Fresnel zone

About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.

Off Axis Fresnel Zone Plates for White Light 3D Microscopy

Abstract: Paraxial thin lens ray model of white light imaging using Fresnel zone plates indicates that axial chromatic aberrations can be reduced and off-axis zone plates can be designed for high-speed 3D microscopy applications.

Optimize Performance of Diffractive Neural Network by Controlling the Fresnel Number

Abstract: To achieve better performance of a diffractive deep neural network, increasing its spatial complexity (neurons and layers) is commonly used. Subject to physical laws of optical diffraction, a deeper diffractive neural network (DNN) would be more difficult to implement, and the development of DNN is limited. In this work, we found controlling the Fresnel number can increase DNN’s capability of expression and its spatial complexity is even less. DNN with only one phase modulation layer was proposed and experimentally realized at 515 nm. With the optimal Fresnel number, the single-layer DNN reached a maximum accuracy of 97.08% in the handwritten digits recognition task.

Holographic radius test plates

Abstract: We evaluate a method for testing the radius of a spherical surface with a hologram that consists of a pair of nested Fresnel zone lenses. The hologram is positioned in the collimated test beam of a Fizeau interferometer. The inner zone lens generates a focus at the test part surface, whereas the wavefront of the first diffraction order of the outer zone lens is confocal with the test part. When the test part radius is equal to the nominal radius, the fringes in both zone lens areas are nulled at the same distance of the test sphere from the zone lens. The radius error of the spherical surface can be calculated from the test sphere displacement between interferometer null positions for the inner and outer zone lenses, or from the defocus term of the outer (confocal) lens at the position of zero defocus of the inner (cat’s-eye) zone lens. The primary benefits of the nested zone lens method are its ease of use, and that it enables radius measurements of spherical surfaces with large radii. We describe the radius measurement of a precise convex sphere with a nominal radius of 80mm.

Maskless Fresnel zone plates for dense embedded optical components

Abstract: Summary from only given. When an intense femtosecond laser pulse is tightly focused into a transparent material, high-order nonlinear absorption allows the energy to be deposited predominantly within the focal volume producing a permanent refractive index modification of up to 10/sup -2/ in the bulk of the transparent material. This process allows local patterning inside transparent media into 3D structures, allowing for instance the assembly of many optical components in a single glass block, producing rigid and environmentally tolerant devices. Using this simple technique of direct writing, we are able to write a maskless Fresnel zone plate (radius of 0.997 mm).

Laser-assisted alignment of multi-station flexographic printing system

Abstract: A multi-station flexographic printing system includes a plurality of flexographic printing stations. Each flexographic printing station includes a flexo master. Each flexo master comprises a Fresnel zone pattern in a unique position. A method of aligning a plurality of flexographic printing stations includes printing a Fresnel zone pattern on a substrate in a unique position for each flexographic printing station. Light is directed through the Fresnel zone patterns on the substrate. The light focused by the Fresnel zone patterns is captured with a sensor device.