A fiber-optic terahertz asynchronous sampling spectroscopy and imaging system
By using an optical fiber terahertz asynchronous sampling system, and by utilizing components such as an asynchronous triggering module and an optical fiber femtosecond laser, the high integration and stability of the terahertz spectroscopy and imaging system are achieved, solving the problems of high adjustment difficulty and unstable trigger signals in existing technologies.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF FLUID PHYSICS CHINA ACAD OF ENG PHYSICS
- Filing Date
- 2023-08-15
- Publication Date
- 2026-06-23
AI Technical Summary
Existing terahertz spectral imaging techniques suffer from problems such as high adjustment difficulty and unstable trigger signals.
A spectral and imaging system based on fiber optic terahertz asynchronous sampling is adopted. Multiple asynchronous trigger signals are generated through an asynchronous trigger module to realize coherent synthesis triggering femtosecond laser triggering technology. Signal processing is performed using a fiber femtosecond laser, polarization-maintaining fiber, attenuator, delay line and coupler.
It achieves higher system integration, smaller size, better stability, and lower cost, and solves the problems of high adjustment difficulty and unstable trigger signals.
Smart Images
Figure CN116879217B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of terahertz imaging technology, and more specifically to a spectral and imaging system based on fiber optic terahertz asynchronous sampling. Background Technology
[0002] Terahertz waves (THz) are a general term for electromagnetic waves with frequencies ranging from 0.1 to 10 THz (wavelengths ranging from 3 mm to 0.03 mm), falling between microwaves and infrared radiation on the electromagnetic spectrum. Terahertz spectral imaging technology possesses characteristics such as "fingerprint spectroscopy," "high security," "high penetration into dielectric nonpolar materials," and "transmission / reflection measurement," giving it unique advantages in non-destructive testing of materials in certain fields. It can serve as an important supplement to traditional testing methods such as X-ray imaging, ultrasonic testing, and optical testing, solving some problems that are difficult to address using traditional methods.
[0003] The most widely used terahertz spectroscopy and imaging measurement system is the terahertz spectroscopy imaging technology based on mechanical delay lines (oscillating delay lines or rotating delay lines). However, due to mechanical inertia, the scanning speed of mechanical delay lines is limited. Asynchronous sampling-based terahertz spectroscopy technology, by eliminating the mechanical delay line structure, can achieve higher terahertz spectral scanning speeds. Currently, most asynchronous terahertz sampling systems employ free-space systems using Ti:sapphire femtosecond lasers, which are large and costly. Methods for triggering terahertz signal acquisition using two-photon or balanced detection suffer from difficulties in adjustment and unstable trigger signals. Summary of the Invention
[0004] The technical problem to be solved by this invention is that existing terahertz spectral imaging technologies suffer from high adjustment difficulty and unstable trigger signals. The purpose of this invention is to provide a spectral and imaging system based on fiber optic terahertz asynchronous sampling. It improves the existing asynchronous sampling terahertz spectral technology by using multiple asynchronous trigger signals from an asynchronous trigger module to achieve coherent synthesis triggering of femtosecond laser triggering technology. This solves the problems of high adjustment difficulty and unstable trigger signals in current two-photon or balanced detection triggering methods for acquiring terahertz signals.
[0005] This invention is achieved through the following technical solution:
[0006] This solution provides a spectral and imaging system based on fiber optic terahertz asynchronous sampling, including:
[0007] The scanning imaging module is used to carry the target sample and perform scanning imaging when the terahertz pulse signal irradiates the target sample;
[0008] A terahertz pulse signal generation module is used to generate a terahertz pulse signal under the first generation signal and irradiate the target sample of the scanning imaging module;
[0009] The terahertz pulse signal receiving module is used to receive the terahertz pulse signal reflected back from the target sample under the trigger signal.
[0010] The signal acquisition module is used to acquire terahertz pulse signals from the terahertz pulse signal receiving module under the third detection signal;
[0011] An asynchronous triggering module is used to generate a first generation signal, a trigger signal, and a third detection signal. The first generation signal and the trigger signal have the same pulse repetition frequency, and the third detection signal and the trigger signal have the same pulse repetition frequency, but the first generation signal and the third detection signal have different pulse repetition frequencies.
[0012] The working principle of this solution: Existing terahertz spectral imaging technologies suffer from problems such as high adjustment difficulty and unstable trigger signals. The purpose of this invention is to provide a spectral and imaging system based on fiber-optic terahertz asynchronous sampling. It improves upon existing asynchronous sampling terahertz spectral technology by using multiple asynchronous trigger signals from an asynchronous trigger module to achieve coherent synthesis triggering of femtosecond lasers. This solves the problems of high adjustment difficulty and unstable trigger signals in current two-photon or balanced detection triggering methods for acquiring terahertz signals. Compared to existing free-space systems using Ti:sapphire femtosecond lasers and dual-laser asynchronous sampling systems, this solution offers higher integration, significantly reduced size, better stability and environmental adaptability, and lower cost.
[0013] A further optimized solution is that the asynchronous triggering module includes: a fiber femtosecond laser, a polarization-maintaining fiber, an attenuator, a delay line, and a coupler;
[0014] The fiber femtosecond laser is used to generate multiple femtosecond lasers:
[0015] A portion of the femtosecond laser power is attenuated by a polarization-maintaining fiber and an attenuator to generate a first generation signal and a third detection signal. The first generation signal is input to a terahertz pulse signal generation module, and the third detection signal is input to a terahertz pulse signal receiving module.
[0016] Another portion of the femtosecond laser power is attenuated by an attenuator and delayed by a delay line before being coupled into a trigger signal input to the signal acquisition module via a coupler.
[0017] A further optimized scheme is that the femtosecond laser includes: a first femtosecond laser, a second femtosecond laser, a third femtosecond laser, and a fourth femtosecond laser;
[0018] The first femtosecond laser generates a first generation signal after its laser power is attenuated by a polarization-maintaining fiber and an attenuator, and the third femtosecond laser generates a third detection signal after its laser power is attenuated by a polarization-maintaining fiber and an attenuator.
[0019] The second femtosecond laser is attenuated by an attenuator and delayed by a delay line before entering the coupler. The fourth femtosecond laser is attenuated by an attenuator before entering the coupler. The coupler couples the second and fourth femtosecond lasers to obtain a trigger signal.
[0020] A further optimized scheme is that the first femtosecond laser and the second femtosecond laser have the same pulse repetition frequency, and the phase difference between the first femtosecond laser and the second femtosecond laser is constant; the third femtosecond laser and the fourth femtosecond laser have the same pulse repetition frequency, and the phase difference between the third femtosecond laser and the fourth femtosecond laser is constant.
[0021] A further optimized scheme is that the first, second, third, and fourth femtosecond lasers are output from the same fiber femtosecond laser, which is controlled by a standard clock source.
[0022] A further optimization scheme is to have a fixed difference Δf between the pulse repetition frequencies of the first femtosecond laser and the third femtosecond laser.
[0023] A further optimized solution is that the terahertz pulse signal generation module includes a first photoconductive antenna and a bias source. The bias source is connected to the photoconductive antenna. After the first generated signal is input to the first photoconductive antenna, a terahertz pulse signal is generated. During the process of the photoconductive antenna generating the terahertz pulse signal, the bias source provides a bias voltage.
[0024] A further optimized solution is that the terahertz pulse signal receiving module includes a second photoconductive antenna, a bias source, and a signal processing unit;
[0025] The third detection signal is input to the second photoconductive antenna to receive the terahertz pulse signal reflected back from the target sample; the second photoconductive antenna transmits the received terahertz pulse signal to the signal processing unit;
[0026] The signal acquisition module acquires terahertz pulse signals from the signal processing unit.
[0027] A further optimized solution would also include an output module;
[0028] Under the third detection signal, the signal acquisition module acquires the terahertz pulse signal, terahertz spectral signal and target sample imaging information from the terahertz pulse signal receiving module.
[0029] A further optimization is that the terahertz pulse signal receiving module is also used to convert the reflected terahertz pulse signal into an electrical signal to realize the transmission spectrum measurement of the target sample.
[0030] In this solution, the scanning imaging module is based on terahertz pulse time-of-flight imaging technology combined with two-dimensional fast scanning imaging technology, which enables the system to not only have terahertz spectral measurement function, but also terahertz imaging detection function.
[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0032] This invention provides a spectral and imaging system based on fiber optic terahertz asynchronous sampling. It improves upon existing asynchronous sampling terahertz spectroscopy techniques by employing multiple asynchronous trigger signals from an asynchronous trigger module to achieve coherent synthesis triggering of femtosecond laser signals. This solves the problems of high adjustment difficulty and unstable trigger signals inherent in current two-photon or balanced detection triggering methods for acquiring terahertz signals. Compared to existing free-space systems using Ti:sapphire femtosecond lasers and dual-laser asynchronous sampling systems, this solution offers higher integration, significantly reduced size, better stability and environmental adaptability, and lower cost. Attached Figure Description
[0033] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:
[0034] Figure 1 This is a schematic diagram of a spectral and imaging system based on fiber optic terahertz asynchronous sampling.
[0035] Figure 2 A schematic diagram illustrating the dual-frequency control principle of a fiber femtosecond laser.
[0036] Figure 3 This is a schematic diagram illustrating the implementation principle of the two-dimensional rapid scanning imaging technology in Example 2;
[0037] Figure 4 This is a schematic diagram illustrating the principle of spectral imaging technology for the target sample in Example 3. Detailed Implementation
[0038] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.
[0039] Example 1
[0040] This embodiment provides a spectral and imaging system based on fiber optic terahertz asynchronous sampling, such as... Figure 1 As shown, it includes:
[0041] The scanning imaging module is used to carry the target sample and perform scanning imaging when the terahertz pulse signal irradiates the target sample;
[0042] A terahertz pulse signal generation module is used to generate a terahertz pulse signal under the first generation signal and irradiate the target sample of the scanning imaging module;
[0043] The terahertz pulse signal receiving module is used to receive the terahertz pulse signal reflected back from the target sample under the trigger signal.
[0044] The signal acquisition module is used to acquire terahertz pulse signals from the terahertz pulse signal receiving module under the third detection signal;
[0045] An asynchronous triggering module is used to generate a first generation signal, a trigger signal, and a third detection signal. The first generation signal and the trigger signal have the same pulse repetition frequency, and the third detection signal and the trigger signal have the same pulse repetition frequency, but the first generation signal and the third detection signal have different pulse repetition frequencies.
[0046] Example 2
[0047] like Figure 1 As shown, this embodiment provides a spectral and imaging system based on all-fiber coupling and asynchronous terahertz sampling, including a standard clock source, a fiber femtosecond laser, a terahertz transmitter head, a terahertz detector head, a bias source, a scanning imaging module, a delay line, an attenuator, a coupler, a PD photodetector, a signal acquisition and amplification module, and a host computer. In this embodiment, the femtosecond laser is transmitted entirely within optical fibers, greatly improving the system's stability and environmental adaptability. High-precision coherent synthesis triggering of the terahertz pulse signal is achieved using a delay line, fiber coupler, and PD photodetector. Terahertz three-dimensional imaging is realized based on time-of-flight and two-dimensional scanning imaging techniques.
[0048] The asynchronous triggering module includes: a fiber femtosecond laser, a polarization-maintaining fiber, an attenuator, a delay line, and a coupler;
[0049] Fiber femtosecond lasers are used to generate multiple femtosecond lasers (corresponding to 1, 2, 3, and 4 in the figure):
[0050] A portion of the femtosecond laser power is attenuated by a polarization-maintaining fiber and an attenuator to generate a first generation signal and a third detection signal. The first generation signal is input to a terahertz pulse signal generation module, and the third detection signal is input to a terahertz pulse signal receiving module.
[0051] Another portion of the femtosecond laser power is attenuated by an attenuator and delayed by a delay line before being coupled into a trigger signal input to the signal acquisition module via a coupler.
[0052] The femtosecond laser includes: a first femtosecond laser (corresponding to 1 in the figure), a second femtosecond laser (corresponding to 2 in the figure), a third femtosecond laser (corresponding to 3 in the figure), and a fourth femtosecond laser (corresponding to 4 in the figure);
[0053] The first femtosecond laser generates a first generation signal after its power is attenuated by a polarization-maintaining fiber and an attenuator, and the third femtosecond laser generates a third detection signal after its power is attenuated by a polarization-maintaining fiber and an attenuator.
[0054] The second femtosecond laser, after its power is attenuated by an attenuator and delayed by a delay line, enters the coupler. The fourth femtosecond laser, after its power is attenuated by an attenuator, enters the coupler. The coupler couples the second and fourth femtosecond lasers to obtain a trigger signal.
[0055] The first and second femtosecond lasers have the same pulse repetition frequency, and the phase difference between the first and second femtosecond lasers is constant; the third and fourth femtosecond lasers have the same pulse repetition frequency, and the phase difference between the third and fourth femtosecond lasers is constant.
[0056] The first, second, third, and fourth femtosecond lasers are output from the same fiber femtosecond laser, which is controlled by a standard clock source.
[0057] There is a fixed difference Δf between the pulse repetition frequencies of the first and third femtosecond lasers.
[0058] The terahertz pulse signal generation module includes a first photoconductive antenna and a bias source. The bias source is connected to the photoconductive antenna. After the first generation signal is input to the first photoconductive antenna, a terahertz pulse signal is generated. During the process of the photoconductive antenna generating the terahertz pulse signal, the bias source provides a bias voltage.
[0059] The terahertz pulse signal receiving module includes a second photoconductive antenna, a bias source, and a signal processing unit.
[0060] The third detection signal is input to the second photoconductive antenna to receive the terahertz pulse signal reflected back from the target sample; the second photoconductive antenna transmits the received terahertz pulse signal to the signal processing unit;
[0061] The signal acquisition module acquires terahertz pulse signals from the signal processing unit.
[0062] It also includes an output module;
[0063] Under the third detection signal, the signal acquisition module acquires the terahertz pulse signal, terahertz spectral signal and target sample imaging information from the terahertz pulse signal receiving module.
[0064] In this embodiment, the fiber femtosecond laser outputs four femtosecond lasers, where the repetition frequency of the first and second femtosecond lasers is f, and the repetition frequency of the third and fourth femtosecond lasers is f+Δf. The first femtosecond laser 1, after its power is attenuated to an allowable range by a polarization-maintaining fiber and an attenuator, excites the fiber-coupled terahertz transmitter. In this embodiment, a photoconductive antenna is used to generate a terahertz pulse signal. The bias source provides the bias voltage required for the terahertz transmitter to generate the terahertz pulse. The generated terahertz pulse irradiates the target sample on the scanning imaging module. The reflected terahertz pulse signal is received by the fiber-coupled terahertz transmitter and converted into an electrical signal under the excitation of the third femtosecond laser (attenuated to an allowable range by an attenuator). This signal is then input to the signal acquisition and amplification module for terahertz signal acquisition, amplification, and preprocessing. Finally, the terahertz pulse signal, spectrum, and image are obtained through the host computer software and displayed and stored on the host computer.
[0065] Laser 2 (the second femtosecond laser) and Laser 4 (the fourth femtosecond laser), after being attenuated to within an acceptable range by an attenuator, are input to a two-in-one fiber coupler. The output coherently combined optical signal is converted into an electrical signal by a PD photodetector and input to the signal acquisition and amplification module. When the amplitude of the trigger electrical signal exceeds a set threshold due to the coherent combination of Laser 2 and Laser 4 (e.g., determined by a high-low level comparator), the signal acquisition and amplification module begins acquiring a terahertz pulse signal. A delay line (manual or electric) is added to the optical path of Laser 2 or Laser 4 to adjust the time delay between the trigger signal and the peak value of the acquired terahertz pulse signal, adapting to the needs of different test samples and test scenarios. The terahertz pulse signal is rapidly acquired using optical asynchronous sampling technology, and the terahertz spectral signal is obtained through Fourier transform. The target is scanned point-by-point using transverse two-dimensional rapid scanning technology to obtain the terahertz pulse waveform at each point, and rapid three-dimensional imaging of the target is achieved based on time-of-flight imaging technology.
[0066] In this embodiment, a standard clock source (typically a rubidium clock) provides a time reference for the fiber femtosecond laser, enabling dual-frequency control of the fiber femtosecond laser. The repetition frequency of laser 1 and laser 2 output by the fiber femtosecond laser is f, and the phase difference between laser 1 and laser 2 is constant (determined by the optical path delay). The repetition frequency of laser 3 and laser 4 is f + Δf, and the phase difference between laser 3 and laser 4 is constant (determined by the optical path delay). Figure 2 As shown, the repetition frequencies of laser pulses 1 and 3 have a fixed difference Δf. This results in a linear increase in the relative time delay between the two pulses. Specifically, assuming that at a certain moment the terahertz pulse generated by laser 1 and the pulse of laser 3 coincide in time, due to their different repetition frequencies, there is a time difference between the two pulses in the next pulse. Each subsequent pulse increases this time difference until they coincide again, thus enabling the sampling and measurement of a terahertz pulse by laser pulse 3, thereby reconstructing the terahertz pulse waveform. Lasers 2 and 4 output from the lasers trigger the acquisition and amplification module to begin acquiring a terahertz pulse signal via a trigger signal generated by coherent synthesis.
[0067] Example 2
[0068] In this embodiment, the scanning imaging module also has an imaging detection function. The imaging detection function is based on terahertz pulse time-of-flight imaging technology combined with two-dimensional fast scanning imaging technology. Its basic principle is as follows: Figure 3 As shown, high-resolution tomography is achieved in the longitudinal direction (z-direction) based on terahertz pulse time-of-flight imaging. Terahertz pulse time-of-flight imaging utilizes the time difference of terahertz pulses reflected from different interfaces within the target to achieve longitudinal tomographic resolution. Under perpendicular incidence conditions, the longitudinal thickness resolution of the target sample is [value missing]. ,in The speed of light in a vacuum. The pulse delay time. The sample refractive index is used. Since the typical pulse width of a terahertz pulse is less than 1 ps, combined with signal processing algorithm optimization, high-resolution longitudinal tomography with a resolution better than 30 μm can be achieved. In the lateral direction (x×y direction), through rapid point-by-point scanning in two-dimensional space, combined with the time-of-flight tomography results in the z-direction of each point, a three-dimensional tomographic image of the target can ultimately be achieved. When obtaining each terahertz pulse using asynchronous sampling technology, it is necessary to synchronously obtain the accurate position coordinates of the two-dimensional imaging scanning module at the same moment, which is crucial for correctly reconstructing the terahertz three-dimensional image. This system obtains the accurate position coordinates corresponding to each terahertz pulse by acquiring the position signal of the two-dimensional imaging scanning module (such as a grating encoder ruler) corresponding to the trigger signal at the start of each terahertz pulse acquisition, thereby accurately reconstructing the terahertz three-dimensional image of the detected target.
[0069] Example 3
[0070] The terahertz pulse signal receiving module in this embodiment can also operate in transmission mode, such as... Figure 4 As shown, the terahertz pulse signal emitted by the terahertz transmitter passes through the target and is incident on the terahertz detector, where it is converted into an electrical signal, thus enabling the measurement of the target's transmission spectrum. By placing the target sample on the two-dimensional scanning module and performing a two-dimensional scan simultaneously while measuring the spectrum, spectral imaging of the target can be achieved.
[0071] This invention operates on a four-channel femtosecond laser mode controlled by a standard clock source. Compared to existing free-space systems using Ti:sapphire femtosecond lasers and asynchronous sampling systems using dual lasers, this system offers higher integration, significantly reduced size, better stability and environmental adaptability, and lower cost. Based on coherent synthesis-triggered femtosecond laser triggering technology, it solves the problems of high adjustment difficulty and unstable trigger signals associated with current two-photon or balanced detection methods for acquiring terahertz signals. By employing terahertz pulse time-of-flight imaging technology combined with two-dimensional fast scanning imaging technology, this system not only possesses terahertz spectral measurement capabilities but also terahertz imaging detection capabilities.
[0072] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A spectral and imaging system based on fiber optic terahertz asynchronous sampling, characterized in that, include: The scanning imaging module is used to carry the target sample and perform scanning imaging when the terahertz pulse signal irradiates the target sample; A terahertz pulse signal generation module is used to generate a terahertz pulse signal under the first generation signal and irradiate the target sample of the scanning imaging module; The terahertz pulse signal receiving module is used to receive the terahertz pulse signal reflected back from the target sample under the trigger signal. The signal acquisition module is used to acquire terahertz pulse signals from the terahertz pulse signal receiving module under the third detection signal; An asynchronous triggering module is used to generate a first generation signal, a trigger signal, and a third detection signal. The first generation signal and the trigger signal have the same pulse repetition frequency, and the third detection signal and the trigger signal have the same pulse repetition frequency, but the first generation signal and the third detection signal have different pulse repetition frequencies. The terahertz pulse signal receiving module includes a second photoconductive antenna, a bias source, and a signal processing unit. After the third detection signal is input to the second photoconductive antenna, the second photoconductive antenna receives the terahertz pulse signal reflected back from the target sample; The second photoconductive antenna transmits the received terahertz pulse signal to the signal processing unit; The signal acquisition module acquires terahertz pulse signals from the signal processing unit.
2. The spectral and imaging system based on fiber optic terahertz asynchronous sampling according to claim 1, characterized in that, The asynchronous triggering module includes: a fiber femtosecond laser, a polarization-maintaining fiber, an attenuator, a delay line, and a coupler; The fiber femtosecond laser is used to generate multiple femtosecond lasers: A portion of the femtosecond laser power is attenuated by a polarization-maintaining fiber and an attenuator to generate a first generation signal and a third detection signal. The first generation signal is input to a terahertz pulse signal generation module, and the third detection signal is input to a terahertz pulse signal receiving module. Another portion of the femtosecond laser power is attenuated by an attenuator and delayed by a delay line before being coupled into a trigger signal input to the signal acquisition module via a coupler.
3. The spectral and imaging system based on fiber optic terahertz asynchronous sampling according to claim 2, characterized in that, The femtosecond laser includes: a first femtosecond laser, a second femtosecond laser, a third femtosecond laser, and a fourth femtosecond laser; The first femtosecond laser generates a first generation signal after its laser power is attenuated by a polarization-maintaining fiber and an attenuator, and the third femtosecond laser generates a third detection signal after its laser power is attenuated by a polarization-maintaining fiber and an attenuator. The second femtosecond laser is attenuated by an attenuator and delayed by a delay line before entering the coupler. The fourth femtosecond laser is attenuated by an attenuator before entering the coupler. The coupler couples the second and fourth femtosecond lasers to obtain a trigger signal.
4. The spectral and imaging system based on fiber optic terahertz asynchronous sampling according to claim 3, characterized in that, The first and second femtosecond lasers have the same pulse repetition frequency, and the phase difference between the first and second femtosecond lasers is constant; the third and fourth femtosecond lasers have the same pulse repetition frequency, and the phase difference between the third and fourth femtosecond lasers is constant.
5. A spectral and imaging system based on fiber optic terahertz asynchronous sampling according to claim 2, characterized in that, The fiber femtosecond laser is controlled by a standard clock source.
6. A spectral and imaging system based on fiber optic terahertz asynchronous sampling according to claim 4, characterized in that, There is a fixed difference Δf between the pulse repetition frequencies of the first femtosecond laser and the third femtosecond laser.
7. A spectral and imaging system based on fiber optic terahertz asynchronous sampling according to claim 1, characterized in that, The terahertz pulse signal generation module includes a first photoconductive antenna and a bias source. The bias source is connected to the photoconductive antenna. After the first generation signal is input to the first photoconductive antenna, a terahertz pulse signal is generated. During the process of the photoconductive antenna generating the terahertz pulse signal, the bias source provides a bias voltage.
8. A spectral and imaging system based on fiber optic terahertz asynchronous sampling according to claim 1, characterized in that, It also includes an output module; Under the third detection signal, the signal acquisition module acquires the terahertz pulse signal, terahertz spectral signal and target sample imaging information from the terahertz pulse signal receiving module.
9. A spectral and imaging system based on fiber optic terahertz asynchronous sampling according to claim 1, characterized in that, The terahertz pulse signal receiving module is also used to convert the reflected terahertz pulse signal into an electrical signal to realize the transmission spectrum measurement of the target sample.