| 摘要 |
PROBLEM TO BE SOLVED: To obtain an objective lens for an endoscope which has a predetermined four group, six element configuration and also has excellent optical performance by excellently correcting aberrations, specially, a power chromatic aberration while having a wide angle of about 135 to 140°and securing necessary back focus by satisfying conditional expressions. SOLUTION: The objective lens comprises a first negative lens L<SB>1</SB>which is concave to the image side, a second positive cemented lens L<SB>2+3</SB>which has a plane on the image side, a lightness stop 3, a fourth positive lens L<SB>4</SB>which has a larger-curvature-radius surface on the object side, and a positive cemented lens L<SB>5+6</SB>of a positive lens and a negative meniscus lens which has a larger-curvature-radius surface on the object side. Here, (1) 1.50<¾d/f<SB>1</SB>¾<2.50, (2) 0.96<f/h<1.04, (3) 2.00<f<SB>2+3</SB>/f<25.0, (4) 15.0<¾ν<SB>2</SB>-ν<SB>3</SB>¾, and (5) 10.0<f×¾ν<SB>5</SB>-ν<SB>6</SB>¾/(R×Bf) are satisfied, (where d is the distance from the concave surface peak of the first lens L<SB>1</SB>to the stop 3). COPYRIGHT: (C)2004,JPO&NCIPI
|
