In nuclear magnetic resonance gyroscope (NMRG) system, circularly polarized light is utilized to pump alkali metal (for instance, rubidium) atoms in order to get them polarized. However, the pump beam is not ideal circularly polarized light in practical applications. In order to research the relationship between the pump beam ellipticity and the Rb polarization, the expression of the pump beam after passing through the quarter-wave plate was calculated, and the ellipticity of the pump beam before going through the rubidium gas cell was obtained. A numerical simulation model was established to study the influence of pump beam ellipticity on Rb polarization, the relationship between Rb polarization and pump beam ellipticity were obtained by experiment at the same time. Both the simulation and experiment results show that the Rb polarization increases with the increase of pump beam ellipticity, and with the further increase of pump beam ellipticity, the rate of Rb polarization growth slows down and gradually becomes saturated; In addition, Rb polarization increases with the increase of pump beam power for the same ellipticity.

Pointing accuracy is the most important parameter to evaluate the performance of the star camera. Laboratory accuracy determination methods for sub-arcsec star camera were presented. Temporal error (TE) was tested with static multiple stars target and collimator considering real signal level of the star camera. Stewart platform was used to adjust the camera with micro-steps, inter-frame difference method was applied to obtain relative distance of tie-points, then high spatial frequency error (HSFE) was calculated with statistics method with the benefit of avoiding planning special paths. Low spatial frequency error (LSFE) introduced by chromatic aberration was measured equivalently with different kind of optical filters; moreover, LSFE in distortion calibration and target measurement was calculated. Test is taken and the result is in line with design value, the validity of the above methods is verified.

CsI(Tl) scintillator is a key part for the transition from X-ray to visible light, its transition efficiency is of crucial importance in X-ray diagnosis for inertial confined fusion. X-rays could deposit energies into the CsI(Tl) scintillator and visible lights were emitted. The detection efficiency of CsI(Tl) scintillator with different thickness was calibrated on the beamline 4B7A at Beijing Synchrotron Radiation Facility in the energy range between 2 000 eV and 2 800 eV. Energy deposition and energy response with the stimulation of X-ray were studied. The whole system included emitting X-ray, standard detector, shutter, CsI(Tl) scintillator, black box and SI1000 CCD. Emitting X-ray was normalized with curve fitting. SI1000 CCD was used to receive the visible light which the counts were kept in the linearity range of CCD. The experiment gets the detector current, CCD counts, the ratio of CCD counts and emitting X-ray counts in the energy region from 2 000 eV to 2 800 eV. The results show the detection efficiency increase with the increase of the thickness of CsI(Tl) scintillator. The experimental method makes foundation for the subsequent selection of a suitable thickness of scintillator of soft X-ray detection.

In order to better realize the pointing function of GSSMP, the rotation accuracy of GSSMP needs to be measured and calibrated, the rotation encoder was calibrated with the laser tracker, and the angle measurement was completed with the laser tracker. First of all, based on the principle of angle measurement, the contact measurement and non-contact measurement methods of single point calibration precision and error of measurement were 23.7″ and 0.71″. It was proved by formula derivation that four Sphere Mounted retro-Reflectors (SMRs) can eliminate the harmonics of all orders other than the multiple harmonics of 6 improving the measurement accuracy. Finally, the angular measurement error of two different arrangement methods of four SMRs was compared, and the uniform distribution error was 11.5″, the non-uniform distribution error was 9.04″, and the measurement error of a single angular reflector was 23.7″. By measuring the rotation precision of the telescope′s azimuth axis with laser tracker, the correctness of the theory and the feasibility of the method were verified. The research were of great significance to the further completion of the work of the 30 m telescope.

According to the bomb falling point coordinate measurement of wide field under complex terrain conditions, a monocular vision measurement method combined with digital elevation model(DEM) was proposed. The object or scene information was not relied on in the method. The 3D coordinate of the bomb falling point can quickly be calculated with only one bomb fall image of single camera in the method. Firstly, the two-dimensional information of the image was used to solve the space linear that camera and the bomb falling point were connected; Then, according to the relative position of the camera and the target to determine the search starting point and step on the line, the line search and digital map of elevation were matched; Finally, the 3D coordinates of bombs were solved. Field test results show that when the distance between the camera and monitoring area is more than 500 m, and the width of the field of view is 300 m, the relative positioning error is better than 0.3%. The advantages of simple structure, low cost, fast operation speed, and is applicable to coordinate measurement of bomb falling point under complicated terrain conditions were proved in the method.的研究。

The reflectance of cirrus clouds is an important parameter in weather, climate and earth energy balance studies. The fast algorithm for calculating the reflectance of cirrus clouds plays an important role in the retrieval characteristics of cirrusclouds. Based on the variations of the reflectance of cirrus clouds with the relevant factors, such as cirrus optical thickness, effective particle size, solar zenith angle, observing zenith angle, the relative azimuth angle et al, a prepared Look-Up-Table(LUT) was developed by using DISORT to compute the reflectance of cirrus clouds. A fast algorithm for calculating the cirrus reflectance was established with utilization of the LUT. The cirrus reflectivity was calculated from the parameters of cirrus clouds, including cirrus optical thickness, effective particle size, solar zenith angle, observing zenith angle, the relative azimuth angle, which were read from the cloud products of MODIS. A comparison between the derived reflectivity with the proposed fast algorithm and the measured one was performed. The correlation coefficient is 0.94 and an average deviation is less than 18.5%. The result indicates that the fast algorithm for calculating cirrus reflectance is reasonable and feasible.

In order to reduce the influence of turntable′s errors on the calibration accuracy of SIMU, the position and the rate test plans of the regular icosahedrons-12 points were designed by using norm observation of the specific force and the angular velocity vectors. Firstly, the twelve static positions were utilized to calibrate the accelerometers′ biases, scale factors and mounting errors in the gravity field. Secondly, using single-axis rate and double-axis position mode, namely the outer axis of the three-axis turntable was working in angular rate mode, both the inner and the middle axes were in the twelve positions, the RLGs′ biases, scale factors and mounting errors were calibrated. At the same time, unification of the accelerometer and the gyro parameter coordinate systems was realized by using the SIMU frame coordinate system. Finally, simulation analysis shows that this method can effectively suppress the influence of turntable′s errors on the calibration results of SIMU, the relative calibration errors of the scale factors of the accelerometers′ and the gyros′, and the calibration errors of the installation error matrix are less than 10-5, the calibration errors of accelerometer biases are less than 10 ?滋g, the calibration errors of gyro biases are less than 0.01(°)/h which are in the same order of magnitude of the measurement noises, in the situation that perpendicularities between the turntable’s adjacent axis lines are at the arc second level and that angular position errors are less than 1′.

In order to get accurate data of external heat fluxes on space camera with two-dimensional changing attitudes, a method was proposed to calculate the external heat fluxes of space camera with two-dimensional changing attitudes in J2000 coordinate system. First, in J2000 coordinate system positions of space camera, position and radiation intensity of sun were calculated. Second, according to the working characteristics of the space camera whose visual axis always points to the sun and the position of the sun, its two-dimensional attitude angles were calculated under extreme conditions. Then, based on the obtained attitude angles, the attitude transformation matrix was calculated. Finally, in one orbital period external heat fluxes of unchanging attitude and two-dimensional changing attitudes were calculated with Matlab programming. The external heat fluxes of this paper were in good agreement with I-deas/TMG software. Compared with the unchanging attitude camera, external heat fluxes of the two-dimensional changing atitudes camera will have a great change, especially for the -Y surface where optical entrance is located. The solar radiation heat fluxes fluctuation range of -Y surface is 0-1 394 W/m2. The obtained attitude angles provide an important reference for the adjustment of the attitude for the thermal simulation model. According to the data of the external heat flux with changing attitudes, it can be seen that the external heat fluxes of the -Z surface is smallest, and the maximum average period external heat fluxes of -Z surface is less than 4 W/m2. In addition, the external heat fluxes of the ±X surfaces and +Y surface are smaller, and the maximum average period external heat fluxes of ±X surfaces are less than 80 W/m2, and the maximum average period external heat fluxes of +Y surface are less than 110 W/m2. In practical application, the external heat fluxes of ±X surfaces and +Y surface will be smaller due to the obstruction of the satellite platform. Therefore, the -Z surface, ±X surfaces and +Y surface can be used as heat dissipation surfaces, which provides a good guide for thermal design work.

In order to obtain 3D moving trajectory of non-rigid object with point feature, two calibrated high-speed cameras were used. A practical 3D motion recovery method of non-rigid object with point feature was proposed. The method included image spatial reconstruction, temporal series reconstruction and other steps. The spatial reconstruction and temporal series reconstruction were the core of 3D motion recovery. In spatial reconstruction, the coordinates of the points on the image were obtained by using ellipse fitting method, and the matching points were searched according to the Mahalanobis distance. Then, triangulation was used to calculate the 3D points. In the aspect of temporal series reconstruction, the searching method was used to match the coordinates of the points between sequential images. So, the 3D motion recovery of the movement process was realized. Then, the reconstruction result was used to calculate the parameters, such as speed, acceleration and curvature change of the non-rigid object. The experimental result shows that the method improves the speed and accuracy of the spatial matching and realizes the temporal series matching simply and effectively. What′s more, the time of the whole reconstruction process is reduced. Through the reconstruction of the target, the 3D motion data of the object is obtained accurately.

Modulation of laser′s left-handed and right-handed polarization was used in the paper. This method has realized all-optical detection of magnetic field and avoided cross talk existing in conventional atomic magnetometer. The detection principle of precession frequency of atomic magnetic moment in magnetic field was demonstrated based on the method, and the signal was analyzed, then the detection and processing system was designed based on the analysis. The in-phase signal was displayed as Lorenz lineshape. The quadrature signal was displayed as dispersion lineshape, and the magnitude was 0 at resonance frequency. The phase signal was displayed as monotonically decreasing function with frequency, and the magnitude was 0 at resonance frequency. Both the quadrature and phase signals can be used to lock resonance frequency and realize measurement of magnetic field.

Based on the basic structural unit of SiO2/Al/SiO2, the optical constants of thin Al films were obtained accurately by fitting the multi angle ellipse polarization spectrum and the transmittance spectrum. And the influences of the thickness of Al film on the optical constants was also studied and analyzed. Theoretically, the three cavity UV induced transmission filter was obtained by using the admittance matching method. And the influence of preparation error of Al and SiO2 dielectric matching layer on the spectral properties of UV filters was systematically analyzed. Based on the low temperature, the high vacuum growth process of Al and SiO2 thin films, the high performance three cavity UV induced transmission filter were successfully prepared. The peak wavelength was located near 218 nm, and the peak transmittance was ~23.1%, and the bandwidth was ~32 nm. The transmittance in the 280 nm, 318 nm bands were about 0.5% and 0.04%, respectively. The cut-off rates of the samples were about 5.0 OD and 4.5 OD in the range of 400-700 nm and 800-1 100 nm, respectively. The results of this study have a good theoretical and practical significance for depositing the visible-near infrared band deep cut-off and UV induced transmission filters.

In order to improve the S/N ratio, reduce the dark current and develop the solar-blind photodetectors with high performance, the dark currents of the AlGaN solar-blind ultraviolet avalanche photodetectors were studied. Firstly, the conventional p-i-n-i-n avalanche photodetectors were examined using two newly designed models of avalanche photodetectors in GaN and AlGaN. Different characteristics of dark current were analyzed and the simulation of the dark current matched the experimental data well. Based on this, the effects of the negative polarization charge at different heterogeneous interfaces, the p-type effective doping and temperature on the dark current in high Al content AlGaN solar-blind avalanche photodetectors were investigated in detail. Results show that the dark current of the AlGaN solar-blind ultraviolet avalanche photodetector is about 2.5×10-13 A near zero bias, the avalanche breakdown occurs at about 138 V in reverse and the open current is about 18.3 nA, temperature coefficient for the breakdown voltage is about 0.05 V/K, which are all consistent with the experiments and the literature results well.

For the application requirements of the indoor lighting scenes, the effect on the frequency characteristics of four types common LEDs caused by the drive current fluctuations was researched, and the conclusion was that the frequency characteristic response of the phosphor LED was almost unaffected by the drive current variations. Combined with the hardware pre-equalization strategy, the theoretical analysis and the hardware circuit design to expand bandwidth of the 1 W phosphor LED were done. The experimental results prove that without the blue filter, the modulation bandwidth of the phosphor LED is increased from 1 MHz to 32 MHz, and 26 Mbit/s phosphor LED VLC covered 3 meters communiations distance using non-return-to-zero on-off-keying(NRZ-OOK)modulation is realized with bit error ratio of 7.55×10-6 , which meets the requirements of the transmission distance in indoor VLC system.

In order to improve the luminous efficiency of conventional GaN-LED, a transmissive surface plasmon enhanced GaN-LED based on nano-grating was proposed. The enhanced LED included a low refractive index SiO2 film and a Ag film in the p-GaN grating slot, and the top layer ITO film. The basic principle of improving LED emission characteristics for this new structure was described in detail, and with simulation software "COMSOLTM-RF Module" based on the finite element method, the parameter optimization and numerical simulation analysis for the structure were studied. The results show that when the period p=280 nm, the duty ratio f=0.5, d■=25 nm, dAg=15 nm, dITO=30 nm, the transmission efficiency of the structure is higher in the visible range, and the 0th order transmittance is 0.716, the 0th order reflectivity is 0.224, the peak of the -1st order transmittance is 0.183, with Purcell factor enhancing nearly 16.4 times. The internal quantum efficiency, light extraction efficiency and SPP extraction efficiency can be improved simultaneously in this new GaN-LED.

The effects of γ-ray irradiation on the subsequent time-dependent dielectric breakdown (TDDB) of partially depleted (PD) silicon-on-insulator (SOI) MOS devices were investigated. By testing and comparing the transfer characteristic curves, threshold voltage, off-state leakage current, the TDDB lifetimes and other electrical parameters of the NMOS and PMOS devices before and after irradiation, the effects of γ-ray irradiation on the TDDB reliability of the devices were analyzed. The results show that the positively charged oxide trap charges induced by γ-ray irradiation in the gate oxide layer affected the distribution of the internal barrier of the device, and reduced the height of the barrier of the electron transition. Therefore, the positive feedback effect of electron tunneling is enhanced and the TDDB lifetime of the device is reduced, resulting in a reliability degradation of the gate oxide of the devices.

In order to improve the air-stability of organic-inorganic lead halide perovskite, two kinds of all-inorganic perovskite CsPbBr3 nanocrystals with different sizes were synthesized by high temperature hot-injection method. Because the nanocrystal size plays a key role in determining electrical performance of nanocrystal film, the effect of CsPbBr3 nanocrystal size on the photoelectric response of thin film photoconductive photodetector was studied. The results show that the photocurrent of nanosheet film is 100 times higher than that of nanocube film, resulting from the large carrier diffusion length of 2D CsPbBr3 nanosheet film with less boundary. Finally, an overall performance evaluation on nanosheet film photodetector with higher photoreponse was conducted, and low noise equivalent power and high specific detectivity demonstrate its good weak light detection capability.

At present, there has been great progress in the field of the point-to-point laser communication technology. In order to search for an effective means of achieving localized laser broadcast communication within a limited range, an effective method of horizontal link laser broadcast communication was presented, and the corresponding verifiable broadcast communication system was designed. In addition, the laser broadcast was systematically studied by one physical model built at the optimal distribution of optical power. First of all, the theoretical model of laser beam expansion and the theoretical model of parallel light curtain were made comparisons and analyzed from the angle of attenuation of optical power, and the optical power loss model of the parallel light curtain was established as a result. Secondly, combined with the theory of optical imaging transformation based on Gaussian beam, the field distribution of far field of parallel light curtain was simulated by one leading optical and illumination design software and the relation between the filed distribution of far field of light curtain and the distance of transmission was revealed. Finally, the superiority and feasibility of the parallel light curtain theory model were verified by field communication experiments in different information channels.

In the dual Mach-Zehnder perimeter security system, it is difficult to achieve pattern recognition accurately and efficiently. To solve this problem, a pattern recognition method based on short-time Fourier transform(STFT) and singular value decomposition was proposed. In order to realize the accurate distinction of three different events, the method consisted of three steps. Firstly, the time-frequency information was obtained by the short-time Fourier transform of the interference signal, finding the event endpoint and filtering the signal according to the information; And then, the singular value of the time-frequency information was got. The characteristic vectors were defined by the characteristic of singular value, according to the physical meaning of the singular value. Finally, SVM was used to classify the events. In order to verify the effectiveness of the method, a fence system of 2 km long for experiment was built. 360 sets of interference signal data of three events (climbing the fence, knocking the cable, and waggling the fence) were collected, each event had 120 sets of data. The result of experiments demonstrates that the proposed scheme can discriminate three common invasive events with a high recognition rate. The recognition rates of the three events were all above 90%. The scheme also improve signal processing speed of the system, which has high application value．fiber sensing; signal analysis

A dispersion flattened fiber (DFF) transmission system was proposed with high bitrate, polarization multiplexing and quadrature amplitude modulation(QAM) signal. The modulation format of the system was PM-16QAM, the bitrates were 160 Gbps and 256 Gbps. The transmission characteristics over DFF link system were experimentally studied, which were compared with those of non-zero dispersion shifted fiber (NZDSF) link and standard single mode fiber (SSMF) link. The experimental results show that the Error Vector Magnitude (EVM) of 160 Gbps and PM-16QAM over 50 km DFF link is 0.5% better than those over 50 km NZDSF link, the BER is 2 orders of magnitude better than that of NZDSF, and the DFF link can better reduce side-mode noise. When bitrate is 256 Gbps and transmission distance are 50 km and 75 km, the PM-16QAM signal can be well demodulated only after the DFF link. And the longer the transmission distance, the smaller the input optical power range is while maintaining good characteristics. Comparing 160 Gbps with 256 Gbps, high bitrate PM-16QAM signal transmission characteristics over the DFF link are superior to those over NZDSF and SSMF links. The higher the transmission rate and the longer the transmission distance, the more obvious the transmission effects are.

In order to design large-aperture mirror with light weight, high rigidity, high accuracy characteristics for the space telescope, a mirror topology optimization method based on the level set method was promoted. Firstly, a finite element model based on the 1-meter aperture mirror body initial structural model was constructed. The surface shape aberration RMS of the mirror was used as the objective function, which was constructed by the DRESP2 technique in Optistruct based on SIGFIT. With the weight constraint, the topology methods based on SIMP and level set method were used to optimize the structure separately during the design process. The separation threshold of the design result was studied based on the OSSmooth function. By analyzing the separation threshold of optimized model, the optimized exported structural model could be achieved. The number of elements with the middle density using the level set topology optimization design method is much smaller than level set method, and the connectivity of the structure is much better. The surface shape RMS value of the optimized model is smaller than λ/50(λ=632.8 nm), which satisfies the technique specification.

Surface error and alignment aberration of mirrors are required precision uniform in space transmission coaxial three mirror system alignment． Based on force analysis and system simulation methods for efficient alignment of the coaxial optical systems, one coaxial three mirror system with large aperture and long focal length was used to illustrate the relationship between aberration characteristics to alignment aberration and surface error． The spherical aberration, coma and astigmatism caused by alignment aberration and surface error were calculated, then wavefront RMS was used as an evaluation standard for system imaging quality. Finally, the weight of alignment aberration and surface error to system imaging quality were obtained． Based on the calculated result, the average RMS was adjusted to below 0.06λ. The lens alignment results demonstrate the possibility and effectiveness of this method, and the proposed methods could be available to shorten the alignment process, and promote system alignment accuracy．

The special requirements of an Electro-Optical(EO) image seeker for large scanning angle of small window, and the Multidisciplinary Design Optimization(MDO) design method was used in the overall design to get the optimum solution. The subspace parallel design with multi-scheme rapid conceptual design was carried out, and through the permutation, combination, and optimization, these schemes could be transferred to the constraints of engineering design, and distributed the design weight of opto-mechanical structure and servo stabilization system. Then the design schemes were dynamically assessed and iteration optimized, and got the final scheme of gyro stabilized mirror objective space scanning: the scanning range is -20°-10°(pitch)/+15°(azimuth), the window area is no more than 2 times of the entrance pupil aperture, and satisfied the dimensional requirements and the image stabilization ability with high-precision and high dynamic range. The image obtained by flying test is almost the same as the ground static test image, and proves that MDO has the effect and superiority of rapid development of the EO stabilized platform.

The principle and optical design method of cooled off-axis reflective optical systems were analyzed. An optical system design of a cooled off-axis three-mirror optical systems based on freeform surfaces was presented. This cooled off-axis three-mirror optical system was composed of two freeform surfaces and one even aspherical surface, which was a re-imaging structure with cold stop as the optical stop that could ensure 100% cold shield efficiency in the optical system. The optical stop could be imaged at the position of the first mirror by the second mirror and third mirror, which could reduce the size of the first mirror obviously. With the three mirrors optimized after optimization design including tilted and decentered methods, the system unobscured could be achieved and the freeform surfaces could be used to enlarge the field of view, correct image aberrations and improve the total image quality of the system. This system is with 450 mm focal length, 3-5 μm working waveband, 2 F-number, 3.662°×2.931° field-of-view. In addition, the modulation transfer function(MTF) of the system is above 0.5 all over the field of view with the working temperature range from -40 ℃ to 60 ℃. The result shows that the system has compact structure and athermalization achievement.

Considering the complexity of internal structure and optical path of the off-axis three-mirror system, it is difficult to directly analyze the effect of deflection error of each mirror inside the off-axis three-mirror system on the line-of-sight. Therefore, a method of simplifying the off-axis three-mirror system model was presented to a single-mirror system model for analysis. Then, based on the model of single reflection system, the formula of the deflection error of the off-axis three-reaction was derived. Finally, the model of off-axis three-mirror system was created by Zemax software, the change of the line-of-sight of the system was simulated by adjusting the position of the mirror and the coordinates of imaging can be obtained, then the deflection value of the system′s line-of-sight was solved by substituting the image coordinates into the calculation formula. From comparing the results, the maximum error of the deflection of the line-of-sight relative to the deflection of the line-of-sight in the simulation is not more than 4%, which verifies the correctness of the theoretical analysis based on the single reflection model.

The importance of complete supplemental lighting system was also more obvious with the continuous improvement of China′s "safe city" project. Firstly, the function and classification of the supplemental lighting system, the advantages and disadvantages of the present supplemental lighting system in the intelligent transportation system were expounded. To solve glare and overexposure these two problems in the supplemental lighting system, an anti-glare supplemental lighting system based on array light emitting diode mixed with infrared and white light was designed. Its hardware and software based on field programmable gate array (FPGA) adaptive algorithms were completed, and its effects were tested in the meantime. The test results show that its supplemental lighting effect is better than the white light, and the glare is significantly reduced. Besides, the binarization distribution of license plate images is even. And it is proved that the anti-glare supplemental lighting system could effectively solve the overexposure problem of the license plate.

Based on application scenarios of infrared target simulator dynamic calibration system, the design characteristics of the optical system in dynamic calibration system were analyzed, then it was pointed out that the optical system should select the refraction-reflective secondary imaging optical structure. Based on the classical optics athermal principle, refraction-reflective system athermal methods was refined by calculating then matching the optics and machine material precisely. By the method, a optical system with F/2, focal length of 370 mm, working band of 3.7 to 4.2 ?滋m, total length of 182 mm was designed. The optical system selected 512×512, 15 ?滋m×15 ?滋m specification Stirling refrigeration detector, and imaging quality in the -40-60 ℃ was close to the diffraction limit. The ghost and Narcissus analysis models were established, the results show that the optical system has strong ability to suppress stray light and others excellent performance. The optical system satisfies the requirement of dynamic calibration system of infrared target simulator used in complex harsh environment.

In order to generate optical vortex with high topological charges, theoretical analysis, simulations and experimental demonstration of quadrupling topological charges of vortex based on spiral phase plate were presented. According to Fresnel diffraction integral, theory of quadrupling topological charges was analyzed. Setup of quadrupling topological charges based on one spiral phase plate was designed, then mathematical model was built and relative intensity of vortex after quadrupling was simulated. Simulated graphs of relative intensity and optical radius were plotted, the radius and intensity were smoothly changed during the quadrupling. Finally, vortices with topological charges 4, 8, 12, 16 were generated and the reason why vortices with high topological charges generated by quadrupling were of poor quality was analyzed.

A frequency-quadruple microwave signal method based on dual-parallel Mach-Zehnder modulator (DPMZM) was proposed. The frequency-quadruple principle was theoretically analyzed. The upper sub-MZM of the DPMZM was modulated by RF signal and operated at the maximum transmission point (MATP), while only an optical carrier was obtained from the bottom sub-MZM of the DPMZM. Then the DPMZM worked at the carrier-suppressed even-order sideband modulation mode. In order to improve the purity of quadruple frequency signal, optical bandpass filter(OBPF) was used to remove the high-order spurious sideband. Microwave photonic frequency-quadruple system was built based on DPMZM, and its performance was tested experimentally. The results demonstrate that the optical sideband suppression ratio (OSSR) and radio frequency spurious suppression ratio(RFSSR) can reach 21.09 dB and 28.41 dB, respectively. Since no extra electronic devices were used, the system can generate radio frequency with frequency up to 80 GHz. DPMZM based microwave photonic frequency-quadruple system had the advantages of simple structure, convenient operation and good frequency-quadruple performance, which can realize high purity and high frequency quadruple frequency generation.

In view of the requirements of high sensitivity, high detection ability and high signal-to-noise ratio of ground-based space exploration infrared imaging system, cold optical infrared imaging technique was studied. It included infrared Dewar cooling system, internal radiation suppression, rapid cooling of terminal system, development of low temperature infrared detector, room temperature adjustment, low temperature application and other key technologies. Based on the technical breakthrough of various systems, a cold optical infrared terminal with a relative aperture of 1:10, resolution of 320×256, compatible with medium wave 3-5 μm and long wave 8-10 μm band was developed. The system terminal works in 42 K temperature, 10-5 Pa vacuum environment. Docking with 1.23 m ground-based telescopes, a good observation result of moon and infrared stars was achieved. It lays an important foundation for ground-based infrared optical detection technology.

In order to increase the detection capability of infrared modulated thermography for defects in composite materials, an infrared image sequence processing method using the complex Morlet wavelet phase analysis was studied. According to the modulation frequency of thermal excitation and the sampling frequency of infrared imaging, the total number of scales used in wavelet transform was selected adaptively, and then a phase image sequence was reconstructed from the raw thermal image sequence by using the complex Morlet wavelet coefficients. An experiment of modulated thermography was performed on a glass fiber reinforced plastic reference sample containing delamination defects, the application effects of the method were quantitatively evaluated and compared with the Fourier transform method by the signal-to-noise ratio. The results show that the complex Morlet wavelet phase method can separate the low frequency and high frequency noise from the thermal image signal, and extract the subsurface defects at different depth robustly; it keeps a good tolerance to the change of the modulation frequency; so it is an effective algorithm of the modulated thermography.

Exhaust plumes of solid rocket motors involve complex flow state, afterburning and radiation effects, which have an important role in the operations of detecting, indentifying, and tracking. To investigate the characteristics of afterburning and radiation effects under different flight conditions, the computational fluid dynamics method and the finite-rate ratio model were used to simulate the flow properties with chemical reactions, and line of sight method was utilized to solve the radiation transmission equations. The influence of afterburning effect on the radiation characteristics of different heights was analyzed. The results show that the afterburning effect can cause the flame temperature rise to 1 000 K, and increase the radiation brightness of the flame band more than 10 times. For different bands, the radiation brightness rises and then decreases along with the height. The maximal position is 20-30 km, with about 17 times radiation enhancement in the short wave 2.7 μm waveband and about 16 times in the 4.3 μm mid wave waveband. It can be seen that the contribution of the H2O molecule caused by the afterburning is greater than that of the CO2 molecule. Theses can provide reference for further theoretical research and engineering application.

The model of infrared system imaging blur effect caused by carrier platform vibration was studied. Considering the theory of infrared system imaging and the vibration regularity of carrier platform, the model of infrared system imaging blur effect caused by carrier platform vibration was established. The pre-generation method of the blur effect texture was studied, on the basis of which the real-time sampling method of the texture mentioned-above was built. Then the infrared system imaging blur effect was simulated dynamically. The degradation degree of the infrared system imaging quality under different vibration conditions was quantitatively analyzed. The results show that, the increase of carrier platform vibration amplitude or frequency would result in more serious degradation of the infrared system imaging quality; Furthermore, the farther the observation distance is, the worse the carrier platform vibration influence on the system imaging quality is.

Due to the development of the satellite laser ranging technology, high orbit satellite laser ranging data volume increases significantly, but high orbit satellite has weak echo signal due to the distance, which requires the telescope system to align satellite accurately in order to receive the valuable echo signal. In this paper, the main factors that affecting the telescope to aim were analyzed, namely satellite velocity aberration and flight-time aberration of laser pulse. Based on Glonass series high orbit satellite as an example, the aberration offset was mainly studied, introduced laser operation, and the station measurement of Glonass satellite series aberration angle offset of 26 μrad was calculated, and in the actual series of Glonass satellite in high orbit satellite laser ranging dozens of times ranging experiment verification. In this paper, it proved that optical line difference influences analysis is correct. Through the research we can improve the capture probability of high orbit satellite laser ranging and greatly enhance the efficiency of observation.aberration compensation

The laser echo signal will cover the certain range while laser ranging to space targets through transmitting laser signal from the ground station. The number of laser echoes per unit time will be obviously increased through utilizing multi-telescopes to receive signal on ground. It′s very helpful to enhance the detection ability of measuring space targets for laser ranging system. According to laser ranging link equation and the theory of signal detecting probability, the analysis of the effect on the detecting probability of laser ranging system with multi-telescopes to receive laser signal was performed to research on the equivalent receiving ability. Based on the 1.56 m aperture of astronomical telescope about 60 m far from the 60 cm telescope at Shanghai Astronomical Observatory, Chinese Academy of Sciences, the activity of laser ranging to artificial satellites with retro-reflector was implemented to research on the detecting ability of dual-telescopes while simultaneously receiving laser echo signal. The number of laser echoes had increased by 4 to 5 times compared with the aperture of 60 cm telescope system. The effect on increasing the detecting ability of measuring space targets was obvious. Considering the laser measuring ability of 1.56 m telescope system, the equivalent receiving aperture of 1.61 m can be derived for 1.56 m/60 cm telescopes. The analysis on the detection ability of laser ranging to space targets with the orbit height of 1 000 km and the size of 10 cm and number of receiving telescopes were also performed. From the experiments the technical feasibility and advantage of multi-telescopes to receive signal are validated, which will play an important role in the weak signal detection and laser ranging in future.

In order to realize the remote sensing detection classification and identification of the rotor, the laser echo feature of extended rotor target based on micro-Doppler effect was studied. The micro-Doppler coherent laser echo model of moving extended rotor was built with the panel method of physical optics. Angular scattering characteristics of laser were analyzed and calculated, which proved that rotor had the same echo reflectivity everywhere under the far field condition. Laser detection echo of three typical rotor shapes was simulated, and the time-frequency features of extended rotor were achieved by Smooth Pseudo Wegener-Villy(SPWV) transform. The electromagnetic scattering mechanism confirms that each frequency band was related to the shape of the rotor, and the number of blades does not affect the expression of features of rotor shape in time-frequency figure as well as the moving velocity. The laser detection calculation methods of rotor shape parameters, including aspect ratio, root-tip ratio and sweep angle of rotor tip, were proposed and proved to be correct through simulation, which layed the foundation for rotor identification.

Porosity defect is the main problem for the double-sided laser beam welding of aluminum alloy T-joints. Based on its technology characteristics, the effects of the surface states, laser incident angles, welding speeds, heat inputs and laser distances on the porosity defects were studied in this work. The results indicate that the pure aluminium cladding layer is beneficial for reducing porosity defects. Using larger laser incident angle and welding speed are good for reducing porosity defects, the reason is that the fluid flow changes from convection to toward to keyhole, which can help pores escape from the weld pool. And, reducing heat input and increasing laser distance are bad for reducing porosity defects, the change of the keyhole shape and fluid flow are the essential reasons. It is necessary to ensure keyhole symmetry and pass-through, which can help the pores escape from the weld pool and reduce the number of the porosity defects.

Laser treatment on dentin has been considered a new method to bring better adhesive effect.The purpose of this study was to observe the ultrastructure of dentin after the treatment of Er:YAG laser by scanning electron microscopy（SEM）and to assess the possibility of laser treatment on dentin to improve the adhesive properties between tooth and restoration. A total of 8 freshly extracted sound human maxillary third molars were prepared according to occlusal veneer. Extracted teeth were treated by Er: YAG laser after tooth preparation. The ultrastructure of dentin was observed by SEM. They were divided into 2 groups, 4 for the control group and 4 for the experimental group. After tooth preparation, the dentin of the experimental group was treated by Er:YAG laser. The specimen were observed by SEM including dentinal tubules, melting and fissure etc. It was observed that in the experiment group there was no smear layer, and the dentinal tubule was clear. Meanwhile, in the control group, there was obvious smear layer in the dentinal tubule therefore the dentinal tubule was not clear. This study suggests that Er:YAG laser treatment on dentin after tooth preparation can remove smear layer in the dentinal tubules, which may improve the adhesive properties between tooth and restoration.

Laser beam combining technique allows increasing the power of laser radiance far beyond what is obtained from a single conventional laser. Moreover, this technique is also able to control the far-field laser combining intensity distribution. Based on the theory, the principle of coherent combining of lasers from multi-core linear fiber array was studied. By using the coherent synthesis model, the coherent combining effect of multi-core linear fiber array was numerically simulated by MATLAB when wavefront of the lasers with and without random phase noise respectively, and the feasibility of angle scanning using actively phase-controlling was analyzed. The coherent combining angle scanning control system was built based on MOPA laser linear array fibers. The experiment shows that active phase-controlling of the laser linear array is able to realize the angle scanning of the main maximal stripe, and the scanning range is between two secondary large stripes. The experimental results are consistent with the theoretical calculation, and that has a guiding significance to the application of coherent combining of linear fiber array lasers.

Considering the optical focusing system in need of compact structure, the small focus spot size and avoiding the plume pollution in laser ablation micro thruster, the traditional ray tracing method was used to study the two typical optical design methods of single lens direct focusing and double lens for collimation and focusing. In the condition of fiber core diameter and numerical aperture for the low power semiconductor laser output and the design requirement of 50 micron focus light spot, the relationship between the design parameters of the lens thickness, the focal length and the working distance was obtained for the single lens focusing system. On the other hand, the relationship between design parameters such as lens thickness, lens center distance and working distance were also discussed, in the light of the design scheme of the double lens system for collimated focusing optical system. According to two typical schemes, the engineering application design parameters were given. The design method proposed in this paper avoids the complicated optical design process and provides a simple and practical method for the laser beam microscale focusing.

In order to improve the measurement accuracy, the high accuracy measurement model of laser triangulation method was proposed, which consisted of variable threshold subpixel grayscale gravity center extraction algorithm and CCD tilt error compensation algorithm. The spot centering algorithm played a decisive role in the accuracy of laser detection. A variable threshold subpixel grayscale gravity center extraction algorithm was proposed according to the defect of the existing laser center localization algorithm. The gradient function and the Gaussian fitting algorithm were used to set the threshold to remove the effect of spot edge noise region on center location, and the polynomial interpolation were used to improve the precision of grayscale gravity method. CCD tilt error compensation algorithm was established to further improve accuracy. The system was established with STM32F407 as the hardware core. Taking taper thread as the measured object, the test was carried out. The results show that the laser spot can be accurate acquisition by the high accuracy measurement model. Precision is obviously higher than the traditional grayscale gravity center method, and successfully controls the error within 10 microns.

Aiming at the mapping requirements of forestry, architecture, offshore, island reef and beach, the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has developed a prototype of airborne dual-frequency laser radar. It can simultaneously carry out mapping of terrain and submarine terrain. The prototype has been tested in Wuzizhou Island of Sanya with a maximum detection depth of 30 m, equivalent to 50 m under class A water quality conditions, the minimum detection depth of 0.22 m. Depth data and single-beam sonar data comparison error is 0.108 m, ranging data and field-measured data comparison error is 0.18 m. The results are in accordance with the design expectations.

Simultaneous wind measurements in stratosphere with high-spatial resolution for gravity waves study are scare. In recent years, lots of gravity waves cases were observed by mobile Rayleigh Doppler lidar of University of Science and Technology of China benefiting from the system with excellent performance. In this paper, a brief introduction of the Rayleigh Dopplar lidar system was made. The wind field gravity waves cases in the altitude region 15-60 km were also performed, which were carried out for 2 months started from October 7th, 2015 in Jiuquan(39.741°N, 98.495°E), China. After the 2-D fast Fourier transform of those mesoscale fluctuations of the horizontal wind velocity, the two dimensional spectra analysis and band-pass filter results of these fluctuations exhibited the presence of dominant oscillatory modes with wavelength of 4-15 km and period of around 10 hours in several cases. The observed cases demonstrate the Rayleigh Doppler lidar′s capacity in measuring and studying gravity waves.

Because of the requirement of autonomous navigation, an integrated lidar of ranging and communication based on pseudorandom code modulation was proposed. The system had the advantages of low power consumption, small volume and multi-function. Adopting pseudorandom code, the lidar system realized the integration of ranging and communication. Adopting silicon photomultiplier (SiPM) to achieve photon counting realized the miniaturization of lidar system. The design principle, component, simulation, and the experiment result of the system were introduced in detail. The result shows that the maximum detection range can reach 1 km for the target with 0.1 reflectivity under daylight, and the range resolution is less than 1 m. The maximum communication range can reach 3.7 km with 10 kbps code rate and error rate less than 10-5.

Underwater 3D triangular range-intensity correlation imaging(RICI) is a novel scannerless 3D imaging technique beyond underwater visibility range, and can fill the current gap between short-range high-resolution conventional video cameras without 3D information and long-range low-resolution sonar systems. The development of 3D RICI was reviewed, and the introduction of 3D triangular RICI in the Institute of Semiconductors, CAS was focused. A 3D triangular RICI with multi-pulse time delay integration method was proposed, and the typical time parameters in the method were given. The prototype 3D range-gated imaging systems of Lvtong, Fengyan, Longjing were established, and can realize 3D imaging with 1 360 pixel×1 024 pixel beyond the visibility range of 4.8 AL. The systems have been used in fishnet detection, marine in situ detection, underwater target detection and recognition.

The encapsulation of ultrafine DFB fiber laser hydrophone probe was studied. A theoretical model of encapsulation structure was built by finite element method. The factors affecting the frequency response and sensitivity fluctuation of ultrafine fiber laser hydrophone were discussed. A balance was found upon sensitivity, frequency response consistency and other indexes. Finally, a fiber laser hydrophone was made. Its diameter was 6 mm, length was 55 mm, sensitivity was -130 dB and sensitivity response fluctuation between 100 Hz -2 kHz was 4 dB. The conformity of theoretical analysis and simulation was verified by experimental test.

China is in the critical period of implementing the strategic deployment of the 21st Century Ocean "Silk Road". The development of ocean optical technology is an important direction to support the country′s medium and long-term development strategy. Ocean laser remote sensing technology is one of the important research fields in ocean optics. As a new active remote sensing technology developing rapidly in recent years, lidar has been widely used in the field of ocean laser remote sensing because of its high precision and high spatial-temporal resolution. In this paper, based on Brillouin scattering lidar and ocean imaging lidar, the research progress of ocean laser remote sensing technology and its application in water parameter measurement, underwater target detection and laser remote sensing of ocean topography in China were introduced.

The colored fraction of dissolved organic matter, CDOM, directly influences water optical properties and spectral quality, playing an important role in aquatic ecosystems, optical remote sensing and carbon circulation in the sea. Measuring in situ CDOM absorption coefficient, however, is difficult because it requires prefiltration of water samples. An analytical laboratory and field instrument for fast diagnosis of chromophoric dissolved organic matter(CDOM) in water was developed. The laser fluorometer was integrated with spectral fluorescent signature(SFS) analysis of the laser stimulated emission excited at 405 nm and hyper spectra for surveillance of CDOM. CDOM and water Raman scattering components were derived from the laser stimulated emission spectra measured in the laboratory and field conditions with SFS technology, which added to analytical Lidar sensing the capability of detecting and identifying trace substances in a variety of targets in the presence of other background matters responding to optical excitation with overlapping signals. The influence of temperature change on CDOM fluorescence data in water was investigated in laboratory, and a temperature calibration method was employed for calibrating fluorometer data. Laboratory and in-situ studies with the laser fluorometer in the East China Sea (ECS) in April 2013 were carried out. Significant and positive correlation in the ECS was observed between CDOM absorption measurements and CDOM fluorescence (R2=0.83). The result demonstrated the possibilities of CDOM monitoring in real time based upon the laser fluorometer.

A diversified array optical receiving antenna was designed for the problem of alignment difficulty in underwater wireless laser communication systems. The optical structures of the composite optical receiving antenna and diversity array optical receiving antenna were designed by the optical design software Zemax, and the field of view angle, the light gathering efficiency and the light source moving range of the two kinds of antenna were analyzed. Besides, the light gathering efficiency as a function of the light source moving range and the incident angle of the light source of the two kinds of optical receiving antennas was given by experiments and Matlab simulations. The results show that when the light source size is 10 mm, the light gathering efficiency of the composite optical receiving antenna is 0.06%, the receiving field angle is ±6°, the moving range of the light source is ±6 mm. And the light gathering efficiency of the diversity array optical receiving antenna is 0.06%, the receiving field angle is ±16°, the moving range of the light source is ±22 mm. Therefore, the diversity array optical receiving antenna was more suitable for underwater laser communication systems.

An optical passive imaging interference system (OPIIS) was proposed for the real-time and long-term detection of hydrothermal methane′s concentration, temperature and pressure. Firstly, the forward model that consisted of deep ocean gas emission model, seawater transmission model and instrument responding model was built by interface description language (IDL), and its forward interference fringers were simulated. The SNRs of the forward interference fringes were in the range of (50-70) in general. And the detection sensitivity of concentration measurement is was at least 0.1 mmol/L, the temperature was at least 2 K, and the pressure was at least 0.1 MPa. Then, OPIIS′s data were processed accurately and rapidly by combining imaging interference technology and partial least squares (PLS) algorithm. The multi-dependent variable PLS regression model of methane was established by using 25 modeling samples, and this PLS regression model was cross-validated by using 25 prediction samples. And the max error for concentration prediction of this regression model was 1.9%, for temperature prediction was 0.38%, and 1.0% for pressure prediction.

Six groups of HfO2-SiO2 mixed films with SiO2 content about 0, 13%, 20%, 30%, 40% and 100% were prepared using ion-assisted e-beam co-evaporation process separately. The Young′s modulus and hardness of the mixed films with different SiO2 content were measured through nanoindentation, and the variation of Young′s modulus and hardness as a function of SiO2 content were studied. The results show that with the increase of SiO2 content, both the Young′s modulus and hardness of the mixed films decrease, and the variation of Young′s modulus of mixed films as a function of SiO2 content can be well fitted by iso-stress model of a two-component composite. In order to illustrate the relation between SiO2 content and mechanical properties of the mixed films, the microstructure of the mixed films was analyzed by XRD, and the influence of microstructure on Young′s modulus and hardness were studied. It was found that the crystallization of thin films had major impact on hardness, but little influence on Young′s modulus. The residual stresses of the mixed films were calculated using the data of surface shape measured by Zygo interferometer, the variation of stress as a function of SiO2 content was obtained, and a reduction of compressive stress with the SiO2 doped in HfO2 was observed.

In order to prepare electromagnetic wave attenuation materials in wide-band, the hydrothermal method was used to prepare graphene/copper nickel ferrite composite (CNFRGO), and the composite was characterized by SEM, XRD, IR and Raman spectrum. Secondly, the electromagnetic parameters of the composite were measured at 2-18 GHz. Moreover, the loss tangent and reflection loss were calculated to analyze its microwave attenuation performance. Finally, its complex refractive index in IR band was measured, and its extinction and absorption properties were calculated and analysed by using the measured data and the T matrix method. The results show that the spinel-type copper nickel ferrite nanoparticles are adsorbed on the surface of reduced graphene oxide, and the particle size is mostly around 20 nm. CNFRGO have both dielectric and magnetic loss, and the bandwidth of its reflection loss lower than -10 dB is 3.7 GHz, and its peak is -14.7 dB at 11.8 GHz. In near-IR band, the strong extinction of CNFRGO is mainly caused by scattering. It′s mainly due to absorption in middle and far IR band, and its absorption ability in near and middle IR band is strong, but it′s relatively weak in far IR atmospheric window. Therefore, microwave and IR radiation can be absorbed simultaneously by CNFRGO, and it′s a good microwave and infrared compatible material.

Traffic sign detection is an important function for driver assistant systems, but the high real-time requirement makes it a very challenging task. A high-performance prohibitory traffic sign detection VLSI (Very Large Scale Integration) architecture was presented. Both color and shape characteristics were utilized in the proposed architecture by detecting circles using circular Hough transform in the red edge bitmap. The local property of circular Hough transform was exploited so that the memory requirement was significantly reduced comparing with common architecture. All the radii were voted concurrently to make full use of the parallelism of logic elements and memory in FPGA. The proposed architecture was implemented on Altera′s EP3C55F484C6 FPGA. The maximum frequency of the implementation was 122 MHz and the resource requirement was acceptable. Experimental results show that the architecture can achieve a throughput up to 115 M pixels/s and was robust to adverse situations such as bad lighting condition, partial occlusion, multiple signs clustered and similar background color.

Image fusion can obtain the richer level and detail information, which is beneficial to the effective acquisition of the detection target information. It is of great significance in applications including 3D reconstruction of space targets. A multi-exposure image fusion method that the non-linear compression of information entropy was used to determine the image fusion weight and the bilateral filter residual was introduced to enhance the weight of the weak texture for the wide dynamic range of space objects proposed. It effectively increased the feature information of the image and the number of 3D reconstruction cloud points. The space object imaging experiment was carried out by using the fusion method. The number of reconstructed point clouds obtained was improved by 35% compared with well-exposure and the reconstruction results were better than other methods. The results show that 3D reconstruction algorithm based on image sequence combined with image fusion could effectively enhance the reconstructed image information and avoid the adverse effects of illumination conditions on the three-dimensional reconstruction of the target, resulting in high quality reconstruction effect, the method can be well applied to the three-dimensional reconstruction of space targets based on image sequences.

In order to improve the speed and quality of video mosaic, Fast Mosaic of Unmanned Aerial Vehicle Video based on Improvement Model Fitting (FMUAVRVIMF) was proposed. Firstly, Fast Adaptive Robust Invariant Scalable Feature Detector (FARISFD) was used for video frames registration. Then, the improved Random Sample Consensus(RANSAC) algorithm was proposed for model fitting, and false matching points were removed. Finally, Fast Mosaic of Reconnaissance Frames algorithm was proposed to calculate homography matrix which transformed frames to orthophoto mosaic image, the video sequence mosaic was compeleted. The experiment results show that Improved Random Sample Consensus ensures the robustness, and the mosaic speed was increased, and the mosaic effect was improved.

Vehicle infrared panoramic scanning imaging system has the characteristics of column single imaging and 360° full field view, which result in that traditional electronic image stabilization methods could not be directly applied, therefore, the panoramic image stabilization algorithm based on region segmentation and fusion was proposed. First, the image pre-compensation was completed by local column offset adjustment method. Then the panoramic image was divided by the area, i.e., the front region, the right region, the end region and the left region, based on vehicle forward direction. Then each region used different image stabilization models for stabilization according to imaging characteristics, and the sliding window strategy was used to shorten the computation time in motion estimation process, the undefined area reconstruction method was used to compensate for missing information in motion compensation process as well. Finally, the local area expansion strategy and the progressive fade-weighted average fusion strategy were adopted to complete the region′s splicing and fusion, resulting in the seamless splicing effect of panoramic images. Experimental results indicate that the proposed method which can meet the requirements of engineering applications can effectively solve image stabilization problems of the system in the course of the vehicle moving forward, the precision of Peak Signal to Noise Ratio(PSNR) is increased by 14.7% compared with the original image sequence, running time is reduced to the 1/10 of traditional algorithms.

The usage specifications of p-value statistic were stimulated by highly visible discussions in the field of Statistics over the last few years. It is generally considered that a p-value can indicate how incompatible sample data are with the alternative hypothesis model. To explore the connection between the p-value of correlation analysis and spectral independence, the deductive reasoning and example verification were carried out. Compared with correlation coefficient(r-value statistic), results show that the band independence can be directly expressed by p-value statistic of correlation analysis. And p-value matrix has a kind of high-level self-sparsity, which can be used to model easily. And then an unsupervised band selection method(p-value sparsity matrix band selection, pSMBS) through p-value statistic modeling independence was proposed, based on the histogram frequency statistics of p-value matrix. Using two typical hyperspectral images (HSI) data, the experiments of supervised classification were carried out. The results indicate that, on Kappa coefficient, overall accuracy(OA) and average accuracy(AA), pSMBS is superior to three kinds of methods, adaptive band selection(ABS), infinite feature selection (InfFS) and Laplacian score feature selection(LSFS). Therefore, the effectiveness and the practicability of pSMBS were verified on HSI band selection, and the characterization ability of p-value of correlation analysis on expressing band independence was evidenced.hyperspectral image

The feature representing method based on encoding has advantages in illumination invariance, calculation efficiency and feature representation. It is one of the new feature extracting methods. The finger-vein images were captured in a perspective view by using infrared light source. Due to the complex biological tissue and the imaging mode, the image quality was usually poor. The Gabor filtering was used to enhance the image texture and the local graph structure encoding was adopted. A new feature encoding method was proposed with emphasis on a new local graph structure which was symmetric and crossed in neighborhood. The image texture of local neighborhood was converted to weighted encoding strings. The filtered image of each channel of Gabor filter was encoded in different directions so as to express the information of position and gradient in the neighborhood adequately, and it was rotation invariant as a result. The experiments results show that new method achieves better performance in finger recognition than common feature encoding methods and is more robust in rotation.