Homologous dual-light-path visibility instrument is a visibility instrument based on digital camera method. The brightness of the light source obtained by the CCD sensor is an important part of the spot extraction algorithm and the visibility inversion model. The background light noise seriouly affects accuracy of visibility inversion. Aiming at the large error of visibility inversion under complex background light disturbance, we use the amplitude modulation method to redesign the modulated light source, and demodulate the CCD image so that the background light is eliminated effectively. The experimental results show that the light source amplitude modulation method can effectively remove the background light, the random noise, and the dark noise of the camera. When the modulation points are within 32 to 128, the image denoising effect is good and the peak signal-noise-ratio (PSNR) of the speckle image after denoising is greater than 30. In this modulation point range, the larger the number of modulation is, the larger the PSNR is and the smaller the root mean square error is. Inversion accuracy of the visibility is greatly improved in the range of the above modulation points, which means that the amplitude modulation method can significantly improve the accuracy of visibility inversion.

Wavefront aberration occurs during laser propagating in the atmospheric turbulence, which reduces the performance of wireless optical communication system. We use a wavefront sensorless adaptive optics correction system based on the stochastic parallel gradient descent (SPGD) algorithm to correct the far field wavefront aberration. The simulation results indicate that the Strehl ratio of the proposed system is increased from 0.15 to 0.81, and the far field spot energy becomes converged. We take the intensity of the far field distorted spot detected by CCD camera as the objective function of the system, and experimentally verify the correction performances for different aberrations by the SPGD algorithm. After correction, the objective functions (the mean gray value of 900 pixels in the center) increase from 26.5 to 77.2, from 44.6 to 93.4, and from 110.6 to 208.5, respectively; the Strehl ratios increase from 0.23 to 0.67, from 0.39 to 0.75, and from 0.48 to 0.86, respectively. The central light intensity increases and the spot energy becomes converged. The experimental results are in good agreement with theoretical results.

In order to analyze the effect of adhesive material on the stress characteristics of the deformable mirror (DM) under thermo-mechanical coupling, we establish a DM model with adhesive material by the finite element method. We analyze and compare the effects of three typical adhesive materials on the stress distributions of the DM using the sequential coupling method, and discuss the variation law of the maximum stress of the DM for adhesive layers with different thicknesses. The results indicate that the characteristics and parameters of the adhesive material greatly affect the stress characteristics of the DM due to thermo-mechanical coupling in an actual DM system. The adhesive material has almost no effect on the stress distribution of the front surface of DM, as well as the peak-valley value of the surface shape, but has a significant influence on the stress distribution on the rear surface. In addition, the stress at the joint between the mirror and the pole is significantly increased. For different kinds of adhesive materials, the smaller the elastic modulus and the thermal expansion coefficient are, the smaller the stress on the DM is. Among the three typical adhesive materials, the stress on the DM glued with the amine-cured epoxy 5222 material is the largest, the stress on the DM glued with the phenolic epoxy resin T300 material is the smallest, and the stress on the DM glued with the phenolic epoxy resin 4221 material is between those of the two materials. In addition, the thickness of the adhesive layer directly affects the stress characteristics on the DM, whose maximum value decreases with the increase of the thickness of the adhesive layer, which means that in the process of the DM manufacturing, a thicker adhesive thickness should be chosen reasonably under the condition of effective controlling the produce of the bubble and other defects inside the adhesive layer.

One of the primary development directions of future diode-pumped solid-state lasers is to realize the "Three highs", namely, the laser output with high power, high efficiency, and high beam quality. However, the thermal effects will degrade the performance of laser device severely. As one of the most promising gain medium materials, laser ceramics have the advantages of strong continuous laser output, high thermal conductivity and high concentration doping. Meanwhile, laser ceramics are easy to achieve large size, batch production and composite structure sample preparation, while the gain medium with composite structure can effectively improve the thermal effect of solid-state lasers. The fabrication of optical waveguide structure in laser ceramics can efficiently dissipate heat, improve pumping efficiency and obtain compact laser system with high gain. This kind of ceramics will hopefully solve the core problem of "Three highs" solid-state lasers. In this paper, the research development, the design principle, the preparation techniques and the material properties of optical waveguide laser ceramics are reviewed and introduced. In the end, the future research of optical waveguide laser ceramics is prospected and analyzed.

Space primary mirror splicing technology is one of the development trends of the future cosmic observation. Compared with the traditional space primary mirror, the splicing primary mirror has the advantages of large aperture, breaking the size limitation of carrier fairing, high resolution, light and active adjustment, etc. Based on the literature and research project at home and abroad and the different forms of splicing structures, the deployable splicing space primary mirrors are divided into on-orbit deployed type, on-orbit splicing type and on-orbit distributed typeo. And the concepts, characteristics and splicing structures of these three forms of space splicing mirror are described, respectively. According to the three classification forms, the research backgrounds and research contents of present known splicing primary mirror projects are introduced. This paper summarizes the key technologies involved in the splicing structure of the primary mirror, and summarizes the two research difficulties which are the splicing precision and the face precision as the starting point.

Silicon photonic mode size converter is the key device for silicon based photonic integrated chip to connect with external optical fiber, it plays an important role in integrated optical path. The mode size of the standard fibers does not match the mode size of the nanometer photonic waveguide, so there is a great coupling loss between the standard fiber and the nanometer silicon waveguide, the silicon photonic mode size converters can significantly reduce the optical loss between them. One end of the silicon based photonic mode size converter has a large mode size that matches with the mode size of the standard fiber; the other end has a smaller mode size, which can be matched with the mode size of nano-silicon photonic waveguide, thereby significantly reducing the optical connection loss between the standard fiber and the nano-silicon photonic waveguide. The characteristics of different structures of converters are reviewed, while the advantages and disadvantages of different types of converters in structure, performance and application are compared and analyzed, and the prospect of silicon photonic mode size converters is prospected and some opinions are put forward.

Aiming at the status of an increasing spread of illegal drugs which brings severe threats to public security in recent years, it is pointed that technologies of analysis and detection on illicit materials play a vital role in on-site screening and evidence extraction of illegal drugs related events. The application of surface enhanced Raman spectroscopy (SERS) detection in several typical illegal drugs, such as opiates, cocaines, amphetamines, ketamines, and so on, are summarized. Challenges for in-field and real time detection of illegal drugs are analyzed. The SERS is expected to be one of the most popular detection technologies due to its excellent performances, such as sensitivity, accuracy, simple operation, etc. The future development trend of the technology is predicted to be constructing high quality substrate with good robustness, exploring new surfactants and stabilizers, developing a new portable Raman spectrometer with a high signal-noise ratio, and developing intelligent recognition algorithm with good generalization.

The laser cleaning technology with the use of short pulsed lasers on material surface for a rapid cleaning has a broad application prospect in the industrial fields of manufacturing, production and repairing, and so on. Three typical laser cleaning methods of laser ablation cleaning, liquid film assisted laser cleaning, and laser shockwave cleaning are introduced. The research status at home and abroad of laser cleaning technology is reviewed. Some representative applications of laser cleaning technology are listed based on the own charateristics of cleaning materials, and their development directions in the domestic manufacturing are prospected.

With the advent of fluorescent probes, the technology of super-resolution imaging has developed rapidly, and a variety of different super-resolution microscopy technologies have been developed and widely used. It provides great convenience for the field of life science research and receives more and more attention from researchers. Because the traditional super-resolution microscopic imaging technologies still have some restrictions in imaging speed, observation field of view, system costs and so on, the development of new super-resolution microscopy technology expands our vision of the field of super-resolution image. Several new super-resolution imaging technologies including expansion sample super-resolution, surface enhanced super-resolution and fluorescence polarization super-resolution are reviewed with the purpose of making a summary of the development of new super-resolution technologies and providing a new technical reference for the application of the field of life science.

The interaction between light and atoms, molecules, and quantum dots in metallic micro-nano structures is a core scientific issue in the field of micro-nano optics. In recent years, scientists have made great progress in realizing surface plasmon amplification by stimulated emission of radiation and developing plasmon lasers due to the rapid development of nano-material preparation methods and nano-processing technology. We review the advances in directionality of surface plasmon amplification by stimulated emission of radiation based on metal micro-nano resonant cavities, list several kinds of resonant cavity structures which improve the directionality and elaborate on the physical mechanism. Meanwhile, we also compare the characteristics and properties of different cavity structures.

Large-diameter aspheric optical elements have superior optical properties, and they are more and more widely applied in the areas such as laser fusion, space technology and large optical telescopes. However, the mass production of large-diameter aspheric elements requires high-precision and high-efficiency numerical control grinding and polishing techniques. Meanwhile, the enormous challenges of mass production of ultra-precision medium and large aspheric optical elements have propelled the modern optical measurement technology toward higher efficiency, higher accuracy and higher level of automation. According to the processing technology of aspheric optical elements, the research status of measurement technology in grinding stage is summarized systematically, and the principles of the above technologies are explained in detail. At last, the development trend of the measurement technology of large aspheric optical elements in grinding stage is prospected.

Noninvasive blood glucose measurement has become a research hot-spot in biomedical field. Photoacoustic technique is an ultrasound-mediated blood glucose measuring method based on the intrinsic optical absorption properties of tissue, and the technique avoids the interference of high optical scattering in principle and provides a noninvasive and effective way with high sensitivity for the noninvasive blood glucose measurement. This paper reviews the development of the noninvasive blood glucose measurement. Firstly, the principle of blood glucose photoacoustic noninvasive measurement is introduced. Then, the blood glucose photoacoustic detection systems in the domestic and foreign are introduced according to the different excitation sources and the experimental progresses in blood glucose photoacoustic detection are summarized to promote the development of domestic blood glucose noninvasive measurement technique.

Laser-induced plasma ignition (LIPI) has the potential to replace the spark plug ignition with the advantages of adjustable ignition position, short ignition delay time, non-invasive structure, and so on. We introduce the basic physical process of LIPI from the perspective of the generation and development of the flame kernel, and analyze the deposition and transformation of energy in ignition process. Based on the existing research, we evaluate the ignition performances of laser ablation plasma ignition, multi-point laser plasma ignition, pre-ionization laser plasma ignition and repetitive frequency pulse laser plasma ignition, and summarize the advantages and disadvantages of each method. The problems of the existing laser plasma ignition system are pointed out, which are imperfect ignition mechanism of the laser plasma ignition, the lack of research on the ignition characteristics of the non-premixed combustion system, and the high energy of the minimum ignition energy. Finally, we propose some suggestions on the future work.

The traditional speckle correlation method has a range limit in the angular displacement measurement of structural members. Aiming at this problem, a speckle correlation method for the angular displacement measurement by using log-polar transformation is presented. Firstly, the log-polar coordinate transformation method is used to convert the angular displacement measurement of the speckle image in the cartesian coordinate system to the displacement measurement under the log-polar coordinates. Secondly, the angular displacement measurement of speckle image is realized by using speckle correlation method and nine-point quadratic surface fitting method. Finally, the effectiveness of the method is verified by simulation experiment and physical experiment. The experimental results show that the mean error of the angular displacement measurement is controlled within 0.06° and the standard deviation is within 0.02° with the angular displacement range of [0°, 90°]. This method effectively improves the range and accuracy of the angle displacement measurement of existing speckle correlation method.

In order to improve the surface shape recovery accuracy of Ricky-Consens test under large F-number, a local sampling impact matrix method is proposed. The impact matrix is built according to the actual incident angle of each pixel point for the compressed ellipse patterns collected from an interferometer, and the surface error of the pixel point is recovered. The shape of flat mirror is obtained through this method traversing the entire mirror surface. The accuracy of local sampling impact matrix method is verified through simulation, and it is compared with the traditional impact matrix method in detail. The results show that compared with the traditional impact matrix method, the accuracy of local sampling impact matrix method is obviously improved in different aberrations of defocus, astigmatism, three levels of coma, three levels of astigmatism and three levels of spherical aberration. It is indicated that the local sampling impact matrix method is more suitable for the surface shape recovery Ritchey-Common test.

Nuclear graphite is the primary structural material of reactor core in the high temperature gas-cooled reactor. It is of great significance for the research of the graphite's fracture property and the analysis of the crack propagation process to analyze the structural integrity of graphite component. The filtering method based on radial basis function (RBF) is suitable for electronic speckle pattern interferometry (ESPI) speckle patterns with low density. A kind of phase measuring method base on RBF filtering and quality-guided phase-unwrapping algorithm is proposed, then this method is tested via application to computer-simulated ESPI phase pattern and compared with the average filtering quantitatively. ESPI technique and three-point bending tests are employed to measure the fracture property of nuclear graphite specimen with pre-cracking. The ESPI wrapping phase patterns are recorded with different loads in the evolutionary process of crack, and the phase contours are extracted by the use of RBF filtering method and quality-guided phase-unwrapping algorithm, then the evolutionary process sketch map of the specimen is given. The experimental results demonstrate that this method is effective to measure the crack evolutionary process of nuclear graphite.

Due to the effect of the noise or the nonlinear response of detector, the intensity of the light intensity of the actual stripes taken by the optical 3D profilometry device has the characteristics of nonsinusoidal distribution, which leads to the problem of computational instability in the application of the existing random phase shift extraction algorithm in the application. A phase shift extraction method of two random temporal phase shifting fringe patterns is proposed. Firstly, the proposed method deals with the fringe patterns based on Gram-Schmidt orthonormalization method. Then a phase shift extraction algorithm based on matrix norm is developed. At last the two step phase shifting algorithm is applied to get the measurement phase. Because of the use of inverse tangent function in solving the phase shift, the proposed method is not sensitive to the nonsinusoidal fringe pattern, and has the characteristics of reliable solution and easy application. The experimental results show that the proposed method has high precision and fast speed, which is superior to the existing typical algorithms.

The study of the impulse coupling characteristics is the basis for analyzing the scheme of laser cleaning space debris. Due to the influences of atmospheric transmission and diffraction limit, the laser spot size is close to the size of the irradiated particles, which are in centimeter order of magnitude. Most of the space debris are non-planar because of explosion, disintegration, and collision. Therefore, it is the key of laser cleaning space debris to study the impulse coupling characteristics of non-planar debris irradiated by a great spot. Taking a typical non-planar space debris (sphere, cube) as example, assuming that direction of the ablation reversal is the vertical direction of the micro surface and the impulse coupling coefficient of any area micro element is the same as that under the point radiation, we deduce the area matrix method from integral viewpoint. We obtain the influence rule of spot size and laser incident angle on the value and direction of impulse based on the area matrix method when the laser energy density or incident laser energy is given. These theoretical research results further enrich the theoretical study of laser cleaning space debris, and provide theoretical guidance for the scheme of laser cleaning space debris.

The grating micro-nano structure is fabricated by picosecond lasers on the 304 stainless steel surface. The size of this micro-nano structure and the surface morphology of this processed stainless steel are characterized. The influences of different laser processing parameters on the micro-nano structure are studied. The result shows that the average power has a significant influence on the laser ablation rate and the size of grating micro-nano structure. If the scanning speed increases, the depth of the grating micro-nano structure decreases, while the width remaines unchanged and the laser ablation rate shows an irregular fluctuation. The laser ablation rate decreases if the processing times increase. The better process conditions for fabricating micro-nano structures on the stainless steel surface are as follows: high average power, high scanning speed and low processing times, under which the superhydrophobic surface of stainless steel can be obtained successfully.

The butt welding of 3 mm thick 7050 aluminum alloy plates by using fiber lasers is conducted. The effect of welding process on weld forming is studied, and microstructures, chemical compositions, mechanical properties and fracture characteristics of joints are also investigated. The results show that well joints can be obtained when laser power of 3 kW, welding speed of 4 m·min-1, and spot diameter of 0.2 mm are chosen. There exist mainly equiaxed grains in the weld center, Al-Cu intermetallic compounds are dispersed in the grain boundaries, there are mainly columnar dendrite grains in the weld edge, and the heat affected zone (HAZ) is relatively narrow. No precipitation is found in the weld and the strengthening phase in the HAZ melts slightly. The microhardness distribution of weld joints is non-uniform, the hardness at the weld is the lowest, and there exists obvious softening in the HAZ. The tensile strength of welded joints is 307 MPa, the joints fracture along the weld after tensile, and there exist small dimples in the fractures, which shows a character of intergranular brittleness fracture.

The orthogonal experiment of laser spot welding is conducted when the DP590 dual phase steel with 1.5 mm thickness is used as the base material and the welding time, the welding power and the defocusing are taken as variables. The internal morphology of the joints is studied, influences of welding parameters on the static performance of the joint are analyzed, and the morphologies of tensile shear fractures are invesitgated. The results show that, when the welding power is 1800 W, the welding time is 1000 ms and the defocusing is -3 mm, the average peak load of adhesively bonded spot welding joints is the maximal, which is 7529.30 N. The ultrasonic C-scan image of the laser welding joints can be divided into the nugget zone, the cavity zone, the heat-affected zone and the adhesive zone, and the ultrasonic C-scan image can be used to effectively measure the nugget diameter. The influence of the welding power on the tensile and shear properties of the joints is the maximal, that of the welding time is the second, and that of the defocusing is the minimal. With different welding parameters, the failure modes of the joints are interfacial fractures, and the elongated dimples are distributed on the fracture surface of solder joints.

The butt welding of SUS301L-MT stainless steels is conducted by means of the metal active gas arc welding (MAG), laser welding and laser-MAG hybrid welding, respectively, and the effects of these three different welding processes on the microstructure and mechanical properties of joints are investigated and compared. The results show that, the welded joints obtained under these three different welding processes are all duplex-phase structures with δ-ferrite and austenite. The width of the heat affected zone of MAG welded joints has a size of 3 mm, while both that of the laser welding and laser-MAG welded joints are only 1 mm. All the residual stress peaks under three welding processes distribute at weld toe, and the MAG welded joints have the highest longitudinal and transverse residual stress peak values. The laser-MAG welded joints show the highest tensile strength with a value of 906 MPa.

Distributed Bragg reflector (DBR) with visible light band is constructed by SiO2/Si. The central cavity made of SU-8 photoresist is added into it to form the traditional Bragg reflector (BRW). The transmission matrix method is used to analyze the transmission of visible light in the distributed Bragg reflector and the Bragg reflector. The effect of various factors such as medium refractive index, thickness and number of cycles on Bragg mirrors and the influence of various parameters of SU-8 on the photonic bandgap are studied. Aiming at the difficult preparation of the traditional Bragg reflective waveguide hardware, a new type of Bragg reflective waveguide is constructed, when Si metasurface is introduced into SU-8. The effect of metasurface on the defect mode is analyzed experimentally. Experiments show that the metasurface has the function of controlling the defect mode wavelength, and the new Bragg reflector waveguide array can complete beam splitting function in the visible light band. Which can be used to improve optical instruments.

A parallel five-microring resonator model is proposed. The output function of parallel microring is modeled by transmission matrix method, and Matlab simulation software is used to analyze the output spectrum intensity. The spectral output characteristics of resonator bands and superposition bands are researched when ratio between microring spacing and microring circumference are 0.25 and 0.50, respectively. By optimizing the coupling coefficient of transmission, system refractive index, microring radius and other parameters, the resonator frequency bands whose shape factor is larger than 0.85 and stopband crosstalk is less than -25 dB are obtained. Four parallel microring arrays are cascaded to achieve 1×4 dense wavelength division multiplexer.

Spectral resolution is the key of acousto-optic tunable filter (AOTF). Based on the working principle of acousto-optic filter, a hyperspectral imaging system based on double-filter structure is designed by connecting two filters in series. By comparing the theoretical calculation and experimental measurement results of single filter and double filter, it can be found that the spectral width of double filter structure is smaller than that of single filter when the center wavelength is equal, which shows that the double filter technology can improve the spectral width. In addition, the microscopic imaging system based on double-filter technology is designed by using dual-filter structure combined with inverted light microscope. Based on a large number of microscopic images of gastric cancer tissue hyperspectral images, three spectral images with a small correlation coefficient are selected and processed using RGB false color image fusion technology. The simulation results show that the hyperspectral image fusion technology can effectively improve the image quality.

Using the sphere-packing theory to generate eight-dimensional modulation formats, we propose a rate-adaptive scheme based on eight-dimensional modulation formats. Compared with the existing rate-adaptive schemes, the proposed scheme can achieve a finer granularity in spectral efficiency only by adaptive switching of modulation alphabet. The simulation results show that the proposed rate-adaptive scheme can adaptively realize the flexible switching of spectral efficiency and the granularity of spectral efficiency is 0.25 bits. Moreover, the bit rate range is 28-84 Gb·s-1 at a fixed symbol rate of 7 GBaud. The proposed rate-adaptive scheme can be applied to the elastic optical network to provide a finer granularity in spectral efficiency and bit rate adjustment.

To realize the demodulation of the fiber grating center wavelength, we fabricate an ultra-short fiber Bragg grating (US-FBG), with grating length of less than 1 mm, reflectivity of over 60%, 3 dB bandwidth of more than 1.5 nm, and the edge linear region of the reflection spectrum of more than 1.5 nm. We use US-FBG as the sensing element, and propose a central wavelength interrogation method based on dual-wavelength laser. When the frequency stabilized laser with the central wavelength in the spectral linear region is incident on the US-FBG, the reflected optical power changes linearly with the drifts of the US-FBG spectrum, whose linearity is 0.998. In order to make full use of the linear region on the two sides of reflection spectrum, we use the complementary interrogation method with dual-wavelength lasers to extend the wavelength demodulation range to 3 nm. The measured values are in great agreement with the actual values. The method has the advantages of simple structure, low power consumption, and high spatial resolution.

A simple and fast dispersion measurement method is proposed based on the fiber laser structure. The resonant cavity is composed of two mirrors, one composed of Sagnac ring and fiber coupler and the other composed of the fiber gratings with different central wavelengths. The fiber lasers are established with different independent wavelengths based on optical switch. Gauging the laser beat frequency, we can obtain the time delay of the optical fiber under different wavelengths and then can obtain the dispersion coefficient. The dispersion of a 500-m-long dispersion compensation fiber is tested by the proposed method. The results show that the method is feasible, easy to implement, and can realize the rapid measurement of the optical fiber dispersion. The method can provide a reference for the selection of fiber parameters such as the fiber type and length in the communication applications.

Aiming at the application of optical transmitter signal distortion analysis, we adopt a coherent detection system with slowly varying phase, analyze the preprocessing of the distorted optical signal by means of cluster analysis, and estimate the distortion coefficients accurately to achieve a better constellation restoration effect. In this system, we adjust the length of the local oscillator fiber link to be equal to the fiber length of the signal link, so that the phase difference between the local oscillator and the signal light can be approximately constant over a long time window. It means that we can do intelligent analysis and preprocessing of the constellation for the long time window data by means of cluster analysis. Then, we obtain the distortion coefficients and cluster centroids based on cluster analysis of signal constellation, and use the location information of cluster centroids to equalization process and carrier phase recovery. This scheme solves signal recovery problems in the presence of signal distortion and phase noise, enabling accurate signal distortion evaluation. In this system, we simulate and experiment three kinds of distorted signals (I-Q gain imbalance, I-Q phase error, and I-Q amplitude uneven distribution) by using cluster analysis and blind-phase-search (BPS) algorithm. The results show that in the experimental system we can accurately estimate the transmitter signal distortion mentioned by using cluster analysis.

A double-loop desensitization structure is designed. The finite element analysis of the 26 mm long desensitization substrate is carried out. The tensile and compressive displacements of 0.065 mm are applied to the left and right ends of the desensitization substrate, respectively. The simulation result shows that the desensitization ratio of the desensitized substrate is about 3.5 and the strain measurement range can reach ±5000 με. The desensitization substrate can be operated within the elastic range of the material without affecting the service life of the sensor. The tensile test of fiber Bragg grating (FBG) with double-loop desensitization structure in the range of 500 με shows that the linearity of the sensor is over 0.999, and the full scale accuracy is about 0.1%. The sensor can achieve real-time accurate online monitoring, rapid system data acquisition, and high reliability. It is expected to be applied to the situations where the larger strain range of key structures is needed to be measured, such as ships, bridges, aircraft, and so on.

Distributed fiber sensor has been widely used in safety monitoring area for long-distance transmission pipe laying or other high-risk work areas. However, the breakage or damage of sensing fiber cables occurs frequently, which restricts the long-term monitoring of the monitored targets. To solve this issue, we establish an intelligent fiber sensor system with the function of self-diagnosis and self-healing, which divide the monitoring area into several regions by controlling nodes and resilient sensing fibers to accomplish the automatic fault location and recovery of sensing service. The proposed system can improve the survivability of the distributed fiber sensor according to simulation analysis results of the sensor's working situation. We use the proposed system in distributed fiber sensor system for the long-distance pipe laying monitoring project and propose the multi-section combination structure to protect fiber cable.

We use single- and double-lens systems to develop the short magnetic focusing image converter tubes respectively, and simulate the electronic motion imaging to study the imaging distortion by the Lorentz 3D-EM software. When the imaging ratio is 1∶1 and the cathode voltage is -3 kV, the spatial resolutions of the single- and double-lens systems are 17.07 lp/mm and 24.49 lp/mm respectively; the imaging distortion rates of single- and double-lens systems are 1.43% and 0.98% at 6 mm off axis respectively; the imaging distortion rates of single- and double-lens systems are 7.5% and 2.5% at 12 mm off axis respectively. Experimental results show that the imaging distortion rates of single- and double-lens systems are 2.4% and 0.9% at 6 mm off axis respectively; the imaging distortion rates of single- and double-lens systems are 8.5% and 3.2% at 12 mm off axis respectively. It is concluded that the double-magnetic-lens imaging system can reduce the imaging distortion and improve the spatial resolution.

The polarization state microimaging technology is proposed to apply to the imaging research of anisotropic crystal growth. The polarization state of the object is used as the physical quantity for imaging. Three Stokes parameters describing the polarization state are converted to three basic colors RGB, then the polarized-chromatic value of the RGB can be used to describe the corresponding polarization state. On this basis, using the confocal microscopy imaging system, we scan the object point by point to obtain the spatial distribution of Stokes parameters of the anisotropic object. Then we characterize the space distribution of the polarization state of the object by the distribution of polarized-chromatic value. The experimental results show that using the polarization state microimaging technology, we can obtain intuitively all the polarization information of the substance, distinguish two samples with the same material but different internal structures effectively, and observe the changes of the anisotropic crystal growth. Thus, a new visualization method for the growth of crystals is presented.

In order to improve the effect and stability of stereo matching algorithm, we propose a guided filtering algorithm based on adaptive aggregation region in Hue-Saturation-Value (HSV) color space. We calculate initial matching cost by the interaction of color and transverse gradient in combination with the structure and texture information of the image. Then, we calculate the length of the adaptive support arm of each point based on the color and distance information in HSV color space, which solves the problem that the change trend of the red, green and blue colors in the picture is similar and cannot effectively reflect the picture information. We construct the adaptive aggregation region using a transverse arm at each point on the longitudinal arm of the center point, and aggregate the cost space in the adaptive aggregation region by guided filtering. In order to avoid the problem that the support window is too small due to the fluctuation of the neighborhood information, we set the minimum range of the arm length. In the process of post-processing, we use the left and right consistency detection and the peak ratio detection method to find mismatching points, and correct the disparity map by the nearest neighbor matching and weighted median filtering. The experiments are carried out on standard images of Middlebury platform. Results show that average matching error of the proposed algorithm is 5.24%, and the matching error is reduced by 0.92% compared with the that of pre-improvement adaptive window algorithm. The proposed algorithm has better edge preservation effect and the robustness of the algorithm parameters is good.

In order to obtain the target spectrum and polarization information at the same time, we design a hyperspectral polarization imaging system with multiple simultaneous apertures based on the orthogonal dual-polarization method and acousto-optic tunable filter. Based on the principle of hyperspectral polarization imaging, we introduce the structure design, optical design, and mechanical design of the imaging system and analyze the system imaging process using the Mueller matrix theory. We use the imaging system to distinguish three kinds of camouflage nets from bushes. The experimental results show that the hyperspectral polarization properties of camouflage nets and bushes are quite different. We can improve the detection ability and classification accuracy by combining the spectral information and dual-polarization information. The hyperspectral polarization imaging system with multiple simultaneous apertures is an effective, compact, and real-time hyperspectral polarization imaging system.

Aiming at the interference of the surface burrs, oil, and other attachments on the corner detection in the visual measurement, we propose a method of sub-pixel location based on curvature and gray. Firstly, we use a morphological and bilateral filtering method to eliminate burrs, oil, and other attachments in the region of interest. Secondly, we detect the candidate corners according to the curvature characteristics, pre-screen the false-corners by the multi-scale invariance of the curvature angle at the corner, and use the gray information in the circular window to further eliminate false-corners to achieve the corner of the rough positioning. Finally, we screen the edge point of the original image according to the connection between the coarse positioning corner and the regional end points, and fit the filtered edge points by using least squares fitting to achieve precise positioning of the corner point. The experimental results show that the method can effectively overcome the interference of the surface attachment of the workpiece surface. The repeatability of corner location reaches 0.01 mm, and the accuracy of corner location algorithm reaches 0.004 mm, and the comprehensive measurement accuracy based on corner points is 0.06 mm.

By the first-principle method based on the density functional theory, the band structure, density of states, conductivity and absorption spectra of Al, Si single- or co-doped wurtzite CdSe are calculated. The results show that, as for the Al single doping system, the formation energy is the minimum and the doping process is the easiest, and the interaction between Al and other lattice cell atoms is strong and this system is the most stable. As for the Si single doping system, the formation energy is the largest, and the doping process is the most difficult. In these two single-doped systems, the population of Si-Se bond which is parallel or vertical to the c-axis of crystal supercell is smaller, but the bond length is longer. Its covalent bond is weaker than the Al-Se bond. The conductivity of the Al/Si co-doped system is the largest, that of the Al single-doped system is less, and that of the Si single-doped system is the smallest. After doping, the minimum optical band gap of each system becomes wider. Meanwhile, the absorption spectrum obviously moves towards the direction of high energy and the absorption becomes weak.

In order to solve the problems of narrow band and high loss related to traditional left-handed materials (LHM), a novel structure of LHM is designed based on the equivalent circuit theory and mirror-symmetry principle. The results show that, as for this structure, its effective permittivity and effective permeability are both negative, its absolute bandwidth reaches 8.9 GHz, and it possesses a low loss characteristic in the frequency range from 16.5 GHz to 25.4 GHz. Compared with those of the traditional microstrip antenna, the gain of the microstrip antenna based on this left-handed structure increases by 3.38 dB, the half power beam width reduces by 41.11°, and the effective radiated power is obviously enhanced.

Based on the construction of flow-field theoretical model of pulsed gas in atomic layer deposition (ALD), the variation trend of precursor concentration in the ALD process is analyzed, and an optimized deposition area in the ALD chamber is obtained. Based on this, the uniformity experiment of Al2O3 and TiO2 films on the hemispheric substrate is conducted. The experimental results show that the maximum inhomogeneities of the Al2O3 and TiO2 films in the best optimized area are 1.81% and 1.74%, respectively, which decrease by 47.1% and 50.8%, respectively, compared with those in the unoptimized areas. When the angle θ between the incident laser and the hemispheric central axis is 0°, the reflectivity of the prepared antireflection films at 550 nm reaches a minimum value of 0.04%; when θ is 60°, the reflectivity reaches a maximum value of 0.5%. There exist shifts with different agrees in the reflectance curves at other places, and the shift reaches a maximum value of 6 nm when θ is 60°.

In some cases of harsh environment, we need to seal zoom telescope in use, and the functions of reversed image and zoom are often integrated into the eyepiece. Which is more conducive to the overall seal design. Therefore, a scheme of the zoom eyepiece of the reversed real image plane in the visible light band is designed. Through the analysis of the initial structure of the eyepiece and the calculation of Gaussian optics, the selected structure is optimized by Zemax software to obtain the zoom eyepiece with three-group and 4×zoom. The position of the entrance pupil keeps constant when the eyepiece is zooming and the exit pupil position changes within 3 mm. The transfer function curve, distortion and chromatic difference of magnification are consistent with the design requirements of the visual optical system. According to the dynamic optical theory, the cam curve is designed with Matlab software, which makes the image plane relatively stable and the focusing smooth in the process of zooming. Although the eyepiece structure is slightly complex, but the optical lenses are spherical, which reduces the overall cost of the eyepiece and makes it easy to process the assembly.

Based on image quilting texture transfer algorithm, we study the effects of texture gradient structure information and brightness error between source texture image and target image on texture transmission. When selecting the candidate texture block, we take both the gradient structure information and color error of the texture block as the criterion. Meanwhile, we remap the brightness of the source texture image to the same level as the brightness of the target image, which can avoid the case where the optimal block cannot be selected due to the too large brightness error. The experimental results show that compared with the traditional texture transfer algorithm, the improved algorithm can achieve a better transmission effect.

An active laser triangulation method based on the telecentric lens is proposed to accurately measure the thickness of the object. The parallel projection method applies to the telecentric lens, and thus the relationship between the image point displacement and the object height change is linear. We establish a model of active laser triangulation based on the telecentric lens, and discusses the factors that influence the accuracy, including optical system error, machine error, and image processing error. In the experiment, we get the mean error less than 5 μm for thickness measurement when combing the active laser triangulation based on the telecentric lens and the compensation interpolation method.

To obtain edge-enhancement images of particle sources, such as high-energy X-rays, α-rays, γ-rays, and neutrons, we propose a spiral zone plate coded imaging (ZPCI) technique, which takes the spiral zone plate as the coded aperture. The spiral zone plate has the properties of both radial Hilbert transformation and Fresnel zone plate focusing, which is equivalent to a further radial Hilbert transformation of the decoded image obtained by Fresnel ZPCI technique. The feasibility of this proposed technique is verified via both numerical simulations and demonstrative experiments to generate edge-enhancement images. This technique can be widely used in many fields such as astronomy, nuclear medicine, and laser inertial confinement fusion.

Image denoising is the most basic problem and a key technology in digital image processing, which has always been difficult in the field of image processing. The quality of image denoising directly affects the follow-up image processing, such as image edge detection, feature extraction, image segmentation, and pattern recognition. In order to effectively remove the influence of multiplicative noise, we propose a denoising method based on deep residual learning, which solves the problem that the gradient gradually disappears when the number of convolutional neural network's layers increases by residual optimization. By comparing with four classical denoising algorithms, we make the conclusions that the proposed method can not only effectively remove the multiplicative noise, but also preserve the edge of the image and the detail information of the texture area, which will lay the foundation for image segmentation, registration, object recognition, and so on.

In order to solve the problems of the low matching rate and the low mosaic efficiency of the traditional image mosaic algorithms, we propose a fast image mosaic algorithm based on area blocking and binary robust invariant scalable keypoints (BRISK). Firstly, we use the frequency domain phase correlation algorithm to find the similar areas between the two images. Secondly, we divide the similar areas into N×N' image blocks evenly and calculate the standard deviation of each image block. Thirdly, selecting two image blocks with large standard deviations in different positions, we coarsely match the feature points by BRISK algorithm. Fourthly, we construct the directed line segments and match the adjacent line segments after obtaining the matching points. Finally, we calculate the projection transformation matrix by the randomly matching point pairs to correct the projection error, and accomplish the image mosaic by weighted fusion and luminance equalization. The experimental results show that the matching correctness of the proposed algorithm is more than 90%, and the mosaic speed is increased by 63.7%.

Most exemplar-based methods find the optimal matching block by translation, which fail to deal with the images when there is rotation or scaling transformation between source and damaged region. We propose an exemplar-based inpainting algorithm with rotation and scaling transformation. Firstly, the optimal patches, with rotation or scaling transformation in those damaged region, are obtained based on the local feature vectors. Then, the energy space function is expanded to adapt the transformation of patch in data filling. Finally, the damaged image with rotation or scaling transformation can be inpainted automatically. The experimental results show that the proposed method can accurately find the optimal matching block when rotation or scaling transformation exists, and achieve better effect, higher effectiveness and robustness.

How to improve the resolution of face images is a classic problem in computer vision. During video surveillance, since the target person is faraway from the camera, the result is often a low-resolution face image. Aiming at this problem, we propose a face super-resolution restoration algorithm combining principal component analysis (PCA) and maximum a posteriori probability (MAP). Firstly, we get the characteristics of the high-resolution face database based on the PCA model. Secondly, we calculate the representation coefficients of the input low-resolution face images on these features by MAP and reconstruct the corresponding high-resolution features. Thirdly, we make the constraint enhancement of the reconstructed features. Finally, we obtain the final super-resolution restoration images based on the average vector of high-resolution face database. In order to verify the effectiveness of this algorithm, we make the experiments that the images in the AR face database are amplified four times using this method and other methods. The result of this method is superior to other methods in either visual effects or evaluation indicators. This algorithm not only improves the resolution of face images, but also maintains the edge information of the image better.

In order to realize real-time gesture recognition based on Kinect and to reduce the recognition time while ensuring the recognition accuracy, we propose a method of gesture image extraction based on Kalman filter, and study a gesture recognition model based on three characteristics. We get depth images and skeleton information via Kinect, and then extract hand regions based on Kalman filter. In order to verify the efficiency of gesture segmentation, we collect 28000 samples of 10 types of gestures, extract two local binary pattern features and histogram of oriented gradient (HOG) feature, and classify the samples by support vector machine (SVM). The experimental results show that the gesture recognition model based on HOG+SVM has the recognition accuracy of 97.09% and the recognition rate of 31 frame/s. In application based on Kinect, HOG+SVM recognition model based on the proposed segmentation method can meet the real-time requirement.

Face recognition of identity authentication may be malicious fraud by photo, video, and other media. After analyzing the characteristics of non-linear changes in face image, we propose a new method of face liveness detection based on image processing according to the changes of edges in photo face and real face. The changes of face edges are described by the improved histogram of oriented gradient. Combining with the statistics characteristics of the positive and negative samples, the support vector machine classifier is trained to detect the liveness face. Finally, the new method is validated by the public NUAA human face database. The results show that the accuracy rate of the proposed method on true and false face detection reaches 97%.

Traditional locality preserving projection (LPP) algorithm directly uses the spatial information of original data, which leads to inaccurately select neighborhood, and ignores data categories information of projection of LPP algorithm. To solve these problems, a face recognition method is proposed based on adaptive neighborhood LPP. In the feature extraction, the objective function is constructed based on the variable similarity, neighborhood information, and data categories information, so that the same class samples are close and different class samples are far away from each other in projected subspace. Adjacency matrix and projection matrix are adaptably optimized by minimizing objective function. Optimized projection matrix is used to reduce the dimension of high-dimensional face data, and low-dimensional data is used to classify and recognize face samples. The experimental results on Yale B, PIE, MSRA and CAS-PEAL databases validate the effectiveness of the proposed algorithm.

In order to evaluate the optical camouflage effect of target objectively and precisely, we propose a camouflage effect evaluation model based on digital image inpainting technology. We use optimized image inpainting algorithm to obtain the ideal camouflage texture in the region, which is covered by camouflaged target, and then use the effect value measured by no-reference-image quality assessment to eliminate error. The comprehensive evaluation which combines structure similarity metric with approximate value of ideal camouflage texture is established to evaluate the camouflage effect of target. The simulation results show that the results of the proposed evaluation model are similar to the visual observed results, which can effectively evaluate the camouflage effects of target.

We propose a convolutional neural network defogging algorithm based on multi-feature fusion to overcome the problem of manual feature extraction, low contrast, and low signal-to-noise ratio in traditional defogging algorithms. The convolution neural network simulates the human visual system to hierarchically process the fog images and automatically extract image features. The algorithm adopts a learning method of the direct mapping from the hazing image to the clear defogging image, which includes feature extraction, multi-scale feature fusion, and shallow and deep feature fusion. Multi-scale feature fusion helps to rebuild details of the image. Shallow and deep feature fusion combines the contour information obtained by shallow convolution with the detail information obtained by deep convolution to enhance the overall effect of defogging. The experimental results show that the peak signal to noise ratio of the multi-feature fusion network increases by 1.280 dB compared with the single-scale network. The proposed algorithm has obvious defogging effect on natural fog image and superior detail information and contrast compared with other algorithms, which provides a new idea for defogging methods.

Stereo matching is the focus of research in the field of computer vision. Most of the stereo matching algorithm take mathematical calculation as digital information, and lack the connection with the actual human visual characteristics. We combine the concentric antagonistic receptive field of the human eye and the HSI colour space model to improve the weight calculation of the original adaptive support weight (ASW), and optimize the parallax by means of left-right consistency check and median filtering. The test results of several groups of international standard images in VS2010 platform show that, this method has higher matching accuracy than that of the original ASW algorithm in the low texture regions and depth discontinuities area. According to the difference of the test images, the improvement ranges from 10% to 20%, and the overall matching accuracy is similar to that of the mainstream local matching method in recent years.

In order to obtain ultra-broadly tunable optical wavelength signal splitting, we design optical signal splitter based on micro resonator in the two-dimensional photonic crystal structure. The performance of the optical signal splitter is qualitatively analyzed by coupled-mode theory under different design conditions. Operating characteristics of optical signal splitter with two symmetrical outputs are studied by the finite-difference time-domain method. The results show that the splitter achieves 29 and 38 passbands by adjusting the structures of micro resonators of 5×5 and relative dielectric constants of the whole rods, respectively. Channel waveguide dropping peak wavelength and bandwidth ranges are 1310.0~1655.5 nm and 2.0~7.4 nm, respectively. The structure has characteristics of broadly tunable passband, effectively removing noise signals, optical signal equal power splitting at the same peak wavelength. The proposed signal splitter structure has potential application value in the fields of coarse wavelength division demultiplexing design, optical signal equal power splitting design, integration of optical design, etc.

In order to improve the spatial resolution of remote sensing images, the nonparametric Bayesian dictionary learning model for natural images super-resolution reconstruction is introduced into the field of remote sensing image processing. Based on nonparametric Bayesian and classified texture patches, an improved method of the single remote sensing image super-resolution reconstruction is proposed. The method uses the Beta-Bernoulli process for dictionary learning, and establishes the probability distribution models of dictionary elements and parameters. The Gibbs sampling is used to calculate the posterior distribution. Finally, the image block is divided into two types: smooth block and non-smooth block during reconstruction. The non-smooth block reconstructs the high resolution remote sensing image by using the posterior distribution of the high-resolution dictionary and the sparse coefficients of the low-resolution image blocks. While the smooth block only uses the bicubic convolution method to reconstruct. Furthermore, different from the shortage of traditional algorithm that needs to set a large dimension dictionary in advance to ensure a higher reconstruction precision, a smaller dimension dictionary is obtained by non-parametrical deviation of dictionary dimension in this paper, which reduces the calculation. The results show that the proposed algorithm outperforms traditional approaches both in visual and quantitative evaluation indexes whether the test image is noisy, and the reconstruction speed is faster.

Drilling fluid has important functions of carrying debris and balancing pressure. In order to adjust its performance, we need to continuously detect the ions in the drilling fluid. The laser induced breakdown spectroscopy (LIBS) technology is adopted to detect metal elements in drilling fluid . From the LIBS analysis of Ca, Na, Mg and K elements in drilling fluid, the optimal detection condition is obtained. The results show that the delay is 400 ns for Ca element, 500 ns for Na, Mg, and K elements. The gate width is 1000 ns for Ca and K elements, and 1500 ns for Na and Mg elements. The application of LIBS on detection of metal elements in drilling fluid is feasible. The establishment of experimental setup, the determination of detection parameters, and other influence factors, can provide valuable reference for further research of LIBS on analysis of drilling fluid.

A detecting system of acetylene (C2H2) gas in near-infrared region is developed based on the tunable diode laser absorption spectroscopy. The wavelength modulation spectroscopy in combination of multi-pass absorption cell is used to improve detecting sensitivity of the system. To optimize detecting conditions of the system, spectral signals of standard C2H2 gas with volume fraction of 5×10-5 are detected under the conditions of pressure of 5.3-12.0 kPa and modulated amplitude of 0.010-0.035 V. The second harmonic signals of C2H2 with different concentrations are detected at the total pressure of 10.7 kPa. To verify stability of the system, spectral signals for 60 s are acquired, and the most suitable detection time as well as the minimum detection limit is obtained by the Allan variance analysis. The results show that the signal intensity of the second harmonic signals is the greatest at pressure of 10.7 kPa and modulation amplitude of 0.030 V. The volume fraction of C2H2 is with a good linear relationship with the amplitude of the second harmonic signals, and the detecting deviation is less than ±2% in the range of volume fraction from 1×10-6 to 5×10-5. The most suitable detection time of the experimental system is 7.2 s, and the minimum detection limit is 2.8×10-11. The instrument adopts a laser driver and a digital lock-in amplifier based on an embedded system, so the instrument has the characteristics of simple mechanical structure, small size, and easy integration with other systems. Therefore, the compact detecting system for C2H2 gas is suitable for industrial process and gas transmission.

We employ the standard fluorescence method to measure the photoluminescence (PL) properties of the single-stranded nucleic acids samples with 56 and 29 base sequences. This method does not need the help of probe and fluorescence or phosphorescence material, does not damage or contaminate the sample during the measurements. It is found that when the excitation wavelength is in the range of 310-410 nm, the PL peak of the samples can be observed in the wavelength range of 410-480 nm. The PL peak red-shifts when the pumping wavelength red-shifts, while the intensity of the PL peak increases and then decreases with the increase of excitation wavelength. The single-stranded nucleic acid samples with two different base sequences show different properties of the PL spectra due to their different electronic band structures. The results are helpful for non-invasively and label-free measurement and identification of nucleic acid materials.