ECEG287 Optical Detection Course Notes Part 2: Radiometry

Jan 2004 Chuck DiMarzio, Northeastern University 10464-2-1

ECEG287 Optical Detection Course Notes

Part 2: Radiometry

Profs. Charles A. DiMarzio

and

Stephen W. McKnight

Northeastern University, Spring 2004


Topic Outline

• Radiometric Quantities and Units

• Radiance Theorem

• Black-Body Spectrum

• Some Radiance/Irradiance Values

• A Little about Color


Radiometric Quantities


Radiometry and Photometry, Flux M, Flux/Proj. Area

I, Flux/ L,Flux/AE, Flux/Area Rcd.

Radiant FluxWattsLuminous FluxLumens

Radiant ExitanceWatts/m2

Luminous FluxLumens/m2=Lux

A /

RadianceWatts/m2/srLuminanceLumens/m2/sr1 Lambert=(1L/cm2/sr)/

1 ftLambert= (1L/ft2/sr)/1mLambert= (1L/m2/sr)/

Radiant IntensityWatts/srLuminous IntensityLumens/sr

1 Candela=1cd=1L/sr

/

IrradianceWatts/m2

IlluminanceLumens/m2=Lux

1 Ft Candle=1L/ft2

Notes: Spectral x=dx/d or dx/d: Add subscript or , divide units by Hz or m.

1 W is 683 L at 555 nm.


The Radiance Theorem

1

2

n1n2

dA

d1

d2


Radiance in Images

dA’

d1

d2

dA1

dA2

z


Resonant Cavity Modes


Resonant Frequencies in Cavity

nx

nz

ny


Counting the Modes

nx

nz

ny


Energy per Mode (1)


Energy per Mode (3)


Total Spectral Energy


Black Body Radiance (1)

A

A’


Black Body Radiance (2)

A

A’


Spectral Radiant Exitance (1)

x

y

z

d

d


Spectral Radiant Exitance (2)


Black-Body Equation (1)

10-1

100

101

102

10-10

10-5

100

105

1010

, Wavelength, m

M,

Sp

ectr

al

Ra

dia

nt

Exi

tan

ce,

W/m

2/

m


Black Body Equations (2)

10-1

100

101

10210

-10

10-5

100

105

1010

, Wavelength, m

M,

Spe

ctra

l Rad

ian

t Exi

tan

ce, W

/m2 /

m

T=300k

500

1000

2000

5000

10000


Solar Irradiance on Earth

0 200 400 600 800 1000 1200 1400 1600 1800 20000

500

1000

1500

2000

2500

3000Data from The Science of Color, Crowell, 1953

, Wavelength, nm

E

, S

pe

ctra

l Irr

ad

ian

ce,

W/m

2/

m

Exoatmospheric filename=m1695.mSea Level

5000 K Black Body Normalized to 1000 W/m2

6000 K Black Body Normalized to 1560 W/m2


Typical Outdoor Radiance Levels

VisibleNear IR

Mid IRFar IR

Atmospheric Passbands

Ultraviolet6000K Sun6.9 G Lux

SunlitCloud6.9 k Lux

BlueSky 300K

night sky


Thermal Imaging

M

/Del

ta T

10-1

100

101

1020

0.5

1

T = 300 K

10-1

100

101

1020

2

4

6

, Wavelength, m

M

/D

elta

TT = 500 K


Luminance and Radiance

400 500 600 700 8000

1

1.8

Wavelength, nm

Ph

oto

pic

Se

nsi

tivity

yThis curve shows the relative sensitivity of the eye. To convert to photometric units from radiometric, multiply by 683 Lumens Per Watt


Some Typical Luminance And Radiance Levels


Emissivity


Color: Tristimulus Values

Wavelength, nm

Tris

timu

lus

Va

lue

• Describe Eye’s Response to Color

• Based on Color Matching Experiments

• Small Number of Observers

• Lines are Approximations

300 350 400 450 500 550 600 650 700 750 8000

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

zy

x


Characterizing Colors

400 500 600 700 8000

1

1.8

Wavelength, nm

Tris

timu

lus

Va

lue

z

xy

ObjectSpectrum

x

y

dLxX

0

ˆ

ZYX

Xx


Recording and Generating Color Images

Camerawith

ThreeFilters

Displaywith

ThreeSources

Eye

ObjectThree SeparateRegistered Images

ECEG287 Optical Detection Course Notes Part 2: Radiometry

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