Showing papers on "Fresnel zone published in 2009"
TL;DR: Testing of the zone plate with the full-field transmission x-ray microscope, XM-1, in Berkeley, showed that the lens clearly resolved 12 nm lines and spaces, a significant step towards 10 nm resolution and beyond.
Abstract: To extend soft x-ray microscopy to a resolution of order 10 nm or better, we developed a new nanofabrication process for Fresnel zone plate lenses. The new process, based on the double patterning technique, has enabled us to fabricate high quality gold zone plates with 12 nm outer zones. Testing of the zone plate with the full-field transmission x-ray microscope, XM-1, in Berkeley, showed that the lens clearly resolved 12 nm lines and spaces. This result represents a significant step towards 10 nm resolution and beyond.
273 citations
TL;DR: F Fresnel zone plates were fabricated by combining electron-beam lithography with atomic layer deposition and focused ion beam induced deposition and for the first time in X-ray microscopy, features below 10nm in width were resolved.
121 citations
TL;DR: The approach combines the diffraction gratings that generate the high-wave-vector-number modes and planar slabs of homogeneous anisotropic metamaterials that propagate these waves and combine them at the subwavelength focal spots to resolve their fundamental limitations.
Abstract: We present a technique capable of producing subwavelength focal spots in planar nonresonant structures not limited to the near-field of the source. The approach combines the diffraction gratings that generate the high-wave-vector-number modes and planar slabs of homogeneous anisotropic metamaterials that propagate these waves and combine them at the subwavelength focal spots. In a sense, the technique combines the benefits of Fresnel lens, near-field zone plates, hyperlens, and superlens and at the same time resolves their fundamental limitations. Several realizations of the proposed technique for visible, near-IR, and mid-IR frequencies are proposed, and their performance is analyzed theoretically and numerically. Generalizations of the developed approach for subdiffractional imaging and on-chip photonics are suggested.
76 citations
TL;DR: In this paper, the authors show that the ray theory criteria cannot be relaxed for low frequency Lamb wave tomography to evaluate the maximum depth of corrosion patch in typical pipe inspection problems, and that the likely points of operation in the low frequency regime respect the wavelength condition but not the more stringent Fresnel zone condition.
Abstract: Corrosion is a major problem in the petrochemical industry. Corrosion patches are often inaccessible, and the majority of the conventional nondestructive evaluation techniques are compromised. There is therefore a need for a rapid, accurate, long range inspection technique to measure the remaining thickness in corrosion patches. Low frequency Lamb wave tomography is a potentially attractive technique to rapidly evaluate the thickness of large sections of partially accessible structures. This approach has been used in the past to detect the shape of defects in a range of applications. Time-of-flight straight-ray tomography relies on the dispersive nature of a guided wave mode to reconstruct the depth profile of a corrosion patch. If the frequency is limited to below the cut-off of the higher order modes the interpretation of the signals and the time-of-flight measurement are easier. In order to reconstruct a thickness map with time-of-flight straight-ray tomography the ray theory needs to be valid. There are two validity criteria: the characteristic size of the defect must be larger than the wavelength and larger than the width of the Fresnel zone. For realistic defect sizes, the likely points of operation in the low frequency regime respect the wavelength condition but not the more stringent Fresnel zone condition. The paper demonstrates, with finite element simulations and experiments, that the ray theory criteria cannot be relaxed for low frequency Lamb wave tomography to evaluate the maximum depth of corrosion patch in typical pipe inspection problems.
65 citations
TL;DR: In this article, the authors derived and analyzed sensitivity densities for two quantities derived from rotational ground-motion measurements: the rms (root-mean-square) amplitude A ω of the rotation seismogram and the apparent shear-wave speed β, where A v denotes the amplitude of the velocity seismogram.
Abstract: We derive and analyze sensitivity densities for two quantities derived from rotational ground-motion measurements: the rms (root-mean-square) amplitude A ω of the rotation seismogram ![Graphic][1] and the apparent shear-wave speed ![Graphic][2] , where A v denotes the rms amplitude of the velocity seismogram. In the case of a plane S wave in a homogeneous and isotropic medium, β a coincides with the true shear-wave speed β . Based on analytical and numerical examples, we demonstrate that the β a kernels attain large absolute values only in the vicinity of the receiver but not in the vicinity of the source. This effect is pronounced in the case of both body S waves and surface waves (Love + Rayleigh). Moreover, the β a kernels are dominated by the higher Fresnel zones while reaching only small absolute values in the first Fresnel zone. This implies (1) that measurements of β a are to the first order independent of the Earth structure near the source, (2) that such measurements may be used for one-station local shear-wave speed tomography, and (3) that comparatively low-frequency signals can be used in order to invert for small-scale structures. The sensitivity densities corresponding to the rotation amplitude measurement A ω resemble those for the velocity amplitude measurements A v . It is, therefore, the combination of A ω with A v , and not one of them alone, that is likely to provide additional constraints on the Earth’s structure near the receiver.
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53 citations
TL;DR: By comparing multilayered zone plates to a conventional monolayering zone plate, the effects associated with the number of building blocks and different dielectric materials in the building block on the efficiency of the transmission are presented.
Abstract: We numerically investigate the optical field enhancement by a metal/dielectric multilayered zone plate. The optical field enhancement at the focal point of a zone plate originates not only from surface plasmon polaritons (SPPs)-assisted diffraction process along the propagation direction of incident light, but also from multiple scattering and coupling of surface plasmons (SPs) along the metal/dielectric multilayer films. By comparing multilayered zone plates to a conventional monolayered zone plate, we present the effects associated with the number of building blocks and different dielectric materials in the building block on the efficiency of the transmission.
46 citations
TL;DR: This is the first report with experimental results that autofocusing in OSH is possible without any searching algorithm or tracking process and synthesizes a real-only spectrum hologram in which its phase term contains information about a distance parameter.
Abstract: We present autofocusing in optical scanning holography (OSH) with experimental results. We first record the complex hologram of an object using OSH and then create the Fresnel zone plate (FZP) that codes the object constant within the depth range of the object using Gaussian low-pass filtering. We subsequently synthesize a real-only spectrum hologram in which its phase term contains information about a distance parameter. Finally, we extract the distance parameter from the real-only spectrum hologram using fringe-adjusted filtering and the Wigner distribution. Using the extracted distance parameter, we reconstruct a three-dimensional image of the object from the complex hologram using digital convolution, which bypasses the conventional blind convolution to reconstruct a hologram. To the best of our knowledge, this is the first report with experimental results that autofocusing in OSH is possible without any searching algorithm or tracking process.
45 citations
TL;DR: In this paper, an analysis technique is proposed for the analysis of reflectarrays placed in the Fresnel zone of the primary feed, which considers the near field radiated by the feed horn instead of ideal feed models.
Abstract: An analysis technique is proposed for the analysis of reflectarrays placed in the Fresnel zone of the primary feed. The technique is based on the classic analysis of reflectarrays considering local periodicity, improved by considering the near field radiated by the feed horn instead of ideal feed models. The incident field on each reflectarray cell is obtained by applying field transformation to the measured far field (FF) of the horn antenna. The stronger variation of the incident field is considered by increasing the number of samples per reflectarray cell for the incident and reflected waves. This enhanced analysis has been applied to the analysis of a multi-fed and multiple-shaped beam reflectarray placed in the Fresnel zone of the feed horns. The antenna was proposed as a central station antenna for a local multipoint distribution system in the 24.5-26.5-GHz band. The antenna was designed by considering an approximate FF feed model in the radiation pattern synthesis and the reflectarray design. The results obtained through the enhanced analysis are compared with those from measurements of a prototype, validating the proposed analysis procedure and providing a significant improvement with respect to conventional analysis.
45 citations
TL;DR: In this paper, a high repetition rate femtosecond laser system is combined with a spatial light modulator (SLM) for diffractive multiple beam processing, and the effect of the zero order beam is eliminated by adding a Fresnel zone lens to defocus the undiffracted beam at the processing plane.
44 citations
TL;DR: In this article, an analytical model was developed to study the subwavelength focusing characteristics of a binary phase Fresnel zone plate (FZP) under the illumination of linear polarized light.
Abstract: An analytical model is developed to study the subwavelength focusing characteristics of a binary phase Fresnel zone plate (FZP). The model shows that high numerical-aperture phase FZP under the illumination of linear polarized light produces rotationally asymmetric focal spot with beamwidth varying from 0.36λ to 0.79λ, where λ is the wavelength. On the other hand, rotationally symmetric focal spot with minimum beamwidth of 0.39λ can be obtained from the illumination of radial polarized light.
42 citations
TL;DR: Gatti et al. as mentioned in this paper provided an experimental detailed study of the three-dimensional coherence properties of light speckles produced by different tunable pseudothermal sources, and confirmed the theoretical prediction of the companion article [A. Gatti et.
Abstract: We provide an experimental detailed study of the three-dimensional coherence properties of light speckles produced by different tunable pseudothermal sources. Our findings confirm the theoretical prediction of the companion article [A. Gatti et al., Phys. Rev. A 78, 063806 (2008)], according to which the longitudinal coherence of the speckles is ruled by ordinary diffraction laws only in the deep-Fresnel zone close to the source, deviates from this behavior in the Fresnel zone, and tends to become infinite when approaching the Fraunhofer zone. A quantitative comparison with theory is presented for Gaussian speckles in all the three regimes and for Airy speckles in the deep-Fresnel zone. Potential applications to three-dimensional imaging techniques are briefly discussed.
TL;DR: A laboratory x-ray microscope based on a compound zone plate that utilizes multiple diffraction orders to achieve high resolution while maintaining reasonable efficiency is presented.
Abstract: Improving the resolution in x-ray microscopes is of high priority to enable future applications in nanoscience. However, high-resolution zone-plate optics often have low efficiency, which makes implementation in laboratory microscopes difficult. We present a laboratory x-ray microscope based on a compound zone plate. The compound zone plate utilizes multiple diffraction orders to achieve high resolution while maintaining reasonable efficiency. We analyze the illumination conditions necessary for this type of optics in order to suppress stray light and demonstrate microscopic imaging resolving 25 nm features.
TL;DR: A theoretical analysis and numerical simulations based on the Rayleigh-Sommerfeld approach have been developed analyzing properties such as the depth of focus and the intensity of the focus in terms of the number of zones as discussed by the authors.
TL;DR: It is proved theoretically that in comparison with a sinusoidal amplitude grating this grating produces better quality of fringes in the near-infrared region.
Abstract: Phase-shifting profilometry requires projection of sinusoidal fringes on a 3D object. We analyze the visibility and frequency content of fringes created by a sinusoidal phase grating at coherent illumination. We derive an expression for the intensity of fringes in the Fresnel zone and measure their visibility and frequency content for a grating that has been interferometrically recorded on a holographic plate. Both evaluation of the systematic errors due to the presence of higher harmonics by simulation of a profilometric measurement and measurement of 3D coordinates of test objects confirm the good performance of the sinusoidal phase grating as a projective element. In addition, we prove theoretically that in comparison with a sinusoidal amplitude grating this grating produces better quality of fringes in the near-infrared region. Sinusoidal phase gratings are fabricated easily, and their implementation in fringe projection profilometry facilitates construction of portable, small size, and low-cost devices.
TL;DR: In this article, a ray time-delay tomography based on a Bayesian inversion formulation is proposed to reconstruct the sound-speed variations in the waveguide using two vertical coplanar densely sampled source and receive arrays.
Abstract: Recent shallow-water experiments in sea channels have been performed using two vertical coplanar densely sampled source and receive arrays. Applying a double-beamforming algorithm on the two arrays both on synthetic numerical simulations and on experimental data sets, we extract efficiently source and receive angles as well as travel times for a large number of acoustic rays that propagate and bounce in the shallow-water waveguide. We then investigate how well sound-speed variations in the waveguide are reconstructed using a ray time-delay tomography based on a Bayesian inversion formulation. We introduce both data and model covariance matrices and we discuss on the synthetic numerical example how to choose the a priori information on the sound-speed covariance matrix. We attribute the partial sound-speed reconstruction to the ray-based tomography and we suggest that finite-frequency effects should be considered as the vertical and horizontal size of the Fresnel zone significantly spreads in the waveguide. Finally, the contribution of a different set of ray angles for tomography goal is also presented.
Patent•
14 Apr 2009TL;DR: In this article, a method for marine seismic surveying includes towing a seismic sensors in a plurality of streamers in the water, actuating a seismic energy source in water at selected times and detecting seismic signals at the sensors resulting from the actuation of the source.
Abstract: A method for marine seismic surveying includes towing a seismic sensors in a plurality of streamers in the water, actuating a seismic energy source in the water at selected times and detecting seismic signals at the sensors resulting from the actuation of the source. A data trace is created for each of the detected signals. At least one Fresnel zone is determined for at least some of the seismic data traces. A contribution of each of the traces to each one of a plurality of bins defined in a predetermined pattern is computed, based on the Fresnel zone associated with each trace. Based on the computed contributions, a maximum lateral distance between corresponding seismic sensors is determined that will result in a contribution sum above a selected threshold.
TL;DR: In this article, a Fresnel zone plate is designed to perform the function of a doubly-hyperbolic lens, and the focusing characteristics of the zone plate and the lens are compared using both measured data and body-of-revolution finite-difference time-domain simulations.
Abstract: A Fresnel zone plate is designed to perform the function of a doubly-hyperbolic lens. The focusing characteristics of the zone plate and the lens are compared using both measured data and body-of-revolution finite-difference time-domain simulations. The results from this comparison are used to evaluate the use of zone plates as focusing elements in a free-space, focused-beam measurement system. A set of two zone plates is used to perform measurements of the material properties of a dielectric sheet, and the results are compared to the results from a standard system which uses two doubly-hyperbolic lenses.
01 Aug 2009
TL;DR: In this article, three different methods of generating digital Fresnel holograms of 3-D real-existing objects illuminated by incoherent light are reviewed, including a unique scanning system in which Fresnel zone plates (FZP) are created by a homodyne rather than the common heterodyne interferometer.
Abstract: We review three different methods of generating digital Fresnel holograms of 3-D real-existing objects illuminated by incoherent light. In the first method, a scanning hologram is generated by a unique scanning system in which Fresnel zone plates (FZP) are created by a homodyne rather than the common heterodyne interferometer. During the scanning, the FZP projected on the observed object is frozen rather than varied as previously. In each scanning period, the system produces an on-axis Fresnel hologram. The twin image problem is solved by a linear combination of at least three holograms taken with three FZPs with different phase values. The second hologram reviewed here is the digital incoherent modified Fresnel hologram. To calculate this hologram, multiple-viewpoint projections of the 3-D scene are acquired, and a Fresnel hologram of the 3-D scene is directly computed from these projections. This method enables to obtain digital holograms by using a simple digital camera, which operates under regular light conditions. The last digital hologram reviewed here is the Fresnel incoherent correlation hologram. In this motionless holographic technique, light is reflected from the 3-D scene, propagates through a diffractive optical element (DOE), and is recorded by a digital camera. Three holograms are recorded sequentially, each for a different phase factor of the DOE. The three holograms are superposed in the computer, such that the result is a complex-valued Fresnel hologram that does not contain a twin image.
TL;DR: By scanning an optically trapped fluorescent sphere, the vignetted collection region of the zone-plate imaging system is measured and the fluorescence collection efficiency is sharply peaked and has a lateral width of 550 nm, which agrees with numerical simulations.
Abstract: We demonstrate a form of scanning microscopy using a short-focal-length Fresnel zone plate and a low-NA relay telescope. Owing to a focal length of only 5 microm, the zone plate produces large wavefront tilt and consequently severe vignetting for off-axis illumination. By scanning an optically trapped fluorescent sphere, we measure the vignetted collection region of the zone-plate imaging system. The fluorescence collection efficiency is sharply peaked and has a lateral width of 550 nm, which agrees with numerical simulations.
TL;DR: Numerical assessment of the suggested structure shows excellent coupling efficiency (up to 59%) of the 10 mum free-space Gaussian beam to the 0.36 mum Si waveguide within a working distance of a few mum.
Abstract: We propose a novel metal slit array Fresnel lens for wavelength-scale optical coupling into a nanophotonic waveguide. Using the plasmonic waveguide structure in Fresnel lens form, a much wider beam acceptance angle and wavelength-scale working distance of the lens was realized compared to a conventional dielectric Fresnel lens. By applying the plasmon waveguide dispersion relation to a phased antenna array model, we also develop and analyze design rules and parameters for the suggested metal slit Fresnel lens. Numerical assessment of the suggested structure shows excellent coupling efficiency (up to 59%) of the 10 mum free-space Gaussian beam to the 0.36 mum Si waveguide within a working distance of a few mum.
TL;DR: The construction of fractal generalized zone plates from a set of periodic diffractive optical elements with circular symmetry allows us, for instance, to increase the number of foci of a conventional fractal zone plate while keeping the self-similarity property within the axial irradiance.
Abstract: The construction of fractal generalized zone plates from a set of periodic diffractive optical elements with circular symmetry is proposed. This allows us, for instance, to increase the number of foci of a conventional fractal zone plate while keeping the self-similarity property within the axial irradiance. The focusing properties of these fractal diffractive optical elements for points not only along but also in the close vicinity of the optical axis are investigated. In both cases analytical expressions for the irradiance are derived. Numerical simulations of the energetic efficiency of fractal generalized zone plates under plane wave illumination are carried out. In addition, some effects on the axial irradiance caused by variations in the area of their transparent rings are shown.
TL;DR: It was found that, in the focal plane of silver zone plates, there were more evanescent waves and the propagating waves occurred at higher spatial frequencies relative to glass zone plates.
Abstract: The field properties of Fresnel zone plates with wavelength-scale focal distances were numerically investigated using the finite-difference time-domain method. The fields in the focal planes are analyzed using the angular spectrum representation, and the components of the propagating and evanescent waves are reconstructed. It was found that, in the focal plane of silver zone plates, there were more evanescent waves and the propagating waves occurred at higher spatial frequencies relative to glass zone plates. The propagating and evanescent wave components vary with the material and the number of zones in the zone plate structures. Our findings suggest that more evanescent waves and higher spatial frequency components of propagating waves can shape the field and obtain a smaller focus.
TL;DR: In this article, Fresnel zone plates, fabricated in a solid surface, can sharply focus atomic Bose-Einstein condensates that quantum reflect from the surface or pass through the etched holes.
Abstract: We show that Fresnel zone plates, fabricated in a solid surface, can sharply focus atomic Bose-Einstein condensates that quantum reflect from the surface or pass through the etched holes. The focusing process compresses the condensate by orders of magnitude despite inter-atomic repulsion. Crucially, the focusing dynamics are insensitive to quantum fluctuations of the atom cloud and largely preserve the condensates' coherence, suggesting applications in passive atom-optical elements, for example zone plate lenses that focus atomic matter waves and light at the same point to strengthen their interaction. We explore transmission zone-plate focusing of alkali atoms as a route to erasable and scalable lithography of quantum electronic components in two-dimensional electron gases embedded in semiconductor nanostructures. To do this, we calculate the density profile of a two-dimensional electron gas immediately below a patch of alkali atoms deposited on the surface of the nanostructure by zone-plate focusing. Our results reveal that surface-induced polarization of only a few thousand adsorbed atoms can locally deplete the electron gas. We show that, as a result, the focused deposition of alkali atoms by existing zone plates can create quantum electronic components on the 50 nm scale, comparable to that attainable by ion beam implantation but with minimal damage to either the nanostructure or electron gas.
TL;DR: In this article, the authors demonstrate subwavelength-resolved bidirectional conjugate imaging between three-dimensional far-field and two-dimensional surface plasmon (SP) by using a SP launching lens (SPLL), which consists of multiple groove zones that is designed according to the Fresnel zone on a gold film.
Abstract: We demonstrate subwavelength-resolved bidirectional conjugate imaging between three-dimensional far-field and two-dimensional surface plasmon (SP) by using a SP launching lens (SPLL), which consists of multiple groove zones that is designed according to the Fresnel zone on a gold film. Resolvable separations between two SP point sources of 704 and 668 nm were obtained for far-field to SP and the contrary, respectively, at λ=830 nm. The SPLL shows similar imaging properties to a traditional optical lens, which can be used to connect multiple channels between far-field and SP.
TL;DR: In this paper, the performance of Fresnel zone plates having a polygonal boundary between zones has been studied and the contribution of the complex amplitude of each zone is calculated analytically and numerically.
Abstract: The performance of Fresnel zone plates having a polygonal boundary between zones has been studied. The contribution of the complex amplitude of each zone is calculated analytically and numerically solved. The case of a continuous phase plate is considered as the limit case in performance for each polygonal shape. This performance is compared with respect to the circular case. Also four different methods to define a polygonal FZP having discrete phase shift are analyzed and compared.
TL;DR: A reduced-size Fresnel Interferometric Imager prototype is designed and optical tests made in the laboratory in order to validate the concept for future space missions, and quantitative measurements of the diffraction limited performances and dynamic range on double sources are given.
Abstract: The Fresnel Interferometric Imager is a space-based astronomical telescope project yielding milli-arcsecond angular resolution and high contrast images with loose manufacturing constraints. This optical concept involves diffractive focusing and formation flying: a first “primary optics” space module holds a large binary Fresnel array, and a second “focal module” holds optical elements and focal instruments that allow for chromatic dispersion correction. We have designed a reduced-size Fresnel Interferometric Imager prototype and made optical tests in our laboratory in order to validate the concept for future space missions. The primary module of this prototype consists of a square, 8 cm side, 23 m focal length Fresnel array. The focal module is composed of a diaphragmed small telescope used as “field lens,” a small cophased diverging Fresnel zone lens that cancels the dispersion, and a detector. An additional module collimates the artificial targets of various shapes, sizes, and dynamic ranges to be imaged. We describe the experimental setup, different designs of the primary Fresnel array, and the cophased Fresnel zone lens that achieves rigorous chromatic correction. We give quantitative measurements of the diffraction limited performances and dynamic range on double sources. The tests have been performed in the visible domain, λ=400-700 nm. In addition, we present computer simulations of the prototype optics based on Fresnel propagation that corroborate the optical tests. This numerical tool has been used to simulate the large aperture Fresnel arrays that could be sent to space with diameters of 3 to 30 m, foreseen to operate from Lyman α (121 nm) to mid IR (25 μm).
TL;DR: In this paper, the feasibility of manufacturing a demultiplexer/multiplexer or even a spectrogram analyzer at millimeter-wave frequencies has been shown by using an extraordinary transmission metamaterial prism and taking advantage of its inherent dispersive behavior.
Abstract: In this work, by using an extraordinary transmission metamaterial prism and taking advantage of its inherent dispersive behavior, the feasibility of manufacturing a demultiplexer/multiplexer or even a spectrogram analyzer at millimeter-waves is shown. Depending on the incoming beam frequency, the outgoing beam suffers in a wedge-shaped configuration a different deflection (governed by Snell's law). Since the frequency dependent index of refraction of this metamaterial can go from negative values to almost zero for the first propagation band (cut-off regime) and also be positive for the second propagation mode (non-cut-off regime), different negative and positive outgoing angles can be obtained and then, diverse paths for each frequency, as the Fresnel zone experimental results confirm.
TL;DR: This work shows that the relation between the Green's functions and the noise cross-correlation function holds under much less restrictive conditions than previously thought.
Abstract: Two-point correlation functions of sufficiently diffuse wave fields generated by uncorrelated random sources are known to approximate deterministic Green's functions between the two points. This property is utilized increasingly for passive imaging and remote sensing of the environment. Here we show that the relation between the Green's functions and the noise cross-correlation function holds under much less restrictive conditions than previously thought. It can even hold when ambient noise sources have correlation ranges large compared to the wavelength. Admissible correlation ranges are limited from above by the size of the Fresnel zone at wave propagation between the points where noise cross correlation is evaluated.
TL;DR: In this work the concept of a Fresnel zone antenna for dual-band detection in the IR and millimeter wave region is presented, based on a Fresnels zone plate lens in theIR that is transformed to serve as a millimeter-wave antenna.
Abstract: In this work the concept of a Fresnel zone antenna for dual-band detection in the IR and millimeter wave region is presented. The design is based on a Fresnel zone plate lens in the IR that is transformed to serve as a millimeter-wave antenna. Two different designs are presented, a circular-zone design that gives a high diffractive efficiency in the IR and a square-zone design that gives a higher response in the millimeter band but a lower focusing efficiency in the IR. Both designs have an operation bandwidth with the same low frequency limit of 400 GHz (750 μm), which can be tailored by changing the number of Fresnel zones, and a high frequency limit of 4.5 THz (65 μm) for the circular-zone design and 5 THz (59 μm) for the square-zone design.
TL;DR: In this paper, the fringe patterns produced by the zone plates in the presence of a quasi-parallel source were analyzed and compared with those obtained by Monte-Carlo simulations.
Abstract: Combination of Fresnel Zone Plates (FZP) can make an excellent telescope for imaging in X-rays. We present here the results of our experiments with several pairs of tungsten made Fresnel Zone plates in presence of an X-ray source kept at a distance of about 45 ft. The quasi-parallel beam allowed us to study sources placed on the axis as well as off the axis of the telescope. We present theoretical study of the fringe patterns produced by the zone plates in presence of a quasi-parallel source. We compare the patterns obtained from experiments with those obtained by our Monte-Carlo simulations. The images are also reconstructed by deconvolution from both the patterns. We compare the performance of such a telescope with other X-ray imaging devices used in space-astronomy.