Novel 1.6 MHz Swept Source for real-time, volumetric in-vivo OCT imaging of the human retina

In this report, a swept source optical coherence tomography (SS-OCT) instrument, equipped with a novel, multi-MHz tuning range swept source is presented. The source, based on an electrically pumped Micro Electro Mechanical System Vertical Cavity Surface Emitting Laser (MEMS-VCSEL) technology, is able to operate at 1.6 MHz with bidirectional sweeping, and emits light at a central wavelength of 1060 nm with a wavelength tuning range of 30 nm at -3 dB. The capabilities of the SS are investigated, and characterized, using an OCT instrument equipped with pupil tracking capabilities. The source provides an experimental axial resolution of 30 μm measured in air. From measuring the sensitivity drop-off, an axial imaging range longer than 90 mm was inferred. To estimate the wavenumber tuning non-linearities of the source and generate images, the Complex Master-Slave (CMS) method was employed. CMS also allowed for real-time visualization of the en-face images of the human retina, in-vivo, without computing the whole volume. By using the novel SS, in-vivo real-time images of the human retina are produced at 4 Hz volume rate when paired with a 2-D orthogonal galvanometer scanner. The increase in speed for A-scan and volume acquisition tends to reduce fragmented and blurry images. Apart from a montage of en-face images generated in real-time from various axial positions, we also present B-scans produced with a galvanometer scanner driven at 1 kHz from the optic nerve area.