Reduced depth of field in incoherent hybrid imaging systems

A hybrid imaging system combines a modified optical imaging module and a digital postprocessing step. We define what to our knowledge is a new metric to quantify the blurring of a defocused image that is more suitable than the defocus parameter for describing defocused hybrid imaging systems. We use this metric to design a pupil phase grating to reduce the depth of field, thereby increasing the axial resolution, of an incoherent hybrid imaging system using quasi-monochromatic illumination. By introducing this grating at the exit pupil and digitally processing the output of the detector, we reduce the depth of field by more than a factor of 2. Finally, we examine the effect of using a CCD optical detector, instead of an ideal optical detector, on the reduction of the depth of field.     

Tumor classification based on non-negative matrix factorization using gene expression data

This paper presents a new method for tumor classification using gene expression data. In the proposed method, we first select genes using nonnegative matrix factorization (NMF) or sparse NMF (SNMF), and then we extract features from the selected genes by virtue of NMF or SNMF. At last, we apply support vector machines (SVM) to classify the tumor samples using the extracted features. In order for a better classification, a modified SNMF algorithm is also proposed. The experimental results on benchmark three microarray data sets validate that the proposed method is efficient. Moreover, the biological meaning of the selected genes are also analyzed.     

Applications of the phase transfer function of digital incoherent imaging systems

The phase of the optical transfer function is advocated as an important tool in the characterization of modern incoherent imaging systems. It is shown that knowledge of the phase transfer function (PTF) can benefit a diverse array of applications involving both traditional and computational imaging systems. Areas of potential benefits are discussed, and three applications are presented, demonstrating the utility of the phase of the complex frequency response in practical scenarios. In traditional imaging systems, the PTF is shown via simulation results to be strongly coupled with odd-order aberrations and hence useful in misalignment detection and correction. In computational imaging systems, experimental results confirm that the PTF can be successfully applied to subpixel shift estimation and wavefront coding characterization tasks.     

基于调和修补模型的图像压缩方案

本文采用调和修补模型,给出了一种新的图像压缩方案。在图像编码端,采用边缘提取技术,仅对边缘扩展图像进行压缩编码,大大减少了需要编码的信息量。在图像解码端,采用调和修补模型来重建原始图像。通过对大量灰度和彩色图像进行实验,结果表明,该压缩方案能够在较少信息量的情况下得到很好的重建图像。     

Phase plate to extend the depth of field of incoherent hybrid imaging systems

A hybrid imaging system combines a modified optical imaging system and a digital postprocessing step. We describe a spatial-domain method for designing a pupil phase plate to extend the depth of field of an incoherent hybrid imaging system with a rectangular aperture. We use this method to obtain a pupil phase plate to extend the depth of field, which we refer to as a logarithmic phase plate. Introducing a logarithmic phase plate at the exit pupil of a simulated diffraction-limited system and digitally processing the detector's output extend the depth of field by an order of magnitude more than the Hopkins defocus criterion. We also examine the effect of using a charge-coupled device optical detector, instead of an ideal optical detector, on the extension of the depth of field. Finally, we compare the performance of the logarithmic phase plate with that of a cubic phase plate in extending the depth of field of a hybrid imaging system with a rectangular aperture.     

基于目标特征的数据压缩预处理方法

随着水下自动监测技术的不断发展,对于数据的实时传输效率和测量精度的要求也越来越高,而高质量无损数据压缩传输技术还存在严重不足。文章利用在广西西江航道上建立的侧扫声呐船舶吃水自动监测系统,提出了一种基于目标特征的数据压缩预处理方法。该方法根据散货船的船体结构和声图成像特点,在进行数据压缩前分别在时间和空间两个维度上实现对目标信号的识别和提取,完成对无关冗余数据的剔除。该预处理方法不仅可以大幅提高数据压缩的压缩比,提高传输效率,节省存储空间,还可以保证用于测量计算的目标关键特征信息不丢失,为进一步突破无损数据压缩的压缩比限制提供新思路。     

Single-lens single-image incoherent passive-ranging systems

We introduce a new system for single-lens single-image incoherent passive ranging. The only a priori object information this system requires is that the objects to be ranged must possess a low-pass spatial frequency spectrum. Physically, this system for passive ranging is a standard optical imaging system that is customized with a special-purpose optical mask or filter. Analytically, this optical mask customizes the transfer function of the optical system in such a way that objects form images that contain range-dependent information. This range-dependent information lies in the spatial spectrum nulls or zeros of the image.     

Improved BER based on intensity noise alleviation using developed detection technique for incoherent SAC-OCDMA systems

The major drawback of incoherent spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems is their inherent intensity noise originating due to the incoherency of the broadband light sources. In this paper, we propose a developed detection technique named the modified-AND subtraction detection for incoherent SAC-OCDMA systems. This detection technique is based upon decreasing the received signal strength during the decoding process by dividing the spectrum of the utilized code sequence. The proposed technique is capable of mitigating the intensity noise effect, as well as suppressing the multiple-access interference impact. Based on modified quadratic congruence (MQC) code, the analytical results reveal that the modified-AND detection offer best bit-error rate (BER) performance and enables MQC code to support higher transmission rate up to 1.25?Gb/s compared to conventional AND detection. Furthermore, we ascertained that the proposed technique enhances the system performance using a simulation experiment.     

基于分类矢量量化器的超声检测数据压缩方法

研究了基于分类矢量量化技术的超声数据压缩算法,提出了基于峰值数的超声数据分类方法以及基于峰值距离失真测度的码字搜索算法。本文提出的算法充分利用了超声信号的特征,能够很好地保存超声信号的峰值信息。实验表明,相对于普通矢量量化器,本文提出的分类矢量量化器能够在保持相同压缩比的情况下提高重构信号的信噪比。将此矢量量化器与霍夫曼编码相结合,其压缩比可达1：50,高于基于小波变换的压缩算法。     

基于反卷积的手机屏下成像图像恢复

随着全面屏手机的发展,手机屏下成像的研究应运而生。但由于手机屏幕存在电路走线和其他不透明部分,光通过屏幕会产生衍射,降低成像结果的图像质量,本文从图像复原的角度,对屏下相机拍摄的图像进行恢复。通过测量得到手机成像系统的点扩散函数(PSF),利用测得的PSF,对图像进行反卷积处理。本文改进了传统的反卷积方法,对原始图像进行颜色空间转换,然后对不同的通道分别处理。相较于传统反卷积方法,改进后的反卷积方法得到的处理结果在结构相似度(SSIM)、峰值信噪比(PSNR)等指标上都有提高,运行时间更短。在分通道反卷积之后,使用非局部平均算法进行去噪处理,进一步提高了屏下图像的质量。     

基于压缩感知的水声数据压缩与重构技术

在水声信号处理中,数据量大造成的数据处理压力不容忽视。为了有效地提取水声数据中的有用信息,同时缓解数据量大带给水声数据传输的压力,研究压缩感知(Compressed Sensing,CS)的基本原理及其关键技术,综述了CS理论框架并着重介绍了稀疏变换、观测矩阵设计和重构算法三个方面。通过仿真实验表明了压缩感知技术能够有效地用于模拟数据的压缩与重构。重点对水声舰船噪声信号进行了基于CS的压缩与重构仿真实验,验证了压缩感知技术运用于水声数据处理的有效性,从而达到提高水声数据传输速率的目的。     

Reliability estimation based on operational data of manufacturing systems

Maintenance management has a direct influence on equipment reliability and safety. However, a large portion of traditional maintenance models and reliability analysis methods usually assumes that only perfect maintenance is performed on the system and the system will restore to as good as new regardless of the kind of preventive maintenance work‐order that is performed. This is not practical in reality and may result in an inaccurate parametric estimation. The research objective of this paper is to develop a maximum likelihood estimation method to obtain more accurately estimated parameters based on the operational data of manufacturing systems, taking into consideration the difference between perfect and imperfect maintenance work‐orders. Weibull distribution is specifically studied for this purpose. A practical case study based on industrial operational data from an automotive assembly line is performed to illustrate the implementation and efficiency of the proposed reliability estimation method. Copyright © 2008 John Wiley & Sons, Ltd.     

改进的Kullback-Leibler复非负矩阵分解语音增强算法

针对单通道非负矩阵分解语音增强算法忽略相位信息的问题,提出了一种改进的Kullback-Leibler复非负矩阵分解的语音增强算法。该算法考虑到传统非负矩阵分解算法在复频域中增强语音时目标函数的影响,构建了一种适用于复频域的Kullback-Leibler散度下的目标函数,同时采用频谱一致性约束相位谱补偿算法,使其重构出的语音数据相位谱得到进一步的调制。实验结果表明,对于不同的非平稳噪声,所提出的算法在不同信噪比下均取得了较好的语音增强效果,尤其在低信噪比条件下（0 dB以下）语音增强效果较为明显,性能评估指标的增量较高,较好地克服了由传统相位谱补偿算法造成的信源失真率较低的缺点,进一步减少失真,抑制背景噪声,实现语音增强。     

采用小波与神经网络的高效图像数据压缩方案

通过构造特别的映射、整函数和BP神经网络,获得一套基于神经网络的无损数据压缩方案。由于该方案能压缩已被小波编码压缩过的数据,因此将其嵌套入一好的小波编码系统就可以获得一种基于小波与神经网络的高效图像数据压缩方案。实验证明,该高效方案对于Lenna图像的压缩比为43∶1, 并且恢复的图像有较好的视觉效果。     

MPEG compression of ultrasound RF channel data for a real-time software-based imaging system

Using software for beamforming in ultrasound systems provides high flexibility, and the large number of computations required in a software-based system can be performed in real time on a PC. However, the very large data transfer rate required from the ultrasound front-end to the PC host for real-time operation is a bottleneck which cannot be overcome without appropriate compression. Previous studies have examined JPEG compression of ultrasound RF channel data, but the schemes do not exploit temporal redundancy between adjacent frames. This study utilized MPEG technology to process the ultrasound RF data to increase the compression efficiency. Our results indicate that MPEG compression generally provides a better compression ratio than does JPEG compression. As an example, the compression ratio of MPEG compression in an 8-bit channel A/D data under 5 μm interframe displacement is smaller than 0.13, thus allowing real-time data transfer requirements to be met. Moreover, the compression efficiency for motions in different directions is shown to be highly dependent on the frame-to-frame correlation.     

Conservative classical and quantum resolution limits for incoherent imaging

Abstract

I propose classical and quantum limits to the statistical resolution of two incoherent optical point sources from the perspective of minimax parameter estimation. Unlike earlier results based on the Cramér-Rao bound (CRB), the limits proposed here, based on the worst-case error criterion and a Bayesian version of the CRB, are valid for any biased or unbiased estimator and obey photon-number scalings that are consistent with the behaviours of actual estimators. These results prove that, from the minimax perspective, the spatial-mode demultiplexing measurement scheme recently proposed by Tsang, Nair, and Lu [Phys. Rev. X 2016, 6 031033.] remains superior to direct imaging for sufficiently high photon numbers.     

Stretch, time lenses, and incoherent time imaging

The stretch, or time-lens, concept is developed further. Alternative formulations that lead to invariant systems are described, as well as methods for synthesizing the time equivalent of spatially and temporally incoherent systems.     

基于稀疏非负矩阵分解的低空声目标识别

借鉴人耳听觉原理和特征学习的优势,提出了梅尔(Mel)频率谱提取和稀疏非负矩阵分解相结合的方法用于低空飞行目标声信号识别。首先,以不同目标的Mel频率谱为特征矩阵,利用稀疏非负矩阵分解方法学习得到各自的模板矩阵;然后,利用按列合并后的模板矩阵对训练/测试样本进行特征分解获得编码系数,该系数可作为分类特征;最后,结合不同目标的特点,采用分频段特征提取和顺序二类分类的方法进行多目标分类,并与Mel频率倒谱系数进行性能比较。结果显示,无论在单类目标辨识还是在多类目标分类中,稀疏非负矩阵分解方法均取得了更好的效果。     

空间变换双靶面成像系统图像配准

针对熔池及熔池前区相连焊缝的双靶面成像系统,采用特征基点标识及基于空间变换的方法,建立双靶面成像系统的图像配准模型。在图像配准模型中应用最小二乘法确定配准模型中的参数,并通过实验证明该方法能够快速、准确地实现图像配准并应用到实际的双靶面成像系统中去,为实现焊接过程中熔池相对焊缝中心偏离量的监测创造条件。     

Modeling and analyzing ghost images for incoherent optical systems

In a previous paper [Proc. SPIEPSISDG0277-786X7428, 742807 (2009)10.1117/12.828564], a methodology was developed to model and analyze incoherent ghosts that are formed by two reflections in the paraxial regime. In this paper, we extend the previously developed methodology to model and analyze ghost images that are formed by N (even) reflections. Rather than dealing with ghosts as spots of light, we apply the concept that each ghost has a structure in the nonparaxial regime that depends on the optical system parameters. A methodology to determine the fourth-order ghost aberration function is developed. We present new key parameters for ghost image formation, namely the ghost sagittal and tangential image surfaces. An expression for the paraxial ghost image irradiance distribution of the point object at the nominal image plane is derived. Since focused ghosts are the most bothersome ghosts, tools are proposed to identify potential problematic ghosts. Simulation examples are provided and are used to validate the developed methodology.