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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.

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ECEG287 Optical Detection Course Notes Part 2: Radiometry


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ECEG287 Optical Detection Course NotesPart 2: Radiometry

Profs. Charles A. DiMarzio

and

Stephen W. McKnight

Northeastern University, Spring 2004

Chuck DiMarzio, Northeastern University

topic outline
Topic Outline
  • Radiometric Quantities and Units
  • Radiance Theorem
  • Black-Body Spectrum
  • Some Radiance/Irradiance Values
  • A Little about Color

Chuck DiMarzio, Northeastern University

radiometric quantities
Radiometric Quantities

Chuck DiMarzio, Northeastern University

radiometry and photometry
Radiometry and Photometry

M, Flux/Proj. Area

Notes: Spectral x=dx/dn or dx/dl: Add subscript n or w, divide units by Hz or mm.

F, Flux

Radiant Flux

Watts

Luminous Flux

Lumens

Radiant Exitance

Watts/m2

Luminous Flux

Lumens/m2=Lux

1 W is 683 L at 555 nm.

Radiance

Watts/m2/sr

Luminance

Lumens/m2/sr

1 Lambert=

(1L/cm2/sr)/p

I, Flux/W

L,Flux/AW

Radiant Intensity

Watts/sr

Luminous Intensity

Lumens/sr

E, Flux/Area Rcd.

Irradiance

Watts/m2

Illuminance

Lumens/m2=Lux

1 ftLambert= (1L/ft2/sr)/p

1mLambert= (1L/m2/sr)/p

1 Ft Candle=1L/ft2

1 Candela=1cd=1L/sr

Chuck DiMarzio, Northeastern University

the radiance theorem
The Radiance Theorem

n2

n1

dW2

dA

q2

q1

dW1

Chuck DiMarzio, Northeastern University

radiance in images
Radiance in Images

dA2

dA’

dA1

dW2

dW1

z

Chuck DiMarzio, Northeastern University

resonant cavity modes
Resonant Cavity Modes

Chuck DiMarzio, Northeastern University

resonant frequencies in cavity
Resonant Frequencies in Cavity

ny

nx

nz

Chuck DiMarzio, Northeastern University

counting the modes
Counting the Modes

ny

nx

nz

Chuck DiMarzio, Northeastern University

energy per mode 1
Energy per Mode (1)

Chuck DiMarzio, Northeastern University

energy per mode 3
Energy per Mode (3)

Chuck DiMarzio, Northeastern University

total spectral energy
Total Spectral Energy

Chuck DiMarzio, Northeastern University

black body radiance 1
Black Body Radiance (1)

A’

A

Chuck DiMarzio, Northeastern University

black body radiance 2
Black Body Radiance (2)

A’

A

Chuck DiMarzio, Northeastern University

spectral radiant exitance 1
Spectral Radiant Exitance (1)

z

dq

q

y

df

f

x

Chuck DiMarzio, Northeastern University

spectral radiant exitance 2
Spectral Radiant Exitance (2)

Chuck DiMarzio, Northeastern University

black body equation 1
Black-Body Equation (1)

Chuck DiMarzio, Northeastern University

black body equations 2

m

10

10

m

/

2

5

10

, Spectral Radiant Exitance, W/m

0

10

-5

10

-10

10

l

M

-1

0

1

2

10

10

10

10

l

m

, Wavelength,

m

Black Body Equations (2)

10000

5000

2000

500

1000

T=300k

Chuck DiMarzio, Northeastern University

solar irradiance on earth
Solar Irradiance on Earth

Data from The Science of Color, Crowell, 1953

3000

Exoatmospheric filename=m1695.m

Sea Level

2

5000 K Black Body Normalized to 1000 W/m

2500

2

6000 K Black Body Normalized to 1560 W/m

m

m

/

2

2000

1500

, Spectral Irradiance, W/m

1000

l

E

500

0

0

200

400

600

800

1000

1200

1400

1600

1800

2000

l

, Wavelength, nm

Chuck DiMarzio, Northeastern University

typical outdoor radiance levels

6000K Sun

6.9 G Lux

Visible

Sunlit

Cloud

6.9 k Lux

Near IR

Mid IR

Blue

Sky

300K

night sky

Far IR

Typical Outdoor Radiance Levels

Ultraviolet

Atmospheric Passbands

Chuck DiMarzio, Northeastern University

thermal imaging

T = 300 K

1

/Delta T

0.5

l

M

D

0

-1

0

1

2

10

10

10

10

T = 500 K

6

/Delta T

4

l

2

M

D

0

-1

0

1

2

10

10

10

10

l

m

, Wavelength,

m

Thermal Imaging

Chuck DiMarzio, Northeastern University

luminance and radiance
Luminance and Radiance

1.8

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

y

1

Photopic Sensitivity

0

400

500

600

700

800

Wavelength, nm

Chuck DiMarzio, Northeastern University

some typical luminance and radiance levels
Some Typical Luminance And Radiance Levels

Chuck DiMarzio, Northeastern University

emissivity
Emissivity

Chuck DiMarzio, Northeastern University

color tristimulus values

z

y

x

Color: Tristimulus Values
  • Describe Eye’s Response to Color
  • Based on Color Matching Experiments
  • Small Number of Observers
  • Lines are Approximations

2

1.8

1.6

1.4

1.2

1

Tristimulus Value

0.8

0.6

0.4

0.2

0

300

350

400

450

500

550

600

650

700

750

800

Wavelength, nm

Chuck DiMarzio, Northeastern University

characterizing colors

1.8

z

y

x

Tristimulus Value

1

0

400

500

600

700

800

Wavelength, nm

Characterizing Colors

Object

Spectrum

y

x

Chuck DiMarzio, Northeastern University

recording and generating color images
Recording and Generating Color Images

Three Separate

Registered Images

Object

Display

with

Three

Sources

Camera

with

Three

Filters

Eye

Chuck DiMarzio, Northeastern University