最新刊期
期 5 ， 2023
- 摘要：Chiral organic semiconductors are promising for miniaturized and integrated circularly polarized light detection due to their spectral tunability and easy processing. In this paper， poly（3-hexylthiophene-block-poly（phenylisocyanide）） （P3HT80 and P3HT80-PPI（L）30） were synthesized by controlled incorporation of chiral isonitrile （PPI）. The experimental results demonstrated that two semiconductor polymers were successfully synthesized. Furthermore， the optical properties of the two semiconductor polymers were tested and the block polymer P3HT80-PPI（L）30 was found to have chiral optical activity. A circularly polarized photodetector based on an organic field effect transistor was prepared to study the performance of the device for differentiating the spin direction of circularly polarized light at 450 nm. The experimental results indicated that the addition of chiral isonitrile （PPI） degraded the electrical properties of P3HT80 but introduced chiral optical activity， enabling the devices based on P3HT80-PPI（L）30 to distinguish the spin direction of circularly polarized light， and the photocurrent asymmetry factor gres at 450 nm reached 0.083.关键词：chiral organic semiconductors;block copolymers;chiral optical activity;organic thin-film transistors;circularly polarized photodetectors
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发布时间：2023-05-09
Material Physics
- 摘要：Adaptive optics is widely used to correct aberrations in the human eye， achieving high-resolution imaging of fundus cells and microvessels. Traditional adaptive optics systems are limited by the dynamic range of the Shack Hartmann wavefront detector and are only suitable for some people， and cannot perform fundus high-resolution imaging in people with high refractive errors. In order to improve the universality of fundus adaptive optical imaging system， this paper designs a high-resolution fundus adaptive optical imaging system based on voice coil deformation mirror. The introduction of the Badal focusing system can perform high-resolution imaging of the fundus with the diopter of the human eye between -8~8 D. In this system， the traditional annular diaphragm is replaced with an adjustable axial cone lens set， the spacing of positive and negative axonal cone lenses are controlled to adjust the inner diameter of annular light in order to adapt the cornea of different eyes， and avoid stray light reflected by the cornea. Large field of view imaging is realized through visual beacon guidance. The simulation results show that the illumination subsystem has a uniform distribution of retinal illumination in the fundus. Within the set tolerance， at least 90% of the MTF values reach 0.21 at 25 lp/mm （corresponding to 4 μm on the retina）. The corresponding optical path was built in the laboratory， and the simulated human eye with large distortion was imaged， and a good imaging effect was obtained.关键词：adaptive optics;Human ocular aberrations;Voice coil deformable mirror;Fundus imaging
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发布时间：2023-05-09 - 摘要：A kind of adjustable even aspheric liquid lens combined with electric wetting effect and electrostatic force is proposed. The aspheric liquid lens is simulated by using Comsol Multiphysics software. The electrostatic force generated by four circular electrodes can flexibly adjust the surface shape of the liquid lens. The zoom optical system is designed by using the liquid lens. The aspheric equation for optimizing and correcting the aberration is obtained by using the Zemax software. As the target surface of the adjustable even aspheric liquid lens， the voltage on the electrowetting electrode and the four-ring electrode is adjusted. The simulated root mean square error of the optical path between the aspheric surface and the target aspheric surface is less than
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发布时间：2023-05-09 - 摘要：With the continuous progress in the manufacturing process of gallium nitride （GaN）-based light-emitting diodes （LEDs）， Micro-LED display is considered as an emerging display technology， which has broad prospects for near-eye display， large-scale displays device， flexible display， and other fields. The inspection of wafer-level Micro-LED chips can improve the yield of the screens and reduce the manufacturing cost of displayers， which is one of the key technologies related to Micro-LED display. For the inspection needs of large quantity （millions of orders） and small size （<50 μm） of wafer-level Micro-LED chip arrays， the existing electrical inspection technology has the disadvantages of low inspection efficiency and high cost. Therefore， Micro-LED chips inspection technology with improving inspection efficiency， improving inspection accuracy， and reducing inspection cost is the future development trend. In this paper， several indicators required for Micro-LED chip inspection are summarized. Then， the existing or proposed inspection methods are introduced and analyzed in detail. Finally， the future development of inspection technology is prospected.关键词：micro-LED;defect inspection;contact inspection;non-contact inspection
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发布时间：2023-05-09 - 摘要：The brightness， color gamut， Mura and other characteristics of the organic light-emitting diode （OLED） display are closely related to its driving current. In order to realize the nondestructive detection of OLED current after packaging， this paper establishes a magnetic detection method which is based on tunneling magnetoresistance （TMR） effect. First， according to the relationship between the brightness and its driving current of OLED display， it is obtained that the driving current is about 40 mA when one row pixels are light on. Through simulation and analysis of the spatial magnetic field distribution of 40 mA current， the sensitivity index requirements of TMR magnetic sensor are estimated. Then， TMR2922 is selected as the magnetic sensor. By lighting two row pixels， the relationship between display magnetic field and current is studied. To research the electromagnetic interference of the display， multi-row pixels are lighted. To determine the ability of TMR2922 current detection， one column of pixels is lighted. Finally， the magnetic field data of TMR2922 and the optical data of Hyperion colorimeter under different driving currents are compared and analyzed. The simulation shows that the noise of the magnetic field sensor should be better than 1.1 nT/
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发布时间：2023-05-09
Device Physics and Device Preparation
- 摘要：A distribution chip specially used for video data distribution is designed in this paper. The distribution chip is composed of four parts： receiving module， memory intercepting module， output module and clock module. The receiving module receives the serial data from the serial bus. Because the LED beads of the LED display screen are driven by 24 bit RGB data， the serial data are converted into 24 bit RGB data. The storage interception module stores 1~N RGB data cycles in RAM， and detects their switches. When they are consistent with the switches， it reads N data in the RAM of this cycle， and sends them to the output module. When they are inconsistent， the number of cycles increases by one. The output module converts RGB into serial data and sends it to the LED display screen. The final design report shows that the power consumption of the distribution chip is 3.662e-05 mW and the area is 3.702
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发布时间：2023-05-09 - 摘要：For the extremely weak magnetic field measurement of atomic magnetometers， the precise and stable control of laser temperature is an essential work. Laser temperature instability can lead to laser wavelength fluctuations and drift， thus reducing the sensitivity of atomic magnetometers. In order to reduce the influence of laser temperature fluctuation on atomic magnetometer， a high precision DBR laser automatic temperature control system based on ADN8834 temperature control chip is designed and implemented. Firstly， a temperature feedback circuit is designed based on ADN8834 and a high precise A/D converter chip LTC2377， so that the analog voltage signal corresponding to the temperature is successfully collected and converted into a digital signal and sent to the FPGA. Then， the incremental digital PID algorithm is implemented in FPGA to automatically calculate the temperature control signal. Then， a D/A converter circuit is designed to convert the temperature control signal into an analog signal and transmit it to ADN8834. Finally， ADN8834 outputs heating or cooling signals to control the semiconductor thermoelectric cooler， so as to realize closed-loop temperature automatic control. The experimental results show that the temperature stability of the automatic temperature control system is ±0.005 ℃ when the target temperature is set at 20， 25， 30 ℃， and the stability of output wavelength is ±2 pm. This DBR laser automatic temperature control system has high temperature stability， convenient operation and flexible design， and basically meets the requirements of atomic magnetometer system for laser temperature control.关键词：ADN8834;digital PID algorithm;temperature control;TEC
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发布时间：2023-05-09
Driving and Controlling
- 摘要：In order to solve the problem that the existing automatic image cropping algorithm mistakenly cuts off the whole person or part of the body parts of the main figure， which leads to the missing of the key information of the image and the poor composition of the image， this paper proposes a real-time automatic image cropping method based on portrait detection. This method divides image cropping into two stages： portrait detection and intelligent composition. It aims to take the extracted portrait coordinate information as the input of the intelligent cropping algorithm， and then combines the composition rule based on aesthetics to automatically compose the picture， so as to ensure the integrity of the portrait information in the cropping result and improve the composition beauty of the picture. The experimental results show that the lightweight detection network modified on the basis of Center-Net in this paper reduces the computation amount by 86% and improves the accuracy by 3.34%， which is convenient to apply the cropping algorithm to mobile devices. The FPS of the whole cropping algorithm reaches 77， and the cropped portrait information is complete， and the overall composition of the picture is improved.关键词：image cropping;human detection;image composition;computer vision
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发布时间：2023-05-09 - 摘要：To address the issue that existing restoration algorithms are prone to artifacts when dealing with large areas missing and inconsistent with the semantics of the original image， a second-order image restoration method based on gated convolution and attention transfer is proposed. The overall semantic consistency of the repair results is ensured by strengthening the influence of the internal semantics of the image to be repaired on the repair network. The rough repair results are then input into the improved refinement repair network， and the gated convolution and attention transfer network are used to repair the image’s internal texture details. The SimAM module is introduced as the attention mechanism in the encoding and decoding processes. Finally， the spectrum normalized Markov discriminator is used to determine authenticity while also providing the confrontation loss. The perceived loss and similarity loss of multiscale structure are considered as the reconstruction loss and then combined as the loss function. The comparative experiments with other image restoration methods show that the proposed method improves the structural similarity by 1.47% and the peak signal-to-noise ratio by 5.48%compared with the best results. The repair results of this method are more realistic and natural， and the ideal repair effect is achieved under various sizes.关键词：image processing;image inpainting;gated convolution;attention transfer;adversarial loss
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发布时间：2023-05-09 - 摘要：Aiming at the problems of halo and color distortion in prior fog removal in dark channel， an image fog removal algorithm based on bright region segmentation is proposed. First， the foggy image is divided into bright areas and non-bright areas by brightness threshold segmentation and region growth. The formulas for calculating the transmittance of bright areas and non-bright areas are improved by using a bright channel prior and a super pixel， respectively. Then， the weighted fusion method is used to fuse the transmittance of these two areas to obtain a rough transmittance. Guided filtering is used to optimize them. At the same time， the foggy image is segmented by a quadtree. The average luminance of the final segmented area pixel is taken as the atmospheric light value， and the defog image is restored through the atmospheric scattering model. The experimental results show that the peak signal-to-noise ratio， the information entropy， the ratio of new visible edges and the gradient mean of the improved defog image are 6.5%， 2.1%， 5.5% and 5.3% higher than those of the original defog image. The improved algorithm can solve the problem of prior defogging in dark channel， and obtain clear and high contrast defogging images.关键词：dark channel prior;bright channel prior;super pixel;atmospheric scattering Model
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发布时间：2023-05-09 - 摘要：Aiming at the problems of incomplete detection targets and blurred edges in light field image saliency detection， this paper proposes an edge-guided light field image saliency detection method. The edge enhancement network is used to extract the main image and edge enhancement image of all-focus image， and the initial saliency map is obtained by combining the features extracted from the main image and focal stack image to improve the accuracy and completeness of detection results. The initial saliency map and edge enhancement further learns the information of edge characteristics and highlights the edge details through the feature fusion module. Finally， the boundary mixing loss function is used to optimize the saliency map with clearer boundaries. The experimental results show that on the latest light field data set， F-measure and MAE are 0.88 and 0.046 respectively， which are better than the existing RGB images， RGB-D images and light field image saliency detection algorithms. The proposed method can more accurately detect complete salient objects from complex scenes， and obtain saliency maps with clear edges.关键词：saliency detection;deep learning;light field image;convolutional neural network;Edge detection network
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发布时间：2023-05-09 - 摘要：The loss function plays an important role in the detection accuracy and model convergence speed of the object detection task， and the bounding box loss function in the loss function is an important factor affecting the detection results and model convergence speed. To address the problems of low accuracy for traditional model localization and slow convergence of the model during training， an improved bounding box loss function is proposed based on the CIoU bounding box loss function， which solves the problem of gradient explosion and early degradation of the model brought by the bounding box aspect ratio during the derivation of CIoU loss function， and introduces the normalized distance between the aspect relationship and centroid of the overlap region and the target box as additional penalty terms to improve the detection accuracy and convergence speed of the model， which is called BCIoU （Better CIoU）. Experimental results on the PASACL VOC 2007 dataset show that the improved BCIoU bounding box loss function improves the IoU loss mAP50 metric by 2.09% and the AP metric by 6.88% relatively under the YOLOv3 network， the CIoU loss mAP50 metric improves by 1.64% and the AP metric improves by 5.35%. The convergence speed of the model is also improved to some extent. The proposed BCIoU loss function improves detection accuracy and convergence speed of the model， and can be easily incorporated into current object detection algorithms.关键词：computer vision;object detection;bounding box regression;gradient;loss function
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发布时间：2023-05-09 - 摘要：Cracks on the surface of rail sleepers may cause hidden dangers to rail transit. Aiming at the problems of poor universality， low accuracy and low recall of rail crack detection methods， a rail crack detection algorithm YOLOv5s-CBE based on improved YOLOv5s is proposed. Firstly， the CA attention module is added to the backbone C3 module and between C3 and SPPF respectively to capture the channel relationship and location information from the two dimensions of channel and space， so as to improve the feature extraction capability of YOLOv5s backbone network. Secondly， in the neck part of YOLOv5s， BiFPN is used to fuse different scale information to obtain the output feature map with rich semantic information； At the same time， the weighted bi-directional feature fusion pyramid structure adjusts the contribution of input feature maps of different scales to the output by introducing weights， optimizes the feature fusion effect， reduces the loss of feature information in the convolution process， and improves the detection accuracy. Finally， the loss function CIoU in the original yolov5s is changed to EIoU. EIoU not only considers the distance and aspect ratio of the center point， but also considers the real difference in width and height between the prediction frame and the real frame， which improves the prediction accuracy of the anchor frame. Compared with the original network YOLOv5s， the model size of YOLOv5s-CBE rail crack detection network on the self-made rail crack data set is reduced by 1.0 MB， the accuracy mAP is increased by 3.7%， the recall rate is increased from 73.5% to 76.2%， and the phenomenon of missing detection of cracks of different sizes is reduced. It has certain advantages and practical value.关键词：rail crack;YOLOv5s;coordinate attention mechanism;feature fusion;loss function
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发布时间：2023-05-09 - 摘要：Aiming at the problem that the model parameters of the current mainstream target detection algorithms are too large and cannot be transplanted to mobile devices and applied to assisted driving， this paper proposes an improved YOLOv5s target detection algorithm. Firstly， CSPDarknet， the backbone network of YOLOv5s algorithm， is replaced by MobileNet-V3， a lightweight network model， which solves the problem of large network model and many parameters， reduces the network depth and improves the data inference speed. Secondly， a weighted bidirectional feature pyramid structure Bi-FPN is used to enhance feature extraction， and multi-scale features are integrated to expand the receptive field. Finally， the loss function is optimized and CIoU is used as the boundary box regression loss function to improve the slow convergence speed of the original GIoU model， so that the prediction box is more consistent with the real box， and at the same time reduce the difficulty of network training. Experimental results show that compared with YOLOv5s， SSD， YOLOv3 and YOLOv4_tiny， the mAP of the improved algorithm on KITTI dataset is improved by 4.4， 15.7， 12.4 and 19.6， respectively. Compared with YOLOv5s and lightweight network YOLOv4_tiny， the model size is reduced by 32.4 MB and 21 MB respectively， and the detection speed is improved by 17.6% and 43% respectively. The improved algorithm meets the requirements of small model and high accuracy， and provides a solution for improving detection speed and accuracy of road target detection in assisted driving.关键词：MobileNetV3;object detection;YOLOv5;feature extraction;CIoU
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发布时间：2023-05-09
Image Processing
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