Deflectometry is widely used to measure three-dimensional profile of a specular free-form surface because of its high
accuracy and short inspection time. With phase data obtained by observing the fringe patterns reflected via the surface,
we can measure the shape, specifically normal vector of the surface. In order to obtain the shape of specular free-form
surfaces, two different phases have to be computed for a single area. Two phases are calculated by using two sets of the
phase-shifting patterns with different direction, and usually eight images are needed. In this paper, we propose a two
dimensional phase-shifting method, called 2D phase-shifting method, to compute two phases with different direction
with a single set of 2D phase with only five images. Therefore, the proposed method is expected to have a strong impact
on measurement industry where reducing the number of acquired images is desirable for increasing measurement speed.
The proposed method is verified by both simulation and experiments, in which phase information is successfully
extracted with 2D phase-shifting method.