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RSS2015 Vol. 39, No. 4
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2015, 39(4): 437-442.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.001
[Abstract]
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Abstract:
On-line inspection of seam quality is one of the most important key technologies in laser welding of cold rolled strips. In order to solve the welding problems of TRUMPF12000 fast-flow axial laser welding equipment used in WISCO, such as misalignment,seam and weld morphology, three sensors were adopted to acquire image information including gap images before welding, penetration images during welding, and seam images after welding and so on. OTSU operation was used to find the threshold automatically. Projective geometry was used to convert image coordinates to workspace coordinates. Codes were written to extract image features. On-line seam quality inspection system was founded. Experiments were performed to test the inspection accuracy of 3mm thickness cold steel at weld velocity of 5m/min. The relative error of seam width was about 4.42%. The results show that the seam inspection system can offer the accurate judgment comparatively.
On-line inspection of seam quality is one of the most important key technologies in laser welding of cold rolled strips. In order to solve the welding problems of TRUMPF12000 fast-flow axial laser welding equipment used in WISCO, such as misalignment,seam and weld morphology, three sensors were adopted to acquire image information including gap images before welding, penetration images during welding, and seam images after welding and so on. OTSU operation was used to find the threshold automatically. Projective geometry was used to convert image coordinates to workspace coordinates. Codes were written to extract image features. On-line seam quality inspection system was founded. Experiments were performed to test the inspection accuracy of 3mm thickness cold steel at weld velocity of 5m/min. The relative error of seam width was about 4.42%. The results show that the seam inspection system can offer the accurate judgment comparatively.
2015, 39(4): 446-449.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.003
Abstract:
In order to verify membrane vibration modes, sinusoidal fringe projecting and Fourier fringe analysis were used in membrane vibration mode analysis and amplitude reconstruction. After theoretical analysis and experimental verification, among 3-D automatic sensor technologies based on structured light, Fourier transform profilometry (FTP) with the advantages of single-frame capture, high resolution and real-time measurement became the practical method in dynamic three-dimensional shape measurement. A sequence of the deformed and partly blurred sinusoidal fringe images on the surface of a vibrating membrane was grabbed by a low sampling rate CCD camera. By FTP, the actual experimental results of membrane vibration modes at different frequencies were obtained. The theoretical vibration results and the vibration measurement results were compared. The results show that the vibration modes reflect the vibrating membrane accurately. The results of 3-D surface shape measurement and actual experiments give the verification of its validity.
In order to verify membrane vibration modes, sinusoidal fringe projecting and Fourier fringe analysis were used in membrane vibration mode analysis and amplitude reconstruction. After theoretical analysis and experimental verification, among 3-D automatic sensor technologies based on structured light, Fourier transform profilometry (FTP) with the advantages of single-frame capture, high resolution and real-time measurement became the practical method in dynamic three-dimensional shape measurement. A sequence of the deformed and partly blurred sinusoidal fringe images on the surface of a vibrating membrane was grabbed by a low sampling rate CCD camera. By FTP, the actual experimental results of membrane vibration modes at different frequencies were obtained. The theoretical vibration results and the vibration measurement results were compared. The results show that the vibration modes reflect the vibrating membrane accurately. The results of 3-D surface shape measurement and actual experiments give the verification of its validity.
2015, 39(4): 450-452.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.004
Abstract:
For high accuracy of curvature measurement, a curvature sensor with polarization-maintaining photonic crystal fiber (PM-PCF) was proposed based on Mach-Zehnder interferometer structure. The fiber structure of the sensor head was formed by single-mode, up-taper, PM-PCF, multimode and single-mode fibers. Dislocation fusion was done between multimode and single mode fibers. After theoretical analysis and experiment verification, the linear relationship between resonance wavelength shift and curvature change in the curvature range of 0.04582m-1~0.054776m-1 and 0.054776m-1~0.06929m-1 was proved. The results show that the curvature sensor can be implied in health monitoring when the sensitivities of the sensor are 93.95nm/m-1 and 30.89nm/m-1.
For high accuracy of curvature measurement, a curvature sensor with polarization-maintaining photonic crystal fiber (PM-PCF) was proposed based on Mach-Zehnder interferometer structure. The fiber structure of the sensor head was formed by single-mode, up-taper, PM-PCF, multimode and single-mode fibers. Dislocation fusion was done between multimode and single mode fibers. After theoretical analysis and experiment verification, the linear relationship between resonance wavelength shift and curvature change in the curvature range of 0.04582m-1~0.054776m-1 and 0.054776m-1~0.06929m-1 was proved. The results show that the curvature sensor can be implied in health monitoring when the sensitivities of the sensor are 93.95nm/m-1 and 30.89nm/m-1.
2015, 39(4): 453-457.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.005
Abstract:
In order to improve measurement efficiency in visual guiding theodolites, a precise guiding method based on camera optical axis was put forward. After calibrating the double-theodolite measuring subsystem and vision guiding subsystem , the system was guided initially according to the theoretical design of workpiece modulus file. Then by using digital image processing technology, the characteristic center point of the camera filed of view was distinguished and the relationship between the characteristic center point and the image center (i.e., the camera optical axis) was obtained so that vision measurement subsystem can be guided to point the characteristic center precisely. According to the calibration relation, the angular deflection between both theodolites was obtained and the theodolites were made to intersect at the target point precisely. The results show that the method can make sure automatic measurement accuracy of the system at 0.3mm and improve measurement efficiency of the system.
In order to improve measurement efficiency in visual guiding theodolites, a precise guiding method based on camera optical axis was put forward. After calibrating the double-theodolite measuring subsystem and vision guiding subsystem , the system was guided initially according to the theoretical design of workpiece modulus file. Then by using digital image processing technology, the characteristic center point of the camera filed of view was distinguished and the relationship between the characteristic center point and the image center (i.e., the camera optical axis) was obtained so that vision measurement subsystem can be guided to point the characteristic center precisely. According to the calibration relation, the angular deflection between both theodolites was obtained and the theodolites were made to intersect at the target point precisely. The results show that the method can make sure automatic measurement accuracy of the system at 0.3mm and improve measurement efficiency of the system.
2015, 39(4): 458-461.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.006
Abstract:
In order to calimate laser beam of laser diodes, the principle of beam collimation was analyzed in the fast and slow axis directions. Based on astigmatic surface microlens, one method was proposed to collimate the laser beam by regarding one laser diode as the collimated unit. The effect of filling factor of laser diode on collimation performance was discussed. As an example of laser diode of 0.5 fill factor, the remaining divergence angle of the fast axis reaches about 0.34 and the remaining divergence angle of the slow axis reaches about 2.69. The results indicate that the microlens can collimate the laser diodes beam with high fill factor and the spot area of the collimated light is very small. The research can provide the new feasible collimation method for high power laser diodes.
In order to calimate laser beam of laser diodes, the principle of beam collimation was analyzed in the fast and slow axis directions. Based on astigmatic surface microlens, one method was proposed to collimate the laser beam by regarding one laser diode as the collimated unit. The effect of filling factor of laser diode on collimation performance was discussed. As an example of laser diode of 0.5 fill factor, the remaining divergence angle of the fast axis reaches about 0.34 and the remaining divergence angle of the slow axis reaches about 2.69. The results indicate that the microlens can collimate the laser diodes beam with high fill factor and the spot area of the collimated light is very small. The research can provide the new feasible collimation method for high power laser diodes.
2015, 39(4): 462-465.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.007
Abstract:
In order to improve the high-temperature oxidation resistance of materials, TiC-TiB2/Fe composite coating was in-situ synthesized by laser cladding. The data of phase, microstructure and oxidation resistance of composite coating were obtained after theoretical analysis and experimental verification. The results indicate that the phases of composite coating are mainly composed of -Fe, TiC, TiB2 and (Fe,Cr)7C3 etc. The fine block-shaped TiC particles and strip-shaped TiB2 disperse on the coating substrate uniformly. The continuous and compact oxidation film is formed on the surface of TiC-TiB2/Fe composite coating after being oxidized isothermally at 600℃ for 60h. The oxidation film consists of fine and spherical oxides such as Fe2O3, FeCr2O4, (Cr,Fe)2O3, rutile TiO2 and Al2O3 and so on, arranged closely. Thermodynamic conditions of oxide formation are satisfied. The oxidation kinetic curve of composite coating at constant temperature of 600℃ is parabolic. The rate of oxidation weight gain is much higher during the initial 10h, and then becomes slower gradually. The oxidation weight gain is 0.75mg/cm2 after being oxidized for 60h. The oxidation resistance of composite coating is 15 times higher than that of semi-steel. The results have some guiding significance to improve the high-temperature oxidation resistance of materials.
In order to improve the high-temperature oxidation resistance of materials, TiC-TiB2/Fe composite coating was in-situ synthesized by laser cladding. The data of phase, microstructure and oxidation resistance of composite coating were obtained after theoretical analysis and experimental verification. The results indicate that the phases of composite coating are mainly composed of -Fe, TiC, TiB2 and (Fe,Cr)7C3 etc. The fine block-shaped TiC particles and strip-shaped TiB2 disperse on the coating substrate uniformly. The continuous and compact oxidation film is formed on the surface of TiC-TiB2/Fe composite coating after being oxidized isothermally at 600℃ for 60h. The oxidation film consists of fine and spherical oxides such as Fe2O3, FeCr2O4, (Cr,Fe)2O3, rutile TiO2 and Al2O3 and so on, arranged closely. Thermodynamic conditions of oxide formation are satisfied. The oxidation kinetic curve of composite coating at constant temperature of 600℃ is parabolic. The rate of oxidation weight gain is much higher during the initial 10h, and then becomes slower gradually. The oxidation weight gain is 0.75mg/cm2 after being oxidized for 60h. The oxidation resistance of composite coating is 15 times higher than that of semi-steel. The results have some guiding significance to improve the high-temperature oxidation resistance of materials.
2015, 39(4): 466-470.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.008
Abstract:
In order to study effect of laser shock times on corrosion resistance of AZ31 magnesium alloy, AZ31 magnesium alloy was processed at different laser shock process (LSP)times by Nd:glass laser with pulse width of 23ns. Microstructures were observed by transmission electron microscopy. Polarization curves and electrochemical impedance spectroscopy were obtained in NaCl solution with 0.035 mass fraction by means of electrochemical measurement technique. The results show that plastic deformation with ultrahigh strain rate happens because of laser shock wave at the surface layer of AZ31 magnesium alloy. High density dislocations with intersect and entanglement of twin crystal exist in the crystal grains and the dislocations led to grain refinement. Polarization curves and electrochemical impedance spectroscopy shows that corrosion potential of AZ31 increases up to 267mV after the first laser shock. Corrosion current increases slightly, reaction resistance increases and corrosion resistance is improved significantly. With the increase of impact times from LSP, corrosion resistance of alloy is not improved significantly. The corresponding impedance spectroscopy has the same conclusion with polarization curves. The study is helpful for improving the corrosion resistance of magnesium alloy during laser shocking processing.
In order to study effect of laser shock times on corrosion resistance of AZ31 magnesium alloy, AZ31 magnesium alloy was processed at different laser shock process (LSP)times by Nd:glass laser with pulse width of 23ns. Microstructures were observed by transmission electron microscopy. Polarization curves and electrochemical impedance spectroscopy were obtained in NaCl solution with 0.035 mass fraction by means of electrochemical measurement technique. The results show that plastic deformation with ultrahigh strain rate happens because of laser shock wave at the surface layer of AZ31 magnesium alloy. High density dislocations with intersect and entanglement of twin crystal exist in the crystal grains and the dislocations led to grain refinement. Polarization curves and electrochemical impedance spectroscopy shows that corrosion potential of AZ31 increases up to 267mV after the first laser shock. Corrosion current increases slightly, reaction resistance increases and corrosion resistance is improved significantly. With the increase of impact times from LSP, corrosion resistance of alloy is not improved significantly. The corresponding impedance spectroscopy has the same conclusion with polarization curves. The study is helpful for improving the corrosion resistance of magnesium alloy during laser shocking processing.
2015, 39(4): 471-475.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.009
Abstract:
In order to solve the problem of the output beam offsets induced by assembling and heat distortion of mirrors in radio frequency slab CO2 lasers, offsets were compensated by means of the outside optics. An offset compensation device was designed based on piezoelectric ceramics. Piezoelectric ceramics actuators were designed and the control accuracy and adaptive control method were analyzed. The results show that laser output power at any duty ratio can meet or exceed the standard reference power value after compensation. The maximum difference of output power is 100W before and after adaptive regulation and the laser output power fluctuation is less than 2% during the running of 2h. The output beam compensation can ensure laser run efficiently, increase the stability of laser power and laser mode. The research has the high practical value.
In order to solve the problem of the output beam offsets induced by assembling and heat distortion of mirrors in radio frequency slab CO2 lasers, offsets were compensated by means of the outside optics. An offset compensation device was designed based on piezoelectric ceramics. Piezoelectric ceramics actuators were designed and the control accuracy and adaptive control method were analyzed. The results show that laser output power at any duty ratio can meet or exceed the standard reference power value after compensation. The maximum difference of output power is 100W before and after adaptive regulation and the laser output power fluctuation is less than 2% during the running of 2h. The output beam compensation can ensure laser run efficiently, increase the stability of laser power and laser mode. The research has the high practical value.
2015, 39(4): 476-479.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.010
Abstract:
In order to satisfy the high precision measurement requirement of angular velocity of platform drift in a platform drift measurement system, an improved Gaussian fitting method of laser spot center positioning was proposed based on the Fourier series. By using this method, Gaussian fitting model was simplified and at the same time the precision of laser spot center positioning was relatively high. Experimental results show that center positioning accuracy of the improved Gaussian positioning algorithm is 0.01pixel, better than 0.1pixel of traditional centroid method and centroid method with threshold significantly. The improved algorithm in this paper has better algorithm stability.
In order to satisfy the high precision measurement requirement of angular velocity of platform drift in a platform drift measurement system, an improved Gaussian fitting method of laser spot center positioning was proposed based on the Fourier series. By using this method, Gaussian fitting model was simplified and at the same time the precision of laser spot center positioning was relatively high. Experimental results show that center positioning accuracy of the improved Gaussian positioning algorithm is 0.01pixel, better than 0.1pixel of traditional centroid method and centroid method with threshold significantly. The improved algorithm in this paper has better algorithm stability.
2015, 39(4): 480-483.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.011
Abstract:
In order to improve the measurement accuracy of laser radar cross section (LRCS) and to avoid the measurement error of LRCS because of the instability of laser energy and atmospheric conditions, multi-channel comparison measurement method was adopted. New equation and calculation expressions were deduced for LRCS. The applicability and limitation of traditional LRCS measurement were discussed. The influence of laser energy instability and random atmospheric fluctuation on LRCS testing was analyzed. The results of two measurement methods were analyzed and compared. The test shows that the new method is more feasible than the traditional method. The measurement results of LRCS by multi-channel comparison are more accurate and could avoid and decrease the measurement error induced by laser energy instability and random atmospheric fluctuation.
In order to improve the measurement accuracy of laser radar cross section (LRCS) and to avoid the measurement error of LRCS because of the instability of laser energy and atmospheric conditions, multi-channel comparison measurement method was adopted. New equation and calculation expressions were deduced for LRCS. The applicability and limitation of traditional LRCS measurement were discussed. The influence of laser energy instability and random atmospheric fluctuation on LRCS testing was analyzed. The results of two measurement methods were analyzed and compared. The test shows that the new method is more feasible than the traditional method. The measurement results of LRCS by multi-channel comparison are more accurate and could avoid and decrease the measurement error induced by laser energy instability and random atmospheric fluctuation.
2015, 39(4): 484-487.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.012
Abstract:
In order to inscribe multi-wavelength array fiber gratings in ribbon fiber including 8 fibers at the same time, ribbon fiber was fixed by a specifically designed fixture and tension was added to the whole ribbon fiber by a programmed control displacement platform. 8 fibers in the ribbon fiber were exposed with phase mask technique one by one and Hamming apodization was realized simultaneously by using scan inscription method. Only with one phase mask, multi-wavelength array fiber gratings in the ribbon fiber including 8 fibers was achieved. The inscription process was controlled by the computer program. The central wavelength, the interval of wavelength and the style of apodization were adjusted freely. The test results of array Bragg fiber grating show that 3dB bandwidth is 0.2nm, wavelength interval is about 0.5nm, deviation is within 50pm, and reflectivity can reach 80%~85%. Inscription technique for ribbon multi-wavelength array fiber gratings is entirely feasible.
In order to inscribe multi-wavelength array fiber gratings in ribbon fiber including 8 fibers at the same time, ribbon fiber was fixed by a specifically designed fixture and tension was added to the whole ribbon fiber by a programmed control displacement platform. 8 fibers in the ribbon fiber were exposed with phase mask technique one by one and Hamming apodization was realized simultaneously by using scan inscription method. Only with one phase mask, multi-wavelength array fiber gratings in the ribbon fiber including 8 fibers was achieved. The inscription process was controlled by the computer program. The central wavelength, the interval of wavelength and the style of apodization were adjusted freely. The test results of array Bragg fiber grating show that 3dB bandwidth is 0.2nm, wavelength interval is about 0.5nm, deviation is within 50pm, and reflectivity can reach 80%~85%. Inscription technique for ribbon multi-wavelength array fiber gratings is entirely feasible.
2015, 39(4): 488-491.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.013
Abstract:
In order to study the photoconduction terahertz radiative process of InSb semiconductors, carrier migration rate and surface current were simulated. Effect of femtosecond pulse lasers with different properties on the near field terahertz (THz) intensity was also analyzed. Surface current in the semiconductor material was analyzed with macroscopic electromagnetic theory and microscopic semiconductor theory respectively. Power spectrum curves of InSb and GaAs material were compared. The researches show that: the longer the InSb carrier auger relaxation time, the bigger the InSb carrier migration rate; the surface current is proportional to the carrier life and relaxation time; macroscopic electromagnetic theory is suitable for analyzing surface current; the bigger the saturated laser energy density, the stronger the near field THz intensity; the shorter the laser pulse width, the stronger the near field THz intensity; InSb material power is higher than GaAs material. The results lay a theoretical foundation for study on InSb photoconduction THz radiation.
In order to study the photoconduction terahertz radiative process of InSb semiconductors, carrier migration rate and surface current were simulated. Effect of femtosecond pulse lasers with different properties on the near field terahertz (THz) intensity was also analyzed. Surface current in the semiconductor material was analyzed with macroscopic electromagnetic theory and microscopic semiconductor theory respectively. Power spectrum curves of InSb and GaAs material were compared. The researches show that: the longer the InSb carrier auger relaxation time, the bigger the InSb carrier migration rate; the surface current is proportional to the carrier life and relaxation time; macroscopic electromagnetic theory is suitable for analyzing surface current; the bigger the saturated laser energy density, the stronger the near field THz intensity; the shorter the laser pulse width, the stronger the near field THz intensity; InSb material power is higher than GaAs material. The results lay a theoretical foundation for study on InSb photoconduction THz radiation.
2015, 39(4): 492-496.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.014
Abstract:
Super resolution reconstruction compound-eye imaging is the combination of super resolution reconstruction technology and compound-eye imaging technology. The low resolution images were acquired by the compound-eye imaging system and the high resolution images were acquired by means of the high resolution reconstruction algorithm. The research status of super resolution reconstruction compound-eye imaging was summarized. The basic principle and the main imaging system at present were set forth. The common reconstruction algorithm was analyzed with the combination of imaging model. The quantitative evaluation and the visual evaluation methods were analyzed. This paper provides a reference for further study of super resolution reconstruction based on compound-eye imaging.
Super resolution reconstruction compound-eye imaging is the combination of super resolution reconstruction technology and compound-eye imaging technology. The low resolution images were acquired by the compound-eye imaging system and the high resolution images were acquired by means of the high resolution reconstruction algorithm. The research status of super resolution reconstruction compound-eye imaging was summarized. The basic principle and the main imaging system at present were set forth. The common reconstruction algorithm was analyzed with the combination of imaging model. The quantitative evaluation and the visual evaluation methods were analyzed. This paper provides a reference for further study of super resolution reconstruction based on compound-eye imaging.
2015, 39(4): 497-500.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.015
Abstract:
In order to complete accurate measurement of surface roughness of precision machinery, the experimental light path of surface roughness measurement was designed based on far-field angular-speckle correlation theory. In the measurement light path, a mirror was fixed together with the measured rough surface. While rotating the rough surface, a light pointer was composed by the mirror, beam splitter and receiving screen for measuring the rotation angle, and the measurement accuracy of the rotation angles was improved. During data processing, the peak value calculation method of angular-speckle correlation degree based on MATLAB software was proposed. By means of this method, the measurement procedure was simplified and the measurement speed was improved. And then, the surface roughness was calculated by using the correlation peak value method. As an example, the surface roughness of milling flat was measured. The measurement results were compared with the standard values. High accuracy of measurement was achieved. The results show that the feasibility of measuring the surface roughness by using laser speckle method is verified and the study is helpful to improve the precision measurement of surface roughness further.
In order to complete accurate measurement of surface roughness of precision machinery, the experimental light path of surface roughness measurement was designed based on far-field angular-speckle correlation theory. In the measurement light path, a mirror was fixed together with the measured rough surface. While rotating the rough surface, a light pointer was composed by the mirror, beam splitter and receiving screen for measuring the rotation angle, and the measurement accuracy of the rotation angles was improved. During data processing, the peak value calculation method of angular-speckle correlation degree based on MATLAB software was proposed. By means of this method, the measurement procedure was simplified and the measurement speed was improved. And then, the surface roughness was calculated by using the correlation peak value method. As an example, the surface roughness of milling flat was measured. The measurement results were compared with the standard values. High accuracy of measurement was achieved. The results show that the feasibility of measuring the surface roughness by using laser speckle method is verified and the study is helpful to improve the precision measurement of surface roughness further.
2015, 39(4): 501-505.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.016
Abstract:
In order to reduce measurement errors with a laser feedback interference system measuring micro displacements of moving objects based on phase freezing technique, system errors induced by intervals of phase shift and vibrating amplitudes of reflecting surface were analyzed theoretically by means of MATLAB numerical simulation, interpolation and curve fit. In system experiments, interference signals produced by moving objects were collected and sampled by phase freezing principle so as to obtain multiple curves of optical power. Feature points were marked on the optical power curves to judge moving direction and reconstruct micro-displacement curves. Polynomial fitting based on the reconstructed micro displacement curves improved system measurement precision. Experimental results show that measurement resolution is superior to /20 (77.5nm) when fixed interval of phase shift is /5 and wavelength of laser is 1550nm. The maximum absolute error of actual measurement of micro-displacements is 47.98nm and the average value of peak-peak errors is less than 1nm. Phase freezing technique provides a new solution for laser feedback interferometer system to identify directions and realize high precision measurement of micro-displacements.
In order to reduce measurement errors with a laser feedback interference system measuring micro displacements of moving objects based on phase freezing technique, system errors induced by intervals of phase shift and vibrating amplitudes of reflecting surface were analyzed theoretically by means of MATLAB numerical simulation, interpolation and curve fit. In system experiments, interference signals produced by moving objects were collected and sampled by phase freezing principle so as to obtain multiple curves of optical power. Feature points were marked on the optical power curves to judge moving direction and reconstruct micro-displacement curves. Polynomial fitting based on the reconstructed micro displacement curves improved system measurement precision. Experimental results show that measurement resolution is superior to /20 (77.5nm) when fixed interval of phase shift is /5 and wavelength of laser is 1550nm. The maximum absolute error of actual measurement of micro-displacements is 47.98nm and the average value of peak-peak errors is less than 1nm. Phase freezing technique provides a new solution for laser feedback interferometer system to identify directions and realize high precision measurement of micro-displacements.
2015, 39(4): 506-509.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.017
Abstract:
In order to study effect of laser surface texturing on tribological properties of face seal materials, GCr15 steel disc was textured by Nd:YAG solid-state pulsed laser to form two surface morphologies of dimple and groove. The tribological performance for polytetrafluoroethylene ring/GCr15 disc (simulating face seal) was tested on the friction tester and the worn surface morphologies were analyzed. The results show that friction coefficient and wear loss of textured samples are lower than the smooth in the oil lubrication condition. And the wear resistance of dimple-textured sample was better than the groove because the groove-textured arrangement caused the oil film thickness uneven and the friction coefficient fluctuated. Under the dry friction condition, the existence of the favorable texturing can maintain the transfer film, capture wear debris and reduce abrasive wear. Compared with the smooth sample, the wear rate of the pair can be reduced.
In order to study effect of laser surface texturing on tribological properties of face seal materials, GCr15 steel disc was textured by Nd:YAG solid-state pulsed laser to form two surface morphologies of dimple and groove. The tribological performance for polytetrafluoroethylene ring/GCr15 disc (simulating face seal) was tested on the friction tester and the worn surface morphologies were analyzed. The results show that friction coefficient and wear loss of textured samples are lower than the smooth in the oil lubrication condition. And the wear resistance of dimple-textured sample was better than the groove because the groove-textured arrangement caused the oil film thickness uneven and the friction coefficient fluctuated. Under the dry friction condition, the existence of the favorable texturing can maintain the transfer film, capture wear debris and reduce abrasive wear. Compared with the smooth sample, the wear rate of the pair can be reduced.
2015, 39(4): 510-514.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.018
Abstract:
In order to compress the dynamic range of the received optical signal in an underwater optical wireless communication system and increase the effective distance of communication, automatic gain control circuit based on variable gain photomultipliers was designed from the basic theory of automatic gain control technology. Single chip microcomputer was the core of the digital control part. The underwater experiment was imitated in the air. The results show that the dynamic range of received optical signal is compressed for 40dB and the effective range of underwater wireless optical communication is improved.
In order to compress the dynamic range of the received optical signal in an underwater optical wireless communication system and increase the effective distance of communication, automatic gain control circuit based on variable gain photomultipliers was designed from the basic theory of automatic gain control technology. Single chip microcomputer was the core of the digital control part. The underwater experiment was imitated in the air. The results show that the dynamic range of received optical signal is compressed for 40dB and the effective range of underwater wireless optical communication is improved.
2015, 39(4): 515-519.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.019
Abstract:
To study the polarized conversion characteristics of vertical cavity surface emitting lasers (VCSEL), frequency-induced polarization switching (PS) and polarization bistability (PB) of 1550nm VCSEL subject to orthogonal optical injection were investigated numerically by adopting extended spin-flip model. The results show that under orthogonal optical injection, PS and PB can be achieved through varying the frequency detuning between the injected field and the x linearly polarized mode in VCSEL consecutively. Furthermore, the variation of injection power and bias current have strong effects on PB width and VCSEL output emission. The controlling of frequency-induced PS and PB in a 1550nm VCSEL can be realized with appropriate selection of operating conditions. This study has reference value for the application of VCSEL in all-optical switching and all-optical memory.
To study the polarized conversion characteristics of vertical cavity surface emitting lasers (VCSEL), frequency-induced polarization switching (PS) and polarization bistability (PB) of 1550nm VCSEL subject to orthogonal optical injection were investigated numerically by adopting extended spin-flip model. The results show that under orthogonal optical injection, PS and PB can be achieved through varying the frequency detuning between the injected field and the x linearly polarized mode in VCSEL consecutively. Furthermore, the variation of injection power and bias current have strong effects on PB width and VCSEL output emission. The controlling of frequency-induced PS and PB in a 1550nm VCSEL can be realized with appropriate selection of operating conditions. This study has reference value for the application of VCSEL in all-optical switching and all-optical memory.
2015, 39(4): 520-524.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.020
Abstract:
To overcome the shortage of mismatch of the calculated value and the measured value of thermal induced birefringence and thermal focal length when applying linear heat conduction model to describe a laser crystal operating in high power, based on nonlinear heat conduction model analysis, the distribution of the thermal induced birefringence ellipse and the radial or tangential thermal focal length in a Nd:YAG laser crystal of common [111]-cut were analyzed. The average thermal focal length data and rotated interference pattern of linearly polarized light were measured. The experimental results fit the theoretical analysis. The results show that nonlinear model provides more realistic and more general description for an Nd:YAG laser crystal in [111]-cut. The result is helpful for the design of radial or tangential polarized high power solid-state lasers.
To overcome the shortage of mismatch of the calculated value and the measured value of thermal induced birefringence and thermal focal length when applying linear heat conduction model to describe a laser crystal operating in high power, based on nonlinear heat conduction model analysis, the distribution of the thermal induced birefringence ellipse and the radial or tangential thermal focal length in a Nd:YAG laser crystal of common [111]-cut were analyzed. The average thermal focal length data and rotated interference pattern of linearly polarized light were measured. The experimental results fit the theoretical analysis. The results show that nonlinear model provides more realistic and more general description for an Nd:YAG laser crystal in [111]-cut. The result is helpful for the design of radial or tangential polarized high power solid-state lasers.
2015, 39(4): 525-527.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.021
Abstract:
In order to analyze effect of structure parameters of 1-D photonic crystal on energy band structure systematically and apply the result in filter design, transmission matrix method was used. Different energy band structures of photonic crystals of different structural parameters were calculated by MALTAB simulation software. Energy band distributions of 1-D photonic crystal with different cycles, different dielectric layer thickness and different media refractive indices were gotten. Through analysis and comparison, the effects of 1-D photonic crystal structure parameters on energy band structure were gotten. The results show that 1-D photonic crystal with larger cycle number has a steeper forbidden band-edge and higher transmission of pass band. In other word, the band distribution is more distinct. Energy distribution and energy width can be adjusted with dielectric layer thickness of photonic crystal. The width of band gap can be changed by the ratio of the refractive index of the medium. The width of band gap increases with the increase of the ratio of the refractive index of the medium. These results are helpful for the design of filters.
In order to analyze effect of structure parameters of 1-D photonic crystal on energy band structure systematically and apply the result in filter design, transmission matrix method was used. Different energy band structures of photonic crystals of different structural parameters were calculated by MALTAB simulation software. Energy band distributions of 1-D photonic crystal with different cycles, different dielectric layer thickness and different media refractive indices were gotten. Through analysis and comparison, the effects of 1-D photonic crystal structure parameters on energy band structure were gotten. The results show that 1-D photonic crystal with larger cycle number has a steeper forbidden band-edge and higher transmission of pass band. In other word, the band distribution is more distinct. Energy distribution and energy width can be adjusted with dielectric layer thickness of photonic crystal. The width of band gap can be changed by the ratio of the refractive index of the medium. The width of band gap increases with the increase of the ratio of the refractive index of the medium. These results are helpful for the design of filters.
2015, 39(4): 528-532.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.022
Abstract:
In order to analyze the intermodal dispersion(IMD) between two random supermodes in a three-core photonic crystal fiber(PCF) with low refractive index material doping into the core, the intermodal dispersion coefficient and zero IMD wavelength as the function of core index and design parameters were investigated by using full-vector finite element method. The results show that zero intermodal dispersion can be achieved at two common wavelengths of 1.31m and 1.55m by adjusting the structure parameters, i.e., core index, core diameter, air hole diameter and the pitch of air holes. The result is helpful to eliminate the pulse distortion due to intermodal dispersion between different modes in PCFs based on mode division multiplexing and realize the zero IMD mode division multiplexing technology.
In order to analyze the intermodal dispersion(IMD) between two random supermodes in a three-core photonic crystal fiber(PCF) with low refractive index material doping into the core, the intermodal dispersion coefficient and zero IMD wavelength as the function of core index and design parameters were investigated by using full-vector finite element method. The results show that zero intermodal dispersion can be achieved at two common wavelengths of 1.31m and 1.55m by adjusting the structure parameters, i.e., core index, core diameter, air hole diameter and the pitch of air holes. The result is helpful to eliminate the pulse distortion due to intermodal dispersion between different modes in PCFs based on mode division multiplexing and realize the zero IMD mode division multiplexing technology.
2015, 39(4): 533-536.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.023
Abstract:
In order to realize beacon acquisition, tracking and pointing(ATP) of laser communication, a high speed laser spot detection system was designed based on field-programmable gate array and embedded image processing technology. Laser spots of targets in the sequence images with 300pixel300pixel resolution and 1000Hz frame rate were extracted. 1-D filtering operator position filter was used to process the images and the hardware was implemented at the same time. After filtering, threshold segmentation, morphological opening operation and connected region analysis, centroid position information of laser spot were extracted. The experimental results show that the system is capable of real-time processing of high-frame rate images containing targets' laser spot. The extracting frequency of target centroid can meet the requirement of the dynamic link setup of laser communication.
In order to realize beacon acquisition, tracking and pointing(ATP) of laser communication, a high speed laser spot detection system was designed based on field-programmable gate array and embedded image processing technology. Laser spots of targets in the sequence images with 300pixel300pixel resolution and 1000Hz frame rate were extracted. 1-D filtering operator position filter was used to process the images and the hardware was implemented at the same time. After filtering, threshold segmentation, morphological opening operation and connected region analysis, centroid position information of laser spot were extracted. The experimental results show that the system is capable of real-time processing of high-frame rate images containing targets' laser spot. The extracting frequency of target centroid can meet the requirement of the dynamic link setup of laser communication.
2015, 39(4): 537-540.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.024
Abstract:
In order to achieve fast quantitative retrieval analysis of Pb in lead slime, PbⅠ:405.78nm was selected as the analytical line. The influences of laser energy on the laser induced breakdown spectroscopy characteristics of Pb in lead slime were discussed from three areas of spectral intensity, the ratio of signal and background and the relative standard deviation of signal. Within the range of 23.1mJ ~ 135.4mJ, line intensity increases linearly with the increase of laser energy, the ratio of signal and background increases at first and then decreases, and eventually stabilizes. The relative standard deviation of the signal decreases at first and then stabilizes with the increase of laser energy. The samples of lead slime with different mass fractions were prepared and the calibration curve of Pb was obtained. The results show that within the range of mass fraction of 0.001118~0.20115, spectrum intensity has the good linear relationship with Pb content. The correlation coefficient reaches 0.991. With this method , the relative error between measurement value and real value of Pb content of lead slime is 8.72%. This method can provide fast and quantitative retrieval measurement of Pb in lead slime.
In order to achieve fast quantitative retrieval analysis of Pb in lead slime, PbⅠ:405.78nm was selected as the analytical line. The influences of laser energy on the laser induced breakdown spectroscopy characteristics of Pb in lead slime were discussed from three areas of spectral intensity, the ratio of signal and background and the relative standard deviation of signal. Within the range of 23.1mJ ~ 135.4mJ, line intensity increases linearly with the increase of laser energy, the ratio of signal and background increases at first and then decreases, and eventually stabilizes. The relative standard deviation of the signal decreases at first and then stabilizes with the increase of laser energy. The samples of lead slime with different mass fractions were prepared and the calibration curve of Pb was obtained. The results show that within the range of mass fraction of 0.001118~0.20115, spectrum intensity has the good linear relationship with Pb content. The correlation coefficient reaches 0.991. With this method , the relative error between measurement value and real value of Pb content of lead slime is 8.72%. This method can provide fast and quantitative retrieval measurement of Pb in lead slime.
2015, 39(4): 541-544.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.025
Abstract:
Double-exposure holography is widely adopted in temperature field visualization because of the output of infinite fringes which directly present the wavefront distortion. When the wall temperature of the natural convection horizontal cylinder in 25mm diameter and 350mm length dropped from 72℃ to 22℃, the simple interferometric fringes were obtained using the double-exposure holography to study temperature field. Stripe displacements at different angels were extracted by fringe center method. Peak values and valley values of R channel of interferogram were corresponding to the centers of bright and dark fringes. Distributions of fringe orders were achieved and temperature field was inversed. The maximum of relative error of wall temperature between inversion values and thermocouple measurement values was 0.059. The results show that the data of double-exposure holography is feasible and reliable. The study is helpful for simple and fast inversion of temperature field.
Double-exposure holography is widely adopted in temperature field visualization because of the output of infinite fringes which directly present the wavefront distortion. When the wall temperature of the natural convection horizontal cylinder in 25mm diameter and 350mm length dropped from 72℃ to 22℃, the simple interferometric fringes were obtained using the double-exposure holography to study temperature field. Stripe displacements at different angels were extracted by fringe center method. Peak values and valley values of R channel of interferogram were corresponding to the centers of bright and dark fringes. Distributions of fringe orders were achieved and temperature field was inversed. The maximum of relative error of wall temperature between inversion values and thermocouple measurement values was 0.059. The results show that the data of double-exposure holography is feasible and reliable. The study is helpful for simple and fast inversion of temperature field.
2015, 39(4): 545-548.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.026
Abstract:
In order to filter the random noise in infrared images effectively, new double filtering algorithm was proposed based on lifting wavelet transform. Firstly, the noise infrared image was decomposed with lifting wavelet at first time. And then, the obtained high-frequency and low-frequency wavelet coefficients were decomposed with lifting wavelet transformation again. The improved threshold function model and nonlocal mean filter algorithm were used to filter the noise of lifting wavelet coefficients. Finally, histogram equalization algorithm was introduced to improve the visual effect of the filtering image. The standard test images, the experimental infrared images, peak signal-noise-ratio (PSNR) and structural similarity (SSIM) were obtained. The results show that, the performance of the algorithm in this paper is good to deal with noise infrared images.
In order to filter the random noise in infrared images effectively, new double filtering algorithm was proposed based on lifting wavelet transform. Firstly, the noise infrared image was decomposed with lifting wavelet at first time. And then, the obtained high-frequency and low-frequency wavelet coefficients were decomposed with lifting wavelet transformation again. The improved threshold function model and nonlocal mean filter algorithm were used to filter the noise of lifting wavelet coefficients. Finally, histogram equalization algorithm was introduced to improve the visual effect of the filtering image. The standard test images, the experimental infrared images, peak signal-noise-ratio (PSNR) and structural similarity (SSIM) were obtained. The results show that, the performance of the algorithm in this paper is good to deal with noise infrared images.
2015, 39(4): 549-551.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.027
Abstract:
In order to analyze effect of three wave-plates compound depolarizer on depolarization of monochromatic light, theoretical analysis was made by using Muller matrix and Stokes vectors. Expression of degree of polarization (DOP) of the output light was computed after monochromatic linear depolarized light passing through a three wave-plates compound depolarizer. The relationship between various parameters and DOP was also discussed. The results show that the structure is able to be depolarized completely. When =0rad and 25rad/s, P1%. The result has important reference of design and research of depolarizers.
In order to analyze effect of three wave-plates compound depolarizer on depolarization of monochromatic light, theoretical analysis was made by using Muller matrix and Stokes vectors. Expression of degree of polarization (DOP) of the output light was computed after monochromatic linear depolarized light passing through a three wave-plates compound depolarizer. The relationship between various parameters and DOP was also discussed. The results show that the structure is able to be depolarized completely. When =0rad and 25rad/s, P1%. The result has important reference of design and research of depolarizers.
2015, 39(4): 552-556.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.028
Abstract:
To improve the thermal shock resistance of roll surface coating and extend the service life under high temperature condition, plasma sprayed thermal barrier coating on the roll surface was remelted using 5kW CO2 laser. The coating surface morphology and microstructure of the laser remelting thermal barrier coating were observed by scanning electron microscopy. The micro-zone elements composition on the interface was analyzed by energy dispersive spectroscopy. By putting specimens at 1000℃ for 10min and then quenching into water directly, the thermal shock resistance was explored and compared with the plasma sprayed coating. The results show that porosity and crack of the laser remelting coating was reduced, and the quality of the coating was improved significantly. Metallurgical bonding was achieved between the coating and the substrate, and the adhesive strength was enhanced obviously. Thermal shock cycling times of the first crack and of the final failure was increased from 14 times and 32 times to 43 times and 94 times respectively. Laser remelting process is helpful to improve the thermal shock resistance of the coating and to extend the life of the roll.
To improve the thermal shock resistance of roll surface coating and extend the service life under high temperature condition, plasma sprayed thermal barrier coating on the roll surface was remelted using 5kW CO2 laser. The coating surface morphology and microstructure of the laser remelting thermal barrier coating were observed by scanning electron microscopy. The micro-zone elements composition on the interface was analyzed by energy dispersive spectroscopy. By putting specimens at 1000℃ for 10min and then quenching into water directly, the thermal shock resistance was explored and compared with the plasma sprayed coating. The results show that porosity and crack of the laser remelting coating was reduced, and the quality of the coating was improved significantly. Metallurgical bonding was achieved between the coating and the substrate, and the adhesive strength was enhanced obviously. Thermal shock cycling times of the first crack and of the final failure was increased from 14 times and 32 times to 43 times and 94 times respectively. Laser remelting process is helpful to improve the thermal shock resistance of the coating and to extend the life of the roll.
2015, 39(4): 557-561.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.029
Abstract:
In order to solve the significant shielding effect of light-induced plasma on laser during high-power diode laser processing, with the help of the mathematical model of electron density of light-induced plasma and ABCD matrix algorithm, the shielding effect of light-induced plasma was studied from the view of absorption and refraction based on a diode laser processing system with wavelength of 976nm, spot size of 0.5mm1mm and the maximum power of 4kW. The results showed that laser beam shielding effect is mainly due to refraction effect of light-induced plasma under the condition of electron density ne1.01018/cm3. Laser beam shielding effect changes laser beam shape, i.e., making the laser focus down-shift, enlarging the spot and making the laser energy density smaller. The effect of induced-laser plasma is similar to a negative lens with non-linear gradient refractive index.
In order to solve the significant shielding effect of light-induced plasma on laser during high-power diode laser processing, with the help of the mathematical model of electron density of light-induced plasma and ABCD matrix algorithm, the shielding effect of light-induced plasma was studied from the view of absorption and refraction based on a diode laser processing system with wavelength of 976nm, spot size of 0.5mm1mm and the maximum power of 4kW. The results showed that laser beam shielding effect is mainly due to refraction effect of light-induced plasma under the condition of electron density ne1.01018/cm3. Laser beam shielding effect changes laser beam shape, i.e., making the laser focus down-shift, enlarging the spot and making the laser energy density smaller. The effect of induced-laser plasma is similar to a negative lens with non-linear gradient refractive index.
2015, 39(4): 562-565.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.030
Abstract:
In order to measure the focal length of a concave and convex lens accurately, theoretical analysis and experimental verification were carried out based on the color digital holographic method, and the measurement difference relative to the nominal value was 1%. The results indicate the digital holographic interferometry is reliable and the same effect as that of lens nominal value reconstruction can be obtained. The result is helpful for digital holographic wavefront reconstruction.
In order to measure the focal length of a concave and convex lens accurately, theoretical analysis and experimental verification were carried out based on the color digital holographic method, and the measurement difference relative to the nominal value was 1%. The results indicate the digital holographic interferometry is reliable and the same effect as that of lens nominal value reconstruction can be obtained. The result is helpful for digital holographic wavefront reconstruction.
2015, 39(4): 566-570.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.031
Abstract:
In order to study effect of gas ratio, pumping electron density and cavity length on output power of pulse transversely excited atmospheric(TEA)CO2 laser, six temperature models were employed to analyze the energy transfer among different molecular vibration modes of working gas and the output power of laser by theoretical analysis and numerical simulation. The simulation was in good agreement with the experimental data. The results show that when the volume ratio of CO2, N2, and He rises from 4:30:65 to 6:30:65, the pulse power increases and the delay time gets shorter. When the volume ratio of CO2, N2, and He rises from 5:15:65 to 5:35:65, the pulse power firstly increases and then decreases, and reaches the maximum at the volume ratio of N2 about 25. When the volume ratio of CO2, N2, and He is 5:30:65, the maximum pumping electron density rises from 41012/cm3 to 61012/cm3, and the cavity length rises from 2m to 4m, the pulse power will gradually increase. The pulse power is greater, the delay time is shorter, and the tailing phenomenon is more longer. The simulation results show that gas ratio, pumping electron density and cavity length have effects on pulse output power. The study provides a reference for design and optimization of CO2 lasers.
In order to study effect of gas ratio, pumping electron density and cavity length on output power of pulse transversely excited atmospheric(TEA)CO2 laser, six temperature models were employed to analyze the energy transfer among different molecular vibration modes of working gas and the output power of laser by theoretical analysis and numerical simulation. The simulation was in good agreement with the experimental data. The results show that when the volume ratio of CO2, N2, and He rises from 4:30:65 to 6:30:65, the pulse power increases and the delay time gets shorter. When the volume ratio of CO2, N2, and He rises from 5:15:65 to 5:35:65, the pulse power firstly increases and then decreases, and reaches the maximum at the volume ratio of N2 about 25. When the volume ratio of CO2, N2, and He is 5:30:65, the maximum pumping electron density rises from 41012/cm3 to 61012/cm3, and the cavity length rises from 2m to 4m, the pulse power will gradually increase. The pulse power is greater, the delay time is shorter, and the tailing phenomenon is more longer. The simulation results show that gas ratio, pumping electron density and cavity length have effects on pulse output power. The study provides a reference for design and optimization of CO2 lasers.
2015, 39(4): 571-575.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.032
Abstract:
In order to study the relationship between the resonant wavelength drift and the grating bending strain of a long period bending photonic crystal fiber grating sensor, based on the coupled mode theory and programming simulation, the resonant wavelength expression of long period bending photonic crystal fiber gratings was deduced. The system model of a general bending photonic crystal fiber grating sensor with long period was designed. The basic principle of the sensor was analyzed. The relationship between the bending curvature, grating refractive index, sensor resonance wavelength and grating bending strain was calculated. The results show that the grating curvature increases with the increase of the bending strain of the grating, and the resonance wavelength drift of the grating sensor increases too. The resonant wavelength drifts 0.014nm with 1 change of the grating.
In order to study the relationship between the resonant wavelength drift and the grating bending strain of a long period bending photonic crystal fiber grating sensor, based on the coupled mode theory and programming simulation, the resonant wavelength expression of long period bending photonic crystal fiber gratings was deduced. The system model of a general bending photonic crystal fiber grating sensor with long period was designed. The basic principle of the sensor was analyzed. The relationship between the bending curvature, grating refractive index, sensor resonance wavelength and grating bending strain was calculated. The results show that the grating curvature increases with the increase of the bending strain of the grating, and the resonance wavelength drift of the grating sensor increases too. The resonant wavelength drifts 0.014nm with 1 change of the grating.
2015, 39(4): 576-580.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.033
Abstract:
In order to get the optical orthogonal codes (OOC) with good performance, all-interval-set with no duplicate number was used. After design and system simulation, OOC had ideal correlation and flexible code capacity. The formula of bit error rate (BER) was derived considering all kinds of noise and multi-user interference. Asynchronous optical code division multiple access (OCDMA) system was designed and constructed with fiber optic delay lines as encoders and decoders. The result shows that the OOC can adapt to the demands of more number of users. The consequence is satisfactory both from the calculation of BER formula and from system simulation. The research is helpful for further development of OCDMA systems with high capacity.
In order to get the optical orthogonal codes (OOC) with good performance, all-interval-set with no duplicate number was used. After design and system simulation, OOC had ideal correlation and flexible code capacity. The formula of bit error rate (BER) was derived considering all kinds of noise and multi-user interference. Asynchronous optical code division multiple access (OCDMA) system was designed and constructed with fiber optic delay lines as encoders and decoders. The result shows that the OOC can adapt to the demands of more number of users. The consequence is satisfactory both from the calculation of BER formula and from system simulation. The research is helpful for further development of OCDMA systems with high capacity.
2015, 39(4): 581-584.
doi: 10.7510/jgjs.issn.1001-3806.2015.04.034
Abstract:
To study the spreading of cosh-Gaussian beams propagating through non-Kolmogorov turbulence, extended Huygens-Fresnel principle was used. The expression of turbulence distance zt of partially coherent cosh-Gaussian beams propagating through turbulence was derived. The influence of turbulence parameters (generalized exponent parameter , inner scale l0 and outer scale L0) and beam parameters (coherence parameter and decentered parameter )on turbulence distance was studied theoretically. The results show that turbulence distance zt decreases firstly and then increases with the increase of . When =3.11, zt is minimum. And zt increases with the increase of l0 and , decreases with the increase of L0(just for 3.64) and . The results will be useful for the applications of cosh-Gaussian beams propagating in non-Kolmogorov turbulence.
To study the spreading of cosh-Gaussian beams propagating through non-Kolmogorov turbulence, extended Huygens-Fresnel principle was used. The expression of turbulence distance zt of partially coherent cosh-Gaussian beams propagating through turbulence was derived. The influence of turbulence parameters (generalized exponent parameter , inner scale l0 and outer scale L0) and beam parameters (coherence parameter and decentered parameter )on turbulence distance was studied theoretically. The results show that turbulence distance zt decreases firstly and then increases with the increase of . When =3.11, zt is minimum. And zt increases with the increase of l0 and , decreases with the increase of L0(just for 3.64) and . The results will be useful for the applications of cosh-Gaussian beams propagating in non-Kolmogorov turbulence.
