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Autodesk® Simulation Moldflow® Insight Stress Birefringence Prediction in Active-Shutter 3D Glasses Roger Corn Engineering Manager, Sony Corporation

© 2012 Autodesk

Class Summary

In this class, you will learn how we used Autodesk Simulation Moldflow Insight Ultimate software to successfully design and develop active-shutter 3D glasses for LCD television. We will focus on the prediction and mitigation of stress birefringence in an optically sensitive injection-molded component. Anyone who is interested in learning more about applying the powerful and specialized modules of Moldflow Insight software in the early stages of product design will gain from this class.

© 2012 Autodesk

Learning Objectives

At the end of this class, you will be able to: Use Moldflow Insight for design investigation before tooling release

Use Moldflow Insight to develop optically sensitive injection-molded parts

Describe how stress birefringence is manifested and evaluated in

polarized light applications Make your designs better and more robust using Moldflow Insight

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Introduction

Consumer Electronics Group B2B Solutions Group

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Introduction

Television Business Group Osaki, Tokyo

http://www.nikken.co.jp/en/projects/office/hq/sony-osaki-west-building.html Designed and built by NIKKEN using AUTODESK software …

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Active-Shutter 3D Glasses Stress Birefringence Prediction and Mitigation

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3D Technologies creating 3D images on 2D displays

Stress Birefringence what it is and why it occurs

Stress Birefringence in 3D Glasses how stress birefringence affects 3D glasses performance

Prediction and Mitigation using ASMI to predict and mitigate birefringence

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3D Technologies creating 3D images on 2D displays

Stress Birefringence what it is and why it occurs

Stress Birefringence in 3D Glasses how stress birefringence affects 3D glasses performance

Prediction and Mitigation using ASMI to predict and mitigate birefringence

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birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation

direction of light (thanks Wikipedia !)

ergo … when polarized light passes through a birefringent material a change in the polarization (angle) and retardation (phase)

of the light is induced

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stress birefringence from injection molding process in clear plastics

clear plastics viewed in polarized light exhibiting stress birefringence effects (rainbow or white clouding)

polarization term retardation term

ф : polarization Δn ・ d : retardation λ : wavelength

optimize (minimize) the polarization and retardation birefringence effects through calculation with ASMI in order to mitigate stress birefringence effects

© 2012 Autodesk

3D Technologies creating 3D images on 2D displays

Stress Birefringence what it is and why it occurs

Stress Birefringence in 3D Glasses how stress birefringence affects 3D glasses performance

Prediction and Mitigation using ASMI to predict and mitigate birefringence

© 2012 Autodesk

why we see 3D : binocular disparity

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Active Shutter 3D Glasses

liquid crystal shutters in glasses alternately block left & right images

to create 3D effect

when shutter does not block image completely crosstalk

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clear plastic

Active Shutter 3D Glasses LCD

polarizer

polarized light from television

transformation of polarized light due to birefringence in clear plastic causes degradation in performance of LCD shutter and crosstalk in 3d glasses standard LCD

has two polarizers

© 2012 Autodesk

3D Technologies creating 3D images on 2D displays

Stress Birefringence what it is and why it occurs

Stress Birefringence in 3D Glasses how stress birefringence affects 3D glasses performance

Prediction and Mitigation using ASMI to predict and mitigate birefringence

© 2012 Autodesk

stress birefringence in clear plastic creates crosstalk or light leakage through LCD shutter

successfully mitigated stress birefringence no crosstalk or light leakage through LCD shutter

how to mitigate stress birefringence in clear plastic part and prevent crosstalk ???

plastic w/ birefringence crosstalk

plastic w/out birefringence (no crosstalk)

white clouding due to birefringence

© 2012 Autodesk

3D Technologies creating 3D images on 2D displays

Stress Birefringence what it is and why it occurs

Stress Birefringence in 3D Glasses how stress birefringence affects 3D glasses performance

Prediction and Mitigation using ASMI to predict and mitigate birefringence

© 2012 Autodesk

Getting started ASMI Ultimate

stress birefringence module

Characterized material stress-optical coefficients and viscoelastic retardation spectrum

Mesh study various gating configurations

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Mesh

Set global length and elements through thickness All others at default settings

model part and hot runner in CAD

660k tetras

allign Z azis to optical axis in part

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Mesh

Place hot runner tetras in separate layer Assign Hot Runner (3D) property

one or multiple injection cones at hot runner tetras

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Process Settings

Fill + Pack + Warp analysis (must have Warp results for birefringence) Check Birefringence Analysis box All other settings at default values for initial analysis

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Results

Standard results evaluation

fill time

no flow balance issues

sink marks

potential areas for sink identified initial values for amount of sink may be acceptable

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Results

Phase shift and Retardation are default results with birefringence analysis Retardation tensor (polarization) needs to be added as user plot

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Results

Choose 「Tensor Principle Vector as Darts」 and 「Principle Value : First」

select user plot then plot properties

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Evaluation

Overlay retardation tensor (polarization) on retardation results plot

Select retardation plot then plot properties

Specify scaling : 0 ~500nm Color : from red to blue

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polarization term retardation term

ф : polarization Δn ・ d : retardation λ : wavelength

Evaluation

polarization term zero when ф is 0°or 180° (tensors straight up or down) retardation term zero when (Δn ・ d ) is 0 or multiple of π (color red and uniform)

birefringence (white clouding)

birefringence mitigated

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Gate option ① : direct gate large change in polarization around gate

fairly even retardation distribution

cause of white clouding in polarized light and crosstalk in 3D glasses

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Gate option ② : side gate change in polarization more uniform but not straight up or down (0°or 180°)

improved retardation distribution

cause of white clouding in polarized light and crosstalk in 3D glasses

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Gate option ③ Slight deviation from straight up / down (0°or 180°) with good uniformity

acceptable retardation distribution

mitigated white clouding in polarized light and eliminate crosstalk

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Gate option summary

Gate ① Gate ③ Gate ②

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Birefringence summary

plastic w/ birefringence crosstalk

plastic w/out birefringence (no crosstalk)

Birefringence from various gating options analyzed No prototype or proof of concept tool produced Best gate option chosen produced acceptable parts from first shot off production tool

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Results

Select CAD faces

sink marks

potential areas for sink identified

Output .fbx file

Import to SHOWCASE

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Results sink marks

potential areas for sink identified

Evaluate with SHOWCASE

sink level acceptable

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Results sink marks

potential areas for sink identified

Always Face Surface Normals to Cameras

© 2012 Autodesk

Autodesk, AutoCAD* [*if/when mentioned in the pertinent material, followed by an alphabetical list of all other trademarks mentioned in the material] are registered trademarks or trademarks of Autodesk, Inc., and/or its subsidiaries and/or affiliates in the USA and/or other countries. All other brand names, product names, or trademarks belong to their respective holders. Autodesk reserves the right to alter product and services offerings, and specifications and pricing at any time without notice, and is not responsible for typographical or graphical errors that may appear in this document. © 2012 Autodesk, Inc. All rights reserved.