Coherent Microscopy and Optical Coherence Tomography for Biomedical Applications - Bioanalysis Advanced Materials Methods and Devices - page 116

Fig. 8.11 Frequency domain
OCT

To/From
Fundus Camera

Line
Scan
CCD

White Light
Source

Grating

To/From
Fundus Camera

Tuneable
Source

Detector

Although there are many ways to implement OCT they all measure the coherent
response of an object when the wavelength of the illumination is varied. An
FD-OCT system can be considered as the superposition of images from a coherent
microscope made at different wavelengths as shown schematically for illumination
with four different wave numbers in Fig. 8.12 .
In a practical system the illumination wavelength is scanned and if the frame rate
of the detector is sufficient, the measured frequencies form a continuum. In this case
the TF of the system can be written as the superposition integral [ 21 ],

ð þ1

j
4 p

Sk ðÞ
k o d

H OCT ð

k Þ¼ ð j k þ k i j k 0 Þ

1

d k 0

q

1

Þ ^ ð k þ k i o

N A

step (8.9)

k o

where SkðÞ is the source spectrum expressed as a function of wave number. Inverse

Fourier transformation of this expression gives the PSF that is shown in Fig. 8.13 .
For the sake of comparison, the PSF has been computed for a system with the