Chinese Version Light学术出版中心
Latest Issue
Issue 4 ， 2007
-
High speed two-photon laser nanofabrication of three-dimensional microstructures
Abstract：A high speed fabrication technique based on two-photon polymerization is proposed for fabricating three-dimensional (3D) microstructures and its spatial fabrication resolution is also studied. Based on the study of high speed scanning, a microfabrication system assembled a set of galvano mirrors and 1D PZT stage is established, and the jump and mark moving mode is used in this fabrication system with line by line scanning mode for improving fabrication speed. Two different kind of structures(a microscaled swift horse and a log-pile photonic crystal) are fabricated in experiments. Experimental results indicate that the fabrication speed can be improved 10 or 1 000 times than that method based on point by point scanning mode. The experimental results also reveal that the spatial fabrication resolution can be improved efficiently with shortening the exposure time under a fixed laser power, and the highest spatial fabrication resolution is achieved as 50 nm,which is higher than the highest resolution of 100 nm published in literatures. With high speed and excellent spatial resolution of fabrication, this technique is a powerful tool for micro/nano parts used for photonic devices and MEMS.Keywords：two-photon polymerization;high speed fabrication;three-dimensional microstructure;fabrication resolution- 30
- |
- 5
- |
- 10
Published：2020-08-12 -
Study on dimensional precision of UV-lithography on SU-8 photoresist
Abstract：The impact of diffraction effect on the dimensional precision of UV-lithography based on SU-8 photoresist was investigated. An improved UV exposure model based on Fresnel diffraction theory was proposed to use in predicting the dimensions of photoresist microchannels and their variations with changes in the lithographic parameters. In four different experiments, the characteristic width of photo masks were 50 μm, 100 μm, 200 μm and 400 μm, respectively, and the exposure dose on the surface of SU-8 photoresist was 400 mJ/cm2. In the experiments, the silicon was chosen as substrate. The top width, bottom width and thickness of SU-8 photoresist of cross section of microchannel in four different experiments were measured with SEM. The distribution of exposure dose in the SU-8 photoresist was simulated numerically with MATLAB. Comparing the simulative results with experimental results, a good agreement between them is acquired. The simulation results can be used to instruct the further experiments.Keywords：SU-8 photoresist;Fresnel diffraction;UV lithography;dimensional precision;MATLAB- 58
- |
- 7
- |
- 5
Published：2020-08-12 -
Optimization of solidification process parameters in micro stereo lithography
Abstract：For analysis on the effect of process parameters on the shape and precision of solidification in photosensitive resin solidification with UV light exposing, the main solidification process parameters are analyzed and optimized based on the experiment data got by self-made equipment. The high precision solidified line is abtained in the thickness of a single layer of liquid resin of 30 μm, the exposing power of 0.15 μW, the scanning speed of 15 μm/s and the working length between objective lens and surface of resin of 650 μm. With the optimized process parameters, 3D micro structures are manufactured successfully.Keywords：micro fabrication;micro stereo lithography;light solidification;process optimization- 48
- |
- 6
- |
- 2
Published：2020-08-12 -
Gray-scale response of spatial light modulator incorporating ferroelectric liquid crystals
Abstract：An equivalent circuit model of Optically Addressed Spatial Light Modulator (OASLM) incorporating Ferroelectric Liquid Crystal (FLC) is proposed. The model is used in studying gray-scale response of the OASLM and intensity transfer characteristics while drive voltage frequency varying from 100~1 kHz and write-light intensity varying from 0~10 mW/cm2. The results indicate that the rise time of electro-optical responses decreases from 1.44 ms to 74 μs as write-light intensity increases from 0.5 mW/cm2 to 10 mW/cm2. It also indicates that write-light intensity has a range over which gray-scales are best produced since output-light intensity increases linearly or nearly linearly with write-light intensity in this region. The intensity transfer characteristic is highly dependent on drive voltage frequency which can be set to adjust the region producing gray-scales, the slope of intensity transfer characteristic in the region producing gray-scales, and so forth. When write-light intensity increases from 0.5 mW/cm2 to 10 mW/cm2, the gray-scale range (0.08 mW/cm2, 1 mW/cm2) is changed to (2 mW/cm2,10 mW/cm2), and the slope of intensity transfer characteristic in the region is decreased. Furthermore, although intensity transfer characteristic is weakly dependent on erase-light intensity, the erase-light is necessary to restrain the unexpected optical response when write-light is not injected and ensure a proper erasure of the device. The simulation results from the model have shown good agreement with the reported experimental results in both magnitude and tendency.Keywords：Ferroelectric Liquid Crystal (FLC);Optically Addressed Spatial Light Modulator (OASLM);circuit model;gray scale response;intensity transfer characteristic- 55
- |
- 8
- |
- 2
Published：2020-08-12 -
Investigation on interference filter within planar waveguides
Abstract：A new narrow-band filtering method based on the theory of multi-layer thin-film optical interference is proposed. A multi-layer interference filter is integrated within a waveguide channel completely in this scheme, so it is actually a part of the waveguide. Two different structures of waveguide interference filters are investigated and the output spectrum of a two-cavity structure with 27 periodic layers and the field distributions of a single-cavity structure are calculated. Finally, by changing the materials and structure, the influence of refractive index, thickness of waveguide thin-film layer and incident angle on peak transmittance, peak width at half-maximum, extinction ratio and effective area are analyzed. and the direction for further development is given too.Keywords：integrated optics;optical switch;waveguide filter;interference filter;transmission spectrum- 53
- |
- 6
- |
- 1
Published：2020-08-12 -
Research on spatial division multiplexing of fiber Bragg grating sensors
Abstract：Controlled by an optical switch, a fiber Bragg grating sensing system based on spatial division multiplexing is developed under a broad-band source illumination. With an isosceles triangle cantilever beam to realize linear tuning of Bragg wavelength of fiber grating without chirping,the system employs an unbalanced Mach-Zehnder interferometer to translate the FBG wavelength signal into phase signal. The strain can be recovered by measuring the phase change with signal processing circuit. With a high resolution characteristic and wide measurement range,this sensor system has the capability of measuring static strain as well as dynamic strain. Experiment demonstrates that the sensing sensitivity of this system is resolution of 7.3/με,and experimental sensitivity of 0.82°/με.Keywords：Fiber Bragg Grating(FBG);stain sensing;interferometric demodulation;spatial division multiplexing;Phase measurement- 42
- |
- 5
- |
- 20
Published：2020-08-12 -
Fiber sensor for biomass' online testing
Abstract：The sensor design, structure theory, light path, theory analysis and experiment are introduced. The light absorption and scattering are related to the light distance and incidence energy, and the change of the biomass concentration makes the changes of the light absorption and scattering, and leads to the change of the receiving energy. Based on the physical phenomena and theory, a new method to measure the biomass concentration is set up. Under the constant temperature(20℃) circumstance, the biomass concentration is tested using a 760 nm lamp-house. The result indicates that the method is good for testing the bacterium liquid concentration; the maximum relative error is less than 0.2%. It is advantage in precise on-line testing, high sensitivity and long life etc and can be used in testing microbial bacterium liquid on-line.Keywords：biomass concentration;online testing;optical fiber sensor;absorption;scattering- 72
- |
- 6
- |
- 10
Published：2020-08-12 -
Design of a new complex imaging object lens
Abstract：Two designing results of a complex imaging object lens and its advanced design method are described. A thin lens with less power is added near the stop location in the advanced design, which can reduce 5th negative spherical aberration and give 5th negative astigmatic(-0.1107) to match the 5th positive astigmatic given by the former design. It also gives -0.0628 negative field curve. The astigmatic and field curve are obviously improved to get a better image, Especially, the value of MTF in 1 field is 0.493 in advanced design.Keywords：image object lens;refraction;optical design- 47
- |
- 8
- |
- 5
Published：2020-08-12 -
Mathematical model of contacting aspheric surface contour measurement
Abstract：After analysis of the possible causes for the measurement error of contacting contour measurement instruments, based on the least square method, a mathematical model was established to correct the errors caused by the inclination in X, Y direction, eccentricity in X, Y, Z direction that exists in the positioning of aspheric lens, inaccuracy of curvature radius, and the random micro-excursion between the circumrotating center and the detecting header of contour measurement instrument. By mathematical simulation, it is proved that this model could achieve high precision in correcting those errors stated above. To eccentricity less than 1 cm and inclination less than 0.1 degree, this model could completely correct these errors, it is also very effective in correcting the errors of curvature radius. The results of practical engineer implementation indicate that this model is very reliable and effective and can provide a loose lens positioning condition and function of automatic fit of optimal curvature radius for the measurement of contacting aspheric lens contour. Especially this model offers the function of automatic correction of measurement errors originated from the random micro-excursion between the circumrotating center and the detecting header of contour measurement instrument, and it will improve the measurement accuracy and measurement result repeatability of the contour measurement instrument.Keywords：aspheric surface contour measurement;contour measurement instrument;data processing;mathematical model;least square method- 61
- |
- 8
- |
- 10
Published：2020-08-12 -
Principle and experiments of swing-arm profilometer
Abstract：The geometric principle of a swing-arm profilometer as a novel method to measure aspherics are introduced. The surface error of an asphere is obtained by testing its relative departure from some reference sphere,and different reference spheres are realized by adjustment of the length of the swing-arm and the angle between rotary axis and optical axis. A measuring set-up is built based on this principle, which consists of an ultra-precise 2-axes rotating-table, a high stiffness, lightweighted measurement arm, a 4-DOF stage and a scanning sensor,the testing software and data-processing software are programmed with the VC++6.0 and Matlab platform, respectively. The profilometer has advantages in shorter measuring range for a sensor and simple rotary measuring motion,and the disadvantages in complicated calibration and large DOF adjustment. A mathematic model is established to gain the error of conic aspheric parameters and surface error based on the nonlinear optimization of measured data and nominal figure,and the full-apearture of a 3D asphere is tested by measuring several transversals. Finally,a grinded paraboloid (D=200 mm,R=1 400 mm) is tested, results indicate that the system has a good repeatability (<0.8 μm) and accuracy (<1 μm).Keywords：aspherics;swing-arm profilometry;profile measurement;contact measurement- 50
- |
- 5
- |
- 9
Published：2020-08-12 -
Optical implementation method of perfect shuffle transformation
Abstract：In order to use optical methods and optical elements to implement perfect shuffle, a perfect shuffle transformation method using micro-blazed grating array was proposed. The left inverse perfect shuffle, right perfect shuffle and the right inverse perfect shuffle are discussed complementally based on some reports on left perfect shuffle in previous papers. According to the different grating period values, a 1×8 micro-blazed grating array element for realizing 8-channel left perfect shuffle transformation is fabricated with Very Large Scale Integration (VLSI), stepping photolithography and Reactive Ion Etching (RIE). Similarly, depending on the micro-blazed grating array with different period values, the left inverse perfect shuffle, right perfect shuffle and the right inverse perfect shuffle transformation also can be accomplished. Experimental results show obviously that, comparing with conventional methods, it has advantages of small size, compact structure, easy to integrate, high diffraction efficiency (95% or so in principle), and high performance. Thus, it should be helpful in constructing multistage perfect shuffle interconnection network.Keywords：optical network;optical interconnection;perfect shuffle;micro optics;blazed grating- 55
- |
- 6
- |
- 1
Published：2020-08-12 -
Covering system for vision field of infrared earth sensor
Abstract：In order to protect the infrared earth sensor of FengYun No.1C and No.3 weather satellite's from sun radiation, a kind of protecting system of vision field is developed, and its merit and demerit, measuring method and calibration algorithms of peak value are studied.The disturbance to the infrared earth sensor by sun radiation is analyzed and two methods for protecting the vision field of infrared earth sensor are compared. A new covering non-scanning mechanical system, named sun sensor is developed, a kind of valid metrical device is designed to determine vision field range of sun sensor, and to deduce the academic formula of signal measurement. A calibration scheme for sun sensor's signal peak value according to theoretics of atmosphere radiation is provided. The running result of FengYun No.1C weather satellite in orbit shows that the sun sensor can protect infrared earth sensor effectively. The conclution is that the sun sensor can be successfully used to measure satellite gesture and also can be used in the infrared earth sensor of FengYun No.3 weather satellite's in future.Keywords：infrared earth sensor;protection for vision field;sun sensor;signal measurement;validating in orbit- 56
- |
- 6
- |
- 1
Published：2020-08-12 -
Study on solar cell testing system and its parameter matching optimization
Abstract：In order to get I-V characteristic curves and characteristic parameters of solar cells, the software system for solar cell testing is developed using Visual C++ based on Windows operator system. The parameters matching in compensative I-V testing circuit is analyzed in details. Analysis results show that series resistance and bridge DC power in the measurement circuit can slightly affect the dark I-V curve, however, they modify the light I-V curve significantly. The measurement data are basically agree with the standard data of solar cells by adjusting and optimizing the matching parameters and this error is only between 1% and 2%. The results show that this software system can meet the practical needs and also can provide accurate basis for the analysis of solar cells performances.Keywords：solar cell;testing system;I-V characteristic curve;parameter matching- 41
- |
- 6
- |
- 5
Published：2020-08-12 -
Study on characteristics of liquid flow through a rectangular microchannel with electrokinetic effects
Abstract：The presence of the Electrical Double Layer (EDL) near a solid-liquid interface results in the electrokinetic effect on pressure-driven liquid flow through microchannels. The equations governing the EDL field and the velocity field in the cross-section of rectangular microchannels are the two-dimensional Poisson-Boltzmann equation and the modified Navier-Stokes equation, respectively. In this paper,the equations are numerically solved employing a finite control volume scheme. The relationship between the pressure gradients and the Reynolds numbers is computed, and the differences between the predicted and the experimental Reynolds number from pressure gradients are well within 5%. It is found that the friction coefficients predicted by the model with electrokinetic effect are higher than that predicted by the macroscale fluid theory in the same microchannel. Stronger deviations are observed as the solution concentration decreases.Keywords：electrokinetic effect;friction coefficient;Reynolds number;finite control volume scheme;Computer simulation- 53
- |
- 6
- |
- 5
Published：2020-08-12 -
Research on a three-link six-DOF micromanipulator with flexure hinges
Abstract：A three-link six degree-of-freedom (DOF) parallel micromanipulator is presented. Three inextensible limbs with the spherical flexure joints and single-axis rotary flexure joints at the two ends are adopted to simplfy the complex stucture and a monolithic base plate that consists of three 2-DOF compliant units is utilized to reduce the assembly error. The piezoelectric elements are used as the high resolution actuators. The kinematics solutions are analyzed using the kinematic influence coefficient theory, as a result, the velocity of a movable platform, the limbs and the flexure hinges are derived. The stiffness model of the micromanipulator is determined considering the elastic deformations of the flexure hinges based on virtue work principle. The design targets and the design principles are discussed and the precise position controller modules are used to control the micromanipulator. Finally, the primary experiment tests are performed and the results show that the nanometer scale precision is attained.Keywords：micromanipulator;flexure hinge;Kinematics;stiffness analysis- 33
- |
- 4
- |
- 9
Published：2020-08-12 -
Coupled electromechanical dynamic model of magnetically suspended table system and its stability analysis
Abstract：A coupled electromechanical dynamic model is set up completely,and the mechanical model is established based on Lagrange equation. Considering the coupled action among every electromagnetics, geometric center of sensors on different positions and the centroid of the magnetic table and based on PID control theory, electrical differential equation of the control system is set up. The coupled action of the mounting of sensors on different positions of electromagnets is analyzed. Finally, the stability analysis for the magnetic table is processed based on the coupled electromechanical dynamic model. The range of the controlling parameters is found when the magnetic table is suspending stably, vertical direction: 0.3＜Kp＜141.5,0＜Kd＜0.052,horizontal direction: 0.3＜Kp＜77.4,0.001＜Kd＜0.038. Experimental results indicate that the magnetic table can suspend stably and has better dynamic and static characteristics just while the controlling parameters are selected at the correct range.Keywords：magnetic suspended table;dynamic model;stability;control parameter- 41
- |
- 5
- |
- 4
Published：2020-08-12 -
Research of a monostabillity micro electromagnetic relay
Abstract：A new optimized structure of micro electromagnetic relay was introduced, and its working principle was presented. By analysis of the driving force and the displacement of the armature, a three-dimensional structure was designed to increase the efficiency of magnetic circuit. A prototype micro electromagnetic relay with dimension of 5 mm×5 mm×1 mm was fabricated based on the MEMS fabrication process. The micro relay consist of a magnetic circuit, an excitation planar coil, a fixed contact pad and a permalloy cantilever (armature). Experimental result shows that when the micro electromagnetic relay in the resistance of the excitation coil of 20 Ω works at 5 V,its contact resistance is 14.5 Ω and respond time is about 1 ms under the electromagnetic actuation.Keywords：electromagnetic micro relay;micro actuator;MEMS- 42
- |
- 6
- |
- 0
Published：2020-08-12 -
A novel micro-gripper integrating micro tri-axial force sensor
Abstract：A novel micro gripper integrating micro tri-axial force sensor and two-grade displacement amplifier is presented bases on piezoresistive detection and using PZT as its micro driving component. The micro tri-axial force sensor consisting of a flexible cross-structure realized by Deep Reactive Ion Etching (DRIE) is fabricated on a single-crystalline-silicon by MEMS technology.The arms of the cross-structure are connected to a silicon frame and to the central part of the cross-structure. After modeling the amplifier structure of micro gripper and the sensor, Finite Element Method (FEM) is used to analyze the displacement of the micro gripper and the deformation of the elastic cantilever. Then the calibration method of tri-axial sensor based on the microscopic vision and the cantilever beam's principle is proposed. The experimental results show that the major feature of the sensor are the high level of intrinsic decoupling of the signals from strain gauge, high resolutions in all three axes, high linearity, repeatability and simple calibration. In addition,they also show the micro gripper is reasonable and practical. The sensor is capable of resolving forces up to 10 mN with resolution of 2.4 μN in x axis and y axis and up to 10 mN with resolution of 4.2 μN in z axis; the maximal gripping displacement of the micro-gripper is 274 μm under a driving voltage of 200 V.Keywords：micro tri-axial force sensor;PZT;Decoupling;micro-gripper;finite element method- 49
- |
- 6
- |
- 7
Published：2020-08-12 -
Precision measurement for small size parts based on support vector regression
Abstract：In order to improve measurement precision and measurement speed of small size parts, a new kind of precision measurement method based on Support Vector Regression(SVR) for micro size parts was put forward. Taking the tooth shape chain board as the study object, its main parameters were measured. Using a transillumination in this system, the digital image of tooth shape chain board was collected by A102FCCD device, and was input into computer by IEEE1394 digital card. Then, the original gray level image was processed by reducing noise with median filtering, creating a binary image with threshold method, extracting contour and rotating the image. The image rotation can be realized using Hough transform to detect the longest line. After the image processing, the original gray level image with noise was changed into edge information with single-pixel width. Based on the theory parameter calculation of the tooth shape chain and SVR principle, the detected regions were determined according to the proportions of the length and width oftooth shape chain board. By pixel points on edges in the detected regions, the training set of corresponding line section was madeup for the support vector regression to obtain the regression function of every detected line section, which is the expression of the sub-pixel, and then the main parameters of the tooth shape chain board were measured. Finally, the measurement error was analyzed. The measurement results meet tolerance requirement of the part. The measurement precision can reach 2 μm. Theory analysis and experimental results show that the proposed method significantly reduces the effect of the discreteness of CCD and the system noise on the measurement precision, and is characterized by high speed and high precision. At the same time, this method is very robust to image in plane rotation, scale varation and noise.Keywords：image processing;precision measurement;CCD;Support Vector Regression (SVR);tooth shape chain board- 46
- |
- 5
- |
- 8
Published：2020-08-12 -
Design of CCD FTF4052M driver system with high sensitivity
Abstract：The driver system of CCD is the key part of a digital camera, which is related to camera's technical parameters.In this paper the inner structure and driver timing of a high sensitive full frame CCD FTF4052M is introduced. The special integrated chips are adopted to design the driver circuit to use in the digital air survey camera. SAA8103 is selected to generate the driver pulse for the CCD. It is combined with the V-driver IC(TDA9991) to generate the vertical driving signals and also connected with the chip 74ACT04 logic drivers to generate horizontal driving signals. It is proved that the CCD driver system designed by special integrated chip can output two groups of CCD signals in data output speed of 2 frame/s.For its good function, low power consume and small volume,the driver system can meet the need of the camera system.Keywords：FTF4052M;CCD driver circuit;pulse pattern generator;H-driver pulse;V-driver pulse- 62
- |
- 6
- |
- 13
Published：2020-08-12 -
New method for detecting and tracking of moving target based on difference and invariant
Abstract：A new method for detecting and tracking moving target is proposed based on combination of image difference and feature invariant. A more complete and clear contour is acquired using three-frame difference. And a feature invariant is constituted without influence of object's size change, shifting, and rotation based the contour.Then a dynamic extremum-matching method is proposed for recognizing and matching the object based on extreme point information and replacing the former moldplate with the new one. The experimental results indicate that the method can successfully detect moving target and accurately estimate its trajectory in the image sequence with less memory even when the object figure is changed during movements. Moreover, it is efficient and adaptable for real-time target detecting and tracking, and it can meet the demands in real-time detecting and tracking moving targets.Keywords：target recognition;tracking;difference image;feature invariant;dynamic matching- 43
- |
- 6
- |
- 23
Published：2020-08-12 -
A novel method of key design in optical encryption system based on JTC architecture
Abstract：After analyzing and summarizing the problem of key design in JTC encryption system, an Iterative Algorithm based on Fuzzy Control Theory (IAFC) in place of G-S was proposed, and the comparison with G-S and Sleek Revise(SR) algorithms was given. Computer simulation experiment, as well as theoretical research show that the amplitude mean square error of the iterative output derived from IAFC is 0.69%, and the amplitude un-uniformity is 1.01%. Therefore the decryption quality of key design from IAFC is better than that of key designed from G-S and SR algorithms.Keywords：optical encryption;JTC;Iterative Algorithm based on Fuzzy Control Theory (IAFC)- 57
- |
- 7
- |
- 5
Published：2020-08-12 -
Regularization algorithm for blind image restoration based on wavelet transform
Abstract：A wavelet based adaptive regularization scheme for blind image restoration is presented. The degraded image is decomposed to obtain its wavelet coefficients in wavelet domain, and the image’s different frequency sub-bands are obtained also. Then, different adaptive regularization image restoration schemes are used in different sub-bands: removing blur in the low frequency sub-bands, while reducing noise and preserving edges in the high frequency sub-bands, and the algorithm finally obtains a restored image by adverse transforming. The experiments show that the MSE has a reduction of 1.60, while the SNR is increased by 1.76. It demonstrates that the blind image restoration method is more efficient compared with traditional space-adaptive regularization method.Keywords：blind image restoration;wavelet transform;regularization- 35
- |
- 7
- |
- 13
Published：2020-08-12 -
Control points' light spot image recognition in light-pen
Abstract：A light-pen single-camera 3D coordinate vision measurement system is introduced in this paper. By analysising characteristics of the system image, a digital method for recognizing the elliptical light spot images of the measured control points is proposed. On the basis of the pixel number of a measured control point' elliptical light spot image contour, too large and too small light spot images can be eliminated. Then, using the method based on the evaluation for elliptical profile error, the measured control points' elliptical light spot image can be recognized. The algorithm for this method is given, and the experimental results show that this algorithm is simple, fast, easy to realize and practical to the vision inspection system with circular measured control points. Compared with the common method, which applies the filter mounted on the CCD camera lens to segregate the noise bright spot image in the image background,it has certain theoretical significance and practical project value.Keywords：image recognition;control point;elliptical light spot;Vision coordinate measurement;light-pen- 47
- |
- 7
- |
- 5
Published：2020-08-12 -
Post-processing of low rate compressed image using edge preserving regularization
Abstract：A regularization method is proposed to implement the post-processing task from the view of image restoration. The mathematical model of regularization is analyzed, also the properties of the regularization function with edge preserving. Then, the potential function is chosen and modified according to the tradeoff among the complexity, robustness and the granularity control,and the half-quadratic regularization strategy is applied for the reason of achieving the fast minimization of the energy function. Finally, the specific alternative iteration for the minimization process is described. The proposed method is adaptive to the edge details of images and can reach the minimum values fastly. The experimental results show that the method can improve the subject and visual quality of image. Compared with the MAP based algorithm, it may preserve more image details.Keywords：image compression;post-processing;low bit-rate;regularization;edge preserving- 48
- |
- 5
- |
- 1
Published：2020-08-12 -
Reconstruction of 3-D surface of mirror by processing fringe pattern
Abstract：The fringe patterns of a measured mirror are captured by Twyman-Green interferometer, the sampling height of the mirror surface is obtained by image processing of fringe patterns, Zernike polynomial is adopted to fit the function of the mirror curved surface and get the 3D measurement of the mirror surface height. The distances between two adjacent fringes to reference mirror space is a standard light source wavelength apart, so the key of this measurement method is to locate the wave crest or wave hollow of fringe pattern accurately, thus the task of sampling height of mirror surface is completed. A Butterworth low-pass filter is used to remove the noise of fringe image, then the bright fringe is segmented by binary conversion and is thinned into its centerline by morphologic method. The thinning result indicates that low-pass filter could reduce the amount of branches and breaks of center lines. Finally, giving the relevant height of every center lines and using the pre-39 items of Zernike polynomial to fit the mirror surface height by least square solution, the 3D data of sample surface of mirror is calcalated. This method can be use to measure the laser-induced deformation of mirror.Keywords：fringe pattern;image processing;noise removal;Zernike polynomial- 50
- |
- 6
- |
- 2
Published：2020-08-12 -
Effect of modulation frequency Jitter on coherent detection and its elimination algorithm
Abstract：The causation of MFJE (Modulation Frequency Jitter and Excursion) is generally introduced,and the error of MFJE in coherent detection is analyzed at the same time, the mathematic models of MFJE error in analog and digital coherent detection process are built. Based on the mathematic models, the effects of MFJE on analog and digital coherent modulation-demodulation process are identified, especially the effect of MFJE on discrete sampling. Finally, a Membership Weighted Function Sampling ( MWFS ) algorithm is proposed. The experimental result shows that the precision of coherent detection has not been affected in a modulation frequency excursion range of ±9.2% with MWFS , compared with the range of ±3% without MWFS . The result also shows that the mathematic models of MFJE error in analog and digital coherent detection process are valuable in coherent detection application field and MWFS proposed in the paper can eliminate the effect of modulation frequency excursion on coherent detection efficiently, which has been certified in practice.Keywords：coherent detection;latent frequency;membership function;fuzzy set- 38
- |
- 9
- |
- 9
Published：2020-08-12 -
Measurement of sparse scatter particulates based on computer vision
Abstract：A method to measure micro particulates based on image processing is presented. The particulate image is collected and pre-processed by CCD combined with a image-processing software system, then segmented by threshold mothod. By using flour as specimens and utilizing the dynamic clustering method coded by C++, the 16 particulates with the maximum radius of 1.600 μm, minimum radius of 1.000 μm, average radius of 1.187 5 μm and standard deviation of radius of 0.661 4 have been obtained. The experiment results indicate that the presented method is effective and feasible.Keywords：particulate radius;field flow fractionation;CCD;dynamic clustering- 47
- |
- 6
- |
- 2
Published：2020-08-12 -
Multiframe postprocessing algorithm of laser active imaging images
Abstract：After fixing on the divergent angle,peak power of laser pulse,parameters of received optical system and the geometrical configuration between laser and received optical system, a faint target image of longer range with higher resolution obtained by active imaging system is constrained by imaging and processing technologies. With longer range and limited laser energy, it is impossible to illuminate the entire scene at once, and the illuminance obtained by each receiver pixel of CCD can not achieve an adequate level. In order to increase the imaging range of imaging system with given per-pulse laser energy, and to reduce atmospheric turbulence effects on image resolution, multi pulses may be employed to obtain image data over the whole scene and radiometric conceptions are used to establish the maximum scene illumination region during each exposure.A unique multiframe postprocessing technique is investigated in this paper. It is shown that in the presence of atmospheric turbulence and coherent speckle effects, this approach can produce superior results to conventional scene flood illumination.Keywords：laser active imaging;multiframe postprocessing;image registration- 64
- |
- 12
- |
- 1
Published：2020-08-12
Loading...
0