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Prof. Dr. Petrich Biophotonics I (WS 2017/18) 1

Biophotonics I W. Petrich

Slides of lecture #01 October 16th, 2017

http://www.kip.uni-heidelberg.de/biophotonik/teaching

Biophotonics I Imaging systems

Scattering of light

Biophotonics II Biospectroscopy

Lasers in medicine

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Prof. Dr. Petrich Biophotonics I (WS 2017/18) 2

Biophotonics I general remarks

BIOPHOTONICS I (WS 2017/18)

I. Imaging Systems human vision

microscopy

II. Light Scattering Mie scattering

light propagation in tissue

BIOPHOTONICS II (SS 2018)

III. Biospectroscopy

IV. Lasers in medicine

Literature:

• Bergmann-Schäfer, Optik (Walter de Gruyter)

• E. Hecht, Optik (Addison-Wesley)

• J. Bille, W. Schlegel, Medizinische Physik 3 (Springer)

• P.N. Prasad, Biophotonics (Wiley)

• T. Vo-Dinh, Biomedical Photonics Handbook (CRC

Press)

• V.V Tuchin, Handbook of Optical Biomedical Diagnostics

(SPIE Press)

• C.F. Bohren, D.R. Huffmann, Absorption and Scattering

of Light by Small Particles (Wiley VCH)

• L.V. Wang, H.-I. Wu, Biomedical Optics (Wiley)

• Lecture „Biophotonics I“ will be credited with 2 CP subject to successfully passing the exam

• The exam („Klausur“) will be a written examination on February 5th, 2018

• If you intend to obtain credit points, i.e. to participate in the exam, you will need to register (further

information will follow)

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Prof. Dr. Petrich Biophotonics I (WS 2017/18) 3

Biophotonics I I.1. human vision

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Prof. Dr. Petrich Biophotonics I (WS 2017/18) 4

Biophotonics I I.1. human vision

H. Helmholtz, Archiv für Ophthalmologie , March 1855, Volume 2, Issue 2, pp 1-74

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Prof. Dr. Petrich Biophotonics I (WS 2017/18) 5

Biophotonics I I.1 human vision

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Prof. Dr. Petrich Biophotonics I (WS 2017/18) 6

Biophotonics I REMINDER: what is a focal length? What is a diopter?

n2 n1

s0 s1

l1 l0 R

R

nn

s

n

s

n

slandsleifor

l

sn

l

sn

Rl

n

l

n

Rl

ns

l

nR

l

ns

l

n

Rl

nRs

l

nR

l

nRs

l

n

RsRl

nRsR

l

n

d

dL

principlesFermat

lnlnL

pathlengthoptical

RsRRsR

RsRRsRl

RsRRsRl

12

1

2

0

1

1100

1

12

0

01

1

2

0

1

1

21

1

2

0

10

0

1

2

1

21

1

22

0

10

0

1

!

1

1

20

0

1

1201

1

2

1

2

1

2

1

22

1

0

2

0

22

0

)1cos..(0

1

0

0sinsinsinsin

0sin)(22

sin)(22

:'

:

cos)(2)(

)180cos()(2)(

cos)(2)(

)(

)(

12

2110

12

1001

lengthfocalbackRnn

nsfsfor

lengthfocalfrontRnn

nsfsfor

R

nn

f

n

f

n

n

n

f

f

Rff

12

0

1

1

2

2

1

1

0

01

Note that 1.)

2.) D

refractive power („Brechkraft“)

unit: 1 Diopter = 1 D = 1/m

„paraxial approximation“:

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Prof. Dr. Petrich Biophotonics I (WS 2017/18) 7

Biophotonics I REMINDER: what is the power of a lens (“Brechkraft”)?

n1

s0 s2

R1

fRRn

ss

followsitnairin

dFdlensesthinfor

dFRR

nns

n

s

n

R

nn

s

n

s

nand

R

nn

s

n

s

n

surfacestwo

111)1(

11

:)00,1(

)0)(;0(

)(11

)(

21

2

20

1

21

12

2

1

0

1

2

21

2

1

1

2

1

12

1

2

0

1

D

„Gauß‘sche Linsenformel“

For two thin lenses (or two near-by surfaces) one can show that D = D1+ D2+ 2D1 D2d/n2

D1+ D2

n2 n1

R2

d

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Biophotonics I I.1 human vision

Snellen chart

Landolt

rings

Picture taken from: wikipedia.org

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Prof. Dr. Petrich Biophotonics I (WS 2017/18) 9

Biophotonics I REMINDER: diffraction limit

d

b

A) diffraction from a thin single slit in the far field (1-D)

p

d

2

d2phase difference between first and last beam:

phase difference between 1st and pth beam:

2

2*

)(0)1(32)(0

2)(03

)(02

)(01

sin

sinsin

~lim~

2sin

2sin

~)1(

;;

b

b

bEEI

p

ep

bEeeeee

p

EE

eep

EEee

p

EEe

p

EE

ttottot

p

tkxipiiiitkxi

tot

itkxiitkxitkxi

B) diffraction from a circular aperture in the far field (2-D)

2

10

sin

)sin(2

ka

kaJII

J1: 0th order Bessel function

• Maximum of J1 at =0

• first minimum of J1 at sin()=1,22/D

Rayleigh‘s criterion for „resolution“: „Diffraction maximum from one

object coincides with diffraction minimum of second object“