Page 28 - Dynamic Vision for Perception and Control of Motion

12 1 Introduction

m/s²) and with 0.5 seconds reaction time] is 15 + 113 = 128 m. For half the magni-
2
tude in deceleration (í 2 m/s , e.g., under unfavorable road conditions) the braking
distance would be 240 m.
Reliable distance estimation for road vehicles occurs under mapping conditions
with at least about 20 pixels on the width of the vehicle (typically of about 2 m in
dimension). The total field of view of a single camera at a distance of 130 m,
where this condition is satisfied, will be about 76 m (for ~ 760 pixel per line). This
corresponds to an aperture angle of ~ 34°. This is certainly not enough to cover an
adequate field of view in the near range. Therefore, at least a bifocal camera ar-
rangement is required with two different focal lengths (see Figure 1.3).

f = 7.5 mm f = 24 mm
Wide Tele

46° 15°
angle
At distance L 5 ~ 20 m (~ 60 m),
the resolution is 5 cm/pixel

Figure 1.3. Bifocal arrangement of miniature TV–cameras on a pan platform in front of
the rear view mirror of test vehicles VaMP and VITA 2, Prometheus, 1994. Left: Fields
of view and ranges (schematically), right: System realized in VaMP

For a rather flexible high performance “technical eye” a trifocal camera ar-
rangement as shown in Figure 1.4 is recommended. The two wide-angle CCD-
cameras with focal length of 4 to 6 mm and with divergent optical axes do have a
central range of overlapping image areas, which allows stereo–interpretation
nearby. In total, a field of view of about 100 to 130 degrees can be covered; this al-
lows surveying about one–third of the entire panorama.
The mild telecamera with three to four times the focal length of the wide-angle
one should be a three–chip color camera for more precise object recognition. Its
field of view is contained in the stereo field of view of the wide-angle cameras
such that trinocular stereointerpretation becomes possible [Rieder 1996].

f = 4.8 mm wide field
of view f = 16 mm f = 50 mm
~45°
Single- Three-chip color camera
chip
~23° ~7°
color
High-sensitivity
cameras Divergent trinocular stereo
b/w–camera
>100°
L = ~30m L ~ 100 m L ~ 300 m
0.05 0.05 0.05
Figure 1.4. Trifocal camera arrangement with wide field of view