adaptive-optics visual simulator (or adaptive-optics...
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Adaptive-optics visual simulator(or adaptive-optics phoropter)
Nicolas [email protected]
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.