29,463 research outputs found
Compressed Sensing with off-axis frequency-shifting holography
This work reveals an experimental microscopy acquisition scheme successfully
combining Compressed Sensing (CS) and digital holography in off-axis and
frequency-shifting conditions. CS is a recent data acquisition theory involving
signal reconstruction from randomly undersampled measurements, exploiting the
fact that most images present some compact structure and redundancy. We propose
a genuine CS-based imaging scheme for sparse gradient images, acquiring a
diffraction map of the optical field with holographic microscopy and recovering
the signal from as little as 7% of random measurements. We report experimental
results demonstrating how CS can lead to an elegant and effective way to
reconstruct images, opening the door for new microscopy applications.Comment: vol 35, pp 871-87
Blur resolved OCT: full-range interferometric synthetic aperture microscopy through dispersion encoding
We present a computational method for full-range interferometric synthetic
aperture microscopy (ISAM) under dispersion encoding. With this, one can
effectively double the depth range of optical coherence tomography (OCT),
whilst dramatically enhancing the spatial resolution away from the focal plane.
To this end, we propose a model-based iterative reconstruction (MBIR) method,
where ISAM is directly considered in an optimization approach, and we make the
discovery that sparsity promoting regularization effectively recovers the
full-range signal. Within this work, we adopt an optimal nonuniform discrete
fast Fourier transform (NUFFT) implementation of ISAM, which is both fast and
numerically stable throughout iterations. We validate our method with several
complex samples, scanned with a commercial SD-OCT system with no hardware
modification. With this, we both demonstrate full-range ISAM imaging, and
significantly outperform combinations of existing methods.Comment: 17 pages, 7 figures. The images have been compressed for arxiv -
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Automated Fourier space region-recognition filtering for off-axis digital holographic microscopy
Automated label-free quantitative imaging of biological samples can greatly
benefit high throughput diseases diagnosis. Digital holographic microscopy
(DHM) is a powerful quantitative label-free imaging tool that retrieves
structural details of cellular samples non-invasively. In off-axis DHM, a
proper spatial filtering window in Fourier space is crucial to the quality of
reconstructed phase image. Here we describe a region-recognition approach that
combines shape recognition with an iterative thresholding to extracts the
optimal shape of frequency components. The region recognition technique offers
fully automated adaptive filtering that can operate with a variety of samples
and imaging conditions. When imaging through optically scattering biological
hydrogel matrix, the technique surpasses previous histogram thresholding
techniques without requiring any manual intervention. Finally, we automate the
extraction of the statistical difference of optical height between malaria
parasite infected and uninfected red blood cells. The method described here
pave way to greater autonomy in automated DHM imaging for imaging live cell in
thick cell cultures
The Role of Nonlinear Dynamics in Quantitative Atomic Force Microscopy
Various methods of force measurement with the Atomic Force Microscope (AFM)
are compared for their ability to accurately determine the tip-surface force
from analysis of the nonlinear cantilever motion. It is explained how
intermodulation, or the frequency mixing of multiple drive tones by the
nonlinear tip-surface force, can be used to concentrate the nonlinear motion in
a narrow band of frequency near the cantilevers fundamental resonance, where
accuracy and sensitivity of force measurement are greatest. Two different
methods for reconstructing tip-surface forces from intermodulation spectra are
explained. The reconstruction of both conservative and dissipative tip-surface
interactions from intermodulation spectra are demonstrated on simulated data.Comment: 25 pages (preprint, double space) 7 figure
Exploiting speckle correlations to improve the resolution of wide-field fluorescence microscopy
Fluorescence microscopy is indispensable in nanoscience and biological
sciences. The versatility of labeling target structures with fluorescent dyes
permits to visualize structure and function at a subcellular resolution with a
wide field of view. Due to the diffraction limit, conventional optical
microscopes are limited to resolving structures larger than 200 nm. The
resolution can be enhanced by near-field and far-field super-resolution
microscopy methods. Near-field methods typically have a limited field of view
and far-field methods are limited by the involved conventional optics. Here, we
introduce a combined high-resolution and wide-field fluorescence microscopy
method that improves the resolution of a conventional optical microscope by
exploiting correlations in speckle illumination through a randomly scattering
high-index medium: Speckle correlation resolution enhancement (SCORE). As a
test, we collect two-dimensional fluorescence images of 100-nm diameter
dye-doped nanospheres. We demonstrate a deconvolved resolution of 130 nm with a
field of view of 10 x 10 \text{\mu m}^2
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