Multiplex imaging with multiple-pinhole cameras
01 Apr 1974-Journal of Applied Physics (American Institute of Physics)-Vol. 45, Iss: 4, pp 1806-1811
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.
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TL;DR: Computer simulations show that the URA with significant shot and background noise is vastly superior to random array techniques without noise, and permits a detector which is smaller than its random array counterpart.
Abstract: A system utilizing uniformly redundant arrays to image non-focusable radiation. The uniformly redundant array is used in conjunction with a balanced correlation technique to provide a system with no artifacts such that virtually limitless signal-to-noise ratio is obtained with high transmission characteristics. Additionally, the array is mosaicked to reduce required detector size over conventional array detectors.
866 citations
TL;DR: Coded aperture imaging in high energy astronomy represents an important technical advance in instrumentation over the full energy range from X-to γ-rays and is playing a unique role in those spectral ranges where other techniques become ineffective or impracticable due to limitations connected to the physics of interactions of photons with matter.
Abstract: Coded aperture imaging in high energy astronomy represents an important technical advance in instrumentation over the full energy range from X- to γ-rays and is playing a unique role in those spectral ranges where other techniques become ineffective or impracticable due to limitations connected to the physics of interactions of photons with matter. The theory underlying this method of indirect imaging is of strong relevance both in design optimization of new instruments and in the data analysis process. The coded aperture imaging method is herein reviewed with emphasis on topics of mainly practical interest along with a description of already developed and forthcoming implementations.
409 citations
TL;DR: A general expression for the signal-to-noise ratio (SNR) has been developed for the URA as a function of the type of object being imaged and the design parameters of the aperture.
Abstract: Uniformly redundant arrays (URA) have autocorrelation functions with perfectly flat sidelobes. The URA combines the high-transmission characteristics of the random array with the flat sidelobe advantage of the nonredundant pinhole arrays. A general expression for the signal-to-noise ratio (SNR) has been developed for the URA as a function of the type of object being imaged and the design parameters of the aperture. The SNR expression is used to obtain an expression for the optimum aperture transmission. Currently, the only 2-D URAs known have a transmission of (1/2). This, however, is not a severe limitation because the use of the nonoptimum transmission of (1/2) never causes a reduction in the SNR of more than 30%. The predicted performance of the URA system is compared to the image obtainable from a single pinhole camera. Because the reconstructed image of the URA contains virtually uniform noise regardless of the original object's structure, the improvement over the single pinhole camera is much larger for the bright points than it is for the low intensity points. For a detector with high background noise, the URA will always give a much better image than the single pinhole camera regardless of the structure of the object. In the case of a detector with low background noise, the improvement of the URA relative to the single pinhole camera will have a lower limit of ~(2f)(-(1/2)), where f is the fraction of the field of view that is uniformly filled by the object.
217 citations
TL;DR: Considering the Hough transformation as a linear imaging process recasts certain well-known problems, provides a useful vocab-ulary, and possibly indicates a source of applicable literature on the behavior of the H Dough transformation in various forms of noise.
Abstract: Considering the Hough transformation as a linear imaging process recasts certain well-known problems, provides a useful vocab-ulary, and possibly indicates a source of applicable literature on the behavior of the Hough transformation in various forms of noise. A consideration of the analytic form of peaks in parameter space sets the stage for the idea of using complementary (negative) votes to cancel off-peak positive votes in parameter space, thus sharpening peaks and reducing bias.
168 citations
Cites background or methods from "Multiplex imaging with multiple-pin..."
...The view of HT presented in this section simply recasts certain well-known problems, provides a small but useful vocabulary, and possibly indicates a source of applicable literature on the behavior of HT in various forms of noise [1], [5]....
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...Two-dimensional complementary codes for imaging applications were developed in [5], and are the intellectual ancestors of CHough feature psf's....
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...sort of formulation is in the tradition of signal detection and certain sorts of coding theory [1] -[5]....
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Patent•
23 May 2006TL;DR: In this article, the use of coded aperture imaging for imaging through a curved optical element is described as the image decoding can automatically remove any aberrations introduced by the curved element.
Abstract: This invention relates to coded aperture imaging apparatus and methods. In one aspect a coded aperture imager has at least one detector array and a reconfigurable coded aperture mask means. A reconfigurable coded aperture mask means can display various coded aperture masks to provide imaging across different fields of view and/or with different resolution without requiring any moving parts or bulky optical components. More than one detector array can be used to provide large area imaging without requiring seamless tiling and this represents another aspect of the invention. The present invention also relates to the use of coded aperture imaging in the visible, ultraviolet or infrared wavebands. The use of coded aperture imaging for imaging through a curved optical element is taught as the image decoding can automatically remove any aberrations introduced by the curved element.
84 citations
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TL;DR: In this paper, a pinhole camera with resolutions better than 10−3 rad is presented. But the apertures are very small, not greater than about 10−4 cm2.
Abstract: In comparison with all other branches of astronomy, X-ray astronomy suffers from a relative dearth of image forming devices. No X-ray lens is known and image formation by reflection requires glancing incidence optics which have small fields of view and are extremely difficult to fabricate, even for the small apertures (about 2 cm2) now employed. The only other imaging device which has been successfully employed is the simplest of all, the pinhole camera. Pinhole cameras with resolutions better than 10−3 rad are easily constructed, but the apertures are very small—not greater than about 10−4 cm2. The new instrument described here is closely related to the pinhole camera and may be viewed as an attempt to overcome the aperture restrictions of this simple device.
144 citations
TL;DR: This paper considers the synthesis of two-dimensional, periodic, binary and nonbinary sequences (arrays) which exhibit similar properties for their two- dimensional autocorrelation functions and methods of constructing arrays based upon good one-dimensional sequences.
Abstract: Considerable effort has been devoted in the literature to the synthesis of one-dimensional, periodic, binary and nonbinary sequences having small values for their out-of-phase autocorrelation functions. This paper considers the synthesis of two-dimensional, periodic, binary and nonbinary sequences (arrays) which exhibit similar properties for their two-dimensional autocorrelation functions. These arrays may have future application in the areas of optical signal processing, pattern recognition, etc. Various procedures are presented for the synthesis of such arrays. Two perfect binary arrays and an infinite class of perfect nonbinary arrays are given. A class of binary arrays is presented which are the two-dimensional analog of the quadratic residue sequences and are shown to have out-of-phase autocorrelation of −1, or to alternate between +1 and −3. The perfect maps of Gordon are shown to have all values of out-of-phase autocorrelation equal to −1. Other methods of constructing arrays based upon good one-dimensional sequences are also discussed. Synthesis procedures are given for constructing pairs of arrays such that their cross-correlation is identically zero for all shifts and, in addition, individually have good autocorrelation functions. Examples are given for the various synthesis procedures.
117 citations