Control system for optics Session(1:00 ~ 1:45, Wednesday 25th April)
Control system for optics Session(1:00 ~ 1:15, Wednesday 25th April)
3pOA01No file submission
Control system for optics Session(1:15 ~ 1:30, Wednesday 25th April)
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
Prec i s ion and Intelligence Laborat
oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN
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
Prec i s ion and Intelligence Laborat
oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN
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
Prec i s ion and Intelligence Laborat
oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN
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
Prec i s ion and Intelligence Laborat
oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN
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’
Prec i s ion and Intelligence Laborat
oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN
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
Prec i s ion and Intelligence Laborat
oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN
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]
Prec i s ion and Intelligence Laborat
oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN
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.
Prec i s ion and Intelligence Laborat
oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN
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)
Prec i s ion and Intelligence Laborat
oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN
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
Prec i s ion and Intelligence Laborat
oryP&IIWPMA 2012, 22nd-25th Apr. 2012, Hirosaki JAPAN
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.
Control system for optics Session(1:30 ~ 1:45, Wednesday 25th April)
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
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