improved image quality in ao-oct through system characterization samelia o. okpodu vision science...
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Improved Image Quality in AO-OCT through System Characterization
Samelia O. OkpoduVision Science and Adanced Retinal Imaging Laboratory, Department of
Ophthalmology & Vision Science, University of California, DavisMentor: Dr. Julia W. Evans
Faculty Advisor: Dr. John S. WernerAdditional Collaborators: Dr. Robert J. Zawadzki, Steve Jones,
Dr. Scot S. OlivierHome Institution: Norfolk State University
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Outline
Background
Importance
AO-OCT vs. OCT
My Research
Installation Process
Data
Proof of Principle
Conclusion &Future Directions
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Background-What is OCT?
Optical Coherence Tomography (OCT) In vivo imaging technique Diagnosis and monitoring treatment of human retinal diseases OCT permits us to see retinal layers
OCT B-Scan. UCD
http://www.99main.com/~charlief/theeyebg.gif
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OCT vs. AO-OCTOCT Allows rapid acquisition of
cross sectional retinal images.
Volumetric reconstruction of retinal structures with micrometer axial resolution.
AO-OCT Improves lateral resolution.
3 microns in all directions.AO-OCT Reconstruction. UCD
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UCD AO-OCT SystemS-H WFS
Far-Field CCD
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My Research
Installing a Far-Field Camera
Proof of principle testing (basic system testing)
Measured errors which affect OCT image quality Used wavefront measurements to simulate the PSF Used the far field camera to measure the PSF
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Installation Process
Proper componentsMachine Shop
Optical ConstraintsFar Field and WFS both require pupil planes
Mechanical/ Space Constraints
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Installation Process
Input Fiber
SH WFS
(14x14cm
)
Far Field
CCD
(14x14cm
)
Pellicle Beamsplitters
Iris
lens
26 cm
•Proper space b/w CCD’s, to avoid beam clipping.
•WFS & Far Field Lens require a pupil plane.
•Far Field has to be located at the focal length of the lens.
•Calibration mode used for proof of principle.
Pupil Plane
Pupil Plane
Pupil PlaneSpherical MirrorFlat Mirror
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Data
Types of Data WFS Far Field Data
Side by Side comparisons
Proof of Principle
0.12 D neg. Cylinder
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Proof of Principle: Defocus
Trial Lens: 0.12 D neg. defocus.
Amount of defocus and spot size are directly proportional.
Change in spot size Measured Simulated
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Proof of Principle: Aberrator
Plastic bag- simulates higher order aberrations
Qualitatively similar
Would prefer quantitatively similar Improved by correlation or
re-sampling
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Conclusion & Future Directions
Far Field Camera is installed and working in calibration mode.
Far Field data compares relatively well to the WFS data in calibration mode.
Understand Calibration Error
Investigate mitigation techniques to improve the performance of the AO-OCT system.
Far Field Camera Software
Adjust optical design (ghost reflections)
Testing with model & human eye
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Acknowledgements Dr. John S. Werner, UCD Dr. Julia W. Evans, UCD, LLNL Dr. Robert J. Zawadzki, UCDMC Center for Adaptive Optics Dr. Patricia Mead, NSU Dr. Demetris Geddis, NSU Dr. Arlene Maclin, NSU
References: R. J. Zawadzki et al., “Adaptive Optics- Optical Coherence Tomography: optimizing
visualization of microscopic retinal structures in three dimensions,”J Opt. Soc. Am. A /Vol. 24, No. 5 (2007)
J.W. Evans et al., “Characterization of an AO-OCT System,” Proceedings of the 6 th International workshop on adaptive optics for Industry and Medicine : University of Galway, Ireland, June 2007.
This work has been supported by the National Science Foundation Scienceand Technology Center for Adaptive Optics, managed by the University ofCalifornia at Santa Cruz under cooperative agreement No. AST - 9876783.
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Light Budget
Light throughput is always important
32% throughput in original system; 29% in current system
Elementmeasured power (mW)
Reflectivity/Transmistivity
predicted power (mW)
coupler 1.2 0.19 1.22
Collimation optics 0.98 1.20
achromatizing lens 0.98 1.17
aperture 0.85 1.00
pellicle 0.92 0.92
S1 0.87 0.98 0.90
Iris 0.78 0.87 0.78
S2 0.98 0.77
Bimorph DM 0.9 0.69
S3 0.67 0.98 0.68
S4 0.98 0.66
MEMS 0.7 0.46
S5 0.45 0.98 0.45
S6 0.98 0.44
Horiz scanner 0.98 0.44
S7 0.43 0.98 0.43
S8 0.98 0.42
Vert scanner 0.98 0.41
S9 0.39 0.98 0.40
S10 0.98 0.39
Flat mirror 0.98 0.39
Total to Eye 0.36 0.39
Transmitted (%)
Power ratio /Through put (%)
Power ratio before Far Field (%)
Pellicle 1 92 75 75
Pellicle 2 92 69.1
Bimorph DM
90 51.9 56
MEMS 70 34.9 37.9
Total input to the eye
29 31.7
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Extra Images
Aberrator Extras