2,736 research outputs found
Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery
One of the main challenges for computer-assisted surgery (CAS) is to determine the intra-opera- tive morphology and motion of soft-tissues. This information is prerequisite to the registration of multi-modal patient-specific data for enhancing the surgeon’s navigation capabilites by observ- ing beyond exposed tissue surfaces and for providing intelligent control of robotic-assisted in- struments. In minimally invasive surgery (MIS), optical techniques are an increasingly attractive approach for in vivo 3D reconstruction of the soft-tissue surface geometry. This paper reviews the state-of-the-art methods for optical intra-operative 3D reconstruction in laparoscopic surgery and discusses the technical challenges and future perspectives towards clinical translation. With the recent paradigm shift of surgical practice towards MIS and new developments in 3D opti- cal imaging, this is a timely discussion about technologies that could facilitate complex CAS procedures in dynamic and deformable anatomical regions
Online Mutual Foreground Segmentation for Multispectral Stereo Videos
The segmentation of video sequences into foreground and background regions is
a low-level process commonly used in video content analysis and smart
surveillance applications. Using a multispectral camera setup can improve this
process by providing more diverse data to help identify objects despite adverse
imaging conditions. The registration of several data sources is however not
trivial if the appearance of objects produced by each sensor differs
substantially. This problem is further complicated when parallax effects cannot
be ignored when using close-range stereo pairs. In this work, we present a new
method to simultaneously tackle multispectral segmentation and stereo
registration. Using an iterative procedure, we estimate the labeling result for
one problem using the provisional result of the other. Our approach is based on
the alternating minimization of two energy functions that are linked through
the use of dynamic priors. We rely on the integration of shape and appearance
cues to find proper multispectral correspondences, and to properly segment
objects in low contrast regions. We also formulate our model as a frame
processing pipeline using higher order terms to improve the temporal coherence
of our results. Our method is evaluated under different configurations on
multiple multispectral datasets, and our implementation is available online.Comment: Preprint accepted for publication in IJCV (December 2018
Self-Supervised Intensity-Event Stereo Matching
Event cameras are novel bio-inspired vision sensors that output pixel-level
intensity changes in microsecond accuracy with a high dynamic range and low
power consumption. Despite these advantages, event cameras cannot be directly
applied to computational imaging tasks due to the inability to obtain
high-quality intensity and events simultaneously. This paper aims to connect a
standalone event camera and a modern intensity camera so that the applications
can take advantage of both two sensors. We establish this connection through a
multi-modal stereo matching task. We first convert events to a reconstructed
image and extend the existing stereo networks to this multi-modality condition.
We propose a self-supervised method to train the multi-modal stereo network
without using ground truth disparity data. The structure loss calculated on
image gradients is used to enable self-supervised learning on such multi-modal
data. Exploiting the internal stereo constraint between views with different
modalities, we introduce general stereo loss functions, including disparity
cross-consistency loss and internal disparity loss, leading to improved
performance and robustness compared to existing approaches. The experiments
demonstrate the effectiveness of the proposed method, especially the proposed
general stereo loss functions, on both synthetic and real datasets. At last, we
shed light on employing the aligned events and intensity images in downstream
tasks, e.g., video interpolation application.Comment: This paper has been accepted by the Journal of Imaging Science &
Technolog
Deep learning in remote sensing: a review
Standing at the paradigm shift towards data-intensive science, machine
learning techniques are becoming increasingly important. In particular, as a
major breakthrough in the field, deep learning has proven as an extremely
powerful tool in many fields. Shall we embrace deep learning as the key to all?
Or, should we resist a 'black-box' solution? There are controversial opinions
in the remote sensing community. In this article, we analyze the challenges of
using deep learning for remote sensing data analysis, review the recent
advances, and provide resources to make deep learning in remote sensing
ridiculously simple to start with. More importantly, we advocate remote sensing
scientists to bring their expertise into deep learning, and use it as an
implicit general model to tackle unprecedented large-scale influential
challenges, such as climate change and urbanization.Comment: Accepted for publication IEEE Geoscience and Remote Sensing Magazin
RGB-D And Thermal Sensor Fusion: A Systematic Literature Review
In the last decade, the computer vision field has seen significant progress
in multimodal data fusion and learning, where multiple sensors, including
depth, infrared, and visual, are used to capture the environment across diverse
spectral ranges. Despite these advancements, there has been no systematic and
comprehensive evaluation of fusing RGB-D and thermal modalities to date. While
autonomous driving using LiDAR, radar, RGB, and other sensors has garnered
substantial research interest, along with the fusion of RGB and depth
modalities, the integration of thermal cameras and, specifically, the fusion of
RGB-D and thermal data, has received comparatively less attention. This might
be partly due to the limited number of publicly available datasets for such
applications. This paper provides a comprehensive review of both,
state-of-the-art and traditional methods used in fusing RGB-D and thermal
camera data for various applications, such as site inspection, human tracking,
fault detection, and others. The reviewed literature has been categorised into
technical areas, such as 3D reconstruction, segmentation, object detection,
available datasets, and other related topics. Following a brief introduction
and an overview of the methodology, the study delves into calibration and
registration techniques, then examines thermal visualisation and 3D
reconstruction, before discussing the application of classic feature-based
techniques as well as modern deep learning approaches. The paper concludes with
a discourse on current limitations and potential future research directions. It
is hoped that this survey will serve as a valuable reference for researchers
looking to familiarise themselves with the latest advancements and contribute
to the RGB-DT research field.Comment: 33 pages, 20 figure
External multi-modal imaging sensor calibration for sensor fusion: A review
Multi-modal data fusion has gained popularity due to its diverse applications, leading to an increased demand for external sensor calibration. Despite several proven calibration solutions, they fail to fully satisfy all the evaluation criteria, including accuracy, automation, and robustness. Thus, this review aims to contribute to this growing field by examining recent research on multi-modal imaging sensor calibration and proposing future research directions. The literature review comprehensively explains the various characteristics and conditions of different multi-modal external calibration methods, including traditional motion-based calibration and feature-based calibration. Target-based calibration and targetless calibration are two types of feature-based calibration, which are discussed in detail. Furthermore, the paper highlights systematic calibration as an emerging research direction. Finally, this review concludes crucial factors for evaluating calibration methods and provides a comprehensive discussion on their applications, with the aim of providing valuable insights to guide future research directions. Future research should focus primarily on the capability of online targetless calibration and systematic multi-modal sensor calibration.Ministerio de Ciencia, InnovaciĂłn y Universidades | Ref. PID2019-108816RB-I0
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