Biomedical subjects

Yasuyuki Unno

Publications and source records attributed to Yasuyuki Unno.

2 recordsLinked to original sources

PubMed2003

Resolution limit for two-dimensional crossed-grating patterns projected by a coherent beam.

The resolution limit for two-dimensional crossed-grating patterns created by projecting mask objects by using a coherent beam has been investigated. We consider first two conventional mask types, a binary-amplitude mask and a two-level phase-shifting mask, in analyzing relationships between a diffraction-beam configuration and an image-intensity distribution. Then we derive, as a mask that overcomes the resolution limit of the conventional ones, a four-level phase-shifting structure with which the minimum image period can be reduced to square root(2)/2 time that of the two-level phase-shifting mask.

Journal Article↗

PubMed2002

Point-spread function for a rotationally symmetric birefringent lens.

Imaging properties of a birefringent lens, in which the fast (or the slow) axis is distributed in the radial direction whereas magnitude of birefringence varies as a quadratic function of the pupil radius, are investigated by calculating a point-spread function. It is found that the point image is analytically described by using the Lommel function as well as the zero-order Bessel function, and a localized intensity null surrounded by bright regions in all directions can be realized at a geometrical focus under certain conditions. The magnitude of birefringence that is tolerable in image formations is also discussed, assuming that the lens is applied to microlithography.

Journal Article↗