最新刊期
期 10 ， 2023
- 摘要：Circularly polarized light is a type of light in which the endpoint trajectory of the light vector forms a circle. During its propagation， the magnitude of the light vector remains constant while the vibration direction changes along with phase. Typically， unpolarized light is first converted to linearly polarized light through a polarizer and then transformed into left-handed or right-handed circularly polarized light using a quarter-wave plate. However， this physical process results in an energy loss higher than 50% for circularly polarized light. By introducing aggregation-induced emission （AIE） properties into chiral liquid crystal molecules， circularly polarized light can be directly obtained with a high fluorescence quantum efficiency and a large asymmetric factor， thereby achieving effective reduction of energy loss. Consequently， AIE chiral liquid crystals have gained increasing attention from researchers in relevant fields. This review summarizes the recent progress in this field， focusing on the design and synthesis of chiral liquid crystal molecules modified with AIE luminophores and the doping of chiral AIE molecule systems into nematic liquid crystal phases. The influence of the chemical structure design of AIE liquid crystal molecules and the formation of aggregates on circularly polarized luminescence and AIE performance are discussed. Finally， the existing challenges and opportunities for this new optical material are prospected.关键词：Aggregation-induced circularly polarized luminescent liquid crystals;Chiral liquid crystal groups;Dissymmetry factor;Fluorescence quantum yield
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发布时间：2023-10-10 - 摘要：The liquid crystal （LC）-based open surface microfluidic can manipulate the liquid in micro-nano scale by utilizing microfluidics principles and micromachining techniques， which is crucial for developing next generation microfluidic platforms. In this work， rational theoretical design and controlled synthesis are conducted to prepare anisotropic functional polymer films including nematic and smectic LC polymer films. According to our study， the flow of droplets on nematic LC polymer films is an order of magnitude faster than on smectic LC polymer films. Moreover， both the nematic and smectic LC polymer films can trigger orientation-dependent flow velocity of droplets， which realize the anisotropic transports of droplets and thereby lays a foundation for the development of specific microfluidic technology based on patterned LC functional surfaces.关键词：liquid crystal;nematic phase;smectic phase;Liquid crystal polymer;Droplet Transport
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发布时间：2023-10-10
Material Physics
- 摘要：Cholesteric liquid crystals （CLCs）， one-dimensional chiral soft photonic crystals， have a wide application in fields such as security tags， nanolasers， and sensing. In this paper， a multi-step UV patterning curing method combined with a washout-refill process was used to realize multi-color free-standing flexible CLC film reflectors. A label printer is used to print PET patterned mask， and a polymerizable CLC material is UV cured to obtain the free-standing flexible patterned CLC film reflector. Based on this， the uncured material was washed-out， refilled with CLC of different chiral dopant content， and the patterned UV light was re-exposed to realize a multi-color flexible free-standing CLC reflector. The effects of different incidence angles， bending radius of curvature and temperature on the optical properties of the reflector are investigated. The experimental results show that the multi-color free-standing reflectors prepared by the above method have good flexibility， the Bragg reflection center wavelength is basically constant at different radii of curvature， and it is red-shifted with the increasing temperature， which has good linearity. This proposed multi-color free-standing flexible film reflector protocol can further expand CLC’s applications in the fields of display， sensing， laser protection and micro-nano optics.关键词：cholesteric liquid crystal;Bragg reflection;free standing flexible film;optical devices
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发布时间：2023-10-10 - 摘要：The optimization ability of LCC (Liquid crystal coated C-plate, LCC) to the RQWP (Reverse wavelength dispersion quarter wave plate, RQWP) compensation characteristics under the oblique incidence is investigated based on the combination of theoretical research and experimental research. The ellipticity of the outgoing light passing through RQWP and RQWP+LCC at any angle and the influence of LCC with different RTH on the ellipticity of the outgoing light are calculated based on extended Jones matrix method. The reflectance of ambient light and color deviation at large viewing-angle of the circular polarizer made by above structures are tested respectively under the case of OLED (Organic light emitting-diode display). It is shown that the LCC can make an increase of more than 10% for the ellipticity at 45° incidence. According to the numerical simulation with different NZ value of RQWP+LCC, NZ=0.5 is proved to be the best ellipticity configuration at any incident angle under R (red light), G (green light) and B (blue light) wavelengths. The structure with RQWP+LCC could reduce the ambient light reflectance by 3% under the oblique incidence at 45° polar angle on OLED. It is difficult to produce the compensation film with NZ=0.5 directly in industrial production, while relevant conclusions in this manuscript have potential to guide similar applications.关键词：oblique incidence;extended jones matrix method;ellipticity;quarter wave plate
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发布时间：2023-10-10 - 摘要：Gallium nitride， as the third generation material of lighting devices has greatly improved， compared with the first generation of silicon and the second generation of gallium arsenide performance. Gallium nitride-based Micro-LED devices are also getting more and more attention. However， the emission efficiency of the traditional c-plane growth of LEDs is not high in practical applications， due to quantum confined stark effect， green gap， carrier transport or other problems. Nonpolar or semipolar LED has the advantages of non-polarized electric field， stronger internal quantum efficiency， and more probability of electron and hole recombination. Therefore， the research and application of nonpolar and semipolar Micro-LED devices have aroused great interest. This paper reviews the research status of nonpolar and semipolar Micro-LED devices. Firstly， the advantages of nonpolar and semipolar gallium nitride materials are introduced from four aspects： quantum confined Stark effect， green gap， carrier transport and efficiency droop. Then， three technologies of chip shaping， pattern etching and array are introduced for solving the problems of defect dislocation， low efficiency of optical extraction and realizing full color display under different current density. Finally， the prospect of Micro-LED as the next generation display leader is given. It is hoped that it will be helpful in the next research for Micro-LED.关键词：gallium nitride;micro-LED;nonpolar;semipolar
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发布时间：2023-10-10 - 摘要：With the advancement of the meta-universe industry， light field display technology has emerged as a research focal point in the realm of information display technology due to its seamless integration of digital and physical worlds. It is exhibiting an upward trend towards more viewpoints， higher viewpoint density， and faster rendering speed. However， extant optical field display technologies are confronted with numerous challenges such as low resolution， limited depth perception， and visual fatigue. Based on the principle of human stereoscopic vision perception， this paper presents a comprehensive overview of the imaging principles and typical schemes employed in current light field display technologies， including double view， multi-view and super-multi-view. Meanwhile， an overview and comparison of current virtual view generation technologies based on single-source and multi-source approaches is provided， with a focus on the feasibility and implementation efficiency of each technology in terms of virtual view quality and rendering speed. Additionally， future development directions for optical field display technology are also anticipated.关键词：near-eye display;Light field display;Virtual viewpoint;neural network
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发布时间：2023-10-10
Device Physics and Device Preparation
- 摘要：The low power consumption TFT can reduce the energy consumption of electronic devices， save energy， extend battery life， reduce device temperature， and improve display quality， which plays an important role in the design and manufacturing of electronic devices. The structure of TFT substrates can be divided into following types： high-temperature polycrystalline silicon， low-temperature polycrystalline silicon， metal oxide semiconductor， and flexible material substrate. This article summarizes and analyzes the research on low power consumption of existing TFT substrate display devices， including two main aspects： optimizing the driving of TFT substrate itself and optimizing the driving of TFT substrate peripherals. The research of low power consumption TFT in recent years at home and abroad is introduced in detail. Based on the characteristics and challenges of the methods introduced， the future development of low power consumption driving for TFT substrate display devices is discussed.关键词：TFT;display;low power consumption;drive
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发布时间：2023-10-10
Driving and Controlling
- 摘要：In order to solve the problems of thermal target information loss， edge structure blur and detail loss in infrared and visible image fusion， an infrared and visible image fusion algorithm is proposed based on structure-texture decomposition. Firstly， the source images are decomposed into detail layer and structural layer by structure-texture decomposition， and the detail layer is fused and enhanced by fusion rule based on structural similarity and L2 norm. Then， a structure-average method is proposed to decompose the structural layer into luminance layer and basic layer. The absolute-value-maximum is used to fuse the luminance layer， and a fusion rule based on multi- indicators is designed for the basic layer. Finally， the fused sub-images are reconstructed to get the final fused image. In order to verify the effectiveness of our algorithm， it is compared with nine infrared and visible image fusion algorithms， and seven objective evaluating indicators are used including spatial frequency， average gradient， edge intensity， variance， visual information fidelity， the metric based on human visual perception and information entropy. The first five indicators are improved by 27.4%，36.5%，38.2%，8.5% and 23.5%， respectively. The experimental results show that the proposed algorithm not only effectively retains the infrared thermal target， but also retains the edge structure and texture details， and achieves better results in the objective evaluating indicators.关键词：image processing;image fusion;structure-texture decomposition;infrared image;visible image
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发布时间：2023-10-10 - 摘要：Aiming at the problems that current few-shot learning algorithms are prone to overfitting and insufficient generalization ability for cross-domain cases， and inspired by the property that reservoir computing （RC） does not depend on training to alleviate overfitting， a few-shot image classification method based on reservoir computing （RCFIC） is proposed. The whole method consists of a feature extraction module， a feature enhancement module and a classifier module. The feature enhancement module consists of a RC module and an attention mechanism based on the RC， which performs channel-level enhancement and pixel-level enhancement of the features of the feature extraction module， respectively. Meanwhile， the joint cosine classifier drives the network to learn feature distributions with high inter-class variance and low intra-class variance properties. Experimental results indicate that the algorithm achieves at least 1.07% higher classification accuracy than the existing methods in Cifar-FS， FC100 and Mini-ImageNet datasets， and outperforms the second-best method in cross-domain scenes from Mini-ImageNet to CUB-200 by at least 1.77%. Meanwhile， the ablation experiments verify the effectiveness of RCFIC. The proposed method has great generalization ability and can effectively alleviate the overfitting problem in few-shot image classification and solve the cross-domain problem to a certain extent.关键词：few-shot learning;reservoir computing;attention mechanism;feature enhancement;image classification
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发布时间：2023-10-10 - 摘要：Rainy images can affect the performance and accuracy of computer vision tasks. Rainy images often contain raindrops or rain marks from different directions， sizes， and shapes. When removing these raindrops and rain marks， the existing methods often do not take into account the feature information of rainy images at different fine scales， and only use a single scale. There is a big defect in image deraining， and it is impossible to restore a clear enough image for visual tasks. Therefore， benefiting from the powerful feature extraction capability of the convolutional neural network architecture， an end-to-end multi-cascade progressive convolution structure operator is proposed， which consists of four convolutional layers connected through a ladder to form an overall module. This module can extract and integrate rainy weather features in multi-scale scenes. The operator module is embedded into the progressive recurrent network structure， the recurrent structure is used to remove rain streaks many times， and finally the rain-free image close to the real image is effectively restored. The method is compared with the existing artificially synthesized rain image datasets Rain100H， Rain100L， Rain800 and the synthetic rain image dataset BDD1000 in the field of automatic driving. The experiment results shows that the PSNR values of the algorithm on the four datasets reach 30.70 ， 37.91， 27.63， 35.74 dB， and the SSIM values reach 0.914， 0.980， 0.894， 0.977. Through the visual display of the rain removal results of the real rain map dataset， the effectiveness of the method in this paper on the rain removal task is fully verified.关键词：image rain removal;Multi-cascade progressive convolution structure;convolutional neural network;deep learning;multi-scale feature;residual structure
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发布时间：2023-10-10 - 摘要：To address the problems of high-frequency information missing and increased noise in images generated by existing image super-resolution reconstruction algorithms， this paper proposes an image super-resolution reconstruction model based on convolutional sparse coding and generative adversarial networks. Firstly， convolutional networks are employed to implement sparse coding and obtain a sparse representation of the image， which makes full use of the prior information of the image and effectively avoids the problems of high-frequency information missing and increased noise in the reconstructed image. After obtaining the sparse representation of the low-resolution image， the sparse representation is reconstructed by the reconstruction module to obtain the super-resolution image. Subsequently， the discriminator discriminates the reconstructed image to alleviate the problem that the reconstructed image tends to be smooth due to the PSNR-dominated algorithm. After continuous adversarial training， the final generated super-resolution images are made to have better visual effects. The super-resolution reconstruction experiments are performed on Set5， Set14， BSD100 and Urban100 general test datasets at 2× and 4× and compared with Bicubic， SRGAN， EDSR and ESRGAN methods. Compared with ESRGAN， the average PSNR improvement is about 0.702 8 dB， the average SSIM improvement is about 0.047， and the average LPIPS improvement is 0.016 on the four datasets.Experimental results show that the proposed model is highly competitive and enables the recovery of more fine-texture details with better definition.关键词：image processing;image super resolution;sparse representation;generative adversarial network
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发布时间：2023-10-10 - 摘要：Aiming at the problems of unclear target contour segmentation and poor granularity in existing optical flow estimation methods， an optical flow estimation via fusing sequence image intensity correlation information is proposed. First， The coding features and contextual features of the images are extracted by the feature encoder and the global encoder， respectively， and the feature sizes are reduced by downsampling processing. Then， before constructing 4D correlation volume， the input two consecutive frames of feature maps are divided into regions to calculate dense visual similarity in the form of strong and weak correlation to build a more refined 4D correlation volume. Finally， in the iterative update stage， the residual convolution filter and the fine-grained module are proposed to be applied to process the correlation volume and optical flow transmission， respectively， which allows to retain more local small displacement information before fusing the correlation volume information and optical flow information. In comparison with other methods on the KITTI-2015 and MPI-Sintel， the optical flow estimation evaluation metric （Endpoint error， EPE） is improved by 8.2% and 6.15%， respectively. The network model given in this paper can better improve the accuracy of optical flow estimation and effectively solve the problems of the optical flow prediction field being over smooth， lacking of fine granularity and ignoring of small object motion.关键词：computer vision;deep learning;optical flow;region matching;iterative update
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发布时间：2023-10-10 - 摘要：Vehicle detection is very vital to the assisted driving system. Due to the serious degradation of the foggy road scene， the vehicle information in the image is not obvious， resulting in missed detection and false detection problems in vehicle detection. Aiming at the above problems， a vehicle detection method in foggy weather combining millimeter-wave radar and machine vision is proposed. First， the dark channel dehazing algorithm is used to preprocess the image to improve the salience of vehicle information in the image under foggy conditions. Then， the knowledge distillation is used to improve the YOLOv5s algorithm， and the knowledge distillation is introduced into the feature extraction network of YOLOv5s， which is used in the target positioning and classification stages to calculate the distillation loss and backpropagate the loss to train a small network model to improve the detection speed while ensuring the accuracy of visual detection. Finally， the distance matching algorithm based on the search of potential target detection areas is used to compare the visual detection results and the millimeter-wave radar detection results decision-making fusion. Based on the type and distance of the detected target， the interference information and erroneous information is filtered out， and the targets with high confidence after fusion in millimeter-wave radar detection and visual detection is retained. Thereby， the accuracy of vehicle detection is improved. The experimental results show that the method has the highest detection accuracy rate of 92.8% and the recall rate of 90.7% in foggy weather， which can realize the detection of vehicles in foggy weather.关键词：vehicle detection;millimeter wave radar;defogging;knowledge distillation;distance matching;decision level fusion
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发布时间：2023-10-10
Image Processing
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