基于小波变换的图像混合噪声自适应滤除算法

为同时滤除图像中的椒盐噪声和高斯噪声,提出了一种基于小波变换的混合噪声自适应滤除算法,该算法首先采用中值滤波去除椒盐噪声,然后借助边缘检测算子区将图像为分边缘与非边缘区域,进一步对非边缘区域引入改进的均值滤波器,有效削弱高斯噪声的同时保护图像边缘细节,既初步削弱高斯噪声又保护了边缘,最后采用改进的小波阈值滤波算法,对不同的小波系数采用不同的阈值函数,通过线性回归得到各最优阈值关系式。实验结果表明,该混合噪声自适应滤除算法能有效滤除椒盐噪声和高斯噪声,在图像主观质量和客观质量上均取得了较好的效果,能提高去噪图像峰值信噪比0.5~2.0 dB。     

非线性时间序列的小波分频预测

基于噪声的小波变换特点，结合小波包分解和模极大重构来抽取含噪信号的主分量，提出了一种基于最佳尺度分解和Volterra自适应滤波的分频预测算法，使用较少的模型训练样本，同时具有强的抗噪能力.该算法克服了传统小波分解尺度选取的盲目性及单纯Volterra预测器抗噪性能的不足，数值仿真表明，针对含强噪声的非线性信号可进行有效预测. 关键词： 小波分解 Volterra自适应滤波器 分频预测     

相干激光雷达图像散斑噪声抑制算法

提出了一种新的用于散斑噪声抑制的非线性加权均值多方向形态滤波算法。运用此算法和先前提出的散斑噪声抑制算法以及小波软阈值算法和Lee滤波算法一并对相干激光雷达图像进行了噪声抑制处理，并且对处理的结果进行了比较，证明了本算法的进步，即在不降低噪声抑制能力的前提下，较好地保持了图像边缘。     

一种新的叠栅层析迭代算法

利用叠栅层析具有的测量动态范围大,对震动环境不敏感的特点,从其偏折原理的本质出发,提出一种利用代数迭代法来重建三维流场的叠栅层析重建算法。在此基础上进行了双峰函数的模拟实验,分别进行了6方向,12方向以及叠加高斯噪声的12方向的数值重建,并在相同条件下与滤波反投影方法和对偏折投影数据积分的代数迭代算法这两种已有的叠栅层析重建算法进行了比较,同时用该新算法结合属性矩阵对包含遮挡物的模拟场进行重建。对比重建结果,本算法具有较强的抗噪声能力,并且对非完全数据下的层析重建也有较好的处理效果。     

软门限去噪法在X射线能谱分析中的应用

从函数空间的剖分和理想滤波器组的角度分析了多分辨率信号的分解与重构，提出了一种X射线能谱去噪的方法，即应用Mallat算法对谱信号进行小波分解，然后应用一个非线性软门限函数在小波域内将噪声抑制和消除，最后重构得到去噪后的能谱。该方法明显改善了能谱定量分析的结果。     

偏折层析的滤波反投影算法及误差分析

对偏折层析投影转换为相位层析投影的转换关系进行了分析,给出明晰的数学关系,并针对偏折层析的滤波反投影算法重建的结果进行误差分析。分析结果表明投影噪声对重建场的作用体现在与由偏折层析滤波反投影算法的滤波器有关的倾斜函数上。因此提出了改进的偏折层析滤波反投影算法,数值模拟表明,改进算法在有效抑制倾斜现象的同时,对重建结果不会造成明显的失真。在此基础上改进的算法被用于真实火箭燃气射流密度场的三维重建中。     

基于FPGA的实时中值滤波器设计

在图像生成和采集过程中引入的各种噪声会使图像质量变差。为了实现对图像的实时预处理，首先介绍中值滤波器的基本原理和算法，然后在现场可编程门阵列（FPGA）上根据中值滤波的根基数算法，采用流水技术设计一种快速实时中值滤波器，给出按行输出的图像处理过程中存储前2行图像数据的方法。仿真结果表明：该中值滤波器可实时完成CCD输出图像的预处理，达到了抑制噪声及保持图像细节的目的。     

闪光照相CCD图像的自适应中值滤波方法

中值滤波是一种在去除噪声的同时能较好地保护图像边缘细节的非线性图像处理方法。为了滤除闪光照相CCD图像中的脉冲噪声，同时能更好地保护图像边缘，提出了一种改进的自适应中值滤波方法。该方法采用局部中值和局部方差作为判断噪声点的阈值，实现了局部自适应的中值滤波，克服了传统自适应中值滤波方法的缺点，对椒盐噪声和随机脉冲噪声均有较好的滤波效果。实验结果表明，该方法消除图像脉冲噪声十分有效，对闪光照相CCD图像的处理结果也较好。     

航空飞机计算机通信中滤波器的优化设计

航空飞机计算机通信系统进行通信的过程中,由于航空飞机上的电子设备相互之间的电磁干扰严重,导致信道中存在大量的干扰信号。提出基于小波变换算法的抗干扰滤波器设计方法。根据小波变换算法相关原理,综合航空飞机通信中特有的软阀值特点,利用自适应调整参数的方法得到高空通信中的最优小波系数阀值,使得高空噪声过滤阀值函数具有更强的适应性。利用新的阀值函数设计了新的滤波器,对行滤波模块和列滤波模块的设计进行了详细阐述。实验结果表明。利用设计的滤波器能够对航空飞机计算机通信过程中的干扰信号进行有效滤波,缩短了滤波时间,提高了高空通信系统的抗干扰能力。     

互补型自适应滤波器在心磁信号处理中的应用

将心磁信号从干扰噪声中加以提取并有效地消除噪声干扰是心磁信号处理中尤为重要的环节 .从改进算法的角度出发，提出互补型自适应滤波器结构以实现心磁信号的消噪处理.该滤波器针对心磁这类非平稳信号进行设计，有效地解决了常规自适应滤波器应用于心磁信号处理时收敛速度和稳态误差的矛盾.通过仿真实验和心磁实验结果表明，该算法能有效地消除心磁信号的背景噪声和工频干扰噪声.同时该算法也可用于其他非平稳信号的消噪处理. 关键词： 自适应滤波 心磁图 最小均方误差     

Decision-based adaptive morphological filter for fixed-value impulse noise removal

A novel adaptive switching morphological filter for removing fixed-value impulse noise is proposed. The proposed filter firstly identifies noise pixels using the two-stage morphological noise detector, in which the initial noise detection is used to identify the noise candidates based on the morphological gradients and the refined noise detection based on the combined conditional morphological operators is adopted to further classify the noise candidates as the noise pixels or noise-free pixels. Then the detected noise pixels are removed by the adaptive morphological filter using the conditional rank-order morphological operators while the noise-free pixels are left unaltered. Extensive simulations show that the proposed filter outperforms a number of existing switching-based filters because of its excellent performance in terms of noise detection and image restoration.     

Design of a Composite Wavelet Matched Filter Using Breeder Genetic Algorithm

We outline a method to design a composite wavelet matched filter using the breeder genetic algorithm. The composite filter consists of a linear combination of wavelet and matched filters. Breeder genetic algorithm has been used to find the optimal weighting coefficients for the wavelet and the matched filters that constitute the composite filter. For the breeder genetic algorithm, the geometric mean has been used as the crossover operator and the creep has been used as the mutation operator. The performance of the filter is tested in the presence of additive white Gaussian noise. The performance of the composite wavelet matched filter has also been compared with that of the phase only filter and the classical matched filter. The designed filter can be used in an optical correlator to separate two classes of input images for fingerprint-based user identification in security systems.     

Image pre-filtering for measurement error reduction in digital image correlation

In digital image correlation, the sub-pixel intensity interpolation causes a systematic error in the measured displacements. The error increases toward high-frequency component of the speckle pattern. In practice, a captured image is usually corrupted by additive white noise. The noise introduces additional energy in the high frequencies and therefore raises the systematic error. Meanwhile, the noise also elevates the random error which increases with the noise power. In order to reduce the systematic error and the random error of the measurements, we apply a pre-filtering to the images prior to the correlation so that the high-frequency contents are suppressed. Two spatial-domain filters (binomial and Gaussian) and two frequency-domain filters (Butterworth and Wiener) are tested on speckle images undergoing both simulated and real-world translations. By evaluating the errors of the various combinations of speckle patterns, interpolators, noise levels, and filter configurations, we come to the following conclusions. All the four filters are able to reduce the systematic error. Meanwhile, the random error can also be reduced if the signal power is mainly distributed around DC. For high-frequency speckle patterns, the low-pass filters (binomial, Gaussian and Butterworth) slightly increase the random error and Butterworth filter produces the lowest random error among them. By using Wiener filter with over-estimated noise power, the random error can be reduced but the resultant systematic error is higher than that of low-pass filters. In general, Butterworth filter is recommended for error reduction due to its flexibility of passband selection and maximal preservation of the allowed frequencies. Binomial filter enables efficient implementation and thus becomes a good option if computational cost is a critical issue. While used together with pre-filtering, B-spline interpolator produces lower systematic error than bicubic interpolator and similar level of the random error. Cubic B-spline interpolator can achieve comparable efficiency as bicubic interpolator, while quintic B-spline interpolator requires about 1.5 times the running time.     

带缓冲层的导模共振滤光片反射光谱特性

将均质多层膜系设计中的缓冲层概念引入到反射导模共振滤光片的设计中,以研究缓冲层的增加对导模共振滤光片反射光谱特性的影响.设计并通过严格的耦合波理论计算了一、二、三、四通道导模共振反射滤光片光谱特性.在膜系设计中增加缓冲层后.随着其厚度的逐渐增加.反射光谱中依次出现二、三、四个窄带反射峰;缓冲层厚度为796.35 nm时.当滤光片光栅层占空比在0.2～O.9范围内、光栅深度在100～200 nm变化时,共振峰的位置、反射率峰值高度几乎不变,保持了很好的多通道滤光片特性.     

自适应中值-加权均值混合滤波器

为了去除图像中混入的脉冲噪声和高斯噪声,提出了一种基于自适应中值滤波和自适应加权均值滤波的混合滤波方法。该方法先将图像分为若干区域,并对每个区域进行噪声检测以实现两类噪声的分离,然后再分别采用自适应中值滤波和自适应加权均值滤波将分离出的脉冲噪声和高斯噪声去除。对这种新方法进行了计算机模拟实验。结果表明:新方法较前人提及的三种混合滤波方法具有更优的滤波性能,在有效抑制混合噪声的同时能很好地保护图像中的细节,为消除图像中的混合噪声提供了一种有效的途径。     

Comparative study of pattern correlation using Mexican hat and Coiflet wavelet-based filtering

In this work, a numerical study on the pattern correlation using wavelet filters is reported. A comparative study of the correlation using the Mexican hat and Coiflets filters is presented. A Coiflet filter acts not only as a band-pass filter but as a high-pass or low-pass filter. Therefore, unlike the Mexican hat-based filter which acts only as a pass-band filter, the Coiflet-based filters allow selecting horizontal, vertical or diagonals details of the original image. Each one of the original images can be discomposed in an average image and several detail images at different levels of multiresolution. We study the numerical correlation between binary patterns using the Mexican hat filter and the first and second multiresolution level obtained by Coiflet filtering. Additionally, an analysis about the noise immunity for the Mexican hat and Coiflet filters is realized. The results show that Coiflet filters are better to identify special characteristics but perform the worst when they are used with noisy images. On the other side, the Mexican filter presents a better noise immunity but performs the worst when is used to compare special characteristics.     

波前功率谱密度(PSD)测量滤波器的设计

在采用波前功率谱密度评价大口径光学元件时，由于测得的原始数据受到测量系统引入的各种噪音和外界干扰的作用，会使检测准确度下降.对比引入带通滤波技术，对原始数据的有效滤波，减小带外的噪音分量和频谱混叠现象的影响.分别设计了无限脉冲响应带通滤波器和有限脉冲响应带通滤波器，通过模拟分析比较了两者的性能，得出在波前波前功率谱密度用于评价大口径光学元件的面形质量时，采用有限脉冲响应滤波器可以得到更高的测量准确度.     

Measurement of X-ray for the dose area product and spectrum by the added filtration in Rando phantom

The most important point in the medical use of radiation is to minimize the patient entrance dose while maintaining the diagnostic information. Low-energy photons (long-wave X-ray) are unnecessary among diagnostic X-ray because they are mostly absorbed and increase the patient's entrance dose. The most effective method to eliminate the low-energy photon is use of a filtering plate. Using a filter appropriate for the image will maintain diagnostic value. Obtaining an effective image allows comparison of the resulting images in a logical objective way. This experiment was performed to determine the quality of image dosimeter when there is no filter, and when 2 mm Al, 0.1 mm Cu + 1 mm Al, 0.2 mm Cu + 1 mm Al filters are used. Using TORECK PD-8100 dose area products meter placed on top of an abdominal phantom, we measured the dose when the filter changes in this condition 85 kVp, 40 mAs, anode angle 13, source image distance 100 cm, 20 cm × 20 cm. We used the SRS-78 program for accurate comparison because we could not evaluate the difference in the image optically. The spectrum changed due to the emission of X-rays as the filter changed. We observed that the use of a filter eliminated the low-energy photons and revealed continuous X-ray and special X-ray. Therefore, the experiment highlighted the advantages of filters and confirmed that there are no changes in the quality of image through signal to noise ratio, peak signal to noise ratio, root mean square error comparison. We found that the use of filter did not lead to distortions in the image or drop in diagnostic value while minimizing the radiation dose. This means that it can help manage long-term patient dose. We conclude that we need to recommend the use of the filter as it reduces the area of dose.     

基于运动补偿的红外图像噪音时域IIR滤波算法

从模式识别的角度出发将图像分为运动区域和非运动区域,采用基于噪音分布模型的运动检测技术与基于概率松弛法的运动区域标号技术相结合对这两种区域进行具体划分,对分类后的图像采用时域IIR滤波,不同区域采用不同的影响因子,以期达到最终的运动补偿.仿真结果表明该方法有效抑制了噪音,同时并未引起明显的运动模糊,图像的视觉效果得到了极大改善.     

中波红外8通道微型集成滤光片的研制

利用组合刻蚀法布里珀罗（F－P）干涉滤光片的谐振腔间隔层的方法,制备了集成在一个基片上的8通道中波红外（λ₀=2.8 μm）窄带滤光片,通道线宽为0.7 mm,光谱通道定位精度优于1%,各通道相对半峰宽为1%,此法有效提高了成品率,并可满足实现通道数更多,集成度更高的滤光器件发展的需求,