X-Ray On-Axis Fresnel Holography Using Three-Block Fresnel Zone Plate Interferometer
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y On-Axis Fresnel Holography Using Three-Block Fresnel Zone Plate Interferometer L. A. Haroutunyana, * and M. K. Balyana aYerevan
State University, Yerevan, Armenia *e-mail: [email protected]
Received April 23, 2020; revised May 19, 2020; accepted May 25, 2020
Abstract—An experimental setup for X-ray on-axis Fresnel holography is suggested. It is based on a three-block Fresnel zone plate interferometer. As a test object, for numerical simulation, a stencil with the text ‘X-RAY OPTICS’ printed on it is considered. Although the quality of the reconstructed image is limited, which should be expected in case of on-axis holography, it is still good enough for clear imaging of the text mentioned. Keywords: X-rays, X-ray interferometer, Fresnel zone plate, Fresnel on-axis holography DOI: 10.3103/S1068337220030044
1. INTRODUCTION In the field of X-ray radiation, various holographic schemes have been proposed: the Fraunhofer holography [1–3], Gabor and Fourier holography [4–9]. In [10], a scheme of the X-ray Fourier holography based on a system of two zone plates was proposed. The dynamic diffraction X-ray holography schemes are also proposed [11–18]. An interferometer based on three Fresnel zone plates (FZP) and operating in the amplitude-division mode was proposed in [19, 20]. A scheme of Fourier holography using the first two blocks of this interferometer was proposed in [21]. The aim of this work is the realization of the on-axis Fresnel holography in the region of hard X-rays. The aforementioned three-block interferometer is used for hologram recording, and the image reconstruction is carried out numerically. 2. AN EXPERIMENTAL SET-UP FOR HOLOGRAM RECORDING A schematic diagram of the proposed experimental setup for recording holograms is presented in Fig. 1. It is based on an interferometer composed of the three FZP which have a common optical axis and are separated from each other by double focal length. A plane wave parallel to the optical axis is incident on the interferometer, and the hologram is recorded after the third block at a distance several times greater than the focal length of the FZP. As an object wave, one considers a wave packet diffracted in the first order on the first and second FZP, and in the zeroth-order (that is, transmitted wave) in the third FZP. The reference wave is a wave packet diffracted in the zeroth-order on the first, and in the first order on the second and third FZP. The object plane coincides with the rear focal plane of the second FZP. As a diffraction grating, the FZP has different diffraction orders. Taking into account only 0, +1, and –1 orders of diffraction, 27 radiation propagation channels are formed in the interferometer. The blocking of 25 ‘unwanted’ channels, as well as the spatial separation of the object and reference wave packets in the object plane, are carried out by a knife edge located immediately after the first FZP and a mask in the object plane. The latter is an opaque screen with a window for the test object and a small hole for the reference wave centered on the
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