SS-OCT System Base Unit
Chapter 5: Imaging Artifacts
Page 36
MTN013142-D02
Chapter 5
Imaging Artifacts
5.1.
Saturation and Non-Linearity
The OCT A-scan data is created by frequency analysis of the spectral data generated by the spectrometer.
Intense reflection from the sample can saturate the sensor of the spectrometer or illuminate very close to
saturation. This effect broadens the signal and leads to a nonlinear response. For example, a sinusoidal optical
signal is interpreted as partially rectangular. Consequently, additional harmonic frequencies of the root signal
appear.
Figure 47
High Surface Reflection Causing Saturation and Nonlinear Response of the Spectrometer
A typical example of this effect is shown in Figure 47. Saturation can be reduced or avoided by:
-
Changing focus position
-
Tilting the sample with respect to the A-scan axis
-
Introduction of a wedge into the optical path (first reflex reflecting outside of NA) and immersion (see
Figure 48)
Figure 48
Avoiding Strong Surface Reflection by Use of an Immersed Wedge
When operating with a wedge, the image will be tilted in the direction of the wedge angle. When scanning in the
orthogonal direction, no tilt occurs.
