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Issue 2 ， 2007
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Optical system of light star tracker with wide field and large aperture
Abstract：Star tracker composing of optical system, photoelectric receiver and image processing element is a key equipment of satellites for star position. In this paper, we present a optical system of light CCD star tracker with wide filed and large aperture in a focal length of 25 mm, a F-number of 1.2, a working wavelength range of 470~750 nm and a view angle of 25 degrees. The optical system is composed of a double-Gauss lens and a piece of positive lens, considering the large F number. In order to decrease the input angles of the axial and off-axial light bundle, the glass with high refractive index is used to produce smaller high-order aberrations and shorten the total length of the system. The imaging analysis results show that the design is a feasible scheme,and the total system length is only 46.51 mm.Keywords：star tracker;refraction;optical design- 31
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Published：2020-08-12 -
Investigation on space optical system of high F number and high resolution
Abstract：Space telescope with high F number can satisfy the requirements that the optical system should have the characteristics of high resolution and light weight. In this paper,we describe a uncoaxial three-mirror system simply and discuss on the rule of variation of laboratory static Modulation Transfer Function(MTF) at Nyquist frequency of the optical system with average wavelength of incident rays. Accordingly, the feasibility of telescope with big F number is analyzed. It is shown that the shorter average wavelength of incident rays and the higher MTF are; the better satisfaction ground resolution requires, which will offer the reference to the lightweight space telescope.Keywords：space telescope;wavelength of incident rays;F number;sensitivity- 46
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Published：2020-08-12 -
Machining reachability in ion beam figuring
Abstract：The conception and theoretical definition of machining reachability problem is proposed, and the existence condition of the solution of Dwell Time(DT) function is analyzed. Furthermore, we analyze and simulate the magnitude of the Extra Material Removal (EMR) in different process condition using different ion beam diameter to remove different spatial frequency surface errors. The analysis results show that the solution of DT function exists for the ion beam removal functions of Gaussian shape. However, for the higher spatial frequency surface error, the larger the solution of DT function is; the larger the magnitude of the EMR is. The magnitude of EMR is an exponential function of the ratio of ion beam diameter to the spatial surface error wavelength (i.e. d/λ). And when d/λ= 0.5, the EMR is 15%, which is acceptable in ion beam figuring process. When d/λ=1, it rapidly increases to 73%, which is unacceptable. Theoretical analysis and simulation results indicate that d/λ should be less than 0.5 in order to obtain acceptable process in IBF.- 39
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Published：2020-08-12 -
Effect of asphericity parameter on Seidal aberration and ablation depth in laser refractive surgery
Abstract：The anterior surface of cornea is the major refracting element of human eye, which contributes over 80 per cent of the refractive power of the whole eye according to the Gullstrand Number 1 relaxed schematic model eye. Small changes in the radius at the corneal apex will greatly affect the refractive power. Corneal ablation in refractive surgery is calculated according to corneal model, it is shown that the precision of corneal model directly affects the accuracy of refractive surgery. The simplest asphericity model is to assume that the corneal is a rotationally symmetric conicoid, and Q is the asphericity parameter of this conicoid. The effect of Q on transmission rate, Seidal aberration and ablation depth based on Littman-Gullstrand model is analyzed,the results indicate that Q greatly affects on the Seidal aberration and the ablation depth.Keywords：laser refractive surgery;asphericity parameter;Seidal aberration;ablation depth- 31
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Published：2020-08-12 -
Analyzing thermal deformation of ultra-thin mirror using Zernike polynomials
Abstract：Thermal deformation plays an important role in large diameter optics system with ultra-thin mirror. For analysing the specific and quantitive thermal deformation of ultra-thin mirror, a simulating method of temperature distribution by Zernike polynomials is pressented. The temperature is spreaded to different thermal modes having their own meanings in thermal field. For example, the tilt thermal mode means that temperature is high in one end and low on the other end. Summing thermal deformation introduced by different thermal modes to get overall deformation based on two rules is as follows: firstly, temperature is scalar and could be summed after divided. Secondly, every thermal mode introduces small deformation which could be simply added. Considering the relative difficult of theoretical analysis in elasticity, finite element method is used. Mirror model is established for large and thin systems in space without gravity and thermal gradient along radius. The fixed point locates in the center of mirror. To demonstrate this method, some geometric parameters are used from NGST(next generation space telescope). And finally, calculation reveales that different thermal modes introduces different types of surface errors:thermal modes of piston, tilt, focus, astigmatism, coma, spherical, mainly create figure errors of focus, tilt, focus, tilt, tilt, spherical, respectively. Also, thermal deformations could be much different: focus, coma and spherical thermal mode create relative large deformation, which means mirror is sensitive to these kinds of thermal modes. With the same 2 K temperature difference across whole mirror surface, thermal mode introducing larger thermal deformation is coma(56 μm PV), spherical & focus (18 μm PV) and focus (19 μm PV). In contrast, tilt thermal mode and coma thermal mode can create figure errors no more than 0.07 μm (PV) which almost have no effects on mirror function. Also, to find which kind of thermal mode is more possible, the environment should be put into consideration. Using Zernike polynomials to simulate mirror temperature distribution can give some meaningful findings and is proved to be useful for analysis of ultra-thin mirror.Keywords：thermal deformation;Zernike polynomial;thin mirror;finite element method- 62
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Published：2020-08-12 -
Effects of different micro-feature structures on warpage and deformation of light guide plate
Abstract：To study the influence of different micro-feature structures on the warpage and deformation of injection molded light guide plate,We applied MoldFlow MPI5.0 to simulate the influence of five different micro-feature structures (micro V groove structure , micro U protrude structure , micro pyramid structure , micro cirque structure and micro lens structure) on the warpage and deformation of light guide plate with 11 mm×3 mm×0.8 mm dimensions for the first time. The results show that the influence of micro lens array structure on the warpage and deformation of the light guide plate is bigger than that of other microfeature structures, the biggest warpage and deformation of micro lens array light guide plate is 0.039 7 mm, and the influence of micro rings array structure is the smallest one. With the same processing parameters,the warpage and deformation of micro rings array light guide plate is 0.028 2 mm, the difference reaches 40.78%, furthermore the influence of convex micro-feature structures is bigger than concave micro-feature structures at all time. It is shown that we should consider the influence of different designs of micro-feature structures on the injection molding of light guide plate in advance, and the preferences are concave micro-feature structures like micro cirque structure.Keywords：light guide plate;warpage and deformation;micro-feature structure;simulation- 43
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Published：2020-08-12 -
Measurement of inside screw curve surface by laser probe
Abstract：The characters and factors were analyzed when the laser probe measurement was used in inside screw surface. According to the noise distribution of the laser speckle on the measured plane, a synthesis filter algorithm combined the median filter and the wavelet threshold denoising method was designed to eliminate noise of the image,in which median filter can effectively wipe off the impulse noise in the speckle image, and the threshold denoising algorithm based on wavelet transform can eliminate Gaussian noise of the image. The algorithm is able to remove the noise influence on measurement accuracy and maintain the image individual character. According to the intensity distribution of the laser speckle image on the declining object surface, the circle-fitting algorithm was proposes to overcome the affect of the laser speckle center shift caused by the slope surface to locate the center of the laser speckle image at the sub-pixel level. The algorithm has the features of high efficiency, less calculation compared with the traditional ones and is more suitable for testing on line. Laser probe scanning measurement base on coordinate machine using the above techniques was designed to measure an internal screw standard gauge. The results show that the internal screw-pitch measurement accuracy, pitch diameter of thread and the thread angle accuracy increase 0.48 mm, 0.44 mm and 0.57°,respectively.Keywords：inside screw measurement;laser probe scanning;filter algorithm;circle-fitting algorithm- 62
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Published：2020-08-12 -
Testing asphere by subaperture stitching interferometric method
Abstract：A subaperture stitching interferometric method was introduced, and the basic principle was analyzed. A reasonable mathematical model and a effective stitching algorithm were established based on homogeneous coordinates transformation, least square method and Zernike polynomial fitting. Meanwhile the computer simulation experiment was carried on with five subapertures for a parabolic mirror, the phase map after stitching is consistent to the inputed map, the difference of the PV and RMS of the full aperture surface error is -0.009 2 λ and 0.0013 λ after stitching, and the relative error of PV and RMS is -0.39% and 0.44%, respectively. The results show that the method is feasible and accurate, and can test large aspheric surfaces without compensators and other auxiliary null optics.Keywords：subaperture stitching;interferometry;aspheric surface;homogeneous coordinates transformation;least square fitting- 54
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Published：2020-08-12 -
Finite element simulation on packaging of hinged high-g micromachined accelerometer
Abstract：A novel packaged hinged high-g micromachined accelerometer was studied by finite element simulations. The mode shape of high-g accelerometer without packaging were analyzed, and then the first ten natural frequency characteristics of packaging structure without and with different potting materials were discussed. Experimental results conclude that the elastic modulus of potting material has a significant influence on the mode shape of the accelerometer packaged. The mode frequency of the packaging structure increases with the elastic modulus of potting material, but the small elastic modulus (E≤1 GPa) will bring a strong distortion of the accelerometer output. The simulation results also show that the potting material with enough large elastic modulus(E>9 GPa) should be optimal selection for high-g accelerometer.Keywords：high-g micromachined accelerometer;packaging;finite element simulation- 38
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Published：2020-08-12 -
Rotation-angle-accuracy measurement of piezo tilt platform
Abstract：A sub-arc-second-accuracy method for measuring rotation-angle was proposed. The tiny rotation-angle of the PZT was obtained using the diameter of the reference flat mirror divide the difference between the PVs when PZT move and don’t move. By measuring and analyzing, the rotation angle accuracy of the PZT is less than 1 μrad(0.2″).The total error changes with the rotation angle of the PZT,but its relative error was smaller than 1%. The result indicates that the measuring technique can meet the resolution of the EUT to 0.8″.Keywords：extra ultraviolet solar telescope (EUT);ZYGO interferometer;piezo tilt platforms (PZT);rotation-angle-accuracy- 37
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Published：2020-08-12 -
Measurement of microchannels of PMMA microfluic chip
Abstract：Based on CCD-image and image processing technology, a measuring system for microchannel's sizes was developed. The non-contact measuring method for geometrical sizes was presented by means of the digital image manipulation technology, including image preprocessing, image binary-conversion, boundary encoding and calculation of microchannel's geometrical sizes, etc. The measured results show that the maximum measuring error by proposed method is 2 μm,which accords with the results measured by a stylus profiler and a universal measuring microscope. The reasons to cause the error were analyzed,results indicate that this method is correct, feasible, simple to use, and can avoid the errors often made by stylus in deeper structures.Keywords：microfluidic chip;microfabrication;CCD image detection;size measurement;image processing;secondary calibration- 62
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Published：2020-08-12 -
Performance research on double-valved and three-valved piezoelectric pumps with double series-wound chambers
Abstract：By analyzing the working principles and structures of double-valved and three-valved piezoelectric pumps with double series-wound chambers, it was proved that the output ability of three-valved pump is better than that of double-valved pump. To explain the theoretical analyis,the pump samples were designed and manufactued,several experiments had been done when inlet chamber and outlet chamber work respectively, and the sum of flowrates was compared with that produced by their double chambers working together alternately. Experimental results show that double-valved and three-valved piezoelectric pumps' maximal output flowrates are 972 ml/min and 1 035 ml/min, maximal output pressures are 28.7 kPa and 40 kPa, and maximal self-suction heights are 0.41 mH2O and 0.43 mH2O, respectively when they are powered by AC 200 V,which indicates that the results agree with the theory very well.Keywords：PZT actuator;piezoelectric pump with double chambers;valve- 57
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Published：2020-08-12 -
A mechanical linkage of double crystal X-ray monochromator for synchrotron radiation
Abstract：A novel mechanism for the fixed-exit double crystal monochromator of Bragg-Bragg diffraction case used widely in synchrotron radiation was presented. The development of double crystal monochromator for synchrotron radiation X-ray was reviewed briefly, especially of the fixed-exit mode. Several kinds of implementation approaches for the energy scanning of the photons were summarized by analyzing the common mechanical linkage schemes. Based on the principle of mechanism with rotation plate coupling motions on fixed cams as well as right-angle linkage device, the L-shaped mechanical linkage used in successfully the double crystal monochromator of X-ray beamlines at National Synchrotron Radiation Laboratory (NSRL) was introduced in detail. It adopted the advantages of the above right-angle and motion coupling mechanism to operate the mechanical linkage in simple configurations and motions. Motion mechanism and position adjustment of the crystals, mechanical design of the related structure, and the incoming improvement were discussed,It is indicated that the mechanical linkage is suit for the experimental researches at 3.1~12.4 keV by off-line testing of the mechanism and on-line measurement of the monochromators.Keywords：mechanical linkage;motion analysis;double crystal monochromator;X-ray;synchrotron radiation- 54
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Published：2020-08-12 -
Mathematical model of all-fiber phase modulators with lead zirconate titanate coating
Abstract：A theoretical model of all-fiber phase modulators with Lead Zirconate Titanate(PZT) coating was proposed by simply considering radial strain in all-fiber phase modulators. It has been shown that piezoelectric coefficient d31 of PZT is as important as d33 to all-fiber phase modulatorsphase modulation of 15%. Effect of thickness and stiffness of the piezoelectric PZT films on the phase modulation efficiency is calculated. Results show that the materials properties of inner and outer electrodes of all-fiber phase modulators can be optimized with this model. This model is suitable for the design and optimization of all-fiber phase modulators.Keywords：all-fiber phase modulator;frequency response;PZT films- 63
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Published：2020-08-12 -
Dexterity measures of parallel machine tool and its application
Abstract：In order to study on dexterity measures of parallel machine tool(PMT) and its application in real processing, a novel 5-Degrees of Freedom (DOF) fully PMT consisting of five actuating limbs and one passive constraint limb is introduced, and its Jacobian matrix is established. The Jacobian matrix is used to define three dexterity measures: conditional number, the smallest singular value and operation. By analyzing three dexterity measures of parallel machine tools, two terms named comprehensive dexterity coefficient and comprehensive dexterity degree are defined to evaluate the dexterity of various configurations and whole cutter location file respectively. Finally, the method for evaluating the dexterity under various tool trajectories is introduced. Experimental results indicate that a relatively optimal trajectory z is 650 mm with a higher isotropy in real processing of circle(radius as 100 mm).It can satisfy the machine requirement of performance of motion and dynamics.Keywords：PMT;Jacobian matrix;comprehensive dexterity coefficient;comprehensive dexterity degree- 45
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Published：2020-08-12 -
Experimental study on power loss of integrated energy storage and attitude control flywheel
Abstract：The calculating method and the testing theory of power loss experiment were introduced, the flywheel power loss testing system was presented. By analyzing the component and influencing element of power loss in experiment, a approach of reducing power loss was given. Power loss of flywheel is composed of mechanical loss, wind loss and electric loss,in which mechanical loss caused by bearing friction is the most proportion. Our results show that the losses of wind and electricity can be decreased by enhancing vacuum degree, However, the mechanical loss is not influenced and it increases with the speed rising. When the speed is less than 10 000 r/min, the flywheel is better in capability because of the low mechanical loss. While the speed exceeds 10 000 r/min, the mechanical loss sharply increases. So the magnetic bearing is used to decrease the mechanical loss.Keywords：integrated energy storage and attitude control;power loss;experimental study;flywheel- 46
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Published：2020-08-12 -
Dynamical research on spherical micro actuator with PZT drivers
Abstract：A 30 mm×30 mm×50 mm spherical micro actuator driven by piezoelectric ceramic stacks (PZT) was developed, and the dynamics of the spherical micro actuator was analyzed, the micro assembly between micro shaft and micro spindle sleeve by the micro actuator was researched. First, this paper set up a space coordinate relationship of the spherical micro actuator to analyze dynamical characteristics. Following that, it used the Runge-Kutta arithmetic to calculate the dynamical parameters of the micro actuator and to built a dynamical model to simulate it by the SIMULINK module of MATLAB. After these, a spherical micro actuator experimental sample was developed, and a micromanipulator with a micro-gripper based on the sample spherical micro actuator was integrated, By the micro assembly experimental research between a micro shaft of Φ180 μm and a micro spindle sleeve of Φ200 μm, the characteristics of the spherical micro actuator impacted by the metal sphere mass of the micro actuator, driving signal frequency, friction coefficient of the contact surface between the metal sphere and the friction block of the micro driving unit were analyzed. The experimental results indicate that the rotate resolution, the rotate positioning precision and the maximum working frequency of the micro actuator are 0.000 1°, 0.000 5° and 1 200 Hz,respectively. The experimental results validate the back rotation and vibration model of the spherical micro actuator,it shows that the micromanipulator integrated by the spherical micro actuator can meet requires of precise micro operation and assembly for MEMS or other microelements in micron fields.Keywords：spherical micro actuator;dynamics;PZT;Micromanipulation- 38
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Published：2020-08-12 -
Analysis and restraining of random noise of optoelectronic tracking system
Abstract：Random noise is one of the key problems in the optoelectronic tracking systems. Two kinds of primary noise affecting the tracking performance-the noise of tracking error and the noise caused by momentum fluctuation and their relationship with the closed bandwidth are analyzed. Then the design strategy of the bandwidths of the velocity loop and the position loop are discussed. The analysis results show that the higher bandwidths of the velocity loop and the position loop are favorable to restrain the random the noise caused by momentum fluctuation. While it’s just reverse to the random noise caused by tracking error. Further analysis shows that the magnitude or the power of the output noise produced by the momentum fluctuation is lower than that caused by the tracking error by a quantitative level, about 1/6~1/10 of the latter, So the noise of momentum fluctuation can be ignored in the decision of the control bandwidth.Keywords：optoelectronic tracking;random noise;momentum fluctuation;tracking error;bandwidth- 50
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Published：2020-08-12 -
Spectral analysis and de-noising of MIMU raw measurement
Abstract：On the time-frequency view, the errors of MIMU signal were classified into long-term errors and short-term errors according to their spectral signature, and the error resources and performance of de-noising in GPS/MIMU integrated system were analyzed. Allan variance method was used to model and compersate the long-term errors, and the short-term errors whose frequency higher than the up band of motion dynamic was eliminated by optimal low-pass filter, the wavelet threshold filter was used to reduce the remained short-term errors. Simulation results show that the performance of integrated GPS/MIMU system has been improved by 20% when GPS is available and 80% while GPS blockages after pre-processing for MIMU signal.Keywords：MEMS IMU;spectral analysis;Allan variance;wavelet threshold filtering;integrated navigation- 47
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Published：2020-08-12 -
Anti-occlusion arithmetic for moving object tracking
Abstract：A new method with occlusion for color-based object tracking is presented. The proposed technique employs mean shift iterations to derive the object candidate which is the most similar to a given object model, then uses Kalman filter to estimate the real states of the object. A color-based histogram with different weights that is robust for partial occlusion is selected as the target feature. The similarity between the target model and the candidates is expressed by a metric on the Bhattacharyya coefficient. An occlusion coefficient is proposed. When the object is occluded seriously, the observation cannot be used for updating by Kalman filter, the former state of the object is regarded as the current state. The simulation experiments show that the tracking is robust to partial and serious occlusion.Keywords：object tracking;mean shift;Bhattacharyya coefficient;occlusion coefficient- 39
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Published：2020-08-12 -
Real time digital correction for distortion in photoelectronical measuring system
Abstract：In the photoelectronical measuring system with a big field of view of 70°, distortion caused by optical system leads to the image of object in linear CCD deviation from the theoretical point, which results in system measuring errors. In the practical project measuring system, in order to improve measurement precision of the point of laser goal in the system, a set of installation for optical detection systematic distortion is designed. This installation on the basis of distortion mechanism and radical character has eleven equidistance points of laser goal. For different optical measurement systems, when distortion is detected in according to three steps, the compensation equation for goal in linear CCD in real-time measurement is fitted. Then the program on data collection and real-time manipulation of imaging position will be compiled to improve the precision of measurement system on real-time nicety measurement. The experiment results show that the installation can reduce error obviously from -0.026 4 mm to -0.002 9 mm in according to the compensation equation when the distance is 1 651.59 mm and the height is 400.007 mm, and raise the whole systematic detection precision from 0.36% to 0.04%.Keywords：photoelectronic measurement;aberration;detection device;digital correction- 41
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Published：2020-08-12 -
Realization of high division number of coarse grating signals by fully digital processing method
Abstract：To meet the requirement of high accuracy measurement in coarse grating system, a fully digital processing method is presented, which consists of digital filter, digital error compensation and software digital subdivision. Two signals are filtered by digital filter in order to get waveforms closed to the ideal state and then, by analyzing the software digital subdivision theory, the expressions are deduced to verify how errors influence on the subdivision result. The errors include quadrature phase shift error, unequal amplitude error, zero offsets and the third harmonic. As a result, corresponded digital compensation methods are proposed. Finally, digital subdivision is adopted to obtain high division number. Simulation is employed to validate that the FIR digital band pass filter based on strict linear phase can effectively shield the noises in both high and low frequency bands, which are involved in signal spectra of grating. Experiment results indicate that fully digital method can raise division number to 500 with the precondition of coarse grating quality.Keywords：coarse grating;Subdivision;digital filtering;error compensation- 36
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Published：2020-08-12 -
Edge detection for image measurement based on nonlinear diffusion filtering
Abstract：Image measurement technique is a new developing method in the non-contact measurement and instrument fields. In this paper, an adaptive nonlinear flow equation process is presented to improve the measurement precision. First, an inverse diffusion is performed to sharpen edges along the normal directions to the isophote lines (edges), while a normal diffusion is done to remove noise and artifacts ("jaggies") along the tangent directions. Then, classical differential operator is employed to detect image edges. With a better edge location,experimental results show that sharper and smoother edges with one pixel are abtained in a relative error of 0.03. The method also shows its advantages in the minuteness measurement for a better edge location. In the case of blurry edges and additional noise in the image, the measurement results would be worse.Keywords：Image measurement;edge detection;edge sharpening;bidirectional diffusion- 56
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Published：2020-08-12 -
Key algorithms of automatic image measurement system
Abstract：In order to realize automatic image measurement for work pieces, an automatic image measurement system is established and the algorithms used in this system such as geometric figure recognition and measurement, height measurement based on autofocus, etc are investigated. The geometric figure recognition algorithms according to the geometric features such as the circle and circularity of area and rectangle are presented and measuring principles and algorithms of typical plane geometric figures are analyzed by taking the measurement of the line and circle geometric figures as an example i.e., the figure fitting is adopted after the edge points of geometric figures are extracted. Then, after the performance of several autofocus evaluating methods is compared, the algorithm of height measurement by visual automatic focusing is analyzed. Finally, the setting method for scale and the error compensation algarithm of raster reading are discussed as well. Experimental results indicate that the precision of the system's scale is 0.5 μm and the measuring precision of figures is within micron, the precision of height measurement is 0.035 mm, which can satisfy the system requirements of non-contact, online, real time, higher precision and rapid speed, as well as strong anti-jamming and stabilization.Keywords：computer vision;edge detection;geometric figure;curve fitting;subpixel- 39
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Published：2020-08-12
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