Most microscope objectives commonly used for two-photon imaging of neurons are optimized for high image quality
under wide-field illumination and for long working distance, constraints that are at odds with the need for high
fluorescence collection efficiency and large field of view dictated by the low fluorescence intensity and the scattering
properties of brain tissue. We present a de novo design of an objective intended specifically for deep-tissue functional
two-photon imaging. Our design has separate imaging and non-imaging pathways for incident and emitted light, making
use of the optical sectioning intrinsic in non-linear fluorescence excitation, which relaxes a number of design constraints.
We show through modeling that a twofold to fourfold improvement in fluorescence collection efficiency over traditional
objective designs is easily achievable while maintaining nearly diffraction-limited performance within a 200-micron
field of view and a long working distance.