999 research outputs found
Image Restoration for Remote Sensing: Overview and Toolbox
Remote sensing provides valuable information about objects or areas from a
distance in either active (e.g., RADAR and LiDAR) or passive (e.g.,
multispectral and hyperspectral) modes. The quality of data acquired by
remotely sensed imaging sensors (both active and passive) is often degraded by
a variety of noise types and artifacts. Image restoration, which is a vibrant
field of research in the remote sensing community, is the task of recovering
the true unknown image from the degraded observed image. Each imaging sensor
induces unique noise types and artifacts into the observed image. This fact has
led to the expansion of restoration techniques in different paths according to
each sensor type. This review paper brings together the advances of image
restoration techniques with particular focuses on synthetic aperture radar and
hyperspectral images as the most active sub-fields of image restoration in the
remote sensing community. We, therefore, provide a comprehensive,
discipline-specific starting point for researchers at different levels (i.e.,
students, researchers, and senior researchers) willing to investigate the
vibrant topic of data restoration by supplying sufficient detail and
references. Additionally, this review paper accompanies a toolbox to provide a
platform to encourage interested students and researchers in the field to
further explore the restoration techniques and fast-forward the community. The
toolboxes are provided in https://github.com/ImageRestorationToolbox.Comment: This paper is under review in GRS
600-GHz Fourier Imaging Based on Heterodyne Detection at the 2nd Sub-harmonic
Fourier imaging is an indirect imaging method which records the diffraction
pattern of the object scene coherently in the focal plane of the imaging system
and reconstructs the image using computational resources. The spatial
resolution, which can be reached, depends on one hand on the wavelength of the
radiation, but also on the capability to measure - in the focal plane - Fourier
components with high spatial wave-vectors. This leads to a conflicting
situation at THz frequencies, because choosing a shorter wavelength for better
resolution usually comes at the cost of less radiation power, concomitant with
a loss of dynamic range, which limits the detection of higher Fourier
components. Here, aiming at maintaining a high dynamic range and limiting the
system costs, we adopt heterodyne detection at the 2nd sub-harmonic, working
with continuous-wave (CW) radiation for object illumination at 600 GHz and
local-oscillator (LO) radiation at 300 GHz. The detector is a single-pixel
broad-band Si CMOS TeraFET equipped with substrate lenses on both the front-
and backside for separate in-coupling of the waves. The entire scene is
illuminated by the object wave, and the Fourier spectrum is recorded by raster
scanning of the single detector unit through the focal plane. With only 56 uW
of power of the 600-GHz radiation, a dynamic range of 60 dB is reached,
sufficient to detect the entire accessible Fourier space spectrum in the test
measurements. A lateral spatial resolution of better than 0.5 mm, at the
diffraction limit, is reached
Removing striping artifacts in light-sheet fluorescence microscopy: a review
In recent years, light-sheet fluorescence microscopy (LSFM) has found a broad application for imaging of diverse biological samples, ranging from sub-cellular structures to whole animals, both in-vivo and ex-vivo, owing to its many advantages relative to point-scanning methods. By providing the selective illumination of sample single planes, LSFM achieves an intrinsic optical sectioning and direct 2D image acquisition, with low out-of-focus fluorescence background, sample photo-damage and photo-bleaching. On the other hand, such an illumination scheme is prone to light absorption or scattering effects, which lead to uneven illumination and striping artifacts in the images, oriented along the light sheet propagation direction. Several methods have been developed to address this issue, ranging from fully optical solutions to entirely digital post-processing approaches. In this work, we present them, outlining their advantages, performance and limitations
Removing striping artifacts in light-sheet fluorescence microscopy: a review
In recent years, light-sheet fluorescence microscopy (LSFM) has found a broad application for imaging of diverse biological samples, ranging from sub-cellular structures to whole animals, both in-vivo and ex-vivo, owing to its many advantages relative to point-scanning methods. By providing the selective illumination of sample single planes, LSFM achieves an intrinsic optical sectioning and direct 2D image acquisition, with low out-of-focus fluorescence background, sample photo-damage and photo-bleaching. On the other hand, such an illumination scheme is prone to light absorption or scattering effects, which lead to uneven illumination and striping artifacts in the images, oriented along the light sheet propagation direction. Several methods have been developed to address this issue, ranging from fully optical solutions to entirely digital post-processing approaches. In this work, we present them, outlining their advantages, performance and limitations
Center for Space Microelectronics Technology 1988-1989 technical report
The 1988 to 1989 Technical Report of the JPL Center for Space Microelectronics Technology summarizes the technical accomplishments, publications, presentations, and patents of the center. Listed are 321 publications, 282 presentations, and 140 new technology reports and patents
Microscopic imaging and photo-stimulation using micro-structured light emitting diodes
Imperial Users onl
Herschel-ATLAS: VISTA VIKING near-IR counterparts in the Phase 1 GAMA 9h data
We identify near-infrared Ks band counterparts to Herschel-ATLAS sub-mm
sources, using a preliminary object catalogue from the VISTA VIKING survey. The
sub-mm sources are selected from the H-ATLAS Phase 1 catalogue of the GAMA 9h
field, which includes all objects detected at 250, 350 or 500 um with the SPIRE
instrument. We apply and discuss a likelihood ratio (LR) method for VIKING
candidates within a search radius of 10" of the 22,000 SPIRE sources with a 5
sigma detection at 250 um. We find that 11,294(51%) of the SPIRE sources have a
best VIKING counterpart with a reliability , and the false
identification rate of these is estimated to be 4.2%. We expect to miss ~5% of
true VIKING counterparts. There is evidence from Z-J and J-Ks colours that the
reliable counterparts to SPIRE galaxies are marginally redder than the field
population. We obtain photometric redshifts for ~68% of all (non-stellar)
VIKING candidates with a median redshift of 0.405. Comparing to the results of
the optical identifications supplied with the Phase I catalogue, we find that
the use of medium-deep near-infrared data improves the identification rate of
reliable counterparts from 36% to 51%.Comment: 20 pages, 20 figures, 3 tables, accepted by MNRA
Fast Objective Coupled Planar Illumination Microscopy
Among optical imaging techniques light sheet fluorescence microscopy stands out as one of the most attractive for capturing high-speed biological dynamics unfolding in three dimensions. The technique is potentially millions of times faster than point-scanning techniques such as two-photon microscopy. This potential is especially poignant for neuroscience applications due to the fact that interactions between neurons transpire over mere milliseconds within tissue volumes spanning hundreds of cubic microns. However current-generation light sheet microscopes are limited by volume scanning rate and/or camera frame rate. We begin by reviewing the optical principles underlying light sheet fluorescence microscopy and the origin of these rate bottlenecks. We present an analysis leading us to the conclusion that Objective Coupled Planar Illumination (OCPI) microscopy is a particularly promising technique for recording the activity of large populations of neurons at high sampling rate.
We then present speed-optimized OCPI microscopy, the first fast light sheet technique to avoid compromising image quality or photon efficiency. We enact two strategies to develop the fast OCPI microscope. First, we devise a set of optimizations that increase the rate of the volume scanning system to 40 Hz for volumes up to 700 microns thick. Second, we introduce Multi-Camera Image Sharing (MCIS), a technique to scale imaging rate by incorporating additional cameras. MCIS can be applied not only to OCPI but to any widefield imaging technique, circumventing the limitations imposed by the camera. Detailed design drawings are included to aid in dissemination to other research groups.
We also demonstrate fast calcium imaging of the larval zebrafish brain and find a heartbeat-induced motion artifact. We recommend a new preprocessing step to remove the artifact through filtering. This step requires a minimal sampling rate of 15 Hz, and we expect it to become a standard procedure in zebrafish imaging pipelines.
In the last chapter we describe essential computational considerations for controlling a fast OCPI microscope and processing the data that it generates. We introduce a new image processing pipeline developed to maximize computational efficiency when analyzing these multi-terabyte datasets, including a novel calcium imaging deconvolution algorithm. Finally we provide a demonstration of how combined innovations in microscope hardware and software enable inference of predictive relationships between neurons, a promising complement to more conventional correlation-based analyses
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