Showing papers on "Zone plate published in 1987"

Millimeter-Wave Characteristics of Phase-Correcting Fresnel Zone Plates

Abstract: A focusing element called the phase-correcting Fresnel zone plate is described, and its characteristics are given when used in the millimeter-wave region for imaging or frequency filtering in place of a lens. Two versions are discussed, one where alternate concentric annular grooves are cut in a single piece of low-loss dielectric, and a second where two (or more) dielectrics are used in alternate concentric rings. For the latter case, an appropriate choice of parameters produces a design of constant thickness (i.e., a flat disk), named the "planar lens." Design formulas and curves, as well as measured results, are given for both types, and an analytical description is derived for the far-field patterns. Compared with lenses, zone plates are simpler to construct and have lower absorption loss, thickness, and weight.

High-resolution Fresnel zone plates for x-ray applications by spatial-frequency multiplication

Abstract: We propose a scheme for deriving a high-resolution zone plate from a coarser one by interfering the light from two positive-order foci. We give a theorteical analysis of the process, which we call spatial-frequency multiplication. The analysis requires calculation of diffracted intensities far off axis, and we derive validity conditions for the application of approximate methods to this calculation. Specifically, we show that the Fresnel approximation is useful in many cases, whereas the method of stationary phase is valid for all cases of technological interest. Some practically useful parameter choices are considered for implementation of the zone-plate fabrication method. An example calculation suggests that a zone plate with smallest zone spacing of 13.8 nm may be possible.

X-ray reflective mask and system for image formation with use of the same

Abstract: X-ray lithography which has been applied, for instance, to reproduction of a pattern for integrated electronic circuit wherein the proximity method is prevailed with use of a transmissive patterned mask But this conventional method is defective for instance, in difficulty of dimensional reduction from an original pattern In contrast, the disclosed invention overcomes such defect by introducing an X-ray reflective mask element, instead of conventional type of transmission The reflective mask element is comprised of a crystalline substrate to reflect incident X-ray according to the Bragg's diffraction rule, which was worked out of a crystalline body having outwardly curved lattice surfaces, wherein the substrate face is formed to have an inclination against the lattice surfaces so that reflection at center of the substrate face will converge to a point on normal line assumed at the same center Another aspect of the disclosure herein is directed to a system for X-ray projection and image formation with use of said mask element, additionally comprising an X-ray source, a Fresnel zone plate

Generation of a single-lobe radiation pattern from a phased-array laser using a near-contact variable phase-shift zone plate

Abstract: A very simple and practical technique to generate a stable, narrow-angle single-lobe far-field radiation pattern from an ordinary twin-lobe phase-locked laser diode array is demonstrated. A variable phase-shift zone plate mounted close to the laser output facet is used to readjust the phase distribution of the array into an all-in-phase distribution producing the desired single narrow-lobe far-field pattern.

Quantitative imaging and microanalysis with a scanning soft X-ray microscope

Abstract: A scanning soft X-ray microscope has been developed that uses synchrotron radiation focused by a Fresnel zone plate to form a submicron beamspot on the specimen. Transmitted X-rays are detected and used to form a quantitative map of specimen absorptivity. Applications of the instrument to the imaging of whole wet cells and to the mapping of calcium in sections of bone are presented, with a resolution of 300 nm and an elemental sensitivity of 2 mu g cm-2.

Equilateral hyperbolic zone plates: their use in the alignment of a Mach-Zehnder interferometer

Abstract: An equilateral hyperbolic zone plate has been recorded by coherent superimposition of two cylindrical waves with coplanar foci. This zone plate has been used to align quickly and easily a Mach-Zehnder interferometer.

Investigation on optical matching of a soft X-ray undulator with some condenser Fresnel zone plates

Abstract: Optical matching characteristics of undulator radiation with some condenser zone plates were investigated in the soft X-ray region using an undulator beamline at the Photon Factory. It was confirmed that the monochromatization of the first harmonic of the undulator radiation was made by meams of a system consisting of a zone plate and a pinhole, but the transmission efficiency and the wavelength resolution of the system were lower than expected. Analyses show that the results can be attributed to the finite source size of the undulator radiation which is determined by the present storage ring operation and also to the longer focal lengths of the zone plates used. It was also found that the virtual source point of the undulator radiation should be assigned at the position of the undulator itself.

Fresnel diffraction by a circular aperture

Abstract: The author presents a method of calculating the radial intensity distribution of the Fresnel diffraction pattern of a circular aperture. The method uses the concept of counting whole or partial Fresnel zones and has an accuracy of about five per cent of the maximum intensity, although it can be refined to improve this figure somewhat. The method can also be applied to calculations of the Fresnel diffraction patterns of more complicated apertures.

Holographically Produced Parabolic Zone Plates

Abstract: Parabolic zone plates are constructed by the off-axis holographic method by recording on a photosensitive material the pattern produced by coherent superposition of two waves, one plane and the other cylindrical. Fraunhofer and Fresnel diffraction patterns are evaluated by the reconstruction process of parabolic zone plates to study their performance. Experimental results are presented.

Diffraction of Gaussian beams through different types of zone plates

Abstract: Serving as lens substitutes in the UV region, zone plates are attractive as transforming devices of the beams generated by lasers operating in that region. The expression for the transmission function of all types of zone plates (circular, elliptical, hyperbolic, linear) is determined, which permits to establish a theory of Fresnel diffraction of a Gaussian beam through a general zone plate. It is shown that, when the Gaussian beam is off-axis, the zone plate acts as a multiple beam splitter, producing a fanlike group of astigmatic elliptical Gaussian beams. These beams belong to different orders and their waists are located in planes whose displacements from the corresponding manyfold focal planes for the zone plate satisfy Self's relations for the Gaussian beam transformation by a lens. To illustrate the general theory, the study of an off-axis Gaussian beam on a general zone plate is given.

Quantization effects on the fields of electron-beam generated cylindrical zone plates.

Abstract: Recently, various high-precision digital graphic systems have been used to generate patterns for diffractive and computer generated holographic optical elements. These plotting systems with submicron accuracy have a common drawback, namely, the patterns drawn have to be quantized. In this paper, the effects of pattern quantization on the optical beams are studied. Specifically, the fields of perfect cylindrical zone plates and cylindrical zone plates with quantized stripes are compared with that of conventional refractive cylindrical lenses. In particular, the effects of quantization on the width of and power in the main lobe and the level of the sidelobes are studied. The results are cast in terms of normalized parameters and are applicable in general.

High speed zone plate alignment systems

Abstract: Zone plate alignment is routinely used in x‐ray exposure tools and in optical step and repeat cameras. As with any alignment technique, the time taken to acquire and analyze the alignment data must be added to the wafer exposure time. This paper describes a technique in which the data may be acquired very rapidly by scanning the focused zone plate spot over a system of slits. For step and repeat systems this may be done during the time the table is moving to the next site. We have obtained alignments of 0.1 μ (3σ) by scanning across slits. In addition, we have developed analog circuitry which extracts the centroid of the focused spot in a few microseconds. With this circuit, the precision of spot location is <1% of the spot width. The combination of these two techniques should minimize the overhead in wafer exposure arising from the alignment process.

Irregular transmission type fresnel zone plate

Abstract: PURPOSE:To obtain a Fresnel zone plate which has high resolution by selecting the widths of a transmissive area and a cutoff area so that proximity effect does not appear CONSTITUTION:A transmissive thin film 9 of SiNx is formed on an annular silicon wafer 8 and cutoff area 10 are formed of Au on the layer 9 concentrically and annularly Therefore, a transmissive area 11 is formed between the cutoff areas 10 and the layers 8 and 9 serve as supporting layers for the cutoff areas 10 made of Au The cutoff areas 10 and transmissive are 11 for the 1st cutoff zone Z1 at the center part, a transmission zone Z2, cutoff zones Z3, 4, and 5, transmission zone Z6, cutoff zone Z7, 8, and 9, and a transmission zone Z1 successively from the 1st cutoff zone at the center part

Optical sensor having stationary co-terminus ends of the input and output optical fibres

Abstract: A spectral filtering optical sensor comprises a stationary zone plate and stationary co-terminous ends of input and output fibres with the interposition in the optical path between the zone plate and the optical fibre ends of a variable optical focussing arrangement the focussing characteristics of which change with changes in magnitude of the particular parameter being sensed and thereby vary the effective optical path length between the zone plate and the optical fibre ends and the wavelength of light impinging on the end of the output fibre

Millimeter Wave Characteristics of Fresnel Zone Plates

Abstract: Characteristics are given for Fresnel zone plates used as quasi-optical focusing or frequency-filtering elements at frequencies from 35 to 210 GHz. An analytical description of the far-field pattern has been developed. Design data, measured results are given for a new type of flat lens.

The Zone Plate: A New Lease Of Life?

Abstract: It has long been known that zone plates can be used to form an image but they have been little used in practice because a lens generally performs better. Since a zone plate distributes light into several diffracted orders the efficiency is low and since the focal length is inversely proportional to wave-length the chromatic aberration is enormous. However, despite these drawbacks the zone plate does possess some attractive features: it is a thin structure so it produces no distortion in the image; it is less bulky and lighter than a lens (which would be particularly important for many infrared applications), and can be replicated so it is amenable to inexpensive mass production. We suggest that there are 3 main reasons why zone plates might become more widely used: a change of requirements; improvements in manufacturing technology; and new applications which take advantage of the unique features of the zone plates.

Scanning transmission x-ray microscopy of unaltered biological specimens

Abstract: A scanning transmission x-ray microscope at the National Synchrotron Light Source was used to image fresh, wet biological specimens at 32 Angstroms, with resolution better than 750 Angstroms. A gold Fresnel zone plate (outer zone width 500 Angstroms) was used to focus the undulator radiation, and the sample was scanned through the spot. Absorption data was recorded digitally as a gridded array. The major accomplishment of the experiment was the demonstration of the ability to image biological samples in their natural state with high resolution and natural elemental contrast mechanisms. This was achieved through the design of a sample holder that maintains an aqueous environment for the sample, yet is transparent to x-rays at 32 Angstroms. The specimens used were isolated zymogen granules (approximately 1 micron diameter) from the pancreatic acinar cells of rats. The absorption data were correlated to protein concentration, and estimates of the protein concentrations within the granules were obtained. The data also yields some information about the spatial organization of the protein in the granules, and our data is compared to models for the internal structure. The success of this experiment points toward future opportunities for dynamical studies on living systems. 6 refs., 28 figs., 2more » tabs.« less

Measuring method of distance between two planes

Abstract: PURPOSE:To measure the distance between two planes with one Fresnel zone plate (FZP), whose focal-point accuracy is gentle, by inputting monochromatic light, whose wavelength is changed, into the FZP that is formed on a facing first plane, and observing the converged state of the light on a second plane. CONSTITUTION:Monochromatic light, whose wavelength is changed, is inputted to a photo-mask 1 and the like, in which an FZP is formed at a facing first plane, through a condenser lens 6, a beam splitter 7, an objective lens 8 and the like. The light is reflected by a wafer 2 and the like, which are a facing second plane. The light is observed by an eye piece 9 through the lens 8 and the splitter 7. When 1/2 of focal distance of the FZP, which is changed based on the wavelength, becomes the distance between the facing planes of the mask 1 and the wafer 2, a bright, clear optical point is obtained. The wavelength lambda of the monochromatic light is determined. The focal distance fA is determined by an expression fA=R 1/lambda, where R1 is the radius of the first ring from the center of the concentric circles of the FZP. Thus the distance between the facing planes is measured. In this way, the distance between the two planes can be measured by one FZP, in which the focal point accuracy is gentle and which can be formed readily, without using many FZPs having high focal point accuracy.

X-ray microscope

Abstract: PURPOSE:To make it possible to obtain the sharp image of a specimen, by taking out X-ray having a single wavelength to converge the same to a specimen and performing scanning with the converged spot by the deflection of electron beam. CONSTITUTION:The electron beam 37 emitted by an electronic gun 22 is converged by a converging lens 23 and deflected by a deflector 24 to irradiate a target 25. The target 25 emits X-ray beam 39 which is, in turn, transmitted through a wavelength filter 27 to be converged to a Fresnel zone plate 28 and the obtained converged spot of X-ray beam 40 with a single wavelength is projected to the specimen 36 positioned in front of an X-ray detector 29. A computer 32 projects the detection image of the detector 29 to a specimen 36 and alters the electron beam deflection condition of a deflector 24 to a predetermined one. An X-ray detector 30 detects the X-rays or secondary electron from the surface of the specimen and the detectors 29, 30 are changed over by a switch 35 to make it possible to simultaneously know the external and internal structures of the specimen.

Projecting and image-forming device for soft x-rays

Abstract: PURPOSE:To perform a reduced projecting and exposing operations using soft X-rays by a method wherein a pattern for projection is arranged between a Fresnel zone plate and a concave reflection mirror. CONSTITUTION:A concave reflection mirror 2, whereon C and W are alternately sputtered, is arranged on a mirror-faced substrate in such a manner that the image on the X-ray radiating region of an X-ray source 1 is formed on the surface of a Fresnel zone plate 4, and a mask pattern 3 for projection is set between the reflection mirror 2 and the Fresnel zone plate 4. The wavelength (lambda) of soft X-rays, the number F of the Fresnel lens plate, and the resolving width W are in the relation of W=1.22XFXlambda. According to this constitution, the number F is 500 times of the visual light of 400nm for the same width of resolution in the case of the soft X-ray of 8Angstrom , and a Fresnel plate of a very small diameter can be used. Also, even when the degree of resolution is set at 1/10, the number F may be 50 times as layer as the visible light, and a pattern having a high degree of resolution can be projected.

Zone Plate Replication by Contact X-ray Lithography, and Its Application to Scanning X-ray Microscopy

Abstract: The resolution obtainable with an x-ray microscope which uses a Fresnel zone plate as the focusing element is primarily dependent on the width of the finest ring of the zone plate and the accuracy of the zone plate pattern (Simpson, 1984). High accuracy zone plates with outermost zone widths of only a few hundred angstroms have been made by carbon contamination e-beam lithography at Kings College London (Buckley et al., 1985). Whilst these zone plates have the finest zone widths yet produced, the fabrication of one zone plate takes ten hours and the carbon material from which the absorbing zones are formed is semitransparent to soft x-rays. This lack of opacity results in a reduction of focusing efficiency of about a factor of ten compared to the theoretical figure. The reduced efficiency increases the length of time required to form an image in a scanning x-ray microscope (Kenney et al., this volume). The time taken to form an image in an x-ray microscope should be as short as possible to minimize specimen deterioration and maximize throughput. For this reason, the replication of carbon zone plates in a higher contrast material, to improve efficiency and minimize imaging times, is highly desirable.

Systematic design method for holographic zone plates with aberration corrections.

Abstract: Holographiczone plates have been reviewed and systematically summarized. For the generalized holographic zone plates proposed to correct aberrations in holographic laser scanners, the concept of origin, wavelength and distortion properties, and holographic optical product operation to generate the hologram are discussed. An off-axis aberration correction method for the generalized holographic zone plate is proposed and experimentally demonstrated. Distortion and wavelength properties for extended form holographic zone plates are discussed. The general form for a holographic zone plate, encompassing all kinds of holographic zone plate, is derived.

Apparatus for measuring shape of convex nonspherical surface

Abstract: PURPOSE:To attain to enhance the measuring accuracy of the shape of a convex nonspherical surface to be measured, by using only one half mirror without using other mirror system at all and further using a reflecting type zone plate. CONSTITUTION:The laser beam emitted from a laser beam source 2 is converted to a plane wave by a collimator mirror 3 and divided into reflected beam and transmitted beam by a half mirror 3. The reflected beam passes through a convex lens 4 to reach the observing surface 9 of an interference fringe by an image forming lens 8 through the half mirror 3. The beam passing through the half mirror 3 to reach the convex lens 5 is diffracted by a reflecting type zone plate 7 and again passes through the convex lens 5 to be reflected by the half mirror 3 while the reflected beam reaches the observing surface of the interference fringe through the image forming lens 8. Herein, the convex lenses 4, 5 have the perfectly same shape and the distances thereof from the half mirror 3 are equal to each other and the reflecting type zone plate 7 is formed so that the diffracted beam of said zone plate 7 becomes equal to the reflected beam of a convex nonspherical surface 6 and, by this constitution, the interference fringe corresponding to the shift part from the original shape of the convex nonspherical surface 6 can be observed on the interference fringe observing surface 9.

Fresnel zone plate for soft x-ray

Abstract: PURPOSE:To enable a further strong image formation than that gotten by usage of a gold by using a nickel and the like other than gold as a material of a shielding part located side by side to a cocentric rings which constitutes a Fresnel zone plate Fzp. CONSTITUTION:Hatched parts in the figure show ring bands made of an X-ray absorber. An incident X-ray which is regarded as a beam parallel along to an positive direction of an Z axis, is focused to a focusing point F by a Fzp. Assuming that a focusing distance is f, a thickness of the X-ray absorber is t and a refraction index of the X-ray absorber at a wave length lambda0 in use, is n=1-delta+ik, a transmissivity t(r) of the Fzp at an arbitrary distance r from a center can be expressed as the equation showed in the figure. The first term of the right side of the equation is the 0 order diffraction which transmits as it is without being affected by any diffraction, and the second term shows the first stage to (2n-1) order diffraction beams according to a value of m. If thicknesses are same, k becomes small, and for a material having larger delta, a greater phase effect can be expected and therefore, when a Fzp having enough thickness are not available by a limitation derived from a fine processing, a Fzp close to a phase-typed one can be manufactured by using a nickel and the like, for example, other than a gold, as an X-ray absorber.

Two–dimensional image–reconstruction method from holograms sampled by fresnel zone plates

Abstract: The hologram of a single-point object is called a Fresnel zone plate (FZP), and the hologram of a general object is represented as a superposition of FZP's. Since a point image can be reconstructed from the FZP at a reasonable location, there can be considered an image reconstruction method based on FZP. This paper proposes the FZP sampled hologram and the corresponding two-dimensional image reconstruction method. The FZP sampled hologram is sampled with small interval at the central part and large interval at the periphery. By multiplying the phase function with the one-dimensional hologram and performing the Fourier transform, the two-dimensional image distribution can be determined for the azimuth and range. By analyzing the point-image distribution, it is seen that the azimuth resolution of 6 mrad is obtained for the millimeter wave frequency of 35 GHz and the hologram length of 25 cm. It is seen also from the distribution that there exist side peaks of −4.8 dB at an azimuth angle of ± 11 mrad apart from the peak. An experiment was made for the millimeter-wave holography with a simple object, and a satisfactory agreement with the theory was observed.