2021 Vol. 42, No. 5

2021, (5): 1-6.
Design of UV optical system with wide ultraviolet spectrum and large relative aperture
YE Jingfei, ZHU Runhui, MA Mengcong, DING Tianyu, SONG Zhenzhen, CAO Zhaolou
2021, 42(5): 761-766. doi: 10.5768/JAO202142.0501001
Most of the current ultraviolet (UV) optical lenses have narrow working band, which results in the decrease of their application adaptability. It is becasue of the fewer lens materials for UV lens design, and further it is difficult for the correction of UV color aberration. By applying the optical structure of negative-positive lenses overlapping distribution together with quasi-double Gaussian symmetry, as well as utilizing the wide spectral transmittance of fused quartz material and calcium fluoride material, an optical system with wide ultraviolet spectrum was designed, which also had the advantages of large relative aperture, wide field of view and high resolution. Its working wavelength was from 240 nm to 360 nm and the UV working bandwidth reached to 120 nm. All of the lenses in the designed UV optical system were spherical lenses, which could be fabricated and measured easily. Taking the central wavelength of 300 nm as the reference wavelength, the maximum lateral color aberration of the designed UV optical system was less than one pixel size over the full field of view. In the cut-off frequency of 50 lp·mm−1, the modulation transfer function (MTF) value was better than 0.4. The root mean square (RMS) value of image spot diagram in each field was better than 10 μm. The design results show that the designed UV optical system with wide UV spectrum has good imaging quality, high resolution and small color aberration, which satisfies the design requirements.
Design of catadioptric middle infrared diffractive telescope system with large aperture
ZHOU Yan, WU Shibin, WANG Lihua, LI Jie, DU Junfeng, BIAN Jiang
2021, 42(5): 767-774. doi: 10.5768/JAO202142.0501002
To achieve the high-resolution detection of space infrared telescopes, based on the Schupmann ach-romatic theory, the design and athermalization model of catadioptric middle infrared diffractive telescope system with large aperture were studied. An optical system which had an aperture of 1 m, F-number of 2, full field of view of 0.12°, waveband of 3.8 μm~4.2 μm was designed, the primary mirror and correction mirror were plane diffractive lenses, the relay system adopted catadioptric Cassegrain structure, and the refocusing and three times imaging systems used refractive structure, then the tolerance, ghost image and cold reflection of the system were analyzed. The design results show that at the temperature of −20℃~60℃, the MTF of the system is greater than 0.7 in the range of 16.7 lp/mm, close to the diffraction limit, and has 100% cold shield efficiency. The tolerance of system satisfies requirements of fabrication, the ghost image energy is 0.1%, which has little influence on the target signal, and the Narcissus induced equivalent temperature difference (NITD) value of cold reflection with temperature is less than noise equivalent temperature difference (NETD). The system can provide reference for the design of larger aperture infrared diffractive telescope system.
Multi-degree of freedom acquisition system based on wide-spectrum phase-shifting interferometry
CAI Yawen, ZHANG Qingjun, LIU Jie, ZHANG Yue, LIU Jiuli
2021, 42(5): 775-781. doi: 10.5768/JAO202142.0501003
To realize high-precision detection of complex products in modern industrial field, a model of multi-degree of freedom joint acquisition system was established. A model of multi-degree of freedom acquisition system based on wide-spectrum phase-shifting interferometry was established, and the optical components in the system were designed. A multi-degree of freedom joint measuring algorithm was proposed based on phase-shifting interferometry, and rationality of the system was verified. The algorithm was implemented by physical and optical parameters. The results based on Simulink show that depth measurement accuracy is at the micron level, and measurement range is at the meter level; spectrum detection resolution is at the nanometer level, the measuring bandwidth is 300 nm, which covers the entire visible light area, and spectrum accuracy is 0.2 nm, error rate is less than 0.1%. The system meets the needs of high depth resolution, wide depth measuring range, high spectrum accuracy and high spectral resolution in modern industrial precision measurement.
Optical system of star sensor with miniaturization and wide spectral band
WU Yanxiong, WANG Liping
2021, 42(5): 782-789. doi: 10.5768/JAO202142.0501004
The star sensor is the key measurement equipment for autonomous attitude navigation of spacecraft. Due to the large volume and mass of the traditional star sensor, it is difficult to meet the application requirements of micro-nano satellites. The optical system is the core and bottleneck technology of star sensor miniaturization. The optical system parameter requirements of star sensor for all-sky star identification were studied and analyzed, and a micro-miniature, wide spectral band and transmission-type optical system design based on the spherical lens was proposed. The optical system has the focal length of 40 mm, the field angle of 26.4°, the relative aperture F of 2.8, and the spectral range of 450 nm~1000 nm.The volume and mass of the optical system are greatly reduced, which is suitable for the micro-nano satellites star sensor.
Compact large relative aperture long wavelength infrared athermalization optical system with chalcogenide glasses
ZHANG Jiyan, LIN Haifeng, HUANG Zhangchao
2021, 42(5): 790-795. doi: 10.5768/JAO202142.0501005
As the substitute material of optical crystal, the characteristics of chalcogenide glass with high spectral transmittance, high thermostability, moldable property and low price received extensive attention. An infrared athermalization optical system was designed based on temperature characteristics of chalcogenide glass and theory of optical passive athermalization. The working band was from 8 μm to 12 μm, the F-number was 1, the field angle was 38°, and the overall length was 16.7 mm. The system was composed of three lenses, which used two chalcogenide glasses materials, IRG202 and IRG206 respectively, only introduced two even aspheric surfaces, and no diffraction surface was used. The system had advantages of compact structure, low cost, and high luminous flux, which was compatible with uncooled infrared area-array detector that had pixel elements of 384×288, and pixel size of 17 μm. From −40 ℃ to 60 ℃, the MTF of designed lens of each field of view is greater than 0.4 at the nyquist frequency, and the imaging performance of optical system is stable. The system can be widely used in the field of vehicle night vision and security monitoring.
Two kinds of making technologies of glass micro-channel arrays and their comparison
WANG Yali, CUI Kaiyuan, LIU Shulin, ZHANG Qian, LI Chonghao, LI Xiaofeng
2021, 42(5): 796-801. doi: 10.5768/JAO202142.0501006
The micro-pore glass array is the base plate of the micro-channel plate made by atomic-layer deposition technology. The distribution uniformity of the micro-pore array and the smoothness of the inner wall of each channel are very important for the subsequent fabrication of qualified micro-channel plates. The hollow-core and solid-core corrosion processes were used respectively to make the aforementioned base plate. The advantages and disadvantages of the two processes were deeply analyzed, and the key technologies of the two processes were expounded. The performance of the micro-channel plate made by atomic-layer deposition technology was compared with that made by conventional technology, and the signal-to-noise ratio of the former was better than that of the latter.
Design of compact fiber microscope objective
REN Xiaonan, CAO Yu, ZHANG Wei
2021, 42(5): 802-809. doi: 10.5768/JAO202142.0501007
The construction, operation and maintenance of optical fiber communication network put forward the portable, compact, accurate and reliable requirements for the use of optical fiber connecting machine. To achieve this goal, an optical fiber objective with compact structure and clear imaging was developed. Based on optical theory and actual usage requirements, the basic optical parameters of the required objective were analyzed. An compact and high- resolution optical fiber microscope objective was designed by the Zemax software. The objective included 5 commonly used glass spherical lenses, with the magnification of 6 times, the numerical aperture of 0.24, and the conjugate distance of 47.3 mm. The objective system had the good imaging quality, in which the MTF was greater than 0.36 at the nyquist frequency of 60 lp/mm, greater than 0.15 at 90 lp/mm within 0.7 field of view. The design results were analyzed by Monte Carlo tolerance, and the yield rate was over 90%. The installation was loose and the cost was low, therefore the objective lens could be produced in large quantities. In addition, the imaging simulation of the designed objective lens shows that the features of the fiber core to be spliced are clear and sharp, which is beneficial to the alignment of the machines.
FPGA -based SPGD algorithm implementation of adaptive optical system
XU Xiangxiang, WU Yang, SU Hang, LIU Jinlong, YANG Huizhen, GONG Chenglong
2021, 42(5): 810-816. doi: 10.5768/JAO202142.0501008
The field programmable gate array (FPGA) has the advantages of repeatable programming and flexible algorithm implementation. With 97-element deformable mirror as the prototype, the general and rapid implementation scheme of the FPGA-based stochastic parallel gradient descent (SPGD) control algorithm was proposed. Firstly, the TimeGen software was adopted to analyze the time sequence of the SPGD algorithm. Secondly, the Vivado software was adopted to configure and programme the FPGA of the SPGD algorithm in the field of random disturbance voltage generation, performance indexes calculation, as well as control voltage calculation and output. Finally, the calculation results of each module and those of Matlab were compared and analyzed. The results prove the rationality and feasibility of the proposed scheme and provide the basis for the next step of hardware implementation and application of FPGA-based SPGD algorithm.
Image quality influencing factors for aerial electro-optical detection
WANG Huilin, LIU Jilong, WU Xiongxiong, LUAN Yadong
2021, 42(5): 817-829. doi: 10.5768/JAO202142.0502001
For the actual demands of the aerial electro-optical detection system, firstly, the qualitative and quantitative factors for evaluating the optical image quality were analyzed from the perspective of image information, an image definition evaluation method based on similar feature region extraction was proposed to achieve the matching between the subjective feeling and objective evaluation of the image definition. Then, from the perspective of the optical evaluation of imaging system, the optical transfer function, aberration, transmittance and other factors affecting the imaging quality were analyzed, and according to the multi-band long focal reflective optical system, the experimental results were verified. Finally, combined with the requirements for engineering practice to improve the imaging quality, several aspects that should be given more attention in the development of optical imaging system were pointed out. And for the multi-band long focal reflective optical system, some specific parameter suggestions were given.
Range-gated imaging of underwater laser based on control laser illumination sources of avalanche cascade circuit
HE Wei, TAN Yuguang, ZHANG Yizhou, CHEN Liangpei, YU Guangwen, CHEN Wei
2021, 42(5): 830-838. doi: 10.5768/JAO202142.0502002
A MARX cascade circuit laser illumination source for underwater laser range-gated imaging was developed based on the avalanche cascade principle. Compared with the ordinary laser drivers, this MARX cascade circuit had the advantages of narrow output pulse, high peak voltage, short rising edge, high repetition frequency, low cost, small volume and light weight. The pulsed laser illumination source developed by the cascade circuit maintained the miniaturization of illumination source system volume on the basis of realizing the pulse width performance with nanosecond (ns) magnitude. The experiment of range-gated imaging of underwater was carried out by the pulsed illumination source combined with laser shaping and homogenizing optical technology. With a pulse width of 10 ns, the range-gated imaging in the range of 7 times attenuation length under the water was achieved. The improvement of circuits and optics is of great significance to the reduction of volume and cost, and the application of laser range-gated imaging system.
Method of microscopic imaging quality evaluation for board lens based on image parameter extraction of pinhole imaging
LI Bo, WANG Fang, LYU Haowen, WU Wei, WEI Hangxin
2021, 42(5): 839-847. doi: 10.5768/JAO202142.0502003
The modulation transfer function area (MTFA) of pinhole imaging and the MTFA relative variation ratio were used as the image surface parameters to quantitatively evaluate the microscopic imaging quality of the board lens. The light spot images located in different fields of view positions were obtained by using the pinhole imaging method to extract the modulation transfer function (MTF) of microscopic imaging system for board lens. The MTF mathematical model of lens system for board lens was established, and the MTFA in sagittal direction and meridian direction of edge field of view as well as the MTFA relative variation ratio were extracted to measure the microscopic imaging definition and image surface flatness of the measured lens. An experiment which was for measuring the board lens was carried out, and the microscopic imaging performance of the measured lens was quantitatively evaluated by using the proposed model and method. The results show that the Lens 2 can obtain the optimal microscopic imaging quality. The definition value of average power spectrum value (APSV), the gray mean gradient (GMG) and the laplacian summation (LS) were calculated respectively from the RGB bitmap images captured by these measured lens. The results show that the maximum parameter value of the APSV, GMG and LS of Lens 2 bitmap images is equal to 2.720 2, 17.024 4 and 94.921 2, respectively. At the same time, the bitmap images have the highest definition, which is consistent with the image surface parameter evaluation results, indicating that the proposed method used in the quantitative evaluation of microscopic imaging performance of board lens is accurate and effective, which is of great significance and engineering value to improve the online image probe design of the on-line visual ferrograph (OLVF).
Calibration of multiple cameras based on ChArUco board
ZHAO Ziliang, ZHANG Zonghua, GAO Nan, MENG Zhaozong
2021, 42(5): 848-852. doi: 10.5768/JAO202142.0502004
A multiple cameras calibration method based on chess augmented reality university of cordoba (ChArUco) board was proposed for the multiple cameras system with limited or non-overlapping field of view. The ChArUco board was used to calibrate the camera; the global optimization was carried out based on the binocular reprojection error to provide precision guarantee for the subsequent pose transfer between cameras with non-overlapping field of view. Finally, the performance was tested by the spatial point reconstruction. The experimental results show that the average measurement error is 0.11 % within the point distance of 25 cm.
Memory tracking method of sensor location based on vision
SHI Yongmin, LOU Shuntian, AN Panpan
2021, 42(5): 853-858. doi: 10.5768/JAO202142.0502005
When some special sensors are used to measure parameters, the original measurement position needs to be determined after the sensor is removed. For example, after using the acupoint sensor to measure the abnormal performance of multiple meridians and acupoints of the patients, it is necessary to determine the actual position of abnormal acupoints and apply the intervention measures to them, which can relieve the pain and improve the physical condition of the patients. To solve this problem, the memory tracking problem of the sensor was studied, and a vision-based memory tracking method of sensor location was proposed. The AprilTag was pasted on the sensor and the tested object respectively. In the process of measurement, the AprilTag detection algorithm was used to calculate the position relationship between the sensor and the tested object. After the sensor was removed, the measurement position of the sensor was tracked by using the position relationship and AprilTag on the tested object, and the tracking accuracy was within 1 mm, which could provide reference for the further disposal
Particle filter algorithm based on whale swarm optimization
WU Fengbo, LIU Yao, ZHU Daixian, WANG Mingbo
2021, 42(5): 859-866. doi: 10.5768/JAO202142.0502006
Aiming at the problem of particle impoverishment in the standard particle filter, a particle filter algorithm based on the whale swarm optimization was proposed. In the algorithm, the particles were used to characterize the individual whales so as to simulate the process of whale swarm for searching preys and guide the particles to move to the high-likelihood region. Firstly, the state value of particles in particle filter was taken as the individual position of the whale swarm, and the state estimation of particles was transformed into the optimization of the whale swarm. Secondly, the importance sampling process of particles was optimized through the spiral motion mode of the whale swarm, which made the particle distribution more reasonable. In addition, the optimal neighborhood random disturbance strategy was introduced for the global optimal value in the whale swarm algorithm, and the adaptive weight factor was added in the process of whale position update. Finally, a typical single-static non-growth model was selected for the simulation test. The test results show that compared with the standard particle filter and the particle filter optimized by the gravitational field, the mean square error of the proposed algorithm is reduced by 28% and 9% respectively under the premise of the same particle number, which verifies that the particle filter algorithm optimized by the whale swarm has the higher estimation accuracy, and in the case of fewer particles, the more accurate state estimation can be achieved.
Object detection and tracking algorithm based on audio-visual information fusion
HUANG Zhanhua, CHEN Zhilin, ZHANG Hanxiao, CAO Yusheng, SHEN Muhong
2021, 42(5): 867-876. doi: 10.5768/JAO202142.0502007
Aiming at the defect that the single vision tracking algorithm is easily affected by the occlusion, an object detection and tracking algorithm based on the audio-video information fusion was proposed. The whole algorithm framework included three modules: video detection and tracking, acoustic source localization, audio-video information fusion tracking. The YOLOv5m algorithm was adopted by the video detection and tracking module as the framework of visual inspection, and the unscented Kalman filter and Hungary algorithm were used to achieve multi-object tracking and matching. The cross microphone array was adopted by the acoustic source localization module to obtain the audio information, and according to the time delay of receiving signals of each microphone, the acoustic source orientation was calculated. The audio-video likelihood function and audio-video importance sampling function were constructed by the audio-video information fusion tracking module, and the importance particle filter was used as the audio-video information fusion tracking algorithm to achieve object tracking. The performance of the algorithm was tested in complex indoor environment. The experimental results show that the tracking accuracy of the proposed algorithm reaches 90.68%, which has better performance than single mode algorithm.
Sequence-interleaving mapping method for direction of polarization
WANG Xia, SU Zihang, ZHAO Jiabi, XU Chao, JIN Weiqi
2021, 42(5): 877-883. doi: 10.5768/JAO202142.0503001
Direction of polarization, as one of the basic information in polarization imaging technology, can reflect the direction information of object surface in the scene. Therefore, the distribution of polarization direction in the scene plays an important role in the interpretation of the scene information. The conventional representation method of polarization direction has two main problems: one is high dimension of mapping results for 2-D or 3-D information mapping methods, another one is low noise-robustness of mapping methods caused by the low distance correlation of mapping relationship. A 1-D numerical value mapping method of polarization direction information based on the interleaved sequence with distance-preserving property was proposed. Firstly, the direction information was extracted from the stokes vector component as the 2-D mapping method of polarization direction. Based on the interleaved sequence method, the 2-D numerical value was mapped into the 1-D numerical value. Then, the relationship between the distance-preserving property and mapping method to noise-robustness was studied, and the distance-preserving property of the proposed mapping method of polarization direction and the conventional mapping method of polarization angle was analyzed. Finally, the simulation experiment and real-scene experiment were conducted. In the simulation experiment, the peak signal to noise ratio (PSNR) mean of the mapping results of proposed method was increased by 6% compared to the mapping method of polarization. In the real-scene experiment, the mapping results of proposed method reduced the information dimension compared to the mapping method of stokes vector and the no-reference PSNR (NRPSNR) mean of the non-negative matrix factorization (NMF) features was increased by 14% compared to the mapping method of polarization angle, which proved that the proposed mapping method has low information dimension and good noise-robustness.
Structured light scanning measurement method based on mechanical splicing
WU Qiong, LIU Wei, ZHOU Zhilong, WANG Yuxin, YUE Yi
2021, 42(5): 884-890. doi: 10.5768/JAO202142.0503002
The measurement of large-size components needs a larger measurement range, while the high-precision scanning sensor has a small field of view in most cases. In order to solve this contradiction, a structured light scanning measurement method based on mechanical splicing was proposed. The partial high-precision point cloud was obtained by structured light scanner and the data splicing was realized by high-precision cross translation platform. Firstly, the composition and measurement principle of the system were analyzed, and an external parameter calibration method based on weighted nonlinear optimization was proposed to solve the transformation relationship of the intangible coordinates between the structured light scanner and the cross translation platform. Finally, it was verified in the experiment that the root-mean-square error (RMSE) of sphere-center distance was better than 45 μm within the measurement range of 300 mm. And the feasibility of the proposed measurement system was verified by measuring the physical components.
Simulation research on instantaneous position measurement of explosion point of general industrial camera
HUANG Zhanhua, ZHANG Guang, CAO Yusheng, ZHANG Hanxiao, SHEN Muhong
2021, 42(5): 891-897. doi: 10.5768/JAO202142.0503003
In order to solve the problems that the structure of existing explosion point spatial location detection system was complex and the cost was expensive, a simulation research was carried out which was on instantaneous position measurement of explosion point based on the general industrial camera. The LED transient flash unit was designed, and the photoelectric sensor detected the light signal generated by the LED and converted it into an electrical signal. After signal processing, the two general industrial cameras were controlled to expose and capture at the same time according to the signal amplitude. The collected images were digitally processed to obtain the position coordinates of center of explosion spot in two images, and then combined with the relative position relationship between two cameras, the spatial location coordinates of explosion point were finally calculated. The experimental results show that at 24 m, 32 m, and 48 m from the measuring system, the absolute maximum error in the horizontal direction \begin{document}$X$\end{document} is 127 mm, in the vertical direction \begin{document}$Y$\end{document} is 68 mm, and in the depth direction \begin{document}$Z$\end{document} is 279 mm. The system has the advantages of fast response speed, high precision, low cost, and etc, which meet the requirements of system detection.
Edge filter temperature demodulation system based onarrayed wave-guide grating
LI Hongqiang, WANG Runjie, ZHANG Meiling, GAO Qian, ZHANG Sai, SONG Wenchao, MAO Quanhua, LI Enbang, Juan Daniel Prades Garcia
2021, 42(5): 898-905. doi: 10.5768/JAO202142.0503004
In order to overcome the large size and high price of the traditional arrayed wave-guide grating demodulation system, a demodulation scheme using a narrow-band light source as the input light source and adopting a combination of edge filter and arrayed wave-guide grating was proposed to realize the temperature demodulation experiment of fiber grating temperature sensor after packaging. Using the narrow-band light source as input, the edge filter method made the central wavelength shift of temperature sensor reflection spectrum correspond to the change in the output light intensity of demodulation optical path. The wavelength division multiplexing of arrayed wave-guide grating was used to realize the simultaneous measurement of multiple sensors, and the distributed measurement with multi-sensor and multi-channel was performed. The experimental results show that the wavelength demodulation range of the demodulation system is 1 545.30 nm~1 560.50 nm, the temperature range of 35 ℃~42 ℃ was detected, and the wavelength demodulation accuracy is ±5.34 pm. The temperature measurement error can reach to ±0.1 ℃.
Calibration method for multi-sky-screen target density based on double theodolites and bullet holes screen
CAO Jing, CHEN Junbiao, TIAN Hui, WANG Fan, LIU Baowei
2021, 42(5): 906-912. doi: 10.5768/JAO202142.0503005
The firing density is an important parameter to evaluate the firing effect of rapid-fire weapons, and the multi-sky-screen target testing system is widely used in the measurement of firing density of rapid-fire weapons. However, due to the influences such as the transportation, repeated installation and movement of multi-sky-screen target, the change of ambient temperature in outfield testing, and the long-time usage, the measurement error of the firing density becomes larger. For the calibration of firing density of multi-sky-screen target, a method based on double theodolites and high-accuracy bullet holes screen was proposed. The coordinates of the bullet holes in the bullet holes screen were measured by intersection measurement of double theodolites, and then the density parameters were calculated by the density formula. The calculated density parameters were compared with that of the multi-sky-screen target to complete the calibration. By the firing practice, the uncertainty of firing density measured by double theodolites combined with bullet holes screen was evaluated. The results show that the uncertainty of the firing density measured by the proposed method is 1.6 mm, which can be used for the calibration of the multi-sky-screen target density.
Laser detection of oil-gas diffusion in central drain pipe of floating-roof tank
LI Dong, GUO Xi, WANG Di, MA Pengbo, SUN Weidong, WANG Mingji
2021, 42(5): 913-918. doi: 10.5768/JAO202142.0507001
The research on oil-gas leak from the central drain pipe of floating-roof tank is of great significance for the timely formulation of reasonable emergency measures and the prevention of major accidents. A method for judging the leak of the central drain pipe was introduced. The influence of different leak locations on the alarm time after the leak of central drain pipe was analyzed through the numerical simulation. The simulation showed that the maximum difference between alarm times of the three leak locations was 1 308 s, which meant that the leak location had a greater impact on the alarm time. The feasibility of laser detection of oil-gas leak in central drain pipe was verified by using CH4 with a concentration of 10% instead of the oil-gas. The results show that the tunable diode laser absorption spectroscopy (TDLAS) technology can be used to detect the oil-gas concentration in the leak alarm system of central drain pipe, which provides a certain reference meaning for the design of the leak alarm system of central drain pipe of floating-roof tank.
Measurement method of repeated positioning accuracy of pinhole runnerbased on combination of laser and CCD
LIANG Weiyu, YE Chao, HU Qiu, LIU Sheng
2021, 42(5): 919-925. doi: 10.5768/JAO202142.0507002
The pinhole runner is the key component of the optical-path automatic calibration system of an experimental device, and the repeated positioning accuracy is one of its important indexes. In order to effectively measure the repeated positioning accuracy of the pinhole runner in vacuum environment, a measurement method based on the combination of laser and charge coupled device (CCD) was proposed, and the position repeatability of laser spot center of runner filtering pinhole was taken as the evaluation index of its repeated positioning accuracy. A complete set of measurement system was built, the laser spot filtered through the runner filtering pinhole was collected by CCD, and the laser spot image was preprocessed by the image processing methods, such as filtering and noise reduction, threshold segmentation, binarization and edge detection. The least square method was used for circle fitting of the laser spot, and the center coordinates of laser spot were obtained. Compared with laser interferometer in non- vacuum environment, the angular deviation between them was only 11″, which showed that the measurement method had high accuracy and met the measurement requirements. Finally, the repeatability measurement of the pinhole runner in vacuum environment was carried out for about 60 times forward and backward reciprocation in about 6 hours. The results show that the method can effectively measure the repeated positioning accuracy of the pinhole runner in vacuum environment.
Temperature sensing characteristics of a microsphere resonator embedded in a capillary
SUN Hang, LIU Xiaochen, WANG Zijie, YU Yang, YANG Yong, ZHANG Xiaobei
2021, 42(5): 926-931. doi: 10.5768/JAO202142.0508001
The coupling mechanism and temperature sensing characteristics based on the micro-sphere resonant cavity coupled apparatus embedded in capillary were investigated. The micro-sphere support the high-order modes, which is easy to meet the phase matching condition with the modes in the quartz capillary, thus the mode of micro-sphere echo wall will be excited. The temperature sensing of a barium titanate micro-sphere was tested. A polymethylmethacrylate (PMMA) micro-sphere was adopted to carry out the temperature sensing experiment for further enhancing the sensing sensitivity. The experimental results show that the temperature sensing sensitivity of PMMA micro-sphere can reach to 83.9 pm/℃, about eight times of that by the barium titanate micro-sphere, which plays an important role for improving the temperature sensing sensitivity.
Research progress of flexible sensor of fiber Bragg grating
XU Xiaoqiang, DU Yang, MAO Yan, SONG Ziqi
2021, 42(5): 932-940. doi: 10.5768/JAO202142.0508002
The fiber grating sensor has the advantages of light weight, small size, high sensitivity, strong anti-electromagnetic interference capability and so on, especially good flexibility and compatibility. The fiber grating and flexible materials can be fabricated into a flexible sensor with high-density distributed perception by means of the special preparation technology. The basic sensing principles of fiber grating were introduced; then the fiber grating flexible sensors using silicone rubber, textile and other polymers as the substrates were introduced in detail, and the preparation technologies, structural characteristics and performance of various flexible sensors were analyzed; finally, the main problems, application fields and future research directions of flexible sensors were discussed.
High spatial resolution distributed optical fiber temperature measurement system for ice cover profile
WANG Dingrui, DENG Xiao, ZHANG Jun, LU Xinshuo, DU Chao, ZHANG Li, ZHANG Lin
2021, 42(5): 941-948. doi: 10.5768/JAO202142.0508003
A distributed optical fiber temperature measurement system with a high spatial resolution was designed to overcome the shortcomings of the existing vertical profile temperature measurement technology for winter ice cover. The measurement principle and overall structure of the system were introduced, and the deconvolution correction algorithm was proposed to avoid the inaccurate temperature measurement caused by the limited bandwidth of the system, thereby enhancing the spatial resolution. At the same time, the relevant temperature measurement experiments were carried out. The algorithm could improve the spatial resolution of the system from 1.3 m to 0.5 m under the premise of ensuring the accuracy of temperature measurement. On this basis, a temperature measurement device with a high vertical resolution was designed, which could accurately detect the temperature change in the vertical direction of the ice cover to achieve the purpose of identifying the thickness of the ice cover.