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Fig. 6.15
Application of the local SfPR algorithm to the raw forged iron surface of the connection
rod (d'Angelo and Wöhler,
2005b
). (
a
) Images of a flawless and of a deformed surface. (
b
)Com-
parison of the three-dimensional surface profiles obtained with the local optimisation scheme.
(
c
) Difference between the two profiles
Fig. 6.16
(
a
) Reflectance and polarisation angle images of the raw forged iron surface of the
connection rod. (
b
) Triangulated stereo reconstruction result
perpendicular to the direction of incident light due to the minor influence of this
gradient on the error function.
In the second experiment, we initialised the global optimisation scheme with the
surface gradients
p
DfD
uv
and
q
DfD
uv
inferred from the depth from defocus result as
described in Sect.
5.3.3.1
. To calibrate the depth from defocus algorithm, a linear
function was fitted to the
(Σ, (z
−
z
0
))
data points (cf. Sect.
4.2.2
). The calibration
curve is shown in Fig.
4.6
, and for illustration purposes, the raw and median-filtered
depth from defocus measurements are shown in Fig.
4.7
(cf. Sect.
4.2.2
). The profile
shows many spurious structures, especially on small scales, such that shape details
are not reliably recovered. Three-dimensional reconstruction was performed based
on a combination of intensity and polarisation angle (Fig.
6.16
a). The albedo
ρ
0
was estimated based on all image pixels according to (
5.24
) with the surface gradi-
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