  The Large Binocular Telescope Interferometer (LBTI) has the longest baseline
in the world, 22.7 m, for performing astronomical interferometry in Fizeau
mode, which involves beam combination in a focal plane and preserves a wide
field-of-view. LBTI can operate in this mode at wavelengths of 1.2 to 5 and 8
to 12 {\mu}m, making it a unique platform for carrying out high-resolution
imaging of circumstellar disks, evolved stars, solar system objects, and
possibly searches for planets, in the thermal infrared. Over the past five
years, LBTI has carried out a considerable number of interferometric
observations by combining the beams near a pupil plane to carry out nulling
interferometry. This mode is useful for measuring small luminosity level
offsets, such as those of exozodiacal dust disks. The Fizeau mode, by contrast,
is more useful for generating an image of the target because it has more (u, v)
(Fourier) plane coverage. However, the Fizeau mode is still in an ongoing
process of commissioning. Sensitive Fizeau observations require active phase
control, increased automation, and the removal of non-common-path aberrations
(NCPA) between the science and phase beams. This increased level of control
will increase the fringe contrast, enable longer integrations, and reduce time
overheads. We are in the process of writing a correction loop to remove NCPA,
and have carried out tests on old and synthetic data. We have also carried out
on-sky Fizeau engineering tests in fall 2018 and spring 2019. In this article,
we share lessons learned and strategies developed as a result of these tests.
