2019 Vol. 48, No. 5
column
2019, 48(5): 503001.
doi: 10.3788/IRLA201948.0503001
Aiming at the problem that it was difficult to achieve large-scale and high-precision 3D reconstruction of land form of geomorphology by visual method in deep-sea environment, a design scheme of line structured light 3D reconstruction vision sensor for deep-sea topography features based on Jiaolong manned submersible was presented. According to the principle of 3D reconstruction of linear structured light, firstly, the Steger algorithm was improved to extract the center line of laser fringes quickly and accurately, then direct calibration method was used to solve the 2D spatial coordinates of topographic features, and the influence of image distortion on reconstruction was overcame. Then, the obtained 2D point cloud was fused with multi-sensor data, and the offset was calculated in real time according to the coordinates of the submersible, and the image was corrected according to the change of sensor position and attitude. Finally, the 3D point cloud data of landform was obtained. According to the reconstruction principle, the hardware and software system of the vision sensor was designed, and an experimental simulation platform was built to verify the feasibility of the scheme. Through underwater experiments, the complete reconstruction of simulated geomorphology can be achieved, with an accuracy of 96.9%, which meets the reconstruction requirements.
Aiming at the characteristics of large-scale, high-resolution, high-efficiency, complex structure of large component shape measurement in aerospace and marine manufacturing filed, a method for measuring the high-resolution geometric shape of large components was proposed, based on the optic-electrical scanning and positioning theory combined terminal shape measurement technology. The fringe projection photogrammetry system was used to project phase fringes on the local surface of the component to obtain high-precision dense point cloud, the pose measurement algorithm was designed to solve the problem that the pose measurement cannot be realized when the complex scene does not meet the intersection condition, the position of fringe projection photogrammetry system in the global measurement network system established by the workshop measurement positioning system(wMPS) can be measured. Therefore, the overall shape measurement of large components was completed through data fusion without relying on the software splicing algorithm. The experimental results show that the point cloud density of the system is 50 points/mm2, and the overall measurement accuracy of the system can reach 0.22 mm.
2019, 48(5): 503003.
doi: 10.3788/IRLA201948.0503003
The security of electronic payment has become an urgent problem. A secure Quick Response(QR) code system was proposed based on the technology of three-dimensional(3D) imaging and 3D authentication information. Firstly, the integral imaging technology was used to generate 3D digital watermark as the logo of the merchant. Secondly, identity based digital signature was carried out. Then, in the Fresnel domain, the 3D digital watermark with signature information was carried by using a secure QR code system, which was then compressed and hidden in the QR code. Finally, the users scan QR code to identify and extract the hidden data. If the signature information of verification was confirmed by users, the algorithm of reconstruction was executed, and the 3D digital watermark images were displayed. The payments were confirmed after the users were authenticated. The process of interactive authentication was completed. According to the results of experiments, the schemes can effectively prevent the 3D digital watermark from being tamper-bent, falsified, and unjustified. The proposed method not only enhances the security of scanning mobile payment, but also improves the real-time and convenience of the system. When multiple parameters of the proposed system are combined as keys, the dimensions of keys are effectively increased. The key space is broadened. The difficulty of illegal attack is enhanced, and the safety and stability of the system are improved too. It can protect the security of personal fund, and also maintain the reputation and property security of enterprises.
2019, 48(5): 503004.
doi: 10.3788/IRLA201948.0503004
The three-dimensional scanning LiDAR can actively acquire three-dimensional information of target. High-speed data acquisition and transmission are key technical issues for three-dimensional real-time imaging. A ground-based three-dimensional scanning LiDAR was designed using data acquisition and control system to achieve three-dimensional imaging with point cloud. The LiDAR hardware design included a transmitting and receiving unit, a ranging unit, and a scanning unit for acquiring the three-dimensional point cloud data of the target. The software design of the LiDAR included upper computer program, lower computer program and USB firmware program design for accomplishing point cloud data acquisition, data transmission, data storage, data analysis and real-time imaging which were collected in lower computer and transmitted into upper computer. Through multiple scene experiments, the results show that three-dimensional scanning LiDAR system has a centimeter-level ranging error, which can realize three-dimensional real-time imaging.
2019, 48(5): 503005.
doi: 10.3788/IRLA201948.0503005
When a flight flies at high speed in the atmospheric, aerodynamic heating, the optical window interacts with the external airflow to form a complex flow field structure. Its refractive index distribution was irregular and non-uniform, so it was difficult to accurately obtain the ray trajectory. In order to obtain accurate ray trajectory, three ray tracing methods with fourth-order accuracy were proposed. Via comparing the results with the analytical solutions of helical rays, it is found that the maximum relative error of the fourth-order Runge-Kutta method is 1.610-8, Richardson extrapolation method is 1.210-8, and Adams method is 1.210-11. The Adams method is a high-precision and high-speed method for ray tracing. An arbitrary point interpolation method based on the polynomial fitting can obtain higher accuracy refractive index field than that computed by distance inverse ratio method. The method was applied to compute the distorted wavefront caused by the flow field around the optical window of a missile, and the calculation results were compared. It is found that Adams linear multi-step method starts with Runge-Kutta method, but Admas method does not neglect the calculation results of the previous step and will not lead to the accumulation of errors, so the results are closer to the real solution, while Richardson extrapolation method calculates the optical path difference significantly different from the other two algorithms.
2019, 48(5): 503006.
doi: 10.3788/IRLA201948.0503006
As an important part of traceability chain for micro-nano geometric quantity, the grid standard template is the basic guarantee for the development of nano-technology. In order to achieve the rapid tracking and calibration of the effective area in the micro-nano grid structure, a tracking structure was designed to quickly locate the effective measurement area and orthogonally scanning direction. In order to meet the calibration requirements of different accuracy and size range, the grid standard template with multi-dimension and multi-parameter structure was designed and integrated in the same substrate. The measurement result error was analyzed and evaluated by the metrological nano measuring machine (NMM), which could characterize the traceability of grid standard template. The experimental results show that the grid standard template has good uniformity, accuracy and stability, and it is verified that the developed grid standard template can be used as an ideal reference standard for nano geometry traceability system.
2019, 48(5): 506001.
doi: 10.3788/IRLA201948.0506001
A laser interference detection method based on phase demodulation had been developed to measure the amplitude of low frequency water surface acoustic waves and identify the changed sound source. Water surface acoustic wave amplitude measurement was achieved by introducing a high frequency carrier into the reference optical path, using the arctangent demodulation algorithm of phase-generated carrier technology, in combination with the determined of initial phase and the modulation depth of the carrier. A set of amplitude measurement system was constructed under laboratory conditions, and the experimental results show that this method can accurately identify the amplitude, and the measurement repeatability is better than 1 nm. The detection result of the amplitude-modulated sound source signal indicates that the method can accurately track the change of the water surface acoustic wave amplitude, which proves the correctness of the method for identifying the changed sound source.
2019, 48(5): 506002.
doi: 10.3788/IRLA201948.0506002
The controllable parameters of shape and size of the scattering points of the plastic optical fiber (POF) core are of great significance to the design of the LCD backlight based on the semiconductor laser diode (LD) and the side-glowing POF. A laser marking method for POF core scattering points with surface damage free was researched. Based on the principle of edge-ray in non-imaging optical theories, the secondary focusing at laser beam for marking POF core scattering points was analyzed, and the formulas for focal point coordinates of laser incident on the POF was derived. The effects of focusing lens height, laser power and marking repeat times on the shape and size of scattering points in the fiber core of POF were studied experimentally by using a 1.06 m laser marking system. Relative intensity distribution of the scattered laser at 650 nm was used to detect scattering points in fiber core,the shape and size of the scattering points are judged by comparison of their micrographs. The experimental results showed that the shape of scattering points in the fiber core was determined by focusing lens height.When the focusing lens height was the focal length of the lens, elongate scattering points along the radial direction can be obtained. With the increase of laser power or marking repeat times, the size of scattering points increased. The laser damage threshold of POF was about 80 W/mm2 under single laser marking. However, the laser power density should be greater than 140 W/mm2 in order to make the scattering points have steady elongated shapes.
2019, 48(5): 506003.
doi: 10.3788/IRLA201948.0506003
In the field of precision measurement such as atom interferometers and atom gyros, the most basic and important step was to obtain cold atoms. When experiments require continuous and highly reproducible measurements, the faster loading rate of cold atoms will be required. In order to load cold atoms faster, a high-flux, low-speed cold atomic beam was required. A 2D cooling system of 87Rb atoms based on 2D-MOT+push beam scheme was built, the 3D-MOT loaded from the 2D-MOT was measured and a loading rate of 2.8109 atoms/s was achieved. Two pairs of cooling beams with two mirrors with /4 coating were implemented. The beams were transformed into a shape which had an ellipse profile with 25 mm short axis and 75 mm long axis, by using cylindrical lenses.
2019, 48(5): 506004.
doi: 10.3788/IRLA201948.0506004
The microstructure and morphology of nano-granular graphite in situ formed on 50 m flake micro-graphite irradiated by different energy density laser were investigated. The rules between process parameters of laser irradiation and in situ formation of nano-graphite on micro-graphite were preliminarily discussed. The morphology and microstructure of samples were studied by scanning electron microscope (SEM), and the crystallinity and microstructure of samples were studied by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The experimental results show that the flake micro-graphite is changed into a large number of spheroidal graphite whose average size is 245 nm when the power density is 5.00 kJ/cm2. When the laser energy density reachs to 6.25 kJ/cm2, the spherical graphite whose average size is 240 nm with agglomerate phenomenon is found. After the laser energy density increases to 12.50 kJ/cm2, samples present as form of spherical particle whose average size is 61.5 nm. When the power density is 13.75 kJ/cm2, the irradiated resultants of flake micro-graphite show a phenomenon that small particles attach to large particles, the size of irradiated resultants have a large range from 150 nm to 280 nm.
2019, 48(5): 506005.
doi: 10.3788/IRLA201948.0506005
Based on a laser emission system of aperture 600 mm, a rolling blinds sealing method was presented. For the rolling blinds, a curly replay structure was applied to drive the synchronous belt through the motor drive roll. At the same time, the rolling blinds was tightened by the elastic tightening mechanism to keep the blinds close to the seal plane to achieve the sealing effect. By theoretical analysis and numerical simulation of Finite Element Analysis, the sealing characteristics were studied. It can be concluded that the structure of the seal plane are the main factors affecting the sealing performance. By analysis and comparison, PVC is selected to be the material for rolling blinds. The designed structure is a sealed protuberance with a chamfering of 30 and thickness of rolling blinds is 0.5 mm. The Finite Element Analysis of the sealing characteristics shows that the center deflection of the rolling blinds is 6.269 mm. Under the limit load allowed by the design requirements, the stress of the rolling blinds is far less than the tensile strength of the material and will not be destroyed. The designed window satisfies the sealing requirements.
2019, 48(5): 506006.
doi: 10.3788/IRLA201948.0506006
On-line calibration of laser displacement meter (LDM) used for monitoring bridge structures is the key to ensure the accuracy of the bridge monitoring systems. Due to the differences of sampling frequency and time delay between different sensors, the measuring value sequence of the sensor to be calibrated (SBC) often has a big deviation with the reference value sequence, which seriously impacts on the on-line calibration results. To solve this problem, a matching algorithm for data sequences based on feature points sectioning was proposed. The data matching test was conducted with bridge beam model. The mismatching problem encountered by the traditional method was well solved. The results show that the proposed algorithm has good adaptability to sampling frequency offset with a matching accuracy of above 98%.
The uniformity of polarization distribution in the cross section of the beam is a key factor affecting the quality of the radially polarized beam and its practical application. The polarization purity of the radially polarized beam was measured and compared by the PBS measurement method, the slit method and the S-wave plate method, the uniformity of the polarization state of the radially polarized beam in the cross section was analyzed. In the process of measuring the radially polarized beam by the PBS measurement method and the slit method, the expression of the radial polarization purity was given, and the purity of the radially polarized beam was determined to be 93.4% and 84.1%, respectively. And the variance formula was used to evaluate uniform distribution of the radial polarization states. Among them, the PBS measurement method expressed the purity of the radially polarized beam more accurately, and the slit method can reflect the polarization distribution characteristics of the radially polarized beam more accurately by comparing the polarization degrees of different regions. The S-wave plate method can indirectly measure the purity of the radially polarized beam using the existing polarization analyzer in the market, and is more suitable for measuring the change of the polarization state of the radially polarized beam during the amplification process.
2019, 48(5): 504001.
doi: 10.3788/IRLA201948.0504001
The infrared flare can decoy the point of the optical axis of the seeker leading to the guidance commands step jumps and reducing the guidance accuracy. To figure out the reason for the step jumps, a jump model based on the line of sight rate(LOS-rate) was established. First, based on the recognition principle of the infrared target, the property of the LOS-rate was analyzed and a LOS-rate jump model was constructed primarily. Second, the set of influencing factors of the jump LOS-rate was determined by a large number of simulation data. Meanwhile, the explanatory variables of the jump model were selected by the Morris sensitivity analysis method to decrease the computational complexity. Finally, combined with the explanatory variables' effects, the stepwise regression analysis was applied to solve the regression parameters. The simulation results test and verify the effectiveness of the jump model and illustrate the prediction accuracy for the jump time and jump amplitude can reach 10-2 s and 10()/s, respectively.
2019, 48(5): 504002.
doi: 10.3788/IRLA201948.0504002
In order to precisely study the detection ability under sea fog conditions for shipborne infrared system and to improve the combat efficiency for shipborne defense system under complex conditions, based on a deep investigation for the actual equipment and working principle of infrared system, a two step method was put forward to calculate the actual detection distance of the system in the sea fog. Firstly, according to the sea fog intensity level, the theoretical detection distance of infrared sensor was got in advance, and then judge whether the second calculation was needed to get the actual effective detection distance by the detection capability index. The detection capability index model took into account the interactions among the human, marine environment and equipment. The model judges the weight of separate parties reasonably, effectively solves the problem of computational failure which is solely dependent on sea fog information.
2019, 48(5): 504003.
doi: 10.3788/IRLA201948.0504003
The existence of internal defects of aviation composites is a serious threat to air safety. In this paper, a novel infrared thermal imaging technique with laser as a heat source was applied to detect the internal defects in the carbon fiber reinforced plastics(CFRP) used in aviation field. With the advantages of remote feature and high-power density of laser, the positioning detection for the internal delamination defects of CFRP could be realized precisely. Multiple differential detection was carried out for the defect specimen as same as the reference specimen by using laser infrared thermal imaging technology. At the same time, according to the spatial position relationship between the specimen and the thermal imager, the max temperature difference in thermographs would be selected to calculate the diameter of the internal delaminate defect. The result shows that the laser infrared thermal imaging technology can effectively detect the internal delamination defects of CFRP. Especially, the differential laser infrared thermal imaging technology used for the first time can effectively eliminate the influence of the uneven laser energy distribution and make the defect image much clearer.
2019, 48(5): 526002.
doi: 10.3788/IRLA201948.0526002
In an augmented reality system, the virtual objects are superimposed on the real scene. In order to integrate the virtual objects into the environment more realistically, it is necessary to estimate the illumination in the scene. An illumination estimation method was proposed, which was suitable for multiple reflection phenomena for scenes with only diffuse reflection or scenes with both diffuse and specular reflections. In this method, a camera was used to shoot multiple-view images, and the presence of specular reflection in the scene was identified by detecting the specular highlights of each view image. If there was no specular reflection, then a single diffuse image estimation lighting algorithm was used to perform multi-view images illumination estimation. If there existed specular reflection, the information provided by the specular reflection was a priori knowledge and then the diffuse reflection estimation illumination method was used to obtain the final result. The experimental results show that this method improves the accuracy of the illumination estimation of multiple reflection phenomena.
2019, 48(5): 524001.
doi: 10.3788/IRLA201948.0524001
The existing light field image depth estimation technique cannot make a balanced estimation between major object and background. In this paper, a novel depth estimation method based on light field structure characteristic and multiview matching was proposed for light field image. The light field structure guided method was used as the basis of depth estimation. In order to maintain a smooth transition of the depth changing region and consider that the light field image has multiview subaperture image arrays, the multiview matching was presented to optimize the depth estimation. In the Markov random field domain, a smooth term was constructed based on the characteristics of the light field structure and a data term was constructed based on multiview stereo matching. Then, an optimization method utilizing the above two terms was proposed to balance object depth boundary and background depth estimation, so as to improve the depth estimation of light field images. Experimental results show that the proposed method can produce high quality depth estimation results with clear depth boundary and accurate depth in background.
2019, 48(5): 524002.
doi: 10.3788/IRLA201948.0524002
Mathematical morphology has a good application effect in the magnetotelluric(MT) data noise suppression. However, it is still in the blank stage of MT imaging processing. It is based on changing the spatial distribution form or structure of the target in the image to achieve the target extraction. The objective is to achieve the extraction of useful geological information in MT imaging processing. Firstly, the morphological expansion-contraction gradient and morphological closed-open gradient algorithm were used to process the TM and TE mode forward imaging, which effectively improved the reflection of the forward image. The target abnormal body contour was selected. Then, the inversion imaging results of the measured MT data in a certain area of Tongchuan city, Shaanxi province were selected for morphological gradient processing. The results show that the morphological gradient can effectively reduce the random error and achieve the purpose of extracting the target anomaly.
2019, 48(5): 524003.
doi: 10.3788/IRLA201948.0524003
In digital image-plane holographic microscopy (DIPHM), the precision and reliability of measurement are limited by noises introduced in recording process. Until now, the noise reduction research was focused on noise with high frequency. Here, a method was proposed to reduce noises not only with high frequency, but also with low frequency. By using the denoising method, the signal-to-noise ratio (SNR) of reconstructed phase was improved at the same time. The denoising method was realized by optimizing the digital image-plane microscopic hologram. The characteristics of the first intrinsic mode function (IMF1) in bi-dimensional empirical mode decomposition (BEMD) were in good accordance with that of gray value information of interference fringes in digital image-plane hologram. Hence, the digital image-plane hologram was decomposed by BEMD to extract the IMF1, utilizing the IMF1 as the optimized digital image-plane hologram. After that, the optimized digital image-plane hologram was reconstructed to retrieve phase to measure the surface profile of tested samples. The surface profile of a standard nano-step was measured by DIPHM with BEMD. By comparing and analyzing the frequency spectrum and measured height profile with and without BEMD, the optimizing method was proved to realize the correctness in surface profile measurement and noise suppression of reconstructed phase.
2019, 48(5): 524004.
doi: 10.3788/IRLA201948.0524004
Projection on curved surface has important applications in display and photolithography. A phase retrieval algorithm, using non-uniform sample, was presented for high resolution projection on curved surface based on the Rayleigh-Sommerfeld Integral. The high spatial frequency means large diffraction angle was incorporated into the design, so that the imaging resolution of projection could be improved effectively. The discrete sampling method was established for the diffraction surface and the imaging surface. Then the theoretical equation of limit resolution was given. Finally diffraction optical elements were designed for projection on cylindrical surface with the diffraction pattern of grid, in order to verify the phase retrieval theory. The results show that reconstructed projecting image matches well with the target image, and the resolution is in agreement with theoretical prediction.
2019, 48(5): 521001.
doi: 10.3788/IRLA201948.0521001
SiO2 thin films is one of the most important low refractive index materials in the field of optical thin film. SiO2 thin films were deposited on Si substrates by different deposition technique. The optical stability of SiO2 thin films were investigated as a function of time placed in the air. Optical constants of SiO2 thin films were calculated using the ellipsometry spectra at different aging times. With the increase of the placed time, the physical thickness and optical thickness of EB-SiO2 thin films and IAD-SiO2 thin films increase, but IBS-SiO2 thin film decreases. The change of optical thickness of SiO2 thin films are separately 1.0%, 2.3% and -0.2%. When the placed time reaches 120 days, the physical thickness and optical thickness of IBS-SiO2 thin films, EB-SiO2 thin films, and IAD-SiO2 thin films tend to be stable. The results indicate that the optical stability of IBS-SiO2 thin film is better than other SiO2 thin films, and in the design of protective coating, SiO2 thin films should be deposited with ion beam sputtering technique.
2019, 48(5): 521002.
doi: 10.3788/IRLA201948.0521002
In order to improve the anti-reflection ability of the optical surface of infrared materials, an anti-reflection super-surface with a double-cycle nested structure was designed. By analyzing the variation of the dielectric constant around the two-cycle nested structure, the reflection efficiency of the double-cycle nested structure was obtained by simulation. The difference between the anti-reflection characteristics of this nested structure and the surface of a single structure was analyzed when the micro structure changed. By changing the surface duty ratio of the nested structure, the diameter ratio of the top and bottom ends, and the aspect ratio simulation, the anti-reflection characteristics of the double-period nested microstructure surface were analyzed, and the double-cycle nesting was finally optimized. The structure could effectively improve the anti-reflection effect in the ultra-wide wavelength range of 2.4-12 m, the reflectance was below 3.5%, and the average reflectance was less than 1% in the practical band range of mid-long infrared wave. The structure effectively protects the micro-structure from damage, realizes the superposition of the anti-reflection characteristics of the single structure, further reduces the reflectivity of the surface of the component, and can be applied as a novel anti-reflection surface in the infrared window.
2019, 48(5): 521003.
doi: 10.3788/IRLA201948.0521003
The biological material has the characteristics of low production cost, wide particle size distribution and no pollution, it can be used as a new type of extinction material. In order to study the atmospheric suspension settling characteristics of biological extinction material FANS 233D, the settling velocity according to the Stokes law and the weighted average algorithm of particle number was calculated. A cluster-cluster aggregation model was used to simulate the fractal structure of the biological aggregated particles while Newton's second law was used to calculate the settling velocity of aggregated particles with different fractal structures. The results indicate that the average settling velocity of the aggregated particles with different original particles increases with the increase of the number of original particles,the settling velocity of aggregated particles with the same number of original particles is related to the porosity and fractal dimension. The study on the atmospheric suspension characteristics of biological extinction material provides a theoretical basis for its practical application.
2019, 48(5): 521004.
doi: 10.3788/IRLA201948.0521004
457 nm and 915 nm continuous lasers were used to study the Yb3+ near-infrared luminescence and up-conversion energy transfer mechanisms in YAG:Ce, Yb phosphors synthesized via solid-state reaction and sol-gel method. Under either excitation, sol-gel samples demonstrated the same Yb3+ near-infrared luminescence quenching concentration of -5%, with similar trends. In solid-state reaction samples, 915 nm excitation yielded a quenching concentration of -5%, while 457 nm excitation resulted in a quenching concentration of 10%, indicating a less homogeneous distribution of dopant ions. Visible up-conversion luminescence from Yb3+-impurity ion and Yb3+-Yb3+ ion pairs can be observed. Solid-state reaction samples demonstrate stronger cooperative luminescence from Yb3+-Yb3+ ion pairs. The results show that clustering of Yb3+ ions is more significant in samples synthesized via solid-state reaction, which could lower the near-infrared down-conversion efficiency of this type of material.
For power amplifier module based on silicon based semiconductor devices, due to improper control of the amplifier's switching time and the slope of the rising or falling edges of the switch caused by the device physical structure itself, modulation of adjacent channel power(ACP)and adjacent channel transient power(ACTP) are poor, causing adjacent channel interference. Based on the silicon based semiconductor device power amplifier module in the digital two-way radio application, a new method was proposed creatively to optimize the amplifier gate bias circuit. The influence of the switching time of the amplifier and the slope of the rising and falling edges of the switch on ACP and ACTP was analyzed and deducted in theory. In practical application, the rising edge and the downward slope of the power amplifier switch were adjusted by properly adjusting the capacitance of the bias circuit and the series resistance of the power amplifier module of the two-way radio. The experimental results show that this can effectively improve the performance of ACP and ACTP, when the channel spacing is 12.5 kHz, the ACP and ACTP are less than -60 dBc and-50 dBc without affecting the output power and efficiency of the amplifier, it has certain practical significance and application value.
2019, 48(5): 517001.
doi: 10.3788/IRLA201948.0517001
In order to realize precise measurement for pF level capacitor, a capacitance measurement system based on laser locking Fabry-Perot interferometer was established and its basic principle, method of interferometer locking and determination of order numbers variation were studied. Firstly, according to the Lampard and Thompson electrical theorem, configurations and operation modes of Fabry-Perot interferometer were presented, and a displacement measurement by locking interferometer was demonstrated.Then the optical layout for Fabry-Perot interferometer was presented, and the operation status of the interferometer locking servo system and the fluctuation of cavity length in close loop were carefully analyzed. After the feasibility of determining the order numbers through the prior value of 1 pF standard capacitor was evaluated, the experiment process for confirming the variation of order numbers was presented. Finally, the character of step moving displacement and measurement repeatability of 1 pF standard capacitor were discussed. Experimental results indicate that the peak to peak fluctuation of the interferometer is 0.4 nm after its locking, and the repeatability of 1 pF standard capacitor measurement is 5.010-9. It can satisfy the requirements of precisely measuring the pF level capacitor. However, further study of the displacement measurement will focus on the uncertainty evaluation and optimization for the displacement measurement system.
2019, 48(5): 517002.
doi: 10.3788/IRLA201948.0517002
Aiming at the problems that the solutions were not unique, the correct solution was difficult to select and the accuracy was not high during processing the solution, an monocular vision pose measurement algorithm based on point features was proposed. Firstly, according to the position relationship between the four coplanar feature points, the parallel and the intersection conditions were analyzed respectively; Secondly, according to the spatial coordinates, image coordinates and spatial position relationships of the feature points, the corresponding unit vectors in the camera coordinate of the three coordinate axes in the world coordinate were derived, then the initial pose of the object to the camera was obtained; Finally, the initial pose was optimized with the LM algorithm to obtain the final pose. The experimental results show that the synthesis error of the article algorithm is 0.54 mm, the errors of the synthesis of the existing EPnP algorithm, two-point one-line algorithm and P3P algorithm are 1.28 mm, 1.52 mm and 4.26 mm, respectively. The synthesis error of the article algorithm is reduced by 57.8%, 64.4% and 87.3% respectively. All in all, the article algorithm is superior to the existing EPnP algorithm, two-point one-line algorithm and P3P algorithm.
2019, 48(5): 517003.
doi: 10.3788/IRLA201948.0517003
To measure the bidirectional reflectance distribution function(BRDF) of the sample, measuring device with less light obscuration, large gyration radius and high positioning accuracy was designed. According to the requirement of measurement space and angle, the azimuth circle rail(Radius 1.3 m) and the zenith arc rail were designed to provide rotary orbit. Synchronous toothed belt were attached to the rails. Servo motors were assembled to realize the motion in two directions. The detector was installed on the zenith arc rail to achieve the sample detection in the range of 180 azimuth angle and 75 zenith angle. To avoid motion lag in the large size structure, the anti-jamming mechanism based on preloaded springs were designed, and the error analysis of introduced pointing accuracy was carried out. Finally, the pointing accuracy of the measuring device was measured. The experimental results show that the azimuth and zenith pointing accuracy of the measuring device is better than 0.147 and 0.358 separately. The measurement results are in agreement with the analysis results, which verifies that the designed BRDF measuring device meets the requirements of the indicators.
2019, 48(5): 517004.
doi: 10.3788/IRLA201948.0517004
The calibration and error analysis of miniaturized atmosphere CO2 detection system were carried out by Li-7500 analyzer. Firstly, the CO2 volume ratio concentration was calibrated according to the measured data of four days. The absorption degree of the system was linear with the concentration CO2 measured by the Li-7500 CO2 analyzer, and the volume of CO2 was in good agreement with the calibration coefficient of the concentration. Secondly, the system was calibrated by the average data. The absolute value of the relative error of carbon dioxide volume ratio was less than 2.0%, and the correlation coefficient of Li-7500 CO2 analyzer was more than 0.9, which showed the stability and reliability of the system. Finally, according to the influence of temperature change on the atmospheric transport effect, the near ground CO2 in Hefei Science Island was analyzed. The characteristics of the diurnal variation showed that there was a strong negative correlation between the change of CO2 concentration and the change of temperature in the near ground. In summary, the accuracy of calibration results was verified, which provided data support for subsequent measurement of vertical profiles of CO2.
2019, 48(5): 517005.
doi: 10.3788/IRLA201948.0517005
The method of pose measurement using computer vision is widely used in modern control, navigation, tracking and other fields. A monocular visual pose measurement method was studied and designd based on P4P rectangular distribution of planar target and EPNP algorithm in this paper. Firstly, a single camera was used to obtain the plane target image. After the image processing, the pixel coordinates of the four feature points were obtained, and the EPNP algorithm was used to perform the attitude calculation. Secondly, the simulation analysis of pose error measurement provides theoretical guidance and basis for improving attitude measurement accuracy. Finally, a coordinate system registration method combined with a high-precision two-dimensional turntable was proposed. The method was used to verify the accuracy of the three-direction attitude angles. The experimental results show that the rotation angle around the x and y axes is[-6, 6], the pose measurement error is less than 0.1 to meet the measurement application requirements.
2019, 48(5): 517006.
doi: 10.3788/IRLA201948.0517006
As an important optical device for changing the polarization state of an optical signal, a retarder has high polarization conversion accuracy, low cost, and simple algorithm. A new method was proposed for polarization modulation of radial vector optical field using a combination of a 1/4 wave plate and a 1/2 wave plate. The Jones matrix algorithm was used to analyze the modulation mechanism of the dual-wave plate. The polarization evolution law of the light field was represented on a Poincar sphere, and the correctness of the theoretical analysis was verified through experiments. The results show that the dual retarder structure can realize complex polarization control of radial vector light field, and obtain a vector field with uniform light intensity distribution and regular polarization state distribution.
2019, 48(5): 517007.
doi: 10.3788/IRLA201948.0517007
Tunable diode laser absorption spectroscopy(TDLAS) is a high sensitive and high resolution gas absorption spectrum detection technology, with fast response, high precision, excellent single mode characteristics and strong versatility. The temperature and concentration of the detected gas were calculated by measuring the absolute absorption intensity in the direct absorption method of TDLAS, but was easily affected by particle concentration and fluctuation of laser intensity. The laser was modulated through high frequency sinusoidal signal in the wavelength modulation method of TDLAS, making the laser output frequency and intensity modulated simultaneously, with the characteristics of high signal-to-noise ratio and sensitivity, but the gas parameters were determined by calibration experiments or complex algorithms. Therefore, the expression of harmonic terms containing molecular absorption information was deduced through the theory of absorption spectrum and wavelength modulation, and the relationship between harmonic signal and absolute absorption intensity of detected gas was analysed, establishing the measurement algorithm of absolute absorption intensity based on harmonic signal. The absorption spectral line of NH3 molecule near 1 531 nm was taken as an example for numerical analysis, and the relative errors between theoretical calculation (a=0) and simulation values were no more than 2% when the modulation amplitude reached up to a=0.032 cm-1(m=2), which further proved the reliability of on-line measurement algorithm.
2019, 48(5): 517008.
doi: 10.3788/IRLA201948.0517008
The roundness error separation technique of three-point method was widely used in the separation algorithm for roundness error of part shapes and rotation error of motors. The key of accurate separation in roundness error depended on setting the angles of three displacement sensor probes logically, in order to avoid that the denominator of transfer function became zero. However, during the process of specific implementation, the angle setting error of displacement sensor probes inevitably existed, which made analyzing the influence of angle setting error become much more important. Based on the classical model of three-point method, and then a new model was presented for analyzing the angle setting error of displacement sensor probes. Taking the diameter results in measuring roundness through three-point method as the goal, according to different parameter settings in actual working situations, the error of measuring results caused by the angle setting error of displacement sensor probes was quantitatively analyzed. Lastly, using capacitive displacement sensor to carry out the research on measuring diameter of circular parts, the effectiveness of error analysis was confirmed in this article and the repeatability accuracy of measuring diameter which can be less than 2 m.
2019, 48(5): 520001.
doi: 10.3788/IRLA201948.0520001
Phase shifter is one of basic integrated optical structures, and wavelength dependence of its phase shift value determines operation wavelength range of devices. An experimental investigation was conducted on silica-based integrated optical phase shifter designed respectively in two different regimes, length difference regime (LDR) and refractive index difference regime (RIDR), aiming at wavelength dependence of phase shifter. Phase shifters of 180 were respectively designed in the two regimes and inserted between two interference arms of Mach-Zehnder interferometers(MZI). Based on these two structures, a quantitative comparison on phase shift wavelength dependence was made by measuring wavelength dependence of MZI insertion loss. Experimental results show that the operation wavelength range of phase shifters designed in the RIDR was approximately 1.8-1.9 times that designed in the LDR. Analysis shows that the experimental results are in agreement with the theoretical calculations, which proves that phase shifter designed in RIDR possesses weaker wavelength dependence and thus wider operation wavelength range.
2019, 48(5): 520002.
doi: 10.3788/IRLA201948.0520002
High insertion loss filter components like tunable bandpass filters(TBPF) are commonly used to tune the sideband output wavelengths in continuous-wave(CW) all-fiber optical parametric oscillators (FOPO). Aiming at reducing the high ring-cavity loss mainly caused by the insertion-loss of the bandpass filter, a low cavity-loss tunable CW FOPO based on multimode interference(MMI) filter was proposed. Cascaded single-mode-multimode-single-mode(SMS) fiber devices were fabricated as filter devices by selecting multimode fibers with different lengths and core-sizes. And their insertion-losses at selected wavelengths were less than 1 dB, and the total losses of the FOPO ring cavity were not more than 5 dB. By applying an axial pulling force to the SMS device to adjust the transmission spectrum of the filter device, the double-sideband output wavelengths could be tunable in the range of 1 494-1 501 nm and 1 638-1 629 nm.
2019, 48(5): 520003.
doi: 10.3788/IRLA201948.0520003
A broadband terahertz (THz) polarization beam splitter (PBS) was proposed. The PBS was based on subwavelength grating sandwiched between silica layers, which could split an arbitrarily polarized optical beam into two orthogonal, linearly polarized components, and then reflected the TE mode and transmit the TM mode. It was shown that THz PBS could efficiently operate from 3.5 THz to 5.5 THz, with high diffraction efficiencies and extinction ratios. In the process of PBS manufacture, there would be unavoidable deviations of the geometric parameters, which may affect its properties, i.e. the diffraction efficiencies and extinction ratios. Therefore, some structure parameters were calculated. Those values suggested that the designed PBS allows sufficient manufacture tolerances. When D1 ranged from 1 m to 1.2 m and thickness D3 ranged from 2.8 m to 3 m, the values of T0TM are always more than 96.9% and those of R0TE are more than 98.7%. And the values of Tc and Rc were respectively kept higher than 31 dB and 33.4 dB. These results show the PBS with a frequency bandwidth of 2 THz, a large angle range of 10, an extinction ratios over 20 dB and a diffraction efficiencies over 90%, is obtained. This work may inspire related studies and achieve some potential applications in THz manipulation system.
2019, 48(5): 520004.
doi: 10.3788/IRLA201948.0520004
Atom Trap Trace Analysis(ATTA) technology, which is based on the theory of laser cooling and trapping, has the capability of high-sensitivity detection of the radioactive isotope of Krypton and wide applications in the fields of geophysics and environmental science. Zeeman slower, as a key component of the ATTA instrument, is used to generate continuous atomic beam with low velocity. With the advantages of stable magnetic distribution, easy installment and debugging, no constant current power or cooling requirement, the Zeeman slower based on permanent magnet is getting more and more attention in recent years. In this paper, a Zeeman slower based on the toroidal permanent magnet was designed, the spatial distribution of the magnetic field of this slower was calculated by finite element analysis, a prototype was manufactured according to the design parameters, and its magnetic field along the axis was also measured. The lengths of the slower and its effective deceleration area were 51.2 cm and 46.9 cm, separately. The maximum deviation between the measured and theoretical magnetic field was less than 3.6 G, and the average deviation was 1.3 G. Furthermore, the deceleration process of the atomic beam in the designed and actual magnetic field distribution was simulated, and the influence of the radial variation of magnetic field distribution on the deceleration process of the atomic beam was analyzed. The result shows that the Zeeman slower in this paper is able to decelerate the velocity of the atomic beam with a diameter less than 20 mm from the maximum initial value of 250 m/s to the final value of 50 m/s.
2019, 48(5): 518001.
doi: 10.3788/IRLA201948.0518001
A kind of simultaneous imaging polarimeter with a high spatial resolution for satellite platform environments was designed which was based on an off-axis three-mirror system as front-view telescope system and combined with simultaneous-amplitude polarization imaging technology, and the simultaneous polarization imager was designed to simultaneously acquire the target Stokes parameters to suppress sea surface glare, sea fog, atmospheric radiation and other disturbances. It provided an effective means to improve the contrast of detection targets, and had obvious advantages in dynamic target detection. According to the optical system, the detailed structural design had been finished. Finally, through the laboratory performance test, the working spectrum was 500-700 nm, the FOV was 8.50.1, the spatial resolution was 5 m@500 km, the optical MTF was more than 0.4@71.4 lp/mm, and under the condition of an elevation angle of 30 and a reflectivity of 0.2, the noise ratio was better than 38 dB, the polarization measurement accuracy is better than 1%(P 0.3), the first-order mode of the whole machine was 195 Hz, and it had good strength and stiffness. The overall performance meets the actual use requirements.
2019, 48(5): 518002.
doi: 10.3788/IRLA201948.0518002
Optical fiber image module is one of the key components of large field of view space-based telescope, whose stiffness characteristics of support structure have a crucial impact on the working life of objective lens. In order to ensure the lifetime of objective lens and reduce the weight of the support structure of the optical fiber image transmission module under vibration load, the braced structure of the optical fiber image transmission module was optimized with the inert strength of optical glass and the fundamental frequency of the structure as the optimization constraints on the basis of topological optimization. Firstly, the calculation method of inert strength of optical element was described and the inert strength boundary value of the coupled-fiber monocentric lens was determined. Secondly, the initial braced structure of the optical fiber image transmission module was designed. Finally, on the basis of topology optimization, an integrated optimization model was established with the inertia strength of the monocentric lens and the fundamental frequency of the braced structure as the optimization constraints, and was calculated by using iSIGHT integrated optimization platform. The numerical result of the simulation demonstrates that under the condition of satisfying the optimization constraint, the quality of the optimized support structure is reduced by 11.4%, achieving the obvious weight loss effect. The proposed optimization method provides a reference for the opto-mechanical structure of objective lens coupled with the optical fiber bundle.
2019, 48(5): 518003.
doi: 10.3788/IRLA201948.0518003
In the development of large ground-based telescope technology, the primary mirror support technology is always a key technology. In this paper, a semi-active support method was researched based on a 2 m SiC lightweight primary mirror, which was used to correct some unpredictable low-order wavefront aberration caused by machining error, assembly error and other factors. Firstly, the finite element simulation model was established, and the finite element simulation was carried out. An unit correction moment (1 Nmm) of Mx or My, which were two orthogonal moments, was separately applied to the 6 Tripod soft hinge, so the primary mirror deformations under a total of 12 cases of the situation were respectively analyzed. And then with the linear superposition principle of small deformation, the correction ability of the moment correction method for low order wavefront aberration was analyzed and calculated. It could be seen from the analysis that the moment correction method could correct the tilt and astigmatism very well. The initial mirror RMS value of the tilt and initial astigmatism which were normalized to 1/10(=632.8 nm), could be respectively corrected to 0.687 nm and 2.97 nm, the correction abilities were respectively 98.9% and 95.3%, and the required maximum correction moments were respectively 6.3 Nmm and 19.9 Nmm. Then, according to the whiffletree support structure of the primary mirror, a structure of the moment correction was designed with the leaf spring at the Tripod soft hinge. Finally, the feasibility of the leaf spring correction structure was verified through experiments, and the feasibility of the semi-active support scheme of moment correction was verified further. And a certain degree of engineering experience for the implementation of the moment correction method has been accumulated with high guiding significance.
2019, 48(5): 518004.
doi: 10.3788/IRLA201948.0518004
In order to accurately and easily obtain four wavelength-dependent Stokes parameters, the intensity modulated polarization spectral imaging technology was used. The process of the restoration of polarization spectrum was calculated and derived from polarization spectrum intensity modulation theory and Fourier transform demodulation analysis, and the basic structure of the system was obtained. According to the modular design concept, the forward telescope objective lens and Offner spectral dispersion system of the spectrometer optical system were designed, which achieved a spectral resolution of 1.24 nm in the 400-1 000 nm spectral range. And then the front polarization spectrum modulation module was designed based on spectral system parameter, so a complete design example was given. Finally, the reasonability of the polarization spectrum modulation module design and feasibility of the Fourier transform demodulation method were verified by experiments, which lays the foundation for the recovery of polarization spectrum.
For traditional flow cytometry, it is necessary to solve the problem of cell subcellular morphological recognition and the change of cell activity by fluorescence staining. According to the physical characteristics of lymphocytes and eosinophils, the model of particle-free eccentric sphere cells and the dual-core cell were established. Afterwards, based on the simulation experiment software of light scattering theory, a simulation experimental light path which can receive both forward and backward scattered spectra of cells was designed. The scattering distribution of the cell model was obtained, and the relationship between the light intensity and the incident wavelength was established under the relative refractive index of the nucleus and cytoplasm. Through the analysis of the characteristics of the forward and backward scattered light spectra, it was found that the forward scattered light signal was set as X-axis, the cell backward scattered light signal was set as Y axis, lymphocytes and eosinophils had distinct classification characteristics so that a classification method for lymphocytes and eosinophils was proposed. Finally, the method of classifying and counting in this paper has some potential application value for designing all optical, non-invasive and unmarked blood cell analyzer.
2019, 48(5): 526001.
doi: 10.3788/IRLA201948.0526001
The dim and small target association of heterogeneous sensors is the first problem to be solved by cooperative detection of sensors. Even in the same field of view, the detection targets of heterogeneous sensors composed of infrared photoelectric systems and radar are not exactly the same, especially in the long-distance detection, the radar detection targets are many and dense, while the detection targets of infrared photoelectric systems are relatively few, so the target track association result has a great uncertainty. Aiming at this problem, the dim and small target association method based on multi-source data and multi-feature fusion was firstly proposed based on the multi-model estimation method, selecting the same type of targets as the potential association target, then making the rough association of the same type of targets based on the track association algorithm, and finally making fine association of targets based on the multi-feature maximum joint probability distribution. The simulation tests of infrared photoelectric systems/radar are verified by the same station site detection that this method effectively improves the accuracy of the association of dim and small targets compared with only using track for target association.
