ppthumanvision[1]

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Human Vision


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Innovation training Philips 2004 2

Human Vision - Overview

Why talk about the human vision system ?

Structure of the eye

Illusions

Other effects (glare, adaptation)

Age defects

Experiences


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White light and colors

Colors exist in the brain !

80

60

40

20

0

400 500 600 700nm

Human Vision

The Eye

Visual Perception


4/25Innovation training Philips 2004 4

Excellent road illumination ... without glare

AFS (adaptive front lighting system) is next step !

That means: take care of lighting to see !



5/25Innovation trainingPhilips 2004 5


Eyeball and

musculature

Image-forming on the retina



ciliary muscle

iris

cornea

pupil

anterior

chamber

lens

sclera

choroid

retina

Fovea centralis(yellow spot)

optic nerve

vitreouschamber

blind spot

Cross-section through the eye




0,2

wavelength (nm)

Rel.Auge

nempfindlichkeit

400

0

0,4

0,6

0,8

1,0

500 600 700

555 nm507 nm

Cones:

Day-time vision (photopic)

Central field of view

Perception of details Color sensitive (RGB)

Rods:

Night-time vision (scotopic)

Peripheral field of view

Detection of movementsand changes

Not color sensitive

CIE standard-

Eye-sensitivity curves

ConesRods

more whitish light (i.e. more blue in spectrum) improves night-time vision !




Structure of the eye - DETAILS

Cones in the fovea, each

with a single-lineconnection

Rods and cones sharingthe same nerve fibre

Several rods connected tothe same nerve fibre

Section through the retina, with rods and cones 0204060

rods

cones

Distribution of rods and cones over the retina

20 40 60

wavelength (nm)

1

10

relative

eyesensitivity

105

102

103

107

106

104

400 500 600 700

rod vision

cone vision

0,2

wavelength

(nm)

relativeeyesensitivity

400

0

0,4

0,6

0,8

1,0

500 600 700

555 nm507 nm


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Incandescent lamp Xenon-metal halide lamp

photopic vision(= day-like situations about > 3cd/m2)

... and is the eye-sensitivity used for photometric measurements !

( ) ( ) dVEKnm

nm

m = 780

380

typical: 25 lm/W

Low efficiencytypical: 100 lm/W

High efficiency

The special eye-sensitivity curve makes some light sources less or more efficient !



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Illusions

1 1

2 2

34 4

5 56 6

illusions !

Visual pathway from the eyes to the brain

1. Retina

2. Optic nerve

3. Optic chiasma

4. Optic tracts

5. Visual cortex6. Nerve connections

to the pineal gland


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Illusion of perspective

Illusions


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Double images

Illusions


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Associative illusion

Illusions


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Illusions

Associative illusion


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Other effects adaptation

time in darkness (min.)

0 5

105

1

10

relativethresholdluminance

10 15 20 25 30

104

102

103

cones

rods


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Other effects contrast

LhighC =

Llow

Lo - LbC =

Lb

o: object

b: background


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Other effects Contrast

Lo - Lb

C = > 0Lb

Positive Contrast

contrast

Negative contrast

Negative contrast

is possible !

Danger: positive and negative

contrast can compensate !

(Philips is also busy in road lighting)

Lo - LbC = < 0Lb

Contrast is decisive

if objects can be perceived or not !


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Other effects glare

disability glare

discomfort glare


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Other effects glare

object

glare source

veiling glare


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veiling glare

dirty cover lens

fog

dirty windshield

...

Other effects glare


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Age defects

reduced accommodation !


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age (years)0 10 20 30 40 50 60 70

12

14

10

8

6

0

2

lightrequir

ement

4

Increased light

requirement with age !

More and more older people !

Increasing mobility !

Age defects


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Lenses become opaque

Reduced resolution capability

Shrinking visual field

Smaller pupil diameter

Slower adaptation

...

8 12

25 47 60

70 82 91

Age defects


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Warm white

2800 K

Cool white

6500 K

Neutral white

4000 K

Experiences

Sunset, camp fire day-light

Relaxation hunting, picking

Vital sleep being alert


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Documents

ppthumanvision[1]