最新刊期
期 4 ， 2021
- 摘要：As an emerging soft 3D photonic material, blue phase liquid crystals have attracted growing attention and research. They can self-assemble into a 3D photonic nanostructure with periodic cubic lattices and has excellent optical properties. Such as no birefringence, fast response speed and selective reflection. Stimulus-responsive 3D nanostructures and dynamic control of their photonic band gap in the visible spectrum are one of the most interesting fields in blue phase research, especially the research on photo-responsive blue phase liquid crystals have received extensive attention. Compared with other stimulus-responsive liquid crystals, it has excellent characteristics such as remote controllability, accuracy and transientness. This paper mainly reviews the discovery and structural characteristics of blue phase liquid crystals, and introduces in detail the research advances and application status of photo-responsive blue phase liquid crystals at home and abroad in recent years.关键词：liquid crystal;blue phase;photo-responsive;azobenzene
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发布时间：2021-04-02 - 摘要：The existence of the image sticking seriously affects the quality of the liquid crystal display, and there are no good solutions because of its complex mechanism at present. In this paper, a new type of tropane based additive was added to the negative liquid crystal to study its effect on image sticking in FFS mode. The image sticking was systematically analyzed by Flickr drift, RDC release and check board test. The results showed that flicker drift had significant improvement; the accumulation of DC reduced by 30% and the rate of residual DC release increased by 95%; the Vcom voltage drift decreased from 0.7 V to 0.02 V and brightness shift which caused by AC image sticking improved from 8 cd/m2 to 2 cd/m2; the line image sticking improved from L3 to L1.This study has a certain guiding significance for improving the image sticking of liquid crystal materials.关键词：fringe field switching;image sticking;negative liquid crystal;tropane additive
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发布时间：2021-04-02
Material Physicsand Chemistry
- 摘要：In order to reduce the focal length of liquid crystal lens without changing the aperture, a short focal length lens array based on liquid crystal material with large Δn is proposed. The liquid crystal layer accumulates large optical path difference under low driving voltage because of the use of the liquid crystal material with large Δn. The bottom substrate adopts the structure of alternating ITO driving electrode and ITO grounding electrode, and the ITO driving electrode is located above the dielectric layer. The ITO grounding electrode causes a weak electric field in its edges, the dielectric layer smooths the electric field in the liquid crystal layer. This design not only realizes the parabolic phase distribution in the large aperture range, but also reduces the driving voltage. The simulation results show that when the driving voltage is 6 V, the phase distribution of the liquid crystal lens array matches well with the ideal parabola. The phase difference between the center and edge of individual liquid crystal lens is approximately 42.17π, which results in a minimum focal length of about 1.72 mm. With the driving voltage increasing from 0 V to 6 V, the focal length of the liquid crystal lens array decreases from ∞ to about 1.72 mm. Therefore, the proposed liquid crystal lens array can be used in many application areas, such as 2D/3D switchable display, and AR display.关键词：large Δn;liquid crystal lens array;short focal length
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发布时间：2021-04-02 - 摘要：The chiral induced liquid crystals (LCs) can be widely used in filter devices due to the Bragg reflection. With templating technology, a single-layer structure multi-wavelength blue phase liquid crystal(BPLC) filters was investigated. By multiple liquid crystal refilling processes, LC filters with two and three reflection peaks was fabricated, and the reflection wavelength and bandwidth of the filters matched well with the design parameters. Meanwhile, the bandwidth tunable cholesteric liquid crystal(CLC) filter of single layer structure was investigated. By multiple refilling the CLCs of designed reflection peak into the CLC template, the broadband single-layer structure CLC filter can be achieved. The experimental results show that the maximum shift of the center wavelength is only 16 nm. Moreover, the bandwidth of the cholesteric liquid crystal can be broadened by 96% and can continue to expand. The manufacturing processes of the single-layer chiral spiral structure liquid crystal filter have good scalability and repeatability.关键词：polymer template;single-layer structure;multi-wavelength;bandwidth tunable;filter
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发布时间：2021-04-02 - 摘要：The phase distribution of the liquid crystal modulation device is unable to achieve accurate regional characterization, and the driving electric field of the phase distribution can only be adjusted by the indirect optical modulation result. Therefore, we constructed an adaptive modulation system of the phase distribution. By converting the phase depth to transmittance and passing the gray scale test of the high-resolution detector, the accurate regional phase depth information can be obtained. The system compares the actual relative transmittance distribution with the expected ideal relative transmittance distribution and substitutes the adaptive algorithm to obtain a new voltage signal, forming an automated closed-loop control loop. Aiming at the complicated problem of iterative debugging, the adaptive modulation system greatly reduces the time in the phase modulation process and improves the modulation accuracy of the phase profile. It can be widely used in phase modulation devices such as liquid crystal gratings and liquid crystal lenses.关键词：phase profile;adaptive system;liquid crystal phase modulator;minimum sum square error
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发布时间：2021-04-02
Device Physicsand Device Preparation
- 摘要：Aiming at the application requirements of AMOLED display driver chips for high precision and low power consumption, a Gamma correction circuit with wide voltage swing, high precision and temperature compensation is designed. The circuit uses amplitude adjustment and slope adjustment, fine-tune key points to change the DAC output curve, and better fitting the grayscale-voltage curve to achieve high accuracy. By using rail-to-rail input stage and output buffer circuit based on constant sub-threshold transconductance design, a wide input voltage range is guaranteed. Cascode Miller compensation structure is used to reduce the size of the compensation capacitor and improve stability and response speed. The circuit uses a temperature compensation structure to balance the effect of temperature changes on the gray-scale voltage. The simulation results show that under the UMC 80 nm process, within the range of 0.2~6.3 V input voltage, the response time of the designed Gamma correction circuit is 20 μs, and the error of the circuit output voltage is within 3 mV. The performance is basically not affected by temperature and meets the design requirements of AMOLED driver chips with a resolution of 1 080×2 160.关键词：AMOLED display driver chip;gamma correction;low drop output;high precision
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发布时间：2021-04-02
Drivingand Controlling
- 摘要：The external polarizer prepared by the traditional polarizer technology, is externally placed on the surface of the display, increasing the thickness of the display and decreasing the light transmittance. In order to meet the requirements for thinner polarizers, high transmittance and low cost, in-cell polarizers have been reported. As the mainstream technology of in-cell polarizers, photoalignment and nanoimprint technology, due to its advantages of no static electricity, no dust pollution, more precise and controllable micro-cell multi-chip orientation and low-cost large-area preparation, are introduced in the display field. To further understand the development of the in-cell polarizer. This article reviews the application of the two manufacturing technologies of photoalignment technology and nanoimprint in the in-cell polarizer and discusses the existing problems of the two technologies, which can provide ideas for the industrial production of in-cell polarizers.关键词：photoalignment technology;nanoimprint;in-cell polarizer;information display
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发布时间：2021-04-02 - 摘要：The ITO etching production line consists of three components: etching equipment, central chemical supply system (CCSS), and etchant management system (EMS). It is necessary to clarify the influence of components interaction on etchant concentration, which is important to ITO etching process. In this article, the changes in the concentration of each ingredient of etchant is explored under different production modes, based on ITO etching production line of Chongqing BOE. In addition, regression analysis, cause-effect analysis and statistical methods are used to analyze the reasons for the changes in the concentration of etchant, and the influence of etchant concentration on etching degree is confirmed. The results show that when only CCSS is turned on, the acid concentration of etchant increases, causing etching ability to gradually increase. Under the premise that the CCSS supply is turned on, and the EMS is enabled for the water and HNO3 replenishment function, the concentration of etchant can keep stable by adjusting the replenishment rate of HNO3 and water, thereby the use time of the etchant can be extended. However, in the mode where both CCSS and EMS replenishment are turned on, the etchant concentration fluctuates in the initial stage, and then gradually stabilizes. And during the period of concentration fluctuation, there will be a stage with a high concentration of HNO3, which has strong etching ability. This research provides a reference for extending the use time of ITO etchant and improving the product yield under mass production conditions.关键词：thin film transistor;wet etch;ITO etchant;concentration change;ITO electrode
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发布时间：2021-04-02
Display Technologyand Applications
- 摘要：The mechanism of defects on Cu process along with the development of new product is studied in this paper, and improvement methods are proposed. The results show that the high flow of O2 used in post ashing corrodes the Cu in PVX1 (The First passivation Layer) etch, and makes the Cu hole blackened. After adding the H2 treatment step, CuO can be reduced to Cu, and the hole appears metallic white color during CD (Critical Dimension) measurement. During 1ITO (The First Indium Tin Oxides Layer) etch process, high temperature annealing results in the occurrence of serious oxidation of exposed SD Cu. Skipping anneal or changing mask design can avoid the defect. In the VIA etch step, high content of O2 oxidizes the Cu, resulting in the break of conduction between gate and SD through the hole which leads to the occurrence of vertical line Mura. Reducing the content of O2 of VIA etch can solve the problem.关键词：array process;Cu corrosion;Cu oxidation;black hole defect;anneal;vertical line Mura
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发布时间：2021-04-02 - 摘要：This article provides a comprehensive description of the technical achievements of ultra-high definition, ultra-high resolution, large size LED displays, and focusing on innovative technological breakthroughs in flip chip integrated packaging, display drive control, uniformity regulation, and compensation. Some key technical issues and research progress are concerned, and the future development trend of micro pitch LED display technology based on flip chip light emitting chips is discussed.关键词：Small space LED display;integrated package;flip chip;uniformity control
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发布时间：2021-04-02 - 摘要：In order to realize the brightness and chromaticity correction of the LED display screen, a lamp point positioning and sorting algorithm that can automatically compensate the dead lamp position of the LED display screen and is suitable for the image tilt during the image acquisition process is studied. Firstly, the image is binarized to calculate the center coordinates of all the light points; then the four-corner light points in the image are pre-positioned by the extreme value method and the two-way sorting method. Then, the boundary points are processed by the linear sorting method positioning and sorting, the dead lights are located by the difference filtering method and automatically added points, all straight lines are sorted using the boundary point coordinates and the theoretical coordinates of the dead lights position to complete the positioning and sorting of all the lights on the display screen. Finally, the calculation method of the brightness uniformity of the LED display is introduced, and the accuracy of the positioning and sorting results of the lamp points is verified through the brightness correction experiment. Experimental results show that the brightness uniformity of the display screen before correction is 73.7%, and the brightness uniformity of the display screen after correction is increased to 98.7%. The brightness uniformity of the display screen has reached the range acceptable to the human eye, the correction effect is better, and the lamp point positioning and sorting accuracy is higher.关键词：LED display screen;light point positioning and sorting;automatic compensation of dead light position;brightness uniformity correction
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发布时间：2021-04-02
Display Technology and Applications
- 摘要：In order to accurately extract the collapse of the surface of the flotation foam, newly synthesized bubbles, and reduce the impact of noise and light, a foam infrared image segmentation method combining non-downsampling Shearlet Transform (NSST) domain saliency detection and graph cutting is proposed. NSST multi-scale decomposition of the foam infrared image, saliency detection of low-frequency subband images using GBVS algorithm, saliency value calculation based on Markov chain feature differences, noise coefficient removal and edge, weak edge coefficients are non-linearly enhanced. NSST reconstruction of the processed multi-scale high-frequency subband and low-frequency subband images is performed. The significance constraint term is constructed based on the saliency detection results of the low-frequency subband image, and the bubble brightness constraint term is constructed using a Gaussian fitting function. Then, the map is constructed Graph (Cut Cuts) energy function, and finally the maximum flow/minimum cut algorithm is used to segment the target area. The experimental results show that this method is less affected by light, and to some extent, it solves the problems of over-segmentation and under-segmentation. The detection accuracy rate of normal flotation under-flotation, and over-flotation are 91.8%, 87.1%, 88.9%, respectively. The segmentation accuracy is significantly improved compared with the existing methods. It can effectively extract collapsed or newly synthesized bubbles, and shows good noise immunity. It has good robustness under different working conditions.关键词：image processing;foam infrared image segmentation;non-downsampling shearlet transform;graph cuts;saliency detection
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发布时间：2021-04-02 - 摘要：Images taken in night hazy environment usually have uneven illumination, low contrast and blurry phenomena. By analyzing the imaging characteristics of night hazy images, An effective nighttime dehazing algorithm is proposed in this paper. First, in estimating atmospheric light, weighted channel difference image is used as a reference to conduct guided filtering to estimate atmospheric light containing contour information. A Laplace-sharpened grayscale image is used as a reference to conduct guided filtering to estimate the atmospheric light supplementing the details, and then the two calculated atmospheric lights are combined to obtain the final atmospheric light. Finally, based on the widely used haze scene imaging model, the dark channel and light channel are combined to construct the transmission function of dual channel joint optimization, and in the process of estimating transmittance, adaptive weight coefficient, contrast limited adaptive histogram equalization and guided filtering are added to improve the accuracy of transmittance function. The experimental results show that the average information entropy calculated on the test pictures is 7.587 2, and the average contrast is 23.809 7, which are better than the comparison algorithms. The dehazing results of the proposed algorithm have a good visual effect and can effectively reduce the loss of details.关键词：Weighted channel difference;Laplace sharpening;dark channel;Light channel;Adaptive weight coefficient
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发布时间：2021-04-02 - 摘要：In this paper, the mapping relation between the rainy image and the clear image is learned through the improved residual network to realize the image rain removal, and a single image deraining algorithm based on the concatenation residual network is proposed. Firstly, the improved residual block is used to simplify the network module, reduce the network parameters and improve the network training speed. Secondly, the designed concatenation structure not only realizes multi-feature extraction, effectively reduces parameters, but also increases the output of feature map, which is beneficial to retain more details of the image. Finally, the single-scale convolution is used to reconstruct the image details, and further improve the visual effect of the de-rained image. Experimental results indicate that the mean values of structural similarity and peak signal-to-noise ratio on the synthetic rainy image sets are both higher than 0.95 and 33 dB, and the blind image quality evaluation values of real rainy image sets are relatively low. The method can not only remove the rain in the image effectively, the rain streak residue is less, but also keep more texture and edge details of the image, and the visual effect is clear and natural.关键词：single image deraining;convolutional neural network;residual learning;concatenation structure;multi-feature extraction;blind image quality evaluation
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发布时间：2021-04-02 - 摘要：In the problem of space infrared weak target detection, traditional algorithms such as correlation template method and center of gravity, etc. have a low discrimination rate and high data quality requirements. To solve this problem, the space infrared weak target detection algorithm based on improved YOLOv4 is proposed in this paper. The algorithm first establishes corresponding data sets for different infrared targets in space. Based on YOLOv4, a special neural network framework for space target detection tasks is established. The k-means clustering algorithm is used to reconstruct the prior frame, and multi-scale fusion is designed according to the characteristics of infrared weak targets to improve the detection accuracy of weak targets. Finally, COCO data set and the infrared image data set collected in the laboratory are used to train the algorithm and test. The test results show that the improved algorithm has a significant improvement in the accuracy of detection compared with the YOLOv4 algorithm. Its average accuracy (AP) can reach more than 93.25%, and the detection speed has reached 38.99 ms/frame, which verifies that the effectiveness of target detection satisfies the needs of space infrared weak target detection tasks.关键词：target recognition;infrared weak target;deep learning;YOLOv4 model
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发布时间：2021-04-02 - 摘要：The Res-Net is used to learn the multi-layer deep features from Synthetic Aperture Radar (SAR) images, among which the effective components are selected based on structural similarity. The joint sparse representation is used to represent and analyze the selected deep features and determine the target label. This method achieves an average recognition rate of 99.02% for 10-class targets. Its performance under depression angle variances and noise interference is also superior over some present methods. This method an effectively combine the advantages of Res-Net and joint sparse representation in feature extraction and decision so the overall recognition performance can be improved. The MSTAR dataset is used for testing.关键词：Synthetic Aperture Radar(SAR);target recognition;Res-Net;structural similarity;joint sparse representation
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发布时间：2021-04-02
Image Processing
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