WO2019232792A1

WO2019232792A1 - Three-dimensional tomography systems and method

Info

Publication number: WO2019232792A1
Application number: PCT/CN2018/090456
Authority: WO
Inventors: 祁春超; 潘子祥; 谭信辉; 刘艳丽
Original assignee: 深圳市华讯方舟太赫兹科技有限公司; 华讯方舟科技有限公司
Priority date: 2018-06-08
Filing date: 2018-06-08
Publication date: 2019-12-12

Abstract

Three-dimensional tomography systems (10, 20, 30) and a method, the systems (10, 20, 30) comprising: a non-diffractive device (101), a condensing device (102), a scanning device (103), and a receiver (104). The non-diffractive device (101) is used for condensing an incident first light beam into a second light beam; the condensing device (102) is disposed at a light emergent side of the non-diffractive device (101), the condensing device (102) is formed thereon with a through hole (1021), and the second light beam is emitted to the scanning device (103) by means of the through hole (1021); the scanning device (103) is used for reflecting the second light beam in a scanning manner to a material to be detected (A), and reflecting a third light beam reflected by the material to be detected (A) to the condensing device (102); and the receiver (104) is disposed in a condensing area of the condensing device (102) and used for receiving the third light beam condensed by the condensing device (102) so as to construct a three-dimensional image of the material to be detected (A) by using information of the third light beam. By means of the described manner, the accuracy of material detection may be improved.

Description

Three-dimensional tomography imaging system and method Ranch

【技术领域】[Technical Field]

The present application relates to the technical field of material detection, and in particular, to a three-dimensional tomography system and method.

【背景技术】【Background technique】

In actual industrial production applications, various materials may produce defects during the manufacturing process, cause quality problems, and even lead to the scrapping of the entire structural parts using the material, causing significant economic losses, especially in the various composites used in the aerospace field. Materials have higher requirements on the quality of materials. Once the internal defects of the materials used, major losses will occur, and even major accidents will occur.

At present, methods such as infrared light detection and X-ray detection can be used to three-dimensionally image the material to detect whether there is a defect in the internal structure of the material. However, the rays used by these methods have a short depth of field, and the resolution of the detection image is low. The structure, especially the internal structure of composite materials, has low detection accuracy.

【发明内容】 [Summary of the Invention]

The present application mainly provides a three-dimensional tomography system and method, which can improve the accuracy of material detection.

In order to solve the above technical problem, a technical solution adopted in the present application is to provide a three-dimensional tomography method, which includes: using a transmitter to emit a first light beam to a non-diffraction device, wherein the first light beam is too small at a frequency of not less than 0.5 THz. Hertz light; using a non-diffractive device to converge the incident first light beam into a second light beam; using a scanning device to scan the second light beam to the test material in a scanning manner, and reflecting the third light beam reflected by the test material to the light collecting device Wherein, the light-condensing device is disposed on the light-exiting side of the non-diffraction device, a through-hole is formed on the light-concentrating device, and the second light beam is transmitted to the scanning device through the through-hole; the receiver receives the third light beam collected by the light-concentrating device, and the receiver The light-condensing device is arranged in the light-concentrating area of the light-concentrating device; the three-dimensional image of the material to be inspected is constructed using the information of the third light beam; wherein the light-concentrating device is a concave mirror, the reflective surface of the concave mirror faces the scanning device, and the diameter of the through hole is 0.3 mm.

In order to solve the above technical problem, another technical solution adopted in the present application is to provide a three-dimensional tomography imaging system, which includes: a non-diffractive device, a light-concentrating device, a scanning device, and a receiver; A light beam is condensed into a second light beam; the light condensing device is arranged on the light-emitting side of the non-diffraction device; a through hole is formed in the light condensing device; the second light beam is radiated to the scanning device through the through hole; The scanning method reflects the material to be inspected, and reflects the third beam reflected by the inspected material to the light-concentrating device; the receiver is arranged in the light-concentrating area of the light-concentrating device, and is used for receiving the third light beam condensed by the light-concentrating device to utilize The information of the third light beam constructs a three-dimensional image of the inspected material.

In order to solve the above technical problem, another technical solution adopted in the present application is to provide a three-dimensional tomography method, which includes: using a non-diffraction device to converge an incident first light beam into a second light beam; using a scanning device to condense the second light beam Reflected to the test material in a scanning manner, and reflected the third light beam reflected by the test material to the light-concentrating device, where the light-concentrating device is arranged on the light exit side of the non-diffraction device, a through-hole is formed on the light-concentrating device, and the second light beam The through-hole is radiated to the scanning device; the receiver is used to receive the third light beam condensed by the light-condensing device, and the receiver is arranged in the light-concentrating area of the light-condensing device;

The beneficial effects of this application are: different from the situation of the prior art, in some embodiments of this application, a non-diffractive device is used to converge the incident first light beam into a second light beam; a scanning device is used to reflect the second light beam in a scanning manner To the inspected material, and the third beam reflected by the inspected material is reflected to the light-concentrating device, and the receiver set in the light-concentrating area of the light-concentrating device receives the third light beam condensed by the light-concentrating device to use the information of the third light beam Construct a three-dimensional image of the inspected material, so that using a non-diffractive device, the first beam can be converged into a second beam that is approximately non-diffracted, so that the second beam does not diverge and light during the subsequent propagation and scanning to the inspected material The field energy is highly concentrated, and the size of the central bright spot is small, so that the resolution of the three-dimensional image of the inspected material constructed by using the information of the third beam after scanning is high, and the accuracy of the material detection is improved.

【附图说明】 [Brief Description of the Drawings]

FIG. 1 is a schematic structural diagram of a first embodiment of a three-dimensional tomography system of the present application;

2 is a schematic structural diagram of a second embodiment of a three-dimensional tomography system of the present application;

3 is a schematic structural diagram of a transmitter and a receiver in a second embodiment of the three-dimensional tomography system of the present application;

4 is a schematic structural diagram of a third embodiment of a three-dimensional tomography system of the present application;

5 is a schematic flowchart of an embodiment of a three-dimensional tomography method according to the present application;

FIG. 6 is a detailed flowchart of each step in FIG. 5.

【具体实施方式】【Detailed ways】

In the following, the technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

As shown in FIG. 1, the first embodiment of the three-dimensional tomography system 10 of the present application includes: a non-diffraction device 101, a light condensing device 102, a scanning device 103, and a receiver 104.

The non-diffraction device 101 is used for converging the incident first light beam into a second light beam; the light-concentrating device 102 is disposed on the light-exiting side of the non-diffraction device 101; a through-hole 1021 is formed in the light-concentrating device 102; 1021 hits the scanning device 103; the scanning device 103 is configured to scan the second light beam to the test material A in a scanning manner, and reflect the third light beam reflected by the test material A to the light collecting device 102; the receiver 104 is provided at the light collecting device 102 The light-condensing area of the optical device 102 is configured to receive a third light beam condensed by the light-concentrating device 102 to construct a three-dimensional image of the material A to be inspected by using the information of the third light beam.

Wherein, the non-diffraction device 101 is a device for converging an incident first light beam into an approximately non-diffraction light beam, that is, the second light beam is an approximately non-diffraction light beam, such as a non-diffraction Bessel beam. The non-diffraction device 101 may be a lens or a lens combination capable of generating an approximately non-diffractive light beam, and may use a super-surface material, high-density polyethylene (high-density) Polyethylene (HDPE), Polytetrafluoroethylene (PTFE), Polypropylene or Poly 4-methylpentene-1 (TPX) and other materials are not limited here. The type of the non-diffraction device 101 can be specifically selected according to the frequency of the incident first light beam. For example, when the incident first light beam is terahertz light, the non-diffraction device 101 can select a non-diffraction lens in the terahertz frequency band.

The first light beam may be a collimated light beam directly generated by a light source, such as a laser beam, or a collimated light beam processed by some devices after the light source is generated. The first light beam may penetrate the material A to be inspected. Rays, such as terahertz light. The tested material can be a composite material with high quality requirements, or it can be other (non-polar) material, which is not specifically limited here. The thickness of the tested material will affect the penetrability of the light beam and is generally not greater than 10 cm.

The condensing device 102 may be a concave mirror, or a combination of a condensing lens and a reflecting mirror. The concave mirror or the reflecting mirror is formed with a through hole 1021 through which the second light beam may enter the scanning device 103. The size of the through hole 1021 is not smaller than the size of the light spot generated by the second light beam. The light-concentrating area of the light-concentrating device 102 may be a light-condensing point or a light-concentrating area, which depends on the specific type of the light-concentrating device 102, and is not specifically limited here.

The scanning device 103 may be a three-dimensionally movable mirror, or may be a set of galvanometers that can change the exit direction of the second light beam, so that the emitted second light beam is reflected to the surface of the material A in a scanning manner. The scanning frequency of the scanning device 103 can be set according to actual requirements such as imaging time and material size. For example, when the size of the inspected material A is 50cm * 50cm * 10cm and the central spot of the second beam is 0.3mm, controlling the scanning frequency of the scanning device 103 can make the imaging time not longer than 5s and the imaging resolution It reaches 0.3 * 0.3 * 1.5mm.

The receiver 104 may include a detector and a signal processor, wherein the detector may detect and receive the third light beam, and the signal processor may acquire information in the received third light beam to construct a three-dimensional image of the material A to be inspected.

Specifically, in an application example, a collimated first light beam generated by a light source is incident on the non-diffraction device 101, and is converged by the non-diffraction device 101 into a nearly non-diffraction second light beam, and the second light beam passes through the condensing The through hole 1021 on the device 102 is incident on the scanning device 103, and the scanning device 103 reflects the second light beam to the surface of the material A to be inspected, wherein the scanning device 103 can be moved, so that the exit direction of the second light beam can be changed By controlling the moving direction and the moving angle of the scanning device 103 (such as a three-dimensionally movable mirror), the second light beam can be reflected in a scanning manner on the surface of the material A to be inspected. The second light beam is reflected and transmitted on the surface of the material A to be inspected, and the flatness, reflectance, and refractive index of the material at different positions of the material to be inspected A are different, and there may be defects in the internal defects. The second light beam is absorbed or reflected to different degrees. Therefore, the information (phase and intensity information) in the third light beam finally reflected back to the scanning device 103 can reflect the structure of the inspected material A. After the third light beam is reflected to the scanning device 103, it is reflected by the scanning device 103 to the light-concentrating device 102. The light-concentrating device 102 converges the incident third light beam into the light-concentrating area and is set in the light-concentrating area. After the receiver 104 receives the third beam using the detector, its signal processor can extract the information in the third beam, so that according to the phase and intensity information in the third beam, it can analyze and know that each position should be The internal structure of the inspection material A can further form a three-dimensional image of the inspection material A.

In this embodiment, a non-diffraction device is used to converge the incident first light beam into a second light beam; a scanning device is used to reflect the second light beam to the test material in a scanning manner, and a third light beam reflected by the test material is reflected to the light beam. The optical device receives a third light beam collected by the light-condensing device by a receiver provided in the light-concentrating area of the light-concentrating device, and uses the information of the third light beam to construct a three-dimensional image of the inspected material. The light beam converges into a second beam with almost no diffraction, so that the second beam does not diverge during subsequent propagation and scanning to the detected material, the light field energy is highly concentrated, and the size of the central bright spot is small. The three-dimensional image of the tested material constructed by the information of the light beam has high resolution and improves the accuracy of material detection.

In other embodiments, the three-dimensional tomography system may further include a light source, that is, a transmitter, which may emit the first light beam.

Specifically, as shown in FIG. 2, the second embodiment of the three-dimensional tomography system 20 of the present application is based on the first embodiment of the three-dimensional tomography system of the present application, and further includes: a transmitter 100, which is disposed at The light incident side of the diffractive device 101 is configured to emit a first light beam to the non-diffractive device 101.

Light waves in the terahertz band not only have good penetrating properties for materials, but also have low photon energy, which will not cause harmful ionization reactions. It can realize non-destructive testing of materials, and is especially suitable for composite materials with high quality requirements and high manufacturing costs. Detection.

In this embodiment, the transmitter 100 may use a terahertz optical transmitter to form a first light beam in the terahertz frequency band, wherein the frequency of the first light beam is not less than 0.5 THz.

Optionally, in this embodiment, the non-diffraction device 101 is a non-diffraction lens, such as a PTFE lens in a terahertz frequency band. The non-diffraction lens 101 can focus the first incident parallel light beam into a second non-diffraction light beam (vortex light), wherein the depth of field of the second light beam is not less than 1.5 m, and the diameter of the central spot can be 0.3 mm.

Optionally, the light condensing device 102 is a concave mirror, the reflective surface of the concave mirror faces the scanning device 103, and the diameter of the through hole formed in the concave mirror is not less than 0.3 mm, so that the second light beam can pass through the through hole When the incident light enters the scanning device 103 and the concave mirror has a light-concentrating effect, when the third light beam reflected by the scanning device 103 is incident on the reflecting surface of the concave mirror, the concave mirror will converge the third light beam to its focus. The concave mirror can be made of the same material as the non-diffraction device 101, such as a PTFE material. The size of the through hole can be set according to actual needs, and is usually a millimeter level, for example, 0.1 mm to 3 mm.

In this embodiment, the transmitter 100 may use solid-state electronic technology to form a terahertz solid-state transmitting front end. Similarly, the receiver 104 may also use solid-state electronic technology to form a terahertz solid-state receiving front-end. Wherein, when the transmitter needs to generate a terahertz wave with a higher frequency, a frequency doubling technology may be used to multiply a lower frequency signal to a required terahertz frequency band.

Optionally, as shown in FIG. 3, in this embodiment, the transmitter 100 includes a signal source 1001, a first frequency multiplier 1002, and a transmitting antenna 1003. The signal source 1001 is used to generate a local oscillator signal, and the frequency of the local oscillator signal is lower than the frequency of the first beam; the first frequency multiplier 1002 is connected to the signal source 1001 and is used to raise the frequency of the local oscillator signal to the terahertz frequency band, so as to A first light beam is formed; the transmitting antenna 1003 is connected to the first frequency multiplier 1002 and is used for transmitting the first light beam.

The first frequency multiplier 1002 may be formed by connecting multiple frequency multipliers (such as a second frequency multiplier, a fourth frequency multiplier, etc.) in series. Specifically, the type and number of frequency multipliers are selected according to the required frequency multiplier. No specific restrictions are made here.

Specifically, in an application example, the signal source 1001 can generate a 12.5 GHz local oscillator signal. The frequency required for the first light beam is 600 GHz (that is, 0.6 THz). The frequency multiplier of the first frequency multiplier 1002 is 48. Times, a third frequency multiplier and two four frequency multipliers can be used in series to form the first frequency multiplier 1002. Of course, two second frequency multipliers, a fourth frequency multiplier, and a third frequency multiplier can also be used. The first frequency multiplier 1002 is formed in series, or a third frequency multiplier and a sixteen frequency multiplier are connected in series to form the first frequency multiplier 1002, or a second frequency multiplier, a third frequency multiplier, and a The eight multiplier is connected in series to form the first multiplier 1002. Of course, in other embodiments, frequency multipliers with other frequency multipliers may also be used, as long as signals of a desired frequency band can be obtained. After receiving the signal outputted by the first frequency multiplier 1002 by the transmitting antenna 1003, the transmitting antenna 1003 can form the signal into a first light beam and transmit it to the non-diffraction device 101.

Optionally, continuing to refer to FIG. 3, the receiver 104 specifically includes a receiving antenna 1041, a baseband signal source 1042, a modulator 1043, a second frequency multiplier 1044, a mixer 1045, and a signal processing device 1046.

The baseband signal source 1042 is used to generate a low-frequency baseband signal, and the frequency of the low-frequency baseband signal is lower than the frequency of the local oscillator signal; the input end of the modulator 1043 is connected to the signal source 1001 and the baseband signal source 1042 respectively, and the output end is connected to the second frequency multiplier. 1044, which is used to modulate the baseband signal to the local oscillator signal and input it to the second frequency multiplier 1044 for frequency doubling; the input ends of the mixer 1045 are connected to the receiving antenna 1041 and the second frequency multiplier 1044, respectively, for Mixing the signal multiplied by the second frequency multiplier 1044 with the signal received by the receiving antenna 1041 to obtain a low frequency signal, wherein the number of frequency multiplications of the second frequency multiplier 1044 is the same as that of the first frequency multiplier 1002; The processing device 1046 is connected to the mixer 1045 and is configured to process the mixed low-frequency signal to obtain information of the third light beam for imaging.

Specifically, in an application example, the receiving antenna 1041 can receive a third beam and generate a third beam signal. When the frequency of the first beam emitted by the transmitting antenna is 600 GHz (that is, 0.6 THz), the frequency of the third beam It is also 600GHz. The baseband signal source 1042 generates a 1MHz low-frequency baseband signal. The modulator 1043 obtains a 12.5GHz local oscillator signal generated by the signal source 1001 of the transmitter 100, and modulates the 1MHz baseband signal onto the 12.5GHz local oscillator signal to form 12.501. GHz signals. The frequency multiplier number of the second frequency multiplier 1044 is the same as that of the first frequency multiplier 1002, both of which are 48 times. After the frequency multiplication of the 12.501GHz signal, a signal of 600.048GHz can be obtained. The second frequency multiplier 1044 A form in which multiple frequency multipliers are connected in series may also be adopted, and the structure may be the same as or different from the first frequency multiplier 1002, as long as the frequency multipliers are the same. Due to the convenience of low frequency signal processing, the mixer 1045 obtains a signal of 600.048 GHz and a signal of the third beam of 600 GHz and then performs mixing to obtain a low frequency signal of 48 MHz. The low frequency signal retains the information of the third beam. After the signal processing device 1046 obtains the 48 MHz low-frequency signal, phase information and intensity information can be extracted from the low-frequency signal, so that the three-dimensional material A can be constructed based on the phase information and intensity information reflecting the structure of the material A to be inspected. The image can further intuitively determine from the three-dimensional image whether there is a defect in the material A to be inspected.

Optionally, referring further to FIG. 3, in the receiver 104, the signal processing device 1046 includes: an orthogonal signal (I / Q) demodulator 10461, an analog-to-digital converter (A / D) 10462, and a field connected in sequence. Programmable gate array (FPGA) 10463 and imaging circuit 10464.

The orthogonal signal demodulator 10461 is used to demodulate the low frequency signal; the analog-to-digital converter 10462 is used to convert the demodulated low frequency signal into a digital signal; the field programmable gate array 10463 is used to collect the digital Data in the signal; the imaging circuit 10464 is used to construct a three-dimensional image of the material A to be inspected using the collected data.

Specifically, in an application example, since digital signal processing is relatively simple and convenient, and the mixed low-frequency signal is a modulated analog signal, the signal processing device 1046 first uses the I / Q signal demodulator 10461 to convert the low-frequency signal. After demodulation, the A / D converter 10462 is used to convert the demodulated analog low-frequency signal into a digital signal, and then FPGA circuit 10463 is used to collect the data (such as phase and amplitude information) in the digital signal. Finally, the imaging circuit 10464 can The collected data is used to analyze the internal structure of the inspected material A, and finally a three-dimensional image of the inspected material A is constructed. Of course, in other embodiments, the receiver 104 may also be directly connected to an independent imaging device, and the independent imaging device constructs a three-dimensional image of the material A to be inspected according to the information of the third light beam.

In this embodiment, a terahertz band optical transmitter is used to transmit a first light beam in the terahertz frequency range to a non-diffractive device. The non-diffraction device converges the incident first light beam into a second light beam, and the scanning device is used to scan the second light beam. The method reflects the material to be inspected, and reflects the third beam reflected by the inspected material to the light-concentrating device, and a receiver provided in the light-concentrating area of the light-concentrating device receives the third light beam condensed by the light-concentrating device to use the third light beam. The three-dimensional image of the inspected material is constructed based on the information of the inspected material, so that the non-diffraction device can be used to converge the first beam into a second beam that is approximately non-diffracted, so that the second beam does not diverge during subsequent propagation and scanning to the inspected material The light field energy is highly concentrated and the size of the central bright spot is small, so that the three-dimensional image of the inspected material constructed by using the information of the third beam after scanning is high in resolution, improving the accuracy of material detection, and using the strong penetration of the terahertz band beam The characteristics of permeability and low photon energy can penetrate the test material with higher thickness without damaging the test material and realize non-destructive testing.

As shown in FIG. 4, the third embodiment of the three-dimensional tomography system 30 of the present application is based on the first embodiment of the three-dimensional tomography system of the present application, and further defines the scanning device 103 as a scanning galvanometer, including the first A lens 1031 and a second vibrating lens 1032. The first vibrating lens 1031 rotates in a first direction, and the second vibrating lens 1032 rotates in a second direction perpendicular to the first direction, so that the second beam is scanned line by line or column by column.测材料 A。 Inspection material A.

The scanning mode of the second light beam may be scanning along a “Z” or “bow” shape. The first vibrating lens 1031 may be a row-direction vibrating mirror, that is, after the first vibrating lens 1031 is rotated, the exit direction of the second light beam may be changed, so that the second beam is scanned in the row direction of the surface of the material A to be inspected; and The second vibrating lens 1032 is a column direction vibrating mirror, that is, after the second vibrating lens 1032 is rotated, the exit direction of the second light beam can be changed, so that the second beam is scanned in the column direction of the surface of the material A to be inspected.

Specifically, in the initial state, the first vibrating lens 1031 and the second vibrating lens 1032 can be set in parallel. When the progressive scanning is started, the first vibrating lens 1031 starts to rotate, and the second vibrating lens 1032 is not moved, and one line is scanned. Then, the second vibrating lens 1032 is rotated by a certain angle, and the first vibrating lens 1031 is not moved, so that the second light beam can be irradiated to the next line, and then the above steps are repeated until the inspected material A is scanned.

Of course, in other embodiments, the first galvanometer lens 1031 may be a column direction galvanometer, and the second galvanometer lens 1032 may be a row direction galvanometer. The scanning method may also be column-by-column scanning, or other scanning methods. No specific restrictions are made here.

Optionally, continuing to refer to FIG. 4, the light-concentrating device 102 may also be formed by using a combination of a plane reflecting mirror 1022 and a condenser lens 1023, wherein the reflecting surface of the plane reflecting mirror 1022 faces the scanning device 103 and the plane reflecting mirror 1022. A through-hole 1021 is formed, and the first light beam can be incident on the scanning device 103 through the through-hole 1021, and the third light beam reflected by the scanning device 103 can be reflected by the reflecting surface of the plane mirror 1022. The condenser lens 1023 is disposed in the reflection area of the plane mirror 1022, that is, the light exit side of the reflected light, and the receiver 104 is disposed in the condenser area (such as the focal position) of the condenser lens 1023. The condenser lens 1023 The third light beam reflected by the plane mirror 1022 can be converged to the receiver 104, and processed by the receiver 104 after receiving.

The three-dimensional tomography system in this embodiment can also be combined with the second embodiment of the three-dimensional tomography system in this application.

As shown in FIG. 5, the three-dimensional tomography method of the present application is applied to the three-dimensional tomography system of the present application. For the specific structure of the three-dimensional tomography system, refer to any one of the first to third embodiments of the three-dimensional tomography system of the present application. Structure. In this embodiment, the three-dimensional tomography method includes:

S101: Converge an incident first light beam into a second light beam using a non-diffraction device.

S102: Use the scanning device to reflect the second light beam to the test material in a scanning manner, and reflect the third light beam reflected by the test material to the light concentrating device.

The light-concentrating device is disposed on the light-exiting side of the non-diffraction device. A through-hole is formed in the light-concentrating device, and the second light beam is transmitted to the scanning device through the through-hole.

S103: Use the receiver to receive the third light beam collected by the light-concentrating device.

The receiver is disposed in a light-concentrating area of the light-concentrating device.

S104: Use the information of the third light beam to construct a three-dimensional image of the test material.

Optionally, before step S101, the method further includes:

S100: Use the transmitter to emit the first light beam to the non-diffraction device.

Wherein, the transmitter is disposed on the light incident side of the non-diffraction device, and the first light beam may be a light beam in a terahertz frequency band with a frequency of not less than 0.5 THz.

Optionally, as shown in FIG. 6, step S100 specifically includes:

S1001: Use the signal source to generate a local oscillator signal with a frequency lower than the frequency of the first beam.

S1002: Use the first frequency multiplier to multiply the local oscillator signal into a signal in the terahertz band.

S1003: Use a transmitting antenna to transform the signal in the terahertz frequency band into a collimated terahertz frequency band first light beam and transmit it to the terahertz non-diffraction lens.

Optionally, step S101 specifically includes:

S1011: using a terahertz non-diffraction lens to condense the first light beam into an approximately non-diffraction second light beam in the terahertz frequency band.

Optionally, step S102 specifically includes:

S1021: Control the scanning galvanometer to reflect the second light beam passing through the through hole on the concave mirror to the surface of the material to be inspected in a scanning manner.

S1022: Use a concave mirror to focus the third light beam reflected by the scanning galvanometer to a focal region.

The focus area is an area of a preset range centered on the focal point of the concave mirror.

Optionally, step S103 specifically includes:

S1031: Use a receiving antenna to receive the third light beam reflected by the concave mirror;

S1032: using a modulator to modulate a low-frequency baseband signal generated by a baseband signal source onto a local oscillator signal;

S1033: using a second frequency multiplier to multiply the modulated signal to the terahertz frequency band;

The frequency multiplier of the second frequency multiplier is the same as that of the first frequency multiplier.

S1034: Use a mixer to mix the frequency-multiplied signal with the received third beam signal to obtain a low-frequency signal.

The low-frequency signal carries information of the third light beam.

Optionally, step S104 specifically includes:

S1041: Use the signal processing device to process the low-frequency signal to obtain phase and intensity information of the third light beam, and analyze the structure of the inspected material according to the phase and intensity information to construct a three-dimensional image of the inspected material.

The above description is only an implementation of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of the application, or directly or indirectly applied to other related technologies The fields are equally covered by the patent protection scope of this application.

Claims

A three-dimensional tomography method, including:

Using a transmitter to emit a first light beam to a non-diffractive device, wherein the first light beam is a terahertz light having a frequency of not less than 0.5 THz;

Using the non-diffraction device to converge the incident first light beam into a second light beam;

Using a scanning device to scan the second light beam to the test material in a scanning manner, and to reflect the third light beam reflected by the test material to the light condensing device, wherein the light condensing device is arranged in the non-diffraction device A light emitting side of the device, a through hole is formed in the light condensing device, and the second light beam is emitted to the scanning device through the through hole;

Using a receiver to receive the third light beam condensed by the light-concentrating device, wherein the receiver is disposed in a light-concentrating area of the light-concentrating device;

Constructing a three-dimensional image of the inspected material by using the information of the third light beam;

Wherein, the light condensing device is a concave mirror, and a reflective surface of the concave mirror faces the scanning device.
The three-dimensional tomographic imaging method according to claim 1, wherein the non-diffraction device is a non-diffraction lens, and the using the non-diffraction device to focus an incident first light beam into a second light beam comprises:

The first incident light beam that is incident in parallel is collected into the second light beam by using the non-diffraction lens, wherein an imaging depth of field of the second light beam is not less than 1.5m.
A three-dimensional tomography system, which includes: a non-diffraction device, a light-concentrating device, a scanning device, and a receiver;

The non-diffraction device is configured to focus an incident first light beam into a second light beam;

The light-concentrating device is disposed on a light-exiting side of the non-diffraction device, a through-hole is formed on the light-concentrating device, and the second light beam is emitted to the scanning device through the through-hole;

The scanning device is configured to reflect the second light beam to the material under inspection in a scanning manner, and reflect a third light beam reflected by the material to be inspected to the condensing device;

The receiver is disposed in a light-concentrating area of the light-concentrating device, and is configured to receive the third light beam condensed by the light-concentrating device, so as to use the information of the third light beam to construct a three-dimensional image of the inspected material .
The system of claim 3, wherein the system further comprises:

The transmitter is disposed on a light incident side of the non-diffraction device and is configured to emit the first light beam to the non-diffraction device, wherein the first light beam is a terahertz light having a frequency of not less than 0.5 THz.
The system according to claim 4, wherein the non-diffraction device is a non-diffraction lens, and the non-diffraction lens is used for converging the first incident light beam which is incident in parallel into the second light beam, wherein the second The imaging depth of field of the light beam is not less than 1.5m.
The system of claim 3, wherein the light concentrating device is a concave mirror, and a reflective surface of the concave mirror faces the scanning device.
The system according to claim 3, wherein the scanning device is a scanning galvanometer, comprising a first vibration mirror and a second vibration mirror, the first vibration mirror rotates in a first direction, and the second vibration mirror moves along The second direction is perpendicular to the first direction, so that the second light beam scans the test material row by row or column by column. Ranch
The system according to claim 4, wherein the transmitter comprises: a signal source, a first frequency multiplier, and a transmitting antenna;

The signal source is used to generate a local oscillator signal, and a frequency of the local oscillator signal is smaller than a frequency of the first light beam;

The first frequency multiplier is connected to the signal source, and is configured to increase the frequency of the local oscillator signal to a terahertz frequency band to form the first light beam;

The transmitting antenna is connected to the first frequency multiplier and is configured to transmit the first light beam.
The system according to claim 8, wherein the receiver comprises: a receiving antenna, a baseband signal source, a modulator, a second frequency multiplier, a mixer, and a signal processing device;

The baseband signal source is used to generate a low-frequency baseband signal, and the frequency of the baseband signal is less than the frequency of the local oscillator signal;

An input end of the modulator is respectively connected to the signal source and the baseband signal source, and an output end is connected to the second frequency multiplier, which is used to modulate the baseband signal onto the local oscillator signal and then input the signal to the local oscillator. The frequency doubling is performed in the second frequency multiplier;

The input end of the mixer is respectively connected to the receiving antenna and the second frequency multiplier, and is configured to mix the frequency-multiplied signal of the second frequency multiplier with a signal received by the receiving antenna, To obtain a low frequency signal, wherein the frequency multiplier of the second frequency multiplier is the same as that of the first frequency multiplier;

The signal processing device is connected to the mixer and is configured to process the low-frequency signal to obtain information of the third light beam for imaging.
The system according to claim 9, wherein the signal processing device comprises: a quadrature signal demodulator, an analog-to-digital converter, a field programmable gate array, and an imaging circuit connected in sequence;

The orthogonal signal demodulator is configured to demodulate the low-frequency signal;

The analog-to-digital converter is configured to convert the demodulated low-frequency signal into a digital signal;

The field programmable gate array is used to collect data in the digital signal;

The imaging circuit is configured to use the collected data to construct a three-dimensional image of the inspected material.
The system of claim 3, wherein the information of the third light beam includes a phase and an intensity of the third light beam.
A three-dimensional tomography method, including:

Converging the incident first light beam into a second light beam using a non-diffraction device;

Using a scanning device to scan the second light beam to the test material in a scanning manner, and to reflect the third light beam reflected by the test material to the light condensing device, wherein the light condensing device is arranged in the non-diffraction device A light emitting side of the device, a through hole is formed in the light condensing device, and the second light beam is emitted to the scanning device through the through hole;

Using a receiver to receive the third light beam condensed by the light-concentrating device, wherein the receiver is disposed in a light-concentrating area of the light-concentrating device;

Use the information of the third light beam to construct a three-dimensional image of the test material.
The three-dimensional tomography method according to claim 12, wherein before the using the non-diffraction device to focus the incident first light beam into a second light beam, comprising:

The first light beam is transmitted to the non-diffraction device by a transmitter, wherein the first light beam is a terahertz light having a frequency of not less than 0.5 THz.
The three-dimensional tomography method according to claim 13, wherein the non-diffraction device is a non-diffraction lens, and the using the non-diffraction device to focus an incident first light beam into a second light beam comprises:

The non-diffraction lens is used to converge the first incident parallel light beam into the second light beam, and the imaging depth of field of the second light beam is not less than 1.5m.
The three-dimensional tomography method according to claim 12, wherein the light condensing device is a concave mirror, and a reflective surface of the concave mirror faces the scanning device.
The three-dimensional tomography method according to claim 12, wherein the scanning device is a scanning galvanometer, comprising a first galvanometer lens and a second galvanometer lens;

The step of using a scanning device to reflect the second light beam to the test material in a scanning manner and to reflect a third light beam reflected by the test material to the light collecting device includes:

Controlling the first vibrating lens to rotate in a first direction and controlling the second vibrating lens to rotate in a second direction perpendicular to the first direction to reflect the second light beam in a row-by-row or column-by-row scanning manner To the tested material;

Using the first vibrating lens and the second vibrating lens to reflect the third light beam reflected by the inspected material back to the condensing device.
The three-dimensional tomography method according to claim 13, wherein the transmitter comprises: a signal source, a first frequency multiplier, and a transmitting antenna connected in order;

The transmitting the first light beam to the non-diffraction device by using a transmitter includes:

Using the signal source to generate a local oscillator signal, wherein the frequency of the local oscillator signal is less than the frequency of the first light beam;

Using the first frequency multiplier to raise the frequency of the local oscillator signal to a terahertz frequency band to form the first light beam;

The first light beam is transmitted using the transmitting antenna.
The three-dimensional tomography method according to claim 17, wherein the receiver comprises: a receiving antenna, a baseband signal source, a modulator, a second frequency multiplier, a mixer, and a signal processing device;

Before the using the information of the third beam to construct a three-dimensional image of the inspected material, the method further includes:

Generating a low-frequency baseband signal by using the baseband signal source, wherein a frequency of the baseband signal is smaller than a frequency of the local oscillator signal;

Using the modulator to modulate the baseband signal onto the local oscillator signal and input the baseband signal to the second frequency doubler for frequency doubling;

Frequency-modulating the modulated signal by using the second frequency multiplier, wherein the frequency multiplier of the second frequency multiplier is the same as that of the first frequency multiplier

Using the mixer to mix the frequency-multiplied signal of the second frequency multiplier with the signal received by the receiving antenna to obtain a low-frequency signal;

The signal processing device is used to process the low-frequency signal to obtain information of the third light beam for imaging.
The three-dimensional tomography method according to claim 18, wherein the signal processing device comprises: an orthogonal signal demodulator, an analog-to-digital converter, a field programmable gate array, and an imaging circuit connected in order;

The constructing a three-dimensional image of the inspected material by using the information of the third light beam includes:

Demodulating the low-frequency signal by using the orthogonal signal demodulator;

Using the analog-to-digital converter to convert the demodulated low-frequency signal into a digital signal;

Collecting data in the digital signal by using the field programmable gate array;

The imaging circuit is used to construct a three-dimensional image of the inspected material according to the collected data.
The three-dimensional tomography method according to claim 12, wherein the information of the third light beam includes a phase and an intensity of the third light beam.