2011 Vol. 32, No. 2

OE System and Engineering
Numerical simulation for optical transmission of aero-optical dome
FAN Zhi-gang, XIAO Hao-su, LI Hui
2011, 32(2): 189-194.
Since the shape and optical properties of a aero-optical dome change as the dome is subjected to aerodynamic heating, the optical transmission of the dome is affected. A finite element analysis model of the dome was established to numerically compute its refractive index distribution based on the theories of thermo-optical and elastic-optical effects. The optical transmission of infrared radiation through the dome was numerically simulated using the ray tracing program based on the fourth order Runge-Kutta algorithm. Two kinds of imaging quality evaluation parameters were presented, wave aberration of the exit pupil and MTF. The research results show that the thermo-optical effect has a much greater influence on optical transmission through the dome compared with the elasto-optical effect and the imaging quality of the dome is seriously affected due to aerodynamic heating. Therefore, the effect exerted by aerodynamic heating on the optical transmission of the dome can not be neglected for improving the guidance precision of missles .
Optical design of microscopic imaging system for ultraviolet-visiblewide spectrum
CHEN Jiao, JIAO Ming-yin, CHANG Wei-jun, KANG Wen-li
2011, 32(2): 195-199.
Design of a wide spectrum ultraviolet-visible microscope objective was introduced. According to the dispersive properties of ultraviolet(UV)optical materials, was selected as positive lens material, apochromatic equations for distributing the optical power of each lens in double-dialyte lens were established, and appropriate deviation angles were assigned for two groups. Based on theoretical calculation with PW method and optimization with CODE-V, the longitudinal chromatic aberration and secondary spectrum were corrected, and apochromatism was achieved. Simulation results show that the radius RMS of spot diagram dispersion circle is less than 5 in the entire field of view, astigmatism is 0.058 and istortion is 0.04% at the maximum field of view for this system.
Real-time detection of tangential displacement deviation in rotating parts
FU Qian, CHEN Chang-ying, CHEN Xi, HONG Yue, ZHAO Hui-shan, MO Chen-xiao, LUO Hong-tu
2011, 32(2): 200-205.
Controlling overprint error is an important for modern printing technology, and the displacement deviation of press cylinder surface in high-speed rotation state is a major cause of overprint error. The real-time monitoring system for detecting the tangential displacement deviation in rotating parts was designed and implemented. Photoelectric detection and A/D mixed-signal processing method was used to realize real-time monitoring of the press overprint error, which could be used for research and manufacturing process of high precision printing machinery. Barcode coding technology, virtual calibration technology and real-time monitoring technology for tangential displacement deviation and self-adaptive dynamic balance technology were used in the system, and the measuring precision was controlled within 10m.
AImplementation of a block processing mode of digital filter on DSP
SUO Liang, LIANG Fang
2011, 32(2): 206-210.
Symmetric finite impulse response (FIR) filter with astrictly linear phase characteristics and system stability is widely used in data transmission, image processing and other fields. Conventional digital filter based on single-point processing mode can process point signal in real-time. H owever, its processing speed is slow, and real-time performance is not very good when dealing with images, or voice frame signals. This paper proposes a block processing model to solve this problem. By analyzing FIR filter theory, a symmetric FIR filter was designed based on block processing mode, and implemented in the TMS320C5510 chip (a DSP chip). The filtering algorithm based on two-pointerscircular addressing was introduced, and the main program was given. Computer simulation shows that the block processing mode of the program significantly improves the processing speed of frame signal, and filtering performance is satisfactory.
Lens design for uniform illumination of rectangle area with LED
LI Jing
2011, 32(2): 211-214.
Lens for uniform illumination of rectangle area with LED light source was designed. Based on differential geometry, a series of partial non-linear equations were constructed. According to the conservation law of energy, energy mapping relations between the source and the target plane were constructed. The points of the surface were obtained by solving the equations with fourth order Runge-Kutta formulas, and the desired free-form surface was got by curve fitting with Rhinoceros software. With ray tracing in ASAP software, the result indicates that the optical efficiency is more than 94.01%, and the illumination uniformity of the predetermined illumination area on the target plane is better than 92.73%. The continuity of the free-form surface was also analyzed, and the result shows that the continuity of the freeform surface is determined by energy mapping relations.
Jones matrix analysis for polarization state distribution on image surface of Pechan prism
LU Jin-jun, YUAN Qiao, LU Hua
2011, 32(2): 215-221.
A vector formula method based on reflection law was used to trace three-dimensional light propagation direction in a complex system. The direction of the light reflected by each side of Pechan prism was calculated, Jones matrix of the reflected plane and the transfer matrix between planes were established using Jones vector, and the distribution of polarization state on image surface was obtained when linearly-polarized parallel light passed through Pechan prism. There were two elliptically polarized beams with different azimuth angles from two roof surfaces, and the angles were dependent on the oscillation direction of incident linearly-polarized light. The distribution of polarization state on image surface of Pechan prism was tested with Stokes parameter measurement. The experimental result agrees with theoretical analysis and indicates that the polarization effect of Pechan prism results in non-uniform distribution of polarization state of the exit light.
Design of retinal projection display system
YANG Zhen, GUO Zhong-da, Yang Zhi-qiang
2011, 32(2): 222-225.
Conventional see-through head-mounted displays (HMDs) provide an effective capability for mixed reality, but images from two-dimensional virtual information are not clear on retina when eyes are accommodated in such systems. In order to overcome this problem, a novel see-through HMD was proposed based on Maxwellian view principle, which directly projected images onto the users retina with a miniature LCD and a laser independent of the accommodation of eyes. This means that images are always clear during accommodation. The display concept of HMDs was discussed, the optical system and overall structure were designed, the functions were tested and verified, and the optical system was optimized with ZEMAX. The results show that MTF value reaches the diffraction limit.
Optical design of three-group telescope zoom eyepiece
YAO Lin, XIANG Yang, HUO Xiao-xin, SUN Yan
2011, 32(2): 226-229.
Based on the operation requirements of an vehicle-borne observation and sighting simulation system and Gaussian optics theory, a three-group telescope zoom eyepiece was designed with Zemax. In order to obtain better image quality and long exit pupil relief, a three-group structure was adopted, and the pupil position was set as an optimized variable to make the entrance pupil position unchanged for continuous zoom. The focal length is f=(13.35~24.11) mm, exit pupil relief is L=(20.1~27.5)mm, exit pupil diameter is about 8 mm, image plane range is y=(3.9~14.06)mm, and zoom ratio of telescope zoom eyepiece is1.83. At 50lp/mm, the MTFs of four configurations are greater than 0.3, the spot diagrams of all configurations are smaller than Airy disk radius and higher than human eye resolution limit, which meet user requirements. Finally, the curves are fitted by Matlab, the corresponding focal length curves are given, and the fitting accuracy reaches 0.01mm.
Incoherently coupled spatial soliton families in centrosymmetric photorefractive crystals
JI Xuan-mang, WANG Jin-lai, JIANG Qi-chang, LIU Jin-song
2011, 32(2): 230-235.
To study the incoherently coupled spatial soliton families in centrosymmetric photorefractive crystals, we derived theoretically the expressions of normalized spatial profiles of the bright, dark and bright-dark soliton families from the soliton theory in centrosymmetric photorefractive crystals and investigated the characteristics of the soliton families. The numerical results show that these soliton families are coupled by the mutually incoherent incident optical beams sharing the same polarization and wavelength. When the incoherent coupled soliton families propagate in centrosymmetric photorefractive crystals, all the components propagate stably. Moreover, the soliton families degenerate to incoherently coupled dark-dark, bright-bright and bright-dark soliton pairs when they contain only two components.
Optical properties of silicon oxide thin films deposited by reactive ion-beam sputtering method
2011, 32(2): 236-240.
Silicon oxide thin films deposited by reactive ion-beam sputtering (RIBS) of Si targets in Ar/O2 producer gas mixture were investigated. The refractive index n, extinction coefficient k, and stoichiometry were dependent on the oxygen concentration in Ar/O2 producer gas mixture and the deposition rate. Silicon oxide films with refractive index of n =1.48 and extinction coefficient of less than 10-5 were deposited with the RIBS method at the wavelength of 0.63 m. An increase in the deposition rate results in the growth of refractive index and extinction coefficient of the film due to incomplete oxidation of silicon and formation of suboxides. In the case of deposition rate more than 0.3 nm/s, even if sputtering is performed in pure oxygen environment, the minimal value of refractive index is more than 1.5. The ana-lysis of the IR transmission spectrum proves that all the deposited films have oxygen deficiency, and the stoichiometry of silicon oxide does not exceed 1.8 based on the investigation of the position of the main absorption peak. The dependence between IR adsorption peak position and refractive index of silicon oxide is established. Thus, depositing silicon-oxide thin films with RIBS without heating the substrates limits the increase of deposition rate.
X-ray imaging diagnosis using spherically bent crystal analyzer
QIAN Jia-yu, XIAO Sha-li, WU Yu-fen, LIU Li-feng
2011, 32(2): 241-244.
A spherical bent crystal was developed based on Bragg diffraction to diagnose laser plasma X-ray. Spatial resolution, spectral resolution and radiation collected by solid angle were increased by using the spherically bent crystal. The spherically bent quartz crystal and X-ray imaging plate were adopted as X-ray analyzer and imaging device respectively. The imaging experiment was carried out with an X-ray diffractometer using Cr-target. The experimental results show that the monochromatic image of two-wire with a space of 0.2mm is obtained, the spectrograph of the spherically bent crystal offers good spectral resolution and signal-to-noise, and the calculated wavelength resolution reaches 1000 in 0.2 nm~0.4 nm. The spherically bent crystal is suitable for diagnosing soft X-ray spectroscopy, and the focusing intensity for spherically bent crystal is an order of magnitude higher than plane crystal at the same condition.
Analysis and processing of field curvature without astigmatism based on diffraction theory
CHANG Shan, WU Bo, SANG Zhi-wen, CHENG Li-bin
2011, 32(2): 245-249.
An intensity distribution integration formula of the image point only with field curvature is obtained from diffraction image, and an analysis formula is given to provide the deviation error of image plane from Gaussian plane. Simulation experiments were conducted, and the field curvature without astigmatism and its image points were discussed. The three dimensional shape map, Strehl ratio and field curvature correction by inverse filtering were analyzed.
OE Information Acquisition and Processing
Image enhancement algorithm based on super resolution reconstruction
ZHANG Yi-fei, LI Liang-fu, WANG Jiao-ying, ZHENG Bao-zhong
2011, 32(2): 250-255.
In order to improve image resolution by software processing, this paper investigates the theory and algorithms for reconstructing high resolution images from low resolution image sequences, and proposes a method to obtain high resolution images from low resolution image sequences. We realized the rough-to-fine image registration by pyramid multi-layer construction based on optical flow field, and obtained the sub-pixel motion estimation. After the multi-frame low resolution image was sub-pixel registered, we proposed a method for dynamically and adaptively determining the regularization parameter, constructed the simple regularization cost function and built the reconstruction model between low resolution image and high resolution image. The experimental results show that the horizontal and vertical resolution achieved with this algorithm is two times better than that of the original image. Compared with the traditional POCS algorithm, this algorithm reconstructs clearer image, and the computation time is reduced by 50%.
Modeling of indirect spatial position algorithm for underwater vehicle
YANG Yong-an, CHEN Fang-bin, JIANG Tao, LI Guang-liang
2011, 32(2): 256-260.
An indirect spatial position algorithm is presented for separated water surface detector and its carrier (e.g. underwater vehicle) under the dynamic baseline. By translation and rotation transformation ofgeodetic coordinates at release position, underwater vehicle coordinates and separated water surface detector coordinates, as well as the double integral displacement vector operation based on linear accelerometer, the modeling of indirect spatial position algorithm for underwater vehicle and separated water surface detector under the dynamic baseline was established Simulation results show that the model reflects the spatial position of the underwater vehicle in the geodetic coordinates relative to separated water surface detector.
Calculative method for fire lift-off capability of perturbation flow basedon image parameters
JIANG Xiao-gang, SHI Kan, LUO Yu-hong, WANG Yong
2011, 32(2): 261-266.
As the research about lift-off fire is the foundation of lift-off extinguishing against jet fire, the calculative method based on image parameters was proposed for studying the fire lift-off capability of perturbation flow surrounding flame. Firstly, the calculative method was explained. Then, the image acquisition and processing were introduced, and the mathematic model was established to calculate the lift-off distance, which represented the fire lift-off capability of the flow. Finally, the experiment was designed and the feasibility of the method was validated.
Numerical analysis of CW laser damage in Germanium
CUI Yun-xia, NIU Yan-xiong, WANG Cai-li
2011, 32(2): 267-271.
A two-dimensional transient physical model of flat-topped laser irradiation Germanium was established based on heat conduction theory and thermoelastic dynamic theory. The thermodynamic field of the irradiated material was simulated to compare the thermodynamic field differences at different irradiation times. The distribution of temperature field and stress field gradients along radius was discussed, as well as the impact of irradiation time on the distribution. The calculation results show that the greatest temperature rise effect occurs at the center of target material, and the temperature goes up as the irradiation time extends, moreover, stress field peak occurs outside the spot radius.The temperature and stress field gradients reach maximum values at the spot edge, and the longer the irradiation time, the greater the temperature and stress fields gradients at a fixed point. Under the given conditions , the damage time of subject material was calculated, and the stress damage threhold was reached first.
Small target detection based on image sequences
HE Peng-fei, SU Xin-yan, WANG jian
2011, 32(2): 272-275.
Based on the moving continuity and trajectory consistency of small targets in the image sequences,a method is put forward for target detection, which combines single frame and multi-frame detection. Firstly, single frame image is preprocessed and segmented, the image is obtained with background and noise removed, and the potential targets are selected and labeled in the image. Secondly, N frames in the processed image sequences are superposed. Finally, eight neighbor search method is used to search the labeled target in the superposed images and detect the target. Experiment results show that the proposed method is simple and fast, which can effectively detect the small moving target in image sequences.
Optical Metrology and Measurement
Rapid 3D shape measurement based on color-encoded fringe projection
WANG Lu-yang, DA Fei-peng
2011, 32(2): 276-281.
A rapid 3D measurement technique based on color coding fringe projection is proposed. The 3D shape information of an object can be obtained by only one color-encoded fringe pattern image. The color-encoded stripes were embedded into a sinusoidal fringe pattern in order to get the absolute shape of an object. Phase unwrapping was performed according to the color-encoded stripes. A novel color coding method using four colors was designed. The sinusoidal G component of a color image was used to obtain the phase by Fourier transform method, the R and B components were used to identify the fringe order so that phase unwrapping can be easily done. Only one frame of color image is needed to get the 3D information of an object, experiments indicate that the 3D information of an object can be obtained accurately and rapidly.
Optical testing of multi-electrode electrostatic membrane mirror
ZHONG Xing, JIN Guang, ZHANG Peng, ZHANG Yuan
2011, 32(2): 282-286.
A membrane mirror prototype of 300 mm diameter was developed and optically tested. Basic optical parameters of membrane mirror were tested by Gaussian optics. The results show that relations between basic parameters of membrane mirror and the applied voltages are consistent with shaping theory. The surface shape characteristics and optical testing methods of membrane mirror are discussed. Laser interferometer was used to test the plat surface when voltages were zero, and the RMS (root mean square) value of surface error was 1.03 (=632.8 nm). Hartmann testing was used to test membrane mirror surface with radius, and the result shows that RMS value of surface error changes from 24.1 m to 14.7 m when different multielectrode voltages are used for optimization. This validates that multiple electrodes with different voltages optimize the surface accuracy of membrane mirror.
AMacro-condenser test of reflection converged paraboloid
SU Cheng-ren
2011, 32(2): 287-290.
Test of parabolic mirror is often completed by measuring the optical path length. Though it is highly accurate, it can only detect the smoothness instead of light convergence. Based on the basic principals, this paper describes the nature of convergence for parabolic mirror. It points out that convergence accuracy depends only on the angle between the direction vectors of surface elements and the incident ray instead of optical path length. Inthe end, methods for testing parabolic mirrors by collimated flood light sourceare provided.
Geometric parameter measurement based on image sequence
LIU Peng, WANG Jian, WANG Shi-qin
2011, 32(2): 291-295.
With the continuous development of measurement technology, modern industry imposes a high demand on product dimension measurement accuracy and speed. This paper presents a method to measure the objects by using image sequences. A digital camera was used to capture calibration template image sequences, and the camera intrinsic parameters were obtained by direct linear transformation (DLT) method. Combined with the knowledge of imaging lens, the object-s image sequences provided by digital camera were processed and measured, and the object-s width and height were calculated ultimately. Experiments show that the method is simple and practical, which overcomes the shortcomings of traditional measurement and could control measurement error within 1%.
LLL Night Vision Device and Imaging
Technical solution on reducing reflectance of MCP inputsurface electrode
LIU Shu-lin, KUANG Lei, SUN Jian-ning, JIA Yong-qian, ZHI Qiang, TAN Yu
2011, 32(2): 296-299.
To reduce scattered noise which results from photons reflected by transparent or semitransparent photocathode at input surface of microchannel plate (MCP), the qualitative analysis of its influence on reflectance of the MCP input surface electrode and the test investigation of electrode film coating, film thickness, electrode depth, and open area ratio of MCP were given. Based on the influence of MCP input electrode on other MCP parameters, a technical solution was obtained which adopted electron gun to heat Ni-Cr alloy for electrode film coating and implemented the control of film thickness by keeping a constant resistance of 100, the electrode depth in channel accounted for 35% of channel diameter and the open area ratio of MCP was as larger as possible. Finally, the reflectivity of MCP input surface electrode is reduced to less than 4% and the photon scattered noise of image intensifier is decreased.
Third generation of image intensifier brightness gain measurement device
SHI Ji-fang, WANG Sheng-yun, SUN Yu-nan, XIE Qi
2011, 32(2): 300-302.
The glimmer intensifier is core component of low light level night vision device, and it is the determining factor of glimmer night vision complete machine performance and price. Since the glimmer intensifier works under weak light , it is the light energy amplifier. Brightness gain is a key parameter of the glimmer intensifier electro-optic property assessment, which effects the complete machine performance directly, therefore, research on the brightness gain test technology of image intensifier has great significance. This paper introduced the principle and equipment of third generation glimmer intensifier brightness gain measurement, and carried on the uncertainty evaluation of the measurement result.
Fiber Sensing and Optical Communication
Polarization-independent all-fiber birefringent filter with adjustablewavelength spacing
ZHONG Yu-guang, ZHANG Zu-xing, QIAO Xue-zeng, TAO Xiang-yang
2011, 32(2): 303-307.
Fiber filter has important applications in fiber sensor and optical fiber communication system. Especially, filter with all-fiber structure and tunable wavelength spacing is worth studying due to its unique characteristics. A polarization-independent all-fiber birefringent filter with adjustable wavelength spacing is proposed. The apparatus consists of a polarization beam splitter (PBS), two sections of polarization-maintaining fiber (PMF), and four halfwave plates (HWPs). The theoretical analysis shows that it operates as a polarization-independent multi-wavelength filter with good channel isolation and adjustable wavelength spacing by controlling the four HWPs in the loop. This filter is applicable for flexible multi-wavelength fiber laser and other optical fiber systems.
Numerical simulation on nonlinear transmissive characteristicsof fiber Bragg grating
TANG Li, PENG Yong-jun
2011, 32(2): 308-316.
Numerical methods for solving a set of nonlinear coupled equations of fiber Bragg grating (FBG) were reviewed. Characteristics of prediction-correction system based on implicit Runge-Kutta method were analyzied.To achieve simple, efficient and high precision numerical simulation for nonlinear coupled mode equations of fiber Bragg grating, we designed a prediction-correction system based on continued fraction correction method, and compared it with other methods. The segment length of grating can be greatly increased to save computing time through this method ,and the convergence of calculation always exists. The comparison of errors shows that the simulation method is accurate. By this method, uniform numerical simulation model is established under static and dynamic circumstances based on physical process of optical wave transmission in grating. Many skills in simulation are researched. Nonlinear transmission characteristics of FBG were studied numerically when continuous wave (CW) and pulse were input.
Power conversion efficiency of tapered fiber
JIANG Yao, XIAO Zhi-gang
2011, 32(2): 317-322.
Since tapered fiber works as a connector between multi-mode fiber and single-mode fiber to improve the coupling efficiency and transmits laser beam with high power and good beam quality under single-mode conditions, the power conversion efficiency of the tapered fiber is important. A method of melting and drawing tapered fiber was introduced and the transmi-ssion characteristic of tapered fiber was discussed. A Gaussian approximation model to calculate the conversion efficiency of tapered fiber was presented based on mode field coupling theory. The simulation result was discussed and an experiment was conducted with 532 nm laser, multi-mode fiber with NA=0.11, a=12.5 m and tapered fiber with NA=0.11, a=(41)m,(51)m(61)m,(71)m and (81)m respectively, to measure the conversion efficiency of tapered fiber. The experimental results agree with the theoretical prediction.
Optical Element and Fabrication
Electro-optic laser scanner for arbitrary scanning in 8 rows
WAN Ling-yu, LU Zhi-yong, WANG Rong-cheng
2011, 32(2): 323-328.
Based on intelligent laser scanning, birefringence effect and electro-optic effect, a scanner for arbitrary scanning in 8 rows is proposed. It mainly consists of a three-order electro-optic deflector and a 81 cascade electro-optic prism group. The three-order electro-optic deflector is composed of three electrooptic shutters and three birefringent crystal plates. The laser beams are switched between rows by controlling half-wave voltage of crystal. The prism group with cascade prisms of optic-axis reciprocatingly scans rows by applied electrical field. Digital or continuous scanning were realized by changing the properties of the applied electrical field. A laser scanner with 17.256 scanning area and 5.822KV maximal voltage was designed by using the cascade electro-optic deflector of trapezium structure. It scans arbitrarily in 8 rows using on-line operation.
Characteristics of three types of OADM
YANG Hua-yong, JIANG Nuan, ZHANG Xue-liang, HU Yong-ming
2011, 32(2): 329-334.
Optical add/drop multiplexer (OADM) is a key device for fiber sensing dense wavelength division multiplexer and future all-optical-net communication to replace electronic router, which is the bottleneck of high-speed information transmission. The work principles of the OADM based on the structure of Mach-Zehnder interferometer and fiber Bragg grating(FBG), the structure of optical circulator, FBG and the structure of integrative fiber grating coupler(FGC) were introduced. Three configurations of OADM were built and were experimentally investigated to test their performance. The advantages and disadvantages were concluded and the basis for the design and fabrication of OADM was provided.
Manufacturing technology for high order aspheric surface
YUAN Lu-jun, CHEN Tao
2011, 32(2): 335-342.
Since high order aspheric surface finds significant applications in optical system, a rapid and effective manufacturing technology is required to meet the demand. Software was developed with VC6.0 for aspheric calculation to help fabrication, and a new compensation test was proposed for high order aspheric surface. Taking a high order aspheric collector with the diameter of 244mm as example, a manufacturing technology was developed and related investigations were conducted. Based on milling process and aspheric surface characteristics, several new grinding methods were proposed and related mathematical models were built. In order to process high order aspheric surface efficiently, computerized numerical control (CNC) milling direct shaping method was tested to reduce the complexity of subsequent processes, and numerical controlled small tool was combined with full aperture craft in polishing process to make aspheric surface smoother. Experimental results demonstrate the high order aspheric manufacturing technology is efficient, low cost and precise.
Infrared Technology
Calculation of cloud infrared radiation based on optical depth
LOU Shu-li, ZHOU Xiao-dong
2011, 32(2): 343-347.
To study the infrared characteristics of clouds with different thicknesses in different wavebands, a method for calculating infrared radiation of cloud based on optical depth is proposed. The infrared model of cloud was established after studing each infrared radiative component. According to the relation of infrared characteristics to waveband and thickness, the emissivity, reflectivity and transmissivity were computed respectively in middle infrared and long infrared wavelength, and the radiance of cloud was computed accordingly. Result shows that the radiation of cloud is a funtion of optical depth, and the actual measurements and the data from the model are consistent. It is proved that infrared radiation calculation of cloud based on optical depth can be used as the data source in infrared characteristic detection, analysis and simulation for the cloud background.
Hardware-in-the-loop simulation of panoramic multi-target infraredstaring tracker
LI Gang, YAN Zong-qun, HE Yong-qiang, LU Xu-guang
2011, 32(2): 348-352.
An infrared multi-target hardware-in-the-loop simulation system is proposed to provide cooperative targets during lab debugging for a panoramic multitarget tracking infrared staring system. The system consists of several controllable heat sources, each of which is installed on a three-dimensional moving table and incorporates a uniformly-heated plate and a temperature controller. Targets in different distances and different sizes were simulated by changing the diaphragm aperture and the temperature distribution, while different target tracks were simulated with heat sources at different velocities and directions. Finally, 600 frames of three infrared simulated targets were acquired and processed, and the whole process of track overlapping, intersection and detachment was simulated, which demonstrated the feasibility and accuracy of this experimental platform.
Laser Technology
Structural finite element analysis of path length control mirror forlaser gyroscopes
ZHANG Ming-hui, LIU Yuan-zheng, LAN Pei-feng, ZHANG Zhen-rong
2011, 32(2): 353-357.
To study the relationship between structural parameters of ring laser gyro (RLG) path length control mirrors and its performance, a method was presented in which finite element (FE) model including elastic and piezoelectric body was established and direct coupled field analysis was conducted. By programming an ANSYS macro file, automatic synchronization between FE model and the structure size was achieved. Simulation results of a specific path length control mirrors indicate that the annular groove inner and outer diameters, and the deformable rib thickness of the mirror have the greatest impact on the light path length adjustment capability. The results are used to optimize the design. Experiments demonstrate that the method is of significance in the path length control mirror design.
Reduced order anti-synchronization between single mode laserLorenz system and Duffing system
LI Zhan-guo, XU Wei
2011, 32(2): 358-362.
A controller was designed with the active control method to realize the reduced order anti-synchronization between a 2-order Duffing system and a 3-order single-model laser Lorenz system. Based on Routh-Hurwitz criteria, the conditions for the error dynamic system to be asymptotically stablized at the origin were given. The numerical experiments verify that the state variables of the 2-order Duffing system and the projection subsystem of the 3-order singlemodel laser Lorenz system vibrate with the same amplitude but opposite direction when the designed controller is used. The anti-synchronization is achieved under random noise interference. It proves that the designed controller is feasible and effective, and has better robustness for achieving the reduced order anti-synchronization between different order Duffing system and Lorenz system.
Key techniques of DMD in laser lithography
HUANG Xin-dong, YIN Tao
2011, 32(2): 363-366.
The maskless laser lithography system using digital micromirror device (DMD) based on digital light processing (DLP) structure was used widely, but the lithography image quality and lithography speed should be improved. A new method for solving these problems is proposed, which adopts FPGA to control DMD. The new structure enables the flexible control of micromirror lock and improves the system lithography image quality accordingly. The synchronization signal and high frame rate of the new structure improve system lithography speed.
Inversion algorithm of laser particle size test based on Projection algorithm
WANG Xue-yan, LIU Chan-lao
2011, 32(2): 367-372.
Inversion of particle size distribution from scattered light intensity distribution with laser particle size analyzer based on Mie theory is a typical process for solving inverse problems, in which particle size inverse algorithm is critical. Projection iterative inverse algorithm is sensitive to noise and it causes particle size measurement distortion in actual applications. Vondrak-s smoothing algorithm was adopted to conduct smoothing processing to Projection inversion, and simulation study on algorithm applications was carried out by writing testing software on VC++6-0. By analyzing and comparing the inversion results obtained before and after smoothing processing, it is concluded that the introduction of Vondrak data smoothing processing algorithm effectively improves the anti-interference ability of Projection inversion. The experiment result shows that the inversion result obtained after Vondrak data smoothing processing reflects the real particle size distribution and meets the measurement requirements on stability, reliability, high precision and strong anti-interference capability for modern powder production industry.
Characterization of 1 064 nm laser induced damagein ALD optical film
LIU Zhi-chao, WEI Yao-wei, CHEN Song-lin, MA Ping
2011, 32(2): 373-376.
Based on Atomic Layer Deposition (ALD) technology, the single layer films were coated on fused silica and BK7 glass substrate respectively. Using small optical damage test facility, the 1064 nm laser induced damage threshold between ALD films and BK7 substrate was compared. The result shows that the ALD film damage threshold is about 10.3 J/cm2. With the use of Nomarski microscope and Atomic Force Microscope, the morphology of damage site was discussed. The result shows that there are two kinds of damage, the peeling damage on the films and the small pits damage on substrate. The pits damage related to melting and vaporization has the depth between 70 nm and 95 nm. The damage precursors may exist in the boundary surface of ALD films and substrate.