Engineering topics

Namioka, Takeshi

Publications and source records attributed to Namioka, Takeshi.

4 records

NASA NTRS1993

Deformed ellipsoidal gratings for far-ultraviolet spectrographs - Analytic optimization

Analytic formulas are developed for the semiaxes and for the deformation coefficients of a deformed ellipsoidal grating that minimize aberrations over a given spectral range. These include the Rowland circle mount and quasi-Rowland circle mounts, as required for systems that combine spectra from multiple gratings on a common detector. It is also shown that the necessary condition for a holographic grating to give a better performance over a conventional grating is the use of a convergent beam and a divergent beam for the recording. Examples applicable to the Far-Ultraviolet Spectroscopic Explorer are given. The light-path function for a deformed ellipsoidal holographic grating is also presented.

Content, David↗

NASA NTRS1992

Layer-by-layer design method for soft-X-ray multilayers

A new design method effective for a nontransparent system has been developed for soft-X-ray multilayers with the aid of graphic representation of the complex amplitude reflectance in a Gaussian plane. The method provides an effective means of attaining the absolute maximum reflectance on a layer-by-layer basis and also gives clear insight into the evolution of the amplitude reflectance on a multilayer as it builds up. An optical criterion is derived for the selection of a proper pair of materials needed for designing a high-reflectance multilayer. Some examples are given to illustrate the usefulness of this design method.

Yamamoto, Masaki↗

NASA NTRS1991

Extended Rayleigh-Fano theory and its application to grating polarization

A simple method of calculating the degree of polarization of light diffracted by a grating having shallow grooves and finite conductivity is developed by extending the Rayleigh-Fano theory. Its validity is examined by comparing the computed degree of polarization with experimental data obtained in the visible and vacuum ultraviolet for the +/- 1st and -2nd orders of Al- and Au-coated blazed gratings and holographic gratings used in the specific mountings. The calculations are in good agreement with the observed polarization behavior of the gratings, verifying the usefulness of the present method.

Koike, Masato↗

NASA NTRS1991

Analysis of polarization properties of shallow metallic gratings by an extended Rayleigh-Fano theory

Rayleigh-Fano theory has been extended for the purpose of calculating the polarization anomaly of a grating having shallow grooves and finite conductivity. Simple analytic formulas are derived for predicting the position and the appearance of the anomalies. Phenomenological explanations are given to the origin of the anomalies. The validity of our analysis is examined by comparing computed degree of polarization with experimental data obtained in the visible region for Al-, Ag-, and Au-coated blazed gratings.

Koike, Masato↗