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RSS2020 Vol. 44, No. 3
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2020, 44(3): 271-277.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.001
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Abstract:
In order to improve the quality of terahertz image and overcome the problem of edge blur of terahertz image, a super-resolution reconstruction method, which combines rational fractal interpolation and gradient field transform, was proposed in this paper for terahertz image reconstruction with frequencies of 0.25THz, 0.50THz, and 0.75THz. Meanwhile, spatial entropy-based image enhancement and bilateral filtering are introduced to optimize the reconstruction. Experimental results illustrate that after processing interpolated terahertz images by super-resolution reconstruction based on gradient field transform, the edge strength of images with frequencies of 0.25THz, 0.50THz, and 0.75THz were respectively improved by 169%, 116%, and 104%, and the average gradient of those images were improved by 16%, 28%, and 24%, respectively. Moreover, signal frequency and intensity would affect the performance of the reconstruction. This method can recover the detail information in terahertz images, sharpen edges of the object, improve the quality of terahertz images without ringing effect, and has practical value.
In order to improve the quality of terahertz image and overcome the problem of edge blur of terahertz image, a super-resolution reconstruction method, which combines rational fractal interpolation and gradient field transform, was proposed in this paper for terahertz image reconstruction with frequencies of 0.25THz, 0.50THz, and 0.75THz. Meanwhile, spatial entropy-based image enhancement and bilateral filtering are introduced to optimize the reconstruction. Experimental results illustrate that after processing interpolated terahertz images by super-resolution reconstruction based on gradient field transform, the edge strength of images with frequencies of 0.25THz, 0.50THz, and 0.75THz were respectively improved by 169%, 116%, and 104%, and the average gradient of those images were improved by 16%, 28%, and 24%, respectively. Moreover, signal frequency and intensity would affect the performance of the reconstruction. This method can recover the detail information in terahertz images, sharpen edges of the object, improve the quality of terahertz images without ringing effect, and has practical value.
2020, 44(3): 278-282.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.002
Abstract:
To solve the measurement and recognition contradiction between macro-scale and micro-feature of trans-scale miniature parts in precision assembly, a high-precision pose measurement system based on orthogonal binocular vision and inclinometer combination was proposed. The system built the coordinate transformation relationship among imaging unit, auxiliary measurement unit of inclinometer, and clamping unit of parts. An analytical algorithm for high-precision measurement of pose measurement of miniature parts based on the coordination transformation and angle measured by inclinometer was introduced. In experiment, fiber array and jumper were the research object, afterwards spatial pose constantly measurement and automatic assembly experimental platform was built. The results show that position and attitude deviation measured by the combined measurement system are less than (±2μm, ±2μm, ±3μm) and (±0.005°, ±0.004°, ±0.005°), respectively, in the field of 3mm×2mm×2mm. Compared with the traditional measurement methods, the system improves the measurement accuracy of the miniature parts significantly. This method can further satisfy the requirements of pose precision measurement and automatic assembly of miniature parts.
To solve the measurement and recognition contradiction between macro-scale and micro-feature of trans-scale miniature parts in precision assembly, a high-precision pose measurement system based on orthogonal binocular vision and inclinometer combination was proposed. The system built the coordinate transformation relationship among imaging unit, auxiliary measurement unit of inclinometer, and clamping unit of parts. An analytical algorithm for high-precision measurement of pose measurement of miniature parts based on the coordination transformation and angle measured by inclinometer was introduced. In experiment, fiber array and jumper were the research object, afterwards spatial pose constantly measurement and automatic assembly experimental platform was built. The results show that position and attitude deviation measured by the combined measurement system are less than (±2μm, ±2μm, ±3μm) and (±0.005°, ±0.004°, ±0.005°), respectively, in the field of 3mm×2mm×2mm. Compared with the traditional measurement methods, the system improves the measurement accuracy of the miniature parts significantly. This method can further satisfy the requirements of pose precision measurement and automatic assembly of miniature parts.
2020, 44(3): 283-287.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.003
Abstract:
In order to obtain the harmonic plateau, contributed by single harmonic emission peak, an effective method to control the harmonic spectrum by using the negative chirped pulse combined with an ultraviolet pulse has been proposed. It is shown that with the control of the negative chirped pulse, not only the harmonic cutoff can achieve the referenced value, but also the harmonic plateau is coming from the single harmonic emission peak. Further, with the proper introduction of an ultraviolet pulse, the intensity of harmonic plateau can be enhanced and reach the referenced value due to the ultraviolet-resonance-ionization. Finally, an ultra-short 36as pulse can be obtained by superposing the harmonics on the plateau. The present investigation provides a new method to obtain the attosecond pulse by using the low-intensity combined field, which is helpful to the development of the laser source.
In order to obtain the harmonic plateau, contributed by single harmonic emission peak, an effective method to control the harmonic spectrum by using the negative chirped pulse combined with an ultraviolet pulse has been proposed. It is shown that with the control of the negative chirped pulse, not only the harmonic cutoff can achieve the referenced value, but also the harmonic plateau is coming from the single harmonic emission peak. Further, with the proper introduction of an ultraviolet pulse, the intensity of harmonic plateau can be enhanced and reach the referenced value due to the ultraviolet-resonance-ionization. Finally, an ultra-short 36as pulse can be obtained by superposing the harmonics on the plateau. The present investigation provides a new method to obtain the attosecond pulse by using the low-intensity combined field, which is helpful to the development of the laser source.
Research status of Ti-6Al-4V manufactured by selective laser melting for medical device applications
2020, 44(3): 288-298.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.004
Abstract:
Selective laser melting (SLM) is used in medical device manufacturing recently due to the unique capability of fabricating high-complexity structures. With the growing popularity of SLM in medical device manufacturing, this paper mainly reviews the research progress of Ti-6Al-4V fabricated by SLM for surgical medical device applications, including the basic technics of SLM-Ti-6Al-4V fabrication, the achievable mechanical properties, cell compatibility, and some application cases. In addition, we summarizes the underlying problems in the field of medical device manufacturing based on the SLM tethnics. Although the development of SLM formed Ti-6Al-4V is relatively slow in the field of medical application, the existing research and potential indicate that with the continuous intensive research of basic manufacture and the continuous clinical practice, the precise treatment of trauma surgery will undoubtedly become possible.
Selective laser melting (SLM) is used in medical device manufacturing recently due to the unique capability of fabricating high-complexity structures. With the growing popularity of SLM in medical device manufacturing, this paper mainly reviews the research progress of Ti-6Al-4V fabricated by SLM for surgical medical device applications, including the basic technics of SLM-Ti-6Al-4V fabrication, the achievable mechanical properties, cell compatibility, and some application cases. In addition, we summarizes the underlying problems in the field of medical device manufacturing based on the SLM tethnics. Although the development of SLM formed Ti-6Al-4V is relatively slow in the field of medical application, the existing research and potential indicate that with the continuous intensive research of basic manufacture and the continuous clinical practice, the precise treatment of trauma surgery will undoubtedly become possible.
2020, 44(3): 288-298.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.014
Abstract:
In order to understand the isosceles triangular subwavelength grating more deeply, the rigorous coupled-wave method was used forin-depth theoretical analysis and research, and the numerical simulation results of isosceles triangular subwavelength grating were obtained. The influence of grating period and incident angle on the characteristics of isosceles triangle subwavelength grating was analyzed, and the high reflection characteristic of isosceles triangle subwavelength grating was explained from the internal magnetic field distribution. The results show that isosceles triangular subwavelength gratings with different grating thicknesses exhibit different characteristics. When the grating thickness is between 0.54μm and 0.57μm, isosceles triangular subwavelength gratings have wide reflection bandwidth, while when the grating thickness is between 0.58μm and 0.66μm, guided mode resonance could be observed. The research can provide theoretical guidance for the preparation of high performance isosceles triangular subwavelength gratings in the future.
In order to understand the isosceles triangular subwavelength grating more deeply, the rigorous coupled-wave method was used forin-depth theoretical analysis and research, and the numerical simulation results of isosceles triangular subwavelength grating were obtained. The influence of grating period and incident angle on the characteristics of isosceles triangle subwavelength grating was analyzed, and the high reflection characteristic of isosceles triangle subwavelength grating was explained from the internal magnetic field distribution. The results show that isosceles triangular subwavelength gratings with different grating thicknesses exhibit different characteristics. When the grating thickness is between 0.54μm and 0.57μm, isosceles triangular subwavelength gratings have wide reflection bandwidth, while when the grating thickness is between 0.58μm and 0.66μm, guided mode resonance could be observed. The research can provide theoretical guidance for the preparation of high performance isosceles triangular subwavelength gratings in the future.
2020, 44(3): 299-303.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.005
Abstract:
In order to study the effect of laser processing parameters on the slit morphology and surface roughness of vascular stent, the experiment of optical fiber laser cutting of cardiovascular stent 316L was carried out by means of comparative analysis of different parameters. The effects of different process parameters such as laser pulse width, laser power, and cutting speed on the slit morphology and roughness of the material were analyzed, and the optimum combination of process parameters for laser cutting support was obtained. The results show that there are differences in slit morphology and surface roughness in different regions, in which the thickness of the vaporization zone is mainly affected by the pulse width and laser power. When the pulse width is 35μs, the maximum thickness of the slit vaporization zone can reach 120μm. In addition, the roughness of the slit vaporization zone of the support decreases at first and then increases with the increase of the cutting speed. When the cutting speed is 6mm/s, the lowest value of slit surface roughness is 650nm. The results lay a theoretical foundation for the research and subsequent finishing of cardiovascular stent optical fiber.
In order to study the effect of laser processing parameters on the slit morphology and surface roughness of vascular stent, the experiment of optical fiber laser cutting of cardiovascular stent 316L was carried out by means of comparative analysis of different parameters. The effects of different process parameters such as laser pulse width, laser power, and cutting speed on the slit morphology and roughness of the material were analyzed, and the optimum combination of process parameters for laser cutting support was obtained. The results show that there are differences in slit morphology and surface roughness in different regions, in which the thickness of the vaporization zone is mainly affected by the pulse width and laser power. When the pulse width is 35μs, the maximum thickness of the slit vaporization zone can reach 120μm. In addition, the roughness of the slit vaporization zone of the support decreases at first and then increases with the increase of the cutting speed. When the cutting speed is 6mm/s, the lowest value of slit surface roughness is 650nm. The results lay a theoretical foundation for the research and subsequent finishing of cardiovascular stent optical fiber.
2020, 44(3): 304-309.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.006
Abstract:
In order to study the effect of process parameters on weld formation, microstructure characteristics, and properties of the joint welded by laser-melt inert-gas (MIG) hybrid welding, laser-MIG hybrid welding of 6mm A7N01 aluminum alloy plates was carried out with different laser powers, welding speeds, and groove forms. The microstructure and properties of the joints were observed and tested. The results show that as the laser power increases, the weld penetration increases linearly. Furthermore, the higher the welding speed, the smaller the weld width and the penetration depth, and the margin is slightly increased. The welded joints have good adaptability to different groove forms. When the hybrid laser-MIG welding was carried out with the laser power of 3.0kW, welding speed of 1.0m/min, and the Y-shaped 30° groove, the sound joint was obtained. The average tensile strength of the joint is 271MPa, which is 60% of the base metal. The center hardness of the weld is 85.4HV, which is 78% of the base metal. In the joint, the grain in the heat-affected zone is coarsened, the hardness is reduced, and the grain in the fusion zone is dendritic grain, which is easy to produce hydrogen holes in the process. In addition, the grain is equiaxed at the center of weld. This research is conductive to obtaining a well-formed laser-MIG hybrid welding joint of A7N01 aluminum alloy. In addition, the grain is equiaxed at the center of weld.
In order to study the effect of process parameters on weld formation, microstructure characteristics, and properties of the joint welded by laser-melt inert-gas (MIG) hybrid welding, laser-MIG hybrid welding of 6mm A7N01 aluminum alloy plates was carried out with different laser powers, welding speeds, and groove forms. The microstructure and properties of the joints were observed and tested. The results show that as the laser power increases, the weld penetration increases linearly. Furthermore, the higher the welding speed, the smaller the weld width and the penetration depth, and the margin is slightly increased. The welded joints have good adaptability to different groove forms. When the hybrid laser-MIG welding was carried out with the laser power of 3.0kW, welding speed of 1.0m/min, and the Y-shaped 30° groove, the sound joint was obtained. The average tensile strength of the joint is 271MPa, which is 60% of the base metal. The center hardness of the weld is 85.4HV, which is 78% of the base metal. In the joint, the grain in the heat-affected zone is coarsened, the hardness is reduced, and the grain in the fusion zone is dendritic grain, which is easy to produce hydrogen holes in the process. In addition, the grain is equiaxed at the center of weld. This research is conductive to obtaining a well-formed laser-MIG hybrid welding joint of A7N01 aluminum alloy. In addition, the grain is equiaxed at the center of weld.
2020, 44(3): 310-314.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.007
Abstract:
In order to study the intensity characteristics of non-uniformly polarized beams in ocean turbulence, the intensity distribution of the non-uniformly polarized (NUP) beams propagating in the oceanic turbulence was obtained by using the extended Huygens-Fresnel diffraction integral formula. The intensity characteristics of the non-uniformly polarized beams propagating in the seawater were investigated in great detail. It is found that the larger the parameters n and K of the non-uniformly polarized beam are, the more obvious the intensity distribution deviates from the Gaussian distribution. However, with the increase of the propagation distance in the ocean, the intensity distribution returns to the Gaussian distribution under the influence of the oceanic turbulence. In addition, the results also show that the larger the χT is, or the smaller the ε is, or the larger the w is, the more the intensity distribution tends to be Gaussian distribution. The research results have potential application value in ocean optical communication and imaging.
In order to study the intensity characteristics of non-uniformly polarized beams in ocean turbulence, the intensity distribution of the non-uniformly polarized (NUP) beams propagating in the oceanic turbulence was obtained by using the extended Huygens-Fresnel diffraction integral formula. The intensity characteristics of the non-uniformly polarized beams propagating in the seawater were investigated in great detail. It is found that the larger the parameters n and K of the non-uniformly polarized beam are, the more obvious the intensity distribution deviates from the Gaussian distribution. However, with the increase of the propagation distance in the ocean, the intensity distribution returns to the Gaussian distribution under the influence of the oceanic turbulence. In addition, the results also show that the larger the χT is, or the smaller the ε is, or the larger the w is, the more the intensity distribution tends to be Gaussian distribution. The research results have potential application value in ocean optical communication and imaging.
2020, 44(3): 315-320.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.008
Abstract:
In order to realize the on-line measurement of a birefringence fiber (BF) loop mirror (Bi-FLM) strain sensor, the theoretical wavelength-demodulation on-line measurements expression of a Bi-FLM strain sensor was deduced. Two different groups of four-adjacent-wave-valley wavelengths near 1550nm and 1310nm were chosen and substituted into the theoretical expression. Both the calculated strains were basically consistent with the given strains. The result shows that the absolute BF length can be calculated by the random four-adjacent-wave-valley wavelengths, the initial BF length, the initial BF birefringence, and the initial strain dependent birefringence coefficient. Then the strain can be calculated according to the absolute BF length after axial strain and the initial BF length. According to the relative positions of any four-adjacent-wave-valley wavelengths which contained strain information, the noises or external sensing can be distinguished when the interference spectrum changes. By this way, the noises can be eliminated, and the measurement accuracy can be improved. These results can provide guidance for realizing the on-line measurement and improving measurement accuracy of the strain, vibration and other sensors of Bi-FLM.
In order to realize the on-line measurement of a birefringence fiber (BF) loop mirror (Bi-FLM) strain sensor, the theoretical wavelength-demodulation on-line measurements expression of a Bi-FLM strain sensor was deduced. Two different groups of four-adjacent-wave-valley wavelengths near 1550nm and 1310nm were chosen and substituted into the theoretical expression. Both the calculated strains were basically consistent with the given strains. The result shows that the absolute BF length can be calculated by the random four-adjacent-wave-valley wavelengths, the initial BF length, the initial BF birefringence, and the initial strain dependent birefringence coefficient. Then the strain can be calculated according to the absolute BF length after axial strain and the initial BF length. According to the relative positions of any four-adjacent-wave-valley wavelengths which contained strain information, the noises or external sensing can be distinguished when the interference spectrum changes. By this way, the noises can be eliminated, and the measurement accuracy can be improved. These results can provide guidance for realizing the on-line measurement and improving measurement accuracy of the strain, vibration and other sensors of Bi-FLM.
2020, 44(3): 321-325.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.009
Abstract:
In order to investigate the 3-D forming characteristics of multi-layer single-pass arc additive manufacture surface, the laser vision sensing system was built to collect the surface stripe images of arc additive manufacture. An region of interest (ROI) extraction method based on boundary constraints was proposed to locate the weld characteristic curve, getting the laser stripe pixel coordinates of ROI. Through theoretical analysis and experimental verification, the 3-D discrete points set of the arc additive surface were obtained, and the discrete points were fitted to form a 3-D solid surface by Delaunay triangulation algorithm. The results show that 3-D reconstruction accuracy is within 0.2mm by linear calibration method of sawtooth, and the ROI extraction method based on boundary constraints can accurately locate the stripe characteristic curve of the top surface and side surface of the arc additive manufacture. The 3-D reconstruction of the arc additive manufacture surface can visually describe the formation of the weld, which provides a new test method for surface forming inspection of arc additive manufacturing. It is beneficial for 3-D forming detection of arc additive manufacture surface.
In order to investigate the 3-D forming characteristics of multi-layer single-pass arc additive manufacture surface, the laser vision sensing system was built to collect the surface stripe images of arc additive manufacture. An region of interest (ROI) extraction method based on boundary constraints was proposed to locate the weld characteristic curve, getting the laser stripe pixel coordinates of ROI. Through theoretical analysis and experimental verification, the 3-D discrete points set of the arc additive surface were obtained, and the discrete points were fitted to form a 3-D solid surface by Delaunay triangulation algorithm. The results show that 3-D reconstruction accuracy is within 0.2mm by linear calibration method of sawtooth, and the ROI extraction method based on boundary constraints can accurately locate the stripe characteristic curve of the top surface and side surface of the arc additive manufacture. The 3-D reconstruction of the arc additive manufacture surface can visually describe the formation of the weld, which provides a new test method for surface forming inspection of arc additive manufacturing. It is beneficial for 3-D forming detection of arc additive manufacture surface.
2020, 44(3): 326-332.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.010
Abstract:
In order to realize the brazing joint of high strength aluminum-steel, took 08Al steel and aluminum alloy for automobile were taken as the experimental object, and pure aluminum powder was selected as solder by filling powder to carry on the experimental study of dissimilar metal laser fusion brazing. Based on energy dispersive spectroscopy energy spectrum analysis and X-ray diffraction phase analysis, the main intermetallic compounds at the interface of the joint are FeAl, Fe2Al5 and Fe4Al13. The effect of adding brazing flux on the whole forming of the joint and the effect of laser offset on the morphology and mechanical properties of the joint were studied. The results show that the addition of the bonding agent improves the joint forming defect and the wettability of the toe area. When the laser offset is 0.8mm~1.6mm, an effective fusion welding joint is formed. With the increase of laser offset, the wetting angle of the joint increases from 35° to 54°, while the thickness of intermetallic compounds in the reaction layer decreases gradually, and the tensile properties of the reaction layer increase at first and then decrease. When the laser offset is 0.8mm, the wetting angle of the joint is 38°, the thickness of the intermetallic compound in the reaction layer is 8μm, and the average mechanical resistance is 210N/mm, which has high engineering application value. The wetting angle of the weld, the width of the joint and the thickness of the intermetallic compound in the reaction layer determine the mechanical resistance level of the joint. The research will provide technical support and important guidance for ensuring the quality of laser welding of the body.
In order to realize the brazing joint of high strength aluminum-steel, took 08Al steel and aluminum alloy for automobile were taken as the experimental object, and pure aluminum powder was selected as solder by filling powder to carry on the experimental study of dissimilar metal laser fusion brazing. Based on energy dispersive spectroscopy energy spectrum analysis and X-ray diffraction phase analysis, the main intermetallic compounds at the interface of the joint are FeAl, Fe2Al5 and Fe4Al13. The effect of adding brazing flux on the whole forming of the joint and the effect of laser offset on the morphology and mechanical properties of the joint were studied. The results show that the addition of the bonding agent improves the joint forming defect and the wettability of the toe area. When the laser offset is 0.8mm~1.6mm, an effective fusion welding joint is formed. With the increase of laser offset, the wetting angle of the joint increases from 35° to 54°, while the thickness of intermetallic compounds in the reaction layer decreases gradually, and the tensile properties of the reaction layer increase at first and then decrease. When the laser offset is 0.8mm, the wetting angle of the joint is 38°, the thickness of the intermetallic compound in the reaction layer is 8μm, and the average mechanical resistance is 210N/mm, which has high engineering application value. The wetting angle of the weld, the width of the joint and the thickness of the intermetallic compound in the reaction layer determine the mechanical resistance level of the joint. The research will provide technical support and important guidance for ensuring the quality of laser welding of the body.
2020, 44(3): 333-337.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.011
Abstract:
In order to improve the efficiency of identification, reduce the cost of detection, and realize the rapid and non-destructive classification of the automotive bumper fragments, a rapid and accurate identification method about the automotive bumper was proposed based on infrared fingerprint spectroscopy, Newton interpolation polynomial, spectral derivation, and discriminant analysis. Infrared spectra of six kinds of brands of bumper samples including 40 different versions were acquired in this paper, and a discriminant model was established by taking Newton polynomial interpolation, spectral derivation, and other methods into account. The results show that the overall accuracy rate of the discriminant model based on the fingerprint zone (80.0%) is higher than that of the full-band model (77.5%). The accuracy rate of the discriminant based on fingerprint spectroscopy combined with 4th Newton interpolation polynomial processing can reach 85%. Selecting DF1 and DF2 as the discriminant axis to construct the discriminant classification model, the accuracy rate of the discriminant can be promoted to 100%. In summary, combining infrared fingerprint spectroscopy, 4th Newton interpolation polynomial, first derivative and discriminant analysis, the new method has higher accuracy in detecting the automotive bumper, and provides a new idea and reference for the identification of other physical evidence in the forensic science.
In order to improve the efficiency of identification, reduce the cost of detection, and realize the rapid and non-destructive classification of the automotive bumper fragments, a rapid and accurate identification method about the automotive bumper was proposed based on infrared fingerprint spectroscopy, Newton interpolation polynomial, spectral derivation, and discriminant analysis. Infrared spectra of six kinds of brands of bumper samples including 40 different versions were acquired in this paper, and a discriminant model was established by taking Newton polynomial interpolation, spectral derivation, and other methods into account. The results show that the overall accuracy rate of the discriminant model based on the fingerprint zone (80.0%) is higher than that of the full-band model (77.5%). The accuracy rate of the discriminant based on fingerprint spectroscopy combined with 4th Newton interpolation polynomial processing can reach 85%. Selecting DF1 and DF2 as the discriminant axis to construct the discriminant classification model, the accuracy rate of the discriminant can be promoted to 100%. In summary, combining infrared fingerprint spectroscopy, 4th Newton interpolation polynomial, first derivative and discriminant analysis, the new method has higher accuracy in detecting the automotive bumper, and provides a new idea and reference for the identification of other physical evidence in the forensic science.
2020, 44(3): 338-342.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.012
Abstract:
In order to research the scattering properties of Hermite-Gaussian beams in anisotropic media, the paper used a cylindrical vector wave function for the scattering field and internal field of an anisotropic cylinder. Using electromagnetic field boundary conditions and projection method, a method was proposed. The accurate semi-analytical method for studying the scattering properties of Hermite-Gaussian beams from uniaxial anisotropic cylinders was analyzed. The normalized intensity distributions of both the internal-field and near fields of the Hermitian-Gaussian beams through an uniaxial anisotropic cylinder were obtained. The analysis and comparison of two different Hermitage beam incidents were carried out. The results show that both beams have a standing wave phenomenon caused by the superposition of incident and reflected waves after passing through the cylinder, while the TEM10(x′) mode Hermite-Gaussian beam has a enhanced near-field intensity and a significant refraction phenomenon after its incidence. The research results have certain reference value for the application of Hermite-Gaussian beam.
In order to research the scattering properties of Hermite-Gaussian beams in anisotropic media, the paper used a cylindrical vector wave function for the scattering field and internal field of an anisotropic cylinder. Using electromagnetic field boundary conditions and projection method, a method was proposed. The accurate semi-analytical method for studying the scattering properties of Hermite-Gaussian beams from uniaxial anisotropic cylinders was analyzed. The normalized intensity distributions of both the internal-field and near fields of the Hermitian-Gaussian beams through an uniaxial anisotropic cylinder were obtained. The analysis and comparison of two different Hermitage beam incidents were carried out. The results show that both beams have a standing wave phenomenon caused by the superposition of incident and reflected waves after passing through the cylinder, while the TEM10(x′) mode Hermite-Gaussian beam has a enhanced near-field intensity and a significant refraction phenomenon after its incidence. The research results have certain reference value for the application of Hermite-Gaussian beam.
2020, 44(3): 343-348.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.013
Abstract:
In order to realize the application system integration and laser function expansion based on excimer laser source, a new type of excimer laser control system was designed in this paper. The personal computer (PC) terminal was based on LabVIEW software platform to realize human-computer interaction, and the laser terminal was based on microcontroller unit (MCU) main control module to control the hardware circuit and detect sensor signal. Optically isolated RS232 communication was adopted in LabVIEW and MCU. Real-time monitoring and control of excimer laser was achieved through virtual instruments on the computer. By theoretical analysis and experimental verification, it is proved that the system combines the good human-computer interaction with the PC terminal and the high-efficiency and stable real-time control of the MCU terminal. It effectively realizes the design of the overall control system under the strong electromagnetic interference of the discharge excitation excimer laser. The control system has great significance for the integration and functional expansion of excimer laser source based application system.
In order to realize the application system integration and laser function expansion based on excimer laser source, a new type of excimer laser control system was designed in this paper. The personal computer (PC) terminal was based on LabVIEW software platform to realize human-computer interaction, and the laser terminal was based on microcontroller unit (MCU) main control module to control the hardware circuit and detect sensor signal. Optically isolated RS232 communication was adopted in LabVIEW and MCU. Real-time monitoring and control of excimer laser was achieved through virtual instruments on the computer. By theoretical analysis and experimental verification, it is proved that the system combines the good human-computer interaction with the PC terminal and the high-efficiency and stable real-time control of the MCU terminal. It effectively realizes the design of the overall control system under the strong electromagnetic interference of the discharge excitation excimer laser. The control system has great significance for the integration and functional expansion of excimer laser source based application system.
2020, 44(3): 353-357.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.015
Abstract:
In order to simultaneously acquire multi-spectral spectral information and multi-test data synchronization processing, a synchronous acquisition and processing system based on field-programmable gate array(FPGA)+digital signal processor(DSP) was designed. The non-uniform fast Fourier transform (NUFFT) algorithm was used to sample the spectral segments containing the target information, and the theoretical analysis and experimental verification for the non-uniform sampling of multi-spectral data were carried out. The experiments were respectively carried out simultaneously for three different laser wavelengths of 632nm, 880nm, and 980nm. The system was compared with the traditional spectral analysis algorithm. The test results show that the signal-to-noise ratio of the system at the peak position of three wavelengths is 31.6dBm, 36.3dBm, and 32.5dBm, respectively, while the signal-to-noise ratio of the traditional spectrometer is only 20.1dBm, 25.4dBm, and 23.7dBm. It can be seen that the hardware design of the system and the NUFFT algorithm can effectively enhance the signal-to-noise ratio in the process of acquiring multi-spectral spectral information. At the same time, the processing speed of the system is also faster, and it has certain application value in multi-spectral fast processing.
In order to simultaneously acquire multi-spectral spectral information and multi-test data synchronization processing, a synchronous acquisition and processing system based on field-programmable gate array(FPGA)+digital signal processor(DSP) was designed. The non-uniform fast Fourier transform (NUFFT) algorithm was used to sample the spectral segments containing the target information, and the theoretical analysis and experimental verification for the non-uniform sampling of multi-spectral data were carried out. The experiments were respectively carried out simultaneously for three different laser wavelengths of 632nm, 880nm, and 980nm. The system was compared with the traditional spectral analysis algorithm. The test results show that the signal-to-noise ratio of the system at the peak position of three wavelengths is 31.6dBm, 36.3dBm, and 32.5dBm, respectively, while the signal-to-noise ratio of the traditional spectrometer is only 20.1dBm, 25.4dBm, and 23.7dBm. It can be seen that the hardware design of the system and the NUFFT algorithm can effectively enhance the signal-to-noise ratio in the process of acquiring multi-spectral spectral information. At the same time, the processing speed of the system is also faster, and it has certain application value in multi-spectral fast processing.
2020, 44(3): 358-363.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.016
Abstract:
In order to solve the problem of low detection accuracy of Mark circle in traditional printed circuit board (PCB), the curve fitting and optimized fitting algorithm were used to improve the Mark circle detection mode, and the theoretical analysis was carried out. The test platform was built by using microsoft foundation classes (MFC) to embed the standard machine vision algorithm package HALCON for experimental verification. The results showes that the success rate of the method was 97%, the detection accuracy was less than 0.3pixel, and the detection time was less than 100ms. It solved the problem of low accuracy of Mark circle in traditional PCB. At the same time, a large number of test data showed that it could still ensure a good detection effect in the environment where the image was panned, rotated, and zoomed. This research has certain reference to the actual PCB production detection.
In order to solve the problem of low detection accuracy of Mark circle in traditional printed circuit board (PCB), the curve fitting and optimized fitting algorithm were used to improve the Mark circle detection mode, and the theoretical analysis was carried out. The test platform was built by using microsoft foundation classes (MFC) to embed the standard machine vision algorithm package HALCON for experimental verification. The results showes that the success rate of the method was 97%, the detection accuracy was less than 0.3pixel, and the detection time was less than 100ms. It solved the problem of low accuracy of Mark circle in traditional PCB. At the same time, a large number of test data showed that it could still ensure a good detection effect in the environment where the image was panned, rotated, and zoomed. This research has certain reference to the actual PCB production detection.
2020, 44(3): 364-370.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.017
Abstract:
In order to solve the problems of low robustness and inaccurate location of power line suspension point location methods, a power line suspension point location method based on laser point cloud combined with local 3-D reconstruction and iterative search was used to study the location of power line suspension point. The spatial characteristics of power line point clouds were analyzed and the spatial constraints of power lines were deduced, which is used as a growth criterion for region growth based on spatial constraints to realize single power line segmentation across multiple stages. Then, the center point of the tower was extracted by clustering the point cloud of the tower, and the spatial segmentation plane of each power line was delineated on the basis of the angular bisector of the connection line of the center point of the tower. After that, the spatial polynomial local 3-D reconstruction of the power line point cloud near each segmentation plane was carried out; Finally, combined with the iterative search of the segmentation plane, the intersection point of the power line was reconstructed, and the spatial location of the power line suspension point was realized. The results show that for three kinds of voltage grade line point clouds and two kinds of data quality point clouds, the average location deviation is less than 0.09m, and the minimum deviation is 0.03m. This method has high robustness and can accurately locate the power line suspension point in each voltage level and mass point cloud data with high robustness and accuracy, which provides a basis for the subsequent safety analysis of power line simulation based on the suspension point.
In order to solve the problems of low robustness and inaccurate location of power line suspension point location methods, a power line suspension point location method based on laser point cloud combined with local 3-D reconstruction and iterative search was used to study the location of power line suspension point. The spatial characteristics of power line point clouds were analyzed and the spatial constraints of power lines were deduced, which is used as a growth criterion for region growth based on spatial constraints to realize single power line segmentation across multiple stages. Then, the center point of the tower was extracted by clustering the point cloud of the tower, and the spatial segmentation plane of each power line was delineated on the basis of the angular bisector of the connection line of the center point of the tower. After that, the spatial polynomial local 3-D reconstruction of the power line point cloud near each segmentation plane was carried out; Finally, combined with the iterative search of the segmentation plane, the intersection point of the power line was reconstructed, and the spatial location of the power line suspension point was realized. The results show that for three kinds of voltage grade line point clouds and two kinds of data quality point clouds, the average location deviation is less than 0.09m, and the minimum deviation is 0.03m. This method has high robustness and can accurately locate the power line suspension point in each voltage level and mass point cloud data with high robustness and accuracy, which provides a basis for the subsequent safety analysis of power line simulation based on the suspension point.
2020, 44(3): 371-376.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.018
Abstract:
In order to measure the stress birefringence of heat strengthened glass quickly and accurately, and to monitor the product quality in real time, the automatic stress birefringence measurement technology of heat strengthened glass based on laser feedback was studied by combining the semi-classical theory and the three-mirror cavity theory model. The measuring equipment was composed of precision optical elements and motion platform, and the main stress direction of the sample was automatically judged by calculating the duty cycle of the low level of polarized light. The measurement efficiency was improved; The fluctuation range of output voltage was controlled within a narrow range by reducing the gradient of input voltage change, which improves displacement stability of piezoelectric ceramics. The experimental results show that the value of the stress birefringence of the sample is determined by the position of the flipping point in a polarization flipping period on the tuning curve. The maximum deviation of multiple measurements is 6.1nm/cm and the standard deviation is less than 2.0nm/cm in multiple measurements. Such technology has the characteristics of short measurement period, high precision and good repeatability, which is suitable for practical production.
In order to measure the stress birefringence of heat strengthened glass quickly and accurately, and to monitor the product quality in real time, the automatic stress birefringence measurement technology of heat strengthened glass based on laser feedback was studied by combining the semi-classical theory and the three-mirror cavity theory model. The measuring equipment was composed of precision optical elements and motion platform, and the main stress direction of the sample was automatically judged by calculating the duty cycle of the low level of polarized light. The measurement efficiency was improved; The fluctuation range of output voltage was controlled within a narrow range by reducing the gradient of input voltage change, which improves displacement stability of piezoelectric ceramics. The experimental results show that the value of the stress birefringence of the sample is determined by the position of the flipping point in a polarization flipping period on the tuning curve. The maximum deviation of multiple measurements is 6.1nm/cm and the standard deviation is less than 2.0nm/cm in multiple measurements. Such technology has the characteristics of short measurement period, high precision and good repeatability, which is suitable for practical production.
2020, 44(3): 377-381.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.019
Abstract:
In order to obtain true-color night vision images loyal to the visual characteristics of human eyes, a three-band true-color night vision spectral division method was proposed based on the principle of minimum Euclidean distance according to the night spectral characteristics of typical targets and the imaging model of low-light-level night vision system. The experiments based on spectral division method proposed in this work and the traditional method were set up in laboratory and outdoor scenes. Compared with the traditional spectral division method, the proposed method has a better color restoration effect for typical target (green vegetation). Through the analysis of the details (spatial frequency) of the true-color night vision image obtained by the proposed method, the results show that the spatial frequency increases by 61.2% and 52.0% respectively compared with the original low-light-level images. Therefore, night visible light can be separated into three bands by spectral division method based on minimum Euclidean distance, and its spectral information can be effectively utilized to obtain true color night vision images with natural color and richer information than the original low-light level images for typical targets.
In order to obtain true-color night vision images loyal to the visual characteristics of human eyes, a three-band true-color night vision spectral division method was proposed based on the principle of minimum Euclidean distance according to the night spectral characteristics of typical targets and the imaging model of low-light-level night vision system. The experiments based on spectral division method proposed in this work and the traditional method were set up in laboratory and outdoor scenes. Compared with the traditional spectral division method, the proposed method has a better color restoration effect for typical target (green vegetation). Through the analysis of the details (spatial frequency) of the true-color night vision image obtained by the proposed method, the results show that the spatial frequency increases by 61.2% and 52.0% respectively compared with the original low-light-level images. Therefore, night visible light can be separated into three bands by spectral division method based on minimum Euclidean distance, and its spectral information can be effectively utilized to obtain true color night vision images with natural color and richer information than the original low-light level images for typical targets.
2020, 44(3): 382-392.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.020
Abstract:
In order to overcome the detects of Savart polarizer, which is the core device of polarizing interference system, such as complex fabrication process and high difficulty in assembling and adjusting, and to solve problems of interference fringe overlying and modulation decline caused by the assembling and processing errors of Savart polarizer, a method of a polarizing interference system based on a single parallel beam splitter (SPBS) was adopted. The structure and principle of this system were analyzed. Jones matrix and coherence intensity of the light exited from the polarizing interferometer system were derived by matrix transfer function. The interference effect is similar to that of the interferometer system based on Savart polarizer. The relationships between the optical path difference of the system and the incident angle and the incident surface were also analyzed. The correctness of the theoretical analysis was verified by experiments. The results show that because SPBS is simple in structure and not required Multiple unit combinations, there is no assembly error, and the processing error will be greatly reduced.
In order to overcome the detects of Savart polarizer, which is the core device of polarizing interference system, such as complex fabrication process and high difficulty in assembling and adjusting, and to solve problems of interference fringe overlying and modulation decline caused by the assembling and processing errors of Savart polarizer, a method of a polarizing interference system based on a single parallel beam splitter (SPBS) was adopted. The structure and principle of this system were analyzed. Jones matrix and coherence intensity of the light exited from the polarizing interferometer system were derived by matrix transfer function. The interference effect is similar to that of the interferometer system based on Savart polarizer. The relationships between the optical path difference of the system and the incident angle and the incident surface were also analyzed. The correctness of the theoretical analysis was verified by experiments. The results show that because SPBS is simple in structure and not required Multiple unit combinations, there is no assembly error, and the processing error will be greatly reduced.
2020, 44(3): 388-392.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.021
Abstract:
In order to study the propagation characteristics of super-Gaussian pulse in super-Gaussian dispersion decreasing fiber with different steepness, the nonlinear evolution of Gaussian pulse in the super-Gaussian dispersion-decreasing fiber was numerically simulated by using the nonlinear Schrödinger equation and the stepwise Fourier transform method. The theoretical analysis and experimental verification of the super-Gaussian pulse in the time domain and frequency domain were carried out with consideration of dispersion and nonlinear effect in the abnormal dispersion zone. The results show that, when the steepness m=4, the super-Gaussian dispersion-decreasing fiber has the best transmission characteristics, so it is concluded that the higher the steepness m is, the better the transmission characteristics of pulse will be.
In order to study the propagation characteristics of super-Gaussian pulse in super-Gaussian dispersion decreasing fiber with different steepness, the nonlinear evolution of Gaussian pulse in the super-Gaussian dispersion-decreasing fiber was numerically simulated by using the nonlinear Schrödinger equation and the stepwise Fourier transform method. The theoretical analysis and experimental verification of the super-Gaussian pulse in the time domain and frequency domain were carried out with consideration of dispersion and nonlinear effect in the abnormal dispersion zone. The results show that, when the steepness m=4, the super-Gaussian dispersion-decreasing fiber has the best transmission characteristics, so it is concluded that the higher the steepness m is, the better the transmission characteristics of pulse will be.
2020, 44(3): 393-398.
doi: 10.7510/jgjs.issn.1001-3806.2020.03.022
Abstract:
The development of metal 3-D printing technology was summarized in this paper. The advantages and disadvantages of various types of 3-D printing technologies were illustrated, main technical features of several typical 3-D printing technologies were discussed though their development history and working principles. On this basis, the future research direction of selective laser melting was put forward: The selective laser melting has a wider range of applications. The metal 3-D printing technology could be improved by promoting material performance, equipment function, structure design, and manufacturing technology. With the development of metal 3-D printing technology, the technologies will be more widely available in metalworking industries, and become the one of most important technology and strategic manufacturing technology.
The development of metal 3-D printing technology was summarized in this paper. The advantages and disadvantages of various types of 3-D printing technologies were illustrated, main technical features of several typical 3-D printing technologies were discussed though their development history and working principles. On this basis, the future research direction of selective laser melting was put forward: The selective laser melting has a wider range of applications. The metal 3-D printing technology could be improved by promoting material performance, equipment function, structure design, and manufacturing technology. With the development of metal 3-D printing technology, the technologies will be more widely available in metalworking industries, and become the one of most important technology and strategic manufacturing technology.
