Effect of system point spread function, apparent size, and detector instantaneous field of view on the infrared image contrast of small objects

1993 ◽  
Vol 32 (10) ◽  
pp. 2598 ◽  
Author(s):  
George V. Poropat
Keyword(s):  
Point Spread Function ◽  
Infrared Image ◽  
Apparent Size ◽  
Image Contrast ◽  
Field Of View ◽  
Point Spread ◽  
Spread Function ◽  
System Point

Improving position accuracy for telescopes with small aperture and wide field of view utilizing point spread function modelling

2020 ◽  
Vol 497 (3) ◽  
pp. 4000-4008
Author(s):  
Rongyu Sun ◽  
Shengxian Yu ◽  
Peng Jia ◽  
Changyin Zhao
Keyword(s):  
Point Spread Function ◽  
Large Scale ◽  
Field Of View ◽  
Wide Field ◽  
Position Measurement ◽  
Small Aperture ◽  
Position Accuracy ◽  
Point Spread ◽  
Wide Field Of View ◽  
Spread Function

ABSTRACT Telescopes with a small aperture and a wide field of view are widely used and play a significant role in large-scale state-of-the-art sky survey applications, such as transient detection and near-Earth object observations. However, owing to the specific defects caused by optical aberrations, the image quality and efficiency of source detection are affected. To achieve high-accuracy position measurements, an innovative technique is proposed. First, a large number of raw images are analysed using principal component analysis. Then, the effective point spread function is reconstructed, which reflects the state of the telescope and reveals the characteristics of the imaging process. Finally, based on the point spread function model, the centroids of star images are estimated iteratively. To test the efficiency and reliability of our algorithm, a large number of simulated images are produced, and a telescope with small aperture and wide field of view is utilized to acquire the raw images. The position measurement of sources is performed using our novel method and two other common methods on these data. Based on a comparison of the results, the improvement is investigated, and it is demonstrated that our proposed technique outperforms the others on position accuracy. We explore the limitations and potential gains that may be achieved by applying this technique to custom systems designed specifically for wide-field astronomical applications.

RECONSTRUCTION OF DYNAMIC PET IMAGES USING ACCURATE SYSTEM POINT SPREAD FUNCTION MODELING: EFFECTS ON PARAMETRIC IMAGES

2010 ◽  
Vol 10 (01) ◽  
pp. 73-94 ◽  
Author(s):  
D. D'AMBROSIO ◽  
G. FIACCHI ◽  
M. MARENGO ◽  
S. BOSCHI ◽  
S. FANTI ◽  
...  
Keyword(s):  
Parameter Estimation ◽  
Point Spread Function ◽  
Physiological Parameters ◽  
Reconstruction Method ◽  
Dynamic Pet ◽  
Partial Volume ◽  
Parametric Images ◽  
Point Spread ◽  
Spread Function ◽  
System Point

Quantitative analysis of positron emission tomography (PET) dynamic images allows to estimate physiological parameters such as glucose metabolic rate (GMR), perfusion, and cardiac output (CO). However, several physical effects such as photon attenuation, scatter and partial volume can reduce the accuracy of parameter estimation. The main goal of this work was to improve small animal PET image quality by introducing system point spread function (PSF) in the reconstruction scheme and to evaluate the effect of partial volume correction (PVC) on physiological parameter estimation. Images reconstructed respectively using constant and spatially variant (SV) PSFs and no PSF modeling was compared. The proposed algorithms were tested on simulated and real phantoms and mice images. Results show that the SV-PSF-based reconstruction method provides a significant contrast improvement of small animals PET cardiac images and, thus, the effects of PVC on physiological parameters were evaluated using such algorithm. Simulations show that the proposed PVC method reduces errors with respect to the true values for parametric images of GMR and perfusion. A reduction of CO percentage error with respect to the original value was also obtained using the SF-PSF approach. In conclusion, SV-PSF reconstruction method provides a more accurate estimation of several physiological parameters obtained from a dynamic PET scan.

scholarly journals Spatial likelihood analysis for MAGIC telescope data

2018 ◽  
Vol 619 ◽  
pp. A7 ◽  
Author(s):  
I. Vovk ◽  
M. Strzys ◽  
C. Fruck
Keyword(s):  
Point Spread Function ◽  
Field Of View ◽  
Source Analysis ◽  
Source Information ◽  
Cherenkov Telescopes ◽  
Point Spread ◽  
Upper Limits ◽  
Spread Function ◽  
Source Models ◽  
Extended Sources

Context. The increase in sensitivity of Imaging Atmospheric Cherenkov Telescopes (IACTs) has lead to numerous detections of extended γ-ray sources at TeV energies, sometimes of sizes comparable to the instrument’s field of view. This creates a demand for advanced and flexible data analysis methods that are able to extract source information using the photon counts in the entire field of view. Aims. We present a new software package, “SkyPrism”, aimed at performing 2D (3D if energy is considered) fits of IACT data that possibly contain multiple and extended sources. The fits are based on sky images binned in energy. Although the development of this package was focused on the analysis of data collected with the MAGIC telescopes, it can further be adapted to other instruments, such as the future Cherenkov Telescope Array. Methods. We have developed a set of tools that in addition to sky images (count maps) compute the instrument response functions of MAGIC (effective exposure throughout the field of view, point spread function, energy resolution, and background shape) based on the input data, Monte Carlo simulations, and the pointing track of the telescopes. With this information, the package can perform a simultaneous maximum likelihood fit of source models of arbitrary morphology to the sky images providing energy spectra, detection significances, and upper limits. Results. We demonstrate that the SkyPrism tool accurately reconstructs the MAGIC point spread function, on- and off-axis performance as well as the underlying background. We further show that for a point source analysis with the MAGIC default observational settings, SkyPrism gives results compatible with those of the standard tools while being more flexible and widely applicable.

scholarly journals The INTEGRAL IBIS/ISGRI System Point Spread Function and Source Location Accuracy

2003 ◽  
Vol 411 (1) ◽  
pp. L179-L183 ◽  
Author(s):  
A. Gros ◽  
A. Goldwurm ◽  
M. Cadolle-Bel ◽  
P. Goldoni ◽  
J. Rodriguez ◽  
...  
Keyword(s):  
Point Spread Function ◽  
Source Location ◽  
Location Accuracy ◽  
Point Spread ◽  
Spread Function ◽  
System Point
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