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RSS2021 Vol. 45, No. 2
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2021, 45(2): 131-136.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.001
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Abstract:
In order to realize the controllable fabrication of sapphire microlens array templates, an etching-assisted laser machining technology was used, a compact sapphire concave microlens array template with controllable morphology and uniform arrangement was obtained. And by combining with the high-temperature casting transfer technology, the rapid preparation of K9 glass convex microlens array was realized; based on the large difference in thermal expansion coefficients between sapphire and glass, the separation of the sapphire template and the glass microlens array plate was realized. The results indicate that the surface roughness of the transferred glass microlens arrays is approximately 2nm, meanwhile, it exhibits high transmittance of up to 80% and shows clear focusing and imaging properties for light of different wavelengths in the visible range. In addition, the sapphire template can be reused with HF solution cleaned. Etching-assisted laser processing combined with high temperature casting transcribing technology can realize the rapid preparation of highly smooth glass microlens array. This technique provides a reference for the rapid preparation of micro-nano-devices with hard materials.
In order to realize the controllable fabrication of sapphire microlens array templates, an etching-assisted laser machining technology was used, a compact sapphire concave microlens array template with controllable morphology and uniform arrangement was obtained. And by combining with the high-temperature casting transfer technology, the rapid preparation of K9 glass convex microlens array was realized; based on the large difference in thermal expansion coefficients between sapphire and glass, the separation of the sapphire template and the glass microlens array plate was realized. The results indicate that the surface roughness of the transferred glass microlens arrays is approximately 2nm, meanwhile, it exhibits high transmittance of up to 80% and shows clear focusing and imaging properties for light of different wavelengths in the visible range. In addition, the sapphire template can be reused with HF solution cleaned. Etching-assisted laser processing combined with high temperature casting transcribing technology can realize the rapid preparation of highly smooth glass microlens array. This technique provides a reference for the rapid preparation of micro-nano-devices with hard materials.
2021, 45(2): 137-142.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.002
Abstract:
In order to improve the detection sensitivity of the laser seeker, the relationship between the bandwidth of the quadrant detector amplification module and the detection sensitivity of the laser seeker was fitted by numerical simulation. The influence of the pulse width of the guided laser irradiation on the bandwidth design of the quadrant detector amplification module was quantitatively analyzed. The bandwidth design method of quadrant detector amplifier was proposed, and the effectiveness of the method was verified by the exam with a laser seeker. The results show that the bandwidth design method of quadrant detector amplifier can effectively reduce the minimum detectable power of laser seeker. After the optimization design of the laser seeker quadrant detector amplifier, the minimum detectable power of the laser seeker can be reduced by about 60% compared with the original design, and the detection sensitivity of the laser seeker can be effectively improved. This study provides a reference for the design of photoelectric detection system of laser seeker.
In order to improve the detection sensitivity of the laser seeker, the relationship between the bandwidth of the quadrant detector amplification module and the detection sensitivity of the laser seeker was fitted by numerical simulation. The influence of the pulse width of the guided laser irradiation on the bandwidth design of the quadrant detector amplification module was quantitatively analyzed. The bandwidth design method of quadrant detector amplifier was proposed, and the effectiveness of the method was verified by the exam with a laser seeker. The results show that the bandwidth design method of quadrant detector amplifier can effectively reduce the minimum detectable power of laser seeker. After the optimization design of the laser seeker quadrant detector amplifier, the minimum detectable power of the laser seeker can be reduced by about 60% compared with the original design, and the detection sensitivity of the laser seeker can be effectively improved. This study provides a reference for the design of photoelectric detection system of laser seeker.
2021, 45(2): 143-146.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.003
Abstract:
In order to avoid the problem that the clamping force is too large to damage the product during assembly or too small to cause slipping, a method of intelligent sensing of fiber sensing was adopted, and a load sensing system based on orthogonal fiber grating array was designed. To analyze the clamping state, the sensing modules were arranged in a way that the fiber gratings were perpendicular to each other to obtain the transverse shear force in two orthogonal directions of the clamping plane. Two 5.0cm×5.0cm rubber blocks were used to make the load sensing module in the experiment. The effect of different parameters on the clamping control was analysed, and the results show that the effective length of the fiber grating is proportional to the sensitivity and inversely proportional to the spatial resolution. The results show that the vertical sensitivity is 31.4pm/N, and the horizontal sensitivity is 29.9pm/N. It can be seen that the system can obtain the force changes of the clamped objects in real time, which is helpful for intelligent adjustment and control.
In order to avoid the problem that the clamping force is too large to damage the product during assembly or too small to cause slipping, a method of intelligent sensing of fiber sensing was adopted, and a load sensing system based on orthogonal fiber grating array was designed. To analyze the clamping state, the sensing modules were arranged in a way that the fiber gratings were perpendicular to each other to obtain the transverse shear force in two orthogonal directions of the clamping plane. Two 5.0cm×5.0cm rubber blocks were used to make the load sensing module in the experiment. The effect of different parameters on the clamping control was analysed, and the results show that the effective length of the fiber grating is proportional to the sensitivity and inversely proportional to the spatial resolution. The results show that the vertical sensitivity is 31.4pm/N, and the horizontal sensitivity is 29.9pm/N. It can be seen that the system can obtain the force changes of the clamped objects in real time, which is helpful for intelligent adjustment and control.
2021, 45(2): 147-154.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.004
Abstract:
In order to solve the contradiction between the steady-state accuracy and overshoot in the application of the high-order control method in the photoelectric servo tracking systems, a fuzzy Ⅱ-order controller optimized by multiple population genetic algorithm (MPGA) was designed. In this method, an integrator was connected in parallel before the speed loop of the classic Ⅰ-type double closed-loop feedback controller to increase the system order to the Ⅱ, thereby speeding up the reaction speed and reducing the steady-state error. Therefore, a fuzzy logic controller (FLC) was introduced to dynamically adjust the gain of the integrator according to the state of the system to achieve dynamic high-order control, which not only suppresses system oscillation but also ensures steady-state accuracy. MPGA was used to optimize the input and output scale factors of FLC to obtain the optimal control parameters. The control system was analyzed theoretically, and the optimized system in each stage was compared with experiments. The results show that under the same experimental conditions, the MPGA-optimized fuzzy Ⅱ-order control system is used to realize the dynamic high-order control of the system, which can not only ensure that the overshoot of the original system remains the same, but also reduce the steady-state error by 88.55%. This study significantly improves the steady-state accuracy of the control system. The research is helpful to optimize the photoelectric servo tracking system.
In order to solve the contradiction between the steady-state accuracy and overshoot in the application of the high-order control method in the photoelectric servo tracking systems, a fuzzy Ⅱ-order controller optimized by multiple population genetic algorithm (MPGA) was designed. In this method, an integrator was connected in parallel before the speed loop of the classic Ⅰ-type double closed-loop feedback controller to increase the system order to the Ⅱ, thereby speeding up the reaction speed and reducing the steady-state error. Therefore, a fuzzy logic controller (FLC) was introduced to dynamically adjust the gain of the integrator according to the state of the system to achieve dynamic high-order control, which not only suppresses system oscillation but also ensures steady-state accuracy. MPGA was used to optimize the input and output scale factors of FLC to obtain the optimal control parameters. The control system was analyzed theoretically, and the optimized system in each stage was compared with experiments. The results show that under the same experimental conditions, the MPGA-optimized fuzzy Ⅱ-order control system is used to realize the dynamic high-order control of the system, which can not only ensure that the overshoot of the original system remains the same, but also reduce the steady-state error by 88.55%. This study significantly improves the steady-state accuracy of the control system. The research is helpful to optimize the photoelectric servo tracking system.
2021, 45(2): 155-161.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.005
Abstract:
To improve the real-time performance and accuracy of the seeker decoder andreduce the effects of missing pulses and interference pulses on laser decoding, an identification method based on the digital matched filter and an adaptive extended real-time gate technique was proposed to search and track the target. The decoder system was designed and implemented based on a field-programmable gate array (FPGA) chip. The simulation and experimental results show that the code pattern identification can be completed within the current period of a set of encoded signals, and the real-time of the decoder system is good. For the 100kHz high pulse repetition frequency interference, the proposed real-time gate technique with a normal gate width of 5μs reduces its interference probability to 50% and effectively improves the anti-jamming performance of the guidance. This study is conducive to improving the accuracy and reliability of semi-active laser-guided weapons.
To improve the real-time performance and accuracy of the seeker decoder andreduce the effects of missing pulses and interference pulses on laser decoding, an identification method based on the digital matched filter and an adaptive extended real-time gate technique was proposed to search and track the target. The decoder system was designed and implemented based on a field-programmable gate array (FPGA) chip. The simulation and experimental results show that the code pattern identification can be completed within the current period of a set of encoded signals, and the real-time of the decoder system is good. For the 100kHz high pulse repetition frequency interference, the proposed real-time gate technique with a normal gate width of 5μs reduces its interference probability to 50% and effectively improves the anti-jamming performance of the guidance. This study is conducive to improving the accuracy and reliability of semi-active laser-guided weapons.
2021, 45(2): 162-167.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.006
Abstract:
In order to optimize the parameter settings of the time-gated digital optical frequency domain reflectometer (TGD-OFDR) system, an experimental system was built based on the optical pulse compression reflectometry. Theoretical analysis and experimental verification were carried out, and simulation and experimental data were obtained. Both of the results show that the system signal-to-noise ratio (SNR) is only related to the chirp rate. When the pulse power of the probe light and the signal power of the local oscillator light have been set, the chirp rate increases with the SNR decreasing. And the phase noise decreases firstly and then increases with the increase of the pulse width with the minimum value of about 2.5μs when the sweep range keeps 80MHz. Hence, the optimal phase noise (minimum value) can be obtained by adjusting the pulse width with the maximum sweep frequency range of the system remains unchanged. The results have certain reference significance to the parameter optimization of the TGD-OFDR system design.
In order to optimize the parameter settings of the time-gated digital optical frequency domain reflectometer (TGD-OFDR) system, an experimental system was built based on the optical pulse compression reflectometry. Theoretical analysis and experimental verification were carried out, and simulation and experimental data were obtained. Both of the results show that the system signal-to-noise ratio (SNR) is only related to the chirp rate. When the pulse power of the probe light and the signal power of the local oscillator light have been set, the chirp rate increases with the SNR decreasing. And the phase noise decreases firstly and then increases with the increase of the pulse width with the minimum value of about 2.5μs when the sweep range keeps 80MHz. Hence, the optimal phase noise (minimum value) can be obtained by adjusting the pulse width with the maximum sweep frequency range of the system remains unchanged. The results have certain reference significance to the parameter optimization of the TGD-OFDR system design.
2021, 45(2): 168-173.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.007
Abstract:
In order to improve the generation efficiency of laser ultrasonic without damaging the measured surface, the spatial distribution of the laser source was changed, and the pulsed ring laser source was used. Using the finite element method, the numerical simulation of the full field ultrasonic wave generated in the aluminum plate was carried out by COMSOL Multiphysics. The generation characteristics of the superposition shear wave on the central axis of the ring laser source were studied, which vary with laser parameters. By simulating the change law of the ultrasonic field caused by defects, a method of detecting cracks on both sides of the ring laser source was proposed. The feasibility and effectiveness of defect detection by superposition shear wave were verified by simulating the change rule of ultrasonic field caused by defects. The results show that the generation efficiency can be significantly improved by using the ring laser source because ring light source loss is usually less than 50%. The direction of shear wave propagation is stable. The superposition depth of the shear wave is related to the ring radius, and the ring half-width can affect the intensity of the wave. The results provide a reference for the application of ring laser source generated ultrasonic in defect detection.
In order to improve the generation efficiency of laser ultrasonic without damaging the measured surface, the spatial distribution of the laser source was changed, and the pulsed ring laser source was used. Using the finite element method, the numerical simulation of the full field ultrasonic wave generated in the aluminum plate was carried out by COMSOL Multiphysics. The generation characteristics of the superposition shear wave on the central axis of the ring laser source were studied, which vary with laser parameters. By simulating the change law of the ultrasonic field caused by defects, a method of detecting cracks on both sides of the ring laser source was proposed. The feasibility and effectiveness of defect detection by superposition shear wave were verified by simulating the change rule of ultrasonic field caused by defects. The results show that the generation efficiency can be significantly improved by using the ring laser source because ring light source loss is usually less than 50%. The direction of shear wave propagation is stable. The superposition depth of the shear wave is related to the ring radius, and the ring half-width can affect the intensity of the wave. The results provide a reference for the application of ring laser source generated ultrasonic in defect detection.
2021, 45(2): 174-181.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.008
Abstract:
AC-130J gunship airborne high energy laser (AHEL) system is a next generation weapon capable of providing scalable effects in complex targeting environments with low acoustic & kinetic signatures. As a first airborne high energy laser which can be used in actual combat, it will be demonstrated in 2022. First, the application goal and development plan of AHEL system were introduced, and its system architecture and technologies challenge was analyzed. Then its development was reviewed, and its fighting capability was deduced from its system parameters. The analyses show that it leverages a rapid prototyping approach to demonstrate integration of a laser weapon system onto an AC-130J aircraft by utilizing a best of breed approach, and much work has down to mitigate risks identified from prior HEL projects during its development. In the end, technical development trends are given.
AC-130J gunship airborne high energy laser (AHEL) system is a next generation weapon capable of providing scalable effects in complex targeting environments with low acoustic & kinetic signatures. As a first airborne high energy laser which can be used in actual combat, it will be demonstrated in 2022. First, the application goal and development plan of AHEL system were introduced, and its system architecture and technologies challenge was analyzed. Then its development was reviewed, and its fighting capability was deduced from its system parameters. The analyses show that it leverages a rapid prototyping approach to demonstrate integration of a laser weapon system onto an AC-130J aircraft by utilizing a best of breed approach, and much work has down to mitigate risks identified from prior HEL projects during its development. In the end, technical development trends are given.
2021, 45(2): 182-185.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.009
Abstract:
An identification method based on fingerprint spectroscopy combined with decision tree, k-nearest neighbor, and Fisher discriminant analysis (DT-KNN-FDA) model was proposed to achieve the rapid and non-destructive identification of the vehicle paints and performed by theoretical analysis and experimental verification. The infrared absorption spectroscopy for a total of 60 samples of car paint were collected and obtained as the experimental data. Through the selection of characteristic wave numbers, a multi-classification model based on the DT, KNN analysis, and FDA was established and compared. 58 sets of adjustment data were extracted through correlation analysis, and a classification model was constructed based on this. The results show that the overall discrimination accuracy of DT classification model, KNN classification model and FDA classification model for each sample is 77.80%, 72.31%, and 85.00%, respectively; infrared spectroscopy combined with DT-KNN-FDA analysis can realize the distinction between products of different brands is ideal for classification. This method is fast, accurate, and effective, and has certain universality and significance.
An identification method based on fingerprint spectroscopy combined with decision tree, k-nearest neighbor, and Fisher discriminant analysis (DT-KNN-FDA) model was proposed to achieve the rapid and non-destructive identification of the vehicle paints and performed by theoretical analysis and experimental verification. The infrared absorption spectroscopy for a total of 60 samples of car paint were collected and obtained as the experimental data. Through the selection of characteristic wave numbers, a multi-classification model based on the DT, KNN analysis, and FDA was established and compared. 58 sets of adjustment data were extracted through correlation analysis, and a classification model was constructed based on this. The results show that the overall discrimination accuracy of DT classification model, KNN classification model and FDA classification model for each sample is 77.80%, 72.31%, and 85.00%, respectively; infrared spectroscopy combined with DT-KNN-FDA analysis can realize the distinction between products of different brands is ideal for classification. This method is fast, accurate, and effective, and has certain universality and significance.
2021, 45(2): 186-190.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.010
Abstract:
In order to improve the low light extraction efficiency(LEE) of graphene UV light-emitting diode (LED) due to the high absorption of indium tin oxide (ITO) thin layer to UV light, the ITO micro nano structure (rectangle and triangle) was used as the buffer layer of graphene UV LED. The ITO micro nano structure was optimized and graphene UV LED was theoretically analyzed by the finite difference time domain method. The results show that when the thickness, duty cycle and period of rectangular micro nano structure are 160nm and 0.7, 220nm respectively, the LEE of UV LED can reach 10.668% under single graphene. The use of rectangular micro structure as the insertion layer is 45.06% higher than that of ITO thin layer as the insertion layer, while when the triangular micro nano structure is in the optimal parameters, the LEE of graphene UV LED is only 6.64%, significantly lower than that of ITO thin layer. This study can provide a theoretical basis for the subsequent preparation of high-power UV LED.
In order to improve the low light extraction efficiency(LEE) of graphene UV light-emitting diode (LED) due to the high absorption of indium tin oxide (ITO) thin layer to UV light, the ITO micro nano structure (rectangle and triangle) was used as the buffer layer of graphene UV LED. The ITO micro nano structure was optimized and graphene UV LED was theoretically analyzed by the finite difference time domain method. The results show that when the thickness, duty cycle and period of rectangular micro nano structure are 160nm and 0.7, 220nm respectively, the LEE of UV LED can reach 10.668% under single graphene. The use of rectangular micro structure as the insertion layer is 45.06% higher than that of ITO thin layer as the insertion layer, while when the triangular micro nano structure is in the optimal parameters, the LEE of graphene UV LED is only 6.64%, significantly lower than that of ITO thin layer. This study can provide a theoretical basis for the subsequent preparation of high-power UV LED.
2021, 45(2): 191-195.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.011
Abstract:
In order to realize the non-destructive identification of wall paints, a method of fast and non-destructive identification of wall paints by microscopic confocal Raman spectroscopy and multiple modeling was proposed. The influence of Savitzky-Golay(SG) smoothing polynomial and points, and compared the identification ability of different models were investigated. The results showed that compared with radial basis function neural network model, multilayer perceptron neural network model has a stronger ability to identify samples. Different brands of wall paints have been identified exactly by multilayer perceptron neural network model after SG smoothing 1-degree polynomial and smoothing points of 27 points. At the same time, primers, surface coatings and varnishes of Meffert samples were also identified accurately. This method improved the efficiency of identification, reduced the cost, which is worth consulting.
In order to realize the non-destructive identification of wall paints, a method of fast and non-destructive identification of wall paints by microscopic confocal Raman spectroscopy and multiple modeling was proposed. The influence of Savitzky-Golay(SG) smoothing polynomial and points, and compared the identification ability of different models were investigated. The results showed that compared with radial basis function neural network model, multilayer perceptron neural network model has a stronger ability to identify samples. Different brands of wall paints have been identified exactly by multilayer perceptron neural network model after SG smoothing 1-degree polynomial and smoothing points of 27 points. At the same time, primers, surface coatings and varnishes of Meffert samples were also identified accurately. This method improved the efficiency of identification, reduced the cost, which is worth consulting.
2021, 45(2): 196-201.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.012
Abstract:
A design of large-mode area photonic crystal fiber (LMA-PCF) was proposed to improve the non-linear effect of high-power fiber laser, which has the properties as large effective mode area, single mode, passive component, and low loss. The perfect matched layer was set as the boundary condition, and the effect of wavelength and structure on the effective mode area of PCF were analyzed by the finite difference time domain method. Further, a program of LMA-PCF was proposed. The results indicate that the transmission of single mode is obtained. At the wavelength of 1.064μm, the effective mode area is able to reach 3118.4μm2, and the non-linear coefficient is only 5.68×10-5 m-1·W-1. Besides, the confinement loss can be reduced to 4.55×10-7 dB·m-1. Therefore, the high-power and high-beam of laser output is realized.
A design of large-mode area photonic crystal fiber (LMA-PCF) was proposed to improve the non-linear effect of high-power fiber laser, which has the properties as large effective mode area, single mode, passive component, and low loss. The perfect matched layer was set as the boundary condition, and the effect of wavelength and structure on the effective mode area of PCF were analyzed by the finite difference time domain method. Further, a program of LMA-PCF was proposed. The results indicate that the transmission of single mode is obtained. At the wavelength of 1.064μm, the effective mode area is able to reach 3118.4μm2, and the non-linear coefficient is only 5.68×10-5 m-1·W-1. Besides, the confinement loss can be reduced to 4.55×10-7 dB·m-1. Therefore, the high-power and high-beam of laser output is realized.
2021, 45(2): 202-207.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.013
Abstract:
Aiming at the problems of the current head-mounted display with large volume, large weight, and small field of view, in order to meet the user's demand for light and small head-mounted displays, the Ranston eyepiece was used as the initial structure, and then was optimized by using ZEMAX software. Image quality evaluation and tolerance analysis were then carried out. The result shows that each channel in the binocular system uses only two lenses, the maximum field of view of the optical structure is 80°, the total length is 54.24mm, the maximum distortion is less than 4.7%, the weight of the two lenses is less than 11.5g. Compared with related research, the field angle and the number of pixels are increased, the volume is reduced, and the modulation transfer function is improved. The head-mounted display has certain market prospects, and can provide a reference for the optical design of the light and small head-mounted display.
Aiming at the problems of the current head-mounted display with large volume, large weight, and small field of view, in order to meet the user's demand for light and small head-mounted displays, the Ranston eyepiece was used as the initial structure, and then was optimized by using ZEMAX software. Image quality evaluation and tolerance analysis were then carried out. The result shows that each channel in the binocular system uses only two lenses, the maximum field of view of the optical structure is 80°, the total length is 54.24mm, the maximum distortion is less than 4.7%, the weight of the two lenses is less than 11.5g. Compared with related research, the field angle and the number of pixels are increased, the volume is reduced, and the modulation transfer function is improved. The head-mounted display has certain market prospects, and can provide a reference for the optical design of the light and small head-mounted display.
2021, 45(2): 208-212.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.014
Abstract:
In order to understand the relation between the harmonic spectra efficiency of H2+ and its isotope molecule with laser wavelength, the relation between the harmonic intensity of H2+ and D2+ with the wavelength in the range of 600nm~1600nm was theoretically studied by solving 2-D time-dependent Schrdinger equation. It is shown that the intensity of harmonic spectrum is decreased as the wavelength increases. In shorter wavelength region, the decrease rate of harmonic intensity of H2+ is greater than that of D2+. In longer wavelength region, the decrease rate of harmonic intensity of H2+ is smaller than that of D2+. Furthermore, driven by lower laser intensity, the harmonic yield of H2+ is always higher than that of D2+. Driven by stronger laser intensity, the harmonic yield of H2+ is lower than that of D2+ in shorter wavelength region; while, it is higher than that of D2+ in longer wavelength region. Theoretical analyses show that the extension of nuclear distance and charge resonance enhanced ionization play the important role in the change of harmonic yield of H2+ and D2+. The results are helpful for molecular harmonic control.
In order to understand the relation between the harmonic spectra efficiency of H2+ and its isotope molecule with laser wavelength, the relation between the harmonic intensity of H2+ and D2+ with the wavelength in the range of 600nm~1600nm was theoretically studied by solving 2-D time-dependent Schrdinger equation. It is shown that the intensity of harmonic spectrum is decreased as the wavelength increases. In shorter wavelength region, the decrease rate of harmonic intensity of H2+ is greater than that of D2+. In longer wavelength region, the decrease rate of harmonic intensity of H2+ is smaller than that of D2+. Furthermore, driven by lower laser intensity, the harmonic yield of H2+ is always higher than that of D2+. Driven by stronger laser intensity, the harmonic yield of H2+ is lower than that of D2+ in shorter wavelength region; while, it is higher than that of D2+ in longer wavelength region. Theoretical analyses show that the extension of nuclear distance and charge resonance enhanced ionization play the important role in the change of harmonic yield of H2+ and D2+. The results are helpful for molecular harmonic control.
2021, 45(2): 213-217.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.015
Abstract:
In order to quickly identify the material evidence of food plastic packaging bags on the scene, 46 samples from different sources and different series of food plastic packaging bags were analyzed and tested by differential Raman spectroscopy and system cluster analysis. The results show that the samples of different sources of food plastic packaging bags can be effectively distinguished according to the different characteristic peaks in the differential Raman spectrum. And 46 samples can be divided into 17 categories by combining with the system cluster analysis. This method does not damage the sample, and the experimental results are ideal, which provides a certain reference for the examination of trace evidence.
In order to quickly identify the material evidence of food plastic packaging bags on the scene, 46 samples from different sources and different series of food plastic packaging bags were analyzed and tested by differential Raman spectroscopy and system cluster analysis. The results show that the samples of different sources of food plastic packaging bags can be effectively distinguished according to the different characteristic peaks in the differential Raman spectrum. And 46 samples can be divided into 17 categories by combining with the system cluster analysis. This method does not damage the sample, and the experimental results are ideal, which provides a certain reference for the examination of trace evidence.
2021, 45(2): 218-223.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.016
Abstract:
Laser diode (LD) pumped passively Q-switched microchip laser has important applications in the field of industry, military, and medical treatment. To improve the output performance and system integration of LD pumped pulse microchip lasers, the Runge-Kutta method was used to solve the passively Q-switched laser rate equation, and the output parameters of LD end-pumped bonded Nd∶YAG/Cr4+∶YAG microchip laser was numerically simulated. The results show that with a 1mm/1.5mm bonded Nd∶YAG/Cr4+∶YAG as the gain medium, when the initial transmittance of Cr4+∶YAG is 75%, the transmittance of output mirror is 30%, and the radii of the pump and fundamental mode are 100μm, a 0.7W average power with pulse-width of 174ps at 16.1kHz can be obtained under the 4.5W pumping. This study has theoretical significance for the optimization and application of the passively Q-switched microchip laser.
Laser diode (LD) pumped passively Q-switched microchip laser has important applications in the field of industry, military, and medical treatment. To improve the output performance and system integration of LD pumped pulse microchip lasers, the Runge-Kutta method was used to solve the passively Q-switched laser rate equation, and the output parameters of LD end-pumped bonded Nd∶YAG/Cr4+∶YAG microchip laser was numerically simulated. The results show that with a 1mm/1.5mm bonded Nd∶YAG/Cr4+∶YAG as the gain medium, when the initial transmittance of Cr4+∶YAG is 75%, the transmittance of output mirror is 30%, and the radii of the pump and fundamental mode are 100μm, a 0.7W average power with pulse-width of 174ps at 16.1kHz can be obtained under the 4.5W pumping. This study has theoretical significance for the optimization and application of the passively Q-switched microchip laser.
2021, 45(2): 224-228.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.017
Abstract:
In order to achieve the effect of pressure sensitization of optical fiber sensor, a photonic crystal fiber structure with high birefringence was designed. The effective refractive index of photonic crystal fiber was calculated by the finite element method when it was applied different stress. Based on the pressure-sensitive characteristics of photonic crystal fiber, the mode of photonic crystal fiber was analyzed. An air hole in the structure was selected and filled with the liquid of specific refractive index. A new pressure sensor was formed by above structures. The pressure sensitivity of the structure was simulated by COMSOL. The simulation results show that the polarization phase sensitivity of photonic crystal fiber sensor increases from 72rad/(MPa·m) to 128rad/(MPa·m). The sensitivity is improved by 77.7% significantly, which contributes to enhance the properties of the sensor.
In order to achieve the effect of pressure sensitization of optical fiber sensor, a photonic crystal fiber structure with high birefringence was designed. The effective refractive index of photonic crystal fiber was calculated by the finite element method when it was applied different stress. Based on the pressure-sensitive characteristics of photonic crystal fiber, the mode of photonic crystal fiber was analyzed. An air hole in the structure was selected and filled with the liquid of specific refractive index. A new pressure sensor was formed by above structures. The pressure sensitivity of the structure was simulated by COMSOL. The simulation results show that the polarization phase sensitivity of photonic crystal fiber sensor increases from 72rad/(MPa·m) to 128rad/(MPa·m). The sensitivity is improved by 77.7% significantly, which contributes to enhance the properties of the sensor.
2021, 45(2): 229-232.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.018
Abstract:
In order to make a nice hologram, a new method to create a color dynamic hologram by computer coding was proposed. According to the colorimetry principles and the sampling principle, an object point of every behaves can be resolved into three primary color objects as red, blue and green, whose coordinate data are coded by the computer in order to let their monochromatic stereoscopic holograms have a pefect overlap when they are placed in a plane and reappeared by conjugate light. The overlapping images interferenced with the reference light to form a dynamic color hologram. The experiment shows that a dynamin visual can be seen with the movement of the position of the eyes when the color hologram is reproduced. This method can effectively solve the problem that difficult overlap of images with low experimental conditions, which also avoid some unnecessary noise with simple operation, and has good application value in 3-D display.
In order to make a nice hologram, a new method to create a color dynamic hologram by computer coding was proposed. According to the colorimetry principles and the sampling principle, an object point of every behaves can be resolved into three primary color objects as red, blue and green, whose coordinate data are coded by the computer in order to let their monochromatic stereoscopic holograms have a pefect overlap when they are placed in a plane and reappeared by conjugate light. The overlapping images interferenced with the reference light to form a dynamic color hologram. The experiment shows that a dynamin visual can be seen with the movement of the position of the eyes when the color hologram is reproduced. This method can effectively solve the problem that difficult overlap of images with low experimental conditions, which also avoid some unnecessary noise with simple operation, and has good application value in 3-D display.
2021, 45(2): 233-239.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.019
Abstract:
To realize the purpose of infrared image de-noising and de-blurring, infrared simulation modeling, guided filtering and blind convolution methods were studied. The principle of guided filtering in visual was analyzed, and the key idea which is guided image was proposed. In order to conquer guided image in guided filtering method, simulation modeling was used to generate guided image to solve guided image. The guided filter and blind convolution were combined to pre-process infrared image in noise and blur. The theoretical analysis and experimental results were also studied. Result shows that guided filtering is better than the classical algorithm in processing time and result (time reduced 25%, from 1.1ms fall to 0.8ms, and peak signal-to-noise ratio result improve at least 4.5%, from 36.7441dB go up to 38.5138dB). This research provides an effective reference for the infrared image pre-process algorithm.
To realize the purpose of infrared image de-noising and de-blurring, infrared simulation modeling, guided filtering and blind convolution methods were studied. The principle of guided filtering in visual was analyzed, and the key idea which is guided image was proposed. In order to conquer guided image in guided filtering method, simulation modeling was used to generate guided image to solve guided image. The guided filter and blind convolution were combined to pre-process infrared image in noise and blur. The theoretical analysis and experimental results were also studied. Result shows that guided filtering is better than the classical algorithm in processing time and result (time reduced 25%, from 1.1ms fall to 0.8ms, and peak signal-to-noise ratio result improve at least 4.5%, from 36.7441dB go up to 38.5138dB). This research provides an effective reference for the infrared image pre-process algorithm.
2021, 45(2): 240-245.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.020
Abstract:
In order to study the spatial correlation properties of tightly focused J0-correlated radially polarized vortex beam through a high numerical aperture dNA, the vectorial Debye diffraction theory and the coherence theory were adopted. After theoretical analysis and numerical simulation of the correlation characteristics of focused field on the optical axis and the focal plane, the expression and simulation data of coherence degrees were obtained.The results show that, the longitudinal coherence degrees in the focal region increase as the topological charge n increases, but it decrease as the coherence parameter or the numerical aperture dNA; The transverse coherence degrees in the focal plane decrease with the increase of the topological charge, coherence parameter or numerical aperture. When n≥5 or dNA≤0.4, the longitudinal coherence near the focal point approximately equals to 1. Further, the coherence degrees are shown to exhibit phase singularities. The results are of great significance to the application of J0-correlated vector vortex beams in many fields.
In order to study the spatial correlation properties of tightly focused J0-correlated radially polarized vortex beam through a high numerical aperture dNA, the vectorial Debye diffraction theory and the coherence theory were adopted. After theoretical analysis and numerical simulation of the correlation characteristics of focused field on the optical axis and the focal plane, the expression and simulation data of coherence degrees were obtained.The results show that, the longitudinal coherence degrees in the focal region increase as the topological charge n increases, but it decrease as the coherence parameter or the numerical aperture dNA; The transverse coherence degrees in the focal plane decrease with the increase of the topological charge, coherence parameter or numerical aperture. When n≥5 or dNA≤0.4, the longitudinal coherence near the focal point approximately equals to 1. Further, the coherence degrees are shown to exhibit phase singularities. The results are of great significance to the application of J0-correlated vector vortex beams in many fields.
2021, 45(2): 246-251.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.021
Abstract:
In order to investigate the excitation mechanism of thermo-elastic laser ultrasound and its application in defect detection, the temperature field and stress field in the material were calculated using the method of finite element analysis. The theoretical basis of the material irradiated by pulse laser was expounded, and the pulse laser was loaded on the surface of the workpiece in the form of heat flux density. Considering the convection and radiation heat transfer boundary conditions at the same time, the temperature field in the material was analyzed. Based on thermo-solid coupling, the temperature field was loaded into the stress field analysis process, and the directivity distribution of the body wave sound field based on the thermo-elastic mechanism was discussed. On the premise of simulating the interaction law of ultrasonic waves with surface defect and internal defect, the time history curve of the displacement of the node on the workpiece surface was extracted, and the obvious defect echo signal was obtained. With the purpose of verifying the results of finite element analysis, a laser thermo-elastic ultrasonic detection system was built using pulsed laser, ultrasonic transducer and oscilloscope for surface crack detection. The excitation of the ultrasonic wave is based on the thermo-elastic mechanism by controlling the energy of the pulsed laser. Through finite element analysis and experimental verification, the relationship that the reflection coefficient increases with the depth of the defect could be obtained. Furthermore, the inflection point of growth corresponds to the wavelength according to the maximum center frequency of the surface wave. A laser spot with a diameter of 1mm is used to detect cracks with a depth of less than 3mm. When the crack depth is greater than 2.2mm, the growth trend of the reflection coefficient becomes slower. The results of finite element analysis can provide reference and basis for the application of thermo-elastic laser ultrasound in defect detection.
In order to investigate the excitation mechanism of thermo-elastic laser ultrasound and its application in defect detection, the temperature field and stress field in the material were calculated using the method of finite element analysis. The theoretical basis of the material irradiated by pulse laser was expounded, and the pulse laser was loaded on the surface of the workpiece in the form of heat flux density. Considering the convection and radiation heat transfer boundary conditions at the same time, the temperature field in the material was analyzed. Based on thermo-solid coupling, the temperature field was loaded into the stress field analysis process, and the directivity distribution of the body wave sound field based on the thermo-elastic mechanism was discussed. On the premise of simulating the interaction law of ultrasonic waves with surface defect and internal defect, the time history curve of the displacement of the node on the workpiece surface was extracted, and the obvious defect echo signal was obtained. With the purpose of verifying the results of finite element analysis, a laser thermo-elastic ultrasonic detection system was built using pulsed laser, ultrasonic transducer and oscilloscope for surface crack detection. The excitation of the ultrasonic wave is based on the thermo-elastic mechanism by controlling the energy of the pulsed laser. Through finite element analysis and experimental verification, the relationship that the reflection coefficient increases with the depth of the defect could be obtained. Furthermore, the inflection point of growth corresponds to the wavelength according to the maximum center frequency of the surface wave. A laser spot with a diameter of 1mm is used to detect cracks with a depth of less than 3mm. When the crack depth is greater than 2.2mm, the growth trend of the reflection coefficient becomes slower. The results of finite element analysis can provide reference and basis for the application of thermo-elastic laser ultrasound in defect detection.
2021, 45(2): 252-258.
doi: 10.7510/jgjs.issn.1001-3806.2021.02.022
Abstract:
In order to study the wander characteristics of partially coherent anomalous vortex beams in anisotropic atmospheric turbulence, based on the anisotropic non-Kolmogorov atmospheric turbulence spectrum model, the analytical expression of the beam wander of partially coherent anomalous vortex beam (PCAVB) propagating in anisotropic turbulence was obtained by using the geometrical optics approximation and Rytov approximation, and the numerical simulation was carried out at the same time. The effects of beam parameters and turbulence parameters such as topological charge, coherence length, anisotropy parameters, refractive index structure constant on root-mean-square beam wander, and relative beam wander of PCAVB in turbulence were studied. The results show that the more coherent the anomalous vortex beam is, the more serious the wander of the beam in the anisotropic turbulence will be. With the increase of topological charge, the influence of turbulence on beam wander can be reduced to some extent. The influence of turbulence on the wander of partially coherent anomalous vortex beams is obviously reduced with the increase of anisotropic factor. When the generalized exponential parameter increases in the range of 3~3.3, it has the largest influence on PCAVB root-mean-square wander and relative wander, while when it increases in the range of 3.3~4, the influence on beam root-mean-square wander and relative wander gradually weakens. This study provides a theoretical reference model for the propagation of anomalous vortex beam in anisotropic atmospheric turbulence.
In order to study the wander characteristics of partially coherent anomalous vortex beams in anisotropic atmospheric turbulence, based on the anisotropic non-Kolmogorov atmospheric turbulence spectrum model, the analytical expression of the beam wander of partially coherent anomalous vortex beam (PCAVB) propagating in anisotropic turbulence was obtained by using the geometrical optics approximation and Rytov approximation, and the numerical simulation was carried out at the same time. The effects of beam parameters and turbulence parameters such as topological charge, coherence length, anisotropy parameters, refractive index structure constant on root-mean-square beam wander, and relative beam wander of PCAVB in turbulence were studied. The results show that the more coherent the anomalous vortex beam is, the more serious the wander of the beam in the anisotropic turbulence will be. With the increase of topological charge, the influence of turbulence on beam wander can be reduced to some extent. The influence of turbulence on the wander of partially coherent anomalous vortex beams is obviously reduced with the increase of anisotropic factor. When the generalized exponential parameter increases in the range of 3~3.3, it has the largest influence on PCAVB root-mean-square wander and relative wander, while when it increases in the range of 3.3~4, the influence on beam root-mean-square wander and relative wander gradually weakens. This study provides a theoretical reference model for the propagation of anomalous vortex beam in anisotropic atmospheric turbulence.
