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RSS2016 Vol. 40, No. 5
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2016, 40(5): 619-624.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.001
[Abstract]
[PDF 2190KB]
Abstract:
When eigenvector method was used to perform numerical simulation on laser resonator with big Fresnel number, the calculation efficiency was low by using trapezoidal integral method. In order to solve the problem, the minimum sampling numbers for numerical simulation were determined by analyzing the space-bandwidth product of resonators output mode and Gaussian quadrature was used to calculate the transmission matrix. This method not only ensured the calculation accuracy of chirp function but also reduced the transmission matrix size.Through numerical simulation of plane-concave resonator with square mirrors which Fresnel number is 10,the results show that, transmission matrix size of trapezoidal integration is 1000010000 and computation time of laser resonator modes is 412.47s. Transmission matrix size of Gaussian quadrature is 36003600 and computation time is 51.34s. These results indicate that the new method greatly improves computational efficiency of eigenvector method and reduces the consumption of computer memory at the same time.
When eigenvector method was used to perform numerical simulation on laser resonator with big Fresnel number, the calculation efficiency was low by using trapezoidal integral method. In order to solve the problem, the minimum sampling numbers for numerical simulation were determined by analyzing the space-bandwidth product of resonators output mode and Gaussian quadrature was used to calculate the transmission matrix. This method not only ensured the calculation accuracy of chirp function but also reduced the transmission matrix size.Through numerical simulation of plane-concave resonator with square mirrors which Fresnel number is 10,the results show that, transmission matrix size of trapezoidal integration is 1000010000 and computation time of laser resonator modes is 412.47s. Transmission matrix size of Gaussian quadrature is 36003600 and computation time is 51.34s. These results indicate that the new method greatly improves computational efficiency of eigenvector method and reduces the consumption of computer memory at the same time.
2016, 40(5): 625-628.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.002
Abstract:
In order to develop a new type of airborne compact repetitive diode-pumped slab laser operating at -40℃~+65℃, a diode-pumped laser without thermoelectric coolers was adoped to overcome the problems of thermoelectric coolers. The experimental results show that the laser can work stably and reliably under the condition of -40℃~+65℃ environment at 20Hz~30Hz pulse repetition frequencies with laser output energy of 100mJ~150mJ and pulse width of 6ns~7ns. The beam divergence becomes 1mrad after passing through 4 telescope. The diode-pumped laser can be used in airborne and carborne laser rangefinders/designators.
In order to develop a new type of airborne compact repetitive diode-pumped slab laser operating at -40℃~+65℃, a diode-pumped laser without thermoelectric coolers was adoped to overcome the problems of thermoelectric coolers. The experimental results show that the laser can work stably and reliably under the condition of -40℃~+65℃ environment at 20Hz~30Hz pulse repetition frequencies with laser output energy of 100mJ~150mJ and pulse width of 6ns~7ns. The beam divergence becomes 1mrad after passing through 4 telescope. The diode-pumped laser can be used in airborne and carborne laser rangefinders/designators.
2016, 40(5): 629-632.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.003
Abstract:
In order to solve the incorrect low-airspeed detection of traditional air data system, a low-airspeed detection method based on optical Doppler frequency shift was founded. An experimental prototype was built by using fast Fourier transform as data processing framework. By the experiment of standard wind tunnel, the system can measure minimum wind speed of 0.22m/s. The results show that the system has high resolution and stability at different wind speeds.
In order to solve the incorrect low-airspeed detection of traditional air data system, a low-airspeed detection method based on optical Doppler frequency shift was founded. An experimental prototype was built by using fast Fourier transform as data processing framework. By the experiment of standard wind tunnel, the system can measure minimum wind speed of 0.22m/s. The results show that the system has high resolution and stability at different wind speeds.
2016, 40(5): 633-637.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.004
Abstract:
Barcodes have been wildly used in commercial retail and e-commerce field with the wide application of smart phones. In order to expand the direct part marking applications in industrial filed, the smart phone recognition characteristics of the laser marking barcodes on aluminum alloy surface were investigated by theoretical analysis and experimental verification. Due to different processing arts, the laser marking area may be in white, grey and black contrast colors. The conventional white barcodes recognition problem can be solved by the combination of complementary laser scanning and mirroring symmetry recognition condition, which has application value for the design of barcode recognition algorithm on smart phones and makes the high efficiency laser marking possible.
Barcodes have been wildly used in commercial retail and e-commerce field with the wide application of smart phones. In order to expand the direct part marking applications in industrial filed, the smart phone recognition characteristics of the laser marking barcodes on aluminum alloy surface were investigated by theoretical analysis and experimental verification. Due to different processing arts, the laser marking area may be in white, grey and black contrast colors. The conventional white barcodes recognition problem can be solved by the combination of complementary laser scanning and mirroring symmetry recognition condition, which has application value for the design of barcode recognition algorithm on smart phones and makes the high efficiency laser marking possible.
2016, 40(5): 638-642.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.005
Abstract:
In order to eliminate effect of fluorescent bead diameter on measurement results in traditional microscopic point spread function measurement method and improve the measurement accuracy, 2-D equivalent concentration distribution of fluorescent beads was deduced based on theoretical simulation and least square fitting method. The imaging process of fluorescent beads was simulated. The relationships among fluorescent beads diameter, full width at half maximum (FWHM) of fluorescent beads intensity distribution and FWHM of system point spread function were analyzed by using the least square fitting method and residual error fitting method. Precise FWHM correction model of point spread function was obtained. The results show that the relative error of point spread function FWHM is about 1% when measuring system point spread function with 100nm fluorescent beads. The precise measurement of point spread function is realizable with the optimized model.
In order to eliminate effect of fluorescent bead diameter on measurement results in traditional microscopic point spread function measurement method and improve the measurement accuracy, 2-D equivalent concentration distribution of fluorescent beads was deduced based on theoretical simulation and least square fitting method. The imaging process of fluorescent beads was simulated. The relationships among fluorescent beads diameter, full width at half maximum (FWHM) of fluorescent beads intensity distribution and FWHM of system point spread function were analyzed by using the least square fitting method and residual error fitting method. Precise FWHM correction model of point spread function was obtained. The results show that the relative error of point spread function FWHM is about 1% when measuring system point spread function with 100nm fluorescent beads. The precise measurement of point spread function is realizable with the optimized model.
2016, 40(5): 643-647.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.006
Abstract:
In order to measure the parameters for screw thread with high-precision, a measuring system of thread parameters based on machine vision technology was established. Contour datas of thread in the parallel back light was obtained by thread workpiece rotation and camera following-shot, and the measurements of thread parameters were realized. The measurement range of the system was expanded and the effect of camera calibration errors was reduced. Coordinate conversion equation was derived, and the coordinate system was unified by system calibration. Calculation formulas of thread parameters were derived. Considering the distortion of thread teeth on the projection of screw line when the optical axis of CCD camera and thread axis were vertical, a mathematical compensation model was built. The experiment results show that the uncertainty of system measurement was less than 2m and repeatability was better than 4m. The system can measure the thread parameters.
In order to measure the parameters for screw thread with high-precision, a measuring system of thread parameters based on machine vision technology was established. Contour datas of thread in the parallel back light was obtained by thread workpiece rotation and camera following-shot, and the measurements of thread parameters were realized. The measurement range of the system was expanded and the effect of camera calibration errors was reduced. Coordinate conversion equation was derived, and the coordinate system was unified by system calibration. Calculation formulas of thread parameters were derived. Considering the distortion of thread teeth on the projection of screw line when the optical axis of CCD camera and thread axis were vertical, a mathematical compensation model was built. The experiment results show that the uncertainty of system measurement was less than 2m and repeatability was better than 4m. The system can measure the thread parameters.
2016, 40(5): 648-653.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.007
Abstract:
In order to satisfy the requirement of miniaturization in measuring defects inside small bores, a new approach was proposed with external light importing and internal images exporting. This method solved the problem of the limited dimensional accessibility of small bores. Compared with the traditional measuring methods, the new method made the breakthrough and the method was without built-in sensors. The key problem of alignment error that had a great influence on measurement results was studied deeply and the measuring system was improved. The reasonable alignment error compensation method based on image correction was presented and a measuring system was built. Several tests were conducted on sample pipe with diameter of 12mm. The simulated point defects with diameter of 0.6mm, 0.8mm, 1.0mm were set on the internal surface of sample pipe. The results showed that after image correction on the unfolding image, the mean deviation of the defect diameter was less than 0.02mm, and the standard deviation was less than 0.03mm. The alignment error compensation method is reliable and able to improve the precision of measurement.
In order to satisfy the requirement of miniaturization in measuring defects inside small bores, a new approach was proposed with external light importing and internal images exporting. This method solved the problem of the limited dimensional accessibility of small bores. Compared with the traditional measuring methods, the new method made the breakthrough and the method was without built-in sensors. The key problem of alignment error that had a great influence on measurement results was studied deeply and the measuring system was improved. The reasonable alignment error compensation method based on image correction was presented and a measuring system was built. Several tests were conducted on sample pipe with diameter of 12mm. The simulated point defects with diameter of 0.6mm, 0.8mm, 1.0mm were set on the internal surface of sample pipe. The results showed that after image correction on the unfolding image, the mean deviation of the defect diameter was less than 0.02mm, and the standard deviation was less than 0.03mm. The alignment error compensation method is reliable and able to improve the precision of measurement.
2016, 40(5): 654-659.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.008
Abstract:
In order to get simulation teeth of ring sprockets with variable cross-section by means of laser cladding direct manu facturing technology, experiments were made based on inside-laser powder feeding technology and motion control of KUKA robot. According to the optimized process parameters, the scanning paths were planed and the lift amount of each layer was accurately controlled based on the incremental method of extra height and extra length. The substrate was preheated and the detection of dimension and microstructure of the formed tooth was made. The problem of edge collapse in the forming of irregular-section parts was solved. The machining allowance was controlled preferably on the basis of promising the sufficient size in different sections. And the cracking and spalling of cladding layer was avoided. The irregular-section tooth was successfully made on 42CrMoV substrate. The results indicate that the powder utilization rate is more than 60% in the processing. The surface of the part was smooth with no powder adhered. The size of the entity was within reasonable limits. The teeth and the substrate formed good metallurgical combination. The microstructure was uniform without microcracks and the microhardness was uniform in every section.
In order to get simulation teeth of ring sprockets with variable cross-section by means of laser cladding direct manu facturing technology, experiments were made based on inside-laser powder feeding technology and motion control of KUKA robot. According to the optimized process parameters, the scanning paths were planed and the lift amount of each layer was accurately controlled based on the incremental method of extra height and extra length. The substrate was preheated and the detection of dimension and microstructure of the formed tooth was made. The problem of edge collapse in the forming of irregular-section parts was solved. The machining allowance was controlled preferably on the basis of promising the sufficient size in different sections. And the cracking and spalling of cladding layer was avoided. The irregular-section tooth was successfully made on 42CrMoV substrate. The results indicate that the powder utilization rate is more than 60% in the processing. The surface of the part was smooth with no powder adhered. The size of the entity was within reasonable limits. The teeth and the substrate formed good metallurgical combination. The microstructure was uniform without microcracks and the microhardness was uniform in every section.
2016, 40(5): 660-664.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.009
Abstract:
In order to reveal the laser thermal-mechanical effect on electrochemical deposition further, a laser electrochemical composite deposition system was constructed, and the system was analyzed and verified. Specimens were prepared in the exposure area by laser round scanning, and mechanical effect and thermal effect was developed in the processing. Finally scanning electron microscope was used to observe surface morphologies of specimens. The results show that laser thermo-mechanical effect could speed up the reduction reaction of metal ions, promote nucleation and grain refinement. The deposition rate is enhanced at 0.198mg/min when laser energy is 0.2mJ(20kHz), and tensile strength is strengthened at 256.38MPa when laser energy is 0.4mJ (20kHz). The results are useful for the development of electrochemical machining technology later.
In order to reveal the laser thermal-mechanical effect on electrochemical deposition further, a laser electrochemical composite deposition system was constructed, and the system was analyzed and verified. Specimens were prepared in the exposure area by laser round scanning, and mechanical effect and thermal effect was developed in the processing. Finally scanning electron microscope was used to observe surface morphologies of specimens. The results show that laser thermo-mechanical effect could speed up the reduction reaction of metal ions, promote nucleation and grain refinement. The deposition rate is enhanced at 0.198mg/min when laser energy is 0.2mJ(20kHz), and tensile strength is strengthened at 256.38MPa when laser energy is 0.4mJ (20kHz). The results are useful for the development of electrochemical machining technology later.
2016, 40(5): 665-669.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.010
Abstract:
In order to simplify the structure of laser diode drivers, improve the power conversion efficiency and dynamic response of the output current, a 2kW single-stage switching power supply was developed with interleaved single ended forward conversion. Static characteristics, dynamic characteristics and power conversion efficiency of the laser diode driver were tested and analyzed. The results show that the power conversion efficiency is up to 85%. The rise time and fall time of output current in range of 0A~100A is 1ms. The ripple coefficient of output current is 0.04% when output current is 100A. Compared with laser diode driver with two-level cascade structure, the power conversion efficiency of the power supply was promoted. The dynamic response of output current is so rapid that the power supply meets requirements of laser processing.
In order to simplify the structure of laser diode drivers, improve the power conversion efficiency and dynamic response of the output current, a 2kW single-stage switching power supply was developed with interleaved single ended forward conversion. Static characteristics, dynamic characteristics and power conversion efficiency of the laser diode driver were tested and analyzed. The results show that the power conversion efficiency is up to 85%. The rise time and fall time of output current in range of 0A~100A is 1ms. The ripple coefficient of output current is 0.04% when output current is 100A. Compared with laser diode driver with two-level cascade structure, the power conversion efficiency of the power supply was promoted. The dynamic response of output current is so rapid that the power supply meets requirements of laser processing.
2016, 40(5): 670-675.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.011
Abstract:
Workshop measuring and positioning system (WMPS) may induce distortion of flexible object surface and there are hidden parts in large-scale space. In order to solve the problems, non-contact measurement method was proposed based on laser rangefinders. A measurement target was designed. Firstly, a measurement model of this method was established, and the target was simplified as the combination of several control points and a vector. Then, an attitude estimation algorithm was deduced from the geometry model of the transmitter, and the initial iteration value was estimated through unit quaternion method. Finally, calibration experiment of the target was conducted and the accuracy of the method was verified on a WMPS experimental platform developed by Tianjin University. The experimental results show that, distance measurement accuracy of the proposed method is better than 2.5mm and repeatability keeps within 1mm. This measurement method can extend the range of measurement and maintain relatively high accuracy of large-scale 3-D coordinate measurement.
Workshop measuring and positioning system (WMPS) may induce distortion of flexible object surface and there are hidden parts in large-scale space. In order to solve the problems, non-contact measurement method was proposed based on laser rangefinders. A measurement target was designed. Firstly, a measurement model of this method was established, and the target was simplified as the combination of several control points and a vector. Then, an attitude estimation algorithm was deduced from the geometry model of the transmitter, and the initial iteration value was estimated through unit quaternion method. Finally, calibration experiment of the target was conducted and the accuracy of the method was verified on a WMPS experimental platform developed by Tianjin University. The experimental results show that, distance measurement accuracy of the proposed method is better than 2.5mm and repeatability keeps within 1mm. This measurement method can extend the range of measurement and maintain relatively high accuracy of large-scale 3-D coordinate measurement.
2016, 40(5): 676-681.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.012
Abstract:
In order to measure radar cross sections (RCS) of metal plates, the RCSs were measured with a terahertz time-domain spectroscopy (THz-TDS) system and a 0.1THz continuous-wave measurement system respectively. RCS measurement modules were analyzed theoretically. The results show that measurement errors increase with the increase of measurement frequency and angles for a THz-TDS. For 0.1THz continuous-wave measurement system, errors increase with the increase of angles, and errors increase first and then decrease with the increase of the size of metal plates. The minimum error is -0.244dB. The results show that RCSs of metal plates can be obtained with both systems. Advantages of a THz-TDS are large frequency range and excellent angular resolution. Advantages of a 0.1THz continuous-wave measurement system are simpler structure, faster imaging speed and convenience.
In order to measure radar cross sections (RCS) of metal plates, the RCSs were measured with a terahertz time-domain spectroscopy (THz-TDS) system and a 0.1THz continuous-wave measurement system respectively. RCS measurement modules were analyzed theoretically. The results show that measurement errors increase with the increase of measurement frequency and angles for a THz-TDS. For 0.1THz continuous-wave measurement system, errors increase with the increase of angles, and errors increase first and then decrease with the increase of the size of metal plates. The minimum error is -0.244dB. The results show that RCSs of metal plates can be obtained with both systems. Advantages of a THz-TDS are large frequency range and excellent angular resolution. Advantages of a 0.1THz continuous-wave measurement system are simpler structure, faster imaging speed and convenience.
2016, 40(5): 682-686.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.013
Abstract:
In order to analyze the influence of radial pressure on the characteristics of a photonic bandgap fiber in 1550nm transmission band, both the limiting loss and refractive index of the photonic bandgap fiber caused by the radial pressure were calculated by using finite element method (FEM). In addition, the differences between simulation and measurement were also compared and analyzed through experiments. The results show that FEM sensitivity of limiting loss of photonic bandgap fibers varying with the change of radial pressure is 0.00067(dB/km)/(N/m), the change rate of the F parameter with the change of radial pressure is 0.6810-6/(N/m) , and the change rate of the refractive index with the change of radial pressure is 1.010-8/(N/m). The study about transmission characteristics of photonic bandgap fibers under radial pressure will support an experiment foundation for fiber optical sense in long wavelength band applications.
In order to analyze the influence of radial pressure on the characteristics of a photonic bandgap fiber in 1550nm transmission band, both the limiting loss and refractive index of the photonic bandgap fiber caused by the radial pressure were calculated by using finite element method (FEM). In addition, the differences between simulation and measurement were also compared and analyzed through experiments. The results show that FEM sensitivity of limiting loss of photonic bandgap fibers varying with the change of radial pressure is 0.00067(dB/km)/(N/m), the change rate of the F parameter with the change of radial pressure is 0.6810-6/(N/m) , and the change rate of the refractive index with the change of radial pressure is 1.010-8/(N/m). The study about transmission characteristics of photonic bandgap fibers under radial pressure will support an experiment foundation for fiber optical sense in long wavelength band applications.
2016, 40(5): 687-690.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.014
Abstract:
In order to improve the efficiency and quality in processing the glass micro channels, excimer laser (=248nm) was used. The relationship between laser parameters and etching quality of glass were obtained after theoretical analysis and experimental verification. The results show that the threshold of laser processing micro channels in glass is 4.54103mJ/mm2. Etching depth increases approximately logarithmically with the increasing of laser energy. The relationship between laser energy and eching depth was described by two linear fitting formulas. Etching depth increases linearly with the increasing of pulse frequency. The relationship between pulse frequency and eching depth was described by linear fitting formula. The roughness of channel bottom increases with the increasing of laser energy and pulse frequency. In the processing of glass micro channels, the optimum range of laser parameters is laser energy 400mJ~600mJ and pulse frequency 4Hz~7Hz. The results are helpful for selecting the laser parameters reasonably to improve processing efficiency and quality of glass micro channels.
In order to improve the efficiency and quality in processing the glass micro channels, excimer laser (=248nm) was used. The relationship between laser parameters and etching quality of glass were obtained after theoretical analysis and experimental verification. The results show that the threshold of laser processing micro channels in glass is 4.54103mJ/mm2. Etching depth increases approximately logarithmically with the increasing of laser energy. The relationship between laser energy and eching depth was described by two linear fitting formulas. Etching depth increases linearly with the increasing of pulse frequency. The relationship between pulse frequency and eching depth was described by linear fitting formula. The roughness of channel bottom increases with the increasing of laser energy and pulse frequency. In the processing of glass micro channels, the optimum range of laser parameters is laser energy 400mJ~600mJ and pulse frequency 4Hz~7Hz. The results are helpful for selecting the laser parameters reasonably to improve processing efficiency and quality of glass micro channels.
2016, 40(5): 691-694.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.015
Abstract:
In order to obtain the optimal pump light intensity of a rubidium atomic magnetometer and improve its sensitivity, the relationships among the polarization, signal to noise ratio, sensitivity of magnetometer and pump light intensity were analyzed. An experimental system was designed. Transverse relaxation time and longitudinal relaxation time of a 20mm diameter spherical vapor cell with different pump light intensity were measured by using free induction decay method. The corresponding polarization data was calculated and the fitting curves of polarization, signal to noise ratio, sensitivity influenced by pump light intensity were received. The results show that the optimal pump light intensity is optimum in the rubidium atomic magnetometer under the pump light intensity of about 10mW/cm2. It will be helpful for using the pump light effectively and optimizing sensitivity of the rubidium atomic magnetometers further.
In order to obtain the optimal pump light intensity of a rubidium atomic magnetometer and improve its sensitivity, the relationships among the polarization, signal to noise ratio, sensitivity of magnetometer and pump light intensity were analyzed. An experimental system was designed. Transverse relaxation time and longitudinal relaxation time of a 20mm diameter spherical vapor cell with different pump light intensity were measured by using free induction decay method. The corresponding polarization data was calculated and the fitting curves of polarization, signal to noise ratio, sensitivity influenced by pump light intensity were received. The results show that the optimal pump light intensity is optimum in the rubidium atomic magnetometer under the pump light intensity of about 10mW/cm2. It will be helpful for using the pump light effectively and optimizing sensitivity of the rubidium atomic magnetometers further.
2016, 40(5): 695-700.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.016
Abstract:
In order to analyze the core factor of cooling effect of jet array impingement unit of disk-laser crystal module, the effect of apertures, hole-to-hole spacing and nozzle-to-plate spacing on jet array impingement cooling was analyzed by numerical calculation under certain total area of each nozzle. Heat transfer coefficient was analyzed comparatively by experiment. The cooling effect was verified in actual disk laser. The results show that nozzle B of hole aperture 0.6mm and hole-to-hole spacing 1.6mm has the highest heat transfer coefficient. Heat transfer coefficient can reach 55000 Wm-2K-1 at water flow rate of 3 L/min and nozzle-to-plate spacing of 3mm. There is optimum value of nozzle-to-plate spacing at different inlet pressures. The optimum value of nozzle-to-plate spacing of nozzle B is 0.5mm at inlet pressure of 0.2 MPa. Verification experiment on actual disk-laser shows that the cooling temperature of nozzle B declines 5℃ lower than of nozzle C, at water flow rate of 6.5 L/min, nozzle-to-plate spacing of 5mm and current of 200A. The conclusion provides a reference for the design and the optimization of jet impingement cooling unit of thin-disk laser crystal module.
In order to analyze the core factor of cooling effect of jet array impingement unit of disk-laser crystal module, the effect of apertures, hole-to-hole spacing and nozzle-to-plate spacing on jet array impingement cooling was analyzed by numerical calculation under certain total area of each nozzle. Heat transfer coefficient was analyzed comparatively by experiment. The cooling effect was verified in actual disk laser. The results show that nozzle B of hole aperture 0.6mm and hole-to-hole spacing 1.6mm has the highest heat transfer coefficient. Heat transfer coefficient can reach 55000 Wm-2K-1 at water flow rate of 3 L/min and nozzle-to-plate spacing of 3mm. There is optimum value of nozzle-to-plate spacing at different inlet pressures. The optimum value of nozzle-to-plate spacing of nozzle B is 0.5mm at inlet pressure of 0.2 MPa. Verification experiment on actual disk-laser shows that the cooling temperature of nozzle B declines 5℃ lower than of nozzle C, at water flow rate of 6.5 L/min, nozzle-to-plate spacing of 5mm and current of 200A. The conclusion provides a reference for the design and the optimization of jet impingement cooling unit of thin-disk laser crystal module.
2016, 40(5): 701-705.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.017
Abstract:
To maintain the stability of emission wavelength of an optical transceiver and break through the routine design that the existing semiconductor laser temperature control systems were mostly implemented by analog devices, a semiconductor laser temperature control system based on digital filtering was proposed. By using digital signal processing in the form of firmware, temperature control of semiconductors was implemented. This system was applied to an optical transceiver module. Through theoretical analysis and experimental verification, the dependence of emission wavelength on the temperature was obtained. The test results show that the system achieves stable performance and good temperature control precision of 0.053℃.
To maintain the stability of emission wavelength of an optical transceiver and break through the routine design that the existing semiconductor laser temperature control systems were mostly implemented by analog devices, a semiconductor laser temperature control system based on digital filtering was proposed. By using digital signal processing in the form of firmware, temperature control of semiconductors was implemented. This system was applied to an optical transceiver module. Through theoretical analysis and experimental verification, the dependence of emission wavelength on the temperature was obtained. The test results show that the system achieves stable performance and good temperature control precision of 0.053℃.
2016, 40(5): 706-710.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.018
Abstract:
In order to analyze the mode stability of an external cavity diode laser during the tuning process, its mode structure was deduced and simulated by using the original multiple-beam interference method. The optimal external-cavity length was derived under the condition of matching the grating angle tuning rate with the external cavity mode tuning rate during the grating rotation when the grating plane and pivot arm were not on the same plane. The range of mode stability, namely, mode hop during the tuning process, was also studied. The effect of the collimating lens location on the system back-coupling efficiency was analyzed by using the method of rigorous coupling theory and the ray transfer matrix. The results show that the back-coupling efficiency is up to 99%. Linewidth of diode laser with center wavelength of 780nm was narrowed extremely. Theoretical linewidth of external cavity diode cavity is 0.96% of that of diode laser without external cavity. Stable range of dynamic mode is up to 6.8nm.
In order to analyze the mode stability of an external cavity diode laser during the tuning process, its mode structure was deduced and simulated by using the original multiple-beam interference method. The optimal external-cavity length was derived under the condition of matching the grating angle tuning rate with the external cavity mode tuning rate during the grating rotation when the grating plane and pivot arm were not on the same plane. The range of mode stability, namely, mode hop during the tuning process, was also studied. The effect of the collimating lens location on the system back-coupling efficiency was analyzed by using the method of rigorous coupling theory and the ray transfer matrix. The results show that the back-coupling efficiency is up to 99%. Linewidth of diode laser with center wavelength of 780nm was narrowed extremely. Theoretical linewidth of external cavity diode cavity is 0.96% of that of diode laser without external cavity. Stable range of dynamic mode is up to 6.8nm.
2016, 40(5): 711-715.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.019
Abstract:
In order to get a controllable fiber laser pulse light sources, multistage amplification of all-fiber pulse laser and improvement of signal-to-noise ratio (SNR) were realized by using pulse laser of narrow pulse width and low repeat frequency as the seed, Yb3+-doped fiber as gain medium, and embedded control technology and pulse pump technology. The results show that this kind of light source, with stable output and good SNR, not only reduces the harm of thermal effect but also enhances the extraction efficiency of pump energy. The light source can be used in general high power optical systems with high application value and wide market prospect.
In order to get a controllable fiber laser pulse light sources, multistage amplification of all-fiber pulse laser and improvement of signal-to-noise ratio (SNR) were realized by using pulse laser of narrow pulse width and low repeat frequency as the seed, Yb3+-doped fiber as gain medium, and embedded control technology and pulse pump technology. The results show that this kind of light source, with stable output and good SNR, not only reduces the harm of thermal effect but also enhances the extraction efficiency of pump energy. The light source can be used in general high power optical systems with high application value and wide market prospect.
2016, 40(5): 716-721.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.020
Abstract:
In order to reveal the interaction mechanism between laser and polymer, the beam profile of diode laser was analyzed by knife-edge method through using nylon 66 (PA66) as research object. The optical properties of PA66, glass fiber reinforced nylon 66(PA66GF30) (mass fraction of 0.3) were measured by ultraviolet-visible-near-infrared spectrophotometer. The effects of thickness and glass fiber on transmittance, reflectance and absorbance were analyzed. The effects of thickness and glass fiber on light scattering of PA66 were studied by the combination of line scanning method and mathematical model. The laser power flux distribution at the weld interface after passing through PA66, PA66GF30 was determined. The experimental results indicate that the transmittance of PA66 decreases with thickness. The reflectance and absorbance increases with thickness and light scattering increases with thickness. When glass fiber is added, transmittance decreases heavily, the reflectance increases slightly and the absorbance and light scattering increase significantly. This study is helpful for determining the light scattering parameters of different thickness of thermoplastic plastics and has the more widely application of numerical simulation in laser transmission welding.
In order to reveal the interaction mechanism between laser and polymer, the beam profile of diode laser was analyzed by knife-edge method through using nylon 66 (PA66) as research object. The optical properties of PA66, glass fiber reinforced nylon 66(PA66GF30) (mass fraction of 0.3) were measured by ultraviolet-visible-near-infrared spectrophotometer. The effects of thickness and glass fiber on transmittance, reflectance and absorbance were analyzed. The effects of thickness and glass fiber on light scattering of PA66 were studied by the combination of line scanning method and mathematical model. The laser power flux distribution at the weld interface after passing through PA66, PA66GF30 was determined. The experimental results indicate that the transmittance of PA66 decreases with thickness. The reflectance and absorbance increases with thickness and light scattering increases with thickness. When glass fiber is added, transmittance decreases heavily, the reflectance increases slightly and the absorbance and light scattering increase significantly. This study is helpful for determining the light scattering parameters of different thickness of thermoplastic plastics and has the more widely application of numerical simulation in laser transmission welding.
2016, 40(5): 722-726.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.021
Abstract:
For monitoring real-time SO2 emissions of industrial flue gas, a SO2 concentration analyzing instrument was constructed based on differential optical absorption spectroscopy (DOAS). The standard absorption cross section data for SO2 matching with the instrument resolution was obtained in the laboratory on the basis of studying processing methods for DOAS data. The gas pool structure was ameliorated applying optical reflectors and UV quartz lenses. The results show that the measured concentration is consistent with the standard concentration, which meets high-precision real-time monitoring SO2 emissions of industrial flue gas.
For monitoring real-time SO2 emissions of industrial flue gas, a SO2 concentration analyzing instrument was constructed based on differential optical absorption spectroscopy (DOAS). The standard absorption cross section data for SO2 matching with the instrument resolution was obtained in the laboratory on the basis of studying processing methods for DOAS data. The gas pool structure was ameliorated applying optical reflectors and UV quartz lenses. The results show that the measured concentration is consistent with the standard concentration, which meets high-precision real-time monitoring SO2 emissions of industrial flue gas.
2016, 40(5): 727-729.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.022
Abstract:
In order to obtain a multiwavelength and single longitudinal mode Brillouin fiber laser, an erbium-doped fiber amplifier was placed outside of an about 10m passive optical cavity. Each order Brillouin laser was fed back to the erbium-doped fiber amplifier to amplify again through the coupler. And then, it was used as pumping laser for the next order Brillouin laser to produce multi-order laser Brillouin laser. After theoretical analysis and experimental verification, the result shows that more than seven orders of Stokes signals are observed in the multi-wavelength single-mode fiber Brillouin laser under the condition of current output power of the erbium-doped fiber amplifier. The study will have very wide range of applications in optical generations of microwave, dense wavelength division multiplexing, optical inertial rotation sensor, ultra high precision spectral analysis and so on.
In order to obtain a multiwavelength and single longitudinal mode Brillouin fiber laser, an erbium-doped fiber amplifier was placed outside of an about 10m passive optical cavity. Each order Brillouin laser was fed back to the erbium-doped fiber amplifier to amplify again through the coupler. And then, it was used as pumping laser for the next order Brillouin laser to produce multi-order laser Brillouin laser. After theoretical analysis and experimental verification, the result shows that more than seven orders of Stokes signals are observed in the multi-wavelength single-mode fiber Brillouin laser under the condition of current output power of the erbium-doped fiber amplifier. The study will have very wide range of applications in optical generations of microwave, dense wavelength division multiplexing, optical inertial rotation sensor, ultra high precision spectral analysis and so on.
2016, 40(5): 730-733.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.023
Abstract:
In order to explore the damage mechanism of charge-coupled device (CCD) detectors under laser irradiation, CCD detectors irradiated by pulsed laser were analyzed theoretically and verified experimentally based on the finite element method. Damage mechanism of CCD detectors irradiated by laser was described and simulation model of thermal effect of CCD detectors irradiated by laser was designed. Simulation calculation was carried out for thermal effect of silicon CCD detectors irradiated by high power laser at wavelength of 532nm by using finite element method. Temperature curve of silicon electrodes and time threshold of silicon electrode damage were obtained. After calculation, the corresponding laser damage threshold for CCD detector was about 220mJ/cm2. Simulation result shows that damage threshold decreases with the increase of laser power density and but it changes slightly. When multi-millisecond pulse laser irradiates CCD detectors, detector temperature returns to the ambient temperature before the next pulse and after the former pulse. The model can accurately simulate the thermal damage effect of CCD detectors under single laser pulse irradiation.
In order to explore the damage mechanism of charge-coupled device (CCD) detectors under laser irradiation, CCD detectors irradiated by pulsed laser were analyzed theoretically and verified experimentally based on the finite element method. Damage mechanism of CCD detectors irradiated by laser was described and simulation model of thermal effect of CCD detectors irradiated by laser was designed. Simulation calculation was carried out for thermal effect of silicon CCD detectors irradiated by high power laser at wavelength of 532nm by using finite element method. Temperature curve of silicon electrodes and time threshold of silicon electrode damage were obtained. After calculation, the corresponding laser damage threshold for CCD detector was about 220mJ/cm2. Simulation result shows that damage threshold decreases with the increase of laser power density and but it changes slightly. When multi-millisecond pulse laser irradiates CCD detectors, detector temperature returns to the ambient temperature before the next pulse and after the former pulse. The model can accurately simulate the thermal damage effect of CCD detectors under single laser pulse irradiation.
2016, 40(5): 734-737.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.024
Abstract:
In order to orientate a non-orthogonal shafting laser theodolite measurement system quickly and accurately, a construction technology of variable-length photoelectric reference scale was proposed based on high-precision photoelectric position sensitive detector . Firstly, the feature of a non-orthogonal shafting laser theodolite was elaborated. According to the features and the orientation requirement of a non-orthogonal shafting laser theodolite measurement system, the general idea of the construction of variable-length photoelectric reference scale was confirmed. After that, the design of hardware circuit was finished and a variable-length photoelectric reference scale was constructed. Finally, spatial position relationship between two photoelectric position sensitive detectors was calibrated to realize the measurement of variable-length reference. The experiment results show that the relative measurement accuracy of variable-length photoelectric reference scale is better than 0.03%. The orientation of a non-orthogonal shafting laser theodolite measurement system can be realized conveniently and in high-precision.
In order to orientate a non-orthogonal shafting laser theodolite measurement system quickly and accurately, a construction technology of variable-length photoelectric reference scale was proposed based on high-precision photoelectric position sensitive detector . Firstly, the feature of a non-orthogonal shafting laser theodolite was elaborated. According to the features and the orientation requirement of a non-orthogonal shafting laser theodolite measurement system, the general idea of the construction of variable-length photoelectric reference scale was confirmed. After that, the design of hardware circuit was finished and a variable-length photoelectric reference scale was constructed. Finally, spatial position relationship between two photoelectric position sensitive detectors was calibrated to realize the measurement of variable-length reference. The experiment results show that the relative measurement accuracy of variable-length photoelectric reference scale is better than 0.03%. The orientation of a non-orthogonal shafting laser theodolite measurement system can be realized conveniently and in high-precision.
2016, 40(5): 738-741.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.025
Abstract:
In order to realize accurate, real-time and nondestructive measurement of viscosity coefficient of sample solution, an improved method was presented based on the light-induced rotation in laser optical tweezers. Firstly, the relationship between viscosity coefficient of liquid and radius of probe particles was simulated numerically. And then, the values of rotational frequency and viscosity coefficient were measured through experimental optical tweezers. The results show that the error of viscosity coefficient is minimum when the radius of probe is 2.0m. The viscosity coefficients of pure water and ethanol solution are measured at different temperatures. Actual deviation is less than 7%, which proves the proposed method is effective. The method has the features of high accuracy and non-contact, and has obvious advantage for measurement of dilute, volatile and harmful liquid solution.
In order to realize accurate, real-time and nondestructive measurement of viscosity coefficient of sample solution, an improved method was presented based on the light-induced rotation in laser optical tweezers. Firstly, the relationship between viscosity coefficient of liquid and radius of probe particles was simulated numerically. And then, the values of rotational frequency and viscosity coefficient were measured through experimental optical tweezers. The results show that the error of viscosity coefficient is minimum when the radius of probe is 2.0m. The viscosity coefficients of pure water and ethanol solution are measured at different temperatures. Actual deviation is less than 7%, which proves the proposed method is effective. The method has the features of high accuracy and non-contact, and has obvious advantage for measurement of dilute, volatile and harmful liquid solution.
2016, 40(5): 742-745.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.026
Abstract:
To explore the gain recovery time of converted signal in detail, rate equations and light field transfer equations were solved based on all-optical wavelength cross-gain modulation (XGM) in a single-port-coupled quantum-dot semiconductor optical amplifier(QD-SOA) by utilizing the segment method and the forth-order Runge-Kutta method. The effects of various parameters, including injection current, rear facet reflectivity and the maximum modal gain on gain recovery time of a single-port-coupled QD-SOA was studied. The results show that the gain recovery time of a single-port-coupled QD-SOA can be decreased by increasing the injected current or rear facet reflectivity and decreasing the maximum modal gain. The low gain recovery time of a single-port-coupled QD-SOA can be achieved by optimizing these parameters.
To explore the gain recovery time of converted signal in detail, rate equations and light field transfer equations were solved based on all-optical wavelength cross-gain modulation (XGM) in a single-port-coupled quantum-dot semiconductor optical amplifier(QD-SOA) by utilizing the segment method and the forth-order Runge-Kutta method. The effects of various parameters, including injection current, rear facet reflectivity and the maximum modal gain on gain recovery time of a single-port-coupled QD-SOA was studied. The results show that the gain recovery time of a single-port-coupled QD-SOA can be decreased by increasing the injected current or rear facet reflectivity and decreasing the maximum modal gain. The low gain recovery time of a single-port-coupled QD-SOA can be achieved by optimizing these parameters.
2016, 40(5): 746-749.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.027
Abstract:
In order to overcome the following defects of high distance drift rate and poor optical fiber interchangeability when the distributed optical fiber and temperature sensing technology were used in blast furnace hot air tube, two terminal and single channel demodulation method(TTSCDM) was proposed. The decay term Zc was offset after arithmetic average operation for Stokes and anti-Stokes light intensity ratio from both directions. The distance drift rate K of TTSCDM was 0.011 and the maximum Raman ratio deviation of replacing fiber was 0.015. Experimental results show that this demodulation method has low distance drift rate. When optical fiber needs to be replaced, the decay coefficient does not need to recalibrate and the effective measurement of temperature field along the optical path can be implemented.
In order to overcome the following defects of high distance drift rate and poor optical fiber interchangeability when the distributed optical fiber and temperature sensing technology were used in blast furnace hot air tube, two terminal and single channel demodulation method(TTSCDM) was proposed. The decay term Zc was offset after arithmetic average operation for Stokes and anti-Stokes light intensity ratio from both directions. The distance drift rate K of TTSCDM was 0.011 and the maximum Raman ratio deviation of replacing fiber was 0.015. Experimental results show that this demodulation method has low distance drift rate. When optical fiber needs to be replaced, the decay coefficient does not need to recalibrate and the effective measurement of temperature field along the optical path can be implemented.
2016, 40(5): 750-755.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.028
Abstract:
For studying characteristics of partially coherent cosh-Gaussian beams propagating through turbulent atmosphere, analysis was carried out based on ABCD matrix and the expressions of the intensity, beam width and power in bucket were obtained to characterize the focusing characteristics of partially coherent cosh-Gaussian beams propagating through turbulent atmosphere. The results show that under different turbulence intensities, the focusing characteristics of partially coherent cosh-Gaussian beams are different from those of totally coherent cosh-Gaussian beams and that the effect of turbulence is more serious to totally coherent cosh-Gaussian beams characterized with the power in bucket and beam width. However, the influence of turbulence on the focused partially coherent cosh-Gaussian is more serious than the collimated beams. The results are useful to study the focusability of partially coherent cosh-Gaussian beams propagating through turbulent atmosphere and helpful to design applicable optical systems for incoherent combination of paraxial beams.
For studying characteristics of partially coherent cosh-Gaussian beams propagating through turbulent atmosphere, analysis was carried out based on ABCD matrix and the expressions of the intensity, beam width and power in bucket were obtained to characterize the focusing characteristics of partially coherent cosh-Gaussian beams propagating through turbulent atmosphere. The results show that under different turbulence intensities, the focusing characteristics of partially coherent cosh-Gaussian beams are different from those of totally coherent cosh-Gaussian beams and that the effect of turbulence is more serious to totally coherent cosh-Gaussian beams characterized with the power in bucket and beam width. However, the influence of turbulence on the focused partially coherent cosh-Gaussian is more serious than the collimated beams. The results are useful to study the focusability of partially coherent cosh-Gaussian beams propagating through turbulent atmosphere and helpful to design applicable optical systems for incoherent combination of paraxial beams.
2016, 40(5): 756-761.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.029
Abstract:
In order to improve the fusion quality of multi-spectral images and panchromatic images, after studying a variety of filters and fusion algorithms, a regional fusion method was proposed based on multistage guide filters. First of all, the new method was adopted to interpolate the multispectral image; then the improved watershed algorithm was used to divide the panchromatic image, and the result was mapped to each multispectral image. Secondly, a multistage guide filter was used to filter the multispectral image and the panchromatic image, and their details were obtained respectively. Finally, according to the local correlation coefficient and the 4-order correlation coefficient between the panchromatic image and multispectral image, the detailed information was fused and the fusion images were obtained. The results show that the algorithm retains the multispectral image spectrum information and at the same time, details of the panchromatic image were put into the fusion image as much as possible. The method improves the effect of multispectral image fusion.
In order to improve the fusion quality of multi-spectral images and panchromatic images, after studying a variety of filters and fusion algorithms, a regional fusion method was proposed based on multistage guide filters. First of all, the new method was adopted to interpolate the multispectral image; then the improved watershed algorithm was used to divide the panchromatic image, and the result was mapped to each multispectral image. Secondly, a multistage guide filter was used to filter the multispectral image and the panchromatic image, and their details were obtained respectively. Finally, according to the local correlation coefficient and the 4-order correlation coefficient between the panchromatic image and multispectral image, the detailed information was fused and the fusion images were obtained. The results show that the algorithm retains the multispectral image spectrum information and at the same time, details of the panchromatic image were put into the fusion image as much as possible. The method improves the effect of multispectral image fusion.
2016, 40(5): 762-766.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.030
Abstract:
In order to improve the problems that the bad morphologies are very bad in the process of laser direct etching, the method of water jet-laser complex etching was adopted. With SiC composite ceramics and Al2O3 ceramics as studying object materials, the etched morphologies of different componential ceramics with or without water jet were analyzed. On this basis, the effects of velocity of water jet on the etched depth and removal amount were studied. The results show that in the process of laser direct etching, a large amount of slag is attached to the etched surface, the etched morphologies are very bad, more than 60% of SiC composite ceramics are directly decomposed, the slag is less, so the morphology is better than Al2O3 ceramics slightly. In the process of water jet-laser complex etching, the etched morphologies are both turned better, and the morphology when velocity of water jet is 24m/s is better than that when 16m/s. The velocity of water jet is bigger, the etched depth and removal amount are smaller. The velocity of water jet increases every 2m/s, the removal amount reduces by an average of about 0.066mm3. In the case of the same velocity of water jet, the removal amount of SiC composite ceramics is about 0.4mm3, bigger than Al2O3 ceramics. This study is helpful to improve the etched morphologies and analyze the etched mechanism of different ceramics.
In order to improve the problems that the bad morphologies are very bad in the process of laser direct etching, the method of water jet-laser complex etching was adopted. With SiC composite ceramics and Al2O3 ceramics as studying object materials, the etched morphologies of different componential ceramics with or without water jet were analyzed. On this basis, the effects of velocity of water jet on the etched depth and removal amount were studied. The results show that in the process of laser direct etching, a large amount of slag is attached to the etched surface, the etched morphologies are very bad, more than 60% of SiC composite ceramics are directly decomposed, the slag is less, so the morphology is better than Al2O3 ceramics slightly. In the process of water jet-laser complex etching, the etched morphologies are both turned better, and the morphology when velocity of water jet is 24m/s is better than that when 16m/s. The velocity of water jet is bigger, the etched depth and removal amount are smaller. The velocity of water jet increases every 2m/s, the removal amount reduces by an average of about 0.066mm3. In the case of the same velocity of water jet, the removal amount of SiC composite ceramics is about 0.4mm3, bigger than Al2O3 ceramics. This study is helpful to improve the etched morphologies and analyze the etched mechanism of different ceramics.
2016, 40(5): 767-771.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.031
Abstract:
In order to explore effects of process parameters of selective laser sintering on polystyrene powder and improve the strength and accuracy of polystyrene (PS) powder by the improved process parameters, thermal gravity/differential scanning calorimetry analysis was made to study thermal properties of PS powder. Sintering experiment of powder was carried out by SLS300 rapid molding machine. After theoretical analysis and experimental verification, the samples had high precision when sintering temperature was between 150℃ and 260℃. The results show that the effects of process parameters on dimensional precision of x axis and y axis are small, the effect on dimensional precision of z axis is great. Bending strength decreases with the increase of laser power, scanning interval and layer thickness. The study provides experimental basis to improve sintering quality of PS by the optimization of process parameters.
In order to explore effects of process parameters of selective laser sintering on polystyrene powder and improve the strength and accuracy of polystyrene (PS) powder by the improved process parameters, thermal gravity/differential scanning calorimetry analysis was made to study thermal properties of PS powder. Sintering experiment of powder was carried out by SLS300 rapid molding machine. After theoretical analysis and experimental verification, the samples had high precision when sintering temperature was between 150℃ and 260℃. The results show that the effects of process parameters on dimensional precision of x axis and y axis are small, the effect on dimensional precision of z axis is great. Bending strength decreases with the increase of laser power, scanning interval and layer thickness. The study provides experimental basis to improve sintering quality of PS by the optimization of process parameters.
2016, 40(5): 772-778.
doi: 10.7510/jgjs.issn.1001-3806.2016.05.032
Abstract:
Space-borne lidar could provide us with high accurate data of global detection and play more and more important role in earth observation. The development of space-borne lidars in USA and Europe was introduced in brief. Working principle, detection system and detection results of geoscience laser altimeter system spaceborne lidar, cloud-aerosol lidar with orthogonal polaritation and atmospheric laser Doppler spaceborne lidar wind measurement were summarized in detail. The construction and materials of the receiving telescopes of the above 3 spaceborne lidars were analyzed. The study provides some reference for the research of space-borne lidars in China.
Space-borne lidar could provide us with high accurate data of global detection and play more and more important role in earth observation. The development of space-borne lidars in USA and Europe was introduced in brief. Working principle, detection system and detection results of geoscience laser altimeter system spaceborne lidar, cloud-aerosol lidar with orthogonal polaritation and atmospheric laser Doppler spaceborne lidar wind measurement were summarized in detail. The construction and materials of the receiving telescopes of the above 3 spaceborne lidars were analyzed. The study provides some reference for the research of space-borne lidars in China.
