Fresnel zone

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

Wavelength agile nonmechanical laser beam steering from Fresnel zone plates imprinted on a liquid crystal spatial light modulator

Abstract: Multibeam, multicolor, large-angle beam-steering is demonstrated in the visible spectral region by imprinting Fresnel zone plates (FZP) on a liquid crystal spatial light modulator. Spectral dispersion, both diffractive and refractive, is observed but does not prevent the use of this technology for beam steering applications. The experimental results show that while diffractive dispersion dominates over refractive dispersion, wavelength-specific FZPs can be rendered to direct those beams on target, either simultaneously or consecutively. Only a slight correction in the FZP positon is necessary to compensate for refractive dispersion. The position, intensity, and wavelength of each beam can be controlled independently.

Pinhole substrate and confocal optical scanner using the same

Abstract: PURPOSE:To realize the pinhole substrate which is improved in light utilization efficiency and provides image formation of high resolution and high sensitivity and the confocal optical scanner using it. CONSTITUTION:The pinhole substrate 1a consists of a substrate, plural Fresnel lenses formed on one surface of the substrate, and plural pinholes arranged at the focus positions of the Fresnel lenses, which are Fresnel zone plates formed by arranging plural dark parts and light parts concentrically and alternately and made of materials differing in transmissivity and refraction index with wavelength or dichroic mirrors for the dark parts or materials which differ in color dispersion for the light parts and dark parts.

Nonlinear fresnel zone plate reflector

Abstract: This paper describes a nonlinear Fresnel zone plate reflector designed to operate at 2.8GHz. The alternating Fresnel zones of the reflector are made from two different nonlinear metamaterials: one that reflects like a short circuit at low incident power levels and another that reflects like an open circuit. Both metamaterials transition from highly reflective to highly transparent as the incident power increases. Additionally, as the metamaterials transition to their transparent state the phase difference between their reflection coefficients decreases substantially, causing the reflector to lose its focusing capabilities. In this way, the field observed at the focus is reduced both as a consequence of the metamaterials becoming transparent as well as the reflector defocusing.

3D Fresnel field computing method based on its propagation reversibility

Abstract: There are many 3D data structures for computing diffraction field, the description based on 3D point-cloud is the elemental method of other descriptions, the diffraction field of 3D scene can be thought as the superposition of the diffraction field of each sampled light point and other descriptions can be thought as grouping with point-cloud by different way. The paper focuses on devising a computation method of 3D Fresnel field which is based on Fresnel diffraction field propagation reversibility. The proposed method combines the reversibility of Fresnel propagation and the requirement of sampling spacing by Nyquist criterion, i.e. to find the best space positions to optimize the number of sampling points and the reconstruction for the 3D Fresnel field. The method can be applied to reduce the computational complexity and improve computational efficiency.