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Research Article
Measurement of density gradient for 2D flow field using grating schlieren deflectometry
MENG Tao, ZHANG Ming-zhao, WANG Ke-jun, GUO Xiao-li, and WANG Bo-xiong
A simple density gradient measurement system for 2D flow fields was proposed.The system introduced a grating into the traditional schlieren system and transformed deflection rays caused by density change of a flow field into the deformation of fringe pattern formed by grating projection,so density gradient information A simple density gradient measurement system for 2D flow fields was proposed.The system introduced a grating into the traditional schlieren system and transformed deflection rays caused by density change of a flow field into the deformation of fringe pattern formed by grating projection,so density gradient information of the flow field could be extracted from the deformed fringe pattern.With wavelet location characteristics,a wavelet transform phase demodulation method was applied to fringe pattern analysis to eliminate effect of invalid data effectively.Experimental results indicate that the measuring range of the system can reach 0.01 g/cm4 and the measurement precision can reach 5×10-6 g/cm4,which shows proposed system is simple in setup,easy in adjustment and suitable for density gradient measurement for flow fields with large density variation..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 973 (2008)
Experiments of sub-aperture stitching interferometry for flat mirrors
DING Ling-yan, DAI Yi-fan, and CHEN Shan-yong
For the purpose of validating a new stitching algorithm—Sub-aperture Stitching and Localization (SASL) algorithm,a measuring and figuring experiment was described for the SiC flat mirror with elliptical shape of 225 mm in major axis and 161 mm in minor axis.A comparative experiment of sub-aperture stitching test with fFor the purpose of validating a new stitching algorithm—Sub-aperture Stitching and Localization (SASL) algorithm,a measuring and figuring experiment was described for the SiC flat mirror with elliptical shape of 225 mm in major axis and 161 mm in minor axis.A comparative experiment of sub-aperture stitching test with full-aperture interferometry on a 100 mm diameter flat mirror was presented in order to determine the algorithm parameters and the precision requirement of stitching equipment.Following this,a sub-aperture stitching process for the SiC flat mirror was carried out,which contained 5 iterations of Ion Beam Figuring (IBF) process and a full-aperture testing.In this process,sub-aperture stitching test offered the surface error data precisely to IBF,which ensured the quick convergence for the process to achieve a final surface RMS error of 50 nm.The experimental results show that SASL algorithm relaxes the precision requirement for the stitching equipment and reduces the influence of stitching process on the results..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 978 (2008)
Near infrared spectrometer with double detectors for food component analysis
ZHANG Jun, CHEN Xing-dan, PIAO Ren-guan, and LI Shang-yu
A Near Infrared (NIR) diffuse spectrometer with double detectors was introduced to improve the stability of spectral signal.The monochromatic beam was separated into two light beams by a splitter in this spectrometer.One light beam was collected directly by a detector,the other was irradiated on the sample's surfacA Near Infrared (NIR) diffuse spectrometer with double detectors was introduced to improve the stability of spectral signal.The monochromatic beam was separated into two light beams by a splitter in this spectrometer.One light beam was collected directly by a detector,the other was irradiated on the sample's surface after passing through an integrating sphere.The diffuse light of the sample was collected with another detector on the integrating sphere.Finally,the values of the two detectors were compared to obtain the absorbency.The instrument was used to detect the diffuse reflectivity of standard diffuse reflectance surface.Detected results show that the mean correlation coefficient between the measured diffuse reflectance and the real values is 0.995.The mean standard deviation is 0.01.In addition,the instrument was used to measure some components including of milk powder,milk and soy sauce also,the correlation coefficients of calibration are over 0.8.It concludes that the homemade spectrometer can get the right diffuse reflectivity,and can be used in food component analysis..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 986 (2008)
Design of planar waveguide concave diffraction gratings
ZHOU Zhe-hai
In order to design a Planar Waveguide Concave Diffraction Gratings (PW-CDG) accurately,especially a special grating structure,a design method named Modified Recursive Definition of Facet Positions(MRD) was presented.The central position of grating facets could be obtained by two constraint functions,and its numerical sIn order to design a Planar Waveguide Concave Diffraction Gratings (PW-CDG) accurately,especially a special grating structure,a design method named Modified Recursive Definition of Facet Positions(MRD) was presented.The central position of grating facets could be obtained by two constraint functions,and its numerical solution was derived from a recursive formula approach.To improve the accuracy of computation,a Newton iteration procedure was introduced in the recursive approach to compute each facet position.Two typical design examples,a flat-fieled mount and a flat-top mount,were given to assess the necessity adopting Newton iteration procedure subsequently.Simulation adopting different design methods were compared with each other,comparison indicates that computed results by MRD are identical with that by Power-series Expansion of Light Path Function(PS) with higher power,both of them are more accurate than that of traditional Recursive Definition of Facet Position(RD).It comes a conclution that the modification is crucial for the accurate definition of grating facet positions..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 993 (2008)
Realization of Fourier telescope technology in laboratory
DONG Lei, LIU Xin-yue, and WANG Jian-li
In order to verify the validity of Fourier telescope technology,the experimental demonstrations were carried out in a lab.The time-modulated return signals containing Fourier information were obtained by scanning object with different space frequency fringes.Then,the object spectra were captured with Fourier demodulateIn order to verify the validity of Fourier telescope technology,the experimental demonstrations were carried out in a lab.The time-modulated return signals containing Fourier information were obtained by scanning object with different space frequency fringes.Then,the object spectra were captured with Fourier demodulated and phase closure techniques,and the constructive images were obtained by two-dimensional inverse Fourier transform.Finally,the constructive images of 3mm object were obtained in a lab.Compared with the computer simulation,the experimental results demonstrate that Fourier telescope imaging in the lab agrees well with the computer simulation,these results will be important references for later lab experiments and field experiments..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 999 (2008)
Multi-sensor joint detection in space-based pointing
ZHOU Yan-ping, TAO Kun-yu, QU Xiao-tong, and LIU Jun-li
A detection method for space-based targets was brought forward.By forecasting the motion track using a land-based radar,the space-based detector could operate in a high reliability and could obtain a better probability for target acquisition with joint detection by infrared pointing,active laser and visible detection.AA detection method for space-based targets was brought forward.By forecasting the motion track using a land-based radar,the space-based detector could operate in a high reliability and could obtain a better probability for target acquisition with joint detection by infrared pointing,active laser and visible detection.At the conditions of effective aperture of 0.5 m and the limiting effetive load,the conclusions are as follows:when the normal sunlight,visible detection of CCD has obvious advantage in detecting distance,the fusion result is mainly decided to visible detection.At the cases of irradiation angle ≥90° or without sunlight,the joint detect ability is concerned with laser beam divergence angle.When beam divergence angle ≤0.5 mrad,active laser is better than infrared detection.It means that this paper provides a reliable solution for space-based detecting and pointing..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1003 (2008)
Preheating method for frequency stabilized Zeman He-Ne laser based on temperature trajectory control
HU Peng-cheng, TAN Jiu-bin, YAN Lei, and FU Hai-jin
In order to stabilize the Zeeman laser accurately within a short period at different ambient temperatures,a preheating method was proposed based on temperature trajectory planning and tracing.The structure of Zeeman-stabilized laser and the basic principle of frequency stabilization were discussed.Then,the tube temperaIn order to stabilize the Zeeman laser accurately within a short period at different ambient temperatures,a preheating method was proposed based on temperature trajectory planning and tracing.The structure of Zeeman-stabilized laser and the basic principle of frequency stabilization were discussed.Then,the tube temperature trajectory was planned as a modified exponential function of preheating time to expedite frequency locking and to improve laser frequency stability,and the Predictive Functional Control(PFC) arithmetic was employed to force the tube temperature to rise along the planned trajectory precisely.Finally,the several experiments were carried out to prove the effectiveness of the proposed preheating method.The experimental results indicate that the Zeeman laser using the proposed method can be preheated effectively at ambient temperature of 15~25 ℃,and the laser frequency can be locked in 16 min with a temperature-dependent frequency drift below 0.25 MHz.The proposed method can satisfy the requirements for improving preheating speed and frequency stability for Zeeman-stabilized lasers..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1009 (2008)
Characteristics of output signal of extrinsic fiber Fabry-Perot acoustic sensors
ZHAO Hong, LI Min, ZHANG Ying, and WANG Ping-ping
Based on multi-beam interference principle,an extrinsic fiber Fabry-Perot (FP) sensor was developed to measure the acoustic signal in liquid,whose interference cavity was consisted of quartz diaphragm,end of pigtail and air film.The sensitivity,amplitude-frequency and the output signals of the sensor were analyzed.The Based on multi-beam interference principle,an extrinsic fiber Fabry-Perot (FP) sensor was developed to measure the acoustic signal in liquid,whose interference cavity was consisted of quartz diaphragm,end of pigtail and air film.The sensitivity,amplitude-frequency and the output signals of the sensor were analyzed.The parameters of FP sensor were obtained to analyze amplitude-frequency characteristics of quartz diaphragm theoretically and experimentally.Finally,a measurement system on acoustic signals in water was developed and the effect of operation points on output signals were discussed and tested in different conditions.The experimental results indicate that the extrinsic fiber FP acoustic sensors in proposed system are able to measure acoustic signal in the liquid.Its fundamental frequency can reach to 140 kHz and sensitivity is 0.005 nm/Pa.The characteristics of output signal of the sensors are dependent on operational points and modulation depths of input signal.The sensitivity of the sensor is optimial when the operational points lie in quadrature point of operation curve.the measurement region will be increased when the output signal is frequency double for over modulation..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1018 (2008)
Analysis of thermal effect of solid state lasers in heat capacity mode
DAI Qin, WU Ri-na, NING Ri-bo, and DU Peng-yuan
A heat transmission model for YAG crystal of a side-pumping solid state laser with triangle uniform distribution was established based on heat capacity mode and considering the diode pumped light intensity distribution,specific heat capacity,thermal conductivity and the properties of YAG materials varied with temperatuA heat transmission model for YAG crystal of a side-pumping solid state laser with triangle uniform distribution was established based on heat capacity mode and considering the diode pumped light intensity distribution,specific heat capacity,thermal conductivity and the properties of YAG materials varied with temperature.The finite element method was used to simulate and analyze the temperature change of laser crystal media,analysed results indicate that YAG operated in heat capacity mode can be affected by thermal effect from asymmetric pumping light.The thermal effects of different YAGs including heat capacity model,continuous pumping and pulse pumping model were compared and analyzed,compared results show that the maximal temperature differences of the three models are 3.59、35.51 and 8.07 K,respectively,which suggests that the smallest temperature difference is at the heat capacity mode and the results can provide a reference for the design of heat capacity laser..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1025 (2008)
Optical thin-film depositing monitoring systems with four-light beams
XU Shi-jun, and REN Xiao-ling
By considering the poor monitoring conditions of universal coating equipments with low stability,precision and automation level,a new kind of photoelectricity-control-analysis system was developed.Based on double-frequency modulation,a photoelectric test system with four-light beams was put forward.A dual-lock-phase ciBy considering the poor monitoring conditions of universal coating equipments with low stability,precision and automation level,a new kind of photoelectricity-control-analysis system was developed.Based on double-frequency modulation,a photoelectric test system with four-light beams was put forward.A dual-lock-phase circuit system and a comprehensive digital processing system with compound filter were used to process monitoring signals,and all automation-monitoring functions were achieved with a control-analysis system.The experimental results show that standard deviation of Thin Film Thickness(TFT) is equal to or less than 0.55%,and signal-noise ratio approaches to 1 000.A very good linearity of numeral display is obtained and the display resolution limit on reflectivity is 0.02%.The linearity of static drift is very high,the drift ratio is less than 1.95%/h,and the static stabilities are double superior to that of universal system.It is concluded that proposed system has advantages of the static and dynamic stabilities,the signal-noise ratio,and the control precision for TFT..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1031 (2008)
Novel reaction-formed joint technology for reaction bonded silicon carbide ceramics
ZHANG Ge, ZHAO Ru-cheng, and ZHAO Wen-xing
A reaction bonded silicon carbide (RB-SiC) was joined with a new-type reaction-formed joint technology based on traditional reaction-formed joint process.The thickness,microstructure,and the mechanical and thermal properties of welding line were tested.The test results show that the welding line's thickness of RB-SA reaction bonded silicon carbide (RB-SiC) was joined with a new-type reaction-formed joint technology based on traditional reaction-formed joint process.The thickness,microstructure,and the mechanical and thermal properties of welding line were tested.The test results show that the welding line's thickness of RB-SiC in novel-formed joint technology is thin to 54~77 μm,and its microstructure is similar to the RB-SiC ceramic,so that mechanical property is excellent,the average bending strength of 10 joints is 307 MPa.The welding line doesn' influence on the surface figure before and after the temperature of the joining blank changes from-10 ℃ to 65 ℃,which shows the thermal property of welding line is suitable for that of RB-SiC ceramic..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1037 (2008)
Analysis on characteristics of optical fiber sensor for atmospheric pressure
XIAO Shao-rong, ZHU Ping, and BEN Fu-lai
By taking a duo-membrane box as a sensing component for atmospheric pressure,a micrometric optical fiber displacement sensor was employed to inspect deformation of membrane box with air pressure changing to avoid the defects in inspecting deformation,or improve and optimize performances of the sensors.A channel opticalBy taking a duo-membrane box as a sensing component for atmospheric pressure,a micrometric optical fiber displacement sensor was employed to inspect deformation of membrane box with air pressure changing to avoid the defects in inspecting deformation,or improve and optimize performances of the sensors.A channel optical fiber sensor was utilized to increase sensitivity and to measure little change in air pressure.The relation between optical fiber sensor output changes and atmospheric pressure changes was calibrated with a standard air pressure gauge.A setup for measuring atmospheric pressure was developed.The experimental results indicate that the measurement range is 900~1 170 hPa,the resolution is 0.2 hPa,and the accuracy is ±0.1 hPa.The measurement area position on air pressure can be changed via the changing of initial distance between optical detector and reflection face,and the measurement range on atmospheric pressure can be expanded via optimization of optical fiber detector parameters..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1042 (2008)
Application of virtual assembly technology to designing six-wafer combustor for silicon micro gas turbine engine
ZHU Lin, XU Jin-liang, KONG Fan-rang, and WANG Hai-ming
By taking a micro-gas turbine engine developed by MIT as a prototype,the theory and process of virtual assembly technology were depicted,and its three-dimensional micro-combustor was constructed successfully in SolidWorks after analyzing the traditional approaches to geometric modeling in Computing Fluid Dynamics(CFD).By taking a micro-gas turbine engine developed by MIT as a prototype,the theory and process of virtual assembly technology were depicted,and its three-dimensional micro-combustor was constructed successfully in SolidWorks after analyzing the traditional approaches to geometric modeling in Computing Fluid Dynamics(CFD).The results show that the created method for micro-combustor based on the virtual assembly technology is prior to the traditional modeling approaches,which can decrease the cost of products in Power MEMS and can promote their industrialization..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1048 (2008)
Influence of structure design and control on movement precision of millimeter-scale omni-directional mobile microrobot
LI Jiang-hao, CHEN Jia-pin, and LI Zhen-bo
An omni-directional mobile microrobot for microassembly in a microfactory was presented.The microrobot was less than one cubic centimeter in size,and was driven by four electromagnetic micromotors with 3 mm diameter.The two important aspects for the microrobot precision,the structure design and control methods were anaAn omni-directional mobile microrobot for microassembly in a microfactory was presented.The microrobot was less than one cubic centimeter in size,and was driven by four electromagnetic micromotors with 3 mm diameter.The two important aspects for the microrobot precision,the structure design and control methods were analyzed.The structure design included the transmission system and the wheel fabrication and the control methods included the path planning and electromagnetic micromotor.In order to eliminate the drawbacks of microrobot structure,several novel control methods and ideas including the path planning and micromotor control were introduced.This path planning method was designed to solve the nonlinear problem of the microrobot during translational movement.Moreover,according to the structure constraint of the electromagnetic micromotor,the vector synthesis control of the torque was presented and the torque self-balance characteristic was utilized to improve the microrobot precision.Experimental results show that the microrobot can achieve 0.07 mm/step during translation,and 0.83 °/step during steering,which is three times that of the common control method.The microassembly experiments demonstrate the validity of these microrobot control methods,which shows the microrobot can satisfy the application requirements of microassembly..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1056 (2008)
Modeling and process of mastering for multi-level run-length-limited optical discs
TANG Yi, SONG Jie, and PAN Long-fa
A photolithographic model for optical disc mastering is established.In this model,vector diffraction is used to calculate the intensity distribution of focused light spot,and the light propagation in multi-layer film structure is used to describe the light propagation in photo-resist.The experimental and simulation resA photolithographic model for optical disc mastering is established.In this model,vector diffraction is used to calculate the intensity distribution of focused light spot,and the light propagation in multi-layer film structure is used to describe the light propagation in photo-resist.The experimental and simulation results are presented,including the influences of key process parameters on typical multi-level pit width and depth.These process parameters consist of photo-resist thickness,development time and developer concentration.Experimental results show that the decrease of photo-resist thickness will cause the increase of width and the decrease of depth.The increases of development time and developer concentration have the same effect,both will cause the increases of width and depth.The deviation between simulation and experiment is kept within ±5 nm,which shows that the experiment is coincident with the simulation well.The analysis results are helpful to practical multi-level disc mastering.Meanwhile,the model can be used to analyze other process parameters and other disc formats..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1063 (2008)
Fluid pressure and its effect on hydrodynamic suspension ultra-smooth machining
CAO Zhi-qiang, ZHAN Jian-ming, ZHU Chong-tao, and ZHAO Ji
A hydrodynamic suspension machining system based on digital machine tool was constructed,and a compliant machining apparatus for controlling mechining pressure was developed.Fluid pressure distribution in the machining clearance was analyzed by hydrodynamic theory.An experiment was carried out to obtain influence of maA hydrodynamic suspension machining system based on digital machine tool was constructed,and a compliant machining apparatus for controlling mechining pressure was developed.Fluid pressure distribution in the machining clearance was analyzed by hydrodynamic theory.An experiment was carried out to obtain influence of machining clearance and motor rotate speed on fluid pressure.Meanwhile,the correlation between the surface roughness of machining clearance and motor rotate speed was revealed by conducting experiments.The experimental results indicate that the fluid pressure increases gradually with increasing of motor rotate speed and decreasing of machining clearance,and then,it decreases relatively after reaching a certain value.When the motor rotate speed is 6 000 r/min,the hydrodynamic pressure shows the maximum value.It also indicates that when the machining clearance is between 5 μm and 40 μm,the machining shows an effect distinctly.In the condition of maintaining clearance of 10 μm and hydrodynamic pressure of 5 N,the machining effect is optimal..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1069 (2008)
Sulfur dioxide poison gas sensor based on MEMS laminated microstructure
SHI Yun-fen, SHI Yun-bo, LIU Yue-hua, FENG Qiao-hua... and LEI Ting-ping|Show fewer author(s)
Aimed at the technical difficulty of low electric conductivity of novel organic semiconductor,a kind of laminated microstructure on porous upper electrode was brought forward.A gas sensitive film was formed using vacuum deposition,then,a gas sensor was developed by MEMS micro-fabrication.According to the equivalent cirAimed at the technical difficulty of low electric conductivity of novel organic semiconductor,a kind of laminated microstructure on porous upper electrode was brought forward.A gas sensitive film was formed using vacuum deposition,then,a gas sensor was developed by MEMS micro-fabrication.According to the equivalent circuit and the technologic boundary condition,the output conductance of the sensor has increased by 1 000 times derived by a conductance formula,which solves the signal gathering problem of organic semiconductor.SEM microcosmic pattern indicates that the best condition is the evaporating electric current of 100~120 A,and evaporating time of 8~12 s.On that condition,the surface of gas sensitive film is covered with activated granules inosculated by the secondary chemical reaction,like rice grain in uniform distribution and ordered holes.The testing result indicates that vitriol doped CuPcxPANI1-x with proportionality coefficient of 0.15~0.35 has the best sensitivity to SO2.The CuPc0.35PANI0.65 is selected in order to reduce the interference of H2S.When heating voltage VH is 1~2.5 V,sensitivity and responsive restorability will be enhanced and responsive time is 30 s.The output characteristic of sensor is single linear logarithmic,the detecting range is 0~200×10-6.Through stability examination for six months,output impedance shift and sensitivity are less than or equal to ±5% and 10%,respectively..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1075 (2008)
Study on vertical drive ultrasonic feeder
JIANG Bin, LIU Xiao-lun, YANG Zhi-gang, TIAN Feng-jun, and Yu Yue
In order to overcome a electromagnetic interference of the electric and magnetic feeder and to reduce the acoustical noise of low frequency piezoelectricity feeder,a new ultrasonic vibration feeder was presented.An ultrasonic transducer based on piezoelectrical ceramic was used to drive the feeder.The vibration model aIn order to overcome a electromagnetic interference of the electric and magnetic feeder and to reduce the acoustical noise of low frequency piezoelectricity feeder,a new ultrasonic vibration feeder was presented.An ultrasonic transducer based on piezoelectrical ceramic was used to drive the feeder.The vibration model and parameters of the ultrasonic transducer were studied and calculated and the relational curve between oscillation amplitude and frequency was obtained.In order to create effective vibration,a vertical-drive was adopted to design its construction.The structure parameters were calculated,and correlative equation was built.Experimental results show that the discharge velocity of thin slice metal of 3 mm diameter reaches 36 cm/min,when frequency is 17.5 kHz and thickness of spring reed is 7 mm.In addition,proposed ultrasonic feeder can carry or feed small solid object without electromagnetic interference..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1082 (2008)
Sensor network design for flexible surface shape measurement
FAN Hong-chao, QIAN Jin-wu, ZHANG Ya-nan, and SHEN Lin-yong
A sensor array was configured using Fiber Bragg Grating (FBG) sensors for building a sensor network with the technologies of Spatial Division Multiplexing (SDM) and Wavelength Division Multiplexing (WDM).The number of sensors was determined according to the scope of demodulation device,and distributions were determinedA sensor array was configured using Fiber Bragg Grating (FBG) sensors for building a sensor network with the technologies of Spatial Division Multiplexing (SDM) and Wavelength Division Multiplexing (WDM).The number of sensors was determined according to the scope of demodulation device,and distributions were determined based on the wave transmitting theory.In combination with the strain and the deformation of a surface,these sensors were distributed at the maxmum amplitude with dense distribution for bigger strain and sparse distribution for smaller.Based on the finite element analysis of the surface,the sensor network in a solar array was simulated.Furthermore,the precision of the sensor array system was calibrated.Experimental results show that there is a linear relationship between the wavelength shifts and the deformation displacements.The distributions of the sensors are in reason and the sensor network could measure many deformations of the surface.The measurement error of sensor is only 0.4% and the flexible error of surface measurement is 4% if the length of FBG packaging is less than 40 mm..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1087 (2008)
Application of double density wavelet transform to surface topographic signal separation
LI Hai-yan, LIU Guo-dong, LIU Bing-guo, and PU Zhao-bang
A novel signal separation method based on Double Density Wavelet Transform (DDWT) was presented to reduce the influence of the locations of sampling points on the filtering results from traditional wavelet in surface evaluation.The original profile signal could be decomposed by DDWT into a linear superposition of wavelA novel signal separation method based on Double Density Wavelet Transform (DDWT) was presented to reduce the influence of the locations of sampling points on the filtering results from traditional wavelet in surface evaluation.The original profile signal could be decomposed by DDWT into a linear superposition of wavelet functions and scaling functions.After reconstruction of wavelet coefficients corresponding to different components,the required surface topographic discrete signal was obtained.The experiment results show that the separation accuracy of roughness,waveness and other frequency components can be higher about 4% than that of other methods.In engineering surface analysis,the new method can provide near shift-invariance in surface texture separation and extraction,and can decrease the influence of sampling points on filtering results and also improve the measurement precision..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1093 (2008)
Image retrieval based on combining local and global features
WANG Hua-zhang, HE Xiao-hai, and ZAI Wen-jiao
In order to organize,manage,browse and retrieve image database effectively,a novel image retrieval algorithm combining global statistical feature and local binary bitmap feature was proposed.The mean value and standard deviation of every image were calculated to obtain the global statistical feature.Then,according to tIn order to organize,manage,browse and retrieve image database effectively,a novel image retrieval algorithm combining global statistical feature and local binary bitmap feature was proposed.The mean value and standard deviation of every image were calculated to obtain the global statistical feature.Then,according to the idea of block truncation code,every image was divided into 4×4 image blocks without overlapping,and mean value of every image block was calculated also.If mean value was larger than that of the whole image,the image block was set as "1",otherwise,the image block as "0",so the image bitmap feature was obtained.Finally,the normalized features were integrated and retrieved by the best similar matching function.Experimental results indicate that the retrieval performance using combined global and local features is prior to that using single feature;compared with other similar schemes,the algorithm is robust,and the mean retrieval precision reaches 63% in the first 100 images,which is 4% higher than that of other two schemes mentioned in the paper.
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1098 (2008)
Design of CCD video amplitude controller and target precise locating algorithm
WANG Hai-yong, and HUANG Jiang-yan
Aiming at the circumstances of time-varying target brightness or multiple targets with different brightnesses,a video amplitude controller feedback system is designed to precisely locate a spot target image on a linear CCD with edge detection by fixed dual thresholds and pixel subdivision by gray weighted centroid algoAiming at the circumstances of time-varying target brightness or multiple targets with different brightnesses,a video amplitude controller feedback system is designed to precisely locate a spot target image on a linear CCD with edge detection by fixed dual thresholds and pixel subdivision by gray weighted centroid algorithm.By adjusting quantitively in tegrating time and program controlling gain,this light adjusting control loop can be kept a constant peak gray value to reduce design difficults for light source and light path and to reduce design cost also.A fixed dual-threshold edge location method is used to truncate a good edge symmetry to aviod the effect of irregularity of the spot peak on location results.Compared with the traditional binarization method with extra external circuits,this system shows its advantages in simple implementation and excellent algorithm,and engineering application gives that it can precisely locate a light spot.Under such circumstance,gray weighted centroid algorithm can reach a better than 1/10 pixel subdivision,so the final spot precise location keeps 2 significant digits after decimal point.Experimental results show that proposed system scheme provides an valuable reference for the future design of multiple-varible light adjusting video system applied in opto-eletctronic measurement..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1105 (2008)
Two-stage uncertainty evaluation of 3D reconstruction
CHEN Jie-chun, DING Zhen-liang, and YUAN Feng
The configuration of a 3D reconstruction system can be optimized by evaluating the reconstructed uncertainties of 3D points located in the working volume of stereo reconstruction system.An evaluation method considering camera calibaration and uncertainty propagation in reconstructing 3D points is presented for 3D reconThe configuration of a 3D reconstruction system can be optimized by evaluating the reconstructed uncertainties of 3D points located in the working volume of stereo reconstruction system.An evaluation method considering camera calibaration and uncertainty propagation in reconstructing 3D points is presented for 3D reconstrution uncertainties,according to the law of uncertainty propagation.The procedure of 3D reconstruction involves two consecutive stages:calibrating camera models and reconstructing a 3D point from its image projections.The output quantities of the first stage,the parameters of camera models,constitute a part of the input quantities of the second stage.The analytical expressions for uncertainty propagation during reconstructing a 3D point are presented.The presented metrod is validated using Monte Carlo simulation,and some typical applications are given.The experimental results show that the evaluated uncertainties associated with the reconstructed coordinates of 3D point have one significant digit at least,and the presented algorithm is feasible..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1110 (2008)
Fast stereo matching algorithm based on adaptive window and graph cuts
YIN Chuan-li, XIANG Chang-bo, SONG Jian-zhong, and QIAO Shuang
According to the disadvantage of large computation of stereo matching algorithm based on graph cuts,a new stereo matching algorithm is presented.By changing adaptively the window based on image edge features,the SSD matching method is used as a similarity decision criterion to determine the initial disparity map.Then,aAccording to the disadvantage of large computation of stereo matching algorithm based on graph cuts,a new stereo matching algorithm is presented.By changing adaptively the window based on image edge features,the SSD matching method is used as a similarity decision criterion to determine the initial disparity map.Then,a left-right conformity verification is adopted to remove mistake matching points.when the energy function is constructed,the initial disparity is used as a reference of function to get the optimization of disparity distribution of the minimum global energy by graph cuts.The proposed algorithm is tested with standard stereo images and compared with other methods,experimental results show that proposed algorithm not only has better performance for processing the large low texture areas and the occluded pixels,but also has shorter matching time,which is two-thirds shorter than that of original algorithm..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1117 (2008)
Point in polygon testing based on normal direction
SUN Xian-bin, YIN Jie, LI De-hua, and XIAO Ben-lin
An algorithm of point in polygon testing based on normal direction is presented.A ray having several crossing points with the edges of polygon is drawn through a fixed point,two vectors are given from undetermined point to the endpoints of edge,then their normal directions is calculated.By using the normal direction asAn algorithm of point in polygon testing based on normal direction is presented.A ray having several crossing points with the edges of polygon is drawn through a fixed point,two vectors are given from undetermined point to the endpoints of edge,then their normal directions is calculated.By using the normal direction as a reference for point in polygon test,the sum of normal directions of points and those edges is calculated.If the numbers of positive normals and negative normals are the same,the point is outside the polygon,otherwise,the point is inside the polygon.In the testing,the presented method can decrease computing time and can aviod some mistakes of other algorithm,its complexity is o(n).Experimental result show this algorithm is suitable for some other cases including self-intersection polygon..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1122 (2008)
Multi-functional digital watermarking technology based on RS error correction code and singular value decomposition
WANG Pei, JIANG Hui-jun, LI Li, and YING Jun
A kind of multi-functional digital watermarking technology based on RS error correction code and singular value decomposition is presented,which consists of copyright protection watermark algorithm and user tracking watermark algoritnm.Based on the characteristic of RS error correction code,the watermarking algorithm fA kind of multi-functional digital watermarking technology based on RS error correction code and singular value decomposition is presented,which consists of copyright protection watermark algorithm and user tracking watermark algoritnm.Based on the characteristic of RS error correction code,the watermarking algorithm for copyright protection designs two different extracting methods for client and certificate authority to meet two different requirements of robustness.The algorithm of embedding watermark doesn't distinguish the two scenes,and produces an asymmetry in process of embedding and extracting,so this method can enhance protection performance and can reduce the computation complexity.The watermarking algorithm for user tracking uses a SVD quantization and grouped inserting watermark to improve robustness.Experimental results indicate that the PSNR of the watermarked image is 47.96 dB.The watermarking algorithm for copyright protection reaches the standard of strong robustness,and the watermarking algorithm for user tracking can achieve 100% extracting in certain attracting..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1127 (2008)
Scale and direction adaptive Mean Shift tracking algorithm
ZHANG Heng, LI Li-chun, and YU Qi-feng
Based on the analysis of scale space theory and current Mean Shift algorithm,a scale and diretion adaptive Mean Shift tracking algorithm is proposed.The method obtains the target areas according to the variance between target and background,and calculates the best ellipse description based on the scale space theory.TheBased on the analysis of scale space theory and current Mean Shift algorithm,a scale and diretion adaptive Mean Shift tracking algorithm is proposed.The method obtains the target areas according to the variance between target and background,and calculates the best ellipse description based on the scale space theory.The best ellipse parameters of the preview frame is used as the original value of the current frame,and the ellipse parameters can be updated according to the Mean Shift principle.The experimental results show that the new Mean Shift tracking algorithm can adapt to the changes of scale and direction of the object effectively..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1133 (2008)
Design of driving circuit for frame transfer area CCD
JIN Long-xu, LI Guo-ning, and LIU Yan-yan
A kind of large area CCD driving circuit with high frame frequency is designed by using a frame transfer area CCD FT18 as its sensor.This kind of high speed driving circuit can increase the angle of visual field under constant video condition in trail to meet the requirement for the big visual field of searching targetA kind of large area CCD driving circuit with high frame frequency is designed by using a frame transfer area CCD FT18 as its sensor.This kind of high speed driving circuit can increase the angle of visual field under constant video condition in trail to meet the requirement for the big visual field of searching target.The structure and specification of the area CCD FT18 sensor are introduced,and the circuits of working clock and power driver for the sensor are proposed.The noises of the video signal (KTC noise and 1/f noise) are filtered by using the Correlated Double Sampling (CDS) technique to enhance the signal-to-noise ratio of the system.Finally a radiation scale is carried out,experiment results show that the respond degree of CCD is linear under the integration time of 0.32 ms,which verifies that the driving circuit works normally.A Field Programmable Gate Array (FPGA) is adopted as the key controller of the system to perform the modularization design from top to bottom.which realizes the hardware design by a software and improves development efficiency..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1140 (2008)
Hyperspectral image compression based on 3D SPIHT algorithm
NIAN Yong-jian, XIN Qin, SUN Lei, and WAN Jian-wei
A 3D SPIHT algorithm is applied to hyperspectral image compression.The band is separated into several groups to obtain the processing unit,and then 3D wavelet transfor(WT) is applied to each group to eliminate both spatial and spectral redundancies.Finally,the 3D SPIHT algorithm is used to encode the wavelet coefficienA 3D SPIHT algorithm is applied to hyperspectral image compression.The band is separated into several groups to obtain the processing unit,and then 3D wavelet transfor(WT) is applied to each group to eliminate both spatial and spectral redundancies.Finally,the 3D SPIHT algorithm is used to encode the wavelet coefficients.Both integer and float wavelets are used for lossless and lossy compression respectively.The experimental results on AVIRIS and OMIS indicate that the average PSNR by proposed algorithm can be 0.91 dB and 1.38 dB higher than that of general 3D WT coding method for lossy compression,but 0.308 bit/pixel and 0.159 bit/pixel higher than the predictive coding technique for lossless compression,respectively.The proposed algorithm has better lossy coding performance,but lossless coding performance is inferior to that of predictive coding technique..
Optics and Precision Engineering
- Publication Date: Sep. 21, 2021
- Vol. 16, Issue 6, 1146 (2008)