Resolution enhancement in a fibre scanning microscope by real-time phase shifting

A method for improving resolution in Lissajous fibre scanning is proposed when line density is restricted by the bandwidth of resonant modes. The approach follows the established route of combining data obtained from scans with different phase shifts applied to one axis. However, the shifts are applied dynamically so that the overall frame time is minimized and are chosen to limit disturbance to the Delaunay triangulation used for image reconstruction. The limited bandwidth of both resonant modes is then exploited, and low- and high-resolution images can be obtained from the same data stream. Suitable drive signals are derived analytically and investigated numerically. The method is implemented with a three-colour confocal scanner based on a piezoelectrically-actuated photonic crystal fibre, multiplexed laser light sources, dual numerical aperture light collection, multiplexed mode stripping detection, optical feedback, and a real-time controller. Predicted phase responses, accurate line interlacing, and enhanced resolution are all demonstrated.