Biophotonics_Concepts_to_Applications

zdepth¼

p

2 dk

¼

Mp

2 Dk

¼

M

4

k^2

Dk

¼

M

2

lc ð 10 : 15 Þ

wherelcis the coherence length of the source andΔk=2πΔλ/λ^2.
The A-scanaxial resolutionΔzis

Dzgaussian¼

4ln2

DkFWHM

¼

4ln2

2 pDk=k^2

ð 10 : 16 Þ

when using a Gaussian source that has a full-width half-maximum bandwidth
kFWHM. For a rectangular source the axial resolution is

zrect¼

p

Dk

ð 10 : 17 Þ

Example 10.6Consider an SS-OCT system for which M = 220,

λ= 1308 nm, andΔλ= 87 nm. (a) What is the scan depth range? (b) What is

the axial resolution when using a Gaussian source?

Solution: (a) Using Eq. (10.15) yields the following scan depth range

zdepth¼

M

4

k^2

Dk

¼

220

4

ð1308 nmÞ^2

87 nm

¼ 1 :08 mm

(b) Using Eq. (10.16) yields the following axial resolution for a Gaussian

source

Dzgaussian¼

4ln2

2 pDk=k^2

¼4ln2

ð1308 nmÞ^2

2 pð87 nmÞ

¼ 8 : 7 lm

Tissue

sample

Fixed

mirror

Reference arm

Optical splitter

SMF

Tunable SMF

laser

source

(^12)
3

AD converter PC

Photodetector

Optical circulator

Fig. 10.8 Schematic of the setup for a swept source OCT system

302 10 Optical Imaging Procedures