最新刊期
期 4 ， 2023
- 摘要：Liquid Crystal （LC）， as an intermediate state between liquid and solid， has the fluidity of liquid and the anisotropy of crystal， and its director is flexible and tunable. It has a wide range of applications from microwave to ultraviolet. In recent years， LC photonics has shown great application prospects in the terahertz band. This paper reviews the research progress of LC-based terahertz sources， tunable terahertz devices and terahertz detectors， and discusses the future development of LC terahertz photonics such as ferroelectric nematic phase， liquid crystal topology， as well as multi-mode and multi-parameter on demand terahertz wave generation， modulation and detection.关键词：liquid crystals;terahertz sources;terahertz devices;terahertz detectors
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发布时间：2023-04-10 - 摘要：In order to enable organic light emitting display technology to meet the colour gamut standard set by the International Telecommunication Union for Ultra HD TV （BT 2020）， the research and development of high colour purity organic light-emitting device （OLED） is important. In this review， we present the latest developments and important research on high colour purity OLEDs in terms of both narrow-band light-emitting materials and microcavity OLEDs， respectively. This paper analyses the effect of vibrational coupling of molecules on the colour purity of organic light-emitting materials， and discusses current methods to improve the colour purity for fluorescent， phosphorescent and thermally-activated delayed fluorescence materials， respectively， and summarizes the latest material design strategies and research results. The principles of the microcavity effect is introduced and its modifying and narrowing effects on the spectra of organic light-emitting devices is analyzed， and then the design of device structures to achieve high colour purity light-emitting using the microcavity effect is presented. Finally， we discuss the future prospects and challenges of high colour purity OLED devices in the display field.关键词：High colour purity OLEDs;BT 2020;vibrational coupling;molecular design;microcavity effect
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发布时间：2023-04-10 - 摘要：At present， VR/AR （virtual reality/augmented reality） display technology has been widely used in the market， and all kinds of near-eye display devices at home and abroad are well received by consumers. Various types of near-eye display devices have different imaging principles and optical elements. In this paper， various near-eye display imaging technologies were summarized and classified， and several common optical systems of near-eye display are introduced. The binocular parallax-type display system， retinal display system， integral imaging near-eye display system and holographic near-eye display system were illustrated in detail， and their technical principles and optical path structures were analyzed respectively. Then， we proposed a binocular retinal projection imaging three-dimensional （3D） device， which combines binocular parallax technology with retinal projection technology together to realize the stereoscopic display effect with compact structure and high definition， without convergence focusing conflict. The development and update of all kinds of near-eye display technologies， as well as the characteristics and application prospect of each technology were analyzed.关键词：near-eye display technology;head-mounted display;binocular parallax;retinal imaging;integral imaging;holographic technology
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发布时间：2023-04-10 - 摘要：In the field of microscopic imaging， the acquisition of high-quality images is closely related to good illumination mode. Traditional microscopes use a condensing lens to provide illumination with uniform intensity and adjust the aperture of the condensing lens to match the objective lenses with different magnification. However， it is difficult to observe the details of colorless biological cells which optical absorption coefficient is low under the traditional microscope. In order to improve the imaging capacity of traditional microscopes， this paper designs a kind of adjustable microscope condenser module. Bright field imaging and differential phase contrast imaging can be achieved by embedding a small twisted liquid crystal device in the back focal plane of the condenser lens to regulate the light transmission effect of the liquid crystal device. The system is refitted from a commercial microscope. The size of the liquid crystal device is 22 mm×18 mm， which realizes the high integration of the system. The imaging performance of the system is verified through experiments and the correlation coefficient between experimental and theoretical curves reaches 0.994 9. The reconstruction of embryonic stem cells shows the effect of the system in practical application.关键词：Microscopy;Computational Imaging;differential phase contrast imaging
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发布时间：2023-04-10 - 摘要：The properties of the dielectric and the flexoelectric effects in a concentric cylinder under electric field are different from those of liquid crystal cells. Flexoelectric effect and dielectric effect on nematic liquid crystal 5CB with chiral dopants in a concentric cylindrical cell with axial strong anchoring conditions in radial electric field are studied. The equations in the bulk are obtained based on the Frank elastic theory and the difference iteration method. It is found that the flexoelectric coefficients e1 and e3 have different orientation effects by numerical calculation. Our method provides an accurate theoretical analysis for the prediction of the chiral nematic liquid crystal director in a concentric cylindrical cell under the action of the electric field and it also has a certain guiding significance for the measurement of the flexoelectric coefficients.关键词：concentric cylindrical cell;nematic liquid crystals;chiral dopant;dielectric effect;flexoelectric effect
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发布时间：2023-04-10 - 摘要：Liquid crystal materials have good modulation characteristics in the microwave band， and have great potential for application in the field of microwave tunable devices. In this paper， a sensor based on the resonance of spoof localized surface plasmon is proposed for the demand of microwave dielectric constant measurement of liquid crystal materials. The ring resonator structure is designed to form narrow-band resonant peaks in the sub-6 GHz band with localized surface surface plasmon. By applying an applied electric field to the liquid crystals， the modulation of the liquid crystal dielectric constant can be achieved. The corresponding dielectric constant can be obtained by fitting the position of the resonant frequency points， thus realizing the measurement of the dielectric constant of the liquid crystal material in the microwave band. The effects of different liquid crystal layer thicknesses and different liquid crystal dielectric constants on the resonant frequency points of the spoof localized surface plasmon are studied. The resonant frequency points f1 and f2 increase gradually with the increases of the liquid crystal layer thickness or the decreases of the liquid crystal dielectric constant. When the thickness of liquid crystal layer is equal or greater than 0.5 mm， the resonant frequency points f1 and f2 have good linearity with the change of the liquid crystal dielectric constant. The proposed sensor has a high sensitivity （>400 MHz/Δε）， which is much larger than that based on other forms of dielectric constant sensors reported so far. At the same time， this sensor structure can apply electric field above and below the liquid crystal layer， thus realizing the measurement of microwave dielectric constant of liquid crystal materials under the action of different applied electric fields， which has potential for application in the field of microwave characterization of liquid crystals.关键词：liquid crystals;microwave dielectric constant;sensor;spoof localized surface plasmon
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发布时间：2023-04-10 - 摘要：Particle Gap is a common defect in LCD panel. It is crucial to evaluate the severity of defect accurately. The traditional methods have poor accuracy and large error. In this paper， the electronic limit sample is designed by using the Photo Shop software based on the shape and color of Particle Gap defect， which greatly improves the accuracy of defect detection. Firstly， Particle Gap defect is divided into four types， and the color of circular defect is isotropic and varied uniformly or non-uniformly from center to edge. Then the electronic limit model is established. The optimal electronic limit samples are found through comparative experiments. Finally， the HSB color gamut of Particle Gap is determined ， H∈［30°， 45°］， S∈［2%， 56%］， B∈［15%， 66%］. As the defect varies from light to heavy， the hue tends to decrease， the saturation gradually increases， and the brightness first increases and then decreases， which provides a reference for making and revising the electronic limit sample. After the application of the electronic limit sample in the panel testing process of H Company， the accuracy of defect detection is increased by more than 7.1%， which brings significant improvement in reducing loss of product and materials. The electronic limit sample has great application value in the field of defect detection.关键词：Particle Gap defect;Limit Sample;HSB color value;Accuracy of Detection
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发布时间：2023-04-10
Device Physics and Device Preparation
- 摘要：In order to meet the requirements of wearable devices for high stability and low operating voltage， a novel microdisplay pixel circuit and its working timing scheme are proposed in this paper. The proposed pixel circuit extracts， stores and compensates the threshold voltage variations to reach high current stability. The maximum driving current is up to 1 017.1 nA. When the threshold voltage variation is between -50 mV and +50 mV， the maximum current error of the conventional pixel circuit is +18.67 LSB， while that of the proposed circuit is between -0.54 LSB and +0.70 LSB. It indicates that the proposed pixel circuit significantly improves the display stability， which is simulated and verified successfully by HSPICE.关键词：wearable devices;microdisplay;pixel circuit;Threshold Voltage Compensation
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发布时间：2023-04-10
Driving and Controlling
- 摘要：In order to suppress the influence of laser speckle noise on the accuracy of quantitative phase reconstruction， a laser speckle noise suppression method based on empirical mode decomposition is proposed in this paper. The method only needs to acquire a holographic image without adding additional hardware equipment and avoids the complicated process of finding optimal processing parameters. Firstly， empirical mode decomposition is used to highlight image details. Secondly， edge detection is used to overcome the problems of poor anti-noise capability and the inability to identify false edges of gradient operators in the anisotropic diffusion equation， and edge detection is performed on images with prominent details. Finally， the diffusion denoising process is guided by the high-precision edge detection results to achieve better speckle suppression. The experimental results show that after processing by the method in this paper， the structural similarity of the reconstructed phase is increased by 12.900 0%， the edge preservation index is increased by 14.386 1%， the speckle suppression index is reduced by 8.129 9%， and the phase cross-section curve is the closest to the original phase. The method proposed in this paper not only has a better denoising effect but also preserves the detailed information more effectively， and the accuracy of phase reconstruction is higher.关键词：speckle noise suppression;empirical mode decomposition;edge detection;anisotropic diffusion equation
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发布时间：2023-04-10 - 摘要：VGGNet can provide high-precision Martian image classification， but consumes vast memory resources. Considering the limitation of memory resources of the onboard computer， a Martian image classification method based on iterative pruning VGGNet is proposed to solve this contradiction. Firstly， the transfer learning is used to train the connectivity of the network in order to evaluate the importance of neurons. Secondly， to reduce the number of fully connected layer parameters and memory consumption， the iterative pruning method is used to prune unimportant neurons. Finally， K-means++ clustering is used to quantify the weight parameters， and Huffman coding compresses the weight parameters of VGGNet after iterative pruning and quantization to reduce the storage capacity and floating point arithmetic. Furthermore， the data augmentation is carried out through five data augmentation methods to address the class imbalance. Experimental results show that the memory， Flops and accuracy of the compressed VGGNet model are 62.63 Mb， 150.6 MFlops and 96.15%， respectively. Compared with lightweight image classification algorithms such as ShuffleNet， MobileNet and EfficientNet， the performance of the proposed model is better.关键词：image classification;convolutional neural networks;iterative methods;clustering algorithms;VGGNet
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发布时间：2023-04-10 - 摘要：In the existing works of eye-movement image annotation algorithms， the fixation points resting on non-targets may introduce localization interference， and produce low annotation accuracy. To solve this problem. Firstly， experimental studies are conducted to explore the eye-movement pattern in the annotation task. Then， the annotated gaze sequences are divided into two stages： visual search and visual recognition， and a fixation points classification method based on the parameter adaptive DBSCAN algorithm is proposed to extract recognition fixation points as the input of the eye-movement image annotation algorithm in order to improve the accuracy of the annotation results. Finally， the experimental comparison and analysis are carried out based on the 2014 DIMITRIOS P data set. The experimental results show that compared with the existing related algorithms， the F1 score is improved by 4%， the algorithm operation efficiency is improved by nearly one time， and the eye-movement image annotation accuracy is improved by 3.34%， which meets the requirements of stability， reliability， high accuracy， and fast running speed.关键词：fixations classification;eye movement image annotation;visual research;visual recognition;adaptive DBSCAN
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发布时间：2023-04-10 - 摘要：Aiming at the problems of edge blurring and artifacts in traditional multi-focus image fusion algorithm， a multi-focus image fusion algorithm based on sum-modified-Laplacian （SML） and difference image is proposed. Firstly， in order to extract the focus feature information of source images， the focus measurement is performed by SML and difference operation between filtered images and source images respectively， and the guided filtering is adopted to obtain more detailed features. Then， the initial fusion decision map is generated by using pixel-wise maximum rule， the small area removal strategy is performed to eliminate the noise caused by the similarity of focus and defocus areas， and inconsistency processing is used to generated final decision map to obtain a more accurate focus region. Finally， the fused image is obtained by the pixel-by-pixel weighted average rule. Experimental results indicate that the proposed algorithm is superior to the comparison algorithm in both subjective visual effect and objective evaluation metrics. The mutual information， feature mutual information and image gradient features are improved by 0.17%， 0.38% and 0.11% respectively on color images. On grayscale images， the improvements are 0.7%， 0.86% and 0.47%， respectively. Furthermore， the average consuming time is less than 0.5 s with high computational efficiency. In addition， the algorithm can better retain the integrity of source image information， and the fusion image has clear edges without artifacts.关键词：multi-focus image fusion;sum-modified-Laplacian;difference image;focus region detection
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发布时间：2023-04-10 - 摘要：Due to the influence of medium particles in the air under hazy weather， the images captured by imaging devices usually suffer from low contrast and color loss. To address these problems， an atmospheric light veil estimation dehazing algorithm based on haze distribution is proposed in this paper. Firstly， the initial haze distribution image extracted by twelve features of the image is subjected to thresholding and refinement to obtain more accurate haze distribution information. Secondly， the atmospheric light veil estimation model is established by analyzing relationships among the depth of field， haze concentration， and atmospheric light veil. Finally， the atmospheric light region is selected by luminance weighting map and adaptive atmospheric light threshold， and then recover the degraded scene. The experimental results show that this algorithm restores images clearly and can retain detailed information in the image.关键词：image dehazing;haze distribution;estimation model of atmospheric veil;luminance deviation;adaptive atmospheric light threshold
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发布时间：2023-04-10 - 摘要：Aiming at the problem of large computational complexity and high mismatch rate caused by the use of random functions to generate planar parameters in the PatchMatchStereo stereo matching algorithm when implementing inclined planes， a stereo matching algorithm based on local consistency constraints is proposed. First， the algorithm obtains support points with high parallax confidence by sparse matching of pixels in the image. Second， the algorithm uses triangulation to determine a triangular plane for each pixel in the image， calculates the plane parameters and assigns them to the points in the plane. Then， a more accurate plane parameter is found for each pixel through iterative propagation， and a local consistent parallel window model is constructed. Finally， the disparity is calculated through the plane parameter and optimized through the disparity post-processing. The algorithm in this paper is tested on the standard test data set of the third edition of the Middlebury evaluation platform. The experimental results show that the average error matching rate after processing is 4.39% lower than that of the PMS algorithm， and the maximum error matching rate of a single image is reduced by 15.42%. The algorithm in this paper improves the efficiency of image processing while reducing the false matching rate， and has significant advantages over other algorithms.关键词：triangulation;parallel windows;iterative propagation;image processing;local consistency
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发布时间：2023-04-10
Image Processing
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