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RSS2015 Vol. 39, No. 2
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2015, 39(2): 145-151.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.001
[Abstract]
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Abstract:
Inside-beam powder feeding nozzle is a new laser cladding coaxial powder feeding nozzle, which has the advantages of hollow beam, good directivity, no interference and co-axis of light, powder and gas. In order to analyze the influence of nozzle's inclination angle and outer collimating gas velocity on the focusing characteristics of powder, FLUENT software was used for numerical simulation. The focusing characteristics of powder out of a single nozzle with changing attitude were analyzed in theory and verified in experiments. The results show that mass concentration distribution of powder nozzle is consistent with Gaussian distribution along the x direction and it remains constant firstly and then decreases to zero gradually along the -y direction of the symmetry axis. When the inclination angle of the head increases, the powder focusing length h decreases in the range of 11mm~17mm and the deviation Δx increases in the range of 0.0mm~0.4mm substantially. When the outer collimating gas velocity increases, the powder focusing length h increases slightly in the range of 1mm~2mm and the deviation Δx presents different trend in the range of 0.05mm~0.15mm. The experimental data and simulation results are basically consistent. The built model and the simulation results have reference value for the selection and optimization of experimental parameters.
Inside-beam powder feeding nozzle is a new laser cladding coaxial powder feeding nozzle, which has the advantages of hollow beam, good directivity, no interference and co-axis of light, powder and gas. In order to analyze the influence of nozzle's inclination angle and outer collimating gas velocity on the focusing characteristics of powder, FLUENT software was used for numerical simulation. The focusing characteristics of powder out of a single nozzle with changing attitude were analyzed in theory and verified in experiments. The results show that mass concentration distribution of powder nozzle is consistent with Gaussian distribution along the x direction and it remains constant firstly and then decreases to zero gradually along the -y direction of the symmetry axis. When the inclination angle of the head increases, the powder focusing length h decreases in the range of 11mm~17mm and the deviation Δx increases in the range of 0.0mm~0.4mm substantially. When the outer collimating gas velocity increases, the powder focusing length h increases slightly in the range of 1mm~2mm and the deviation Δx presents different trend in the range of 0.05mm~0.15mm. The experimental data and simulation results are basically consistent. The built model and the simulation results have reference value for the selection and optimization of experimental parameters.
2015, 39(2): 152-156.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.002
Abstract:
For real-time measurement of digital holographic microscopy (DHM), a parallel algorithm was proposed. Firstly, real-time recording strategy was adopted to record hologram, intensity of object wave and intensity of reference wave according to light path of DHM. Zero-order of hologram was removed by this strategy. So, the product of spatial band-width of image sensor was efficiently utilized. Then, parallel reconstructing software was developed. The captured image was separated to four partitions and was sent to four procedures which run simultaneously. After the partitions were reconstructed by the corresponding procedure, each reconstructed result was separated to four regions. The corresponding regions were combined to four groups and were sent to four procedures for superposing and calculating phase and intensity. Finally, the whole phase and intensity map were obtained by merging four regions of phase and intensity. The experimental results reveal that the speed for image capture and hologram reconstruction is up to 18frame/s. Real-time measurement is realized with the proposed system.
For real-time measurement of digital holographic microscopy (DHM), a parallel algorithm was proposed. Firstly, real-time recording strategy was adopted to record hologram, intensity of object wave and intensity of reference wave according to light path of DHM. Zero-order of hologram was removed by this strategy. So, the product of spatial band-width of image sensor was efficiently utilized. Then, parallel reconstructing software was developed. The captured image was separated to four partitions and was sent to four procedures which run simultaneously. After the partitions were reconstructed by the corresponding procedure, each reconstructed result was separated to four regions. The corresponding regions were combined to four groups and were sent to four procedures for superposing and calculating phase and intensity. Finally, the whole phase and intensity map were obtained by merging four regions of phase and intensity. The experimental results reveal that the speed for image capture and hologram reconstruction is up to 18frame/s. Real-time measurement is realized with the proposed system.
2015, 39(2): 157-165.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.003
Abstract:
In order to detect the surface defect quantitatively with laser ultrasonic technique, the interaction between the laser-generated surface wave and the open rectangular defect was simulated by means of the finite element method. After comparing the displacement signals at the same receiver generated in the near-field and far-field laser irradiation, it was found that reflected waves could be separated the from the mode-converted waves sufficiently when the laser was located in the far field of the defect, which may be helpful to analyze the complicated process of the interaction between the incident wave and the defect. Then, the wave interaction with either the front or the back of the defect was studied in detail, and Huygens principle was further employed to interpret the possible interaction features among the reflected signals. Finally, the influences of depth and width of the defect on the scattered echo were also studied. The results show that the arrival time difference of the scattered echo is linearly related to the depth and width of the defect. This research may provide the theoretical basis to quantify the defect.
In order to detect the surface defect quantitatively with laser ultrasonic technique, the interaction between the laser-generated surface wave and the open rectangular defect was simulated by means of the finite element method. After comparing the displacement signals at the same receiver generated in the near-field and far-field laser irradiation, it was found that reflected waves could be separated the from the mode-converted waves sufficiently when the laser was located in the far field of the defect, which may be helpful to analyze the complicated process of the interaction between the incident wave and the defect. Then, the wave interaction with either the front or the back of the defect was studied in detail, and Huygens principle was further employed to interpret the possible interaction features among the reflected signals. Finally, the influences of depth and width of the defect on the scattered echo were also studied. The results show that the arrival time difference of the scattered echo is linearly related to the depth and width of the defect. This research may provide the theoretical basis to quantify the defect.
2015, 39(2): 166-169.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.004
Abstract:
In order to improve the stability and adjustability of the output of the driving system of high power laser diodes, improve the beam quality and increase the service life, based on the principle of differential amplifier circuit and open-circuit time constant, the static working point and the frequency response characteristics of the driving circuit were analyzed in theory and verified in experiments. The results show that the drive circuit can guarantee the output current to achieve the peak current of 0A~60A under the premise of no overshoot, the pulse width adjustable range from 20μs to continuous, the repetition frequency from 500Hz to 10kHz, the maximum power of 130W. This method improves the output stability, widens the adjustability of pulse width and repetition frequency and has more outstanding performance than the traditional methods.
In order to improve the stability and adjustability of the output of the driving system of high power laser diodes, improve the beam quality and increase the service life, based on the principle of differential amplifier circuit and open-circuit time constant, the static working point and the frequency response characteristics of the driving circuit were analyzed in theory and verified in experiments. The results show that the drive circuit can guarantee the output current to achieve the peak current of 0A~60A under the premise of no overshoot, the pulse width adjustable range from 20μs to continuous, the repetition frequency from 500Hz to 10kHz, the maximum power of 130W. This method improves the output stability, widens the adjustability of pulse width and repetition frequency and has more outstanding performance than the traditional methods.
2015, 39(2): 170-175.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.005
Abstract:
In order to simulate the transient formation of a keyhole during the welding process accurately, the gas-liquid interface of the keyhole was traced by means of the level set method, the solid-liquid phase transition process was disposed by the mixture model, and the gas, liquid and solid coupling model was established. The factors, such as surface tension, buoyancy, recoil pressure, friction between solid and liquid, latent heat, convection and radiation were taken into account in this model. The dynamic process of the keyhole and the behavior of the metal vapor inside and outside the keyhole were obtained by numerical calculation. The simulation results show that the morphology of the keyhole was transient, had convex deformation in anterior and posterior and became stable gradually. The size of the keyhole was about 1mm. The keyhole and the metal vapor interacted each other. The greatest vapor velocity was 5.3m/s. A modified "sandwich" novel method was used to conduct laser welding experiment verification. The simulation results matched well with the experimental results. The results show that the level set method to track the free surface of a keyhole in laser deep penetration welding has good adaptability and can provide the theoretical basis for the study of keyhole.
In order to simulate the transient formation of a keyhole during the welding process accurately, the gas-liquid interface of the keyhole was traced by means of the level set method, the solid-liquid phase transition process was disposed by the mixture model, and the gas, liquid and solid coupling model was established. The factors, such as surface tension, buoyancy, recoil pressure, friction between solid and liquid, latent heat, convection and radiation were taken into account in this model. The dynamic process of the keyhole and the behavior of the metal vapor inside and outside the keyhole were obtained by numerical calculation. The simulation results show that the morphology of the keyhole was transient, had convex deformation in anterior and posterior and became stable gradually. The size of the keyhole was about 1mm. The keyhole and the metal vapor interacted each other. The greatest vapor velocity was 5.3m/s. A modified "sandwich" novel method was used to conduct laser welding experiment verification. The simulation results matched well with the experimental results. The results show that the level set method to track the free surface of a keyhole in laser deep penetration welding has good adaptability and can provide the theoretical basis for the study of keyhole.
2015, 39(2): 176-181.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.006
Abstract:
In order to study the influence of wave front reconstruction methods on the reconstruction field quality and the calculation speed during the application of color digital holographic detection and the accurate integration of different wavelengths and reconstruction field, the method of accurate overlap of the reconstruction field of the different color and object light and the detailed process of wavefront reproduction in real time of digital holographic color were given by theoretical analysis and experimental verification. The characteristics and the calculation rate of several wavefront reconstruction algorithms were analyzed and compared. The results show that variable magnification wavefront reconstruction algorithm using spherical wave as reconstruction light can adapt to objects in various size, obtain higher resolution images with less computing time and it is better for color digital holographic detection applications.
In order to study the influence of wave front reconstruction methods on the reconstruction field quality and the calculation speed during the application of color digital holographic detection and the accurate integration of different wavelengths and reconstruction field, the method of accurate overlap of the reconstruction field of the different color and object light and the detailed process of wavefront reproduction in real time of digital holographic color were given by theoretical analysis and experimental verification. The characteristics and the calculation rate of several wavefront reconstruction algorithms were analyzed and compared. The results show that variable magnification wavefront reconstruction algorithm using spherical wave as reconstruction light can adapt to objects in various size, obtain higher resolution images with less computing time and it is better for color digital holographic detection applications.
2015, 39(2): 182-184.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.007
Abstract:
Long-distance high speed weak photoelectric detection technology is widely used in laser communication. To detect the weak signal which is not buried in the noisy environment, balanced detection technology becomes more and more important. Single pipe coherent detection and balanced coherent detection were compared firstly. After theoretical analysis and numerical simulation, signal-to-noise ratio of the balanced detection was greatly superior to that of the single tube detection when the consistency coefficient was bigger than 0.6. The minimum detectable optical power of the single tube detection and balanced detection was analyzed. The results prove the superiority of balanced detection technology used in high speed weak optical signal detection.
Long-distance high speed weak photoelectric detection technology is widely used in laser communication. To detect the weak signal which is not buried in the noisy environment, balanced detection technology becomes more and more important. Single pipe coherent detection and balanced coherent detection were compared firstly. After theoretical analysis and numerical simulation, signal-to-noise ratio of the balanced detection was greatly superior to that of the single tube detection when the consistency coefficient was bigger than 0.6. The minimum detectable optical power of the single tube detection and balanced detection was analyzed. The results prove the superiority of balanced detection technology used in high speed weak optical signal detection.
2015, 39(2): 185-189.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.008
Abstract:
In order to investigate the detection capability of terahertz nondestructive inspection technology for the bonding adhesive quality of the adhesive layer between composite material and metal plates, some artificial defects with different characteristics were made on insulation boards in advance and detected with the German SynViewScan 300 continuous terahertz imaging system. The results show that terahertz wave can penetrate the composite material and retrieve two-dimensional terahertz image of the adhesive layer. Those different defects can be clearly distinguished from the terahertz images. The results demonstrate that terahertz non-destructive analysis provides attractive features for the inspection of adhesive quality and the off sticky situation of the composite material.
In order to investigate the detection capability of terahertz nondestructive inspection technology for the bonding adhesive quality of the adhesive layer between composite material and metal plates, some artificial defects with different characteristics were made on insulation boards in advance and detected with the German SynViewScan 300 continuous terahertz imaging system. The results show that terahertz wave can penetrate the composite material and retrieve two-dimensional terahertz image of the adhesive layer. Those different defects can be clearly distinguished from the terahertz images. The results demonstrate that terahertz non-destructive analysis provides attractive features for the inspection of adhesive quality and the off sticky situation of the composite material.
2015, 39(2): 190-193.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.009
Abstract:
In order to obtain terahertz isolators with simple structure and without the need of additional low temperatures and strong magnetic fields, a silicon-based photonic crystal heterostructure THz isolator was ananlyzed and optimized by using three-dimensional finite-difference time-domain method (3-D-FDTD). The isolator can work at room temperature, with simple structure and without external magnetic field. The results show that the isolation characteristics depends on the ratio of the pore size of both the photonic crystals. In the right ratio of the aperture (optimized aperture ratio R1/R2=0.49 at 0.52THz),maximum isolation of 25dB can be achieved.
In order to obtain terahertz isolators with simple structure and without the need of additional low temperatures and strong magnetic fields, a silicon-based photonic crystal heterostructure THz isolator was ananlyzed and optimized by using three-dimensional finite-difference time-domain method (3-D-FDTD). The isolator can work at room temperature, with simple structure and without external magnetic field. The results show that the isolation characteristics depends on the ratio of the pore size of both the photonic crystals. In the right ratio of the aperture (optimized aperture ratio R1/R2=0.49 at 0.52THz),maximum isolation of 25dB can be achieved.
2015, 39(2): 194-197.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.010
Abstract:
In order to improve the rotational frequency of a CaCO3 crystal rotor, based on optical rotation caused by the transfer of spin angular momentum from the laser beam to birefringence crystal particles, an experimental system of optical tweezers was designed and further improved with the circular polarized light beam. The relation between the rotation frequency of a calcium carbonate rotor and the thickness was simulated under different laser power. The rotation frequency of the calcium carbonate rotor with different thickness was measured in the experiment. The primary affecting factors of rotation frequency, such as thickness, radius, and orientation of the optic axis were analyzed. The results show that experimental curve of rotation frequency and thickness is periodic cosine function meanwhile the rotation frequency of the crystal rotor is proportional to the effective power. The maximum frequency of the crystal rotor can reach 8.9Hz in the experiment when effective power is 10mW, which is consistent with the theoretical simulation result. The conclusion supply the theoretical basis and technological guarantee for the classification of living biological cells, the study on properties of micro-mechanical rotor in the microscopic fields.
In order to improve the rotational frequency of a CaCO3 crystal rotor, based on optical rotation caused by the transfer of spin angular momentum from the laser beam to birefringence crystal particles, an experimental system of optical tweezers was designed and further improved with the circular polarized light beam. The relation between the rotation frequency of a calcium carbonate rotor and the thickness was simulated under different laser power. The rotation frequency of the calcium carbonate rotor with different thickness was measured in the experiment. The primary affecting factors of rotation frequency, such as thickness, radius, and orientation of the optic axis were analyzed. The results show that experimental curve of rotation frequency and thickness is periodic cosine function meanwhile the rotation frequency of the crystal rotor is proportional to the effective power. The maximum frequency of the crystal rotor can reach 8.9Hz in the experiment when effective power is 10mW, which is consistent with the theoretical simulation result. The conclusion supply the theoretical basis and technological guarantee for the classification of living biological cells, the study on properties of micro-mechanical rotor in the microscopic fields.
2015, 39(2): 202-205.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.012
Abstract:
In order to improve corner detection probability and obtain satisfactory marking quality in laser marking systems, a corner detection algorithm based on slope difference was proposed and theoretical analysis and experimental verification were carried out. After calculating the slopes of adjacent points, the corner points were picked up in terms of slopes difference. The simulation results show that the proposed algorithm can achieve accurate corner points with less computation complexity compared with the traditional algorithms. This algorithm can solve inflection point processing problems in the traditional marking systems, save storage space and reduce the computational complexity in the process of extracting image inflection points.
In order to improve corner detection probability and obtain satisfactory marking quality in laser marking systems, a corner detection algorithm based on slope difference was proposed and theoretical analysis and experimental verification were carried out. After calculating the slopes of adjacent points, the corner points were picked up in terms of slopes difference. The simulation results show that the proposed algorithm can achieve accurate corner points with less computation complexity compared with the traditional algorithms. This algorithm can solve inflection point processing problems in the traditional marking systems, save storage space and reduce the computational complexity in the process of extracting image inflection points.
2015, 39(2): 206-208.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.013
Abstract:
To solve the operation deviation due to rough-localization of workpieces in a computer numberical control(CNC) machining system, the coordinates of two points on the workpiece in the actual CNC coordinate system deviating from the ideal coordinate system was detected so that the robot autocalibrate. The mathematical model of the workpiece coordinate correction, algorithm design and algorithm implementation were described. 6 sets of simulation data show that the displacement error is less than 0.01mm and angle error is less than 0.02°. The correctness of the method is verified.
To solve the operation deviation due to rough-localization of workpieces in a computer numberical control(CNC) machining system, the coordinates of two points on the workpiece in the actual CNC coordinate system deviating from the ideal coordinate system was detected so that the robot autocalibrate. The mathematical model of the workpiece coordinate correction, algorithm design and algorithm implementation were described. 6 sets of simulation data show that the displacement error is less than 0.01mm and angle error is less than 0.02°. The correctness of the method is verified.
2015, 39(2): 209-214.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.014
Abstract:
In order to study the mechanism of the welding parameters on the welding quality and optimize the welding parameters, optical microscopy and tensile testing machine were applied to observe and test the welding strength under different laser power, welding speed, material thickness. A 3-D physical model with axial symmetry was implemented to simulate the temperature field based on software ABAQUS and the effect of parameters on welding quality was obtained from orthogonal test. The results suggest that most important factor is laser power, followed by welding speed and material thickness. Meanwhile, higher temperature may cause bubbles to increase and affect welding strength.
In order to study the mechanism of the welding parameters on the welding quality and optimize the welding parameters, optical microscopy and tensile testing machine were applied to observe and test the welding strength under different laser power, welding speed, material thickness. A 3-D physical model with axial symmetry was implemented to simulate the temperature field based on software ABAQUS and the effect of parameters on welding quality was obtained from orthogonal test. The results suggest that most important factor is laser power, followed by welding speed and material thickness. Meanwhile, higher temperature may cause bubbles to increase and affect welding strength.
2015, 39(2): 215-219.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.015
Abstract:
In order to study the diffraction effect of deposition substrate on laser standing wave field, 3-D motion trail and stripe structure were simulated using the fourth-order Runge-Kutta algorithm under straight edge diffraction effect based on the semi-classical theory. The distance from laser beam waist center to mirror and the effect of the radius of Gaussian laser beam waist on the process of final deposition were discussed. The results show that diffractive degree will be changed by adjusting the experiment parameters reasonably. The quality of deposition stripe structure will be achieved optimally when the mirror is placed on the cross section of laser beam waist, and the radius of Gaussian laser beam waist equals 62.5μm. It provides the useful theoretical foundation and data information in the field of atomic lithography study.
In order to study the diffraction effect of deposition substrate on laser standing wave field, 3-D motion trail and stripe structure were simulated using the fourth-order Runge-Kutta algorithm under straight edge diffraction effect based on the semi-classical theory. The distance from laser beam waist center to mirror and the effect of the radius of Gaussian laser beam waist on the process of final deposition were discussed. The results show that diffractive degree will be changed by adjusting the experiment parameters reasonably. The quality of deposition stripe structure will be achieved optimally when the mirror is placed on the cross section of laser beam waist, and the radius of Gaussian laser beam waist equals 62.5μm. It provides the useful theoretical foundation and data information in the field of atomic lithography study.
2015, 39(2): 220-223.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.016
Abstract:
In order to study the influence of temperature on the depolarization performance of optical fiber Lyot depolarizers accurately, based on the structural parameters of fiber depolarizers provided in previous references, an optical fiber Lyot depolarizer was made with a polarization maintaining fiber welding machine and its degree of polarization (DOP)P≤0.5% under the total temperature conditions(-40℃~80℃). The test system of the output DOP of the depolarizer under constant and variable temperature conditions was built. The causes of the change of DOP were analyzed. The measurement results show that the output DOP of the depolarizer remains unchanged basically when the temperature is constant at -40℃ and 80℃.The output DOP will change when the temperature changes at a certain gradient. The study has a certain reference value for the research in optical fiber sensing application.
In order to study the influence of temperature on the depolarization performance of optical fiber Lyot depolarizers accurately, based on the structural parameters of fiber depolarizers provided in previous references, an optical fiber Lyot depolarizer was made with a polarization maintaining fiber welding machine and its degree of polarization (DOP)P≤0.5% under the total temperature conditions(-40℃~80℃). The test system of the output DOP of the depolarizer under constant and variable temperature conditions was built. The causes of the change of DOP were analyzed. The measurement results show that the output DOP of the depolarizer remains unchanged basically when the temperature is constant at -40℃ and 80℃.The output DOP will change when the temperature changes at a certain gradient. The study has a certain reference value for the research in optical fiber sensing application.
2015, 39(2): 224-227.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.017
Abstract:
To control the speed of light to achieve all-optical router and all-optical buffer in optical fiber communication network, the transmission model of coupled mode is constructed. By utilizing the modified time-domain transfer matrix method, the slow-light characteristics of nonlinear fiber Bragg gratings(NLBG) have been studied numerically based on optical power control. The results show that the photonic stopgap critically depends on the power of light and the variation of input power can effectively change the group velocity of light. Considering the case that the output pulse is not broadened, slow-light systems can generally obtain an output pulse delay time beyond 100ps. Furthermore, for the fixed input power, changing the length of NLBG can observably influence the group velocity of light.
To control the speed of light to achieve all-optical router and all-optical buffer in optical fiber communication network, the transmission model of coupled mode is constructed. By utilizing the modified time-domain transfer matrix method, the slow-light characteristics of nonlinear fiber Bragg gratings(NLBG) have been studied numerically based on optical power control. The results show that the photonic stopgap critically depends on the power of light and the variation of input power can effectively change the group velocity of light. Considering the case that the output pulse is not broadened, slow-light systems can generally obtain an output pulse delay time beyond 100ps. Furthermore, for the fixed input power, changing the length of NLBG can observably influence the group velocity of light.
2015, 39(2): 228-232.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.018
Abstract:
In order to solve the problems existing in cold rolling production line of silicon steel side cutting, such as micro crack, stress, burr, edge waves, experiments of high speed laser cutting with fiber laser were carried out. The data of cutting speed and cutting quality were obtained. The results show that cutting speed can reach 400m/min when power is 3000W. Because of the closed keyhole and the flat cutting front, with the increasing of cutting speed, the growth factor of cutting speed reduces from 1 to 0.3 and cutting quality becomes poor with burr height from 5μm to 22μm. The cutting quality can be improved using light-gas eccentrically laser cutting technology and the burr height is less than 15μm. The study provides theory support and technology guidance for high speed laser cutting.
In order to solve the problems existing in cold rolling production line of silicon steel side cutting, such as micro crack, stress, burr, edge waves, experiments of high speed laser cutting with fiber laser were carried out. The data of cutting speed and cutting quality were obtained. The results show that cutting speed can reach 400m/min when power is 3000W. Because of the closed keyhole and the flat cutting front, with the increasing of cutting speed, the growth factor of cutting speed reduces from 1 to 0.3 and cutting quality becomes poor with burr height from 5μm to 22μm. The cutting quality can be improved using light-gas eccentrically laser cutting technology and the burr height is less than 15μm. The study provides theory support and technology guidance for high speed laser cutting.
2015, 39(2): 233-236.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.019
Abstract:
In order to achieve synchronous discharge of dual-chambers of an ArF excimer laser based on master oscillation power amplifier(MOPA) structure, synchronization logic was used to respond to dual-chamber discharge timing sequence quickly. According to synchronization control logic, an automatic precision adjustment to dual-chamber delay was made. Coarse search was implemented by using a high-speed synchronous modulo-16 binary counter and dual-chamber delay difference was narrowed quickly. Small precision delay adjustment was achieved by using universal digital programmable delay chip. The results show that discharge time differences steadies at about 23ns less than ±3ns synchronization jitter after dual-chamber discharge synchronous adjustment. It can meet MOPA structure excimer laser synchronous control requirements under high repetition frequency of 4kHz.
In order to achieve synchronous discharge of dual-chambers of an ArF excimer laser based on master oscillation power amplifier(MOPA) structure, synchronization logic was used to respond to dual-chamber discharge timing sequence quickly. According to synchronization control logic, an automatic precision adjustment to dual-chamber delay was made. Coarse search was implemented by using a high-speed synchronous modulo-16 binary counter and dual-chamber delay difference was narrowed quickly. Small precision delay adjustment was achieved by using universal digital programmable delay chip. The results show that discharge time differences steadies at about 23ns less than ±3ns synchronization jitter after dual-chamber discharge synchronous adjustment. It can meet MOPA structure excimer laser synchronous control requirements under high repetition frequency of 4kHz.
2015, 39(2): 237-241.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.020
Abstract:
In order to get laser output with high average power and good beam quality, the method of sequence combing technology of pulsed lasers was developed based on the synchronizing and delay controlling technique of pulses. The multiple beam combination was performed through the optical beam combination device (OBCD).Three pulsed beams were combined successfully with this method, and the high combining efficiency of 95.8% was achieved. Experimental results show that the power of the combined beam is nearly equal to the total power of every single beam with high beam quality.
In order to get laser output with high average power and good beam quality, the method of sequence combing technology of pulsed lasers was developed based on the synchronizing and delay controlling technique of pulses. The multiple beam combination was performed through the optical beam combination device (OBCD).Three pulsed beams were combined successfully with this method, and the high combining efficiency of 95.8% was achieved. Experimental results show that the power of the combined beam is nearly equal to the total power of every single beam with high beam quality.
2015, 39(2): 242-246.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.021
Abstract:
In order to search at long distance and take photos at short distance in criminal investigation, a mechanical-compensation solar blind ultraviolet zoom lens system was designed with binary diffractive elements and aspherical elements. Its zooming region was 40mm~80mm with F number of 4, operating at 0.24μm~ 0.28μm wavelength. The 2.54cm S8844-0909 ultraviolet CCD was selected as a sensor with pixel size of 24μm×24μm and corresponding field of view of 6°~12°. The optical system was composed of seven lenses with simple structure and small size. The results show that in full zooming range, MTF over all fields of view is above 0.7 at back focus length of 10mm and cut off frequency of 21cycles/mm, close to the diffraction-limited curve. The distortion is less than 5%. The zoom lens system has good image quality and stable image plane, and meets the overall design requirements of the optical system.
In order to search at long distance and take photos at short distance in criminal investigation, a mechanical-compensation solar blind ultraviolet zoom lens system was designed with binary diffractive elements and aspherical elements. Its zooming region was 40mm~80mm with F number of 4, operating at 0.24μm~ 0.28μm wavelength. The 2.54cm S8844-0909 ultraviolet CCD was selected as a sensor with pixel size of 24μm×24μm and corresponding field of view of 6°~12°. The optical system was composed of seven lenses with simple structure and small size. The results show that in full zooming range, MTF over all fields of view is above 0.7 at back focus length of 10mm and cut off frequency of 21cycles/mm, close to the diffraction-limited curve. The distortion is less than 5%. The zoom lens system has good image quality and stable image plane, and meets the overall design requirements of the optical system.
2015, 39(2): 247-251.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.022
Abstract:
In order to reconstruct high quality infrared video images from the degraded images, an image restoration algorithm was adopted based on the improved ridge wavelet transform. Firstly, the ridge wavelet transform was carried out for the degraded images. Then, one weighted improved adaptive pseudo median filtering algorithm was used to process the ridge wave coefficients. Finally, adaptive Wiener filtering algorithm was introduced to suppress for "wrap around" effect of images after filtering. After theoretical analysis and experimental verification, the relevant simulated degraded images, the real degraded images and the peak signal to noise ratio were obtained. The results show that the algorithm in this paper is superior to the algorithms, such as the pseudo median filtering and two types of ridge wavelet transform denoising algorithms. The study is helpful for the research of infrared video degraded image restoration.
In order to reconstruct high quality infrared video images from the degraded images, an image restoration algorithm was adopted based on the improved ridge wavelet transform. Firstly, the ridge wavelet transform was carried out for the degraded images. Then, one weighted improved adaptive pseudo median filtering algorithm was used to process the ridge wave coefficients. Finally, adaptive Wiener filtering algorithm was introduced to suppress for "wrap around" effect of images after filtering. After theoretical analysis and experimental verification, the relevant simulated degraded images, the real degraded images and the peak signal to noise ratio were obtained. The results show that the algorithm in this paper is superior to the algorithms, such as the pseudo median filtering and two types of ridge wavelet transform denoising algorithms. The study is helpful for the research of infrared video degraded image restoration.
2015, 39(2): 252-258.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.023
Abstract:
Structured light measurement is widely used in various areas due to non-contact, high speed, high measurement accuracy and low cost. The measurement accuracy of structured light measurement system depends on the calibration accuracy. The existing calibration methods were reviewed including the photogrammetry based on matrix transformation, geometry-based triangulation, and polynomial method. Photogrammetry can be further divided into inverse camera, pseudo-camera, and light-stripe plane. All the calibration methods were compared in the view of error propagation, dependence on projector calibration, precise auxiliary calibration gauge, and operation complexity. It is pointed out that the trend of calibration method is from laboratory to factory techniques, which require simple calibration device, convenient calibration process, fast calibration and high calibration precision.
Structured light measurement is widely used in various areas due to non-contact, high speed, high measurement accuracy and low cost. The measurement accuracy of structured light measurement system depends on the calibration accuracy. The existing calibration methods were reviewed including the photogrammetry based on matrix transformation, geometry-based triangulation, and polynomial method. Photogrammetry can be further divided into inverse camera, pseudo-camera, and light-stripe plane. All the calibration methods were compared in the view of error propagation, dependence on projector calibration, precise auxiliary calibration gauge, and operation complexity. It is pointed out that the trend of calibration method is from laboratory to factory techniques, which require simple calibration device, convenient calibration process, fast calibration and high calibration precision.
2015, 39(2): 259-265.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.024
Abstract:
Laser-arc hybrid welding, integrating the advantages of laser welding process and arc welding, is a new, high-quality welding technology which can be widely used in industry. Firstly, the characteristics of laser-arc hybrid welding, and laser-arc interaction were introduced. Secondly, the research progress of the general laser-arc hybrid welding technologies was reviewed. Finally, the applications of laser-arc hybrid welding technologies in automotive body manufacture were described.
Laser-arc hybrid welding, integrating the advantages of laser welding process and arc welding, is a new, high-quality welding technology which can be widely used in industry. Firstly, the characteristics of laser-arc hybrid welding, and laser-arc interaction were introduced. Secondly, the research progress of the general laser-arc hybrid welding technologies was reviewed. Finally, the applications of laser-arc hybrid welding technologies in automotive body manufacture were described.
2015, 39(2): 266-269.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.025
Abstract:
In order to improve the accuracy of digital holographic reconstruction, theoretical analysis and experimental verification of digital holographic reconstruction phase were made by using Hilbert transform. Firstly, the zero order item of the hologram was filtered through Fourier transform. Secondly, the hologram without zero order item was shifted 90° through the Hilbert transform so that the analytic signal was constructed and the object's wrapped phase was found. Finally, the object's real phase was obtained by using the least square method to unwrap the phase. The experimental results of Hilbert transform reconstruction and conventional Fourier transform reconstruction were compared. The data of the standard deviation was obtained and compared. The results indicate that the reconstruct precision of this method is higher than the conventional Fourier transform method. The research results are helpful to improve the precision of the phase reconstruction.
In order to improve the accuracy of digital holographic reconstruction, theoretical analysis and experimental verification of digital holographic reconstruction phase were made by using Hilbert transform. Firstly, the zero order item of the hologram was filtered through Fourier transform. Secondly, the hologram without zero order item was shifted 90° through the Hilbert transform so that the analytic signal was constructed and the object's wrapped phase was found. Finally, the object's real phase was obtained by using the least square method to unwrap the phase. The experimental results of Hilbert transform reconstruction and conventional Fourier transform reconstruction were compared. The data of the standard deviation was obtained and compared. The results indicate that the reconstruct precision of this method is higher than the conventional Fourier transform method. The research results are helpful to improve the precision of the phase reconstruction.
2015, 39(2): 270-273.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.026
Abstract:
In order to decrease the effect of noisy environment on quantum teleportation, the scheme of quantum teleportation in the dephasing noisy environment based on the disentanglement-free state and quantum error-avoiding code was proposed. In this scheme, disentanglement-free atomic four quantum bit state was taken as the quantum entanglement channel, and the teleportated quantum information was encoded into two quantum bits. The results show the whole teleportation process is not affected by the noisy environment and the success probability for this teleportation scheme is 100%. This research is helpful to improve quality of the quantum communication
In order to decrease the effect of noisy environment on quantum teleportation, the scheme of quantum teleportation in the dephasing noisy environment based on the disentanglement-free state and quantum error-avoiding code was proposed. In this scheme, disentanglement-free atomic four quantum bit state was taken as the quantum entanglement channel, and the teleportated quantum information was encoded into two quantum bits. The results show the whole teleportation process is not affected by the noisy environment and the success probability for this teleportation scheme is 100%. This research is helpful to improve quality of the quantum communication
2015, 39(2): 274-279.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.027
Abstract:
The alloyed layers of Mn-Al2O3 and Mn-Al2O3-NiWC were fabricated on 1Cr18Ni9Ti stainless steel by laser surface alloying to improve wear-corrosion resistance of stainless steel blades. High Mn-matrix composite coatings were in-situ fabricated which were composed of dendrites, eutectics and undissolved Al2O3 particles. Microstructure, wear and corrosion behavior of both the alloyed layers were investigated by orthogonal experiments. The results show that wear resistance is improved under all 9 sets of orthogonal parameters, while corrosion resistance is improved or decreased, varying with parameters. Wear resistance of the alloyed layers is influenced most by the addition amount of Al2O3, followed by scanning speed and laser power, while corrosion resistance is influenced inversely. Addition amount of Al2O3 affects the hard phase amount in the alloyed layers, determining hardness and wear resistance of the alloyed layers. Intergranular corrosion in combination with pitting in the grains and grain boundaries are observed in both kinds of alloyed layers. Corrosion resistance is determined by the various microstructure, phases, the unique chemical composition and corrosion characteristic of the phases and the homogeneity of the microstructure.
The alloyed layers of Mn-Al2O3 and Mn-Al2O3-NiWC were fabricated on 1Cr18Ni9Ti stainless steel by laser surface alloying to improve wear-corrosion resistance of stainless steel blades. High Mn-matrix composite coatings were in-situ fabricated which were composed of dendrites, eutectics and undissolved Al2O3 particles. Microstructure, wear and corrosion behavior of both the alloyed layers were investigated by orthogonal experiments. The results show that wear resistance is improved under all 9 sets of orthogonal parameters, while corrosion resistance is improved or decreased, varying with parameters. Wear resistance of the alloyed layers is influenced most by the addition amount of Al2O3, followed by scanning speed and laser power, while corrosion resistance is influenced inversely. Addition amount of Al2O3 affects the hard phase amount in the alloyed layers, determining hardness and wear resistance of the alloyed layers. Intergranular corrosion in combination with pitting in the grains and grain boundaries are observed in both kinds of alloyed layers. Corrosion resistance is determined by the various microstructure, phases, the unique chemical composition and corrosion characteristic of the phases and the homogeneity of the microstructure.
2015, 39(2): 280-283.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.028
Abstract:
In order to study Raman spectral characteristics of ammonium thiocyanate solution,geometry of SCN- was optimized based on 6-31G(d) basis set and its Raman spectra was calculated using Hartree-Fock (H-F)method. The Raman spectra of ammonium thiocyanate solution with different concentrations were measured experimentally. It was found that the relationship between the concentration of SCN- and the corresponding Raman peakintensity waslinear.The results show that absolute error and relative error of the experiment result(752cm-1)and the theoretical calculation (740cm-1) of Raman vibrationalfrequency of SCN- is a little. However,envelopes appear in another Raman region.The resultsprovide a help for measurement of ammonium thiocyanate solution withdifferent concentrations inindustry.
In order to study Raman spectral characteristics of ammonium thiocyanate solution,geometry of SCN- was optimized based on 6-31G(d) basis set and its Raman spectra was calculated using Hartree-Fock (H-F)method. The Raman spectra of ammonium thiocyanate solution with different concentrations were measured experimentally. It was found that the relationship between the concentration of SCN- and the corresponding Raman peakintensity waslinear.The results show that absolute error and relative error of the experiment result(752cm-1)and the theoretical calculation (740cm-1) of Raman vibrationalfrequency of SCN- is a little. However,envelopes appear in another Raman region.The resultsprovide a help for measurement of ammonium thiocyanate solution withdifferent concentrations inindustry.
Measurement of total viable count on chilled mutton surface based on hyperspectral imaging technique
2015, 39(2): 284-288.
doi: 10.7510/jgjs.issn.1001-3806.2015.02.029
Abstract:
In order to obtain non-destructive assessment of total viable count (TVC) on chilled mutton surface, different kinds of recognition models were established based on different wavelength range hyperspectral imaging systems, then theoretical analysis and experiments were carried out. The hyperspectral imaging information of chilled mutton samples were collected in the region of 400nm~1100nm and 900nm~1700nm. The predictive models were established by partial least squares (PLS) and artificial neural network (back propagation artificial neural network and radial basis function artificial neural network (RBF-ANN)). The results show that the model which is on the basis of artificial neural network is better than PLS to predict TVC of chilled mutton surface. The best prediction result is based on the RBF-ANN model, the correlation coefficient and the root mean square error of prediction are 0.9872, 0.9988 and 0.8210, 0.2507 in the region of 400nm~1100nm and 900nm~1700nm. Meanwhile, the region of 900nm~1700nm is the best modeling wavelength. Therefore, hyperspecctral imaging technique can be used for the non-destructive detection of total viable count on chilled mutton surface.
In order to obtain non-destructive assessment of total viable count (TVC) on chilled mutton surface, different kinds of recognition models were established based on different wavelength range hyperspectral imaging systems, then theoretical analysis and experiments were carried out. The hyperspectral imaging information of chilled mutton samples were collected in the region of 400nm~1100nm and 900nm~1700nm. The predictive models were established by partial least squares (PLS) and artificial neural network (back propagation artificial neural network and radial basis function artificial neural network (RBF-ANN)). The results show that the model which is on the basis of artificial neural network is better than PLS to predict TVC of chilled mutton surface. The best prediction result is based on the RBF-ANN model, the correlation coefficient and the root mean square error of prediction are 0.9872, 0.9988 and 0.8210, 0.2507 in the region of 400nm~1100nm and 900nm~1700nm. Meanwhile, the region of 900nm~1700nm is the best modeling wavelength. Therefore, hyperspecctral imaging technique can be used for the non-destructive detection of total viable count on chilled mutton surface.
