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Holography, Diffractive Optics, and Applications V
Editor(s): Yunlong Sheng; Chongxiu Yu; Linsen Chen
Date Published: 11 December 2012
Transparent 3D display for augmented reality
Author(s): Byoungho Lee; Jisoo Hong
Two types of transparent three-dimensional display systems applicable for the augmented reality are demonstrated. One of them is a head-mounted-display-type implementation which utilizes the principle of the system adopting the concave floating lens to the virtual mode integral imaging. Such configuration has an advantage in that the threedimensional image can be displayed at sufficiently far distance resolving the accommodation conflict with the real world scene. Incorporating the convex half mirror, which shows a partial transparency, instead of the concave floating lens, makes it possible to implement the transparent three-dimensional display system. The other type is the projection-type implementation, which is more appropriate for the general use than the head-mounted-display-type implementation. Its imaging principle is based on the well-known reflection-type integral imaging. We realize the feature of transparent display by imposing the partial transparency to the array of concave mirror which is used for the screen of reflection-type integral imaging. Two types of configurations, relying on incoherent and coherent light sources, are both possible. For the incoherent configuration, we introduce the concave half mirror array, whereas the coherent one adopts the holographic optical element which replicates the functionality of the lenslet array. Though the projection-type implementation is beneficial than the head-mounted-display in principle, the present status of the technical advance of the spatial light modulator still does not provide the satisfactory visual quality of the displayed three-dimensional image. Hence we expect that the head-mounted-display-type and projection-type implementations will come up in the market in sequence.
Fourier holographic display system of three-dimensional images using phase-only spatial light modulator
Author(s): Hao Zhang; Yan Zhao; Huarong Gu; Qiaofeng Tan; Liangcai Cao; Guofan Jin
We propose a holographic 3D display system which can produce images with adjustable viewing parameters and eliminated zero-order interruption. The 3D scene is generated from a 3D CAD tool, and point source algorithm is used to generate the holograms. A two-step model is introduced in the computing to generate precise Fourier holograms. A phase-only spatial light modulator (SLM) is used in the optical reconstruction, which can replay clear images for 3D diffusive objects. During optical reconstructing, the viewing angle and image size of the system can be adjusted by changing the parameters of the replay lens. A filter is introduced in the replay system to eliminate the zero-order interruption and increase the 3D image quality. Optical experiments are performed, and the results show that our proposed holographic display system can produce noiseless 3D image reconstructions.
Comparative analysis on light field reconstruction characteristics of autostereoscopic three-dimensional display technologies
Author(s): Jae-Hyeung Park
Multi-view technique, integral imaging, and holography are major techniques of autostereoscopic three-dimensional displays. In this presentation, we provide a comparative analysis on image characteristics of these autostereoscopic three-dimensional displays. Due to different optical configuration and light source coherency, these techniques reconstruct the desired light field with different spatial and angular sampling, which eventually affects the image quality and viewing limitations. By analyzing light field reconstructed by three techniques, it is expected that not only image characteristics of individual technique can be understood but also optimum technique for a given application can be identified.
Binocular and multi-view parallax images acquisition for three dimensional stereoscopic displays
Author(s): Hongsheng Ge; Xinzhu Sang; Tianqi Zhao; Jinhui Yuan; Junmin Leng; Ying Zhang; Binbin Yan
It is important to acquire the proper parallax images for the stereoscopic display system. By setting the proper distance between the cameras and the location of the convergent point in this capturing configuration, the displayed 3D scene with the appropriate stereo depth and the expected effect in front of and behind the display screen can be obtained directly. The quantitative relationship between the parallax and the parameters of the capturing configuration with two cameras is presented. The capturing system with multiple cameras for acquiring equal parallaxes between the adjacent captured images for the autostereoscopic display system is also discussed. The proposed methods are demonstrated by the experimental results. The captured images with the calculated parameters for the 3D display system shows the expected results, which can provide the viewers the better immersion and visual comfort without any extra processing.
An experimental study on the relationship between maximum disparity and comfort disparity in stereoscopic video
Author(s): Zaiqing Chen; Junsheng Shi; Yonghang Tai
It is well known that some viewers experience visual discomfort when looking at stereoscopic displays. The disparity is one of the key factors that affect visual comfort in 3D contents, and there is a comfortable disparity range for a person. In this paper, we explore the comfort disparity, which correlates with the optimal viewing distance, as a function of the maximum disparity for an individual. Firstly, the individual maximum disparities of 14 subjects were measured. Then the subjects were asked to rate the comfort scores for a 3D video sequence with different disparity, to evaluate the individual comfort disparity. The results show that as the individual maximum disparity increased, the corresponding comfort disparity increased, and we found a correlation coefficient of r=0.946. The average ratio between the comfort disparity and the maximum disparity was approximately 0.72, and this ratio can be used for one to determine the optimal 3D viewing distance by a rapid method.
A novel super-orthogonal modulation scheme for high speed optical OFDM system
Author(s): Qi Zhang; Xiangjun Xin; Lijia Zhang; Yongjun Wang; Chongxiu Yu; Nan Meng; Houtian Wang
High speed optical communication is one of the research hotspot in optical communication field at present. A novel super-orthogonal modulation method based on quadrature amplitude modulation (QAM) and frequency shift key (FSK) is proposed for high speed optical orthogonal frequency division multiplexing (OFDM) system. The coding-modulation and demodulation-decoding scheme is designed. The principle and transmission performance of optical OFDM system with proposed super-orthogonal modulation method is simulated and analyzed. The research result will lay the foundation of optical communication realizing with high speed, large capacity and high efficiency transmission.
Impact of surface waves on the electromagnetic enhancement by a metallic nano-cavity
Author(s): Haitao Liu; Zhiwen Zeng
To investigate the impact of surface waves on the electromagnetic enhancement, here we consider a simple geometry of a T-shaped metallic nano-groove that is composed of a narrow central groove and of a wide top trench under illumination by a plane wave. The T-shaped groove is found to have a much higher enhancement factor than a single bare groove without the top trench. By building up an intuitive surface-wave model, the improved field enhancement is attributed to the surface waves that are collected by the top trench and are coupled into the central groove.
Enhanced subwavelength light spot of vertically tapered metallic aperture based on plasmonics
Author(s): Jun-Bum Park; KyuHo Kim; Il-Min Lee; Dawoon Choi; Byoungho Lee
We propose an approach that improves the characteristics of a subwavelength light spot from a tapered aperture without increment of the subwavelength spot size, via simply introducing a taper along the aperture shape. Two advantageous features of the proposed tapered structure are investigated: At first, by enlarging the entrance area of the aperture, it could collect more light with respect to the regular one. Thus the funneled light contributes to the field enhancement. Furthermore, the tapered edges of the exit surface of the aperture provide confined field, a wedge mode, which is bounded strongly and enhances the local electric field around the edge of the aperture. The enhanced characteristics of subwavelength spot in vertically-tapered aperture, including peak intensity, power throughput, and full width half maximum were obtained numerically using finite difference time domain method. The proposed device is fabricated using conventional planar fabrication techniques and focused ion beam milling to realize the tapered structure. The relative tapered angle-dependent enhancements are presented with experimental and quantitative demonstrations of the proposed structure.
Theory on the quasi-cylindrical wave diffracted by a sub-wavelength metallic slit and its enhancement by surface plasmon resonance
Author(s): Yann Gravel; Yunlong Sheng
A rigorous theoretical analysis of the diffraction of light on a sub-wavelength metallic slit is presented. Solution of the 2D Sommerfeld integral shows that the so-called quasi-cylindrical wave is a convolution of a first order cylindrical harmonic with the transit surface Plasmon polariton, a 1D spatial distribution along the metallic interface extending outside the slit. The quasi-cylindrical wave is not a surface wave but is a scattered field propagating along the interface but also in the entire space of the media adjacent to the slit. We demonstrate that this field can be enhanced by the surface Plasmon resonance, when the dielectric function of the metal tends to the negative of the permittivity of the medium above the slit.
Tunable nano-pattern generation based on surface plasmon polaritons
Author(s): Chinhua Wang; Fuyang Xu; Yiming Lou; Bing Cao
We present a numerical observation of a tunable 1D and 2D nano-pattern generation and photolithography technique based on a surface plasmon resonant cavity formed by a metallic grating and a metallic thin-film layer separated by a photoresist layer. The tuning capability is implemented by varying the cavity length combined with the polarization of the incident light, from which different surface plasmon interferometric patterns can be generated in the cavity of photoresist layer with a fixed phase mask. The technique opens a new possibility to generate tunable ultra-deep subwavelength patterns by using a fixed diffraction-limited mask with capability of large area, deep exposure depth and flexibility of arbitrary 2D patterns.
Digital holographic display for a single user
Author(s): Joonku Hahn; Hwi Kim
Even though digital holography was invented a number of decades ago, many people think there are still several problems for holographic display to be commercialized. The main problem results from the small space-bandwidth product of the spatial light modulators, since the holographic displays generally need enormous data capacity in comparison with other traditional display. But, if we define our target as a holographic display for a single user, it is feasible to build a holographic display with a reasonable screen size. In this paper, we introduce two kinds of digital holographic displays recently studied.
A JPEG-based enhanced compression algorithm of digital holograms
Author(s): Hanming Yu; Zibang Zhang; Jingang Zhong
We present a modified version of the general JPEG encoder for digital holograms. Since digital holograms are characterized by most of their information concentrated at first-order term, to compress digital holograms only with their first-order term is available. The proposed algorithm performs 2D-DCT (discrete cosine transform) on digital holograms as the general JPEG, then quantizes and encodes the low-frequency section extracted with an adaptive mask. Compatible with the general JPEG, the compressed holograms can be directly decoded by the general decoders. Our simulation and experimental results show that this algorithm has higher compression ratio than the general JPEG and more accurate retrieved phase while the compression is equal.
Effect of phase-shift step on hologram reconstruction in Fresnel incoherent correlation holography
Author(s): Hao Chen; Yuhong Wan; Tianlong Man; Zhuqing Jiang; Dayong Wang
Fresnel Incoherent Correlation Holography (FINCH) enables holograms to be created from incoherent light illumination of 3D objects. The optical setup of FINCH is usually simple and compact owe to its in-line geometry while the reconstruction of hologram suffers from the obstruction of zero-order item and twin image. Phase-shift technology is combined with FINCH in order to obtain zero-order-free and twin-image-free reconstruction. Three-step phase-shifting is adopted in all the publications of FINCH and the application of other multi-step phase-shift technology in FINCH are not investigated yet. The Fresnel holograms are sequentially recorded with different multi-step phase-shifting (including four, three, and two-step) to form the complex hologram and the quality of the reconstructed images are compared by simulations and experiments respectively in this study. Several parameters including resolution, SNR and normalized cross-correlation are applied to evaluate the quality of reconstruction images. Although various noises would be introduced by the optical elements and the experimental environment in practice, four-step phase-shifting provides the best quality of the reconstructed image but the system resolution is not different from others. In addition, the influence of different phase shift plus to the quality of reconstruction images in the three-step phase-shifting FINCH is investigated and the results show that the quality of reconstruction images which use the π/2 is better than that 2π/3.
Detection of silver ions induced morphological changes on E. coli membrane using digital holographic microscopy
Author(s): Farzaneh Borji; Ali Mohebi; Ali-Reza Moradi; Sharareh Tavaddod
In this work, we utilize digital holographic microscopy technique and also conventional video microscopy to detect the dynamic morphological changes of bacteria membrane in presence of silver ions. Silver ions have shown strong inhibitory effects on bacteria and can be used as antibacterial. We used E. coli as a sample and the influences of the ions were compared in terms of the variations in volume of E. coli for different concentration of silver ions in the buffer and various incubation times. In a controlled experiment using a microinjecting pump the concentration of antibacterial is increased, the movement of a single or a set of bacteria are monitored live, and successive digital holograms are recorded. The recorded holograms by digital camera can be post-processed to three dimensional reconstruction of the samples and measurement of quantitative structural changes in various interacting time of the bacteria.
Slanted volume holographic gratings design based on rigorous coupled-wave analysis
Author(s): Ting Li; Liangcai Cao; Qingsheng He; Guofan Jin
A model for slanted volume holographic grating based on the rigorous coupled-wave analysis (RCWA) is proposed and analyzed. In this model an oblique coordinate system related to the grating fringes simplifies the mathematical analysis. And the S-matrix algorithm gives the RCWA results. Based on the vector theory, the RCWA can present more details of the diffraction process. Compared with the traditional approximate theory, the RCWA for volume grating can analyze the angular selectivity and the diffraction efficiency more accurately and flexibly. Through the simulation results, the Fresnel diffraction on the interface can be analyzed. The effect of the grating fringe error the grating is also provided. The effect of the grating thickness, an important grating parameter, has been described particularly.
A parameters study of the multi-plane diffraction iterative algorithm of the single-beam phase retrieval
Author(s): Yuanyuan Sun; Zibang Zhang; Jingang Zhong
Phase retrieval techniques have been used for the measurement of 3-D objects. The phase of the transmitted or reflected light beam is modulated by different characteristics of the object and reveals valuable information. The multi-plane diffraction iterative algorithm is a method of phase retrieval with a single beam. Based on numerical phase-error correction system, the method obtains the phase and amplitude of a wavefront with a sequence of intensity patterns recorded at different planes. There are various parameters involved in this method. The parameters impact the retrieval in common. For the optimization in implementation and guidance to experiments, we study six parameters of this method by a series of simulations. The six parameters are the number of sampling planes, the round trip number of iterative, the initial phase, the distance between the object and the first sampling plane, the distance between sampling planes and the wavelength. A discussion on the result of the simulations is also presented.
Fast generation of hologram from range camera images based on the sub-lines and holographic interpolation
Author(s): Peter Tsang; W. C. Situ; W.-K. Cheung; T.-C. Poon; Changhe Zhou
The intensity image and the depth images of a three-dimensional object scene can be captured with a commodity range camera, and converted into a Fresnel hologram. However, for some cameras, the images are subject to radial distortion, and too small to be visible in optical reconstruction. Moreover, the conventional hologram generation process with numerical means is significant. In this paper, we present a fast method to overcome the above-mentioned problems. First, the intensity and the depth images are transformed to reduce the radial distortion. Next, the images are interpolated horizontally, and converted into a sequence of sub-lines. Finally, the sub-lines are swiftly converted into a Fresnel hologram through padding along the vertical direction. The pair of interpolation process effectively increases the size and visibility of the reconstructed image. Although our method can be applied to different kinds of range cameras, we have selected the Swissranger model as a showcase to demonstrate the feasibility of the approach.
High-efficient design method of large diffractive optical elements by vectorial field analysis based on boundary element method
Author(s): Jun-ichiro Sugisaka; Toyohiko Yatagai
An efficient approach to design the structure of diffractive optical elements is presented. We have developed a novel vectorial diffraction method that the amount of memory consumption is almost free from the entire size of dielectric structure. In the process of the device design, we update the diffracted wave by adding groove patterns on the surface one by one so that the updated wave approaches to the desired one. The necessary memory for two-dimensional structure is only around 20 MB, and our method is sufficient with a desktop computer to perform an accurate designing even including the polarization characteristics.
Dynamic holographic interferometry with matrix LC modulator
Author(s): S. A. Pulkin; V. Yu. Venediktov; V. Ivanov; V. I. Korotkov; I. M. Pasechnik; A. A. Sevrygin; M. A. Solov'ev
The method of holographic intereferometry with increased sensitivity was applied for measurements of height of nanosteps (from 10 nm and higher) with standard uncertainty about 0.5 nm. The initial microinterferogram with fringes of equal width was obtained in Michelson micro-interferometer with nano-step sample in one of legs. This interferogram was registered by CCD–camera and the digital interference pattern was reproduced on matrix phase modulator with spatial resolution 30 lines/mm. The matrix phase modulator was placed at the output of the two-beam Mach-Zehnder interferometer and illuminated by two plane laser beams. These two beams diffracted on phase modulator, were focused and spatially filtered by the pinholes in (+ 1-st ) and (– 1-st ) orders of diffraction. The second digital interferogram with twofold increase of sensitivity was obtained on CCD–camera and so on. The increase of sensitivity was obtained due to the interference of waves with complex conjugated phases. One can obtain the interference of higher orders too if working with the nonlinear interferogram. It is possible to obtain any carrier fringe space frequency by using of two plane waves in the interferometer. The increase of sensitivity may be obtained in research of flatness less than λ/100, and topography of surfaces with height difference less than few nanometers as well.
The influence of modified squeezing ratio on the birefringence characteristics of photonic crystal fibers
Author(s): Peng Song
We study the birefringence characteristics of photonic crystal fiber with squeezed lattice and elliptical air holes in the cladding, based on the supercell lattice method. A definition of modified squeezing ratio is introduced, which describes the complex effect of elliptical air holes and squeezed lattice on the birefringence characteristics. Studies show that the birefringence simply varies with the modified squeezing ratio in a certain range. So the concept of modified squeezing ratio can be used to design the high birefringence photonic crystal fiber.
3D measurement system with two detecting channels using structured light
Author(s): Shengbin Wei; Changhe Zhou; Shaoqing Wang
In this paper we propose a 3D measurement system based on a structured light with a special pattern. The structured light is projected on an object by a projector. Two calibrated digital cameras are used to capture the images of projected area on the object separately. Artificial corner points generated by the structured light are detected. We defined a simple but effective feature parameter of the corner points. The corner points are clustered into several groups by adopting k-means cluster to analyze the feature parameter of corner points. We propose a stereo matching method using the cluster result and geometric constraint. A sequence of images is captured to enhance the measuring resolution. According to triangulation, the 3D point clouds are obtained from the pair of images. Experiment result demonstrated the feasibility of this 3D measuring system. The system with the advantages of high measuring precision and good robustness is highly attractive for applications in 3D measurement, 3D display and so on.
Beam splitters of metal-dielectric reflective gratings
Author(s): Anduo Hu; Changhe Zhou; Hongchao Cao; Jun Wu; Jia Wei
Beam splitters are important optical components. In this paper, reflective 1×2 and 1×3 beam splitters based on metaldielectric gratings are designed at wavelength of 1064 nm for TE polarization. Alumina, silver, alumina and fused silica films are coated on substrate in sequence. On the top fused silica film, grating with rectangular grooves are etched. Rigorous coupled-wave analysis (RCWA) and simulated annealing (SA) algorithm are employed to optimize grating parameters such as period, depth, thickness of connecting layer and incident angle. An optimized 1×2 beam splitter can achieve perpendicular beam splitting with diffraction efficiency of 49.2% at the -1st order and 49.1% at the 0th order for incident angle of 30°. When incident angle is 5°, the diffraction efficiencies of the optimized 1×3 beam splitter are 32.66% at the -1st order, 32.71% at the 0th order and 32.72% at the 1st order. To guide the fabrication and operation of beam splitters, the tolerance of grating period, depth, thickness of connecting layer are calculated. The optimized 1×2 and 1×3 beam splitters exhibit high efficiencies and uniformity, which should be useful in applications.
Three-dimensional optical techniques using Dammann gratings
Author(s): Changhe Zhou; Junjie Yu; Shaoqing Wang; Shengbin Wei
This paper summarized our work on three-dimensional optical technologies using Dammann gratings, e.g., threedimnensional Dammann gratings, three dimensional imaging using a Dammann grating, etc.. We developed threedimensional Dammann grating which can produce three-dimensional array with equal distance and equal intensity with a high-numerical-aperture lens. As we know, a lens usually has a single focal point. Fresnel zone plate can generate several axial focal points, but the intensity between them is unequal. By introducing the concept of Dammann grating into the circular phase plate, we invented Dammann zone plate(DZP) which can produce a series of axial focal points with equal intensity. Combining DZP with a Dammann grating, three-dimensional Dammann array will be generated, which is highly interesting for various applications. We also built a three–dimensional measuring system using a Dammann grating, with two cameras as the right eye and right eye, respectively. We used a 64×64 Dammann grating for generation of a square array of light spots for parallel capturing the three-dimensional profile of an object. The two cameras and the illuminating part are packaged together. After scanning the object, its three-dimensional profile will be obtained. Experimental results demonstrated the effectiveness of this technique.
The study on the focusing property of the VLS grating with different types of beams
Author(s): Chunzhi Wang; Weiping Zhang; Yanchun Gao
The VLS grating has the ability of self-focusing and eliminating aberration, and it has been widely used in many fields. The plane VLS grating has two types, one is the one-dimensional VLS grating and another is two-dimensional VLS grating. In some practical applications, we need to know the focusing property of the two-dimensional VLS grating, so it is important to research the focusing property of the two-dimensional VLS grating illuminated by different types of light beams. In this paper, we mainly studied the focusing property of the two-dimensional VLS grating whose grating lines are arc. Light beams diffracted by this kind of the VLS grating can form a focal point in one position or form a horizontal focal line and a vertical focal line respectively in two different positions. We experimentally studied the change of the focusing position under different incident angles using the monochromatic plane wave or spherical wave as incident light, and studied the influence of different wavelengths of the monochromatic plane wave on the focusing position. The difference between the positions of two focal lines which relates with the focusing property of the two-dimensional VLS grating is also discussed in our work.
Absorption enhancement in thin-film solar cell using grating structure
Author(s): Jun Wu; Changhe Zhou; Hongchao Cao; Anduo Hu; Wei Jia
The enhancement of absorption in thin-film amorphous silicon solar cell based on guided mode resonance is theoretically investigated. This is achieved by patterning a grating with waveguide layer in the absorbing layer and an antireflective layer on the top. The optimized grating parameters are obtained by use of rigorous coupled-wave analysis and the simulated annealing algorithm in the visible region. The absorption at normal incidence is higher than 50% in the wavelength range 300-660 nm, and the peak absorption is higher than 95% for both TE and TM polarization. We studied the angle dependence of the integrated absorption spectrum in solar cell structures. The integrated absorption for TM polarization is larger than TE polarization in the angular range of 0-88o. In general, the averaged integrated absorption decreases as the incident angle increasing, but it is higher than 60% in the range 0-66o. So it is very weakly dependent on the angle of incidence. A physical understanding of enhanced absorption based on guided mode resonance effect is presented. It is found that the effect can effectively trap light in the absorber layer and enhance absorption in the active layer. Double-groove grating structure is also discussed for the sake of reducing reflection and enhancing absorption. The designed solar cells have high integrated absorption and are weakly dependent on incident angle, which should be of highly practical significance.
Calibration and pre-compensation of direct laser writing system
Author(s): Feng Zhu; Changhe Zhou; Jianyong Ma
The Direct Laser Writing (DLW) technique has become a well-established, flexible and multi-functional method of micro- and nano-technology. A DLW system, mainly containing blue light writing module and red light autofocus module, is established and efficiently applied for the fabrication of diffractive optical elements (DOEs). In the DLW system, the stability of the writing beam is always a concern. Although the autofocus module is employed to eliminate the influence of the drifting focus point resulting from ambient vibration, the inherent defocusing error still has a serious impact on the lithography accuracy of the DLW system. As the refractive index of the lithography objective lens with a high numerical aperture (NA, 0.9) for blue light (405nm) differs from that for the auto-focus red light (650nm), the focal planes of the two beams will not coincide. Furthermore, the two beams can't be mounted seriously parallel to the axis of the objective lens in practice. The misalignment will impact the location of the focus point axially and laterally. The above defocusing error is determined experimentally, and then is pre-compensated, which improves the fabrication accuracy dramatically. The relationship between defocusing amounts and line widths of the stripes is obtained, which can be used for writing gratings with different line widths. A 100×100 mm sized fused-silica grating with a period of 2 μm is obtained with the DLW system, and some microscope images are presented to show the effectiveness of the error-eliminating methods.
Quantitative evaluation of spatial phase light modulator characteristics in Fresnel incoherent correlation holography
Author(s): Tianlong Man; Yuhong Wan; Hao Chen; Zhuqing Jiang; Dayong Wang
Fresnel incoherent correlation holography (FINCH) is one of the methods for recording holograms of 3D samples under incoherent illumination. The FINCH combines the theory of spatial self-coherence and the in-line phase-shift technology together to form a complex hologram. A spatial phase light modulator (SPLM) plays important roles as the dynamic diffraction optical element (DOE) and phase shifter. When the incoherent light generated from each object point of the 3D samples incidents to a SPLM, it can be split into two spatial self-coherent beams with different curvatures. The hologram caused by these two beams can then be captured by an image detector. Three holograms with different phase shift are recorded sequentially for eliminating the zero-order and twin image, and then a complex valued hologram is obtained by superposing the three holograms. In this paper, the modulation characteristics of SPLM and phase shift error in FINCH are investigated. Based on digital holography, phase modulation characteristics of SPLM are measured under coherent and narrow-bandwidth incoherent illumination respectively. Phase shift error due to quasi monochromatic light illumination is then analyzed in FINCH. The effect of phase shift error on the quality of reconstructed image is also investigated. It is demonstrated the FINCH setup has a smaller phase shift error by experiment.
An optically addressed liquid crystal light valve with high transmittance
Author(s): Dajie Huang; Wei Fan; Xuechun Li; Zunqi Lin
We present an optically addressed liquid crystal light valve based on a twisted nematic liquid crystal layer associated to a photoconductive BSO layer. Based on the optical addressing of a continuous layer of liquid crystal, the spatial transmittance distribution of 1053nm coherent light through the light valve has a corresponding relationship with the intensity distribution of 470nm incoherent light projected onto the photoconductive BSO layer. This relationship has been studied experimently. As a transmissive device, it has the advantage of high transmittance and it can overcome the problem of black-matrix effect. The aperture of our device has reached 22mm× 22mm.
Tunable photonic structures from liquid crystal elastomers
Author(s): Marko Gregorc; Hui Li; Valentina Domenici; Irena Drevenšek-Olenik
We investigated one-dimensional and two-dimensional optical diffraction structures fabricated in thin films of a sidechain light-sensitive liquid crystal elastomer (SC-LS-LCEs) by optical holographic lithography methods. The emphasis was on analysis of modifications of the periodicity of the recorded patterns induced by application of an external strain and by temperature modifications. The results show that due to rubber elasticity of the LCE films, relative modifications of the periodicity by 10% can easily be reached. In most cases tuning is reversible and linear with respect to the strain. Temperature induced tuning is most efficient in the region of phase transition from the nematic to the paranematic phase and provides relative periodicity modifications up to 30%.
Optical path difference characteristics of the fluorescence holographic system
Author(s): Xiaomin Lai; Shaoqun Zeng
Over recent years, a research of wide-band light interference has led to new hope for three-dimensional fluorescence detecting without scanning. The research is the Fresnel incoherent correlation holography (FINCH) based on splitting light with a spatial light modulator (SLM). However, the conventional FINCH system is not that much effective to record weak fluorescent signal. It is mainly because the key parameter, optical path difference (OPD), that affects wideband light interference is not small enough. We note that the OPD can be decreased by adopting a spherical reference wave whose focal length is close to that of the object wave. And the hologram recordable area can be shifted from the area that is at a long distance from image plane to its neighborhood. This leads to the improvements of signal-to-noise ratio (SNR) of images and makes this method more suitable for recording weak fluorescent signal. In this investigation, we analyze the OPD character of this fluorescence holographic system and present how the OPD effects the choosing of experimental parameters to obtain high quality interference patterns. We also find that the central part of a wavefront is more likely to be decoded compared with the edge part.
Speckle noise reduction in digital holography due to angular diversity by spatial light modulator
Author(s): Pu-hui Meng; Da-yong Wang; Lu Rong; Yun-xin Wang
The reconstructed amplitude distribution of digital holography suffers from the contamination of speckle noise. We introduced and demonstrated an approach using phase SLM (spatial light modulator) to reduce speckle noise in digital holography. Multiple holograms were recorded through different illumination angle via SLM modulation. The speckle noise in the reconstructed image is suppressed by averaging these fields. The modulation interval of SLM exceeds the minimum angle of uncorrelated speckle pattern. Both reflective and transmissive experiments were conducted using USAF test target as the sample. The results show that the speckle noise was obviously suppressed and the contrast dropped to 36% of the initial value using 25 different angles. With the help of SLM modulation of illumination angle, the operation speed, accuracy and stability of the experiment has been greatly improved.
Iterative partial quantization method for the error reduction of low-quantized kinoforms
Author(s): Shiyuan Yang; Seiichi Serikawa
The iterative stepwise quantization method can reduce the quantization error of low-quantized kinoforms much with few calculation time. We suggest an iterative partial quantization method to improve the performance of the conventional iterative stepwise quantization method. The iterative partial quantization method uses the same process of stepwise quantization but only partial points of kinoform phase are quantized. This partial quantization gives a relaxation of kinoform phase constraint to overcome the stagnation in the Fourier repetition. The conventional iterative stepwise quantization process is performed after the iterative partial quantization and the reconstruction error caused by phase quantization can be reduced.
Computer simulation and optimization design of the holographic photonic crystal template fabrication process
Author(s): Ying Liu
According to the holographic theory, the influence factors in fabricating photonic crystal templates in photoresist such as the arrangement of interference beam, exposure and developing process and the polarization direction adjustment were discussed in this paper. The fabrication process was simulated by computer program and the optimization parameters of fabricating three-dimensional photonic crystal templates in photoresist were presented.
Numerical simulation of polarization dependent characteristics of the structured thin-films phase grating
Author(s): Yi Yu Li; Chuan Hu; Yu Chen Wu; Hai Hua Feng; Jiao Jie Chen
Diffraction efficiency of the structured thin-films phase grating (STFPG) at the visible wavelength is analyzed by the rigorous coupled wave analysis (RCWA) method demonstrating that the TM polarization can be separated from the 0th transmitted order of the TE polarization by ±1st order diffraction. The far field diffraction pattern is simulated by the finite-difference time-domain (FDTD) method to show the polarization beam splitting effect of the STFPG at wavelength of 633nm. In the near field, polarization dependent Talbot effect of the STFPG is also elaborated. FDTD simulations reveal that the spatial distribution of the interference fringes forming the self-image can be shifted by a half of grating period by changing the incident wave polarization within a particular wavelength range.
Design and Fabrication of nanowire-grid polarizer in near-infrared broadband
Author(s): Qiufeng Jin; Quan Liu; Jianhong Wu; Yu Cheng
The infrared polarizers are widely used in the infrared imaging systems as the core components, such as infrared stealth, target acquisition and mine detection, automobile night-vision instrument and other systems. For the requirements of near-infrared imaging systems, a nanowire-grid is designed by Finite Difference Time Domain (FDTD) method. Herein, considering the high reflection of metal aluminum in the manufacturing process, we propose a structure with aluminum-copper nanowire-grid. FDTD method is adapted to analyze the effects of the thickness of aluminumcopper in different combinations on the TM and TE polarization transmission efficiency as well as the extinction ratio when the grating's period is 300nm. Numerical results and theoretical analysis show that: the reflection on the substrate is suppressed with the optimal thickness of the Cu layer. Considering the resist-substrate reflectivity and the final performance of the polarizer, the structure with an 120nm Al layer, and a 50nm anti-reflection Cu layer is chosen; and the TM transmission efficiency is more than 71%, and the extinction ratio is more than 25dB. At last we used Holographic lithography and IBE to fabricate a prototype of the nanowire-grid.
Phase imaging for photorefractive holographic gratings with dual-wavelength digital holography
Author(s): Zhirui Gao; Zhuqing Jiang; Yujia Wang; Jiangtao Wu; Yunxin Wang
In this paper,the phase-type grating recorded in a Fe:Cu:LiNbO3 crystal is measured by dual-wavelength digital holography. In the experiment, a volume hologram, which is recorded in a 3-mm-thick Fe:Cu:LiNbO3 crystal by interference of two recording beams at the wavelength of 532 nm, is reconstructed to be imaging by dual-wavelength digital holography. Two lasers of the different wavelengths 660 nm and 671 nm are used to obtain a larger beat wavelength. Each laser output, which is spatially-filtered and collimated, is split into a reference and object beams in an interferometer setup based on the Mach-Zehnder configuration. In dual-wavelength phase unwrapping, two individual phase images are obtained by using each wavelength, respectively, and the phase image of beat wavelength is obtained by subtracting one single wavelength phase image from the other and then adding 2π whenever the resultant value is less than zero. In the final synthetic image, the discontinuities are removed after reduce the noise of the beat wavelength phase image. Thus, a 3D surface profile of the phase grating is obtained.
A novel iterative computation algorithm for Kinoform of 3D object
Author(s): Xiao-yu Jiang; Pei Chuang; Xi Wang; Yantao Zong
A novel method for computing kinoform of 3D object based on traditional iterate Fourier transform algorithm(IFTA) is proposed in this paper. Kinoform is a special kind of computer-generated holograms (CGH),which has very high diffraction efficiency since it only modulates the phase of illuminated light and doesn't have cross-interference from conjugate image. The traditional IFTA arithmetic assumes that reconstruction image is in infinity area(Fraunhofer diffraction region), and ignores the deepness of 3D object ,so it can only calculate two-dimensional kinoform. The proposed algorithm in this paper divides three-dimensional object into several object planes in deepness and treat every object plane as a target image,then iterate computation is carried out between one input plane(kinoform) and multi-output planes(reconstruction images) .A space phase factor is added into iterate process to represent depth characters of 3D object, then reconstruction images is in Fresnel diffraction region. Optics reconstructed experiment of kinoform computed by this method is realized based on Liquid Crystals on Silicon (LCoS) Spatial Light Modulator(SLM). Mean Square Error(MSE) and Structure Similarity(SSIM) between original and reconstruction image is used to evaluate this method. The experimental result shows that this algorithm speed is fast and the result kinoform can reconstruct the object in different plane with high precision under the illumination of plane wave. The reconstruction images provide space sense of three-dimensional visual effect. At last, the influence of space and shelter between different object planes to reconstruction image is also discussed in the experiment.
Experiment study on measurement of the optical fiber refractive index based on digital holography
Author(s): Duocheng Wang; Zheng Chang; Sujuan Huang
The characteristics of optical fiber are quite important for improving the performance in various application of the optical fiber including communication and sensor systems. Based on optical Mach-Zehnder interferometer, a new measuring method of optical fiber refractive index profiling using digital holography is proposed in this paper, which simplifies the experimental setup compared to traditional holography. Several kinds of fiber samples such as multimode fiber, polarization-preserving fiber and special fiber are tested and their holograms are recorded by CCD. After filtering of the hologram, the phase distribution of fiber sample can be reconstructed and extracted. At last the experimental results of refractive index profiling of fiber are given.
Factors of influencing the value of w in the bi-grating diffraction imaging equation
Author(s): Weiping Zhang; Feng Zhu; Chunzhi Wang; Yanchun Gao; Lei Liu
The bi-grating diffraction imaging effect is the effect that a clear object image can be seen after the polychromatic beam coming from object is diffracted twice by two gratings. And the bi-grating diffraction imaging equation reflects the relationship between the spatial frequencies, diffraction orders, and positions of the two gratings, it plays an important role during the use of the bi-grating imaging. This paper reported on factors of influencing the value of w in the bi-grating diffraction imaging equation. The coefficient W is approximately equal to 1 when the bi-grating system under the ideal conditions, but in fact, it is not strictly equal to 1. This paper researched factors of influencing the value of W and studied the law of these values deviate from 1 for the bi-grating system when the two gratings are parallel to each other by experiments. The experiment results show that: when the center of the second one grating G2 is set in the side of wavelength shorter than centre wavelength of the diffraction beam of the first grating G1, the value of W decreases, otherwise, it increases.
Electro-holography display using computer generated hologram of 3D objects based on projection spectra
Author(s): Sujuan Huang; Duocheng Wang; Chao He
A new method of synthesizing computer-generated hologram of three-dimensional (3D) objects is proposed from their projection images. A series of projection images of 3D objects are recorded with one-dimensional azimuth scanning. According to the principles of paraboloid of revolution in 3D Fourier space and 3D central slice theorem, spectra information of 3D objects can be gathered from their projection images. Considering quantization error of horizontal and vertical directions, the spectrum information from each projection image is efficiently extracted in double circle and four circles shape, to enhance the utilization of projection spectra. Then spectra information of 3D objects from all projection images is encoded into computer-generated hologram based on Fourier transform using conjugate-symmetric extension. The hologram includes 3D information of objects. Experimental results for numerical reconstruction of the CGH at different distance validate the proposed methods and show its good performance. Electro-holographic reconstruction can be realized by using an electronic addressing reflective liquid-crystal display (LCD) spatial light modulator. The CGH from the computer is loaded onto the LCD. By illuminating a reference light from a laser source to the LCD, the amplitude and phase information included in the CGH will be reconstructed due to the diffraction of the light modulated by the LCD.
Holographic two-dimensional photonic crystal of LED decorative illumination
Author(s): Gaoming Li; Yidan Zheng; Yishen Qiu; Aixian Huang
The film of holographic two-dimensional (2D) photonic crystal is used for the led illumination system. According to the decorative patterns, the structure sizes of 2D photonic crystal and relevant led luminaire have been reasonably designed. Then the master mask of 2D photonic crystal is produced with the method of multiple-beam interference. With the experiment of LED illumination, the results show that it is able to meet the expected decorative patterns of LED illumination. While the master mask is used to copy optical coating of polycarbonate, it will provide a better option for LED decorative illumination under low cost.
Theoretical analysis of volume moiré tomography based on double orthogonal gratings for real 3D flow fields diagnosis
Author(s): Nan Sun; Yang Song; Jia Wang; Zhen-hua Li; An-zhi He
Moiré tomography is an important technique to diagnose the flow field. However, the traditional moiré deflectometry cannot meet the requirements of Volume Moiré Tomography (VMT). In this Letter, an improved moiré deflected system based on double orthogonal gratings is introduced for real 3-D reconstruction. The proposed method could obtain the first-order partial derivatives in two vertical directions of the projection in one time. Comparing with the traditional moiré deflectometry, the proposed system is more effective and easier to realize the multi-direction data acquisition.
A novel 2D wavelength-time chaos code in optical CDMA system
Author(s): Qi Zhang; Xiangjun Xin; Yongjun Wang; Lijia Zhang; Chongxiu Yu; Nan Meng; Houtian Wang
Two-dimensional wavelength-time chaos code is proposed and constructed for a synchronous optical code division multiple access system. The access performance is compared between one-dimensional chaos code, WDM/chaos code and the proposed code. Comparison shows that two-dimensional wavelength-time chaos code possesses larger capacity, better spectral efficiency and bit-error ratio than WDM/chaos combinations and one-dimensional chaos code.
Defect mode in a one-dimensional photonic crystal with a dielectric-superconducting pair defect
Author(s): Jijiang Wu; Jinxia Gao
The one-dimensional dielectric photonic crystals (PCs) with complex defect layers, consisting of superconducting (SC) and dielectric sublayers are theoretically studied. Transfer matrix method (TMM) has been used throughout this study. The influence of a substitutional defect on the transmittivity spectra is analyzed for normal incidence of light on the structure. The two-fluid model and wavelength-dependent dispersion formula were adopted to describe the optical response of the low temperature superconducting defect sublayer. The pronounced difference in the transmittivity spectra of the photonic crystals with right-handed (RH) and left-handed (LH) positions of the superconducting defect sublayer with respect to the dielectric defect sublayer is demonstrated. We have showed that in contrast to the usual defect modes, the position of the defect modes is nearly invariant with the position of the defect layer from one end to the other end of the PC. It is observed that, for the case of RH SC defect sublayer, the position of the defect mode and the transmittivity at the defect mode frequency strongly depend on the thickness of the superconducting sublayer as well as on the temperature. It is also shown that in contrast to the case of the PCs with RH SC defect, the defect modes of the PCs with LH SC defect sublayer are nearly invariant upon the change of the thickness of the superconducting sublayer and the temperature. This study may be valuable in designing optical devices.
Effective design of diffractive optical elements for beam splitting with SA algorithm
Author(s): Hui Pang; Shaoyun Yin; Qiling Deng; Yongqi Fu; Chunlei Du
In this paper, quite effective method for the design of phase-only and quantized diffractive optical element (DOE) for beam splitting with simulated annealing algorithm (SA) is presented. For this method employs the character that periodic DOE could generate periodic point array, design time and number of sampling point of DOE could be greatly reduced. Besides, the relation of the DOE parameters including the sampling size, number of sampling point and divergence angle are analyzed. The cause and elimination of the high diffraction orders is also investigated. Design result shows that our method is quite effective and can keep the higher diffraction efficiency and lower uniformity error compared to the Gerchberg-Saxton algorithm (GS).
Improving the phase measurement by the apodization filter in the digital holography
Author(s): Shifeng Chang; Dayong Wang; Yunxin Wang; Jie Zhao; Lu Rong
Due to the finite size of the hologram aperture in digital holography, high frequency intensity and phase fluctuations along the edges of the images, which reduce the precision of phase measurement. In this paper, the apodization filters are applied to improve the phase measurement in the digital holography. Firstly, the experimental setup of the lensless Fourier transform digital holography is built, where the sample is a standard phase grating with the grating constant of 300μm and the depth of 150nm. Then, apodization filters are applied to phase measurement of the sample with three kinds of the window functions: Tukey window, Hanning window and Blackman window, respectively. Finally, the results were compared to the detection data given by the commercial white-light interferometer. It is shown that aperture diffraction effects can be reduced by the digital apodization, and the phase measurement with the apodization is more accurate than in the unapodized case. Meanwhile, the Blackman window function produces better effect than the other two window functions in the measurement of the standard phase grating.
Rectification of gridline structure in integral image using radon transform and perspective transformation
Author(s): Bi-yun Wang; Yang Song; An-zhi He
Integral imaging is one of the most promising techniques for capturing and displaying the three-dimensional information of the object. Most integral image analysis and processing tasks require each elemental image can be identified with high precision, which is difficult to implement in a real pick-up process. For the acquisition of the three-dimensional information in integral imaging process, the lens array should be aligned precisely with respect to the CCD. In this paper, we present a method to accurately correct geometric distortions triggered by the misalignment between lens array and CCD. The method for calculating the skew angle of deviation and the accurate gridline structure in the three-dimensional integral images is based on the Radon Transform algorithm. Then using projective image transformation, the geometrical distortion in the elemental image set can be rectified. The size and position information of the rectified element images also can be calculated by the gridline structure, which will prevent the image splitting, shifting along the lateral or longitudinal direction, or blurring according to reconstruction distance in the optical or computational reconstruction process.
Study on effects of organic solvents on Hela cells by digital holography
Author(s): Liting Ouyang; Dayong Wang; Yunxin Wang; Xinlong Wang; Lisa Marx
In the anticancer research with traditional Chinese medicine, many medicinally effective components can only dissolve in higher polar organic solvents, such as ethanol, dimethyl sulfoxide (DMSO) etc. However, organic solvents may directly interfere with the accuracy of therapeutic efficacy evaluation. Therefore the study on effects of organic solvents with different concentrations on Hela cells is of great significance. The digital holography is a non-destructive and non-contact method to image the transparent sample without staining and with the high precision and high resolution. In this paper, the digital holography is proposed to replace the methyl-thiazol-tetrazolium (MTT) or the Giemsa dye method. Based on the pre-magnification off-axis Fresnel digital holographic theory, an inverted microscopy system is built to obtain the phase-contrast images of the Hela cells, which are added different concentrations of organic solvents. Compared to the control group, there is significantly differences with the shapes of Hela cells with different organic solvents. The size of cell with ethanol 25% is no significantly difference with the control group. But the sizes of cells in the solutions with ethanol 12.5% and 50% are smaller than the control group. Next, the sizes of cells in the solutions with DMSO 12.5%, 25% and 50% are great smaller, compared with the control group. The results show that the digital holography has high practical value in detecting the changes in the shape of cells and is helpful in the choice of organic solvents for further apoptosis study.
Iterative phase difference constraint method for the speckle elimination of kinoforms
Author(s): Toshinori Hora; Shiyuan Yang; Seiichi Serikawa
Speckle noise is a serious problem in the reconstruction of computer-generated holograms (CGHs). Especially for a kinoform (a phase-only CGH), the speckles lead to a large reconstruction error and it is important to eliminate the speckles. The speckles are caused by the isolated zero points in the reconstruction of a CGH, so the speckles can be avoided if there are no isolated zero points. In this study, we suggest a new method that restricts the existence range of the phase differences between the sampled points of reconstruction. The phase differences have the range of two times the phase period and we restrict them into half of the phase period after wrapping the phase differences. This strategy can successfully avoid the existence of isolated zero points so that speckles can be eliminated. The phase difference constraint process can be incorporated into the general iterative algorithms for the optimization of a kinoform. Speckleless reconstruction can be obtained after a sufficient number of iterations and the also the kinoform conditions are satisfied (i.e., the kinoform amplitude uniform condition and its phase quantization). In addition, this speckleless reconstruction has noise immune when the reconstruction phase noise is under a quarter of phase period. We will show some simulation results to show the effect of the iterative phase difference constraint method for the speckle elimination of kinoforms in our presentation.


❚ HITS ON SHAPERSOFTHE80s ROCKETED YESTERDAY, driven by web searches for the name of Roman Kemp, the 19-year-old musician and 6ft 1in fashion-model son of Martin Kemp, the TV soap star, film producer and bass player with Spandau Ballet. Evidently, sharp-eyed fans had been excited to catch three glimpses of both Roman and his sister Harleymoon Kemp, an upcoming celebrity photographer who turns 23 this weekend, cheering on their dad as he entered the Celebrity Big Brother house this week on the UK's Channel 5. He was immediately tipped at 5/2 as bookies' favourite to win the three-week competition.
In response to this surge of interest in the model showbiz family, Shapersofthe80s rounds up a few links to reports we have published in the past — not forgetting mother Shirlie Kemp who was herself a popstar in the 80s in a double act with Pepsi Demacque, as well as being one of the jive girls in Wham!, behind George Michael.
But Google search reveals Roman to be the star of the moment, just as his career switches into gear as a fashion model. Earlier this year the Models 1 agency introduced him as one of their hot new additions to its men's division, saying: "His sharp features, sweep of hair and bright blue eyes are sure to land him a campaign or two." Fans can feast their eyes on our slideshow of shots from his agency card. The associated publicity generates the obligatory celebrity questionnaire in which he reveals: Subtract's album was the last he listened to on his iPod; his idea of fun is making films; his dislikes include Keanu Reeves; he wants to have dinner with Arsène Wenger; and he flies planes.
Shapersofthe80s also happens to know he's a nifty bass guitarist in his father's footsteps, and was on hand to give Martin some tips when dad had to relearn his bass parts for Spandau Ballet's reunion tour of the world in 2009, having spent the previous two decades as one of British TV's highest paid actors. Over the past year or so, we followed Roman's band Paradise Point through a hectic schedule of dates, during which the teen wonder also shot and edited a stunning video of their own song Run In Circles which you can view below. Then suddenly last summer, with a Facebook apology but no explanation, PP stopped performing.
The hot news for Paradise Point fans is that the group is planning a relaunch pretty soon, with a twist. You read it here first.
➢ Not forgetting mum — When Shirl asked Peps if she fancied an arena tour, Peps said to Shirl, Why not?


Aaron McGruder of "The Boondocks" and Tyler Perry of "House of Payne" and "Meet The Browns" are on the same TV team. They both produce hit shows for Turner Broadcasting.
But executives for the broadcaster, which owns TBS and the Cartoon Network (home of "The Boondocks") might be wise not to sit the two at the same table at the next company retreat.
The latest episode of "The Boondocks," the satirical animated series that airs on Cartoon Network's Adult Swim slate, makes vicious fun of Perry and his brand, which blends melodrama, raucous comedy and religious themes. Coming under ridicule is his portrayal of Madea, the foul-mouthed, gun-toting grandmother at the center of many Perry movies and plays.
The installment features a thinly disguised version of Perry as a closeted cross-dressing cult leader whose professed love of the Christian faith is a mask for his true sexuality.
For the full story, read "Aaron McGruder's "Boondocks" lampoons Tyler Perry"


Embracing social media as part of your business will help it grow in areas other than marketing, according to a report by Deloitte.
The report said the development of "social business" will mean very radical changes not only to businesses' relationships with customers, but also to their operations and nature.
Deloitte said organisations are realising that establishing a social media presence and acquiring the necessary technology is only the first step, and Australian businesses are at different stages in their uptake of social media.
"Some local pioneers are adapting their operating models to incorporate social-derived data, tools, software and channels," Deloitte said.
Deloitte consulting partner Niki Alcorn said more companies will need to proactively respond to what they hear and learn from customers via social sources.
"Right now the emphasis is still on brand management and the use of social tools by business to help market or sell products," she said.
Ms Alcorn said companies now recognise that developing into a social business offers the potential for progress across many dimensions.
"As corporate ambitions grow, so will the use of social media tools, as they allow organisations to be global while removing many of the hurdles associated with going global," she said.


Welcome to the Old United States Coast Guard Cutter Alert WSC-127.
1942-1945 assigned to the United States Navy as a sub-chaser.
The Alert is the oldest operational, engine-driven, ex-United States military combat ship in the world.


text:
Q: How to get the referred string of an Action delegate? I have a method that expects an Action<string>
I call the method as follows:
commandProcessor.ProcessCommand(s=> ShowReceipt("MyStringValue"))

ProccessCommand(Action<string> action)
{
  action.Invoke(...); // How do I get the reffered string?
}

Do I have to use Expression<Action<string>> ? If so, how do I get the parameter values?

A: You would indeed have to use Expression<Action<string>>... and even then you'd have to make some assumptions or write quite a lot of code to make it very robust.
This post may help you - it's pretty similar - but I would try to think of an alternative design if possible. Expression trees are great, and very interesting... but I typically think of them as a bit of a last resort.

A: Usually you would call it like this:
 commandProcessor.ProcessCommand(s=> ShowReceipt(s))

or simply
 commandProcessor.ProcessCommand(ShowReceipt)

and supply the string to the action in the called method:
 ProcessCommand(Action<string> action)
 {
  action("MyStringValue");
 }

redpajama_set_name: RedPajamaStackExchange


text:
Q: Why does tokio::net::TcpListener connection shut off on its own in Windows? I am following along a video tutorial on making a basic chat TCP server. The code is simple:
use tokio::{
    io::{AsyncReadExt, AsyncWriteExt},
    net::TcpListener,
};

#[tokio::main]
async fn main() {
    let listener = TcpListener::bind("localhost:8080").await.unwrap();

    let (mut socket, _addr) = listener.accept().await.unwrap();
    let mut buffer = [0u8; 1024];
    let bytes_read = socket.read(&mut buffer).await.unwrap();
    socket.write_all(&buffer[..bytes_read]).await.unwrap();
}

When run on a Windows 10 machine, the server allows connection from telnet, but shuts down as soon as I type anything. After messing around, I tried the same code on a Linux machine, and everything works fine.
What could be the issue and is there a way to keep the connection alive on Windows?

A: Basically what is happening is that telnet on Windows sends each key to the server as soon as it is typed, which causes the server to reply immediately, and as it doesn't not show what is typed, it appears the server is closing the connection on its own without doing anything.
So there is nothing wrong with the code, but for the sake of accommodating Windows' telnet, the code can be modified to wait for a full line instead:
let listener = TcpListener::bind("localhost:8080").await.unwrap();

let (socket, _addr) = listener.accept().await.unwrap();
let mut socket = BufReader::new(socket);
let mut buffer = String::new();
socket.write(r" ".as_bytes()).await.unwrap();
socket.read_line(&mut buffer).await.unwrap();
if buffer == "exit" {
   break;
}
socket.write_all(buffer.as_bytes()).await.unwrap();
tokio::time::sleep(tokio::time::Duration::from_secs(5)).await;


text:
Fernando's maiden ODI ton propel Sri Lanka to 338
Img Source : ICC Twitter
"Avishka Fernando composed a sensational knock of 104 runs off 103 balls that included of 9 fours and 2 sixes."
The Sri Lankan batters never showed that firepower and consistency in their game so far in the ICC World Cup 2019, but at a crucial stage of the tournament, the batting has certainly stood up. In the first half of their must-win clash against the Windies at the Riverside Ground in Chester-le-Street, Lanka's batting-led by Avishka Fernando's sensational century posted a daunting first innings total on the scoreboard. The Windies bowlers, on the other hand, had a pretty tough outing as they struggled to find the right length.
Perera and Karunaratne provide solid opening foundation
Windies skipper Jason Holder won the toss and opted to bowl first as he reckoned that it is a fresh wicket and thus there will be assistance for the bowlers early on. The two Sri Lankan openers, Dimuth Karunaratne and Kusal Perera came out with a pretty positive intent as both the batters played their respective natural game with complete freedom from the word go. The opening duo added 63 runs in the first 11 overs to give a clear evidence of their intentions.
Kusal Perera reached his third half-century of the tournament and was looking in a solid touch to carry on from here. Windies skipper Holder then removed Karunaratne in the 16th over to provide his team with the opening breakthrough and in turn broke the 93-run opening stand as well. Perera, who was looking well-set at the other end, also got out pretty soon after scoring a 51-ball 64.
Fernando racks up maiden World Cup ton
The pair of Kusal Mendis and Avishka Fernando then got together to resurrect the Lankan innings. Both Mendis and Fernando showed remarkable composure to stitch an impressive partnership of 85 runs before the former got dismissed in the 32nd over. After Mendis' dismissal, Fernando took the charge of the innings, notching up his maiden World Cup fifty.
Along with Angelo Mathews, he compiled a vital stand of 58 runs to prepare a solid platform for the final 10 overs. Mathews failed to convert his start of 26 runs into a bigger score, falling victim to Holder in the 40th over. However, even after losing his partner, Fernando never lost his focus and progressed to bring up his maiden ODI and World Cup hundred. Fernando played a sensational innings of 104 runs off 103 balls and stitched an important stand of 67 runs along with Lahiru Thirimanne.
In the end, Thirimanne remained unbeaten at the score of 45 runs and helped Sri Lanka finish with an imposing total of 338 runs in their quota of 50 overs. For West Indies, Holder finished with two wickets, while the trio of Cottrell, Thomas and Allen picked up a scalp each.
Brief Scores
Sri Lanka 338/6 in 50 overs (Avishka Fernando-104, Kusal Perera-64, Lahiru Thirimanne-45*; Jason Holder 2/59) vs Windies.

redpajama_set_name: RedPajamaCommonCrawl


What are the Differences Between Pokemon Omega Ruby and Alpha Sapphire?
The new Pokemon games are out today, and as always, this presents the frugal gamer with a difficult choice: which version should I get?
Luckily, Omega Ruby and Alpha Sapphire are basically the same game, with just a few variations.
The biggest difference is the game's antagonists. If you pick up Omega Ruby, the primary villains will be Team Magma. Meanwhile in Alpha Sapphire, you'll be going up against Team Aqua.
The other big difference are 24 Pokemon that are exclusive to a particular version (12 for each game). Half of these are Legendary Pokemon.
* denotes a Legendary Pokemon.
Fortunately for everyone, it does not appear that the Mega Stones are version specific like in X and Y, meaning you can collect all of them without buying both games.


text:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<meta http-equiv="Content-Type" content="text/html" charset="utf-8">
<title>org.apache.solr.cloud (Solr 4.6.1 API)</title>
<meta name="date" content="2014-01-23">
<link rel="stylesheet" type="text/css" href="../../../../stylesheet.css" title="Style">

org.apache.solr.cloud

Classes

AbstractDistribZkTestBase

AbstractFullDistribZkTestBase

AbstractFullDistribZkTestBase.CloudJettyRunner

AbstractZkTestCase

ChaosMonkey

ZkTestServer

ZkTestServer.HostPort

redpajama_set_name: RedPajamaGithub


text:
What 'win-win'?
Lee Sang-ryeol
* The author is the international news editor of the JoongAng Ilbo.
Trade protectionism from U.S. President Donald Trump's administration was promised from the very beginning. So was a revision of the 2012 Korea-U.S. free trade agreement (FTA). In a summit last June with new South Korean President Moon Jae-in, Trump bluntly said that Washington would renegotiate the terms of the bilateral trade deal. Seoul cast doubts on his remarks. Koreans also thought Trump would not target its long-term ally in trade disputes, but that was wishful thinking.
After reaching an agreement on revisions to the six-year-old trade pact, Treasury Secretary Steven Mnuchin called it "a perfect win-win." But no deal can benefit both parties. Calling the renegotiation a win-win is condescending words of comfort to the loser from the winning party. Timed with the settlement of the FTA, Seoul decided to disclose details of its foreign exchange transactions. Announcing the revised FTA, Washington declared that the two sides have agreed to ensure more transparency in currency policy to level the field in bilateral trade.
Although the move cannot be criticized as a breach of Korea's sovereignty, Seoul authorities' maneuvering room nevertheless will be impaired. As Korea's authorities cannot interfere in currency markets as they want, the local currency has become easy prey to speculative forces.
Foreign exchange policy is a pivotal fiscal tool for an economy heavily reliant on external trade as Korea's is. Individuals also pay close attention to the exchange rate as overseas travel has become commonplace. Korean exporters can no longer expect relief from the state in terms of currency policy. The question is whether Korea Inc. is ready to face the music. Some points should be made on the government's concessions on the foreign exchange front.
The first is a lack of transparency and communication. Foreign media outlets were first to report that Seoul and Washington were engaged in talks to enhance transparency in Korean currency market engagements soon after the two sides wound up renegotiations on the FTA. The Moon administration claimed that discussion on the trade deal and foreign exchange were totally different. But experts were doubtful. They compared the government's stance to separating the activities of ground troops and navy after a war has begun.
Second, our negotiating logic was too weak. The government tried to play down repercussions from the new agreement by claiming that South Korea is the only member in the Organization for Economic Cooperation and Development that does not disclose the details of state involvement in currency operation. But few other economies suffer massive capital flight like Korea whenever international markets shake. For instance, the Korean market had little involvement in the Wall Street-triggered financial meltdown in 2008. But the Korean won shot up to 1,500 won from the 1,000 won level against the U.S. dollar. As a result, authorities had to use $50 billion from our foreign exchange reserves to stabilize the currency. The job of defending a weak currency from speculative forces has gotten costlier.
Third, misconceptions of Korea's economic condition is another worry. A number of officials in the liberal administration think the economy should reduce its reliance on exports and be led more by domestic demand. A stronger won helps cut import costs and thus stimulates domestic consumption, they argue. But such a naïve belief won't work in our current economic conditions. A stronger won won't likely hoist stubbornly sluggish consumption. Instead, it would give more reason for people to travel overseas and make use of the appreciated won.
The revised terms to the FTA and foreign exchange concessions add more challenges to a fragile economy. The Trump administration got its way, but Seoul played a weak defense. Its will and preparations against Washington's offensives were too weak. Deputy Prime Minister for the Economy Kim Dong-yeon will be visiting Washington Thursday to meet with Mnuchin and International Monetary Fund Managing Director Christine Lagarde to fine-tune Seoul's disclosure of foreign exchange engagements. The devil is in the detail. Kim must do his upmost to safeguard the national interests.
JoongAng Ilbo, April 16, Page 28
Grief suffocates businesses in Itaewon 3 months after tragedy
Hong's 'In Water' invited to Berlin Film Festival's Encounters selection
Thousands stranded on Jeju as cold grounds hundreds of flights
[Editorial] Clear concerns about the nuclear threat
[Editorial] Clear concerns about the nuclear threat (KOR)


text:
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Home Security in Belmont, MA
Welcome to Alarm New England's business and home security page for Belmont, Massachusetts. This informational page provides important crime data along with additional information for those living in or considering moving to Belmont.
County: Middlesex
Belmont Business and Home Security Facts
Based in New England since 1972, we've worked in the Belmont area for decades. We know the landscape and we have good relationships with local authorities. Our team of dedicated employees live in the communities we serve. Our customers are our neighbors.
Belmont has a crime rate sitting at 15 per 1000 residents. With this statistic, Belmont has a crime rate of near average when compared to all cities and towns in America. According to FBI crime data, your chances of falling victim to a crime in Belmont is 1 in 66. Although Belmont has a high crime rate when compared to other cities in Massachusetts, its crime rate is low compared to other cities with similar population densities.
Belmont has a violent crime rate of one per one thousand residents as opposed to 14 per 1,000 residents for property crime. The chances of falling victim to a violent crime in Belmont is 1 in 874.
History of Belmont
Belmont was created in 1859, carved out from land bordering the towns of Waltham, Watertown, Arlington, and West Cambridge. Belmont was christened after Bellmont, the 200-acre estate belonging to its biggest donor, John Cushing. Cushing Square in Belmont is named after John Cushing while the surviving portion of his estate has been transformed into a branch of the Belmont Public Library.
Interestingly, the western part of Fresh Pond was annexed by Cambridge after initially belonging to Belmont. It was added to Cambridge in the aftermath of a dispute caused by a slaughterhouse so that Cambridge could oversee the maintenance of Fresh Pond.
Things to See and Do in Belmont
Belmont is home to quite a number of historical monuments and houses. Red Top is one of Belmont's top attractions for tourists. Designated a national landmark, Red Top is associated with writer William Howells. Red Top is a shingle design house located in Somerset Street. The house was designed by William Howell's brother-in-law; a man named William Rutherford.
Belmont is also the location of the famous Boston Massachusetts Temple. It is the 100th temple of The Church of Jesus Christ of Latter-day Saints (LDS Church). The Boston Massachusetts Temple is notable as it was the last temple built to attain LDS church's goal of building 100 temples. Finished with white granite, the beautiful, sprawling structure sits on a total of 69,600 square feet. Belmont also attracts visitors to its famous Wellington Hill Railroad Station which was built in 1840.
Lastly, visitors pour in droves to the William Flagg Homer House. The Homer House, as it often referred to in informal circles, served as an inspiration for many of American landscape artist Homer Winslow's earlier paintings and illustrations in the eighteen-sixties. The house was purchased by the Belmont Women's club in 1923, saving it from being destroyed.
Notable Residents
Belmont is situated near highly rated universities such as MIT and Harvard. Perhaps that is why it has been a place of abode for quite a few number of academicians. Franco Modigliani, who was a professor at MIT and a winner of the Nobel Memorial Prize, once lived in Belmont. Paul A. Samuelson, a Nobel Memorial Prize in Economics winner lived in Belmont at a point in his life. Mitt Romney, a former Governor and presidential candidate also lived in Belmont together with his wife, Ann Romney.
https://www.graceyhealth.com/history-belmont-ma/
https://patch.com/massachusetts/belmont/amp/26527755/6-best-things-do-belmont
http://www.belmontwomansclub.org/history.html
https://www.neighborhoodscout.com/ca/belmont/crime
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"Delhi Riots were planned" – Delhi High Court says what everyone knew all along
by Shweta Kashyap
On Monday, the Delhi High Court while refusing to grant bail to an accused named Mohd Ibrahim involved in a case concerning the northeast Delhi riots of 2020, declared that "there was a pre-planned and pre-meditated conspiracy to disturb law and order in the city" and the events "did not take place in a spur of the moment".
Source: oneindia
While dealing with a bail application moved forward by accused Mohd Ibrahim concerning the murder of Delhi Police head constable Ratan Lal, Justice Subramonium Prasad observed that "there was a systematic disconnection and destruction of the CCTV cameras in areas near the place of the incident" and "innumerable rioters ruthlessly descended with sticks, dandas, bats, etc. upon a hopelessly outnumbered cohort of police officials".
Ibrahim was arrested in a murder case last year in March and now he had claimed that he was falsely accused. Although the court acknowledged the fact that Ibrahim cannot be seen at the scene of the crime but he "has been clearly identified on multiple CCTV footages, carrying a sword and instigating the crowd", which was "quite egregious" and sufficient to keep him under custody.
PC India Today
The Delhi high court observed that "This Court has previously opined on the importance of personal liberty in a democratic polity, but it is to be categorically noted that individual liberty cannot be misused in a manner that threatens the very fabric of civilised society by attempting to destabilise it and cause hurt to other persons."
Read more: Delhi Court recognises role of media in twisting narratives in the Delhi Riots case
Back in May this year, the Delhi high court dismissed the bail request applied by Tahir Hussain, former AAP councillor, regarding his connection with two Northeast Delhi riots cases, the court claimed that he used his "muscle power and political clout to act as a kingpin in planning" and this further instigated the communal riots. The court further stated that "Hussain did not use his hands and fists" but the rioters were used as "human weapons" that could have killed anybody, and denied his bail.
"The criminal conspiracy had instigated the rioters of a particular community and provided logistic support like lathis, dandas, stones, acid bottles, knives, swords, firearms, etc. to the rioters at the roof of his house itself," Special Public Prosecutor Amit Prasad further added
Read more: 'Wanted to teach Hindus a lesson,' Tahir Hussain confesses of masterminding Delhi Riots, met Umar Khalid for planning
As extensively reported by TFI earlier, Tahir Hussain has admitted to having masterminded the entire riots, in order to teach 'Hindus a lesson'. Hussain told the police that he wanted to do so using his money and political power. It must be remembered that Tahir Hussain was suspended by the AAP only after his role in orchestrating the riots to specifically target Hindus was revealed.
Jamia student Asif Iqbal Tanha who was arrested in May 2020 for his alleged role in the Delhi riots during interrogation to the Special Cell of the Delhi Police confessed to instigating people to start riots over CAA in Delhi. He also confessed to torching buses and laid bare his desire to turn India into an Islamic republic, according to Zee News.
Read more: 'Wanted to turn India into an Islamic state,' Jamia student confesses to torching buses, says Delhi riots were pre-planned
Hence, it is pretty evident that Delhi Riots did not occur naturally at the spur of the moment, instead, the riots were systematically orchestrated and a planned conspiracy by anti-India elements and this has already been researched and predicted by TFI previously. The Delhi HC's dismissal of bail to Mohd Ibrahim and other anti-Indian elements is indeed a tight slap on the so-called liberals and leftist media from spreading fake propaganda.
Tags: Delhi High CourtDelhi Riots 2020Mohd IbrahimTahir Hussain
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IAS officer Mohammad Iftikharuddin must be sacked
To stop public sector banks from becoming a liability, the government comes up with a solution
Shweta Kashyap
Trying and learning to be the best version of myself.