Programmable Cone Shell Configuration Based Depth-Sensitive Fluorescence Spectroscopy With Flexible Target Depth and Depth Sensitivity

Depth sensitive fluorescence spectroscopy can extract the depth dependent distribution of fluorophores, which is closely associated with disease progresses in layered tissues. However, the conventional contact fiber-optic probe or non-contact lens setup based fluorescence measurements often suffer from insufficient depth sensitivity for precise diagnosis. Although a modified non-contact lens setup, using axicon lens instead of conventional convex lens, has successfully achieved improved depth sensitivity by forming a cone-shell configuration, challenges remain in incompletely flexible target depth and limited depth sensitivity. In this study, a programmable cone shell configuration based depth-sensitive fluorescence spectroscopy was proposed and tested on a two-layered agar phantom. According to the experimental results, the target depth can be altered arbitrarily by digitally tuning the ring beam radius, even switching between two distant target depths. In addition to better depth sensitivity than conventional methods, its capability of flexibly narrowing the ring beam width can promote further improvement on depth sensitivity. Various aspects can benefit from its capabilities of flexibly switching among different target depths and depth sensitivities, thus the proposed programmable cone shell configuration based depth-sensitive fluorescence spectroscopy is expected to promote its wider applications in biomedicine.