Total external reflection

About: Total external reflection is a research topic. Over the lifetime, 829 publications have been published within this topic receiving 22213 citations.

Optical filter and color separation prism

Abstract: PROBLEM TO BE SOLVED: To provide an optical filter which can be manufactured easily and has superior effects of suppressing luminance shading and color shading. SOLUTION: The optical filter 21 is made, by alternately layering a first optical film H having a first refractive index and a second optical film M1, having a second refractive index on light transmissive substrates (base plates) 11W, 12W, wherein the first refractive index is higher than the refractive index of the substrate, and the second refractive index is higher than the refractive index of the substrate and is lower than the first refractive index. By using an intermediate refractive index film, having a refractive index higher than that of the substrate and lower than that of the first optical film H as the second optical film M1, the difference in the refractive index, between first and second optical films, is reduced, and the spectroscopic characteristics shift in the optical thickness, with respect to a change in an incident angle of light, is suppressed. COPYRIGHT: (C)2008,JPO&INPIT

On the “supercollimation” of X-ray beams in rough interfacial channels

Abstract: The transmission of x rays through rough submicron narrow channels is investigated by numerical simulation with diffraction and decay of coherence taken into account. It is found that transmission is strongly increased for directions within the diffraction limit λ/d (d is the channel width). For larger angles strong roughness scattering results in rapid decay of coherence and absorption of the x-ray beams. When the coherent part is a significant portion of the transmitted beam, its divergence is also within the diffraction limit, which can be an order of magnitude smaller than the Fresnel angle of total external reflection. The effects are explained with the statistical theory of x-ray scattering in a rough transitional layer. Such “supercollimation” can be used for fine angular discrimination of x radiation and for the production of very narrow diffraction-quality x-ray beams.

High reflectivity and high flux x-ray optic element and method of making same using atomic layer deposition techniques

Abstract: This invention relates to a method of forming multiple bilayers on a substra te using an atomic layer deposition process. The reflecting layer of the bilaye r pair can be a high electron density metal and the spacing layer of the bilay er pair can be a low electron density material. Because atomic layer deposition can deposit atomic layer controlled and conformal films, multiple bilayers c an be deposited on the internal surfaces of monocapillary tubes. By applying a graded multiple bilayer, much higher reflectivity and higher flux optical elements can be obtained than those based on total external reflection. Deposition of a graded multiple bilayer on an elliptic or parabolic tapered tube leads to focused or collimated output from a point source input. Variou s atomic, layer deposition techniques are described to produce the graded multiple bilayer high quality X-ray focusing devices, especially for "hard" X- ~rays.

Grazing incidence optics for X-ray astronomy

Abstract: Cosmic X-ray sources are usually very weak and their detection, therefore, needs large area telescopes to gather light and sensitive detectors to enhance quantum efficiency. Conventional telescopes for visible light use refracting or reflective optics which is impractical for X-ray wavelengths because photon energies are greater than the binding energies of the typical atomic electrons leading to a refractive index for X-rays being less than unity. Thus single surface reflectivity for near-normal incidence is negligible for X-rays. However, by Snell’s Laws, total external reflection occurs and X-rays can be reflected from a surface up to a critical angle (usually about a degree for energies below 10 keV) given by cosine θ = n. This is known as the grazing angle. X-ray telescopes are made to exploit the grazing incidence from a set of co-axial and con-focal shells of paraboloidal and hyperboloidal mirrors. X-ray reflectors having high atomic number surfaces with low scattering are used to realize imaging capability for a telescope. I describe here various configurations required, and the various technologies used and their limitations, to make practical X-ray telescopes. A soft X-ray imaging telescope (SXT) using grazing incidence has been built at TIFR for ASTROSAT—an Indian Multiwavelength Satellite designed to cover a very broad band of X-rays, UV and optical. Astrosat is planned to be launched by a Polar Satellite Launch Vehicle in 2012 into a near-Earth Equatorial orbit. I will also describe the ongoing R&D for realizing telescopes for hard X-rays above 10 keV useful for both Astronomy and medical diagnostics.