2014 Vol. 43, No. 6
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2014, 43(6): 1699-1703.
An electro-optical feed-forward line width compression system based on single side-band modulation was put-forward, which included phase noise extraction as well as single side-band modulation. The phase noise extraction outputted an error voltage signal proportional to the phase error, and the voltage signal modulated the laser signal through the linear frequency modulation's effects on the single side-band intensity modulator. The single side-band modulator, adopting the structure of MZ intensity modulator, equivalent to inline four phase modulators, achieved intensity modulation through phase modulation, and finally got the line width compression laser signal. The experiment aims at DFB semiconductor laser, with wavelength of 1 552.52 nm, power of 10 mW, and through the construction and simulation of the closed-loop system, the laser line width decreases from 0.5 nm to 0.016 nm, which realized the compression of DFB semiconductor lasers.
2014, 43(6): 1704-1709.
One of the core issues of the large plane optical components topography measurement system is calculating the centroid coordinates of laser spots quickly and accurately, which determines the accuracy and repeatability of the measurement. According to visual perception, a 1D detection window with radius as r was defined, to find the local maximum energy in the field with a convolution template depending to center distance. Then traditional centroid method was used to calculate the subpixel centroid. Finally, 3 rule of error processing was applied. The experimental results show that the detection accuracy of proposed algorithm is 0.1 pixel, and the index was improved about 1 time than existing threshold weighted centroid method. The similarity and PV of topography is closer to interferometer than threshold weighted measurment. It has been successfully applied in actual projects.
2014, 43(6): 1710-1714.
A non-invaded and high resolution color schlieren system was developed to diagnose the hypersonic flow field with complex shock wave structures, intensive shock interactions and different shock intensity. The key technique of color schlieren system is the color filter. A high sensitive color filter with 6 regions is designed. High speed color camera and synchronization technique are employed to meet the needs of high speed photography. Space and time resolution were brought up to 0.1mm and 1s, respectively. Experiments were performed in hypersonic shock tunnel with Mach 5.0 and 6.0. Regular reflection and Mach reflection generated by interaction of oblique shocks, and type IV shock interaction generated by oblique shock and bow shock were detected. Clear color schlieren images were obtained at the 3 conditions. The complex structures of the 3 kinds of shock interactions are disclosed, which proves that the color schlieren system was efficient and reliable. And it also supplies an alternate method in the diagnostics of hypersonic flow field.
2014, 43(6): 1715-1721.
Laser conditioning technique is an effective method to improve the laser induced damage threshold (LIDT) of the optical elements. In this paper, the influence of N-on-1, R-on-1 and raster scan laser conditioning techniques with sing and multi-steps of energy increments on the HfO2/SiO2 high reflection films at 1 064 nm were investigated. Moreover, the 1-on-1 test was adopted to evaluate the laser conditioning effects of different techniques. The results indicate that the damage probability data deviation, fitting tolerance and LIDT deviation of 1-on-1 curves were able to characterize the reproducibility of measurements. Also, it is found that the single step modes of N-on-1 are less effective on improving the laser resistance ability than multi-steps, while the slight differences are difficult to distinguish between the single steps or multi-steps modes due to the uncertainty and deviation of 1-on-1 tests. Furthermore, the successive increasing energy steps will only lead to the improvement of the nonzero damage threshold except the 0% damage threshold.
2014, 43(6): 1722-1727.
Wavelength modulation spectroscopy (WMS) technique uses high-frequency modulation signal which is superimposed on the slow scanning signal. The signal is applied to the semiconductor laser drive current, so the laser frequency linear sweep as well as the modulation sweep. The absorption intensity of the lines is also modulated by the same frequency. 2f signal extraction of WMS was achieved by harmonic wavelet, which is the tool for data demodulation. The absorption spectroscopy data was obtained by scanning the beams from a tunable diode laser operating near the 7 185.6 cm-1 with the modulation frequency of 180 kHz. The 2f signal of high quality was obtained after harmonic wavelet processing for the data. The 2f signal's identification of its peak center is very clear, and data smoothness, anti-interference ability of the signal is better than method of digital lock-in.
2014, 43(6): 1728-1734.
A new optical design of laser beam expander is introduced. It suits for three laser beams to be expanded and focused. Its operation wavelength is 1 080 nm and its full field of view 0.6 degrees. A two-mirror catoptrical telescope is designed for expanding and focusing three beams which are arranged in a close configuration. Its primary is an ellipsoid mirror with aperture diameter of 303 mm. Its focusing performance approaches to the diffraction limitation. And focusing at different target ranges is implemented through control of the axial position of the secondary mirror. The power density distribution and power in the bucket curve of combined and focused laser spots are calculated with the aid of computer simulation. When focused at one kilometer, the ratio of the spot power in the bucket of 9 mm radius to the total power is over 95 percent. This new kind beam expander has the advantages of simple and low length-to-aperture-diameter ratio. The system focusing performance satisfied the usage requirement. The power of laser spots is effectively combined.
2014, 43(6): 1735-1739.
Based on Mie theory, an optical system design method was established which can improve the measurement accuracy of the particle size analyzer. In the particle size analyzer's optical system design process, the diaphragm within the measuring range of the sample cell used a zoom method, it not only constrained the reference rays trace data for every field point at the ring detector to make the spot diagrams minimum, but also constrained the reference rays trace data for every field point of each zoom position at the ring detector to make the spot diagrams minimum. The optical systerm converges rays, which truly reflects the physical meaning of the particle size analyzer's measurement theory, improves the measurement accuracy.
2014, 43(6): 1740-1744.
According to laser photo-thermal method, the measurement system of high temperature superconducting (HTS) tapes thermal diffusivity was built in low temperature and vacuum condition. Through the research on the relationship among thermal diffusivity, modulation frequency of heating laser and phase difference of heat wave when passing through specimen, novel idea to deal with experimental data from the thermal diffusivity testing by using laser photo-thermal method was put forward, and the systematic error influence was eliminated. To verify the reliability of the measurement system, the copper was used as reference material and the thermal diffusivity of copper was measured. On that basis, the thermal diffusivity of YBCO HTS tape was measured by using laser photo-thermal method, and the thermal diffusivity of YBCO HTS tape has been got when the temperature scope was from 40 K to 120 K. The thermal diffusivity decreases with the temperature increasing. Especially, decreasing sharply in the temperature range of 40-60 K.
2014, 43(6): 1745-1749.
Thermoelectric cooler (TEC) had an extensive prospect for the application of refrigeration system for laser diode (LD) for its advantage such as small in size, easy to control and so on. But it was necessary to ensure the match between the cooling power of TEC and the thermal power of the target;otherwise it would lead inadequate cooling or excessive power dissipation. In this paper, a high precision thermostat system with TEC for laser diode was designed. In this system, the cooling power of TEC was determined by the thermal load of LD, proportional-integral-derivative (PID) control method was used to optimize the parameters of the thermostat system. An experiment was executed to verify the design. The experimental results showed that the work temperature of LD could be controlled between 5℃ and 41℃ with a control accuracy of 0.05℃ and the steady state error was small. The system could be a good solution for the high-precision wavelength testing.
2014, 43(6): 1750-1754.
Planar laser induced fluorescence (PLIF) is the most intuitive and effective measurement technology, which shows a broad application prospects in the complex combustion flow field diagnostics because of its abundant information, non-contact, high spatial and temporal resolutions, visualization and other advantages. PLIF technology can provide a two-dimensional imaging and many parameters such as temperature, velocity, component concentration and pressure of some special cross-section in the flame and other flows. A two-excitation planar laser-induced fluorescence (PLIF) system was set up based on the two line PLIF technology. Two dimensional instantaneous temperature distribution of premixed CH4/air flame was measured quantitative by picking two proper spectrum lines. In experiments, by acquiring the power of laser pulses and the profile distribution and revising the spatial positions of the ICCD imaging, the precision was elevated. The measurement results are more precise compared with the results of thermoelectric couple and the uncertainty is less than 5%, which can suffice with the applications in supersonic combustion diagnostics.
2014, 43(6): 1755-1760.
A three-dimensional transient state finite element model of the temperature field of laser milling has been established based on ANSYS software. As an example, Al2O3 ceramic material has been milled by laser to simulate the temperature field. The dynamic distribution of the temperature field was simulated during the laser milling process. A group data were chosen to analyze the change orderliness of the temperature on the sample surface. The milling width and depth were determined along different scanning route. An indirect verification method was put forward to test the result of the simulation. The milling layer width and depth of the temperature simulation were compared with the experimental data. The result shows all the data can be coincided, which show the finite element model can predict the effect of laser milling.
2014, 43(6): 1761-1766.
The supersonic anti-ship missile infrared radiation characteristic research has the important reference value to naval battle offense and defense both sides. Provided an in-depth analysis of the infrared radiation characteristics in sea battlefield environment, introduced cumulative factor, the environment radiation computation model was established in view of the multiple scattering effects of particle, Focus on cloud radiation calculations, the model feasibility had been confirmed by simulation. Established the computation model of the IR radiation characteristics and radiating area of missile skin and plume, carried on the simulation computation to the missile infrared radiation brightness and the radiation intensity. Finally, by comparison and analysis of the simulation results, the result indicates that this algorithm can be applied in the radiation calculation of particle system effectively, can be used for generation infrared image sequences.
2014, 43(6): 1767-1771.
To ensure the accuracy of radiation measurement, it is necessary to calibrate the infrared radiation measurement system. Based on the analysis of working principle of infrared radiation measurement system, a calibration method combined internal and external calibration was proposed which was different from the traditional calibration method. It separated measurement system to calibration step-by-step, no longer as a whole black box. Through theoretical derivation the internal and external calibration calculated formula was given. The experiments show that the calibration accuracy of the new method is accord with traditional full-aperture blackbody calibration method, within 1% relative error. This method reduces the requirements of temperature range of the external full-aperture blackbody, also reduces the development difficulty and cost of blackbody.
2014, 43(6): 1772-1776.
For infrared imaging meeting the development needs of high-speed aircraft, a target detection method under the condition of high heat dome infrared radiation was proposed. Firstly, the current small target detection method used in current engineering application and its flaws was described when facing aero-thermal effect during high speed fly. Then infrared radiation characteristics of heat dome were analyzed in aspect of the energy intensity distribution, the target contrast, target gray and edge changes. According to radiation characteristics and features, target detection method was proposed based on the gradient domain saliency. And the detail processes was given in the paper;finally, target contrast after background suppressing, running time, detection rate, etc. were compared between the proposed method and the commonly used small target detection algorithms. The experiments showed that the proposed method performs superiority under the conditions of thermal radiation target detection.
2014, 43(6): 1777-1781.
The anti-tank missile javelin developed by America was a kind of portable single soldier anti-tank missile. Javelin was nowadays a sort of when shooted no controlling anti-tank missile. So it was one of the most advanced anti-tank missiles. The core technology of Javelin was the advanced guided mode. The advanced guided mode was analyzed and studied. Firstly the technical characters and the system composing were summarized. Secondly we mainly analyzed the guided mode, including aiming, emission, flying and hitting. Then the guided process and principle were studied. The main technical performance and the key technologies were analyzed. Finally, the technical improvement program and the developing trends were introduced.
2014, 43(6): 1782-1787.
A 3232 readout integrated circuit (ROIC) for very long wavelength (VLWIR) detector was designed, which uses buffered direct injection (BDI) unit cell as input circuit to reduce the input resistance, increase the injection efficiency of signal current, and provide precise biasing voltage to the detector. Due to very low output impedance of VLWIR detectors, a high gain feedback amplifier was used to provide the inverting gain by a differential stage. By means of novel current mode background suppression, the integration time and the signal-to-noise ratio (SNR) of image data was increased when VLWIR FPAs run at high background environment. At the same time, better contrast and dynamic range was also achieved. The final chip was fabricated with HHNEC CZ6H 0.35 m 1P4M process technology. The test results show that the output dynamic range is over 2.0 V, the linearity could reach up to 99%, the readout frequency is more than 2.5 MHz, the RMS noise is less than 0.3 mV, and the power dissipation is less than 100 mW when the ROIC operates at the temperature of 50 K.
2014, 43(6): 1788-1793.
The plume IR image simulation based on the particle system needed large computation and was difficult to be integrated with the IR calculation model. To solve the problem, firstly based on the chemical reaction formula, the gas fraction calculation model of the aero engine's plume was established, and the engineering plume flow field calculation method was improved. Then based on the figure envelope model, the simulation model of the plume IR image was established. And three relative problems were studied: how to establish the figure envelope, how to combine the figure envelope model with the flow field calculation model and gas IR lightness calculation model, and the relation between the figure envelope and plume IR image. Finally, the plume IR image was generated by numerical simulation. The results show that the plume IR image is defined by the high temperature gas of the core area;the plume IR image is unrelatable with the figure envelope when the envelope is enlarged to a certain extent;the plume IR image is generated more effective and accurate when the figure envelope is easy to be divided into meshes, is small but can reflect the plume radiation distribution characters.
2014, 43(6): 1794-1800.
In order to achieve enhanced lethality by implementing the aimable warhead, the aiming direction of the warhead was parameterized in missile coordinate system，and the missile-target terminal encounter parameters were derived with space analytic geometry method based on IR-imaging guidance and laser-ranging integrated fusing technology. According to the two encounter concepts of the aimable warhead side-attack target and forward-intercept target at endgame, the coordination models of fuse and aimable warhead were studied separately in detail, so that the aimable warhead system could aim at target and detonate the warhead after the optimum time delay to place fragments on the target during endgame. Simulation results show that IR-imaging guidance and laser-ranging integrated fusing is able to provide the required information to the aimable warhead, so the two models are valuable reference for the design of ranging-imaging guidance integrated fusing and the engineering application of the aimable warhead.
2014, 43(6): 1801-1806.
When established association cost, traditional multi-dimension assignment data association algorithm for multi-infrared-sensor ignored the random errors introduced by least square estimation. To overcome the problem, a modified cost function that can get second-order accuracy was proposed. The first two items of Taylor series for nonlinear measurement function was kept down. The pseudo measurements can be got by using the mean and covariance of position estimation according to the preserved series. Then the statistical distances between real measurements and pseudo ones worked as the association costs. Finally, the correct data association ratio of the several association algorithms were compared through simulation experiments. Simulation results show that the modified cost function can reflect the association probability more accurately and the algorithm based on it can achieve better performance than the others.
2014, 43(6): 1807-1811.
Due to the influence of material, fabrication technology and so on, blind-pixels exist on infrared focal plane array detectors. It reduces the infrered image quality and object detection capability, improves the object inveracious rate. Effective blind-pixels detection for infrared image process is an important development issue. Based on the analysis of the model for the effective pixel corrected response, the approach was proposed that, when the corrected response was uniform, the means (MEAN) and the standard deviation (STD) were both normal distributed random variables for all effective pixels. Through adaptive projective decomposition of MEAN and STD histograms, the MEAN and STD distribution range of effective pixel could be effectively estimated, and the detection rule for blind-pixel was got finally. The experimental result by applying real infrared image shows the proposed method for IRFPA blind-pixel detection is scientific and effective.
2014, 43(6): 1812-1817.
The traditional methods for spacecraft autonomous navigation need several sensors, such as star sensor, infrared horizon sensor and magnetometer, to collect navigation data. As a result the load of spacecraft will gain in weight, size and power. Based on the advantages of multi-field of view (FOV) star tracker, an autonomous navigation method was proposed which used multi-FOV star tracker (MFST) to image the star and the earth respectively and got the orientation vectors of them. Combining with the orbit parameters of the spacecraft and the layout of the MFST, a mathematic model of the earth imaging was set up to implement the earth edge images in every single FOV. The Steger method was used to determine the earth edge in the images. Considering the earth oblateness, the orientation vector of the earth will be obtained through circle-fitting the earth edge points in each FOV. With the configuration that one FOV measures the navigation star and the other two FOV measures the earth edge, the autonomous orientation based on the starlight angle is simulated and the result indicates that the accuracy of the earth vector and the spacecraft position respectively reaches 0.017 2(1) and 190 m(1)。
2014, 43(6): 1818-1822.
The classifier plays an important role for cloud detection in remote sensing image. Traditional Classifiers demand excessive training samples and have risks to fall into local optimum. To solve these deficiencies, SVM was presented as the classifier to achieve cloud detection based on SVD as feature vectors. Meanwhile, the method of minimizing the support vector count was introduced to substitute cross-validation method for optimal parameters selection. Experiment over high resolution remote sensing images QuickBird showed, with this method, the correction rate of cloud detection could be higher than 99%. It also suggested support vector count could reflect the classifier's estimation accuracy and was more easy to compute. The SVM classifier established in this way, compared with BP neural network, needed fewer training samples but achieved higher accuracy, it showed better performance in cloud detection field.
2014, 43(6): 1823-1829.
The 45-degree-rotated scanning mirror (RS mirror) was employed into the field of Wide-of-View (FOV) imaging with a scanning TDICCD camera by using the Coordinate Transformation method of building sub-satellite point image motion model with the Satellite Borne TDICCD camera. The imaging characteristics of the RS mirror and the Offsetting Image Rotation principle of the K Mirror were fully discussed. The effect diagram after offsetting image rotation with the K Mirror was further simulated to verify the rationality of K Mirror. Based on the light vector transformation matrix of the RS Mirror and K Mirror, the image rotation model was finally derived when bearing scanning TDICCD camera was used, which could support the theoretical foundation of subsequent image rotation analysis.
2014, 43(6): 1836-1841.
As the highest measurement precision attitude sensor, attitude determination is the most basic and critical section in navigation. To analyze the impact of star distribution on least square attitude measuring precision, the definition of the attitude angle was described, the problem-solving process by least square method was researched, and the condition number of the coefficient matrix, that leads to poor precision under a certain observational error, was derived from the view of mathematical. Lastly, three sets of typical star distribution under different conditions were simulated, calculate the results and conduct the statistics, the simulation results indicate that measurement precision is influenced by different locations of the star group in image and different device parameter models for star sensor, besides the relative position of the star group described by condition number.
2014, 43(6): 1842-1849.
A positioning errors equation of airborne LIDAR point clouds was founded based on its positioning equation. Errors of point clouds were classified into three categories-systematic errors, mission errors and random errors-according to LIDAR positioning equation. The influences of slope and scanning angle for positioning errors of point clouds were analyzed in detail under planar surface, down-sloping surface and up-sloping surface conditions. The influences of scanning angle errors, mounting errors, attitude errors as well as scanning angle for positioning errors of point clouds were discussed. Except of analyzing systematic errors, influences of time deviations, GPS positioning errors, lever-arms errors and random errors for positioning errors of point clouds were also emphasized and analyzed. The results of research showed that flight height and scanning angle were crucial error sources, down-sloping surface and scanning angle errors in all error sources had great impacts on positioning errors of point clouds, mounting errors could be eliminated by calibration method, attitude errors were only rely on IMU's accuracy alone.
2014, 43(6): 1830-1835.
In order to complete the testing of very high precision star sensor, a high precision static multi-star simulator which can achieve accurate simulation of star point was designed. The collimating optical system has wavelength range of 500-900 nm, at 20℃, the effective focal length of 150 mm, and distortion less than 0.02%, MTF reaches diffraction limit within the full filed of view of 7.2. For temperature changes from -45℃ to 65℃, used ZEMAX software to analyze athermal performance of the optical system, applied ANSYS software to complet finite element analysis of the mechanic structure. The results show that, athermal performance of the optical system is fine, shape change and deformation stress on mechanical structure are small, the anti-defocus performance of the simulator can meet the requirement of technique index. Calculate theoretical accuracy of the designed simulator and provided a group of measured data. Depends on the measurement results, the error of position for single star 3, the error of angular distance between stars 10, are both better than required calibration accuracy of the star sensor.
2014, 43(6): 1850-1856.
Extreme ultraviolet Lithography (EUVL) has been considered as the strong candidate for next generation commercial projection lithography to print sub -22 nm half-pitch (HP) features in microelectronics field. Performance and technology of resists is one of the key parts of EUVL. In order to improve the research work in China, recent progress of EUV resists reported in near years was reviewed. The history and current status of EUVL were introduced. EUVL' features and targets on resists were presented. EUV resist research portfolio and its classification were summarized. Composition, mechanism and performances for EUVL of representative resists were focused. Performance possibility and problems of the different resists were also analyzed;Routes in the future to improve EUVL performances for them were finally discussed.
2014, 43(6): 1857-1862.
The characteristics of multi-alkali cathode, making process as well as the application in the second generational image intensifier was introduced, the sealing process between cathodes and envelops was explained, and cathode was fed to pre chamber of XPS analysis instrument. The percentage of atoms of each element in the thickness of different layer of multi alkali cathode was obtained by XPS analysis. First wide spectrum scan on the top surface of multi alkali cathode was made, and then the narrow spectrum scan was made on every element, following by argon ion etching. Etching after a certain time, wide spectrum and narrow spectrum scan on the multi alkali cathode were made;an argon ion etching was carried out until to the interface of glass window. Argon ion etching combined with XPS spectra analysis, atomic percentage of Na elements, K elements and Sb elements was obtained within the multi-alkali cathode film thickness. The results show that the multi-alkali cathode structure is a two-layer structure, i.e. Na2KSb base layer and adsorbed Cs atoms layer. In two film layer, Na2KSb layer is thicker, while the Cs atomic layer is thin, only 2.7% for the entire cathode film thickness. In addition, the number percentage of Na atoms, K atom, Sb atoms does not follow 2:1:1 stoichiometric ratio, and in the entire cathode layer thickness range, the percentage of atoms of the three elements does not remain constant, and does not appear in the ideal state of the atomic percentage of the three elements at a position reached 2:1:1. Theory and practice has proved it is possible to obtain high sensitivity only with strict stoichiometric ratio Na2KSb film. Thus by molecular beam epitaxy, multi-alkali cathode with higher composition control accuracy stoichiometric ratio 2:1:1 could be produced, the higher cathode sensitivity will be obtained.
2014, 43(6): 1863-1868.
Based on the birefringence effect, a novel duel-core photonic crystal fiber polarization beam splitter was proposed. The birefringence of the splitter was improved by introducing dual elliptical air holes into each fiber core of the rectangle lattice structure photonic crystal fiber. Using the full-vector finite element method (FEM), the impacts of structural parameters of duel-core photonic crystal fiber on birefringence and coupling length were analyzed. And the characteristics of the splitter, such as coupling length, extinction ratio and bandwidth, were investigated. Numerical simulation results demonstrate that the coupling length is decreased while the birefringence is increased by increasing the ellipticity, and the isolation of the polarization state can be achieved and the polarized light extinction ratio is-45.42 dB when the working wavelength and transfer-length of the fiber are 1.55 m and 282 m, respectively. Besides, the extinction ratio is less than-10 dB when the bandwidth is 89 nm as well as the range of the wavelength is 1.507-1.596 m.
2014, 43(6): 1869-1872.
A photonic crystal containing defect layer was composed of a medium (n-type doped GaAs) and b medium (TiO2). Numerical calculations indicate that there are 5 defect mode of 1 transmittance within 3.0-4.5 THz for the photonic crystal. These defect mode have following characteristics: when the doping concentration n of GaAs increases within 1017/cm3 to 1019/cm3, the center, the full width at half maximum (FWHM) and the transmittance of the defect mode remain unchanged, However, if n increased to 1020/cm3, the transmittance of the defect mode began to decline. With increasing angle of incidence, the transmittance of the defect mode remain unchanged, but their center blue-shift, the mobile rate are variable, and FWHM narrows. The central position of the defect mode occurs red shift with increasing the thickness of the media layer a, b or the defect layer c respectively, while both the transmittance and FWHM remain constant. These phenomena provide theoretical guidance for this type of photonic crystal to realize the comb filtering in terahertz frequency range.
The two-dimensional(2D) photonic crystal(PC) was constructed with the substrate of SiO2 and the surface coating medium of TiO2, and rigorous coupled-wave analysis (RCWA) theory was used to analyze the optical propagation property of 2D PC. The effects of the lattice period, refractive index and thickness of waveguide layer on optical properties of 2D photonic crystal were analyzed. Analysis results show that: While the lattice period and thickness of the waveguide layer are constant, with the increase of refractive index of waveguide layer, the reflective peak wavelength value (PWV) appears red shift, and there is a good linear relationship between above two. When the refractive index of waveguide layer is constant, photonic crystal reflection PWV increases with the increase of thickness or lattice period, the linear relationship between the two and PWV is in certain range. The non-uniform characteristic of surface adsorbing medium is obtained by analyzing the spectrum of non-uniform distribution of surface adsorbing medium of 2D PC.
2014, 43(6): 1878-1882.
The diamond-like carbon(DLC) films were prepared by plasma-enhanced chemical vapor deposition(PECVD) with CH4 as the gas at different working pressure, on substrates of 316L stainless steel. The microstructures and properties of the films were characterized with Raman spectroscopy, scanning electron microscopy, nano-indenter and tribo-test. With the increase of working pressure from 7 Pa to 15 Pa, the sp3 content and mechanical properties of the films increased and the tribological properties decreased obviously. However, with the increase of working pressure from 15 Pa to 31 Pa, the sp3 content and mechanical properties of the films decreased and the tribological properties increased obviously.
2014, 43(6): 1883-1888.
A multi-function driving power supply system for the organic light emitting device (OLED) was proposed to improve the single function, circuital complexity and high cost of exiting systems. The proposed system was based on a single-chip microcomputer STC89C52 and a character liquid crystal display module LCM1602. This power supply system could flexibly provide four different power sources, i.e, a variable constant voltage source, a variable constant current source, a pulse voltage source and a hybrid current-voltage source (a voltage-controlled constant current source for direct bias and a voltagecontrolled constant voltage source for reverse bias) with adjustable frequency and duty cycle. The output was regulated according to the actual testing condition of an OLED sample. Testing results show that the system was competent for demand of power design, with high stability, high resolution, low ripple quotient and small error. Meanwhile, the system had characteristics of simple structure, convenient operation, easy expansion and low cost.
2014, 43(6): 1889-1893.
Dealing with some non-rotational symmetrical residual error in low-frequency Zernike polynomials surface is needed in the manufacture of large-reflecting mirror. These errors greatly increase the difficulty of processing. Propose to change the mirror surface for reducing the fabrication difficulty by active support technique. Study the method of compensating some non-rotational symmetrical residual error in low-frequency Zernike polynomials surface by active support technique. Firstly, apply the all-floating support method in axial support system to control the deformation of the mirror's surface. Then, apply force as the control variable in the system. Do the correction process on the solution which can not satisfy the principles of Resultant equal to zero and Total torque equal to zero. Successfully achieve the compensation of low-frequency Zernike coefficient surface by active support technique. The results of simulation by Ansys-Workbench software prove the feasible.
2014, 43(6): 1894-1898.
High-resolution imaging of living cell at the micro-/nano-scale is important for life science research. It may help to observe biological activities of cells, and to detect cell responses to external stimuli and even movements of some protein molecules in cell membranes. However, there have not been effective methods to realize such objectives yet. Scanning ion conductance microscope (SICM) has been widely applied in many fields and is receiving increasing attention due to its non-contact, force-free, and high-resolution imaging features. Herein, a design of SICM, including hardware integration and scanning algorithms, was introduced from the point of view of system firstly;then the feasibility and effectiveness of the system was evaluated through comparison of PDMS gratings measurements by SICM and AFM;finally, in situ experiments of living-cell imaging in physiological environment had been carried out, and the topography of living neuro-2A cell had been successfully obtained. The well-established scanning ion conductance microscope will provide an effective tool for investigating functional mechanism and microstructure on the surface of living biological samples.
2014, 43(6): 1899-1904.
Based on rigorous coupled wave analysis, the models for grating-embedded multilayer structure planar diffraction were generalized to the case of conical diffraction. The proposed method can be used to calculate the light diffracted from the grating-embedded multilayer structure with arbitrary wavelength, polarization, azimuthal angle and incident angle. For the micromachined optoacoustic sensor, the convergence performance of the diffraction efficiencies of the reflected +1st order in conical diffraction was investigated. The simulations show that using a 4m grating period and TM (Transverse Magnetic) polarization, when the numbers of harmonics M(2n+1) are 67, 69 and 71, the diffraction efficiencies of the +1st order are 28.86%, 28.84% and 28.86%, respectively. Then the displacement sensitivity of the micromachined optoacoustic sensor was optimized. When the incident angle, the azimuthal angle and the grating period are 22, 10and 1 m, respectively, compared with the +1st diffracted orders of 4 m grating period, the displacement sensitivity of the 0th and +1st orders under TE and TM polarization was nearly doubled. It can be used to accurately monitor the metal membrane displacement induced by the acoustic pressure or electrostatic actuation voltage.
2014, 43(6): 1905-1908.
During the process of optical design and assembly，it is necessary to estimate the performance of optical system based on the surface quality of the mirrors. The traditional way is to use the Zernike polynomial, which is restricted to depict the consecutive and smooth surface. Otherwise, get the ideal surface during aspherical surface polishing is very difficult, the mid-and-high frequency errors which is very harmful to the optical system's image quality will be produced at the same time. In this paper, a new point-to-point method was introduced, any surface with mid-and-high frequency errors could be exactly simulated, and the optical system's performance can be estimated accurately. An example of the optical system was cited, it was revealed that the camera's simulated performace is very close to the measurement, the coincident to real system is over 90%.
2014, 43(6): 1909-1913.
A hollow-core porous microstructured terahertz fiber based on Topas cyclic-olefin polymer (COC) was designed and manufactured. The loss characteristics of an optical fiber with outer diameter 10 mm was simulated using comsol software in the 0.2-1.5 THz band. There are several low-loss bands in the 0.85-1.5 THz, and there are three windows in which the loss is lower than 3 dB/m in the 0.85-1.1 THz band, the loss is about 0.208 dB/m especially in the 0.99 THz. By comparing the loss characteristics of the fiber with core diameter of 3 mm, 4.8 mm and 6 mm in 0.8-1.5 THz band, the loss was reduced with increasing the diameter. The outer diameter of designed THz fiber was enlarged to 7 cm, and a dedicated mold was designed for manufacturing preform. A 22 cm long THz fiber preform with a standard structure and smooth surface was manufactured by the hot extrusion molding method. Finally,through the laboratory's unique draw tower, the terahertz fiber of the core diameter of 3 mm, 4.8 mm and 6 mm were manufactured. The loss analysis result show that the average loss of the fiber with core diameter of 6mm is 2.175 dB/m in 1.27 THz and it is near the theoretical loss (1.95 dB/m).
2014, 43(6): 1914-1919.
A flexible support structure was designed to make the mirror surface figure error and the stiffness of the structure fulfill the requirements of the design of a 2m telescope's K mirror. KM1 was the support at three points on the rear of mirror. The position of support points was optimized by the FEA software ANSYS to minimum the mirror surface's RMS. And the flexibility matrix of the flexible support bar was built by theadjoint transformation. Then based on the flexibility matrix, the thickness, length and the width of the flexure hinge were optimized to reduce the thermal stress and assembly stress and fulfill the requirement of the mirror support's stiffness. KM2 was the support at three points which are uniformly spaced around the circum of mirror. The flexible support bar of KM2 was the same as KM1's. The FEA simulation results of KM1 and KM2 under the work condition of gravity and temperature drop met the design requirements. The RMS of KM1 was less than /40, and the RMS of KM2 was less than/60. Their first order resonant frequency was all over 100 Hz.
2014, 43(6): 1920-1924.
In order to solve the problem evaluating the stitching accuracy of large-diameter reflecting mirror, a kind of stitching accuracy evaluating method called self-test was proposed in the article, realizing the analysis and evaluation to the stitching accuracy of large-diameter reflector mirror, while providing a method measuring the stitching precision. Self-test was a kind of method testing the accuracy of stitching result with sub-aperture measuring result. In the article, relative accuracy evaluation indexes and their calculation methods were discussed. As a project example, 800 mm plane mirror was splicing measured with a 600 mm interferometer and stitching accuracy was evaluated with the self-test method. It shows that the stitching is accurate and it's reliable and precise to assess stitching accuracy by the way of self-test at the same time.
2014, 43(6): 1925-1929.
To tackle the problem that traditional focus measure technologies cannot measure the focus shifting caused by thermal distortion in single pulse high power laser system, a system, composed with double vertical wedge groups producing array spots, can make instantly focus measure available. Two pairs of wedge-mirror groups which are placed vertically to each other are utilized as beam splitting system in this system. All those rays are finally detected by a detector, and formed a matric of spots with various sizes. Through single detection of spots matrix, various focus position shifts and the focus shifting measurement of the high power laser with single shot are obtained. After theoretical analyzing, software simulating and experiment testing, this technique has the advantages such as the adjustable detecting accuracy and range, good disperse quality, and the ability of restraining the effect of parasitic light.
2014, 43(6): 1930-1935.
In order to realize velocity and acceleration measurement at low speed, a new type method of velocity measurement at low speed was designed which is based on the method of Moirfringe and nonlinear tracking differentiator. First of all, the electric signal of Moirfringe was analyzed. Then the electric signal from photoelectric encoder was filtered by nonlinear tracking differentiator and the phase delays were compensated. Finally, velocity and acceleration measurement was realized by using cascaded nonlinear tracking differentiators. The test proves that the stationarity and precision of velocity measurement at low speed are improved, as well as the sampling frequency. The method was applied in a system with a 21-bit encoder as the angle sensor, and velocity and acceleration could be measured. When the speed is 0.001 7()/s and sampling time is 5 ms, sampling numbers is 20 times than that of ordinary methods. The real-time performance, stationarity and precision of velocity measurement at low speed can be improved by using the method.
2014, 43(6): 1936-1942.
Overhead line system is the high voltage transmission line for pantograph obtaining electric current which is built above the rails in electrified railways. Its key task is to transport the electric energy from traction substation to electric locomotive. Aiming at the problem of low precision and low efficiency in traditional measuring method of geometric parameters, a measuring system is designed which is fast and of high precision. The system is based on principle of binocular vision. It produces the feature using a laser, acquires images using two high-resolution cameras and makes three-dimensional calculation, which makes it possible to measure the geometric parameters of the overhead line system in real time. Experimental result indicates that the repeatability precision of the system can reach up to 1 mm, and that the reliable real-time measurement of geometric parameters of the overhead line system has been accomplished, which provides useful theoretical basis for operating repairs.
2014, 43(6): 1943-1949.
Synthetic beacon technique provides beacon signal for adaptive optical system, which is used to correct the wavefront aberration caused by atmospheric turbulence successfully in astronomical observation and laser transmission. However, anisoplanatic errors is one of some insuperable difficulties. Many academic research works were studied but there were few reports for experiment measurement all over the world. In this paper, the measurement method of anisoplanatic errors was proposed, and the high precision measurement system was independently designed, which concluded two Hartmann wavefront sensors using high sensitive EMCCD detectors to get the wavefront of Rayleigh beacon and the natural star simultaneity. Two basic experiments were finished, one was focal anisoplanatism errors measurement experiment at the altitude from 8 to 18 km of Rayleigh beacon, another measurement experiment is at the Rayleigh altitude of 12 km with the angle varying from 0 to 100 rad between the synthetic beacon and the natural star. The exact and reasonable measurement result is gained.
2014, 43(6): 1950-1954.
In strong laser host device, various optical lens with different focal length are needed to expand and collimate the beam, the accurate of the lens'focal length directly affect the overall performance of the system, so it is particularly important to accurately measure the focal length of lens. A new method of measuring the infrared optical system with long focal length by using the Hartmann-Shack wave-front detected device and rotated plane mirror was proposed. The measuring principle of the system was given. Using optical simulation software ZEMAX, the influence of different aperture on the measurement of focal length was analyzed. Then the relationship between the rotation angle of the plane mirror and the system measurement error was deducted by using error theory. Finally the experiment was done to obtain the real result, the result of measurement shows that when the plane mirror rotated to a certain angle, set an appropriate optical aperture, the system measurement precision can be better than 3, much higher than the traditional measuring method. In addition, the measurement method is also conveniently to use, high stability in measure, etc.
A novel automatic testing and analyzing system with seven channels for MEMS accelerometers was introduced in this article. This system was designed with multi-function and high level of integration based on multi-channel and parallel configuration, leading to high-efficient testing and analyzing. Based on the conventional testing systems, the Labview-based top level application software in this system was used to realize manipulation of the electro-mechanical vibrator, temperature humidity chamber, the voltage bias and so on. Meanwhile, parameters such as sensitivity, linearity, repeatability, hysteresis behavior, temperature behavior and frequency behavior were able to be measured and exported as reports all in once. Normally, the efficiency of sensor testing could achieve 50 devices/h, much higher than traditional manual systems. Experimental results show that the system is built up with high accuracy, stability and reliability, with the testing error less than 2.5%. This prototype enables the cost reduction of MEMS sensors, thus the mass application in the domain of internet of things (IOT).
2014, 43(6): 1960-1965.
A novel deeply strapdown guidance control (DSGC) framework based on strapdown seeker and strapdown inertial measurement unit was presented for miniature guided munitions applied to UAV, soldier shoulder and other platforms. Due to that there was no available guidance information of DSGC, the theoretic transform equations based on missile-target geometric relationship and roll-stabilized simplified equations were introduced, then a nonlinear differentiator was proposed for stable digital angular rate calculation. A PI compensated two-loop acceleration autopilot was presented as the inner loop of guidance system. The trajectory simulation for UAV platform and soldier shoulder was analyzed, respectively. The results showed that the DSGC technology was a well solution for the precisely guided miniature munitions especially the short-range. Wherein, the multiple-constraints design for guidance control system was the critical factor for application.
2014, 43(6): 1966-1971.
The leakage of toxic or hazardous gases not only pollutes the environment, but also threatens people's lives and property safety. Many countries attach great importance to the rapid and effective gas leak detection technology and instrument development. To address this issue, a wide-band gas leak IR imaging detection system design was proposed, mainly including wide-band IR optical lens, the sub-band filters and switching device, wide-band Uncooled Focal Plane Array (UFPA) detector, video processing and system control circuit, which takes full advantage of the spectrally non-selective characteristic of the uncooled focal plane array detector. The system can sensitively detect and visualize a considerable number of different kinds of gases, which are not visible to the naked eyes, by using the IR image nonuniformity correction technology and Digital Detail Enhancement (DDE) technology. The resulting gas leak video easy to be observed for the human eye was provided. Many advantages are commendable, such as scanning a wide range simultaneously, locating the leaking source quickly, visualizing the gas plume intuitively, and so on.
2014, 43(6): 1972-1976.
In order to solve the acquisition problem of the multispectral images in the process of the research on Optical-Electronic weapons, a method of generating infrared multispectral simulation images by 3D scene was presented. The infrared image at any observation angle of the scene and a data cube of specific waveband could be generated by the method. Some experiments were done in waveband 3-5 m to generate a data cube involving 401 infrared simulation images in the wavelength step 0.005 m. A BRDF calculation model based on the Phong model was derived and used in the calculation of the reflection intensity of solar direct radiation which had strong directionality, and a data cube in waveband 3-5 m involving infrared images with directionality was generated when the BRDF calculation mode was applied. The experiments results show that the simulation method presented in this paper could generate infrared multispectral images data cube rapidly, and the BRDF calculation model could reflect the directionality of the reflected light, which improves the fidelity of the simulation images.
2014, 43(6): 1977-1981.
In the use of Fourier transform infrared spectroscopy to build the multi-component gases quantitative analysis model, it is necessary to reduce the dimensions and select characteristics wavelength according to the target gas spectral. Through the regularization algorithm analysis, least absolute shrinkage and selection operator (LASSO) and Elastic Net method were used to do these for seven kinds of mixed gases of methane, ethane, propane, iso-butane, n-butane, iso-pentane and n-pentane. The minimum mean square error (MSE) and prediction deviation were used as the criteria to select LASSO and Elastic Net parameters. Finally, the resolution of 4cm-1 measured spectral data was analyzed. The dimension of spectra were reduced from 2 542 d to 2d and 3d respectively by using LASSO and Elastic Net method under the condition of the MSE of 0.001 9 and 0.002 1. The cross sensitivity of maximum and minimum were 10.271 8% and 1.420 5% by LASSO method. The cross sensitivity of maximum and minimum were 5.494 5% and 0.749 3% by Elastic Net. Results show that the Elastic Net method was better in the characteristic variable selection and the spectral dimension reduction for gas spectral quantitative analysis，and it was foundation to establish the accurate quantitative analysis model.
2014, 43(6): 1982-1987.
Dual dispersive prisms are the key dispersive component of high resolution space-borne imaging spectrometer. Their opto-mechanical mounting is an important problem which must be resolved during imaging spectrometer engineering development phase. Firstly, the working principle of dual dispersive prisms was introduced and their opto-mechanical mounting requirements were also presented. Furthermore, after taking into account coefficient of expansion matching, density, modulus of elasticity, machining property and so on, dual dispersive prisms mounting material was confirmed. Moreover, the great difference of coefficient of expansion between one of dual dispersive prisms and its mounting material was compensated using the temperature compensation method. Afterward, the dual dispersive prisms were mounted by the semikinematic mounting method. Finally, Mechanics analysis and thermoanalysis results were proposed, subsequently corresponding tests were also carried out. Tests results indicate that the nature frequency of dual dispersive prisms assembly is 301.5 Hz, integrative OPD of dual dispersive prisms assembly is better than 0.021 (=632.8 nm) at 20℃ 5℃ . The results proved the dual dispersive prisms assembly satisfied the requirements of imaging spectrometer.
2014, 43(6): 1988-1993.
To improve the video's image quality of airborne imaging systems, we proposed a real-time image stabilization system, based on fast smoothing point-feature trajectories. In this paper, a system framework was established to eliminate the accumulative errors between frames in global motion estimation and achieve fast and long-time video stabilization. This framework was different from the traditional real-time video stabilization. Firstly, an improved SURF algorithm was introduced to extract unstable feature points from original shaky video. Secondly, we determined the adjacency of these feature points, generated point feature trajectories with Delaunay triangulation algorithm and smoothed them with Kalman filtering. Then, we could estimate the global motion vectors which directly needed to be compensated from the original point-feature trajectories and the smoothing point-feature trajectories. The experiment results indicate that the proposed method can be used to stabilize unstable aerial video in real time. Also, it can effectively improve the image quality of the airborne imaging systems and estimate global motion vectors between independent frames. So it can be used in long-time image stabilization.
2014, 43(6): 1994-1999.
Automatic marking points extracting with high accuracy is basic for calibration, stereo calculation, visual navigation and other applications. The bottle-neck is the accuracy and robustness. Based on the rough point from the cross of lines of the neighbor barycenters in two directions, the ridge points were detected by the symmetric function and refined by an iterative least square method, based on the refined ridge points, the Hough transform was improved for determining the lines and their intersections. At last, the position of the marking points was to be adjusted by the penalty function with a changing step along the descent direction both in deflection and rotation separately. Our algorithm is robust to noisy, rotation, illumination variations and a certain degree of distortions, the accuracy could be less than 5 percents of a pixel.
2014, 43(6): 2000-2006.
The deblurred images obtained by traditional frequency-wavelet domain based image restoration algorithms always result in prominent boundary ringing and smoothing artifacts. And the more effective space domain based alternating restoration algorithms usually work slowly. To overcome these problems, an algorithm named TwIST-TV which combines the two-step iterative shrinkage/thresholding (TwIST) and total variation (TV) regularization were proposed. This method first introduced the TV regularization constraint on the objective function, and then applied the TV-denoising method to regularize the midrestored image in each iteration before whose wavelet coefficients were processed by the TwIST method, and eventually obtained the deblurred image. Experimental results show that, in contrast to the frequencywavelet domain based image restoration algorithms, TwIST-TV can effectively suppress the boundary ringing and smoothing artifacts. The restored images can achieve 1-7 dB higher values of the signal-tonoise ratio (SNR), the peak signal-to-noise ratio (PSNR) and 0.05 higher value of the mean structural similarity (MSSIM) index. Proposed method has more than 6 times the speed advantage comparied with the methods which need alternating optimization in the space domain while maintain the accuracy of the solution.
2014, 43(6): 2007-2012.
Expensive weapons cannot repeat the experiment and affect the performance of detection and tracking algorithms, for this problem we use a virtual platform to simulate real missile flight and simulate different flight status by changing the parameters. It uses conversion between different coordinate systems and rotation mapping technology to solve the problem that detecting two-dimensional tracking algorithm performance in the three-dimensional simulation target. The experimental results show that: the average frame rate of rotation mapping techniques on stable tracking of gravity algorithm or correlation algorithm is 85 frames/s. And the time it takes less than direct mapping technology. The experiments show that the goal that detecting two-dimensional tracking algorithm performance in the three-dimensional simulation target is successfully achieved.
2014, 43(6): 2013-2020.
In order to solve the problem that traditional local invariant descriptors extracted inaccurate main direction and spent too much time in matching vectors, a new method for fast image registration based on RI-LBP algorithm and hybrid spill-tree was proposed. Firstly, stable feature points of template image and image to be matched were extracted by the proposed FAST-Difference Algorithm. Feature vectors were calculated using rotation invariant RI-LBP descriptors. At last feature vector sets were matched using hybrid spill-tree and mismatching points were eliminated by RANSAC. The problem that the main direction couldn't be extracted accurately was conquered because of the rotation invariant of RI-LBP, which means the feature descriptors were more stable. At the same time the feature vectors contain contained 53 dimensions, which are more simple. Spill-tree had better matching efficiency for high-dimensional data because it omitted the process of backtracking. The experiment results indicated that the proposed method cost much less time while retained nearly the same describing performance with SURF and achieved better performance in rotation and illumination changes.
2014, 43(6): 2021-2026.
The picture quality of the video is very poor under the low illumination night environment, it often appears low contrast, blurred, color offset, etc, and it has influence on interpretation and understanding of the video. For solving the problem of nighttime video, the different time space background fusion technology was proposed based on moving object and a new Retinex image enhancement algorithm. This method improved the whole brightness and the contrast of the video through the strategy of adaptive brightness adjustment. Then the illumination components of brightness images were extracted by the trilateral filter based on the theory of Retinex. The reflecting components of images were obtained through compressing illumination. It was because that the reflecting components of images included large number of particulars and marginal information of images, reflecting components were enhanced through integrating Sigmiod non-linear stretching function. At last, it enhanced the saturation component to get more bright colors. The experiments show that the algorithm can improve the visual effect of the low illumination video at nighttime. The image brightness, contrast, sharpness is improved, and the method not only enhanced the video image detail, but also retained the important content of the video. The method avoid the distortion of images, such as, halo, ghost, color deviation.
2014, 43(6): 2027-2034.
For unsighted detail and texture of images due to many factors during imaging, a novel technique of image enhancement by two-dimensional histogram with self-adaptive window was proposed based on two-dimensional histogram theory of Turgay Celik. This method considered image details and texture. By analyzing the relationship between two-dimensional histogram and texture characteristics and defect of fixed window, self-adaptive window was proposed by average grads. It was suited the region characteristics to construct two-dimensional histogram and accomplish enhancement through comparing the distributing with ideal one. Many experimental results and comparison show that this method can overcome badly adaptability, excessive enhancement, local weakening and other problems caused by fixed window. The enhanced images display clear texture and more pleasing visual content so that the method is useful for engineering.
2014, 43(6): 2035-2039.
The two disadvantages were known in traditional imaging system for target tracking, which were small instantaneous field of view and the need to scan the target airspace for the realization of the large coverage. In order to solve the problem of the wide field of view coverage and high resolution, a new method for target tracking was proposed based on spatial-multiplexing imaging technology, in which the target position was determined directly in the wide field of view. And a starring imaging system structure with an optically multiplexed path, a common focal plane and a wide field of view was formed by the use of multi-lens array, which requires a specific overlapping and encoding relationship between each of the divided sub-field of view to decode the target location after imaging simultaneously. Focused on the one-dimensional lens array, the spatial relationship of the lens array, encoding and decoding principle of the field of view and its employment in target tracking technology were all analyzed. In addition the target decoding algorithm was studied and simulated, the simulation results demonstrate that this method can solve the target tracking problem of a wide field of view effectively.
2014, 43(6): 2040-2045.
Aiming at the contradiction between high compression ratio and high fidelity of the return image in man-in-the-loop (MITL) of infrared imaging guidance weapons, a hierarchical infrared image compression algorithm based on visual attention model was proposed. On the basis of salient regions of infrared image extracted by visual attention model, salient regions, background regions and transition regions were divided and compressed by different compression methods according to the importance of information of different image regions, in this way the compression of the whole image was realized. The experimental result shows that the proposed algorithm can not only preserve the important information of typical targets, but also decrease the data size in image transmission, and it is more suitable for MITL operation mode than the traditional full image compression method.
2014, 43(6): 2046-2050.
Aiming at the light-spot positioning in the digital simulation image for the target observation and aiming in the target-tracking simulation systems, a method for the light-spot positioning based on monocular vision was proposed. Firstly, the rough positions of the light-spot in the camera image plane were predicted with the Kalman filter method. Then the light-spot image region with the center of the rough positions was obtained. Secondly, the precise positions of the light-spot center in the image were extracted based on the Hessian matrix in the light-spot image region. Finally, according to the positioning model calculation which was established from the point in the camera image plane to the point in the digital simulation image, the positions of the light-spot in the digital simulation image were obtained knowing its precise positions in the camera image plane. Experiment results show that the RMS error for the light-spot positioning is 0.4 pixel, and the time of processing each image is 0.32 ms. The proposed method can locate the light-spot in real time with high dynamic and high precision in the target-tracking simulation systems.
