Showing papers on "Zone plate published in 1980"

Multifocal phase place

Abstract: A phase plate construction suitable for use in optical systems with multifocal requirements. It is designed as a phase plate in order to provide sharp and clear focii with bright images. This is accomplished by adjusting the Fresnel echelettes and the zone plate spacings, of the phase plate, such that the Fresnel lens focii coincide with particular zone plate focii.

Zone-plate X-ray microscopy.

Abstract: The scope of this article is to describe a transmission X-ray microscope, possible biological applications of soft X-ray microscopy and preliminary results.For soft X-ray microscopy of biological specimens the wavelength range of 1–10 nm is best suited. Microscopy in this wavelength range requires intense X-ray sources as well as high-resolution X-ray lenses. Intense X-radiation is provided by the synchrotron radiation of electron and positron storage rings. Suited X-ray lenses are zone plates.A theoretical treatment of the contrast mechanism and the radiation damage as well as first experiments yield the following results. Firstly, relatively thick (1–10 μm) biological specimens can be investigated. This means that unsectioned dried and even wet cells and cell organelles in a natural state can be examined. Second, it will be possible to resolve cellular aggregates in live cells with a resolution in the region of ≤10nm.

Method and apparatus for aligning mask and wafer members

Abstract: Zone plate patterns (12,20,61,62) formed on spaced-apart mask and wafer members (10,60) are utilized for alignment purposes in the fabrication of integrated circuits. By providing off-axis illumination of the patterns, a significant mask-to-wafer alignment capability is provided in an X-ray lithographic system. This capability includes being able to correct for so-called magnification errors that arise from physical distortions in the mask and/or wafer or in other components of the system. These errors are compensated for by utilizing the zone plate patterns to form alignment marks that serve as a basis for adjusting the mask-to-wafer separation.

Acousto-optic device utilizing Fresnel zone plate electrode array

Abstract: A Fresnel zone plate lens in the form of a plurality of electrodes is provided on the transducer surface of a Bragg acousto-optic device (modulator or deflector). The thickness of the electrodes decrease away from the center electrode, the spacing between electrodes also decreasing as the electrodes are spaced from the center electrode. One end of each electrode in the electrode is connected to common the other end of each electrode being connected to a voltage level in a manner such that the voltage applied to adjacent electrodes are 180° out of phase.

Imaging and focusing of neutrons by a zone plate

Abstract: The use of refractive lenses for long-wavelength neutrons,although possible1, is severely limited by the fact that the refractive index differs only very slightly from unity (forexample, n − 1 = 2.3 × 10−4for quartz at λ = 20 A). However, the fact thatonly a relatively thin layer of material is needed to produce an optical path difference of half a wavelength (for example, 2.4 µm of Cu at λ = 20 A) led us to propose2 previously that neutrons could be focused by diffraction froma phase grating of variable spacing; this is , in fact, a type of zone plate. Zone plates, first described by Soret3, have been used satisfactorily over a large part of the electromagneticspectrum4–6. We now report the successful focusing and imaging of a slow neutron beam by means of a Fresnel zone plate8.

X‐ray microscopy of biological specimens with a zone plate microscope

Abstract: X-ray microscopy, with wavelengths of a few tenths of a nanometer generated by conventional x-ray sources, has been used for several decades. Besides the technique of contact microradiography, various methods have been developed to obtain magnified images with x-rays by using grazing incidence mirror optics or projection techniques. This classical work, done mainly for biological and partly for medical and physical, (e.g., metallographic) research, has been described in many reviews.'-5 The resolution achieved was not significantly better than that of a light microscope. The reasons for this were the lack of high resolution optical elements, the great penetration of the hard x-rays used, and the weakness of the classical x-ray sources. During the last several years, the situation has changed substantially. First, synchrotron radiation sources now give a high flux in the wavelength range from 1 to 10 nm. Second, methods to make x-ray lenses for this wavelength range have developed rapidly. Finally, the technique of contact microradiography has progressed considerably through the use of high resolution photosensitive resist materials in combination with scanning electron microscopes. The wavelength range 1-10 nm is best suited for high resolution x-ray microscopy of biological specimens, mainly because of the higher total absorption cross sections, the absence of scattering, and the low photon energy in comparison to the harder x-ray photons. This latter fact has already been stressed by several and has been theoretically investigated by Sayre et al. lop '' when they compared radiation dosages in electron and soft x-ray microscopy of biological materials in a natural state. Synchrotron radiation was not used for soft x-ray microscopy before 1972, when Horowitz and Howell'' demonstrated the feasibility of scanning microscopy, though with a resolution of only 2 pm. In 1976, Niemann el aL13 made enlarged

Orbiting objective lens telescope system and method

Abstract: A large objective lens is placed in a highly eccentric orbit about the earth. The orbit and orientation of the lens are carefully chosen so that it focuses light or other radiation from a preselected astronomical object into an image which slowly moves across the surface of the earth. A row of optical sensing units is located on the surface of the earth so that the image focused by the orbiting objective lens will travel substantially perpendicularly across the row during an observation. Output data generated from the sensing units may be multiplexed and fed to a real time processor which produces display signals. Each of the sensing units provides one scan line of the image being observed. The display signals are fed to a suitable display device which produces a picture of the preselected astronomical object. The objective lens may comprise a large flexible Fresnel zone plate or a flexible convex lens carried by a bicycle wheel-type supporting structure. The lens and supporting structure may be unfolded from compact cargo configurations and rotated after being placed into orbit.

Color-corrected Fresnel lens for solar concentration.

Abstract: A new linear convex Fresnel lens with its groove side down is described. The design philosophy is similar to that of the highly concentrating two-focal Fresnel lens but includes a correction for chromatic aberration. A solar-concentration ratio as high as 80 is achieved. For wide-acceptance angles, the concentration nears the theoretical maximum.

Neutron holography using Fresnel zone plate encoding

Abstract: Zone plate shadow casting is a complementary technique to the Leith–Upatnieks modification of Gabor's interferometric method for producing holograms1,2. Suggested originally by Mertz3 in 1961 for use in X-ray astronomy, the technique has received considerable attention in nuclear medicine4 for imaging radioactive organs via emitted X-rays and γ-rays and, more recently, for examining in a tomographic sense the microscopic spatial source distributions of X rays and charged particles in laser-produced plasmas5. A series of simple experiments are described here which demonstrate that zone plate encoded neutron holography can be used to image objects. An object placed in a cold neutron beam from a research reactor scatters neutrons through a Fresnel zone plate, with alternate zones of gadolinium and aluminium, which produces a hologram of the object on an X-ray film. The image is constructed by placing the hologram, linearly reduced in size, in a converging laser beam which produces a real image of the original object. Results are presented for two objects, a pair of 0.01 m diameter rubber spheres and a 0.04 m square Maltese cross made from poly-tetrafluoroethylene (PTFE).

Modified Zone-plate Interferometer for Testing Aspheric Surfaces

Abstract: A new type of common path interferometer using a modified zone-plate developed for testing aspheric surfaces is described The modified zone-plate is made by combining two kinds of zone-plates; the semicricular part of the plate produces the spherical wave, and the remainder the desired aspheric wave These are synthesized by digital computation A method of computation for synthesizing the modified zone-plate and some experimental results of the test of parabolic mirrors are given

Measuring apparatus for fresnel lens

Abstract: PURPOSE:To achieve a simultaneous measurement of a focal distance and diffusing property in a handy and accurate manner for a Fresnel lens of a single lens reflex camera CONSTITUTION:A light from the pin hole of a chart 4 is made parallel with a collimeter lens 5 and enters a Fresnel lens 6 to be measured The parallel light flux converges on a certain point after passing the Fresnel lens 6 A pinhole plate 7 and a photo dtector 8 are moved together along the optical axis to find such a position of the photo detector 8 that an ammeter 9 rises to the highest value in the reading At this point, the distance between the Fresnel lens 6 and the photo detection surface of the pin hole plate 7 is measured to obtain the focal distance of the lens 6 When the peak of the measured value is compared with the peak value previously obtained from a sample master having a mat surface arranged to be varied in the roughness, the diffusion peroperty of the Fresnel lens can be determined as well

Imaging with microwave lens

Abstract: A microwave lens that is based on the principles of holography is described. It consists of a zone plate, and it has been shown theoretically and experimentally that it has the limit of resolution, which is predicted by the aperture and the wavelength used. Another experiment was performed to compare the limit of resolution of a one-dimensional one with that of a plane zone plate. Finally the lens was used in an experimental setup to image a flat object.

Micro‐fresnel structures for microscopy of laser generated bright x‐ray sources*

Abstract: A brief parametric survey of the x-ray characteristics of a gold micro-disk irradiated at 3 x 10/sup 14/ watt/cm/sup 2/ by a 1 nsec Nd-glass laser pulse has been provided as an example of a laser generated bright x-ray source. It was shown that a simple phenomenological model of the laser generated x-ray source as a microscopic equilibrium plasma radiating as a blackbody for a finite time determined by its hydrodynamic disassembly and radiation losses, serves to provide an adequate approximation to the x-ray characteristics of such sources. The current state of x-ray microscopy within the LLL laser fusion program was briefly reviewed. Kirpatrick--Baez grazing incidence reflection x-ray microscopes are being used to provide 3 to 5 ..mu..m resolution, broadband images (..delta..E/E approx. 0.3) over a spectral range from .6 keV to 3.5 keV. Zone Plate Coded Imaging is used to provide 5 to 10 ..mu..m resolution, broadband (..delta..E/E approx. 0.5) images over a spectral range from 3 keV to 50 keV. Efficient x-ray lensing elements with anticipated submicron resolution are being developed for narrowband (..delta..E/E approx. 10/sup -2/) imaging applications over a spectral range .1 keV to 8 keV. The x-ray lens design is that of a transmission blazedmore » Fresnel phase plate. Micro--Fresnel zone plates with 3200 A minimum linewidth have been fabricated and preliminary resolution tests begun. The first resolution test pattern, having minimum linewidth of 2.5 ..mu..m, was imaged in lambda = 8.34 A light with no difficulty. Newer test patterns with submicron minimum line are being prepared for the next stage of resolution testing. An off-axis Fresnel zone plate with 1600 A minimum linewidth is presently being fabricated for use as an imaging spectrometer in order to provide spatially separated, chromatically distinct images of characteristic line emissions from laser fusion targets.« less

Ultrasonic imaging using trapped energy mode Fresnel lens transducers

Abstract: A focusing transducer utilizing trapped energy modes can be easily fabricated by plating a number of concentric rings of electrodes on a suitable piezoelectric plate of uniform thickness. The concentric ring structure acts as a Fresnel lens and can be used to obtain excellent lateral focusing of ultrasonic waves. Several transducers operating in the 2–5 MHz range have been produced using PZT-7A as the piezoelectric material. The near field radiation pattern has been observed directly in front of the plate using the first order diffraction peak from a laser probe. It is confirmed that there is good acoustic isolation between the rings and that they radiate in the trapped energy mode. The ultrasonic radiation pattern of the Fresnel lens has been observed at various distances from the plate and compared with computed results which show excellent agreement. Furthermore, the axial diffraction pattern of the lens can be optimized by adjusting ring spacings. During the course of this study a new, previously unreported mode of energy trapping has been discovered. The explanation for this method of trapping is briefly discussed. Finally an acoustic through-transmission imaging system incorporating one focusing transducer is used for imaging of flaws in composite materials.

Fresnel zone plates for ultrasonic focussing - made with circular or elliptical grating esp. of methacrylic! polymer

Abstract: Fresnel zone plates (acoustic grating) are produced from an acoustically appropriate material, such as polymethacryl, into which a grating defined by specific equations is formed. Pref. the grating is incorporated directly into the electrode of the oscillator. It may then have a rotationally symmetrical focusing zone of concentric rings for perpendicular noise transmission or, as illustrated, an elliptical form of rings for oblique transmission. In thise case the larger axis lies in the plane of transmission. Fresnel zone plates (acoustic gratings) as above amy be used for ultrasonic focusing in various applications in non- destructive testing, medical diagnostics, etc.

Coded Aperture Imaging System For Nuclear Fuel Motion Detection

Abstract: A Coded Aperture Imaging System (CAIS) has been developed at Sandia National Laboratories to image the motion of nuclear fuel rods undergoing tests simulating accident conditions within a liquid metal fast breeder reactor. The tests require that the motion of the test fuel be monitored while it is immersed in a liquid sodium coolant precluding the use of normal optical means of imaging. However, using the fission gamma rays emitted by the fuel itself and coded aperture techniques, images with 1.5 mm radial and 5 mm axial resolution have been attained. Using an electro-optical detection system coupled to a high speed motion picture camera a time resolution of one millisecond can be achieved. This paper will discuss the application of coded aperture imaging to the problem, including the design of the one-dimensional Fresnel zone plate apertures used and the special problems arising from the reactor environment and use of high energy gamma ray photons to form the coded image. Also to be discussed will be the reconstruction techniques employed and the effect of various noise sources on system performance. Finally, some experimental results obtained using the system will be presented.

Acoustic‐zone‐plate variable‐illuminating‐angle system for acoustic microscopes

Abstract: The scanning acoustic microscope utilizes a beam of fixed angular illumination with large numerical aperture limiting the amount of information that is obtainable. It is suggested that a multizone transducer–spherical‐lens configuration can yield a more flexible acoustic illumination source. Numerical calculations indicate that it should be possible to vary the half‐angle of the illumination from about 5° to 57°, thus allowing an estimate of the specimen acoustic impedance to be made and critical angles determined experimentally. A fast, programmed microprocessor will be essential for phase‐amplitude control of individual zones and signal detection.

An x‐ray source for characteristic radiation and zone plate and grating efficiency measurements

Abstract: We built a soft x-ray tube and a device for testing all x-ray optics that we need for our imaging x-ray microscope.'*2 The tests that we had to do included: measuring the diffraction efficiency of x-ray zone plates and x-ray gratings; determining the detective quantum efficiency of some photographic films and of some detectors, such as channeltrons, channel plates, and proportional counters; measuring the reflectivity of some x-ray mirrors; and making imaging tests with zone plates. These measurements require an intense monochromatic x-ray beam that has a constant flux for the duration of the measurements. For simplicity's sake, the tests are made with carbon K, radiation (44.8 A). At this wavelength, we have the fewest problems with carbon contamination and window materials. And because we work at wavelengths longer than the carbon absorption edge, a polycarbonate film 2 pm thick, for example, still transmits 50% of the radiation:

Emission tomographic reconstruction by matrix inversion

Abstract: Emission tomographic techniques are currently being used to increase the sensitivity for detection of myocardial perfusion defects in thallium scintigrams. Many of these methods, multiple pinhole and fresnel zone plate in particular, are hindered by transfer of information from one plane to another. This work describes a desuperposition technique which accounts for the three dimensional distribution of radioactivity in the object. This technique was applied to data obtained from a non-redundant pinhole coded aperture. Initial tomographic reconstructions were created by cross-correlation.