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1.
High color rendering index phosphorescent white organic light-emitting diodes (PHWOLEDs) were developed using a yellowish green dopant with broad light emission. A yellowish green phosphorescent dopant derived from difluorophenylquinoline ligand was synthesized and showed maximum emission peak at 550 nm and broad light emission with a full width at half maximum of 77 nm in addition to high quantum efficiency of 20.5%. The yellowish green dopant was used in PHWOLEDs to enhance the color rendering index and high color rendering index of 86.8 was obtained with a high quantum efficiency of 15.7%. 相似文献
2.
Color rendering and luminous efficacy of trichromatic and tetrachromatic LED-based white LEDs 总被引:1,自引:0,他引:1
Zhang Lei Guo Xia Liang Ting Gu Xiaoling Lin Qiao Ming Shen Guangdi 《Microelectronics Journal》2007,38(1):1-6
White light-emitting diode (LED) spectra for general lighting should be designed for high luminous efficacy as well as good color rendering, which are generally in a trade-off relationship. White LEDs have uncountable metameres, they have different luminous efficacy and color rendering. Appropriate designed trichromatic and tetrachromatic LED-based white LEDs are presented that have acceptable color rendering as well as good luminous efficacy. Triachromatic white LEDs, with a wavelength combination of 460, 540, and 615 nm, offer high general color rendering index exceeding 89, and luminous efficacy 336 lm/W. The general color rendering index of tetrachromatic LED-based white LEDs combined from 460, 525, 590, and 640 nm is 95, the luminous efficacy is 306 lm/W. Further analysis shows the changing trends of the luminous efficacy, color rendering and the chromaticity coordinate of the optimized trichromatic and tetrachromatic white LEDs depending on the wavelength shift of the primary LEDs. For the optimized trichromatic white LEDs, both the luminous efficacy and color rendering change more with the wavelength shifts of the primary red LEDs than with the wavelength shifts of the blue and green LEDs. For the optimized tetrachromatic white LEDs, the changes of the luminous efficacy caused by the wavelength shifts of one red LED are smaller than the changes of trichromatic white LEDs. And the wavelength shifts of the red primary LED that have shorter wavelength affect the color rendering more than the other primary LEDs. The wavelength shifts of the blue primary LED change the chromaticity coordinate of the white LEDs more. The small changes of the chromaticity coordinate of the white LED do not mean small changes of the k and Ra. 相似文献
3.
We introduce a set of distortion adaptive Sobel filters for the direct estimation of geometrically correct gradients of wide angle images. The definition of the filters is based on Sobel’s rationale and accounts for the geometric transformation undergone by wide angle images due to the presence of radial distortion. Moreover, we show that a local normalization of the filters magnitude is essential to achieve state-of-the-art results. To perform the experimental analysis, we propose an evaluation pipeline and a benchmark dataset of images belonging to different scene categories. Experiments on both, synthetic and real images, show that our approach outperforms the current state-of-the-art in both gradient estimation and keypoint matching for images characterized by large amounts of radial distortion. The collected dataset and the MATLAB code of the proposed method can be downloaded at our web page http://iplab.dmi.unict.it/DASF/. 相似文献
4.
We report our study on white organic light-emitting diodes (WOLEDs) implemented in a down-conversion scheme based on an ITO-free, cavity-enhanced blue phosphorescent OLED and a micro-structured color conversion layer (CCL) containing red and green phosphors. Cavity resonance induced by a ZnS/Ag/MoO3 anode structure enables both efficiency enhancement/spectral refinement of blue phosphorescent OLED. In accordance with the resonance-induced effect, outcoupling assistance provided by micro-structuring of CCLs works to yield WOLEDs with both high efficiency and illumination-quality color rendering. Highly flexible WOLEDs are also demonstrated in the proposed scheme and tested at a radius of curvature of 10.8 mm to illustrate its advantages in realizing versatile next-generation light sources. 相似文献
5.
A fast and accurate assessment of visual masking effects is desirable while encoding in order to utilize such effects to improve the quality of compressed videos through an adaptive quantization (AQ) scheme. Here, we propose a method of estimating the contrast masking threshold on natural scene patches, using texture cues imparted by steerable filter responses. We then employ the estimated thresholds to perform AQ for AV1 encoding. Our experimental results establish that the proposed method is able to outperform existing visual masking models in terms of estimation performance while being relatively computationally inexpensive than these models, and is also able to improve the variance based AQ algorithm that is currently deployed in the SVT-AV1 codec. Using the multi-scale structural similarity index measure (MS-SSIM) as the quality model, our approach achieves an average BD-rate of -1.82% using the uniform quantization scheme as anchor as compared to 5.83% obtained with the variance based method. We note that the proposed approach produces less visible compression artifacts than the variance based AQ approach at lower bitrates, while maintaining similar encoding complexity. 相似文献
6.
7.
提出一种抛物线插值的体绘制分段积分方法,并改进了基于剪切几何纹理化的体数据剖切绘制.首先将采样段内的颜色值用抛物线插值近似代替,计算各采样段的光强值,代替采样点用于体绘制积分方程,即使低采样率下仍能获得较好的图像质量.对体数据进行剖切绘制时,与传递函数相结合,根据剪切几何形状和位置修改体数据中的相应体素值,使之对最终绘制图像不作贡献,达到剪切绘制的目的,并实现了基于剪切几何和基于体数据阈值分割的剖切算法.试验结果表明,本文方法明显提高了绘制图像的质量,降低了剖切绘制时的内存使用,同时提高了剖切绘制的速度. 相似文献
8.
Reference signal generator for active power filters using improved adaptive predictive filter 总被引:1,自引:0,他引:1
Byung-Moon Han Byong-Yeul Bae Ovaska S.J. 《Industrial Electronics, IEEE Transactions on》2005,52(2):576-584
The performance of an active power filter (APF) depends on the inverter characteristics, applied control method, and the accuracy of the reference signal generator. The accuracy of the reference generator is the most critical item in determining the performance of APFs. This paper introduces an efficient reference signal generator composed of an improved adaptive predictive filter. The performance of the proposed reference signal generator was first verified through a simulation with MATLAB. Furthermore, the application of feasibility was evaluated through experimenting with a single-phase APF prototype based on the proposed reference generator, which was implemented using the TMS320C31 floating-point signal processor. Both simulations and experimental results confirm that our reference signal generator can be used successfully in practical APFs. 相似文献
9.
In this paper, an efficient depth image-based rending (DIBR) with depth reliability maps (DRM) is proposed to improve the quality of synthesized images. First, a DRM-based occlusion-aware approach is developed to obtain a segmentation mask, which can explicitly indicate where the information in an intermediate image should be blended preferably. Next, an improved weight model for view creation is introduced to enhance the quality of synthesized images. Finally, a distance and depth-based sub-pixel weighted (DDSPW) algorithm is presented to solve the visibility and resampling problems. Experimental results demonstrate that the treated DIBR schemes have better performance for view synthesis than the other three methods through the subjective visual perception and objective assessments in terms of peak signal to noise ratio and structural similarity index. 相似文献
10.
We packaged a series of high power white LEDs by covering the blue LED chips with yellow phosphor, red phosphor and the two phosphors mixed by appropriate mass ratio, respectively, and discussed the excitation and emission spectrum of yellow phosphor and red phosphor and the characteristics of the LEDs. We found that the luminous efficacy of the white LEDs covered with the two phosphors mixed by appropriate mass ratio was lower than that of the white LEDs covered with yellow phosphor, but the color rendering index was improved observably. 相似文献
11.
Single-emitting-layer hybrid white organic light-emitting diodes (SEL-hybrid-WOLEDs) are promising candidates for large-area lightings, however, ideal hybrid WOLEDs with a simple structure and high-efficiency, low roll-off, high color rendering index (CRI) and superior CIE coordinates have been rarely reported. In this paper, high-performance SEL-hybrid-WOLEDs are demonstrated by utilizing a thermally activated delayed fluorescence (TADF) host emitter combined with green and red phosphors. The optimized WOLED exhibits an external quantum efficiency (EQE) of 20.2%, CIE coordinates of (0.360, 0.390) and a CRI of 85. Remarkably, an extremely low efficiency roll-off is also realized, with an EQE of 19.4% remained even at the practical luminance of 1000 cd/m2, resulting from the wide recombination zone as well as the well-tuned energy transfer in the emitting layer. Moreover, benefited from the stable recombination zone, superior color stability was also achieved. The intriguing results, we believe, greatly manifest the great potential of such a strategy and may pave the way towards real applications. 相似文献
12.
We present a novel GPU‐based ray‐casting algorithm for volume rendering of unstructured grid data. Our volume rendering system uses a ray‐casting method that guarantees accurate rendering results. We also employ the per‐pixel intersection list concept in the Bunyk algorithm to guarantee an accurate result for non‐convex meshes. For efficient memory access for the lists on the GPU, we represent the intersection lists for all faces as an array with our novel construction algorithm. With the intersection lists, we perform ray‐casting on a GPU, and a GPU thread handles each ray. To increase ray‐coherency in a thread block and improve memory access efficiency, we extend a prior image‐tile‐based work distribution method to fit modern GPU architectures. We also show that a prior approach using a per‐thread local buffer to reduce redundant computation is not appropriate for modern GPU architectures. Instead, we take an on‐demand calculation strategy that achieves better performance even though it allows duplicate computations. We applied our method to three unstructured grid datasets with different characteristics. With a GPU, our method achieved up to 36.5 times higher performance for the ray‐casting process and 19.7 times higher performance for the whole volume rendering process compared with the Bunyk algorithm using a CPU core. Also, our approach showed up to 8.2 times higher performance than a GPU‐based cell projection method while generating more accurate rendering results. These results demonstrate the efficiency and accuracy of our method. 相似文献
13.
Existing single image haze removal algorithms could suffer from noise amplification in sky regions and possible color distortion in restored images due to noise in haze images. In this paper, a simple pre-processing tool is introduced for single image haze removal so as to reduce the effect of noise in the restored image. The input image is first decomposed into base and detail layers by using a weighted guided image filter (WGIF). The airlight and transmission map are estimated from the base layer. In order to restore the objects close to the camera well, the decomposition of haze image is adaptive to the value of the transmission map. If the transmission map of a pixel is small, it is decomposed into two layers, otherwise, not decomposed. Since the noise is included in the detail layer, the base layer is amplified in the final image if the haze image is decomposed. Experiments show that the proposed pre-processing tool can indeed be applied to improve the state-of-the-art haze removal algorithms. 相似文献
14.
Adaptive quantization proves to be an effective tool to improve coding performance. In this paper, we propose an adaptive spatiotemporal perception aware quantization algorithm to increase subjective coding performance. To measure the spatiotemporally perceptual redundancy, the perceptual complexity models are firstly established with spatial and temporal characteristics respectively. With the help of the models, the adaptive spatial and temporal quantization parameter (QP) offsets are then calculated for each coding tree unit (CTU), respectively. Finally, the perceptually optimal Lagrange multiplier of each CTU is determined with the spatial–temporal QP offset. Experimental results show that the proposed algorithm reduces 8.6% and 8.4% Bjontegaard-Delta Rate (BD-Rate) with Structural Similarity Index Metric (SSIM) in average over the second generation of Audio Video Coding Standard (AVS2) reference software RD17.0 in Low-Delay-P (LDP) and Random-Access (RA) configurations, respectively. The subjective assessment proves that the proposed algorithm can reduce the bitrates with the same subjective quality significantly. 相似文献
15.
The joint estimation of direction of arrivals (DOA) and carrier frequencies of band-limited source signals is considered in this paper. A novel technique based on nonlinear Kalman filters is proposed for this joint angular and spectral estimation problem for cognitive radio (CR). Since sampling a wideband spectrum at Nyquist rate increases the analog-to-digital converter (ADC) requirements, we propose executing Kalman filter algorithm over a spatial state space model. Thus, one time sample is required and hardware complexity is reduced. Two types of nonlinear Kalman filters, extended Kalman filter (EKF) and unscented Kalman filter (UKF), are proposed. We consider their sub-optimal performance and show how to control their convergence. However, the proposed algorithms can detect a number of source signals limited to the number of elements in employing arrays. 相似文献
16.
针对脉冲涡流技术在油气井套管检测过程中易受到环境影响而产生的噪声干扰问题,提出一种油气井套管电磁检测数据的分段动态自适应降噪方法。通过对比分析仿真信号、实验井检测信号与实测井检测信号的差异,结合实际检测过程中的噪声来源分析,建立了基于偏心-抖动-温度影响因素的检测信号补偿模型。基于该补偿模型训练得到油气井套管电磁检测数据的分段动态自适应降噪模型。测井数据消噪实验结果表明,所研究方法与常用的降噪方法相比能更好地抑制实际检测过程中偏心、抖动及温度因素带来的噪声影响,具有应用和借鉴价值。 相似文献
17.
This paper presents the design optimization of fully pipelined architectures for area-time-power-efficient implementation of finite impulse response (FIR) filter. The architectures are designed to obtain a suitable area-time tradeoff. Analysis of the performance of different filter orders and different address lengths of partial tables indicate the choice of four input partial tables presents the best of area-time-power-efficient realizations of FIR filter compared with the existing LUT-less DA-based implementations of FIR filters in both high-speed and medium-speed. Moreover, a number of further experiments not only shows the pipeline register’s significant influence to the maximum frequency of the FIR filters but also indicates it also has area usage. Final experiment shows that with the help of using pipeline register, the choice of 4-bits-per-clock (4BPC) of the architecture for word-length N=8 with four input partial table yields the best cost-effective when comparing with other different cases in both high-speed and medium-speed implementations. 相似文献
18.
基于区域互信息的特征级多光谱图像配准 总被引:2,自引:0,他引:2
提出了一种基于点特征的多光谱图像配准方法.利用SUSAN算法提取角点特征,采用域互信息(RMI)作为相似性测度获取初始匹配特征点集;在精匹配阶段,首先计算初始匹配征点对的匹配强度和明确度,进行松弛迭代,得到匹配强度和明确度都较大的一一对应关系的特征点对,然后利用马氏距离的仿射不变性筛选出正确的点对,将不正确的点对从初始匹配特征点集中删除,重新进行松弛迭代,重复上面的步骤,直到筛选不出新的正确点对为止;获取了足够多的同名控制点后,用最小二乘法估计初始仿射变换参数并迭代修正.实验结果表明,算法可以达到亚像素级的配准精度. 相似文献
19.
《Journal of Visual Communication and Image Representation》2014,25(4):698-708
In general, excessive colorimetric and geometric errors in multi-view images induce visual fatigue to users. Various works have been proposed to reduce these errors, but conventional works have only been available for stereoscopic images while requiring cumbersome additional tasks, and often showing unstable results. In this paper, we propose an effective multi-view image refinement algorithm. The proposed algorithm analyzes such errors in multi-view images from sparse correspondences and compensates them automatically. While the conventional works transform every view to compensate geometric errors, the proposed method transforms only the source views with consideration of a reference view. Therefore this approach can be extended regardless of the number of views. In addition, we also employ uniform view intervals to provide consistent depth perception among views. We correct color inconsistency among views from the correspondences by considering importance and channel properties. Various experimental results show that the proposed algorithm outperforms conventional approaches and generates more visually comfortable multi-view images. 相似文献
20.
Traditional multi-path routing mechanisms aim to establish complete node or link disjoint paths.However,under some circumstances if multiple paths cannot be established based on the current network topology,the traditional multi-path routing mechanism will degenerate into single path routing mechanism,thus the advantages of multi-path routing cannot be exhibited.To enhance the end-to-end path reliability,an adaptive multi-path routing mechanism with path segment is proposed,in which multi-path can be establ... 相似文献