Transcript Slide 1

Improved Image Quality
in AO-OCT through
System Characterization
Samelia O. Okpodu
Vision Science and Adanced Retinal Imaging Laboratory, Department of
Ophthalmology & Vision Science, University of California, Davis
Mentor: Dr. Julia W. Evans
Faculty Advisor: Dr. John S. Werner
Additional Collaborators: Dr. Robert J. Zawadzki, Steve Jones,
Dr. Scot S. Olivier
Home Institution: Norfolk State University
Outline

Background

Data

Importance

Proof of Principle

AO-OCT vs. OCT

Conclusion &Future
Directions

My Research

Installation Process
2
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
http://www.99main.com/~charlief/theeyebg.gif
OCT B-Scan. UCD
3
OCT vs. AO-OCT
OCT
 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
4
UCD AO-OCT System
S-H
WFS
FarField
CCD
5
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
6
Installation Process

Proper components
 Machine

Optical Constraints
 Far

Shop
Field and WFS both require pupil planes
Mechanical/ Space Constraints
7
Installation Process
Pellicle Beamsplitters
Pupil Plane
26 cm
Spherical
Flat Mirror
Mirror
Input Fiber
Iris
Pupil Plane
•Proper space b/w CCD’s,
to avoid beam clipping.
•WFS & Far Field Lens
require a pupil plane.
lens
Pupil Plane
•Far Field has to be
located at the focal length
of the lens.
•Calibration mode used for
proof of principle.
8
Data

Types of Data


WFS
Far Field Data

Side by Side
comparisons

Proof of Principle
0.12 D neg. Cylinder
9
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
10
Proof of Principle: Aberrator

Plastic bag- simulates
higher order aberrations

Qualitatively similar

Would prefer quantitatively
similar
 Improved
by correlation or
re-sampling
11
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 AOOCT system.

Far Field Camera Software

Adjust optical design (ghost reflections)

Testing with model & human eye
12
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 6th
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 Science
and Technology Center for Adaptive Optics, managed by the University of
California at Santa Cruz under cooperative agreement No. AST - 9876783.
13
Element
measured
power (mW)
coupler
Light Budget

Light throughput is
always important
1.2
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
Transmitted Power ratio
(%) /Through
Bimorph DM
put (%)
S2
32% throughput in
original system; 29% in
current system
Pellicle 1
Pellicle 2
0.69
0.68
0.98
0.66
0.7
0.46
0.98
0.45
56 0.98
0.44
0.98
0.44
0.98
0.43
0.98
37.9
0.42
0.98
0.41
0.98
0.40
S10
0.98
0.39
Flat mirror
0.98
0.39
S4
MEMS
92
S6
75
69.1
0.45
90
51.9
Horiz scanner
S8
0.43
70
34.9
Vert scanner
Total input
to the eye
0.77
0.98
75
S7
MEMS
Power ratio
0.98
before Far
0.9
Field (%)
0.67
92
S5
Bimorph
DM
predicted
power (mW)
0.19
S3

Reflectivity/
Transmistivity
S9
Total to Eye
29
0.39
0.36
31.7
14
0.39
Extra Images
Aberrator Extras
15