红外光谱信号的预处理

介绍了一种对光谱信号进行预处理的高低通综合滤波法，它对高频噪声和低频扰动分别采用不同的措施进行处理，高频噪声采取平滑滤波法进行去除，低频扰动采取低通数字滤波器进行去除，试验结果表明，这样做既去除了高频噪声和低频扰动，同时又保留了光谱的细节部分，最后，文中将高低通滤波法和带通滤波法的处理结果进行了比较。     

宽带信号的中频正交采样

在回顾并对比低通滤波法、插值法和多相滤波法三种中频正交采样方法的基础上,研究它们在宽带信号情况下的适用性,讨论宽带信号的中频正交采样方法及其工程实现,并进行计算机仿真。结果表明,低通滤波法更适合于宽带信号的中频正交化处理。     

多相滤波法和低通滤波法实现正交插值的比较

正交插值可以由低通滤波法和多相滤波法来实现,文中从实现方式、采样率、滤波器方面进行了比较,使用matlab对两种方法进行了仿真分析,并在分析的基础上分别使用Xilinx公司的Virtex4 FPGA实现了两种结构.通过比较得出,多相滤波法相对于低通滤波法有很多优点:结构简单、资源占用少且易于实现.     

基于多相滤波原理的数字正交采样技术

针对传统正交采样方法存在运算数据量大,镜频抑制比小及硬件实现资源消耗大等方面的不足,分析了一种基于多相滤波结构的数字正交采样方法.首先对多相滤波法实现数字正交变换的原理进行了分析,然后根据多速率信号处理理论推导并给出了基于多相滤波结构的子滤波器的实现方法,最后,通过仿真验证了该方法的有效性.实验结果表明该方法较之传统的低通滤波法有很大的优越性.     

一种脉冲激光雷达回波信号自适应处理

对均匀大气脉冲激光散射回波信号降噪方法进行研究。对回波信号频谱进行分析,并对低通滤波与自适应滤波对激光雷达信号处理效果进行对比,采用信噪比这一指标对信号的处理效果进行评估。     

基于组合积分系统的滤波

在信号分析与处理中,为获取信号中反映其特征的有用成分,常采用滤波方法去掉干扰成分。针对在工业控制领域数据分析与处理问题,提出基于组合积分系统滤波算法。分析数字滤波器滤波原理,由组合积分环节均值滤波本质,设计组合积分系统滤波算法,实现低通、高通、带通滤波的功能。利用Simulink建模仿真,实验结果表明,该设计效果良好,表明所提方法的可行性及有效性。     

数字合成莫尔条纹的频谱分析与滤波处理

莫尔轮廓术是实现物体三维面形测量的主要方法之一,它基于莫尔条纹产生和分析技术。莫尔条纹产生方法主要有阴影法、投影法和数字合成法三种。对于数字合成法,目前通常采用低通滤波提取莫尔条纹,低频区域含有许多无用频率成分,会降低所提取的莫尔条纹的质量。通过分析参考条纹图像和变形条纹图像经相乘、相加、相减运算结果图像的频谱,比较不同滤波处理方法对提取莫尔条纹的影响,提出一种采用带通滤波提取莫尔条纹的新方法。与低通滤波相比,带通滤波可以产生衬比度更高的强度分布为标准余弦分布的莫尔条纹;此外,相加和相减运算产生的莫尔条纹之间相位相差p,明暗反转。计算机模拟和实际实验均验证了上述分析结论的正确性和该方法的有效性与可行性。     

生物视觉同时对比机制在高通滤波中的应用

本文首先比较了生物视觉同时对比现象与各向异性高通滤波之间的相似性,再对各向异性高通滤波器方向与边缘方向之间的夹角和滤波效果之间关系进行了研究,从而提出了一种基于角度搜索的各向异性高通滤波方案,并从实现方式和滤波效果实验等两个方面将该方案与采用灰度梯度方向估计的滤波方案进行了比较。实验表明,采用灰度梯度方向估计的边缘方向与实际边缘方向尚存在较大的差距,这将直接导致高通滤波效果的下降;而新的滤波方案却能大大地改善高通滤波效果。根据角度搜索时所设定的搜索精度大小,该滤波方案将具有不同的工程应用价值。     

基于MOCCII多功能二阶电流模式滤波器设计

文中提出了一种基于M OCC II(多端输出第二代电流传输器)的单输入三输出二阶滤波器电路模型,由该模型可得出几种不同的滤波器电路,每种滤波器电路都由四个M OCC II、两个接地电容和电阻组成。不但能同时实现二阶高通滤波、低通滤波和带通滤波功能,还可以通过对输出端的直接组合,实现带阻和全通滤波功能及其他任意形式的二阶信号传输功能。滤波器的角频率和品质因数独立可调,应用非常灵活。与同类滤波电路相比较,该电路不但结构简单,而且使用灵活,有利于集成。同时,对其中一种滤波器的滤波特性进行了测试,实验结果表明,滤波器的滤波性能良好,电路模型完全正确。     

基于MOCCⅡ多功能二阶电流模式滤波器设计

文中提出了一种基于MOCCⅡ(多端输出第二代电流传输器)的单输入三输出二阶滤波器电路模型,由该模型可得出几种不同的滤波器电路,每种滤波器电路都由四个MOCCⅡ、两个接地电容和电阻组成.不但能同时实现二阶高通滤波、低通滤波和带通滤波功能,还可以通过对输出端的直接组合,实现带阻和全通滤波功能及其他任意形式的二阶信号传输功能.滤波器的角频率和品质因数独立可调,应用非常灵活.与同类滤波电路相比较,该电路不但结构简单,而且使用灵活,有利于集成.同时,对其中一种滤波器的滤波特性进行了测试,实验结果表明,滤波器的滤波性能良好,电路模型完全正确.     

DOAS技术中光学密度计算方法对测量结果的影响

差分光学吸收光谱技术(DOAS)中,通过不同高通滤波方法获得差分光学密度,与经过相同数字滤波处理的实验室的标准参考谱作最小二乘拟合,反演出各种气体的浓度.通过几种平滑滤波和多项式滤波对相同测量信号进行光谱分析,比较其反演浓度的精度、残差的标准方差和峰峰值.结果表明,3点500次平滑滤波重复两次的高通滤波方法各项指标都优于其它方法,能有效地提高测量精确度和降低检测下限.     

基于疑似目标区域提取的空间图像降噪

对于空间目标图像的降噪预处理,要求能够完整地保留目标的边缘同时保证目标内部灰度分布不变,直接利用传统降噪增强方法难以取得理想效果.针对空间目标可见光图像,分析可能引入的噪声种类及其特性,提出了一种通过提取疑似目标区域达到降噪目的的方法.该方法首先使用SUSAN滤波结合频域分析、背景杂波抑制获得目标区域,然后从原始图像中提取出没有背景噪声的图像,从而实现图像的降噪.为了验证降噪效果,从整体视觉效果、局部星点视觉效果和信噪比三方面,与中值滤波、低通滤波、小波变换方法处理结果进行比较,实验结果显示,该方法在去除背景噪声的同时,能够更好地保留目标的边缘和内部灰度分布.     

An asymmetric post-processing for correspondence problem

This paper presents a novel approach that performs post-processing for stereo matching. We improve the performance of stereo matching by performing consistency check and adaptive filtering in an iterative filtering scheme. The consistency check is only done with asymmetric information so that very few additional computational loads are necessary. The information in the valid pixels is propagated into invalid pixels through the adaptive filtering. The proposed post-filtering method can be used in various methods for stereo matching. We demonstrate the validity of the proposed method by applying it to hierarchical belief propagation and semi-global matching. The performance of the post-processing method for hierarchical belief propagation is comparable to state-of-the-art methods in the Middlebury stereo datasets. In order to verify the performance of asymmetric consistency check, we compare it with other reliability estimation methods in the proposed post-processing scheme. Moreover, in order to verify the performance of post-filtering method in noisy environment, the proposed post-filtering method is applied to the stereo images denoised by NL-means algorithm. We find that the iterative filtering scheme reduce an error which may be caused in stereo matching for the denoised images and improve the performance of stereo matching.     

可见光目标检测中图像增强方法研究

文中对目前常用的图像增强技术进行了研究,首先对目标图像特性进行了分析,介绍了常用的滤波方法,包括中值滤波、高通滤波和winner滤波等方法,用这些方法对给定的图像进行了滤波;接着提出了一种和最大值滤波的图像增强方法,也用该方法对给定的图像进行了滤波,并比较了各种方法处理图像中对目标信噪比的改善情况,给出了相应的结果,结果表明和最大值滤波要优于其他的方法。     

A cost-effective VLSI architecture for anisotropic texture filtering in limited memory bandwidth

Texture mapping is one of the techniques that express realism in three-dimensional (3-D) graphics. To produce high-quality images, various anisotropic filtering methods have been proposed for texture mapping. These methods require more texels than isotropic (trilinear) filtering method. In spite of increases to texture memory bandwidth, however, texture memory bandwidth is still a bottleneck of texture-filtering hardware. Consequently, an exact filtering method is required for good-quality images in a limited texture memory bandwidth. In this paper, we propose anisotropic texture filtering based on edge functions. Our method proposes an exact footprint-shape approximation with edge functions for generating weights. For real-time filtering, the weight plays a key role in effective filtering of the restricted texels loaded from memory. The normalized value of the edge function gives the distance relative to the contribution of texels to a final intensity. Calculating a Gaussian filter using this normalized value, generates a good weight. The quality of rendered images is superior to other anisotropic filtering methods with the same restricted number of texels. For images of the same quality, our method requires less than half the texels of other methods. Consequently, the improvement in performance is more than twice that of other methods. With low hardware overheads, our method can be implemented at a reasonable cost. In practice, the algorithm is demonstrated through VLSI implementation. The hardware, which is described by verilog and synthesized with a 0.35-/spl mu/m 3.3-V standard cell library, is operated at 100 MHz and it generates 100 M texture-filtered RGB pixel-color values per second.     

一种针对不良主题的文本过滤方法

针对不良文本的过滤问题,文章提出了一种基于SVM分类器改进的文本过滤方法。该方法将传统的基于词语的分类方法改为基于词语元组的分类,增强了特征项的分辨率,实验表明该方法同传统的过滤方法相比具有较高的准确率和召回率。     

一种基于小波和Wiener相结合图像去噪新方法

本文提出了一种新的小波变换和维纳滤波相结合的图像滤波方法.该滤波方法首先使用小波变换,将图像信号从时域变换到频域,结合新的wiener方法对图像的高低频结果进行滤波处理。改进的自适应Wiener滤波器可以根据图像特性,在给定的多个模板间对图像进行自适应模板选择,使得滤波效果更加理想。实验结果表明,本文提出的方法比传统的维纳滤波和小波阈值去噪方法有较大的改善。     

Detection and extraction of periodic noises in audio and biomedical signals using Kalman filter

This paper studies the subject of adaptive noise cancelation using the Kalman filtering technique to achieve high precision and fast convergence. It is shown that the Kalman filter can successfully be designed to detect and extract periodic noises which may be constituted of different sinusoidal components with possibly unknown and/or time-varying frequencies. This highlights the feature of Kalman filter in synthesizing periodic noises in the time-domain which is not possible using Fourier-based methods such as DFT. Usefulness of the method is discussed in the context of two examples: active cancelation of periodic noises from audio waveforms and filtering of electrocardiogram measurements.     

基于×字形窗口的自适应中值滤波算法

传统的中值滤波方法在去除脉冲噪声的同时会损失部分图像细节,且运行速度也不能很好地满足实时性要求。在此对Matlab工具箱中的中值滤波算法进行改进,提出一种基于×字形滤波窗口的自适应中值滤波算法。该方法具有根据3×3的×字形窗口中噪声点个数自适应调整滤波窗口大小及根据矩阵的对称性及基本的逻辑运算实现×字形窗口的特点。实验结果表明,与传统的方形窗口中值滤波算法相比,该方法在有效去除椒盐噪声和脉冲噪声的同时,较好地保持了图像细节,缩短了运行时间。     

Combining the discrete wavelet transform and mixed-domain filtering

A novel filtering method is proposed that combines the discrete orthogonal wavelet transform (DWT) with the mixed-domain (mixed-D) filtering method. The method uses the DWT to pre- and postprocess those dimensions of the signal that are transformed to the discrete-frequency domain by mixed-D filtering. Using the DWT in this manner provides a controlled mechanism to partition the spectrum of the input signal into subband signals, which then may be selectively filtered during the linear difference equation (LDE) step of the mixed-D algorithm. It is shown that, when the DWT is computed using filters with ideal high- and lowpass frequency responses, the LDE filters used in the mixed-D filtering stage are unchanged by the introduction of the DWT (although the frequency tuple associated with each LDE filter is altered). This indicates that the mixed-D filtering scheme can be easily used in subband coding systems. Results are given for the filtering of a three-dimensional (3-D) linear trajectory signal, representing a common application in video processing.