This PDF file contains the front matter associated with SPIE Proceedings Volume 12061, including the Title Page, Copyright information, and Table of Contents.

Imaging scenes or detecting objects hidden from a camera’s view have extensive applications. Previous studies have recently demonstrated impressive results in time-of-flight-based non-line-of-sight (NLOS) imaging systems, but several limitations remain. Measurements are captured by time-resolved detectors based on scanning sampling spots at the diffuse wall. Setting numerous sampling points slows down the process of data acquisition, but reconstruction quality cannot be ensured with limited sampling points. Here, we propose a method, transient interpolation to original sample data, to solve the contradiction between the time of data collection and imaging quality. We calculate the flight time of photons and simulate the photon count data with 15×15 sampling points and multiply them based on our method to obtain high-quality reconstruction within a shorter time. The simulated experiment shows that compared to the original data, transient multiplied data achieves high-quality reconstruction and shortens the measurements-captured time theoretically. Furthermore, our method is robust to different algorithms and can potentially be used in real-time imaging fields.

To make a low-cost and effective infrared polarizer, we designed a mid-infrared polarizer with double-sided silica anti-reflection films. Double-sided silica was oxidized on a silicon substrate. Then, micro gratings were fabricated on silica by using soft nanoimprint lithography and metal thermal evaporation process. The transverse magnetic wave (TM) transmittance exceeds 70% in the wavelength range of 2.56-2.95μm and 3.93-4.97μm. The extinction ratio exceeds 20dB in 2.5-5.5μm band. The mid-infrared polarizer has potential applications in fields such as polarization detection, communication, and spectral analysis.

We demonstrated the application of optical frequency combs in the realization of programmable microwave photonic filters. A reconfigurable high-order PF filter based on a wide-bandwidth optical frequency comb was designed, and the increasing of the tap (comb tooth) numbers results in the increasing of the order of the microwave photonic filter. In this article, the repetition frequency of the optical frequency comb is 12.5 GHz, and the optical spectral coverage reaches 25.6 nm. The order of the RF filter obtained in the experiment reaches 256, the free spectrum range (FSR) reaches 11 GHz, the 3dB-passband width is from 300 MHz to 2.6 GHz, and the sidelobe suppression is as high as 26 dB. A progressive optical pulse shaper was used to program the tap weights, which allow us to shape the bandpass of the filter. In addition, by adjusting the spectral distribution of the optical frequency comb, two types of RF filters with different passband shapes can be realized, namely, Gaussian and Sinc filters.

With the increasing demanding for miniaturization utility in infrared detectors, high operating temperature (HOT) and reduced size, weight and power consumption (SWaP) of infrared detectors are getting attention. A “diode-like” nBn barrier structure which can eliminate SRH generation-recombination dark current and operator at 130K has been realized in our lab. InAsSb/AlAsSb materials are grown by means of epitaxial on lattice-matched GaSb substrate. Material and device technology is being discussed, and a 30μm pitch 320×256 Focal Plane Array is displayed. NETD of this device is 14.4mK and the cut-off wavelength is 4.16μm at 130K. The non-uniformity increased form 2.88% to 3.55% during the temperature increased form 80K to 130K. At the end, photos taken by this FPA at 80K, 130K and 150K are displayed.

Infrared small target detection technology is an important subject in computer vision. In infrared detection system, it is required to quickly read and accurately segment moving small targets from sequence images, and the clutter suppression effect of image preprocessing algorithm directly affects the detection probability of the system. However, due to the traditional detection using fixed threshold segmentation, the poor segmentation effect leads to a large amount of data for small targets to be detected, which often takes a long time to process in embedded platform, and does not meet the real-time requirements. In addition, the long-distance infrared small targets have low signal-to-noise ratio, few pixels and lack of geometric features, which often lead to false alarms in detection, thus reducing the reliability of the detection system. Based on the above analysis, this paper designs an infrared small target adaptive detection system based on DSP+FPGA by using adaptive threshold segmentation and small target feature information, and transplants the improved algorithm to the embedded platform of DSP+FPGA. Moreover, the actual images are collected for verification. The experimental results show that the system designed in this paper can suppress the background clutter well, implement the adaptive detection of small infrared targets, and meet the real-time and reliability of detection.

Aiming at the serious noise and low signal-to-noise ratio of the fringe images obtained by industrial cameras under high-speed projection, a high-speed fringe projection measurement method based on convolutional neural network is proposed, which can achieve high-quality phase recovery and high-precision three-dimensional reconstruction in high-speed scenes. Using the designed convolutional neural network, the noise fringe images obtained at high frame rate and the wrapped phase images recovered by the traditional 12-step phase-shifting method at low frame rate are input into the convolutional neural network for training. After learning the mapping relationship between a large number of noise fringe images in the data set and the corresponding high-quality wrapped phase, a trained network model is obtained. And using this model, the high-quality wrapped phase information can be directly recovered from the input noise fringe images. The experiment results demonstrate that the method proposed in this paper can achieve with an accuracy of about 32μm through three noise fringe images at the camera frame rate of 700 frames per second.

In this paper we introduce the principle of the monocular ranging algorithm based on constraints on trajectory and line of sight, focusing on the long-distance detection for moving point targets. Simulations and experiments based on the proposed algorithm are carried out, in which the various factors related to the performance are analyzed. The results show that the improved algorithm is more suitable for long-distance air-to-air detection than traditional methods. As for the accuracy in the long ranging detecting situations, increasing the measurement time and the acceleration of the flying platform can improve the ranging accuracy. Furthermore, enhancing the angle measurement accuracy of the optical components can effectively improve the ranging accuracy.

Binocular stereo vision technology is an important research direction in the field of computer vision. It is based on the binocular disparity to accurately obtain three-dimensional information on the surface of space objects. Similar to the human eyes system, the binocular stereo vision is supposed to shoot the same scene with two cameras to capture the accurate distance. With the distance information, a three dimension picture can be rebuilt. The thesis includes the characteristics of the human eye's visual system, camera calibration and correction, and the stereo matching algorithm. After that, the image pair acquired by the binocular camera is used to perform the matching process. By combining with the human eye gaze model to simulate the effect of the human eye observation scene. Through simulation, the advantages and disadvantages of different matching algorithms are analyzed and combined with the foveation model to simulate the gaze effect of the human eye, which conforms to the intuitive experience of human vision.

In order to solve the technical problems of distributed acoustic sensor(DAS)system in many kinds of acoustic signal recognition, In this paper, an implementation path of acoustic signal machine recognition technology is proposed, which realizes the voice print and acoustic wave restoration of DAS machine recognition, and improves the quality of recognition and restoration.. Methods by preprocessing the optical fiber signal caused by sound, including signal framing, windowing, short-time Fourier transform and signal enhancement, the signal was transformed into a spectrogram, and the convolution neural network (CNN) was used to train the 13400 datas collected from the scene to machine judge the four types of acoustic signals: mechanical excavation, manual operation, vehicle passing and gas leakage Type. According to 800 test datas, the accuracy, recall and F1 value of the model are 96.4%, 96.5% and 96.0% respectively, and the average recognition speed is 30s. The feasibility of CNN model to realize and improve the quality of DAS machine voice print recognition and acoustic reduction was verified by field tests.

The precondition of clearing space non-cooperative targets is to obtain the relative position and attitude of space noncooperative target. In this paper, a new pose estimation method based on the geometric features in the depth image is proposed to obtain the relative position and attitude of the space non-cooperative target. The proposed method detects the docking ring and other geometric features of various payloads in the depth image of time-of-flight (TOF) camera, and then converts the detected image into a smaller point cloud utilizing the TOF camera parameters. Finally, we register the filtered point cloud of every two frames with Iterative Closest Point (ICP) method and calculate the rotation and translation matrix. The experimental results verifies that the proposed method can estimate the relative position and attitude with less errors and calculation, which meets the requirement of on-orbit service.

An adjustable electromagnetically induced transparency (EIT) metamaterial embedded with vanadium dioxide (VO₂) is demonstrated at terahertz (THz) region. The unit cell of metamaterial consists of a quartz substrate and two parallel wire metal resonators with different length on top layer. The two ends of the shorter wire metal resonator are filled with VO₂. The short wire metal resonator (SWMR) and the long wire metal resonator (LWMR) are acted as bright mode, which can be directly coupled with the incident THz wave to produce the EIT. Due to the insulator-to-metal transition of VO₂, the amplitude of EIT peak can be actively modulated and the modulation is implemented only in the EIT window with slight changes in transmission dips. When VO₂ is transformed from the insulating phase to the metallic phase with the conductivity changed from 2×10² S/m to 2×10⁵ S/m, the amplitude of the EIT peak can decrease from 0.91 to 0.03, which indicates that the EIT metamaterial achieves a large modulation depth. The physical mechanism of this phenomenon is explained by the magnetic field and current distributions. In addition, it is found that the slow-light effect gradually weakens and disappears with VO₂ changing from the insulating phase to the metallic phase. This work provides a strategy to achieve an adjustable EIT effect in THz metamaterial structure embedded with VO₂ and exhibits potential applications in THz modulators and slow-light devices.

The range analysis of the infrared detection system is the first task in the design of the detection system. The traditional range model based on the signal-to-noise ratio is only suitable for a uniform background. For complex backgrounds, the fluctuation of background clutter is the main factor restricting the detection distance, and the results based on the signal-to-noise ratio model may deviate greatly from the actual situation. Based on the characteristics of the re-entry process, this paper analyzes the dynamic process, and establishes an infrared detection distance analysis model based on the signal-to-clutter ratio. The radiation flux between the background and the target is calculated, and the infrared detection band selection is simulated. On this basis, the analysis and calculation of the infrared detection distance under different cloud conditions are carried out, and the similarities and differences between the signal-to-noise ratio model and the signal-to-clutter ratio model are compared, which can provide references for the design of infrared detection systems in practical applications.

Aiming at complex military application scenarios, this paper proposes a vision and lidar fusion scheme, and designs an algorithm for real-time construction of local scenes and real-time local path planning. It satisfies that the vehicle can avoid ground obstacles and aerial obstacles in real time under the state of no navigation and no map, and realize autonomous navigation. Experiments have verified that the algorithm has high execution efficiency and can meet the application requirements of autonomous driving.

We report on the two modelling effects of energy transmission and electric field enhancement of GaN high electron mobility transistor (HEMT) terahertz (THz) detectors integrated with spiral antennas. The models proposed in this paper not only explain the two different coupling methods applicable to THz detection, but also make comparisons between them. The computing results indicate that although the two methods are coupling with THz wave in different ways, the efficiency of improving the responsivity of THz detectors is almost the same. The conclusions in this paper exhibit the excellent application prospects in THz detection and imaging.

Given that the existing nonuniformity correction algorithms still struggle to achieve low noise images, good real-time performance, and more texture details, a shearlet deep neural network from the perspective of transforming domain is put forward in the paper. The proposed method uses the non-subsampled shearlet transform to track the stripe noise. And then defines the regularization method according to the features extracted by the shearlet to help restore the image details. The experiments based on simulation datasets and real datasets show that the proposed method is superior to several classical denoising algorithms in quantitative and qualitative evaluation.

Space environment above Quasi-equatorial ground has an advantage of relative quietness and friendliness. It is preferred to deploy satellites of demanding stability and longer lifespan. For these satellites, the communication via VHF between ground stations and satellites has become one of the difficulties when it comes to the satellite engineering. To make a quantitative assessment, the satellite VHF coverage of ground stations are carried out for two typical orbits, of which the altitude are roughly 500km and 550km,and the inclination is 2.5 deg. Ground stations for VHF communication include the 88 stations, which are distributed along the belt with latitude less than +/-30deg. The cutoff angles for VHF communication are 10 deg. Two antenna for communication are fixed in the satellite body along +Z axis and –Z axis respectively, and the half beam angle of the boresight is 90 deg. Simulations of satellites based VHF coverage of 88 ground stations are carried out. During case 1, satellite orbit altitude is assumed to be 500km,and inclination is 2.5 deg. For case 2, satellite orbit altitude is assumed to be 550km,and inclination is 2.5 deg. Satellite-based VHF coverages of 88 ground stations are 63.3% for case 1,and 66.5% for case 2. For case 1, yearly VHF communication opportunities are 34594 times. Average duration is 576 seconds. Daily VHF communication opportunities are 95 times. Daily available communication interval is 912 minutes. The unavailable time interval is 28.2 minutes. For case 2, yearly VHF communication opportunities are 29161 times. Average duration is 718 seconds. Daily VHF communication opportunities are 80 times. Daily available communication interval is 957 minutes. The unavailable time interval is 26.4 minutes. Case 1 is preferred if satellite engineering demands more quiet space environment. Case 2 is preferred if satellite engineering demands longer lifespan and better coverage. It is suggested that case 2 be a good choice for space science mission devoted to observe astronomical events in remote space.

Combined with the research achievements of silicon material characteristics, the asymmetric depletion layer with mesa structure is used in the design of engineering parameters for the 225GHz pulsed-mode IMPATT device to improve the output power. Based on the operating frequency, output power, and other constrained conditions, the epitaxial layer parameters of IMPATT device are designed by theoretical calculation and equivalent derivation. The tolerance of the epitaxial layer parameters is simulated, analyzed, and optimized by Silvaco TCAD device process simulation software. A test system, built based on standard instruments and frequency multipliers and mixers, is employed to evaluate the electrical property of the IMPATT device samples. The test results are consistent with the design values. The operating frequency of the samples is (225±1)GHz and the output power is about 170mW.

Ice cloud parameters have an important influence on global climate research and weather forecast. According to the atmospheric radiation theory, THz is the best frequency band for ice cloud remote sensing. In this paper, the principle and research status of ice cloud remote sensing is analyzed. The detection capabilities of different ice cloud sounders are compared, and a THz ice cloud imager for the next generation meteorological satellite is designed. The THz ice cloud imager covers five detection frequencies of 183GHz, 243GHz, 325GHz, 448GHz and 664GHz, and uses cone scanning mode, with the spatial resolution better than 10km, noise temperature better than 3000K.

In this paper, the thermal resistance radiant heat flow sensor and the automatic balance thin film radiant heat flow sensor are calibrated according to the small-scale heat flow in the cold vacuum environment, and the stability time is analyzed, the calibration data is linearly fitted, and then the calibration process is analyzed. The errors that may occur in the It provides a method basis for the engineering use of the heat flow meter in a similar environment.

The ultra-thin terahertz functional devices have huge application prospects in information communication, national defense security and energy exploration. However, traditional devices based on propagation phase accumulation often face the problems of large size and low efficiency, unable to achieve complex control of terahertz spectrum and wavefront distribution. These problems seriously hinder the development of terahertz technology in practical applications. The Pancharatnam-Berry(PB) phase metasurface is composed of the same artificial microstructure with different rotation angles. It can realize the phase mutation of the reflected (transmitted) wave by simply changing the rotation angle of the microstructure, thereby realizing the phase gradient or distribution. In this paper, we design a onedimensional focusing lens and a one-dimensional deflector working at 1.17 THz with the designed meta-atoms based on the working principles of PB metasurface, and the thickness of these two devices is only 26 um.

In this work, a field-of-view(FOV) expanded tight focusing up-conversion imaging system at 1550 nm is proposed. To satisfy the non-collinear phase-matching and increase the field-of-view, three groups 4f system are inserted. To enhance the intensity of converted images, the signal pulse at 1550 nm with the average power of 0.14mW is tight focused into a 1mm thick periodically poled lithium niobate (PPLN) bulk by a lens with 30mm focal length. Pumped by a continue-wave beam with the power of 1W, the 1550 nm pulse is converted to 863 nm and the pattern of target is captured by an industry camera. According to the experiment, the converted image with the pixel of 1000 × 1000 is reached and the diameter of FOV reaches 7.15 mm.

A switchable narrowband THz metasurface filter based on vanadium dioxide (VO₂) is demonstrated which can be switched between the “ON” and “OFF” state by applying a bias current to VO2. In the initial “ON” state without applying the bias current, the transmittance of the filter is greater than 80% from 0.72 to 0.78 THz and reaches a maximum of 92% at the center frequency of 0.75 THz. After applying 300 mA current to VO2, the filter is in the “OFF” state and the transmittance is almost zero over the entire frequency range from 0.4 to 1.1 THz. Furthermore, considering the influence of the substrate thickness of the filter on the actual application of the device, the response of the filter with different thicknesses of the substrate is numerically simulated, and the results show that the filter performance is still good when the thickness of the substrate increases to 500 μm.

The fiber-coupled type terahertz time-domain spectroscopy system (THz-TDS) has the characteristics of small size, convenience, robustness and flexibility. In this paper, we use the grating pulse stretcher to compensate for the nonlinear effect of the fiber, and build a compact fiber THz-TDS with a spectrum range of 0-4THz based on the all-fiber terahertz emission and detection module of the photoconductive antenna. Through hyperspectral imaging of biological tissues, K-means clustering algorithm is used for image segmentation, different K values are selected to determine the boundary between different regions of the sample, then the region of interest is selected for absorption coefficient calculation. The changes in absorption coefficients represent differences in the types of tissue components and their contents, these are important for the diagnosis of cancer and biomedicine applications.

For the problems of large viewpoint variation, heavy distortion and small overlap area in UAV images registration, this paper proposes a density analysis based method to remove mismatches in putative feature correspondences. Our method uses intra-cluster topological constraints for mismatch filtering, which is based on a density-based hierarchical clustering algorithm. Compared with other methods that perform mismatch filtering based on neighborhood topological relationship, our method is more robust to viewpoint changes both in horizontal and vertical directions. The algorithm in this paper uses a coarse-to-fine strategy, which starts with establishing putative feature correspondences based on local descriptors, such as SIFT, ORB, etc. After that we focus on removing outliers by clustering these feature points and verifying topology consistency of the clusters in different images. We view the feature point matching problem as a correspondence problem of the same visual model in two images, and clustering the feature points based on density can approximate the separation of multiple visual patterns. We tested our algorithm on a UAV image dataset which includes several pairs of images and their ground truth. These image pairs contain viewpoint changes in horizontal, vertical and their mixture which produce problems of low overlap, image distortion and severe outliers. Experiments demonstrate that our method significantly outperforms the state-of-the-art in terms of matching precision.

THz Atmospheric Limb Sounder (TALIS) is a microwave radiometer designed by the National Space Science Center (NSSC) of the Chinese Academy of Sciences (CAS) for sounding the vertical distribution of the atmosphere, focusing on measuring the temperature and the chemical composition of the middle and upper atmosphere. Fast Fourier transform spectrometer (FFTS) is the core component of TALIS back-end, which mainly undertakes the function of spectral analysis. In this paper, a new wideband, real-time FFTS design and implementation scheme is proposed to obtain the power spectrum of the signal through the core radix 16 real-time complex FFT algorithm. The analysis bandwidth and the number of channels of FFTS are 2 GHz and 1 k, respectively. The simulations and tests are performed using sinusoidal signals, and the results show that the effective number of bits (ENOB) is better than 3-bit, the signal-to-noise ratio (SNR) is better than 20 dB, and the spectral resolution is constant at 2.3 MHz. Moreover, the peak frequencies of the simulation and test are consistent, which can meet the requirements of the spectral line detection in TALIS.

This paper proposes a recognition network for small-scale objects in cluttered point clouds. The network consists of two components: improved semantic segmentation for large-scale 3D point clouds and an adaptive instantiation algorithm. In semantic segmentation, based on the backbone, we introduce the grid sampling module and the normal-angle feature to improve the efficiency and accuracy of segmentation respectively. Then the network outputs point-wise semantic labels. After that, we propose an adaptive instantiation algorithm to group points that are closely packed together and obtain the objects. In this way, our network completes the recognition of the small-scale objects. We conducted experiments on real aero-engine datasets and the results reveal that the proposed network can recognize a small-sized component in the cluttered point cloud scene of aero-engine.

Infrared non-contact testing has great prospects under epidemic prevention and control. The current infrared thermometer on the market generally has low-temperature measurement accuracy and weak anti-interference. This paper designs and implements an infrared thermography thermometer, which can detect the body temperature of a wide range of people at the same time, quickly find out the abnormal temperature of people, and issue alarms through the implementation of powerful front-end processing and back-end conversion algorithms, outputting high-quality infrared thermography video with full-screen detection, non-contact, fast, and intuitive characteristics. The thermometer implemented in this paper is as high as ±0.2℃ in temperature measurement accuracy, optimizes the correspondence between grayscale value and temperature, and designs the temperature control system to make corresponding compensation for ambient temperature and testing distance. The experiment proves that the pyrometer designed in this paper has strong anti-interference and high accuracy, and can be applied to various application scenarios.

At present, motion recognition plays an important role in the field of computer vision, and the result of action recognition depends on the extracted feature mode and the expression type of action. Therefore, it is particularly important to propose a relatively fast and robust feature extraction method and apply it to action recognition. In this paper, we propose two feature extraction methods for motion recognition using the information provided by the depth camera, and achieve good recognition accuracy. The two feature extraction methods are as follows: The extraction of temporal and spatial information (ETS) and the clean extraction of temporal and spatial information (CETS). We compare the accuracy of the two feature extraction methods for action recognition, and find that the CETS method has a very good improvement compared with the ETS method. This will have a big significance to our exploration in the aspect of motion recognition.

Three-dimensional (3D) Dirac semimetal Cd₃As₂ has an important application prospect in future for broad-spectrum photodetector due to its unique topological energy-band layout and excellent optical absorption capacity. However, extremely high dark current of individual Cd₃As₂ is the key bottleneck limiting its photoelectric detection performance. Herein, the strategies of Zn element doping and construction hetero-structure with Sb₂Se₃ are co-adopted for maximize the performance of Cd₃As₂ based device. The constructed 3D Dirac semimetal (Zn_xCd_1-x)₃As₂/Sb₂Se₃ film heterojunction photodetector prototype has efficiently achieve broad-spectra photoelectric detection from visible (450 nm) to nearinfrared region (1550 nm) wavebands at room temperature with superior performance, including high responsivity (Ri), detectivity (D*) as well as outstanding fast response time (τ). The excellent performance of the device may be attributed to high-quality of hetero-structure interface, strong light absorption capacity and suppressed dark current in (Zn_xCd_1-x)₃As₂/Sb₂Se₃ heterojunction system. This work has laid a solid foundation for the construction of a high-performance new topological semi-metal photodetector.

Infrared detectors for astronomy application are supposed to work under cryogenic temperature due to lower dark current and readout noise. A prototype for infrared detector front electronics which can operate under cryogenic temperature is presented on this paper. Several commercial off-the-shelf (COTS) devices from different technologies were extensively characterized at as low as 4K including voltage reference, operational amplifier, ADC, MCU and etc.. The results demonstrate that AD8616 could perfectly work under 4K, Cortex-M4 ARM MCU operates well above roughly around 35K, AD7983 start to loss code at 180K and XFET reference ADR433 begin to show a significant voltage drop at 120K. The failure mechanism of COTS devices is also analyzed based on the cryogenic test results.

In this paper, the imaging characteristics and motion characteristics of small targets in infrared images are analyzed from the perspective of space domain and time domain respectively, and a real-time infrared small target search and tracking algorithm based on adaptive track correlation is proposed. From the perspective of spatial domain, the curvature filtering algorithm is used to suppress the background according to the feature that the small target usually presents a sharp peak on the 3D surface with gray value as Z-axis. From the perspective of time domain, according to the difference of motion state between the target and the false alarm point, the track correlation method is used to further suppress the false alarm rate and realize the search and tracking of the target. In this paper, the concept of cosine similarity is introduced to judge the matching degree between suspected target and track on the basis of the traditional track correlation algorithm based on the idea of "nearest neighborhood", so as to reduce the probability of wrong track correlation. At the same time, based on residual analysis, the correlation gate size is selected adaptively and the observation results are smoothing by adaptive first-order low-pass filtering. Experiments show that the search and tracking algorithm proposed in this paper has real-time performance and high accuracy, and has good adaptability to different scenes.

Aimed at the requirement of terminal guidance simulation test for a certain infrared seeker, an infrared target simulator which is used to complete the non-uniformity correctionand target tracking performance detection was developed. The simulator integrates black body and infrared target simulation system, and switches two working modes (testing and non-uniformity correction) by means of electronic control. This article introduces the main composition, working principle and realization of each subsystem, and tests the key performance indicators of the system. The results show that the parameters of the system meet the design requirements and achieve the desired application results.

As the application of UAVs in military and civilian fields becomes more and more widespread, the detection of UAVs in the low-altitude range has also become an important research direction. Compared with radar and visible light detection, infrared technology has become the major UAV detection method with its advantages of all-weather and long range. Most of the current infrared target detection methods are based on convolutional neural networks (CNN), which achieve target detection through feature extraction and feature classification. The performance of all such detection algorithms is highly dependent on their training set. A data set with a large number of samples and wide coverage tends to train a more robust and accurate detector. So, to obtain better detection effects, we perform data augmentation on the infrared UAV dataset by adversarial generative network (GAN). First, we extract the targets from the training set and train a GAN network, using its generator to obtain many new targets which are different from the training set samples, then we randomly extend these targets to the original dataset, and finally we retrain the detectors using the new dataset to achieve better detection. We created an infrared UAV image dataset for our experiments, with only a single target on each image. After data augmentation, multiple UAV targets are randomly generated. The experiments demonstrate that the new dataset trains the model with better detection results. And the GAN data augmentation can be combined with many advanced detectors to make a large improvement in detection.

In this paper，we propose a new GAN-based end-to-end image fusion network (VIFGAN) for fusion of visible and infrared images. VIFGAN contains a generator and a discriminator. We added the DenseNet module to the generator，and this module can extract deeper features and details. We also propose a Two-way regulation loss function(TWR-Loss). The loss function considers both the radiation information and texture information in the image, which can make the network suitable for image fusion tasks of different spectrum combinations. The experimental results show that in the fusion task of visible light and infrared images, the proposed network has better fusion performance than the existing fusion algorithm, the visual effect of the fused image is better, and the extracted details are more abundant.

For APD-type four-quadrant pulsed laser detection system, the conventional peak extraction method cannot detect the input laser energy when the output waveform is saturated in the nonlinear region. After investigating the response mechanism of this type of system to the input light intensity, an energy inversion model is proposed to invert the input energy using the half-height width of the output waveform for the saturated waveform in the nonlinear region.The simulation and experimental results verify that this model can perform the energy inversion of the saturated waveform in the nonlinear region well. The experimental data show that the half-height-width energy inversion model can widen the detection range by 8.15 times compared with the traditional peak extraction method, and the maximum absolute error is 0.69 mW, and the corresponding relative error is 2.13%.

In order to improve the detection sensitivity of single-photon detection infrared imaging camera image sensor, the study is based on the structure of InGaAs infrared focal plane detector array. By using ZEMAX software, the size and position changes of the imaging light spot of the micro-lens array in the case of incident at different field of view angles are compared and analyzed, and the structural parameters are optimized. A 64×64 Si refracted micro-lens array is designed and manufactured. The study established a microoptical measuring system for micro-lens arrays, including light source, optical fiber, collimation, imaging and measuring devices. The measuring method and process of the parameters are introduced briefly. The morphology, geometric structure parameters and focal length of the micro-lens can be measured, therefore, the micro-lens can be evaluated effectively. The results show that the micro-lens array has good surface profile, good geometric uniformity and good optical properties.

Modern long-distance detection of ships at sea mainly uses two major types of means: radar and infrared. In the field of ship stealth, in order to reduce the range and probability of being detected by radar, modern ships often adopt a large area of hull plate design with a certain inclination angle. This design is simple and clean, avoiding the exposure of external equipment, and making the ship's radar cross-sectional area smaller. However, the large-area inclined hull plate is more likely to be heated by external heat sources such as the sun, thereby increasing the range and probability of being detected by infrared devices. In order to analyze the influence of the hull plate inclination on the marine infrared and radar detection, this paper establishes the infrared and radar detection calculation model, taking into account the target characteristics, atmospheric transmission and other factors. On this basis, the influence of the hull plate inclination on the range of infrared and radar in different bands, under different pitch and elevation observation angles, and under different sea conditions is analyzed. Finally, considering the two major types of radar and infrared detection, the optimal range of inclination angles for the ship’s stealth is given.

The original image bit width of a cooled thermal imaging camera is 14Bit. 14Bit has a wider grayscale range, higher accuracy, and more image details compared to 8Bit, but the maximum grayscale range that can be displayed by a general display is 8Bit, so the original image data of 14Bit needs to be compressed effectively. In this paper, we propose an image compression and display algorithm based on guided image filtering (GIF). First, the image is layered using guided image filtering, i.e., the base layer and the detail layer. Then the adaptive platform histogram equalization (APHE) process is applied to the base layer to improve the contrast of the image; the adaptive detail enhancement is applied to the detail layer to enhance the details while reducing the noise. Finally, the images processed separately after layering are linearly fused to achieve dynamic compression and detail enhancement of high Bit images. Through simulation and comparison experiments with commonly used algorithms, as well as comprehensive comparison of visual effects and quantitative evaluation parameters, the proposed algorithm in this paper achieves significant improvements in both performance and effectiveness.

A method for measuring the incident angle of the light beam based on an axicon lens which defined by cone length and cone angle is presented in this letter. The system is mainly composed of a stop, an axicon lens, a telescopic system, an image receiving device, a display device and a digital image processing device. The light beam is refracted to a larger incident angle when passing through the telescopic system. It then goes through the aperture and the axicon lens, whose refraction times in axicon lens correlate with the incident angle, resulting in different spots captured by image sensor. The angle can be figured out with rich image characteristic information, which includes symmetry axis direction, area, the mass position center, the inertia moment, etc. In a practical design example, the image processing of the spot image shows that the rotational inertia of the spot has a one-to-one correspondence with the incident angle of the light beam, which features an obvious monotonicity. The angle measurement range can reach up to 3°, with an accuracy up to 1×10^-3 ". Compared with the traditional angle measurement method, the measurement accuracy of this method based on axicon lens is improved by an order of magnitude. The system has the advantages of high accuracy, compact but simple structure, and no cumbersome installation and debugging. It can be used not only as a high-precision collimator, but also as a high-precision goniometer.

Infrared cameras can benefit the extended dynamic range by changing the integration time, especially for infrared high dynamic range imaging. But many proposed non-uniformity correction methods based on the two-point correction model incur a degradation of image quality when the integration time changes from the calibrating values. The paper describes a linear infrared camera response model and uses it to analyze the failure of the two-point correction method when change integration time. The analysis result reveals that, with the linear response model, the two-point correction offset parameter needs to be updated according to the immediate integration time, and calculated by a linear equation. Thus, the non-uniformity correction method with the ability to vary the integration time arbitrarily is proposed. To reduce the impact of the nonlinearity in real response and the temporal noise on computing the correction parameters, a parameter calculation method is also proposed of using multiple images of different temperature uniform references under different integration times. The correction effect under arbitrary integration time of the proposed method is verified by correcting images of an extended-area blackbody from 5°C to 100°C covering a wide range of the integration times from 0.4ms to 26ms. The mean value of the non-uniformity of all blackbody images corrected by our method can reach about 0.1%.

In response to the current increasing demand for calibration of low-temperature infrared radiation sources with a large dynamic range, this paper studies a calibration method for low-temperature infrared radiation sources with a temperature range of 100-450K. The improvement of the signal-to-noise ratio of the input signal by related detection techniques is analyzed. Developed a radiation calibration device, also called a radiometer, analyzed the calibration and measurement process of the radiometer, and established a corresponding mathematical model. The experimental results show that the minimum radiation intensity that can be measured by the radiometer is 2.47×10^-12 W, and the response rate of the radiometer is 102878.38 V/W. Use the calibrated radiometer to measure the target simulator. The source and contribution of the uncertainty of the radiometer in the measurement process are analyzed.

By reducing the working temperature of opto-mechanical structures, the infrared system signal to noise ration can be effectively improved. Normally, structures close to the focal plane radiate more noise. Signal to noise ration can be improved by cooling the opto-mechanical in front of the focal plane. In this paper, an infrared lens working at both room and low temperature is designed. The first four lenses work at room temperature and the other three lenses close to the focal plane work at 200K. The cryogenic lens is cooled by space pulse tube cryocooler. UG TMG thermal analysis results show that the working temperature of each lens meets the requirements, and the temperature gradient of each lens is less than 0.2K. Modal analysis results show that the first modal frequency is 97.2Hz. The finite element analysis results show that the maximum stress of the structure is 227.8MPa, which is far less than the allowable stress of TC4. Thermal-structure-optical analysis show that the system MTF has a small decrease from root temperature to working temperature. By adjusting the position of the focal plane, the system MTF can recover to the design results. The results of the vacuum experiment show that the working temperature of the lens is close to the simulation results. The wavefront error is measured both at room temperature and working temperature. The average wavefront error is 0.060λ (λ=632.8nm) at working temperature and 0.070λ at room temperature. Experiment results verify the correctness of the thermal design and opto-mechanical design.

Fringe projection profilometry (FPP) is a popular three-dimensional (3D) shape measurement technique and has been widely used in industry. However, measuring surface with high reflectivity is still challenging because image saturation leads to absolute phase errors and reconstruction errors. In this paper, a novel adaptive fringe projection method is proposed. First, a projection intensity model is built. Adjusting the exposure time only once can easily calculate the low projection intensity. Then, using fringe patterns with low intensity we can get the coordinate mapping relationship. By mapping and filtering the sub-pixel coordinates in the projector image, we can obtain more accurate coordinate correspondence and gray value correspondence of the projector and the camera. Finally, the parameters of the projection intensity model are fitted to calculate the optimal intensity and generate accurate adaptive fringe patterns. The measurement experiments demonstrate that the proposed method is effective in obtaining high-precision and complete 3D profile of surface with high reflectivity.

In order to study the optical transmission and radiation characteristics in a hypersonic shock layers over infrared optical window, an approximation calculation approach is proposed. With this method, the formal solution for shock layer radiative transport equation is derived considering both target signature and windows thermal radiance. Consequently, the transmissivity of heating shock layer can be expressed quantitatively, which shows that the shock layer is optically thick in the 4~4.5μm band mainly. Besides, the radiance flux density of shock layer is calculated when temperature is 800K, pressure is 7atm and thickness is 1cm. Shock layer radiance is found to be larger in the mid-wave infrared band compared with long-wave infrared band and short-wave infrared band.

Quantum cascade laser (QCL) is a new type of unipolar semiconductor laser. It has the advantages of narrow line width, tunable wavelength, high output power, etc. The QCL is widely used in gas detection, medical diagnosis, petrochemical industry, environmental pollution prevention and control, communications and military fields. Because it is difficult to cover the absorption peaks of multiple gases, a single QCL laser cannot detect and identify multiple different gases at the same time. Therefore, beam combination of multiple QCL laser is a feasible solution to achieve simultaneous online detection of multiple gases. This paper demonstrates a multi-wavelength QCL laser system based on spatial parallel beam combination. Four QCL lasers with wavelengths of 1274.70 cm^-1, 1606.68 cm^-1, 1831.84 cm^-1, and 2226.18 cm^-1 are integrated. The power of a single QCL reaches more than 100mW, and the total output power reaches 0.81W. By controlling the temperature of the heat sink, the wavelength tuning ranges of 9.65nm, 6.54nm, 7.54nm, and 10.45nm can be achieved respectively. The temperature tuning coefficients are 0.85nm/℃, 1.06 nm/℃, 1.25 nm/℃, 0.80 nm/℃, and the wavelength tuning accuracy is 85pm, 106pm, 125pm, 80pm. The system designed in this paper can simultaneously detect the gas whose absorption peak locates at the above four wavelength ranges, and can also customize a QCL laser with matched wavelength according to the absorption peak of the gas to be measured, which has good scalability.

In this paper, we designed a sandwich microfluidic chip and combined it with terahertz technology to study the effects of histidine on the absorption characteristics of terahertz waves. By observing the intensity of its time domain spectrum in the range of 0.2-2.6 THz, it was found that the terahertz transmission gradually decreased with the increase of histidine concentration. In addition to this, the characteristic absorption peaks of histidine and its aqueous solutions were measured in the experiment using the terahertz time-domain system and the vibrational modes of their theoretical absorption peaks were attributed using Gaussian16 software. In the future, we will delve into the absorption peaks of liquid amino acid solutions and compare them to solid amino acids. As far as possible, terahertz technology is used to identify liquid amino acids in solution.

The design of the dual-channel projection collimator for the dynamic infrared scene projector is introduced in this paper. The optical system is the combination of a telescope system and two imaging systems of the target channel and the inference channel. The scenes from two optical channels are combined into one scene by the beam combiner. The optical system consists of twelve elements and aspheric surfaces are used in the imaging system to increase the image quality and simplify the configuration of the optical system. The optical system is capable of operation over the 8~12μm wavelength range and testing an infrared seeker over 12°field of view (FOV). The effective focal length of the optical system is 228.3mm and the exit pupil distance is 800mm.The image quality and the formats of the system meet the requirements of the projector.

When the infrared imaging system measuring the radiation characteristics of the target, the internal stray radiation is an important factor affecting the measurement results, and the environmental temperature will directly lead to the change of the internal stray radiation. This paper analyzes the phenomenon of the gray drift of the system output caused by the environmental temperature change, and derives the functional relationship between the drift amount and the ambient temperature. A simulation analysis model of internal stray radiation was established to verify the theoretical analysis.

In this paper, we reported the design, fabricate, and characterize of an electronically controlled terahertz (THz) amplitude modulator composed of a four-open ring metamaterial structure and a high electron mobility transistor (HEMT) structure, HEMT area is located at the openings of the four-opening ring metamaterial structure. The concentration of 2D electron gas of the HEMT is adjusted by applying an external electrical field and results in the resonance shifts. Both static and dynamic characterizations of the modulator were carried out by using an optical fiber-coupled terahertz time-domain spectroscopy (THz-TDS) system in the transmission type. Experimental results show that the amplitude modulator can modulate the incident THz waves with two orthogonal polarization directions. The modulation depths are 56% at 0.32 THz for vertical polarized beam and 40% at 0.34 for horizontal polarized beam respectively. The modulator has potential application in wireless communication and real-time imaging.

The vibrational and rotational energy levels of many biological macromolecules fall in the THz band, so terahertz spectroscopy can be used to identify the species of substances and detect the structure of substances. Due to the strong absorption of THz wave by water, it is difficult to study liquid biological samples by THz spectroscopy. Microfluidic technology is a kind of micro scale fluid control technology, which has the advantages of light volume, less sample usage and fast reaction speed. The combination of terahertz technology and microfluidic technology can increase the accuracy of liquid sample measurement and reduce the amount of sample. In this paper, COC5013 material with high terahertz transmittance was used to prepare microfluidic chip, and then the terahertz transmittance of two kinds of food additives sodium carboxymethyl cellulose solution and guar gum solution was studied. The results show that the terahertz transmittance of sodium carboxymethyl cellulose solution and guar gum solution with different mass fraction are different.

Exhaled breath analysis has attract growing attention as a promising noninvasive medical detection method. Carbon monoxide in human exhaled breath is of great value in the diagnosis of diseases, such as hematolysis and neonatal jaundice. However, conventional methods for the detection of CO was limited in practical application. In view of this, we have developed a highly sensitive system based on wavelength modulation spectroscopy by using an interband cascade laser at the optical wavelength of 4.71 μm. The temperature and pressure of gas example are extremely controlled by the proportional-integral-derivative control algorithm. As a proof of concept, the spectrometer was utilized to detect standard samples and real breath samples. The results show that the spectrometer has a good sensitivity with a detection limit of 3 ppb, and the concentration of CO in exhaled breath of non-smoking health people is flutuated little and not influenced significantly by the normal diet.

Anti-counterfeiting technologies of banknotes are essential to avoid financial fraud and maintain the stability of the socio-economic system. In recent years, the technologies used by counterfeiters have become more and more advanced, bringing great challenges to traditional methods of authenticity check. Therefore, the identification technologies of banknotes urgently need to be improved. Terahertz spectroscopy is widely used for analysis and material identification due to its properties (such as biomolecular fingerprinting spectrum, ultra-weak photon emission, non-destructive and time-resolution detection). In this paper, we apply the transmission terahertz imaging to the identification of anti-counterfeit labels of RMB. We designed and built a THz-TDS confocal imaging system, which has higher image resolution than traditional THz-TDS imaging systems. We used this system to perform terahertz imaging on anti-counterfeit labels of banknotes. The results show that our designed and built THz-TDS confocal imaging system not only provides higher image quality, but also can identify more details of the anti-counterfeit labels of banknotes.

Infrared detectors have the advantages of passive detection, strong anti-jamming ability and easy to carry. Narrow bandgap antimonide semiconductor is recognized as the preferred material system for the third generation of focal plane array infrared detector. Since 2000, InAs/GaSb type II superlattice(T2SL) have a great progress in preparation of molecular beam epitaxy and detector technology. The defect level associated with Ga near the center of the gap band increase the recombination rate, which will lead to the fatal problem of short minority carrier lifetime. The InAs/InAsSb (Ga-free) T2SL has emerged as a promising candidate to improve the minority carrier lifetime and inhibition the SRH recombination, and these photodetectors can offer a cut-off wavelength ranging from 4 to 15 μm. However, the superior performance of T2SLs detectors are not realized, and the dark current has been proved as an important limited factor. In order to suppress the generation-recombination current and other dark currents, kinds of structures have been applied to T2SL infrared detectors. In this brief review paper, we overview the suppression methods of the dark current which is the important factor that affect the performance of detectors.

Radiation temperature measurement is a non-contact temperature measurement, which has important applications in quantitative remote sensing, industrial thermal monitoring, biomedical engineering and military field. The infrared radiation of an object is directly proportional to its emissivity, which is an important parameter that affects radiation temperature measurement. In order to obtain the spectral emissivity of an object, this paper proposes a method for measuring spectral emissivity based on the radiation at multiple temperatures. Based on Planck's law of radiation, the expression of spectral emissivity is theoretically given by deriving the relationship between spectral emissivity, contact temperature and radiation. The simulation is carried out based on theoretical derivation. The spectral emissivity of three samples is simulated. The waveband of the samples is 8-14μm, and the spectral emissivity does not change with temperature. Two algorithms are used to avoid the problem of singular values in direct calculation. Based on the constrained linear least-squares method, the average relative errors of the three samples are 7.0%, 7.2%, and 6.2%. The maximum relative errors are 22.1%, 18.9% and 15.0%. Based on the improved constrained linear least-squares method, the average relative errors of the three samples are 2.2%, 1.1%, and 3.0%, and the maximum relative errors are 6.7%, 3.2%, and 4.2%. The simulation results verify the feasibility of inversion of spectral emissivity at multiple temperatures. The results show that the improved constrained linear least-squares method has smaller average relative errors.

The infrared focal plane assemblies (FPA) are usually integrated in ambient temperature, and operate in 80K~40K. Mechanical cryocoolers are typically used to provide the cryogenic temperature. The mechanical designs of FPA have to take a variety of constraints into consideration, such as thermal stresses, temperature uniformity of detectors, vibration from cold fingers, stray light of dewar (optical stops), flatness of the detector arrays, thermal insulation, severe vibrations during launch and optical alignment stability. For large format focal plane assemblies, the stress and deformation caused by thermal mismatch of HgCdTe detector chip, silicon readout integrated circuit (ROIC) and mounting structures become worse. This paper presents an innovative thermo-mechanical designed for Visual and Infrared Multispectral Imager (VIMI) onboard GaoFen-5 satellite. It proposed a symmetrical sandwich configuration to ensure the flatness of detector arrays, and a flexure adaptor plate module made of molybdenum-copper to mitigate thermal stress of detectors and Low Temperature Co-fired Ceramic (LTCC). Finally, a series of mechanical and thermal tests were conducted to verify the reliability of the thermo-mechanical design of FPA.

The sensitive parameters affecting the dark current characteristics are further studied by using InAs/GaSb type II superlattice (T2SL) pBpp structure long wavelength Infrared photodetectors.Generation of recombination (G-R), surface leakage current and tunneling current are the main components of dark current. Using pBpp structure can suppress them effectively, thereby decreasing dark current. Based on the k ∙ p method, the band structure of InAs/GaSb T2SL and InAs/AlSb T2SL can be obtained by solving the 8-band k ∙ p model. We have calculated different doping levels of pB_pp detector and different layer thicknesses of pB_pp detector. For pB_pp device, we consider the dark current for different contact layer doping and different absorber layer doping. We also study the influence of different contact layer thicknesses and different absorber layer thicknesses on dark current. The dark current of pB_pp detector is dominant by tunneling current at low temperature, and diffusion is the main limiting mechanism in dark current at high temperature, for barrier layer inhibits generation-recombination contribution. Eventually, the dark current of a pB_pp structure has been calculated for versus voltage at 77 K.

Field radiometric calibration is an important technical means to ensure the observation accuracy of satellite remote sensors on-orbit operation. Accurately obtaining the spectral radiometric characteristics of the site is of great significance to improve the accuracy of field radiometric calibration. In order to better meet the field calibration requirements of thermal infrared band satellite remote sensors, a Multi-channel Self-calibration Infrared Radiation Thermometer (MSIRT) with automatic observation capabilities has been developed, which is used to measure the atmospheric downward radiance and ground surface radiance in field. In this paper, the structure, working principle and laboratory calibration of the MSIRT was introduced. In optical design, the automatic switching of four spectral channels in the range of 8 ~ 14μm was realized by using the filter wheel, and the instrument was equipped with an ambient temperature blackbody and a heated blackbody, respectively. The real-time calibration of the detector can be realized through the alternate measurement of high and low temperature blackbody, which ensures the high precision measurement requirements. The developed instrument also has the ability of automatic observation and remote data transmission. In the laboratory calibration of MSIRT, the liquid bath blackbody was used as the standard radiation source, and the calibration uncertainty was 0.5 %, corresponding uncertainty of the equivalent radiance temperature was 0.3 K (@ 303 K, 11 μm). The experimental results show that the MSIRT can meet the measurement requirements of high precision, and has important applications in the field calibration of thermal infrared satellite remote sensor.

This paper combines the information processing technology for target detection with the sensor parameter design. A design method which is suitable for the staring infrared sensor in geosynchronous orbit has been proposed. The signal-to-noise ratio (SNR) has been introduced to evaluate the detection performance. The sensor temporal-spatial noise and background clutter time-domain residual have been comprehensively analyzed. First, the temporal noise and the spatial noise have been separated and compared, and then the background clutter and time-domain residual with different ground sample distance (GSD) have been analyzed based on the on-orbit remote sensing image. The results showed that selecting the appropriate GSD and applying the target detection method of time domain correlation, under the background-limited photodetection (BLIP), the design threshold of the noise equivalent target (NET) can be improved, and the detection and information processing efficiency can be maximized. The method proposed in this paper provide information for the design and optimization of space-based staring infrared sensor parameter.

During the final approach phase of the on-orbit service, high accuracy positional measurement of the non-cooperative target is critical to the success of the mission. In this paper, a convergent trinocular stereo vision measurement model is studied. First, trinocular stereo vision non-linear solving methods were investigated; then, the relationship between the structural parameter configuration of the stereo vision measurement model and the 3D coordinate measurement accuracy, as well as the relationship between the stereo vision camera position placement structure and the effective detection field of view of the measurement system is studied, providing a theoretical basis for the system configuration and optimal configuration design of the trinocular stereo vision camera; afterwards, the three cameras were designed with a baseline distance of 1.3m and the optical axis of each camera was tilted 18° towards the centre of the "Y" bracket, which could meet the continuous position measurement of large non-cooperative targets at close range with high accuracy. Finally, the simulation result of the motion of the non-cooperative target from 15.0 to 1.8m validates that the model has high accuracy and strong robustness in positional solution.

Dynamic infrared scene projection system can provide infrared detectors such as infrared seeker with target infrared radiation characteristics equivalent to the real environment in the laboratory. It can produce dynamic infrared scene to simulate the infrared radiation characteristics of real objects and their environment. The system constitutes a hardware in the loop simulation test system together with multi axis motion platform, seeker system, control system and other related equipment. This paper presents a scheme of infrared scene projection system based on dual digital micro mirror device (DMD), describes the main functions and composition of the system, and focuses on the working mechanism of dual DMD to improve gray level and frame rate. The system consists of dual DMD infrared scene projector, synchronization control device and scene generation computer. Two DMDs are used to modulate the infrared radiation intensity of each frame image and the spatial distribution characteristics of the image, and jointly complete the modulation of the gray level and spatial distribution of the output image. At the same time, the synchronization control device works synchronously with the test equipment or seeker to ensure that the generated infrared field frame rate is synchronized with the image collected by the test system. At present, the high frame rate infrared scene projection system based on dual DMD can meet the index requirements of maximum frame rate of 100Hz and minimum integration time of 2ms, which can vary with the synchronization signal frequency, and meet the integration time and synchronization test requirements of a variety of infrared detection equipment.

It is crucial to obtain infrared emission coating materials with emissivity close to one unit for remote sensing temperature measurement, earth climate monitoring and other fields. In order to obtain large-area uniform high emissivity coating, multi-layer spraying and multi-walled carbon nanotubes doping were used to enhance the emissivity of commercial black paint NVC811-21 from 8μm to 14μm. Compared with the coating directly sprayed with NVC811-21, the emissivity of the coating in the normal band from 8μm to 14μm in the atmosphere can be increased from 0.965 to 0.978. In addition, from the spectral emissivity of the coating in this band, the doping of carbon nanotubes can improve the emissivity near 10μm of the coating. For NVC811-21, this improves the uniformity of the spectral emissivity of the coating material. Due to the application of NVC811-21 in the actual service of the on-orbit blackbody, this paper's preparation method may help improve the emissivity of the on-orbit blackbody and the measurement accuracy of satellite remote sensors.

Based on collection effect of photogenerated carrier, the front-illuminated planar type InGaAs short-wave infrared (SWIR) detectors were fabricated by using N-InP/i-In_0.53Ga_0.47As/N-InP double-hetero structure materials. The series of detectors with the same dimension of 200μm×200μm contain several lateral collection regions and the width of each collection region is 15μm. The photoelectric characteristics of the photoresponse, I-V, spectral response and detectability of detectors with the lateral collection structure and normal structure were further analyzed. The build-in electrical field could effectively collect the electron/hole pairs generated in the lateral collection regions, so the photoresponse of lateral collection detector at 296 K is quite uniform by the laser beam induced current (LBIC) technology. Furthermore, the average peak detectivity and the density of dark current of the detectors with lateral collection structure reached 2.90× 10¹² cm·Hz1/2/W and 3.94 nA/cm² at -0.1 V respectively. It turns out that the lateral collection structure could effectively improve the dark current properties compared with the normal structure.

To achieve an accurate evaluation of the effect of laser interference, this paper studies on the image simulation model of laser interference infrared detectors. According to different interference densities, the characteristics of the laser interference detector spots are investigated. First, based on the laser interference transmission link, a simulation model of the gray response of the detector image and the laser interference power is established. Then, a set of NEFD measurement methods for infrared detector response models are established based on the response characteristics of the detector. Finally, according to the different NEFD values at the entrance pupil optical system, theoretically simulation is carried on the relationship between the laser interference effect and the power density irradiated to the entrance pupil surface of the optical system. The results show that when the irradiance density at the entrance of the pupil optical system exceeds 1*10⁶ of the NEFD value, the point target can be effectively interfered. Further, when the irradiance density at the entrance of the pupil optical system exceeds 1*10⁷ of the NEFD value, the area target can be effectively interfered. The proposed model is verified by the ground test as the ground test results have the same trend and magnitude as the simulation results.

A kind of frequency tracking circuit based on phase-locked loop (PLL) is studied for the resonant infrared sensor in the paper. The operating principle of the PLL is analyzed. 74HC4046 as the core component of the circuit is selected; starting the lock circuit is researched; a closed-loop frequency tracking circuit based on 74HC4046 is built. Software simulation proves that the frequency tracking of the circuit can achieve the order of MHz and has good frequency stability and tracking performance, which lays a foundation for the construction of the follow-up resonant sensor excitation/detection circuit.

Measurement of infrared radiation with low intensity in level of 10⁻⁶ W / cm² is difficult. Because both background and the components used in the measurement system will generate infrared radiation, which results in a low signal-to-noise ratio (SNR). Except of using photodetector with high sensitivity, weak signal processing method is crucial. In this paper an infrared radiation intensity measurement setup based on intercomparison method is introduced. A reflective chopper is used to modulate the detected infrared radiation. By using a MCT Detector with Dewar the infrared signal is transferred to electric signal. To process the weak modulated signal with strong noise an extended Duffing oscillator is introduced. Both amplitude and phase of the modulation signal with known frequency is obtained by step-time-delay technique (equivalent to phase shifting in frequency-domain). The measurement error can be maintained below 16.1% even when the SNR is as low as -67 dB. The corresponding received infrared radiation power is only 1.05×10^-9 W. The proposed signal processing method shows superior ability and great potential applications compared with commonly used method, such as lock-in amplification.

In many industrial fields, the camera is often used to capture the movement of the geometric figure and measure the movement speed of the object through image processing, but the camera is very expensive and has high requirements for the field installation environment. In this paper, a new low-cost velocity measurement method based on CIS (contact image sensor) is proposed. Because CIS is a kind of linear array image sensor, so if the sampling rate is not high enough, it is easy to produce image blur. Therefore, CIS is not suitable for scanning high-speed moving targets. However, the blurring degree just reflects the moving speed of the scanned object. When CIS image scans the triangle figure with high speed, the gray level will change gradiently due to the influence of the hypotenuse of the triangle. In this paper, a CIS scanning system is setup with a triangle icon as scanned color tag. Through many tests and digital signal processing, the relationship between the gradient change of pixel gray value data and the moving speed of target is linear fitted. The measurement results show that the method can measure the motion speed of color tag. The accuracy of measurement depends on the resolution of CIS sensor and the sampling rate of the system.

It was an effective way to keep the pivotal element of the lens under a specific temperature in order to increase the detection sensitivity, so that the thermocurrent caused by thermal radiation of the lens itself could be control under a lower level, But it was difficult to decide which element was the correct one and what was the temperature should be kept. To solve this problem, we, We used LightTools to simulate the cold optical lens deign and established a calculation and analysis method. which can be applied to the analysis of most infrared systems and has universal applicability.

The band structures of the InAs/GaSb type-Ⅱ superlattice are investigated using the 8-band k.p method. The finite difference method (FDE) is used for solving the Schrödinger equation. It is found that a small variation in the valence band offset (VBO, one of the input parameters) could cause a great change in cut-off wavelength, especially at the long-wavelength range. We also developed a GUI application based on this method. Users could quickly get band structure details, such as bandgap energy, miniband energy, and wavefunctions with this GUI. The program and its code are available at https://github.com/STONEDIY/K.p-Mehtod-for-InAs-GaSb-Superlattice-Band-Structure-Calculation.

In this paper, a widely tunable Cr:LiSAF laser with an external cavity was employed as the pump source. By using a triangular prism and double output couplers in the cavity, the line width can be narrowed and the pump center wavelength can be adjusted to the ideal value. The FWHM in spectrum of a pump laser can be narrowed to as small as 0.5 nm. The absorptivity of Ho:BYF at the center wavelength from 885 nm to 890 nm was measured, and the optimal pump center wavelength has been determined to 888.5 nm. Then the focal length of a focusing lens and the curvature radius of a laser output coupler have been optimized through a series of experiments. Finally, we have obtained the laser output at 3.9 μm with the optical-to-optical efficiency larger than 10% at the relatively low repetitive rate. The results might be helpful for the construction of a real laser system.