Towards endoscopes with no distal optics

This paper reports on a step toward scanning endomicroscopy without distal optics. A video-rate lensless point scanning endoscope where the size of the endoscope distal probe was reduced to the fundamental limit - the 400 μm diameter of the endoscope fiber itself is realized. Following in the footsteps of coherent laser beam combining, the focusing of the beam at the distal end of a fiber bundle is achieved by imposing a parabolic phase profile across the bundle exit face with the aid of a two-dimensional spatial light modulator (SLM). A bundle of single mode fiber (SMF) cores specifically designed for the purpose which exhibits extremely low cross-talk between the individual cores was used. This allows video-rate transverse scanning of the focal spot by using scan mirrors before the SLM.