Abstract:Digital infrared thermography is suitable for monitoring the planar two-dimensional temperature distribution of curved surfaces of objects by sensing their infrared radiation. Cardiac infrared thermography also has a thermal coronary angiography alias. This study proposes a digital image processing methodology for locating blood clot blockage. This methodology contains four consequent processes. The two-dimensional gray scale infrared thermograph pixels are first binarized and classified as background or coronary arteries using multi-thresh adaptive segmentation. The coronary artery contours are extracted from segmented raw pixels using continuous pepper-like pixel removal, erosion, subtraction, recursive neighborhood visiting, contour point-list construction and short edge deletion. In the third process one coronary artery branch is selected by physicians for calculating the longest curved central axis using morphological thinning and neighborhood analysis. In the last process the nearest left and right distances from each pixel along the directional central axis to its corresponding boundary contour are added as the coronary artery variable diameter at the current pixel's position. A variable diameter versus straighten length diagram along this axial curved path is plotted to provide useful physiological information to the physician. An obstruction rate equation is then defined to calculate the possible vascular blockage positions with the local minimal rates. Finally, preoperative cases are tested to prove the predictive positions are correct in comparison to individual patient myocardial perfusion imaging.

Abstract:In this work, the experimental system for optically controlled capturing and orientating is designed. Using the system, we demonstrate optically capturing of lithium niobate micro crystal particle. Moreover, the captured particle becomes aligned with the direction of linear polarization. Finally, we present optically controlled orientation theory of lithium niobate crystal particle. The work illustrates that the alignment of lithium niobate micro crystal particles can be optically orientation by the linear polarization’s direction of laser light. These results can be further used in micro sensors, photonics, MEMS, light-induced micro motor, and micro manipulation fields.

Abstract:Germanium (Ge) films with physical thickness of 1600nm was deposited on ZnSe substrates by an electron beam evaporation system. The transmittance of Ge film in the range of 2 to 15 μm was measured by a PerkinElmer FTIR cryogenic testing system from 80 K to 300 K with a step length of 20 K. Then, the relationship between the refractive index and wavelength in the 2~12 μm region at different temperatures was obtained by the full spectrum inversion method fitting. It can be seen that the relationship confirms to the Cauchy formula. The relationship between the refractive index of Ge film and the temperature / wavelength can be expressed as n(λ,T)=3.29669+0.00015T+5.96834×10-6T2+0.41698λ2+0.17384λ4, which was obtained by the fitting method based on the Cauchy formula. Finally, the accuracy of the formula was verified by comparing the theoretical value obtained by the formula with the measured result.

Abstract:Scaled InAlN/GaN heterostructure field-effect transistors (HFETs) with high unity current gain cut-off frequency (fT) were realized by employing nonalloyed regrown n+-GaN Ohmic contacts, in which the source-to-drain distance (Lsd) was scaled to 600 nm. By processing optimization of dry etching and n+-GaN regrowth, a low total Ohmic resistance of 0.16 Ω·mm is obtained, which is a recorded value regrown by metal organic chemical vapor deposition (MOCVD). A 34 nm rectangular gate was fabricated by self-aligned-gate technology. The electrical characteristics of the devices, especially for the RF characteristics, were improved greatly after the reduction of ohmic resistance and gate length. The fabricated InAlN/GaN HFETs show a low on resistance (Ron) of 041 Ω·mm and a high drain saturation current density of 2.14 A/mm at Vgs=1 V. Most of all, the device shows a high fT of 350 GHz, which is a recorded result reported for GaN-based HFETs in domestic.

Abstract:The non-periodic high-index contrast grating with a given period and duty was designed to manipulate the wave-front phase shift of the beam and further realize multi-angle beam steering. The finite difference time domain method was used to simulate the grating bars with a specific sorting order, and the beam steering angles of -10.644°, -21.176°, -28.307°,10.644°,21.447°, and 28.418° were obtained. Based on the multi-angle steering high contrast grating (HCG) array, a vertical cavity surface emitting laser (VCSEL) source with multi-deflection angle beam steering ability was proposed to meet the requirement of wide-field light detection and ranging (LIDAR) source. The tiny and easy integration of wide-angle emitting VCSEL light source system can cater to the compact and miniature LIDAR systems.

Abstract:Carbon (C) atoms can be replaced by other atoms in specifically designed spots to regulate the properties of graphene. This is established by introducing impurities such as B and N into graphene. The band gap can be opened while the Dirac cone shifts above or below the Fermi level. This behavior is the same as p-type or n-type doping in semiconductors. Electronic states are observed at the Fermi level, and the charges are transferred from the impurities to C or vice versa. The static dielectric function ε1(0) increases greatly, a new absorption peak appears in the low-energy region corresponding to visible light and the following energy. The decrease in plasma excitation due to the B or N doping results in a reduction of the number of peaks in the electron energy loss function. Only one obvious peak is observed at the same position as that of the highest peal of pristine graphene. The height of this peak increases significantly.

Abstract:A wide spectral range and fast Single-photon avalanche diode (SPAD) chip which can be integrated with actively quenching circuit for large array realization is designed and implemented. The precise circuit model of SPAD for simulating the static and dynamic behaviors in Geiger-mode is used. The device with an 8 μm diameter active area is fabricated in GSMC 180 nm CMOS image sensor (CIS) technology. With the efficient device’s structure, the low breakdown voltage is 15.2 V and quenching time is 7.9 ns. Additionally, the device achieves wide spectral sensitivity and enables maximum photon detection probability (PDP) of 15.7% from 470 to 680 nm of wavelength at low excess voltage. Moreover, it exhibits a relatively low dark count rate (DCR) at room temperature.

Abstract:The composition and control structure of fine tracking system of free space laser communication are briefly described. The error sources of the beacon positioning of fine tracking detector using centroid algorithm of the acquisition, tracking and pointing system are analyzed. And the Fourier frequency domain of the beacon positioning process of fine tracking detector is analyzed too. The theoretical scheme for eliminating the systematic error of centroid algorithm is derived, that is, the product of the beacon light wavelength and the F number of the fine tracking system need to be larger than the pixel size of the fine tracking detector. The selection process of the key parameters in the implementation of the fine tracking system is analyzed，and considering the coupling relation of system parameters of fine tracking system, in order not to lose fine tracking field of view, the optimization of fine tracking system by adding aperture diaphragm before fine tracking detector lens is implemented for eliminating the systematic error of centroid algorithm. The theoretical calculation and experimental results show that when the aperture diameter is less than 9.32 mm, the relative aperture of the fine tracking system is less than 0.045, and the fine tracking error is only 0.03 pixel, and the tracking accuracy is improved by 1.9 times.

Abstract:A compact IOT node based on linear variable filter and InGaAs focal plane array was presented. The long-wavelength near-infrared spectral data can be collected and transferred with wireless communication method. Performance experiments were carried out to test the parameters of the node, such as wavelength range, spectral resolution, wavelength accuracy and stability. Experimental results demonstrate that the wavelength range is from 950nm to 1700 nm, and the spectral resolution is approximately 1% of peak wavelength. The wavelength accuracy and wavelength stability are less than 1.3 nm and 0.1 nm respectively. The proposed node can meet the demand of near infrared spectral analysis in IOT applications.

Abstract:ZnTe:Cu crystals were successfully prepared on TG-II spacecraft by Te solvent Method. The quality of crystal growing in the microgravity is much better than those growing on the ground at the same experiment conditions. The size of crystals prepared on TG-II is larger than those prepared on the ground. Cathodoluminescence was used to measure ZnTe:Cu crystals at 5 kV、15 kV、25 kV voltages. CL mapping and spectra were conducted at different voltages. It was found the crystals growing in microgravity possess lower density of defects.

Abstract:In this paper, based on photonic crystal (PC), a coarse-wavelength-mode-division hybrid multiplexer/de-multiplexer is proposed. The coarse wavelength division multiplexing (CWDM) and mode division multiplexing (MDM) can be integrated on a chip of PC. According to coupled mode theory in time, point-defect cavities and wavelength-selective cavities were introduced in the PC to filter the optical wave. According to the lateral coupled mode theory, asymmetric parallel waveguides (APWs) consisted of single-mode waveguides (SMWs) and multi-mode waveguides (MMWs) were introduced in the PC to achieve mode conversion. The finite-difference time-domain (FDTD) method is used for property analysis. The simulation results show that the device achieves the multiplexing/de-multiplexing of four signals, i.e., the 1550 nm TE0 mode, 1570 nm TE0 mode, 1550 nm TE1 mode and 1570 nm TE1 mode. The device exhibits not only a low insertion loss (<0.23 dB) but also low mode crosstalk (<-15.21 dB). It has considerable potential for application in the CWDM-MDM system and great value to improve the capacity of metropolitan area network.

Abstract:Terahertz is expected to be the best waveband for remote sensing of cirrus. However, the retrieval results of satellite terahertz passive remote sensing are susceptible to different atmospheric conditions. The terahertz radiation was simulated under the clear sky and the cloudy situations, based on the atmospheric radiative transfer simulator. The influences of the surface reflectivity, atmospheric profiles and the middle-low level water clouds to terahertz radiation were analyzed. The retrieval errors caused by these factors were calculated based on the multiple lookup-tables method. The results indicate that the influence caused by changing the surface reflectivity mainly range below 300 GHz, and there is no influence on the selected channels. Among the atmospheric profiles, only changing water vapor profiles and temperature profiles have effects on the retrieval results. When the temperature profile changes are between ±2 K, or the water vapor profile changes are between ±20%, for cirrus whose particle size is above 50 μm and ice water path is above 10 g/m2, the retrieval errors stay below ±20%. For low-level water clouds (cloud base height below 2 km), the effects on retrieval errors can be ignored. The retrieval errors caused by middle-level water clouds increase with the increases of the cloud base height and cloud optical depth.

Abstract:The large number of array elements leads to the high cost and high design complexity of forward-looking array SAR system. How to obtain higher imaging quality with fewer array elements is a difficult problem for forward-looking array SAR system. According to the quality requirements of system imaging, combined with beam scanning and grating lobe suppression technique, a design method of sparse transmitting and receiving antenna array is proposed. Theoretical analysis and simulation results show that the method can effectively reduce the number of array elements and improve the signal-to-noise ratio of the system, and has a certain application value.

Abstract:The conventional shape similarity measurements face the problems of robustness and accuracy in noise interference, partial information occlusion and missing situation. A method of shape similarity measurement based on principal curvature enhancement distance transformation is proposed. The distance transformation is carried out to extend the range of the shape contour, improving the robustness of the similarity measure. The distance map is enhanced by the principal curvature of the shape contour, improving the response of rich information contours in the transformation map, and enhancing the accuracy of measurement results. Simulation experiments show that the robustness and accuracy of the method in the situation of noise interference and partial contour occlusion or absence are verified. Application experiments of road vector and GPS signal and optical remote sensing image show that the method is effective in practical application. Compared with traditional shape similarity measure methods, the method based on principal curvature enhancement distance transformation is suitable for the non-rigid target shape similarity measure, and the robustness and accuracy are better.

Abstract:The monitoring of heavy metal pollution in crops is one important application of hyperspectral remote sensing study. Heavy metal pollution can cause spectral distortion of crop, but the crop spectra of different pollution degrees still have very high similarity in shape, so one of the key problems in monitoring its distortion is how to extract the weak difference information between similar spectra. In this study, a VMD-CR-ED measurement model was established by introducing the variational mode decomposition (VMD) theory into weak change monitoring of spectral information and combining with the continuum removal (CR) and euclidean distance (ED) methods. The model was proved to be superior in distinguishing the different pollution degrees of corn leaves by compared with SA and SCC. At the same time, the correlation between VMD-CR-ED model and eight characteristic sub-bands of corn leaf spectrum was analyzed. Finally, based on the test data, it is proved that the VMD-CR-ED measurement model is feasible and reliable in the monitoring of copper and lead pollution of crops.

Abstract:A grating-type infrared absorber based on LiF and NaF material composite grooves is designed. The finite-difference frequency-domain (FDFD) method is used to analyze the absorption mechanism. In addition, the influence of the structure parameters of the absorber, the wavelength of the incident wave and the incident angle on the absorption characteristics are investigated. The results show that this absorber will form different optical resonators for incident light of different wavelengths in infrared region, which can strongly absorb infrared light over a wide wavelength range. The absorber has a good absorption performance in the range of 18~70 μm wavelength range and 0~80° of incident by using the optimized parameters. The research work of this paper provides a theoretical basis for the design, fabrication and application of the grating-type infrared absorber.

Abstract:Influence of Hg vapor to CZT substrate during LPE growth of HgCdTe process were studied, CZT substrates were characterized by combining with Microscope, White-light Interferometer (WLI) and Energy Dispersive Spectrometer (EDS) . Results show that the CZT substrates mainly suffered the Hg vapor during LPE process，Hg vapor has no effect on the precipitations in CZT substrates surface. Two kinds of typical Hg erosion defects are found on CZT substrates after Hg vapor treatment process. One is a kind of large defect that had size of 25 μm and distributed uniformly, while the other is smaller size of 7 μm presented nonuniform distribution. Furthermore, fish scale like surface morphology on CZT substrate is found after Hg vapor treatment process during LPE growth of HgCdTe, surface roughness increase more than 50%.

Abstract:Microscopic hyperspectral imaging technology of biological material is the forefront of biological spectroscopy study. It is important to make sure whether the dermal substitute transplanted in patient’s wounds gets into normal vascularization process when burned or deeply traumatic patients are treated. This is the key to evaluating the quality of repair material and is also an important index of patient’s wounds recovery. This paper proposes and realizes a method of rapid vascularization identification based on G-SA-SVM. This method is based on the microscopic hyperspectral imaging. First, the blank correction is used in hyperspectral data. Second, an adaptive Gamma correction model is employed to take advantage of the spectral and spatial features. Finally, simulated annealing is used to optimize the parameters of support vector machine (SA-SVM). SA-SVM is applied to locating the red blood cells effectively and then locating the blood vessels quickly. The experimental results confirm that the proposed method called G-SA-SVM has higher classification accuracy. Hence, it can be applied to evaluating the vascularization process.

Abstract:In recent years, near-infrared laser absorption spectroscopy detection technique has developed rapidly, and spectral analysis of absorption lines is one of the important research contents of spectrum detection. The experimental platform for gas laser absorption spectroscopy measurement was established in this study, moreover the experiment of ammonia characteristic spectroscopy analysis at 6528.8 cm-1 and algorithm research were carried out. Experimental results show that the root mean square error of the measured signal reduced 4.45 times after combined with wavelet denoising method, and the fitting residual error of overlapped absorption lines was lower than 2% by using multi-line Voigt line profile fitting algorithm. In the experiment, the ammonia characteristic absorption spectrum of different pressures at room temperature was obtained, and the line strength parameters of each absorption line were also calculated. The relative deviation between the measured results and Hitran database was between 5.67~8.2%，and the uncertainty of calculated line strength was about 4.6%. The accurate measurement of line strength by the effective spectrum analysis algorithm of overlapped absorption lines is in favor for improving the accuracy of ammonia concentration inversion.

Abstract:Vegetation height is an important parameter for biomass assessment and ecosystem structure monitoring. However, vegetation height data over large areas are difficult to obtain. Vegetation heights can be retrieved by using large-footprint satellite altimeter system GLAS waveforms, but the current method can only be used in relatively flat forest regions because over sloping mountainous areas, the effects of ground and canopy are mixing on the waveforms and cannot be distinguished. By establishing analytical model of forest target echo, the separation requirement of vegetation echo and ground echo from aliasing waveforms is derived. It is pointed out that the factors of leading to echo aliasing in addition to target roughness and slope, and beam divergence angle is also a factor. The broadening effect and waveform decomposition related to the beam divergence angle, surface roughness and topography slope is analyzed. By using the waveform simulation and GLAS actual waveforms, it is verified to decrease beam divergence angles can reduce the sensitivity of forest echo to sloping mountainous terrains and be more conducive to the retrieval of canopy heights. For laser altimeter to carry on satellite in the orbit of 500~600 km, the beam divergence angles is 40~60 μrad better. The result provides a meaningful reference for designing of satellite laser altimeter system for the retrieval of canopy heights over high sloping terrains.

Abstract:In the case of hyperspectral anomaly detection, in order to make hyperspectral low-dimensional data preserve the spectral information more completely, a band selection method based on the optimal linear prediction of principal components in subspace was proposed. Hyperspectral bands are divided into different subspaces by spectral clustering with the improved correlation measure. The principal component analysis (PCA) of bands is presented in each subspace, and main components are selected as the reconstructed targets. The subspace tracking method serves as the search strategy, and several bands are selected from each subspace to perform the joint optimal linear prediction of reconstructed targets. The selected bands in each subspace are combined to obtain the optimal band subset. Experimental results show that, the proposed method can reconstruct the original data more completely. Compared with original data, and the band subsets obtained by adaptive band selection (ABS) method, linear prediction (LP) method, maximum-variance principal component analysis (MVPCA) method, auto correlation matrix-based band selection (ACMBS) method and optimal combination factors-based band selection (OCFBS) method, the band subset of proposed method has superior performance of anomaly detection.