Method and device for evaluating effect of terahertz band smoke screen jamming

Abstract

The application discloses a method and device for evaluating the effect of a terahertz band smoke screen jamming, and belongs to the field of terahertz imaging. A long-distance terahertz band smoke screen jamming characteristic measuring device is designed, so that the optical path of a generation path is lengthened, a smoke box device can be placed on the generation path, terahertz waves can penetrate a real smoke screen to form an image, and the optical path difference between the generation path and a detection path is set to n times of a laser period, so that the terahertz waves and detection light can meet, and it is ensured that the terahertz waves can be detected. The imaging evaluation method can simultaneously consider the attenuation and scattering effects of the smoke screen on the terahertz waves, so that the smoke screen jamming characteristics are evaluated by using real and accurate measurement results, and the accuracy of the evaluation of the terahertz band smoke screen jamming effect can be improved.

Description

Technical Field

[0001] This invention relates to the field of imaging technology, and in particular to an imaging evaluation method and apparatus for smoke interference effects in the terahertz band. Background Technology

[0002] Smoke screens, as artificially generated obscuring objects, are typically composed of countless particles floating in the air. These particles have a strong attenuation effect on light waves, infrared waves, and millimeter waves in traditional detection bands, resulting in a significant reduction in the power of electromagnetic waves after passing through the smoke screen. This effectively weakens the signal energy received by the system and shortens its effective range. At the same time, smoke screen particles are close to terahertz wavelengths (submillimeter), resulting in a large scattering effect, which makes the imaging target more blurred. The combined effect of these two factors makes the target difficult to detect and identify.

[0003] Currently, the evaluation of anti-smoke interference characteristics in the terahertz band, according to existing literature, is limited by the volume and transmission distance of the terahertz time-domain spectroscopy system. As a substitute for measuring the transmittance of the smoke particle press, there are many test schemes that measure the real smoke. However, this method differs greatly from the real situation, affecting the accuracy of the evaluation results. Summary of the Invention

[0004] This invention provides an imaging evaluation method and apparatus for terahertz band smoke screen interference effects, which is more scientific and accurate. The technical solution is as follows:

[0005] On the one hand, a device for measuring the characteristics of smoke screen interference in the terahertz band is provided, comprising:

[0006] Fiber laser, transmitting antenna, receiving antenna, delay line, smoke box equipment, and data acquisition and control card;

[0007] The fiber laser emits laser pulses that are split into pump light and probe light. The pump light passes through the front generation path to the transmitting antenna to form a terahertz wave, and then passes through the rear terahertz transmission optical path to reach the receiving antenna. The probe light reaches the receiving antenna through the probe path. The optical path of the generation path is greater than that of the probe path, and the difference between the optical path of the generation path and the probe path is n times the laser period, where n is an integer not less than 1. The optical path of the generation path is the sum of the optical paths of the front generation path and the rear terahertz transmission optical path. The smoke box device is set on the rear terahertz transmission optical path. After the smoke box device is filled with smoke, the terahertz wave will penetrate the smoke screen and be directed toward the target, and then reach the receiving antenna after being reflected by the target.

[0008] The delay line is located on the front generation path and is used for optical path compensation so that the terahertz wave and the probe light can meet.

[0009] The data acquisition and control card is used to collect the reflected signals of the target before and after the smoke box equipment is filled with smoke.

[0010] On the one hand, a method for evaluating the effectiveness of terahertz band smoke screen interference is provided, the method comprising:

[0011] Using any of the terahertz band smoke screen interference characteristic measurement devices described above, the target reflection signals before and after the smoke box equipment is filled with smoke are obtained.

[0012] Imaging is performed using the target reflection signals before and after smoke filling to obtain a first target image before smoke filling and a second target image after smoke filling;

[0013] Calculate the similarity between the first target image and the second target image, and determine the interference effect based on the similarity calculation results.

[0014] On the other hand, a device for evaluating the effectiveness of terahertz band smoke interference is provided, the device comprising:

[0015] The acquisition unit is used to acquire the target reflection signal before and after the smoke box equipment is filled with smoke using any of the terahertz band smoke interference characteristic measurement devices described above.

[0016] The imaging unit is used to perform imaging using the target reflection signals before and after smoke filling, to obtain a first target image before smoke filling and a second target image after smoke filling.

[0017] The evaluation unit is used to calculate the similarity between the first target image and the second target image, and to determine the interference effect based on the similarity calculation results.

[0018] On the other hand, a computer device is provided, the computer device including a memory and a processor, the memory for storing computer programs, and the processor for executing the computer programs stored in the memory to implement the steps of the above-described method for evaluating the effectiveness of terahertz band smoke screen interference.

[0019] On the other hand, a computer-readable storage medium is provided, wherein a computer program is stored therein, and when the computer program is executed by a processor, the steps of the above-described method for evaluating the effectiveness of terahertz band smoke interference are implemented.

[0020] On the other hand, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of the above-described method for evaluating the effectiveness of terahertz band smoke interference.

[0021] The technical solution provided by this invention can bring at least the following beneficial effects:

[0022] By designing a long-distance terahertz band smoke interference characteristic measurement device, the generation path is lengthened, allowing the smoke box equipment to be placed along the long generation path. This enables terahertz waves to penetrate the real smoke screen for imaging. Furthermore, the optical path difference between the generation path and the detection path is set to n times the laser period, and optical path compensation is performed using a delay line to ensure that the terahertz waves and the detection light can meet, guaranteeing that the terahertz waves can be detected. Thus, by using real and accurate measurement results to evaluate the smoke interference characteristics, the accuracy of the evaluation of the terahertz band's smoke interference effect imaging can be improved. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a terahertz band smoke interference characteristic measurement device provided in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of a detection principle provided by an embodiment of the present invention;

[0026] Figure 3 This is a flowchart of a method for evaluating the effectiveness of terahertz band smoke interference, provided by an embodiment of the present invention.

[0027] Figure 4 This is a waveform diagram of the target reflection signal before and after smoke filling, provided by an embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of a first target image before smoke filling, provided by an embodiment of the present invention;

[0029] Figure 6 This is a schematic diagram of a second target image after being filled with smoke, provided in an embodiment of the present invention;

[0030] Figure 7 This is a structural diagram of a device for evaluating the effectiveness of terahertz band smoke interference, provided in an embodiment of the present invention.

[0031] Figure 8 This is a hardware architecture diagram of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] As mentioned earlier, existing smoke interference characteristic evaluation experiments are limited by the size and transmission distance of terahertz time-domain spectroscopy systems, typically only able to measure sheet-like samples, which cannot represent real dynamic smoke screens. If measuring real smoke screens, due to the penetrability of terahertz waves through conventional smoke screens, short transmission distances result in insufficient attenuation (below the signal's own amplitude), making accurate measurement difficult. Longer transmission distances place higher demands on the control of terahertz wave transmission and coherent detection. Furthermore, traditional methods only consider the attenuation of terahertz waves by smoke particles, neglecting the impact of terahertz wave scattering during long-distance transmission within smoke particles, even if the terahertz image becomes more blurred. Therefore, it is necessary to significantly extend the terahertz transmission path.

[0034] Based on this, the inventive concept of this invention is to design a long-distance terahertz band smoke screen interference characteristic measurement device, so that the generation path is longer, and the smoke box equipment can be placed on the long-distance generation path, so that the terahertz wave can penetrate the real smoke screen for imaging, thereby using the real measurement results to evaluate the smoke screen interference characteristics; and considering the requirements of long-distance transmission of terahertz waves and coherent detection, the optical path difference between the generation path and the detection path is designed to be n times the laser period, and a delay line is used to ensure that the terahertz wave and the detection light meet.

[0035] The following describes the specific implementation of the above concept.

[0036] Please refer to Figure 1 This invention provides a device for measuring the characteristics of smoke screen interference in the terahertz band, comprising: a fiber laser, a transmitting antenna, a receiving antenna, a delay line, a smoke box device, and a data acquisition and control card (not shown in the figure);

[0037] The fiber laser emits laser pulses that are split into pump light and probe light. The pump light passes through the front generation path to the transmitting antenna to form a terahertz wave, and then passes through the rear terahertz transmission optical path to reach the receiving antenna. The probe light reaches the receiving antenna through the probe path. The optical path of the generation path is greater than that of the probe path, and the difference between the optical path of the generation path and the probe path is n times the laser period, where n is an integer not less than 1. The optical path of the generation path is the sum of the optical paths of the front generation path and the rear terahertz transmission optical path. The smoke box device is set on the rear terahertz transmission optical path. After the smoke box device is filled with smoke, the terahertz wave will penetrate the smoke screen and be directed toward the target, and then reach the receiving antenna after being reflected by the target.

[0038] The delay line is located on the front generation path and is used for optical path compensation so that the terahertz wave and the probe light can meet.

[0039] The data acquisition and control card is used to collect the reflected signals of the target before and after the smoke box equipment is filled with smoke.

[0040] In this embodiment of the invention, if it is necessary to increase the optical path of the generation path to make the transmission optical path longer and the measurement results more accurate, then the optical paths of the generation path and the detection path may not be equal. For a terahertz time-domain spectroscopy system, the required detection condition is that the optical paths of the generation path and the detection path are equal. If the optical path of the generation path is greater than the optical path of the detection path, the optical path can be adjusted so that the optical path of the generation path exceeds the optical path of the detection path by exactly n periods, that is:

[0041]

[0042] Where n is an integer not less than 1, L 产生 To generate the length of the path, L 探测 Let c be the length of the detection path, c be the speed of light, and T be the pulse period.

[0043] The detection principle will be explained below using n=1 as an example.

[0044] Please see Figure 2 This is a schematic diagram of the detection principle. The pulsed lasers are numbered 1, 2, 3, ..., N, and are divided into two paths: a generation path and a detection path. The terahertz pulses (terahertz waves in terahertz pulse form) emitted by the pulsed laser in the generation path are represented in blue, and their repetition period is the same as the repetition period of the laser pulse. When the optical path length of the generation path is greater than that of the detection path, adjusting the optical path length of the generation path to be greater than that of the detection path by one pulse cycle allows the terahertz pulse and the detection pulse (detection light in detection pulse form) to meet, thus achieving terahertz detection. Figure 2 Middle 1 探测 and 1 产生 All of these are generated from the first laser pulse splitting. This detection mode differs from equal optical path detection; it is not 1. 探测 Pulse and 1 产生The terahertz pulses excited by the pulse arrive simultaneously at the detection antenna for detection, but 1 产生 Pulse-excited terahertz pulses and 2 探测 The laser pulses arrive at the detection antenna simultaneously, using 2 探测 Laser Pulse Detection 1 产生 The same applies to pulse-excited terahertz pulses.

[0045] Thus, by designing a long-distance terahertz band smoke interference characteristic measurement device, the optical path of the generation path is lengthened, allowing the smoke box equipment to be placed on the long-distance generation path, enabling terahertz waves to penetrate the real smoke screen for imaging. Furthermore, the optical path difference between the generation path and the detection path is set to n times the laser period, ensuring that the terahertz wave meets the detection light and guaranteeing the accuracy of the detection signal. By using real and accurate measurement results to evaluate the smoke interference characteristics, the accuracy of the terahertz band's smoke interference effect imaging can be improved.

[0046] In one embodiment of the present invention, the front-side generation path, and between the fiber laser and the delay line, further includes a voice coil motor.

[0047] Since the pulse width of the pulsed laser emitted by the fiber laser is relatively narrow, at the femtosecond level, while the pulse width of the terahertz wave is wider, at the picosecond level, in order to ensure that the terahertz wave and the probe light at the receiving antenna position can meet at the appropriate position to complete the scanning of the entire terahertz waveform, a nanosecond-level long-stroke delay line is used to achieve distance compensation, and a voice coil motor (scanning length 100ps) is used to scan the terahertz waveform.

[0048] In one embodiment of the present invention, the rear terahertz transmission optical path includes the following mirror components in sequence according to the transmission order of the terahertz wave: a first collimating mirror, a first focusing mirror, a beam expander, a reflecting mirror, a beam reducer, a second collimating mirror, and a second focusing mirror; the terahertz wave is emitted from the transmitting antenna and reaches the receiving antenna after passing through the above mirror components;

[0049] The smoke box device is located behind the reflector. The terahertz wave is emitted from the reflector, passes through the inside of the smoke box device, and enters the target. After being reflected by the target, it reaches the beam shrinking mirror.

[0050] Since the terahertz waves emitted by the transmitting antenna are divergent, collimation, focusing, and beam expansion are required to improve measurement accuracy. The first collimating lens collimates the terahertz waves, outputting parallel light to the first focusing lens. The first focusing lens focuses the terahertz waves to the beam expander, widening the terahertz waves. The reflecting mirror then projects the terahertz waves to the target. A smoke box is placed between the transmitting lens and the target; after the smoke box is filled with smoke, the terahertz waves can penetrate the real smoke screen and reach the target. The target's reflected signal reaches the beam reducer, narrowing the terahertz waves. The second collimating lens then collimates the terahertz waves, outputting parallel light to the second focusing lens. The second focusing lens focuses the terahertz waves onto the receiving antenna, and simultaneously, the probe light also reaches the receiving antenna, thus achieving terahertz wave detection.

[0051] In this embodiment of the invention, by expanding the terahertz wave beam, the terahertz wave can be transmitted over a long distance, thereby lengthening the generation path to enable the setting of the smoke box device, completing the measurement of the attenuation characteristics of the real dynamic smoke screen, and simultaneously performing imaging evaluation of the target after smoke screen interference, and then evaluating the smoke screen interference effect through image features.

[0052] To achieve long-distance transmission of terahertz waves, in one embodiment of the present invention, the first collimating lens, the first focusing lens, the second collimating lens, and the second focusing lens are all parabolic mirrors of a first size; the beam expander and the beam reducer are both parabolic mirrors of a second size, and the second size is m times the first size; m is an integer not less than 2. For example, the first size is 2 inches and the second size is 6 inches, thereby widening the terahertz wave by 3 times.

[0053] In order to achieve target imaging, in one embodiment of the present invention, the target is set on a scanning frame, and the data acquisition control card is used to control the movement of the scanning frame to perform point-by-point scanning of the target and acquisition of the reflection signal when acquiring the reflection signal of the target before and after the smoke box equipment is filled with smoke.

[0054] In this embodiment of the invention, the reflected signal can be selected as a time-domain peak signal, or the energy at a certain frequency point obtained after Fourier transform can be used as the value of the reflected signal at that point.

[0055] Please refer to Figure 3 This invention also provides a method for evaluating the effectiveness of terahertz band smoke screen interference, the method comprising:

[0056] Step 300: Using any of the terahertz band smoke screen interference characteristic measurement devices described above, acquire the target reflection signal before and after the smoke box equipment is filled with smoke;

[0057] Step 302: Image the target reflection signals before and after smoke filling to obtain a first target image before smoke filling and a second target image after smoke filling;

[0058] Step 304: Calculate the similarity between the first target image and the second target image, and determine the interference effect based on the similarity calculation result.

[0059] Since the target reflection signal is measured by a terahertz band smoke interference characteristic measurement device, it is possible to obtain target reflection signals with and without real dynamic smoke interference.

[0060] Please refer to Figure 4 The figures show the target reflection signal waveforms before and after smoke filling. Based on the target reflection signals, an image of the first target before smoke filling and a second target image after smoke filling can be obtained. Please refer to [the provided text]. Figure 5 and Figure 6 .

[0061] To evaluate the interference effect of a real dynamic smoke screen on terahertz waves, the similarity between the first target image and the second target image can be used for evaluation. The higher the similarity, the weaker the interference capability of the smoke screen on terahertz waves, and vice versa.

[0062] In this embodiment of the invention, the similarity can be calculated based on the normalized cross-correlation coefficient method:

[0063] The normalized cross-correlation coefficient reflects the similarity between two images. Assuming a first target image A (size m×n) and a second target image B (size m×n), the correlation coefficient between the two target images is calculated using the cross-correlation coefficient formula to determine their similarity. The definition of ρ is as follows:

[0064]

[0065] Where σ(A,B) is the covariance of A and B, and D A Let A be the variance, and D be the variance. B This is the variance of B. The covariance of A and B is... A and B are the gray values ​​of the image, where A is the average gray value of A and B is the average gray value of B. The variance of A... Variance of B Therefore, ρ can be expressed as:

[0066]

[0067] The correlation coefficient ranges from -1 to ρ, where ρ is 1 when two target images are identical and -1 when their grayscale distributions are completely opposite. The correlation coefficient ρ characterizes the similarity between two target images.

[0068] The similarity between two target images is s = |ρ| × 100%, where s ranges from [0, 1]. The closer s is to 100%, the more similar the two target images are.

[0069] Please refer to Figure 7 This invention provides a device for evaluating the effectiveness of terahertz band smoke screen interference, the device comprising:

[0070] The acquisition unit 700 is used to acquire the target reflection signal before and after the smoke box equipment is filled with smoke using any of the terahertz band smoke interference characteristic measurement devices described above.

[0071] Imaging unit 702 is used to perform imaging using target reflection signals before and after smoke filling, to obtain a first target image before smoke filling and a second target image after smoke filling.

[0072] Evaluation unit 704 is used to calculate the similarity between the first target image and the second target image, and to determine the interference effect based on the similarity calculation result.

[0073] It should be noted that the terahertz band smoke screen interference effect evaluation device provided in the above embodiments is only an example of the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the terahertz band smoke screen interference effect evaluation device and the terahertz band smoke screen interference effect evaluation method embodiment provided in the above embodiments belong to the same concept, and the specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0074] Embodiments of this application also provide a computer device, please refer to... Figure 8 The computer device includes a processor and a memory, the memory storing at least one instruction, at least one program, code set or instruction set, the at least one instruction, at least one program, code set or instruction set being loaded and executed by the processor to implement the terahertz band smoke screen interference effect evaluation method provided in the above method embodiments.

[0075] The embodiments of this application also provide a computer-readable storage medium storing at least one instruction, at least one program, code set, or instruction set, wherein the at least one instruction, at least one program, code set, or instruction set is loaded and executed by a processor to implement the terahertz band smoke screen interference effect evaluation method provided in the above-described method embodiments.

[0076] Embodiments of this application also provide a computer program product, which includes a computer program. A processor of a computer device reads the computer program from a computer-readable storage medium and executes the computer program, causing the computer device to perform any of the terahertz band smoke screen interference effect evaluation methods described in the above embodiments.

[0077] For ease of description, the above systems or devices are described separately as various modules or units based on their functions. Of course, in implementing this application, the functions of each unit can be implemented in one or more software and / or hardware components.

[0078] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0079] Finally, it should be noted that in this document, relational terms such as first, second, third, and fourth are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0080] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A device for measuring the characteristics of a terahertz band smoke screen jamming, characterized in that, The device comprises a fiber laser, a transmitting antenna, a receiving antenna, a delay line, a smoke tank device and a data acquisition control card. The fiber laser emits laser pulses which are divided into pump light and probe light. The pump light passes through a front side generation path to the transmitting antenna to form a terahertz wave, and then passes through a rear side terahertz wave transmission path to the receiving antenna. The probe light passes through a probe path to the receiving antenna. The optical path of the generation path is longer than that of the probe path, and the difference between the optical paths of the generation path and the probe path is n times the laser period, where n is an integer not less than 1. The optical path of the generation path is the sum of the optical paths of the front side generation path and the rear side terahertz wave transmission path. The smoke tank device is arranged on the rear side terahertz wave transmission path. After the smoke tank device is filled with smoke, the terahertz wave penetrates the smoke and is emitted to the target, and then is reflected by the target to reach the receiving antenna. The delay line is arranged on the front side generation path and is used for optical path compensation to enable the terahertz wave to meet the probe light. The data acquisition control card is used for acquiring the reflection signals of the target before and after the smoke tank device is filled with smoke. The front side generation path further comprises a voice coil motor between the fiber laser and the delay line.

2. The terahertz band smoke screen jamming characteristic measuring device according to claim 1, characterized in that, The rear side terahertz wave transmission path comprises, in the order of terahertz wave transmission, a first collimating mirror, a first focusing mirror, a beam expander, a reflecting mirror, a beam reducer, a second collimating mirror and a second focusing mirror. The terahertz wave is emitted from the transmitting antenna, passes through the above mirror assemblies and reaches the receiving antenna.

3. The terahertz band smoke screen jamming characteristic measuring device according to claim 2, characterized in that, The smoke tank device is arranged behind the reflecting mirror. The terahertz wave is emitted from the reflecting mirror, penetrates the smoke tank device and is emitted to the target, and then is reflected by the target to reach the beam reducer. The first collimating mirror, the first focusing mirror, the second collimating mirror and the second focusing mirror are parabolic mirrors of a first size. The beam expander and the beam reducer are parabolic mirrors of a second size, and the second size is m times the first size. m is an integer not less than 2.

4. The terahertz band smoke screen jamming characteristic measuring device according to claim 3, characterized in that, The target is arranged on a scanning frame. When the data acquisition control card acquires the reflection signals of the target before and after the smoke tank device is filled with smoke, the data acquisition control card controls the movement of the scanning frame to perform point-by-point scanning of the target and acquisition of the reflection signals.

5. The device for measuring the properties of a terahertz band smoke screen interference according to any of claims 1 to 4, characterized in that, The device comprises:

6. A method for evaluating the effect of a terahertz band smoke screen jamming, characterized in that, The device comprises: The device comprises: The device comprises: ​ 7. A device for evaluating the effect of a terahertz band smoke screen jamming, characterized in that, ​ ​ ​ ​ 8. A computer device, comprising: The computer device comprises a memory for storing a computer program and a processor for executing the computer program stored on the memory to realize the steps of the method in claim 6.

9. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, and the computer program is executed by the processor to realize the steps of the method in claim 6.

10. A computer program product, characterised in that, The computer program is executed by the processor to realize the steps of the method in claim 6.

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