最新刊期
期 9 ， 2020
- 摘要：By using the photoalignment technique and the chiral liquid crystal with various components, the micro periodic structure of the liquid crystal system excited by the external electric field is observed. The morphology of the periodic structure strongly depends on the structure of the surface orientation, the concentration of the chiral doping and the properties of the driving electric field. Especially, with the increase of doping concentration, the periodic direction of microstructure changes greatly. The work of this paper is an extension of the traditional optical control field of the achiral liquid crystal. It is expected to realize the multiple adjustment of the light field, electric field and concentration field of the liquid crystal grating, and its periodic orientation can be adjusted at a large angle. The tunable grating is expected to play an important role in image processing, optical switch, beam modulation and other optical communication fields.关键词：liquid crystal;gratings;photoalignment;chiral;threshold voltage
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发布时间：2020-09-08 - 摘要：In order to explore the influence of exciplex on the performance of organic light-emitting diodes (OLED), a series of devices based on the structure with or without exciplex have been fabricated. Firstly, it is determined that NPB:TPBi is not effective to form exciplex, while TCTA:TPBi possesses exciplex performance requirements by comparing and analyzing the photoluminescence spectra of N, N'-bis(naphthalene-1-yl)-N, N'-bis(phe-nyl)-benzidine (NPB), 4, 4', 4″-tris(Ncarbazolyl)-triphenylamine (TCTA), 1, 3, 5-tris(Nphenylbenzimidazole-2-yl) benzene (TPBi), NPB:TPBi and TCTA:TPBi films. Then, a series of monochromatic and white OLED devices have been fabricated by combining ultrathin emission layer of blue phosphorescence bis[(3, 5-difluoro-2-(2-pyridyl) phenyl-(2-carboxypyridyl) iridium(Ⅲ) (FIrpic) and orange phosphorescence bis(4-phenylthieno[3, 2-c]pyridinato-N, C2') acetylacetonate iridium(Ⅲ) (PO-01), and the thickness of ultrathin phosphor layers are optimized to achieve high brightness and efficiency. Compared with devices without exciplex, the performance of monochromatic blue, orange and two-color white devices based on the exciplex have been greatly improved, with the maximum brightness of 5 823, 29 000, 23 790 cd/m2 and the maximum power efficiency (PE) of 15.3, 47.8, 51.0 lm/W, respectively. These improved device performances are attributed to the reverse inter system crossing (RISC) from triplet exciton to singlet exciton and the efficient host-guest energy transfer, which provides a feasible idea for the preparation of high-efficiency OLED devices with simple structure.关键词：organic light-emitting diode;exciplex;ultrathin emitting layer;efficiency;luminance
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发布时间：2020-09-08 - 摘要：The structure based on a refractive index matching layer on light emitting diode (LED) microdisplay is designed to improve its optical performance. The light-emitting surface of the flip-chip LED microdisplay device is a sapphire (refractive index about 1.76), which is significantly different from the refractive index of air (refractive index about 1.0). A large part of the light is reflected back to the internal of the device due to total reflection, resulting in low luminous efficiency. By coating a refractive index matching layer of silica gel (refractive indexes about 1.41~1.53), the surface layer of the device is changed to match the refractive index of the air to increase the light escape cone angle to improve the luminous efficiency of the device. The results show that:the application of the silica gel layer can improve the luminous efficiency by about 25.75%, and then covering a glass (refractive index about 1.47) on the silica gel layer can improve the luminous efficiency to about 32.78%, and the device has good electrical, optical and junction temperature stability before and after silicone coating. Although the increased light flux is in the lateral direction, this technique provides a reference for a realization of high-efficiency LED microdisplay.关键词：LED;microdisplay;refractive index matching layer;light escape cone angle;luminous efficiency
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发布时间：2020-09-08 - 摘要：In order to solve the problem that the refractive index distribution of the traditional modal-control liquid crystal lens deviates from the ideal parabola, a design scheme of a modal-control liquid crystal lens with a sheet resistance step distribution of a high-resistance layer is proposed. The resistance-capacitance equivalent circuit model of the modal-control liquid crystal lens is used to simulate the refractive index distribution of the liquid crystal lens of this design scheme. The sheet resistance is divided into equally different steps. The deviation between the refractive index distribution of the liquid crystal lens and the ideal refractive index distribution was calculated, and the minimum number of segments was obtained at different focal lengths. The deviation of the refractive index distribution of the liquid crystal lens from the ideal distribution when the driving voltage and frequency were used to adjust the focal length of the liquid crystal lens under a fixed condition of the sheet resistance step distribution was studied. The sheet resistance distribution of the liquid crystal lens with a focal length ranging from 280 mm to infinity was obtained.关键词：liquid crystal lens;focusing;step sheet resistance;simulation
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发布时间：2020-09-08 - 摘要：In order to achieve good performance of liquid crystal display (LCD) with wide viewing angle, the transmittance and response time of negative fringe field switching (FFS) mode are analyzed and optimized. To achieve high transmittance of the FFS mode, the parameters is analyzed and selected by simulation. The results of simulation analysis and optimization are verified by experiments and the parameters affecting the transmittance and response time are discussed. Compared to FFS mode with positive dielectric liquid crystal (LC), the transmittance of negative LC is increased by 18% through optimization, the response time is comparative (26 ms). Under the same conditions, the highest transmittance is reached when the transmittance curve integral of the whole pixel area is the biggest. The pixel pitch of FFS with negative LC is confirmed in this way. In addition, the response time is determined by slit angle and cell gap, and not relevant with pixel pitch or electrode width-space ratio (W/S).关键词：negative liquid crystal;fringe field switching;transmittance;response time
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发布时间：2020-09-08 - 摘要：Liquid crystal diffusion is a common defect in TFT-LCD products. The defect is that there are small irregular bubbles in the LCD screen. The main reason for this kind of small bubble is the incomplete diffusion of liquid crystal. In this paper, Washburn model is used to simulate the liquid crystal diffusion process to solve this problem. It is verified that the liquid crystal flow time and the initial position of liquid crystal have a great influence. The experiment is designed with the above two key factors. The results show that the liquid crystal droplet shape is changed from 2×5 type to '工'-shape, which effectively solves the non-uniform diffusion. It is found that the increase of vacuum time by 50 s is helpful to solve this problem. In addition, the heating time is extended to 100 min, which is also conducive to solve the problem. Therefore, changing the initial position of the liquid crystal drop, increasing the vacuum time and heating curing time can effectively improve the liquid crystal diffusion unevenness.关键词：liquid crystal;cell;diffusion inhomogeneity
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发布时间：2020-09-08 - 摘要：Various Mura, especially in large size products which need high requirement for display uniformity, can appear during the production of TFT-LCD. There are many types of Mura phenomena which reasons are very different. The Mura analyzed in this paper belongs to the special defect of TV models. In order to solve the black Mura of TV, this paper firstly carries out defect analysis and research. Through the characteristics of cell and surface microscopic & electric analysis, it is confirmed that the defect is not obviously observed and extremely microscopic. There is no way to carry out further analysis using the practical methods currently, and it is necessary to rely on the factory process verification to find the crux of the problem. It is verification that the defect is related to the PI cleaner, but the cleaning machine has a large number of independent units, so five related feasibility tests are designed:reducing cleaning speed, increasing laying time after PI cleaner, increasing UV cleaning intensity, removing brush away from the glass and adjusting cleaner HPMJ pressure. The process results show that the mechanism is inferred, also two reasonable and feasible improvement directions are proposed:reducing glass retention under cleaner HPMJ and increasing monitoring or shutting down HPMJ. The defect can be reduced from 0.94% to 0.00%.关键词：TFT-LCD;black Mura;cleaner;process verification;electrostatic remain
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发布时间：2020-09-08 - 摘要：In order to enhance the transmittance of LCD, optimize the white balance and enhance the color temperature, this study uses All Dye Blue photoresist in LCD industry for the first time, and evaluates a series of application in actual product. Firstly, based on the rational analysis of All Dye Blue photoresist, the dye materials transmittance, optical stability and thermal stab ility are preliminarry evaluated. Then, the material spectrum is used for color simulation and it is tested by products in production line. Experimental results indicate that this All Dye Blue photoresist has the improvement of transmittance about 9% in contrast of the traditional blue which is the hybrid of pigment and dye. After assemble with the backlight, the product performance has a large improvement. The transmittance increase about 3%, and the CCT can be up to 10 700 K (customer specifications is 10 000 K+ 1 000 K) for one specific TV product. With the evaluation of line application test and reliability evaluation of G8.5 generation, it can be concluded that the All Dye Blue photoresist has more excellent performance and could meet the production standards of G8.5 generation line.关键词：All Dye;photoresist;transmittance;stability
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发布时间：2020-09-08
Materials and Devices
- 摘要：To meet the requirements of small area, high precision and low power consumption of AMOLED driver chip, a high performance output buffer with DAC function is designed. This buffer adopts rail-to-rail input stage and Class AB output stage to adapt to a large input and output voltage range, and uses Cascode Miller compensation to reduce the size of the compensation capacitor. Its tail current source is programmable to implement 4 bit DAC function interpolation, saving overall power consumption and chip area. Under the UMC80 nm CMOS process, the simulation results show that in the input voltage range of 0.2~6.3 V, the DC gain of the buffer is greater than 70 dB, the phase margin is greater than 60°, the quiescent current can be as low as 0.5 μA, and the settling time as low as 1.49 μs. With a typical medium voltage of 3.3 V, the DC gain can reach 129 dB, the phase margin is 75°, the gain bandwidth is 9.4 MHz, and the quiescent current is 1.3 μA. After 4 bit interpolation of the 60 mV input voltage, the output error is less than 0.255 mV. The designed buffer has high accuracy, fast settling time, and low power consumption. The output buffer realizes the role of the second-stage DAC, which meets the application requirements of AMOLED source driving.关键词：AMOLED source driver;rail-to-rail;tail current source programmable;Class AB output stage;Cascode Miller
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发布时间：2020-09-08 - 摘要：According to the complexity of the hardware design and the validation problem of display control without models in large and medium LED cube system, the LED cube virtual simulation model and its universal drive component model are proposed and designed using the principle of parallel projection and the modeling technology of Proteus software. The models are built by the example of 3D8 cube, and the driving timing and character pattern display are also simulated and verified. Based on the modeling method, 3D16, 3D32 and 3D64 LED cubes and driving components are designed, and the display effect of Chinese characters and point cloud models are also verified. The results show that the modeling method can reflect the operating principle of the software and the hardware for the LED cube system, as well as providing a pseudo-three-dimensional virtual visualization method for the LED cube's design and verification. The results can provide a modeling method for the diversified show and expansion of the large and medium LED cube, and the proposed method can be used for engineering application design of three-dimensional display.关键词：LED cube;visualization model;3D display;Proteus software
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发布时间：2020-09-08
Driving Circuits
- 摘要：The existence of mixed pixels is the main reason that restricts the application accuracy of hyperspectral remote sensing, so hyperspectral unmixing is necessary. As the key of hyperspectral unmixing, the endmember extraction is often susceptible to noise and outliers. In order to improve the accuracy of endmember extraction, a spatial-spectral combined preprocessing method for hyperspectral endmember extraction is proposed in this paper. Firstly, a new concept of spectral purity index (SPI) is defined, which is used to estimate the spectral purity of each pixel in hyperspectral image. Secondly, a spatial de-redundancy method based on SPI is provided, utilizing the continuity of spatial distribution of real objects in the image to judge and eliminate redundant pixels in hyperspectral image, and finally a fine set of candidate endmembers is formed. Experimental results show that after using the proposed preprocessing method, for the simulated hyperspectral image, the angle between the extracted endmembers and the original endmembers is reduced by 9.022 3° on average, and the number of candidate endmembers is less than 10% of the number of original pixels. The proposed preprocessing method not only eliminates the interference of noise and outliers effectively and improves the accuracy of endmember extraction, but also reduces the time complexity greatly.关键词：hyperspectral;unmixing;endmember extraction;preprocessing;spectral purity index
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发布时间：2020-09-08 - 摘要：Faced with tracking difficulties such as illumination variation, occlusion, background clutters, in-plane and out-of-plane rotation, the Tracking-Learning-Detection (TLD) algorithm is prone to drift and cause tracking failures, and its tracking performance needs to be improved. Based on the traditional TLD algorithm, an improved TLD algorithm based on artificial fish swarm particle filtering is proposed. Firstly, the artificial fish swarm particle filter tracker is used to replace the optical flow tracker. The color histogram feature and histogram of oriented gradient feature are fused to establish the target appearance model. The image pyramid multi-scale idea is introduced for scale matching to improve the robustness of target tracking. Then, the target area is predicted through the particle filtering process. The global scanning of TLD algorithm detection module is improved to be the local scanning. A large number of non-target areas are eliminated, and the detection efficiency is improved. The experimental results show that the improved TLD algorithm based on artificial fish swarm particle filtering has good tracking performance. Compared with the traditional TLD algorithm, its average success rate and precision have improved by 19.04% and 28.00%, and the average tracking speed can reach 33.87 FPS, which has improved by 38.78%.关键词：computer vision;target tracking;tracking-learning-detection algorithm;artificial fish-swarm;particle filter
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发布时间：2020-09-08 - 摘要：Aiming at the problems of shallow network and lack of high-level semantic information in Receptive Fields Network(RF-Net), a new network based on Residual Network(ResNet) and RF-Net is proposed for the matching of remote sensing images. Firstly, the new remote sensing image datasets are setup, which consist of images and homography matrices. The images are obtained by cropping, illumination changing and affine transforming of the original remote sensing images. The matrices are obtained by calculating the homography between different images of one sequence. Secondly, a dual-channel network structure is proposed for the keypoints detection. Specifically, the dual-channel network composed by Receptive Fields Detection(RF-Det) and ResNet, respectively extracts receptive feature maps with detail information, and the deep layer feature maps with semantic information. The L2-Net is introduced at descriptor extraction module to obtain the 128-dimension feature vectors as description of keypoints. Lastly, the strategies of the nearest neighbor, nearest neighbor with a threshold and nearest neighbor distance ration are used to match the descriptors. Experiments on remote sensing images show that the matching scores of the proposed network are 0.002, 0.117, 0.104, higher than RF-Net, when testing on different datasets. It outperforms on keypoints detection and matching accuracy.关键词：image matching;keypoints detection;feature descriptor extraction;affine transform;feature vectors
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发布时间：2020-09-08
Image Processing
- 摘要：As the display industry continues to focus on healthy display, how different factors may affect the human eye were investigated systematically. The paper explains the concept of healthy display. The summary shows that different factors like blue-light, polarized light, flicker, dazzle may affect the human eye. Healthy display doesn't simply focus on product performance, but pay more attention to the user's experience from the system perspective. Through the interaction between the user and the product, the display product can realize the intelligent output according to the user's needs, and when the user uses it with good habits, it can achieve both physical and psychological comfort. Finally, the development and promotion strategies are discussed.关键词：healthy display;impact analysis;direction of improvement
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发布时间：2020-09-08
Industrial Technology
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