| 摘要 |
PURPOSE:To easily correct the distance between an original and a lens array by arranging a parallel plane plate on an optical path connecting an image forming element and a reading element and varying the length of the optical path substantially. CONSTITUTION:Lens arrays 2a and 2b for image formation are arranged symmet rically about a field lens array 2c between the original 1 brought into contact with the top surface of contact glass 6 and the photodetection surface 3 of a photodetector. Then, the transparent parallel plane plate 4 made of glass, etc., is arranged between the array 2a and original 1. The arrangement of the plane plate 4 which has thickness (d) and a refractive index (n) varies the length of the optical path between the array 2a and original 1 by DELTAL=L(1-na/ n)d, where na is the refractive index of air. For the purpose, plural kinds of plane plates 4 which differ in thickness are used and when the distance between the array 2a and original 1 becomes longer than the distance between the array 2b and photodetection surface 3, a plane plate 4 having thickness (d) correspond ing to the distance DELTAL is arranged. Consequently, the optical path is corrected from a broken line to a solid line to equalize both distances to each other substantially.
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