Optical Engineering
Part 17: Human eye Herbert Gross
Summer term 2020 www.iap.uni-jena.de 2 Contents
. Introduction . data . Optical properties . Eye models . Resolution and quality . Diseases The Human Eye
Ref: Wikipedia The Human Eye
muscle outer skin
choroid conjunctiva membrane
front chamber fibres retina
rear chamber cornea macula pupil lens vitreous (yellow) body iris
tear liquid fibres
nerve conjunctiva
muscle blind spot The Human Field of View
. Ranges: < 10° central < 30° near peripheral < 60° mid peripheral . Black circle: blind spot
Ref: Wikipedia Optical Data of the Eye
Property relaxed accomodated Refractive power 58.63 dptr 70.57 dptr Focal length in air 17.1 mm 14.2 mm Power of the crystalline lens 19 dptr 33 dptr Pupil diameter, smallest value for high brightness 1.5 mm Pupil diameter, largest value for night vision 8.0 mm Abbe number (approx.) 50.23 Petzval radius -17.58 mm Location of entrance pupil -3.047 mm Field of view maximum 108° Field of foveated seeing 5° Diameter eye ball 24 mm Distance rotation point from cornea vertex 13.5 mm Nodal point location 7.33 mm Principal plane location 1.6 mm Eye Data - Overview
temporal . Terms posterior chamber . Sizes and lengths vitreous anterior humor chamber fovea
optical disc crystalline lens blind spot cornea lens capsule
7.33 mm iris retina 13.5 mm nasal
1.6 mm
1.8 mm 2.5 mm F C PP' NN' F' 4 mm
0.5 mm 1.8 mm 3.6 mm
3.6 mm 15.7 mm 24.4 mm Refractive Index
cornea crystalline lens lens capsule retina n anterior . Distribution of the index chamber vitreous humor 1.5
along z 1.45
. Smooth index variation 1.4 of crystalline lens 1.35 1.3
1.25
1.2
1.15
n 1.1 1.42 1.05 z 1 1.4 0 5 10 15 20 25 [mm]
1.38
1.36
1.34
1.32
z 1.3 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 [mm] Spectral Transmission of the Eye
. Absorption of the eye media prevents retina damage . Special truncation of UV and IR contributions
T [%] visible 100 after cornea before lens after lens 80 at retina
60
40
20
[nm] 0 300 400 500 600 800 1000 1400 2000 Receptors, rods and cones
. Cones : Fovea, bright light, colour . Rods : Peripheral, dim light, no colour . Blind spot :
no receptors Property cones rods . Fovea : 2° field Location in the fovea outside the fovea Field of view small, 5° large, 108° eccentric Resolution and visual acuity large small Brightness sensitivity small, for daylight vision large, vision at night Colour sensitivity yes no Total number of elements 5 million 120 million Limiting brightness 683 lm / W 1699 lm / W Spectral maximum 555 nm 507 nm
Range Diameter Cones Rods [mm] number :3500 Foveola 0.35 density 190000/mm2 no rods pitch 2.3 m density : 100000/mm2 Macula lutea Fovea 1.85 a few rods pitch : 3.2 m Prafovea 2.85 density : 160000/mm2 Perifovea 5.85 pitch : 2.5 m density : 5000/mm2 density : 50000/mm2 Periphery pitch : 14.0 m pitch : 4.5 m 4 mm off axis Papille, blind spot 1.8 no cones no rods nasal
Spectral Sensitivity of the Eye
. Spectral sensitivity of the eye: - Depends on brightness . Daylight / high brightness: cones, peak sensitivity at 550 nm . At night/ low Brightness: rods, peak sensitivity at 507 nm, shifted towards blue No color distinction
V() Log V() 10 0 1 night 0.9 day scotopic photopic 10-1 0.8 rods cones 0.7 10-2
0.6 10-3 0.5
0.4 10-4 0.3
0.2 10-5 0.1
0 400 450 500 550 600 650 700 750 400 450 500 550 600 650 700 750 cyan green Accomodation
. Change of accomodation range due to aging
D [dpt]
16
mean dpt 12
4 relaxed 8 eye 0 maximum
-4 minimum immobile point 4 -8 strongest accomodation -12 age [years] 0 0 20 40 60 80 0 20 40 60 age in years Adaptation
pupil diameter [mm]
. Aging effect on adaptation 8 . Aging effect on adaptation speed
rods 6
Log Ithresh [a.u.] kink of Helmholtz 4 8 rod mono- chromate cones 7 2 night blindness 6 0 0 20 40 60 age in years 5 80 years
4
50 years 3 30 years 17 years 2 time 7 10 20 30 40 [min] Gullstrand Model Eye
. Six media 30° . Crystalline lens with shell . Data for relaxed and accomodated eye 10° . Simple version : single crystalline lens 0°
486 nm 587 nm 656 nm
Relaxed Accomodated
Parameter Notation Value Value 0° Focal length object sided f [mm] 17.055 14.169 Focal length image sided f' [mm] 22.785 18.930 Refractive power F [dpt] 58.636 70.57 Location entrance pupil p [mm] 3.045 2.667 10° Location exit pupil p' [mm] 3.664 3.211 Principal point object sided P [mm] 1.348 1.772 Principal point image sided P' [mm] 1.602 2.086 Nodal point object sided N [mm] 7.078 6.533 Nodal point image sided N' [mm] 7.332 6.847 20° Length L [mm] 24.387
Resolution of the Eye
a) letter b) grating c) two points 5' 2' 1' . Resolution of the eye depends on the shape . The quantitative measure is given as angle
. Rough measure : 1' d) nonius e) binocular 5'' 10''
x'c = 75 m
c x
distance cones so = 250 mm
L = 22 mm Visual Acuity a) b)
. Recognition of simple geometrical a shapes : 3a
1. Landolt ring with gap 3a a 2. Letter 'E' 5a a . Blur of image on retina with distance
3a
distance 6.096 m
image height E 8.9 25 m mm eye block letter original blur : a/2 blur : a blur : 2a blur : 3a blur : 4a
3a Spectacles
. Correction of refraction error by spectacle lenses
. 1. Myopia : negative lens eye binocular
. 2. Hyperopia : positive lens eye binocular
Eye Diseases
. Four major defects
original a) refraction error b) glaucom
c) retina defects d) cataract