| 摘要 |
PURPOSE:To eliminate stray light in a prism which guides light from a light source to a data carrier as parallel luminous flux and to make a data image sharp by providing the prism with a light projection surface for reflected light and a reflection preventive area adjacently to said surface. CONSTITUTION:The convergent light from a lamp 11 is converted into parallel light through the prism 12 to illuminate a liquid-crystal plate 13, thereby eliminating the blur of the contour of a data image imprinted on the surface of a film 7. Further, the light is shaped into a rectangular pattern and projected to light up only a specific area uniformly. The majority of a light beam which reaches a light projection surface S3 through an irregular optical path exits from the prism 12 from a transparent surface after reflected by the surface S3 and never becomes stray light in the prism 12, and the transparent surface operates as the reflection preventive area which does not rereflect reflected light from the surface S3 into the prism 12. Thus, the stray light in the prism is prevented, so a sharp data image is obtained.
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