Transcript Presentation

SARATOV FALL MEETING – SFM’2015
International Symposium “Optics and Biophotonics – III”
September 22 – 25, 2015
Saratov, Russia
METHOD FOR DEFOCUS CORRECTION
IN OPTICAL COHERENCE MICROSCOPY
Dmitry Lyakin1, Anton Sdobnov2, Vladimir Ryabukho2,1
1Institute
of Precision Mechanics and Control, RAS, Russia
2Saratov
State University, Russia
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CONTENT OF PRESENTATION
• Optical Coherence Microscopy
• Defocus Problem
• Known Methods for Defocus Correction
• Main Idea of Presented Method
• Experimental Setup
• How Does It Work
• Experimental Results
• Conclusions
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OPTICAL COHERENCE MICROSCOPY (OCM)
OCM = Optical Coherence Tomography (OCT) +
+ High-Numerical Aperture (High-NA) Optics
Single-point OCM
•Low temporal coherence (broadband) light
•High spatial coherence (point) source
•Point photodetector
•En-face imaging by point-by-point object scanning
[1] J.A.Izatt, M.R.Hee, G.M.Owen, E.A.Swanson, J.G.Fujimoto,
Optical coherence microscopy in scattering media //
Optics Letters,1994, Vol.19, No.8, p.590-592.
Fig.1. Fiber single-point optical coherence microscope (from [1]).
Full-field OCM
•Low temporal coherence (broadband) light
•Low spatial coherence (extended) source
•Area camera as photodetector
•En-face imaging by single z-scan
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[2] A. Dubois, L. Vabre, A.-C. Boccara, E. Beaurepaire,
High-resolution full-field optical coherence tomography with a Linnik
microscope // Applied Optics, 2002, Vol.41, No.4, P.805-812.
Fig.2. Linnik-type full-field optical coherence microscope (from [2]).
DEFOCUS PROBLEM
Optical Coherence Tomography (OCT) Signal
zOCT  d  ngroup
d – geometrical thickness;
ngroup≈n(λ0) - λ0δn/δλ – group
refractive index
Confocal Microscopy (CM) Signal
zCMpar  d 
nim
n
n=n(λ0) – phase refractive index of
object medium; nim=nim(λ0) – phase
refractive index of immersion
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Fig.3. Degradation of the signal of an Otical Coherence Microscope from the depth of the two layer object
(microscope cover glass + air gap between glass and metal mirror) at increasing NA
KNOWN METHODS FOR DEFOCUS CORRECTION
Extending Depth of Focus
J. Ojeda-Castaneda, L.R. Berriel-Valdos, Zone plate for arbitrarily high focal depth // Applied Optics, 1990, Vol.29, No.7, P.994-997.
E.R. Dowski, Jr., W.T. Cathey, Extended depth of field through wave-front coding // Applied Optics, 1995, Vol.34, No.11, P.1859-1866.
Z. H. Ding, H. W. Ren, Y. H. Zhao, J. S. Nelson, and Z. P. Chen, High-resolution optical coherence tomography over a large depth range
with an axicon lens // Optics Letters. 2002, Vol.27, No.4, P.243–245.
R.A. Leitgeb, M. Villiger, A.H. Bachmann, L. Steinmann, T. Lasser, Extended focus depth for Fourier domain optical coherence microscopy //
Optics Letters, 2006, Vol.31, No.16, P.2450-2452.
K. S. Lee and J. P. Rolland, Bessel beam spectral-domain high-resolution optical coherence tomography with micro-optic axicon providing
extended focusing range // Optics Letters, 2008, Vol.33, No.15, P.1696–1698.
A. Zlotnik, Y. Abraham, L. Liraz, I. Abdulhalim, Z. Zalevsky, Improved extended depth of focus full field spectral domain Optical Coherence
Tomography // Optics Communications, 2010, Vol.283, P.4963-4968.
Numerical Correction
S. Labiau, G. David, S. Gigan, A.C. Boccara, Defocus test and defocus correction in full-field optical coherence tomography // Optics Letters,
2009, Vol.34, No.10, p.1576-1578.
A.A. Grebenyuk, V.P. Ryabukho, Numerical correction of coherence gate in full-field swept-source interference microscopy // Optics Letters,
2012, Vol.37, P.2529-2531.
Mechanical Adjustment of Optical Elements
J.M. Schmitt, S.L. Lee, K.M. Yung, An optical coherence microscope with enhanced resolving power in thick tissue // Optics Communications,
1997, Vol.142, P.203–207.
A. Dubois, G. Moneron, C. Boccara, Thermal-light full-field optical coherence tomography in the 1.2 μm wavelength region //
Optics Communications, 2006, Vol.266, Iss.2, P.738-743.
J. Binding, J. Ben Arous, J.-F. Léger, S. Gigan, C. Boccara, L. Bourdieu, Brain refractive index measured in vivo with high-NA defocus-corrected
full-field OCT and consequences for two-photon microscopy // Optics Express, 2011, Vol.19, No.6, P.4833-4847.
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Fig.4. Adjustment of axial position of microscope objective in object arm of an optical coherence microscope
to overlap coherence and focal planes (gates) (from[3])
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[3] A. Dubois, G. Moneron, C. Boccara, Thermal-light full-field optical coherence tomography in the 1.2 μm wavelength region //
Optics Communications, 2006, Vol.266, Iss.2, P.738-743.
MAIN IDEA OF PRESENTED METHOD
USAGE OF ILLUMINATING INTERFEROMETER AS LIGHT SOURCE
FOR AN OPTICAL COHERENCE MICROSCOPE
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EXPERIMENTAL SETUP
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HOW DOES IT WORK
Interference peak (2) from the rear plane of a single-layer object in the signal of an interference
microscope arising at
z  zCM
and posses its maximal value when the shift Δz1 of the mirror M1 of illuminating interferometer
from its zero path length position becomes equal to the value δzcomp
zcomp  zOCT  zCM
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EXPERIMENTAL RESULTS
Fig.5. Experimental results obtaned at single-laer object measurement
SLD: λ0=0.831 μm, Δλ=16 nm
Microscope objective lenses: LOMO® SHP-OPA-20-50, 20x, NA=0.50, ∞/0
Object: Menzel-Gläser® microscope cover slip #1 (Shott ® D263 glass), d=145±1 μm, n(λ0)=1.517,
nim(λ0)=1
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CONCLUSIONS
We have presented the method for correction of defocus in an optical
coherence microscope caused by mismatch of the refractive index of a
layered object and immersion and leading to degradation of the interference
signal from the depth of the object. This method is based on the usage of an
illuminating low-coherence interferometer as a light source for the optical
coherence microscope. We have demonstrated experimentally that we are
able to compensate this index-induced defocus creating corresponding
optical path difference in arms of illuminating low-coherence interferometer.
This method can be applied for defocus correction in commercially available
interference microscopes which construction does not allow moving optical
parts within microscope, for example such as Mirau microscopes. This
method can also be used to simultaneous determination of geometrical
thickness and refractive index of an object becouse the two quantities δzCM
and δzcomp are obtained experimentally.
THANK YOU
FOR YOUR ATTENTION!!!
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