© 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