2005 Vol. 26, No. 4

A Summary of Airborne Photoelectronic Systems on Drones
CHENG Gang, YANG Suihu
2005, 26(4): 1-4.
The airborne photoelectronic systems on drones developed by Israel, United States of America, Russia and the countries in West Europe,and the new technologies,such as highprecision stabilized sighting systems, US Generation Ⅳ electrooptical camera, advanced FLIR systems and multispectral information compression/transmission technology,are introduced in this paper. It will be of a certain value to the reference for designing a new generation airborne photoelectronic system for our own country.
Image Processing
Filtering Methods of the Digital Speckle fringe Pattern
FU Si-hua, YU Qi-feng
2005, 26(4): 5-8.
In modern digital speckle measurement method, we usually adopt subtraction to derive a digital speckle fringe pattern, which is information carrier for postprocessing and inherently full of multiplicative noise. Noise reduction is needed before next processing step in order to guarantee the measurement precision. Which filtering methods should be adopted is much important. The authors expatiate some often used filtering methods in the digital speckle fringe pattern after reading a lot of concerned papers. Some representative filtering methods are selected for the purpose and the results are analyzed. At the end of the paper, the development direction of the filtering methods of digital speckle fringe pattern is presented.
Realization of Region Splitting of Multi-gray Level Picture with Optical Method
SU Cheng-yue, ZHENG Guang-zhao, CHEN Li, HE Rong-li, ZHOU Dong-yue
2005, 26(4): 9-12.
In this paper,the region splitting of multigray level picture is directly brought about with a optical step filter. It is discussed in theory that a step filter processes a multigray picture with hard and soft boundaries to realize the region splitting of the multigray level picture. The discussion shows that with the step filter. The boundary enhancement in the region will appear when the noncontinuous gray grade (a hard boundary) and the epoch emerge in the multi-gray picture .
Theoretical Study
The Implementation of Straightforward Mie Scattering Numerical Calculation
WANG Jun, HE Jun-fa, WANG Lian-fen, WANG Hong-xia, ZHOU You-jie
2005, 26(4): 13-16.
Based on a short retrospect of the developmental history of light scattering theory, the problems in conventional Mie scattering calculations are analyzed. A simple yet accurate algorithm for the improved Mie scattering calculations is described in detail. A new data type named“EDecimal” is defined, and its basic mathematical operation and trigonometric functions are developed. The dynamic chain is used in implementing the efficient C++ code for fast and accurate Mie calculation.The code can handle extreme cases in Mie scattering calculations and reduce the time complexity of this algorithm. By comparison with Wiscombe's MIEV0 code requiring a same precision,this method shows up its the accuracy and reliability.
Analyses of Jones Matrix of Birefringent Grystals
SUN Gang, JIN Shi-long
2005, 26(4): 17-21.
he Jones matrix of birefringent crystals is derived according to the separate transmitting theory of the two eigen polarization states of a birefringent crystal. The Jone's matrix that the eigen optical wave is line, circle or ellipse is analyzed and discussed. The direct factors affecting polarization state while light goes through a crystal is found and their relation curves are drawn. The opticity of the crystal and its change is analysed. It has a directive function for the installation of crystal in differential laser gyro.
ifference of the Image Deformation Formulas with the Textbooks
WANG Jin-li, WANG Fei-fei
2005, 26(4): 61-65.
:Cut a regular hexahedron into innumerable parallel fracture planes, in each of which there is a light cone. With observing in the innumerable light cones the variations of the fracture plane sections with the projective sections, and the sections with their own projections,we came to the following conclusions :1) Xray image deformation is due to the function of light cones;2) no matter whether the object projective plane make an angle,the function of the direct incidence and oblique incidence of the lightcone axial beam keeps constant;3) the elliptical eccentricity of each fracture plane section reflects the space deflection of the object, which is the real deformation factor;4) if the elliptical eccentricity of the projective section is respectively bigger than, equal to or less than the elliptical eccentricity of the fracture plane section,the projection length of fracture surface’s centre vertical diameter and the real length is respectively bigger than,equal to or less than the projection length of the horizontal diameter across the centre of that projection and the real length;5) if the object is at an angle to the projective plane,it will lead to the unequal amplification of the fracture surface’s projection;6) the deformation degree is in direct proportion to the thickness of the object, and it is in inverse change to the distance from the point source to the object, but bears no relation to the distance from the object to projective plane;7) the dissertation in the textbooks stands in error.
Night Vision
Improvement of Space Construction and FOV Definition of MCP with Small Aperture by Gas Sinter Technology
LIU Shu-lin, DENG Guang-xu, MAO Jiaming
2005, 26(4): 22-25.
Image intensifiers with high resolution are strict with the pore, space construction and FOV definition of microchannel plate (MCP) with a large number of experiments, we extended progress in the MCP making technique and then fabricated some MCPs whose pores are 6μm and pitches are 8μm. Comparing our MCPs with the MCPs delivered by Photonis Company, we found the rosettes in our MCPs are less than the ones in theirs. In the case of standard input(10-11A/cm2), the gain of MCP is high, the uniformity of gain is improved, the fixedpattern noise is in the level of 0~1, the definition of FOV is high.
Laser Technology
Stability of Passively Modelocked Femtosecond Fiber Laser
ZHAO De-shuang, LIU Yong-zhi, HUANG Xiu-jiang, ZHANG Chang-ming
2005, 26(4): 26-29.
The stability of passively modelocked femtosecond fiber laser affected by different factors,especially pump power and fast saturable absorber, has been thoroughly studied in this paper. The results show that it is necessary to make laser work with proper driving of fast absorber and mediate pumping power for stable pulse output.
Reliability Prediction for a Certain Type of Laser Range Finder
WU Han-ping
2005, 26(4): 30-32.
In the case of the condition of finite test data, in order to solve the problem of reliability prediction for a certain type of laser range finders, which are produced on a small scale and complicated, reliability models are established with analyses of the operating modes of the rangefinders. On the basis of the test data from the previous similar products, reliability of the system is predicted with the method of similar circuit. According to the life of laser crystal, dye piece,totally reflecting mirror, light focusing cavity and so on, laser life is predicted.These predicting values are verified in actual use. This serves the function of reference in system design and application.
Experiment Analysis of Influence of Atmosphere Stochastic Channel on Laser Transmission
YIN Zhi-guo, HE Jun, HUANG Chang-chun, DENG Dai-zu
2005, 26(4): 33-35.
This paper introduces two types of real time systems developed for measuring laser beam and laser power,and for analysing the influence of atmosphere stochastic channel on laser transmission. One system is used for the realtime measurement and record of the laser facula,and another for the realtime measurement and record of the optical intensity. Lots of outfield experiments have been done and the experimental data have been recorded with the two systems. From the processing of the experimental data,some influence rules of atmosphere have been deduced.
Fiber Optics
Study on Techniques of Signal Demodulation in Fiber Bragg Grating Sensing System
LI Zhi-quan, XU Ming-yan, TANG Jing, CHEN Ying, ZHAO Yan-tao
2005, 26(4): 36-41.
Wavelengthencoded signal demodulation is one of the key techniques for the fiber Bragg grating sensing systems to enter into a practicable step. This paper discusses the general principle in demodulation of FBG sensing signal. The mechanism of operation, characteristics and function of commonly used demodulating methods are analyzed.Moreover,the main technical problems and development direction in signal demodulation of FBG are summarized. This paper provides foundation for the design of the demodulation based on FBG sensor system.
Yb3+Doped Fiber Laser with Chirped Fiber Grating
HUANG Xiu-jiang, LIU Yongzhi, SUI Zhan, LI Mingzhong, LIN Honghuan, CHEN Haiyan
2005, 26(4): 42-45.
Chirped fiber grating can be used in compensating fiber dispersion and compressing pulse.With the coupledmode theory,some parameters are analyzed, including grating length,coupled functions, chirped coefficient having relations with the reflectivity coefficient, timedelay character, dispersion and compression character. With the results , an Yb3+doped ultrashort pulse fiber laser is designed and an allfiber ring cavity with chirped fiber grating is brought forward. Comparing with the other structures of the nonallfiber lasers,the structure we designed is more efficient and has less power loss.
Interrogation Project for Encoding Fiber Bragg Grating Sensor Array
FAN Dian, JIANG De-sheng, MEI Jia-chun
2005, 26(4): 46-49.
The construction of the encoding fiber Bragg grating sensor array and the characteristic of its sensing signal are introduced. A new type of interrogator for encoding fiber Bragg grating sensor array, which has a comb structure and employs the logarithm of the output ratio between the adjacent two channels of arrayed waveguide grating to determine the measured wavelength,is proposed. The paper demonstrates the feasibility of this interrogation project in theory in the cases of background reflectance and the ideal case respectively and analyzes the error caused by the noise. This system is suitable for interrogating a large number of wavelength information, and can carry out a fast and simultaneous interrogation of multiple wavelengths without any mechanically moving parts.
Strain Measuring System Based on Chirped Gratings and Edge Linear Filtering Demodulation Technology
ZHU Dan-dan, WANG Hai-fang, ZHANG Ran, LI Ya-ping1, YAN Li-juan, ZHANG Jun-jie
2005, 26(4): 50-52.
In this paper, strain measuring system based on chirped gratings and edge linear filtering demodulation technology is presented. In the system,the probe works with the wavelength difference of two fiber Bragg gratings as sensing information. This can eliminate the temperature influence on measuring result, and enhance the sensitivity and resolution doubly.Demodulation method adopts chirped grating and long period grating edge linear filtering technology. The system whose measuring range is 0~500με,is feasible in theory. The system can be used in monitoring marine platform, skyscraper,largescale structure and concrete dam.
Thin Film
Coating of Beamsplitting Film System Working in aUltra Wide Spectral Range
TAN Yu, ZHAO Xing-mei
2005, 26(4): 53-55.
A beamsplitting film system working in two ultra wide spectral ranges(hightransmissivity at 550~1100nm and highreflectance at 8000~12000nm) is designed. The film system adopts a basic film structure of |ZnS|Ag|ZnS| with a protective coating. With the film system, we obtained a flat splitter which can transmit the visible and nearinfrared bands, and reflect the middleinfrared and farinfrared bands. The actual application shows that the splitter is effective.
The Uncertainty Analysis of the Calibration Measurement of Main Performances for Laser Rangefinders
YANG Ye-ping, YANG Zhao-jin, HOU Min
2005, 26(4): 56-57.
The configuration of the calibration equipment for the main performances maximum detectable range, minimum detectable range. range accuracy,repetition frequency, beam divergence angle of laser rangefinders is briefly introduced. This paper presents the detailed uncertainty analysis of the main performances of laser rangefinder calibration. The standard degree of the calibration equipment for the main performances of laser rangefinder will be evaluated through these uncertainty analyses.
Design of Spectral Reflectance Measuring System in Original Position
WANG Shu-jun, ZHANG Bao-zhou
2005, 26(4): 58-60.
A spectral reflectance measuring system consisting of several optical fibers and a doublechannel spectrometer is introduced. The main technology of the spectral reflectance measuring system is discussed. Before and after the samples were oxidized, utilizing this system to measure them in vacuum chamber the measuring results,we obtain, is consistent with the nominal value.