共查询到20条相似文献,搜索用时 936 毫秒
1.
仿生复眼成像系统设计与制作的研究进展 总被引:2,自引:0,他引:2
基于仿生复眼光学成像系统体积小、重量轻、视场大、灵敏度高等优点,对其研究现状和发展前景进行了综述。简要介绍了生物复眼的结构与分类;分别从平面型和曲面型仿生复眼成像系统的设计概述了仿生复眼的研究进展,给出了国内外典型复眼成像系统的结构、模型和成像功能;总结了仿生复眼成像系统应用于不同领域的特点和优势。最后,分析了目前仿生复眼的工艺现状,指出仿生复眼的功能主要受微器件制作工艺的限制,而超精密加工技术是一种革新的、综合的微细加工方法,具有制作更高精度透镜阵列,提高人工仿生复眼应用能力的潜力。 相似文献
2.
We report the fabrication of artificial ommatidia, the imaging units of insects' compound eyes, by use of polymer integrated optics. These biomimetic structures are obtained by configuring microlenses to play dual roles for self-writing of waveguides (during the fabrication) and collection of light (during the operation). The artificial ommatidium, consisting of a microlens, a spacer, and a waveguide, directly resembles the structure of its biological counterpart. Optical characterizations reveal single-peak angular sensitivity with a +/- 0.75 degrees acceptance angle that is comparable to those found in nature. Using geometric and physical optics, we also investigate the relationship between angular sensitivity and the geometry of artificial ommatidia. 相似文献
3.
4.
基于Gross-Pitaevskii(G-P)平均场能量泛函和变分方法,对囚禁在谐振势阱中的玻色凝聚气体,在T=0K时的基态波函数提出一种新解法.运用这一方法能得到基态波函数的解析表达式,求解出系统的化学势与凝聚原子数的关系等.其结果与Edwards和Dalfovo等人直接数值求解G-P方程所得到的结果相一致,并在Nas/a1大原子数N的极限条件下,与托马斯-费米近似模型的结论也趋向一致.该方法计算简单,而且能够进行解析处理.
关键词:
玻色凝聚气体
G-P泛函
谐振势阱
基态波函数 相似文献
5.
The gamma-gamma probability density function is commonly used to model the scintillation of a single laser beam propagating through atmospheric turbulence. One method proposed to reduce scintillation at the receiver plane involves the use of multiple channels propagating through independent paths, resulting in a sum of independent gamma-gamma random variables. Recently, a novel approach for an accurate, closed-form approximation for the sum of independent, identically distributed gamma-gamma random variables was introduced by Chatzidiamantis et al. [GLOBECOM 2009--2009 IEEE Global Telecommunications Conference (2009)]. Using this approximation, we present the first analytic model for the distribution of irradiance due to propagating multiple independent beams. This model compares favorably to wave-optics simulations. 相似文献
6.
基于Delta-P1近似漫反射光学模型, 推导了双点源近似下空间分辨漫反射解对于Henyey-Greenstein散射相函数的二阶参量γ的灵敏度表达式, 研究了参量γ对漫反射分布的影响. 研究表明, 与漫射近似模型相比, Delta-P1近似漫反射光学模型不仅含有散射相函数的二阶参量γ, 而且在弱吸收或强吸收的情况下, 参量γ对于光源附近(ρ<1.0 mm)的空间分辨漫反射都存在较大的影响(极值大于30%). 因此利用γ研究漫反射光分布对于获取组织光学信息具有重要的意义. 相似文献
7.
8.
9.
Cynthia Y. Young Aaron J. Masino Fredrick E. Thomas Christopher J. Subich 《Waves in Random and Complex Media》2004,14(1):75-96
The Rytov perturbation method can be used to derive analytic expressions governing statistical quantities of an optical wave propagating through the Earth's atmosphere. It is generally accepted that the validity of these expressions is restricted to the weak fluctuation regime, and that the wave structure function for plane and spherical waves obtained via the Rytov method is valid in all fluctuation regimes, for sufficiently small separation distances. Data from experimental results for the wave structure function as a function of the fluctuation strength for a fixed value of the separation distance indicate that the Rytov method does not accurately model the behaviour of the wave structure function in moderate to strong fluctuation regimes. This is similar to what is observed for the scintillation index. Recently, however, it was shown that the integral definition of the scintillation index obtained via the Rytov perturbation yields analytic expressions that are valid in all fluctuation regimes when a filter function is applied to the atmospheric spectrum. The underlying physical theory is that as the wave propagates, intermediate refractive index scale sizes fail to refract or diffract the beam. Hence, these scale sizes do not contribute to the scintillation index. In this paper, we investigate the results of applying this concept to the wave structure function. Specifically, we apply a filter function to the atmospheric spectrum and develop analytic expressions for the wave structure function for plane, spherical and Gaussian beam waves using the Rytov perturbation method. It is shown that in weak fluctuations these expressions yield similar results to standard expressions obtained where no filter function is applied. However, in moderate to strong fluctuations, these new expressions predict a decrease in the value of the wave structure function as compared to the standard expressions, following the trend of the experimental data presented by Gurvich.
(Some figures in this article are in colour only in the electronic version) 相似文献
(Some figures in this article are in colour only in the electronic version) 相似文献
10.
人眼视觉的传递特性及模型 总被引:10,自引:4,他引:10
介绍了国内外对人眼视觉特性及其调制传递函数的研究 ,对几种典型的人眼视觉模型进行了分析。较之以往采用的具有低通特性的指数型和高斯型 ,及具有带通特性的Barten模型和复合模型更符合人眼视觉传递特性。在此基础上将两种带通模型和国内外一些典型的试验数据进行了比较研究 ,得出 :Barten模型参数简单 ,计算方便 ,但实用的范围较复合模型小。复合模型综合考虑了人眼瞳孔、显示器亮度、视场角、量子效率、积分时间等因素的影响 ,是一种更全面的反映人眼传递特性的视觉模型 相似文献
11.
12.
We measured the wavefront aberrations of the eyes of five subjects with a Shack-Hartmann sensor sampling at 21.2 Hz and decomposed the measurements into Zernike aberration terms up to and including the fifth radial order. Coherence function analysis was used to determine the common frequency components between the aberrations within subjects. We found the results to be highly subject dependent. The coherence values were typically <0.4. Possible reasons for this are discussed. Coherence function analysis is a useful tool that can be used in future investigations to determine correlations between the aberration dynamics of the eye and other physiological mechanisms. 相似文献
13.
An Artificial Compound Eye Using a Microlens Array and Its Application to Scale-Invariant Processing 总被引:1,自引:0,他引:1
An artificial compound eye corresponding to apposition eyes of insects has been demonstrated using a two-dimensional array of gradient-index rod lenses known as a Selfoc lens plate (a SLP). A single erect Moiré image is reconstructed from a number of inverted micro-images by an experimental optical system composed of the SLP, a pinhole array and a plano-concave lens. Characteristics of the compound eye is briefly discussed from the viewpoints of space-bandwidth product, viewing angle, and focal depth. Capability of a scale-invariant image sensor that has been proposed as an application of the compound-eye-type imager was also proved experimentally. 相似文献
14.
15.
Carlile R.N. Webster S.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1988,16(1):17-21
The authors discuss an analytic solution of the Boltzmann equation which describes the relaxation in time of the electron distribution function for electrons in a plasma derived from the monatomic gases He, Ne, Ar, and Xe. It is assumed that there are no perturbing forces on the electrons and that at t =0 they have a Maxwellian distribution function corresponding to an average energy of 2 eV. The electrons then lose energy through elastic collisions with neutrals and eventually energy-equilibrate with the neutrals, which are assumed to be cold. The evolution of the electron distribution function in time and velocity space is calculated for each gas. This model is approximately correct for the afterglow period of an electrical discharge in a monatomic gas. It is possible to calculate a time which is a measure of the decay time of the electron energy in an afterglow plasma 相似文献
16.
Dariouchy A Aassif E Maze G Décultot D Moudden A 《The Journal of the Acoustical Society of America》2008,124(2):1018-1025
A new approach is used to predict the acoustic form function (FF) for an infinite length cylindrical shell excited perpendicularly to its axis using the artificial neural network (ANN) techniques. The Wigner-Ville distribution is used like a comparison tool between the FF calculated by the analytical method and that predicted by the ANN techniques for a stainless steel tube. During the development of the network, several configurations are evaluated for various radius ratios ba (a: outer radius: b: inner radius of the tube). The optimal model is a network with one hidden layer. It is able to predict the FF with a mean relative error about 1.61% for the cases studied in this paper. 相似文献
17.
单次散射相函数对电磁辐射传输模拟过程的准确性和计算效率有重要的影响.基于电磁散射与辐射传输中的基本理论,对单次散射相函数的解析表达式进行了研究,提出了一种新的单次散射相函数解析表达式.比较了单个粒子的Henyey-Greenstein相函数、Henyey-Greenstein*相函数与新的相函数随角度的分布,发现新的散射相函数提高了后向散射峰值,可以更合理地描述单个粒子的散射特性.按三种气溶胶粒子谱分布模式计算了Henyey-Greenstein*相函数和新的相函数对应的数值结果,并与多分散系Mie散射相函数进行对比,发现新的相函数提高了与多分散系Mie散射相函数的符合程度.研究表明,对于大角度(大于90°)后向散射,新的相函数与Mie散射相函数均方根差较小的占73.3%,高于Henyey-Greenstein*相函数的26.7%,证明了新的相函数可以显著提高后向散射峰值.新的相函数对准确模拟辐射传输过程具有重要意义. 相似文献
18.
It is shown that, in the case of asymmetric nuclear interactions, the application of the traditional dihadron correlation approach to determining a two-particle correlation function C may lead to a form distorted in relation to the canonical pair correlation function C2. This result was obtained both by means of exact analytic calculations of correlation functions within a simple string model for proton–nucleus and deuteron–nucleus collisions and by means of Monte Carlo simulations based on employing the HIJING event generator. It is also shown that the method based on studying multiplicity correlations in two narrow observation windows separated in rapidity makes it possible to determine correctly the canonical pair correlation function C2 for all cases, including the case where the rapidity distribution of product particles is not uniform. 相似文献
19.
Using the spin-boson model with coupling to Ohmic bath, an analytical approach is developed to study the dynamics of the current correlation function in dissipative two-state systems with the view of understanding the effects of environment and tunneling on the coherent oscillation and the long-time decay of the current correlation function in these systems. An analytic expression of current correlation function is obtained and the results agree very well with that of numerical simulations. 相似文献
20.
Biomimetic compound eyes with a high numerical aperture on a curved surface were successfully fabricated by intelligent integration of traditional top-down and bottom-up micro- and nanofabrication methods together. In addition, the new hybrid micro- and nanofabrication method allows us to fabricate the antireflective nanostructures on each ommatidium to increase its vision sensitivity by improving the light transmission. The fabricated compound eye was optically characterized and was shown to have a numerical aperture of 0.77 for each ommatidium. Furthermore, it is shown that the transmission of the compound eye can be improved by 2.3% for the wavelength of 632.8 nm and a clearer image can be formed by the fabricated compound eye with antireflective nanostructures compared with that without antireflective nanostructures. In addition, the developed hybrid manufacturing method can be adapted to the fabrication of other complex micro- and nanodevices for photonics or other research areas. 相似文献