Direct demodulation technique for rotating modulation collimator
imaging

Chen, Yong; Li, T. P.; Wu, Mei‐Hwan

doi:10.1051/aas:1998147

Cited by 9 publications

(6 citation statements)

References 11 publications

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“…Direct Demodulation (DDM) [8] is one such technique, which solves the system of equations iteratively while enforcing a positivity condition as a physical constraint on the reconstruction. DDM has been previously shown by its authors to provide super-resolution for RMCs [9], and we have shown the same ability with RMs in simulation where little or no noise exists [10]. Unlike a statistical technique, however, any algebraic reconstruction method inherently requires that the reconstructed image agrees exactly with the data.…”

Section: Image Reconstructionsupporting

confidence: 60%

Image reconstruction with a LaBr3-based rotational modulator

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Case

Cherry

2011

Nuclear Instruments and Methods in Physics Research Section A:

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A rotational modulator (RM) gamma-ray imager is capable of obtaining significantly better angular resolution than the fundamental geometric resolution defined by the ratio of detector diameter to mask-detector separation. An RM imager consisting of a single grid of absorbing slats rotating ahead of an array of a small number of position-insensitive detectors has the advantage of fewer detector elements (i.e., detector plane pixels) than required by a coded aperture imaging system with comparable angular resolution. The RM therefore offers the possibility of a major reduction in instrument complexity, cost, and power. A novel image reconstruction technique makes it possible to deconvolve the raw images, remove sidelobes, reduce the effects of noise, and provide resolving power a factor of 6 -8 times better than the geometric resolution. A 19-channel prototype RM developed in our laboratory at Louisiana State University features 13.8• full-angle field of view, 1.9• geometric angular resolution, and the capability of resolving sources to within 35 ′ separation. We describe the technique, demonstrate the measured performance of the prototype instrument, and describe the prospects for applying the technique to either a high-sensitivity standoff gamma-ray imaging detector or a satelliteor balloon-borne gamma-ray astronomy telescope.

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Section: Image Reconstructionsupporting

confidence: 60%

Image reconstruction with a LaBr3-based rotational modulator

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Case

Cherry

2011

Nuclear Instruments and Methods in Physics Research Section A:

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“…The DD technique has been successfully applied to improving the angular resolution of the Wolter I type telescope PSPC aboard ROSAT mission (Chen et al 1998). A strong evidence for an X-ray jet associated with SNR G54.1 +0.3 has been found with PSPC/ROSAT and DD technique (Lu et al 2001).…”

Section: Direct Demodulation Methodsmentioning

confidence: 99%

“…The results obtained show that the DD technique can improve the spatial resolution and sensitivity significantly. Mont Carlo simulations show that, comparing with the conventional cross-correlation deconvolution technique the DD technique can improve the image quality for rotation modulation telescope (Chen et al 1998) and coded mask telescope (Li 1995). Figure 2 shows the simulation results of the DD image reconstruction for a rotating modulation telescope (Chen et al 1998).…”

Section: Direct Demodulation Methodsmentioning

confidence: 99%

Imaging in Hard X-ray Astronomy

Li¹

2003

Symp. - Int. Astron. Union

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Abstract. The energy range of hard X-rays is a key waveband to the study of high energy processes in celestial objects, but still remains poorly explored. In contrast to direct imaging methods used in the low energy X-ray and high energy gamma-ray bands, currently imaging in the hard X-ray band is mainly achieved through various modulation techniques. A new inversion technique, the direct demodulation method, has been developed since early 90s. With this technique, wide field and high resolution images can be derived from scanning data of a simple collimated detector. The feasibility of this technique has been confirmed by experiment, balloon-borne observation and analyzing simulated and real astronomical data. Based the development of methodology and instrumentation, a high energy astrophysics mission -Hard X-ray Modulation Telescope (HXMT) has been proposed and selected in China for a four-year Phase-A study. The main scientific objectives are a full-sky hard X-ray (20-200 keY) imaging survey and high signal-to-noise ratio timing studies of high energy sources.

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“…The ideal modulation function I m (θ ) means the probability of detecting counts from a point source located at position m, when the collimator is at angle θ 5,6) :…”

Section: Principle Of Image Reconstructionmentioning

confidence: 99%

Gamma-ray Imaging System with a Rotation Collimator

Kim

2011

Progress in Nuclear Science and Technology

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The performance of a gamma-ray imaging system consisting of a gridded collimator and coaxial NaI(Tl) detector was investigated. A gamma-ray imaging system with rotation collimators does not require a position-sensitive detector so as to find the location of gamma-ray sources and therefore this feature allows for significant amount of flexibility not only detector selection but also the geometry of the system. A reconstructed image from the 137 Cs gamma-ray source have been obtained by using the simple flat-fielded back-projection algorithm. The background events are jumbled together in the correct modulation-patterns. Therefore a possibility may be caused by those events that the image is reconstructed at random on the image plane. The theoretical image resolution for the current proof-of-principle gamma-ray imager is ∼ 1 o with a FOV ∼ 53.6 o . The image resolution with FWHM shows about 11.2 o . Therefore our gamma-ray imaging system is required the more collimators, because the reconstructed image was significantly affected by the modulation patterns. Future research will be to focus on the improvement of the image resolution with two or more collimators.

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Direct demodulation technique for rotating modulation collimator imaging

Cited by 9 publications

References 11 publications

Image reconstruction with a LaBr3-based rotational modulator

Image reconstruction with a LaBr3-based rotational modulator

Imaging in Hard X-ray Astronomy

Gamma-ray Imaging System with a Rotation Collimator

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