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A High Speed MEMS Scannerfor 140-kHz SS-OCT
A High Speed MEMS ScannerA High Speed MEMS Scannerfor 140for 140--kHz SSkHz SS--OCTOCT
IEEE Int. Conf. on Optical MEMS and Nanophotonics,Istanbul, Turkey, Aug. 8-10, 2011
Keiji Isamoto, Kohki Totsuka, Toru Sakai, Takuya Suzuki, Atsushi Morosawa, Changho Chong
(Santec Corporation)Hiroyuki Fujita, Hiroshi Toshiyoshi
(The University of Tokyo)
This research is supported by Optoelectronic Industry and Technology Development Association (OITDA), subsidized by JKA through its Promotion funds from KEIRIN RACE.
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Power Supply(λ 1.5 µm)
Optical Fiber
Collimator
Photovoltaic Cell
Beam Splitter
Focal Lens
MEMS Scanner
OCT Probe(λ 1.3 µm)
10 mW, λ 1.5 µm, max 10 V
OCT Probe(λ 1.3 µm)
Tissue under Test
Electrical Interconnection
MEMS in OCT EndoscopeMEMS in OCT Endoscope
■ Powering at 1.5 µm■ OCT measurement at 1.3 µm
Optical MEMS 2008 Freiburg
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PC
AttenuatorOptical
Delay Line PolarizationController
BalancedDetector
Pre-Amplifier
DAQI/O InterfaceSynchronizer
WDM Coupler
Powering Light 1.5 um
Optical Circulator
Endoscope
OCT Probe 1.3 um
Delay Line Equalizer
Another MEMS in OCT TodayAnother MEMS in OCT TodayFast Scanner Slow Scanner
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High Coherence Source
Wavelength Scan(A Scan)
B Scan
A S
can
FFT
A S
can
!"#$%&'#(")*+$",,*-",().$*/0!
Advantage of SSAdvantage of SS--OCTOCT
Reference Arm
Sample Arm
!1",*2'34
Time-Domain OCT (TD-OCT) Swept-Source OCT (SS-OCT)
TD-OCT SS-OCTSensitivity dB ~ 90 dB ~ 110
Frame Rate fps 1 54Resolution µm 10~15 5~10
Fast and High-Resolution
cornea
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MEMS Scanner
Scanner
BeamExpander
DiffractionGrating
Gain ChipOutput
External Cavity Laser
SweptSwept--Source with MEMSSource with MEMS
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0
200
400
600
800
1000
1200
1400
0 20 40 60 80 100 120 140 160Scan Speed kHz
Fine
sse
(= B
andw
idth
/ FW
HM
)
OphthalmologyAxial Length
λ = 1 um∆λ = 20~40 nm
δλ = 0.02~0.03 nmf = 1~5 kHz
Dental λ = 1.3 um
∆λ = 100 nm δλ = 0.15 nm f = 30~100 kHz
IndustrialEndoscope
Vascular Inspection∆λ = 80~100 nm
δλ = 0.12 nmf = 40~100 kHz
Anterior Segmentλ = 1 um, ∆λ = 100 nm
δλ = 0.1 nm, f = 20~100 kHz
Retina Inspectionλ = 1 um, ∆λ = 100 nm
δλ = 0.1 nm, f = 50~140 kHz
2nd Gen. 3rd Gen.
MEMSScanner
R&D of OCT Light SourcesR&D of OCT Light SourcesHigher Resolution, Faster Imaging
PolygonScanner
Target : Over 100 kHz
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2DoF MEMS Scanner2DoF MEMS Scanner
Mirror
CombElectrodes
CombElectrodes
(a)
(b)
(c)
See (b)See (c)
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Mirror Mirror
Actuator ActuatorActuator Actuator
Hinge Hinge OuterHinge
OuterHinge
Inner Hinge
Frequency Frequency
Am
plitu
de
ActuatorPlate
MirrorLeverage
5 ~ 10 x
2DoF MEMS Scanner2DoF MEMS ScannerWith Angle Magnifying Mechanism
Co-developed by Epson and Santec in 2005M. Yoda, K. Isamoto, C. Chong, H. Ito, A. Murata, and H. Toshiyoshi, "Design and Fabrication of A MEMS 1-D Optical Scanner using Self-Assembled Vertical Combs and Scan-Angle Magnifying Mechanism," IEEE/LEOS Int. Conf. on Optical MEMS and Their Applications, August 1-4, 2005, Oulu, Finland. (oral B2)
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SOI (60 um)
Photoresist
BOX (4 um)
Substrate (400 um)
Aluminum (100 nm)
Photoresist
DRIE
DRIE
MirrorComb
ElectrodesComb
Electrodes
Stiction Assembly
(1)
(2)
(3)
Fabrication ProcessFabrication ProcessOnly Two Photolithography Steps
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2 ms / frame
3 mm
OCT with Conventional 35 kHzOCT with Conventional 35 kHz
100 µm
Poor Resolution ~ 50 µm
A-scan35 kHz
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100 µm
3 mm
2 ms / frameHigh Resolution ~ 10 µm
OCT of This Work 140 kHzOCT of This Work 140 kHz
A-scan140 kHz
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Experimental Results NoteScan Speed 140 kHz Round-Trip ScanBand Width 100 nm
1310 nm(in Air)
OCT Resolution 9 µmSpectrum Width 0.25 nm
Coherence Length 3 mmMaximum Power 20 mWDynamic Range 60 dB
Summary: High Speed OCTSummary: High Speed OCT
114 mm174 mm
75 mm
6.5 deg70 kHz70Vdc +/- 70Vac
MEMS Scanners for Both Endoscope Head and Light Source
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