Showing papers on "Zone plate published in 1973"
TL;DR: The general theory of coded-aperture imaging is presented, first for an arbitrary code and then for an on-axis zone plate, an off-axis Zone Plate, and a one-dimensional zone plate (or linear chirp).
Abstract: The use of a Fresnel zone plate as a coded aperture for imaging incoherent radiation such as gamma rays has been previously reported. The coded image is in many respects similar to a hologram and can be decoded or reconstructed with a coherent optical system. In this paper, the general theory of coded-aperture imaging is presented, first for an arbitrary code and then for an on-axis zone plate, an off-axis zone plate, and a one-dimensional zone plate (or linear chirp). With the on-axis plate, a matched imaging condition is suggested as a guide to optimizing image contrast. With the off-axis zone plate and the linear chirp, it is necessary to use a half-tone screen to spatially heterodyne the object spectrum into the passband of the aperture. In all three cases, expressions for the resolution, depth of field, field of view, and relative efficiency are derived. A simplified noise analysis is presented, and some practical system constraints are discussed.
139 citations
TL;DR: In this article, the use of a Fresnel zone plate as a spatially-coded source or aperture can avoid the trade-off between spatial resolution and radiation flux, and the system is tomographic with information about all planes contained in a single film.
Abstract: X-ray tubes and gamma ray cameras have traditionally involved trade-offs between spatial resolution and radiation flux. Recently we have shown that the use of a Fresnel zone plate as a spatially-coded source or aperture can avoid this trade-off. In radiology, this technique can eliminate the need for a rotating anode and give higher resolution, while in nuclear medicine it can be used either to decrease patient dose or exposure time, or to increase resolution and greatly simplify the apparatus. With a coded source or aperture, the image is also coded, like a hologram and can be reconstructed optically. The system is tomographic with information about all planes contained in a single film.
27 citations
TL;DR: In this article, the use of a lead Fresnel zone plate aperture in conjunction with an image intensifier camera to produce coded images of gamma sources is described, which possess properties similar to holograms.
Abstract: One of the principal concerns in nuclear medicine is imaging the spatial distribution of tracer amounts of gamma emitting radiopharmaceuticals which have been intravenously administered to patients. These images are customarily formed on a gamma ray detector by means of lead pinholes or multichannel collimators. In practice these apertures yield only 1 cm spatial resolution and geometric efficiencies of 10-4. This paper describes the use of a lead Fresnel zone plate aperture in conjunction with an image intensifier camera to produce coded images of gamma sources. These images possess properties similar to holograms. This method shows promise of a factor of 4 or 5 improvement in resolution, a factor of 10 improvement in efficiency and gives 3 dimensional information about the object.
25 citations
TL;DR: In this paper, a self-supporting Fresnel zone plate with empty transparent zones was used to focus vacuum-ultraviolet (vuv) radiation with wavelengths as short as 565 A. The zone plate was used as a simple converging lens to form an optical image of an object mesh on a sodium salicylate film, where it was photographically recorded.
Abstract: A self-supporting Fresnel zone plate with empty transparent zones has been used to focus vacuum-ultraviolet (vuv) radiation with wavelengths as short as 565 A. The radiation was produced by two broad-band sources, (i) the molecular continuum of a helium gas-discharge lamp, which extends from 600 to 1100 A with a broad peak at 810 A, and (ii) the synchrotron continuum of an electron storage ring filtered by a Sn filter, which extends from 520 to 750 A with a broad peak at 565 A. The zone plate was used as a simple converging lens to form an optical image of an object mesh on a sodium salicylate film, where it was photographically recorded. Magnifications of 20× and linear resolutions within an order of magnitude of the theoretical resolution limit of the zone plate were obtained. Applications of this device as a vuv microscope are discussed.
25 citations
01 Jan 1973
TL;DR: In this article, the use of a Fresnel zone plate as a spatially-coded source or aperture can avoid the trade-off between spatial resolution and radiation flux, and the system is tomographic with information about all planes contained in a single film.
Abstract: X-ray tubes and gamma ray cameras have traditionally involved trade-offs between spatial resolution and radiation flux. Recently we have shown that the use of a Fresnel zone plate as a spatially-coded source or aperture can avoid this trade-off. In radiology, this technique can eliminate the need for a rotating anode and give higher resolution, while in nuclear medicine it can be used either to decrease patient dose or exposure time, or to increase resolution and greatly simplify the apparatus. With a coded source or aperture, the image is also coded, like a hologram and can be reconstructed optically. The system is tomographic with information about all planes contained in a single film.
20 citations
TL;DR: In this paper, an analysis of the lens-like property of plane and spherical zone plate antennas is made, and source distance-image distance relations are derived, and expressions for the focal lengths are also obtained.
Abstract: An analysis is made of the lens-like property of plane and spherical zone plate antennas, and source distance-image distance relations are derived. Expressions for the focal lengths are also obtained. The source-distance discriminating property of the spherical zone plate antenna is studied and computations for the axial variation of intensity for the plane and the spherical zone plate antennas are mode for various situations.
17 citations
TL;DR: The point spread function of such zone plates is measured with a rotating cube scanner and found to agree closely with theory over more than one order of magnitude.
Abstract: Arrays of ~2-mm diam, f/9, diffraction-limited Fresnel zone plates are made and measured. Amplitude zone plates are fabricated by conventional photolithographic techniques, while a specially developed evaporation/etching technique is used for phase zone plates. The point spread function of such zone plates is measured with a rotating cube scanner and found to agree closely with theory over more than one order of magnitude.
16 citations
TL;DR: In this paper, a method for obtaining thin film planar optical phase elements using photolithographic and specially developed evaporation/etching techniques is described, and the fabrication of a phase Fresnel zone plate in which the outermost zone measures 4.3 microns is described.
13 citations
TL;DR: In this article, it was shown that two properly-scaled Fresnel zone plates in series constitute a useful coded aperture for imaging X-rays, gamma rays or other incoherent radiation.
12 citations
Patent•
02 Aug 1973
TL;DR: In this paper, a method of forming a Fresnel lens from a body of light-sensitive material of the type which undergoes changes in its optical path-length when exposed to light is described.
Abstract: In a method of forming a Fresnel lens from a body of light-sensitive material of the type which undergoes changes in its optical path-length when exposed to light, the step of exposing each portion of such body of light-sensitive material to light to the extent necessary to impart to the respective portion the optical path-length requisite for the corresponding portion of the Fresnel lens to be formed.
11 citations
TL;DR: In this article, it was shown that high quality images can be obtained with Mertz' original encoding method under certain well-defined conditions, under the assumption that the on-axis Fresnel zone plate apertures are fixed.
Abstract: Coded aperture imaging of X ray or y ray emitting objects using on-axis Fresnel zone plate apertures was the original method suggested by Mertz in 1961. Since then other forms of coded aperture imaging have become more popular. We show in this paper that, under certain well-defined conditions, high quality images can be obtained with Mertz' original encoding method.
TL;DR: In this paper, a number of formulae describing the characteristics of spherical and plane zone plate antennas are derived and a considerable reduction in the aperture dimension can be achieved by using a spherical zone plate antenna.
Abstract: The possibility of a microwave spherical zone plate antenna has been discussed. A number of formulae describing the characteristics of spherical and plane zone plate antennas are derived. Both the plane and spherical incident wave-fronts are used in the derivation of the formulae. Numerical results comparing the spherical and plane zone plate antennas have been given. It is found that a considerable reduction in the aperture dimension can be achieved by using a spherical zone plate antenna.
Patent•
14 May 1973TL;DR: In this paper, a nuclear imaging system for mapping the source of high energy nuclear particles from a living organ which has selectively absorbed a radioactive compound by spatially coding the energy from the source in a Fresnel pattern on a detector and decoding the detector output to produce an image of the source.
Abstract: A nuclear imaging system for mapping the source of high energy nuclear particles from a living organ which has selectively absorbed a radioactive compound by spatially coding the energy from the source in a Fresnel pattern on a detector and decoding the detector output to produce an image of the source. The coding is produced by a Fresnel zone plate interposed between the nuclear energy source and the detector whose position is adjustable with respect to the detector to focus the slices of the nuclear source on the detector. By adjusting the zone plate to a plurality of positions, data from a plurality of cross-sectional slices are produced from which a three-dimensional image of the nuclear source may be obtained.
TL;DR: In this paper, the intensity distribution in the Fresnel diffraction pattern of a slit aperture illuminated with partially coherent light is obtained, as a function of the coherence condition across the aperture, by evaluating the formula developed in a previous paper.
TL;DR: In this paper, a theoretical investigation of the spherical, the plane and the paraboloidal microwave zone plate antennas has been made on the basis of the Fresnel-Huyghen's diffraction theory.
Abstract: A theoretical investigation of the spherical, the plane and the paraboloidal microwave zone plate antennas has been made on the basis of the Fresnel-Huyghen's diffraction theory. Rigorous formulae for the field amplitude at an axial point for the three zone plates have been derived. Some approximate expressions have also been given by assuming that the obliquity factor remains almost a constant over a zone.
TL;DR: In this paper, a comparison between the image of a field ion plane and a Fresnel zone plate was made, and it was shown that the relationship between their focal lengths and the imaging parameters is more complex than previously believed.
Abstract: Comparisons previously drawn between the image of a field ion plane and a Fresnel zone plate are reexamined. It is shown that such images are more generally described as aberrated binary zone plates, and that the relationship between their focal lengths and the imaging parameters is more complex than previously believed.
TL;DR: In this paper, it was shown that small-area sources, with such a system, will always produce strong ghost images or artifacts, and it was also shown that a half-tone screen is necessary to use a Fresnel zone plate as a coded aperture to image large-area X-rays or gamma rays.
Abstract: When a Fresnel zone plate is used as a coded aperture to image large-area sources of X-rays or gamma rays, it is necessary to use a half-tone screen. It is shown here that small-area sources, with such a system, will always produce strong ghost images or artifacts.
TL;DR: Sector or angular scanning is added to the arsenal of scanning techniques useful in acoustical holography as mentioned in this paper, which produces a distortion that can be used to counteract the distortion due to wavelength disparity in the recording and reconstruction steps.
Abstract: Sector or angular scanning is added to the arsenal of scanning techniques useful in acoustical holography. This method produces a distortion that can be used to counteract the distortion due to wavelength disparity in the recording and reconstruction steps. A first-order analysis based on the zone plate, preliminary experimental results, and possible applications are presented.
TL;DR: Using a Fresnel zone plate to obtain a reference point source as well as object illumination, a hologram was produced with quasi-thermal light as mentioned in this paper, which is a scaled up simulation of a proposed experiment to produce soft X-ray holograms.
TL;DR: In this article, a simple technique is described and demonstrated as well that Fourier-transform holograms can be made with a zone plate, which can be used to make a Fourier transform hologram.