2,398 research outputs found
Semi-Blind Spatially-Variant Deconvolution in Optical Microscopy with Local Point Spread Function Estimation By Use Of Convolutional Neural Networks
We present a semi-blind, spatially-variant deconvolution technique aimed at
optical microscopy that combines a local estimation step of the point spread
function (PSF) and deconvolution using a spatially variant, regularized
Richardson-Lucy algorithm. To find the local PSF map in a computationally
tractable way, we train a convolutional neural network to perform regression of
an optical parametric model on synthetically blurred image patches. We
deconvolved both synthetic and experimentally-acquired data, and achieved an
improvement of image SNR of 1.00 dB on average, compared to other deconvolution
algorithms.Comment: 2018/02/11: submitted to IEEE ICIP 2018 - 2018/05/04: accepted to
IEEE ICIP 201
Methods to calibrate and scale axial distances in confocal microscopy as a function of refractive index
Accurate distance measurement in 3D confocal microscopy is important for
quantitative analysis, volume visualization and image restoration. However,
axial distances can be distorted by both the point spread function and by a
refractive-index mismatch between the sample and immersion liquid, which are
difficult to separate. Additionally, accurate calibration of the axial
distances in confocal microscopy remains cumbersome, although several high-end
methods exist. In this paper we present two methods to calibrate axial
distances in 3D confocal microscopy that are both accurate and easily
implemented. With these methods, we measured axial scaling factors as a
function of refractive-index mismatch for high-aperture confocal microscopy
imaging. We found that our scaling factors are almost completely linearly
dependent on refractive index and that they were in good agreement with
theoretical predictions that take the full vectorial properties of light into
account. There was however a strong deviation with the theoretical predictions
using (high-angle) geometrical optics, which predict much lower scaling
factors. As an illustration, we measured the point-spread-function of a
point-scanning confocal microscope and showed that an index-matched,
micron-sized spherical object is still significantly elongated due to this PSF,
which confirms that single micron-sized spheres are not well suited to
determine accurate axial calibration nor axial scaling.Comment: 8 pages, 5 figure
Extended depth-of-field imaging and ranging in a snapshot
Traditional approaches to imaging require that an increase in depth of field is associated with a reduction in
numerical aperture, and hence with a reduction in resolution and optical throughput. In their seminal
work, Dowski and Cathey reported how the asymmetric point-spread function generated by a cubic-phase
aberration encodes the detected image such that digital recovery can yield images with an extended depth of
field without sacrificing resolution [Appl. Opt. 34, 1859 (1995)]. Unfortunately recovered images are
generally visibly degraded by artifacts arising from subtle variations in point-spread functions with defocus.
We report a technique that involves determination of the spatially variant translation of image components
that accompanies defocus to enable determination of spatially variant defocus. This in turn enables recovery
of artifact-free, extended depth-of-field images together with a two-dimensional defocus and range map
of the imaged scene. We demonstrate the technique for high-quality macroscopic and microscopic imaging
of scenes presenting an extended defocus of up to two waves, and for generation of defocus maps with an
uncertainty of 0.036 waves
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