2,112 research outputs found
Non-parametric PSF estimation from celestial transit solar images using blind deconvolution
Context: Characterization of instrumental effects in astronomical imaging is
important in order to extract accurate physical information from the
observations. The measured image in a real optical instrument is usually
represented by the convolution of an ideal image with a Point Spread Function
(PSF). Additionally, the image acquisition process is also contaminated by
other sources of noise (read-out, photon-counting). The problem of estimating
both the PSF and a denoised image is called blind deconvolution and is
ill-posed.
Aims: We propose a blind deconvolution scheme that relies on image
regularization. Contrarily to most methods presented in the literature, our
method does not assume a parametric model of the PSF and can thus be applied to
any telescope.
Methods: Our scheme uses a wavelet analysis prior model on the image and weak
assumptions on the PSF. We use observations from a celestial transit, where the
occulting body can be assumed to be a black disk. These constraints allow us to
retain meaningful solutions for the filter and the image, eliminating trivial,
translated and interchanged solutions. Under an additive Gaussian noise
assumption, they also enforce noise canceling and avoid reconstruction
artifacts by promoting the whiteness of the residual between the blurred
observations and the cleaned data.
Results: Our method is applied to synthetic and experimental data. The PSF is
estimated for the SECCHI/EUVI instrument using the 2007 Lunar transit, and for
SDO/AIA using the 2012 Venus transit. Results show that the proposed
non-parametric blind deconvolution method is able to estimate the core of the
PSF with a similar quality to parametric methods proposed in the literature. We
also show that, if these parametric estimations are incorporated in the
acquisition model, the resulting PSF outperforms both the parametric and
non-parametric methods.Comment: 31 pages, 47 figure
Compressing Images Using Multi-Level Wavelet Transform Algorithm (MWTA)
This study aims to use Wavelet Transform Algorithm for image compression. Multi-levels were used in this study with the aim to produce better results for compressing images.The Multi-level Wavelet Transform Algorithm (MWTA) consists of three phases namely, first level compression, second level compressing in the first level, and algorithm validation by compare.Therefore, Vaishnavi method is used to design and develop the prototype model.In this study, the experiment was conducted using different images (RGB). The algorithm and comparison was simulated using Matlab application. The results revealed that Multi-level Wavelet Transform Algorithm (MWTA) can be used in more than one level in this algorithm but the efficiency of this algorithm for compressing was found to be in the first level in terms of size
A Hybrid Approach of Using Wavelets and Fuzzy Clustering for Classifying Multispectral Florescence In Situ Hybridization Images
Multicolor or multiplex fluorescence in situ
hybridization (M-FISH) imaging is a recently developed molecular
cytogenetic diagnosis technique for rapid visualization of genomic
aberrations at the chromosomal level. By the simultaneous use of
all 24 human chromosome painting probes, M-FISH imaging
facilitates precise identification of complex chromosomal
rearrangements that are responsible for cancers and genetic
diseases. The current approaches, however, cannot have the
precision sufficient for clinical use. The reliability of the
technique depends primarily on the accurate pixel-wise
classification, that is, assigning each pixel into one of the 24
classes of chromosomes based on its six-channel spectral
representations. In the paper we introduce a novel approach to
improve the accuracy of pixel-wise classification. The approach is
based on the combination of fuzzy clustering and wavelet
normalization. Two wavelet-based algorithms are used to reduce
redundancies and to correct misalignments between multichannel
FISH images. In comparison with conventional algorithms, the
wavelet-based approaches offer more advantages such as the
adaptive feature selection and accurate image registration. The
algorithms have been tested on images from normal cells, showing
the improvement in classification accuracy. The increased accuracy
of pixel-wise classification will improve the reliability of the
M-FISH imaging technique in identifying subtle and cryptic
chromosomal abnormalities for cancer diagnosis and genetic
disorder research
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