This PDF file contains the front matter associated with SPIE Proceedings Volume 12555, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Precision ceramic bonded structural parts have an irreplaceable position in the aerospace business and are widely used in various industries due to their various advantages, but at the same time, the uneven thickness of the adhesive layer will affect the quality of ceramic adhesive structural par. In this paper, terahertz time-domain spectroscopy is used for nondestructive detection of the adhesive layer inside the sample, and the thickness information is reconstructed from the experimental data using an autoregressive spectral extrapolation method based on improved covariance, and the difference in the time of flight of the echoes on the upper and lower surfaces of the adhesive layer is used to find the thickness of the adhesive layer. This paper analyzes the thickness of the adhesive layer of 0.5mm and 1mm respectively, and finally gets the error rate of 7.2% and 6.3%. This error rate is basically in line with the quality of the product and provides reliable technical support for the aerospace business.

In this study, a classification model for THz spectral data of coffee is constructed using an integrated learning approach, an AELM optimization model is proposed, the ELM is improved using the AO population optimization algorithm, the connection weights of the input and implicit layers of the ELM and the threshold of the implicit layer are searched for, the AELM is used as a weak classifier of FSAMME for integrated learning, the weights of the FSAMME algorithm are improved The update method is used to increase the weight of misclassified sample data and reduce the weight of weak classifiers with high classification error rate in the final classifier by dynamically weighting them during the iteration process according to the classification accuracy, and finally normalize all weak classifier weights to integrate the strong classifier AE-dynamic FS integrated learning model. The accuracy of AO-ELM-dynamic FSAMME model on the test set sample data set of five coffee origins is 99%, the classification accuracy of coffee samples from China, Brazil, Colombia, Ethiopia and Honduras is 100%, 100%, 100%, 94.4% and 100% respectively, and the number of samples misclassified is 1 sample from Ethiopia,realizing excellent classification performance.

In this paper, a terahertz axicon (n=1. 55) with a base angle of 10 degrees is designed, introduced into a Terahertz Time domain spectroscopy(THz-TDS) (0. 1-1THz), and a transmission beam scanning experiment is built. At each waveform of the raster scan of each section, the spectrum is calculated using a Fast Fourier Transform (FFT) to obtain the beam cross section for each frequency. The measured central beam width at different frequencies varies between 7mm and 2. 5mm, and the distance between the measurement plane and the tip of the axicon is 80mm; by numerically processing the information of each plane, the beam reconstruction results at different frequencies can be obtained. From the analysis results, it can be seen that the THz-TDS can generate non-diffracting beams with depth of field exceeding 160mm via an axicon with a base angle of 10 degrees, the central spot width does not exceed 7 mm, and there are almost no side lobes. The results show that the Bessel beam can provide a significant depth of field expansion capability for the THz-TDS, which will have a positive impact on the non-destructive testing of samples with large thickness and uncertain defect locations.

A rotary dual-channel roll and pitch tracking scheme is proposed, and a dual-channel rotation control algorithm is designed to solve the problem of detector front and phase plane rotation, expand the field of view, and improve detection efficiency. The light and miniaturized platform design in space improves the control speed and accuracy. In the strong maneuvering state of the terminal target, the dual-channel infrared tracking reduces the amount of target misses and improves the performance of the control system to precisely hit the target. In this paper, the research results obtained are expounded from the two aspects of the rotary dual-channel system tracking principle and the rotary dual-channel tracking control method. Firstly, the design of the dual-channel rotation control algorithm is introduced; secondly, the dual-channel rotation tracking loop is designed; finally, the research results are verified by experiments, which illustrate the advantages of the rotation-based tracking in fast response, dual-channel interaction and precise guidance.

With the further development of the technology, the application of infrared imaging detection system environment gradually extended to the external field, high altitude, near space and outer space, etc. Its working temperature range is getting wider and wider, low temperature can reach -50°C below, high temperature can reach 70°C above. Infrared imaging detection system needs to meet the requirements of quantitative detection technology in a wide temperature range to ensure the completion of corresponding functions. In order to ensure that the infrared detection system can perform performance testing, radiometric calibration and quantitative traceability in the whole temperature range, this paper developed a large-aperture high-precision fixed-point infrared radiation source with a wide temperature range, and its phase change medium is water. It mainly includes diaphragm assembly, radiation cavity, inner wall coating of radiation cavity, heating assembly, temperature control assembly, etc. After development, verification tests were carried out in high and low temperature environment, and the following indexes were achieved: effective emissivity ≥0.999, cavity opening diameter ≥60mm, and temperature measurement uncertainty: 5mK (k=2). It has been proved that it can meet the measurement and testing requirements of infrared detection system under wide temperature range.

In the process of guiding the target device, the pointing and guidance accuracy of the on-board electro-optical reconnaissance system is affected by the relative installation position of the equipment, as it can not realize the coaxial installation with the guided device. According to the structural characteristics of the equipment, the mathematical model of target orientation function from the image plane coordinate system of the electro-optical reconnaissance system to the equipment base coordinate system is constructed, the error sources affecting the target pointing accuracy are analyzed, and the target pointing error model is established. The Monte Carlo method is used to analyze the relationship between the pointing error and its error sources. The probability density distribution of each error source is established. The target pointing accuracy performance under the influence of different errors is analyzed. And the sensitive factors affecting the pointing accuracy are figured out, which provides a certain theoretical guidance for the error allocation in the accuracy design stage.

With the widespread application of polarizers in infrared detection, military, medical and other fields, infrared polarizers have developed rapidly in the last decade, and it is becoming increasingly crucial to fabricate high-performance and low-cost polarizers. The paper presents a design for fabricating a linear polarizer operating in the 7-14 um by metal-assisted chemical etching. A subwavelength gold grating is fabricated on a silicon substrate by the lift-off process, then a subwavelength silicon grating structure is fabricated by the metal-assisted chemical etching process of silicon, an aluminum film is coated on the bottom of the groove and the ridge of the fabricated subwavelength silicon grating by electron beam evaporation coating. The structure is optimized by the rigorous coupled-wave analysis, we assess the effect of the grating parameters on the extinction ratio and transverse magnetic wave transmittance and optimize the parameters, and finally determined that the grating period is 400 nm, the duty cycle is 0.5, and the groove depth is 1200nm. The numerical simulation results demonstrate that the polarizer has the advantages of high extinction ratio and wide manufacturing tolerance in long wave infrared region (7-14um). Grating structures with high aspect ratio can be fabricated by metal-assisted chemical etching, which makes it possible to enhance the transmission of the silicon substrate. Therefore, anti-reflection structures can be designed to enhance the transmission of the silicon substrate in the long-wave infrared based on the effective medium theory.

The uncooled infrared detector is the core of the uncooled infrared camera. As the connection part of infrared detector and signal processing system, the performance of the focal plane circuit directly restricts the final imaging quality of the camera. According to the characteristics of power supply and temperature control of space-borne 640×512 uncooled infrared detector, a focal plane circuit is designed, which consists of a detector power supply circuit, a detector temperature feedback circuit and a detector temperature control circuit. In the detector power supply circuit, the bias generation circuit composed of DCDC, LDO and operational amplifier is designed for the characteristics of the 640×512 uncooled infrared detector with many kinds of bias and high precision. According to the working requirements of the temperature measuring diode of 640×512 uncooled infrared detector, a 1mA constant current circuit is designed to generate 1mA constant current, and a voltage conditioning circuit is responsible for detecting the voltage value of the temperature measuring diode. In the temperature control circuit of detector, the temperature control system of uncooled infrared detector based on temperature control chip is designed. The system can realize the closed-loop automatic control of thermoelectric cooler (TEC), which has the advantages of low power consumption, high precision and high reliability. The experimental results show that the system can effectively control the temperature of infrared detector at room temperature. When the operating temperature of the detector is -10°C, the accuracy can reach 0.07°C, which meets the requirements of the detector in orbit. After introducing the design method and design idea of each component of focal plane circuit in detail, the designed circuit is tested. The test results show that the design scheme is correct and feasible, and meets the design requirements of the focal plane circuit of the uncooled infrared camera.

In order to study the space-based infrared remote sensing characteristics of hypersonic vehicles, this paper takes the simplified projectile model of HIFIRE-1 aircraft as the object to carry out simulation research. Firstly, the infrared radiation calculation model of the target projectile is established, including the aerodynamic thermal effect engineering simulation model, the projectile temperature calculation model and the projectile infrared radiation calculation model; Secondly, the space-based infrared detection model of hypersonic targets by calculating the spectral contrast between the target and the background is established; Finally, space-based infrared remote sensing characteristics of high orbit infrared early warning satellite for hypersonic vehicles under typical conditions are simulated and analyzed. The results show that, when the hypersonic vehicles fly at a speed of 6Ma at 25km, the detection ability of high orbit infrared early warning satellite for hypersonic target projectile is weak.

The radiation spectrum of the xenon lamp ranges from ultraviolet to mid-infrared. When the skin is irradiatedbythexenon lamp, the skin temperature will change due to the absorption of the radiation. In order to evaluate whether theskintissue will be damaged when the human body is irradiated with a xenon lamp, it is necessary to obtain the temperaturefield of the skin irradiated by the xenon lamp.In this paper, two methods of numerical calculation and thermal effect test were used to compare and study the instantaneous temperature field of the skin irradiated by a 10Kw xenon lamp.Firstly, the three-layer structure model of human skin tissue was analyzed. Secondly, the heat transfer process of theskinirradiated by the xenon lamp was studied, and the instantaneous temperature field model was established. Thirdly, athermal effect test device was built, and the human skin tissue was replaced by the isolated pigskin tissue. In anindoorenvironment, the experiment of irradiating the pigskin tissue with a xenon lamp was carried out, and the temperatureofseveral positions of the pigskin tissue at different irradiation time was recorded by contact temperature measurement. Finally, using the Heat Transfer in Solids Module in COMSOL Multiphysics 5.5 software, the 3D transient temperaturefield of the skin was solved. The results of experimental test and numerical calculation were compared and analyzed. At the same irradiation time, the numerically calculating temperature value was higher than the experimental test value. Themean value of the absolute error between the numerically calculating temperature value and the experimental test valuewas 6.0°C, and the mean value of the relative error was 14%. The research results provide a scientific basis for thesafeuse of the xenon lamp.

There are deviations in the images of the same target at different angles, so the multi-angle infrared images contain additional classification and identification feature information. Therefore, the multi-angle image acquisition system can effectively solve the problems such as occlusion and small target size that cannot be recognized with high precision. Combined with the multi-angle acquisition system, a multi-angle infrared vehicle target recognition algorithm based on Light-Head R-CNN was proposed. Firstly, inputted the multi-angle infrared images of the same target into the ConvNeXt backbone network for feature extraction; Secondly, in order to reduce the amount of model parameters and realize the lightweight of the network, the traditional convolution in the backbone network was replaced with Ghost Module, which reduced the amount of FLOPs and parameters by about 50%; At the same time, according to the characteristics of infrared vehicle targets, the Light-Head R-CNN target recognition algorithm was improved, and an ultra-lightweight ECA module without dimensionality reduction local cross-channel interaction was added to improve the performance of the network for infrared vehicle target recognition; Finally, the Dempster synthesis rule was used to perform data fusion on the recognition accuracy of images from different angles predicted by the network to obtain the final recognition accuracy. It had been verified that compared with single-angle images, when the number of input angles was 2, the recognition accuracy of the algorithm in the constructed data set was improved by 3.8%; The recognition accuracy reached 90.1%, it was optimal, while the input infrared images were distributed at a certain angle and the number was 5, at the same time the speed achieved 44fps. The results fully demonstrated the feasibility of the proposed algorithm in improving the recognition accuracy, and provided a theoretical and experimental basis for enhancing the performance of the target recognition algorithm.

Leakage of volatile organic compounds (VOC) gas is one of the main sources of air pollution, and it poses a great threat to health and safety in many ways. Optical gas imaging (OGI) technique utilizes mid-wave infrared camera to visualize VOC gas and helps people observe the leakage of VOC gas. In this paper, we propose a novel method that utilizes deep learning technique and convolutional neural networks to detect the leakage of VOC gas from single-frame mid-wave infrared image. The proposed method consists of three components: color transformation pre-processing unit, feature extraction networks, and single-stage object detection sub-networks. Location-aware deformable convolution, which adjusts its sampling grid to fit the ever-changing shape of VOC gases, is employed for better feature extraction. Besides, a new loss function called leakage center loss is introduced to estimate where leakage comes from, and it forces the network to pay more attention to leakage center where the density of VOC gases is higher than dissipated parts. The proposed method is evaluated using a self-collected dataset where thousands of gas images are captured and annotated. Experimental results show that location-aware deformable convolution contributes to around 7%mAP improvement, while leakage center loss contributes to around 4% mAP improvement. Finally, our method achieves 81%mAP, which is better than existing general-purpose object detection methods. By simplifying the network architecture, our proposed method can also be implemented on embedded system for handheld VOC leakage detection devices.

Quartz enhanced photoacoustic spectroscopy (QEPAS) is a high performance trace gas detection technique that plays an important role in food safety, pollution monitoring and breath analysis applications. It is well known that the sensitivity of QEPAS gas detection system is proportional to excitation laser power and thus the performance of QEPAS-based sensors can benefit from the high output power levels achieved as a result of technology developments by the high power laser. This paper mainly introduces three kinds of QEPAS gas sensor based on fiber-ring laser.

In this paper, the dual laser induced measurement of thermal conductivity of solids is studied based on the laser-induced technique. Perfected the principle of dual-wavelength infrared laser-induced measurement of thermal conductivity of solids, and built an experimental system. According to the principle of measuring the thermal conductivity of solid with dualwavelength infrared laser, an experimental system was built. Taking the fully oxidized 304 stainless steel as an example, the feasibility of the method and the stability of the system are verified; the relationship between thermal conductivity and temperature of 304 stainless steel is obtained; and the influence of the temperature inconsistency between the reference sample and the sample to be tested on the measurement results of the correction factor is analyzed. The results show that the experimental system for measuring the thermal conductivity of solids has good stability, and the stability is within 2% in the range of 873k ~ 1173k; the relationship between thermal conductivity and temperature of 304 stainless steel is K₃₀₄=0.0144T+14.455; when the temperature is 973K and 1073K, the temperature deviation of the two samples is within 1K, the effect of temperature inconsistency is within 1.3%.

In this paper, according to the detection requirements of space infrared camera with large dynamic range and high sensitivity, a Time Delay and Integration (TDI) infrared imaging circuit with large dynamic range is introduced. The designed imaging circuit consists of 1024×7 TDI infrared detector, analog conditioning circuit and data processing circuit. 1024×7 TDI infrared detector is composed of 1024 pixel of seven photosensitive elements on which Time Delay and Integration is performed through the readout integrated circuit. In Time Delay and Integration part, an adaptive TDI stages adjustment circuit is presented, which can automatically switch seven TDI stages or one TDI stage for each pixel according to the intensity of camera detection signal，and the TDI stage mark for each pixel is provided. In analog conditioning circuit part，background subtraction circuit，programmable gain amplification circuit and 14bit ADC are designed. The background signal level is produced by 12bit DAC and the digital data of DAC is calculated from the downloaded image data of the space camera. On the basis of downloaded image data, the digital data can be dynamically uploaded to digital to analog converter by upper computer. The output analog signal of infrared detector is subtracted from background signal level, and then the effective analog signals after the background subtraction are amplified by programmable gain amplification circuit to adapt to the input scale of high precision ADC, which can reduce the equivalent input noise and can improve the dynamic range of space camera. Digital data processing circuit is implemented with FPGA. According to TDI stage mark for each pixel, the TDI stages normalization of each pixel is performed to reconstruct the pixel data in data processing circuit, and the normalized pixel data is corrected by pixel response non-uniformity correction algorithm to improve the quality of images. The designed imaging circuit system is tested, and test results show that the design scheme of the imaging circuit system is reasonable and feasible, which can effectively improve the dynamic range of space infrared camera.

In this paper, a lightweight design is carried out for the rectangular reflector of a small space telescope project. This study suggests a lightweight optimization design strategy based on three-point support in accordance with the high surface figure accuracy and low weight requirements of the project's rectangle reflective mirror. The fundamental structure of the mirror based on SiC material is first obtained, starting from the features of material selection and support method. Then, we get some parameters such as the radius-thickness ratio of the mirror through theoretical calculation and analysis, and preliminarily optimized these parameters. By using the maximization of the overall stiffness as the objective function, and the mirror RMS value as the design restraint, the topology optimization of the mirror is carried out. Finally, considering factors such as processing and manufacturing, we take the methods of size optimization to get an optimal structural model. Through simulation analysis, it can be measured that the weight of the mirror is only 3.94kg, the lightweight rate is 58%, and the RMS value in the X, Y, Z three axes under 1 g gravity condition is far less than 1/25λ(632.8nm) of the design index. This optimization method can well meet the design requirements.

HgTe colloidal quantum dots (CQDs) are appealing candidates for infrared photodetection due to their facile tuning of infrared absorption, solution-processability and compatibility with silicon electronics for imaging. Traditional HgTe CQD synthesis suffers from CQD aggregation or air-sensitive tellurium (Te) precursor. Here, monodisperse HgTe CQDs with sharp excitonic absorption edge and tunable response from 1.7 μm to 6.3 μm are synthesized via a ligand-engineered approach. Thanks to their accessible CQD surface, both the carrier concentration and polarity can be readily tuned by ligand-induced surface gating. The transport property studies present a record electron mobility up to 18 cm² V^-1 s^-1. Short wave infrared photodetectors achieve a high room-temperature detectivity beyond 10¹¹ Jones at the wavelength of 1550 nm. The synthesis strategy is expected to enrich the applications of HgTe CQDs and promote the fast development of CQD infrared detection technology.

Air pollution monitoring is an important aspect of environment preservation, which is of more and more significance in modern society due to the increasing demand of healthy living condition and sustainable development. Infrared (IR) gas imaging is a fast and sensitive way of gas monitoring utilizing the signatures of different gas molecules in absorption spectrum. Our research and development on IR photodetectors based on the InAs/GaSb type-II superlattice (T2SL) material system with a cut-off wavelength beyond long wavelength infrared (LWIR) atmospheric window covering the absorption of sulfur hexafluoride (SF₆) around 10.55 μm will be reported. A new detector structure was designed with a reduced bandgap of the absorber, in conjunction with the unipolar barrier and other parts with specific band alignments. The material was grown by molecular beam epitaxy (MBE) with high structural quality. Single element detectors have been fabricated and shown high performances, including low dark current density 1.0 × 10⁻³ A/cm² and high resistance 1.0 × 10⁷ Ω for 30 × 30 μm diode at −0.1 V bias, and the surface leakage is also reduced effectively. The LWIR FPA fabrication for SF₆ detector is underway

With the efficient use of energy, the study of emissivity is considered to be of great importance. In industrial production, temperature measurement technology, and many other fields, emissivity research is performed an important role. The emissivity is considered to be an important quantitative parameter for the infrared radiation characteristics of high-temperature coatings. Although the experimental measurement technique for high-temperature infrared spectral emissivity by the integrated blackbody method has been studied, little research has been reported on the integrated blackbody temperature field measurement and the simulation study of the emissivity of the integrated blackbody cavity. Therefore, in this paper, the temperature distribution of integrated blackbody cavity with the graphite cavity bottom is measured at 800°C, 1000°C. Besides, the above results are adopted, and the effective emissivity of the integrated blackbody is numerically simulated, based on the measurement results and the Monte-Carlo ray-tracing method. Thus, the feasibility of integrating the blackbody is demonstrated, the infrared radiation properties of integrated blackbodies are also studied as influenced by the temperature of the blackbody cavity.

Accurate measurement of the true surface temperature of high-temperature materials is very important in many fields, such as modern industrial systems, solar heat utilization and metrology. At present, passive radiation thermometry is mainly used to measure the real surface temperature of high-temperature materials. This technology cannot get rid of the influence of emissivity on temperature measurement accuracy. The active laser infrared radiation thermometry is a new emissive-free temperature measurement technology. Based on the active thermometry of dual-wavelength infrared laser, with the condition of environmental reflection interference and unknown emissivity, the true surface temperature of high-temperature material is precisely measured and studied. Based on the theoretical model of active dual-wavelength infrared laser thermometry, an active laser thermometry system was built and upgraded in this study. The active temperature measurement experiments of changing laser power were carried out to analyze the influence of laser power on the accuracy of active temperature measurement. Then the active temperature measurement experiments were carried out by changing the laser modulation frequency to analyze the influence of the laser modulation frequency on the active temperature measurement accuracy. The results show that the reasonable selection of laser parameters(laser power and laser modulation frequency) is the key to carrying out precision temperature measurement based on active laser infrared radiation thermometry.

In the experiment of measuring the emissivity distribution characteristics by integrating sphere reflection method, the laser output power stability is an important guarantee for the accurate emissivity measurement. However, there is a lack of research on the influence of laser power stability on measurement results. Therefore, a measurement system for the infrared radiation source emissivity distribution characteristics is designed and built based on the complete hemispherical laser integrated reflection scheme in this paper. The stability of the laser light source subsystem is evaluated, and the laser power drift is corrected by means of a alternating measurement sequence. The experiment of measuring the flat plate radiation source emissivity distribution characteristics is carried out with a laser power of 3 W. The results show that the laser power shows a periodic drift and one period is about 70 s. The macroscopic power of the laser increases linearly throughout the measurement process. After correcting the laser power drift, the relative standard deviation of the flat plate radiation source is 0.56%, and the volatility is 2.99%. After drift correction, the measurement accuracy is improved by 28.2%.

In order to explore new fiber materials that can be used for discrete Raman amplifier, first and second order Raman amplifiers are designed based on TiO₂-doped fiber. A pump parameter configuration scheme with high power conversion efficiency and flat gain is given. The gain characteristics of first-order and second-order Raman amplifiers based on TiO₂-doped fiber and second-order Raman amplifiers based on GeO₂-doped fiber are compared with the same total pump power. The simulation result shows that in the 60nm bandwidth range of L-band, 32dBm pump light is injected forward into 6km long TiO₂-doped fiber to amplify 3dBm signal light. Its power conversion efficiency can reach 41.57%, and the gain flatness is only 1.14dB. Compared with the second-order Raman amplifier doped with GeO₂ fiber, it has a more stable output gain.

With the development of the next generation of intelligent battlefield situation awareness technology, infrared multi-target tracking plays an increasingly important role in complex background. However, the commonly used infrared target tracking algorithm, weak small target enhanced motion information ignores the apparent feature, large target enhanced apparent feature ignores the motion information. To solve the above problems, this paper proposes a target tracking method based on the fusion of location, detection and feature matching, constructs the target motion information predictor information and target detection response, so as to achieve fast target tracking. Firstly, the Bayesian multi-target filter is used, and the weight factor of the corresponding Gaussian component is added to the Kalman filter to obtain the number and state set of the targets in the scene at a certain time, and the target position predictor is established to complete the primary correlation based on the fast position prediction. Then, according to the feature distribution of the detection response, the secondary correlation based on the effective features of the targets is completed, Form the final complete track of the target. In this paper, the multi-target complex scene multi-target motion environment simulation experiments, the experimental results show that the algorithm can better track the target in complex motion environment.

The long-wave InAs/GaSb type II superlattice graded barrier structure was grown by MBE and applied to fabricate the various area diodes. The anodic sulfidization treatment, SiO2 film deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD) and ion beam deposition (IBD) were combined into three methods to passivate the diodes. The variation of dark current density and the forming mechanism as related to diode sizes and measurement temperature was characterized and analyzed. The anodic sulfidization and IBD treated diodes show the worst dark current. The two groups of diodes passivated by anodic sulfidization and ICP-CVD obtained the lowest surface leakage current 3.74×10^-5 A/cm² and 5.08×10^-5 A/cm², the maximal surface resistivity 4.48×10⁵ Ω·cm² and 9.68×10⁵ Ω·cm² respectively.