Coherent Microscopy and Optical Coherence Tomography for Biomedical Applications - Bioanalysis Advanced Materials Methods and Devices - page 117

Fig. 8.12 TF of an OCT
system

Measured
Frequencies

k z

k x

Fig. 8.13 PSF of an OCT
system (positive real part
shown)

¼ l ¼

previous NA 600 nm and

a Gaussian spectral distribution with bandwidth of 100 nm (FWHH@1/ e 2 ). It can be
seen that in comparison with the PSF of DHM shown in Fig. 8.7 , the total intensity
of the OCT PSF reduces in planes orthogonal to the viewing direction and OCT
therefore provides greatly enhanced 3D information. In OCT the extent of the PSF
in the axial (i.e., observation) and lateral (perpendicular to the observation)
directions are inversely proportional to the source bandwidth and the NA, respec-
tively. It is important to point out that most commercial OCT systems operate with
much reduced aperture (NA

0.55 operating with the same mean wavelength of

¼ 0.01) resulting in a PSF with proportionately larger

lateral dimensions.
Fig. 8.14 provides a good example of OCT in medical imaging taken from an
in vivo study of human skin by Alex et al. [ 35 ]. Depth sections (B-scans) through
the surface clearly identify the different layers up to a depth of around 3 mm.