tunable optofluidic aperture

Tunable Optofluidic ApertureMaster thesis presentation

CONFIDENTIAL

Zürich, February 4th 2011

Joep Mutsaerts

This information is confidential to Optotune and is not to be copied or forwarded to any 3rd party without our prior written consent.2

Content

• Tunable aperture- Concept- Trapped liquid- Conclusion

• Membrane model identification- Experiments- Analysis- Simulations

This information is confidential to Optotune and is not to be copied or forwarded to any 3rd party without our prior written consent.

ApertureConceptTrapped liquidConclusion

What is a tunable aperture?

• Most common: Leaflet structure

• Control of:- Light- Depth of Field- Optical quality- F number

3



What is a tunable aperture?

4

f/32 – slow shutter f/5.6 – fast shutter



Why create a tunable aperture?

• Optical quality in mobile phone market• Small size• Low part count• Available design

5



Aperture design

6



Aperture design

7



Aperture design

8



Aperture design

9



ML Demonstrator 1

• Trapped fluid problem- Spot depends on speed

• Identified possible causes- Particle size- Concentration

10



“trapped fluid” analysis

11

Possible solution Argument pro ContraLow concentration Less aggregationSmall particle size Less aggregation



ML Demonstrator 2

• Goal: test lower concentration, filtered particles (< 1 μm)

• Aperture seems clear, but:- Lens effect caused by remaining fluid- Optical quality depends on speed- Lens effect on aperture edge

• Identified possible solution- Surface tension- Coated glass

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Lens effect

13




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Possible solution Argument pro ContraLow concentration Less aggregation Lens effect in soft edgeSmall particle size Less aggregation Lens effect in soft edgeHigh surface tension Less wettingGlass coating Less wetting



ML Demonstrator 3

• Goal: Test influence of- Surface tension of water- Glass silicon coating

• Trapped fluid problem- High surface tension is not enough- Speed dependent

• Identified possible solution- Increase contact angle

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Fluid Surface Tension

Mercury 470Water 73…. << 60




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Possible solution Argument pro ContraLow concentration Less aggregation Lens effect in soft edgeSmall particle size Less aggregation Lens effect in soft edgeHigh surface tension Less wetting Does not solve problemGlass coating Less wetting Does not solve problemContact angle Less wetting



ML Demonstrator 4

• Goal: test influence of contact angle

• Trapped fluid problem- Soft edge with lens effect

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Possible solution Argument pro ContraLow concentration Less aggregation Lens effect in soft edgeSmall particle size Less aggregation Lens effect in soft edgeHigh surface tension Less wetting Does not solve problemGlass coating Less wetting Does not solve problemContact angle Less wetting Does not solve problemPositive pressure Force pushes liquid away

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Possible solution Argument pro ContraLow concentration Less aggregation Lens effect in soft edgeSmall particle size Less aggregation Lens effect in soft edgeHigh surface tension Less wetting Does not solve problemGlass coating Less wetting Does not solve problemContact angle Less wetting Does not solve problemPositive pressure Force pushes liquid away



Positive Pressure Test

• Air pressurized bulge pushes fluid away.• Particles < 5µm: Clear aperture result but soft edge• Particles > 5µm: trapped fluid problem

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Possible solution Argument pro ContraLow concentration Less aggregation Lens effect in soft edgeSmall particle size Less aggregation Lens effect in soft edgeHigh surface tension Less wetting Does not solve problemGlass coating Less wetting Does not solve problemContact angle Less wetting Does not solve problemPositive pressure Force pushes liquid away Potential Solution

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Double liquid positive pressure prototype

• Optotune lens design with two liquid compartments

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Double liquid positive pressure prototype

• Prototype results: trapped fluid appears again (speed dependent)• Over time, pigments migrate through membrane into transparent fluid• Particles were not filtered small enough

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Feasibility of concept

• Use transparent fluid• Is concept pigment dependent?



Aperture: Conclusions and Outlook

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• Trapped fluid problem has not been solved• Surface profile of transparent lens should be measured• Particle size and concentration play a large role

• Lens effect can be solved by double fluid• Bigger and more complicated to produce• Pigments leak through the membrane

• Feasibility study advises to put the project on hold• Uncertainty of product quality and costs• Not the lowest hanging fruit


Content

• Tunable aperture- Concept- Trapped liquid- Conclusion

• Membrane model identification- Experiments- Analysis- Simulations


Membrane modelExperimentsModelSimulation

Membrane model identification

Input: Membrane

•Material SE0904

• t Thickness •ԑ0 Prestrain

• r Aperture radius•p Pressure

Process:Model

•Bulge test results•Linear model•Mooney Rivlin model

Output: Deflection

•Center•Ring

•Visualisation tool




Actuation force

Focal length

Deflection

Pressure



Design of experiment



Deflection versus pressure - radius

0 500 1000 1500 2000 2500 3000 3500 4000 45000

1

2

3

4

5

6

7x 10

-3

Pressure (Pa)

Def

lect

ion

(m)

Deflection vs Pressure

d = 10 mm11

12

131415

d



Deflection versus pressure - radius

0 500 1000 1500 2000 2500 3000 3500 4000 45000

0.5

1

1.5

2

2.5

3

3.5

4

4.5x 10

-5 Deflection vs Pressure, normalized to Aperture area

Pressure (Pa)

Def

lect

ion

/ Ape

rtur

e Ar

ea (m

/m2 )

d



0 1000 2000 3000 4000 5000 6000 7000 8000 90000

1

2

3

4

5

6

7

8

9x 10

-3

Pressure (Pa)

Def

lect

ion

(m)

Pressure vs Deflection

Deflection versus pressure - Prestrain

0%

20%

70%

40%60%



Deflection versus pressure - Thickness

0 1000 2000 3000 4000 5000 6000 7000 80000

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

Pressure (Pa)

Def

lect

ion

(m)

Pressure vs Deflection

200 μm100 μm



Measurements statistics

• 148 bulge measurements done

• Thickness 10 – 200 μm• Radius 5 – 40 mm• Pressure 0 – 30000 Pa



Modelling

Isotropic – constant Youngs Non Isotropic – variable Youngs

Further challenges• Bulge loading• Material model might change



Bulge loading

• Thickness not constant• Thickness proportional to stretch• Where to measure thickness / stretch?



Stress calculation

• ‘Math slide’



Stress Strain calculated

0 0.5 1 1.5 2 2.50

1

2

3

4

5

6

7

8x 10

6

Strain (-)

Stre

ss (

Pa)

Stress Strain curve



Stress strain fit

1 1.5 2 2.5 3 3.50

1

2

3

4

5

6

7

8x 10

6

Stretch (-)

Stre

ss (

Pa)

Stress Strain fit - Mooney Rivlin

Stress-Strain point cloudMooney Rivlin fit

C10 = 210400 PaC01 = 16005 Pa



Deflection versus Pressure - Simulation

Error model RMSMooney Rivlin 0.0549

Linear model 0.1146




Input: Membrane

•Material SE0904

• t Thickness •ԑ0 Prestrain

• r Aperture radius•p Pressure

Process:Model

•Bulge test results•Linear model•Mooney Rivlin model

Output: Deflection

•Center•Ring

• Visualisation tool



Shape Predictor

41

Tunable Optofluidic ApertureMaster thesis presentation

CONFIDENTIAL

Zürich, February 4th 2011

Joep Mutsaerts

tunable optofluidic aperture

Documents

prior written consent

aperture edge

trapped fluid problemspot

fluidoptical quality

speedlens effect

f32 slow shutter f5

countavailable design

leaflet structure control