A method for determining the position of a scanned object in security inspection CT

Abstract

The present invention relates to a method for determining the position of a scanned object in a security inspection CT, which belongs to the technical field of security inspection CT and solves the problem that the existing method for determining the position of a scanned object in a security inspection CT is inaccurate, resulting in a large amount of data for reconstructing the object image and difficulty in ensuring the integrity of the scanned object. The method comprises: collecting detector empty scan data that does not contain an object, and when an object trigger signal is received, collecting complete detector data; obtaining edge row projection data based on the empty scan data and the complete data, and obtaining edge row one-dimensional projection data after morphological processing of the edge row projection data; obtaining the object entry angle and the object departure angle based on the edge row one-dimensional projection data, and determining the position of the scanned object in the security inspection CT. The method can obtain accurate position information of the object scanned by the security inspection CT, so that when the security inspection CT performs image reconstruction, the amount of reconstruction data is small, and the reconstructed image includes complete object information.

Description

Technical Field

[0001] The present invention relates to the technical field of security inspection CT, and in particular to a method for determining the position of a scanned object in a security inspection CT. Background Art

[0002] The current security inspection system based on X-ray computed tomography (CT) technology obtains the internal structure information of the scanned object by reconstructing the projection data of the object at multiple angles. It is necessary to determine the position of the object scanned by the security inspection CT to reduce the amount of reconstructed data. The current security inspection system is usually equipped with one or more groups of light barrier devices (opposite-beam photoelectric switches) set at different heights in the security inspection channel to obtain the scanning position of the object. The light barrier device includes a light barrier sending module and a light barrier receiving module. The entry or exit of the object is determined by the state of the light barrier. If the light barrier enters the blocked state from the unobstructed state, the security inspection system considers that an object has entered, and then starts the subsequent security inspection process, such as turning on the X-ray and the detector starting to collect images; if the light barrier enters the unobstructed state from the blocked state, it is determined that the object has completely passed through the area where the light barrier is located.

[0003] However, since the shapes of objects for security inspection are often diverse, the light barrier set at a fixed height cannot determine whether there are objects at other heights. For example, the wheels of a flat wheeled suitcase are at a higher height than the light barrier set at the bottom of the security inspection channel, which will cause a delay in judging the entry of the object or an early judgment of the object leaving. In the security inspection reconstructed image, it may appear as a part of the object is missing, that is, the scan is incomplete, and the bag is cut. In order to solve the bag cutting problem, the current security inspection system usually sets a fixed advance and delay amount during the data collection process after receiving the light barrier signal to try to avoid bag cutting. However, this method inevitably increases the data processing volume of scanning a single item and cannot completely avoid bag cutting.

[0004] In summary, the current method for determining the position of an object in a security CT scan is difficult to obtain an accurate object scanning position, resulting in a large amount of data for object image reconstruction, and the existing method is difficult to ensure the integrity of the scanned object. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide an image reconstruction method for security inspection CT, so as to solve the problem that the existing method for determining the position of an object scanned by security inspection CT is inaccurate, resulting in a large amount of data for object image reconstruction and difficulty in ensuring the integrity of the scanned object.

[0006] The embodiment of the present invention provides a method for determining the position of a scanned object in a security inspection CT, comprising the following steps:

[0007] Collect the detector's empty scan data without objects, and collect the detector's complete data when receiving the object trigger signal;

[0008] Obtain edge row projection data based on the air scan data and the complete data, and obtain edge row one-dimensional projection data after morphological processing on the edge row projection data;

[0009] The object entry angle and the object exit angle are obtained based on the one-dimensional projection data of the edge row, and the position of the object scanned in the security inspection CT is determined.

[0010] Furthermore, when the object trigger signal is received, the complete data of the detector is obtained, including:

[0011] When the received signal is a trigger signal when an object enters the security inspection CT, the complete data of the object entering the security inspection CT is collected;

[0012] When the received signal is a trigger signal when the object leaves the security inspection CT, the complete data of the object leaving the security inspection CT is collected;

[0013] The complete data is the detector data collected by the detector rotating from the initial collection angle to the set rotation interval angle by the set angle; the rotation of the detector by the set angle is regarded as a collection cycle.

[0014] Further, the edge row projection data includes a start row projection data and an end row projection data, and the edge row projection data is obtained based on the air scan data and the complete data as follows:

[0015] If it is the complete data when the object enters, extract the starting row data from the complete data, and extract the starting row data of the corresponding acquisition angle from the air scan data; subtract the starting row data of the complete data from the starting row data of the air scan data to obtain the starting row projection data;

[0016] If it is the complete data when the object leaves, extract the end row data in the complete data, and extract the end row data of the corresponding acquisition angle in the air scan data; subtract the end row data of the complete data from the corresponding end row data of the air scan data to obtain the end row projection data;

[0017] Among them, the edge row that first receives the attenuation signal of the object in the detector when the object enters the security inspection CT is taken as the starting row, and the edge row that last receives the attenuation signal of the object in the detector when the object leaves the security inspection CT is taken as the ending row; the empty scan data is the detector data collected when the detector rotates one circle along the set rotation interval angle when there is no object in the security inspection CT.

[0018] Furthermore, the edge row projection data is subjected to morphological processing to obtain edge row one-dimensional projection data, specifically:

[0019] After binarizing the edge row projection data based on a set first threshold, a morphological opening operation is performed on the processed edge row projection data, and then data corresponding to regions whose areas are smaller than the area threshold are set to 0 through connectivity analysis to obtain first image data;

[0020] Performing filtering on the first image data to obtain second image data;

[0021] Perform hole filling on the second image data based on a morphological closing operation to obtain third image data;

[0022] The data of each detection unit corresponding to each acquisition angle in the third image data are accumulated to obtain one-dimensional projection data of the edge row.

[0023] Furthermore, filtering is performed on the first image data to obtain second image data, specifically: low-pass filtering is performed on the first image data to obtain fourth image data; and binarization is performed on the fourth image data based on a set second threshold to obtain second image data.

[0024] Furthermore, the edge row one-dimensional projection data includes a starting row one-dimensional projection data and an ending row one-dimensional projection data; the object entry angle is obtained based on the starting row one-dimensional projection data; and the object departure angle is obtained based on the ending row one-dimensional projection data.

[0025] Furthermore, the object entry angle is obtained based on the one-dimensional projection data of the starting row, specifically:

[0026] If all data in the starting row of one-dimensional projection data are less than the set third threshold value, the corresponding complete data does not contain the object, and the starting row of one-dimensional projection data of the complete data of the next acquisition cycle when the object enters the security inspection CT is obtained for re-judgment;

[0027] If each data in the initial row of one-dimensional projection data is greater than or equal to the set third threshold, the corresponding complete data has an object at each acquisition angle, and the initial acquisition angle of the corresponding complete data is used as the object entry angle;

[0028] Otherwise, the first data in the starting row of one-dimensional projection data that meets the following conditions is determined as the first critical data: the data is greater than or equal to the set third threshold value and the first n1 data of the data in the starting row of one-dimensional projection data are all less than the third threshold value; and then the object entry angle is obtained according to the first critical data, where n1>0.

[0029] Further, the obtaining of the object entry angle according to the first critical data is specifically:

[0030] Determine the last data in the starting row of one-dimensional projection data that is greater than or equal to the set third threshold as the second critical data, and obtain the number of data n2 between the first critical data and the second critical data; and determine the number of data n0 before the first critical data and the number of data n3 after the second critical data in the starting row of one-dimensional projection data;

[0031] When n0 is greater than or equal to the fourth threshold,

[0032] If n1 is greater than or equal to the fourth threshold and n2 is greater than or equal to the fifth threshold, the collection angle of the first critical data is used as the object entry angle;

[0033] If n1 is greater than or equal to the fourth threshold and n2 is less than the fifth threshold, the corresponding complete data does not contain an object or is abnormal, and the complete data of the next acquisition cycle when the object enters the security inspection CT is obtained for re-judgment;

[0034] Otherwise, if the corresponding complete data already has an object at the initial acquisition angle, the initial acquisition angle is used as the object entry angle;

[0035] When n0 is less than the fourth threshold,

[0036] If n1 is equal to n0 and n2 is greater than or equal to the fifth threshold, the acquisition angle of the first critical data is used as the object entry angle;

[0037] If n1 is equal to n0 and n2 is less than the fifth threshold, the corresponding complete data does not contain an object or is abnormal, and the complete data of the next acquisition cycle when the object enters the security inspection CT is obtained and re-judged;

[0038] Otherwise, if the corresponding complete data already has an object at the initial acquisition angle, the initial acquisition angle is used as the object entry angle;

[0039] The fifth threshold is the minimum value of n3 and the length threshold.

[0040] Furthermore, the object departure angle is obtained based on the end row of one-dimensional projection data, specifically:

[0041] If all data in the final row of one-dimensional projection data are less than the set third threshold, the corresponding complete data does not contain an object, and the initial acquisition angle of the corresponding complete data is used as the object departure angle;

[0042] If all data in the one-dimensional projection data of the end row are greater than or equal to the set third threshold, the corresponding complete data has an object at each acquisition angle, and the complete data of the next acquisition cycle when the object leaves the security inspection CT is obtained for re-judgment;

[0043] Otherwise, the last data in the ending row of one-dimensional projection data that meets the following conditions is determined as the third critical data: the data satisfies a third threshold that is greater than or equal to the set third threshold and the last m1 data of the data in the ending row of one-dimensional projection data are all less than the third threshold; and then the object departure angle is obtained according to the third critical data, where m1>0.

[0044] Further, the obtaining of the object departure angle according to the third critical data is specifically:

[0045] Determine the first data in the end row of the one-dimensional projection data that is greater than or equal to the set third threshold as the fourth critical data, and obtain the number of data between the third critical data and the fourth critical data m2; and determine the number of data after the third critical data m0 and the number of data before the fourth critical data m3 in the end row of the one-dimensional projection data;

[0046] When m0 is greater than or equal to the sixth threshold,

[0047] If m1 is greater than or equal to the fourth threshold and m2 is greater than or equal to the seventh threshold, the collection angle of the third critical data is used as the object departure angle;

[0048] If m1 is greater than or equal to the fourth threshold and m2 is less than the seventh threshold, the corresponding complete data does not contain an object or has an abnormality, and the initial acquisition angle of the corresponding complete data is used as the object departure angle;

[0049] Otherwise, the corresponding complete data has objects at all acquisition angles, and the complete data of the next acquisition cycle when the object leaves the security inspection CT is obtained for re-judgment;

[0050] When m0 is less than the sixth threshold,

[0051] If m1 is equal to m0 and m2 is greater than or equal to the seventh threshold, the collection angle of the third critical data is used as the object departure angle;

[0052] If m1 is equal to m0 and m2 is less than the seventh threshold, the corresponding complete data does not contain an object or has an anomaly, and the initial acquisition angle of the corresponding complete data is used as the object departure angle;

[0053] Otherwise, the corresponding complete data has objects at all acquisition angles, and the complete data of the next acquisition cycle when the object leaves the security inspection CT is obtained for re-judgment.

[0054] The seventh threshold is the minimum value of m3 and the length threshold.

[0055] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0056] The present invention provides a method for determining the position of a scanned object in a security inspection CT.

[0057] 1. Obtain edge row projection data through the empty scan data and complete data of the detector. After eliminating the noise and isolated points of the edge row projection data based on morphological processing, calculate the edge row one-dimensional projection data, obtain the position information of the object at each acquisition angle, and then determine the angle information of the object entering or leaving the security inspection CT. The accurate position information of the object scanned by the security inspection CT can be obtained, so that the amount of reconstruction data is small during subsequent image reconstruction, and the integrity of the object can be guaranteed;

[0058] 2. By subtracting the collected detector air scan data that does not contain objects from the edge row data that contains complete data of objects, the influence of factors such as conveyor belts and bad pixels in the security inspection system is eliminated, making the collected data more accurate, further ensuring the accuracy of subsequent determination of the object's entry angle and object departure angle.

[0059] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0061] Figure 1 A schematic flow chart of a method for determining the position of a scanned object in a security inspection CT provided by an embodiment of the present invention;

[0062] Figure 2 This is a schematic diagram of the structure of the security inspection CT.

[0063] Reference numerals:

[0064] 1-CT ray source; 2-CT slip ring; 3-CT detector; 4-object; 5-transmission belt; 6-transmission belt motor; 7-motion control computer; 8-slip ring motor; 9-data processing computer. DETAILED DESCRIPTION

[0065] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0066] A specific embodiment of the present invention discloses a method for determining the position of a scanned object in a security inspection CT. Figure 1As shown, the following steps are included:

[0067] S1. Collect the detector's empty scan data that does not contain the object. When the object trigger signal is received, collect the detector's complete data.

[0068] Specifically, collecting the detector air scan data without objects in step S1 is specifically: when there is no object in the security inspection channel and the radiation source is turned on, collecting the bright field data collected along the set rotation interval angle for one circle as the air scan data, wherein the detector includes several rows of detection units.

[0069] Preferably, when the ray source is turned off, dark field data that does not contain an object is collected, and the gain coefficient of the detector is obtained based on the collected bright field data and dark field data, and the data is corrected to obtain the corrected bright field data as the air scan data. It can be understood that correcting the bright field data according to the gain coefficient can eliminate the inconsistency between different detection units of the detector caused by the inconsistency of ray response due to the difference in ray distribution and the inconsistency between the back-end electronic modules under ray irradiation, so that the obtained air scan data is more accurate.

[0070] During implementation, when the object trigger signal is received in step S1, the complete data of the detector is obtained, including:

[0071] When the received signal is a trigger signal when an object enters the security inspection CT, the complete data of the object entering the security inspection CT is collected;

[0072] When the received signal is a trigger signal when the object leaves the security inspection CT, the complete data of the object leaving the security inspection CT is collected;

[0073] The complete data is the detector data collected by the detector rotating from the initial collection angle to the set rotation interval angle by the set angle; the rotation of the detector by the set angle is regarded as a collection cycle.

[0074] Specifically, the rotation interval angle can be set according to actual needs, and can be set to 0.5 degrees, 1 degree, etc.

[0075] Specifically, the set angle can be set as needed. For example, 360 degrees can be selected, that is, the detector rotates one circle. Preferably, the set angle is less than or equal to 360 degrees. It should be noted that the set angle can be set to different, variable angles, or can be set to a fixed angle to meet different needs.

[0076] Specifically, the initial acquisition angle can be the angle between the detector rotation center and the detector direction relative to the detector rotation center and the object direction along the rotation direction, and the detector data collected at the set angle of the detector rotation relative to the initial acquisition angle is complete data; and the set angle of the detector rotation is taken as an acquisition cycle, and the overall scanning data of the object includes complete data of several acquisition cycles.

[0077] Specifically, the security inspection CT system includes a light barrier device, which includes a light barrier sending module and a light barrier receiving module, which are respectively arranged at both ends of one side of the entrance of the security inspection channel, and the light barrier device controls the collection of detector data. When an object enters the security inspection CT, the light barrier receiving module cannot receive the pulse signal of the light barrier sending module, that is, the light barrier device changes from an unobstructed state to a blocked state, and the light barrier is triggered to generate a trigger signal of the object entering the security inspection CT, and starts to obtain the complete data of the object entering the security inspection CT; when the object leaves the security inspection CT, the light barrier receiving module receives the pulse signal of the light barrier sending module again, that is, the light barrier device changes from a blocked state to an unobstructed state, and the light barrier is triggered to generate a trigger signal of the object leaving the security inspection CT, and starts to obtain the complete data of the object leaving the security inspection CT. Among them, the object entering and leaving the security inspection CT refers to the object entering and leaving the scanning area of ​​the security inspection CT detector.

[0078] It should be noted that there is a certain distance between the light barrier device and the detector in the security inspection CT. The time for collecting data can be set according to the trigger signal of the light barrier device to ensure the integrity of the collected object data; and during the period from the time when the light barrier is triggered by the entry of an object to the time when the object leaves the trigger, the detector continues to collect data for image reconstruction.

[0079] Exemplarily, the detector includes 36 rows of detection units, each row includes 700 detection units, and the angle is set to 360 degrees, that is, the detector rotates one circle, and the detector data is collected every 1 degree, then the data volume of the complete data is 36×700×360.

[0080] S2. Obtain edge row projection data based on the air scan data and the complete data, and perform morphological processing on the edge row projection data to obtain edge row one-dimensional projection data.

[0081] During implementation, the edge row projection data in step S2 includes the starting row projection data and the ending row projection data, and the edge row projection data obtained based on the air scan data and the complete data is specifically:

[0082] If it is the complete data when the object enters, extract the starting row data from the complete data, and extract the starting row data of the corresponding acquisition angle from the air scan data; subtract the starting row data of the complete data from the starting row data of the air scan data to obtain the starting row projection data;

[0083] If it is the complete data when the object leaves, then extract the end row data in the complete data, and extract the end row data of the corresponding acquisition angle in the air scan data; subtract the end row data of the complete data from the corresponding end row data of the air scan data to obtain the end row projection data; it can be understood that the air scan data is the detector data that does not contain objects at various acquisition angles when the detector rotates one circle, and all acquisition angles within the set angle of the complete data can find corresponding acquisition angles in the air scan data.

[0084] The edge row that first receives the attenuation signal of the object in the detector when the object enters the security inspection CT is taken as the starting row, and the edge row that last receives the attenuation signal of the object in the detector when the object leaves the security inspection CT is taken as the ending row.

[0085] It can be understood that after subtracting the starting row data of the complete data from the starting row data of the empty scan data or subtracting the ending row data of the complete data from the ending row data of the empty scan data, m×s two-dimensional data T is obtained, where m is the number of detector units for a single row of data, and s is the number of acquisition angles of the detector when it rotates to a set angle.

[0086] Preferably, after subtracting the starting row of data of complete data from the starting row of data of empty scan data or subtracting the ending row of data of complete data from the ending row of data of empty scan data, the data which is less than zero is set to zero to eliminate the interference of erroneous data.

[0087] Preferably, after correcting the acquired start row data or end row data using the gain coefficient and dark field data obtained in step S1, subsequent processing is performed on the corrected air scan data, which can further eliminate interference and improve data accuracy.

[0088] It can be understood that by subtracting the collected detector air scan data that does not contain objects from the edge row data that contains complete data of objects, the influence of factors such as conveyor belts and bad pixels in the security inspection system is eliminated, making the collected data more accurate, further ensuring the accuracy of subsequent determination of the object's entry angle and object departure angle.

[0089] During implementation, in step S2, the edge row projection data is subjected to morphological processing to obtain edge row one-dimensional projection data, specifically:

[0090] S21. After binarizing the edge row projection data based on a set first threshold, a morphological opening operation is performed on the processed edge row projection data, and then data corresponding to regions whose areas are smaller than the area threshold are set to 0 through connectivity analysis to obtain first image data.

[0091] More specifically, the first threshold is set by taking into account the difference in data when the ray source and the detector fluctuate, and by counting the bright field data fluctuation when no object exists; the area threshold is determined according to actual needs.

[0092] More specifically, the binarized edge row projection data is processed through a morphological opening operation of first erosion and then dilation to remove noise; that is, the binarized edge row projection data is used as the image to be processed, the highlighted part of the image is first eroded to reduce the highlighted area, and then the highlighted area is dilated to expand the highlighted area. This operation can remove noise and filter out objects that are too small in the image.

[0093] Preferably, the morphological opening operation selects a 3×3 erosion template and a dilation template; the connectivity analysis uses an 8-neighborhood to determine connectivity.

[0094] It can be understood that the highlight part (the part with large pixel value of the data) and the low-brightness part (the part with small pixel value of the data) in the edge row projection data are highlighted through binarization processing, and then the noise is removed through the morphological opening operation of first corrosion and then expansion, and then the data corresponding to the area where the connected area in the edge row projection data is smaller than the area threshold is set to 0 through connectivity analysis, that is, the smaller isolated area in the edge row projection data is eliminated to obtain the first image data.

[0095] S22: Filter the first image data to obtain second image data.

[0096] Specifically, step S22 is to perform low-pass filtering on the first image data to smooth edge burrs in the first image data to obtain fourth image data; and to perform binarization processing on the fourth image data based on a set second threshold to remove edge burrs in the first image data to obtain second image data.

[0097] Preferably, a 3×3 all-1 convolution kernel is used for low-pass filtering, and the second threshold is set to a value of 8. It can be understood that the convolution kernel is an all-1 matrix, the maximum value after data convolution is 9, and the second threshold is set to 8, which can better remove edge glitches in the data.

[0098] S23. Perform hole filling on the second image data based on a morphological closing operation to obtain third image data.

[0099] More specifically, the holes in the second image data are filled through a morphological closing operation of first dilation and then erosion to ensure that the data in the continuous area of ​​the second image data is all 1; that is, the highlight area in the second image data is first dilated to expand the highlight area, and then the highlight part is eroded to reduce the highlight area. Through this operation, the disconnected object area in the second image data is repaired and connected.

[0100] Preferably, the morphological closing operation selects a 3×3 dilation template and an erosion template.

[0101] S24, accumulating the data of each detection unit corresponding to each acquisition angle in the third image data to obtain edge row one-dimensional projection data. It can be understood that a one-dimensional vector with a length of s will be obtained, and each data in the vector represents the number of detector units occupied by the object at each acquisition angle.

[0102] Preferably, the obtained one-dimensional projection data of the edge row is subjected to filtering processing to eliminate possible isolated points with large fluctuations.

[0103] S3. Obtaining the object entry angle and the object exit angle based on the edge row one-dimensional projection data, and determining the position of the object scanned in the security inspection CT. It can be understood that by determining the object entry angle during the scanning process, the starting position of the object in the data scanned by the security inspection CT is determined, and by determining the object exit angle during the scanning process, the position of the object in the data scanned by the security inspection CT is determined, thereby determining the accurate position of the object scanned in the security inspection CT.

[0104] It should be noted that after obtaining the object entry angle and the object exit angle of the current object, the object entry angle and the object exit angle of the next object are then confirmed according to the light barrier signal.

[0105] During implementation, the edge row one-dimensional projection data in step S3 includes the starting row one-dimensional projection data and the ending row one-dimensional projection data; the object entry angle is obtained based on the starting row one-dimensional projection data; and the object departure angle is obtained based on the ending row one-dimensional projection data.

[0106] In a specific implementation, the object entry angle is obtained based on the one-dimensional projection data of the starting row, specifically:

[0107] If all data in the starting row of one-dimensional projection data are less than the set third threshold value, the corresponding complete data does not contain the object, and the starting row of one-dimensional projection data of the complete data of the next acquisition cycle when the object enters the security inspection CT is obtained for re-judgment;

[0108] If each data in the initial row of one-dimensional projection data is greater than or equal to the set third threshold, the corresponding complete data has an object at each acquisition angle, and the initial acquisition angle of the corresponding complete data is used as the object entry angle;

[0109] Otherwise, the first data in the starting row of one-dimensional projection data that meets the following conditions is determined as the first critical data: the data is greater than or equal to the set third threshold value and the first n1 data of the data in the starting row of one-dimensional projection data are all less than the third threshold value; and then the object entry angle is obtained according to the first critical data, where n1>0.

[0110] More specifically, the obtaining of the object entry angle according to the first critical data is specifically:

[0111] Determine the last data in the starting row of one-dimensional projection data that is greater than or equal to the set third threshold as the second critical data, and obtain the number of data n2 between the first critical data and the second critical data; and determine the number of data n0 before the first critical data and the number of data n3 after the second critical data in the starting row of one-dimensional projection data;

[0112] When n0 is greater than or equal to the fourth threshold,

[0113] If n1 is greater than or equal to the fourth threshold and n2 is greater than or equal to the fifth threshold, the collection angle of the first critical data is used as the object entry angle;

[0114] If n1 is greater than or equal to the fourth threshold and n2 is less than the fifth threshold, the corresponding complete data does not contain an object or is abnormal, and the complete data of the next acquisition cycle when the object enters the security inspection CT is obtained for re-judgment;

[0115] Otherwise, if the corresponding complete data already has an object at the initial acquisition angle, the initial acquisition angle is used as the object entry angle;

[0116] When n0 is less than the fourth threshold,

[0117] If n1 is equal to n0 and n2 is greater than or equal to the fifth threshold, the acquisition angle of the first critical data is used as the object entry angle;

[0118] If n1 is equal to n0 and n2 is less than the fifth threshold, the corresponding complete data does not contain an object or is abnormal, and the complete data of the next acquisition cycle when the object enters the security inspection CT is obtained and re-judged;

[0119] Otherwise, if the corresponding complete data already has an object at the initial acquisition angle, the initial acquisition angle is used as the object entry angle;

[0120] The fifth threshold is the minimum value of n3 and the length threshold.

[0121] In a specific implementation, the object departure angle is obtained based on the one-dimensional projection data of the end row, specifically:

[0122] If all data in the final row of one-dimensional projection data are less than the set third threshold, the corresponding complete data does not contain an object, and the initial acquisition angle of the corresponding complete data is used as the object departure angle;

[0123] If all data in the one-dimensional projection data of the end row are greater than or equal to the set third threshold, the corresponding complete data has an object at each acquisition angle, and the complete data of the next acquisition cycle when the object leaves the security inspection CT is obtained for re-judgment;

[0124] Otherwise, determine the last data in the ending row of one-dimensional projection data that meets the following conditions as the first critical data: the third critical data, the third critical data satisfies a third threshold value that is greater than or equal to the set third threshold value and the last m1 data of the third critical data in the ending row of one-dimensional projection data are all less than the third threshold value; and then obtain the object departure angle according to the third critical data, where m1>0.

[0125] More specifically, the obtaining of the object departure angle according to the third critical data is specifically as follows:

[0126] Determine the first data in the end row of the one-dimensional projection data that is greater than or equal to the set third threshold as the fourth critical data, and obtain the number of data between the third critical data and the fourth critical data m2; and determine the number of data after the third critical data m0 and the number of data before the fourth critical data m3 in the end row of the one-dimensional projection data;

[0127] When m0 is greater than or equal to the sixth threshold,

[0128] If m1 is greater than or equal to the fourth threshold and m2 is greater than or equal to the seventh threshold, the collection angle of the third critical data is used as the object departure angle;

[0129] If m1 is greater than or equal to the fourth threshold and m2 is less than the seventh threshold, the corresponding complete data does not contain an object or has an abnormality, and the initial acquisition angle of the corresponding complete data is used as the object departure angle;

[0130] Otherwise, the corresponding complete data has objects at all acquisition angles, and the complete data of the next acquisition cycle when the object leaves the security inspection CT is obtained for re-judgment;

[0131] When m0 is less than the sixth threshold,

[0132] If m1 is equal to m0 and m2 is greater than or equal to the seventh threshold, the collection angle of the third critical data is used as the object departure angle;

[0133] If m1 is equal to m0 and m2 is less than the seventh threshold, the corresponding complete data does not contain an object or has an anomaly, and the initial acquisition angle of the corresponding complete data is used as the object departure angle;

[0134] Otherwise, the corresponding complete data has objects at all acquisition angles, and the complete data of the next acquisition cycle when the object leaves the security inspection CT is obtained for re-judgment.

[0135] The seventh threshold is the minimum value of m3 and the length threshold.

[0136] Preferably, the third threshold is set to a smaller integer to eliminate possible errors; more preferably, the third threshold ranges from 0 to 5.

[0137] Preferably, the fourth threshold and the sixth threshold are set according to the distance between objects scanned by the security inspection CT, and can be set as a function that is proportional to the distance. The length threshold can be set according to the length of the object.

[0138] Preferably, after determining the position of the scanned object in the security inspection CT based on the object entry angle and the object departure angle in step S3, the object image is reconstructed by acquiring the tomographic data at different positions of the object, as follows:

[0139] Figure 2 Schematic diagram of the structure of the security inspection CT in this embodiment. The security inspection CT includes a CT ray source 1, a CT slip ring 2, a CT detector 3, an object 4, a conveyor belt 5, a conveyor belt motor 6, a motion control computer 7, a slip ring motor 8, and a data processing computer 9.

[0140] The process of reconstructing the three-dimensional data of the security inspection CT image is as follows: first, the object (luggage) 4 is placed on the conveyor belt 5, and driven by the conveyor belt motor 6, it moves at a constant speed along the conveyor belt 5 and enters the CT scanning area for scanning; the slip ring motor 8 controls the CT slip ring 2 to rotate at a constant speed, the CT ray source 1 emits an X-ray beam to transmit the object 4, and the CT detector 3 receives the attenuation signal transmitted through the object 4, and continuously transmits the received signal to the data processing computer 9. The data processing computer 9 determines the starting position and the ending position of the object to be reconstructed according to the object entry angle and the object departure angle calculated according to the collected data, and then obtains the tomographic data of different positions of the object, and then displays the three-dimensional data composed of all tomographic layers in three dimensions on the screen to achieve image reconstruction.

[0141] Compared with the prior art, the method for determining the position of a scanned object in a security inspection CT provided by the present invention obtains edge row projection data through the empty scan data and complete data of the detector, eliminates the noise points and isolated points of the edge row projection data based on morphological processing, and calculates to obtain the one-dimensional projection data of the edge row, thereby obtaining the position information of the object at each acquisition angle, and then determining the angle information of the object entering or leaving the security inspection CT, and can obtain the accurate position information of the object scanned by the security inspection CT, so that when the image is reconstructed subsequently, the amount of reconstructed data is small and the integrity of the object can be guaranteed.

[0142] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0143] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for determining the position of a scanned object in a security inspection CT, characterized in that: The following steps are involved: Collect the detector's empty scan data without objects, and collect the detector's complete data when receiving the object trigger signal; The edge row projection data is obtained based on the air scan data and the complete data, and the edge row projection data is morphologically processed to obtain the edge row one-dimensional projection data; wherein the edge row projection data includes the starting row projection data and the ending row projection data; the edge row projection data is obtained based on the air scan data and the complete data specifically as follows: If it is the complete data when the object enters, extract the starting row data from the complete data, and extract the starting row data of the corresponding acquisition angle from the air scan data; subtract the starting row data of the complete data from the starting row data of the air scan data to obtain the starting row projection data; If it is the complete data when the object leaves, extract the end row data in the complete data, and extract the end row data of the corresponding acquisition angle in the air scan data; subtract the end row data of the complete data from the corresponding end row data of the air scan data to obtain the end row projection data; The edge row that first receives the attenuation signal of the object when the object enters the security inspection CT is taken as the starting row, and the edge row that last receives the attenuation signal of the object when the object leaves the security inspection CT is taken as the ending row; the empty scan data is the detector data collected when the detector rotates one circle along the set rotation interval angle when there is no object in the security inspection CT; Based on the one-dimensional projection data of the edge row, an object entry angle and an object exit angle are obtained to determine the position of the object scanned in the security inspection CT; The edge row one-dimensional projection data includes the starting row one-dimensional projection data and the ending row one-dimensional projection data; the object entry angle is obtained based on the starting row one-dimensional projection data; the object departure angle is obtained based on the ending row one-dimensional projection data; The object entry angle is obtained based on the one-dimensional projection data of the starting row, specifically: If all data in the starting row of one-dimensional projection data are less than the set third threshold value, the corresponding complete data does not contain the object, and the starting row of one-dimensional projection data of the complete data of the next acquisition cycle when the object enters the security inspection CT is obtained for re-judgment; If each data in the initial row of one-dimensional projection data is greater than or equal to the set third threshold, the corresponding complete data has an object at each acquisition angle, and the initial acquisition angle of the corresponding complete data is used as the object entry angle; Otherwise, the first data in the starting row of one-dimensional projection data that meets the following conditions is determined as the first critical data: the data is greater than or equal to the set third threshold value and the first n1 data of the data in the starting row of one-dimensional projection data are all less than the third threshold value; and then the object entry angle is obtained according to the first critical data, where n1>0; The method of obtaining the object departure angle based on the end row of one-dimensional projection data is specifically as follows: If all data in the final row of one-dimensional projection data are less than the set third threshold, the corresponding complete data does not contain an object, and the initial acquisition angle of the corresponding complete data is used as the object departure angle; If all data in the one-dimensional projection data of the end row are greater than or equal to the set third threshold, the corresponding complete data has an object at each acquisition angle, and the complete data of the next acquisition cycle when the object leaves the security inspection CT is obtained for re-judgment; Otherwise, the last data in the ending row of one-dimensional projection data that meets the following conditions is determined as the third critical data: the data satisfies a third threshold that is greater than or equal to the set third threshold and the last m1 data of the data in the ending row of one-dimensional projection data are all less than the third threshold; and then the object departure angle is obtained according to the third critical data, where m1>0.

2. The method for determining the position of a scanned object in a security inspection CT according to claim 1, characterized in that: When receiving the object trigger signal, obtaining the complete data of the detector includes: When the received signal is a trigger signal when an object enters the security inspection CT, the complete data of the object entering the security inspection CT is collected; When the received signal is a trigger signal when the object leaves the security inspection CT, the complete data of the object leaving the security inspection CT is collected; The complete data is the detector data collected by the detector rotating from the initial collection angle to the set rotation interval angle by the set angle; the rotation of the detector by the set angle is regarded as a collection cycle.

3. The method for determining the position of a scanned object in a security inspection CT according to claim 1, characterized in that: After morphological processing is performed on the edge row projection data, the edge row one-dimensional projection data is obtained, specifically: After binarizing the edge row projection data based on a set first threshold, a morphological opening operation is performed on the processed edge row projection data, and then data corresponding to regions whose areas are smaller than the area threshold are set to 0 through connectivity analysis to obtain first image data; Performing filtering on the first image data to obtain second image data; Perform hole filling on the second image data based on a morphological closing operation to obtain third image data; The data of each detection unit corresponding to each acquisition angle in the third image data are accumulated to obtain one-dimensional projection data of the edge row.

4. The method for determining the position of a scanned object in a security inspection CT according to claim 3, characterized in that: The first image data is filtered to obtain the second image data, specifically: the first image data is low-pass filtered to obtain the fourth image data; and the fourth image data is binarized based on a set second threshold to obtain the second image data.

5. The method for determining the position of a scanned object in a security inspection CT according to claim 1, characterized in that: The obtaining of the object entry angle according to the first critical data is specifically as follows: Determine the last data in the starting row of one-dimensional projection data that is greater than or equal to the set third threshold as the second critical data, and obtain the number of data n2 between the first critical data and the second critical data; and determine the number of data n0 before the first critical data and the number of data n3 after the second critical data in the starting row of one-dimensional projection data; When n0 is greater than or equal to the fourth threshold, If n1 is greater than or equal to the fourth threshold and n2 is greater than or equal to the fifth threshold, the collection angle of the first critical data is used as the object entry angle; If n1 is greater than or equal to the fourth threshold and n2 is less than the fifth threshold, the corresponding complete data does not contain an object or is abnormal, and the complete data of the next acquisition cycle when the object enters the security inspection CT is obtained for re-judgment; Otherwise, if the corresponding complete data already has an object at the initial acquisition angle, the initial acquisition angle is used as the object entry angle; When n0 is less than the fourth threshold, If n1 is equal to n0 and n2 is greater than or equal to the fifth threshold, the acquisition angle of the first critical data is used as the object entry angle; If n1 is equal to n0 and n2 is less than the fifth threshold, the corresponding complete data does not contain an object or is abnormal, and the complete data of the next acquisition cycle when the object enters the security inspection CT is obtained and re-judged; Otherwise, if the corresponding complete data already has an object at the initial acquisition angle, the initial acquisition angle is used as the object entry angle; The fifth threshold is the minimum value of n3 and the length threshold.

6. The method for determining the position of a scanned object in a security inspection CT according to claim 1, characterized in that: The obtaining of the object departure angle according to the third critical data is specifically as follows: Determine the first data in the one-dimensional projection data of the end row that is greater than or equal to the set third threshold as the fourth critical data, and obtain the number of data between the third critical data and the fourth critical data m2; and determine the number of data after the third critical data m0 and the number of data before the fourth critical data m3 in the one-dimensional projection data of the end row; When m0 is greater than or equal to the sixth threshold, If m1 is greater than or equal to the fourth threshold and m2 is greater than or equal to the seventh threshold, the collection angle of the third critical data is used as the object departure angle; If m1 is greater than or equal to the fourth threshold and m2 is less than the seventh threshold, the corresponding complete data does not contain an object or has an abnormality, and the initial acquisition angle of the corresponding complete data is used as the object departure angle; Otherwise, the corresponding complete data has objects at all acquisition angles, and the complete data of the next acquisition cycle when the object leaves the security inspection CT is obtained for re-judgment; When m0 is less than the sixth threshold, If m1 is equal to m0 and m2 is greater than or equal to the seventh threshold, the collection angle of the third critical data is used as the object departure angle; If m1 is equal to m0 and m2 is less than the seventh threshold, the corresponding complete data does not contain an object or has an anomaly, and the initial acquisition angle of the corresponding complete data is used as the object departure angle; Otherwise, the corresponding complete data has objects at all acquisition angles, and the complete data of the next acquisition cycle when the object leaves the security inspection CT is obtained for re-judgment; The seventh threshold is the minimum value of m3 and the length threshold.

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