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Journal ArticleDOI

An advanced coded imaging without side lobes

01 Dec 1978-Optics Communications (North-Holland)-Vol. 27, Iss: 3, pp 339-344
TL;DR: An advanced coded imaging is proposed which makes it possible to clear away the side lobes from reconstructed images by using a pair of coherent codes.
About: This article is published in Optics Communications.The article was published on 1978-12-01. It has received 27 citations till now. The article focuses on the topics: Side lobe.
Citations
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Journal ArticleDOI
TL;DR: This process greatly simplifies previous approaches, by separating the construction of Golay arrays from the enumeration of all possible projections of these arrays to lower dimensions.

85 citations

Journal ArticleDOI
TL;DR: Methods for synthesizing sets of one-dimensional Welti codes with vanishing cross-correlation functions, and conditions upon their existence are discussed, and construction methods of sets of two and higher dimensional WeltI codes are presented.
Abstract: A Welti code is a binary sequence with an impulse-like autocorrelation function. A set of such codes may possess vanishing cross-correlation functions. The elements of Welti codes must be members of a set of at least two orthogonal vectors or subcodes. First, methods for synthesizing sets of one-dimensional Welti codes with vanishing cross-correlation functions, and conditions upon their existence are discussed. Then, construction methods of sets of two and higher dimensional Welti codes are presented. Based on these constructions, further sets of mutually orthogonal complementary codes in one or more dimensions can be derived. The use of such signals relates to various topics such as communication, radar and navigation systems, measuring and identification in one or higher dimensional systems, synchronization and spatial alignment, or coded aperture imaging.

74 citations

Journal ArticleDOI
TL;DR: This paper explains and expands previously known constructive and nonexistence results in the binary case for multi-dimensional Golay complementary array pairs.
Abstract: Constructions and nonexistence conditions for multi-dimensional Golay complementary array pairs are reviewed. A construction for a d-dimensional Golay array pair from a (d + 1)-dimensional Golay array pair is given. This is used to explain and expand previously known constructive and nonexistence results in the binary case.

63 citations


Additional excerpts

  • ...Keywords Array · Binary · Complementary · Complex-valued · Construction · Golay · Multi-dimensional · Nonexistence · Sequence AMS Classifications 05B20 · 94A05...

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Journal ArticleDOI
TL;DR: Pairs of binary odd-periodic complementary sequences are introduced, which can be constructed using q-ary m-sequences for many more lengths.
Abstract: A pair of binary sequences is called complementary if the sum of their aperiodic autocorrelation functions is zero except for zero shift Such sequences are known for relatively few lengths This correspondence therefore introduces pairs of binary odd-periodic complementary sequences, which can be constructed using q-ary m-sequences for many more lengths

43 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a survey of the state-of-the-art in the problem of finding the best sequences with small aperiodic autocorrelations relative to the sequence length.
Abstract: The extent to which a sequence of finite length differs from a shifted version of itself is measured by its aperiodic autocorrelations. Of particular interest are sequences whose entries are 1 or $$-1$$-1, called binary sequences, and sequences whose entries are complex numbers of unit magnitude, called unimodular sequences. Since the 1950s, there is sustained interest in sequences with small aperiodic autocorrelations relative to the sequence length. One of the main motivations is that a sequence with small aperiodic autocorrelations is intrinsically suited for the separation of signals from noise, and therefore has natural applications in digital communications. This survey reviews the state of knowledge concerning the two central problems in this area: How small can the aperiodic autocorrelations of a binary or a unimodular sequence collectively be and how can we efficiently find the best such sequences? Since the analysis and construction of sequences with small aperiodic autocorrelations is closely tied to the (often much easier) analysis of periodic autocorrelation properties, several fundamental results on corresponding problems in the periodic setting are also reviewed.

39 citations

References
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Journal ArticleDOI
TL;DR: In this article, the advantages and problems arising with such a camera are discussed, and expressions are derived to describe the relative efficacy of three exposure/postprocessing schemes using multiple-pinhole cameras.
Abstract: When making photographs in x rays or γ rays with a multiple‐pinhole camera, the individual images of an extended object such as the sun may be allowed to overlap; then the situation is in many ways analogous to that in a multiplexing device such as a Fourier spectroscope. Some advantages and problems arising with such use of the camera are discussed, and expressions are derived to describe the relative efficacy of three exposure/postprocessing schemes using multiple‐pinhole cameras.

69 citations

Journal ArticleDOI
Hermann Weiss1, Erhard Ing Grad Klotz1, R. Linde1, G. Rabe1, Ulf Ing Grad Tiemens1 
TL;DR: In this paper, four different versions of flash tomosynthesis are compared, and the obtainable image qualities and other practical features of these four new methods are compared in terms of image quality and image quality.
Abstract: So far, three-dimensional X-ray imaging methods like tomography, etc. require exposure times of a few seconds or more. Hence, moving objects like the pulsating heart cannot be observed. This obstacle can be overcome by using an array of synchronously flashed X-ray sources. The source array acts as the coded aperture. The X-ray photograph is decoded optically, showing arbitrary layers of the object. We present four new versions of ‘flashing tomosynthesis’, as this approach is called. The obtainable image qualities and other practical features of these four new methods will be compared.

48 citations

Journal ArticleDOI
TL;DR: A method is proposed and analyzed for gamma-ray imaging by stochastic time modulation and cross-correlation and it is seen to provide a theoretical basis for obtaining a smooth three-dimensional point response.
Abstract: The spatial distribution of a radioactive fluid can be measured indirectly by observing the emerging gamma rays. A method is proposed and analyzed for gamma-ray imaging by stochastic time modulation and cross-correlation. Theoretical comparison is made to collimation and coded aperture techniques in gamma-ray image formation. Computed results are presented that illustrate the mean response and statistical error characteristics of this technique. Monte Carlo simulations are performed as a further verification. Because it relies upon a point-by-point reconstruction, rather than upon the integral properties of any particular aperture, the time modulation approach is seen to provide a theoretical basis for obtaining a smooth three-dimensional point response.

27 citations

Journal ArticleDOI
TL;DR: Extended source Fourier transform holography for single image synthesis of multiple identical images produced by multiple pinhole camera in X ray astronomy was proposed in this paper, where a single image was synthesized from a single pinhole image.

23 citations