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RSS2014 Vol. 38, No. 6
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2014, 38(6): 723-728.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.001
[Abstract]
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Abstract:
In order to solve the coordinate measurement of hidden parts in large equipment, a laser probe based on optical target and rangefinder was proposed, which was combined with a total station instrument or a laser tracker to form a non-contact measurement system. During the measurement, the laser beam from the rangefinder was set to touch the measurement point and the distance between the rangefinder and the point was measured. And then, the optical target was aimed at by the total station instrument or the laser tracker. The spatial coordinates and the attitude angles of the laser probe were gotten. Finally, the spatial coordinates of the measured point was calculated by coordinate transformation. After theoretical analysis and experimental verification, the results show that the measurement system could expand the measurement range and achieve reliable and higher measurement precision.
In order to solve the coordinate measurement of hidden parts in large equipment, a laser probe based on optical target and rangefinder was proposed, which was combined with a total station instrument or a laser tracker to form a non-contact measurement system. During the measurement, the laser beam from the rangefinder was set to touch the measurement point and the distance between the rangefinder and the point was measured. And then, the optical target was aimed at by the total station instrument or the laser tracker. The spatial coordinates and the attitude angles of the laser probe were gotten. Finally, the spatial coordinates of the measured point was calculated by coordinate transformation. After theoretical analysis and experimental verification, the results show that the measurement system could expand the measurement range and achieve reliable and higher measurement precision.
2014, 38(6): 729-732.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.002
Abstract:
In order to get understand the process of the heat exchanging and flow field and design heat exchangers with more flexibility, computational fluid dynamics was used to design the heat exchanger of 4kW fast axial flow CO2 laser. The flow resistance of the heat exchanger is 154.5Pa and its heat transfer is 8888.5W. The heat exchanger can ensure the long-term stability of fast axial flow CO2 laser. The research proves that computational fluid dynamics theory can make the design process of heat exchanger more efficient and accurate.
In order to get understand the process of the heat exchanging and flow field and design heat exchangers with more flexibility, computational fluid dynamics was used to design the heat exchanger of 4kW fast axial flow CO2 laser. The flow resistance of the heat exchanger is 154.5Pa and its heat transfer is 8888.5W. The heat exchanger can ensure the long-term stability of fast axial flow CO2 laser. The research proves that computational fluid dynamics theory can make the design process of heat exchanger more efficient and accurate.
2014, 38(6): 733-737.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.003
Abstract:
In order to study the welding of high-strength aluminum alloy, understand the interaction mechanism between laser and metal inert gas (MIG) and optimize the welding process parameters further, experimental investigation on 6005A aluminum alloy with 3mm thickness in laser-MIG hybrid welding was performed using fiber laser and MIG welding machine. The influence of process parameters on weld quality was analyzed after combining weld morphology with mechanical properties of joints. The results show that a joint with good deformation for 6005A aluminum alloy under appropriate process parameters can be achieved in laser-MIG hybrid welding. Phases in the weld are mainly composed of -Al solid solution and the second phase Mg2Si dispersed in the matrix. It also is found that the hardness in the weld zone is significantly lower than that of the heat affected zone and the base metal. The fracture of welded joint occurs in the weld zone on account of microstructure coarsening and porosity defect induced by welding thermal cycle. It ruptures in the form of ductile fracture, where a lot of dimples appear. The tensile strength of the joint is 251.52MPa, 89.19% of the parent material. The weld quality meets the project requirements.
In order to study the welding of high-strength aluminum alloy, understand the interaction mechanism between laser and metal inert gas (MIG) and optimize the welding process parameters further, experimental investigation on 6005A aluminum alloy with 3mm thickness in laser-MIG hybrid welding was performed using fiber laser and MIG welding machine. The influence of process parameters on weld quality was analyzed after combining weld morphology with mechanical properties of joints. The results show that a joint with good deformation for 6005A aluminum alloy under appropriate process parameters can be achieved in laser-MIG hybrid welding. Phases in the weld are mainly composed of -Al solid solution and the second phase Mg2Si dispersed in the matrix. It also is found that the hardness in the weld zone is significantly lower than that of the heat affected zone and the base metal. The fracture of welded joint occurs in the weld zone on account of microstructure coarsening and porosity defect induced by welding thermal cycle. It ruptures in the form of ductile fracture, where a lot of dimples appear. The tensile strength of the joint is 251.52MPa, 89.19% of the parent material. The weld quality meets the project requirements.
2014, 38(6): 738-741.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.004
Abstract:
In order to obtain effect of material dispersion on the light field distribution of the total reflection tunnel in 1-D photonic crystal, the light field formula of 1-D photonic crystal was deduced based on the characteristic matrix. The effect of material dispersion on the light field distribution of total reflection tunnel in 1-D photonic crystal was studied by the light field distribution formula and the material dispersion formula. The results show that the dispersion can affect the light field of total reflection tunnel. The dispersion can change the peak of the light field and make obvious change of the periodicity of the light field. The study makes deeper understanding of the phenomenon of the total reflection tunnel of 1-D photonic crystal.
In order to obtain effect of material dispersion on the light field distribution of the total reflection tunnel in 1-D photonic crystal, the light field formula of 1-D photonic crystal was deduced based on the characteristic matrix. The effect of material dispersion on the light field distribution of total reflection tunnel in 1-D photonic crystal was studied by the light field distribution formula and the material dispersion formula. The results show that the dispersion can affect the light field of total reflection tunnel. The dispersion can change the peak of the light field and make obvious change of the periodicity of the light field. The study makes deeper understanding of the phenomenon of the total reflection tunnel of 1-D photonic crystal.
2014, 38(6): 742-746.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.005
Abstract:
In order to satisfy the need of high resolution, large operation area and miniaturization of the scanning system, one f- lens with super wide angle and diffraction-limited focusing performance was designed. On this basis, the resolution reduction and the linear distortion increasing caused by the pupil deviation due to the polygonal mirror were analyzed. After calculation, it was found that the pupil deviation had an aspheric nonlinear relationship with the scanning angle. Using the higher order terms of free surfaces to correct the deviation of pupil, the models of polygonal mirror f- scanning system was optimized with ZEMAX and the multiple structures and the practical example was given. Due to the telephoto type of lens, the overall length of the scanning system and the aperture of the lens were effectively reduced. The simulation result shows that the f- performance is significantly improved through optimization and correction. Within the scanning angle of 115, linear distortion is less than 0.5% and 60% of incident light energy is gathered in a circle in 30m radius. The practical f- scanning system has the advantages of compact structure, high resolution and low linear distortion.
In order to satisfy the need of high resolution, large operation area and miniaturization of the scanning system, one f- lens with super wide angle and diffraction-limited focusing performance was designed. On this basis, the resolution reduction and the linear distortion increasing caused by the pupil deviation due to the polygonal mirror were analyzed. After calculation, it was found that the pupil deviation had an aspheric nonlinear relationship with the scanning angle. Using the higher order terms of free surfaces to correct the deviation of pupil, the models of polygonal mirror f- scanning system was optimized with ZEMAX and the multiple structures and the practical example was given. Due to the telephoto type of lens, the overall length of the scanning system and the aperture of the lens were effectively reduced. The simulation result shows that the f- performance is significantly improved through optimization and correction. Within the scanning angle of 115, linear distortion is less than 0.5% and 60% of incident light energy is gathered in a circle in 30m radius. The practical f- scanning system has the advantages of compact structure, high resolution and low linear distortion.
2014, 38(6): 747-752.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.006
Abstract:
In order to investigate the relationship between the truncated Gaussian beam and wavefront aberration, the parameter of Gaussian beam factor was proposed to evaluate the beam quality of the truncated Gaussian laser. The influence of wavefront aberration of optical system on Gaussian beam quality was analyzed by using numerical simulation method and the fitting relationship between Gaussian beam quality factor and wavefront aberration was given. As an example, the relationship between Gaussian beam quality and atmospheric turbulence strength with Kolmogoroff spectral was discussed and their fitting formula was given. The calculating results show that the fitted curve is in good agreement with the corresponding simulated data in a relatively wide range of turbulence strength, which further validate the correctness of the fitting formula between Gaussian beam factor and wavefront aberration.
In order to investigate the relationship between the truncated Gaussian beam and wavefront aberration, the parameter of Gaussian beam factor was proposed to evaluate the beam quality of the truncated Gaussian laser. The influence of wavefront aberration of optical system on Gaussian beam quality was analyzed by using numerical simulation method and the fitting relationship between Gaussian beam quality factor and wavefront aberration was given. As an example, the relationship between Gaussian beam quality and atmospheric turbulence strength with Kolmogoroff spectral was discussed and their fitting formula was given. The calculating results show that the fitted curve is in good agreement with the corresponding simulated data in a relatively wide range of turbulence strength, which further validate the correctness of the fitting formula between Gaussian beam factor and wavefront aberration.
2014, 38(6): 753-758.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.007
Abstract:
In order to measure the sound pressure signals generated by the breakdown of pulse laser through the electrolyte and discuss the impact and influence of shock cavitations on laser electrochemical composite processing, a laser electrochemical composite processing detection system was established. At first, the sound pressure signal was stored with an oscilloscope and the acoustic pressure and waveform was analyzed and calculated with the XVIEWER software. Then, pictures of the composite laser electrochemical machining area were taken and the effect of cavitations on laser-electrochemical machining area's the characteristics morphology and surface quality was analyzed. The experimental results indicate that because pulsed laser is focused in the electrolyte, cavitations effect is generated and three different sound pressure signals are radiated. With the increase of laser energy, three acoustic pressures of laser-induced shock cavitations increase and the radius and energy of laser-induced bubble increase. In the applications of laser electrochemical machine, when the laser energy increases, the laser plasma shock wave and jet force will improve and the material removal will increase. Meanwhile bubble oscillation promotes the electrolyte flow, it plays a key role on the morphology of the processing area and surface quality. The result is very useful for complex machining process and morphology.
In order to measure the sound pressure signals generated by the breakdown of pulse laser through the electrolyte and discuss the impact and influence of shock cavitations on laser electrochemical composite processing, a laser electrochemical composite processing detection system was established. At first, the sound pressure signal was stored with an oscilloscope and the acoustic pressure and waveform was analyzed and calculated with the XVIEWER software. Then, pictures of the composite laser electrochemical machining area were taken and the effect of cavitations on laser-electrochemical machining area's the characteristics morphology and surface quality was analyzed. The experimental results indicate that because pulsed laser is focused in the electrolyte, cavitations effect is generated and three different sound pressure signals are radiated. With the increase of laser energy, three acoustic pressures of laser-induced shock cavitations increase and the radius and energy of laser-induced bubble increase. In the applications of laser electrochemical machine, when the laser energy increases, the laser plasma shock wave and jet force will improve and the material removal will increase. Meanwhile bubble oscillation promotes the electrolyte flow, it plays a key role on the morphology of the processing area and surface quality. The result is very useful for complex machining process and morphology.
2014, 38(6): 759-763.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.008
Abstract:
In order to solve the low measurement precision of all optical fiber current sensors induced by the bend and twist of sensor fiber and the change of external environment, a new method was proposed to realize the temperature compensation based on the longer axis slope of elliptic polarized light. It was demonstrated that elliptical polarized light long axis slope can response the change of the output light elasticity. The slope was calculated by TMS320F28335 and some algorithms. The sensor was modified by the elliptical polarized light long axis slope and some actual measurements was done. The experiment results show that the measurement system based on the revised method can meet the required precision of 0.2s in a single temperature change of 20℃~60℃.The result is helpful for the research of all optical fiber current sensors.
In order to solve the low measurement precision of all optical fiber current sensors induced by the bend and twist of sensor fiber and the change of external environment, a new method was proposed to realize the temperature compensation based on the longer axis slope of elliptic polarized light. It was demonstrated that elliptical polarized light long axis slope can response the change of the output light elasticity. The slope was calculated by TMS320F28335 and some algorithms. The sensor was modified by the elliptical polarized light long axis slope and some actual measurements was done. The experiment results show that the measurement system based on the revised method can meet the required precision of 0.2s in a single temperature change of 20℃~60℃.The result is helpful for the research of all optical fiber current sensors.
2014, 38(6): 764-770.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.009
Abstract:
The laser nano-material surface engineering (LNMSE) technology is established by combining surface engineering technology, nano technology and laser technology. All the important laser surface treatment methods of LNMSE were introduced. The summarization, analysis and research of the existing literature prove that laser surface treatment methods can get the nano-crystallization surface and get the cladding surface with nano-particles.
The laser nano-material surface engineering (LNMSE) technology is established by combining surface engineering technology, nano technology and laser technology. All the important laser surface treatment methods of LNMSE were introduced. The summarization, analysis and research of the existing literature prove that laser surface treatment methods can get the nano-crystallization surface and get the cladding surface with nano-particles.
2014, 38(6): 771-775.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.010
Abstract:
In order to study the effect of incident optical intensity on coherent interaction of multi bright screening spatial solitons, evolution equations of solitary wave were solved by numerical simulation. Under the conditions of the giving distance of interaction and relative phase, the coherent interactions of two and three solitons were analyzed respectively under different optical intensity of incident solitons. The result shows that, under the in-phase conditions, two solitons have the period of fusion-separate-fusion. For three solitons, this period will disappear and the energy transfer will emerge. The direction of energy transfer can be controlled by varying the value of the incident optical intensity. Under the out-of-phase conditions, both two solitons and three solitons show the interaction of repulsion each other. The value of repulsion is affected by the incident optical intensity. Both two solitons and three solitons show the energy transfer when the phase difference is =/2 and the direction of energy transfer is determined by the sign of phase difference. For three solitons, small repulsion will emerge accompanied with the energy transfer when the incident optical intensity increases. All the results show that the incident optical intensity can affect the coherent interaction of solitons.
In order to study the effect of incident optical intensity on coherent interaction of multi bright screening spatial solitons, evolution equations of solitary wave were solved by numerical simulation. Under the conditions of the giving distance of interaction and relative phase, the coherent interactions of two and three solitons were analyzed respectively under different optical intensity of incident solitons. The result shows that, under the in-phase conditions, two solitons have the period of fusion-separate-fusion. For three solitons, this period will disappear and the energy transfer will emerge. The direction of energy transfer can be controlled by varying the value of the incident optical intensity. Under the out-of-phase conditions, both two solitons and three solitons show the interaction of repulsion each other. The value of repulsion is affected by the incident optical intensity. Both two solitons and three solitons show the energy transfer when the phase difference is =/2 and the direction of energy transfer is determined by the sign of phase difference. For three solitons, small repulsion will emerge accompanied with the energy transfer when the incident optical intensity increases. All the results show that the incident optical intensity can affect the coherent interaction of solitons.
2014, 38(6): 776-779.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.011
Abstract:
In order to eliminate the defects of false detection of mixed Gaussian model under sudden illumination, a new algorithm combining Gaussian model with average background method was proposed to count the foreground pixels. Firstly, the background of Gaussian mixture model was initialized by using multi-frame averaging method when building the background model. Secondly, a counter for the number of foreground pixels of every frame was established and the false detection was eliminated based on the counter. Finally, the target was detected by using mathematical morphology and the foreground of the image was gotten. The results show that this improved algorithm not only overcomes the interference of the initial background but also eliminates the false detection when the illumination changes, and improves the detection rate of the moving targets.
In order to eliminate the defects of false detection of mixed Gaussian model under sudden illumination, a new algorithm combining Gaussian model with average background method was proposed to count the foreground pixels. Firstly, the background of Gaussian mixture model was initialized by using multi-frame averaging method when building the background model. Secondly, a counter for the number of foreground pixels of every frame was established and the false detection was eliminated based on the counter. Finally, the target was detected by using mathematical morphology and the foreground of the image was gotten. The results show that this improved algorithm not only overcomes the interference of the initial background but also eliminates the false detection when the illumination changes, and improves the detection rate of the moving targets.
2014, 38(6): 780-784.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.012
Abstract:
In order to achieve a high sensitive fiber sensor for liquid refractive index (RI) measurement through a simple and efficient method, a Fabry-Prot interferometer (F-PI) cavity in fiber with double-openings was fabricated by femtosecond laser micromachining followed by fiber fusion. Firstly a rectangular groove was ablated at the end of fiber by femtosecond laser direct writing. Then the fiber end with the groove was spliced with another fiber end to form the F-PI cavity with double-openings. The responses of the fiber sensor based on the F-PI cavity with double-openings to the liquid RI and temperature were investigated. The experiment results show that the sensitivity of the sensor for RI measurement can achieve 1107.76nm/RIU, and the crosstalk by temperature is less than 0.0025nm/℃. The application of the sensor for seawater salinity measurement was also discussed and its sensitivity achieves 0.171nm/(mgmL-1). This liquid RI fiber sensor based on the F-PI cavity with double-openings can have great application in the fields of biology, medicine, chemistry and environment due to its advantages of high constrast of the reflection spectrum, linear response, high sensitivity, low crosstalk of temperature, small size and simple fabrication.
In order to achieve a high sensitive fiber sensor for liquid refractive index (RI) measurement through a simple and efficient method, a Fabry-Prot interferometer (F-PI) cavity in fiber with double-openings was fabricated by femtosecond laser micromachining followed by fiber fusion. Firstly a rectangular groove was ablated at the end of fiber by femtosecond laser direct writing. Then the fiber end with the groove was spliced with another fiber end to form the F-PI cavity with double-openings. The responses of the fiber sensor based on the F-PI cavity with double-openings to the liquid RI and temperature were investigated. The experiment results show that the sensitivity of the sensor for RI measurement can achieve 1107.76nm/RIU, and the crosstalk by temperature is less than 0.0025nm/℃. The application of the sensor for seawater salinity measurement was also discussed and its sensitivity achieves 0.171nm/(mgmL-1). This liquid RI fiber sensor based on the F-PI cavity with double-openings can have great application in the fields of biology, medicine, chemistry and environment due to its advantages of high constrast of the reflection spectrum, linear response, high sensitivity, low crosstalk of temperature, small size and simple fabrication.
2014, 38(6): 785-789.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.013
Abstract:
In order to study the influence of straight edge diffraction on the deposition characteristics in the process of laser-focused Cr atoms, the improved fourth-order Runge-Kutta algorithm was adopted to simulate the 3-D trajectory and deposition grating of Cr atoms in the straight edge diffraction laser standing wave field based on the semi-classical model. The influence of the distance from diffraction edge to mirror and from laser medial axis to substrate surface on laser focused atomic deposition process were described. The results show that diffraction effect on the deposition effect will be changed by the different substrate placement. When the distance from diffraction edge to mirror equals 0.81cm and the distance from laser medial axis to substrate surface equals 0.01mm, the full width at half maximum of nanograting reaches the minimum, at the same time, the contrast reaches the maximum. The research results provide a richer theoretical guidance for atomic lithography experiments.
In order to study the influence of straight edge diffraction on the deposition characteristics in the process of laser-focused Cr atoms, the improved fourth-order Runge-Kutta algorithm was adopted to simulate the 3-D trajectory and deposition grating of Cr atoms in the straight edge diffraction laser standing wave field based on the semi-classical model. The influence of the distance from diffraction edge to mirror and from laser medial axis to substrate surface on laser focused atomic deposition process were described. The results show that diffraction effect on the deposition effect will be changed by the different substrate placement. When the distance from diffraction edge to mirror equals 0.81cm and the distance from laser medial axis to substrate surface equals 0.01mm, the full width at half maximum of nanograting reaches the minimum, at the same time, the contrast reaches the maximum. The research results provide a richer theoretical guidance for atomic lithography experiments.
2014, 38(6): 790-793.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.014
Abstract:
In order to improve the laser marking efficiency, based on the stroke tracking algorithm and the greedy algorithm, an optimum algorithm of galvanometer scanning laser marking for Chinese characters was put forward. Firstly, the continuous strokes of Chinese characters were extracted. Then, the optimal output path of Chinese character strokes was obtained by means of greedy algorithm. Finally laser marking was realized according to the optimal output path. Experimental results show that this algorithm makes the laser jump times decrease and improves the efficiency of Chinese characters laser marking significantly.
In order to improve the laser marking efficiency, based on the stroke tracking algorithm and the greedy algorithm, an optimum algorithm of galvanometer scanning laser marking for Chinese characters was put forward. Firstly, the continuous strokes of Chinese characters were extracted. Then, the optimal output path of Chinese character strokes was obtained by means of greedy algorithm. Finally laser marking was realized according to the optimal output path. Experimental results show that this algorithm makes the laser jump times decrease and improves the efficiency of Chinese characters laser marking significantly.
2014, 38(6): 794-797.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.015
Abstract:
In order to measure energy of the third harmonic (TH) of a large aperture high power laser experiment platform, with a concave mirror sampling the beam, with a novel absorbing glass element filtering the beam, the influence of the absorbing glass element on the measurement result was experimentally tested. According to the data analysis, by using such a novel absorbing glass element, pure TH laser can be obtained and the influence of the residual fundamental and the second harmonic light is about 0.4%. The uncertainty of energy measurement of the entire TH laser energy can be controlled within 5%, which guarantees the reliability of energy measurement for the laser facility.
In order to measure energy of the third harmonic (TH) of a large aperture high power laser experiment platform, with a concave mirror sampling the beam, with a novel absorbing glass element filtering the beam, the influence of the absorbing glass element on the measurement result was experimentally tested. According to the data analysis, by using such a novel absorbing glass element, pure TH laser can be obtained and the influence of the residual fundamental and the second harmonic light is about 0.4%. The uncertainty of energy measurement of the entire TH laser energy can be controlled within 5%, which guarantees the reliability of energy measurement for the laser facility.
2014, 38(6): 798-803.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.016
Abstract:
In order to study effects of process parameters on kerf quality of fiber laser cutting, the relationship between process parameters and kerf quality was analyzed based on the test of laser cutting T4003 stainless steel. The prediction model between the main process parameters, such as laser power, cutting speed, assistant gas pressure and kerf roughness was established based on error back propagation artificial neural network. The samples collected by the cutting test was network trained and the training model was inspected by the test samples. The results show that, kerf roughness increases while laser power increases and kerf roughness decreases while cutting speed and assist gas pressure increase. The neural network prediction model has high precision and the network training has good effect. The maximum relative error between the predictive values and the test sample value is 2.4%. After training, the prediction model has high inspection precision, the maximum relative error of the test sample is only 6.23%. The model can predict the laser cutting kerf roughness effectively and can provide the experiment basis for selecting and optimizing process parameters and improving laser cutting quality.
In order to study effects of process parameters on kerf quality of fiber laser cutting, the relationship between process parameters and kerf quality was analyzed based on the test of laser cutting T4003 stainless steel. The prediction model between the main process parameters, such as laser power, cutting speed, assistant gas pressure and kerf roughness was established based on error back propagation artificial neural network. The samples collected by the cutting test was network trained and the training model was inspected by the test samples. The results show that, kerf roughness increases while laser power increases and kerf roughness decreases while cutting speed and assist gas pressure increase. The neural network prediction model has high precision and the network training has good effect. The maximum relative error between the predictive values and the test sample value is 2.4%. After training, the prediction model has high inspection precision, the maximum relative error of the test sample is only 6.23%. The model can predict the laser cutting kerf roughness effectively and can provide the experiment basis for selecting and optimizing process parameters and improving laser cutting quality.
2014, 38(6): 804-806.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.017
Abstract:
In order to get practical high power quasi-continuous wave (QCW) laser at 355nm, the 1064nm and 532nm QCW lasers were synchronized by radio frequency drive source with double channels via an acousto-optic modulator. The two wavelengths were coupled into type Ⅱ LBO crystal simultaneously by an achromatic lens and the ultraviolet laser at 355nm was generated. The highest output power of 355nm laser is 6.8W, pulse width is 67ns, conversion efficiency of the 355nm laser is about 1.56% when the injected electrical power is 436W and the repetition frequency is 6kHz. The results show that the high power 355nm QCW laser can be obtained by extra-cavity sum-frequency with double wavelength synchronized lasers.
In order to get practical high power quasi-continuous wave (QCW) laser at 355nm, the 1064nm and 532nm QCW lasers were synchronized by radio frequency drive source with double channels via an acousto-optic modulator. The two wavelengths were coupled into type Ⅱ LBO crystal simultaneously by an achromatic lens and the ultraviolet laser at 355nm was generated. The highest output power of 355nm laser is 6.8W, pulse width is 67ns, conversion efficiency of the 355nm laser is about 1.56% when the injected electrical power is 436W and the repetition frequency is 6kHz. The results show that the high power 355nm QCW laser can be obtained by extra-cavity sum-frequency with double wavelength synchronized lasers.
2014, 38(6): 807-812.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.018
Abstract:
As a main illumination tool, light emitting diode (LED) light can be utilized in optical communication system because of the high sensitivity. In order to study and verify the receiving performance and the transmission distance of a LED indoor visible light voice communication system, referring to the channel model of an infrared communication and the effect of the reflected lights, the signal power of the receiving point on the desktop was calculated according to indoor illumination standard by multipath overlay grid algorithm and the sending and receiving circuits of LED visible light voice single-direction communication system was designed and realized. The results show that when the emissive power of LED light is above 2W and the communication rate in the signal physical layer is less than 1Mbit/s, the system is suitable for the actual requirements of the received power and the received signal-noise-rate and can achieve the no-distortion decoding and clear listening in 10m limit. This result is helpful for the research and application of LED visible-light communication systems.
As a main illumination tool, light emitting diode (LED) light can be utilized in optical communication system because of the high sensitivity. In order to study and verify the receiving performance and the transmission distance of a LED indoor visible light voice communication system, referring to the channel model of an infrared communication and the effect of the reflected lights, the signal power of the receiving point on the desktop was calculated according to indoor illumination standard by multipath overlay grid algorithm and the sending and receiving circuits of LED visible light voice single-direction communication system was designed and realized. The results show that when the emissive power of LED light is above 2W and the communication rate in the signal physical layer is less than 1Mbit/s, the system is suitable for the actual requirements of the received power and the received signal-noise-rate and can achieve the no-distortion decoding and clear listening in 10m limit. This result is helpful for the research and application of LED visible-light communication systems.
2014, 38(6): 813-816.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.019
Abstract:
In order to study the effect on the laser scanning accuracy because of a certain eccentricity between the laser scanning center and the spherical test center during the measurement, after setting up a mathematical mode and deducing a calculation formula, the laser scanning deviation caused by eccentricity e was analyzed theoretically. The relationship of the several effect factors of laser scanning contour deviation was analyzed. The conclusion was reached that that eccentricity error does not exceed 2e with the increase of radius R. The results show that the impact of eccentricity e on the laser scanning contour deviation can be reduced after both the axes of the scan center and the measured spherical center are transformed to the same coordinate system equivalently.
In order to study the effect on the laser scanning accuracy because of a certain eccentricity between the laser scanning center and the spherical test center during the measurement, after setting up a mathematical mode and deducing a calculation formula, the laser scanning deviation caused by eccentricity e was analyzed theoretically. The relationship of the several effect factors of laser scanning contour deviation was analyzed. The conclusion was reached that that eccentricity error does not exceed 2e with the increase of radius R. The results show that the impact of eccentricity e on the laser scanning contour deviation can be reduced after both the axes of the scan center and the measured spherical center are transformed to the same coordinate system equivalently.
2014, 38(6): 817-821.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.020
Abstract:
In order to investigate effect of the peak refractive index on the defect modes of 1-D sine function photonic crystals, the sine function medium was discretized at first, then the transmission spectrum of the 1-D sine function photonic crystal (AB)mC(BA)m was computed by applying the method of optical transmission matrix, and the effect of peak refractive index of sine function medium on defect modes was analyzed. The results show that the defect modes are red-shifted with the increasing of peak refractive index, and the higher the frequency is, the more obvious the red-shift of defect modes is. The obvious effect of frequency shift of defect modes results from the increasing of the peak refractive index of low refractive index medium. The results have a certain reference value for the design of photonic crystal.
In order to investigate effect of the peak refractive index on the defect modes of 1-D sine function photonic crystals, the sine function medium was discretized at first, then the transmission spectrum of the 1-D sine function photonic crystal (AB)mC(BA)m was computed by applying the method of optical transmission matrix, and the effect of peak refractive index of sine function medium on defect modes was analyzed. The results show that the defect modes are red-shifted with the increasing of peak refractive index, and the higher the frequency is, the more obvious the red-shift of defect modes is. The obvious effect of frequency shift of defect modes results from the increasing of the peak refractive index of low refractive index medium. The results have a certain reference value for the design of photonic crystal.
2014, 38(6): 822-825.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.021
Abstract:
In order to apply near-infrared focal plane array detectors in imaging spectrometer polarization instruments to get the high-quality image information, a new type of imaging spectrometer detection techniques on basis of near-infrared focal plane array detectors was proposed combining with a photo-elastic modulator-based imaging spectro-polarimeter (PEM-ISP). A FPA-640512 InGaAs focal plane array detector was used as an optical detector receiving element and a high-speed field-programmable gate array (FPGA) was used as the signal processing unit to get fast acquisition and parallel processing of the optical signal and meet the other requirements of the high-speed, real-time signal transmission and processing.The data collected by the high-speed A/D was storaged in the expanding outside SRAM of the FPGA in order to ensure the data integrity. And then, the data was ultimately transmitted to the host computer via USB for image restoration.The experimental results show that the system can be applied to PEM-ISP, achieve accurate detection and acquisition of the measurement signals and get complete image information.
In order to apply near-infrared focal plane array detectors in imaging spectrometer polarization instruments to get the high-quality image information, a new type of imaging spectrometer detection techniques on basis of near-infrared focal plane array detectors was proposed combining with a photo-elastic modulator-based imaging spectro-polarimeter (PEM-ISP). A FPA-640512 InGaAs focal plane array detector was used as an optical detector receiving element and a high-speed field-programmable gate array (FPGA) was used as the signal processing unit to get fast acquisition and parallel processing of the optical signal and meet the other requirements of the high-speed, real-time signal transmission and processing.The data collected by the high-speed A/D was storaged in the expanding outside SRAM of the FPGA in order to ensure the data integrity. And then, the data was ultimately transmitted to the host computer via USB for image restoration.The experimental results show that the system can be applied to PEM-ISP, achieve accurate detection and acquisition of the measurement signals and get complete image information.
2014, 38(6): 826-829.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.022
Abstract:
To study the laser jamming of CCD comparatively, three lasers at wavelengths of 532nm, 808nm and 1064nm were adopted in the jamming experiments. The experiments results reveal that the jamming of three lasers to CCD is effective. However, the jamming effect is different because of the difference of the jamming wavelength, the power and the working mode. For pulsed lasers, 532nm laser has the lower light saturation threshold than 1064nm laser. When the output laser power reaches a certain value, the saturation crosstalk phenomenon occurs in a CCD. It provides an experimental basis for better jamming against CCD imaging systems.
To study the laser jamming of CCD comparatively, three lasers at wavelengths of 532nm, 808nm and 1064nm were adopted in the jamming experiments. The experiments results reveal that the jamming of three lasers to CCD is effective. However, the jamming effect is different because of the difference of the jamming wavelength, the power and the working mode. For pulsed lasers, 532nm laser has the lower light saturation threshold than 1064nm laser. When the output laser power reaches a certain value, the saturation crosstalk phenomenon occurs in a CCD. It provides an experimental basis for better jamming against CCD imaging systems.
2014, 38(6): 830-834.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.023
Abstract:
In order to study the effect of stray noise on measurement accuracy of a position sensitive detector (PSD), three kinds of the stray noise was described firstly. Then the mathematical model of measurement accuracy of PSD was built by using the method of variance analysis. The error of the system was analyzed. The results show the experimental data is consistent with the calculation data and the mathematical model is valid.
In order to study the effect of stray noise on measurement accuracy of a position sensitive detector (PSD), three kinds of the stray noise was described firstly. Then the mathematical model of measurement accuracy of PSD was built by using the method of variance analysis. The error of the system was analyzed. The results show the experimental data is consistent with the calculation data and the mathematical model is valid.
2014, 38(6): 835-838.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.024
Abstract:
In order to analyze the relationship between spectra and gas volume fractions of NO2 which is one of the main pollution gases, laser whose center wavelength was located in the peak of NO2 absorption was chosen as light source and a gas spectra detection system was built. The spectrum was analyzed according to Lambert-Beer law, using time-sharing differential method, comparing with authoritative database and considering the spectral area and other factors. The data were fitted by the least squares method and the relationship curve between NO2 absorption spectra and NO2 volume fractions was obtained. The data of volume fractions was inversed and the error was analyzed. The experimental results agree well with the theoretical analysis. The research value and the application value of the experimental system are verified.
In order to analyze the relationship between spectra and gas volume fractions of NO2 which is one of the main pollution gases, laser whose center wavelength was located in the peak of NO2 absorption was chosen as light source and a gas spectra detection system was built. The spectrum was analyzed according to Lambert-Beer law, using time-sharing differential method, comparing with authoritative database and considering the spectral area and other factors. The data were fitted by the least squares method and the relationship curve between NO2 absorption spectra and NO2 volume fractions was obtained. The data of volume fractions was inversed and the error was analyzed. The experimental results agree well with the theoretical analysis. The research value and the application value of the experimental system are verified.
2014, 38(6): 839-844.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.025
Abstract:
In order to enhance the real-time and improve the accuracy of on-line Raman spectrometer during the testing of composition of aromatic hydrocarbon unit, the prediction model was created based on partial least square (PLS) algorithm and particle swarm optimization (PSO) algorithm. Some samples of aromatic hydrocarbons were tested. Firstly, Raman spectroscopy of aromatic composition was gotten by spectroscopy. Then, the main factors of Raman data were extracted by means of PLS algorithm in order to reduce the redundancy between data. The quick search of composition content of aromatics hydrocarbons were made by PSO algorithm to find the optimal solution. Finally, the correlation of actual values and predictive values of samples was analyzed. The results show that, compared with the old method, the new created model (Raman spectrum with PSO and PLS) has high precision and quick analysis speed. It provides a new method for detection of components of aromatic hydrocarbons unit.
In order to enhance the real-time and improve the accuracy of on-line Raman spectrometer during the testing of composition of aromatic hydrocarbon unit, the prediction model was created based on partial least square (PLS) algorithm and particle swarm optimization (PSO) algorithm. Some samples of aromatic hydrocarbons were tested. Firstly, Raman spectroscopy of aromatic composition was gotten by spectroscopy. Then, the main factors of Raman data were extracted by means of PLS algorithm in order to reduce the redundancy between data. The quick search of composition content of aromatics hydrocarbons were made by PSO algorithm to find the optimal solution. Finally, the correlation of actual values and predictive values of samples was analyzed. The results show that, compared with the old method, the new created model (Raman spectrum with PSO and PLS) has high precision and quick analysis speed. It provides a new method for detection of components of aromatic hydrocarbons unit.
2014, 38(6): 845-847.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.026
Abstract:
In order to measure the thickness of ZnO film, optical coherence tomography (OCT) technique was used for theoretic analysis and experimental verification. The 1-D depth image including thickness information and the 2-D cross-sectional image including structure information were obtained simultaneously. The results show that the measuring result is almost as same as the theoretical value. It is illustrated that the measurement of the spectral-domain OCT is real and effective. It can be used for the measurement of thickness and quality of the film.
In order to measure the thickness of ZnO film, optical coherence tomography (OCT) technique was used for theoretic analysis and experimental verification. The 1-D depth image including thickness information and the 2-D cross-sectional image including structure information were obtained simultaneously. The results show that the measuring result is almost as same as the theoretical value. It is illustrated that the measurement of the spectral-domain OCT is real and effective. It can be used for the measurement of thickness and quality of the film.
2014, 38(6): 848-853.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.027
Abstract:
In order to analyze the speckle noise distribution model of optical coherence tomography (OCT) images before and after logarithm transformation and provide references for image de-noising and other image processing, theoretical distribution model of the speckle noise was deduced firstly and then was verified by experimental results. First of all, the statistical properties of the speckle noise before the logarithm transformation were analyzed. The distribution model of the speckle noise after logarithm transform was derived through the mathematical theory. Then, the smooth regions of cardiovascular OCT images were selected as the experimental data to obtain the histogram distribution of the speckle noise before and after the logarithm transformation. Finally, the experimental data were fitted by the theoretical distribution model and the evaluated data, such as R-square, root mean square error and X-square tests. The results prove that the noise distribution after logarithm transformation presents Fisher-Tippett distribution. The results are helpful for the de-noising on OCT images.
In order to analyze the speckle noise distribution model of optical coherence tomography (OCT) images before and after logarithm transformation and provide references for image de-noising and other image processing, theoretical distribution model of the speckle noise was deduced firstly and then was verified by experimental results. First of all, the statistical properties of the speckle noise before the logarithm transformation were analyzed. The distribution model of the speckle noise after logarithm transform was derived through the mathematical theory. Then, the smooth regions of cardiovascular OCT images were selected as the experimental data to obtain the histogram distribution of the speckle noise before and after the logarithm transformation. Finally, the experimental data were fitted by the theoretical distribution model and the evaluated data, such as R-square, root mean square error and X-square tests. The results prove that the noise distribution after logarithm transformation presents Fisher-Tippett distribution. The results are helpful for the de-noising on OCT images.
2014, 38(6): 854-858.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.028
Abstract:
In order to realize non-line-of-sight (NLOS) laser scattering communication in atmosphere, the NLOS communication link model was founded according to Mie scattering theory and 1.06m laser scattering communication in atmosphere was studied. The relationship of laser receiving power, laser transmitting power, laser beam divergence angle, receiver field of view, detector sensitivity, emission inclination angle, receiver inclination angle, atmosphere attenuation and communication distance were analyzed. After establishing the experimental system, an experiment of 1km scattering communication was taken on and laser scattering signal was gotten. The experimental result shows that atmosphere scattering communication at long distance can be realized by choosing 1.06m laser for signal communication under a certain weather condition.
In order to realize non-line-of-sight (NLOS) laser scattering communication in atmosphere, the NLOS communication link model was founded according to Mie scattering theory and 1.06m laser scattering communication in atmosphere was studied. The relationship of laser receiving power, laser transmitting power, laser beam divergence angle, receiver field of view, detector sensitivity, emission inclination angle, receiver inclination angle, atmosphere attenuation and communication distance were analyzed. After establishing the experimental system, an experiment of 1km scattering communication was taken on and laser scattering signal was gotten. The experimental result shows that atmosphere scattering communication at long distance can be realized by choosing 1.06m laser for signal communication under a certain weather condition.
2014, 38(6): 859-862.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.029
Abstract:
In order to improve the accuracy and speed of image reconstruction, the generalized linear reconstructing algorithm based on homomorphic signal processing was analyzed by combining theoretical analysis and experimental verification in the digital holographic microscopy. The experimental results of the same field under different reference intensity ratio to object were compared. The results show that: with the increase of the intensity ratio, the reconstruction image quality of the generalized linear reconstructed algorithm is improved obviously. However, the reconstructed image quality decreases when the ratio increases to a certain value. Finding an appropriate ratio is important for obtaining high quality reconstructed images for the generalized linear reconstruction algorithm in digital holography.
In order to improve the accuracy and speed of image reconstruction, the generalized linear reconstructing algorithm based on homomorphic signal processing was analyzed by combining theoretical analysis and experimental verification in the digital holographic microscopy. The experimental results of the same field under different reference intensity ratio to object were compared. The results show that: with the increase of the intensity ratio, the reconstruction image quality of the generalized linear reconstructed algorithm is improved obviously. However, the reconstructed image quality decreases when the ratio increases to a certain value. Finding an appropriate ratio is important for obtaining high quality reconstructed images for the generalized linear reconstruction algorithm in digital holography.
2014, 38(6): 863-866.
doi: 10.7510/jgjs.issn.1001-3806.2014.06.030
Abstract:
In order to improve the quality of image segmentation, graph theory and minimal cut set algorithm were used. Firstly, using the pixel points of image as the mapping nodes of the graph theory, the node weight were calculated by the ratio of the balance factor and the shared nearest neighbor nodes. Then, the minimum cut set of the image was established based on the minimized energy equation, the gray value of the segmentation block was extracted as the block feature vector and the image was segmented by minimum spanning tree. The adjacent regions were judged to be combined or to be segmented by judging function. Finally the algorithm flow was given. The results show that the target information can be segmented by this algorithm. This algorithm has good robustness and small peak memory.
In order to improve the quality of image segmentation, graph theory and minimal cut set algorithm were used. Firstly, using the pixel points of image as the mapping nodes of the graph theory, the node weight were calculated by the ratio of the balance factor and the shared nearest neighbor nodes. Then, the minimum cut set of the image was established based on the minimized energy equation, the gray value of the segmentation block was extracted as the block feature vector and the image was segmented by minimum spanning tree. The adjacent regions were judged to be combined or to be segmented by judging function. Finally the algorithm flow was given. The results show that the target information can be segmented by this algorithm. This algorithm has good robustness and small peak memory.
