Control system for optics Session · P r e c i s i o n a n d I n t e l l i g e n c e L a b o r a t...

Control system for optics Session(1:00 ~ 1:45, Wednesday 25th April)


3pOA01No file submission


3pOA02

Variable-Focus Optical LensUsing Viscoelastic Materialand Acoustic Radiation Force

Daisuke Koyama, Ryoichi Isago, Kentaro Nakamura

Precision and Intelligence Laboratory,Tokyo Institute of Technology

Prec i s ion and Intelligence Laborat

oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN

MotivationCamera lens for mobile electronic devices

Lens + Actuators + Gearing system

2

*JMAG HP

Bulky & Low-speed response

Liquid lenses

Lens surface = Water/Oil boundaryDeformation of lenses (by electrowetting, acoustic radiation force...）Without moving mechanical partsSimple structure, Miniaturization Temperature instability, Bubble generation OFF

Oil

Water

ONElectrodes

Variable-focus lens with a simple structure and temperature stability



Acoustic radiation force on a liquid surface 3

Projection on a surface of liquids caused by acoustic radiation force

Air

Water Deformation

AtomizationAir

WaterSoundwave

When ultrasound of MHz range was radiated to a surface...

The surface is deformed or atomized due to the acoustic radiation force.

Lens surface



Liquid lens using acoustic radiation force 4

Off

Lig

ht axis

On

Acoustic radiation force

D. Koyama, et al, Opt. Express, 18, 25158 (2010)D. Koyama, et al, IEEE UFFC, 58, 596 (2011)D. Koyama, et al, JJAP, 50, 07HE26 (2011)

Aluminum cell

TransducerWater

Silicone oil

Glass

Laser light

3 m

m

6 mm

Lens profile changes by acoustic radiation forceVariable-focus lens

Small-sized (radius of 6 mm)High-speed response (6.7 ms)

Temperature instability, Bubble generation



Configuration 5

Deformaiton of the lens by acoustic radiation force

PZT Transducer

Gel

Light axis 2

3015

Unit: mm

PET film Gel

OffLight axis

Lens

On

Acoustic radiation force

Silicone gelKE-1052(A/B) (Shin-Etsu Silicone)Refractive index: 1.4Density: 1400 kg/m3

Speed of sound: 1030 m/sTemperature stability: -30-150 ℃

Viscoelastic material



Vibration mode & Acoustic field (FEA) 6

z

r

ur

r

PZT

PZT

a a’

Vibration mode in the radial direction (222 kHz)

Sound pressure distribution in the lens:acoustic standing wave with two concentric nodal circles (same distribution as Bessel function )

1.0

0.8

0.6

0.4

0.2

0.0

Sound pressure amplitude p [arb.]

-10 -5 0 5 10Radial direction [mm]

Calculated by FEAFitting(Bessel function)

a a’



Lens profiles 7

0.3

0.2

0.1

0.0

-0.1

Axial direction [mm]

-6 -4 -2 0 2 4 6Radial direction [mm]

0 V12 V15 V18 V21 V

Air

Gel

0p2 [arb.] 1

Experimental

FEA

Acoustic radiation force is function of p2

Measured by optical coherence tomography (OCT)

The lens surface was deformed only at the center axis, which corresponds with the predicted peak position of p2

Larger displacement with larger input voltage: displacement of 150 µm with 21 Vpp



Beam profiles 8

18 V

0 V

12 V

Lens

15 V

21 V

6040200 [mm]

Ray-tracing simulationLens aperture of 2 mmLens profiles imported from experimental results Focal length controlled by input voltage

120

100

80

60

40

20

0

Focal length [mm]

2520151050Input voltage [Vpp]



Spherical aberration 9

2.0

1.5

1.0

0.5

0.0

Radial direction [mm]

50403020100Axial direction [mm]

Relationship between the focal point and the radial position of a ray for input voltage 21 Vpp

Typical curve for spherical aberration: the focal length decreases as the distance between the central axis and the radial position of the ray increases.



Captured images 10

High-speed camera Lens Resolutiontest target “Swallow”

10 mm

23 mm

Commercial lens

10 mm: test target23 mm: “swallow”Captured by a high-speed camera with a commercial lensON (20 Vpp) to OFF: (Change of the focal length from 10 to 23 mm)



Dynamic response 11

20 Vpp at t < 0, 0 Vpp at t > 0The transient motion of the lens surface was observed by M-mode OCTThe response time was 0.3 s.

0.3

0.2

0.1

0.0

-0.1

-0.2

Axial direction [mm]

0.50.40.30.20.10.0-0.1Time [s]

1 mm

0 s 0.01 s 0.05 s 0.1 s 0.3 s



Conclusions 12

A variable-focus optical lens that employs a viscoelastic material and acoustic radiation force was proposed.

The lens has a simple and thin structure and consists of a PZT ring and silicone gel.

The optical profile of the lens was investigated. The focal point could be controlled by varying the input voltage so that the lens acted as a variable-focus lens.

The response time was approximately 3.0 s. The lens response time depends on the viscoelastic properties of the gel. We intend to reduce the response time in future research.


3pOA03

Hideyuki Ikeda1, Tomoyuki Kugoh2, Sze Keat Chee 3,

Takeshi Yano3 and Takeshi Morita1

A Self-Sensing Piezoelectric Actuator for

the Auto-Focusing Application

1The University of Tokyo2Namiki Precision Jewel Co., Ltd.,

3Mechano Transformer Corporation

Outline

• Purpose of study

• Principle and basic experiments of self-sensing

using a bimorph piezoelectric actuator

• Practical application of self-sensing piezoelectric

actuator for an auto-focusing unit

• Conclusions

Purpose of study

Demonstrating the self-sensing control for a

practical application

Advantages:

– Simple system

– High accuracy

– Low cost

Principle and basic experiment of

self-sensing using bimorph actuator

Relationship between permittivity and displacement

Linearity between permittivity

and displacement was discovered

6

Domain change contribution

The domain structure is related to

permittivity AND piezoelectric displacement

Schematic diagram of permittivity detection

Relationship between piezoelectric

displacement and permittivity change

-70

-60

-50

-40

-30

-20

-10

0

10

0 5 10 15 20 25 30 35 40

Dis

pla

cem

ent

(m

)

Voltage (V)

-80

-60

-40

-20

0

20

-300 -200 -100 0 100 200D

isp

lace

men

t(u

m)

Reltive Permittivity

= 0.13m

Voltage-Displacement Permittivity-Displacement

Self-sensing control for a bimorph actuator

9

0

20

40

60

80

0 2 4 6 8 10

Dis

pla

cem

ent

(m

)

Time (sec) Accuracy was +/- 0.5%

Practical application of self-

sensing piezoelectric actuator for

the auto-focusing unit

Auto focusing unit with stacked piezo actuator

Manufactured by Namiki Precision Jewel Co. Ltd.

8.5mm×8.5mm×3.8mm

Lever mechanism of the auto-focusing actuator

Displacement of PZT：4μm

Displacement of the 1st lever：100μm

Displacement of 2nd(final) lever：300μm

1st magnification 2nd magnification

Requirements for the auto focusing actuator

⇒Self-sensing control is useful

• Stroke 200m

• Accuracy +/-5m

• Small enough to be installed in a mobile phone

• No space for positioning sensor

Demonstration of self-sensing control

•Move the auto-focusing actuator over the

range of 0m－200μm, with 40μm step

•Actual displacement is measured by a laser

displacement monitor

•Compare the result with open-loop control

Result of open-loop control

Maximum error > 20m

-40

0

40

80

120

160

200

240

0 2 4 6 8 10

Open loop control

Dis

pla

cem

ent(

m)

Tims(sec)

Out of requirement spec.

Target

positions

Admittance property of the actuator

0

1 10-7

2 10-7

3 10-7

4 10-7

5 10-7

6 10-7

7 10-7

-150

-100

-50

0

50

100

150

200

0 2 104

4 104

6 104

8 104

1 105

NMK10_No3_100kHz

Admttance

Phase

Adm

ttance

Phase(d

eg)

Frequency(Hz)

We chose 25kHz for permittivity monitoring

Displacement hysteresis of the actuator

-50

0

50

100

150

200

250

0.05 0.055 0.06 0.065 0.07 0.075 0.08D

ispla

cem

ent(

m)

Capacitance(F)

-50

0

50

100

150

200

250

-5 0 5 10 15 20 25 30

Dis

pla

cem

ent(

m)

Voltage(V)

V-D Hysteresis C-D Hysteresis

Capacitance-Displacement hysteresis is smaller than Voltage-

Displacement hysteresis

Self-sensing setup

By detecting permittivity change,

PID control was carried out.

Self-sensing control using permittivity detection

-40

0

40

80

120

160

200

240

0 2 4 6 8 10

Closed loop control

Dis

pla

cem

ent(

m)

Tims(sec)

-40

0

40

80

120

160

200

240

0 2 4 6 8 10

Open loop control

Dis

pla

cem

ent(

m)

Tims(sec)

Self-sensing control

-20

-15

-10

-5

0

5

10

15

20

0 2 4 6 8 10

Closed loop control

Dis

pla

cem

ent(

m)

Tims(sec)

20

25

30

35

40

45

50

55

60

0 2 4 6 8 10

Closed loop control

Dis

pla

cem

ent(

m)

Tims(sec)

60

65

70

75

80

85

90

95

100

0 2 4 6 8 10

Closed loop control

Dis

pla

cem

ent(

m)

Tims(sec)

100

105

110

115

120

125

130

135

140

0 2 4 6 8 10

Closed loop control

Dis

pla

cem

ent(

m)

Tims(sec)

140

145

150

155

160

165

170

175

180

0 2 4 6 8 10

Closed loop controlD

ispla

cem

ent(

m)

Tims(sec)

180

185

190

195

200

205

210

215

220

0 2 4 6 8 10

Closed loop control

Dis

pla

cem

ent(

m)

Tims(sec)

0μm 40μm 80μm

120μm 160μm 200μm

Self-sensing control using permittivity detection

(enlarged at each step)

The error at each step was within +/- 5m

Conclusions

• The self-control example with bimorph actuator

was introduced.

•We could control the auto-focusing actuator

with the accuracy of +/-5m over the range

of 0-200m when moving it 40m step.

•The error is related to the hysteresis between final

displacement and permittivity change.

Now, we are studying this phenomenon.

3pOA023pOA03

Control system for optics Session · P r e c i s i o n a n d I n t e l l i g e n c e L a b o r a t...

Documents

Transcript of Control system for optics Session · P r e c i s i o n a n d I n t e l l i g e n c e L a b o r a t...