基于相移结构光照明的浮雕成像技术研究

详细介绍了一种基于相移结构光照明的浮雕成像技术,对该成像技术的原理和成像特性进行了实验研究,并采用相移结构光照明的方法实现彩色浮雕成像。实验中,将多幅相移正弦条纹光场斜投射到被拍摄物体上,数码相机依次拍摄被照明的物体,再利用拍摄到的多幅相移图像,通过计算的方法重建出所需要的图像。理论分析和实验结果表明,相移结构光照明成像技术能有效地消去环境不均匀光照的影响,获取的反射率分布图像只与结构光照明有关,突显了斜投射照明所形成的阴影,图像的明暗变化反映出物体表面的法线变化,因而在视觉上形成了明显的浮雕效果。     

在电子散斑干涉中利用反相位法进行三维变形测量

提出一种可将离面位移与面内位移分离的三维位移计算方法。在双光束电子散斑干涉系统中增加一路参考光,使这一路参考光为两光束所共用。两束光各自独立地对变形物体进行测量,分别计算相位分布,并对其中之一进行反相位计算。理论分析表明,对二路检测光所得到的相位进行相减运算,就能够较好地减少电子噪声的影响,分离面内位移场与离面位移,实现物体变形的三维测量。介绍该方法的原理,并利用典型实验证实了该方法的可行性。     

Supercontinuum laser illumination applied to traditional optical flow imaging methods

The schlieren method of refractive flow visualization traditionally requires non-coherent illumination in order to avoid problems with coherent artifact noise and binary cutoff by the knife-edge. Related shadowgraph and Wollaston-prism schlieren-interferometer methods, however, work well with light sources of high spatial coherence. Here we apply a supercontinuum laser as a light source for these methods, providing spatially coherent white-light illumination. Excellent results are obtained with shadowgraphy and schlieren-interferometry, but the schlieren method still requires a modified cutoff in place of the traditional knife-edge for laser illumination. Once they become widely available, supercontinuum lasers will find frequent use in these optical instruments, especially the schlieren-interferometer.     

电子散斑干涉位移场分离技术及其在三维测量中的应用

提供了一种可将离面位移与面内位移分离的三维位移场测量方法.在双光束电子散斑干涉中增加参考光,使这一路参考光为两光束所共用.两束光各自独立地对变形物体进行测量,结合相移技术,可分别得到包含离面和面内位移信息的二幅位相图.只需简单的位相运算就能够将面内位移场与离面位移场分离.在竖直方向上,采用两光束对称照明被测物,直接测量面内位移竖直方向分量.本文将该技术应用到柴油机油泵测量上,得到了油泵的三维位移场.该技术为三维位移场的测量提供了一种新的有效途径,也为柴油机零部件的强度和刚度分析评价提供了新的方法.     

Enhance sensitivity to illumination and synchronization in light-dependent neurons

When a phototube is activated to connect a neural circuit, the output voltage becomes sensitive to external illumination because the photocurrent across the phototube can be controlled by external electromagnetic wave. The channel currents from different branch circuits have different impacts on the outputs voltage of the neural circuit. In this paper, a phototube is incorporated into different branch circuits in a simple neural circuit, and then a light-controlled neuron is obtained for further nonlinear analysis. Indeed, the phototube is considered as exciting source when it is activated by external illumination, and two kinds of light-sensitive neurons are obtained when the phototube is connected to capacitor or induction coil, respectively. Electric synapse coupling is applied to detect possible synchronization between two functional neurons, and the energy consumption along the coupling channel via resistor is estimated. The analog circuits for the two kinds of light-sensitive neurons are supplied for further confirmation by using Multisim. It is found that two light-sensitive neurons and neural circuits can be synchronized by taming the coupling intensity carefully. It provides possible clues to understand the synchronization mechanism for eyes and artificial sensors which are sensitive to illumination. Finally, a section for open problems is supplied for further investigation about its collective behaviors in the network with/without synapse coupling.     

光源角度对金属表面图像边缘的影响分析

在机器视觉的图像处理中影响图像优劣的因素有很多,其中光源照射角度是主要因素之一。为了得到更好的图像数据,对视觉系统中光源照射最佳角度进行了仿真分析与实验研究,实验中采用单一变量法,只改变光源照射角度,通过理论计算、模拟仿真和实验验证相结合,得到了最佳的光源照射角度。结合Sobel算法检验在最佳角度下和其他角度下的图像边缘质量,结果表明在光照角度为57.17°的倾角下图像光照数据和边缘图像表现最好。该实验结果对更深层次的图像处理和图像采集具有指导意义。     

Application of reflectance transformation imaging for the display of handwriting traces

In our Letter, two kinds of handwriting traces, colored and colorless, are studied by means of reflectance transformation imaging. The illumination direction and rendering mode can be changed alternatively to obtain two-dimensional and three-dimensional details of the traces that are not recognized easily by naked eyes.Furthermore, an objective evaluation method without reference is applied to evaluate the reconstructed images,which provides a basis for setting the illumination direction and rendering mode. Therefore, the handwriting trace information including the written content, the writing features, and the stroke order features can be obtained objectively and accurately.     

A compact ESPI system for displacement measurements of specular reflecting or optical rough surfaces

A stable and compact speckle interferometer for doing out-of-plane displacement measurements on reflective as well as diffusely scattering object surfaces is demonstrated. The set-up is based on a nearly path length compensated interferometer of the Fizeau type and uses diffuse illumination of the object combined with a speckled reference wave. This combination eliminates the need for special optical components, and the interferometer can be built of commonly available components. The diffuse illumination wave is obtained by scattering coherent light from a diffusely scattering surface. The speckled reference wave is established by reflecting a part of the diffuse illumination wave from a glass plate placed in front of the object. Besides relaxing the alignment tolerances of the set-up, the diffuse illumination eliminates the need for any preparation of the surface under test, which turns the system into a candidate for testing micro mechanical systems. When using the interferometer for measurements of the eye, the risk of focusing the laser beam on the retina is decreased due to the diffuse object illumination.     

An optimisation design of adaptive illumination for a multi-reflective 3D scene

An illumination optimisation technique applied to multi-reflective 3-D machine vision based on a projector-camera system is introduced, in which the projector plays a key role to compensate for surface reflectance at each pixel to be inversely proportional to the brightness of the pixel under ambient light. The adaptive illumination technology was achieved by iterations emphasising different illumination intensities according to different surface orientations and requiring an accurate correspondence between the projector pixels and the camera pixels. In order to establish the most effective correspondence to prepare for subsequent adaptive illumination, 4 kinds of grating patterns, including sinusoidal, rectangular, triangular, and dual-frequency sinusoidal grating patterns, were projected and compared. The iterations were halted when an optimally lit scene was obtained; the further experiments under weak and strong light searched for the best method of illumination optimisation and confirmed the reliability of the adaptive illumination. The proposed optimisation design could run in real time and became a viable solution for industry.     

彩色视觉测量中的LED照明系统设计

设计并制作了一套基于发光二极管(LED)的具有多颜色特征的光源系统,分析了光源工作原理,进行了光学结构设计.应用MAX16807芯片和脉宽调制(PWM)技术设计专用驱动电路,实现了LED的恒流驱动和亮度数字调制.实验证明,该光源预热后的照度、主波长和色品坐标稳定,辐照均匀度达到90%以上,可以满足彩色视觉测量的需要并取...     

Muonium studies of p-type semi-conducting diamond under conditions of UV-visible illumination

This work reports on the promptly forming fraction and the spin relaxation rate of the isotropic muonium (Mu_T) component in p-type semi-conducting diamond, measured under the condition of illumination. The data are the first such investigations for diamond. A broad band illumination with wavelengths ranging from 0.5 μm to 3 μm was obtained from a Xenon lamp. The energy of the photons was sufficient to excite electrons from the valence band to the 0.28 ppm boron impurity band (0.37 eV). The Transverse Field Muon Spin Rotation (TF-μSR) measurements were conducted as a function of temperature, ranging from 5 K to 300 K. An illumination effect at temperatures below 100 K is observed. It is not yet clear from these data whether the effect is due to Mu_t scattering off delocalized holes, which are removed by illumination or whether there is prompt trapping of Mu_t at boron impurities (passivation) which is affected by illumination. This revised version was published online in August 2006 with corrections to the Cover Date.     

Emission curves vs charging conditions in phosphorescent pigments embedded in sintered glass: Is there a reciprocity law?

Applications of phosphorescent materials are derived from their light emission properties at short and long times since the end of stimulation. The enhancement of such properties affects its performance in safety signs systems. Light emission power is conditioned by the time of excitation and the illumination received by the phosphorescent material, so that the total incoming energy is the product of both. For a given spectral profile, there is at least one upper limit of storable energy, resulting in effects of saturation for high values of illumination and excitation times. This work examines the emission curves of phosphorescent pigments embedded in sintered glass, in experiments where the total incoming energy is kept constant for combinations of illumination and time, in order to analyze the existence and the degree of reciprocity between these pairs. In addition, using a simple model we simulate some of the results obtained experimentally.     

应用于投影光刻离轴照明的自由曲面设计

离轴照明是现代投影光刻中的一种重要的分辨率增强技术.针对不同的照明模式要求,提出了一种利用自由曲面来实现离轴照明的方法.根据入射面和目标面之间的坐标拓扑和能量守恒关系,利用数值求解法得出自相应的折射式自由曲面并对结果进行模拟,分别设计了环形、二极和四极照明,照明效率均达到90%以上,照明均匀性均优于93%.结果表明,可...     

Complete-angle projection diffuse optical tomography by use of early photons

We present the first, to our knowledge, experimental images of complex-shaped phantoms embedded in diffuse media by use of optical tomography. Imaging is based on a complete-angle projection tomographic technique that utilizes transmitted early photons. Results are contrasted with measurements obtained at later gates as well as pseudocontinuous-wave data. The scanning system developed employs noncontact illumination and detection technologies that allow for high spatial sampling of transmitted photons. Combining this system with complete-angle illumination is found to be an important strategy toward improved imaging performance, resulting in a better-posed inversion problem. The appropriateness of reconstruction algorithms similar to those employed in x-ray computed tomography are showcased, and suggestions for model improvements are provided.     

Broadband dispersion characteristics of diffractive microlenses based on the finite-difference time-domain method

The broadband dispersion characteristics of diffractive microlenses are studied using the finite-difference time-domain (FDTD) method. The distributions of the diffracted electric fields obtained through a diffractive microlens are presented for illumination wavelengths ranging from 0.35 to 1.30 μm, along with the corresponding broadband dispersion curves. It is shown that both the principal focal length and the diffracted order of the principal focal point are dependent on the illumination wavelengths. The broadband dispersion characteristics of a diffractive microlens may be used to optimise light coupling for a broadband optical fibre source.     

神光-Ⅲ原型装置两极驱动的均匀照明研究

梳理了两极驱动的研究思路和神光-Ⅲ原型装置两极驱动的研究内容;提出了针对靶丸表面均匀照明设计的光束近似原则,基于该原则建立了"逐次递进"的方法,优化设计了不同条件下靶丸表面均匀照明的激光条件,并对设计方法进行了数值模拟分析,设计内容在神光一III原型装置上进行了初步的实验验证,结果进一步支持了靶丸表面均匀照明设计的合理性,研究结果为后续的实验设计和理论研究提供了指导方向。     

Optically induced internal fields in ferroelectrics

The internal fields generated by inhomogeneous illumination of a ferroelectric electric are calculated on the basis of the theory for the bulk photovoltaic effect. The expressions derived agree well with the experimental results obtained in connection with volume hologram storage and optical damage.     

Optical efficiency of solar concentrators by a reverse optical path method

A method for the optical characterization of a solar concentrator, based on the reverse illumination by a Lambertian source and measurement of intensity of light projected on a far screen, has been developed. It is shown that the projected light intensity is simply correlated to the angle-resolved efficiency of a concentrator, conventionally obtained by a direct illumination procedure. The method has been applied by simulating simple reflective nonimaging and Fresnel lens concentrators.     

One-dimensional steady-state bright photovoltaic solitons in LiNbO3:Fe crystal with background illumination

We investigate theoretically and experimentally one-dimensional bright photovoltaic solitons in LiNbO₃:Fe crystal by use of the background illumination. We find that, in LiNbO₃:Fe crystal, bright photovoltaic solitons can be obtained with background illumination for κ>1, where κ is the ratio of the background illumination photovoltaic constant to the soliton optical beam's photovoltaic constant. For κ<1, dark photovoltaic solitons are generated. On the other hand, our experiments show good agreement with theoretical prediction for the soliton existence curve in a special intensity ratio.     

基于均匀照明的LED反射器的设计

为了创造良好的视觉环境,并提高光能利用率,设计了一种基于均匀照明的LED反射器。之所以选用球面环形阵列LED光源,第一是为扩大照明范围,其次是为了避免面光源垂直照射产生光强过强而导致的眩晕。设计的反射器是运用划分网格的方法获得自由曲面面型,运用机械建模软件拟合曲面的实体模型,进行了照明仿真模拟及分析。结果表明,与传统的反光器相比,自由曲面的反射器能较大程度地利用光源发出的能量,而且均匀性也有很大的提高。