Method for determining spatial contour of object to be inspected

Abstract

The invention is based on the use of X-ray radiation and can be used for inspecting movable and immovable objects for safety purposes, in particular motor vehicles, lightweight structures, shipping containers, luggage and other objects; and analysing for industrial purposes whether foreign matter inclusion and / or defects exist in the near-surface layer of the object. The working principle of the invention is based on recording the ionizing radiation scattered by the object to be inspected towards the radiation source, which allows all the devices of the device to be arranged on the same side of the object. The invention makes it possible to carry out an inspection and / or secretly carry out an inspection process when it is impossible to carry out a geometry inspection by transmission. The claimed invention allows a high quality spatial pseudo 3D profile of an object under test to be obtained by measuring the profile of a scattered radiation field. Due to the improvement of the information content of the image, the pseudo 3D profile allows an operator of the device to analyze the scattering ability of the object segments and evaluate their geometry. The technical and economic efficiency of the claimed invention consists in increasing the reliability thereof, reducing the cost of implementation thereof, and increasing the inspection accuracy as a result of increasing the quality of the composite image.

Description

Technical Field

[0001] The invention relates to a non-destructive inspection tool based on X-rays for inspecting various types of transport vehicles, lightweight structures and luggage. The operating principle of the claimed method is based on the recording of ionizing radiation scattered by the inspected object towards the radiation source, which allows all the equipment of the system to be arranged on the same side relative to the object, thus enabling the inspection process to be performed covertly. An important advantage of this type of inspection technology is the basic possibility of obtaining images of objects located behind a barrier. In places where opaque walls are provided (trucks, containers, cladding elements and body parts of vehicles), the penetrating probing radiation is mainly scattered by the bulky objects, which makes it possible to ignore the scattering of thin barriers when analyzing the radiographic images. Background Art

[0002] In most cases, the known methods are based on backscattering (BackScatter) and aim to produce a planar image of the inspected object, where the scanning is performed by mutual displacement of the detection radiation beam and the inspected object. Conventional BackScatter systems involve the use of a representation of the recorded radiation intensity, which characterizes the ability of the object fragments (image pixels) to scatter the radiation of the detection radiation beam. In the proposed invention, the image can be characterized by an additional parameter - the spatial profile of the scattering surface of the object (known as pseudo 3D), without changing the inspection process.

[0003] Remote control method [1] It is known in the art and allows one to perform remote (hidden) inspection. The known method is implemented by forming a needle-shaped X-ray beam directed towards the object to be inspected, recording the scattered X-ray radiation and forming a radiographic image of the object to be inspected based on the intensity of the scattered X-ray radiation. However, it is difficult to accurately assess the spatial contour of the object to be inspected using the known method.

[0004] Method for constructing a three-dimensional image of a surface of an object [2] It is known in the art. In this patent, the test object is alternately irradiated by two detection beams and the backscattered radiation is recorded by a detector. When forming a three-dimensional image, due to the limitation of the detection beam by a shutter synchronized with the rotation of the collimator, the information about the image pixels is formed by beams that have different geometric paths through the interior of the object. Since a precise mutual displacement of the object to be inspected relative to the collimator is required, the process of constructing the three-dimensional profile of the object becomes very complicated and cannot be carried out secretly. Moreover, when using this method, the use of two radiation sources increases the labor intensity.

[0005] A systematic approach to constructing three-dimensional images based on backscattering [3]is known in the art. The technique described in this patent makes it possible to obtain a three-dimensional image of an object, since the detector is equipped with a collimator which allows the detector to independently record scattered radiation generated at different depths inside the object. However, the implementation of the known method is labor-intensive, since independent displacements of the radiation source and the detector relative to the object are required in order to obtain a set of angles that provide sufficient data for the reconstruction of the shape of the object. In addition, the use of a collimator reduces the efficiency of the backscattered radiation recording, which leads to an increase in the time and dose of absorbed radiation required to obtain an image of satisfactory quality.

[0006] In the prior art, a method based on X-ray backscattering is known to visualize the shape of the object under inspection, which is closest to the method described in the patent [4] The invention claimed is described in and is used as a prototype. The known method involves X-ray technology and is designed to perform inspection and detection of hidden objects and has the ability to determine the spatial contours of the inspected object. The known method involves the use of a pulsed ionizing radiation source for generating a detection radiation beam and a time-of-flight technique (time-of-flight method). The known method involves measuring the time interval starting from the moment of the generation of the radiation pulse and recovering the scattering point positions from the results thereof and based on data on the rotation collimator phase and the time of transmission of the scattered radiation to different detectors.

[0007] Disadvantages of prototypes for determining the spatial contours of inspected objects include:

[0008] - Noise caused by the hypothetical time signal generated by quanta reflected from the barrier, located behind a light-tight barrier separating the object under inspection from the system (screen, container, body and housing)

[0009] Poor image quality of objects;

[0010] - requires the use of complex and expensive pulsed radiation sources that generate radiation pulses with sub-nanosecond leading edges at frequencies of approximately 100 kHz;

[0011] - High system costs, for example, in order to obtain high-quality radiographic images using backscatter systems, a large sensitive surface area of ​​the detector is required - on the order of several square meters. At the same time, for acceptable time resolution, single crystals of minimum size (no more than a few centimeters) are required in order to minimize the distortion of the time-stamp signal caused by fluctuations in the collection time of the scintillation signal. These two conditions lead to the fact that the detector module should contain hundreds of discrete detectors, which significantly complicates the electronic path of the system and increases the unit price.

[0012] The claimed method for determining the spatial contour of an inspected object does not have the above-mentioned disadvantages. Summary of the invention

[0013] The technical result of the method claimed is a significant extension of the inspection area of ​​inspected objects hidden behind a light-tight barrier, with high image quality, using commercially available industrially produced X-ray sources operating in continuous mode and enabling the use of a significantly smaller number of discrete detectors, each with a much larger sensitive area, thereby reducing the labor costs associated with the implemented method and its own costs.

[0014] The technical results listed are achieved due to the claimed method for determining a spatial profile by an inspection unit, which is based on irradiating the inspected object with an X-ray beam and recording the backscattered radiation with an ionizing radiation detector. Therein, according to the claimed invention, during the formation of a single pixel of a radiographic image in synchronization with the movement of the detection beam on the surface of the inspected object, a logical signal from each ionizing radiation detector is collected in a synchronization and interface system. The data generated within one pixel of the radiographic image enters the processor from the synchronization and interface system, and at the same time, for each pixel of the radiographic image, the signals from different ionizing radiation detectors are grouped, a differential signal and an integral signal are calculated based on the signals from each group, and a normal vector component of the scattering surface is calculated based on the magnitude and sign of the signal ratio, and then a pseudo spatial profile of the inspected object is formed in a visualization device by displaying the normal vector component using grayscale pixel coding.

[0015] The implementation of this method is Figure 1 , which shows a scheme of an examination unit comprising a set of identical ionizing radiation detectors 1, and an X-ray source 2 placed in a rotating collimator 3. The rotating collimator is equipped with an angle sensor 4. All detectors 1 and angle sensors 4 are connected to a synchronization and interface system 5, which is connected to a processor 6 via a high-performance logic electronic interface. DETAILED DESCRIPTION

[0016] The claimed method is implemented as follows. An X-ray source 2 with a collimator 3 forms a pencil X-ray beam. The detection radiation beam falls on the object to be inspected and is also scattered towards the detector 1. The logic signals from the detector 1 enter the synchronization and interface system 5 and are accumulated synchronously with the movement of the detection radiation beam. The accumulated data are transmitted to a processor 6 to synthesize the image of the object with its subsequent visualization through a device 7 for displaying the inspection result.

[0017] The claimed method allows to measure the scattered radiation intensity independently by means of spaced detectors, which makes it possible to extract additional information about the object contour due to the determination of the spatial characteristics of the scattered radiation field. This possibility allows one to effectively evaluate the scattering power of object fragments and take into account their shape and / or relative position, i.e., provides a major opportunity to perceive the spatial shape (pseudo-3D) of the inspected object. The main advantage of the system for visualizing the pseudo-3D contour of the inspected object is the ability to distinguish objects with the same projection on a plane when generating an image. In fact, the projections of various three-dimensional objects on a plane all look similar. In addition, due to the absorption of scattered radiation by objects in the foreground, the actual brightness of the elements of the object in the plane image can change significantly. In this case, the combined use of classical radiographic images and images describing the spatial pseudo-3D contour of the object contributes to the quality improvement of the information content of the image and increases the reliability of the inspection process.

[0018] Laboratory studies have been conducted that have demonstrated certain technical results as shown by the specific examples of the following embodiments.

[0019] Example

[0020] Figure 2 A specific embodiment is shown for inspecting an object having a cylindrical or parallelepiped shape.

[0021] When the front side of the parallelepiped facing the detection unit is irradiated, the radiation field is homogeneous, since the quanta scattered into the detectors located to the left and to the right of the detection radiation beam pass through the material of the object in the same way and therefore experience the same attenuation. In the case of an inspection of a cylindrical object, the scattered radiation field should be homogeneous only when the central part of the object is irradiated. Otherwise, a stronger scattered radiation signal would be recorded by the detectors located to the left or to the right of the detection beam, depending on whether the left or right side of the cylinder is irradiated.

[0022] Below, a possible implementation of the present invention is provided in the form of an algorithm for visualizing the spatial contours of real objects using grayscale representation. For this purpose, an alternating criterion reflecting the orientation (expressed by a sign) and the normal projection value (expressed by a magnitude) of the scattering surface fragments is constructed, which has the form:

[0023] N x =(I L -I R ) / (I L +I R ),

[0024] Among them I L and I RThe scattered radiation intensity recorded on the right and left sides of the detection beam, respectively. Obviously, the range of possible values ​​from "-1" to "1" corresponds to the constructed standard, although actual measurements show that the actual range of possible values ​​of the standard lies in the interval [-0.5; 0.5].

[0025] Figure 3 (a, b and c) show the normal N x The graphical representation of the position values ​​corresponds to the real object image, where black pixels correspond to the minimum value of the parameter and white to the maximum value. Figure 3 (d, e and f) show these same objects visualized in a conventional backscatter system representation when the brightness of the pixel is determined by the integrated intensity of the scattered radiation of the form:

[0026] Int=I L +I R .

[0027] from Figure 3 (a, b and c) It can be seen that the proposed algorithm produces parameters indicating radiographic image regions corresponding to object segments producing an inhomogeneous scattered radiation field. In this case, the asymmetry is directly related to the direction of the normal to the object.

[0028] You can Figure 3 Typical images are shown, presented to the operator of the system individually or in pairs: (a and d), (b and e), (c and f). By using known models employed in three-dimensional modeling and computer graphics programs, such as Lambert's cosine law, a joint representation of the pairs of images can be obtained. In this case, the method of determining the pseudo 3D contour allows the estimation of the normal position of each object segment. The combination of the flat image layers, for which the brightness and shape factors of the objects are known, together constitutes the so-called scene [5] The visualization of the scene is performed on a display, in that black and white outlines are acquired through the objects of the scene, which is typical for large volumetric objects illuminated by conventional light sources, where the radiation source position is a dynamic representation parameter.

[0029] The technical and economic efficiency of the claimed method lies in the increased reliability thereof, the reduced costs of its implementation and the increased accuracy of the inspection due to the increased quality of the resultant image.

[0030] The invention can be used to inspect movable and immovable objects, particularly motor vehicles, lightweight structures, shipping containers, luggage and other objects for safety purposes, and to analyze near-surface layers of objects for foreign material inclusions and / or defects for industrial purposes.

[0031] refer to

[0032] 1. Russian Patent 145 863 (13) U1, IPC H05G 1 / 00 ​​(2006.01)

[0033] 2. US Patent 9,989,483B2, IPC GOIN 23 / 20

[0034] 3. US Patent 9,442,083B2, IPC GOIN 23 / 20

[0035] 4. US Patent 9,128,198B2, IPC GOIN 23 / 203 (Prototype of the system and method)

[0036] 5. Buss S., Buss S.R. 3D Computer Graphics: A Mathematical Introduction to OpenGL. - Cambridge University Press, 2003.

Claims

1. A method for determining the spatial profile of an object to be inspected by means of a backscatter inspection unit, comprising irradiating the object to be inspected with a pencil X-ray beam and recording the backscattered radiation with an ionizing radiation detector, characterized in that collecting logic signals from each ionizing radiation detector in a synchronization and interface system during formation of a single pixel of a radiographic image in synchronization with movement of the detection beam over the surface of the object under examination; Data accumulated in one pixel of the radiographic image are transmitted to a processor, signals from different ionizing radiation detectors are grouped for each pixel of the radiographic image, a differential signal and an integral signal are calculated based on the signals from each group, and a normal vector component of the scattering surface is calculated based on the magnitude and sign of the signal ratio, and then a pseudo-space contour of the inspected object is formed in a visualization device by displaying the normal vector component using grayscale pixel encoding.

Images