Segmentation of holographic images using the level set method

Image segmentation, which is to distinguish objects from background, has played an important role in holographic image processing. In this work, we propose a technique that uses the combination of rough segmentation and the level set methods for segmentation of holographic images with zero-order diffraction interference. To improve the image quality, we eliminate the interference of zero-order diffraction in digital holography using Sobel differential gradient algorithm based on digital image processing. After reconstruction, the rough segmentation including intensity transformations and Morphology methods is applied to acquire the rough contour of the reconstruction image. Finally, we adopt level set methods to smooth the object contour and improve its accuracy. Segmentation results for objects in holographic images are presented.     

Numerical reconstruction and twin-image suppression using an off-axis Fresnel digital hologram

In this work we proposed a novel approach for the numerical reconstruction of digital holography that uses only an off-axis Fresnel digital hologram and can easily be carrying out in a personal computer. From the presented off-axis holographic principle, the reference wave accompanies to the numerically reconstructed image, also makes the separation to the zero-order and twin images. Therefore, the concept can be applied to suppress the blurring of numerical reconstruction by adding the extra reconstruction plane and the formularized numerically reference wave in the reconstruction procedure. As expected, the blurring images can be separated out and removed from the reconstructed image. Then, by performing the back propagating to the exact reconstruction plane, one can obtain the pure object image without the blurring. In contrast to the temporal phase-shifting digital holographic-based scheme that employs multiple exposures the technique can be more effectively and easily overcome the blurring problem, also provide the practical feasibility in the digital holographic application. PACS 42.40.-I; 42.30.Wb; 42.40.Ht     

Formation of the holographic image of a diffuse object in second-harmonic radiation generated by a nonlinear medium

Results of experiments on recording three-dimensional holographic images of extended diffuse objects using an SHG hologram generating the second harmonic are presented. In this case, the object image is formed by the second-harmonic radiation whose wavelength is smaller than the wavelength of object and reference waves recorded on a hologram by a factor of two. Elements of the theory of an SHG hologram are considered. A holographic image of a transparency object illuminated with diffuse light is obtained. It is shown that the resolving power of this image is close to the limit determined by diffraction effects. An experiment on defocusing the reconstructed image showed that it was localized in one spatial plane and, therefore, was three-dimensional.     

Conjugate Image Plane Correlator with Holographic Disk Memory

A conjugate image plane correlator with holographic disk memory is proposed. Optical correlation between conjugate images reconstructed from a holographic disk and an input image on liquid-crystal television is executed with the rotation of the disk. Regardless of Fourier hologram recording with the pseudorandom diffuser, it is found possible to take out the diffuser from the original hologram recording scheme using an image reconstruction process and to get correlation signals between input and reconstructed conjugate images in the output plane of a two-lens imaging system. Generation of conjugate replicas with high contrast causes exact matching with an input image which results in high recognition performance for autocorrelation signals. The transfer function of an optical system can be controlled by adjustment of either hologram size or hologram area illuminated with a laser beam. Hence, the output intensity distribution can be adjusted by selecting a proper pupil function and the size of an output pupil defined by the input pupil size and the optical system magnification factor. The real-time character recognition by optical parallel high-speed processing for two dimensional images with position normalization is demonstrated.     

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.     

Superparallel holographic correlator for ultrafast database searches

We describe a superparallel holographic optical correlator that performs two-dimensional spatial and angular multiplexing simultaneously. The key step in this architecture is the use of a holographic multiplexer to split a query image into many copies before it applies them to the holographic database. A holographic demultiplexer, in conjunction with an aperture, is used to identify the location and the angle of the brightest correlation peak. This architecture uses only O(square root of N) detector elements to search through N unsorted images in a single query. We demonstrate the basic features of this architecture, using three spatial locations with eight angle-multiplexed images in each location.     

Reflected light holographic microscopy of moving objects

A holographic system that images front-illuminated, fast-moving microscopic objects is described. Focused micrographs can be generated under circumstances when ordinary microscopy (due to object movements) and transilluminated holographic microscopy (due to object opaqueness) cannot be used. Details of the experimental arrangements, easy-to-use working formulae for obtaining optimum image reproduction, and results from the application of the system to studies of droplet and solid particle suspensions in liquids are presented.     

Use of focus stacking and SfM techniques in the process of registration of a small object hologram

In this Letter, a method for shape visualization of small objects(microscopic) in the form of a hologram is presented. It consists of a standard optical set-up for small object registration(i.e., stereoscopic or biological microscope). The focus stacking technique is used to obtain a series of images with increased depth of field and on them a shape reconstruction procedure(structure from motion, SfM) is made. With use of a dense cloud of points, a sequence of parallax-related images suitable for Geola's digital holographic printing is generated. The holographic printer produces single-parallax holographic(full three-dimensional) images of real or virtual objects.     

Visible reconstruction by a circular holographic display from digital holograms recorded under infrared illumination

A circular holographic display that consists of phase-only spatial light modulators is used to reconstruct images in visible light from digital holograms recorded under infrared (10.6?μm) illumination. The reconstruction yields a holographic digital video display of a three-dimensional ghostlike image of an object floating in space where observers can move and rotate around it.     

Three-dimensional object recognition from digital Fresnel hologram by wavelet matched filtering

We propose and demonstrate a digital holographic technique for 3D object recognition and classification. One Fresnel digital hologram of each of the 3D objects to be classified is recorded. The electronic holograms are processed digitally to retrieve 3D object information as 2D digital complex images. We use this method to classify four physical objects in a 3D scene into two classes. Results are presented from an experiment to demonstrate the proof of the concept.     

A simplified holography based superresolution system

In this paper we are proposing a simple idea based on holography to achieve superresolution. The object is illuminated by three fibers which maintain the mutual coherence between the light waves. The object in-plane rotation along with fiber-based illumination is used to achieve superresolution. The object in a 4f optical system is illuminated by an on-axis fiber to make the central part of the object׳s spectrum to the pass through the limiting square-aperture placed at the Fourier plane and the corresponding hologram of the image is recorded at the image plane. The on-axis fiber is switched off and the two off axis fibers (one positioned on the vertical axis and the other positioned on diagonal) are switched on one by one for each orientation of the object position. Four orientations of object in-plane rotation are used differing in angle by 90°. This will allow the recording of eight holographic images in addition to the one recorded with on-axis fiber. The three fibers are at the vertices of a right angled isosceles triangle and are aligned toward the centre of the lens following the fiber plane to generate plane waves for object illumination. The nine holographic images are processed for construction of object׳s original spectrum, the inverse of which gives the super-resolved image of the original object. Mathematical modeling and simulations are reported.     

Occlusion removal technique for improved recognition of partially occluded 3D objects in computational integral imaging

In this paper, we propose an occlusion removal technique for improved recognition of 3D objects that are partially occluded in computational integral imaging (CII). In the reconstruction process of a 3D object which is partially occluded by other objects, occlusion degrades the resolution of reconstructed 3D images and thus this affects negatively the recognition of a 3D object in CII. To overcome this problem, we introduce a method to eliminate occluding objects in elemental image array (EIA) and the proposed method is applied to 3D object recognition by use of CII. To our best knowledge, this is the first time to remove occlusion in CII. In our method, we apply the elemental image to sub-image (ES) transform to EIA obtained by a pickup process and those sub-images are employed for occlusion removal. After the transformation, we correlate those sub-images with a reference sub-image to locate occluding objects and then we eliminate the objects. The inverse ES transform provides a modified EIA. Actually, the modified EIA is considered to be an EIA without the object that occludes the object to be reconstructed. This can provide a substantial gain in terms of the image quality of 3D objects and in terms of recognition performance. To verify the usefulness of the proposed technique, some experimental results are carried out and the results are presented.     

基于解码技术的全息显微术研究

提出了一种利用解码技术对全息显微畸变图像进行校正的方法。把全息记录中的显微镜预放大过程作为物光波产生畸变的编码过程;在波前再现过程中,用全息记录中的预放大显微镜对再现的赝实像再次放大进行解码,从而获得清晰的全息显微图像。实验验证了该方法的有效性。     

Improved Quantum Image Median Filtering in the Spatial Domain

In some image processing algorithms, such as those for image feature extraction and segmentation, filtering is a significant pre-processing step to remove noises and improve image quality. An improved quantum image median filtering approach is proposed, and its corresponding quantum circuit is designed in this work. The main idea of the approach is that first the classical image is converted into a quantum version based on the novel enhanced quantum representation (NEQR) of digital images, and then a unique quantum module is designed to realize the median calculation of neighborhood pixels for each pixel point in the image. Finally, in order to improve the filtering effect, extremum detection is employed to distinguish noises from true signals. The experimental results show that a competitive filtering performance is obtained compared with previous methods. In addition, a network complexity analysis of the quantum circuit suggests that the proposed filtering approach can perform enormous speed-up over its corresponding classical counterparts.

     

多焦距多通道全息光学元件

本文介绍了由不同焦距与不同衍射方向的全息透镜组合而成的一种新型全息元件。这种元件中的每个透镜具有相同的物方光轴和不同的象方光轴。它可以把物方空间沿光轴方向上的不同物距上的物面分别成像在对应的通道上,从而把一个三维物场变为多个二维像进行显示。文中给出了应用此元件对三线粒子场进行检测的初步结果。     

动态全息三维显示研究最新进展

全息三维显示是真三维显示技术, 其原理是利用光学干涉记录和衍射再现将物体或场景的三维信息全部重建出来, 所以观看全息三维图像与观看真实物体或场景的效果一样. 近期全息研究领域有一些突破性的成果被报道, 将推动全息显示的应用不断走向成熟. 本文将重点介绍基于光学材料和空间光调制器为全息图承载载体的动态全息三维显示最新发展状况. 虽然动态全息三维显示研究仍然存在挑战, 但最近研究中已经利用光学材料实现了实时动态全息三维视频显示, 这为未来实现大尺寸、高分辨率、彩色全息真三维视频显示提供了可能.     

Optical computing by a vector holographic memory system

We propose what is to our knowledge a novel holographic memory system that is simultaneously applicable to data storage and optical computing. We introduce a polarization-modulated reference beam into holographic recording. A desired spatial-frequency component of an object beam is recorded as a polarization-modulated grating, and the other component is recorded as an intensity-modulated grating. Since the polarization-modulated grating rotates the polarization axis of the incident light by 90 degrees , it is possible to distinguish the desired spatial-frequency component of the retrieved image. Utilizing this property, we have successfully performed spatial-frequency filtering and frequency-selective matched filtering. The system is capable of a variety of optical computations, depending on the design of the polarization modulation.     

Scale invariant recognition in optical correlators using prior estimation of object size

A new perspective of scale-invariant pattern recognition is proposed in this paper. Instead of computing a filter from one of many orthogonal components of the reference object, the scaling factor is estimated from the Fourier spectrums of reference and test images and utilized in rescaling of the spectrum. The test image is correlated with the reference image after rescaling its Fourier spectrum with classical matched filtering. Computer simulation results are presented for a reference object at several scaling versions as well as some non-target objects.     

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...     

Electromagnetically Induced Quantum Holographic Imaging

We study the quantum holographic imaging of one-dimensional electromagnetically induced grating created by a strong standing wave in an atomic medium. Entangled photon pairs, generated in a spontaneous parametric down-conversion process, are employed as the imaging light to realize coincidence recording. By theoretical analysis and numerical simulation, we find that both the amplitude and phase information of the object can be imaged with the characteristic of imaging nonlocally and of arbitrarily controllable image variation in size.