Journals >Optics and Precision Engineering
Contents
2015
Volume: 23 Issue 8
37 Article(s)
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Research Article
Plane holographic varied-line-space grating for DCLS in EUV region
JIANG Yan-xiu, Bayanheshig, ZHAO Xu-long, YANG Shuo, and WU Na
According to the demands of a free electron laser( Dalian Coherent Light Source, DCLS) at extreme ultraviolet (EUV) for high resolution plane holographic varied-line-space grating, a plane holographic varied-line-space grating was fabricated based on optical path difference and aberration principle. By using the improvAccording to the demands of a free electron laser( Dalian Coherent Light Source, DCLS) at extreme ultraviolet (EUV) for high resolution plane holographic varied-line-space grating, a plane holographic varied-line-space grating was fabricated based on optical path difference and aberration principle. By using the improved local optimization algorithm, recording parameters of the varied-line-space grating were calculated. The varied-line-space grating at EUV with a center groove density of 600 gr/mm, a duty cycle of 0.46,a groove depth of 550 nm and an effective score area 30 mm×30 mm was fabricated on a silicon substrate by using the holographic method. The groove density of the varied-line-space grating was measured by Littrow diffraction and its theoretical resolution was analyzed by aberration theory. The results show that the groove density in an active area is less than 0.175 gr/mm, namely the resolution is far above 12 000 in 50-150 nm EUV region, which meets the demand of the DCLS. It concludes that these theories and research findings provide theoretical and technical supports for improving the quality of plane varied-line-space gratings..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2117 (2015)
Alignment of aerial multi-angle infrared camera
Song Jun-ru, XING Hui, MU Sheng-bo, JIAO Wen-chun, and HE Xu-hua
The structural characteristics of aerial infrared cameras were analyzed, and the key technologies of alignment of this type of cameras were validated. A method for adjustment and validation of a single camera was proposed. The method adjusted the camera coarsely based on measuring the line array direction and optical aThe structural characteristics of aerial infrared cameras were analyzed, and the key technologies of alignment of this type of cameras were validated. A method for adjustment and validation of a single camera was proposed. The method adjusted the camera coarsely based on measuring the line array direction and optical axis direction of a detector by a theodolite, and adjusted the camera finely by combining with the sub-pixel subdivision location algorithm. A scheme to complete a one-time adjustment by covering all lenses was proposed based on a large diameter parallel light pipe and a high precision controlled turntable, by which the grouped alignment and validation for the aerial infrared camera were implemented. The simulation results show that the method meets the demands of aerial infrared camera for high accuracy alignment and small tolerances. The adjustment precision of the angle among the boresights of multi-angle camera has reached 0.57 pixel, which is about 20 times that of the traditional methods. The proposed method provides a practical and feasible way to adjust precisely aerial infrared cameras and can be used in adjustment for other aerial sensors with similar structures..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2125 (2015)
Tracking and recognition of projective spots for cooperation targets in vehicle simulation test
HUO Ju, YANG Ning, and YANG Ming
To track and recognize the projective spots of a cooperation target in the vehicle simulation test, a tracking and recognition method is proposed by combining the advantages of statistical methods and heuristic methods. This method tracks and recognizes the projective spots in a "prediction-recognition-modificatioTo track and recognize the projective spots of a cooperation target in the vehicle simulation test, a tracking and recognition method is proposed by combining the advantages of statistical methods and heuristic methods. This method tracks and recognizes the projective spots in a "prediction-recognition-modification" loop. In the prediction phase, the traditional Kalman filter is improved based on the movement characteristics of projective spots so as to precisely predict the projective spot positions. According to the predicted positions, the recognition of the projective spots in the recognition phase is divided into two parts. If a projective spot is in the field-of-view at next time instance, its optimal matching spot in the image will be rapidly searched with the gain function and matching strategy. If the projective spot is out of the field-of-view at next time instance, its position on the image plane will be calculated with the measuring system information, and the calculated position will be added into the corresponding trajectory. Once the recognition of the projective spots is completed, the parameters related to projective spots are modified with the recognition results. Simulation and real experimental results indicate that the proposed method can effectively track and recognize the projective spots, whose maximum error is no more than 2.5 pixel, even if the projective spots exit and enter the scene during the measurement..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2134 (2015)
Automatic balancing of wavefront aberrations in high-numerical aperture lithographic lenses
XU Ming-fei, and HUANG Wei
As high-numerical aperture (NA) lithographic lenses have larger fields of view(FOVs) and nonuniform wavefront aberration distributions, this paper proposes an automatic optimized design method to reduce the the largest wavefront aberration of all FOVs in design processing. The method adds an external loop optimization As high-numerical aperture (NA) lithographic lenses have larger fields of view(FOVs) and nonuniform wavefront aberration distributions, this paper proposes an automatic optimized design method to reduce the the largest wavefront aberration of all FOVs in design processing. The method adds an external loop optimization procedure which can automatically adjust sampling weight into the local optimization procedure of a lithographic lens to balance wavefront aberrations and to reduce the largest wavefront aberration automatically. By using the proposed method, the uniformity of wavefront aberrations gets better and the largest wavefront aberration has been reduced to 63% of the primary value. It shows that the method has a better application in Code V. Meanwhile, it not only reduces the design time consumption but also the dependence on the design experiences of the designers. this method can also be applied in design of other optical systems with higher imaging quality..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2143 (2015)
Wavelet transform analysis of optic fiber force sensing signals at puncture needle tip
YANG Tang-wen, CHEN Pan-fei, HAN Jian-da, and XU Wei-liang
During a percutaneous soft tissue puncture, a puncture needle is inserted into the layered tissues with various material properties, and the interactive force at the needle tip occurs discriminately. To measure the force and identify the boundaries of the layered tissues in the puncture path, a fiber optic force sensorDuring a percutaneous soft tissue puncture, a puncture needle is inserted into the layered tissues with various material properties, and the interactive force at the needle tip occurs discriminately. To measure the force and identify the boundaries of the layered tissues in the puncture path, a fiber optic force sensor was fabricated, and the force data acquired with the sensor were analyzed. In terms of a Fabry-Perot interferometer, the measuring principle of the fiber optic sensor was presented, and its optical link, its integration into the needle and calibration approach were introduced. Then, based on the insertion force signal analysis, the force signals were decomposed via the Mallat algorithm into wavelets, and their patterns were recognized and used to identify the layered tissue boundaries. Finally, needle insertion tests were performed with the swine liver and belly tissue phantoms. The experimental results show that the working range of the force sensor is 0-3.20 N and the measuring resolution is under 0.01 N. Moreover, the insertion test results indicate that the Mallat algorithm is effective to the discrimination of layered tissues. It concludes that the fabricated fiber optic sensor meets the requirements of working range, accuracy and reliability to measure an insertion force. The proposed wavelet transform algorithm is able to identify the boundaries of the layered tissues and is expected to used in the percutaneous control by a robot..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2149 (2015)
Integrated microfluidic nitrite fluorescence optical fiber sensor based on optical fiber with microholes on surface
ZHAO En-ming, LI En-tao, TENG Ping-ping, LIU Chun-lan... and YANG Xing-hua|Show fewer author(s)
An in-fiber integrated fluorescence online optofluidic sensor was developed by using a hollow optical fiber with a suspended core, in which the micro-region of the sensor for fluorescence quenching reaction was built in the hollow optical fiber. Microholes on the surface of the fiber were etched by a CO2 laser, the fluAn in-fiber integrated fluorescence online optofluidic sensor was developed by using a hollow optical fiber with a suspended core, in which the micro-region of the sensor for fluorescence quenching reaction was built in the hollow optical fiber. Microholes on the surface of the fiber were etched by a CO2 laser, the fluorescence reagents could be injected into the optical fiber via the microholes and was mixed to form stable microflows in the fiber. Concurrently, indicator molecules were excitated by the evanescent field of the suspended core, the fluorescence was well coupled into the core and was detected in the exited end. The concentration of nitrite was determined by fluorescence quenching reaction during optofluidic reaction in the optical fiber. Experimental results indicate that the microflows could flow through the optical fiber in a short time, therefore, the sensor detects the solution concentration in a fast response rate.Moreover, the fluorescence response of the sensor is nearly linear depending on the concentration of nitrate in the range of 0.1-2.6 mmol/L, which reveals the feasibility of the integrated in-fiber optofluidic method for trace fluorescence detection..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2158 (2015)
Imaging area and contrast of THz focal plan array CW transmission imaging system
TIAN Li, JIN Wei-qi, CAI Yi, LIU Jing, and WANG Xia
The characteristics of THz radiation and a THz Focal Plane Array(FPA) detector were researched, and the energy transmitting processing of a continuous wave imaging system in the FPA detector was analyzed. In consideration of the atmospheric attenuation, device limitation, and the signal transfer relation of continuous The characteristics of THz radiation and a THz Focal Plane Array(FPA) detector were researched, and the energy transmitting processing of a continuous wave imaging system in the FPA detector was analyzed. In consideration of the atmospheric attenuation, device limitation, and the signal transfer relation of continuous laser irradiation, target scene and the FPA detector, two parameter models for the imaging area and contrast ratio of the continuous wave imaging system were derived. Then, a continuous wave imaging system was designed. According to derived models, the imaging areas and contrasts of two different objects(one is the envelope with cyclotrimethylene trinitramine (RDX) powders and the other is the plastic case with metal blades) were calculated. The obtained results show that the imaging areas of the two examples are 4.74 cm×6.32 cm , 3.534 cm×4.712 cm, and the contrasts are 0.242 2 and 0.306 respectively. The results are compared with that of the imaing system with the imaging area of 3 cm×3 cm or 4 cm×4 cm from the Massachusetts Institute of Technology(MIT). They are derived in the same order of magnitude, which verifies that the proposed models and method are reasonable and effective..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2164 (2015)
Multi-channel heterophotonic crystal filter
LI Chuan-qi, FAN Qing-bin, LU Ye, and LUO De-jun
On the basis of the two-dimensional square lattice photonic crystal with dielectric rods, a novel multi-channel drop filter consisting of four linear gradient microcavities and a heterophotonic crystal reflector was designed. The working mechanism of the heterophotonic crystal filter was analyzed by using Plane Wave ExOn the basis of the two-dimensional square lattice photonic crystal with dielectric rods, a novel multi-channel drop filter consisting of four linear gradient microcavities and a heterophotonic crystal reflector was designed. The working mechanism of the heterophotonic crystal filter was analyzed by using Plane Wave Expansion(PWE) method and two-dimensional Finite Difference Time Domain(2D-FDTD) method, then the influence of the distance between the reference plane of microcavity and the hetero-interface on the drop efficiency was explored. The results show that the heterophotonic reflector in the filter is able to achieve 100% reflection so that to improve the drop efficiency of the three-port channel drop filter greatly. Each channel of the designed filter has the ability to drop the light wave effectively, in which the channel space is 10 nm, the rates of normalized transmission are all above 90%, and the full-widths at half-maximum(FWHM) of the transmission spectrums are all below 0.54 nm. The filter has achieved a higher quality factor and shows a compact size of 15.15 μm×13.91 μm and a high filtering efficiency. It is suitable for multiplexing and demultiplexing in a wavelengh division multiplexing system and has potential application values to integrated optics circuits..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2171 (2015)
Inversion of complex refractive index for rough-surface objects
ZHAN Yong-hong, LIU Qing, YANG Di, and WANG Ya-ping
As the complex refractive index of a rough-surface object is difficult to be inverted precisely, the current Vimal-Milo method for inversion was improved in this paper. The characteristics of the polarimatic bidirectional reflection from the rough surface were analyzed, and the defects of current Vimal-Milo method withAs the complex refractive index of a rough-surface object is difficult to be inverted precisely, the current Vimal-Milo method for inversion was improved in this paper. The characteristics of the polarimatic bidirectional reflection from the rough surface were analyzed, and the defects of current Vimal-Milo method with a mode of "polarization ratio - angle correlation" were pointed out. Then, a improved Vimal-Milo inversion method was proposed based on the model of " relative polarization component - angle correlation". The inversion formula for the complex index was derived and a global searching was designed. According to the measurement data of polarization characteristics from green paint and aluminum, the inversion algorithm for the complex index was verified and the polarimatic bidirectional reflection characteristics of materials were also verified by the forward deducing and inverting. The inversion data with proposed method show that the inversion precision of the complex index of rough-surface aluminum has more improved than that of the Vimal-Milo method and the parameter errors for real and imaginary parts are within ±0.01 with the assessment index less-than 0.07. The inversion data by the forward deducing and inverting show that the error of radiance intensity of green paint has decreased 5 times that of Vimal-Milo method, and the difference from measuring data is within 0.01. These results all demonstrate that proposed inverting method can be used in the inversion for complex indexes of rough-surface objects and flat-surface objects..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2178 (2015)
Fabrication and properties of ultra-lightweight SiC mirror
DONG Bin-chao, and ZHANG Ge
Vacuum pressure assisted gel-casting and reaction sintering were applied to fabrication of Φ200 and Φ500mm ultra-lightweight SiC mirrors with the area densities of 9.17 kg/m2 and 10.8 kg/m2 respectively. The main properties of the SiC mirrors were tested. The results show that the green bodies of the SiC mirrors have nVacuum pressure assisted gel-casting and reaction sintering were applied to fabrication of Φ200 and Φ500mm ultra-lightweight SiC mirrors with the area densities of 9.17 kg/m2 and 10.8 kg/m2 respectively. The main properties of the SiC mirrors were tested. The results show that the green bodies of the SiC mirrors have no macroscopic defects due to its pouring in a vacuum environment. The mirror materials have high flexural strength (335 MPa) and fracture toughness (4.5 MPa·m12) because of the fine SiC particles. The metallographic structures of the mirror materials do not show the directional alignment of SiC particles, which means the mirror materials possess a high isotropy ratio, in which the relative deviation of Coefficient of Thermal Expansion(CTE) is less than 3%, and the relative deviation of modulus reaches 1.3%. After polishing, the surface profile accuracy (RMS) of the mirror is 0.043λ (λ=632.8 nm), and the toughness is better than 5 nm. These results demonstrate that the ultra-lightweight SiC mirrors fabricated by vacuum-assisted gel-casting and reaction sintering have excellent performance, and are suitable for fabrication of the mirrors of space cameras..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2185 (2015)
Microstructure and interface distribution of Fe-Cr-Si-B-C laser cladding alloy coatings assisted by mechanical vibration
LIU Hong-xi, TAO Xi-de, ZHANG Xiao-wei, and YANG Xin-tian
Fe-Cr-Si-B-C alloy coatings were fabricated on 45 medium carbon steel by combination of a laser cladding and a mechanical vibration surface modification process. The microstructures, element distributions, phase compositions and microhardnesses of the Fe-Cr-Si-B-C cladding coatings were investigated by the X-ray DiffraFe-Cr-Si-B-C alloy coatings were fabricated on 45 medium carbon steel by combination of a laser cladding and a mechanical vibration surface modification process. The microstructures, element distributions, phase compositions and microhardnesses of the Fe-Cr-Si-B-C cladding coatings were investigated by the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) , Energy Disperse Spectroscopy (EDS) and the HVS-1000 hardness tester. The results show that the cladding coatings are mainly composed of α-(Fe, Cr)solid solution, M7C3(M=Fe, Cr)carbide, Fe2B boride and a small amount of Fe0.9Si0.1 compound. The microstructure of cladding coating interface transforms from a plane crystal to a banded structure and a columnar crystal under the mechanical vibration condition, and the grain refinement effect is the most obviousy when the amplitude is 0.13 -0.18 mm. Moreover, the enhanced phases in cladding coatings transform from the short rod to granular, lamellar and banded structures with the increase of vibration frequency, and the distribution patterns change from random distribution to dispersed and network distributions. Compared with the normal laser cladding coating, more less pores and cracks exist in the cladding coating under mechanical vibration condition, and the maximum microhardness increases by 13.9%. These results mean that the microstructures and distributions in the cladding coatings are influenced by a synergetic mechanism of amplitude and frequency..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2192 (2015)
Adaptive inverse control for tip/tilt mirror in adaptive optical system
WANG Yu-kun, HU Li-fa, WANG Chong-chong, WANG Shao-xin, and XUAN li
To overcome the hysteresis of a tip/tilt mirror(TTM) in an adaptive optical system and to improve its linearity and control precision, this paper researches the nonlinear effects of the TTM. A compensation method based on the frequency-dependent Mutified-Prandtl-Ishlinskii (MPI) model is proposed for online adaptive inTo overcome the hysteresis of a tip/tilt mirror(TTM) in an adaptive optical system and to improve its linearity and control precision, this paper researches the nonlinear effects of the TTM. A compensation method based on the frequency-dependent Mutified-Prandtl-Ishlinskii (MPI) model is proposed for online adaptive inverse compensation of the hysteresis nonlinearity of the TTM. By combining with PID feedback control algorithm, an adaptive inverse feedforward composite control algorithm is proposed. In which, the adaptive inverse feedforward overcomes the hysteresis curve changes due to the frequency factors, and the PID algorithm improves the overall control performance. A second-order model of the TTM is established to estimate the output of the TTM system, which solves the reference signals of the MPI model, avoids adding extra feedforward sensors, and ensures the utilization of light energies. Experiment results indicate that this algorithm effectively solves the problem of hysteresis nonlinearity of the TTM, the 15 Hz hysteresis ratio of the TTM fells from 24.28% to 1.17%,and the linearity is improved by about 95%. As compared with the traditional PID algorithm, the control precision has increased by about 60%. It concludes that this composite control algorithm can compensate the hysteresis nonlinearity of the TTM effectively, and the control precision of the TTM is improved in adaptive optical systems..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2203 (2015)
Composite compensation for load torque of active magnetic bearing in DGMSCMG
XIE Jin-jin, LIU Gang, and WEN Tong
By combining with the angular rate feedforward controller and a load torque observer, a composite compensation method for the load torque of an active magnetic bearing was proposed to improve the suspension accuracy of the magnetically suspended rotor in a Double-gimbal Magnetically Suspended Control Moment Gyro(DGMSCMBy combining with the angular rate feedforward controller and a load torque observer, a composite compensation method for the load torque of an active magnetic bearing was proposed to improve the suspension accuracy of the magnetically suspended rotor in a Double-gimbal Magnetically Suspended Control Moment Gyro(DGMSCMG). The dynamical model of the magnetically suspended rotor in the DGMSCMG was established, and the load torque of the active magnetic bearing with inner and outer gimbal movements was analyzed. Then the composite compensation control method based on the angular rate feedforward controller and the load torque observer was designed, and the system stability after compensation was discussed. Finally, the performance of the proposed method was verified by a prototype developed by the our laboratory. The experimental results show that the displacement jitters at the end Ax of the rotor have reduced to 44.8% when angular rates of the gimbal starts from 120(°)/s2 to 10(°)/s. Moreover, the displacement jitters have reduced to 23.4% and 35.5% at the end Ax and end By of the rotor when angular rates of the gimbal are excited by the sinusoidal signal with the amplitude 10(°)/s and frequency of 10 Hz,respectively. The results indicate that the proposed method increases the control accuracy of the magnetically suspended rotor with the load torque by gimbal movements..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2211 (2015)
Motion-precision control in bonnet-polishing
WANG Fei, ZHANG Jian, PENG Li-rong, WANG Gao-wen, and SUI Yong-xin
To meet the ultra-high precision manufacture demands of spherical surfaces and aspherical surfaces in an optical system of Deep Ultra Violet (DUV) and Extreme Ultra Violet (EUV), a series of motion-precision control methods in bonnet-polishing were proposed. Firstly, the temperatures of main operation units were finelyTo meet the ultra-high precision manufacture demands of spherical surfaces and aspherical surfaces in an optical system of Deep Ultra Violet (DUV) and Extreme Ultra Violet (EUV), a series of motion-precision control methods in bonnet-polishing were proposed. Firstly, the temperatures of main operation units were finely controlled to allow the motion-precision of polishing to be to 50 μm. Then, the coordinates transmitting method was used to guarantee the two-dimension unity between measured data and operating data to be 0.30 -0.70 mm. Furthermore, the convergence efficiency of surface-error in fine polishing was improved by bonnet removal estimation method and feedback correction method. Finally, the vertical position accuracy between bonnet and work piece was improved to 10 μm by probing-correction method. The experiment results on a actual polishing by using motion-precision control methods indicate that the surface machining accuracy is 0.8 nm(RMS) in polishing a flat with a diameter of 280 mm , and that is 1.1 nm(RMS) in polishing a concave with a diameter of 160 mm. The proposed methods realize ultra-high precision polishing for spherical surfaces and aspherical surfaces, and they are also suitable for other contact small tool computer controlled polishing..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2220 (2015)
Ultrasonic assisted grinding for silicon carbide
LIU Li-fei, ZHANG Fei-hu, and LIU Min-hui
A grinding experiment was performed for silicon carbide (SiC) materials by Ultrasonic Assisted Grinding (UAG) and Normal Grinding (CG) methods. The effects of grinding parameters in different modes on the grinding force ratio, surface damage and sub-surface damage of the SiC materials were researched by using a dynamomA grinding experiment was performed for silicon carbide (SiC) materials by Ultrasonic Assisted Grinding (UAG) and Normal Grinding (CG) methods. The effects of grinding parameters in different modes on the grinding force ratio, surface damage and sub-surface damage of the SiC materials were researched by using a dynamometer and a Scanning Electron Microscopy(SEM). Then the action mechanism of the UAG was researched. The experimental results show that brittle fracture is the main removal mode in grinding process. The grinding force ratio of the grinding wheel increases with the increases of cutting depth and feed rates slowly and decreases with the increase of pindle speed slightly. In the normal grinding, the sub-surface damage depth of a SiC workpiece increases with the increase of cutting depth and feed rates gradually, and that in the UAG has a smaller change. Under the same grinding parameters, the grinding force ratio in UAG process is reduced nearly 1/3 as compared with the results in CG process, and its surface damages, such as surface cracks, fall off of SiC grains, flaking of SiC are reduced and the thickness of surface damage layer is thinned. In addition, the density and depths of sub-surface cracks are reduced in a greater degree. It concludes that the UAG method can obtain ideal surface quality and high processing efficiency..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2229 (2015)
Positive seal in large-diameter and wide-band laser emission pipe
CHEN Wen-tao, GAO Yun-guo, and SHAO Shuai
To prevent dust and moisture to enter the laser emission pipe of a high-energy laser emission system with large-diameter and wide-band, a positive pressure ventilation seal method for the laser emission pipe is proposed. This method uses purified, dry and clean air to exhaust original air, and allow a positive pressureTo prevent dust and moisture to enter the laser emission pipe of a high-energy laser emission system with large-diameter and wide-band, a positive pressure ventilation seal method for the laser emission pipe is proposed. This method uses purified, dry and clean air to exhaust original air, and allow a positive pressure flow on an emission port to resist the air diffusion into the laser emission pipe from outside and to achieve the sealing for the pipe. The numerical simulation and analysis for a flow field of the positive pressure ventilation in the laser emission pipe are performed by the CFD software-Fluent, and it shows that the clean air keeps a certain velocity and pressure on the emission port and could form a positive pressure airflow to resist the backflow from outside. For a long wavelength 10.6 μm laser, the variation of refractive index in the pipe is estimated to be a magnitude of 10-7 based on the pressure change, which causes a 1 μm optical path difference. The simulation results are experimentally verified and the results show that the velocity varies of interior have nearly no difference, though its' velocity is a litter bigger than that of simulation, and there is a positive pressure airflow with 0.64 m/s.Moreover, the relative humidity of clean air has dropped to 29% from 59%, which basically reaches the design sealing requirements of the positive pressure ventilation system for dust-proof and dehumidification..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2236 (2015)
Precision grinding of micro V-groove array on optical fiber quartz glass substrate
XIE Jin, FENG Yan-ke, CHENG Jian, and WU Ke-ke
As quartz glass is hard to be micro-machined, a self-researched truing technique of diamond wheel micro-tip was utilized to develop the grinding technique of micro V-groove arrays on the quartz glass. The influences of profile errors of 60° micro V-grooves on the coupling losses of optical fibers were analyzed. ThAs quartz glass is hard to be micro-machined, a self-researched truing technique of diamond wheel micro-tip was utilized to develop the grinding technique of micro V-groove arrays on the quartz glass. The influences of profile errors of 60° micro V-grooves on the coupling losses of optical fibers were analyzed. Then, the error compensation truing for grinding wheel micro-tip was researched. Finally, the grinding accuracy for micro V-grooves on quartz glass was experimentally investigated. The theoretical analysis indicates that when the angle, interval and the width of micro V-groove range ±0.42°, ±1.04 μm and ±1.2 μm, respectively, the coupling loss is less than 0.5 dB. The experimental results show that the Numerical Control( NC) precise grinding technique proposed can machine higher precise arrays, and the the V-tip angle and the radius of trued diamond wheel may reach 10.46 μm and (60±0.22)° by NC path and angle compensation truing, respectively. After micro-grinding of quartz glass, the micro V-groove shows an angle error of 0.4°, a tip radius of 10.5 μm, a width error of 0.3 μm and an interval error of 0.5 μm, which assures the precision connection of optical fiber arrays..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2243 (2015)
Modal method based dynamic analysis of cantilever type elastic structures
XUE Zhi-peng, LI Ming, JIA Hong-guang, and LUO Ze-yong
For the elastic deformation of cantilever type elastic structures in a flat spring landing gear, a new modal warp method was proposed to improve the calculation precision of the traditional modal method. Firstly, the description of a rotational component in infinitesimal deformation was deduced based on the finite elemFor the elastic deformation of cantilever type elastic structures in a flat spring landing gear, a new modal warp method was proposed to improve the calculation precision of the traditional modal method. Firstly, the description of a rotational component in infinitesimal deformation was deduced based on the finite element theory. Then the general modal method was summarized and how to introduce the rotational deformation into the dynamic equation in a modal coordinate was proposed. By which, the rotational deformation was introduced into the analysis of structure dynamics, so that the modal method could simulate the large bending and/or twisting deformation. Finally, the static simulation and experiments were performed and compared on the flat spring landing gear. The analysis results show that when the load mass is less than 100 kg, the relative errors are below 5% for both the linear modal method and modal warping method. However, when the load reaches to 180 kg(which represents the maximum realistic condition for landing), the error of the modal warp method remains within 10% and the error of linear modal has been more than 35%. Moreover, the time steps of both modal methods are 1 ms. As comparied with the traditional method, the modal warping method provides higher calculation and efficiency in the simulation of large rotational deformation..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2250 (2015)
Piezoelectric fast steering mirror with large excursion angle
YUAN Gang, WANG Dai-hua, and LI Shi-dong
To extend the excursion angle of the Piezoelectric Ceramic Stack Actuator (PCSA) based fast steering mirror (FSM), a piezoelectric FSM with a large excursion angle and a fixed rotation axis was proposed and explored. The output displacement of the PCSA was amplified by a bridge-type flexure hinge and applied to a mirroTo extend the excursion angle of the Piezoelectric Ceramic Stack Actuator (PCSA) based fast steering mirror (FSM), a piezoelectric FSM with a large excursion angle and a fixed rotation axis was proposed and explored. The output displacement of the PCSA was amplified by a bridge-type flexure hinge and applied to a mirror to generate a fixed axis deflection with the large excursion angle. On this basis, the configuration and the corresponding output equation of the piezoelectric FSM were established, and the characteristics of the FSM, including the maximum excursion angle, the maximum stress, and the natural frequency, were analyzed through theoretical derivation and finite element simulation. Finally, the principle and characteristics of the proposed piezoelectric FSM were validated through experiments and tests. The results show that the output equation of the piezoelectric FSM estimates exactly the mechanical defection angles of the piezoelectric FSM based on the output displacement of the PCSA and improves the design efficiency. Moreover, the developed piezoelectric FSM provides a mechanical excursion angle larger than 3°with natural frequency of 180 Hz, which satisfies the requirements of the high-speed image stabilization system for the large excursion angle and rapid response..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2258 (2015)
Thermal design of attitude control flywheel system for small satellites
WANG Hui, WU Jun-feng, LI Yin, and WU Yi-hui
To meet the thermal design requirements of an attitude control flywheel system for small satellites, the thermal performance of the flywheel system was analyzed and an experimental verification was carried out. According to the flywheel operating conditions, the electronically controlled loss and the mechanical loss ofTo meet the thermal design requirements of an attitude control flywheel system for small satellites, the thermal performance of the flywheel system was analyzed and an experimental verification was carried out. According to the flywheel operating conditions, the electronically controlled loss and the mechanical loss of the flywheel system were calculated in theory to determine the distribution of the main heat source of the system. Then, an equivalent thermal network model was established based on the whole mechanical topology structure. The Finite Element Method (FEM) was applied to analysis of the thermal performance of the main components and the whole system under the swinging condition, respectively. Finally, a prototype was developed and the thermal vacuum test was carried out to validate the analysis results. The results show that the final equilibrium temperature of the monitoring point is about 57.8 ℃ under the swinging operating condition for 8 hours with the ambient temperature 45.0 ℃. The error is 8.6% relative to the FEM result of 53.2 ℃, which indicates that the temperature values obtained in the analysis and the experiment are coincident with well and the thermal design meets the thermal requirements of the satellite systems. This analysis provides an important reference for the thermal design of attitude control flywheel systems..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2265 (2015)
Compensation for dynamic creep of stack piezoelectric actuator
ZHANG Cheng-jin, ZHAO Xue-liang, and LIU Hong-bo
The dynamic creep phenomenon of a piezoelectric actuator was confirmed by experiments. Based on the high frequency response of the piezoelectric actuator and the higher real time ability of the PID, a composite controller was proposed to compensate the dynamic creep. The composite controller used a direction inverse coThe dynamic creep phenomenon of a piezoelectric actuator was confirmed by experiments. Based on the high frequency response of the piezoelectric actuator and the higher real time ability of the PID, a composite controller was proposed to compensate the dynamic creep. The composite controller used a direction inverse controller with Prandtl Ishlinskii operators as the feed-forward controller, and an increment PI as the feed-backward controller based on the online test results and demanded real time abilities, in which the parameters of PI were tuned by a fuzzy logic controller . The validity of compensating dynamic creep phenomenon of the piezoelectric actuator by the composite controller was verified. The results show that when a 0.1 Hz sine-wave is discretized into 20, 40, 80 stairs respectively, the dynamic creep corresponding the equal voltages has different creep processing and different creep ranges. It verifies that the dynamic creep is complex nonlinearity. It concludes that the proposed controller compensates both static creep and dynamic creep in different discretization stairs and the root-mean square errors(RMSE) of compensated creep have decreased by 71.4%, 69.0% and 64.6% respectively..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2273 (2015)
Design and alignment of support structure for off-axis multi-mirror system
MEI Gui, ZHAI Yan, MIAO Jian-yu, and PU Qian-shuai
A support structure with an adhesive truss was designed for a space camera with off-axis multi-mirror systems. The struts of this truss were manufactured with T700 made of carbon fiber composites, fittings were manufactured with titanium alloys, the adhesive was J133 epoxy resin and casting titanium fittings were bondeA support structure with an adhesive truss was designed for a space camera with off-axis multi-mirror systems. The struts of this truss were manufactured with T700 made of carbon fiber composites, fittings were manufactured with titanium alloys, the adhesive was J133 epoxy resin and casting titanium fittings were bonded on both ends of the truss struts to provide interfaces for other subassemblies of the camera. The methods and steps for assist alignment equipment and gluing the subassemblies were described particularly. Firstly, preliminary assembly and alignment were done to ensure the precise locations of struts and fittings using the assistance equipment. Then, the formal alignment was performed with the help of locating pins, and the struts and fittings were restored in the correct initial positions and bonded with adhesives. Finally, the structure was solidified at room temperature for 5-7 days, and the assembly and alignment were finished after dismantling the assistance equipment and pins.The results of finite element analysis and vibration test indicate that the first-order natural frequencies of the truss and the lens supported by the truss are more than 90 Hz and 70Hz, respectively. Interfaces of mirror subassemblies were measured before and after vibration tests, and the results show that the flatness has been reached to 0.15 mm and the maximum relative error of interface flatness is 5.3%. The conclusion is that the stiffness and dimensional stability of the truss well meet the design requirements..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2280 (2015)
Combustion characteristics of aluminum and boron nanoparticles based on flame color images
KONG Cheng-dong, YU Dan, YAO Qiang, ZHUO Jian-kun, and LI Shui-qing
The combustion characteristics of aluminum and boron nanoparticles were studied based on the optical diagnostics using a color digital camera and subsequent image processing and their morphologic features, temperature characteristics and the ignition time were obtained. In the experiments, the multi-diffusion flat flamThe combustion characteristics of aluminum and boron nanoparticles were studied based on the optical diagnostics using a color digital camera and subsequent image processing and their morphologic features, temperature characteristics and the ignition time were obtained. In the experiments, the multi-diffusion flat flame burner (i.e. Hencken burner) was used to support a tunable high temperature ambience. A series of processes including dissolving the nanoparticles into the ethanol, ultrasonically dispersing, atomization, and diffusion-drying were used to generate well-dispersed nanoparticle aerosol. The flame images of the nanoparticles were recorded by a color digital camera under different experimental conditions. The signals of red, green and blue channels were derived from the color images to obtain the radiation intensity and the information of particle temperatures based on the Planck's law. The results indicate different particle temperature profiles at different ambient temperature. At a high temperature, the particle temperatures of Al and B decrease directly after ignition. At a low temperature, the particle temperature of Al increases slowly to a peak and then decreases due to the polymorphic phase transition of the alumina shell, while the particle temperature of B is nearly constant. The ignition process of B is divided into ignition delay and ignition stage, and the time could be defined from the flame images. The time of ignition delay for B ranges from 1.17 ms to 2.98 ms and the ignition time ranges from 0.31 ms to 0.85 ms..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2288 (2015)
ADRC control system for airborne opto-electronic platform
WEI Wei, DAI Ming, LI Jia-quan, MAO Da-peng... and SUN Jing-hui|Show fewer author(s)
A model for aerial photoelectrical stabilized platforms was analyzed and it was simplified with a current loop. The disturbance influencing the platform stability was explained and a disturbance rejection method was illustrated. An Active Disturbance Rejection Controller(ADRC) was designed based on forecast revision. FA model for aerial photoelectrical stabilized platforms was analyzed and it was simplified with a current loop. The disturbance influencing the platform stability was explained and a disturbance rejection method was illustrated. An Active Disturbance Rejection Controller(ADRC) was designed based on forecast revision. Firstly, a method is proposed to reduce the time lag and the overshoot of disturbance observing values by amending followed by forecasting. Then , a new controller was designed based on the two stage extended state observer to isolate the disturbance linearly and dynamically. Finally, a speed stability experiment and a target tracking experiment were taken on a vibration platform and the robustness of the system was also analyzed. The experimental results show that the designed controller method improves the disturbance isolation by 5.88 dB as compared with conventional method. Moreover, the designed control system has good robustness while the system parameters vary by 15%. As the proposed control system has good practicability and stronger robustness, it observably improves the disturbance isolation of the opto-electronic platforms..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2296 (2015)
Acceleration measurement model and uncertainty evaluation of 10-6 order precision centrifuge
LING Ming-xiang, LI Qi-sheng, ZHANG Rong, LI Ming-hai... and LU Yong-gang|Show fewer author(s)
To obtain the high accuracy acceleration inputs for calibration of inertial instruments, the mathematical modeling, measurement and associated uncertainty evaluation of the acceleration produced by a precision centrifuge were investigated. An acceleration measurement model and an associated uncertainty propagation modeTo obtain the high accuracy acceleration inputs for calibration of inertial instruments, the mathematical modeling, measurement and associated uncertainty evaluation of the acceleration produced by a precision centrifuge were investigated. An acceleration measurement model and an associated uncertainty propagation model were established for the 10-6 order high precision centrifuge. Then, major components, static and dynamic diameters and static and dynamic longitudinal misalignment angles, in the acceleration measurement model were measured precisely by using our proposed methods. Based on identification and quantization of measurement uncertainty sources, the uncertainty evaluation of acceleration measurement was implemented respectively by employing the uncertainty evaluation mathematical model of acceleration and Monte Carlo Method(MCM). Finally, some issues were discussed and summarized on the mathematical model and uncertainty evaluation . Test results indicate that the acceleration relative standard uncertainty of the developed precise centrifuge is less than 3×10-6 under the spectrum of 1g-100g. The precision of the developed precise centrifuge reaches the international advanced level and the proposed measuring model and associated uncertainty evaluation method can provide some references for other precise centrifuges..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2306 (2015)
Nonlinear model predictive control of agile satellite attitude maneuver
FAN Guo-wei, CHANG Lin, DAI Lu, XU Kai, and YANG Xiu-bin
By taking a pyramid configuration Control Moment Gyro( CMG) as the actuator, an advanced maneuver control algorithm was explored. In consideration of the constraint or incremental constraint of control torque for the CMG, the control law and manipulation law for the satellite attitude fast maneuver were designed based By taking a pyramid configuration Control Moment Gyro( CMG) as the actuator, an advanced maneuver control algorithm was explored. In consideration of the constraint or incremental constraint of control torque for the CMG, the control law and manipulation law for the satellite attitude fast maneuver were designed based on the Nonlinear Model Predictive Control (NMPC) method, and the impact of satellite attitude maneuver controller parameters on tracking performance was analyzed by different simulations. The simulation results indicate that increasing tracking performance weighting matrix and lengthening predicting time domain,the satellite attitude maneuver speed can be improved and the maneuver time can be shortened. The designed control method can achieve 40 ° attitude maneuver in the 18 s, and the corresponding pointing accuracy and stability are 0.01°and 0.04(°)/s, respectively. Simulation results were also compared with that the terminal sliding-mode control method,and it shows that the control performance of satellite attitude maneuver has been improved . The proposed control method in this paper provides a theoretical support for the in-orbit applications of agile small satellites..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2318 (2015)
Detection of super wide-field infrared target based on spatial-temporal fusion processing
HUANG Fu-yu, SHEN Xue-ju, LIU Xu-min, and CUI Tie-cheng
When a super wide-field infrared staring system is used to detect a target, it may show complex background, more noise jamming and little target information. Therefore, this paper proposes a spatial-temporal fusion algorithm. In spatial processing, the single image was filtered by an improved Robinson operator, and theWhen a super wide-field infrared staring system is used to detect a target, it may show complex background, more noise jamming and little target information. Therefore, this paper proposes a spatial-temporal fusion algorithm. In spatial processing, the single image was filtered by an improved Robinson operator, and the primary detection of the target was carried out. Then, the image auto-partition and spatial false-alarm suppression were presented to eliminate the suspected target from a non-target detection region. In temporal processing, the temporal characteristics of the target was considered, the neighbor judgment method was improved to confirm the real target. A detection experiment for the space target was carried out in a moon light, and this proposed algorithm was vilified. It shows that the background interference of original image is suppressed greatly, the local Signal to Noise Ratio(SNR) can be improved more than 1.3 times, the false target number decreases by 70% after spatial processing. Moreover, the infrared weak target is detected successfully with the detection probability of higher than 95%, the false-alarm probability of less than 1.5% and the minimum detection SNR of 2.86 after spatial processing. It concludes that this algorithm is suitable for the infrared weak target detection of super wide-field image and can detect the moving point targets effectively.It has a good suppression effect for background interference, isolated point sources and instantaneous noise..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2328 (2015)
Efficient target tracking by TLD based on binary normed gradients
CHENG Shuai, CAO Yong-gang, SUN Jun-xi, LIU Guang-wen, and HAN Guang-liang
To improve the tracking precision and processing speed of the Tracking-Learning-Detection(TLD) algorithm under a complex environment, an efficient TLD target tracking algorithm based on BInary Normed Gradient(BING) algorithm was proposed. The local tracker failure predicting method based on spatial-temporal context andTo improve the tracking precision and processing speed of the Tracking-Learning-Detection(TLD) algorithm under a complex environment, an efficient TLD target tracking algorithm based on BInary Normed Gradient(BING) algorithm was proposed. The local tracker failure predicting method based on spatial-temporal context and the global motion model estimation algorithm was introduced into the tracker to improve its precision and robustness. Then, the BING algorithm was used to replace a sliding window for searching the target to detect the candidate target by combining with a cascaded classifier, so that to reduce the search space and improve the processing speed of the detector. The sample weight was integrated into the online learning procedure to improve the accuracy of the classifier and to alleviate the drift to some extents. The experimental results on variant sequences demonstrate that the accurate rate and the frame rate of the improved TLD are 85% and 19.79 frame/s, respectively. Compared with original TLD and state-of-the-art tracking algorithm under the complex environment, the improved TLD has the superior performance on robustness, tracking precision and tracking speeds..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2339 (2015)
Fast object recognition under multiple varying background using improved SIFT method
NIE Hai-tao, LONG Ke-hui, MA Jun, and LIU Jin-guo
An improved Scale Invariant Feature Transform (SIFT) method was proposed to implement the fast object recognition under a multiple varying background. Firstly, the scale space of object image was established, SIFT feature points were extracted and classified by their sizes. Only by comparing the same kinds of feature pAn improved Scale Invariant Feature Transform (SIFT) method was proposed to implement the fast object recognition under a multiple varying background. Firstly, the scale space of object image was established, SIFT feature points were extracted and classified by their sizes. Only by comparing the same kinds of feature points , the target recognition could be completed. Then, four new angles were computed from the sub-region orientation histogram to represent the orientation information of each SIFT feature. Meanwhile, the feature point matching range was limited according to angle information in the target recognition to improve the calculation speeds of the SIFT algorithm. Finally, the scale factor between object image and target image was calculated and the object feature points were matched under the constraint by the scale factor to increase the number of correct matches and to insure the robustness of object recognition. Object recognition experiments were operated under object external occlusions, object rotation, scale change and illumination conditions. Results show that improved SIFT method has better performance of object recognition, and its computation speed has raised more than 40% as comparing with that of original SIFT algorithm..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2349 (2015)
Accuracy and robust estimation of homography based on feature point location noise
ZHAO Chun-Yang, and ZHAO Huai-Ci
The feature location noise from feature-based homography estimation methods is isotropic and non-identical distribution, and it effects the accuracy and robustness of homography estimation methods significantly in practical applications. Therefore, this paper proposes a high accuracy and robust homography estimation meThe feature location noise from feature-based homography estimation methods is isotropic and non-identical distribution, and it effects the accuracy and robustness of homography estimation methods significantly in practical applications. Therefore, this paper proposes a high accuracy and robust homography estimation method based on location noise of feature points. The method uses a covariance matrix to characterize the location noise of feature points and takes an inner point verification method based on Covariance matrix Weight SAmple Consensus(CWSAC) to improve the robustness of the homography estimation method. Finally, a high accuracy homography matrix refined method, Covariance matrix Weight Levenberg-Marquardt( CW L-M) is proposed by combining covariance matrix with Levenberg-Marquardt method, and it improves the estimation accuracy of homography matrix by redefining a optimized object function. The experiments on simulation data and real images show that as compared with state-of-the-art methods, such as RANSAC(RANdom SAmple Consensus),LMedS(Least Median of Squares), PROSAC(PROgressive SAmple Consensus), M-SAC(M-estimator SAmple Consensus)and MLESAC(Maximum Likelihood SAmple Consensus), the accuracy of homography estimation has improved greatly and the root mean squares of reproject error has reduced 3%- 21% than that of the subprime method in the same location noise and the same inlier proportion. In addition, the proposed method is robust to the noise level and inlier proportion changing..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2357 (2015)
Intersection measurement for field tests
TAO Jia-yuan, WANG Ke-yi, and LUO Guo-xiong
An intersection measurement method by combination of coordinate system transformation with Row-wised Weighted Total Least Squares(RWTLS) was proposed for field tests. The angles of the target points on a geodetic coordinate system was obtained by using the space coordinate transformation method. Then,the angle relationAn intersection measurement method by combination of coordinate system transformation with Row-wised Weighted Total Least Squares(RWTLS) was proposed for field tests. The angles of the target points on a geodetic coordinate system was obtained by using the space coordinate transformation method. Then,the angle relationship between the initial data was determined through condition equation established by redundant observation numbers, and the moving object's space coordinate of position at any moment was acquired by using the RWTLS and Gauss-Newton method. Finally, the base distance was get through the observations of the static target, and the targets' trajectory curve was obtained with the target space angle coordinates. The experimental results show that the errors of the coordinates of the observation station are within ±0.15 m, and the target point errors in X, Y, Z directions are within ±0.4 m. The method avoids the correction of theodolite coordinate and does not need to give the position parameters of the observation station, so it reduces calculation of starting data and the number of the observation stations and is characterized by quick convergence, high accuracy and good practicability in field tests of flying targets..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2369 (2015)
Lossless compression of hyperspectral images using backward search in context window
GAO Fang, LIU Yu, and GUO Shu-xu
An efficient lossless compression scheme of hyperspectral images based on one-band-prediction was proposed by using backward search in a context window to improve the compression ratio of the hyperspectral images. Firstly, the context window for a pixel to be tested was defined and the prediction reference value under An efficient lossless compression scheme of hyperspectral images based on one-band-prediction was proposed by using backward search in a context window to improve the compression ratio of the hyperspectral images. Firstly, the context window for a pixel to be tested was defined and the prediction reference value under testing was calculated. Then,the candidate predictors which were mostly closed to the prediction reference value were selected as the final prediction results of the pixel to be measured. Finally, the predicted residual image was coded by a first-order arithmetic to implement the image compression. The method proposed was used in the experiments on hyperspectral images from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) 1997, and the results show that the method has obtained the best prediction results of backward search by optimizing the context window, equivalent coefficients and effective pixel thresholds. After coding by an arithmetic coder, the average compression ratio is 3.63。 The method has a lower computing complexity and smaller memory requirements, and outperforms all other lossless compression schemes for hyperspectral images that have been previously reported..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2376 (2015)
Explicit phase height model and its calibration
ZHANG Xu, LI Xiang, and TU Da-wei
As the phase height model in traditional Phase Measuring Profilometry( PMP)has a larger storage space and higher calibration cost, this paper deduces an explicit function model of phase difference height according to the relationship between absolute phase and depth coordinate, and proposes a flexible calibration methoAs the phase height model in traditional Phase Measuring Profilometry( PMP)has a larger storage space and higher calibration cost, this paper deduces an explicit function model of phase difference height according to the relationship between absolute phase and depth coordinate, and proposes a flexible calibration method based on unknown calibration plane. The model can calculate 15 model parameters only by 9 nonlinear pixel data, so it saves the memory space and reduces the computing cost. The proposed calibration method does not need any movement platform and position posture, and brings the advantage of small calibration board and well flexible ability. The simulation and experiment on the model and calibration method are performed. The simulation results verify the validity of explicit function model of phase difference height and the availability of the proposed calibration method. Moreover, an actual experiment for the model and the calibration method is done in a structure light system. The calibrated system is used to test a real objective, and the results show that the 3D curved surface has higher quality, which demonstrates the proposed method is feasibility..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2384 (2015)
Rapid restoration and real-time detection on spot image of atmospheric laser communication
GAO Shi-jie, SHENG Lei, WU Zhi-yong, and ZHU Li-lu
For the effects of atmospheric turbulence on Acquisition, Tracking and Pointing (ATP) of the beacon in laser communication, a rapid restoration and real-time detection algorithm based on blind deconvolution was proposed. A local degradation model was proposed based on one dimensional Point Spread Function (PSF) insteadFor the effects of atmospheric turbulence on Acquisition, Tracking and Pointing (ATP) of the beacon in laser communication, a rapid restoration and real-time detection algorithm based on blind deconvolution was proposed. A local degradation model was proposed based on one dimensional Point Spread Function (PSF) instead of the normal two dimensional model.Then the constraint operator of the classic constrained conjugate gradient algorithm was improved, and the original image was estimated by the improved conjugate gradient iterative algorithm. Finally, the centroid of the beacon was calculated from the estimation image by connected component analysis. To meet the real-time requirement, a Field Programming Gate Array( FPGA) and Digital Signal Processors(DSPs) were used to realize the proposed algorithm and to extract the central position of a spot . Experimental results indicate that the real-time restoration on the image with 200×200 pixels and 100 Hz frame rate have been obtained by the proposed algorithm. The error between the real-time result and the after one calculation is less than 1 pixel, which meets the requirements of the laser communication system for real-time tracking on the beacon..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2393 (2015)
Fast Arclet transform and its application in circle measurement of industrial CT images
LI Zong-jian, and ZOU Xiao-bing
To accurately describe the circular structures of industrial CT images, a measurement algorithm based on multi-scale geometric analysis tool, named Arclet, was presented. Firstly, a fast mono-scale Arclet numeric transform algorithm was designed through analysis of the spatial relationship between mono-scale Arclet basTo accurately describe the circular structures of industrial CT images, a measurement algorithm based on multi-scale geometric analysis tool, named Arclet, was presented. Firstly, a fast mono-scale Arclet numeric transform algorithm was designed through analysis of the spatial relationship between mono-scale Arclet basis functions. Then, the candidate circular features at mono-scale were extracted based on the mono-scale numeric transform transform. By considering the spatial relationship between Arclet basis functions at adjacent scales and the multi-scale tree structure, the candidate circular features between adjacent scales were chosen from a root to leafs. Finally, the surplus circular feature of each scale was fused to obtain the extracted results, and to calculate the related parameters such as radius based on the extracted results. The circle measurement for an actual industrial CT image was performed and the measurement results show that the absolute value of maximum radius absolute error is less than 0.1 mm and that of maximum radius relative error is less than 5%. Even if adding the Gauss noise of different intensities into the original industrial CT image, the measurement results are still can meet the requirements. The measurement algorithm based on fast Arclet transform has better ability to inhibit the noise interference and meet the requirements of industrial CT images for circular structure description..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2400 (2015)
Research and development of mineral identification utilizing hyperspectral remote sensing
ZHANG Cheng-ye, QIN Qi-ming, Chen Li, Wang Nan, and Zhao Shan-shan
This paper reviews the current progress of mineral identification based on hyperspectral remote sensing. The physicochemical mechanisms of mineral spectra and their feature measurement and analysis are introduced. The properties of current and future main hyperspectral sensors are concluded. Then, three series of methoThis paper reviews the current progress of mineral identification based on hyperspectral remote sensing. The physicochemical mechanisms of mineral spectra and their feature measurement and analysis are introduced. The properties of current and future main hyperspectral sensors are concluded. Then, three series of methods (based on spectral absorption feature, full spectral profile matching, and spectral unmixing, respectively) for mineral identification based on hyperspectral data sets are comparatively analyzed and summarized. Finally, the main problems of mineral identification by using hyperspectral data on theory, data sets, methods and applications, are analyzed and its developing trends are discussed. It points out that the trend will focus on the direction from the qualitative identification to the quantitative mineral analysis. During this trend, spectral unmixing, the design of new hyperspectral sensors for mineral identification, intellectualization of mineral information extraction, and mineral identification in a complex geological environment will be the main research focuses..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2407 (2015)
Blind navigation aid system with Kinect sensor in complex indoor environments
ZHANG Ke-hua, WANG Shu-ping, YIN Xiao-hong, and CHENG Guang-ming
A blind navigation aid system was designed to improve the poor detection, complex structure and inconvenient to carry for the existing guide equipment. The system could detect all the obstacles between the ground and the user's head, and could deliver accurately the traffic information through a voice prompt to theA blind navigation aid system was designed to improve the poor detection, complex structure and inconvenient to carry for the existing guide equipment. The system could detect all the obstacles between the ground and the user's head, and could deliver accurately the traffic information through a voice prompt to the user, so as to complete the navigation. The depth image rotation algorithm and detection obstacle technology were applied in this system to identify three types of obstacles including ground obstacles, ground pits and hanging obstacles. Meanwhile, the depth image filtering algorithm and obstacle distance calculation were used to determine the position of the obstacle in an effective range. A prototype was developed, and the experiments on the obstacle recognition and obstacle position detection were carried out in various scenes at a laboratory. The experimental results show that the navigation system can accurately identify the obstacle with an area more than 10-3 m2 and the holes with a height difference more than 0.02 m and can determine the best way to avoid the obstacle in an effective range by voice prompt to the user, so as to meet the daily demand to blind navigation. The development of this system and the applications of various algorithms not only have important effect on the blind navigation, but also have reference significance for the robot walking dependently..
Optics and Precision Engineering
- Publication Date: Oct. 22, 2015
- Vol. 23, Issue 8, 2419 (2015)
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