January 2004 Chuck DiMarzio, Northeastern University 10471-2-1 ECEU692 Subsurface Imaging Course...

January 2004 Chuck DiMarzio, Northeastern University 10471-2-1

ECEU692Subsurface Imaging

Course NotesPart 2: Imaging with Light (1)

Profs. Brooks and DiMarzio

Northeastern University

Spring 2004


Lecture Overview• Optical Spectrum and Sources• Interaction of Light with Matter• A Bit of Geometric Optics• A Bit of Physical Optics• Microscopes (1)

– Point-Spread Function

– Optical Transfer Function

• Detectors and Cameras


Classical Maxwellian EM Waves

E E

E

x

y

z H

HH

λ

v=c

λ=c/υ

c=3x108 m/s (free space)

υ = frequency (Hz)

Thanks to Prof. S. W.McKnight


Electromagnetic Spectrum (by λ)

1 μ 10 μ 100 μ = 0.1mm

0.1 μ10 nm =100Å

VIS=

0.40-0.75μ

1 mm 1 cm 0.1 m

IR=

Near: 0.75-2.5μ

Mid: 2.5-30μ

Far: 30-1000μ

UV=

Near-UV: 0.3-.4 μ

Vacuum-UV: 100-300 nm

Extreme-UV: 1-100 nm

MicrowavesX-Ray Mm-waves

10 Å1 Å0.1 Å

Soft X-Ray RFγ-Ray

(300 THz)

Thanks to Prof. S. W.McKnight


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


Input DiffuseReflection

Absorption

Diffuse Transmission

Scattering

SpecularReflection

Direct Transmission

Light in a Turbid Medium


Example InteractionsSlab Absorption

Two-Layer

Slab Absorption and Scattering

Semi-Infinite Medium


Camera Lens Image Location

F’

F A’

A

Lens Equation

f f’

s s’


Camera Lens Magnification

A’

A

s s’

s

s

x

xm

''

x

-x’


Field of View

Film=ExitWindow


Diffractionx1 x

What is the light distribution in the spot?


Fraunhofer Diffraction


Point Spreadand Optical Transfer Functions

x’

x’

x

R

d0

object

perfect image

actual image

scale

Convolvewith PSF

FourierTransform

OBJECT

PERFECT IMAGE

ACTUAL IMAGE

SCALE

MULTOTF


Fraunhoffer Examples


Coherent and Incoherent OTF

• Incoherent Image– Irradiance rather than

field.

– PSFinc is |PSFcoh|2

• Fourier Transform– OTFinc is |OTFcoh|2

– Meaning of Phase is a bit complicated


An Extreme Example

20 40 60 80 100 120 140 160 180

20

40

60

80

100

120

140

160

180

20 40 60 80 100 120 140 160 180

20

40

60

80

100

120

140

160

180

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

20 40 60 80 100 120 140 160 180

20

40

60

80

100

120

140

160

180

Object

Point-SpreadFunction ofSystem

Image

Colorbar for all


Bright-Field Microscopy

F

F’A

A’

f’f

s’s

ImagePlane

ObjectPlane


Semiconductor Detector

ValenceBand

ConductionBand

h

e-

EmissionAbsorption

10057p1-2 here


Remember N-FET Structure?

Channel Length1 to 10 m

B, Body

n+ n+

S, Source G, Gate D, Drain

P-Type Material

SiO2 Insulator20-100m

Channel: 2 to 500 m into page

NMOSMetal-Oxide-Semiconductor


Charge-Coupled Device (CCD)

Channel Length1 to 10 m

B

S G D S D

B

~10 m X nRows


CCD Charge Transfer

Clock Signals

m10057_1.mFigure 1

time, Clock Cycles

Row

Num

ber

Clock Voltage

0 0.5 1 1.5 2 2.5 3

2

4

6

8

10

120

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

time

OneLineV

V


Computer Interfacing

• Analog Camera and Frame Grabber

• Digital Camera

Analog CameraComputer withFrame Grabber

AnalogMonitor

ComputerMonitor

Digital Camera

Computer

ComputerMonitor


Linearity and AGC

0 0.2 0.4 0.6 0.8 10

0.2

0.4

0.6

0.8

1

Input Voltage

Ou

tpu

t Vol

tage

Gxy

21

5.0

• Automatic Gain Control (AGC)

• Feedback– Control G– Based on...

• Peak Signal• Average Signal• Peak in a Region

• Not Desirable for Quantitative Work


Pixelation and Digitization

“Brightness”

Count

0

255


Digitization and Dynamic Range

Signal Voltage

2N-1

0

Pedestal

Saturation

Step Size

Dark

MinimumSignal

MaximumSignal


Some Standard and Extreme Parameters

• VGA Frame Size: 640 by 480– Up to 4k Square?

• Standard Update Rate: 30 Hz. Interlaced– Up To few kHz.

• Standard Digitization: 8 Bits– Up To 12.

• Pixel Size: 10 micrometers.• Color Camera: 3 Channels, 8 Bits Each

January 2004 Chuck DiMarzio, Northeastern University 10471-2-1 ECEU692 Subsurface Imaging Course...

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