2013 Vol. 42, No. 7
2013, 42(7): 1654-1659.
The operating range is an important parameter of the IR alarm system, and its value is decided by the characteristics of the alarm system, the target and the background. A research was done specially on the operating range of ground-based IR alarm system in clear sky. The traits of the transmission and radiation of the atmosphere were fully considered, and then the theoretic calculating model of the operating range was established. Combining the model and typical data, and considering the two situation of cover target and spot target, the effects of the atmosphere on the operating range were calculated for different target altitude and high angle. The results show that the target can be detected only when the target's high angle is larger than a certain value if the altitude of the target is fixed, and this angle decreases as the target attitude increases.
2013, 42(7): 1660-1664.
Passive ranging an aerocraft using its exhaust plume infrared radiation was studied. Exhaust system of an aircraft or a missile is the main infrared radiant point in 3-5 m wave-band. The infrared radiant characteristic of rectangular nozzle flame was calculated by modeling. The result shows that the infrared radiation intensity color ratio of an exhaust plume is same in different direction. When the infrared radiation transmitted in the atmosphere, it would be attenuated by the absorption and dispersion of the atmosphere. The attenuation was different according to different wavelength. The radiation intensity color ratio of different wavelength would change along with the change of transmission distance. The radiation intensity color ratio contains distance information. The relationship among the color ratio of exhaust plume and its temperature, its transmission distance, and atmosphere attenuation coefficient were deduced. The relationship between color ratio of an exhaust plume and its temperature was calculated. Infrared three color ratio ranging equations were deduced. The three wavelength of 4.5, 4.6, 4.7 mm was used to study passive ranging method. A ranging figure was drawn using the equations. The result shows that the method can be used to range an exhaust plume.
2013, 42(7): 1665-1668.
Stray radiation refers to the unwanted radiation reached on the detector surface in infrared detection system. Stray radiation will add the system's noise after photoelectric conversion, decrease the system's output signal-noise-ratio, and reduce the system's detection ability for space target. In order to improve the detection ability of infrared system for space dim and small target, the sources of stray radiation in infrared detection system were analyzed. The formula of the sun's incident angle on infrared detection system at certain geographic latitude and time was deduced. The equivalent number of noise electrons from the sun, sky and the infrared detection system's thermal radiation was calculated based on a typical system parameter. The noises arisen from stray radiation and detector's inherent noise were compared, the noises limit of infrared detection system was analyzed. Results prove that noise limit of infrared detection system is background noise after analysis of the system designed.
2013, 42(7): 1669-1673.
The advantages and disadvantages in nonuniformity correction(NUC) algorithms based on calibration and scene of infrared focal plane arrays(IRFPA) were analyzed separately. Firstly, according to the binary nonlinear nonuniformity theory model of IRFPA, a novel nonuniformity considering S curve correction method was proposed. Then, the original signal was captured using FLIR long-wavelength(8-14 microns) un-cooled infrared detector. And the response model of IRFPA was established. The algorithm flow based on FLIR long-wavelength un-cooled infrared detector with FPGA platform was described. The S curve correction method was implemented on the platform. By these ways, the whole infrared image quality was improved. The experimental results show that the fringe nonuniformity of infrared image is reduced after the S curve correction and the nonuniformity of IRFPA module is decreased from 6.45% to 2.06%.
2013, 42(7): 1674-1679.
As an important performance index of infrared warning-reconnaissance system, operating range was usually assessed by the dynamic flight test in open air range. However, the dynamic flight test merely evaluated operating range under the typical weather conditions. Because of this, an equivalent calculation method based on the digital image injection simulation test was proposed, which could evaluate the operating range of IR warning-reconnaissance system under different weather conditions. Then, the test mode of the digital image injection simulation named as film-replay was presented, the generation method of digital image using for the equivalent calculation of operating range was described in detail, and a simulation test instance was realized to prove the validity and precision of the digital image injection simulation method.
2013, 42(7): 1680-1684.
A design for integration of diode infrared detectors based on SOI and its readout interface circuit was presented for the low cost and high performance applications of uncooled infrared technology. Basic principle and fabrication technology of uncooled diode infrared detectors were elaborated. Through theoretical derivation of the electrical characteristics of detectors, circuit design specifications were given. The circuit used continuous time auto-zero technique to reduce offset voltage and suppress low frequency noise. It amplified the signals and cascaded a filter to decrease effects of non-ideal switches. Capacitors in chip were chosen to sample and hold, and as a result, the layout of the circuit had fewer I/O pads and smaller area. It was simulated using spectre tool and fabricated in CSMC 0.5 m 2P3M CMOS process. Experimental results show that this circuit has a good performance, achieving a closed-loop gain of 65.8 dB, equivalent input noise power spectral density of 450 nV/Hz, equivalent input offset voltage smaller than 100 V and power consumption of 5 mW, can accurately read out the outputs of detectors.
2013, 42(7): 1685-1690.
Aiming at developing a method for defects detection in heat-resistant alloy coating structure by pulsed infrared thermography, test was applied to heat-resistant alloy coating structure plates with blind-bottom holes, combining finite element simulation and experimental study. In order to provide a theoretical basis for the determination of sampling frequency and time in tests, finite element method was adopted to analyze the transfer process of heat pulse excited to the specimen. Flash lamps were used as active heat source into the sample, and the thermal-wave image sequences were collected with FLIR SC7000 infrared camera. Fitting-correlation algorithm(FCA), pulsed phase thermography(PPT) and principal component analysis(PCA) method were used to process the image sequences. Experimental results show that the SNR of processed images by PPT and PCA increases significantly under given test parameters, and can be used to detect the defects in heat-resistant alloy coating structure plates.
2013, 42(7): 1691-1699.
To deal with the low contrast infrared images in complex background for infrared imaging guidance, a new fast recursive method based on Kapur's maximum entropy threshold discriminant was presented, coarse-fine searching strategy with successive approximation was adopted to reduce the threshold searching area, and the best threshold was searched by pixel in the possible area. The analysis of the methods' complexity and the segmentation experiments of the real infrared images show that, Kapur's maximum entropy threshold discriminant is more suitable for low contrast infrared images' segmentation, the running time and memory cell needed by the presented method are all less than existing fast maximum entropy threshod recursive methods based on two-dimensional histogram vertical or oblique segmentation, the running time is about 14% of the original method. In the result image, the noise is less, the boundary is more elaborate and complete, the applicability is stronger. The presented method meets the engineering practical requirement of the infrared imaging guidance system.
2013, 42(7): 1748-1753.
In order to get high-magnification and large field of view in zoom system designing, adopts new methods in zoom lens designing with multiple moving lends groups. The design a kind of high-magnification continuous zoom lens, the systems adopts 5 moving lens groups has achieved the continuous zoom from 7 mm to 1 400 mm and the field of view from 0.25to 47.44. By choosing 10 positions of focal length for the design and calculation, The results show that this continuous zoom has the characteristics of high magnification and large field of view, and the imaging quality high.
2013, 42(7): 1754-1757.
In view of the characteristics of the imaging spectrometer, a telescope system applied to the imaging spectrometer was designed, which was composed of a pre-telescope and post spectrometer. Pre-telescope system parameters and imaging quality of the application of the imaging spectrometer is very important. Designed a spectral range of 1-2.5 m, field of view of 28.10.3, a relatively large diameter of 1/4, 60 mm focal length of the telescope system. Systems in a wide spectral 1-2.5 m spectral range by the glass and two matching spectral correction of chromatic aberration, distortion control at 0.2%, to ensure good follow-up spectroscopy with the butt, could be used for aviation the large field, high-resolution imaging.
2013, 42(7): 1758-1764.
For the requirements of performance testing and evaluation of IR guidence system which works in dual-bands of MW/LW, a DMD based dual-bands infrared scene simulation system was designed, including a projection lens and illumination optical system. The aberration characteristics and design methods of the IR dual-bands projection system with long exit pupil relief and back focal length were discussed. An inverted-telephoto structure with a harmony diffraction surface was used to solve the aberrations such as coma, astigmatism, distortion and chromatic aberration which were difficult to balance. In the design of the illumination system, directly irradiation combined with the Khler illumination principle was adopted to achieve a uniform illumination in the case of oblique incidence, also the improvement of light energy utilization and suppression of the stray light as well. The designed IR MW/LW scene simulator has a full field of view of 5, F# of 2.4, and exit pupil relief of 190 mm. The distortion of the lens is less than 0.1%. At the Nyquist frequency of 36 lp/mm, the modulation transfer function(MTF) is higher than 0.4 in the band of MWIR; at the intermediate frequency of 20 lp/mm, the MTF is higher than 0.38 in the band of LWIR, at every field of view. The relative illumination is higher than 98.5%, which meets the requirement of the scene simulation.
2013, 42(7): 1765-1769.
On the background of practical engineering application, comprehensive research on the effect of bending compliance and equivalent rotation radius dc with different cutout radius r and the minimum section thickness t of the single-axis circular flexure hinge, has been performed through Finite Element Analysis(FEA) by using tested material property. A simplified model which was used to calculate bending deformation of single-axis circular flexure hinge, had also been drawn from series analysis results study. A test setup had been constructed to verify the simplified model. And the difference between calculated value and tested result was within 10%, it indicates that the simplified model can satisfy engineering requirement. Based on the simplified model, a simplified model which was used to calculate deformation of two-axis flexure mirror support structure was proposed, and it can save lots of effort by using traditional theoretical model to design this kind of flexure mirror mount. This model acts as a good reference for the parameter design and size optimization of this kind of flexure mirror support structure.
2013, 42(7): 1770-1775.
Ion beam sputtering is one of the best important technologies for preparing Ta2O5 thin films. The correlation properties of Ta2O5 thin films and preparative parameters(substrate temperature, ion beam voltage, ion beam current and oxygen flow) were systemic researched by using the orthogonal experiment design method. The Ta2O5 thin films properties(refractive index, extinction coefficient, deposition rate, stress and inhomogeneity of refractive index) were studied. The refractive index, extinction coefficient, physical thickness and inhomogeneity of refractive index were measured by multiple wavelength curve-fitting method from the reflectance and transmittance of samples. The stress of thin film was measured by elastic deformation of thin film-substrate system. An experimental design strategy used substrate temperature, ion beam voltage, ion beam current, and oxygen flow as the variables. The experimental results indicate that the temperature of substrate is key influence parameter on Ta2O5 thin films properties and other preparative parameters are correlation with specific thin films properties. The results can be used to select the proper preparative parameters for preparing Ta2O5 thin films with different applications.
2013, 42(7): 1776-1782.
The mid-infrared atmospheric transmittance and the absolute deviation were calculated with three different HITRAN databases using LBL software. Results show that the average absolute deviation of HITRAN2k and HITRAN04 decreases with the increase of initial height, the absolute deviation of HITRAN2k and HITRAN04 increases as the resolution increases. The average absolute deviation of HITRAN04 was less than the HITRAN2k at the four initial height. For example, the maximum absolute deviation of HITRAN04 and HITRAN2k was 0.338 and 0.394 with 1 cm-1 spectral resolution only considering the absorption of CO2. The maximum absolute deviation of HITRAN04 and HITRAN2k was 0.950 and 0.936 with 0.1 cm-1 spectral resolution considering the absorption of all kinds molecules. The deviation caused by old versions of the database should be considered for calculating infrared atmospheric transmittance. The difference caused by different versions of the database and spectral resolution should be considered for calculating infrared atmospheric transmittance.
2013, 42(7): 1783-1787.
The parameters measurement method and operating principle of the conical scanning MWIR optical system were introduced. The adjustment methods of the measurement system were discussed, and the stray light analysis had been done by using the FRED software in allusion to the no ideal imaging. After analysis of the spread spot, the blur was introduced from the stray light of high reflection metal coating on pinhole substrate of infrared collimator. The stray light was restricted effectively by co-centered mica plate close to the substrate. In addition, if the infrared under tested correcting lens coating transmission was not high enough, there would be regular shape stray light at four corner of infrared detector. This kind of influence could be eliminated with image process program. Finally, the accuracy of the parameters measurement system for the conical scanning MWIR optical system was practical tested, and the results showed that the accuracy met the requirement.
2013, 42(7): 1788-1792.
It was necessary to use the Pulsed Laser Radar to measure the distance with the deep space target or space small target. When the distance varied from tens of kilometers to tens meters, the energy range that photoelectric detector received reaches above 60 dB. To assure the detector not saturated, the multiplex AGC(Automatic Gain Control) technology was required. Except for the electronics method, a method of adjusting aperture of receive optical automatically was put forward, which made the luminous flux of detector changes 2 times by adjustment of Motorized lens' aperture regulation ring step by step, which was driven by direct current motor. The driven and control circuits of motorized lens were designed and realized to adjust aperture, zoom and focusing through FPGA software. Optical path was established to calibrate the aperture. The result showed that aperture can be divided into 8 levels, which have good repetition characteristic. This make it is impossible to realize laser ranging with centimeter grade precision in the whole detecting field.
2013, 42(7): 1793-1797.
In order to solve stitching testing problem of large-diameter optical flat mirror, based on triangulation and least squares fitting, a reasonable stitching algorithms and mathematical models were established and relative program was written. With engineering examples, a rounded rectangle plane mirror of 612 mm180 mm was stitching measured with a 600 mm interferometer. In the testing, the relative position between the sub-apertures was determined based on the target, completing the alignment between the sub-apertures, and based on different mirror locations, the repeatability of stitching testing was verified with several experiments. The experimental results show that there is no trace in the stitching result and the relative deviation of the PV and RMS between the two experiments based on different mirror location are 2.07% and 0.52%. The stitching result is consistent and the reliability and accuracy of the stitching testing are verified.
2013, 42(7): 1798-1803.
In this paper, the Raman spectroscopy measurement system was presented, where Shell-isolated Nanoparticle Enhanced Raman Spectroscopy(SHINERS) technique was used to amplify the Raman signal. This technique used gold nanoparticles coated with a thin, uniform, fully enclosed and optically transparent shell of silica or alumina so that the gold core generated a large surface enhancement. Based on this technique, the hardware framework of this measurement system was mainly composed of double central control chips(ARM and DSP), a laser diode source, a spectrometer, a fiber probe and a nanoparticle giving device; and the software of this system can achieve the Raman spectrogram automatically. The giving device was used to spread the SHINERS particle into the samples for improving automation. The experiments were performed to detect the food added melamine and malachite green for verifying the effectiveness of SHINERS. The results show that the measurement system is of high detection sensitivity and short testing time effectively, which can be widely adopted in the rapid detection of trace substances in food safety.
2013, 42(7): 1804-1808.
In order to meet the requirements of the non-contact detection system's position detection accuracy which was applied to detect the movement characteristics of scanning mirror. The analysis on various error sources of the detection system was made and all the errors which affect the position detection accuracy of the scanning mirror were detailed. The mathematical model with errors was set up and the transferring coefficients of the error sources were calculated based on the coordinate transformation method and the relevant parameters of the system. According to the error transferring coefficients and the related data of the current processing and assembly, the calculation of error distribution was given with the Monte Carlo method. The results show that the current processing, assembly capacity can't meet the accuracy requirements of the system, and a new method of the error distribution based on the current detection was put forward. The scanning mirror position detection limits of error was better than 2.5. In order to realize the detection accuracy of the system requirements, the line laser was used as the light source, and the 0.5 Lycra theodolite and micrometer were applied to detect the assembly.
2013, 42(7): 1809-1814.
In order to solve high-speed data acquisition for rotating photoelectric encoder in the dynamic detection, the method of encoder angle data collection was proposed and the acquisition system of dynamic errors for absolute photoelectric encoder was designed. Firstly, it was proposed that the exact time of acquisition for error data was at the edge of data by the analysis of the exact time for the output of encoder. Secondly, the circuit was designed with FPGA and USB chips by the analysis of quantity, acquisition speed and transmission speed of error data. Finally, the computer software finished the calculation, displaying and printing. By the results of experiment, the system can collect the error data of rapid rotating encoder accurately, meanwhile suited for the detection of the dynamic characteristics for small absolute optical encoder. This system can achieve the data acquisition of 16 bits photoelectric encoder below the speed of 90 r/min accurately.
2013, 42(7): 1882-1889.
MIMO technology has been intensively studied in RF communications, enable space as a kind of resources that can be used in improving communication performance. There are lot of differences between wireless optical communication and RF communication, such as modulation/demodulation method and channel characteristics. The research progress of wireless optical MIMO technology at domestic and abroad was reviewed, a detail analysis of the background of the wireless optical MIMO was carried out. The effects of MIMO inhibits atmospheric turbulence was illustrated by the experiment at last. The results show that the wireless optical MIMO not only make the space as a kind of resources that can be improve the capacity of wireless optical communication channel, but also inhibit atmospheric turbulence effect, expanded field of wireless optical communication applications.
2013, 42(7): 1890-1895.
The coaxial two-mirror reflective telescope was usually used within a typical satellite laser communication terminal, which has the disadvantage of small field of view and low emission efficiency. In order to eliminate the inherent defects of the existing coaxial two-mirror reflective telescope, and improve the pointing and tracking efficiency of the satellite laser communication system, off-axis three-reflective optical telescope was designed for satellite laser communication terminal. The initial structure of the off-axis telescope was deduced according to the basic aberration theory, and the off-axis three-mirror reflective telescope with more lager field of view and higher efficiency was given. Simulation results of modulate transfer function, spot diagram, diffraction encircled energy and wavefront error all show that the off-axis three mirror reflective structure has the better performance compared with the coaxial two-mirror reflective structure, and meets the increasing design requirements of satellite laser communication system.
A location method based on the extended Lissajous figure was proposed for fiber-optic distributed disturbance sensor based on Mach-Zehnder interferometer. The disturbance was located by the fiber-optic distributed disturbance sensor due to the time delay between the two signals from clockwise and counter- clockwise Mach-Zehnder interferometer. In the Lissajous figure of the two signals, a fitting ellipse with constant semimajor and azimuths was induced to evaluate the time delay. The relationship between the time delay and semiminor of the ellipse was obtained by linear fitting. Then, the time delay could be calculated by the semiminor of the fitting ellipse. By the simulation with experimental data and experimental test, it is found that the proposed lower location errors can be obtained by the location method than current cross correlation function based method without phase generation carrier technique.
2013, 42(7): 1902-1906.
Four-quadrant detectors is widely used in the align process in the space lase communications. However, its adverse effects, such as deformation and spot broken, caused by the atmospheric turbulence, appear while the laser beam go through the atmosphere, which severely limits the alignment accuracy of the four-quadrant devices. Since four-quadrant detectors provide less message then the CCD, it's difficult to suppress the influence generated from the atmosphere. In this paper, a optical axis alignment method was proposed based on the four-quadrant detector. The value of the output miss distance of the four-quadrant detector for a certain time was calculated, the original formula was weighted by using the entropy that computing the entropy from the distribution probability of each quadrants. By taking advantage of the high frame rate of the quadrant detector, insufficient information was made up for to suppress the effect of the atmospheric turbulence, an experimental platform was set up, and a certain effect was achieved.
2013, 42(7): 1907-1911.
In this article Zernike polynomials was used to produce atmospheric turbulence phase screen. Besides, the atmospheric coherence length and the phase structure function were used to verify whether the atmospheric turbulence phase screen is right or not. Simulation results show that, in the low spatial frequency components, the atmospheric turbulence phase screen generated with Zernike polynomial method was consistent with the theoretical values, but in the high spatial frequency components, the simulation results had big difference with the theoretical values. This is because Zernike polynomials method has inherent limitations. In addition, the simulation results also show that, the distribution of turbulence in the atmospheric turbulence phase screen can be changed by increasing the Zernike polynomials of orders or changing the receiving apertures, but which involves great and complex calculation. Therefore, in the specific application of the laser communication system, the best experimental program should be considered.
2013, 42(7): 1912-1922.
The state estimation for boost phase is an important issue in the missile defense program, both the target state estimate and the associated error covariance are cuing information for radar in BMD program. In the condition of the space-based observations, the state estimation is the solution of the nonlinear LSE problem. Firstly, the dynamic model for the boost phase based on the net acceleration profile was established. The major difficulties of this problem include the ill-conditioning of the estimation problem due to poor observability of the target motion via LOS measurements, the estimation of the unknown launch time, and the incorporation of inaccurate target thrust profiles to model the target dynamics during the boost phase. Considering the complications mentioned above, a maximum likelihood (ML) estimator based on the Levenberg-Marquardt algorithm that provides both the target state estimate and the associated error covariance was presented. Specially, the explicit derivation of the state estimation under three cases were deduced, and its application conditions were illuminated. Finally, Monte Carlo simulation studies on two typical scenarios were performed. The results indicate that the estimated errors are closed to the CRLB, thus illustrating that the proposed estimator is efficient.
2013, 42(7): 1923-1927.
Single-point noise(SPN) and stripe non-uniformity (SNU) noise are two typical noises in infrared star map of daytime star observation, which seriously affect subsequent processing of star recognition. Considering the causes and characteristics of the two noises, an improved SPN denoising algorithm was proposed to denoise SPN. The full map was scanned by a local window to detect SPN, and the SPN was instead by global mean value. And a colum histogram offset correction (CHOC) algorithm was proposed to denoise SNU noise. According to the colum offset correction model, the offset of histogram peak position between colum histogram and global histogram was corrected. Experimental results indicate that the algorithms proposed could achieve good denoising effects with infrared star map, and the peak signal-to-noise ratio of star point target could be raised from 7.4 to 12.8, meanwhile, the algorithms could finish in one frame time with low computation complexity, so the algorithms meet the requirements of real-time star map preprocessing application.
2013, 42(7): 1928-1932.
The column fixed pattern noise(CFPN) of the CMOS image sensors have severe influence on image quality. A column fixed pattern noise correction method for CMOS image sensors was proposed based on the analysis of emerge mechanism, noise characteristic and the behavior in the output image of the fixed pattern noise. It sampled the uniform and parallel light source which radiated from a integrating sphere more times use a CMOS image acquiring system and then estimated the column fixed pattern noise using these images. Then, the estimation result was used to correct the column fixed pattern noise in the CMOS image acquisition system. Experimental results show that with this method, the fixed pattern noise can be effectively reduced and the quality of the image can be increased.
2013, 42(7): 1933-1939.
All of self-check figures are almost digital ones which can only test the FPGA component and image data transmitting component on the digital path and the video AD component is not tested because the complexity cannot satisfy the high reliability demands in space projects. A kind of circuit composed of the driving chip and the DAC chip was put forward. This circuit can generate analog signals which are similar to CCD video signals and make these signals directly couple with actual CCD signals into the input port of video AD. The key part was made up of a FPGA chip and a driver chip-EL7156. The FPGA chip generated the signals whose frequency was same as CCD video signals and then sends to the driver as logical input. The driver chip can switch low or high level according to the logical input. The low level was supplied by a DAC chip which is controlled by FPGA. When CCD circuit was working, FPGA can make the analog self-check circuit into three-state and have no effect to CCD work. Many experiments' results indicate that the analog self-check circuit and the CCD video circuit can work separately in different time with no interference.
2013, 42(7): 1940-1944.
In recent years, the use of unmanned aerial vehicle(UAV) for power transmission line detection is a hot technology, and it can detect the transmission line and discriminate the failure without power off. According to the features of power transmission line equipments, a method of equipments recognition based on image processing and pattern recognition was put forward. It preprocessed the aerial images by median filtering, dilating and eroding. Then, wavelet eigenvalues of preprocessed images were calculated. Finally, the objects, such as insulator, vibration damper and transmission tower, were classified and recognized by affinity propagation(AP) clustering algorithm. The results of experiments show that this method can recognize the insulator, vibration damper and transmission tower, and it has better robustness, accuracy and validity.
2013, 42(7): 1945-1949.
2-D microwave imaging is an effect method to diagnose the amplitude and spatial distribution of radar scatters. Conformal antenna as a part of plane-skin, its radar cross section (RCS) can not be measured by general RCS measurement method. A new method was presented to extract the scattering characteristic of conformal antenna from 2-D microwave image of target, by spectrum transforming from 2-D image domain to 2-D spatial spectrum domain, spatial spectrum information of conformal antenna can be extracted, and scattering characteristic of target at certain frequency and angle can be gained by interpolating data form descartes coordinate system to polar coordinate system. The same processing to a reference sphere, by scale calibrating, then the RCS of conformal antenna can be achieved accurately. Experiment results show that the method is effective.
2013, 42(7): 1700-1705,1753.
An optic-electronic disturbance experiment was done since there is no same proportion long distance experiment validation in the mid-infrared optic-electronic disturbance research currently. The laser power was 10 W, the wavelength was 5.4 m, the camera of mid-infrared wavelength with the disturbance distance of 15 km was disturbed by the mid-infrared laser in this experiment. Many group experiments were done under some different conditions. A lot of laser disturbance image under the conditions were gained. The laser power density could be calculated using the data. The camera would not distill aim when the laser power being 5.6 W from these images, in this condition the radiation angle of the laser was 15 mrad, the distance between the laser and camera was 15 km, the focus of the mid-infrared camera was 384 mm, the visibility was 0.452 and the power density was 0.064 mW/m2. This experiment can validate the 15 km long distance mid-infrared laser disturbance to missile camera system being coming true using now domestic mature technology. These experiment data can sustain the adding research about the parameter in reversing deducing and confirm in exactitude atmosphere permeation rate mode and mid-infrared optic-electronic confrontation evaluation mode.
2013, 42(7): 1706-1709.
With advanced minute time interval measurement chip TDC-GP21 which is an application specific integrated circuit(ASIC), a high precision pulse laser ranging finder system was designed and achieved in this paper. Meanwhile, the workflow chart and external circuits were discussed. Optical signal receiving and amplifying circuit were also studied; the basic theory of transimpendance amplifier was also discussed and analyzed in detail. Further more, the method of triangle wave fixed propagation delay was put forward for time distinction which could greatly reduce the requirements of echo signal amplitude. That was pretty important to laser ranger finder. The results of the experiment prove that a centimeter accuracy system can be achieved with the above technology. At last, the pulse laser ranging system with small size which is easy to acquire has really simple structure and can achieve high degree accuracy which meets high precision laser distance measurement requirement with low power consumption and cost.
2013, 42(7): 1710-1715.
In order to solve the problem of the high-repetition- frequency laser jamming effect, experiments of the high-repetition-frequency laser jamming the real laser seeker was designed, models of the jamming effect based on measured data were built. By comparing the different working state between experimental condition and mathematical simulation scenario, the reliability of the model was verified. The effect of the guidance signal on the different laser spot size and energy distribution, the different angle between incident ray and seeker axis, and the different received energy density was studied. By using Monte Carlo method, the laser guided bomb trajectory was simulated under the high-repetition-frequency laser bait jamming and disturbing jamming, the impact point distribution was analyzed.
2013, 42(7): 1716-1719.
Anti-interference of cloud and smoke is a hard problem for laser fuse. In this paper, a technology of polarization dection was presented based on the polarization degree difference in reflection of artificial entity targets and backscattering of smoke. The backscattering signal received by laser fuse was redused selectively as the extinction effect on smoke backscattering signal was much larger than the target reflection signal. The detection probability calculated theoreticaly has been reduced to 0.4% of the original detection system by using the principle of threshold detection and detection probability curve. Finally, analysis shows that the system was expected to be a new anti-interference method since it can not only detect the target but also reduce the detection probability of the smoke significantly according to the experience in engineering development.
2013, 42(7): 1720-1724.
An all-fiber coherent Doppler lidar was developed, and had been applied to XXX project as a test prototype. Concept of this lidar, which could detect long-distance wind speed, was using eye-safety wavelength, compact-designed and reliable performance. By wind retrieval algorithm based on VAD, the velocity precision of coherent wind lidar was analyzed firstly. To evaluate its performances, this lidar was compared with an ultrasonic wind direction located at the top of the tower(103 m height) and a air exploration balloon. The lidar and ultrasonic wind direction measured wind field distribution simultaneously. Measured data were compared and analyzed, which include velocity data and wind direction data. Data correlation of measured velocity was about 95%, and standard deviation was about 0.8 m/s. Data correlation of measured wind direction was about 98.6%, and standard deviation was about 5. The results can correspond to the abroad level, which means the lidar has excellent performance and will be one of the widely-used sensors for wind detection instruments in the near future.
2013, 42(7): 1725-1729.
One of the greatest drawbacks of range-gated laser active imaging system lies in the plight that the two-dimensional slice could not provide complete spatial information on some remote objects. Aiming at this problem, a three-dimensional reconstruction method that combines the threshold method to cut off the measured gray-scale curve and cross-correlation method to draw range information and could provide relatively high precision was proposed. In the paper, threshold method was firstly utilized to remove the zero points from the measured gray-scale curve to mitigate the following effect on the distance computation that adopts cross-correlation method. Correlate the interceptive measured gray-scale curve of every pixel and the ideal gray-scale curve, the distance of each pixel with the time delay corresponding to the peak value could be deduced and the three-dimensional coordinates of each pixel with the combination of the system parameters were computed. Finally, the three-dimensional reconstruction of the arbor from 1.2 km could be obtained with the procession of the slices.
2013, 42(7): 1730-1736.
In order to study the polarization properties of scattered light from far ship wakes, the polarized Monte Carlo program for light propagation was used to simulate the 2-dimensional spatial distributions of degree of polarization(DOP) of ship wakes with different polarized incident lights. Radial distributions of DOP of scattered light from far ship wakes were analyzed with different bubble radius, scattering coefficients and thicknesses of bubbles film. The results show that spatial distributions of DOP have the properties of azimuth selecting which decreases with the increase of bubble radius, and the difference could be observed with different polarization states of the incident light. Besides, DOP of forward scattering light of ship wakes decreases with the increase of the scattering coefficients and thicknesses of bubble film.
2013, 42(7): 1737-1742.
Due to the non-linear and non-stationary characteristics of laser gyro drift time series, it can not be predicted precisely by single forecasting model. A hybrid multi-scale modeling method based on empirical mode decomposition (EMD) and least squares support vector machines(LSSVM) was proposed, and its application in drift forecasting of laser gyro was also studied. Firstly, the drift data was decomposed into a series of intrinsic mode function via empirical mode decomposition. Secondly, Least Squares Support Vector Machines predicting models with appropriate kernel functions were constructed to predict each intrinsic mode function respectively. Thirdly, output of each predicting model were equally weighted and integrated into one output. In the end, the proposed method was used for laser gyro drift prediction. The experimental results show that the proposed prediction method which is capable of forecasting drift data precisely outperforms single Least Squares Support Vector Machines method, and can provide reference for drift compensation, fault prediction and reliability diagnoses of laser gyro.
2013, 42(7): 1743-1747.
Many fundamental progress and applications of metamaterials in millimeter wave or microwave have been found, but it is still important to design the metamaterials device in the terahertz frequency regime to fill THz-gap in future. Four subwavelength split-ring resonators(SRRs) were designed and fabricated in the terahertz frequency regime, and the transmission properties of four metamaterials was simulated by CST Studio, which can be used to analyze the resonance frequency. The power transmission properties of the devices in the frequency ranging from 1.04 THz to 4.25 THz were investigated by continuous waves terahertz lasers, the measured results revealed a total transmission peak at 2.52 THz and several local transmission peaks. The total transmission peak was related to the microstructures and electronic configurations of specific SRR arrays. In order to find a best SRR array for terahertz sensing with relatively high transmission efficiency, the normalized power transmission performances and sensing differences of four types of metamaterials microstructures were compared.
2013, 42(7): 1815-1818.
The performance of InSb detectors with anodic oxide and photo-CVD oxide had been compared in this paper. It showed that leak current of detectosr with anodic oxide was less than those with photo-CVD oxide,and breakage voltage of the former detectors was as much as 5 times of the latter ones, but the photocurrent and impedance of the former ones was the same as the latter.The results of capacitance-voltage(C-V) characteristics showed that fixed charge density of the anodic detectors was 21011 cm-2, and the latter was 1.51011 cm-2. After ageing experiment, when inversion bias was 1 V, the change rate of leak current ratio of the former was only 50% of the latter, while the photocurrent of detectors with both methods increase,which was possible related to photosensitive area's expansion.The anodic oxide passivation of detector had the three advantage of the process control, the fabricate uniformity and the stability of interface state.
2013, 42(7): 1819-1824.
In order to perfect the theoretical basis of Multi-Pixel Photon Counter(MPPC) serving as the detector of laser ranging or laser radar, the detection and false-alarm probability of MPPC were studied in this paper. The model of the detection and false-alarm probability based on MPPC was proposed and the analytical expressions were derived by using Poisson theory. The numerical analysis was also done. Some interesting characteristics were found which were not existed in conventional single point detectors. The numerical results show that the system requirements of laser ranging can be obtained just by adjusting the photoelectron equivalent threshold of MPPC, without the gating technology, if using MPPC as the detector. The sensitivity can reach the photon level and the photon number can be resolved. This model and results have certain significance in theory and to promote the application of MPPC in laser range and laser radar for high sensitivity and fast detection.
2013, 42(7): 1825-1829.
In order to improve the resolution and interpolation precision of the small photoelectric encoder without increment of size and weight, some research has been carried out on the high-resolution interpolation method. Firstly, main factors which affected the resolution and interpolation precision of the small photoelectric encoder were analyzed, and then the analog-to-digital conversion gain error and imbalance error were calibrated by microcontroller of ADuC841. Finally, the electronic interpolation algorithm was optimized, and a small photoelectric encoder signal processing circuit with high interpolation precision was designed. Experimental results showed that precise code signal interpolation of 1 024 parts of the encoder could be realized with this design, and peak-to-peak value of the interpolation cycle error could be reduced from 163 to 70. The resolution of the small photoelectric encoder with an exterior diameter of 40 mm could be improved by 4 times up to 4.98, and its precision could be improved to 30. The method improves the resolution and interpolation precision of the encoder.Because of its simple circuit structure and high resolution interpolation the method could be applied to absolute and incremental photoelectric encoders with the limitation of size and weight.
2013, 42(7): 1830-1834.
As an important parameter affecting the isolation of seeker,disturbance torque had an important effect on guidance system, so it was demanded to reduce the disturbance torque's effect on designing of fast guidance system. According to the nonlinear and nonsteady characteristics of the disturbance torque,modeling errors of stabilized platform and guidance-loop constrains, a control method of disturbance torque adaptive compensation was proposed. The design ideas were as follows: band constraints of disturbance rejection rate obtained from guidance precision analysis, and scroll friction(dominant term of the disturbance torque) was estimated by use of state filtering and a nondestructive dither signal addition on guidance command, then, bandpass filtering and state feedback were used to compensate for unwanted disturbance torque effects. The simulation results show that, the estimation accuracy and rapidity of scroll friction coefficient can meet guidance system's demand under the condition of parameter perturbation, and the adaptive compensation method presented can be applied to more realistic case where cross-coupling effects are important.
2013, 42(7): 1835-1841.
Based on a numerical solution involving time-dependent imposed square voltage pulse and time-dependent thermal boundary conditions, the transient supercooling behavior was theoretically analyzed, as well as the response to the pulse operation parameters during the periods of pulse start-up, pulse-on time and pulse-off time, which was served as a theoretical basis for exploiting the coupling interaction of the thermoelectric effects(Peltier cooling effect, Joule heating effect and Fourier thermal effect) on the heat diffusion in the short time scale. The results indicate that, the transient thermoelectric supercooling effect can be enhanced by keeping on increasing the Peltier cooling effect as the additional cooling capacity for a period long enough against the earlier arrival of the excessively the Joule heating effect and Fourier heat conduction effect arriving at the cold junction, in which a transient cold spike can be produced by superimposing an additional shaped voltage pulse of the reasonable range on the original steady-state optimum value. The discussions may not only facilitate to put forward the theory basis for the optimization control strategy on pulse mode, but also develop a new method of transient supercooling effect for application in TE devices.
2013, 42(7): 1842-1847.
The internal structure and work patterns of the surface array CCD485, were described and the basic drive circuit design was given. And then through the array CCD485 drive timing diagram analysis, based on the timing segments and the general purpose of the finite state machinetype full frame area array CCD drive timing generator, the grouping method by the CCD drive timing, the timing waveforms of each group was divided into a number of basic output state, so that the drive timing of the CCD for each session canby combination of the basic state, and Moore finite state machine to describe the timing-driven modular design. The specific design of each module was given, the timing generator of the design process easier, and finally using Xilinx Virtex-Ⅱ Pro series FPGA-XC2VP20 and Xilinx's ISE software platform, CCD drive timing generator was designed, and simulation waveform analysis was completed. The output meet the timing requirements of 485-chip driver, the effectiveness of the design method is proven.
2013, 42(7): 1848-1852.
The color controlling method and its realization of single DMD colorized video displaying system were studied in detail. Based on analyzing the advantages and shortcomings of three types of DMD projection system, spatial gray-level modulation and temporal gray-level modulation, one single DMD colorized video displaying system was proposed. The color controlling method based on pulse selection gray-level modulation was analyzed deeply. In this method, the frame-period was evenly divided into R, G, B section, and each of the R, G, B sections was divided proportionally to be some bit-time sections. In every bit-time section, the status of micromirror in DMD was controlled according to the bit value of corresponding pixel gray-level. Considering that the data sent to DMD was the bit-plane data of video pixels, the format conversion from image gray-value to bit-plane data was analyzed in detail. At last, considering the feature of DMD, the operating scheduling was given. The whole scheme is doable. The analysis could provide academic basis for the realization of the system.
2013, 42(7): 1853-1857.
This paper proposed a novel method for investigating the characteristics of an electrically tunable liquid crystal(LC) Fabry-Perot(FP) hyperspectral imaging detectors. The device would be used to sequentially choose the specific wavelength in the range of 3 to 5. Based on the method proposed that the directing vector of liquid crystal materials would be changed in an electric field applied over the electrodes of the device, the refractive index of the FP cavity filled by LC film could be changed electrically. Through the thin film matrix equation, we calculated the transmissivity of the infrared light incident upon the photosensitive plane directly, and then obtained the relationship among the transmissivity, the applied voltage signal, and the wavelength value selected. The most key features of the proposal approach was that the device will be composed of main very thin electrically refractive-index parts, which are two FP interferometers connected closely so as to accurately perform the choice of each single wavelength desired in the spectral range by the device developed.
2013, 42(7): 1858-1862.
Compared with spectral imager based on the flat or concave grating, the Offner spectral imager which utilizes convex grating as the diffractive element has several advantages, such as large numerical aperture, no Smile, small spectral Keystone, compact volume, easy manufacturing and alignment, etc. Consequently, it's becoming widely applied in many fields. In order to meet the requirements of highly integrated, broad working spectrum and miniaturized payload for deep space exploration mission, in this article, an Offner spectral imager with dualband was designed. At the same time, a neatly spectral splitting method using different part of grating was implemented. The system which met the design requirements had fine image quality, small volume and compact configuration. All reflective curves of the optics were designed sphere, which had loose tolerance and were convenient for manufacturing and alignment. The convex grating was framed and its diffraction efficiency was analyzed. The result shows that the dynamic range of the whole system can be enlarged effectively using the elaborate design.
2013, 42(7): 1863-1865.
The high-qualified optical systems which are used in imaging spectrometers must have some advantages, such as large linear FOV, large relative aperture, wide-spectral imaging, light weighted, etc, which makes the off-axis all reflective optical systems an important research direction in this field. A method for the design of off-axial reflective 3-mirror optical system with large linear field of view(FOV) and large relative aperture was described in this paper. The method was based on the 3rd-order aberration theory. After the constrained optimization of a set of Seidel aberration coefficient functions, the designer could achieve the initial construction parameters of the optical system, i. e. the radii and separations of lenses. And during the designing process, decenters and tilts of mirrors were adjusted continuously to eliminate the obscurations under the premise of assurance of image quality. In the end, the design results were given, and the MTF curves prove the feasibility of this method.
2013, 42(7): 1866-1870.
In order to solve the problem that classical mutual information images registration may lead to local extremum, a new matching algorithm combining the bilateral filter and cross accumulated residual entropy combination was proposed in multispectral image registration. In this algorithm, firstly, according to multispectral images characteristics, bilateral filter edge extraction algorithm was put forward based on the probability density. Secondly, cross cumulative residual entropy(CCRE) was used as the similarity measure to match the reference images and transformed images effectively. Bilateral filter is an edge-preserving and noise reducing smoothing filter, and CCRE is more general than Shannon Entropy. This function can effectively avoid the emergence of the local extremum, overcome noise influence on the the local extremum. Experimental results proved that the registration had good robustness, the effect was obvious.
2013, 42(7): 1871-1881.
Field imaging spectrometer can be used to analyze growth information of individual and group crop relying on its data advantage with combination image and spectra as one, so it has great application potential in agricultural quantitative research. In this research, hyperspectral images of corn and soybean in different growth period were collect using visible and near-infrared imaging spectrometer (VNIS), and spectra of four components as illuminated soil, shadow soil, illuminated vegetation and shadow vegetation were gradually extracted, then spectral vegetation index was constructed based on different sensitive bands. On the basis, through analyzing bands correlation between chlorophyll density and spectral vegetation index, those influences for different components on chlorophyll density inversion of crop were explored. Some results can be found that when spectral information came from mixed canopy including vegetation and soil, sensitive bands for chlorophyll density were red light and near-infrared light. When soil spectra was removed, sensitive bands enlarged and showed in blue and green light region, and when spectra of shadow leaves were removed, sensitive bands indicated that visible light bands increased and near-infrared light bands decreased, there was the highest determination coefficient in red light region. Those change characteristics had same trend in different crops, this paper has important meaning for exploring inversion of biochemistry parameters on crop using data with combination image and spectra as one.
