Optical Coherence Tomography (OCT) is the ideal solution for high-resolution visualization of turbid samples. Whether the application is live sample imaging or in-situ inspection of microelectronics, this novel optical imaging technique provides real-time 2D and 3D imaging with micron-level image resolution for image depths up to a few millimeters. Thorlabs now offers two different types of OCT systems: the Spectral Radar (SR-OCT) and Swept Source (SS-OCT) systems. We also offer OCT tools for design engineers or OEM integrators, including swept source lasers, interferometers, detectors, fiber optic components, and OCT lenses.

Thorlabs’ Fourier Domain OCT Systems

Fourier Domain Optical Coherence Tomography (FD-OCT) achieves greater sensitivity and higher imaging speed than time domain OCT and has become a powerful tool for biomedical and material applications. Thorlabs now offers two types of FD-OCT imaging systems: the Spectral Radar OCT (SR-OCT) and the Swept Source OCT (SS-OCT). The SS-OCT has an optional Doppler Imaging upgrade. Both systems are based on FD-OCT technology but incorporate different technical approaches. The SR-OCT system employs a spectrometer and broadband light source to detect the OCT interference fringe signals as a function of optical frequency, while the SS-OCT system uses a frequency swept light source to generate the same type of interference signals. The signal processing and image construction methods in the two systems are very similar.

Choosing an OCT System

The appropriate OCT system for a given application depends on the desired scan speed and measurement wavelength, since these characteristics ultimately determine the image depth and resolution that can be achieved. In general, the resolution depends on the coherence length of the light source. Shorter coherence lengths, which are associated with broader spectral bandwidths and shorter center wavelengths, lead to better axial (longitudinal) image resolution. For most OCT applications, the axial resolution is ~10µm. Typical image depth for OCT systems can be from 1 – 3mm, depending on the absorption and scattering properties of the sample. For instance, water is most transparent to light in the 600 – 900nm range. Therefore, since the outer portion of the eye (i.e. cornea, vitreous, and lens) is comprised largely of water, it has been shown that for standard ophthalmic applications, an 800 – 900nm light source is ideal. On the other hand, for multilayered biological tissue samples, the 900 – 1400nm range is preferable because most biological materials have lower optical scattering coefficients at these longer wavelengths.

To help our customers choose the appropriate OCT system for their application, a few key parameters of two standard OCT systems (OCP930SR and OCM1300SS) are listed below.