In the phase measuring deflectometry, the phase error caused by the nonlinear intensity response, called the gamma distortion, can negatively affect the measurement quality of specular surfaces. Based on the generic exponential four-step phase-shifting fringe modal, this paper proposes a flexible and simple phase retrieval method to eliminate the phase errors without complex calibration or additional fringe patterns. The experimental results illustrate that the proposed method can accurately retrieve the phases from the distorted fringe patterns with the Gamma distortion, and the measurement precision can henceforth be improved.
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