A Quarter Ellipsoidal Reflector Enhancing Fluorescence Collection Efficiency For Multiphoton Microscopes

In this paper, we present a fluorescence collection enhancement method for multiphoton microscopy by a quarter ellipsoidal reflector (QER). It is proven to be compatible with commercially available two-photon microscopes without significant customization. The structure and working principle of the QER is demonstrated. A QER was fabricated to collect most backscattered photons not collected by an objective lens of an epifluorescence microscope and then reflected photons into an external detector. Fluorescence collection efficiency improvement of 2.75-fold in numerical simulation is obtained. The method is also validated by imaging turbid phantoms and ex vivo biological tissue. Quantum efficiency (QE) corrected experimental results obtained by our method are comparable with those obtained by a nondescanned detection (NDD) scheme of a commercially available multiphoton microscope system. Finally, our method is shown to have potential in neuroscience research for deep tissue imaging.