2012 Vol. 33, No. 2

OE System and Engineering
Optical system design of grating-based imaging spectrometer
HAN Jun, LI Xun, WU Ling-ling, LU Shao-jun, YU Xun, ZHAN Chun-lian
2012, 33(2): 233-239.
Imaging spectrometer is a kind of optical remote sensing instruments which combining image with spectrum. Grating-based imaging spectrometer has a wide range of applications because of concise principle, stable performance, and nature of the technology. This article designs a kind of grating-based imaging spectrometer optical system using ZEMAX. The fore optic adopts reflection structure, aiming at the issue that the traditional Cassegrain structure has limited ability of aberration correction and makes system processing complex when both the primary and secondary mirror all use aspheric surface, this design adopts the improved Cassegrain structure for aberration correction. The transfer function of final fore optic is 0.5 at 50 lp/mm, the field curvature is less than 0.078 and there is no distortion .The Czerny-Turner structure based on plane grating that the spectral imaging system usually adopts has low spectral resolution, and the image quality is so bad as not to meet the requirement of the instrument. So the spectral imaging system based on convex grating is used, it has compact structure, strong ability to correct aberrations and high spectral resolution. The final spectral resolution is less than 5 nm, MTF is 0.75 at 50 lp/mm.According to the principle of matching, the grating-based imaging spectrometer is achieved by combinatorial optimization of the fore optic and spectral imaging system. The RMS radius of spot diagram of the spectrometer is always less than 0.2 with the change of wavelength, 80% of the wavelength energy concentrates in 6 m and the MTF is greater than 0.5 at 50 lp/mm over the whole FOV.The entire optical system is characterized by simple structure ,good capability of aberration correction and small size.
Structure design and adjustment of multiple-field-of-view fixed-focal-length CCD camera system
XIA Yuan-jie, DUAN Hong-jian, SHI Xin, LIU Zhi-dong, YANG Xiao-qiang, WANG Tao
2012, 33(2): 240-244.
In order to solve the problems of more deviation of optical axis and larger space occupancy induced by traditional structural method, this paper presents a CCD camera with the structure of multiple fields of view(FOVs) and fixed focal length which is based on a precision casting to cast the inner rough shape of every FOV in the casting. Through the numerical control (NC) machining and the reliable assembling and adjustment method, the parallelism and stability of optical axis for this system are guaranteed efficiently. Impact and vibration tests are carried out and the measurement results show that the opticalaxis parallelism error of the multiple FOV system is less than 0.2mrad; its optical-axis stability error is less than 0.1mrad. So the structure design method is feasible and effective .It has the advantages of compact structure, lighter weight, more reliable optical-axis parallelism and stability, high reliability.
Three-proofing design of shipborne optic-electronic equipment
QIAO Jian, CAO Li-hua, SHI Long
2012, 33(2): 245-249.
The moisture-mildew-saltspray proofing design of shipborne optic-electronic equipment is an important mission for the shipborne optic-electronic equipment. It should be considered overall from the materials application, structure design, process engineering and so on at the time of the product development. In this paper the three-proofing issue of shipborne optic-electronic equipment was studied. The three-proofing design was detailedly introduced in optic lens, machine structure and electronics. The proper choice of material is the basis of the design. The rationality of the structural design is the key factor for moisture-mildew-saltspray proofing design of the shipborne optic-electronic equipment. It would improve the proofing capability farther that the correct use of the material modification, surface coating/depositing, encapsulation, insulation process and so on. It was proved by engineering practice that the design could make the shipborne optic-electronic equipment have excellent three-proofing performance and work steadily in sea climate environment for longer time.
Optical design of uncooled high zoom ratio continuous-zoom lens
ZHANG Liang, LIU Hong-xia
2012, 33(2): 250-254.
Aiming at the long-wave uncooled vanadium oxide focal plane arrays ( FPA) detector with 320240 pixels and 25 m25 m pixel pitch, an long-wave infrared continuous zoom optical system is designed, based on the optical zoom theory, as well as the aspheric and diffractive aberration balancing method. Its spectral range is 8 m~12 m, field of view(FOV) is 2.86~50,F number is 1.2 and zoom ratio is 18∶1. In the all optical zoom range, the modulation transfer function (MTF) is above 0.5 approaching the diffraction limit, and 70 % of the encircled energy is concentrated in one pixel of detector. Moreover, only one common infrared material of germanium is used to balance the aberration.
Measurement system for atmospheric aerosol extinction coefficient
XIAO Shao-rong, ZHU Run, WANG Ya-ji
2012, 33(2): 255-259.
A method for measuring atmospheric aerosol extinction coefficient was introduced. The coefficient was obtained by detecting the attenuation of light intensity when semiconductor laser passed through the aerosol. The light intensity values were detected, and after photoelectric conversion, signal processing and AD sampling, the aerosol extinction coefficient was calculated according to Lambert-Beer theorem. The dual-channel measurement method was used in the design, in order to reduce the effect of atmospheric molecules and the instability of the semiconductor laser light. The aerosols of different concentrations were tested. The results showed that the relative error was less than 4%. The atmospheric aerosol measurement system has the advantages of small size, simple operation and fast detection. It could be used to monitor air pollution and visibility.
Features of 3D naval vessel models using clustering technology
YU Ji-Hong, BAI Xiao-Ming, GUO Ning
2012, 33(2): 260-264.
Creating a sufficient feature base for all of the viewpoints or extracting an invariable feature of different viewpoints are the common methods for 3D target recognition. They share the shortcomings of big size feature base, enormous computation and low recognition rate. It is almost impossible to find the recognition feature of robustness. The method for establishing the 3D naval vessel models feature base with clustering technology was studied. The affinity propagation (AP)clustering algorithm requires no initializing cluster centers and it is suitable to cluster view points space. Experiment of AP was done using computer based on the Hu moments, and the clustering results validied the method by Silhouette index.
Rotating mirror design of ultra-high speed camera based on eigenvalue sensitivity analysis
LI Chun-bo, YU Chun-hui, CHAI Jin-long, LIU Chun-ping, LI Jing-zhen, HUANG Hong-bin
2012, 33(2): 265-270.
Eigenvalue sensitivity analysis model of rotating mirror has been established by means of numerical analysis based on the theory of dynamic modification. The loop files of eigenvalue sensitivity were got based on the modal analysis. With the Latin hypercube sampling of Monte Carlo, the data of structure parameters were sampled by the probability density of the structure size of rotating mirror. The Spearman rank correlation coefficient between eigenvalue and structure size was obtained by calculation. The result shows that the spearman rank correlation coefficient of basic variables is different from each other, which reveals that the variables impact the natural frequency in different ways. According to the result, the circumcircle radius of the mirror body was modified, the numerical analysis and experiments of the two rotating mirror were done. The results show that the first-order modal rotating mirror is increased 101.8%, the first critical speed is 8.7 105 r/m and the dynamic performance of rotating mirror is effectively changed. This indicates that the way of eigenvalue sensitivity analysis based on the results of numerical analysis to optimize the structure size of the rotating mirror is a practical and effective method.
Parameters calibration algorithm in electronic whiteboard system
HUANG Li-na, YU Zhong-qiu
2012, 33(2): 271-277.
In order to avoid complicated process of camera calibration and achieve the function to calibrate parameters automatically at start-up, a new method of electronic whiteboard system calibration was proposed based on CCD camera. Image pixel coordinates of reference points were extracted by using Harris corner detection algorithm. According to the basic property of projective geometry, the relationship between image pixel points and actual points was derived, and the optical center coordinates of CCD camera were obtained. The factors affecting calibration precision were analyzed, the project for decreasing calibration error was designed, and the experiment platform was constructed to calibrate parameters. Experimental results show that the calibration algorithm has simple realization and convenient application, and the calibration error of the calibration block with 1 cm length is less than 0.04 cm.
Image stabilizer for improving definition of image
XIE Guan-bao, GUO Xi-qing
2012, 33(2): 278-283.
The principle and effect of image stabilizer for improving the definition of image are studied. First, the influence of shaking on imaging is analyzed according to the light path of camera and the expression of offset d caused by shaking is given; second, the paper establishes the control model of the image stabilizer, uses the proportional-integral-derivative (PID) control algorithm and gets the result of anti-shaking effects with the simulation of MATLAB; last, some objects are shot by a digital camera respectively under the conditions of opening and closing image stabilizer. Two groups, 8 images of 150112 pixels are obtained. Based on the histogram in frequency domain, the image shot with image stabilizer has 10 more high-frequency components than the image shot without image stabilizer on average; based on the energy gradient curve in spatial domain, the order of magnitude of the image shot with image stabilizer increases from 104 to 105.
OE Information Acquisition and
Technology of image space scanning
DENG Jian, LI Rui-gang, ZHENG Chang-sheng
2012, 33(2): 284-287.
Based on the principle of photomicrography, image space scanning is studied to be as the method to expand the optical system-s field of view (FOV). An optical design model is introduced, which has secondary imaging structure, including a large FOV fixed front objective lens set and a spherical motion relay lens set. The field curvature of the first image plane of the front lens set is optimized, and the motion trochoid of the relay lens set is according to the curve radii. The relay lens set image the different fields of the first imaging plane and get the image space scanning. Optical passive athermaliztion technology is used to ensure the system imaging quality at different temperatures. The model relative aperture is 1∶3, the wavelength is 3.7m~4.8m ,the focal length is 90mm, the instantaneous staring FOV is 4, and the scan FOV is 24. The whole optical system has 7 lenses with 3 asphere surfaces, which is approximate to diffraction limit over the full FOV.
Autocollimation location system of aerial camera lens- focus plane based on image processing technology
ZHAO Yu-liang, XU Zhao-lin
2012, 33(2): 288-292.
A measuring method of aerial camera lens- focus plane is presented, which locates focus plane using autocollimation theory. The system chooses two kinds of image definition evaluation function to extract the characteristics of image definition, and detects focus plane quickly using hill-climbing algorithm. Simulation experiment result proves that measuring and calibrating the focus plane of aerial camera using the autocollimation measuring system is characterized by high precision, high speed and good real-time performance, and has little influence by the artificial factors. The system is adapted for the focus plane calibration and auto-focusing system of aerial CCD camera.
Definition evaluation algorithm based on regional contrast
ZHANG Ya-tao, JI Shu-peng, WANG Qiang-feng, GUO Zheng-yu
2012, 33(2): 293-299.
The accurate and efficient evaluation of image definition is a critical step in automatic focusing. In the available evaluation methods, there are a variety of limitations due to different parameters used. After analyzing the advantages and disadvantages of existing methods for image clarity evaluation, a new evaluation method for image definition based on regional contrasting is proposed based on image analysis and statistics. The mathematical model is established and analyzed, and the experimental results are given. It is proved that, this evaluation method satisfies the basic tactic requirements, and has high sensitivity and reliability in automatic focusing.
Colour transfer for grayscale images based on morphology transformation and FFCM cluster
HE Dong, YANG Feng-bao, LIN Su-zhen, ZHOU Xiao
2012, 33(2): 300-304.
To deal with the problem that the traditional color transfer algorithms can not transfer the image colour accurately and have large amount calculation, we proposed a colour transfer algorithm for colorizing grayscale images based on morphology transformation and fast fuzzy C-means (FFCM) cluster. We used morphology transformation to process the target image for removing the non-uniform luminance region first, and adopted the FFCM algorithm to cluster the target image accurately.Then we established the correspondence between the swatches of source and target images to complete the color transfer of swatches which were as the references to complete the target image-s colorization.The experimental results showed that, compared with Welsh and fuzzy C-means (FCM),the elapsed time decreased by 64.2% and 54.25% respectively and the result image was more natural in clusters- junction which proved the validity of our algorithm proposed.
Super resolution reconstruction based on L1-norm and orthogonal gradient operator
JIN Xiao-juan, DENG Zhi-liang
2012, 33(2): 305-312.
For the ill-posed problem of super resolution reconstruction, a new adaptive algorithm for image sequence was proposed. The new algorithm was based on the framework of L1-norm. In the new algorithm, the pyramidal algorithm coupled with Lucas-Kanade algorithm was used for images registration to obtain the sub-pixel motion estimation. Displacement operator was introduced to achieve the regular term based on the orthogonal gradient operator and the regularization parameter was determined adaptively. Finally, the steepest descent method was used to solve the minimum of the constraint equation. The simulation experiments and the true sequence experiments show that the method proposed has advantages over spline interpolation, Tikhonov reconstruction and bilateral total variation reconstruction. On the one hand it can provide better reconstructing results, on the other hand the reconstruction time is reduced at the same time since the regularization item is simple.
Synchronous acquisition circuits of image data in different places
Lu Pei-sen, NI Jin-ping, MA Shi-liang
2012, 33(2): 313-321.
In the test of proving ground, in order to obtain the images of projectiles exploding at the same time in different places, multiple cameras at testing stations in different places were controlled to achieve the synchronous acquisition of the image data. This paper presented a method for synchronous acquisition of image and a design of high precision timing system based on global position system (GPS) technology. This system used the GPS timing signal, realized the local clock through a uniform time circuit and a counter circuit, and could record the starting shooting time of the camera at each station to achieve the synchronous acquisition of the image data. The synchronous precision of the system could be microsecond level.
Optical Metrology and Measurement
High precision angle measurement method of dynamic tank turret
QUAN Gui-Qin, FENG Wei-Qiang, ZHANG Jian-feng, YU Xun
2012, 33(2): 321-326.
Tank turret rotation angle measurement accuracy relative to the chassis directly determines the precision of the stable sighting system and the inertial navigation system. At present, the main battle tank equipped with a tank turret in the angle measurement device which has low measurement accuracy relative to the chassis can solve the problem of steering the tank body only. This paper proposed a high-precision angle measurement device which was composed of location and orientation system, mechanical drive system and resolver. It firstly introduced the working principle and work process, followed by the angle measuring device calibration and the theoretical analysis of error, the final joint commissioning proved this angle measuring system met the actual demand. Results indicate that this measurement system can confirm the location when instantaneously powered and has absolutely zero memory function, the angular accuracy is 42.
Double-parameter monitoring technology of ocean red tide temperature and salinity
LIN Hong, LIANG Kun, WANG Xin-min, LI Wei-zhong
2012, 33(2): 327-332.
Aming at the monitoring and forecasting of the growth of ocean red tide, an ocean environment monitoring and forecasting technology based on the detecting of the Brillouin scattering echo signal is proposed. This technology can detect the double parameters about the ocean red tide temperature and salinity information. Based on the Brillouin scattering theory, the relationship of the blue-green laser-s Brillouin scattering frequency shift value and energy value with the seawater temperature and salinity is found. Then, the detecting model of the seawater emperature and salinity is established. The blue-green laser-s Brillouin scattering frequency shift value and energy value are evaluated by simulating and calculating, and the temperature and salinity of the seawater at 0~50 m are known. Based on the double-parameter monitoring technology, the growth and decline of the ocean red tide can be monitored and forecasted.
Temperature stability analysis of static angle calibration devices
2012, 33(2): 333-336.
Static angle calibration devices are applied to detect the static angle measuring accuracy of large scale photoelectric theodolites, and the stabilization accuracy of angle datum which is affected by the optical axis orientation of autocollimator is required less than 2 (rms) in 24 hours. According to the requirement, the impact of ambient temperature on angle datum was studied. Experiment results proved that the optical axis orientation of Cassegrain reflective collimator used in the static angle calibration devices was not influenced when the ambient temperature changed in a certain range, but the static angle calibration devices no longer met the precision requirement when the environmental temperature was beyond the range of specified operation temperature. In order to ensure the measurement accuracy, specific requirements of laboratory infrastructure were put forward. In addition, the calculation results of optical design software showed that the inhomogeneity of the collimator manufacturing material, assembly tolerance, stress were the main factors affecting the optical axis orientation.
Resolution and FOV quality of UV image intensifier
HE Ying-ping, LI Min, YIN Lei, HU Hui-ping, BAI Xiao-feng, HU Wen
2012, 33(2): 337-341.
To analyze the optic imaging characteristics and the FOV quality of ultraviolet (UV) image intensifier, a method for testing the resolution and FOV quality of UV image intensifier was put forward. Under the condition of the photocathode irradiated by the typical 254nm UV light, we applied working voltage on the image intensifier, focused the testing targets on the focus plane of the coaxial reflect optic system, and the image was trebly reduced on the screen of image intensifier. The imaging could be seen distinctly by adjusting the objective and ocular, and the lowest line pair observed by 30 video microscope was the resolution. We used digital camera to take photo of the image on the screen, and the spots were measured through image processing software. The testing results of the field showed that the measurement precision was about 5%,which validated the feasibility of the testing method.
Enhanced measurement precision of angular surface plasmon resonance sensor
LI Wei-xiang, MA Xiao-hong, Lu Hui, ZHAO hua, feng
2012, 33(2): 342-346.
An angular surface plasmon resonance measurement system based on prism was designed. The mechanical structure with coaxial double layer rotating table was setup. We proposed a novel scanning angular measurement method and obtained the surface plasmon resonance curve. The impact factors on the consistency of multiple measurements were studied, the new method decreased the measuring point number, increased the sample data on one point, and used three kinds of variable steps. The measurement time was decreased to 1/10, and the precision reached 4E-5 refractive index level from 1E-4 refractive index level.
Optoelectronic measuring method for height of burst point of bouncing projectile
TIAN Hui, NI Jin-ping, XIN Bin
2012, 33(2): 347-350.
An optoelectronic measuring method was put forward to measure the height of the burst point in the air of bouncing projectile. The mathematical model of the method was established based on the projectile falling in the uniformly retarded motion after bouncing into the air. This measuring system was composed of a sonic transducer, a light screen, a flame detector and a twin-channel chronograph, which could measure the time intervals of several characteristic points. The height of the burst point was calculated in accordance with the formula by means of cooperating with the measured time intervals and the structure parameters of the light screen. The uncertainty of the method was analyzed, which was less than 20mm theoretically. The result proves that the method has the advantages of high accuracy, good instantaneity, and high reliability. Besides, it is simple and convenient to integrate. The method is applied on the occasions of measuring the height of the burst point of the projectile bouncing back after falling to the ground and of the civil aerial display shells exploding in the air.
Measurement and research on sky background radiance luminance
LIU Wei-feng, XIE Yong-jie, ZHAO Le-zhi
2012, 33(2): 351-354.
Sky background luminance is very important for space target detection and identification. In order to research on it, the measurement system of sky background luminance was introduced, compared with the sun photometer CE318 made by CIMEL Co. in French, a good consistency was achieved. On the time when a certain space target transited, the sky background luminance on the target orbit was measured by the system. The data was analyzed and studied. The primary variation characteristic of the sky background luminance on the target orbit was acquired. Important information is provided for application.
Preparation and photochromic properties of Ag nanoparticles deposited on TiO2 surfaces
ZHANG Lu, JIAO Yang, GAO Ping-an, SHANG Yi-bo, JIN Wei, YAO He-bao
2012, 33(2): 360-364.
Ag/TiO2 film was prepared by photochemical reduction method with depositing Ag nanoparticles on TiO2 surfaces. The influence of TiO2 annealed at different temperatures on the photocatalytic deposition of Ag nanoparticles was analyzed by ultravioletvisible (UV-Vis) absorption spectra, and TiO2 films annealed at 500℃ were helpful to the reduction of Ag nanoparticles. By the 650 nm red laser irradiation, Ag/TiO2 films annealed at 500℃ exhibited photochromic properties well. The mechanisms of photochromism were studied, and we found the response rate of photochromism of Ag/TiO2 films improved with the increase of Ag depositing time, but excess Ag nanoparticles inhibited the photochromic response rate of the Ag/TiO2 thin film.
Gradient force pattern of cosine-squared Gaussian beams through lens without aperture
HAO Zhong-qi, LIU Li
2012, 33(2): 365-369.
The intensity distribution and gradient force pattern of cosine-squared Gaussian beams focused by a thin lens without aperture were derived based on the Collins formula. Through the numerical simulation, the influence of the beams parameter, relative incident separation and beams Fresnel number on the distribution of gradient force pattern, the number, position and size of the optical traps were discussed. The results indicated that the bigger the beams parameter b, the more the optical traps; the position of optical trap changed with the beams relative incident separation, and the size decreased with the increase of Fresnel number of the system while the position stayed unchanged.
Helmet-mounted displays based on retinal projection display
YANG Min-na, GUO Zhong-da, YANG Zhi-qiang
2012, 33(2): 370-373.
Conventional see-through head-mounted displays can display virtual image; however, virtual image can not keep clear on the retina from beginning to end when the eyes adjusts the focus length.So a new technology of see-through head-mounted displays which can catch sight of external features and see the virtual image on the micro-display chip has been introduced. It is an advantage of virtual image, which can always keep clear, no matter how to adiust the focus of eyes. The principle of display technology was discussed.The overall optical system was designed by using Zemax and reached the diffraction limit after optimization.The MTF of filtering projection system was 0.7 at 60 lp/mm. The structure of head-mounted displays was designed by Autocad. The imaging experiment result shows that both the external features and the virtual image could be seen clearly in the presence of eyes focusing on external features. Though the external features would be fuzzy when eyes defocus on external features, the virtual image could still be seen as clearly as before.
Simulation and analysis for road lighting with LED luminaries
KAN Zi-xiong, WAN Qiao-bin, REN Hao, CHEN Zhen-qiang
2012, 33(2): 374-379.
With the dramatic development of semiconductor industry and the pressing need of environment protection, LED has acted as a new energy source to be applied to lighting industry. This paper selected several typical kinds of LED street lamps as the research objects which have different shapes in their respective light distribution curves. By using the light designing software Dialux,this paper simulated the LED street lamps- illuminance distribution on the road and made an analytic comparison between two different street lamps-array methods, then summed up the features of LED-s light distribution curve which were suitable for roadway lighting to provide reference for the design of LED luminaries.
Spectral control of 1-D photonic crystal
LING Jun, ZHANG Shuan-qin, YANG Hui, LU Yan-li, PAN Jia-liang
2012, 33(2): 380-384.
The forbidden band characteristics of photonic crystal provide a new technology for the study of spectral control of camouflage materials. This paper built the spectral transmi-ssion and reflection theoretical model of one-dimensional photonic crystal with transmission matrix. Aiming at the demand of high reflection in near infrared and low emission in middle-far infrared wavebands of camouflage materials, Ag, MgF2 and ZnS were optimized as thin-film materials of photonic crystal, and by the way of vacuum evaporation filming, Ag/MgF2, Ag/MgF2/ZnS 1-D photonic crystals with different periodical structures were prepared. Spectral reflection and transmission characteristics of these 1-D photonic crystals were studied experimentally. Experimental results show that the materials and periodical structures influence the spectral characteristics of 1-D photonic crystals and by optimum design the photonic crystal can realize the spectral characteristics in camouflage waveband.
Optical Element and Fabrication
High precision positioning based on chirped-pulse interferometry
LI Bai-hong, YAN Zheng-xin, ZHANG Tao, LIU Wei, LI Min
2012, 33(2): 355-359.
A new scheme is presented for high precision positioning based on chirped-pulse interferometry(CPI). In this scheme, a pair of oppositely chirped optical pulses with strong classical frequency correlations are combined at a beamsplitter. The output beams with two different paths are recombined and focused onto a nonlinear crystal. High precision positioning with magnitude of micron is obtained theoretically by detecting sum frequency interference signal as a function of relative delay between two different paths.The impact of difference between chirp and anti-chirp pulse on positioning is studied. It is shown that positioning has a high tolerance of difference between chirp and anti-chirp parameter. Our scheme exhibits all the advantages of quantum spatial positioning based on the Hong-Ou-Mandel(HOM) quantum interference, but with more simple experimental setup ,robustness against loss and greater signals, which provide more improvements in practical maneuverability.
Infrared Technology
Design and analysis of dual-channel infrared projection optical system
ZHENG Ya-wei, QIANG Hua, GUO Yun-ping, GAO Jiao-bo, WANG Jun, LI Jun-na, GAO Ze-dong, WU Wen-li
2012, 33(2): 391-394.
This paper analyzes ray paths of the dual-channel projection system and introduces the design of the projection collimator optics. The projection system consists of a target source generator and an inference source generator sharing the same optics. The optics uses a re-imaging configuration to meet the packaging requirement. The beam splitter is located between the last surface and the focal plane of the optics to combine the target source channel. By reducing the thickness of the beam splitter, the aberration of the optics in the inference source channel is reduced. The optics collimates the output from an infrared source in the 8 m~12 m waveband and enables an imaging system with 8.5 field of view to be tested. The effective focal length of the optics is 315.69 mm and the entrance pupil relief is 900 mm.The obtained performance shows the optics meet the requirements of the projection system.
Common-aperture dual-channel infrared scanning imaging optical system
LIU Kai, CHEN Rong-li, CHANG Ling-ying, LEI Guang-zhi, ZOU Gang-yi
2012, 33(2): 395-401.
A scanning imaging optical system of dual infrared spectrum is studied, and combined with the triple imaging technology and 100% cold shield efficiency technology, a common-aperture dual-channel infrared scanning imaging optical system was designed. The system was composed of a common twomirror system, a beamsplitter, a collimation system, a scanning mirror and an imaging system. Light was divided into the mid-wavelength infrared (MWIR,3 m~5 m) waveband and the long-wavelength infrared (LWIR, 10 m~12 m) waveband by the beamsplitter, then they were converged on the two detectors through the collimation system and imaging system, and the MWIR and LWIR optical systems realized common-aperture synchronization imaging. The use of small scanning mirror greatly reduced the scanning mirror-s difficulty of manufacture and test, the difficulty of designing the control mechanism, and reduced the system size and weight. The result shows that the LWIR system transfer function is above 0.4 at 18 lp/mm, and the MWIR transfer function is above 0.78 at 18 lp/mm, which satisfies the needs of practical applications.
Laser Technology
Laser semi-active seeking guided seeker optical system
HU Bo, CHANG Wei-Jun, SUN Ting, HE Yu-Lan
2012, 33(2): 402-405.
According to principles of quadrant detector, light spots of laser semi-active seeking guided seeker optical systems should be formed on the target surface of quadrant detector uniformly. This paper firstly analyzed the aberration characteristics of these optical systems and presented a method for correcting the aberrations, then designed an optical system by CODE V, evaluated the spots quality of the optical system qualitatively by the footprint and the encircled energy. 1106 rays were traced by LightTools to obtain the distribute of the rays on the quadrant detector for various fields of view. The target angle-output response curve which could evaluate the performance of light spots precisely was plotted by Matlab. The article provides reference for the optical system design of laser semi-active seeking guided seeker.
Measurement for beam quality in intracavity passive confocal unstable resonator OPO laser
LI Gang, MAO Shao-juan, ZHANG Chu, LI Li, WANG Yuan-bo
2012, 33(2): 406-410.
Based on the theoretic optimized values of intracavity passive confocal unstable resonator, the beam quality of optical parametric oscillator (OPO) laser is tested experimentally. The transmission energy of laser is about 70.6 mJ/pulse and far-field divergence angle is below 5mrad. The possible factors of affecting beam quality are analyzed. The high quality of 1.57 m laser can be obtained through optimized design.
High efficiency LD side-pumped green laser
PAN Jiang-ni, REN Zhao-yu, GUO Teng, WANG Si-yuan, BAI Jin-tao
2012, 33(2): 411-414.
According to ABCD transmission matrix theory, A Z-type resonator used for laser diode (LD) side-pumped intracavity frequency-doubled Nd:YAG /KTP laser was analyzed and calculated by software Matlab. We selected a set of proper cavity parameters, at 9kHz repetition frequency and 302.5W input electrical power, a 17.27W green laser was obtained with an electrical-optical conversion efficiency of 5.7% and divergence angle of 0.68mrad, the beam quality was M2x=3.351, M2y=3.759,output instability was less than 0.9%.
Methods for improving real-time ranging performance of short-range moving targets
HAN Wan-peng, MENG Wen, LI Yun-xia, LI Da-wei
2012, 33(2): 415-420.
In order to improve laser ranging accuracy and frequency of docking guidance system, several aspects were researched on the methods of distance measurement, the influence of the pulse spreading, the received SNR, the receiver bandwidth and the methods of threshold setting. The ranging performance of short-range moving targets was improved by improving the self-triggering pulsed time-of-flight laser ranging method, increasing the peak power of radio signal, using the appropriate filter, reducing the bandwidth of the receiving system and setting the adaptive threshold. Finally, the semiphysical simulation experiment was adopted to test the system-s ranging performance, and the results show that the dynamic ranging accuracy is less than 2cm which meets the design requirement of docking guidance system.
Fiber Sensing and Optical Communication
Simulation analysis of temperature characteristic of fiber coil
YU Zhong-quan, ZHANG Min, CHEN Xi-yuan, LIANG Ren-ren
2012, 33(2): 421-426.
The fiber coil is the core part of fiber-optic gyroscope, its stability and anti-interference ability directly influences the whole function of fiber-optic gyroscope. The temperature characteristic of fiber coil was investigated and the temperature gradient of each element in coil was determined by finite element analysis. According to the Shupe effect theory, we designed the analysis software on temperature characteristic for the fiber coil, the software combined the analytical result of finite element of the fiber coil with the output of fiber-optic gyroscope, which is the phase difference between the two directions of propagation light. We analyzed the temperature characteristic for the fiber coil based on different conditions such as different hot radiation methods, with or without the buffer layer, different winding methods and the asymmetry of the fiber coil.
Properties of various metal cladding waveguides modulated by voltage
ZHANG Yi, FENG Guo-ying, ZHOU Guo-rui, SUI Zhan, WANG Jian-jun, MA Zi
2012, 33(2): 427-432.
In this article, the ultrahigh-order modes which exist in the symmetrical metal cladding optical waveguide are excited by using free-space coupling method. The refractive index and thickness of LiNbO3 slab are changed through adding different voltages between the two metal films which are in symmetrical metalcladding optical waveguide. The attenuated total reflection (ATR) spectrum with different parameters is obtained. The experimental results show that the ultrahigh-order mode is polarization independence and very sensitive to the thickness and refractive index of the waveguide layer. The experimental results agree better with theoretical predictions. Under the same conditions, the sensitivity of the symmetrical Al-cladding optical waveguide is higher than the symmetrical Au-cladding optical waveguide. The results have certain reference value for the development of the integrated optoelectronic devices.
Satellite-to-ground optical communication-s usability with different weathers and ground station location
JIANG Xiao-feng, ZHAO Shang-hong, LI Yong-jun, WANG Xiang, LI Rui-xin
2012, 33(2): 433-436.
The attenuation of satellite-to-ground optical link in fog, rain, snow and cloud is calculated with empirical formulas. The result of simulation shows the longer the length of the light wave, the smaller the attenuation of the laser in the fog; the attenuation in the snow is 10~100 times higher than that in the rain; when the optical depth of cloud is 4.7, the laser attenuation is higher than 20 dB. Considering the geographic distribution, meteorological features and cloud cover statistics, it is suggested that the Tarim basin, the desert of western Inner Mongolia and the northwestern part of Loess Plateau in northwest of China should be favorable for satellite-to-ground optical communication ground station location.
Structure and adjustment of mobile wireless laser communication base station
WANG Gang, GAO Tian-yuan
2012, 33(2): 437-440.
The application of wireless laser communication has been increasing recently; therefore, design of a portable, fast network wireless laser communication base station is very important. This paper mainly focuses on the structure of the mobile wireless laser communication base station and the adjustment of the parallelism of 5 optical axes, and meets the needs of communication in the final system. The paper introduces the fixing and adjusting mechanism of the right angle prism in communication receiving system, analyzes the error of the parallelism of 5 optical axes. The result satisfies the requirement that the depth of parallelism is 10.