China
Africa
Explore chapters and articles related to this topic
Special Techniques
Published in Harry E. Martz, Clint M. Logan, Daniel J. Schneberk, Peter J. Shull, X-Ray Imaging, 2016
Harry E. Martz, Clint M. Logan, Daniel J. Schneberk, Peter J. Shull
If one wanted to make a zone plate with a focal length of 50 mm at a wavelength of 4.5 nm (0.28 keV), then the radius of the central zone would be 15 μm. According to the Rayleigh criterion, the spatial resolution, Rs, of a zone plate is given by Rs=(1.22λf)OD.(15.20)
Sharp focusing of light with microoptics components
Published in V. A. Soifer, Diffractive Optics and Nanophotonics, 2017
The high‐quality zone plate was made by lithography from ZEP resist (the refractive index of the resist n = 1.52). Fig. 3.56 shows an image of the ZP in the electron microscope: the depth of the relief 510 nm, diameter 14 μm, the outer zone 0.5λ=266 $ 0.5\lambda = 266 $ nm. ZP has 12 rings and a central disk. Fig. 3.57 shows a side view (a) and the view from above (b) of the ZP in an atomic force scanning microscope.
Holography
Published in Daniel Malacara-Hernández, Brian J. Thompson, Advanced Optical Instruments and Techniques, 2017
The Fresnel zone plate is a diffractive structure that acts as a lens: it diffracts an incident plane wave into a point. This type of diffractive structure is particularly interesting for electromagnetic radiation where there is no refractive material (such as for x-rays), or the refractive materials are too expensive.
High-diffraction-efficiency Fresnel lens based on annealed blue-phase liquid crystal–polymer composite
Published in Liquid Crystals, 2019
Hua-Yang Lin, Nejmettin Avci, Shug-June Hwang
To fabricate a switchable BPLCFL, the PIPS technique is applied, in which uniform binary layers of the BPLC and polymer are simply achieved by the spatially modulated ultraviolet (UV) light intensity of a photomask, as shown in Figure 1. The photomask with a circular pattern includes opaque odd zones and transparent even zones, in which the radius r1 of the innermost zone designed is 0.4 mm and the radius of the nth zone (rn) is given by rn2 = nr12, with n denoting the zone number. The primary focal length f depends on the innermost radius r1 as f = r12/λ, where λ is the wavelength of the incident beam. Our Fresnel zone plate consists of 100 zones in an approximately 1 cm aperture and has a primary focal length f of ~25 cm for λ = 632.8 nm.