2008 Vol. 29, No. 5

Optoelectronic Engineering
Optical properties of Cr-Cr2O3 cermet films deposited by DC magnetron sputtering
LU Jin-jun, PAN Yong-qiang
2008, 29(5): 665-669.
Cr-Cr2O3 cermet films were deposited by DC reactive magnetron sputtering under different target currents. The optical constants of the films were measured by a spectroscopic ellipsometer in VISNIR. The optical constants of Cr-Cr2O3 cermet films were theoretically calculated with the modified M-G (Maxwell-Gannett) theory, and the calculated results were compared with the experimental data. The results indicate that with the increase of target current, the metal volume fraction and the radius of the metal particles of Cr-Cr2O3 cermet films increases, and the metal particles become oblate spheroids. The results obtained by the modified M-G theory agree with the experimental results.
Photoelectron properties in silver halide with uniformly doped formate ions
ZHOU Xian, YANG Shao-peng, FU Guang-sheng
2008, 29(5): 670-674.
As a hole-to-electron converter doped in silver halide emulsion, formate ion can enhance photoelectron yield in latent image formation, trap the photogenerated holes, eliminate or reduce the electron loss caused by electronhole recombination in latent image formation process, and also release an extra electron to improve the photosensitivity. The decaying signal of photoelectrons generated by laser pulses in cubic AgCl and AgBr emulsions uniformly doped with different concentrations of formate ions was measured with the microwave absorption and dielectric spectrum detection technology. By the comparison of the decaying time and lifetime of photoelectrons, the influence of hole-trap effect of formate ions on photoelectron decay behavior in cubic AgCl and AgBr emulsions was analyzed, and it was founded that the optimal uniformly doping concentration was 10-5 mol/molAg.
Research on photon counting imaging technology
KOU Song-feng, CHEN Qian, GU Guo-hua, JI Er-you
2008, 29(5): 675-678.
Based on the response characteristics of the avalanche photodiode array (APD), a 1-D point process model of the photon counting imaging was established by using the statistics description of the random points. The effects of the photon density, APD′s quench time, gate time and sample periods on the quality of the photon counting imaging were analyzed with the random sample theory of Poisson point process. The qualities of photon counting imaging was simulated at different photon density in the near-infrared band with Monte Carlo simulation method. The simulation results are presented.
Analysis of polarization characteristic of Newton telescope with common-path heterodyne method
ZHANG Xu-guo, JIANG Yue-song, LI Fang
2008, 29(5): 679-683.
The polarization characteristic of Newton telescope is analyzed with the common-path heterodyne interferometry. The reflectance formulas of both s-polarized light and p-polarized light incident on each point of the telescope were derived based on the Fresnel law. The schematic diagram of the experimental setup for measuring phase difference and analyzing the polarization characteristics of Newton telescope with the common-path heterodyne interferometry is given. The influences of Newton telescope on s-polarized light and p-polarized light reflectance, phase difference and incident light polarization degree are analyzed with 632.8nm heterodyne laser source. The curves corresponding to reflectance, phase difference and polarization degree at different incident angles were drawn. The results show that the Newton telescope coated with aluminum produces little influence on the polarization characteristic of incident light, the reflectance difference between s-polarized and p-polarized lights is less than 0.01, and the variation range of the polarization degree is less than 0.07. Therefore, it is suitable for the receiving subsystem of the laser remote polarization imaging system.
Precise calculation for multimode interferometer and its energy loss analysis under weak constrain
GONG Jiao-li, LI Zhi-yang
2008, 29(5): 684-688.
The propagation constant and the optical field distribution of the multimode interferometer were calculated precisely, and the results were compared with the results of the analytical approximate calculation. From the results, it is founded that there are two reasons for the decrease of output optical power under weak constrain. Firstly, the quantity of guided modes supported by the waveguide is small, which causes the poor self-imaging quality and great loss of the highfrequency components, forms the big dispersed spots, and results in the loss of the output coupling. Secondly, the partial energy is taken away by the direct radiation of the high-frequency radiating mode.
Design of scattering netted dots on light guide plate of edge-lighting LED backlight
HUANG Chong, JIANG Yan-sen, SHEN Yi, WU Yong-jun
2008, 29(5): 689-692.
The light guide plate is a key component of backlight units, which determines efficiency and uniformity of light emission. Taking the edge-light from two LEDs as examples, a model was set up to derive the rule of scattering netted dot arrangement by the optical theory. A brief formula for dot arrangement was obtained. In order to achieve wider applications, the rule of the dot arrangement on the light guide plate was deduced for more LEDs. In order to achieve equivalent application, a rule of dot arrangement on the plate with linear light source was acquired.
Morphological filter algorithm to improve positioning accuracy of multi-laser convergent spot center
TANG Shu-gang, DANG Li-ping, BAI Bo
2008, 29(5): 693-696.
In a laser command transmission application, many laser diodes with identical features are arranged in matrix to form a combined light source to achieve a bigger coverage area and longer range. Since the image spot emitted from the lattice multi-laser source has multiple energy centers in open space, the opening and closing calculation in the morphological filtering were used to remove the background noise spots, smooth irregular fringe and holes caused by the small spots overlap and interference. With this method, a full boundary similar to that of an actual image could be achieved with a simplified algorithm of segmentation and location. The mean square error for the position accuracy of the spot center is less than 1.2% in repeated measurements. The center of the overlapping spots can be rapidly and accurately located by this method. It provides the necessary accuracy and speed for laser alignment and measurement at long distance.
Simulation and analysis of thermal deformation for optical elements based on Ansys
CHENG Gang, CHEN Fang-bin, YUAN Xiao-min, LI Guang-liang, JIANG Tao
2008, 29(5): 697-700.
Since the thermal deformation of optical elements in the ambient temperature affects the system performance greatly, the simulation and analysis for the thermal distortion of optical elements are carried out with FEA to support the design of optical elements. A simulation and analysis method for the thermal deformation is put forward. It was implemented in following steps: problem analysis, thermal deformation simulation based on Ansys and data analysis. Each step was discribed. Taking the key elements of an optical system as the research objects, the thermal deformation simulation was performed by the method, data analysis was implemented with Matlab software. The parallelism of the two reflection mirrors is 7.62412″ at 40℃ of ambient temperature and it is 8.56317″ at -10℃. The results are basically consistent with the tested ones, and the validity of the method is verified.
Effect of aspect ratio of target images on characteristics of Vander Lugt correlator
YAO Guang-tao, SHEN Xue-ju, WANG Yong-zhong, HU Wen-gang
2008, 29(5): 701-704.
The effect of the aspect ratio change of target images on the distortion tolerance of matched filter and output correlation peak value is analyzed when VLC is used for the optical correlation recognition according to the diffraction theory. The matched filter was designed with the algorithm for the unconstrained phasematched-only filter and the method of the detour phase coding. The optical correlation recognition was carried out to the rectangular targets whose area and transmissivity are fixed but the length-width ratio is different. The simulated and tested results show that the image symmetry becomes better, the distortion tolerance of matched filter and the correlation peak value are decreased with the increase of the aspect ratio of the target image, and VLC is easier to recognize the target image whose aspect ratio approaches to 1.
Relation between ultra-smooth surface formation and polishing time
WANG Song-wei, YAO He-bao, JIANG Jun-biao, HU Zhi-qiang
2008, 29(5): 705-707.
Since the classical polishing method to polish ultra-smooth surface requests much experience form workers and each worker has different understanding on polishing time, the accurate control of polishing time decides the processing quality of ultra-smooth surface. Therefore, a series of experiments on polishing quality of an ultra-smooth surface and polishing time were designed, which was judged according to the size of a scattering facula and luminance under the condition of total reflection. Finally, the variation of the polishing quality of ultrasmooth surfaces with polishing time is presented. It is concluded that the processing quality of ultra-smooth surfaces is affected by the change of polishing time. Some techniques for the polishing process and the criteria to assess the polishing quality were summarized.
Correction of transversal magnification for framing system in high-speed rotating mirror framing camera
WANG Wei, SHANG Chang-shui, TAN Xian-xiang
2008, 29(5): 708-712.
The reasons of the magnification inconsistency for the framing system in the high-speed rotating mirror framing camera were analyzed theoretically. The correction method of transversal magnification for the framing system was introduced. Taking model FJZ-250 rotating mirror framing camera as an example, the magnification and correcting coefficient of each frame are presented. The measurement results indicate that the magnification inconsistency of the framing system is different significantly with the theoretically calculated value. The spatial test accuracy would be improved by processing the experimental negatives with the corrected coefficient.
Characteristic analysis and correction of conformal radome aberration
SUN Jin-xia, SUN Qiang, LU Zhen-wu, WANG Jian, LIU Jian-zhuo
2008, 29(5): 713-718.
Since the conformal structure has excellent aerodynamical performance and does not have the thermal gradient caused by the discontinuous surfaces, the missile radome with such structure may improve the velocity and effective range of the missile system. However, the curved surface of the aspherical radome used in the conformal structure allows the radome to have many dynamic characters different from the spherical structure, which makes it difficult to design the optical system in a target seeker. Based on analysis of the firstorder characteristics of conformal structure, the reason why the primary order aberration is generated and its characteristics are analyzed according to the vector aberration theory, and a method to tradeoff the aberration in all the observation FOVs is proposed. The result of simulation shows that the addition of the tilt and off-center elements can magnify the aberration in narrow FOV, and can improve the imaging quality of this conformal structure.
Aberration comparison of biconvex and plane-convex Fresnel lenses
TANG Dan-ying, LI Xiang-ning, YANG Peng-qian, HU Ming-kai
2008, 29(5): 719-723.
The optical aberration difference between the biconvex Fresenl lens and the plane-convex Fresenl lens was investigated by designing a large aperture Fresenl lens. Generally, the Fresenl lens is used for collimation and its structure is planeconvex, but the analysis and comparison of the biconvex and the plane-convex Fresenl lenses with P-W method show that the biconvex Fresenl lens is better because of its specific imaging requirement. The two kinds of the Fresenl lenses were modeled in ZEMAX to validate the conclusion. However, it does not indicate that the biconvex Fresenl lens has advantages in all applications since it is application dependent. Therefore, Fresenl lenses should have different parameters for different applications.
Night Vision
Theoretical limit for SNR of LLL image intensifiers
XIANG Shi-ming
2008, 29(5): 724-726.
Signal-to-noise ratio (SNR) is an important parameter of image intensifiers, which determines the detection range and image quality of the photoelectronic imaging systems operating in low-light-level condition. On the basis of SNR chain theory of linear systems, the theoretical limiting SNR of the low-light-level image intensifier was analyzed by the noise factor expression of the system. The expression of maximum SNR for the photocathode quantum efficiency η is given in the precondition of no additional noise in each part of the system, that is NF=1, or in the ideal condition being restricted only by input photons and noise caused by the fluctuation of photoelectron quantity. The theoretical limiting SNR of the tube is ≤ 64, which is derived under the limiting condition of η=1.
Influence of integration time on IRFPA imaging system
LI Fu-wei, ZHANG Yun-qiang
2008, 29(5): 727-730.
The relationship between integration time and the output signal of IRFPA imaging system was theoretically analyzed with the CTIA readout circuit. The results indicate the variation of the output voltage is proportional to the integration time when the parameters of the circuit are fixed. The relationship between integration time and noise, and the relationship between integration time and specific detectivity were analyzed with the electrons method. The non-linear relationship of the integration time, noise and specific detectivity was derived. The influence of the integration time variation on the non-uniformity was analyzed. The changing trend and the influence result were proved by the experiments. It shows that the integration time is very important to the design of IRFPA imaging systems.
Ultraviolet image intensifier with response at 120 nm~200 nm
CAO Xi-bin, ZHAO Bao-sheng, SAI Xiao-feng, WEI Yong-lin, ZHU Xiang-ping, ZHOU Wei, WANG Jun-feng, DONG Gai-yun
2008, 29(5): 731-734.
An ultraviolet image intensifier with response at 120~200nm is introduced. It is a vacuum optoelectronic device, with CsI directly evaporated on its MCP to form a reflective photocathode, with MgF2 as input window, and optical fiber as output window. The proximity focus structure is adopted for reducing dispersion and image distortion. It has high quantum efficiency and spatial resolution. Under the static condition, the spatial resolution of the ultraviolet image intensifier reaches 18Lp/mm, and it has great potentials in space science and astronomy observation.
Optoelectronic inspection of in-pipe surfaces
WANG Ying, WANG Jian-lin
2008, 29(5): 735-739.
Transportation pipes are widely used in liquid and gas transportation because of its special advantage, but the accident of pipeline leakage comes up frequently because of the inevitable aging and rot of pipelines, which may cause loss of human lives and properties, and pollute environment. Therefore, the pipe inspection becomes an important way to prevent leakages. The optoelectronic detection technology has been used for in-pipe inspection successfully thanks to its visibility and huge information. Because the space inside a pipe is narrow, especially for small diameter pipes, the sensor miniaturization is critical in the optoelectronic detection techniques. Some kinds of optoelectronic techniques such as laser array, PSD detection, light ring section detection and structure light detection are introduced, and their principle and configuration are elaborated. Their characteristics are analyzed and compared.The analyzed result shows that the optoelectronic detection technology is applied to the inspection of in-pipe surfaces, and its development trends towards the fast recognition of defects, the accurate 3-D detection and 3-D image display of in-pipe surface blemishes.
Parallax measurement of HUD based on computer vision
TIAN Miao, LIU Jun, GAO Ming
2008, 29(5): 740-744.
In order to improve the parallax measurement accuracy of the head-up display (HUD), a new method based on the computer vision, CCD and digital image processing technology is put forward based on the analysis of various traditional measurements. The principle was discussed and formulas were deduced. The design of the optical system was performed, and the method of image processing was investigated. This method adopts CCD instead of the subjective interpretation, thus the measuement accuracy of parallax is within 30″. The new method is not only fast and accurate, but also straightford and qunatilized. The alignment accuracy and efficiency of HUDs are improved greatly.
Bidirectional displacement measurement of large buildings
YE Mei, WANG Hao
2008, 29(5): 745-749.
A novel optoelectronic detecting method based on projective geometry is proposed to monitor the horizontal and vertical displacement of measured points of a structure such as dam and huge straight building. In the method, a transparent mask is taken as a substrate, a measurement grating is made on the substrate and the mask is fixed on the measured structure. The relative space relationship of the datum line and mask is represented by the beam from GRIN lens. The return beam with mask mode information is transferred by the receiving lens to the monitoring centre through a cable. The horizontal and vertical displacement of measured points of the structure is obtained with optoelectronic transform, A/D and signal analysis. Experiments show that the measurement accuracy of horizontal and vertical displacements can reach 0.005mm and 0.1mm respectively. The sensors at measured spots do not have any electronic element and they have good adaptability and anti-interference performance in the harsh environment.
Tea color measurement with fiber spectrometer
CHEN Xiao-xiao, CAO Yuan-sheng, XIE Xing-yao, TAN He-ping
2008, 29(5): 750-752.
Surface color of tea is an important parameter to estimate the quality of tea. A method based on a fiber spectrometer to detect the surface color of tea is introduced. The reflective spectrum of tea is detected by the spectrometer and normalized by the reflective spectrum of a white standard ceramic plate. Then the CIE tristimulus values of tea are calculated according to the corresponding theoretical expressions and used to characterize the surface color of tea. A tungsten bromine light is used as light source in the experiment. The reflective spectra of tea and white ceramic standard plate are automatically and repeatedly recorded by the spectrometer. The experimental results indicate that this method is simple, rapid, and it has the reproducibility of about 1%.
Optical Design
Design of Newton optical system with zero-power corrector
XIAO Guang-hui, HAO Pei-ming
2008, 29(5): 753-757.
Since a zero-power corrector itself has no achromatic aberration and Petzval curvature, and has such variables as curvature PW, powers φ11 and φ12, etc, it makes the correction of the aberrations of an optical system easier. A Newton optical system with a zero-power corrector, whose stop is before the primary mirror, is proposed. The parameters of the system are the clear aperture Φ=300mm, relative aperture A=1/2, stop position lp2/f=-0.75, and the eccentricity of the primary mirror e2=0. Based on the ray calculation, aberration analysis and optimization of the optical system, the corrector lens optimal power φ11=5, and the optimized on-axis wavefront aberration W=0.0001λ were obtained.
Optimization design of binary optics elements based on ant colony algorithm
LI She-lei, LI Hai-tao, YANG Xi-juan
2008, 29(5): 758-762.
A method to design the BOE by ant colony optimization algorithm is presented to increase the speed of optimization for the BOE and to improve its diffraction efficiency. The digraph diagram of optimization design for a BOE (rectangular aperture multi-level phase-modulated grating) using ant colony optimization algorithm was structured. The structured result was simulated by Matlab. It shows that the run time is reduced and the diffraction efficiency is improved with this algorithm.
Analysis and design of Ge0.05Si0.95/Si heterojunction single-mode coplanar Bragg reflection waveguide grating
XU Qin-chang, LIU Shu-ping, GUO Yun-xiang
2008, 29(5): 763-766.
GeSi/Si heterojunction single-mode coplanar Bragg reflection grating is an important optoelectronic integrated device in silicon based optoelectronic integrated circuits (OEIC). Optical transmission properties of GeSi/Si heterojunction and Bragg conditions are analyzed. The coupling coefficient and the coupling efficiency were derived by solving the Bragg grating equation. According to the above principle, the 1.3μm Ge0.05Si0.95/Si heterojunction single-mode coplanar Bragg reflection grating was designed, whose incident angle was 66°, waveguide thickness was 2μm, coupling width was 4252μm, groove depth was 0.05μm, grating period was 0.456μm, filtering bandwidth was 0.214nm and coupling efficiency was 84.1%. The distribution of the electric fields of the incident and the reflected guide modes was numerically simulated.
Design of two-mega-pixel mobile phone camera lens
HUANG Cheng, WEN Tong-qiang, LU Jian-hua, CHEN Ting-ting, DING Gui-lin
2008, 29(5): 767-771.
Based on the conventional spherical glass lens and the aspherical lens principle, a low cost and fixed-focus lens system is designed with the optical system design software CODE V to meet the requirement of the mobile communication on miniaturization and simplification camera lenses. The total length of the lens system is less than 5mm and it has excellent imaging performance. An aspherical lens made of polyolefin-plastic is used to reduce the size and save production cost. The pixel size of the lens is 2.52μm×2.52μm, the corresponding Nyquist frequency is 196 lines/mm, the relative resolution performance (modulation transfer function) of the design can reach 40% at half of Nyquist frequency, the spherical aberration of this lens is between -0.05mm and 0.05mm, and the maximal distortion is less than 0.17%. The compact, low-cost, high-precision and miniature lens can meet the requirement of the two-mega pixels.
Laser Technology
Semi-external cavity Nd∶YAG microchip laser with orthogonal linear polarized dual-frequency output and its application in precision angle measurement
REN Cheng, TAN Yi-dong, ZHANG Shu-lian
2008, 29(5): 772-776.
The Nd∶YAG microchip laser with orthogonal linear polarized dual-frequency output was designed. Two quarter-wave plates in which one is static, another rotates around in 360°, are set in the laser cavity. The intra-cavity variable birefringence caused by relative rotation of two wave plates in laser cavity results in changeable frequency difference of dual frequency. Thus, the output of the tunable dual-frequency laser is realized. The eigen-mode of laser in the cavity was analyzed with Jones matrix. The theoretical description for the frequency diversity of dual-frequency is presented. The potential laser goniometer with small volume, high resolution and ability of precision 360°measurement is discussed.
Development of polarization Mie-scattering lidar
CHI Ru-li, LIU Dong, FAN Ai-yuan, ZHOU Jun, HU Huan-ling
2008, 29(5): 777-784.
The polarization Mie-scattering lidar (PML) can be used for detecting the depolarization ratio of cirri and aerosol backscattering wave, and investigating the extinction characteristic of aerosols in the atmosphere. In order to improve the detection capability in daytime, a narrow band interference filter and diaphragm are employed in the system to separate the received laser return signals consisting of Mie-scattering signal and Rayleigh scattering signal from the background noise. The overall structure, specifications and measurement method of PML are described. The fundamental principle of PML is briefly introduced. The main performance parameters of PML were determined, and the results were analyzed. The typical detected results of extinction characteristic of aerosols and the structure of cirri at Hefei(117.16°E, 31.90°N) are presented and discussed. The primary observational results over Hefei show that the performance of this lidar is reliable. And it has the ability to detect the physical and optical characteristics of the cirrus and aerosols.
Influence of bubble concentration on lidar backscattering characteristic
ZHENG Yi, YANG Ke-cheng, XIA Min, RAO Jiong-hui
2008, 29(5): 785-788.
The theoretical analysis and experimental research were performed for the light backscattering property of underwater bubble layers with different concentration. The experimental data show that there are the signal peaks caused by the bubble scattering, in addition to the signal peak caused by the water backscattering in the return wave curves of the underwater backscattering signals produced by lidar. The scattering peaks are overlain on the backscattering signal peaks of the water, the location is directly related to the location of the underwater bubble layers, and its amplitude is affected by the concentration of the bubble layers. It can be concluded from these curves that there is a second backscattering peak in the total backscattering signal curves caused by bubble layer underwater. The return time of the second peak is related to the distance between detector and bubble layer. The backscattering signal increases with the concentration increase of the bubble layer, which was predicted by theoretical analysis. The variation trend of the backscattering signal is mainly affected by the optical parameters of the water.
Quantitative analysis of lead in soil by laser-induced breakdown spectroscopy
LI Yong, LU Ji-dong, LIN Zhao-xiang, XIE Cheng-li, LI Jie, LI Peng-yan
2008, 29(5): 789-792.
Fast quantitative analysis of lead in the simulated soil made of chemical reagents(PbCl2, SiO2, CaCO3 and KBr)was carried out with the laser-induced breakdown spectroscopy. The result shows that the signal-to-noise ratio increases and then decreases with the time delay. The calibration curves of Pb content were constructed with the spectrogram acquired in experiments. It is found by the investigation that the average relative error of the method for the fast quantitative analysis of lead in soil is 8.33% and the minimum detection limit is 89μg/g. The experimental result proves LIBS is capable of being used in the detection of lead in soil.
Study on laser absorptivity of metal material
CHEN Jun, ZHANG Qun-li, YAO Jian-hua, FU Ji-bin
2008, 29(5): 793-798.
To reduce the error between the calculated value of metal absorptivity by Fresnl formula and the measured value, the factors affecting metal absorptivity in the laser heat treatment were analyzed, and the mathematical model of metal absorptivity was improved by simulation. The model was used to calculate the absorptivity of aluminium, copper, platinum, iron and 3Cr13 stainless steel. The calculation result agrees with the value measured with lumped parameter method, which proved the validity of the improved laser absorptivity formula.
Fiber Optics
Optic-circuit encoding of video digitized signal in fiber-optic transmission system
WANG Heng-yun
2008, 29(5): 799-803.
A fiber system for realizing digitized video transmission by two encoding methods is introduced in this paper. The circuit encoding, data serialized methods and construction in the fiber transmission system are briefly described. The multiplex/demultiplex of parallel data and their different encoding function were realized by choosing a serializer/deserializer circuit with parallel input. The advantages and defects of these data encodings are described. The superiority of the two encoding methods compared to the traditional encoding methods, and the effect of the different encoding methods on the receiving characteristics of the system are given. A schematic diagram of the signal connection and the encoding table for each encoding method are presented. The function and the applied fields of the system with four-layer PCB are provided.
Study on strain and temperature cross sensitivity of fiber Bragg grating sensor
WANG Hong-liang, ZHANG Jing, QIAO Xue-guang, WANG Yu
2008, 29(5): 804-807.
The cross sensitivity of strain and temperature is a key problem for fiber Bragg grating (FBG) sensors. Based on the physical mechanism of the strain and temperature cross sensitivity, several schemes for the discrimination measurement of temperature and strain are presented. They are dualwavelength matrix, two FBGs with different cladding diameters and chirped Bragg grating techniques. Based on dual-wavelength matrix technique, a new structure of FBG sensor based on an elastic strain-sensitive element is proposed. Simultaneous discrimination measurements of the pressure and temperature are demonstrated in 20MPa and 150℃, and its temperature sensitivity is 0.02nm/℃.
Design of fiber light-focusing device for sunlight illumination system
GAO Wei-xia, SUN Chang-wei, CHANG Jing-jing, YU Rong-jin
2008, 29(5): 808-811.
Using sunlight transferred through an energy-transfer fiber for indoor illumination is a new development of solar energy utilization, but there is a technical problem to couple the sunlight into a fiber. A light-focusing device which could couple the sunlight into a energy-transfer fiber was put forward based on the study of plastic fiber characteristics and various light-focusing technology. Based on the traits of the aspherical lens, the sunlight was focused on a very small spot, and then it was transferred into a plastic fiber by an aspherical lens and a selfoc lens. A formula for calculating the optimal length of selfoc lens is presented. The optimal assembly of the aspherical lens and selfoc lens was implemented by the aid of this formula. Therefore, sunlight is coupled into a plastic fiber efficiently. The feasibility of this device is proved theoretically.
Theoretical analysis of sensing probe in fiber microphone
ZHANG Hong-ju, YAO Sheng-li, MI Lei
2008, 29(5): 812-814.
Because of the fiber sensor′s excellent characteristics, such as small volume, simply structure, high sensitivity, low loss, resistance to electromagnet interference and corrosion resistance, it is used in a microphone to reduce the size of the microphone, and improve its sensitivity and electromagnetic immunity performance. A new design for a reflective fiber microphone is proposed. The Y type reflective multimode fiber sensing probe is adopted. The block diagram of the fiber microphone system is given. Based on the theory of the optic field distribution of the exit light from a fiber, the relationship between the offcentering quantity h and the optical intensity modulate function I(Z″) is presented for the deformed film in sound field.
Theoretical Study
Atmosphere transmission in detection of nuclear explosion light radiation
WU Jian-hui, YANG Kun-tao, ZHANG Nan-yang-sheng
2008, 29(5): 815-820.
Based on the characteristic of light radiation by nuclear explosion, in combination with the atmospheric characteristic in the middle latitude area in China, the atmospheric transmission performance of light radiation at (0.2~1.2)μm wave band was studied. It is found, through the analysis of the actual measured data, that the main compositions in atmosphere to affect the (0.2~1.2)μm light radiation are the molecular absorption and the scattering of steam, carbon dioxide and ozone, as well as the scattering of big aerosol granules. The atmospheric transmission empirical formula for the horizontal transmission of the (0.2~1.2)μm light radiation was improved with these factors. The result of computer simulation indicates that the formula can best describe the atmospheric transmission of the light radiation in middle latitude area in China in the (0.4~0.8)μm visible light wave band. The result of quantitative calculation for (0.4~0.8)μm wave band light radiation was directly used in the nuclear explosion subsystem, which took the visible light radiation to simulate the nuclear explosion. The experimental result indicates that more accurate measurement can be achieved with the atmosphere transmission software.
Theoretical analysis of polarization state for polarizing microscope
KONG Fan-mei, LI Guo-hua, PENG Han-dong
2008, 29(5): 821-824.
In order to investigate the polarization state variation of the light passing through transparent optical crystals and to evaluate the optical characteristics of crystals with polarizing microscope, the optical structure of the polarizing microscope was introduced, the geometrical optical path which natural light went through in the polarizing microscope was analyzed, and the polarization state transformation happened when the natural light passed through the polarizing microscope was investigated with Stokes parameters and Muller matrix. The principle of polarization state transformation was given theoretically. The theoretical fundamentals are provided for operating the polarizing microscope and understanding its operation principle.
Propagation characteristics of electromagnetic wave in slab waveguide filled with negative refraction index material
KE Zun-gan, WU Shao-ping, ZHENG Dan
2008, 29(5): 825-829.
The propagation characteristics of the electromagnetic wave in three-layer slab waveguides filled with negative refraction index materials was studied and numerically calculated according to Maxwell theory. The propagation properties of TE and TM waves in the flat plate was analyzed, the mode equations were derived. The propagation characteristics of the electromagnetic wave in the slab waveguide filled with right-hand material were compared with the above mentioned propagation characteristics. And the energy-flow density of the TE mode was investigated. The results show that the base mode and the single mode do not exist, and every mode has a cut-off thickness. The quantity of the modes increases with the increase of the thickness. It is found that the slab waveguide can transmit more modes simultaneously at a specific thickness, and the higher the incident frequency is, the higher possibility of more modes in the slab waveguide. The slab waveguide filled with lefthand material can transmit more energy than the waveguide filled with right-hand material.
Rigorous vector analysis for effect of wavelength drift on Fresnel lens
JIA Wen-wu, WANG Yue-feng, HUANG Feng
2008, 29(5): 830-832.
In order to analyze the effect of the incident wavelength drift from the design wavelength of phase Fresnel lens on the focusing property of phase Fresnel lens, the dependent curves of focal power-wavelength and diffractive efficiencywavelength for the phase Fresnel lens were obtained by adopting the finitedifference time-domain method (FDTD) as a rigorous vector analysis tool. The simulation results show that the focal power of a Fresnel lens increases with the wavelength, which is similar to the result of scale theory, the diffractive efficiency declines with the drifting of the incident wavelength, and it is lower than the analysis result of scale theory.
Optical characteristics of right-angle roof prism and corner-cube prism
LI Zheng-yang, FU Yue-gang
2008, 29(5): 833-836.
In optical engineering application, the prisms′ beam folding function is often used to implement the image rotation, detection and measurement. In this paper, considering the effect of the machining error of prisms on the optical axes in the engineering application, the matrix, characteristic direction and extreme-value axial direction of the right-angle roof prism and corner-cube prism were obtained with the dynamic optical theory and the derivation formula. Thus, the mathematic models of optical axes of the two prisms were derived. According to the actual machining error, the theoretical error sources of the two prisms were deduced, and the comparative analysis for both prisms was conducted. Finally, it is concluded that the right-angled roof prism should be used instead of the corner-cube prism.