采用罗奇光栅离焦投影的位相测量轮廓术

Phase-Measuring Profilometry Using Defocused Projection of the Ronchi Grating

本文提出一种采用罗奇光栅离焦投影的位相测量轮廓术。给出由离焦引起的光学低通滤波和N-位相算法表征的数字滤波的解析描述。证明由于采用罗奇光栅离焦投影而引起的误差只具有很小量级,在大多数实际应用中可以忽略。文中给出了计算机模拟和实验结果。

A new method is presented for phase measuring profilometry (PMP) in which de-focused image of the projected square-wave Ronchi grating, and a phase shifting techniqueare chosen for the optical phase evaluation. We present an analytical description of the low-pass optical filtering performed by defocused imaging and of the additional low-pass digitalfiltering of the same signal due to the inherent properties of the N-step phase shifting algo-rithm. It is shown that for appropriately selected (N) the quasi-sinusoidality is causing a neg-ligible error in most of the foreseeable applications. It is demonstrated by computer simulation, and proved by experiment that for the largerange of defocusing, this method preserves it(?) accuracy.