Simulation of Atmospheric Wave-Fronts with Turbulence Intermittency

A new extendable method for the simulation of atmospheric wave-fronts with turbulence intermittency is reported. The purpose is to generate simulations consistent with the distributions observed for the turbulence parameters and the seeing, not available with standard methods. The intermittency is included by entering log-normal distributed arrays for the Fried parameter and the spatial coherence outer scale length into an extended form of the phase spectrum. The method is tested on large samples of simulated long-exposure point-source images. The tests show the agreement of the simulations with literature data. The simulations show that the intermittency affects negligibly the long-term median image size but breaks the symmetry of the wave-front phase spectrum, scatters the phase structure function and changes the image profile.

正交余弦光栅的衍射场

为了研究正交余弦光栅的衍射场,采用波前相因子判断法并考虑到光栅孔径的影响,对正交余弦光栅的衍射进行了理论分析,得到了正交余弦光栅衍射场所含基元成分,导出了像面波前函数、像面振幅分布函数和光强分布函数,并得出主焦斑的半角宽度。结果表明,该研究可为光栅用于光学信息处理技术提供理论依据。

正六边孔的衍射场

为了研究正六边形小孔的衍射场,采用波前相因子判断法并考虑到孔径的影响对正六边形小孔的衍射场进行研究,得出正六边形小孔衍射场所含基元成份及衍射场的波前函数、像面上的振幅分布函数和光强分布函数,然后利用数值模拟的方法得出正六边形小孔在像面上的衍射图样;结果表明,在验证衍射理论的同时拓展了衍射的概念,能为深入理解光的衍射提供参考。

用相因子判断法分析双缝的衍射场

用波前相因子判断法并考虑到孔径的影响分析双缝的衍射场。得出衍射场波前函数,像面衍射场的振幅和光强公式,并用数值模拟出像面衍射场振幅和光强分布,最后得出中央主极大的半角宽度。本研究为双缝衍射提供了一种新的分析方法。

用相因子判断法分析多缝衍射

采用波前相因子判断法并考虑到光栅孔径的影响来分析多缝的衍射。得出多缝衍射的波前函数、像面上多缝衍射振幅和光强公式,并模拟出像面衍射振幅分布和光强分布,最后得出中央主极大的半角宽度。结果表明该研究为多缝衍射分析提供了一种新的分析方法。

分析五方孔的衍射场

采用波前相因子判断法研究五方孔的衍射场,得出五方孔衍射场所含基元成份。根据惠更斯-菲涅耳原理,导出像面上的振幅分布公式及像面上的光强分布公式等。并利用数值模拟的方法得出五方孔的衍射图样。结果表明,在验证衍射理论的同时,还拓展了衍射的概念,为深入理解光的衍射提供理论基础。

Measurements of AIM for Visible Wavelength Based on Individual Eye Model

We measure and calculate the aerial image modulation （AIM） of human retina for visible wavelengths based on the individual eye model. By employing the optical design software ZEMAX, we obtain the modulation transfer function （MTF） of human eye in visible wavelengths. Using CSV-1000 and VAF-1000, the contrast sensitivity function （CSF） and the visual acuity （VA） for the same eye are measured. Then the AIM of human retina could be acquired by the relations between MTF and CSF and between MTF and VA. The AIM of human retina is independent of MTF, and the values of AIM for normal eyes （without retina disease） are similar, so the assembly average for large numbers of normal eyes can be a standard AIM curve, which is helpful for the diagnosis of diseases in the retina system.

Generation of orbital angular momentum and focused beams with tri-layer medium metamaterial

We propose a metal/dielectric tri-layer metamaterial for wavefront shaping. By arranging the element in an array with a constant phase gradient and irradiated it with a plane wave, focused and focused vortex beams can be obtained. The designed metamaterial features the excellent capability of focused/focused vortex beams generation within the operating frequency range of 30 GHz–34 GHz. The simulation results are consistent with the theoretical analyses.

Extending Dynamic Range of Phase Diversity

A method for extending dynamic range of phase diversity （PD） is proposed.The estimating of pupil phase is divided into two steps.Low-order Zernike coefficients of the phase are estimated firstly before all of the Zernike coefficients estimated.The method is based on the assumption that the aberrations of the system are dominated by low order Zernike modes,which is true to most practical situations.The algorithm of BroydenFletcher-Goldfarb-Shanno（BFGS） is used in the two steps for optimizing process.Computer simulations are conducted after the theoretical analysis.The result shows that this method can effectively avoid the trap in local minimum during iteration process,and the dynamic range that PD can detect extends from about 2λ to about 4λ.

GLOBAL EXISTENCE OF SOLUTIONS FOR A MULTI-PHASE FLOW: A BUBBLE IN A LIQUID TUBE AND RELATED CASES

In this paper we study the problem of the global existence （in time） of weak entropic solutions to a system of three hyperbolic conservation laws, in one space dimension, for large initial data. The system models the dynamics of phase transitions in an isothermal fluid; in Lagrangian coordinates, the phase interfaces are represented as stationary contact discontinuities. We focus on the persistence of solutions consisting in three bulk phases separated by two interfaces. Under some stability conditions on the phase configuration and by a suitable front tracking algorithm we show that, if the BV-norm of the initial data is less than an explicit （large） threshold, then the Cauchy problem has global solutions.

Wave-front correction of high-intensity fs laser beams by using closed-loop adaptive optics system

We developed an adaptive optics system to correct the wave-front distortion of an intense fs laser beam from our multi-TW laser system, Jiguang II. In this paper, the instruments of the adaptive optical system are described and the experimental results of the closed-loop wave-front correction are presented. A distorted laser wave-front of 20 wavelengths of P-V values was corrected to 0.15 wavelength of P-V values. The beam quality of the laser system varies from 3.5 diffraction limit to 1.5 diffraction limit.

Focal plane wave-front sensing algorithm for high-contrast imaging

High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star.A major limitation for such direct imaging is the speckle noise that is induced from the wave-front error of an optical system.We derive an algorithm for the wave-front measurement directly from 3 focal plane images.The 3 images are achieved through a deformable mirror to provide specific phases for the optics system.We introduce an extra amplitude modulation on one deformable mirror configuration to create an uncorrelated wave-front,which is a critical procedure for wave-front sensing.The simulation shows that the reconstructed wave-front is consistent with the original wave-front theoretically,which indicates that such an algorithm is a promising technique for the wave-front measurement for the high-contrast imaging.

Optical study on the vision correction and supernormal vision based on the wave-front aberrations of human eye

In this paper we present the recent research results in the field of vision correction and supernormal vision according to the actual measurements of the wave-front aberrations and the corneal surface topography,the clinical detection of the visual function and the laser corneal refractive surgery,and the optimization of the optical system. These include the features of the aberrations of human eye with different pupil sizes,different fields of view and temporal accommodation,the influence of the polychromatic illumination of the visible wavelength on the supernormal vision,and the effect of the existing laser corneal refractive surgery on the wave-front ab-errations of the eye. It is shown that the wave-front aberration of human eye is of temporal variation and of synthesis with multi impact factors. To achieve super-normal vision,an optimum engineering data for the customized laser corneal sur-gery should be firstly acquired,which may involve the dynamic free-form optical surface. Although the myopia can be corrected by the laser in situ keratomileusis(LASIK) in a certain degree,it brings about negative effects under scotopic condi-tions.

Principle demonstration of fine pointing control system for inter-satellite laser communication

Due to high data rates and reliability,inter-satellite laser communication has developed rapidly in these days.However,the stability of the laser beam pointing is still a key technique which needs to be solved;otherwise,the beam pointing jitter noise would reduce the communication quality or,even worse,would make the inter-satellite laser communication impossible.For this purpose,a bench-top of the fine beam pointing control system has been built and tested for inter-satellite laser communication.The pointing offset of more than 100rad is produced by the steering mirror.With beam pointing control system turned on,the offset could be rapidly suppressed to lower than 100 nrad in less than 0.5 s.Moreover,the pointing stability can be kept at 40 nrad for yaw motion and 62 nrad for pitch motion,when the received beam jitter is set at 20rad.

A non-stationary channel model for 5G massive MIMO systems

We propose a novel channel model for massive multiple-input multiple-out （MIMO） communication systems that incorporate the spherical wave-front assumption and non-stationary properties of clusters on both the array and time axes. Because of the large dimension of the antenna array in massive MIMO systems, the spherical wave-front is assumed to characterize near-field effects resulting in angle of arrival （AoA） shifts and Doppler frequency variations on the antenna array. Additionally, a novel visibility region method is proposed to capture the non-stationary properties of clusters at the receiver side. Combined with the birth-death process, a novel cluster evolution algorithm is proposed. The impacts of cluster evolution and the spherical wave-front assumption on the statistical properties of the channel model are investigated. Meanwhile, corresponding to the theoretical model, a simulation model with a finite number of rays that capture channel characteristics as accurately as possible is proposed. Finally, numerical analysis shows that our proposed non-stationary channel model is effective in capturing the characteristics of a massive MIMO channel.

Revisiting the Parallel Strategy for DOACROSS Loops

DOACROSS loops are significant parts in many important scientific and engineering applications,which are generally exploited pipeline/wave-front parallelism by loop transformations.However,previous work almost statically performs iterations in parallel threads,thus causing a waste of computing resources in thread synchronization.This paper proposes a brand-new parallel strategy for DOACROSS loops that provides a dynamic task assignment with reduced dependences to achieve wave-front parallelism through loop tiling.The proposed strategy uses a master-slave parallel mode and some customized structures to realize dynamic and flexible parallelization,which effectively avoids threads from waiting in communication.An efficient tile size selection(TSS)approach is also proposed to preserve data reuse in cache for tiled codes.The experimental results show that the proposed parallel strategy obtains good and stable speedups over six typical benchmarks with different problem sizes and different numbers of threads on an Intel■Xeon■32-core serve?.And it outperforms two static strategies,a barrier-based strategy and a post/wait-based strategy,by 32% and 20% in average performance,respectively.This strategy also yields a better performance than a mutex-based dynamic strategy.Besides,it has been demonstrated that the proposed TSS approach can achieve a near-optimal performance and is comparable with a state-of-the-art TSS approach.