2017 Vol. 38, No. 4
column
- Oe System and Engineering
- System and Engineering
- Information Acquisition and Processing
- Information Information Information Acquisition and Processing
- Information Information Acquisition and Processing
- Optical Metrology and Measurement
- Optical Element and Fabrication
- Infrared Technology
- Laser Technology
- Fiber Sensing and Optical Communication
Display Method:
2017, 38(4): 521-525.
doi: 10.5768/JAO201738.0401001
Abstract:
In order to maximizing performance of search and track systems using focal plane array detectors, special optical de-scanning techniques are adopted in this paper. Form and composition of de-scanning path of object and image are given, and features of different de-scanning technique such as parallel and converging de-scanning are analyzed. Optical problems in de-scanning process and relative solutions are also described. Viewpoint of maximum optical principle error of less than 1/3~1/4 pixel is also proposed.
In order to maximizing performance of search and track systems using focal plane array detectors, special optical de-scanning techniques are adopted in this paper. Form and composition of de-scanning path of object and image are given, and features of different de-scanning technique such as parallel and converging de-scanning are analyzed. Optical problems in de-scanning process and relative solutions are also described. Viewpoint of maximum optical principle error of less than 1/3~1/4 pixel is also proposed.
2017, 38(4): 526-532.
doi: 10.5768/JAO201738.0401002
Abstract:
Due to the instant destroying process, complexity of the reaction process and high cost of testing, it is very difficult to evaluate laser weapon damage power through experimental approach. Hence, the offensive-defensive performance can be effectively evaluated through numerical simulation of the destructive power. The current work considered the thermal conductivity variation and the melting latent heat when the material phase changed to modify the temperature field. In addition, the corresponding displacement field and stress field model were established and calculated. Finally, multiple physical field models were integrated into a simulation system and the attacking process of target by laser weapon was simulated. Moreover, the damage effect of target on different working conditions was also simulated. The simulation results show that when the laser irradiation of Al material is 3.01 s, the laser real-time power density is 0.930 8 W/cm2, the outer wall temperature of the Al material reaches 600℃, and the inner wall temperature is 352.522℃. At this time, the surface of the Al material is just melting, but its stress has made the material brittlely fractured.
Due to the instant destroying process, complexity of the reaction process and high cost of testing, it is very difficult to evaluate laser weapon damage power through experimental approach. Hence, the offensive-defensive performance can be effectively evaluated through numerical simulation of the destructive power. The current work considered the thermal conductivity variation and the melting latent heat when the material phase changed to modify the temperature field. In addition, the corresponding displacement field and stress field model were established and calculated. Finally, multiple physical field models were integrated into a simulation system and the attacking process of target by laser weapon was simulated. Moreover, the damage effect of target on different working conditions was also simulated. The simulation results show that when the laser irradiation of Al material is 3.01 s, the laser real-time power density is 0.930 8 W/cm2, the outer wall temperature of the Al material reaches 600℃, and the inner wall temperature is 352.522℃. At this time, the surface of the Al material is just melting, but its stress has made the material brittlely fractured.
2017, 38(4): 533-537.
doi: 10.5768/JAO201738.0401003
Abstract:
The f-theta lens is an important essential component in laser scanning systems that plays a decisive role in working surface, measuring speed and measurement accuracy, etc. A wide-angle f-theta lens operating at 486 nm ~ 656 nm is designed to change the range of small f-theta lens scanning range and single operating wavelength.Through the primary aberration analysis, the primary structure parameters of the system are determined, and the chromatic aberration correction is carried out by using the optical power distribution with different dispersion properties. The final design result shows that the lateral color is less than 3 μm, the calibrated f-Theta distortions are all less than 0.015% and the energy utilization rate is nearly 90%, which means that the focusing performances are close to the diffraction-limited. The system meets the requirements of high-precision laser marking systems with different waves.
The f-theta lens is an important essential component in laser scanning systems that plays a decisive role in working surface, measuring speed and measurement accuracy, etc. A wide-angle f-theta lens operating at 486 nm ~ 656 nm is designed to change the range of small f-theta lens scanning range and single operating wavelength.Through the primary aberration analysis, the primary structure parameters of the system are determined, and the chromatic aberration correction is carried out by using the optical power distribution with different dispersion properties. The final design result shows that the lateral color is less than 3 μm, the calibrated f-Theta distortions are all less than 0.015% and the energy utilization rate is nearly 90%, which means that the focusing performances are close to the diffraction-limited. The system meets the requirements of high-precision laser marking systems with different waves.
2017, 38(4): 538-542.
doi: 10.5768/JAO201738.0401004
Abstract:
With development of vehicle-borne opto-electronic system, the sight with multi-functions has become a trend. This paper presents common path design for TV sight/visual sight. For visual direct-view sight, magnification, field of view, exit pupil diameter and eye relief are 8×, 5°, φ4 mm and not less than 15 mm respectively, while F number and focal length are 6 and 110 mm respectively for TV sight. Then tolerence of the results is analyzed. Finally, strict tolerance of parts fabrication and system assembly are formulated according to the analysis of tolerance. For 2.3 m×2.3 m target, identification distance is more than 4 km, which can meet imaging demands.
With development of vehicle-borne opto-electronic system, the sight with multi-functions has become a trend. This paper presents common path design for TV sight/visual sight. For visual direct-view sight, magnification, field of view, exit pupil diameter and eye relief are 8×, 5°, φ4 mm and not less than 15 mm respectively, while F number and focal length are 6 and 110 mm respectively for TV sight. Then tolerence of the results is analyzed. Finally, strict tolerance of parts fabrication and system assembly are formulated according to the analysis of tolerance. For 2.3 m×2.3 m target, identification distance is more than 4 km, which can meet imaging demands.
2017, 38(4): 543-548.
doi: 10.5768/JAO201738.0401005
Abstract:
In view of shortcomings of existing LED lighting system with large volume, complicated structure and short working distance, a new design method of single LED projection system with light weight, good uniformity and long distance illumination is proposed. Based on the theory of illumination design, combined with non-imaging design and imaging design method, a projection lighting system composed of single high power LED, condenser lens, aperture stop and projection objective is designed. Firstly, the condenser concentrates lights emitting from LED and converges them to lightening plane, and then objective lens project light spot at lightening plane onto receiving surface with specified distance. The system uses a full-transmission structure, easy to process and install.Single high-power LED as a light source can effectively reduce the system size and mass. Experimental results show that this system can form illumination with uniformity of more than 90% in the range of 3 m~3 km.The system ensure good image quality and distortion of projection plane being less than 5%, which can satisfy requirements of uniform illumination and projection over a long distance.
In view of shortcomings of existing LED lighting system with large volume, complicated structure and short working distance, a new design method of single LED projection system with light weight, good uniformity and long distance illumination is proposed. Based on the theory of illumination design, combined with non-imaging design and imaging design method, a projection lighting system composed of single high power LED, condenser lens, aperture stop and projection objective is designed. Firstly, the condenser concentrates lights emitting from LED and converges them to lightening plane, and then objective lens project light spot at lightening plane onto receiving surface with specified distance. The system uses a full-transmission structure, easy to process and install.Single high-power LED as a light source can effectively reduce the system size and mass. Experimental results show that this system can form illumination with uniformity of more than 90% in the range of 3 m~3 km.The system ensure good image quality and distortion of projection plane being less than 5%, which can satisfy requirements of uniform illumination and projection over a long distance.
2017, 38(4): 549-554.
doi: 10.5768/JAO201738.0401006
Abstract:
While high-speed aircraft are flying in the atmosphere, its optical-hood is subjected to severe aerodynamic heating. The supersonic gaseous film cooling method can effectively isolate the external heating, but the mixed layer formed by the cooling gas and main stream can cause the beam degradation and affect the imaging quality. To reduce the beam degradation and improve the supersonic gaseous film cooling optical performance, based on the simultaneous matching of refractive index and pressure, two design methods were proposed, respectively, which configured the specific cooling gas temperature to achieve the mixed layer refractive index and pressure matching at the same time, and configured the specific cooling gas component to achieve the mixed layer refractive index and pressure matching at the same time. The feasibility and effectiveness of these two methods were verified. The simulation prove that, for the latter method, the mass ratio of the cooling gas is related to the static temperature of the cooling gas only without the changing of the external flow parameters, which is the basis for the synchronous design of cooling and optical performances of the gaseous film.
While high-speed aircraft are flying in the atmosphere, its optical-hood is subjected to severe aerodynamic heating. The supersonic gaseous film cooling method can effectively isolate the external heating, but the mixed layer formed by the cooling gas and main stream can cause the beam degradation and affect the imaging quality. To reduce the beam degradation and improve the supersonic gaseous film cooling optical performance, based on the simultaneous matching of refractive index and pressure, two design methods were proposed, respectively, which configured the specific cooling gas temperature to achieve the mixed layer refractive index and pressure matching at the same time, and configured the specific cooling gas component to achieve the mixed layer refractive index and pressure matching at the same time. The feasibility and effectiveness of these two methods were verified. The simulation prove that, for the latter method, the mass ratio of the cooling gas is related to the static temperature of the cooling gas only without the changing of the external flow parameters, which is the basis for the synchronous design of cooling and optical performances of the gaseous film.
2017, 38(4): 555-561.
doi: 10.5768/JAO201738.0401007
Abstract:
A merit function based on modified spatial frequency domain(UV) sampling method is proposed, which can be used to optimize the geometny of long baseline astronomy optical interferometer telescope array. The UV region to be sampled is firstly divided in both radial and rotational directions, then the number and density of UV sampling points of each segment are calculated. The deviation of UV sampling point density distribution from the ideal Gaussian distribution is taken as the merit function value. The genetic algorithm is used as the optimization algorithm, due to its global convergence capability which can reduce the dependence on initial array. A 6 apertures telescope array was optimized with the proposed merit function using genetic algorithm. Moreover, the optimized array(Array-6 array) was compared with the CHARA array. Analysis results show that the Array-6 array UV sampling points distribution in the radial direction is intensive in low frequencies and continuous, which is beneficial to the reconstruction of observation target contour and structure. The binary star observation and image reconstruction simulations show that the array optimized using the proposed merit function has better imaging performance, compared with the CHARA array. The error of reconstructed image using Array-6 is 21.34, which is 18.16% smaller than the error of reconstructed image using CHARA. Additional, the proposed merit function can be used to optimize arrays with large aperture numbers, so it also has a large application prospect for the optimal design of the radio-band telescope array.
A merit function based on modified spatial frequency domain(UV) sampling method is proposed, which can be used to optimize the geometny of long baseline astronomy optical interferometer telescope array. The UV region to be sampled is firstly divided in both radial and rotational directions, then the number and density of UV sampling points of each segment are calculated. The deviation of UV sampling point density distribution from the ideal Gaussian distribution is taken as the merit function value. The genetic algorithm is used as the optimization algorithm, due to its global convergence capability which can reduce the dependence on initial array. A 6 apertures telescope array was optimized with the proposed merit function using genetic algorithm. Moreover, the optimized array(Array-6 array) was compared with the CHARA array. Analysis results show that the Array-6 array UV sampling points distribution in the radial direction is intensive in low frequencies and continuous, which is beneficial to the reconstruction of observation target contour and structure. The binary star observation and image reconstruction simulations show that the array optimized using the proposed merit function has better imaging performance, compared with the CHARA array. The error of reconstructed image using Array-6 is 21.34, which is 18.16% smaller than the error of reconstructed image using CHARA. Additional, the proposed merit function can be used to optimize arrays with large aperture numbers, so it also has a large application prospect for the optimal design of the radio-band telescope array.
2017, 38(4): 562-568.
doi: 10.5768/JAO201738.0401008
Abstract:
The technology of optic-electronic oscillator(OEO), characterized by low noise, high frequency stability and anti-electromagnetic interference ability, is a research hotspot in microwave photonics, which breaks through the limitation of microwave signal suchac frequency, improves the stability of signal and the big noise based on the electronic technology.The technologies of optic-electronic oscillator, such as the theory, theoretical models and the implementation method, etc and its application are researched. Key technologies and solutions to be used in microwave signal processing system are proposed, such as multi-pass noise reduction, temperature and stress-compensation of optical fiber and optoelectronic integration, which are urgently in need of breakthrough.
The technology of optic-electronic oscillator(OEO), characterized by low noise, high frequency stability and anti-electromagnetic interference ability, is a research hotspot in microwave photonics, which breaks through the limitation of microwave signal suchac frequency, improves the stability of signal and the big noise based on the electronic technology.The technologies of optic-electronic oscillator, such as the theory, theoretical models and the implementation method, etc and its application are researched. Key technologies and solutions to be used in microwave signal processing system are proposed, such as multi-pass noise reduction, temperature and stress-compensation of optical fiber and optoelectronic integration, which are urgently in need of breakthrough.
2017, 38(4): 569-574.
doi: 10.5768/JAO201738.0401009
Abstract:
A chaotic-pulse hybrid signal optical time-domain reflectometer(OTDR) was developed. The working principle is to measure the Fresnel reflection and backward Rayleigh scattering in the fiber by continuous chaotic light and discrete pulsed light respectively, and finally to obtain the optical fiber fault measurement curve by linear superposition of the measurement results. The instrument can solve the problem that traditional chaotic optical time domain reflectometer can not measure fiber loss events. By using G.652.B single mode fiber as the test fiber, the parameter specifications of the instrument are tested and analyzed. Results show that the instrument can realize a range-independent resolution of 35 cm within at least 104 km. The instrument also has a good detection effect on fiber loss events.
A chaotic-pulse hybrid signal optical time-domain reflectometer(OTDR) was developed. The working principle is to measure the Fresnel reflection and backward Rayleigh scattering in the fiber by continuous chaotic light and discrete pulsed light respectively, and finally to obtain the optical fiber fault measurement curve by linear superposition of the measurement results. The instrument can solve the problem that traditional chaotic optical time domain reflectometer can not measure fiber loss events. By using G.652.B single mode fiber as the test fiber, the parameter specifications of the instrument are tested and analyzed. Results show that the instrument can realize a range-independent resolution of 35 cm within at least 104 km. The instrument also has a good detection effect on fiber loss events.
2017, 38(4): 575-580.
doi: 10.5768/JAO201738.0401010
Abstract:
In fringe reflection technique, the phase ambiguous error can influence the measurement result directly. The existing error reduction methods to compensate this error are inflexible and can only reduce a part of this error. An accurate phase-slope analytical model without phase ambiguous problem is deduced. Based on the simulation of the deduced model, it is found that phase ambiguous error can close to zero when the system light rays are both perpendicular to the reference plane and the display screen. A system based on the co-axial optical path is proposed to achieve this system setup. In our experiment, with the increasing of the test surface height from 0 to 3 mm, the proposed co-axial system is proved to have the phase ambiguous error always close to zero. Meanwhile, the phase ambiguous error in the tradition system increases from 0 to 1.5 rad when the test surface height rises from 0 to 3 mm.
In fringe reflection technique, the phase ambiguous error can influence the measurement result directly. The existing error reduction methods to compensate this error are inflexible and can only reduce a part of this error. An accurate phase-slope analytical model without phase ambiguous problem is deduced. Based on the simulation of the deduced model, it is found that phase ambiguous error can close to zero when the system light rays are both perpendicular to the reference plane and the display screen. A system based on the co-axial optical path is proposed to achieve this system setup. In our experiment, with the increasing of the test surface height from 0 to 3 mm, the proposed co-axial system is proved to have the phase ambiguous error always close to zero. Meanwhile, the phase ambiguous error in the tradition system increases from 0 to 1.5 rad when the test surface height rises from 0 to 3 mm.
2017, 38(4): 581-586.
doi: 10.5768/JAO201738.0402001
Abstract:
The steering approach of blazed grating limits the number and distribution of deflection angles of beam.Aiming at this disadvantage, a new liquid-crystal beam deflection wave control method based on phased-array radar model is proposed. The method controls the same phase difference between liquid crystal electrodes.The beam direction can be controlled by changing phase difference between liquid crystal electrodes.Finally, it is proved by experiment that this method can realize beam scanning with arbitrary resolution, continuous beam deflection accuracy is better than 20 μrad within the range of 0.15° light beam scanning.
The steering approach of blazed grating limits the number and distribution of deflection angles of beam.Aiming at this disadvantage, a new liquid-crystal beam deflection wave control method based on phased-array radar model is proposed. The method controls the same phase difference between liquid crystal electrodes.The beam direction can be controlled by changing phase difference between liquid crystal electrodes.Finally, it is proved by experiment that this method can realize beam scanning with arbitrary resolution, continuous beam deflection accuracy is better than 20 μrad within the range of 0.15° light beam scanning.
2017, 38(4): 587-591.
doi: 10.5768/JAO201738.0402002
Abstract:
In order to meet the demand for 3D shape acquisition of large-depth objects in modern industry and solve the problem of small depth in conventional structured light 3D shape measurement, a new 3D shape acquisition technology of object with large depth based on integral imaging is proposed by the array multi-viewpoint acquisition technique. According to integral imaging principle, the relationship between corresponding image points and object points is analyzed, then relationships between max depth and integrated imaging optical acquisition system parameters are obtained. On this basis, an integral imaging 3D shape acquisition system is built with scanning cameras and motorized platform. Furthermore, 3D shapes of large-depth object, constituted by 2 objects relatively independent with depth of 600 mm to 3 600 mm, are captured by the proposed system.Optical experiment results show that this proposed integral imaging large-depth-object 3D shape acquisition technology can capture 3D shape of 3D object with depth up to 3 600 mm at one time, which can offer technical support for 3D shape acquisition of objects with large depth.
In order to meet the demand for 3D shape acquisition of large-depth objects in modern industry and solve the problem of small depth in conventional structured light 3D shape measurement, a new 3D shape acquisition technology of object with large depth based on integral imaging is proposed by the array multi-viewpoint acquisition technique. According to integral imaging principle, the relationship between corresponding image points and object points is analyzed, then relationships between max depth and integrated imaging optical acquisition system parameters are obtained. On this basis, an integral imaging 3D shape acquisition system is built with scanning cameras and motorized platform. Furthermore, 3D shapes of large-depth object, constituted by 2 objects relatively independent with depth of 600 mm to 3 600 mm, are captured by the proposed system.Optical experiment results show that this proposed integral imaging large-depth-object 3D shape acquisition technology can capture 3D shape of 3D object with depth up to 3 600 mm at one time, which can offer technical support for 3D shape acquisition of objects with large depth.
2017, 38(4): 592-598.
doi: 10.5768/JAO201738.0402003
Abstract:
A Gaussian mixture model(GMM) based grayscale image enhancement algorithm using particle swarm optimization(PSO) is proposed. The algorithm uses GMM to build a model for gray level histogram of the input image, and uses the significant interaction points of Gaussian components in the model to partition the histogram into a certain amount of sub intervals. Then, according to mapping function, the gray value in each interval is transformed to appropriate output interval. The enhanced image is generated by transforming output interval data according to PSO optimized parameters. Experimental results show that image visual effects generated by Gaussian mixture gray image enhancement algorithm with PSO are better. After image processing of original image and texture rich image, the information entropy of enhanced image is 4.746 6 and 7.952 6 respectively, the average gray gradient is 6.970 6 and 37.386 1.
A Gaussian mixture model(GMM) based grayscale image enhancement algorithm using particle swarm optimization(PSO) is proposed. The algorithm uses GMM to build a model for gray level histogram of the input image, and uses the significant interaction points of Gaussian components in the model to partition the histogram into a certain amount of sub intervals. Then, according to mapping function, the gray value in each interval is transformed to appropriate output interval. The enhanced image is generated by transforming output interval data according to PSO optimized parameters. Experimental results show that image visual effects generated by Gaussian mixture gray image enhancement algorithm with PSO are better. After image processing of original image and texture rich image, the information entropy of enhanced image is 4.746 6 and 7.952 6 respectively, the average gray gradient is 6.970 6 and 37.386 1.
2017, 38(4): 599-605.
doi: 10.5768/JAO201738.0402004
Abstract:
Based on light-mixing technology and Chebyshev method of simulating Planckian locus, the relationships between chromaticity coordinate, luminous flux, relative color temperature and duty ratio of three-channel pulse width modulation (PWM) are derived in the paper, and limitation of three channels' PWM dimming is established. On the basis of this method, intelligent light-control system is designed, which can realize dimming and tunable color temperature of white-light LED clusters [the warm white/green/ blue (WW/G/B)] with high color rendering index (CRI) Ra by mobile client. Experiments show that maximum flux error between the setting value and the test value is 0.74% while the correlated color temperature (CCT) of the LED clusters is 3 600 K and the luminous flux is less than 600 lm. The deviation mean of CCT is less than 1.82% and luminous flux fluctuation is no more than 4% while the luminous flux is 300 lm and the range of CCT is from 3 200 K and 7 600 K. Meantime, CRI is generally more than 90, and the maximum value is 95.3 in the tunable range of the white-light LED clusters.
Based on light-mixing technology and Chebyshev method of simulating Planckian locus, the relationships between chromaticity coordinate, luminous flux, relative color temperature and duty ratio of three-channel pulse width modulation (PWM) are derived in the paper, and limitation of three channels' PWM dimming is established. On the basis of this method, intelligent light-control system is designed, which can realize dimming and tunable color temperature of white-light LED clusters [the warm white/green/ blue (WW/G/B)] with high color rendering index (CRI) Ra by mobile client. Experiments show that maximum flux error between the setting value and the test value is 0.74% while the correlated color temperature (CCT) of the LED clusters is 3 600 K and the luminous flux is less than 600 lm. The deviation mean of CCT is less than 1.82% and luminous flux fluctuation is no more than 4% while the luminous flux is 300 lm and the range of CCT is from 3 200 K and 7 600 K. Meantime, CRI is generally more than 90, and the maximum value is 95.3 in the tunable range of the white-light LED clusters.
2017, 38(4): 606-612.
doi: 10.5768/JAO201738.0103001
Abstract:
In order to measure deviations of intelligent sniper system's line of sight and improve firing accuracy by controlling firing time, filter weighted fusion method and linear predicting firing criterion are proposed in this paper.Kalman predicting filter is firstly used to compensate missing distance delay and line of sight deviation is obtained, meanwhile data filtered of gyroscope is integrated and another line of sight deviation is obtained. Secondly, weighted line of sight deviation based on weighted fusion algorithm is obtained. As a result, linear predicting firing criterion is built, which is based on data of gyroscope, weighted fusion algorithm and characteristic of electric firing device. Finally, dSPACE test system is built for experimental measurement of line of sight deviation and simulation of firing contrast experiment respectively. Results indicate that data of filter weighted fusion can basically present real line of sight deviation. When firing simulation is carried with filter weighted fusion method and linear predicting firing criterion, chances of impact point distributed in a circle with a diameter of 0.05 mrad is 85.7%, higher than chance of simple control firing mode which is 53.33%.
In order to measure deviations of intelligent sniper system's line of sight and improve firing accuracy by controlling firing time, filter weighted fusion method and linear predicting firing criterion are proposed in this paper.Kalman predicting filter is firstly used to compensate missing distance delay and line of sight deviation is obtained, meanwhile data filtered of gyroscope is integrated and another line of sight deviation is obtained. Secondly, weighted line of sight deviation based on weighted fusion algorithm is obtained. As a result, linear predicting firing criterion is built, which is based on data of gyroscope, weighted fusion algorithm and characteristic of electric firing device. Finally, dSPACE test system is built for experimental measurement of line of sight deviation and simulation of firing contrast experiment respectively. Results indicate that data of filter weighted fusion can basically present real line of sight deviation. When firing simulation is carried with filter weighted fusion method and linear predicting firing criterion, chances of impact point distributed in a circle with a diameter of 0.05 mrad is 85.7%, higher than chance of simple control firing mode which is 53.33%.
2017, 38(4): 613-616.
doi: 10.5768/JAO201738.0403002
Abstract:
A multi-optical parametric imaging system is introduced and established in order to improve the contrast of object in fog and haze weather. A few targets in multiple scenes are observed in fog and haze weather based on system-level radiation response model for multi-optical parametric imaging and separated calibration of model parameters.Results show that the building's windows can be distinguished clear in the images of linear polarization, circular polarization and polarizing angle because of the strong reflected polarization light of the glass. The vehicles in intersection can be hardly seen in the intensity image, and it is fuzzy in degree of linear polarization and angle of polarization images because of the doped polarization information of trees near in fog. The circular polarization image raises the contrast of the vehicles by 20% because the circle polarization of the trees is less in the fog.
A multi-optical parametric imaging system is introduced and established in order to improve the contrast of object in fog and haze weather. A few targets in multiple scenes are observed in fog and haze weather based on system-level radiation response model for multi-optical parametric imaging and separated calibration of model parameters.Results show that the building's windows can be distinguished clear in the images of linear polarization, circular polarization and polarizing angle because of the strong reflected polarization light of the glass. The vehicles in intersection can be hardly seen in the intensity image, and it is fuzzy in degree of linear polarization and angle of polarization images because of the doped polarization information of trees near in fog. The circular polarization image raises the contrast of the vehicles by 20% because the circle polarization of the trees is less in the fog.
2017, 38(4): 617-621.
doi: 10.5768/JAO201738.0403003
Abstract:
In order to improve measurement accuracy of deformation for large parabolic satellite antenna in vacuum and cryogenic environment, photogrammetry form is studied in this paper, which is one of main factors has effect on accuracy. Theory analysis show that surrounding network has an advantage over strip network in improving accuracy of deformation measurement of parabolic antenna. To verify this analysis, contrast test for different network is designed, moving mechanism is set up, and antenna model with diameter of 5 m is measured. Repeatability of shape error and length error are used as evaluation standard in contrast test. Measuring conclusion is consistent with the aboved analysis.
In order to improve measurement accuracy of deformation for large parabolic satellite antenna in vacuum and cryogenic environment, photogrammetry form is studied in this paper, which is one of main factors has effect on accuracy. Theory analysis show that surrounding network has an advantage over strip network in improving accuracy of deformation measurement of parabolic antenna. To verify this analysis, contrast test for different network is designed, moving mechanism is set up, and antenna model with diameter of 5 m is measured. Repeatability of shape error and length error are used as evaluation standard in contrast test. Measuring conclusion is consistent with the aboved analysis.
2017, 38(4): 622-626.
doi: 10.5768/JAO201738.0403004
Abstract:
In order to solve the problem that hole diameter of hard disk is easy to be affected by local strong reflection and external noise, and low accuracy of measurements, a method for measuring the diameter of circular parts based on wavelet transform, mathematical morphology and machine vision is proposed.Hole image is collected by camera, high/low-frequency images are resolved through wavelet transform, and wavelet transform is used to extract edge of high frequency part and mathematical morphology is used to extract low frequency part, then wavelet edge fusion is used to obtain effective hole edge.Finally, the least square method is utilized to calculate pore size. It is verified experimently that, compared with other algorithms, in the case of effectively preserving edge information of round hole and suppressing surrounding noise effectively, detection accuracy is controlled within 0.01 mm.Experimental results show that this method is simple and feasible, and has a high accuracy.
In order to solve the problem that hole diameter of hard disk is easy to be affected by local strong reflection and external noise, and low accuracy of measurements, a method for measuring the diameter of circular parts based on wavelet transform, mathematical morphology and machine vision is proposed.Hole image is collected by camera, high/low-frequency images are resolved through wavelet transform, and wavelet transform is used to extract edge of high frequency part and mathematical morphology is used to extract low frequency part, then wavelet edge fusion is used to obtain effective hole edge.Finally, the least square method is utilized to calculate pore size. It is verified experimently that, compared with other algorithms, in the case of effectively preserving edge information of round hole and suppressing surrounding noise effectively, detection accuracy is controlled within 0.01 mm.Experimental results show that this method is simple and feasible, and has a high accuracy.
2017, 38(4): 627-631.
doi: 10.5768/JAO201738.0405001
Abstract:
The main object of this paper is precise alignment and inspection process technology for reflecting collimator with focus length of 4 000 mm and aperture diameter of 400 mm. As the detection and calibration datum of a certain type of optical system, this reflecting collimator has a very high demand in system imaging quality, resolution and beam parallel difference. Therefore, this paper focuses on key processes such as micro-stress bonding method, spacing precise adjustment method, optical axis consistency adjustment method of primary and secondary mirror of the Cassegrain system. Then precise alignment and inspection is carried out with optical self-collimation method. Final system resolution of reflecting collimator is better than or equal to 0.8 second, the parallel deviation is better than or equal to 3 seconds, star energy is concentrated without obvious aberration, and vertical line of cross-graduation could be perpendicular to the base plane.Results show that optical self-collimation method used in reflecting collimator can meet design requirements.
The main object of this paper is precise alignment and inspection process technology for reflecting collimator with focus length of 4 000 mm and aperture diameter of 400 mm. As the detection and calibration datum of a certain type of optical system, this reflecting collimator has a very high demand in system imaging quality, resolution and beam parallel difference. Therefore, this paper focuses on key processes such as micro-stress bonding method, spacing precise adjustment method, optical axis consistency adjustment method of primary and secondary mirror of the Cassegrain system. Then precise alignment and inspection is carried out with optical self-collimation method. Final system resolution of reflecting collimator is better than or equal to 0.8 second, the parallel deviation is better than or equal to 3 seconds, star energy is concentrated without obvious aberration, and vertical line of cross-graduation could be perpendicular to the base plane.Results show that optical self-collimation method used in reflecting collimator can meet design requirements.
2017, 38(4): 632-638.
doi: 10.5768/JAO201738.0405002
Abstract:
To improve optical performance of vacuum camera as the goal, feasibility of existing corrector lens as a vacuum camera window is studied. Through existing geometric model of corrector lens, mechanics field is mapped into the finite element model, and deformation of corrector lens under atmospheric pressure difference is calculated. The least squares method is used to solve 6-order coefficients of Zernike polynomial and the fitting solution are used to solve corrector lens shape equation. Effect of modified corrector lens on vacuum camera image quality is analyzed. Results show that deformation radius of the latent image of vacuum camera is 41.9% higher than that of original image, but CCD focal length changes from 249.554 mm to 249.574mm, so that CCD diffuse radius of bitmap is between 0.301% and 1.09% of the original, and the original image quality of LAMOST low-resolution spectrometer camera is maintained. Therefore, existing corrector lens can be used directly in vacuum camera design.
To improve optical performance of vacuum camera as the goal, feasibility of existing corrector lens as a vacuum camera window is studied. Through existing geometric model of corrector lens, mechanics field is mapped into the finite element model, and deformation of corrector lens under atmospheric pressure difference is calculated. The least squares method is used to solve 6-order coefficients of Zernike polynomial and the fitting solution are used to solve corrector lens shape equation. Effect of modified corrector lens on vacuum camera image quality is analyzed. Results show that deformation radius of the latent image of vacuum camera is 41.9% higher than that of original image, but CCD focal length changes from 249.554 mm to 249.574mm, so that CCD diffuse radius of bitmap is between 0.301% and 1.09% of the original, and the original image quality of LAMOST low-resolution spectrometer camera is maintained. Therefore, existing corrector lens can be used directly in vacuum camera design.
2017, 38(4): 639-643.
doi: 10.5768/JAO201738.0405003
Abstract:
Three-lens Offner compensator was designed for off-axis aspheric surface with fast ratio and large asphericity. Because tolerance requirement of centering errors and air gap distances is very severe, corresponding barrel structure of compensator is designed. The structure separates line-centering error adjustment and angle-centering error adjustment, which can achieve high accuracy adjustment of the compensator. According to measuring results of center deviation measuring apparatus, finally angle-centering error between compensating lenses is 4.4″, line-centering error is 3.5 μm, and air gap distance error is 3.8 μm.Angle-centering error between compensating lenses series and field lens is 5.3″, line-centering error is 4.2 μm, and air gap distance error is 7.2 μm, which meet the demand of testing.Off-axis aspherical surface is tested by 4D interferometer and the compensator, PVq value is 0.135λ and RMS value is 0.019 5λ, better than designing requirements.
Three-lens Offner compensator was designed for off-axis aspheric surface with fast ratio and large asphericity. Because tolerance requirement of centering errors and air gap distances is very severe, corresponding barrel structure of compensator is designed. The structure separates line-centering error adjustment and angle-centering error adjustment, which can achieve high accuracy adjustment of the compensator. According to measuring results of center deviation measuring apparatus, finally angle-centering error between compensating lenses is 4.4″, line-centering error is 3.5 μm, and air gap distance error is 3.8 μm.Angle-centering error between compensating lenses series and field lens is 5.3″, line-centering error is 4.2 μm, and air gap distance error is 7.2 μm, which meet the demand of testing.Off-axis aspherical surface is tested by 4D interferometer and the compensator, PVq value is 0.135λ and RMS value is 0.019 5λ, better than designing requirements.
2017, 38(4): 644-648.
doi: 10.5768/JAO201738.0405004
Abstract:
The mirror of static Fourier transform spectrometer employs a micro stepped mirror, which allows the spectrometer to perform simultaneous sampling at various levels without a space driven device. Based on theoretical analysis and test data analysis and comparison, the method of using wedge shaped glass strips is eventually determined to make micro stepped reflection mirror.This method uses general optical elements and process to manufacture 1 wedge shaped glass block and 10 wedge shaped glass strips, then selects wedge shaped glass strip by sequence and cements them on the cant of wedge shaped glass block one by one, and uses UV adhesive to cement contact surface of adjacent wedge shaped glass strips.Horizontally it repeatedly pushs adjacent wedge shaped glass strip and uses instrumentation to measure adjacent stepped thickness until meeting the requirements, then cures UV adhesive with UV light.Steps above are repeated to create a micro step mirror with required step number.Compared with other methods, this method is safe and feasible, and has characteristics of consistency and step thickness controllable. It can be used to produce micro step mirror with height error of step only 0.124 μm and surface roughness 12 nm, satisfying system design requirements.
The mirror of static Fourier transform spectrometer employs a micro stepped mirror, which allows the spectrometer to perform simultaneous sampling at various levels without a space driven device. Based on theoretical analysis and test data analysis and comparison, the method of using wedge shaped glass strips is eventually determined to make micro stepped reflection mirror.This method uses general optical elements and process to manufacture 1 wedge shaped glass block and 10 wedge shaped glass strips, then selects wedge shaped glass strip by sequence and cements them on the cant of wedge shaped glass block one by one, and uses UV adhesive to cement contact surface of adjacent wedge shaped glass strips.Horizontally it repeatedly pushs adjacent wedge shaped glass strip and uses instrumentation to measure adjacent stepped thickness until meeting the requirements, then cures UV adhesive with UV light.Steps above are repeated to create a micro step mirror with required step number.Compared with other methods, this method is safe and feasible, and has characteristics of consistency and step thickness controllable. It can be used to produce micro step mirror with height error of step only 0.124 μm and surface roughness 12 nm, satisfying system design requirements.
2017, 38(4): 649-654.
doi: 10.5768/JAO201738.0406001
Abstract:
According to the image jitter of airborne infrared turret under low temperature, the main factors inducing the image jitter are analyzed.Through modeling, thermodynamic analyzing and statics analyzing, the max deflection of the pitch stents is 0.34 mm under low temperature, and is 0.46 mm under acceleration overload.By assembling the pitch stents and solidifying the configuration, deflection of the pitch stents is controlled less in 0.05 mm, which makes the pitch stents turn smoother.Moreover, improvement measures are proposed for spin wiring mode and motor brush installation location and control data is provided, which solves the problem of image jitter of airborne infrared turret under low temperature.
According to the image jitter of airborne infrared turret under low temperature, the main factors inducing the image jitter are analyzed.Through modeling, thermodynamic analyzing and statics analyzing, the max deflection of the pitch stents is 0.34 mm under low temperature, and is 0.46 mm under acceleration overload.By assembling the pitch stents and solidifying the configuration, deflection of the pitch stents is controlled less in 0.05 mm, which makes the pitch stents turn smoother.Moreover, improvement measures are proposed for spin wiring mode and motor brush installation location and control data is provided, which solves the problem of image jitter of airborne infrared turret under low temperature.
2017, 38(4): 655-659,678.
doi: 10.5768/JAO201738.0406002
Abstract:
According to the development needs of on-line infrared thermometry of metal organic chemical vapor deposition(MOCVD), a three-wavelength infrared thermometry is proposed, which can avoid the calibration of the effective area of detector hole and the modification of reflectivity. The design scheme of the three-wavelength (1 300 nm, 1 150 nm, 940 nm) on-line infrared thermometry probe and the light path are presented. The probe is used in the 5.08 cm(2 inch) silicon (111) substrate growing 10 μm GaN epitaxial wafer in THOMAS SWAN CCS MOCVD system.Result shows that the accuracy is within 1℃ in the range from 950℃ to 1 100℃, referring to the EpiTT infrared thermometry.The repeatability is within 1.0℃ from 700℃ to 1 100℃.The distance tolerance is 2 mm.Moreover, the probe is used in the 5.08 cm silicon (111) substrate growing blue light LED epitaxial wafer with InGaN/GaN MQW structure in homemade MOCVD system. Result shows that the lowest range of the probe is equally 435℃.The measurement noise of n-GaN layer during growing is at 0.75℃. The analysis of the measured results indicate that the method for single layer thin film epitaxial growth has the certain practicability, however, further improvements are needed for the multi-layer complex structure epitaxial growth.
According to the development needs of on-line infrared thermometry of metal organic chemical vapor deposition(MOCVD), a three-wavelength infrared thermometry is proposed, which can avoid the calibration of the effective area of detector hole and the modification of reflectivity. The design scheme of the three-wavelength (1 300 nm, 1 150 nm, 940 nm) on-line infrared thermometry probe and the light path are presented. The probe is used in the 5.08 cm(2 inch) silicon (111) substrate growing 10 μm GaN epitaxial wafer in THOMAS SWAN CCS MOCVD system.Result shows that the accuracy is within 1℃ in the range from 950℃ to 1 100℃, referring to the EpiTT infrared thermometry.The repeatability is within 1.0℃ from 700℃ to 1 100℃.The distance tolerance is 2 mm.Moreover, the probe is used in the 5.08 cm silicon (111) substrate growing blue light LED epitaxial wafer with InGaN/GaN MQW structure in homemade MOCVD system. Result shows that the lowest range of the probe is equally 435℃.The measurement noise of n-GaN layer during growing is at 0.75℃. The analysis of the measured results indicate that the method for single layer thin film epitaxial growth has the certain practicability, however, further improvements are needed for the multi-layer complex structure epitaxial growth.
2017, 38(4): 665-669.
doi: 10.5768/JAO201738.0407002
Abstract:
Mirror flatness greatly affects beam quality of output laser in laser system. In order to quantitatively evaluate influence of mirror defects on laser beam quality, parameters τ of describing relevance between mirror surface defects and laser beam, and δ of influence of mirror surface defects on distal light field are proposed. Influence of different mirror defects on laser beam quality is studied by simulation. Variation rules of parameters δ and correlation τ are obtained, ie, intrinsic linear relationship between parameters δ and correlation τ. For any TEM00 mode, TEM01 mode and TEM02 mode, this linear relationship is similar and universal. For example, when transmittance rate of mirror surface defects is 0, slope of linear curve that δ varies with τ is equal to 1.8 approximately, despite of whichever mode laser beam is.
Mirror flatness greatly affects beam quality of output laser in laser system. In order to quantitatively evaluate influence of mirror defects on laser beam quality, parameters τ of describing relevance between mirror surface defects and laser beam, and δ of influence of mirror surface defects on distal light field are proposed. Influence of different mirror defects on laser beam quality is studied by simulation. Variation rules of parameters δ and correlation τ are obtained, ie, intrinsic linear relationship between parameters δ and correlation τ. For any TEM00 mode, TEM01 mode and TEM02 mode, this linear relationship is similar and universal. For example, when transmittance rate of mirror surface defects is 0, slope of linear curve that δ varies with τ is equal to 1.8 approximately, despite of whichever mode laser beam is.
2017, 38(4): 660-664.
doi: 10.5768/JAO201738.0407001
Abstract:
In order to effectively improve thermal insulation performance of filter components in subsequent optical system of spaceborne lidar, and ensure center wavelength tuning accuracy of F-P etalon which is core component by using hot-light characteristic of material, preliminary thermal structure for filter assembly is designed in this paper. Steady-state thermal analysis for initial structure of filter components is conducted by finite element software Ansys Workbench and heating power range is determined. Then key parameters of thermal structure are optimized by multi-objective based on sensitivity analysis and optimal value of each parameter is determined. Results show that maximum heating power is 7.05 W when temperature of F-P etalon reaches at 48℃, which saves power consumption of 11.3%. And maximum temperature difference of F-P etalon surface is reduced from 0.253℃ to 0.05℃, which meets requirements of design specifications.
In order to effectively improve thermal insulation performance of filter components in subsequent optical system of spaceborne lidar, and ensure center wavelength tuning accuracy of F-P etalon which is core component by using hot-light characteristic of material, preliminary thermal structure for filter assembly is designed in this paper. Steady-state thermal analysis for initial structure of filter components is conducted by finite element software Ansys Workbench and heating power range is determined. Then key parameters of thermal structure are optimized by multi-objective based on sensitivity analysis and optimal value of each parameter is determined. Results show that maximum heating power is 7.05 W when temperature of F-P etalon reaches at 48℃, which saves power consumption of 11.3%. And maximum temperature difference of F-P etalon surface is reduced from 0.253℃ to 0.05℃, which meets requirements of design specifications.
2017, 38(4): 670-673.
doi: 10.5768/JAO201738.0407003
Abstract:
Laser with higher frequency, smaller dimension and wider band is required in underwater detection.We proposed the 1 064 nm miniaturization laser with high repetition frequency could be obtained by side-pumped laser technology and EO Q-switched technology, and 532 nm laser output could be achieved by extra-cavity-doubled frequency conversion.1 064 nm laser with output energy of 36 mJ and 532 nm laser with output energy of 20 mJ were obtained under conditions of 100 A power input current and 1 kHz Q-drive frequency.Results indicate that dual-band miniaturization laser with output of high pulse repetition frequency and narrow pulse width can be realized by diode-pumped laser technology and frequency conversion technology.
Laser with higher frequency, smaller dimension and wider band is required in underwater detection.We proposed the 1 064 nm miniaturization laser with high repetition frequency could be obtained by side-pumped laser technology and EO Q-switched technology, and 532 nm laser output could be achieved by extra-cavity-doubled frequency conversion.1 064 nm laser with output energy of 36 mJ and 532 nm laser with output energy of 20 mJ were obtained under conditions of 100 A power input current and 1 kHz Q-drive frequency.Results indicate that dual-band miniaturization laser with output of high pulse repetition frequency and narrow pulse width can be realized by diode-pumped laser technology and frequency conversion technology.
2017, 38(4): 674-678.
doi: 10.5768/JAO201738.0408001
Abstract:
A method to design coupling lens of fiber lighting based on the free-form surface is proposed. Through non-imaging optics design, based on the Etendue and the Snell's law, the iterative optimization of free-form surface is conducted, and the low-loss coupling between light source and optical fiber is realized. Simulation results show that using the LED chip as the light source, this lens can improve the flux transmission efficiency above 89% and has good applications and development prospects.
A method to design coupling lens of fiber lighting based on the free-form surface is proposed. Through non-imaging optics design, based on the Etendue and the Snell's law, the iterative optimization of free-form surface is conducted, and the low-loss coupling between light source and optical fiber is realized. Simulation results show that using the LED chip as the light source, this lens can improve the flux transmission efficiency above 89% and has good applications and development prospects.
2017, 38(4): 679-684.
doi: 10.5768/JAO201738.0408002
Abstract:
Optical fiber interference spectrometer is widely used in various fields of substance detection, because it has many characteristics such as small size, high resolution, anti-electromagnetic interference, high temperature resistance, etc. A spectrum measuring system based on Mach-Zehnder optical fiber interferometer is designed, which uses an electric optical fiber delay line to modulate the optical path difference.System constitution is introduced, spectrum calculation formula and spectral resolution calculation formula are deduced.Then experimental platform is setup, and a light source with wide spectrum is measured by the system, interference signal is collected and its spectrogram is demodulated.Results show the spectral resolution is 2.085 4 cm-1, when the maximum optical path difference is 0.479 5 cm. Analysis on the system shows that, performance of the optical fiber delay line, to a great extent, determines the resolution, accuracy and precision of the final demodulation spectrum, especially the accuracy of the speed and the delay time, and the linearity.
Optical fiber interference spectrometer is widely used in various fields of substance detection, because it has many characteristics such as small size, high resolution, anti-electromagnetic interference, high temperature resistance, etc. A spectrum measuring system based on Mach-Zehnder optical fiber interferometer is designed, which uses an electric optical fiber delay line to modulate the optical path difference.System constitution is introduced, spectrum calculation formula and spectral resolution calculation formula are deduced.Then experimental platform is setup, and a light source with wide spectrum is measured by the system, interference signal is collected and its spectrogram is demodulated.Results show the spectral resolution is 2.085 4 cm-1, when the maximum optical path difference is 0.479 5 cm. Analysis on the system shows that, performance of the optical fiber delay line, to a great extent, determines the resolution, accuracy and precision of the final demodulation spectrum, especially the accuracy of the speed and the delay time, and the linearity.
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