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SD-OCT Base Unit Chapter 3: Description
Rev C, June 25, 2021 Page 21
changed again but its composition stays the same so that the intensity measured in each sensor, for s- and for
p-polarized components, reflects the polarization and birefringence properties of the sample.
Based on the intensity and phase differences in the interference patterns detected by both sensors, net
polarization changes as a function of depth in the sample are determined with the typical spatial resolution of
an SD-OCT system. As a parameter to display the cumulative polarization effect, the phase retardation, optical
axis and degree-of-polarization uniformity (short: DOPU) are available. Details about this are provided in the
“2D Polarization-Sensitive Mode” chapter of the ThorImage
® OCT Software Manual.
Nomenclature in OCT Imaging
Figure 19 A-Scan Data Set
As described before, the SD-OCT engine creates a depth profile from the interference of photons reflected off
layers of the sample with photons reflected in the reference arm. This depth profile is referred to as an A-scan.
Figure 19 shows an A-scan into a tomato (the ordinate of this graph represents the modulation amplitude in dB
based on the number of measured electrons per camera pixel).
The imaging application can make use of up to two scanning directions. Scanning one direction while collecting
multiple A-scans creates a 2-dimensional cross-sectional image, referred to as a B-scan. Here, the depth
information is typically displayed from top to bottom, while the scan axis is from left to right. Figure 20 shows a
B-scan data set.
Figure 20 B-Scan Data Set