Seawater is a complex system, which involves variety of organic, inorganic, dissolved and suspended substances. However, the main components in seawater are the inorganic salt, such as NaCl, MgCl2, KCI, NaHCO3, MgSO4, and so on. These elements have a big influence on laser′s transmission underwater. To further understand the optical properties of seawater, the transmittance in these salt waters with different concentrations of salt is measured. The transmission spectra of dissolved substance solution is measured by ultraviolet- visible- infrared spectrophotometer. The transmission characteristics of different salt waters are studied by using the wavelength of 450, 532, 633 nm lasers. Then a first- order exponential curve is gotten from experimental data, which shows the relationship between transmittance and the conductivity in different solute concentrations. From the figures, a conclusion that transmittance decreases with the increasing of concentration is gotten. With the same transmission distance and different concentrations, the attenuation characteristics of light are different. The work is hoped to be helpful for the research about underwater target detection and laser communication in the sea.

Considering the low contrast, fuzzy edge of infrared images, an enhancement algorithm based on the luminance and contrast masking characteristics of the human visual system is presented, the parametric contrast is computed, then non-linear gain function is used to process the parametric contrast, which enhances low contrast more than high contrast, to improve image details and image contrast, then to suppress small coefficients by threshold denoising method. The incomplete beta function is applied to improve global brightness of image. Experimental results demonstrate the ability of the proposed algorithm to achieve simultaneous local and global enhancements. The phenomenon of over-enhancement is avoided. The enhanced image is of good visual perception.

In order to improve reality of pencil sketching, convolution threshold algorithm is established. Streamline of pencil is generated. Image texture is generated with function of line integral convolution, streamline is integrated by pixel along the vector and negative direction obtained, input noise of all pixel of streamline as kernel are convoluted, output texture pixel value is obtained. Different ranges of gray are processed by two different thresholds of gray，and process is described. The experiment shows this algorithm made edge of pencil sketching clearly and delicately, and has pencil texture, processing time is 2.2 s, it takes less time and is more like hand-painted.

The point cloud data filtering is always an important problem in the research of airborne LiDAR data. A LiDAR point cloud data filtering algorithm based on region prediction is proposed. The method creates a regular grid with point cloud data and removes outliers, divides the experimental area into different blocks and uses sub-blocks′ elevation standard deviation to predict the terrain slope parameters, finally determines the ground points. The proposed algorithm has an advantage of obtaining threshold adaptively by the conditions of topographic relief of the region. The international society for photogrammetry and remote sensing (ISPRS) reference dataset is used to test the method. The experimental results show that the proposed method can effectively remove non-ground points, keep the ground points and is effective at minimizing total error rates.

Simulation modeling and analysis of laser radar echo signal is an important research content of ladar imaging,detection and target recognition. A novel way based on coordinate transform is proposed to solve the light travel distance of object scene by studying the mathematical model of airborne scanning ladar laser echo. A method of solving the light travel distance based on a coordinate change is proposed. The simulation computation only depends on the number of laser spot segmentation in the simulation, thus has large advantages in simulation modeling of complex target scene. Based on these methods, the Z scanning airborne ladar laser echo in complex target scene with shelter is simulated, and the experimental result is obtained. The simulation datas indicate that laser echo not only has the information of target distance, but also has target surface type information and surface reflectivity information. The results provide the foundation in future study on detection of obscure target based on the ladar echo.

The structure of three sub-mirrors sparse aperture two-mirror system is introduced. The generalized pupil function and imaging principle of the system are derived. One of the three sub-mirrors has piston error and tilt error. The errors are represented by Zernike polynomials, which are imported in simulation of imaging with Matlab. Relative ambiguity resolution is advanced to evaluate imaging quality of the system. Through the relationship between the errors and the relative ambiguity resolution, the influence of sub-mirror errors to imaging quality is analyzed. The results show that the impact on imaging quality with piston error is different from that with tilt error. With the increase of the error, the relative ambiguity resolution periodically changes with piston error but monotonically increases with tilt error. Tilt error affects the quality of imaging more than piston error does, so we should control tilt error more strictly than piston error.

Focusing technique of space camera has relation to camera image quality, being one of the key technologies of on- orbit test of spacecamera. Image based focusing technique with simple structure is highly intergrated, which is used in space camera. The key of Image based focusing is to estabilish focusing evaluation function. Focusing evaluation function can provide guidance for the focusing process. This paper discusses the influence caused by defocus. Based on the study on focusing evaluation function methods of foreign space camera, some instructional conclusions about choosing focusing evaluation function method and advantages and disadvantages are obtained, which provide reference and help for space camera focusing technique.

Terahertz inline digital holography with lower photon energy and higher penetrating power to nonmetallic and nonpolar substances has attracted increasing attention. However, the zero- order diffraction light and conjugate image will degrade the details of reconstructed image and cause the loss of image quality. The applications of phase retrieval algorithm in the visible and terahertz digital holography are compared and analyzed by simulation, and the imaging method that the number of hologram recording is reduced from two to one can be verified after studying the mean square error of reconstructed image changing with the recording distance and recording interval. The influence of noise on the simplified imaging is discussed, and the results show that when the hologram and background are both contaminated by noise, the phase cannot be restored to the predetermined value and with the increase of noise, the reconstructed image becomes more and more blurred until the image is covered completely by noise.

The methods of measuring the terahertz backward scattering characteristics of the background materials which are irradiated by quasi- plane wave have a great influence on the measuring results. To reduce the influence of the fluctuation of continuons wave laser output on measuring results, the backward scattering of the wall is measured before the foam plastic boards. Meanwhile, to eliminate the impact of wall on measuring result, the relative backward scattering intensity of different foam plastic boards and different azimuth angles of the same material are given, which is based on the biggest backward scattering intensity. The experimental results show that the scattering measurement errors of the three kinds of foam plastic boards which are relative to the wall have a significant decrease and thus the measurement accuracy of the relative backward scattering intensity in the follow-up parts is increased.

Dynamic simulation process of line of sight between bomb and target in the high frequency laser jamming test on hardware in the loop system for laser guided weapon countermeasure is researched, and the whole process of simulation precision analysis of line of sight between bomb and target is proposed. Then the geometric error，control error and optical assembling error, which influence the simulation precision, are analyzed in total, the error model of line of sight between bomb and target is set up by adopting multi-body error analysis theory. Experimental testing method of simulation error of line of sight between bomb and target is designed, and the unknown error in the error model is identified by means of actual test combined with error modeling. The simulation accuracy analysis of line of sight between bomb and target is proposed using Monto-Carlo mothod or residual analysis, and the estimated value and its variation are calculated.

The application of photonic crystal in the solution concentration detection is investigated by using plane wave expansion method. A two-dimensional triangular lattice photonic crystal (Si and Ge) is chosen as the substrate,filling the air hole with different percentage concentration of mixed binary solution materials which will be measured,and the photonic band gap of the photonic crystal filled with binary solution under different polarization modes is obtained. The results show that when the binary solution is used as the dielectric material in the air hole, the photonic band gap (PBG) changes with the different percentage concentrations of the solution quality. This has a certain guiding function in solution mass percentage concentration detection applications.

The metal nanoparticles have excellent local enhancements. The Bloch wave of the array structure couples with single particle localized surface- plasma resonances (LSPRs) by designing array structure, forming arrays support surface lattice resonances (SLRs)，which can obtained a larger quality factor and small pattern volume and increased the efficiency of the spontaneous emission. Diamond structure of nanoparticles can effectively gather charge, form a strong dipole resonance, which can achieve excellent characteristics including lower lasing threshold and higher spatial coherence.

A stable and reliable optical parametric oscillator (OPO) with the best coherence and tunable spectral range is an ideal laser source. It is widely used in spectrum analysis, laser interference measurement, remote sensing, laser differential absorption radar, etc. The structure of resonant cavity, focusing parameters, pump threshold ratio, thermal effect, group velocity dispersion and other nonlinear effects affect the stability of the OPO system. Various factors which influence the stability of optical parametric transformation are analyzed, the most effective way to eliminate the noise of the OPO system is pointed out, which is the realization of single frequency operation.

Key forming parameters of laser engineering net shaping are laser power, scanning speed and stratification height. The relationship between the key parameters and residual stress must be mastered, because the residual stress influences the forming quality and deformation. Mastering the relationship is an effective way to reduce residual stress and to choose forming parameters. Using the life and death element technology and thermo-mechanical coupled field model, 8 groups of different key parameters of the laser engineering net shaping of titanium alloy are computed. The distribution cloud of the residual stress is obtained and three samples are selected. Through the multivariate regression of different key parameters and the residual stress, the multiple regression equation is obtained. The validity of the multiple regression equation is proved by finite element analysis and experiment. The multiple regression analysis is the effective way to reduce the time of simulation and experience of the different key parameters and to estimate the residual stress of the established parameters.

Based on the actual situation of CO2 laser beam heating packaging material, a mathematical model of CO2 laser irradiating packaging materials is established. Combining with the actual boundary conditions, the analytical expression of relationship between cutting depth and laser beam parameter is built up by calculus. Experiments are designed to examine the mathematical model. Diagrams of each parameter are drawn using Matlab software. Theoretical analysis and experimental results indicate that the lower speed of laser beam moves and higher power of laser, the deeper the hole will be, and the model has been revised to be in accord with experimental results. The model can be used to predict the capability of low-power laser cutting.

In the laser drilling process, the interaction between laser and rock is a complicated three dimensional (3D) unsteady problem. The thermal conduction model is established according to energy conservation equations, and the stress distribution is obtained in accordance with thermal stress theory and generalized Hooke′ s law. Based on the 3D finite element models, the effects of fragmentation and vaporization of malmstone under five kinds of continuous Gaussian distribution lasers with a fixed 0.2 mm spot diameter are estimated. The simulation results are that the primary failure mode of malmstone is vaporization if a specified continuous laser is used to break a rock with a large ultimate strength, however, the primary failure mode of malmstone is fragmentation if a rock has a small ultimate strength.

The application of galvanized steel tailor-welded blanks not only improves the corrosion resistance property of a car, but also reduces vehicle weight while the intensity maintains the same. Compared with other welding technologies, laser welding has lots of advantages, such as a narrow welding line, a high strength joint and a small heat-affected zone. However, the gap between the plates can cause surface depression and intensity deficiency. After obtaining suitable parameters of side-blown shielding gas, orthogonal experiment is designed to have a research on laser power and welding speed′s influence on weld formation through tailored blank fiber laser welding. After that, metallurgical experiments, tensile tests and cupping tests are used to detect the performance, mechanical and deep stamping properties of the welding line. The result shows an optimum parameter when the laser power is 3 kW and the welding speed is 4 m/min. On the basis of optimal parameters obtained, a further study is made on gap′s influence on weld formation. The result shows that a nice welding line can be obtained when the gap is not more than 0.15 mm（about 11.1% of the plate thickness）.

Spatial chirp is a common phenomena in ultrashort pulses. The focusing characteristics of Gaussian pulsed beams with the first-order spatial chirp (FSC) are investigated, and the analytical expression for the FSC beam on the output plane is derived. The analytical expressions for the pulse width, beam width and amplitude coupling coefficient of the FSC beam after focusing without chromatic aberration are derived. The intensity distribution before and after focusing is simulated. The pulse width, beam width and amplitude coupling coefficient of the FSC beam after focusing are analyzed numerically with the variation of propagation distance when the chromatic aberration is considered, which are compared with the corresponding results when the chromatic aberration is not considered. It is found that the FSC beam keeps the form after focusing without chromatic aberration; the chromatic aberration has no effect on beam width and amplitude coupling coefficient,but broadens the pulse width of FSC beam.

In this study, the impact of laser quenching on 45 steel (V-shaped notch) is researched and the effect of laser power on the fracture toughness is investigated. The specimens surface and fracture morphology are examined by optical microscope and scanning electronic microscope (SEM). Dimple characteristics are observed on the fracture surface of original specimens. As comparison, there are brittle fracture characteristics in the crack initiation zone of laser hardened specimens. Our results indicate that the fracture toughness of laser hardened specimen is reduced. Moreover, the surface fracture toughness decreases with increasing of the laser power.

Solar simulator is an important application in non-imaging optics, its optical path is long because of the special optical system, and the collimating system accounts for nearly half of the whole optical path when the dual separation collimating lens are used. In order to achieve the miniaturization of solar simulator, the telephoto lens is used, and the telephoto lens has a short back focal length. When the dual separation collimating lens is replaced by the telephoto lens, the optical path of the collimating system can be shorter and the whole solar simulator optical path can be more compact. The collimating system with three- piece telephoto lens is designed, and the impact on the solar simulator technical specifications is studied through LightTools software simulation analysis. The simulation results show that although the solar simulator technical specifications change little. The simulator optical path becomes shorter, therefore the solar simulator can be miniaturized by using the telephoto lens as collimating optical system.

Based on requirements of infrared target detection and laser ranging, laser/ infrared optical system with common optical path and athermalization is designed. According to user requirements, the parameters of the optical system are defined as: the focal length is 150 mm, the F number is 2, the operating waveband covers 1.57 μm and 3~5 μm . A RS-RTM-31243-001-C1 InGaAs photoelectric detector is selected for 1.57 μm laser wavelength; and a 2/3 inch (1 inch=2.54 cm) detector of ULIS company is selected for 3~5 μm waveband (the full field of view is 4.2°). The evaluation results of image quality show that, in temperature range of -50 ℃~70 ℃, maximum value of root mean square (RMS) radius of the spot diagram at each field of view is 8.166 μm , which is far less than the effective receive radius of detector (75 μm ) and the energy concentration is very high at 1.57 μm laser wavelength; at cut- off frequency of 15 lp/mm, modulation transfer function (MTF) of the 3~5 μm infrared waveband are all above 0.78 for each field of view, which is closed to the diffraction-limited curve. So the system has good image quality, simple structure, and meets the user requirements of the optical overall design.

Geometrical deformation of lens surface caused by kinematic mount clamping force is analyzed with finite element method and lens surface displacements are extracted and fitted with Zernike polynomials. Analytical results show that Defocus、Pri Trefoil and Pri Hexafoil are the main aberrations under clamping force. During the process of optical testing, repeating assembly of the kinematic mount apparatus may influence the testing accuracy, so relations between assembly repeatability and surface deformation are also investigated. In order to evaluate the repeatability for assembling, variations of peak valley (PV) and root mean square (RMS) values changed with clamping force and clamping placement in circumferential and radial direction are also shown in this paper. The results indicate that PV and RMS values do not obviously change as clamping force and clamping placement change, which means that slight assembly errors of the kinematic mount apparatus are allowed.

By decreasing the radius of dielectric rods rather than removing a circle of dielectric rods in the photonic crystal ring resonator(PCRR), an annular line defect is constructed. A new type of photonic crystal ring resonator is proposed. By using the finite difference time domain (FDTD),the transmission property of lightwave through the ring resonator is analyzed. Further more, by changing the radius of dielectric rods, the influences on the filtering property is discussed. The result shows that the narrowband filter with single mode can be realized when the radius of rods is in the range of 0.43R~0.51R. At the same time, the center wavelength is close to 1550 nm at the third communication window, the rates of normalized transmission are all over 85% and the bandwidths are all below 17 nm. It provides available reference for the wavelength division multiplexing (WDM) multiplexer/demultiplexer.

As the electric power of high-power light emitting diode (HP-LED) increasing, the challenge of heat dissipation is also becoming higher and higher. The heat which can′ t be dissipated from chip effectively will raise the junction temperature of the LED devices. High junction temperature will not only affect the optical power, flux and other performance of LED devices, but also decay the lifetime of device rapidly. Therefore,knowing the temperature rising rules of HP- LED devices well becomes the key to improve the reliability of devices. The effects of different drive current, different substrate temperatures and different packaging materials on thermal resistance of LED devices are studied. The results show with the increase of current or with the substrate temperature increases, the thermal resistance of LED devices trend to decline and then rise. The changes of thermal resistance of LED devices packaged by aluminum substrates and ceramic substrates are different. When the substrate temperature increases, the thermal resistance of LED devices interconnected by the Al substrate keeps declining because of the higher pn- junction temperature of the LED device. The tested results of the thermal resistance of LED devices interconnected by different materials show that the thermal resistance are obviously effected by the interconnect layer and the substrate.

We make test and comparison for the photoelectricity and thermal parameter of light emitting diode (LED) different substrates like glass, ceramic and find that luminous flux of glass substrate chip on board (COB) packaging is very close to that of ceramic substrate. We design two heat dissipation methods: the layer with silver brushed on back and aluminum slot model both improve heat- conducting property of glass substrate COB. When the thickness of silver reaches to 75 μm and light becomes stable, the temperature of light emitting diode rubber surface is 91.5 ℃, thus better heat dissipation and glowing effect has been reached.

Using the optical coherent superposition principle, the transmittance formula of band is derived for one-dimensional finite-period photonic crystal, and the coherent superposition theory is established. The coherent superposition theory and the characteristic matrix theory are compared and the simulated results are consistent. The coherent superposition theory has advantages of the characteristic matrix theory, and overcomes the lack of the characteristic matrix theory. It is a better way to study band of one-dimensional finite number cycles photonic crystal.

Based on the Huygens-Fresnel principle, the influence of astigmatism on the generation of radial polarized non-diffracting beams by the axicon is investigated. Research results show that when the value of the axicon astigmatism is 0.1 λ , the radial polarized distribution of radial polarized non-diffracting beams generated by axicon focusing radial polarized beams vanishes. Non-diffracting property of the radial polarized non-diffracting beams loses gradually, when the value of astigmatism increases. Particularly when the value of the astigmatism is 0.2 λ , the non-diffracting property vanishes. The vanishing of the radial polarized distribution and the non-diffracting property are not synchronized. This result demonstrates that in the generation of radial polarized non-diffracting beams by the axicon, the polarization property of beams is affected more by the astigmatism than the non-diffracting property.By using of the divergence between the optical axial and the central axial of the axicon in the experiments, the influence of astigmatism on the generation of radial polarized non-diffracting beams is verified. The experimental results are basically consistent with theoretical analysis. The research results will enable the generation of the radial polarized non-diffracting beams more flexible and accurate.

The propagation characteristic of optical vortex beams in the free space is studied. By using the Huygens-Fresnel formula and ABCD optical matrix, the propagation expression of the Laguerre-Gaussian beams in the free space is derived. The properties of vortex beams in several different rotationally symmetric optical systems are analyzed. The result shows that the rotationally symmetric optical system just influences the diffraction properties or radius of curvature of the beam, but does not influence the orbital angular momentum of the vortex beams.

Diode pumped metastable rare gas lasers (DPRGLs) are a new type optically pumped gas laser analogue to diode pumped alkali vapor lasers (DPALs). It can overcome the hidden danger of chemical reaction while possessing similar advantages of DPALs. In this paper, the basic principle and research development of DPRGLs are presented. The key technologies and power scaling potentials of DPRGLs are analyzed. The possible further development and applications are discussed.

Subwavelength metal grating has special properties which the traditional grating does not have. As a kind of optical element, it has a sort of excellent performances, including high transmission and extinction ratio,wide spectrum range, great polarization properties and so on. It plays an important role in the field of applications of subwavelength optical components. Furthermore, it can reduce the optical components and increase flexibility in the optical systems due to the advantages of small volume, compact structure and easy integration. It has the potential to improve and replace traditional optical devices. This paper presents the development of the analysis theories, as well as the trends of the innovation of structures, study of multidimensional,theoretical simulation to experiment, and applicable band extending to terahertz and ultraviolet band, for the subwavelength metal gratings. It also describes the wide application prospect of the subwavelength metal grating in the fields of laser system, polarization imaging, photoelectric detection, thin film solar cells,optical sensing, etc.

Resolution of traditional fluorescence microscopy is limited by the diffraction of light. Diffraction limit can be broken by structured illumination to get higher resolution. Compared to other super-resolution microscopy techniques, structured illumination fluorescence microscopy can achieve higher imaging speed and need a simple setup, which has an important application life science research. In this paper, we first illustrate the principle and reconstruction algorithm to obtain 2D and 3D super-resolution images as well as non-linear structured illumination. Then the generally used structured illumination method and setup based on grating, spatial light modulator (SLM) as well as digital micro-mirror device (DMD) are introduced and compared. At last we summarize the application of structured illumination fluorescence microscopy for observing biological structures and processes.

As one of main processes in automobile industry, welding technologies are widely utilized. It is important for welding quality that automotive steel sheets and welding methods are employed. Classifications and characteristics for automotive steel sheets are illustrated from the strengthening toughening mechanisms and coating types. The features and application range of many welding technologies in automotive industry, such as spot welding, laser welding and arc welding, are discussed in detail. The development of influencing factors for these welding technologies are reviewed by coating and chemical compositions of sheets, welding parameters, joint properties. Combining the research and application of the third generation advanced high strength steel, aluminum alloy and magnesium alloy for automotive industry, many new hybrid welding technologies are also investigated. The future of welding technologies for automotive steel sheets is also discussed.

Optically pumped mid-infrared gas laser is a potential way to achieve high beam quality and high power mid-infrared laser output, showing great development prospective in the future due to its extremely high quantum efficiency, outstanding heat dissipation, great ability for power scaling and extraordinary compactness. The basic principle and history of optically pumped mid-infrared gas laser are introduced, the critical blocks and difficulties in its progress are analyzed, and the expectation of optically pumped mid-infrared gas laser is forecased.

Reducing or decreasing light scattering effects of suspended particles in water is one of the key technical issues of the direct spectroscopy chemical oxygen demand (COD) water quality detection. Therefore, based on the Mie scattering theory, the improved continued fractions combining with backward recursion algorithm is used to study ultraviolet (UV)- visible light scattering properties on the alga and sand suspended particles in water. The light scattering models of spherical particles in water is built. The changes of light scattering intensity and scattering angle are analyzed and calculated with particle size in the range of 1~200 μm and the incident wavelength in the range of 200~1000 nm. The simulation results show that when the particle size and the wavelength of incident light change, the scattered light intensity and angle are significantly changed with two types of suspended particles. It is helpful to improve resolution and degrade the effect of scattering of detection of water quality using UV-visible absorption spectroscopy.

In order to improve the stress and the thermal stability of diamond like carbon (DLC) film, by adding two bubblers connected to mass flow controller into the improvement of the radio frequence plasma enhanced chemical vapor deposition (RF-PECVD) equipment, the DLC films with Si doping prepared by Rf-PECVD technology with CH4 as the reactants, liquid tetra methyl silane (TMS) as the reaction precurs and Ar as the carrier gas. The measurements of the stress, the hardness, roughness and the thermal stability demonstrate that the stress, roughness and the thermal stability of the DLC films doped Si are improved at a certain degree with the increase of the flow rate of the carrier gas, but the hardness decreases obviously, as the flow rate of the carrier gas is equal to 30 mL/min (standard state), the stress decreases to 0.65 GPa and the temperature of graphitization increases to more than 600 ℃, the roughness of the surface is decreased to 0.566 nm, but the hardness decreases to 12.6 GPa.

Pulsed laser deposition is a potential preparation method for optical fiber hydrogen sensor. Pd/Ag thin films are prepared through pulsed laser deposition at a low temperature by excimer laser. It is found that Pd/Ag thin films with fine crystal structure are obtained under high pulse laser energy at low temperature by X-ray diffraction (XRD) and atomic force microscope (AFM) methods. The F-P sensor is packaged in a casing structure that can limit the expansion direction of Pd/Ag thin films which absorbs hydrogen. Hydrogen sensing probe is made to test the hydrogen sensing properties of Pd/Ag thin films for the characteristic that the expansion of Pd/Ag thin films which absorbs hydrogen can lead to the change of the F-P cavity. Experiment results show that the sensor can be used to detect the changes of the hydrogen concentration.

Multi spectral remote sensor image synthesis is directly extracted from R, G, B bands of the multispectral images. Because of the mismatch between the spectral response characteristics of multi spectral imaging detector and international commission on illumination (CIE) color matching functions, color images appear serious color distortion. In order to correct the color distortion, color correction is needed. Aiming at the shortcoming of traditional white balance method and color synthesis method, improved multi point color synthesis method based on spectral tunable light emitting diode (LED) integrating sphere is proposed. This method not only contains the spectral features of the objects but also is easy to realize. It is proved that the color chromaticity error of the target can reach 0.15 corrected by white balance. However the color chromaticity error of the target can be limited less than 0.05 when the method is used to correct the color distortion.