2011 Vol. 32, No. 4
Display Method:
2011, 32(4): 591-598.
Abstract:
Inertial stabilization of line of sight (LOS) achieved by controlling the motion of a mirror in the optical path is used widely in various electro-optical reconnaissance systems on aircrafts, ships and ground vehicles. To improve the mirror stabilization performance, the system configurations and applications of the stabilized mirror systems are introduced. The optical path of the mirror and the system stabilization concept with half angle mechanism based on kinematics are described. The configurations and servo control techniques of several strap-down mirror systems are given. The key factors influencing the mirror stabilization are discussed for further engineering developments.
Inertial stabilization of line of sight (LOS) achieved by controlling the motion of a mirror in the optical path is used widely in various electro-optical reconnaissance systems on aircrafts, ships and ground vehicles. To improve the mirror stabilization performance, the system configurations and applications of the stabilized mirror systems are introduced. The optical path of the mirror and the system stabilization concept with half angle mechanism based on kinematics are described. The configurations and servo control techniques of several strap-down mirror systems are given. The key factors influencing the mirror stabilization are discussed for further engineering developments.
2011, 32(4): 598-601.
Abstract:
Direct attack with satellite guided weapon is one of the most important means for precision ground strike. The direct attack operation needs high precision target position, which cannot be satisfied by conventional positioning methods. The relative GPS guidance is the key technology for airborne satellite guided weapon direct attack. This paper presented the direct attack concept of satellite guided weapon, and analyzed the errors of relative GPS guidance technology. The errors were induced by relative GPS position and airborne sensor relative position. The position precisions of them were analyzed. The simulation results indicated that the overall error of the relative GPS guidance was less than 7.5 m, which satisfied the requirement for the satellite guided weapon direct attack.
Direct attack with satellite guided weapon is one of the most important means for precision ground strike. The direct attack operation needs high precision target position, which cannot be satisfied by conventional positioning methods. The relative GPS guidance is the key technology for airborne satellite guided weapon direct attack. This paper presented the direct attack concept of satellite guided weapon, and analyzed the errors of relative GPS guidance technology. The errors were induced by relative GPS position and airborne sensor relative position. The position precisions of them were analyzed. The simulation results indicated that the overall error of the relative GPS guidance was less than 7.5 m, which satisfied the requirement for the satellite guided weapon direct attack.
2011, 32(4): 602-606.
Abstract:
The specifications of inertial navigation system (INS) such as volume and operation speed are dependent on hardware circuit, and an optimal hardware implementation of INS can enhance the system precision. According to the volume and operation speed demands of a micro INS, an INS for a specific engineering application is presented. The field programmable gate array (FPGA) is used as the core of sampling and controlling inertial sensor, a parallel sampling plan is designed, and the inertial calculation is implemented by using a 32-bit floating-point digital signal processor (DSP). The results obtained from rotation table and field tests show that this system has strong anti-interference ability, rapid response, convenient calibration for initial unit and easy implementation.
The specifications of inertial navigation system (INS) such as volume and operation speed are dependent on hardware circuit, and an optimal hardware implementation of INS can enhance the system precision. According to the volume and operation speed demands of a micro INS, an INS for a specific engineering application is presented. The field programmable gate array (FPGA) is used as the core of sampling and controlling inertial sensor, a parallel sampling plan is designed, and the inertial calculation is implemented by using a 32-bit floating-point digital signal processor (DSP). The results obtained from rotation table and field tests show that this system has strong anti-interference ability, rapid response, convenient calibration for initial unit and easy implementation.
2011, 32(4): 607-612.
Abstract:
In order to improve the luminance and brightness uniformity of mobile phone side backlighting light guide plates (LGP), a wedge-shaped LGP with the upper surface of 41mm26mm was simulated. The printing scattered dots on bottom surface, the wedge angle of LGP underside and hemispherical convex hull arrangement on the surface were researched. The results showed that the brightness uniformity of upper surface was poor and the percentage of output luminous flux was less than 26% when the LGP bottom was printed with scattered dots, the brightness uniformity of upper surface was improved and the percentage of output luminous flux is increased by 10% when the hemispherical convex hulls were arranged on the LGP bottom. The lighting effect of LGP with 81 wedge angle was better than 85.
In order to improve the luminance and brightness uniformity of mobile phone side backlighting light guide plates (LGP), a wedge-shaped LGP with the upper surface of 41mm26mm was simulated. The printing scattered dots on bottom surface, the wedge angle of LGP underside and hemispherical convex hull arrangement on the surface were researched. The results showed that the brightness uniformity of upper surface was poor and the percentage of output luminous flux was less than 26% when the LGP bottom was printed with scattered dots, the brightness uniformity of upper surface was improved and the percentage of output luminous flux is increased by 10% when the hemispherical convex hulls were arranged on the LGP bottom. The lighting effect of LGP with 81 wedge angle was better than 85.
2011, 32(4): 613-617.
Abstract:
The characteristics of the light emitting diode （LED）limit its applications in various lighting fields. The allocation of LED power to form an ideal luminance on a target plane was investigated. This paper analyzed the designs of optical systems on different applications, obtained the formula of the lens by adopting etendue conservation method in non-imaging optics, achieved round uniform illumination with 85% uniformity and rectangular uniform illumination with 75% uniformity, established the 3D model of the freeform lens, and conducted the ray tracing based on TracePro. The simulation results meet the corresponding standard, which validates the design.
The characteristics of the light emitting diode （LED）limit its applications in various lighting fields. The allocation of LED power to form an ideal luminance on a target plane was investigated. This paper analyzed the designs of optical systems on different applications, obtained the formula of the lens by adopting etendue conservation method in non-imaging optics, achieved round uniform illumination with 85% uniformity and rectangular uniform illumination with 75% uniformity, established the 3D model of the freeform lens, and conducted the ray tracing based on TracePro. The simulation results meet the corresponding standard, which validates the design.
2011, 32(4): 618-622.
Abstract:
In order to enable Ternary Phase-amplitude Filters (TPAFs) to be implemented in commercially-available Spatial Light Modulators (SLMs) to offer good performances in distortion tolerance, clutter noise suppression and correlation peaks sharpness, OT-TPAFs (Optimal Tradeoff TPAFs) were proposed and the design method was researched. The optimal threshold line angle and region of support can be determined by maximizing a single criterion, so the design procedure was simplified. The experimental results indicate, compared with BPOFs (Binary Phase-only Filters), this kind of filters can give sharp correlation peaks for targets within 30 degrees rotation distortion range in complicated background, which enhances the detection veracity of correlation peaks.
In order to enable Ternary Phase-amplitude Filters (TPAFs) to be implemented in commercially-available Spatial Light Modulators (SLMs) to offer good performances in distortion tolerance, clutter noise suppression and correlation peaks sharpness, OT-TPAFs (Optimal Tradeoff TPAFs) were proposed and the design method was researched. The optimal threshold line angle and region of support can be determined by maximizing a single criterion, so the design procedure was simplified. The experimental results indicate, compared with BPOFs (Binary Phase-only Filters), this kind of filters can give sharp correlation peaks for targets within 30 degrees rotation distortion range in complicated background, which enhances the detection veracity of correlation peaks.
2011, 32(4): 623-629.
Abstract:
This paper presents a photonic crystal add-drop filter (ADF) based on ring resonators. The filter was designed in a 2D square lattice dielectric cylinder photonic-crystal structure which consisted of one input port and two output ports. The transmission properties of the ADF with one photonic crystal ring resonator (PCRR) and two PCRRs were studied by time-domain finite-difference method. The results of investigations show that this structure has high drop efficiency in the third communication window, and the signals dropped by ADF can be propagated along upward, downward, forward and backward directions. This structure has the advantages of tunable switch wavelength, broad band, and high normalized transmission rate. It is applicable in the fields of photonic crystal integration and optical device manufacture.
This paper presents a photonic crystal add-drop filter (ADF) based on ring resonators. The filter was designed in a 2D square lattice dielectric cylinder photonic-crystal structure which consisted of one input port and two output ports. The transmission properties of the ADF with one photonic crystal ring resonator (PCRR) and two PCRRs were studied by time-domain finite-difference method. The results of investigations show that this structure has high drop efficiency in the third communication window, and the signals dropped by ADF can be propagated along upward, downward, forward and backward directions. This structure has the advantages of tunable switch wavelength, broad band, and high normalized transmission rate. It is applicable in the fields of photonic crystal integration and optical device manufacture.
2011, 32(4): 630-635.
Abstract:
As a non-contact measurement technique, charge-coupled device (CCD) intersection measurement is used for the coordinates positioning of flying targets. The model of the double CCD intersection positioning system for public diagnosis carrying platform was established. The imaging system with the object height of 8 mm, the lens resolution of 8.3 m and the MTF of greater than 0.5 at 61 lp/mm was designed for the positioning system, as well as the adjustment system which adopted double universal joints structure to achieve the 2D pointing adjustment and processed the video images to offer an accurate pointing to diagnosis equipment. The error analysis results indicated that the positioning accuracy of the system was better than 16 m, and the system could be installed on the front end of the public diagnosis carrying platform.
As a non-contact measurement technique, charge-coupled device (CCD) intersection measurement is used for the coordinates positioning of flying targets. The model of the double CCD intersection positioning system for public diagnosis carrying platform was established. The imaging system with the object height of 8 mm, the lens resolution of 8.3 m and the MTF of greater than 0.5 at 61 lp/mm was designed for the positioning system, as well as the adjustment system which adopted double universal joints structure to achieve the 2D pointing adjustment and processed the video images to offer an accurate pointing to diagnosis equipment. The error analysis results indicated that the positioning accuracy of the system was better than 16 m, and the system could be installed on the front end of the public diagnosis carrying platform.
2011, 32(4): 636-640.
Abstract:
Based on the optical image de-rotation implemented by the transmission mechanism of a panoramic observation sight, the advantages and weaknesses of traditional optical de-rotation methods were analyzed. By simplifying the mechanism, the mathematical model of the controlled object was established. According to the system requirements of real-time controlling and processing, the digital-analog control hybrid circuits were designed, which improved the stability and reliability of the system. A typical instance of the control system was simulated with MATLAB/SIMULINK, the results show that the electric circuit can meet the requirements of stability and real-time processing.
Based on the optical image de-rotation implemented by the transmission mechanism of a panoramic observation sight, the advantages and weaknesses of traditional optical de-rotation methods were analyzed. By simplifying the mechanism, the mathematical model of the controlled object was established. According to the system requirements of real-time controlling and processing, the digital-analog control hybrid circuits were designed, which improved the stability and reliability of the system. A typical instance of the control system was simulated with MATLAB/SIMULINK, the results show that the electric circuit can meet the requirements of stability and real-time processing.
2011, 32(4): 641-645.
Abstract:
A mathematic model for calculating the ellipticity of the output beams in slightly noncoplanar resonators is given. By analyzing the error in the patent registed by R. H. Moore and taking the stress effect of the output mirror into account, the ellipticity of the output beams was analyzed. And it is found that the stress effect of the output mirror has the unsymmetrical influence on the clockwise and counterclockwise ellipticities of output beams. Moreover, the validity of the theoretical analysis is vertified by the experiment. Based on these results, the method proposed by R. H. Moore, S. W. Hammons et al.for aligning the light path can not reduce the magnetic effect by controlling the distortion angle of square ring resonators effectively.
A mathematic model for calculating the ellipticity of the output beams in slightly noncoplanar resonators is given. By analyzing the error in the patent registed by R. H. Moore and taking the stress effect of the output mirror into account, the ellipticity of the output beams was analyzed. And it is found that the stress effect of the output mirror has the unsymmetrical influence on the clockwise and counterclockwise ellipticities of output beams. Moreover, the validity of the theoretical analysis is vertified by the experiment. Based on these results, the method proposed by R. H. Moore, S. W. Hammons et al.for aligning the light path can not reduce the magnetic effect by controlling the distortion angle of square ring resonators effectively.
2011, 32(4): 646-651.
Abstract:
To meet visual tracking requirements in complex environment where obscuration, illumination change and size variation may occur, this paper presents a particle filter algorithm based on posterior probability measurement. Compared with Bhattacharyya coefficient similarity measurement index, the posterior probability measurement index has stronger peak value characteristic. This paper uses the posterior probability index as similarity measurement function, and realizes the tracking algorithm by particle update, propagation, observation and estimation. The video image sequences were tested for object tracking. The experimental results show that only 50% of the image sequences can be scale-adaptive by the traditional algorithm, while this algorithm can converge to the real contrail of object by 25% particles of the traditional algorithm, the obscuration resistant capability is improved, and 90% of image sequences can get scale-adaptive effect.
To meet visual tracking requirements in complex environment where obscuration, illumination change and size variation may occur, this paper presents a particle filter algorithm based on posterior probability measurement. Compared with Bhattacharyya coefficient similarity measurement index, the posterior probability measurement index has stronger peak value characteristic. This paper uses the posterior probability index as similarity measurement function, and realizes the tracking algorithm by particle update, propagation, observation and estimation. The video image sequences were tested for object tracking. The experimental results show that only 50% of the image sequences can be scale-adaptive by the traditional algorithm, while this algorithm can converge to the real contrail of object by 25% particles of the traditional algorithm, the obscuration resistant capability is improved, and 90% of image sequences can get scale-adaptive effect.
2011, 32(4): 652-656.
Abstract:
One advantage of interferential spectrometer is that it provides high-resolution spectrum, which can be used to recognize and analyze objects through spectral matching. The Fourier transform is a necessary step in converting inferferogram to spectrum, while it is complex and time-consuming. A spectral recognition technology based on interferogram matching is proposed without Fourier transform. The interferogram of object to be matched is obtained by interferential spectrometer, and it is matched to the expected one through correlation calculation， which is a relatively rapid process. The simulation result validates the feasibility of the technology.
One advantage of interferential spectrometer is that it provides high-resolution spectrum, which can be used to recognize and analyze objects through spectral matching. The Fourier transform is a necessary step in converting inferferogram to spectrum, while it is complex and time-consuming. A spectral recognition technology based on interferogram matching is proposed without Fourier transform. The interferogram of object to be matched is obtained by interferential spectrometer, and it is matched to the expected one through correlation calculation， which is a relatively rapid process. The simulation result validates the feasibility of the technology.
2011, 32(4): 657-661.
Abstract:
Photography measurement can be used for measuring target flight attitude in test field. Since the target attitude is described by its axis orientation in space, its interpretation can be achieved by obtaining the axis orientation of the target. For the image interpretation, different methods should be adopted to different types of targets. This paper presents three methods for image interpretation: the interpretation based on head-tail spots, the line-based interpretation, and the model-based interpretation.The interpretations of different targets are achieved effectively.
Photography measurement can be used for measuring target flight attitude in test field. Since the target attitude is described by its axis orientation in space, its interpretation can be achieved by obtaining the axis orientation of the target. For the image interpretation, different methods should be adopted to different types of targets. This paper presents three methods for image interpretation: the interpretation based on head-tail spots, the line-based interpretation, and the model-based interpretation.The interpretations of different targets are achieved effectively.
2011, 32(4): 664-666.
Abstract:
Based on range-gate principle, a Nd∶YAG laser, whose frequency was doubled to yield a wavelength of 532 nm, was used as the light source, and rangegated Integrated Circuit Card Device(ICCD) system was used as the receiver. The experiment with range-gated method was conducted in 8 m depth water with diffuse attenuation coefficient k0.45. Maximum underwater detection depth of 7 m and 10 ns image gate were achieved. The experimental results show that the range-gated imaging method is a rapid and effective technology for underwater object detection and reorganization.
Based on range-gate principle, a Nd∶YAG laser, whose frequency was doubled to yield a wavelength of 532 nm, was used as the light source, and rangegated Integrated Circuit Card Device(ICCD) system was used as the receiver. The experiment with range-gated method was conducted in 8 m depth water with diffuse attenuation coefficient k0.45. Maximum underwater detection depth of 7 m and 10 ns image gate were achieved. The experimental results show that the range-gated imaging method is a rapid and effective technology for underwater object detection and reorganization.
2011, 32(4): 667-670.
Abstract:
An adaptive temporal recursive filtering algorithm is developed to improve noise and visual range performance in low level light (LLL) imaging. The proposed algorithm improves the SNR and extends the visual range by adjusting the coefficient of temporal recursive filter. The extension of visual range using the adaptive temporal recursive filtering agrees with the theory, and the experimental results indicate this algorithm can maintain a clear motion image, and improve the noise and visual range performance of LLL imaging system.
An adaptive temporal recursive filtering algorithm is developed to improve noise and visual range performance in low level light (LLL) imaging. The proposed algorithm improves the SNR and extends the visual range by adjusting the coefficient of temporal recursive filter. The extension of visual range using the adaptive temporal recursive filtering agrees with the theory, and the experimental results indicate this algorithm can maintain a clear motion image, and improve the noise and visual range performance of LLL imaging system.
2011, 32(4): 678-682.
Abstract:
Based on the shortcomings of standard median filtering, this paper puts forward two improved median filtering algorithms referred as the weighted fast median filtering algorithm and the weighted adaptive median filtering algorithm. The experiment results with MATLAB show that both of them can retain the original image details and edge nicely. The two improved algorithms are compared and the comparison indicates that the weighted fast median filtering algorithm has a significant effect on low-density impulse noise, while having non-ideal effect on high-density impulse noise, it could improve the speed of median filtering operation and could be used for digital images real-time processing; the weighted adaptive median filtering algorithm could effectively eliminate the high-density impulse noise from polluted images, and it has more superior filtering performance than the standard median filtering while having better robustness on de-noising than the weighted fast median filtering algorithm.
Based on the shortcomings of standard median filtering, this paper puts forward two improved median filtering algorithms referred as the weighted fast median filtering algorithm and the weighted adaptive median filtering algorithm. The experiment results with MATLAB show that both of them can retain the original image details and edge nicely. The two improved algorithms are compared and the comparison indicates that the weighted fast median filtering algorithm has a significant effect on low-density impulse noise, while having non-ideal effect on high-density impulse noise, it could improve the speed of median filtering operation and could be used for digital images real-time processing; the weighted adaptive median filtering algorithm could effectively eliminate the high-density impulse noise from polluted images, and it has more superior filtering performance than the standard median filtering while having better robustness on de-noising than the weighted fast median filtering algorithm.
2011, 32(4): 683-687.
Abstract:
Distortion and mass data are difficult problems in image sequence mosaic on vehicle-borne camera platform. A fast image sequence mosaic method was proposed for solving the problems. Firstly, the distortion was removed after image preprocessing. Secondly, the speeded up robust features (SURF) were extracted from preprocessing images and the features were matched. The rate of feature matching was defined as a similarity measure of frames to extract key frames. Then, by using the improved image registration method without accumulated error, a global model was established. Finally, the image sequence mosaic was obtained through image fusion of the maximum. The experimental results show that the method is robust and fast.
Distortion and mass data are difficult problems in image sequence mosaic on vehicle-borne camera platform. A fast image sequence mosaic method was proposed for solving the problems. Firstly, the distortion was removed after image preprocessing. Secondly, the speeded up robust features (SURF) were extracted from preprocessing images and the features were matched. The rate of feature matching was defined as a similarity measure of frames to extract key frames. Then, by using the improved image registration method without accumulated error, a global model was established. Finally, the image sequence mosaic was obtained through image fusion of the maximum. The experimental results show that the method is robust and fast.
2011, 32(4): 688-692.
Abstract:
Since the portable X-ray machine has been widely used, the de-noising of its images is important. This paper discusses the noise sources and characteristics of the portable X-ray system, proposes a new compound algorithm of image de-noising to overcome the drawbacks of conventional algorithms. This compound algorithm can effectively filter out Gauss noise and impulse noise, while retaining image details. The simulation result verifies the feasibility and efficiency of the proposed method.
Since the portable X-ray machine has been widely used, the de-noising of its images is important. This paper discusses the noise sources and characteristics of the portable X-ray system, proposes a new compound algorithm of image de-noising to overcome the drawbacks of conventional algorithms. This compound algorithm can effectively filter out Gauss noise and impulse noise, while retaining image details. The simulation result verifies the feasibility and efficiency of the proposed method.
2011, 32(4): 671-677.
Abstract:
With the rapid development of image fusion technology, image fusion quality evaluation plays a very important guiding role in selecting or designing image fusion algorithms. Objective image quality assessment is an interesting research subject in the field of image quality assessment. The ideal objective evaluation method is consistent with human perceptual evaluation. The paper gives an overview of existing image fusion quality assessment algorithms. Firstly, basic objective evaluation specifications are presented briefly. Secondly, objective image quality assessment algorithms are classified into 4 categories: based on edge information preservation, based on structural similarity (SSIM), based on information theory and based on contrast. They are introduced with emphasis on their strategies and characteristics. At last, the trends of future research are summarized. Objective image quality assessment considering features of the human visual system or based on specific visual tasks is more and more popular. Quality assessments of no reference image and color fusion image are important development directions in future.
With the rapid development of image fusion technology, image fusion quality evaluation plays a very important guiding role in selecting or designing image fusion algorithms. Objective image quality assessment is an interesting research subject in the field of image quality assessment. The ideal objective evaluation method is consistent with human perceptual evaluation. The paper gives an overview of existing image fusion quality assessment algorithms. Firstly, basic objective evaluation specifications are presented briefly. Secondly, objective image quality assessment algorithms are classified into 4 categories: based on edge information preservation, based on structural similarity (SSIM), based on information theory and based on contrast. They are introduced with emphasis on their strategies and characteristics. At last, the trends of future research are summarized. Objective image quality assessment considering features of the human visual system or based on specific visual tasks is more and more popular. Quality assessments of no reference image and color fusion image are important development directions in future.
2011, 32(4): 693-697.
Abstract:
Talbot-Moir based methods utilizes Talbot self-image effect and amplification of Moir fringe for long focal length measurement. Because of the phase transformation of lens, the measurement based on Talbot effect and Moir fringes of Ronchi gratings is suitable to long focal length. The focal length of measured lens is calculated according to its relation to the slope coefficient of Moir fringes taken with CCD camera. Since the focal length of measured lens is much greater than its thickness,the phase transformation of lens to Gauss light beams is approximately expressed by the phase transformation of thin lens to spherical wave.Therefore, the measurement of long focal length is applicable for both Gauss and non-Gasussian lights. Finally, the concept, error and precision limit are analyzed, and the pitch error of the grating is the major contributor.
Talbot-Moir based methods utilizes Talbot self-image effect and amplification of Moir fringe for long focal length measurement. Because of the phase transformation of lens, the measurement based on Talbot effect and Moir fringes of Ronchi gratings is suitable to long focal length. The focal length of measured lens is calculated according to its relation to the slope coefficient of Moir fringes taken with CCD camera. Since the focal length of measured lens is much greater than its thickness,the phase transformation of lens to Gauss light beams is approximately expressed by the phase transformation of thin lens to spherical wave.Therefore, the measurement of long focal length is applicable for both Gauss and non-Gasussian lights. Finally, the concept, error and precision limit are analyzed, and the pitch error of the grating is the major contributor.
2011, 32(4): 698-704.
Abstract:
The radiant temperature measurement of the flame plays an important role in steel smelt and welding or dynamic launch system for the description of steel components and flying object status, as well as cauterization of the trajectory. Due to its extremely high temperature and transient process, the radiant temperature of the flame can hardly be measured by traditional methods. A novel pyrophotometer based on classical theory of Planck-s law (Blackbody radiation law) and multi-spectral radiation method was put forward. With this pyrophotometer, any spectrum can be selected from the wavelength of 300 nm to 860 nm within 2 ns. The use of hig-resolution diffraction grating and fibers ensures the accuracy of the selected spectrum. This instrument provides accurate radiant temperature measurements of object surface and real-time spectral emissivity. The experiments of high-speed flying object and bromine tungsten bulb were conducted. Experimental results indicate that this method is feasible and accurate.
The radiant temperature measurement of the flame plays an important role in steel smelt and welding or dynamic launch system for the description of steel components and flying object status, as well as cauterization of the trajectory. Due to its extremely high temperature and transient process, the radiant temperature of the flame can hardly be measured by traditional methods. A novel pyrophotometer based on classical theory of Planck-s law (Blackbody radiation law) and multi-spectral radiation method was put forward. With this pyrophotometer, any spectrum can be selected from the wavelength of 300 nm to 860 nm within 2 ns. The use of hig-resolution diffraction grating and fibers ensures the accuracy of the selected spectrum. This instrument provides accurate radiant temperature measurements of object surface and real-time spectral emissivity. The experiments of high-speed flying object and bromine tungsten bulb were conducted. Experimental results indicate that this method is feasible and accurate.
2011, 32(4): 705-708.
Abstract:
Refractive index is one of the basic parameters of optical material. A device for measuring the refractive index in the UV waveband was developed based on right angle illumination method, in which an electro-optical stabilized sight was adopted to detect the ultraviolet (UV) light, a high precision goniometer with gas bearing was adopted to measure the angle, a lock-in amplifier was used to amplify the weak UV voltage signal, customized software was used to analyze the angle value and the variation of light intensity, and computer automatic control was incorporated to realize measurement automation. Refractive indices of quartz glass in 250 nm~450 nm were measured and the measurement results were given.
Refractive index is one of the basic parameters of optical material. A device for measuring the refractive index in the UV waveband was developed based on right angle illumination method, in which an electro-optical stabilized sight was adopted to detect the ultraviolet (UV) light, a high precision goniometer with gas bearing was adopted to measure the angle, a lock-in amplifier was used to amplify the weak UV voltage signal, customized software was used to analyze the angle value and the variation of light intensity, and computer automatic control was incorporated to realize measurement automation. Refractive indices of quartz glass in 250 nm~450 nm were measured and the measurement results were given.
2011, 32(4): 709-713.
Abstract:
A real-time test system for moving targets was designed to test the system coordination accuracy of weapon system operating at 0-fly mode, and measure the tracking and pointing error. In the surveillance of long range moving targets, the system adopted double optical paths, a binocular tube of long focus and short focus, and an electric switching device to carry out the real-time observation for long and short range targets. The binocular tube was installed at the same machine body to ensure the concentricity by means of eccentric frame and eccentric ring. The fixture had fine tuning mechanism of pitch and azimuth to regulate the boresight between optical axis and gun axis. The measurement data with high precision and high fidelity were obtained. The static angle measurement accuracy of the tubes with 50 mm and 300 mm focal length was tested, and the experimental results showed that the accuracy was less than 0.4 mrad and 0.2 mrad respectively, which met the target requirements. This modular test system is reliable and can be widely used in military and civil applications.
A real-time test system for moving targets was designed to test the system coordination accuracy of weapon system operating at 0-fly mode, and measure the tracking and pointing error. In the surveillance of long range moving targets, the system adopted double optical paths, a binocular tube of long focus and short focus, and an electric switching device to carry out the real-time observation for long and short range targets. The binocular tube was installed at the same machine body to ensure the concentricity by means of eccentric frame and eccentric ring. The fixture had fine tuning mechanism of pitch and azimuth to regulate the boresight between optical axis and gun axis. The measurement data with high precision and high fidelity were obtained. The static angle measurement accuracy of the tubes with 50 mm and 300 mm focal length was tested, and the experimental results showed that the accuracy was less than 0.4 mrad and 0.2 mrad respectively, which met the target requirements. This modular test system is reliable and can be widely used in military and civil applications.
2011, 32(4): 714-717.
Abstract:
In the applications of collimator with large diameter and long focal length, the position accuracy of the collimator objective and its sensitive tuning during the process of assembly and adjustment are very important. This paper introduces the primary mirror structure of the large-diameter optical collimator and its test method, presents the assembly and adjustment methods for optical systems with three different apertures, analyzes the primary mirror structure and tuning method of the 700 mm collimator, and uses 4D interferometer to detect the effects of assembling-adjusting device on surface shape. The results show that the assembling-adjusting device moves freely and the movement has no impact on the precision of surface shape, the pitch and rotation accuracies are better than 3 and have six degrees of freedom.
In the applications of collimator with large diameter and long focal length, the position accuracy of the collimator objective and its sensitive tuning during the process of assembly and adjustment are very important. This paper introduces the primary mirror structure of the large-diameter optical collimator and its test method, presents the assembly and adjustment methods for optical systems with three different apertures, analyzes the primary mirror structure and tuning method of the 700 mm collimator, and uses 4D interferometer to detect the effects of assembling-adjusting device on surface shape. The results show that the assembling-adjusting device moves freely and the movement has no impact on the precision of surface shape, the pitch and rotation accuracies are better than 3 and have six degrees of freedom.
2011, 32(4): 718-722.
Abstract:
Parallax test result is subjective and difficult to give quantitative results during head-up display (HUD) debugging process. Based on machine vision, a set of automatic HUD parallax detection device was developed. The device consists of a traditional optical system and a CCD optical coupling device. The CCD optical coupling device was manually adjusted to image the large field of view collimator reticule, the image was processed and parallax was given based on calculation. Comparing the results obtained from this device with those of manual testing, the results show that parallax instrument greatly improved the HUD parallax detection accuracy, which reaches 28.
Parallax test result is subjective and difficult to give quantitative results during head-up display (HUD) debugging process. Based on machine vision, a set of automatic HUD parallax detection device was developed. The device consists of a traditional optical system and a CCD optical coupling device. The CCD optical coupling device was manually adjusted to image the large field of view collimator reticule, the image was processed and parallax was given based on calculation. Comparing the results obtained from this device with those of manual testing, the results show that parallax instrument greatly improved the HUD parallax detection accuracy, which reaches 28.
2011, 32(4): 723-729.
Abstract:
A set of all fiber optical beam breakout measurement system was designed and used in interior projectile velocity measurement. This system was based on the principle of optical beam breakout and advanced photoelectric technique. More than 100 shots were conducted on the one stage gas gun, two stage gas gun and powder gun. The result analysis showed that this projectile velocity measurement system could meet the accuracy and reliability requirements in precise physical experiments. The velocity measurement measurement extending uncertainty of this system is less than 0.8%. The velocity measurement range of this system is from tens of m/s to 7 km/s.
A set of all fiber optical beam breakout measurement system was designed and used in interior projectile velocity measurement. This system was based on the principle of optical beam breakout and advanced photoelectric technique. More than 100 shots were conducted on the one stage gas gun, two stage gas gun and powder gun. The result analysis showed that this projectile velocity measurement system could meet the accuracy and reliability requirements in precise physical experiments. The velocity measurement measurement extending uncertainty of this system is less than 0.8%. The velocity measurement range of this system is from tens of m/s to 7 km/s.
2011, 32(4): 730-735.
Abstract:
Nonlinear errors were introduced by non-ideal 1/4 wave plate and polarizing beam splitter (PBS) when using a homodyne Mach-Zehnder interferometer to monitor the optical frequency of a tunable laser. The error formula of the system was theoretically deduced by mathematically modeling the interferometer with Jones matrix. Theoretical analysis and numerical simulation indicated that the nonlinear errors of the system were the linear superposition of first and second harmonic wave errors, the first harmonic wave errors were mainly caused by the unbalance of the two PBSs- alignment errors, the second were mainly caused by wave-plate-s alignment errors, PBS-s alignment errors and wave plate-s phase delay errors, and the overall second harmonic wave errors were approximately the linear superposition of the errors caused independently by these three error sources, errors caused by polarization leakage of the PBS could be neglected if the leakage was small.
Nonlinear errors were introduced by non-ideal 1/4 wave plate and polarizing beam splitter (PBS) when using a homodyne Mach-Zehnder interferometer to monitor the optical frequency of a tunable laser. The error formula of the system was theoretically deduced by mathematically modeling the interferometer with Jones matrix. Theoretical analysis and numerical simulation indicated that the nonlinear errors of the system were the linear superposition of first and second harmonic wave errors, the first harmonic wave errors were mainly caused by the unbalance of the two PBSs- alignment errors, the second were mainly caused by wave-plate-s alignment errors, PBS-s alignment errors and wave plate-s phase delay errors, and the overall second harmonic wave errors were approximately the linear superposition of the errors caused independently by these three error sources, errors caused by polarization leakage of the PBS could be neglected if the leakage was small.
2011, 32(4): 736-738.
Abstract:
A three-dimensional reconstruction method of large-size object was presented. A sinusoidal grating was projected to the surface of the object, and a deformed fringe intensity image of sub-region was collected through the camera. Correlation algorithm was used to confirm the accurate overlapped area of the sub-region images, and a deformed fringe intensity image of the object was obtained by splicing. The object-s three-dimensional image was obtained by Fourier transform profilometry, and the experimental results was presented.
A three-dimensional reconstruction method of large-size object was presented. A sinusoidal grating was projected to the surface of the object, and a deformed fringe intensity image of sub-region was collected through the camera. Correlation algorithm was used to confirm the accurate overlapped area of the sub-region images, and a deformed fringe intensity image of the object was obtained by splicing. The object-s three-dimensional image was obtained by Fourier transform profilometry, and the experimental results was presented.
2011, 32(4): 739-743.
Abstract:
The dynamic linearity is an important technical parameter for instantaneous radiation pyrometer, which has great impact on measurement accuracy. In order to study the factors which influence the dynamic linearity of radiation pyrometer, a test technique is proposed for measuring pulse dynamic linearity, which is based on pulse LED and high linearity photodetector. An instantaneous radiation pyrometer，based on photomultiplier tubes (PMT)，is tested and measured under various conditions. The measurement results show that the factors such as PMT type, voltage divider and operation voltage have impact on the dynamic current linearity of pyrometer.
The dynamic linearity is an important technical parameter for instantaneous radiation pyrometer, which has great impact on measurement accuracy. In order to study the factors which influence the dynamic linearity of radiation pyrometer, a test technique is proposed for measuring pulse dynamic linearity, which is based on pulse LED and high linearity photodetector. An instantaneous radiation pyrometer，based on photomultiplier tubes (PMT)，is tested and measured under various conditions. The measurement results show that the factors such as PMT type, voltage divider and operation voltage have impact on the dynamic current linearity of pyrometer.
2011, 32(4): 744-748.
Abstract:
Conventional fiber cladding only has leaking evanescent wave with low energy, which prevents the application of cladding sensing. Guiding light in the full cladding is expected to improve the sensitivity of hollow-core photonic crystal fiber (HC-PCF) application for material sensing. An approach to increase the energy transmitting in the cladding was theoretical analyzed. The light guidance experiments of air-hole cladding of HC-PCF were carried out by using a cold light source and a laser. The contrast experiments between total internal reflection-photonic crystal fiber (TIR-PCF) and single-mode fiber (SMF) were done. The results indicated that, by choosing appropriate wavelength, the light in HC-PCF leaked entirely into the cladding and propagated in the air-suspended silica cores between the air holes, which was different from TIP-PCF and SMF-28.
Conventional fiber cladding only has leaking evanescent wave with low energy, which prevents the application of cladding sensing. Guiding light in the full cladding is expected to improve the sensitivity of hollow-core photonic crystal fiber (HC-PCF) application for material sensing. An approach to increase the energy transmitting in the cladding was theoretical analyzed. The light guidance experiments of air-hole cladding of HC-PCF were carried out by using a cold light source and a laser. The contrast experiments between total internal reflection-photonic crystal fiber (TIR-PCF) and single-mode fiber (SMF) were done. The results indicated that, by choosing appropriate wavelength, the light in HC-PCF leaked entirely into the cladding and propagated in the air-suspended silica cores between the air holes, which was different from TIP-PCF and SMF-28.
2011, 32(4): 749-752.
Abstract:
The single-polarization single-mode (SPSM) micro-structure polymer optical fiber (MPOF) was designed based on polymethyl methacrylate (PMMA). A full vector finite element method together with beam propagation method was adopted to study the SPSM properties. By optimal designing, we found that only one polarization state of the fundamental mode could be transmitted within the visible light region from 0.52 m to 0.63 m according to the different cutoff wavelengths of the two orthogonal polarization modes. For MPOF with 11 rings of hexagonally arrayed air-holes, the confinement loss of 1.13 dB/m was obtained at 0.57 m. This low loss SPSM-MPOF can greatly eliminate the polarization crosstalk and polarization mode dispersion.
The single-polarization single-mode (SPSM) micro-structure polymer optical fiber (MPOF) was designed based on polymethyl methacrylate (PMMA). A full vector finite element method together with beam propagation method was adopted to study the SPSM properties. By optimal designing, we found that only one polarization state of the fundamental mode could be transmitted within the visible light region from 0.52 m to 0.63 m according to the different cutoff wavelengths of the two orthogonal polarization modes. For MPOF with 11 rings of hexagonally arrayed air-holes, the confinement loss of 1.13 dB/m was obtained at 0.57 m. This low loss SPSM-MPOF can greatly eliminate the polarization crosstalk and polarization mode dispersion.
2011, 32(4): 753-760.
Abstract:
The ion beam figuring (IBF) technology is widely used for precision and deterministic process. This paper introduced the principles and characteristics of IBF, described its development status at home and abroad, summarized the research focus of IBF such as the technology to control the mid-high spatial frequency error, the algorithm to solve dwell time, and the processing technique.
The ion beam figuring (IBF) technology is widely used for precision and deterministic process. This paper introduced the principles and characteristics of IBF, described its development status at home and abroad, summarized the research focus of IBF such as the technology to control the mid-high spatial frequency error, the algorithm to solve dwell time, and the processing technique.
2011, 32(4): 761-766.
Abstract:
Modified SiO2 sols were prepared by base-catalyzed co-hydrolysis and condensation reaction of tetraethylorthosilicate (TEOS) and hexamethyldisilazane (HMDS). The effects of polyvinyl pyrrolidone (PVP) on the properties of coatings were investigated. The single film of SiO2 was deposited on fused silica by dip coating method. The coatings with different components were processed with heat treatment or ultraviolet irradiation, and then modified by the octadecyltrichlorosilane (OTS)/toluene solution. The well water-repellent nano-silica films were obtained by self-assembled technique. The influences of different treatments on film-s transmission spectra, contact angle, surface morphology and laser damage threshold were analyzed. The results indicated the coatings modified by OTS exhibited excellent hydrophobic properties and the performances of laser damage thresholds were improved. The surface of SiO2 thin film became smoother when PVP was added.
Modified SiO2 sols were prepared by base-catalyzed co-hydrolysis and condensation reaction of tetraethylorthosilicate (TEOS) and hexamethyldisilazane (HMDS). The effects of polyvinyl pyrrolidone (PVP) on the properties of coatings were investigated. The single film of SiO2 was deposited on fused silica by dip coating method. The coatings with different components were processed with heat treatment or ultraviolet irradiation, and then modified by the octadecyltrichlorosilane (OTS)/toluene solution. The well water-repellent nano-silica films were obtained by self-assembled technique. The influences of different treatments on film-s transmission spectra, contact angle, surface morphology and laser damage threshold were analyzed. The results indicated the coatings modified by OTS exhibited excellent hydrophobic properties and the performances of laser damage thresholds were improved. The surface of SiO2 thin film became smoother when PVP was added.
2011, 32(4): 767-772.
Abstract:
Switch-zoom dual field-of-view long-wave infrade (LWIR) telescopes are widely used in IR system，and they have the advantages of high transmission in narrow field view (FOV) and high resolution in wide FOV. This paper established the configuration of a switch-zoom dual FOV telescope, explained the athermalization theory of the switch-zoom dual FOV telescope, and designed a passively athermalised switch-zoom dual FOV LWIR telescope operating in 7.7 m~10.3 m. Diffractive surface and aspheric surface were used to improve the quality of optical system.The MTF was 0.45 @18 lp/mm at -55℃~+70℃. Finally, 2 other lenses were designed based on the designing result of the switch-zoom dual FOV telescope, which indicated that the configuration and arrangement of the passively athermalised switch-zoom dual FOV telescope are applicale in a variety of designs.
Switch-zoom dual field-of-view long-wave infrade (LWIR) telescopes are widely used in IR system，and they have the advantages of high transmission in narrow field view (FOV) and high resolution in wide FOV. This paper established the configuration of a switch-zoom dual FOV telescope, explained the athermalization theory of the switch-zoom dual FOV telescope, and designed a passively athermalised switch-zoom dual FOV LWIR telescope operating in 7.7 m~10.3 m. Diffractive surface and aspheric surface were used to improve the quality of optical system.The MTF was 0.45 @18 lp/mm at -55℃~+70℃. Finally, 2 other lenses were designed based on the designing result of the switch-zoom dual FOV telescope, which indicated that the configuration and arrangement of the passively athermalised switch-zoom dual FOV telescope are applicale in a variety of designs.
2011, 32(4): 773-778.
Abstract:
A fast multi-rule track initiation algorithm used in an infrared staring tracking system is proposed to overcome the deficiency of conventional track initiation algorithm. Based on the analysis of the target signatures and its kinematics in the infrared staring system, an initiation rule for determining the threat probability and course variance of low-speed or even static targets with high threat probability or targets with fragmentary plots is put forward, and fast track of these targets in the staring system is initiated. Simulation result indicates that the algorithm controls the probability of false track below 10%, and initiates tracks after only 3 or 4 sampling periods. The validity and robustness of the algorithm is verified in clutter environment.
A fast multi-rule track initiation algorithm used in an infrared staring tracking system is proposed to overcome the deficiency of conventional track initiation algorithm. Based on the analysis of the target signatures and its kinematics in the infrared staring system, an initiation rule for determining the threat probability and course variance of low-speed or even static targets with high threat probability or targets with fragmentary plots is put forward, and fast track of these targets in the staring system is initiated. Simulation result indicates that the algorithm controls the probability of false track below 10%, and initiates tracks after only 3 or 4 sampling periods. The validity and robustness of the algorithm is verified in clutter environment.
2011, 32(4): 779-783.
Abstract:
Passive dynamic FTIR spectrometer can be used for the spectral analysis of environmental radiation, and infrared signal detection plays an important role in spectrometry. Based on the design concept of circuit, it requires high signal to noise ratio (SNR), high sensitivity, small temperature drift and strong antijamming capability. Using a filtered power supply, and a high-speed, low-noise and high-precision operational amplifier, a circuit was designed for IR signal detection. The infrared spectrometer with the IR signal detection circuit was used to sense the atmosphere remotely, and the experimental results were analyzed and discussed. Experimental results show that the detection circuit is operated with good stability, high SNR, and high accuracy, which enables the IR remote sensing of atmospheric environment.
Passive dynamic FTIR spectrometer can be used for the spectral analysis of environmental radiation, and infrared signal detection plays an important role in spectrometry. Based on the design concept of circuit, it requires high signal to noise ratio (SNR), high sensitivity, small temperature drift and strong antijamming capability. Using a filtered power supply, and a high-speed, low-noise and high-precision operational amplifier, a circuit was designed for IR signal detection. The infrared spectrometer with the IR signal detection circuit was used to sense the atmosphere remotely, and the experimental results were analyzed and discussed. Experimental results show that the detection circuit is operated with good stability, high SNR, and high accuracy, which enables the IR remote sensing of atmospheric environment.
2011, 32(4): 784-790.
Abstract:
Based on electromagnetic similitude theory, the scale model of an airport environment equipped with a microwave landing system (MLS) was set up to simulate the propagation of the navigation signal transmitted by the MLS according to the propagation of the laser in the scale model of the airport. This simulation system used the MATLAB/RTW rapid prototyping target (i.e. xPC target) to carry out the real-time simulation of the airborne receiver signal processing. The critical technologies of the optical subsystem for this simulation system were researched. The azimuth error curve of the flight test of an airport environment in U.S. was obtained, and the experimental results agreed with flight test results, which proved the effectiveness of the MLS simulation test.
Based on electromagnetic similitude theory, the scale model of an airport environment equipped with a microwave landing system (MLS) was set up to simulate the propagation of the navigation signal transmitted by the MLS according to the propagation of the laser in the scale model of the airport. This simulation system used the MATLAB/RTW rapid prototyping target (i.e. xPC target) to carry out the real-time simulation of the airborne receiver signal processing. The critical technologies of the optical subsystem for this simulation system were researched. The azimuth error curve of the flight test of an airport environment in U.S. was obtained, and the experimental results agreed with flight test results, which proved the effectiveness of the MLS simulation test.
2011, 32(4): 791-796.
Abstract:
The stability of laser output power is one of the important parameters to evaluate the laser performance. This paper introduced the operation principle and the structural features of a laser-diode (LD) end-pumped single-frequency Nd∶YAG laser at 1 064 nm , analyzed the main factors that affected the stability of the Nd∶YAG laser output power , proposed and experimentally studied a control scheme for stabilizing the Nd∶YAG laser output power. Since the output power of the Nd∶YAG laser was proportional to the LD-s injection current when the temperature of the LD and the Nd∶YAG crystal rod was stable, the control scheme strictly controlled the temperature of the LD and the Nd∶YAG crystal rod, and the LD-s injection current was adjusted through a negative feedback control system when the Nd∶YAG laser output power fluctuated. The experimental results indicated that when the output power of the LD-pumped single-frequency Nd∶YAG laser at 1 064 nm was about 11.5 mW, the laser output power stability was better than 1.3％ within 130 min using the designed control system.
The stability of laser output power is one of the important parameters to evaluate the laser performance. This paper introduced the operation principle and the structural features of a laser-diode (LD) end-pumped single-frequency Nd∶YAG laser at 1 064 nm , analyzed the main factors that affected the stability of the Nd∶YAG laser output power , proposed and experimentally studied a control scheme for stabilizing the Nd∶YAG laser output power. Since the output power of the Nd∶YAG laser was proportional to the LD-s injection current when the temperature of the LD and the Nd∶YAG crystal rod was stable, the control scheme strictly controlled the temperature of the LD and the Nd∶YAG crystal rod, and the LD-s injection current was adjusted through a negative feedback control system when the Nd∶YAG laser output power fluctuated. The experimental results indicated that when the output power of the LD-pumped single-frequency Nd∶YAG laser at 1 064 nm was about 11.5 mW, the laser output power stability was better than 1.3％ within 130 min using the designed control system.
2011, 32(4): 797-800.
Abstract:
Based on the traditional optical scanning and the effective combination of a high-frequency resonant scanner and a galvanometer scanner, a novel highspeed laser scanning method with sampling rate of 4M/s was proposed. The hardware platform of control system was built, the PC-client and microcontroller software were designed. The experimental results prove that the control system is rapid and stable, can realize real-time confocal scanning imaging.
Based on the traditional optical scanning and the effective combination of a high-frequency resonant scanner and a galvanometer scanner, a novel highspeed laser scanning method with sampling rate of 4M/s was proposed. The hardware platform of control system was built, the PC-client and microcontroller software were designed. The experimental results prove that the control system is rapid and stable, can realize real-time confocal scanning imaging.
2011, 32(4): 801-805.
Abstract:
Electro-optical detectors are widely used in many fields. However, temperature rise due to the absorption of laser and other phenomena may damage detectors. Using thermal elastic theory, the investigation on K9 material radiated by CO2 laser is done. According to the two-dimensional planar model, the transient distributions of temperature field and thermal stress field which result from laser radiation on semiconductor material are obtained by analytical calculation. The results show that the K9 glass damage threshold of laser radiation is dependent on the radiation time and beam radius. Under the same conditions, the thermal stress damage threshold is lower than the melting damage threshold, so the damage reason of K9 glass material is thermal stress damage.
Electro-optical detectors are widely used in many fields. However, temperature rise due to the absorption of laser and other phenomena may damage detectors. Using thermal elastic theory, the investigation on K9 material radiated by CO2 laser is done. According to the two-dimensional planar model, the transient distributions of temperature field and thermal stress field which result from laser radiation on semiconductor material are obtained by analytical calculation. The results show that the K9 glass damage threshold of laser radiation is dependent on the radiation time and beam radius. Under the same conditions, the thermal stress damage threshold is lower than the melting damage threshold, so the damage reason of K9 glass material is thermal stress damage.
2011, 32(4): 806-809.
Abstract:
A microscopic imaging system with a 405 nm blue laser as light source and a 0.65 numerical aperture objective lens was studied. We carried on the microscopic imaging for CD-R and DVD-R discs by using the system, eliminated the laser imaging speckles, observed and stored the microscopic images in real time by utilizing the CCD image sensor technology and the image capturing technology, and compared them with the one using halogen lamp as the light source. The results showed that when this system used the white light of halogen lamp as the light source, the information points on CD-R disc could be clearly resolved, while the image on DVD-R disc couldn-t; however, images on both CD-R and DVD-R discs were clear when the 405 nm laser was used as the light source, and the resolution was better than 400 nm, significantly higher than the ordinary halogen lamp white lighting system.
A microscopic imaging system with a 405 nm blue laser as light source and a 0.65 numerical aperture objective lens was studied. We carried on the microscopic imaging for CD-R and DVD-R discs by using the system, eliminated the laser imaging speckles, observed and stored the microscopic images in real time by utilizing the CCD image sensor technology and the image capturing technology, and compared them with the one using halogen lamp as the light source. The results showed that when this system used the white light of halogen lamp as the light source, the information points on CD-R disc could be clearly resolved, while the image on DVD-R disc couldn-t; however, images on both CD-R and DVD-R discs were clear when the 405 nm laser was used as the light source, and the resolution was better than 400 nm, significantly higher than the ordinary halogen lamp white lighting system.
2011, 32(4): 810-816.
Abstract:
Based on the two-temperature theory, a numerical model to solve the heating process in surface vicinity irradiated by ultrashort pulse laser is established to investigate the influence of temperature-dependent properties of material on temperature field in metal(Au) irradiated by ultrashort pulse laser. Taking account of the temperature-dependent properties of material which includes the electron-phonon coupling factor, electron thermal conductivity, electron heat capacity, lattice heat capacity, as well as the spatial and temporal shapes of the laser pulse, the transient temperature field irradiated by ultrashort pulse laser in metal(Au) is numerical simulated by the finite element method (FEM). The electron and lattice transient temperature distributions in the vicinity of laser-irradiated region are obtained. Moreover, the temperature fields obtained from considering and neglecting the temperature-dependent properties of material are compared. The numerical results indicate that the temperature-dependent properties of material make the electron and lattice temperatures rise faster, the temperature maximum and the irradiated become higher. This study establishes a theory basis for stress field and ultrasound field in metal generated by femto-second laser.
Based on the two-temperature theory, a numerical model to solve the heating process in surface vicinity irradiated by ultrashort pulse laser is established to investigate the influence of temperature-dependent properties of material on temperature field in metal(Au) irradiated by ultrashort pulse laser. Taking account of the temperature-dependent properties of material which includes the electron-phonon coupling factor, electron thermal conductivity, electron heat capacity, lattice heat capacity, as well as the spatial and temporal shapes of the laser pulse, the transient temperature field irradiated by ultrashort pulse laser in metal(Au) is numerical simulated by the finite element method (FEM). The electron and lattice transient temperature distributions in the vicinity of laser-irradiated region are obtained. Moreover, the temperature fields obtained from considering and neglecting the temperature-dependent properties of material are compared. The numerical results indicate that the temperature-dependent properties of material make the electron and lattice temperatures rise faster, the temperature maximum and the irradiated become higher. This study establishes a theory basis for stress field and ultrasound field in metal generated by femto-second laser.
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