Contents
2009
Volume: 29 Issue 9
54 Article(s)
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Research Article
Application of Ronchi Grating to the Quantitative Measurement of Large-aperture Aspheric Surfaces
Lei Baiping, Wu Fan, and Zhou Chenbo
The Ronchi grating is used to test the large error of aspheric surfaces during the grinding and advance polishing combining with the technology of photo sensors and the technology of digital image processing in the quantitative way. This paper discusses the basic principle of this method, sets up the mathematical modelThe Ronchi grating is used to test the large error of aspheric surfaces during the grinding and advance polishing combining with the technology of photo sensors and the technology of digital image processing in the quantitative way. This paper discusses the basic principle of this method, sets up the mathematical model and works out the corresponding software. A concave parabolic mirror with the diameter of 140 mm and the F number is 2 is tested by using this method. The result of the quantitative measurement fits well with the one of the interferometer. This analysis software and test method provide a valid and credible quantitative measurement way for the exact-grinding and advance polishing aspheric surfaces..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2441 (2009)
Atmospheric Optics and Oceanic Optics
A New Method of Aerosol Particles' Time-of-Flight Accurate Measurement Based on Differentiation
Huang Shuhua, Liu Jianguo, Liu Wenqing, Lu Yihuai, Zhang Yujun, Gui Huaqiao, Sun Shijie, Jiang Yu, Chen Jun, and Wang Yaping
Time-of-flight aerosol beams spectrometry is a typical method of accurate size and concentration measurement in aerosol particles' size distribution monitoring. Accurate measurement of aerosol particles' time-of-flight is the key to monitor the distribution of particles' size. A method of accurate measuremeTime-of-flight aerosol beams spectrometry is a typical method of accurate size and concentration measurement in aerosol particles' size distribution monitoring. Accurate measurement of aerosol particles' time-of-flight is the key to monitor the distribution of particles' size. A method of accurate measurement of aerosol particles' time-of-flight is designed by improving the threshold level comparison method, and the comparison of zero-level instead of the changing threshold level is realized based on differentiation since the maximum value of the original singal is corresponding to zero-level of the differential singal. By using this method, the time-of-flight can be accurately measured when the strength of the scattered light changes, or when the two peaks of the scattered light are not symmetrical..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 29, Issue 9, 1 (2009)
Modified Retrieval Algorithm on Decreasing Detection Limits in Differential Optical Absorption Spectroscopy
Ma Jinji, and Li Suwen
Differential optical absorption spectroscopy (DOAS) has become a widely used method to measure trace gases in the atmosphere. It can identify trace gases through narrow-band molecular absorption. Concentration of trace gases is retrieved using method of least-squares fits of reference spectra to the measurement spectraDifferential optical absorption spectroscopy (DOAS) has become a widely used method to measure trace gases in the atmosphere. It can identify trace gases through narrow-band molecular absorption. Concentration of trace gases is retrieved using method of least-squares fits of reference spectra to the measurement spectra. A novel retrieval method based on radial basis function (RBF) neural network was developed to retrieve the concentration of trace gases in DOAS system. The coefficient of the hidden layer was trained by modified nearest neighbor clustering algorithm, and that of the output layer was trained by gradient descent algorithm. These result in a fast speed of convergence of network. At last, there was comparison between the novel retrieval method and the conventional least-squares fitting. The experimental results show that the reliability and accuracy of DOAS are improved and detection limits are decreased by using the novel retrieval method..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2351 (2009)
Study on the High-Accuracy Fluid Refractive-IndexSensor Based on an Arrayed-Waveguide Grating
Wang Youbin, and Huang Xuguang
A high-accuracy fluid refractive-index sensor based on an arrayed-waveguide grating (AWG) is designed. This system measures the refractive-index of a fluid in the groove using the characteristic of the sensibility of the phase shift of arrayed-waveguides. The phase shifts of the arrayed waveguides (AWs) lead to the posA high-accuracy fluid refractive-index sensor based on an arrayed-waveguide grating (AWG) is designed. This system measures the refractive-index of a fluid in the groove using the characteristic of the sensibility of the phase shift of arrayed-waveguides. The phase shifts of the arrayed waveguides (AWs) lead to the position change of the maximum of the light intensity in the image plane of the output slab. The high accuracy real-time refractive-index of the fluid can be obtained from the power rate between two output waveguides via a narrow band source. A mathematical model based on the theory of Fourier optics and wave optics is established with reasonable parameters and the consideration of every factor. The analytic expression of the relationship between the refractive-index of the fluid and the power rate is obtained via fitting. The method can eliminate the instability, the inner loss of the instrument and the measurement error caused by the environment to improve the measurement accuracy of refractive index..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2378 (2009)
Fiber Optics and Optical Communications
Analysis of Edge Characteristics of Grating and Cavity of Fiber Grating-Based Fabry-Pérot Cavity
Li Wenbo, Zhou Wangmin, Wei Zhiwu, Cheng Zhenlong, Wei Guanghu, and Shi Yalong
The initial phase of the two fiber Bragg gratings used in FabryPérot cavity was considered and the reflectivity and transmissivity expressions of fiber grating-based FabryPérot cavity at any FBG’s initial phase were derivated by coupledwave equation. The phase factors in the expression include cavity lengtThe initial phase of the two fiber Bragg gratings used in FabryPérot cavity was considered and the reflectivity and transmissivity expressions of fiber grating-based FabryPérot cavity at any FBG’s initial phase were derivated by coupledwave equation. The phase factors in the expression include cavity length modulated by propagation constant, phase mutation of the fiber Bragg grating, initial phase of the two fiber Bragg gratings and fiber grating length modulated by space frequency of the fiber Bragg grating. The influence of the latter two factors on reflection spectrum was analyzed, and a method to regard a fiber grating-based Fabrypérot cavity as ideal FabryPérot cavity was presented..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2355 (2009)
Degenerate Four-Wave-Mixing Noise in Dispersion Managed Wavelength-Division-Multiplexed System
Du Jianxin
A generalized model to evaluate variance of four-wave-mixing (FWM) noise in dispersion managed wavelength-division-multiplexing (WDM) system with intensity modulation scheme is presented. The information sequence of bits and initial phase of bit sequences are random. The model gives the statistical results of them. SimA generalized model to evaluate variance of four-wave-mixing (FWM) noise in dispersion managed wavelength-division-multiplexing (WDM) system with intensity modulation scheme is presented. The information sequence of bits and initial phase of bit sequences are random. The model gives the statistical results of them. Simultaneously, the positions of inter-channel pulse collisions are also included in the model, which are more difficult to be located in dispersion managed fiber link than in constant dispersion fiber link due to inter-channel pulse walk-off. Some examples show that optimized dispersion management schemes are important to decrease FWM noise, and meanwhile make pulses transmit steadily. It is also shown that when the pulse duty cycle is small, initial relative time delay of bit sequence plays an important role in obtaining minimized value of FWM noise variance..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2361 (2009)
Influence of Vibration on Optical Receiving Power in Rectilinear Mobile Wireless Optical Communication
Fu Xinghu, Chen Zhenyi, Guo Qiang, Pang Fufei, and Wang Tingyun
The beam offset in rectilinear mobile optical communication is investigated thoroughly, and the relation between mobile distance and spot radius, optical receiving power and the relation between angle offset and optical receiving power, image offset are presented. The experiments on optical receiving power are done at The beam offset in rectilinear mobile optical communication is investigated thoroughly, and the relation between mobile distance and spot radius, optical receiving power and the relation between angle offset and optical receiving power, image offset are presented. The experiments on optical receiving power are done at the rectilinear orbit with immobile optical transmitter and mobile optical receiver,and with mobile optical transmitter and immobile optical receiver . The space light receiving performance is compared between big aperture optical fiber and solid optical taper. The optical taper is presented as the space light coupling receiving component. The result of the experiment shows that the solid coupling optical taper can receive the focused light signal effectively when the beam is deflected, and suitable to the rectilinear mobile wireless optical communication with the mobile distance scope of 80 m..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2368 (2009)
High-Resolution Optical Fiber Accelerometer
Lin Qiao, Li Shu, Pan Jianbin, Wu Xingkun, Chen Liuhua, and Ni Wei
A novel high-resolution optical fiber accelerometer is developed, featuring compact-size, low-cost and easy to be mass produced. The accelerometer probe has an all-fiber structure. Phase-generated carrier (PGC) technology is adopted to modulate and demodulate the interference signals to obtain a high-resolution phase sA novel high-resolution optical fiber accelerometer is developed, featuring compact-size, low-cost and easy to be mass produced. The accelerometer probe has an all-fiber structure. Phase-generated carrier (PGC) technology is adopted to modulate and demodulate the interference signals to obtain a high-resolution phase signal. Measurement of prototype shows the high-resolution optical fiber accelerometer can resolve an acceleration up to 3×10-4 g in 0-100 g dynamic range and the maximum resolution reaches 10-6. The probe consists of a circular mesh flexture and silicon micro-mirror, capable of generating the displacement interference signal under acceleration. Strain analysis of the structure by Cosmosworks and experimental measurement is carried out. The result of the overall design agrees reasonably well with experimental measurement..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2374 (2009)
Image Processing
Study on Precollimation Based on Hough Transformsand Color Character
Lian Ming, Fu Hongya, and Fu Sen
In order to realize auto-alignment of terminal in ground laser communication simulation experiment, a precollimation method based on image recognition is proposed. First, indication cursor are extracted and reference cursor according to the color character of image. On the basis of the size of scale facula, the method In order to realize auto-alignment of terminal in ground laser communication simulation experiment, a precollimation method based on image recognition is proposed. First, indication cursor are extracted and reference cursor according to the color character of image. On the basis of the size of scale facula, the method establishes proportion relation between image and real object is built, and then the radius of target circle is estimated. Then based on Hough transform, the algorithm finds the centre of communication terminal caliber in the picture and calculates compensation angle between the centre and indication cursor. by sending the compensation angle to motion control card, it would make laser directly collimate to the terminal. At last, starting rose scanning and the process is terminated until capturing beacon light. Experimental results indicate that this method can detect the target exactly, and the calculation time is 0.94 s. It has perfect anti-jamming character. The method satisfies the requirements of auto-recognition and rapid collimation between two communication terminal..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2385 (2009)
Image Denoising Method Based on Curvelet Transform and Total Variation
Ni Xue, Li Qingwu, Meng Fan, Shi Dan, and Fan Xinnan
Curvelet transform can preserve more details for image denoising, but it always has the ‘warp-around’ artifacts in image edges. Total variation, another effective image denoising method, can preserve edges better, but image texture information will be also smoothed. An efficient image denoising method based on combinatCurvelet transform can preserve more details for image denoising, but it always has the ‘warp-around’ artifacts in image edges. Total variation, another effective image denoising method, can preserve edges better, but image texture information will be also smoothed. An efficient image denoising method based on combination of curvelet transform and total variation is proposed. Firstly, the image is denoised by curvelet thresholding method and total variation method. Then, the two denoised images are fused using curvelet transform. Here the weighted average algorithm and maximizing absolute value algorithm are used respectively to process the low-frequency coefficients and the high-frequency coefficients. Finally, the denoised image is reconstructed by the inverse curvelet transform. Experimental results show that the new method is effective in removing white noise, and the detail of the image is kept well. It has better denoising effect than single curvelet thresholding method and total variation method..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2390 (2009)
Selecting Regularization Parameter In Image Restoration Based On the Variance Of Noise
Liu Peng, and Liu Dingsheng
The fixed point iteration is employed when we restore the image by total variation, and we propose to select the regularization parameter by variance of noise in the iteration. The initial noise statistical properties in observe image is known hypothetically. In order to correctly estimate the variance of noise in iterThe fixed point iteration is employed when we restore the image by total variation, and we propose to select the regularization parameter by variance of noise in the iteration. The initial noise statistical properties in observe image is known hypothetically. In order to correctly estimate the variance of noise in iteration, a pure synthesis noise as an image is synchronously iterated with the observation image in de-convolution, and we take variance of pure noise image as the estimation of the variance of noise in observation image to compute the regularization parameter by the variance. Against the anisotropy of the regularization, the novel regularization term that can ensure the synchronous changing of the statistical properties of two noises was propose in this article. The new regularization term is put into use only in iteration of pure noise image, and the similarity of statistical properties between actual image noise and pure noise can be maintained in iteration. Under the condition of knowing the variance of noise of image in iteration, the relationship between the variance of synthetic noise and the regularization parameter λ can be established. The adaptability of total variation based image restoration is dramatically improved..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2395 (2009)
Image Preprocessing Algorithm for Space Target Space-Based Detection
Pan Haibin, Zhang Wei, Cong Mingyu, Chen Jun, Meng Xianglong, and Cao Yiming
Space-based detection algorithm in American SBV named moving target indicator(MTI) algorithm was improved. The improved algorithm could detect target streak ‘submerged’ in noise and clutter more quickly and more effectively. MTI improved algorithm used a new two-dimensional image detection preprocessing algorithm namedSpace-based detection algorithm in American SBV named moving target indicator(MTI) algorithm was improved. The improved algorithm could detect target streak ‘submerged’ in noise and clutter more quickly and more effectively. MTI improved algorithm used a new two-dimensional image detection preprocessing algorithm named windowed detection in probability algorithm. There were more the non-zero points in target detection window than in pure noise detection window with the same size. According to the characteristic, windowed detection in probability algorithm used threshold filter in detection window. The threshold filter extremely suppressed noise along with eliminating portion target points. Then, doubtful target streak was eliminated by three-point collinear streak detection algorithm. The streak detection algorithm reduced false-alarm probability and increased detection probability. By algorithm was performance analysis, false-alarm probability of MTI improved algorithm was reduced fifteen times than MTI algorithm, and needed signal-to-noise ratio (SNR) was reduced from 6 to 3 when detection probability equals to 99%. Furthermore, the calculation amount of MTI improved algorithm was reduced six order of magnitude than MTI algorithm. According to algorithm performance, MTI improved algorithm avails real-time processing in engineering application..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2402 (2009)
Characteristic-Selecting Filtering in Infrared Small Target Detection
Cao Qi, and Bi Duyan
For solving the pre-processing problem of dim small target detection in infrared images, a characteristic-selecting filtering (CSF) method is proposed. The method applied anistropic diffusion to images’ spatial domain creatively. Through analyzing the properties of various kinds of characteristic regions, the method imFor solving the pre-processing problem of dim small target detection in infrared images, a characteristic-selecting filtering (CSF) method is proposed. The method applied anistropic diffusion to images’ spatial domain creatively. Through analyzing the properties of various kinds of characteristic regions, the method improved the coefficient distribution function to suppress clutter, smooth edge and enhance target. The filtering characteristic analysis and experimental results were given, which were compared with those by some other methods. The results show that this approach can provide good performance of suppressing clutter and enhancing target signal, and its structure is simple to be implemented in real-time system..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2408 (2009)
Imaging Systems
On-Orbit Modification of Pointing Error for Imager in Geostationary Satellite Based on Star Sensing
Guo Qiang, and Xian Di
Based on the on-orbit modification model of pointing error for geostationary imager, several important parameters, including lowest star brightness level, stars and spatial positions for staring observation, are figured out. Moreover, the influences of digital delay integration (DDI) and point spread function (PSF) on Based on the on-orbit modification model of pointing error for geostationary imager, several important parameters, including lowest star brightness level, stars and spatial positions for staring observation, are figured out. Moreover, the influences of digital delay integration (DDI) and point spread function (PSF) on the accuracy of the estimated pointing error are analyzed and a feasible scheme with pointing error as accurate as 1″ is also established. Real star sensing observations from GOES-9 imager are used to validate partial characteristics of this model quantitatively. This method will benefit the operational modes design and engineering application of high accuracy on-orbit modification of pointing error for imager in the following up Fenyun-4 satellite..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2413 (2009)
A Pilot Investigation into Shape-Based DOT Methodology with Elliptic Parameterization of Multi-Domains
Ruan Pingqiao, Liu Yanfang, Gao Feng, Zhao Huijuan, and Yang Fang
Acquisition of the optical structures within a biological body is critical to all the diffuse light imaging modalities, such as diffuse optical tomography(DOT) and fluorescence molecular tomography(FMT). On an assumption of the optical homogeneity within the organs, it can be cast as a shape-based DOT issue, which aimsAcquisition of the optical structures within a biological body is critical to all the diffuse light imaging modalities, such as diffuse optical tomography(DOT) and fluorescence molecular tomography(FMT). On an assumption of the optical homogeneity within the organs, it can be cast as a shape-based DOT issue, which aims to simultaneously recover the smooth region boundaries and optical properties of the biological tissue. The boundary element method (BEM) is used for the forward modeling and implemented in two dimensions, and compared with those obtained from the finite element method (FEM) approach for the validation. A truncated singular value decomposition(truncated-SVD) optimization method is implemented for the inverse problem, which is evaluated in a domain with 3 heterogeneous inclusions at 40 dB noise level. The numerical simulations show that the methodology is very promising and of good convergence. The shape parameters and the optical coefficients can be reconstructed with good accuracy at a reasonable noise level..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2421 (2009)
A Method of Improving Image Quality in Diffuse Optical Tomography Based on Spline Interpolation of Measurement Space
Yang Fang, Gao Feng, Ma Yiwen, Zhao Huijuan, and Ruan Pingqiao
A method of improving image reconstruction quality for time-domain breast diffuse optical tomography is proposed based on panel detection. A measurement space expanded scheme is presented that uses cubic spline interpolation to obtain more measurements from less source-detector pairings to alleviate the problem that thA method of improving image reconstruction quality for time-domain breast diffuse optical tomography is proposed based on panel detection. A measurement space expanded scheme is presented that uses cubic spline interpolation to obtain more measurements from less source-detector pairings to alleviate the problem that the number of boundary measurements data is generally far fewer than that of unknown parameters to be reconstructed in reconstructing process. Compared with traditional algorithm, this method can efficiently improve the reconstruction quality and spatial resolution. The proposed methodology is validated by reconstructing the image of the slab phantom containing two deeply-located absorption and scattering contrasting cubes. And the reconstruction contrast is analysed here for the quantification of the spatial resolution.Numerical simulation results illustrate that the spatial resolution of reconstructed image is 4 mm edge-to-edge..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2427 (2009)
Instrumentation, Measurement and Metrology
Cophasing Methods of Segmented Space Telescope
Wang Shanshan, Zhu Qiudong, and Cao Genrui
Most of the common-used methods for cophasing are summarized and their applicabilities for using in space are discussed. A novel method which is based on dispersed Rayleigh interferometry (DRI) is proposed with data processing algorithm. The basic theory of DRI is introduced and the configuration to measure cophasing eMost of the common-used methods for cophasing are summarized and their applicabilities for using in space are discussed. A novel method which is based on dispersed Rayleigh interferometry (DRI) is proposed with data processing algorithm. The basic theory of DRI is introduced and the configuration to measure cophasing error of segmented primary mirror is given. An experimental system to validate the DRI algorithm is established, preliminary results indicate that the measurement range reaches 200 μm, repeatability is better than 2 nm，and accuracy is 6.56 nm with the range of δ≤1 μm, which meet the requirements of cophasing the primary mirror in the orbit..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2435 (2009)
Improvement of Measurement Accuracy in Fiber Bragg Grating Sensors by Using Time Delay Estimation Techniques
Wu Yanqun, Hu Yongming, Jiang Nuan, and Yang Huayong
The Phase-spectrum method (PS), widely used in time delay estimation techniques in the fields of radar and sonar, is applied to detect the wavelength shift for any shape of reflection or transmission spectrum of fiber Bragg grating sensors in homogeneous strain or temperature fields. The peak detection sensitivity to nThe Phase-spectrum method (PS), widely used in time delay estimation techniques in the fields of radar and sonar, is applied to detect the wavelength shift for any shape of reflection or transmission spectrum of fiber Bragg grating sensors in homogeneous strain or temperature fields. The peak detection sensitivity to noise is analyzed, and the results show that for single mode FBG sensors, the larger the fiber length and the refractive index is, the more seriously the SNR influences on the peak detection. The experimental results show that compared with conventional algorithms, the proposed method can effectively suppress the random excursion of the central wavelength, and its estimation accuracy is not limited by the wavelength accuracy. Besides, it needs no assumption of the spectrum shapes and no interpolations, and thus reduces the computational consumption. The wavelength detection accuracy is on a scale of pm..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2447 (2009)
Analysis on Optical Coordinate Measurement Based on Phase Target
Mao Xianfu, Su Xianyu, Liu Yuankun, and Chen Wenjing
On the basis of regarding traditional aided measuring probe as target ,adopted phase and fringe technique to calibrate a camera system or to measure a 3-D object, A new target-phase target, is proposed. Comparing with traditional method, the new calibration result of camera system is more reliable because of more accurOn the basis of regarding traditional aided measuring probe as target ,adopted phase and fringe technique to calibrate a camera system or to measure a 3-D object, A new target-phase target, is proposed. Comparing with traditional method, the new calibration result of camera system is more reliable because of more accurate to extract the grids based on fringe analysis and phase technique. Camera is calibrated by calibration target which is built by 2-dimensional sinusoidal fringe having been projected on the computer screen.A new and portable phase target is designed originally,optical coordinate measurement is carried through the phase target. Moreover,coordinate system transformation formula and the moving distance of phase target is calculated. Exact measuring result is obtained in our experiments, which proves that the method is effective..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2452 (2009)
Determination of Plume by Hyperspectral Imaging Differential Optical Absorption Spectroscopy
Si Fuqi, Xie Pinhua, Liu Yu, Dou Ke, Xu Jin, Liu Wenbing, and Liu Wenqing
An optical remote sensing method for measuring the air pollutants (such as SO2, NO2) emitted from sources is studied by use of a hyperspectral imaging differential optical absorption spectroscopy (DOAS) instrument to scan the plume from pollution source on a scan table. The column density of air pollutant is retrieved An optical remote sensing method for measuring the air pollutants (such as SO2, NO2) emitted from sources is studied by use of a hyperspectral imaging differential optical absorption spectroscopy (DOAS) instrument to scan the plume from pollution source on a scan table. The column density of air pollutant is retrieved from processing of the scattered sun light spectra collected by the instrument by means of the spectral analysis method of passive DOAS. Combing with the scan table during the measurement, the map of trace gases can be estimated. The hyperspectral imaging differential optical absorption spectroscopy system consisted of imaging DOAS spectrometer、UV lens and scan table is described in detail, which was carried to scan the plume from a fossil power plant in a field measurement. This technique provides a simple and quick method for imaging the air pollutants..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2458 (2009)
A Method of Improving the Measuring Accuracy of the Pose of Targets Based on Outliers-Removal
Zhao Rujin, Zhang Qiheng, Zuo Haorui, and Xu Yong
Based on the circumstance that the outliers appear sometimes when the pose of target is measured by mono-vision method, a new method is presented for estimating the pose (position & attitude) based on outliers-removal (ORPE). The optimization function is established based on the principle of max-min error. Then theBased on the circumstance that the outliers appear sometimes when the pose of target is measured by mono-vision method, a new method is presented for estimating the pose (position & attitude) based on outliers-removal (ORPE). The optimization function is established based on the principle of max-min error. Then the outliers can be detected and removed through eliminating frontier of maximum error. Furthermore the impact of outliers’ error on the accuracy of pose estimation can be eliminated. The pose of 1 m×1 m×1 m cube target is measured by ORPE, which proves the validity of the algorithm. The pose of Boeing plane model is measured by ORPE. As a result, the average attitude error is 2.07°, and the average position error is 1.6%. Comparatively, the average error of ORPE is less than the one of the lest-square pose estimation (LSPE) method. Consequently, it’s demonstrated that ORPE can do outliers-removal effectively, and improve the accuracy of pose estimation simultaneously..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2463 (2009)
Measuring Refractive Index of Micro-Quantity Liquid by Focus Method
Li Qiang, Han Guanghui, Xing Mannan, and Pu Xiaoyun
A new method for measuring the refractive index of micro-quantity liquid based on imaging principle of a coaxial spherical surface optical system is introduced. LED (λ=580 nm，FWHM: 32 nm) is used as light source and CCD camera as the equipment of receiving image. The required sample is less than 0.002 mL. The liquid toA new method for measuring the refractive index of micro-quantity liquid based on imaging principle of a coaxial spherical surface optical system is introduced. LED (λ=580 nm，FWHM: 32 nm) is used as light source and CCD camera as the equipment of receiving image. The required sample is less than 0.002 mL. The liquid to be measured is closed in a glass capillary, so that is benefited to measure the poisonous, volatile and absorptive liquid samples. Four liquid mediums, water, ethanol, ethylene glycol and glycerin have been measured, and the precision of obtained refractive index is 0.0001, 0.0002, 0.0003 and 0.0003, respectively. Based on an analysis on the sensitivity of refractive index and the depth of field of the measurement system, the ways to improve the measurement precision are proposed..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2468 (2009)
Lasers and Laser Optics
Stable Second Harmonic Generation 461 nm Blue Radiation by PPKTP Crystal
Zhao Yang, Li Ye, Peng Yu, Cao Jianping, Fang Zhanjun, and Zang Erjun
The experiment presents an external ring cavity for frequency doubling, which is used to generate 461 nm blue radiation, with PPKTP as a laser frequency doubling crystal. By the incorporate ring cavity and the locking circuit system, the output power of 461 nm reaches the maximum. More than 208 mW of the second harmoniThe experiment presents an external ring cavity for frequency doubling, which is used to generate 461 nm blue radiation, with PPKTP as a laser frequency doubling crystal. By the incorporate ring cavity and the locking circuit system, the output power of 461 nm reaches the maximum. More than 208 mW of the second harmonic generation is gotten from 350 mW IR input power in the experiment. The coupling conversion efficiency is 73.3%. By analyzing and amending the loss error the reflectivity of coupling mirror is optimized. The effect of two different reflectivity coupling mirrors, PPKTP crystal’s linear absorption effect and thermal lens effect are discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 29, Issue 9, 23 (2009)
Characteristics of Fiber Loop Applied to Phase Locking Array of Fiber Lasers
Lei Bing, Feng Ying, Wei Li’an, and Liu Zejin
The characteristics of fiber loop have important effect on the performance of the phase locking array of fiber lasers based on a common fiber loop. The configuration, properties of the array and the functions of the loop are introduced. The theoretical model of the loop is established, and its power transmission and reThe characteristics of fiber loop have important effect on the performance of the phase locking array of fiber lasers based on a common fiber loop. The configuration, properties of the array and the functions of the loop are introduced. The theoretical model of the loop is established, and its power transmission and resonance properties are analyzed by the intensity and amplitude addition methods respectively. It is proved that they are consistent when the line-width of input light-wave is considered. The research results indicate that increasing the fiber coupler's coupling ratio can increase the coupling strength among component lasers of the phase locking array, and the output power and combining efficiency will not decrease obviously if the loop's loss is low. The filtering effect of fiber loop is observed in experiment, and the output power decreases slightly and regularly with the increase of coupling ratio, which is consistent with the conclusions obtained from theoretical analysis..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2479 (2009)
Investigation of Four-Arm Cavity for Generating Single Longitudinal Mode Operation of TEA CO2Laser
Qu Yanchen, Jiao Chenghong, Zhao Weijiang, Wang Yuanhu, Liang Zhiqiang, Ren Deming, and Hu Xiaoyong
A new method for generating single longitudinal mode operation of TEA CO2 laser-using four arm cavity to select single longitudinal mode is proposed. The new cavity’s reflectivity character has been theoretically studied, and its mode selectivity is predicted. In experiment, single longitudinal mode TEA CO2 laser pulseA new method for generating single longitudinal mode operation of TEA CO2 laser-using four arm cavity to select single longitudinal mode is proposed. The new cavity’s reflectivity character has been theoretically studied, and its mode selectivity is predicted. In experiment, single longitudinal mode TEA CO2 laser pulses are readily achieved using this method, with laser pulse energy up to 225mJ and single longitudinal mode repetition more than 90%..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2486 (2009)
A Novel Resonator with the Functions of Thermal Induced Depolarization Compensation and Self-Selecting Mode
Zhu Guangzhi, Zhu Xiao, Zhu Changhong, and Qi Lijun
A novel resonator for compensating thermal induced birefringence and self-selecting mode is designed. Based on the depolarization characteristics analysis of Nd:YAG rod, the properties of compensating depolarization loss and self-selecting mode, and the stability of resonator are discussed. The technology uses a feedbaA novel resonator for compensating thermal induced birefringence and self-selecting mode is designed. Based on the depolarization characteristics analysis of Nd:YAG rod, the properties of compensating depolarization loss and self-selecting mode, and the stability of resonator are discussed. The technology uses a feedback mirror to compensate depolarization, which makes the resonator contain three sub-resonators with different abilities of mode selection. The resonator is applied to a diode-pumped Nd:YAG laser operating at acoustic optical (AO)-Q switch for acquiring high quality beam..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2491 (2009)
Light Scattering Characteristics of Laser Colloid
Li Mi, and Xu Zheng
A kind of colloid mixed with Nd2O3nano-particles is introduced. The light scattering characteristics and the extinction coefficient are analyzed and simulated. When the Nd atom concentration is 1.386×10-20 cm-3, the radius of Nd2O3 nano-particles is about 5 nm and the relative refractive index is less than 1.25, tA kind of colloid mixed with Nd2O3nano-particles is introduced. The light scattering characteristics and the extinction coefficient are analyzed and simulated. When the Nd atom concentration is 1.386×10-20 cm-3, the radius of Nd2O3 nano-particles is about 5 nm and the relative refractive index is less than 1.25, the results show that the scattering loss of the laser colloid at 1064 nm wavelength is less than 0.002 cm-1. Therefore, the laser colloid with Nd2O3 nano-particles may be is a kind of excellent laser medium..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2499 (2009)
Coherent Beam Combination Based on Active Phase Controlling at the High-Power Output Port
Zhou Pu, Ma Yanxing, Wang Xiaolin, Ma Haotong, Xu Xiaojun, and Liu Zejin
Two W-level fiber laser beams have been coherently combined by active phase controlling at the high-power output port employing the piezoelectric ceramic transducer phase modulator. The visibility of the long-exposure far-field intensity pattern is 98% and the peak intensity is increased by a factor of 1.87 when the syTwo W-level fiber laser beams have been coherently combined by active phase controlling at the high-power output port employing the piezoelectric ceramic transducer phase modulator. The visibility of the long-exposure far-field intensity pattern is 98% and the peak intensity is increased by a factor of 1.87 when the system is in close-loop..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2503 (2009)
Machine Vision
Application of Laws′ Masks to Stereo Matching
Ge Liang, Zhu Qingsheng, and Fu Sisi
Stereo matching is always the crucial problem of the computer vision. The less-textured area stereo matching problem can be solved by region-based stereo matching algorithm, in which the key steps are dividing and matching of less-textured area. According to the characters of less-textured area, a novel approach is proStereo matching is always the crucial problem of the computer vision. The less-textured area stereo matching problem can be solved by region-based stereo matching algorithm, in which the key steps are dividing and matching of less-textured area. According to the characters of less-textured area, a novel approach is provided for less-textured area dividing. It describes the texture with Laws′ masks and gets the less-textured area by histogram-based segmentation. It can get the best result for various scene images by comparing various combinations of Laws′ masks. Experimental results on the international standard image data show that our algorithm has better recognition rate of less-textured area and better robustness of choosing the dividing threshold than the previous method which describes the texture with gray level co-occurrence matrix and gets the less-textured area by region growing-based segmentation. This new algorithm is helpful to increase the accuracy and usability of region-based stereo matching algorithm..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2506 (2009)
A Computational Model of Visual Attention Based on Visual Entropy
Dou Yan, Kong Lingfu, and Wang Liufeng
A computational model of visual attention is proposed to simulate biologic visual information processing based on visual entropy. It is achieved by using low-level features of images and considering the human eye on the subjective measure of image information in visual entropy. First image is divided into 4×4 blocA computational model of visual attention is proposed to simulate biologic visual information processing based on visual entropy. It is achieved by using low-level features of images and considering the human eye on the subjective measure of image information in visual entropy. First image is divided into 4×4 block images, images are calculated for each block of the mean, variance, range and rate of change in brightness. A center-surround operator is used to produce the conspicuous map of the images and incorporate them into a saliency map. Calculating each of the conspicuous regional’s visual entropy and regarding the most salient region as the focus of attention, the inhibition of return mechanism is used to transfer the visual focus to simulate the whole process of visual attention. The experimental results show that the model corresponds with the procedure of visual attention. Besides, it has low complexity and high utility value..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2511 (2009)
Optical Design and Fabrication
Research on Law of Luminance in Light Guide Plate with Fused Micro-Prisms on Bottom Surface
Chen Xiangxian, Xu Ping, Huang Jiefeng, Zhang Xulin, Wang Bing, and Li Beibei
Based on an integrated light guide plate (LGP) with fused micro-prisms replacing the common plane reflective film and the dot structures in the existing backlight system (BLS), the expressions of the bottom angles of the prisms and the direction of the emitting luminance are derived by using the geometric optics equatiBased on an integrated light guide plate (LGP) with fused micro-prisms replacing the common plane reflective film and the dot structures in the existing backlight system (BLS), the expressions of the bottom angles of the prisms and the direction of the emitting luminance are derived by using the geometric optics equations. The LGP with micro-prisms is modeled in Light Tools software. The relation between the bottom angles and the direction of peak emitting luminance is established. Simulation results are consistent with the analytical ones. Based on the analytical derivation and simulation, an integrated LGP is designed with the micro-prisms close angle of 86° and the far angle of 37°. The luminance of the integrated LGP meets the demand of the existing 3M BLS..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2516 (2009)
Design of Extreme Ultraviolet Lithographic Objectives
Yang Xiong, and Xing Tingwen
Using radiation with a wavelength of 14 nm, Extreme ultraviolet lithography (EUVL) can reach a high resolution and remain relative large depth of focus, and it is a promising future-generation lithographic technique for manufacturing VLSI. EUVL operates in step-and-scan mode, and utilize all-reflective unobstructed redUsing radiation with a wavelength of 14 nm, Extreme ultraviolet lithography (EUVL) can reach a high resolution and remain relative large depth of focus, and it is a promising future-generation lithographic technique for manufacturing VLSI. EUVL operates in step-and-scan mode, and utilize all-reflective unobstructed reduction ring-field projection system. The starting configurations designing of unobstructed projection system is a nontrivial and important issue. A paraxial search method is introduced, which imposes constraints, such as rigorous telecentricity on the image side, quasi-telecentricity on the object, fixed magnification, Petzval condition and conjugated object-image. Curvatures of first mirror and last mirror, object distance and image distance are all solved consequently. And curvature of a reflecting surface coinciding with stop surface is solved. Paraxial search program is developed and some starting configurations are found. Two objectives are designed by optimizing two starting configurations. One is composed of four mirrors with the NA of 0.1, image field of 26 mm×1 mm, distortion of 10 nm, and the resolution better than 6000 cycle/mm. The other objective is composed of six mirrors with the NA of 0.25, image field of 26 mm×1 mm, distortion of 3 nm, and the resolution better than 18000 cycle/mm..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2520 (2009)
Optimal Design of Superfocusing Lens Configuration Based on Surface Plasmon Polariton Coupling Plate
Zhang Zhiyou, Du Jinglei, Li Min, and Niu Xiaoyun
A superfocusing system is presented based on the theory of silver superlens and multi-phase binary optical elements. We get a single focal light spot with diameter of 0.36 λ and focal depth reached over 10 λ which calculated by finite-difference time-domain method (FDTD) and scalar diffraction theory. This feature makeA superfocusing system is presented based on the theory of silver superlens and multi-phase binary optical elements. We get a single focal light spot with diameter of 0.36 λ and focal depth reached over 10 λ which calculated by finite-difference time-domain method (FDTD) and scalar diffraction theory. This feature makes it a promising to replace the probe of NSOM and to realize the super-resolution imaging and lithography and other applications..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2524 (2009)
Optical Devices
Characterization on Linearity and Conversion Efficiency of All-Optical Sampling Based on Semiconductor Optical Amplifiers
Zhang Shangjian, Liu Yong, Zhang Qianshu, Li Heping, and Liu Yongzhi
The all-optical sampling based on the nonlinear polarization rotation in semiconductor optical amplifiers has the advantages of high-speed operation and small pump power, and it shows a possible solution for high-speed all-optical analog-to-digital (A/D) conversion. A novel method to characterize the linearity and effiThe all-optical sampling based on the nonlinear polarization rotation in semiconductor optical amplifiers has the advantages of high-speed operation and small pump power, and it shows a possible solution for high-speed all-optical analog-to-digital (A/D) conversion. A novel method to characterize the linearity and efficiency of the all-optical sampling is proposed. The all-optical sampling transfer curve is fitted by a polynomial function, and the sampling system is described by the polynomial function. The efficiency and the harmonic distortion of the sampling process can be analytically expressed by the polynomial coefficients after substitution and expansion of the cosine function. It is not necessary to execute a complicated Fourier transform, and the results from our method are agreeable with those obtained by the Fourier analysis method. This method is simple but accurate and is useful for the full characterization on the linearity and efficiency of all-optical sampling based on semiconductor optical amplifier and can be extended to the nonlinear distortion of the analogue signal modulation..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2529 (2009)
All-Optical SOA-Based Microwave Filter with Passband and Stopband Interchanged
Xu Enming, Zhang Xinliang, Zhou Lina, Zhang Yu, and Huang Dexiu
In order to satisfy the applications requirement in fiber-radio links and phased array antennas,a novel microwave photonic filter with passband and stopband interchanged is proposed and demonstrated. The filter is based on a recirculating delay line loop with a semiconductor optical amplifier (SOA) followed by a tunablIn order to satisfy the applications requirement in fiber-radio links and phased array antennas,a novel microwave photonic filter with passband and stopband interchanged is proposed and demonstrated. The filter is based on a recirculating delay line loop with a semiconductor optical amplifier (SOA) followed by a tunable narrowband optical filter. The negative tap is generated by using the wavelength conversion employing the cross-gain modulation of the amplified spontaneous emission spectrum of the SOA. When the central wavelength of the optical filter is aligned with the laser wavelength, a microwave bandpass filter is obtained. On the other hand, when the optical filter detunes from the laser wavelength a little, a narrow notch filter with flat passband is realized. The structure can be operated as a high Q or notch filter with flat passband by tuning the central wavelength of the optical filter..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2534 (2009)
Optimization and Simulation of an Electro-Optic Polymer Microring Resonator Switch Array
Yan Xin, Ma Chunsheng, Chen Hongqi, Zheng Chuantao, Wang Xianyin, and Zhang Daming
In terms of the coupled-mode theory, microring resonance theory and electro-optic modulation theory, a structural model is proposed for designing an electro-optic polymer microring resonator switch array. This device consists of N－1 microrings and N parallel channels. By applying operation voltages in different mannersIn terms of the coupled-mode theory, microring resonance theory and electro-optic modulation theory, a structural model is proposed for designing an electro-optic polymer microring resonator switch array. This device consists of N－1 microrings and N parallel channels. By applying operation voltages in different manners on the microrings, the switching functions can be realized in the N channels. Taking 7 microrings and 8 channels as an example, the optimization and simulation are performed under the resonant wavelength of 1550 nm. The results are as follows: the core size of the microring is 1.7 μm×1.7 μm, the buffer layer thickness between the core and the electrode is 2.5 μm, the electrode thickness is 0.2 μm, the microring radius is 13.76 μm, the coupling gap between the micoring and the channel is 0.14 μm, the 3 dB bandwidth of the output spectrum is about 0.05 nm, the switching voltage is about 8.1 V, the insertion loss is about 0.23~4.6 dB, and the crosstalk is less than -20 dB..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2540 (2009)
OPTOELECTRONICS
Study on Energy Distribution at Electrode of Electrical Discharge Machining Based on Photon Emission
Qiu Mingbo, Huang Yinhui, Liu Zhidong, Tian Zongjun, and Wang Wei
In order to study the mechanism of electrical discharge machining(EDM), the energy distribution of cathode and anode was calculated based on photon emission. The matter waves of positive ion and electron were firstly obtained and knowledge was got that the positive ion mainly moved in vibration and produced photon emisIn order to study the mechanism of electrical discharge machining(EDM), the energy distribution of cathode and anode was calculated based on photon emission. The matter waves of positive ion and electron were firstly obtained and knowledge was got that the positive ion mainly moved in vibration and produced photon emission in discharge channel, and that the electron mainly moved in diffraction and produced photon emission at anode. The photon emission was assumed equal probability, and several equations had been attained about heat density, heat and average heat density, and a newly explanation was submitted that large polar action expressed when using small duration charge, and small polar action expressed when using large duration charge. At last, the affection of this mechanism was applied to micro EDM, finish machining and rough machining, showed that small duration charge matched with normal polarity (work piece to positive electrode) and compacting discharge channel which could guarantee the precision, and that large duration charge matched with reversed polarity (work piece to negative electrode) and no need to compact discharge channel which could guarantee machining efficiency and surface quality..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2546 (2009)
Physical Optics
Propagation Properties of Oblique and Off-Axial Gaussian Beams Passing Through Cat-Eye Optical Lens
Zhao Yanzhong, Sun Huayan, Song Fenghua, and Dai Dede
The propagation equations for oblique and off-axial Gaussian beams passing through cat-eye optical lens are deduced by using the theory of matrix optics and expanding the aperture function into a finite sum of complex Gaussian functions. By numerical computation, the laws governing the variation of the intensity distriThe propagation equations for oblique and off-axial Gaussian beams passing through cat-eye optical lens are deduced by using the theory of matrix optics and expanding the aperture function into a finite sum of complex Gaussian functions. By numerical computation, the laws governing the variation of the intensity distribution of the cat-eye reflected light with the obliquity factor and the off-axis magnitude are given. The result shows that the intensity distribution of the cat-eye reflected light under oblique condition has asymmetric aberrance, and the distribution rules at small and large different obliquity factors differ greatly. Furthermore, the feasibility of cat-eye effect reflected light used in the active laser detection system is determined by the obliquity factor and the off-axis magnitude..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2552 (2009)
The Beam Propagation and Transformation in Axicon-Lens System
Wu Fengtie, Lu Wenhe, and Ma Baotian
A complete picture of the evolution of a plane wave passing through axicon-lens system was theoretical analyzed, numerical simulated and experimental demonstrated. A non-diffracting beam was obtained as plane wave passing axicon. A bottle beam can be generated if a focal lens kept within the maximum non-diffracting disA complete picture of the evolution of a plane wave passing through axicon-lens system was theoretical analyzed, numerical simulated and experimental demonstrated. A non-diffracting beam was obtained as plane wave passing axicon. A bottle beam can be generated if a focal lens kept within the maximum non-diffracting distance, and the size of the bottle beam easy adjusted by changing the focal length of the lens. As the beam further propagation, self-reconstruction of the Bessel beam generated. The divergence of the self-reconstruction beam causes the beam intensity decreasing and the bright spot size increasing as the beam propagating. A second focal lens was introduced to rectify the divergence of the self-reconstruction beam. The intensity profiles of the beam cross-section were captured using the optical system of the microscope and CCD camera. The theoretical analysis and numerical simulation were confirmed by the experimental results..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2557 (2009)
Inverse Problem of Frequency Tripling of Pulses Stacking Laser
Zeng Shuguang, and Zhang Bin
A method for solving the inverse problem of frequency tripling, i.e., how to calculate the shape of the fundamental field (1ω), and how to obtain the required 1ω pulse by pulses stacking method for a given shape of the third-harmonic field (3ω), was proposed. Based on some numerical techniques such as split-step FourieA method for solving the inverse problem of frequency tripling, i.e., how to calculate the shape of the fundamental field (1ω), and how to obtain the required 1ω pulse by pulses stacking method for a given shape of the third-harmonic field (3ω), was proposed. Based on some numerical techniques such as split-step Fourier transform and fourth-order Runge-Kutta, the quantitative relation between the input 1ω intensity and the output 3ω intensity was obtained by curve fitting method.Taking the shaping pulse with a certain shape as the required output 3ω pulse, the corresponding shape of the 1ω pulse can be determined by the inverse calculation. Furthermore, the parameters of the pulse stacker, such as attenuation and time delay, etc, were worked out. Consequently, the temporal pulse shaping for 1ω pulse can been realized, leading to the realization of the required output 3 pulse.The results indicate that the inverse problem can be solved quickly and precisely with the method proposed in this paper, and this method is useful for pulse shaping of frequency tripling..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2561 (2009)
Quantum Optics
Experimental Investigation of Electromagnetically-Induced-Transparency-Like Effect in Optical Coupled-Resonator
Gao Feng, Ye Chenguang, Wang Pengjun, and Zhang Jing
An optical coupled-resonator may simulate the phenomenon of electromagnetically induced transparency (EIT) in atomic vapors. We utilize the separated optical cavity mirrors to set up the coupled-resonator, which is easy to adjust the parameters of optical coupled-resonator. The reflection spectra of the coupled-resonatAn optical coupled-resonator may simulate the phenomenon of electromagnetically induced transparency (EIT) in atomic vapors. We utilize the separated optical cavity mirrors to set up the coupled-resonator, which is easy to adjust the parameters of optical coupled-resonator. The reflection spectra of the coupled-resonator with the middle cavity mirror of different transmittance are measured. The EIT-like effect is observed in the optical coupled-resonator due to the classical destructive interference. This system can be used to study the slow and fast light experiments due to its simplicity and flexibility..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2565 (2009)
The Entanglement of Two Atoms in a Coherent Field of Time-Varying Frequenry
Cai Xunming, and Fan Menghui
The entanglement of two two-level atoms in a coherent field of time-varying frequency have been investigated. The properties of the entanglement of two atoms for two typical——the frequency of field varying with time in the forms of sine function and rectangular pulses——have been considered. The numerical calculation shThe entanglement of two two-level atoms in a coherent field of time-varying frequency have been investigated. The properties of the entanglement of two atoms for two typical——the frequency of field varying with time in the forms of sine function and rectangular pulses——have been considered. The numerical calculation show: for the frequency changing with time in sinusoidal form, the frequency and the mean photon number of field affect the entanglement of two atoms and in the condition of a small number of photons, small-amplitude fast oscillations occur during half period. For the frequency changing with time in rectangular form, The sudden jumping of the field with rectangular pulsed frequency-modulation can change the coherence of the two atoms, and induce the new entanglement phenomenon of the two atoms. The entanglement of two atoms is small-amplitude fast oscillations during the pulse. The changes of optical field frequency can change the coherence of atoms, and then change entanglement between atoms. The paper prove to be constructive in entanglement preparation and control in quantum information technique..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2570 (2009)
Remote Sensing and Sensors
Selecting Per-Pixel Endmembers Set Based on Bayesian Inference
Li Xi, Guan Zequn, Qin Kun, Zhang Li, and Cao Lingling
A Bayesian inference model was developed to select per-pixel endmembers set. Considering the uncertainty of endmembers’ spectra, based on Bayesian inference and linear spectral mixture model, the posterior probability of per-pixel endmembers set was obtained. Using the prior knowledge of endmembers’ coexistence, combinA Bayesian inference model was developed to select per-pixel endmembers set. Considering the uncertainty of endmembers’ spectra, based on Bayesian inference and linear spectral mixture model, the posterior probability of per-pixel endmembers set was obtained. Using the prior knowledge of endmembers’ coexistence, combined with the normal distribution function of endmembers’ spectra, the optimal endmembers set was selected based on maximal liklihood. The experiment on an ETM+ image including 147431 pixel showed that, compared with the MRES and PG algorithms provided by IDRISI, the Bayesian approach reduced 70% redundant endmembers, and the unmixing error induced by inaccurate endmembers was reduced to 28%. The result showed that, considering the uncertainty of endmemebers′ spectra and the coexistence of endmembers, Bayesian inference can increase the accuracy rate of endmembers′ selection, so the unmixing accuracy was improved significantly..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2577 (2009)
Study on Airborne Scanning Ladar
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The compact 3-D imaging ladar system was established, which uses high PRF laser pulses and a C30659-1060-R8B avalanche photo-diode (APD) detectors with independent digital time-of-flight counting circuits. The scanner uses galvanometer-oscillating mirror. Range resolution is 35 cm and scanner angle is 0~±25°.The compact 3-D imaging ladar system was established, which uses high PRF laser pulses and a C30659-1060-R8B avalanche photo-diode (APD) detectors with independent digital time-of-flight counting circuits. The scanner uses galvanometer-oscillating mirror. Range resolution is 35 cm and scanner angle is 0~±25°. Scan frequency is: 20 Hz for±25°,50 Hz for±10°. With appropriate optics, the digital time value represents a 3-D spatial image frame of the scene. Successive image frames illuminated with the multi-kilohertz pulse repetition-rate laser are accumulated into range histograms to provide 3-D volume and intensity information..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2584 (2009)
Ultrariolet Ozone Vertical Profile Probe for FY-3A Meteorological Satellite
Wang Shurong, Li Futian, Song Kefei, Wang Lipeng, Wang Longqi, Lin Guanyu, Huang Yu, Huang Fuxiang, and Wang Weihe
Ultraviolet ozone vertical profile probe for FY-3A meteorologic satellite was developed and launched successfully in May 2008. It is a compact, high-precision, ultraviolet-vacuum ultraviolet spctroradiometer used to measure atmospheric solar backscattering spectral radiance and solar spectral irradiance. The solar specUltraviolet ozone vertical profile probe for FY-3A meteorologic satellite was developed and launched successfully in May 2008. It is a compact, high-precision, ultraviolet-vacuum ultraviolet spctroradiometer used to measure atmospheric solar backscattering spectral radiance and solar spectral irradiance. The solar spectral irradiance at altitude 830 km in 160~400 nm and the backscatterion solar spectral radiance in the ultraviolet ozone absorption band at 12 wavelengths from 250 nm to 340 nm are obtained. Test results on orbit show that all the function is carried out successfully and the performance is stable..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2590 (2009)
Spectroscopy
Experimental Investigation on Time and Spatial Evolution of Emission Spectra of Al Atom in Laser-Induced Plasmas
Cong Ran, Zhang Baohua, Fan Jianmei, Zheng Xianfeng, Liu Wenqing, Zheng Rong′er, and Cui Zhifeng
The time and spatial-resolved emission spectrum in laser-induced Al plasma was measured for the 390.068,394.4,396.152 and 466.3056 nm spectral lines. The electron density of the plasmas was calculated from the measured spectral line intensity and Stark broadening of emission spectral lines respectively. The time and spThe time and spatial-resolved emission spectrum in laser-induced Al plasma was measured for the 390.068,394.4,396.152 and 466.3056 nm spectral lines. The electron density of the plasmas was calculated from the measured spectral line intensity and Stark broadening of emission spectral lines respectively. The time and spatial evolution property of the electron density was discussed according to the experimental results. It is shown that the plasma electron density varies from 0.02×1017 to 1.4×1017 cm-3 when the time delay is in the range from 100 to 1500 ns. It is also concluded that the plasma electron density varies from 0.28×1017 to 0.95×1017 cm-3 along the direction on the laser beam when the distance of the measured zone from the target surface is in the range from 0 to 1.8 mm. The distribution of the plasma electron density along the direction of the laser beam has well symmetry..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2594 (2009)
Research on the Adjustable Balance Probe for Laser Polarization Spectroscopy
Wu Jizhou, Han Qiang, Ma Jie, Zhao Yanting, Xiao Liantuan, and Jia Suotang
Polarization spectroscopy is of high sensitivity and resolution. A method based on the adjustable balance probe polarization spectroscopy is proposed, the change of the spectroscopy shapes in different polarization planes is investigated, and the retroflexion of the lineshapes with the rotation of the polarization platPolarization spectroscopy is of high sensitivity and resolution. A method based on the adjustable balance probe polarization spectroscopy is proposed, the change of the spectroscopy shapes in different polarization planes is investigated, and the retroflexion of the lineshapes with the rotation of the polarization plate is observed. The retroflexion of the lineshapes is illustrated by combining the polarization theory and the balance probe theory, which is in good accordance with the experiment. The relationship between the peak-to-peak value of the dispersion-like spectroscopy and the power of pump beam is also demonstrated, and it is found that the saturation of spectroscopy amplitude appears when the power ratio of pump beam to probe beam is about 100, which provides a theoretical reference on choosing parameters in the laser frequency stabilization by using polarization spectroscopy..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2601 (2009)
Nonlinear Correlation Coefficient Based Kernel Method for Hyperspectral Data Classification
Zhang Miao, Shen Yi, and Wang Qiang
Under the framework of support vector machines using one against one strategy, a novel kernel method based on nonlinear correlation coefficient is proposed to raise the classification accuracy under the most conditions of no ground truth reference map. This method takes into account the non-uniform information distribuUnder the framework of support vector machines using one against one strategy, a novel kernel method based on nonlinear correlation coefficient is proposed to raise the classification accuracy under the most conditions of no ground truth reference map. This method takes into account the non-uniform information distribution of remote sensing hyperspectral data, and assigns nonlinear correlation coefficients as weights for the corresponding bands to make the band with greater correlation information play a more important role during the process of classification. Meanwhile a new estimated reference map based on nonlinear correlation coefficient is proposed to solve the realistic problem that the real one is usually unavailable. The experimental results show that for the support vector machines based on radial basis function, after adopting the proposed kernels, the average accuracy and the overall accuracy in multi-classification are increased by 2.90% and 3.11% with typical parameter configuration and no ground truth reference map, besides the computational time increment is unobvious..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2607 (2009)
Thin Films
Multilayer Film Reflective Mirror at 30.4 nm
Bai Liang, Zhu Jingtao, Xu Jing, Huang Qiushi, Wu Wenjuan, Wang Xiaoqiang, Wang Zhanshan, and Chen Lingyan
Observation of the He-II spectrum at the wavelength of 30.4 nm, a key spectrum in solar spectrum, is of great significance in investigating solar activity and space environment. Multilayer film reflective mirrors are usually adapted in solar observation at extreme ultraviolet (EUV) wave range. Reflection at the wavelenObservation of the He-II spectrum at the wavelength of 30.4 nm, a key spectrum in solar spectrum, is of great significance in investigating solar activity and space environment. Multilayer film reflective mirrors are usually adapted in solar observation at extreme ultraviolet (EUV) wave range. Reflection at the wavelength of 30.4 nm of the multilayer films composed of Mg is studied. The multilayer film is designed using evaluation function expressing as highest reflectivity. SiC/Mg, B4C/Mg, C/Mg multilayer films are fabricated by using direct current (DC) magnetron sputtering, and the multilayer structures are measured using X-ray diffractometer. The multilayer mirror of B4C/Mg has highest reflectivity in theory but SiC/Mg multilayer film has the best quality and the highest reflectivity in practice. The reflectivity of SiC/Mg multilayer mirror was measured by the reflectometer in synchrotron radiation laboratory. At incidence angle of 10°, the reflectivity is 44.6%..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2615 (2009)
Novel Design Method for Initial Structure of Dispersion Compensation Filters
Luo Zhenyue, Liu Xu, Shen Weidong, Xue Hui, Gu Peifu, and Zhang Yueguang
Chirped pulse oscillation (CPO) and femtosecond laser microscopy both require large dispersion compensation amount within a certain bandwidth. This required compensation amount is too large to achieve for those dispersion compensation filters that has already used in femtosecond laser system. A novel design method was Chirped pulse oscillation (CPO) and femtosecond laser microscopy both require large dispersion compensation amount within a certain bandwidth. This required compensation amount is too large to achieve for those dispersion compensation filters that has already used in femtosecond laser system. A novel design method was introduced based on a conjugate cavity and Gires-Tournois cavity hybrid initial structure, dispersion compensation requirement of the system can be fulfilled by subsequent computer optimization. To prove the validity of this method, we apply two design examples were provided which meet the practical requirement of CPO and femtosecond laser microscopy. Compared with those designs by singly computer optimization, this design is much more simpler and in order, so it is easier for preparation..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2619 (2009)
Research on Surface Modification of Space Used SiC Mirror
Gao Jinsong, Shen Zhenfeng, Wang Xiaoyi, Wang Tongtong, Chen Hong, and Zheng Xuanming
The SiC material can't meet the application requirement of high quality space-used optical system because the considerable surface scattering on the SiC mirror after polish. So the surface modification must be taken on in order to obtain high quality optical surface on the SiC mirror before use. The two prevailing The SiC material can't meet the application requirement of high quality space-used optical system because the considerable surface scattering on the SiC mirror after polish. So the surface modification must be taken on in order to obtain high quality optical surface on the SiC mirror before use. The two prevailing international methods for surface modification are to use of Si coating and SiC coating. Surface modifications are made by the two means using e-beam evaporation with ion assisted. Test results show that the Si coating is cubic phase. Surface roughness(rms) of the SiC substrate is reduced to 0.620 nm and scattering coefficient is reduced to 1.52% after Si coating modification. The SiC coating is amorphous. Surface roughness(rms) of the SiC substrate is reduced to 0.743 nm and scattering coefficient is reduced to 2.79% after SiC coating modification. The modification coatings both have a good temperature stability and a high adhesion to the SiC substrate. Evaluated by the reliability the method of using Si coating is much more compatible for the engineering application interiorly. After the surface modification by means of using Si coating, the wastage of surface scattering is reduced greatly and the quality of optical surface is improved obviously. The surface reflectance with Ag coating is obviously enhanced to that of fine polished zerodur glass, thus it can meet the application requirement of high quality space-used optical system..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2624 (2009)
Ultrafast Optics
High Efficiency Frequency-Doubling of Femtosecond Laser Pulses with Simultaneously Spatial Walk-Off and Phase Velocity Compensation
Zhou Xugui, Wang Yanling, Wu Hong, and Ding Liang′en
Frequency-doubling is investigated using two BBO crystals with 70-fs, 800-nm laser pulses at the repetition of 10 Hz . The size of crystals are both 10 mm×10 mm×0.2 mm . Focused on spatial walk-off and phase velocity mismatching, the angle between the axes of the two crystals and the phase velocity mismatchinFrequency-doubling is investigated using two BBO crystals with 70-fs, 800-nm laser pulses at the repetition of 10 Hz . The size of crystals are both 10 mm×10 mm×0.2 mm . Focused on spatial walk-off and phase velocity mismatching, the angle between the axes of the two crystals and the phase velocity mismatching of the fundamental pulse are adjusted respectively. It is experimentally demonstrated that the spatial walk-off could be compensated by use of two crystals placed anti-parallel, and angle mismatching with some degree may compensate phase velocity mismatching of the frequency-doubled pulse. The frequency-doubled pulse with bandwidth of 6.7 nm and energy of more than 2.8 mJ is achieved. The frequency-doubling conversion efficiency reaches 35.7%, which is improved by a factor of 1.7 related to a single crystal in the same condition..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2630 (2009)
Experimental Research of Ultraviolet Filamentation of Intense Femtosecond Laser in Ar Gas
Wang Yanling, Zhou Xugui, Wu Hong, Dai Xiaomin, and Ding Liang′en
The ultrafast ultraviolet(UV) laser source with central wavelength of 268 nm, spectrum width of 1.5 nm and single pulse energy of 0.58 mJ which is obtained by third harmonic generation of Ti:sapphire laser system with pulse duration of 70 fs and central wavelength of 808 nm can generate a plasma channel due to the nonlThe ultrafast ultraviolet(UV) laser source with central wavelength of 268 nm, spectrum width of 1.5 nm and single pulse energy of 0.58 mJ which is obtained by third harmonic generation of Ti:sapphire laser system with pulse duration of 70 fs and central wavelength of 808 nm can generate a plasma channel due to the nonlinear effect when it is injected into Ar gas cell after focusing. We studied the filament feature of UV laser at 268 nm and the modulation of spectrum by UV filament under the condition of different gas pressure, focal length and gas category. The spectrum width of 3.3 nm can be obtained with 2.2 atm Ar pressure and 1000 mm focal length which is a factor-of-2.2 improvement compared with input spectrum. We observed that both the increase of gas pressure and focal length are beneficial to the increase of plasma channel length and spectrum broadening. The plasma channel induced by UV pulses could provide a valid approach for attaining extremely ultrafast pulses in the UV range..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2635 (2009)
X-Ray Optics
Obtaining High-Power-Density Soft X-ray Source by Using Lens
Chen Dingyang, Xu Zeping, Qin Yi, and Ning Jiamin
We made soft X-ray lens and combined it with high-temperature plasma radiation which was produced on Qiang-Guang Ⅰ facility. The transmission characters of lens were measured. It is shown that, for the lens manufactured of 2401 X-ray capillaries, when the power density of the incident soft X-ray is 1.0×108 W/cm2, We made soft X-ray lens and combined it with high-temperature plasma radiation which was produced on Qiang-Guang Ⅰ facility. The transmission characters of lens were measured. It is shown that, for the lens manufactured of 2401 X-ray capillaries, when the power density of the incident soft X-ray is 1.0×108 W/cm2, the average transmission efficiency of lens is 9.6%, and the power density 1.15×109 W/cm2 of soft X-ray source without plasma fragment can be obtained at focal point..
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 9, 2640 (2009)
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