6th International Workshop on Adaptive Optics for Industry and Medicine
Galway, June 2007
Development, calibration and
performance of an electromagnetic
mirror based adaptive optics
system for visual optics
Enrique Gambra, Lucie Sawides, Carlos Dorronsoro
Lourdes Llorente & Susana Marcos
Instituto de Optica, CSIC
Goal
Accommodative response
Impact of ocular aberrations
Rosales et al (2006) Journal of Vision 6, 1057-1067
Visual function
Motivation
• Aberrations may play a role in:
– Determining the direction of accommodation
• References: Chen et al (2006) JOSA 1, 1-8
Fernández and Artal (2005) JOSA 9, 1732-1738
– Differences in accommodative lag in
emetropes and myopes
• References: Mutti et al (2006) IOVS 3, 837-846
He et al (2005) Vision Research 45, 285-290
Motivation
• The role of ocular aberrations in vision
needs better understanding
Applications:
–in refractive and presbyopic corrections
–visual adaptation
–tolerance to blur
AO Set-up
Deformable mirror
SLD : 827 nm
Artificial
Pupil Camera
eye
Minidisplay
Badal
System
Hartmann-Shack
wavefront sensor
AO Set-up
• Hartmann-Shack Wavefront sensor :
HASO 32
Array of 32 x 32 microlenses
Imagine Eyes Haso 32
Maximum pupil diameter : 3.65 mm
AO Set-up
Magnetic deformable mirror
MIRAO32d
Number of actuators : 52
Effective diameter : 15 mm
Interval between actuator : 2.5 mm
Stroke : up to 50 microns
Bandwith : >200 Hz
Fernández et al (2006) Opt. Exp. 20, 8900-8918
Imagine Eyes MIRAO52d
deformable mirror
AO Set-up
• Other components:
– Source: SLD (λ = 827 nm, Pmáx = 2.5mW)
Superlum Ireland
– Stepping motor controller for Badal system:
VXM-1 Velmex
– Minidisplay 640x480
OLED screen for psychophysics
– Pupil camera. Teli, IC Imaging Control
Eye tracker
System calibration
System calibration
• Achromatic double lens + diffuser
• Artificial eye #2
Aberrations provided by
manufacturer (RMS microns)
–
–
–
–
–
Defocus : 5.17
Astigmatism : 0.83
Coma : 0.46
Spherical aberration : 0.17
Other : 0.01
System calibration
Mirror flatness
RMS =0.015 μm
Stability
up to 7th order
Astigmatism at 0º
Coma at 0º
Aberrations stability
1.2
rms (microns)
Spherical aberration
Variability(%)
1
0.8
Up to 7th order
0.3
0.6
Astgmatism at 0º
2.0
Coma at 0º
0.6
Spherical
0.3
0.4
0.2
0
0
0.5
1
1.5
t (h)
2
2.5
3
System calibration
Artificial eye #2:
Comparison with manufacturer data
Eye#2 aberrations
AO
Manufacturer
1
cofficient (microns)
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
Z2-2
Z2+2
Z3-3
Z3-1
Z3+1
Z3+3
Z4-4
Z4-2
Zernike aberration term
Z40
Z4+2
Z4+4
System calibration
Compensation: Artificial eye #2
Wavefront
RMS = 1.350 μm
PSF
RMS = 0.046 μm
Correction : 96.6 %
System calibration
Zernike coefficients before and after close loop correction
Before compensation
Compensation:
After compensation
1.8
96.6%
1.3
0.8
0.3
-0.2
Zernike aberration term
ta
l
To
+4
Z4
+2
Z4
0
Z4
-2
Z4
-4
Z4
+3
Z3
+1
Z3
-1
Z3
-3
Z3
+2
Z2
-2
-0.7
Z2
coefficient (microns)
Eye#2
Measurements
Real eyes:
• Bite bar
• Natural viewing conditions
• Badal system compensating
defocus = 0D for subject
• 4 subjects
#1, age 35, sphere +1D
#2, age 25, sphere – 3.25D
#3, age 31, cylinder 2.0D
#4, age 36, sphere – 5.5D, contact lenses
Measurements
Wave aberrations (defocus corrected, 0D):
Subject #1:
rms=0.858μm
Subject #2:
rms=0.260μm
Pupil: 6.9mm
pupil: 5.0mm
Subject #3:
rms=2.542μm
Subject #4:
rms=0.907μm
pupil: 5.9mm
pupil: 5.7mm
Measurements
Close loop compensation. Subject #1
Wavefront
RMS = 0.710 μm
Pupil diameter: 6.6 mm
RMS =0.039 μm
Measurements
Close loop compensation.
Zernike coefficients
Real eye aberrations
Subject #1
Compensation:
94.5%
0.4
0.2
Without compensation
With compensation
0.1
0
-0.1
-0.2
-0.3
Aberration
Z4
0
Z4
+2
Z4
+4
To
ta
l
-0.4
Z2
-2
Z2
+2
Z3
-3
Z3
-1
Z3
+1
Z3
+3
Z4
-4
Z4
-2
rms (microns)
0.3
Measurements
Close loop compensation.
Total aberrations
1.4
witout correcting
1.2
rms (microns)
with correction
1
0.8
0.6
0.4
0.2
0
S1
Pupil diameter = 4.8 mm
S2
S3
S4
Measurements
Close loop compensation.
Different accommodative demands
Eye aberrations
Subject #1
rms (microns)
0.500
Without compensation
With compensation
0.400
0.300
0.200
0.100
0.000
-1
0
1
2
3
4
Accommodative demand (D)
Pupil diameter = 4.8 mm
5
6
Measurements
Effect of aberrations on accommodative response
• 0D, 3D and 5D accommodative demand
measurements
– All aberrations
– Compensating all aberrations for 0D
– Inducing spherical and residual defocus for 0D
Measurements
Accommodative lag
Accommodative response (D)
7
real behaviour
6
ideal behaviour
5
4
3
2
1
0
0
1
2
3
4
Accommodative demand (D)
5
6
7
Measurements
S#1, Age: 35
Accommodative effort Vs estimulus
Accommodative response (D)
Sphere: +1D
6
total aberr.
5
wo 0D aberr. CD
4
w 0D def&spher CD
3
2
1
0
0
1
2
3
4
5
Accommodative demand (D)
S#1 show worse response for the higher accommodative demand when spherical
aberration is induced
6
Measurements
S#2, Age: 25
Accommodative effort Vs estimulus
Accommodative response (D)
Sphere: - 3.25D
6
Total aberr. JC
5
wo 0D aberr. JC
4
w 0D def&spher JC
3
2
1
0
0
1
2
3
4
5
Accommodative demand (D)
S#2 takes advantage of both correcting all aberrations and keeping spherical
aberration free
6
Measurements
S#3, Age: 31
Accommodative effort Vs estimulus
Sphere: - 2.25D
Accommodative response (D)
Cylinder:
6
Total aberr. CM
5
wo 0D aberr. CM
4
w 0D def&spher CM
3
2
1
0
0
1
2
3
4
Accommodative demand (D)
S#3 also takes advantage of both correcting all aberrations and keeping
spherical aberration without compensation
5
6
Measurements
S#4, Age: 37
Accommodative effort Vs estimulus
Corrected with contact
lenses
Accommodative response (D)
Sphere: - 5.5D
6
Total aberr. SM
5
wo 0D aberr. SM
4
w 0D def&spher SM
3
2
1
0
0
1
2
3
4
Accommodative demand (D)
However, S#4’s better response occurs with his own aberrations
5
6
Measurements
Spherical aberration
Spherical aberration (μm)
Spherical aberration Vs estimulus. S#1
0.2
total aberr. CD
0.15
wo 0D aberr. CD
w 0D def&spher CD
0.1
0.05
0
-0.05
-0.1
0
1
2
3
4
5
Accommodative demand (D)
6
Measurements
Spherical aberration (μm)
Spherical aberration Vs estimulus. S#2
0.2
0.15
Total aberr. JC
wo 0D aberr. JC
0.1
0.05
w 0D def&spher JC
0
-0.05
-0.1
-0.15
-0.2
0
1
2
3
4
Accommodative demand (D)
5
6
Measurements
Visual Experiments
Thru – Luminance visual Acuity: Snellen E
• High resolution and high brightness minidisplay (LiteEye)
• Optical bench with badal system
(changes vergence without affecting the magnification).
• 4 alternative forced choice paradigm (Snellen E)
• QUEST algorithm for threshold estimation using Psychtoolbox + MatLab.
• Stimulus: One E each 0.5 seconds.
• 50 trials per luminance position (Using neutral density filters).
• With and without adaptive optics correction
Brainard, D. H., Spatial Vision 10:433-436 (1997)
Pelli, D. G., Spatial Vision 10:437-442 (1997)
Thru – Luminance Visual Acuity
Natural
Subject 1
Corrected (AO)
1.2
1.1
VA (log mar)
1
0.9
0.8
0.7
0.6
0.5
0.01
0.1
Luminance level (arbitrary units)
1
Conclusions
• A new AO system has been presented
• We have calibrated the system with two artificial
eyes
• We have achieved a close loop compensation
higher than 90% in both artificial and real eyes
• Some subjects seem to use some aberrations
clues (spherical) for better accomodating, while
others take advantage of correcting their
aberrations to focus more accurately.
• Phycophysics…
Future work
• To evaluate the effects of the aberrations on visual
performance
• Test relationships between optical & visual quality
• To evaluate the effects of dynamic aberrations on
accomodation
• Simulation of refractive and multifocal corrections