2016 Vol. 37, No. 1
Display Method:
2016, 37(1): 1-5.
doi: 10.5768/JAO201637.0101001
Abstract:
In order to capture and aim target promptly for operators，we developed a new liner motion compensation (LMC) algorithm for EO system of aeroplane including helicopter and unmanned aerial vehicle (UAV).By recounting the velocity vector of ground target in initial east-north-up (ENU) coordinates，the angular velocity of ground target relative to EO system in inertial coordinates can be obtained, the servo software then used the value to compensate.This method could drive the line of sight (LOS) of EO system to focus on the ground target area automatically while the operator does not operate the turret in systems manual mode.This method has been validated by a UAVs flying experiment.The result indicates that in the narrow field of view (NFOV，0.70.5) of TV camera，the opening angle between ground target point and LOS point to the UAV point is all less than 1/6 FOV of the observing camera in azimuth and elevation direction.
In order to capture and aim target promptly for operators，we developed a new liner motion compensation (LMC) algorithm for EO system of aeroplane including helicopter and unmanned aerial vehicle (UAV).By recounting the velocity vector of ground target in initial east-north-up (ENU) coordinates，the angular velocity of ground target relative to EO system in inertial coordinates can be obtained, the servo software then used the value to compensate.This method could drive the line of sight (LOS) of EO system to focus on the ground target area automatically while the operator does not operate the turret in systems manual mode.This method has been validated by a UAVs flying experiment.The result indicates that in the narrow field of view (NFOV，0.70.5) of TV camera，the opening angle between ground target point and LOS point to the UAV point is all less than 1/6 FOV of the observing camera in azimuth and elevation direction.
2016, 37(1): 6-11.
doi: 10.5768/JAO201637.0101002
Abstract:
The power of single EO detector is limited, so EO netting is used to improve the overcast power in airspace and time domain. In order to improve the detecting probability and ability of EO netting to against the attacting target, an optimal dispostion method based on genetic algorithm（GA） was presented for EO netting. A mathematical model was established for optimal disposition to getting the maximal overcast region, then the optimal disposition scheme and the coordinates of EO detectors in the netting were afforded by using the genetic algorithm. At last, the optimal disposition scheme and the figures of the detecting overcast region for 4 kinds of targets were given by Matlab simulation, and the maximal overcast region fmax was 0.681 after 60 times of iteration. The feasibility of the proposed method was proved.
The power of single EO detector is limited, so EO netting is used to improve the overcast power in airspace and time domain. In order to improve the detecting probability and ability of EO netting to against the attacting target, an optimal dispostion method based on genetic algorithm（GA） was presented for EO netting. A mathematical model was established for optimal disposition to getting the maximal overcast region, then the optimal disposition scheme and the coordinates of EO detectors in the netting were afforded by using the genetic algorithm. At last, the optimal disposition scheme and the figures of the detecting overcast region for 4 kinds of targets were given by Matlab simulation, and the maximal overcast region fmax was 0.681 after 60 times of iteration. The feasibility of the proposed method was proved.
2016, 37(1): 12-16.
doi: 10.5768/JAO201637.0101003
Abstract:
In order to realize the cultural heritage digital protection of Mogao Grottoes in Dunhuang, a real scene 3D modeling method based on the four-camera vision system was designed. At first, aiming at the problem of low accuracy of the feature points matching in binocular stereo vision system, a four-camera stereo vision system and high-accuracy stereo matching strategy adapted to it were designed. Using the redundant design and self-checking function of the fourcamera vision system, the high-accuracy spatial point cloud data can be obtained. Then, aiming at the problem of error connection between the uncorrelated objects in the Delaunay triangulation results, the length of triangle constraint condition in the image coordinate system and the world coordinate system were increased. It can be used to prevent the error triangle. The condition can be obtained adaptively according to the point cloud data distribution characteristic. The system has been applied to the 3D reconstruction of the 172nd cave in Mogao Grottoes. The results show that the system can reconstruct the complex scenes with multiple objects and large depth changes efficiently. The 172nd cave has 41649 effective point clouds, and the 3D modeling time is about half an hour.
In order to realize the cultural heritage digital protection of Mogao Grottoes in Dunhuang, a real scene 3D modeling method based on the four-camera vision system was designed. At first, aiming at the problem of low accuracy of the feature points matching in binocular stereo vision system, a four-camera stereo vision system and high-accuracy stereo matching strategy adapted to it were designed. Using the redundant design and self-checking function of the fourcamera vision system, the high-accuracy spatial point cloud data can be obtained. Then, aiming at the problem of error connection between the uncorrelated objects in the Delaunay triangulation results, the length of triangle constraint condition in the image coordinate system and the world coordinate system were increased. It can be used to prevent the error triangle. The condition can be obtained adaptively according to the point cloud data distribution characteristic. The system has been applied to the 3D reconstruction of the 172nd cave in Mogao Grottoes. The results show that the system can reconstruct the complex scenes with multiple objects and large depth changes efficiently. The 172nd cave has 41649 effective point clouds, and the 3D modeling time is about half an hour.
2016, 37(1): 17-23.
doi: 10.5768/JAO201637.0101004
Abstract:
The twin primary rainbows scattered by a liquid-filled micro-channel with circular cross-section were investigated with Debye theory and geometric optics. The twin primary rainbows do not always exist because of the total reflection. Therefore with numerical simulation, a critical radius ratio of the core to the coating was proposed to judge the existence of the twin primary rainbows. On the premise that the and rainbows exist, the rainbow can always be detected. However, the a rainbows sometimes cannot be detected when submerging in the other scattering structure. It is observed that the rainbow can be detected only when it locates at the right side of the secondary rainbow. And therefore the situation that the locations of the peaks of second-order rainbow and rainbow coincide was analyzed. Then a judgment criterion for whether the rainbow can be detected was proposed. Also an experiment system was built and a borosilicate capillary filled with deionized water was taken for experiment research. When the internal radius of the cylinder is 550 m and the external radius of the cylinder is 600 m, the twin primary rainbows exist due to the radius ratio is larger than the critical value 0.7485. But the rainbow cannot be observed according to the proposed judgment method. It accords with the phenomenon in the captured pattern that only therainbow can be seen.
The twin primary rainbows scattered by a liquid-filled micro-channel with circular cross-section were investigated with Debye theory and geometric optics. The twin primary rainbows do not always exist because of the total reflection. Therefore with numerical simulation, a critical radius ratio of the core to the coating was proposed to judge the existence of the twin primary rainbows. On the premise that the and rainbows exist, the rainbow can always be detected. However, the a rainbows sometimes cannot be detected when submerging in the other scattering structure. It is observed that the rainbow can be detected only when it locates at the right side of the secondary rainbow. And therefore the situation that the locations of the peaks of second-order rainbow and rainbow coincide was analyzed. Then a judgment criterion for whether the rainbow can be detected was proposed. Also an experiment system was built and a borosilicate capillary filled with deionized water was taken for experiment research. When the internal radius of the cylinder is 550 m and the external radius of the cylinder is 600 m, the twin primary rainbows exist due to the radius ratio is larger than the critical value 0.7485. But the rainbow cannot be observed according to the proposed judgment method. It accords with the phenomenon in the captured pattern that only therainbow can be seen.
2016, 37(1): 24-28.
doi: 10.5768/JAO201637.0101005
Abstract:
In order to meet the practical requirement of EMCCD investigation and detection device, a three-field-of-view(FOV) optical system was designed．The electron multiplying charged coupled device (EMCCD) was used for receiving, and the size of the image pixel was 16 m16 m．By comparing the advantages and disadvantages of 4 different imaging structures, the initial structure of three-FOV optical system was chosen. Furthermore,the system was optimized by using CODEV software to guarantee the excellent image quality of the three-FOV optical system in the wavebands from 600 nm to 850 nm. The design results show that the MTF of three-FOV optical system is larger than 0.5 at 35 lp/mm, the size of the root-mean-square(RMS) spot is less than the size of the pixel, the distortion is less than 0.2%, and the image contrast satisfies the use requirement well.
In order to meet the practical requirement of EMCCD investigation and detection device, a three-field-of-view(FOV) optical system was designed．The electron multiplying charged coupled device (EMCCD) was used for receiving, and the size of the image pixel was 16 m16 m．By comparing the advantages and disadvantages of 4 different imaging structures, the initial structure of three-FOV optical system was chosen. Furthermore,the system was optimized by using CODEV software to guarantee the excellent image quality of the three-FOV optical system in the wavebands from 600 nm to 850 nm. The design results show that the MTF of three-FOV optical system is larger than 0.5 at 35 lp/mm, the size of the root-mean-square(RMS) spot is less than the size of the pixel, the distortion is less than 0.2%, and the image contrast satisfies the use requirement well.
2016, 37(1): 29-38.
doi: 10.5768/JAO201637.0101006
Abstract:
An automatic single-point imaging compressive sampling (CS) system was developed in the present work based on the concept of manual CS system. The design of the rotating coding disc and the way for obtaining the information of coding block were presented. A series of optimized coding blocks were used as sensing matrix and the minimum mean square error linear estimate (MMSE) algorithm was employed for image reconstruction. The quality of image reconstruction could be guaranteed when low sample rate of 7.8% was used. It is demonstrated that the proposed automatic system can work better than the manual one, with lower error, higher efficiency and more flexible in measurement times.
An automatic single-point imaging compressive sampling (CS) system was developed in the present work based on the concept of manual CS system. The design of the rotating coding disc and the way for obtaining the information of coding block were presented. A series of optimized coding blocks were used as sensing matrix and the minimum mean square error linear estimate (MMSE) algorithm was employed for image reconstruction. The quality of image reconstruction could be guaranteed when low sample rate of 7.8% was used. It is demonstrated that the proposed automatic system can work better than the manual one, with lower error, higher efficiency and more flexible in measurement times.
2016, 37(1): 39-44.
doi: 10.5768/JAO201637.0101007
Abstract:
A digital fish-eye lens for dome-screen projector applied to 0.63 inch 3-liquid crystal on silicon(3LCD) projectors was designed in Zemax based on the principle of non-similarity. The lens is composed of 6 spherical lenses, and has the retrofocus optical structure. Its image quality is excellent with the advantages of simple structure, low cost and easy process. The full field of view (FOV) of the lens is 180, the effective focal length (EFL) is 3.28 mm, the relative aperture is 1/1.9,the back focus length( BFL) is 35.8 mm and the length of optical system is 196 mm. Its modulation transfer function (MTF) in all field is higher than 0.4 at 50 lp/mm. The lateral color is less than 4.5 m. The absolute value of F-Theta distortion of the full of view is less than 3%. The relative illumination of the image in the maximum of view is 96.27%.
A digital fish-eye lens for dome-screen projector applied to 0.63 inch 3-liquid crystal on silicon(3LCD) projectors was designed in Zemax based on the principle of non-similarity. The lens is composed of 6 spherical lenses, and has the retrofocus optical structure. Its image quality is excellent with the advantages of simple structure, low cost and easy process. The full field of view (FOV) of the lens is 180, the effective focal length (EFL) is 3.28 mm, the relative aperture is 1/1.9,the back focus length( BFL) is 35.8 mm and the length of optical system is 196 mm. Its modulation transfer function (MTF) in all field is higher than 0.4 at 50 lp/mm. The lateral color is less than 4.5 m. The absolute value of F-Theta distortion of the full of view is less than 3%. The relative illumination of the image in the maximum of view is 96.27%.
2016, 37(1): 45-51.
doi: 10.5768/JAO201637.0101008
Abstract:
Aiming at the increasing requirements of image quality in traffic monitoring, a day-and-night optical system with large aperture and big target plane was designed. Through using the near-symmetric configuration, the design idea for adjustmenting the structural parameters of the first component and balancing day-and-night confocal plane was adopted to realize a large aperture and sensor optical system with excellent controlling of the vertical axis aberration and defocus amount. The multi-configuration optimization design was conducted in visible wavelengths and near-infrared wavelength of 0.79um. The day-and-night defocus amount of less than 0.005 mm could be achieved, the modulation transfer function (MTF) in full field of view is beyond 0.3 at the spatial frequency of 130 lp/mm in full field. Moreover,tolerance analysis and discussion for the optical system were done, and the deciding tolerance was suggested to be controlled for reducing the big deviation between- actual image and theoretical image resulted from manufacturing and producting.
Aiming at the increasing requirements of image quality in traffic monitoring, a day-and-night optical system with large aperture and big target plane was designed. Through using the near-symmetric configuration, the design idea for adjustmenting the structural parameters of the first component and balancing day-and-night confocal plane was adopted to realize a large aperture and sensor optical system with excellent controlling of the vertical axis aberration and defocus amount. The multi-configuration optimization design was conducted in visible wavelengths and near-infrared wavelength of 0.79um. The day-and-night defocus amount of less than 0.005 mm could be achieved, the modulation transfer function (MTF) in full field of view is beyond 0.3 at the spatial frequency of 130 lp/mm in full field. Moreover,tolerance analysis and discussion for the optical system were done, and the deciding tolerance was suggested to be controlled for reducing the big deviation between- actual image and theoretical image resulted from manufacturing and producting.
2016, 37(1): 52-56.
doi: 10.5768/JAO201637.0101009
Abstract:
For the digital micromirror device (DMD) digital lithography, a ten-lenses projection objective was designed for DMD of model 0.7XGA by using Zemax optical design software. The projection objective uses the non-symmetrical structure, which has improved air-spaced triplet as front group and Petzval objective with flat field lens as back group, making it own higher resolution with 2 m. Its paraxial magnification is -0.15,the image-side numerical aperture (NA) is 0.158, the wavefront aberration is less than /20,the distortion is less than 0.014% and focal depth is 20 m. Through using Zemax to simulate, the system reaches diffraction limit theoretically. After tolerance analysis, by using Monte Carlo method, 100 groups of lenses were simulated for fabricating and assembling,results show that 90% of them could realize MTF＞0.46 and 50% could realize MTF＞0.51, which proves the possibility of fabricating and assembling such a non-symmetrical structure.
For the digital micromirror device (DMD) digital lithography, a ten-lenses projection objective was designed for DMD of model 0.7XGA by using Zemax optical design software. The projection objective uses the non-symmetrical structure, which has improved air-spaced triplet as front group and Petzval objective with flat field lens as back group, making it own higher resolution with 2 m. Its paraxial magnification is -0.15,the image-side numerical aperture (NA) is 0.158, the wavefront aberration is less than /20,the distortion is less than 0.014% and focal depth is 20 m. Through using Zemax to simulate, the system reaches diffraction limit theoretically. After tolerance analysis, by using Monte Carlo method, 100 groups of lenses were simulated for fabricating and assembling,results show that 90% of them could realize MTF＞0.46 and 50% could realize MTF＞0.51, which proves the possibility of fabricating and assembling such a non-symmetrical structure.
2016, 37(1): 57-63.
doi: 10.5768/JAO201637.0102001
Abstract:
Multiframe blind deconvolution algorithm,which is one of the primary methods for restoring image,can enhance the resolving power of the adaptive optical images. However,the multiframe blind deconvolution algorithm takes the alternate minimization, optimize deconvolution methods to solve the images and the point spread functions (PSFs) of the objects, the arithmetic is complexed and time-consuming,it always needs several minutes even up to several quarters to solve the problem. Via developing the central processing unit-graphics processing unit (CPU-GPU) heterogeneous system architecture, through the combination of using library function and modulating the structure of the algorithm, we optimized the most time-consuming part, matrix convolution, and achieved the parallel methods of restoring image.Results show that for more than 16 frames of spatical target images with 256256 pixels,the speed-up ratio of 17 could be realized.This paper can provide a feasible scheme for real-time/quasi real-timeimage restoration.
Multiframe blind deconvolution algorithm,which is one of the primary methods for restoring image,can enhance the resolving power of the adaptive optical images. However,the multiframe blind deconvolution algorithm takes the alternate minimization, optimize deconvolution methods to solve the images and the point spread functions (PSFs) of the objects, the arithmetic is complexed and time-consuming,it always needs several minutes even up to several quarters to solve the problem. Via developing the central processing unit-graphics processing unit (CPU-GPU) heterogeneous system architecture, through the combination of using library function and modulating the structure of the algorithm, we optimized the most time-consuming part, matrix convolution, and achieved the parallel methods of restoring image.Results show that for more than 16 frames of spatical target images with 256256 pixels,the speed-up ratio of 17 could be realized.This paper can provide a feasible scheme for real-time/quasi real-timeimage restoration.
2016, 37(1): 64-68.
doi: 10.5768/JAO201637.0102002
Abstract:
Phase shifting interferometry enjoys a wide application in optical precision measurement. However, the common phase extraction algorithm is vulnerable to phase stepping errors of the phase shifters. The former least square iterative phase extraction algorithm can suppress the influence of phase stepping errors ，but it takes long time. We presented a high-efficiency least square iterative phase extraction algorithm based on selective sampling. Firstly the interferogram pixels were sampled with an equal interval to reduce the calculation time; Next the low quality pixels were filtered out based on the interference contrast to prevent the phase error from growing; In the experiment, when the sampling interval was set to 2, the proposed algorithm took only 0.725 s, compared with the 6.687 s of the former iterative method, and the discrepancy of phase shift was only 0.032 9. The experiment verifies that the proposed algorithm can greatly reduce the calculation time with little compromise of phase extraction accuracy, which is highly suitable for highspeed phase shifting measurement applications.
Phase shifting interferometry enjoys a wide application in optical precision measurement. However, the common phase extraction algorithm is vulnerable to phase stepping errors of the phase shifters. The former least square iterative phase extraction algorithm can suppress the influence of phase stepping errors ，but it takes long time. We presented a high-efficiency least square iterative phase extraction algorithm based on selective sampling. Firstly the interferogram pixels were sampled with an equal interval to reduce the calculation time; Next the low quality pixels were filtered out based on the interference contrast to prevent the phase error from growing; In the experiment, when the sampling interval was set to 2, the proposed algorithm took only 0.725 s, compared with the 6.687 s of the former iterative method, and the discrepancy of phase shift was only 0.032 9. The experiment verifies that the proposed algorithm can greatly reduce the calculation time with little compromise of phase extraction accuracy, which is highly suitable for highspeed phase shifting measurement applications.
2016, 37(1): 69-73.
doi: 10.5768/JAO201637.0102003
Abstract:
In order to improve the performance of three-dimensional reconstruction and overcome the highly dependent relationship on calibration board, an efficient generation 3D printing model method was proposed. Without using the calibration board to calculate the camera parameters in this method,the image captured by single camera can be used to generate 3D model. However, this self-calibration method is deeply influenced by the image quality and point matching accuracy, which limits the 3D printing model generation with high efficiency. In order to overcome these effects, firstly the background area and restrain noise are removed by interactive and graph partition to enhance the images region-of-tnterest(ROI).Second feature point is extracted from sequences pictures by improved speed-up robust features (SURF) algorithm and is matched based on its matching factor, which shows faster than the previous program. Then camera model parameters are calculated by self-calibration matching information. Finally, dense 3D object is reconstructed by combining camera model and feature point matching information. A series of experiments show the proposed method is characterized by effectiveness, convenience and wide application.
In order to improve the performance of three-dimensional reconstruction and overcome the highly dependent relationship on calibration board, an efficient generation 3D printing model method was proposed. Without using the calibration board to calculate the camera parameters in this method,the image captured by single camera can be used to generate 3D model. However, this self-calibration method is deeply influenced by the image quality and point matching accuracy, which limits the 3D printing model generation with high efficiency. In order to overcome these effects, firstly the background area and restrain noise are removed by interactive and graph partition to enhance the images region-of-tnterest(ROI).Second feature point is extracted from sequences pictures by improved speed-up robust features (SURF) algorithm and is matched based on its matching factor, which shows faster than the previous program. Then camera model parameters are calculated by self-calibration matching information. Finally, dense 3D object is reconstructed by combining camera model and feature point matching information. A series of experiments show the proposed method is characterized by effectiveness, convenience and wide application.
2016, 37(1): 71-79.
doi: 10.5768/JAO201637.0103001
Abstract:
For high accuracy observation of atmosphere radiation characteristics about the ground calibration of satellite remote sensor, a solar irradiance spectraradiometer that can realize high accuracy measurement has been developed. Considering the attenuation and loss of the instrument when worked in the field, the self-calibration system that suited to long-term application was designed. The enantiomorphous design of double-channel was adopted in the self-calibration system, and the coupling mirror based on spherical lens was designed to switch light direction, so the monochromatic light entering the prism was achieved. Based on the design of light path, the reflector which was driven by the stepping motor was designed to switch the optical path, and the flux of incident/emergent light was acquired by the monolithic detector, finally the transmission of the prism was acquired by ratio calculation. The performance of self-calibration system was tested in and out the laboratory, the repeatability error was less than 2.5% indoor and the relative deviation of transmission indoor and outdoor was less than 2%, the results show that the self-calibration system can be used for monitoring and correction of field equipment.
For high accuracy observation of atmosphere radiation characteristics about the ground calibration of satellite remote sensor, a solar irradiance spectraradiometer that can realize high accuracy measurement has been developed. Considering the attenuation and loss of the instrument when worked in the field, the self-calibration system that suited to long-term application was designed. The enantiomorphous design of double-channel was adopted in the self-calibration system, and the coupling mirror based on spherical lens was designed to switch light direction, so the monochromatic light entering the prism was achieved. Based on the design of light path, the reflector which was driven by the stepping motor was designed to switch the optical path, and the flux of incident/emergent light was acquired by the monolithic detector, finally the transmission of the prism was acquired by ratio calculation. The performance of self-calibration system was tested in and out the laboratory, the repeatability error was less than 2.5% indoor and the relative deviation of transmission indoor and outdoor was less than 2%, the results show that the self-calibration system can be used for monitoring and correction of field equipment.
2016, 37(1): 80-86.
doi: 10.5768/JAO201637.0103002
Abstract:
The high-quality flat reflector with 2 m aperture can be used for image quality evaluation and performance testing of large-aperture optical instruments. However, by the impact of usage environment, the surface accuracy of large flat reflector cannot maintain long-term stability. Therefore, the surface quality needs to fast calibration on site before using. But the conventional full-caliber or sub-aperture interferometry measurement methods are difficult to meet these needs. Due to the high frequency error of mirror introduced in the manufacturing process being in a steady state, the environmental perturbations introduce only low frequency aberrations. And the selected reconstructed wave-front profile followed with sub-aperture slope scanning is more suitable for surface quality calibration on site of large flat reflector. A double-pentaprism with dual-goniometer synchronize differential measurement method was proposed, which could reduce the random error caused by environmental disturbances in long measurement cycle. Moreover,the optical, mechanical and control system of measurement instrument was designed. And two S-H sensors were proposed to use to instead of traditional goniometer for subapertures slope measurement. Currently validation tests show that the wave-front reconstruction algorithms and instrument angular accuracy meet the demand of accuracy for surface quality, the mutual difference is less than 20 nm (root-mean-square,RMS) with the test result of ZYGO interferometric measurement.
The high-quality flat reflector with 2 m aperture can be used for image quality evaluation and performance testing of large-aperture optical instruments. However, by the impact of usage environment, the surface accuracy of large flat reflector cannot maintain long-term stability. Therefore, the surface quality needs to fast calibration on site before using. But the conventional full-caliber or sub-aperture interferometry measurement methods are difficult to meet these needs. Due to the high frequency error of mirror introduced in the manufacturing process being in a steady state, the environmental perturbations introduce only low frequency aberrations. And the selected reconstructed wave-front profile followed with sub-aperture slope scanning is more suitable for surface quality calibration on site of large flat reflector. A double-pentaprism with dual-goniometer synchronize differential measurement method was proposed, which could reduce the random error caused by environmental disturbances in long measurement cycle. Moreover,the optical, mechanical and control system of measurement instrument was designed. And two S-H sensors were proposed to use to instead of traditional goniometer for subapertures slope measurement. Currently validation tests show that the wave-front reconstruction algorithms and instrument angular accuracy meet the demand of accuracy for surface quality, the mutual difference is less than 20 nm (root-mean-square,RMS) with the test result of ZYGO interferometric measurement.
2016, 37(1): 87-90.
doi: 10.5768/JAO201637.0103003
Abstract:
The influencing factors on optical path collimation between transmitter and receiver were analyzed based on long baseline transmittance meter. Aiming at the measurement principle of transmittance meter,the mechanism of optical path collimation influencing transmittance meters measurement precision was presented,which was realized by influencing the receiving intensity of receiver. And the impact of the deviation of transmitting/receiving end optical path collimation on the receiving intensity of receiving end was studied by simulation. The results show that there is a linear relationship between the receiving intensity error and the transmittance meters measurement error,and the transmitting/receiving end collimation has a great influence on the receiving intensity of receiving end, the receiving intensity of receiver can change by 0.02 mW when the transmitter attitude angle changes by 0.01. The change of transmitter attitude angle can decrease the receiving intensity obviously and increase the measurement error, therefore, the probe optical path collimation is an important influencing factor on the visibility measurement.
The influencing factors on optical path collimation between transmitter and receiver were analyzed based on long baseline transmittance meter. Aiming at the measurement principle of transmittance meter,the mechanism of optical path collimation influencing transmittance meters measurement precision was presented,which was realized by influencing the receiving intensity of receiver. And the impact of the deviation of transmitting/receiving end optical path collimation on the receiving intensity of receiving end was studied by simulation. The results show that there is a linear relationship between the receiving intensity error and the transmittance meters measurement error,and the transmitting/receiving end collimation has a great influence on the receiving intensity of receiving end, the receiving intensity of receiver can change by 0.02 mW when the transmitter attitude angle changes by 0.01. The change of transmitter attitude angle can decrease the receiving intensity obviously and increase the measurement error, therefore, the probe optical path collimation is an important influencing factor on the visibility measurement.
2016, 37(1): 91-95.
doi: 10.5768/JAO201637.0103004
Abstract:
Considering the requirement of measurement for video probe, a method for measuring points, lines and surfaces of object by using line-structured laser was presented. The line-structured light imaging model was built, where the linear laser was used as an auxiliary light source irradiating on the surface of the object. Compared to the object image, the proportional coefficient was calibrated with multiplying factor in different distances and laser line positions. The geometry parameters were calculated based on the measurement platform. The experimental results show that the measuring error is less than 10%, which indicates the method can satify the requirements of the video probe.
Considering the requirement of measurement for video probe, a method for measuring points, lines and surfaces of object by using line-structured laser was presented. The line-structured light imaging model was built, where the linear laser was used as an auxiliary light source irradiating on the surface of the object. Compared to the object image, the proportional coefficient was calibrated with multiplying factor in different distances and laser line positions. The geometry parameters were calculated based on the measurement platform. The experimental results show that the measuring error is less than 10%, which indicates the method can satify the requirements of the video probe.
2016, 37(1): 96-99.
doi: 10.5768/JAO201637.0103005
Abstract:
In the process of local imaging detection, due to the difference of parts with complex outline or placement state, the parts and image plane coordinates have a certain angle, which can cause the problem that there are asymmetric point sets or no symmetric points in the acquired symmetric sets. When using traditional Hough transform or fitting method to detect assembly coaxality, it has much error. A detection algorithm of assembly coaxality in local imaging was proposed to solve the above problem.This algorithm firstly extracts the upper and lower edge point sets and then counts the parameter space points projecting in Hough space from two point sets based on Hough linear transform. Finally, it searches the maximum point of parameter points cumulative number, the point corresponds to the symmetric axis which is the optimal symmetric axis. The simulated result shows that the method can extract the optimal symmetric axis with high accuracy, and the coaxality error is only 0.002 7 . Therefore, the algorithm of assembly coaxality in local imaging is feasible.
In the process of local imaging detection, due to the difference of parts with complex outline or placement state, the parts and image plane coordinates have a certain angle, which can cause the problem that there are asymmetric point sets or no symmetric points in the acquired symmetric sets. When using traditional Hough transform or fitting method to detect assembly coaxality, it has much error. A detection algorithm of assembly coaxality in local imaging was proposed to solve the above problem.This algorithm firstly extracts the upper and lower edge point sets and then counts the parameter space points projecting in Hough space from two point sets based on Hough linear transform. Finally, it searches the maximum point of parameter points cumulative number, the point corresponds to the symmetric axis which is the optimal symmetric axis. The simulated result shows that the method can extract the optimal symmetric axis with high accuracy, and the coaxality error is only 0.002 7 . Therefore, the algorithm of assembly coaxality in local imaging is feasible.
2016, 37(1): 100-104.
doi: 10.5768/JAO201637.0103006
Abstract:
An improved method was presented based on the slanted-edge method. It uses the Canny algorithm to detect edge in the acquired image, and calculates the high threshold which is significant to the Canny algorithm by using the Otsu algorithm combined with the bimodal characteristics of the edge image histogram. The centroid of each row is regarded as the center of edge spread function (ESF), then the two-dimensional edge data sampled with subpixel spacing from a region along the direction of the detected edge is reprojected to a one-dimensional array of sub-pixel bins, the ESF is obtained after averaging under improving the sampling rate. It increases the signal-to-noise ratio of the measurement. We used this method to test the modulation transfer function (MTF) of charge couple-device (CCD) camera in the laboratory, and analyzed the influences of parameter settings on accuracy of the MTF measurement.Result shows that the relative errors between the theoretical values and the experimental results are within 5%.
An improved method was presented based on the slanted-edge method. It uses the Canny algorithm to detect edge in the acquired image, and calculates the high threshold which is significant to the Canny algorithm by using the Otsu algorithm combined with the bimodal characteristics of the edge image histogram. The centroid of each row is regarded as the center of edge spread function (ESF), then the two-dimensional edge data sampled with subpixel spacing from a region along the direction of the detected edge is reprojected to a one-dimensional array of sub-pixel bins, the ESF is obtained after averaging under improving the sampling rate. It increases the signal-to-noise ratio of the measurement. We used this method to test the modulation transfer function (MTF) of charge couple-device (CCD) camera in the laboratory, and analyzed the influences of parameter settings on accuracy of the MTF measurement.Result shows that the relative errors between the theoretical values and the experimental results are within 5%.
2016, 37(1): 105-112.
doi: 10.5768/JAO201637.0105001
Abstract:
A compact mobile phone lens based on the wavefront coding(WFC) was designed, the depth of field (DOF) of the original system was 0.017 mm. The cubic phase mask (CPM) was utilized and the parameters of phase mask could be optimized base on Strehl ratio (SR) to keep the stability of the modulation transfer function (MTF) at different positions. Finally the designed DOF reached 0.136 mm,which extended 8 times. The effect of DOF extension was verified by simulation through Zemax software. Results indicate that it can increase the DOF of fixed mobile phone system,make the structure compact as well as overcome the field effect through using WFC.
A compact mobile phone lens based on the wavefront coding(WFC) was designed, the depth of field (DOF) of the original system was 0.017 mm. The cubic phase mask (CPM) was utilized and the parameters of phase mask could be optimized base on Strehl ratio (SR) to keep the stability of the modulation transfer function (MTF) at different positions. Finally the designed DOF reached 0.136 mm,which extended 8 times. The effect of DOF extension was verified by simulation through Zemax software. Results indicate that it can increase the DOF of fixed mobile phone system,make the structure compact as well as overcome the field effect through using WFC.
2016, 37(1): 113-117.
doi: 10.5768/JAO201637.0105002
Abstract:
In order to asure high machining precision and improve polishing efficiency, a new removal function of annular polishing pad based on translation-rotation motion was investigated and deduced, which was needed in disc hydrodynamic polishing. Based on translation-rotation motion, compared with the round polishing pad which is the most widely used, the highest tending factor of annular polishing pad improves by 10.25% and its form of removal function is more closer to the impulse function form. Therefore, it can reduce the convolution effect and smooth out mid-to-high spatial frequency errors. Setting the initial surface error, the pulse iteration method was used to compute the residual error and the dwell time with the same parameters. After 50 times iteration, the simulation result proves that the residual error of annular polishing pad reduces by 3.65% than round polishing pad. The polishing removal efficiency can be improved.
In order to asure high machining precision and improve polishing efficiency, a new removal function of annular polishing pad based on translation-rotation motion was investigated and deduced, which was needed in disc hydrodynamic polishing. Based on translation-rotation motion, compared with the round polishing pad which is the most widely used, the highest tending factor of annular polishing pad improves by 10.25% and its form of removal function is more closer to the impulse function form. Therefore, it can reduce the convolution effect and smooth out mid-to-high spatial frequency errors. Setting the initial surface error, the pulse iteration method was used to compute the residual error and the dwell time with the same parameters. After 50 times iteration, the simulation result proves that the residual error of annular polishing pad reduces by 3.65% than round polishing pad. The polishing removal efficiency can be improved.
2016, 37(1): 118-123.
doi: 10.5768/JAO201637.0105003
Abstract:
Notch filter has been widely applied in laser damage resistance, laser protection and optoelectronic countermeasure fields, how to improve the passband transmittance and lower the notch transmittance is one of the hot research topics. A Rugate notch filter with a central wavelength of 1 550 nm was designed at the band of 400 nm~2 500 nm, a sensitivity analysis was undertaken in which several reflectance spectra were generated as a function of variations in the refractive index profile. Moreover,the designed filter was deposited on a single surface K9 substrate by plasma enhanced chemical vapor deposition (PECVD) technology. The experimental filter has 3.62% transmittance at 1 550 nm and 88.54% average transmittance at the pass band.
Notch filter has been widely applied in laser damage resistance, laser protection and optoelectronic countermeasure fields, how to improve the passband transmittance and lower the notch transmittance is one of the hot research topics. A Rugate notch filter with a central wavelength of 1 550 nm was designed at the band of 400 nm~2 500 nm, a sensitivity analysis was undertaken in which several reflectance spectra were generated as a function of variations in the refractive index profile. Moreover,the designed filter was deposited on a single surface K9 substrate by plasma enhanced chemical vapor deposition (PECVD) technology. The experimental filter has 3.62% transmittance at 1 550 nm and 88.54% average transmittance at the pass band.
2016, 37(1): 131-135.
doi: 10.5768/JAO201637.0105005
Abstract:
Illumination system of solid-state volumetric true 3D display requires high brightness and high stability. In order to improve the intensity of solid-state volumetric true 3D display, a kind of double-lamp illumination system based on direct current( DC) driving, parallel rays and features of light-rod illumination system was proposed. Based on the principle of etendue conservation, the converge distance was extended to realize double-lamp illumination. The doublelamp illumination system was optimized by optical simulation analysis to improve the efficiency and uniformity of the illumination system. Furthermore,the practical test system was built and measured. The result shows that the brightness on the 2-layer liquid crystal shutters in the scattering state is 41 711 cd/m2, which is 1.4 times of the brightness of the single lamp. The imaging luminance of solid-state volumetric true 3D display is efficiently improved.
Illumination system of solid-state volumetric true 3D display requires high brightness and high stability. In order to improve the intensity of solid-state volumetric true 3D display, a kind of double-lamp illumination system based on direct current( DC) driving, parallel rays and features of light-rod illumination system was proposed. Based on the principle of etendue conservation, the converge distance was extended to realize double-lamp illumination. The doublelamp illumination system was optimized by optical simulation analysis to improve the efficiency and uniformity of the illumination system. Furthermore,the practical test system was built and measured. The result shows that the brightness on the 2-layer liquid crystal shutters in the scattering state is 41 711 cd/m2, which is 1.4 times of the brightness of the single lamp. The imaging luminance of solid-state volumetric true 3D display is efficiently improved.
2016, 37(1): 136-142.
doi: 10.5768/JAO201637.0105006
Abstract:
Since the general reflectors cannot control the surface source effectively and there is unavoidable chromatic dispersion in lens, we proposed a freeform reflector design method. In our scheme, the surface source was located at the top of the reflector, whose luminous surface back faced the target plane. The surface source was divided to micro surfaces by finite element method, which were treated as point sources. According to the rectangular illumination distribution, the energy relationship between surface source and target plane was established. Meanwhile, the mathematical model of the reflector could be directly computed based on the theory of the differential geometry and Snell's law, then the numerical solution of freeform reflector could be calculated by Matlab software without feedback optimizing. By example,the numerical solution of the reflector of the table lamp was obtained by using associated software and the performance of the reflector was simulated by optical software. It is revealed that the illumination uniformity on target plane is above 0.8, while the energy efficiency can reach about 0.9.
Since the general reflectors cannot control the surface source effectively and there is unavoidable chromatic dispersion in lens, we proposed a freeform reflector design method. In our scheme, the surface source was located at the top of the reflector, whose luminous surface back faced the target plane. The surface source was divided to micro surfaces by finite element method, which were treated as point sources. According to the rectangular illumination distribution, the energy relationship between surface source and target plane was established. Meanwhile, the mathematical model of the reflector could be directly computed based on the theory of the differential geometry and Snell's law, then the numerical solution of freeform reflector could be calculated by Matlab software without feedback optimizing. By example,the numerical solution of the reflector of the table lamp was obtained by using associated software and the performance of the reflector was simulated by optical software. It is revealed that the illumination uniformity on target plane is above 0.8, while the energy efficiency can reach about 0.9.
2016, 37(1): 124-130.
doi: 10.5768/JAO201637.0105004
Abstract:
Thin film coatings in actual application are always characterized by some kind of, slight or large, refractive index inhomogeneity. Its accurate characterization can be vital to the process parameters calibration of coating machine, and to the design and manufacture of ultra low loss coatings. According to Schr?der approximation, the characteristic matrix of a slightly inhomogeneous thin film was derived, and an approximation model for the spectral characteristics calculation of slightly inhomogeneous multilayer coatings was presented by the matrix method. Based on the effective medium approximation theory and infinite division into large homogeneous sublayers, the effectiveness, calculation accuracy and time consumption of the approximation model were discussed in details. It shows that this model presents a fast and effective tool for the reverse determination of the refractive index inhomogeneity defect of multilayer system, and lays a foundation for the numerical optimization algorithm application into the data fitting based on the measured broadband spectral characteristics of actual multilayer coatings.
Thin film coatings in actual application are always characterized by some kind of, slight or large, refractive index inhomogeneity. Its accurate characterization can be vital to the process parameters calibration of coating machine, and to the design and manufacture of ultra low loss coatings. According to Schr?der approximation, the characteristic matrix of a slightly inhomogeneous thin film was derived, and an approximation model for the spectral characteristics calculation of slightly inhomogeneous multilayer coatings was presented by the matrix method. Based on the effective medium approximation theory and infinite division into large homogeneous sublayers, the effectiveness, calculation accuracy and time consumption of the approximation model were discussed in details. It shows that this model presents a fast and effective tool for the reverse determination of the refractive index inhomogeneity defect of multilayer system, and lays a foundation for the numerical optimization algorithm application into the data fitting based on the measured broadband spectral characteristics of actual multilayer coatings.
2016, 37(1): 142-146.
doi: 10.5768/JAO201637.0107001
Abstract:
In order to develop the laser remote sensing ways for the acquisition of ocean optical parameters, a new method was presented to measure the ocean internal optical parameters using subsurface backscattering signal of lidar, based on the application of high spectral resolution lidar (HSRL) in the measurement of atmosphere backscattering. In theory,the system building and the method of separation measurement of the backscattering signal from water molecules (Rayleigh scattering) and suspended particles (Mie scattering) using iodine molecules absorption filter were introduced. In result, the specific inversion algorithm for calculating the backscattering coefficient and the extinction coefficient of the sea water was presented.
In order to develop the laser remote sensing ways for the acquisition of ocean optical parameters, a new method was presented to measure the ocean internal optical parameters using subsurface backscattering signal of lidar, based on the application of high spectral resolution lidar (HSRL) in the measurement of atmosphere backscattering. In theory,the system building and the method of separation measurement of the backscattering signal from water molecules (Rayleigh scattering) and suspended particles (Mie scattering) using iodine molecules absorption filter were introduced. In result, the specific inversion algorithm for calculating the backscattering coefficient and the extinction coefficient of the sea water was presented.
2016, 37(1): 147-151.
doi: 10.5768/JAO201637.0107002
Abstract:
Cat-eye effect occurs when a parallel beam or a laser beam illuminates a focal plane imaging system in the direction of optical axis, where the orthogonality and defocus of the detector in relation with the optical axis and focal plane affects directly the property of the reflected light beam, further affects the performance of cat-eye effect based detecting system. The relation between the defocus amount and the divergence of reflected beam was investigated through both theoretical analysis and numerical calculation.When the defocus is 0.16mm, the minimum divergence angle is 0.019 mrad. Furthermore, an experimental system was set up to test the defocus and divergence, When the defocus is 0.15 mm, the minimum divergence angle is 0.25 mrad,indicating the test result agrees well with the calculation. The conclusions drawn from the investigation are as follows：1） the impact of negative defocus on the divergence of reflected beam is greater than that of positive defocus； 2）the divergence angle of the cat-eye reflected beam increases virtually along with the increasing of absolute defocus, but the function diagram of the divergence is not symmetric in shape with respect to the zero defocus point, rather, a unique minimal divergence exists at a certain positive defocus point.
Cat-eye effect occurs when a parallel beam or a laser beam illuminates a focal plane imaging system in the direction of optical axis, where the orthogonality and defocus of the detector in relation with the optical axis and focal plane affects directly the property of the reflected light beam, further affects the performance of cat-eye effect based detecting system. The relation between the defocus amount and the divergence of reflected beam was investigated through both theoretical analysis and numerical calculation.When the defocus is 0.16mm, the minimum divergence angle is 0.019 mrad. Furthermore, an experimental system was set up to test the defocus and divergence, When the defocus is 0.15 mm, the minimum divergence angle is 0.25 mrad,indicating the test result agrees well with the calculation. The conclusions drawn from the investigation are as follows：1） the impact of negative defocus on the divergence of reflected beam is greater than that of positive defocus； 2）the divergence angle of the cat-eye reflected beam increases virtually along with the increasing of absolute defocus, but the function diagram of the divergence is not symmetric in shape with respect to the zero defocus point, rather, a unique minimal divergence exists at a certain positive defocus point.
2016, 37(1): 152-156.
doi: 10.5768/JAO201637.0108001
Abstract:
To make clear the differences of optical path transmission and output signal between full-integrating sphere and semi-integrating sphere, the optical transmission models of the two integral spheres under fiber detection manner were established respectively. The formulas of output signal intensity and detection sensitivity were derived for the two kinds of integrating sphere tests. Based on the derived formulas, the theoretic analysis and verification experiments were conducted. It is found that both the signal intensity and the detection sensitivity for the two kinds of sphere tests depend on the coating reflectivity, the radius of integral sphere and the numerical aperture angle of optical fiber. Whether the semi-sphere performance is better than the fullsphere depends on the selection of the diffuse coating reflectivity and the mirror reflectivity. High reflectivity of mirror coating can improve the semiintegrating sphere sensitivity, while the low value can reduce the output. When the reflectivity of mirror coatings tends to 1, the output signal intensity of semisphere can be 2 times as the one of full-sphere.
To make clear the differences of optical path transmission and output signal between full-integrating sphere and semi-integrating sphere, the optical transmission models of the two integral spheres under fiber detection manner were established respectively. The formulas of output signal intensity and detection sensitivity were derived for the two kinds of integrating sphere tests. Based on the derived formulas, the theoretic analysis and verification experiments were conducted. It is found that both the signal intensity and the detection sensitivity for the two kinds of sphere tests depend on the coating reflectivity, the radius of integral sphere and the numerical aperture angle of optical fiber. Whether the semi-sphere performance is better than the fullsphere depends on the selection of the diffuse coating reflectivity and the mirror reflectivity. High reflectivity of mirror coating can improve the semiintegrating sphere sensitivity, while the low value can reduce the output. When the reflectivity of mirror coatings tends to 1, the output signal intensity of semisphere can be 2 times as the one of full-sphere.
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