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RSS2013 Vol. 37, No. 6
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2013, 37(6): 705-711.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.001
[Abstract]
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Abstract:
In order to find a new method to dress super-abrasive grinding wheels, experiments were carried out on bronze-bonded diamond grinding wheels with a pulsed fiber laser irradiating in radial orientation. Its basic principle was analyzed. After the ablation of bronze-bonded wheel by means of a pulsed fiber laser, the surface morphology and depth of ablated craters were observed by 3-D video microscopy system with super depth of field and surfagauge, and the influences of laser average power, pulse repetition frequency and defocusing amount on the ablation effect were summarized. According to the experimental results, the laser dressing experiments were carried out with the best process parameters(Pm=20W, f=70kHz,Δ=0.0mm), and the surface topography after laser dressing was observed by a 3-D video microscopy system with super depth of field. The results show that, dressing of bronze-bonded diamond grinding wheels with a pulsed fiber laser irradiating in radial orientation can bring out good dressing effect with the reasonable processing parameters.
In order to find a new method to dress super-abrasive grinding wheels, experiments were carried out on bronze-bonded diamond grinding wheels with a pulsed fiber laser irradiating in radial orientation. Its basic principle was analyzed. After the ablation of bronze-bonded wheel by means of a pulsed fiber laser, the surface morphology and depth of ablated craters were observed by 3-D video microscopy system with super depth of field and surfagauge, and the influences of laser average power, pulse repetition frequency and defocusing amount on the ablation effect were summarized. According to the experimental results, the laser dressing experiments were carried out with the best process parameters(Pm=20W, f=70kHz,Δ=0.0mm), and the surface topography after laser dressing was observed by a 3-D video microscopy system with super depth of field. The results show that, dressing of bronze-bonded diamond grinding wheels with a pulsed fiber laser irradiating in radial orientation can bring out good dressing effect with the reasonable processing parameters.
2013, 37(6): 712-717.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.002
Abstract:
Magnesium is an important strengthening alloying element in aluminum alloy, the burning loss of which will greatly reduce such mechanical property of the welds as the tensile strength during laser lap welding of aluminum alloy. In order to eliminate the negative effect of the burning loss of magnesium on mechanical property of the welds, filling magnesium powder is adopted filled in laser welding aluminum alloy. The contents of magnesium in the welds were measured both in the vertical and horizontal directions, and the effect of welding velocity on the burning loss of magnesium was experimentally studied. Then, the tensile strength of the welds was tested. Compared after comparing the tensile strength of the welds under different magnesium contents, the relationship between the content of magnesium element of the welds and tensile strength was studied. The results show that the reduction of magnesium content due to the burning loss of magnesium can greatly affect the tensile strength of the welds, filling magnesium during laser welding can effectively improve the tensile strength of the welds, the maximum of the improvement can reach to 36.06% compared to those without filling magnesium. When the mass fraction of the magnesium element in the welds is about 0.026,the tensile strength of the welds reaches the maximum. This study provides new theoretical basis and methods to improve the strength of aluminum alloy laser welded joints.
Magnesium is an important strengthening alloying element in aluminum alloy, the burning loss of which will greatly reduce such mechanical property of the welds as the tensile strength during laser lap welding of aluminum alloy. In order to eliminate the negative effect of the burning loss of magnesium on mechanical property of the welds, filling magnesium powder is adopted filled in laser welding aluminum alloy. The contents of magnesium in the welds were measured both in the vertical and horizontal directions, and the effect of welding velocity on the burning loss of magnesium was experimentally studied. Then, the tensile strength of the welds was tested. Compared after comparing the tensile strength of the welds under different magnesium contents, the relationship between the content of magnesium element of the welds and tensile strength was studied. The results show that the reduction of magnesium content due to the burning loss of magnesium can greatly affect the tensile strength of the welds, filling magnesium during laser welding can effectively improve the tensile strength of the welds, the maximum of the improvement can reach to 36.06% compared to those without filling magnesium. When the mass fraction of the magnesium element in the welds is about 0.026,the tensile strength of the welds reaches the maximum. This study provides new theoretical basis and methods to improve the strength of aluminum alloy laser welded joints.
Mechanical analysis of paint film stripping from aluminum plate surface by means of nanosecond laser
2013, 37(6): 718-722.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.003
Abstract:
In order to study the laser stripping mechanism, paint film stripping from aluminum plate surface experiments were demonstrated using the radiation of 1064nm nanosecond pulse laser. According to thermal conductivity theory, the temperature distribution of the film and the aluminum surface under laser irradiation were simulated. The separating force generated by the aluminum plate at the interface due to thermal expansion was calculated. The formation of the plasma shock wave on the removal of the paint film was also analyzed. The result shows that the effect of force is the key factor for nanosecond laser removal of the film, separation force due to thermal expansion provides necessary condition for the removal of the film, and the constraint of the film on the laser plasma eventually leads to its own cracking and spalling. A conclusion was made that thermodynamic theory can be used for analysis of removal mechanism of metal surface coating with nanosecond laser.
In order to study the laser stripping mechanism, paint film stripping from aluminum plate surface experiments were demonstrated using the radiation of 1064nm nanosecond pulse laser. According to thermal conductivity theory, the temperature distribution of the film and the aluminum surface under laser irradiation were simulated. The separating force generated by the aluminum plate at the interface due to thermal expansion was calculated. The formation of the plasma shock wave on the removal of the paint film was also analyzed. The result shows that the effect of force is the key factor for nanosecond laser removal of the film, separation force due to thermal expansion provides necessary condition for the removal of the film, and the constraint of the film on the laser plasma eventually leads to its own cracking and spalling. A conclusion was made that thermodynamic theory can be used for analysis of removal mechanism of metal surface coating with nanosecond laser.
2013, 37(6): 723-727.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.004
Abstract:
In order to reduce the precision requirements of random-phase pupil, an optical scanning holography method using a binary random-phase pupil was proposed, which can be used to acquire the holographic information of a multi-section object. Series of theoretical analysis and numerical simulation were conducted. It is found that, similar as the optical scanning holography using a continuous random-phase pupil, the one using a binary phase pupil can also effectively eliminate the haze risen from the de-focus sections when the in-focus image is reconstructed. Furthermore, the reconstructed image quality has a close relationship with the degree of randomness on binary random-phase pupil, and an acceptable reconstructed image can still be obtained if randomness degree is not too low. This result is helpful for reducing the requirements of experimental conditions.
In order to reduce the precision requirements of random-phase pupil, an optical scanning holography method using a binary random-phase pupil was proposed, which can be used to acquire the holographic information of a multi-section object. Series of theoretical analysis and numerical simulation were conducted. It is found that, similar as the optical scanning holography using a continuous random-phase pupil, the one using a binary phase pupil can also effectively eliminate the haze risen from the de-focus sections when the in-focus image is reconstructed. Furthermore, the reconstructed image quality has a close relationship with the degree of randomness on binary random-phase pupil, and an acceptable reconstructed image can still be obtained if randomness degree is not too low. This result is helpful for reducing the requirements of experimental conditions.
2013, 37(6): 728-730.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.005
Abstract:
In order to help shot athletes improve their score quickly,a new shot motion parameter measuring system was designed. The system consists of a set of laser parallel light curtain based on Fresnel lens and photodiode array, using field-programmable gate array (FPGA) for processing signals. The method can measure the shot angle and velocity conveniently and display the measurement results on the liquid crystal display(LCD) monitor intuitively. The results show that the system design is novel, structure-simple and low-cost,which can be used by athletes for daily training and has wide application prospects.
In order to help shot athletes improve their score quickly,a new shot motion parameter measuring system was designed. The system consists of a set of laser parallel light curtain based on Fresnel lens and photodiode array, using field-programmable gate array (FPGA) for processing signals. The method can measure the shot angle and velocity conveniently and display the measurement results on the liquid crystal display(LCD) monitor intuitively. The results show that the system design is novel, structure-simple and low-cost,which can be used by athletes for daily training and has wide application prospects.
2013, 37(6): 731-735.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.006
Abstract:
Optical network-on-chip(ONoC) has many characteristics superior to electrical interconnection and has emerged as a promising alternative. To improve the performance of optical on-chip networks, a novelring-based 4×4 nonblocking silicon optical router was proposed by means of optical module method.This structure just composes evenmicroring-resonator-based switching elements and six waveguide crossings,which reduce power consumption, device area and insertion loss. Finally, the topology performance were evalutated in terms of insertion loss and power consumption. The simulation results demonstrate that the proposed architecture consumes 8% less power and 7%less optical insertion loss.
Optical network-on-chip(ONoC) has many characteristics superior to electrical interconnection and has emerged as a promising alternative. To improve the performance of optical on-chip networks, a novelring-based 4×4 nonblocking silicon optical router was proposed by means of optical module method.This structure just composes evenmicroring-resonator-based switching elements and six waveguide crossings,which reduce power consumption, device area and insertion loss. Finally, the topology performance were evalutated in terms of insertion loss and power consumption. The simulation results demonstrate that the proposed architecture consumes 8% less power and 7%less optical insertion loss.
2013, 37(6): 736-741.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.007
Abstract:
In order to eliminate imperfect fringes captured by an interlaced CCD camera when measuring a dynamic object, the Fourier transform de-interlacing algorithm was proposed. The blurring fringe pattern grabbed by the interlaced CCD is divided into two single-field images, each of which is processed into the restored frame image with this algorithm, then their corresponding 3-D shape were reconstructed by means of fringe analysis method. Theoretical analysis shows that the singe-field image disposed by the Fourier transform de-interlacing algorithm is identical with the corresponding exact full frame image. The results of simulation and experiment demonstrate that the imperfect fringe patterns can be restored and real objects can be reconstructed with this method. The method is simple and practical, so it can be applied in 3-D shape measurement for dynamic objects based on spatial phase detection, phase measurement profilometry and Fourier transform profilometry.
In order to eliminate imperfect fringes captured by an interlaced CCD camera when measuring a dynamic object, the Fourier transform de-interlacing algorithm was proposed. The blurring fringe pattern grabbed by the interlaced CCD is divided into two single-field images, each of which is processed into the restored frame image with this algorithm, then their corresponding 3-D shape were reconstructed by means of fringe analysis method. Theoretical analysis shows that the singe-field image disposed by the Fourier transform de-interlacing algorithm is identical with the corresponding exact full frame image. The results of simulation and experiment demonstrate that the imperfect fringe patterns can be restored and real objects can be reconstructed with this method. The method is simple and practical, so it can be applied in 3-D shape measurement for dynamic objects based on spatial phase detection, phase measurement profilometry and Fourier transform profilometry.
2013, 37(6): 742-746.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.008
Abstract:
In order to study influence of material dispersion on defect modes of 1-D photonic crystal, the transmission spectrum of the 1-D photonic crystal with dispersive material was calculated based on optical transmission matrix, and the dispersive material was described by the Lorentz oscillator model. The effect of material dispersion on defect modes of photonic crystals was analyzed. The results show that whether the dispersion of high and low refractive index medium or the dispersion of defect will bring frequency shift or splitting of defect modes; the defect mode will bring red-shift if the optical thickness of dispersive medium is thicker than the thickness of common medium, and the defect mode will bring blue-shift when the optical thickness of dispersive medium is thinner than the thickness of common medium; the most obvious effect of frequency shift of defect modes results from the dispersion of low refractive index medium. The results have certain reference value to the design and research of photonic crystal.
In order to study influence of material dispersion on defect modes of 1-D photonic crystal, the transmission spectrum of the 1-D photonic crystal with dispersive material was calculated based on optical transmission matrix, and the dispersive material was described by the Lorentz oscillator model. The effect of material dispersion on defect modes of photonic crystals was analyzed. The results show that whether the dispersion of high and low refractive index medium or the dispersion of defect will bring frequency shift or splitting of defect modes; the defect mode will bring red-shift if the optical thickness of dispersive medium is thicker than the thickness of common medium, and the defect mode will bring blue-shift when the optical thickness of dispersive medium is thinner than the thickness of common medium; the most obvious effect of frequency shift of defect modes results from the dispersion of low refractive index medium. The results have certain reference value to the design and research of photonic crystal.
2013, 37(6): 747-751.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.009
Abstract:
In order to make large scale gratings,errors of holographic mosaic gratings were analyzed. The gratings' phase and rotation were designed by monitoring the Moiré fringes formed on the reference grating. The orientation and period of the Moiré fringes can show the grating's rotation condition, and the phase can express the grating's phase condition. The phase congruence of the Moiré fringes and the mosaic gratings is researched when the planes of reference grating and the mosaic grating's substrate are not parallel. In addition mosaic gratings' phase error brought by the drift of optical path difference was studied. The errors of mosaic gratings caused by the movement of workbench were analyzed. Considering all of the factors, the mosaic gratings' error is about 0.15λ.The value can meet the requirement of mosaic grating which is designed to be used for pulse compressor. Finally the precision of mosaic gratings' error was confirmed by the experiment. The results show that it is feasible to make the holographic mosaic grating by using the reference grating. The research of holographic mosaic gratings' error provides the method for making meter-order gratings.
In order to make large scale gratings,errors of holographic mosaic gratings were analyzed. The gratings' phase and rotation were designed by monitoring the Moiré fringes formed on the reference grating. The orientation and period of the Moiré fringes can show the grating's rotation condition, and the phase can express the grating's phase condition. The phase congruence of the Moiré fringes and the mosaic gratings is researched when the planes of reference grating and the mosaic grating's substrate are not parallel. In addition mosaic gratings' phase error brought by the drift of optical path difference was studied. The errors of mosaic gratings caused by the movement of workbench were analyzed. Considering all of the factors, the mosaic gratings' error is about 0.15λ.The value can meet the requirement of mosaic grating which is designed to be used for pulse compressor. Finally the precision of mosaic gratings' error was confirmed by the experiment. The results show that it is feasible to make the holographic mosaic grating by using the reference grating. The research of holographic mosaic gratings' error provides the method for making meter-order gratings.
2013, 37(6): 752-755.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.010
Abstract:
To study the absorption coefficients for the ultraviolet polarized light in the iceland crystal, two crystal samples in different length and width were manufactured. Using the dual beam path spectrometer and inserting polarizers whose polarization directions are parallel separately into the sample and the reference paths, the transmission spectra of the light passing through the crystal in different lengths were measured. Canceling out the losses on the crystal surfaces, the absorption coefficients of the o light and the e light in the ultraviolet region in both the crystal samples were achieved. The absorption coefficients of e light in the ultraviolet region are usually smaller than o light in the same crystal and as the wavelength gets shorter, their difference becomes larger. The absorption coefficient in the ultraviolet region varies greatly in the different crystals. The results show that it is important for making high performance ultraviolet polarizers to get the ultraviolet polarization spectra of the raw materials and to pick out the crystals with low absorption coefficients.
To study the absorption coefficients for the ultraviolet polarized light in the iceland crystal, two crystal samples in different length and width were manufactured. Using the dual beam path spectrometer and inserting polarizers whose polarization directions are parallel separately into the sample and the reference paths, the transmission spectra of the light passing through the crystal in different lengths were measured. Canceling out the losses on the crystal surfaces, the absorption coefficients of the o light and the e light in the ultraviolet region in both the crystal samples were achieved. The absorption coefficients of e light in the ultraviolet region are usually smaller than o light in the same crystal and as the wavelength gets shorter, their difference becomes larger. The absorption coefficient in the ultraviolet region varies greatly in the different crystals. The results show that it is important for making high performance ultraviolet polarizers to get the ultraviolet polarization spectra of the raw materials and to pick out the crystals with low absorption coefficients.
2013, 37(6): 756-759.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.011
Abstract:
In order to study the change rule of water backscattering light energy received by a intensified charge-coupled detector(ICCD) in the process of searching for underwater targets by the equal step length, a model of water backsca-ttering light energy received by the ICCD was built, and the formula of water backscattering light power received by the ICCD was deduced in a single imaging. Simulation computation and experiment validation were carried through. According to dependence of mean grayscale of the image on the water backscattering light energy, the data of the change rule of water backscattering light energy was obtained. The result shows that water backscattering light energy descends along with the distance of water accretion in exponent rule approximately.
In order to study the change rule of water backscattering light energy received by a intensified charge-coupled detector(ICCD) in the process of searching for underwater targets by the equal step length, a model of water backsca-ttering light energy received by the ICCD was built, and the formula of water backscattering light power received by the ICCD was deduced in a single imaging. Simulation computation and experiment validation were carried through. According to dependence of mean grayscale of the image on the water backscattering light energy, the data of the change rule of water backscattering light energy was obtained. The result shows that water backscattering light energy descends along with the distance of water accretion in exponent rule approximately.
2013, 37(6): 760-765.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.012
Abstract:
In order to understand the laser micro-joining mechanism better, based on the ANSYS, finite element simulation software, the Gaussian heat source model was adopted to simulate the dynamic temperature filed in the process of welding polyethylene terephthalate (PET) and biomedical Ti. The transition highest peak temperature variation during the process of welding was recorded with a thermal infrared imager and the actual welding seam width was measured with a digital microscope in super depth of field. The simulation results are conforming to the experimental results. Simulation result suggests that the isotherm is as an ellipse. Meanwhile, there is intensive isotherm and larger temperature gradient in the front of the spot center, on the contrary, sparser isotherm and smaller temperature gradient at the back of the spot center, which verifies the applicability of the model established by moving heat source during the laser welding based on PET/Ti sheets applying to the temperature field simulation.
In order to understand the laser micro-joining mechanism better, based on the ANSYS, finite element simulation software, the Gaussian heat source model was adopted to simulate the dynamic temperature filed in the process of welding polyethylene terephthalate (PET) and biomedical Ti. The transition highest peak temperature variation during the process of welding was recorded with a thermal infrared imager and the actual welding seam width was measured with a digital microscope in super depth of field. The simulation results are conforming to the experimental results. Simulation result suggests that the isotherm is as an ellipse. Meanwhile, there is intensive isotherm and larger temperature gradient in the front of the spot center, on the contrary, sparser isotherm and smaller temperature gradient at the back of the spot center, which verifies the applicability of the model established by moving heat source during the laser welding based on PET/Ti sheets applying to the temperature field simulation.
2013, 37(6): 766-768.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.013
Abstract:
Maximum range, as a combination property for evaluating ranging performance of a laser range finder, one of the important factors that affect the operational effectiveness of weapon systems, is paid more and more attention. In order to realize high beam quality and narrow pulse width seed source of the laser ranging system,the electro-optic Q-switch rubidium titanyle phosphate RbTiOPO4 (RTP) crystal used to be used in the low-repetition-rate Q-switch was used in high repetition rate laser. A laser at 1064nm was obtained at repetition rate of 25Hz,pulse width of 1.8ns,pulse energy of 1.5mJ,beam quality of M2<1.3. The results show that this laser provides a qualified seed source for narrow pulse width of 1ns~3ns,pulse energy of 200mJ and no water-cooled all-solid-state laser ranging system. These results are helpful to the laser design with high beam quality and narrow pulse width.
Maximum range, as a combination property for evaluating ranging performance of a laser range finder, one of the important factors that affect the operational effectiveness of weapon systems, is paid more and more attention. In order to realize high beam quality and narrow pulse width seed source of the laser ranging system,the electro-optic Q-switch rubidium titanyle phosphate RbTiOPO4 (RTP) crystal used to be used in the low-repetition-rate Q-switch was used in high repetition rate laser. A laser at 1064nm was obtained at repetition rate of 25Hz,pulse width of 1.8ns,pulse energy of 1.5mJ,beam quality of M2<1.3. The results show that this laser provides a qualified seed source for narrow pulse width of 1ns~3ns,pulse energy of 200mJ and no water-cooled all-solid-state laser ranging system. These results are helpful to the laser design with high beam quality and narrow pulse width.
2013, 37(6): 769-772.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.014
Abstract:
Eye location is the precondition to monitor drivers fatigue state with the help of image processing technique. In order to achieve the purpose of detecting eyes location, a method was put forward to locate a driver's eyes based on infrared difference and gray integral projection. Firstly, two images for bright and dark pupils were collected for the pupil's different condition under the adaxial and abaxial infrared irradiation. Secondly, the collected parity frame images contained only binary pupil images by means of differential morphological processing. Finally, precise horizontal and vertical coordinates of the left and right eyes were obtained based on the vertical and horizontal projection on the left and right eyes respectively. Good results were achieved. The experimental results show that the method has high accuracy and real-time performance. This result is of great help to the next step of driver fatigue detection.
Eye location is the precondition to monitor drivers fatigue state with the help of image processing technique. In order to achieve the purpose of detecting eyes location, a method was put forward to locate a driver's eyes based on infrared difference and gray integral projection. Firstly, two images for bright and dark pupils were collected for the pupil's different condition under the adaxial and abaxial infrared irradiation. Secondly, the collected parity frame images contained only binary pupil images by means of differential morphological processing. Finally, precise horizontal and vertical coordinates of the left and right eyes were obtained based on the vertical and horizontal projection on the left and right eyes respectively. Good results were achieved. The experimental results show that the method has high accuracy and real-time performance. This result is of great help to the next step of driver fatigue detection.
2013, 37(6): 773-776.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.015
Abstract:
Bias control of Mach-Zehnder electro-optic modulators(EOM) is of great importance in radio over fiber links. In order to study the impact of dither tone-based modulator bias control on radio frequency(RF)signal, the output signal component of the system was theoretically analyzed by means of spectrum analysis after it was turned into the Bessel series, a system for arbitrary bias point was designed to confirm the analysis experimentally. The results of MATLAB simulation show that when the input RF power is 18dBm, only when the amplitude of dither tone is smaller than 45mV, the suppression ratio of the second harmonic of RF signal to signal caused by dither tone can be greater than 20dB. When the input RF power is 10dBm, the amplitude should be smaller than 19mV accordingly. When the amplitude of dither tone changes, the error between the experimental data of the suppression ratio of the second harmonic of RF signal to signal caused by dither tone and the simulation results is maintained at about from 3dB to 3.2dB. The results demonstrate that when Mach-Zehnder EOM works at linear bias-point, frequency components caused by dither tone can be ignored, however, when Mach-Zehnder EOM works at smallest bias-point, the impact of dither tone cannot be ignored.
Bias control of Mach-Zehnder electro-optic modulators(EOM) is of great importance in radio over fiber links. In order to study the impact of dither tone-based modulator bias control on radio frequency(RF)signal, the output signal component of the system was theoretically analyzed by means of spectrum analysis after it was turned into the Bessel series, a system for arbitrary bias point was designed to confirm the analysis experimentally. The results of MATLAB simulation show that when the input RF power is 18dBm, only when the amplitude of dither tone is smaller than 45mV, the suppression ratio of the second harmonic of RF signal to signal caused by dither tone can be greater than 20dB. When the input RF power is 10dBm, the amplitude should be smaller than 19mV accordingly. When the amplitude of dither tone changes, the error between the experimental data of the suppression ratio of the second harmonic of RF signal to signal caused by dither tone and the simulation results is maintained at about from 3dB to 3.2dB. The results demonstrate that when Mach-Zehnder EOM works at linear bias-point, frequency components caused by dither tone can be ignored, however, when Mach-Zehnder EOM works at smallest bias-point, the impact of dither tone cannot be ignored.
2013, 37(6): 777-780.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.016
Abstract:
A set of automatic detection and protection device of the laser was designed in order to realize the automatic detection and protection against arbitrary wavelength laser according to the principle of phototriode,electromagnetic relay and liquid crystal electro-optic effect experiments. Based on the theoretical analysis and experimental verification, phototriode photocurrent was formed when exposed to the laser radiation. The amplification circuit and an electromagnetic relay switch were used to control the output voltage of 5V and close liquid crystal voltage switch in a short time. When subjected to laser irradiation, the liquid crystal screen was substantially opaque, and returned to the transparent state at the end of the laser pulse. The results showed a design of laser protective glasses, blocking the laser irradiation and allowing ordinary bright light through at ordinary time.
A set of automatic detection and protection device of the laser was designed in order to realize the automatic detection and protection against arbitrary wavelength laser according to the principle of phototriode,electromagnetic relay and liquid crystal electro-optic effect experiments. Based on the theoretical analysis and experimental verification, phototriode photocurrent was formed when exposed to the laser radiation. The amplification circuit and an electromagnetic relay switch were used to control the output voltage of 5V and close liquid crystal voltage switch in a short time. When subjected to laser irradiation, the liquid crystal screen was substantially opaque, and returned to the transparent state at the end of the laser pulse. The results showed a design of laser protective glasses, blocking the laser irradiation and allowing ordinary bright light through at ordinary time.
2013, 37(6): 781-785.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.017
Abstract:
By adopting the positive defocusing amount, the effect of fiber laser-metal inert-gas welding(MIG) hybrid welding parameters on the weld morphology of 304 stainless steel, mainly including wire feeding speed, arc length, laser power, the distance between laser and MIG arc, welding direction and butt joint, was studied through many welding experiments. Results indicate that the good welding effects can be obtained by matching proper wire feeding speed and arc length when the extension length is 15mm and the distance between laser and MIG is 2mm. The results also show that small diameter wire will help to make the narrow weld width and low weld reinforcement, end tab will solve the problem of bad welding morphology at welding initial position. A conclusion is drawn that good welding quality of 304 stainless steel can be achieved when the proper welding procedure of laser-MIG hybrid welding is adopted.
By adopting the positive defocusing amount, the effect of fiber laser-metal inert-gas welding(MIG) hybrid welding parameters on the weld morphology of 304 stainless steel, mainly including wire feeding speed, arc length, laser power, the distance between laser and MIG arc, welding direction and butt joint, was studied through many welding experiments. Results indicate that the good welding effects can be obtained by matching proper wire feeding speed and arc length when the extension length is 15mm and the distance between laser and MIG is 2mm. The results also show that small diameter wire will help to make the narrow weld width and low weld reinforcement, end tab will solve the problem of bad welding morphology at welding initial position. A conclusion is drawn that good welding quality of 304 stainless steel can be achieved when the proper welding procedure of laser-MIG hybrid welding is adopted.
2013, 37(6): 786-790.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.018
Abstract:
In order to solve the limitation of single resolution in optical signal processing with traditional frequency domain denoising method, a multi-resolution wavelet denoising method was put forward. The effectiveness of wavelet denoising method was verified through contrast. According to the high requirements of hardware platform in wavelet denoising method, a field-programmable gate array (FPGA) was put forward as hardware platform. The wavelet denoising method based on distributed algorithm transforms complicated multiplication to simple parallel look-up table accumulation process. It improved the computational efficiency and completed the hardware transplantation. A storage testing system based on FPGA was designed and the hardware verification was realized. Experimental results showed that the denoising effect was well realized on FPGA.
In order to solve the limitation of single resolution in optical signal processing with traditional frequency domain denoising method, a multi-resolution wavelet denoising method was put forward. The effectiveness of wavelet denoising method was verified through contrast. According to the high requirements of hardware platform in wavelet denoising method, a field-programmable gate array (FPGA) was put forward as hardware platform. The wavelet denoising method based on distributed algorithm transforms complicated multiplication to simple parallel look-up table accumulation process. It improved the computational efficiency and completed the hardware transplantation. A storage testing system based on FPGA was designed and the hardware verification was realized. Experimental results showed that the denoising effect was well realized on FPGA.
2013, 37(6): 795-798.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.020
Abstract:
In order to eliminate the impact of negative disturbance on the all-optical-fiber interferential system, a new method to resist time-varying disturbance was proposed. There are two routes of interferential signals with a constant phase difference, by means of simple signal modulation and mathematic computation, to avoid the problem that the useful signal to noise ratio in the single-channel signal easily affected by the differences of optical path bias phase angle and modulation phase difference, while improving the quality of signals. Experiments show that the system can effectively eliminate the disturbing noise without strict requirements on coupler prismatic ratio, and is more practical.
In order to eliminate the impact of negative disturbance on the all-optical-fiber interferential system, a new method to resist time-varying disturbance was proposed. There are two routes of interferential signals with a constant phase difference, by means of simple signal modulation and mathematic computation, to avoid the problem that the useful signal to noise ratio in the single-channel signal easily affected by the differences of optical path bias phase angle and modulation phase difference, while improving the quality of signals. Experiments show that the system can effectively eliminate the disturbing noise without strict requirements on coupler prismatic ratio, and is more practical.
2013, 37(6): 799-802.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.021
Abstract:
Optical tweezers was used to study the changing rule of the activity of the red blood cells in static magnetic field. Red blood cells irradiated by Gaussian laser beam were deformed. When the laser was cut off, the relative deformation value of blood cells was obtained, which was associated with the cells' activity. After comparing the decay process of cells activity between static red blood cells and red blood cells in magnetic field, the results showed the activity of the red blood cells increased by 0.20T magnetic field, meanwhile the cells' energy consumption increased. The death of cells has accelerated because of energy consumption. The research can provide valuable reference for the study of cells viability and dynamic analysis.
Optical tweezers was used to study the changing rule of the activity of the red blood cells in static magnetic field. Red blood cells irradiated by Gaussian laser beam were deformed. When the laser was cut off, the relative deformation value of blood cells was obtained, which was associated with the cells' activity. After comparing the decay process of cells activity between static red blood cells and red blood cells in magnetic field, the results showed the activity of the red blood cells increased by 0.20T magnetic field, meanwhile the cells' energy consumption increased. The death of cells has accelerated because of energy consumption. The research can provide valuable reference for the study of cells viability and dynamic analysis.
2013, 37(6): 803-807.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.022
Abstract:
In order to solve the core reset problem of a magnetic pulse compression switch in a high repetition rate excimer laser power supply, the working process of the magnetic switch was analyzed. With the theoretical analysis as a guide, combined with the operating characteristics of the magnetic switch, an accurate reset circuit was designed. The saturated magnetic switch can be reset quickly and precisely by this circuit. After measuring the performance of the reset circuit, the reset current subsided in 200μs after the magnetic switch saturated. The results show that the design can meet the requirement of the power working at 4kHz repetition rate.The research is helpful for the design of high repetition rate excimer laser power supply in the future.
In order to solve the core reset problem of a magnetic pulse compression switch in a high repetition rate excimer laser power supply, the working process of the magnetic switch was analyzed. With the theoretical analysis as a guide, combined with the operating characteristics of the magnetic switch, an accurate reset circuit was designed. The saturated magnetic switch can be reset quickly and precisely by this circuit. After measuring the performance of the reset circuit, the reset current subsided in 200μs after the magnetic switch saturated. The results show that the design can meet the requirement of the power working at 4kHz repetition rate.The research is helpful for the design of high repetition rate excimer laser power supply in the future.
2013, 37(6): 808-811.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.023
Abstract:
In order to study the spectroscopy emission characteristics of chromium in water enriched with graphite based on laser induced breakdown spectroscopy, the characteristic spectral line of 425.435nm was selected for chromium in the experiment when a Nd:YAG laser in 1064nm wavelength was used as an excitation source, the echelle spectrometer and intensified charge coupled device detector with high resolution and wide spectral range were used for spectral separation and high sensitive detection. The results show that detection optimal delay time is 1100ns and gate width time is 1800ns. The calibration curve of chromium was plotted based on different concentration measurement results, and the limit of detection was 0.520mg/L. The results of the experiment provide the data reference for fast measurement of chromium in water based on laser-induced breakdown spectroscopy.
In order to study the spectroscopy emission characteristics of chromium in water enriched with graphite based on laser induced breakdown spectroscopy, the characteristic spectral line of 425.435nm was selected for chromium in the experiment when a Nd:YAG laser in 1064nm wavelength was used as an excitation source, the echelle spectrometer and intensified charge coupled device detector with high resolution and wide spectral range were used for spectral separation and high sensitive detection. The results show that detection optimal delay time is 1100ns and gate width time is 1800ns. The calibration curve of chromium was plotted based on different concentration measurement results, and the limit of detection was 0.520mg/L. The results of the experiment provide the data reference for fast measurement of chromium in water based on laser-induced breakdown spectroscopy.
2013, 37(6): 812-815.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.024
Abstract:
In order to realize quantum teleportation efficiently, a new scheme for quantum teleportation of atomic qubit states was presented based on entangled cavity fields. This scheme was realized based on the interaction between a single three-level atom in high quality light cavity and light field under large detuning. The effect of the damping of cavity field on quantum teleportation was discussed. The result shows that one atomic state is transmitted directly to another atom without help of auxiliary atoms in this scheme, efficiency of quantum teleportation reaches 100% in case of ideal light cavity and fidelity of quantum teleportation is close 1.0 for any the transmitted states in case of small damping.
In order to realize quantum teleportation efficiently, a new scheme for quantum teleportation of atomic qubit states was presented based on entangled cavity fields. This scheme was realized based on the interaction between a single three-level atom in high quality light cavity and light field under large detuning. The effect of the damping of cavity field on quantum teleportation was discussed. The result shows that one atomic state is transmitted directly to another atom without help of auxiliary atoms in this scheme, efficiency of quantum teleportation reaches 100% in case of ideal light cavity and fidelity of quantum teleportation is close 1.0 for any the transmitted states in case of small damping.
2013, 37(6): 816-819.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.025
Abstract:
In order to reduce the laser initiation energy and understand effect of laser wavelength on initiation sensitivity of explosives, the weak chemical bond and sensitive laser wavelength of PETN, RDX, HMX and HNS explosives were analyzed through spectrum, thermal decomposition mechanism and quantum mechanics calculation. Results show that the weakest chemical bond of PETN, RDX, HMX and HNS are nitryl whose correspondent resonant coupling laser wavelength is around 6300nm,and the laser wavelength inducing electronic transition of PETN, RDX, HMX and HNS explosives is among 190nm~250nm. Under the action of laser at these characteristic wavelengths, laser initiation energy of explosives can be decreased.
In order to reduce the laser initiation energy and understand effect of laser wavelength on initiation sensitivity of explosives, the weak chemical bond and sensitive laser wavelength of PETN, RDX, HMX and HNS explosives were analyzed through spectrum, thermal decomposition mechanism and quantum mechanics calculation. Results show that the weakest chemical bond of PETN, RDX, HMX and HNS are nitryl whose correspondent resonant coupling laser wavelength is around 6300nm,and the laser wavelength inducing electronic transition of PETN, RDX, HMX and HNS explosives is among 190nm~250nm. Under the action of laser at these characteristic wavelengths, laser initiation energy of explosives can be decreased.
2013, 37(6): 820-824.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.026
Abstract:
The micro-bulk forming with laser shock under the restriction of micro-extrusion die is a kind of new forming technology, which utilizes shockwave induced by laser to produce volume deformation of local sheet metal under the constraint of the die. A model of micro-extrusion of laser shock was developed to analyze the forming depth of different sheet thickness (0.12mm, 0.15mm, 0.17mm and 0.22mm) of 3003 aluminum alloy under different diameters of the micro-dies (0.4mm, 0.7mm, 0.9mm and 1.1mm). After establishing finite element model for numerical analysis, theoretical analysis and experimental verification were carried out and the data of the forming depth were obtained under different thickness and different diameters of the micro-dies. The results show that the forming depth increases sharply, then slowly with the increase of sheet thickness. For the same thickness, the sheet forming depth increases with the increase of diameter of the micro-die in a non-linear way. For the single shock, the number of shock has a great influence on the sheet forming depth. It is found that the simulation results are in accordance with experimental results, which gives support for the quality control of micro-bulk forming.
The micro-bulk forming with laser shock under the restriction of micro-extrusion die is a kind of new forming technology, which utilizes shockwave induced by laser to produce volume deformation of local sheet metal under the constraint of the die. A model of micro-extrusion of laser shock was developed to analyze the forming depth of different sheet thickness (0.12mm, 0.15mm, 0.17mm and 0.22mm) of 3003 aluminum alloy under different diameters of the micro-dies (0.4mm, 0.7mm, 0.9mm and 1.1mm). After establishing finite element model for numerical analysis, theoretical analysis and experimental verification were carried out and the data of the forming depth were obtained under different thickness and different diameters of the micro-dies. The results show that the forming depth increases sharply, then slowly with the increase of sheet thickness. For the same thickness, the sheet forming depth increases with the increase of diameter of the micro-die in a non-linear way. For the single shock, the number of shock has a great influence on the sheet forming depth. It is found that the simulation results are in accordance with experimental results, which gives support for the quality control of micro-bulk forming.
2013, 37(6): 825-828.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.027
Abstract:
In order to study the reason of porosity formation in laser welding of magnesium and aluminum dissimilar metal, AZ91 magnesium alloy in 1.8mm thick and 6016 aluminum alloy in 1.2mm thick were weld by means of laser lap welding. By using scanning electron microscope(SEM) and comes energy dispersive spectroscopy(EDS), the micro-morphology and element distribution of the average area, the interior region and the surrounding area of the porosity as well as the base material of magnesium and aluminum dissimilar metal weld was studied. The results show that the element evaporation burning, the oxide film remaining on the surface of the base material and the pre-existing micro-pores in the base material are the main sources of porosity in the laser welding of magnesium and aluminum dissimilar metal. Adding material to suppress element evaporated burning, cleaning the oxide film of the upper and lower surfaces of magnesium plates and aluminum plates before welding and eliminating the original hydrogen micro-pores in magnesium plate are the important measures to prevent the porosity formation in the laser welding of magnesium and aluminum dissimilar metal.The study is helpful to obtain low porosity ratio welded joints of Mg/Al and improve the welding quality.
In order to study the reason of porosity formation in laser welding of magnesium and aluminum dissimilar metal, AZ91 magnesium alloy in 1.8mm thick and 6016 aluminum alloy in 1.2mm thick were weld by means of laser lap welding. By using scanning electron microscope(SEM) and comes energy dispersive spectroscopy(EDS), the micro-morphology and element distribution of the average area, the interior region and the surrounding area of the porosity as well as the base material of magnesium and aluminum dissimilar metal weld was studied. The results show that the element evaporation burning, the oxide film remaining on the surface of the base material and the pre-existing micro-pores in the base material are the main sources of porosity in the laser welding of magnesium and aluminum dissimilar metal. Adding material to suppress element evaporated burning, cleaning the oxide film of the upper and lower surfaces of magnesium plates and aluminum plates before welding and eliminating the original hydrogen micro-pores in magnesium plate are the important measures to prevent the porosity formation in the laser welding of magnesium and aluminum dissimilar metal.The study is helpful to obtain low porosity ratio welded joints of Mg/Al and improve the welding quality.
2013, 37(6): 829-832.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.028
Abstract:
In order to study intensity distribution of a broadband laser with flattened-Gaussian transverse modes passing through a hard-edged aperture, the propagation expression of each frequency component of the broadband laser was deduced on the basis of the diffraction integral, and then the propagation expression in spatial domain was obtained by means of Fourier transform. Effect of the aperture and the bandwidth on the intensity distribution was analyzed. The results show that the intensity distribution keeps somewhat flattened profile and the profile become narrower with increasing bandwidth when the truncation parameter is large in the near field. When the truncation parameter is small, the intensity distribution is Gaussian profile and the bandwidth has little effect on the profile. In the far field, however, the profile of the intensity also presents narrowing effect with increasing bandwidth when the truncation parameter is small and the narrowing effect tends to decrease with increasing truncation parameter. The results have significant value for applications of broadband laser with flattened-Gaussian transverse mode.
In order to study intensity distribution of a broadband laser with flattened-Gaussian transverse modes passing through a hard-edged aperture, the propagation expression of each frequency component of the broadband laser was deduced on the basis of the diffraction integral, and then the propagation expression in spatial domain was obtained by means of Fourier transform. Effect of the aperture and the bandwidth on the intensity distribution was analyzed. The results show that the intensity distribution keeps somewhat flattened profile and the profile become narrower with increasing bandwidth when the truncation parameter is large in the near field. When the truncation parameter is small, the intensity distribution is Gaussian profile and the bandwidth has little effect on the profile. In the far field, however, the profile of the intensity also presents narrowing effect with increasing bandwidth when the truncation parameter is small and the narrowing effect tends to decrease with increasing truncation parameter. The results have significant value for applications of broadband laser with flattened-Gaussian transverse mode.
2013, 37(6): 833-837.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.029
Abstract:
In order to improve the performance of wireless optical communication, the low density parity check (LDPC) code is used for the channel coding. When the channel state information is known, the performance of system LDPC+binary pulse position modulation(BPPM) and system LDPC+on-off keying(OOK) was compared respectively in additive white Gaussian noise(AWGN), weak, medium and strong turbulence channels. The result shows that the performance of LDPC+BPPM is better than that of LDPC+OOK, and with the increase of the turbulence intensity, the advantage of LDPC+BPPM becomes more apparent. The coding gain of OOK and BPPM was studied in various strength turbulence channels, both of the BPPM's and OOK's in AWGN, weak and medium turbulence channel, increase with the increase of the turbulence intensity. The difference is OOK coding gain in medium turbulence channel is bigger than that in strong turbulence, However, BPPM coding gain and OOK's are opposite. When coding, from 4PPM to 256PPM, when the number of binary is doubled, there is about 1dB loss than the original system. Therefore, system LDPC+PPM has a large coding gain in turbulence channel, and low complexity, and a certain application prospect in optical wireless communication.
In order to improve the performance of wireless optical communication, the low density parity check (LDPC) code is used for the channel coding. When the channel state information is known, the performance of system LDPC+binary pulse position modulation(BPPM) and system LDPC+on-off keying(OOK) was compared respectively in additive white Gaussian noise(AWGN), weak, medium and strong turbulence channels. The result shows that the performance of LDPC+BPPM is better than that of LDPC+OOK, and with the increase of the turbulence intensity, the advantage of LDPC+BPPM becomes more apparent. The coding gain of OOK and BPPM was studied in various strength turbulence channels, both of the BPPM's and OOK's in AWGN, weak and medium turbulence channel, increase with the increase of the turbulence intensity. The difference is OOK coding gain in medium turbulence channel is bigger than that in strong turbulence, However, BPPM coding gain and OOK's are opposite. When coding, from 4PPM to 256PPM, when the number of binary is doubled, there is about 1dB loss than the original system. Therefore, system LDPC+PPM has a large coding gain in turbulence channel, and low complexity, and a certain application prospect in optical wireless communication.
2013, 37(6): 838-842.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.030
Abstract:
In order to improve the optical-optical conversion efficiency of the pulse amplification system model, the output characteristics of the dual-pass pulse amplification were studied by means of modeling and simulation. From the transmission characteristics, the relationship between output power and pump power, the relationship between output single pulse energy and pulse repetition frequency, and the relationship between conversion efficiency and repetition rate were obtained. The optical to optical conversion efficiency was 29.1% when the repetition frequency was 40kHz. Therefore, this dual-pass pulse amplification model improved the efficiency of energy conversion.
In order to improve the optical-optical conversion efficiency of the pulse amplification system model, the output characteristics of the dual-pass pulse amplification were studied by means of modeling and simulation. From the transmission characteristics, the relationship between output power and pump power, the relationship between output single pulse energy and pulse repetition frequency, and the relationship between conversion efficiency and repetition rate were obtained. The optical to optical conversion efficiency was 29.1% when the repetition frequency was 40kHz. Therefore, this dual-pass pulse amplification model improved the efficiency of energy conversion.
2013, 37(6): 843-848.
doi: 10.7510/jgjs.issn.1001-3806.2013.06.031
Abstract:
In 3-D shape measurement based on projection grating, the carrier frequency component will be introduced inevitably in wrapped phase extraction process. In order to accurately reduce the true phase modulated by 3-D shape of objects, the carrier frequency must be eliminated. The shearing principle was used to eliminate the carrier frequency in the projection gating. Firstly, the new optical field of phase gradient distribution was formed by shearing optical field, and then the phase was unwrapped with the least square algorithm. After comparing the existing methods, it was found the method used in this paper is valid. Simulation and experiments proved that this method can effectively eliminate the carrier frequency, reduce the reconstruction error,not only the algorithm is simple, but also the reconstructed phase is more close to the true measured phase. This method is feasible and effective on study about removal of carrier frequency in grating projection.
In 3-D shape measurement based on projection grating, the carrier frequency component will be introduced inevitably in wrapped phase extraction process. In order to accurately reduce the true phase modulated by 3-D shape of objects, the carrier frequency must be eliminated. The shearing principle was used to eliminate the carrier frequency in the projection gating. Firstly, the new optical field of phase gradient distribution was formed by shearing optical field, and then the phase was unwrapped with the least square algorithm. After comparing the existing methods, it was found the method used in this paper is valid. Simulation and experiments proved that this method can effectively eliminate the carrier frequency, reduce the reconstruction error,not only the algorithm is simple, but also the reconstructed phase is more close to the true measured phase. This method is feasible and effective on study about removal of carrier frequency in grating projection.
