Patent attributes
An image forming optical system comprises, in order from an object side, a front lens group having negative refracting power, and a rear lens group having positive refracting power, wherein said front group comprises, in order from the object side, a first lens element having the negative refracting power, and a second lens element of a meniscus form having a convex surface directed toward an image side; wherein said first lens element has an aspherical surface that is a concave surface directed toward the object side in the vicinity of the optical axis, and negative refracting power at a position on the aspherical surface becomes weak as a distance between the position and the optical axis becomes large, and a surface directed toward the image side that is concave at least in the vicinity of the optical axis; and further the following conditions (1) and (2) are satisfied:1.0<|fG1|/FA<10 (1)1.0<fG2/FA<10 (2)where FA is a focal length of the whole optical system, fG1 is a focal length of said front group, and fG2 is a focal length of said rear group.
