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3 Holographic Interferometry for Studying …
Fig. 3.5 Dependence of the normalized distribution of intensity (a) and contrast (b) for a wedgeshaped surface. Reprinted from [94] with permission
3.1.4 Study of the Absolute Surface Relief Through
the Immersion Method
Another solution for determining the absolute surface relief is to use two immersion
media. This method is a double-exposure one, and to obtain the contour map, the
refractive index of the immersion medium changes. The phase difference emerging
due to the change of the refractive index is proportional to the difference between
the walls of the immersion chamber and the object. This made it possible to form
interference fringes characterizing the surface relief. In order the contrast of the
interference pattern to change from band to band along with the increase of the
thickness of the immersion medium layer as it occurs in the two-long-wave absorptive
method, at least one of the two applied media must be a narrow absorption line.
Using the approach implemented in the two-long-wave contouring method, it can
be considered that two-wave fronts interfere after reconstruction with the amplitudes,