Aspects of vignetting in a polygon mirror-based spectral filter for swept source optical coherence tomography (SS-OCT)

Optical Coherence Tomography (OCT) is a technology capable of producing 3-D volumes of microscopic structures with micron-scale resolution. Its main area of application remains ophthalmology and in particular retinal imaging. The quality and usability of the images depends upon the frame rate and the properties of the light being used. Swept source OCT (SS-OCT) can offer a speed advantage; variants using polygon mirrors (PMs) as spectral filters in SS-OCT have resulted in a variety of different arrangements. Although their application has been successfully demonstrated, a more detailed study of the particular aspects and requirements of beam propagation through the filter and their overall impact on the system performance have not been reported. Examining aspects related to vignetting at the PM facet leads to maximizing light throughput and system performance, which is the aim of this work. A swept source spectral filter consisting of a transmission grating, a two-lens telescope, an off-axis PM, and an end reflector mirror has been evaluated in terms of the beam width at the PM facet and how this parameter varies across the entire width of the spectrum at the input of the spectral filter.