最新刊期
期 7 ， 2023
- 摘要：The excellent optoelectronic characteristics of quantum dots， such as high quantum yield， wide absorption range， narrow emission spectrum and adjustable emission wavelength， make them show great application prospects in displays. Quantum dots synthesized by chemical-solution methods not only have the advantages of a simple preparation process and low cost， but also can be used to achieve high-resolution displays in various ways. The excellent electroluminescence and photoluminescence of quantum dots make them play an important role in the research of displays. Electroluminescent quantum-dot light-emitting diodes have achieved a rapid development in the research of material synthesis and device structure， which provides a foundation for the realization of commercial displays. The displays using the photoluminescence of quantum dots have attained a wider color gamut and presented a richer visual effect. This paper introduces the characteristics， electroluminescence and photoluminescence of quantum dots， and their applications in displays， summarizes the research status of quantum-dot devices， and analyzes the existing problems in the development of quantum-dot devices.关键词：quantum dots;electroluminescence;photoluminescence;displays
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发布时间：2023-07-06 - 摘要：The liquid crystal system represented by the organic molecule RM734 is a nematic liquid crystal with ferroelectric properties. In order to explore its response to light stimulation， the UV-visible absorption spectrum measurement and UV illumination experiment were carried out on the liquid crystal molecule. The results show that when the liquid crystal molecule is in the low temperature ferroelectric nematic phase， there is an absorption peak at 357 nm， and the peak absorbance is up to 1.74. The experimental phenomenon of illumination shows that it can undergo isothermal phase transformation when conducting photodegradation reaction under the UV light induction of 365 nm wave band， from low temperature ferroelectric nematic phase to high temperature traditional nematic phase， and this phase transformation behavior is repeatable. Further experimental results show that changing the polarization direction or intensity of the incoming polarized light can control the phase transition speed. In general， ferroelectric nematic liquid crystals with optical response ability are controllable to a certain extent， which broadens the application range of ferroelectric liquid crystals and provides new ideas for the application of their optical devices.关键词：liquid crystal;Ferroelectric properties;Absorption spectrum;Isothermal transformation;Polarization direction
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发布时间：2023-07-06 - 摘要：This article investigates the holographic storage performance of a dual monomer acrylic ester photo-polymer （TMPTA/EP828） doped with nanoceria （CeO2）. By introducing nanoceria and optimizing the formula ratio， the holographic performance of the material is improved. The effect of CeO2 doping concentration and pre-polymerization temperature on diffraction efficiency is analyzed. Experimental results show that the transmission grating sample with a thickness of 100 μm exhibits excellent performance in terms of diffraction efficiency （~95%）， spectral transmittance （96.1%）， shrinkage （0.504%）， bandwidth， and angular selectivity. The introduction of CeO2 can effectively improve the compatibility between the cross-linked network structure of the TMPTA/EP828 system and the recording medium， promote the polymerization reaction， suppress volume shrinkage， and reduce the angle interval of multiplexing， thereby improving the angle-multiplexing performance of holographic storage and the stability of the material. Further verification through photopolymerization and aging experiments confirms that the optimized photopolymer formulation has anti-aging and high-temperature resistance properties. Meanwhile， the material preparation process is simple， the cycle is short， and it is easy to store. It can record multiple multiplexed holographic images and has great application prospects in high-density data storage and other fields.关键词：Diffractive optics;Nano-cerium oxide;Photoinduced polymer;Holographic optical storage
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发布时间：2023-07-06
Material Physics
- 摘要：Aiming at the problem that the oblique incidence of beam during the propagation of cascaded liquid crystal polarization gratings will change its ellipticity and reduce the diffraction efficiency， an optimization method of diffraction efficiency of cascaded liquid crystal polarization gratings based on polarization compensation is proposed. The effect of oblique incidence on retardation of liquid crystal polarization grating is analyzed by using extended Jones matrix. Combined with Stokes parameter， the ellipticity of liquid crystal polarization grating outgoing beam at different oblique incidence angles is analyzed. Based on the vector diffraction theory， the diffraction efficiency model of cascaded liquid crystal polarization gratings is established. Based on the liquid crystal molecular direction vector distribution， the coordinate system of liquid crystal variable retarder under oblique incidence is established. The influence of oblique incidence angle on retardation of liquid crystal variable retarder is analyzed， and the relationship between retardation and ellipticity is derived. By optimizing the operating voltage of liquid crystal variable retarder， the depolarization caused by oblique incidence is compensated to realize the polarization compensation of ellipticity. The experimental platform is set up to verify the accuracy of the theory and the effectiveness of the method. According to the measurement results， when the beam deflection angle is from -5° to 5°， the proposed method improves the diffraction efficiency of the cascaded liquid crystal polarization gratings by 3%~4%.关键词：cascaded liquid crystal polarization gratings;diffraction efficiency;extended Jones matrix;stokes parameter;liquid crystal variable retarder
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发布时间：2023-07-06 - 摘要：Micro-LED is considered as a crucial and one of the fastest growing display technologies in the world as it finds its applications in variety of products from visible light communication applications to large flat panel displays， virtual reality and wearable displays， televisions and light sources for the optogenetics and neural interface. Though the prospects are bright， Micro-LEDs still face some technological problems which needs to be addressed in order to get high volume commercialization， which include improving efficiency of LEDs with longer wavelengths， improving efficiency at low current densities， full color schemes， mass transfer， defects and yield management， repair technology and cost control. This review highlights the different challenges and their optimum solutions for Micro-LEDs.关键词：Micro-LEDs;Display technologies;efficiency of LEDs;mass transfer;Ⅲ-nitride
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发布时间：2023-07-06 - 摘要：With the emergence and development of self-luminous micron-pixel-sized Micro-LED （Micro light-emitting diode， μLED）， using μLED as the light and image source have become possible for ultra-compact projection optical engines. It greatly simplifies the structure of traditional projection display optical engines. In this paper， a μLED-based super miniature projection optical engine is proposed， and a high image quality pico-projection lens is designed based on 3.302 mm（0.13 in） μLED display chip. The divergence angle of μLED display chip matched with the pupil of pico-projection lens is optimized according to the light distribution characteristics of μLED chip， which effectively improves the light efficiency of μLED based pico-projection optical system. The results show that the volume of the system is only 18.35 mm3， and the MTF value of the center field of view of the projection lens exceeds 0.57 at the cut-off frequency. The μLED based pico-projection display optical engine achieves a good trade-off between system volume and image quality， and has a wide application prospect in near-eye display devices such as AR/VR in the future.关键词：micro-LED;near-eye display;Pico-projection display;optical design;System efficiency
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发布时间：2023-07-06 - 摘要：In order to meet the development of the new generation of electronic technology， it is increasingly important to develop different kinds of new memory. Compared with traditional memory， the new generation memory is required to have higher performance memory features， and meet the needs of specific applications such as flexibility， transparency， or neuromorphic functions. In this paper， an organic transparent memory （transparency ≥83%） is proposed with organic semiconductor material C8-BTBT as semiconductor layer and PVP quantμm dot blending as floating gate. The device has a memory window of more than 40 V， and the programming/erasing current ratio is more than 103， the switching state can be resolved stably after 104 s. This paper provides a new solution for transparent flexible devices and foreshadows their potential applications in the next generation of transparent organic electronics.关键词：organic thin film transistor;memory;transparent device;quantμm dots;floating gate
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发布时间：2023-07-06 - 摘要：In view of the technical pain points of the traditional three-color chip light source in the field of adjustable color gamut technology， such as the chip light decay， different temperature characteristics， discontinuous spectrum， and complex structure of the five-color light source process， a three primary color COB LED light source with high colour rendering index（CRI） and adjustable color gamut is designed and manufactured by appling fluorescent powder zonal sprayed on the surface of blue LED chip based on COB package. The test result shows that by adjusting the driving current of the chip in each region， the luminous intensity of the three-color light can be changed to realize the intelligent color matching. At 3 000~6 000 K color temperature， six groups of color coordinates under the seven color temperatures of the selected sample light source are located on the Planck curve. The lowest CRI is 72.9 and the highest is 83.4， higher than the 34.2 and 44.5 of the traditional RGB chip light source， and the spectrum continuity is better. It opens up the technological innovation of adjustable color gamut， can be better applied to the commercial lighting with high requirement of display finger.关键词：COB package;adjustable color gamut;zoned coating;colour coordinate;colour rendering index
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发布时间：2023-07-06
Device Physics and Device Preparation
- 摘要：In order to overcome the problems of low contrast， serious lack of details and textures in traditional algorithms， and noise sensitivity， weak adaptability and anti-interference ability of saliency-based detection algorithms， a non-subsampled contourlet transform （NSCT） infrared and visible light fusion method based on improved frequency tuning （FT） saliency detection is proposed. Firstly， an improved saliency map extraction algorithm is used to target the infrared image to distinguish the target from the background. Secondly， the infrared image and visible light image are decomposed into high and low frequency subbands using NSCT. The coefficients are used to guide the fusion， which can well preserve the contrast between the target and the background. For the high-frequency part， the rule of local weighted energy is used to make a decision， the weighted least squares （WLS） optimization can obtain more detailed information and reduce the influence of noise， and the fused high-frequency and low-frequency subbands coefficients are processed. Finally， the fused image is obtained by inverse NSCT transform. The experimental comparison results of four sets of images show that the method in this paper has better visual effect than other methods in terms of prominent target， rich details extraction， and obvious elimination of edge artifacts， subjectively. It is in the best state on the average gradient （AG）， information entropy （IE）， spatial frequency （SF）， and mutual information （MI） of four objective evaluation indicators. Compared with the average of the five comparison methods， the AG， IE， SF， and MI are increased by 8.19%， 5.34%， 8.54%， and 68.18%， respectively. Thus， the proposed method is reliable and effective.关键词：image fusion;Non-subsampled Contourlet transform;frequency-tuned saliency detection;Infrared saliency map;Weighted least squares optimization
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发布时间：2023-07-06 - 摘要：Image-oriented multi-scale object detection algorithms often have the problem of mutual restriction between detection accuracy and system cost. Therefore， a lightweight and high-precision object detection algorithm based on YOLO framework is proposed. Under the YOLO framework， the mechanism of down-sampling and channel attention based on MobileNetv3 network is improved to accurately extract target features and reduce unnecessary overhead. The feature pyramid and single-stage headless fusion structure are designed， and different receptive fields are constructed to obtain different scale information， so as to enhance the adaptability of the algorithm for multi-scale targets. At the same time， SIOU is used as regression loss and Soft-NMS is used for redundant frame processing to improve the accuracy of the algorithm. Experiments are conducted on the MS COCO and UA-DETRAC. Compared with the original YOLOXs， the results show that the proposed improved algorithm reduces the number of model parameters and the computational cost reduced by 64.98% and 57.14% without reducing the accuracy. On the UA-DETRAC， mAP@0.5 reaches 70.5% which is improved by 3.52%， and FPS increases by 14.4%. The experimental results show that our algorithm greatly reduces the system overhead， improves the accuracy， and effectively guarantees the dual performance of detection.关键词：object detection;YOLOXs;Mechanism of attention;lightweight;SIOU;Soft-NMS
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发布时间：2023-07-06 - 摘要：Most of the existing human pose estimation algorithms have designed complex network structures to obtain high accuracy but lead to low speed. The YOLO-Pose algorithm has taken advantages of state-of-the-art object detection algorithm and obtained higher accuracy and speed， but it still has the problems of missed detection and false detection. In this paper， a new lightweight human pose estimation algorithm is proposed according to the characteristics of non-rigidness of human poses and the distribution diversity of human landmarks so as to improve the YOLO-Pose algorithm. Firstly， the lightweight channel and spatial attention network （LCSA-Net） are designed to enhance the feature extraction capability. Secondly， a distance-based adaptive weighting strategy is presented to calculate the regression loss of human landmarks during model training so as to enhance the regression ability of the model to long-distance human landmarks. The experimental results on the COCO 2017 human pose dataset indicate that both of the improved strategies can effectively promote the performance of human pose estimation compared with the baseline model， and achieves improvement of 2% mAP， 1.5% AP50 and 1.7% AR.关键词：human pose estimation;YOLO-Pose;attention net;adaptive weighting;regression loss
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发布时间：2023-07-06 - 摘要：For the existing helmet wearing detection algorithm for dense targets and small targets having the phenomenon of missed detection， many parameters， large computation， and not suitable for deployment in the embedded device side and other problems， this paper proposes an improved YOLOv5 helmet wearing detection algorithm YOLOv5-Q. Firstly， on the original network 80×80 feature map， the 2 times up-sampling operation is made to form a 160×160 feature map， and the new feature map fuses the three-layer feature information of the original model to form a four-scale detection， which improves the detection accuracy of dense targets and small targets. Secondly， the feature extraction is achieved by replacing the original YOLOv5 backbone network with a lightweight GhostNet， which reduces the parameters of the network and can be ported to the embedded devices for target detection. Finally， the attention mechanism CA is added to boost the weight of important information in the feature map and suppress the weight of non-relevant information， thus improving the accuracy of the model. The experimental results show that the model size of YOLOv5-Q is 26.47 MB， the number of parameters is 12 696 640， and the accuracy is 0.937. Compared with YOLOv5， the YOLOv5-Q algorithm reduces the number of parameters by 39.12%， the model size by 37.2%， but the accuracy by only 1.2%. The YOLOv5-Q algorithm increases the detection accuracy of small targets in dense environments and meets the requirements for deployment on the embedded side.关键词：YOLOv5;Lightweight;safety helmet;embedded;attention mechanisms
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发布时间：2023-07-06 - 摘要：The training data of many current semantic segmentation models are RGB images， and the stability of the model is easily affected in some extreme environments. It cannot meet the actual demand of automatic driving at night. ResNet-152 is used as a feature extraction network to construct a multi-modal dual encoder-decoder model integrating lightweight attention module. The dual encoder extracts key information from the two modes of RGB-T and fuses it through the attention module. Then， the extracted feature information is sent to the decoder. The upsampled feature map and the feature map extracted by the encoder of each layer are spliced in stages， the feature is extracted by the convolution layer， the resolution is restored by upsampling， and the semantic segmentation is carried out at the last. The experimental results show that the mean accuracy and mean intersection over union of the proposed model on the MFNet test set are 76% and 55.7%， respectively， which makes a certain improvement compared with other network models. This model can basically achieve the requirement of accurate semantic segmentation of RGB-T modal images both day and night关键词：night semantic segmentation;multimodal;lightweight attention module;multiple scale information
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发布时间：2023-07-06 - 摘要：To overcome the problems of low efficiency in manual meter reading and inaccurate recognition for double half-characters by existing image recognition methods， an image-based intelligent meter reading system based on narrow band Internet of things （NB-IoT） and lightweight convolutional neural network （CNN） is designed. Firstly， the image acquisition terminal uses NB-IoT module to upload the meter image collected by the camera to cloud platform. Then， the method of local feature extraction and matching is applied to estimate an affine transform matrix and convert the input meter image to the coordinate space of the template image， and every sub-image of reading character is segment out. Finally， a multi-label classification-based lightweight CNN model is proposed to recognize these sub-images， and the final reading result is obtained by post-processing. Experimental results indicate that the sleep current of the image acquisition terminal of the designed system is less than 10 μA，which can ensure two Li/SOCl2 batteries working for more than 5 years， and that the proposed CNN model based on multi-label classification can accurately recognize both single characters and double half-characters and has achieved a character accuracy rate of 96.36% and a reading accuracy rate of 94.15%， which is superior to other recognition algorithms.关键词：NB-IoT;automatic meter reading system;CNN;double half-character recognition;multi-label classification
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发布时间：2023-07-06
Image Processing
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