Accurate fringe analysis
in a 3D range sensor
for the fast measurement
of shapes
G. Sansoni, F. Docchio, E. Redaelli
Laboratory of Optoelectronics
University of Brescia, Italy
Context of the work
National Italian Project: Low-cost 3D imaging and
modeling automatic system (LIMA3D)
BRESCIA
BRESCIA
Laboratory
FIRENZE
MILANO
of Optoelectronics
Design, development and metrological characterization
of a low-cost optical digitizer
based on the projection of
VERONA
a single grating of non-coherent light
GENOVA
PALERMO
Field of View (FOV): up to 300X400mm2
Depth range: up to 100mm
Measurement uncertainty: 0.3mm
2
What the system is not
• Optical active triangulation
• Time-space coding of the meas. volume
Fringe projector
Video camera
Assembly system
OPL-3D
3
Winged Victory
Sestertius
Ferrari 250 MM
4
What the system is
• Use of low-cost projection device
Slide projector
Video beam
• Optical active triangulation
• Projection of a single pattern of light
• Time space coding of the scene
5
Measurement principle
i
j
Map of labels
FW
LT
Projection Label: LS
Projector
Xp
Up
d
i
LS
l
T
Zp
S(iS, jS, LS)
S
Oc
Zc
Xc
Xg
Yc
S’(iS,jS)
T(iS, jS, LT)
FH
L
j
Video camera
t
Yp
Op
Phase mapping
Og
Zg
S(XS, YS, ZS)
Yg
T(XT,YT, ZT)
Camera-projector Calibration
6
Phase mapping
Input GC(i,j)
Normalization
Gc(i,j)
GC,n(i,j)
Binarization
Low-pass filtering
gr,f(i,j)
gf,f(i,j)
Amplitude
normalization
gr,n(i,j)
gf,n(i,j)
%
ATAN2
Rad
gf(i,j)
Intensity
Intensity
Intensity
Intensity
Intensity
Edge detector
200
200
150
150
150
150
100
300
100
1,5
100
100
50
4
200
50
150
50
3
10000
0,5
-50
2000100
100
-50
100
100
-100
10100
-50
-50
-100
-100
-150
0100
-0,5
-100
-150
-200
100
-1
-1
-150
-300
-2
-1,5
gr,f(i,j), gf,f(i,j)
gr,n(i,j), gf,n(i,j)
FW(i,j)
Intensity
GC,b(i,j)
gr(i,j)
Gc,n(i,j)
Gc,b(i,j)
gr(i,j), gf(i,j)
250
-3
-4
120
120
120
120
120
140
140
140
140
140
160
160
160
160
160
120
140
120
140 Pixel
Pixel
Pixel
180
180
180
180
180
200
200
200
200
200
160
180
200
160
180
200
Pixel
Pixel
Pixel
Rise
Fall
Rise
Fall
Rise
Pixel Fall
FW(i,j)
7
The phase unwrapping
• Pure spatial approach
• Spatio-temporal approach (optional)
8
Camera-Projector calibration
9
The prototype
Hitachi KP-D50
Color
Sanyo PROxtraX
LCD
10
Experimental results (1)
11
Exprimental results (2)
12
Metrological characterization
13
Metrological characterization
14
Conclusions
•
•
•
•
Low-cost 3D system based on phase measurement
Characterization of the measurement performance
Experimentation with high resolution cameras
Experimentation with a 3CCD color camera
15