F R A U N H O F E R I N S T I T U T E O F O P T R O N I C S , S Y S T E M T E C H N O L O G I E S A N D I M A G E E X P L O I TAT I O N I O S B
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Purity
Automatic Inspection of
transparent Materials
Currently industrial image processing faces
Fraunhofer Institute of Optronics,
the challenge to detect inclusions and air
System Technologies and Image
bubbles within transparent materials of any
Application Examples
• Inspection of clear plastic granulates
shape. The shapes range from flat glass to
Granulates of clear plastic are an inter-
curved glass and from lenses and spherical
mediate product used in manufacturing
Fraunhoferstraße 1
objects to granulates and similar objects.
plastic items. Irregularities in shape or
76131 Karlsruhe
The patented Purity system, developed by
bubbles are usually of no importance if
Fraunhofer IOSB (Institute of Optronics, Sys-
the granulate is melted down again later
tem Technologies and Image Exploitation),
in the production process. Soiling or tur-
detects and distinguishes changes in trans-
bidity, on the other hand, can result in
parency, inclusions of foreign objects and
faults in the finished product and must
air bubbles – nearly independent of object
therefore be identified and distinguished
shape. In contrast to conventional systems,
from irregularities in shape and bubbles.
Purity allows in most cases complete in-
The Figure above shows an example im-
spection from a single perspective.
age taken of such granulates using Purity.
The core of this flexible, reliable inspection
Foaming (white) and turbidity as well as
system is either a line scan camera or a la-
embedded foreign objects (black) can
ser scanner, depending on the particular
be reliably detected. Faulty items can be
task.
sorted out in free fall or during ejection
Images are acquired and analysed in real
from a conveyor belt.
Exploitation IOSB
Contact
Visual Inspection Systems
Prof. Dr. Thomas Längle
Phone +49 721 6091-212
[email protected]
www.iosb.fraunhofer.de
time, allowing inspection and sorting of
materials at flow velocities of up to 3 m/s.
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• Inspection of curved glass
Device Options
Technical Properties
Inspection of flat objects, such as granu-
• Inspection of transparent objects
As is the case with other glass objects,
soiling, scratches, cracks and local tension can reduce the quality of curved
glass. Faults can also be caused by embedded defects in laminated glass. A
laser scanner-based solution is able to
lates, fragments or flat glass, is performed
using single or multi-channel systems based
on line scan cameras.
detect such defects in three-dimension-
Three-dimensionally expanded objects,
ally expanded glasses. Faults can be
such as hollow glass or curved glass, are
classified using a multi-channel system.
inspected using a single or multi-channel
Two-channel sensor modules, provid-
laser scanner.
ing an inspection width of 380 mm are
available. They can be combined, thus
enabling the inspection of large curved
glasses with a depth extension of up
to 300 mm. It is possible to automatically detect point defects, hair, fuzz, foil
defects and scratches within the glass
object passing the measuring field only
once.
In both applications, one channel is used
having even complex shapes
• Detection of variations in transparency
• Minimal influence of object shape on
inspection result
• Systems based on line scan cameras for
inspecting flat objects
• Systems based on laser scanners for
to determine the transparency profile of
inspecting three-dimensionally expanded
the object. This is compared with a speci-
objects (e. g. curved laminated glass)
fied (good) profile. Faults detected in the
transparency profile can be the result of
deviations in shape, deviations in transmission, embedded foreign objects or surface
faults. The type of fault can be determined
• Detection and classification of particle
inclusions and bubbles according to
DIN ISO 10110-3
• Optional high resolution measurements
and classified using additional inspection
of induced birefringence (better
channels. Alternatively, the colour gradient
0,1 nm). For given object geometries
A dual axis sensor arrangement allows for
within the inspected item can be checked
allowing:
the entire inspection of glass tubes and
when inspecting flat objects.
- object classification according to
• Inspection of glass tubes and cylinders
cylinders on-line.
• In line measurements of drawing
Optionally object dependent changes in
the state of polarization of the light by the
forces
objects are detected and precisely meas-
An additional polarization option allows
ured. Polarization of illumination and de-
precision measurements of polarization
tection are adaptable on the specific task.
effects in the material. One application
This option allows the visualization and
of this option is the measurement and
measurement of induced birefringence or
control of drawing forces in production
the rotation of polarization in optical active
pro-cesses. The drawing forces are meas-
materials (e. g. solutions with different con-
ured by an evaluation of induced birefrin-
centration of sugar).
gence.
DIN-ISO 10110-2
- in line measurement of drawing forces
• Material flow velocities of up to 3 m/s
• Real-time image acquisition and analysis:
sortingdecisions within milliseconds