基于叠栅技术的二维亚波长周期结构成像设计

用光子学方法研究了叠栅技术中,当试件光栅被拉压和旋转后,叠栅条纹的空间周期和相对于基准光栅的取向,试件光栅被拉压后的节距等相关问题。根据衍射光波的空间周期可能大于试件光栅空间周期的特点,对二维亚波长周期结构衍射成像进行了设计研究。首先,对二维亚波长周期结构衍射物进行编码,以获得包含编码光栅空间信息的均匀波;其次,使编码得到的均匀波通过光学系统,并被放大到CCD相机所能辨识的大小;再次,经解码光栅解码,滤掉编码波,最终获得二维亚波长周期结构物的空间结构信息,达到超分辨的目的。同时,对成像过程进行了较为详尽的分析,对编码器、解码器的位置以及它们相对衍射物的取向进行了设计研究,对滤波器的选择给予了必要的说明,指出了取得超分辨成像的关键。     

Direct amplitude detection of Zernike modes by computer-generated holographic wavefront sensor: Modeling and simulation

A fast holographic wavefront sensor is proposed using a computer-generated hologram (CGH). This CGH is a multiplexed hologram of different Zernike mode–amplitude combinations, and is designed in such a manner as to get the corresponding spots on the detector according to the presence and strength of a particular aberration. Interference between the aberrated wavefront (with a single mode–amplitude combination) and the Fourier transform of an image with single bright pixel (defined as dot image) is numerically calculated for one hologram. Different mode–amplitude combination and corresponding different positions of bright pixels (dots) are taken to compute various holograms and then all the holograms are multiplexed to get the final hologram. When the aberrated wavefront with a particular mode–amplitude combination is incident onto the multiplexed hologram, the corresponding dot is generated in the Fourier plane. A lens performs the Fourier transform in optical domain and provides the instant detection of amplitude of the respective Zernike mode. The main advantage of the scheme is to avoid the need of any computations, which makes it really fast. The simulation results are presented with the cross-talk analysis for few Zernike terms.     

Point-diffraction interferometer for atmospheric adaptive optics in strong scintillation

This paper evaluates the performance of a point-diffraction interferometer for closed-loop adaptive optics. A point-diffraction interferometer was built using a modified Mach-Zehnder set-up. The system was used in closed-loop using a SLM to implement a square, 12 × 12, piston-only segmented corrector with a stroke of ±π. Its performance was tested for the case of atmospheric turbulence aberrations. The investigation showed, through simulation and experiment, that the point-diffraction interferometer worked in closed-loop operation in both uniform intensity and scintillated aberrations. Its robustness in the presence of phase discontinuities makes it a promising option for wavefront sensing in strong scintillation.     

基于空间光调制器的波面重建优化方法研究

针对不同非球面面形的实时检测需求,研究了基于空间光调制器的标准波面重建技术.基于空间光调制器波面重建的原理设计了干涉测量系统,依据空间光调制器的自身特点选取修正离轴计算全息编码方式实现对标准球波面的编码.针对实验中空间光调制器作为全息再现介质引起重建波面质量下降问题,提出了错位叠加优化方案,并将这一过程进行了模拟实验....     

All-optical method of developing a phase encoded latch by using EDFA

Optics has already proved its meaningful application in information processing and computation, where the parallelism of light is exploited to achieve the desired result. In this communication a novel concept of all-optical memory unit based on phase encoding process is proposed. The unit is simple in architecture comprising phase sifters, mirrors (M′) and two blocks of Erbium doped fiber amplifier. The optical feedback is supported by use of beam splitters and mirrors. It is independent of intensity and therefore requires a small switching power and can work at a bit rate far above 100 Gb/s.     

Two-dimensional shift-orthogonal random-interleaving phase-code multiplexing for holographic data storage

A novel phase encoding technology for phase-code multiplexing in holographic data storage (HDS) system called two-dimensional shift-orthogonal random-interleaving (2-D SORI) phase encoding is proposed. Compared with the traditional one-dimensional orthogonal phase-code multiplexing methods, the 2-D method is less sensitive to the variations of the diffraction amplitude and to the phase error of the phase mask. Phase masks for the 2-D SORI phase-code multiplexing can be generated by shifting an elaborately designed phase plate at a certain step, which can avoid the use of a high-cost phase spatial light modulator for the generation of multiple orthogonal phase masks. The cross-talk arising from the systematic phase defects of the static phase modulator is eliminated by the shift operation of the phase plate. Phase codes are interleaved under a predetermined random mapping rule to prevent unauthorized users from accessing the data and eliminate the Bragg degeneration cross-talk. A 2-D SORI phase plate with the size of 5.12 mm × 10.24 mm is designed and fabricated, from which 128 orthogonal phase patterns are generated. The feasibility of the 2-D SORI phase-code multiplexing method for HDS is experimentally demonstrated.     

Spin-spin coupling edition in chiral liquid crystal NMR solvent

The application of the G-SERFph pulse sequence is presented on enantiomeric mixtures dissolved in a chiral liquid crystal. It aims at editing, within one single 2D spectrum, every proton coupling which is experienced by a given proton site in the molecule, and leads to real phased T-edited spectroscopy (T=J+2D). This NMR experiment is based on the combination of homonuclear semi-selective refocusing techniques with a spatial frequency encoding of the sample. This approach, which consists in handling selectively each coupling in separate cross sections of the sample, is applied to the visualization of enantiomers dissolved in a chiral liquid crystalline phase. Advantages and limits of this methodology are widely discussed.     

Image encryption scheme by using iterative random phase encoding in gyrator transform domains

An image encryption is discussed based on the random phase encoding method in gyrator domains. An iterative structure of image encryption is designed for introducing more random phases to encrypt image. These random phase functions are generated by a two-dimensional chaotic mapping with the help of computer. The random phases are utilized for increasing the security of this encryption algorithm. In the chaotic mapping relation, the initial value and expression can serve as the key of algorithm. The mapping relation is considered secretly for storage and transmission in practical application in comparison to traditional algorithms. The angle parameter of gyrator transform is an additional key. Some numerical simulations have been given to validate the performance of the encryption scheme.     

三维成像中相位级次自编码的相位测量方法

提出一种相位级次自编码技术的相位测量方法.与传统的相位测量技术不同,该方法利用截断相位的微分值作为编码通道,完成对各条纹级次的编码.构造的代码序列总长度为投影条纹的周期数,每个周期作为一个码元,由相邻若干码元构成一个代码子序列.相位计算后,根据截断相位的微分信息,可以提取出各周期及其码元值,通过在设计的代码序列中进行代...