| 摘要 |
PURPOSE: To provide a retrofocus type projecting lens for a liquid crystal projector composed of five elements of lenses having an F-number of >=5.6, a half angle of view of about 19 to 24, and a back focal length of about 1.5 times the focal length. CONSTITUTION: A first lens group G1 having a negative refracting power has a negative meniscus lens L1 convex to a large conjugation side, a second lens group G2 having a positive refracting power has a biconvex positive lens L2 and a third lens group G3 having the positive refracting power has a biconcave negative lens L3 , a positive meniscus lens L4 convex to a small conjugation side and a biconvex positive lens L5 . This retrofocus type projecting lens satisfies the conditions 0.25<D1 /f<0.55, 0.05<f2 /f3 <0.4 and 0.8<|f1|/f<1.2 when the air spacing between the first lens group G1 and the second lens group G2 is defined as D1 and the focal lengths of the first lens group G1 , the second lens group G2 , the third lens group G3 and the entire lens system are respective defined as f1 , f2 , f3 , f.
|
