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Adaptive-optics visual simulator(or adaptive-optics phoropter)

Nicolas Chateaunchateau@imagine-eyes.com

The "crx" projet team

Imagine Eyes F. Harms, E. Lavergne, J. Legrand, X. Levecq, F. Martins

Observatoire de Paris L. Vabre

Laboratoire d'AstrOphysique de Grenoble J. Charton

Clinique de la Vision J.L. Nguyen Khoa

Imaging through the earth atmosphere

Blur and speckle

Perfect optical medium

Earth atmosphere= turbulent,

aberrated medium

Diffraction-limited image

Aberrations => LOWER RESOLUTION

Observer

The adaptive-optics loop

Correctwavefront using

deformable optics

Measureresidual wavefront

using a sensor

Calculate control parameters

Real-time adaptive-optics imaging

AOON

AOOFF

OFFON

Observation of the moon surface

No football field on the moon

AO

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Imaging through the eye

Wavefront Aberrations

Resolution (acuity) = a critical performance criterionImperfect optical media (aberrations)Wavefront Aberrations change with timeObservation is impaired in both ways

Adaptive-optics retinal imaging

Adaptive-optics retinal imaging Adaptive-optics visual simulation

AO visual simulator= AO phoropter

= an ophthalmic instrument able to:

+ Deformablemirror

WavefrontAberrometer

= AO visual simulator

Visual stimulusdisplay+

•Manipulate and control ocular wavefront aberrations

•Subjectively assess visual performance in the presence of user-defined aberration

Functions:Wavefront measurementWavefront correctionWavefront generationPsychophysical testing

Potential applications

ResearchExplore the visual neuro-sensor systemwithout the limitations set by ocular aberrationsMeasure the effects of aberrations on visual performance

Ophthalmic industry R&DDevelop improved optical designs

DiagnosisSame as an aberrometerAmblyopia

Prescription and treatmentCustom-wavefront optics and surgeryOptimized presbyopic corrections

Objectives of the crx project

Adaptive-optics implementation Very Large Telescope

Development of an AO visual simulator for:

- Research

- Clinical use

Technical challenges:

- Miniaturization

- Compatibility witha wide variety of eyes

- Low voltage

- Reduced cost

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Design principles

Pupiltracker

Badalsystem

Deformablemirror

Wavefrontsensor

IRdiodes

Microdisplay

Visual stimulation

Design principles

Pupiltracker

Badalsystem

Deformablemirror

Wavefrontsensor

IRdiodes

Microdisplay

Measurementand dynamic

correction

Design principles

Pupiltracker

Badalsystem

Deformablemirror

Wavefrontsensor

IRdiodes

Microdisplay

Static aberrationcorrection and

generation

Main technology components

Shack-Hartmann wavefront sensorWide measuring range – ex. astigmatism 0 to more than 10 DHigh precision – ex. higher-order wavefront repeatability < 0.05 µmResolution 220 µm (1024 samples)

Organic LED microdisplay800 x 600 pixels, luminance up to 400 cd/m-2

Deformable mirror = the most critical componentDevelopment of a new electromagnetic deformable mirror

Electromagnetic deformable mirror: principle

V1 V2

V3 V4 V7 V8

Adjustable current supply

Mini-coil array

Mini-magnet array

Flexiblemembrane

LIGHT

Electromagnetic deformable mirror: layer structure

Flexible membrane

Mini-coil array

Connectionboard

Mini-magnet array

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Electromagnetic deformable mirror: mirao52d version

52 actuators

Effective diameter: 15 mm

Overall size : 66 mm

Voltage range: -1.0 to +1.0 V

Electromagnetic deformable mirror: test setup

Flat mirror

Conjugation lens

Circularaperture

Collimation lens

Beam splitter

Beam splitter

Microscope lens

Wavefront sensor

Laser diode

CCD camera

Deformable Mirror

+ 0.5 V

- 0.5 V

Electromagnetic deformable mirror: linearity

R2 = 0.9981

R2 = 0.9981

0

5

10

15

20

25

30

-1.1 -0.9 -0.7 -0.5 -0.3 -0.1

(V)

R2 = 0.9999

R2 = 0.9995

0

5

10

15

20

25

30

0 0.2 0.4 0.6 0.8 1 (V)

(µm)

RMS

PV PV

RMS

Electromagnetic deformable mirror: time characteristics

Typical Bode diagram:

Phase (d°)

Frequency (Hz)

Bandwidth: 250 Hz

Gain

Electromagnetic deformable mirror: surface quality

When actively flattened:

Surface quality = 0.006 µm RMS

Wavefront quality = 0.012 µm RMS

Integration in a AO visual simulator

Size = similar to that ofa regular aberrometer

Field of view = 2.0 x 1.5°

Pixel size = 0.15 arcmin

CRX1

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Dynamic ocular wavefront correction (closed-loop)

Residual RMS error : between 0.04 and 0.1 µm (6 mm pupil)

Static ocular wavefront correction

Residual RMS error :between 0.06 µm and…much more !

Correction quality strongly depends on centering

Static wavefront correction : first VA results

Eye LH OS NC OD GM OD AR OS

Rx 4.25 (-0.50) 78°

-0.25(-1.25) 162°

+1.50(-3.50) 172°

+0.75(-0.50) 97°

VA sphere correction 1.22 1.37 0.84 1.10

VA wavefront correction 1.89 2.12 1.92 2.11

Pure Zernike mode generation

Residual RMS wavefront errorUsing 20% of the dynamic range : < 0.020 µm

Range of Zernike aberrations generated in an artificial eye:

2nd order: -18 to 18 µm PV

3rd order: -10 to 10 µm PV

4th order : -6 to 6 µm PV

Range of astigmatism in a 6 mm pupil: 0 to 4 D

Pre-testing presbyopic corrections

Simulation of progressive / multifocal designs

Pre-op assessment of through-focus visual performance

FAR Intermediate NEARVisual target

vergence

-2.0

-1.0

0.0

+1.0

+2.0

CONCLUSION

The first AO ophthalmic device that combines:• Compact size• Compatibility with a wide variety of eyes• Electrical safety (low voltages)

Based on a new technology: electromagnetic deformable mirror

A clinical application: allow patients to preview the outcome of laser procedures and complex lenses.

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Credits (retinal images)J.F. Le Gargasson (CHNO XV-XX, Paris)F. Lacombe, M.Glanc (Observatoire de Paris)

Thanks