Masking, photobleaching, and spreading effects in Hadamard transform imaging and spectroscopy systems
Masking, photobleaching, and spreading effects in Hadamard transform imaging and spectroscopy systems
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DOI：
10.1366/0003702011951722
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发表时间：
2001-03-01
影响因子：
3.5
通讯作者：
Hanley, QS
中科院分区：
文献类型：
--
作者：
Hanley, QS
在分析光学切片显微镜中阿达玛变换成像光谱系统的行为时，观察到了先前未描述的掩蔽效应。在表征这种伪影的过程中，人们注意到，尽管先前在文献中已经报告了许多掩蔽错误，但没有人试图对它们进行分类或以各种成像和光谱安排系统地处理它们的影响。以前的报告已经记录了基于长度为2“-1的序列的一维Hadamard掩模系统中的回波伪影，对于该序列，回波被很好地定义。其他有效的循环S序列，例如素数长度为Im+3不等于2”-1的序列，没有表现出这样的行为。掩蔽错误可能存在于这些序列中，但它们不以回声的形式出现。观察到恢复的强度具有分布在整个变换轴上的正和负幅度。这些掩蔽缺陷表面上看起来是“噪音”，使得相关的错误更难诊断。二维系统中的掩蔽效应以前没有报道过。在这些情况下，原始图像和由此产生的“回声”之间的关系可能非常复杂。本文从理论上对各种掩蔽效应进行了处理，并在此基础上进行了仿真。根据编码通过掩码是一次还是两次，掩码错误分为一阶和二阶效果。一维Hadamard变换系统中的对称、非对称和静态掩蔽误差在一阶和二阶排列中都被处理。在有先前数据的情况下，已经尝试收集和分类已知的与掩膜相关的人工制品，并在适当的情况下提供额外的文档。掩模误差可以在掩模上或在给定像素内在空间上变化或在空间上不变。在空间变化的系统中，通过组成掩模的元素对图像或光谱进行适当的采样是成功校正数据的先决条件。应用于来自具有空间变化误差的掩模的数据的校正可能导致出现伪影，并且在某些情况下，完全校正可能是不可能的。研究了一维和二维掩模系统中由衍射或像差等过程引起的光漂白和掩模扩散的影响。当指数衰减模型适用时，光漂白相对容易修正。在二阶系统中，掩模扩展即使在完美实现的掩模中也会引起回声或失真。在许多情况下，掩模扩展可以通过分析观察到的“回波”并建立校正矩阵或通过使用系统的点、线或其他扩展函数的知识来校正。最后，在长度为2(N)-1的掩码中，一些简单的规则对诊断掩码效果有很大帮助。
In analyzing the behavior of a Hadamard transform imaging spectroscopic system in an optical sectioning microscope, a previously undescribed masking effect was observed. During the process of characterizing this artifact, it was noted that while many masking errors have been reported previously in the literature, no attempt has been made to classify them or to systematically treat their effects in a variety of imaging and spectroscopy arrangements. Previous reports have documented echo artifacts in one-dimensional Hadamard mask systems based on sequences of length 2" - 1, for which the echoes are well defined. Other valid cyclic S-sequences, such as those of prime length Im + 3 not equal 2" - 1, do not exhibit such behavior. Masking errors may be present with these sequences, but they do not appear as echoes. Recovered intensities are observed having both positive and negative magnitude distributed throughout the transform axis. These masking defects appear superficially to be "noise", making associated errors more difficult to diagnose. Masking effects in two-dimensional systems have not been previously reported. in these, the relationship between the original image and resulting "echoes" can be quite complicated. This paper treats a variety of masking effects theoretically and presents simulations based on that treatment. Mask errors are divided into first- and second-order effects depending on whether the encoding passes through a mask once or twice. Symmetric, asymmetric, and static masking errors in one-dimensional Hadamard transform systems are treated in both first- and second-order arrangements. Where prior data exist, an attempt has been made to collect and categorize known mask-related artifacts and where appropriate provide additional documentation. Mask errors may be spatially varying or spatially invariant over the mask or within a given pixel. In systems which are spatially variant, proper sampling of the image or spectrum hy the elements composing the mask is a prerequisite for successful correction of the data. Corrections applied to data from masks with spatially variant errors may cause artifacts to appear and, in some instances, complete correction may be impossible. The effects of photobleaching and mask spreading due to processes such as diffraction or aberrations in both one- and two-dimensional-mask systems are investigated. Photobleaching is relatively easy to correct when an exponential decay model is applicable. In second-order systems, mask spreading gives rise to echoes or distortion even in perfectly implemented masks. Mask spreading can, in many cases, be corrected by analyzing the observed "echoes" and building a correction matrix or by using knowledge of the point, line, or other spreading function of the system. Finally, in masks of length 2(n)- 1, a few simple rules greatly assist in diagnosing masking effects.