Information Technology Reference
In-Depth Information
1.2
Augmented reality
Augmented reality (AR) is something more than VR; virtual entities become
hybrid entities and can include and manage real objects. Their main task is to
mediate interaction between real and virtual resources.
As Azuma [1] says in his Survey of Augmented Reality 'Augmented
Reality (AR) is a variation of Virtual Environments (VE) or Virtual Reality
as it is more commonly called. VE technologies completely immerse a user
inside a synthetic environment. While immersed, the user cannot see the
real world around him. In contrast, AR allows the user to see the real world,
with virtual objects superimposed upon or composited with the real world.
Therefore, AR supplements reality, rather than completely replacing it'.
AR allows all that can be generated by a computer to be superimposed on
physical reality, from simple description data up to complex virtual structures
in VW.
Reality is then enriched with contextual contents as well as with new
models and contents that can develop from invention.
2
AR technologies
AR technologies are partly the same for VW because in both cases we have
the need for advanced visualizers and immersive environments. As far as
visualizers are concerned we can use
•
HHD: handheld display,
•
HMD: head-mounted display,
•
SID: spatially immersive display.
In VW, these devices allow a user to see only computer-generated virtual
images. In AR, the same devices allow a user to see virtual objects super-
imposed on real objects.
2.1
HMD (head-mounted display)
There are three main types of advanced HMD systems: optical HMD (OHMD),
video HMD (VHMD) and retinal scanning display (RSD). All displays can
be monocular or binocular. A monocular display shows images to one eye
(Figure 1), while binocular displays show the same image to both eyes. In this
case, images are a bit different to achieve a stereoscopic view and let human
eyes give a volumetric representation of the observed objects (Figure 2).
The main advantage of HMD is that user hands are free and can operate
comfortably. The disadvantage is that users cannot see anything else than
