Fig. 1: Design and characterization of a commercial two-photon laser scanning microscope with a Bessel focus module.
From: High-speed volumetric two-photon fluorescence imaging of neurovascular dynamics
a Schematic of the microscope. A half-wave plate (HWP), a polarizing beamsplitter (PBS), and a removable mirror allow switching between Bessel (red) and Gaussian (yellow) beam paths. In the Bessel path, a spatial light modulator (SLM) and a lens generate an annular illumination pattern, which after spatial filtering by an annular mask is imaged via a 4f system onto the galvos and subsequently imaged via a scan and tube lens pair onto the objective lens back focal plane. b Lateral and axial point spread functions for Gaussian and Bessel foci. X and Y scale bars: 1 µm. Z scale bar: 5 µm. Results from one 0.2-µm-diameter bead. c Schematic comparison of Gaussian and Bessel volumetric TPLSM methods. Gaussian volumetric imaging requires multiple 2D frames taken at different Z-positions, while Bessel volumetric imaging is achieved with a single frame.
