Showing papers on "Zone plate published in 1974"
TL;DR: In this article, phase reversal zone plates are designed for regions of the electromagnetic spectrum where the index of refraction is complex, with a real part close to 1.0, and materials with suitable optical and mechanical properties exist throughout most of the 1-800-A wavelength range for their construction.
Abstract: Phase-reversal zone plates can be designed even for regions of the electromagnetic spectrum where the index of refraction is complex, with a real part close to 1.0. These devices are superior to Fresnel zone plates both in their light collection, and in their signal-to-noise characteristics. Materials with suitable optical and mechanical properties exist throughout most of the 1–800-A wavelength range for their construction. Imperfections in fabrication, such as incorrect plate thickness, sloping zone edges, or an error in the width of alternate zones result in only moderate deterioration in optical performance.
403 citations
TL;DR: A developed form of the Fresnel zone-plate interferometer is described, associated with the real and virtual first order foci of a zone plate, and its properties are discussed.
Abstract: A developed form of the Fresnel zone-plate interferometer is described. Three basic configurations are distinguished, associated with the real and virtual first order foci of a zone plate. Related versions and higher order variants are also educed. Compensated phase zone plates used in this application are found to produce uniform amplitude wavefronts. The properties of the interferometer in this form are discussed and an example given of its high-quality performance.
56 citations
TL;DR: Experimental focal plane intensity distributions are presented for a 10-zone acoustic zone plate operating at approximately 10 MHz in this article, where the results are related to the spatial frequency response of the transducer.
Abstract: Experimental focal plane intensity distributions are presented for a 10‐zone acoustic zone plate operating at approximately 10 MHz. The results are related to the spatial frequency response of the transducer. Some initial imaging experiments with this transducer are described along with preliminary results for an acoustic phase plate.
41 citations
TL;DR: It is shown that the largest SNR advantage occurs for a point source, while for very large, uniform sources there may be a slight net disadvantage to using a zone plate, and that optical processing does not give the highest possible SNR.
Abstract: A Fresnel zone plate, used as a coded aperture, offers a great advantage in geometric collection efficiency over a conventional pinhole or collimator. We present a detailed analysis of the signal-to-noise ratio (SNR) of a quantum-limited zone plate camera. The magnitude and spatial distribution of the noise field and its dependence on the source distribution and the characteristics of the optical processing system are derived. It is shown that the largest SNR advantage occurs for a point source, while for very large, uniform sources there may be a slight net disadvantage to using a zone plate. It is also shown that optical processing does not give the highest possible SNR.
40 citations
01 Jan 1974
TL;DR: The main deficiency of B-scan is the low lateral resolution, which has its origin in the large diameter of the ultrasound beam as discussed by the authors, which is the main reason for its poor performance.
Abstract: B-scan displays a picture of a cross-section through the body and is widely used in ultrasonic diagnosis. The main deficiency of B-scan is the low lateral resolution, which has its origin in the large diameter of the ultrasound beam.
39 citations
TL;DR: Experiments performed with a stable single-mode Nd(3+)-YAG laser demonstrate that the MZP can be important tool for laser machining purposes and a simple method of recording wavelength-shift corrected in-line holograms is described.
Abstract: Machining of small holes with arbitrary contours can be performed by focusing a laser beam with a modulated zone plate (MZP). MZP's use the structure of the Fresnel zone plate as the carrier of a modulation function, which contains complete information about the contour to be machined. Spherically corrected MZP's produce aberration-free images within a field angle of 10(-3) rad. It is shown that the background noise due to higher diffraction orders is unimportant under typical machining conditions. A manufacturing procedure for high resolution MZP's with up to 2500 zones etched in chromium or quartz layers deposited on glass substrates is discussed. As in-line holograms have properties similar to MZP's, a simple method of recording wavelength-shift corrected in-line holograms is described. Experiments performed with a stable single-mode Nd(3+)-YAG laser demonstrate that the MZP can be important tool for laser machining purposes.
23 citations
TL;DR: In this article, the authors discuss a variety of closely related coded apertures, including an annulus, an inverted zone plate, a spiral zone plate and the Girard grill.
Abstract: Mertz and Young introduced the idea of using a Fresnel zone plate as a shadow-casting reticle, or coded aperture, in X-ray astronomy More recently, considerable progress has been made toward using the zone-plate aperture for gamma-ray imaging in nuclear medicine The most successful configuration has used an off-axis section of a zone plate in conjunction with a halftone screen In this paper, we discuss a variety of closely related coded apertures, including an annulus, an inverted zone plate, a spiral zone plate, and the Girard grill In most cases, the technique of grid-coded subtraction is used to suppress the zero-order (DC) background light usually associated with zone-plate imaging The first application of this technique, reported by Stoner et al, used a sequence of two to four on-axis zone plates In the present paper it is shown that the method can be extended to other apertures and is also very useful in synthesizing the spatial filters for optical decoding
22 citations
TL;DR: In this paper, the use of the multiwire proportional chamber in a Fresnel zone plate coded aperture gamma-ray imaging system is described, where image reconstruction is by computer using the fast Fourier transform algorithm.
Abstract: The use of the multiwire proportional chamber in a Fresnel zone plate coded aperture gamma-ray imaging system is described. Image reconstruction is by computer using the fast Fourier transform algorithm. Criteria for design parameters of the imaging system are established. A calculation of the signal/noise ratio of images reconstructed from computer-generated on-axis zone plate holograms gives values, for larger numbers of gamma-ray events, which are somewhat smaller than theoretical values based on a shot-noise formula. The use of a positive and a negative zone plate combination is shown to eliminate the large background usually associated with on-axis zone plate imaging.
16 citations
TL;DR: A two-step autoradiographic imaging technique utilizing a coded aperture in the form of a lead on-axis Fresnel zone plate is presented, and several isotope-filled plastic phantoms were successfully imaged.
Abstract: A two-step autoradiographic imaging technique utilizing a coded aperture in the form of a lead on-axis Fresnel zone plate is presented. Several isotope-filled plastic phantoms were successfully imaged. These images contain tomographic information of very good quality. The advantages and disadvantages of the technique are discussed.
12 citations
TL;DR: In this paper, a theoretical investigation of the imaging of extended objects using a Fresnel zone plate as a coded aperture with coherent-optical image reconstruction is presented, where artifacts are introduced in the images of large objects.
Abstract: A theoretical investigation of the imaging of extended objects is presented using a Fresnel zone plate as a coded aperture with coherent-optical image reconstruction. Faithful images are obtained only for small objects; artifacts are introduced in the images of large objects. Attempts to increase image fidelity are shown to be only moderately successful.
7 citations
TL;DR: In this paper, a new holographic shear interferometer is described in which both the radial and the lateral shear can be simultaneously introduced by using an off-axis zone plate.
TL;DR: In this article, Barrett and Horrigan used a Fresnel zone plate as a coded aperture for X-ray imaging of sources which emit their own radiation rather than scattering radiation from another source.
Abstract: A MAJOR obstacle to the formation of images with scattered X rays is the lack of a suitable X-ray lens. Radiation at such short wavelengths is not appreciably refracted by matter, which means that a lens, in the optical sense of the word, cannot exist. To overcome this difficulty, a concept can be applied which has previously been used to form an image of sources which emit their own radiation rather than scattering radiation from another source. Basically, the concept consists of a two-step process in which the radiation is used to cast shadows of a coded aperture which are recorded on film. The encoded image is then decoded by one of several possible methods, depending on the type of aperture used. This technique was first proposed for use in X-ray astronomy1 and has been applied to imaging distribution of γ emitters (refs 2–5, and H. H. Barrett, and F. A. Horrigan, not yet published). We have used a Fresnel zone plate as a coded aperture. This is by no means the only possible aperture, but it does offer some advantages over other types. The advantages involve primarily the ease with which decoding can be accomplished.
TL;DR: In this article, a general mothod for the zone construction of a microwave piane zone plate antenna is presented on the basis of the Fresnel-Huygcn diffraction theory.
Abstract: A general mothod for the zone construction of a microwave piane zone plate antenna is presented on the basis of the Fresnel-Huygcn diffraction theory. It is found that the classical mode of zone plate construction, on the basis of path differences, fits in admirably in this more general framework. The method is also applicable to the case of spherical zone plates.
01 Mar 1974
TL;DR: In this article, a variety of closely related coded apertures, including an annulus, an inverted zone plate, a spiral zone plate and the Girard grill, are discussed.
Abstract: Mertz and Young introduced the idea of using a Fresnel zone plate as a shadow-casting reticle, or coded aperture, in x-ray astronomy. More recently, considerable progress has been made toward using the zone-plate aperture for gamma-ray imaging in nuclear medicine. The most successful configuration has used an off-axis section of a zone plate in conjunction with a halftone screen. In this paper, we discuss a variety of closely related coded apertures, including an annulus, an inverted zone plate, a spiral zone plate and the Girard grill. In most cases, the technique of grid-coded subtraction is used to suppress the zero-order (DC) background light usually associated with zone-plate imaging. The first application of this technique, reported by Stoner et al., used a sequence of two to four on-axis zone plates. In the present paper it is shown that the method can be extended to other apertures and is also very useful in synthesizing the spatial filters for optical decoding.
01 Sep 1974
01 May 1974
TL;DR: A coded aperture consisting of a planar array of three off-axis zone plates oriented at 120° with respect to each other has been used to image gamma-ray sources up to ten inches in diameter as mentioned in this paper.
Abstract: A coded aperture consisting of a planar array of three off-axis zone plates oriented at 120° with respect to each other has been used to image gamma-ray sources up to ten inches in diameter The zone plates do not have a common axis, and the high frequency zones of each zone plate are located in the central region The maximum radius and fringe spacing are chosen so that the spatial frequency bandpasses for the individual zone plates do not overlap, and a hexagonal array of holes is used as a sampling screen (half-tone) to shift the object spectrum into the bandpass of the three zone plates The aperture configuration permits more uniform sampling of a large object as compared with a system consisting of a single large off-axis zone plate Design parameters are discussed, particularly those related to the imaging of bar phantoms and the generation of coherent artifacts Reconstructed images of gamma-ray sources using the three zone plate system are presented© (1974) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only
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Journal Article•
Journal Article•
TL;DR: In this paper, a point source focused by a Fresnel zone plate may interfere constructively or destructively with the undiffracted background, and the point source with unusually small dark centers empirically leads to constructive interference.