Abstract
Purpose :
In broadband Line-scanning SD-OCT, chromatic aberrations and spatial-spectral crosstalking prevent diffraction limit imaging. We demonstrate these two problems can be resolved by dividing the original broadband spectrum into sub-bands, digital refocusing separately, and registering them afterward.
Methods :
The LS SD-OCT system is based on a Michelson interferometer that is powered by a supercontinuum laser (SuperK, NKT Photonics, Birkerød, Denmark). A custom band-pass filter was utilized to select a spectral range of 600 nm – 980 nm. The spectrum after digital filtering is centered at 800 nm, and the effective FWMH bandwidth is 160 nm. The interference signal is detected by a 2D CMOS camera (Dimax S4, PCO, Germany) with a detection aera of 1920 * 500 pixels (spectral-spatial) at a 2.95 kHz frame rate. Volumetric (500 A-scans × 500 B-scans × 1920 pixels) images were acquired, with a field of view (FOV) ~ 0.5 mm × 0.8 mm (x × y) and depth scanning range 1.2 mm (z). The 3 micrometer diameter microbeads were imbedded in transparent agar-based gel. Cucumbers were cut into thin slice and covered by cover glasses. The rat cornea was ex-vivo imaged within 2h after sacrifice.
Results :
Fig. 1A shows the images of enface microbeads images. From left to right, the image corresponds to the original OCT signal, refocused OCT signal using the full spectrum, and the registered sub-bands method. The line profiles comparison in (B) suggests that both the x- and y- resolution are improved using the proposed method. (C) and (D) show the original and corrected tilted projection images of cucumber seeds. (E) and (F) show the original and corrected enface image of the middle stroma in the rat cornea. Both the keratocytes and nerves are refocused. (G) and (H) show the original and corrected endothelium cells of the rat cornea.
Conclusions :
Our proposed method was successfully used to refocus the microbeads, cucumber, and rat cornea LS-OCT images. The chromatic aberrations and spatial-spectral crosstalking in broadband LS SD-OCT have been reduced which makes broadband LS SD-OCT suitable for cellular resolution imaging.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.