On-chip room-temperature terahertz detector imaging system based on signal enhancement function

Abstract

The present invention relates to the field of detection imaging technology, and in particular, to a detection imaging system of an on-chip room-temperature terahertz detector based on a signal enhancement function. It includes a terahertz radiation source: used to generate terahertz waves; a transmitter: used to reflect the terahertz waves to a sample to be detected, and the terahertz waves carry information of the sample to be detected; a detector: used to capture the terahertz wave signal carrying the information of the sample to be detected, and perform signal enhancement on the terahertz wave signal, and finally convert it into a digital signal and transmit it to a processing and display unit; a processing and display unit: used to receive and process the digital signal, convert the received digital signal into spatial image information, and obtain information of the sample to be detected. The system can improve the conversion efficiency in the mixing process, thereby improving the generation efficiency of the terahertz wave, and can also improve the receiving intensity of the terahertz wave signal, and can also enhance the directionality and sensitivity of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of detection imaging, and in particular to a detection imaging system of an on-chip room-temperature terahertz detector based on a signal enhancement function. Background Art

[0002] The detection imaging system of terahertz detectors is a technical platform that uses terahertz waves for non-destructive detection and imaging. Terahertz waves (THz waves) are located between microwave and infrared bands and have unique physical and chemical properties, such as high penetration, low photon energy, and the ability to detect specific "fingerprint" vibration modes of certain substances. These characteristics make terahertz imaging technology have broad application potential in security inspection, biomedical diagnosis, materials science research and other fields.

[0003] The working principle of terahertz detectors usually involves receiving terahertz waves and converting them into measurable signals. These detectors can be based on different physical mechanisms, such as thermal effect, photoelectric effect, quantum effect, etc. The system usually consists of a terahertz wave source, a transmission path, a detector, a signal processing and an imaging display unit. The terahertz wave source can be pulsed or continuous wave, and the detector is selected according to its response mechanism and sensitivity.

[0004] In the existing terahertz wave generation technology, the conversion efficiency is usually not high, which limits the application scope of terahertz waves. At the same time, during the terahertz wave reception process, the signal strength may change significantly due to environmental factors (such as distance, obstructions, atmospheric conditions, etc.), and the antenna array may not be able to effectively enhance the signal in a specific direction. Therefore, a detection and imaging system based on an on-chip room-temperature terahertz detector with signal enhancement function is designed. Summary of the invention

[0005] The purpose of the present invention is to provide a detection imaging system of an on-chip room-temperature terahertz detector based on a signal enhancement function, so as to solve the problem that the conversion efficiency of the terahertz wave generation technology proposed in the above background technology is usually low, which limits the application scope of terahertz waves and the antenna array may not be able to effectively enhance the signal in a specific direction.

[0006] To achieve the above object, the present invention aims to provide a detection imaging system of an on-chip room-temperature terahertz detector based on a signal enhancement function, comprising:

[0007] Terahertz radiation source: used to generate terahertz waves and focus and direct them through optical elements;

[0008] Transmitter: used to reflect the terahertz wave to the sample to be tested. The physical and chemical properties of the sample to be tested are absorbed by the terahertz wave, so that the terahertz wave carries the information of the sample to be tested.

[0009] Detector: used to capture the terahertz wave carrying the information of the sample to be detected, and perform signal enhancement on the terahertz wave signal carrying the information of the sample to be detected, convert the enhanced terahertz wave signal into an electrical signal, amplify and filter the electrical signal for pre-processing, and finally convert it into a digital signal and transmit it to the processing and display unit;

[0010] Processing and display unit: used to receive and process digital signals, obtain information of terahertz wave signals, convert the received digital signals into spatial image information, and display and analyze the spatial image to obtain information of the sample to be tested.

[0011] As a further improvement of the technical solution, the detailed steps of the terahertz radiation source generating terahertz waves are as follows:

[0012] S11, selecting a quantum-level laser capable of emitting infrared light within a desired frequency range, wherein the quantum-level laser can be modulated by an external modulator to change the emitted light frequency;

[0013] S12, selecting a nonlinear crystal capable of achieving the required frequency conversion;

[0014] S13. By adjusting the temperature of the nonlinear crystal and combining the periodic polarization method for phase matching to achieve the required phase matching conditions, the light wave of the quantum laser is mixed with another light wave of a fixed frequency in the nonlinear crystal, and the frequency difference between the two light waves is converted into a terahertz wave; wherein the influence of nonlinear crystal loss is introduced into the phase matching for optimization;

[0015] S14. Extract the generated terahertz wave signal from the nonlinear crystal and use an antenna to focus and direct the terahertz radiation.

[0016] As a further improvement of the technical solution, in S13, the phase matching is performed as follows:

[0017] Determine the initial phase mismatch:

[0018]

[0019] in, is the initial phase mismatch; is the wave vector of the terahertz wave signal; and are the wave vectors of the two light waves involved in the mixing;

[0020] Reducing the phase mismatch by temperature tuning:

[0021] ;

[0022] in, is the amount of phase mismatch reduced by temperature tuning; is the initial temperature; is the final temperature; is the wavelength of the terahertz wave signal; is the refractive index of the terahertz wave signal in the nonlinear crystal; is the wavelength of the light wave of the quantum-level laser involved in the mixing; is the refractive index of the light wave of the quantum laser involved in the mixing in the nonlinear crystal; is the wavelength of the fixed frequency light wave involved in the mixing; is the refractive index of the fixed frequency light wave involved in mixing in the nonlinear crystal;

[0023] Remaining phase mismatch:

[0024]

[0025] in, is the remaining phase mismatch;

[0026] Periodic poling cycle:

[0027]

[0028] in, is the polarization period; is the effective wavelength; is the effective refractive index; is the angle of incidence relative to the principal axis of the nonlinear crystal;

[0029] Adjust the periodic poling period to meet the phase matching condition:

[0030]

[0031] in, is the modulus of the remaining phase mismatch.

[0032] As a further improvement of the technical solution, in S13, the influence of nonlinear crystal loss is introduced in phase matching for optimization, and the optimization is as follows:

[0033]

[0034] in, is the additional phase mismatch due to nonlinear crystal loss; is the imaginary part of the refractive index of the terahertz wave signal in the nonlinear crystal; is the imaginary part of the refractive index of the quantum laser light wave in the nonlinear crystal; is the imaginary part of the refractive index of a light wave of fixed frequency in a nonlinear crystal;

[0035] Remaining phase mismatch:

[0036]

[0037] in, is the remaining phase mismatch after optimization;

[0038] Phase matching conditions:

[0039]

[0040] in, is the modulus of the remaining phase mismatch after optimization.

[0041] As a further improvement of the technical solution, during the operation of the transmitter, the sample to be detected is fixed by a sample holder and is placed at a position that the terahertz wave can reach.

[0042] As a further improvement of the technical solution, in the detector, the signal enhancement of the terahertz wave signal carrying the information of the sample to be detected is specifically as follows:

[0043] S31. Design an antenna array in advance according to the required terahertz wavelength, integrate the antenna array into the front end of the detector, and adjust the antenna array. At the same time, introduce an adaptive configuration function for optimization during the adjustment of the antenna array;

[0044] S32, perform real-time phase control through a digital signal processor, optimize phase distribution to achieve optimal signal directivity and signal enhancement, realize signal superposition through a phased array method, and optimize phase distribution to achieve enhanced signal effect;

[0045] S33. On the basis of enhancing the signal effect, a differential self-mixing power detection circuit is adopted, and an adaptive frequency tracking function is introduced to convert the terahertz wave signal into a low-frequency signal that is easy to process;

[0046] S34. After the terahertz wave signal is converted into a low-frequency signal, automatic gain control is implemented, and fuzzy logic control is used to perform fine gain adjustment to adapt to terahertz wave signals of different intensities.

[0047] As a further improvement of the technical solution, in S31, the method for adjusting the antenna array is specifically as follows:

[0048] Antenna spacing:

[0049]

[0050] in, is the distance between two adjacent antennas;

[0051] Phase difference control:

[0052]

[0053] in, For the The phase of the antennas; is the desired terahertz wave signal pointing angle; For the The distance between the first antenna and the second antenna;

[0054] Signal Enhancement:

[0055] ;

[0056] in, is the signal amplitude; is the total number of antennas; ; For the The terahertz wave signal amplitude of each antenna; Is an imaginary unit.

[0057] As a further improvement of the technical solution, in S31, an adaptive configuration function is introduced to optimize the antenna array during adjustment, as follows:

[0058]

[0059] in, After optimization The distance between each antenna and the previous antenna; It is the adaptive configuration function; For the The terahertz wave signal strength received by each antenna; For the The angle of the terahertz wave signal received by each antenna relative to the normal line of the antenna array;

[0060]

[0061] in, After optimization The phase of the antennas; After optimization The distance between the first antenna and the second antenna; is the desired pointing angle of the terahertz wave signal after optimization;

[0062] ;

[0063] in, is the optimized terahertz wave signal amplitude.

[0064] As a further improvement of the technical solution, the specific steps of S32 are as follows:

[0065] The effect of phase control is measured according to the objective function:

[0066] ;

[0067] in, Phase The objective function of is the target terahertz wave signal amplitude; is the target phase;

[0068] Introducing weights Optimizing Phase Distribution:

[0069] ;

[0070] in, To maximize the amplitude of the synthesized terahertz wave signal; is the weight vector; For the The weight of each antenna; To find the optimal weight ;

[0071] Define the Lagrangian function:

[0072] ;

[0073] in, is the Lagrangian function; is the Lagrange multiplier;

[0074] Solve for the optimal weights:

[0075] ;

[0076] ;

[0077] in, for about The partial derivative of for about The partial derivative of For the The terahertz wave signal amplitude of each antenna; After optimization The phase of the antenna.

[0078] As a further improvement of the technical solution, the S34 is specifically:

[0079] First, the short-time energy of the input terahertz wave signal is calculated, the threshold of gain adjustment is set according to the application requirements, the gain factor is calculated based on the comparison result between the signal energy and the threshold, and the calculated gain factor is applied to the terahertz wave signal;

[0080] Secondly, fuzzy sets are defined according to different ranges of terahertz wave signal intensity, appropriate membership functions are defined for each fuzzy set, and fuzzy rules are established. The optimal gain adjustment amount is obtained based on the membership function and fuzzy rules of the input terahertz wave signal intensity, and the fuzzy output is converted into a gain adjustment value.

[0081] Finally, the obtained gain adjustment value is applied to the terahertz wave signal, the quality of the output terahertz wave signal is checked regularly, and the parameters of the fuzzy logic control are adjusted according to the quality feedback of the output terahertz wave signal.

[0082] Compared with the prior art, the present invention has the following beneficial effects:

[0083] 1. In the detection imaging system of the on-chip room-temperature terahertz detector based on signal enhancement function, the non-ideality of the nonlinear crystal is taken into account when calculating the phase mismatch, so that the phase matching condition is more in line with the actual situation; the actual phase mismatch after temperature tuning and material loss is taken into account, so as to more accurately adjust the periodic polarization period to achieve phase matching; it can improve the conversion efficiency in the mixing process, thereby improving the efficiency of terahertz wave generation.

[0084] 2. In the detection and imaging system of the on-chip room-temperature terahertz detector based on signal enhancement function, an adaptive configuration function is introduced in the adjustment of the antenna array, which can automatically adjust the configuration of the antenna array according to the real-time signal conditions, so as to adapt to the changing environmental conditions; at the same time, it combines the advantages of traditional automatic gain control with the flexibility of fuzzy logic, which can not only significantly improve the receiving intensity of terahertz wave signals, but also enhance the directionality and sensitivity of the system. At the same time, real-time phase control and phased array technology are used to further optimize the signal quality and improve the accuracy of detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 It is the overall flow chart of the present invention;

[0086] The meaning of each number in the figure is:

[0087] 1. Terahertz radiation source; 2. Transmitter; 3. Detector; 4. Processing and display unit. DETAILED DESCRIPTION

[0088] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0089] Example

[0090] See also Figure 1 As shown, a detection imaging system of an on-chip room-temperature terahertz detector based on a signal enhancement function is provided. The on-chip room-temperature terahertz detector is a sensor integrated on a single chip that can effectively detect electromagnetic radiation within the terahertz frequency range at room temperature. The simplified steps are as follows: first, a terahertz radiation source generates terahertz waves, which are focused and directed by optical elements (such as lenses and reflectors); the terahertz waves reflect the sample to be detected, and the terahertz waves absorb, scatter or refract the physical and chemical properties of the sample, and the terahertz wave signal carries information on the surface or inside of the sample; secondly, the detector captures the terahertz wave signal and directly enhances the signal on the chip, and then converts the terahertz signal into an electrical signal, which is then converted into a digital signal after amplification and filtering preprocessing; then, a processing system receives the digital signal, processes the digital signal, reconstructs a two-dimensional or three-dimensional image of the sample based on the collected data, and finally displays the image, interprets and analyzes it, and obtains information about the sample to be detected. The system includes a terahertz radiation source 1, a transmitter 2, a detector 3, and a processing and display unit 4;

[0091] The terahertz radiation source 1 is used to generate terahertz waves, and focus and direct them through optical elements; the detailed steps of the terahertz radiation source 1 generating terahertz waves are as follows:

[0092] S11. Select a quantum laser that can emit infrared light in the required frequency range. The quantum laser can be modulated by an external modulator to change the frequency of the emitted light. These lasers usually operate in the mid-infrared region, such as between 3 and 25 microns, depending on the specific application requirements. In this way, the frequency of the quantum laser can be changed to achieve frequency mixing with another light source, which can provide pump light of sufficient intensity and adjustable frequency.

[0093] S12. Select a nonlinear crystal that can achieve the required frequency conversion; it has a good nonlinear coefficient and can achieve the required frequency conversion. Commonly used crystals include , GaAs, ZnTe, etc., select the appropriate nonlinear crystal according to the required frequency conversion requirements and ensure that the crystal can achieve the required nonlinear effect;

[0094] S13. By adjusting the temperature of the nonlinear crystal and combining the periodic polarization method for phase matching to achieve the desired phase matching conditions, the light wave of the quantum laser is mixed with another light wave of a fixed frequency in the nonlinear crystal, and the frequency difference between the two light waves is converted into a terahertz wave; wherein, the influence of nonlinear crystal loss is introduced into the phase matching for optimization; the phase matching conditions are optimized by temperature tuning and periodic polarization to achieve efficient frequency conversion.

[0095] In S13, phase matching is performed as follows:

[0096] Determine the initial phase mismatch:

[0097]

[0098] in, is the initial phase mismatch; is the wave vector of the terahertz wave signal; and are the wave vectors of the two light waves involved in the mixing; by adjusting the temperature Approaching 0;

[0099] Reducing the phase mismatch by temperature tuning:

[0100] ;

[0101] in, is the amount of phase mismatch reduced by temperature tuning; is the initial temperature; is the final temperature; is the wavelength of the terahertz wave signal; is the refractive index of the terahertz wave signal in the nonlinear crystal; is the wavelength of the light wave of the quantum-level laser involved in the mixing; is the refractive index of the light wave of the quantum laser involved in the mixing in the nonlinear crystal; is the wavelength of the fixed frequency light wave involved in the mixing; is the refractive index of the fixed frequency light wave involved in mixing in the nonlinear crystal;

[0102] The relationship between wave vector and refractive index:

[0103]

[0104] in, For the The wave vector of a light wave; For the The wavelength of a light wave; For the The wavelength of a light wave at temperature The refractive index under

[0105] Remaining phase mismatch:

[0106]

[0107] in, is the remaining phase mismatch;

[0108] Periodic poling cycle:

[0109]

[0110] in, is the polarization period; is the effective wavelength; is the effective refractive index; is the angle of incidence relative to the principal axis of the nonlinear crystal;

[0111]

[0112] in, and are the wavelengths of the light waves participating in the interaction;

[0113] Adjust the periodic poling period to meet the phase matching condition:

[0114]

[0115] in, is the modulus of the remaining phase mismatch. This formula is used to adjust the periodic poling period To meet the phase matching condition. , so that The modulus value is equal to , thereby achieving the best phase matching; through the above steps, the phase matching conditions can be gradually optimized, and finally efficient frequency mixing and terahertz wave generation can be achieved;

[0116] However, the nonlinear crystals actually used may not be completely ideal and may have certain losses or nonlinear effects. Therefore, the influence of these factors needs to be considered when calculating the phase mismatch, and the influence of nonlinear crystal loss is introduced into the phase matching for optimization. After optimization, the specific results are:

[0117]

[0118] in, is the additional phase mismatch due to nonlinear crystal loss; is the imaginary part of the refractive index of the terahertz wave in the nonlinear crystal; is the imaginary part of the refractive index of the quantum laser light wave in the nonlinear crystal; is the imaginary part of the refractive index of a light wave of fixed frequency in a nonlinear crystal;

[0119] Remaining phase mismatch:

[0120]

[0121] in, is the remaining phase mismatch after optimization;

[0122] Phase matching conditions:

[0123]

[0124] in, is the modulus of the remaining phase mismatch after optimization.

[0125] By introducing , the non-ideality of the nonlinear crystal is taken into account when calculating the phase mismatch, making the phase matching condition more in line with the actual situation; , the actual phase mismatch after considering temperature tuning and material loss can be obtained, so as to adjust the periodic poling period more accurately. To achieve phase matching; through the careful adjustment of the phase mismatch, the conversion efficiency in the mixing process can be improved, thereby improving the efficiency of terahertz wave generation.

[0126] S14. Extract the generated terahertz waves from the nonlinear crystal, specifically using antennas to focus and guide the terahertz radiation. The antenna can be used to focus the terahertz waves into a smaller area, which is very useful for improving detection sensitivity and spatial resolution. The antenna can guide the propagation direction of the terahertz waves so that they can accurately reach the target location or detection equipment. By focusing and guiding the terahertz waves, the energy loss during the propagation process can be reduced, and the overall efficiency of the system can be improved.

[0127] The transmitter 2 is used to reflect the terahertz wave to the sample to be detected. The physical and chemical properties of the sample to be detected are absorbed by the terahertz wave, and the terahertz wave signal carries the information of the sample to be detected.

[0128] The sample to be tested is fixed by a sample holder and placed at a position where the terahertz wave can reach, ensuring that the sample is aligned with the terahertz wave path;

[0129] The physical properties of the samples to be tested include density, thickness, surface roughness and crystallinity; the chemical properties include molecular structure, moisture content, chemical composition and purity.

[0130] Among them, terahertz waves can be used to measure the density of samples, because materials with different densities have different absorption and reflection characteristics for terahertz waves; terahertz waves can penetrate samples of a certain thickness, and the thickness of the sample can be inferred by measuring the transmittance of terahertz waves; the roughness of the sample surface will affect the reflection and scattering characteristics of terahertz waves; terahertz waves can be used to measure the crystallinity of samples, because different crystallinity will cause the shape of the absorption spectrum of terahertz waves to change;

[0131] Terahertz waves can be used to identify specific molecular structures in samples, because different molecular structures will show different absorption peaks in the terahertz frequency band; terahertz waves are very sensitive to water molecules, so they can be used to measure the moisture content in samples; the chemical composition of the sample can be identified through terahertz wave signal spectrum analysis, because different chemical compositions have different absorption characteristics; terahertz waves can be used to detect the purity of samples, because the presence of impurities will affect the absorption and reflection of terahertz wave signals.

[0132] The detector 3 is used to capture the terahertz wave signal carrying the information of the sample to be detected, and perform signal enhancement on the terahertz wave signal carrying the information of the sample to be detected, convert the enhanced terahertz wave signal into an electrical signal, amplify and filter the electrical signal, and finally convert it into a digital signal and transmit it to the processing and display unit 4;

[0133] In the detector 3, the signal enhancement of the terahertz wave signal carrying the information of the sample to be detected is specifically as follows:

[0134] S31. Design the antenna array in advance according to the required terahertz wavelength, integrate the antenna array into the front end of the detector, and adjust the antenna array. At the same time, introduce an adaptive configuration function for optimization during the adjustment of the antenna array; integrate the antenna array on the detector to enhance the capture and focusing capabilities of terahertz waves. The antenna array can be designed to match the terahertz wavelength to maximize the collection and enhancement of the signal. The antenna array can achieve signal directionality and enhancement through phased array technology, improving the sensitivity and directional resolution of the detector.

[0135] In S31, the method for adjusting the antenna array is specifically as follows:

[0136] Antenna spacing:

[0137]

[0138] in, is the distance between two adjacent antennas;

[0139] Phase difference control:

[0140]

[0141] in, For the The phase of the antennas; is the desired terahertz wave signal pointing angle; For the The distance between the first antenna and the second antenna;

[0142] Signal Enhancement:

[0143] ;

[0144] in, is the terahertz wave signal amplitude; is the total number of antennas; ; For the The terahertz wave signal amplitude of each antenna; is an imaginary unit;

[0145] Suppose we have a terahertz wavelength The antenna array has a spacing of ;

[0146] Phase difference calculation: If the terahertz wave signal is Angle of incidence, the phase difference between two adjacent antennas for:

[0147] Signal enhancement calculation: Assume that there are 5 antennas in the antenna array and the output signal amplitude of each antenna is the same ( ), then the amplitude of the composite signal for: ;

[0148] Here, we need to calculate Assuming that the terahertz wave signal points at an angle (i.e. directly in front), then the phase difference for: , therefore, the amplitude of the synthesized terahertz wave signal is for: .

[0149] The adaptive configuration function is introduced in the adjustment of the antenna array for optimization, which can automatically adjust the layout of the antenna array based on the signal strength and direction of the terahertz wave, as follows:

[0150]

[0151] in, After optimization The distance between each antenna and the previous antenna; It is the adaptive configuration function; For the The terahertz wave signal strength received by each antenna; For the The angle of the terahertz wave signal received by each antenna relative to the normal line of the antenna array;

[0152] Based on signal strength and signal direction Dynamically adjust the antenna spacing to maximize signal capture efficiency. In different application scenarios, the strength and direction of the signal will vary. The adaptive configuration function allows the system to automatically adjust the configuration of the antenna array according to real-time signal conditions, thereby adapting to changing environmental conditions.

[0153]

[0154] in, After optimization The phase of the antennas; After optimization The distance between the first antenna and the second antenna; is the desired pointing angle of the terahertz wave signal after optimization;

[0155] ;

[0156] in, is the optimized terahertz wave signal amplitude.

[0157] S32. Real-time phase control is performed through a digital signal processor to optimize the phase distribution to achieve the best signal directionality and signal enhancement. Signal superposition is achieved through a phased array method, and the phase distribution is optimized to achieve the signal enhancement effect. This can not only significantly improve the receiving intensity of the terahertz wave signal, but also enhance the directionality and sensitivity of the system. At the same time, real-time phase control and phased array technology can further optimize the signal quality and improve the accuracy of detection.

[0158] The specific steps of S32 are as follows:

[0159] The effect of phase control is measured according to the objective function:

[0160] ;

[0161] in, Phase The objective function of is the target terahertz wave signal amplitude; is the target phase; this objective function attempts to minimize the difference between all antenna signals and the target terahertz wave signal by minimizing , we can find a set of phases , so that the synthesized signal is as close as possible to the target terahertz wave signal;

[0162] Introducing weights Optimizing Phase Distribution:

[0163] ;

[0164] in, To maximize the amplitude of the synthesized terahertz wave signal; is the weight vector; For the The weight of each antenna; To find the optimal weight ; By solving The maximum value of , so that the amplitude of the synthetic terahertz wave signal reaches the maximum.

[0165] Define the Lagrangian function to balance the objective function and constraints:

[0166] ;

[0167] in, is the Lagrangian function; is the Lagrange multiplier;

[0168] Solve for the optimal weight and find the optimal weight and Phase :

[0169] ;

[0170] ;

[0171] in, for about The partial derivative of for about The partial derivative of For the The terahertz wave signal amplitude of each antenna; After optimization The phase of the antenna.

[0172] Through these formulas, we define an objective function To measure the effect of phase control, and by introducing weights To optimize the phase distribution to maximize the amplitude of the synthesized terahertz wave signal. Use the Lagrange multiplier method to solve the constrained optimization problem and find the optimal weights and Phase , which can effectively improve the performance and signal quality of terahertz wave detectors.

[0173] S33. On the basis of enhancing the signal effect, a differential self-mixing power detection circuit is adopted, and an adaptive frequency tracking function is introduced to convert the terahertz wave signal into a low-frequency signal that is easy to process; the differential self-mixing power detection circuit can improve the dynamic range and signal-to-noise ratio of the signal;

[0174] S34. After the terahertz wave signal is converted into a low-frequency signal, digital automatic gain control is used to implement automatic gain control, and fuzzy logic control is used to perform fine gain adjustment to adapt to terahertz wave signals of different intensities. The circuit design may include a preamplifier, a filter, and an automatic gain control circuit to optimize the signal amplification and filtering process and reduce the impact of noise;

[0175] S34 is specifically as follows: first, a short-time energy calculation is performed on the input terahertz wave signal to evaluate the strength of the terahertz wave signal, a gain adjustment threshold is set according to application requirements, such as the maximum and minimum gain levels, a gain factor is calculated based on the comparison result between the terahertz wave signal energy and the threshold, and the calculated gain factor is applied to the terahertz wave signal; the dynamic range of the terahertz wave signal can be effectively expanded, so that weaker terahertz wave signals become recognizable, while avoiding saturation or distortion caused by stronger terahertz wave signals; the gain adjustment method based on the terahertz wave signal energy can cope with changes in the strength of various terahertz wave signals, thereby improving the robustness and adaptability of the system.

[0176] Secondly, fuzzy sets are defined according to different ranges of terahertz wave signal intensity, such as "very weak", "weak", "moderate", "strong", etc., and appropriate membership functions are defined for each fuzzy set to express the relationship between signal intensity and fuzzy sets. Fuzzy rules are also established, such as "if the terahertz wave signal intensity is 'very weak', the gain should be increased more; if it is 'moderate', the gain remains unchanged", etc. The optimal gain adjustment amount is obtained by analyzing the membership function and fuzzy rules of the input terahertz wave signal intensity, and the fuzzy output is converted into a gain adjustment value.

[0177] Fuzzy logic can provide a more sophisticated gain adjustment method, especially for terahertz wave signal strengths between two thresholds, which may not be accurately processed by traditional threshold methods. Fuzzy logic can achieve nonlinear mapping relationships through membership functions, which helps to better match the complex relationship between signal strength and required gain; and by analyzing the membership of terahertz wave signal strength and combining it with fuzzy rules, a more accurate gain adjustment amount can be obtained, improving the adaptability of the system.

[0178] Finally, the obtained gain adjustment value is applied to the terahertz wave signal, the quality of the output terahertz wave signal is checked regularly, and the parameters of the fuzzy logic control are adjusted according to the quality feedback of the output terahertz wave signal. Based on the feedback of the quality of the output terahertz wave signal, the parameters of the fuzzy logic control can be continuously optimized to keep the system at its optimal performance in a changing environment.

[0179] The antenna array is designed and integrated in S31, which provides the basis for capturing terahertz waves in subsequent steps; S32 optimizes the performance of the antenna array and improves the quality of terahertz wave signals through real-time phase control and signal enhancement; S33 converts terahertz waves into easy-to-process low-frequency signals through mixing and frequency tracking functions, while ensuring that the circuit can adapt to terahertz waves of different frequencies; S34 ensures stable signal output through automatic gain control, and makes fine adjustments through fuzzy logic control to adapt to signals of different intensities.

[0180] The processing and display unit 4 is used to receive and process digital signals, obtain information about terahertz waves, convert the received digital signals into spatial image information, and display and analyze the images to obtain information about the sample to be tested. Image processing can enhance the contrast between different substances and make details more clearly visible.

[0181] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only preferred examples of the present invention, and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A detection imaging system based on an on-chip room temperature terahertz detector with a signal enhancement function, characterized in that: include: Terahertz radiation source (1): used to generate terahertz waves and focus and direct them through optical elements; Transmitter (2): used to reflect the terahertz wave to the sample to be detected, and the physical and chemical properties of the sample to be detected are absorbed by the terahertz wave, so that the terahertz wave carries information of the sample to be detected; Detector (3): used to capture the terahertz wave signal carrying the information of the sample to be detected, and to enhance the terahertz wave signal carrying the information of the sample to be detected, convert the enhanced terahertz wave signal into an electrical signal, amplify and filter the electrical signal, and finally convert it into a digital signal and transmit it to the processing and display unit (4); Processing and display unit (4): used to receive and process digital signals, obtain information of terahertz wave signals, convert the received digital signals into spatial image information, and display and analyze the spatial image to obtain information of the sample to be detected; The detailed steps of the terahertz radiation source (1) generating terahertz waves are as follows: S11, selecting a quantum-level laser capable of emitting infrared light within a desired frequency range, wherein the quantum-level laser can be modulated by an external modulator to change the emitted light frequency; S12, selecting a nonlinear crystal capable of achieving the required frequency conversion; S13. By adjusting the temperature of the nonlinear crystal and combining the periodic polarization method for phase matching to achieve the required phase matching conditions, the light wave of the quantum laser is mixed with another light wave of a fixed frequency in the nonlinear crystal, and the frequency difference between the two light waves is converted into a terahertz wave; wherein the influence of nonlinear crystal loss is introduced into the phase matching for optimization; S14, extracting the generated terahertz wave signal from the nonlinear crystal, and using an antenna to focus and direct the terahertz radiation; In S13, phase matching is performed as follows: Determine the initial phase mismatch: ； in, is the initial phase mismatch; is the wave vector of the terahertz wave signal; and are the wave vectors of the two light waves involved in the mixing; Reducing the phase mismatch by temperature tuning: ； in, is the amount of phase mismatch reduced by temperature tuning; is the initial temperature; is the final temperature; is the wavelength of the terahertz wave signal; is the refractive index of the terahertz wave signal in the nonlinear crystal; is the wavelength of the light wave of the quantum-level laser involved in the mixing; is the refractive index of the light wave of the quantum laser involved in the mixing in the nonlinear crystal; is the wavelength of the fixed frequency light wave involved in the mixing; is the refractive index of the fixed frequency light wave involved in mixing in the nonlinear crystal; Remaining phase mismatch: ； in, is the remaining phase mismatch; Periodic poling cycle: ； in, is the polarization period; is the effective wavelength; is the effective refractive index; is the angle of incidence relative to the principal axis of the nonlinear crystal; Adjust the periodic poling period to meet the phase matching condition: ； in, is the modulus of the remaining phase mismatch; In S13, the influence of nonlinear crystal loss is introduced into the phase matching for optimization, and the optimization is as follows: ； in, is the additional phase mismatch due to nonlinear crystal loss; is the imaginary part of the refractive index of the terahertz wave signal in the nonlinear crystal; is the imaginary part of the refractive index of the quantum laser light wave in the nonlinear crystal; is the imaginary part of the refractive index of a light wave of fixed frequency in a nonlinear crystal; Remaining phase mismatch: ； in, is the remaining phase mismatch after optimization; Phase matching conditions: ； in, is the modulus of the remaining phase mismatch after optimization.

2. The detection imaging system of the on-chip room temperature terahertz detector based on the signal enhancement function according to claim 1, characterized in that: During the operation of the transmitter (2), the sample to be tested is fixed by the sample holder and is placed at a position that can be reached by the terahertz wave.

3. The detection imaging system of the on-chip room temperature terahertz detector based on the signal enhancement function according to claim 2, characterized in that: In the detector (3), the signal enhancement of the terahertz wave signal carrying the information of the sample to be detected is specifically performed as follows: S31. Design an antenna array in advance according to the required terahertz wavelength, integrate the antenna array into the front end of the detector, and adjust the antenna array. At the same time, introduce an adaptive configuration function for optimization during the adjustment of the antenna array; S32. Real-time phase control is performed through a digital signal processor to optimize the phase distribution to achieve the best signal directionality and signal enhancement. Signal superposition is achieved through a phased array method, and the phase distribution is optimized to achieve the effect of signal enhancement.

4. The detection imaging system of the on-chip room temperature terahertz detector based on the signal enhancement function according to claim 3 is characterized in that: In the detector (3), the signal enhancement of the terahertz wave signal carrying the information of the sample to be detected also includes: S33. On the basis of enhancing the signal effect, a differential self-mixing power detection circuit is adopted, and an adaptive frequency tracking function is introduced to convert the terahertz wave signal into a low-frequency signal that is easy to process; S34. After the terahertz wave signal is converted into a low-frequency signal, automatic gain control is implemented, and gain adjustment is performed using fuzzy logic control to adapt to terahertz wave signals of different intensities.

5. The detection imaging system of the on-chip room temperature terahertz detector based on the signal enhancement function according to claim 4, characterized in that: In S31, the method for adjusting the antenna array is specifically as follows: Antenna spacing: ； in, is the distance between two adjacent antennas; Phase difference control: ； in, For the The phase of the antenna, is the desired terahertz wave signal pointing angle, For the The distance between the first antenna and the second antenna; Signal Enhancement: ； in, is the terahertz wave signal amplitude, is the total number of antennas, ; For the The terahertz wave signal amplitude of each antenna is Is an imaginary unit.

6. The detection imaging system of the on-chip room temperature terahertz detector based on the signal enhancement function according to claim 5, characterized in that: In the S31, an adaptive configuration function is introduced to optimize the antenna array during adjustment, as follows: ； in, After optimization The distance between each antenna and the previous antenna; It is the adaptive configuration function; For the The terahertz wave signal strength received by each antenna; For the The angle of the terahertz wave signal received by each antenna relative to the normal line of the antenna array; ； in, After optimization The phase of the antennas; After optimization The distance between the first antenna and the second antenna; is the desired pointing angle of the terahertz wave signal after optimization; ； in, is the optimized terahertz wave signal amplitude.

7. The detection imaging system of the on-chip room temperature terahertz detector based on the signal enhancement function according to claim 6, characterized in that: The specific steps of S32 are as follows: The effect of phase control is measured according to the objective function: ； in, Phase The objective function of is the target terahertz wave signal amplitude; is the target phase; Introducing weights Optimizing Phase Distribution: ； in, To maximize the amplitude of the synthesized terahertz wave signal; is the weight vector; For the The weight of each antenna; To find the optimal weight ; Define the Lagrangian function: ； in, is the Lagrangian function; is the Lagrange multiplier; Solve for the optimal weights: ； ； in, for about The partial derivative of for about The partial derivative of For the The terahertz wave signal amplitude of each antenna; After optimization The phase of the antenna.

8. The detection imaging system of the on-chip room temperature terahertz detector based on the signal enhancement function according to claim 7, characterized in that: The S34 is specifically: First, the short-time energy of the input terahertz wave signal is calculated, the threshold of gain adjustment is set according to the application requirements, the gain factor is calculated based on the comparison result between the signal energy and the threshold, and the calculated gain factor is applied to the terahertz wave signal; Secondly, fuzzy sets are defined according to different ranges of terahertz wave signal intensity, appropriate membership functions are defined for each fuzzy set, and fuzzy rules are established. The optimal gain adjustment amount is obtained based on the membership function and fuzzy rules of the input terahertz wave signal intensity, and the fuzzy output is converted into a gain adjustment value. Finally, the obtained gain adjustment value is applied to the terahertz wave signal, the quality of the output terahertz wave signal is checked regularly, and the parameters of the fuzzy logic control are adjusted according to the quality feedback of the output terahertz wave signal.

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