相关哈特曼-夏克波前传感器波前重构新方法

对相关哈特曼-夏克波前传感器的波前重构方法进行了研究,提出了一种基于相邻子图像间相对平移量的波前重构新方法。与常用的基于单一参考子图像的波前重构方法相比,新方法的动态范围有了很大提高。在8×8去4角的子孔径划分下,测量离焦波面时,新方法的动态范围可提高约16倍,子孔径数目越多,动态范围提高的倍数也越高。精度分析表明,两种波前重构方法在8×8去4角的子孔径划分下精度相近,在子孔径数目更多时,相邻子图像处理法的波前重构精度低于单一参考子图像法。     

Three-dimensional imaging with detector arrays on arbitrarily shaped surfaces

Conventional multiview imaging systems commonly utilize a planar lenslet array and a rigid, flat image sensor in the pickup stage to capture different views of the scene. In this Letter, we remove this constraint by proposing the concept of three-dimensional (3D) imaging with detector arrays that may conform to arbitrarily shaped surfaces or platforms. A nonplanar detector array configuration can be used in combination with a flexible lenslet array to capture different views. The orientation and optical axes of individual image sensing elements could vary. A point-by-point 3D reconstruction algorithm is described and the feasibility of the proposed approach is demonstrated through simulated imagery.     

基于小波重构的木材表面缺陷检测系统研究

设计了木材加工业中木材纹理表面的检测系统,提出了一种有效的选取小波频带重建图像的纹理瑕疵检测方法。设计的检测系统由新型LED光源,明暗域结合成像光学系统,高速高分辨率线阵CCD器件等组成。应用小波基函数在较优的分解级数上对纹理图像进行分解,然后在最佳的分辨率级数上正确选取平滑图像或者细节图像来重建图像。在重建图像中均匀纹理图案被有效地移除,仅仅保留了局部瑕疵区域,小波频带选取是基于小渡系数的能量分布自动确定最佳重构参数。重构后的图像经阈值处理得到二值图像,最后运用数学形态学的方法对二值图像后处理。实验表明,该方法可用于实时在线检测木材表面的瑕疵。     

Noise in superresolution reconstruction

Recently there has been a significant interest in reconstructing a high-resolution (HR) image based on a set of low-resolution (LR) images with relative displacement. These images are typically undersampled with respect to the image spectrum of a HR image. I show that, although ideally a resolution increase of N times is possible with N LR images, in a practical system noise is a limiting factor that increases substantially as we approach this theoretical superresolution limit. For one dimension and a special case with two LR images, I present an analytical result of the noise amplification as a function of their displacement. This is defined as a condition number of the superresolution system, with the associated definitions of a well-conditioned and ill-conditioned superresolution reconstruction system.     

基于双阈值Huber范数估计的图像正则化超分辨率算法

多帧图像超分辨率算法利用图像间的互补信息, 可以从一系列具有亚像素位移的低分辨率影像数据中重建出高分辨率图像. 在众多超分辨率算法中, 正则化方法以其求解病态问题的有效性而被广泛应用, 但在此类方法中, 最优估计算子的估计准确度对最后的重建结果有着较大的影响. 本文在现有正则化超分辨率重建算法的基础上, 提出了一种基于双阈值Huber范数的极大似然估计算子, 可以提高Huber范数对于阈值取值的容忍性和算子估计精度; 并给出了基于该算子的正则化超分辨率算法的迭代公式. 通过对仿真图像进行重建, 结果表明算法可有效地抑制各种噪声并保证重建效果; 同时将此算法应用于实际图像的超分辨率重建, 有效地提高了目标影像的空间分辨率. 关键词： 图像处理 图像重建 超分辨率 正则化     

Encryption of color images using MSVD in DCST domain

In this paper, a new image encryption and decryption algorithm based on Multiresolution Singular Value Decomposition (MSVD) and Discrete Cosine Stockwell Transform (DCST) is proposed. An original image is first transformed in DCST domain and then decomposed into four subbands using MSVD, all the four subbands are further decomposed into four subimages according to their indexing and masked by the parameters generated by MSVD. We have used number of bands of DCST, arrangement of MSVD subbands, arrangement of various subimages obtained from MSVD subbands, values and arrangement of a 4×4 matrix generated by MSVD and the arrangement of masked subimages as encryption and decryption keys. To ensure the correct decryption of encrypted image, it is indeed necessary to have correct knowledge of all keys in correct order along with their exact values. If all the keys are correct but a single key is wrong even though it would be almost impossible to guess the original image. The efficiency of proposed algorithm is evaluated by comparing it with some recent published works and it is evident from the experimental results and analysis that the proposed algorithm can transmit the images more securely and efficiently over the network.     

一种基于改进频域图像配准技术的超分辨力图像处理方法

为提高光电成像系统的空间分辨力,提出了一种基于改进的频率域图像配准技术的超分辨力图像处理方法。首先利用改进的频域图像配准方法估算出低分辨力图像之间的微位移量,然后采用Papoulis-Gerchberg超分辨力处理方法完成图像复原。利用不同重构方法进行了仿真及实验研究,给出了评价参数。模拟和实际显微热图像的处理结果表明:该算法可使图像质量得到改善,分辨的细节更多,可有效地提高光电成像系统的空间分辨力;处理算法简单,计算量小,可实现快速处理。该算法还可应用于其他不可控光学微扫描成像系统中,具有广泛的应用前景。     

基于区域协方差的惯性组合导航景象匹配算法

 针对景象匹配辅助惯性组合导航系统需要快速准确获取飞行器位置和航向偏差的要求,提出了一种基于区域协方差的实时图像匹配算法.算法采用区域协方差矩阵的距离作为图像匹配时的相似性度量.首先,对图像进行高斯平滑滤波,提取图像的多种特征计算区域协方差矩阵,利用金字塔多级匹配技术进行全局搜索,获得测试图在参考图中像素级匹配位置.然后,利用全局匹配的结果,在实测图上选取多个局部区域,分别进行局部搜索匹配,获取参考图和实测图中一一对应的局部匹配集.最后,利用RANSAC算法和最小二乘算法计算出两幅图像间的最优相似变换参量.仿真分析表明,该算法能满足景象匹配辅助惯性组合导航系统实时性、精确性和鲁棒性的要求.     

光学系统超分辨的光源编码技术

本文从Wolf的部分相干理论出发,提出了采用编码光源照明的新的光学像超分辨方法,并用实验证实了这种方法的正确性.它克服了以往超分辨术的一些缺点,为超分辨的实用化研究展现了新的途径.     

Analysis on axial squeeze distortion in resolution-priority integral imaging display systems

When the three-dimensional (3D) image is out of focus, a significant axial squeeze distortion is generally produced by position mismatching between the geometric convergences of the lenslet array and the convergence of each lenslet. In this paper, a rigorous explanation of a phenomenon that produces axial distortions is first presented. Then, the phenomenon is theoretically analyzed and the axial shifted position of the 3D image point is derived based on geometrical optics and the modulation transform function (MTF) theory. Simulated results show the dependence of 3D image axial shift error on the focal length of the lenslet array. Finally, a solution for eliminating the axial shift and the axial distortion is brought out and the suitable range of the focal length is discussed.     

基于实时帧迭代反向投影算法的图像序列超分辨率处理

提出一种实时帧迭代反向投影算法实现对图像序列的超分辨率处理。通过建立虚拟全景图像及其迭代权阵,实现迭代反向投影的逐帧处理,从而可实时地对视频图像序列作超分辨率处理。另外还采用了基于光流计算的分层迭代图像配准、双线性插值模拟采样、阈值先验约束、坐标系同步变换等技术来提高算法的有效性。通过对仿真和实际视频序列的处理对算法进行了验证。     

Super-resolution image restoration algorithm based on orthogonal discrete wavelet transform

By using orthogonal discrete wavelet transform(ODWT)and generalized cross validation(GCV),and combining with Luck-Richardson algorithm based on Poisson-Markovmodel (MPML),several new superresolution image restoration algorithms are proposed.According to simulation experiments for practical images,all the proposed algor ithms could retain image details better than MPML,and be more suitable to low signal-to-noise ratio(SNR)images.The single operation wavelet MPML(SW-MPML)algorithm and MPML algorithm based on single operation wavelet transform(MPML-SW)avoid the iterative operation of self-adaptive parameter in MPML particularly,and improve operating speed and precision.They are instantaneous to super-resolution image restoration process and have extensive application foreground.     

Three-dimensional imaging and visualization of partially occluded objects using axially distributed stereo image sensing

In this Letter, we propose a multiperspective three-dimensional (3D) imaging system using axially distributed stereo image sensing. In this proposed method, the stereo camera is translated along its optical axis and multiple axial elemental image pairs for a 3D scene are collected. The captured elemental images are reconstructed in 3D using a computational reconstruction algorithm based on ray back-projection. The proposed method is applied to partially occluded object visualization. Optical experiments are performed to verify the approach.     

基于Markov随机场的新型景像匹配算法

为了提高景像匹配导航系统的定位精度,给出了一种基于Markov随机场理论和极大后验概率估计的新型景像匹配算法。考虑到在x方向和y方向位置偏差的实时图与基准图之间的灰度分布关系,利用图像上的灰度分布服从Markvov随机场分布这一特性,建立了景像匹配问题的条件概率分布模型。应用最小二乘法和噪声的先验统计信息估计位置偏差的方差,给出了描述基准图与实时图之间灰度偏差的测量模型,确定了测量的统计特性。基于极大后验概率估计准则计算了位置偏差的估值。由于新算法在计算位置偏差估值时用到了被估量和噪声的统计信息,因此具有很高的精度。将该算法与最小二乘景像匹配算法进行了仿真比较。仿真结果表明,新算法的匹配精度达到了0.1~0.2像素,高于最小二乘匹配算法的匹配精度。     

Resolution-enhanced 3D image correlator using computationally reconstructed integral images

In this paper, a novel resolution-enhanced three-dimensional (3D) image correlator using the computationally reconstructed integral images is proposed in order to extract target object’s 3D location data in a scene. Elemental images of the reference and target objects are picked up by lenslet arrays and using these elemental images, reference and target plane images are reconstructed on the output plane by means of a modified computational integral imaging reconstruction technique. Then, through cross-correlations between the reconstructed reference and the target plane images, 3D location data of the target object can be extracted from the correlation outputs. With the purpose of showing the feasibility of the proposed method, some computational and optical experiments on the target objects in space are carried out and the results are presented.     

基于直线的射影不变性和极线约束标定摄像机参数

提出一种用图像对标定摄像机参数的新方法。传统自标定方法需要先由图像特征计算基础矩阵,该方法则是从图像中提取一组未知长度和长度比的平行直线,以图像中心坐标为主点初值,利用直线的射影不变性先求得摄像机焦距、旋转矩阵和平移向量的初值;再由图像对固有的极线约束来优化摄像机的参数,从而得到高精度的主点、焦距、旋转矩阵和平移向量。使用该方法对图像目标进行三维重建,仿真实验表明：该方法对场景要求较少,原理简单,方法易行,标定摄像机参数精度较高。     

Performance-enhanced recognition of a far and partially occluded 3-D object by use of direct pixel-mapping in computational curving-effective integral imaging

In this paper, we propose a novel approach to enhance the recognition performance of a far and partially occluded three-dimensional (3-D) target in computational curving-effective integral imaging by using the direct pixel-mapping (DPM) method. With this scheme, the elemental image array (EIA) originally picked up from a far and partially occluded 3-D target can be converted into a new EIA just like the one virtually picked up from a target located close to the lenslet array. Due to this characteristic of DPM, resolution and quality of the reconstructed target image can be highly enhanced, which results in a significant improvement of recognition performance of a far 3-D object. In addition, the computational time required for reconstruction of a far 3-D target could be also reduced because the distance between the lenslet array and image plane is virtually shortened in the new EIA transformed by DPM. Experimental results reveal that image quality of the reconstructed target image and object recognition performance of the proposed system have been improved by 1.75 dB and 4.56% on the average in PSNR (peak-to-peak signal-to-noise ratio) and NCC (normalized correlation coefficient), respectively, compared to the conventional system.     

Long-range three-dimensional active imaging with superresolution depth mapping

We present a technique to overcome the depth resolution limitation for 3D active imaging. Applying microsecond laser pulses and sensor gate width, a scene of several hundred meters is illuminated and recorded in a single image. The trapezoid-shaped range intensity profile is analyzed to obtain both the reflectivity and the depth of scene. We demonstrate a 3D scene reconstruction in a depth of 650 to 1550 m from only three images with an accuracy of <30 m. This depth accuracy is 10 times better than estimated from the classical resolution limit obtained for depth scanning active imaging with a similar number of images. Therefore, this technique enables superresolution depth mapping with a reduction of image data processing.     

Multifocus image fusion based on features contrast of multiscale products in nonsubsampled contourlet transform domain

In this paper, an efficient multifocus image fusion approach is proposed based on local features contrast of multiscale products in nonsubsampled contourlet transform (NSCT) domain. In order to improve the robustness of the fusion algorithm to the noise and select the coefficients of the fused image properly, the multiscale products, which can distinguish edge structures from noise more effectively in NSCT domain, is developed and introduced into image fusion field. The selection principles of different subband coefficients obtained by the NSCT decomposition are discussed in detail. To improve the quality of the fused image, novel different local features contrast measurements, which are proved to be more suitable for human vision system and can extract more useful detail information from source images and inject them into the fused image, are developed and used to select coefficients from the clear parts of subimages to compose coefficients of fused images. Experimental results demonstrate the proposed method performs very well in fusion both noisy and noise-free multifocus images, and outperform conventional methods in terms of both visual quality and objective evaluation criteria.     

基于二进制比特串描述符的惯性组合导航高速景象匹配算法

针对景象匹配辅助惯性组合导航系统需要快速准确获取飞行器位置、航向偏差的要求,提出了一种基于二进制比特串描述符的高速景象匹配算法,尤其适合于计算资源有限的景象匹配场合.算法首先提取环绕中心极值局部特征,然后计算特征点的二进制比特串描述符,接着利用描述符之间的汉明距离进行快速特征匹配.最后,利用分组采样一致算法和最小二乘算法获取高准确度的航向和位置偏差信息.景象匹配性能评价实验表明：在匹配适应性、匹配速度、准确度和鲁棒性方面,算法都很优越,在参考图为250×250 pixels,实测图为160×160 pixels情况下,整个算法的计算约为40 ms,可以满足景象匹配导航系统高速匹配修正的要求,优于传统的景象匹配算法.