2014 Vol. 35, No. 4

OE System and Engineering
Object positioning and error analysis of vehicular electro-optical reconnaissance system
Peng Fu-lun, Wang Jing, Wu Yi-lei, Guo Cheng
2014, 35(4): 557-562.
During the process of object positioning, the vehicle electro-optical reconnaissance system needs to establish a series of coordinate systems, such as electro-optical platform coordinate system, inertial guidance coordinate system, local coordinate system, geocentric coordinates and the reference ellipsoid based longitude and latitude representation coordinates. Considering the differences of operation mode and mounting position of electro-optical platform and inertial guidance system, the object position model was derived, the longitude, latitude and height were calculated, and the accurate positioning of object was realized. The main error sources of electro-optical system were analyzed and experimentally simulated through the model, the result shows that the model meets the precision requirement of object positioning. The result of system field test shows that the object positioning accuracy is better than 15 m.
Error compensation for dead reckoning in fiber optical gyroscop inertial navigation system
Chen Ying, Ji Ming, Kang Zhen, Yang Meng, Li Ying-juan, Liu Bing, Deng Chun-lin
2014, 35(4): 563-567.
Aiming at the inherent disadvantage of inertial navigation system (INS)that the positioning error are accumulated over time, the method of compensating errors in INS /dead reckoning(DR) integrated system was put forward. The main factors which begot errors in dead reckoning were analyzed, and the positioning error equation was given,then the Kalman filter was built for errors compensation of integrated system. The difference of velocity between INS and DR was used as the input of Kalman filter, the attitude error, velocity error, positioning error and the scale factor error of odometer were to be estimated which compensated the errors of integrated navigation system by feedback closed loop rectification. Two non-closed paths were selected in verification experiments.The positioning error of the first path is 3.49 and 2.3 before and after compensation respectively. And that of the second path is 2.4 and 2 before and after compensation respectively. Experiment results indicate that the system position accuracy is improved effectively by dead reckoning compensation method.
Optical and mechanical design for V-prism refractometer with high accuracy
Cao Miao, Guo Xiao-xue, Liu Ming, An Zhi-yong
2014, 35(4): 568-573.
For the problems that the traditional V-prism refractometer employs the optical dial and the visual alignment is unable to meet the demands for the production line of modern optical glass and high-precision refractivity measurement, a kind of new general design scheme of high precision V-prism refractometer based on charge-coupled device (CCD) machine vision alignment was put forward in this paper, and the optical and mechanical structure design of the main components of the system, such as collimator, transmission mechanism, locking and fine adjustment mechanism, orientation measuring mechanism of shaft encoder was done. Additional, the detection error of the instrument was analyzed on the basis of the correction formula considering the air refractive index factors. The results show that the refractive index test accuracy reaches up to 310-6, the technical index requirements of the high accuracy V-prism refractometer are well satisfied.
Method to extend dynamic range of transmittance meter
Xiao Shao-rong, Wu Qun-yong, Zhou Jia, Xu Meng, Shang Guo-qing
2014, 35(4): 574-579.
A method to extend the dynamic range of transmittance meter with a combination of optical attenuator and motor was introduced. In this system, the emission intensity of the LED was controlled by the variation amplitude of modulation signal which was loaded. Furthermore, we selected fixed transmittance attenuator and established the reasonable threshold when the data measurement was carried on. According to fitting analysis of data, the result shows that the system-s dynamic range is extended 0.6 times, when using neutral density attenuator whose transmittance is 40%. And it is extended 6.3 times when the transmittance is 87%. Meanwhile, by choosing neutral density attenuator of different transmittance, the system-s dynamic range can be flexibly extended.
Design of fore continuous zoom optical system of AOTF spectral camera
Zhao Zhao, An Zhi-yong, Gao Duo-rui, Wang Jin-song, Cai Hong-xing, Zhong Liu-jun
2014, 35(4): 580-585.
Based on performance and application requirements of acousto-optic turnable filter (AOTF) spectral camera, the positive mechanical compensation was introduced to achieve a visible optical system which was 10 continuous zoom configuration with high speed. Details were given to present the process of focal power distribution and computation of initial structure, the simulation was conducted with Zemax to show the results. Then the image quality evaluation was done, the cam curve was solved and the aberration was analyzed. Results show that the system can realize 30 nm~300 mm continuous zoom at 0.38 m~0.7 m, and the maximum modulation transfer function (MTF) is 0.7 at 50 lp/mm . The system is characterized by large zoom ratio and smooth cam curve, which make the system reach the target of AOTF spectral camera.
Design of initial structure of infrared zoom optical system with PW solution
Cui En-kun, Zhang Bao, Hong Yong-feng
2014, 35(4): 586-591.
The solving for the initial structure of continuous zoom optical system by using PW method was introduced. The structure was obtained by distributing the power and length between them for each element on the base of the exchange principle of object and image. The PW values were changing for choosing best glass, controlling aberration,calculating the shape of glass. Finally an mid-wave infrared zoom system(50 mm~200 mm) was designed according to this method, the system had 5 lenses with 2 aspherics, satisfied 100% cold shield efficiency with simple structure.Moreover, the initial structure was optimized with Zemax.Result shows that the continuous optical system has high image quality and high energy transmission, which can meet the requirements of practical applications. In conclusion, the PW solution has practical meaning for the initial structure of zoom optical system design.
Key technology of adjustment for multi-axes calibration device
Zhang Xiang-ming, Zhang Jin-liang, Wang Yang-yun, Jiang Feng, Zhao Hong-jun, Liu Yi-chen, Kong Long-yang
2014, 35(4): 592-597.
In order to adjust the optical axes in the multi-sensor electro-optical system, a kind of new calibration device with a wide span of spectral-axes is introduced, of which working principle are described in detail. The Cassegrain system is the core of this device, whose primary mirror uses a new kind of adhesive and optical-centering techniques to relieve deformation, and the experimental results verify the feasibility of the proposed techniques. In addition, by precisely adjusting the Cassegrain system and multi-axes of detecting optical paths, the detection precision of this new calibration device can up to 10 theoretically. Therefore, using the proposed device and the large aperture off-axis reflective collimator, the parallelism of optical axes of multi-sensor electro-optical system can be calibrated precisely in different environments.
Uniform illumination design based on LED array and diffuse reflection freeform surface
Liu Bai-fen, Jin Xiao-long, Zhu Zhen-min
2014, 35(4): 598-602.
An indirect illumination pattern with flat LED array and diffuse reflection freeform surface was proposed. Based on the Lambertian characteristic of LEDs and ideal diffuse surface, a mathematical model was constructed. A set of differential equations were established according to the expected energy distribution on the target plane. Through solving these equations numerically, the outline of the diffuse surface was obtained. By importing the entity model of the diffuse reflection illumination system into optical software to perform non-sequential ray tracing, the simulation result shows that the irradiance uniformity of the detection area is above 90% and demonstrates that the proposed method is correct and effective.
Enhanced heat transfer characteristics of high-power LED with shroud
Wang Zhi-bin, Liu Yong-cheng, Zhang Jian, Liu Li-jun, Kong Ya-nan
2014, 35(4): 603-607.
In view of heat dissipation existed in the high-power LED light, an optimization design was applied to the radiator of the high-power LED with a shroud under the air-cooling condition. A fluid analysis software was used to optimize the internal diameter and height of the shroud, the diameter of the inlet and the angle of the heat sink-s fins while the parameters of the fin structure were fixed. By changing these parameters, the parameters of the gas on the surface of the heat sink were changed in fluid shape and wind speed, and finally the convective heat transfer coefficient of the fin was changed. Through optimizing, a series of optimum parameters belonging to the shroud and the heat sink were obtained: the shroud-s height was 85mm, the inlet diameter was 76 mm, the outlet diameter was 83 mm and the angle of the heat sink was 9.It is concluded that the temperature of the heat sink has a certain degree of reduction after optimization, which can provide an optimized scheme for the cooling design of high-power LED lamps.
Design of reflector using zoned method based on non-imaging optics
Liu Xi
2014, 35(4): 608-613.
A brief and fundamental method for design of rotational symmetric reflector, called zoned method, was introduced based on non-imaging optics. The design idea of zoned method was presented: the light distribution of light source and luminaire were divided into pieces of zone bands by equal angle interval, the comparative analysis of flux difference of these two series of zone was did, and the relation between rays from light source and that from luminaire was determined, then the slope of the reflective curve at each reflective points was confirmed, finally the total shape of reflective curve was shown in 3D software. Moreover, detail design steps were described, and the precise design of reflector was verified with a high design matching ratio of 98.4%, by taking a special application for LED source for example.
OE Information Acquisition and Processing
Space object detection method for observation image in stare mode
Wang Kun-peng, Ma Chao-wei, Hou Wang, Wang Dong-ya
2014, 35(4): 614-618.
Aiming at the problem of tiny object detection in stare observation image sequence, a new method based on frequency feature accumulation was proposed. First, star matching and difference of neighbor frames were used to eliminate background of images, and then by analyzing time-frequency feature, the method for accumulating frequency feature of image was applied in tiny object detection. The experiment shows that the method proposed can increase the signal-noise ratio (SNR) of image by 3 times, and favors tiny object detection.
Diffusion and confusion analysis of optical encryption algorithm based on phase encoding
Lin Chao, Shen Xue-ju, Wang Zhao-hui, Cao Duan-chao, Zhao Cheng
2014, 35(4): 619-623.
To clarify the diffusion and confusion characteristic of phase encoding optical encryption algorithm, based on the spatial shift theorem of Fourier transform together with the block cipher design criterion, the diffusion and confusion characteristic of 2-f system utilizing single random phase mask is analyzed. Process of single random phase encryption is divided into two individual procedures. The analysis results indicate that the confusion operation is introduced mainly by the Fourier transform and the diffusion operation is achieved by combining the Fourier transform and random phase mask. Numerical simulation is performed to verify the theoretical analysis. The entropy is introduced to evaluate the statistical property of ciphertext. The diffusion and confusion characteristics of optical phase encoding algorithm in the Fresnel domain and fractional Fourier domain are further investigated. The research results indicate the entropy for single random phase encryption and double random phase encryption are 7.038 and 7.157,respectively,while entropy for random amplitude encryption is 4.521. Hence, random phase encoding algorithm can achieve better diffusion on plaintext than random amplitude encoding algorithm.
Color image encryption by additional key multiplexing
Guo Fei-peng, Li Jing, Gong Qiong, Liu Hong-zhao, Qin Yi
2014, 35(4): 626-631.
In order to avoid the record and transmission of color image with complex ciphertext, we proposed to encrypt color images with a modified joint transform correlator by additional key multiplexing. First of all, a color image was separated into 3 components: red, green, and blue. Then the 3 grey images were encrypted with different additional keys to generate corresponding joint power spectra, and the encryption results were got, namely multiplexed joint power spectra by superposing the above mentioned joint power spectra. Furthermore, the decryption of the multiplexed joint power spectra with the correct additional key could give the corresponding primary grey images. Computer simulations show that the proposal can hide a color image into a single intensity pattern. Since recording intensity image is free from the reference wave, our method relaxes the environment and avoids interference equipment. In addition, compared with previous methods that encrypt image into complex ciphertext, the size of ciphertext of our approach is only half of it, thus the efficiency of the encryption is further improved.
Analysis and application of bi-grating imaging effect of finite width
Liu Yun
2014, 35(4): 632-637.
The complex amplitude distribution of diffraction light was analyzed by stationary phase integral method, when the point light source was passing through the system composed of two parallel placed transmission gratings with finite width. When the bi-grating imaging condition was satisfied, the comparison between the diffraction image of finite-width bi-grating and that of infinitely wide bi-grating was conducted. It is concluded that the position of bi-grating diffraction image has no effects from the finite-width grating;however,the size of diffraction image is affected by the relative distance and diffraction orders between two gratings. The size of diffraction image was calculated, which was enlarged by 1.22 times, when the condition of bi-grating imaging and some experimental parameters were satisfied. Furthermore,the study on the color of white light ordinary transmission hologram was done based on its principles.
Optical Metrology and Measurement
Dual-screen triggering system for CCD vertical target
Dong Tao, Hua Deng-xin, Li Yan, Ni Jin-ping
2014, 35(4): 638-642.
On the request of the stable and reliable trigger required in charge-coupled device (CCD) vertical target measurement system in the condition of firing range, a dual-screen trigging system was presented . The trigging detecting screen was composed of lens-type screen detector, working with the high-intensity LED slow-scattering light, and the velocity-measuring system consists of two identical screen detectors working together with chronometer, and then it judged whether the projectile passing through the screen was real based on the measured velocity and whether to output the trigging signal or not. The time for projectile flying from impacting screen to detecting screen was achieved according to the velocity value V and the distance between impacting screen and detecting screen, and then the triggering signal was output while the projectile was approaching to CCD detecting screen. The proposed scheme can improve the stability of the system, prevent the system from being interfered by unreal targets, and can transmit trigging signal at the precise time to followup CCD image-acquisition system. It has been proved by experiment that the speed measurement error of the designed dual-screen triggering system is not more than 0.4%, fully meeting the demand of the stable and reliable trigger requirement of the CCD vertical target.
Color smokescreen shielding effect measurement based on RGB color mode
Chai Guo-qing, Li Wu-zhou, Zhou Zhe
2014, 35(4): 643-647.
The type and operation of smokescreen were described, the masking principle of jet smokescreen was analyzed .According to the three-primary-color principle, a measurement utilizing red-green-blue (RGB) color mode to assess the chroma of color smokescreen was presented. The attenuation rate data matrix difference method which was currently widely-used to measure the forming time of smokescreen and its errors were analyzed, and a new method using color smokescreen RGB data matrix was proposed to measure the forming time of color smokescreen. The method can eliminate the systematic errors caused by the factors such as the shape and forming way of smokescreen , the target amount, the disposition pattern and so on .Analysis result shows that the measurement accuracy of the method for jet smoke formation time improves 90%, which has the advantages of high accuracy and easy data processing, and provides an effective measure for the smokescreen shielding effect assessment.
Research and application of logarithmic integral amplifier in weak optical detection
Li Chang-qing, Yang Xiao-ya
2014, 35(4): 648-651.
In order to solve the problems in weak optical signal detection with wide dynamic range and high background noise, a circuit for detecting weak light based on the principle of logarithmic integral amplification was designed and fabricated. And the Si photodiodes with two different properties (PN and PIN) were used as the photoelectric conversion element to verify the circuit characteristics. Measurement results show that for the incident light power characteristics, the two photodiodes- output are similar and have signal compression. For the incident light frequency characteristics, when f20 Hz, the output amplitude of PN type is 1.2 times more than PIN type, the PN type has higher sensitivity; when f40 Hz, the output amplitude of PN type varied about 90%, the PIN type output is more stable with about 50% maximum variation. Additional, the spectra measured by two photodiodes have the same trend and peak wavelength as the actual spectra.
Adjustment method of testing conic aspheric optical elements based on wavefront contour map
Chao Ge-ping, Yang Peng-li, Yang Zi-jian, Fu Xiao-qing, Wang Yan-wei
2014, 35(4): 652-655.
In order to improve the testing accuracy and efficiency of aspheric surface optical elements and reduce the adjusting time, the influence of adjustment error of testing elements in aspheric surface interference measurement on wavefront information of testing result was analyzed. The adjustment method which could judge the adjustment orientation accurately by taking advantage of the wavefront contour map trend was presented on this basis. The relation between adjustment orientation and alignment amount of testing elements was established. Using the optical design software Zemax,the measuring ray path of a conic aspheric surface was simulated, and the amount of adjustment was determined through analyzing the tolerance. According to this method, a hyperbolic mirror with an aperture of 50 mm was tested by Zygo laser interferometer, and the final testing result was 0.014 (RMS). Experiments show that the method is simple and feasible.
Crack detection for metallic materials based on eddy-current pulsed-phase thermography
Hu De-zhou, Zuo Xian-zhang, Li Wei
2014, 35(4): 656-662.
The surface and near surface crack of metallic materials can be detected efficiently and accurately by eddy current thermography. In this paper, combining with eddy current thermography and pulsed phase analysis, 45# steel with surface and subsurface cracks were studied by inductive heating simulation and experiments, which were aimed to solve the problem of the phase spectrum distribution and the influence of temperature distribution on the phase spectrum. It shows that, the phase spectrum distribution has nothing to do with temperature value, but is closely related to temperature trend. The phase image has good suppression to inhomogeneous heating, and can also broaden the detection range. Crack can be easily detected when frequency is below 12.5 Hz. The conclusions are experimentally verified, in order to provide guidance for quantitative crack detection with the phase information in the future study.
Optical Element and Fabrication
Preparation of Parylene-N ultrathin films and their applications in organic light emitting diodes
Hu Yong-mao, Li Ru-heng, He Yun, Zhang Xue-qing, Li Mao-qiong, Zhu Yan
2014, 35(4): 663-669.
Ultrathin poly-p-xylylene (PPXN) films were prepared by using a home-made Knudsen cell (KC). By special design and optimization of the KC, the growth rate was well controlled in the range of 0.01nm/s -0.02 nm/s at room temperature in a relatively lower reaction pressure of 10-3 Pa. The PPXN films were identified by infrared (IR) spectra. The morphology of PPXN films were measured by atomic force microscope (AFM). It was resulted that the PPXN surface showed a spike-free undulated morphology. The well controlled PPXN thin films were used as buffers in organic light emitting diodes to control carrier injection and transport, and improvements of more than 80% in device current efficiency were achieved.
ZnS/Al2O3/MgF2 antireflection coating with wide spectrum forGaAs multi-junction solar cells
Xiao Xiang-jiang, Tu Jie-lei, Bai Hong-yan
2014, 35(4): 670-674.
ZnS/Al2O3/MgF2 three-layer antireflection coating with wide spectrum (300 nm~1800 nm) was designed in order to improve the photoelectric conversion efficiency of GaAs multi-junction solar cells. The influence of each layer-s thickness and refractive index on the effective reflectance of film system was analyzed. The results show that the impact of the film thickness of ZnS is greater than that of Al2O3 and MgF2 on the effective reflectance in the whole wavelength,and the impact of MgF2 is the lowest; decreasing the refractivity of MgF2 or increasing the refractivity of ZnS proportionally can get lower effective reflectance. Furthermore, when the optimal physical thickness of ZnS,Al2O3 and MgF2 is 52.77 nm,82.61 nm and 125.17 nm respectively by programming calculation,the minimum effective reflectance is 2.31%.
Direct optical polishing research on surface of aluminum alloy
Zhang Yi, Yin Zi-qiang, Yin Guo-ju
2014, 35(4): 675-680.
Single point diamond turning can make the surface of the aluminum alloy have good quality and precision, but the left turning grains cause scattering phenomenon that affects the optical effect which hardly meets the requirement of high quality optical system. Direct optical polishing on the surface of the aluminum alloy can remove the turning grains which are caused on the surface and can improve the optical performance of reflecting surface. This experiment adopted the new polishing disk and polishing solution to conduct the polishing test over the surface of the aluminum alloy by single point diamond turning. The result shows that we can remove the periodic turning blade lines remained on the surface of the aluminum alloy through reasonable control of the technological parameter, and by which there is no new superficial scratch, so that we can get better optical superficial quality of the aluminum mirror. The roughness on the surface of the aluminum mirror is 2.6 nm.
Key technologies of flat planetary lapping of optical lens
Qi Xiao-yuan, Li Da-qi, Chen Yong, Lu Wei-guo
2014, 35(4): 681-685.
In the flat planetary lapping process, the lapping quality of optical lens has close relation with the uniformity of abrasion of lapping plate. In this paper, the motion law of optical lens in the flat planetary lapping process was analyzed. The model of lens motion trajectory and lens motion velocity in the conditions of differential gear trains was set up. Besides, the simulation program was developed with Matlab software. In addition, combined with the actual production process, the lens motion trajectory and lens motion velocity were simulated in the conditions of planetary gear train. The influence law of lapping machine speed ratio on the uniformity of abrasion of lapping plate was confirmed. When the speed radio I1-1.5, the lapping plate is covered by the lens motion trajectory in short time and the abrasion of lapping plate is uniform. Therefore, the lapping process has better quality and higher efficiency than before. Finally, the high quality optical lens, which consistency of lens thickness was better than 0.002 mm and parallelism was better than 0.002 mm, was obtained by optimized process parameters based on the simulation result.
Design of diamond turning tool for binary diffractive optics
Wang Zhi-bin, Su Jun, Li Jun-qi, Zhang Yun-long, Zhang Feng, Zhao Min
2014, 35(4): 686-690.
As the EO products are developing, the requirements for the processing accuracy of binary diffractive optical element (DOE) become higher, especially the diffractive efficiency, the profile precision, etc. And shadow effect affects the diffractive efficiency efficiently,which is closely associated with the tool parameters. The single crystal diamond tool for DOE manufacturing was designed, based on the analysis of the relationship between diamond tool and shadow effect, surface roughness, wear resistance. According to the turning experiment, the results indicate that the designed single signal crystal diamond tool satisfies the demand for processing DOE, and the wear resistance improves by two times than before strengthened.
Sapphire nanostructure and optical property eroded by different ion beam parameters
Wang Meng-jiao, Chen Zhi-li
2014, 35(4): 691-695.
This dissertation aimed at the research direction of the etching result and optical property of sapphire. The microwave cyclotron resonance ion source was selected as the research instrument. The incident angle and incident energy of Ar+ ion beam were the parametric variables of the research. The research indicates that different variables can lead to different results. When the incident energy is limited to the levels of 800 eV, 1 000 eV and 1 200 eV, the transmittance achieves a big improvement from 50% to around 75%. The biggest and smallest increase of transmittance appear with the incident energy of 1000ev and 1200ev respectively. Besides, under the circumstances of same incident energy and different incident angles, the roughness of etched sapphire shows the tendency of firstly increasing and then decreasing. However, under the opposite circumstances the roughness does not show significant regularity. In addition, the surface morphology test after etching also receives different results. When the incident angle is constant and the incident energy is 1 000 eV, the point-like nanostructure turns up. Increasing the energy to 1 200 eV, the columnar nanostructure turns up. After variables are swapped, the incident energy is constant,the regular point-like nanostructure or strip-like nanostructure show up with the incident angles of 10, 50 and 80. When the incident angle is set in 30, the surface of sapphire is smooth.
Design and fabrication of torsional micromachined scanning gratings based on SOI technology
Jin Qian
2014, 35(4): 696-700.
For the wide use of micro-spectrometer in diverse applications, its core device,torsion-type micromachined scanning gratings, were designed, fabricated and characterized. In order to obtain large scanning range and low resonant frequency at low driving voltage, the structure without additional starting electrodes was designed and studied by silicon-on-insulator (SOI) fabrication technology. The micromachined scanning gratings fabricated by SOI wafers were characterized, which prove that the micromachined scanning gratings has good modulation performances. The maximum deflection angles can reach 4.8, corresponding to a total optical scanning range of 19.2at a driving voltage of 25 V.
Infrared Technology
New scene-based nonuniformity correction algorithm based onGaussian mixture model
Jia Jun-tao
2014, 35(4): 701-706.
A new self-adaptive calibration algorithm for infrared images based on Gaussian mixed model (GMM) was put forward according to traditional temporal highpass filter (THPF). GMM is applied in the new algorithm for background modeling, and only the pixels whose output values satisfy certain conditions can be updated to the correction coefficient, and the background is updated selectively so as to avoid the influence of the foreground target on the update of the background. The performance of the proposed algorithm was evaluated through infrared image sequences with simulated and real fixed-pattern noise, and the simulated sequences quantitative evaluation was carried out by using the peak signal noise ratio (PSNR). Results show that the PSNR of the new algorithm increases by about 9 dB compared with the THPF. The subjective qualitative evaluation was adopted for real images, the correction results in the traditional method show obvious ghosting artifact while the results of the new algorithm are in the absence of ghosting artifact.
Measurement of screening rate and its distribution of infrared smoke screen
Ma De-yue, Li Xiao-xia, Guo Yu-xiang, Zhao Ji-jin
2014, 35(4): 707-712.
The contrast of targets and backgrounds is a key feature detected by IR imager and a physical index reduced focally by smoke jamming. Combining the theory of radiance calibration with the radiation contrast, the apparent radiant brightness of the target and background was used to express the apparent radiation contrast, and as well connected with the gray values of the scene on IR images. Based on the change of contrast before and after screening with infrared smoke screen, the obscuring rate of infrared smoke screen was represented. It was proposed to determine the gray value of the background. The result of a certain jamming experiment was described with screening rate given by this method. Caculation results show that the gray values of background of three experiments are 91.902 4, 88.002 0, 33.285 6, respectively,and the visual distribution diagram of screening rate in the target region is given, which is superior to the traditional evaluation methods, and has a higher value in assessing the ability of infrared smoke.
Laser Technology
Locked frequency accuracy experiment of transmission spectrum of F-P cavity under different sweep frequencies
An Pan-long, Zheng Yong-qiu, Li Xiao-feng, Zhang Jian-hui, Duan Mei-ling, Xue Chen-yang, Yan Shu-bin
2014, 35(4): 713-719.
Aiming at the problem that the output spectrum of narrow linewidth laser is narrow and difficult to be locked, the Fabry-Perot(F-P) cavity which has the unique narrow linewidth and high-definition features was used to do linewidth narrowing and the frequency locking. Based on the advantages of F-P cavity, the experiment plan was designed and a test platform was built, the external cavity optical feedback technology was employed to improve the accuracy of locked frequency. The transmission line was monitored under the sine wave modulation of F-P cavity with different laser piezoelectricity (PZT) sweep frequencies at four direct current(DC) voltages, then the demodulation was conducted and the locked frequency accuracy was tested. As a result, when using 73 V DC high voltage amplifier to sweep the narrow linewidth laser, the laser feedback locked frequency precision can be up to 1.5 MHz.
Experimental study on foam-s camouflage performance
Li Zhi-gang, Wang Jia-chun, Zhao Da-peng, Chen Zong-sheng, Wang Qi-chao, Shi Jia-ming
2014, 35(4): 720-724.
In order to study the application of liquid foam to realize laser camouflage, the experimental camouflage performance of liquid foam on the 1.06 m laser was discussed. The 1.06 m laser echo attenuation values were tested measured under the different parameters of liquid foam. The results show that the attenuation value is up to 66% and down to 36%. Then, the application feasibility of foam on laser camouflage was analyzed with the case of grass and steel combined with the laser camouflage requirements. The results show that the attenuation value reaches 36% while steel camouflaging using 2 cm liquid foam, and the value is in the requested range from 30% to 40% of the grass camouflage. So the liquid foam has fine performance in 1.06 m laser camouflage, and it can realize laser camouflage of ground targets using liquid foam.
Identification of axial RLG drift in single-axis inertial navigation system based on artificial fish swarm algorithm
Lei Wen
2014, 35(4): 725-728.
Single-axial rotation can compensate the vertical errors of the inertial apparatus automatically, but can not compensate the axial vertical errors in inertial navigation system. Therefore, the axial drift of ring laser gyroscope (RLG) is an important factor for affecting the accuracy of inertial navigation system. The accurate identification of axial RLG drift can improve the precision of inertial navigation system. The identification model of axial RLG drift based on artificial fish swarm algorithm (AFSA) was introduced and the steps and method were given. The experimental results show the identification model by AFSA is accurate and the drift instability of RLG after it is compensated is 0.000 4 /h. The proposed method is an effective approach and has a better identification precision and engineering practice value.
Dual-wavelength fiber laser for generating interval-adjustable microwave
Xu Yu-meng, Wang Guo-zheng, Peng Ling-ling, Liu Xin-nan, Kou Yan-qiang, Wu Ke-xin
2014, 35(4): 729-732.
In order to obtain dual-wavelength output with different intervals, an equipment to generate dual-wavelength laser based on simulated Brillouin effect was put up. The tunable microwave signal was got through beat frequency experiment for the different intervals dual-wavelength output signal. A segment of 10 km single-mode fiber (SMF) was used as the Brillouin gain medium and a 5 kHz distributed feedback (DFB) semiconductor laser was used as the Brillouin pump (BP). An un-pumped polarization maintaining erbium-doped fiber (PM-EDF) was used as the saturable absorber to suppress unwanted side-modes. Different-interval dual-wavelength output was obtained by changing the length of un-pumped PM-EDF. In the experiment, dual-wavelength outputs with 0.170 nm and 0.085 nm spacing were achieved, corresponding to 20 GHZ and 10 GHZ microwave signals.
Fiber Sensing and Optical Communication
Quality assessment of fiber coil based on BOTDA fiber sensing technology
Han Zheng-ying, Gao Ye-sheng, Zhao Yao
2014, 35(4): 733-736.
Based on the analysis of the influence of fiber coil on the overall performance of fiber optic gyro(FOG), we proposed to assess the quality of fiber coil by utilizing the Brillouin optical time-domain analysis (BOTDA) optical fiber sensing technology. Through the on-line testing, thermal stress testing and framework performance testing for fiber coil, we could discover and eliminate the stress spike and layering switch phenomena in time,also the optic fiber stress curve reversing induced by framework and heat stress could be removed.