无透镜傅里叶变换数字全息术中非共面误差的自动补偿算法

无透镜傅里叶变换数字全息术对活细胞进行显微相衬成像测量时,由于细胞处于运动状态导致记录物体与参考点源难以共面,从而引入成像误差.本文提出了一种有效可靠的基于位相分布的自动对焦再现算法,只需通过一幅全息图,即可确定出记录距离的优化数值解,并结合一次位相线性拟合,成功补偿掉非共面误差.将这种算法应用到活体宫颈癌细胞的相衬成像实验中获得了较为理想的实验结果,表明了这种自动补偿非共面误差算法的可行性. 关键词： 数字全息 无透镜傅里叶变换全息 自动对焦 位相畸变校正     

通过保留相位进行全息图信息压缩的方法

从全息图的特点出发,研究了全息图的记录和再现原理,提出了一种对离轴菲涅耳全息图信息压缩的方法。对全息图进行傅里叶变换,滤除零级噪声及物光波的共轭波前,仅仅保留物光波的相位信息,而后以采用较低的采样频率对全息图重新抽样,从而大大减少了数字全息图的信息冗余。压缩后的全息图也可以获得良好像质的再现像。理论和实验均证明了该方法的可行性,为全息图的信息存贮与传输提供一条新的途径。     

数字全息周期像的产生机理及在抑制零级衍射上的应用

在数字全息成像中, 利用CCD的RGB模式采样全息图时, 全息重构像会出现特定的周期性分布. 本文从理论和实验上详细研究了这种周期像产生的机理、分布特性和应用. 研究结果显示, 由于CCD的光谱滤镜会使全息图的RGB三个单色采样阵列出现部分像素信号的缺失, 因此, 需要通过特定的demosaicing数学算法对缺失的像素信号进行重建以形成完整的单色采样阵列, 这是数字全息再现像周期分布产生的根源. 而基于demosaicing算法的采样阵列重建会在全息图频谱中引入调制函数, 导致物体再现像和零级衍射斑的周期分布差异. 本文揭示了全息图的RGB采样、demosaicing算法与全息重构像周期性之间的内在关联. 最后, 讨论了结合空间移位和图像形态学技术, 利用重构像的周期性抑制零级衍射斑的应用. 所有理论与实验研究结果完全一致. 关键词： 数字全息 图像周期性 零级斑抑制     

Digital holographic image fusion for a larger size object using compressive sensing

Digital holographic imaging fusion for a larger size object using compressive sensing is proposed. In this method, the high frequency component of the digital hologram under discrete wavelet transform is represented sparsely by using compressive sensing so that the data redundancy of digital holographic recording can be resolved validly, the low frequency component is retained totally to ensure the image quality, and multiple reconstructed images with different clear parts corresponding to a laser spot size are fused to realize the high quality reconstructed image of a larger size object. In addition, a filter combing high-pass and low-pass filters is designed to remove the zero-order term from a digital hologram effectively. The digital holographic experimental setup based on off-axis Fresnel digital holography was constructed. The feasible and comparative experiments were carried out. The fused image was evaluated by using the Tamura texture features. The experimental results demonstrated that the proposed method can improve the processing efficiency and visual characteristics of the fused image and enlarge the size of the measured object effectively.     

复数滤波器在数字全息图处理中的应用

数字全息图在微电路检测、粒度分析、透明场测量等小孔径、小视场对象测量和细胞观测等显微测量方面有着广泛的应用前景。根据离轴数字全息图的频谱特点,提出采用复数滤波器,利用计算机及相关算法对离轴数字全息图进行滤波,消除其零级及共轭像,同时可以得到全息图的相位分布。讨论了复数滤波器的设计方法,给出了实验结果。为数字全息图的压缩、再现和相息图制作提供了方便。     

基于有限脉冲响应滤波器的数字全息零级像消除

针对数字全息中零级像的存在影响数字再现像的质量,分析数字全息图的记录、再现原理及频谱特性,提出了一种利用有限脉冲响应滤波器消除全息图数字再现中零级像的方法.该方法只需记录一幅数字全息图,不需要相移器材或其他辅助设备,直接利用数字图像处理对数字全息图在空域进行预处理,消除全息再现时的零级像干扰.对比了数字模拟和实验拍摄到的全息图在应用有限脉冲响应滤波器消除零级像前后的再现结果,表明该方法可消除零级衍射像,改善重建像质量,并且算法简单.     

大尺寸物光波面彩色数字全息高质量重建研究

为解决检测面尺寸较大时CCD难以得到高质量数字全息图的问题,本文利用负透镜设计光学系统让CCD接收来自物体的缩小虚像,以球面波为参考波,使用单色CCD近距离得到三种色光照射下的大尺寸彩色物体的数字全息图,然后采用可控放大率波面重建算法得到同一尺寸的数字全息重建像,合成彩色数字全息重建像.同时,使用两种消零级方法去除零级干扰,提高重建像质量,一种方法利用空间光调制器相移技术在参考光中加入一次任意相移,记录两幅数字全息图,消除重建零级像|另一种方法使用“无干扰全息图”消除重建零级像及共轭像.本文讨论结果可为大物体彩色数字全息及多波长数字全息检测应用提供有益的参考.     

一种基于超复数系的数字全息图像生成方法

提出了一种基于超复数系的数字全息图像生成方法，通过定义超复数系，由此构成n维向量空间，然后采用分形迭代方法在n维向量空间中选择不同截面来绘制分形图像，因而能够在高维空间生成分形数字图像序列，并能够制作出具有动态效果和美感的激光全息图。由于分形数字全息图像生成具有较好的参数可控制性和不可逆转性，全盛的防伪标专难以仿制，在激光全息防伪领域有着良好的应用前景。     

Securing information by use of digital holography

An information security method that uses a digital holographic technique is presented. An encrypted image is stored as a digital hologram. The decryption key is also stored as a digital hologram. The encrypted image can be electrically decrypted by use of the digital hologram of the key. This security technique provides secure storage and data transmission. Experimental results are presented to demonstrate the proposed method.     

Digital holographic microscope with automatic focus tracking by detecting sample displacement in real time

We propose a new method for focus tracking during the recording of a sequence of digital holograms while the sample experiences axial displacement. Corrected reconstruction distances can be automatically calculated, and well-focused amplitude and phase-contrast images can be obtained for each digitized hologram. The method is demonstrated for inspection of microelectromechanical systems subjected to thermal load. The method can be applied as a quasi-real-time procedure.     

用改进的Fienup迭代算法进行数字全息重建

数字全息成像中往往包括再现像、共轭像和零级项,再现像的分离是常见而又难以彻底解决的问题。提出一种新的全息图重建算法,即利用相干衍射成像（CDI）中的迭代方法处理数字全息图,实现仅有一个实像的再现结果,从而彻底解决该问题。该方法包括两个步骤：首先通过CCD分别测量样品单独存在、样品和参考光同时存在以及参考光的远场衍射分布;然后通过计算机进行迭代运算。由于干涉光的存在,该算法比传统的CDI算法有更快的收敛速度和重建质量。同时进行了数值模拟验证并对生物切片进行了物像重建。     

Driving and analysis of micro-objects by digital holographic microscope in microfluidics

We propose an optical configuration in which floating particles in a microfluidic chamber can be characterized by an interference microscopy configuration to obtain quantitative phase-contrast maps. The configuration is simply made by two laser beams from the same laser source. One beam provides the optical forces for driving the particle along appropriate paths, but at same time works as the object illumination beam in the holographic microscope. The second beam plays the role of the reference beam, allowing recording of an interference fringe pattern (i.e., the digital hologram) in an out-of-focus image plane. The system and method are illustrated and experimental results are offered for polymeric particles as well as for in vitro cells with the aim to demonstrate the approach.     

基于数字全息及离散余弦变换的图像数字水印技术

提出了一种以数字全息和离散余弦变换为基础的数字水印技术,实现了在原始图像中嵌入数字全息水印。考虑到数字全息图的不可撕毁性,使得数字全息水印本身就具有良好的抗剪切能力,并且与传统的二维灰度水印相比嵌入的信息更多。数字全息图通过傅里叶变换全息的方法获得,为了提高抗有损压缩能力,在数字全息水印嵌入过程中采用了基于(JPEG模型和分解离散余弦变换(DCT)系数的方法。实验表明,通过该算法获得的数字全息水印对JPEG有损压缩和剪切等图像处理操作均有很好的稳健性,并且采用密钥加强了水印的安全性。因此该算法能成为数字多媒体产品版权保护的有效方案。     

Calculating depth maps from digital holograms using stereo disparity

Depth extraction is an important aspect of three-dimensional (3D) image processing with digital holograms and an essential step in extended focus imaging and metrology. All available depth extraction techniques with macroscopic objects are based on variance; however, the effectiveness of this is object dependent. We propose to use disparity between corresponding points in intensity reconstructions to determine depth. Our method requires a single hologram of a scene, from which we reconstruct two different perspectives. In the reconstruction the phase information is not needed, which makes this method useful for in-line digital holography. To our knowledge disparity based 3D image processing has never been proposed before for digital holography.     

Digital holographic imaging of aerosol particles in flight

This work describes the design and application of an apparatus to image aerosol particles using digital holography in a flow-through, contact-free manner. Particles in an aerosol stream are illuminated by a triggered, pulsed laser and the pattern produced by the interference of this light with that scattered by the particles is recorded by a digital camera. The recorded pattern constitutes a digital hologram from which an image of the particles is computationally reconstructed using a fast Fourier transform. This imaging is validated using a cluster of ragweed pollen particles. Examples involving mineral-dust aerosols demonstrate the technique's in situ imaging capability for complex-shaped particles over a size range of roughly 15-500 μm micrometers. The focusing-like character of the reconstruction process is demonstrated using a NaCl aerosol particle and is compared to a similar particle imaged with a conventional microscope.     

Copyright protection in digital museum based on digital holography and discrete wavelet transform

A new method to protect the copyright of digital museum based on digital holography is proposed. The Fresnel hologram of watermark image is embedded in the object to be protected through discrete wavelet transform （DWT）. After the watermark detection, the copyright information appears in the reconstructed hologram. With the higher redundancy feature in the hologram, the proposed technique can actually survive several kinds of image processing. Experimental results prove that the presented method has good robustness in image protection.     

Watermarking of three-dimensional objects by digital holography

We present an optical method for information watermarking of three-dimensional (3D) objects by digital holography. A hidden image is embedded by double phase encoding in a phase-shift digital hologram of the 3D object. We decode the watermarked hologram to reconstruct the hidden image and the 3D object. We use either the entire hologram or a part of it to decode the hidden image. Experiments are presented to illustrate the ability to recover both the 3D object and the decoded hidden image. Digital holograms of the 3D object are obtained by optical experiments. The watermarking process, 3D object reconstruction, and hidden image recovery are performed digitally. To the best of our knowledge, this is the first report of 3D object watermarking by use of a phase encoding technique and digital holography.     

复杂三维场景数字全息图隐藏面问题研究

从数字全息图制作原理出发,分析了隐藏面对数字全息图再现像的影响,得出在制作复杂场景数字全息图时必须进行消隐.在此基础上提出了一种消隐方法,通过寻找连接全息面上每一采样点与场景中每一采样点之间的虚拟光线与场景的交点中到全息面距离最短的交点集来消隐.最后给出了这种方法的原理和计算机模拟结果.     

大尺寸物光波面彩色数字全息高质量重建研究

为解决检测面尺寸较大时CCD难以得到高质量数字全息图的问题,本文利用负透镜设计光学系统让CCD接收来自物体的缩小虚像,以球面波为参考波,使用单色CCD近距离得到三种色光照射下的大尺寸彩色物体的数字全息图,然后采用可控放大率波面重建算法得到同一尺寸的数字全息重建像,合成彩色数字全息重建像.同时,使用两种消零级方法去除零级...     

Gyrator变换全息图及其在图像加密中的应用

提出了gyrator变换全息图,利用gyrator变换快速算法模拟实现了gyrator变换全息图的产生和再现,并研究了基于相移数字全息的gyrator变换全息图.在此基础上提出了采用正弦相位光栅实现光学图像加密的新方法.该方法利用gyrator变换在相空间的旋转特性,将gyrator变换的角度、光栅的频率及光栅的旋转角度作为加密密钥,并利用两个或两个以上的gyrator变换系统的级联实现图像加密,增加了系统的安全性.依据相移数字全息进行的两个gyrator变换系统级联的仿真实验验证了该方法的可行性、有效性及其良好的安全性能.