The reflectance of strong absorption band in condition of cirrus atmosphere is simulated by the general atmospheric radiation transmission software. The effects of cirrus particle’s shape and effective size, optical thickness and cirrus altitude on atmospheric top reflectance and background radiation are analyzed. A radiation intensity calculation model of high-temperature gas target is established and the spectral radiation characteristics of target radiation transmitted to the top of atmosphere in cirrus atmosphere are obtained by simulation. The target background contrast at the top of atmosphere is computed, and the influences of cirrus characteristic parameters and target altitude on target background contrast are also discussed. Results show that cirrus atmospheric reflectance increases with the increasing of cirrus altitude and optical thickness, and decreases with the increasing of cirrus particle effective size in the strong absorption band of vapor. The target background contrast is greatly affected by cirrus parameters. The presence of cirrus has a big disturbance to target observation, especially when the target altitude is below 7 km.

The remote detection of gas infrared radiation signal in high temperature kiln is carried out based on Fourier transform infrared spectrometry technique. According to industrial site conditions, a passive radiation model is built based on the principle of atmospheric radiation, and the high temperature gas transmittance in the cement-kiln is calculated. Aiming at the influence of turbulence noise on the signal to noise ratio, a data processing method for spectrum inversion of infrared interference signal is studied, and the average signal of multiple scanning interference signal is obtained when we align the interference signal on the basis of zero optical path difference. The noise and the amount of computation are reduced, and the spectral data rate is improved. Based on the HITRAN database and the high temperature reference spectrum model, the nonlinear least square fitting method is used for the spectrum line strength and corrected and transmission spectra obtained by line width correction, and the concentration of high temperature gas in cement-kiln in different absorption bands is inverted. The results show that the proposed method for on-line monitoring of high temperature gas in the cement-kiln and other industrial combustion processes is feasible and reliable.

An automated radiation calibration method is proposed based on the automated multichannel spectral radiometer (ATR), 6SV radiometric transfer model, historical hyperspectral reflectance model of Dunhuang site and moderate-resolution imaging spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF). The proposed method can be used for radiation calibration continuously when the weather and satellite observation geometry parameters satisfy the conditions. Experiments are carried out at Dunhuang radiometric calibration site from August 2015 to March 2016, and effective observation data in 17 days is obtained. AQUA/MODIS is used as radiation benchmark to verify the accuracy and calibration frequency. Results show that the radiometric calibration for a satellite remote sensor can be conducted per average 10-15 days. The reflectivity at top of the atmosphere obtained by the proposed method is compared with the observed data by each channel of AQUA/MODIS, and we find that the relative deviation is less than 5%, the mean relative deviation is less than 2%, and the standard deviation is less than 2%.

Two particulate organic carbon (POC) concentration retrieval models are developed with remote sensing reflectance at 745 nm (model 1) and 680 nm (model 2) based on the data collected near the Yellow River Estuary. The average percentage differences (APD) of the two models are less than 26%, and model 1 performs better. Accuracy evaluation is carried out with geostationary ocean color imager (GOCI) images and the measured data, and the average relative error is less than 30%. The developed models are used to analyze the temporal and spatial variation of POC concentration in the seawater near the Yellow River Estuary on the time scales of hour, day (for strong wind process) and season, respectively. The results show that the POC concentration is high in winter, and the POC concentration is low in summer. The peak value of POC concentration is found near the Bohai Bay. The variations of POC concentration are of the same order of magnitude under the three conditions, which shows that the obvious change of POC concentration may happen even in shorter time scale, while the seasonal mean effect is significant.

A new method for cold atom number stabilization in a integrating sphere cold atom clock is proposed. The stabilization of cold atom number is realized by periodically monitoring the absorption signal of cold atom, adjusting the diffraction efficiency of acoustic optical modulation in cooling laser, and changing the cooling light power. The loop function of the cold atom number stabilization system is deduced, and its suppression effect on the fluctuation of cold atom number is analyzed. The normalized fluctuation of stabilized cold atom number is 1±0.001 in 3 h, and the maximum suppression of power spectral density is about 30 dB in the range of 0.001-0.2 Hz. The reason for fluctuation suppression is that the stabilization loop not only compensates the output light power of cooling laser, but also corrects the cold atom number drift induced by environment. When the cold atom number is stable, the atom clock frequency stability induced by the fluctuation of cold atom number is decreased to 7×10-14τ-1/2(τis the integral time).

A research for optical fiber distributed sensing technique based on optical frequency-domain reflectometry is conduct to realize the health monitoring for aircraft structure with high accuracy and high resolution. The principle of cross-correlation distributed sensing based on Rayleigh scattering spectrum is introduced, and the limitation factor of sensing gauge length in traditional cross-correlation method on spectral resolution is analyzed. A Fourier interpolation method is proposed to enhance the spectral resolution, and experiments are carried out to verify the spectral resolution. The experimental results show that continuous distributed sensing can be obtained with the proposed method when we use a 14.2 m single mode fiber with spectral resolution of 1.6 pm and sensing gauge length of 1 cm. The proposed method with high accuracy and high resolution is promising in short and medium health monitoring applications.

An all-solid dual-concentric-core microstructure fiber for dispersion compensation is proposed. In order to form dual-concentric-core structure, a high refractive index silica cylinder doped with Ge and two low refractive index silica cylinders doped with fluorine or boron are introduced in pure silica to adjust refractive index distribution of cross-section. The evolution and coupling characteristics of fiber mode are theoretical analyzed. The relationships among mode coupling position, intensity and fiber structure parameters are studied by multi-pole method, and the relationship between dispersion characteristic and fiber structure parameter is studied. Two kinds of optical fiber are designed when we optimize fiber structure parameters. Fiber 1 with dispersion value of -8465 ps/(nm·km) at 1550 nm and its splicing loss with SMF-28 fiber is only 1.89 dB, and a dispersion value of SMF-28 single mode fiber with 500-fold length of fiber 1 can be compensated. The splicing loss is only 1.41 dB at 1550 nm, and a dispersion value of SMF-28 single mode fiber with 15.5-fold length of fiber 2 in the C band can be compensated. The maximum residual dispersion absolute value is only 1.38 ps/nm. Compared with silica-air microstructure fibers, the all-solid dispersion compensating microstructure fiber proposed is easier to fabricate and splice to the traditional communication fiber.

LED can provide both illumination and data communication in indoor visible light communication (VLC). LED layout plays an important role in maintaining stable optical power distribution on receiving plane. LED rectangular layout can not provide a full coverage on the receiving plane in which receiving optical power interruption area exists, and can not achieve optimal performance of VLC system. Layouts of LED at different positions considering the first reflection of each wall and floor are studied. LED layouts are analyzed by particle swarm optimization (PSO) algorithm, and a LED circular layout with optimal energy consumption is designed. Rectangular layout and circular layout of LEDs are analyzed through simulation of the received optical power distribution, signal interruption rate, energy consumption and signal noise ratio distribution. The results show that, for the VLC system, the performance of the LED circular layout is better than that of the LED rectangular layout, and the LED circular layout can reduce the inter symbol interference with almost half number of LEDs used in the LED rectangular layout.

Achieving large system capacity is a challenge due to the narrow modulation bandwidth of the white light-emitting diode (LED) in visible light communication. The system capacity can be improved by the non-orthogonal multiple access (NOMA) technique which can reuse power. A NOMA-DCO-OFDM system which is a combination of NOMA technology and direct-current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) is proposed. Furthermore, a modeling method for VLC multipath channel is proposed based on the recursive method when a single LED is used. The signal to interference and noise ratio of users is derived when the clipping noise is considered. We also study the relationship among average sum rate of system, half power semi-angles of LED, field of views (FOV) of photoelectric detector and power distribution factor with methods of fractional order power allocation, gain ratio power allocation and static power allocation. The simulation results indicate that the average sum rate of system changes with the changing of half power semi-angles of LED, field of views (FOV) of photoelectric detector and power distribution factor, and the maximum average sum rate can be achieved when we optimize the half power semi-angles, FOV and power distribution factor.

An embedded pattern recognition method for heterodyne phase-sensitive optical time-domain recognition (Φ-OTDR) technique with high signal-to-noise ratio (SNR), high resolution and low cost is proposed based on analog down conversion, digital IQ demodulation and back propagation (BP) neural network. When we use a digital signal processor (DSP), field programmable gate array (FPGA) and a peripheral circuit to replace GHz data acquisition and signal generator, cost and size are reduced. A method based on time and space two-dimensional extracting morphological features is designed, and the BP neural network is used to multi-class recognition. Compared with the traditional mode recognition for one-dimensional signal, the proposed method can achieve lower false alarm rate and higher recognition rate. Experiment results show that designed embedded parallel signal processing architecture based on FPGA+DSP can satisfy the real-time monitoring requirements. SNR of the system is 12.43 dB and the event recognition rate is 97.78%.

In order to highlight the fusion result and dig out more details, a fusion method of infrared image and visible image based on the target extraction and guidance filtering enhancement is proposed. Firstly, the two-dimensional Tsallis entropy and graph-based visual saliency model are used to extract the target region of infrared image. Then the visible image and the infrared image are decomposed by non-subsampled shearlet transform (NSST), respectively. The low-frequency components of the visible image and the infrared image are enhanced with guided filtering, respectively. The low-frequency component of the fused image is obtained from the enhanced low-frequency component of the infrared image and the visible image based on the fusion rule of target extraction, and the high-frequency components of the fused image are gained according to the maximization criterion of the directional sub-band information sum. Finally, the fused image is obtained by inverse NSST transform. A large number of experimental results demonstrate that the proposed method can improve the spatial resolution of the fused image, effectively highlight the target, and is superior to the method based on the Laplacian pyramid transform, the method based on wavelet transform, the method based on stationary wavelet transform, the method based on non-subsampled contourlet transform (NSCT), the method based on target extraction and NSCT in the quantitative evaluation indexes such as information entropy and average gradient.

In terms of the low resolution of the depth image subjects to imaging noise interference acquired by time of flight camera, a second-order total generalized variation(TGV) depth image super-resolution reconstruction method based on the joint constraint of interpolated depth image and high resolution color image is proposed. Firstly, to obtain the gradient information of the interpolated depth image, the depth image with low-resolution is preprocessed by using the traditional interpolation and the multi-scale morphology methods. Then, the gradient information of the interpolated depth image and the high-resolution color image of the same scene are combined, and the regularization term in the second-order TGV model can be optimized as follows, the gradient information of the interpolated depth image is combined in calculating the anisotropic diffusion tensor. And to control the diffusion intensity during the reconstruction, a weighting factor determined by the gradient information of the interpolated depth image is introduced. Finally, the primal-dual algorithm is performed to complete the high-resolution reconstruction of the depth image. Experimental results show that the proposed method can effectively preserve the depth edge on the basis of the noise suppression, and a better high-resolution depth image can be achieved.

According to the characteristics of the staring imaging of Jilin-1 No.3 video satellite, in order to improve the spatial resolution of the image and overcome the insufficient resolution of optical system, a new algorithm of super-resolution reconstruction of a video satellite,intermediate convex sets mapping, is proposed. The characteristics of satellite staring imaging are analyzed based on the active view, and the degraded model is established based on the staring imaging. In order to solve the inverse process of the degraded model, the residual constraint set and the corresponding point projection operators in the intermediate degradation process are set up based on the convex set theory. The gray value of the high resolution image is corrected by the point projection operators, and finally the reconstructed high resolution image is constrained to the intersection of convex sets. The experimental results show that the new algorithm improves the image resolution by nearly 30%, and overcomes the disadvantages of the similar algorithms such as projection error and overlapping artifact. The image quality evaluation index is better than that of the other algorithms, and the convergence solution of the eight frames is obtained. It is feasible and robust to the image reconstruction with different definitions. All those show that the new algorithm is suitable for the super-resolution reconstruction of video satellite images.

Aiming at the problems of interference and noise in image recognition of aerial asphalt pavement, a pavement crack recognition algorithm applied to aerial image is put forward. According to the difference of gray level distribution of the surface area and the roadside landscape area, a method of regional growth based on multi-directional fitting and threshold segmentation in HSV color space for road region segmentation is proposed. The single channel pavement which contains integral crack information is extracted, the large area of interference is eliminated by the improved morphological filtering, and an edge detection algorithm based on saliency analysis to recognise the crack fragment of pavement is proposed, realizing the distinction between complex cracks and pavement texture noise. The images with crack are screened automatically and the crack length is marked and calculated combined with human eye assistance observation. The experimental results show that the proposed method can effectively remove the interference and noise in the image, and well identify asphalt pavement cracks. The precision of crack width is 9.7 mm. The classification accuracy is over 80.0%. The accuracy of length measurement is over 75.0%.

The dual four-channel simultaneous interference imaging spectrometer, using a field view stop instead of the slit filter, without rotating and moving parts, divides the incident light into four coherent beams through achromatic beam splitters and Savart polariscopes. Four interference fringes with different polarization informations are obtained in the detectors. Spectral images can be acquired with the Fourier transform algorithm and image processing. Expressions for interference intensities are presented. The total intensity of the target image is obtained by summation of the four interferograms. The difference between interference intensities in the same CCD is equivalent to the pure interference fringes. The difference or summation of two pure interference fringes of different CCDs is equivalent to the single-channel interference fringes, which improves the signal-noise ration of the system. The optical path differences varying with wavelength, incidence angle, incident azimuth angle and Savart polariscope thickness are described based on the analysis of dispersing result from crystal. Considering the paraxial approximation, the fringe distribution is analyzed, and then the lateral displacement and the focal length of the lens are designed. The thickness of the crystal is discussed. This spectrometer is characterized by the simultaneous acquisition of four target images with different polarization informations. The background intensity is suppressed, and the spatial filtering and the jitter noise caused by moving or rotating parts are avoided. The results show that high resolution imaging is realized. This study provides a new solution for the design and application of interference imaging spectroscopy.

Imaging technology through scattering materials has been attracting a wide research interest because of its application values in medical imaging and security. Although different technologies have been proposed to conquer the scattering disturbance, it is still a challenge to achieve real-time imaging. A method for fast imaging through scattering medium is presented based on the speckle illumination, Fourier holography and curtain effect. The information of the hidden object can be recovered by a Fourier transform to a single original speckle image. The simple image processing makes the system has the capability of real-time imaging. The non-invasive real-time imaging ability of the proposed method is verified both theoretically and experimentally. The object hidden between scatters is reconstructed successfully and real-time imaging is realized. In addition, a formula for calculating the size of the object is provided. The proposed method can promote the practical application of imaging through turbid media.

Computed laminography (CL) has a unique advantage for the inspection of flat objects. Geometric parameter calibration of the CL system is an important step in acquiring high quality reconstruction images. However, the existing calibration methods for the CL system can not solve all parameters in one calibration. A novel iterative geometric parameter calibration method based on the classical method for computed tomography (CT) is proposed, which can calibrate all geometric parameters by using a simple phantom. Firstly, the CT calibration method is applied to the CL system to determine the parameter sensitive to the CT method. Secondly, a new non-linear least square cost function according to the error between the practical system and the ideal system is presented, thus the sensitive parameter and other parameters are optimized by the iterative method. Experimental results prove that the proposed method can accurately calibrate all the geometric parameters, and the precision of the sensitive parameter as well as those affected by the sensitive parameter are all significantly improved. Meanwhile, the corrected geometric parameters are used to reconstruct the Shepp-Logan phantom and the printed circuit board phantom, and there are no geometric artifacts in the reconstructed images, which prove the validity of the proposed method.

Different from the conventional imaging methods, the correlated imaging is an emerging technology which realizes the separation of the detection from the imaging. The correlated imaging broads the application prospect in the field of radar imaging, and brings new ideas for the development of radar imaging. We introduce the implementation approaches of the stochastic radiation field, and lay special stress on analyzing one of them. The variation trend of radiation field by changing the model parameters is analyzed, and the influence of signal bandwidth and scatter point spacing on image resolution is elaborated. The research results can play reference for the parameter setup of radar correlated imaging system.

Temperature response of 780 nm acousto-optic modulator (AOM) is calculated theoretically in detail. The research shows that the temperature response coefficient of polarization angle of diffraction light of AOM is much larger than that of diffraction efficiency and diffraction angle. Aiming at the temperature response of polarization angle of diffraction light of AOM, it is experimentally verified in the ground laboratory environment. In space microgravity environment, temperature response of AOM may become one of the main reasons that restricts the improvement of the operating temperature range and performance index of optical platform in space program. Based on the pulse working mode of AOM in practical space application, the variation curve between the temperatures of the acousto-optic crystal in AOM and environmental temperature is given by simulation modeling . And the optimization measures are given.

Particle tracking technology is one of the most important research tools for dynamic process in biology. To obtain the relative biology information, three-dimensional position measurement of micro-nano scale particles is needed. During the actual measurement, due to the interaction force between particles and the interaction force between particles and other in the liquid environment, the overlap phenomenon of the particle patterns is unavoidable. Overlapped particle patterns lead to the feature cross of rings, and the feature is hard to be recognized by traditional methods. So we can not obtain the position of the particles. In order to solve this problem, holographic reconstruction focusing method (HRFM) is proposed, as it can measure three dimensional position of particles by accurately locating their horizontal position. According to the experimental results, HRFM for locating the position of particles is more accurate than traditional method, especially for the measurement of overlapped particle position. The three-dimensional displacement resolution of the proposed method for single particle measurement and overlapped particles measurement can both reach 2 nm.

As the recording density increasing in hard disk drives (HDDs), the head disk interface (HDI) spacing is decreasing during its operation of reading and writing. The meniscus is formed or the lubricant picks up when the head slider contacts with the liquid lubricant film on the disk surface, which makes the lubricant to transfer. Therefore, the transfer process of observing lubricant film and its dynamic change characteristics on the head are important aspects for studying the performance of lubricant. A vertical-objective-based ellipsometric microscope (VEM) is developed. The linear relationship between the thickness and the light intensity is obtained by phase shift of polarizer, which realizes the dynamic visualization of lubricant film on the surface of the head. The present microscope and illumination system are improved. In the experiment, the nonpolar perfluoropolyether(PFPE) lubricant Z03 is applied on the head to calibrate the ellipsometric microscope. The polar PFPE lubricant Zdol4000 is applied as the sample. Its dewetting phenomenon on the surface of the head is observed. The result shows that the lateral resolution of the microscope is 0.36 μm. The proposed method can be used for the visual observation of the nanometer-thick lubricant films.

An optical system of reflective static Fourier transform spectrometer is designed based on the double right-angle beam splitter, and the prototype is built. The light splitting device of the spectrometer optical system adopts double right-angle beam splitter, and the other optical paths adopt the reflective structure to fold the optical path effectively. Compared with the transmission-type static Fourier spectrometer, the volume of the system is reduced by more than half. The peak spectrum lines of 404.7,435.8,546.1, 577.0 nm are obtained by using mercury lamp as the light source of static Fourier spectrometer. The result shows that the actual spectrum of the mercury lamp is well reconstructed. The experimental results show that the spectral resolution is about 5.93 nm at the laser wavelength of 650 nm, which is consistent well with the result of theoretical calculation. The optical system has many advantages, such as compact structure, small size, light weight, strong seismic resistance, etc. It can provide the technical support for the development of miniaturized and portable static Fourier spectrometer.

There are many machining errors in the ultra-precision machining process that affect the surface-shape error of devices, so they also affect the optical performance. Manufacturers always evaluate machining accuracy based on surface form accuracy. But optical performance is the final evaluated index for the optical system, so it is insufficient to evaluate the effect of the machining error on the surface-shape error of only one mirror in machining process. The effect of machining error on optical performance needs further research. Analysis model of machining error influence is established based on the multi-body system theory and the optical ray tracing theory. The effect of the machining errors on the surface-shape error and the optical performance is researched. The main form of the surface-shape error in the system and its influences on modulation transfer function (MTF) are obtained. Then, the tolerance of the machining errors,main surface-shape error and angle error are obtained based on the requirements of optical performance. The main machining errors are found, which affect the optical performances of three-mirror system. The results provide a theoretical support to the control of the main machining errors and the realization of the performance-controllable manufacture for the off-axis three-mirror system.

A nondestructive laser detection method is proposed by combining the spatial laser injection into fibers with the coherent detection technique. The transmission characteristics of laser ultrasonic signals and the principle of coherent light detection are analyzed, and the signal processing and noise suppression methods in the nondestructive laser detection are discussed. The experimental system is established based on the laser excitation and detection where the laser injection and polarization-maintaining transmission are the cores, and the human-machine interactive system based on the graphical programming language LabVIEW is the monitoring way. The experimental results show that this system can reduce the influence of background light jitter on signal detection. By controlling the spot diameter and energy, one can obtain the reflection peaks of different ultrasonic signals. The sensitivity and smoothness of the ultrasonic echo signal detection on material defects are improved effectively. The testing method provides a new technique for engineering applications.

In video tracking, the use of a single feature to describe the target is difficult to adapt to the changes in complex scenes. Futhermore, the scale change, deformation, occlusion of target and other factors will lead to tracking failure. In order to improve the robustness of tracking, an adaptive feature fusion and model updating tracking algorithm is proposed based on the circulant structure of with kernel, and the scale updating mechanism is also introduced. Firstly, the response maps are calculated using the gray and local binary pattern features of the target respectively and fused by the weights assigned according to the peak to sidelobe ratio(PSR), and the best location is estimated. The PSR of the fused response map is also used to judge the tracking quality to decide whether to update the model. Finally, according to the scale pyramid constructed with the histograms of oriented gradients features extracted around the target location,the scale correlation filter is trained to estimate the optimal scale of the target. The experiment selects the sequences with illumination variations, occlusion and scale changes from the visual tracker benchmark datasets. The results show that the proposed algorithm can track the target robustly in complex scenes, and the distance precision and success rate are also superior to the compared algorithms.

Aiming at the problem of plane target pose measurement, a monocular vision measurement method is proposed based on the checkerboard target. The method does not need to design and install complexly, and simplifies the measurement process while ensuring the measurement precision. Firstly, the camera is calibrated based on the checkerboard target. Then, to obtain the three pose angles, the external parameter matrix is solved by taking advantage of the homography condition, hereafter, it is decomposed with Givens matrix. Finally, when the target is installed arbitrarily the self-calibration method of the target installation deviations is studied based on the constraint conditions of the rotation matrix. Experimental results show that with a distance of 3 m, the static measurement precision of the pose angle which is perpendicular to the optical axis is 0.02°, and the measurement precision of two other pose angles is 0.05°. The dynamic measurement precision of the pose angle which is perpendicular to the optical axisis is 0.1°, and the measurement precision of two other pose angles is 0.5°.

On the issues about the robustness in visual object tracking, a novel visual tracking algorithm based on convolutional neural network (CNN) and conformal predictor (CP) is proposed. A two-input CNN model is constructed to extract the high level features from the sampled image patches and target template simultaneously, and the logistic regression is used to separate the object from the background. The CNN classifier is embedded into the CP framework, and the reliability of classification is evaluated via algorithms randomness testing. The classification result with credibility is obtained by region prediction at a specified significance level. The image patches with high credibility are selected as candidate objects, thus, the target trajectory is obtained through spacetime optimization. Experimental results show that the proposed algorithm can adapt to the occlusion, target appearance changes and complex background, and it has a better robustness and higher precision than the current algorithms.

Raw material powders of Yb3+/Al3+co-doped silica fiber core are fabricated with the SiCl4 hydrolysis method, and the α-silica phase is precipitated after the sintering treatment of removing hydroxyl at 1100 ℃ under the atmosphere of O2. The Yb3+/Al3+co-doped silicic acid gels are treated by the normal temperature aging and the high-temperature high-pressure aging in an autoclave. The test results show that the aging treatment can effectively suppress the crystallization of Yb3+/Al3+co-doped silica glass raw material powders and the fluorescence intensity and lifetime of Yb3+ are enhanced. It is validated that the autoclave treatment can shorten the aging time and enhance the fluoresence property, which is an important process of preparing Yb3+/Al3+co-doped silica glass raw material powders.

Gold nanorods (GNRs) are aligned in a uniform orientation with the electrospinning method and GNRs-nanofiber composite films are prepared. Anisotropic saturated absorption property of films is found by using the polarization-dependent open-aperture z-scan method. The aligned GNRs-nanofiber composite film has important application prospects in the field of fiber lasers.

A novel ultra-thin microwave metamaterial absorber design is proposed and experimentally demonstrated. The metamaterial absorber consists of three metallic structural layers and two dielectric-material layers. Two identical metallic circular rings are used as the double composite resonant structural units. Compared to the traditional resonant unit with a single-layered pattern, this new design has an efficient enhancement in the absorptivity of electromagnetic wave as well as an obvious reduction in the thickness of the whole structure. The electromagnetic simulation based on the finite element method is employed to simulate and analyze the distributions of inner spatial electromagnetic field and surface current of this absorber, and the absorption mechanism of electromagnetic waves is expounded. The simulated and experimental results both confirm this absorber is polarization-independent and stable for the wide oblique angle incidence. This ultra-thin metamaterial absorber with a simplified structure and a low duty cycle has potential applications in many practical areas such as electromagnetic window shielding.

A series of copper thin films with different thicknesses are fabricated on glass substrates by vacuum electron beam evaporation technology and subsequent thermal oxidation technology. The crystal structure and element compositions of these copper thin films are characterized by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The absorption spectra and surface enhanced Raman spectroscopy (SERS) activity of these copper thin films are analyzed by using UV-Vis-IR spectroscopy and Raman spectrometer, respectively. With the increase of film thickness, the amorphous state of the annealed thin film samples changes to a polycrystalline state with a preferred orientation in the (111) plane, and the red-shift of absorption edge appears. The single-phase nano-Cu2O thin films are obtained when the annealing temperature is 200 ℃ and the annealing time is 60 min. The SERS activity increases with the increase of light absorbance of the nano-Cu2O thin films.

Based on the working principle of depolarizer, the general relationship between the structural parameters of depolarizer and the polarization sensitivity of optical system is established by applying Mueller matrix and Stokes vector. With numerical analysis, it is pointed out that the depolarizer has excellent depolarization performance when the angle between the optical axes of two wedge crystals is 90°. Under this orientation, selecting proper crystal thickness can further reduce the polarization sensitivity of optical system. Finally, taking grating imaging spectrometer as an example, we design a depolarizer and evaluate its performance.

High numerical aperture (NA) projection objectives with anamorphic magnification are demanded for extreme ultraviolet (EUV) lithography down to 10 nm resolution, which results in extreme increase of incident angle and incident angle range of objective lens system. Traditional normalized multilayer film and laterally graded multilayer film cannot satisfy the requirement of reflectivity and image quality in the projection objectives. A method combining laterally graded multilayer film with depth graded multilayer film is presented. The laterally graded multilayer film is used to increase the reflectivity and the depth graded multilayer film is used to enhance the reflectivity uniformity and compensate the wavefront aberration introduced by the laterally graded multilayer film. The method is used to design the multilayer film of an anamorphic magnification EUV lithographic objective with NA of 0.50. The results show that the average reflectivity of each mirror is higher than 60% and the reflectivity peak-to-valley value of each mirror is less than 3.5% with imaging performance unchanged. Which satisfies the lithographic requirement, and verifies the feasibility of this method.

An illumination-computation acceleration structure based on the sparse voxel directed acyclic graph (SVDAG) is proposed. By merging the same nodes from bottom to top, the sparse voxel octree is converted into a SVDAG, and the polysemy of spatial positions can be eliminated by using the traversal paths and the child masks of the given nodes. Aiming at the closed geometry, an algorithm based on the double depth maps can be used to merge adaptively the nodes located in the closed region, which can further reduce the storage cost while the performance of illumination computation is maintained. A inter-frame multiplex method of SVDAG based on the time correlation is proposed in which all frames of the dynamic scene are used to constitute an integral SVDAG acceleration structure, which can improve the update rate. The experimental results indicate that the rendering efficiency of three-dimensional scene based on the new algorithm is enhanced. When a high resolution dynamic scene is conducted, a relatively high frame rate still can be obtained.

The development of the vector polarized beam presents a new requirement for the mode calculation of the polarization-sensitive resonator. Derived from Fox-Li iterative method and Jones vector theory, a vector Fox-Li iterative method for polarization-sensitive resonator is presented, which can calculates the vector polarization mode in the polarization-sensitive resonator, including the azimuthally polarized TE01* mode and the radially polarized TM01* mode. The vector polarization modes of a spherical polarization-sensitive resonator are obtained by Matlab numerical calculation with this method. The result is coincident with the theory. Then, the 2.17 kW azimuthally polarized beam is obtained based on a fast axial flow (FAF) CO2 laser platform using the combined axicon as the rear mirror of the resonator. And it is consistent with the simulated results with vector Fox-Li iterative method, which experimentally corroborates the validity and accuracy of the vector Fox-Li iterative method. The vector Fox-Li iterative method is of great significance for the analysis and design of polarization-sensitive resonator.

High order Bessel beam can be generated by using spiral phase plate-axicon system. Based on Kirchhoff diffraction integral theory, the expression of diffraction light field after the axicon illuminated by an oblique vortex beam is derived. The influence of astigmatism introduced by oblique illumination of light on high order Bessel beam generated by axicon fucusing vortex beams is analyzed. A simple and feasible scheme for detecting topological charge number is proposed. Results show that when the deflection angle of axicon is small, the center bright ring of high order Bessel beam becomes elliptical. The ellipticity of center bright ring increases with the increasing of reflection angle, and the phenomenon of dark core splitting can be found. With the continuous increasing of the reflection angle, the bright ring will split one by one from inside to outside, and ultimately it will evolve into caustics beam with point array structure. Experiments are designed to verify above researches. Experimental results are in good agreement with theoretical analysis and numerical simulation.

Based on the fluctuation of light, a spiral nanoantenna structure for solar energy harvesting is proposed and analyzed using finite difference time-domain method. The nanoantenna structure consists of two coplanar Archimedes spiral arms and a substrate layer as supporting. The radiation efficiency and polarization characteristics of the nanoantenna are analyzed. The new spiral nanoantenna achieves a total radiation efficiency of 74.49% within the wavelength range from 400 nm to 1600 nm (takes up 85% of the total solar energy), which is higher than that of dipole antenna structure proposed by previous researchers. Meanwhile, for linearly polarized plane waves from different directions, local electric field enhancement with the same level at the spiral antenna feed gap can be obtained, which indicates that the antenna can process arbitrary polarization characteristics of sunlight.

In the model of photonic band gap, the entanglement dynamical evolution of a system where three two-level atoms interact with a heat reservoir is investigated. The entanglement among systems is described by using the pseudo-mode theory and the tripartite negative eigenvalue method. The effects of the heat-reservoir spectral density function, the detuning between the atoms and pseudo modes, and the interatomic dipole-dipole interaction strength on the three-atom entanglement evolution are analyzed by means of numerical calculation. The results show that in a perfect band gap model, the trapping phenomenon appears in the interatomic entanglement evolution versus time. The detuning between the atoms and pseudo modes makes the interatomic entanglement show a non-monotonic transition. The three-atom entanglement degree increases with the increase of the interatomic distance.

Traditional image registration techniques are inadaptable to aerial remote sensing image which does not have obvious feature points, such as ocean, desert,and grassland. A registration algorithm is proposed for aerial remote sensing image based on geo-location information. Using aircraft position and attitude information measured by airborne position and orientation system and the gimbal angle from the encoder in an aerial camera, the projection of registration point in geodetic coordinate system is solved by homogeneous coordinate transformation. Using the earth ellipsoidal model which is defined by the world geodetic system-84, the longitude and latitude information for matching points are solved, and the matching points with the same geo-location information are registered. The influence of the aircraft position and attitude and the gimbal angle on geo-location accuracy and registration accuracy is analyzed with Monte Carlo method. Experiments were carried out using actual aerial remote sensing images. Experimental results show that the registration accuracy is less than 3 m, and the positioning accuracy of sea control point in remote sensing image is less than 35 m, when the flight height of plane is below 2000 m and the photography inclination angle is less than 18°.

A new kind of transverse-stress sensor which uses photonic crystal fiber (PCF) with dual-core structure as an optical waveguide is designed based on the surface plasmon resonance (SPR) effect. The relationship between the shift of the fundamental mode resonance peak and the transverse-stress is obtained when we build the model of the SPR coupled wave and the deformation model of the PCF structure by the vector finite element method. Results show that the wavelength shift of the resonance peak is linear with the added stress. A high measurement sensitivity is obtained when the optimal design for the cross section structure of PCF, and the number of layers, the diameter and the period of air holes are selected. This study can provide theoretical guidance for the design of PCF transverse-stress sensor based on SPR.

A high accuracy image mosaicking method based on big virtual camera is proposed for multi-camera system on the optical remote sensing satellite to realize the high-precision stitching of multi-camera images. A big virtual camera is built according to the geometric imaging model of each single camera, and the geometric correction is performed by coordinate forward and back calculation based on their imaging models to obtain each single virtual image in the virtual camera image coordinate system. The final stitched image can be obtained by stitching single virtual image based on its coordinate information. By using the concept of big virtual camera, the high accuracy stitched image and corresponding rational function model for post processing are obtained at the same time. It can be used for multi-camera system with different quantities and resolutions to realize automatic intelligent ground preprocessing.

Point cloud data filtering of airborne light detection and ranging (LiDAR) is the focus in the current study of point cloud data processing field. In order to deal with the difficulty of point cloud data filtering at present, an improved filtering method based on hierarchical pseudo-grid and parallel computing is presented. In this method, hierarchical pseudo-grid is established by point cloud data, and the grid is multi-scale decomposed. The original gross error points of LiDAR data are eliminated. The ground point and planimetric point are obtained. According to the principle of double threshold filtering, more refined ground points are obtained by filtering process gradually with the order from big to small mesh scale. And the parallel programming process for point cloud data is combined to reduce the error accumulation of filtering algorithm. Experimental results show that the filtering accuracy of the improved algorithm is enhanced greatly compared to other classical filtering algorithms. The type II errors are controlled effectively in different terrain conditions. Meanwhile, the total errors are decreased, the efficiency of filtering process and the reliability of digital elevation model (DEM) are enhanced.

In order to improve classification effect of hyperspectral image, a classification algorithm with two levels is proposed based on spectral clustering and sparse representation. Pixels to be classified and its neighborhood pixels are divided into two parts by spectral clustering. The class of selected pixels is identified by the joint sparse representation model. This algorithm makes full use of hyperspectral image spectral and spatial information of hyperspectral images, and both of the two levels. Finally, the proposed algorithm is corrected with the spatial information, namely, neighboring pixels' class is associated and classification results is smoothed. Numerical experiments demonstrate that this algorithm has high classification accuracy, good stability and anti-noise performance.

In order to improve the imaging performance and image quality of space cameras with an optical focal plane assembly, the radiometric calibration researches in the whole develop process of the space cameras are conducted which include the radiation response performance analysis, the radiometric calibration and screening of the image sensors, the focal plane radiometric calibration, the system-level radiometric calibration, and the applications of radiometric calibration data. The radiometric calibration experiment is conducted for the space cameras with a reflector-based mosaic focal plane. The results show that the vignetting can be effectively eliminated when the image is corrected by using the relative radiometric correction coefficient, and the nonuniformity of the image decreases from 14.1% to 0.4% with an obvious enhancement in the image quality. Moreover, the radiometric response difference between the image sensors is reduced by utilizing the screening of the image sensors and the radiometric calibration of focal plane components, and the relative calibration uncertainty is less than 1.0%.

Multi-wavelength transmittance spectra of bacteria in water contain lots of information on their characteristics such as structure, constituent and concentration, and the effective extraction of the information is the foundation of rapid identification and detection of bacteria. The transmittance spectrum of Escherichia coli is recorded with a ultraviolet-visible spectrophotometer. According to Mie scattering theory and absorption and scattering properties, bacterial multi-wavelength transmittance spectrum analytical model in 240-900 nm band is constructed. Based on the model, the spectrum in the range of 250-750 nm is analyzed, the related parameters such as volume, diameter, structure and concentration of Escherichia coli cells are obtained, and these parameters are then compared with the literature data or experimental data. It is shown that the proposed multi-wavelength transmission spectrum model can accurately characterize the spectral features of bacteria in water, and the model can provide important parameters for the rapid analysis and detection of bacteria in water.

An experimental device of wavelength modulated off-axis integrated cavity output spectroscopy (WM-OA-ICOS) technique is reported. A distributed feedback (DFB) laser with central wavelength of 1.392 μm is chosen as light source. A resonant cavity is composed of two mirrors with reflectivity of 99.8% and 60 cm distance, and the cavity is used as gas absorption cell. The absorption line of CH4 at 7185.87 cm -1 is selected to detect CH4 with different concentrations. The stability time of the system is obtained to be 203 s by optimizing the instrument parameters (pressure, modulation frequency, phase and amplitude) combining with Allan variance. The detection limit of CH4 is obtained to be 8.7×10-7 by selecting the measurement time of 100 s, and the corresponding minimum detectable absorption is 2.2×10-6 Hz-1/2. Compared with that of off-axis integrated cavity output spectroscopy technique, the sensitivity of WM-OA-ICOS technique increases by 21 times. The second harmonic peak height and the ratio of the peak height of second harmonic to the medium of first harmonic (2f/1f) are used to measure the concentration of CH4, and the results show that the latter has better stability and higher degree of linearity correlation.