| 摘要 |
PROBLEM TO BE SOLVED: To provide a reading lens suitable for an image pickup camera built in a coin counter or the like. SOLUTION: The reading lens is constituted of a plane convex 1st lens 1 having positive refractive power and having a convex face S1 on an object side, an aperture diaphragm 3 having a prescribed aperture, and a 2nd meniscus lens 2 having negative refractive power and having a concave face S4 on the object side in this order from the object side to an image field side. Then, a moderate back focus (a distance from the rear face of the 2nd lens to the image pickup face of an image pickup element) can be secured by the 2nd lens as a principal lens, and also, an image side telecentric performance can be improved, and also, a shading phenomenon is reduced, further, various aberration including distortion is satisfactorily corrected, and a good photographic image having satisfactory brightness can be obtained. COPYRIGHT: (C)2005,JPO&NCIPI
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