基于邻域彩色变化矢量场的图像边缘检测技术研究*

首先进行了边缘检测系统结构设计,建立了图像邻域彩色变化矢量场的数理模型,提出了用图像邻域彩色变化方向锐度描述图像边缘,进而应用模糊聚类自适应检测边缘.实验表明:与基于梯度的边缘检测技术相比,该方法在噪声抑制以及边缘准确定位上均取得了好的效果,是一种应用广泛的优秀边缘检测算法.     

图像质量快速盲检测及其在视觉系统中的应用

提出了一种新的图像质量快速盲检测方法,以锐利度作为图像质量准则,而锐利度可以归结为图像的模糊特性,并由边缘信息估计得到。为了提高系统效率,采用边缘对比度的估计方法,并以边缘对比度作为边缘锐利度的判据准则。分析了邻近边缘的相互影响,因而只需从有限的边缘点来提取出合理的线扩展函数(LSF),进而得到模糊参数。在LSF计算中,采用一种新的插值计算方法。实验结果表明:当图像不是特别模糊时,测量结果是准确的。     

融合梯度信息与HVS滤波器的无参考清晰度评价

目的 目前无参考图像质量评价算法的性能存在较大的提升空间,为了提高清晰度评价技术,提出了一种基于梯度信息与HVS滤波器的无参考清晰度评价算法(GI-F)。方法 该算法首先利用梯度算子计算各像素点的梯度信息,再通过HVS滤波器得到加权和作为图像的清晰度指标。结果 在公开数据库LIVE、TID2008和CSIQ上进行的实验,GI-F与S3(Spectral and Spatial Sharpness)、CPBD(Cumulative Probability of Blur Detection)和LPC-SI(Local Phase Coherence-based Sharpness Index)相比,性能指标RMSE(Root Mean Squared Error)、PLCC(Pearson Linear Correlation Coefficient)和SROCC(Spearman Rank-Order Correlation Coefficient)分别提升了20.66%、4.61%和3.33%;同时GI-F还具有更低的计算复杂度,即使与目前最好的BRISQUE(Blind/Referenceless Image Spatial QUality Evaluator)算法相比,耗时也降低了79.72%。结论 该算法只需耗费更少的时间即可计算出与人眼感知更加接近的客观清晰度指标,可广泛用于无参考图像情况下的清晰度指标计算场合,同时还可以通过并行计算进一步降低其计算时间。     

Sharpness and noise characteristics of a half‐mirror stereoscopic display

Stereoscopic displays are becoming popular in entertainment and industrial applications. We characterize the spatial resolution and noise properties of a stereoscopic display with a half‐mirror and passive polarizing glasses. The upper display images reflected off the mirror have slightly degraded sharpness and reduced high spatial‐frequency noise resulting in modulation transfer functions (MTFs) of 0.59 and 0.50 at the Nyquist frequency with corresponding noise power spectra (NPS) values of 4.79 × 10^?6 and 5.17 × 10^?6 mm² at 10 mm^?1 in the horizontal and vertical directions. These results are compared to the characteristics of the individual displays with MTF values of 0.64 and 0.53 and NPS values of 6.24 × 10^?6 and 5.87 × 10^?6 mm². The polarizing glasses cause minimal reduction in sharpness and high‐frequency noise. The MTFs in the upper images observed with glasses are decreased to 0.54 and 0.47, while the NPS are decreased to 2.86 × 10^?6 and 2.01 × 10^?6 mm². When both displays are turned on and using the mirror and glasses, the observed luminance for each eye is increased from the luminance of the individual displays owing to crosstalk. We find that sharpness and noise are not affected by the interaction between the displays at the particular geometry tested in this study.     

No reference image blurriness assessment with local binary patterns

In this paper, we put forward an effective and efficient no reference image blurriness assessment metric on the basis of local binary pattern (LBP) features. In this proposal, we reveal that part of the LBP histogram bins present monotonously with the degree of blurriness. The proposed method contains the following steps. Firstly, the LBP maps of an input image are extracted with multiple radiuses. And then, the frequency of pattern histogram is analyzed before part of bins are chosen as the features. In addition, we also take the entropy of these bins as another feature. Finally, we learn the extracted features to predict the image blurriness score. Validation of the proposed method is conducted on the blurred images of LIVE-II, CSIQ, TID2008, TID2013, LIVE3D IQA Phase I and LIVE3D IQA Phase II. Experimental results demonstrate that compared with the state-of-the-art image quality assessment (IQA) methods, the proposed algorithm has notable advantage in correlation with subjective perception and computational complexity.     

Measurement of binocular disparity in polarized based stereoscopic display by using digital camera

This work presents an image displacement measurement by using a box pattern and the edge spread function analysis in the polarized based stereoscopic displays. The measurement determines to identify three factors (i.e., box size, image displacement, and spatial frequency response (SFR)) from the box patterns. The polarized based stereoscopic displays might sacrifice pixels for producing 3D images, which might produce errors in the image displacement and then affect the depth perception indirectly. Based on the measurement, the errors can be quantified by using the three factors. Owing to the light leakage distorting the edge spread function to obtain an inferior SFR, exactly how light leakage affects the edge spread function can be resolved on the basis of the SFR results, especially at a frequency (1/display pixel) of 1.9 in the case of the horizontal displacement. Light leakage also induces the error of the box height in even and odd intervals of the vertical displacements more than 2 pixels and 0.5 pixels, respectively. The image displacement measurement provides a simple and comprehensive means of evaluating the optical characteristics, disparity, and sharpness of the stereoscopic displays, via the three factors.     

Trade‐Offs in Seed Dispersal Strategies Across Riparian Trees: The How Matters as Much as the When

Riparian Salicaceae are prolific producers of short‐lived seeds that require very restrictive hydro‐geomorphic conditions for establishment. It is generally assumed that if floods are able to create nursery sites timed with seed dispersal, recruitment will occur. Other spatial and temporal seed dispersal patterns besides the dispersal period have historically received little attention. However, seed dispersal patterns can be highly variable between regions, species and over the years. In this paper, we report the seed dispersal patterns of three dominant riparian Salicaceae trees in Europe: Populus alba, P. nigra and Salix alba to suggest possible trade‐offs between seed dispersal patterns, germinability, longevity and establishment. Seed rain of the three species was monitored in 33 glue‐coated traps for three months yearly from 2006 to 2008 in an 8‐km stretch of the Middle Ebro River (N Spain), which has a pluvio‐nival regime. P. alba dispersed seeds earlier during a shorter time period and with a fewer number of seed release pulses compared with P. nigra, and especially with S. alba. With overlapping seed dispersal periods, the two latter species occupy similar landform units but rarely compete with P. alba, usually at higher elevations, as shown in a previous study in the same study area. The three species had very high germinability immediately after release (>90%), but longevity in S. alba was eight times shorter than that of its two Populus counterparts. We suggest that S. alba has compensated its lower seed quality with a more spaced seed release in several pulses of similar magnitude. With similar seed dispersal patterns and germinability but a higher longevity, P. nigra had a much higher density of individuals than S. alba in the recruitment zones of the study area. We hope that our results may inform river managers about how to optimize river flows to promote sexual regeneration of these species. Copyright © 2015 John Wiley & Sons, Ltd.     

手机模组生产线被动自动对焦技术研究

自动对焦系统在手机中得到越来越广泛的应用。根据手机镜头焦距短,可调范围窄等特点,全面分析了噪声,视场,清晰度评价函数,窗口选取等各种因数的影响。构建了适于生产线检测的自动对焦系统,并成功地实现快速调焦。     

基于图像清晰度评价的摄像头辅助调焦系统

提出一种新的图像清晰度(包括锐度和对比度)评价函数,对比传统的图像清晰度评价算法,新算法速度最快且准确,以及和功率谱算法一样优良的灵敏度,适合各种实时自动对焦系统.本文使用一系列不同程度的离焦图片演示了所有算法的性能。同时将新算法应用于一种实际的摄像头模块辅助调焦系统中,系统把采集的每帧图像实时显示在屏幕上,用新算法评价图像的清晰度,从而指导作业员对摄像头模块进行调焦。实践表明该摄像头辅助调焦系统在批量生产摄像头模块时对提高生产效率和稳定质量方面有很大作用。     

基于图像清晰度评价的跟踪望远镜自动调焦算法研究

为了减小跟踪望远镜调焦时间,分析了自动调焦的光学原理及数字图像处理相关技术,提出一种适合跟踪望远镜的实时自动调焦算法。该算法基于对图像清晰度的评价,通过步进电机驱动次镜移动来搜索最佳成像位置,并且综合了全局搜索法与传统爬山法的优点。在实验中,完成了对远处静态目标自动对焦,有效地避免了局部峰值导致的对焦失败,在保证系统调焦精度的前提下使对焦速度小于3s。