Phase measuring deflectometry is an emerging technique to measure specular complex surface, such as aspherical
surface and free-form surface. It is very attractive for its wide dynamic range of vertical scale and application range.
Because it is a gradient based surface profilometry, we have to integrate the measured data to get surface shape. It can be
cause of low accuracy. On the other hand, interferometry is accurate and well-known method for precision shape
measurement. In interferometry, the original measured data is phase of interference signal, which directly shows the
surface shape of the target. However interferometry is too precise to measure aspherical surface, free-form surface and
usual surface in common industry. To assure the accuracy in ultra-precision measurement, reliability is the most
important thing. Reliability can be kept by cross-checking. Then I will propose measuring method using both
interferometer and deflectometry for reliable shape measurement. In this concept, global shape is measured using
deflectometry and local shape around flat area is measured using interferometry. The result of deflectometry is global
and precise. But it include ambiguity due to slope integration. In interferometry, only a small area can be measured,
which is almost parallel to the reference surface. But it is accurate and reliable. To combine both results, it should be
global, precise and reliable measurement. I will present the concept of combination of interferometry and deflectometry
and some preliminary experimental results.