1. SCIENTIFIC BULLETIN OF
THE „POLITEHNICA” UNIVERSITY OF TIMISOARA, ROMANIA
TRANSACTIONS ON MECHANICS
BULETINUL ŞTIINŢIFIC AL
UNIVERSITĂŢII „POLITEHNICA” DIN TIMIŞOARA, ROMÂNIA
SERIA MECANICĂ
Tom 53 (67) ISSN 1224 - 6077 Fasc. z, 2008
3D SHAPE ANALYSIS
Elena-Octavia HERMAN*
, Doreen STEGLICH**
*
Electronics and Telecommunications Faculty, bv. Vasile Parvan No.2 RO 300223, Timisoara, Romania;
herman.elena@yahoo.com
**
Fraunhofer Institute for Manufacturing Engineering and Automation, Stuttgart, Germany
doreen.steglich@ipa.fraunhofer.de
Abstract. Topographical measurements made on test pieces at a micro scale require modern devices. These devices use
different physical principles as interferometer or variation from focus, instead of the physical inspection and thus
damaging of the object. The devices used for this scientific research were: Polytec TMS 100, to illustrate the
interferometer technique, and Alicona InfiniteFocus, for the shape from focus. Measurements using these different
optical devices are compared in order to determine the strengths, the weaknesses and limitations of each device.
Evaluation is done taking into account different aspects, such as: dimension of the surface, material, roughness or
smoothness of the surface, degree of reflection form the test object. According to the results, the user can choose a
certain device, based on the criteria above and can determine the defects of the object. This type of analysis is common
in the industry, where the quality of the products is important for the customer. For improving the effectiveness of the
production line, these devices allow the development of automatic scripting languages that perform the calculation of
parameters and the evaluation of the quality based on the image generated by the program.
Keywords: topography, micro scale, interferometer, shape from focus, parameters, automatic scripting language
1. Introduction
The 3D shape analysis is a vital part in
determining the quality of the produced items in
an industry. It can be seen as a basic method to
determine the defaults in a part, the impact
on its functioning and deciding whether a
component is classified as waste or it can be
reused in other processes.
In the past years, a new technique to
measure 3D objects was developed, different from
the tactile one. This method is non-contact,
because it measures without touching the object
directly, measuring the whole surface and
providing a realistic image of the object. This
tecnique is called Focus-Variation and its
operation principle is based on the variation of
focus of an optical system and on vertical
scanning, which comprise in the realisation of a
complete 3D data set which can be further
analysed.
Alicona InfiniteFocus is one optical device
which uses this Focus-Variation technique. The
user can choose from a variety of lens with
different objectives, for both the vertical and
lateral resolution. The light coming from a source
of white light is focused on the object using an
objective. The light emerged from the object is
gathered by a light sensitive sensor behind a beam
splitting mirror. This process is repetead during
the vertical scanning of the object, which implies a
sharp focusing of the whole object in each
moment. An image of the whole the equipment is
presented in Fig.1

2. Fig.1. The Focus-Variation Implementation
Fig.2. The functional principle of Polytech TMS-100
On the other part of the study, stands the Polytec
TMS-100 TopMap Metro.Lab. It uses also a non-
invasive method for all types of measuring large-
area topography, having a good resolution and
being used on almost any surfaces, even under
difficult conditions. The difference is that here, the
method is called Smart Surface Scanning and is
based on the principle of Michelson
interferometer. It also has a light source which is
splitted into a reference beam and an object beam.
The reference beam hits a mirror, while the object
beam hits the object itself. The light coming back
from the two reflected beams is composed back at
the beam splitter again and forms an image into
the CCD camera. While performing also a vertical
scan, only the reference beam or the object is
moved relative to the beam splitter. After a
measurement run, the digitezed picture of the
topographical structure is stored and ready to be
interpreted.
The principle described above is ilustrated in
Fig.2.
2. Measurements
2.1. Performed measurements for visible defects
using Polytec and Alicona
First of all, 25 objects were chosen to be
tested using the two measuring tools, in order to
determine the major faults on their surfaces and on
the ring part. The visible defects were stored in
tables, coresponding to each device, so as to set a
contrast between them, see Table 1 and Table 2
Table 1: Surface defects
Part
ID
Polytec Alicona
A1
Small channel
formed next to
the holes
Fault on the two holes
A2
Discontinuity in the
centre
Discontinuity in the centre
A3 Fault inthecentre Discontinuity in the centre
A4
Discontinuity in the
centre
Fault, defect in the centre
and outer part of the surface
A5
Discontinuity in the
centre
Fault onouterpart
A6
Defect inthecentre Surface with discontinuity
and cracks on edges
A7
Discontinuities on
the
surface
Small scratch and faults
A8
Defect inthecentre Two discontinuities on the
edge of the surface
A9
Small damages near
the
holes
Small faults and ring forms
on the surface
A10
Discontinuities on
the
surface
Small irregularities on the
edges and ring forms on the
surface
A11
Defect inthecentre Small irregularities
and scratches on the
edges
B
Discontinuities on the
surface
Small discontinuities and
damage in centre
C
Discontinuity near
the holes and
additional ring
shapes
Additional ring and small
cracks near the holes
D
Small damages near
the
holes
Damage in the centre and
small cracks
E
Fault inthecentre Small holes all over the
surface, cracks and
scratches
F1
Defect inthecentre Twoscratches andsmall
holes all over the
surface
F2 Defect inthecentre Small defects (scratches and
holes)
F3 Additional ring and Superficial scratches and
2

3. Part
ID
Polytec Alicona
small
cracks near the holes
additional ring shapes
F4
Defect in the centre Two discontinuities on the
edge of the surface
F5
Defect in the centre,
discontinuities on the
surface
Superficial scratches,
discontinuities on the surface
and on the edges
G1 Defect inthe centre Discontinuityin the centre
G2 Defect inthe centre Discontinuityin the centre
G3 Defect inthe centre Discontinuity in the centre,
on the edges
H1 Defect inthe centre Discontinuity in the centre,
superficial damage
H2
Small crack on the
outer part
of the surface,
discontinuity
near the holes
Discontinuity in the centre,
superficial damage, small
discontinuities inthe centre
Table 2: Ring defects
Part
ID
Polytec Alicona
A1
Residue of material,
very large damage on
the side of the ring
Damaged aluminium disk
with defects on the lateral
parts, scratches
A2
Additional material on
the lateral side, very large
damage on the side of the
ring
Damagedaluminium
disk withdefectsonthe
lateral parts, small
scratches
A3
Damage on the lateral
part of
the ring
Damaged aluminium disk
with minor defects on the
lateral parts
A4
Damage on the lateral
part of the ring, very large
damage on the side of the
ring
Damaged aluminium
disk on the lateral size,
large scratch
A5
Small axial damage and
lateral faults
Small lateral damages of
the ring
A6 Residue of material
Superficial lateral
damages
ofthering
A7
Large and many
damages of
the lateral part
Very large damages
of the lateral part of the
ring
A8
Large and many
damages of
the lateral part
Superficial lateral
damages of the ring,
superficial scratches
A9
Crack on the lateral
part of the ring and
many damages of the
lateral part
Very large damages
of the lateral part of the
ring, large scratch
A10
Residue of material,
large and many
damages of the lateral
part
Superficial lateral
damages of the ring,
superficial damage of the
inner part
All Residue of material
Superficial lateral
damages of the ring,
superficial damage of
the inner part
B
Additional material
on the lateral side,
residue of material
Superficial lateral
damages of the ring,
superficial
scratches
C Crack on the lateral Small lateral damage,
Part
ID
Polytec Alicona
part of the ring
small crack on the inner
circle
D
Damage on the
lateral part of the
ring, residue of
material
Very small scratch on
the ring surface
E
very large damage
on the side of the ring
Very small scratches
on the ring surface
Fl
Crack on the lateral
part of the ring
Very small lateral
damage, superficial
scratch
F2
Large and many
damages of the
lateral part
Small fault on the
lateral side
F3
Large and many
damages of the
lateral part
Small lateral faults
2.2 Screenshots taken for the defects found with
both devices
Screenshots of the most common found
defects were presented in tables, for Alicona and
Polytec, to set the images obtained by the two
devices in contrast, see Table 3 and Table 4.
The main difference between Alicona and
Polytec is their analytical software, based on 3D
shaping. First of all, the use of Polytec requires
filtering and approximation, while Alicona presents
a more realistic image of the faults. Additionally,
Polytec is better at making measurement even in drill
holes, without appreciable shadowing due to
magnification errors. It has a high degree of
accuracy in details, because it can easily determine
the minimum deviations from a curved surface. It
provides quality raw data without smoothing, but you
can post-process it if you want by filtering or
smoothing. On the other hand, Alicona is an expert
in a more realistic image. Among its advantages,
there are the robust measurement of surfaces with
steep flanks and extreme reflections, which is very
useful for welding spots. It is used also to judge the
quality of cutting tools, because of its complex
geometry and wear measurements.
3

4. Table 3. Screenshots of typical defects on the surface
Polytec Alicona Defects
A formed
channel
going down
across the
hole and the
discontinuity
near the hole
of the object
A
discontinuity
on the top in
the middle
area of the
object
Defect in the
center near
one of the
holes
Small crack
in the center
Damage on
the top ring
A crack on
the side of
the top
surface
Lack of
material in
the center of
the piece
Irregular
hole due to
lack of
material
A formed
channel
going down
across the
hole and the
discontinuity
near the hole
of the object
Table 4. Screenshots of typical defects on the ring
Polytec Alicona Defects
Smacll
cracks all
around the
ring
The ring is
damaged
on the
inside part
and lateral
part of the
ring
Spike on
the
aluminium
ring
Damage on
the outside
of the
aluminium
ring
Residues
on the
aluminium
disc
2.3 Evaluation of the object parameters
Alicona is best used for the roughness
measurement of newly developed roughness
standards with sinusoidal profiles. It can be also
used in form measurement, the most typical
engineering example is the measurement and
inspecting of the welding spots which can be
difficult to analyze due to their reflection. On the
other hand Polytec is better suited for ripple and
flatness measurements relative position of two
surfaces and determination of shape. Therefore
Alicona is the ideal soultion when it comes to
determining roughness parameters while Polytec is
best used for calculating the radius of a ring.
4

5. Table 5. Measured parameters
Parameter Alicona InfiniteFocus Polytec TMS-100
Average
roughnes
s
RMS
value of
roughnes
s
Radius of
the ring
2.4 Decision criteria for each device
In order to measure a metallic object, both
devices are suitable, because they both have
satisfying measuring sensors, the lightning is
sufficient for the measurements; the defects can be
detected easily with both tools. When it comes to
plastic objects, depending on the dimensions and
degree of reflectance, both devices can be used. If
we encounter low- reflecting surfaces, though, we
should use Alicona rather than Polytec because the
last one needs a minimum degree of reflection.
Criteria Alicona Polytec
Reflectance
Is suited for all
kinds of
material
(plastic,
metallic)
The material
needs minimum
reflection to get
the surface
(wood is not
suitable)
Dimension Small surfaces Large surfaces
Roughness Rough surfaces
Smooth
(e.g.mirrors)
surfaces
5

6. Colour
Realistic
colours
Colours for
horizontal
scaling
Angle of
measurement
Slopes over 80
degrees
Slopes up to 80
degrees
Lightning
More
possibilities to
set the light:
50 x the
objective
Only one
lightning
possibility is
available
Sensor
difference
100 mm x 100
mm
Field of view
of 40 mm x 30
mm
a) b)
Fig.3. Measurements of a plastic object using:
a)Polytec, b)Alicona
3. Automatic script inspection with Alicona
software
The program is supposed to determine the
3D image of a surface. It also has a graphical
interface to be easier for the user to utilize it.
The main steps of the program are listed below:
• After opening the Alicona software and focusing
the image on the object, set the centre of the desired
surface and also set the LiveView mode
• Run the function from the Automation Editor
and click OK
• Set the scan height (um) and also the vertical
height (um), then start capturing
• The program starts an autofocus on the centre
position and informs the user about this
• A dialog box appears, informing the user that the
device is moving to the top-left position : start surface
position 1
• The device moves to position 1, starts auto focusing
and stores the measured image in a file specified in the
program at folderName, together with projectName
• A dialog box appears also for position 2 and so on
until position 4 is reached
4. Conclusions
First of all, I analysed sets of data both
with Polytec and Alicona. The conclusion of the
analysis was that Polytec can be used for large and
smooth surfaces, while Alicona is used for more
detailed applications on relatively small and rough
surfaces, due to its possibility to automatically filter
the image. Alicona is used best for a realistic image
of the object, while Polytec uses a range of colours
to determine the level of the object and not to
provide a 'nice picture for the eye'. Both use
filtering, but at a different level: while Alicona does
this automatically, Polytec needs a certain degree of
user interface to determine the exact level of
filtering, depending on what the user measures. The
last one argues that the original data is determined at
its best quality this way, without smoothing.
References
1. R. Danzl1, F. Helmli and S. Scherer (2009):
Focus Variation- a new technology for high
resolution optical 3D surface metrology, The 10th
International Conference of the Slovenian Society
for Non-Destructive Testing Application of
Contemporary Non-Destructive Testing in
Engineering, Ljubljana, Slovenia
2. Scherer, S. (2007): Focus-Variation for optical
3D measurement in the micro- and nano-range,
Handbuch zur Industriellen Bildverarbeitung:
Qualitätssicherung in der Praxis, Fraunhofer
3. Alicona hadbook (2009): available on
http://www.alicona.com
4. Polytec hadbook (2007): available on
www.topmap.info
Analiza 3D a formei
Rezumat
Măsurătorile topografice făcute asupra pieselor la scară
microscopică necesită dispozitive modern. Aceste
dispozitive folosesc diferite principii fizice ca
interferometrul sau variaţia de la focus, în loc de
inspecţia fizică a obiectului şi astfel avarierea acestuia.
Dispozitivele folosite în cadrul acestei lucrări au fost:
Polytec TMS 100 şi Alicona InfiniteFocus. Sunt
comparate rezultatele măsurătorilor realizate cu aceste
dispozitive pentru a determina aspectele pozitive şi
negative ale utilizării acestor dispozitive şi limitările
lor. Evaluările sunt făcute luând în considerare diferite
aspecte cum ar fi dimensiunea suprafeţei, natura
materialului, rugozitatea suprafeţei, gradul de reflecţie
al materialului testat.
6

7. Colour
Realistic
colours
Colours for
horizontal
scaling
Angle of
measurement
Slopes over 80
degrees
Slopes up to 80
degrees
Lightning
More
possibilities to
set the light:
50 x the
objective
Only one
lightning
possibility is
available
Sensor
difference
100 mm x 100
mm
Field of view
of 40 mm x 30
mm
a) b)
Fig.3. Measurements of a plastic object using:
a)Polytec, b)Alicona
3. Automatic script inspection with Alicona
software
The program is supposed to determine the
3D image of a surface. It also has a graphical
interface to be easier for the user to utilize it.
The main steps of the program are listed below:
• After opening the Alicona software and focusing
the image on the object, set the centre of the desired
surface and also set the LiveView mode
• Run the function from the Automation Editor
and click OK
• Set the scan height (um) and also the vertical
height (um), then start capturing
• The program starts an autofocus on the centre
position and informs the user about this
• A dialog box appears, informing the user that the
device is moving to the top-left position : start surface
position 1
• The device moves to position 1, starts auto focusing
and stores the measured image in a file specified in the
program at folderName, together with projectName
• A dialog box appears also for position 2 and so on
until position 4 is reached
4. Conclusions
First of all, I analysed sets of data both
with Polytec and Alicona. The conclusion of the
analysis was that Polytec can be used for large and
smooth surfaces, while Alicona is used for more
detailed applications on relatively small and rough
surfaces, due to its possibility to automatically filter
the image. Alicona is used best for a realistic image
of the object, while Polytec uses a range of colours
to determine the level of the object and not to
provide a 'nice picture for the eye'. Both use
filtering, but at a different level: while Alicona does
this automatically, Polytec needs a certain degree of
user interface to determine the exact level of
filtering, depending on what the user measures. The
last one argues that the original data is determined at
its best quality this way, without smoothing.
References
1. R. Danzl1, F. Helmli and S. Scherer (2009):
Focus Variation- a new technology for high
resolution optical 3D surface metrology, The 10th
International Conference of the Slovenian Society
for Non-Destructive Testing Application of
Contemporary Non-Destructive Testing in
Engineering, Ljubljana, Slovenia
2. Scherer, S. (2007): Focus-Variation for optical
3D measurement in the micro- and nano-range,
Handbuch zur Industriellen Bildverarbeitung:
Qualitätssicherung in der Praxis, Fraunhofer
3. Alicona hadbook (2009): available on
http://www.alicona.com
4. Polytec hadbook (2007): available on
www.topmap.info
Analiza 3D a formei
Rezumat
Măsurătorile topografice făcute asupra pieselor la scară
microscopică necesită dispozitive modern. Aceste
dispozitive folosesc diferite principii fizice ca
interferometrul sau variaţia de la focus, în loc de
inspecţia fizică a obiectului şi astfel avarierea acestuia.
Dispozitivele folosite în cadrul acestei lucrări au fost:
Polytec TMS 100 şi Alicona InfiniteFocus. Sunt
comparate rezultatele măsurătorilor realizate cu aceste
dispozitive pentru a determina aspectele pozitive şi
negative ale utilizării acestor dispozitive şi limitările
lor. Evaluările sunt făcute luând în considerare diferite
aspecte cum ar fi dimensiunea suprafeţei, natura
materialului, rugozitatea suprafeţei, gradul de reflecţie
al materialului testat.
6