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This is a presentation prepared for Arlon meeting, for the case if somebody have questions on Univer

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Title: This is a presentation prepared for Arlon meeting, for the case if somebody have questions on Univer


1
This is a presentation prepared for Arlon
meeting, for the case if somebody have questions
on University of Latvia as a partner of the
projecta) owerviev oin eventual UL
contribution,b) slides from a presentation
Electrically Controlled Eye Occluders in
Vision Science(to kind of obstacles to
simulate light scattering)c) info on ISSP on UL
(some sheets and internet access to info)d) a
scheme presented oin the University conference in
Riga this February, on the topic Vision in
unfavourable conditions.
2
Objectives.Studies of visual perception and
visual search of stimuli in unfavourable wieving
conditions. Optimizing stimuli spectral and size
characteristics for better recognition.Parameter
s to measure visual acuity, search
time, neural response.
3
Variable parameters environmental
illumination, weather (fog, rain) subjective
age, pathologies (cataract, eye aberrations
after refractive surgery)vision correction
appliances (goggles, filters)
4
Scheme of studies Stimuli characterization -
emission, reflection, colour
characteristics. Simulation of viewing
conditions indoors, using special
appliances simulating light scattering,
various illumination and glare conditions,
etc. Sudies of visual information reaching the
eye. Subjective psychophysical and objective
electrophysical response to the visual
stimuli.
5
Equipment available - Various type of
equipment to assess vision functions - PC
controled electrophysiology equipment
Neurosoft to control
electrically visual response EOG
(electrooculogramms), ERG (electroretinograms),
VEP visual evoked potentials)
- On Ocean Optics based developed
photospectrometer, to charecterize
colour coordinates of reflective stimuli.
- Fast eye tracker SMI.
6
Equipment valuable for further developments For
current measurements - Minolta (type)
videocolorimeter - Installation of the
darkroom facilities with controllable
illumination. - Upgrading of Ocean Optics
spectrometrer To develop modelling of visual
information transfer - Optical bench, set of
optical element to install optical measurements
scheems - Whitelaser - CCD (cooled)
camera
7
Electrically Controlled Eye Occluders in Vision
Science  Maris Ozolinsh Institute of Solid
State Physics University of Latvia
10th European Meeting on Ferroelectricity 3-8
August 2003 - Cambridge U.K.
8
Some slides from presentation
are following
9
perception and recognition
optical part of the eye - optics -
accomodation - iris function - vergence
neural response
  • depth sensation
  • can be also as
  • monocular -
  • acquired from
  • experience, or - true stereopsis
  • by correct
  • binocular
  • vision)

oculomotoric response - ensuring of correct
binocular correspondence
10
Experiments using obstacles with controllable
optical parameters allow to make easier visual
science studies minimizing trouble to find
subjects having various eye pathologies at
different development stages, thus avoiding also
a variety of systematic errors.What kinds of
results are obtainable, performing experiments
using an device with controllable optical
characteristics placed in front of the
eye?First, investigator is trying to look into
the eye, to see what is the influence of the
obstacle onto the retinal image. Secondly
objective measurements of the neural activity
using different diagnostic techniques. Thirds
psychophysical evaluation of different
characteristics of the subject visual response
(acuity, contrast sensitivity, colour
discrimination, stereovision threshold, etc.)
11
Image blurring control. - simulation of
artificial cataract Cataract develops
practically to all people with their age.
In the non-pathalogical cases that becomes
apparent as small changes in the
colour transfer, and in image resolution.
For pathological cases up to a full
loss of visual function,
curable by extraction of the cataract lens and
replacement with the
intraocular (IOL) lens. Other scientific
interests - how various degree of blurring
affects different aspects of visual response in
order to find subjective and objective criteria
for early cataract diagnostics. Problems size
effects and refractive indices differences of the
scatterers in the eye and in the artificial
cataract obstacle, wavelength dependencies of the
scattered light.
12
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13
Eye model with artificial cataractDiffraction
patterns at the retinal plane of the artificial
eye formed by a double slit (slit separation -
1mm, l 633 nm, corresponding angular
resolution - 2.2 arc min). E 0 (1) 8.4 kV/cm
(2) 9 kV/cm (3). Ozolinsh M, Lacis I, Paeglis
R, Sternberg A, Svanberg S, Andersson-Engels S,
and Swartling J. Electrooptic PLZT Ceramics
Devices for Vision Science Applications
Ferroelectrics 2002 273 131-136.
14
In other experiments in order to simulate
artificial cataract we used polymer dispersed
liquid crystal (PDLC) cell scattering light
when non activated, transparent when voltage
applied
15
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16
Spectral characteristics of attenuation of
directly transmitted light through PDLC cell
17
Visual acuity screen depicted with a CCD camera
(f 18 mm) - left side with one PDLC cell in
front of camera lens (U 0 V) - right side
without PDLC
B blue
G green channel
R red channel of RGB picture
18
Time dependencies of CRT visual stimuli
intensities looking through the PDLC cell
obtained by scanning CCD pictures of CRT. Applied
sinusoidal 30V voltage (30 Hz) makes the cell
transparent. Blue phosphor is attenuated at the
highest degree, besides it has the fastest
emission decay, that is observable within the
area where electron beam scans screen when CCD
shutter is closed.
19
Eye visual performance tests various colour
Landolt C visual acuity optotype, and screen for
displaying colour contrast sensitivity test
stimuli
20
Dependence of the PLDC cell transmittance vs.
applied AC voltage, and corresponding visual
acuity of human eye looking through the cell on
various colour visual acuity charts
21
Eye retina Distribution of L cones (red), M cones
(green) and S cones (blue) within the central
part of fovea. One can see the lack of S cones
in the middle and greater distance between S
cones as compared with M and L cones.
Spectral sensitivity of cones (linear and log
scales) Smith Pokorny Cone sensitivity curves
(1975).
22
Visual evoked potentials, when red-black (a) and
green-black (b) check board reversals are
demonstrated (monocular) through PLDC cell with
different AC voltage applied. Two maxima -
negative N80 and positive P100 occur with delay
ca. 80 and 100ms, respectively, after stimuli
reversal. VEP amplitude (the potential
difference between two maxima points) decreases
at higher scattering extent (c) for red (curve 1)
and green (curve 2) stimuli.
23
European Center of ExcellenceKengaraga
Str.8Riga 1063LatviaTel. 371-7187816, Fax
371-7132778www.cfi.lu.lv www.cfi.lu.lv/cfi.pdf
http//tiger.cfi.lu.lv/optometry/http//www.cfi.
lu.lv/optometry/lab_opt_materials.pdf
24
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25
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26
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27
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28
Nedaudz par temu Redze nelabveligos
apstaklos Maris Ozolin Latvijas Universitates
Optometrijas nodala
Latvijas Universitates gada konference Optometrist
u un optiku asociacijas seminars 14. Feb. 2004.
29
oferi
30
? is subjecs response similar in all kind of fog
and all kind of simulation
subjective response to stimuli in real fog and
simulations
physical parameters of the stimuli image
transformation
Real static stimulus
real fog migla
fog chamber
PC simulated static or dynamic
stimuli
(portable) fog simulator
set of the best subjective response criteria
fog simulator
?
subjects response
autodrom for youngs and adults and researchers
optical filter
31
subjektu reakcija uz stimuliem
fizikalie attela transformacijas
parametri
reals statisks stimuls
ista migla
datora simulets statisks vai dinamisks
stimuls
miglas maja
subjektivo kriteriju kopums
miglas simulators
miglas simulators
?
subjektu reakcija
autodroms bernu un pieauguo
optiskais filtrs
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