A baggage ct article inspection system and a reconstruction region determination method

Abstract

The present application relates to a kind of luggage CT article inspection systems and image reconstruction area determination method, belong to safety system technical field, solve the problem of computer's computing resource waste caused by the large area of blank area in the system reconstruction area in prior art.Luggage CT article inspection system includes CT ray source, CT slip ring, CT detector, conveying belt, conveying belt motor, motion control computer, slip ring motor, data processing computer, also includes light curtain emitting end, light curtain receiving end;Multiple light emitting devices are provided on the light curtain emitting end, multiple light receivers are provided on the light curtain receiving end, light beams are emitted by multiple light emitting devices, and the light receiver receives light beams from the light emitting device to form detection light curtain.The reconstruction area is the area where the object is located, and the large area of blank area in the system reconstruction area is avoided.

Description

Technical Field

[0001] This invention relates to the field of security system technology, and in particular to a baggage CT item inspection system and a method for determining the image reconstruction region. Background Technology

[0002] In X-ray-based explosives inspection technology, X-ray computed tomography (CT) imaging technology is highly valued in the field of security inspection due to its unique advantages. X-ray CT security inspection technology obtains tomographic images of the scanned object by reconstructing CT data, and identifies dangerous items in the scanned object by analyzing the feature data in the tomographic images.

[0003] In security CT scanners, there is typically a detection channel. The size of this channel determines the maximum size of the package the system can detect. To accommodate the reconstruction of the largest package, the CT reconstructed image area must cover the area of ​​the largest detectable package. However, in actual inspections, the size of the package being inspected is usually much smaller than the maximum package size. This results in large blank areas within the system's reconstruction area, significantly wasting the computer's computing resources. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a baggage CT item inspection system and an image reconstruction area determination method to solve the problem that the actual size of the inspected bag is usually much smaller than the maximum bag size, resulting in a waste of computer computing resources.

[0005] On one hand, embodiments of the present invention provide a baggage CT item inspection system, including a CT radiation source, a CT slip ring, a CT detector, a conveyor belt, a conveyor belt motor, a motion control computer, a slip ring motor, a data processing computer, and also includes a light curtain transmitter and a light curtain receiver;

[0006] The light curtain emitting end is provided with multiple light emitters, and the light curtain receiving end is provided with multiple light receivers. The light emitters emit light beams, and the light receivers receive the light beams from the light emitters to form a detection light curtain.

[0007] Among them, the multiple light emitters and light receivers are arranged vertically at equal intervals, with one light emitter corresponding to one light receiver; the distance between the light emitters may be non-equal.

[0008] Wherein, the distance f between the i-th light emitter and the transmitting device i satisfy:

[0009] f i+1 -f i >0

[0010] fi ≥0

[0011] Where i is a positive integer;

[0012] f1 is the distance between the lowest-end light emitter and the transmission device;

[0013] The conveying device is either a conveyor belt or a roller.

[0014] Based on further improvements to the above system, when an object enters the detection light curtain area, the light receivers in the light curtain receiver end change from being able to receive the light beam completely to some or all of them not receiving the light beam.

[0015] On the other hand, embodiments of the present invention provide a method for determining the reconstruction area of ​​baggage CT, which includes determining the reconstruction area using the three-dimensional data of the reconstructed image from the baggage CT item inspection system according to any one of claims 1-3.

[0016] Further improvements to the above method include:

[0017] Step 1: Use the baggage CT item inspection system to obtain data on when an object intrudes into the detection light curtain area;

[0018] Step 2: Process the obtained data to reconstruct the three-dimensional data of the image;

[0019] Step 3: Determine the reconstruction region based on the two-dimensional array X.

[0020] Based on a further improvement of the above method, in step 1, the data includes the status data of the light receiver in the light curtain receiver.

[0021] When an object intrudes into the detection light curtain, the light receivers in the light curtain receiver end change from being able to receive the light beam completely to some or all of them not receiving the light beam.

[0022] Based on a further improvement of the above method, step 2 includes:

[0023] S21: Define the state in which the light receiver can receive a signal as 0, otherwise as 1;

[0024] S22: Construct a two-dimensional array X based on the state data of the light receiver.

[0025] Based on a further improvement of the above method, step S22 includes:

[0026] S221: Record the signals of each photodetector in vector form according to their positions from low to high;

[0027] S222: The detection light curtain signals of the entire process of an object not entering the detection light curtain, entering the detection light curtain, and leaving the detection light curtain are continuously recorded and arranged in chronological order to form a two-dimensional array X.

[0028] Based on a further improvement of the above method, step S3 includes:

[0029] S311: Accumulate the two-dimensional array X along the row direction to obtain the column vector p;

[0030] S312: Record the position m of the first element that is 0 and all subsequent elements that are 0 in the column vector p;

[0031] S313: When reconstructing an object, the reconstruction area of ​​a single slice is located in the height region between the conveyor belt and fm;

[0032] Where m is a non-negative integer, at this time, the light receiver at a height of fm from the conveyor belt and above it has always received the light beam normally and has never been blocked by an object.

[0033] Based on a further improvement of the above method, step S3 includes:

[0034] S321: Extract the columns in the two-dimensional array X that are in the time intervals t6-s1 / v1–d and t6-s1 / v1+tt+d to obtain the two-dimensional vector group Z;

[0035] S322: Accumulate the two-dimensional array Z along the row direction to obtain the column vector Q;

[0036] S323: Record the position e of the first element that is 0 and all subsequent elements that are 0 in the column vector Q;

[0037] S324: When reconstructing an object, the reconstruction area of ​​a single slice is located on the conveyor belt and f. e The height region between them is used to obtain the reconstructed height of fault K;

[0038] In the reconstruction of fault k, the required time for generating projection data is between t6 and t6+tt; where tt is the time required for the detector to acquire fixed angle data, which can be the time required for the detector to rotate one revolution.

[0039] d represents the set time extension;

[0040] e is a non-negative integer, where f is the height from the position on the conveyor belt. e The location and its receiver consistently received the light beam normally and were never blocked by any object.

[0041] s1 is the distance between the detection light curtain and the CT scan area;

[0042] v1 represents the conveyor belt speed.

[0043] Based on a further improvement of the above method, in step S3, the image background value is 0-10.

[0044] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0045] 1. This invention employs multiple emitters and multiple receivers to form a detection light curtain between the light curtain transmitter and the light curtain receiver to determine the height of the object. Then, after determining the height of the object, only the area where the object is located needs to be reconstructed. This not only ensures the integrity of the data and avoids packet fragmentation, but also reduces the data reconstruction area by analyzing the size of the reconstruction area, minimizing the amount of computational data, avoiding waste of computing resources, and saving reconstruction time.

[0046] 2. By reconstructing the three-dimensional data of the security inspection CT image and determining the height of the object, only the area where the object is located can be reconstructed, which reduces the data reconstruction area, reduces the amount of computational data, and thus avoids the waste of computing resources.

[0047] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0048] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0049] Figure 1 This is a schematic diagram of the baggage CT item inspection system of the present invention;

[0050] Figure 2 This is a flowchart of the method for determining the CT reconstruction area of ​​luggage in this invention.

[0051] Figure label:

[0052] 1-CT X-ray source; 2-CT slip ring; 3-CT detector; 4-object; 5-conveyor belt; 6-conveyor belt motor; 7-motion control computer; 8-slip ring motor; 9-data processing computer; 10-light curtain transmitter; 11-light curtain receiver; 12-light emitter; 13-light receiver. Detailed Implementation

[0053] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form 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 intended to limit the scope of the present invention.

[0054] Existing security screening systems based on X-ray computed tomography (CT) technology obtain information about the internal structure of scanned objects by reconstructing projection data from multiple angles. This requires determining the position of the object being scanned by the CT scan to reduce the amount of data reconstructed. Security screening systems typically use one or more light barrier devices (through-beam photoelectric switches) positioned at different heights within the security checkpoint to determine the object's scanning position. Each light barrier device includes a light barrier transmitting module and a light barrier receiving module. The light barrier's state determines whether an object has entered or left. If the light barrier changes from unobstructed to obstructed, the security screening system considers an object to have entered and begins subsequent security processing, such as activating the X-ray and starting image acquisition. If the light barrier changes from obstructed to unobstructed, the system considers the object to have completely passed through the area where the light barrier was located.

[0055] However, since the shapes of objects being checked at security checkpoints are often diverse, light barriers set at a fixed height cannot determine whether there are objects at other heights. For example, the wheels of a flat-lying wheeled suitcase are at a height higher than the light barrier set at the bottom of the security checkpoint, which may cause a delay in determining whether an object has entered or an early determination that an object has left. In the security check reconstruction image, this may appear as a missing part of the object, i.e., an incomplete scan, resulting in a bag-cutting phenomenon.

[0056] To address the issue of bag snatching, current security inspection systems typically set fixed lead and delay values ​​during data collection after receiving a light barrier signal to minimize the risk of bag snatching. However, this method inevitably increases the data processing volume for scanning a single item and cannot completely prevent bag snatching.

[0057] To solve the above problems, the present invention provides a baggage CT item inspection system, including: CT X-ray source 1, CT slip ring 2, CT detector 3, conveyor belt 5, conveyor belt motor 6, motion control computer 7, slip ring motor 8, data processing computer 9, light curtain transmitter 10, and light curtain receiver 11.

[0058] Multiple emitters 12 are provided on the light curtain transmitter 10, and multiple receivers 13 are provided on the light curtain receiver 11. The multiple emitters 12 emit light beams, and the receivers 13 receive the light beams from the emitters 12 to form a detection light curtain to detect objects 4 that have entered the detection light curtain area and obtain detection light curtain trigger feedback data.

[0059] In other words, when object 4 enters the detection light curtain area, it will cause light blocking, and any light receiver 13 will not receive the light beam. The system will then determine that object 4 has entered, obtain relevant data on object 4 entering the detection light curtain area, and determine the height of the object. After determining the height of object 4, only the area where object 4 is located needs to be reconstructed, thus avoiding large blank areas in the reconstructed area and reducing the waste of computer computing resources.

[0060] Among them, multiple emitters 12 and multiple receivers 13 can be arranged vertically with equal spacing, with one emitter 12 corresponding to one receiver 13; the distance between emitters 12 and receivers 13 can be non-equal, and the correspondence between emitters 12 and receivers 13 is not one-to-one; the emitter 12 emits a light beam, and the receiver 13 can receive the light beam from the emitter 12.

[0061] Wherein, the distance f between the i-th light emitter 12 and the transmission device i satisfy:

[0062] f i+1 -f i >0

[0063] f i ≥0

[0064] Where i is a positive integer;

[0065] f1 is the distance between the lowest-end light emitter and the transmission device;

[0066] The conveying device is either a conveyor belt or a roller.

[0067] In one possible real-time configuration, the emitters 12 and receivers 13 are arranged vertically at equal intervals, with one emitter 12 corresponding to one receiver 13.

[0068] In this process, the CT X-ray source emits a beam of light, and the CT detector receives the beam of light emitted by the CT X-ray source to form the CT scanning area.

[0069] Compared with the prior art, the present invention uses multiple emitters 12 and multiple receivers 13 to form a detection light curtain between the light curtain emitting end 10 and the light curtain receiving end 11. After the object being inspected enters the light curtain, the receivers 13 in the light curtain receiving end 11 change from being able to receive the light beam to some or all of them not receiving the light beam. That is, detection can be achieved at all height positions within the detection light curtain. Thus, when inspecting irregularly shaped objects, it is not necessary to set fixed advance and delay amounts to obtain complete detection data of the object being inspected, ensuring data integrity, avoiding packet sniffing, and providing data support for reducing the reconstruction area in the future.

[0070] When an object enters the detection light curtain, the detection light curtain will trigger feedback data to be transmitted to the data processing computer 9.

[0071] Among them, the detection light curtain will trigger feedback data including the state data of the light receiver 13 in the light curtain receiver 11 changing from being able to receive the light beam to some or all of the light receivers 13 not receiving the light beam when an object enters the detection light curtain.

[0072] Among them, the conveyor belt motor 6 is used to control the movement state of the transmission belt 5, and the motion control computer 7 is used to control the working state of the conveyor belt motor 6.

[0073] Among them, CT X-ray source 1 and CT detector 3 are used to detect object 4 in order to obtain the object's projection data;

[0074] The CT slip ring 2 is used to move the CT X-ray source 1 and the CT detector 3 to adjust the angle of the projection data;

[0075] The slip ring motor 8 is used to control the movement state of the CT slip ring 2.

[0076] The conveyor belt 5 transports the object at a constant speed and passes sequentially through the area between the light curtain transmitter 10 and the light curtain receiver 11, and the area between the CT radiation source 1 and the CT detector 3.

[0077] During the detection process, the object 4, i.e., the luggage, is first placed on the conveyor belt 5. Driven by the conveyor belt motor 6, it moves at a constant speed with the conveyor belt 5. As the object 4 intrudes into the detection light curtain, the light receivers 13 in the light curtain receiver 11 change from being able to receive the light beam completely to being unable to receive the light beam in some or all of them. In this way, the detection light curtain signal feedback is obtained.

[0078] When object 4 enters the scanning area, the slip ring motor 8 controls the CT slip ring 2 to rotate at a constant speed. The CT radiation source 1 emits an X-ray beam that penetrates object 4. The CT detector 3 receives the attenuated signal transmitted through object 4 and continuously transmits the received signal to the data processing computer 9. The data processing computer 9 processes the data.

[0079] Among them, the data processing computer 9 obtains the internal structural information of the scanned object by reconstructing the projection data of the object from multiple angles.

[0080] In addition, the present invention also provides a method for determining the reconstruction region of baggage using CT scans, comprising determining the reconstruction region using three-dimensional data of the reconstructed image from the aforementioned baggage CT inspection system. Specifically, the method includes the following steps:

[0081] Step 1: Use the baggage CT item inspection system to obtain data on when an object intrudes into the detection light curtain area;

[0082] Specifically, object 4 is first placed on conveyor belt 5, and then moves at a constant speed along with conveyor belt 5 under the drive of conveyor belt motor 6.

[0083] When an object intrudes into the detection light curtain, the light receivers 13 in the light curtain receiver 11 change from being able to receive the light beam completely to some or all of the light receivers 13 not receiving the light beam.

[0084] The data includes the status data of the light receivers 13 in the light curtain receiver 11, that is, when an object enters the detection light curtain, the light receivers 13 in the light curtain receiver 11 change from being able to receive the light beam to some or all of the light receivers 13 not receiving the light beam.

[0085] Step 2: Process the obtained data to reconstruct the three-dimensional data of the image;

[0086] S21: Define the state in which the light receiver 13 can receive a signal as 0, otherwise define it as 1;

[0087] S22: Construct a two-dimensional array X based on the state data of the light receiver 13.

[0088] Specifically, including:

[0089] S221: Record the signals of each photodetector 13 in vector form according to their positions from low to high;

[0090] S222: The light curtain signal feedback of object 4 during the entire process of not intruding into the detection light curtain, intruding into the detection light curtain, and leaving the detection light curtain is continuously recorded and arranged in chronological order to form a two-dimensional array X.

[0091] For example, when the object does not intrude into the detection light curtain, the signal is represented as [0,0,0,0,0,….,0]. T When an object enters the detection light curtain, the signal is represented as [0,0,….,1,1,1,….,1,….,0,0]. T Once the object leaves the detection light curtain and no further object enters the light curtain, the signal is represented as [0,0,0,0,0,….,0]. T .

[0092] In this context, each column of X represents the detection light curtain signal feedback at a certain moment, where a position with a 1 indicates the area intruded by the object, and each row represents the signal change of a certain light receiver.

[0093] The two-dimensional array X can be used to determine the relevant data of the process of object 4 entering the CT scanning area for scanning. For example, it includes the time when object 4 enters the detection light curtain, the time when object leaves the detection light curtain, and the time when object passes through the CT scanning area.

[0094] Specifically, the time when the two-dimensional array X appears with the value 1 is defined as t1, at which time t1 represents the time when the object enters the light curtain; after a period of time, the time when the object leaves the light curtain is defined as t2, and the signal feedback time interval of the light receiver is t3.

[0095] Specifically, after object 4 enters the detection light curtain at time s1 / v1 (i.e., after time t1+s1 / v1), object 4 enters the CT scanning area for scanning; after time t2+s1 / v1+t4, it leaves the CT scanning area, completing the scan. During this period, slip ring motor 8 controls the CT slip ring 2 to rotate at a constant speed, and CT X-ray source 1 emits an X-ray beam that penetrates object 4. CT detector 3 receives the attenuated signal transmitted through object 4 and continuously transmits the received signal to data processing computer 9. Data processing computer 9 processes the data within both time ranges.

[0096] Where s1 is the distance between the detection light curtain and the CT scanning area; v1 is the conveyor belt speed.

[0097] Wherein, t4 is the time required for the thin-film object to pass through the CT scanning area. This time is generally fixed and determined by the system settings. For example, it can be determined by the conveyor belt speed parameters and the rotation speed parameters of the rotating body, and can be obtained through experiments.

[0098] Step 3: Determine the reconstruction region based on the two-dimensional array X.

[0099] Specifically, including:

[0100] S311: Accumulate the two-dimensional array X along the row direction to obtain the column vector p;

[0101] S312: Record the position m of the first element that is 0 and all subsequent elements that are 0 in the column vector p;

[0102] Where m is a non-negative integer, and at this point, the height from the conveyor belt position is f. m The location and the receiver there have always received the light beam normally and have never been blocked by any object.

[0103] S313: When reconstructing an object, the reconstruction area of ​​a single slice is located on the conveyor belt and f. m The height range between them.

[0104] The image background value is 0-10; for example, it is 0.

[0105] The reconstruction algorithm typically reconstructs a series of two-dimensional images perpendicular to the conveyor belt's transport direction to obtain a tomographic image of the object in that direction, i.e., a slice.

[0106] Once the height of the object is determined, only the area where the object is located can be reconstructed. This reduces the data reconstruction area, decreases the amount of computational data, and avoids wasting computational resources.

[0107] This process involves acquiring all fault data at different locations of the object, and then displaying the three-dimensional data composed of all faults on the screen to reconstruct the image.

[0108] Furthermore, in reconstructing fault K, step 3 above includes:

[0109] S321: Extract the columns in the two-dimensional array X that are in the time intervals t6-s1 / v1–d and t6-s1 / v1+tt+d to obtain the two-dimensional vector group Z;

[0110] In the reconstruction of fault k, the required time for generating projection data is between t6 and t6+tt; where tt is the time required for the detector to acquire fixed angle data, which can be the time required for the detector to rotate one revolution.

[0111] Where d represents the set time extension.

[0112] S322: Accumulate the two-dimensional array Z along the row direction to obtain the column vector Q;

[0113] S323: Record the position e of the first element that is 0 and all subsequent elements that are 0 in the column vector Q;

[0114] Where e is a non-negative integer, and at this point, the height from the conveyor belt position is f. e The location and the receiver there have always received the light beam normally and have never been blocked by any object.

[0115] S324: When reconstructing an object, the reconstruction area of ​​a single slice is located on the conveyor belt and f. e The height range between the two faults is used to obtain the reconstructed height of fault K.

[0116] The image background value is 0-10; for example, it is 0.

[0117] Once the height of the object is determined, only the area where the object is located can be reconstructed. This reduces the data reconstruction area, decreases the amount of computational data, and avoids wasting computational resources.

[0118] This process involves acquiring all fault data at different locations of the object, and then displaying the three-dimensional data composed of all faults on the screen to reconstruct the image.

[0119] Compared with the prior art, the present invention uses multiple emitters 12 and multiple receivers 13 to form a detection light curtain between the light curtain emitting end 10 and the light curtain receiving end 11. After the object being inspected enters the light curtain, the receivers 13 in the light curtain receiving end 11 change from being able to receive the light beam to some or all of them not receiving the light beam. That is, detection can be achieved at all height positions within the detection light curtain. Thus, when inspecting irregularly shaped objects, it is not necessary to set fixed advance and delay amounts to obtain complete detection data of the object being inspected, ensuring data integrity, avoiding packet sniffing, and providing data support for reducing the reconstruction area in the future.

[0120] This invention employs multiple emitters 12 and multiple receivers 13 to form a detection light curtain between the light curtain emitting end 10 and the light curtain receiving end 11 to determine the height of object 4. Then, after determining the height of object 4, only the area where object 4 is located needs to be reconstructed. In this way, not only can the integrity of the data be guaranteed and packet fragmentation be avoided, but also the data reconstruction area can be reduced by analyzing the size of the reconstruction area, minimizing the amount of computational data, avoiding the waste of computing resources, and saving the time used for reconstruction.

[0121] Example 1

[0122] A baggage CT inspection system includes: a CT radiation source 1, a CT slip ring 2, a CT detector 3, a conveyor belt 5, a conveyor belt motor 6, a motion control computer 7, a slip ring motor 8, a data processing computer 9, a light curtain transmitter 10, a light curtain receiver 11, a light emitter 12, and a light receiver 13.

[0123] The light curtain emitting end 10 is provided with multiple light emitters 12, and the light curtain receiving end 11 is provided with multiple light receivers 13. The multiple light emitters 12 and multiple light receivers 13 are arranged vertically at equal intervals, with one light emitter 12 corresponding to one light receiver 13. The multiple light emitters 12 emit light beams, and the light receivers 13 receive the light beams from the light emitters 12, thereby forming a rectangular detection light curtain.

[0124] In the case where the light emitters are arranged at equal intervals, the distance f between the i-th light emitter 12 and the conveyor belt 5 is... i satisfy:

[0125] f i =s+(i-1)*h

[0126] Where i is a positive integer;

[0127] h is the spacing between the light emitters 12;

[0128] s is the distance between the lowest light emitter 12 and the conveyor belt 5.

[0129] During the detection process, object 4, i.e., luggage, is first placed on conveyor belt 5 and then moved at a constant speed by conveyor belt motor 6. As object 4 intrudes into the detection light curtain, the light receivers 13 in the light curtain receiver 11 change from being able to receive all light beams to being unable to receive light beams by some or all of them. In this way, relevant data on the area where object 4 intrudes into the detection light curtain are obtained, and the height of object 4 is determined. Then, after determining the height of object 4, only the area where object 4 is located needs to be reconstructed, avoiding large blank areas in the system reconstruction area and reducing the waste of computer computing resources.

[0130] Example 2

[0131] A method for determining the area to be reconstructed by CT scan of luggage, including the following steps:

[0132] Step 1: Use the baggage CT item inspection system to obtain data on when an object intrudes into the detection light curtain area;

[0133] Specifically, object 4 is first placed on conveyor belt 5, and then moves at a constant speed along with conveyor belt 5 under the drive of conveyor belt motor 6.

[0134] When object 4 enters the light curtain, the light receivers 13 in the light curtain receiver 11 change from being able to receive the light beam completely to some or all of the light receivers 13 not receiving the light beam.

[0135] The data includes the status data of the light receivers 13 in the light curtain receiver 11, that is, when an object enters the detection light curtain, the light receivers 13 in the detection light curtain receiver 11 change from being able to receive the light beam to some or all of the light receivers 13 not receiving the light beam.

[0136] Step 2: Process the obtained data to reconstruct the three-dimensional data of the image;

[0137] S21: Define the state in which the light receiver 13 can receive a signal as 0, otherwise define it as 1;

[0138] S22: Construct a two-dimensional array X based on the state data of the light receiver 13.

[0139] Specifically, including:

[0140] S221: Record the signals of each photodetector 13 in vector form according to their positions from low to high;

[0141] S222: The detection light curtain signals of object 4 throughout the entire process of not entering the detection light curtain, entering the detection light curtain, and leaving the detection light curtain are continuously recorded and arranged in chronological order to form a two-dimensional array X.

[0142] Specifically, when an object does not intrude into the detection light curtain, the signal is represented as [0,0,0,0,0,….,0]. T When an object enters the detection light curtain, the signal is represented as [0,0,….,1,1,1,….,1,….,0,0]. T Once the object leaves the detection light curtain and no further object enters the detection light curtain, the signal is represented as [0,0,0,0,0,….,0]. T .

[0143] In this array, each column of the two-dimensional array X represents the light curtain signal feedback at a certain moment. The position with 1 indicates the area invaded by the object 4, and each row represents the signal change of a certain light receiver 13.

[0144] The two-dimensional array X can be used to determine the relevant data of the object 4 entering the CT scanning area for scanning. For example, it includes the time when the object enters the detection light curtain, the time when the object leaves the detection light curtain, and the time when the object passes through the CT scanning area.

[0145] Specifically, the time when the two-dimensional array X appears with the value 1 is defined as t1, at which time t1 represents the time when object 4 enters the detection light curtain; after one time, the time when object 4 leaves the detection light curtain is defined as t2, and the signal feedback time interval of the light receiver 13 is t3.

[0146] Specifically, after object 4 enters the detection light curtain at time s1 / v1 (i.e., after time t1+s1 / v1), object 4 enters the CT scanning area for scanning; after time t2+s1 / v1+t4, it leaves the CT scanning area, completing the scan. During this period, slip ring motor 8 controls the CT slip ring 2 to rotate at a constant speed, and CT X-ray source 1 emits an X-ray beam that penetrates object 4. CT detector 3 receives the attenuated signal transmitted through object 4 and continuously transmits the received signal to data processing computer 9. Data processing computer 9 processes the data within both time ranges.

[0147] Where s1 is the distance between the detection light curtain and the CT scanning area; v1 is the conveyor belt speed.

[0148] Wherein, t4 is the time required for the thin-film object to pass through the CT scanning area. This time is generally fixed and is determined by the conveyor belt speed parameters and the rotational speed parameters of the rotating body, and can be obtained through experiments.

[0149] Step 3: Determine the reconstruction region based on the two-dimensional array X.

[0150] Specifically, including:

[0151] S311: Accumulate the two-dimensional array X along the row direction to obtain the column vector p;

[0152] S312: Record the position m of the first element that is 0 and all subsequent elements that are 0 in the column vector p;

[0153] Where m is a non-negative integer, at this time, the light receiver 13 at a height of s+(m-1)*h from the position of the conveyor belt 5 and above it has always received the light beam normally and has never been blocked by the object 4.

[0154] S313: When reconstructing an object, the reconstruction area of ​​a single slice is located in the height region between conveyor belt 5 and s+(m-1)*h.

[0155] The background value of the image is 0.

[0156] The reconstruction algorithm typically reconstructs two-dimensional images perpendicular to the conveyor belt's transport direction to obtain a tomographic image of object 4 in that direction, i.e., a slice.

[0157] Once the height of the object is determined, only the area where object 4 is located can be reconstructed. This reduces the data reconstruction area, decreases the amount of computational data, and avoids wasting computational resources.

[0158] Example 3

[0159] A method for determining the CT reconstruction region of luggage, which differs from Example 2, is as follows:

[0160] Step 3 includes:

[0161] S321: Extract the columns in the two-dimensional array X that are in the time intervals t6-s1 / v1–d and t6-s1 / v1+tt+d to obtain the two-dimensional vector group Z;

[0162] In the reconstruction of fault k, the required time for generating projection data is between t6 and t6+tt; where tt is the time required for CT detector 3 to acquire fixed angle data and tt is the time required for CT detector to rotate one revolution.

[0163] Where d represents the set time extension.

[0164] S322: Accumulate the two-dimensional array Z along the row direction to obtain the column vector Q;

[0165] S323: Record the position e of the first element that is 0 and all subsequent elements that are 0 in the column vector Q;

[0166] Where e is a non-negative integer, at this time, the light receiver 13 at a height of s+(e-1)*h from the position 5 of the conveyor belt and above it has always received the light beam normally and has never been blocked by an object.

[0167] S324: When reconstructing an object, the reconstruction area of ​​a single slice is located in the height region between the conveyor belt and s+(e-1)*h, and the reconstruction height of the fault K is obtained.

[0168] The background value of the image is 0.

[0169] Once the height of object 4 is determined, only the area where object 4 is located can be reconstructed. This reduces the data reconstruction area, decreases the amount of computational data, and avoids wasting computational resources.

[0170] The process involves acquiring all fault data at different locations of object 4, and then displaying the three-dimensional data composed of all faults on the screen to reconstruct the image.

[0171] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0172] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A baggage CT inspection system, comprising a CT radiation source, a CT slip ring, a CT detector, a conveyor, a conveyor belt motor, a motion control computer, a slip ring motor, and a data processing computer, characterized in that: It also includes a light curtain transmitter and a light curtain receiver; The light curtain transmitter is equipped with multiple emitters, and the light curtain receiver is equipped with multiple receivers. The emitters emit light beams, and the receivers receive the light beams from the emitters to form a detection light curtain to determine the height of the luggage. Then, after determining the height of the luggage, only the area where the luggage is located needs to be reconstructed. Among them, the multiple light emitters and light receivers can be arranged vertically with equal spacing, and one light emitter corresponds to one light receiver; the distance between the light emitters can be non-equal; Wherein, the distance between the i-th light emitter and the transmission device satisfy: ； ； Where i is a positive integer; The distance between the lowest-end light emitter and the transmission device; The conveying device is either a conveyor belt or a roller.

2. The system according to claim 1, characterized in that: When an object enters the detection light curtain area, the light receivers in the light curtain receiver end change from being able to receive the light beam completely to some or all of them not receiving the light beam.

3. A method for determining the CT reconstruction region of luggage, characterized in that: This includes using three-dimensional data from reconstructed images obtained from the baggage CT item inspection system according to any one of claims 1-2 to determine the reconstruction area.

4. The method according to claim 3, characterized in that, include: Step 1: Use the baggage CT item inspection system to obtain data on when an object intrudes into the detection light curtain area; Step 2: Process the obtained data to reconstruct the three-dimensional data of the image; Step 3: Determine the reconstruction region based on the two-dimensional array X.

5. The method according to claim 4, characterized in that: In step 1, the data includes the status data of the light receiver in the light curtain receiver; When an object intrudes into the detection light curtain, the light receivers in the light curtain receiver end change from being able to receive the light beam completely to some or all of them not receiving the light beam.

6. The method according to claim 4, characterized in that, Step 2 includes: S21: Define the state in which the light receiver can receive a signal as 0, otherwise as 1; S22: Construct a two-dimensional array X based on the state data of the light receiver.

7. The method according to claim 6, characterized in that, Step S22 includes: S221: Record the signals of each photodetector in vector form according to their positions from low to high; S222: The detection light curtain signals of the entire process of an object not entering the detection light curtain, entering the detection light curtain, and leaving the detection light curtain are continuously recorded and arranged in chronological order to form a two-dimensional array X.

8. The method according to claim 6, characterized in that, Step 3 includes: S311: Accumulate the two-dimensional array X along the row direction to obtain the column vector p; S312: Record the position m of the first element that is 0 and all subsequent elements that are 0 in the column vector p; S313: When reconstructing an object, the reconstruction area of ​​a single slice is located on the conveyor belt and... The height range between them; Where m is a non-negative integer, and at this time, the height from the conveyor belt position is... The location and the receiver there have always received the light beam normally and have never been blocked by any object.

9. The method according to claim 6, characterized in that, Step 3 includes: S321: Extract the columns in the two-dimensional array X that are in the time intervals t6 - s1 / v1 – d and t6 - s1 / v1 + tt + d to obtain the two-dimensional vector group Z; S322: Accumulate the two-dimensional vector group Z along the row direction to obtain the column vector Q; S323: Record the position e of the first element that is 0 and all subsequent elements that are 0 in the column vector Q; S324: When reconstructing an object, the reconstruction area of ​​a single slice is located on the conveyor belt and... The height region between them is used to obtain the reconstructed height of fault K; When reconstructing fault k, the required time to generate projection data is between t6 and t6 + tt; where tt is the time required for the detector to acquire data at a fixed angle, and tt is the time required for the detector to rotate one revolution. d represents the set time extension; e is a non-negative integer, where the height from the conveyor belt position is . The location and its receiver consistently received the light beam normally and were never blocked by any object. s1 is the distance between the detection light curtain and the CT scan area; v1 represents the conveyor belt speed.

10. The method according to claim 4, characterized in that: In step 3, the image background value is 0-10.

Images