Osram HQI-E 150 W/NDL CL Technical Information download pdf (Page 45)

45

8 L

ig

ht and colou

r

Li

g

ht is the part o

f

the electroma

g

netic spectrum

which can be seen with the e

y

e. B

y

de

f

inition, the per

-

ceptible wavelength range is 380-780 nm, although

ra

di

at

i

on can a

l

so

b

e

p

erce

i

ve

d

as co

l

our

i

n t

h

e nea

r

infrared ran

g

e.

S

imilar to visible li

g

ht, ultraviolet and

in

f

rared variation belon

g

to the electroma

g

netic spec-

t

r

u

m

.

Di

ff

erent wavelengths can be perceived to di

ff

erent

extents. The maximum o

f

the sensitivit

y

curve

f

o

r

photopic vision is at 555 nm. The li

g

ht output

(

lumi

-

nous flux

)

is ascertained by multiplyin

g

the physical

radiation output with the e

y

e sensitivit

y

curve V

(

λ

)

(

see Fi

g

. 43

).

I

f

the entire radiation out

p

ut is emitted monochromati-

cally in the wavelen

g

th o

f

maximum eye sensitivity

(

555 nm

)

, then the theoretical maximum luminous effi

-

cac

y

is 683 lm

/

W. With uniform distribution of radiation

over the ran

g

e of 380 – 780 nm, approx. 196 lm

/

W is

p

oss

ibl

e

.

Fig. 41: Visible light as part o

f

the electromagnetic

sp

ectru

m

Luminous flux is the light output

of a light source.

Unit: 1 lumen (lm)

Luminous flux

Fi

g

. 42: De

f

inition o

f

luminous

f

lu

x

(Night vision)

(Day vision)

L < 0,1 cd/m

2

V’(λ)

V(λ)

L > 30 cd/m

2

Fig. 43:

S

pectral brightness sensitivity

V(

λ

(

(

) for photopic vision and

λ

V'(

λ

(

(

) for scotopic vision

λ

Lu

m

i

n

ous

= Irradiated li

g

ht in Lumen

(

lm

)

(G

l. 9.1

)

e

ff

icac

y

s

p

ent e

l

ectr

i

ca

l

p

ower

i

n watt

Light intensity is the measure

of lightoutput in a specified

direction.

Unit: 1 candela (cd)

Light intensity

Light intensity

Average illumination of a

surface is luminous flux

per unit area.

Illumination

Lux

Luminance is the measure of

the brightness that the eye has

of a surface.

Unit: 1 candela/m

2

(cd/m

2

)

Luminance depends on the

surface of the area seen by the

eye and on the luminous

intensity, radiated from the

surface towards the eye.

Luminance

visible surface

illuminated

surface

Light intensity

Fi

g

. 44: De

f

inition o

f

luminous intensit

y

Fi

g

. 45: De

f

inition o

f

illuminance

Fi

g

. 46: De

f

inition o

f

luminanc

e

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