14-02-2013, 01:14 PM
Recent Advances in Augmented Reality
Recent Advances in Augmented Reality.pdf (Size: 1.89 MB / Downloads: 221)
Introduction
The field of Augmented Reality (AR) has existed for just
over one decade, but the growth and progress in the past
few years has been remarkable. In 1997, the first author
published a survey [3] (based on a 1995 SIGGRAPH
course lecture) that defined the field, described many
problems, and summarized the developments up to that
point. Since then, the field has grown rapidly. In the late
1990s, several conferences specializing in this area were
started, including the International Workshop and
Symposium on Augmented Reality [29], the International
Symposium on Mixed Reality [30], and the Designing
Augmented Reality Environments workshop. Some wellfunded
interdisciplinary consortia were formed that focused
on AR, notably the Mixed Reality Systems Laboratory
[50] in Japan and Project ARVIKA [61] in Germany. A
freely-available software toolkit (the ARToolkit) for
rapidly building AR applications is now available [2].
Because of this wealth of new developments, an updated
survey is needed to guide and encourage further research in
this exciting area.
The goal of this new survey is to cover the recent
advances in Augmented Reality that are not covered by
the original survey. This survey will not attempt to
reference every new paper that has appeared since the
original survey; there are far too many new papers.
Instead, we reference representative examples of the new
advances.
What is Augmented Reality? The basic goal of an AR
system is to enhance the users perception of and
interaction with the real world through supplementing the
real world with 3D virtual objects that appear to coexist
in the same space as the real world. Many recent papers
broaden the definition of AR beyond this vision, but in
the spirit of the original survey we define AR systems to
share the following properties:
1) Blends real and virtual, in a real environment
2) Real-time interactive
3) Registered in 3D
Registration refers to the accurate alignment of real and
virtual objects. Without accurate registration, the illusion
that the virtual objects exist in the real environment is
severely compromised. Registration is a difficult problem
and a topic of continuing research.
Note that this definition of AR is not restricted to
particular display technologies, such as a Head-Mounted
Display (HMD). Nor is it limited to the visual sense.
AR can potentially apply to all senses, including touch,
hearing, etc. Certain AR applications also require
removing real objects from the environment, in addition
to adding virtual objects. For example, an AR
visualization of a building that used to stand at a certain
location would first have to remove the current building
that exists there today. Some researchers call the task of
removing real objects Mediated or Diminished Reality,
but this survey considers it a subset of Augmented
Reality.
Computers & Graphics, November 2001
Milgram defined a continuum of Real to Virtual
environments, where Augmented Reality is one part of the
general area of Mixed Reality (Figure 1). In both
Augmented Virtuality and Virtual Environments (a.k.a
Virtual Reality), the surrounding environment is virtual,
while in AR the surrounding environment is real. This
survey focuses on Augmented Reality and does not cover
Augmented Virtuality or Virtual Environments.
Figure 1: Milgram’s Reality-Virtuality Continuum
(adapted from [49])
This new survey will not duplicate the content of the
1997 survey. That paper described potential applications
such as medical visualization, maintenance and repair of
complex equipment, annotation and path planning. It
summarized the characteristics of AR systems, such as the
advantages and disadvantages of optical and video
approaches to blend virtual and real, and problems in the
focus and contrast of displays and the portability of AR
systems. Registration was highlighted as a basic
problem. The survey analyzed the sources of registration
error and described strategies for reducing the errors.
Please refer to the original survey for details on these
topics.
The remainder of this survey organizes the new
developments into the following categories: Enabling
Technologies, Interfaces and Visualization, and New
Applications. Enabling Technologies are advances in the
basic technologies required to build a compelling AR
environment: displays, tracking, registration, and
calibration. The Interfaces and Visualization section
describes new research in how users interact with AR
systems and what they see displayed. This covers new
user interface metaphors, data density and occlusion
problems, more realistic rendering and human factors
studies. New Applications include outdoor and mobile
systems, collaborative AR, and commercial
developments. This survey concludes by describing
several areas requiring further research.
Enabling Technologies
See-Through Displays
Display technology continues to be a limiting factor in
the development of AR systems. There are still no seethrough
displays that have sufficient brightness,
resolution, field of view, and contrast to seamlessly blend
a wide range of real and virtual imagery. Furthermore,
many technologies that begin to approach these goals are
not yet sufficiently small, lightweight, and low-cost.
Nevertheless, the past few years have seen a number of
advances in see-through display technology.
Presence of well-known companies: Established
electronics and optical companies, such as Sony and
Olympus, now produce opaque, color, LCD-based
consumer head-worn displays intended for watching
videos and playing video games. While these systems
have relatively low resolution (180K240K pixels), small
fields of view (ca. 30° horizontal), and do not support
stereo, they are relatively lightweight (under 120 grams)
and offer an inexpensive option for video see-through
research. Sony introduced true SVGA resolution optical
see-through displays, including stereo models (later
discontinued), which have been used extensively in AR
research.