半導体レーザを用いた段差を持つ粗面の形状計測: 3波長での位相測定を用いる方法

The authors propose a new method which can measure a shape of rough step like surface by means of a speckle interferometry with a wavelength-changeable laser. A speckle phase available in the interferometry is usually affected not only by an optical path difference but also by a random component associated with surface roughness. The phase shifting method using two different wavelengths (λ1, λ2) is, therefore, limited to a single phase map about the optical path difference, because of the random component which remains without cancel. The single phase map is available only for the calculation of the shape of a continuous surface. In the proposed method, the authors use three different wavelengths (λ1, λ2, λ3) to obtain a double phase map, which is capable of a discontinuous surface shape calculation by means of a fringe-counting two-wavelength method. The validity of the method is experimentally demonstrated and discussion is extended to an accuracy of the measurement and an extent of the measurement range