67 research outputs found
Compressive Raman imaging with spatial frequency modulated illumination
We report a line scanning imaging modality of compressive Raman technology
with spatial frequency modulated illumination using a single pixel detector. We
demonstrate the imaging and classification of three different chemical species
at line scan rates of 40 Hz
Nonlinear imaging through a golden spiral multicore fiber
We report two-photon lensless imaging through a novel golden spiral multicore
fiber. This unique layout optimizes the sidelobe levels, field of view,
cross-talk, group delay and mode density to achieve a sidelobe contrast of
atleast 10.9 dB. We demonstrate experimentally the ability to generate and scan
a focal point with a femtosecond pulse and perform two-photon imaging.Comment: Submitted to Optics Letter
Line-scan Compressive Raman imaging with spatio-spectral encoding
We report a line-scanning imaging modality of Compressive Raman technology
with a single-pixel detector. The spatial information along the illumination
line is encoded onto one axis of a digital micromirror device, while spectral
coding masks are applied along the orthogonal direction. We demonstrate imaging
and classification of three different chemical species
Ultra-thin rigid endoscope: Two-photon imaging through a graded-index multi-mode fiber
Rigid endoscopes like graded-index (GRIN) lenses are known tools in
biological imaging, but it is conceptually difficult to miniaturize them. In
this letter, we demonstrate an ultra-thin rigid endoscope with a diameter of
only 125 microns. In addition, we identify a domain where two-photon endoscopic
imaging with fs-pulse excitation is possible. We validate the ultra-thin rigid
endoscope consisting of a few cm of graded-index multi-mode fiber by using it
to acquire optically sectioned two-photon fluorescence endoscopic images of
three-dimensional samples.Comment: 17 pages, 15 figures, submitted to Opt. Expres
Extended field-of-view in a lensless endoscope using an aperiodic multicore fiber
We investigate lensless endoscopy using coherent beam combining and aperiodic
multicore fibers (MCF). We show that diffracted orders, inherent to MCF with
periodically arranged cores, dramatically reduce the field of view (FoV) and
that randomness in MCF core positions can increase the FoV up to the
diffraction limit set by a single fiber core, while maintaining MCF
experimental feasibility. We demonstrate experimentally pixelation-free
lensless endoscopy imaging over a 120 micron FoV with an aperiodic MCF designed
with widely spaced cores. We show that this system is suitable to perform beam
scanning imaging by simply applying a tilt to the proximal wavefront.Comment: Submitted to Optics Letter
Single-shot non-interferometric measurement of the phase transmission matrix in multicore fibers
A simple technique for far-field single-shot non-interferometric
determination of the phase transmission matrix of a multicore fiber with over
100 cores is presented. This phase retrieval technique relies on the aperiodic
arrangement of the cores.Comment: Submitted to Optics Letter
Interferometric lensless imaging: rank-one projections of image frequencies with speckle illuminations
Lensless illumination single-pixel imaging with a multicore fiber (MCF) is a
computational imaging technique that enables potential endoscopic observations
of biological samples at cellular scale. In this work, we show that this
technique is tantamount to collecting multiple symmetric rank-one projections
(SROP) of an interferometric matrix--a matrix encoding the spectral content of
the sample image. In this model, each SROP is induced by the complex sketching
vector shaping the incident light wavefront with a spatial light modulator
(SLM), while the projected interferometric matrix collects up to image
frequencies for a -core MCF. While this scheme subsumes previous sensing
modalities, such as raster scanning (RS) imaging with beamformed illumination,
we demonstrate that collecting the measurements of random SLM
configurations--and thus acquiring SROPs--allows us to estimate an image of
interest if and scale log-linearly with the image sparsity level This
demonstration is achieved both theoretically, with a specific restricted
isometry analysis of the sensing scheme, and with extensive Monte Carlo
experiments. On a practical side, we perform a single calibration of the
sensing system robust to certain deviations to the theoretical model and
independent of the sketching vectors used during the imaging phase.
Experimental results made on an actual MCF system demonstrate the effectiveness
of this imaging procedure on a benchmark image.Comment: 13 pages, keywords: lensless imaging, rank-one projections,
interferometric matrix, inverse problem, computational imaging, single-pixe
Flexible lensless endoscope with a conformationally invariant multi-core fiber
The lensless endoscope represents the ultimate limit in miniaturization of
imaging tools: an image can be transmitted through a (multi-mode or multi-core)
fiber by numerical or physical inversion of the fiber's pre-measured
transmission matrix. However, the transmission matrix changes completely with
only minute conformational changes of the fiber, which has so far limited
lensless endoscopes to fibers that must be kept static. In this letter we
report for the first time a lensless endoscope which is exempt from the
requirement of static fiber by designing and employing a custom-designed
conformationally invariant fiber. We give experimental and theoretical
validations and determine the parameter space over which the invariance is
maintained
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