PURPOSE: To obtain a hologram lens having higher mechanical strength and higher resistance to environmental influence by diffusing ions having different contribution to refractive index from ions in a transparent substrate into the surface of the transparent substrate in accordance with a specified pattern.
CONSTITUTION: Thin film 7 of a univalent metal, for example, of Ag, is deposited on the surface 6a of a transparent substrate 6, then thin film 8, 8, of a metal having ≥2 valency, for example, Al, is deposited on the both surfaces 6a, 6b of the transparent substrate 6. When the transparent substrate 6 is heated at high temp. and a potential difference is generated on the thin film 8, 8 in such a manner that electric field is generated in the direction from the surface 6a to the surface 6b, then, atomic ions constituting the thin film 7 are diffused into the inside of the transparent substrate 6. Since the degree of contribution of the atomic ions to the refractive index is different from the degree of contribution of atomic ions constituting the transparent substrate 6, stripe distribution 9 of refractive index is formed corresponding to the thin film 7 is formed in the transparent substrate 6 in accordance with the distribution of concn. of the atomic ion of the thin film 7. Finally, when the thin film 7, thin film 8, 8 are removed by etching or polishing, etc., a hologram, namely, a hologram lens provided with a refractive index distribution 9, is formed in the transparent substrate, and plane wave 4 being parallel to an optical axis 3 is transformed to spherical wave 5, therefore, incident light is converged to a point.
TATSUMI KENJI
TAJIME TORU
