Patent ID: 6476981
Filing Date: 2002-11-05
Classification: G02B

Abstract:
A retrofocus lens system comprising, in order from a large conjugate side:a first lens group having a negative refracting power; a second lens group having a positive refracting power; and a third lens group having a positive refracting power; said first lens group including, in order from the large conjugate side, a first lens from which projection light is sent out, a meniscus-shaped second lens which has a negative refracting power and a convex surface facing the large conjugate side, a third lens having a negative refracting power, and a fourth lens; said second lens group including a fifth lens having a positive refracting power; said third lens group including, in order from the large conjugate side, a sixth lens having a negative refracting power, both surfaces of which are concave, a seventh lens having a positive refracting power, both surfaces of which are convex, said seventh lens being joined with said sixth lens, an eighth lens having a positive refracting power, both surfaces of which are convex, and a ninth lens having a positive axial refracting power; wherein said retrofocus lens system satisfies the following conditional expressions (1) to (4): 1.232/f3<1.8â€ƒâ€ƒ(1) 1.51|/f<2.7â€ƒâ€ƒ(2) |f4|/f>30â€ƒâ€ƒ(3) f5/f>6â€ƒâ€ƒ(4) where f is a focal distance of the whole lens system, |f1| is an absolute value of a focal distance of said first lens group, f2 is a focal distance of said second lens group, f3 is a focal distance of said third lens group, |f4| is an absolute value of a focal distance of said first lens, and f5 is an axial focal distance of said ninth lens;wherein said first lens has an aspherical surface, and said ninth lens has an aspherical surface.