| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens for projection, which achieves a wide angle of view and a high variable power ratio, makes good aberration including chromatic difference of magnification without using a plurality of aspherical lenses, and is suitable for a projector device for projection using a DMD. SOLUTION: The zoom lens for projection is constituted of three groups, that is, negative, positive and positive groups from an enlargement side. The first group G<SB>1</SB>comprises a positive lens L<SB>1</SB>, a negative meniscus lens L<SB>2</SB>, a negative lens L<SB>3</SB>, a positive lens L<SB>4</SB>and a negative lens L<SB>5</SB>. The positive lens L<SB>4</SB>and the negative lens L<SB>5</SB>constitute a cemented lens. The second group G<SB>2</SB>comprises a biconvex lens L<SB>6</SB>and a biconvex lens L<SB>7</SB>. The third group G<SB>3</SB>comprises an aspherical lens L<SB>8</SB>, a negative lens L<SB>9</SB>, a positive lens L<SB>10</SB>and a positive lens L<SB>11</SB>. The zoom lens satisfies following conditional expressions (1) and (2): (1) ¾M3/f3¾<¾M1/f1¾<¾M2/f2¾; and (2) 0.40<¾M2/f2¾<0.80, provided that Mi is the moving amount of the i-th lens group between a wide angle end and a telephoto end when varying power, and fi is the focal distance of the i-th lens group. COPYRIGHT: (C)2008,JPO&INPIT
|
