Trends in Physics, Budapest, Hungary

University of Latvia

Trends in Physics, Budapest, Hungary

Electro-optical solutionElectro-optical solution for visual acuity and for visual acuity and

contrast sensitivity modelingcontrast sensitivity modelingRoberts Paeglis and Maris Ozolinsh

University of Latvia, Dept. of Optometry and Vision Science

EuropeanComissionCentre 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

University of Latvia

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)

What happens in the eye?

University of Latvia

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

Why modeling?

University of Latvia

• Light scattering in human eyes

• Electro-optic ceramics in an eye model

• “Single-pass”experiments

• “Double-pass”experiments

• Final remarks

Where we are…

University of Latvia

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

We used PLZT….

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Scattering in the PLZT materialis sensitive to the changes in temperature

The increase of scattering is reversible

Golden electrodesGolden 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

To keep an eye on...

University of Latvia

• Light scattering in human eyes

• Electro-optic ceramics in an eye model

• “Single-pass”experiments

• “Double-pass”experiments

• Final remarks

Where we are…

University of Latvia

1301

PLZT ceramics

& lens

Voltagegenerator

Microscopewithout the ocular & the CCD without the objective

Resolution test

Microscope& CCD

Single-pass method... incoherent light

University of Latvia

1301

Laser(633 nm)

Double slit

PLZT ceramics &

lens

Voltagegenerator

Microscopewithout the ocular & the CCD without the objective

Microscope& CCD

Single-pass method... laser source

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Changes in the quality of images were observed starting from

E=5…7 kV/cm.

The range used does not harm the PLZT

As a result….

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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

Clinical applications

University of Latvia

1

I

Pixels

2

3

One bit scans of interference images: E=0; E=8.4 kV/cm;E=9.0 kV/cm

Changes can be visualised...

Interference patterns are used in clinics to evaluate the neural functions of the eye

with a cataract

University of Latvia

The system can visualize the changes in contrast and intensity of

contrast sinusoids and bright incoherently illuminated objects

(Vistech Consultants, Inc.)

Standard tests can be tried...

University of Latvia

• Light scattering in human eyes

• Electro-optic ceramics in an eye model

• “Single-pass”experiments

• “Double-pass”experiments

• Final remarks

Where we are…

University of Latvia

Double-pass optical set-up

In collaboration with the Laboratory of Optics, the University of Murcia, Spain

University of Latvia

ApertureL2M4

L1Spatialfilter

Laser(543 nm)

Beam splitter

M3 M1

M2

Focusing system

CCD

L4 L3

Eyepositioning

1302Voltage

generator

PLZT ceramics & lens

Double-pass scheme

Courtesy of H.M.Bueno

University of Latvia

E=8,7 kV/cmE=8,7 kV/cmE=8,3 kV/cmE=8,3 kV/cmE=8,0 kV/cmE=8,0 kV/cmE=7,7 kV/cmE=7,7 kV/cmE=7,3 kV/cmE=7,3 kV/cmE=6,7 kV/cmE=6,7 kV/cmE=5,4 kV/cmE=5,4 kV/cmE=4,0 kV/cmE=4,0 kV/cmE=0 kV/cmE=0 kV/cm

The centre loses energy...

Intensity distribution of a point image

Electric field

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0 20 40 60 80 100 1200

500

1000

1500

2000

2500

3000

3500D

P r

adia

l pro

file,

arb

.uni

ts

- green laser beam- polarizer after the second pass crossed to the polarization of the point source

0.73 kV/mm (3)0.6 kV/mm (2)E=0 kV/mm (1)3

2

1

Arc min (retina)

We can register the “migration” of energy to the tails...

…higher spatial frequencies gain the energy

University of Latvia

0 20 40 60 80 100 1200

500

1000

1500

2000

2500

3000

3500D

P r

adia

l pro

file,

arb

.uni

ts

- green laser beam- polarizer after the second pass parallel to the polarization of the point source)

E = 0 kV/mm (1) 0.6 kV/mm (2) 0.73 kV/mm (3)

3

2

1

Arc min (retina)

Depolarisation of light in the model and the eye differ…

Light maintains polarisation...

University of Latvia

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

University of Latvia

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

University of Latvia

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

Furthermore…

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Resolution can be limited by high aberrations of the optical device

(chromatic aberrations, coma), CCD geometry and digital processing

Scattering effects are temperature-dependent

However...

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HAVE I LEFT ANY TIMETIME

FOR QUESTIONS?

Thank you!

University of Latvia