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RSS2020 Vol. 44, No. 6
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2020, 44(6): 657-663.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.001
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Abstract:
Bi-doped optical fibers have broad application prospects in fiber amplifiers and lasers due to the unique luminescence characteristics. In order to understand the luminescence mechanism of Bi-doped optical fiber and develop the Bi-doped material with high-efficiency and high-performance, the research achievements in the luminescence mechanism of Bi-doped optical fiber were summarized. Based on the atomic structure and luminescence characteristics of bismuth active centers(BAC), the authors summarized the relationship between different structures and luminescence wavelength in Bi-doped optical fiber. Due to their advantages of long fluorescence life and wide spectral range, Bi-doped materials are expected to be more widely used in the fields of ultra-wideband light sources, ultra-wideband amplifiers, tunable lasers, and so on.
Bi-doped optical fibers have broad application prospects in fiber amplifiers and lasers due to the unique luminescence characteristics. In order to understand the luminescence mechanism of Bi-doped optical fiber and develop the Bi-doped material with high-efficiency and high-performance, the research achievements in the luminescence mechanism of Bi-doped optical fiber were summarized. Based on the atomic structure and luminescence characteristics of bismuth active centers(BAC), the authors summarized the relationship between different structures and luminescence wavelength in Bi-doped optical fiber. Due to their advantages of long fluorescence life and wide spectral range, Bi-doped materials are expected to be more widely used in the fields of ultra-wideband light sources, ultra-wideband amplifiers, tunable lasers, and so on.
2020, 44(6): 664-667.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.002
Abstract:
In order to reduce the affect of the deformation offset of different installation platforms on the ground thermal drift calibration of multiple star sensors, a multiple star sensor ground thermal drift calibration position error detection method was proposed. Theoretical analysis and experimental verification were carried out. The position deviation data of the reference square prism deformation in the system under the vacuum of -25℃~60℃ was obtained. And the accuracy analysis of calibration position error was carried out.The results show that, the maximum offsets of the multi-star sensor positions around each axis are -39.341″/℃, -0.060″/℃, and -24.137″/℃, repectively. By establishing the error detection model which was established according to the method of measuring position error, the position error was removed from the offset of the attitude measurement result to obtain a more accurate star sensor attitude measurement quaternion. And the system accuracy after removing the position error was improved by at least 11%, which means it has a good application prospect in improving the accuracy of star sensor thermal drift calibration.
In order to reduce the affect of the deformation offset of different installation platforms on the ground thermal drift calibration of multiple star sensors, a multiple star sensor ground thermal drift calibration position error detection method was proposed. Theoretical analysis and experimental verification were carried out. The position deviation data of the reference square prism deformation in the system under the vacuum of -25℃~60℃ was obtained. And the accuracy analysis of calibration position error was carried out.The results show that, the maximum offsets of the multi-star sensor positions around each axis are -39.341″/℃, -0.060″/℃, and -24.137″/℃, repectively. By establishing the error detection model which was established according to the method of measuring position error, the position error was removed from the offset of the attitude measurement result to obtain a more accurate star sensor attitude measurement quaternion. And the system accuracy after removing the position error was improved by at least 11%, which means it has a good application prospect in improving the accuracy of star sensor thermal drift calibration.
2020, 44(6): 668-673.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.003
Abstract:
In order to evaluate the plane mirror surface shape error, the surface shape detection principle based on the fringe reflection method was adopted, and the method for realizing the plane shape error evaluation by the plane mirror normal offset was used. The sine fringe was projected on the light screen, reflected by the plane mirror to the camera, and the normal of a point on the plane mirror was obtained through the imaging principle of the small hole and the four-step phase shift method. And this point was reconstructed by the least square algorithm surface shape. Theoretical normal comparison was used to obtain the normal offset of the point, and the surface shape evaluation of the plane mirror was achieved by using the normal offset. Computer simulation of the measurement method to prove its correctness; set up an experimental measurement system, and perform measurement experiments on a certain mobile phone screen. The results show that the repeatability accuracy of this measurement method is better than 1mrad, and the measurement repeatability is high. This study provides a reference for the flat surface shape error of glass panels and other products with high reflection characteristics.
In order to evaluate the plane mirror surface shape error, the surface shape detection principle based on the fringe reflection method was adopted, and the method for realizing the plane shape error evaluation by the plane mirror normal offset was used. The sine fringe was projected on the light screen, reflected by the plane mirror to the camera, and the normal of a point on the plane mirror was obtained through the imaging principle of the small hole and the four-step phase shift method. And this point was reconstructed by the least square algorithm surface shape. Theoretical normal comparison was used to obtain the normal offset of the point, and the surface shape evaluation of the plane mirror was achieved by using the normal offset. Computer simulation of the measurement method to prove its correctness; set up an experimental measurement system, and perform measurement experiments on a certain mobile phone screen. The results show that the repeatability accuracy of this measurement method is better than 1mrad, and the measurement repeatability is high. This study provides a reference for the flat surface shape error of glass panels and other products with high reflection characteristics.
2020, 44(6): 674-677.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.004
Abstract:
In order to improve the amplification efficiency of high repetition frequency Nd:YVO4 laser, a new method of double-pass amplification for the uniaxial crystal like Nd:YVO4 was introduced. The Faraday isolator and Nd:YVO4 was placed with a rotation angle of 45°, and this method could be applied to keep the polarization direction of the seed laser in parallel with the Nd:YVO4 c-axis. The simulation results show that the seed laser with 1W average power could be amplified to 36.2W in this double-pass amplification, and the amplification factor was improved 41.5% corresponding to a amplification method consisted with a polarizer and a quarter wave plate. This study is very important for laser amplify of weak seeds with Nd:YVO4 as laser amplification.
In order to improve the amplification efficiency of high repetition frequency Nd:YVO4 laser, a new method of double-pass amplification for the uniaxial crystal like Nd:YVO4 was introduced. The Faraday isolator and Nd:YVO4 was placed with a rotation angle of 45°, and this method could be applied to keep the polarization direction of the seed laser in parallel with the Nd:YVO4 c-axis. The simulation results show that the seed laser with 1W average power could be amplified to 36.2W in this double-pass amplification, and the amplification factor was improved 41.5% corresponding to a amplification method consisted with a polarizer and a quarter wave plate. This study is very important for laser amplify of weak seeds with Nd:YVO4 as laser amplification.
2020, 44(6): 678-683.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.005
Abstract:
In order to improve the accuracy and speed of LiDAR point cloud registration, a point cloud coarse entropy that used particle swarm algorithm based on the improved beetle algorithm was adopted. The method useed the point cloud distribution entropy as the optimization target to find the optimal spatial transformation matrix, and provided a good initial condition for the precise registration of the point cloud. Through theoretical analysis and simulation verification, it was proved that the point cloud entropy is an evaluation method which has faster calculation speed than the traditional mean squared difference, and the particle swarm optimization algorithm improved by beetle antennae algorithm has the characteristics of strong global search ability and fast calculation speed. Compared with the traditional point cloud coarse registration method, the registration method has improved the registration speed by nearly 25%. Under the condition of large amount of point cloud data, it still shows a faster registration speed. This method has a reference significance for how to improve the registration speed of laser point cloud.
In order to improve the accuracy and speed of LiDAR point cloud registration, a point cloud coarse entropy that used particle swarm algorithm based on the improved beetle algorithm was adopted. The method useed the point cloud distribution entropy as the optimization target to find the optimal spatial transformation matrix, and provided a good initial condition for the precise registration of the point cloud. Through theoretical analysis and simulation verification, it was proved that the point cloud entropy is an evaluation method which has faster calculation speed than the traditional mean squared difference, and the particle swarm optimization algorithm improved by beetle antennae algorithm has the characteristics of strong global search ability and fast calculation speed. Compared with the traditional point cloud coarse registration method, the registration method has improved the registration speed by nearly 25%. Under the condition of large amount of point cloud data, it still shows a faster registration speed. This method has a reference significance for how to improve the registration speed of laser point cloud.
2020, 44(6): 684-687.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.006
Abstract:
A photoelectric thermometer was designed based on the temperature measurement principles of double line of atomic emission spectroscopy, which could be used to measure the transient high temperature in complicated environment. The static constant calibration experiment was conducted, where CuⅠ 510.5nm and CuⅠ 521.8nm were selected from the atomic spectra database as the temperature measurement element spectral lines. In the obtained constant values, A and B were 0.1083 and 628.387, respectively. Cu combustion temperature field was measured by the calibrated photoelectric thermometer. The obtained data was compared with temperatures measured by M5 infrared thermometer calibrated by the metrology department. The results show that the average relative error for the two methods is 1.3%, which provides a theoretical basis for the accurate measurement of transient high temperature by the atomic emission spectroscopy method.
A photoelectric thermometer was designed based on the temperature measurement principles of double line of atomic emission spectroscopy, which could be used to measure the transient high temperature in complicated environment. The static constant calibration experiment was conducted, where CuⅠ 510.5nm and CuⅠ 521.8nm were selected from the atomic spectra database as the temperature measurement element spectral lines. In the obtained constant values, A and B were 0.1083 and 628.387, respectively. Cu combustion temperature field was measured by the calibrated photoelectric thermometer. The obtained data was compared with temperatures measured by M5 infrared thermometer calibrated by the metrology department. The results show that the average relative error for the two methods is 1.3%, which provides a theoretical basis for the accurate measurement of transient high temperature by the atomic emission spectroscopy method.
2020, 44(6): 688-694.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.007
Abstract:
Mid- and long-infrared detector based on antimonide type-Ⅱ superlattice has drawn extensive attention and research due to its excellent performance. The detection mechanism, material structure, device performance and current application of antimonide type-Ⅱ superlattice detectors are reviewed. Additionally, the research progress of type-Ⅱ superlattice in mid- and long-infrared avalanche photodiodes is also introduced. Some indicators of the antimonide type-Ⅱ superlattice detectors have approached, or even exceeded those of the HgCdTe detectors. Such superlattice detectors have been applied in some infrared equipment. Avalanche photodetectors based on antimonide type-Ⅱ superlattice are still in their infancy in the field of mid- and long-infrared week light detection. On the other hand, they show great development potential when compared with HgCdTe avalanche detectors.
Mid- and long-infrared detector based on antimonide type-Ⅱ superlattice has drawn extensive attention and research due to its excellent performance. The detection mechanism, material structure, device performance and current application of antimonide type-Ⅱ superlattice detectors are reviewed. Additionally, the research progress of type-Ⅱ superlattice in mid- and long-infrared avalanche photodiodes is also introduced. Some indicators of the antimonide type-Ⅱ superlattice detectors have approached, or even exceeded those of the HgCdTe detectors. Such superlattice detectors have been applied in some infrared equipment. Avalanche photodetectors based on antimonide type-Ⅱ superlattice are still in their infancy in the field of mid- and long-infrared week light detection. On the other hand, they show great development potential when compared with HgCdTe avalanche detectors.
2020, 44(6): 695-699.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.008
Abstract:
The laser-silicon interaction process was investigated with the superposed radiation of two pulsed lasers. A pulse duration of 1ms was superposed by 7ns pulses, creating a combined pulse laser (CPL). The experimental study of single millisecond pulse laser and CPL irradiation on silicon wafer was carried out, respectively. Along with numerical calculation, the surface damage morphology caused by the two laser operation modes was compared. It can be divided into three kinds according to different delays of CPL. Further research was done on the melting depth and damage radius. The results show that the damage effect induced by CPL is more severe, including cleavage cracks, ablation and fold. The damage radius on the surface mainly depends on the energy density of incident ms laser, and the melting depth decreases with the increase of delay time. The better damage effect of CPL is ascribed to the pre-heating ms laser and the interaction of the follow-up ms laser with the surface damage formed by the ns laser. The results can be used as a reference for the processing of semiconductor materials by combined pulse laser in the future.
The laser-silicon interaction process was investigated with the superposed radiation of two pulsed lasers. A pulse duration of 1ms was superposed by 7ns pulses, creating a combined pulse laser (CPL). The experimental study of single millisecond pulse laser and CPL irradiation on silicon wafer was carried out, respectively. Along with numerical calculation, the surface damage morphology caused by the two laser operation modes was compared. It can be divided into three kinds according to different delays of CPL. Further research was done on the melting depth and damage radius. The results show that the damage effect induced by CPL is more severe, including cleavage cracks, ablation and fold. The damage radius on the surface mainly depends on the energy density of incident ms laser, and the melting depth decreases with the increase of delay time. The better damage effect of CPL is ascribed to the pre-heating ms laser and the interaction of the follow-up ms laser with the surface damage formed by the ns laser. The results can be used as a reference for the processing of semiconductor materials by combined pulse laser in the future.
2020, 44(6): 700-705.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.009
Abstract:
In order to avoid the distort of the edge area of the image from the acquired data through a fisheye lens, a simple method of combining a mobile phone camera and a linear polarizer was adopted in this study. The method was used for theoretical analysis and practical verification, and data on the distribution of the atmospheric polarization pattern and the position of the neutral points were obtained. The results show that the deviation of the altitude angle between the actual measured the area of the neutral point and the result of theoretical simulation is 2.4°±2.6°; the deviation of the azimuth angle is 1.4°±0.8°, which proves the feasibility of the measurement method. As the increasing of the clouds in the sky, the image of the polarization pattern distribution of sky light will be distorted, especially the polarization angle image. However, it is still possible to determine the position of the neutral points, thereby determining the navigation reference line, and providing a reference for polarized bionic navigation of sky light. The research can also be used to determine the position of the sun, achieve self-orientation, and navigation positioning. The method used in this research has the advantages of easy operation and portability. This method reduces the cost of sky light polarized bionic navigation to a certain extent, and improves the civilian value.
In order to avoid the distort of the edge area of the image from the acquired data through a fisheye lens, a simple method of combining a mobile phone camera and a linear polarizer was adopted in this study. The method was used for theoretical analysis and practical verification, and data on the distribution of the atmospheric polarization pattern and the position of the neutral points were obtained. The results show that the deviation of the altitude angle between the actual measured the area of the neutral point and the result of theoretical simulation is 2.4°±2.6°; the deviation of the azimuth angle is 1.4°±0.8°, which proves the feasibility of the measurement method. As the increasing of the clouds in the sky, the image of the polarization pattern distribution of sky light will be distorted, especially the polarization angle image. However, it is still possible to determine the position of the neutral points, thereby determining the navigation reference line, and providing a reference for polarized bionic navigation of sky light. The research can also be used to determine the position of the sun, achieve self-orientation, and navigation positioning. The method used in this research has the advantages of easy operation and portability. This method reduces the cost of sky light polarized bionic navigation to a certain extent, and improves the civilian value.
2020, 44(6): 706-709.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.010
Abstract:
In order to explore the effects of the initial first-order phase modulation on the long distance propagation properties of Gaussian optical pulses in optical fibers, evolutions of initially first-order phase modulated Gaussian optical pulses in terms of their shapes, amplitudes, and temporal trajectories, were numerically investigated by starting from the nonlinear evolution equation governing the optical pulse propagation and using the split-step Fourier algorithm. The results show that, the Gaussian pulses exhibit damped oscillation behavior in terms of their amplitudes on the one hand and shift towards the leading or trailing edges of the pulses along straight lines in terms of their temporal trajectories on the other hand due to the first-order phase modulation. The shifting magnitude and direction respectively depend on the absolute value and sign of the phase modulation parameters. This work can extend study on long distance propagation properties of non-soliton pulses. Moreover, it can also be applied in straight-line manipulating of temporal trajectories.
In order to explore the effects of the initial first-order phase modulation on the long distance propagation properties of Gaussian optical pulses in optical fibers, evolutions of initially first-order phase modulated Gaussian optical pulses in terms of their shapes, amplitudes, and temporal trajectories, were numerically investigated by starting from the nonlinear evolution equation governing the optical pulse propagation and using the split-step Fourier algorithm. The results show that, the Gaussian pulses exhibit damped oscillation behavior in terms of their amplitudes on the one hand and shift towards the leading or trailing edges of the pulses along straight lines in terms of their temporal trajectories on the other hand due to the first-order phase modulation. The shifting magnitude and direction respectively depend on the absolute value and sign of the phase modulation parameters. This work can extend study on long distance propagation properties of non-soliton pulses. Moreover, it can also be applied in straight-line manipulating of temporal trajectories.
2020, 44(6): 710-715.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.011
Abstract:
Cigarette ash is an important material evidence at the scene of the case. In order to achieve the purpose of rapid non-destructive detection of cigarette ash, 83 collected cigarette ash samples were theoretically analyzed and then tested by energy dispersive X-ray fluorescence spectrometer. A classification model of cigarette ash based on chemometrics was established. First of all, cluster analysis was used to distinguish samples, and the accuracy of clustering results was tested by regression analysis. Then, the material elements were used as variables and the discriminant classification model was established by discriminant analysis. The results show that the clustering results are good, and the regression analysis shows that the cluster analysis categories and elements can establish a good fitting relationship. The accuracy of the classification model obtained by the discriminant analysis is 100%. If you want to classify the unknown cigarette ash samples, you only need to input the relevant variables of the discriminant model, which will show its location in the discriminant distribution map, and then you can classify the samples. This method is simple, fast, accurate and reliable. This study provides a reference for the actual handling of cases at the grassroots of public security.
Cigarette ash is an important material evidence at the scene of the case. In order to achieve the purpose of rapid non-destructive detection of cigarette ash, 83 collected cigarette ash samples were theoretically analyzed and then tested by energy dispersive X-ray fluorescence spectrometer. A classification model of cigarette ash based on chemometrics was established. First of all, cluster analysis was used to distinguish samples, and the accuracy of clustering results was tested by regression analysis. Then, the material elements were used as variables and the discriminant classification model was established by discriminant analysis. The results show that the clustering results are good, and the regression analysis shows that the cluster analysis categories and elements can establish a good fitting relationship. The accuracy of the classification model obtained by the discriminant analysis is 100%. If you want to classify the unknown cigarette ash samples, you only need to input the relevant variables of the discriminant model, which will show its location in the discriminant distribution map, and then you can classify the samples. This method is simple, fast, accurate and reliable. This study provides a reference for the actual handling of cases at the grassroots of public security.
2020, 44(6): 716-720.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.012
Abstract:
In order to extract the characteristic information of the target echo signal and improve the simulation accuracy of the echo signal, a digital simulation method was adopted to record the echo data in the ground verification test. Quadric surface element was used as the basic element of geometric modeling to establish the target geometric model. Based on the material of the target surface and the measured data of bidirectional reflectnace distrbution function (BRDF), five-parameter modeling was carried out for samples of different wavelength from different angles by combining genetic optimization algorithm. The amplitude of point return wave of target under different environment was verified by the method of region joint discrimination of echo envelope rising rate. The results show that the deviation between the voltage in the cloud environment and the ideal environment is about 65.3%, the enveloped trend satisfies the criterion of target recognition, and the anti-interference is realized in the cloud environment, which can modify and improve the simulation model of target echo signal in the cloud and smoke environment and improve the simulation accuracy.
In order to extract the characteristic information of the target echo signal and improve the simulation accuracy of the echo signal, a digital simulation method was adopted to record the echo data in the ground verification test. Quadric surface element was used as the basic element of geometric modeling to establish the target geometric model. Based on the material of the target surface and the measured data of bidirectional reflectnace distrbution function (BRDF), five-parameter modeling was carried out for samples of different wavelength from different angles by combining genetic optimization algorithm. The amplitude of point return wave of target under different environment was verified by the method of region joint discrimination of echo envelope rising rate. The results show that the deviation between the voltage in the cloud environment and the ideal environment is about 65.3%, the enveloped trend satisfies the criterion of target recognition, and the anti-interference is realized in the cloud environment, which can modify and improve the simulation model of target echo signal in the cloud and smoke environment and improve the simulation accuracy.
2020, 44(6): 721-725.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.013
Abstract:
In order to understand the effect of nuclear motion of H2+ and T+ 2on harmonic intensity and attosecond pulse generation, the intensity changes in the harmonic cutoff region from H2+ and T2+ driven by a 10fs and 20fs lasers were theoretically studied by numerically solving the time-dependent SchrÖdinger equation. The results show that the harmonic intensity follows as H2+ > T2+ under shorter pulse duration case; it follows as T2+ > H2+ under longer pulse duration case. According to the changing law of harmonic intensity, the high intensity and high energy harmonic plateau can be obtained by introducing the half-cycle laser pulse under the optimal harmonic emission intensity, and then the attosecond pulse with pulse duration of 37as can be obtained. The study provides a new way to detect isotopic molecules and generate high intensity and high energy attosecond pulses.
In order to understand the effect of nuclear motion of H2+ and T+ 2on harmonic intensity and attosecond pulse generation, the intensity changes in the harmonic cutoff region from H2+ and T2+ driven by a 10fs and 20fs lasers were theoretically studied by numerically solving the time-dependent SchrÖdinger equation. The results show that the harmonic intensity follows as H2+ > T2+ under shorter pulse duration case; it follows as T2+ > H2+ under longer pulse duration case. According to the changing law of harmonic intensity, the high intensity and high energy harmonic plateau can be obtained by introducing the half-cycle laser pulse under the optimal harmonic emission intensity, and then the attosecond pulse with pulse duration of 37as can be obtained. The study provides a new way to detect isotopic molecules and generate high intensity and high energy attosecond pulses.
2020, 44(6): 726-731.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.014
Abstract:
In order to study the characteristics of laser-induced droplet plasma, based on the synchronous system of pulsed laser and droplet, the direct imaging method and the shadow method were used to study the expansion characteristics of droplet plasma and the motion of droplets. Firstly, the evolution of the plume of water droplet plasma over time was studied by using the intensified charge-coupled device (ICCD) direct imaging method. Then, the shadow image evolution of laser water droplets was studied by shadow method. The changes of the shock wave and the droplet clusters generated by the laser droplets were observed, the expansion speed and the expansion distance of the shock wave with time were calculated and analyzed. The results show that the plasma expansion shape of droplets induced by laser is approximately elliptical, with one side along the incident direction of the laser having a higher radiation intensity. The expansion of the plasma within 100ns is approximately linear expansion, and the expansion tends to be stable after 100ns. In addition, the shock wave expansion radius increases linearly with time and the shock wave expands at a rate of approximately 90m/s. These findings can provide a reference for laser-induced droplet experiments.
In order to study the characteristics of laser-induced droplet plasma, based on the synchronous system of pulsed laser and droplet, the direct imaging method and the shadow method were used to study the expansion characteristics of droplet plasma and the motion of droplets. Firstly, the evolution of the plume of water droplet plasma over time was studied by using the intensified charge-coupled device (ICCD) direct imaging method. Then, the shadow image evolution of laser water droplets was studied by shadow method. The changes of the shock wave and the droplet clusters generated by the laser droplets were observed, the expansion speed and the expansion distance of the shock wave with time were calculated and analyzed. The results show that the plasma expansion shape of droplets induced by laser is approximately elliptical, with one side along the incident direction of the laser having a higher radiation intensity. The expansion of the plasma within 100ns is approximately linear expansion, and the expansion tends to be stable after 100ns. In addition, the shock wave expansion radius increases linearly with time and the shock wave expands at a rate of approximately 90m/s. These findings can provide a reference for laser-induced droplet experiments.
2020, 44(6): 732-737.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.015
Abstract:
In order to achieve the purpose of suppressing the peak current harmonics of the power grid after the laser pulse output, a method suitable for active power factor correction in pulsed power applications was used. Theoretical analysis and experimental verification were performed. The results show that its operating frequency is 75kHz, output voltage is 380V, output voltage ripple is less than 2%, the total harmonic content after correction is reduced to 10%, and the power factor reaches 98%; active power factor correction technology achieves power factor correction under pulse power applications, which is effective to improve the energy transfer efficiency and the stability of the output pulse energy. This study will help to improve the performance of the laser and meet its application needs in scientific research and medical fields.
In order to achieve the purpose of suppressing the peak current harmonics of the power grid after the laser pulse output, a method suitable for active power factor correction in pulsed power applications was used. Theoretical analysis and experimental verification were performed. The results show that its operating frequency is 75kHz, output voltage is 380V, output voltage ripple is less than 2%, the total harmonic content after correction is reduced to 10%, and the power factor reaches 98%; active power factor correction technology achieves power factor correction under pulse power applications, which is effective to improve the energy transfer efficiency and the stability of the output pulse energy. This study will help to improve the performance of the laser and meet its application needs in scientific research and medical fields.
2020, 44(6): 738-741.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.016
Abstract:
In order to explore the dose effect relationship of blue laser dazzle effect, electroretinogram was used to evaluate the dazzle effect of a 456nm semiconductor blue laser on rabbit eyes. The dazzle effect of blue laser and its characteristics were evaluated by the recovery time of electroretinogram b-wave amplitude, the dazzling recovery time curves corresponding to different doses were drawn, and the damage of retina after laser irradiation was observed with fundus camera. The results show that the recovery time of b-wave amplitude of electroretinogram (ERG) is prolonged with the increase of laser irradiation dose, and there is a good linear relationship between the recovery time and the dose. No damage is found in the fundus immediately after irradiation and 24h later. This study will provide reference value for the application of blue laser dazzle.
In order to explore the dose effect relationship of blue laser dazzle effect, electroretinogram was used to evaluate the dazzle effect of a 456nm semiconductor blue laser on rabbit eyes. The dazzle effect of blue laser and its characteristics were evaluated by the recovery time of electroretinogram b-wave amplitude, the dazzling recovery time curves corresponding to different doses were drawn, and the damage of retina after laser irradiation was observed with fundus camera. The results show that the recovery time of b-wave amplitude of electroretinogram (ERG) is prolonged with the increase of laser irradiation dose, and there is a good linear relationship between the recovery time and the dose. No damage is found in the fundus immediately after irradiation and 24h later. This study will provide reference value for the application of blue laser dazzle.
2020, 44(6): 742-748.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.017
Abstract:
To reduce the time costs on approximating vector quantization of image features and training codebooks for high-dimensional vectors, a projection-based enhanced residual vector quantization was proposed. Based on previous research on enhance residual quantization (ERVQ), the principle component analysis (PCA) was combined with ERVQ, then both training codebooks and quantizing feature vectors were done in low-dimensional vector space to improve the efficiency. The features for training codebooks were projected into low-dimensional vector spaces. The overall errors generated by projection and quantization were both considered in training procedure to increase the codebook discrimination. For the proposed quantization method, a method to fast computing the approximate Euclidian distance between vectors was designed to retrieve approximate nearest neighbor exhaustively. The experimental results show that the proposed approach only takes near 1/3 training time compared to ERVQ on the condition of same retrieval accuracy. Meanwhile, the proposed approach outperforms the other state-of-the-arts over time efficiency on training codebooks, retrieval accuracy and efficiency. This study provides a reference for the effective combination of PCA with other quantization models.
To reduce the time costs on approximating vector quantization of image features and training codebooks for high-dimensional vectors, a projection-based enhanced residual vector quantization was proposed. Based on previous research on enhance residual quantization (ERVQ), the principle component analysis (PCA) was combined with ERVQ, then both training codebooks and quantizing feature vectors were done in low-dimensional vector space to improve the efficiency. The features for training codebooks were projected into low-dimensional vector spaces. The overall errors generated by projection and quantization were both considered in training procedure to increase the codebook discrimination. For the proposed quantization method, a method to fast computing the approximate Euclidian distance between vectors was designed to retrieve approximate nearest neighbor exhaustively. The experimental results show that the proposed approach only takes near 1/3 training time compared to ERVQ on the condition of same retrieval accuracy. Meanwhile, the proposed approach outperforms the other state-of-the-arts over time efficiency on training codebooks, retrieval accuracy and efficiency. This study provides a reference for the effective combination of PCA with other quantization models.
2020, 44(6): 749-753.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.018
Abstract:
In order to achieve the purpose of minimizing the flatness of Raman gain under the condition of high net gain, particle swarm optimization (PSO) algorithm was used to optimize the pump parameters of As-S fiber and tellurium based fiber amplifier. Theoretical analysis and experimental verification were carried out. Using the above method to compare the obtained three sets of optimization results, it is found that the average gain is 53.25dB and the corresponding gain flatness is 0.30dB on the cascaded Raman fiber amplifier with a bandwidth of 40nm. The results show that, compared with the traditional fiber amplifiers, the performance of the cascaded fiber amplifier will be significantly improved after the optimization of the power and wavelength of each pump light by using particle swarm optimization algorithm, which has a certain practical value in the future fiber communication.
In order to achieve the purpose of minimizing the flatness of Raman gain under the condition of high net gain, particle swarm optimization (PSO) algorithm was used to optimize the pump parameters of As-S fiber and tellurium based fiber amplifier. Theoretical analysis and experimental verification were carried out. Using the above method to compare the obtained three sets of optimization results, it is found that the average gain is 53.25dB and the corresponding gain flatness is 0.30dB on the cascaded Raman fiber amplifier with a bandwidth of 40nm. The results show that, compared with the traditional fiber amplifiers, the performance of the cascaded fiber amplifier will be significantly improved after the optimization of the power and wavelength of each pump light by using particle swarm optimization algorithm, which has a certain practical value in the future fiber communication.
2020, 44(6): 754-761.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.019
Abstract:
The capillary nozzle with cone angle, which is suitable for the water jet guide laser processing technology, has complex internal flow state. In order to obtain the highly stable water beam in the nozzle, using the method of finite element fluid calculation software simulation and analysis, the flow field in the contracted nozzle which is suitable for the water guide laser technology was simulated and analyzed, and the numerical verification was carried out. The parameter data of generating high-speed and stable water beam were then obtained. The simulation results show that with the increase of the inlet pressure of the plane nozzle, the ratio of the length to diameter of the capillary section decreases, and the fluid enters the nozzle and completely separates from the wall of the capillary section. During this process, no obvious cavitation phenomenon occurs, and the constricted water jet was formed. With the nozzle inlet pressure of 50MPa, the length of the water jet reattachment wall inside the nozzle can reach 90% of the capillary length when the capillary diameter is set to be 0.128mm, 0.07mm, and 0.03mm, respectively. When the tapered tube is 10°, the water beam passing through the tapered section will attach to the wall again. The parameters obtained from the simulation analysis can provide guidance for the selection of the nozzle.
The capillary nozzle with cone angle, which is suitable for the water jet guide laser processing technology, has complex internal flow state. In order to obtain the highly stable water beam in the nozzle, using the method of finite element fluid calculation software simulation and analysis, the flow field in the contracted nozzle which is suitable for the water guide laser technology was simulated and analyzed, and the numerical verification was carried out. The parameter data of generating high-speed and stable water beam were then obtained. The simulation results show that with the increase of the inlet pressure of the plane nozzle, the ratio of the length to diameter of the capillary section decreases, and the fluid enters the nozzle and completely separates from the wall of the capillary section. During this process, no obvious cavitation phenomenon occurs, and the constricted water jet was formed. With the nozzle inlet pressure of 50MPa, the length of the water jet reattachment wall inside the nozzle can reach 90% of the capillary length when the capillary diameter is set to be 0.128mm, 0.07mm, and 0.03mm, respectively. When the tapered tube is 10°, the water beam passing through the tapered section will attach to the wall again. The parameters obtained from the simulation analysis can provide guidance for the selection of the nozzle.
2020, 44(6): 762-767.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.020
Abstract:
Waterborne wood coating is a kind of trace evidence commonly found in crime scenes, and it is widely concerned in the forensic science field. In order to detect and classify the complex chemical components in waterborne wood paints, Raman spectrum, which has high resolving power and non-destructive testing characteristics, were used in this study. Combined with two data mining techniques of principal component analysis and radial basis function neural network, the Raman spectra of 38 waterborne wood lacquer samples from 3 brands were analyzed. The results show that the classification accuracy of 78.9% is obtained under the radial basis function model. Fourier Raman spectroscopy combined with radial basis function model was used to identify and classify waterborne wood coating, which provided new ideas for the classification of wood lacquers in practice.
Waterborne wood coating is a kind of trace evidence commonly found in crime scenes, and it is widely concerned in the forensic science field. In order to detect and classify the complex chemical components in waterborne wood paints, Raman spectrum, which has high resolving power and non-destructive testing characteristics, were used in this study. Combined with two data mining techniques of principal component analysis and radial basis function neural network, the Raman spectra of 38 waterborne wood lacquer samples from 3 brands were analyzed. The results show that the classification accuracy of 78.9% is obtained under the radial basis function model. Fourier Raman spectroscopy combined with radial basis function model was used to identify and classify waterborne wood coating, which provided new ideas for the classification of wood lacquers in practice.
2020, 44(6): 768-772.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.021
Abstract:
In order to investigate the influence of vacuum environment on the performance of the optical coatings, a low-loss highly reflective (HR) coating sample at 1064nm fabricated by ion assisted deposition was stored in a stainless steel vacuum chamber with pressure less than 1×10-5Pa. And we observed the variation of absorptance and reflectance of the HR sample. The experimental results show that the reflectance of the sample decreased from 99.9823% to 99.9543% and the absorptance increased from 6.8×10-6 to 59.5×10-6 after 335h of storage in the vacuum chamber. By wiping the sample with mixed alcohol/ether solution, the optical performance of the sample is totally recovered. Combined with theoretical analysis, we concluded that a thickness increase of an organic contamination layer on the coating surface and human errors during the experimental procedure are major sources for the performance degradation of the HR coating. The results are helpful to improve the stability of high energy/high power laser optics used in vacuum.
In order to investigate the influence of vacuum environment on the performance of the optical coatings, a low-loss highly reflective (HR) coating sample at 1064nm fabricated by ion assisted deposition was stored in a stainless steel vacuum chamber with pressure less than 1×10-5Pa. And we observed the variation of absorptance and reflectance of the HR sample. The experimental results show that the reflectance of the sample decreased from 99.9823% to 99.9543% and the absorptance increased from 6.8×10-6 to 59.5×10-6 after 335h of storage in the vacuum chamber. By wiping the sample with mixed alcohol/ether solution, the optical performance of the sample is totally recovered. Combined with theoretical analysis, we concluded that a thickness increase of an organic contamination layer on the coating surface and human errors during the experimental procedure are major sources for the performance degradation of the HR coating. The results are helpful to improve the stability of high energy/high power laser optics used in vacuum.
2020, 44(6): 773-778.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.022
Abstract:
In order to study the ultrafast dynamic process of highly charged state Be2+ ions in a strong laser, the spectral response of Be2+ ions was analyzed by solving the system's density matrix. It is found that the strong laser field causes a change of the electron motion in the excited state due to the transient Stark effect, corresponding to a phase change of 0.5π to the Be2+ system's dipole; the spectral response of Be2+system extends to the high and low frequencies and the line shape is changed from an isolated Lorentz line to a "wave-like" structure with the intensities of both near infrared laser pulses set to be 0.94×1012 W/cm2; the absorption spectral line depends on the intensity of the incident laser field, pulse duration, and relative delay time, which indicates that the movement of electrons outside the nucleus in highly charged ions can be controlled by adjusting the parameters of the pump laser fields. It also find us a possible pulse-shaping scheme for soft X-rays.
In order to study the ultrafast dynamic process of highly charged state Be2+ ions in a strong laser, the spectral response of Be2+ ions was analyzed by solving the system's density matrix. It is found that the strong laser field causes a change of the electron motion in the excited state due to the transient Stark effect, corresponding to a phase change of 0.5π to the Be2+ system's dipole; the spectral response of Be2+system extends to the high and low frequencies and the line shape is changed from an isolated Lorentz line to a "wave-like" structure with the intensities of both near infrared laser pulses set to be 0.94×1012 W/cm2; the absorption spectral line depends on the intensity of the incident laser field, pulse duration, and relative delay time, which indicates that the movement of electrons outside the nucleus in highly charged ions can be controlled by adjusting the parameters of the pump laser fields. It also find us a possible pulse-shaping scheme for soft X-rays.
Research on solder joint defect recognition algorithm based on improved convolutional neural network
2020, 44(6): 779-783.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.023
Abstract:
In order to quickly identify a variety of solder joint defect types and solve the problem of high false detection rate and missed detection rate of traditional welding abnormal image recognition algorithms, a deep learning algorithm based on an improved convolutional neural network was designed. The self-organizing map classification technology improves the data selection adaptability of the convolutional neural network. At the same time, it combines the adaptive moment estimation analysis to restrict the convergence conditions of the feature set in the welding abnormal image. In the experiment, five kinds of common welding anomaly images were randomly distributed into the training set, verification set, and test set in the form of a random distribution of equal proportions. They were tested by traditional recognition algorithms (canny algorithm and k-means algorithm) and this deep learning algorithm, respectively. The results show that, three methods have no false detection and no missed detection for bridge defects. Three methods meet the requirements for small ball defects, and the detection ability of the canny algorithm is the best. For partial ball defects, the false detection rates of three algorithms are 12.4%, 7.3%, and 1.4%, and the missed detection rates of three algorithms are 13.3%, 6.5%, and 1.1%, respectively. For virtual soldering and tin-less defects, the accuracy of this algorithm is about an order of magnitude higher than that of traditional algorithms. It can be seen that this algorithm has obvious advantages in identifying multiple types of solder joint defects.
In order to quickly identify a variety of solder joint defect types and solve the problem of high false detection rate and missed detection rate of traditional welding abnormal image recognition algorithms, a deep learning algorithm based on an improved convolutional neural network was designed. The self-organizing map classification technology improves the data selection adaptability of the convolutional neural network. At the same time, it combines the adaptive moment estimation analysis to restrict the convergence conditions of the feature set in the welding abnormal image. In the experiment, five kinds of common welding anomaly images were randomly distributed into the training set, verification set, and test set in the form of a random distribution of equal proportions. They were tested by traditional recognition algorithms (canny algorithm and k-means algorithm) and this deep learning algorithm, respectively. The results show that, three methods have no false detection and no missed detection for bridge defects. Three methods meet the requirements for small ball defects, and the detection ability of the canny algorithm is the best. For partial ball defects, the false detection rates of three algorithms are 12.4%, 7.3%, and 1.4%, and the missed detection rates of three algorithms are 13.3%, 6.5%, and 1.1%, respectively. For virtual soldering and tin-less defects, the accuracy of this algorithm is about an order of magnitude higher than that of traditional algorithms. It can be seen that this algorithm has obvious advantages in identifying multiple types of solder joint defects.
2020, 44(6): 784-788.
doi: 10.7510/jgjs.issn.1001-3806.2020.06.024
Abstract:
In order to solve the positional accuracy difference of plane data and the low calculation precision of plane model's constant term, a robust plane fitting method based on least squares-weighted total least square (LS-WTLS) was proposed. This method uses least squares model and robust estimation of IGGⅢ scheme to calculate the error parameters of plane model. Meanwhile, after rejecting the gross error data by setting the threshold, the constant term of plane model was calculated by using least square model. And based on this model, the accuracy of plane parameters was further improved. The new method shows favorable resistant to gross errors in experiments of fit the simulated plane data, meanwhile, the observed plane data fitting experiments show that compared with LS method, TLS method, LS-TLS method, IGGⅢ-LS-TLS method, the new method's mean square error of unit weight increased by 53.6%, 195.0%, 47.5%, and 5.1%, respectively, and its plane fitting accuracy increased by 53.6%, 195.0%, 47.5%, and, 5.1%, respectively. The results effectively verify this new method's superiority and reliability in the field of plane fitting.
In order to solve the positional accuracy difference of plane data and the low calculation precision of plane model's constant term, a robust plane fitting method based on least squares-weighted total least square (LS-WTLS) was proposed. This method uses least squares model and robust estimation of IGGⅢ scheme to calculate the error parameters of plane model. Meanwhile, after rejecting the gross error data by setting the threshold, the constant term of plane model was calculated by using least square model. And based on this model, the accuracy of plane parameters was further improved. The new method shows favorable resistant to gross errors in experiments of fit the simulated plane data, meanwhile, the observed plane data fitting experiments show that compared with LS method, TLS method, LS-TLS method, IGGⅢ-LS-TLS method, the new method's mean square error of unit weight increased by 53.6%, 195.0%, 47.5%, and 5.1%, respectively, and its plane fitting accuracy increased by 53.6%, 195.0%, 47.5%, and, 5.1%, respectively. The results effectively verify this new method's superiority and reliability in the field of plane fitting.
