Peculiarities of high-frequency filtering (contouring) of images of symmetric thick (extended along the optical axis) edge are investigated in analytical form by the Kirchhoff–Fresnel approximation. They are based on a model of equivalent diaphragms (transparencies) earlier proposed by the authors [J. Opt. Soc. Am. <b>71</b>, 483 (1981)]. Expressions for the fields in special cases of perfect absorption and reflection are derived. For the case of slight volumetric effects, a structure of the contoured images of the front and back faces is shown to be similar to a structure of the contoured image of the plane edge. But the influence of the extension causes a shift of the basic minimum position proportional to the size of the Fresnel zone. When volumetric effects are significant, the profile of the filtered image of the front face has a single maximum (instead of a double one). Here the structure of the filtered image of the back face depends to a great extent on the reflection properties of the inner surface, changing from the form with a double maximum to the form with a single one. There is agreement between theoretical and experimental results.
© 1998 Optical Society of America
Yu. V. Chugui and V. A. Sokolov, "High-frequency filtered images of an optically thick edge," J. Opt. Soc. Am. A 15, 611-621 (1998)