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Issue 3 ， 2022
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Design of laser scanning confocal spectroscopy system
Abstract：A spectral structure for the double Amici prism was designed to improve the spectroscopic performance of a laser scanning confocal microscope spectroscopy module. Linear and nonlinear mathematical models were formulated for the Amici and double Amici prisms， and the structure parameters of direct-viewing prism were chosen according to the prism dispersion characteristics. The structures of the Amici and double Amici prisms were compared for the same dispersion conditions， and the double Amici prism group was found to provide better dispersion linearity. A common optical axis direct vision spectroscopic system was developed using a double Amici prism for a 400-700 nm spectral range and 5 nm spectral resolution， with central wavelength deviation angle of 0° and maximum dispersion angle of 4°. The experimental results show that the dispersion linearity of this structure is significantly better than that of a single prism. Spectral resolution issues caused by the nonlinear spectroscopic characteristics of prisms are greatly reduced.Keywords：Laser scanning confocal;Amici prism;dispersion linearity;common optical axis direct vision- 431
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Published：2022-02-17 -
Polarization modulation range-finding system based on waveguide phase modulator
Abstract：To improve the range-finding accuracy of a polarization modulation range-finding method and eliminate the thermal effect of bulk phase modulators， we propose waveguide phase modulators to substitute the bulk phase modulators. First， the polarization modulation range-finding method and system based on waveguide phase modulator were studied. The functional relationship between the frequency of the modulation signal， the intensity of the polarization light， and the distance was established by analyzing the polarization state change of light in the transmitted path of the system with the Jones matrix. Then， the characteristics of the waveguide phase modulator were tested. The test results show that the half-wave voltage ranges in 3.5-7 V and the consistency of the forward half-wave and backward half-wave voltages ranges in －2%-3%. Finally， a polarization modulation range-finding system with straight waveguide phase modulator was set up to verify the operation of the polarization modulation range-finding system. The average measurement error of the fixed-length fiber is 0.46 mm， and its measurement repeatability is 0.54 mm. The average measurement error is 0.39 mm according to a variable distance test. The experimental results demonstrate that this system can be employed for laser ranging. The system presents a simple structure that can help realize low power consumption and miniaturization.Keywords：laser ranging;waveguide phase modulator;polarization modulation;polarization maintaining fiber- 134
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Published：2022-02-17 -
Forward simulation of solar backscattered ultraviolet radiation for satellite over the Tibetan plateau
Abstract：To quantitatively evaluate the influence of elements such as reflectivity of the underlying pixel surface on the precision of ozone data from satellite remote sensing over the Tibetan plateau， a forward simulation calculation of solar backscattered ultraviolet radiation for a satellite over the Tibetan plateau was conducted. First， observation data of the underlying pixel surface from NOAA satellites SBUV/2 over the Tibetan plateau were extracted and combined with the extracted ozone vertical profile. The input parameters of the forward simulation calculation for the Tibetan plateau were adjusted. Then， the parameters were input to the forward simulation system of the FY-3 Solar Backscatter Ultraviolet Sounder for forward simulation calculation. Finally， we investigated the characteristics of the observation value changes from the Solar Backscatter Ultraviolet Sounder channel radiation with different parameters through the calculated results. The results show that， when the solar zenith angle varies in the range of 30°–88°， the radiance observation values for each channel of the instrument decrease with an increase in the solar zenith angle. The rate of variation ranges from -0.002% to -46.24%. The variability increases with an increase in wavelength， and the maximum value of the 12-th channel was -46.24%. When the reflectivity of the underlying pixel surface changes within the range of 0-0.8， the variation characteristics of the observed radiance value from the instrument channel significantly vary with the wavelength. For the short-wavelength channels from 1 to 6， the variation of the channel observations was almost negligible. For the long-wavelength channels from 7 to 12， the observed value increases as the reflectivity of the underlying surface increases. Moreover， this rate of change increases rapidly as the wavelength increases， with a maximum variation of 2 903.2% for channel 12. The variation of the effective air pressure on the underlying pixel surface has almost negligible influence on the observation of the radiance from the instrument channel.Keywords：satellite remote sensing;Tibetan plateau;Solar Backscatter Ultraviolet Sounder;forward calculation;radiation transmission- 114
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Published：2022-02-17 -
Gas quality monitoring for sterilizer based on fiber Bragg grating
Abstract：The monitoring of target physical parameters in sterilizers includes temperature and air pressure monitoring. The aim of air pressure monitoring is to ensure that the dry and pure saturated water steam is working properly for sterilization. In our previous study，we have accomplished real-time， dynamic temperature monitoring of the whole process of sterilization using fiber Bragg gratings （FBG）. In this work，we aim to obtain an integrated monitoring system of physical parameters based on FBGs for sterilizers. The proposed method is based on a polyimide-coated FBG to monitor gas quality during sterilization. Firstly， we evaluate both temperature stability and sensitivity of the polyimide-coated FBG. Then， the response to water vapor density is examined during the exhaust and drying periods of the qualified sterilizer. Finally，a system is proposed for the monitoring of gas quality through a polyimide-coated FBG and for the monitoring of temperature by a FBG encapsulated in capillary stainless-steel tubes. The polyimide-coated FBG showed excellent temperature stability during sterilization with a sensitivity of 0.014 3 nm/°C. The response of the sensor to water vapor density can be represented by the piecewise lines，and their individual sensitivities were 8.994 2×10-4， 1.783 7×10-5， 2.227 2×10-4and 1.623 6×10-4 nm/（g- 199
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Published：2022-02-17 -
FBG sensor of double-layer cross beam structure based on SSA-ELM three-dimensional force decoupling
Abstract：Aiming to address the problem of severe inter-dimensional coupling interference of three-dimensional force sensors， a decoupling algorithm based on the sparrow search algorithm–extreme learning machine （SSA–ELM） is proposed considering a fiber Bragg grating （FBG） three-dimensional force sensor with a double-layer cross beam structure as the research object. First， the sensing and force measurement principle of FBGs is studied， the mapping relationship between wavelength drift and the force of the three-dimensional force sensor is revealed， and its structural coupling characteristics are analyzed. Then， a calibration experiment system is constructed to perform calibration experiments. Finally， a nonlinear decoupling model of extreme learning machine （ELM） is established， and the sparrow search algorithm （SSA） is used to optimize the model to obtain the optimal initial weight and threshold of the network. Considering the decoupling accuracy and efficiency， the optimal number of ELM hidden layer nodes and optimal number of SSA iterations are determined. After decoupling， the maximum type I error is 1.18%， the maximum type II error is 1.14%， and the decoupling training time is 1.778 6 s. At the same time， in order to verify the decoupling effect， the decoupling results of the SSA–ELM algorithm are compared with least squares and ELM algorithm. The experimental results show that the SSA–ELM algorithm has a short decoupling training time， can more effectively construct the dimensional coupling relationship of the three-dimensional force， reduce the type I and II errors of the sensors， and has a good nonlinear decoupling ability.Keywords：fiber Bragg grating;three-dimensional force sensor;inter dimensional decoupling;extreme learning machine;sparrow search algorithm;error analysis- 120
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Published：2022-02-17
Modern Applied Optics
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Performance optimization of chaotic flow micromixer
Abstract：In order to improve the efficiency of passive micromixers under laminar flows at low Reynolds numbers， this study conducts a series of operations on fluids including "extrusion stretching，" "curved folding，" "secondary folding，" and "inverse transformation intersection" based on a mathematical model of 3D horseshoe transformation. The considered chaotic flow micromixer contains six mixing units with a total length of 15 mm. Simulations show that in the low flow rate-diffusion dominated stage， the mixer enters a stable state after t=300 s when u=2×10-4 m/s， and the mixing index αOutlet=97.82% at the mixer outlet. In the medium velocity-turbulence development stage， the mixer enters a stable state after t=70 s when u=5×10-3 m/s， and the mixing index αInlet4=98.89% at the inlet of mixing unit 4. In the high velocity-turbulence dominated stage， the mixer enters a stable state after t=22 s when u=8×10-2 m/s， and the mixing index αInlet3=99.35% at the inlet of mixing unit 3. The entire mixer chip is fabricated as a whole by 3D printing technology based on surface projection micro-stereo lithography. The performance of the mixer at different injection flow rates is verified by visualization using a microscope. The results of the tracer color change experiment are consistent with the simulation results of the mixer surface concentration cloud map.Keywords：microfluidic;chaotic mixer;three-dimensional horseshoe transform;3D printing;integration preparation- 115
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Published：2022-02-17 -
Micro plasma jet devices for micron sterilization range control
Abstract：In order to achieve precise sterilization using micro plasma， a novel micro plasma jet device was designed， and the distribution range of the reactive oxygen species （ROS） and reactive nitrogen species （RNS） generated by the device and the sterilization range of the device were investigated. First， iodine ions （I-） in a potassium starch iodide mixture were oxidized to iodine monomers （I2） by the ROS and RNS generated by microplasma jets. The range of distribution of the ROS and RNS in the jet of the device was characterized using an agar medium containing the starch-potassium iodide mixture， based on the color development principle of starch， which turns blue when exposed to iodine. Next， a bacterial solution was coated on an agar medium and incubated overnight at 37 °C in a biochemical incubator using a micro plasma jet device for different times under the same conditions for characterization of the sterilization range. Finally， the sterilization ranges were observed under a Ts2FL Nikon inverted fluorescence microscope. The experimental results indicate that the sterilization range can be controlled within diameters of 30， 65， and 75 μm at an AC voltage amplitude of 5 kV， a center frequency of 10 kHz， and an action time of 10， 20， and 30 s， respectively. A plasma jet does not directly contact the surface of the object， whereas plasma directly contacts the surface of the object； the former has a smaller sterilization range， and it is easier to achieve accurate control. This device improves the current millimeter-scale sterilization range accuracy to the micron scale， which is of great significance for plasma medical research.Keywords：Micro plasma;sterilization;starch-potassium iodide mixture;micron scale- 102
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Published：2022-02-17 -
Inertial focusing effect of particles in spiral microchannel with asymmetric cross-section
Abstract：An inertial microfluidic chip with a spiral microchannel of asymmetric cross-section was proposed to achieve a precise control of biological microparticles/cells. The inertial focusing behavior of particles of different sizes in the microchannel was studied through simulation and experiment. A spiral channel with L shaped cross-section was designed， and the secondary flow field distribution and particle trajectory in the channel were analyzed using COMSOL simulation software. The prototype chip was fabricated by UV laser cutting and plasma cleaning bonding. The trajectories of particles of sizes 6， 10， and 15 μm at different flow rates in the channel were captured by a high speed camera and fluorescent microscope. Finally， the images of particle trajectories were stacked and analyzed and the inertial focusing and migration mechanism of the particles were investigated. The results show that two asymmetric secondary flow vortexes of different strengths are produced in the L shaped cross-section. Furthermore， the particles of 10 and 15 μm sizes focus tightly in the outer ring of the microchannel， whereas those of 6 μm size focus in it roughly. The particle focusing position can be adjusted using asymmetric secondary flow， thus providing new insights into precise particle and cell manipulation.Keywords：microfluidics;asymmetric flow;inertial focusing;particle manipulation;UV laser cutting- 97
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Published：2022-02-17
Micro/Nano Technology and Fine Mechanics
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Infrared and visible image fusion based on WEMD and generative adversarial network reconstruction
Abstract：To overcome the problem of blurred edges and low contrast in the fusion of infrared and visible images， a two-dimensional window empirical mode decomposition （WEMD） and infrared and visible light image fusion algorithm for GAN reconstruction was proposed. The infrared and visible light images were decomposed using WEMD to obtain the intrinsic mode function components （IMF） and residual components. The IMF components were fused through principal component analysis， and the residual components were fused by the weighted average. The preliminary fused image was reconstructed and input into the GAN to play against the visible light image， and some background information was supplemented to obtain the final fusion image. The average gradient （AG）， edge strength （EI）， entropy （EN）， structural similarity （SSIM）， and mutual information （MI） are used for objective evaluation， and they increased by 46.13%， 39.40%， 19.91%， 3.72%， and 33.10%， respectively， compared with the other five methods. The experimental results show that the proposed algorithm achieves better retention of the edge and texture details of the sources image while simultaneously highlighting the target of the infrared image， has better visibility， and has obvious advantages in terms of objective evaluation indicators.Keywords：image fusion;infrared and visible image;window empirical mode decomposition;generative adversarial network- 138
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Published：2022-02-17 -
Detection of leaky cable fixture in high-speed railway tunnel with layered continuous gradient fusion feature
Abstract：Deep mining algorithms and multi-feature fusion algorithms based on local binary patterns are effective methods for extracting the fixture features of leaky cables in railway tunnels； however， there are disadvantages that the descriptors are not expressive enough and that their feature dimensions are too high. In this paper， layered continuous gradient local binary pattern （LCG-LBP） was proposed， which could realize the scale transformation of leaky cable fixture features. It could reduce the feature dimension of the fusion descriptor extracted from down-sampling feature maps. It could also improve the classification accuracy of faulty fixture images effectively. First， the improved algorithm based on center-symmetric local binary pattern （CS-LBP） and the adaptive threshold obtained by the global gray average value were used to calculate the gradient direction feature in a circle domain unit， and the complete preliminary gradient direction feature map was obtained in this way. Then， two consecutive down-sampling iterations were performed on this preliminary feature map to obtain two down-sampling feature maps， and the continuous gradient features were extracted from these two down-sampling feature maps. Finally， the two layers of continuous gradient features in different scales were connected in series as a fusion descriptor， and a support vector machine （SVM） was used to complete the defect detection process using faulty cable fixture images obtained from railway tunnels. The experimental results show that the recall and accuracy of the algorithm proposed in this paper are 0.923 and 0.857， respectively， which show that the proposed algorithm has obvious advantages compared with local binary pattern （LBP）， CS-LBP， and other variants.Keywords：defect detection;leaky cable fixture;scale transformation;continuous gradient;local binary pattern- 106
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Published：2022-02-17 -
Multi-stage boundary reference network for action segmentation
Abstract：Over-segmentation leads to incorrect predictions and reduces segmentation quality in existing action segmentation algorithms. To address this， the reference from video action boundary information was independently introduced for each stage in the backbone， which was based on a multi-stage temporal convolutional network. To avoid the model solidification caused by the application of the same boundary information at all stages， a weight adjusting block composed of multilayer parallel convolution was proposed to adjust the boundary values involved in the output calculation of each stage and process various samples differently. The reference from the adjustable boundary information was used to smoothen the output of each stage according to the time sequence， significantly reducing the over-segmentation error. Experimental results show that the proposed method outperforms existing methods in the three video action segmentation datasets GTEA， 50Salads and Breakfast. Compared with the boundary-aware cascade networks（BCN） algorithm， the segmentation edit score is increased by 1.7% on average， and the reconciliation score between accuracy and recall rate is increased by 1.5% on average.Keywords：video action segmentation;temporal convolutional networks;video action boundary;untrimmed video- 88
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Published：2022-02-17 -
Adaptive Canny operator edge detection under strong noise
Abstract：The traditional Canny operator cannot effectively filter out the salt and pepper noise generated during the decoding process and transmission of an image， and cannot retain the edge details. To overcome this， an improved Canny operator image edge detection algorithm for operation under strong noise was proposed. According to the extreme value and gray difference of salt and pepper noise， the pixel points were divided into noise points and suspected noise points. The size and weight of the filter window were adaptively changed according to the pixel points after classification， which could reduce the influence of noise while retaining the image details. Then， the Sobel operators for eight directional templates were introduced to calculate the gradient amplitude to improve the edge positioning effect after filtering. Finally， iterative adaptive threshold algorithm and Otsu algorithm were used to select the best threshold to achieve adaptive threshold setting and improve the edge connection effect. The results of the comparative experiment show that after denoising the noisy image， the structural similarity is 0.949， the peak signal-to-noise ratio is increased by 10.97 dB compared with the traditional algorithm， the average edge evaluation is increased by 27.2%， and the F1 value is increased by 34.6%. The proposed algorithm retains the excellent performance of the Canny operator， can effectively remove salt and pepper noise， and has better edge detail protection capabilities.Keywords：computer vision;edge detection;image denoise;Canny operator;adaptive filter;adaptive threshhold- 268
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Published：2022-02-17
Information Sciences
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