共查询到20条相似文献,搜索用时 15 毫秒
1.
Algorithms for coplanar camera calibration 总被引:5,自引:0,他引:5
Abstract. Coplanar camera calibration is the process of determining the extrinsic and intrinsic camera parameters from a given set
of image and world points, when the world points lie on a two-dimensional plane. Noncoplanar calibration, on the other hand,
involves world points that do not lie on a plane. While optimal solutions for both the camera-calibration procedures can be
obtained by solving a set of constrained nonlinear optimization problems, there are significant structural differences between
the two formulations. We investigate the computational and algorithmic implications of such underlying differences, and provide
a set of efficient algorithms that are specifically tailored for the coplanar case. More specifically, we offer the following:
(1) four algorithms for coplanar calibration that use linear or iterative linear methods to solve the underlying nonlinear
optimization problem, and produce sub-optimal solutions. These algorithms are motivated by their computational efficiency
and are useful for real-time low-cost systems. (2) Two optimal solutions for coplanar calibration, including one novel nonlinear
algorithm. A constraint for the optimal estimation of extrinsic parameters is also given. (3) A Lyapunov type convergence
analysis for the new nonlinear algorithm. We test the validity and performance of the calibration procedures with both synthetic
and real images. The results consistently show significant improvements over less complete camera models.
Received: 30 September 1998 / Accepted: 12 January 2000 相似文献
2.
The aim of the work reported here is the recovery, from a single image taken inside a roughly cylindrical brick sewer pipe
of diameter up to one meter, of the pose of the camera relative to the central axis of the pipe. It is shown that the vanishing
point associated with the longitudinal mortar lines carries valuable information about the pose. A method for the automatic
detection of this point is presented and used to analyse the camera rotations underlying a number of sewer survey videos.
It is similarly shown how the angles between the images of the longitudinal lines can be used to recover information about
camera pose. The techniques might form an active part of a more comprehensive image understanding system recovering the three-dimensional
shape of a surveyed pipe from survey videos and/or be used as an experimental tool during the design of such a system.
Received: 24 June 1997 / Accepted: 17 March 1998 相似文献
3.
Is it possible to calibrate a camera in the air and then use the calibration results to infer a new calibration corresponding
to the embedding of the camera in another fluid (possibly water)? This problem is dealt within the paper. It is important
to avoid direct underwater calibration, as it is much more inconvenient for experiments than the usual (air) calibration by
human workers. Optical laws that must be considered when using underwater cameras are investigated. Both theoretical and experimental
point of views are described, and it is shown that relationships can be found between results of air and water (or any other
isotropic fluid in which the camera can be submerged) calibration.
Received: 22 April 2000 / Accepted: 13 May 2002
Correspondence to: J.M. Lavest 相似文献
4.
Abstract. Automatic acquisition of CAD models from existing objects requires accurate extraction of geometric and topological information
from the input data. This paper presents a range image segmentation method based on local approximation of scan lines. The
method employs edge models that are capable of detecting noise pixels as well as position and orientation discontinuities
of varying strengths. Region-based techniques are then used to achieve a complete segmentation. Finally, a geometric representation
of the scene, in the form of a surface CAD model, is produced. Experimental results on a large number of real range images
acquired by different range sensors demonstrate the efficiency and robustness of the method.
Received: 1 August 2000 / Accepted: 23 January 2002
Correspondence to: I. Khalifa 相似文献
5.
In this paper, we systematically assess the performance of an automatic calibration chart detector. Through simulation we
establish the optimal set of control parameters and the rate of successful detection as a function of pose. We validate the
simulation results on real images taken from a camera mounted on a robot arm. The results confirm the utility of such simulation
studies. The feedback obtained suggested a number of modifications for the chart detection system, which led to a significant
improvement in performance. In particular, the chart design was changed to accommodate wider range and better stability in
detection.
Received: 16 December 1999 / Accepted: 15 October 2000 相似文献
6.
We present a system for classifying the color aspect of textured surfaces having a nearly constant hue (such as wooden boards,
textiles, wallpaper, etc.). The system is designed to compensate for small fluctuations (over time) of the light source and
for inhomogeneous illumination conditions (shading correction). This is an important feature because even in industrial environments
where the lighting conditions are controlled, a constant and homogeneous illumination cannot be guaranteed. Together with
an appropriate camera calibration (which includes a periodic update), our approach offers a robust system which is able to
“distinguish” (i.e., classify correctly) between surface classes which exhibit visually barely perceptible color variations.
In particular, our approach is based on relative (not absolute) color measurements. In this paper, we outline the classification
algorithm while focusing in detail on the camera calibration and a method for compensating for fluctuations of the light source.
Received: 1 September 1998 / Accepted: 16 March 2000 相似文献
7.
8.
Registration of technical drawings and calibrated images for industrial augmented reality 总被引:1,自引:0,他引:1
Despite tremendous progress in 3D modelling technology, most sites in traditional industries do not have a computer model
of their facilities at their disposal. In these industries, 2D technical drawings are typically the most commonly used documents.
In many cases, a database of fully calibrated and oriented photogrammetric images of parts of the plant is also available.
These images are often used for metric measurement and 3D as-built modelling. For planning revamps and maintenance, it is
necessary to use industrial drawings as well as images and 3D models represented in a common “world” coordinate system. This
paper proposes a method for full integration of technical drawings, calibrated images and as-built 3D models. A new algorithm
is developed in order to use only a few correspondences between points on a technical drawing and multiple images to estimate
a metric planar transformation between the drawing and the world coordinate system. The paper describes the mathematical relationship
between this transformation and the set of homographies needed for merging the technical drawing with all the calibrated images.
The method is implemented and fully integrated into an industrial software we developed for 3D as-built reconstruction. We
present examples of a real application, in which the method is successfully applied to create an augmented reality representation
of a waste water plant.
Accepted: 13 August 2001 相似文献
9.
Efficient extraction of primitives from line drawings composed of horizontal and vertical lines 总被引:6,自引:0,他引:6
The performance of the algorithms for the extraction of primitives for the interpretation of line drawings is usually affected
by the degradation of the information contained in the document due to factors such as low print contrast, defocusing, skew,
etc. In this paper, we are proposing two algorithms for the extraction of primitives with good performance under degradation.
The application of the algorithms is restricted to line drawings composed of horizontal and vertical lines. The performance
of the algorithms has been evaluated by using a protocol described in the literature.
Received: 6 August 1996 / Accepted: 16 July 1997 相似文献
10.
Summary. We present a new fault-tolerant intersection function , which satisfies the Lipschitz condition for the uniform metric and is optimal among all functions with this property. thus settles Lamport's question about such a function raised in [5]. Our comprehensive analysis reveals that has exactly the same worst-case performance as the optimal Marzullo function , which does not satisfy a Lipschitz condition. The utilized modelling approach in conjunction with a powerful hybrid fault
model ensures compatibility of our results with any known application framework, including replicated sensors and clock synchronization.
Received: September 1999 / Accepted: November 2000 相似文献
11.
Hideaki Goto Hirotomo Aso 《International Journal on Document Analysis and Recognition》1999,2(2-3):111-119
In order to enhance the ability of document analysis systems, we need a text line extraction method which can handle not
only straight text lines but also text lines in various shapes. This paper proposes a new method called Extended Linear Segment
Linking (ELSL for short), which is able to extract text lines in arbitrary orientations and curved text lines. We also consider
the existence of both horizontally and vertically printed text lines on the same page. The new method can produce text line
candidates for multiple orientations. We verify the ability of the method by some experiments as well.
Received December 21, 1998 / Revised version September 2, 1999 相似文献
12.
Location Models from the Perspective of Context-Aware Applications and Mobile Ad Hoc Networks 总被引:1,自引:0,他引:1
Location models are crucial for providing location-dependent data to context-aware applications. In this paper, we present
two approaches for modeling location information taken from an infrastructure-based and an ad hoc network-based application scenario. From these approaches we derive requirements for a general location modeling language
for ubiquitous computing.
Correspondence to: M. Bauer, Fakult?t Informatik, Universit?t Stuttgart, Breitwiesenstr. 20-22, D-70565 Stuttgart, Germany. Email: mabauer@informatik.uni-stuttgart.de 相似文献
13.
When specifying, designing and implementing technology for work, it is very important to consider the whole of the potential
user group, and not to forget that this might include people with disabilities. Obvious reasons for this are demography, disabled
people forming a significant and growing proportion of the workforce, and legal obligations caused by equal opportunities
legislation. There are more subtle reasons, however, which link so-called ‘disabled people’ with the rest of the population.
The paper notes that most people have some disabilities, sometimes temporarily due to accident, or permanently due to ageing
and other processes. In addition it notes that even otherwise fully functioning people can be seriously handicapped by hostile
environments, and a parallel is drawn between the human interface needs of disabled people operating in ordinary situations
and able-bodied people operating in high workload and stress situations. The paper concludes by suggesting a research agenda
for the field on the basis of these considerations. 相似文献
14.
Laura M. Haas Michael J. Carey Miron Livny Amit Shukla 《The VLDB Journal The International Journal on Very Large Data Bases》1997,6(3):241-256
In this paper, we re-examine the results of prior work on methods for computing ad hoc joins. We develop a detailed cost model for predicting join algorithm performance, and we use the model to develop cost formulas
for the major ad hoc join methods found in the relational database literature. We show that various pieces of “common wisdom” about join algorithm
performance fail to hold up when analyzed carefully, and we use our detailed cost model to derive op
timal buffer allocation schemes for each of the join methods examined here. We show that optimizing their buffer allocations
can lead to large performance improvements, e.g., as much as a 400% improvement in some cases. We also validate our cost model's
predictions by measuring an actual implementation of each join algorithm considered. The results of this work should be directly
useful to implementors of relational query optimizers and query processing systems.
Edited by M. Adiba. Received May 1993 / Accepted April 1996 相似文献
15.
16.
Abstract. In this paper, we present a system that was developed for the European Space Agency (ESA) for the support of planetary exploration.
The system that is sent to the planetary surface consists of a rover and a lander. The lander contains a stereo head equipped
with a pan-tilt mechanism. This vision system is used both for modeling the terrain and for localization of the rover. Both
tasks are necessary for the navigation of the rover. Due to the stress that occurs during the flight, a recalibration of the
stereo-vision system is required once it is deployed on the planet. Practical limitations make it unfeasible to use a known
calibration pattern for this purpose; therefore, a new calibration procedure had to be developed that could work on images
of the planetary environment. This automatic procedure recovers the relative orientation of the cameras and the pan and tilt
axes, as well as the exterior orientation for all the images. The same images are subsequently used to reconstruct the 3-D
structure of the terrain. For this purpose, a dense stereo-matching algorithm is used that (after rectification) computes
a disparity map. Finally, all the disparity maps are merged into a single digital terrain model. In this paper, a simple and
elegant procedure is proposed that achieves that goal. The fact that the same images can be used for both calibration and
3-D reconstruction is important, since, in general, the communication bandwidth is very limited. In addition to navigation
and path planning, the 3-D model of the terrain is also used for virtual-reality simulations of the mission, wherein the model
is texture mapped with the original images. The system has been implemented, and the first tests on the ESA planetary terrain
testbed were successful. 相似文献
17.
Juliano Lopes de Oliveira Marcos André Gonçalves Claudia Bauzer Medeiros 《International Journal on Digital Libraries》1999,2(2-3):190-206
Geographic data are useful for a large set of applications, such as urban planning and environmental control. These data are,
however, very expensive to acquire and maintain. Moreover, their use is often restricted due to a lack of dissemination mechanisms.
Digital libraries are a good approach for increasing data availability and therefore reducing costs, since they provide efficient
storage and access to large volumes of data. One major drawback to this approach is that it creates the necessity of providing
facilities for a large and heterogeneous community of users to search and interact with these geographic libraries. We present
a solution to this problem, based on a framework that allows the design and construction of customizable user interfaces for
applications based on Geographic Digital Libraries (GDL). This framework relies on two main concepts: a geographic user interface
architecture and a geographic digital library model.
Received: 15 December 1997 / Revised: June 1999 相似文献
18.
Mark Moir 《Distributed Computing》2001,14(4):193-204
Summary. We present a simple and efficient wait-free implementation of Lazy Large Load-Linked/Store-Conditional (Lazy-LL/SC), which
can be used to atomically modify a dynamically-determined set of shared variables in a lock-free manner. The semantics of
Lazy-LL/SC is weaker than that of similar objects used by us previously to design lock-free and wait-free constructions, and
as a result can be implemented more efficiently. However, we show that Lazy-LL/SC is strong enough to be used in existing
non-blocking universal constructions and to build new ones.
Received: December 2000 / Accepted: September 2001 相似文献
19.
In this paper, we present some of the results from our ongoing research work in the area of ‘agent support’ for electronic
commerce, particularly at the user interface level. Our goal is to provide intelligent agents to assist both the consumers
and the vendors in an electronic shopping environment. Users with a wide variety of different needs are expected to use the
electronic shopping application and their expectations about the interface could vary a lot. Traditional studies of user interface
technology have shown the existence of a ‘gap’ between what the user interface actually lets the users do and the users’ expectations.
Agent technology, in the form of personalized user interface agents, can help to narrow this gap. Such agents can be used
to give a personalized service to the user by knowing the user’s preferences. By doing so, they can assist in the various
stages of the users’ shopping process, provide tailored product recommendations by filtering information on behalf of their
users and reduce the information overload. From a vendor’s perspective, a software sales agent could be used for price negotiation
with the consumer. Such agents would give the flexibility offered by negotiation without the burden of having to provide human
presence to an online store to handle such negotiations.
Published online: 25 July 2001 相似文献
20.
Abstract. The image sequence in a video taken by a moving camera may suffer from irregular perturbations because of irregularities
in the motion of the person or vehicle carrying the camera. We show how to use information in the image sequence to correct
the effects of these irregularities so that the sequence is smoothed, i.e., is approximately the same as the sequence that
would have been obtained if the motion of the camera had been smooth. Our method is based on the fact that the irregular motion
is almost entirely rotational, and that the rotational image motion can be detected and corrected if a distant object, such
as the horizon, is visible.
Received: 14 February 2001 / Accepted: 11 February 2002
Correspondence to: A. Rosenfeld 相似文献