2013 Vol. 42, No. 12
2013, 42(12): 3163-3167.
The time response characterisitics of In0.53Ga0.47As/InP heterojunction infrared photocathode was studyed in this paper, such photocathode worked at transmission mode with a wide spectral response range from 1.0-1.7 m. Under certain field-assisted bias voltage, the transmission characteristics of photo-excited electrons inside the phococathode were simulated. The results show that the response speed of the photocathode are accelerated with the increasing of the field-assisted bias voltage. While P-InGaAs photo-absorbing layer is thickened, the response speed gets slow. The response speed also gets slow when increasing the doping concentration of InGaAs photo-absorbing layer. When increasing the thickness and doping concentration of P-InP photoelectron-emitting layer, the respose time will be prolonged. Based on all these conclusions, the structure parameters and doping concentration of each layer were optimized. The optimization results show that when the thickness of the photo-absorbing layer and the photoelectron-emitting layer are about 2 m and 0.5 m respectively, and the doping concentration of photo-absorbing layer and photoelectron-emitting layer are about 1.51015 cm-3 and 1.01016 cm-3 respectively, the response time of photocathode can be reduced to less than 100 ps.
2013, 42(12): 3168-3174.
Near infrared (NIR) spectroscopy combined with successive projections algorithm (SPA) was investigated for determination of water content in oil. A total of 57 oil samples were scanned, the correlation coefficient (R) and root mean square error (RMSE) were used as the model evaluation indices, the full-spectrum partial least squares (PLS) model was developed for the prediction of water content in oil after the performance comparison of different pretreatments. Simultaneously, successive projections algorithm was applied for the extraction of effective wavelengths, the selected effective wavelengths were used as the inputs of partial least squares (PLS). The results indicated that a total of 24 variables, only 4.68 percent in the full spectrum, selected by SPA are employed to construct the model with 0.994 4 as the correlation coefficient and 5.455 110-5 as the root of mean square error of validation set, PA-PLS model is better than full-spectrum PLS model. An excellent prediction precision was achieved. In conclusion, successive projections algorithm is a powerful way for effective wavelength selection, and it is feasible to determine the water content in oil using near infrared spectroscopy and SPA-PLS, and an excellent prediction precision was obtained. This study supplied a new and alternative approach for further application of near infrared spectroscopy in on-line monitoring of contamination such as water content in oil.
2013, 42(12): 3175-3179.
The frequent environmental events about the polluted gases ask for some kinds of multi-gases analyzer. Limited to the general aim of design and incomplete function in software, the conventional Fourier Transform Infrared spectrometer can't be effectively involved in the field of gases analysis. To solve this problem, a new method was studied using the magnetic encoded signal to drive the moving cube and collect the spectrum data, instead of the conventional laser interference signal. It was in this way that a concise structure of analyzer was established and it facilitated the procedure of debugging and setting-up. At the same time, in order to meet the demands of continuous and immediate analysis, an improved quantitative algorithm with the ability of baseline compensation automatically was illustrated. The related experiments with the designed gases analyzer which is verified to be an effective tool for environmental gases monitoring can execute the multi-gases quantitative analysis rapidly and continuously.
2013, 42(12): 3180-3184.
The image quality of re-imaging infrared optical system is quite sensitive to temperature, compared with common optical system,its characteristics and effect was discussesed in the paper. And the optical-passive design theory of athermalization was described. An instance of a cooled re-imaging infrared optical system was given, the heating contrast experiment was carried out and the test result was shown. The athermal ability of the designed optical system and the common non-athermal optical system were tested by experiment with the same optical parameters such as focal length, field of views etc. The design result shows that the system is athermalized because the image quality of the system is close to the diffraction limit in the temperature range -40 ℃~+80 ℃ without focusing mechanism, and the shift rate of the focal length is relatively low. The test result shows the athermal ability of this system can remain its image quality in high temperature environment without refocusing.
2013, 42(12): 3185-3189.
The high-repetition 3-5 m mid-infrared solid-state laser has gain a lot of attention for its potential applications in civil and military. Because of the characteristic of solid-state laser, the temperature gradient of resonator and the environmental vibration in the transmission will influence the pointing of laser to generate quite large jitter and drift, which cannot be applied in some fields that the requirement of pointing precision is quite high. In such case, the monitoring and alignment system after laser are installed to control jitter and drift of laser beam. Therefore, there are two kinds of detector will conduct the comparable experiments to verify the performance. One is the infrared quadrant detector and the other is pyroelectric array camera. The experimental results show that the pointing errors for these two detectors are about 9. The pointing error of pyroelectric detector is 5.39. The quadrant detector has wider bandwidth than the pyroelectric array camera and the pyroelectric array camera based on the thermal image is more intuitive. Therefore, for the mid-infrared laser, corresponding detector can be chosed to built up the monitor system based on the applications requirement.
2013, 42(12): 3190-3195.
Infrared face recognition, being light- independent, and not vulnerable to facial skin, expressions and posture, can avoid or limit the drawbacks of face recognition in visible light. In this paper, a fast infrared face recognition system based on local features was proposed. Firstly, the original IR images captured by an IR camera thermoVision A40 were 320240 pixels. The sensitivity was as high as 0.08 ℃, the face image was normalized to size of 6080 by preprocessing and face detection. Secondly, based on the symmetry of face, the whole infrared face image was divided into small sub-blocks. To make full use of the local features of infrared face image, a local binary pattern (LBP) was chosen to get the composition of micropatterns of sub-blocks. Finally, Kruskal-Wallis (KW) feature selection method was proposed to improve the effectiveness of discriminant feature extraction. The experiment results illustrate that the system recognition rate can reach 98.6%, outperform the traditional methods based on Principal Component Analysis(PCA) and Linear Discriminant Analysis (LDA). Furthermore, the speed of proposed system is much faster than the traditional methods and can be used in real-time face recognition system.
2013, 42(12): 3196-3200.
To detect and identify pollutant gases in the distance speedily and accurately with IR remote sensing spectrometer,it is necessary to remove high-frequency noise and low-frequency baseline,of which the purpose is to extract feature information. For the deficiencies of the existing methods, EMD was proposed to preprocess IR remote sensing spectrum. EMD is a preprocessing algorithm which works self-adaptively and without parameters. After High-frequency noise and low-frequency baseline was removed, the global assessment factor RMS1, the partial assessment factor RMS2, and the comprehensive assessment factor RMS* reached 0.141, 0.182 and 0.026 respectively. The perfomace of EMD is better than wavelet decomposition method obviously.The result shows that EMD is convenient and reliable for denoising and baseline correction of IR remote sensing spectrum.
2013, 42(12): 3201-3206.
The performance of the multispectral infrared camera is seriously influenced by the stray radiation. In order to ensure that the camera can work properly in all situations, the stray radiation in different working conditions needs to be analyzed. The main sources of the stray radiation in the infrared optical system of a camera were analyzed. The model of the multispectral infrared camera was established in the stray light analysis software. The irradiance of the imaging plane was used to evaluate the stray radiation level. Taking the influence of the solar azimuth and the off-axis angle into consideration, around the hood, 8 solar azimuths and 16 different off-axis angles were selected to carry out the ray tracing. Thus the irradiance of the imaging plane for every certain condition was obtained. And the effect to the irradiance of the imaging plane caused by the rotation of the pointing mirror which was composed of roller shaft and pitching axis was analyzed. Meanwhile the influence of the earth atmosphere stray radiation was also discussed. The results show that the earth atmosphere stray radiation is tolerable. And the system can basically satisfy the requirement to the imaging plane irradiance when the off-axis angle is greater than 58. The infrared optical system of the multispectral camera can work well within this range.
2013, 42(12): 3207-3212.
The effect of active impurity on double barrier photonic quantum well filter was studied by transmission matrix method. The results show that when there was no active impurity in medium, the quality of double barrier quantum well filter increased with the periodicity of barrier layer increase, and the frequency of filtering channel shifted at same time. When there was active impurity in inner-barrier and well layer respectively, the resonant tunneling modes appeared high magnification, but the frequency of tunneling modes were constant. The quality of quantum well filtering increased quickly with the increase of value of imaginary part of dielectric, especially when there was active impurity in well layer, the quality reached 8.010104. These properties can achieve functions of high-quality optical filtering and optical signal amplification, providing positive guidance for design and application of photonic quantum well.
2013, 42(12): 3213-3217.
The measurement of laser intensity temporal-spatial distribution is of great importance for diagnosing and evaluating the performance of laser system. Spatially sampling large size laser beam is the first step to measure the laser beam parameters, decreasing the influence on measurement result from the laser incident angle and sampling large size laser beam with high spatial resolution and high duty ratio are very critical for accurately measuring laser beam intensity temporal-spatial distribution. Base on the principle of diffuse scattering, which means the distribution of scattering light has nothing to do with incident light, scattering sampling and attenuating method was put forward in array detectors for the measurement of laser intensity distribution. The diffuse scattering principle was briefly introduced. The construction of sampling and attenuating was given, the transmission laser intensity computation model was set up, the intensity formula was deduced and verified through experiments. The applications of scattering sampling unites and photodiode array or CCD were introduced. There are notable advantages, high resolution which is 2 mm or so; high duty ratio which is up to 40%; wide use angle which can be up to 30 and adjustable multiple attenuation which wants. Scattering sampling and attenuating provide a new method for array detector to sample laser beam, which overcome the shortages of technologies available, improves the measuring ability and measuring accuracy significantly and is of great significance to laser intensity distribution measurement device, the method can be widely used to development the measurement systems of laser beam parameters.
2013, 42(12): 3218-3222.
The relay mirror system is a new optical system which can effectively decrease the atmospheric aberrations and enlarger the laser attack scope. The standard used to judge the advantage of beam propagation through a relay mirror system and the method used to calculate its advantageous application scope are key contents in the relay mirror technology. In the present paper, model of beam propagation through a relay mirror system was established, the equivalent Fresnel number of beam propagation through a relay mirror system was ratiocinated in detail, the performance evaluation factor used in the relay mirror system was defined, the relationship between the factor and the equivalent Fresnel number was analyzed, and the method used to calculate the advantageous application scope of a relay mirror system was analyzed. Under the Hufnagel-Valley 5/7 turbulent model, performance of a 30 km relay mirror system with 3.8 m ground-based laser source was calculated. Results show that the relay mirror system can improve laser attack effect to long-distance and high-altitude targets, and enlarger the laser attack scope.
2013, 42(12): 3223-3227.
In order to study the propagation characteristics of Gaussian Schell-model (GSM) beams in electromagnetically induced transparency atomic vapor, the analytical expression was obtained for the cross-spectral density function of a Gaussian Schell-model beam passing through the electromagnetically induced transparency atomic vapor based on the matrix optics theory, diffraction integral theory and unified theory of coherence and polarization. The formula can be used in the study of the changes in the spectral density and spectral degree of coherence of the beam through the EIT atomic vapor. Numerical examples show that both the spectral density and the spectral degree of coherence of the GSM beam can be modulated by the Rabi frequency of the control light. The results have been provided a new method and technique for modulation the beam propagation. The findings indicate a new technique for controlling the spectral density and the spectral degree of coherence of the partially coherent light beam.
2013, 42(12): 3228-3233.
The active laser detection basing on cat's eye effect can detect space optical observation equipments. The laser pulse transmitting in the atmosphere will be broadened to affect the echo waveform distribution from the target, and the echo pulse width is different from the dissimilar reflective target, which can be used to determine detecting target. Based on the photon scattering theory, the pulse broadening caused by the aerosol scattering effect near the ground was analyzed, the calculation physical model was built to resolve cat's eye and diffuse reflection echo pulse broadening and the main factors affecting pulse broadening were provided. The active detecting dynamic tests aiming at the optical cabin loaded on the aeroboat were implemented to validate the physical model, the test results show that the cat's eye and background diffusion reflection echo signals are respectively broadened 20-30 ns and 90 ns after 8～10 km slant path atmospheric transmission. Based on the built physical model, the theoretical pulse broadening on dynamic test condition is accordance with the actual test results, which provides theoretical proof to distinguish and pickup cat's eye echo signal.
2013, 42(12): 3234-3238.
Pseudorandom modulation rate which used to modulate 1 550 nm fiber laser was prompted from 622 MHz to 1 GHz in the laser ranging system based on high speed pseudorandom modulation and photon counting technology. Ranging performance was compared and demonstrated under two different modulation rates using the optical fiber delay method. 10 order M-sequence pseudorandom code and the same InGaAs/InP single photon detector with detection efficiency of 10% were implemented in the system. Under condition of input signal average energy of 1.9410-17 J, the similar SNRs were acquired in the two systems and the ranging accuracy was improved by 1.58 times under high modulation rate which was in good agreement with theory result. The actual ranging platform was established and ranging experiment was carried out indoor. The ranging accuracy of 2.1 cm was obtained when measuring a high-reflected target which was about 4.5 m away. The result is useful for outdoor ranging system.
2013, 42(12): 3239-3244.
A high efficiency laser active detection controlling and processing system based on LabVIEW was designed. The principle of system design was presented, as well as the basic construction and diagram of the system. The advantages of muti-thread and modulated designed method of LabVIEW such as function integrity, friendly user interface, strong extensibility, high efficiency and stability were discussed. Experiments were done using the system. The results show that using this system, the data could be acquired, processed and displayed visible in time, which could meet the need of laser active detection. The system designed provides a new way for laser active detection technology.
2013, 42(12): 3245-3248.
A guidance control scheme based on strapdown laser detector and proportional navigation guidance (PNG) for rocket projectile was presented in details since the precise guidance improvement requirement. Because the strapdown detector can only measure the error angle between airframe axis and target directly and could not provide the inertial line-of-sight (LOS) angular rate necessarily to PNG, a LOS rate algorithm using detector's error angle and airframe attitude rate from onboard gyro was proposed. A two-loop acceleration autopilot was designed with respect to the autopilot-guidance match principle. The non-dimensional miss distance analysis and trajectory simulation results validate that the proposed approach is feasible.
2013, 42(12): 3249-3253.
Optical information storage is the main method of digital information storage. The storage density and the possibility to further improve storage capacity were limited for the deficiencies existing in the conventional two-dimensional optical information storage. The confocal/two-photon fluorescence scanning microscope system was constructed based on the three-dimensional optical information storage mechanism on the photobleaching material. Three-dimensional optical information storage and retrieval were achieved by means of femtosecond laser on a new photobleaching ATFTBAr fluorene derivative as a storage material. The storage reached four layers and each layer spacing and information point spacing were respectively up to 10 m and 8 m. The signal intensity of the information point was identified and contrasted, and a detailed analysis of the refractive index mismatch caused by a signal crosstalk was made. Research shows that the experimental system and the establishment of the storage material can be used to achieve better three-dimensional optical information storage.
2013, 42(12): 3254-3258.
A new direct writing device was designed. It consisted of a V-shaped hole made by Ag, the matching fluid and the organic layer for high exposure depth. 200 nm light spots were obtained by V-shaped hole which focued the incident light beams. Direct-writing head moved onto the photoresist through the matching fluid, and the matching fluid combined with the quartz substrate constructed a surface plasmon polariton(SPP) coupling cavity, which amplified the intensity of the light field in it by SPP effect and resonance. The transmission depth of the standing wave formed by forward and reflected light reached hundreds of nanometers. Simulation results show that using the new direct-write head can achieve deep exposure depth in the resist by F-P effect and SPP effect(multiple excitations). When the distance between the direct-write head and resist is greater than 90 nm, it can not only avoid the relative wear between the direct-write head and resist, but also help reduce the requirement of the mechanical movement process. Therefore it has high application potential in fabrication of nano-mask and nanophotonic structures.
2013, 42(12): 3259-3264.
Recently, the research of micro-Doppler effect provides a new approach for accurate target identification, which possess an important application prospect of helicopter detection, classification and recognition. In this paper, the radar scattering cross section was predicted with the physical optics method, and micro-Doppler model of a helicopter rotor blade was modified. Based on the model, the echo signal of double blades and three blades with different shape and rotating speed was calculated and micro-Doppler effect was analyzed with STFT. The results show that different quantity, height and rotating speed have different influence on the curve shape, amplitude and period of the micro-Doppler, and some reference for helicopter identification by micro-Doppler is provided.
2013, 42(12): 3265-3269.
A photon up-conversion system was proposed based on low-rate RZ-OOK signal injected into the Fabry-Perot cavity laser diode(FP-LD) without local oscillator. External injected optical signal locked one of FP-LD free oscillation mode, a high-frequency microwave oscillation was generated, and the injection locking mechanism of the up-conversion principle was analyzed, and experimentally verified the feasibility of the scheme. In the experiments, the 2 Gb/s RZ-OOK signal was respectively converted into 12 GHz and 14.28 GHz subcarrier signals.
2013, 42(12): 3270-3276.
Strabismus of wide baseline mapping camera is benefit for ground elevation measurements. Front view of small baseline mapping camera is benefit for location with high precision, reducing distortion and decreasing shelter. Double baseline is a novel mapping means, combining the advantages of wide baseline mapping and small baseline mapping. But it requires efficient cooling for high power equipment and high precision temperature gradient for large-scale mirror, which put forwards harsh requirements for thermal control system. In this paper, some measurements were adopted to design thermal control system for double baseline mapping camera, such as coupling the radiating surfaces, designing aluminum heat shield in the back of large-scale mirrors, disposing many thermal control loops, and using high-performance heat pipe enhanced thermal conductivity. Based on the analysis about camera's external heat flux, two extreme working conditions were determined. Hot working condition is =17,and focal plane assembly, electronics devices and controllers were all working. Cold working condition is =27, and the camera was in standby model. Considering with the interior heat fluxs and interface conditions, detailed thermal control schemes were established, and simulation results revealed the correctness of the thermal control schemes, and the temperature of various components met the design requirements. Our work can offer some thermal technique supports to study about mapping camera with double baseline.
2013, 42(12): 3277-3282.
In order to reduce the effect of the assembling process on the accuracy of the surface shape of the mirror, based on a space camera's mirror subassembly, a flexible support structure was designed, and the assembling method was formulated. First, the thickness and the area of the adhesive, the flexible hinge as well as other parameters were given based on the formula. Second, the finite element analysis for the mirror subassembly was carried out under the combined effect of gravity and 5 ℃ temperature change. Third, according to the assembling process of the mirror subassembly, the viscose and curing treatment for the mirror subassembly was carried out. Finally, mechanical test and thermal vacuum test of the mirror assembly was conducted so as to verify the alignment method. Experimental results indicate that, under the mechanical and thermal vacuum environment the viscose of the mirror subassembly is not destroyed, and the accuracy of the surface shape of the mirror is better than 1/50 . It can verify the effectiveness of the mirror support structure and assembling method for the mirror subassembly.
2013, 42(12): 3283-3288.
The relative position and stability between primary mirror and aspherical secondary mirror(SM for short) is important to test and checkout for the collimator. First, the supporting system of secondary mirror was analyzed according to the theory, and the dynamics model of supporting trusses was built. Then, the secondary supporting system was designed, optimized according to the disposal of decreasing dimension by FEA. Finally, effects caused by temperature were analyzed. The results show that tangential spider van support could reduce the masking and keep the stiffness at the same time. The ratio of rigidity of the improved supporting truss is uprated, which make the 1st resonance of the whole system arrive at 62 Hz. The effect of temperature also can be decreased by change material of local structures, making the wavefront error of system change from /20 to /30. The scheme has fine accuracy, well stability and meet the design requirement.
2013, 42(12): 3289-3294.
The bearing in Rotator assembly of TMT tertiary mirror system was designed, and the rule of parameter choice was discussed. Firstly, the load case of tertiary mirror system was analyzed, after that, the load-deformation equations of double-rows angular contact ball bearing were established and solved with Newton iteration method, the axial, radial and angular displacement were obtained, the load and deformation of every ball as also, the effect of different parameters were discussed at last. The result shows that, when the azimuth varies in 0-65, the displacement in optical axial direction is less than 0.022 mm, the displacement in rollaway plain is less than 0.042 mm, the maximum angular displacement is less than 3.5, the design requirement is satisfied, there are enough margin compared to the index. The load distribution equation and parameter choice rule of double-rows angular contact ball bearing can be applied in different cases.
2013, 42(12): 3295-3299.
In order to meet the increasing requirements of the electromagnetic shielding, the principle and manufacture process of a film-taped metallic mesh were introduced and the influence of the parameters (such as the line width, period, duty ratio,et al) on optical and electromagnetic features were analyzed. By using the flexographic printing technology, the metal mesh film with the line widthes of 20, 30, 40 m and the periods of 300, 400 m on PET substrate were made, and the maximal electromagnetic shield effectiveness was more than 15 dB, while the UV-Vis transmission of metallic mesh on PET substrate was between 70% and 80%. The results indicate that the optical and electrical performance of metallic mesh film is inconsistent, and it is better to select a thinner line width and smaller period to obtain optimal shielding effectiveness.
2013, 42(12): 3300-3308.
In order to concurrently and flexibly test the control unit with different numbers of channels in complex multi-channel motor control system, a parallel simulation real-time test method supporting variable numbers of channels in multi-channel control system was proposed. Object-oriented test methodology for variable numbers of channels was put forward. The acquisition and processing program for variable numbers of channels control system was presented, and the efficient data storage method in high-speed asynchronous FIFO converted by dual-port SRAM and data transmission means by combining DMA with burst transmission were adopted to achieve efficient data storage and high-speed asynchronous data transmission between the system and computer. The FPGA-based parallel acquisition, real-time processing and PCI bus transfer strategy were used to improve traditional PCI interrupt application data transmission mode and the PCI interrupt transmission control mechanism, which overcome the system instability caused by the variable-number of channels of the measured object, the different computer configuration or the application program mutual interference, also achieved the stable and reliable data transmission between the system and the computer. A parallel test experiments on random variation of 4-channel to 64-channel control unit was conducted, the results showed that, the number of channels was flexible, multi-channel control unit parallel test state was stable, reliable, and met the expected requirements.
2013, 42(12): 3309-3314.
The seeker disturbance rejection rate not only severely degrades seeker tracking accuracy, but also has greatly issues for the missile guidance performance. The generation mechanism of disturbance rejection rate was analyzed, and the models of disturbance rejection rate caused by spring torque and damping torque were established. Based on the Routh criterion, the stability zone of parasitical loop was obtained. The effect of the parasitical loop on effective guidance time constant and effective navigation ratio was studied. The result shows that the limits for important guidance parameters should be determined to insure the stability of parasitical loop; both the effective guidance time constant and effective navigation ratio are changed on the action of parasitical loop. The conclusion is helpful for engineers at the preliminary stage of guidance and control system design.
2013, 42(12): 3315-3319.
In order to reduce noise in the laser-pumped magnetometer, the virtual instrument technology was applied to the detection module for the first time. With Labview programming tools and the PXIe-bus based control system, the integrated design of the data acquiring module, the signal processing module and the signal generating module was completed. Analysis of the three modules was performed with emphasis on the digital signal processing algorithm. By improving the structure of the low-pass filter, the conflict between bandwidth and noise level was resolved. By using trapezoidal integration incremental PID control algorithm, the system's robustness and anti-interference ability were greatly improved. The control system noise level reached the magnitude of the 0.01 V. Combined with laser frequency and power stabilization technique, the noise introduced by the the laser frequency drift and power jitter was effectively eliminated. The magnetometer noise was reduced to 0.7 pT/Hz0.5@1 Hz.
2013, 42(12): 3320-3324.
According to the analysis the changes of the cavity temperature and particle population ratio in a continuous wave DF laser, it was pointed out that the quantum number of maximum small signal gain and shortwave direction quantum number of zero small signal gain will move to high rotational states during with cavity temperature and particle population ratio increasing, and they must be corresponding to a certain range of cavity temperature and particle population ratio. The integer quantum numbers of zero small signal gain are difficultly obtained under measured spectrum. The conditions were given that small signal gain of shortwave direction cut-off quantum was greater than zero and small signal gain of reduce one shortwave direction cut-off quantum was less than zero. Combining with the same cavity temperature range of three spectral bands, calculation based on spectral data of DF laser that the cavity temperature range was 305-368 K, the particle population ratio of 1P band, 2P band and 3P band were 1.77-2.09, 1.65-2.05, 1.19-1.72, respectively.
2013, 42(12): 3325-3329.
Integral diffraction coefficient including high diffraction order is the basis of identification of X-ray line, study of X-ray crystal characteristy, X-ray line intensity quantitative measurement and X-ray monochromatic image diagnosis. On the automatic X-ray diffractometer (XRD), based on the stability and precision control of and 2 goniometer, special plane crystal holder was made. Bremsstrahlung and Cu K line were attenuated for 5 orders by 40 m-thick pure Nickel filter in 15 kV and 20 mA supply to X-ray Cu tube, X-ray source of Cu taget is to be Cu K monochromatic source, transmission coefficient of Nickel filter is the criterion of Cu K monochromatic source. For X-ray Pentaerythritol(002) crystal,integral diffraction coefficient of 1-3 order diffraction on Cu K energy were calibrated. The results show that integral diffraction coefficient of the 2nd order and the 3rd order is only 14.36% and 4.07%, the Cu K1 intensity ratio of the 2nd order and the 3rd order is only 7.7% and 1.3% compared with the 1st order diffraction. This kind of calibration is efficient and convenient on XRD in common laboratory.
2013, 42(12): 3330-3334.
To evaluate the maximum range of laser rangefinder quantificationally, and to get the performance in different visibility rapidly, a new numerical algorithm was put forward. The empirical formula of atmospheric transmissivity was plugged into laser range equation, so a transcendental equation was generated and solved, the maximum range was calculated correspondingly. Based on the numerical algorithm, proportional method was applied to deduce maximum range in different visibility. The numerical simulative calculation of maximum range in different conditions was made by using this theory, and relation curves between maximum range and different visibility(Rmax-V) were drawn to explain the influence of visibility on maximum range visually. The simulation results show that the new numerical algorithm works well in calculating the maximum range of laser rangefinder. It has many virtues, such as quantitative results and high precision, etc. It provides a new approach to evaluate and assess the maximum range of laser rangefinder in lots of different situations.
2013, 42(12): 3335-3338.
The quantitative schlieren measurement is new development of schlieren technology. A color filter was made for the substitute of the typical Z schlieren knife. The quantitative color schlieren method was advanced for measurement of the density of the axial symmetry field. A new approach was researched for the development of the quantitative schlieren technology based on the typical schlieren setting. The measurement theory and calibration method were introduced, and the typical setting was given as an applied example. Take the axial symmetry free jet as an object, the theory analysis and computer simulation results were contrasted with the experimental data. The results show the given method is suitable for the density quantitative measurement of axial symmetry field.
2013, 42(12): 3339-3346.
The extended object cost function was proposed based on the time-to-go exponential function and for constant target maneuver, a family of extended optimal trajectory shaping guidance law was deduced. The missile non-dimensional position and angle miss distance vs non-dimensional terminal guidance time was studied using the non-dimensional method and adjoint technique when the constant/random maneuver target was introduced into the one single lag system. The adjoint simulation results were validated by the direct simulation results. The results show that the position and angle miss distance produced by the final impact angle approaches to zero when the missile terminal guidance time is about 15 times of the system lag time while the constant target maneuver is about 20 times. If the exponential number n and the system navigation ratio increase, the non-dimensional position and angle miss distance is oscillatory more worse and the convergence time of the miss distance is larger than before. With the increasing of the terminal guidance time, the position and angle miss distance of the random target maneuver approaches to a stable value but not near zero and also, the miss of which is larger when the exponential number n increases.
2013, 42(12): 3347-3352.
Remaining useful life(RUL) prediction of the fiber-optic gyroscopes(FOG) working in the space environment is the key issue in health management of satellite. Among the literature about the reliability estimation of the FOGs based on degradation process, the current methods didn't consider the unit-to-unit variation of the equipments with the same type. Therefore, in this paper a random variable model based on Wiener process was presented to model the degradation process of the FOG for satellite. In the presented model, the drift parameter of the Wiener process was considered as a random variable to describe the unit-to-unit variation of different equipments, and the traditional Wiener process turns out to be its special case. Based on the model, the information of reliability and RUL can be obtained. The simulation results show that the proposed method can generate reasonably better results than the traditional model and thus can be potentially applied in practice.
The optical absorption coefficient of KDP crystal is an important parameter to evaluate its quality. Especially, in the Inertial Confinement Fusion (ICF) facility, the amount of the optical absorption coefficient determines the energy and frequency conversion efficiency of output pulses directly. So it is need to measure it with extreme precision. Since the magnitude of optical absorption coefficient of the KDP crystal is generally 10-3/cm~10-5/cm, traditional detection methods cannot meet the measurement resolution requirement. In this paper, an interferometry method based on the photothermal displacement principle was proposed to solve the problem of measuring the optical absorption coefficient with extreme precision in connection with the characteristics of KDP crystal. The mathematical model within interferometry method of KDP crystal optical absorption coefficient was established by the integral transfer method firstly, then the structure parameters of the measuring system was simulated and optimized based on the above model, and the design parameters of the system were obtained.
2013, 42(12): 3358-3362.
High quantum efficiency, high UV/VIS rejection ratio, fast response and wide spectral response are the main objects for the design of AlGaN photodetectors. To obtain suitable detector structure for UV focal plane array, combining with the characteristics of epitaxial materials grown by MOCVD, a design of back-illuminated solar-blind AlGaN photodetectors with high quantum efficiency was demonstrated based on simulations and experiments. The design basis and process of the AlxGa1-xN-pin photodetectors were introduced in detail, and then the design was optimized by experiments. Moreover, the photodiodes were fabricated according to the design, and the performance of device was also presented, exhibiting high peak unbiased EQE of 57% at 270 nm, responding to the spectral range between 250 nm and 282 nm. It is indicated that an optimal design is achieved.
2013, 42(12): 3363-3366.
Antimonide semiconductor lasers have a wide range of applications in the mid-infrared band. Based on the exist problems of GaSb-based material of the etching process, then the improvement was made. The hydrofluoric acid and phosphoric acid was used to make wet etching on GaSb respectively, and tartaric acid was added into the two acid-based solution to compare the effects. The experimental analysis shows that both of the two etching solution have a good etching effect on GaSb material, and the rate of corrosion is stable. The adjustments of the etching solution component can regulate the corrosion rate, and after etching, the morphology is good, and the material surface is smoothy. With the increase of the diluting ratio of the solution, the etch decline rate of hydrofluoric acid which add tartaric acid is fast then slow down, until it almost does not change any more. By adjusting the system components of Phosphate which add tartaric acid can reduce the widely exists undercut effect as well as the undercut phenomenon in the wet etching process.
2013, 42(12): 3367-3372.
As full solid-state low-light night vision devices, InxGa1-xAs could adjust the composition x to vary the response wavelength, which can cover the main wavelength of the night sky radiation. In addition to this, the quantum efficiency of the InxGa1-xAs material is high, and the device dark current is low, so performance of the InxGa1-xAs devices is high for the night vision system, as consequence the longer detecting distance for the system. Besides, the InxGa1-xAs arrays are made from the conventional semiconductor process without sealed in the ultrahigh vacuum. CMOS ROIC is adopted to read, transport and amplify the signal, then the signal datum is easy to handle and improve for the InxGa1-xAs low-light devices comparing the vacuum devices. The above advantages made the InxGa1-xAs devices a novel low- light device. There are lots of differences concerning the working mechanism, fabrication method, as well as the performance between InxGa1-xAs devices and vacuum one. Based on the comparison results the technique feature and the important application requirement for InxGa1-xAs solid-state low-light night vision devices were analyzed.
2013, 42(12): 3373-3378.
A novel octagonal photonic crystal fiber (PCF) was designed using an elliptical air hole and large circular air hole in the core region in order to enhance the performance of modal nonlinearity, birefringence and to get the low confinement loss at the same time. Its effective mode area, nonlinearity, birefringence and confinement loss were investigated simultaneously by using finite element method(FEM) with anisotropic perfectly matched layers. The numerical simulation results show that by choosing suitable relative structure parameters that the proposed fiber has high birefringence up to the order of 1.6810-2 at wavelength 1.55 m, it is about two orders of magnitude higher than that of the regular polarization maintaining fiber. High nonlinearity =60 W-1km-1, and low confinement loss 0.6 dB/km at wavelength 1.55 m. This highly birefringence PCFs with high nonlinear coefficient have received growing attention in telecommunication, various polarization sensitive devices and supercontinuum applications systems.
2013, 42(12): 3379-3385.
Design and manufacture of higher rejection rate filters which meet the needs of accurate measurement of BaTiO3 single crystal film high-speed electro-optic modulator waveguide devices were focused on. The filters were used to improve the signal-to-noise ratio of the test system and eliminate stray light interference. The films were prepared by the depositing method of dual ion beam sputtering, Nb and SiO2 were chosen as deposition materials. The coating was designed and optimized with the help of Macleod and TFCalc software, orthogonal matrix method was used to optimize the process parameters of assist ion source. The absorption of film was reduced by using optimized process parameters, the problem of film thickness accuracy controlling was solved by using the method of real-time calibration of the deposition rate. Test transmission spectrum of the filter, center wavelength is 1 550.1 nm, the pass band width is 5.1 nm, the wavelength interval of optical density from -0.1 dB to - 30 dB is 1.9 nm, the using requirements of the waveguide accurate measurement system is achieved.
2013, 42(12): 3386-3389.
A novel surface passivation of InP, combined wet passivation to dry passivation was proposed. In this work, the density of surface state was decreased efficiently so the strong luminescence property was obtained. The stability of InP surface was confirmed, which was exposed in air some day. Photoluminescence (PL) was performed in room temperature to achieve intensity measures. The high-resolution X-ray photoelectron spectroscopy (XPS) for InP revealed that a In-S bonding was increased with the annealing treatment. The density of surface was decreased further. The surface morphology of the sample was reflected with atomic force microscopy (AFM).
2013, 42(12): 3390-3395.
The performance test of Electron multiplying CCD(EMCCD) is an important adjunct and design basis of electron multiplying CCD chip and the whole imaging system. In this paper, the working principles of EMCCD were introduced, and then the characteristic parameters of EMCCD was presented. Aiming at the problem of unit conversion in the process of testing, the concept of conversion gain was introduced.The parameters test of the electron multiplying CCD was proposed based on improved photon transfer technology, the EMCCD performance parameter testing system also was established. The system included a high stability and controllable standard tungsten lamp, optical system, the black box, data acquisition and processing system.These parameters were tested, such as convert gain, full well, multiplication gain,noise factor, readout noise, dark current noise and clock induced charge noise of Andor Luca camera.The experimental results are really good and agree with the device specifications .These also verify the feasibility and reliability of the test method.
2013, 42(12): 3396-3401.
CMOS image sensor have the advantages of simple drive signals, single power supply voltage, high integration, low power consumption and strong radiation resistance. But in the field of space optical remote sensing, CMOS image sensor is not widely applied. The large-scale, high reading rate, high dynamic range CMOS image sensor is urgently in need. The 4 Megapixel CMOS image sensor of LUPA4000 is just such one. So LUPA4000 was chosen as the research target and its performance was tested. The image processing was conducted according to the results of performance test. In the research work, the parameters of defective pixels, response non uniformity(PRNU) and signal to noise ratio(SNR) were tested. The test results show that the CMOS image sensor of LUPA4000 has the following problems: the defective pixels are numerous, the PRNU is not ideal and the SNR is low. So the following image processing methods were adopted: dark background deduction to decrease the dark signal noise, defective pixels replacement to reduce the influence of defective pixels, and nonuniformity correction to reduce PRNU. The different processing combination among the three methods was applied .In order to evaluate the treatment effect of above processing combination, the contrasts of SNR and imaging quality between the original images and processed images were executed. The contrast results show that the method that combined defective pixels replacement with nonuniformity correction is the best combination.
2013, 42(12): 3402-3409.
Digital micromirror device(DMD) which is a spatial light modulator, combined with the image sensor, is able to capture the high dynamic range image data and solve the problem of bright and dark target detection. It can extend the optoelectric imaging device's dynamic range to 130 dB or more theoretically. In order to implement the light intensity control at pixel level fast and get the high dynamic image data of the real scene in high quality, a pixel level dimming algorithm, named adaptive spatial area method was proposed. This method based on the slowly change of adjacent pixels in non-edge region, was fast convergence and suitable for driving the DMD. The diming coefficient could be found after N/I times in the worst case. Then a platform, which was controlled by FPGA, was described in the paper, and the timing analysis of the DMD driver was given below. At last, the method was tested on the platform. The results show that the adaptive spatial area method is strong enough to complete the bright and dark target detection in high dynamic range scene. It has high quality in light intensity control and strong adaptability in scenes that have light intensity change of parts.
2013, 42(12): 3410-3416.
Considering the characteristics of space debris, high-speed spinning around its main axis, Single Range Matching Filtering(SRMF) method can be used for ISAR imaging of space debris with small dimension. By introducing coherent CLEAN technique, high sidelobe problem brought by Fourier transform can be solved with SRMF-CLEAN method effectively . However, under the condition of low signal-to-noise ratio, the position error of scattering centers extracted by SRMF-CLEAN method is big, and even some weak scattering centers cannot be extracted. When the distance between the scattering centers is close, some of scattering centers extracted by the method are false. Therefore, an improved SRMF-CLEAN imaging method was proposed in this paper. The method utilizes sequence CLEAN instead of coherent CLEAN to effectively solve the above problems of high sidelobe and false scattering centers. The experiment results verify effectiveness of the proposed method.
2013, 42(12): 3417-3422.
Auto-Focus technique is a main approach to hunt clear images which plays an important role in digital camera application. According to several unknown target under complicated condition, a novel auto-focus algorithm was proposed based on optical flow estimation. By calculating the optical flow of each input frame, the moving targets in scene image were tested as well as according to the moving characteristic, the interested real target was judged. Brenner sharpness evaluation method was improved. Meanwhile the evaluation function was established using two dimensions edge-gradient information. The response sensitivity of evaluation function was also increased via nonlinear-gain coefficient the impact of noise on evaluation value was decreased. Experimental results show that the proposed method can distinguish the interested main target in 50 times depths of field of different targets and evaluate the definition of varied images with random noise in 0.02 variance value effectively. And it is of a good ability of robustness for different images, Brenner function improves the peak stability margin 1 to 4 times by the algorithm, and it can be easily achieved on hardware.
2013, 42(12): 3423-3427.
Gate length of range-gated imaging system as a key characteristics was theoretically and experimentally analyzed in this paper. A frequency doubled 532 nm Nd:YAG laser that the pulse full width at half of maximum(FWHM) was 20 ns and ICCD was used to build up range-gated imaging system, what effects on imaging performance with the change of the bandwidth of the gate signal and gate delay time were studied through a straightforward method, which place white board signs at relevant distances in the field of view. Examples of imagery collected for different range and gate conditions will be presented and discussed with respect to the intensity at the signs in a gated images. When gate signal width is 10 ns, measurement result of the effective temporal gate length is 35 ns.
2013, 42(12): 3428-3432.
Phase-Diverse Speckle (PDS) method integrates two image restoration methods of Phase Diversity (PD) and speckle imaging. PD method collects focused image and defocused image of known phase diverse at the same time, then target image is restored and wave-front phase is calculated. PDS technique extends PD by calculating the wave-front distortion of a series of short-expose frames to restore the images. Each frame is composed of two images with one in focus and the other defocus. To validate PDS method, experiments indoor and outdoor were carried out in the paper. The deformable mirror was used to simulate optics aberration in lab, and the single CCD collected focused image and defocused image at different time by shifting accurate translation stage. The resolution of restored image increased 12% compared with origin image. Outdoor experiment was also carried out. The cube beam splitter was used to divide the beam into two ways, one for focused CCD and the other for defocused CCD, and cameras were externally triggered to collect short-expose images at the same time. Images of target which was 20 kilometers away were collected, and image resolution was obviously improved by single-frame recovery and multi-frame recovery. Experiments confirm that PDS method can be widely used for optics equipments in shooting range and large aperture ground-based telescopes.
2013, 42(12): 3433-3439.
Accurate calculation of the spotlight center position on the image is important to improve target localization accuracy for compound eye system. A method of calculating the spotlight position was introduced based on the symmetric property of the energy field. The position of main light on the image was defined as the position of the light spot on the image, and can be get by calculating the point of the spot energy centre on the image. Simulation and real images were used both with gray gravity method and energy method respectively, and the results show that energy method agrees with ideal position. Incident angle was calculated from the position of the image spot, the result shows energy method is also better than gray gravity method.
2013, 42(12): 3440-3446.
Aim at problem of stars have interfered with the detection of small target in the drift-scanning image of low signal-to-clutter ratio, a real-time processing method was presented, based on detecting candidate targets in single frame and tracking to judge the real target with multi-frames. The reason of filtering out the star hardly in the image through multi-frames match was analyzed, and then a single frame processing method was adopted. With the order statistics filter, the star endpoint shelter was made to filter out false targets detected in single frame. The candidate targets from the single frame processing were used for particle generation in particle filter, and the likelihood function map based on the target moving information was used for updating the particle weight in particle filter. The above operation made the particle filter can be applied to the processing of small target detection on drift-scanning images. Experiments on the actual low signal-to-clutter ratio drift-scanning image and analysis on the different related methods have shown that the method proposed has improved the ability of dim target detection.
2013, 42(12): 3447-3452.
For the dim optical object difficult to fast and accurate detection, a novel algorithm based on the row and column maximum projection of image sequences into the 2D frequency domain was proposed. Firstly, in order to reduce the computation complexity and separate the moving object from the background, through projecting into the 2D frequency domain and removing the zero frequency components, the input video with global background motion compensation was transformed into image sequences comprising of dim small moving object and noise. Secondly, after the row and column maximum projection, the higher signal-to-noise ratio image sequences with dim moving target was obtained. Thirdly, through the principal motion filtering and image reconstruction, the dim moving object was detected. Finally, the proposed algorithm was applied to the dim moving object detection in the strong background noise. The simulation experiment results show the proposed algorithm can not only effectively detect the dim moving object but also have good signal-to-noise ratio of detection.
2013, 42(12): 3453-3457.
A new detecting algorithm based on gray-weighted kernel function was proposed to solve the proplem of low running rate and high false alarm within the moving target detection(MTD) in dynamic series of image. This algorithm firstly realized image sequence registration by using the biggest gradient block, then divided the image into 3232 sub-images. It could calculate gray-weighted kernel function for every sub-image and detect changing of gray-weighted kernel function by using Bhattacharyya coefficient as similarity principle for every sub-image. The moving target could be detected in sub-image which gray-weighted kernel function has changed. The testing result shows that the algorithm with batter performance of real-time and robustness can detect the moving target in real-time and suppress the influence due to image registration error and gray fluctuation effectively.
2013, 42(12): 3458-3463.
In order to improve the diagnosis accuracy of the transmission line defect, and reduce the influence on identifying the structure of the transmission line made by complicated background texture and light. Starting from Gestalt perception theory, a multiple perceptual identification method was developed to identify transmission line structure. Firstly, line with different directions and different width was extracted and sorted. Through a kind of multilevel searching algorithm with similarity, continuity and colinearity of Gestalt Law, the contour of transmission line was obtained accurately and completely. Secondly, a method based on block partition was developed, which can visually perceive near parallel lines and near symmetrical cross structure. A three level classifier for clustered parallel line group was designed. Lastly, combined with prior knowledge of the transmission line model, constraint mechanism was built to recognize the structure of transmission lines, and then uniquely identify the semantically structure of transmission lines. Experimental results show that the method can effectively identify the transmission line consisting of the tower, conductor, earth wire and the insulator region through recognition of the UAV inspection acquisition transmission line image.
2013, 42(12): 3464-3469.
Raman spectroscopic data often suffers from common problems of bands overlapping and random Gaussian noise. Spectral resolution can be improved by mathematically removing the effect of the instrument response function. In this paper, a novel method to deconvolute the degraded spectrum with the Laplacian-Markov priori was proposed, solving by split Bregman optimization scheme, which was fast, robust to noise and easy to implement. The Laplacian-Markov priori was proposed to save the shape peaks and suppress the noise. A data weighted operator was introduced to spectral deconvolution to find a balance between band narrowing and noise suppression. The method could estimate spectral structural details as well as suppress the noise effectively. Experimental results with real Raman spectra manifest that this algorithm can deconvolute the overlapping peaks as well as suppress the noise effectively. Owing to the fast of computing time, it is expected that the proposed method has considerable value in practice.
2013, 42(12): 3470-3474.
Digital micro mirror device(DMD) replacing the mobile mechanical template as the spatial light modulator is the new developmental direction of Hadamard transform spectroscopy. In the actual engineering design, the dispersed spectrum on Hadamard encoding mask cannot be encoded according to the S matrix perfectly, this phenomenon will bring errors to the spectral recovery. A method to correct the recovered spectral images with a series of stepping factors was proposed according to the different spatial positions of the pixels on the image. Different stepping factors were added to their corresponding encoding equations based on S-matrix. The experimental results show that the spectral images after correction are improved obviously.
2013, 42(12): 3475-3480.
The empirical mode decomposition(EMD) theory was applied and the features extraction method based on intrinsic mode function(IMF) was proposed in order to eliminate the errors of parameters estimation(such as covariance matrix) and retain the detail spectral information. The maximum value, minimum value and mean of hyperspectral data were calculated to estimate the IMF. IMF can express the spectral absorption features with different scales of hyperspectral data. The raw hyperspectral data was projected the IMF dimension to implement the spectral features extraction of hyperspectral data. The airborne hyperspectral data collected by push-broom hyperspectral imager(PHI) was applied to analyze and evaluate the performance of the proposed method. The results show that the effect of covariance singularity and inaccurate parameters estimation of hyperspectral data is avoided, the main and important information of data is retained and the classes' separability is increased.
2013, 42(12): 3481-3485.
In order to realize infrared image adaptive correction, a method to adaptive correct the non-uniformity(NU) based on wavelet transform histogram normalization was introduced. The new algorithm used the orthogonal wavelet transform to analyze image, calculated the decomposition image histogram of the neighborhood elements of a single pixel, got median histogram by sorting pixels neighborhood histogram and completed decomposition image non-uniformity correction using the mean histogram normalization. Finally, a final result in all scales after the correction by using the inverse wavelet transform was obtained. According to the practical application, this algorithm has the advantage of fast convergence speed and high precision.
2013, 42(12): 3486-3490.
Atmospheric turbulence is an important form of movement in the atmosphere, which makes the vertical and horizontal's exchange interaction of momentum, heat, water vapor and pollutants significantly enhanced, and this interference has a great impact on the target resolution of optical imaging system. There also have lucky regions in the degraded images because of turbulence, so the appropriate algorithm can obtain high resolution restored image. To obtain the atmospheric turbulence blurred images which contains lucky regions, the artificial turbulence was used in the laboratory and combined with the short-exposure technique to take a serial of atmospheric turbulence blurred images. The rectangle overlapped partition method was used and the image restoration algorithm was improved based on nonlinear partial-derivative equations(PDE's), to process the obtained short exposure serial images. The results show that, the image quality of the composite image is improved obviously, this algorithm has great restoration effect on images' quality degradation caused by atmospheric turbulence.
2013, 42(12): 3491-3495.
For SNR of sea-sky-line is low and there is a certain inclination so thay are difficult to extract, a new extraction algorithm was proposed. Firstly, the image preprocessing was taken by applying Laplacian template filtering to enhance waves on the surface, followed by order-statistics filters and morphologic closing. After the image preprocessing step, the SNR of sea-sky-line was enhanced. Finally, seeking for the inclined sea-sky-line by using a novel matrix, the matrix should be produced by scanning infrared image horizontally, the maximal element of the matrix identified the position and angle of the sea-sky-line. The experimental result shows that the method can locate sea-sky-line efficiently and correctly, requiring a few computation and be used for engineering applications. Innovations are the use of templates and morphological operators to improve SNR of sea-sky-line and find matrix can simply locate the position and angle of sea-sky-line, reducing the computational complexity.
2013, 42(12): 3496-3501.
For the rotation, translation, scale invariant properties of SIFT(Scale Invariant Feature Transform) feature, it has been widely applied in imaging matching. But there are two defects of using SIFT while matching. Firstly, the matching performance is directly affected by the matching parameters, and there is always mismatching and error matching existed. Secondly, it only fits for matching under similarity transformation, while at the affine transformation situation it fails. In this paper, a novel iterative matching algorithm based on transformation estimation was proposed. The SIFT matching problem was turned into an optimization problem about SIFT feature vector and the geometry distribution of the point sets. By searching for the affine transformation and correspondences under the iterative deterministic annealing frame, the algorithm got the optimal matching result of SIFT point sets. Experiment results show that even at large affine transformation, the algorithm can still get the right matching results.
2013, 42(12): 3502-3508.
Current algorithms of registration of aerial imagery with airborne LiDAR data has the major issue of strong dependency upon the matching feature, so these methods are impressionable to the texture feature of image and the density of LiDAR point cloud. A new method of auto-registration of aerial imagery with airborne LiDAR data based on structure feature was proposed. The first step was the automated extraction of structure feature from LiDAR range image and aerial imagery. After that the LiDAR structure features were projected onto aerial imagery and corresponding features were determined using geometry constraints. The second step was the wrong matches eliminating by two points geometric constraint after calculating the DLT parameters as the initial value, and iteration strategy was adopted to obtain optimal results. The last step was the pose parameters calculated by the optimal matching results using quaternion-based solution of space resection. Experimental studies have demonstrated that this algorithm is effective in auto-registration of aerial imagery with airborne LiDAR data and little influenced by noise.
2013, 42(12): 3509-3516.
PTZ(pan-tilt-zoom) cameras have been widely used in visual surveillance domain due to their ability to cover wide field of view and large scale range. For the large demand of intelligent visual surveillance, a novel multi-resolution active tracking method was presented based on two PTZ cameras. The proposed method consists of two stages: off-line calibration and on-line cooperative tracking. In off-line calibration stage, a novel method was presented that combines feature based single-PTZ camera self-calibration and object motion based dual-PTZ cameras self-calibration. The proposed approach doesn't require calibration tools and manual operation. Two important properties of proposed system were also inferred based on above calibration method. In on-line tracking stage, a piecewise cooperative tracking strategy was designed. The verification of proposed algorithm framework was implemented on real outdoor surveillance environment. Experimental results show that the proposed method can track the moving object effectively. The proposed framework can be used in intelligent visual surveillance with wide application prospect.
2013, 42(12): 3517-3521.
In order to solve the space registration problems of multi-sensor in the photoelectric theodolite measurement, a space registration model based on the extreme learning machine(ELM) algorithm was proposed in this paper. Firstly, the ELM theory and the modeling steps of ELM space registration model were introduced. Then, the star measurement data was used to build ELM space registration model. Finally, the ELM space registration model was compared with single error correction model and spherical harmonics correction model. Experimental results indicate that ELM space registration method can improve the measuring precision of photoelectrical theodolite from about 17 to less than 1; the accuracy of the ELM space registration model is improved by more than 35% than single error correction model and spherical harmonics correction model. The results indicate that compare with the single error correction model and spherical harmonics correction model, space registration model based on ELM algorithm has higher prediction accuracy and stronger generalization capability.
