| 摘要 |
A light source (11) directs light into the gap between the pair of reflectors (41, 42). The light will only reach a detector (12) after multiple reflections across the gap and in the absence of a sheet (12), for example microfilm in a rotary camera. A shield (13) may be located in the gap in front of the light source to prevent light reaching the detector directly, and the shield may have a reflecting surface, for example, wedge or conical, may be pivoted to direct light onto the reflectors. The reflectors may be plane and parallel, or semi-cylindrical and concentrically curved about an axis parallel to the transport path. |
