3D Time-of-flight distance measurement with custom - Universität ...

OPTICAL TOF RANGE MEASUREMENT 25
δz z
Measurement uncertainty
10 -1
10 -2
10 -3
10 -4
10 -5
10 -6
10 -7
10 -8
Depth of focus
Projected fringe
White-light IF
Triangulation
Interferometry
Time-of-flight measurement
Photogrammetry
Speckle IF Multi λ IF
Theodolite
1mm 1cm 10cm 1m 10m 100m 1km 10km
Distance z
Figure 2.6 Performance map of conventional optical 3D systems [SC1].
Absolutely independent of the progress and steady improvements in rangefinders,
we experience a continuously improving and rapidly growing field of industry:
microelectronics. For sure, each of the optical ranging methods introduced before
has profited in its own way from the ongoing miniaturization in microelectronics.
However, while triangulation and interferometry saw more cost-effective
implementations, their measurement accuracy was not substantially affected. In the
case of triangulation, the measurement range and precision is critically determined
by the triangulation baseline. Obviously, miniaturization of the complete system
leads to a reduced triangulation baseline and therefore to reduced accuracy. The
precision in interferometry is basically given by the wavelength of the employed
coherent light source, a parameter that cannot be influenced greatly. The situation
is completely different for time-of-flight (TOF) range imaging techniques. They have
not only become cheaper, smaller and simpler to realize but their measurement
accuracy is also increasing steadily. This is because, generally speaking, with
decreasing minimum feature size, devices become faster and hence, a better time
resolution is possible. Therefore, we believe that the time-of-flight measurement
principle will be used in more and more future applications.