Terahertz tomography system and method

Abstract

The invention discloses a terahertz tomography system and method, and the system comprises a terahertz receiving and transmitting module which is used for generating and transmitting terahertz light, receiving the terahertz light passing through a to-be-tested sample, and obtaining data parameters containing the information of the to-be-tested sample; the imaging scanning module is used for collimating the divergent terahertz light so as to form parallel light beams for irradiating the sample to be detected; the imaging scanning module is further used for controlling the to-be-tested sample to intermittently rotate at a preset angle within a preset range, the to-be-tested sample is always located in the parallel light beams, and the parallel light beams penetrating through the to-be-tested sample are focused to the terahertz receiving and transmitting module; and the host module is connected with the terahertz transceiver module and the imaging scanning module. The invention relates to the technical field of terahertz imaging, through the arrangement, in the data acquisition process, multi-point scanning imaging is not needed, and only the to-be-detected sample needs to be controlled to rotate to the preset angle, so that the time required for data acquisition can be effectively shortened, and the purpose of improving the imaging rate is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of three-dimensional imaging, relates to terahertz imaging technology, and specifically is a terahertz tomography system and method. Background Art

[0002] Terahertz light generally refers to electromagnetic radiation with a fluctuation frequency between 0.1-10THz and a wavelength between 0.03mm-3mm. Terahertz imaging technology has extremely high technical application value in detection imaging, biomedicine, aerospace, industrial manufacturing, agricultural product testing and other industries. Terahertz light can penetrate non-polar substances for imaging, and has strong penetration for materials such as clothing and paper, and its imaging resolution is high. At the same time, due to the low energy of single photons, there is no ionization damage to organisms, so terahertz light is suitable for various detection methods.

[0003] Terahertz tomography technology can currently achieve three-dimensional imaging, but most terahertz tomography methods are based on point scanning imaging, which requires long-term data collection during the imaging process and requires the scanning mechanism to be able to operate stably with high precision for a long time.

[0004] Therefore, a terahertz tomography system and method are needed to solve the above problems. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art; to this end, the present invention proposes a terahertz tomography system and method to shorten the data acquisition time and improve the imaging rate. The present invention sets a terahertz transceiver module, an imaging scanning module and a host module, wherein the imaging scanning module can control the sample to be tested to intermittently rotate at a preset angle within a preset range, and always ensure that the sample to be tested is located in a parallel light beam formed by the terahertz light emitted by the terahertz transceiver module, so that the terahertz transceiver module can obtain the data parameters formed by the terahertz light irradiation of the sample to be tested at different angles, so as to cooperate with the host module to complete the reconstruction of the three-dimensional tomography of the sample to be tested. In this process, there is no need to perform scanning imaging at multiple points, and it is only necessary to control the sample to be tested to rotate to a preset angle, so that the time required for data acquisition can be effectively shortened, thereby achieving the purpose of improving the imaging rate.

[0006] To achieve the above object, a first aspect of the present invention provides a terahertz tomography system, comprising:

[0007] A terahertz transceiver module is used to generate and transmit terahertz light, and receive the terahertz light that passes through the sample to be tested, and obtain data parameters containing information of the sample to be tested;

[0008] An imaging scanning module, arranged between the terahertz transceiver modules, for collimating the divergent terahertz light to form a parallel light beam for irradiating the sample to be measured;

[0009] The imaging scanning module is also used to control the sample to be tested to intermittently rotate at a preset angle within a preset range, and the sample to be tested is always located in the parallel light beam, and the parallel light beam passing through the sample to be tested is focused to the terahertz transceiver module, so that the terahertz transceiver module obtains data parameters formed by the sample to be tested under terahertz light irradiation at different angles;

[0010] The host module is connected to the terahertz transceiver module and the imaging scanning module, and uses an algorithm to complete the reconstruction of the three-dimensional tomography of the sample to be tested based on the data parameters containing the information of the sample to be tested obtained by the terahertz transceiver module.

[0011] Furthermore, the terahertz transceiver module includes a quantum cascade laser and a surface array detector;

[0012] The quantum cascade laser is used to output terahertz light;

[0013] The surface array detector is connected to the host module, and is used to receive the terahertz light passing through the sample to be tested, obtain data parameters containing information of the sample to be tested, and transmit the data parameters to the host module.

[0014] Further, the imaging scanning module includes a first high-density polyethylene lens, an electric rotating stage and a second high-density polyethylene lens which are arranged in sequence;

[0015] The first high-density polyethylene lens is used to collimate the divergent terahertz light and irradiate it onto the sample to be tested;

[0016] The electric rotating stage is connected to the host module and is used to control the sample to be tested to intermittently rotate at a preset angle within a preset range;

[0017] The second high-density polyethylene lens is used to focus the parallel light beam passing through the sample to be tested onto the surface array detector.

[0018] Furthermore, the fluctuation frequency of the terahertz light output by the quantum cascade laser is 2.5THz-2.9THz.

[0019] Furthermore, the preset range is 0°-180°, and the preset angle is 1°.

[0020] Furthermore, the spot size of the parallel light beam is not less than 40×40 mm.

[0021] Furthermore, the host module is configured as a main control computer and has a built-in storage unit for storing data parameters formed by terahertz light irradiation of the sample to be tested at different angles.

[0022] Furthermore, the algorithm includes a filtered back projection method.

[0023] On the other hand, the present invention further proposes a terahertz tomography method, which is implemented by using a terahertz tomography system described in the above embodiment, and the method comprises the following steps:

[0024] Step 1: Initialize the quantum cascade laser, set the terahertz light emission parameters, and turn on the quantum cascade laser;

[0025] Step 2: Read the data parameters acquired by the current array detector and store the data parameters in the host module as background parameters;

[0026] Step 3: Place the sample to be tested at the center of the electric rotating table to ensure that the terahertz light is vertically incident on the surface of the sample to be tested;

[0027] Step 4: Control the electric rotating table to drive the sample to be tested to rotate, and the rotation angle is 1°;

[0028] Step 5: read the data parameters acquired by the surface array detector in step 4, and store the data parameters in the host module;

[0029] Step 6: Repeat steps 4 to 5 until the cumulative rotation angle reaches 180°, obtain the matrix of data parameters of the sample to be tested, input the data parameter matrix into the reconstruction algorithm, and obtain the three-dimensional tomographic image of the sample to be tested.

[0030] Furthermore, the steps of reconstructing three-dimensional tomography by a reconstruction algorithm include:

[0031] Calibrate the obtained data parameter matrix of the sample to be tested according to the background parameters to obtain the plane transmission data of the sample to be tested;

[0032] The two-dimensional tomographic image is inverted and reconstructed according to the plane projection data of the sample to be tested by the filtered back projection method to obtain the internal structure image information of the sample to be tested on each row of cross section;

[0033] The internal structure image information of each row is stacked and reconstructed in the vertical direction to obtain a three-dimensional tomographic image of the sample to be tested.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] By setting up a terahertz transceiver module, an imaging scanning module and a host module, wherein the imaging scanning module can control the sample to be tested to intermittently rotate at a preset angle within a preset range, and always ensure that the sample to be tested is located in a parallel light beam formed by the terahertz light emitted by the terahertz transceiver module, so that the terahertz transceiver module can obtain data parameters formed by the terahertz light irradiation of the sample to be tested at different angles, so as to cooperate with the host module to complete the reconstruction of the three-dimensional tomographic imaging of the sample to be tested. In this process, there is no need to perform scanning and imaging at multiple points, and it is only necessary to control the sample to be tested to rotate to a preset angle, so that the time required for data acquisition can be effectively shortened, thereby achieving the purpose of improving the imaging rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 It is a schematic structural diagram of a terahertz tomography system in one embodiment of the present invention;

[0038] Figure 2 It is a schematic diagram of the structure of a terahertz tomography system in one embodiment of the present invention when terahertz light penetrates a sample to be measured;

[0039] FIG3( a ) is a schematic diagram of an example of a terahertz tomography system measuring a sample to be tested in one embodiment of the present invention;

[0040] FIG3( b ) is a cross-sectional view of a terahertz tomography system measuring a sample to be measured in one embodiment of the present invention;

[0041] FIG3( c ) is a diagram showing the cross-sectional imaging result of a sample to be measured by a terahertz tomography system in one embodiment of the present invention;

[0042] Figure 4 FIG. 4 is a flow chart of a terahertz tomography method according to another embodiment of the present invention.

[0043] Figure Number:

[0044] 1. Quantum cascade laser; 2. First high-density polyethylene lens; 3. Sample to be tested; 4. Electric rotating table; 5. Second high-density polyethylene lens; 6. Surface array detector; 7. Host module. DETAILED DESCRIPTION

[0045] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Embodiment 1

[0047] See also Figure 1 to Figure 2 The first aspect of the present invention provides a terahertz tomography system and method, including:

[0048] The terahertz transceiver module is used to generate and emit terahertz light, and receive the terahertz light that passes through the sample 3 to be tested, obtain data parameters containing information of the sample 3 to be tested, and provide a basis for subsequent imaging of the sample 3 to be tested.

[0049] The imaging scanning module is arranged between the terahertz transceiver modules and is used to collimate the divergent terahertz light to form a parallel light beam for irradiating the sample 3 to be tested, so that the terahertz light can better pass through the sample 3 to be tested, thereby obtaining more accurate data parameters.

[0050] The imaging scanning module is also used to control the sample 3 to rotate intermittently at a preset angle within a preset range, and the sample 3 to be tested is always located in the parallel light beam, and the parallel light beam passing through the sample 3 to be tested is focused to the terahertz transceiver module, so that the terahertz transceiver module obtains data parameters formed by terahertz light irradiation of the sample 3 to be tested at different angles. That is, only by controlling the rotation of the sample 3 to be tested, the data parameters formed by terahertz light irradiation of the sample 3 to be tested at different angles can be obtained, so that the imaging of the sample 3 to be tested can be completed through subsequent algorithms. Compared with the method of collecting data by horizontal and vertical scanning mechanisms relative to the sample 3 to be tested in the prior art, the operation is more convenient, so it can effectively shorten the time required for data collection and achieve the purpose of improving the imaging rate.

[0051] The host module 7 is connected to the terahertz transceiver module and the imaging scanning module, and uses an algorithm to complete the reconstruction of the three-dimensional tomography of the sample 3 to be tested based on the data parameters containing the information of the sample 3 to be tested obtained by the terahertz transceiver module.

[0052] The system is provided with a terahertz transceiver module, an imaging scanning module and a host module 7, wherein the imaging scanning module can control the sample 3 to be tested to rotate intermittently within a preset range and at a preset angle, and always ensure that the sample 3 to be tested is located in a parallel light beam formed by the terahertz light emitted by the terahertz transceiver module, so that the terahertz transceiver module can obtain data parameters formed by the terahertz light irradiation of the sample 3 to be tested at different angles, so as to cooperate with the host module 7 to complete the reconstruction of the three-dimensional tomographic imaging of the sample 3 to be tested. In this process, there is no need to perform scanning and imaging at multiple points, and it is only necessary to control the sample 3 to be tested to rotate to a preset angle, so that the time required for data acquisition can be effectively shortened, thereby achieving the purpose of improving the imaging rate.

[0053] In this embodiment, a specific terahertz transceiver module is proposed to improve the emission and reception effects of terahertz light.

[0054] Specifically, the terahertz transceiver module includes a quantum cascade laser 1 and a planar array detector 6 .

[0055] The quantum cascade laser 1 is used to output terahertz light. The surface array detector 6 is connected to the host module 7 to receive the terahertz light passing through the sample 3 to be tested, obtain data parameters containing information of the sample 3 to be tested, and transmit the data parameters to the host module 7.

[0056] In other embodiments, a specific imaging scanning module is also proposed to cooperate with the terahertz transceiver module to better obtain data parameters of the sample 3 to be tested.

[0057] Specifically, the imaging scanning module includes a first high-density polyethylene lens 2, an electric rotating platform 4 and a second high-density polyethylene lens 5 which are arranged in sequence.

[0058] Among them, the first high-density polyethylene lens 2 is used to collimate the divergent terahertz light and irradiate it onto the sample to be tested 3, so that the divergent terahertz light can form a parallel light beam to better illuminate the sample to be tested 3, so that the subsequent surface array detector 6 can obtain data parameters about the sample to be tested 3 more accurately.

[0059] The electric rotating stage 4 is connected to the host module 7 and is used to control the sample 3 to rotate intermittently at a preset angle within a preset range, so that the surface array detector 6 can obtain data parameters formed by the sample 3 under terahertz light irradiation at different angles.

[0060] Among them, high-density polyethylene lens is an optical element made of high-density polyethylene material. High-density polyethylene is a polyethylene material with high crystallinity and high density. It has good chemical stability, corrosion resistance and mechanical properties. Lenses made of this material have unique applications in the field of optics. This is a prior art, so it will not be described here.

[0061] It should be noted that the preset range is 0°-180°, and the preset angle is 1°. That is, after the electric rotating stage 4 is controlled to rotate 1° once, the data parameters formed by the sample 3 to be tested at this position are collected by the surface array detector 6, and then the electric rotating stage 4 is controlled to rotate 1° again, and the data parameters are collected again, until the electric rotating stage 4 drives the sample 3 to be tested to rotate 180°, the acquisition of the data parameter matrix of the sample 3 to be tested can be completed, so the reconstruction of the imaging of the sample 3 to be tested can be completed through the algorithm.

[0062] It should also be noted that since a rotation of 180° can cover most of the three key angles of the sample to be tested and can provide sufficient information for the reconstruction of the three-dimensional structure, the preset range is set to 0°-180°. Compared with the existing method, the range collected by this system is smaller, so the time required for data collection can be further shortened, thereby achieving the purpose of improving the imaging rate.

[0063] The second high-density polyethylene lens 5 is used to focus the parallel light beam passing through the sample 3 to be tested onto the surface array detector 6 to complete the collection of data parameters.

[0064] In this embodiment, by setting the first high-density polyethylene lens 2 as a device for collimating the light path, and making the quantum cascade laser 1, the sample to be tested 3 and the surface array detector 6 all arranged in the same direction of the same horizontal plane, the purpose of simplifying the light path and facilitating the adjustment of the light spot is achieved.

[0065] In this embodiment, the fluctuation frequency of the terahertz light output by the quantum cascade laser 1 is 2.5THz-2.9THz.

[0066] It should be particularly noted that the spot size of the parallel light beam is not less than 40×40 mm, so as to completely cover the sample 3 to be tested, thereby improving the accuracy of obtaining data parameters of the sample 3 to be tested.

[0067] In a further embodiment, the host module 7 is configured as a main control computer and has a built-in storage unit for storing data parameters formed by terahertz light irradiation of the sample 3 under test at different angles.

[0068] Among them, the algorithm includes a filtered back projection method.

[0069] As shown in Figures 3(a), 3(b) and 3(c), in this embodiment, a specific example is also proposed to reflect the application process of the system. Specifically, as shown in Figure 3(a), a small ball with a through hole in the center is used as the sample to be tested 3, and the main control computer is used to set the parameters of the quantum cascade laser 1 and the electric rotating table 4.

[0070] Among them, the main parameters of the quantum cascade laser 1 are set as follows: output terahertz light frequency: 2.5 THz; output terahertz light form: continuous wave output; output terahertz light power: 3 mW.

[0071] The electric rotating table 4 is set as follows: rotation axis step: 1°; rotation axis range: 180°.

[0072] Figure 3(b) and Figure 3(c) are respectively the result image after reconstructing the collected cross-sectional data using the filtered back-projection algorithm and the three-dimensional reconstruction image of the entire sample 3 to be tested. It can be seen from the figure that the holes of the sample 3 to be tested, that is, the internal structure imaging of the object is accurately realized, and the entire sample 3 to be tested can be reconstructed in three dimensions, that is, the system can complete the three-dimensional reconstruction of the sample 3 to be tested by controlling the rotation of the electric rotating table 4, the terahertz transceiver module and the host module 7. In addition, since in this process it is only necessary to control the electric rotating table 4 to intermittently rotate to 180° to complete the measurement, compared with the method of measuring by scanning multiple surfaces of the sample 3 to be tested in the prior art, it can effectively shorten the data acquisition time, and accordingly, achieve the purpose of improving the imaging rate.

[0073] Embodiment 2

[0074] like Figure 4 As shown, this embodiment further proposes a terahertz tomography method based on the first embodiment, which is implemented by using a terahertz tomography system described in the first embodiment. The method includes the following steps:

[0075] Step 1: Initialize the quantum cascade laser 1, set the terahertz light emission parameters, and turn on the quantum cascade laser 1;

[0076] Step 2: read the data parameters acquired by the current array detector 6, and store the data parameters in the host module 7 as background parameters;

[0077] Step 3: Place the sample 3 to be tested at the center of the electric rotating table 4 to ensure that the terahertz light is vertically incident on the surface of the sample 3 to be tested;

[0078] Step 4: Control the electric rotating table 4 to drive the sample 3 to rotate, and the rotation angle is 1°;

[0079] Step 5: read the data parameters acquired by the surface array detector 6 in step 4, and store the data parameters in the host module 7;

[0080] Step 6: Repeat steps 4 to 5 until the cumulative rotation angle reaches 180°, obtain the matrix of data parameters of the sample 3 to be tested, input the data parameter matrix into the reconstruction algorithm, and obtain the three-dimensional tomographic image of the sample 3 to be tested.

[0081] In this embodiment, the three-dimensional tomographic image of the sample 3 to be tested can be acquired through the above steps, and in this process, it is only necessary to control the rotation of the sample 3 to be tested through the electric rotating table 4. Therefore, compared with the scanning method of the prior art through the horizontal and vertical scanning mechanisms, this method only needs to perform rotation scanning to obtain all the data, shortening the time required for data acquisition and achieving the purpose of improving the imaging rate.

[0082] It should be noted that, in this embodiment, the steps of performing three-dimensional tomography reconstruction by using a reconstruction algorithm include:

[0083] The obtained data parameter matrix of the sample 3 to be tested is calibrated according to the background parameters to obtain the plane transmission data of the sample 3 to be tested;

[0084] The two-dimensional tomographic image is inverted and reconstructed according to the plane projection data of the sample 3 to be tested by the filtered back projection method to obtain the internal structure image information of the sample 3 to be tested on each row of cross section;

[0085] The internal structure image information of each row is stacked and reconstructed in the vertical direction to obtain a three-dimensional tomographic image of the sample 3 to be tested.

[0086] The filtered back projection method is based on the projection slice theorem (also called the center slice theorem). In the two-dimensional case, this theorem states that the one-dimensional Fourier transform of the projection of an object at a certain angle (for example, the intensity distribution formed on the detector after the X-ray passes through the object) is a slice of the two-dimensional Fourier transform of the object at the corresponding angle. Simply put, when we project an object from one direction, this projection contains a certain "compressed" form of the structural information of the object in this direction. The filtered back projection method can reconstruct the image by back-projecting the filtered projection data. Therefore, by adopting the filtered back projection method, the reconstruction of the 3D tomographic image of the sample to be tested can be accurately completed, achieving the purpose of stable imaging and good imaging effect.

[0087] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A terahertz tomography system, characterized in that: include: A terahertz transceiver module is used to generate and transmit terahertz light, and receive the terahertz light that passes through the sample to be tested (3), and obtain data parameters containing information of the sample to be tested (3); An imaging scanning module, arranged between the terahertz transceiver modules, for collimating the divergent terahertz light to form a parallel light beam for irradiating the sample to be measured (3); The imaging scanning module is also used to control the sample to be tested (3) to intermittently rotate at a preset angle within a preset range, and the sample to be tested (3) is always located in the parallel light beam, and the parallel light beam passing through the sample to be tested (3) is focused onto the terahertz transceiver module, so that the terahertz transceiver module obtains data parameters formed by the terahertz light irradiation of the sample to be tested (3) at different angles; The host module (7) is connected to the terahertz transceiver module and the imaging scanning module, and uses an algorithm to complete the reconstruction of the three-dimensional tomography of the sample (3) to be tested based on the data parameters containing information of the sample (3) to be tested acquired by the terahertz transceiver module.

2. A terahertz tomography system according to claim 1, characterized in that: The terahertz transceiver module comprises a quantum cascade laser (1) and a surface array detector (6); The quantum cascade laser (1) is used to output terahertz light; The surface array detector (6) is connected to the host module (7) and is used to receive the terahertz light that passes through the sample to be tested (3), obtain data parameters containing information of the sample to be tested (3), and transmit the data parameters to the host module (7).

3. A terahertz tomography system according to claim 2, characterized in that: The imaging scanning module comprises a first high-density polyethylene lens (2), an electric rotating platform (4) and a second high-density polyethylene lens (5) which are arranged in sequence; The first high-density polyethylene lens (2) is used to collimate the divergent terahertz light and irradiate it onto the sample to be tested (3); The electric rotating platform (4) is connected to the host module (7) and is used to control the sample to be tested (3) to intermittently rotate at a preset angle within a preset range; The second high-density polyethylene lens (5) is used to focus the parallel light beam passing through the sample to be measured (3) onto the surface array detector (6).

4. The terahertz tomography system according to claim 2, characterized in that: The terahertz light output by the quantum cascade laser (1) has a fluctuation frequency of 2.5 THz-2.9 THz.

5. The terahertz tomography system according to claim 1, characterized in that: The preset range is 0°-180°, and the preset angle is 1°.

6. The terahertz tomography system according to claim 1, characterized in that: The spot size of the parallel light beam is not less than 40×40 mm.

7. The terahertz tomography system according to claim 1, characterized in that: The host module (7) is configured as a main control computer and has a built-in storage unit for storing data parameters formed by irradiating the sample (3) to be tested with terahertz light at different angles.

8. The terahertz tomography system according to claim 1, characterized in that: The algorithm includes a filtered back projection method.

9. A terahertz tomography method, characterized in that: The method is implemented by using a terahertz tomography system as claimed in claim 3, and the method comprises the following steps: Step 1, initializing the quantum cascade laser (1), setting terahertz light emission parameters, and turning on the quantum cascade laser (1); Step 2: reading the data parameters acquired by the current array detector (6), and storing the data parameters in the host module (7) as background parameters; Step 3: Place the sample to be tested (3) at the center of the electric rotating table (4) to ensure that the terahertz light is vertically incident on the surface of the sample to be tested (3); Step 4: Control the electric rotating table (4) to drive the sample to be tested (3) to rotate, and the rotation angle is 1°; Step 5: reading the data parameters acquired by the surface array detector (6) in step 4, and storing the data parameters in the host module (7); Step 6: Repeat steps 4 to 5 until the cumulative rotation angle reaches 180°, obtain a matrix of data parameters of the sample to be tested (3), input the data parameter matrix into the reconstruction algorithm, and obtain a three-dimensional tomographic image of the sample to be tested (3).

10. A terahertz tomography method according to claim 9, characterized in that: The steps of 3D tomographic reconstruction by the reconstruction algorithm include: Calibrate the obtained data parameter matrix of the sample to be tested (3) according to the background parameters to obtain the plane transmission data of the sample to be tested (3); Inverting and reconstructing a two-dimensional tomographic image based on the plane projection data of the sample to be tested (3) by a filtered back-projection method, and obtaining internal structural image information of the sample to be tested (3) on each row of cross-sections; The internal structure image information of each row is stacked and reconstructed in the vertical direction to obtain a three-dimensional tomographic image of the sample to be tested (3).

Images