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1.
Automatic window size selection in Windowed Fourier Transform for 3D reconstruction using adapted mother wavelets 总被引:1,自引:0,他引:1
Fringe pattern analysis in coded structured light constitutes an active field of research. Techniques based on first projecting a sinusoidal pattern and then recovering the phase deviation permit the computation of the phase map and its corresponding depth map, leading to a dense acquisition of the measuring object. Among these techniques, the ones based on time-frequency analysis permit to extract the depth map from a single image, thus having potential applications measuring moving objects. The main techniques are Fourier Transform (FT), Windowed Fourier Transform (WFT) and Wavelet Transform (WT). This paper first analyzes the pros and cons of these three techniques, then a new algorithm for the automatic selection of the window size in WFT is proposed. This algorithm is compared to the traditional WT using adapted mother wavelet signals both with simulated and real objects, showing the performance results for quantitative and qualitative evaluations of the new method. 相似文献
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Abeer D. Algarni Ghada El Banby Sahar Ismail Walid El-Shafai Fathi E. Abd El-Samie Naglaa F. Soliman 《Entropy (Basel, Switzerland)》2020,22(12)
The security of information is necessary for the success of any system. So, there is a need to have a robust mechanism to ensure the verification of any person before allowing him to access the stored data. So, for purposes of increasing the security level and privacy of users against attacks, cancelable biometrics can be utilized. The principal objective of cancelable biometrics is to generate new distorted biometric templates to be stored in biometric databases instead of the original ones. This paper presents effective methods based on different discrete transforms, such as Discrete Fourier Transform (DFT), Fractional Fourier Transform (FrFT), Discrete Cosine Transform (DCT), and Discrete Wavelet Transform (DWT), in addition to matrix rotation to generate cancelable biometric templates, in order to meet revocability and prevent the restoration of the original templates from the generated cancelable ones. Rotated versions of the images are generated in either spatial or transform domains and added together to eliminate the ability to recover the original biometric templates. The cancelability performance is evaluated and tested through extensive simulation results for all proposed methods on a different face and fingerprint datasets. Low Equal Error Rate (EER) values with high AROC values reflect the efficiency of the proposed methods, especially those dependent on DCT and DFrFT. Moreover, a comparative study is performed to evaluate the proposed method with all transformations to select the best one from the security perspective. Furthermore, a comparative analysis is carried out to test the performance of the proposed schemes with the existing schemes. The obtained outcomes reveal the efficiency of the proposed cancelable biometric schemes by introducing an average AROC of 0.998, EER of 0.0023, FAR of 0.008, and FRR of 0.003. 相似文献
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The present paper contributes to the development of new efficient solutions aimed at improving vehicle functional safety through the implementation of new transmission diagnostic methods. The study focuses on a new perspective of the diagnostic frequency range for hypoid gear condition monitoring, using acoustic emission and vibro-acoustic signal measurements and the Discrete Wavelet Transform for data analysis. The identification of the most sensitive diagnostic parameters and determination of frequency intervals using the Discrete Wavelet Transform, in which the most significant increase in the values of diagnostic parameters can be seen, has been presented. In addition, the identification of the sensitivity of the above-introduced non-destructive methods is presented. Diagnostic results in the extended frequency range were compared with the results of the classical method, and it was found that the selected parameter in the proposed measuring range could better characterize the condition of the gear unit. 相似文献
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In this paper, an encryption, compression and transmission scheme is proposed. The scheme is based on fractional-order chaotic systems combined with Discrete Wavelet Transform (DWT) and Quadrature Phase Shift Keying (QPSK) modulation. The cipher performs rounds of digital operations between the vector states of the fractional-order system and the image to be encrypted. The implementation of the transmission process is made between a pair of software defined radio modules through a QPSK modulation scheme. The experimental results and security analysis show adequate performances for several applications in the presence of multiple attacks and environmental noise. 相似文献
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提出了一种采用加速鲁棒特征算法匹配运动物体的特征点,实现在线三维测量的方法.该方法只需投影一固定的正弦光栅到在线运动中的被测物体表面上,使投影光栅线垂直运动方向,当物体每移动相同的距离,由CCD采集到相应的变形条纹图,从中提出对应的背景光场,借助SURF算法对各帧背景光场的物体进行特征匹配,即可获得一组具有等步相移量的等效相移条纹图,从而采用等步相移算法可重构出在线运动物体的三维面形.实验验证了该方法的有效性和可行性,并与在线FTP方法进行了比较,所提方法的平均绝对误差小于在线FTP方法的二分之一,均方根误差小于在线FTP方法的四分之一. 相似文献
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针对红外偏振与光强图像彼此包含共同信息和特有信息的特点,提出了一种基于双树复小波变换和稀疏表示的图像融合方法.首先,利用双树复小波变换获取源图像的高频和低频成分,并用绝对值最大值法获得融合的高频成分;然后,用低频成分组成联合矩阵,并使用K-奇异值分解法训练该矩阵的冗余字典,根据该字典求出各个低频成分的稀疏系数,通过稀疏系数中非零值的位置信息判断共有信息和特有信息,并分别使用相应的规则进行融合;最后,将融合的高低频系数经过双树复小波反变换得到融合图像.实验结果表明,本文提出的融合算法不仅能较好地凸显源图像的共有信息,而且能很好地保留它们的特有信息,同时,融合图像具有较高的对比度和细节信息. 相似文献
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Three frames of deformed patterns are needed at least in conventional Phase Measuring Profilometry (PMP). It is generally applied to the profile measurement of a static object. For on-line measurement, because of the moving object, it is difficult to capture three or more frames of deformed patterns that satisfy the requirement of PMP. A new method of on-line 3-D shape measurement through only one frame deformed pattern in PMP is presented. A static sinusoidal fringe is projected and any one frame of real-time deformed patterns is captured by CCD. N frames of sub-images are extracted from the captured deformed pattern. Improved Stoilov algorithm is proposed to get phase. Computer simulation and experimental results show its feasibility and affectivity to reconstruct a 3-D shape and the accuracy is higher than Fourier Transform Profilemetry (FTP) which is also a method that only needs one frame of deformed pattern. 相似文献
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Giuseppe Schirripa Spagnolo Dario Ambrosini Domenica Paoletti 《Optics and Lasers in Engineering》1998,30(2):213-223
A projected-fringe fiber-based moiré interferometer is proposed to measure the local amplitude vibration of a diffuse surface. The technique is based on an optical fiber interferometer which projects interference fringes on the object surface. The visibility of these carrier fringes is modulated by a function of local amplitude vibration. Full-field quantitative analysis is performed by analyzing the fringe pattern with a 2-D Fourier transform method. Theoretical details, and experimental results are presented. 相似文献
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应用傅里叶变换轮廓术测量物体三维面形时,当被测物体形状复杂或是被噪声严重污染时,导致频谱分布展宽,发生频谱混叠现象,基频提取困难,无法准确恢复物体的三维面型.提出了基于小波分解的傅里叶变换轮廓术,采用小波变换的方法对变形条纹图进行二维多尺度分解,重构被测物的背景图像,滤出图像的零频成分,得到相对变形条纹.运用小波变换与傅里叶变换轮廓术相结合的方法,只需拍摄一幅变形条纹图,将被测物体与背景分离,不受背景成分的影响,且易于基频信息的提取,降低了对滤波器的要求.实验证明该方法较好地防止了频谱的混叠问题,提高了测量范围与解相精度. 相似文献
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We propose the real time optical reconstruction of a three-dimensional (3D) object from a digitally recorded hologram. Phase distribution of the recorded hologram is numerically calculated by 1-dimensional Continuous Wavelet Transform (1D-CWT) for digital reconstruction with phase only information. Also, the phase distribution of 1D-CWT transferred to the spatial light modulator (SLM) is used to obtain optically reconstructed image. It is observed that an efficient real-time analysis can be achieved, if phase of 1D-CWT is used. In the same time, optically reconstructed 3D objects obtained by only phase information are about three times brighter than bleached hologram intensity's. So the minimum power loss can be obtained. Numerical and experimental results are presented. 相似文献
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The model of linear frequency modulation continuous wave (LFMCW) applied in underwater detection and the method for the detection of echo signal and the estimation of target parameters were studied. By analyzing the heterodyne signal, an algorithm with the structure of heterodyne-Practional Fourier Transform (FRFT) was proposed. To reduce the computation of searching targets in a two-dimensional FRFT result, the heterodyne signal would be processed by FRFT at a specific order, after Radon-Ambiguity Transform (RAT) was applied to estimate the sweep rate of the signal. Simulations proved that the algorithm can eliminate the coupling phenomenon of distance and velocity of LFMCW, and estimate targets' parameters accurately. The lake trial results showed that the processing gain of LFMCW processed by the algorithm in this paper was 13 dB better than that of the LFM processed by matched filter. The research results indicated that the algorithm applied in LFMCW underwater detection was feasible and effective, and it could estimate targets' parameters accurately and obtain a good detection performance. 相似文献
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Infrared thermography as a tool of non-destructive testing is method enabling visualization and estimation of structural anomalies and differences in structure’s topography. In presented paper problem of osmotic damage in submerged glass reinforced polymer structures is addressed. The osmotic damage can be detected by a simple humidity gauging, but for proper evaluation and estimation testing methods are restricted and hardly applicable. In this paper it is demonstrated that infrared thermography, based on estimation of heat wave propagation, can be used. Three methods are addressed; Pulsed thermography, Fast Fourier Transform and Continuous Morlet Wavelet. An additional image processing based on gradient approach is applied on all addressed methods. It is shown that the Continuous Morlet Wavelet is the most appropriate method for detection of osmotic damage. 相似文献
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Small target enhancement is one of the crucial stages in infrared small target detection. In this paper, we propose a new method using phase spectrum of Quaternion Fourier Transform to enhance small targets while suppressing backgrounds for infrared images. This is inspired by the property that regularly Gaussian-like shape small targets could be considered as attractively salient signal in infrared images and the location information of such signal is implicitly contained in the phase spectrum from frequency domain. Formally, in the proposed method, we adopt the phase spectrum of Quaternion Fourier Transform instead of using traditional Fourier Transform to enhance the targets since the quaternion provides at most four data channels than only one for the latter, which could be helpful to broad types of background clutters by adding more information. For the construction of the quaternion, we present a second-order directional derivative filter via facet model to compute four second order directional derivative maps from four directions respectively as the four data channels. This filter is used to suppress noises and distinguish the targets and backgrounds into separably different textures so that it would boost the robustness of small target enhancement. In experiments, some typical infrared images with various scenes are tested to validate the effectiveness of the proposed method. The results demonstrate that our method actually has good performance and outperforms several state-of-the-art methods, which can be further used for infrared small target detection and tracking. 相似文献
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Bin Wang 《Optics Communications》2011,284(14):3504-3508
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针对在一幅载体图像中隐藏三维目标序列图像的问题,本文利用主分量分析法获取三维目标的本征图像,将本征图像的小波域系数嵌入到载体图像的小波域系数中,利用分解系数和提取得到的本征图像重构出三维目标的系列图像.本文所提出的方法不是直接存储目标图像,而是存储能够反映三维目标特征的一组本征图像.研究结果表明,该方法有效地将三维目标的特征隐藏在了载体图像中,隐藏信息量大.
关键词:
信息隐藏
三维目标
主分量分析
小波变换 相似文献
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S变换引导的窗口傅里叶变换相位提取 总被引:3,自引:0,他引:3
提出了一种基于S变换引导的自适应窗口傅里叶变换相位提取方法.通过连续S变换,得到局部条纹的最佳变换窗口,可以保证窗口尺寸随变形条纹的频率变化而自动调整,适合复杂物体的面形测量.计算机模拟和实验验证表明,该方法克服了传统窗口傅里叶变换窗口大小固定的缺点,相位提取的误差由-2~8rad降低为-1~1rad,而且还可以得到被... 相似文献