The measured focal radius of 0.68λ (peak-to-null) agrees with the Rayleigh diffraction limit prediction of 0.61 λ/NA (NA = 0.88) for a low-aberration lens. Measured focal gains up to 20 dB agree with theoretical predictions for normal and oblique incidence. Laboratory measurements at 200 kHz indicate that the rubber foam can be accurately modeled as a lossy fluid with an acoustic impedance approximately 1/10 that of water.
An ultra-thin (0.0068λ) FZP that achieves higher gain is also proposed and simulated which uses low-volume fraction, bubble-like resonant air ring cavities to construct opaque zones. We experimentally and numerically investigate an alternative approach of creating a FZP with thin (0.4λ) acoustically opaque zones made of soft silicone rubber foam attached to a thin (0.1λ) transparent rubber substrate. For underwater sound below MHz frequencies, a large FZP that blocks sound using high-impedance, dense materials would have practical disadvantages. Nicholas, Michael Layman, Christopher N.Ī Fresnel zone plate (FZP) lens of the Soret type creates a focus by constructive interference of waves diffracted through open annular zones in an opaque screen. Thin Fresnel zone plate lenses for focusing underwater soundĬalvo, David C. Furthermore, the Fibonacci-like zone plate beams are found to possess the self-reconstruction property, and would be promising for 3D optical tweezers, laser machining, and optical imaging. The results demonstrate that the Fibonacci-like zone plates possess the self-similar property and the multifocal behavior. The focusing properties and the evolution of transverse diffraction pattern for the Fibonacci-like zone plates have been analytically investigated both theoretically and experimentally and compared with the corresponding Fresnel zone plates of the same resolution. We present a new family of diffractive lenses, Fibonacci-like zone plates, generated with a modified Fibonacci sequence. Block Island Southeast Light, Spring Street & Mohegan Trail at Mohegan Bluffs, New Shoreham, Washington County, RIĬheng, Shubo Liu, Mengsi Xia, Tian Tao, Shaohua (no plate) Lens, lens pedestal, mercury float, shade holder installation, drawing # 3101, sheet 2 of 2. (no plate) Lens, lens pedestal, mercury float, shade holder. Furthermore, we present a spatially resolved characterization method using multiple diffraction orders to identify manufacturing errors, alignment errors and pattern distortions and their effect on diffraction efficiency.ĥ1. Using a compact experimental setup with piezo actuators for alignment, we demonstrated 47.1% focusing efficiency at 6.5 keV using a pair of 500 μm diameter and 200 nm smallest zone width.
We use a coarse zone plate with Ï€ phase shift and a double density fine zone plate with Ï€/2 phase shift to produce an effective 4- step profile. To overcome the manufacturing problems of high resolution and high efficiency multistep zone plates, we investigate the concept of stacking two different binary zone plates in each other's optical near-field. The focusing efficiency of binary Fresnel zone plate lenses is fundamentally limited and higher efficiency requires a multi step lens profile. High efficiency x-ray nanofocusing by the blazed stacking of binary zone plates Block Island Southeast Light, Spring Street & Mohegan Trail at Mohegan Bluffs, New Shoreham, Washington County, RI (no plate) Lens, lens pedestal, mercury float, drawing # 3101, sheet 1 of 2. Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Surveyĥ0. (no plate) Lens, lens pedestal, mercury float, drawing #. Comparison of the Ti/Al multilayer zone plate with the Ag/Al zone plate is discussed in terms of focusing efficiency.ĥ0.
A Bragg-Fresnel lens has been made by combining this zone plate with a Ge(422) crystal. Koike, M Suzuki, I H Komiya, S Amemiya, Yīy using a helicon plasma sputtering technique, a one-dimensional Ti/Al multilayer zone plate with an outermost layer width of 76 nm has been successfully fabricated. Ti/Al multilayer zone plate and Bragg-Fresnel lens.