  An improved phase retrieval method based Hilbert transform is introduced to
quantitatively calculate the phase distribution from distorted fringe pattern.
Also phase measurement deflectomety are widely used in specular type samples.
The background noise or bias should be suppressed prior to apply Hilbert
transform. A method for suppression background noise double Hilbert transform
is presented, which requires only one image. The method is easy to implement,
and it is able to conducting automated fast measurements. We have demonstrated
the double Hilbert transform method to retrieve the phase and background
suppression by computer simulation and experiment in phase measuring
deflectometry method.

Instrumentation and Detectors