A computer simulation platform for the estimation of measurement uncertainties in dimensional X-ray computed tomography

The knowledge of measurement uncertainty is of great importance in conformance testing in production. The tolerance limit for production must be reduced by the amounts of measurement uncertainty to ensure that the parts are in fact within the tolerance. Over the last 5 years, industrial X-ray computed tomography (CT) has become an important technology for dimensional quality control. In this paper a computer simulation platform is presented which is able to investigate error sources in dimensional CT measurements. The typical workflow in industrial CT metrology is described and methods for estimating measurement uncertainties are briefly discussed. As we will show, the developed virtual CT (VCT) simulator can be adapted to various scanner systems, providing realistic CT data. Using the Monte Carlo method (MCM), measurement uncertainties for a given measuring task can be estimated, taking into account the main error sources for the measurement. This method has the potential to deal with all kinds of systematic and random errors that influence a dimensional CT measurement. A case study demonstrates the practical application of the VCT simulator using numerically generated CT data and statistical evaluation methods.     

LCD组件检测中用MTF评估自动聚焦分辨率的方法

液晶检测设备在自动聚焦后由于焦距变化,成像分辨率也不可避免的发生变化,为此必须提供一种快速评估检测设备实际分辨率的方法。由于检测设备总分辨率为镜头分辨率与相机分辨率的乘积,因此论文提出先根据相机的各种噪声模型建立相机对比度分辨值,接着用频率渐变的LCD黑白样条光栅评估不同频率下镜头MTF的像质退化情况,最后通过分析分辨率与对比度关系,得出相机最高对比度下能够分辨出的经过成像系统像质退化产生亮暗模糊所对应的空间截止频率。实验表明在使用光学检测设备对手机背光源进行缺陷检测时,论文的方法评估实际分辨率>17μm,用背光源标定样品实际检测后可以得到,对于17μm以上缺陷检测设备都能清晰成像,因此结果证明了该方法的有效性。     

Otto Schade——探索图像质量奥秘的先驱

OttoH.Schade,Sr.创建了一套权威的度量标准,用于预测和评估成像部件及成像系统的性能,这就是现今已被全世界广泛运用的调制传递函数(MTF)。当信息显示协会(SID)准备就显示器件性能及图像质量研究授出第一个OttoSchade奖时,让我们来认识一下以其名命名此奖的OttoH.Schade,Sr.。     

一种测量CCD调制传递函数的新方法

介绍了一种测电荷耦合器件（ＣＣＤ）调制传递函数（ＭＴＦ）的新方法。该法利用动态变频正弦光栅获得的频率可连续变化的正弦信号以测出ＣＣＤ的调制传递函数，因此数据处理非常简单，同时由于靶函数的引入无需经过任何光学系统，从而消除了光学系统给测量带来的影响。     

一种红外变焦距像面变化量的测量方法

大变倍比连续变焦红外成像系统能够同时应用于大视场下的目标搜索和小视场下的高精度跟踪测量。由于变倍比很大,在整个变焦范围内均保持良好的成像质量就成了其设计验证的难点。为了解决这一问题,本文利用调制传递函数对变焦距像面的变化量进行测量和验证。红外成像系统整机调制传递函数的主要测试方法有斜狭缝法和斜刃边法。在对两者的测试特点和影响要素进行分析比较后,选取斜刃边法作为红外成像系统整机调制传递函数的测试手段。通过用调制传递函数对现有的大变倍比测试样品在各特征焦距下的离焦曲线进行标定,得到了最优像面位置。与理论设计值相比较,最大偏差为36μm。依据该数据对调焦补偿进行了修正。复测后,该偏差的最大值降至5μm。     

基于码书索引变换的高通量DNA序列数据压缩算法

提出一种高通量DNA序列数据的压缩算法。该算法先采用码书索引变换模型,将传统码书索引值的表示方法变换成由四个标准碱基字符替代的四进制数值方式,并采用一种界定替换串与非替换串的简明编码方法,接着通过信息熵的大小来决定是否进行块排序压缩变换（BWT ）,最后进行前移编码变换和Huffman熵编码。在多种测序数据集上的实验结果表明,CITD在大多数情况下可以获得比本文所对比的高通量DNA专用压缩方法更优的压缩性能。     

基于MTF值的光栅图像清晰程度判别

针对编制软件评价光学元件的质量问题,文章提出了MTF值的计算方法,并且以此值作为光栅图像的对焦评价函数。通过计算光栅图像实时得出MTF值。这种方法具有使用方便,抗干扰等优点,最后利用实验证明此法确实能判别图像清晰程度。     

Geometric and radiometric characteristics of a prototype surveillance system

This paper reports the research findings regarding the quality of the captured video of a prototype Near-Infrared imaging system which was developed for night-time surveillance. The prototype required the incorporation of a 3D optical stereo adapter and a set of external near-infrared filters onto the optics of a conventional video camera. The study found that the video captured by the prototype was approximately 85% of the original video camera resolution and the radial lens distortion increased from one to approximately two pixels. The distortion was easily reduced to sub-pixel value using suitable image processing techniques. The standard deviation of the 3D measurement between any two facial anthropometric marks was better than 2 mm for all the tested models. The image radiometric quality was sufficient to provide accurate facial landmark identification for three test subjects. The results confirmed that the prototype was suitable for 3D spatial data capture and feature interpretation of crime suspects in court.     

288×4红外TDI探测器光敏元尺寸与间距设计研究

针对国外进口Sofradir公司长波288×4扫描型时间延迟积分(TDI)探测器,通过分析其沿扫描和沿线列方向上光敏元尺寸和间距对整个成像系统的系统调制传递函数(MTF)的影响,给出了探测器光敏元尺寸和间距与整个成像系统分辨率之间的相互关系,为新型TDI型探测器阵列光敏元排列设计提供了理论参考。     

基于旋转阵列的多帧合成孔径图像复原

针对光学合成孔径成像系统的调制传递函数 (MTF)在中-低频段的衰减以及造成的合成图像降质问题,以6孔径Y型 阵列 为例,提出子孔径阵列旋转成像以获取包含互补信息的多帧图像;通过截止频率与中频能量 比确定旋转角度,并 利用多帧迭代盲解卷积算法进行图像复原。实验表明,与现有的代表性工作相比,本文方法 对于Y型阵列的合成孔径图像有较好的复原效果和重建的准确性。