2014 Vol. 43, No. 1
2014, 43(1): 1-5.
In infrared detection systems, when the target signal is relatively weak, the noise caused by a spot of stray light will greatly reduce the SNR of system, thus reduce the system's detection capability. For highly sensitive infrared imaging system and low temperature environment simulation system, the thermal radiation emitted from the optical surfaces is the largest source of stray light. In this paper, the certainty and near-field property of self-emitted thermal radiation stray light were analyzed, and a new computational model based on ray optics was proposed. Some key problems in the calculation model were discussed, the solutions were proposed. Moreover, the near-field thermal radiation of objects was accurately numerical simulated. Distribution of irradiance on the detector was gained, the effects of temperature, distance, radiation coefficient and other parameters on the stray light level were analyzed, which has a guiding significance on reducing the system' s thermal radiation noise reasonably and efficiently.
2014, 43(1): 48-52.
In order to solve the problem of automatic selection of tracking point in target tracking after automatic target recognition of IR warship targets in the infrared imaging and tracking systems, a new automatic detection algorithm of ship aimpoint was proposed. Based on the waterline' s geometrical relationship below the warship and the high brightness characteristics of engine compartment, the cross part of the waterline and engine compartment was detected. This cross part was taken as the primary aimpoint of IR warship target. Otherwise, the central part of the waterline would be taken as the aim point of IR warship target. First of all, the de-noising pretreatment of target area was used, through the Canny egde-detection, edge closed and two connected domain de-noising operations, the background texture clutter was removed to determine the edge of target. Then, piecewise linear fitting on the target bottom edge was used and the curve fitting results would be taken as the waterline. Finally, the gray In order to solve the problem of automatic selection of tracking point in target tracking after automatic target recognition of IR warship targets in the infrared imaging and tracking systems, a new automatic detection algorithm of ship aimpoint was proposed. Based on the waterline' s geometrical relationship below the warship and the high brightness characteristics of engine compartment, the cross part of the waterline and engine compartment was detected. This cross part was taken as the primary aimpoint of IR warship target. Otherwise, the central part of the waterline would be taken as the aim point of IR warship target. First of all, the de-noising pretreatment of target area was used, through the Canny egde-detection, edge closed and two connected domain de-noising operations, the background texture clutter was removed to determine the edge of target. Then, piecewise linear fitting on the target bottom edge was used and the curve fitting results would be taken as the waterline. Finally, the gray value statistics was calculated to get the brightest area as the position of engine compartment. The experimental results show that this method has stability testing results and good robustness. It can be applied to detect the aim point of IR warship target in different viewing directions. The algorithm provides an effective solution for the problem of automatic selection of tracking point in target tracking.
2014, 43(1): 6-12.
Practical ways of modeling aerodynamic heating under supersonic flight conditions, flow and heat transfer inside aero-engine nacelle, and plume heating on the rear fuselage of aircraft were introduced for simulating the aircraft skin temperature distributions. Infrared radiation characteristics in 8-14 m band of skin and engine wall was studied by numerical calculation method. Contribution of head, fuselage (including inlet entrance), wing, engine compartment (including rear fuselage), vertical stabilizer, horizontal stabilizer and engine nozzle cavity to infrared radiation were analyzed. The results show that skin infrared radiation is the major component of the infrared radiation in 8-14 m band and the infrared radiation of the engine wall is mainly focused on the aircraft tail in the visual range of 50. The individual infrared radiation of skin compartment takes different proportion of total infrared radiation in different observation plane. The main sources of infrared radiation are aircraft body, wing, aero- engine nacelle and upward vertical tail. Aerodynamic heating effect is exacerbated with the rising of flight Mach number, as a result of which proportion of each part of the aircraft infrared radiation changed.
2014, 43(1): 13-18.
In recent infrared warning experiments, an abnormal phenomena was discovered in which the target radiance increased with the active range. In this paper, how to solve the problem was discussed. Based on the theory of radiance detection equation and by the atmospheric radiance software LOWTRAN, a particular analysis was given about the factors affecting the infrared warning such as the infrared radiant characteristics of the target, the atmospheric irradiancy of the sky background, the irradiancy and the transmittance of the atmospheric path, the detection range, the effective area of the target facing the detector, and the principle. As a result, with the active range increased, the increment of the background radiance was dominant in all influenced factors, so the target radiance was larger and larger. Through the discussion, the abnormal phenomena were interpreted reasonably, and the conclusion was of great significance to develop the algorithm of target extraction for the infrared detective and tracking systems.
2014, 43(1): 19-25.
Based on split-type Sagnac interferometer, principles of static high-flux interferential imaging spectroscopy were introduced. Equal-ratio depolarizing beam-splitting films working in long-wave infrared were designed and achieved. Design methods of interferometer sizes were given, and interferential light path was verified through TracePro software. By utilizing cryogenic and noncryogenic detectors, the project of infrared interferometer imaging spectrometer was tested with a plastic film transmittance. Measured values from the test turned out to be highly matching with those of high precise Michelson spectrometer, which verified the accuracy of that project. In the end, methods about data rearrangement, baseline correction and apodization were given to preprocess data from push-broom experiment. The results, in turn, verified the feasibility of that systematic working mode.
2014, 43(1): 26-32.
Since the advent of the first infrared guidance system, its excellent properties countries have invested a lot of effort to study the infrared guidance technology. After the rapid development of three generations of the detector type changing, it has made a lot of sophisticated applications. The past 20 years, the application of imaging infrared seeker technology -infrared imaging guided weapons, wars abroad have played a decisive role. And with the scientific and technological progresses and changes in battlefield needs, infrared imaging technology is faced new opportunities and challenges. In this article, the course of development of IR imaging guidance technology and weapons was described, and the characteristics and development trend of IR imaging guidance technology in modern war was discussed. Finally, the summary of the status and expectations was elaborated.
2014, 43(1): 33-38.
In order to research the desired imaging spatial resolution of IR targets under different discrimination levels, including detection, recognition, and identification, a new method based on feature entropy, which is used to estimate IR imaging operating spatial resolution, was proposed. Firstly, IR target images under different resolution grades were obtained by down sampling. Secondly, IR target features extracted, including texture, shape and global statistical features, were normalized to the corresponding feature spaces to obtain the feature histograms. Thirdly, feature entropies of IR targets were calculated in order to measure the information of targets. Finally, according to the set thresholds, the desired lowest imaging spatial resolutions of IR targets under different discrimination levels were obtained, and taking the computer simulated IR targets for example, the presented method was demonstrated. The experiment results show that the conclusions are in good agreement with identification results, which can provide reference for optimization design and analysis of the infrared recognition system.
2014, 43(1): 39-47.
Since the low contrast and lack of details in infrared imagery, a polarization imaging based enhancement method was proposed. Fusing the infrared polarization image and intensity image, this infrared image enhancement approach made the target areas prominent. Firstly, the polarization imaging theory was analyzed, and then polarization images were obtained using the polarization imaging technology. Secondly, the information of polarization images could be well acquired with the help of Shearlets based multi-scale image decomposition. Finally, the enhanced fused result was got with region feature matching. To test the effectiveness of this method, experimental device was built to get real images. Compared with original image, both the subjective and objective evaluation results indicate that the enhanced images have much more image details and polarization information, which is useful for target detection and recognition.
2014, 43(1): 53-60.
Based on CFD/IR numerical calculations, the temperature distribution of rotor skin and the effect on the infrared radiation characteristics of helicopter were studied systematically. The results show that: (1) The temperature distribution on the rotor blades shows an increasing tendency from the rotor shaft to wingtip, the maximum temperature is 316 K, 29 K higher than the ambient temperature; The maximum temperature of radiation shield is 317 K, 30 K higher than the ambient temperature; (2) At the same detection angle, rotor infrared radiation intensity fluctuates along of time, the change of infrared radiation intensity with time in 3-5 m and 8-14 m bands is consistent; (3) The proportion of 3-5 m and 8-14 m band infrared radiation intensity increment of aerodynamic heating rotor in the same band infrared radiation intensity of overall solid are 15%-16%、5%-6%; (4) 8-14 m band infrared radiation intensity of aerodynamic heating rotor is about thirty times as much as that of 3-5 m band, the proportion of aerodynamic heating rotor 8-14 m band infrared radiation intensity in the same band Based on CFD/IR numerical calculations, the temperature distribution of rotor skin and the effect on the infrared radiation characteristics of helicopter were studied systematically. The results show that: (1) The temperature distribution on the rotor blades shows an increasing tendency from the rotor shaft to wingtip, the maximum temperature is 316 K, 29 K higher than the ambient temperature; The maximum temperature of radiation shield is 317 K, 30 K higher than the ambient temperature; (2) At the same detection angle, rotor infrared radiation intensity fluctuates along of time, the change of infrared radiation intensity with time in 3-5 m and 8-14 m bands is consistent; (3) The proportion of 3-5 m and 8-14 m band infrared radiation intensity increment of aerodynamic heating rotor in the same band infrared radiation intensity of overall solid are 15%-16%、5%-6%; (4) 8-14 m band infrared radiation intensity of aerodynamic heating rotor is about thirty times as much as that of 3-5 m band, the proportion of aerodynamic heating rotor 8-14 m band infrared radiation intensity in the same band infrared radiation intensity of overall solid is about 30%-40%, but reduction of rotor surface emissivity is the effective method to reduce the 8-14 m band infrared radiation intensity and the proportion in the same band infrared radiation intensity of overall solid.
2014, 43(1): 61-66.
In view of the fact that the response of IRFPA will drift with time and temperature and the IR imaging system will be used to measure and watch, an long-wave infrared uncooled imaging system which has adaptive correction function was designed. The system is based on FPGA, in which FPGA performs system control and image processing. Architecture of the system is simple and with less power dissipation. In order to improve the performance of the detector, a temperature control circuit based on ADN8830 was introduced, which could set temperature of the detector to a fixed point. In order to correct non-uniform responses of the detector's individual elements, an adaptive non-uniformity correction algorithm was proposed based on shutter, which could compensate the response drift according to temperature and time. The system had both analog and digital video output, in which analog video could be used to watch, while digital video with 12 bit precision could be used to measure. The results show that the imaging system has the advantages of good image quality, good environmental adaptability and low power consumption.
2014, 43(1): 67-71.
A generalized variation (GV) regularization based infrared image denoising method was proposed in this paper. In the new method, a p-norm was used as regularized term to replace total variation (TV) norm in traditional TV based image denoising methods which were used popular in image processing domain. Then a smoothing functional was constructed for noised removal. Thus, the problem of image denoising was transformed to a problem of a functional minimization. A nonlinear partial differential equation (PDE) was deduced from the new image denoising model. To solve the nonlinear PDE, the fixed point iteration (FPI) scheme was introduced to linear the PDE. The stability and convergence of regularized solution were ensured by FPI scheme. The numerical experimental results show that comparison with TV regularized method, the GV regularized method can preserve image edge including those small width edges more efficiently while removing noise. The GV regularized method is an efficient image noise removed method with better performance of noise removal and edge preserving.
2014, 43(1): 72-76.
The simulated distance data with high precision, good stability and adjustability are needed in the performance testing of an infrared range finder. The optical fiber as an ideal distance-simulating component is of many excellent characteristics such as high accuracy and good stability, but with the increase of the simulated distance, it shows some shortcomings, i.e. large physical dimension, weak portability and flexibility. To make up for the lack of fiber-delay simulated testing method, the distance- simulating technique based on circuit-delay was studied. The simulated echo producing circuit and simulated echo high precision delay time control circuit corresponding to the method were designed. The inherent delay and error of the system were analyzed. The verification of the simulated test circuits was implemented by Time-to-Digital-Converter circuit and the simulated distance control precision can achieve 0.5 m. It supplements the simulated testing technique for infrared range finders by fiber-delay.
2014, 43(1): 94-97.
High power narrowed linewidth pump source is needed with diode pumped alkali laser developed. But the linewidth of the commercial diode laser is far exceed the absorption linewidth of the alkali atom. So the Littrow external cavity is used to narrowed the spectrum of high power diode laser array. The linewidth of high power diode laser array is directly affected by the parameters of elements in Littrow external cavity. In this paper, the model of external cavity diode laser was set up by using ray tracing method. By replacing cylindrical lens with sphere lens, the influence of micro-cylindrical lens array, beam shaping optics and grating were analysed. The resutls show that, to obtain narrower output laser linewidth, the focal length of micro-cylindrical lens array should be smaller, the grating grooves is denser, and the focal of spherical lens is larger. And the theoretical conclusions is demonstrated by experimental results.
2014, 43(1): 77-80.
High harmonic generation driven by two-color laser f ield in CO2 molecules were investigated experimentally. The optimized intensity of the 24th harmonic was obtained by changing filling gas pressure. In additional, harmonic output was improved by moving the laser focus with respect to the gas cell. There are two maximum values in two regions. The result is ascribed to different phase matching in the gas cell, favoring long and short electron trajectories during high harmonic generation respectively. The experiment results indicate that molecular high harmonic generated in two-color field may be a promising multi-wavelength tunable coherent XUV source.
2014, 43(1): 81-87.
Temperature is an important factor for affecting the accuracy of ring laser gyroscope (RLG). The relationship of RLG's bias to temperature should be established accurately which can improve the precision of RLG strapdown inertial navigation system. Temperature characteristic of RLG was introduced. Temperature compensation method for RLG's bias based on improved artificial fish swarm algorithm (IAFSA) was established and the steps and methods were given. The traditional modeling method of stepwise regression was also investigated to provide a comparison with the IAFSA. The result shows that the temperature compensation model by IAFSA is accurate. The bias instability of RLG output after compensation is 0.001 85 ()/h and its precision is 15.5% which is higher than that of the traditional stepwise regression. The results of two typical temperature tests show that temperature compensation model by IAFSA can compensate RLG's bias real-time.
2014, 43(1): 88-93.
The relationship between atmospheric column-averaged CO2 concentration measurement errors and operating wavelengths of space-borne integrated path differential absorption (IPDA) lidar was studied. The column-averaged CO2 concentration measurement principle was presented, and the system random error, temperature uncertainty error, frequency drift error and H2O interference error as a function of the operating wavelengths of lidar were analyzed. The operating wavelengths were optimized to minimize the total concentration measurement error. For optimal IPDA lidar on-line and off-line wave number of 6 361.225 0 cm-1 and 6360.99cm-1, the total column-averaged CO2 concentration measurement error was calculated to be 0.58710-6 with 1K temperature error and 0.6MHz frequency drift error, which meets the requirement of the column- averaged CO2 concentration measurement with 110-6 accuracy. The optimized wavelengths are applicable for retrieval of column-averaged CO2 concentration with high precision for space-bore IPDA system.
2014, 43(1): 98-102.
Pulse coherent laser radar has the characteristics of high frequency, wide frequency band, sparse sampling points of the echo in the range gate. It is difficult to use the traditional signal processing methods to improve the radar spectrum resolution. Based on the study of radio radar signal spectrum technique, the Zoom FFT method was used combining with the digital filter banks. Through the simulation experiment, it is showed that the method for improving the pulse coherent laser radar spectral resolution have good results. The principle of Zoom FFT and digital filter banks was introduced, and it is proved that this algorithm is effective to improve the spectrum resolution through the simulation of low- frequency and high-frequency signal. The idea is also verified by the real wind data.
2014, 43(1): 103-107.
Pulse shaping technique is of great significance for high power laser facility. In this paper, a new method used in laser pulse shaping system was proposed. An arbitrary waveform generator was fabricated to generate shaping electrical pulse. GaAs Field Effect Transistor (FET) has good ability of generating voltage-controlled current and on-off characteristic, while the semiconductor laser contains direct modulate characteristic. The unit-pulse was generated based on the on-off characteristic of GaAs FET, and then the arbitrary waveform electrical pulse was generated by stacking a set of unit-pulses. Impedance tapered micro-strip line was designed to maintain the consistency of each unit-pulse. The arbitrary waveform electrical pulse was used as shaping electrical pulse to modulate the semiconductor laser directly to realize the laser pulse shaping. With this method, a laser pulse waveform was generated with duration less than 10 ns, 330 ps time-domain adjustment. The experiment results show that the shaped laser pulse is determined only by shaping electrical pulse.
2014, 43(1): 108-112.
The synthesis method of a new metalphthalocyanine compound was introduced. Optical nonlinearity of the sample solution in both picoseconds and nanoseconds regimes at 532 nm wavelength was investigated by Z-scan technique. Strong reserve saturable absorption and positive nonlinear refraction were observed from the experiments. The equivalent nonlinear absorptive coefficient and nonlinear refractive index were obtained from the experiment data via computer simulations, which were: ps=4.110-11m/W,ps=4.510-19m2/W and ps=5.110-9m/W, ps=1.510-16m2/W. The mechanism of reverse saturable absorption and positive nonlinear refraction showed in Z-scan experiment was illustrated, excited state optical nonlinearity was considered as the origin of the sample's nonlinear optical property. Excited singlet and triplet energy levels play the key role in picoseconds and nanoseconds regimes, respectively. Optical limiting experiment was performed using nanoseconds pulse laser and results showed that when T/T0=0.5, the threshold value was 2.0 J/cm2. The results of optical limiting experiment showed that the sample has novel optical limiting performance.
2014, 43(1): 113-118.
Laser-Induced Breakdown Spectroscopy (LIBS) was used to detect the components of coal particle flow. The influences of different parameters of laser on the plasma characteristics of coal particle flow were studied. The parameters included different laser wavelengths and laser energies. The coal commonly used in the power plants in China was chosen as the experimental sample. Before the experiment, the diameter of coal particle was less than 0.2 mm by sieving method. Then the experiment was carried out at different laser wavelengths and laser energy. The results show that the variations trends of the plasma temperature, electron density and the lines intensity with laser energy are consistent under different laser wavelengths. However, as the laser energy increases, these characteristic parameters increase faster under 1 064 nm than that under 532 nm. The main reason is that the short wavelength (532 nm) with higher photon efficiency would reach the saturated state under lower laser energy.
2014, 43(1): 119-122.
In order to obtain high-stable erbium-doped fiber source used fiber-optic gyroscope and improve the stability of conventional erbium-doped superfluorescent fiber source, erbium-doped photonic crystal fiber as a superfluorescent fiber source of gain medium was proposed and employed. A superfluorescent fiber source with a double-pass forward configuration was constructed and the output properties of the new fiber source were studied. The influences of fiber length and pump power on output power, spectral width and mean wavelength of fiber source were analyzed. The results show that the superfluorescent fiber source had an output power of 35.4 mW, an optical conversion efficiency of 16.09%, a spectral width of 30.9 nm and a mean wavelength of 1 548.3 nm by choosing the optimized fiber length of 10 m and pump power of 220 mW. This result would set the foundation to further investigate the stability and adaptability of erbium-doped photonic crystal fiber superfluorescent source in the different environment temperatures.
2014, 43(1): 123-128.
Because of high power and low temperature level requirement, thermoelectric coolers were used for heat dissipation of CCDs on a geostationary earth orbit satellite camera. Experimental setup for evaluating thermoelectric coolers' performance was designed. Domestic and oversea thermoelectric coolers were tested in atmosphere and vacuum respectively. Effects of installation, environment pressure, input power and heat load on the temperature difference of thermoelectric coolers' hot and cold faces were obtained experimentally. The experimental results showed that, for present CCDs' heat load on a geostationary orbit satellite, the maximum temperature difference between cold and hot faces was 45.8℃, which satisfied the requirement for running at low temperature level.
2014, 43(1): 129-132.
Microchannel Plate (MCP) with ion barrier films (IBFs) is one of the key components in Low Light Level (LLL) Image Intensifier (I2) tubes in Generation III. Vacuum high-temperature baking process plays a destructive role in the particle blocking and transmitting performance of ion barrier film. Al2O3 thin film density as a function of the temperature of the environment was studied using molecular dynamics simulation. Electron transmittance and ion barrier blocking ratio of Al2O3 thin film versus the energy of incident particles were simulated and calculated using the Monte Carlo method. The dead voltage of Al2O3 thin films was about 235 V, and with the decrease of the incident ion energy, ion blocking ratio increased. When the incident energy was 250 eV, the preventing ability of Al2O3 films on C, N, O ions was 96%-99%. Based on the above factors analysis, with the increase of the external temperature, electron transmittance increased linearly, while the blocking ratio of ion barrier decreased nonlinearly. Optimization and adjustment of high temperature baking time and quantity will contribute to the ion barrier film performance improvement.
2014, 43(1): 133-139.
Laser array with the scale of 116 for optical vector-matrix multiplier as long as its driven circuit was designed and implemented. A 116 laser array was constructed by coupling 16 commercial discrete distributed feedback (DFB) lasers with a 116 fiber array. Calibrating module adopting feedback algorithm was equipped with the laser array driven circuit, successfully solving problems encountered due to differences of threshold current and P-I conversion efficiency among lasers of the same type. And the same mapping relationship was acquired between the input vector and output intensity power among different channels of the source array. The proposed light source array system together with its driven circuit not only reduces cost, but also possesses excellent high-frequency response,ensuring the stability and accuracy of the optical vector matrix multiplier's computing performance.
2014, 43(1): 140-144.
The silicon APD performance is dependent on its device structure and processes. In this paper, the device performance and key processes for epi-planar n+-p--p+ structure silicon APD were simulated with Silvaco, in order to guide the silicon APD device design. The parameters of device processes such as ion implantation and dopant diffusion were simulated to get the impurity distribution and doping depth. Furthermore, the key parameters which were used to characterize the APD performance, such as the electric field distribution, the dark current and photocurrent, the gain, the quantum efficiency and the responsibility of the APD were simulated. The experiment results show that the maximum responsibility is up to 55A/W when the gain is 100. The device is most sensitive in the spectral range of 600 nm to 900 nm. The peak responsivity of the device is 810 nm.
2014, 43(1): 145-150.
In order to measure the wavefront aberration of the EUVL objective system with the super high accuracy, the double-fiber phase-shifting point diffraction interferometer was introduced, its working principle was introduced, and the adjustment scheme of interferometer was designed critically. All the components were positioned accurately, the test beam and reference beam were ensured to be strictly vertical, the maximum coupling efficiency between the coupling system and optical fiber and maximum fringe contrast were realized, which provided preparation for ultimately ultra high precision test of the wavefront aberration of EUVL objective system. After the alignment was completed, an optical system was measured by the experimental device, the tested optical system wavefront aberration was restored by the 13-frame phase-shifting algorithm, the good results were obtained. The results are: PV value is 37.82 nm, RMS value is 7.83 nm.
2014, 43(1): 151-154.
ZnO thin film is a new type of wide bandgap oxide semiconductors, it has excellent physical and chemical properties. It has potential applications in the low-light-level image intensifier. It was found that ZnO thin film can be used as the buffer layer to fabricate GaN UV photocathode with high performance by the investigation on the lattice parameter of ZnO material. It was indicated that ZnO thin film could be used as the negative-affinity (NEA) photocathode itself. Once the p-type ZnO obtained, it was more benefit for the formation of NEA photocathode. Furthermore, according to the Monte Carlo simulation results, it was shown that the stopping ability of ZnO thin film on positive ions was stronger than that of traditional Al2O3 ion barrier film. So ZnO thin film can substitute for Al2O3 thin films and be used as the ion barrier film in the third generation low-light-level image intensifier. It is also found that ZnO can be used as the dynode due to its high secondary electron emission and suitable resistivity.
2014, 43(1): 155-159.
Correlated double sampling technique is widely used in CCD video capture, and can effectively eliminate the reset noise, white noise CCD output noise. However, when the CCD works in the state of the high frame rate, the need for high-speed output of data faster pixel clock appears the sampling position is unstable. This article used adaptive correlated double sampling technique, could adaptively adjust the phase of sampling pulses, so that the correlated double sampling of two sampling pulses were collected at a reasonable sampling positions, and pixel information could be collected correctly. Adaptive technology was used to adjust the CCD correlated double sampling location, to make HD high-speed CCD pixels high frequency, correlated double sampling also could be adopted in a reasonable sampling location, the CCD working in good condition.
Low-level-light night-vision system is an important equipment of sight and navigation for pilot. Objective lens is an important part of the low-level-light night-vision system. An all-sphere objective lens was designed based on a six elements initial lens, then a modified system of plastic lens with hybrid refractive/diffractive and freeform surfaces was developed. The optimization process was also presented. The performance of the couple systems were presented and analysed. It is shown that the modified system not only has better performance, for example lateral color, distortion, astigmatic and modulate transfer function (MTF), but also has greatly improved in weight, total length and max diameter, which can meet the demands of night-vision objective lens. It also provides a new approach for modern lightweight and compact low-level-light night-vision system design.
2014, 43(1): 166-172.
For 620 mm diameter active optics telescope, surface error correction for primary mirror and system wavefront aberration correction experiment were carried out respectively. The support system of primary mirror consisted of 36 axial active supports and 6 lateral passive supports, in which 33 axial supports were used for active correction, and 3 were used as dummy hard points for controlling the position of primary mirror. The Shack-Hartmann wavefront sensor was used as testing equipment and the least square method was used to calculate the active corrective forces. In the experiment, low frequency Zernike terms were selected for correction through analyzing the correction ability of the system. Through fixing the S-H sensor at the curvature center of primary, the mirror surface error correction experiment was carried out at different elevation, and around 0.6RMS surface error of the initial state can be corrected to /12-/15 RMS. Then the wavefront error of the telescope system was corrected using the star object of collimator, around 0.65RMS of the initial state was corrected to 0.2RMS, and the resolution is improved from 18 lp/mm to 45 lp/mm correspondingly.
2014, 43(1): 173-177.
The calculation formula of Glan -Taylor prism's transmittance between emanative lights'azimuth, incident angle and structure angle of prism was obtained by using refraction law and Fresnel formula as well as the ray-tracing method. The relationship between the extinction ratio and transmittance was indicated. By computer simulation of Matlab, the characteristic of extinction ratio in the whole azimuth was analyzed; the extinction ratio's transformation relationship along with incident angle and structure angle was investigated. From simulation results, we discover that the extinction ratio is unacted on the incident angle when the angle is in the vertical azimuth of prism's optical axis. And the ratio becomes bad with increasing of the structure angle. The theoretical results are in good agreement with problems appeared from practical system which verifies its correctness, and it explains the problem in project item. The work of this article has great guiding significance in the design and use of Glan-Taylor prism.
2014, 43(1): 178-183.
To the testing of large-diame ter optical mirror, with the increase in the size of the reference mirror, it can't be treated as an ideal plane mirror because of the constraints of the machining accuracy, gravity deformation, temperature, environment impact. Based on the maximum likelihood estimation, Zernike polynomials fitting, a reasonable stitching algorithms and mathematical models was established for non-ideal standard lens sub-aperture stitching. Stitching experiment was accomplished on the computer with a 2.5m3.5m oval plane mirror as an engineering example. The full-aperture surface error distribution after stitching was consistent with the original. PV and RMS deviation were 0.022 and 0.001 3 . The full aperture phase distribution of the PV value and the RMS value of relative error was 2.81% and 0.81% respectively. The experimental results show that: large-diameter plane mirror can be tested with non-ideal reference mirror in high precision using the ML algorithm.
2014, 43(1): 184-189.
Due to the onconflict between the wide spectral range of measuring (276-700 nm) and the limited imaging area of CCD detector (14.3 mm10.5 mm), classical Czerny-Turner structure was not able to meet the requirements of design. Based on it, an innovative method applying two uniform plane diffraction gratings to separate the whole spectral range into two different sections was presented. The two separate spectral range, rotation and tilt angles of two gratings were obtained through theoretical computation. The optical software ZEMAX was used to simulate and optimize the optical system by multiple configuring parameters. The simulation results show that two spectral bands are detected on the imaging plane. Their spectrum width is 14mm respectively, and the center distance between them is 8 mm. The spectral resolution is less than 1 nm and the aberration is substantially corrected. It indicates that the method is a good solution for the situation of wide spectral measurement range and limited imaging dimension of CCD detector in the meanwhile.
2014, 43(1): 190-194.
Fourier telescopy is an unconventional imaging technique that combines the advantages of the laser active lighting and synthetic aperture techniques. The different spatial frequency components of target are received by changing the location of any of the two launch telescopes. After collected a sufficient number of Fourier component values, target image can be obtained by signal processing. To reduce system cost and try to get the details of the target, in this paper, a configuration program was proposed which T-sparse emitter array of laser beam. A comparative study of four kinds of targets and evenly spaced emitter array reconstructed image. The number of each arm of T type placed launch telescopes was 11. First, the eight low-frequency information of target was gotten continuously. Then three high-frequency components were extracted. By comparison with the single arm 11 and 16 of evenly spaced emitter array reconstructed image: the emission array that we used reconstructed image is much better than the same number of the number of evenly launch array, compared with configuration of homogeneous 16, overall imaging capability slightly difference, which is inevitable.
2014, 43(1): 195-200.
Based on the vector wavefront aberration theory, the misalignment induced aberration's characteristic of Cassegrain optical system was analyzed in this paper. It is shown that a misaligned Cassegrain has three residual 3rd aberrations. The 3rd order spherical aberration is constant over the field and the 3rd order coma increases linearly with the field but the zero coma point no longer locates at the field center. Moreover, the astigmatism aberration field in system without symmetric contains two zero astigmatism point, neither of which is necessarily located on the field center of view. It has been demonstrated that a Cassegrain under assembly is only measured to have perfect performance on-axis but not aligned in any significant way, so the measurements of multiple field points for the Cassegrain are required in the process of alignment.
2014, 43(1): 201-207.
Interference imaging spectroscopy (IIS) is a novel high technology integrated by the two-beam interference technique, 2D imaging technique and spectroscopy with high resolution. The wide-field-of- view polarized type is an attractive scheme in IIS. It employs polarized components to realize interference and thus the image quality and spectrum reconstruction are principally determined by the characteristics of these polarization components. In this work, theoretical analysis of the interference visibility was performed by considering the polarization deviations and the retardation deviation of elements. The theoretical expression of interference visibility was deduced by polarization tracing method. The varying characteristics of interference visibility with incident angle, wavelength, azimuth angle, polarization direction and phase retardation were presented and the permissible deviation was quantitatively analyzed. This work would provide suggestions for system design, hyperspectral reconstruction and engineering practice of spectrometers composed of polarization components.
2014, 43(1): 208-211.
Design method of spectral calibration device for ultraviolet-visible band hyperspectral imager was studied. The optical principle of echelle grating was discussed. According to the theory of spectral calibration and taking the advantages of large working angle, high diffraction order and high spectral resolution of echelle grating, a spectral calibration equipment based on echelle grating was founded. Design method of spectral calibration device based on echelle grating for hyperspectral imager was proposed. Taking the ozone monitoring instrument (OMI) carried on Aura satellite as an example, the design process of spectral calibration device was discussed. The spectral calibration device bandwidth effect on the precision of spectral calibration was analysed by simulation. The calculation methods of the main performance parameters of spectral calibration device such as the diffraction order, spectral resolution of grating and the focal length of collimator were given, providing the design basis of spectral calibration device based on echelle grating.
2014, 43(1): 212-216.
Visible light imaging detection of electro-optic (EO) system plays a key role in space-object detection. How to detect space-object in strong background luminance has always been a choke point in limiting EO system's detection ability. The primary specification for expressing detection ability is signal- to-noise ratio(SNR). Based on analysis of the effect factors, a calculation formula of detection ability and the fundamental of detection probability were derived. The influence of the sky strong background luminance on the detection ability was analyzed, and the SNR of EO system versus spectral filtering mode and different observation stations were given in the paper. The theoretical results show that the detection ability of EO system can be improved, increased by 100 percent, through the propriety spectral filtering technology. The detection probability is increased by 45 percent (from 51 percent to 96 percent) through changing the observation station of EO system. Theoretical results fit with the experimental research.
In the designing process of the satellite borne optical remote sensor, the technology of remote sensor imaging simulation can assess the feasibility of remote sensing system designing, and predict the imaging capability of the remote sensor. A high-resolution satellite borne optical remote sensor imaging simulation method was presented, which was based on the low-altitude remote sensing system. The data sources of the simulation were low-altitude wide-field image and multi-spectral image. Firstly, low- altitude multi-spectral wide field of simulation image was generated by image classification and classification fitting. Secondly, the ground surface reflectance image was calculated by the empirical linear method. Thirdly, the satellite borne optical remote sensing radiances image of sensors was simulated by the characteristics of spatial resolution, MTF, spectral response and atmospheric radiation transmission. The QuickBird satellite was used as a simulated object, the simulation experiment was operated, and the simulation precision was assessed. According to the experimental results, there is a high similarity between the simulation image and satellite image.
2014, 43(1): 226-231.
In order to establish a complete set of simulation system for space-based optical remote sensing imaging, the importance of the atmosphere effects simulation was considered. Aimed at the space-based optical remote sensing system working in the VIS and LWIR spectral regions (0.4-14 m), an at-sensor radiometric equation which took the interaction mechanisms between targets and backgrounds into account was introduced. By a linear model, the adjacency effect was simulated. An atmosphere look up table was designed to calculate the atmosphere transmission, upwelled radiance and downwelled radiance. The effects of water vapor column density, meteorological range, target altitude and the position relation between sun, sensor and target on these parameters were analyzed. Finally, by the modulation transfer functions for long and short exposures images, the influence of atmospheric optical turbulence on space-based optical remote sensing imaging was analyzed.
2014, 43(1): 232-237.
A new neighborhood selection method was proposed based on the image patch distance and applied to the manifold learning. Thus, a new nonlinear methods for hyperspectral dimensionality reduction was obtained. Considering the physical characters of hyperspectral imagery, the proposed methods combined both spectral and spatial information and, thus, kept the original characters of dataset well with the less loss in the useful information and less distortion on the data structure. Compared with other dimensionality reduction methods for hyperspectral imagery, the proposed methods can reserve effectively the spatial relationships between observation pixels in hyperspectral imagery after transformation. Meanwhile, the proposed methods can discard efficiently the redundant information of original data sets along both spectral and spatial dimensions. Experimental results on real hyperspectral data demonstrate that the proposed methods have higher classification accuracy than the other methods when applied to the classification of hyperspectral imagery after dimensionality reduction.
2014, 43(1): 238-242.
A compression and reconstruction solution based on coded aperture was proposed. In this system, the 3D spatial-spectral information about a scene of interest was coded by a random binary element pattern which was achieved by Digital Micro-Mirror Device (DMD), and the processing was snapshot. As a result the 3D information was encoded into a 2D representation. In decoding, a Fast Iterative Shrinkage-Thresholding Algorithm (FISTA) was proposed on the basis of the Two-Step Iterative Shrinkage-Thresholding (TwIST) algorithm. The method developed in this paper did not require more than one gradient evaluation at each iteration, but just an additional point was smartly chosen and easy to compute. The experiments show that the reconstruction performance is much better than TwIST and GPSR both in spatial dimension and spectral dimension.
2014, 43(1): 243-248.
The multi-temporal leaf area index (LAI) data retrieved from remote sensing images have been widely used in climate simulation, crop growth monitoring and etc. However,there might be some missing data owing to temporal resolution, weather and some other factors. The support vector machine (SVM) is a kind of machine learning algorithm that has excellent properties. The least squares support vector machine (LS-SVM) algorithm is an improved algorithm of SVM. In this paper, the LS-SVM and SVM models were used to predict the LAI time series products of MODIS data of Naqu in year 2011, based on The multi-temporal leaf area index (LAI) data retrieved from remote sensing images have been widely used in climate simulation, crop growth monitoring and etc. However,there might be some missing data owing to temporal resolution, weather and some other factors. The support vector machine (SVM) is a kind of machine learning algorithm that has excellent properties. The least squares support vector machine (LS-SVM) algorithm is an improved algorithm of SVM. In this paper, the LS-SVM and SVM models were used to predict the LAI time series products of MODIS data of Naqu in year 2011, based on the MODIS LAI from 2003 to 2011. The results show that LS-SVM method performs better than SVM method. Therefore the predicted LAI data is proved to be very supportive for making up for the loss of remote sensing LAI time-series data, the LS-SVM method proposed in this study is significant to improve the quality of the LAI time series remote sensing products.
2014, 43(1): 249-253.
Based on the retrieval of atmospheric carbon dioxide using infrared spectral data detected by GOSAT, a method of building error matrixes of Bayesian theory was proposed and validated. Firstly, the effect on retrieval results by different initial guesses, different building results of priori information error matrix Sa and measurement error matrix S was simulated, and then two combinations of Sa and S building results were validated in the retrieval using part of GOSAT measurements of Taklimakan desert during 2009. The result shows that the retrieved results are more concentrate in the case of bigger priori information variance or smaller measurement error, and the retrieved results are dispersed under the converse circumstance. It is difficult to get real error matrixes in atmospheric remote sensing, therefore, this study will be significant for getting more accurate error matrixes and improving retrieval precision.
2014, 43(1): 254-259.
The length measurement method based on Optoelectronic Oscillator (OEO) introduces a free optical space, containing the measured length, into the optical cavity of OEO. The measured length is derived from the oscillation frequency corresponding to the cavity length. By virtue of the high sensitivity between oscillation frequency and group delay of the loop, this method promises high accuracy absolute length measurement at long range. However, long optical fiber, which is the high Q component of the cavity, is too sensitive to ambient temperature, leading to serious deterioration in accuracy and stability. In this paper, the influence of temperature variation was theoretically analyzed. The relation among thermally -induced error, temperature variation and length of optical fiber was established and analyzed, and optimization method of parameter was proposed. Experiments on optical fiber with different length and thermally-induced error were carried out. Experimental results consist with the error model, providing important basis for error compensation.
2014, 43(1): 260-266.
The problems on disturbance rejection rate of strapdown imaging seeker and the stability of disturbance rejection rate parasitical loop were analyzed in this paper. Firstly, two calculation methods of line of sight (LOS) rate were given based on the information from seeker and inertial measurement unit (IMU). The calculation model got simplified in order to analyze the influence to disturbance rejection rate from different disturbance items. Then the magnitude and phase of disturbance rejection rate caused by the aerodynamic model, time delays of signals and graduate scales were analyzed, especially in the low frequency bandwidth. Finally, the disturbance rejection rate parasitical loop model based on strapdown seeker was derived. Through discussing the stability zones of parasitical loop, the permitted maximum values for different disturbances were given. The results present that disturbance sources mention above will cause the terrible disturbance rejection rate problem and make the parasitical loop become unstable, so it is necessary to rectify them when calculating LOS rate.
2014, 43(1): 267-273.
In the vision-aided inertial navigation system, optimal information fusion depends on accurate calibration of the six degrees-of-freedom transformation between a camera and an inertial measurement unit. Considering the measurement information optimal fusion problem of autonomous navigation during soft landing on Mars, a sensor-to-sensor relative pose calibration algorithm was proposed based on the extended Kalman filter. The proposed algorithm can accurately calibrate the relative pose of the camera and inertial measurement unit, and simultaneously estimate the position, velocity and attitude of the spacecraft. Moreover, obtaining this calibration information requires no additional measurement equipment except the landmark features on the surface of the Mars. Furthermore, high fidelity sensor models for wide field-of-view camera and inertial measurement unit were developed taking into account effects of the probe maneuver and the Mars rotation. Finally, the validity of the sensors calibration algorithm presented in this paper was demonstrated by mathematical simulation.
2014, 43(1): 274-278.
In order to increase the angular position measurement accuracy and improve structure design of a precise turntable, the angular position measurement precision of its azimuth shafting was detected. The error included axial error, encode error and other errors. Fourier harmonic analysis was adopted in data processing. Harmonic waves with different orders were used to fit the data, low order harmonic waves were removed, which could increase the position measure accuracy. Meanwhile, the error sources had been found. The error look up table could be used to correct the measure data afterward. As the result shows, the value of angular position measurement error after corrected is 1/4 of the value before corrected, the amplitude is about 0.8, the angular position measurement accuracy has been increased a lot. A look up table was built to correct post -measurement data; the error sources were found, which will help to improve the shafting structure.
2014, 43(1): 279-283.
In the passive infrared detection conditions, according to the dynamic target detection reliability and military defense needs, a dynamic/static double coordinate sensing system was put forward in this paper. Static sensing system was not only a standard -two -dimensional coordinate system, but also a benchmark of moving target detection; and moving coordinate sensing system was a cross coordinate system in the horizontal plane, swinging back and forth in the range of 90 at a constant angular speed. So the proposed system solved the problem of pyroelectric infrared sensor that perceived distance was inversely proportional to the angle of field contradictions, and it realized full range perception of battlefield. A theoretical model and mathematical model of perception system was presented. Verified by experiment, the theory, which has a certain practical value, is practicable, and the system established is reliable.
2014, 43(1): 284-287.
A kind of method by means of laser was suggested and experimental set-up was constructed to study wet resistance in fuel pipe and its measurement. The wet resistance force would be acted on the fluid by the surface of the pip because of the wet effect between the liquid and the pip surface. The expression of wet resistance force was derived under small pip condition based on the liquid principle. A laser measurement set-up was constructed based on the light reflected from curved liquid surface and automatic electron-optics detection. The diameter of the special optics pattern depended on both the aperture diameter and curved degree of liquid surface. The analytic expression of light pattern diameter related with the slope of curved liquid surface and aperture diameter was arrived theoretically. The force depended linearly on the liquid surface tension and cosine of contact angle. A special pattern reflected from curved liquid surface was observed which was circle with clear interference fringes. The slop of liquid surface and contact angle was detected by means of the pattern scale and the experimental value of wet resistance force was archived. It has no-touch, no-damage and automatic properties.
2014, 43(1): 288-293.
The laser speckle is a kind of noise in triangulation displacement measurement. It's meaningless to restrain speckles when the light spot is so weak that facular image can not be extracted from speckles. But the speckle is also a kind of carrier of displacement information. For the above reasons, digital correlation method was used in laser triangulation displacement measurement system to measure the displacement of rough surface with strong scattering and the results had been analyzed. The results show that the digital correlation method is feasible in triangulation displacement measurement system, the measuring range reached micron grade and the experimental errors are below 2% . This method can overcome the disadvantage of laser triangular displacement measurement system in rough surface with strong scattering, improve the accuracy and expand its range of application.
2014, 43(1): 294-299.
For high-speed, high-resolution images of steel strip surface online inspection, a machine vision system based on TDI (Time Delayed Integration) imaging technology was researched and developed. TDI CCD sensor was used and cooperated with adaptive illumination LED light in this system. The acquired images of steel strip were sent to the image splitter through the fiber and then real-time processed by the Image Processing Units (IPU). Surface defects on tin strip were detected in this system. Application and results show effectiveness for tin strip surface defect inspection of the system (SIS) based on TDI(Time Delayed Integration) imaging technology.
2014, 43(1): 306-310.
An image retrieval algorithm was proposed based on Contourlet transform (CT) and Hu invariant moments in this paper. Firstly, each image was decomposed into low frequency sub-band and high frequency sub-bands by using Contourlet transform. The Hu invariant moments of the low frequency sub-band coefficient, as well as the mean and the standard deviation of each high frequency sub-band coefficients were computed and used as image feature vector. Secondly, Manhattan distance was used as similarity measure between the query image and every image in the image database. After these two procedures, the content -based image retrieval was achieved. In order to evaluate the effect of the proposed algorithm, the algorithm based on CT and Hu invariant moments were tested respectively. Comparing the results of the average retrieval rate, the experimental results of the proposed algorithm were superior to other image retrieval algorithms. The proposed algorithm gets a higher average retrieval rate and the average retrieval rate is up to 73.94%.
2014, 43(1): 300-305.
Image quality assessments are the basis for evaluations of dual-band color fusion algorithms and systems. A method of quality evaluation for visible and infrared color fusion images was explored. A comprehensive evaluation metric, image perceptual quality based on scene understanding (PQSU) was proposed, and color fusion images of three typical scenes were selected to perform a psychophysical experiment. The prediction model of PQSU was derived by multiple linear regression analysis of the experimental data for conventional image quality metrics and the proposed evaluation metric. The results show that the positive correlation between color harmony and color naturalness is very high. The variation of PQSU can be predicted effectively by color harmony and sharpness. In the three image categories, the proportional coefficients in prediction models for PQSU are different; whereas, the basic forms of Image quality assessments are the basis for evaluations of dual-band color fusion algorithms and systems. A method of quality evaluation for visible and infrared color fusion images was explored. A comprehensive evaluation metric, image perceptual quality based on scene understanding (PQSU) was proposed, and color fusion images of three typical scenes were selected to perform a psychophysical experiment. The prediction model of PQSU was derived by multiple linear regression analysis of the experimental data for conventional image quality metrics and the proposed evaluation metric. The results show that the positive correlation between color harmony and color naturalness is very high. The variation of PQSU can be predicted effectively by color harmony and sharpness. In the three image categories, the proportional coefficients in prediction models for PQSU are different; whereas, the basic forms of prediction models are unchanged. The proposed comprehensive evaluation metric and its prediction model provide a foundation for further developing objective quality evaluation of color fusion images.
2014, 43(1): 311-317.
Specific to the drawback that favoritism and average methods for low frequency coefficient fusion are weaken in maintaining the contrast of fusion image in traditional signal level image fusion, combining with the superiorities of signal level and feature level fusion, a novel fusion algorithm based on edge feature was proposed. Firstly, the registered multi-sensor images from the same scene were transformed by wavelet transforms. Secondly, the high and low frequency coefficients were fused separately by using different fusion strategies: the low frequency coefficient was fused by adaptive regional energy, while the high frequency coefficient fusion was conducted by using the edge feature fusion of low frequency coefficient. Finally, the target image was obtained by performing inverse wavelet transforms. The algorithm has been used to fuse infrared and visible images, and multi-focus images. The experimental results indicate that the fused image obtained by the proposed method has a better subjective visual effect and objective evaluation criteria, it performs dramatically better than traditional fusion methods.
2014, 43(1): 318-322.
According to the character of fuzzy image edge, noise image, difficult to extract the edge information collected by infrared thermal imager, a new edge detection method was proposed. The method combined LOG operator improved by mathematical morphology with Roberts operator. First the thermal infrared camera images with random noise was filtered using opening and closing operation of mathematical morphological. Then the Laplace algorithm was used for edge detection of thermal infrared images. Second, Roberts operator was introduced to extract edge information. Fusing edge information of images detected by two methods, at the same time, establishing corresponding fusion rule and the threshold condition were applied for this images, the final fused image was obtained. Finally, MATLAB was introduced to perform the experimental simulation for adding salt and pepper noise image. The experimental results show that the method has the advantages of two detection operators and has a good effect in noise suppression and positioning accuracy. Meanwhile the proposed algorithm is insensitive to noise and ideal detection results are obtained.
2014, 43(1): 323-327.
Traditional gradient auto-focus algorithms have large amount of calculation which will cause the reduction of real-time performance. These algorithms are also weak in anti-noise capability which will result in the decline of unimodality and sensitivity. So a gradient threshold auto-focus algorithm was proposed to improve the focusing performance to meet the requirements of real time and accuracy in auto-focusing subsystem of photoelectric tracking system. The proposed algorithm took the local variance as a local threshold to distinguish the edge pixels from non-edge pixels. Then it used a kind of new standard deviation of the whole image as a global threshold to weaken the effects of noise and background. At last, it used one of traditional gradient auto-focus algorithms to calculate the focusing value of the pre-processed image for clarity-evaluation. The results of lots of experiments show that the proposed algorithm has good real- time performance, strong unimodality, high sensitivity and powerful anti-noise capability. When the proposed algorithm is used in the auto-focusing subsystem of photoelectric tracking system, all the attractive performances remain, which traditional gradient auto-focus algorithm can't achieve.
2014, 43(1): 328-331.
First of all, the working principle of the single pulse tracking system,in which TM01 mode is the common mode and TE21 mode is the differential mode, was demonstrated in the paper. Secondly, a designing scheme of the digital tracking receiver was presented. The influence on the tracking performance by phase difference between the common channel and the differential channel was analyzed. And a zero cross point detection plus digital phase shift compensation method was proposed, which could be implemented in a tracking receiver design. The performance of this method was carried out. In experimental prototype, the cross coupling comparison before the phase compensation and after was presented at last. This method which is given in the paper has very good stability and is independent of frequency of the tracking system. The application in experimental system shows that this method can calibrate phase error with a very high speed. And the cross coupling performance of the system satisfies the design requirement. The tracking process is stable and reliable.
2014, 43(1): 332-337.
A method of acquiring parameters of the five-parameter BRDF statistic model in object sample using the genetic simulated annealing algorithm was introduced. using four parameters in the shadowing function as unknown parameters in BRDF model, a nine-parameter BRDF model was obtained when the genetic simulated annealing algorithm was applied to the parameter reversion of the BRDF statistic model of the object surface according to the BRDF experimental data at laser wavelength 1.06 m. The results show that, mean square errors of the nine -parameter BRDF model were small compared with that of five-parameter BRDF model. The distribution of shadowing function with scattering angle is obtained for different incident angles by retrieving the four parameters of shadowing function, which reflect the surface roughness of object sample.
2014, 43(1): 338-344.
In order to develop the application of time-of-flight algorithm in fire detection and simplify the algorithm to improve detection rate and accuracy, according to the time-of-flight-depth-map method, considering with the characteristics of depth map of fire flame, fire flame identification algorithm based on variation rate of time-of-flight-depth-map was designed. Several groups of fire flame identification experiments, including n-heptane flame, ethanol flame, paper flame, lamplight interference and pedestrian interference test, were carried out with 3-D depth camera acted as main equipment. The captured maps were processed and computed. A simplified algorithm was proposed for fire flame identification which was used to analyze the characteristics of depth map, frequency spectrogram, concentration ratio and area fluctuation of fire flame. The results indicate that the identification precision rate is greater than 91.5%, and the misrecognition rate is less than 3.8%. Fire flame could be efficiently identified with this algorithm.
