Lnear Phase FIR Filter on Measuring 3—D Surface

An optical technology for 3-D surface measurement is se up.The technology,based on a deformed projected grating pattern which carries the 3-D information of the measured object,can automatically and accurately obtain the phase map of a measured object by using a linear-phase FIR filter.In contrast to the 2-D fast Fourier transform technique,it‘s more than fast.Only one image pattern is sufficient for measuring .The phase map can be processed without assigning fringe orders and making distinction between a depression and an elevation.Theoretical analysis and experimental result are presented.     

Multi-spectral and hyperspectral image fusion using 3-D wavelet transform

Image fusion is performed between one band of multi-spectral image and two bands of hyperspectral image to produce fused image with the same spatial resolution as source multi-spectral image and the same spectral resolution as source hyperspeetral image. According to the characteristics and 3-Dimensional （3-D） feature analysis of multi-spectral and hyperspectral image data volume, the new fusion approach using 3-D wavelet based method is proposed. This approach is composed of four major procedures： Spatial and spectral resampling, 3-D wavelet transform, wavelet coefficient integration and 3-D inverse wavelet transform. Especially, a novel method, Ratio Image Based Spectral Resampling （RIBSR）method, is proposed to accomplish data resampling in spectral domain by utilizing the property of ratio image. And a new fusion rule, Average and Substitution （A＆S） rule, is employed as the fusion rule to accomplish wavelet coefficient integration. Experimental results illustrate that the fusion approach using 3-D wavelet transform can utilize both spatial and spectral characteristics of source images more adequately and produce fused image with higher quality and fewer artifacts than fusion approach using 2-D wavelet transform. It is also revealed that RIBSR method is capable of interpolating the missing data more effectively and correctly, and A＆S rule can integrate coefficients of source images in 3-D wavelet domain to preserve both spatial and spectral features of source images more properly.     

An improved radial basis function based method for image warping

A new image warping method is proposed in this letter, which can warp a given image by some manual defined features. Based on the radial basis interpolation function algorithm, the proposed method can transform the original optimized problem into nonsingular linear problem by adding one-order term and affine differentiable condition. This linear system can get the steady unique solution by choosing suitable kernel function. Furthermore, the proposed method demonstrates how to set up the radial basis function in the target image so as to achieve supports to adopt the backward re-sampling technology accordingly which could gain the very slippery warping image. The experimental result shows that the proposed method can implement smooth and gradual image warping with multi-anchor points‘ accurate interpolation.     

Geometrically invariant watermarking based on radon transformation

The weakness of classical watermarking methods is the vulnerability to geometrical distortions that widely occur during normal use of the media. In this letter, a new imagewatermarking method is presented to resist Rotation, Scale and Translation (RST) attacks. The watermark is embedded into a domain obtained by taking Radon transform of a circular area selected from the original image, and then extracting Two-Dimensional (2-D) Fourier magnitude of the Radon transformed image. Furthermore, to prevent the watermarked image from degrading due to inverse Radon transform, watermark signal is inversely Radon transformed individually.Experimental results demonstrate that the proposed scheme is able to withstand a variety of attacks including common geometric attacks.     

A visual model weighted cosine transform for hiding watermark in images

Watermarking is a technique for labeling digital pictures by hiding secret information into images. Watermark embedding is a method to discourage unauthorized copying and identify the owner or distributor of digital data. In this paper, a new method is proposed. The watermark is processed as a visually recognizable pattern-binary image, which includes more information than the traditional symbol or ID number and is "extracted" instead of only "detected" to characterize the owner. The watermark is hidden in the host image by selectively modifying the middle-frequency part of the host image in conjunction with the human visual system(HVS) and the image discrete cosine transform(DCT). The experimental results show that this method can survive image cropping and image compression, and get better results, this is also a prospective method.     

Subpixel Target Location Techniques for 3—D Coordinate Measuring System

The close photogrammetric 3-D coordinate meaurement is a new measuring technology in the fields of the coordinate measurement machine (CMM) in recent yearsl.In this method,we usually place some targets on the measured object and take image of targets to determine the object coordinate.The subpixel location of target image plays an important role in high accuracy 3-D coordinate measuring procedure,In this paper,some subpixel location methods are reviewed and some factors which affect location precision are analyzed. Then we propose bilinear interpolation centroid algorithm.The experiments have shown this algorithm can improve accuracy of target centroid by increasing available pixels.     

Double Beams to Measure Three-dimensional Rigid Body Displacements^①

A new method for measuring 3-D rigid body displacements is proposed,in which two perpendicular beams are emitted onto two sensitive planes of PSDs leing perpendicular to each other.The method can be used to measure 1-D or 2-D displacements when required.Moreover,the experimental results are presented,which demonstrate that the new method has high accuracy,fast processing speed,high reliability,and easily being realized.     

RANGE AMBIGUITY DISTRIBUTION CHARACTERISTIC OF SPACEBORNE SAR AND ITS DESIGN CONSIDERATION

A new approach is proposed which can satisfy the range ambiguity requirement while keep the antenna width not to be enlarged and get the high quality image also. Here the chirp slope of the transmitted linear frequency modulated pulses is reversed alternately. Therefore, during the range compression significant portion of the ambiguous return which is due to the mismatching with the signal reference function is suppressed. The suggested method provides significant improvement in range ambiguity ratio and can be utilized in attaining wider swath.     

Automatic wavefront reconstruction on single interferogram with spatial carrier frequency using Fourier transform

Optical interferometry can be applied to obtain the wavefront phase and reconstruct the three-dimensional wavefront by analyzing interference fringes. Single interferogram analysis based on two-dimensional Fourier transform is proposed. This method just needs to acquire and analyze single interferogram to solve the wavefront phase. Compared with phase-shift method, Single interferogram analysis can reduce experiment cost and the limitation of measuring e nvironment like vibration, airflow and noise, and meet the requirement of real-time and dynamic interferometry. Because the wavefront phase information is included in the carrier frequency components of single interferogram, an image edge detection method is used to automatically extract the center and boundary of the first-order carrier component of the spatial spectrum of the interferogram in the frequency domain.     

Image Denoising by the Curvelet Transform for Doppler Frequency Extraction

In Doppler radar scoring systems,the echo can be represented as a gray image by time-frequency transform, so Doppler frequency extraction becomes curve detection in the image-view. In order to improve the performance of curve detection in low signal-noise-ratio environment, this paper proposes an image denoising method based on curvelet transform. Firstly, the gray image is divided into a nolse-image and a signal-linage by region partition. The noise-image is used to estimate the noise level of the signal-image in curvelet domain. And the signal- image is denoised in curvelet domain with processes as signal judgment, orientation detection and soft-threshold detection block by block. Inside each block~ signal judgment is used to check true signal,orientation detection is used to determine the direction and soft-threshold detection is used to filter the curvelet coefficients. The experimental results show the efficiency of the proposed method.     

基于FTP的三维轮廓测量方法及实验

为了快速、高精确度地得到物体的三维轮廓信息,在此利用傅里叶变换轮廓术,将被测物体置于光栅投影下,采集变形光栅图像,根据被测物体表面的高度与相位差之间的映射关系,通过在计算机中与参考光栅原像的比较分析,以获得被测物体的三维轮廓信息。实验中搭建了由LCD投影仪、CCD摄像机、图像采集卡和光学导轨等组成的光栅投影测量系统的硬件平台,提出了用1台计算机同时控制投影和采集处理光栅图像,根据映射关系在多次实验中不断修改优化测量参数,做到既不影响视场范围,又保证较高的测量精度,并给出了由计算机重建后较好的三维轮廓图像精度及其实验的测量误差分析。     

主动三维视觉传感技术的研究

主动三维视觉传感技术主要有飞行时间法、点结构光扫描法、线结构光扫描法和编码面结构光法、莫尔法、相位测量轮廓术、傅里叶变换轮廓术等.介绍了上述各种技术的基本原理和优缺点.提出了一种新的技术,即单幅二维图像不标定自适应三维场景重构技术,给出了它的原理并讨论了其特点.     

基于FTP的二维傅里叶变换的研究

傅里叶变换轮廓术(FTP)是三维物体形貌测量的重要方法,一维傅里叶变换可用于一般曲面相位解调,但对高频干扰和低频背景噪声敏感.连续应用一维傅里叶变换或反傅里叶变换可实现二维傅里叶变换,采用二维傅里叶变换,进行二维频谱分析,可用来分离和提取有用三维信息.具体实验验证表明,二维傅里叶变换能消除沿非栅线方向造成的灰度变化以及高频噪声,减小计算结果沿Y方向的波动,更好反映三维物体细节信息,提高相位解调的精度.     

基于傅里叶变换去隔行图像的动态3维面形测量

为了解决动态面形测量中隔行扫描CCD相机记录动态物体表面变形条纹图像存在缺陷的问题,提出了傅里叶变换去隔行算法,即把隔行扫描CCD获取动态物体的错位模糊帧图像分成两个单场图像,分别对每一单场图像进行傅里叶变换去隔行处理,再利用条纹分析法重建对应时刻的3维面形。理论分析得出单场傅里叶变换去隔行图像与对应的准确满帧图像相同的结论。结果表明,该方法可以很好地恢复条纹和重建物体,且简单实用,可用于基于空间相位检测、相位测量轮廓术、傅里叶变换轮廓术等条纹分析方法的动态物体3维测量中。     

Linear Phase FIR Filter on Measuring 3-D Surface

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往复冲击条件下磨痕三维形貌的测量

提出一种采用傅里叶变换轮廓术(FTP,fourier transform profilometry)对磨痕三维形貌进行测量的方法,具有只需采集一帧条纹图、数据处理少、简单易行和测量速度快等优点,适于自动化测量。采用一种新的产生正弦光强方法,将正弦光强投影到试件表面产生包含三维形貌信息的光栅条纹,利用FTP重建磨痕的三维形貌。实验对不加润滑油状态下往复105次冲击后的磨痕形貌进行测量,并将实验结果与四步相移所测结果进行对比,验证了本文方法用于测量往复冲击条件下磨痕形貌的可行性,并为进一步研究往复冲击时接触润滑效应提供了新的实验依据。     

基于隔行扫描奇偶场图像的动态物体三维面形测量

存基于傅里叶变换轮廓术(FTP)的动态物体三维面形测量中,选用隔行扫描CCD相机记录动态图像,由于其一帧中两场图像时间上的分离性,导致帧图像错位模糊,使测量误差增大甚至产生错误.针对这一问题,提出利用隔行扫描CCD获取动态物体的错位模糊帧图像分成两个单场图像,各自直接利用FTP重建物体面形的新方法.理论分析得出单场图像与准确的满帧图像重建物体三维面形是完全相同的结论;仿真及实验结果都表明该方法的有效性.该方法既保持了原有准确帧图像的重建精度,又使整个测量系统的时间分辨率提高了1倍;实现简单快捷.     

咀嚼过程人脸颊外形动态变化的光学三维测量

通过CCD摄像机快速获取由罗奇(Rochi)光栅投影到处于动态变化过程中人脸表面上的一系列变形条纹,经过傅立叶变换、频谱滤波、逆傅立叶变换及相位展开等处理后得到重建的一系列脸部颊面面形,再现处于咀嚼过程中的人脸颊部动态变化过程。     

基于点测量法的非定步长相移恢复算法

提出了一种新的计算光栅相移量点测量法。利用该方法可精确地计算出光栅相移量,精度达到1nm。该方法抛弃了非定步长算法中利用傅立叶变换获取光栅相移量的方式,使非定步长相移算法在三维曲面形貌测量中的应用进一步趋向完善。