Nanometric depth resolution from multi-focal images in microscopy

We describe a method for tracking the position of small features in three dimensions from images recorded on a standard microscope with an inexpensive attachment between the microscope and the camera. The depth-measurement accuracy of this method is tested experimentally on a wide-field, inverted microscope and is shown to give approximately 8 nm depth resolution, over a specimen depth of approximately 6 µm, when using a 12-bit charge-coupled device (CCD) camera and very bright but unresolved particles. To assess low-flux limitations a theoretical model is used to derive an analytical expression for the minimum variance bound. The approximations used in the analytical treatment are tested using numerical simulations. It is concluded that approximately 14 nm depth resolution is achievable with flux levels available when tracking fluorescent sources in three dimensions in live-cell biology and that the method is suitable for three-dimensional photo-activated localization microscopy resolution. Sub-nanometre resolution could be achieved with photon-counting techniques at high flux levels.     

Creating a system of aspects of a three-dimensional scene

We consider two schemes of creating a matrix of the holograms of aspects of a three-dimensional stage. The holographic variant is supplementary to the method of photographic registration of the system of aspects described previously.     

Depth resolution in stereoscopic systems

In television stereoscopic systems the magnification and the effective eye separation can be varied at will. This study shows that, under carefully chosen experimental conditions, depth resolution can be closely predicted by the use of geometrical optics and can be enhanced by increases in magnification and effective eye separation. The limited spatial resolution of conventional television or other photoelectronic systems may, however, prevent high levels of stereoacuity, comparable with naked-eye viewing, from being achieved in a wide-field system. In more complex environments the inevitable conflict of perceptual cues might be expected to reduce depth resolution further.     

Enhanced three-dimensional reconstruction from confocal scanning microscope images. II. Depth discrimination versus signal-to-noise ratio in partially confocal images

The enhanced depth discrimination of a confocal scanning optical microscope is produced by a pinhole aperture placed in front of the detector to reject out-of-focus light. Strictly confocal behavior is impractical because an infinitesimally small aperture would collect very little light and would result in images with a poor signal-to-noise ratio (SNR), while a finite-sized partially confocal aperture provides a better SNR but reduced depth discrimination. Reconstruction algorithms, such as the expectationmaximization algorithm for maximum likelihood, can be applied to partially confocal images in order to achieve better resolution, but because they are sensitive to noise in the data, there is a practical trade-off involved. With a small aperture, fewer iterations of the reconstruction algorithm are necessary to achieve the desired resolution, but the low a priori SNR will result in a noisy reconstruction, at least when no regularization is used. With a larger aperture the a priori SNR is larger but the resolution is lower, and more iterations of the algorithm are necessary to reach the desired resolution; at some point the a posteriori SNR is lower than the a priori value. We present a theoretical analysis of the SNR-toresolution trade-off partially confocal imaging, and we present two studies that use the expectationmaximization algorithm as a postprocessor; these studies show that a for a given task there is an optimum aperture size, departures from which result in a lower a posteriori SNR.     

Depth extraction of three-dimensional objects using block matching for slice images in synthetic aperture integral imaging

We describe a computational method for depth extraction of three-dimensional (3D) objects using block matching for slice images in synthetic aperture integral imaging (SAII). SAII is capable of providing high-resolution 3D slice images for 3D objects because the picked-up elemental images are high-resolution ones. In the proposed method, the high-resolution elemental images are recorded by moving a camera; a computational reconstruction algorithm based on ray backprojection generates a set of 3D slice images from the recorded elemental images. To extract depth information of the 3D objects, we propose a new block-matching algorithm between a reference elemental image and a set of 3D slice images. The property of the slices images is that the focused areas are the right location for an object, whereas the blurred areas are considered to be empty space; thus, this can extract robust and accurate depth information of the 3D objects. To demonstrate our method, we carry out the preliminary experiments of 3D objects; the results indicate that our method is superior to a conventional method in terms of depth-map quality.     

Depth rendition of three-dimensional displays

The third dimension in the reproduction of real scenes in three-dimensional displays is commonly subject to scale changes. The geometry of the situation is laid out, permitting the depth rendition of displays to be characterized and subjected to empirical examination. Psychophysical experiments are presented showing, even when geometrical deformations have been factored out, specific deviations from veridicality in observers' depth reports for stereograms of simple static patterns devoid of secondary cues.     

Determination of the depth resolution in Auger depth profiling measurements

The depth resolution Δz of the Auger depth profiling method was studied in multilayer thin films comprising alternate layers of nickel and molybdenum or of cobalt and molybdenum. The composition-depth profiles of several interfaces located at different depths within the same film were compared. Thus changes which depended on the sputtering depth z could be distinguished from effects which were independent of z. According to a statistical theory the profiles of the interfaces can be described by a gaussian error function. An empirical formula $\text{Δz = αz}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{+ β}$ was determined from the width of the profiles. The first term agrees with the statistical theory and the constant term is explained by the roughness of the interface. The order of magnitude of β (≈ 3 nm) suggests that the depth resolution in the films is not limited by the escape depth of the Auger electrons (? 1.5 nm). The relative depth resolution $\text{Δz}\text{z}$ improves with increasing sputtering depth.     

择优溅射对深度剖析谱和深度分辨率的影响

择优溅射是深度剖析实验中导致所测量元素的成分分布偏离实际的一个重要因素.本文首先在广泛应用于溅射深度剖析定量分析的MRI模型基础上,引入了一个描述择优溅射效应的参数,推导出了这个参数对所测量的深度剖面引起改变的一个解析式,并定量地模拟了择优溅射效应在深度剖析中对深度剖面形状和深度分辨率的影响.最后,应用拓展的MRI模型,定量分析了Ar+和N2+溅射Ni/Cr多层膜所得到的AES深度剖析数据,比较了相应的择优溅射比率和深度分辨率.     

EFSA—a new evaluation method of the depth resolution in depth profiling of multilayer structures

A new evaluation method called EFSA (error function superposition approximation) is proposed, to obtain depth resolution functions on any multilayer structure in agreement with the conventional absolute depth resolution. The quantitative evaluation of Δz measured on multilayer samples helps in clearing up the relations of different interface broadening effects and makes the evaluation independent of the measuring system. It is shown that this method can be successfully applied to both SIMS and AES depth profile measurements and that it has proved to be useful in comparing results obtained in different laboratories.     

医学虚拟训练的视觉与触觉场景三维同步匹配

基于高精度虚拟中国人男性一号数据集和虚拟现实开发工具Open Inventor,利用由主动式立体眼镜和力反馈设备构建的仿真平台,实现了视觉场景图和触觉场景图的三维同步匹配。论述了开发环境的具体要求,分析了视觉和触觉场景图三维同步匹配的实现策略,给出了三维同步匹配和注射模拟实验的仿真结果。结果表明,虚拟系统的视觉场景图和触觉场景图的三维同步匹配准确,可实时、快速实现视觉和触觉的立体模式医学虚拟训练。     

Building three-dimensional images using a time-reversal chaotic cavity

The design of two-dimensional (2-D) arrays for three-dimensional (3-D) ultrasonic imaging is a major challenge in medical and nondestructive applications. Thousands of transducers are typically needed for focusing and steering in a 3-D volume. In this article, we propose a different concept allowing us to obtain electronic 3-D focusing with a small number of transducers. The basic idea is to couple a small number of transducers to a chaotic reverberating cavity with one face in contact with the body of the patient. The reverberations of the ultrasonic waves inside the cavity create at each reflection virtual transducers. The cavity acts as an ultrasonic kaleidoscope multiplying the small number of transducers and creating a much larger virtual transducer array. By exploiting time-reversal processing, it is possible to use collectively all the virtual transducers to focus a pulse everywhere in a 3-D volume. The reception process is based on a nonlinear pulse-inversion technique in order to ensure a good contrast. The feasibility of this concept for the building of 3-D images was demonstrated using a prototype relying only on 31 emission transducers and a single reception transducer.     

Depth resolution enhancement in optical scanning holography with a dual-wavelength laser source

In this paper, we use two point sources to analyze the depth resolution of an optical scanning holography (OSH) system with a single-wavelength source. A dual-wavelength source is then employed to improve it, where this dual-wavelength OSH (DW-OSH) system is modeled with a linear system of equations. Object sectioning in DW-OSH is obtained with the Fourier domain conjugate gradient method. Simulation results show that, with the two source wavelengths at 543 nm and 633 nm, a depth resolution at 2.5 μm can be achieved. Furthermore, an OSH system emulator is provided to demonstrate the performance of DW-OSH compared with a conventional OSH system.     

基于连通域的图像中场景文本定位

提出了一种基于连通域的自动定位图像中场景文本的方法.该方法充分利用了场景文本的两类特征--字符特征和文本区域特征,同时对一些字符特征进行组合,组合得到的新字符特征能够对字符的大小、字体等有很好的不变性.该方法利用级联弱分类器将所有的特征组合到一个框架中,提高了处理速度.实验结果显示,该方法对字符的大小、颜色、语言等具有很好的鲁棒性,并具有较高的召回率.     

Analysis of an optical depth converter used in a three-dimensional integral imaging system

An optical depth converter that uses a lens array pair is analyzed theoretically and experimentally. We present a theory of depth conversion and explain the effects of the system parameters in the optical depth converter by using wave-optical analysis. Ray-optical analysis is applied to the investigation of the tendencies of the system parameter effects. We also show that the optical depth converter can be used for the three-dimensional screen in projection-type integral imaging systems.     

Three types of computer-generated hologram synthesized from multiple angular viewpoints of a three-dimensional scene

We describe various techniques to synthesize three types of computer-generated hologram (CGH): the Fresnel-Fourier CGH, the Fresnel CGH, and the image CGH. These holograms are synthesized by fusing multiple perspective views of a computer-generated scene. An initial hologram is generated in the computer as a Fourier hologram. Then it can be converted to either a Fresnel or an image hologram by computing the desired wave propagation and imitating an interference process of optical holography. By illuminating the CGH, a 3D image of the objects is constructed. Computer simulations and experimental results underline the performance of the suggested techniques.     

Unsteady three-dimensional sources for a two-layer fluid of finite depth and their applications

To our friend Ernie Tuck, in celebration of his multi-faceted talents. The velocity potentials of various unsteady point sources are derived in this paper for a two-layer fluid of finite depth. Two-layer fluids are often used to study effects of density stratification on hydrodynamics of marine systems. The sources here are restricted to the upper fluid layer and the potentials of the induced flows are given for the whole fluid domain. The velocity potentials of a transient source of arbitrary strength and in arbitrary three-dimensional motion are derived first. The potentials of a time-harmonic source without forward speed, and then with forward speed, are obtained from the transient source by specifying the appropriate source strength and motion. These potentials are fundamental to the analyses of various types of body motion in finite water depths under the influence of surface and interfacial waves. As a sample application, a numerical solution of the radiation and diffraction problem for a floating rectangular barge is presented. The results indicate that internal waves can have a strong effect on the motions of the floating barge over a wide range of incident-wave frequencies.     

Subnanometer resolution in depth profiling using glancing Auger electrons

A new method for Auger depth profiling, employing a difference in the escape depth of the Auger electrons emitted at nearly normal and glancing angles, is proposed and verified. The depth profiles obtained under optimum ion sputtering conditions with registration of the glancing Auger electrons exhibit a subnanometer (0.8 nm) depth resolution. This technique was successfully applied to the study of high-quality In_xGa_1−x As/GaAs heterostructures with quantum wells grown by the method of metalorganic chemical vapor deposition.     

Reconstruction of three-dimensional chemiluminescence images with a maximum entropy deconvolution algorithm

Three-dimensional (3D) images of flame emission are reported using a single direction of optical access. A Cassegrain system was designed with narrow depth of field. Images from this system are dominated by emission from the focused object plane with defocused contributions from out-of-plane structures. Translation of one mirror in the system allows for scanning the object plane through the flame. Images were taken at various depths to create a family of images. Reconstruction of the 3D flame structure was accomplished using a maximum entropy algorithm adapted for use with 3D imaging. Spatial resolution in the direction of imaging is examined using laminar flames with variable offset.