| 摘要 |
PROBLEM TO BE SOLVED: To provide a large-diameter wide-angle lens with which various aberration over the entire distance of an object can be adequately corrected even though an F-number is approximately 1.4, assuring brightness, and an angle of view is approximately 60°or more, and which has optical performance ensuring high resolution and high contrast. SOLUTION: In the large-diameter wide-angle lens, a first group G<SB>1</SB>of negative power and a second group G<SB>2</SB>of positive power are disposed in this order from the object side. The first group G<SB>1</SB>comprises in order from the object side: a first lens L<SB>1</SB>of positive power whose convex face is disposed on the object side, a second lens L<SB>2</SB>of negative power whose convex face is disposed on the object side; a third lens L<SB>3</SB>of negative power; and a fourth lens L<SB>4</SB>of positive power. The second group G<SB>2</SB>comprises in order from the object side: a fifth lens L<SB>5</SB>whose convex face is disposed on the image side; a sixth lens L<SB>6</SB>and a seventh lens L<SB>7</SB>, one having positive power and the other negative power, which compose a cemented lens; and an eighth lens L<SB>8</SB>and a ninth lens L<SB>9</SB>, one having positive power and the other negative power, which compose a cemented lens. The large-diameter wide-angle lens is focused by moving the second group G<SB>2</SB>on the optical axis. By satisfying prescribed conditional expressions, various aberrations (esp., coma aberration) are adequately corrected. COPYRIGHT: (C)2006,JPO&NCIPI
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