Focus on the Distal Assembly of a Nonlinear Endomicroscope: A Gradient Index Lens Coupled with a Piezoelectric Scanner for Fluorescence Lifetime Measurements
Résumé
Today, prototypes of nonlinear endomicroscopes are appearing in order to transfer technics of multiphoton characterization of biological samples to humans in vivo in situ. But they require several optical optimizations to be adapted for a clinical use. Among them, the ideal distal lens, coupled with the ideal scanning system is not yet highlighted. In this paper, we are using a gradient index (GRIN) lens coupled with a piezoelectric scanning system (PZT). The main part is dedicated to a spectral analysis in the context of fluorescence lifetime measurements (FLIM), a well-known technic used to complete multiphoton characterization and discriminate healthy and tumors cells. We spectrally highlight the presence of a background fluorescence perturbing the spectral measurement through the GRIN lens in specific conditions of image space working distance. In a second part, we evaluate the resolution available with the GRIN lens and numerically determine the optimal object working distance depending on the position of the fiber imposed by the PZT.