| 摘要 |
PURPOSE:To prevent the formation of interference fringes and to improve resolving power by specifying the refractive indexes and thicknesses of a single crystal thin plate, a single crystal substrate, a transparent conductive film, an adhesive layer, and an optical thin film in accordane with a prescribed relation with the wavelength of readout light. CONSTITUTION:On one end surface of a single crystal thin plate 2 (refractive index n0) made of BSO, etc., a transparent conductive film 2 (refractive index n4 and thickness d4) made of In2O2, etc., is provided and on the other end surface, a transparent insulating film 4, a transparent conductive film 3', and a protective film 4' of polyparaxylene, etc., are formed. On one surface of a substrate 20 (n0) which principally has electrooptic effect while having photoelectric effect reduced by doping BSO with impurities, optical thin films 22 (n1 and d1) and 23 (n2 and d2) are laminated, and on the other surface, a reflection preventing film 29 is formed. In the figure, 21 is transparent adhesive layer (n3 and d3) and when the wavelength of readout light is denoted as lambda, n1d1=n2d2=n4d4=lambda/4, n1n3=n2n4, and n0n2=n1n4. |
