Abstract
A radial Walsh filter is a phase binary diffractive optical element characterized by a set of concentric rings that take the phase values 0 or π, corresponding to the values + 1 or -1 of a given radial Walsh function. Therefore, a Walsh filter can be re-interpreted as an aperiodic multifocal zone plate, capable to produce images of multiple planes simultaneously in a single output plane of an image forming system. In this paper, we experimentally demonstrate for the first time the focusing capabilities of these structures. Additionally, we report the first achievement of images of multiple-plane objects in a single image plane with these aperiodic diffractive lenses.
Highlights
Fresnel zone plates (FZPs) are essential for focusing and imaging in many scientific and technological areas, as for example in THz [1] or X-Ray [2] applications. As it is well-known, conventional FZPs consist of alternating transparent-opaque circular rings whose radii are proportional to the square root of the natural numbers [3]
In order to extend the range of applications of conventional FZPs several non-linear transformations of the phase of periodic zone plates were proposed, mainly to obtain multifocal zone plates [4,5,6]
The property of self-similarity in axial intensity distributions of radial Walsh filters was reported in the far field diffraction patterns [20]. We have extended this property to the axial irradiances provided by Walsh Zone Plate (WZP) working as aperiodic diffractive lenses
Summary
Fresnel zone plates (FZPs) are essential for focusing and imaging in many scientific and technological areas, as for example in THz [1] or X-Ray [2] applications As it is well-known, conventional FZPs consist of alternating transparent-opaque circular rings (or alternating 0 and π phase shift ring zones) whose radii are proportional to the square root of the natural numbers [3]. Fractal Zone Plates [7,8,9] (characterized by its fractal structure along the squared radial coordinate ς) demonstrated self-similar focusing properties [7] and extended depth of field imaging [8]. We demonstrate that amplitude WZPs are capable of achieving images of multiple-plane object in a single image plane
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