| 摘要 |
PROBLEM TO BE SOLVED: To obtain a lens barrel which is capable of holding a "Koban" shaped (old Japanese coin having elliptical shape) irregular shaped lens block, in a positioning state substantially equal to the case of a circular lens, even under high temperatures. SOLUTION: The lens barrel is provided with a lens chamber which holds a lens system which focuses an original manuscript image one-dimensionally in the main scanning direction Y with respect to an imaging element. Among lens blocks giving a diffraction effect and composing a lens system, a lens block 28 having a largest effective diameter in the main scanning direction Y has an irregular shape, which is longer in the main scanning direction Y and shorter in the subscanning direction Z which intersects with the main scanning direction Y and an optical axis A, the both sides in the main scanning direction have a circular shape part 28a and is engaged in the arc parts 32 of the barrel 31. The linear expansion coefficient in the main scanning direction of the lens block 28 is smaller than that in the main scanning direction of the barrel 31. The regulation means, which regulates the position of the lens block 28 in the subscanning direction Z, is the arc parts 32 which engage with the arc parts 28a, on both the sides in the main scanning direction at a reference temperature, and worm screws 35 to which the lower edge part 28b is abutted against when subscanning direction Z at high temperature. COPYRIGHT: (C)2008,JPO&INPIT
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