SD-OCT Base Unit
Chapter 3: Description
Rev C, June 25, 2021
Page 19
Thorlabs SD-OCT System Technology
SD-OCT is a measurement method based on the detection of optical path length differences within an
interferometer. The technology incorporates a broadband light source with a high-speed spectrometer to provide
depth profiles acquired using a Fast Fourier Transform, which can be assembled into cross-sectional images.
These cross-sectional images can then be used for 3-dimensional reconstructions.
The light of a broadband source travels to the sample and illuminates it perpendicularly and with a small focus
designed to provide a good lateral resolution. The back-scattered light travels to the spectrometer where the
unique phase delay for each wavelength is detected. To gain access to this back-scattered light, it is necessary
to insert a splitting device into the optical path. In Thorlabs' SD-OCT systems, this device could be either a fiber
coupler or a circulator.
The two main features of a 2-dimensional scanned image are the axial and lateral resolutions. The axial
resolution does not depend on the optics; it is determined by the spectral bandwidth of the light source used.
The lateral resolution, on the other hand, is affected by the chosen application optics.
The OCT system has three main parts: the base unit, a PC and a scanner with an OCT-STAND (scanner type
dependent). The schematic setup of the SD-OCT system with coupler and circulator is shown in the figures
below:
Figure 16 Schematic Diagram of a SD-OCT System with Internal Coupler
Figure 17 Schematic Diagram of a SD-OCT System with Internal Circulator
