| 摘要 |
PROBLEM TO BE SOLVED: To make chromatic aberrations satisfactory, while attaining wide field angle by employing four-group, five-element constitution as the lens constitution, and to obtain optical performance which is suitable for a read of a color image, while making the constitution small-sized and inexpensive. SOLUTION: The lens comprises, in the order starting from the object side, a negative meniscus lens L<SB>1</SB>which is a concave surface to the image side, a positive meniscus lens L<SB>2</SB>which is a convex surface to the object side, a stop 1, a biconcave lens L<SB>3</SB>, a biconvex lens L<SB>4</SB>, and a negative meniscus lens L<SB>5</SB>which is concave to the object side, L<SB>3</SB>and L<SB>4</SB>cemented together. Further, five conditional expressions prescribing respective values r<SB>1</SB>/f, f<SB>2</SB>/.f, f<SB>3</SB>/f, r<SB>8</SB>/r<SB>9</SB>, andθ<SB>gd</SB>(f: focal length of whole system, f<SB>2</SB>: focal length of L<SB>2</SB>, f<SB>3</SB>: composite focal length of L<SB>3</SB>and L<SB>4</SB>, r<SB>1</SB>: radius of curvature of the object-side surface of L<SB>1</SB>, r<SB>8</SB>: radius of curvature of the image-side surface, r<SB>9</SB>: radius of curvature of the object-side surface, abnormality dispersionθ<SB>gd</SB>=(N<SB>g</SB>-N<SB>d</SB>)/(N<SB>F</SB>-N<SB>C</SB>) of a constitution material of L<SB>2</SB>), are satisfied. COPYRIGHT: (C)2005,JPO&NCIPI
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