| 摘要 |
PURPOSE:To improve the contrast of an uneven surface and to reduce the size of a detector by arranging an optical element at distance from the uneven surface contacting part of a transparent flat plate and leading out and detecting only projection part information incoming while by being reflected totally. CONSTITUTION:When the uneven surface 5 such as a fingerprint is irradiated by a light source 2 while pressed against the transparent flat plate 1, light 16 scattered by a recessed part 10 is made incident on and refracted by the transparent flat plate 10, and then all projected from the transparent flat plate 1 at the angle of the incidence on the transparent flat plate 1. Light scattered by a projection part 9, on the other hand, enters the transparent plate 1 and its component less than the critical angle is projected to below the transparent plate, but the component larger than the critical angle is propagated in the transparent plate 1 while reflected totally by transparent plate/air interfaces. The light propagated in the transparent plate 1 reaches the optical element 3, where its total reflection condition is not satisfied, so the light enters the optical element 3 from its interface and is guided out. Then, an external detector 4 detects pattern information from only the projection part 9. |
