Showing papers on "Zone plate published in 1985"

Variable-Focus Liquid-Crystal Fresnel Lens

Abstract: Liquid-crystal lens-cells shaped like a plano-convex Fresnel lens with homogeneous alignment are prepared. Their focal length can be varied from the value fe for an extraordinary ray to nearly fo for an ordinary ray by applying an electric field across the cell. The response and recovery times within several seconds are attained in the liquid-crystal lenses. More transparent (\gtrsim80%) variable-focus liquid-crystal lenses are achieved in the double-layered structure of two identical liquid-crystal Fresnel lenses with a mutually orthogonal optic axis.

Analysis of the Lau effect and generalized grating imaging

Abstract: The images formed under incoherent illumination by two gratings in tandem are analyzed using the theory of grating imaging. The images are categorized on the basis of various integer parameters that arise in the analysis. A transfer function is introduced for describing the imaging process. The image positions are related to the foci of a Fresnel zone plate.

The Fresnel Zone-Plate Lens

Abstract: A description is given of the use of the Fresnel zone plate as a focusing or a frequency-filtering device at millimeter wavelengths. Sample design data are given, as well as references to prior results. A newer type of zone plate is discussed which employs two dielectrics of equal thickness to produce a flat zone plate.

Contamination Lithography For The Fabrication Of Zone Plate X-Ray Lenses

Abstract: A VG HB5 STEM has been modified to allow computer controlled contamination writing on thin Carbon substrates. Line widths of 20 nM and height to width aspect ratios of better than 5:1 can be drawn. This writing has been used to fabricate Fresnel zone plates. A patching process is involved with registration to an accuracy of 2.5 nM. Methods and techniques have been developed to compensate for non-linearity of the field scans together with specimen drift. Zone plates of 50 NM diameter and outer zone widths of 40 nM have been con-structed.

Fresnel lens fabrication

Abstract: A Fresnel lens is fabricated by depositing concentric layers of first and second materials in alternation on a substrate surface. The substrate and deposited layers are then drawn down to provide a predetermined Fresnel lens zone structure.

Fresnel zone transforms in spatially incoherent illumination.

Abstract: Two-dimensional sine, cosine, and Fourier transforms are obtained for objects illuminated by spatially incoherent, bandlimited light. A lensless Fresnel zone processor consisting of a double-imaging interferometer, a CCD array, and a digital computer is described and analyzed. Excellent bias removal and shot-noise level performance are obtained using a 14-bit digitizer. Experimental optical transforms are presented for an offset circular aperture and for a binary zone plate transmittance. The space–bandwidth product is derived, and excellent comparison with experiment is obtained.

Mask-to-wafer alignment utilizing zone plates

Abstract: Mask-to-wafer alignment in X-ray lithography is advantageously carried out utilizing zone plate marks formed on the mask and wafer. In practice, it has been observed that the intensity and in some cases even the location of the centroid of the light spot formed by a zone plate mask can vary during alignment as the mask-to-wafer spacing is changed. In accordance with the invention, the zone plate (18) on the mask (12) is encompassed within an illumination blocking layer (72) for preventing undesired transits and reflections of the illuminating beams.

Higher-order suppressed phase zone plates.

Abstract: A new phase zone plate with suppressed higher-order flux is proposed and optimum design calculations are made for Al. While the first-order collecting efficiency is equal to that of conventional Fresnel zone plates (∼10%), the ratio of the higher-order flux energy to the first-order energy can be suppressed to <10−3–10−6 in the 300–600-A wavelength range.

X-ray optical system

Abstract: PURPOSE:To provide an X-ray optical system device of high resolution and high magnification by providing an oblique incident reflecting type optical member for magnifying the X-ray image of a sample, and a zone plate for further magnifying an intermediate image formed by this optical member. CONSTITUTION:An X-ray microscope is provided with an X-ray magnifying optical system formed of an oblique incident reflecting mirror 4 and a zone plate 5. X-rays emitted from an X-ray source 1 is converged on a sample 3 by a lighting optical system 2, and the X-ray image of the sample 3 is magnified by the oblique incident reflecting mirror 4. An intermediate image magnified by the oblique incident reflecting mirror 4 is further magnified by the zone plate 5 and picked up by an image pickup device 6. As the lighting optical system 2, it is desirable to use the one matching the number-of-openings of the oblique incident reflecting mirror 4 of the magnifying optical system.

An interferometer with a zone plate as beam-splitter

Abstract: A Fresnel zone plate splits an incoming wavefront into three wavefronts of different focal powers and is a suitable beam-splitter in an interferometer for testing concave mirrors. The zone plate may replace the scatter plate of a scatter-plate interferometer.

Planar-Structure Focusing Lens for Acoustic Microscope

Abstract: In most of the scanning acoustic microscope (SAM), an acoustic lens with a spherical concave 1s used for focusing the sound beam on a small portion of an object to be imaged Since the acoustic microscope operates in a very high frequency range such as VHF and UHF, the tiny spherical lens requires to be fabricated with very high accuracy by a skillful technician Therefore, it is desirable that the spherical lens in the acoustic microscope could be replaced by an alternative one, of which the fabrication is much easier This paper presents a new planar-structure acoustic lens for the acoustic microscope On the radiation surface of the lens are formed a number of concentric annular grooves of uniform depth, whose width and diameter are designed according to the theory of Fresnel zone plate This planar lens can easily be fabricated using the conventional photolithographic technique because of its simple configuration with no spherical surface The lens design and the principle of operation are described, along with the experimental and theoretical evaluation of the focusing capability of a fabricated lens operating at 100 MHz

X‐ray zone plates fabricated using electron beam lithography and reactive ion etching

Abstract: A Fresnel zone plate, a focusing element that operates using diffraction, is a promising candidate for x‐ray optical elements since the index of refraction of all materials in this region is slightly less than unity. In this report, a new fabrication method for zone plates using electron beam lithography and reactive ion etching is described. By this method, it is possible to obtain a high resolution zone plate with a large aspect ratio. Focusing characteristics of fabricated zone plates are measured by synchrotron radiation. At the wavelength of 9 nm, the spot size of 2 μm is obtained at the focal point of 100 mm.

Fresnel zone plate for focusing microwave radiation for a microwave antenna

Abstract: A reflecting Fresnel zone plate is described for focusing microwave radiation for a microwave antenna. The alternating zones are constructed to be either reflective and absorbent or permeable to radiation or are both reflective, measures being provided for phase shifting of the radiation which is reflected by adjacent zones. The reflective zone plate can be produced, for example, using printed circuit board technology.

Symmetry-restricted profiles for maximizing the output diffraction efficiencies of zone plates in the soft-x-ray range

Abstract: A zone-plate transfer function of importance in practical optical systems is the output efficiency, I(1)/IOUT, where I(1) is the total power diffracted into the first order by the zone plate. We apply variational analysis to derive a special symmetry-restricted zone-plate profile that maximizes this output efficiency. Our solution, which we have named the generalized symmetry-restricted output efficiency maximizing zone plate, is demonstrably the optimum such symmetry-restricted solution for materials of arbitrary indices of refraction n^ [n^=(1-δ)+ik], where k is the absorption constant and δ is the phase-difference constant. For purely absorbing materials, i.e., for δ = 0, we show that a simple extension of our general solution in the far field leads to the well-known, but less-efficient, Gabor zone plate, which also has the desirable property of suppressing all diffracted orders higher than the first and minus first. Our theoretical solution, which is optimum in both the near and far fields, is of importance for research in the soft-x-ray range, where most materials are in fact both absorbers and phase shifters, i.e., where neither k nor δ is evanescent.

New progress in X‐ray microscopy

Abstract: SUMMARY Interest has recently revived in microscopy at X-ray wavelengths, stimulated in part by work for microelectronic lithography. The use of synchrotron radiation and other intense sources of X-rays, the development of plastic foils in place of photo-emulsions for recording and the fabrication of Fresnel zone lenses for focusing X-ray beams have all played a part. Some progress has already been made in improving the resolution and contrast of this method of microscopy, in the wavelength range 2–4 nm. The limitation imposed by radiation damage in biological specimens still has to be explored.

Manufacture and tests of objective zone plates for use in a scanning transmission X-ray microscope

Abstract: SUMMARY A method of making high resolution zone plates for use as the focusing elements in soft X-ray microscopy is briefly described. Tests carried out on these zone plates indicate a first-order diffraction efficiency of ∼0.3% rather than the calculated value of ∼0.9%. This indicates that the zones are not positioned as accurately as expected, a conclusion also drawn from tests at optical wavelengths on electron micrographs of the zone plates. Modifications to the manufacturing method to enable zone plates with improved imaging properties to be made are described.

Zone plate interferometers for verifying three coordinate measuring machines

Abstract: This thesis is concerned with the use of zone plate interferometers for the precise location of position. The thesis begins by discussing the use of the zone plate as an optical component and examines the wavefront aberrations that can occur in higher orders of diffraction. Interferometers applicable to the measurement of position are then reviewed, including interferometers that incorporate optical zone plates as beam dividers and beam combiners. A zone plate interferometer for defining and locating multiple positions in three-dimensions is reported. Here, a three-dimensional array of positions is defined by a two-dimensional array of reflective zone plates. An optical probe containing two zone plates completes the interferometer, and is used to locate the positions. The displacement sensitivity of the probe can be controlled at the optical design stage. The variation of sensitivity with wavefront geometry is explored and expressions are derived for the transverse and axial sensitivity in terms of the conjugates of the illuminating wavefronts. Various wave front configurations were experimented with and the resulting position location patterns recorded. The measured values of sensitivity to displacement are compared to theory. A version of this interferometer was designed and developed by the author, for checking the performance of three-coordinate measuring machines used in engineering metrology. The results of trials with the interferometer, comparing the performance of measuring machines in several government laboratories, are reported. The averaged repeatability of setting, on one optically defined position, was found to be 1 µm in the transverse directions and 6 µm in the axial direction. Resulting from this work, two simple devices for pointing are described. Each uses a pair of zone plates to define an optical axis. In one case, the axis is precisely located by positioning a coherent light source and observing the interference bands generated by the device. In the other, moire bands are observed in incoherent illumination.

Zone-plate Radial-shear Interferometers a Study of Possible Configurations

Abstract: Two zone plates in series can be used to set up a simple radial-shear interferometer. The possible configurations for such an interferometer are analysed and their relative advantages are discussed. Experimental results with one configuration, which appears near optimum, are presented.

The elliptical gaussian wave transformation due to diffraction by an elliptical hologram

Abstract: Realized as an interferogram of a spherical and a cylindrical wave, the elliptical hologram is treated as a plane diffracting grating which produces Fresnel diffraction of a simple astigmatic gaussian incident wave. It is shown that if the principal axes of the incident beam coincide with the principal axes of the hologram, the diffracted wave field is composed of three different astigmatic gaussian waves, with their waists situated in parallel but distinct planes. The diffraction pattern, observed on a transverse screen, is the result of the interference of the three diffracted wave components. It consists of three systems of overlapped second-order curves, whose shape depends on the distance of the observation screen from the hologram, as well as on the parameters of the incident wave beam and the hologram. The results are specialized for gratings in the form of circular and linear holograms and for the case of a stigmatic gaussian incident wave, as well as for the normal plane-wave incidence on the three mentioned types of hologram.

Pattern generator of fresnel zone plate

Abstract: PURPOSE:To form an interference pattern of a Fresnel zone plate for X-ray imaging by bisecting the luminous flux from one spot light source with a beam splitter, reflecting respectively the split beams with spherical mirrors and condensing the beams to different two points on the common optical axis of both spherical mirrors which are optically superposed. CONSTITUTION:The laser beam from a laser light source 1 is condensed to a point P to form a divergent luminous flux which is then bisected by a beam splitter 3. The luminous flux reflected by the splitter 3 is made incident to a concave spherical mirror M by which the luminous flux is reflected to condense at the point O. The luminous flux transmitted through the splitter 3 is reflected by a concave spherical mirror M' and is corrected in spherical aberration by an aberration correcting lens L. The corrected flux is reflected by the splitter 3 and is condensed at the point I. The point I is on the optical axis of the mirror M together with the point O and the recording carrier F for the interference pattern is set at the intermediate of the point O and the point I and said pattern is recorded thereto.

The phase-correcting zone-plate

Abstract: A description is given of the use of the zone plate as a focusing or a frequency-filter device at millimeter wavelengths. Sample design data are given, as well as references to prior results. A newer type of zone plate is discussed which employs two dielectrics of equal thickness to produce a flat or planar zone plate.

Fresnel zone plate

Abstract: PURPOSE:To reduce an aberration in case a titled zone plate is used by a shorter wavelength than a wavelength used for a holography by recording an interference fringe by the holography on a curve surface which is curved symmetrically in its rotation. CONSTITUTION:In case a Fresnel zone plate is made by an interference on a plane plate P of two optical waves of luminous flux W1 and W2, it is the same as what is called a hologram of a point image, and if a wavelength is the same as a wavelength of a recording light source in case of condensing a light from a point O to I, the focal position is constant with regard to any annular zone, and a point image of non-aberration is obtained in a position of I. In case the Fresnel zone plate prepared in this way is used by other wavelength than a wavelength of a recording light source, a large aberration is generated and it does not become practical, therefore, the aberration is corrected by forming a hologram of a point image on the spherical surface. That is, in case a relative relation of the recording light source is constant, the aberration can be corrected by forming the zone plate to a spherical surface, therefore, the Fresnel zone is improved remarkably by forming it on a curved surface.

Optical coupling device

Abstract: PURPOSE:To make positioning of a high accuracy unnecessary, and to manufacture the titled device easily by constituting the titled device so that a zone plate constituted of a hologram is stuck to the end face of a substrate through an intermediate substrate, this focus is positioned in an optical waveguide, and the end face of an optical fiber stands face to face with it. CONSTITUTION:An optical coupling device 1 couples an optical waveguide 2 and an optical fiber 3. This optical waveguide 2 is a three-dimensional optical waveguide made on a substrate 4, and constituted of an input part 2a and an output part 2b. Also, an input end face 2c and an output end face 2d appear on the end face. A zone plate 7 is stuck through an intermediate substrate 6 to an input side end face of the substrate 4. As for this zone plate 7, a circular hologram 8 is formed directly on the end face of a transparent intermediate substrate 7. Its center coincides roughly onto the center of the optical waveguide 2 and the focus is positioned in the optical waveguide 2. Also, a prescribed interval is held between the zone plate 7 and the substrate 4. As for the optical fiber 3, the end face is provided so as to stand face to face with the zone plate 17, and it is converged to the optical waveguide 2.

Practical Examples of Diffraction Theory

Abstract: The best way to understand the principles associated with a given discipline is through examples which apply these principles. This chapter devotes itself to illustrating methods for solving specific problems, and also serves as a collection of practical examples involving diffraction phenomena.