PURPOSE: To enable stopping down of a beam to the size smaller than the diffraction limiting value of a lens by providing two sheets of reflective films which allow partial transmission of the amplitude of light waves and partly reflect said amplitude and are parted from each other at a prescribed space between the exit face and focus of the lens for focusing the light.
CONSTITUTION: A protective film 3 is formed on the hologram lens 2 formed on a transparent substrate 1 by subjecting the surface to spin coating, etc., of; for example, Si coating material to about 1μm. Al or Ag or the like is thereafter deposited by evaporation on the protective film 3 to the thickness at which the prescribed reflectivity R and transmissivity T are obtd., by which the reflective film 5 is formed. For example, an Si film or dielectric film or the like is laminated on the reflective film 5 up to a prescribed thickness to form a thin transparent film 4. Another reflective film 6 is formed on the thin transparent film 4 in the same manner as for the reflective film 5 and finally the protective film 7 is formed therein in the same manner as for forming the protective film 3. The extremely small spot diameter below the diffraction limiting value of the conventional lens is thus obtd. by utilizing the multiple reflections between two sheets of the reflective films and the crossinterferences of the light waves obtd. by said reflections.
YAMAGISHI FUMIO
IKEDA HIROYUKI
INAGAKI YUSHI
| JPS58184925A | 1983-10-28 |