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We present a novel method for measuring a curved specular surface profile, which is the moiré deflectometry under
incoherent (white light) illumination. In our proposed system, moiré is produced by a superposition of two pairs of
Ronchi gratings to obtain orthogonal components of a normal vector on a surface under test. The grating pair was moved
along an axis perpendicular to the grating plane to modulate a spatial frequency of the moiré. The moiré is reflected by a
specular object, then observed with a calibrated stereo camera. Normal vector distribution of the tested surface was
measured by analysis of intensity oscillations captured by the stereo camera as a function of the position of the moved
grating. A surface profile was reconstructed by an integration calculation. We successfully measured surface profiles of
deeply curved mirrors with the curvature from -20 to 20 m-1 by our system. Moreover, part of a miniature vehicle body,
which has a complex curved specular surface, was also measured. Additionally, we theoretically and experimentally
studied a measurable angle variation of the normal vector on the tested surface by our measurement system. We found
that our system can allow to measure the angle deviation of 0.05 deg of the normal vector. This method has no ambiguity
of slope and height measurements which is appeared in conventional deflectmetric metrologies. Furthermore, our
proposed system only needs a single step calibration. Hence, the methodology we proposed has a potential to be
developed into a 3D profiler for complex specular surfaces.
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