is d. Detector channel 1 is the outermost channel. The angle between the ray from detector channel 1 and the central beam is represented by . Because it has a large angle with the central beam, its equivalent sampling interval is different from that of the central channel. Therefore, it is necessary to use interpolation to make its spacing equal to the spacing d of the central channel.

[0113] (4) The uniform spacing scan image is subjected to orientation standardization processing to obtain a standardized scan image.

[0114] Specifically, based on the directional characteristics of the channel arrangement in the original image, a uniform coordinate rotation process is performed on all scanned images. This rotation aligns one axis of the image with the scanning direction of the turntable, and the other axis with the channel index of the linear array detector. In this standardized coordinate system, the horizontal axis represents the sampling sequence generated as the turntable moves, and the vertical axis represents the channel number, ensuring that each column corresponds to the same spatial sampling position. This facilitates subsequent empty scan area cropping, overlapping area localization, and stitching processing based on channel angle order. The specific steps for determining the rotation angle are as follows:

[0115] (A) Obtain the direction vector of the reference channel in the original image plane, and calculate the angle between the direction vector and the direction of the central beam.

[0116] Specifically, the direction vector of the reference channel in the original image plane is extracted. This vector can be calculated through channel pixel arrangement, edge features, or channel index gradient. Using the system's default center beam direction as the target reference direction, the angle between the reference channel direction vector and the target direction is calculated to obtain the angle value θ.

[0117] (B) Using the included angle value as the image rotation angle, the scanned image is rotated by the corresponding angle through the center of the scanned image.

[0118] Specifically, using the included angle θ as the rotation angle of the scanned image, and the center of the scanned image as the rotation center, the original image is rotated around the center by θ, aligning the reference channel direction with the central beam direction in the standardized image. After rotation, the horizontal axis of the standardized image represents the sampling sequence generated by the turntable movement, and the vertical axis represents the channel number. Each column corresponds to the same spatial sampling position, thus providing a unified reference for subsequent cropping, stitching, and spatial reconstruction processing. In a preferred embodiment, when the reference channel is the central channel, geometric distortion is minimized; if the reference channel is another channel, the rotation angle can be adapted to special installation or scanning requirements through alignment processing. Through the above steps, a standardized image coordinate system can be achieved, ensuring that the directions of each channel are consistent, facilitating subsequent geometric correction, sampling interval adjustment, and stitching processing.

[0119] Figure 5 This is a schematic diagram illustrating the scanning image rotation process of an exemplary embodiment of this application. Please refer to... Figure 5 , Figure 5This diagram illustrates the effect of rotating the scanned image 90° with the reference channel as the center channel. The left side of the image shows the scanned image after alignment and interpolation, where the horizontal axis represents the linear array detector channel index and the vertical axis represents the number of samples, showing the arrangement of scanned data as the turntable moves. The right side shows the image after 90° rotation. After rotation, the original sampling number direction is adjusted to the horizontal axis, and the detector channel direction is adjusted to the vertical axis. Now, each column corresponds to the same spatial sampling interval, and each row corresponds to the same detector channel. The rotated image clearly demonstrates the redefined horizontal and vertical axes and their spatial correspondence with the scanned data.

[0120] Furthermore, the second-direction image is flipped horizontally to eliminate mirror differences caused by the opposite motion direction. Specifically, based on the motion direction markers recorded during acquisition, the image belonging to the second direction is identified, and then the rotated image is flipped along the vertical axis to ensure its column index order is consistent with the scanned image in the first direction. After the flipping process, all scanned images are unified in scanning direction, detector channel direction, and column index order, ensuring that images acquired from different motion directions can be directly stitched together.

[0121] Furthermore, after completing the orientation standardization process, the obtained standardized scan images are unified in terms of scanning direction, detector channel direction, and column index order. However, each image only corresponds to a limited angular range of a single rotation of the turntable. In order to cover the entire workpiece and obtain complete projection data, multiple consecutive scan images need to be stitched together according to the rotation angle of the turntable, so that the scan data from different angles are continuously arranged in the same coordinate system to form complete projection data of the workpiece.

[0122] Figure 6 This is a schematic diagram illustrating scanned image stitching as an exemplary embodiment of this application. Please refer to... Figure 6 , Figure 6 This demonstrates the effect of stitching multiple scanned images horizontally, where the horizontal axis represents the number of samples (sampling interval) and the vertical axis represents the sampling angle corresponding to the detector channel. Each image corresponds to a scanned image with a single rotation angle β of the turntable. By stitching them horizontally in sequence according to the sampling angle, a complete projection data sequence covering the entire workpiece can be obtained.

[0123] The scanning sampling method and apparatus provided in this application achieve complete projection data acquisition of large-sized workpieces through scanning path planning of the linear array detector and a multiple round-trip scanning strategy. First, the motion path through the single-scan area of ​​the linear array detector is determined, ensuring that the maximum width of the single-scan area is less than the size of the workpiece to be scanned, thus guaranteeing that the scanning area can controllably cover and move across the object's surface. Then, the single-rotation angle interval of the turntable is determined based on the fan beam angle of the linear array detector, ensuring that the coverage angle of each round-trip scan meets the continuous acquisition requirements, thereby providing a reliable angular basis for subsequent projection stitching. During the scanning process, the turntable moves back and forth according to the motion path, and the linear array detector acquires the corresponding scan image in each unidirectional movement. Depending on the turntable's movement direction, the scan image includes at least a first-direction image and a second-direction image, with opposite directions. Before starting a single scan, a rotation value is calculated based on the current rotation angle and a preset single-rotation angle interval, causing the turntable to rotate to the target angle before scanning, ensuring continuous image coverage within the angular domain. Finally, the scan images acquired at adjacent times are stitched together according to their temporal order and spatial correspondence to obtain complete projection data of the workpiece. This method achieves multi-view reciprocating scanning by controlling the movement of the workpiece on a turntable, thereby obtaining a larger scanning range than a single field of view of a detector. This allows the method to cover and acquire complete projection data of large-sized workpieces. Simultaneously, precise control of the turntable's movement speed ensures the positional accuracy and temporal consistency of the projection data during the scanning process, thus improving scanning precision and imaging quality.

[0124] Optionally, in one possible implementation, after obtaining the standardized scanned image, the method further includes:

[0125] (1) Calculate the overlapping area between adjacent scanned images based on the single rotation angle and the start and end column indices of each scanned image.

[0126] Specifically, the overlapping region refers to the column data segments that cover the same spatial location during adjacent scans. It can be calculated by analyzing the correspondence between column index ranges and rotation angles, thus identifying which columns need to participate in the fusion process. This embodiment uses rotation angles to calculate the overlapping region. The column index of each image is mapped to the corresponding rotation angle, and the angular overlap region is determined based on the interval between single rotation angles. For example, if the angle ranges of two scans overlap: the first scan image covers 0°–30°, and the second scan image covers 25°–55°, the common angle range of 25°–30° is the overlapping angle range, thus obtaining the overlapping columns that need to be fused.

[0127] (2) Within the overlapping area, the projection data is smoothed column by column to obtain the fused column data of the overlapping area.

[0128] Specifically, for overlapping columns within an overlapping region, the data can be smoothed along the column direction. Specific smoothing methods can include weighted averaging, linear interpolation, or other filtering algorithms to fuse the data from overlapping columns of adjacent scanned images into a single column. This eliminates abrupt changes in intensity or positional deviations caused by incomplete overlap of scan start and end points or minor differences in beam dose. Through this fusion, fused column data for the overlapping region can be generated, ensuring continuous and consistent projection information of adjacent scanned images within the overlapping area.

[0129] (3) Discard the original column data of adjacent scanned images in the overlapping area and use the fused column data to participate in the stitching.

[0130] Specifically, the original column data in the overlapping area of ​​adjacent scanned images is discarded and replaced with the aforementioned fused column data. Then, the fused scanned images are stitched together according to the sampling angle to obtain complete projection data covering the entire workpiece. This process ensures both the continuity and uniformity of the stitched area and avoids brightness or geometric deviations that may be caused by repeated superposition of overlapping areas.

[0131] Corresponding to the aforementioned embodiment of a scanning sampling method, this application also provides an embodiment of a scanning sampling device.

[0132] Figure 7 This is a schematic diagram of the structure of Embodiment 1 of the scanning sampling device provided in this application. Please refer to... Figure 7 The apparatus provided in this embodiment includes a 701 determining module, a 702 processing module, and a 703 splicing module; wherein,

[0133] The 701 determining module is used to determine the motion path through a single scan area of ​​the linear array detector, wherein the maximum width of the single scan area is smaller than the size of the workpiece to be scanned.

[0134] The 701 determining module is used to determine the fan beam angle of the linear array detector and determine the single rotation angle interval of the turntable based on the fan beam angle.

[0135] The 702 processing module is used for the turntable to move back and forth according to the motion path. The linear array detector acquires a scan image of the workpiece above the turntable in a single motion. The scan image includes at least a first direction image and a second direction image depending on the motion direction of the turntable. The first direction and the second direction are parallel and opposite in direction. Before a single motion, the rotation value of the turntable is calculated based on the single rotation angle interval and the current rotation angle of the turntable. The turntable rotates by the angle corresponding to the rotation value.

[0136] The 703 stitching module is used to stitch together at least one first-direction image and at least one second-direction image acquired at adjacent acquisition times to obtain complete projection data of the workpiece.

[0137] The apparatus of this embodiment can be used to perform... Figure 1 The steps of the method embodiment shown are similar in principle and process, and will not be repeated here.

[0138] The specific implementation process of the functions and roles of each unit in the above device can be found in the implementation process of the corresponding steps in the above method, and will not be repeated here.

[0139] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this application according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0140] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method of scan sampling, characterized by, The method comprises: determining a motion path of a single scan area of a line array detector, the maximum width of the single scan area being less than the size of a workpiece to be scanned; determining a fan beam included angle of the line array detector, and determining a single rotation angle interval of a rotary table according to the fan beam included angle; the rotary table moves back and forth according to the motion path, and the line array detector collects a scan image of the workpiece above the rotary table in a single motion, wherein the scan image comprises at least a first direction image and a second direction image according to different motion directions of the rotary table, the first direction and the second direction are parallel and opposite in direction, before the single motion, a rotation value of the rotary table is calculated based on the single rotation angle interval and a current rotation angle of the rotary table, and the rotary table rotates by an angle corresponding to the rotation value; splicing at least one first direction image and at least one second direction image collected at adjacent acquisition times to obtain complete projection data of the workpiece.

2. The method of claim 1, wherein, The method further comprises: acquiring the number of channels of the line array detector and the included angle values between the channels, and calculating a fan beam included angle according to the number of channels and the included angle values; determining a single rotation angle interval of a rotary table according to the fan beam included angle, the single rotation angle interval being less than or equal to the fan beam included angle.

3. The method of claim 1, wherein, Before the splicing, the method further comprises: acquiring parameters of the line array detector and rotary table motion data, the rotary table motion data comprising at least a rotary table motion speed; time aligning the scan images according to the parameters and the rotary table motion data to obtain aligned scan images; unifying the sampling intervals of the channels in the aligned scan images to the same interval according to the parameters and the rotary table motion data to obtain uniform interval scan images; standardizing the direction of the uniform interval scan images to obtain standardized scan images.

4. The method of claim 3, wherein, The time aligning the scan images according to the parameters and the rotary table motion data to obtain aligned scan images comprises: calculating the time offset of each channel relative to a reference channel according to the parameters and the rotary table motion speed; calculating the sample offset of each channel according to the time offset and the parameters; mapping the sampling data of each channel to a unified target time reference according to the sample offset.

5. The method of claim 4, wherein, The calculating the time offset of each channel relative to a reference channel according to the parameters and the rotary table motion speed comprises: selecting one channel as a reference channel, and calculating the difference in equivalent projection distance between each channel and the reference channel; calculating the time offset according to the difference in equivalent projection distance and the rotary table motion speed.

6. The method of claim 3, wherein, The unifying the sampling intervals of the channels in the aligned scan images to the same interval according to the parameters and the rotary table motion data to obtain uniform interval scan images comprises: calculating the original sampling interval of each channel according to the sampling frequency of the line array detector and the rotary table motion speed; According to the original sampling interval, a reference channel is selected, and a sampling interval corresponding to the reference channel is determined as a target sampling interval; According to the target sampling interval, sampling intervals of each channel are unified as the same interval.

7. The method of claim 3, wherein, After the standardized scan image is obtained, the method further comprises: According to the single rotation angle and the start and end column indexes of each scan image, an overlapping area between adjacent scan images is calculated; In the overlapping area, the projection data is smoothed by column to obtain fused column data of the overlapping area; The original column data of the adjacent scan images in the overlapping area is discarded, and the fused column data participates in splicing.

8. The method of claim 1, wherein, The turntable moves back and forth according to the motion path, and the linear array detector collects scan images of the workpiece above the turntable in a single motion, wherein according to different motion directions of the turntable, the scan images at least include first direction images and second direction images; comprising: The turntable is controlled to move uniformly from the starting point of the motion path to the ending point, the linear array detector starts to collect images when the turntable is at the starting point, and stops collecting when the turntable reaches the ending point, and the obtained scan image is recorded as the first direction image; The turntable is controlled to move uniformly from the ending point of the motion path to the starting point, the linear array detector starts to collect images when the turntable is at the ending point, and stops collecting when the turntable reaches the starting point, and the obtained scan image is recorded as the second direction image.

9. The method of claim 1, wherein, Before the turntable moves back and forth according to the motion path, the method further comprises: The scanning sampling method uses an accelerator as a radiation source, controls the accelerator to enter a preheating beam-out stage, detects the beam-out dose rate of the accelerator within a preset time window until the rate is lower than a preset threshold; The accelerator is kept continuously emitting beams until all the scan images are collected.

10. A scanning sampling device, characterized by The device comprises a determination module, a processing module and a splicing module; wherein, The determination module is used to determine a motion path passing through a single scan area of the linear array detector, and the maximum width of the single scan area is smaller than the size of the workpiece to be scanned; The determination module is used to determine a fan beam included angle of the linear array detector, and a single rotation angle interval of the turntable is determined according to the fan beam included angle; The processing module is used to move the turntable back and forth according to the motion path, and the linear array detector collects scan images of the workpiece above the turntable in a single motion, wherein according to different motion directions of the turntable, the scan images at least include first direction images and second direction images, the first direction and the second direction are parallel and opposite in direction, before a single motion, a rotation value of the turntable is calculated based on the single rotation angle interval and the current rotation angle of the turntable, and the turntable rotates an angle corresponding to the rotation value; The splicing module is used to splice at least one first direction image and at least one second direction image collected at adjacent collection times to obtain complete projection data of the workpiece.

Images