A multi-modal terahertz wave imaging system and imaging method

Abstract

The present application relates to the technical field of optical imaging, and more particularly to a multi-mode terahertz wave imaging system and imaging method, the system comprising a light source module, a mode conversion module, first and second power feedback modules, and a multi-mode imaging module; the mode conversion module is used to convert the light source emitted by the light source module into light sources of different modes, which are then emitted to the multi-mode imaging module for imaging; the first and second power feedback modules are respectively used to capture the light beam energy information of the light source module and the multi-mode imaging module. The method comprises: selecting a light source and an imaging light path; when the selected light source comprises a collimated emitted terahertz wave laser source, the first power feedback module is used to obtain the first power, the second power feedback module is used to obtain the second power, and then normalization is performed; and when the selected light source does not comprise a collimated emitted terahertz wave laser source, the second power feedback module is used to obtain the second power. The present application can achieve wide spectrum coverage, can also perform multi-mode fast switching, and can achieve stable imaging.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and more specifically, to a multimodal terahertz wave imaging system and imaging method. Background Technology

[0002] Terahertz waves, as an electromagnetic wave frequency band between microwaves and infrared, have shown significant application value in fields such as biomedical imaging, non-destructive testing, materials characterization, and safety screening due to their characteristics such as low photon energy, strong penetration into non-polar materials, and fingerprint spectrum recognition capabilities. However, traditional terahertz imaging systems are limited by low optical power, narrow spectral coverage of single-wavelength light sources, mode monotony due to fixed optical path configurations, and poor signal stability caused by environmental disturbances, making it difficult to meet the detection requirements of high resolution and multi-dimensional information fusion in complex scenarios. Currently, terahertz light sources mostly rely on broadband radiation sources, resulting in insufficient spectral flexibility and adaptability of the system. Furthermore, terahertz waves are susceptible to environmental vibrations and fluctuations in light source power during transmission, leading to imaging distortion. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technology systems that are prone to imaging distortion, and to provide a multimodal terahertz wave imaging system and method that can achieve wide spectral coverage, perform rapid switching between multiple modes, and achieve stable imaging.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A multimodal terahertz wave imaging system is provided, comprising a light source module, a mode conversion module, a first power feedback module, a second power feedback module, and a multimodal imaging module. The mode conversion module is used to convert the light emitted by the light source module into light sources of different modes, which are then emitted to the multimodal imaging module for imaging. The first power feedback module is used to capture the beam energy information of the light source module, and the second power feedback module is used to capture the beam energy information of the multimodal imaging module during imaging. The multimodal imaging module includes a confocal transmission scanning imaging optical path, a confocal reflection scanning imaging optical path, a reflection micro-area scanning imaging optical path, and a focal plane scanning imaging optical path.

[0005] The present invention discloses a multimodal terahertz wave imaging system. A mode conversion module is used to convert the light emitted by the light source module into light sources of different modes, which are then emitted to the multimodal imaging module for imaging. A first power feedback module is used to capture the beam energy information of the light source module, and a second power feedback module is used to capture the beam energy information of the multimodal imaging module during imaging. The configuration of a confocal transmission scanning imaging optical path, a confocal reflection scanning imaging optical path, a reflection micro-area scanning imaging optical path, and a focal plane scanning imaging optical path enables wide-spectrum coverage and meets various scanning imaging requirements, achieving stable imaging.

[0006] Preferably, the confocal transmission scanning imaging optical path includes a first multi-axis displacement stage, and further includes a third off-axis parabolic mirror and a fourth off-axis parabolic mirror located on opposite sides of the first multi-axis displacement stage; the focal points of the third off-axis parabolic mirror and the fourth off-axis parabolic mirror are both located within the scanning working plane of the first multi-axis displacement stage; and the distance between the third off-axis parabolic mirror and the fourth off-axis parabolic mirror is equal to the sum of the reflection focal lengths of the third off-axis parabolic mirror and the fourth off-axis parabolic mirror; it also includes a fifth off-axis parabolic mirror and a first pinhole. An aperture stop; the light source module emits a light beam, which is collimated into the confocal transmission scanning imaging optical path after passing through the mode conversion module. In the confocal transmission scanning imaging optical path: the light beam is focused onto the object to be imaged on the first multi-axis displacement stage by the third off-axis parabolic mirror. Then, the light beam carrying the object's transmission information is collimated by the fourth off-axis parabolic mirror. The collimated light beam is then focused by the fifth off-axis parabolic mirror. After stray light is filtered out by the first aperture stop, the light is irradiated onto the second power feedback module.

[0007] Preferably, the confocal reflection scanning imaging optical path includes a first multi-axis displacement stage, and further includes a sixth off-axis parabolic mirror and a seventh off-axis parabolic mirror located on the same side of the first multi-axis displacement stage; the focal points of the sixth off-axis parabolic mirror and the seventh off-axis parabolic mirror are both located within the scanning working plane of the first multi-axis displacement stage; and the sixth off-axis parabolic mirror and the seventh off-axis parabolic mirror both satisfy the following: ; In the formula, Indicates the actual focal length. Indicates the focal length of the reflection. The angle between the incident side or the reflecting side and the normal to the plane containing the object to be imaged on the first multi-axis displacement stage is indicated. The system also includes an eighth off-axis parabolic mirror and a second pinhole aperture. The light source module emits a light beam, which is then collimated into the confocal reflection scanning imaging optical path after passing through the mode conversion module. In the confocal reflection scanning imaging optical path: the light beam is focused onto the object to be imaged on the first multi-axis displacement stage by the sixth off-axis parabolic mirror; then, the light beam carrying the object's reflection information is collimated by the seventh off-axis parabolic mirror; then, the collimated beam is focused by the eighth off-axis parabolic mirror; and finally, stray light is filtered out by the second pinhole aperture before illuminating the second power feedback module.

[0008] Preferably, the reflective micro-area scanning imaging optical path includes a second multi-axis displacement stage, a reflective objective lens, a silicon wafer, and a seventh plane mirror arranged sequentially; the focal point of the reflective objective lens is located within the scanning working plane of the second multi-axis displacement stage; the light source module emits a light beam, which enters the reflective micro-area scanning imaging optical path after passing through the mode conversion module. In the reflective micro-area scanning imaging optical path: the light beam is reflected by the silicon wafer and enters the reflective objective lens; the focused light beam illuminates the object to be imaged located on the second multi-axis displacement stage; the reflected light beam is collected by the reflective objective lens and transmitted through the silicon wafer; subsequently, the light beam illuminates the second power feedback module after passing through the seventh plane mirror.

[0009] Preferably, the reflective micro-area scanning imaging optical path further includes an imaging element; when not in operation during the scanning imaging process, the reflected visible light is observed by the imaging element.

[0010] Preferably, the focal plane scanning imaging optical path includes a ninth off-axis parabolic mirror and a third multi-axis displacement stage; the distance between the scanning working plane of the third multi-axis displacement stage and the ninth off-axis parabolic mirror is equal to the reflecting focal length of the ninth off-axis parabolic mirror; the light source module emits a light beam, which enters the focal plane scanning imaging optical path after passing through the mode conversion module; in the focal plane scanning imaging optical path, the light beam is focused by the ninth off-axis parabolic mirror onto the object to be imaged located on the third multi-axis displacement stage, and the transmitted light beam information is captured by the second power feedback module.

[0011] Preferably, the light source module includes a collimated terahertz laser source, and the mode conversion module includes a beam splitter, a steering and shaping mirror group, and a steering mirror group. The light source emitted from the collimated terahertz laser source is split into a first beam and a second beam by the beam splitter. The first beam enters the first power feedback module; the second beam enters the focal plane scanning imaging optical path; and / or, the second beam sequentially passes through the steering and shaping mirror group and the steering mirror group before entering any one or more imaging optical paths of the confocal transmission scanning imaging optical path, the confocal reflection scanning imaging optical path, and the reflection micro-area scanning imaging optical path.

[0012] Preferably, the light source module further includes a visible light laser source and a terahertz wave source with an emitted electromagnetic wave having a divergence angle. The steering and shaping mirror group includes a flip-out first plane mirror, a second plane mirror, and a first off-axis parabolic mirror, and the first plane mirror, the second plane mirror, and the first off-axis parabolic mirror are respectively configured to correspond one-to-one with the collimated emitted terahertz wave laser source, the visible light laser source, and the terahertz wave source with an emitted electromagnetic wave having a divergence angle. The first plane mirror is used to reflect the light source emitted by the collimated emitted terahertz wave laser source to the steering mirror group, the second plane mirror is used to reflect the light source emitted by the visible light laser source to the steering mirror group, and the first off-axis parabolic mirror is used to steer and shape the terahertz wave source with an emitted electromagnetic wave having a divergence angle and emit it to the steering mirror group.

[0013] Preferably, the steering mirror assembly includes a fixed third plane mirror and a sixth plane mirror, and further includes a flip-out fourth plane mirror and a fifth plane mirror; the light source emitted from the light source module can sequentially pass through the steering and shaping mirror assembly, the third plane mirror, and the fourth plane mirror before entering the confocal transmission scanning imaging optical path; the light source emitted from the light source module can sequentially pass through the steering and shaping mirror assembly, the third plane mirror, the fifth plane mirror, and the sixth plane mirror before entering the confocal reflection scanning imaging optical path; the light source emitted from the light source module can sequentially pass through the steering and shaping mirror assembly and the third plane mirror before entering the reflection micro-area scanning imaging optical path.

[0014] This invention also provides an imaging method applied to the aforementioned multimodal terahertz wave imaging system. The light source module includes a collimated terahertz wave laser source, a visible light laser source, and a terahertz wave source with an electromagnetic wave emission divergence angle. The mode conversion module includes a beam splitter, a steering and shaping mirror group, and a steering mirror group. The imaging method includes the following steps: S1. Select any one or more light sources from the collimated terahertz laser source, the visible light laser source, and the terahertz wave source with a divergence angle in the electromagnetic wave output, and select any one or more imaging optical paths in the multi-mode imaging module. S2. If the selected light source includes the collimated terahertz laser source, proceed to step S3; otherwise, proceed to step S5. S3. The collimated terahertz laser source emits a light source that is split into a first beam and a second beam by the beam splitter. The first beam enters the first power feedback module and obtains the corresponding first power reading. The second beam and other light sources enter one or more imaging optical paths selected in the multi-mode imaging module. Then, the second power feedback module captures the beam energy information after imaging for each imaging optical path to obtain the corresponding second power reading. Then proceed to step S4; S4. Check the first power reading and the second power reading Normalization is performed to obtain parameters ,in: ; In the formula, This indicates the maximum power value in a single scan imaging by the first power feedback module. i Indicates the row number in a single scan image. j Indicates the column number in a single scan image; S5. The light source emitted from the light source module passes sequentially through the steering and shaping mirror group and the steering mirror group before entering any one or more of the following imaging optical paths: the confocal transmission scanning imaging optical path, the confocal reflection scanning imaging optical path, and the reflection micro-area scanning imaging optical path. Then, the second power feedback module captures the beam energy information after imaging for each imaging optical path to obtain the corresponding second power reading. .

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. The mode conversion module is used to convert the light emitted by the light source module into light sources of different modes, and then emit them to the multi-mode imaging module for imaging; the first power feedback module is used to capture the beam energy information of the light source module, and the second power feedback module is used to capture the beam energy information of the multi-mode imaging module during imaging; the setting of the confocal transmission scanning imaging optical path, the confocal reflection scanning imaging optical path, the reflection micro-area scanning imaging optical path, and the focal plane scanning imaging optical path can achieve wide spectral coverage and meet various scanning imaging requirements, and achieve stable imaging; 2. The setting of the steering and shaping lens group can be used for rapid switching between multiple imaging optical paths, which can improve the imaging mode switching efficiency of the imaging system. 3. In the imaging method, by simultaneously recording the power meter reading changes during the imaging process, the power changes in the generated image information can be normalized, thereby improving the comparability of parallel scanning imaging experiments. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a multimodal terahertz wave imaging system according to the present invention; Figure 2 This is a schematic diagram of the structure of a first embodiment of a multimodal terahertz wave imaging system according to the present invention; Figure 3 This is a schematic diagram of the structure of a third embodiment of a multimodal terahertz wave imaging system according to the present invention; Figure 4 This is a flowchart of an imaging method for a multimodal terahertz wave imaging system according to the present invention.

[0017] In the attached diagram: 100, Light source module; 110, Collimated terahertz laser source; 120, Visible laser source; 130, Terahertz wave source with a divergence angle; 200, Mode conversion module; 210, Beam splitter; 220, First plane mirror; 230, Second plane mirror; 240, First off-axis parabolic mirror; 250, Third plane mirror; 260, Fourth plane mirror; 270, Fifth plane mirror; 280, Sixth plane mirror; 290, First chopper; 310, Second off-axis parabolic mirror; 320, First power meter; 330, Second power meter; 340, Third power meter; 350, Fourth power meter; 360, Fifth power meter; 410, First multi-axis displacement stage; 420 430. Second multi-axis displacement stage; 500. Third multi-axis displacement stage; 510. Confocal transmission scanning imaging optical path; 520. Third off-axis parabolic mirror; 530. Fourth off-axis parabolic mirror; 540. Fifth off-axis parabolic mirror; 600. First pinhole aperture; 610. Confocal reflection scanning imaging optical path; 620. Sixth off-axis parabolic mirror; 630. Seventh off-axis parabolic mirror; 640. Second pinhole aperture; 700. Reflective micro-area scanning imaging optical path; 710. Silicon wafer; 720. Reflective objective lens; 730. Seventh plane mirror; 740. Imaging sample; 800. Focal plane scanning imaging optical path; 810. Ninth off-axis parabolic mirror; 820. Second chopper; 900. Optical platform. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0019] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0020] Example 1 like Figures 1 to 2 The diagram shows a first embodiment of a multimodal terahertz wave imaging system according to the present invention, including a light source module 100, a mode conversion module 200, a first power feedback module, a second power feedback module, and a multimodal imaging module. The mode conversion module 200 is used to convert the light source emitted by the light source module 100 into light sources of different modes, and then emits them to the multimodal imaging module for imaging. The first power feedback module is used to capture the beam energy information of the light source module 100, and the second power feedback module is used to capture the beam energy information of the multimodal imaging module during imaging. The multimodal imaging module includes a confocal transmission scanning imaging optical path 500, a confocal reflection scanning imaging optical path 600, a reflection micro-area scanning imaging optical path 700, and a focal plane scanning imaging optical path 800.

[0021] The mode conversion module 200 is used to convert the light source emitted by the light source module 100 into light sources of different modes, and then emit them to the multi-mode imaging module for imaging; the first power feedback module is used to capture the beam energy information of the light source module 100, and the second power feedback module is used to capture the beam energy information of the multi-mode imaging module during imaging; the setting of the confocal transmission scanning imaging optical path 500, the confocal reflection scanning imaging optical path 600, the reflection micro-area scanning imaging optical path 700, and the focal plane scanning imaging optical path 800 can achieve wide spectral coverage and meet various scanning imaging requirements, and achieve stable imaging.

[0022] like Figure 2As shown, in this embodiment, the second power feedback module includes a second power meter 330, a third power meter 340, a fourth power meter 350, and a fifth power meter 360. The second power meter 330 is used for capturing beam energy information of the confocal transmission scanning imaging optical path 500, the third power meter 340 is used for capturing beam energy information of the confocal reflection scanning imaging optical path 600, the fourth power meter 350 is used for capturing beam energy information of the reflection micro-area scanning imaging optical path 700, and the fifth power meter 360 is used for capturing beam energy information of the focal plane scanning imaging optical path 800.

[0023] like Figure 2 As shown, the confocal transmission scanning imaging optical path 500 includes a third off-axis parabolic mirror 510, a first multi-axis displacement stage 410, a fourth off-axis parabolic mirror 520, a fifth off-axis parabolic mirror 530, and a first pinhole aperture 540 arranged sequentially along the optical path. The third off-axis parabolic mirror 510 and the fourth off-axis parabolic mirror 520 are located on opposite sides of the first multi-axis displacement stage 410. The focal point of the third off-axis parabolic mirror 510 is located within the scanning working plane of the first multi-axis displacement stage 410, and the focal point of the fourth off-axis parabolic mirror 520 is also located within the scanning working plane of the first multi-axis displacement stage 410. Furthermore, the distance between the third off-axis parabolic mirror 510 and the fourth off-axis parabolic mirror 520 is equal to the sum of the reflective focal lengths of the third off-axis parabolic mirror 510 and the fourth off-axis parabolic mirror 520. This arrangement enables clear imaging. As a preferred option, both the third off-axis parabolic mirror 510 and the fourth off-axis parabolic mirror 520 are off-axis parabolic mirrors with an off-axis angle of 90° and a reflection focal length of 4 inches.

[0024] Specifically, the light source module 100 emits a light beam, which is then collimated into the confocal transmission scanning imaging optical path 500 after passing through the mode conversion module 200. In the confocal transmission scanning imaging optical path 500, the light beam is focused onto the object to be imaged on the first multi-axis displacement stage 410 by the third off-axis parabolic mirror 510. Then, the light beam carrying the object's transmission information is collimated by the fourth off-axis parabolic mirror 520. The collimated light beam is then focused by the fifth off-axis parabolic mirror 530. After the stray light is filtered out by the first pinhole aperture 540, the light beam illuminates the second power meter 330, which can capture the corresponding light beam energy information.

[0025] like Figure 2As shown, the confocal reflection scanning imaging optical path 600 includes a sixth off-axis parabolic mirror 610, a first multi-axis displacement stage 410, a seventh off-axis parabolic mirror 620, an eighth off-axis parabolic mirror 630, and a second pinhole aperture 640 arranged sequentially according to the optical path; wherein, the sixth off-axis parabolic mirror 610 and the seventh off-axis parabolic mirror 620 are both located on the same side of the first multi-axis displacement stage 410, the focal point of the sixth off-axis parabolic mirror 610 is located in the scanning working plane of the first multi-axis displacement stage 410, and the focal point of the seventh off-axis parabolic mirror 620 is located in the scanning working plane of the first multi-axis displacement stage 410; and, the sixth off-axis parabolic mirror 610 and the seventh off-axis parabolic mirror 620 both satisfy: ; In the formula, Indicates the actual focal length. Indicates the focal length of the reflection. This represents the angle between the incident or reflecting side and the normal to the plane containing the object to be imaged, located on the first multi-axis displacement stage 410; this setting enables clear imaging. Specifically, the actual focal length of the sixth off-axis parabolic mirror 610 is equal to the reflected focal length of the sixth off-axis parabolic mirror 610. ,and This indicates the angle between the incident side and the normal to the plane containing the object to be imaged, located on the first multi-axis displacement stage 410; the actual focal length of the seventh off-axis parabolic mirror 620 is equal to the reflected focal length of the seventh off-axis parabolic mirror 620. ,and This indicates the angle between the reflecting side and the normal to the plane containing the object to be imaged, located on the first multi-axis displacement stage 410. Preferably, both the sixth off-axis parabolic mirror 610 and the seventh off-axis parabolic mirror 620 are off-axis parabolic mirrors with an off-axis angle of 45° and a reflecting focal length of 4 inches.

[0026] Specifically, the light source module 100 emits a light beam, which is then collimated into the confocal reflection scanning imaging optical path 600 after passing through the mode conversion module 200. In the confocal reflection scanning imaging optical path 600, the light beam is focused onto the object to be imaged on the first multi-axis displacement stage 410 by the sixth off-axis parabolic mirror 610. Then, the light beam carrying the object reflection information is collimated by the seventh off-axis parabolic mirror 620. The collimated light beam is then focused by the eighth off-axis parabolic mirror 630. After the stray light is filtered out by the second pinhole aperture 640, the light beam illuminates the third power meter 340, which can capture the corresponding light beam energy information.

[0027] It should be noted that the confocal transmission scanning imaging optical path 500 and the confocal reflection scanning imaging optical path 600 can either share the same first multi-axis displacement stage 410 according to the above settings, or they can use different first multi-axis displacement stages 410 respectively.

[0028] like Figure 2 As shown, the reflective micro-area scanning imaging optical path 700 includes a second multi-axis displacement stage 420, a reflective objective lens 720, a silicon wafer 710, a seventh plane mirror 730, and an imaging element 740 arranged sequentially. Specifically, the second multi-axis displacement stage 420, the reflective objective lens 720, the silicon wafer 710, the seventh plane mirror 730, and the imaging element 740 are arranged in a straight line along a first direction. The focal point of the reflective objective lens 720 is located within the scanning working plane of the second multi-axis displacement stage 420. The silicon wafer 710 and the seventh plane mirror 730 are both flip-mounted. In the process, the light source module 100 emits a light beam, which enters the reflective micro-area scanning imaging optical path 700 after passing through the mode conversion module 200. In the reflective micro-area scanning imaging optical path 700, the light beam is reflected by the silicon wafer 710 and enters the reflective objective lens 720. The focused light beam illuminates the object to be imaged located on the second multi-axis displacement stage 420. The reflected light beam is collected by the reflective objective lens 720 and transmitted through the silicon wafer 710. Subsequently, the light beam passes through the seventh plane mirror 730 and illuminates the fourth power meter 350. The fourth power meter 350 can capture the corresponding light beam energy information.

[0029] In this embodiment, the imaging device 740 is a CCD camera; specifically, when it is not working in the scanning imaging process, that is, when the silicon wafer 710 and the seventh plane mirror 730 are flipped into the optical path, the visible light collected by the reflective objective lens 720 is imaged by the CCD camera, which facilitates the observation of the features of the object to be imaged and the scanning area.

[0030] Specifically, silicon wafer 710 is a high-resistivity silicon wafer, specifically a silicon wafer slice with a resistivity greater than 10000 Ω·cm, a thickness of 200μm-2000μm (polished or unpolished), and an area greater than 1 inch. The main working material of the reflective objective lens 720 is any one of quartz, calcium fluoride, zinc fluoride, zinc selenide, zinc sulfide, sapphire, BK7, Teflon, polymethylpentene, diamond, silicon, germanium, gallium nitride, and indium phosphide, or materials with variations in the composition of the aforementioned semiconductor materials and their nitrogen oxides; preferably, the reflective objective lens 720 is made of TPX (poly-4-methylpentene) and has a diameter of 2 inches.

[0031] like Figure 2As shown, the focal plane scanning imaging optical path 800 includes a ninth off-axis parabolic mirror 810 and a third multi-axis displacement stage 430 arranged sequentially along the optical path. Specifically, the ninth off-axis parabolic mirror 810, the third multi-axis displacement stage 430, and the fifth power meter 360 are arranged in a straight line along the first direction. The distance between the scanning working plane of the third multi-axis displacement stage 430 and the ninth off-axis parabolic mirror 810 is equal to the reflective focal length of the ninth off-axis parabolic mirror 810. Preferably, the ninth off-axis parabolic mirror 810 is an off-axis parabolic mirror with an off-axis angle of 90° and a reflective focal length of 4 inches.

[0032] Specifically, the light source module 100 emits a light beam, which enters the focal plane scanning imaging optical path 800 after passing through the mode conversion module 200. In the focal plane scanning imaging optical path 800, the light beam is focused by the ninth off-axis parabolic mirror 810 onto the object to be imaged located on the third multi-axis displacement stage 430, and the transmitted light beam information is captured by the fifth power meter 360.

[0033] It should be noted that the first multi-axis displacement stage 410, the second multi-axis displacement stage 420, and the third multi-axis displacement stage 430 are all three-axis motorized displacement stages. The minimum movement increment of each three-axis motorized displacement stage is greater than 1 nm, the backlash is less than 2 μm, and the distance deviating from the ideal straight line or plane during movement is less than 2.5 μm / m. Furthermore, they are single-axis or multi-axis motorized displacement devices driven by piezoelectric ceramics, stepper motors, servo motors, or linear electrodes. It should also be noted that the first multi-axis displacement stage 410, the second multi-axis displacement stage 420, and the third multi-axis displacement stage 430 can be the same three-axis motorized displacement stage moved to different imaging optical paths for imaging, or a separate three-axis motorized displacement stage can be set in each imaging optical path.

[0034] like Figure 2 As shown, the imaging system also includes an optical platform 900, a light source module 100, a beam splitter 210, a steering and shaping mirror group, a steering mirror group, a first power feedback module, a second power feedback module, a confocal transmission scanning imaging optical path 500, a confocal reflection scanning imaging optical path 600, a reflection micro-area scanning imaging optical path 700, and a focal plane scanning imaging optical path 800, all mounted on the optical platform 900. The optical platform 900 is designed to provide a stable and vibration-damping support plane for the light source module 100, the mode conversion module 200, the first power feedback module, the second power feedback module, and the multi-mode imaging module. Specifically, the passive vibration isolation efficiency of the optical platform 900 is between 80% and 99%, its natural frequency is less than 2Hz, its surface flatness is less than 0.1mm / m, its load-type variable is less than 10μm / 100kg, and its working air pressure fluctuation is less than 10%.

[0035] In this embodiment, the imaging system further includes a computer, and the first power feedback module and the second power feedback module are both communicatively connected to the computer. Specifically, the first power meter 320, the second power meter 330, the third power meter 340, the fourth power meter 350, and the fifth power meter 360 are all electrically connected to the computer, so that the beam energy information captured by each power meter can be transmitted to the computer.

[0036] Example 2 This embodiment is a second embodiment of a multimodal terahertz wave imaging system. This embodiment is similar to the first embodiment, except that, as shown in the following... Figure 2 As shown, the light source module 100 includes a collimated terahertz laser source 110, a visible light laser source 120, and a terahertz laser source 130 that emits electromagnetic waves with a divergence angle; wherein, the collimated terahertz laser source 110 is electrically connected to a computer through a feedback circuit to realize feedback adjustment and recording of the output power.

[0037] In this embodiment, the collimated terahertz laser source 110 is any one or more of a continuous terahertz gas laser, a photoconductive antenna, a quantum cascade laser, a solid-state frequency doubler, a free-electron laser, and a plasma terahertz source; the visible light laser source 120 is any one or more of a solid-state laser, a gas laser, a semiconductor laser, and a dye laser; and the terahertz laser source 130 with an electromagnetic wave emission and a divergence angle is any one or more of a continuous terahertz gas laser, a photoconductive antenna, a quantum cascade laser, a solid-state frequency doubler, a free-electron laser, and a plasma terahertz source.

[0038] In this embodiment, the first power feedback module includes a second off-axis parabolic mirror 310 and a first power meter 320; the mode conversion module 200 includes a beam splitter 210, a steering and shaping mirror group, and a steering mirror group. The light source emitted from the collimated terahertz laser source 110 is split into a first beam and a second beam by the beam splitter 210. The first beam illuminates the first power meter 320 after passing through the second off-axis parabolic mirror 310. The first power meter 320 can capture the corresponding beam energy information. The second beam enters the focal plane scanning imaging optical path 800; and / or, the second beam sequentially passes through the steering and shaping mirror group and the steering mirror group and then enters any one or more imaging optical paths among the confocal transmission scanning imaging optical path 500, the confocal reflection scanning imaging optical path 600, and the reflection micro-area scanning imaging optical path 700.

[0039] Specifically, the steering and shaping mirror assembly includes a flip-out first plane mirror 220, a second plane mirror 230, and a first off-axis parabolic mirror 240, and the first plane mirror 220, the second plane mirror 230, and the first off-axis parabolic mirror 240 are respectively configured to correspond one-to-one with the collimated terahertz laser source 110, the visible light laser source 120, and the terahertz wave source 130 with a divergence angle in the emitted electromagnetic wave. The first plane mirror 220 is used to reflect the light source emitted from the collimated terahertz laser source 110 to the steering mirror assembly, the second plane mirror 230 is used to reflect the light source emitted from the visible light laser source 120 to the steering mirror assembly, and the first off-axis parabolic mirror 240 is used to steer and shape the terahertz wave source 130 with a divergence angle in the emitted electromagnetic wave and emit it to the steering mirror assembly.

[0040] In this embodiment, the steering mirror assembly includes a fixed third plane mirror 250 and a sixth plane mirror 280, and also includes a flip-out fourth plane mirror 260 and a fifth plane mirror 270. The light source emitted from the light source module 100 can sequentially pass through the steering and shaping mirror assembly, the third plane mirror 250, and the fourth plane mirror 260 before entering the confocal transmission scanning imaging optical path 500. The light source emitted from the light source module 100 can sequentially pass through the steering and shaping mirror assembly, the third plane mirror 250, the fifth plane mirror 270, and the sixth plane mirror 280 before entering the confocal reflection scanning imaging optical path 600. The light source emitted from the light source module 100 can sequentially pass through the steering and shaping mirror assembly and the third plane mirror 250 before entering the reflection micro-area scanning imaging optical path 700.

[0041] Preferably, the beam splitter 210, the first plane mirror 220, and the ninth off-axis parabolic mirror 810 are arranged in a straight line along the second direction; the first off-axis parabolic mirror 240 is an off-axis parabolic mirror with a through hole, and the first plane mirror 220, the second plane mirror 230, the first off-axis parabolic mirror 240, and the third plane mirror 250 are arranged in a straight line along the first direction, and the third plane mirror 250, the fourth plane mirror 260, and the fifth plane mirror 270 are arranged in a straight line along the second direction, and the first direction and the second direction are perpendicular to each other.

[0042] In this embodiment, the first plane mirror 220, the second plane mirror 230, the first off-axis parabolic mirror 240, the third plane mirror 250, the fourth plane mirror 260, the fifth plane mirror 270, the sixth plane mirror 280, the second off-axis parabolic mirror 310, the third off-axis parabolic mirror 510, the fourth off-axis parabolic mirror 520, the fifth off-axis parabolic mirror 530, the sixth off-axis parabolic mirror 610, the seventh off-axis parabolic mirror 620, the eighth off-axis parabolic mirror 630, the seventh plane mirror 730, and the ninth off-axis parabolic mirror 810 are all rigid optical elements with metal coatings and operating under electromagnetic waves with wavelengths of 200~30000nm. It should be noted that the metal coating is made of metals such as aluminum, silver, and gold.

[0043] Specifically, the aforementioned flip-up setting can be achieved by combining a manually flipped frame with a standard frame. After multiple flips, the positional offset in the orthogonal direction within the horizontal plane should be less than 4 μrad. Alternatively, the combination of a manually flipped frame with a standard frame can be replaced by using a motor drive, changing the position of optical elements via a translation stage, rapidly adjusting the angle of the reflector via piezoelectric ceramics or voice coil electrodes, rapidly changing the phase accumulation of transmitted or reflected electromagnetic waves by altering the refractive index of the crystal through electro-optic / acoustic-optic effects, rapidly changing the angle and transmittance of transmitted or reflected light through a digital micromirror array or spatial light modulator, and abruptly changing the optical path difference of the coherent beam through thermo-optic / magneto-optic / acoustic-optic / mechanical displacement, etc., to achieve rapid direction switching, blocking, and deflection of the propagating beam.

[0044] It should be noted that when the second plane mirror 230 is replaced with a double-sided polished high-resistivity silicon wafer, the collimated terahertz laser source 110, the visible light laser source 120, and the terahertz wave source 130 with a divergence angle can be used simultaneously. When the first plane mirror 220, the fourth plane mirror 260, and the fifth plane mirror 270 are all replaced with double-sided polished high-resistivity silicon wafers, the confocal transmission scanning imaging optical path 500, the confocal reflection scanning imaging optical path 600, the reflection micro-area scanning imaging optical path 700, and the focal plane scanning imaging optical path 800 can be used simultaneously.

[0045] Example 3 This embodiment is a third embodiment of a multimodal terahertz wave imaging system. This embodiment is similar to Embodiment 1 or 2, except that, as shown in the following... Figure 3As shown, a first chopper 290 can be disposed between the third plane mirror 250 and the fourth plane mirror 260. The first chopper 290 can provide specific optical chopping frequencies for the second power meter 330, the third power meter 340, and the fourth power meter 350. Furthermore, the focal plane scanning imaging optical path 800 also includes a second chopper 820 disposed between the ninth off-axis parabolic mirror 810 and the third multi-axis displacement stage 430. The second chopper 820 can provide a specific optical chopping frequency for the fifth power meter 360.

[0046] Example 4 like Figure 4 The illustration shows an embodiment of an imaging method for a multimodal terahertz wave imaging system according to the present invention, applied to the multimodal terahertz wave imaging system described in any of embodiments one to three. The imaging method includes the following steps: S1. Select any one or more light sources from collimated terahertz laser source 110, visible light laser source 120, and terahertz wave source 130 with an electromagnetic wave with a divergence angle, and select any one or more imaging optical paths in the multi-mode imaging module, and place the object to be imaged on the multi-axis displacement stage in the corresponding selected imaging optical path. S2. If the selected light source includes the collimated terahertz laser source 110, proceed to step S3; otherwise, proceed to step S5. S3. The collimated terahertz laser source 110 emits a first beam and a second beam, which are split by the beam splitter 210. The first beam enters the first power feedback module and obtains the corresponding first power reading. The second beam and other light sources enter one or more imaging optical paths selected in the multi-mode imaging module. Then, the second power feedback module captures the beam energy information after imaging for each imaging optical path to obtain the corresponding second power reading. Then proceed to step S4; S4. Reading the first power value Second power reading Normalization is performed to obtain parameters ,in: ; In the formula, This indicates the maximum power value in a single scan imaging session using the first power meter (320). i Indicates the row number in a single scan image. j Indicates the column number in a single scan image; S5. The light source emitted from the light source module 100 passes sequentially through the steering and shaping mirror group and the steering mirror group before entering any one or more of the following imaging optical paths: the confocal transmission scanning imaging optical path 500, the confocal reflection scanning imaging optical path 600, and the reflection micro-area scanning imaging optical path 700. Then, the second power feedback module captures the beam energy information after imaging for each imaging optical path to obtain the corresponding second power reading. .

[0047] In this embodiment, the beam splitter 210 is a 1:9 beam splitter, and step S3 specifically includes the following steps: S31. If the selected light source is only the collimated terahertz laser source 110, proceed to step S32; otherwise, proceed to step S33. S32. The collimated terahertz laser source 110 emits a beam of 1 / 10 energy and a beam of 9 / 10 energy, which is split by a beam splitter 210. The 1 / 10 energy beam is focused by a second off-axis parabolic mirror 310 onto a first power meter 320, and the corresponding first power reading is obtained. A beam with 9 / 10 energy enters one or more imaging optical paths selected in the multi-mode imaging module. Then, the second power feedback module captures the beam energy information after imaging for each imaging optical path to obtain the corresponding second power reading. Then proceed to step S4; S33. The collimated terahertz laser source 110 emits a beam of 1 / 10 energy and a beam of 9 / 10 energy, which is split by a beam splitter 210. The 1 / 10 energy beam is focused by a second off-axis parabolic mirror 310 onto a first power meter 320, and the corresponding first power reading is obtained. A beam with 9 / 10 energy enters one or more imaging optical paths selected in the multi-mode imaging module. The remaining light sources sequentially pass through a steering and shaping mirror group and a steering mirror group before entering one or more imaging optical paths selected from confocal transmission scanning imaging optical path 500, confocal reflection scanning imaging optical path 600, and reflection micro-area scanning imaging optical path 700. Then, the second power feedback module captures the beam energy information after imaging for each imaging optical path to obtain the corresponding second power reading. Then proceed to step S4.

[0048] For example, in step S1, when the selected light source is a collimated terahertz laser source 110, and two imaging optical paths are selected, namely the confocal transmission scanning imaging optical path 500 and the confocal reflection scanning imaging optical path 600, after imaging in step S3, the first power meter 320 obtains the corresponding first power reading. The second power meter 330 obtains the second power reading of the corresponding confocal transmission scanning imaging optical path 500. The third power meter 340 obtains the second power reading corresponding to the confocal reflection scanning imaging optical path 600. Therefore, in step S4, the corresponding parameters will be obtained. ,parameter ,in, , .

[0049] In this embodiment, step S6 is further included: after step S4 or S5, the number of flips of each flipable optical element is counted, that is, the number of flips of the flipable plane mirror and the off-axis parabolic mirror is counted; for optical elements with more than n flips, their positional offset in the orthogonal direction in the horizontal plane is checked. If the positional offset is less than 4 μrad, the corresponding optical element can continue to be used; otherwise, a new optical element needs to be replaced before returning to step S1 for imaging. Here, n can be set to 20 times.

[0050] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.

[0051] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A multimodal terahertz wave imaging system, characterized in that, The system includes a light source module (100), a mode conversion module (200), a first power feedback module, a second power feedback module, and a multi-mode imaging module. The mode conversion module (200) is used to convert the light emitted by the light source module (100) into light sources of different modes, and then emit them to the multi-mode imaging module for imaging. The first power feedback module is used to capture the beam energy information of the light source module (100), and the second power feedback module is used to capture the beam energy information of the multi-mode imaging module during imaging. The multi-mode imaging module includes a confocal transmission scanning imaging optical path (500), a confocal reflection scanning imaging optical path (600), a reflection micro-area scanning imaging optical path (700), and a focal plane scanning imaging optical path (800). The confocal transmission scanning imaging optical path (500) includes a first multi-axis displacement stage (410), and further includes a third off-axis parabolic mirror (510) and a fourth off-axis parabolic mirror (520) located on opposite sides of the first multi-axis displacement stage (410); the focal points of the third off-axis parabolic mirror (510) and the fourth off-axis parabolic mirror (520) are both located within the scanning working plane of the first multi-axis displacement stage (410); and the distance between the third off-axis parabolic mirror (510) and the fourth off-axis parabolic mirror (520) is equal to the sum of the reflective focal lengths of the third off-axis parabolic mirror (510) and the fourth off-axis parabolic mirror (520); it also includes a fifth off-axis parabolic mirror (530) and a first pinhole aperture (540). The light source module (100) emits a light beam, which is then collimated into the confocal transmission scanning imaging optical path (500) after passing through the mode conversion module (200). In the confocal transmission scanning imaging optical path (500): the light beam is focused by the third off-axis parabolic mirror (510) onto the object to be imaged located on the first multi-axis displacement stage (410). Then, the light beam carrying the object's transmission information is collimated by the fourth off-axis parabolic mirror (520). The collimated light beam is then focused by the fifth off-axis parabolic mirror (530), and after stray light is filtered out by the first aperture stop (540), it illuminates the second power feedback module. The confocal reflection scanning imaging optical path (600) includes a first multi-axis displacement stage (410), and further includes a sixth off-axis parabolic mirror (610) and a seventh off-axis parabolic mirror (620) located on the same side of the first multi-axis displacement stage (410); the focal points of the sixth off-axis parabolic mirror (610) and the seventh off-axis parabolic mirror (620) are both located within the scanning working plane of the first multi-axis displacement stage (410); and the sixth off-axis parabolic mirror (610) and the seventh off-axis parabolic mirror (620) both satisfy the following: ； In the formula, Indicates the actual focal length. Indicates the focal length of the reflection. This indicates the angle between the incident side or the reflecting side and the normal to the plane containing the object to be imaged, located on the first multi-axis displacement stage (410); It also includes the eighth off-axis parabolic mirror (630) and the second pinhole aperture (640); The light source module (100) emits a light beam, which is then collimated into the confocal reflection scanning imaging optical path (600) after passing through the mode conversion module (200). In the confocal reflection scanning imaging optical path (600): the light beam is focused by the sixth off-axis parabolic mirror (610) onto the object to be imaged located on the first multi-axis displacement stage (410). Then, the light beam carrying the object reflection information is collimated by the seventh off-axis parabolic mirror (620). The collimated light beam is then focused by the eighth off-axis parabolic mirror (630), and then stray light is filtered out by the second aperture stop (640) before it illuminates the second power feedback module. The reflective micro-area scanning imaging optical path (700) includes a second multi-axis displacement stage (420), a reflective objective lens (720), a silicon wafer (710), and a seventh plane mirror (730) arranged in sequence; the focal point of the reflective objective lens (720) is located in the scanning working plane of the second multi-axis displacement stage (420); The light source module (100) emits a light beam, which enters the reflective micro-area scanning imaging optical path (700) after passing through the mode conversion module (200). In the reflective micro-area scanning imaging optical path (700), the light beam is reflected by the silicon wafer (710) and enters the reflective objective lens (720). The focused light beam illuminates the object to be imaged located on the second multi-axis displacement stage (420). The reflected light beam is collected by the reflective objective lens (720) and transmitted through the silicon wafer (710). Subsequently, the light beam passes through the seventh plane mirror (730) and illuminates the second power feedback module.

2. The multimodal terahertz wave imaging system according to claim 1, characterized in that, The reflective micro-area scanning imaging optical path (700) also includes an imaging element (740); when not in operation during the scanning imaging process, the reflected visible light is observed by the imaging element (740).

3. The multimodal terahertz wave imaging system according to claim 1, characterized in that, The focal plane scanning imaging optical path (800) includes a ninth off-axis parabolic mirror (810) and a third multi-axis displacement stage (430); the distance between the scanning working plane of the third multi-axis displacement stage (430) and the ninth off-axis parabolic mirror (810) is equal to the reflection focal length of the ninth off-axis parabolic mirror (810); The light source module (100) emits a light beam, which enters the focal plane scanning imaging optical path (800) after passing through the mode conversion module (200). In the focal plane scanning imaging optical path (800), the light beam is focused by the ninth off-axis parabolic mirror (810) onto the object to be imaged located on the third multi-axis displacement stage (430), and the transmitted light beam information is captured by the second power feedback module.

4. The multimodal terahertz wave imaging system according to any one of claims 1 to 3, characterized in that, The light source module (100) includes a collimated terahertz laser source (110), and the mode conversion module (200) includes a beam splitter (210), a steering and shaping mirror group, and a steering mirror group. The light source emitted from the collimated terahertz laser source (110) is split into a first beam and a second beam by the beam splitter (210), and the first beam enters the first power feedback module. The second beam enters the focal plane scanning imaging optical path (800); and / or, the second beam passes sequentially through the steering and shaping lens group and the steering lens group and then enters any one or more of the confocal transmission scanning imaging optical path (500), the confocal reflection scanning imaging optical path (600), and the reflection micro-area scanning imaging optical path (700).

5. The multimodal terahertz wave imaging system according to claim 4, characterized in that, The light source module (100) further includes a visible light laser source (120) and a terahertz wave source (130) emitting electromagnetic waves with a divergence angle. The steering and shaping mirror assembly includes a flip-out first plane mirror (220), a second plane mirror (230), and a first off-axis parabolic mirror (240). The first plane mirror (220), the second plane mirror (230), and the first off-axis parabolic mirror (240) are respectively aligned with the collimated terahertz wave laser source (110) and the visible light laser source (120). Terahertz wave sources (130) with a divergence angle of emitted electromagnetic waves are arranged one-to-one; the first plane mirror (220) is used to reflect the light source emitted by the collimated terahertz wave laser source (110) to the steering mirror group; the second plane mirror (230) is used to reflect the light source emitted by the visible light laser source (120) to the steering mirror group; and the first off-axis parabolic mirror (240) is used to turn and shape the terahertz wave sources (130) with a divergence angle of emitted electromagnetic waves and emit them to the steering mirror group.

6. The multimodal terahertz wave imaging system according to claim 5, characterized in that, The steering mirror assembly includes a fixed third plane mirror (250) and a sixth plane mirror (280), and also includes a flip-out fourth plane mirror (260) and a fifth plane mirror (270); the light source emitted from the light source module (100) can sequentially pass through the steering and shaping mirror assembly, the third plane mirror (250), and the fourth plane mirror (260) before entering the confocal transmission scanning imaging optical path (500); the light source emitted from the light source module (100) can sequentially pass through the steering and shaping mirror assembly, the third plane mirror (250), the fifth plane mirror (270), and the sixth plane mirror (280) before entering the confocal reflection scanning imaging optical path (600); the light source emitted from the light source module (100) can sequentially pass through the steering and shaping mirror assembly and the third plane mirror (250) before entering the reflection micro-area scanning imaging optical path (700).

7. An imaging method applied to the multimodal terahertz wave imaging system according to any one of claims 1 to 6, characterized in that, The light source module (100) includes a collimated terahertz laser source (110), a visible light laser source (120), and a terahertz wave source (130) with an electromagnetic wave emission divergence angle. The mode conversion module (200) includes a beam splitter (210), a steering and shaping mirror group, and a steering mirror group. The imaging method includes the following steps: S1. Select any one or more light sources from the collimated terahertz laser source (110), the visible light laser source (120), and the terahertz wave source (130) with an electromagnetic wave output with a divergence angle, and select any one or more imaging optical paths from the multi-mode imaging module. S2. If the selected light source includes the collimated terahertz laser source (110), proceed to step S3; otherwise, proceed to step S5. S3. The light source emitted from the collimated terahertz laser source (110) is split into a first beam and a second beam by the beam splitter (210). The first beam enters the first power feedback module and obtains the corresponding first power reading. The second beam and other light sources enter one or more imaging optical paths selected in the multi-mode imaging module. Then, the second power feedback module captures the beam energy information after imaging for each imaging optical path to obtain the corresponding second power reading. Then proceed to step S4; S4. Check the first power reading and the second power reading Normalization is performed to obtain parameters ,in: ； In the formula, This indicates the maximum power value in a single scan imaging by the first power feedback module. i Indicates the row number in a single scan image. j Indicates the column number in a single scan image; S5. The light source emitted from the light source module (100) passes sequentially through the steering and shaping mirror group and the steering mirror group, and then enters any one or more of the following imaging optical paths: the confocal transmission scanning imaging optical path (500), the confocal reflection scanning imaging optical path (600), and the reflection micro-area scanning imaging optical path (700). Then, the second power feedback module captures the beam energy information after imaging for each imaging optical path to obtain the corresponding second power reading. .

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