Terahertz fast tomography system and method

Abstract

The invention discloses a terahertz fast tomography system and method.The system comprises a scanning rack and a scanning device, the scanning device comprises a terahertz emission source, a first beam conversion assembly, a second beam conversion assembly and a terahertz detection array which are sequentially arranged, and the scanning rack comprises an inner ring and an outer ring which are rotationally matched with each other; a to-be-detected station is arranged in the middle of the inner ring, the to-be-detected station is located between the first beam conversion assembly and the second beam conversion assembly, and the terahertz emission source, the first beam conversion assembly, the to-be-detected station, the second beam conversion assembly and the terahertz detection array are sequentially arranged on the inner ring in the diameter direction. And a flexible mechanical arm for grabbing a sample to be detected is arranged on one side of the scanning rack. According to the terahertz fast tomography system and method, the imaging time is short, and the system and method are not limited by the appearance structure of a sample.

Description

Technical Field

[0001] The present invention relates to the field of terahertz rapid tomography, and in particular to a terahertz rapid tomography system and method. Background Art

[0002] Terahertz (THz) waves refer to electromagnetic waves with a frequency between 0.1THz-10THz and a wavelength between 30μm-3mm. In some cases, they specifically refer to electromagnetic waves with a frequency of 0.3-3THz. Since terahertz waves have the characteristics of both infrared waves and microwaves, terahertz imaging has broad application prospects in security inspections, non-destructive testing, and medical diagnosis (such as CT). Terahertz waves are between microwaves and infrared waves, with a higher resolution than microwave imaging and better penetration, so terahertz imaging can be used as a supplement to existing imaging technology.

[0003] In 2002, Academician Zhang Xicheng first proposed a terahertz computer tomography (CT) system by combining X-ray CT technology and terahertz imaging technology. In 2020, China's invention application CN111208095A disclosed a fan-beam terahertz tomography system, proposing that fan-beam terahertz beams have the characteristics of short time consumption, accurate data and large depth of field. The detection units on the detector are distributed at equal intervals, and the data is collected at equal intervals. The sample must be placed and fixed by the staff before scanning and imaging can be performed, which limits the morphology of the sample. Summary of the invention

[0004] The purpose of the present invention is to provide a terahertz fast tomography system and method, which has a short imaging time and is not limited by the appearance structure of the sample.

[0005] To achieve the above-mentioned purpose, the present invention provides a terahertz fast tomography system, comprising a scanning frame and a scanning device, the scanning device comprising a terahertz emission source, a first beam conversion assembly, a second beam conversion assembly, and a terahertz detection array arranged in sequence, the scanning frame comprising an inner ring and an outer ring that rotate with each other, a station to be measured is arranged in the middle of the inner ring, the station to be measured is located between the first beam conversion assembly and the second beam conversion assembly, the terahertz emission source, the first beam conversion assembly, the station to be measured, the second beam conversion assembly, and the terahertz detection array are arranged in sequence on the inner ring along the diameter direction; a flexible mechanical arm for grabbing a sample to be measured is provided on one side of the scanning frame.

[0006] As a further improvement of the present invention, the outer ring is provided with a driving device linked to the inner ring; the driving device is electrically connected to a control circuit module, and the control circuit module is electrically connected to a protection circuit and an error indication circuit module.

[0007] As a further improvement of the present invention, the driving device includes a driving motor arranged on the outer ring, the output end of the driving motor is connected to a driving gear, the inner ring is provided with a driven gear arranged coaxially therewith, and the driving gear is meshed with the driven gear of the inner ring.

[0008] As a further improvement of the present invention, the first beam conversion assembly includes a first beam conversion element and a second beam conversion element which are sequentially arranged along the transmission direction of the terahertz wave.

[0009] As a further improvement of the present invention, the second beam conversion assembly includes a third beam conversion element and a fourth beam conversion element which are sequentially arranged along the transmission direction of the terahertz wave.

[0010] As a further improvement of the present invention, the station to be tested is a through hole arranged in the middle of the inner circle.

[0011] As a further improvement of the present invention, the flexible robotic arm includes a base, a second joint axis, a second joint axis, and a flexible gripper which are arranged in sequence, and the base and the second joint axis, and the second joint axis and the second joint axis are respectively connected by a rotating motor; the clamping end of the flexible gripper is made of a material with a low terahertz wave absorption coefficient.

[0012] To achieve the above-mentioned purpose, the present invention also provides a terahertz fast tomography method, which adopts a terahertz fast tomography system, moves the sample to be tested to the test station through a flexible mechanical arm, and then performs step a): the terahertz beam emitted by the terahertz emission source passes through the first beam conversion assembly, the sample to be tested, the second beam conversion assembly in sequence and reaches the terahertz detection array, the detector of the terahertz detection array converts the light intensity signal of the detected terahertz wave into an analog photocurrent signal and transmits it to a data acquisition card, the data acquisition card converts the analog photocurrent signal into a digital voltage signal and transmits it to a computer for storage; then the scanning device rotates a fixed angle relative to the outer ring of the scanning frame, and repeats the above step a) until the positions of the first detector and the second detector of the terahertz detection array coincide, and the data acquisition of a certain cross section of the sample to be tested is completed.

[0013] As a further improvement of the present invention, after completing the data collection of a certain cross section of the sample to be tested, the sample to be tested is translated along the y-axis for a certain distance by the flexible robotic arm and step a) is repeated until the data collection of the entire sample to be tested is completed.

[0014] Beneficial Effects

[0015] Compared with the prior art, the terahertz fast tomography system and method of the present invention have the following advantages:

[0016] 1. Use a flexible robotic arm to flexibly grasp and transfer the sample to be tested, and the appearance of the sample to be tested can be ignored, thus expanding the application scope of the terahertz CT detector.

[0017] 2. Multiple terahertz detectors are distributed on the fan-shaped surface to form a terahertz detection array, which can detect all projection data at the same angle at one time. It is very convenient to increase or decrease the number of terahertz detection arrays or replace terahertz detectors.

[0018] 3. The traditional terahertz tomography system detects the test sample by fixing the terahertz scanning device and moving the test sample; the terahertz fast tomography system can not only realize the rotation of the scanning device, but also realize the rotation of the test sample, which can further shorten the imaging time.

[0019] The present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, which are used to illustrate embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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.

[0021] Figure 1 This is a stereogram of the terahertz fast tomography system;

[0022] Figure 2 This is an exploded view of the scanning rack;

[0023] Figure 3 The internal structure diagram of the scanning rack;

[0024] Figure 4 is a split diagram of the first beam conversion element;

[0025] Figure 5 This is the layout diagram of the terahertz detector;

[0026] Figure 6 is a stereogram of the flexible robotic arm;

[0027] Figure 7 This is the circuit schematic. DETAILED DESCRIPTION

[0028] Embodiments of the present invention will now be described with reference to the accompanying drawings.

[0029] Example

[0030] The specific embodiments of the present invention are as follows Figures 1 to 7As shown, a terahertz fast tomography system comprises a scanning frame 1 and a scanning device, wherein the scanning device comprises a terahertz emission source 2, a first beam conversion assembly, a second beam conversion assembly, and a terahertz detection array 7 which are arranged in sequence, the scanning frame 1 comprises an inner ring 105 and an outer ring 106 which are rotatably matched with each other, a station to be measured is arranged in the middle of the inner ring 105, and the station to be measured is located between the first beam conversion assembly and the second beam conversion assembly, and the terahertz emission source 2, the first beam conversion assembly, the station to be measured, the second beam conversion assembly, and the terahertz detection array 7 are arranged in sequence on the inner ring 105 along the diameter direction; a flexible mechanical arm 8 for grabbing a sample to be measured is arranged on one side of the scanning frame 1. The arrangement direction of the scanning device is perpendicular to the rotation axis of the inner ring 105.

[0031] A display control screen 9 and a circuit control box 10 are also provided outside the scanning frame 1. The display control screen 9 is fixed to one side of the scanning frame 1. The circuit control box 10 is placed below the display control screen 9 and carries control circuit wires inside the scanning frame and control circuit wires of the flexible mechanical arm.

[0032] The station to be tested is a through hole arranged in the middle of the inner circle 105 . The through hole is larger than the sample to be tested, so as to ensure that the flexible mechanical arm 8 can transmit the test sample without obstruction.

[0033] In this embodiment, the scanning frame 1 includes a housing 101, a first holder 102, a cylindrical roller 103, a second holder 104, an inner ring 105 and an outer ring 106. The through hole on the inner ring 105 is used to transmit the sample to be tested. The first holder 102 and the second holder 104 are both ring-shaped. Among them, the outer side of the housing 101 is a rounded square with a side length of 900mm, the radius of the rounded corner is 100mm, and the inner side is a circle with a diameter of 860mm. The inner diameter of the first holder 102 is 810mm, the outer diameter is 850mm, and thin cylinders with a diameter of 35mm are arranged on it, and the spacing between the thin cylinders is 61.5mm. The inner diameter of the cylindrical roller 103 is 800mm, the outer diameter is 880mm, the cylinder diameter is 30mm, the center distance between two adjacent cylinders is 66.5mm, and the height is 60mm. The inner diameter of the inner ring 105 is 830 mm, the outer diameter is 850 mm, and the height is 20 mm. The outer side of the outer ring 106 is a rounded square with a side length of 900 mm, a rounded radius of 100 mm, and the inner side is a circle with a diameter of 860 mm.

[0034] The cylindrical rollers 103 are carried between the outer ring 106 and the inner ring 105. The first retainer 102 and the second retainer 104 are used to fix the cylindrical rollers 103. Each cylindrical roller 103 passes through a plurality of fixed shafts on the first retainer 102. The second retainer 104 prevents the cylindrical rollers 103 from escaping from the fixed shafts.

[0035] The outer ring 106 and the outer shell 101 serve as a casing for fixing the driving device, and the interlayer part formed by the outer ring 106 and the outer shell 101 is provided with a control circuit module 901, a protection circuit and an error indication circuit module 902, wherein the control circuit module 901 mainly realizes the rotational movement of the inner ring 105 by controlling the driving device, and the protection circuit and error indication circuit module 902 is used to timely cut off the power supply to the faulty part when encountering sudden conditions such as faults during the movement of the inner ring 105.

[0036] The outer ring 106 is provided with a driving device linked to the inner ring 105 ; the driving device is electrically connected to a control circuit module 901 , and the control circuit module 901 is electrically connected to a protection circuit and error indication circuit module 902 .

[0037] The driving device includes a driving motor 108 disposed on the outer ring 106, the output end of the driving motor 108 is connected to a driving gear 107, the inner ring 105 is provided with a driven gear coaxially arranged therewith, and the driving gear 107 is meshed with the driven gear of the inner ring 105. By driving the driving gear 107 by the driving motor 108, the inner ring 105 and the scanning device can be driven to rotate relative to the sample to be tested.

[0038] The first beam conversion assembly includes a first beam conversion element 3 and a second beam conversion element 4 arranged in sequence along the terahertz wave transmission direction, and the second beam conversion assembly includes a third beam conversion element 5 and a fourth beam conversion element 6 arranged in sequence along the terahertz wave transmission direction. The four beam conversion elements are all diffractive optical elements, which are respectively mounted on their own frames, and the frames are fixed on the inner ring 105. When the terahertz beam passes through the diffractive optical element, it will be collimated or converged in the y-axis direction and will not change in the x-axis direction, wherein the y-axis is a direction parallel to the through hole in the middle of the inner ring 105, and the x-axis is a direction perpendicular to the y-axis.

[0039] The structure of the terahertz detection array 7 is a circular arc array formed by a plurality of terahertz detectors. Two adjacent terahertz detectors are connected by an ABS fan-shaped block with a central angle of 15°. The terahertz detectors close to the vertex of the fan-shaped block are almost in contact. The spacing between each detector is 20 mm. Figure 5 shown.

[0040] The flexible manipulator 8 includes a base 801, a second joint axis 802, a second joint axis 803, and a flexible gripper 804, which are arranged in sequence. The base 801 and the second joint axis 802, and the second joint axis 802 and the second joint axis 803 are connected by a rotating motor 805 respectively; the clamping end of the flexible gripper 804 is made of a material with a low terahertz wave absorption coefficient. Specifically, two motors are used inside the flexible gripper 804 to realize the rotation movement of the flexible gripper and the placement of the sample to be tested; the base 801 has a fixed control panel inside, which is connected to each motor, and a display control screen 9 is provided outside to realize the control of the motion trajectory of the flexible manipulator. The outer side of the flexible gripper 804 is made of Full Cure 835VeroWhite material with a very small terahertz wave absorption coefficient, and the inner side is pasted with foam with a very small terahertz wave absorption coefficient.

[0041] A terahertz rapid tomography method, the specific steps are as follows:

[0042] Step 1: Turn on the terahertz fast tomography system;

[0043] Step 2: Set the rotation spacing and rotation range of the flexible robotic arm 8 or scanning frame 1 around the y-axis direction; wherein the y-axis coincides with the through hole axis in the middle of the inner ring 105; the rotation spacing is the rotation angle each time, and the rotation range is the total rotation angle.

[0044] Step 3: setting the translation interval and translation range of the flexible mechanical arm 8 in the y-axis direction according to the volume of the sample to be tested; wherein the translation interval is the distance of each translation, and the translation range is the total translation distance;

[0045] Step 4: Move the sample to be tested to the through hole of the testing station by the flexible mechanical arm 8;

[0046] Step 5: The terahertz beam emitted by the terahertz emission source 2 is collimated by the first beam conversion unit 3 and focused by the second beam conversion unit 4, and then propagates to the sample to be tested held by the flexible mechanical arm 8;

[0047] Step 6: The terahertz beam passing through the sample to be tested is collimated by the third beam conversion unit 5 and the fourth beam conversion unit 6 before reaching the terahertz detection array 7;

[0048] Step 7: The detectors on the terahertz detection array 7 convert the detected light intensity signal of the terahertz wave into an analog photocurrent signal and transmit it to the data acquisition card.

[0049] Step 8: The data acquisition card converts the analog photocurrent signal into a digital voltage signal and transmits it to the computer for storage;

[0050] Step 9: Under the action of the driving motor 108, the inner ring 105 drives the scanning device to rotate 0.01° relative to the outer ring 106 of the scanning frame 1, and then repeat steps 5 to 8;

[0051] Step 10: Repeat step 9 until the positions of the first detector and the second detector of the terahertz detection array 7 coincide with each other, thus completing the data collection of a certain cross section of the sample to be tested.

[0052] Step 11: After completing the data collection of a certain cross section of the sample to be tested, the sample to be tested is translated along the y-axis for a certain distance by the flexible mechanical arm 8 and steps 5 to 10 are repeated until the data collection of the entire sample to be tested is completed.

[0053] The present invention has been described above in conjunction with the best embodiments, but the present invention is not limited to the embodiments disclosed above, but should cover various modifications and equivalent combinations based on the essence of the present invention.

Claims

1. A terahertz fast tomography system, characterized in that: The invention comprises a scanning frame (1) and a scanning device, wherein the scanning device comprises a terahertz emission source (2), a first beam conversion assembly, a second beam conversion assembly, and a terahertz detection array (7) which are arranged in sequence, the scanning frame (1) comprises an inner ring (105) and an outer ring (106) which are rotatably matched with each other, a workstation to be tested is arranged in the middle of the inner ring (105), the workstation to be tested is located between the first beam conversion assembly and the second beam conversion assembly, and the terahertz emission source (2), the first beam conversion assembly, the workstation to be tested, the second beam conversion assembly, and the terahertz detection array (7) are arranged in sequence on the inner ring (105) along the diameter direction; and a flexible mechanical arm (8) for grabbing a sample to be tested is arranged on one side of the scanning frame (1).

2. A terahertz fast tomography system according to claim 1, characterized in that: The outer ring (106) is provided with a driving device linked to the inner ring (105); the driving device is electrically connected to a control circuit module (901), and the control circuit module (901) is electrically connected to a protection circuit and an error indication circuit module (902).

3. The terahertz fast tomography system according to claim 1, characterized in that: The driving device comprises a driving motor (108) arranged on an outer ring (106), the output end of the driving motor (108) is connected to a driving gear (107), the inner ring (105) is provided with a driven gear coaxially arranged therewith, and the driving gear (107) is meshed with the driven gear of the inner ring (105).

4. The terahertz fast tomography system according to claim 1, characterized in that: The first beam conversion assembly comprises a first beam conversion element (3) and a second beam conversion element (4) which are arranged in sequence along the terahertz wave transmission direction.

5. A terahertz fast tomography system according to claim 1, characterized in that: The second beam conversion assembly comprises a third beam conversion element (5) and a fourth beam conversion element (6) which are arranged in sequence along the terahertz wave transmission direction.

6. The terahertz fast tomography system according to claim 1, characterized in that: The station to be tested is a through hole arranged in the middle of the inner ring (105).

7. The terahertz fast tomography system according to claim 1, characterized in that: The flexible mechanical arm (8) comprises a base (801), a second joint shaft (802), a second joint shaft (803), and a flexible gripper (804) which are arranged in sequence; the base (801) and the second joint shaft (802), and the second joint shaft (802) and the second joint shaft (803) are respectively connected via a rotating motor (805); and a clamping end of the flexible gripper (804) is made of a material with a low terahertz wave absorption coefficient.

8. A terahertz rapid tomography method, characterized in that: The terahertz fast tomography system according to any one of claims 1 to 7 is used, and the sample to be tested is moved to the test station by a flexible mechanical arm (8), and then step a) is performed: the terahertz beam emitted by the terahertz emission source (2) passes through the first beam conversion assembly, the sample to be tested, the second beam conversion assembly in sequence and reaches the terahertz detection array (7), the detector of the terahertz detection array (7) converts the light intensity signal of the detected terahertz wave into an analog photocurrent signal and transmits it to a data acquisition card, the data acquisition card converts the analog photocurrent signal into a digital voltage signal and transmits it to a computer for storage; then the scanning device is rotated by a fixed angle relative to the outer ring (106) of the scanning frame (1), and the above step a) is repeated until the positions of the first detector and the second detector of the terahertz detection array (7) coincide with each other, and the data acquisition of a certain cross section of the sample to be tested is completed.

9. The terahertz rapid tomography method according to claim 8, characterized in that: After the data collection of a certain cross section of the sample to be tested is completed, the sample to be tested is translated along the y-axis for a certain distance by the flexible mechanical arm (8) and step a) is repeated until the data collection of the entire sample to be tested is completed.

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