Showing papers on "Zone plate published in 1990"
TL;DR: A 2-D array of 10 x 10 diffractive lenslets was fabricated and tested, and the performance of the lenslets is based on the diffraction of light at a Fresnel zone plate (FZP).
Abstract: A 2-D array of 10 x 10 diffractive lenslets was fabricated and tested Each lenslet has a rectangular aperture and a size of 15 mm x 15 mm The focal length of each lenslet is 47 mm The array was produced by depositing thin films of silicon monoxide on a quartz glass substrate and by using photolithographic techniques The performance of the lenslets is based on the diffraction of light at a Fresnel zone plate (FZP) The FZP pattern was implemented as a phase structure with eight discrete levels The diffraction efficiency was measured to be 91%
212 citations
TL;DR: The properties and construction of a polarization-independent Fresnel lens array using nematic liquid crystals in which the diffraction efficiency of lenses can be electrically controlled is described.
Abstract: In successive zones of a layer of nematic liquid crystal material, the principal axes of at least some of the material in each zone are established orthogonal to the axes of at least some of the material in adjacent zones. By applying a uniform electric field to the zones of the entire layer, an electrically controlled polarization-independent Fresnel lens is achieved.
147 citations
TL;DR: It is shown that a zone plate with a prespecified number of foci, which are separated axially by Rayleigh's limit of resolution, can create an arbitrarily high focal depth when used as an apodizer over an otherwise clear aperture.
Abstract: We show that a zone plate with a prespecified number of foci, which are separated axially by Rayleigh’s limit of resolution, can create an arbitrarily high focal depth when used as an apodizer over an otherwise clear aperture. We discuss the resolution and light gathering power of this method.
106 citations
TL;DR: The scanning photoelectron microscope at the National Synchrotron Light Source (NSLS) has recently recorded micrographs with a resolution below half a micron as discussed by the authors.
Abstract: The scanning photoelectron microscope at the National Synchrotron Light Source (NSLS) has recently recorded micrographs with a resolution below half a micron To demonstrate elemental and chemical sensitivity at the submicron level, an artificial structure consisting of Al and SiO2 lines on a boron‐doped silicon substrate was examined Al 2p and Si 2p primary photoelectrons as well as O KVV Auger electrons were used for image formation Contrast reversal between the the Si and SiO2 areas was observed in images formed from Si 2p and oxide‐shifted Si 2p photoelectrons The soft x‐ray undulator at the NSLS provides coherent illumination of a zone plate to produce the microprobe The sample is mechanically scanned through the beam allowing the formation of images from photoelectrons detected by a single‐pass cylindrical mirror analyzer, or a more complete spectroscopic examination of a selected area of the sample
105 citations
Patent•
3M1
TL;DR: A multifocal ophthalmic lens includes first and second lens members as discussed by the authors, each lens member has a smooth outer surface and an inner surface with an edge about its perimeter, and a hole through one of the lens members functions as a fluid transport mechanism to permit transfer of the medication between the cavity and eye.
Abstract: A multifocal ophthalmic lens includes first and second lens members. Each lens member has a smooth outer surface and an inner surface with an edge about its perimeter. A multifocal diffractive zone plate on at least one of the lens members is characterized by an index of refraction. The lens members are joined at the edges by ultrasonic welding to form a cavity adjacent the diffractive zone plate. The cavity is filled with a liquid medication having an index of refraction which is different than the index of refraction of the diffractive zone plate. A hole through one of the lens members functions as a fluid transport mechanism to permit transfer of the medication between the cavity and eye.
99 citations
Patent•
18 Apr 1990
TL;DR: An optical device suitably employable in intraocular and contact lenses that employs a phase zone plate of a Cohen lens design that relies on a small number of zones to provide multifocal images is described in this article.
Abstract: An optical device suitably employable in intraocular and contact lenses that employs a phase zone plate of a Cohen lens design that relies on a small number of zones to provide multifocal images.
82 citations
TL;DR: In this article, the authors describe the implementation of an 8 keV microscope that operates with a conventional x-ray source in their lab, where samples are scanned pixel-by-pixel through a focused X-ray spot produced by a phase modulating zone plate fabricated with the sputtered-sliced technique.
Abstract: We describe the implementation of an 8 keV microscope that operates with a conventional x-ray source in our lab. Samples are scanned pixel-by-pixel through a focused x-ray spot produced by a phase-modulating zone plate fabricated with the sputtered-sliced technique. The micro- focused x-ray source uses a Cu target and produces 8 keV photons that are detected with a Si(Li) spectroscopy system. The microscope currently achieves 10 µm resolution.
36 citations
20 May 1990-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the authors describe the instrumentation of a scanning photoelectron microscope (SPEM) at the X1A beamline of the National Synchrotron Light Source (NSLS).
Abstract: We describe instrumentation of a scanning photoelectron microscope (SPEM), which we are presently developing and commissioning at the X1A beamline of the National Synchrotron Light Source (NSLS). This instrument is designed to use the soft-X-ray undulator (SXU) at the NSLS as a high-brightness source to illuminate a Fresnel zone plate, thus forming a finely focused probe, ≤ 0.2 μm in size, upon the specimen surface. A grating monochromator selects the photon energy in the 400–800 eV range with an energy resolution better than 1 eV. The expected flux in the focus is in the range 5 × 107–109 photons s−1. A single pass cylindrical mirror analyzer (CMA) is used to record photoemission spectra, or to form an image within a fixed electron energy bandwidth as the specimen is mechanically scanned. As a first test, a 1000-mesh Au grid was successfully imaged with Au 4f primary photoelectrons, achieving a resolution of about 1 μm.
33 citations
TL;DR: A spatially divided beam splitter is designed, by which the laser diode light couples into multiple fibers using a cylindrical lens and a phase type linear zone plate array, and simultaneous focusing and separation of the laser output are achieved.
Abstract: A spatially divided beam splitter is designed, by which the laser diode light couples into multiple fibers using a cylindrical lens and a phase type linear zone plate array. Using skew ray tracing, the focusing characteristics of a spatially divided beam splitter are predicted. A three-section linear zone plate array with the linewidth changing from 1.1 to 2.05 μm was fabricated by holographic mask patterning and deep UV printing. In oblique incident conditions close to the Bragg angle, the diffraction efficiency reached 60%. By combining the linear zone plate array with a cylindrical lens, simultaneous focusing and separation of the laser output are achieved.
21 citations
IBM1
TL;DR: The refractive index of the amorphous carbon layers inside multilayer soft x-ray mirrors is derived in the lambda = 42-58-A wavelength range by measuring the shift in the Bragg angle caused by refraction.
Abstract: The refractive index of the amorphous carbon layers inside multilayer soft x-ray mirrors is derived in the λ = 42–58-A wavelength range by measuring the shift in the Bragg angle caused by refraction. Reflectivity curves are measured with a reflectometer behind a zone plate monochromator at the National Synchrotron Light Source. The monochromator consists only of a freestanding zone plate of gold and an exit slit and is free of any of the contamination problems often found in monochromators that contain mirrors.
18 citations
TL;DR: A new type of zone plate has been designed for soft x-rays, based on radial modulation of the refractive indices of the material, that is made with titanium and chromium and its x-ray focusing efficiency is 34%.
Abstract: A new type of zone plate has been designed for soft x-rays, based on radial modulation of the refractive indices of the material. It is made with two materials; the concentration of one material increases gradually and that of the other decreases with increasing radius in each pair of zones. When such a zone plate is made with titanium and chromium and their concentrations are optimized for use at the wavelength of 2.74 nm, its x-ray focusing efficiency would be 34%. This value is 3.4 and 1.4 times the efficiencies of the Fresnel zone plate and the π-radian phase shifting zone plate, respectively.
Patent•
23 May 1990TL;DR: In this paper, a diffractive bifocal eye lens, an optical system, and processes for fabrication of such lenses are disclosed, which includes the following principal elements in optical alignment along an optical axis (10), for accomplishing the indicated steps of the process: a laser (12) for emission of ultraviolet light along the optical axis, a zone plate mask (18) in the path of irradiation by the laser; and an imaging lens (20) to project, with radiation from the laser, an image of the mask on the concave inner surface (30) of an
Abstract: A diffractive bifocal eye lens, an optical system, and processes for fabrication of such lenses are disclosed. The optical system includes the following principal elements in optical alignment along an optical axis (10), for accomplishing the indicated steps of the process: a laser (12) for emission of ultraviolet light along the optical axis (10); a zone plate mask (18) in the path of irradiation by the laser; and an imaging lens (20) to project, with radiation from the laser (12), an image of the mask on the concave inner surface (30) of an eye lens mounted coincident with the image surface of the optical system, thereby ablating the eye lens imagewise of the mask to generate a phase zone plate on the eye lens. The laser beam scans the zone plate mask (18) to generate a composite image on the image surface. Alternatively, the phase zone plate (18) is generated on the concave surface of a glass blank at the image surface to form a tool from which molds, and in turn lenses, are replicated. The light source is an argon fluoride excimer laser (12), emitting at 193 nm. The lens is a variable magnification lens to project various size images of the mask for producing zone plates of various powers as desired.
TL;DR: In this article, a new kind of computer-generated zone plate called a modulated circular zone plate is presented, which is able to focus light on a line segment along the optical axis.
Abstract: This paper presents a new kind of computer-generated zone plate, which we call a modulated circular zone plate. These plates reconstruct a special class of focal curves. The curves are three-dimensional and lie on the lateral surface of a cylinder. As a particular case, we propose zone plates which are able to focus light on to a line segment along the optical axis. The experimental results illustrate the focusing properties of the zone plates.
TL;DR: Experimental results of focusing and imaging by a lens array and an elliptical zone plate are given and two methods of fabricating holographic zone plates for an IR or UV wavelength are proposed.
Abstract: Holographic microlens arrays and elliptical zone plates are fabricated on holographic plates and photoresists by interference between the first- and second-order diffracted waves from an ion etched Fresnel zone plate, which is made by electron-beam scanning and deep UV lithography. This method of fabrication is simple, and a holographic lens with a large numerical aperture and short focal length is obtained. Experimental results of focusing and imaging by a lens array and an elliptical zone plate are given. Two methods of fabricating holographic zone plates for an IR or UV wavelength are also proposed.
TL;DR: In this article, a scanning photoelectron microscopy (SPEM) at the X1A beamline of the National Synchrotron Light Source (NSLS) is presented.
Abstract: We are in the process of developing and commissioning a scanning photoelectron microscopy (SPEM) at the X1A beamline of the National Synchrotron Light Source (NSLS). It is desigend to make use of the Soft X-ray Undulator (SXU) at the NSLS. This high brightness source illuminates a Fresnel zone plate, which forms a focused probe, ≤0.2 µm in size, on the specimen surface. A grating monochromator selects the photon energy in the 400-800 eV range with an energy resolution of better than 1 eV. The expected flux in the focus is in the 5 × 107-109 photons/s range. A single pass Cylindrical Mirror Analyzer (CMA) is used to record photoemission spectra, or to form an image within a fixed electron energy bandwidth as the specimen is mechanically scanned. As a first test, a 1000 mesh Au grid was successfully imaged with a resolution of about 1 µm and the CMA tuned to the Au 4f photoelectron peak. Once it is commissioned, a program is planned which will utilize the microscope to study beam sensitive systems, such as thin oxide/sub-oxide films of alumina and silica, and ultimately various adsorbates on these films.
Patent•
24 Dec 1990TL;DR: In this article, an X-ray optical apparatus comprises an Xray optical system which is capable of projecting an enlarged sample image by soft X-rays and a visible optical system to observe the sample with a visible radiation.
Abstract: An X-ray optical apparatus comprises an X-ray optical system which is capable of projecting an enlarged sample image by soft X-rays and a visible optical system to observe the sample with a visible radiation. To enable simultaneous observation using both optical systems, the systems utilize a common objective zone plate. The objective zone plate includes a base plate having an opening at the center thereof to pass the soft X-rays which have passed through the sample and also having a visible radiation passing section to the outside of the opening. A zone plate is supported centrally on the base plate for converging soft X-rays which have passed through the sample and forming the sample image at a predetermined position. An eyepiece is provided in a position displaced from the X-ray optical axis to enable visual observation of the sample with the light passed through the visible radiation transmitting section of the objective zone plate.
TL;DR: The NSLS X1A beamline is dedicated to soft x-ray microscopy as mentioned in this paper, and two types of instruments are developed, both dependent on the remarkable brightness of the undulator source.
Abstract: Soft x-rays are attractive for microscopy because they tend to be less damaging to specimens than charged probes. In addition their interactions with specimens can result in element-specific information and the penetration depth is adjustable by choice of the beam energy. Resolution on the order of 50 nm has been demonstrated, and further improvements are anticipated. The experimental program at the NSLS X1A beamline is dedicated to soft x-ray microscopy. We are developing two types of instruments, both dependent on the remarkable brightness of the undulator source. One of these uses a Fresnel zone plate to focus the beam to a small size. This microprobe is used either to study biological specimens, or, in a different apparatus, to study surfaces by photoelectron microscopy. The other type of instrument makes use of x-rays diffracted by the specimen. In this category we are involved in the development of Gabor holography, Fourier transform holography, and in imaging by soft x-ray diffraction.
20 May 1990-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, a Fourier transform holographic microscope with an anticipated resolution of better than 100 nm has been built, which employs a charge-coupled-device (CCD) detector array of 576 × 384 elements.
Abstract: A Fourier transform holographic microscope with an anticipated resolution of better than 100 nm has been built. Extensive testing of the apparatus has begun. Preliminary results include the recording of interference fringes using 3.6-nm X-rays. The microscope employs a charge-coupled-device (CCD) detector array of 576 × 384 elements. The system is illuminated by soft X-rays from a high-brightness undulator. The reference point source is formed by a Fresnel zone plate with a finest outer zone width of 50 nm. Sufficient temporal coherence for hologram formation is obtained by a spherical grating monochromator. The X-ray hologram intensities at the recording plane are to be collected, digitized and reconstructed by computer. Data acquisition is under CAMAC control, while image display and off-line processing takes place on a VAX graphics workstation. Computational models of Fourier transform hologram synthesis, and reconstruction in the presence of noise, have demonstrated that numerical methods in two dimensions are feasible and that three-dimensional information is potentially recoverable.
Patent•
28 Feb 1990
TL;DR: In this paper, a diffractive multifocal optical element comprising a phase zone plate of a Cohen lens design containing rotationally symmetrical, curved repetitive patterns designed to operate at a specific wavelength and which are also curved in r2 space is presented.
Abstract: NPD1708 A diffractive multifocal optical element comprising a phase zone plate of a Cohen lens design containing rotationally symmetrical, curved repetitive patterns designed to operate at a specific wavelength and which are also curved in r2 space.
07 May 1990
TL;DR: In this article, the far-field antenna pattern of phase-correcting Fresnel zone plates is analyzed, based primarily on work done in the optical regime, and measured characteristics of zone-plates in the microwave-millimeter-wave region are also presented.
Abstract: The far-field antenna pattern of phase-correcting Fresnel zone plates is analyzed, based primarily on work done in the optical regime. Measured characteristics of zone-plates in the microwave-millimeter-wave region are also presented. Since the zone plate accomplishes focusing through diffraction and interference, rather than refraction, the overall efficiency for collecting the radiation flux that passes through the aperture is an important consideration. This efficiency has been determined analytically to be approximately 40.5% for a phase-reversal plate and 81% for a quarter-period plate. Thus, the intensity at the focus, relative to that produced by a hyperboloidal lens, is 3.9 dB down or 0.9 dB down respectively, for the phase-reversal or quarter-period cases. Early investigations in the microwave-to-millimeter-wave range developed formulas for calculating the radii and depth of annular cuts, and measured the axial intensity variation near the focus and the antenna patterns at 10, 140, and 210 GHz. Measurements have been made of off-axis image intensity and image position errors at 140 GHz, and the results are excellent. >
TL;DR: In this paper, electron beam lithography and reactive ion etching in crystalline silicon membranes are used to fabricate open stencil patterns for two novel applications: transmission reticles containing resolution test patterns for projection soft x-ray lithography at λ=36 nm; and a Fresnel zone plate for focusing beams of cold neutral atoms.
Abstract: Free standing microstructures become necessary when transparent materials are unavailable as supporting layers in transmission components. In this work we use electron beam lithography and reactive ion etching in crystalline silicon membranes to fabricate open stencil patterns for two novel applications: transmission reticles containing resolution test patterns for projection soft x‐ray lithography at λ=36 nm; and a Fresnel zone plate for focusing beams of cold neutral atoms. Various schemes are described for making components with minimum zone plate feature sizes down to 0.23 μm and grating features below 0.1 μm. We also report on several materials and processing issues which limit feature sizes and distortions in these microstructures.
TL;DR: A novel procedure is described that leads to an analytical formula for shaping the focus power spectrum by using apodizers expressible as the Legendre series, which act on cells of arbitrary opening ratio.
Abstract: By apodizing the cells of a zone plate and changing the opening ratio, it is possible to shape the relative power spectrum of its foci. We describe a novel procedure that leads to an analytical formula for shaping the focus power spectrum by using apodizers expressible as the Legendre series; these act on cells of arbitrary opening ratio. Our general result is used to design zone plates that have missing foci and to discuss a synthesis procedure using apodizers with various opening ratios. Our applications can also be used for shaping the power spectrum of 1-D gratings.
TL;DR: In this article, the authors analyzed the image formation by zone plates (ZP's) in X-ray microscopy using ZP's as optical devices and showed that images overlapping with one another can be separated by means of an off-axis diaphragm.
Abstract: It is of great importance to understand image formation by zone plates (ZP's) in X-ray microscopy using ZP's as optical devices. Image formation by a ZP is diagrammatically analyzed. First, an object is illuminated by a monochromatic plane wave. It is shown that images overlapping with one another can be separated by means of an off-axis diaphragm. Secondly, the object is illuminated by undulator radiation (UR). Finally, a one-dimensional transmission grating used as an object is illuminated by UR. It is shown that its diffraction images appear on various parabolic curves. The experimental result agrees quite well with the calculated one.
01 Jan 1990
TL;DR: Gabor zone-plate (GZP) apertures have been developed for use in EG&G EM's mercuric iodide (HgI2) gamma-ray camera as mentioned in this paper.
Abstract: Gabor zone-plate (GZP) apertures have been developed for use in EG&G EM's mercuric iodide (HgI2) gamma-ray camera. The purpose of such an aperture is to increase efficiency, while maintaining good resolution. The GZP is similar to the Fresnel zone plate (FZP) but it has continuous transitions between opaque and transparent regions. Because there are no sharp transitions in the transmission, the inherent interference noise in GZP imaging is lower than that in FZP imaging. GZP parameters were chosen by considering the effects of constraints such as detector pixel size, number of pixels, minimum field of view required, maximum angle of incidence tolerated, and the Nyquist criterion for the minimum sampling rate. As a result an aperture was designed and fabricated with eight zones and a diameter of 3 cm. Lead was chosen as the aperture medium due to its high attenuation coefficient. Experimental data were obtained from the camera with the above GZP aperture. The point spread function was determined and compared to the calculated response. Excellent agreement was obtained. The reconstruction process involves simulating, by computer, planar-wave illumination of a scaled transparency of the image and recording the intensity pattern at the focal plane.
20 Dec 1990-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: Gabor zone-plate (GZP) apertures have been developed for use in EG&G EM's mercuric iodide (HgI2) gamma-ray camera as mentioned in this paper.
Abstract: Gabor zone-plate (GZP) apertures have been developed for use in EG&G EM's mercuric iodide (HgI2) gamma-ray camera. The purpose of such an aperture is to increase efficiency, while maintaining good resolution. The GZP is similar to the Fresnel zone plate (FZP) but it has continuous transitions between opaque and transparent regions. Because there are no sharp transitions in the transmission, the inherent interference noise in GZP imaging is lower than that in FZP imaging. GZP parameters were chosen by considering the effects of constraints such as detector pixel size, number of pixels, minimum field of view required, maximum angle of incidence tolerated, and the Nyquist criterion for the minimum sampling rate. As a result an aperture was designed and fabricated with eight zones and a diameter of 3 cm. Lead was chosen as the aperture medium due to its high attenuation coefficient. Experimental data were obtained from the camera with the above GZP aperture. The point spread function was determined and compared to the calculated response. Excellent agreement was obtained. The reconstruction process involves simulating, by computer, planar-wave illumination of a scaled transparency of the image and recording the intensity pattern at the focal plane.
TL;DR: The physical theory, of testing optics by the Ronchi sine grating interferometer is developed and the value of the spherical aberration associated with the third-order wavefront of the zone plate under test can be determined.
Abstract: The physical theory, of testing optics by the Ronchi sine grating interferometer is developed. In the experiment a sine grating splits the third-order wavefront of the zone plate under test into three displaced wavefronts, which then interfere with one another to form interference fringes. The intensity distribution of the interference pattern can be recorded for various positions of the sine grating. By subtracting the contribution of the inherent diffractive aberration of the sine grating, the value of the spherical aberration associated with the third-order wavefront of the zone plate under test can be determined. Theory and experiment are compared.
TL;DR: A simple theory of positioning using two coherent wavefronts is proposed and a few examples, already described in the literature as well as new ones, are presented as an illustration of the theory.
Abstract: The use of zone plates in optical alignment and displacement measurement is discussed. A simple theory of positioning using two coherent wavefronts is proposed. A few examples, already described in the literature as well as new ones, are presented as an illustration of the theory. The application of the specific case of the offaxis cylindrical zone plate (so-called parabolic zone plate) and off-axis conical zone plate for sensing the motion along a straight line parallel and inclined to the hologram plane is established. There are also adduced results of simple experiments supporting the analysis.
TL;DR: In this article, a phase-reversing Fresnel zone-plate (FZP) made of metal foil to microwave antennas was analyzed using the Kirchhoff-Huygens diffraction integral, and it was shown that a sharp circularly polarized beam with a half-power beamwidth of 9 deg is obtained when the outermost radius of the FZP is about 4 wavelengths.
Abstract: This paper discusses applications of the Fresnel zone-plate (FZP) made of metal foil to microwave antennas. First, the focusing effect and the far-field pattern for the FZP are analyzed using the Kirchhoff-Huygens diffraction integral. It is found that a phase-reversing FZP, in which the phase of either its even or odd zones is inverted, has a sharp beam with a low sidelobe level.
On the basis of the fundamental analysis, an antenna syctem in which a reflector-type FZP fed by a backfire helix is proposed as an application of the phase-reversing FZP. It is pointed out that a sharp circularly polarized beam with a half-power beam-width of 9 deg is obtained when the outermost radius of the FZP is about 4 wavelengths.
Next, the gain variation by the change in the ground plate radius of the axial-model helical antenna is explained by the Fresnel zone principle, and an axial-mode helical antenna with a zoned ground plate is proposed. An absolute gain of 12.2 dB is realized by a two-turn short helix with a zoned ground plate.
TL;DR: In this article, the angle-resolved scattering from several phase Fresnel zone plates (lenses) and Dammann gratings (beam splitters) was calculated by random perturbations of the surface-relief pattern.
Abstract: We have calculated the angle-resolved scattering from several phase only Fresnel zone plates (lenses) and Dammann gratings (beam splitters). We simulate manufacturing errors by random perturbations of the surface-relief pattern, and calculate the irradiance in the far-field by evaluating the Fresnel diffraction integral. Scattering from perturbations of the etch depth is found to be proportional to the square of the ratio of the perturbation divided by the wavelength. Random perturbations of the pattern edges in Fresnel zone plates causes more scattering with shorter wavelengths than with longer wavelengths, but in Dammann gratings this scattering is independent of wavelength. Scattering increases for either small apertures or small f-numbers; but does not depend on either the number of levels in a Fresnel zone plate, the pattern in a Dammann grating, or the form of the probability distribution function.
04 Dec 1990
TL;DR: In this article, the design, construction, and performance of an experimental broadband polyvinylidene fluoride (PVDF) Fresnel lens are discussed, and the potential application of a lens of this type in medical imaging is addressed.
Abstract: The design, construction, and performance of an experimental broadband polyvinylidene fluoride (PVDF) Fresnel lens are discussed. The potential application of a lens of this type in medical imaging, particularly for shallow features such as the carotid artery, is addressed. A model for the lens is proposed. A general pressure transfer function which is used to obtain theoretical on-axis and focal plane beam profiles is derived. The construction of a seven-zone, 15-mm PVDF zone plate is discussed, and experimental self-convolution results are presented. >