Journals >Acta Photonica Sinica
Contents
2011
Volume: 40 Issue 8
31 Article(s)
Export citation format
Research Article
Effects of Integrating Sphere Non-neutrality on Output Spectrum
LU Li-gen, ZHANG Bao-zhou, and ZHANG Jun-yuan
Changes in spectral properties of output light are analyzed from the angle of integrating sphere non-neutrality.Based on integrating-sphere theory,the relationship between non-neutrality of integrating-sphere spectral transmittance and that of spectral reflectance of inner coating is derived.It shows that non-neutralitChanges in spectral properties of output light are analyzed from the angle of integrating sphere non-neutrality.Based on integrating-sphere theory,the relationship between non-neutrality of integrating-sphere spectral transmittance and that of spectral reflectance of inner coating is derived.It shows that non-neutrality of integrating spheres is usually greater than that of inner coatings,and integrating sphere non-neutrality increases with the rise of coating reflectance when coating non-neutrality remains unchanged.Then spectral distribution,chromaticity coordinates and color temperature of output light are measured under illumination of light source A and a Xenon lamp respectively.The measurement results indicate that effects of non-neutrality of barium sulfate and polytetrafluoroethylene integrating spheres on output spectrum are both the increase of chromaticity coordinates and decrease of color temperature.For the polytetrafluoroethylene integrating sphere,color temperature of output spectrum is reduced for about 20 K and 70 K respectively when incident light source is light source A and a Xenon lamp.While for the barium sulfate integrating sphere,color temperature is reduced for about 300 K and 1 000 K respectively,which implies more remarkable influence on output spectrum..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1127 (2011)
UVE-LLE Classification of Apple Mealiness Based on Hyperspectral Scattering Image
WANG Bo-jin, HUANG Min, ZHU Qi-bing, and WANG Shuang
Hyperspectral scattering is a promising technique for noninvasive measurement of apple mealiness. An uninformative variable elimination (UVE) coupled with locally linear embedding (LLE) algorithm was proposed for assessing apple mealiness. After the algorithm, the number of effective wavelengths decreased to 23.5% of fHyperspectral scattering is a promising technique for noninvasive measurement of apple mealiness. An uninformative variable elimination (UVE) coupled with locally linear embedding (LLE) algorithm was proposed for assessing apple mealiness. After the algorithm, the number of effective wavelengths decreased to 23.5% of full wavelengths of hyperspectral scattering images. LLE was utilized to reduce the dimensionality of images composed of effective wavelengths. Partial least squares discriminant analysis was applied to develop classification model. Compared with mean reflectance (75.8%) and UVE coupled with mean reflectance algorithm (77.4%), LLE and UVE coupled with LLE model yielded better results (79.0%). UVE coupled with LLE model with the presevation of classification accuracy only used 23.5% wavelength of LLE model. Therefore, it provides a useful algorithm for online classification and data saving..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1132 (2011)
Novel Compact Low Refractive Index Contrast Silica-on-Silicon AWG
WANG Wen-min, LIU Wen, and MA Wei-dong
Arrayed waveguide grating (AWG)-type optical components are widely used in optical transmission system, and the low cost AWG chips are in more and more urgent need. Among all the methods for lowering the AWG cost, reducing the AWG chip size is one of the most effective methods. A novel compact AWG based on low refractiArrayed waveguide grating (AWG)-type optical components are widely used in optical transmission system, and the low cost AWG chips are in more and more urgent need. Among all the methods for lowering the AWG cost, reducing the AWG chip size is one of the most effective methods. A novel compact AWG based on low refractive index contrast silica-on-silicon (SoS) technology was proposed. In this AWG, only the segments connected with the slab waveguides in the input and output waveguides are air trench (AT) waveguides. By using these AT segments, the distance between the adjacent output waveguides connected with the output slab was decreaced greatly, so the focuses of slab waveguides, and the number of arrayed waveguides were decreaced greatly. Thus, the size of AWG chip was decreased dramatically. The arrayed waveguides and the segments coupling to fibers in the input or output waveguides were all fabricated with low refractive index contrast waveguides, for the purpose to obtain low coupling losses with fibers and good performances as traditional SoS AWGs. The size of an AWG designed consisting 40 channels on 100 GHz ITU grid is only 23.88 mm×10.5 mm, which area is about 1/6 of a traditional AWG with the same function..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1137 (2011)
Tunable Filters Based on SOI Microring-resonator
LI Shuai, WU Yuan-da, YIN Xiao-jie, AN Jun-ming, LI Jian-guang, WANG Hong-jie, and HU Xiong-wei
Microring-resonator filters were fabricated based On Silicon on Insulator (SOI) nano-wire waveguide, adopting Electron-Beam photolithography (EBL) and Inductive-Coupled-Plasma (ICP) etching technology, etc. The cross-section size of the strip waveguides were (350～500 nm)×220 nm, respectively, and the bending radiuMicroring-resonator filters were fabricated based On Silicon on Insulator (SOI) nano-wire waveguide, adopting Electron-Beam photolithography (EBL) and Inductive-Coupled-Plasma (ICP) etching technology, etc. The cross-section size of the strip waveguides were (350～500 nm)×220 nm, respectively, and the bending radius of the microring was around 5 μm. The measured results show that performance of devices are much better with waveguide width 450 nm, the free spectral range (FSR) is 16.8 nm, and extinction ratio (ER) around the wavelength 1 550 nm is 22.1 dB. After thermally tuned, the tuning bandwidth reaches 4.8 nm, and the tuning efficient is 0.12 nm/℃. Meanwhile, multi-channel filters were fabricated and studied based on single-ring and double-ring. After experiments, some conclusions were drawn: crosstalk exists in the signal transmission in multi-channel filters, mainly among different transmission channels, and the crosstalk is fairly distinct when there are signals input to add ports..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1143 (2011)
Non-reciprocity of Collinear Acousto-optic Tunable Filter
HUO Lei, ZENG Xiao-dong, FENG Zhe-jun, CAO Chang-qing, and LI Bin
Dynamic formulas of acoustic frequency and diffraction efficiency are proposed. Distributions of diffraction efficiency of the acousto-optic cell at different driving frequencies are analyzed, and its approximate expression is also given. However, it is found that the non-reciprocal effect also appears at low frequencyDynamic formulas of acoustic frequency and diffraction efficiency are proposed. Distributions of diffraction efficiency of the acousto-optic cell at different driving frequencies are analyzed, and its approximate expression is also given. However, it is found that the non-reciprocal effect also appears at low frequency (e.g. 100 MHz), which usually occurs at above 1 GHz frequency. Through introducing scale factor δF/ΔF， the non-reciprocal effect experiment is carried out with the laser wavelengths of 532 nm and 632.8 nm in Tellurium dioxide crystals. The obtained results show that the total change in the diffraction bandwidth is 50% to 60%, which basically matches the calculated result. According to this result, the non-reciprocal effect can be applied in the development of directional couplers (optical router) and other optoelectronic devices..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1149 (2011)
Analysis of Pulse Trapping Characteristic in Highly Birefringent Photonic Crystal Fiber
ZHANG Xiao-juan, ZHAO Jian-lin, and FANG Liang
A theoretical investigation of the pulse trapping in a highly birefringent photonic crystal fiber was presented. The strict coupled nonlinear Schrdinger equations were numerically solved using a split-step Fourier algorithm. Different incidence conditions were discussed when the two pulses were polarized along the samA theoretical investigation of the pulse trapping in a highly birefringent photonic crystal fiber was presented. The strict coupled nonlinear Schrdinger equations were numerically solved using a split-step Fourier algorithm. Different incidence conditions were discussed when the two pulses were polarized along the same polarization axes. The pump pulse in abnormal dispersion regime traped the signal pulse in the normal dispersion regime, and the signal pulse shifted to shorter wavelength with the pump pulse of the longer wavelength in order to keep the same group velocity. Different initial temporal separation between the pump pulse and the signal pulse leaded to different effect in the pulse trapping. As the input peak power of the pump pulse was increased, the red-shift of pump pulse was considerably enhanced with the simultaneous further blue-shift if the trapped pulse to satisfy the condition of group velocity matching. Pulse trapping was inconspicuous as the full width at half maximum of the pump pulse was increased. In order to realize pulse trapping, the wavelengths of the pump and signal pulses should be near the zero dispersion point and the discrepancy between two group velocities should be small..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1154 (2011)
Frequency Up- and Down-conversions in Two-mode Cavity
LI Bin, FENG Xun-li, and ZHANG Zhi-ming
A scheme was proposed to construct bilinear and quadratic Hamiltonians for frequency up- and down-conversions in cavity quantum electrodynamics (QED). Generally, in nonlinear optics, the interaction that the energe swaps between different optic modes without atomic transition is named frequency conversion. The proposedA scheme was proposed to construct bilinear and quadratic Hamiltonians for frequency up- and down-conversions in cavity quantum electrodynamics (QED). Generally, in nonlinear optics, the interaction that the energe swaps between different optic modes without atomic transition is named frequency conversion. The proposed scheme was based on the interactions of a single four-level atom simultaneously with two classical driving fields and a two-mode cavity field, which is in the domain of four-wave mixing . By initially preparing the atom in a suitable state, each pump light was resonant with its transition, and two quantum modes were large tune to the other two transition, respectively, In the strong laser regime, the atomic degrees of freedom could be decoupled from the cavity degrees of freedom and the frequency conversion could be realized for the cavity modes. Due to the different initial states and interactions between optic fields and atom, frequency up- and down-conversions arose, respectively. After the preparation of squeezed operation respect to Frequency down-conversion, a discussion on the feasibility of experiment was given and the theoretical value was obtained. The advantage of this proposal is to realize the transition using two cascade photons, which is dipole-forbidden in a cascade structure atom, with high efficiency. The proposal will be useful for optical quantum control and fundamental tests of quantum theory..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1161 (2011)
Research on High Power Laser Induced Diffraction Ring in 5CB Liquid Crystal
ZHAO Xiang-jie, ZHANG Da-yong, WANG Hai-feng, LUO Yong-quan, and LUO Fei
Self-phase modulation phenomena was found in 5CB liquid crystal, which accounted for the far field diffraction ring phenomena induced by high power laser traversing thin liquid crystal cell. Experimental and numerical methods were employed to study the mechanism of the self-phase modulation in 5CB. Experimental resultsSelf-phase modulation phenomena was found in 5CB liquid crystal, which accounted for the far field diffraction ring phenomena induced by high power laser traversing thin liquid crystal cell. Experimental and numerical methods were employed to study the mechanism of the self-phase modulation in 5CB. Experimental results indicate that diffraction ring phenomena can be found when the incident laser intensity rise to 10 kW/cm2 and 60 W/cm2 for 532 nm and 1 064 nm laser separately, but will disappear when the effect of laser interaction with liquid crystal sustained hundreds of mili-second. Numerical results applying Kirhoff diffraction integral formula were in good agreement with experimental results. Based on thermal conductivity theory, the relationship of the third order nonlinearity with the incident laser spot and wavelength in 5CB liquid crystal was discussed qualitatively. It was indicated that thermal effects take the main role in the nonlinear self-phase modulation phenomena which is greatly associated with the absorption coefficient and the laser spot diameter..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1166 (2011)
Optical Feedback Interferometry Based on Phase-freezing Technology
LIU Hui-lan, ZHANG Xiao-qing, CAO Wen-juan, and WANG Jun-jie
For optical feedback interferometry, a modulation and demodulation method based on phase-freezing technology was brought forward to increase the measurement resolution. And a displacement measurement system with phase modulator was designed. The phase of the outer cavity was modulated by the modulator, and interferenceFor optical feedback interferometry, a modulation and demodulation method based on phase-freezing technology was brought forward to increase the measurement resolution. And a displacement measurement system with phase modulator was designed. The phase of the outer cavity was modulated by the modulator, and interference signals that have fixed modulation phases were collected. Then displacement information of the target can be observed by demodulation and reconstruction. Signal modulation, sampling, reconstruction technology and error analysis were studied, and the feasibility of this method was verified by simulation. The results demonstrate that the accuracy can be up to λ/20 using five-point phase-freezing sampling. This method can enhance the accuracy of optical feedback interferometry, and process signals in real time. So it can be used in real time displacement measurement..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1172 (2011)
Design of Gires-Tournois Mirrors Used for Dispersion Compensation in Cr∶LiSAF Laser
LIAO Chun-yan, FAN Zheng-xiu, and SHAO Jian-da
Femtosecond-pulse generation relies on net negative intracavity group-delay dispersion.Solid-state gain media and other optical components always introduce a certain amount of frequency-dependant positive dispersion in the cavity,which must be balanced as well.Brewster-angled prism pairs were popular choices in the lasFemtosecond-pulse generation relies on net negative intracavity group-delay dispersion.Solid-state gain media and other optical components always introduce a certain amount of frequency-dependant positive dispersion in the cavity,which must be balanced as well.Brewster-angled prism pairs were popular choices in the last years.However,in prism-pair-controlled lasers,higher-order dispersion of the prism pair will be introduced,which increases the sensitivity and affects the size and repetition rate of femtosecond-pulse solid-state laser oscillators of the pulse width to the cavity and prism alignment.Gires-Tournois mirrors may not introduce above defects and can exhibit high reflectivity and precise control of the frequency-dependent group delay over a large bandwidth.They have played and will continue to play an important role in ultrashort pulse laser systems.Basic structure、dispersion performance and principle of design of Gires-Tournois mirrors are discussed.The optimized multilayer mirror used in a Cr∶LiSAF laser is reported.This mirror exhibit high reflectance(>99.9%) and smooth group delay dispersion(－35±8 fs2) from 750 nm to 900 nm.Most group delay dispersion of a 3 mm Cr∶LiSAF crystal can be compensated by four bounces..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1177 (2011)
Experimental Study on Self-phase Modulation in Hundred-picosecond Pulse Amplification
CHANG Li-ping, FAN Wei, and GUO Shu-qin
The single hundred-picosecond pulse amplification (the repetition rate is 1 Hz) was studied experimently in the Ytterbium-doped double clad fiber amplifier. The characteristic of time-domain and frequency-domain pulse waveform influenced by the self phase modulation (SPM) effect was presented. In the experiment, the smThe single hundred-picosecond pulse amplification (the repetition rate is 1 Hz) was studied experimently in the Ytterbium-doped double clad fiber amplifier. The characteristic of time-domain and frequency-domain pulse waveform influenced by the self phase modulation (SPM) effect was presented. In the experiment, the small mode area double clad fiber was adopted with core diameter 6.5 μm as the gain media. As the gain of the amplifier from the small-signal gain to the deeply saturated gain, the evolution of the spectrum broadening, the pulse waveform and intensity distribution because of the SPM effect were observed. Then to overcome the difficulty for measuring the single pulse spectrum, the Bragg fiber grating scanning was introduced to investigate the changing of spectrum broadening. The results indicate that different from the SPM effect in the passive fibers, as the increase of the pump power, due to the competition mechanism of the gain saturation and SPM in the hundred-picosecond pulse amplification, the spectrum exhibits asymmetric double-peak and the pulse intensity is shifting to short wavelength firstly and then to the long wavelength..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1181 (2011)
Compensation for Axes Shifting during Detection of Roller Shape by CCD
GUO Yuan, and WANG Yu-tian
Based on the technology of laser-linear array CCD,a kind of high speed and high accuracy method on detecting the roller shape was put forward.Also the composition of the detective system and the operation process were expatiated.Aiming at the axes shifting of the roller during the detecting process,compensation steps wBased on the technology of laser-linear array CCD,a kind of high speed and high accuracy method on detecting the roller shape was put forward.Also the composition of the detective system and the operation process were expatiated.Aiming at the axes shifting of the roller during the detecting process,compensation steps were adopted from vertical and parallel the detecting surface.And it enhanced the accuracy of the detecting system effectively.At the same time the gradient intensity averaging method to process the signal of the CCD was adopted,which reduced the influence of the noise to the CCD image contrast,and enhanced the speed of data processing effectively.It also enhanced the accuracy and the resolution of the system remarkably.The experiments prove that the accuracy of the system can reach to the demand of practical production process.It provides a new method for the high speed,accurate and automatic on line detection of the roller shape..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1186 (2011)
Interferogram Processing Method of Optical Surfaces
CHEN Wei
Interferometers are used to test the surface shape data of optical component for further processing to provide guidance. Various spatial point on the tested optical component are given by interferogram analysis. The binary image is get from the raw data, then the edge of optical component is differentiated with a sobelInterferometers are used to test the surface shape data of optical component for further processing to provide guidance. Various spatial point on the tested optical component are given by interferogram analysis. The binary image is get from the raw data, then the edge of optical component is differentiated with a sobel exactly. A coefficient constraint condition is incorporated into the least squares method for geometric parameters of circles, and the location of the centre of the circle and the size of the radius will be calculated by the method. Various spatial points on the tested optical component are given by calculation method, and arithmetic average value of equal precision is provied. The coordinate of the interferogram can be established exactly..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1191 (2011)
Diagnosis of Electron Density by Polarized X-ray Lines for Al Laser-produced Plasmas
WANG Hong-jian, XIAO Sha-li, and SHI Jun
In order to accurately diagnose the electron density of laser-produced plasma, the method of relative intensity ratio of helium-like resonance to combination lines was proposed based on the polarization spectrum. It took into account polarization characteristics of the X-ray in laser-produced plasma, modified the real In order to accurately diagnose the electron density of laser-produced plasma, the method of relative intensity ratio of helium-like resonance to combination lines was proposed based on the polarization spectrum. It took into account polarization characteristics of the X-ray in laser-produced plasma, modified the real intensity ratios of the resonance to intercombination lines of He-like ions, then derivated the density of plasma. The experiment was carried out at the 2×10 J laser facility at Laser Fusion Research Center of, China Academy of Engineering Physics (CAEP). X-ray spectra emitted from the aluminum plasmas were recorded by polarized PET(002) crystal spectrometer. By correcting two Al helium-like spectra, it was calculated that the electron density was about 1.5×1 020 cm－3. The experimental results showed that the arithmetic was adapted to diagnose laser-produced high temperature high-density plasmas..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1196 (2011)
Optimization of Long-period Fiber Grating for Refractive-index Sensor
JIN Qing-li, HUANG Xiao-hong, YAN Li-fen, WANG Zhen-guo, and ZHANG Yao-ju
Optimization structure of cladding radius and grating periods of long-period fiber grating (LPFG) was proposed, in order to achieve a high sensitivity of sensing the refractive-index of the external medium. Based on the coupled-mode theory of the LPFG, a theoretical analyzation was carried out between the cladding radiOptimization structure of cladding radius and grating periods of long-period fiber grating (LPFG) was proposed, in order to achieve a high sensitivity of sensing the refractive-index of the external medium. Based on the coupled-mode theory of the LPFG, a theoretical analyzation was carried out between the cladding radius and grating period, and surrounding refractive-index, respectively. Effects of the variation of the cladding radius and grating period on the refractive- index sensing were discussed. Both of these parameters were found to be equivalently important to control the refractive-index sensing. Optimizing parameters of the grating are Λ=380 μm and rcl=17 μm in order to achieve a good apply of the LPFG with resonance wavelength in the 1.55 μm common application region. Variation of external medium refractive-index from 1.26 to 1.38 was tested and the achieved refractive-index sensing sensitivity is 0.000 12. Optimization structure of the LPFG achieves a good result..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1201 (2011)
Light Intensity Distribution of Fiber-coupled Laser Beam and Analysis of Impact Factors
LIN Lin, LI Bing-bin, GUO Zhen, WANG Shi-yu, LIU Hai-qiang, CAI De-fang, and LIAN Tian-hong
Based on analysis of light intensity distribution over exit face, effects of direction angle of laser beam on exit optical field distribution were investigated during transmission process through optical fiber. A new influencing factor was proposed, which was a complement to the two proverbial factors-numerical aperturBased on analysis of light intensity distribution over exit face, effects of direction angle of laser beam on exit optical field distribution were investigated during transmission process through optical fiber. A new influencing factor was proposed, which was a complement to the two proverbial factors-numerical aperture and core diameter of the optical fiber. Beams of laser diode were resolved into a large amount of ray during transmission process. On the condition of a constant entrance optical field distribution, influences of single beam and multi-beam direction angle and optical fiber length were analyzed by ray tracing method. Results indicate that, in optical fiber, deviation of a single beam direction angle can lead to extremum position excursion on the exit face, while with more beams, deviation of direction angle can bring about an obvious ring form light intensity distribution. It can be concluded that direction angle of a beam is an important factor which influences the light intensity distribution and extremum position over the exit face, and the length of optical fiber also takes effect..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1205 (2011)
Analysis of Speckle Reduction by the Vibrating Fiber
WANG Li-juan, QIU Yi-shen, CHEN Huai-xi, and LI Gao-ming
In the laser projection displays technology, The method by vibrating the fiber can effectively suppress the speckle and reduce the light loss. Generalized van Cittert - Zernike theorem was used in the theoretical analysis of speckle reduction in the laser projection display, where the vibrating fiber was used as specklIn the laser projection displays technology, The method by vibrating the fiber can effectively suppress the speckle and reduce the light loss. Generalized van Cittert - Zernike theorem was used in the theoretical analysis of speckle reduction in the laser projection display, where the vibrating fiber was used as speckle reduction approach. The results show that the speckle contrast depends on number of optical fiber model and the projection system pupil size. For the same size of the image plane, more models of multimode fibers should be collected and pupil diameter of projection system should be enlarged in order to reduce speckle contrast. In the projection system, the comparison experiment using two different multimode fibers were carried out and the results confirmed this conclusion qualitatively. This result provides a guidance for choosing the fiber production program and designing the illumination mode..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1211 (2011)
Comparision Research of Er:YAG Laser Pulses Ablation of Urinary Calculus and Gall-Stone
LV Tao, XIAO Qing, and LI Zheng-jia
Two-dimension and three-dimension topography of pulsed lasers ablation of tissues were scanned by means of optical coherent microscopy, in order to analyze the ablation characteristics of pulsed Erbium:YAG lasers for hard biological tissues. Experimental results indicate that under the same laser parameters, ablation eTwo-dimension and three-dimension topography of pulsed lasers ablation of tissues were scanned by means of optical coherent microscopy, in order to analyze the ablation characteristics of pulsed Erbium:YAG lasers for hard biological tissues. Experimental results indicate that under the same laser parameters, ablation efficiency for gall-stone is higher than that for urinary stone. The higher the intensities of pulsed lasers are, the higher the ablation efficiency will be for both gall-stone and urinary stone. The higher ablation efficiency mainly embodies that wider surface diameter, deeper height, and bigger volume for craters will be obtained. Measurements for stone craters using the optical coherent microscopy are higher by about one order than those using the optical coherent tomography. Optical coherent microscopy system can contribute to quantitatively measure hard tissues irradiated by pulsed lasers much better than optical coherent tomography system..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1215 (2011)
Image Fire Detection Based on Color Model and Sparse Representation
MA Zong-fang, CHENG Yong-mei, PAN Quan, and WANG Hui-qin
Some single feature information or their effective combinations which fire flame behaves are extracted as the basis of image fire flame recogniton in common algorithms. And large number of training samples are needed for learning procedure and parameters optimization. Moreover the recognition rate depends on the selectSome single feature information or their effective combinations which fire flame behaves are extracted as the basis of image fire flame recogniton in common algorithms. And large number of training samples are needed for learning procedure and parameters optimization. Moreover the recognition rate depends on the selection of features. Considering the global feature of fire flame, an algorithm was proposed based on color model and sparse representation for fire detection. Firstly, the regions with fire-like colors were roughly separated by color modeling in the space of HIS. Secondly, sparse representation model was built, and then the codebook of flames and suspected objects were constructed using PCA. Finally, the classification of fire flames and disturbances was implemented by calculating the minimum approximation residual error between testing samples and training samples using l1-minimization. The experiment results show that the algorithm can effectively improve the classification precision and recognition speed, and also it achieves higher accuracy..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1220 (2011)
Stereo Visual Localization Based on Generalized Orthogonal Iterative Algorithm
XU Yun-xi, JIANG Yun-liang, and CHEN Fang
A new stereo visual localization method was proposed based on generalized orthogonal iterative algorithm. Firstly, CensurE features and U-SURF descriptors were extracted, sub-pixel stereo matching were performed based on SAD method, and features between two consecutive image frames were matched using U-SURF descriptor.A new stereo visual localization method was proposed based on generalized orthogonal iterative algorithm. Firstly, CensurE features and U-SURF descriptors were extracted, sub-pixel stereo matching were performed based on SAD method, and features between two consecutive image frames were matched using U-SURF descriptor. Then, 3D-3D motion estimation was carried out to obtain initial motion parameters in the framework of RANSAC. 3D-3D motion estimation could obtain the minimum error of Euclidean distance between 3D points. The 3D coordinates of feature points were greatly affected by noise, so the motion estimation error was large. In this paper, generalized orthogonal iterative algorithm was applied to visual stereo localization to obtain motion estimation parameters by minimising object-space collinearity error of points sensed by stereo cameras. The motion estimation error was greatly reduced because Euclidean distance error between 3D points was more affected by noise than collinearity error of points. Simulation experiment and outdoor intelligent vehicle experiment show that the proposed method can be run at real-time, and achieves a high accuracy and robustness, better than traditional methods..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1225 (2011)
Application of Maximum Average Correlation Height Filter Algorithm in Distorted Target Recognition
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Maximum Average Correlation Height (MACH) algorithm was applied on JTC to achieve distortion target recognition to solve the problem of inaccurate recognition for distorted target (the targets rotated in plane or scale changed) in cluttered background with Joint Transform Correlator (JTC). First of all, three performanMaximum Average Correlation Height (MACH) algorithm was applied on JTC to achieve distortion target recognition to solve the problem of inaccurate recognition for distorted target (the targets rotated in plane or scale changed) in cluttered background with Joint Transform Correlator (JTC). First of all, three performance control parameters of MACH filter were optimized in frequency domain, and then the optimized MACH frequency domain filter was projected to object space; the MACH reference template could be obtained. As practical examples, the optical experiments on warship and car in clutter background were presented. The results show that when the control parameters of the filter are γ=1, α=0 and β=0.1, the obtained MACH reference template is clearest, the correlation peak of the target is sharpest and brightest. In this way, the obtained scale distortion tolerance on the JTC is 28%, and rotation distortion tolerance is 20°. For the target which exceeding the distortion tolerance range, the correlation peak is weaker and weaker, but some can still be recognized. In the field of distorted target detection, the improved MACH filter has a powerful advantage and a good application prospect..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1231 (2011)
High-speed Scene Matching Algorithm Based on BRIEF Descriptor for INS Integrated Navigation System
CHEN Fang, and XU Yun-xi
For the scene matching aided inertial integrated navigation system needs to get both the aircraft position errors and the course deviation relative to the present flight path simultaneously,a high-speed scene matching algorithm based on BRIEF descriptor is proposed,especially for device with the limited computing resouFor the scene matching aided inertial integrated navigation system needs to get both the aircraft position errors and the course deviation relative to the present flight path simultaneously,a high-speed scene matching algorithm based on BRIEF descriptor is proposed,especially for device with the limited computing resources.First,center surround extremas is extracted.Then,feature points’s binary robust independent elementary features descriptor and match features are calculated by computing hamming distance between descriptors.Finally,group sampling consensus is adopted to remove the false matching points and the least square algorithm for getting the high accurate aircraft position and course deviation.Performance evaluation experiments for scene matching show that the proposed method is superior,better than traditional algorithm in matching adaptability,speed,accuracy and robustness.In the reference image with 250×250 pixels and real image with 160×160 pixels,the total computing time of algorithm is about 40ms.Therefore,the proposed algorithm can meet the high performance needs for matching navigation in the INS integrated navigation system..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1238 (2011)
Entanglement Concentration of Entangled Coherent States
CAI Xin-hua, PENG Guang-han, and QIAO Nao-sheng
With linear optical components to manipulate quantum states of optical fields, the quantum entanglement control and quantum communication can be implemented remotely.By analyzing optical splitter and its use of coherent states, it was found that when the initial state was a direct product of two partially entangled cohWith linear optical components to manipulate quantum states of optical fields, the quantum entanglement control and quantum communication can be implemented remotely.By analyzing optical splitter and its use of coherent states, it was found that when the initial state was a direct product of two partially entangled coherent states; another two modes would collapse to a new entangled state using optical splitter and photon-detectors on two modes. Based on this feature, the scheme on entanglement concentration was presented. In this scheme, the two partially entangled coherent states were utilized as the quantum channel, when zero photon and odd photons were detected in two modes separately, and another two modes would collapse to the maximum entangled state, thereby completing the process of the entanglement concentration. It was proved that, no matter how small the initial entanglement is, to distill some maximally entangled states from partially entangled pure states is possible..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1244 (2011)
Quantum Secret Sharing Scheme with N-ordered Entangled Photon pairs
YUAN Su-zhen, SUN Zhi-fu, and TIAN Jun-long
A new quantum secret sharing scheme is proposed,based on N-ordered entangled photon pairs.Entangled photons are used as information carrier.Alice,the private key administrator,will divide the entangled photons into two sequences.One of the sequences will be sent to one of the partners Bob directly.After the safety of tA new quantum secret sharing scheme is proposed,based on N-ordered entangled photon pairs.Entangled photons are used as information carrier.Alice,the private key administrator,will divide the entangled photons into two sequences.One of the sequences will be sent to one of the partners Bob directly.After the safety of the first sequence ensured,the second sequence will be encoded and sent to another partner Charlie.Bob and Charlie will make Bell-based joint measurements with what they have received respectively,thus they obtain keys that Alice released.It needs the administrator and all the partners′ collaboration to get the whole information.Relative to there-particle entangled state,this scheme adopts two bodies entanglement,and can be experimentally realized easier.It only needs linear optical elements and simple entanglement source..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1248 (2011)
Growth and Field Emission Properties of Globe-like Diamond Microcrystalline-aggregate
GAO Jin-hai, LI Zhen, ZHANG Wu-Qin, and ZHANG Bin-lin
The globe-like diamond microcrystalline aggregates were grown in the different growing time by microwave plasma chemical vapor deposition method on the ceramic substrate with a Ti metal layer. The carbon films were evaluated by Raman scattering spectroscopy, X-ray diffraction spectrum, and scanning electron microscopy.The globe-like diamond microcrystalline aggregates were grown in the different growing time by microwave plasma chemical vapor deposition method on the ceramic substrate with a Ti metal layer. The carbon films were evaluated by Raman scattering spectroscopy, X-ray diffraction spectrum, and scanning electron microscopy. The field emission properties were tested by using a diode structure in a vacuum. The growth mechanism of the carbon films and field emission properties of the globe-like diamond microcrystalline aggregates were discussed. It was found that different carbon films prepared by deposition time greatly changes in morphology, and field emission results also change a lot. The decrease of field enhancement factor and the growth of conductive channel are the main reasons for deterioration of the field emission effect..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1253 (2011)
Photoluminescent Properties in Zinc Oxide Samples with Network Surface Microstructure
WANG Ma-hua, and ZHU Guang-ping
In order to investigate influences of microstrucral Znic Oxide samples′ superficial nanotructure on their photoluminescence characteristics, ZnO sample with 2-Dimension network surface nanostructure was fabricated based on vapor phase transport method using zinc powder as a source. Their superficial structure was examiIn order to investigate influences of microstrucral Znic Oxide samples′ superficial nanotructure on their photoluminescence characteristics, ZnO sample with 2-Dimension network surface nanostructure was fabricated based on vapor phase transport method using zinc powder as a source. Their superficial structure was examined by X-ray diffraction pattern. Scanning electron microscopy picture and photoluminescence spectra excited with 355 nm laser pulse at room temperature were measured. The measuring results show that the structures are composed of three ordered multi-aperture gratings and the special photoluminescent properties, similar to structural colours, resulted from tne network surface, which works as photonic crystals here. The mechanism of this photoluminescent performance was discussed based on finite difference time-domain, rigious coupled-wave analysis methods and the reasonable explaination was present. Finally, the theoretically analysis conclusion was verified by experiment results..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1257 (2011)
Tolerance Analysis of Stitching System Based on Equivalent Nodal Point
LIU Zhi-ying, SONG Yu-long, FU Yue-gang, and GAO Tian-yuan
In sub-aperture stitching system, image quality will be affected directly by tilt and shift errors of sub-apertures. The equivalent nodal point concept of dynamic optics was applied. During alignment of sub-aperture stitching system, if the sub-aperture was tilted and shifted, the circle center of sub-aperture would beIn sub-aperture stitching system, image quality will be affected directly by tilt and shift errors of sub-apertures. The equivalent nodal point concept of dynamic optics was applied. During alignment of sub-aperture stitching system, if the sub-aperture was tilted and shifted, the circle center of sub-aperture would be tilted and shifted consequently. The equivalent nodal point will shift would sub-apertures. The spot size variation due to sub-apertures image displacement was analyzed in detail. The effect of sub-aperture tilt and shift on image quality in stitching system was simplified with equivalent nodal point concept. Through application in structure design and tolerance analysis of sub-aperture stitching prototype, the tilt tolerance and displacement tolerance is 4 μrad and 6 μm respectively. Consequently the alignment tolerance was controlled effectly in stiching prototype..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1261 (2011)
Design of Light Weight Small Wide-angle Projection Lens
CHEN Chen, LIU Xiao-chan, LI Wei-shan, ZHANG Yu, and LIU Hong-jun
To realize the miniaturization and light weight of the digital projector, a wide-field angle mini lens for 0.55 inch DLP was designed. The total length is 69 mm, the full aperture is 25 mm, and it is composed of five glass lenses and two plastic lenses(4 aspheric surfaces).The lens used an inverted telephoto structure,To realize the miniaturization and light weight of the digital projector, a wide-field angle mini lens for 0.55 inch DLP was designed. The total length is 69 mm, the full aperture is 25 mm, and it is composed of five glass lenses and two plastic lenses(4 aspheric surfaces).The lens used an inverted telephoto structure, with ZEMAX software as the optimize tool. Its F-number is F/2.4, the projection ratio is 0.73∶1, and it can project a 40 inch picture from 60 cm away. The distortion of the full field is less than 1%. Its image quality is excellent that the MTF of center field is 0.75, and the MTF of 1.0 field is 0.42，with advantages of small size, light weight, low cost, simple structure and easy process..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1266 (2011)
Design of Outdoor Concentration Test System
ZHAO Hui-fu, LIU Hua, SUN Qiang, JING Lei, LIU Ying, WANG Yao, and LU Zhen-wu
In order to improve the concentration efficiency of optical concentration system,an outdoor concentration test system was disigned.The second order Fresnel concentration system was chosen as the test object,and its performances were tested by localized measurement.Using Tracepro software,transmittance,concentration effIn order to improve the concentration efficiency of optical concentration system,an outdoor concentration test system was disigned.The second order Fresnel concentration system was chosen as the test object,and its performances were tested by localized measurement.Using Tracepro software,transmittance,concentration efficiency and concentration spots of the concentration system were simulated.The second order Fresnel concentration system was experimentally tested by outdoor concentration system. Compared the simulation result with experiment result,it was found that the spots uniformity of the two systems are close,and transmittance differences and differences between concentration efficiencies are 1.800% and 4.346% respectively.The differences of concentration efficiencies mainly come from the manufacturing error and measuring error.So this experimental data can provide information and feedback for the designer and manufacturer of the system to improve the processing technology and raise the concentration efficiency..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1270 (2011)
Phase Conjugation Properties and Holographic Associative Storage of Zn∶Mn∶Fe∶LiNbO3 Crystals
ZHANG Chun-lei, XU Chao, FAN Ye-xia, LENG Xue-song, XU Lei, FANG Gui-zhen, GUAN Cheng-xiang, and XU Yu-heng
Zn∶Mn∶Fe∶LiNbO3 crystals with 1%, 3%, 5%, 7% and 9%, ZnO(in mole) and MnCO3 and Fe2O3, added at concentration of 0.03%and 0.08(in mass)respectively, were grown by Czochralski method from congruent LiNbO3 melting. The OH- infrared absorption spectra, the optical damage resistance and phase conjugate properties of Zn∶Mn∶Zn∶Mn∶Fe∶LiNbO3 crystals with 1%, 3%, 5%, 7% and 9%, ZnO(in mole) and MnCO3 and Fe2O3, added at concentration of 0.03%and 0.08(in mass)respectively, were grown by Czochralski method from congruent LiNbO3 melting. The OH- infrared absorption spectra, the optical damage resistance and phase conjugate properties of Zn∶Mn∶Fe∶LiNbO3 crystals were tested. When Zn2+ concentration reaches 7% and 9%, OH- absorption peaks shift to 3 528 cm-1. The mechanism of OH-1 absorption peaks shift were discussed. The optical damage resistance ability of Zn∶Mn∶Fe∶LiNbO3 crystals increase, with the increase of Zn2+ concentration. When Zn2+ concentration reaches to 7% (reaches threshold value), the optical damage resistance ability are two orders of magnitude higher than that of LiNbO3 crystals. The enhancement mechanism of optical damage resistance of highly doping zinc Mn:Fe: LiNbO3 crystals was researched. The bhase conjugate reflectivity decreases and phase conjugate response speed increases, with the increase of Zn2+ concentration. The phase conjugate mirror has eliminate optical wave phase distortion. The holographic associative storage experiment was carried out using Zn∶Mn∶Fe∶LiNbO3 crystals as storage medium. The working principle of holographic associative storage was discussed. Using 25% and 50% addressing, the intact storage image was received in output plane..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1276 (2011)
A Method for Accurate Phase Shift in Two-step Phase-shifting Digital Holography
QIN Yi, GONG Qiong, and YANG Xing-qiang
The quality of reconstruction in phase-shifting digital holography was determined by the accuracy of phase shift. An approach to obtain accurate phase shift in two-step digital holography was proposed. This approach employed an ordinary open-loop controlled piezoelectric actuator, and a serial of phase shift holograms The quality of reconstruction in phase-shifting digital holography was determined by the accuracy of phase shift. An approach to obtain accurate phase shift in two-step digital holography was proposed. This approach employed an ordinary open-loop controlled piezoelectric actuator, and a serial of phase shift holograms corrisponding to different phase shift angles would be obtained by means of changing the volgate exerted on the piezoelectric actuator continuously. Then the holograms could be used to reconstruct the object intensity on the CCD plane. The object intensity on the CCD plane that already recorded by CCD would be used as a criterion to evalutae the quality of the reconstuction. The correlation coefficients between the criterion and the same intensity reconstructed with different phase shift holograms were obtained. The correlation coefficient reached its maximum when the phase shift hologram is with the accurate phase shift angle. Simulation was carried out and thereafter the approach was employed in experiment. The quality of the reconstructed field by using the accurate value and the nominal value were compared. The feasibility of this method has been verified by both computer simulations and experiments..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 1282 (2011)
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20