  Quantitative phase imaging (QPI) recovers the exact wavefront of light from
the intensity measured by a camera. Topographical maps of translucent
microscopic bodies can be extracted from these quantified phase shifts. We
demonstrate quantitative phase imaging at the tip of an optical fiber endoscope
with a chromatic silicon nitride metalens. Our method leverages spectral
multiplexing to recover phase from multiple defocus planes in a single capture.
The half millimeter wide metalens shows phase imaging capability with a 280
field of view and 0.1{\lambda} sensitivity in experiments with an endoscopic
fiber bundle. Since the spectral functionality is encoded directly in the
imaging lens, no additional filters are needed. Key limitations in the scaling
of a phase imaging system, such as multiple acquisition, interferometric
alignment or mechanical scanning are completely mitigated in the proposed
scheme
