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RSS2008 Vol. 32, No. 5
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2008, 32(5): 449-452.
[Abstract]
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Abstract:
A new polarization-Mie lidar(PML) used for detecting extinction and polarization characteristic of aerosol and cirrus is described.Three methods for validate reliability of PML are presented.Firstly,the main performance parameters of PML itself are determined.Secondly,the comparison experiments between PML and homogeneous lidar are completed.Finally,aerosol optical depth compared between PML and solar radiometer are finished.The validation results show that PML is steady and reliable.The detected results of depolarization ratio for cirrus over Hefei from February to May in 2007 are also presented and discussed.The cirrus is generally present in the altitude from 7km to 12km,and the depolarization ratio varies from 0.2 to 0.5 with average 0.36±0.06.At the meanwhile,depolarization ratio appears a climbing tendency with the increased height.
A new polarization-Mie lidar(PML) used for detecting extinction and polarization characteristic of aerosol and cirrus is described.Three methods for validate reliability of PML are presented.Firstly,the main performance parameters of PML itself are determined.Secondly,the comparison experiments between PML and homogeneous lidar are completed.Finally,aerosol optical depth compared between PML and solar radiometer are finished.The validation results show that PML is steady and reliable.The detected results of depolarization ratio for cirrus over Hefei from February to May in 2007 are also presented and discussed.The cirrus is generally present in the altitude from 7km to 12km,and the depolarization ratio varies from 0.2 to 0.5 with average 0.36±0.06.At the meanwhile,depolarization ratio appears a climbing tendency with the increased height.
2008, 32(5): 453-455,459.
Abstract:
In order to obtain the spectral response of ultraviolet detector more exactly,a measuring system of spectral response,based on the photoacoustic spectroscopy with the photoacoustic detector of high sensitivity as a reference one,was established.Due to this technique,the relative spectral response of two kinds of ultraviolet detector was measured.The experimental results show that this measuring system is simple,reliable and easily repeated.Between the 250nm and 450nm,it can exactly measure the spectral response of ultraviolet detector.Furthermore,it also can be used to measure the spectral response of visible photo-electronic detector and analyse the photoacoustic spectroscopy of solids samples.
In order to obtain the spectral response of ultraviolet detector more exactly,a measuring system of spectral response,based on the photoacoustic spectroscopy with the photoacoustic detector of high sensitivity as a reference one,was established.Due to this technique,the relative spectral response of two kinds of ultraviolet detector was measured.The experimental results show that this measuring system is simple,reliable and easily repeated.Between the 250nm and 450nm,it can exactly measure the spectral response of ultraviolet detector.Furthermore,it also can be used to measure the spectral response of visible photo-electronic detector and analyse the photoacoustic spectroscopy of solids samples.
2008, 32(5): 456-459.
Abstract:
In order to measure the velocity of bullets,a photoelectric target design methods is put forwarded.When the photoelectric target work,firelight or ambient light will bring an error trigger signal or can not capture the shot off target signal.These may affect accuracy and sensitivity of the system.The basic principle of the photoelectric target was described,using the large effective screen area technology and design of the photo compensation circuit.It can get rid of the signal that caused by ambient light interference.Experiments were performed to validate the correctness of the design.At the end,it is proved the validity and the usability of the system through the ball firing.As a result,the system of photoelectric target could resolve the effect of ambient light interference.
In order to measure the velocity of bullets,a photoelectric target design methods is put forwarded.When the photoelectric target work,firelight or ambient light will bring an error trigger signal or can not capture the shot off target signal.These may affect accuracy and sensitivity of the system.The basic principle of the photoelectric target was described,using the large effective screen area technology and design of the photo compensation circuit.It can get rid of the signal that caused by ambient light interference.Experiments were performed to validate the correctness of the design.At the end,it is proved the validity and the usability of the system through the ball firing.As a result,the system of photoelectric target could resolve the effect of ambient light interference.
2008, 32(5): 460-464.
Abstract:
In order to analyze the general astigmatism of laser resonator cavities,the general analytical formula of misalignment sensitivity for complex astigmatic resonator cavities with several optical components has been derived by adopting augmented 8×8 misaligned matrix and symbol operation functions of MATLAB.This formula is applicable to the complex astigmatic cavity including several optical components with general astigmatic characteristics,and it can be used to analyze quantitatively the misalignment sensitivity of these resonator cavities in x-O-z plane and y-O-z plane.Calculation results indicate that mode distributions in the complex astigmatic cavity and the misalignment sensitivities of the complex astigmatic cavity have coupling in x-O-z plane and y-O-z plane.These results afford some references for the design and analysis of complex astigmatic cavities.
In order to analyze the general astigmatism of laser resonator cavities,the general analytical formula of misalignment sensitivity for complex astigmatic resonator cavities with several optical components has been derived by adopting augmented 8×8 misaligned matrix and symbol operation functions of MATLAB.This formula is applicable to the complex astigmatic cavity including several optical components with general astigmatic characteristics,and it can be used to analyze quantitatively the misalignment sensitivity of these resonator cavities in x-O-z plane and y-O-z plane.Calculation results indicate that mode distributions in the complex astigmatic cavity and the misalignment sensitivities of the complex astigmatic cavity have coupling in x-O-z plane and y-O-z plane.These results afford some references for the design and analysis of complex astigmatic cavities.
2008, 32(5): 465-467.
Abstract:
In order to improve the surface properties of aluminum,the Al-Y alloy coating was fabricated by laser cladding directly melting the preplaced Y powder on substrate.With optimum process parameters,the coating layer with good metallurgical bonding performance was formed,and the grain size in cladding layer was smaller than the substrate.The microstructure characteristics of coating layer were studied by using metallogenetic microscope,energy disperse spectroscopy,X-ray diffraction and micro-hardness analysis.The results showed that the surface modified layer consisted of some inter-metallic compound phase,such as YAl3,Y4Al2O9.The micro-hardness of the coating ranging from 43HV0.2 to 58HV0.2,was 50%~60% higher than that of the substrate,ranging from 30HV0.2 to 40HV0.2.The highest hardness was obtained in the top of the coating.It can be concluded that the surface properties of aluminum can be improved by laser cladding Y powers.
In order to improve the surface properties of aluminum,the Al-Y alloy coating was fabricated by laser cladding directly melting the preplaced Y powder on substrate.With optimum process parameters,the coating layer with good metallurgical bonding performance was formed,and the grain size in cladding layer was smaller than the substrate.The microstructure characteristics of coating layer were studied by using metallogenetic microscope,energy disperse spectroscopy,X-ray diffraction and micro-hardness analysis.The results showed that the surface modified layer consisted of some inter-metallic compound phase,such as YAl3,Y4Al2O9.The micro-hardness of the coating ranging from 43HV0.2 to 58HV0.2,was 50%~60% higher than that of the substrate,ranging from 30HV0.2 to 40HV0.2.The highest hardness was obtained in the top of the coating.It can be concluded that the surface properties of aluminum can be improved by laser cladding Y powers.
2008, 32(5): 468-470.
Abstract:
In order to study the requirements of space polarizing radiometer on measurement accuracy of degree of polarization,the influence of angular error of Wollaston prism on degree of polarization is presented based on the inversion of the polarization parameters and the method of the radiometric calibration.The results show that measurement errors of degree of polarization change with polarization state of incident light while keeping angular error of Wollaston prism fixed.Measurement accuracy of degree of polarization meets the specification of space polarizing radiometer if the angular error of Wollaston prism is less than 0.1°.
In order to study the requirements of space polarizing radiometer on measurement accuracy of degree of polarization,the influence of angular error of Wollaston prism on degree of polarization is presented based on the inversion of the polarization parameters and the method of the radiometric calibration.The results show that measurement errors of degree of polarization change with polarization state of incident light while keeping angular error of Wollaston prism fixed.Measurement accuracy of degree of polarization meets the specification of space polarizing radiometer if the angular error of Wollaston prism is less than 0.1°.
2008, 32(5): 471-473,557.
Abstract:
In order to achieve stable and high conversion efficiency,the influence of fundamental pulse shape on third-harmonic generation was analyzed and different physical insights of third-harmonic conversion with flat-top pulse and Gaussian pulse were studied respectively.In the case of Gaussian fundamental pulse and 3GW/cm2 input intensity,the calculated optimal second-harmonic conversion efficiency was 56.8%,lower than 66.7% predicated in theory.Furthermore,the dependence of optimal second-harmonic conversion efficiency on fundamental pulse shape was calculated under different input intensity.The spatial walk-off effect will influence the optimal second-harmonic conversion efficiency,lowering it to 62% in the case of fundamental pulse with flat-top spatial and temporal distribution.The optimal second-harmonic conversion efficiency will decrease to 51% when the spatial distribution of fundamental pulse is Gaussian.It is discovered that when the fundamental pulse is not ideal flat-top pulse shape,the third-harmonic conversion efficiency can be improved by lowering the second-harmonic conversion efficiency properly.
In order to achieve stable and high conversion efficiency,the influence of fundamental pulse shape on third-harmonic generation was analyzed and different physical insights of third-harmonic conversion with flat-top pulse and Gaussian pulse were studied respectively.In the case of Gaussian fundamental pulse and 3GW/cm2 input intensity,the calculated optimal second-harmonic conversion efficiency was 56.8%,lower than 66.7% predicated in theory.Furthermore,the dependence of optimal second-harmonic conversion efficiency on fundamental pulse shape was calculated under different input intensity.The spatial walk-off effect will influence the optimal second-harmonic conversion efficiency,lowering it to 62% in the case of fundamental pulse with flat-top spatial and temporal distribution.The optimal second-harmonic conversion efficiency will decrease to 51% when the spatial distribution of fundamental pulse is Gaussian.It is discovered that when the fundamental pulse is not ideal flat-top pulse shape,the third-harmonic conversion efficiency can be improved by lowering the second-harmonic conversion efficiency properly.
2008, 32(5): 474-476,526.
Abstract:
In order to heighten the manipulative accuracy of the ruled engine,a new measurement system auto-collimating grating heterodyne interferometer was proposed.Based on the diffraction and polarization of grating and some theories of the electronics,the system was analyzed.After the benchmark grating was designed,and lots of experiments were carried out.Because the interferometer measurement system takes grating constant as the measurement standard,the effect of environment on measurement accuracy is reduced.Thanks to the auto-collimation diffraction,the structure is simple and steady,and easy to assemble and adjust.Moreover,using the dual-frequency,high gain and signal-to-noise ratio can be obtained.Using the interferometer system to control the ruled engine,the biased error for ruling span is less than 10nm,and the cumulative error is about 0.3μm within 3mm displacement.The results show that the resolution of the interferometer system is small to nm scale,and it can be used in the real-time measurement control system and that it achieves high accuracy that the special diffraction gratings such as echelon gratings request to a ruling engine completely.
In order to heighten the manipulative accuracy of the ruled engine,a new measurement system auto-collimating grating heterodyne interferometer was proposed.Based on the diffraction and polarization of grating and some theories of the electronics,the system was analyzed.After the benchmark grating was designed,and lots of experiments were carried out.Because the interferometer measurement system takes grating constant as the measurement standard,the effect of environment on measurement accuracy is reduced.Thanks to the auto-collimation diffraction,the structure is simple and steady,and easy to assemble and adjust.Moreover,using the dual-frequency,high gain and signal-to-noise ratio can be obtained.Using the interferometer system to control the ruled engine,the biased error for ruling span is less than 10nm,and the cumulative error is about 0.3μm within 3mm displacement.The results show that the resolution of the interferometer system is small to nm scale,and it can be used in the real-time measurement control system and that it achieves high accuracy that the special diffraction gratings such as echelon gratings request to a ruling engine completely.
2008, 32(5): 477-479,489.
Abstract:
In order to study the multiple scattering characteristics of light propagation through clouds,received power was analyzed,the laser transferring process in clouds was simulated with Monte Carlo method,and the waveform broadened temporal signal was obtained.Results illustrate the broadened signal has a steep rise edge followed by an exponential tail,and that the broadened shape is affected by some parameters such as asymmetry factor,clouds thickness,extinction coefficients,receiver field of view,especially strongly by asymmetry factor and clouds thickness.
In order to study the multiple scattering characteristics of light propagation through clouds,received power was analyzed,the laser transferring process in clouds was simulated with Monte Carlo method,and the waveform broadened temporal signal was obtained.Results illustrate the broadened signal has a steep rise edge followed by an exponential tail,and that the broadened shape is affected by some parameters such as asymmetry factor,clouds thickness,extinction coefficients,receiver field of view,especially strongly by asymmetry factor and clouds thickness.
2008, 32(5): 480-483.
Abstract:
In order to use non-diffracting beams to extend the depth-of-field of optical imaging systems,the variation rules of the central spot of non-diffracting beams were investigated.Based on the theory of Fresnel diffraction,the diffraction patterns were analyzed when the point source was placed in front of focal plane,at focal plane and behind focal plane.Then the radius and intensity calculation formula of the central spot of non-diffracting beams correspond to the distance from the point source to the lens or the distance between the partial coherent point source and the lens,were deduced according to the theory of partial coherent light.Finally,experiments were done by using a red high brightness LED as the quasi-monochromatic light source.The experimental results showed that the radius of the central spot decreased with the increase of the distance from the point source to the lens,and the intensity of the central spot increased with the increasing of the distance from the point source to the lens.The outcome provides stated academic gist to the applications of non-diffracting beams in imaging system.
In order to use non-diffracting beams to extend the depth-of-field of optical imaging systems,the variation rules of the central spot of non-diffracting beams were investigated.Based on the theory of Fresnel diffraction,the diffraction patterns were analyzed when the point source was placed in front of focal plane,at focal plane and behind focal plane.Then the radius and intensity calculation formula of the central spot of non-diffracting beams correspond to the distance from the point source to the lens or the distance between the partial coherent point source and the lens,were deduced according to the theory of partial coherent light.Finally,experiments were done by using a red high brightness LED as the quasi-monochromatic light source.The experimental results showed that the radius of the central spot decreased with the increase of the distance from the point source to the lens,and the intensity of the central spot increased with the increasing of the distance from the point source to the lens.The outcome provides stated academic gist to the applications of non-diffracting beams in imaging system.
2008, 32(5): 484-486.
Abstract:
In order to get the polarization mode dispersion feed-forward information,a real-time estimation model for the first and second polarization mode dispersion was presented,by means of which the first and second polarization mode dispersion(PMD) value and orientation can be determined.The results of PMD value by numerical simulation are similar to that estimated by Jones matrix when differential group delay is less than a bit period.The PMD vector from our model will give the feed-forward information for high order PMD compensation.The result is useful for the design of feed forward compensation of PMD.
In order to get the polarization mode dispersion feed-forward information,a real-time estimation model for the first and second polarization mode dispersion was presented,by means of which the first and second polarization mode dispersion(PMD) value and orientation can be determined.The results of PMD value by numerical simulation are similar to that estimated by Jones matrix when differential group delay is less than a bit period.The PMD vector from our model will give the feed-forward information for high order PMD compensation.The result is useful for the design of feed forward compensation of PMD.
2008, 32(5): 487-489.
Abstract:
In order to study the surface tissue variation of the magnesium alloy treated by laser,the surface of AZ91 magnesium alloy was treated by CO2 laser under the protection of helium gas.The treated workpiece was observed through optical microscope,and the microhardness value of the cross section was tested by microhardness tester.The result of the experiment showed that the grain size of the treated magnesium alloy was refined to the primitive magnesium alloy,the grain size of the magnesium alloy becoming smaller with the decrease of the scanning speed,and that the β phase along the grain boundary decreased distinctly.The microhardness test of the cross section showed that the microhardness value of the treated section enhanced distinctly,and the smaller of the grain size,the harder of the cross section,according to the Hall-Petch formula.
In order to study the surface tissue variation of the magnesium alloy treated by laser,the surface of AZ91 magnesium alloy was treated by CO2 laser under the protection of helium gas.The treated workpiece was observed through optical microscope,and the microhardness value of the cross section was tested by microhardness tester.The result of the experiment showed that the grain size of the treated magnesium alloy was refined to the primitive magnesium alloy,the grain size of the magnesium alloy becoming smaller with the decrease of the scanning speed,and that the β phase along the grain boundary decreased distinctly.The microhardness test of the cross section showed that the microhardness value of the treated section enhanced distinctly,and the smaller of the grain size,the harder of the cross section,according to the Hall-Petch formula.
2008, 32(5): 490-492.
Abstract:
Carotenoid molecules are powerful antioxidants that play important role throughout the human body.The level of carotenoid in human body can be used to reflect the human's health condition.Experiments were carried to detect the carotenoid in human.After tests repeatedly,suitable experimental parameters were determined.That is to say the best location to perform the measurement is thrum,laser's wavelength is 473nm,intensity of laser is 20mW and exposure time is 5s.At last obvious resonance Raman spectra of carotenoid in human skin was obtained after the fluorescence background was fitted and subtracted from the original spectra by means of fitted differential algorithm.Experimental results prove that resonance Raman spectra is applicable for carotenoid detection in human.
Carotenoid molecules are powerful antioxidants that play important role throughout the human body.The level of carotenoid in human body can be used to reflect the human's health condition.Experiments were carried to detect the carotenoid in human.After tests repeatedly,suitable experimental parameters were determined.That is to say the best location to perform the measurement is thrum,laser's wavelength is 473nm,intensity of laser is 20mW and exposure time is 5s.At last obvious resonance Raman spectra of carotenoid in human skin was obtained after the fluorescence background was fitted and subtracted from the original spectra by means of fitted differential algorithm.Experimental results prove that resonance Raman spectra is applicable for carotenoid detection in human.
2008, 32(5): 493-495.
Abstract:
To increase sub-pixel matching speed with a certain sub-pixel accuracy,the conventional algorithms to obtain sub-pixel accuracy in template matching was discussed,a new algorithm was proposed to combine the resampling and surface fitting methods.At first,it should use the sequential similarity detection algorithm to find the best match point,then only the model was need to be resampled n-times,next the normalization correlations among each sub-template and the image in the best match point was calculated,and the position of the sub-template which was corresponded to the maximum normalization correlation in the image was calculated.At last the method of curve fitting in the 3×3 area of that position was applied to obtain the absolute coordinates of the positioning with sub-pixel accuracy.The experiment shows that the accuracy obtained by the new method base on 10 times resampling is less than 0.04 pixel.
To increase sub-pixel matching speed with a certain sub-pixel accuracy,the conventional algorithms to obtain sub-pixel accuracy in template matching was discussed,a new algorithm was proposed to combine the resampling and surface fitting methods.At first,it should use the sequential similarity detection algorithm to find the best match point,then only the model was need to be resampled n-times,next the normalization correlations among each sub-template and the image in the best match point was calculated,and the position of the sub-template which was corresponded to the maximum normalization correlation in the image was calculated.At last the method of curve fitting in the 3×3 area of that position was applied to obtain the absolute coordinates of the positioning with sub-pixel accuracy.The experiment shows that the accuracy obtained by the new method base on 10 times resampling is less than 0.04 pixel.
2008, 32(5): 496-498,520.
Abstract:
In order to measure the damping constant of the liquid surface acoustic waves at low-frequency,steady and visible diffraction patterns were obtained by means of diffraction method and it was found that the variation of intensity distribution was related with the position of light spot.After analyzing the relationship between the intensity distribution of the diffraction rings and the liquid surface wave amplitude,the damping constant was obtained.The experimental data are in good agreement with classic hydrodynamics theory,which proves that the diffraction method is applicable for measurement of liquid parameters.
In order to measure the damping constant of the liquid surface acoustic waves at low-frequency,steady and visible diffraction patterns were obtained by means of diffraction method and it was found that the variation of intensity distribution was related with the position of light spot.After analyzing the relationship between the intensity distribution of the diffraction rings and the liquid surface wave amplitude,the damping constant was obtained.The experimental data are in good agreement with classic hydrodynamics theory,which proves that the diffraction method is applicable for measurement of liquid parameters.
2008, 32(5): 499-501,516.
Abstract:
Optical feedback self-mixing interferometry is an emerging sensing and measurement technique,which is quite different with traditional double-beam interferometry.To perform precision displacement measurement under the condition of moderate optical feedback,a displacement measurement method was proposed based on moderate optical feedback self-mixing interference.Firstly,rough measurement of displacement was carried out by counting the fringe numbers with the resolution of half wavelength.Then based on the study of fractional fringe structure details,a measurement means for displacement within half wavelength was derived.Calibration results with a commercial piezoelectric ceramics which translates in the order of 3nm show that a displacement accuracy of nanometers scale is achieved in the common laboratorial environment.The results indicate the relative standard deviation of bΔL is 1.20% within the displacement less than 3μm.
Optical feedback self-mixing interferometry is an emerging sensing and measurement technique,which is quite different with traditional double-beam interferometry.To perform precision displacement measurement under the condition of moderate optical feedback,a displacement measurement method was proposed based on moderate optical feedback self-mixing interference.Firstly,rough measurement of displacement was carried out by counting the fringe numbers with the resolution of half wavelength.Then based on the study of fractional fringe structure details,a measurement means for displacement within half wavelength was derived.Calibration results with a commercial piezoelectric ceramics which translates in the order of 3nm show that a displacement accuracy of nanometers scale is achieved in the common laboratorial environment.The results indicate the relative standard deviation of bΔL is 1.20% within the displacement less than 3μm.
2008, 32(5): 502-504,507.
Abstract:
In order to detect the oceanic red tides based on lidar,the infrared laser can be used to reflect the alga particles'density effectively.The interaction between 1.064μm laser and several marine matters,including water,phytoplankton,yellow substance and suspended particulates was analyzed.The detecting model of 1.064μm laser in the seawater was built.Based on the model and simulation,a conclusion is drawn that the infrared lidar can detect the underwater area within 0.8m effectively so that 1.064μm laser can satisfy the need of detecting the oceanic alga particles'density.
In order to detect the oceanic red tides based on lidar,the infrared laser can be used to reflect the alga particles'density effectively.The interaction between 1.064μm laser and several marine matters,including water,phytoplankton,yellow substance and suspended particulates was analyzed.The detecting model of 1.064μm laser in the seawater was built.Based on the model and simulation,a conclusion is drawn that the infrared lidar can detect the underwater area within 0.8m effectively so that 1.064μm laser can satisfy the need of detecting the oceanic alga particles'density.
2008, 32(5): 505-507.
Abstract:
In order to achieve the intensity in the vector light field applicable not far away from the laser diode when applying diffractive optics to shape the beam of laser diode,Kirchhoff diffractive theory and Fresnel approaching method under nonparaxial condition was adopted to derive out each electromagnetic component's distribution and the MATLAB language was adopted to compute the numerical result.The results show that the diode laser is a mixture of TE mode and TM mode except in some special directions,and the function of computing distribution of each electro-magnetic field is realized.The study should be useful for design and analysis of the diffractive optics for LD laser beam shaping.
In order to achieve the intensity in the vector light field applicable not far away from the laser diode when applying diffractive optics to shape the beam of laser diode,Kirchhoff diffractive theory and Fresnel approaching method under nonparaxial condition was adopted to derive out each electromagnetic component's distribution and the MATLAB language was adopted to compute the numerical result.The results show that the diode laser is a mixture of TE mode and TM mode except in some special directions,and the function of computing distribution of each electro-magnetic field is realized.The study should be useful for design and analysis of the diffractive optics for LD laser beam shaping.
2008, 32(5): 508-509,512.
Abstract:
For photonic crystals whose certain wavelength is forbid band or permit band,how to gain the photonic crystals structure from the photonic band gap structure was studied by means of transfer matrix method.Simulation result was obtained about the photonic crystals of the certain wavelength band gap.The result shows the method can completely gain the photonic crystals whose the certain wavelength is forbid band or permit band.The result conduces to the extensive application of the photonic crystals.
For photonic crystals whose certain wavelength is forbid band or permit band,how to gain the photonic crystals structure from the photonic band gap structure was studied by means of transfer matrix method.Simulation result was obtained about the photonic crystals of the certain wavelength band gap.The result shows the method can completely gain the photonic crystals whose the certain wavelength is forbid band or permit band.The result conduces to the extensive application of the photonic crystals.
2008, 32(5): 510-512.
Abstract:
The principle of laser transmission welding of plastics and holographic technology,and laser simultaneous welding technology based on laser holographic technology were introduced.In order to achieve simultaneous welding of plastics with small weld joint,the facula figure of laser beam was modulated the same as the figure of desired weld joint using interferential method to record the figure of desired weld joint and then using diffractive method to make the figure of desired weld joint reappearance.Using the modulated laser beam to weld plastics simultaneously,the figure of ideal weld joint was identical with the desired one.The result shows that this technology is applied when the figure of weld joint is small and complex.
The principle of laser transmission welding of plastics and holographic technology,and laser simultaneous welding technology based on laser holographic technology were introduced.In order to achieve simultaneous welding of plastics with small weld joint,the facula figure of laser beam was modulated the same as the figure of desired weld joint using interferential method to record the figure of desired weld joint and then using diffractive method to make the figure of desired weld joint reappearance.Using the modulated laser beam to weld plastics simultaneously,the figure of ideal weld joint was identical with the desired one.The result shows that this technology is applied when the figure of weld joint is small and complex.
2008, 32(5): 513-516.
Abstract:
By means of the approximate Vander Hulst numeration method,based on Bouguer-Lamber law,the effect of the smoke screens with different particles on the interference of different wavelength lasers was calculated.Numeric simulation indicated there was an optimum smoke particle parameter for a certain laser wavelength in order to obtain the best laser interference results.The study is valuable for both the evaluation and efficient interference on laser guidance weapon.
By means of the approximate Vander Hulst numeration method,based on Bouguer-Lamber law,the effect of the smoke screens with different particles on the interference of different wavelength lasers was calculated.Numeric simulation indicated there was an optimum smoke particle parameter for a certain laser wavelength in order to obtain the best laser interference results.The study is valuable for both the evaluation and efficient interference on laser guidance weapon.
2008, 32(5): 517-520.
Abstract:
Owing to small and coupled response of control channels of the continuous membrane deformable mirror(CMDM) and effect of system error on the its influence function,sometimes,the control voltage of wavefront modal reconstruction is beyond the the control voltage range.The modal reconstruction of wavefront based on the simulated annealing was put forward,which was used to find the optimal control voltages of the CMDM through verifying the total solutions in the feasible field.By the way the target function can be optimal and influence of incidence aberration can be reduced to minimum.Initial aberration of the adaptive optics can be replaced by the random wavefront aberration of human eye.Compared to the ways such as direct-solution or close-loop,the simulated annealing have prefer precision,credibility and least residual error.Because this algorithm has some better performance to reconstruct the incident wavefront,and refers to the nonlinear responses of the influence function,a new solution to correct the wavefront aberration by the CMDM is found.
Owing to small and coupled response of control channels of the continuous membrane deformable mirror(CMDM) and effect of system error on the its influence function,sometimes,the control voltage of wavefront modal reconstruction is beyond the the control voltage range.The modal reconstruction of wavefront based on the simulated annealing was put forward,which was used to find the optimal control voltages of the CMDM through verifying the total solutions in the feasible field.By the way the target function can be optimal and influence of incidence aberration can be reduced to minimum.Initial aberration of the adaptive optics can be replaced by the random wavefront aberration of human eye.Compared to the ways such as direct-solution or close-loop,the simulated annealing have prefer precision,credibility and least residual error.Because this algorithm has some better performance to reconstruct the incident wavefront,and refers to the nonlinear responses of the influence function,a new solution to correct the wavefront aberration by the CMDM is found.
2008, 32(5): 521-522,530.
Abstract:
In order to measure the crystal thickness accurately,a measurement method based on the birefringence characteristics of crystal was proposed and the feasibility was analyzed.Furthermore the realization process of measuring system and arithmetic of calculating thickness was validated by experiments.The experiment result shows that the root mean square of measuring error was less than 20nm.
In order to measure the crystal thickness accurately,a measurement method based on the birefringence characteristics of crystal was proposed and the feasibility was analyzed.Furthermore the realization process of measuring system and arithmetic of calculating thickness was validated by experiments.The experiment result shows that the root mean square of measuring error was less than 20nm.
2008, 32(5): 523-526.
Abstract:
In order to provide a theoretical basis for the actual application such as laser ranging and laser detection of the atmosphere,line-by-line integration was used to calculate the optical thickness of atmosphere molecular absorption.Discrete coordinate method was employed to study property of cirrus clouds at 1.064μm with the single scattering properties of cirrus clouds and the atmospheric absorption.The influence of cirrus clouds on laser transmission was analyzed by changing the incident angle,the observation location and some physical parameters of cirrus clouds.The results showed that the main effect of the cirrus clouds on laser transmission is scattering at 1.064μm and the absorption take a very small part in the extinction.The spatial distribution of the radiation is changed by scattering of the cirrus clouds significantly and the direction changes of scattering are decided by scattering phase function,observation zenith angles and scattering angle.This results are helpful to the actual application.
In order to provide a theoretical basis for the actual application such as laser ranging and laser detection of the atmosphere,line-by-line integration was used to calculate the optical thickness of atmosphere molecular absorption.Discrete coordinate method was employed to study property of cirrus clouds at 1.064μm with the single scattering properties of cirrus clouds and the atmospheric absorption.The influence of cirrus clouds on laser transmission was analyzed by changing the incident angle,the observation location and some physical parameters of cirrus clouds.The results showed that the main effect of the cirrus clouds on laser transmission is scattering at 1.064μm and the absorption take a very small part in the extinction.The spatial distribution of the radiation is changed by scattering of the cirrus clouds significantly and the direction changes of scattering are decided by scattering phase function,observation zenith angles and scattering angle.This results are helpful to the actual application.
2008, 32(5): 527-530.
Abstract:
The temperature and stresses distributions on film systems were simulated.A steady-state analysis of the temperature field and stress field of TiN film irradiated by a moving Gaussian laser was made with finite element analysis program.As a result,the temperature field is moving along with the lamp house,the largest temperature of temperature field is in the center of laser facula,and there is an obvious sluggish phenomenon in the backside temperature field of laser facula moving way.The stress field of film-substrate mainly concentrates in the film.The study of temperature and stress field is important for the research of film shape deformation.
The temperature and stresses distributions on film systems were simulated.A steady-state analysis of the temperature field and stress field of TiN film irradiated by a moving Gaussian laser was made with finite element analysis program.As a result,the temperature field is moving along with the lamp house,the largest temperature of temperature field is in the center of laser facula,and there is an obvious sluggish phenomenon in the backside temperature field of laser facula moving way.The stress field of film-substrate mainly concentrates in the film.The study of temperature and stress field is important for the research of film shape deformation.
2008, 32(5): 531-533.
Abstract:
By means of optical transfer maxtrix,the band function and the optical transmission properties of mirror symmetrical photonic crystals with an imaginary part of dielectric constant defect were studied,especially in the case of negation imaginary part and the λ0/2 optical thickness of the defect.The investigation results show that a large transmittance gain appears at the photonic band edges if an imaginary part of dielectric constant defect is added in the photonic crystals.With the increasing of the imaginary and the real part of defect's dielectric constant,the transmittance gain is increasing firstly then decreasing and in the middle the transmittance gain apex appears.However,the place and altitude of the defect film are invariable.The conclusion is useful for narrow band filter and optical amplification device synchronously.
By means of optical transfer maxtrix,the band function and the optical transmission properties of mirror symmetrical photonic crystals with an imaginary part of dielectric constant defect were studied,especially in the case of negation imaginary part and the λ0/2 optical thickness of the defect.The investigation results show that a large transmittance gain appears at the photonic band edges if an imaginary part of dielectric constant defect is added in the photonic crystals.With the increasing of the imaginary and the real part of defect's dielectric constant,the transmittance gain is increasing firstly then decreasing and in the middle the transmittance gain apex appears.However,the place and altitude of the defect film are invariable.The conclusion is useful for narrow band filter and optical amplification device synchronously.
2008, 32(5): 534-535,538.
Abstract:
The phase fluctuation of the beam propagating through the atmospheric turbulence,can induce the angle-of-arrival fluctuation on the receiver plane.In order to find the relation between them on a certain spot,based on the known phase distribution on the receiver plane,the wavefront geometric shape was constructed to calculate the angle-of-arrival distribution.The feasibility of the method was analyzed and the calculated variance by the geometric method was compared with the theoretic value.The results show that the calculated variance accords with the statistics of the angle-of-arrival well.The obtained results are useful for the study of the configuration and statistics characteristics of the beam propagating through the atmospheric turbulence.
The phase fluctuation of the beam propagating through the atmospheric turbulence,can induce the angle-of-arrival fluctuation on the receiver plane.In order to find the relation between them on a certain spot,based on the known phase distribution on the receiver plane,the wavefront geometric shape was constructed to calculate the angle-of-arrival distribution.The feasibility of the method was analyzed and the calculated variance by the geometric method was compared with the theoretic value.The results show that the calculated variance accords with the statistics of the angle-of-arrival well.The obtained results are useful for the study of the configuration and statistics characteristics of the beam propagating through the atmospheric turbulence.
2008, 32(5): 536-538.
Abstract:
The influence of nonlinear shock on the focusing property of femtosecond pulsed beams was studied through numerical simulation by using the modified(3+1)-dimensional nonlinear Schrodinger equation,taking into account of diffraction effects,space-time coupling,normal dispersion,and cubic nonlinearity.The self-focusing properties of the 90fs pulsed beam were analyzed and discussed in the absence and in presence of shock effect respectively.The results show:The space-time coupling,dispersion,and Kerr effect together will cause the pulse filament,amplitude descending and its width broadening.As implied by the functional form,space-time coupling relates to the dispersion will produce a time shift.The shift increases with distance and dispersion,and that the self-steepening effect will result in the peak power decreasing greatly,moreover it will weak the pulse self-focusing effect.
The influence of nonlinear shock on the focusing property of femtosecond pulsed beams was studied through numerical simulation by using the modified(3+1)-dimensional nonlinear Schrodinger equation,taking into account of diffraction effects,space-time coupling,normal dispersion,and cubic nonlinearity.The self-focusing properties of the 90fs pulsed beam were analyzed and discussed in the absence and in presence of shock effect respectively.The results show:The space-time coupling,dispersion,and Kerr effect together will cause the pulse filament,amplitude descending and its width broadening.As implied by the functional form,space-time coupling relates to the dispersion will produce a time shift.The shift increases with distance and dispersion,and that the self-steepening effect will result in the peak power decreasing greatly,moreover it will weak the pulse self-focusing effect.
2008, 32(5): 542-544.
Abstract:
In order to study near-infrared laser safety problem,the thermal model of biological tissue induced by continuous lasers was set up and the precise expression of transient temperature distribution induced by laser both in irradiation and diffusion process was obtained through discrete variable method.Taking skin tissue irradiated by chemical oxygen-iodine laser as an example,the skin temperature distribution was calculated and analyzed.The calculation showed that temperature increased with the power density and irradiation time,temperature of biological tissue subjected to the surface decreased slowly when the irradiation ended,but the temperature in the deep biological tissue increased at first and then decreased slowly.The analyzing result is in accordance with the relative experimental result,which proves the laser irradiation model correct.The result is helpful to the research of thermal damage induced by continuous laser in material.
In order to study near-infrared laser safety problem,the thermal model of biological tissue induced by continuous lasers was set up and the precise expression of transient temperature distribution induced by laser both in irradiation and diffusion process was obtained through discrete variable method.Taking skin tissue irradiated by chemical oxygen-iodine laser as an example,the skin temperature distribution was calculated and analyzed.The calculation showed that temperature increased with the power density and irradiation time,temperature of biological tissue subjected to the surface decreased slowly when the irradiation ended,but the temperature in the deep biological tissue increased at first and then decreased slowly.The analyzing result is in accordance with the relative experimental result,which proves the laser irradiation model correct.The result is helpful to the research of thermal damage induced by continuous laser in material.
2008, 32(5): 545-547,550.
Abstract:
The holographic characteristic parameters of the material such as the diffraction efficiency,the exposure sensitivity,the refractive index modulation and the dynamic range with different thickness were studied.As the thickness of the photopolymer increases,the diffraction efficiency increases at first and then decreases;the exposure sensitivity and the refractive index modulation decreases continuously;the dynamic range decreases at first and then increases.And the trends of these changes are simply analyzed in theory.From the contract of the holographic characteristic parameters in different thickness,it can be seen that this photopolymer has an optimal thickness.
The holographic characteristic parameters of the material such as the diffraction efficiency,the exposure sensitivity,the refractive index modulation and the dynamic range with different thickness were studied.As the thickness of the photopolymer increases,the diffraction efficiency increases at first and then decreases;the exposure sensitivity and the refractive index modulation decreases continuously;the dynamic range decreases at first and then increases.And the trends of these changes are simply analyzed in theory.From the contract of the holographic characteristic parameters in different thickness,it can be seen that this photopolymer has an optimal thickness.
2008, 32(5): 548-550.
Abstract:
In order to study irradiance scintillation after laser propagating though atmospheric turbulence,the method of phase screen was adopted to simulate the optical field in the receiving plane.The computed error of root mean square of the scintillation was compared with that in theory and they accord with each other to a certain extent.The above result is helpful for all near-earth laser application.
In order to study irradiance scintillation after laser propagating though atmospheric turbulence,the method of phase screen was adopted to simulate the optical field in the receiving plane.The computed error of root mean square of the scintillation was compared with that in theory and they accord with each other to a certain extent.The above result is helpful for all near-earth laser application.
2008, 32(5): 554-557.
Abstract:
Aiming at the cutting quality problems of high power CO2 laser cutting of small hole on middle-thick steel plates,the cutting technology of small hole on middle-thick steel plates was studied by using Rofin DC025 slab CO2 laser cutting system.At the same time,the effects of laser power,cutting speed and oxygen pressure on cutting quality were also studied.The key effect of temperature on cutting quality was analyzed.The results show that the best cutting quality can be obtained at the conditions of laser power 950W,cutting speed 1.0m/min,the oxygen pressure 1.0×105Pa.The cutting quality problems of high power CO2 laser cutting of small hole on middle-thick steel plates have been solved.
Aiming at the cutting quality problems of high power CO2 laser cutting of small hole on middle-thick steel plates,the cutting technology of small hole on middle-thick steel plates was studied by using Rofin DC025 slab CO2 laser cutting system.At the same time,the effects of laser power,cutting speed and oxygen pressure on cutting quality were also studied.The key effect of temperature on cutting quality was analyzed.The results show that the best cutting quality can be obtained at the conditions of laser power 950W,cutting speed 1.0m/min,the oxygen pressure 1.0×105Pa.The cutting quality problems of high power CO2 laser cutting of small hole on middle-thick steel plates have been solved.
2008, 32(5): 558-560.
Abstract:
In order to collect photoacoustic signals and reconstruct images quickly,photoacoustic signal collecting and image reconstructing system based on virtual instrument is applied to collect photoacoustic signals.Then the program of MATLAB is used to process collected data by LABVIEW.The photoacoustic imaging of phantom is obtained with filtered back projection algorithm in the end.The resolution of reconstructed image is 0.15mm.The reconstructed image is corresponded well with phantom.The methodology and equipment show that this imaging system features high speed and convenience.Furthermore,it is likely to be developed into a cheaper and practical clinical diagnosis instrument.
In order to collect photoacoustic signals and reconstruct images quickly,photoacoustic signal collecting and image reconstructing system based on virtual instrument is applied to collect photoacoustic signals.Then the program of MATLAB is used to process collected data by LABVIEW.The photoacoustic imaging of phantom is obtained with filtered back projection algorithm in the end.The resolution of reconstructed image is 0.15mm.The reconstructed image is corresponded well with phantom.The methodology and equipment show that this imaging system features high speed and convenience.Furthermore,it is likely to be developed into a cheaper and practical clinical diagnosis instrument.
