2014 Vol. 7, No. 5
2014, 7(5): 759-767.
doi:10.3788/CO.20140705.0759
Abstract
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Abstract:
To overcome the limitations of inertia weight adjustment mechanism when the particle swarm optimization algorithm is applied to object tracking, an improved particle swarm optimization object tracking algorithm is proposed. Firstly, the object and the parameters in particle swarm optimization algorithm are initialized. Secondly, the inertia weight adjustment mechanism is improved by using the evolution rate of particle, and the inertia weight is achieved by taking the conditions of different particles in each generation into consideration. Then the speed, the position, the individual optimum and the global optimum of the particles are updated simultaneously while the next iteration is proceeding. Finally, the area which has the largest similarity function value is defined as the object by comparing the fitness value of each particle with the others. Experimental results indicate that the method reduces the iterations to obtain the same fitness value, and improves the operation efficiency by 42.9% in comparison with the particle swarm optimization object tracking method which uses self-adapted inertia weight adjustment mechanism. The accurate positioning of the object is achieved in the case of the similarity function presenting multimodal, and the method is well adapted to the situation when partial occlusion occurs in object tracking.
To overcome the limitations of inertia weight adjustment mechanism when the particle swarm optimization algorithm is applied to object tracking, an improved particle swarm optimization object tracking algorithm is proposed. Firstly, the object and the parameters in particle swarm optimization algorithm are initialized. Secondly, the inertia weight adjustment mechanism is improved by using the evolution rate of particle, and the inertia weight is achieved by taking the conditions of different particles in each generation into consideration. Then the speed, the position, the individual optimum and the global optimum of the particles are updated simultaneously while the next iteration is proceeding. Finally, the area which has the largest similarity function value is defined as the object by comparing the fitness value of each particle with the others. Experimental results indicate that the method reduces the iterations to obtain the same fitness value, and improves the operation efficiency by 42.9% in comparison with the particle swarm optimization object tracking method which uses self-adapted inertia weight adjustment mechanism. The accurate positioning of the object is achieved in the case of the similarity function presenting multimodal, and the method is well adapted to the situation when partial occlusion occurs in object tracking.
2014, 7(5): 786-793.
doi:10.3788/CO.20140705.0786
Abstract:
We proposed a method to accurately acquire the sin wave curve of strap-down north seeking signal acquisition system at different latitudes. According to the current value of dynamically tuned gyro output at different latitude we designed a system which can automatically adjust the sample resistor value using digital potentiometer. The data processing system calculates the latitude automatically based on dynamically tuned gyro signal and then the signal acquisition system resets the acquisition resistor value, and thus we can acquire the sin wave curve efficiently. Using this method we ensure that the north finder can meet the accuracy requirements at different geographical latitudes, and has strong adaptability and high stability.
We proposed a method to accurately acquire the sin wave curve of strap-down north seeking signal acquisition system at different latitudes. According to the current value of dynamically tuned gyro output at different latitude we designed a system which can automatically adjust the sample resistor value using digital potentiometer. The data processing system calculates the latitude automatically based on dynamically tuned gyro signal and then the signal acquisition system resets the acquisition resistor value, and thus we can acquire the sin wave curve efficiently. Using this method we ensure that the north finder can meet the accuracy requirements at different geographical latitudes, and has strong adaptability and high stability.
2014, 7(5): 768-778.
doi:10.3788/CO.20140705.0768
Abstract:
In order to quickly navigate with the known rough azimuth and location information by three FOVs positioning and orientation device, a fast recognition method for local star pattern is proposed. First, we analyse the reasons of the low efficiency when performing the stars identification using global recognition database. Next, we note that it is a preferred method to perform star identification in one FOV firstly and identify the remaining stars between different FVOs, and give the angular distance error threshold. Then, we propose a method to generate the local recognition database, which can reduce the redundancy of identification information and improve recognition efficiency. The simulaion and field experiment results show that the correct identification rate using this recognition method is improved up to 99.19%, and rocognition time is about 24.3 ms, which can satisfy the system requirements for fast and efficient navigation. It also proves the correctness of the preferred recognition order.
In order to quickly navigate with the known rough azimuth and location information by three FOVs positioning and orientation device, a fast recognition method for local star pattern is proposed. First, we analyse the reasons of the low efficiency when performing the stars identification using global recognition database. Next, we note that it is a preferred method to perform star identification in one FOV firstly and identify the remaining stars between different FVOs, and give the angular distance error threshold. Then, we propose a method to generate the local recognition database, which can reduce the redundancy of identification information and improve recognition efficiency. The simulaion and field experiment results show that the correct identification rate using this recognition method is improved up to 99.19%, and rocognition time is about 24.3 ms, which can satisfy the system requirements for fast and efficient navigation. It also proves the correctness of the preferred recognition order.
2014, 7(5): 779-785.
doi:10.3788/CO.20140705.0779
Abstract:
Image segmentation based on level set method is one of the most widely used methods in segmentation domain. Due to a large field of view for aerial image, traditional methods usually can not obtain a global segmentation, and segmentation result is often very poor. In this paper, a new segmentation method with region information for aerial image is proposed. First, a new signed press function is proposed to enhance the capture range, which also can obtain global segmentation result. Second, compared with Chan-Vese model, proposed model is not limited by initial condition, and can enhance the capture range further. Third, proposed model utilizes the region information of an image, which can automatically segment inside and outside of an object simultaneously. In the proposed model, level set function doesn't need to be initialized to signed distance function, which can reduce a lot of computation cost. Moreover, the proposed model has no curvature item compared with traditional level set method, and is easy for numerical implementation. Experiment results demonstrate that proposed model has a higher accuracy of 3%, and 6 times faster than GAC model and Chan-Vese model.
Image segmentation based on level set method is one of the most widely used methods in segmentation domain. Due to a large field of view for aerial image, traditional methods usually can not obtain a global segmentation, and segmentation result is often very poor. In this paper, a new segmentation method with region information for aerial image is proposed. First, a new signed press function is proposed to enhance the capture range, which also can obtain global segmentation result. Second, compared with Chan-Vese model, proposed model is not limited by initial condition, and can enhance the capture range further. Third, proposed model utilizes the region information of an image, which can automatically segment inside and outside of an object simultaneously. In the proposed model, level set function doesn't need to be initialized to signed distance function, which can reduce a lot of computation cost. Moreover, the proposed model has no curvature item compared with traditional level set method, and is easy for numerical implementation. Experiment results demonstrate that proposed model has a higher accuracy of 3%, and 6 times faster than GAC model and Chan-Vese model.
2014, 7(5): 794-800.
doi:10.3788/CO.20140705.0794
Abstract:
To decrease the risk of bilirubin encephalopathy and minimize the need for exchange transfusion effectively,the most efficient absorption spectrum of standard bilirubin tested by the experiment was regarded as the target spectrum. On the basis of spectral constructing theory, monochromatic light-emitting diodes(LEDs) with different peak wavelength and full width at half maximum(FWHM) were used as matching sources. The simple genetic algorithm(SGA) was first proposed as the spectral matching method in this study. The optimal combination ratios of LEDs were obtained by calculating the non-negative least square of the overdetermined equations. The required LED number at each peak wavelength was then calculated. Simulation experimental results show that the fitting spectrum is very comparable to the target spectrum with 98.39% matching degree, and a new spectral power distribution of LED-based jaundice therapeutic device was obtained finally. With simplicity, high efficiency, and small fitting error, this algorithm is very suitable for the study of LED-based spectral power distribution matching technology.
To decrease the risk of bilirubin encephalopathy and minimize the need for exchange transfusion effectively,the most efficient absorption spectrum of standard bilirubin tested by the experiment was regarded as the target spectrum. On the basis of spectral constructing theory, monochromatic light-emitting diodes(LEDs) with different peak wavelength and full width at half maximum(FWHM) were used as matching sources. The simple genetic algorithm(SGA) was first proposed as the spectral matching method in this study. The optimal combination ratios of LEDs were obtained by calculating the non-negative least square of the overdetermined equations. The required LED number at each peak wavelength was then calculated. Simulation experimental results show that the fitting spectrum is very comparable to the target spectrum with 98.39% matching degree, and a new spectral power distribution of LED-based jaundice therapeutic device was obtained finally. With simplicity, high efficiency, and small fitting error, this algorithm is very suitable for the study of LED-based spectral power distribution matching technology.
2014, 7(5): 844-854.
doi:10.3788/CO.20140705.0844
Abstract:
In this paper, a build-up aspherical solar concentrating mirror and its design method are presented. It is composed of 38 pieces of revolution surfaces, and each piece of revolution surface is the part of the aspheric surface defined by a set of specific coefficients C,a2,a4,a6,a8,a10. According to the even aspherical equation and the law of reflection in vector form, the relationship between the direction vectors of rays of light reflected from the inner wall of aspheric surface and the coefficients of an aspherical equation, C,a2,a4,a6,a8,a10, has been derived. By appropriately choosing these aspherical coefficients, namely, appropriately adjusting an aspherical surface type, the reflected light beam can have specific direction vectors, which can make the sunbeams incident on an aspherical inner wall focus on a particular area and form a small spot. Each group of specific coefficients is obtained by using particle swarm optimization algorithm. The focusing effect of the solar concentrating mirror with the specific coefficients is demonstrated by using computer simulations and proved experimentally. The theoretical compression ratio for this concentrating mirror is 330:1. The focused spot can be used as a high temperature heat source and the concentrating mirror can be used in a solar heating device.
In this paper, a build-up aspherical solar concentrating mirror and its design method are presented. It is composed of 38 pieces of revolution surfaces, and each piece of revolution surface is the part of the aspheric surface defined by a set of specific coefficients C,a2,a4,a6,a8,a10. According to the even aspherical equation and the law of reflection in vector form, the relationship between the direction vectors of rays of light reflected from the inner wall of aspheric surface and the coefficients of an aspherical equation, C,a2,a4,a6,a8,a10, has been derived. By appropriately choosing these aspherical coefficients, namely, appropriately adjusting an aspherical surface type, the reflected light beam can have specific direction vectors, which can make the sunbeams incident on an aspherical inner wall focus on a particular area and form a small spot. Each group of specific coefficients is obtained by using particle swarm optimization algorithm. The focusing effect of the solar concentrating mirror with the specific coefficients is demonstrated by using computer simulations and proved experimentally. The theoretical compression ratio for this concentrating mirror is 330:1. The focused spot can be used as a high temperature heat source and the concentrating mirror can be used in a solar heating device.
2014, 7(5): 837-843.
doi:10.3788/CO.20140705.0837
Abstract:
In this article, the individual intraocular lens in accordance with human visual characterists has been designed based on individual eye structure with optical design software ZEMAX, which can correct not only the defocus and astigmatism, but also the spherical aberrations by aspheric surface design. The power calculated from the individual intraocular lens is compered with that caculated from the experiential formula, showing an improvement of precision higher than 0.25D. The variation of the modulation and the resolution of human eye has been shown visually before and after the implantation of intraocular lens. The resolution has been improved from 28 L/mm to 118 L/mm, while the modulation has been improved from 0.02 to 0.51. The results show that the individual intraocular lens design has more accuracy, and the difference exists in correct effect because of the different optical properties of human eyes.
In this article, the individual intraocular lens in accordance with human visual characterists has been designed based on individual eye structure with optical design software ZEMAX, which can correct not only the defocus and astigmatism, but also the spherical aberrations by aspheric surface design. The power calculated from the individual intraocular lens is compered with that caculated from the experiential formula, showing an improvement of precision higher than 0.25D. The variation of the modulation and the resolution of human eye has been shown visually before and after the implantation of intraocular lens. The resolution has been improved from 28 L/mm to 118 L/mm, while the modulation has been improved from 0.02 to 0.51. The results show that the individual intraocular lens design has more accuracy, and the difference exists in correct effect because of the different optical properties of human eyes.
2014, 7(5): 823-829.
doi:10.3788/CO.20140705.0823
Abstract:
To get irradiation distribution of arbitrary form on a specific plane, the free-form surface reflector is constructed with the Supporting-Ellipsoid design method in this paper. Firstly, the design idea and design process are introduced, and then a specific optical system of free-form surface is constructed. Simulation results show that the system efficiency reaches 97% without regard to reflection loss, which is three times more than that of the optical system of traditional solar simulator. The irradiance non-uniformity reaches 5.26%, which has a certain gap with the ideal state, resulting from the consideration on both the calculate time and the smoothness of the free-form surface in the design.
To get irradiation distribution of arbitrary form on a specific plane, the free-form surface reflector is constructed with the Supporting-Ellipsoid design method in this paper. Firstly, the design idea and design process are introduced, and then a specific optical system of free-form surface is constructed. Simulation results show that the system efficiency reaches 97% without regard to reflection loss, which is three times more than that of the optical system of traditional solar simulator. The irradiance non-uniformity reaches 5.26%, which has a certain gap with the ideal state, resulting from the consideration on both the calculate time and the smoothness of the free-form surface in the design.
2014, 7(5): 830-836.
doi:10.3788/CO.20140705.0830
Abstract:
The stitching interferometer systems with larger relative movement will show a significantly lower positioning accuracy of subapertures. As a consequence a stitching method based on detection of artificial circular mark center to find the necessary translation between two neighborly subapertures is implemented. Firstly, we take coordinates of mark centers as the marks' coordinates by which the translation is computed. Then all the subaperture data are unified into the same reference by homogeneous coordinate transformation and the full aperture phase are stitched by using mechanical system error compensation algorithm. A subaperture stitching process for a 468 mm flat mirror was carried out including surface accuracy tests during the polishing. In this process, subaperture stitching test offered the surface data precisely for polishing, which ensured the surface error converged quickly to a final RMS of 35 nm. The experimental results show that the method relaxes the precision requirement for subaperture location and can get the full aperture phase for large optical element correctly.
The stitching interferometer systems with larger relative movement will show a significantly lower positioning accuracy of subapertures. As a consequence a stitching method based on detection of artificial circular mark center to find the necessary translation between two neighborly subapertures is implemented. Firstly, we take coordinates of mark centers as the marks' coordinates by which the translation is computed. Then all the subaperture data are unified into the same reference by homogeneous coordinate transformation and the full aperture phase are stitched by using mechanical system error compensation algorithm. A subaperture stitching process for a 468 mm flat mirror was carried out including surface accuracy tests during the polishing. In this process, subaperture stitching test offered the surface data precisely for polishing, which ensured the surface error converged quickly to a final RMS of 35 nm. The experimental results show that the method relaxes the precision requirement for subaperture location and can get the full aperture phase for large optical element correctly.
2014, 7(5): 816-822.
doi:10.3788/CO.20140705.0816
Abstract:
This paper demonstrates the design and fabrication of the dual-band antireflection coating in 0.8-1.7 m and 3.7-4.8 m wavelength region at 0 incident angle on the ZnS substrate based on oxide materials. The choosing on evaporation materials, optical coating design and fabrication method, et al. are discussed in detail. The dual-band IR antireflection coating has been successfully produced by Plasma Ion Assisted Deposition(PIAD) technique on both side of the ZnS substrate. Transmittance and environment test results show that the average transmittance is larger than 95% during 0.8-1.6 m wavelength region and larger than 96% during 3.7-4.8 m wavelength region, respectively. The firm adhesion and good tribology ability have been obtained referring to the general specification for optical coatings.
This paper demonstrates the design and fabrication of the dual-band antireflection coating in 0.8-1.7 m and 3.7-4.8 m wavelength region at 0 incident angle on the ZnS substrate based on oxide materials. The choosing on evaporation materials, optical coating design and fabrication method, et al. are discussed in detail. The dual-band IR antireflection coating has been successfully produced by Plasma Ion Assisted Deposition(PIAD) technique on both side of the ZnS substrate. Transmittance and environment test results show that the average transmittance is larger than 95% during 0.8-1.6 m wavelength region and larger than 96% during 3.7-4.8 m wavelength region, respectively. The firm adhesion and good tribology ability have been obtained referring to the general specification for optical coatings.
2014, 7(5): 749-758.
doi:10.3788/CO.20140705.0749
Abstract:
The material properties and processing method of beryllium mirrors are reviewed and their applications and development are also proposed. Firstly, the material properties of beryllium mirrors widely used in present and the current state-of-the-art of mirror substrate production, machining, grinding, nickel plating, polishing are introduced. Then, the latest application of the beryllium and beryllium-aluminum in the JWST(the James Webb Space Telescope) and the F-9120 high altitude dual band(EO/IR) tactical reconnaissance sensor are given. Finally, the future developments and application of beryllium and beryllium-aluminum for optical systems are discussed.
The material properties and processing method of beryllium mirrors are reviewed and their applications and development are also proposed. Firstly, the material properties of beryllium mirrors widely used in present and the current state-of-the-art of mirror substrate production, machining, grinding, nickel plating, polishing are introduced. Then, the latest application of the beryllium and beryllium-aluminum in the JWST(the James Webb Space Telescope) and the F-9120 high altitude dual band(EO/IR) tactical reconnaissance sensor are given. Finally, the future developments and application of beryllium and beryllium-aluminum for optical systems are discussed.
2014, 7(5): 691-700.
doi:10.3788/CO.20140705.0691
Abstract:
In this paper, major developments in Surface Plasmon Microscope(SPM) technology are reviewed. Theory, experiment setup and application examples are presented. Two SPM technology trends, i.e., enhancing lateral resolution close to optical diffraction limit and combining with electrochemical/mechanical micro/nano manipulation methods, are suggested and discussed.
In this paper, major developments in Surface Plasmon Microscope(SPM) technology are reviewed. Theory, experiment setup and application examples are presented. Two SPM technology trends, i.e., enhancing lateral resolution close to optical diffraction limit and combining with electrochemical/mechanical micro/nano manipulation methods, are suggested and discussed.
2014, 7(5): 701-711.
doi:10.3788/CO.20140705.0701
Abstract:
In this paper, the basic principle of the optical-thermal and optical-acoustics detecting methods is reviewed. The common optical-thermal and optical-acoustics detecting methods are described. Combined with specific applications such as absorption test of optical films, characterization of laser irradiation and laser damage to the thin films and characterization of the mechanical properties of thin films, some typical detecting methods are analyzed including laser calorimetry technique, photothermal deflection technique, surface acoustic waves and so on. The advantages and disadvantages of these methods are indicated. Finally, some achievement in the field by these methods are summarized, and the prospect of these methods is presented.
In this paper, the basic principle of the optical-thermal and optical-acoustics detecting methods is reviewed. The common optical-thermal and optical-acoustics detecting methods are described. Combined with specific applications such as absorption test of optical films, characterization of laser irradiation and laser damage to the thin films and characterization of the mechanical properties of thin films, some typical detecting methods are analyzed including laser calorimetry technique, photothermal deflection technique, surface acoustic waves and so on. The advantages and disadvantages of these methods are indicated. Finally, some achievement in the field by these methods are summarized, and the prospect of these methods is presented.
2014, 7(5): 739-748.
doi:10.3788/CO.20140705.0739
Abstract:
In this paper, the image stabilization system of large aperture space telescope on orbit or being designed is introduced, including HUBBLE, JWST, ATLAST-8m and ATLAST-16m in free flying mode, and SOFIA, OPTⅡX in space-borne mode. The composition, working principle, major component, performance requirements and control algorithm of image stabilization system are discussed in detail. Then, the disturbance-free payload design concept based on the magnetically suspend technology and design idea of space telescope directly driven by the manipulator are introduced. Analysis results indicate that the precise image stabilization and active vibration isolation system based on the magnetically suspend and manipulator technology is the future development tendency.
In this paper, the image stabilization system of large aperture space telescope on orbit or being designed is introduced, including HUBBLE, JWST, ATLAST-8m and ATLAST-16m in free flying mode, and SOFIA, OPTⅡX in space-borne mode. The composition, working principle, major component, performance requirements and control algorithm of image stabilization system are discussed in detail. Then, the disturbance-free payload design concept based on the magnetically suspend technology and design idea of space telescope directly driven by the manipulator are introduced. Analysis results indicate that the precise image stabilization and active vibration isolation system based on the magnetically suspend and manipulator technology is the future development tendency.
2014, 7(5): 723-730.
doi:10.3788/CO.20140705.0723
Abstract:
Dual-wavelength optical parametric oscillator is a new-type of nonlinear laser devices. In this paper, the principle of dual-wavelength optical parametric oscillators is introduced. The research advances in dual-wavelength optical parametric oscillators are reviewed. Scientific and technological problems that dual wavelength optical parametric oscillators encountered are discussed. Several applications of dual-wavelength optical parametric oscillators are presented.
Dual-wavelength optical parametric oscillator is a new-type of nonlinear laser devices. In this paper, the principle of dual-wavelength optical parametric oscillators is introduced. The research advances in dual-wavelength optical parametric oscillators are reviewed. Scientific and technological problems that dual wavelength optical parametric oscillators encountered are discussed. Several applications of dual-wavelength optical parametric oscillators are presented.
2014, 7(5): 712-722.
doi:10.3788/CO.20140705.0712
Abstract:
The principle of color measurement is introduced, and the characteristics requirements and technical difficulties of on-line color measurement are summarized. The development process and the current state of the art of on-line color measurement technology are also presented. The specifications, applications and system structures of several advanced on-line spectrophotometes abroad are presented in detail. The characteristics and advantages of every instrument are highlighted. The development trend of on-line spectrophotometer is discussed from two aspects of technical perspective and application requirements in this paper, which will provide a reference for study on the development of on-line spectrophotometer.
The principle of color measurement is introduced, and the characteristics requirements and technical difficulties of on-line color measurement are summarized. The development process and the current state of the art of on-line color measurement technology are also presented. The specifications, applications and system structures of several advanced on-line spectrophotometes abroad are presented in detail. The characteristics and advantages of every instrument are highlighted. The development trend of on-line spectrophotometer is discussed from two aspects of technical perspective and application requirements in this paper, which will provide a reference for study on the development of on-line spectrophotometer.
2014, 7(5): 731-738.
doi:10.3788/CO.20140705.0731
Abstract:
The principle of waveguide holographic head-mounted display technology is introduced, which explains its advantages and practicability. Then some examples are shown with detailed indexes and parameters of current waveguide holographic head-mounted display technology. Finally the key enabling technology of waveguide holographic head-mounted display is analyzed, based on which the technology bottleneck and development trend are summarized.
The principle of waveguide holographic head-mounted display technology is introduced, which explains its advantages and practicability. Then some examples are shown with detailed indexes and parameters of current waveguide holographic head-mounted display technology. Finally the key enabling technology of waveguide holographic head-mounted display is analyzed, based on which the technology bottleneck and development trend are summarized.
2014, 7(5): 855-862.
doi:10.3788/CO.20140705.0855
Abstract:
To keep the advantages of fiber point diffraction interferometer which is easy to align and control the diffracted light, we design a new wavefront reference source(WRS). WRS can keep the advantages of fiber point diffraction interferometer and pin-hole point diffraction interferometer, and it also can be used to test the wavefront aberration of larger NA optical system for Extreme Ultraviolet Lithography(EUVL). The analysis of error for this new WRS and calibration of the system error is very important for realizing a more accurate test of wavefront aberration. Based on the analysis of various errors, we study the calibration algorithm in detail, and obtain the tolerance of several WRS important components including that the angle tolerance of rotation stage is 0.5 and the deviation factor is 0.5% when rotation is away optical axis.
To keep the advantages of fiber point diffraction interferometer which is easy to align and control the diffracted light, we design a new wavefront reference source(WRS). WRS can keep the advantages of fiber point diffraction interferometer and pin-hole point diffraction interferometer, and it also can be used to test the wavefront aberration of larger NA optical system for Extreme Ultraviolet Lithography(EUVL). The analysis of error for this new WRS and calibration of the system error is very important for realizing a more accurate test of wavefront aberration. Based on the analysis of various errors, we study the calibration algorithm in detail, and obtain the tolerance of several WRS important components including that the angle tolerance of rotation stage is 0.5 and the deviation factor is 0.5% when rotation is away optical axis.
2014, 7(5): 801-807.
doi:10.3788/CO.20140705.0801
Abstract:
Double laser beam combination accuracy of wavelength multiplexing is carried in this article. Two beams with wavelengths of 532 nm and 515 nm are combined into one in the combination and detection system using light filter with special optical thin films, and the combination accuracy is detected. Based on this system, the corresponding theoretical model is established, and the comprehensive analysis on the error source and the value in combination and detection are given in this paper. When the pointing stability of both beams is 50 rad, the theoretical value of combination accuracy is 14.69, and the proportion of pointing stability is 99.26%. The system gets an excellent anti interference ability against the unstable factor such as the error of centroid location(error rate 3 times), and the variation in accuracy rate is less than 2.4 . When the laser pointing stability is increased to 23.51 rad, the highest theoretical value of combination accuracy is 7.09 and the proportion of pointing stability is 96.77%. The system still has a high ability of anti-interference and the variation in the accuracy rate is less than 1%. Factors that affect the beam combination accuracy of near field and small power are laser beam pointing stability, mechanical adjustment and centroid location error are all the factors to affect the combination accuracy of the near field beam with low power, among which the laser pointing stability is the main factor. Adjusting the proportion of each factor, we can control the ability of anti interference of beam combination.
Double laser beam combination accuracy of wavelength multiplexing is carried in this article. Two beams with wavelengths of 532 nm and 515 nm are combined into one in the combination and detection system using light filter with special optical thin films, and the combination accuracy is detected. Based on this system, the corresponding theoretical model is established, and the comprehensive analysis on the error source and the value in combination and detection are given in this paper. When the pointing stability of both beams is 50 rad, the theoretical value of combination accuracy is 14.69, and the proportion of pointing stability is 99.26%. The system gets an excellent anti interference ability against the unstable factor such as the error of centroid location(error rate 3 times), and the variation in accuracy rate is less than 2.4 . When the laser pointing stability is increased to 23.51 rad, the highest theoretical value of combination accuracy is 7.09 and the proportion of pointing stability is 96.77%. The system still has a high ability of anti-interference and the variation in the accuracy rate is less than 1%. Factors that affect the beam combination accuracy of near field and small power are laser beam pointing stability, mechanical adjustment and centroid location error are all the factors to affect the combination accuracy of the near field beam with low power, among which the laser pointing stability is the main factor. Adjusting the proportion of each factor, we can control the ability of anti interference of beam combination.
2014, 7(5): 808-815.
doi:10.3788/CO.20140705.0808
Abstract:
To meet the requirements for different practical applications, we investigate the properties of single LaF3 layer deposited by resistive heating Mo-boat(RH) and ion beam sputtering(IBS) in this paper. First, transmittance and reflectance spectra of LaF3 thin films were measured by an UV-visible spectrophotometer, and the refractive indexes and extinction coefficients were obtained by using different models. Second, stress-temperature curves of LaF3 thin films during heating and cooling cycles were carried out by a stress measurement system. Finally, the X-ray diffraction(XRD) was used to characterize the microstructure of LaF3 layers. Experimental results indicate that LaF3 thin film fabricated by thermal evaporation(RH LaF3) had an inhomogeneous refractive index; the refractive index and extinction coefficient at 193 nm are 1.687 and 510-4 for RH LaF3, and 1.714 and 910-4for IBS LaF3, respectively. RH LaF3 and IBS LaF3 exhibited inverse stress status. RH LaF3 had a tensile stress and IBS LaF3 showed a compressive stress, which decreased after annealing. The transmittances are 99.4% and 99.2% for RH deposited MgF2/LaF3 AR coating and IBS deposited AlF3/LaF3 AR coating, and the corresponding measured reflectances are 0.04% and 0.1%,respectively.
To meet the requirements for different practical applications, we investigate the properties of single LaF3 layer deposited by resistive heating Mo-boat(RH) and ion beam sputtering(IBS) in this paper. First, transmittance and reflectance spectra of LaF3 thin films were measured by an UV-visible spectrophotometer, and the refractive indexes and extinction coefficients were obtained by using different models. Second, stress-temperature curves of LaF3 thin films during heating and cooling cycles were carried out by a stress measurement system. Finally, the X-ray diffraction(XRD) was used to characterize the microstructure of LaF3 layers. Experimental results indicate that LaF3 thin film fabricated by thermal evaporation(RH LaF3) had an inhomogeneous refractive index; the refractive index and extinction coefficient at 193 nm are 1.687 and 510-4 for RH LaF3, and 1.714 and 910-4for IBS LaF3, respectively. RH LaF3 and IBS LaF3 exhibited inverse stress status. RH LaF3 had a tensile stress and IBS LaF3 showed a compressive stress, which decreased after annealing. The transmittances are 99.4% and 99.2% for RH deposited MgF2/LaF3 AR coating and IBS deposited AlF3/LaF3 AR coating, and the corresponding measured reflectances are 0.04% and 0.1%,respectively.
