RÉSUMÉ

This paper describes the properties of a nonequidistant array used as a spatial filter for recording discrete holograms of scenes comprising objects of different dimensions and reflectivity.
A distinguishing feature of well-known methods for local or bandpass spatial filtering is that these methods allow us to isolate specific regions of the spatial frequency spectrum of holographic objects [1]. However, in this case the images of all objects are generally filtered to the same extent, without regard for their dimensions and reflection characteristics. The use of filter masks applied over a hologram and transparent in certain continuous regions of the spatial spectrum results in blurring the target image or in emphasizing its boundaries (isolation of characteristic points) at the expense of finer details. In such a case the holographic resolution is adversely affected [2]. The matched holographic filtering technique [1] provides a comparison between the spectrum of the reference hologram and the spectrum of the scene comprising different objects. In this case the resulting correlated response shows a degree of matching of the analyzed spectrum to the reference one. If a priori information is incomplete and the matched filter cannot be constructed, or if it is necessary to obtain and analyze a target image while suppressing the images of other objects that significantly differ in size and reflection characteristics from the selected (target) one, well-known methods of spatial filtering are inadequate.
A study of nonequidistant arrays has shown that these arrays have the capability of filtering spatial frequencies [3]. This paper demonstrates that the use of nonequidistant arrays for hologram recording allows us to isolate target images in the presence of other objects, and moreover to improve the image contrast of selected objects as compared to their contrast in the holographic scene.