An InGaAs/GaAs strained quantum well structure semiconductor laser diode with an emission wavelength of 880 nm was grown to achieve linear polarized laser outputs with high powers and better beam quality.Based on the PICS 3D software, Laser Diode Arrays (LDA) with a stripe width of 100 μm and filling factor of 50% was fabricated.The output power of 1 cm bars on conductively cooled package with continuous wave (CW) reaches to 60.8 W at a current of 70 A, the threshold current is 11.1 A and the peak wavelength is 878 nm with a Full Width Half Maximum(FWHM)of 2.4 nm.To improve the beam quality and increase the end pumping power of the DLA,a pair of micro step-mirrors were developed to shape the laser beams come from the high power DLA, and then a high power optical fiber couple module was developed.Results show that the couple module with a core diameter of 400 μm and a Number Aperture(NA) of 0.22 can offer the output power of 44.9 W and couple efficiency of 73.8%.

In order to overcome the drawbacks of traditional fluorescence imaging methods and to achieve a biochip fluorescence imaging technique with high sensitivity and low costs,a novel biochip fluorescence imaging technique,line-scanning quasi-confocal fluorescence imaging method,was proposed and a prototype system was set up.By using a line scanning to replace a point scanning and changing the 2-D scan into the 1-D scan, the system can provide higher sensing speeds, simpler structures and lower costs while maintaining the high sensitivity.To verify the feasibility of the method, the prototype system was used to sense the fluorescence image of a manually prepared low density DNA microarray.Experimental results indicate that the spatial resolution of the system is better than 18 μm, and the Signal to Noise Ratio(SNR) of the system is 5.5×102 by using the pixel-averaging method to reduce noises.By combining the low cost and simple structure of the area imaging method with the high sensitivity of the confocal point-scanning imaging method,the technique is suitable for the biochip study in laboratories.

A new outdoor simulation system on the basis of the electric heating cloth is developed to simulate infrared radiance of outdoor targets.The cloth is taken as an infrared radiant material and appended to a rectangle target filled with air.Then a temperature control system is used to control the surface temperature of the cloth according to the temperature setting and to implement the infrared radiance simulation of outdoor targets.There are two major contributions in the paper.Firstly, uneven distribution of temperature field of the cloth surface is considered and a long wave infrared thermal imager is used as a link of temperature control system.On the basis of many experiments, an expression is concluded on the relation of the temperature measurement results, the setting temperature of control system and the environmental temperature at an experimental scene.This expression can help for setting temperature of the cloth surface through temperature control system according to the giving infrared radiance of targets.Secondly, the influence of the environment at the experimental scene on the infrared radiance of the cloth surface is thought over.By two considerations above,the simulation precision of infrared radiance has been up to 2 ℃.The outdoor experimental results demonstrate that the system could simulate infrared radiance of outdoor targets in a certain range accurately.

To compensate the nonlinear errors of heterodyne interferometers in nanometer measurement, an experimental investigation is conducted.Based on the polarization properties of a coated corner-cube retro-reflector, a model is derived for describing the effect of the axial rotation of a measuring cube-corner retro-reflector in the motion direction on the first-harmonic nonlinearity when a laser emits the elliptical polarized light.The simulation results indicate that the first-harmonic nonlinearity can be reduced by the axial rotation of the cube-corner retro reflector.The experimental result shows that the first harmonic nonlinearity is reduced from 3.48 to 1.39 nm when the axial orientation rotation angle of the measuring cube-corner retro reflector increases from 0° to 100°,which is 40% that of the original one.The method simplies the complexes of light path and circuit systems for nonlinear error compensation approaches.

A multi-lens imaging stitching method was come up for opto-electronic theodolites to achieve the images with high resolution and large fields of view.Several possible stitching forms were analyzed on the basis of the characteristics of opto-electronic theodolites, then a mathematics model was established by taking the four-lens lay cross stitching for an example.Furthermore, the inclination between the lens and the relative positions was decided and the sizes of azimuth and elevation systems in the gimbal of an opto-electronic theodolite were given.Finally, the precision of the stitching inclination was calibrated.The design result shows that the biggest fields of view are 6.6° and 3.52° in azimuth and elevation,respectively, when the pixel quantity is 1 280×1 024 in the camera target plane, the pixel size is 12 μm and the focus length is 400 mm.The inclination errors in two directions are all no more than 10″, which can meet the requirements of data processing for transforming a single image coordinate into opto-electronic theodolite coordinates in image stitching.The method enlarges the fields of view and expands the application areas of opto-electronic theodolites.

A miniature all-fiber Fabry-Perot high temperature sensor with a thin film is presented.The sensor is fabricated by splicing a hollow fiber with a grinded multimode fiber thin film on the end of a single mode fiber.The change of the optical path difference of the Fabry-Perot cavity are composed of two parts, the thermal expansion of the hollow fiber and the deflection of the thin film induced by temperature change.As the optical path difference of the sensor is langer than those of common sensors at the same temperature,it can offer a higher sensitivity.A temperature measurement experiment is carried out,results show that the sensor has a linearity of 0.996 7, sensitivity of 1.029 nm/℃ and the resolution of measuring system about 1.5 ℃.It is concluded that the miniature all-fiber Fabry-Perot high temperature sensor with a thin film will be a candidate in the field of micro-region multipoint quasi-distributed high temperature measurement.

A precise optical system for measuring wavefront aberrations of human eyes was designed and developed to precisely measure the high and low order wavefront aberrations of human eyes.The system adopted a Shack-Hartmann wavefront sensor to test the wavefront aberrations and could precisely measure wavefront aberrations of human eyes with different pupil diameters, different field angles under different accommodations.By simulating and analyzing with ZEMAX, the system precision was proved, and the diopter adjustment process was analyzed.Some experiments were carried out with the system,in which the effects of the distribution of all kinds of order aberrations, pupil diameters and different accommodations on the human eye wavefront aberrations were analyzed and the aberrations changed with time and space(frequence about 3 Hz，isoplanatic angle about 1.5°) were discussed.It is concluded that the system is precise(PV <1/20λ), convenient and is a good instrument for study on eye aberrations and customized cornea surgeries.

In order to measure micro-cavity dimensions precisely, an aiming and triggering measurement method by a double optical fiber coupler based on the location of Orthogonal Fourier-Mellin moments (OFMM’s) is proposed.By transmitting reversely the light between different optical fibers through the coupler，the method transforms the transverse displacement of the fiber probe into the displacement of laser, and the laser displacement then is transformed into a large displacement of a CCD by a lens.To improve accuracy, the rotation invariance and particular description capability of OFMM’s is used to locate the edge of image at subpixel, and a compensation based on OFMM’s real position is proposed to improve the precision of edge location.The location accuracy of OFMM’s and performance of sensor are experimentally measured.According to JJF(hei)8-2008, the proposed method with a researched micro-hole machine are used to measure the diameter of a blind micro-hole with the depth of 2000 μm and diameter of 200 μm, and the obtained repeatability uncertainty is less than 0.25 μm.

To meet the requirement of Multi-mode Combined Manufacturing (MCM) in a large aperture mirror polishing process, a JP-01 NC polishing manipulator was developed.The manipulator adapted cylindrical coordinates with axes of ρ-θ,and the motions of axis ρ and axis θ were linked to realize all trajectories demanded by MCM.Based on the Preston hypothesis, a mathematical model of material removal was established by analysis on the relative velocity, pressure and dwell time at any point of the optical surface.Meanwhile, the position transform matrix of the manipulator was deduced.Furthermore,the model was used to simulate the usual motion modes of a single lap for zonal errors and local errors in the process of MCM and to achieve deterministic processes.A spherical surface with a diameter of 240 mm, and F number of 1.5 was polished by the manipulator and obtained results show that it can offer a surface accuracy of 14.6nm (RMS).The experiments indicate that the theoretical analysis is coincident with observed experiment results.Moreover,the mathematical model can correctly reflect the practical material removal and can conduct deterministic processes.The polishing manipulator provides better motion modes for the MCM in the polishing process.

In order to realize the 3D measurement and reconstruction for a curved shape, a quasi-distributed measuring system based on curvature fiber optic sensors is presented and its algorithms such as the layout of sensors, measurements of curvature and torsion angles, and 3D reconstruction methods are investigated.Firstly, a number of looped fiber optic sensors are arranged on the two symmetrical surfaces of a flexible tape,and a quasi-distributed measuring system is established to measure bend and torsion deformations simultaneously using linear superposition theorem.Based on the bend and torsion data provided by curvature fiber optic sensors, a moving coordinate system is established by the curve tangent and curvature using a differential geometry method, and the osculating plane is determined by a torsion angle in the moving coordinate system.Then, the curve bending is calculated and the recursion of coordinate system is analyzed in the osculating plane.The correlative formulas are deduced and the method is validated by examples.Finally, the quasi-distributed measuring system is used to reconstruct the curve of a simply supported beam with a length of 500 mm.Results show that when 20 points are inserted between two measured points, the maximum deviation of reconstructed curve is 1.1 mm,which means the measurement system and the reconstruction method can reconstruct 3D shapes precisely.

Supporting trusses with high specific stiffness were studied to lighten the mass of light space remote sensors and to improve the natural frequencies of support trusses.According to a coaxial optical system with long focal length, a carbon fibre truss with six rods was designed, then the design was optimized by finite element method.After optimization, the mass of the supporting truss is reduced by 11%.To verify the feasibility of the truss,a model prototype was developed and the error sources were discussed.Analysis and test results show that prototype’s natural frequency is higher than 120 Hz.These research verifies that the truss can satisfy the application requirements of space remote sensors when the mass of the truss is controlled lower than 13 kg.It solves the problem that this kind of space remote sensor has a low natural frequency and has been applied to a space camera practically.

A theoretical analysis model for a space cable-strut deployable articulated mast worked at its on-orbit state was developed by using Euler beam theory, which aimed to a working state that the mast was extended out the spacecraft and its load mass was supported by the mass tip.The natural frequency and the root bending strength of the mast when mast worked on-orbits were analyzed.The primary parameter design method of the mast were studied based on the natural frequency constraint and root moment constraint,then the relationships between the primary design parameters of the mast such as line density, mast radius, longeron section area and the natural frequency and the root bending moment were discussed through calculation examples.A prototype of space cable-strut deployable articulated mast was developed, and its bending stiffness and bending strength are 0.388 MN·m2 and 562.12 N·m, respectively, which validates that the mast has very high bending stiffness and strength.Meanwhile, the repetitive deployable orientation precision of the mast prototype was measured on the ground.Results show that the mast prototype can offer higher repetitive precisions in 0.127, 0.645 and 0.588 mm for axis, horizontal and vertical directions, respectively.

A high precision angular driving device was developed for a Large-Scale and High Accurate Turntable( its positioning accuracy should be less than 0.5″) for calibration and test of cameras.The whole structure of the turntable was introduced, and the principle and structure of the developed angular driving device were given in detail.By using a new angular displacement conversion mechanism, the angular driving device could convert the straight-line displacement into a angular displacement to obtain a high angular resolution.Meanwhile, the angular micro driving device scarcely generates the axial force or radial force to influence on the axis accuracy in driving turntable.Furthermore, a new positioning method combined coarse and fine positionings was proposed to improve the positioning accuracy, in which a torque motor was used for coarse positioning and the angular driving device for fine positioning.Finally, the angular resolution of the angular driving device was calculated and verified, results show that it is superior to 0.08″ and can meet the requirement of the turntable for positioning accuracy.

Nonlinear friction is one of the main factors that effect both static and dynamic properties of high-precision mechanical servo systems.Considering the different friction characteristics of high-precision experimental platforms at different positions，a modified friction model based on the LuGre model is presented.By taking velocity and position signals as input variables, both static and dynamic parameters of the model are identified using the genetic algorithm.Based on the modified friction model, the experiments and simulations of the friction phenomenon and the friction feed-forward compensation are performed by a high-precision experimental platform and a corresponding simulation servo platform,respectively.Experiments show that the following error after compensation is 1/3 that of original one and the static error of system decreases from 1.4 μm to 0.4 μm with compensation, which is basically consistent with the simulation results without and with compensations.This modified friction model can describe accurately the friction characteristics of the experimental platform,and can be used in the feed-forward compensation to decrease following errors and improve the positioning accuracy for the system.

To establish an accurate target track model for capturing both the flight states and real movement characteristics, a new method to generate a target track based on the variable parameter control is proposed in the hardware-in-loop simulation system for photoelectric countermeasures.On the basis of the flight control principle,a flight dynamic model is regarded as a control object，then function models of proportional parameters and differential parameters are constructed on analyzing the characteristics of flight track control.By making the control error as the independent variable of the model,it can modify its parameters to adapt the nonlinear trait during the course of track control and to reduce the track error.Finally, a mathematical simulation is carried out by taking airplane data as examples.Compared with the setting track, the largest relative error of distance is 3.9% and the steady-state relative error of distance is 0.1%.Moreover,the largest relative error of tracking course is 1.8%, and its steady-state relative error is 0.056% .The simulation results validate the universality of the method and show that the model can meet the need of target track simulation in simulation systems.

In order to meet the needs of surgical guide plates for short-time design and producing circles, precise positioning and convenient operation, a method of all-digital rapid design and manufacture for metal customized surgical guide plates was proposed by using reverse-engineering, forward-design and selective laser melting technologies.Based on analysis of surgical needs, the method for shortening manufacture time, reducing plate weight and improving plate dimensional accuracy was figured out and both near-full-density-state forming and porous-state forming were investigated.The later used a high scanning speed to produce porous light part and shorten producing time, meanwhile it used offsetting scanning lines in two adjacent layers, orthogonal scanning and partition scanning to improve dimensional accuracy.Finally, according to the above ideas, a surgical guide plate model was designed successfully, and two metal guide plates were manufactured by porous-state forming and near-full-density-state forming , respectively.Results show that the dimensional accuracies of two plates are all ± 0.5 mm,but the manufacture time and weight of the porous plate have decreased by 43.3% and 18.2% as compared with that of the near-full density plate.The guide plate made by this method has been successfully applied to a surgery.

To improve the simulation accuracy of the Hardware-in-loop Simulation (HILS) of a guidance and control system, an idea is proposed to well balance the relationship between calculation ability and simulation accuracy of the system by selecting reasonable sampling steps and optimizing real time ability of the system.A mode for the HILS of guidance and control system is established, and the restraining conditions for sampling steps of the HILS are deduced according to the sampling principle.Furthermore, the restraining conditions are optimized and the optimized sampling steps are determined to implement the restraining conditions of calculation accuracy and stability.Finally, a HILS is carried out for the guidance and control system.In the simulation, the aircraft six Degree-of-freedom ( 6DOF) differential equation is written by C MEX S-function, and the hardware consists of a three axis turntable , a real-time calculator and a flight-motion-simulator.It is concluded that the HILS can meet the requirement of guidance and control systems for the simulation accuracy and real time stability in an optimized sampling step of 1 ms and can improve the simulation accuracy without adding any software or hardware.

The micro acceleration switch is an important inertial device for measuring itself acceleration and triggering switch in a flight control system.A micro spiral acceleration switch was fabricated in this paper by using UV-LIGA technology combining with SU-8 thick resist process, micro electroforming and sacrificial layer technology.The fabrication processes of the microstructures, such as sacrificial layer technology, SU-8 lithography and the distortion control of spiral spring structures, were studied in detail.The properties of various sacrificial layer materials were analyzed and the Zn film was chosen as a sacrificial layer to avoid the desquamation of microstructures.The flat spiral spring and mass block structures were obtained by optimizing the electroforming parameters to minimize the inner stress of Ni microstructures and controlling the releasing process of sacrificial layer to avoid the impact of chemical reaction on the Ni spiral films.The obtained spiral spring and the mass block show their thicknesses to be 20 μm and 200 μm,respectively.The result indicates that it is reliable to produce micro spiral acceleration switches in batches by using this fabrication process.

In order to maintain the high reliability of Space Optical Remote Sensors (SORS) in a stratospheric thermal environment, the thermal-analysis for a SORS was carried out.The stratospheric environment over 25 km was described, including the atmosphere pressure, density and temperature,then a thermal analysis model was established.The convection heat transfer coefficients on the forward face, side surface and rear surface of SORS were calculated.Results show that the coefficients on the three surfaces are 5.009，8.259 and 3.33 W/(m2·K) respectively when the airship sails against the wind, and 2.609，2.959 and 1.005 W/(m2·K) respectively when the airship sails before the wind.Furthermore, the two temperature profiles in extreme conditions, the high temperature condition and the low temperature condition,were analyzed with the software of IDEAS.Experimental results demonstrate that the axial temperature difference of the SORS after thermal control has decreased from 15~2.7 ℃ and the convection heat transfer coefficients of an airship to the wind are increased with the increase of their relative speeds.It is concluded that the thermal control method is effective and obtained temperature data can provide references for the thermal distortion analysis and the selection of thermal control strategy.

To improve the high temperature properties of touch mode capacitive pressure sensors, a Double-cave Touch Mode Capacitive Pressure Sensor(DTMCPS) is proposed and its overall performance in high temperature environment is analyzed significantly.Firstly, the theories of heat transfer and thermo-elasticity are deduced, and effects of many temperature dependence factors on thermal analysis of this sensor are described.Then, Finite Element Method and ANSYS software are used to simulate the thermal effect of the full dimension sensor during this analysis.The results indicate that the influence of temperature on the input (pressure load) and output (capacitance) characteristics is linear in a touch operation state of this DTMCPS, and its initial pressure of linear range reduces with temperature increasing.Furthermore, the sensitivity of double-cave structure sensor is 1.21×10-6 pF/Pa at 550 K, which has been 50% up on 0.8×10-6 pF/Pa of the traditional single-cave structure.These results show that this sensor has excellent high-temperature performance.

A-sandwich radome structure with Frequency Selective Surface (FSS) was designed based on a mutual admittance approach, and the experimental objects of planar and conical radome were manufactured, which verified the integral technique of composite structures.Tests on the planar sample and FSS conical radome were carried out in an anechoic chamber, and some of which were compared with computation results.The results show that the dual-layer FSS loaded by A-sandwich structure has a small loss of in-band transmission with flat-peak characteristics, and the incidence angle and polarization of the bandwidth show a good stability.At a large incidence angle of 60°, the difference of -3 dB bandwidth between TE and TM polarizations of a dual-layer FSS is 1.3 GHz less than that of sigle-layer FSS.When the thickness of honeycomb sandwich layer is large (about 1/4λ), the coupling between the two side FSS layers is little, so dual and single layer FSSs have the same resonant frequency.Furthermore, the transmission properties of the curved FSS radome are related to both antenna polarization and incident direction,and the experimental results of the radome in the main polarization plane are consistent with that of the planar objects.These results indicate that the influence of curvature is quite small in a test of local near-field, so the local planar approximation can be used in the design stage.

In order to realize the miniaturization of spaceborne photoelectric encoders, minish the sizes and weights of the spaceflight equipment effectively and to satisfy the requirement of the cold copy of photoelectric converting circuits, a signal process system is designed for the spaceborne photoelectric encoder with dual-reading system.Firstly, the process methods of the coarse and precise code signals are presented for the spaceborne photoelectric encoder with dual-reading system and the miniaturized and reliable design of the signal process system is described.Then, the accuracy of the spaceborne photoelectric encoder with dual-reading system is analyzed based on the error sources and distribution characteristics.Finally, using a 23-bit high precision photoelectric encoder as the angle standard, the accuracy of the designed photoelectric encoder is tested based on a comparison method.The experiment results show that the resolution and the accuracy of the photoelectric encoder with dual-reading system are 20″ and less than 30″,respectively.By applying to practical projects,the process system has satisfied the technique requirement of the spaceborne equipment.

Ultrasonic bonding was presented to bond the polymer micro devices in this paper.An ultrasonic precise bonding device was established and an adaptive pressure control method was also proposed.Considering the accuracies of shape and position of joining, a 60 kHz ultrasonic energy converter and a driving source were chosen to provide the higher frequency and lower amplitude for the micro device to reduce the damage of micro structure in bonding.Then, a high resolution stepper motor and a linear guide were chosen to control the longitudinal movement, and positioning accuracy of ultrasonic horn and to realize the real-time monitoring of the mechanical behaviors of polymer materials during bonding.Aiming at the problem of instable joining quality from the difference of surface roughness,an adaptive pressure control method based on material mechanical behavior feedback was proposed.Experiment results show that the stability of bonding is improved obviously by this bonding method and the precision bonding is achieved.

In order to realize stable working of giant vehicular photo-electric trackers, a method of vibration isolation is proposed for a tracking frame in a photo-electric tracker,in which a air spring and an electromagnet actuator is used to isolate the vibration.The layout of electromagnet actuator is differential, so the force of electromagnet actuator and the control current are linear.Several kinds of control methods are analyzed,and the absolute velocity feedback control method is chosen to keep the vibration isolation capability in high frequency and avoid syntony in low frequency vibration.The results of MATLAB simulation and experiment indicate that the high frequency amplitudes of z-DOF ,θx -DOF and θy -DOF have been reduced from 5×10-5 m to 1.8×10-5 m, 2.2×10-5 m to 0.6×10-5 m and 2.0×10-5 m to 0.4×10-5 m, respectively,meanwhile the syntony can be avoided.These results show that this vibration isolation method by absolute velocity feedback control can evidently promote the vibration isolation capability.

In order to measure the mechanical properties of micron-scale thin films, an integrated uniaxial tensile test system with lower cost is developed for measuring mechanical properties of MEMS materials.Firstly, test chips are optimized by Finite Element Method(FEM) to be gripped tightly and aligned in the pulling direction accurately.Furthermore,test chips with thin Ni films are fabricated on a glass substrate with UV-LIGA technology, which significantly reduces fabricating time and steps and eliminates the effect of wet anisotropic etching process on mechanical properties.Then, according to tensile test processes and facilities in the tensile system, a data acquiring and analysis system is designed by Visual Basic.Finally, the integrated tensile system is used to measure the mechanical properties of the Ni thin film.Experimental results show that the system precision is 0.01 μm for strain measurment, and mN level for stress measurement.Obtained Young’s modulus and the ultimate tensile strength of the Ni thin film are about 94.5 GPa and 1.76 GPa, respectively.The integrated system with higher precision and lower cost can be used to study mechanical properties of electroplated metal materials.

An interpolation algorithm based on multi-direction Neural Networks(NN) is presented to solve the problems on lost data and fuzzy boundary in CT images caused by the unevenness exposure and noise.The information in every section and between different sections is integrated for the super-resolution reconstruction of focal zones.Firstly,a forecast net is extended to a 3D space,then optimal initial weights are designed according to the special gray feature distribution of pulmonary nodules.Finally,lost data are forecasted to improve the resolution.The results of simulation experiments indicate that this approach can improve performance in several respects such as location ,real-time and PSNRs as compared with the present representative three methods,PCGLS,180° linear interpolation and one-way neural network.It is shown that the deviations of centre and centroid are averagely reduced by 27.1% and 23.0% respectively,and the target area and the iterations are averagely reduced by 21.5% and 25.9%,respectively.Moreover,the average PSNR is increased by 1.59 dB.The proposed method can be used in not only pulmonary CT images but also biological and remote sensing images.

To improve the bandwidth of digital video transmission of an optic-electronic tracker, enhance the anti-jamming performance of the system and ease the workload of a slip-ring, a fiber transmission system for high-speed digital video image signals was designed.By making use of the anti-jamming and high bandwidth characteristics of the fiber data transmission technology, the image transmission quality was improved and the transmission capacity was enlarged.At the sending end, the parallel digital video signals were serialized and the serial data were transferred into optical signals by a fiber module.At the receiving end, the optical signals were transferred back into the electronic signals by another fiber module, and the serial data were de-serialized back to the parallel data format.The frame signals, line signals and data signals were transmitted together and the processed clock signals were transmitted separately as system clock signals.Experiment results indicate that the image signals can be correctly transmitted by the fiber transmission system, and the bandwidth and the clock frequency have been up to 1.25 Gbit and 62.5 MHz,respectively.Furthermore, the data transmission latency of the system is less than 236 ns, and the clock edge can be located at the valid data position.

A new image correction method based on projection sinograms is proposed to remove ring artifacts in industrial Computerized Tomography (CT) and to improve the precisions of post processing and quantitative analysis.A S-L filter is adopted to filter original projection data and to enhance artifact information.Then, the filtered projection data are processed by line integral and difference to further increase the difference between artifact edges and work piece contours.Furthermore, the differenced projection data are averaged according to the number of interpolations, and the artifact location is automatically searched according to the threshold selected by normal distribution.Finally, the projection data of ring artifacts are corrected by combining the linear interpolation and linear extrapolation.A correction experiment is carried out in the actual CT images including ring artifacts.The result indicates that the SNR of gray image using the proposed method has increased by 1.688 dB, which shows that proposed method effectively eliminates the ring artifacts and keeps the image edges and resolution as compared with the methods of polar coordinate transformation or Wave-FFT.The proposed method is suitable for correcting the discontinuous ring artifacts caused by detector faults and unstable performance.

To overcome the shortcomings of long time-consuming and low efficiency from the exemplar-based image inpainting algorithm proposed by Criminisi, an image inpainting algorithm was presented,in which the bilinear interpolation algorithm was used to downscale the original image and to improve inpainting efficiency.Firstly,the dimension of the original image was downscaled by a factor 0.2-0.5, then the inpainted point with the highest priority from a target region was evaluated and a best-exemplar was searched from the source region in the downscaled image.Furthermore, those counterparts were obtained by the proposed rules from the original image and were filled into the whole damaged region in the origin image.The above steps were iterated until the target regions were completely filled.Experimental results demonstrate that the proposed image inpainting algorithm can inhance 5-40 times the inpainting efficiency of the Criminisi’s, while good inpainting images are achieved.This method can obtain good inpainting results in efficiency and quality.