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RSS2019 Vol. 43, No. 6
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2019, 43(6): 735-740.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.001
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Abstract:
In order to evaluate the feasibility of miniature near infrared spectroscopy (NIRS) in detecting sugar content of fruits in situ, non-destructive, high-precision and fast detection method of apple sugar content was established by combining particle swarm optimization with back propagation (BP) neural network. The spectral data obtained by NIRscan(micro-NIRS) using single wavelength measurement mode and Hadamard transform measurement mode were studied. A variety of different data preprocessing methods and multiple linear regression, partial least squares, particle swarm optimization (PSO), BP neural network and other algorithms were used to establish the analysis model. The results show that the spectral data obtained by the working mode of Hadamard transform are better. First derivative combined with Savizky-Golay smoothing algorithm is used for data preprocessing. The prediction model of apple sugar content based on PSO and BP neural network has higher prediction accuracy. Predictive correlation coefficient and root mean square error are 0.9911 and 0.1502, respectively. NIRscan (micro-NIRS) is feasible for rapid and high-precision non-destructive testing of apple sugar content in the field.
In order to evaluate the feasibility of miniature near infrared spectroscopy (NIRS) in detecting sugar content of fruits in situ, non-destructive, high-precision and fast detection method of apple sugar content was established by combining particle swarm optimization with back propagation (BP) neural network. The spectral data obtained by NIRscan(micro-NIRS) using single wavelength measurement mode and Hadamard transform measurement mode were studied. A variety of different data preprocessing methods and multiple linear regression, partial least squares, particle swarm optimization (PSO), BP neural network and other algorithms were used to establish the analysis model. The results show that the spectral data obtained by the working mode of Hadamard transform are better. First derivative combined with Savizky-Golay smoothing algorithm is used for data preprocessing. The prediction model of apple sugar content based on PSO and BP neural network has higher prediction accuracy. Predictive correlation coefficient and root mean square error are 0.9911 and 0.1502, respectively. NIRscan (micro-NIRS) is feasible for rapid and high-precision non-destructive testing of apple sugar content in the field.
2019, 43(6): 741-746.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.002
Abstract:
In order to measure thickness of optical elements with low cost and high precision in optical factories, astigmatism thickness measurement technology was used to build the measurement system. Theoretical analysis and experimental verification were carried out. In this system, astigmatism was introduced into cylindrical mirror to form elliptical spot with thickness-dependent aspect ratio. The thickness of components was obtained based on real-time image processing with high measuring efficiency. Finally, measurement experiments were carried out with commercial glass plates and concave lenses. The results show that measurement uncertainty of the system is less than 2μm when confidence probability is 95%. Measuring range of center thickness is 25mm and it can meet current general processing tolerance requirements. The device has the advantages of simple operation, high accuracy and low cost. It can be used to measure transparent and opaque materials with a wide range of application. The device provides a low-cost, non-contact and high-precision thickness measurement scheme for enterprises and is suitable for small and medium-sized optical processing enterprises. It has broad application prospects.
In order to measure thickness of optical elements with low cost and high precision in optical factories, astigmatism thickness measurement technology was used to build the measurement system. Theoretical analysis and experimental verification were carried out. In this system, astigmatism was introduced into cylindrical mirror to form elliptical spot with thickness-dependent aspect ratio. The thickness of components was obtained based on real-time image processing with high measuring efficiency. Finally, measurement experiments were carried out with commercial glass plates and concave lenses. The results show that measurement uncertainty of the system is less than 2μm when confidence probability is 95%. Measuring range of center thickness is 25mm and it can meet current general processing tolerance requirements. The device has the advantages of simple operation, high accuracy and low cost. It can be used to measure transparent and opaque materials with a wide range of application. The device provides a low-cost, non-contact and high-precision thickness measurement scheme for enterprises and is suitable for small and medium-sized optical processing enterprises. It has broad application prospects.
2019, 43(6): 747-752.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.003
Abstract:
In order to improve the accuracy and stability of terahertz spectroscopic quantitative analysis of multicomponent mixtures, Tchebichef image moment combined with partial least squares (PLS) regression modeling method was introduced into terahertz spectral quantitative analysis. The mixture of rubber additive zinc oxide, silica and nitrile-butadiene rubber was used as experimental sample. The zinc oxide in the mixture was quantitatively analyzed. After obtaining the terahertz absorbance data of the sample, 3-D spectra of samples were constructed by self-construction method of 3-D spectra. Tchebichef image moments were used to extract the feature information of the 3-D spectral gray image of the sample. Then a quantitative model was established by PLS to quantitatively analyze zinc oxide. The experimental results show that, the correlation coefficient and root mean square error of the sample prediction set obtained by this method are 0.9993 and 0.0351, respectively. Compared with the absorbance data modeling directly by PLS and support vector regression, the results are more accurate and stable. This method can be used for accurate and stable quantitative analysis of zinc oxide in mixtures. It provides a new idea for terahertz spectroscopic quantitative analysis of multicomponent mixtures.
In order to improve the accuracy and stability of terahertz spectroscopic quantitative analysis of multicomponent mixtures, Tchebichef image moment combined with partial least squares (PLS) regression modeling method was introduced into terahertz spectral quantitative analysis. The mixture of rubber additive zinc oxide, silica and nitrile-butadiene rubber was used as experimental sample. The zinc oxide in the mixture was quantitatively analyzed. After obtaining the terahertz absorbance data of the sample, 3-D spectra of samples were constructed by self-construction method of 3-D spectra. Tchebichef image moments were used to extract the feature information of the 3-D spectral gray image of the sample. Then a quantitative model was established by PLS to quantitatively analyze zinc oxide. The experimental results show that, the correlation coefficient and root mean square error of the sample prediction set obtained by this method are 0.9993 and 0.0351, respectively. Compared with the absorbance data modeling directly by PLS and support vector regression, the results are more accurate and stable. This method can be used for accurate and stable quantitative analysis of zinc oxide in mixtures. It provides a new idea for terahertz spectroscopic quantitative analysis of multicomponent mixtures.
2019, 43(6): 753-756.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.004
Abstract:
In order to suppress the stimulated Brillouin scattering effect in narrow linewidth pulse fiber amplifiers, the linewidth of single-frequency seed source was expanded by using multi-spectral line technology. The experimental verification of high peak power pulse all-fiber laser based on three-line master oscillator power amplifier was carried out. The results show that, after two-stage preamplifier and one-stage power amplifier, the maximum average power of laser output is 303W, pulse width is 2.8ns, repetition rate is 3.1MHz, and the corresponding peak power is 35kW. At the highest power output, the beam quality of the laser is less than 1.3. The structure of three spectral lines has obvious inhibition effect on stimulated Brillouin scattering. This study provides a reference for the amplification technology of high peak power pulsed fiber lasers.
In order to suppress the stimulated Brillouin scattering effect in narrow linewidth pulse fiber amplifiers, the linewidth of single-frequency seed source was expanded by using multi-spectral line technology. The experimental verification of high peak power pulse all-fiber laser based on three-line master oscillator power amplifier was carried out. The results show that, after two-stage preamplifier and one-stage power amplifier, the maximum average power of laser output is 303W, pulse width is 2.8ns, repetition rate is 3.1MHz, and the corresponding peak power is 35kW. At the highest power output, the beam quality of the laser is less than 1.3. The structure of three spectral lines has obvious inhibition effect on stimulated Brillouin scattering. This study provides a reference for the amplification technology of high peak power pulsed fiber lasers.
2019, 43(6): 757-762.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.005
Abstract:
To explore characteristics of asymmetric couplers, a broadband coupler was fabricated by using two optical fibers with different refractive index. The distribution of optical field of fiber couplers with different refractive index differences and the curve of output optical power with stretching length were simulated by numerical calculation. Bandwidth difference between two broadband couplers and the influence of melting degree on power conversion ratio were analyzed. The theoretical bandwidth was obtained by simulation based on the beam propagation method. The results show that, the coupling power conversion ratio varies with the asymmetry of two optical fibers. When the power conversion ratio is adjusted to the splitting ratio of the coupler, the bandwidth of the coupler is the widest. The melting degree can regulate the beam splitting ratio of broadband couplers. The wavelength response of 3dB fiber coupler in C+L band is gentle. The bandwidth range is 150nm. The bandwidth ranges of couplers with beam splitting ratios of 3:7 and 1:9 are 210nm and 330nm, respectively. The bandwidth range of the coupler with beam splitting ratio of 1:99 is 420nm. The results provide a reference for the fabrication of asymmetric broadband couplers.
To explore characteristics of asymmetric couplers, a broadband coupler was fabricated by using two optical fibers with different refractive index. The distribution of optical field of fiber couplers with different refractive index differences and the curve of output optical power with stretching length were simulated by numerical calculation. Bandwidth difference between two broadband couplers and the influence of melting degree on power conversion ratio were analyzed. The theoretical bandwidth was obtained by simulation based on the beam propagation method. The results show that, the coupling power conversion ratio varies with the asymmetry of two optical fibers. When the power conversion ratio is adjusted to the splitting ratio of the coupler, the bandwidth of the coupler is the widest. The melting degree can regulate the beam splitting ratio of broadband couplers. The wavelength response of 3dB fiber coupler in C+L band is gentle. The bandwidth range is 150nm. The bandwidth ranges of couplers with beam splitting ratios of 3:7 and 1:9 are 210nm and 330nm, respectively. The bandwidth range of the coupler with beam splitting ratio of 1:99 is 420nm. The results provide a reference for the fabrication of asymmetric broadband couplers.
2019, 43(6): 763-767.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.006
Abstract:
Real-time target detection is one of the important research directions of infrared imaging spectral systems. In order to guarantee the data processing speed and spectral reproducing accuracy of the system at the same time, a high-speed spectral inversion system was studied. The system was implemented by a field-programmable gate array (FPGA) chip. Non-uniformity correction and windowed toe-cutting were applied to the interference fringe image to suppress the direct current noise and spurious noise in interference fringe data. Then spectral distribution was obtained after fast Fourier transform, phase correction and spectrum calibration. The results show that the algorithm has a good suppression effect on spurious noise. Coefficient of inhomogeneity decreases from 11.23% to 1.05%. In the experiment of spectral inversion, the spectral distribution obtained by this system is basically consistent with that obtained by MATLAB. The accuracy of spectral details is better. The system uses pipeline mode to shorten the data processing cycle. And the development module based on FPGA chip has better compatibility. The system has the advantages of fast processing speed, small volume, high stability and good compatibility. It has good application prospect in the field of infrared target real-time detection.
Real-time target detection is one of the important research directions of infrared imaging spectral systems. In order to guarantee the data processing speed and spectral reproducing accuracy of the system at the same time, a high-speed spectral inversion system was studied. The system was implemented by a field-programmable gate array (FPGA) chip. Non-uniformity correction and windowed toe-cutting were applied to the interference fringe image to suppress the direct current noise and spurious noise in interference fringe data. Then spectral distribution was obtained after fast Fourier transform, phase correction and spectrum calibration. The results show that the algorithm has a good suppression effect on spurious noise. Coefficient of inhomogeneity decreases from 11.23% to 1.05%. In the experiment of spectral inversion, the spectral distribution obtained by this system is basically consistent with that obtained by MATLAB. The accuracy of spectral details is better. The system uses pipeline mode to shorten the data processing cycle. And the development module based on FPGA chip has better compatibility. The system has the advantages of fast processing speed, small volume, high stability and good compatibility. It has good application prospect in the field of infrared target real-time detection.
2019, 43(6): 768-772.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.007
Abstract:
In order to study transmission characteristics of terahertz wave in new asymptotic porous photonic crystal fibers, finite element numerical analysis method was used for numerical simulation. The effects of effective mode area and core porosity on effective material loss, confinement loss and power distribution fraction were analyzed. The results show that, within the range of 0.5THz to 0.85THz, by introducing an asymptotic rectangular array of holes and elliptical holes into the optical fiber, zero dispersion, high birefringence of 0.0532, effective material loss of 0.1157/cm and confinement loss of 1.47×10-4 dB/cm are achieved. This study can be used to fabricate polarized THz waveguides, filters, etc. It is of great significance to study the long-distance and high-performance transmission of the new generation terahertz waveguides.
In order to study transmission characteristics of terahertz wave in new asymptotic porous photonic crystal fibers, finite element numerical analysis method was used for numerical simulation. The effects of effective mode area and core porosity on effective material loss, confinement loss and power distribution fraction were analyzed. The results show that, within the range of 0.5THz to 0.85THz, by introducing an asymptotic rectangular array of holes and elliptical holes into the optical fiber, zero dispersion, high birefringence of 0.0532, effective material loss of 0.1157/cm and confinement loss of 1.47×10-4 dB/cm are achieved. This study can be used to fabricate polarized THz waveguides, filters, etc. It is of great significance to study the long-distance and high-performance transmission of the new generation terahertz waveguides.
2019, 43(6): 773-778.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.008
Abstract:
In order to investigate cutting characteristics of negative plate composites, the temperature field of negative plate composite material of the lithium ion battery by laser cutting was numerically simulated based on finite element model. The size of the width and depth of the negative electrode slit was obtained from the temperature field distribution. The effect of laser power, cutting speed and spot radius on the slit width and depth of negative surface material was studied. The results show that, the width of the slit on the surface of the negative electrode increases with the increase of laser power and the radius of the spot. It decreases with the increase of cutting speed. The slit depth increases with the increase of laser power. It decreases with the increase of cutting speed and spot radius. After cutting to the middle copper foil, the change rate of the slit depth is slowing down. The composite structure of the negative electrode material has a significant effect on the depth of the slit. When the power is 170W, the radius of the spot is 47μm, and the cutting speed varies to about 600mm/s, the effect is most obvious. The cutting depth reaches 60μm under this parameter. After breaking through this threshold, the growth rate is increased significantly until the polar plate is completely cut off. The results can provide a reference for laser cutting of lithium ion battery plate composite material.
In order to investigate cutting characteristics of negative plate composites, the temperature field of negative plate composite material of the lithium ion battery by laser cutting was numerically simulated based on finite element model. The size of the width and depth of the negative electrode slit was obtained from the temperature field distribution. The effect of laser power, cutting speed and spot radius on the slit width and depth of negative surface material was studied. The results show that, the width of the slit on the surface of the negative electrode increases with the increase of laser power and the radius of the spot. It decreases with the increase of cutting speed. The slit depth increases with the increase of laser power. It decreases with the increase of cutting speed and spot radius. After cutting to the middle copper foil, the change rate of the slit depth is slowing down. The composite structure of the negative electrode material has a significant effect on the depth of the slit. When the power is 170W, the radius of the spot is 47μm, and the cutting speed varies to about 600mm/s, the effect is most obvious. The cutting depth reaches 60μm under this parameter. After breaking through this threshold, the growth rate is increased significantly until the polar plate is completely cut off. The results can provide a reference for laser cutting of lithium ion battery plate composite material.
2019, 43(6): 779-783.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.009
Abstract:
In order to study the feasibility and effect of fabrication of metal films with high reflectivity based on near infrared nanosecond pulsed laser, high reflectivity aluminium films were fabricated by nanosecond pulsed laser. Under the conditions of different laser spot sizes and different laser energy, the change of ablation morphology on the surface of aluminium film was measured. The results show that, even if surface reflectivity of aluminium film is as high as 96%, the aluminum film can still be processed by laser. The ablation pattern of defocusing (energy density less than 1000J/mm2) on the surface of aluminium film by high power laser is more regular than that of focusing (energy density greater than 2000J/mm2) on the surface of aluminium film by low power laser. The relevant experimental results can play a guiding role in the selection of laser parameters in laser processing of high reflectivity material.
In order to study the feasibility and effect of fabrication of metal films with high reflectivity based on near infrared nanosecond pulsed laser, high reflectivity aluminium films were fabricated by nanosecond pulsed laser. Under the conditions of different laser spot sizes and different laser energy, the change of ablation morphology on the surface of aluminium film was measured. The results show that, even if surface reflectivity of aluminium film is as high as 96%, the aluminum film can still be processed by laser. The ablation pattern of defocusing (energy density less than 1000J/mm2) on the surface of aluminium film by high power laser is more regular than that of focusing (energy density greater than 2000J/mm2) on the surface of aluminium film by low power laser. The relevant experimental results can play a guiding role in the selection of laser parameters in laser processing of high reflectivity material.
2019, 43(6): 784-788.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.010
Abstract:
In order to solve the step temperature problem during test of thermocouple time constant, fuzzy control algorithm was used to feedback control the laser output power, a new parameter adaptive fuzzy proportion-integration-differentiation control algorithm was implemented and the hardware of closed-loop control system was analyzed. The experimental results show that, the time constant data of K-type thermocouple is 421.1ms. The algorithm can effectively shorten the balance time and enhance the anti-interference ability of the temperature control system. This research is helpful for the calibration research of thermocouples, and has certain engineering reference and application value.
In order to solve the step temperature problem during test of thermocouple time constant, fuzzy control algorithm was used to feedback control the laser output power, a new parameter adaptive fuzzy proportion-integration-differentiation control algorithm was implemented and the hardware of closed-loop control system was analyzed. The experimental results show that, the time constant data of K-type thermocouple is 421.1ms. The algorithm can effectively shorten the balance time and enhance the anti-interference ability of the temperature control system. This research is helpful for the calibration research of thermocouples, and has certain engineering reference and application value.
2019, 43(6): 789-794.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.011
Abstract:
In order to study nonlinear dynamic characteristics of a semiconductor ring laser (SRL) under external cross-optical feedback, the time series and power spectra under various feedback parameters were obtained by numerical simulation based on the SRL rate equation, and the effect of feedback coefficient on chaotic bandwidth and time delay characteristics was studied. The results show that SRL exhibits a variety of dynamic states such as single period, multi-period, low-frequency anti-phase fluctuation and chaotic state under various external feedback parameters. The maximum chaotic bandwidth of 3.7GHz can be obtained with symmetric optical feedback, and the time delay characteristics of chaotic signals generated by time-asymmetric optical feedback are well suppressed. The results of this study can provide some theoretical reference for the practical application of SRLs.
In order to study nonlinear dynamic characteristics of a semiconductor ring laser (SRL) under external cross-optical feedback, the time series and power spectra under various feedback parameters were obtained by numerical simulation based on the SRL rate equation, and the effect of feedback coefficient on chaotic bandwidth and time delay characteristics was studied. The results show that SRL exhibits a variety of dynamic states such as single period, multi-period, low-frequency anti-phase fluctuation and chaotic state under various external feedback parameters. The maximum chaotic bandwidth of 3.7GHz can be obtained with symmetric optical feedback, and the time delay characteristics of chaotic signals generated by time-asymmetric optical feedback are well suppressed. The results of this study can provide some theoretical reference for the practical application of SRLs.
2019, 43(6): 795-799.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.012
Abstract:
In order to study the immunity of calibration-free wavelength modulation spectroscopy to laser intensity change and external interference, multi-path absorption spectra based on calibration-free wavelength modulation technology were adopted. Taking acetylene as the measurement target, theoretical analysis and experimental verification were carried out. The results show that, the amplitude of wavelength modulated second harmonic signal varies significantly under different laser power. But the signal obtained by the calibration-free method changes little. It is less affected by external disturbance such as airflow, partial shading and system vibration. The spectral signals with volume fraction in the range of 5×10-6 ~9×10-5 obtained by calibration-free method have good linearity. The correlation coefficient is 0.9997. Allan variance analysis shows that the minimum detection limit of the experimental system can reach 1.2×10-8. This study shows that calibration-free wavelength modulation spectroscopy can avoid the interference of light intensity jitter, air flow and system vibration. The system stability and detection sensitivity are improved.
In order to study the immunity of calibration-free wavelength modulation spectroscopy to laser intensity change and external interference, multi-path absorption spectra based on calibration-free wavelength modulation technology were adopted. Taking acetylene as the measurement target, theoretical analysis and experimental verification were carried out. The results show that, the amplitude of wavelength modulated second harmonic signal varies significantly under different laser power. But the signal obtained by the calibration-free method changes little. It is less affected by external disturbance such as airflow, partial shading and system vibration. The spectral signals with volume fraction in the range of 5×10-6 ~9×10-5 obtained by calibration-free method have good linearity. The correlation coefficient is 0.9997. Allan variance analysis shows that the minimum detection limit of the experimental system can reach 1.2×10-8. This study shows that calibration-free wavelength modulation spectroscopy can avoid the interference of light intensity jitter, air flow and system vibration. The system stability and detection sensitivity are improved.
2019, 43(6): 800-803.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.013
Abstract:
In order to suppress the stimulated Brillouin scattering effect and increase the amplification power of single frequency narrow linewidth seed source, master oscillator power amplifier (MOPA) structure was adopted. Fiber length, core diameter and pumping parameters were optimized. Optical output of 42W signal at 1064nm was realized. In the experiment, the first stage amplification used 914nm semiconductor laser as pumping source with gain fiber core diameter of 10μm and length of 8m. The second stage amplifier used 976nm semiconductor laser as the pumping source with gain fiber core diameter of 20μm and length of 2.4m. When seed power is 40mW, pump power of the first stage amplification is 6.8W and pump power of the second stage amplification is 85W, optical output 42W of the signal at 1064nm was obtained. The results show that light-to-light conversion efficiency is about 49.4%, polarization extinction ratio is 27.5dB; central wavelength of output signal light is 1064.5nm, and linewidth is about 70MHz. Single-frequency characteristics of seed light are maintained. Stimulated Brillouin scattering is not observed at 42W continuous output. Continuous increase of pump power is expected to achieve higher power amplification.
In order to suppress the stimulated Brillouin scattering effect and increase the amplification power of single frequency narrow linewidth seed source, master oscillator power amplifier (MOPA) structure was adopted. Fiber length, core diameter and pumping parameters were optimized. Optical output of 42W signal at 1064nm was realized. In the experiment, the first stage amplification used 914nm semiconductor laser as pumping source with gain fiber core diameter of 10μm and length of 8m. The second stage amplifier used 976nm semiconductor laser as the pumping source with gain fiber core diameter of 20μm and length of 2.4m. When seed power is 40mW, pump power of the first stage amplification is 6.8W and pump power of the second stage amplification is 85W, optical output 42W of the signal at 1064nm was obtained. The results show that light-to-light conversion efficiency is about 49.4%, polarization extinction ratio is 27.5dB; central wavelength of output signal light is 1064.5nm, and linewidth is about 70MHz. Single-frequency characteristics of seed light are maintained. Stimulated Brillouin scattering is not observed at 42W continuous output. Continuous increase of pump power is expected to achieve higher power amplification.
2019, 43(6): 804-808.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.014
Abstract:
In order to solve the problem of measuring the position and posture of a coal mine roadheader, a set of reverse coaxial industrial cameras and strapdown inertial navigation system were assembled into a bias measurement unit. Combining vision measurement and inertial navigation technology, a real-time pose measurement method was proposed based on space vector constraints. In this method, the spatial vector of the light spot of laser pointer, the spatial vector of the light spot of palm face and the attitude information of roadheader were measured by the deviation measuring unit. Space vector constraint equation and coordinate system conversion were established. The location information of the roadheader was obtained. Theoretical analysis and experimental verification were carried out. The results show that, the six degrees of freedom information of the real-time position and posture of the roadheader can be obtained by this method. This method can be used to measure the position and posture of coal mine roadheaders, and has broad application and development prospects.
In order to solve the problem of measuring the position and posture of a coal mine roadheader, a set of reverse coaxial industrial cameras and strapdown inertial navigation system were assembled into a bias measurement unit. Combining vision measurement and inertial navigation technology, a real-time pose measurement method was proposed based on space vector constraints. In this method, the spatial vector of the light spot of laser pointer, the spatial vector of the light spot of palm face and the attitude information of roadheader were measured by the deviation measuring unit. Space vector constraint equation and coordinate system conversion were established. The location information of the roadheader was obtained. Theoretical analysis and experimental verification were carried out. The results show that, the six degrees of freedom information of the real-time position and posture of the roadheader can be obtained by this method. This method can be used to measure the position and posture of coal mine roadheaders, and has broad application and development prospects.
2019, 43(6): 809-814.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.015
Abstract:
The acquisition, pointing and tracking (APT) system of laser wireless energy transfer for unmanned aerial vehicles (UAV) is the guarantee of stable energy at the receiving end of the system. In order to solve the problem of high efficiency and reliability of charging link in energy transmission process, considering the characteristics and practical requirements of UAV laser energy transmission system, an adaptive region of interest was established in the design for improving image processing speed, reducing noise and accurately extracting target coordinates. Considering multiple errors, Kalman prediction algorithm was used to achieve stable tracking. According to the characteristics of the system, the calculation scheme of power transmission efficiency of the system was put forward. The results show that, when the flight speed of UAV is within 18km/h, APT system can track the UAV accurately from 300m to 500m. The tracking accuracy is within 320μrad. The scheme can ensure the tracking accuracy and reliability of laser energy transmission process.
The acquisition, pointing and tracking (APT) system of laser wireless energy transfer for unmanned aerial vehicles (UAV) is the guarantee of stable energy at the receiving end of the system. In order to solve the problem of high efficiency and reliability of charging link in energy transmission process, considering the characteristics and practical requirements of UAV laser energy transmission system, an adaptive region of interest was established in the design for improving image processing speed, reducing noise and accurately extracting target coordinates. Considering multiple errors, Kalman prediction algorithm was used to achieve stable tracking. According to the characteristics of the system, the calculation scheme of power transmission efficiency of the system was put forward. The results show that, when the flight speed of UAV is within 18km/h, APT system can track the UAV accurately from 300m to 500m. The tracking accuracy is within 320μrad. The scheme can ensure the tracking accuracy and reliability of laser energy transmission process.
2019, 43(6): 815-820.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.016
Abstract:
In order to realize the early and small-scale oil spill detection and warning, surface plasmon resonance (SPR) sensing technology, which was sensitive to small changes in refractive index of external media, was used. A set of small oil spill detection experimental device was designed and built. A GUI interface based on SPR was created to select sensing parameters. A set of software with functions of data acquisition, storage, processing and display was compiled by C++ for data processing and early warning. The theoretical analysis and experimental verification were carried out. SPR data of crude oil samples with refractive index of 1.4451, 1.4774 and 1.5299 were obtained. The results show that the experimental data are in agreement with the simulation results. The device can be used in the experimental study of oil spill detection at sea. Its software design meets the needs of early warning. This result is helpful to the detection of oil spill at sea.
In order to realize the early and small-scale oil spill detection and warning, surface plasmon resonance (SPR) sensing technology, which was sensitive to small changes in refractive index of external media, was used. A set of small oil spill detection experimental device was designed and built. A GUI interface based on SPR was created to select sensing parameters. A set of software with functions of data acquisition, storage, processing and display was compiled by C++ for data processing and early warning. The theoretical analysis and experimental verification were carried out. SPR data of crude oil samples with refractive index of 1.4451, 1.4774 and 1.5299 were obtained. The results show that the experimental data are in agreement with the simulation results. The device can be used in the experimental study of oil spill detection at sea. Its software design meets the needs of early warning. This result is helpful to the detection of oil spill at sea.
2019, 43(6): 821-828.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.017
Abstract:
8μm~14μm long-wave infrared coherent radiation has important application value in many fields such as atmospheric laser remote sensing and communication, high-resolution molecular fingerprint spectrum and national security. Several kinds of optical sources which can obtain 8μm~14μm coherent radiation are summarized, including CO2 gas laser, semiconductor quantum cascade laser, infrared free electron laser, infrared supercontinuum spectrum source and non-linear variable frequency mid-infrared solid-state laser. The basic principles of different technologies and their progress at home and abroad are introduced. The advantages and disadvantages, development direction and application scope of each method are analyzed and compared. Nonlinear variable frequency mid-infrared solid-state lasers have outstanding advantages of 8μm~14μm continuous tuning, femtosecond, picosecond, nanosecond and continuous wave operation, and 1Hz~GHz tunable repetition frequency. Full solid structure, high reliability and good beam quality are also obtained. It will be the best choice for developing practical and precise long-wave infrared coherent radiation sources.
8μm~14μm long-wave infrared coherent radiation has important application value in many fields such as atmospheric laser remote sensing and communication, high-resolution molecular fingerprint spectrum and national security. Several kinds of optical sources which can obtain 8μm~14μm coherent radiation are summarized, including CO2 gas laser, semiconductor quantum cascade laser, infrared free electron laser, infrared supercontinuum spectrum source and non-linear variable frequency mid-infrared solid-state laser. The basic principles of different technologies and their progress at home and abroad are introduced. The advantages and disadvantages, development direction and application scope of each method are analyzed and compared. Nonlinear variable frequency mid-infrared solid-state lasers have outstanding advantages of 8μm~14μm continuous tuning, femtosecond, picosecond, nanosecond and continuous wave operation, and 1Hz~GHz tunable repetition frequency. Full solid structure, high reliability and good beam quality are also obtained. It will be the best choice for developing practical and precise long-wave infrared coherent radiation sources.
2019, 43(6): 829-833.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.018
Abstract:
To study the incoherent beam combination characteristics of fiber lasers, a beam combination model of a circular array of multiple fiber lasers was established, and effect of waist radius w0, wave-front distortion of unit beam and beam separation distance on the far field beam quality of incoherent and coherent combination was simulated and analyzed. In addition, the influence of axis parallelism of multiple laser beams on the incoherent beam combination effect was studied, and experimental verification was carried out. The results show that, when the beam separation distance is d0=2.8w0, the beam quality β factor of incoherent combination of multiple laser beams without wave-front distortion is equal to that of coherent combination. The beam separation distance d0 decreases when the wave-front phase of laser beam is distorted, and the influence of wave-front distortion on the incoherent combination is less than that on the coherent combination. With the increasing of the parallel error among multiple laser beams, the beam quality of incoherent combination becomes worse. And the better the beam quality of unit beam is, the higher the demand for the axis parallelism of multiple laser beams. This research can provide references for the design and analysis of beam combination system of fiber lasers.
To study the incoherent beam combination characteristics of fiber lasers, a beam combination model of a circular array of multiple fiber lasers was established, and effect of waist radius w0, wave-front distortion of unit beam and beam separation distance on the far field beam quality of incoherent and coherent combination was simulated and analyzed. In addition, the influence of axis parallelism of multiple laser beams on the incoherent beam combination effect was studied, and experimental verification was carried out. The results show that, when the beam separation distance is d0=2.8w0, the beam quality β factor of incoherent combination of multiple laser beams without wave-front distortion is equal to that of coherent combination. The beam separation distance d0 decreases when the wave-front phase of laser beam is distorted, and the influence of wave-front distortion on the incoherent combination is less than that on the coherent combination. With the increasing of the parallel error among multiple laser beams, the beam quality of incoherent combination becomes worse. And the better the beam quality of unit beam is, the higher the demand for the axis parallelism of multiple laser beams. This research can provide references for the design and analysis of beam combination system of fiber lasers.
2019, 43(6): 834-840.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.019
Abstract:
In order to investigate the propagation characteristics of electromagnetic elliptical multi-Gaussian-Schell mode (EEMGSM) beams, based on the generalized Huygens-Fresnel principle and the second moment theory of Wigner distribution function, the analytical expression of M2 factor of EEMGSM beams propagating in anisotropic turbulence was derived theoretically. Through numerical calculation and analysis, the variations of initial polarization, initial coherence, waist width, wavelength and turbulence structure constant with M2 factor were investigated. The results show that, M2 factor of EEMGSM beam decreases with the increase of order, wavelength and waist width. It decreases with the decrease of initial coherence and turbulence structure constant. Under the same conditions, the beam quality of EEMGSM beams with large initial polarization is less affected by anisotropy than that of EEMGSM beams with small initial polarization. Under the same conditions, the quality factor of EEMGSM beam is smaller than that of scalar elliptical Gaussian-Schell mode (EGSM) beam. EEMGSM beam has the advantage of alleviating the influence of anisotropic turbulence. The study has certain theoretical reference value for the research of free space optical communication.
In order to investigate the propagation characteristics of electromagnetic elliptical multi-Gaussian-Schell mode (EEMGSM) beams, based on the generalized Huygens-Fresnel principle and the second moment theory of Wigner distribution function, the analytical expression of M2 factor of EEMGSM beams propagating in anisotropic turbulence was derived theoretically. Through numerical calculation and analysis, the variations of initial polarization, initial coherence, waist width, wavelength and turbulence structure constant with M2 factor were investigated. The results show that, M2 factor of EEMGSM beam decreases with the increase of order, wavelength and waist width. It decreases with the decrease of initial coherence and turbulence structure constant. Under the same conditions, the beam quality of EEMGSM beams with large initial polarization is less affected by anisotropy than that of EEMGSM beams with small initial polarization. Under the same conditions, the quality factor of EEMGSM beam is smaller than that of scalar elliptical Gaussian-Schell mode (EGSM) beam. EEMGSM beam has the advantage of alleviating the influence of anisotropic turbulence. The study has certain theoretical reference value for the research of free space optical communication.
2019, 43(6): 841-845.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.020
Abstract:
In order to study propagation characteristics of Gaussian-Schell model Gaussian-Schell model(GSM) pulses in single-mode fibers, the characteristics of GSM pulses propagating through the single-mode fibers were studied by means of temporal coherence function propagation analysis. Based on the analytical expression of temporal coherence function, the changes of pulse width, coherence time and power spectrum were analyzed. The generalized van Citter-Zernike theorem in time domain for single-mode fibers under remote conditions is also derived. The results show that there are two conserved quantities of power spectrum and global coherence in the transmission of GSM pulses in single-mode optical fibers, and they are consistent. The study has important theoretical and practical significance in the field of laser transmission.
In order to study propagation characteristics of Gaussian-Schell model Gaussian-Schell model(GSM) pulses in single-mode fibers, the characteristics of GSM pulses propagating through the single-mode fibers were studied by means of temporal coherence function propagation analysis. Based on the analytical expression of temporal coherence function, the changes of pulse width, coherence time and power spectrum were analyzed. The generalized van Citter-Zernike theorem in time domain for single-mode fibers under remote conditions is also derived. The results show that there are two conserved quantities of power spectrum and global coherence in the transmission of GSM pulses in single-mode optical fibers, and they are consistent. The study has important theoretical and practical significance in the field of laser transmission.
2019, 43(6): 846-849.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.021
Abstract:
In order to study the propagation characteristics and energy density distribution of femtosecond laser beam quality factor M2 based on Gaussian beam, on the basis of theoretical study of femtosecond laser beam quality factor, the corresponding data were calculated. The measurement method of annular spot width formed by femtosecond laser pulse irradiating the screen surface was given. An experimental platform consisting of femtosecond laser, lens and dielectric glass screen was established. The method was compared with the knife-edge method and the CCD method.The range of laser beam quality factor at different positions of femtosecond laser beam waist was confirmed by knife-edge method and CCD method. The results show that the measured values of beam quality factor M2 in x and y directions are 2.04 and 1.24, respectively. The experimental results are basically consistent with the theoretical analysis. Compared with knife-edge method and CCD method, the structure is simple. The data obtained are reliable and easy to carry out. It has certain reference value for precise measurement.
In order to study the propagation characteristics and energy density distribution of femtosecond laser beam quality factor M2 based on Gaussian beam, on the basis of theoretical study of femtosecond laser beam quality factor, the corresponding data were calculated. The measurement method of annular spot width formed by femtosecond laser pulse irradiating the screen surface was given. An experimental platform consisting of femtosecond laser, lens and dielectric glass screen was established. The method was compared with the knife-edge method and the CCD method.The range of laser beam quality factor at different positions of femtosecond laser beam waist was confirmed by knife-edge method and CCD method. The results show that the measured values of beam quality factor M2 in x and y directions are 2.04 and 1.24, respectively. The experimental results are basically consistent with the theoretical analysis. Compared with knife-edge method and CCD method, the structure is simple. The data obtained are reliable and easy to carry out. It has certain reference value for precise measurement.
2019, 43(6): 850-854.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.022
Abstract:
In order to improve the short circuit current density and conversion efficiency of crystalline silicon thin film solar cells, a silicon dielectric grating and an aluminium metal grating were integrated on the front and back of single crystal silicon thin film solar cells respectively. The effect of the period, thickness and duty cycle of both the gratings on the short-circuit current density and optical conversion efficiency of single crystal silicon thin film solar cells were simulated with finite difference time-domain software. The results show that, the short-circuit current density can reach 35.15mA/cm2 and the conversion efficiency is 43.35% when both the front and back gratings are at the optimum value (for the dielectric grating, duty cycle F=0.8, period P=0.632μm, thickness hg=0.42μm; for the metal grating, duty cycle F1=0.9, period P=0.632μm and thickness hm=0.005μm). After comparing the optimal grating monocrystalline silicon thin film solar cells with traditional monocrystalline silicon thin film solar cells, the grating monocrystalline silicon thin film solar cells have a significant improvement in both optical path and absorption efficiency. This study provides theoretical guidance for the preparation of high performance thin film solar cells in the future.
In order to improve the short circuit current density and conversion efficiency of crystalline silicon thin film solar cells, a silicon dielectric grating and an aluminium metal grating were integrated on the front and back of single crystal silicon thin film solar cells respectively. The effect of the period, thickness and duty cycle of both the gratings on the short-circuit current density and optical conversion efficiency of single crystal silicon thin film solar cells were simulated with finite difference time-domain software. The results show that, the short-circuit current density can reach 35.15mA/cm2 and the conversion efficiency is 43.35% when both the front and back gratings are at the optimum value (for the dielectric grating, duty cycle F=0.8, period P=0.632μm, thickness hg=0.42μm; for the metal grating, duty cycle F1=0.9, period P=0.632μm and thickness hm=0.005μm). After comparing the optimal grating monocrystalline silicon thin film solar cells with traditional monocrystalline silicon thin film solar cells, the grating monocrystalline silicon thin film solar cells have a significant improvement in both optical path and absorption efficiency. This study provides theoretical guidance for the preparation of high performance thin film solar cells in the future.
2019, 43(6): 855-862.
doi: 10.7510/jgjs.issn.1001-3806.2019.06.023
Abstract:
In order to improve the uniformity of intensity distribution of the reconstructed images and improve the imaging quality in the design of the diffractive optical elements, the design algorithm is optimized by adding a mixed amplitude degree of freedom to the target image due to the fact that there must be leakage in the light field propagation process, and the effectiveness of the method was verified by designing a Fourier transform type diffractive optical element. The simulation results show that, compared without amplitude degree of freedom, the reconstructed image's intensity uniformity of the elements designed by this method is reduced from about 14% to less than 1%, and the mean square error is reduced from about 10% to less than 0.1%, and the method is applicable to both Gerchberg & Saxton(GS) algorithm and simulated annealing algorithm.
In order to improve the uniformity of intensity distribution of the reconstructed images and improve the imaging quality in the design of the diffractive optical elements, the design algorithm is optimized by adding a mixed amplitude degree of freedom to the target image due to the fact that there must be leakage in the light field propagation process, and the effectiveness of the method was verified by designing a Fourier transform type diffractive optical element. The simulation results show that, compared without amplitude degree of freedom, the reconstructed image's intensity uniformity of the elements designed by this method is reduced from about 14% to less than 1%, and the mean square error is reduced from about 10% to less than 0.1%, and the method is applicable to both Gerchberg & Saxton(GS) algorithm and simulated annealing algorithm.
