Real 
World 
| HMD 
ice that 
the user 
iall spot 
pattern. 
^ht. Fig. 
a VRD 
  
  
  
  
Figure 7. Virtual Retinal Display: Nomad Personal Display 
System made by MICROVISION 
3.2 Applications 
Augmented reality has a wide scope of application domains — 
like medicine, entertainment, military training, engineering, 
design, robotics and telerobotics, manufacturing, maintenance 
and repair. À overview is given in Fig. 8. 
  
E 
| | | 
ii: | : | 
medicine | entertainment | engineering 
| | 
| 
i 
manu | mainten- 
: e ance and 
facturing 4 repair 
  
| 
MAT TTA | 
robotics and | 
design telerobotics | 
[man training | 
  
Figure 8. Applications in augmented reality 
3.2.1 State of the art — medical applications 
For example researchers from the Department of Computer 
Science at the University of North Carolina, Chapel Hill, 
investigated the use of three-dimensional medical images 
superimposed over the patient's body for noninvasive 
visualisation of internal human anatomy. A physician wearing a 
HMD viewed a pregnant woman with an ultrasound scan of the 
fetus overlaid on the women stomach walking around the 
patient allowed the physician to observe the fetus in 3D 
perspective and to determine its placement relative to the other 
internal organs. Other researchers used augmented-reality 
environments for medical visualisation. In the application of 
Gleason, three-dimensional images were used to assist 
preoperative surgical planning and to simulate of neurosurgical 
and craniofacial interventions (Barfield, 2001). 
Further developments are: 
  
- Researchers at the Aachen University of Technology in 
Germany have developed a "Computer Assisted Surgery" 
module for use in ENT surgical procedures (Adams, 1990). 
- A group at TIMB in Grenoble, France has developed a 
*Computer Assisted Medical Intervention" module (Lavallee, 
1990). 
- A group at the University of Chicago has developed a method 
for “Interactive 3D Patient - Image Registration" (Pelizzari, 
1991). 
- A group at MIT’s Artificial Intelligence Laboratory has 
developed “An Automatic Registration Method for Frameless 
Stereotaxy, Image Guided Surgery, and Enhanced Reality 
Visualization" (Grimson, 1994). 
- A group at Stanford University has developed "Treatment 
Planning for a Radiosurgical System with General Kinematics" 
(Schweikard, 1994). 
- A group at the University of North Carolina has developed a 
method for “Merging Virtual Objects with the Real World" 
(Bajura, 1992). 
Other work in the area of image-guided surgery using 
augmented reality can be found in (Betting, 1995; Grimson, 
1995; Lorensen, 1993; Mellor, 1995; Uenohara, 1995). 
Current research efforts in enhanced-reality visualisation differ 
in many implementation details. The one thing they all have in 
common is the requirement to align a model with an image of 
the real world. 
3.3 Augmented reality issues 
In the following text we describe the issues for AR approaches. 
According to (Rolland, 2000) we describe technological issues 
in a short form and mention human factor and perceptual issues 
and design issues. From these aspects we derive the clinical and 
technical requirements for our AR approach in liver surgery. In 
Fig. 9 the relationship between technological and human factors 
/perceptual issues are illustrated. 
  
| 
| Technological || Human Factors / 
Issues | Perceptual Issues 
i | | 
| System Latency User Acceptance | 
| and Safety | 
| Real Scene la 
| Resolution and | 
| Distortion Perceived Depth | 
| | 
Field of View Adaption | 
| ET p uu L0 [7 MUTTER 
| Eyepoint Matching Peripheral Field | 
| Engineering and p UNUS ee | 
  
Cost Factors Depth of Field 
Qualitative Aspects 
Figure 9. Relationship between technological and human 
factors/ perceptual issues according to (Rolland, 
2000) 
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A. AP MC, MI