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RSS2001 Vol. 25, No. 4
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2001, 25(4): 241-246.
[Abstract]
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Abstract:
This paper describes the developing strategy and high-level roadmap of American high energy laser weapons.The significant progress of various laser weapon systems developed in the last year is reviewed.And finally,the technical challenges and possible measures are discussed and analyzed.
This paper describes the developing strategy and high-level roadmap of American high energy laser weapons.The significant progress of various laser weapon systems developed in the last year is reviewed.And finally,the technical challenges and possible measures are discussed and analyzed.
2001, 25(4): 247-249.
Abstract:
In the paper,the composition and equipment for on-site repair of damaged tubes by circular Nd：YAG laser deep penetration welding of inner sleeves are introduced.The inner sleeve is designed to be concave to reduce their axial constraints so that the residual stress of the welded part can be reduced and the tendency of stress corrosion can be decreased.Laser light is transmitted into the inner sleeve through an optical fiber,then reflected by a rotating mirror onto the inner wall;finally a circular weld of deep penetration is produced.The melted metal connects the inner sleeve with the outer tube,and prevents liquid seeping to the damaged part of the tube.Experimental results indicate that the grain growth of heat affected zone of parent metal caused by laser welding is small,the connection width is influenced by pulse power and that the tensile shear strength is influenced by pulse power and that the tensile shear strength is influenced by connection width.The tensile shear strength of the welded joint is about 62% of the tensile strength of Inconel 600 tube.
In the paper,the composition and equipment for on-site repair of damaged tubes by circular Nd：YAG laser deep penetration welding of inner sleeves are introduced.The inner sleeve is designed to be concave to reduce their axial constraints so that the residual stress of the welded part can be reduced and the tendency of stress corrosion can be decreased.Laser light is transmitted into the inner sleeve through an optical fiber,then reflected by a rotating mirror onto the inner wall;finally a circular weld of deep penetration is produced.The melted metal connects the inner sleeve with the outer tube,and prevents liquid seeping to the damaged part of the tube.Experimental results indicate that the grain growth of heat affected zone of parent metal caused by laser welding is small,the connection width is influenced by pulse power and that the tensile shear strength is influenced by pulse power and that the tensile shear strength is influenced by connection width.The tensile shear strength of the welded joint is about 62% of the tensile strength of Inconel 600 tube.
2001, 25(4): 250-253.
Abstract:
The plasma-ion assisted deposition (Plasma-IAD) process has been applied in deposition of large aperture shift-free polarizers at 1054nm.The shift of the center wavelength is less than 1nm when the polarizer is put in high temperature and high humidity environment.
The plasma-ion assisted deposition (Plasma-IAD) process has been applied in deposition of large aperture shift-free polarizers at 1054nm.The shift of the center wavelength is less than 1nm when the polarizer is put in high temperature and high humidity environment.
2001, 25(4): 254-257.
Abstract:
Two new techniques used to directly manufacture metal components and their characteristics have been introduced in the paper.The exist problems and prospects have also been pointed out.
Two new techniques used to directly manufacture metal components and their characteristics have been introduced in the paper.The exist problems and prospects have also been pointed out.
2001, 25(4): 258-268.
Abstract:
In the paper,the bending behavior of low carbon steel sheets is studied after being irradiated by an axial CO2 laser beam.The results show that the final bending angle of the sheets in a multiple-irradiation laser bending process is related to many process parameters,especially laser power,beam diameter,path feed rate,number of irradiation and sheet thickness.Through qualitative analysis of the experimental results,the conclusion obtained may provide basis for theoretical investigation and possible industrial application of laser bending process in the future.
In the paper,the bending behavior of low carbon steel sheets is studied after being irradiated by an axial CO2 laser beam.The results show that the final bending angle of the sheets in a multiple-irradiation laser bending process is related to many process parameters,especially laser power,beam diameter,path feed rate,number of irradiation and sheet thickness.Through qualitative analysis of the experimental results,the conclusion obtained may provide basis for theoretical investigation and possible industrial application of laser bending process in the future.
2001, 25(4): 263-267.
Abstract:
Monte Carlo method is the only effective solution in the study of light distribution in biological tissues irradiated by a complex surface source. However,direct Monte Carlo simulation demands large computational capacity because of its low rate of convergence.In this paper,the concept of impulse response function in biological tissues is introduced,thus light distribution in certain depth of the biological tissue can simply be obtained by calculating the convolation of incident source function and the impulse response function. On the basis of computer simulation,a criterion is proposed to evaluate the results of Monte Carlo simulation. By means of the criterion,the influence of impulse response function and dispersed quantity of the light source is analysed comprehensively,which shows that the calculating efficiency is greatly improved by the introduction of impulse response function in Monte Carlo simulation of light distribution in biological tissues.
Monte Carlo method is the only effective solution in the study of light distribution in biological tissues irradiated by a complex surface source. However,direct Monte Carlo simulation demands large computational capacity because of its low rate of convergence.In this paper,the concept of impulse response function in biological tissues is introduced,thus light distribution in certain depth of the biological tissue can simply be obtained by calculating the convolation of incident source function and the impulse response function. On the basis of computer simulation,a criterion is proposed to evaluate the results of Monte Carlo simulation. By means of the criterion,the influence of impulse response function and dispersed quantity of the light source is analysed comprehensively,which shows that the calculating efficiency is greatly improved by the introduction of impulse response function in Monte Carlo simulation of light distribution in biological tissues.
2001, 25(4): 268-271.
Abstract:
The approximate formula of the laser induced molecular reorientation angle,refractive index change,threshed field strength and rise time in nematic liquid crystal are obtained by means of the hydrodynamic equation of liquid crystal molecule motion.The dependence of the above parameters on the liquid crystal material parameters,laser intensity and its propagation inside liquid crystal is discussed and calculated.The essential condition which laser can induce molecular reorientation in nematic liquid crystal is given.The essential cause of molecular reorientation in nematic liquid crystal is anisotropy of its molecules have been obtained.
The approximate formula of the laser induced molecular reorientation angle,refractive index change,threshed field strength and rise time in nematic liquid crystal are obtained by means of the hydrodynamic equation of liquid crystal molecule motion.The dependence of the above parameters on the liquid crystal material parameters,laser intensity and its propagation inside liquid crystal is discussed and calculated.The essential condition which laser can induce molecular reorientation in nematic liquid crystal is given.The essential cause of molecular reorientation in nematic liquid crystal is anisotropy of its molecules have been obtained.
2001, 25(4): 272-274.
Abstract:
A new method has been developed to fabricate micro-lens by etching ammonium dichromate gelatin(ADG) with enzyme.The optimum technical parameters of the process are presented.This process is very simple and time saving.It also doesn't need expensive equipment.Based on this method,a continuous micro-lens array is made.Experimental results are evaluated.
A new method has been developed to fabricate micro-lens by etching ammonium dichromate gelatin(ADG) with enzyme.The optimum technical parameters of the process are presented.This process is very simple and time saving.It also doesn't need expensive equipment.Based on this method,a continuous micro-lens array is made.Experimental results are evaluated.
2001, 25(4): 275-278.
Abstract:
Based on general feature of the telescope resonator laser and the focusing and mode-selection properties of a liquid crystal lens,a conception of liquid crystal telescope laser is put forward.The possibility of this kind of laser is analyzed in theory.Its excellent characteristics are introduced in the end.
Based on general feature of the telescope resonator laser and the focusing and mode-selection properties of a liquid crystal lens,a conception of liquid crystal telescope laser is put forward.The possibility of this kind of laser is analyzed in theory.Its excellent characteristics are introduced in the end.
2001, 25(4): 279-281.
Abstract:
With a grating as the shearing part,a nondestructive inspection technique is presented in the paper.Its principle is discussed in detail and the experimental results show that it is feasible.
With a grating as the shearing part,a nondestructive inspection technique is presented in the paper.Its principle is discussed in detail and the experimental results show that it is feasible.
2001, 25(4): 282-286.
Abstract:
The origins of various holographic noises and methods for restricting noises are discussed in the paper.While making hologram,the contrast of interference fringes is supposed to be increased in order to increase the diffraction.In order to obtain optimum diffraction efficiency and whole result,the ration of reference light and object light is chosen different with objects.In consideration of external environment,the exposure time should not be too long.In a certain condition,there is an optimum exposure time.Under the observation of electronic micrograph,it is shown that the information of interference fringes will be destroyed if the resolution of the recording materials is not high enough.Finally,some related problems are discussed.
The origins of various holographic noises and methods for restricting noises are discussed in the paper.While making hologram,the contrast of interference fringes is supposed to be increased in order to increase the diffraction.In order to obtain optimum diffraction efficiency and whole result,the ration of reference light and object light is chosen different with objects.In consideration of external environment,the exposure time should not be too long.In a certain condition,there is an optimum exposure time.Under the observation of electronic micrograph,it is shown that the information of interference fringes will be destroyed if the resolution of the recording materials is not high enough.Finally,some related problems are discussed.
2001, 25(4): 287-288.
Abstract:
Color blurring which occurs when reconstructed image point is not located in the plane of whole parallax rainbow hologram formed by a grating is quantitatively calculated.Viewed at a fixed point,the lateral and longitudinal displacement of image point caused by wavelength change is obtained.A conclusion is drawn that the color blurring of corresponding image point will disappear when the object point is in the plane of holographic plane.
Color blurring which occurs when reconstructed image point is not located in the plane of whole parallax rainbow hologram formed by a grating is quantitatively calculated.Viewed at a fixed point,the lateral and longitudinal displacement of image point caused by wavelength change is obtained.A conclusion is drawn that the color blurring of corresponding image point will disappear when the object point is in the plane of holographic plane.
2001, 25(4): 290-292.
Abstract:
The feasibility and the state-of-the-art for laser cutting on a large angle plane are analyzed in the paper.The results show that a 6mm-thick 15Cr2Mo1 steel with a large angle oblique plane can be cut by laser when the laser power is set up to 1260W,the spot size at 0.18mm,the oxygen pressure at 0.08MPa,the cutting speed at 1.4m/min,the distance between nozzle and the workpiece at 0.5～0.8mm and appropriate linear interpolation steps in CNC programs are taken.A good laser cutting kerf can be obtained.
The feasibility and the state-of-the-art for laser cutting on a large angle plane are analyzed in the paper.The results show that a 6mm-thick 15Cr2Mo1 steel with a large angle oblique plane can be cut by laser when the laser power is set up to 1260W,the spot size at 0.18mm,the oxygen pressure at 0.08MPa,the cutting speed at 1.4m/min,the distance between nozzle and the workpiece at 0.5～0.8mm and appropriate linear interpolation steps in CNC programs are taken.A good laser cutting kerf can be obtained.
2001, 25(4): 293-296.
Abstract:
The electro-optic crystals used in optical fiber voltage transducers are introduced in the paper.Their point group structures,electro-optic characteristics,possible optical activity,thermo-optic effects,pyroelectric effects and natural birefringence are described.BGO is the best sensing material at present.At the end of the paper,the transducer design is introduced.
The electro-optic crystals used in optical fiber voltage transducers are introduced in the paper.Their point group structures,electro-optic characteristics,possible optical activity,thermo-optic effects,pyroelectric effects and natural birefringence are described.BGO is the best sensing material at present.At the end of the paper,the transducer design is introduced.
2001, 25(4): 297-301.
Abstract:
On the basis of the light scattering theory of spherical particles and the characteristic of the water mist,the optimum optical path for 3D APV(adaptive phase/Doppler velocimeter) and reasonable layout of the system are designed.The particle size,the velocity distribution and the water mist volume flux of the water mist flow field are obtained through experiments.
On the basis of the light scattering theory of spherical particles and the characteristic of the water mist,the optimum optical path for 3D APV(adaptive phase/Doppler velocimeter) and reasonable layout of the system are designed.The particle size,the velocity distribution and the water mist volume flux of the water mist flow field are obtained through experiments.
2001, 25(4): 302-305.
Abstract:
Investigation has been carried out into the laser cladding of several Co-base hard alloy.It shows that the flowability of the molten bath improves and the emerging of gas holes in cladding coating can be eliminated when Al material with low melting point is added and that the wettability of TiC obviously improves and the claddability of hard alloy coating increases when Ni material is added.The hardness of WC-Co cladding coating can reach up to HV0.2 1100.Adding TiC to coating obviously enhances the hardness of cladding coating.The hardness values range from HV0.2 1200 to HV0.2 1300.
Investigation has been carried out into the laser cladding of several Co-base hard alloy.It shows that the flowability of the molten bath improves and the emerging of gas holes in cladding coating can be eliminated when Al material with low melting point is added and that the wettability of TiC obviously improves and the claddability of hard alloy coating increases when Ni material is added.The hardness of WC-Co cladding coating can reach up to HV0.2 1100.Adding TiC to coating obviously enhances the hardness of cladding coating.The hardness values range from HV0.2 1200 to HV0.2 1300.
2001, 25(4): 305-307.
Abstract:
Based on the principle of two-beam coupling,the method of three-stage coherent optical amplification is put forward.Which not only makes it possible that tress pieces of low quality crystals can yield the result that one piece of high quality crystal can reach,but also solves the problem that the amplification coefficient can not be greatly increased by means of one-stage amplification.The feasibility of the method has proved through theoretical analysis.
Based on the principle of two-beam coupling,the method of three-stage coherent optical amplification is put forward.Which not only makes it possible that tress pieces of low quality crystals can yield the result that one piece of high quality crystal can reach,but also solves the problem that the amplification coefficient can not be greatly increased by means of one-stage amplification.The feasibility of the method has proved through theoretical analysis.
2001, 25(4): 308-311.
Abstract:
A new technique of light-section method is proposed to measure 3D profile.A closed light strip in a certain section of foot is formed by laser sheet illumination. Its image can be obtained by 3 CCD cameras, then the real world coordinate of the section of the foot can be worked out through transformation between the coordinate of the section plane and the camera coordinate. Finally,the coordinate of the 3D foot profile can be obtained through measurement along the direction vertical to the light section plane.
A new technique of light-section method is proposed to measure 3D profile.A closed light strip in a certain section of foot is formed by laser sheet illumination. Its image can be obtained by 3 CCD cameras, then the real world coordinate of the section of the foot can be worked out through transformation between the coordinate of the section plane and the camera coordinate. Finally,the coordinate of the 3D foot profile can be obtained through measurement along the direction vertical to the light section plane.
2001, 25(4): 312-316.
Abstract:
The elegant Laguerre-Gaussian(L-G) beams and their propagation properties are studied in detail using the propagation equation derived from the generalized Huygens-Fresnel diffraction integral. The beam propagation factor(M2 factor) and power in the bucket(PIB) are used to characterize beam quality,a comparison of the beam quality of elegant and standard L-G beams is made and the results are analyzed.
The elegant Laguerre-Gaussian(L-G) beams and their propagation properties are studied in detail using the propagation equation derived from the generalized Huygens-Fresnel diffraction integral. The beam propagation factor(M2 factor) and power in the bucket(PIB) are used to characterize beam quality,a comparison of the beam quality of elegant and standard L-G beams is made and the results are analyzed.
2001, 25(4): 317-321.
Abstract:
The theoretical analysis of the performance parameters of measurement volume with off-axis alignment of the LDA-probe has been carried out.The calculated equations of the location,the fringe spacing of the measurement volume,the direction of measured flow velocity in the flow has been deduced.The proportion of the displacements between measurement volume and the LDA-probe has been determined.The results show that the measurement volume with off-axis of the LDA-probe has different performance from that with on-axis probe.
The theoretical analysis of the performance parameters of measurement volume with off-axis alignment of the LDA-probe has been carried out.The calculated equations of the location,the fringe spacing of the measurement volume,the direction of measured flow velocity in the flow has been deduced.The proportion of the displacements between measurement volume and the LDA-probe has been determined.The results show that the measurement volume with off-axis of the LDA-probe has different performance from that with on-axis probe.
