Abstract:Detection in ultraviolet and infrared ranges is essential for remote atmospheric sounding which includes important information closely related to human life. Based on finite difference time domain method (FDTD) and finite element method (FEM), the mechanism of Pt/CdS and InSb ultraviolet-infrared dual-color focal-plane arrays are investigated. It is found that a high ultraviolet photo response can be achieved for Pt/CdS Schottky junction under an ultrathin Pt top contact. Further simulations show that the ultrathin top contact can efficiently couple the infrared radiation for the dual-color focal-plane arrays detector. The center to center spacing of each pixel of 50μm in the ultraviolet and infrared dual-color focal-plane arrays detector based on Pt/CdS and InSb junctions can significantly reduce crosstalk. Our work provides fundamental guidance for optimization and design of ultraviolet and infrared dual-color detector.

Abstract:Nano–scale metallic films have been proven to be an effective infrared absorption layer for pyroelectric detector operated at 14-16um spectral range for space applications. Improved infrared absorption can be achieved by adjusting the thickness and surface characteristics of nano–scale Nickel–chromium (NiCr) film deposited on the LT (lithium tantalite) crystal materials. By regulating the thickness of the crystal materials, the absorption wavelength is adjustable as well by changing the depth of anti-reflection cavity. To enhance the infrared absorption further, chemical corrosion is applied on this film, which generates rough nano–scale surface structure and greatly increases the absorption surface area. By combining this two methods, specified infrared wavelength absorption could be distinctly enhanced, and the manufacturing process is fully compatible and easily to realize. Experiment results suggest that the absorption performance which could be controlled agree well with the simulation and design.

Abstract:Straw returning to the field has the regulation effect for ammonia emission pollution in agricultural surface source. Monitoring regional volatilization concentration to accurately obtain the ammonia dynamic characteristics is the precondition for emission rule studying. The infrared absorption spectral characteristics of ammonia were studied. Moreover, the quantitative inversion algorithm model was established, especially the correlation analysis and temperature correction function were optimized. The ammonia volatilization experiment was carried out in the demonstration area in Guoyang, Anhui in 2015 by the ammonia regional monitoring system based on open-path Tunable Diode Laser Absorption Spectroscopy(OPTDL). Then, ammonia dynamic volatilization character of corn and wheat straw returning to the field was studied. The monitoring results show that the ammonia concentration has a certain diurnal variation trend: it increased during the daytime and got to the maximum value at midday, then reduced gradually at night to the minimum. The typical hourly concentration varied from 0.6 10-3 to 1.34 10-3mmol/mol in summer, and it varied from 1.14 10-3 to 1.82 10-3mmol/mol in autumn. In autumn, the maximum daily average of ammonia volatilization from corn straw returning was 4.6 10-4mmol/mol, and it was 1.7 10-3mmol/mol from wheat straw returning in summer. The results indicate that the emission concentration rises significantly after more than one month of straw returning which has some certain seasonal difference in farmland scale. This infrared spectroscopy technology provides technical support for clarifying the ammonia emission rules in soil environment.

Abstract:Bi/Yb3 co-doped germanate glasses were prepared by conventional melting-quenching technique. Near infrared (NIR) luminescence properties in Bi/Yb3 co-doped germanate glasses were investigated by the absorption spectrum, NIR luminescence spectra, and fluorescence lifetime measurement, respectively. NIR luminescence of both Yb3 and Bi ions was observed simultaneously, either under 980 or 808 nm excitation LD. The results show that ET process existed between Bi-related NIR emission centre and Yb3 ions. With the increasing in Yb3 ions concentration, both ET efficiency from Yb3 ions to Bi ion and optical basicity of glass matrix are increased. The competitive effect of enhancing by the ET process and weakening by optical basicity on NIR luminescence property of Bi ions is investigated.

Abstract:—This paper presents a W-band stepped-frequency three-dimensional near-field surveillance imaging system together with an effective radar imaging algorithm. W-band signal is able to penetrate common clothing barriers to form an image of a person as well as any concealed items. Performing the image reconstruction procedure in the frequency–wavenumber domain, the algorithm is able to completely compensate the wavefront curvature in the near field through interpolation process. The interpolation relationship in frequency–wavenumber domain between sampled data and desired data is demonstrated. Moreover, the difference between algorithm model and experimental data are revealed. High range resolution and lateral resolution are obtained by emitting wideband stepped frequency signal and adopting high operating frequency. The cross-range resolution of the imaging result is better than 5mm. The scheme of imaging system is described in detail along with a set of imaging results to show its superior imaging precision and sensitivity compared with existing Ka-band equipment.

Abstract:The Mg_xNi_1-xMn₂O₄(MNM x=0, 0.05, 0.10, 0.15, 0.20) films were grown on Al₂O₃ substrate by chemical solution deposition method. The effect of Mg doping on the structural properties of MNM thin films was studied by x-ray diffraction and field emission scanning electron microscopy. The results show that the films have a single cubic spinel structure and the films aresmooth and uniform, which have good crystallinity. The electrical measurements show that the conduction of MNM thin films was described by a variable range hopping model. The values of resistivity, characteristic temperature T₀, negative resistance temperature coefficient α for MNM thin films were obtained. The Mg concentration dependence of structural and electrical properties for MNM films was investigated.

Abstract:The influence of the InP cap layer doping density of InGaAs/InP SPAD is studied through theoretical calculation and comparative experiment. Theoretical results show that lower cap layer doping density is beneficial to suppress premature edge breakdown, reduce tunneling carrier generation rate, and increase breakdown probability. Experimental results show that devices with unintentionally doped cap layer have achieved 20% single photon detection efficiency and 1 kHz dark count rate at 223K. Compared to devices with cap layer doping density of 5E15/cm^3, the single photon detection efficiency increases by 3%～8%, and the dark count rate decreases by about an order of magnitude. It is demonstrated that reduce the cap layer doping density is beneficial to improve the performance of InGaAs/InP SPAD.

Abstract:Based on the Stokes-Mueller matrix polarization algorithm, the polarization control mechanism of biplate that consists of double single quarter wave-plates or half wave-plates was analyzed in detail. We have derived the analytical relations between the modulated polarization state and the fast-axis direction for the biplate and obtained the movement trajectory of modulated polarization state on the Poincaré sphere, which helped us to propose a polarization control measurement system using a biplate to complete the measurement of the Mueller matrix based on the projection matrix algorithm for the incident and exiting Stokes vectors and the analysis of polarization control accuracy for the exiting Stokes vector. Experimental results performed on such a biplate that the fast axis direction error is ± 2 °, and the retardance error is λ/300 demonstrated that the maximum measurement error of Mueller matrix is 0.0402, When the azimuth error caused by the error of the biplate is less than 0.16 rad, the elliptic angle error caused by the fast axis direction is not more than 0.032 rad, the ellipsometry error caused by the retardance is less than 0.015 rad, and it has no influence on the degree of polarization.

Abstract:For high reflective targets with smooth surface,single or even none texture,a large area of data void may appear on the reconstruction surface since the traditional three-dimensional reconstruction method depending on texture and reflective characteristic.While three-dimensional reconstruction method based on polarization vision does not rely on the texture information on the surface of objects,and the polarization imaging can restrain highlight to a certain extent,which can effectively solve the problems existing in the traditional three-dimensional reconstruction method.However,the depth information obtained by three-dimensional reconstruction method based on polarization vision is under pixel coordinates.Therefore,polarization and binocular three-dimensional reconstruction method is put forward,taking absolute three-dimensional coordinate of a few feature points obtained by binocular stereo vision as the “bridge”,using the camera parameters obtained by binocular calibration to transform the point cloud data acquired by polarization in image pixel coordinates into absolute data in world coordinates.

Abstract:The matching between imaging remote sensing equipment and non-imaging remote sensing equipment refers to the space conversion between the image data and other data of observation target in the same reference coordinate system. Due to the difference of data and the difficulty of matching of different types of equipment, the previous studies are mostly between the same type of equipment and little attention to the matching of different data types of equipment. Such as molecular spectral level remote sensing applications require the matching between high spatial resolution image and hyperspectral resolution spectrum of the target. Taking the hyperspectral resolution of Spatial Heterodyne Spectrometer (SHS) as an example, this paper proposes a method to match and correct the pointing error of SHS, which is extracted the characteristics of the ground surface interferometric data with SHS by using the feature of large area uniform landform and abrupt change of the surface reflectance in coastline area of the high spatial resolution remote sensing image. And this method is used to realize the matching application between non-coaxial imaging remote sensing equipment and non-imaging remote sensing equipment. The SHS was used to perform ground-based testing experiment on the results of interferometric data at several earth observation points and high spatial resolution image data in the same latitude and longitude region. The results of the calibration correction were compared with their nominal values, and the error ranged from -3 % to 5%.The results show that the proposed method can be used as a reference for matching application between non-coaxial imaging remote sensing equipment and non-imaging remote sensing equipment on board the satellite.

Abstract:A 310-330GHz receiver front-end with Schottky diode is designed and tested. The receiver first stage is a subharmonic mixer (SHM), in order to lower conversion loss (CL) and improve receiver sensitivity, the diode parasitic parameters such as the air-bridges inductance and their mutual inductance are discussed. The diode RF, LO and IF port impedance are calculated with embedding analysis for circuit optimization and the simulated CL accuracy is improved. The LO sources is realized by a ×6×2 multiplying chain, in which the sextupler is a commercial active multiplying chip, and the balanced doubler is realized by a anti-series Schottky diode mounted on a suspended line. The chain can generate 10dBm output power at 165GHz and its generated power is applied to pump the receiver SHM. The receiver second stage is a low noise IF amplifier for lowering system noise figure. In the frequency range of 310-330GHz, the measured receiver noise figure is lower than 10.5dB, and its minimum value is 8.5dB at 325GHz. The receiver gain is 31±1dB.

Abstract:The skylight polarization models can simulate the polarization state distribution of the skylight, and are key tools to study the quantitative relationship between the polarization state distribution of the skylight and the characteristic parameters of the atmosphere. A skylight polarization model of various weather conditions was modelled, which based on adding and doubling method for solving the radiative transfer equation and T matrix method for calculating the scattering properties of particles. The comparison between the simulation results of this model and the calculation results of Hovenier et.al showed that more than 95% points’ relative error is less than 5%. The measurement experiment results with the polarization imaging system based on LCVR showed measurements are most consistent with the simulation results in degree of polarization in 80% of the area. It can be concluded that the model can accurately simulate the distribution of the polarization state of the sky light under various weather conditions.

Abstract:Transition-metal oxides LiTi2O4 thin film was epitaxially grown on MgAl2O4 (001) substrate by pulsed-laser deposition. The X-ray diffraction indicates that the film was successfully grown with high quality and single cubic spinel phase. The Raman-active phonons were studied by Raman spectroscopy. Using spectroscopic ellipsometry, we also determine the refractive index and extinction coefficient of the film in visible-near-infrared region. Band structure and density of states (DOS) of LiTi2O4 were carried out by first-principles calculations. The theoretical calculations are consistent with the experimental results, and the optical constants is well identified by the theoretical band structure.

Abstract:This paper presents a visual to infrared transducer based on an infrared image converter chip fabricated by micro electro mechanical systems (MEMS). The infrared image projector consists of three parts, which are visible light image generation system, infrared image converter and the infrared image projection system. This infrared image transducer covers the radiation band of 8-12μm.Its resolution is 20lp/mm and the apparent temperature range is 20 ° C to 150 ° C. Non-uniformity of the image generated by infrared image projection device is less than 5% and its geometric distortion is less than 3%.

Abstract:A novel target spectrum learning method for small target detection in hyperspectral imagery is proposed to obtain a more accurate target spectrum for better supervised target detection. This method is composed of two components: adaptive weighted learning method and self-completed background dictionary. Given a complete background dictionary, the former component refines the target spectrum through sparse coding and gradient descent algorithm. The latter component guarantees the background dictionary completeness by gradually size enlarging. Both experimental results on simulated and real hyperspectral data show that the proposed method has an advantage in extracting the accurate target spectrum, which enables better detection results.

Abstract:Due to the high temporal resolution and wide area coverage, Geostationary Doppler weather radar (GDWR) is becoming a hot issue all over the world. The observation of GDWR is more vulnerable to the surface clutter for its scanning mode. Therefore, it is significant to simulate the GDWR measurement and investigate the surface clutter suppression of the GDWR data. Firstly, a brief introduction of the GDWR was described. Secondly, based on the Satellite-Earth geometry model, observational data of GDWR were simulated using the APR-2 data, and the rainfall intensity and velocity field data were analyzed. Finally, by combining the characteristics of power spectrum data and time domain signals, the surface clutter was restrained using the Gaussian model adaptive processing method (GMAP) and fifth-order elliptic infinite impulse response ground clutter filter (IIR). The comparisons were carried out between the filtered data and the original data, which indicates that the weather radar echo influenced by the ocean surface clutter can be correctly recovered using IIR and GMAP methods.

Abstract:Bistatic forward-looking synthetic aperture radar (BFSAR) has many potential applications, such as self-landing in bad weather, military detection. Millimeter-wave SAR has high resolution, light weight small size and short synthetic aperture time advantages. Therefore, this paper combines millimeter-wave and BFSAR techniques, carry out the research of imaging algorithms for millimeter-wave BFSAR. However, imaging algorithms for BFSAR are the difficulties of the study. Due to the special forward-looking geometry, imaging algorithms for bistatic SAR can not be applied to BFSAR directly. So, this paper proposes a modified Loffeld's Bistatic Formula (MLBF). The new method compared with other extended Loffeld's Bistatic Formula (ELBF) can obtain a bistatic point target reference spectrum, which is accurate enough for bistatic forward-looking configuration. Then, an Omega-k algorithm based on the reference spectrum is derived. Finally, simulations validate the accuracy of the MLBF method and the effectiveness of the Omega-k imaging algorithm.

Abstract:Infrared focal plane array detector suffers from problems including the lack of localization technology of infrared devices, intrinsic non-uniformity, low signal-to-noise ratio (SNR). Image acquisition, transmission, and storage cost more and more high for the application of aerospace imaging. To overcome these difficulties, this paper analyzed the principle of computational imaging system, and then the compressive sensing theory was introduced for imaging. Next the imaging prototype was built, and compressed and uncompressed imaging had been experimented. Finally, the method of the signal subspace analysis was introduced for the quality evaluation of reconstructed image, and then the SNR of the reconstructed image was estimated using this method. Experimental results demonstrate that the SNR estimation method is more accurate and effective, and can be as an experimental conclusion that give a reasonable number of samples required for the actual compressed imaging.

Abstract:A kind of human body image privacy protection algorithm was proposed for active millimeter-wave imaging security systems, the imaging effect of which was not affected by the height and the standing posture. The background noise of the millimeter-wave image was decreased and the edge details were increased by pretreatment of human body image. The morphological processing and binarization were used to distinguish human body image from background. The pixel traversal method and human body proportion determination method were initially used to locate the private parts of human body with standard posture. Subsequently, the calibration algorithm was used to locate the privacy parts of human body with different height and non-standard posture and thus improved the identity rate of location. Finally, the already positioned privacy parts were blurred to protect the privacy of people under inspection. The algorithm has been applied to the actual imaging products. Compared with the conventional ones, the proposed algorithm has high portability, fast running speed and high positioning accuracy.

Abstract:This paper presents a novel flip-chip (FC) structure design for 340GHz Schottky diode detectors, which are designed and fabricated based on the gallium arsenide (GaAs) process. A ceramic thin-film supporting layer is used to provide a package for such detector. Conductive adhesive is typically used as attachment material between the antenna and output circuit. The behaviour of terahertz (THz) detectors with and without the novel FC structure was studied. For comparison, the FC structure model and wire bonding structure one (free of FC) were characterized using the same test system. A comparison analysis for the gains of the THz detector measured with and without the ceramic thin-film layer indicated that the novel FC structure offers a low-cost and practical solution for packaging the array of THz detectors.