Full Field Optical Coherence Tomography (FF-OCT) is one of the most upcoming methods for in vivo imaging, but there is always a need to improve imaging speed, depth and quality. Fourier Domain (FD-) FF-OCT is most used for retinal imaging due to its speed and innate possibility to digitally correct aberrations [1]. Usually, interferometers for this kind of imaging are based on symmetrical, 50/50 beam splitters, thus by default losing over a half of the overall light and most importantly – more than half of the signal, since intensity of light that can be sent to an eye safely is limited.
Also, even with an increace of signal, coherent light sources are known to produce images of lesser quality due to inherent coherence noice, that presents it self in a form of speckles in OCT images [2].
Fig. 1. The principal imaging system is shown (a), acquired in vivo retinal image showing various retinal layers (1 – nerve cell layer, 2 -external limiting membrane , 3 – photoreceptors, 4 – choroidal stroma )(b).
Due to these reasons, the goal of this work is to optimize beam splitting ratios for FF-OCT in Fourier FF-OCT and reduce spatial coherence of a laser in order to improve imaging Signal to Noise Ratio (SNR). We used 90/10 cube beam splitter for FD-OCT imaging in order to improve SNR and a deformable membrane was utilised for laser coupling as a means to distort spatial coherence of a laser beam, before inputing in the system (Figure 1. a). As a result, it was shown that asymmetric, high throughput beam splitter configurations increase FD-FF-OCT systems’ SNR by 2,5 times and that reduced spatial coherence visibly increaces the quality of in vivo retinal images (Figure 1. b).
[1] Borycki, D., Auksorius, E., Węgrzyn, P., & Wojtkowski, M. (2020). Computational aberration correction in spatiotemporal optical coherence (STOC) imaging. Optics Letters, 45(6), 1293. https://doi.org/10.1364/ol.384796
[2] Auksorius, E., Borycki, D., & Wojtkowski, M. (2019b). Crosstalk-free volumetric in vivo imaging of a human retina with Fourier-domain full-field optical coherence tomography. Biomedical Optics Express, 10(12), 6390. https://doi.org/10.1364/boe.10.006390
