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© 2006 Autodesk 1 Dipl. Ing. (BA) Tobias Tauber
Birefringence Analysis ...brief explanation
Tech Sales Engineer
Digital Simulation
EMEA
Dipl.- Ing. Frank Raunak
© 2009 Autodesk Dipl.- Ing. Frank Raunak
optical plastic parts are used in many industries ...
© 2009 Autodesk Dipl.- Ing. Frank Raunak
Definition:
The most important optical properties of a transparent material is its refractive index n.
The refractive index shows how much slower "seems" the light through the material in
compared to vacuum.
Material (isotropic) = Refractive index n same in all directions.
Material (not isotropic) = Refractive index n different in all different
Difference is known as birefringence B
Double refraction of light caused some blurring of images, displaced images, reducing
of optical properties, etc ....
The prediction of birefringence with Autodesk Simulation Moldflow contributes to these effects
to take into consideration during the design phase and to reduce these phenomena.
© 2009 Autodesk Dipl.- Ing. Frank Raunak
double refraction n (or B): Shows the difference of the refractive index of the target value.
(Value of 0.1 is acceptable).
Retardation (phase difference and disability): Shows the wavelength difference (horizontal and vertical) of polarized light in nanometers.
(max. value should be below 25% of incident light).
Phase shift: Difference of horizontally and vertically polarized light.
(max. value should be below 90 °).
Für Licht, das aus einer bestimmten
Richtung und Reisen durch einen Teil, ist
die Verzögerung der Unterschied in der
Länge des optischen Pfades (nm)
Abhängig von der Richtung
Entspricht, wie weit außerhalb der Phase
werden die beiden Komponenten der
Lichtwelle
Kann an jedem Punkt eines Objektes
verschiedene
retardation double refrection wallthickness / part
12 nnB
Results - Definition
© 2009 Autodesk Dipl.- Ing. Frank Raunak
Material Properties for Birefringence - Analysis
© 2009 Autodesk Dipl.- Ing. Frank Raunak
Running a Birefringence Analysis
© 2009 Autodesk Dipl.- Ing. Frank Raunak
Verzugsneigung direction of the light
wave lenght
assumption of the wavelength = 546.1 nm (green light).
In many devices for measuring the birefringence.
Running a Birefringence Analysis
© 2009 Autodesk Dipl.- Ing. Frank Raunak
Example: Lens
film gate
© 2009 Autodesk Dipl.- Ing. Frank Raunak
Volumetric shrinkage can be used to judge how far off the molded part
dimensions will be compared to the intended dimensions that the part is
designed for.
volumetric Shrinkage (Cutting Plane)
© 2009 Autodesk Dipl.- Ing. Frank Raunak
Deflection results will indicate how the part will deform out of shape.
Even slight changes from the designed lens shape can introduce serious
performance issues for a plastic optical part.
Deflection (Cutting Plane)
© 2009 Autodesk Dipl.- Ing. Frank Raunak
Change in Refractive Index
© 2009 Autodesk Dipl.- Ing. Frank Raunak
Retardation
© 2009 Autodesk Dipl.- Ing. Frank Raunak
Phase Shift