Abstract

Studies relating to the imaging phenomenon due to periodic apertures include Fourier imaging, Lau effect, imaging by gratings in tandem, and the geometrical optics approach. Most of these investigations involve relatively high frequency gratings to constitute the periodic object and the imaging pupil which is usually located midway between the object and the image planes. In this paper we consider a restricted class of grating imaging of a low frequency object where the ratio of its period to that of the pupil is very high, typically of the order of 10³. The images are produced in the close vicinity of the pupil at extremely high demagnifications. In the geometrical optics approach, an analogy has been drawn with the micropinhole imaging¹ where each slit in the imaging pupil is considered to be the 1-D analog of the pinhole. The phenomenon has also been investigated from the standpoints of the Fresnel-Kirchhoff diffraction theory and the MTF concepts. Furthermore, the associated high magnification obtained by interchanging the conjugate planes has been employed for microdisplacement sensing with a submicron resolution. The analysis also includes the characterization of the magnified images and details of the detection technique.

© 1985 Optical Society of America