| 摘要 |
PROBLEM TO BE SOLVED: To reduce lens costs by reducing the total number of lenses to partially share lenses, which are rotationally symmetrical with respect to the optical axis in an image reading optical system for reading image information. SOLUTION: The image reading optical system illuminates a document by an illumination means, images the image information of the document on imaging devices which are one-dimensionally arranged through an imaging optical system and reads image information. When the direction of the line of the one-dimensional imaging devices is defined as the main scanning and the direction orthogonal to it is defined as the auxiliary scanning, the read optical system is an in-mirror optical system which is foaled back by a mirror placed in a section orthogonal to the optical axis, including the main scanning and the auxiliary scanning and passes through the same optical system twice, and additional lenses are provided on one of the incident side and the exit side or on both sides of the optical system used in common.
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