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RSS2013 Vol. 37, No. 3
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2013, 37(3): 277-280.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.001
[Abstract]
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Abstract:
Theoretical analysis and experiments about laser-EMAT(electromagnetic-acoustic transducer) technique were carried out for the purpose of noncontact and nondestructive detection of inner defects of metal parts.The test slab contains a Ф3mm×30mm artificial hole about 40mm beneath the surface.The testing error was about 5%.The result shows that the laser-EMAT technique is suitable for noncontact and nondestructive detection of inner metal defects.
Theoretical analysis and experiments about laser-EMAT(electromagnetic-acoustic transducer) technique were carried out for the purpose of noncontact and nondestructive detection of inner defects of metal parts.The test slab contains a Ф3mm×30mm artificial hole about 40mm beneath the surface.The testing error was about 5%.The result shows that the laser-EMAT technique is suitable for noncontact and nondestructive detection of inner metal defects.
2013, 37(3): 281-283.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.002
Abstract:
In order to realize high-range piezoelectric(PZT)frequency tuning and temperature frequency tuning of a narrow line width Nd:YAG nonplanar ring laser,applying high voltage modulation signals on a thin PZT affixed to a monolithic laser crystal and changing the temperature of the laser crystal on a large scale,the tuning range is up to 210MHz,the response bandwidth is larger than 90kHz and the PZT tuning coefficient is more than 1MHz/V.When the temperature of the laser crystal is changed from 10℃ to 47℃,the laser frequency can be tuned continuously by 8GHz between the mode-hops covering an overall frequency tuning range of 61GHz.The experimental results show that the distortion of the beat signal in high frequency tuning is caused by the distortion of the PZT driving signal.With the advantages of PZT tuning and temperature tuning,good results of laser frequency tuning were obtained in the experiments.
In order to realize high-range piezoelectric(PZT)frequency tuning and temperature frequency tuning of a narrow line width Nd:YAG nonplanar ring laser,applying high voltage modulation signals on a thin PZT affixed to a monolithic laser crystal and changing the temperature of the laser crystal on a large scale,the tuning range is up to 210MHz,the response bandwidth is larger than 90kHz and the PZT tuning coefficient is more than 1MHz/V.When the temperature of the laser crystal is changed from 10℃ to 47℃,the laser frequency can be tuned continuously by 8GHz between the mode-hops covering an overall frequency tuning range of 61GHz.The experimental results show that the distortion of the beat signal in high frequency tuning is caused by the distortion of the PZT driving signal.With the advantages of PZT tuning and temperature tuning,good results of laser frequency tuning were obtained in the experiments.
2013, 37(3): 284-288.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.003
Abstract:
In order to study the effect of phase difference between frequency modulation and amplitude modulation on both the second harmonic signal and its line shape,the mathematical derivations for wavelength modulation spectroscopy were presented in consideration of residual amplitude modulation,and then the theoretical calculation formulas of considering FM-AM phase difference were deduced.In addition,the impact of FM-AM phase difference on harmonic signal line shape was also simulated and calculated.The results show that the second harmonic signal positive peaks and the left and right negative peak as well as the signal baseline are all changed with the FM-AM phase difference.However,the distance between left and right negative peak value is not affected by it,remaining unchanged.The calculation results have important significant on tunable diode laser absorption spectroscopy gas detection.
In order to study the effect of phase difference between frequency modulation and amplitude modulation on both the second harmonic signal and its line shape,the mathematical derivations for wavelength modulation spectroscopy were presented in consideration of residual amplitude modulation,and then the theoretical calculation formulas of considering FM-AM phase difference were deduced.In addition,the impact of FM-AM phase difference on harmonic signal line shape was also simulated and calculated.The results show that the second harmonic signal positive peaks and the left and right negative peak as well as the signal baseline are all changed with the FM-AM phase difference.However,the distance between left and right negative peak value is not affected by it,remaining unchanged.The calculation results have important significant on tunable diode laser absorption spectroscopy gas detection.
2013, 37(3): 289-292.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.004
Abstract:
In order to improve the quality of the infrared image significantly and improve the recognition rate of an artificial target,because the degree of polarization of the image can better highlight the artificial target,the polarization angle can better describe the different objects surface alignment and image I reflects the information about the intensity of the scene,the fusion algorithm of infrared polarization images based on wavelet transform was put forward.Firstly,three infrared images at polarization angle of 0°,60° and 120° were collected with an infrared camera and a polarizer.Secondly,after calculating the I,Q,U images,the images of polarization and polarization angle were obtained.Finally,high-quality infrared polarization images were obtained by fusing image I,the images of degree of polarization and polarization angle together.After analyzing the performance data of each image,the results show that the obtained image data by means of fusion algorithm of infrared polarization image based on wavelet transform is reasonable,the quality of the infrared image and the recognition rate of the artificial objects were improved.
In order to improve the quality of the infrared image significantly and improve the recognition rate of an artificial target,because the degree of polarization of the image can better highlight the artificial target,the polarization angle can better describe the different objects surface alignment and image I reflects the information about the intensity of the scene,the fusion algorithm of infrared polarization images based on wavelet transform was put forward.Firstly,three infrared images at polarization angle of 0°,60° and 120° were collected with an infrared camera and a polarizer.Secondly,after calculating the I,Q,U images,the images of polarization and polarization angle were obtained.Finally,high-quality infrared polarization images were obtained by fusing image I,the images of degree of polarization and polarization angle together.After analyzing the performance data of each image,the results show that the obtained image data by means of fusion algorithm of infrared polarization image based on wavelet transform is reasonable,the quality of the infrared image and the recognition rate of the artificial objects were improved.
2013, 37(3): 293-296.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.005
Abstract:
Rotating inclined optical parallel plate is a kind of optical microscanning method.In order to overcome rigorous requirement for size of optical parallel plate,a large step method of optical microscanning was proposed.Firstly,its effect on the image aliasing and modulation transfer function(MTF) of the detector was theoretically analyzed.Then,it was experimentally confirmed by quantitative comparison of super-resolution image quality.The results indicate that not only machining difficulty is reduced,but also the aliasing is restrained and the MTF is sustained by using the large step microscanning.
Rotating inclined optical parallel plate is a kind of optical microscanning method.In order to overcome rigorous requirement for size of optical parallel plate,a large step method of optical microscanning was proposed.Firstly,its effect on the image aliasing and modulation transfer function(MTF) of the detector was theoretically analyzed.Then,it was experimentally confirmed by quantitative comparison of super-resolution image quality.The results indicate that not only machining difficulty is reduced,but also the aliasing is restrained and the MTF is sustained by using the large step microscanning.
2013, 37(3): 297-300.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.006
Abstract:
In order to improve the performance of a terahertz polarizing beam splitter,a sub-wavelength period metal wire-grid terahertz polarizing beam splitter,based on a copper grating on polyimide(PI) substrate,was fabricated by the way of laser induced and non-electrolytic plating.The good polarization characteristics in the range of 0°~180° polarization angle were verified experimentally using backward wave oscillator at the fixed frequency of 340GHz at the incident angle of 45°,the extinction ratio of 27.3dB and 10.5dB as well as the insertion losses of 0.13dB and 0.32dB were measured for the transmitted and reflected beams,respectively.The broadband transmission of TM wave of the splitter was also measured by terahertz time-domain spectroscopy,and the extinction ratio larger than 18dB was obtained in the frequency range of 0.2THz~1.5THz.The experimental results are in good agreement with the simulation results by means of the finite element method.
In order to improve the performance of a terahertz polarizing beam splitter,a sub-wavelength period metal wire-grid terahertz polarizing beam splitter,based on a copper grating on polyimide(PI) substrate,was fabricated by the way of laser induced and non-electrolytic plating.The good polarization characteristics in the range of 0°~180° polarization angle were verified experimentally using backward wave oscillator at the fixed frequency of 340GHz at the incident angle of 45°,the extinction ratio of 27.3dB and 10.5dB as well as the insertion losses of 0.13dB and 0.32dB were measured for the transmitted and reflected beams,respectively.The broadband transmission of TM wave of the splitter was also measured by terahertz time-domain spectroscopy,and the extinction ratio larger than 18dB was obtained in the frequency range of 0.2THz~1.5THz.The experimental results are in good agreement with the simulation results by means of the finite element method.
2013, 37(3): 301-305.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.007
Abstract:
Theoretical analysis and numerical simulation on the process of ring laser shock forming were conducted with software ABAQUS in this paper to investigate the propagation of shock wave induced by ring laser and its effect on spalling.By defining nodal path,the propagation rule of shock wave induced by ring laser along the direction of thickness was obtained,which shows the occurring time and position of maximum tensile stress along thickness under certain condition.Spalling rule of sheet metal with ring laser shock forming was explored in the perspective of stress wave,whose results indicate that spalling is liable to occur in shocked areas for ring laser while in center of sheet metal for solid area laser,which provides a new approach to study laser shock forming.
Theoretical analysis and numerical simulation on the process of ring laser shock forming were conducted with software ABAQUS in this paper to investigate the propagation of shock wave induced by ring laser and its effect on spalling.By defining nodal path,the propagation rule of shock wave induced by ring laser along the direction of thickness was obtained,which shows the occurring time and position of maximum tensile stress along thickness under certain condition.Spalling rule of sheet metal with ring laser shock forming was explored in the perspective of stress wave,whose results indicate that spalling is liable to occur in shocked areas for ring laser while in center of sheet metal for solid area laser,which provides a new approach to study laser shock forming.
2013, 37(3): 306-309.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.008
Abstract:
In order to increase the surface strength and wear resistance of the parts,TiC-TiB2 reinforced Co-based composite coating was successfully in situ synthesized by laser cladding with preplaced powder method on steel Q235 using TiO2,Al,B4C and KF-Co50 alloy powders as the binding material.The microstructure and phases analysis of the coating were performed with metallographic microscope,scanning electron microscope and X-ray diffractometer.The microhardness and wear resistance of the coating were also tested.The results show that the coating is uniform,continuous and free of pores and cracks.An excellent bonding between the coating and the substrate was ensured by the strong metallurgical interface.The microstructure of the coating is mainly composed of γ-Co,TiC,TiB2 and Cr23C6.The average microhardness of the coating is 770HV0.2 and the coating presents excellent wear resistance.The results have positive significance to improve service life of the parts.
In order to increase the surface strength and wear resistance of the parts,TiC-TiB2 reinforced Co-based composite coating was successfully in situ synthesized by laser cladding with preplaced powder method on steel Q235 using TiO2,Al,B4C and KF-Co50 alloy powders as the binding material.The microstructure and phases analysis of the coating were performed with metallographic microscope,scanning electron microscope and X-ray diffractometer.The microhardness and wear resistance of the coating were also tested.The results show that the coating is uniform,continuous and free of pores and cracks.An excellent bonding between the coating and the substrate was ensured by the strong metallurgical interface.The microstructure of the coating is mainly composed of γ-Co,TiC,TiB2 and Cr23C6.The average microhardness of the coating is 770HV0.2 and the coating presents excellent wear resistance.The results have positive significance to improve service life of the parts.
2013, 37(3): 310-313.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.009
Abstract:
In order to study the effect of wet steam characteristics on the normal operation of the steam turbine unit,a new method was proposed to measure the diameter of the wet steam based on laser scattering principle and co-CCD imaging principle.After simulation,the effect of the size parameter,acceptance angle and other parameters on the backscatter intensity was obtained,optimal parameters were known.When the acceptance angle is 180°and receiver distance is 0.5m,a higher proportion of the scattering can be obtained.The results can provide a good reference for actual measurements.
In order to study the effect of wet steam characteristics on the normal operation of the steam turbine unit,a new method was proposed to measure the diameter of the wet steam based on laser scattering principle and co-CCD imaging principle.After simulation,the effect of the size parameter,acceptance angle and other parameters on the backscatter intensity was obtained,optimal parameters were known.When the acceptance angle is 180°and receiver distance is 0.5m,a higher proportion of the scattering can be obtained.The results can provide a good reference for actual measurements.
2013, 37(3): 314-316.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.010
Abstract:
In order to satisfy the especial requirement of depositing multi-layer coating on the end of fiber,the difficulties in the coating deposition on the end of fiber was analyzed.Firstly,an initial formula was designed by means of resolution method.Then it was optimized with gradient optimization method by using TFCalc formula design software.Finally,the formula of interference edge filter film on the end of fiber was obtained with good spectral properties.The internal structure and deposition technology of LEYBOLD APS1104 deposition machine made in Germany was improved to deposit the designed formula by using ion assistant deposition at low temperature,coating with good performance was acquired.The results show that it is difficult to deposit interference edge filter film on the fiber end,however,the requirements of the interference edge filter film can be met if choosing suitable formula and deposition technology.
In order to satisfy the especial requirement of depositing multi-layer coating on the end of fiber,the difficulties in the coating deposition on the end of fiber was analyzed.Firstly,an initial formula was designed by means of resolution method.Then it was optimized with gradient optimization method by using TFCalc formula design software.Finally,the formula of interference edge filter film on the end of fiber was obtained with good spectral properties.The internal structure and deposition technology of LEYBOLD APS1104 deposition machine made in Germany was improved to deposit the designed formula by using ion assistant deposition at low temperature,coating with good performance was acquired.The results show that it is difficult to deposit interference edge filter film on the fiber end,however,the requirements of the interference edge filter film can be met if choosing suitable formula and deposition technology.
2013, 37(3): 317-320.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.011
Abstract:
The conical microstructures on the silicon wafer surface shaped by irradiating from femtosecond or picosecond laser pulses in SF6 atmosphere was shown and its forming processes were analyzed.The feasibility and necessity were proposed to use nanosecond laser pulses irradiating the surface to enhance some characteristics of the silicon wafer.The forming processes and results of conical microstructures on the silicon wafer surface irradiated by pulsed laser with 6ns width in SF6 atmosphere were described.The silicon wafers both with and without laser pulses treatment were put into product line at the same time to produce silicon solar cell.Then,the two type cells were both measured to compare the photovoltaic conversion efficiency.A preliminary analysis was also given to discuss the experiment results from the point of the surface of silicon wafer.The results showed that the former had higher conversion efficiency in the range of 15% to 25%.
The conical microstructures on the silicon wafer surface shaped by irradiating from femtosecond or picosecond laser pulses in SF6 atmosphere was shown and its forming processes were analyzed.The feasibility and necessity were proposed to use nanosecond laser pulses irradiating the surface to enhance some characteristics of the silicon wafer.The forming processes and results of conical microstructures on the silicon wafer surface irradiated by pulsed laser with 6ns width in SF6 atmosphere were described.The silicon wafers both with and without laser pulses treatment were put into product line at the same time to produce silicon solar cell.Then,the two type cells were both measured to compare the photovoltaic conversion efficiency.A preliminary analysis was also given to discuss the experiment results from the point of the surface of silicon wafer.The results showed that the former had higher conversion efficiency in the range of 15% to 25%.
2013, 37(3): 321-325.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.012
Abstract:
In order to exactly study thermal effects of LD end-pumped rod heat capacity laser crystal Nd:YAG,based on the theory of semi-analytical thermal analysis and the theory of elasticity,the temperature field and thermal stress field,and semi-analytical calculation expression of distortion on end face of rod Nd:YAG heat capacity laser crystal for pumping stage and cooling stage were obtained respectively.These results show that when using the total pump power of 200W LD with 4-order super-Gaussian distribution end-pumped rod Nd:YAG crystal for 2s,the maximum stress on end face is 52.9MPa,which is below the half of the minimum value of crystal fracture threshold.The distortion on the end face is 3.05μm.These results provide a theoretical basis for the optimized design of heat capacity laser.
In order to exactly study thermal effects of LD end-pumped rod heat capacity laser crystal Nd:YAG,based on the theory of semi-analytical thermal analysis and the theory of elasticity,the temperature field and thermal stress field,and semi-analytical calculation expression of distortion on end face of rod Nd:YAG heat capacity laser crystal for pumping stage and cooling stage were obtained respectively.These results show that when using the total pump power of 200W LD with 4-order super-Gaussian distribution end-pumped rod Nd:YAG crystal for 2s,the maximum stress on end face is 52.9MPa,which is below the half of the minimum value of crystal fracture threshold.The distortion on the end face is 3.05μm.These results provide a theoretical basis for the optimized design of heat capacity laser.
2013, 37(3): 326-329.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.013
Abstract:
Laser transparent ceramics has good material properties and optical properties,and has the great advantage of preparation.It's a kind of laser material with good prospects.Correspondingly,transparent ceramic laser has aroused widespread concern in recent years.The progress of the YAG ceramic laser at home and abroad was introduced.Although the history of the YAG ceramic laser is just more than a decade,the YAG ceramic laser develops rapidly;with the further development of the preparation process of the ceramic laser,it may have better development prospects.
Laser transparent ceramics has good material properties and optical properties,and has the great advantage of preparation.It's a kind of laser material with good prospects.Correspondingly,transparent ceramic laser has aroused widespread concern in recent years.The progress of the YAG ceramic laser at home and abroad was introduced.Although the history of the YAG ceramic laser is just more than a decade,the YAG ceramic laser develops rapidly;with the further development of the preparation process of the ceramic laser,it may have better development prospects.
2013, 37(3): 330-333.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.014
Abstract:
In order to achieve synchronous transmission in multimode optical fiber communication,a light injected multimode semiconductor laser open-loop chaotic communication system was constructed,and its performance was numerically simulated.The results show that multimode semiconductor laser chaotic communication system is able to achieve complete synchronization if selecting appropriate system parameters.Corresponding modes of transmitted laser diode(T-LD) and received laser diode(R-LD) can achieve complete synchronization,and the system has a good tolerance to the internal parameter mismatch between T-LD and R-LD.
In order to achieve synchronous transmission in multimode optical fiber communication,a light injected multimode semiconductor laser open-loop chaotic communication system was constructed,and its performance was numerically simulated.The results show that multimode semiconductor laser chaotic communication system is able to achieve complete synchronization if selecting appropriate system parameters.Corresponding modes of transmitted laser diode(T-LD) and received laser diode(R-LD) can achieve complete synchronization,and the system has a good tolerance to the internal parameter mismatch between T-LD and R-LD.
2013, 37(3): 334-337.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.015
Abstract:
In older to monitor all kinds of regional perimeter and identify the intrusion accurately,an all-fiber regional perimeter alarm system was presented based on the non-equilibrium Mach-Zehnder interference.Theoretical analysis and experiments were carried out.The alarm software was developed on the labview platform.The alarm rate of the system reached 95.1% in ten days so that it could distinguish emergencies efficiently and could be used in perimeter alarm system.
In older to monitor all kinds of regional perimeter and identify the intrusion accurately,an all-fiber regional perimeter alarm system was presented based on the non-equilibrium Mach-Zehnder interference.Theoretical analysis and experiments were carried out.The alarm software was developed on the labview platform.The alarm rate of the system reached 95.1% in ten days so that it could distinguish emergencies efficiently and could be used in perimeter alarm system.
2013, 37(3): 338-341.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.016
Abstract:
In order to study the dispersion characteristics of 1-D square doped photonic crystal waveguide,the defect modes of TE wave and TM wave in 1-D square doped photonic crystal waveguide were studied based on the characteristic matrix.Response curves of the defect mode of TE wave and TM wave versus dispersion strength and dispersion thickness were obtained.Dispersion strength and dispersion thickness can produce apparent effect on the defect mode.The defect mode of TE wave and TM wave in 1-D square doped photonic crystal waveguide can be effectively controlled according to the dispersion characteristics of defect mode.
In order to study the dispersion characteristics of 1-D square doped photonic crystal waveguide,the defect modes of TE wave and TM wave in 1-D square doped photonic crystal waveguide were studied based on the characteristic matrix.Response curves of the defect mode of TE wave and TM wave versus dispersion strength and dispersion thickness were obtained.Dispersion strength and dispersion thickness can produce apparent effect on the defect mode.The defect mode of TE wave and TM wave in 1-D square doped photonic crystal waveguide can be effectively controlled according to the dispersion characteristics of defect mode.
2013, 37(3): 347-352.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.018
Abstract:
In order to calculate hologram of 3-D objects quickly,a novel computer-generated hologram method based on iterative Fourier transform was proposed.Considering Fourier transform characteristics of a lens,parallel light reconstruction was changed to point lamp-house irradiation by introducing coding spherical phase factors.Adding the spherical phase factor to iterative computation process to represent depth characteristics,the holograph of 3-D object was obtained.A lookup table was used to reduce the influence of phase factor operation and improve the speed of iterative calculation.The experiment based on spatial light modulator shows that the convergent speciality of this algorithm is good and computational holograph can reconstruct matching object layer in different distance,which has three-dimensional vision effect.
In order to calculate hologram of 3-D objects quickly,a novel computer-generated hologram method based on iterative Fourier transform was proposed.Considering Fourier transform characteristics of a lens,parallel light reconstruction was changed to point lamp-house irradiation by introducing coding spherical phase factors.Adding the spherical phase factor to iterative computation process to represent depth characteristics,the holograph of 3-D object was obtained.A lookup table was used to reduce the influence of phase factor operation and improve the speed of iterative calculation.The experiment based on spatial light modulator shows that the convergent speciality of this algorithm is good and computational holograph can reconstruct matching object layer in different distance,which has three-dimensional vision effect.
2013, 37(3): 353-356.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.019
Abstract:
In order to improve the precision of phase-shift measurement,a kind of high frequency phase method,laser distance measuring system based on high frequency digital detection,was used to improve the measurement precision instead of the analog phase measurement.10MHz laser modulation frequency and the design of digital phase detector were achieved.The collimator lens was designed and the design specifications was listed.Comparative analysis was made before and after beam collimation with ZEMAX.The feasibility of the optical system was verified by the experiments.The maximum standard deviation is 0.12°,and the distance precision can be improved to about 1mm.In addition,the maximum error is 0.09°,while the minimum is 0.011°.These resucts show that the system meets the requirement of accuracy and achieves the purpose of improving the accuracy.
In order to improve the precision of phase-shift measurement,a kind of high frequency phase method,laser distance measuring system based on high frequency digital detection,was used to improve the measurement precision instead of the analog phase measurement.10MHz laser modulation frequency and the design of digital phase detector were achieved.The collimator lens was designed and the design specifications was listed.Comparative analysis was made before and after beam collimation with ZEMAX.The feasibility of the optical system was verified by the experiments.The maximum standard deviation is 0.12°,and the distance precision can be improved to about 1mm.In addition,the maximum error is 0.09°,while the minimum is 0.011°.These resucts show that the system meets the requirement of accuracy and achieves the purpose of improving the accuracy.
2013, 37(3): 357-361.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.020
Abstract:
In order to analyze the influence of heat treatment on the laser cladding layer microstructure,ordering and properties of the intermetallic compounds,the theoretical analysis and experimental verification were carried out using X-ray diffraction experiment and hardness test methods.Through the above experiment,the X-ray diffraction curve of the coated metal,the phase analysis results of the X-ray diffraction of the coated metal and the hardness test data of laser cladding layer were got.The results of the X-ray diffraction experiments showed that the NiAl phase got ordering while the Ni3Al phase did not get ordering in the laser cladding process.The Ni3Al phase got ordering after 4h heat treatment at 1000°C,and the ordering of NiAl phase was retained during the process.The hardness test results showed that the average hardness of the laser cladding alloy layer was 440HV and the average hardness of the coating was 412HV after the heat treatment,with hardness decreased.Heat treatment is conducive to the ordering of the phase of the Ni-Al metal compound,makes laser cladding defects disappear and release stress.
In order to analyze the influence of heat treatment on the laser cladding layer microstructure,ordering and properties of the intermetallic compounds,the theoretical analysis and experimental verification were carried out using X-ray diffraction experiment and hardness test methods.Through the above experiment,the X-ray diffraction curve of the coated metal,the phase analysis results of the X-ray diffraction of the coated metal and the hardness test data of laser cladding layer were got.The results of the X-ray diffraction experiments showed that the NiAl phase got ordering while the Ni3Al phase did not get ordering in the laser cladding process.The Ni3Al phase got ordering after 4h heat treatment at 1000°C,and the ordering of NiAl phase was retained during the process.The hardness test results showed that the average hardness of the laser cladding alloy layer was 440HV and the average hardness of the coating was 412HV after the heat treatment,with hardness decreased.Heat treatment is conducive to the ordering of the phase of the Ni-Al metal compound,makes laser cladding defects disappear and release stress.
2013, 37(3): 362-364.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.021
Abstract:
In order to overcome the shortcomings of the two-step phase-shift digital holography,i.e.,the need to record multiple images and the phase shift error between actual phase shift and theoretical phase shift,a new method was presented to reconstruct the real image based on a single in-line hologram.The method uses characteristics of the Hilbert transform which can achieve digital phase shift and filter the direct-current(DC)component at the same time,Hilbert transform was used twice to the recorded hologram,no DC component holograms with π/2 phase-shift and without phase shift were obtained in turn,and then the two-step phase-shift digital holography method was used to reconstruct the real image.The feasibility of the method was verified through experiments.The experiment results show that the method can well restructure the original image of the object.
In order to overcome the shortcomings of the two-step phase-shift digital holography,i.e.,the need to record multiple images and the phase shift error between actual phase shift and theoretical phase shift,a new method was presented to reconstruct the real image based on a single in-line hologram.The method uses characteristics of the Hilbert transform which can achieve digital phase shift and filter the direct-current(DC)component at the same time,Hilbert transform was used twice to the recorded hologram,no DC component holograms with π/2 phase-shift and without phase shift were obtained in turn,and then the two-step phase-shift digital holography method was used to reconstruct the real image.The feasibility of the method was verified through experiments.The experiment results show that the method can well restructure the original image of the object.
2013, 37(3): 365-370.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.022
Abstract:
To construct a real-time optical encryption system with spatial light modulator,the parameters of phase modulation were analyzed when utilizing spatial light modulator as phase modulators in the double random phase encoding system by means of simulation method.The influence of two important parameters,i.e.,the phase modulation range and the independent point numbers of phase modulation on the encryption quality was investigated extensively.A correlation coefficient was introduced to evaluate the difference between the original image and encrypted image.The simulation results indicate that a satisfying encrypted image can be obtained when the independent point numbers of phase modulation is approaching to 128×128 and the phase modulation range is set to 2π assuming that the correlation coefficient is 0.1.The results are significant for the design of real-time optical encryption system with spatial light modulator.
To construct a real-time optical encryption system with spatial light modulator,the parameters of phase modulation were analyzed when utilizing spatial light modulator as phase modulators in the double random phase encoding system by means of simulation method.The influence of two important parameters,i.e.,the phase modulation range and the independent point numbers of phase modulation on the encryption quality was investigated extensively.A correlation coefficient was introduced to evaluate the difference between the original image and encrypted image.The simulation results indicate that a satisfying encrypted image can be obtained when the independent point numbers of phase modulation is approaching to 128×128 and the phase modulation range is set to 2π assuming that the correlation coefficient is 0.1.The results are significant for the design of real-time optical encryption system with spatial light modulator.
2013, 37(3): 371-375.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.023
Abstract:
A single laser-acoustic pulse is not available in long distance underwater acoustic communication due to its spike pulse and wide frequency spectrum.To improve the spectrum of the leaser acoustic signal,and improve its communication performance,the source was modulated.The mathematical model for modulated laser-acoustic code element was established,a source design method for underwater laser-acoustic communication was presented based on the model.The energy of the code element modulated by the method was concentrated at the frequency that represents the modulation,and the band of the signal was reduced,which made it transmit a further distance in underwater acoustic channel.The modulating parameters of code element induced by laser breakdown and thermoelastic mechanism were calculated.The code element modulated with the method was simulated based on laser signals collected in experiments,whose frequency spectrum proved the validity and the serviceability of the method.
A single laser-acoustic pulse is not available in long distance underwater acoustic communication due to its spike pulse and wide frequency spectrum.To improve the spectrum of the leaser acoustic signal,and improve its communication performance,the source was modulated.The mathematical model for modulated laser-acoustic code element was established,a source design method for underwater laser-acoustic communication was presented based on the model.The energy of the code element modulated by the method was concentrated at the frequency that represents the modulation,and the band of the signal was reduced,which made it transmit a further distance in underwater acoustic channel.The modulating parameters of code element induced by laser breakdown and thermoelastic mechanism were calculated.The code element modulated with the method was simulated based on laser signals collected in experiments,whose frequency spectrum proved the validity and the serviceability of the method.
2013, 37(3): 376-379.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.024
Abstract:
In order to solve the problem that how to keep the thermal effect constant during the procedure of laser heat treatment on a cam,a so-called algorithm,instantaneous concentric reducing tee algorithm(ICRTA) was put forward to control the laser spot moving at an uniform velocity.It can be realized under three presuppositions,i.e.,the relative speed keeps the same when laser spot scans the curved surface of the workpiece,the distance between the focused laser spot and the profile of the workpiece keeps unchanged,the laser beam is incident along the normal direction of the work piece surface all the time.The surface of the work piece contour and the corresponding points of equidistant line have the same center point at the same time.For a certain constant scan speed at the work piece contour surface,the speed of laser head at the corresponding point of equidistant line can be calculated,so that the movement of the laser head can be controlled.Simulation results with MATLAB show the algorithm is feasible.
In order to solve the problem that how to keep the thermal effect constant during the procedure of laser heat treatment on a cam,a so-called algorithm,instantaneous concentric reducing tee algorithm(ICRTA) was put forward to control the laser spot moving at an uniform velocity.It can be realized under three presuppositions,i.e.,the relative speed keeps the same when laser spot scans the curved surface of the workpiece,the distance between the focused laser spot and the profile of the workpiece keeps unchanged,the laser beam is incident along the normal direction of the work piece surface all the time.The surface of the work piece contour and the corresponding points of equidistant line have the same center point at the same time.For a certain constant scan speed at the work piece contour surface,the speed of laser head at the corresponding point of equidistant line can be calculated,so that the movement of the laser head can be controlled.Simulation results with MATLAB show the algorithm is feasible.
2013, 37(3): 380-384.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.025
Abstract:
To improve the ability of optoelectronic countermeasure and defensive and offensive capabilities,the methods of anti-detection should be studied as well as the cat-eye active detecting technology.Influence factors of anti-detection ability were qualitatively and quantitively analyzed by numerical simulation based on the reflected wave power.The simulation results show that reflected wave power is changed with the changing of incident power of detector,optical window area of receiver system,transmittance of emission system,divergent angle of incident laser,diameter and focal length of objective lens and maladjustment of reflector,and it is influenced by diffuse background and system operating wavelength.The research of influence factors provides theoretical basis for anti-detection strategy.
To improve the ability of optoelectronic countermeasure and defensive and offensive capabilities,the methods of anti-detection should be studied as well as the cat-eye active detecting technology.Influence factors of anti-detection ability were qualitatively and quantitively analyzed by numerical simulation based on the reflected wave power.The simulation results show that reflected wave power is changed with the changing of incident power of detector,optical window area of receiver system,transmittance of emission system,divergent angle of incident laser,diameter and focal length of objective lens and maladjustment of reflector,and it is influenced by diffuse background and system operating wavelength.The research of influence factors provides theoretical basis for anti-detection strategy.
2013, 37(3): 385-388.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.026
Abstract:
To achieve accurate spatio-temporal superposition between two femtosecond laser pulses,a CCD imaging system was used to adjust the spatial superposition of both the beams and an energy meter was applied to measure the core energy of the probe pulses so that the temporal separation between the pulses could be adjusted.The dependence of the core energy on the time delay and the corresponding plasma fluorescence distribution were obtained.The experimental result proves that this method can achieve a higher time accuracy(femtosecond scale) than the traditional method,even when the crossing angle between the two femtosecond laser beams is vertical.
To achieve accurate spatio-temporal superposition between two femtosecond laser pulses,a CCD imaging system was used to adjust the spatial superposition of both the beams and an energy meter was applied to measure the core energy of the probe pulses so that the temporal separation between the pulses could be adjusted.The dependence of the core energy on the time delay and the corresponding plasma fluorescence distribution were obtained.The experimental result proves that this method can achieve a higher time accuracy(femtosecond scale) than the traditional method,even when the crossing angle between the two femtosecond laser beams is vertical.
2013, 37(3): 389-393.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.027
Abstract:
In order to solve the problem of the resonant frequency drift caused by the heat produced by high-frequency vibration in a photoelastic modulator interferometer,its thermal regime model was built based on similarity and modeling theory.The nonlinear function relationship among resonant frequency,temperature of the interferometer and outside drive signal was obtained.Finally,the thermal feedback current,the phase relationship between the feedback current and driving voltage,the change rates of the temperature and resonant frequency with time were deduced and the state equation of frequency stability of the interferometer thermal regime model was obtained.Analysis shows that according to thermal feedback mechanism,phase locked tracking theory must be used to maintain drive frequency consistent with resonant frequency of the interferometer all the time so that the interferometer can work stably.
In order to solve the problem of the resonant frequency drift caused by the heat produced by high-frequency vibration in a photoelastic modulator interferometer,its thermal regime model was built based on similarity and modeling theory.The nonlinear function relationship among resonant frequency,temperature of the interferometer and outside drive signal was obtained.Finally,the thermal feedback current,the phase relationship between the feedback current and driving voltage,the change rates of the temperature and resonant frequency with time were deduced and the state equation of frequency stability of the interferometer thermal regime model was obtained.Analysis shows that according to thermal feedback mechanism,phase locked tracking theory must be used to maintain drive frequency consistent with resonant frequency of the interferometer all the time so that the interferometer can work stably.
2013, 37(3): 394-399.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.028
Abstract:
A grating diffraction laser warning system is a type of electro-optic countermeasure equipment based on grating diffraction,it can detect the parameter information of the incident laser in real-time.To get the wavelength and the azimuth of the incident laser,with the grating diffraction principle,the image signal was acquired by a area planar array CCD,the image processing was done by digital signal processor,and the image processing algorithms were exploited.The theory was analyzed and experimental results were verified,the image acquisition and processing of the grating diffraction laser warning system based on area planar array CCD was designed,the detection of the incident laser was realized.The experimental results show that the system can detect and mark the incident laser effectively,the system is stable and real-time.
A grating diffraction laser warning system is a type of electro-optic countermeasure equipment based on grating diffraction,it can detect the parameter information of the incident laser in real-time.To get the wavelength and the azimuth of the incident laser,with the grating diffraction principle,the image signal was acquired by a area planar array CCD,the image processing was done by digital signal processor,and the image processing algorithms were exploited.The theory was analyzed and experimental results were verified,the image acquisition and processing of the grating diffraction laser warning system based on area planar array CCD was designed,the detection of the incident laser was realized.The experimental results show that the system can detect and mark the incident laser effectively,the system is stable and real-time.
2013, 37(3): 400-403.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.029
Abstract:
In order to solve the problem of uneven brightness and decreased sharpness of the projected image caused by the laser speckle rising from the coherence of the light source in the laser projection display,introducing laser into a vibrating multimode optical fiber,the output laser mode field beats between the various modes at high frequency,and homogenized and incoherent results were obtained.The results show that the speckle contrast ratio of the projected image is significantly reduced to 4% or less,which the human eye is difficult to distinguish.
In order to solve the problem of uneven brightness and decreased sharpness of the projected image caused by the laser speckle rising from the coherence of the light source in the laser projection display,introducing laser into a vibrating multimode optical fiber,the output laser mode field beats between the various modes at high frequency,and homogenized and incoherent results were obtained.The results show that the speckle contrast ratio of the projected image is significantly reduced to 4% or less,which the human eye is difficult to distinguish.
2013, 37(3): 404-408.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.030
Abstract:
In order to solve the difficulty of the performance testing of high precision sighting telescope,i.e.,testing its sight-line alteration under various environmental test conditions,a test system was designed based on CCD image test technology.Firstly,the position difference of the anchor was measured through measuring the positions of the connection seat anchor points before and after test.Secondly,according to this data,the fixing base of the precision sighting telescope was adjusted to make the connection seat anchor recover to the initial position.Finally,the alteration of the sight-line was measured and figured out.Based on an optical collimator,the focal length of the CCD optical system was measured and the system accuracy was analyzed.Inpractical engineering applications,the measurement error was less than 2.16" and measuring range was larger than 4320",which met the project requirements.The results show that the test method is accurate and reliable and detection precision is high.This test system offers a method for testing the sight-line alteration of high precision sighting telescopes.
In order to solve the difficulty of the performance testing of high precision sighting telescope,i.e.,testing its sight-line alteration under various environmental test conditions,a test system was designed based on CCD image test technology.Firstly,the position difference of the anchor was measured through measuring the positions of the connection seat anchor points before and after test.Secondly,according to this data,the fixing base of the precision sighting telescope was adjusted to make the connection seat anchor recover to the initial position.Finally,the alteration of the sight-line was measured and figured out.Based on an optical collimator,the focal length of the CCD optical system was measured and the system accuracy was analyzed.Inpractical engineering applications,the measurement error was less than 2.16" and measuring range was larger than 4320",which met the project requirements.The results show that the test method is accurate and reliable and detection precision is high.This test system offers a method for testing the sight-line alteration of high precision sighting telescopes.
2013, 37(3): 409-412.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.031
Abstract:
In order to obtain the frequency spectrum of a photoelastic modulator interferometer,it needs spectrum recovery.Because of the nonlinear phase,the effect of spectrum recovery is poor by using the fast Fourier transform,so the non-uniform fast Fourier transform algorithm was proposed for spectrum recovery of the interference data.Firstly,the interference data with 652.6nm laser passing through the photoelastic modulator interferometer was obtained by the virtual oscilloscope based on high-speed data acquisition card PCI-5122.Then,the spectrum interference data was recovered with Matlab software.The recovery results show that the wavelength measurement error of the collected 652.6nm laser data is less than 1nm,the recovered error is less than 0.1%,which verifies the feasibility of the algorithm for the spectrum recovery of non-uniform photoelastic modulation interference data and have reference value for the design of high-performance photoelastic modulator-Fourier transform spectrometer.
In order to obtain the frequency spectrum of a photoelastic modulator interferometer,it needs spectrum recovery.Because of the nonlinear phase,the effect of spectrum recovery is poor by using the fast Fourier transform,so the non-uniform fast Fourier transform algorithm was proposed for spectrum recovery of the interference data.Firstly,the interference data with 652.6nm laser passing through the photoelastic modulator interferometer was obtained by the virtual oscilloscope based on high-speed data acquisition card PCI-5122.Then,the spectrum interference data was recovered with Matlab software.The recovery results show that the wavelength measurement error of the collected 652.6nm laser data is less than 1nm,the recovered error is less than 0.1%,which verifies the feasibility of the algorithm for the spectrum recovery of non-uniform photoelastic modulation interference data and have reference value for the design of high-performance photoelastic modulator-Fourier transform spectrometer.
2013, 37(3): 413-416.
doi: 10.7510/jgjs.issn.1001-3806.2013.03.032
Abstract:
To evaluate the effectiveness of infrared countermeasure jamming,the evaluation method of infrared countermeasure jamming effect was put forward based on image feature after analyzing the principle of IR imaging guidance,and the structure of image characteristic vector was given.The experiment approves that this method can evaluate the effectiveness of infrared countermeasure jamming effectively and quantitatively,which is helpful to measure the effectiveness of infrared countermeasure jamming.
To evaluate the effectiveness of infrared countermeasure jamming,the evaluation method of infrared countermeasure jamming effect was put forward based on image feature after analyzing the principle of IR imaging guidance,and the structure of image characteristic vector was given.The experiment approves that this method can evaluate the effectiveness of infrared countermeasure jamming effectively and quantitatively,which is helpful to measure the effectiveness of infrared countermeasure jamming.
