540 research outputs found
Deep Eyes: Binocular Depth-from-Focus on Focal Stack Pairs
Human visual system relies on both binocular stereo cues and monocular
focusness cues to gain effective 3D perception. In computer vision, the two
problems are traditionally solved in separate tracks. In this paper, we present
a unified learning-based technique that simultaneously uses both types of cues
for depth inference. Specifically, we use a pair of focal stacks as input to
emulate human perception. We first construct a comprehensive focal stack
training dataset synthesized by depth-guided light field rendering. We then
construct three individual networks: a Focus-Net to extract depth from a single
focal stack, a EDoF-Net to obtain the extended depth of field (EDoF) image from
the focal stack, and a Stereo-Net to conduct stereo matching. We show how to
integrate them into a unified BDfF-Net to obtain high-quality depth maps.
Comprehensive experiments show that our approach outperforms the
state-of-the-art in both accuracy and speed and effectively emulates human
vision systems
Recent Progress in Image Deblurring
This paper comprehensively reviews the recent development of image
deblurring, including non-blind/blind, spatially invariant/variant deblurring
techniques. Indeed, these techniques share the same objective of inferring a
latent sharp image from one or several corresponding blurry images, while the
blind deblurring techniques are also required to derive an accurate blur
kernel. Considering the critical role of image restoration in modern imaging
systems to provide high-quality images under complex environments such as
motion, undesirable lighting conditions, and imperfect system components, image
deblurring has attracted growing attention in recent years. From the viewpoint
of how to handle the ill-posedness which is a crucial issue in deblurring
tasks, existing methods can be grouped into five categories: Bayesian inference
framework, variational methods, sparse representation-based methods,
homography-based modeling, and region-based methods. In spite of achieving a
certain level of development, image deblurring, especially the blind case, is
limited in its success by complex application conditions which make the blur
kernel hard to obtain and be spatially variant. We provide a holistic
understanding and deep insight into image deblurring in this review. An
analysis of the empirical evidence for representative methods, practical
issues, as well as a discussion of promising future directions are also
presented.Comment: 53 pages, 17 figure
Variational Disparity Estimation Framework for Plenoptic Image
This paper presents a computational framework for accurately estimating the
disparity map of plenoptic images. The proposed framework is based on the
variational principle and provides intrinsic sub-pixel precision. The
light-field motion tensor introduced in the framework allows us to combine
advanced robust data terms as well as provides explicit treatments for
different color channels. A warping strategy is embedded in our framework for
tackling the large displacement problem. We also show that by applying a simple
regularization term and a guided median filtering, the accuracy of displacement
field at occluded area could be greatly enhanced. We demonstrate the excellent
performance of the proposed framework by intensive comparisons with the Lytro
software and contemporary approaches on both synthetic and real-world datasets
Depth Estimation Through a Generative Model of Light Field Synthesis
Light field photography captures rich structural information that may
facilitate a number of traditional image processing and computer vision tasks.
A crucial ingredient in such endeavors is accurate depth recovery. We present a
novel framework that allows the recovery of a high quality continuous depth map
from light field data. To this end we propose a generative model of a light
field that is fully parametrized by its corresponding depth map. The model
allows for the integration of powerful regularization techniques such as a
non-local means prior, facilitating accurate depth map estimation.Comment: German Conference on Pattern Recognition (GCPR) 201
Learning Wavefront Coding for Extended Depth of Field Imaging
Depth of field is an important factor of imaging systems that highly affects
the quality of the acquired spatial information. Extended depth of field (EDoF)
imaging is a challenging ill-posed problem and has been extensively addressed
in the literature. We propose a computational imaging approach for EDoF, where
we employ wavefront coding via a diffractive optical element (DOE) and we
achieve deblurring through a convolutional neural network. Thanks to the
end-to-end differentiable modeling of optical image formation and computational
post-processing, we jointly optimize the optical design, i.e., DOE, and the
deblurring through standard gradient descent methods. Based on the properties
of the underlying refractive lens and the desired EDoF range, we provide an
analytical expression for the search space of the DOE, which is instrumental in
the convergence of the end-to-end network. We achieve superior EDoF imaging
performance compared to the state of the art, where we demonstrate results with
minimal artifacts in various scenarios, including deep 3D scenes and broadband
imaging
Depth Acquisition from Digital Images
Introduction: Depth acquisition from digital images captured with a conventional camera, by analysing focus/defocus cues which are related to depth via an optical model of the camera, is a popular approach to depth-mapping a 3D scene. The majority of methods analyse the neighbourhood of a point in an image to infer its depth, which has disadvantages. A more elegant, but more difficult, solution is to evaluate only the single pixel displaying a point in order to infer its depth. This thesis investigates if a per-pixel method can be implemented without compromising accuracy and generality compared to window-based methods, whilst minimising the number of input images.
Method: A geometric optical model of the camera was used to predict the relationship between focus/defocus and intensity at a pixel. Using input images with different focus settings, the relationship was used to identify the focal plane depth (i.e. focus setting) where a point is in best focus, from which the depth of the point can be resolved if camera parameters are known. Two metrics were implemented, one to identify the best focus setting for a point from the discrete input set, and one to fit a model to the input data to estimate the depth of perfect focus of the point on a continuous scale.
Results: The method gave generally accurate results for a simple synthetic test scene, with a relatively low number of input images compared to similar methods. When tested on a more complex scene, the method achieved its objectives of separating complex objects from the background by depth, and produced a similar resolution of a complex 3D surface as a similar method which used significantly more input data.
Conclusions: The method demonstrates that it is possible to resolve depth on a per-pixel basis without compromising accuracy and generality, and using a similar amount of input data, compared to more traditional window-based methods. In practice, the presented method offers a convenient new option for depth-based image processing applications, as the depth-map is per-pixel, but the process of capturing and preparing images for the method is not too practically cumbersome and could be easily automated unlike other per-pixel methods reviewed. However, the method still suffers from the general limitations of the depth acquisition approach using images from a conventional camera, which limits its use as a general depth acquisition solution beyond specifically depth-based image processing applications
Non-convex optimization for 3D point source localization using a rotating point spread function
We consider the high-resolution imaging problem of 3D point source image
recovery from 2D data using a method based on point spread function (PSF)
engineering. The method involves a new technique, recently proposed by
S.~Prasad, based on the use of a rotating PSF with a single lobe to obtain
depth from defocus. The amount of rotation of the PSF encodes the depth
position of the point source. Applications include high-resolution single
molecule localization microscopy as well as the problem addressed in this paper
on localization of space debris using a space-based telescope. The localization
problem is discretized on a cubical lattice where the coordinates of nonzero
entries represent the 3D locations and the values of these entries the fluxes
of the point sources. Finding the locations and fluxes of the point sources is
a large-scale sparse 3D inverse problem. A new nonconvex regularization method
with a data-fitting term based on Kullback-Leibler (KL) divergence is proposed
for 3D localization for the Poisson noise model. In addition, we propose a new
scheme of estimation of the source fluxes from the KL data-fitting term.
Numerical experiments illustrate the efficiency and stability of the algorithms
that are trained on a random subset of image data before being applied to other
images. Our 3D localization algorithms can be readily applied to other kinds of
depth-encoding PSFs as well.Comment: 28 page
Light field reconstruction from multi-view images
Kang Han studied recovering the 3D world from multi-view images. He proposed several algorithms to deal with occlusions in depth estimation and effective representations in view rendering. the proposed algorithms can be used for many innovative applications based on machine intelligence, such as autonomous driving and Metaverse
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