Terahertz imaging system

Abstract

The present application relates to the field of physical optics technology, and more specifically, to a terahertz imaging system. The terahertz imaging system comprises a first signal generating device, a second signal generating device and an imaging device. The first signal generating device is used to generate a coded laser and project it to the second signal generating device. The second signal generating device is used to generate an initial terahertz wave with a spatially coded intensity distribution under the excitation of the coded laser, and project it to a target sample to obtain a target terahertz wave, and project it to the imaging device, the target terahertz wave carrying the spatial information of the target sample in the terahertz wave frequency band. The imaging device is used to obtain a sample image of the target sample according to the target terahertz wave. The terahertz imaging system provided in the embodiment of the present application can simultaneously ensure that the sample image has a high super-diffraction resolution and signal-to-noise ratio.

Description

Technical Field

[0001] The present application relates to the technical field of physical optics, and in particular to a terahertz imaging system. Background Art

[0002] Terahertz waves refer to electromagnetic waves with frequencies ranging from 0.1THz to 10THz and wavelengths ranging from 0.03mm to 3mm. Because its photons have many superior properties such as low energy, fingerprint spectrum, and high transmittance, they have great application value in physics, chemistry, biology, etc. However, the spatial resolution of traditional imaging technology is limited by the diffraction limit and is usually difficult to break through the millimeter level. Therefore, it also greatly limits the imaging application of terahertz waves in the microscopic world. Usually, to achieve super-resolution imaging of the target sample, it is necessary to sense the evanescent wave of the target sample in the near field.

[0003] Taking the non-scanning super-resolution terahertz microscope in the prior art as an example, the microscope uses a terahertz spatial modulator to partially modulate the terahertz spot according to a preset mask, thereby realizing spatial encoding of a uniform terahertz beam. However, the terahertz spatial modulator only has photoconductor materials or phase change thin film materials. The former is usually a bulk material and cannot guarantee a sufficiently close perception distance. Its spatial resolution is constrained to more than 0.01 mm, which greatly reduces the super-diffraction resolution of the image. The latter is a nano-thin film material. Although it guarantees a sufficiently close perception distance, its terahertz modulation depth is less than 50%, which greatly reduces the signal-to-noise ratio of the image. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a terahertz imaging system to solve the technical problem in the prior art that a non-scanning super-resolution terahertz microscope cannot simultaneously ensure that the sample image has a high super-diffraction resolution and a signal-to-noise ratio.

[0005] The terahertz imaging system provided in the embodiment of the present application includes a first signal generating device, a second signal generating device and an imaging device;

[0006] The first signal generating device is used to generate coded laser light and project it to the second signal generating device;

[0007] The second signal generating device is used to generate an initial terahertz wave with a spatially coded intensity distribution under the excitation of the coded laser, and project it to the target sample to obtain a target terahertz wave, and project it to the imaging device. The target terahertz wave carries the spatial information of the target sample in the terahertz wave frequency band;

[0008] The imaging device is used to obtain a sample image of a target sample according to the target terahertz wave.

[0009] In the embodiment of the present application, the terahertz imaging system includes a first signal generating device, a second signal generating device and an imaging device. The first signal generating device generates a coded laser and projects it to the second signal generating device. Under the excitation of the coded laser, the second signal generating device generates an initial terahertz wave with a spatially coded intensity distribution and projects it to the target sample to obtain a target terahertz wave, which is then projected to the imaging device. The target terahertz wave carries the spatial information of the target sample in the terahertz wave frequency band. In this way, the imaging device can obtain a sample image of the target sample according to the target terahertz wave, and can simultaneously ensure that the sample image has a high super-diffraction resolution and signal-to-noise ratio.

[0010] In combination with the above-mentioned terahertz imaging system, the embodiment of the present application further provides a first optional implementation of the terahertz imaging system, wherein the first signal generating device includes a laser generator and a spatial light modulator;

[0011] The laser generator is used to generate original laser light and project it to the spatial light modulator;

[0012] The spatial light modulator is used to spatially encode the original laser to obtain coded laser.

[0013] In the embodiment of the present application, the first signal generating device includes a laser generator and a spatial light modulator. The laser generator generates original laser light and projects it to the spatial light modulator, and then the spatial light modulator performs spatial encoding on the original laser light to obtain coded laser light. Therefore, based on the simple structural composition of the first signal generating device, the coded laser light generation process is simple and highly controlled.

[0014] In combination with the above terahertz imaging system or the first optional implementation of the above terahertz imaging system, the embodiment of the present application further provides a second optional implementation of the terahertz imaging system, wherein the first signal generating device further includes a first focuser;

[0015] The first focuser is used to focus the coded laser according to a first preset magnification, and project the focused coded laser to the second signal generating device.

[0016] In the embodiment of the present application, the first signal generating device further includes a first focuser, which is used to focus the coded laser at a first preset magnification and project the focused coded laser to the second signal generating device. Since the first preset magnification can be set according to actual needs, that is, the first focuser can be selected according to actual needs, thus enhancing the controllability and application range of the terahertz imaging system.

[0017] In combination with the above-mentioned terahertz imaging system, the embodiment of the present application further provides a third optional implementation of the terahertz imaging system, wherein the second signal generating device includes a terahertz wave generator and a magnetic field generator;

[0018] The terahertz wave generator is used to form a spin current with the same spatial distribution as the coded laser under the excitation of the coded laser;

[0019] The magnetic field generator is used to generate a static magnetic field at the setting position of the terahertz wave generator, so that the spin current is converted into a conduction current under the excitation of the static magnetic field, thereby generating an initial terahertz wave with a spatially encoded intensity distribution, and projecting it to the target sample to obtain the target terahertz wave, and projecting it to the imaging device.

[0020] In the embodiment of the present application, the second signal generating device includes a terahertz wave generator and a magnetic field generator. The terahertz wave generator is used to form a spin current with the same spatial distribution as the coded laser under the excitation of the coded laser. The magnetic field generator is used to generate a static magnetic field at the setting position of the terahertz wave generator, so that the spin current is converted into a conduction current under the excitation of the static magnetic field, thereby generating an initial terahertz wave with a spatially coded intensity distribution, and projecting it to the target sample to obtain a target terahertz wave, and projecting it to the imaging device. Therefore, based on the simple structural composition of the second signal generating device, the generation process of the target terahertz wave is simple and highly controlled.

[0021] In combination with the third optional implementation of the terahertz imaging system described above, the embodiment of the present application further provides a fourth optional implementation of the terahertz imaging system, wherein the second signal generating device further includes an azimuth adjustment device;

[0022] The azimuth adjustment device is used to set the magnetic field generator so that the magnetic field generator can change its azimuth orientation under the action of the azimuth adjustment device to change the magnetic field direction of the static magnetic field, thereby changing the polarization state of the initial terahertz wave.

[0023] In the embodiment of the present application, the second signal generating device further includes an azimuth adjustment device. The azimuth adjustment device is used to set the magnetic field generator so that the magnetic field generator can change its azimuth orientation under the action of the azimuth adjustment device to change the magnetic field direction of the static magnetic field, thereby changing the polarization state of the initial terahertz wave, so as to further improve the image quality of the sample image.

[0024] In combination with the fourth optional implementation of the terahertz imaging system described above, the embodiment of the present application further provides a fifth optional implementation of the terahertz imaging system: the azimuth adjustment device includes a rotating frame;

[0025] The rotating frame is in a ring structure, the terahertz wave generator is arranged at the center of the rotating frame, and the magnetic field generator is arranged on the rotating frame.

[0026] In the embodiment of the present application, the azimuth adjustment device includes a rotating frame. The rotating frame is annular in structure, the terahertz wave generator is arranged at the center of the rotating frame, and the magnetic field generator is arranged on the rotating frame. Therefore, the entire azimuth adjustment device has a simple structure, which effectively reduces the design cost of the terahertz imaging system.

[0027] In combination with the fifth optional implementation of the terahertz imaging system described above, the embodiment of the present application further provides a sixth optional implementation of the terahertz imaging system: the magnetic field generator includes a first magnetic member and a second magnetic member;

[0028] The first magnetic component and the second magnetic component are both arranged on the rotating frame, and the N pole of the first magnetic component is opposite to the S pole of the second magnetic component.

[0029] In the embodiment of the present application, the magnetic field generator includes a first magnetic member and a second magnetic member. The first magnetic member and the second magnetic member are both arranged on a rotating frame, and the N pole of the first magnetic member is opposite to the S pole of the second magnetic member. Therefore, the entire magnetic field generator has a simple structure, which effectively reduces the design cost of the terahertz imaging system.

[0030] In combination with the above-mentioned terahertz imaging system, the embodiment of the present application further provides a seventh optional implementation of the terahertz imaging system, wherein the imaging device includes a terahertz detector and a processor;

[0031] The terahertz detector is used to detect the target terahertz wave to obtain the intensity information of the target terahertz and send it to the processor;

[0032] The processor is used to obtain a sample image of the target sample according to the intensity information.

[0033] In the embodiment of the present application, the imaging device includes a terahertz detector and a processor. The terahertz detector is used to detect the target terahertz wave to obtain the intensity information of the target terahertz and send it to the processor. The processor is used to obtain a sample image of the target sample based on the intensity information. Based on the simple structural composition of the imaging device, the process of obtaining the sample image is simple and highly controlled.

[0034] In combination with the seventh optional implementation of the terahertz imaging system described above, the embodiment of the present application further provides an eighth optional implementation of the terahertz imaging system, wherein the second signal generating device further includes a second focuser;

[0035] The second focuser is used to focus the target terahertz wave according to a second preset magnification, and project the focused target terahertz wave to the terahertz detector.

[0036] In the embodiment of the present application, the second signal generating device further includes a second focuser. The second focuser is used to focus the target terahertz wave according to the second preset magnification, and project the focused target terahertz wave to the terahertz detector, thereby further improving the signal-to-noise ratio of the sample image. Since the second preset magnification can be set according to actual needs, that is, the second focuser can be selected according to actual needs to further enhance the controllability and application range of the terahertz imaging system.

[0037] In combination with the above-mentioned terahertz imaging system, the embodiment of the present application further provides a ninth optional implementation of the terahertz imaging system, wherein the terahertz imaging system further includes a display device;

[0038] The display device is used to connect with the imaging device to acquire and display the sample image.

[0039] In an embodiment of the present application, the terahertz imaging system further includes a display device, which is used to connect to the imaging device to acquire and display a sample image, so that an operator can observe the acquired sample image. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 A schematic diagram of the structure of a terahertz imaging system provided in an embodiment of the present application.

[0042] Figure 2 Another structural schematic diagram of the terahertz imaging system provided in an embodiment of the present application.

[0043] Figure 3 This is an auxiliary illustration of the working principle of a second signal generating device provided in an embodiment of the present application.

[0044] Figure 4 A schematic diagram of a single-pixel imaging process of a sample image of a target sample provided in an embodiment of the present application.

[0045] Figure 5 This is a diagram to assist in explaining the working principle of an imaging device provided in an embodiment of the present application.

[0046] Figure 6 Another structural schematic diagram of the terahertz imaging system provided in an embodiment of the present application.

[0047] Icon: 10- terahertz imaging system; 100- first signal generating device; 110- laser generator; 120- spatial light modulator; 130- first focuser; 200- second signal generating device; 210- terahertz wave generator; 220- magnetic field generator; 221- first magnetic member; 222- second magnetic member; 230- azimuth adjustment device; 231- rotating frame; 240- second focuser; 300- imaging device; 310- terahertz detector; 320- processor; 400- display device; 20- target sample. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0049] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0050] See also Figure 1 An embodiment of the present application provides a terahertz imaging system 10 , including a first signal generating device 100 , a second signal generating device 200 and an imaging device 300 .

[0051] The first signal generating device 100 is used to generate a coded laser and project it to the second signal generating device 200. The second signal generating device 200 is used to generate an initial terahertz wave with a spatially coded intensity distribution under the excitation of the coded laser, and project it to the target sample to obtain a target terahertz wave, and then project it to the imaging device 300. The target terahertz wave carries the spatial information of the target sample in the terahertz wave frequency band. The imaging device 300 is used to obtain a sample image of the target sample according to the target terahertz wave, and can simultaneously ensure that the sample image has a high super-diffraction resolution and signal-to-noise ratio.

[0052] Please combine Figure 2 In an embodiment of the present application, the first signal generating device 100 may include a laser generator 110 and a spatial light modulator 120 .

[0053] The laser generator 110 may be, but is not limited to, a solid laser, a gas laser, a liquid laser or a semiconductor laser, which is used to generate an original laser and project it to the spatial light modulator 120. The spatial light modulator 120 is used to spatially encode the original laser to obtain an encoded laser, that is, a light intensity distribution with spatial encoding. In the embodiment of the present application, the spatial light modulator may be, but is not limited to, an amplitude-type spatial light modulator, a digital micromirror array spatial light modulator, or a phase-type liquid crystal spatial light modulator.

[0054] In addition, in the embodiment of the present application, the first signal generating device 100 may further include a first focuser 130. The first focuser 130 is disposed between the spatial light modulator 120 and the second signal generating device 200, and is used to focus the coded laser at a first preset magnification, so that the focused coded laser is projected to the second signal generating device 200, thereby improving the clarity of the image formed by the coded laser. The first focuser 130 may include a first convex lens, and in actual implementation, the central thickness, radius of curvature and other property parameters of the first convex lens may be set according to actual needs, that is, in actual implementation, the first preset magnification may be set according to actual needs, and the embodiment of the present application does not impose specific restrictions on this, so as to enhance the controllability and application scope of the terahertz imaging system.

[0055] In the embodiment of the present application, the second signal generating device 200 may include a terahertz wave generator 210 and a magnetic field generator 220 .

[0056] The terahertz wave generator 210 may be a spin terahertz wave transmitter, which is used to form a spin current with the same spatial distribution as the coded laser under the excitation of the coded laser. The magnetic field generator 220 is used to generate a static magnetic field at the location where the terahertz wave generator 210 is set, so that the spin current is converted into a conduction current under the excitation of the static magnetic field, thereby generating an initial terahertz wave with a spatially coded intensity distribution, and projecting it to the target sample 20 to obtain a target terahertz wave, and then projecting it to the imaging device 300.

[0057] It should be noted that, in actual implementation, the target sample 20 needs to be closely attached to the side of the terahertz wave generator 210 away from the first signal generating device 100 . It can also be understood that the distance between the target sample 20 and the terahertz wave generator 210 needs to be less than 1 um.

[0058] The following will be combined Figure 3 , taking the terahertz wave generator 210 as a spin terahertz wave transmitter as an example, the working principle of the second signal generating device 200 is described.

[0059] The spin terahertz wave emitter is a heterojunction including a ferromagnetic (FM) layer and a nonferromagnetic (NM) layer, and its thickness is generally 5nm to 10nm. Under the excitation of the coded laser, a spin current will be formed in the heterojunction flowing from the FM layer to the NM layer. When there is no external static magnetic field, the probability of electron spin up and spin down in the FM layer is equal, and the conduction current cannot be stimulated in the NM layer. Under the action of an external static magnetic field, the electron spin in the FM layer will be polarized in the direction of the static magnetic field, and the polarized spin current can stimulate the conduction current propagating along the surface in the NM layer. The relationship is:

[0060] j c =γj s ×B / |B|

[0061] Wherein, jc is the conduction current, γ is the spin Hall angle of the NM layer, js is the spin current, B is the magnetic field strength of the static magnetic field, and |B| is the modulus of the magnetic field strength of the static magnetic field.

[0062] Since the conduction current will radiate linearly polarized electromagnetic waves outward, and the spin current formed by the spin terahertz wave emitter excited by the femtosecond laser, under the excitation of the static magnetic field, the radiated electromagnetic waves fall exactly in the terahertz frequency band, that is, in the embodiment of the present application, when the coded laser is a femtosecond laser, the initial terahertz wave can be generated. In addition, it can be seen from the above formula that the direction of the conduction current must be perpendicular to the static magnetic field, so in the embodiment of the present application, the polarization direction of the initial terahertz wave must also be perpendicular to the direction of the static magnetic field.

[0063] Since the thickness of the spin terahertz wave emitter is very thin, as mentioned above, it is generally 5nm to 10nm. Therefore, it can ensure a sufficiently close perception distance, that is, it can ensure that the sample image has a high super-diffraction resolution. At the same time, because the spin terahertz wave emitter has a very high terahertz wave emission efficiency under the action of an external static magnetic field, for example, when the intensity of the coded laser is the same, it has a comparable terahertz wave emission efficiency to that of pulsed terahertz generators such as zinc telluride ZnTe crystals and photoconductive antennas (PCA). Therefore, it can ensure that the sample image has a high signal-to-noise ratio.

[0064] In addition, in the embodiment of the present application, the second signal generating device 200 may further include an azimuth adjustment device 230, which is used to set the magnetic field generator 220 so that the magnetic field generator 220 can change its azimuth orientation under the action of the azimuth adjustment device 230, thereby changing the magnetic field direction of the static magnetic field, and ultimately changing the polarization state of the initial terahertz wave.

[0065] As an optional implementation, the azimuth adjustment device 230 includes a rotating frame 231. The rotating frame 231 is an annular structure, for example, a circular ring structure, and the plane where the rotating frame 231 is located is perpendicular to the optical axis direction of the coded laser, and the terahertz wave generator 210 is arranged at the center of the rotating frame 231, that is, the center of the terahertz wave generator 210 coincides with the center of the rotating frame 231, and the magnetic field generator 220 is arranged on the rotating frame 231.

[0066] In addition, in the embodiment of the present application, the magnetic field generator 220 may include a first magnetic member 221 and a second magnetic member 222. The first magnetic member 221 and the second magnetic member 222 are both disposed on the rotating frame 231, and the N pole of the first magnetic member 221 is opposite to the S pole of the second magnetic member 222. In the embodiment of the present application, the first magnetic member 221 and the second magnetic member 222 may be both permanent magnets or both electromagnets. When the first magnetic member 221 and the second magnetic member 222 are both electromagnets, the magnitude of the magnetic field may be controlled by the magnitude of the current of the energized coil, and the direction of the magnetic field may be controlled by the direction of the current of the energized coil. Therefore, the controllability is stronger.

[0067] In the embodiment of the present application, the imaging device 300 may include a terahertz detector 310 and a processor 320 .

[0068] The terahertz detector 310 is used to detect the target terahertz wave to obtain the intensity information of the target terahertz and send it to the processor 320. The processor 320 is used to obtain a sample image of the target sample 20 according to the intensity information. In addition, the processor 320 can also be connected to the spatial light modulator 120 to control the working state of the spatial light modulator 120. In the embodiment of the present application, the processor 320 can be an integrated circuit chip with signal processing capabilities. The processor 320 can also be a general-purpose processor, for example, it can be a digital signal processor (Digital Signal Processor, DSP), an application-specific integrated circuit (Application Specific Integrated Circuit, ASIC), a discrete gate or transistor logic device, a discrete hardware component, and can implement or execute the various logic block diagrams disclosed in the embodiment of the present application, and the general-purpose processor can be a microprocessor or any conventional processor, etc.

[0069] In addition, the terahertz detector 310 has a small size feature (the radius of the detection surface is usually less than 1 mm), and the target terahertz wave has a large divergence ability in free space. Based on this, in the embodiment of the present application, the second signal generating device 200 may also include a second focuser 240. The second focuser 240 is used to focus the target terahertz wave according to the second preset magnification, and project the focused target terahertz wave to the terahertz detector 310, thereby improving the signal-to-noise ratio of the sample image. The second focuser 240 may be a second convex lens, and in actual implementation, the property parameters such as the center thickness and curvature radius of the second convex lens may be set according to actual needs, that is, in actual implementation, the second preset magnification may be set according to actual needs, and the embodiment of the present application does not impose specific restrictions on this, so as to further enhance the controllability and application scope of the terahertz imaging system.

[0070] The following will describe the working principle of the imaging device 300. It should be noted that in the embodiment of the present application, the imaging method used may be single-pixel imaging (SPI), also known as ghost imaging (GI).

[0071] First, in the embodiment of the present application, the second signal generating device 200, under the excitation of the coded laser, will generate a sequence of initial terahertz waves having the same spatial coded intensity distribution as the coded laser according to the coding timing of the coded laser, and the spatial coded intensity distribution is generated under the guidance of the preset measurement matrix set in the spatial light modulator 120, and the preset measurement matrix set includes a plurality of measurement matrices for forming a mask. Therefore, it can be understood that in the embodiment of the present application, the plurality of measurement matrices included in the preset measurement matrix set and the plurality of groups of initial terahertz waves included in the aforementioned sequence of initial terahertz waves have a one-to-one correspondence. After the initial terahertz wave is projected onto the target sample 20, the target terahertz wave obtained will be projected onto the terahertz detector 310. Therefore, it can be understood that after the aforementioned sequence of initial terahertz waves is projected onto the target sample 20, the target terahertz waves obtained are recorded one by one on the coding timing to form a target matrix as the intensity information of the target terahertz, and sent to the processor 320. Thereafter, the processor 320 may obtain a sample image of the target sample 20 according to the intensity information of the target terahertz.

[0072] by Figure 4 As an example, a schematic diagram of a single pixel imaging process of a sample image corresponding to a target sample 20 provided in an embodiment of the present application is provided. After any group of initial terahertz waves in the above sequence of initial terahertz waves is emitted by the second signal generating device 200 (including a terahertz wave generator 210 and a magnetic field generator 220) and projected onto the target sample, a target terahertz wave is obtained and projected onto the terahertz detector 310, which is recorded in the form of a vector by the terahertz detector 310.

[0073] Based on the above description, in the embodiment of the present application, after any group of initial terahertz waves in the above sequence of initial terahertz waves is emitted and projected onto the target sample 20, the sample image formed by the target terahertz waves obtained can be pixelated into an L*L matrix, denoted as Om, and all elements included in the matrix Om can be rearranged into an N×1 vector O, where N=L*L, that is, in the above sequence of initial terahertz waves, the i-th group of initial terahertz waves can be pixelated into an L*L matrix, denoted as φ m，i , the matrix φ m，i All elements included in can be rearranged into an N×1 vector φ iThen, the terahertz detector 310 projects the i-th group of initial terahertz waves to the target sample 20, and detects the obtained target terahertz waves, and can obtain the intensity information y of the target terahertz waves i , and the intensity information y i It can be expressed as vector O and vector φ i The inner product of:

[0074] y i =<φ i ,0>

[0075] Please combine Figure 5 Based on the single-pixel imaging process of the sample image, the terahertz detector 310 projects the above sequence of initial terahertz waves to the target sample 20, and the obtained sequence of target terahertz waves is detected in sequence. The sum of the intensity information of the obtained target terahertz waves can be expressed as:

[0076]

[0077] In this way, we can use the inverse matrix Φ of the observation matrix -1 The sample image of the target sample 20 is calculated. The specific calculation logic may be:

[0078] X=Φ -1 ×Y=Φ -1 ×(Φ×0)0

[0079] Please combine Figure 6 In the embodiment of the present application, the terahertz imaging system 10 may further include a display device 400, which is used to be connected to the imaging device 300, specifically connected to the processor 320, to obtain and display the sample image.

[0080] The following is an overall description of the workflow of the terahertz imaging system provided in the embodiments of the present application.

[0081] In the process of imaging the target sample 20 by the terahertz imaging system 10 provided in the embodiment of the present application, the laser generator 110 generates an original laser and projects it to the spatial light modulator 120. The spatial light modulator 120 spatially encodes the original laser to obtain an encoded laser. The encoded laser is expanded by the first focuser 130 and then projected to the terahertz wave generator 210. The terahertz wave generator 210 forms a spin current with the same spatial distribution as the encoded laser under the excitation of the encoded laser. At the same time, the magnetic field generator 220 generates a static magnetoelectric field at the setting position of the terahertz wave generator 210. field, so that the spin current is converted into a conduction current under the excitation of the static magnetic field, thereby generating an initial terahertz wave with a spatially encoded intensity distribution, and projecting it to the target sample 20, so as to obtain a target terahertz wave carrying the spatial information of the target sample 20 in the terahertz wave frequency band. The target terahertz wave is focused by the second focuser 240 and then projected to the terahertz detector 310, so that the terahertz detector 310 detects the target terahertz wave, obtains the intensity information of the target terahertz, and sends it to the processor 320. Finally, the processor 320 obtains a sample image of the target sample 20 according to the intensity information.

[0082] In the above process, the azimuth adjustment device can be adjusted, that is, the azimuth orientation of the magnetic field generator 220 can be changed by rotating the rotating frame 231 to change the magnetic field direction of the static magnetic field, thereby changing the polarization state of the initial terahertz wave, and finally achieving the purpose of further improving the signal-to-noise ratio of the target sample 20 image and further improving the image quality of the target sample 20.

[0083] In summary, in the embodiment of the present application, the terahertz imaging system 10 includes a first signal generating device 100, a second signal generating device 200 and an imaging device 300. The first signal generating device 100 generates a coded laser and projects it to the second signal generating device 200. Under the excitation of the coded laser, the second signal generating device 200 generates an initial terahertz wave with a spatially coded intensity distribution and projects it to the target sample to obtain a target terahertz wave, which is then projected to the imaging device 300. The target terahertz wave carries the spatial information of the target sample in the terahertz wave frequency band. In this way, the imaging device 300 can obtain a sample image of the target sample according to the target terahertz wave, and can simultaneously ensure that the sample image has a high super-diffraction resolution and signal-to-noise ratio.

[0084] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connection" and "setting" should be understood in a broad sense. For example, it can be a mechanical fixed connection, a detachable connection or an integral connection. It can be an electrical connection or a communication connection. The communication connection can be a wired communication connection or a wireless communication connection. In addition, it can be a direct connection, an indirect connection through an intermediate medium, or a connection between two elements. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0085] In addition, in the description of the present application, the terms “first”, “second”, etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0086] The above description is only a partial embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A terahertz imaging system, characterized in that: It includes a first signal generating device, a second signal generating device and an imaging device; The first signal generating device is used to generate coded laser light and project it to the second signal generating device; The second signal generating device is used to generate an initial terahertz wave with a spatially coded intensity distribution under the excitation of the coded laser, and project it to the target sample to obtain a target terahertz wave, which is projected to the imaging device. The target terahertz wave carries the spatial information of the target sample in the terahertz wave frequency band; The imaging device is used to obtain a sample image of the target sample according to the target terahertz wave; Wherein, the first signal generating device includes a laser generator and a spatial light modulator; The laser generator is used to generate original laser light and project it to the spatial light modulator; The spatial light modulator is used to perform spatial encoding on the original laser to obtain encoded laser; Wherein, the first signal generating device further comprises a first focuser; The first focuser is used to focus the coded laser according to a first preset magnification, and project the focused coded laser to the second signal generating device; Wherein, the second signal generating device includes a terahertz wave generator and a magnetic field generator; The terahertz wave generator is used to form a spin current with the same spatial distribution as the coded laser under the excitation of the coded laser; The magnetic field generator is used to generate a static magnetic field at the location where the terahertz wave generator is set, so that the spin current is converted into a conduction current under the excitation of the static magnetic field, thereby generating an initial terahertz wave with a spatially encoded intensity distribution, and projecting it to a target sample to obtain the target terahertz wave, and projecting it to the imaging device; Wherein, the second signal generating device further comprises an azimuth adjustment device; The azimuth adjustment device is used to set the magnetic field generator so that the magnetic field generator can change its azimuth orientation under the action of the azimuth adjustment device to change the magnetic field direction of the static magnetic field, thereby changing the polarization state of the initial terahertz wave.

2. The terahertz imaging system according to claim 1, characterized in that: The azimuth adjustment device comprises a rotating frame; The rotating frame is in a ring structure, the terahertz wave generator is arranged at the center of the rotating frame, and the magnetic field generator is arranged on the rotating frame.

3. The terahertz imaging system according to claim 2, characterized in that: The magnetic field generator includes a first magnetic member and a second magnetic member; The first magnetic member and the second magnetic member are both disposed on the rotating frame, and the N pole of the first magnetic member is opposite to the S pole of the second magnetic member.

4. The terahertz imaging system according to claim 1, characterized in that: The imaging device includes a terahertz detector and a processor; The terahertz detector is used to detect the target terahertz wave to obtain the intensity information of the target terahertz and send it to the processor; The processor is used to obtain a sample image of the target sample according to the intensity information.

5. The terahertz imaging system according to claim 4, characterized in that: The second signal generating device further comprises a second focuser; The second focuser is used to focus the target terahertz wave according to a second preset magnification, and project the focused target terahertz wave to the terahertz detector.

6. The terahertz imaging system according to claim 1, characterized in that: The terahertz imaging system also includes a display device; The display device is used to be connected to the imaging device to acquire and display the sample image.

Images