Transcript University of Latvia - EPS-12

University of Latvia
Trends in Physics, Budapest, Hungary
Electro-optical solution
for visual acuity and
contrast sensitivity modeling
Roberts Paeglis and Maris Ozolinsh
University of
Latvia, Dept. of
Optometry and
Vision Science
European
Comission
Centre of
Excellence
University of Latvia
Outline
• Light scattering in human eyes
• Electro-optic ceramics in an eye model
• “Single-pass”experiments
• “Double-pass”experiments
• Final remarks
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What happens in the eye?
During the lifetime, light scattering in
the human eyes increases 2 to 3 times
7 of 10 people over 65
have opacities in the
eye lens(es).
For 2 of the 7 opacities
cause problems,
the cataracts
Opaque eye lens
(B.Masters, 2001)
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Why modeling?
Modeling of light scattering could
promote understanding of physical
and physiological changes in the eye
In this way we could also assess the
limits of diagnostical methods without
a threat to harm or exhaust volunteers
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Where we are…
• Light scattering in human eyes
• Electro-optic ceramics in an eye model
• “Single-pass”experiments
• “Double-pass”experiments
• Final remarks
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We used PLZT….
PLZT ceramics is largely transparent for
the visible light. Applied electric field,
however, induces formation of polar
regions that cause considerable light
scattering
By changing the electric field that we
apply, we can vary the amount of
scattering induced
PLZT stands for Pb0.91La0.09Zr0.65Ti0.35O3
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To keep an eye on...
Scattering in the PLZT material
is sensitive to the changes in temperature
The increase of scattering is reversible
Golden electrodes are applied in tiny
islets on the surface. The plate with
electrodes has stronger absorption in the
blue spectrum. So does the cataract
in the human eye, however
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Where we are…
• Light scattering in human eyes
• Electro-optic ceramics in an eye model
• “Single-pass”experiments
• “Double-pass”experiments
• Final remarks
University of Latvia
Single-pass method... incoherent light
Resolution
test
PLZT
ceramics
& lens
Voltage
generator 1301
Microscope
& CCD
Microscopew
ithout the
ocular &
the CCD
without the
objective
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Single-pass method... laser source
PLZT
ceramics &
lens
Laser
(633 nm)
Double
slit
Voltage
generator
1301
Microscope
& CCD
Microscopew
ithout the
ocular & the
CCD
without the
objective
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As a result….
Changes in the quality of images
were observed starting from
E=5…7 kV/cm.
The range used
does not harm the PLZT
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Clinical applications
Alterations in intensity and contrast of
the digital images were registered.
At E=9 kV/cm the interference
patterns for the conventional “good
vision” (V=1.0 or 20/20) could be
resolved no more.
Evaluation of reliability and
comparison of diagnostic methods
could be made
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Changes can be visualised...
1
2
I
3
One bit scans of
interference images:
E=0; E=8.4 kV/cm;
E=9.0 kV/cm
Pixels
Interference patterns
are used in clinics to
evaluate the neural
functions of the eye
with a cataract
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Standard tests can be tried...
The system can visualize the
changes in contrast and intensity of
contrast sinusoids and bright
incoherently illuminated objects
(Vistech Consultants, Inc.)
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Where we are…
• Light scattering in human eyes
• Electro-optic ceramics in an eye model
• “Single-pass”experiments
• “Double-pass”experiments
• Final remarks
University of Latvia
Double-pass optical set-up
In collaboration with the Laboratory of
Optics, the University of Murcia, Spain
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Double-pass scheme
Eye
positioning
Focusing
system
L3
L4
M2
M3
CCD
Aperture
Laser
(543 nm)
Spatial
filter
L1
PLZT
ceramics
& lens
Voltage
1302
Courtesy of H.M.Bueno generator
M1
M4
L2
Beam
splitter
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The centre loses energy...
Intensity
distribution of
a point image
E=8,7
kV/cm
E=6,7
E=0
kV/cm
E=7,3
E=8,0
E=7,7
E=8,3
kV/cm
E=5,4
kV/cm
E=4,0
Electric field
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…higher spatial frequencies gain the energy
DP radial profile, arb.units
3500
- green laser beam
3000
1 - polarizer after the second pass
crossed to the polarization of
2500 2
the point source
2000
1500
E=0 kV/mm (1)
0.6 kV/mm (2)
0.73 kV/mm (3)
3
1000
500
0
0
20
40
60
80
100
120
Arc min (retina)
We can register the “migration” of energy to the tails...
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Light maintains polarisation...
DP radial profile, arb.units
3500
E = 0 kV/mm (1)
0.6 kV/mm (2)
0.73 kV/mm (3)
1
3000
2500
2000 2
1500
1000
3
- green laser beam
- polarizer after the second pass
parallel to the polarization of
the point source)
500
0
0
20
40
60
80
100
120
Arc min (retina)
Depolarisation of light in the model and the eye differ…
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Where we are…
• Light scattering in human eyes
• Electro-optic ceramics in an eye model
• “Single-pass”experiments
• “Double-pass”experiments
• Final remarks
Finis coronat opus
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In brief,
A device consisting of PLZT
ceramics, a +55.6 D lens, a
microscope and a CCD can visualize
the changes in images that are
caused by light scattering
Reliability and the limits of
interferometry diagnostics
can be studied
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Furthermore…
Interdependence of scattering and
ocular aberrations, and their impact
on the image can be explored with a
PLZT plate in the double-pass setup
Light of high energy can be used to
see the effects more profoundly
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However...
Resolution can be limited by high
aberrations of the optical device
(chromatic aberrations, coma), CCD
geometry and digital processing
Scattering effects are temperaturedependent
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Thank you!
HAVE I LEFT ANY
TIME
FOR QUESTIONS?
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