| 摘要 |
PROBLEM TO BE SOLVED: To obtain a compact projection lens which is bright and has high projection performance. SOLUTION: The projection lens is constituted by arranging a first group G<SB>1</SB>having negative refractive power, a second group G<SB>2</SB>having positive refractive power, and a third group G<SB>3</SB>having positive refractive power in order from an enlargement side, and its reduction side is made nearly telecentric. The first group G<SB>1</SB>includes a first lens L<SB>1</SB>having a negative lens and a second lens L<SB>2</SB>having a negative aspherical lens whose both surfaces are aspherical in order from the enlargement side. The second group G<SB>2</SB>includes only a third lens L<SB>3</SB>having a positive lens. The third group G<SB>3</SB>includes four lenses L<SB>4</SB>to L<SB>7</SB>. Furthermore, the projection lens satisfies 1.4<D<SB>G23</SB>/D<SB>G12</SB><5.0. Provided that D<SB>G12</SB>is a distance between the first group G<SB>1</SB>and the second group G<SB>2</SB>, and D<SB>G23</SB>is a distance between the second group G<SB>2</SB>and the third group G<SB>3</SB>. COPYRIGHT: (C)2009,JPO&INPIT
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