Journals >Optics and Precision Engineering
Contents
2013
Volume: 21 Issue 3
37 Article(s)
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Research Article
Rapid measurement of spatial azimuth by using polarized light
LU Wei-guo, WU Yi-ming, GAO Li-min, XIAO Mao-sen, and WANG Hai-xia
To measure the spatial azimuths of different instruments in the upper and lower planes rapidly, an angle-measuring system based on magneto-optical modulation and a polarization splitter was proposed. An angle-measuring model of the system was deduced by describing the Jones vector of polarized light, and the influence To measure the spatial azimuths of different instruments in the upper and lower planes rapidly, an angle-measuring system based on magneto-optical modulation and a polarization splitter was proposed. An angle-measuring model of the system was deduced by describing the Jones vector of polarized light, and the influence of light source fluctuation on the angle-measuring precision was eliminated through signal processing method of “difference divided by addition”. Then, the relationships between the transmittance and the incidence angle, azimuth for the two pathways of optical signals from the Wollaston prism were analyzed, as well as their effects on the measurement results. Furthermore, the dependence of gain differences from optical signal attenuations, device drifts, and circuit performance of opto-electronic elements in two optical paths on the measurement precision were discussed. Finally, a magneto-optical modulation method was proposed to eliminate the difference of transmittances and gain coefficients of the two signals for the achievement of high-precision measurement. The experimental observation demonstrates that the measurement time is 15 s and angle-measuring accuracy is better than 5" within +8～-8°. These results show that the proposed method has some advantages on the fast angular measurement velocity, high precision, and so on..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 539 (2013)
Laser scattering of rough surfaces generated by superposition of periodic and random processes
WU Yao-jun, WANG Qun-shu, YE Xi-sheng, TANG Chuan-xiang... and WU Li-xiong|Show fewer author(s)
The characteristics of laser scattering of rough surfaces composed of periodical and random components generated by mechanical machining were researched. Based on the Helmholtz-Kirchhoff integration theorem and some statistic theories, the formula for calculating the scattering field distribution in the space of rough The characteristics of laser scattering of rough surfaces composed of periodical and random components generated by mechanical machining were researched. Based on the Helmholtz-Kirchhoff integration theorem and some statistic theories, the formula for calculating the scattering field distribution in the space of rough surfaces was derived. According to the derived formula, the scattering coefficients of rough surfaces with different amplitudes of the periodic component and different roughnesses of the random component were obtained. Meanwhile, the spatial distribution characteristics of the scattering field and its formation were analyzed. The experiments show when the roughness of random component is far less than the laser wavelength, the number of the diffraction fringes augment with the increase of the amplitude of the periodic component. While the roughness of random component is comparable with the magnitude of the laser wavelength, the amplitude of the periodic component has a little effect on the scattering field distribution within the range of laser wavelength and the diffraction fringes are disappear. In this circumstance, the scattering field distribution in the space is considered to be modulated by changing the amplitude of the periodic component..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 546 (2013)
Improvement on nonuniformity for sphere mirrors with large radius of curvature
BAI Man-she, LI Pan, ZHANG Jin-kuan, and TENG Lin
On the basis of continuous polishing, a new polishing process was developed to meet the special requirements of ring lasers, synchrotron radiation accelerators and optical oscillators for the sphere mirrors with a large radius of curvature. Based on the Preston hypothesis, a mathematical model of material removal was eOn the basis of continuous polishing, a new polishing process was developed to meet the special requirements of ring lasers, synchrotron radiation accelerators and optical oscillators for the sphere mirrors with a large radius of curvature. Based on the Preston hypothesis, a mathematical model of material removal was established by analysis on the relative velocity at the radial point of an optical sphere surface in the classic polishing process. Via computer simulation, it explored that the reasons of the nonuniformity in sphere mirrors were that the mirrors cannot stay in the polishing pan during the polishing process and the rotation rate of the polishing pan is asynchronous with the mirrors. Two improvements were enlarging the size of the polishing pan and synchronizing the mirror rotation with the polishing pan. With the proposed process, a spherical mirror with the radius of 6 000 mm was polished. Obtained results show that the nonuniformity ΔR/R in a sphere is less than 0.02, the roughness is less than 0.25 nm and the surface defect reaches a zero grade..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 554 (2013)
Design of compact integral structure of two-mirror system
YU Lin-yao, WEI Qun, ZHANG Xin, ZHANG Tian-yi, and JIA Hong-guang
A compact integer structure with two mirrors was presented to solve the problems that the R-C reflect IR system is difficult to be installed into a seeker and the second mirror support is not stable in missile flight. The primary and secondary mirrors were integrated the both surfaces of a lens. Then, the front and reaA compact integer structure with two mirrors was presented to solve the problems that the R-C reflect IR system is difficult to be installed into a seeker and the second mirror support is not stable in missile flight. The primary and secondary mirrors were integrated the both surfaces of a lens. Then, the front and rear surfaces of lens were machined and the inner reflect films were coated on two surfaces. The two mirrors were assembled in one lens to allow the installation of the two mirrors to be easier and the structure of the second mirror to be more stable. A compact relay imaging optical system for middle infrared was designed. It has good imaging capability and its Modulation Transfer Function(MTF) for all field of view is more than 0.6(very close to the diffraction limitation). The optics system can implement the athermal between -40~60 ℃ by a Diffractive Optical Element(DOE). Finally, a Ment-Karol simulation was performed to analyze the tolerance and some ways to resist the stray light of this system was given. The design satisfies the need of machining and application..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 561 (2013)
In-lab calibration of space-borne differential optical absorption spectrometer
ZHAO Min-jie, SI Fu-qi, JIANG Yu, ZHOU Hai-jin... and LIU Wen-qing|Show fewer author(s)
A space-borne differential optical absorption spectrometer was designed on the basis of a four channel Offer imaging spectrometer with a convex grating. It could acquire high accuracy radiation scattered by earth surfaces or air in a nadir push-broom mode, and could quantitatively obtain the trace gas distribution baseA space-borne differential optical absorption spectrometer was designed on the basis of a four channel Offer imaging spectrometer with a convex grating. It could acquire high accuracy radiation scattered by earth surfaces or air in a nadir push-broom mode, and could quantitatively obtain the trace gas distribution based on the “fingerprint” absorption of the trace gas at different spectral information and the differential optical absorption spectrum algorithm. According to the characteristics of large field, wide wavelength range, high spatial and spectral resolution of the spectrometer, the corresponding methods of spectral calibration and radiometric calibration were presented, and a calibration system was built. Then the spectral and radiometric calibrations of the spectrometer were realized, and the calibration uncertainty was analyzed. Experimental results show that spectral calibration uncertainty of the instrument is 0.027 nm and the radiation uncertainty is 2.96%. The calibration accuracy meets the given requirements and can provide a foundation for quantitatively inversion of the instrument..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 567 (2013)
Measurement of chroma of LED displays with color CCD camera
ZHAO Zi-quan, WANG Rui-guang, ZHENG Xi-feng, and Wang Yang
A method by combination of a colorimeter and a color CCD to measure the brightness and chroma of color pixels of a Light Emitting Diode(LED) was proposed. Firstly, the color pixels of the LED were processed by the CCD camera and the brightness and chroma values of the LED pixels in RGB color space were calculated by imA method by combination of a colorimeter and a color CCD to measure the brightness and chroma of color pixels of a Light Emitting Diode(LED) was proposed. Firstly, the color pixels of the LED were processed by the CCD camera and the brightness and chroma values of the LED pixels in RGB color space were calculated by image processing. Then, the multi-channel and adaptive matrix between RGB color space and CIE1931XYZ color space were established and the measured data of a few LED pixels were obtained by the colorimeter. With the RGB values and the measured data, the adaptive matrix could be calculated. Finally, the tristimulus values of the LEDs were calculated with the adaptive matrix. Experimental results indicate that the color difference between calculated data and measured data is less than 1 in an appropriate size of adaptive matrix, which can obtain the brightness and chroma of color pixels of the LED rapidly and precisely, and can correct the brightness and chroma of the LED screen. The method can be used to measure hundreds of thousands of LEDs accurately in a short time..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 575 (2013)
Pulse-duration compression of ultra-short laser pulse by cascaded second-order nonlinearity
YE Rong, ZENG Shu-guang, ZHANG Bin, and LI Ke-yu
The pulse-duration compression principle of a ultra-short laser pulse by cascaded second-order nonlinearity from a single β-barium borate (BBO) crystal was studied theoretically and experimentally. By using the split-step Fourier transformation and fourth-order Runge-Kutta methods, the type I coupled wave equations desThe pulse-duration compression principle of a ultra-short laser pulse by cascaded second-order nonlinearity from a single β-barium borate (BBO) crystal was studied theoretically and experimentally. By using the split-step Fourier transformation and fourth-order Runge-Kutta methods, the type I coupled wave equations describing for Second Harmonic Generation (SHG) process of femtosecond pulse were simulated and calculated. The influences of the phase mismatch between fundamental harmonic(FH) and second harmonic(SH) pulses, the length of nonlinear crystal, peak intensity and the initial pulse-duration of the FH pulse on the pulse-duration compression were analyzed quantitatively and the experimental parameters were also optimized. Furthermore, the experiment of the pulse-width compression was performed for the ultra-short laser pulse with a center wavelength of 800 nm and a pulse width of 140 fs, and the pulse-width compression of more than two times was achieved. Finally, the experimental and simulation results for different fundamental peak intensities and initial pulse-widths were compared. Obtained results show that some factors like the phase mismatch between fundamental harmonic(FH) and second harmonic(SH) pulses, peak intensity, pulse chirp and the initial pulse-duration of the FH pulse have much influence on the pulse compression, so these facts mentioned above should be taken into consideration..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 583 (2013)
Design and epitaxial growth of quantum-well for 852 nm laser diode
XU Hua-wei, NING Yong-qiang, ZENG Yu-gang, ZHANG Xing, and QIN Li
An InAlGaAs/AlGaAs strained quantum-well laser with high temperature stability was designed and grown to overcome the emission wavelength shift occurred in high temperature for a 852 nm laser diode. Based on a comprehensive model, the gains and wavelengths versus the operation temperatures of InAlGaAs, InGaAsP, InGaAs An InAlGaAs/AlGaAs strained quantum-well laser with high temperature stability was designed and grown to overcome the emission wavelength shift occurred in high temperature for a 852 nm laser diode. Based on a comprehensive model, the gains and wavelengths versus the operation temperatures of InAlGaAs, InGaAsP, InGaAs and GaAs quantum-wells were calculated and compared. The results indicate that In0.15Al0.11Ga0.74As quantum-well is the most appropriate candidate for the quantum well of the 852 nm laser diode with the higher gain and better temperature stability simultaneously. Then, Metal-organic Chemical Vapor Deposition(MOCVD) was used to grow compressive-strained In0.15Al0.11Ga0.74As/Al0.3Ga0.7As active region and Reflectance Anisotropy Spectroscopy (RAS) and Photoluminescence Measurements (PL) were applied to the evaluation of crystalline quality for InAlGaAs/AlGaAs interfaces. It is proved that the indium segregation effect can be effectively suppressed by lowering the growth temperature and using the interruption time between InAlGaAs quantum-well and AlGaAs barriers, and an abrupt interface and good crystalline quality for InAlGaAs/AlGaAs quantum-well can be obtained. Finally, an InAlGaAs/AlGaAs strained quantum-well laser was grown with optimized growth conditions. Experimental results indicate that the laser has a Full Width Half Maximum (FWHM) of 1.1 nm, the slope efficiency of 64 W/A and the wavelength shift with temperature of 0.256 nm/K. The theoretical calculation results are in good agreement with experimental results, which verifies that the laser meets the work requirements at a high temperature..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 590 (2013)
Control of multiple filamentation induced by ultrafast laser pulses
GAO Hui, ZHAO Jia-yu, and LIU Wei-wei
The filamentation phenomena come from the propagation of intense ultrafast laser pulses in transparent optical media is explored. It shows that the irregular distribution of filaments will reduce the quality of laser beams, effect on its energy distribution and constitute a serious drawback in practical applications. TThe filamentation phenomena come from the propagation of intense ultrafast laser pulses in transparent optical media is explored. It shows that the irregular distribution of filaments will reduce the quality of laser beams, effect on its energy distribution and constitute a serious drawback in practical applications. Therefore, this paper studies how to control the multiple filaments come from higher power laser propagation in optical media and analyzes and compares these control methods. It points out that the amplitude modulation and phase modulation are the main methods to control the multiple filamentation currently, which can decrease or eliminate the intensity perturbance and refractive index perturbance of transmission media, and avoids the interrelation between the multiple filamentations and their energy competition so that the multiple filamentations can be arranged in a preconceived form. It summarized that the existing problems for multiple filamentation control are how to control the length and spacing of the filamentation precisely..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 598 (2013)
Wavelength calibration of absolute irradiance spectra-radiometer
LIU En-chao, ZHENG Xiao-bing, LI Xin, and ZHANG Yan-na
To improve the wavelength calibration accuracy of a solar absolute irradiance spectra-radiometer, a wavelength calibration scheme that a linear CCD was used as position sensor to control the wavelength was presented. The wavelength calibration was implemented from 0.4 μm to 1.0 μm. Based on the install configuration ofTo improve the wavelength calibration accuracy of a solar absolute irradiance spectra-radiometer, a wavelength calibration scheme that a linear CCD was used as position sensor to control the wavelength was presented. The wavelength calibration was implemented from 0.4 μm to 1.0 μm. Based on the install configuration of the instrument and the parameters of Fèry prism, the relationship between wavelength and CCD pixels was described and the calibration and calculation methods were depicted in detail. The selection of devices, the designs of a clock driver and an output signal processor for CCD were introduced. For wavelength calibration in a lab, a tunable laser was used as source, and the relationship between CCD pixels and center wavelength was confirmed and verified by spectral scanning. Furthermore, the outdoor measurement was developed and the results were compared with that of a visible-short wave infrared spectrometer. Experimental results indicate that the precision of wavelength orientation is better than 0.5 nm, and the absorbing peak of spectral curve measured is accord with the absorbing spectra of typical atmosphere exactly. The feasibility of spectral scanning scheme and the reasonability of electronic design of CCD were demonstrated finally..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 608 (2013)
Nondestructive measurement of refractive index of capillary in non-paraxial conditions
LI Qiang, YANG Rui-fen, ZHAI Ying, and PU Xiao-yun
A new method to calculate the refractive index of a capillary wall simply and accurately was proposed to reduce the effects of the spherical aberration and the depth of field on measurement results under a non-paraxial condition. Firstly, two kinds of standard liquids with known refractive indexes were filled into a caA new method to calculate the refractive index of a capillary wall simply and accurately was proposed to reduce the effects of the spherical aberration and the depth of field on measurement results under a non-paraxial condition. Firstly, two kinds of standard liquids with known refractive indexes were filled into a capillary, respectively, and the distance between two focal positions were measured when the collimated light passed through the capillary. Then, by using the formula of the refractive index of capillary wall and the focal length, the refractive index of the wall-material could be obtained. The experimental results indicate that the measurement accuracy of refractive index is better than 0.003 when the refractive index of wall-material is less than 1.51 in the proper inner and outer diameters of a capillary. It is demonstrated when two kinds of low (high) refractive index liquids are chosen as standard liquids, the measurement accuracy can be improved. The introduced method has a simpler calculation process and its measurement precision of refractive index meets the requirements of general scientific research..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 616 (2013)
Measurement of transmittance for highly transparent liquid
WANG Jian, WEI Jian-ping, YANG Bo, GAO Zhi-yang, and YANG Xue-feng
This paper analyzes the reasons that the mistaken transmittance results are prone to occur in a highly transparent liquid measurement by employing a visible spectrophotometer in traditional methods. On the basis of the analysis results, two kinds of simple ways for measuring the transmittance of highly transparent liquThis paper analyzes the reasons that the mistaken transmittance results are prone to occur in a highly transparent liquid measurement by employing a visible spectrophotometer in traditional methods. On the basis of the analysis results, two kinds of simple ways for measuring the transmittance of highly transparent liquid are proposed.One way is to fit both kinds of transparent faces of a colorimetric ware closely together, in which the film is formed with the pending liquid to be tested. This structure is known as the “liquid film reference cell”. The other way is to fit the pending liquid into a 1 cm length colorimetric ware as the reference cell, and fill the pending liquid into a 2 cm length colorimetric ware as the sample cell. With the two methods, several kinds of common liquids are measured and almost identical results are obtained. Measurements show that the transmittances of measured liquids such as alcohol, water are all in 98%~100% at the visible light range. These ways eliminate the mistaken transmittance results and provide effective methods for the measurement of transparent liquid..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 624 (2013)
Focusing range of space off-axial TMA optical camera
LIU Lei
To improve the adaptive capacity of a space camera to environment temperatures and to enhance its imaging quality, this paper explores how to implement the thermal control by relaxing thermal control indictors. A mathematical formula of intercept and defocus affected by temperatures is derived for a pure off-axis ThreeTo improve the adaptive capacity of a space camera to environment temperatures and to enhance its imaging quality, this paper explores how to implement the thermal control by relaxing thermal control indictors. A mathematical formula of intercept and defocus affected by temperatures is derived for a pure off-axis Three Mirror Anastigmatism(TMA) optical system. The analysis shows that camera defocus amount and temperature are a linear relationship. Then, a constant K value is calculated. Furthermore, it indicates when reflector and camera structures have the same coefficient of linear expansion, the defocus does not occur. However, the greater the difference between two material linear expansion coefficients is, the greater the amount of defocus is. With defocusing formula, it suggests that mechanical focusing methods must be used to request for compensation when the camera temperature level changes more than ± 1 ℃(corresponding to the defocus amount of 0.05 mm). Using integrated photo-thermal simulation method , the temperature range Δt is obtained to ensure the image quality of the camera. Finally, camera′s focus range is derived by using the formula of defocus. The result of defocus test under thermal vacuum environment verifies the correctness of the defocus formula and the defocus amount of ± 0.184 mm is a proper focus range corresponding camera temperature levels changed in ± 4 ℃..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 631 (2013)
Design of outer baffle of earth observation optical system on geostationary orbit
QIAN Jing, DOGN De-ping, and SUN Sheng-li
The affects of direct sunlights before and after midnights on the imaging quality and thermal stability of an earth observation optical system on geostationary satellite in space were investigated. According to the characteristics of solar heat flux on the geostationary orbit, the energy density of direct sunlight projThe affects of direct sunlights before and after midnights on the imaging quality and thermal stability of an earth observation optical system on geostationary satellite in space were investigated. According to the characteristics of solar heat flux on the geostationary orbit, the energy density of direct sunlight projecting to the optical system was analyzed and a dimensionless parameter named sunlight inhibitory ratio determined by outer baffle′s height ,shape dimension and sun inclination was deduced. It was used to describe the inhibitory ability of outer baffle in the optical system for the direct sunlight and also used as a design principle for the height of outer baffle. The program based on Monte-Carlo method was compiled to solve the sunlight inhibitory ratio of different shape outer baffles in different sun inclination scenarios. In a real design, the sunlight inhibitory ratio was selected to be 0.5 at equinox and the final outer baffle height is about 1.8 times of the east-west axis length of the outer baffle’s bottom side. This way, the incidence sunlight in the optical system from the baffle is three hours. The result satisfies the dimension requirements of satellite payloads..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 637 (2013)
Laser differential cofocal sensor for ICF capsule measurement
GUO Jun-jie, QIU Li-rong, WANG Yun, MENG Jie, and GAO Dang-zhong
As Atomic Force Microscope can only measure the outside surface of a capsule in the Inertial Confinement fusion (ICF) , a high precision, non-contact, miniaturized Laser Differential Confocal Sensor (LDCS) is developed. Based on the differential confocal principle, the sensor positions respectively the test points on tAs Atomic Force Microscope can only measure the outside surface of a capsule in the Inertial Confinement fusion (ICF) , a high precision, non-contact, miniaturized Laser Differential Confocal Sensor (LDCS) is developed. Based on the differential confocal principle, the sensor positions respectively the test points on the outer surface, inner surface and spherical center of the ICF capsule in sequence by the absolute zero point of a laser differential axial intensity curve. Then it implements the high-precision measurement of the ICF capsule by combing with the high precision displacement sensor. This method reduces the influences of the surface reflectivity and tilt of the capsule and other factors on pointing characteristics and improves the anti-interference ability. Combining the traditional microscopic imaging and differential confocal optical path organically, the precision pointing is achieved. Theoretical analysis and preliminary experiments indicate that the axial resolution of LDCS is better than 5 nm, the standard deviation of absolute zero is 10 nm and the signal to noise ratio is better than 1160 when the Numerical Aperture(NA) is 0.65. The sensor provides a new way for measuring capsules in the ICFs..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 644 (2013)
Absolute interferometric testing of mid-spatial frequency wavefront by rotation and displacement technique
YUAN Qun, GAO Zhi-shan, ZHANG Cong-yang, CHENG Jin-long, and ZHU Bo
Traditional absolute interferometric testing methods are all based on Zernike’s polynomial fitting of tested wavefront, where the wavefront is smoothed and the mid-frequency element is lost, so they can only get the real figure of test optics. This paper adopts the rotation and displacement technique to the absolute inTraditional absolute interferometric testing methods are all based on Zernike’s polynomial fitting of tested wavefront, where the wavefront is smoothed and the mid-frequency element is lost, so they can only get the real figure of test optics. This paper adopts the rotation and displacement technique to the absolute interferometric testing of mid-frequency wavefront. The real wavefront of the test optic is separated into a rotationally symmetric component and a rotationally asymmetric component. The rotationally asymmetric component is determined by rotating the test optics for N times, while the rotationally symmetric component is determined by the pseudo shearing data through displacing the test optics. As compared with traditional absolute interferometric testing methods, there is no need to fit the wavefront of test optics with Zernike′s polynomials and can preserve whole wavefront with the proposed method. Because the rotationally symmetric component is retrieved using the even polynomials, the computation speed is enhanced and the fitting error is reduced with the mid-frequency element retained. The numerical simulation shows that the proposed method has much superiority than the traditional method and can achieve the nanometer accuracy. An experimental measurement for a flat surface is carried on with a ZYGO interferometer. The self-comparison of the experimental data is implemented by changing the pseudo shearing ratio and substituting the standard lens and the experimental data is also compared with the horizontal and vertical profiles derived from three-flat testing. Obtained results prove the accuracy of the rotation and displacement technique..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 652 (2013)
Nano-CMM stage with zero Abbe error and its error analysis
HUANG Qiang-xian, YU Fu-ling, GONG Er-min, WANG Chen-chen, and FEI Ye-tai
A new type nanometer Coordinate Measuring Machine(CMM) stage which meets the Abbe principle in three-dimensional directions is proposed to avoid the Abbe error in conventional CMMs and reduce the guide motion error that influences on the nano-CMM measurement uncertainty. The stage can move in three dimensional directioA new type nanometer Coordinate Measuring Machine(CMM) stage which meets the Abbe principle in three-dimensional directions is proposed to avoid the Abbe error in conventional CMMs and reduce the guide motion error that influences on the nano-CMM measurement uncertainty. The stage can move in three dimensional directions and its x guide and y guide are in a coplanar structure. The three measuring lines of the stage are orthogonal and intersect at one point which coincides with the center of a probe. Moreover, the measuring lines of x measurement system and y measurement system are coplanar with the plane of the xy stage. According to the characteristics of this stage, the impacts of various errors on the stage are analyzed, the main source errors to the measurement uncertainty are given and new correction methods for those errors are proposed. Finally, two pieces of first gauge block are measured on the developed stage. Measurement results show that the standard deviation of flatness error of first gauge block working surface is 11 nm, and that of step height is about 21 nm and the difference between the average of step heights and the calibrated value is about 1 nm. The theoretical analysis and experiment show that the nano-CMM avoids the impact of various error sources, especially the impact of Abbe error, and can be used in high-precision three-dimensional measurement..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 664 (2013)
Optimization and validation of differential interferometric surface plasmon resonance sensor
WANG Yi-jia, ZHANG Chong-lei, WANG rong, ZHU Si-wei, and YUAN Xiao-cong
The sensitivity and dynamic range are main performance parameters of a Surface Plasmon Resonance(SPR) biosensor with phase modulation. In this paper, the main effect factors on sensitivity and dynamic range of the sensor were analyzed, and the influence of nonlinear change of phase difference on the results of real-timThe sensitivity and dynamic range are main performance parameters of a Surface Plasmon Resonance(SPR) biosensor with phase modulation. In this paper, the main effect factors on sensitivity and dynamic range of the sensor were analyzed, and the influence of nonlinear change of phase difference on the results of real-time monitoring biological reaction was analyzed. A high resolution SPR system based on a Mach-Zehnder configuration was set up. The phase difference curves of a series gold membrane thicknesses and incident angles were simulated by matlab software, and the effect of several factors on the resolution and dynamic range were evaluated. In addition, the real-time monitoring of binding reaction between Bovine Serum Albumin(BSA) and BSA antibodies was also demonstrated. Obtainecl results show that the influence of membrane thickness is significant and nonlinear, but the incident angle shows little effect on the resolution and dynamic range. The influence of narrow dynamic range on biology reaction measurement can be minimized by optimizing some parameters, such as membrane thickness, incident angle and reactants concentration. Experimental results show that the sensitivity and dynamic range can be optimized by adjusting gold membrane thicknesses. This paper analyzed several influence factors of the sensitivity and dynamic range of phase modulation SPR biosensors. For a light source with 633 nm wavelength, the most optimal membrane thickness is 48 nm when the reaction between BSA and its antibody is measured. In this situation, the dynamic range is 0.013 6RIU and the sensitivity is 6.67×10-7RIU/0.01°..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 672 (2013)
Prediction of grinding induced subsurface damage of optical materials
L Dong-xi, WANG Hong-xiang, and HUANG Yan-hua
On the basis of indentation fracture mechanics, a theoretical model was developed to evaluate the relationship between surface roughnesses (SRs) and Subsurface Damage Depths (SSDs) of brittle optical materials and to predict their grinding induced SSDs. For validating the feasibility of this method, the SSDs generated On the basis of indentation fracture mechanics, a theoretical model was developed to evaluate the relationship between surface roughnesses (SRs) and Subsurface Damage Depths (SSDs) of brittle optical materials and to predict their grinding induced SSDs. For validating the feasibility of this method, the SSDs generated with various process parameters were measured by Magnetorheological Finishing (MRF) wedge technique. The influences of processing parameters on the SRs and SSDs were investigated, and a process strategy was also proposed to improve the material removal rate. The prediction results of this theoretical model show that the SSDs are nonlinear monotone increasing with the square of SR values during grinding processes. The SSDs and SRs increase with the increasing of cutting depth and feed rate, while reduce with the increasing of spindle speed. The measurement results of SSDs are consistent with the prediction values of the model, which demonstrates the feasibility of utilizing this model to accurately and non-destructively predict the SSDs..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 680 (2013)
Design of low power telemetry capsules for physiological parameters of entire digestive tract
LU Li, YAN Guo-zheng, WANG Zhi-wu, JIANG Ping-ping, and ZHAO Kai
A low power consumption telemetry capsule was designed for monitoring the gastrointestinal tract’s parameters in long-term and continuation. The capsule consisted of a sensor module, a low power consumption special integrated chip and a wireless emission module mainly. First, to reduce the integrated chip power consumpA low power consumption telemetry capsule was designed for monitoring the gastrointestinal tract’s parameters in long-term and continuation. The capsule consisted of a sensor module, a low power consumption special integrated chip and a wireless emission module mainly. First, to reduce the integrated chip power consumption, a three-state clock management unit was used to choose the appropriate clock frequency for the internal modules of the integrated chip and to shut down the clocks of correcting idle modules. Then, the simplex communication, data temporary storage, reducing transmitting power, etc, were used to reduce the power consumption of the RF module. Finally, the capsule was controlled at work intermittently by the software to reduce the system overall power consumption. Test results show that the work current of the special integrated chip is about 300 μ A @ 2 MH and its dormancy current is about 4 μ A @ 28 kHz. Furthermore, the emission current from the RF module is about 12 mA, and the current of collecting data by a microcontroller is about 300 μ A. As compared with the second generation parameter capsule, the power consumptions of the RF module and the microcontroller are reduced by about 47% and 24% , respectively, and the work time is about 136 h continuously, which basically meets the demands of the capsules for monitoring the gastrointestinal tract’s parameters in long-term and continuation..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 687 (2013)
Design and fabrication of transverse electromagnetic vibration energy harvester
LI Wei, CHE Lu-feng, and WANG Yue-lin
A transverse electromagnetic vibration energy harvester based on Micro-electro-mechanical System(MEMS) was designed to convert the vibration mechanical energy around our environments to electrical powers. It mainly consisted of two vertically polarized rectangle permanent magnets, a mass-spring vibration system with a A transverse electromagnetic vibration energy harvester based on Micro-electro-mechanical System(MEMS) was designed to convert the vibration mechanical energy around our environments to electrical powers. It mainly consisted of two vertically polarized rectangle permanent magnets, a mass-spring vibration system with a copper coil and a substrate. The structure parameters of system were analyzed and optimized by Finite Element Analysis (FEA), and a harvester prototype was fabricated. During the fabrication of the harvester, electroplating technology was employed to fabricate a spiral copper coil, KOH wet etching and Deep Reaction Ion Etching(DRIE) technology were employed to fabricate mass-spring vibration system, then the harvester prototype was formed together with permanent magnets. The volume of the harvester was about 100 mm3. The test results for vibration characteristics show that the natural frequency of the mass-spring vibration system is 241 Hz. The electromagnetic vibration energy harvester can generate a peak-peak voltage of 9.2 mV at an external acceleration of 2.8 ms-2 and frequency of 241 Hz. Furthermore, by adjusting the parameters of mass-spring vibration system, the harvester with different natural frequencies can obtained. The havester can convert the mechanical energy to the electrical energy and have significance for the clevelopment and application of the wireless sensor devices..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 694 (2013)
General layout and structure design of ICF facility
ZHU Ming-zhi, WANG Mei-cong, CHEN Xiao-juan, WU Wen-kai, and CHEN Gang
By taking the National Ignition Facility (NIF) from the USA and the Laser Mégajoule (LMJ) from the France for examples, this paper analyzes the general layout and general structure engineering features of Inertial Confinement Fusion (ICF) laser facility. NIF is designed with a U-shaped building layout, and it not By taking the National Ignition Facility (NIF) from the USA and the Laser Mégajoule (LMJ) from the France for examples, this paper analyzes the general layout and general structure engineering features of Inertial Confinement Fusion (ICF) laser facility. NIF is designed with a U-shaped building layout, and it not only can provide an optimum laser experimental equipment configuration but also allow the equipment to attach a second target chamber in future. The bundles of LMJ are arranged in an in-line building. Its layout decreases the optical path-length between the output of each beamline and the focusing system also provides an option for a second target chamber exists. The paper suggests that the general layout of an ICF laser facility should meet the requirements of the physical experimental purposes and should be characterized by operation stability ,good integration and higher maintainability. Furthermore, it should design convenient interfaces for future development. In overall design of the equipment, optical elements are packaged into a optical-mehanical assemblies, and replaceable units (LRUs) are assembled with kinematic mounts. The general structure of ICF design should match the arrangement of the laser beams in structural layout and configuration. Moreover, the structure design can not dispense with the function, stability and cleanliness. The assignments of general structure design should meet the requirements of the installation and localization, integration and debugging, operation and maintenance of the optical components and the physical/optical diagnostic equipment..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 701 (2013)
Design and control of miniature piezoelectric actuator based on strain gauge sensor
WANG Geng, GUAN Chun-lin, ZHANG Xiao-jun, ZHOU Hong, and RAO Chang-hui
A kind of miniature precise piezoelectric actuator with strain gauges is designed. The actuator uses a displacement-amplified mechanism to amplify the small strain and measure the output change of the wheat-stone bridge composed of strain gauges to obtain the displacement output indirectly. The experiments show that thA kind of miniature precise piezoelectric actuator with strain gauges is designed. The actuator uses a displacement-amplified mechanism to amplify the small strain and measure the output change of the wheat-stone bridge composed of strain gauges to obtain the displacement output indirectly. The experiments show that the accuracy of the actuator is 80 nm. Due to the complex hysteresis characteristics, it is very difficult to control this actuator. However, PID control algorithm is suitable for control of this actuator effectively in the closed loop. A position test and a tracking test at the quasi-static condition are performed to verify the performance of the actuator. Experimental results show that the control performance of the PID control algorithm is good for this actuator. It has effective positioning performance, the positioning error does not exceed 0.059 μm; the maximum tracking errors for single-frequency signal and multi-frequency signal do not exceed 0.085 μm and 0.092 μm, respectively. These results prove the validity of the control algorithm in the quasi-static condition..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 709 (2013)
Workspace of macro/micro actuated parallel mechanism
FENG Hai-bing
The workspace of the 4-HSPS/PRPUR macro/micro actuated parallel mechanism applied to a scanning electron microscope is analyzed. The 4-HSPS/PRPUR macro/micro actuated parallel mechanism is composed of a base and a moving platform connected by four HSPS branches and a middle PRPUR branch. It has three translational degrThe workspace of the 4-HSPS/PRPUR macro/micro actuated parallel mechanism applied to a scanning electron microscope is analyzed. The 4-HSPS/PRPUR macro/micro actuated parallel mechanism is composed of a base and a moving platform connected by four HSPS branches and a middle PRPUR branch. It has three translational degrees of freedom and two rotational degrees of freedom about the X axis and Y axis. Because the macro actuation and micro actuation are integrated together in this mechanism, this paper analyzes the constant orientation workspace and the dexterous workspace of this mechanism. The analysis shows that this mechanism can move flexibly in large workspace and the link length of the middle branch has considerable influence on the shapes of the workspaces. On the analysis of the constant orientation and dexterous workspaces of this mechanism, it demonstrates that the mechanism is suitable for the work condition of smaller platform mount space, large workspace and higher positioning accuracy. This study provides a theoretical basis for the application of the 4-HSPS/PRPUR parallel mechanism..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 717 (2013)
Compressive sensing multiple description image coding with hybrid sampling
WANG Liang-jun, SHI Guang-ming, LI Fu, and SHI Si-qi
A Compressive Sensing(CS) multiple description coding scheme with hybrid sampling was proposed to improve the coding efficiency of the traditional CS coding system and to maintain the ability of resisting packet loss. In the scheme, both 2-D Discrete Cosine Transformation( DCT) matrix and sub-Gaussian matrix were used A Compressive Sensing(CS) multiple description coding scheme with hybrid sampling was proposed to improve the coding efficiency of the traditional CS coding system and to maintain the ability of resisting packet loss. In the scheme, both 2-D Discrete Cosine Transformation( DCT) matrix and sub-Gaussian matrix were used to measure the image signal simultaneously. Then, a Golomb code and its improved version were used to encode for the resulted measurements, respectively. As a result, the 2-D DCT measurement bit streams with complete code words and the Gaussian measurement bit streams with incomplete code words were obtained respectively. In the decoder, these incomplete code words could be decoded successfully with a Maximum A posteriori Probability (MAP) estimator, and the deficient code words could be estimated by the relevance between 2-D DCT and Gaussian measurements. Finally, these decoded measurements were grouped together again to reconstruct the image signal by solving a 1-norm optimization problem. Experimental results on both natural and remote sensing images show that the Peak Signal to Noise Ratio(PSNRs) of the images reconstructed by proposed method can be superior to that of traditional CS coding scheme by 2~4 dB at different packet loss rates, meanwhile, it has a robust resisting packet loss ability..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 724 (2013)
Blurred palmprint recognition under defocus status
LIN Sen, and YUAN Wei-qi
As the defocus status in non-contact signal acquisition for palmprint recognition might blur palmprint and degrade the performance of a recognition system, a novel scheme based on stable features was proposed for the blurred palmprint recognition. Firstly, a mathematical model of defocus degeneration was established. TAs the defocus status in non-contact signal acquisition for palmprint recognition might blur palmprint and degrade the performance of a recognition system, a novel scheme based on stable features was proposed for the blurred palmprint recognition. Firstly, a mathematical model of defocus degeneration was established. Then, the blur mechanism was analyzed in detail and the Laplacian Smoothing Transform (LST) was employed to extract low-frequency coefficients from blurred palmprint as stable features. Furthermore,the Euclidean distance between the feature vectors was used for matching and discriminating. With the experiments, the operation steps of the algorithm were given and the number of low-frequency coefficients were determined. The experiments based on the self-made SUT-D blurred palmprint database were performed. Obtained results show that the proposed algorithm can get Equal Error Rate (EER) of 17.101 7%, which has been maximally reduced by 7.908 4% compared with those from other typical recognition methods, such as traditional Discrete Cosine Transform (DCT), Eigen Palm and the Palm Code. These results show that the proposed scheme not only has higher recognition efficiency but also has a low dimension, so it significantly improves the performance of the blurred palmprint recognition systems..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 734 (2013)
Active assessment of color image quality based on visual perception
CHEN Yong, LI Yuan, L Xia-fu, XIE Zheng-xiang, and FENG Peng
According to the shortages existing in passively color image quality assessment currently, this paper researched the five parameters of color image feature quality perceived by human visual: average contrast, average information entropy, mean brightness(gray level),average level factor, and average bandwidth factor. OnAccording to the shortages existing in passively color image quality assessment currently, this paper researched the five parameters of color image feature quality perceived by human visual: average contrast, average information entropy, mean brightness(gray level),average level factor, and average bandwidth factor. On the basis of research mentioned above, the quality assessment function of color image(CAF) actively based on disturbance transform was constructed. It found that CAF was the functions of disturbance parameters Delta and Theta. Through the transformation of disturbance parameters, the overall quality evaluation function of color image would achieve the maximum value of CAF, so that the single color image quality could be assessed and improved. Several kinds of color images with narrower band, wider band and whole band spectra were assessed, and it demonstrates that the active assessment method of color image quality by considering the average bandwidth factor and average hierarchy factor conforms to the requirement of human visual subjective evaluation, and can allow the color image obtained by disturbance transformation to be more soft and more hierarchical. This method can not only evaluate the quality of single color image , but also can improve the color image quality by disturbance transformation..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 742 (2013)
On-axis tracking based on ELM data fusion
WANG Wei-li, Guo Jin, Cao Li-hua, and CHEN Juan
To realize the on-axis tracking in an electro-optical tracking servo system, a nerve net Extreme Learning Machine (ELM) was adopted to obtain the velocity and acceleration of the target motion through learning, training and fusing data. Through algorithm optimization, the amount of computing is reduced by about 50 percTo realize the on-axis tracking in an electro-optical tracking servo system, a nerve net Extreme Learning Machine (ELM) was adopted to obtain the velocity and acceleration of the target motion through learning, training and fusing data. Through algorithm optimization, the amount of computing is reduced by about 50 percent in the ELM system, and the period of computing is 3.5 ms, so as to meet the real-time of electro-optical tracking system. The fused target information was filtered through the 6 step Butterworth filter. The simulation result verifies that the predicted target velocity error is about ± 3 (°) / s at the peak of velocity when the target velocity is 50 (°) / s and the target acceleration is 30 (°) / s2. Finally, the electro-optical tracking system was used to track an optical dynamic target equipment. When the system is in a double-loop and on-axis control, tracking results show that the maximal system tracking error has decreased from 11.35′to 0.88′, and the random error decreased from 8.2″to 7.6″. As compared with other control methods, the proposed method has better real time performance and higher accuracy, and improves the system tracking precision significantly..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 751 (2013)
Near lossless ROI compression for medical images
JIANG Hui-qin, LI Ping, WANG Zhong-yong, and LIU Yu-min
A near lossless Region of Interest(ROI)compression algorithm based on the shearlet transform was proposed for medical images to improve the Mean Structural SIMilarity(MSSIM) between the original image and the reconstructed image. Firstly, the ROI was designated in a medical image and the rests were regard as the BackgrA near lossless Region of Interest(ROI)compression algorithm based on the shearlet transform was proposed for medical images to improve the Mean Structural SIMilarity(MSSIM) between the original image and the reconstructed image. Firstly, the ROI was designated in a medical image and the rests were regard as the Background (BG). Then, the ROI and BG were transformed into shearlet domains respectively, and the significant coefficients which could approximate the original region accurately were selected to be denoised and compressed. Furthermore, the main coefficients in ROI were coded by lossless Huffman coding and those in BG were quantized and coded by Huffman coding. Finally, the reconstructed image was obtained by Huffman decoding and inverse shearlet transform. Experiment results show that the MSSIM and Peak Signal Noise Ratio (PSNR) between the original ROI and the reconstructed image ROI obtained by the new algorithm have increased by 4 percent and 135 percent respectively as compared to the modified Set Partitioning in Hierarchical Trees (SPIHT) algorithm with the same compression ratio. Moreover, for the whole image, the MSSIM and PSNR have increased by 3 percent and 28 percent, respectively. With configurable ROI’s and BG’s quality, the proposed algorithm is suitable for the medical image compression in the Picture Archiving and Communication System(PACS)..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 759 (2013)
Application of depth from defocusing based on logarithmic power spectrum to multi-spectral imager
ZHANG Yan-chao, SUN Qiang, and ZHAO Jian
According to the characteristics of a multi-spectral imager, an auto-focusing method was proposed based on the depth from defocusing of logarithmic power spectrum. By making use a CCD as the image sensor, the auto-focusing of the multi-spectral imager was quickly implemented by using a host computer for focusing controAccording to the characteristics of a multi-spectral imager, an auto-focusing method was proposed based on the depth from defocusing of logarithmic power spectrum. By making use a CCD as the image sensor, the auto-focusing of the multi-spectral imager was quickly implemented by using a host computer for focusing controlling and data processing. Firstly, the sensor was placed in three equally spaced positions in turn, and it was used to acquire an image in each position. Then, according to the three-point location judgment method, the positional relationship between the second image and accurate focus position was determined. By using the second image as the reference, the related calculation with logarithmic power spectrum of the image was carried out to get the value of accurate focus position. Finally, the sensor was placed to the calculated position, and the auto-focusing process was finished. Experimental results indicate that the standard deviations of the focus position value are ±0.159 9 mm, and the maximum deviation is 0.4 mm or less. The method can meet the real-time auto-focusing requirement better. With the advantages of fast focusing and high accuracy, the auto-focusing process can be realized just by making use of three images..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 767 (2013)
Video coding system based on fractal and H.264
ZHU Shi-ping, and ZHANG Ling
On the basis of the fractal encoding technology with a higher speed, a new H.264 P frame prediction method and a corresponding fast coding system were proposed to decrease the video compression coding time and bit rate . Firstly, the main ideas of intra-/inter-prediction in H.264 and their advantages and disadvantages On the basis of the fractal encoding technology with a higher speed, a new H.264 P frame prediction method and a corresponding fast coding system were proposed to decrease the video compression coding time and bit rate . Firstly, the main ideas of intra-/inter-prediction in H.264 and their advantages and disadvantages in P frame encoding were analyzed. Then, the new video compression method based on the fractal video compression and its characteristics were discussed. Furthermore, by combining the advantages of new standard H.264 with fractal video compression method, the P frame in H.264 was predicted by proposed method. Finally, the fractal coefficients coding and residual coding generated from fractal prediction encoding were given. Experimental results show that the proposed coding system has reduced the bit rate and the encoding time to 65% and 19% respectively comparing to those of the H.264 reference software JM15.1, while the Peak Signal Noise Ratio(PSNR) can be ignored (average reduce 0.09 dB). These results can satisfy the requirements of variable motion video sequences and can improve the overall performance of the H.264 video coding system..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 774 (2013)
Initial calibration of tracking turntable for vehicle-borne opto-electronic tracking system
XU Tao, LI Bo, LIU Ting-xia, XUE Le-tang, and Chen Tao
An initial turntable calibration method based on coordinate transformation was proposed to improve the target tracking precision of a vehicle-borne tracking system. First, according to the coordinate transformation theory, a precise turntable calibration model was established and a transformation matrix for the turntabAn initial turntable calibration method based on coordinate transformation was proposed to improve the target tracking precision of a vehicle-borne tracking system. First, according to the coordinate transformation theory, a precise turntable calibration model was established and a transformation matrix for the turntable calibration was obtained. Then, an approximate calibration approach based on the practical need was derived with reasonable analysis and careful approximation. Finally, a combined calibration method by using both approximate calibration and precise calibration was implemented in the turntable initial calibration process for a practical vehicle-borne opto-electronic tracking system. Experimental results show that the combined calibration method can improve the efficiency of turntable initial calibration. After precise calibration, the tracking error of the turntable is smaller than 0.1° for a remote target larger than 10 km away, which completely satisfies the precision requirements of the vehicle-borne opto-electronic tracking system. This calibration method has been successfully used in several vehicle-borne opto-electronic tracking systems..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 782 (2013)
Line-based matching for high-resolution images with robustness for scale, rotation and illumination
SHAO Zhen-feng, and CHEN Min
A line feature matching method for high-resolution images was proposed to improve the low significant level of a point feature and to overcome the matching shortage between weak texture images. Firstly, the edges of images were extracted and tracked to fit straight-lines. All straight-lines were classified into two groA line feature matching method for high-resolution images was proposed to improve the low significant level of a point feature and to overcome the matching shortage between weak texture images. Firstly, the edges of images were extracted and tracked to fit straight-lines. All straight-lines were classified into two groups: long-lines and short-lines. The long-lines were matched based on the direction relationship primarily. Then, the relationship-descriptors of short-lines were constructed using the angle and the Euclidean distance between the short-line and long correspondences. Finally, short-lines were matched according to the similarity of their relationship-descriptors. The experimental results demonstrate that the proposed line matching algorithm is robust for the scale, rotation and illumination. As all the lines have corresponding linear equations in the same image, the image feature has higher significant level and can avoid the mismatching. The probability of correct matches of the algorithm exceeds 90% and its root mean square error has achieved sub-pixel level. The performance of the proposed algorithm is better than that of the point-based method, especially in weak texture areas..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 790 (2013)
Fast DCT algorithms based on multi-dimensional vector matrix
SANG Ai-jun, WU Yang, CUI Hai-ting, and CHEN He-xin
With the aim to improve the speed and reduce the time of color video stream compression transform, this paper proposed a fast Discrete Cosine Transform (DCT) algorithm based on multi-dimensional vector matrix. The algorithm combined a fast DCT based on multi-dimensional vector orthogonal matrix transform algorithm withWith the aim to improve the speed and reduce the time of color video stream compression transform, this paper proposed a fast Discrete Cosine Transform (DCT) algorithm based on multi-dimensional vector matrix. The algorithm combined a fast DCT based on multi-dimensional vector orthogonal matrix transform algorithm with a existing fast DCT algorithm for the first time. Firstly, it corrected and supplemented the fast 1D-DCT algorithm with strong practicality, and extended two most representative 2D-DCT fast algorithms, the rank decomposition method and the linear combination method, to the multi-dimensional field. Then, two DCT fast algorithms and their butterfly diagrams were deduced by combining multi-dimensional vector matrix theory, and the times of multiplications were analyzed. Finally, two methods were applied to test of the video in the standard video library meanwhile comparative experiments were performed. The experimental results show that the required time of the two methods is both less 0.25 s in DCT and these meet the real-time requirements of video. The proposed two methods ensure the reconstructed video quality, and not only reduce the computation time significantly, but also expand the DCT fast algorithm from a low-dimension to the multi-dimension..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 799 (2013)
Auto-focusing and control of micro-vision system
ZHOU Li-ping, SUN Zhi-jun, and Zhang Quan
The auto-focusing evaluation function and a controller were researched based on an automated microscopy. At first, the Discrete Wavelet Transform (DWT) and Sobel-Tenengrad function were introduced, and a new auto-focusing evaluation function was proposed by combining the DWT with the Sobel-Tenengrad operator. Then, theThe auto-focusing evaluation function and a controller were researched based on an automated microscopy. At first, the Discrete Wavelet Transform (DWT) and Sobel-Tenengrad function were introduced, and a new auto-focusing evaluation function was proposed by combining the DWT with the Sobel-Tenengrad operator. Then, the defocused and focused sample pictures were used to train the Self-organizing Map (SOM) algorithm in a unsupervised method, and the Particle Swarm Optimization (PSO) was used to accelerate the training process. Finally, an auto-focusing experiment was carried out by using the trained SOM controller. The experimental results show that the new auto-focusing function has the characters of single steep peak and strong robustness to different samples and objective lenses. The results also indicate that the SOM based controller only takes 7.6 steps for auto-focusing process on average, and the focusing speed and stability have been greatly improved compared with that using the mountain climbing method. Moreover, it processes or recognizes the input image only for about 120 ms. The proposed method has met the requirements of auto-focusing of micro-vision system, and obtained good results..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 807 (2013)
Effect of system parameters on ranging and pulse width in ocean satellite laser altimeter system
MA Yue, LI Song, ZHOU Hui, and YI Hong
The system parameters such as the centroid and pulse width of a laser altimeter system have great effects on its accuracy in ranging and inversion under the condition of a common sea state. Therefore, this paper deduces the functions referred to influencing factors of centroid and pulse width and corrects the received The system parameters such as the centroid and pulse width of a laser altimeter system have great effects on its accuracy in ranging and inversion under the condition of a common sea state. Therefore, this paper deduces the functions referred to influencing factors of centroid and pulse width and corrects the received photon function of ocean surface according to the theory of Fresnel diffraction, the character of specular reflection, the statistical regularity of ocean surface profile and the error theory of laser altimeter systems. It gives complete influencing factors on the centroid and pulse width, which include the transmitted and received instruments, nadir angles, pointing jitters and wind speeds. Among them, the first three factors are all system parameters, and the wind speed is a surface characteristic. Combined with the parameters of Geoscience Laser Altimeter System)GLAS, the error of range and the accuracy of pulse width are calculated and analyzed. The results show that the ranging error of GLAS is from 2 to 15 cm, and that of the pulse width is from 0.5 to 3.5 ns under different wind speeds. The obtained conclusion is significant for the design and accuracy analysis of ocean laser altimeter systems..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 813 (2013)
Image segmentation based on activity degree with pulse coupled neural networks
ZHENG Xin, and PENG Zhen-ming
As Pulse Coupled Neural Network(PCNN) in image segmentation has to adjust the network parameters by manual operation for several times, this paper proposed a automatic image segmentation method based on the PCNN. The effect factors on setting PCNN parameters in an image were analyzed and an adaptive segment protocol waAs Pulse Coupled Neural Network(PCNN) in image segmentation has to adjust the network parameters by manual operation for several times, this paper proposed a automatic image segmentation method based on the PCNN. The effect factors on setting PCNN parameters in an image were analyzed and an adaptive segment protocol was invited to divide the images into several sub-pieces with the similar inside complexities. By which, the weakness that the same parameter could not segment exactly the region with quite different complexities in an image at the same time was overcome. Furthermore, the index of Activity Degree of Local Area(ADLA) proposed by the paper was used to determine the PCNN model parameters for different sub-pieces adaptively and to avoid the manual operation for important parameter selection in the traditional PCNN image segmentation. Finally, the best result was chosen from the binary-result sequences with the max two-dimension Tallis entropy protocol. The experiments proved that segmented figure is clear, complete and has excellent performance, even in conditions of a low contrast or a changeable background. Compared with the traditional PCNN segmentation methods, the proposed method not only can determine the PCNN model parameters automatically, and its indexes on quantitative evaluation of the segmentation result, such as Uniformity Measure(UM), Regional Contrast (CR), Shape Measure (SM) and Comprehensive Index (CI) are all 12% better than those of the traditional PCNN method..
Optics and Precision Engineering
- Publication Date: Apr. 08, 2013
- Vol. 21, Issue 3, 821 (2013)
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