WO2019222885A1

WO2019222885A1 - Three-dimensional tomographic imaging system and method

Info

Publication number: WO2019222885A1
Application number: PCT/CN2018/087703
Authority: WO
Inventors: 祁春超; 潘子祥; 谭信辉; 杨正华
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: 2018-05-21
Filing date: 2018-05-21
Publication date: 2019-11-28

Abstract

A three-dimensional tomographic imaging system (10) and method. The system (10) comprises a diffraction-free device (101), a polarizing assembly (102), a scanning device (103), and a receiver (104); the diffraction-free device (101) is used for converging incident first light beams into second light beams, the first light beams being terahertz light; the polarizing assembly (102) is disposed at the light exit side of the diffraction-free device (101) and used for emitting light in a preset polarization direction in the second light beams to the scanning device (103); the scanning device (103) is used for reflecting the light in the preset polarization direction to a tested material in a scanning manner and reflecting third light beams reflected by the tested material to the polarizing assembly (102); the polarizing assembly (102) is also used for changing the polarization direction of the third light beams and reflecting the third light beams in the changed polarization direction to the receiver (104); the receiver (104) is disposed at the reflection side of the polarizing assembly (102) and used for receiving the third light beams reflected by the polarizing assembly (102) to construct a three-dimensional image of the tested material according to information of the third light beams.

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. 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-diffractive device, the first light beam is terahertz light; using non-diffraction The device converges the incident first light beam into a second light beam; uses a polarizing component to output light of a predetermined polarization direction in the second light beam to a scanning device; and uses the scanning device to reflect the light of the predetermined polarization direction to the test material in a scanning manner , And reflects the third light beam reflected by the inspected material to the polarizing component; using the polarizing component to change the polarization direction of the third light beam, and reflecting the third light beam after changing the polarization direction to the receiver; using the receiver to receive the reflected light from the polarizing component The third light beam is used to construct a three-dimensional image of the tested material according to the information of the third light beam. The non-diffraction device is a non-diffraction lens. The use of the non-diffraction device to focus the incident first light beam into a second light beam includes: using non-diffraction The lens focuses the first incident parallel light beam into a second light beam, wherein the depth of field of the second light beam is not less than 1.5m.

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 polarizing component, a scanning device, and a receiver; The light beam is converged into a second light beam, the first light beam is terahertz light; the polarizing element is arranged on the light-exiting side of the non-diffraction device, and is used to output the light of the preset polarization direction in the second light beam to the scanning device; The light with the preset polarization direction is reflected to the test material in a scanning manner, and the third light beam reflected by the test material is reflected to the polarizing component; the polarizing component is also used to change the polarization direction of the third light beam and change the polarization direction after The third light beam is reflected to the receiver; the receiver is disposed on the reflective side of the polarizing component, and is used for receiving the third light beam reflected by the polarizing component, so as to construct a three-dimensional image of the inspected material according to the information of the third light beam.

In order to solve the above technical problem, another technical solution adopted in the present application is to provide a three-dimensional tomographic imaging method, which includes: using a non-diffraction device, converging an incident first light beam into a second light beam, the first light beam being a terahertz Light; using a polarizing component to output the light of a predetermined polarization direction in the second beam to the scanning device; using the scanning device to scan the light of the predetermined polarization direction to the test material in a scanning manner, and reflecting the third light reflected by the test material The light beam is reflected to the polarizing component; the polarization direction of the third light beam is changed by the polarizing component, and the changed third light beam is reflected to the receiver; the third light beam reflected by the polarizing component is received by the receiver to construct according to the information of the third light beam Three-dimensional image of the tested material.

The beneficial effects of the present application are: different from the situation of the prior art, in some embodiments of the present application, a non-diffractive device is used to converge the incident first light beam into a second light beam; a polarization component is used to preset polarization in the second light beam The light in the direction is emitted to the scanning device; the scanning device is used to scan the light of the preset polarization direction to the test material in a scanning manner, and the third light beam reflected by the test material is reflected to the polarizing component; the third light beam is changed using the polarizing component The polarization direction of the light beam and reflects the changed third light beam to the receiver; the receiver receives the third light beam reflected by the polarizing component to construct a three-dimensional image of the inspected material according to the information of the third light beam, thereby using a non-diffraction device, The first beam can be converged 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, thereby making scanning The three-dimensional image of the inspected material constructed later using the information of the third beam has high resolution and improves the accuracy of material detection. In addition, because the first incident light beam is terahertz light, the terahertz light has good penetrability and can penetrate the inside of the test material, so that the test material can be tomographically imaged based on the reflected light signal to improve the three-dimensional image Resolution.

【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 polarizing component 102, a scanning device 103, and a receiver 104.

The non-diffraction device 101 is configured to converge the incident first light beam into a second light beam; the polarizing component 102 is disposed on the light-exiting side of the non-diffraction device 101 and is configured to output light of a predetermined polarization direction in the second light beam to the scanning device 103; The scanning device 103 is configured to scan the light of the preset polarization direction to the test material A in a scanning manner, and reflects the third light beam reflected by the test material A to the polarizing component 102; the polarizing component 102 is also used to change the third light beam. And the third beam after the polarization direction is changed is reflected to the receiver 104; the receiver 104 is disposed on the reflection side of the polarizing component 102, and is configured to receive the third beam reflected by the polarizing component 102, so that The information constructs a three-dimensional image of the inspected material A.

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 may be a composite material with high quality requirements, or other non-polar materials, etc., which is not specifically limited herein. The thickness of the tested material will affect the penetrability of the light beam and is generally not greater than 10 cm.

The polarization component 102 is a polarization component that integrates multiple functions of generating polarized light, changing the polarization direction of the light, and reflecting the polarized light after changing the polarization direction. The polarization direction of the generated polarization light is different from the polarization direction of the reflected polarization light. The polarizing component 102 may be a combination of independent components having one of the functions described above, such as a combination of a polarizer, a polarization beam splitter, and a quarter-wave plate, or a device integrating the above functions. Be specific.

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 center spot of the second beam is 0.3mm, controlling the scanning frequency (such as 2kHz) of the scanning device 103 can make the imaging time not longer than 5s. , The imaging resolution reaches 0.3mm * 0.3mm * 1.5mm, which can improve the speed of material detection and imaging accuracy.

The receiver 104 may include a detector and a signal processor, wherein the detector is disposed on the reflective side of the polarizing component 102 and can detect and receive a third light beam reflected by the polarizing component 102, and the signal processor can obtain the received third light beam Information in order to construct a three-dimensional image of the inspected material A.

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 has a preset polarization. The light in the direction passes through the polarizing element 102 and is incident on the scanning device 103. The scanning device 103 reflects the light beam with a preset polarization direction to the surface of the material A to be inspected, wherein the scanning device 103 can be moved, so that the The exit direction of the light beam with the preset polarization direction, and the movement direction and angle of the scanning device 103 (such as a three-dimensionally movable mirror) can be controlled so that the light beam with the preset polarization direction is reflected to the material A to be inspected in a scanning manner. surface. The light beam with the preset polarization direction is reflected and transmitted on the surface of the material A to be inspected, and the flatness, thickness, reflectance, and refractive index of the material at different positions of the material to be inspected A are different, and internal defects may be There are defects, etc., the beams of the preset polarization direction are absorbed or reflected to different degrees at different positions, so the information (phase and intensity information) in the third beam that is finally reflected back to the scanning device 103 can reflect the inspected material The structure of A. After the third light beam is reflected to the scanning device 103, it is reflected by the scanning device 103 to the polarizing component 102. The polarizing component 102 changes the polarization direction of the incident third light beam, and reflects the third light beam after changing the polarization direction. After the receiver 104 disposed on the reflective side of the polarizing component 102 receives the third beam using a detector, its signal processor can extract information in the third beam to obtain information such as phase and intensity in the third beam. , Can analyze and know the internal structure of the tested material A at each position, and then can form a three-dimensional image of the tested material A.

Compared with the existing complex visible light optical systems that require various devices such as collimation, diffusion, focusing, etc., in this embodiment, a non-diffractive device can be used to converge the incident first light beam into an approximately non-diffraction second light beam, while using polarized light. The component enables the polarized light with a preset polarization direction to be scanned to the material to be inspected, the optical system is simple, and the light beam with the preset polarization direction that is almost non-diffractive does not diverge and the light field energy during subsequent propagation and scanning to the material to be inspected The high concentration and small size of the central bright spot can make the 3D image of the inspected material constructed using the information of the third beam after scanning high resolution and improve the accuracy of material detection. At the same time, the polarizing component can make the scanning and subsequent propagation process The light signal is more pure and reduces the influence of the external environment light signal, which is conducive to improving 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.

Since the light waves in the terahertz band are not only highly permeable to most non-polar materials (polytetrafluoroethylene, single crystal silicon, ceramic sheets, cloth, paper), they can penetrate foam materials that cannot be penetrated by ultrasonic waves. Compared with ultrasound, it has a higher resolution, so the use of terahertz imaging technology can detect the internal structure of materials, which is especially suitable for tomography of non-polar materials. Moreover, the terahertz photon energy is low, and the photon energy at a frequency of 1THz is only about 4 millielectron volts, which is only one millionth of the energy carried by X-rays. It does not cause harmful ionization reactions and can achieve non-destructive testing of materials, especially Suitable for testing composite materials with high quality requirements and high manufacturing costs.

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, referring further to FIG. 2, the polarizing component 102 specifically includes a polarizer 1021, a polarization beam splitter 1022, and a quarter wave plate 1023.

The polarizer 1021 is disposed on the light-exiting side of the non-diffraction device 101, and is configured to output light of a predetermined polarization direction in the second beam to the polarization beam splitter 1022; the polarization beam splitter 1022 is disposed on the light output of the polarizer 1021. Side, for transmitting light with a predetermined polarization direction, and reflecting light with a polarization direction perpendicular to the predetermined polarization direction; a quarter-wave plate 1023 is provided on the light-emitting side of the polarization beam splitter 1022, and is used to pass twice through four The polarization direction of the light of the half-wave plate is rotated by 90 degrees.

The types of the polarizer 1021, the polarization beam splitter 1022, and the quarter wave plate 1023 are selected according to the working frequency band of the first light beam. For example, if the first beam works in the terahertz frequency band, the polarizer 1021, the polarization beam splitter 1022, and the quarter wave plate 1023 should all select a device that operates in the terahertz (THz) frequency band, that is, a THz polarizer. , THz polarizing beam splitter and quarter THz wave plate.

Specifically, in an application example, the transmitter 100 emits a first beam of 0.5 THz. After passing through the non-diffraction lens 102, the first beam is converged into a second beam that is approximately non-diffracted, and the second beam is elliptically polarized. Polarized light with a central spot diameter of 0.3mm. The second light beam is incident on the THz polarizer 1021 (such as a THz polarizer). Since the THz polarizer 1021 can only transmit light of a predetermined polarization direction, only the light of the predetermined polarization direction in the second light beam passes through the The THz polarizer 1021 reaches the THz polarization beam splitter 1022. Since the THz polarization beam splitter 1022 can transmit linearly polarized light with a preset polarization direction and reflect linearly polarized light with a polarization direction perpendicular to the preset polarization direction, the light of the preset polarization direction continues to pass through the THz polarization beam splitter. 1022 reaches the quarter THz wave plate 1023, and the light of the preset polarization direction directly passes through the quarter THz wave plate 1023 for the first time and enters the scanning device 103, and the scanning device 103 sets the preset polarization direction The light is reflected in a scanning manner on the surface of the material A to be inspected.

The test material A absorbs and reflects the light of the preset polarization direction, and forms a third beam to be reflected to the scanning device 103. Because the optical path is reversible and the speed of light is fast, and the scanning speed of the scanning device 103 is generally lower than the speed of light, the third The light beam is reflected back to the quarter THz wave plate 1023 in the reverse direction of the original optical path. Since the quarter THz wave plate 1023 rotates the polarization direction of the second passing light by 90 degrees, the polarization direction of the third light beam passing through the quarter THz wave plate 1023 is perpendicular to the incident preset polarization. Direction of light. When the third beam after the polarization direction changes continues to propagate to the THz polarization beam splitter 1022, the THz polarization beam splitter 1022 reflects the third beam. At this time, the The receiver 104 can detect and receive the third beam, and after processing the signal of the third beam, the information of the third beam can be obtained to construct the material A to be inspected based on the information (phase and intensity information) of the third beam. Three-dimensional image.

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 100 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, 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. 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 demodulator 10461 to perform the low-frequency signal. After demodulation, the A / D converter 10462 is used to convert the demodulated analog low-frequency signal to a digital signal, and then FPGA is used. 10463 collects data (such as phase and amplitude information) in the digital signal. Finally, the imaging circuit 10464 can use the collected data to analyze the internal structure of the material A to be inspected, and finally construct a three-dimensional image of the material A to be inspected. 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 non-diffractive device can be used to converge the incident first light beam into an approximately non-diffraction second light beam. At the same time, a polarizing component composed of a polarizer, a polarization beam splitter, and a quarter wave plate is used to make the The linearly polarized light with the polarization direction can be scanned to the material to be inspected. The optical system is simple, and the beam with the preset polarization direction that is almost non-diffractive does not diverge during the subsequent propagation and scanning to the material to be inspected. The small size of the central bright spot can make the 3D image of the inspected material constructed using the information of the third beam after scanning high resolution and improve the accuracy of material detection. At the same time, the polarizing component can make the optical signal during scanning and subsequent propagation more It is pure and reduces the influence of external ambient light signals, which is conducive to improving the accuracy of material detection. Besides, the strong penetrability and low photon energy of the terahertz band light beam can penetrate the material to be inspected with a high thickness without Damage to the tested material to achieve non-destructive testing.

In other embodiments, the scanning device of the three-dimensional tomography system may also use a plurality of movable galvanometers.

Specifically, 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 vibrating lens 1031 and a second vibrating lens 1032. The first vibrating lens 1031 is rotated in a first direction, and the second vibrating lens 1032 is rotated in a second direction perpendicular to the first direction, so that the second beam is scanned line by line or column by column. Tested 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.

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 a polarizing component to output light of a preset polarization direction in the second light beam to the scanning device;

S103: using a scanning device to scan the light of a preset polarization direction to the test material in a scanning manner, and reflect the third light beam reflected by the test material to the polarizing component;

S104: Use a polarizing component to change the polarization direction of the third beam, and reflect the changed third beam to the receiver;

S105: Use the receiver to receive the third light beam reflected by the polarizing component, so as to construct a three-dimensional image of the inspected material according to the information of the third light beam.

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: Use a polarizer to output light of a preset polarization direction in the second light beam to a polarization beam splitter.

S1022: using a polarization beam splitter and a quarter-wave plate to sequentially transmit the light of the preset polarization direction, and output the light of the preset polarization direction to the scanning device.

Optionally, step S103 specifically includes:

S1031: Control the scanning galvanometer to reflect the light of the preset polarization direction to the surface of the material to be inspected in a scanning manner.

S1032: Use the scanning galvanometer to reflect the third light beam reflected by the test material back to the quarter wave plate.

Optionally, step S104 specifically includes:

S1041: Use a quarter-wave plate to rotate the polarization direction of the third beam by 90 degrees, and then output the third beam to the polarization beam splitter.

S1042: Reflect the third light beam after the polarization direction is changed by using a polarization beam splitter.

Optionally, step S105 specifically includes:

S1051: Use a receiving antenna to receive the third light beam reflected by the polarization beam splitter;

S1052: using a modulator to modulate a low-frequency baseband signal generated by a baseband signal source onto a local oscillator signal;

S1053: 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.

S1054: Mix the frequency-multiplied signal with the received third beam signal by using a mixer to obtain a low-frequency signal.

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

S1055: Use the signal processing device to process the low-frequency signal to obtain phase and intensity information of the third 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.

In this embodiment, a non-diffractive device can be used to converge the incident first light beam into an approximately non-diffraction second light beam. At the same time, a polarizing component composed of a polarizer, a polarization beam splitter, and a quarter wave plate is used to make the The linearly polarized light with the polarization direction can be scanned to the material to be inspected. The optical system is simple, and the beam with the preset polarization direction that is almost non-diffractive does not diverge during the subsequent propagation and scanning to the material to be inspected. The small size of the central bright spot can make the 3D image of the inspected material constructed using the information of the third beam after scanning high resolution and improve the accuracy of material detection. At the same time, the polarizing component can make the optical signal during scanning and subsequent propagation more Purity, reducing the impact of external ambient light signals, is conducive to improving the accuracy of material detection.

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. Ranch

Claims

A three-dimensional tomography method, including:

Using a transmitter to emit a first light beam to a non-diffraction device, the first light beam is terahertz light;

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

Using a polarizing component to emit light of a preset polarization direction in the second light beam to a scanning device;

Using the scanning device to reflect the light of the preset polarization direction to the test material in a scanning manner, and to reflect a third light beam reflected by the test material to the polarizing component;

Using the polarizing component to change the polarization direction of the third light beam, and reflecting the third light beam after changing the polarization direction to the receiver;

Using a receiver to receive the third light beam reflected by the polarizing component to construct a three-dimensional image of the inspected material according to the information of the third light beam;

Wherein, the non-diffraction device is a non-diffraction lens, and the using the non-diffraction device to focus the incident first light beam into a second light beam includes:

The first incident light beam that is incident in parallel is collected into the second light beam by using the non-diffraction lens, wherein a depth of field of the second light beam is not less than 1.5m.
The method according to claim 1, wherein the polarizing component comprises: a polarizer, a polarization beam splitter, and a quarter wave plate;

The step of using a polarizing component to emit light of a preset polarization direction in the second light beam to a scanning device includes:

Using the polarizer to output light of a preset polarization direction in the second light beam to the polarization beam splitter;

Using the polarization beam splitter and the quarter-wave plate to sequentially transmit light in the preset polarization direction, so that the light in the preset polarization direction is emitted to the scanning device;

The changing the polarization direction of the third light beam by using the polarizing component and reflecting the changed third light beam to the receiver includes:

Rotating the polarization direction of the third light beam by 90 degrees using the quarter wave plate;

The polarization beam splitter is used to reflect the third light beam rotated in the polarization direction, so that the third light beam is reflected to the receiver.
A three-dimensional tomography system, which includes: a non-diffraction device, a polarizing component, a scanning device, and a receiver;

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

The polarizing component is disposed on a light emitting side of the non-diffraction device, and is configured to output light of a preset polarization direction in the second light beam to the scanning device;

The scanning device is configured to reflect the light of the preset polarization direction to the material under inspection in a scanning manner, and reflect a third light beam reflected by the material under inspection to the polarizing component;

The polarization component is further configured to change a polarization direction of the third light beam, and reflect the third light beam after the polarization direction is changed to the receiver;

The receiver is disposed on a reflective side of the polarizing component, and is configured to receive the third light beam reflected by the polarizing component to construct a three-dimensional image of the inspected material according to information of the third light beam.
The system of claim 3, wherein the system further comprises:

The transmitter is disposed on the 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 terahertz light having a frequency of not less than 0.5 THz.
The system according to claim 3, wherein the non-diffraction device is a non-diffraction lens for converging the first light beam incident in parallel into the second light beam, wherein the second The depth of field of the light beam is not less than 1.5m.
The system of claim 3, wherein the polarizing component comprises: a polarizer, a polarization beam splitter, and a quarter wave plate;

The polarizer is disposed on a light-exiting side of the non-diffraction device, and is configured to output light of a preset polarization direction in the second light beam to the polarization beam splitter;

The polarization beam splitter is disposed on a light exit side of the polarizer, and is configured to transmit light of the preset polarization direction and reflect light having a polarization direction perpendicular to the preset polarization direction;

The quarter wave plate is disposed on a light exit side of the polarization beam splitter, and is configured to rotate a polarization direction of light passing through the quarter wave plate twice by 90 degrees.
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 for modulating the local oscillator signal and the baseband signal and inputting the signal Frequency doubling 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, the first light beam being terahertz light;

Using a polarizing component to emit light of a preset polarization direction in the second light beam to a scanning device;

Using the scanning device to reflect the light of the preset polarization direction to the test material in a scanning manner, and to reflect a third light beam reflected by the test material to the polarizing component;

Using the polarizing component to change the polarization direction of the third light beam, and reflecting the changed third light beam to the receiver;

The receiver receives the third light beam reflected by the polarizing component to construct a three-dimensional image of the inspected material according to the information of the third light beam.
The 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, further 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 method according to claim 12, wherein the non-diffraction device is a non-diffraction lens, and the using the non-diffraction device to focus the 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 a depth of field of the second light beam is not less than 1.5m.
The method according to claim 12, wherein the polarizing component comprises: a polarizer, a polarization beam splitter, and a quarter wave plate;

The step of using a polarizing component to emit light of a preset polarization direction in the second light beam to a scanning device includes:

Using the polarizer to output light of a preset polarization direction in the second light beam to the polarization beam splitter;

Using the polarization beam splitter and the quarter-wave plate to sequentially transmit light in the preset polarization direction, so that the light in the preset polarization direction is emitted to the scanning device;

The changing the polarization direction of the third light beam by using the polarizing component and reflecting the changed third light beam to the receiver includes:

Rotating the polarization direction of the third light beam by 90 degrees using the quarter wave plate;

The polarization beam splitter is used to reflect the third light beam rotated in the polarization direction, so that the third light beam is reflected to the receiver.
The 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 the scanning device to reflect the light of the preset polarization direction in a scanning manner to the test material and reflect the third light beam reflected by the test material to the polarization component 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, so that the light of the preset polarization direction is scanned line by line or column by column The inspected material;

Using the first vibrating lens and the second vibrating lens to reflect the third light beam reflected by the test material back to the polarizing component.
The method according to claim 13, wherein the transmitter comprises: a signal source, a first frequency multiplier, and a transmitting antenna;

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 having a frequency lower than 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 method according to claim 17, wherein the receiver comprises: a receiving antenna, a baseband signal source, a modulator, a second frequency doubler, a mixer, and a signal processing device;

The step of using the receiver to receive the third light beam reflected by the polarizing component to construct a three-dimensional image of the inspected material according to information of the third light beam includes:

Using the receiving antenna to receive the third light beam reflected by the polarization beam splitter;

Using the modulator to modulate a low-frequency baseband signal generated by the baseband signal source onto the local oscillator signal, where the frequency of the baseband signal is less than the frequency of the local oscillator signal;

Frequency-modulating the modulated signal by using the second frequency multiplier, where the number of frequency multiplications of the second frequency multiplier is the same as that of the first frequency multiplier;

Using the mixer to mix a frequency-multiplied signal with a 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 method according to claim 18, 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 processing the low-frequency signal by using the signal processing device to obtain information of the third light beam for imaging 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 method according to claim 12, wherein the information of the third light beam includes a phase and an intensity of the third light beam.