Master Thesis - Hochschule Bonn-Rhein-Sieg

3. Hard- and software Master Thesis Björn Ostermann page 27 of 126
c being the speed of light
f being the used modulation frequency
c 1
� � camera range
f 2
m
299 792 458
s 1
� � 7.
5m
20MHz
2
Equation 2: Calculation of the maximum range
Longer ranges would theoretically be possible by choosing other modulation frequencies. Due to the
physical restrictions of the used sensor chip (saturation time, etc.) 7.5 meters is the maximum range
for which the camera is usable, according to the manufacturer [55].
The advantage in using near infrared light is that the every other part of the spectrum, including the
visible light, can be filtered out before measuring.
The camera’s main characteristics are summarized in Figure 12, additional information can be found
in the first project report [77].
Model No. SR-3100
Pixel array resolution 176 x 144 pixels
Field of view 47.5 x 39.6 degrees
Non-ambiguity range 7.5 m
Frame rate Variable, max 50fps
Estimated Error 1% of measured distance
Figure 12: Table containing Camera Data, taken from [55]
As shown in the first project [77], recognition of the humans hand is assured for a distance of up to
three meters.
Detailed studies on the accuracy of the camera have been done by another BGIA project [80]. Their
result is that the camera’s accuracy does not depend on temperature in a range between -10°C and
+50°C. The camera delivers sufficiently reliable and repeatable results in a distance between 2 and 5
meters, provided that no material is present that does absorb most of the emitted light wave.
In the studies of this project only two materials (a grey jeans and a black shirt) have been found that do
not reflect the emitted waves sufficiently. In the case of the given application, this problem can be
handled as described in chapter 7.2.