基于小波变换的拼接重叠区域融合方法

为了解决大口径光学元件面形高精度测量问题,建立了拼接测量系统,通过测量得到整体表面面形。在拼接测量过程中,需要将待测面形进行划分,按着一定的顺序进行测量,再根据各个子口径之间的相对位置进行拼接。各个子口径存在重叠部分,采用均化的处理方法会导致高频面形数据的丢失。采用小波变换的拼接重叠区域融合方法可以减少高频数据的丢失。首先,对各个子口径的重叠区域分别进行小波变换得到低频和高频系数矩阵;然后,根据不同的方法对低频和高频系数矩阵进行融合得到新的系数矩阵;最后,通过小波逆变换得到整体面形。对尺寸为120 mm×40 mm的长方形反射镜面形进行拼接干涉测量,并用功率谱密度对本文方法和平均融合结果进行客观比较。实验结果表明,该方法可以保留更多的高频面形数据。     

基于子孔径拼接的Hindle球检测法

为了能够准确获取基于子孔径拼接的Hindle球检测大口径双曲面镜的Hindle球参数,研究了Hindle球检测凸双曲面镜的理论模型,并从几何光学入手,讨论了基于子孔径拼接的Hindle球检测法的系统结构,推导了符合子孔径拼接要求的小口径Hindle球的参数计算式。对一个凸双曲面镜进行了在不同测量环带数目下的基于子孔径拼接的Hindle球检测法和经典Hindle球检测法的Hindle球参数对比。结果表明该Hindle球检测方法使Hindle球参数更合理。     

基于小波框架的红外/可见光图像融合

针对小波框架所具有的冗余性和平移不变性在图像处理中能较好保留图像细节特征的特点,提出了一种将l2上的离散小波框架和交叉子带像素融合方案(Cross band pixel selection)结合起来的融合算法,并用于红外和可见光图像的融合。仿真试验表明该算法较好地保留了源图像的细节信息,是一种行之有效的融合算法。     

基于中值预滤波的航空图像小波去噪算法研究

结合航空图像的噪声来源与图像特性,提出一种基于中值预滤波的图像小波去噪算法.图像首先经中值滤波器进行预滤波,滤除随机的脉冲式噪声,然后对处理后的图像进行小波变换,与给定阈值相比,对可明显判为信号或噪声的系数进行相应处理;对不确定为信号或噪声的系数进行多尺度上的相关性追溯,判别其归属后进行处理.实验结果表明:该方法客观上提高了图像的信噪比,主观上使去噪后的图像纹理分明,能更好地适合人眼的视觉特性,有利于航空图像的分析、判读.     

基于多尺度小波变换的同名点匹配方法研究

针对一类特殊小波变换系数不同尺度下的模极大点能提供在不同尺度下信号急速变化点的位置信息,提出了一种基于小波变换的模极大位置的图像点为匹配基元的同名点匹配方法。该方法采用由粗到细的匹配策略,应用顺序约束,减少了小尺度的小波变换模极大值的位置的图像点的匹配空间,为了避免误匹配和误差传播,舍弃了以小波变换的模极大值比较作为匹配准则,采用了基于米字条形窗口的互相关函数的匹配准则。这种特征匹配与区域匹配相结合的方法,解决了同名点准确匹配难、计算量大等问题。采用该方法对篦冷机内水泥熟料高度进行测量,实验表明该方法能较精确的得出水泥熟料料层的分布状况。     

Aspheric surface measurement based on sub-aperture stitching interferometry

In order to test convex aspheric surfaces without the aid of other null optics, a novel method combined sub-aperture stitching and interferometry called SSI （sub-aperture stitching interferometry） is introduced. In this letter, the theory, basic principle, and flow chart of SSI are researched. A synthetical optimization stitching mode and an effective stitching algorithm are established based on homogeneous coordinate＇s transformation and simultaneous least-squares fitting. The software of SSI is devised, and the prototype for testing of large aspheres by SSI is designed and developed. The experiment is carried out with five sub- apertures for a convex silicon carbide （SIC） aspheric mirror with a clear aperture of 130 ram. The peak-to- valley （PV） and root-mean-square （RMS） error are 0.186 λand 0.019 λ, respectively. For the comparison and validation, the TMA system which contained the convex asphere is tested by interferometry. The wavefront error of the central field of the optical system is 0.068 λRMS which approaches to diffraction limitation. The results conclude that this technique is feasible and accurate. It enables the non-null testing of aspheric surfaces especially for convex aspheres.     

SFCVQ and EZW coding method based on Karhunen-Loeve transformation and integer wavelet transformation

A new hyperspectral image compression method of spectral feature classification vector quantization (SFCVQ) and embedded zero-tree of wavelet (EZW) based on Karhunen-Loeve transformation (KLT) and integer wavelet transformation is represented. In comparison with the other methods, this method not only keeps the characteristics of high compression ratio and easy real-time transmission, but also has the advantage of high computation speed. After lifting based integer wavelet and SFCVQ coding are introduced, a system of nearly lossless compression of hyperspectral images is designed. KLT is used to remove the correlation of spectral redundancy as one-dimensional (1D) linear transform, and SFCVQ coding is applied to enhance compression ratio. The two-dimensional (2D) integer wavelet transformation is adopted for the decorrelation of 2D spatial redundancy. EZW coding method is applied to compress data in wavelet domain. Experimental results show that in comparison with the method of wavelet SFCVQ (WSFCVQ),the method of improved BiBlock zero tree coding (IBBZTC) and the method of feature spectral vector quantization (FSVQ), the peak signal-to-noise ratio (PSNR) of this method can enhance over 9 dB, and the total compression performance is improved greatly.     

基于子孔径拼接原理检测大口径光学元件

 为了实现小口径干涉仪对大口径光学元件的低成本、高分辨力检测,可采用子孔径拼接方法。在对拼接算法进行改进的基础上,开发了拼接检测软件;建立了一套拼接检测系统,开展了大口径平面光学元件的子孔径拼接检测实验研究。利用9个60 mm×60 mm子孔径拼接来检测120 mm×120 mm的光学元件,检测结果表明:峰谷值误差为2.37%,均方根值误差仅为0.27%。     

基于子孔径拼接原理检测大口径光学元件

为了实现小口径干涉仪对大口径光学元件的低成本、高分辨力检测,可采用子孔径拼接方法。在对拼接算法进行改进的基础上,开发了拼接检测软件;建立了一套拼接检测系统,开展了大口径平面光学元件的子孔径拼接检测实验研究。利用9个60 mm×60 mm子孔径拼接来检测120 mm×120 mm的光学元件,检测结果表明:峰谷值误差为2.37%,均方根值误差仅为0.27%。     

Symplectic wavelet transformation

Usually a wavelet transform is based on dilated-translated wavelets. We propose a symplectic-transformed-translated wavelet family psi(*)(r,s)(z-kappa) (r,s are the symplectic transform parameters, |s|(2)-|r|(2)=1, kappa is a translation parameter) generated from the mother wavelet psi and the corresponding wavelet transformation W(psi)f(r,s;kappa)=integral(infinity)(-infinity)(d(2)z/pi)f(z)psi(*)(r,s)(z-kappa). This new transform possesses well-behaved properties and is related to the optical Fresnel transform in quantum mechanical version.     

临界频带子波变换用于混叠语音分离的研究

以反映听觉特性的临界频带子波变换为工具,对混叠语音进行了分析,提出了一种基于临界频带子波变换的混叠语音源信号基音分离和检测方法,在此基础上利用数字多谐振荡器的选频特性,有效地获取构成混叠语音的每个语音信号的各谐波分量,以此实现从混叠语音中分离出各源信号。实验结果表明混叠语音分离方法是可行有效的。     

基于小波变换和图论方法识别乳腺微钙化点簇

成簇的微钙化点是早期乳腺癌的一个重要表征,用计算机辅助诊断时需要在乳腺片图像中判断有无钙化点簇。提出了一种利用Daubechies小波对乳腺图像进行增强,用二维熵阈值分割法对增强后的图像进行阈值分割,然后采用图论方法提取出成簇钙化点的方法。从而实现了计算机辅助诊断系统辅助医师判断恶性钙化。     

基于子孔径拼接的衍射干涉靶丸形貌检测技术

为实现惯性约束聚变实验中核心部件球形靶丸表面形貌的高精度、高效率、无遗漏检测,建立了基于子孔径拼接和衍射干涉技术相结合的靶丸形貌测量装置,给出了测量的基本原理及系统单孔径横向分辨率的计算方法,并对靶丸旋转扫描时子孔径的排布进行了划分。针对点云数据横向间隔过大导致匹配算法迭代收敛速度缓慢,甚至不收敛的问题,提出以虚拟的极小半径代替实际曲率半径,将点云进行横向压缩的方法,在保持形貌特征不变的同时提高算法的匹配速度和准确性。最后,对直径1 mm的镀金球靶进行了实际测量,得到拼接后相对形貌误差峰谷值和均方根值分别为1.332和0.479的检测结果,可以同时获得表面形貌的整体起伏特征,以及局部的形貌细节。     

基于子孔径拼接的衍射干涉靶丸形貌检测技术

为实现惯性约束聚变实验中核心部件球形靶丸表面形貌的高精度、高效率、无遗漏检测,建立了基于子孔径拼接和衍射干涉技术相结合的靶丸形貌测量装置,给出了测量的基本原理及系统单孔径横向分辨率的计算方法,并对靶丸旋转扫描时子孔径的排布进行了划分。针对点云数据横向间隔过大导致匹配算法迭代收敛速度缓慢,甚至不收敛的问题,提出以虚拟的极小半径代替实际曲率半径,将点云进行横向压缩的方法,在保持形貌特征不变的同时提高算法的匹配速度和准确性。最后,对直径1 mm的镀金球靶进行了实际测量,得到拼接后相对形貌误差峰谷值和均方根值分别为1.332和0.479的检测结果,可以同时获得表面形貌的整体起伏特征,以及局部的形貌细节。     

Entangled symplectic wavelet transformation

The symplectic wavelet transformation proposed in Opt. Lett. 31, 3432 (2006), which is related to the optical Fresnel transform in the quantum optics version, is developed into an entangled symplectic wavelet transformation (ESWT) after pointing out the contrast between the single-mode Fresnel operator and the entangled Fresnel operator. The ESWT possesses well-behaved properties and corresponds to the entangled Fresnel transform [Phys. Lett. A334, 132 (2005)].     

Laser ultrasonic propagation imaging method in the frequency domain based on wavelet transformation

A wavelet-transformed ultrasonic propagation imaging method capable of ultrasonic propagation imaging in the frequency domain was developed and applied as a new structural damage or flaw visualization algorithm. Since the wavelet-transformed ultrasonic propagation imaging method has strong frequency selectivity, it can visualize the propagation of ultrasonic waves of a specific frequency (for example, to isolate ultrasonic mode of interest and a damage-related ultrasonic wave). The strong frequency selectivity of the wavelet-transformed ultrasonic propagation imaging method was demonstrated, isolating only the zeroth-order asymmetrical mode of the fundamental Lamb wave modes in an anisotropic carbon fiber-reinforced plastic plate with a thickness of 5 mm. The wavelet-transformed ultrasonic propagation imaging method can also convert a complex time domain multiple wavefield into a simple frequency domain single wavefield. This feature enables easy interpretation of the results, and facilitates the precise evaluation of the location and size of structural damage or flaws. We demonstrated this capability by detecting a disbond in a sandwich structure made of Al-alloy skins and a foam core. A disbond with a diameter of 20 mm, which is representative of a common manufacturing flaw, was successfully detected, localized, and evaluated. Since a method to determine the allowable maximum pulse repetition frequency depending on target materials and structures was found by investigating the residual wave caused from the previous laser impinging, our laser ultrasonic system can scan rapidly the target with an optimal pulse repetition rate. In addition, the proposed wavelet-transformed ultrasonic propagation imaging method can visualize damage or flaw without the need for reference data from the intact state of the structure. Hence, we propose the wavelet-transformed ultrasonic propagation imaging approach for automatic inspection of in-service engineering structures, or in-process quality inspection in manufacturing.     

子孔径拼接技术应用的研究

大口径光学元件的检测开拓了子孔径拼接应用的新领域。采用小口径干涉仪对大口径被测元件不同区域进行波前检测,然后恢复计算出被测波前。使用光学设计软件ZEMAX对子孔径检测拼接技术进行了模拟,模拟结果表明：波前检测相对误差小于4.3λ‰,实现了对大口径光学元件面形的高精度检测,避免了相同口径检测干涉仪的使用,降低了检测成本及难度。     

基于小波分解的医学显微图像融合

提出了基于小波分解的医学显微图像融合。通过先将图像进行小波分解,并对小波分解后的不同频率域分别进行了讨论,即分别讨论了选择高频系数和低频系数的原则。选择低频系数时,设计了两种选择方案,即区域能量法和边缘选择法。选择高频系数时,设计了两种选择方案,即区域能量法和目标清晰与模糊判据法。最后选择了在低频系数时采用边缘选择法,在高频系数时采用目标清晰与模糊判据法。从仿真结果的比较来看,在将多个目标聚焦图像融合后,图像能很好地保留多幅原来图像清晰部分的信息,融合后,提高了整幅图像的信噪比,从而获得了整幅高清晰图像。     

On the wavelet transformation of fractal objects

The wavelet transformation is briefly presented. It is shown how the analysis of the local scaling behavior of fractals can be transformed into the investigation of the scaling behavior of analytic functions over the half-plane near the boundary of its domain of analyticity. As an example, a Weierstrass-like fractal function is considered, for which the wavelet transform is related to a Jacobi theta function. Some of the scalings of this theta function are analyzed, and give some information about the scaling behavior of this fractal.     

Color image encoding using fractional Fourier transformation associated with wavelet transformation

Color image encoding and decoding using fractional Fourier transformation (FRFT) associated with wavelet transformation (WT) are proposed in this paper, which is calculated using discrete fractional Fourier transformation and discrete wavelet transformation. A new method for color image encoding and decoding is given. Some examples of computer simulation results are proposed and verified.