Journals >Optics and Precision Engineering
Contents
2010
Volume: 18 Issue 12
26 Article(s)
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Research Article
Calibration method for wirelessly localizing capsule endoscopy
GUO Xu-dong, YAN Rong-guo, and YAN Guo-zheng
In order to non-invasively track a capsule endoscopy in the gastrointestinal tract, a telemetric localization method using alternating magnetic fields was presented. Focusing on the method, a Bayesian-regularization neural network based on the Levenberg-Marquart algorithm was investigated to reduce system errors. FirstIn order to non-invasively track a capsule endoscopy in the gastrointestinal tract, a telemetric localization method using alternating magnetic fields was presented. Focusing on the method, a Bayesian-regularization neural network based on the Levenberg-Marquart algorithm was investigated to reduce system errors. Firstly, the neural network structure for localization calibration was designed. Then, both Bayesian-regularization and Levenberg-Marquart algorithms were used to train the neural network to limit an over-fitting. Using an experimental platform for localization, both the calibration table for training the network and the validation table for verifying the calibration quality were established,and the location data were calibrated by the trained neural network. The calibration experiment shows that the proposed neural network can be trained well enough to efficiently compensate the errors in electromagnetic localizing system. The mean errors of X, Y, Z, α, β respectively have been reduced to 8.7 mm,10.1 mm,7.3 mm,0.086 rad and 0.081 rad after calibration. Comparing with the standard Back-Propagation(BP) algorithm, the Bayesian-regularization neural network based on Levenberg-Marquart algorithm has better performance in the generalization capability and convergence precision.信息科学.
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2650 (2010)
Design of conjugated reflectometer for reflectance measurement
WU Li-xiong, WANG Li-jun, LIN Xin-wei, and LIU Feng
A conjugated reflectometer was designed to measure both the total hemispherical reflectance and the specular reflectance of samples in real-time, and it could also be used for temperature-dependent reflectance measurement. The primary component of the conjugated reflectometer is a hemi-ellipsoidal shape shell (axis ratA conjugated reflectometer was designed to measure both the total hemispherical reflectance and the specular reflectance of samples in real-time, and it could also be used for temperature-dependent reflectance measurement. The primary component of the conjugated reflectometer is a hemi-ellipsoidal shape shell (axis ratio 10∶9∶9) with relatively high specular reflectance (>70% in the spectral ranges from visible light to long-wave infrared) on its inner surface. The measuring principle and configuration of the reflectometer were introduced. The main influencing factors of collection efficiency including the position of incident port, incident direction, incident beam diameter, collecting aperture, and the reflection property of interior surface of the hemi-ellipsoidal shell were analyzed and simulated by the ray tracing method qualitatively. Obtained results indicate that a collection efficiency of 97.8% ratio to entire collection can be obtained by the detecting laser beam with a diameter of 10 mm and collecting aperture of 38.1 mm. Furthermore, the higher degree of fineness is required for a shorter wave measurement; and the collection efficiency for certain area is mainly decided by the specular reflectance of inner surface with a perfect shape. It is concluded that the key factor for the accuracy and reliability of measurement is the machining precision of interior surface of hemi-ellipsoidal shell, therefore,the shape accuracy, degree of fineness and the reflectivity of inner surface are all very important..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2521 (2010)
Calibration of deposition rates of multilayer coatings by sputtering depositions
ZHANG Li-chao
A calibration method for deposition rates of multilayer coatings by sputtering depositions was proposed to eliminate the random thickness errors and to realize the accurate control of film thicknesses. In this method,the deposition rates were acquired by the least square fitting for results of different deposition expeA calibration method for deposition rates of multilayer coatings by sputtering depositions was proposed to eliminate the random thickness errors and to realize the accurate control of film thicknesses. In this method,the deposition rates were acquired by the least square fitting for results of different deposition experiments. An analysis on the basic properties of random variables shows that deposition rates can be converged to the true values in a case that the number of depositions is large enough. On the basis of above principle, accurate deposition rates can be acquired, random thickness errors can be extracted, and the thickness control accuracy of the coating machine can be determined as well. Furthermore, the complete information to realize the accurate control of film thicknesses can be also obtained. Experiments based on this calibration method were carried out by using two deposition systems. Results indicate that control accuracies are different for different deposition systems. The low cost deposition system shows a relative low thickness control accuracy in 0.1 nm,and the other one with high deposition performance could realize the thickness control accuracy in 0.01 nm..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2530 (2010)
Application of fiber Fourier transform spectroscopy to fiber Bragg grating demodulation
ZHU Ling, CHEN Ming-xing, FANG Jie, LIU Yong, and WANG An
The elementary principle of a fiber Mach-Zehnder interferometer and the structure of a Fiber Fourier Transform Spectroscopy(FFTS) were introduced. Then, a novel demodulation scheme for the fiber Bragg grating sensor based on the fiber Mach-Zehnder interferometer and the FFTS was designed to achieve highly stable and acThe elementary principle of a fiber Mach-Zehnder interferometer and the structure of a Fiber Fourier Transform Spectroscopy(FFTS) were introduced. Then, a novel demodulation scheme for the fiber Bragg grating sensor based on the fiber Mach-Zehnder interferometer and the FFTS was designed to achieve highly stable and accurate wavelength demodulation. In demodulation,the light emitted from a broadband light source was through the fiber coupler into a fiber Bragg grating,and the reflected light of fiber Bragg grating came back from the fiber coupler into the FFTS. The optical path difference of FFTS is up to 10 cm and the maximum spectral resolution is 0.05 cm-1 when the unilateral Fourier transform algorithm is used, which means the wavelength resolution is 0.012 nm in near infrared scope of 1 550 nm. The strain characteristics and temperature characteristics of a fiber Bragg grating were measured by the FFTS, respectively. Experimental results indicate that the strain sensitivity is 0.833 pm/με and the temperature sensitivity is 19.78 pm/℃. Obtained data show that the FFTS system has advantages of high spectral resolution and wide measuring ranges and it can satisfy the wavelength demodulation requirements of fiber Bragg grating sensors..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2537 (2010)
Extreme ultraviolet single photon-counting imaging system based on induced charge position-sensitive anode
NI Qi-liang, HE Ling-ping, LIU Shi-jie, DONG Ning-ning, and CHEN Bo
A new prototype of two-dimensional photon-counting imaging system with an induced charge position-sensitive anode in extreme ultraviolet (EUV) region was developed for a moon-based EUV camera. The detector system is mainly composed of microchannel plate (MCP) stacks operating in a pulse-counting mode,a wedge-strip induA new prototype of two-dimensional photon-counting imaging system with an induced charge position-sensitive anode in extreme ultraviolet (EUV) region was developed for a moon-based EUV camera. The detector system is mainly composed of microchannel plate (MCP) stacks operating in a pulse-counting mode,a wedge-strip induced-charge position-sensitive anode and correlative analog and data processing circuits. A three-electrode wedge-strip induced-charge position-sensitive anode with a 1.5 mm period and a 47 mm diameter active area was designed and fabricated, and the front-end analog and data circuits with the maximum counting rate of 200 kHz were also developed. The operating characteristics of the prototype MCP detector including the background rate, pulse height distribution, gain, image linearity and the spatial resolution were measured. The measured results show that the spatial resolution has been 7.13 lp/mm(0.14 mm), which means it can completely satisfy the requirement of moon-based EUV camera for the spatial resolution..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2543 (2010)
Design and fabrication of two-dimensional photonic crystal waveguides on silicon films
CUI Nai-di, LIANG Jing-qiu, LIANG Zhong-zhu, ZHOU Jian-wei... and WANG Wei-biao|Show fewer author(s)
In order to fabricate two-dimensional photonic crystal waveguides on silicon films, the design method and fabrication techniques were investigated. Firstly, the TE bands of the two-dimensional square lattice and triangular lattice air hole structures were calculated by using the plane wave expansion method，and the two-In order to fabricate two-dimensional photonic crystal waveguides on silicon films, the design method and fabrication techniques were investigated. Firstly, the TE bands of the two-dimensional square lattice and triangular lattice air hole structures were calculated by using the plane wave expansion method，and the two-dimensional triangular lattice air hole structure was chosen. Then, by adding a line defect,the photonic band gaps of the two-dimensional triangular lattice were calculated also by using the plane wave expansion method. The reasonable photonic band gap whose normalized frequency was 0.295 7 was chosen, and the structure parameters of two dimensional photonic crystal waveguides used in the 1.55 μm were designed as the period of the lattice in 458 nm and the diameter of the air hole in 339 nm.Furthermore,the tolerances of structure paremeters were calculated as -3.95-5.65 nm. Finally, the photonic crystal waveguides were fabricated by using the focused ion beam etching. The testing shows that the period of the lattice is 463 nm, and the diameter of the hole is 344 nm, which are 5 nm larger than the design values，but still in the tolererce range..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2549 (2010)
Fabrication and testing of precise off-axis convex aspheric mirror
ZHANG Feng
To improve the fine surface figure accuracy and optical axis accuracy of an off-axis convex aspheric mirror, the fabrication and testing technologies of the off-axis convex aspheric mirror were studied. Firstly, a Three Mirror Anastigmat (TMA) optical system and the specification requirements of the second off-axis conTo improve the fine surface figure accuracy and optical axis accuracy of an off-axis convex aspheric mirror, the fabrication and testing technologies of the off-axis convex aspheric mirror were studied. Firstly, a Three Mirror Anastigmat (TMA) optical system and the specification requirements of the second off-axis convex aspheric mirror in the TMA optical system were presented. Then, the technique of Computer-controlled Optical Surfacing(CCOS)for manufacturing the aspheric mirror and the FSGJ numerical control machine for processing aspheric surface were introduced. Finally, the contour testing in a lapping stage and the back transmission null testing in a polishing stage for the convex aspheric mirror were described, and the controlling technology for the optical axis accuracy of off-axis convex aspheric mirror was studied. The testing results indicate that the surface figure accuracy and the optical axis accuracy of the off-axis convex aspheric mirror are 0.017λ RMS and 9.4″,respectively. All the specifications of the off-axis convex aspheric mirror can meet the requirements of the optical design..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2557 (2010)
Moon-based imaging of earth plasmaspheric extreme ultraviolet radiation
HE Fei, CHEN Bo, and ZHANG Xiao-xin
The extreme ultraviolet radiation properties of the earth plasmasphere was firstly studied, which shows that the plasmapause is mainly located near 35 081.75 km, the typical scale of the plasmasphere structures is 637.85 km, and the He+ 30.4 nm emission intensity is between 0.02 and 11.4 Rayleigh when the plasmasphere The extreme ultraviolet radiation properties of the earth plasmasphere was firstly studied, which shows that the plasmapause is mainly located near 35 081.75 km, the typical scale of the plasmasphere structures is 637.85 km, and the He+ 30.4 nm emission intensity is between 0.02 and 11.4 Rayleigh when the plasmasphere is detected from the moon. Then,the orbital characteristics and surface environmental properties of the moon were described and it is pointed out that the total imaging period of an extreme ultraviolet imager is 12 d, in which the maximum latitudinal drift of the positioning of the camera is 7° while the maximum longitudinal drift is 6°. The extreme ultraviolet radiation of the lunar surface was analyzed,and results indicate that the extreme ultraviolet radiation reflected by lunar surface is 2.0 Rayleigh at solar maximum,which has the same order in the magnitude as compared with the plasmasphere emission. Based on the SELENE observation data, topographic properties in the five planned landing sites were explored,it proves that the extreme ultraviolet radiation reflected by lunar surface in these sites can not enter the field of view of the camera. For the five sites, Sinus Iridum is the most ideal site for moon-based extreme ultraviolet imaging. The proton and electron fluxes on the lunar surface were analyzed using Apollo-12 and Apollo-15 SWC experiment data,results show that the total fluences of protons and electrons are both approximately 5×1015 cm-2 in one-year period. During a lunation, the lunar surface temperature changes from 80 K at lunar night to 390 K at lunar noon according to Apollo-12 observation. Above results provide an important basis for the design of moon-based extreme ultraviolet imagers..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2564 (2010)
Design of two-axis elastic support for fast steering mirror
LU Ya-fei, FAN Da-peng, FAN Shi-xun, ZHANG Zhi-yong, and ZHOU Qing-kun
A new elastic support based on the lumped compliance of flexure hinges was presented for a two-axis Fast Steering Mirror(FSM) system,and the methods to analyze the static and dynamic performance of the elastic support were researched. Firstly,the principle of two-axis FSM and the performance demand of an elastic supporA new elastic support based on the lumped compliance of flexure hinges was presented for a two-axis Fast Steering Mirror(FSM) system,and the methods to analyze the static and dynamic performance of the elastic support were researched. Firstly,the principle of two-axis FSM and the performance demand of an elastic support were analyzed,and the advantages and disadvantages of several existing elastic supports were researched.Then, a new elastic support based on a right-corner flexure hinge structure was put forward and the static and dynamic performance of the new elastic support was studied in detail. By taking a designed two-axis FSM with the performance in Φ90 mm beam aperture, ±2 mrad deflection angle and 300 Hz closed-loop bandwidth for an example, the characteristics of the elastic support were analyzed and the rotational stiffness of the elastic support was measured based on the dSPACE simulation system. Experimental results indicate that the elastic support can meet the performance of FSM well, and its first-order resonance frequency is 78 Hz, and the close-loop bandwidth tested is 340 Hz. It is concluded that the two-axis elastic support based on the lumped compliance of flexure hinge structure can be used for the FSM which needs several mrad deflection angles and several hundred Hz close-loop bandwidths,and it has advanteges in easy machining and a stable rotation center..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2574 (2010)
Implementation and experiments of micromechanical differential silicon resonant accelerometer
SHI Ran, QIU An-ping, and SU Yan
To improve the performance of MEMS accelerometers, a micromechanical Silicon Resonant Accelerometer (SRA) prototype fabricated by Deep Dry Silicon on Glass (DDSOG) process was introduced, and some experiments for the accelerometer were performed. The structure, processing methods and the interface circuit of SRA were dTo improve the performance of MEMS accelerometers, a micromechanical Silicon Resonant Accelerometer (SRA) prototype fabricated by Deep Dry Silicon on Glass (DDSOG) process was introduced, and some experiments for the accelerometer were performed. The structure, processing methods and the interface circuit of SRA were discribed in detail. The SRA adopted the differential structure composed of two identical resonators to eliminate common mode errors, and used the micro lever mechanism to magnify the scale factor. An interface circuit using the Automatic Gain Control (AGC) circuit was designed to maintain the oscillator stability, which could drive the resonator to achieve self-oscillation and to detect the frequency output. The relation between input acceleration and SRA frequency output was researched and the performance parameters of the prototype resonant accelerameter were tested. The test results show these performance parameters to be the sensitivity in 143 Hz/g, input range in ±50 g, bias stability in 1.2 mg, bias repeatability in 0.88 mg and the threshold in 170 μg. Moreover, it is found that the temperature coefficient of glass substrate is larger than that of the silicon structure in the DDSOG process, which affects the bias temperature sensitivity of resonators. Therefore,it points out that the processing method should be improved further..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2583 (2010)
Design of coordinated gain scheduled attitude controller for reusable booster vehicle
XU Jiang-tao, CUI Nai-gang, and L Shi-liang
In consideration of the serious coupling and distributions in the attitude control of a reusable booster with a high angle of attack, a new kind of gain-scheduled attitude control strategy was presented. Firstly, each of the pitch, yaw and roll channels was treated separately by ignoring the intentional coupling among In consideration of the serious coupling and distributions in the attitude control of a reusable booster with a high angle of attack, a new kind of gain-scheduled attitude control strategy was presented. Firstly, each of the pitch, yaw and roll channels was treated separately by ignoring the intentional coupling among the channels, and the linear control model of each channel was established in a way different from that considering small perturbation linearization. Then, the gain-scheduled controller for each channel was designed, and the theory of coordinated gain scheduled control strategy was put forward based on the single gain-scheduled controller. Finally, the coordinated scheduled controller was designed to deal with the intentional cross coupling among different channels. The results of nonlinear real-time simulation validate that the tracking error of the attack angle has reduced about 2°, and the control accuracy of sideslip angle has improved about 0.4° by proposed strategy. The control system can satisfy the control performance requirement of the reusable booster, and the strategy of controller design is characterized by its clear physical concepts and easy engineering applications..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2590 (2010)
Array micro Faraday cup ion current detector for FAIMS
TANG Fei, WANG Xiao-hao, and ZHANG Liang
An array micro Faraday cup ion current detector is presented. With its design，a simpler and smaller High-field Asymmetric Waveform Ion Mobility Spectrometry(FAIMS) could be achieved. Compared with other types of detectors, it has advantages in simplicity, stability, low noise, high measuring range, and atmosphere compaAn array micro Faraday cup ion current detector is presented. With its design，a simpler and smaller High-field Asymmetric Waveform Ion Mobility Spectrometry(FAIMS) could be achieved. Compared with other types of detectors, it has advantages in simplicity, stability, low noise, high measuring range, and atmosphere compatibility. The Array Micro Faraday Cup(AMFC) is made up of three parts:grid electrode, sensing array and shielding electrode,in which the sensing array is formed by dozens of 200-micron-diameter silicon cylinders in a staggered arrangement. The structure of the micro Faraday cup can be fabricated in a typical MEMS fabrication process, for it is totally compatible with the planar FAIMS micro chip. Fluent simulation results show that the design could realize a small fluid resistance force, and the flow field of the carrier gas is in favor of a better absorption of the ions. When it is combined with a KEITHLEY 237 electrometer, the noise level of the AMFC is about 0.5 pA, while the output signal of an acetone sample is about 120 pA. Obtained results show that the AMFC satisfies the requirements of FAIMS systems..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2597 (2010)
Trigger control of touch probe for nano-CMM
CHENG Fang, and FEI Ye-tai
A high precision and high efficiency trigger control scheme for the touch probe in a high-sensitive nano Coordinate Measurement Machine(nano-CMM) is developed,and a self-developed 4-DVD touch probe is used in the proposed scheme. When the probe touches the workepiece, the tiny deformation of the probing system will genA high precision and high efficiency trigger control scheme for the touch probe in a high-sensitive nano Coordinate Measurement Machine(nano-CMM) is developed,and a self-developed 4-DVD touch probe is used in the proposed scheme. When the probe touches the workepiece, the tiny deformation of the probing system will generate a high-sensitive trigger signal. By integrating different driving modes of an ultrasonic motor, the trigger control scheme realizes the combination of high-speed approaching and low-speed touching.Furthermore, a double-trigger method is used in the touching process. The first trigger is to determine the rough range of the trigger point and the second trigger is to record the trigger signal in detail by a very low speed and to work out the turning point of the trigger signal curve by a linear fitting i.e. the trigger position. This method solves the paradox between traveling range and driving resolution. Experimental results show that the proposed method will avoid the permanent deformation during touching process and the repeatability of the trigger point is within 10 nm. It concludes that this trigger control method for a nano-CMM touch trigger probe not only offers the higher precision and reliability,but also shows the acceptable control efficiency..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2603 (2010)
U-bending process of T2 copper foil
WANG Chun-ju, GUO Bin, and SHAN De-bin
A U-bending test was designed by using a micro female mold with different groove widths and corner radii on a micro extension tester made by SANS company. The effects of the mold dimension and foil thickness on the maximum punch load, springback and surface quality were analyzed during the micro U-bending process. The A U-bending test was designed by using a micro female mold with different groove widths and corner radii on a micro extension tester made by SANS company. The effects of the mold dimension and foil thickness on the maximum punch load, springback and surface quality were analyzed during the micro U-bending process. The results indicate that the reductions of groove width or radius leads to the increases of maximum punch load and the rates of increasing or decreasing of punch load increase greatly.By comparison of the punch loads of foils with different thicknesses,it is shown that the decreasing rate of punch load is larger than that of cross section area, and the size effect occurs obviously. Furthermore,the springback angle increases with the decreasing of thickness or radius, which reduces the accuracy of microparts. As the scratch appears at the side surface of a micro bending part, it suggests that the surface quality of the mold should be improved and the lubricating should be taken. The results have an important significance on the design of foil microforming process..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2610 (2010)
Contamination failure analysis and repairing for double side two dimensional silicon microstrip detectors
HAN Li-xiang, LI Zhan-kui, LU Wan, HU Jun... and WANG Zhu-sheng|Show fewer author(s)
Silicon micro-strip detectors are fabricated by a micro-electronic process. Their performance will become worse, even failure when they suffer from various contaminations. Moreover, the naked bond wires are also easily disabled by external forces. The research for above mentioned events is available to repair and maintSilicon micro-strip detectors are fabricated by a micro-electronic process. Their performance will become worse, even failure when they suffer from various contaminations. Moreover, the naked bond wires are also easily disabled by external forces. The research for above mentioned events is available to repair and maintain these detectors, and to improve their performance. This paper analyses the detectors' structure and fabrication process, and cleans them in different conditions according to the characters of contamination. After a measurement, it repairs them based on the chip graphics, packaging means and the electronics demand. Finally, the α isotope energy spectrum is used to measure the repaired detectors. A repaired detector shows that when the N-side is earthed and the P-side is biased negative 170 V, the detector is depleted and its average leakage current is 2.94 μA. By bonding again, the ghost peaks in the energy spectra caused by the strips whose bond wire is invalid on the other side are eliminated. The results also indicate that most disabled detectors can be revived by reasonable cleaning and repairing, but the cleaning might damage the surface or structure of the detector, so it must be careful and not frequently. Furthermore, when a bond wire is invalid, the electric charge could not be led out, so they are accumulated and influence other sensitive region by charge effect. It points out that the detector should be stored a place in cleaning, thermostatic and low-humidity conditions and without light and strong electromagnetic waves. these methods would be beneficial to improving their energy resolution, position resolution ,stability and working life..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2616 (2010)
Design of support distribution for attitude-adjusting mechanism of large lens
ZHANG Ya-nan, SHEN Li-li, SHEN Wei-xing, and CHEN Ming-yi
To design an attitude adjusting mechanism for large lenses, the adjusting characteristics of a three-pod adjusting structure and its effect on the force and deformation were analyzed. On the basis of the geometrical method, the relationship between the length of each pod and the plate angle variation was obtained underTo design an attitude adjusting mechanism for large lenses, the adjusting characteristics of a three-pod adjusting structure and its effect on the force and deformation were analyzed. On the basis of the geometrical method, the relationship between the length of each pod and the plate angle variation was obtained under the arbitrary triangle layout of 3-pod adjusting structure,and the correlation coefficient was thus defined. Furthermore,the Finite Element Method(FEM) was used to analyse the deformation of the adjusting plate with three types of support layouts. The results show that the adjusting values of 3-pod mechanism can be calculated.For a plate with the size of 580 mm×570 mm×20 mm, the maximum deformation caused by gravity could be 12.51 μm while the isoscele triangle support layout is adopted. Finally,the attitude adjusting mechanism based on the 3-pod isoscele triangle support layout was calibrated and adjusted,the results prove that it is effective in attitude adjusting and accuracy stability in target-firing experiments..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2624 (2010)
Combined supporting structure of thin wall joint cylinder and supporting bar between primary mirror and second mirror in space camera
LI Wei, LIU Hong-wei, GUO QUAN-feng, and WANG HAI-ping
To meet the relative position request of the second mirror and the primary mirror in a large-aperture and long-focal-length space camera, a combined supporting structure between the primary mirror and the second mirror was designed and manufactured,and the stability of the combined supporting structure was confirmed thTo meet the relative position request of the second mirror and the primary mirror in a large-aperture and long-focal-length space camera, a combined supporting structure between the primary mirror and the second mirror was designed and manufactured,and the stability of the combined supporting structure was confirmed through the analysis and tests. Firstly, according to the optical system，the combined supporting structure which combined a thin wall joint cylinder and a supporting bar was designed. The structure forms of supporting bar and joint cylinder were compared and their connection modes were discussed. Then，the gravity response，characteristic frequency and sinusoidal vibration responses of the supporting structure were analyzed. Finally, the supporting structure stability was validated by the mechanical tests and optical measurement. The results indicate that the angle displacement between the primary mirror and the second mirror is less than 10″ and the first-order natural frequency of supporting structure is greater than 75 Hz,which shows that the supporting structure has a better structure stability, and can satisfy the usage requirements of space cameras..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2633 (2010)
Spectral calibration for dispersive hyperspectral sensor based on doped reflectance standard panel
CHEN Hong-yao, and ZHANG Li-ming
Spectral calibration is a key to realize the quantification of hyperspectral remote sensing. Traditionally, the spectral calibration for a hyperspectral sensor is performed by a monochromator scanning method with disadvantages of expensive, time-consuming,etc.,which is difficult to achieve the real-time and high-accuraSpectral calibration is a key to realize the quantification of hyperspectral remote sensing. Traditionally, the spectral calibration for a hyperspectral sensor is performed by a monochromator scanning method with disadvantages of expensive, time-consuming,etc.,which is difficult to achieve the real-time and high-accuracy spectral calibration in the field or in-flight.In this paper,an accuracy and fast system level spectral calibration method was described for determining the center wavelengths for every spectral channel simultaneously. The reflective signals of a diffuse reflectance standard panel and a diffuse reflectance standard panel doped with a rare earth oxide were measured by the hyperspectral sensor. The ratio of two signals was optimized to remove the effects of sensor spectral response and lamp spectral output. By assuming a certain parametric model of the sensor and performing a nonlinear least squares fit of the measured ratio to the expected ratio, the center wavelength and bandwidth could be derived. A field spectroradiometer, FieldSpec UV/VNIR,was calibrated by proposed method,and the factors that effect on the calibration accuracy were analyzed. The results show that the wavelength accuracy is less than 0.5 nm,which indicates that the technology can meet the urgent needs of high accuracy and fast spectral calibration of hyperspectral sensors..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2642 (2010)
Efficient image inpainting based on region segmentation and varying exemplar
LIU Yang, WANG Hao-jing, TIAN XIAO-jian, and YIN Yu-mei
As existed exemplar-based image inpainting algorithms have low efficiency and poor quality for searching the best match exemplar using global searching methods, this paper analyzes the reasons that effect on the efficiency and quality of these algorithms and proposes an image inpainting algorithm based on the regional As existed exemplar-based image inpainting algorithms have low efficiency and poor quality for searching the best match exemplar using global searching methods, this paper analyzes the reasons that effect on the efficiency and quality of these algorithms and proposes an image inpainting algorithm based on the regional segmentation and varying exemplar. Firstly, an original image is shrunken to a downscaling image with a size in 0.02-0.25 times that of an original one by the downscaling method, and the pre-selected regions in the downscaled image are segmented as the source regions. Then, the adjustment rule of adaptive window size is used to determine the fixed window size. By searching a best-exemplar from pre-selected region, the image is inpainted. For the inpainted downscaled image, the sub-image segmentation method is used to inpaint the regions of incomplete restoration again, and then fill them into the inpainted region of the original image. Iterating the above steps until the whole image inpainting is completed. Obtained results demonstrate that this method is 5~100 times the efficiency of the existed method, meanwhile it shows good image quality..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2656 (2010)
High-accuracy TDC for laser range finder
FENG Zhi-hui, and LIU En-hai
A low-density Field Programmble Gate Array(FPGA) was chosen to realize a high-accuracy, low nonlinearity Time-to-Digital Converter(TDC) circuit to a laser range finder,for the high-density FPGA TDC circuit showed a worst linearity. The high-speed counter, interpolator methods and the encoder algorithm were studied, andA low-density Field Programmble Gate Array(FPGA) was chosen to realize a high-accuracy, low nonlinearity Time-to-Digital Converter(TDC) circuit to a laser range finder,for the high-density FPGA TDC circuit showed a worst linearity. The high-speed counter, interpolator methods and the encoder algorithm were studied, and the factors effecting on the high-resolution and nonlinearity of TDC circuit implemented in a single FPGA were analyzed.Then, a method to reduce the nonlinearity of TDC circuit was proposed. Focusing on the method, a high-speed latch problem was settled based on the above factors, and a TDC circuit was designed by a low-density FPGA XC2V250. A USB interface was used to transfer the time signal into the digital code to a PC to be calculated and displayed. Finally, a time measurement circuit was designed to measure the delay time of TDC delay cells. Obtained delay time was processed and analyzed,and experimental results indicate that the single plot precision of the TDC circuit is about 80 ps, and the time interval resolution after calibration can reach 40 ps. The differential nonlinearity and integral nonlinearity of TDC circuit are between -0.524LSB and +0.448LSB,-1.598LSB and +1.492LSB,respectively..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2665 (2010)
Frame skipping video transcoding based on adaptation of both encoding quality and error resilience
ZHOU Yi-ran, and CHEN Yao-wu
In order to balance the encoding quality and error-resilience after video transcoding, a frame skipping video transcoding method based on the adaptation of both encoding quality and error resilience was researched. Firstly, a frame skipping transcoding algorithm based on the optimum encoding quality was introduced, in In order to balance the encoding quality and error-resilience after video transcoding, a frame skipping video transcoding method based on the adaptation of both encoding quality and error resilience was researched. Firstly, a frame skipping transcoding algorithm based on the optimum encoding quality was introduced, in which the best frame skipping approach in a sliding window was selected based on a quality impact index.That means the method is to calculate the impacts of different frame skipping approaches on the coding quality and to preserve and encode the frames with larger motion intensities to improve the encoding quality. Following this frame skipping algorithm, the error sensitivity and the error impact index due to the frame skipping were also calculated and evaluated,then a frame skipping method based on the adaptation of both encoding quality and error resilience was presented to implement the dynamic balance between the coding efficiency and the error-resilient capability. Extensive experiments prove that the Peak Signal Noise Ratio(PSNR) of re-decoded video can be improved by 0.05-1.2 dB with the proposed method when the data transmittion is with packet losses. For mobile systems and devices, the proposal can meet the needs of accurate frame rate, good quality, and good error resilience..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2672 (2010)
Neural network control to image scanning system with nonequilibrium load and wide coverage
XU Zheng-ping, LI You-yi, and GE Wen-qi
To extend the imaging coverage of a remote sensing instrument,a dynamic scanning assembly actuated by a cam is proposed based on the existing CCD assembly methods.A motor and a cam were coaxially installed and were rotated at a constant speed. Four pieces of linear TDI CCDs were driven by the cam to reciprocate on the To extend the imaging coverage of a remote sensing instrument,a dynamic scanning assembly actuated by a cam is proposed based on the existing CCD assembly methods.A motor and a cam were coaxially installed and were rotated at a constant speed. Four pieces of linear TDI CCDs were driven by the cam to reciprocate on the focal plane. The imaging areas of the two neighbor piece of CCDs in the scanning direction were overlapped to realize the scanning assembly. The nonequilibrium load feature of the system caused by the special structure of the cam was analyzed in detail. In consideration of that the cam speed would be fluctuated greatly due to the load variation by using the conventional speed control method,a neural network controller combined with the conventional speed control method was put forward. The proposed method was analyzed,and the analysis indicates that the load torque on the cam axis is directly proportional to the camera azimuth and cam speed,respectively. Furthermore, compared with that of conventional speed control method,the speed precision is enhanced by 41% when the neural network controller is used,meanwhile,the speed-fluctuation is reduced by 20%. The whole design could satisfy project requirements..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2680 (2010)
Evaluation of non-invasive detection of blood glucose using OCT
XU Quan-sheng, FENG Shu, and YE Da-tian
To improve the evaluation method of non-invasive detection of blood glucose by Optical Coherence Tomography(OCT), a method combining the relative variance of OCT signal slope with the relative standard error was presented to evaluate the measurement effect and to obtain the theoretical precision of blood glucose detectTo improve the evaluation method of non-invasive detection of blood glucose by Optical Coherence Tomography(OCT), a method combining the relative variance of OCT signal slope with the relative standard error was presented to evaluate the measurement effect and to obtain the theoretical precision of blood glucose detection. Firstly, the effect of the OCT confocal function on the blood glucose detection and the computing method of the relative error of OCT signal slope were given. Then, the relative variance and standard error of the OCT signal slope via a vivo experiment on 3 New Zealand rabbits were carried out to evaluate the non-invasive detection of blood glucose. Obtained results indicate that the relative variance and standard error of OCT signal slope are (3.7 %)/mmol & 0.068,(3.4 %)/mmol & 0.026,(0.93 %)/mmol & 0.019, respectively,and the theoretical measuring precision of blood glucose detection are ±3.7 mmol,±1.5 mmol and ±4.1 mmol,respectively. It concludes that the the evaluation method of combining the relative variance and standard error of OCT signal slope can greatly improve the theoretical measuring precision of blood glucose detection,and the larger the fitting interval is,the higher the measuring precision is..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2688 (2010)
Detection of pulmonary CT scanned images based on fast 3D PCA
WANG Qing-zhu, WANG Ke, LI Yong, WANG Xin-zhu, and WANG Bin
To solve the problem that the current Computer Aided Diagnosis(CAD) based 2D schemes only processes the formation for each scanned image itself and ignors the relation between the images, moreover, to reduce the computational complexity of high-order technology in an actual project, a more effective algorithm to detectTo solve the problem that the current Computer Aided Diagnosis(CAD) based 2D schemes only processes the formation for each scanned image itself and ignors the relation between the images, moreover, to reduce the computational complexity of high-order technology in an actual project, a more effective algorithm to detect pulmonary lesions in CT scanned images based on the fast Three Dimension Principle Component Analysis (3DPCA) was presented. Firstly, the Higher-Order Singular Value Decomposition (HOSVD) was introduced to design the 3D PCA. Then, by choosing the feature points as the seed points, the region grow was used to obtain the whole suspected lesion. Finally, a fast decomposition algorithm was presented according to the feature of CT scanned images. The technique was tested against more than 500 CT images form 10 typical cases of Jilin Tumor Hospital. The results confirm the validity of technique as well as enhanced performance. Comparing with other algorithms, the ratio of detection is improved by 10%-21%, and the computation is reduced to 1/3 of the original algorithm. Obtained data show that the fast 3D PCA could excavate more information exiting in the successive CT images. Moreover, improved high order technology can be more effectively applied in actual projects..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2695 (2010)
Calculation of spatial relative position between catheter and vessel centerline in coronary artery
WANG Ling, CHEN Xiao-dong, and YU Dao-yin
The calculation of spatial relative position between the catheter and the vessel centerline was investigated,which is a key in the fusion of the single-plane coronary angiograms and the intravascular ultrasound images for segments of coronary arteries. Firstly, the parameters of geometric transformation matrix were optThe calculation of spatial relative position between the catheter and the vessel centerline was investigated,which is a key in the fusion of the single-plane coronary angiograms and the intravascular ultrasound images for segments of coronary arteries. Firstly, the parameters of geometric transformation matrix were optimized by constructing six pairs of matched points and energy functions. Then, the function relationship among the matched points was figured out based on the method of optimal vertical plane, and the measurement method and error analysis method of the lengths and angles for the spatial relative position between the catheter and the vessel centerline were given. Finally,the relative positions were calculated through the single-plane coronary angiograms. The experimental results indicate that the average error and the standard deviation of reconstruction have reduced to 2.284 3 mm and 2.483 1 mm, the average errors of the length and angle between the catheter and the vessel centerline to 0.498 0 mm and 6.029 9°,and the standard deviation to 0.574 7 mm and 7.861 9°, respectively.It concludes that the calculation of spatial relative position can improve the accuracy of image fusion and can provide an assistance for doctors in the clinical diagnosis of coronary disease and the interventional treatment..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2702 (2010)
[in Chinese]
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 12, 2710 (2010)
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