2006 Vol. 27, No. 5

Theoretical Study
Construction and characteristic analysis ofa frequency-hop timespread code
AN Xiao-qiang, QIU Kun, ZHANG Chong-fu
2006, 27(5): 363-368.
Taking one dimensional quadratic congruence code (QCC) as time-spread mode, optical orthogonal code (OOC) and QCC as frequency-hop mode, two types of frequency-hop time spread codes of QCC/QCC and QCC/OOC applicable to two dimensional optical code division multipleaddress (OCDMA) systems were constructed by combining time domain and frequency domain. The correlation and capacity of the codes were analyzed. In comparison with one dimensional QCC, the capacity of QCC/QCC is enlarged p1 times, where p is code weight, and the correlation is improved, outofphase autocorrelation is λa=1 and crosscorrelation isλc=2. QCC/OOC with better correlation and larger capacity are obtained. Its outofphase auto-correlation is λa=0. All the code words can be divided into p1 groups according to a certain law, crosscorrelation of code words in the same group is λa=1 and in different groups is λa=2. The study provides a new method for constructing frequency-hop timespread codes in OCDMA systems.
Optimization algorithm and design of FrFT filter
YAO Hong-yu, LIU Yue-qian
2006, 27(5): 369-375.
As Fourier transform is limited in dealing with certain kinds of signals, an improved method of Fourier transform which is called the fractional Fourier transform (FrFT) is put forward. FrFT, a manifestation of the classical Fourier transform, appears to be potentially useful. It depends on a parameter and can be interpreted as a counterclockwise rotation of coordinate system taking the original point as an axis by an angle on the timefrequency plane. It is a normal representation of the classical Fourier transform. Through mathematic ratiocination, a conclusion was reached that FrFT is better than Fourier transform in dealing with signal reconstruction. To explain FrFT systemically, the optimization algorithm of FrFT filter was given,then Matlab was used as a tool, which can provide emulator, to test and analyze FrFT’s implement effects . At last, all kinds of designs of FrFTbased filters was put forward and explained.
Resonant modes in quantum well structure composed of photonic crystals with different lattice constants
GE Xiang-you, LI Ping, WANG Xiao-jie, CHEN Xiao-han, FENG Chuan-sheng
2006, 27(5): 376-379.
The resonant photonic modes in a quantum well (QW) structure composed of three slabs of different photonic crystals with different lattice constants is analyzed with planewave based transfer matrix method (TMM). It is found that the energy band of the well slab submerged into the band gap of barrier slab is discretized into resonant modes and the number of the resonant modes changes with the well slab thickness. A model structure of asymmetrical photonic QW consisting of two slabs of 2D photonic crystals with different lattice constants and one uniform dielectric slab in between is firstly proposed and the resonant modes in it are investigated. A useful numerical simulation method for theoretical discussion as well as for practical application about photonic QW structure of photonic crystals with different lattice constants is proposed.
Largeshearing electronic speckle pattern interference system with carrierfrequency modulation techniqu
SUN Ping, HAN Qing, WANG Xiao-feng
2006, 27(5): 380-384.
Largeshearing electronic speckle pattern interferometry (LSESPI) offers many advantages such as good fringe quality and no reference beam needed. The fringe pattern obtained by the LSESPI is easy to be observed. The new electronic speckle pattern interferometer is formed by introducing carrierfrequency modulation for interference fields to LSESPI. The new system does not have strict requirement for environment on isolating vibration. The displacement fields could be quantitatively measured with the system. The principle of carrierfrequency modulation of LSESPI is discussed. A typical experiment is implemented with a centralloaded and peripheralclamped plate. And a step motor system controlled by a computer is designed. With the step motor system the reference object can be rotated accurately so that the electronic speckle pattern can be modulated automatically. At last, Fourier transform is used to demodulate the modulated fringes and obtain the phase of deformed field, then acquire the precision deformation of the object by the transformation calculation of the phase and displacement. The experimental results indicate that the interference field of the speckle pattern can be modulated and the displacement of the object can be measured accurately by this system.
Micro-mechanism interacting between high polymer and light field
XUE Chun-rong, MA Li
2006, 27(5): 385-389.
The micromechanism interacting between optical field and high polymer is analyzed, the polarization process of high polymer and small molecule under the effect of the light field is introduced. The distribution of polarization on the high polymer chain which has been polarized is analyzed in narrowbeam optic field. The analysis indicates that for the tensionthinning film made from polymer, the dipole model can not be used to explain the mechanism interacting between high polymer and optic field. An antenna model is adopted and investigated in detail. The polarization formula of high polymer chain of aerial mode is theoretically derived, and its validity is verified through calculating the polarization distribution with DVM. Assuming the polarization distribution is the same as the distribution of the electric current on the aerial, the angle distribution of the aerial secondary radiation is calculated, and the modification factor of electric dipole model is obtained.
Optoelectronic Engineering
Application of photonic crystal in radar crosssection reduction of scattering on airplane canopy
YIN Yan, YUAN Nai-chang
2006, 27(5): 390-393.
A metallicdielectric photonic crystal thinfilm is presented. Its reflectivity and transmissivity are calculated with the transmission matrix method. The numerical results show that the photonic crystal film has an up to 99% reflectivity for millimeter and centimeter waves and about 50% average transmissivity for the visible light in microwave spectrum. The effects of the dielectric layer thickness, the metallic layer thickness and the total thickness of metallic layers on the transmissivity are examined, and the principles of material selection and structure design are presented. Due to these characteristics, the metallicdielectric photonic crystal film can be employed in effective reduction of radar crosssection of scattering on airplane canopy.
Effect of micro-scanning on spatial resolution
PENG Fu-lun, FENG Zhuo-xiang
2006, 27(5): 394-399.
The pixel transfer function (PTF) for analyzing microscanning technology′s effect on spatial resolution is given based on the detailed analyses of the aliasing effect decreased by the microscanning technology. The analysis, calculation and discussion on PTF are carried out for two modes of microscanning (2×2,4×4). The result shows that the microscanning technology can increase the focal plane spatial resolution, decrease the image aliasing effectively and improve the imaging quality significantly for FPA thermal imager. It is pointed out that even if highspatialresolution imaging device is not available, high spatial resolution images can still be obtained with lowresolution imaging devices by utilizing the microscanning technology.
Nonlinearity analysis and application of optoelectronic position sensitive detector
LI Tian-ze, WANG Sheng-de, LU Heng-wei, WANG Ya-jing
2006, 27(5): 400-404.
The principle, structure and property of optoelectronic position sensitive detector (PSD) are briefly introduced. The nonlinearity caused by PSD is analyzed according to the principle and characteristics of PSD. The location equation of PSD output signal independent of light intensity was derived. PSD nonlinearity modulation circuit was designed to achieve low temperature drift and high precision. The validity of correcting PSD nonlinearity with differential algorithm, optimization method of neural network and analytic method is analyzed. Some of the data obtained during the experiment are also analyzed. The prospects of PSD′s application in optical trigonometry, automatic check and highprecision measurement are discussed.
Technology analysis of adding CCD camera to gunner′s periscopic sight
WU Ming-di
2006, 27(5): 405-408.
Feasibility of adding a CCD camera to the gunner′s periscopic sight is analyzed. The principle and scheme of adding the CCD camera are brought forward in this paper. The requirement for keeping the periscopic height at the original point, changing the internal structure of the gunner′s periscopic sight as little as possible and reducing the cost of the whole project was met by selection of suitable mounting position and structure distribution of the CCD camera. The selection of CCD camera, the calculation of the beam path and the variation of laser emission path film are discussed by aid of relative theories. It is pointed out that the automatic video tracking can be realized if an automatic tracking assembly with the function of data processing is mounted on the system after the CCD camera is added to the gunner periscope, and the original observationaiming function in visible light is still retained. The whole research has significant value for improving fire control system function and tactics technique function of whole tanks.
Optical Design
Optical design of infrared coupling system
DING Xu-ming, XIONG Wang-er, YU Chong-zhen, LIANG Zhi-yi
2006, 27(5): 409-411.
The infrared target simulator is composed of infrared target image transmitter and the optical projection system. The infrared coupling optical system is a middleinfrared system with a long focal length, larger field and telecentric beam path in image space, which is required to match with the parameters of two homing optical systems. The optical design of infrared coupling system applied to infrared target simulator is presented in this paper. The combination of infrared coupling system and homing optical system can constitute an infrared projective optical system with a magnification of 4.5. The IRCRT image can be projected on the receiver of homing optical system through an infrared projective optical system. SiGeSi is selected as optical material based on the design characteristics and technical specification of infrared coupling system, and the design of the optical system with a Cooke threelens structure has been implemented. The design and assessment results indicate that the optical performance and image quality of the system can meet the design specification.
A novel optical system for laser panoramic fuse
2006, 27(5): 412-414.
Based on the analysis of the luminous characteristics of typical lasers and optical properties of cylindrical lenses, a novel optical system for laser panoramic fuse, which uses two sets of cylindrical lenses with orthogonal sagittal planes to improve the scattering angle of laser beam and uses four sectors to realize the panoramic function, is proposed in this paper. Since the distribution uniformity of the light energy of the system is satisfactory on the circle of 0.5~10m radius and the beam path of the system offers an advantage of invertibility, it can be used in the fuse of the missile with the feature of WFOV emission and reception. The system is comparable to its counterpart abroad. The system is compact in structure and easy to be fabricated. The demonstration in the test range proves the new optical system is feasible and practical. The reflective optical system available will be replaced by this system in the future.
Film system Design for shortwavelength pass filter
ZHAO Xing-mei, SHI Jian-tao, GUO Hong-xiang
2006, 27(5): 415-418.
The principle and calculation method to design shortwavelength pass filters with a concept of equivalent refractive index is presented in this paper. TiO2 was chosen as the material of high refractive index and SiO2as the material of low refractive index based on the principle and method. Periodicity of shortwavelength pass filter at wavelength λ=950~1150nm was theoretically designed according to the concept of equivalent refractive index. The main film system and the spectrum curve of the shortwavelength pass filterare presented. The design of the film system was corrected since its transmissivity did not meet the requirement at the range of wavelength λ=750~810nm. The effect of the main processing technology and the film thickness on the optical characteristics of the shortwavelength pass filter is described. As a result of the correction, the best way to make the film system was found. The film system prepared in this way was tested in different environment conditions. The experiment result shows that the specification of this film system can meet the requirement of the design.
Infrared Technology
Pseudocolor coding and processing for infrared images
LIU Chan-lao, TAN Li-xun, LI Chun-yan, MA Gang
2006, 27(5): 419-422.
The thermal distribution of objects can be transformed into the visual pictures by the infrared thermal imaging system and displayed on the monitor in grey level or pseudocolor, thus the temperature distribution of objects can be obtained. According to the thermal imaging principle of temperature measurement and the characteristics of infrared images, the pseudocolor coding of infrared images is studied in this paper. A new pseudocolor coding, automatic threshold method, is presented. This method was proved by TMS320C6202 and FPGA thermal imaging systems at room temperature. Experimental results show that gradations of infrared images can be discriminated and different temperature regions can be easily resolved by the method.
Laser Technology
Structure and properties of thickfilm capacitors fabricated by laser microcladding rapid prototype
LI Hui-ling, ZENG Xiao-yan
2006, 27(5): 423-427.
To overcome the shortcomings of thickfilm capacitors (limited size, low capacity and high dissipation) fabricated by traditional thickfilm technology, which limit their applications to some specific areas, a technology fabricating the thickfilm capacitors on ceramic substrate by laser microcladding rapid prototype is put forward. The novel technology does not take the mask as a necessity as in the former capacitor. The structure and properties of the capacitor fabricated by laser microcladding and the traditional sintering method, which includes capacity, dielectric crystal, quality factor and insulation resistance, are analyzed. The forming mechanism of the capacitor is studied. The results prove that, compared with those made with traditional sintering techniques, the capacitors fabricated by laser microcladding rapid prototype method have better repeatability and higher capacity, it is more compact and also minimizes the composition diffuseness between interfaces.
Micromachining of wide-band optical materials with ultra-short laser pulses
LIU Qing, CHEN Jun-jun, GUO Li-li
2006, 27(5): 428-431.
Through discussion on the damage mechanism of wide-band optical transparent dielectrics and comparison of the damage levels of wideband optical transparent dielectrics ablated by ultra-short laser pulses and long laser pulses, a powerful tool applicable to processing wideband optical transparent dielectrics with ultrashort laser pulse is obtained. When laser pulse with wavelength of 800nm and pulse time of 150fs is focused into the inside of transparent dielectrics (K9 glasses and ZK6 glasses) with different band widths, the gratings with different constants can be made. The far-field relative diffraction efficiency and the diffraction efficiency of the grating were measured under the vertical illumination of He-Ne CW laser at 635nm.
Fiber Optics
Sapphire fiber thermal probe based on wavelet transform
WANG Shu-tao, CHE Ren-sheng, WANG Yu-tian, WANG Dong-sheng, CUI Li-chao
2006, 27(5): 433-437.
A sapphire fiber fluorescence thermal probe with Cr3+iondoped end was grown from the laser heated pedestal growth method. The fluorescence thermal probe offers the advantages of compact in structure, high performance and ability to detect temperature ranging from the room temperature to 450℃. The data processing based on the wavelet transform can effectively decrease the noise out of the signal so that the signaltonoise ratio can be improved. Based on the theoretical analysis of the fluorescence temperature measurement methodology and fiber technology, a phaselock loop technology is adopted to make the realtime measurement without the interference of the exciting light. Taking advantage of the different features indicated by noise and signal when wavelet transformation is applied, the temperature signal extraction and noise elimination method based on the wavelet transformation theory is given. In comparison with other processing methods, the wavelet transform method overcomes the shortcoming in the fast Fourier transform and can be applied to mutation signals, and it has a variable window that the Gabor transform does not has. Therefore, the method can shorten the process of signal processing and improve the measurement resolution.
Dynamic demodulation method for external pressure measurement with fiber grating sensor
ZHU Jun, QU Bin, JIAO Sheng-jie, HU Zhi-xin
2006, 27(5): 438-441.
A demodulation method for measuring the pressure with the fiber Bragg dualgrating is put forward to improve the precision of fiber Bragg grating (FBG) pressure sensors and reduce the cost of the measurement systems. Under the action of external pressure, the reflected wavelength drift of sensing FBG is transformed into time interval variation of light pulse reflected by the grating, which is modulated by means of driving the equally intense cantilever beam into up and down bending periodically. The experimental result shows that the detection range for the reflected wavelength drift of FBG is 0~3 nm, the uncertainty of wavelength detection is 1 pm, and the uncertainty of the pressure measurement is 0.005 MPa when the measurement range of the pressure sensor is 0~6 MPa.
Implementation and design of dynamic measurement system of grating torque
YU Hong-lin, ZHU Chuan-xin, YANG Zhang-li
2006, 27(5): 442-445.
There is no good solution to the torque measurement of mechanic principal axes working under various loads at home and abroad. Through installing the circular grating and indicative grating at both ends of a principal axis, the noncontact dynamic measurement of the principal axis torque can be realized by computing and subdividing grating Moiré fringes. After the photoelectric conversion of the Moiré fringes, the signal is amplified, filtered and compared with integrated programmable analog devices. Here, a microprocessor of soft core is used to realize data acquisition, processing and controlling, and to substitute the method of FPGA+MCU. During the experiment, the circular grating with 1200 grating lines was adopted, and the precision of the twist angle (less than 0.001°) was acquired while the rotational speed of the principal axis is within the range of 0~1500r/min. The experiment shows that the adoption of Moiré fringes of the circular grating can make highprecision torque measurement of the principal axis meet the requirement, which offers a new noncontact method for the measurement of mechanic principal axes.
Accuracy analysis of stitching interferometry for test of largediameter mirror
ZHANG Ming-yi, LI Xin-nan
2006, 27(5): 446-449.
The principle of stitching interferometry for testing the large plane optics is presented in this paper. The relative placements of both interferometer and the mirror under test can be adjusted, and interferometric test of subaperture can be done over the whole part of the mirror surface under test. The wavefront data in the overlapping areas of adjacent subapertures are analyzed by using the leastsquare algorithm. The relationship between the tested subapertures is clarified step by step. Finally subapertures are stitched together, and full aperture surface shape under test is synthesized. The error between the spliced surface by stitching interferometry and the actual surface is analyzed, and the accuracy of stitching interferomertry is evaluated. The experiment based on the theory of stitching interferometry was done. The results indicate that the stitching interferometry is an effective means to measure largeaperture optics accurately.
Application of phaseshifting interferometer for angle test of CCRs
GUO Ren-hui, HE Yong, ZHU Ri-hong, GAO Zhi-shan
2006, 27(5): 450-454.
The application of phaseshifting interferometers for measuring angles of the cone cube reflectors (CCR) is studied so as to realize the realtime and high accuracy test for optical elements. The relationship between the dihedral angle errors of CCRs and the interference pattern is obtained by calculating the dihedral angle errors of CCRs. The relationship between the shape of interference wavefront and the synthetic errors of CCRs is analyzed. A program to test the dihedral angle errors and the synthetic errors of CCRs is designed. After lots of experiments and comparison of the results by the digital phaseshifting interferometer and the ZYGO interferometer, it is proved that, in the program of CCR test, the measurement error of the dihedral angular difference is less than 0.3″ and the measurement error of RMS is in λ/50 with the application of digital phaseshifting interferometer.
Laser-induced fluorescence spectra measurement of combustion product components
2006, 27(5): 455-459.
Laserinduced fluorescence (LIF) spectrum technique is introduced to study combustion process. The experimentation for LIF spectrum of small molecules common in combustion process is described and its results are given. Experimental schemes are designed to measure the spectrum of OH and NO freeradicals by the technique of LIF. OH freeradical in alcohol burner and candle flame and NO freeradical in B/KNO3 pyrolyzing and laser ignition are measured by instruments of YAG laser, dye laser, CO2 laser, spectrometer and ICCD. Experiment results show that fluorescence spectrum is independent with excitation wavelength, but the fluorescence intensity may be decreased when the excitation wavelength changes because the fluorescence deviates from optimal wavelength. The experiment shows that the results agree with fluorescence spectrum characteristics. In comparison with other techniques, the LIF spectrum technique possesses the advantages of superior selectivity and sensitivity.
Measurement technology for spectral responsivity of infrared detector
FAN Ji-hong, HOU Xi-qi, YANG Zhao-jin, YIN Tao, QIN Yan, LIU Jian-ping
2006, 27(5): 460-462.
The spectral responsivity is one of the important parameters of detector. With the development of infrared detect technique, accurate measurement for the spectral responsivity of infrared detector becomes more and more important. The technique on how to measure the spectral responsivity of infrared detector is introduced. Based on an infrared spectral responsivity facility in the institute,the cavity pyroelectric detector is used to calibrate the relative spectral responsivity of infrared detector in several wavelengths on the facility. After repeated measurement,different results are achieved and their average is given in the paper. At last the uncertainty which influences the results is analyzed. Since the wavelength range of infrared spectral responsivity facility is 1~20μm, the relative spectral responsivity of InSb detector and HgCdTe detector can also be measured. The analysis of the uncertainty shows that the measurement accuracy of the spectral responsivity of infrared detector meets the requirement.
A novel method measuring rotation speed based on linear CCD
HAN Wei, ZHANG Yu-cun
2006, 27(5): 463-466.
In order to measure instantaneous rotation speed, the rotation speed of the shaft in the spatial coordinate system is investigated and the measurement model for measuring instantaneous rotation speed of rotation mechanism is proposed. A novel system for measuring the rotation speed is designed based on linear CCD and the realtime processing of measurement data is carried out by threeorder structure. The test results show that the deficiencies of the instantaneous rotation speed measurement in the instantaneous characteristic analysis of rotation mechanism were solved. A simple speed compression model was build up and the reference for other speed measurement applications was provided.