OP

TIK

A

Dr. Seres István

Photometry

Sn

eso

r P

hys

ics

Seres István 2 http://fft.szie.hu

Fotometry

Used quantities:

angle: length fo arc/radius

Solid angle: area/radius squared

r

i

r

i

2r

Asr

Central angle of a circle: 2 (radian)

Central angle of a sphere: 4 (steradián)

(steradián = sr)

Sn

eso

r P

hys

ics

Seres István 3 http://fft.szie.hu

Fotometry

The solid angle of an elementary area:

2r

cosdAd

d

r

dA

dA cos

Sn

eso

r P

hys

ics

Seres István 4 http://fft.szie.hu

FotometryOverview:

Radiometrical quantity Unit Fotometrical quantity

Unit

Emitted power (Φe) W Luminous flux (Φv)

lm

Irradiation (Ee)

(Power density)

W m-2 Illumination (Ev) lx

Irradiation density (Le) W m-2 sr-1

Brilliancy (Lv) cd m-2

Sn

eso

r P

hys

ics

Seres István 5 http://fft.szie.hu

Fotometry

Luminous flux

Spectral sensitivity of the eye(visibility function)

Sensitivity max of the human eye: 555 nm

Power: 1 wattLuminous flux: 683 lumen

Maximal spectral utilization

watt

lumen683Km

Sn

eso

r P

hys

ics

Seres István 6 http://fft.szie.hu

Fotometry

láthatósági függvény

0

0.2

0.4

0.6

0.8

1

350 450 550 650 750

hullámhossz (nm)

(nm) V

480 0.139

490 0.208

500 0.323

510 0.503

520 0.71

530 0.862

540 0.954

550 0.995

555 1

560 0.995

570 0.952

580 0.87

590 0.757

600 0.631

610 0.503

620 0.381

630 0.265

640 0.175

Luminous flux

Sn

eso

r P

hys

ics

Seres István 7 http://fft.szie.hu

Fotometry

The energy emitted by a unit time:

dt

dW n/ /lumelm

)683(,__max:

_:)(

__:

)(

1

2

1

WlmnutilizatiospectralimalKm

functionvisibilityV

powerspectralemitted

dVKm

e

e

Luminous flux

Sn

eso

r P

hys

ics

Seres István 8 http://fft.szie.hu

Fotometry

Luminous flux

Sn

eso

r P

hys

ics

Seres István 9 http://fft.szie.hu

Fotometry

Illumination:Luminous flux on a unit surface

/lux/E

lxdA

dE

Sn

eso

r P

hys

ics

Seres István 10 http://fft.szie.hu

Fotometry

Light utilization

watt

lumen

W

lm

P

Sn

eso

r P

hys

ics

Seres István 11 http://fft.szie.hu

Fotometry

Fotometers

Important properties of light sensors

1. The spectral dependence of the sensor is coincidence with the visibility function V(λ)

2. The photocurrent is proportional to the illumination

3. The angled irradiation is detected as the cosine of the incliment angle

Sn

eso

r P

hys

ics

Seres István 12 http://fft.szie.hu

Fotometry

Photometers

•Subjektiv photometry

• Photocell

• semiconductor diode

Sn

eso

r P

hys

ics

Seres István 13 http://fft.szie.hu

Fotometry

Subjektive photometry

Sn

eso

r P

hys

ics

Seres István 14 http://fft.szie.hu

Fotometry

Subjective photometry

Weber photometer

Bunsen fotometer:

Relative measurement

Sn

eso

r P

hys

ics

Seres István 15 http://fft.szie.hu

Fotometry

Photocell

Sn

eso

r P

hys

ics

Seres István 16 http://fft.szie.hu

Fotometry

Photodiode

Sn

eso

r P

hys

ics

Seres István 17 http://fft.szie.hu

Fotometry

Photodiode

Sn

eso

r P

hys

ics

Seres István 18 http://fft.szie.hu

Fotometry

Photodiode

Sn

eso

r P

hys

ics

Seres István 19 http://fft.szie.hu

Fotometry

Köszönöm a figyelmet!