| 摘要 |
PURPOSE:To obtain an image-forming optical device with a few of output nonuniformity and large brightness, by forming the aperture diameter of an image- forming lens as the arranging pitch of an optical sensor in a main scanning direction, and forming it as a rectangular lens larger than the arranging pitch of the optical sensor in a subscanning direction. CONSTITUTION:In a lens array 2, since it is constituted in such a way that the rectangular lens 3 having the aperture diameter in the subscanning direction Y larger than that in the main scanning direction X is arranged in a line shape in the main scanning direction X with a pitch equal to the arranging pitch of the optical sensor 5, the real aperture diameter of the rectangular lens 3 goes to (y) Therefore, since only the center part (x) of the lens where the amount of lowering of an ambient light quantity is few is used in the main scanning direction X, the change of the light quantity in reflected light from an original 1 made incident on the optical sensor 5 is scarcely generated, therefore, the output of the optical sensor 5 can be uniformized extending over entire width. Also, by increasing the convergence ability of the lens in the subscanning direction by setting the aperture diameter of the lens as (y), the reflected light from the original 1 can be converged efficiently, thereby, the image- forming optical device with large brightness can be obtained.
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