  We introduce the white light quantitative phase imaging unit (WQPIU) as a
practical realization of quantitative phase imaging (QPI) on standard
microscope platforms. The WQPIU is a compact stand-alone unit which measures
sample induced phase delay under white-light illumination. It does not require
any modification of the microscope or additional accessories for its use. The
principle of the WQPIU based on lateral shearing interferometry and phase
shifting interferometry provides a cost-effective and user-friendly use of QPI.
The validity and capacity of the presented method are demonstrated by measuring
quantitative phase images of polystyrene beads, human red blood cells, HeLa
cells and mouse white blood cells. With speckle-free imaging capability due to
the use of white-light illumination, the WQPIU is expected to expand the scope
of QPI in biological sciences as a powerful but simple imaging tool.
