| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a zoom projection lens. <P>SOLUTION: The zoom projection lens 100 includes a negative first lens group 10, a positive second lens group 20, a positive third lens group 30, a negative fourth lens group 40, and a positive fifth lens group 50, which are arranged in that order from a projecting surface to an imaging surface. The first to fourth lens groups are installed so as to be movable along an optical axis. The fifth lens group is fixedly installed. The first, second, and fourth lens groups respectively have first, second, and third aspheric plastic lenses, and satisfy conditional expression below. -2.4≤F<SB POS="POST">a1</SB>/F<SB POS="POST">W</SB>≤-2.1, 2.9≤F<SB POS="POST">b1</SB>/F<SB POS="POST">W</SB>≤3.2, and -3.8≤F<SB POS="POST">a2</SB>/F<SB POS="POST">W</SB>≤-3.6. In the expressions, F<SB POS="POST">a1</SB>, F<SB POS="POST">b1</SB>, and F<SB POS="POST">a2</SB>respectively represent effective focal distances of the first, second, and third aspheric plastic lenses. Fw is the effective focal distance of the zoom projection lens at a wide angle end. <P>COPYRIGHT: (C)2012,JPO&INPIT |
