| 摘要 |
PURPOSE:To impart a beam splitting function to the hologram element itself and to decrease the number of parts of an optical head by forming a dielectric film which reflects the incident light on the surface of a dry plate of a light transmission type on the side opposite to an interference fringe recording surface. CONSTITUTION:The hologram element 1 is constituted by forming a prescribed grating 11 on one surface of the dry plate 15 of the light transmission type and forming the dielectric film 13 which reflects a part or the whole of the incident light on the surface opposite thereto on this surface. The dielectric film 13 is formed by vapor deposition of a dielectric material using, for example, SiO2, etc., to a film shape. This dielectric film 13 is so formed as to reflect a part of the incident laser beam at about 45 deg. with the surface of the dry plate 15 or the whole thereof. |
