| 摘要 |
PURPOSE:To prevent the image of a microfilm from being projected to a screen by using an electrooptical shutter changing light transmissivity in accordance with an impressed voltage and driving the shutter at the time of retrieval as necessary. CONSTITUTION:A liquid crystal shutter 35 consists of an electrooptical shutter changing light transmissivity in accordance with the impressed voltage and a transparent plate corresponding to the position of a microfilm 3 in accordance with the width of an optical path from a light source 16 is mounted on an upper transparent plate 15. When the address of a required image 19 is inputted to a microcomputer 26 and a retrieval key on a controller 27 is turned on, a shutter ON signal is outputted to the shutter 35 prior to the start of retrieval processing. Consequently, the shutter 35 is driven and light passed from the light source 16 and projected to the screen 21 through the image 19 of the microfilm 3 is shielded. Thereby, the image 19 of the microfilm 3 can be prevented from being projected to the screen 21 during the retrieval.
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