Space Variant PSF – Deconvolution of Wide-Field Astronomical Images

The properties of UWFC (Ultra Wide-Field Camera) astronomical systems along with specific visual data in astronomical images contribute to a comprehensive evaluation of the acquired image data. These systems contain many different kinds of optical aberrations which have a negatively effect on image quality and imaging system transfer characteristics, and reduce the precision of astronomical measurement. It is very important to figure two main questions out. At first: In which astrometric depend on optical aberrations? And at second: How optical aberrations affect the transfer characteristics of the whole optical system. If we define the PSF (Point Spread Function) [2] of an optical system, we can use some suitable methods for restoring the original image. Optical aberration models for LSI/LSV (Linear Space Invariant/Variant) [2] systems are presented in this paper. These models are based on Seidel and Zernike approximating polynomials [1]. Optical aberration models serve as suitable tool for estimating and fitting the wavefront aberration of a real optical system. Real data from the BOOTES (Burst Observer and Optical Transient Exploring System) experiment is used for our simulations. Problems related to UWFC imaging systems, especially a restoration method in the presence of space variant PSF are described in this paper. A model of the space variant imaging system and partially of the space variant optical system has been implemented in MATLAB. The “brute force” method has been used for restoration of the testing images. The results of different deconvolution algorithms are demonstrated in this paper. This approach could help to improve the precision of astronomic measurements.

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Advanced Processing of Images Obtained from Wide-field Astronomical Optical Systems

Acta Polytechnica ◽

10.14311/1334 ◽

2011 ◽

Vol 51 (1) ◽

Author(s):

M. Řeřábek ◽

P. Páta

Keyword(s):

Image Data ◽

Optical Systems ◽

General View ◽

Wide Field ◽

Optical Aberrations ◽

Transfer Characteristics ◽

Astronomical Image ◽

Wide Range ◽

Spread Function ◽

Space Variant

The principal aim of this paper is to present a general view of the special optical systems used for acquiring astronomical image data, commonly referred to as WFC or UWFC (Ultra Wide Field Camera), and of their transfer characteristics. UWFC image data analysis is very difficult in general, not only because the systems have so-called space variant (SV) properties. Images obtained from UWFC systems are usually incorrectly presented due to a wide range of optical aberrations and distortions. The influence of the optical aberrations increases towards the margins of the field of view. These aberrations distort the point spread function of the optical system and rapidly cut the accuracy of the measurements. This paper deals with simulation and modelling of the UWFC optical systems used in astronomy and their transfer characteristics.

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The Point Spread Function Variations inside Wide-field Astonomical Images

Acta Polytechnica ◽

10.14311/1696 ◽

2013 ◽

Vol 53 (1) ◽

Author(s):

Elena Anisimova ◽

Jan Bednář ◽

Petr Páta

Keyword(s):

Point Spread Function ◽

Imaging System ◽

Wide Field ◽

Optical Aberrations ◽

Atmospheric Scattering ◽

Function Fitting ◽

Astronomical Imaging ◽

Point Spread ◽

Spread Function ◽

Field Imaging

The Point Spread Function (PSF) of the astronomical imaging system is usually approximated by a Gaussian or Moffat function. For simplification, the astronomical imaging system is considered to be time and space invariant. This means that invariable PSF within an exposed image is assumed. If real wide-field imaging systems are considered, this presumption is not fulfilled. In real systems, stronger optical aberrations are expected (especially coma) at greater distances from the center of the captured image. This impacts the efficiency of stellar astrometry and photometry algorithms, so it is necessary to know the PSF variation. In this paper, we perform the first step toward assigning PSF changes: we study the dependence of the Moffat function fitting parameters (FWHM and the atmospheric scattering coefficient ) on the position of a stellar object.

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The space variant PSF for deconvolution of wide-field astronomical images

10.1117/12.787800 ◽

2008 ◽

Cited By ~ 4

Author(s):

M. Řeřábek ◽

P. Páta

Keyword(s):

Wide Field ◽

Astronomical Images ◽

Space Variant

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Optical Aberration Correction via Phase Diversity and Deep Learning

10.1101/2020.04.05.026567 ◽

2020 ◽

Author(s):

Anitha Priya Krishnan ◽

Chinmay Belthangady ◽

Clara Nyby ◽

Merlin Lange ◽

Bin Yang ◽

...

Keyword(s):

Deep Learning ◽

Blind Deconvolution ◽

Spherical Aberration ◽

Coefficient Of Determination ◽

Wide Field ◽

Optical Aberrations ◽

Microscopy Imaging ◽

Light Sheet Microscopy ◽

Optical Aberration ◽

Spatially Variant

AbstractIn modern microscopy imaging systems, optical components are carefully designed to obtain diffraction-limited resolution. However, live imaging of large biological samples rarely attains this limit because of sample induced refractive index inhomogeneities that create unknown temporally variant optical aberrations. Importantly, these aberrations are also spatially variant, thus making it challenging to correct over wide fields of view. Here, we present a framework for deep-learning based wide-field optical aberration sensing and correction. Our model consists of two modules which take in a set of three phase-diverse images and (i) estimate the wavefront phase in terms of its constituent Zernike polynomial coefficients and (ii) perform blind-deconvolution to yield an aberration-free image. First, we demonstrate our framework on simulations that incorporate optical aberrations, spatial variance, and realistic modelling of sensor noise. We find that our blind deconvolution achieves a 2-fold improvement in frequency support compared to input images, and our phase-estimation achieves a coefficient of determination (r2) of at least 80% when estimating astigmatism, spherical aberration and coma. Second, we show that our results mostly hold for strongly varying spatially-variant aberrations with a 30% resolution improvement. Third, we demonstrate practical usability for light-sheet microscopy: we show a 46% increase in frequency support even in imaging regions affected by detection and illumination scattering.

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Wide-field Imaging System and Rapid Direction of Optical Zoom (WOZ)

10.21236/ada534705 ◽

2010 ◽

Author(s):

Greg A. Finney

Keyword(s):

Imaging System ◽

Wide Field ◽

Field Imaging ◽

Wide Field Imaging

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Optical Aberration Calibration and Correction of Photographic System Based on Wavefront Coding

Sensors ◽

10.3390/s21124011 ◽

2021 ◽

Vol 21 (12) ◽

pp. 4011

Author(s):

Chuanwei Yao ◽

Yibing Shen

Keyword(s):

Imaging System ◽

Optical Design ◽

Computational Imaging ◽

Large Field ◽

Wavefront Aberration ◽

Imaging Method ◽

Image Deconvolution ◽

Pupil Function ◽

Wavefront Coding ◽

Blurred Images

The image deconvolution technique can recover potential sharp images from blurred images affected by aberrations. Obtaining the point spread function (PSF) of the imaging system accurately is a prerequisite for robust deconvolution. In this paper, a computational imaging method based on wavefront coding is proposed to reconstruct the wavefront aberration of a photographic system. Firstly, a group of images affected by local aberration is obtained by applying wavefront coding on the optical system’s spectral plane. Then, the PSF is recovered accurately by pupil function synthesis, and finally, the aberration-affected images are recovered by image deconvolution. After aberration correction, the image’s coefficient of variation and mean relative deviation are improved by 60% and 30%, respectively, and the image can reach the limit of resolution of the sensor, as proved by the resolution test board. Meanwhile, the method’s robust anti-noise capability is confirmed through simulation experiments. Through the conversion of the complexity of optical design to a post-processing algorithm, this method offers an economical and efficient strategy for obtaining high-resolution and high-quality images using a simple large-field lens.

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