Multiphoton microscopic endoscopy (MPM-E) is a promising medical in vivo diagnostic imaging technique because it
captures intrinsic fluorescence and second harmonic generation signals to reveal anatomical and histological information
about disease states in tissue. However, maximizing light collection from multiphoton endoscopes remains a challenge:
weak nonlinear emissions from endogenous structures, miniature optics, large imaging depths, and light scattering in
tissue all hamper light collection. The quantity of light that may be collected using a dual-clad fiber system from
scattering phantoms that mimic the properties of the in vivo environment is measured. In this experiment, 800nm
excitation light from a Ti:Sapphire laser is dispersion compensated and focused through a SM800 optical fiber and lens
system into the tissue phantom. Emission light from the phantom passes through the lens system, reflects off the dichroic
and is then collected by a second optical fiber actuated by a micromanipulator. The lateral position of the collection fiber
varies, measuring the distribution of emitted light 2000μm on either side of the focal point reimaged to the object plane.
This spatial collection measurement is performed at depths up to 200μm from the phantom surface. The tissue phantoms
are composed of a 15.8 μM fluorescein solution mixed with microspheres, approximating the scattering properties of
human bladder and dermis tissue. Results show that commercially available dual-clad optical fibers collect more than
47% of the total emission returning to the object plane from both phantoms. Based on these results, initial MPM-E
devices will image the surface of epithelial tissues.