The moiré profile form and intensity levels

Abstract

We have seen in Chapter 2 that the moiré patterns obtained in the superposition of periodic structures can be described at two different levels. The first, basic level is only concerned with geometric properties within the x,y plane, such as the periods and angles of the original images and of their moiré patterns. The second level also takes into account the amplitude properties, which can be seen as a surface z = g(x,y) on top of the planar 2D description of each of the original structures or their moiré patterns, showing their intensity levels.¹ This 3D description of the moiré is called its intensity profile or intensity surface. Note that the term intensity refers here to the reflectance (or transmittance) values ranging along the z axis between 0 and 1 (see Sec. 2.2). The term profile originates from the simple moiré bands that occur in the superposition of two line-gratings, in which a ID plot (a side view or profile) is enough to describe the intensity levels of the moiré-bands (see Fig. 2.9). However, in more complex cases where the moiré patterns are no longer simple bands, the term moiré intensity surface is more appropriate for describing the shape and the intensity variations of the moiré pattern. In the discussions which follow we will use all of these terms interchangeably as synonyms.