Chinese Version Light学术出版中心
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Issue 2 ， 2006
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All-fiber flat-top interleaver based on double single mode couplers
Abstract：The transmission function of a interleaver consisting of a 2×2 and 3×3 single mode fiber coupler in series was analyzed. Based on the Fourier series digital approximation method, the relationship among the splitting ratios of the couplers, the length difference of interference arms and intensity transmission spectrum was discussed. The results indicate that this configuration can achieve an approximate rectangular wavelength response when the length difference of interference arms and coupling coefficients of the couplers are given by a certain value in order, its stability and isolation is improved greatly. An advantage of this interleaver is that the coupling ratio of coupler and the proportion of the length differences can be controlled accurately because light interference effect can be sheered away in fabricating. A novel structure of interleaver is fabricated with fused biconical taper technics in experiment. The experiment results are in good agreement with the theoretical analysis.Keywords：applied optics;comb-filter;Mach-Zehnder interferometer;interleaver;directional coupler- 46
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Published：2020-08-12 -
Yb3+-doped double cladding microstructure fiber laser with output power exceeded 10 W
Abstract：A high power air cladding pump microstructure fiber laser with output power exceeded 10 W was demonstrated using Fabry-Perot resonance cavity configuration. The output power and slope efficiency of the double-clad ytterbium-doped large mode-area microstructure fiber laser are 8.38 W and 87%,respectively, and the highest output power can achieve to 11.69 W.Keywords：microstructure fiber;Yb3+-doped fiber;double cladding fiber;optical fiber laser- 42
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Published：2020-08-12 -
Broadband gain-flattened multiwavelength pumped Raman fiber amplifier
Abstract：Based on analyzing the principle of the Raman Fiber Amplifier(RFA), optimal design of a backward pumping Raman fiber amplifier with five different pump wavelengths was carried out. With seven pump lasers at five different wavelengths and a 100.8 km dispersion-shift fiber, a broadband optical Raman fiber amplifier with gain band over 90 nm, on-off gain of 15.55 dB, gain flatness below 0.87 dB and average effective noise coefficient of -3.5 dB was demonstrated experimentally. The experimental results agree with the theoretical calculation.Keywords：Raman fiber amplifier;DSF;on-off gain;gain flatness;effective noise coefficient- 32
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Published：2020-08-12 -
Motion analysis of lapping machine for end-face of optical fiber connector
Abstract：The motion principle of a two-motor driven lapping machine with an epicyclic gear and 2 degrees of freedom for Optical Fiber Connectors (OFC) was analyzed. The lapping motive path of OFC relative to lapping tool (lapping film) was also figured out. The rotating speed relationship between two independent driving components of lapping machine was established by introducing the definition on "velocity ratio". In order to solve the problems existing duration of lapping OFC, considering the velocity ratio and building relationship of lapping motion, lapping process and lapping quality, the optimal results of motion parameters of lapping machine for OFC were obtained with the aid of lapping motive path curves, lapping distance difference, cutting velocity and transform coefficient of velocity cycle. When rotating speed of the tie bar is 132 r/min, according to coarse or fine lapping processes, the rotating speed of the ring gear should be between 31~54 r/min. Here, the transform coefficients of velocity cycle and lapping distance differences are less than 2.2 and 0.5%,respectively, lapping motive paths are very dense and not overlapped. The analyzing results are proved by experimental results.Keywords：optical fiber connector;lapping machine;lapping motion path;velocity ratio;apex offset- 48
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Published：2020-08-12 -
Theoritical and experimental research on lens duct for LDA coupling
Abstract：Based on the numerical analysis of ray tracing, the general expressions of the parameters in optimization design of the lens duct were theoretically deduced. Using the theoretical model, the light transmission trace in the duct was simulated, and the light intensity distribution of the output beam was calculated. The influence of the parameter’s value on the coupling effect was also analyzed. Based on the optimum designing, a lens duct was fabricated and applied to a laser system, and the coupling experiment was implemented. The experimental results show that a smooth and symmetric beam with a good quality can be obtained at the output duct end. The coupling efficiency of the lens duct is above 91%. The results of the experiment agree well with the theoretical analysis,and are better than the results reported previously.Keywords：laser technique;lens duct;laser diode array;coupling system- 36
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Published：2020-08-12 -
Structural error correction and simulation of capacitive displacement sensor for segmented mirrors
Abstract：Based on kinematics of the segment mirror system,the movement relationship between the segmented mirror and the sensor electrode plate was established,and processing method of the induced sensor reading error defined as structural error of the capacitive displacement sensor was analyzed. Thereafter,the capacitive sensor with round electrode plates in shape was specifically analysed for its reading in detail,which involved with numeric polynomial fitting technique in terms of measured displacement of the sensor and inclination angle of the electrode plate. The method has proved its efficient and effective in computer simulation. For the variable inclination angle,inclusion of the second order is enough to achieve 3 nm fitting precision,meanwhile,the fourth order is still needed for the variable measured displacement. Further analysis indicates that fiting the polynomial with the inclination angle directly obtained from the displacement sensors reading can still afford fitting precision of 5 nm at worst case,which well meets the technical requirements of the segmented mirror active optics application.Keywords：segmented mirror;capacitive displacement sensor;error analysis;error correction;numeric fit- 42
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Published：2020-08-12 -
Design, fabrication and testing of space-borne SiC mirror
Abstract：Silicon carbide (SiC) is an attractive mirror material due to its superior mechanical and thermal physical properties compared to conventional optical materials. In this paper,a space-borne mirror blank was fabricated by reaction bonded silicon carbide (RB-SiC),and full density SiC thin film was coated on the surface of mirror blank by Chemical Vapor Deposition(CVD) process. The space-borne mirror is lightweight structure with honeycomb back opened. The microstructure and properties of a 250 mm diameter circular mirror were studied and tested.Experimental results show that the mirror blank is Si/SiC two-phase structure and the film is SiC single phase; SiC mirror has excellent mechanical and thermal property; the adhesion strength stress between substrate and film is 345.5 MPa. After grinding,mirror surface precision is 1.487 nm rms. The space-borne SiC mirror of meter class diameter can be fabricated by both reaction bonded and CVD process.- 87
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Published：2020-08-12 -
Spectral radiance responsivity calibration of ultraviolet remote sensing spectroradiometer in space using integrating sphere
Abstract：A calibration technique based on internally illuminated integrating sphere was presented,and the large area uniform (~2%) source of radiance close to ideal source was achieved, the radiance responsivities of the ultraviolet remote sensing spectroradiometer in space under development were obtained. Under the condition that FEL standard lamp was assumed to be a uniform point source, the illuminating factors of both sources were corrected, in the mean time, two kinds of diffusers were involved in the experimental research for this correction. A conclusion is given that the radiance responsivities of the spectroradiometer obtained through these two kinds of diffusers are consistent within 1%. A preliminary analysis of calibration data shows that the uncertainty of the spectral irradiance measurement in the quartz tungsten halogen lamp and the uncertainty in distance measurement are the major factors of uncertainty in the sphere calibration technique. This technique can be used to improve the precision of calibration in ultraviolet wavelength range,and the uncertainty in calibration can be reduced significantly too.Keywords：spectral radiance calibration;ultraviolet remote sensing spectroradiometer in space;Integrating sphere;diffuser- 88
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Published：2020-08-12 -
Error analysis of moving mirror in Fourier transform interferometer
Abstract：Based on the coordinate correspondence of the moving mirror,fixed mirror and interference surface in Fourier transform interferometer,the interference mode was analyzed under moving mirror tilted in several directions. In tilting status, a two dimension mathematical model of the interference plane was brought out, and the function of the interferogram was established. By analyzing the modulation depth, phase error and frequency noise,the error of the moving mirror were studied theoretically. It is found out that the different titling directions of moving mirror affect the system error independently, at the same time they can be added. The original phase of the interferogram is changed slowly or rapidly with the optical path difference changed, and the phase error is different too. Based on the error analysis, the max titling angle can be computed, two methods to keep adaptive alignment are also discussed.Keywords：Fourier transform spectrometer;tilting of the moving mirror;modulation depth;adaptive alignment;error analysis- 38
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Published：2020-08-12 -
Fabrication of a controllable curved surface grating
Abstract：A fabrication method of VLSG(Varied-line-space Grating) was presented. The grating was fabricated on plane substrate,and then it was transferred on curved surface by a macromolecule material(PDMS) used as a carrier. The hybrid gel film on curved surface can replace traditional light-sensitive lacquer,and improve the grating's stability. The VLSG with the line density of 80 l/mm was fabricated on a concave lens surface with curved radius of 100 mm. The grating line density distribution was detected with SEM and digital image process technique. For having the functions of the lens and plane grating, the results show that the high quality grating can replace lens and plane grating in good processing,efficiency and cost.Keywords：varied-line-space grating;curved surface grating;polydimethylsiloxane(PDMS);hybrid sol-gel glass- 41
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Published：2020-08-12 -
Improving precision of null lens method with correction technique
Abstract：Based on the wavefront aberration, a technique expressed by Zernike’s circle polynomials was developed to test and separate the unsymmetrical error of null lens. By turning the null lens or the tested surface in different angles along their optic axis, the different testing results were obtained. According to these results, the wavefront aberration’s unsymmetrical coefficients of Zernike’s circle polynomials caused by the error of null lens were obtained, then a corrective file to correct the last testing result can be given. With this technique, the demands on the material, manufacturing, and assembly of null lens is not so critical, and the test accuracy is improved observably. The experimental results show, before and after the correction technique is used, the test result is 0.105λ and 0.026λ, respectively,and the difference among four testing results of the mirror in four different orientations is less than 0.001λ, so that the technique has been successfully applied to test a hyperboloid convex surface.Keywords：test accuracy;null lens;unsymmetrical error;Zernike’s circle polynomial;correction technique- 42
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Published：2020-08-12 -
Layout model and analysis of annular subaperture stitching technique for testing large aspheric mirror
Abstract：Annular subaperture stitching technique is a feasible method for testing rotationally symmetric aspheric mirror without any additional elements. Based on the testing principle, a subaperture layout model was established with geometry optics theory, and the numerical solving method was provided in detail. Taking a paraboloidal mirror with clear aperture of 700 mm, center obscuration of 160 mm, and vertex curvature radius of 3000 mm as a example,the paper analysized and explained the numerical results of model with the corresponding physical optics theory. The experimental results show that the model is better in predictability, and it will provide the theory basis for the practical measurement and also will make the measurement process more controllable,quantitative and repeatable.Keywords：optical test technique;Interferometry;layout model;numerical computing;annular subaperture;large aspheric mirror- 59
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Published：2020-08-12 -
Research of the phase-only modulation characterization of a liquid crystal spatial light modulator
Abstract：The principle of phase-only modulation of a liquid crystal spatial light modulator(SLM) was introduced,and its phase characteristics were measured by a Twyman-Green interferometer system. The response curves of phase and voltage of the SLM with 256256 pixels patented by Boulder Nonlinear Systems (BNS) were measured. The program to retrieve the phases of an arbitrary intensity pattern was developed with an optimal algorithm. With the phase-only modulation method, the directions and intensities of laser beams could be controlled by the program easily. An experimental set-up was constructed to generate arbitrary 2-D diffractive pattern with generating pattern time in less than 200 ms. This experimental study is of value in the fields of multi-object tracing, laser guiding and multi-object defense.Keywords：spatial light modulator;Interferometry;Optimal algorithm;phase modulation- 48
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Published：2020-08-12 -
Analysis of material removal mechanism in fluid jet polishing by finite element method
Abstract：Distribution of removed material in Fluid Jet Polishing (FJP) was investigated in experiments. The characteristics of fluid velocity and pressure on the sample surface were simulated using Finite Element Method (FEM) when the fluid jet impacts the work piece. The experimental and simulating results show that the distribution of removed material is related to that of fluid velocity field after collision of the slurry jet with wok piece, that is to say, the maximum amount of removed material appears on the edge of impacted area where the fluid velocity has the maximum value; In the outside, the less material removal is due to the smaller velocity. Thus, it is concluded that the collision and shearing actions caused by the radial flowing of slurry play a dominant role in material removal in FJP.Keywords：Fluid Jet Polishing(FJP);Finite Element Method(FEM);removal mechanism;impact wear- 56
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Published：2020-08-12 -
Analysis of groove density for diffraction grating during bending
Abstract：In order to derive the effect of an arbitrary bending curve in tangential orientation on a grating,a general expression about the transform of groove density was represented in theory,and simulated by Finite Element Method(FEM) using ABAQUS/Standard. The results show that the groove density was severely determined by the attribute of diffractive grating and bending curve. Sequentially,the imaging properties of grating monochromator due to bending were numerically pointed out with a simple example. As a result of shape change and groove density variation,it not only improves the focusing condition,but also affectes higher order aberrations such as coma aberration of the imaging system.Keywords：bending grating;groove density;FEM- 34
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Published：2020-08-12 -
An algorithm for singularity detection and center point calculation based on fingerprint segmentation
Abstract：A novel and simple algorithm for singularity detection and center point calculation in a fingerprint image was presented. Based on analysising of the property of singular points,the Gabor filter,variance analysis were introduced to segment the fingerprint on ridge orientation effectively. By the binary image addition of the fingerprint segmentation,the singular regions were detected according to the change times of gray levels and the intensity in each pixel’s neighborhood. The calculation of singular points and center point of the same fingerprint was discussed. The experimental results show that the proposed algorithm can detect more sorts of singular points than other conventional methods and can realize the location of the singular point and center point correctly.Keywords：orientation filter;Gabor filtering;fingerprint enhancement;singular point;center point- 40
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Published：2020-08-12 -
Application of pattern search method to fiber-optic active alignment automation
Abstract：Application of the pattern search method to fiber active alignment automation was developed for adjusting misalignments on multiple axial directions simultaneously. The interaction problem among axes was solved and the potential risk of missing the real peak was avoided, so that the alignment process time was reduced, and the alignment accuracy for locating the optimal fiber-optical coupling position was improved. The comparison of simulation and experimental results between pattern search and hill-climbing method was presented. Simulation results indicate that the convergence of pattern search algorithm is nine times as fast as the hill-climbing method; it converges to the maximum coupling efficiency within 20 iterations for the five degrees of freedom alignment between the laser diode and the single mode fiber. The experimental results also demonstrate that the average time for locating the optimal coupling position in x -y plane using pattern search algorithm is 10 s faster than that of hill-climbing method; and the global convergence of the pattern search algorithm is much better than that of the hill-climbing method.Keywords：fiber-optic alignment automation;pattern search algorithm;hill-climbing method- 57
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Published：2020-08-12 -
Fast and precision image mosaic based on grating
Abstract：In order to improve the speed and precision of image mosaic for IC vision inspection, a fast and accurate image mosaic technique based on precision grating measurement system was presented. The self-calibration method can solve the problem of conventional calibration affected by the manufacturing precision of standard unit and light intensity, and can increase the calibration accuracy and decrease the cost. After accurate calibration, the image mosaic model based on grating precision location was established. The experiments demonstrate that this system has high image mosaic precision, average error within 0.4 μm, and 0.872 μm in 2σ, which is up to sub-pixel precision; also the system has high mosaic speed,the time of two image mosaic is about 10 ms.Keywords：image mosaic;grating;self-calibration- 41
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Published：2020-08-12 -
Gabor wavelet neural network algorithm based on parallel structure
Abstract：A Gabor wavelet neural network algorithm was presented based on parallel structure. According to the characteristics of multi- CPU parallel structure and neural network parallel, the algorithm for recognizing image target was designed based on the Gabor wavelet neural network. The algorithm input layer involved operation on scale, translation and frequency modulated parameter of Gabor wavelet, the hide layer realized and optimized the neural network algorithm on parallel CPU and the algorithm output layer gave the the classification result of Gabor wavelet network algorithm. The simulation experiment was processed by four types plane image targets, and the results indicate that the recognition rate is 98%, recognition time is 40 ms.Keywords：target recognition;Gabor wavelet neural network;multi-CPU;parallel structure- 39
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Published：2020-08-12 -
Error analysis of fabricating isometric mesh on the concave of a spherical substrate by concentric optical scanning
Abstract：An isometric mesh on the concave of a spherical substrate was formed by latitude line intersection each other, in which latitude lines was generated by a concentric optical scanning method. An optical axis, erection turning spindle, horizontal dividing spindle and a pitching dividing spindle were positioned on the concave center of the spherical substrate in concentric scanning. The concentric error between these spindles with the concave center may bring on the defocus of optical system and the error of the mesh period, but because the ratio of the period error to the period is very small, the latter may be ignored. The theoretical analytical result shows that the line width of mesh is restricted by the dimension of focal spot and the defocus of optical system determines the smallest dimension of focal spot, so the line width of mesh is restricted by the concentric error,i.e. the smaller the concentric error is, the smaller the line width is also.Keywords：Filter;electromagnetic shield;Lithography;metallic mesh;sphere surface- 42
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Published：2020-08-12 -
Research on cylindricity evaluation based on the Particle Swarm Optimization(PSO)
Abstract：A cylindricity evaluation approach based on the Particle Swarm Optimization (PSO) was proposed. The fundamentals and implementation techniques of PSO were discussed. The problem of cylindricity evaluation was presented and its optimization goal and variables were given. The fitness function of PSO with real number encoding of particles was also described. Taking a example for verifying the feasibility and computation precision of the approach,the computation results show that the PSO-based approach is a useful tool for solving such nonlinear optimization problems as cylindricity evaluation with complicated goal function and more parameters. It is superior to that given by the Least Square Method (LSM) and a little better than or equal to those given by GA-based method and another Minimum Zone Method (MZM). Moreover, the PSO-based approach is not only effective but also simple and easy to implement for computers.Keywords：Particle Swarm Optimization (PSO);cylindricity;error evaluation- 46
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Published：2020-08-12 -
Interpolation method for calculating gamut boundaries of digital imaging output devices
Abstract：A interpolation method to define the gamut boundaries of digital imaging devices was presented, and the calculating precision was given experimentally. Based on the connectivity of sample points and the triangular interpolation technique, regularly spaced gamut boundary points were solved directly in the CIELAB L*a*b* coordinates. Experiments were carried out with 386 samples for three devices of different types, and the mean/maximum CIELAB ΔEab for 296 test samples were 2.31/6.93,2.03/6.70, and 0.40/2.11, respectively, which were close to their corresponding device errors induced by their stability. Besides, by mapping gamut boundary into a gamut sphere and by using a pre-searching process, the interpolation triangle researching time was reduced from 2.5 min to 10 s, decreased 15 times.Keywords：color gamut;gamut boundary;gamut sphere;triangular interpolation- 48
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Published：2020-08-12 -
Image fusion algorithms using discrete cosine transform
Abstract：An image fusion algorithm based on discrete cosine transform (DCT) and an image fusion scheme using wavelet transform combined with DCT were proposed. The former based on DCT fused the corresponding areas of the original images according to the DCT coefficient high frequency energy and the latter using wavelet transform and DCT fused the low frequency submaps by use of DCT coefficient high frequency energy. The wavelet high frequency coefficients of the highest wavelet decomposition level were decided by the wavelet low frequency coefficients. The wavelet high frequency coefficients of the other wavelet decomposition levels were selected with the greater local deviation. The fused images of the algorithms purposed were evaluated by some parameters such as average error, peak signal noise rate, and root mean square error, compared with other conventional image fusion methods based on wavelet transform or DCT. The experimental results show that the new algorithm based on wavelet transform combined with DCT provides the best performance with 40.8% to 69.5% reduction in average error, 9.9% to 15.6% improvement of peak signal noise rate and 34.8% to 47.5% reduction in root mean square error. It is superior to the conventional methods using wavelet transform. This algorithm improves the quality of the fused image effectively,the evaluation results coincide with the visual effect very well. The algorithm based on DCT needs less computational burden and is more suitable for the real-time processing.Keywords：image fusion;discrete cosine transform;image processing;wavelet transform;compressed domain- 53
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Published：2020-08-12 -
Ultra-low speed research on friction drive for astronomical telescope
Abstract：The theory and characteristics of friction drive for a large astronomical telescope were presented. The results of experiment indicate that there are many factors influencing on the stability of low speed of friction drive. The main factors include:measuring error of encoder ;error of environment variance;errors of friction torque and motor fluctuating torque and error of manufacturing and installing. In addition, the friction torque of total drive chain is fluctuation also. The results of experiments also indicate that the nonlinear characteristic of increment parameter of nonlinear PID control algorithm can achieve prompt response and non-overshooting of the control system. The nonlinear PID also enhances the stability to resist the influence of friction drive low speed. In this experiment, the low speed is 0.2″/s and position precision is 0.032″(RMS),which proved that this method is effective.Keywords：astronomical telescope;friction drive;ultra-low speed;nonlinear PID control- 43
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Published：2020-08-12 -
Equivalent combined control technique based on Kalman filter
Abstract：Equivalent combined control is an ideal tracking measure with high tracking precision. The basic principles of the combined control and equivalent combined control were described, the random acceleration model of maneuvering object was also analysed and how to realize the Kalman filting was given in the paper. An equivalent combined control system was constructed on an optoelectronic theodolite based on Kalman fiter by assuming the object maneuvers with random acceleration model. Aiming to the problem of delay of tracking error, a new method of predicting the right maneuvering parameter of object from the synthesized value of the tracking error and delayed encoder data was put forward to eliminate the effect of the problem. The results of simulation show that the equivalent combined control system has only 0.2' when tracking the equivalent sine object of 60°sin 0.573 t,it is 10 times better than that of the traditional velocity delay method. In the end,the validity of the equivalent combined technique is testified by experiment.Keywords：photoelectric tracking;equivalent combined control;random acceleration model;kalman filtering- 44
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Published：2020-08-12 -
Visual servoing with modified Smith predictor for micromanipulation
Abstract：A control scheme with a Modified Smith Predicator (MSP) for the position-based dynamic look-and-move visual servoing for the control of micromanipulation was proposed. The position-based dynamic look-and-move control scheme was applied to the vision servoing system with a dual-loop control scheme,in which the local controller was used as a position-controlled device,and the outer one as a vision servoing controller. The control scheme with a similar structure to the Smith predictor called modified Smith predictor was employed to eliminate the vision delay. The detailed analysis and experiments show that the vision control system with the proposed control scheme has better dynaimics performance than the vision control system with a single PID controller. The proposed control scheme resolves the problems of vision servoing’s inherent time delay induced by time consuming image acquisition transfering and processing and improves the dynamic response properties and antijamming ability of the vision servoing.Keywords：Micromanipulation;vision delay;modified Smith predictor;timing modeling;performance- 61
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Published：2020-08-12 -
Study on dynamic imaging on push-broom TDI CCD optical remote sensor
Abstract：For the dynamic imaging test of push-broom TDI CCD (Time Delay Integration Charge Coupled Devices) space optical remote sensor, a kind of special test system was designed. A precise rotary platform with dual bearing and a U type frame was designed to simulate the satellite push-broom in the system. Within ±5° range it could be turned at the angle rate of 0.555°/s with rotary precision of 0.3% with the remote sensor being carried. A drone at Nequist Frquency was designed in which bar target in a/n tolerance of arithmetical progression was added between each group rectangle vertical bar in the drone. When the remote sensor worked under push-broom mode, the problem of the matching uncertainty between the target image and the CCD pixel be solved,which could simplify the registration and improve the measuring accuracy. The results prove that the drone image can be obtained at the Nequist Frquency in the field of view of 0 and ±0.86 in the vertical, horizontal and 45°directions. TDI CCD remote sensor is provided with high imaging quality based on push-broom technique.Keywords：applied optics;optical remote sensor;TDI CCD;push-broom technology;alternate location target;image quality evaluation- 41
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Published：2020-08-12 -
Reconstructing 3D buildings based on airborne CCD image and laser scanning rangefinder data
Abstract：3D building reconstruction automatically using airborne CCD image and laser scanning rangefinder data was studied. The geometry shape of building is shown clearly in airborne high resolution CCD image, so adaptive Canny edge detection operator is used to extract the edges of buildings first, and cross direction projection histogram and line matching are used to extract the contours of buildings. The height of the building is determined from laser sample data based on the contour of the building, then the 3D information of each building is reconstructed. The practical data processing results show that 3D buildings are reconstructed correctly by using real airborne CCD image and laser rangefinder data.Keywords：CCD image;laser scanning rangefinder;contour extraction;3D reconstruction- 51
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Published：2020-08-12 -
Application of real time polynomial fitting based on orthogonal basis function algorithm to encoder rate measurement
Abstract：A real time polynomial fitting algorithm based on orthogonal basis function was proposed to encoder angular rate measurement. The algorithm can avoid the ill-conditioned status leading to degrading the rate-measuring precision in normal equation when the rank of fitting polynomial is more than three. The ground target tracking experiment with photoelectric tracking survey equipment shows that the algorithm is effective to decrease the effect of angular random errors on angular rate measureemnt when calculating the differential of the angular fitting output. Typically, the standard deviation of rate-measuring errors using this algorithm is 0.01343°/s by contrast with the 0.02815°/s using the normal method. Therefore the improved algorithm applied to engineering can improve the angular rate measurement precision obviously.Keywords：real time fitting;angle encoder;polynomial fitting;normal equation;angular rate measurement- 26
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Published：2020-08-12 -
A new algorithm for human eye’s wave-front aberration fitting with Zernike polynomial
Abstract：A new precise algorithm for computing the fitting coefficients of the Zernike polynomial was presented. The concept of human eye’s aberration and the mathematical function of wave-front aberration expressed by Zernike polynomial were introduced. The matrix of inconsistent equation group of the algorithm was orthogonalized and triangulated by Householder transformation,and the Zernike coefficients were given directly. The fitting coefficients of the Zernike polynomial of the big and small pupil were computed respectively by using this new algorithm and by constructing normal equation group. The computational results show that two algorithms have equivalent computational precision with relative error of each order coefficient in less than 10%. By avoiding the computational error introduced by constructing normal equation group, the algorithm is easy to used in programming and has proved to be an efficacious algorithm.Keywords：wave-front aberration;Zernike polynomial;Householder transformation;fitting coefficient- 33
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Published：2020-08-12 -
Feature-oriented coupled bidirectional flow equation for image denoising and edge sharpening
Abstract：A new type of diffusion process simultaneously denoising and sharpening images was considered. According to the image features such as edges, textures, and fine parts, the feature-oriented coupled bidirectional flow process could switch from a forward diffusion to a backward (inverse) one along the normal directions to the isophote lines (edges), while a forward diffusion was performed along the tangent directions. To eliminate the conflict between the backward and the forward force, the diffusion process was splitted into a coupled scheme. In order to enhance image features, the nonlinear diffusion coefficients were locally adjusted according to the directional derivatives of the image. Experimental results demonstrate that the algorithm can substantially enhance features on denoising smoother areas of the image.Keywords：image enhancement;edge sharpening;bidirectional diffusion;inverse flow;anisotropic diffusion;shock filter;splitting and coupling;directional derivatives- 45
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Published：2020-08-12 -
An algorithm applied in frontal-view face images for automatically localizing eyes
Abstract：Based on the ellipse-like outline of human eyes, an algorithm for localizing eyes was presented. After edge extracting from the face image, least square ellipse fitting was performed on all points on the edges. According to the proportions of eyes width and height, a threshold was given to confirm eyes candidate regions. A trained Support Vector Machine (SVM) classifier was applied to identify eyes regions. Finally, a circle detection operator based on directional Circle Hough Transform (CHT) was used to localize the eyeball center in the regions resulting from SVM classifier. The experiments were carried out on ORL and self-built face database. The results indicate that the method can accomplish the localization in 1.25 s and 3.0 s respectively, while accurate identification can reach 91.6% and 95%, the average localization errors are 7.26 and 3.45 pixels respectively. At the same time, the results also demonstrate that the method is very robust to face's in-plane rotation, scale and facial expression variation.Keywords：edge extraction;ellipse fitting;Support Vector Machine (SVM);detection operator- 60
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Published：2020-08-12 -
Classification of digital mammograms using multi-resolution histogram features
Abstract：A classification approach of digital mammograms using multi- resolution histogram representation in conjunction with kernel-based learning methods was presented. The approach didn't rely on the feature selection step and learned to classify various kinds of Region Of Interest (ROI) as normal/abnormal using its high-dimensional multi-resolution histogram features. Receiver Operating Characteristic (ROC) analysis of classification performance of the proposed approach shows that the sensitivity is about 89% and the Area Under Curve (AUC) is nearly 0.91. Compared to previous approaches, the proposed approach does not need to select abnormality-specific features so that it can detect various kinds of abnormalities simultaneously, which simplifies the detection process and improves the detection efficiency. The results demonstrate that multi-resolution histogram features can clearly distinguish the normal or abnormal classes in mammograms and the feature selection step of certain classification tasks can be eliminated or limited by using kernel-based learning method.Keywords：pattern classification;computer-aided diagnosis;multi-resolution histogram;kernel- based learning method- 33
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Published：2020-08-12 -
Breast tumor classification based on shape features of ultrasonic images
Abstract：The shape features of breast tumor in ultrasonic images are of great significance in the diagnosis of breast cancer. A computer-aided diagnosis system based on shape features was proposed to increase the accuracy of ultrasonic diagnosis of breast tumors. The tumor boundaries were firstly obtained using the gray-level threshold segmentation and dynamic programming and three shape features were subsequently calculated. Finally, the Fisher linear discriminant, neural network with error back propagation algorithm and radial basis function network were applied respectively to classify breast tumors as benign or malignant. Experiments on 157 cases (including 81 benign tumors and 76 malignant ones) show that all of three classifiers can achieve a higher precision, and the accuracy, sensitivity and specificity are as high as 94.95 %, 95.74% and 94.23 % respectively for both of two neural networks. Therefore, it is concluded that the proposed system based on shape features performs well in the ultrasonic classification of breast tumors as benign or malignant.Keywords：ultrasonic image;shape feature;breast tumor;Fisher discriminant;neural network- 31
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Published：2020-08-12
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