138 research outputs found
The Application of Preconditioned Alternating Direction Method of Multipliers in Depth from Focal Stack
Post capture refocusing effect in smartphone cameras is achievable by using
focal stacks. However, the accuracy of this effect is totally dependent on the
combination of the depth layers in the stack. The accuracy of the extended
depth of field effect in this application can be improved significantly by
computing an accurate depth map which has been an open issue for decades. To
tackle this issue, in this paper, a framework is proposed based on
Preconditioned Alternating Direction Method of Multipliers (PADMM) for depth
from the focal stack and synthetic defocus application. In addition to its
ability to provide high structural accuracy and occlusion handling, the
optimization function of the proposed method can, in fact, converge faster and
better than state of the art methods. The evaluation has been done on 21 sets
of focal stacks and the optimization function has been compared against 5 other
methods. Preliminary results indicate that the proposed method has a better
performance in terms of structural accuracy and optimization in comparison to
the current state of the art methods.Comment: 15 pages, 8 figure
Learning Lens Blur Fields
Optical blur is an inherent property of any lens system and is challenging to
model in modern cameras because of their complex optical elements. To tackle
this challenge, we introduce a high-dimensional neural representation of
blurand a practical method for acquiring
it. The lens blur field is a multilayer perceptron (MLP) designed to (1)
accurately capture variations of the lens 2D point spread function over image
plane location, focus setting and, optionally, depth and (2) represent these
variations parametrically as a single, sensor-specific function. The
representation models the combined effects of defocus, diffraction, aberration,
and accounts for sensor features such as pixel color filters and pixel-specific
micro-lenses. To learn the real-world blur field of a given device, we
formulate a generalized non-blind deconvolution problem that directly optimizes
the MLP weights using a small set of focal stacks as the only input. We also
provide a first-of-its-kind dataset of 5D blur fieldsfor smartphone cameras,
camera bodies equipped with a variety of lenses, etc. Lastly, we show that
acquired 5D blur fields are expressive and accurate enough to reveal, for the
first time, differences in optical behavior of smartphone devices of the same
make and model
Optical module for single-shot quantitative phase imaging based on the transport of intensity equation with field of view multiplexing
We present a cost-effective, simple, and robust method that enables single-shot quantitative phase imaging (QPI) based on the transport of intensity equation (TIE) using an add-on optical module that can be assembled into the exit port of any regular microscope. The module integrates a beamsplitter (BS) cube (placed in a non-conventional way) for duplicating the output image onto the digital sensor (field of view - FOV - multiplexing), a Stokes lens (SL) for astigmatism compensation (introduced by the BS cube), and an optical quality glass plate over one of the FOV halves for defocusing generation (needed for single-shot TIE algorithm). Altogether, the system provides two laterally separated intensity images that are simultaneously recorded and slightly defocused one to each other, thus enabling accurate QPI by conventional TIE-based algorithms in a single snapshot. The proposed optical module is first calibrated for defining the configuration providing best QPI performance and, second, experimentally validated by using different phase samples (static and dynamic ones). The proposed configuration might be integrated in a compact three-dimensional (3D) printed module and coupled to any conventional microscope for QPI of dynamic transparent samples
Tunable lenses: Dynamic characterization and fine-tuned control for high-speed applications
Tunable lenses are becoming ubiquitous, in applications including microscopy,
optical coherence tomography, computer vision, quality control, and presbyopic corrections.
Many applications require an accurate control of the optical power of the lens in response to a
time-dependent input waveform. We present a fast focimeter (3.8 KHz) to characterize the
dynamic response of tunable lenses, which was demonstrated on different lens models. We
found that the temporal response is repetitive and linear, which allowed the development of a
robust compensation strategy based on the optimization of the input wave, using a linear
time-invariant model. To our knowledge, this work presents the first procedure for a direct
characterization of the transient response of tunable lenses and for compensation of their
temporal distortions, and broadens the potential of tunable lenses also in high-speed
applicationsVA and EL acknowledge financial support from Comunidad de Madrid and Marie Curie
Action of the European Union FP7/2007-2013 COFUND 291820; XB from Comunidad de
Madrid Doctorado Industrial IND2017/BMD-7670; EL from Spanish Government Ramon y
Cajal Program RyC-2016-21125; EG from Spanish Government Torres-Quevedo Program
PTQ-15-07432; LS from EU H2020 SME Innovation Associate GA-739882; EG from EIT
Health; SM from ERC Grant Agreement ERC-2011-AdC 294099 and Spanish Government
Grants FIS2014-56643-R; SM and CD from Spanish Government Grant FIS2017-84753-R; and CD from DTS16-0012
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