4,898 research outputs found
Large Scale 3D Image Reconstruction in Optical Interferometry
Astronomical optical interferometers (OI) sample the Fourier transform of the
intensity distribution of a source at the observation wavelength. Because of
rapid atmospheric perturbations, the phases of the complex Fourier samples
(visibilities) cannot be directly exploited , and instead linear relationships
between the phases are used (phase closures and differential phases).
Consequently, specific image reconstruction methods have been devised in the
last few decades. Modern polychromatic OI instruments are now paving the way to
multiwavelength imaging. This paper presents the derivation of a
spatio-spectral ("3D") image reconstruction algorithm called PAINTER
(Polychromatic opticAl INTErferometric Reconstruction software). The algorithm
is able to solve large scale problems. It relies on an iterative process, which
alternates estimation of polychromatic images and of complex visibilities. The
complex visibilities are not only estimated from squared moduli and closure
phases, but also from differential phases, which help to better constrain the
polychromatic reconstruction. Simulations on synthetic data illustrate the
efficiency of the algorithm.Comment: EUSIPCO, Aug 2015, NICE, Franc
High dynamic range imaging with a single-mode pupil remapping system : a self-calibration algorithm for redundant interferometric arrays
The correction of the influence of phase corrugation in the pupil plane is a
fundamental issue in achieving high dynamic range imaging. In this paper, we
investigate an instrumental setup which consists in applying interferometric
techniques on a single telescope, by filtering and dividing the pupil with an
array of single-mode fibers. We developed a new algorithm, which makes use of
the fact that we have a redundant interferometric array, to completely
disentangle the astronomical object from the atmospheric perturbations (phase
and scintillation). This self-calibrating algorithm can also be applied to any
- diluted or not - redundant interferometric setup. On an 8 meter telescope
observing at a wavelength of 630 nm, our simulations show that a single mode
pupil remapping system could achieve, at a few resolution elements from the
central star, a raw dynamic range up to 10^6; depending on the brightness of
the source. The self calibration algorithm proved to be very efficient,
allowing image reconstruction of faint sources (mag = 15) even though the
signal-to-noise ratio of individual spatial frequencies are of the order of
0.1. We finally note that the instrument could be more sensitive by combining
this setup with an adaptive optics system. The dynamic range would however be
limited by the noise of the small, high frequency, displacements of the
deformable mirror.Comment: 11 pages, 7 figures. Accepted for publication in MNRA
Physics-Driven Turbulence Image Restoration with Stochastic Refinement
Image distortion by atmospheric turbulence is a stochastic degradation, which
is a critical problem in long-range optical imaging systems. A number of
research has been conducted during the past decades, including model-based and
emerging deep-learning solutions with the help of synthetic data. Although fast
and physics-grounded simulation tools have been introduced to help the
deep-learning models adapt to real-world turbulence conditions recently, the
training of such models only relies on the synthetic data and ground truth
pairs. This paper proposes the Physics-integrated Restoration Network (PiRN) to
bring the physics-based simulator directly into the training process to help
the network to disentangle the stochasticity from the degradation and the
underlying image. Furthermore, to overcome the ``average effect" introduced by
deterministic models and the domain gap between the synthetic and real-world
degradation, we further introduce PiRN with Stochastic Refinement (PiRN-SR) to
boost its perceptual quality. Overall, our PiRN and PiRN-SR improve the
generalization to real-world unknown turbulence conditions and provide a
state-of-the-art restoration in both pixel-wise accuracy and perceptual
quality. Our codes are available at \url{https://github.com/VITA-Group/PiRN}.Comment: Accepted by ICCV 202
Sensory information processing (1 January 1976 - 30 June 1976)
technical reportThe removal of the effects of atmospheric turbulence from optical images is a significant problem of long standing. Recent investigations by Knox and Thompson have led to the development of a restoration procedure which shows considerable promise. This procedure has not been successfully applied to real data as yet, however, nor has it been sufficiently well analyzed and simulated to provide a thorough quantitative understanding of their properties. Furthermore, these procedures will very likely require modification before they can be practically applied to large quantities of real data. We have begun an investigation of Knox's method aimed at finding suitable ways to apply it to real data
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