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